Assay of different photoproducts after UVA, B and C irradiation of DNA and human skin explants

A ³²P-HPLC method was applied to study the induction of UVB-and UVC-induced DNA lesions (cyclobutane dimers, 6-4 photoproductsand Dewar isomers) in human skin explants. The employed techniquewas sensitive enough to detect the lesions at a dose of 10 J/m²UVB. Comparison of photoadduct formation under UVC and UVB indicatedthe importance of photosensitization pathways in DNA damage.Dewar isomers were detected only at a high dose of UVB. Thecompounds were identified by their photochemical reactivityand by spiking with prepared standards. Treatment with nucleaseP1 was used to identify the 5'-terminal nucleotide. UVA causedno detectable adducts.     

Isolation and characterization of mutants as an approach to a transformation system in Kluyveromyces marxianus

 A method to obtain K. marxianus mutants has been developed. Different auxotrophic mutants were isolated by nystatin and snail-enzyme enrichment procedures using an incubation time of 2 h before adding the antibiotic or the enzyme respectively. All his mutants analyzed by complementation tests turned out to belong to the same complementation group. Some of them were transformed and complemented by the S. cerevisiae HIS3 gene. These non-reverting his3 mutants contain no heterologous sequence, which is essential to make them acceptable for application in the food industry. Received: 15 November/21 December 1995     

Verhalten der menschlichen Haut gegenüber elektromagnetischer Strahlung im sichtbaren und nahen IR-Bereich

In der Gerichtsmedizin, aber auch in anderen medizinischen Bereichen besteht of die Notwendigkeit, biologische Proben optisch eindeutig zu beschreiben.Es wird daher ein Verfahren zur Beschreibung solcher Proben im Wellenlängenbereich 400 nm bis 1100 nm des elektromagnetischen Spektrums vorgestellt.     

Interactions of Phenytoin and Phenobarbital in Terms of Order and Temporal Spacing of Administration in Monkeys

The present study investigated order and temporal spacing interactions of phenytoin and phenobarbital in terms of plasma levels during multiple dosing in monkeys. Phenytoin at a dose of 30 mg/kg and phenobarbital at a dose of 3 mg/kg were administered separately to 4 animals (control group) by nasogastric intubution daily for 10 days. In four subsequent 10-day periods the drugs were administered together in 4 other animals (interaction group) at different times of the day (immediately following one another, 1/2 hr apart, and 6 hr apart) and in a different order of administration (either phenobarbital first and phenytoin later, or the reverse). Blood samples were obtained on the 5th, 8th, and 10th day of each 10-day period. The plasma data indicated: (a) phenytoin is capable of autoinduction, (b) phenobarbital lowers the levels of phenytoin under the four methods of administration studied here, and (c) phenytoin can affect the levels of phenobarbital. The latter interaction is a function of order and temporal spacing of drug administration.     

Propylene polymerization on titanium-magnesium catalysts, 3. Influence of the products resulting from the interaction of trialkylaluminium with aromatic esters on the activity and stereospecificity

The influence of the conditions of interaction between AlR₃ and aromatic esters (D) and of the products formed on the activity and stereospecificity of the actalytic system TiCl₄/ethyl benzoate/MgCl₂ + Al(i-Bu)₃ + D in propylene polymerization was studied. An increase of the polymerization temperature above 60°C leads to a decrease in the activity of the titaniummagnesium catalyst (TMC) and in the isotacticity of the polypropylene produced. A preliminary interaction of AlR₃ with D at elevated temperatures diminishes the isotacticity of the polymer and has no influence on the activity of TMC. IR spectroscopy was employed to study the influence of the temperature and time of AlR₃ interaction with the esters as well as that of the composition of AlR₃ (AlEt₃ or Al(i-Bu)₃) on the process of reduction of these esters. Reduction products such as aldehydes, ketones, and primary alkoxy derivatives of aluminium cannot provide of high stereopecificity of TMC. High stereospecificity is rather thought to be provided by the interaction of active sites with a free ester or tertiary alkoxy derivaties of aluminium. The contribution of each of these processes depends on the catalyst composition and on the polymerization conditions.     

Development of Methods of Assisted Circulation with Artificial Heart Ventricles

A comparative study of two methods of bypassing the heart with artificial ventricles (AV) was conducted: left atrium-aorta and left ventricle-aorta. The following factors permit left ventricular bypass to compete successfully with left ventricle-aorta bypass: creation of perfected pumps with low input impedance, use of materials with high resistance to thrombus formation for preparation of the AV and main connecting lines, and development of optimum methods of anticoagulant, disaggregation, and cardiac therapy so that there is no danger of thrombosis and hemorrhage, either experimentally or clinically. Thrombosis was the primary cause of death in only one case in a series of experiments on 15 calves with AV connected according to the atrium-aorta scheme. The positive changes in hemodynamics were approximately the same with the two methods.     

Growth of Human Marrow in Plasma Clot Diffusion Chambers

Unseparated as well as nonadherent human bone marrow cells produced colonies while suspended within plasma clots contained within diffusion chambers implanted into irradiated mice. The majority of colonies consisted of granulocytes or macro-phages. Colony size was significantly increased by the administration of endotoxin prior to implantation of the chambers.     

Modeling and Prospects for Study of Cardiovascular Pathology with the Artificial Heart

A series of models of the artificial heart has been developed for simulating different heart defects including stenosis of the atrioventricular ostium and mitral and tricuspid incompetence. Simulation of ventricular fibrillation is also possible. Repeated perturbation and restoration of artificial heart function are possible in the same animal. These processes are controlled externally. The surgical technique of implanting the artificial heart does not differ from the usual technique. Models of the artificial heart permit the study of fundamental problems in the physiology and pathology of the cardiovascular system.     

Cardiac effects of stroke

Opinion statement Our brain regulates all bodily functions either directly or indirectly, and cardiovascular control is no exception. There is strong clinical evidence of cerebrogenic cardiac arrhythmias and myocardial changes during ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. Alternative scenarios include cardioembolic stroke, multisystem diseases with stroke-like and cardiac features, and coincidental detection of cardiac disorders in a stroke patient. Cardiac effects of stroke may be severe or even fatal and worsen the prognosis. Clinical and experimental studies suggest that cortical and subcortical structures such as the insular cortex and amygdala play a pathogenic role. The peripheral mechanisms involve abnormal sympathetic activity, altered parasympathetic activity, and raised levels of circulating catecholamines, whereas the central mechanisms are largely unknown. Because stroke patients are best managed in an acute stroke unit during their initial presentation, a cardiocerebral approach is desirable with close cardiovascular and neurologic monitoring. Prolonged and intensive cardiovascular monitoring is recommended in patients manifesting cerebrogenic cardiovascular disturbances and in high-risk patients with insular involvement, rightsided stroke, advancing age, coexisting hypertensive or coronary artery disease, or intense emotional stress. Although the best management is largely unknown, treatment of cardiac effects of stroke is largely supportive according to the type of disturbance. Severely affected patients should be evaluated by a cardiologist prior to the initiation of appropriate therapy. Much more clinical and basic research is needed to allow a full understanding of the brain-heart control, the consequences of disruption of this control, the true incidence of cardiac effects of stroke, and the evidence-based treatment options.     

Cardiac Autonomic Modulation by Estrogen in Female Mice Undergoing Ambulatory Monitoring and In Vivo Electrophysiologic Testing

Introduction: Estrogen is an important modulator of cardiovascular risk, but its mechanism of action is not fully understood. We investigated the effect of ovariectomy and its timing on the cardiac electrophysiology in mice. Methods: Thirty female mice (age 18.8 ± 3.1 weeks) underwent in vivo electrophysiologic testing before and after autonomic blockade. Fifteen mice were ovariectomized prepuberty (PRE) and ten postpuberty (POST), 2 weeks prior to electrophysiologic testing. Five age‐matched sham‐operated female mice (Control) served as controls. A subset of 13 mice (5 PRE, 3 POST, and 5 Controls) underwent 24‐hour ambulatory monitoring. Results: With ambulatory monitoring, the average (668 ± 28 vs 769 ± 52 b/min, P = 0.008) and minimum (485 ± 47 vs 587 ± 53 b/min, P = 0.02) heart rates were significantly slower in the ovariectomized mice (PRE and POST groups) compared to the Control group. At baseline electrophysiologic testing, there were no significant differences among the ovariectomized and intact mice in any of the measured parameters. With autonomic blockade, the Control group had a significantly larger change (?) in the atrioventricular (AV) nodal Wenckebach (AVW) periodicity (?AVW = 11.3 ± 2.9 vs 2.1 ± 7.3 ms, P = 0.05) and functional refractory period (?FRP = 11.3 ± 2.1 vs 1.25 ± 6.8 ms, P = 0.02) compared to the ovariectomized mice. These results were not altered by the time of ovariectomy (PRE vs POST groups). Conclusion: Our results suggest that estrogen modulates the autonomic inputs into the murine sinus and AV nodes. These findings, if replicated in humans, might underlie the observed clustering of certain arrhythmias around menstruation and explain the higher incidence of arrhythmias in men and postmenopausal women.