Showing papers by "Lund University published in 1984"

The density and distribution of ischemic brain injury in the rat following 2–10 min of forebrain ischemia

Abstract: The density and distribution of brain damage after 2-10 min of cerebral ischemia was studied in the rat. Ischemia was produced by a combination of carotid clamping and hypotension, followed by 1 week recovery. The brains were perfusion-fixed with formaldehyde, embedded in paraffin, subserially sectioned, and stained with acid fuchsin/cresyl violet. The number of necrotic neurons in the cerebral cortex, hippocampus, and caudate nucleus was assessed by direct visual counting. Somewhat unexpectedly, mild brain damage was observed in some animals already after 2 min, and more consistently after 4 min of ischemia. This damage affected CA4 and CA1 pyramids in the hippocampus, and neurons in the subiculum. Necrosis of neocortical cells began to appear after 4 min and CA3 hippocampal damage after 6 min of ischemia, while neurons in the caudoputamen were affected first after 8-10 min. Selective neuronal necrosis of the cerebral cortex worsened into infarction after higher doses of insult. Damage was worst over the superolateral convexity of the hemisphere, in the middle laminae of the cerebral cortex. The caudate nucleus showed geographically demarcated zones of selective neuronal necrosis, damage to neurons in the dorsolateral portion showing an all-or-none pattern. Other structures involved included the amygdaloid, the thalamic reticular nucleus, the septal nuclei, the pars reticularis of the substantia nigra, and the cerebellar vermis.

Models for studying long-term recovery following forebrain ischemia in the rat. 2. A 2-vessel occlusion model

Abstract: A model is described in which transient ischemia is induced in rats anaesthetized with N2O:O2 (70:30) by bilateral carotid artery clamping combined with a lowering of mean arterial blood pressure to 50 mm Hg, the latter being achieved by bleeding, or by bleeding supplemented with administration of trimetaphan or phentolamine. By the use of intubation, muscle paralysis with suxamethonium chloride, and insertion of tail arterial and venous catheters, it was possible to induce reversible ischemia for long-term recovery studies. Autoradiographic measurements of local CBF showed that the procedure reduced CBF in neocortical areas, hippocampus, and caudoputamen to near-zero values, flow rates in a number of subcortical areas being variable. Administration of trimethaphane or phentolamine did not affect ischemic and postischemic flow rates, nor did they alter recovery of EEG and sensory-evoked responses, but trimetaphan blunted the changes in plasma concentrations of adrenaline and noradrenaline. Recovery experiments showed that 10 min of ischemia gave rise to clear signs of permanent brain damage, with a small number of animals developing postischemic seizures that led to the death of the animals in status epilepticus. After 15 min of ischemia, such alterations were more pronounced, and the majority of animals died. It is concluded that the short revival times noted are explained by the fact that the model induces near-complete ischemia, and that recovery following forebrain ischemia is critically dependent on residual flow rates during the period of ischemia.

Assay of intestinal disaccharidases.

Abstract: A modified and updated description of the author's method for the assay of intestinal disaccharidases. The principle of the method is the following: an intestinal homogenate is incubated with the appropriate disaccharide. The disaccharidase activity is then interrupted by the addition of TRIS, and the glucose liberated is measured with a glucose oxidase reagent.

Pathoanatomy and pathophysiology of nerve root compression.

Abstract: The anatomy and physiology of the nerve root complex in the lumbar spine are reviewed, with special reference to the effects of mechanical deformation of nerve roots in association with intervertebral disc herniation and spinal stenosis. Biomechanical aspects of nerve root deformation induced by compression are discussed. The functional changes induced by compression can be caused by mechanical nerve fiber deformation but also may be a consequence of changes in nerve root microcirculation, leading to ischemia and formation of intraneural edema. Nerve root compression can, by different neurophysiologic mechanisms, induce motor weakness and altered sensibility or pain. Intraneural edema and demyelination seem to be critical factors for the production of pain in association with nerve root compression.

Neuropeptide Y potentiates the effect of various vasoconstrictor agents on rabbit blood vessels

Abstract: The contractile effect of neuropeptide Y (NPY) was tested on isolated segments of basilar artery, central ear artery, gastro-epiploic artery and vein, and femoral artery and vein from the rabbit. At 30 nM NPY did not evoke vasoconstriction; at 300 nM NPY evoked a weak and variable response. NPY greatly potentiated the response of the gastro-epiploic and femoral arteries to noradrenaline without affecting the maximum response. As tested on the gastro-epiploic artery NPY was effective at concentrations of 1 nM and higher. As tested on the femoral artery the potentiating effect of 30 nM NPY on noradrenaline-evoked contractions was apparent immediately and 30 min after the application of NPY, but not after one hour. NPY (30 nM) potentiated the contractile response to noradrenaline and histamine but not to 5-hydroxytryptamine or high K+. The response to histamine was augmented in both arteries and veins, whereas the response to noradrenaline was enhanced in arteries but not in veins. NPY failed to potentiate the prostaglandin F2 alpha-evoked contraction except in the gastro-epiploic vein.

Intrahippocampal septal grafts ameliorate learning impairments in aged rats

Abstract: Grafts of fetal septal tissue rich in cholinergic neurons were implanted as a dissociated cell suspension into the depth of the hippocampal formation in aged rats with severe impairments in spatial learning abilities. After 2 1/2 to 3 months, the rats with grafts, but not the controls, had improved their performance in a spatial learning test. Their improvement was due, at least in part, to an increased ability to use spatial cues in the task. In all animals the grafts had produced an extensive acetylcholinesterase-positive terminal network in the surrounding host hippocampal formation. Thus, the action of cholinergic neurons in the graft onto elements in the host hippocampal circuitry may be a necessary, but perhaps not sufficient, prerequisite for the observed functional recovery.

The distribution of hypoglycemic brain damage.

Abstract: Rats were exposed to insulin-induced hypoglycemia resulting in periods of cerebral isoelectricity ranging from 10 to 60 min. After recovery with glucose, they were allowed to wake up and survive for 1 week. Control rats were recovered at the stage of EEG slowing. After sub-serial sectioning, the number and distribution of dying neurons was assessed in each brain region. Acid fuchsin was found to stain moribund neurons a brilliant red. Brains from control rats showed no dying neurons. From 10 to 60 min of cerebral isoelectricity, the number of dying neurons per brain correlated positively with the number of minutes of cerebral isoelectricity up to the maximum examined period of 60 min. Neuronal necrosis was found in the major brain regions vulnerable to several different insults. However, within each region the damage was not distributed as observed in ischemia. A superficial to deep gradient in the density of neuronal necrosis was seen in the cerebral cortex. More severe damage revealed a gradient in relation to the subjacent white matter as well. The caudatoputamen was involved more heavily near the white matter, and in more severely affected animals near the angle of the lateral ventricle. The hippocampus showed dense neuronal necrosis at the crest of the dentate gyrus and a gradient of increasing selective neuronal necrosis medially in CA1. The CA3 zone, while relatively resistant, showed neuronal necrosis in relation to the lateral ventricle in animals with hydrocephalus. Sharp demarcations between normal and damaged neuropil were found in the hippocampus. The periventricular amygdaloid nuclei showed damage closest to the lateral ventricles. The cerebellum was affected first near the foramina of Luschka, with damage occurring over the hemispheres in more severely affected animals. Purkinje cells were affected first, but basket cells were damaged as well. Rare necrotic neurons were seen in brain stem nuclei. The spinal cord showed necrosis of neurons in all areas of the gray matter. Infarction was not seen in this study. The possibility is discussed that a neurotoxic substance borne in the tissue fluid and cerebrospinal fluid (CSF) contributes to the pathogenesis of neuronal necrosis in hypoglycemic brain damage.

Cell Damage in the Brain: A Speculative Synthesis

Abstract: All cells in living organisms have a limited life span, and when the time set by their biological clocks has run out, they will die , their highly orga­ nized macromolec ular structure will disintegrate, and the low-molec ul ar degrad ation products be­ come part of the disorder of the surroundings . In thermodynamic terms, this series of events consti­ tutes what has been c alled the entropic doom. We know little about those molec ul ar mechanisms that limit the life span of cells in the absence of dise ase. For the clinician, therefore, the important task is to prevent or tre at dise ases that jeopardize the proper functioning and viability of cells whose biologic al clocks have not yet run out . Measures instituted to prevent brain cell death have a special importance . This i s partly due t o the fact that w e equate human life with the functioning of the brain. However, this importance also resides in the v ulnerability of brain cells to conditions that allow cells of most other tissue to survive , and to continue or res ume their activitie s . The clinically most important conditions leading to brain cell death are those associated with cere­ brovascul ar dise ase, particularly stroke, and with head trauma. We will begin, though, by rec alling the traditional view of the occ urrence and loc alization of neuronal damage in four conditions that lead to more disseminated alterations, e specially since they have been considered to c ause nerve cell injury of a

Aminoglycoside toxicity – a review of clinical studies published between 1975 and 1982

Abstract: The present survey of aminoglycoside nephro- and ototoxicity covers approximately 10,000 patients reported on in clinical trials published between 1975 and 1982. Included in the survey were clinical trials with at least 15 patients evaluable for nephro and/or ototoxicity provided relevant data were given on methodology, patient material and aminoglycoside dosage. Each publication was evaluated by both investigators and relevant data entered into a chart. One hundred and forty-four published trials were surveyed; 139, 63 and 34 for renal, cochlear and vestibular side effects, respectively. Frequencies were calculated as number of patients with side effect of total number of evaluated patients. In the average overall figures toxicity labelled by respective authors as 'definitely', 'probably' and 'possibly' related to study drug is included. When available, frequencies of toxicity 'definitely' and 'probably' related to study drug were analysed separately. The average daily dosages of gentamicin, tobramycin, netilmicin and amikacin were 3.9, 3.8, 5.2 and 15.4 mg/kg, respectively. The average frequencies of nephrotoxicity for gentamicin and tobramycin were 14.0 and 12.9%, respectively, and of netilmicin and amikacin 8.7 and 9.4%, respectively. The average frequency of cochlear toxicity was 13.9% for amikacin, 8.3 and 6.1% for gentamicin and tobramycin, respectively, and 2.4% for netilmicin. The material available for evaluation of vestibular toxicity was considerably smaller. The average frequencies for gentamicin, tobramycin and amikacin were similar (3.2 to 3.7%) while netilmicin again exhibited a somewhat lower figure (1.4%). The overall figures and the clinical ranking that they imply were basically substantiated when prospective comparative trials were analysed separately. However, some inconsistencies go unexplained: for example the frequency of gentamicin nephrotoxicity was markedly higher in trials where it was compared to tobramycin (20 trials) than when it was compared to netilmicin (16 trials).

Functional neuronal replacement by grafted striatal neurones in the ibotenic acid-lesioned rat striatum

Abstract: In rats, striatal neuronal destruction by so-called excitotoxic amino acids, kainic acid or ibotenic acid (IA) produce neuropathological and neurochemical changes in the basal ganglia which resemble those seen in patients with Huntington's chorea. Such lesioned animals show a behavioural syndrome which is reminiscent of the cardinal symptoms of the disease, accompanied by a substantial increase in local cerebral metabolic activity in several striatal target structures within the extrapyramidal motor system. The study was designed to explore the potential of grafted fetal striatal neurones implanted into the IA-lesioned striatum to compensate for the structural, neurochemical, metabolic and behavioural defects of IA-lesioned rats. Extending previous studies, we report here that such striatal implants can significantly ameliorate the lesion-induced locomotor hyperactivity and at least partly normalize the metabolic hyperactivity in the extrapyramidal neuronal system.

Software QRS detection in ambulatory monitoring--a review.

Abstract: The QRS detection algorithm is an essential part of any computer-based system for the analysis of ambulatory ECG recordings. This review asserts that most one-channel QRS detectors described in the literature can be considered as having the same basic structure. A discussion of some of the current detection schemes is presented with regard to this structure. Some additional features of QRS detectors are mentioned. The evaluation of performance and the problem of multichannel detection, which is now gaining importance, are also briefly treated.

Preparation and polypeptide composition of chlorophyll‐free plasma membranes from leaves of light‐grown spinach and barley

Abstract: Chlorophyf l-free preparations of plasma membranes from leaves of barley (Hordeum vulgare L. cv. Kristina) and spinach (Spinada oleracea L. cv. Viking II) were obtained by partition in an aqueous dextran-polyethylene glycol two-phase system. CJlu-can synthetase II (EC 2.4,1.34), a marker for the plasma membrane, was highly enriched in both preparations. Silicotungstic acid, a specific stain for the plasma membrane, indicated a purity close to 100% for the barley preparation. Both plasma membrane preparations contained a light-reducible b-cytochrome, as shown by low temperature spectroscopy. The plasma membranes had a tow protein content compared to the bulk of intracellular membranes. The polypeptide composition of the barley and spinach plasma membranes showed striking similarities, with.the most prominent polypeptides in the 49-58 kdalton region, and some further prominent bands in the 30 kcialton region. Some high molecular weight polypeptides in the 73-110 kdalton region were also typical for the plasma membranes compared to the microsomal fractions.

DEADSPACE AND THE SINGLE BREATH TEST FOR CARBON DIOXIDE DURING ANAESTHESIA AND ARTIFICIAL VENTILATION Effects of tidal volume and frequency of respiration

Abstract: Using the single breath test for carbon dioxide (SBT-CO2) the component of physiological deadspace were investigated during anaesthesia with IPPV in 58 patients. A square-wave inspiratory flow and an end-inspiratory pause (25% and 10% of cycle time, respectively) were used. At tidal volumes of 0.45 litre (f = 17 b.p.m.),and 0.75 litre (f = 9 b.p.m.), median values for VDphys/VT were 0.44 and 0.31. Increasing VT and decreasing f did not change airway deadspace (VDRW) so that the fraction VDRW/VT was decreased (P

Density-functional exchange-correlation potentials and orbital eigenvalues for light atoms

Abstract: Using accurate correlated wave functions calculated earlier by Bunge and by Larsson, we have constructed the Hohenberg-Kohn-Sham density functionals and exchange-correlation (ground-state) potentials and have obtained orbital energy eigenvalues for a number of light atoms by in principle exact numerical algorithms. While the uppermost occupied density-functional eigenvalue always gives an exact excitation energy as has been shown earlier, we find that eigenvalues for deeper shells lie above the corresponding excitation energy. We have compared our essentially exact density-functional (DF) results with those obtained in the local-density (LD) approximation. We find that the LD theory approximates the exchange-correlation energy rather well, but that it gives larger errors in the exchange-correlation potential and in the DF orbital eigenvalues. In all cases we have found that the LD error in the orbital eigenvalue is larger than the difference between the true DF eigenvalue and the corresponding exact excitation energy. Possible implications of these results for solid-state work are briefly discussed.

High-resolution studies of sulfur- and selenium-related donor centers in silicon

Abstract: High-resolution infrared absorption and photoconductivity spectra of several S- and Se-related donor centers in silicon are presented. These include isolated, probably substitutional, impurities and impurity pairs, as well as more complex centers. The spectra of the isolated impurities are consistent with ${T}_{d}$ symmetry and those of impurity pairs with ${D}_{3d}$ symmetry. The binding energies of excited states are recalculated in accordance with effective-mass theory. The results agree better with experiments than previously published calculations. The spectra are discussed in detail with emphasis on valley-orbit splittings of excited states in ${T}_{d}$ and ${D}_{3d}$ symmetry.

Biological evaluation of substance P antagonists.

Abstract: Five undeca- and six C-terminal heptapeptide substance P (SP) analogues were tested for their capacity to block the contractile effect of SP on the guinea-pig isolated taenia coli. They had one feature in common, namely substitutions in positions 7 and 9 in the SP molecule. In the majority of analogues D-tryptophan was used for these substitutions. All analogues tested were found to be competitive antagonists to exogenous SP and to be capable of blocking the electrically induced non-cholinergic, non-adrenergic neuronal contraction of the taenia. Of the undecapeptides, (D-Arg1, D-Pro2, D-Trp7,9, Leu11) SP and (D-Arg1, D-Trp7,9, Leu11) SP (Spantide) had the highest pA2 value, 7.1-7.2, and the lowest IC50 value, 10(-6) M. The pA2 values of the heptapeptides were generally lower. Three of the most potent antagonists were tested for specificity and found to block the smooth muscle contraction induced by SP, physalaemin, eledoisin and bombesin but not that induced by bradykinin, carbachol, 5-hydroxytryptamine, histamine, prostaglandins and vasopressin. The SP antagonists were also tested for spasmogenic effect on the taenia and for their capacity to release histamine from rat isolated peritoneal mast cells. The spasmogenic activity displayed by most of the SP antagonists tested is likely to be related to their ability to release histamine since the contractile response was reduced by mepyramine, a histamine H1-receptor antagonist. (D-Arg1, D-Trp7,9, Leu11) SP was notable for combining a high antagonistic potency with a weak spasmogenic effect (and poor histamine releasing effect).