Showing papers in "Drug Research in 1995"

Enhancement of glucose disposal in patients with type 2 diabetes by alpha-lipoic acid

Abstract: Insulin resistance of skeletal muscle glucose uptake is a prominent feature of Type II diabetes (NIDDM); therefore pharmacological interventions should aim to improve insulin sensitivity. Alpha-lipoic acid (CAS 62-46-4, thioctic acid, ALA), a natural occurring compound frequently used for treatment of diabetic polyneuropathy, enhances glucose utilization in various experimental models. To see whether this compound also augments insulin mediated glucose disposal in NIDDM, 13 patients received either ALA (1000 mg/Thioctacid/500 ml NaCl, n = 7) or vehicle only (500 ml NaCl, n = 6) during a glucose-clamp study. Both groups were comparable in age, body-mass index and duration of diabetes and had a similar degree of insulin resistance at baseline. Acute parenteral administration of ALA resulted in a significant increase of insulin-stimulated glucose disposal; metabolic clearance rate (MCR) for glucose rose by about 50% (3.76 ml/kg/min = pre vs. 5.82 ml/kg/min = post, p < 0.05), whereas the control group did not show any significant change (3.57 ml/kg/min = pre vs. 3.91 ml/kg/min = post). This is the first clinical study to show that alpha-lipoic acid increases insulin stimulated glucose disposal in NIDDM. The mode of action of ALA and its potential use as an antihyperglycemic agent require further investigation.

Microglia, the first line of defence in brain pathologies.

Abstract: Microglial cells account for approximately 20% of the total glial population in the central nervous system. They are distributed with no significant local differences in the white and grey matters. In contrast to astrocytes they cover non-overlapping territories. They belong to the mononuclear phagocyte system and form the resident macrophages in the brain tissue, the spinal cord and the retina. Their function in the normal neural parenchyma is unknown. However, in various pathologies they form a most reactive sensor to threats to the nervous system. Within a few hours they exhibit an activation program that we have studied in seven different experimental paradigms, e.g. following nerve section, direct brain trauma, toxic lesion, spreading depression, ischemic lesion, fiber degeneration, autoimmune diseases. Activated microglial cells become immuno-competent and are MHC (major histocompatibility complex) class 1 and class 2 positive. They express the amyloid precursor protein, APP. The complement receptor CR3bi is quickly upregulated. The mitotic activity depends on the colony stimulating factors M-CSF and GM-CSF and the appropriate receptors. Molecules discussed as signals in the activation process of microglia are cytokines such as IL-1, IL-2, IL-6, TGF beta 1. An important role could also be attributed to the unique potassium channel of microglia. Brain macrophages of microglial origin have a strong respiratory burst activity, meaning that they produce oxygen radicals. They also possess Cathepsin B and L and thus are potentially cytotoxic. Taken together, microglia are highly reactive, mobile and multifunctional immune cells of the CNS that can play a universal role in the defence of the neural parenchyma.

Free radical mechanisms in dementia of Alzheimer type and the potential for antioxidative treatment.

Abstract: Neurodegenerative diseases, e.g. dementia of Alzheimer type and Parkinson's disease, are characterized neurochemically by a transmitter-specific loss of neurons, which progresses and extends to several neuronal systems over the course of the disease. At present, no single specific pathomechanism may explain the heterogeneous disorder of familial and sporadic dementia of Alzheimer type, both with early and late onset of the disease. The hypothesis has been proposed that cellular events involving "oxidative stress" may be one basic pathway leading to neurodegeneration in e.g. dementia of Alzheimer type and Parkinson's disease. There are indications for an increased activity or impaired defense mechanisms of free oxygen radicals in dementia of Alzheimer type, although less clear than in Parkinson's disease. Primary and secondary factors interact and may result in a self-propagating cascade of neurodegenerative events. Since these mechanisms of neuronal death involve different areas of cell metabolism, therapeutic strategies for "neuroprotection" also have to encompass different approaches. Since a specificity of oxygen radical toxicity in dementia of Alzheimer type has not been proven, "partial" neuroprotective drugs might be more beneficial in clinical practice than specific drugs affecting only one selective pathomechanism.

Biochemical and pharmacokinetic aspects of oral treatment with chondroitin sulfate.

Abstract: Chondroitin sulfate (Condrosuf®) was characterized for structure, physicochemical properties and purity. This glycosaminoglycan has a relative molecular mass of about 14,000, a sulfate-to-carboxyl ratio of 0,95 due to the high percentage of monosulfated disaccharides (38% 6-monosulfate and 55% 4-monosulfate) and a low amount of disufated disaccharides (1.1%) inside the polysaccharide chains. No other glycosaminoglycans were detected in the preparation. Chondroitin sulfate was labelled by reduction with sodium 3 H-borohydride and administered by oral route in the rat and dog More than 70 % of radioactivity was absorbed and found in urine and tissues. The plasma radioactivity was fractionated by size-exclusion chromatography in three fractions : radioactivity associated with high, intermediate and low molecular mass compounds. The peak value of the concentration of high molecular mass radioactivity compounds in plasma was reached after 1.6 and 2.1 h for the rat and dog, respectively. After 36 h the high molecular mass radioactivity compounds were still present in plasma of dog and rat. After 24 h radioactivity was higher in the intestine, liver, kidneys, synovial fluid and cartilage than in other tissues. Condroitin sulfate was orally administered to man (healthy volunteer) in a single daily dose of 0.8 g and in two daily doses of0.4 g The results showed that both forms of administration determined a significant increase of plasma concentration of chondroitin sulfate as compared with predose value over a full 24 h period. Elimination constant values and t max (of the first administration in the case of fractionated dose) were almost the same for the two administrations. Some biochemical parameters (number of leukocytes, proteins, sulfated glycosaminoglycans and hyaluronic acid amounts, and N-acetylglucosaminidase activity) of synovial fluid were evaluated in controls and treated osteoarthritic subjects. No variations were observed in the patient who did not receive chondroitin sulfate. Five days of chondroitin sulfate administration led to a significant increase of concentration and molecular mass of hyaluronan and a decrease of a lysosomal enzyme, N-acetyl-glucosaminidase. No significant differences in leukocyte count and protein content were detected.

Myocardial effects of flavonoids from crataegus species

Abstract: The influence of the main flavonoids from Crataegus species (hawthorn, Rosaceae) on coronary flow, heart rate and left ventricular pressure as well as on the velocity of contraction and relaxation was investigated in Langendorff perfused isolated guinea pig hearts at a constant pressure of 70 cmH2O Drug action was evaluated in a concentration range of 10(-7) to 5 x 10(-4) mol/l An increase of coronary flow caused by the O-glycosides luteolin-7-glucoside (186%), hyperoside (66%) and rutin (66%) as well as an increase of the relaxation velocity (positive lusitropism) by luteolin-7-glucoside (104%), hyperoside (62%) and rutin (73%) were the major effects observed at a maximum concentration of 05 mmol/l Furthermore, slight positive inotropic effects and a rise in heart rate were seen Similar but less intensive actions were found with the C-glycosides vitexin, vitexin-rhamnoside and monoacetyl-vitexin-rhamnoside Possible beta-adrenergic activities of the flavonoids could be excluded by the addition of propranolol in fixed concentrations of 10(-8) to 10(-5) mol/l Moreover, pretreatment of the animals with reserpine (7 mg/kg) did not influence myocardial activity of hyperoside (10(-4) mol/l) As previous experiments showed an inhibition of the 3',5'-cyclic adenosine monophosphate phosphodiesterase, the results suggest an inhibition of this enzyme as the possible underlying mechanism of cardiac action of flavonoids from Crataegus species

Activity of nimesulide on constitutive and inducible cyclooxygenases

Abstract: Prostaglandins are pro-inflammatory but are gastroprotective. The gastric mucosa synthesizes prostaglandins mainly via constitutive cyclooxygenase (COX-1), whereas leucocytes have inducible enzyme (COX-2). Nimesulide (CAS 51803-78-2) differentially inhibited prostanoid synthesis in these human tissues as well as with in vitro enzyme assays, and was less potent than indometacin (CAS 53-86-1) on COX-1. Fresh human gastric mucosa was cut finely, washed and pre-incubated (100 mg in 1 ml phosphate buffered saline pH 7.4) with or without nimesulide or indometacin (0.1-100 micrograms/ml; 0 degree C; 30 min). The fluid was replaced with fresh identical solution, incubated (37 degrees C; 30 min) and the solution assayed. Isolated leucocytes from human peripheral blood were incubated (1-1.5 x 10(6), 2 ml Krebs' solution) with or without nimesulide or indometacin (0.1-100 micrograms/ml; 37 degrees C; 1 h), stimulated with lipopolysaccharide (5 micrograms/ml), further incubated for 24 h at 37 degrees C and the medium assayed for the prostanoids PGE, TXB2, 6-keto-PGF1 alpha and the leukotriene LTB4 by radioimmunoassay (RIA). In vitro assays with COX-1 from ram seminal vesicles, or COX-2 from sheep placenta, were performed by pre-incubating the enzymes with vehicle alone (controls) or with drug for 5 min at 37 degrees C. Arachidonate (10 mumol/l) was added and further incubated for 2 min at 37 degrees C. Reactions were terminated and PGE determined by RIA. Both drugs caused concentration-related inhibitions of prostanoid accumulation in incubates of both tissues. Nimesulide reduced PGE accumulation more potently in incubates of stimulated leucocytes than of gastric mucosa. With gastric tissue, nimesulide was less potent than indometacin by approximately 6-22 fold (IC50 for PGE, TXB2, 6-keto-PGF1 alpha, respectively; 14.8 vs 2.5; 12.8 vs 1.0; 31.1 vs 1.4 mumol/l; p < 0.05 to 0.02). With the leucocytes, the concentrations of both drugs, particularly indometacin were not low enough to calculate the IC50. With the in vitro assay, nimesulide (0.01 to 100 mumol/l) did not inhibit PGE formation by COX-1 but caused a concentration-related inhibition of PGE formation by COX-2 (4-60%). These results are consistent with the effective analgesic/anti-inflammatory activity of nimesulide coupled with better gastric tolerance compared to indometacin.

Pharmacological profile of hypericum extract. Effect on serotonin uptake by postsynaptic receptors.

Abstract: In the present study is is reported that the methanolic Hypericum extract LI 160 (Jarsin 300) exerts no protective effect against N-methyl-D-aspartate (NMDA-) or gp120- (from the HIV virus) induced cytotoxicity. Moreover, it is established that Hypericum extract causes no activation of arachidonic acid release from neurons activated by gp120; hence it displays no sensitization effect on the NMDA receptor channel. The main outcome of this study is the finding that Hypericum extract causes a 50% inhibition (IC50 value) of serotonin uptake by rat synaptosomes at a concentration of 6.2 microglml. Therefore it is concluded that the antidepressant activity of Hypericum extract is due to an inhibition of serotonin uptake by postsynaptic receptors. Future studies might focus on the effect of Hypericum extract on serotonin binding to neurons, serotonin storage in granules, the rate of synthesis of serotonin, and on the activity of monoamine oxidase.

Effects of flavonoids on parietal cell acid secretion, gastric mucosal prostaglandin production and Helicobacter pylori growth.

Abstract: The effect of the flavonoids flavone, flavanone and quercetin on parietal cell acid production, H+/K(+)-ATPase activity, gastric mucosal prostaglandin E2 biosynthesis and Helicobacter pylori growth was studied. All flavonoids inhibited acid production in isolated parietal cells in response to histamine and dibutyryl-cAMP stimulation (IC50 values between 26 and 139 mumol/l) and inhibited H+/K(+)-ATPase activity. Inhibition of H+/K(+)-ATPase activity was dependent on the ATP concentration. Fluorescence measurements showed that flavanone reacts with ATP. These findings indicate that the inhibitory action of flavonoids on H+/K(+)-ATPase activity is related to their ability to complex ATP. Flavone and flavanone (10 and 100 mumol/l) stimulated prostaglandin E2 production in isolated gastric mucosal cells. Furthermore, the compounds inhibited Helicobacter pylori growth in a concentration-dependent manner. From these finding it appears that flavonoids are a group of compounds which could have a therapeutic potential for treatment of gastrointestinal diseases associated with Helicobacter pylori infection.

Strategic infarcts in vascular dementia. A clinical and brain imaging experience.

Abstract: The mechanisms of dementia resulting from small deep infarctions are incompletely understood. The thesis underlying the concept of "multi-infarct dementia" is that multiple lesions have a synergistic effect on mental functions, resulting in dementia irrespective of specific location or volume. In this report, we summarize our experience with six patients reported previously along with additional patients examined subsequently, whose clinical features and brain imaging findings allow an alternative formulation for dementia resulting from lacunar stroke. The six initial patients presented with an abrupt change in behavior after acute infarction involving the inferior genu of the internal capsule documented by computed tomography (CT) and magnetic resonance imaging (MRI). The acute syndrome featured fluctuating alertness, inattention, memory loss, apathy, abulia, and psychomotor retardation suggesting frontal lobe dysfunction. Contralateral hemiparesis and dysarthria were generally mild, except when the infarct extended into the posterior limb. Neuropsychological testing in five patients with left-sided infarcts revealed severe verbal memory loss. Additional cognitive deficits consistent with dementia were evident in four patients. A right-sided infarct caused transient impairment in visuospatial memory. Functional brain imaging in three patients using 133xenon regional cerebral blood flow (rCBF) and single photon emission computed tomography (SPECT) showed focal reduction in hemispheric perfusion most prominent in the ipsilateral inferior and medial frontal cortex. Perfusion was also defective in the medial and laterial temporal cortex. Important pathways of the limbic system traverse the inferior capsule in the region of the genu. Corticothalamic and thalamocortical fibers form the thalamic peduncles which detach from the internal capsule and enter the thalamus at its rostral and caudal poles and along its dorsal surface. The anterior thalamic peduncle, conveys reciprocal connections between the dorsomedial nucleus and the cingulate gyrus, as well as the prefrontal and orbitofrontal cortex. The inferior thalamic peduncle carries fibers which connect the thalamus with orbitofrontal, insular, and temporal cortex, as well as the amygdala via the ansa peduncularis to the ventral amygdalofugal pathway. Thus, damage to one or both white-matter tracts may occur with infarctions in the region of the inferior genu, causing striking frontal behavioral effects and memory loss in our patients associated with functional deactivation of the ipsilateral frontal and temporal cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro study on the interaction of Valeriana officinalis L. extracts and their amino acids on GABAA receptor in rat brain.

Abstract: This work studied in vitro the interaction of aqueous and hydroalcoholic extracts of Valeriana officinalis L. and compounds that are present in the extracts (amino acids and valerenic acid) with the GABAA (gamma-aminobutyric acid) receptor, using the [3H] muscimol binding technique to crude synaptic membranes from rat brain cortices. Both extracts displaced [3H]muscimol bound and this effect is probably due only to their amino acid content, specially GABA. This fact explains the in vitro effect of valerian extracts on GABAA receptor but not their sedative effect.

Immunoregulatory Effects of the Herba Epimediia Glycoside Icariin.

Abstract: The in vitro effects of the Chinese Herba Epimediia glycoside icariine (ICA), a chinese herbal extract, on human immune responses were investigated. ICA induced a weak and delayed proliferation of peripheral blood mononuclear cells from healthy donors when compared to phytohemagglutinin. Both T- (TCR alpha beta+) and B cells were the ICA-responding cells. Within T-cells, the relative proportion of CD4-8+ cells increased but that of CD4+8- cells decreased. ICA in certain concentrations could increase lymphokine-activated killer cell (LAK) activity (0.1 to 1.0 microgram/ml) in both tumor patients and healthy donors, and natural killer cell (NK) activity (1.0 to 5.0 micrograms/ml) in tumor patients. Moreover, ICA stimulated the production of tumor necrosis factor-alpha in monocytes from healthy donors. These findings provide evidence that ICA could be applied to adoptive immunotherapy. Generation of LAK cells in presence of an appropriate dose of ICA might be superior to interleukin-2 alone.

The solubility and bioequivalence of silymarin preparations

Abstract: Seven silymarin products (pharmacies only), two of them with two batches each, were analysed for their ingredients, in particular silibinin (CAS 22888-70-6) and tested in vitro for their liberation of active agents. Founded on the results of these tests three products were checked for bioequivalence. Therefore, a typical phase I 3 fold crossover study was performed showing one product (Legalon) to be qualified by an approx. 2 fold higher silibinin availability compared to the two other preparations.

Effect of oral pyridoxine hydrochloride supplementation on arterial blood pressure in patients with essential hypertension.

Abstract: The purpose of this study was to test the effect of vitamin B6 (pyridoxine-HCl, CAS 58-56-0) supplementation on arterial blood pressure in essential hypertension. The trial comprised 9 normotensive subjects (7 men and 2 women, aged between 32-58 years; mean +/- SD, 48 +/- 11) and 20 patients with essential hypertension (16 men and 4 women, aged between 32-69 years; mean +/- SD, 56 +/- 12). The patients were treated during 4 weeks with a single oral dose of pyridoxine (5 mg/kg body weight/day). After a 5-min rest, measurements were made in the supine position. When compared with the normotensive subjects, the hypertensive subject group had a significantly higher systolic and diastolic blood pressure (p < 0.001) and higher level of plasma norepinephrine (NE) (p < 0.01) before pyridoxine treatment. On the other hand, there were no significant differences in plasma epinephrine (E) and heart rates. Treatment of hypertensive patients with pyridoxine significantly reduced systolic (p < 0.01) and diastolic blood pressure (p < 0.005), plasma NE (p < 0.005) and E (p < 0.05) within 4 weeks. However, there was no significant difference in heart rate at the end of pyridoxine treatment. These results indicate a relationship between pyridoxine status and arterial blood pressure in the essential hypertensive patients.

Antioxidative properties of alcoholic extracts from Fraxinus excelsior, Populus tremula and Solidago virgaurea.

Abstract: Aqueous-ethanolic extracts from Fraxinus excelsior, Populus tremula and Solidago virgaurea inhibit biochemical model reactions representing inflammatory situations to various extents. These model reactions include xanthine oxidase, diaphorase in the presence of the autoxidizable quinone juglone, lipoxygenase and photodynamic reactions driven by riboflavin or rose bengal. The tested extracts are the components of the phytomedicine Phytodolor N (abbreviated as PD) which possesses antipyretic, analgesic, antiinflammatory and antirheumatic activity. Since several reactive oxygen species produced by the mentioned model systems are also involved in inflammatory processes, the beneficial activities of the complete drug may at least in part be due to the reported antioxidative functions of the individual components.

Propofol binding to human blood proteins.

Abstract: The binding of the intravenous anesthetic propofol (CAS 2078-54-8) to human native plasma, hemoglobin and serum albumin was studied by means of equilibrium dialysis. Propofol binding to plasma over the large concentration range from 0.04 to 150 micrograms/ml was independent on the substrate concentration and amounted 97.4-98.6%. Serum albumin and hemoglobin also showed a marked binding for propofol. A 4% solution of albumin bound 88.7% and hemoglobin 86.2% of the anesthetic. In studies with constant protein concentration and variation of the propofol concentration a decrease of the percentage bound with increasing substrate concentration was seen for hemoglobin, indicating saturable binding sites. The opposite was found for the interaction between propofol and albumin: increase of the binding extent with increasing substrate concentration.

Inflammation as a pathogenic mechanism in Alzheimer's disease.

Abstract: Numerous markers of inflammation have been reported in the Alzheimer's disease brain. Although other pathogenic mechanisms certainly apply, there is now compelling evidence that inflammation is not simply a response to already existing Alzheimer's pathology, but ultimately becomes a significant source of pathology. The pathogenic potential of inflammation in Alzheimer's disease follows from the inherent destructiveness of inflammatory mechanisms, the postmitotic status of neurons, and the unique interactions of inflammatory markers and cells with pathologic hallmarks of Alzheimer's such as amyloid β-peptide. These conclusions from basic science are borne out by recent clinical efforts, though the latter are still limited and require further confirmation

Bioequivalence. An updated reappraisal addressed to applications of interchangeable multi-source pharmaceutical products

Abstract: This paper reviews study procedures for bioequivalence trials, mainly addressed to the New Drug Application (NDA) of generic drugs, strictly referring to EU and USA guidelines on this matter. Specific attention is devoted to the most appropriate experimental designs, the size of the volunteer sample, the ethical issues involved, statistics to assess bioequivalence and the accepted standard format for final research reports. Some aspects which create serious problems in bioequivalence trials, most of which not fully covered by the EU and USA specific guidelines, are comprehensively discussed. These include a) drugs with elevated variability; b) endogeneous substances and the management of baseline value; c) modified release formulations; d) prodrugs; e) restrictions to be contained in forthcoming guidelines on chiral medicinal products; f) superbioavailability; g) drugs with elevated half-life and h) cases in which bioequivalence trials should not be needed. As generic drugs cost less than the innovator product, agencies have facilitated their NDA procedures by requiring a dossier on chemistry and pharmacy and a pivotal bioequivalence study to demonstrate that the generic formulation is fully interchangeable with the innovator product. Bioequivalence is thus the key requirement for an NDA of a generic drug, and trials should be planned, conducted and reported in the most appropriate way. With this in mind, this review is an up-to-date reappraisal that should stimulate the attention of scientists and regulatory authorities on some open questions on bioequivalence.

Age-associated memory impairment and early Alzheimer's disease. Only time will tell the difference.

Abstract: A reliable and early diagnosis of incipient Alzheimer's disease (AD) is one of the obligatory requirements for timely and potentially succesful therapeutic intervention. The potential diagnostic significance of mild cognitive impairment and subjective memory complaints was examined. Groups of patients with age-associated memory impairment (AAMI) and with AD were examined prospectively and their subjective complaints, cognitive performance and neuroimaging findings were compared with those of healthy elderly controls. Subjective complaints were most severe in the AD group. Both, memory complaints and depressive disturbances had high loadings on one underlying principal component. There was no statistical correlation between a global score of cognitive performance and subjective complaints in the patient groups, but the correlation between performance and brain atrophy, but not subjective complaints (or the diagnostic distinction between AAMI and AD) were associated with the severity of cognitive deterioration during a 2-year follow-up period. This, and the observation of an increased frequency of the apolipoprotein E allele 4 in the AD and AAMI groups, suggest that biological risk markers will be of greater significance for the early diagnosis of AD than the patient's subjective complaints. Patients satisfying criteria for AAMI need to be followed-up, because no reliable diagnostic markers for the earliest or preclinical stages of AD are available to date

Effect of nimesulide action time dependence on selectivity towards prostaglandin G/H synthase/cyclooxygenase activity.

Abstract: PGHS (cyclooxygenase, prostaglandin endoperoxide synthase, 8.11,14,-icosatrienoate hydrogen donor oxygen oxidoreductase, EC 1.14.99.1) is a bifunctional, membrane-bound hemoprotein that catalyzes both the bisoxygenation of arachidonic acid to form PGG 2 and the peroxidative reduction of PGG 2 to form PGH 2 . Recently two forms of cyclooxygenase have been isolated, one (COX-1) being constitutive, the other (COX-2) being mitogen-inducible. Nimesulide (CAS 51803-78-2) has been shown to inhibit with high selectivity COX-2 without affecting COX-1 activity, so explaining the previous observations about the selectivity of the anti-prostaglandin effect of the drug. The potency of the effect, however, seems to be different according to these works. The time dependence of COX-2 inhibitors might afford some clues to a better understanding of the mechanism of COX-2 selective inhibition, on the discrepancy between some authors about the potency of the drug and on the relationship between COX-2 inhibition and inhibition of superoxide anion production, an event also characterized by a time dependence. So we evaluated the time dependency of the effect of nimesulide on COX-1 and COX-2. COX-1 was isolated from ram seminal vesicles, and COX-2 was from sheep placenta. Nimesulide inhibited COX-2 activity in a concentration-dependent manner. The inhibition of COX-2 was characterized by the time dependence, so the IC 50 varied according to the time of pre-incubation (from 70 ± 35 μmol/l to 0.07 ± 0.05 μmol/l). Nimesulide did not affect COX-1 activity until 1 μmol/l and with an IC 50 > 100 μmol/l. In conclusion nimesulide's selective inhibitory effect on COX-2 is time-dependent whereas its weak effect on COX-1 is not time-dependent. This observation agrees with the time dependence effect of COX-2 reported by other workers with NS-398 (N-(2-cyclohexyloxy-4-nitrophenyl) methane sulphonamide) and with flosulide and explains the different values of IC 50 reported by other workers. Nimesulide shares with other sulfanilide-like drugs the time dependence of its selective effect on COX-2.

Antihypertensive effect of oral nitrite uptake in the spontaneously hypertensive rat.

Abstract: The lower blood pressure of vegetarians might partly be due to the high dietary load with nitrate which--to a certain extent--is further reduced to nitrite and finally to nitric oxide. To test this hypothesis, spontaneously hypertensive rats received drinking water containing 0, 25, 50 or 100 mmol/l NO2 during 56 days. Food was offered ad libitum or was restricted by 20% (pair-feeding) to simulate the lower energy consumption of vegetarians. Blood pressure, which was monitored at regular intervals, was lowered in a dose-dependent manner by nitrite. This effect was reversible and could not be enhanced by energy restriction. In volunteers plasma nitrate levels increased by a factor of 8 to 32 following the ingestion of a nitrate-rich meal, and mean methemoglobin concentrations increased from 1.2% to 2.4% indicating the endogenous formation of nitrite under these conditions.

Pharmacokinetics and bioavailability of different formulations of aciclovir

Abstract: The pharmacokinetics and bioavailability of aciclovir (CAS 59277-89-3) were examined after administration of newly developed 200 mg and 400 mg tablets. Two studies, each with 24 subjects of either sex, were performed. In the three-way study I, two different tablets containing 200 mg of aciclovir (test and reference products) and a short infusion of 250 mg aciclovir were compared. In the two-way study II, the bioequivalence of a newly developed 400 mg aciclovir tablet was tested against a standard product. Irrespective of dose, the peak plasma aciclovir levels were obtained 1.5 h after administration of the tablets. In the case of the 200 mg tablets, the mean Cmax-values were 454 ng/ml (pilot test formulation, T) and 525 ng/ml (reference formulation, R), whereas the mean Cmax-values after administration of the 400 mg tablets were 779 (T) and 800 (R) ng/ml for test and reference formulation, respectively. The mean AUC calculated to the time of the last measurement in each instance was in the order of 2290 (T) and 2275 (R) ng/ml x h (200 mg tablets) or 3726 (T) and 3855 (R) ng/ml x h (400 mg tablets). The amount of the dose renally excreted as unchanged aciclovir was measured at 20.8 (T) - 21.8 (R)% with the 200 mg tablets and 14.3 (T) - 15.1% (R) with the 400 mg tablets.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of memantine on synaptic transmission in the hippocampus in vitro.

Abstract: CA 1 pyramidal cell response (population spike) in the hippocampal slice preparation was monitored after electrical stimulation of the Schafer collaterals at CA 2 in the presence of different concentrations of memantine (1-amino-3,5-dimethyladamantane, Akatinol Meman tine®, CAS 41100-52-1) currently being prescribed for the treatment of e.g. dementia. Memantine increased the amplitude of the population spike by 100% compared to the predrug level with an EC 50 of approximately 8 μmol/l. Long-term potentiation induced by a brief theta stimulus was likewise increased by a factor of 2. The concentration dependent action of D-serine, an agonist acting at the strychnine insensitive glycine-site of theNMDA (N-methyl-d-aspartic acid) receptor was enhanced in the presence of 1 μmol/l of memantine. These effects of memantine were antagonized completely by very low concentrations of the selective non-NMDA receptor antagonist NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzoe (F) quinoxyline) as well as by less selective antagonists such as DNQX (6,7-dinitroquinoxaline -2,3-dione) and CNQX (6-cyano-7-nitroquinoxaline-2,3-dione). In contrast, dizocilpine tested under identical conditions and in concordance with the literature decreased long-term potentiation. Thus, memantine clearly has different effects on glutamatergic synaptic transmission compared to dizocilpine, The ability of memantine to enhence synaptie transmission in the hippoeampus is in concordance with the reported positive influence on cognition deficits in humans

Influence of the susceptibility genes apolipoprotein E-epsilon 4 and apolipoprotein E-epsilon 2 on the rate of disease expressivity of late-onset Alzheimer's disease.

Abstract: Apolipoprotein E-epsilon 4 (APOE4, gene; apoE4, protein) is a susceptibility gene or risk factor for Alzheimer's disease. The genetic relevance of APOE4 has been widely confirmed. The APOE gene is not a disease locus, with specific mutations causing Alzheimer disease. Allelic variations at the APOE locus affect the rate of disease progression. The association of specific inherited APOE alleles with age of onset distributions describes biological effects based on genotype. The inheritance of polymorphic genes with single amino acid differences between apoE4 and apoE3 (and between apoE3 and apoE2) at the protein level is associated with differences in the mean age of disease onset spanning almost two decades. The isoform-specific metabolism of apoE resulting in a faster rate of disease expression can now be studied with the expectation that genetically relevant processes are being investigated. There is now an opportunity to develop theories directed at the genetically relevant apoE metabolism that can significantly delay disease expression.

Quantitative determination of lectins in mistletoe preparations.

Abstract: Assay of lectins in mistletoe preparations was based on an improved and validated version of ELLA (enzyme-linked lectin assay) to meet the requirements given in the guidelines for drug tests. The monoclonal antibody used has more than 90% cross reactivity with the three known mistletoe lectins, so that total lectin content is determined with much greater accuracy. With the detection and quantitative analysis limit below 5 ng/ml and a linear measuring range of 5-50 ng/ml, dosages in therapeutic range can be assayed. Tests to establish the accuracy of the analytical method showed that up to 26% of lectin activity is suppressed by other constituents of the extract, so that the recovery must be taken into account. The recovery increases following ultrafiltration to remove low-molecular constituents. Analysis for precision gave a variation coefficient of < or = 7.7% and a confidence interval < or = 5.7% (p = 0.05) for total lectin concentrations of approx. 250 ng/ml. This level of precision, which is good for an immunologic assay, makes it possible to standardize mistletoe preparations.

Effect of a hawthorn extract on contraction and energy turnover of isolated rat cardiomyocytes.

Abstract: The hawthorn extract LI 132 (crataegus), prepared from leaves and flowers, and standardised to 2.2% flavonoids, was investigated with respect to its effect on (1) the contraction, (2) the energy-turnover and (3) the apparent refractory period (t(ref)) of isolated cardiac myocytes from adult rats. (1) The contractile behaviour of attached myocytes was analyzed by an image processing system. (2) The energy turnover was calculated from the decrease in oxygen content in the myocyte suspension, brought about by cellular respiration. It was differentiated between energy turnover related to cell shortening and that required for ionic transport processes by application of the contraction-inhibiting agent 2,3-butanedione monoxime. (3) The apparent refractory period (t(ref)) was evaluated by pacing the myocytes with increasing stimulation rates and determining the frequency at which failure of single contractions occurred. For these purposes, the myocytes were incubated in a stimulation chamber, which is part of a computer-assisted system allowing to simultaneously evaluate the mechanics and energetics of electrically induced contraction. Within a range of 30-180 microg/ml, the hawthorn extract exhibited a positive inotropic effect on the contraction amplitude accompanied by a moderate increase of energy turnover both for mechanical and ionic processes. In comparison with other positive inotropic interventions, such as application of the beta-adrenergic agonist isoprenaline, or of the cardiac glycoside ouabain (g-strophantin), or elevation of the extracellular Ca++-concentration, the effects of the hawthorn extract were significantly more economical with respect to the energetics of the myocytes. Furthermore the extract prolonged the apparent refractory period in the presence and the absence of isoprenaline, which be indicative for an antiarrhythmic potential.

Absorption of [7,8-14C]rac-a-lipoic acid from in situ ligated segments of the gastrointestinal tract of the rat.

Abstract: rac-a-Lipoic acid (CAS 62-46-4, thioctic acid) is used in human therapy besides the parenteral route also orally in gastric juice soluble galenic formulations in patients suffering from diabetic polyneuropathy which also involves the gastrointestinal tract (GI) tract in about 20% of the diabetic population. In those patients the most common manifestation of the disease due to small intestine dysfunction is diarrhoea as a consequence of which malabsorption of orally administered drugs may result. Due to the importance of the knowledge on absorption characteristics, in preclinical studies on pharmacokinetics the extent of [14C]absorption from a solution of [7,8-14C]rac-a-lipoic acid was investigated in the rat after oral administration by means of comparison of the AUCs from the [14C]plasma concentrations vs those from the intravenous route, yielding 66%. An alternative evaluation by comparison of [14C]material excreted into the urine yielded 93% [14C]absorption. Despite this high and nearly complete absorption, due to the gastroenteral disturbances mentioned above, the question was investigated if the absorption is restricted to only a small area of the GI tract or is extended over a wider area. The latter is expected to make the absorption less sensitive against variations caused by gastrointestinal disturbances due to longer residence times in the GI tract. In order to approach most closely the physiological situation--as compared with different in vitro incubation techniques using isolated GI tract sacs--the in situ technique on 5 ligated areas of the GI tract of the aneasthetized rat (stomach, duodenum, jejunum, ileum, and colon with caecum) was established.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the efficacy of unconventional therapies. Problems and designs.

Abstract: Many unconventional therapies (e.g. dietary, phytotherapy, acupuncture, homeopathy) are well known and often applied, but their efficacy has hardly been proven. New trial designs and study components must be found to meet the specific demands of the particular unconventional therapy on one hand and keep the high methodological standard of controlled clinical trials on the other hand. Biometricians and unconventional therapists are challenged to develop such designs. Typical problems in designing studies of unconventional therapies include that placebo is not possible, therapies cannot be masked, outcome variables are not reliable, therapy is highly individualized, and studies on the efficacy of soft therapies require many patients and long treatment periods. Studies with unconventional therapies should be performed by practitioners (because they use these therapies), but this leads to further problems. Some solutions are given in examples: A study is described investigating the herbal remedy Kava-Kava for patients in the state of anxiety, tension and restlessness; a study on classical homeopathy for chronical headaches is specified; some designs for dietary studies in patients with rheumatoid arthritis are compared. A design called "cross-allocation of patients to two treatments with randomization option" and the "N-of-1 design", also called "single case design" are described and discussed. The "change-to-open-label design" could be useful to investigate soft and natural therapies which require studies with many patients and long-term treatment.

Antiandrogenic properties of nomegestrol acetate.

Abstract: Nomegestrol acetate (NOM-Ac; TX 066, 17 alpha-acetoxy-6-methyl-19-nor-4,6-pregnadiene-3,20-dione, CAS 58652-20-3), a 19-nor-progesterone derivative showed a significant antiandrogenic effect on ventral prostate and seminal vesicles weights of immature castrated rats treated with testosterone. However, this effect was 20 times less potent than that of cyproterone acetate (CYP-Ac). In contrast to norethindrone acetate, a 19-nor-testosterone derivative. NOM-Ac was totally devoid of androgenic effect on male accessory sex organs. Relative binding affinity against 3H-testosterone for androgen receptor of rat ventral prostate showed an IC50 of 22.6 +/- 4.0 and 21.1 +/- 5.3 nmol/l for NOM-Ac and CYP-Ac, respectively, while Dixon analysis disclosed a Ki of 7.58 +/- 0.94 and 4.30 +/- 0.17 nmol/l. Then, Scatchard plot analysis of 3H-NOM-Ac binding revealed a KD of 20.9 +/- 3.1 nmol/l and a Bmax of 217 +/- 27 fmol/mg protein.

Effect of schistosomal infection and its treatment on some key enzymes of glucose metabolism in mice livers.

Abstract: Three antischistosomal drugs, praziquantel (CAS 55268-74-1, EMBAY 8440, Prz), oxamniquine (CAS 21738-42-1, Oxa) and oltipraz (CAS 64224-21-1, Olt) were examined for their ability to reverse the disturbances in carbohydrate metabolism induced by Schistosoma mansoni (S. mansoni) infection. The infected mice were screened every 2 weeks for 16 weeks for their body and liver weights in addition to assessment of the activities of liver pyruvate kinase (PK), phosphofructokinase (PFK) (glycolysis), citrate synthase (CS) (Krebs' cycle) glycogen phosphorylase (GP) (glycogenolysis), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) (hexose monophosphate shunt). Results of the study showed that infection with S. mansoni caused the following changes in mice livers: 1. significant increase in liver weights from the 6th week of infection, which coincided with schistosomal egg deposition, whereas body weights were reduced, 2. remarkable increase in the activities of PK and PFK from the 4th week of infection, 3. marked reduction in CS, GP, G6PDH and 6PGDH. These results lead to the conclusion that glycolysis is largely stimulated in the livers of infected mice on the expense of other metabolic pathways of glucose utilization. Administration of Prz to infected mice caused normalization of all measured enzyme activities almost from the 2nd week of infection, whereas liver and body weights were improved from the 10th week. Oxa was less effective in these regards while Olt was the least. These data support the selection of Prz as a drug of choice for S. mansoni infection.

Inhibition of the production of platelet activating factor and of leukotriene B4 in activated neutrophils by nimesulide due to an elevation of intracellular cyclic adenosine monophosphate.

Abstract: Nimesulide (CAS 51803-78-2) has been shown to exert a marked anti-inflammatory effect in several in vivo models of inflammation. Recent studies indicate that nimesulide not only inhibits prostaglandin synthesis in certain cell types, but also has pleiotropic effects on neutrophil functions, including the respiratory burst, integrin-mediated adherence and synthesis of platelet-activating factor (PAF). In the present study, the effect of nimesulide on PAF synthesis was compared with its effect on the production of leukotriene B 4 (LTB 4 ). Nimesulide dose-dependently inhibited both processes in neutrophils stimulated by serum-treated zymosan (STZ) with a comparable efficacy (IC 50 values between 10 and 20 μmol/l). In formyl-methionyl-leucyl-phenylalanine-stimulated neutrophils (treated with cytochalasin B), these IC 50 values were 30 and 50 μmol/l for PAF and LTB 4 synthesis, respectively. These results indicate an inhibition by nimesulide of common step in the release of these lipid mediators, i.e. the activation of phospholipase A 2 , possibly by elevating intracellular cAMP. In support of this latter hypothesis, it was observed that nimesulide increased the level of cAMP almost 3-fold after STZ stimulation, whereas in fMLP-stimulated neutrophils these changes in cAMP levels were more dramatic. Furthermore, the inhibitory effects of nimesulide on PAF and LTB 4 production could largely be prevented by addition of H89, an inhibitor of cAMP-dependent protein kinase (PK-A). It is concluded that an increase in intracellular cAMP is instrumental in the observed effects of nimesulide on the release of PAF and LTB 4 by activated neutrophils and that limited availability of arachidonic acid, also the substrate for the cyclooxygenase pathway, may very well contribute to the effects of nimesulide on prostaglandin synthesis observed in other cell types.