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Biomedical subjects

M Roger

Publications and source records attributed to M Roger.

At least 235 records · Page 13Linked to original sources
PubMed1977

Activity of the crayfish caudal photoreceptor submitted to a conditioning paradigm.

The activity of the crayfish caudal photoreceptor (Ph) was studied during the application of a classical conditioning paradigm. This cell is a primary photoreceptor and, at the same time, a secondary neuron in the mechanoreceptive pathway. The electrical stimulation of afferent mechanoreceptor fibers, the analog of the conditioned stimulus (ACS), produced a slight increase in the Ph firing rate. The photic stimulation, the analog of the unconditioned stimulus (AUS), produced a marked increase in the Ph firing rate. After ACS-AUS pairing, a decrease in the Ph firing rate appeared during the ACS-AUS interval, and it was considered the analog of the conditioned response (ACR). This inhibitory response gradually vanished during extinction. The application of ACS or AUS series alone did not produce a response similar to the ACR, this excluding sensitization as a possible cuase. The ACR meets several conventional criteria accepted in learning, supporting the idea that the crayfish caudal photoreceptor is part of a small neuronal network able to learn in the isolated nerve cord preparation.

Animals↗
PubMed1977

Mismatch excision and possible polarity effects result in preferred deoxyribonucleic acid strand of integration in pneumococcal transformation.

Heteroduplex deoxyribonucleic acid molecules having a drug resistance marker on one strand and its wild-type allele on the other have been used as donors in pneumococcal transformation. Opposite strands are not equally effective in producing transformants, and this strand bias is not the same, either in direction or magnitude, for various different genetic markers. Selective excision of mismatched base pairs is probably responsible for the large differences in strand efficiency seen with discriminating (hex+) strains, for when the recipient is nondiscriminating (hex-), and therefore presumably lacking an excision enzyme system, strand bias is drastically reduced or altered. The evidence also indicates that excision occurs after integration, as it is provoked by specific donor-recipient mismatch and not by the same mismatch when introduced within donor heteroduplex molecules. Excision can extend to include a neighboring linked marker which would otherwise not be excised, thus altering its intrinsic strand bias as well as its efficiency in transformation. There is a small bias in relative strand efficiency for some markers, not caused by mismatch excision, which perhaps is due to polarity in the integration process itself.

Aminopterin↗
PubMed1977

Pituitary LH and FSH and testosterone secretion in infants with undescended testes.

Twelve male infants with undescended testes (5 bilaterally, 7 unilaterally) were studied between the ages of 1 week and 11 months. As in older pre-pubertal cryptorchid boys, a significant decrease of the LH response to LH-RH test was found, while basal plasma levels of gonadotrophins and FSH response to LH-RH were normal. Plasma testosterone levels were in the normal range, and Leydig cells responded to stimulation by HCG, the degree of this response being significantly and positively correlated to the LH peak elicited by LH-RH. It may be concluded that some early defect of the pituitary-Leydig cell axis is associated with undescended testis.

Chorionic Gonadotropin↗
PubMed1977

Correlation of pituitary and testicular responses to stimulation tests in cryptorchid children.

LH-RH test and HCG stimulation test were performed in 154 cryptorchid boys aged 1 month to 15 years (64 unilateral and 90 bilateral). Basal plasma LH levels and LH response to LH-RH were significantly lower from infancy to early puberty in cryptorchids compared with controls. Basal FSH levels and FSH response to LH-RH were normal. The post-HCG rise of plasma testosterone was reduced until mid-puberty. A significant positive correlation was found between post-HCG testosterone levels and pre- and post-LH-RH levels of LH. This correlation suggests that testicular maldescent and the decreased ability of Leydig cells to respond to a short course of HCG may result from an early defect or a delay of pituitary LH secretion.

Adolescent↗
PubMed1977

[Biological criteria for the surveillance of hydatidiform moles and choriocarcinomas].

Secretion of choriogonadotropin (hCG) remains until now the more accurate biochemical label of trophoblastic disease and a close follow-up is possible by means of sensitive and specific radioimmunoassays. After hydatidiform moles, drawing the decreasing curve of hCG concentrations by weekly measurements in plasma or urine, would generally allow distinguishing within a few weeks cases with and without retention of active trophoblastic tissue, although in only 30 p. 100 of moles hCG spontaneously disappears within a month. In some choriocarcinoma under therapy, low persisting hCG levels (lower than 100 or 50 I.U./24 hours) could only be evidenced by repeated radioimmunoassays. Even with apparently physiological hLH/hCG concentrations, the use of anti-beta hCG antiserum could demonstrate, if any, a secretion of choriogonadotropin. In castrated women the same technique would elude the interference of hLH and make easier the diagnostic of relapses.

Castration↗
PubMed1976

[The effects of somatostatin in acromegaly].

Somatostatine is the hypothalamic factor which inhibits the secretion of growth hormone. The administration of a synthetic form decreased growth hormone levels by 50 to 75% in 5 acromegalic patients. The action is rapid but the effect is not prolonged. Prolactin was reduced in only case with galactorrhea. Thyreostimulin, as well as gastrin, are unaffected. Plasma insulin levels, and to a lesser extent those of glucagon, are decreased by somatostatine which causes no variation in either cortisol or blood glucose. Somatostatine, by correcting the pathological secretion of hormone, opens the way to medical treatment of acromegaly.

Acromegaly↗
PubMed1976

[Remarks on the modifications of cell wall during the sporulation of Saccharomyces cerevisiae Hansen (author's transl)].

Evolution of cell wall during sporulation was studied by means of scanning electron microscopy and by immunological techniques. Experiments were done simultaneously with a strain a/alpha able to sporulate and a strain alpha/alpha unable to sporulate. Under such conditions it was possible to clarify whether the changes observed were related to the sporulation or to the culture conditions. Cell wall structure modifications during sporulation were not obvious morphologically but have been revealed by immunological methods. During vegetative growth, antigenic sites of strains a/alpha and alpha/alpha were different. During incubation in the sporulation medium, antigenic structure of the cell wall was modified. Some antigenic sites seem to be specific of sporulation.

Cell Wall↗
PubMed1976

[Evaluation of gonadotropic and gonadal secretions in primary abnormalities of the gonads and male pseudohermaphrodism before and after the age of puberty].

Blood levels of gonadotropins (FSH and LH) and gonadal steroids (testosterone or estradiol) have been evaluated in 72 children and adolescents with primary gonadal defects (45 agonadal patients, 7 with asymetrical gonadal dysgenesis, 9 with Klinefelter syndrome, 4 with partial testicular dysgenesis and 7 with partial ovarian dysgenesis) and in 17 cases of male pseudohermaphrodism. A LH-RH test has been performed in most cases, and a testicular stimulation test with chorionic gonadotropin in patients with testicular tissue. Agonadal subjects had increased blood and pituitary releasable gonadotropins: very high in infants and young children, much less from 7 to 11 years, a high spurt being observed at 12 years. This diphasic pattern relates to the varying sensitivity of hypothalamic receptors and suggests that adrenal steroids may restrain gonadotropic secretion at 7-8 years. As a diagnostic tool, the increase of gonadotropins may be missing in the 7-11 years group. In the 1-12 years patients with partially defective gonads, blood and pituitary releasable gonadotropins and blood steroids are usually normal, but testosterone response to chorionic gonadotropin may be already blunted. From 13 years the gonadotropic secretion is usually increased, even when testosterone secretion and reserve are within normal range. Most male pseudohermaphrodites showed normal gonadotropic and testicular secretions. But four patients had highly increased responses to LH-RH, suggesting a defect of testicular secretion or of receptors, and demonstrating some heterogeneity in the male pseudohermaphrodism group.

Adolescent↗
PubMed1975

[Simultaneous study of plasma gonadotropins, estrogens, progesterone and 17-hydroxyprogesterone during the ovulatory cycle].

Plasma levels of gonadotrophins, estrone, estradiol, 17-hydroxyprogesterone and progesterone were studied throughout an ovulatory cycle in 11 normal women. For each of these hormones, the initiation of a secretory cycle occured at a different time: on the 10th day after mid-cycle surge for gonadotrophins, on the 3 rd day of menses for estradiol and somewhat later for estrone, on the 8th day of cycle for 17-hydroxyprogesterone and on the day of the LH surge for progesterone. Mean plasma levels and range were reported for every studied hormone. The mid-cycle surges of LH and FSH were found always coincident, after which their concentration decreased simultaneously; during the late follicular phase the increasing LH curve intersected the decreasing FSH curve. A peak of estradiol occured in every subject except one on the day before the mid-cycle surge of LH; a peak of plasma estrone occured either on the day of the LH peak or on the day before. For these two hormones the luteal phase range is always below the peak level. A peak of 17-hydroxyprogesterone occured in every subject on the same day than the mid-cycle LH peak, but the plasma level increased during the luteal phase up to higher levels. Progesterone concentration increased on the day of the LH surge, indicating the initiation of luteinization prior to ovulation.

Adult↗