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Biomedical subjects

R Betz

Publications and source records attributed to R Betz.

At least 73 records · Page 4Linked to original sources
PubMed1989

Isolation and characterization of Saccharomyces cerevisiae mutants supersensitive to G1 arrest by the mating hormone a-factor.

Nine independent mutants which are supersensitive (ssl-) to G1 arrest by the mating hormone a-factor were isolated by screening mutagenized Saccharomyces cerevisiae MAT alpha cells on solid medium for increased growth inhibition with a-factor. These mutants carried lesions in two complementation groups, ssl1 and ssl2. Mutations at the ssl1 locus were mating type specific: MAT alpha ssl1- cells were supersensitive to a-factor but MATa ssl1- were not supersensitive to alpha-factor. In contrast, mutations at the ssl2 locus conferred supersensitivity to the mating hormone of the opposite mating type on both MAT alpha and MATa cells. The alpha-cell specific capacity to inactivate externally added a-factor was shown to be lacking in MAT alpha ssl1- mutants whereas MAT alpha ssl2- cells were able to inactivate a-factor. Complementation analysis showed that ssl2 and sst2, a mutation originally isolated as conferring supersensitivity to alpha-factor to MATa cells, are lesions in the same gene. The ssl1 gene was mapped 30.5 centiMorgans distal to ilv5 on chromosome XII.

Alleles↗
PubMed1989

Investigation into the age-dependence of release of serotonin and noradrenaline in the rat brain cortex and of autoreceptor-mediated modulation of release.

Slices of cerebral cortex from young adult and aged rats, preincubated with [3H]serotonin or [3H]noradrenaline were superfused and the electrically (3 Hz) evoked overflow of tritium and its modulation by the respective agonists and antagonists were studied. The electrically evoked overflow in slices preincubated with [3H]serotonin from 2.5-year-old rats was smaller (by about 35%) than in slices from 3-month-old animals. No difference was found for the inhibition by serotonin and the facilitation by metitepine of the evoked overflow and for the metitepine-induced shift of the concentration-response curve for serotonin to the right. There was no difference between slices preincubated with [3H]noradrenaline from 3 months, 1, 2 and 2.5-year-old rats, with respect to the electrically evoked overflow, its inhibition and facilitation by noradrenaline and phentolamine, respectively, and the phentolamine-induced shift of the concentration-response curve for noradrenaline to the right. The present results suggest that the release of serotonin is reduced in the cerebral cortex of aged rats whereas the release of noradrenaline and the autoreceptor-mediated modulation of the release of either monoamine is not altered.

Adrenergic alpha-Agonists↗
PubMed1989

[The detection of bovine herpesvirus type 1 (BHV 1) using an intradermal test. I. Field studies].

An intradermal test (delayed hypersensitivity test) for the diagnosis of BHV1 infection was evaluated in 791 cattle of 16 dairy farms. The skin reactions were compared with the results of serological examinations using a commercial BHV1 ELISA kit (Trachitest). As antigen concentrated, purified and inactivated BHV1 was used. The skin reaction (increase of the skin fold thickness) was used for the interpretation of test results. The best results were obtained with the control of the skin reaction on the third day after injection of the antigen. From 393 serologically BHV1 negative cattle with an age of more than 6 months 391 (99.5%) had a skin reaction up to 1.0 mm and 2 animals (0.5%) had a reaction of 1.3 and 1.9 mm, respectively. The mean increase of skin fold thickness was 0.2 mm. Out of 291 serologically BHV1 positive cattle with an age of more than 6 months 270 had antibodies from natural infection and, partially, from additional vaccination with inactivated BHV1 vaccine. 266 (98.5%) of these animals showed a skin reaction of more than 2.0 mm, in 3 animals (1.1%) a skin reaction up to 1.0 mm was observed and 1 animal (0.4%) had a reaction of 2.0 mm. The mean increase of the skin fold thickness was 6.3 mm. 21 animals had BHV1 antibodies only because of vaccination with inactivated BHV1 vaccine. Only 4 animals had a skin reaction of more than 2.0 mm. Among 107 animals with an age up to 6 months 30 were serologically BHV1 positive and 77 were BHV1 negative. In all animals the skin reaction was less than 1.0 mm, the mean was 0.2 mm.

Animals↗
PubMed1988

Structure of Saccharomyces cerevisiae mating hormone a-factor. Identification of S-farnesyl cysteine as a structural component.

Mating type a cells of the yeast Saccharomyces cerevisiae produce a mating hormone, the a-factor, that we have previously characterized as a very hydrophobic, modified dodecapeptide (Betz, R., Crabb, J. W., Meyer, H. E., Wittig, R., and Duntze, W. (1987) J. Biol. Chem. 262, 546-548). We have investigated the molecular structure in detail using mass spectrometry and proton NMR spectrometry of the intact hormone and authentic component molecules. Tandem mass spectrometry confirms the previously determined peptide sequence of the hormone and shows that it contains additional structural components with masses of 205 and 15 daltons. These were identified by proton NMR and mass spectrometry as a farnesyl (C15H25) residue and a terminal methyl ester group. The farnesyl moiety is attached to the sulfur atom of the carboxyl-terminal cysteine residue, as revealed by NMR of synthetic S-farnesyl cysteine methyl ester. The stereochemical configuration of the farnesyl moiety was determined to be trans,trans by comparison of gas chromatography retention times, mass spectra, and NMR spectra with those of standards. These results define the structure of a-factor as: (Sequence: see text). Replacement of the farnesyl by a methyl group leads to a partial reduction in specific biological activity of the a-factor, whereas hydrolysis of the carboxyl-terminal methyl ester causes a complete loss of activity.

Amino Acid Sequence↗
PubMed1988

Identification of presynaptic 5-HT1 autoreceptors in pig brain cortex synaptosomes and slices.

Pig brain cortex synaptosomes and slices preincubated with 3H-5-hydroxytryptamine (3H-5-HT) were superfused with physiological salt solution containing citalopram (an inhibitor of 5-HT uptake), and the effects of indolethylamines and 5-HT receptor antagonists on the potassium- or electrically evoked 3H overflow were determined. The potassium (25 mmol/l)-evoked tritium overflow from cortex synaptosomes was inhibited by 5-HT; the inhibitory effect of 5-HT was counteracted by metitepine, which, by itself, did not affect the evoked overflow. 5-Methoxytryptamine (examined in the absence of citalopram) also produced an inhibition of the evoked overflow. In cortex slices, the electrically (3 Hz) evoked overflow was inhibited by 5-HT and 5-carboxamidotryptamine. The inhibitory effect of 5-HT was antagonized by metitepine, which, given alone, increased the evoked overflow, but was not attenuated by ketanserin and ICS 205-930 ([3 alpha-tropanyl]-1H-indole-3-carboxylic acid ester), which, by themselves, did not influence the evoked overflow. The present results suggest that the serotoninergic nerve fibres of the pig brain cortex are endowed with presynaptic 5-HT1 receptors, which can be activated by endogenous and exogenous 5-HT.

Animals↗
PubMed1988

Histamine H3 receptor-mediated inhibition of serotonin release in the rat brain cortex.

Rat brain cortex slices preincubated with 3H-serotonin were superfused with physiological salt solution (containing citalopram, an inhibitor of serotonin uptake) and the effect of histamine on the electrically (3 Hz) evoked 3H overflow was studied. Histamine decreased the evoked overflow in a concentration-dependent manner. The inhibitory effect of histamine was antagonized by impromidine and burimamide, but was not affected by pheniramine, ranitidine, metitepine and phentolamine. Given alone, impromidine facilitated the evoked overflow, whereas burimamide, pheniramine and ranitidine had no effect. The results suggest that histamine inhibits serotonin release in the rat brain cortex via histamine H3 receptors, which may be located presynaptically.

Animals↗
PubMed1988

[Procyanidin polymers, the crucial ingredients of the almond seed coat].

The seed coat of almond (Prunus amygdalus Batsch) contains up to 30% procyanidins with different degrees of polymerisation and, in addition, fatty oils, lignin, polysaccharides and cutin. Monomer units of dimers to tetracosamers are (-)-epicatechin and (+)-catechin. Prodelphinidins could not be detected. The dimers B-1, B-3, B-4, trimers and oligomers are soluble in acetone/water. The bulk material is large polymer, that is only soluble, by thiolysis, in thioglycolic acid. The large polymer procyanidins are crucial to the structure and attributes of the seed coat.

Biflavonoids↗
PubMed1988

Antagonistic properties of RU 24969, a preferential 5-HT1 receptor agonist, at presynaptic alpha 2-adrenoceptors of central and peripheral neurones.

The effect of RU 24969 (5-methoxy-3(1,2,3,6-tetrahydropyridin-4-yl)-1 H-indole) on the electrically evoked 3H overflow was studied in superfused rat brain cortex slices preincubated with 3H-noradrenaline or 3H-serotonin and in superfused segments of the rat vena cava preincubated with 3H-noradrenaline. In cortex slices preincubated with 3H-noradrenaline, RU 24969 facilitated the electrically (3 Hz) evoked 3H overflow. This effect was abolished by phentolamine but was not affected by desipramine or the 5-HT3 receptor antagonist ICS 205-930. The concentration-response curve of noradrenaline for its inhibitory effect on the evoked overflow (determined in the presence of desipramine) was shifted to the right by RU 24969 32 and 100 mumol/l. In this respect, RU 24969 was about 500 times less potent than phentolamine. In cortex slices preincubated with 3H-serotonin, the inhibitory effect of 3.2 mumol/l RU 24969 on the electrically evoked 3H overflow was increased by phentolamine. In segments of the vena cava, RU 24969 inhibited the electrically (0.66 Hz) evoked 3H overflow. The concentration-response curve of RU 24969 was U-shaped, since at concentrations higher than 0.1 mumol/l the extent of inhibition decreased with increasing concentrations of RU 24969. In the presence of phentolamine, the concentration-dependent attenuation of the RU 24969-induced inhibition of overflow was no longer detectable. The present results suggest that RU 24969 is a weak antagonist at presynaptic alpha 2-adrenoceptors (by more than 2.5 log units less potent than as an agonist at presynaptic 5-HT1B auto- and heteroreceptors).

Adrenergic alpha-Antagonists↗
PubMed1987

Amino acid sequences of a-factor mating peptides from Saccharomyces cerevisiae.

The molecular structure of a-factor, the mating hormone produced by mating type a cells of Saccharomyces cerevisiae, has been investigated. In culture filtrates of a cells four oligopeptides (a1 to a4) exhibiting a-factor activity have been found. These peptides have been isolated and their amino acid sequences have been determined. The a-factor peptides comprise two (apparently identical) pairs, a1/a2 and a3/a4, which differ in an interchange at position 6 of a valine in a1/a2 for a leucine in a3/a4. a1 and a4, which can be obtained by oxidation with H2O2 of purified a2 and a3, respectively, obviously represent oxidation artifacts formed under the conditions of culture. The amino acid sequences determined for the a-factor peptides are Tyr-Ile-Ile-Lys-Gly-Val Leu-Phe-Trp-Asp-Pro-Ala-Cys. Several lines of evidence suggest that the carboxyl-terminal cysteine residue is S-alkylated by a hydrophobic moiety.

Amino Acid Sequence↗
PubMed1987

Myocardial and circulatory effects of inosine.

The action of inosine (2.5, 5, or 10 mg.kg-1.min-1 iv) was investigated in open chest rats (n = 46) and guinea pigs (n = 16). Left ventricular and aortic pressures, dP/dtmax, and stroke volume were measured. Additionally, isovolumic peak pressure and peak dP/dtmax were measured during short occlusions of the aorta for assessing myocardial performance independent of circulatory changes. In rats inosine caused a dose dependent decrease in dP/dtmax (-5%, -21%, -40% of preinfusion values), heart rate (-7%, -23%, -55%), and mean aortic pressure. Additionally, a subgroup of seven rats was paced at their initial preinfusion heart rate, but independently from the heart rate there was a reduction in dP/dtmax (-15%). The isovolumic measurements confirmed the negative inotropic effect of inosine in rats. Peak dP/dtmax was reduced to 85% of preinfusion values with a dose of 2.5 mg.kg-1 min-1 (to 70% of preinfusion values with 10 mg.kg-1.min-1). Similarly, the maximum isovolumic pressure for a defined filling volume was decreased by 30 mmHg (at 350 microliter; 5 mg.kg-1.min-1; p less than 0.05). The mean aortic pressure decreased with 2.5 mg.kg-1.min-1 inosine indicating vasodilative properties. In contrast to the significant effects in rats even 10 mg.kg-1.min-1 inosine did not have an effect on heart rate, mean aortic pressure, or dP/dtmax in guinea pigs. The isovolumic peak left ventricular pressure in guinea pigs was also unchanged after inosine infusion. Thus the haemodynamic effects of inosine were species dependent.

Animals↗
PubMed1983

Microprocessor-based long term cardiorespirography. I. Heart rate changes and apneic attacks.

Cardiorespirography is a well-known method of continuous monitoring in neonatal intensive care. Apneic attacks, bradycardia and tachycardia are registered. In our experience we connected a cardiorespirography recorder to a microprocessor system. The processor consisted of a hardware part including a program (software) and a printer which provided printouts of alarm events. As alarm situations, which cause an alarm printout, we defined: 1. apneic episodes (duration 10, 20 or 30 seconds) 2. tachycardiac (beat-to-beat rate greater than 180/minute) 3. V-shaped and U-shaped bradycardia (beat-to-beat heart rate less than 80/min) and combinations. The reliability of the system of recognizing and classifying alarm situations was tested by comparing the alarm printouts with the simultaneously recorded cardiorespirograms. Fifty eight 12 hour records of 41 patients were evaluated. Six hundred alarm situations were counted. The alarm printouts were found in concordance with the cardiograms in all tachycardia alarms. Nearly all bradycardia (V-shaped, U-shaped bradycardia, combination of bradycardia and apnea) were correctly classified. A preset apnea duration of 10 seconds resulted in many false positive alarm printouts. With 20 second apnea time only few false positive alarms were seen, but nine apneic attacks were not recognized. Altogether 81.5% of alarm printouts were correct, 16.8% were false alarms, or V-shaped bradycardia were really U-bradycardia. Only 2% of all alarms were not recognized by the microprocessor system. We suggest to combine the microprocessor with a special alarm recorder, which is able to store beat-to-beat heart rate and respiration wave before alarm situations.

Apnea↗
PubMed1983

Microprocessor-based long term cardiorespirography. II. Status evaluation in term and premature newborns.

In 1965 URBACH et al. and RUDOLPH et al. [35, 39] described a loss of heart rate variability in severely ill neonates. In this study we investigated the correlation between instantaneous heart rate patterns and status diagnosis. We used a microprocessor-based cardiorespirography system. Seventy five newborn infants (51 prematures and 24 term neonates) were studied for about 12 hours each. Twenty nine patients had a second record after the first investigation. Parameters were: Type of frequency and oscillation, long time variability (LTV), short time variability (STV) and the newly introduced P-value (maximal difference between two successive R-peaks in five minutes). We found clear differences between the study groups. With increasing severity of illness mean values ("group mean values") of long time variability, short time variability and P-value decreased. Fixed heart rate became predominant. The most pronounced loss of heart rate variability was seen in infants with severe intracranial bleeding, thus offering a tentative diagnosis. For statistical analysis long time variability and the silent oscillation type have been proved as best parameters for this diagnosis. Severely decreased heart rate variations also have been seen in infants with acute renal failure--possibly because of brain edema--, after application of muscle relaxants, repeated doses of sedatives, and after prolonged anesthesia. Otherwise, the heart rate variability was probably dependent on age and gestational age in prematures and newborn infants without intracranial bleeding. It is possible to use microprocessor-based long time cardiorespirography as a simple screening method for the diagnosis of neonatal intracerebral bleeding. In future experiences transcutaneous measurements of oxygen tension should be included.

Cerebral Hemorrhage↗
PubMed1979

Purification and partial characterization of a factor, a mating hormone produced by mating-type-a cells from Saccharomyces cerevisiae.

Cells of Saccharomyces cerevisiae exhibiting the a mating type secrete into the culture medium a mating-type-specific hormone activity (a factor), which specifically causes a transient arrest of DNA replication and cell division in cells of the opposite mating type, alpha. Three compounds exhibiting a factor activity have been found in culture filtrates from a cells. The most active compound has been purified more than 10(5)-fold and appears to be homogeneous on the basis of thin-layer chromatography and thin-layer electrophoresis in different systems. We propose that this compound, which exhibits in alpha cells the biological activities that have been attributed to a factor, represents pure a factor. a factor has been characterized as a very hydrophobic undecapeptide with the following amino acid composition: H2N-Tyr (Asx1, Gly1, Ala1, Val1, Ile2, Phe1, Lys1, Trp1, Pro1). Although in their respective target cells the biological effects of a factor and of alpha factor, the corresponding mating hormone of mating-type-alpha cells, are remarkably similar, the primary structures of both hormones appear to be quite different.

Agglutination↗
PubMed1977

Stimulation of yeast mating hormone activity by synthetic oligopeptides.

The biological activities of two synthetic oligopeptides (His-Trp-Leu-Gln-Leu and Trp-Leu-Gln-Leu), which represent part of the primary structure of the mating hormone alpha factor from Saccharomyces cerevisiae, were studied. The peptides did not exhibit hormonal activity by themselves. However, both intensified the mating-type-specific inhibitory effect of native alpha factor on the division of haploid cells of mating type a. Random peptides or mixtures of the corresponding amino acids did not stimulate alpha factor activity. Likewise, a synthetic peptide representing another part of the alpha factor sequence was ineffective. In addition, the activity of a factor, the mating hormone produced by a cells, was not influenced by the synthetic peptides, indicating that the compounds specifically affect the interaction between alpha factor and its target cells. The analysis of the utilization of the tetrapeptide as a source of amino acids for auxotrophic a strains suggested an extracellular site of action for the observed enhancement of alpha factor activity.

Amino Acid Sequence↗
PubMed1977

a-Factor from Saccharomyces cerevisiae: partial characterization of a mating hormone produced by cells of mating type a.

Conjugation between haploid cells of Saccharomyces cerevisiae is mediated through the action of diffusible mating hormones, two of which have been designated as a-factor and alpha-factor. Partially purified fractions exhibiting a-factor activity have been obtained from culture filtrates of a cells by ultrafiltration, ion-exchange chromatography, and gel filtration. The a-factor preparations specifically caused both G1 arrest and morphological alterations in cells of alpha-mating type, whereas a cells, a/alpha diploids, and nonmating alpha mutants were not affected. The a-factor activity was found in the culture filtrates of all a strains tested, but not in filtrates of alpha or a/alpha cell cultures. The hormone is sensitive to various proteases, showing that it is associated with a peptide or protein. Gel filtration studies suggest an apparent molecular weight greater than 600,000; however, this result may be due to aggregation with carbohydrate present in the preparations. Although the biological activities of a-factor are analogous to those described previously for alpha-factor, the chemical properties of these two hormones appear to be quite different.

Cell Division↗
PubMedDate not supplied

[Impedance cardiography, a method to evaluate quantitatively cardiac output? Comparison with the Fick principle (author's transl)].

In 36 children without shunts nearly 280 electrical impedance measurements were carried out in order to estimate the accuracy of the impedance cardiography as a means of calculating output. During evaluation up to 22 combinations of test conditions and possibilities of evaluation per child were tested. As a reference method the Fick Principle was used. The reproducibility of impedance measurements showed itself to be high, but no agreement of the results by impedance cardigraphy and corresponding values by the Fick method could be found. Some reasons give rise to suppose that impedance cardiography only reflects changes in the intrathoracic fluid level occurring during heart action from which because of formal reasons no interference should be drawn about the original cardiac output. Besides physical arguments tell against the possibility of picking up these volume-changes quantitatively by analyzing transthoracic electrical impedance.

Adolescent↗