Studies on secretory glycoproteins in the rat exocrine pancreas. III. Intracellular transport of fucose-labeled proteins as studied by cell fractionation

The transcellular movement of fucosylated glycoproteins has been studied in vitro using rat pancreatic lobules and cell fractionation procedures, and has been compared with the well established pathway of secretory proteins. Using tritiated leucine as pulse label for the latter, their translocation from the rough endoplasmatic reticulum into the Golgi complex and finally into zymogen granules could be followed. In the case of glycoproteins, 14C-fucose was incorporated mainly into the smooth microsomal fraction (representative of the Golgi complex) and only one third of this specific activity was transported into the zymogen granule fraction. A detailed analysis of this fraction after separation of the content of zymogen granules from their membranes revealed a predominant labeling of membrane glycoproteins by 14C-fucose. In comparison, leucine-labeled bulk proteins were found almost exclusively in the zymogen granule content fraction, with little radioactivity in the membrane fraction. The data indicate a concomitant synthesis of fucosylated glycoproteins destined in part for the zymogen granule membrane and to a greater amount associated with the smooth microsomal fraction. The results are discussed in the light of recent findings indicating that about 40% of the proteins in the zymogen granule membrane are made up of one major glycoprotein which could be involved in the mechanism of exocytosis.

Effect of glucagon on the secretory process in the rat exocrine pancreas

Glucagon was infused into conscious rats in doses of 10 to 80 microgram/h for periods up to 24 h. The effect on the secretory process of the exocrine pancreas was studied in vitro using isolated pancreatic lobules. A pronounced inhibition of the rate of protein synthesis and discharge of stored and newly synthesized proteins combined with increased enzyme content in the pancreas were observed after 30 min infusion. This effect was absent after longer infusion periods of up to six hours. After 12 to 24 h infusions a marked degranulation and decrease in enzyme content was observed. While the rate of protein synthesis was not significantly enhanced, both the basal and stimulated discharge of enzymes from the pancreas were increased. The results suggest a biphasic response of the pancreas to prolonged glucagon infusion.

Learning child psychiatry skills on the adult inpatient service

Integration of child psychiatry training into general psychiatric residency programs is often unsuccessful. The authors describe an innovative model of training in child psychiatry that involves the children of adult inpatients. This model offers several advantages: splitting of child-adult psychiatric training is avoided, child diagnostic and evaluative skills tend to be learned rapidly, preventive orientations develop, and family process is both learned and used. Preliminary experience with this model on two inpatient services suggests that it is both didactically effective and economical in child psychiatry staff hours.

Regulation of exocrine pancreatic secretory process by insulin in vivo

The three major phases in the secretory process in the exocrine pancreas (synthesis, intracellular transport, zymogen discharge) have been tested in vitro after changing circulating insulin levels in rats in vivo. One group of rats received a continuous infusion of glucose for periods up to 72 hours, which keeps blood glucose levels above 200 mg/100 ml and immunoreactive insulin (IRI) raised to 130 muU/ml. As a result of this treatment, amylase content in the pancreas increases by 25% while chymotrypsinogen and lipase show a comparable decrease. The rate of total protein synthesis increased by 40% after 48 hours of infusion. The basal and carbamylcholine stimulated discharge of newly synthesized proteins are not altered. The baseline discharge of amylase is increased significantly, while the discharge of lipase and chymotrypsinogen decreased below control levels. Similar results are obtained, if circulating insulin levels are raised by the application of glibenblamide (HB419) for a period of 24 hours. Protein synthesis increases by 26.5% and baseline discharge of amylase by 50%. In chronic alloxan diabetic animals the alteration of the exocrine pancreatic function depends on the severity of the diabetes and relates to circulating insulin levels. Animals with highest blood glucose levels and low or undetectable insulin concentrations show a disappearance of amylase from the exocrine pancreas and a depression of the rate of protein synthesis by 30%. The results suggest a direct effect of insulin on protein biosynthesis and zymogen discharge, most pronounced for amylase.

The effect of age on -adrenoceptor activity in tracheal smooth muscle

There was an age-related reduction of the sensitivity of rat and guinea-pig isolated tracheal smooth muscles to stimulation of beta-adrenoceptors, but the ability of tracheal smooth muscle to relax to isoprenaline was not completely lost.

Early clinical responsibility for medical students

Trends in medical education point to accelerated training in medical schools and postgraduate medical education. In a shortened curriculum, opportunities for major clinical responsibility may decrease, though it is generally acknowledged that medical students learn most effectively when given such responsibility. This paper presents the results of a questionnaire evaluating the experience of third- and fourth-year medical students who assumed major clinical responsibility on a short-term psychiatric inpatient service in a general hospital. An open-ended questionnaire was sent to the twenty-seven medical students who were on the service during the 1968–69 academic year. All but one student in each year described a positive experience in assuming major clinical responsibility. An important finding was that much anxiety and depression were present in both years, particularly in the third year. One of the implications of this study is the possibility that major patient responsibility for medical students can be successful even earlier than the third year in psychiatry and other clinical areas provided that the staff can anticipate and supportively help the students with their probably even greater anxiety and depression.