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Biomedical subjects

M Conti

Publications and source records attributed to M Conti.

At least 307 records · Page 17Linked to original sources
PubMed1982

Regulation of follicle-stimulating hormone and dibutyryl adenosine 3',5'-monophosphate of a phosphodiesterase isoenzyme of the Sertoli cell.

The regulatory role of FSH on phosphodiesterase was studied in immature Sertoli cells in culture. Cells were prepared from 15-day-old immature rats, cultured for 3 days in defined medium, and then stimulated for 24 h with gonadotropin or with other factors known to regulate Sertoli cell cAMP. All agents that increased cAMP intracellular levels also had an effect on the total phosphodiesterase activity of cell homogenates, FSH and dibutyryl cAMP being the most potent stimulators. Further, stimulation was more evident when phosphodiesterase was measured at cAMP concentrations below micromolar. With 1 microM cGMP as substrate, no modification of the activity could be detected. Reversal of phosphodiesterase activation was observed at 24 or 40 h when dibutyryl cAMP was removed from the incubation medium. Separation of the isoenzymes present in the soluble fraction of Sertoli cell made it possible to demonstrate a selective stimulation of one isoenzyme. FSH and dibutyryl cAMP increased 10- and 50-fold, respectively, the activity of a high affinity cAMP phosphodiesterase, while the Ca2+-dependent cGMP hydrolyzing enzymes were not apparently affected. The enzyme regulated by FSH and dibutyryl cAMP had an apparent Km for cAMP of 2 microM, was Ca2+ and calmodulin insensitive, and migrated on sucrose density gradients with a sedimentation coefficient of 5.5S. These results indicate that FSH, after stimulation of intracellular cAMP, induces an increase in a high affinity phosphodiesterase and, therefore, an increased cAMP turnover in the Sertoli cell. This, in turn, might be a relevant phenomenon in the control of the responsiveness of this cell to gonadotropin.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Prevention of catheter-associated urinary tract infections. Efficacy of daily meatal care regimens.

To evaluate the efficacy of daily cleansing of the urethral meatus-catheter junction in preventing bacteriuria during closed urinary drainage, randomized, controlled trials of two widely recommended regimens for meatal care were completed. In 32 (16.0 percent) of 200 patients given twice daily applications of a povidone-iodine solution and ointment bacteriuria was acquired, as compared with 24 (12.4 percent) of 194 patients not given this treatment. In 28 (12.2 percent) of 229 patients given once daily meatal cleansing with a nonantiseptic solution of green soap and water bacteriuria was acquired, as compared with 18 (8.1 percent) of 23 patients not given special meatal care. There was no evidence in either trial of a beneficial effect of meatal care. Moreover, each of four different statistical methods indicated that the rates of bacteriuria were higher in the treated groups than in the untreated groups. In subsets of female patients at high risk in both studies significantly higher rates of bacteriuria were noted in the treated groups than in the untreated groups. Current methods of meatal care appear to be hazardous, as well as expensive, and cannot be recommended as measures to control infection.

Administration, Topical↗
PubMed1977

RNA synthesis in spermatocytes and spermatids and preservation of meiotic RNA during spermiogenesis in the mouse.

The rate of RNA synthesis at different stages of spermatogenesis in the mouse, and the preservation of RNA from the diploid to the haploid phase of spermatogenesis were studied in homogeneous germ cell fractions separated by velocity sedimentation at unit gravity. The uridine pool expansion method was used for determining the rate of RNA synthesis: seminiferous tubules were labelled in culture with increasing concentrations of [3H]-uridine and the incorporated radioactivity was estimated in cell fractions separated by velocity sedimentation. The results indicate that before nuclear elongation, round spermatids (steps 1 to 8 of spermiogenesis) synthesize RNA at the same rate per DNA content as middle-late pachytene spermatocytes. The preservation of RNA molecules synthesized in meiosis was investigated by labelling pachytene spermatocytes with T3H]uridine in vivo and collecting samples of germ cells at definite stages of spermatogenesis at various time intervals thereafter. The results show that a considerable proportion the RNA synthesized during the pachytene stage is preserved through spermatid development until late spermiogenesis.

Animals↗
PubMed1976

Gonadotropin-induced loss of hormone receptors and desensitization of adenylate cyclase in the ovary.

Gonadotropin receptor sites and adenylate cyclase activity were analyzed in luteinized rat ovaries following injection of human chorionic gonadotropin (hCG). Gonadotropin binding capacity and hormonal stimulation of adenylate cyclase declined rapidly to a minimum at 6 to 12 h, remained depressed for 4 days, and returned to the control level between 5 and 7 days. Total adenylate cyclase activity measured in the presence of fluoride fell by 50% within a few hours but returned to normal by 24 h. A close correlation was observed between the number of gonadotropin receptors and the ability of adenylate cyclase to be stimulated by hormone. Assay of tissue-bound hormone showed that the initial loss of hormone sensitivity and binding capacity was associated with occupancy of luteinizing hormone receptor sites, but that the prolonged changes in these activities were not attributable to receptor occupancy. These studies have demonstrated that induction of a refractory or desensitized state in ovarian adenylate cyclase by gonadotropin results from the loss of specific hormone receptor sites.

Adenylyl Cyclases↗
PubMed1976

An evaluation of echography in the diagnosis of pancreatic disease.

In the present study an attempt to evaluate the efficacy of echography as a diagnostic tool has been made. A total of 52 patients (chronic pancreatitis (42); pancreatic cysts (three); and carcinoma of the pancreas (seven)) were studied and the results compared with those from other diagnostic techniques. In 65.7% of chronic pancreatitis patients, and in all cases of carcinoma of the pancreas, echography provided evidence of pancreatic abnormality but in no case could an unambiguous diagnosis of the disease be made. However, in all cases of pancreatic cyst, echography gave precise and unequivocal diagnostic information. There was good agreement between the echographic picture and surgical findings. Cholangiography and duodenography indicated duodenal and choledochal compression in a high proportion of cases in which echography revealed enlargement of the head of the pancreas. It is concluded that echography is a simple, safe, and valuable addition to the techniques available for studying the pancreas.

Adolescent↗