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Biomedical subjects

G Fuchs

Publications and source records attributed to G Fuchs.

At least 91 records · Page 5Linked to original sources
PubMed1988

Anaerobic metabolism of cyclohexanol by denitrifying bacteria.

Three strains of denitrifying bacteria were anaerobically enriched and isolated from oxic or anoxic habitats with cyclohexanol or cyclohexanone as sole electron donor and carbon source and with nitrate as electron acceptor. The bacteria were facultatively anaerobic, Gram-negative and metabolism was strictly oxidative with molecular oxygen, nitrate, or nitrite as terminal electron acceptor. Cyclohexanol and cyclohexanone were degraded both anaerobically and aerobically. Aromatic compounds were oxidized in the presence of molecular oxygen only. One of the bacterial strains was further characterized. During anaerobic cyclohexanol degradation approximately 40% of the substrate was oxidized to phenol, which accumulated as dead-endproduct in the growth medium; 60% of cyclohexanol was completely oxidized to CO2 and assimilated, respectively. In addition to phenol formation, transient accumulation of cyclohexanone, 2-cyclohexenone and 1,3-cyclohexanedione was observed. Based on these findings we propose a pathway for anaerobic cyclohexanol degradation involving these intermediates.

Anaerobiosis↗
PubMed1988

Open comparative study with treatment-refractory depressed patients: electroconvulsive therapy--anesthetic therapy with isoflurane (preliminary report).

Isoflurane is the only routine volatile anesthetic which leads to a burst-suppression EEG in nontoxic concentrations and for which no memory impairments can be expected subsequent to anesthesia. After electrically induced spike-wave activity in electroconvulsive therapy (ECT), a brief period of a very flat EEG can be observed. This phenomenon may be closely related to the therapeutic effects of ECT. The results which have been achieved up to now in comparing ECT to anesthetic therapy with isoflurane, without seizures being induced, are presented.

Adult↗
PubMed1987

Autotrophic synthesis of activated acetic acid from CO2 in Methanobacterium thermoautotrophicum. Synthesis from tetrahydromethanopterin-bound C1 units and carbon monoxide.

The synthesis of acetyl-CoA from CO2, H2, and various C1 compounds was studied in vitro with extracts and with protein fractions of Methanobacterium thermoautotrophicum. Acetyl-CoA synthesis from CO2 and H2 by extracts required CO2 reduction to CH4 to proceed. Both processes were highly stimulated by formaldehyde which served as the carbon precursor of both CH4 and the CH3 group of acetate. Carbon monoxide in combination with formaldehyde dramatically stimulated the acetyl-CoA synthesis up to 150-fold. In this system, which did not require CO2 reduction to the formaldehyde and CO level, acetyl-CoA synthesis was no longer dependent on CH4 formation. The soluble (100,000 X g supernatant) cell protein was resolved into a protein fraction [45-60% (NH4)2SO4-fraction] which catalyzed acetyl-CoA synthesis at a specific rate of 15 nmol X min-1 X (equivalent of mg cell protein)-1 (60 degrees C). This oxygen-sensitive enzyme reaction required dithioerythritol for activity and was strictly dependent on coenzyme A, CO, and N5,N10-methylene tetrahydromethanopterin, N5-methyl tetrahydromethanopterin or formaldehyde plus tetrahydromethanopterin. The incorporation of formaldehyde is explained by the spontaneous formation of methylene tetrahydromethanopterin. The product of the reaction, acetyl-CoA, was quantitatively derived from CO (carboxyl of acetate) and a C1 derivative of tetrahydromethanopterin (methyl of acetate). The C1 derivative of tetrahydromethanopterin could not be replaced by a C1 derivative of tetrahydrofolate or by methyl-coenzyme M; ATP was not required. The active protein fraction contained CO dehydrogenase and at least on corrinoid protein. These results provide strong biochemical arguments for the proposed mechanism of autotrophic acetyl-CoA synthesis in Methanobacterium.

Acetyl Coenzyme A↗
PubMed1987

Anaerobic degradation of phenol by pure cultures of newly isolated denitrifying pseudomonads.

From various oxic or anoxic habitats several strains of bacteria were isolated which in the absence of molecular oxygen oxidized phenol to CO2 with nitrate as the terminal electron acceptor. All strains grew in defined mineral salts medium; two of them were further characterized. The bacteria were facultatively anaerobic Gram-negative rods; metabolism was strictly oxidative with molecular oxygen, nitrate, or nitrite as electron acceptor. The isolates were tentatively identified as pseudomonads. Besides phenol many other benzene derivatives like cresols or aromatic acids were anaerobically oxidized in the presence of nitrate. While benzoate or 4-hydroxybenzoate was degraded both anaerobically and aerobically, phenol was oxidized under anaerobic conditions only. Reduced alicyclic compounds were not degraded. Preliminary evidence is presented that the first reaction in anaerobic phenol oxidation is phenol carboxylation to 4-hydroxybenzoate.

Anaerobiosis↗
PubMed1987

Purification of alpha-toxin from Staphylococcus aureus and application to cell permeabilization.

Crude alpha-toxin was produced by Staphylococcus aureus, strain Wood 46. The amount of exotoxin was monitored during growth and all subsequent purification steps by determination of its hemolytic activity against rabbit erythrocytes. The culture supernatant was treated with ammonium sulfate (75% saturation). The resulting precipitate was dialyzed and subjected to cation-exchange chromatography. The fractions containing the hemolytic activity were further purified by gel chromatography. The final product was enriched by a factor of 8.5 compared to the crude toxin. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified toxin exhibited one major band. It caused the release of 86Rb+ and ATP from rat insulinoma (RIN A2) as well as pheochromocytoma cells (PC12) in culture, indicating efficient permeabilization of their plasma membranes for small molecules.

Adenosine Triphosphate↗
PubMed1987

Transurethral ultrasonic ureterolithotripsy using a solid-wire probe.

A multicenter study evaluates a new technique for transurethral ultrasonic ureterolithotripsy utilizing a solid-wire probe. The transverse vibrations of the probe cause greater stone disintegration. A small ureteroscope is used and a basket is not required. There was a 96.6 per cent success rate in 118 cases. This technique has significantly improved ultrasonic lithotripsy. It has proved to be useful for upper ureteral stones not amenable to extracorporeal shock-wave lithotripsy and lower ureteral stones including "steinstrasse."

Evaluation Studies as Topic↗
PubMed1987

A clinical study of the selective MAO-A-inhibitor moclobemide (Ro 11-1163): a comparison of 2 different dosages with particular reference to platelet MAO-activity and urinary MHPG-excretion.

A new selective MAO-A-inhibitor (noclobemide) was used in a double-blind comparative study of 23 patients with severe unipolar or bipolar depressive disorder. Two different doses of medication were given for 4 weeks. Effectiveness was measured by improvements in the Hamilton Rating Scale for Depression, a self-rating scale and clinical global impression. Platelet MAO-activity and urinary MHPG-excretion was also determined. Moclobemide proved to be a well-tolerated and effective antidepressant, with both groups showing improvement. Platelet MAO-activity was not markedly influenced by moclobemide, possibly because it selectively inhibits MAO-A. Urinary MHPG did not change significantly with treatment.

Adult↗
PubMed1986

Sodium-dependence of the saturability of carrier-mediated noradrenaline efflux from noradrenergic neurones in the rat vas deferens.

The carrier-mediated transport of 3H-noradrenaline out of noradrenergic neurones was studied in vasa deferentia obtained from rats after pretreatment with reserpine and pargyline (to inhibit vesicular storage and monoamine oxidase, respectively). The tissue was first preincubated with various concentrations of 3H-noradrenaline (0.3--100 mumol/1; 30 min) and then washed out for 110 min with amine-free medium. During the last 10 min of washout, carrier-mediated neuronal efflux of 3H-noradrenaline was elicited by exposure to either Na+-free medium or 100 mumol/l veratridine; it was measured at 1-min intervals. While the peak rates of carrier-mediated 3H-noradrenaline efflux elicited by Na+-free medium were linearly related to the 3H-noradrenaline content of the tissue (which cannot be raised beyond a certain maximal value, since uptake is saturable), those evoked in response to veratridine approached saturation as the 3H-noradrenaline level in the tissue was raised. Hence, saturation of 3H-noradrenaline outward transport was demonstrated at high (exposure to veratridine), but not at low (exposure to Na+-free medium) intraneuronal Na+ concentrations. The results indicate that the Km for the mediated outward transport of noradrenaline across the plasma membrane of noradrenergic neurones is inversely related to the internal Na+ concentration, just as the Km for the mediated inward transport of noradrenaline (i.e., the neuronal noradrenaline uptake) is inversely related to the external Na+ concentration.

Animals↗
PubMed1986

Nomifensine and psychological dependence--a case report.

This case report indicates that nomifensine has not only a specific antidepressant profile but also a dose dependent addictive potential in patients with "addictive problems". Nomifensine supports not only norepinephrine transmission, but also acts on dopamine metabolism and this may be responsible for the stimulation of motor activity. This is in contrast to more frequently used tri- and tetracyclic antidepressants. This case report further supports other observations that several patients have psychological withdrawal difficulties after long term treatment with nomifensine in high doses (400-600 mg).

Adult↗
PubMed1986

Pathogenesis of Shigella diarrhea: rabbit intestinal cell microvillus membrane binding site for Shigella toxin.

This study examined the binding of purified 125I-labeled shigella toxin to rabbit jejunal microvillus membranes (MVMs). Toxin binding was concentration dependent, saturable, reversible, and specifically inhibited by unlabeled toxin. The calculated number of toxin molecules bound at 4 degrees C was 7.9 X 10(10) (3 X 10(10) to 2 X 10(11))/micrograms of MVM protein or 1.2 X 10(6) per enterocyte. Scatchard analysis showed the binding site to be of a single class with an equilibrium association constant, K, of 4.7 X 10(9) M-1 at 4 degrees C. Binding was inversely related to the temperature of incubation. A total of 80% of the labeled toxin binding at 4 degrees C dissociated from MVM when the temperature was raised to 37 degrees C, but reassociated when the temperature was again brought to 4 degrees C. There was no structural or functional change of MVM due to toxin as monitored by electron microscopy or assay of MVM sucrase activity. These studies demonstrate a specific binding site for shigella toxin on rabbit MVMs. The physiological relevance of this receptor remains to be determined.

Animals↗