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Biomedical subjects

E Simon

Publications and source records attributed to E Simon.

At least 307 records · Page 17Linked to original sources
PubMed1965

Recombination in bacteriophage T4: a mechanism.

Genetic recombination between rIl mutants of T4 bacteriophage grown in Escherichia coli can occur under conditions where DNA synthesis is strongly inhibited by 5-fluorodeoxyuridine. The small amount of DNA synthesized under these conditions cannot account for the observed frequency of recombinants. The major mechanism of recombination in this system is a process of breakage and rejoining.

Chloramphenicol↗
PubMedDate not supplied

Arterial baroreceptor function in differential cardiovascular adjustments induced by central thermal stimulation.

Dogs were anesthetized with sodium pentobarbital, relaxed with succinyl choline and were kept under artificial ventilation. Both carotid bifurcations were denervated and the Vagus nerves were cut in the neck. Regional blood flow in the skin and the intestine, cardiac output, heart rate and arterial pressure were determined before, during and after spinal cord heating and cooling. Further experiments were performed in which, in addition, sympathetic effects on the heart were excluded by exstirpation of the caudal cervical and stellate ganglia or by beta-receptor blockade. The cardiovascular responses were compared with those obtained in a preceding investigation from dogs with intact baroreceptors and vagus nerves. As in intact dogs, appropiate thermoregulatory adjustments of skin blood flow were induced by thermal stimulation of the spinal cord after baroreceptor denervation and vagotomy. However, blood pressure homeostasis was lost. The pattern of cardiovascular ajustments during heating consisted in cutaneous vasodilatation intestinal vasoconstriction and, due to sympathetic activation an increase of heart rate and cardiac output. This pattern was qualitatively identical with that intact animals. During spinal cord cooling the cardiovascular response pattern consisted in cutaneous vasoconstriction, intestinal vasoconstriction and, depending on cooling intensity, a reduced or unchanged sympathetic influence on the heart. This pattern differed considerably from what in intact animals but basic features were still present as indicated by opposite changes of cardiac and vascular sympathetic tone during cooling. It is concluded that the baroreceptor signals play no primary role in the generation of differential vasomotor responses under the present experimental conditions. This confirms assumptions made on the basis of observations in animals with intact baroreceptor input. However, baroreceptor signals contribute significantly to blood pressure homeostasis which is normally maintained during spinal thermal stimulation.

Animals↗
PubMedDate not supplied

Blood pressure and arginine vasotocin in normonatremic and hypernatremic ducks.

As a model to study effects of chronic, excessive salt loading on circulation, Pekin ducks were adapted to 2% saline solution as their sole water supply, while fresh-water-adapted animals were used as controls. Due to the development of salt-eliminating glands, salt-adapted ducks are able to cope indefinitely with this salt stress which means a daily ingestion of 5-6 g NaCl per kg body weight per day, associated with a chronic elevation of plasma osmolality and plasma sodium by 5-8% above normal and an up to 3-fold increase of antidiuretic hormone concentration in comparison to animals maintained on fresh water. Salt loading for up to 14 months did neither increase arterial mean, nor diastolic, nor pulse pressure. On the contrary, arterial mean and diastolic pressure were slightly lower in the salt-adapted than in the fresh-water-adapted animals, while pulse pressure and heart rate did not differ. Circulatory adaptation to removal and reinfusion of 10% of the estimated blood volume was identical in salt-water and fresh-water-adapted ducks. It is concluded that even excessive chronic salt loading resulting in chronic hyperosmolality with high plasma levels of sodium and antidiuretic hormone does not alter hemodynamic adaptation, provided that efficient compensating mechanisms are at the animal's disposal.

Animals↗
PubMedDate not supplied

[Tuberculosis of the lymphatic nodes and coexisting invasion with Toxoplasma gondii].

Six cases of the peripheral lymphatic nodes tuberculosis with positive serologic reactions to Toxoplasma gondii antigen are presented. It was shown, that independently of a complex of clinical examinations histologic examination is decisive for the diagnosis of lymphatic nodes tuberculosis with coexisting toxoplasmosis. A positive serologic reaction with T. gondii antigen in patients with lymphatic nodes tuberculosis may reflect inactive infection with T. gondii. Use of anti-toxoplasmosis drugs may be not necessary in such cases.

Adult↗
PubMedDate not supplied

[Sarcoidosis in coexistence with Toxoplasma gondii invasion].

Two cases of sarcoidosis with peripheral lymphatic nodes involvement and coexisting toxoplasmosis are presented. Both cases illustrate diagnostic and differentiating problems in patients with chronic lymphatic nodes enlargement and positive serological reaction to T. gondii antigen. An emphasis is on the importance of the histological examination of the lymphatic nodes for the sarcoidosis diagnosis and contribution of T. gondii to the disease. Positive serological reaction to T. gondii antigen in patients with sarcoidosis may reflect inactive toxoplasmosis; however, periodical serological tests are necessary monitoring the due immunosuppressive treatment used in patients with sarcoidosis.

Adult↗
PubMedDate not supplied

[Thanatophoric nanism: a case of early ultrasonic diagnosis].

The diagnosis of a thanatophorous nanism is evoked in the presence of an abnormality of the size of the long bones. This study records the symptoms which, on sonograms, permit to recognize this fatal form of nanism among other forms of metaphysis chondrodysplasia, in order to establish a diagnosis before deciding to interrupt the pregnancy.

Adult↗
PubMedDate not supplied

[Epidemiologic aspects of extrauterine pregnancy and therapeutic approach. Apropos of 200 cases in a continuous series].

The study of 200 files has enabled to define a few epidemiological aspects of ectopic pregnancy: large frequency of this pregnancy with ectopic location, for 42 births, in an average, occurrence in young women, between 25 and 35 years, hypofertile, nulli or primiparous, importance of utero-adnexal infections and their sequelae, found in 50% of the cases, and linked to the increase of sexually transmissible diseases and the frequency of voluntary interruptions of pregnancy, importance also of histological lesions of the isthmo-interstitial segment of the tube. The different therapeutic approaches are presented: the authors explain the reasons for a deliberately conservative therapy (in 82% of the cases) without compromising the maternal prognosis: absence of anatomical abnormality justifying the excision of the tube, or, often bilateral anatomical lesions requiring a subsequent radiological work-up, and a secondary treatment. Finally, desire of another pregnancy in a population which is infertile, most of the time, and of which the mean age is 28 years.

Adolescent↗
PubMedDate not supplied

[When should one operate on polyps of the isthmo-interstitial portion of the fallopian tube?].

The authors analyze the diagnosis and the results of the treatment of 43 patients presenting simple polyps of the isthmo-interstitial segment of the tube with at least a 2 years follow-up. The study was carried out between 1980 and 1983. It was a prospective, non-randomized study. They conclude that the medical treatment, which gives excellent results, is advantageous. Microsurgical treatment (reimplantation or isthmo-ostial anastomosis) is only used after failure of the medical treatment.

Fallopian Tube Neoplasms↗
PubMedDate not supplied

Are black-box models of thermoregulatory control obsolete? The importance of borrowed knowledge.

Black-box models of thermoregulatory control have gained increasing importance in describing the properties of the biological thermostat and in devising working hypotheses for further experimental analysis. Incorporation of knowledge acquired independently from the systems analysis approach into black-box models of thermoregulation has proven useful in improving their predictive ability. The pieces of "borrowed knowledge" from independent analysis which are currently utilized in devising models of homeothermic thermoregulation comprise: the proportional control property of the biological thermostat, the Sherringtonian principles of synaptic interaction, the multiple input control of thermoregulatory effectors with differential input-effector coupling, the lack of significant thermosensory contribution from the hypothalamus in birds, the existence of warm and cold receptors and the thermal characteristics of their responses, and the Q10-type temperature dependence of temperature signal transmission within the central nervous system. Consideration of these pieces of borrowed knowledge has resulted in black-box models of temperature regulation in which explicit set-point terms are avoided.

Animals↗