Showing papers by "University of Graz published in 1988"

White matter signal abnormalities in normal individuals: correlation with carotid ultrasonography, cerebral blood flow measurements, and cerebrovascular risk factors.

Abstract: We studied 52 asymptomatic subjects using magnetic resonance imaging, and we compared age-matched groups (51-70 years old) with and without white matter lesions with respect to carotid ultrasonography, cerebral blood flow (xenon-133 injection), and cerebrovascular risk factors. In the group with white matter signal abnormalities, we noted a higher frequency of extracranial carotid artery disease, a lower mean gray matter blood flow (F1), and a significant reduction (p less than 0.05) in blood flow of the slow-flowing (F2) compartment. Hypertension, diabetes mellitus, and cardiac diseases (p less than 0.002) were found more often in this group. Our results indicate that a higher incidence of changes known to be associated with an increased risk for stroke exists in the presence of white matter lesions in normal elderly individuals.

Release of multiple tachykinins from capsaicin-sensitive sensory nerves in the lung by bradykinin, histamine, dimethylphenyl piperazinium, and vagal nerve stimulation.

Abstract: Recent evidence suggests that activation of airway C-fibers, besides causing afferent transmission, also causes release of transmitters from peripheral endings, probably via local axon reflexes, resulting in effects on vascular and bronchial smooth muscle, i.e., vasodilatation, increase in vascular permeability, and bronchoconstriction. In the present study, the release of tachykinins was investigated in the perfused guinea pig lung by various ways of neuronal activation. Substance-P-like immunoreactivity (SP-LI) and neurokinin-A-like immunoreactivity (NKA-LI) was determined by radioimmunoassay in the perfusates. A significantly increased outflow of both SP-LI and NKA-LI was observed during perfusion of the lung with high potassium concentration (60 mM), the C-fiber activator capsaicin (1 µM), bradykinin (1 µM), histamine (100 µM), or the nicotinic agonist dimethylphenyl piperazinium (DMPP) (32 µM). Release of both SP-LI and NKA-LI could also be achieved by electrical stimulation of vagal nerves. The perc...

Criteria for an increased specificity of MRI interpretation in elderly subjects with suspected multiple sclerosis

Abstract: We reviewed the MRIs of 49 asymptomatic volunteers (age range, 31 to 77 years) and of 50 MS patients (age range, 14 to 63) for areas of increased signal (AIS) and features discriminating MS lesions from lesions seen with normal aging. We obtained optimal specificity of MRI interpretation (100%) if we required at least two of the following three AIS features--size greater than or equal to 6 mm, abutting ventricular bodies, infratentorial location--for a positive MRI diagnosis of MS. Applying these criteria to the MRIs of elderly patients with suspected MS should significantly improve specificity (p less than 0.001) over current quantitative criteria (at least three AIS greater than or equal to 3 mm) without significantly decreasing sensitivity.

Lipoprotein Lp(a). A risk factor for myocardial infarction.

Abstract: The aim of this study was to test plasma lipoprotein Lp(a) and other lipid and lipoprotein levels for association with the incidence of myocardial infarction. Total plasma cholesterol, triglycerides, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, and Lp(a) were measured in 1486 men at the age of 18 years. In addition, the Broca Index (a measure of relative body weight) and other data were recorded. The sample was divided into probands whose mothers or fathers suffered a myocardial infarction (case group, n = 52) and into probands whose parents had no myocardial infarction (control group, n = 1434). In the case group, 32% had Lp(a) plasma concentrations greater than 25 mg/dl, but only 13.4% of the control group had this level of concentration, a highly significant difference (p less than 0.01). In addition, there was a statistically significant difference in the ratio of LDL cholesterol/HDL cholesterol (p less than 0.05) and the Broca Index (p less than 0.01) between cases and controls. The parents of the case group were significantly older than the parents of the control group; however, when a control group was matched for parents' age, the results were similar. These data suggest that parents of male children with Lp(a) plasma concentrations greater than 25 mg/dl have a 2.5-fold higher incidence of myocardial infarction. Considering the familial aggregation of elevated Lp(a) levels, we conclude that increased levels of this lipoprotein may be a significant risk factor for myocardial infarction.

Diesel fuel derived from vegetable oils, III. Emission tests using methyl esters of used frying oil

Abstract: The preparation of methyl esters of used frying oil, available as waste from restaurants and households, is described. Fuel specifications of this fuel are given, and values for gaseous (HC, CO, NOx) and particulate emissions, measured with a vehicle powered by a turbocharged, direct injection diesel engine, are shown. The ester fuel shows slightly lower HC and CO emissions but increased NOx values compared with reference US-2D fuel. The particulate emissions, however, are significantly lower with used frying oil. Preliminary results of an engine road test are described.

Nuclear magnetic resonance image white matter lesions and risk factors for stroke in normal individuals.

Abstract: The incidence, average number, and localization of lesions of the white matter detected by the T2-weighted nuclear magnetic resonance images among volunteers without cerebrovascular symptoms have been correlated with the number of risk factors for stroke. Accepted risk factors were arterial hypertension, diabetes mellitus, smoking, hypercholesterolemia, and cardiac disease. The 42 subjects examined were divided into Group A (0-1 risk factor, mean age 59.36 +/- 5.73 years), Group B (2 risk factors, mean age 61.54 +/- 8.33 years), and Group C (greater than or equal to 3 risk factors, mean age 62.57 +/- 9.83 years). Multiple risk factors among the age-matched groups was accompanied by a highly significant increase (p less than 0.001, Group A versus Group B; p less than 0.01, Group A versus Group C) of the incidence of white matter lesions. The average number of white matter lesions was increased (p less than 0.001) when Group A was compared with Groups B and C. Ninety-two percent of the white matter lesions were localized in watershed zones. Only 11 of the 155 abnormalities of the white matter detected by nuclear magnetic resonance imaging could be detected by computed tomography. White matter lesions in T2-weighted images appear to be an early stage of cerebrovascular disease.

Structural and functional domains of cellobiohydrolase I from trichoderma reesei

Abstract: Limited proteolysis (papain) of the cellobiohydrolase I (CBH I, 65 kDa) from Trichoderma reesei led to the seperation of two functional domains: a core protein (55 kDa) containing the active site, and a C-terminal glycopeptide (10 kDa) implicated in binding to the insoluble matrix (cellulose). The quaternary structures of the intact CBH I and its core in solution are now compared by small angle X-ray scattering (SAXS) measurements. The molecular parameters derived for the core (Rg=2.09 nm, Dmax=6.5 nm) and for the intact enzyme (Rg=4.27 nm, Dmax=18 nm) indicate very different shapes. The resulting models show a “tadpole”-like structure for the intact enzyme where the isotropic part coincides with the core protein and the flexible tail part should be identified with the C-terminal glycopeptide. Thus in this enzyme, functional differentiation is reflected in structural peculiarities.

Serological Examinations for Antibodies against Legionella Species in Dental Personnel

Abstract: Serum samples from 107 dentists, dental assistants, and dental technicians were examined with an indirect immunofluorescence test for antibodies to Legionella pneumophila SG1-SG6, L. micdadei, L. bozemanii, L. dumoffii, L. gormanii, L. jordanis, and L. longbeachae SG1 + 2. Thirty-six (34%) employees from dental personnel from 13 practices showed a positive reaction for antibodies to Legionella pneumophila. Only five samples (5%) from a control group (non-medical workers) were positive. Of the 36 positive serum samples, 13 (36%) reacted with Serogroup 6, 12 with SG 1 (33%), 12 with SG 5 (33%), and three with SG 4 (8%), and eight samples were positive for antibodies to other Legionella species. Dentists had the highest prevalence (50%) of L. pneumophila antibodies, followed by assistants (38%) and technicians (20%). These results indicate that dental personnel are at an increased risk of legionella infection.

Comparisons of global topographic/isostatic models to the Earth's observed gravity field

Abstract: The Earth's gravitational potential, as described by a spherical harmonic expansion to degree 180, was compared to the potential implied by the topography and its isostatic compensation using five different hypothesis. Initially, series expressions for the Airy/Heiskanen topographic isostatic model were developed to the third order in terms of (h/R), where h is equivalent rock topography and R is a mean Earth radius. Using actual topographic developments for the Earth, it was found that the second and third terms of the expansion contributed 30 and 3 percents, of the first of the expansion. With these new equations it is possible to compute depths (D) of compensation, by degree, using 3 different criteria. The results show that the average depth implied by criterion I is 60 km while it is about 33 km for criteria 2 and 3 with smaller compensation depths at the higher degrees. Another model examined was related to the Vening-Meinesz regional hypothesis implemented in the spectral domain. Finally, oceanic and continental response functions were derived for the global data sets and comparisons made to locally determined values.

The effect of omega conotoxin GVIA, a peptide modulator of the N-type voltage sensitive calcium channels, on motor responses produced by activation of efferent and sensory nerves in mammalian smooth muscle.

Abstract: 1. The effect of omega-conotoxin (CTX) GVIA, a peptide which blocks neuronal calcium channels, were investigated on nerve-mediated motor responses in a variety of isolated smooth muscle preparations from rats and guinea-pigs. 2. In the rat or guinea-pig isolated vas deferens CTX (1 nM − 1 μM) produced a concentration and time-related inhibition of the response to field stimulation, while the responses to KCI, noradrenaline or adenosine triphosphate were unaffected. In the presence of CTX a series of tetrodotoxin-resistant contractions could be elicited by field stimulation by increasing pulse width and/or voltage. 3. In the rat or guinea-pig isolated urinary bladder, CTX produced a concentration and time-dependent inhibition of twitch responses to field stimulation without affecting the response to exogenous acetylcholine. In the rat bladder the maximal effect did not exceed 25% inhibition while a much larger fraction of the response (about 70%) was inhibited in the guinea-pig bladder. The CTX-resistant response was abolished, in both tissues, by tetrodotoxin. 4. The effects of CTX in the rat bladder were also studied with a whole range of frequencies of field stimulation (0.1–50 Hz). Maximal inhibition was observed toward contractions elicited at frequencies of 2–5 Hz. At low frequencies the inhibitory effects of CTX and atropine were almost additive while at high frequencies of stimulation a large component of the atropine-sensitive response was CTX-resistant. 5. In the rat isolated proximal duodenum, field stimulation in the- presence of atropine and guanethidine produced a primary relaxation followed by a rebound contraction. Both responses were abolished by tetrodotoxin, indicating the activation of intramural nonadrenergic noncholinergic nerves. The primary relaxation was totally CTX resistant while the rebound contraction was slightly inhibited. 6. The motor responses produced by capsaicin (1 μM) in the rat or guinea-pig bladder (contraction) and in the rat proximal duodenum (relaxation) were unaffected by CTX. Likewise, the release of substance P-like immunoreactivity from sensory nerves of the guinea-pig bladder muscle was unaffected by CTX. 7. These findings indicate that CTX-sensitive calcium channels modulate transmitter release in autonomic nerve terminals of mammals, but noticeable species and organ related variations exist in sensitivity to this peptide, possibly reflecting the existence of a heterogenous population of voltage-sensitive calcium channels. CTX-sensitive calcium channels are apparently not involved in the excitatory action of capsaicin on sensory nerve terminals.

Fiberoptic Oxygen Sensor Based on Fluorescence Quenching and Energy Transfer

Abstract: A new type of oxygen sensor is described that is based on electronic energy transfer from a donor (whose fluorescence is efficiently quenched by molecular oxygen) to an acceptor (which is less affected by oxygen). We use pyrene as the donor and perylene as the acceptor. The fluorescence emission band of the donor shows good overlap with the absorption band of the acceptor. When excited at 320 nm, the two-fluorophore system shows strong fluorescence at 476 nm, where pyrene itself is nonfluorescent. Although perylene is not efficiently quenched by oxygen, the system strongly responds to oxygen because fluorescence is quenched with an efficiency that by far exceeds the quenching efficiency for pyrene or pyrelene alone. The principle has been applied in order to devise a fiberoptic oxygen sensor by incorporating the two dyes in a polymer matrix that has been attached to the end of an optical fiber. Oxygen can be detected in the 0-150 kPa range with ±0.3 kPa precision. The detection limit is 60 Pa oxygen.

Semicorrin Metal Complexes as Enantioselective Catalysts. Part 1. Synthesis of chiral semicorrin ligands and general concepts

Abstract: An efficient synthesis of chiral semicorrin ligands is described (see 6–9, Schemes 2 and 3). Both enantiomers are readily obtained in enantiomerically pure form starting either from D-or L-pyroglutamic acid (1). Semicorrins of this type possess several features that make them attractive ligands for enantioselective control of metal-catalyzed reactions. Their structure is characterized by C2 symmetry, a conformationally rigid ligand system, and two stereogenic centers adjacent to the coordination sphere. In a metal complex, the two substituents at the stereogenic centers shield the metal atom from two opposite directions and, therefore, are expected to have a pronounced effect on the stereochemical course of a reaction occurring in the coordination sphere. The structure of these two substituents can be easily modified in a variety of ways. A series of (semicorrinato)copper(II) complexes (see 10–14, Scheme 4) has been prepared, and in one case (14), the three-dimensional structure has been determined by X-ray analysis (Fig. 1).

AM1 calculations of rotation around essential single bonds and preferred conformations in conjugated molecules

Abstract: Equilibrium twist angles, rotational barriers around essential single bonds, and preferred conformations for over 60 conjugated organic molecules were calculated using the semiempirical AM1 (Austin model 1) method. Comparison with ab initio and experimental data shows that AM1 can be applied quite successfully to conformational problems of this type. Relatively large errors are, however, found for compounds in which lone pair–hydrogen and especially lone pair–lone pair interactions are decisive for their conformational behavior. AM1-calculated rotational barriers in conjugated molecules, however, are found to be much too low. Moreover, AM1 does not seem to even correctly reproduce the trend of rotational barriers within a series of structurally related compounds. E/Z energy differences obtained by AM1 are also frequently considerably too low. In contrast to rotational barriers, their trends and thus conformational preferences, however, are quite satisfactorily calculated by this method. Ionization potentials obtained by AM1 are too high by about 0.5 eV. However, trends are quite well predicted.

Magnesium- and Titanium-induced Reductive Coupling of Carbonyl Compounds: Efficient Syntheses of Pinacols and Alkenes

Abstract: Finely dispersed magnesium on graphite was found to be a totally selective single-electron transfer reagent of general utility for the reduction of various kinds of carbonyl and dicarbonyl compounds to pinacols, a reaction quite compatible with a number of functional groups. Similarly, titanium on graphite proved to be a universally applicable reducing agent for the efficient conversion of pinacols, carbonyl and dicarbonyl compounds into alkenes and cycloalkenes respectively and for the cyclization of oxo alkanoates to enol ethers, facilitating and unifying the highly useful McMurry reaction. The practicability of the presently known carbonyl coupling methods is discussed in the light of these results.

Calcitonin gene-related peptide: release by capsaicin and prolongation of the action potential in the guinea-pig heart.

Abstract: The mechanisms underlying the stimulatory effects of capsaicin on the contractility of the guinea-pig heart were studied in vitro. Capsaicin (10(-7) to 10(-5) M) caused an increased overflow of immunoreactive material, suggesting release of calcitonin gene-related peptide (CGRP)-and neurokinin A (NKA)-like immunoreactivity (-LI), but not of neuropeptide Y (NPY)-LI from the isolated Langendorff-perfused whole heart. The capsaicin-induced release was calcium-dependent. During exposure to capsaicin, the heart rate was increased, while the contractile force was reduced. In addition to releasing CGRP and NKA-LI, potassium (60 mM) also increased the overflow of NPY-LI. The potassium-induced release of peptides was less calcium-dependent than the response to capsaicin. Considerably higher tissue levels of CGRP-LI were found in the atria (about 30 pmol g-1) than in the ventricles (about 10 pmol g-1). In experiments on the right atria using transmembrane action-potential recordings of myocytes, CGRP induced a prolongation of the action potential concomitantly with an increase in rate and contractile force, which was similar to the effect of noradrenaline. Furthermore, CGRP increased the contractile force and relaxation velocity of the electrically stimulated atria. Capsaicin (10(-7) M) also increased the duration of the atrial action potential. In conclusion, CGRP-like material is released by capsaicin from the isolated guinea-pig heart. Both CGRP and capsaicin prolong the plateau phase of the action potential of atrial myocytes. Therefore, the present data give further evidence that CGRP release from sensory nerves within the heart underlies the cardiostimulatory actions of capsaicin.

Atrial natriuretic peptide in the central nervous system of the rat

Abstract: 1. Studies of the presence of atrial natriuretic peptide immunoreactivity and receptor binding sites in the central nervous system have revealed unusual sites of interest. 2. As a result, numerous studies have appeared that indicate that brain atrial natriuretic peptide is implicated in the regulation of blood pressure, fluid and sodium balance, cerebral blood flow, brain microcirculation, blood-brain barrier function, and cerebrospinal fluid production. 3. Alteration of the atrial natriuretic peptide system in the brain could have important implications in hypertensive disease and disorders of water balance in the central nervous system.