Showing papers by "Nelson Dusetti published in 1990"

Changes in growth and pancreatic mRNA concentrations during postnatal development of rat pancreas.

Abstract: Changes in pancreatic growth and in mRNA concentrations in rat pancreas were monitored by dot-blot hybridization with cloned cDNAs of rat amylase, chymotrypsinogen B, proinsulin I, and actin during the pre- and postnatal period in the rat. Wistar rats were killed at the 18th day of gestation and at the 1st, 10th, 20th, 35th, and 87th day of postnatal life. It was concluded from the ratio of pancreatic weight/body weight that pancreatic growth preceded body growth. Pancreatic protein and total RNA concentration increased 2.9 times during the period studies. All studied mRNAs increased in concentration during the postnatal development period. Messenger RNA for chymotrypsinogen B and proinsulin I exhibited a significant increase after birth, decreased by the 10th day of life, and increased thereafter. For amylase mRNA, no significant changes were observed around birth, a progressive increase occurring thereafter up to the 87th day of life. The mRNA for actin showed a progressive increase between the 18th day of gestation and the 20th postnatal day, after which it remained stable. We concluded that each mRNA showed a singular profile of increase during postnatal development.

Time-dependent effect of melatonin on actin mRNA levels and incorporation of 35S-methionine into actin and proteins by the rat hypothalamus.

Abstract: The synthesis of the cytoskeletal protein actin exhibits, in the rat hypothalamus, a diurnal variation with maxima during morning hours. The objective of the present study was to assess whether melatonin injection could affect the in vitro incorporation of 35S-methionine into actin, as well as the levels of actin mRNA, in the hypothalamus of adult male rats treated either acutely or chronically with the hormone at 10:00 or 18:00. Injection of 100 micrograms/kg of melatonin for ten days at either time induced a significant depression in the incorporation of 35S-methionine into a 43 kDa protein with the electrophoretic mobility of actin. The specific activity of total soluble proteins after labeled methionine incubations decreased only after evening melatonin administration (100 micrograms/kg, ten days). Hypothalamic actin mRNA levels, quantitated by dot-blot analysis, decreased only after the injection of 100 micrograms/kg melatonin for ten days at 10:00. Neither a 10-micrograms/kg dose of melatonin, nor a single injection of 100 micrograms/kg melatonin, caused any significant change in the parameters examined. Melatonin (100 micrograms/kg for ten days) did not modify hypothalamic somatostatin or H-Ras mRNA concentration. These results suggest the existence of an inhibitory effect of melatonin on hypothalamic actin synthesis.

Diurnal changes in actin mRNA levels and incorporation of 35S-methionine into actin in the rat hypothalamus.

Abstract: 1. Thein vitro incorporation of35S-methionine into actin and total soluble proteins, as well as the levels of actin mRNA, were studied in the hypothalamus and frontal cerebral cortex of adult male rats killed at six different time intervals during a 24-hr cycle. 2. The specific activity of total soluble proteins after labeled methionine incubations did not vary as a function of time of day in any of the examined brain regions. 3. The incorporation of35S-methionine into a 43-kDa protein, corresponding to the electrophoretic mobility of actin, varied diurnally in the hypothalamus, exhibiting a maximum at 1200 hr. Such a diurnal variation was not found in frontal cerebral cortex. 4. Similar results were obtained when labeled methionine incorporation into actin was assessed in hypothalamus and cerebral cortex by an immunoprecipitation procedure. 5. An increase in actin hypothalamic mRNA levels, quantitated by dot-blot analysis, was found at 0800, 4 hr in advance to the maximum in35S-methionine incorporation to actin. 6. The levels of actin mRNA did not vary significantly as a function of time of day in the frontal cerebral cortex.