PubMed Health⌕ Search

Biomedical subjects

A E Lambert

Publications and source records attributed to A E Lambert.

At least 73 records · Page 4Linked to original sources
PubMed1975

Cobalt inhibition of insulin secretion and calcium uptake by isolated rat islets.

Cobalt (Co'++) inhibited glucose-, leucine-, and K'+-induced immunoreactive insulin (IRI)release by isolated rat islets. This inhibition of the insulinotropic effect of glucose was dose dependent, affected both phases of secretion, was very rapid, and was well reversible. It exhibited a kinetics similiar to that of Ca'++ omission, and the metal (2.5 mM) prevented Ca'++ reintroduction from restoring a normal rate of IRI release. Theophylline (2 mM) partially overcame the inhibitory effect of 0.5 mM Co'++, but not that of 2.5 mM. Glucose-induced secretion was lessmarkedly reduced by 0.5 mM Co'++ in the absence of Mg'++ or in the presence of 7.5 mM Ca'++. Even at 12.5 mM, the metal did not alter glucose oxidation by theislets. By contrast, Ca uptake by islet cells was reversibly diminished (55%) in the presence of 1.25 mM Co'++. Calcium influx (measured after 2.5 min) was aslo reduced by Co'++ to a degree that did not change after longer incubation periods. It is concluded that Co'++ inhibits IRI release mainly through an antaognistic action on Ca entry in beta cells.

Animals↗
PubMed1973

Pronase effect on pancreatic beta cell secretion and morphology.

Pronase at low concentration (4 micrograms per milliliter) produces a reversible increase of glucose-stimulated insulin release in isolated islets of Langerhans. Pronase also affects the ultrastructure of the beta cells by inducing extensive development of tight junctions as well as the accumulation of secretory product within the extracellular spaces.

Animals↗
PubMed1971

Morphological and biochemical studies of B cells of fetal rat endocrine pancreas in organ culture. Evidence for (pro) insulin biosynthesis.

Fetal rat pancreases explanted on the 18th day of gestation and maintained in organ culture for 1-10 days were utilized for this series of studies. Ultrastructurally, at the time of explantation, the majority of fetal B cells was sparsely granulated and characterized by numerous free ribosomes and undeveloped rough endoplasmic reticulum (RER) and Golgi complexes. During the culture period, extensive development of the RER and Golgi complexes preceded an increasing accumulation of beta-granules. This later increase in the number of beta-granules and in the concentration of immunoreactive insulin was paralleled by a reduction of RER and Golgi complex activity. High resolution radioautographic studies of pulse-chase experiment over a 1 hr period demonstrated the shift of silver grains from the elements of the RER, through the Golgi region, and finally to the beta-granules. Incubation with (14)C-labeled leucine demonstrated the incorporation of radioactivity into molecules possessing the immunological and electrophoretic properties of insulin. These studies indicate that de novo synthesis of (pro)insulin occurs also during culture of fetal rat pancreas explanted relatively late in gestation.

Animals↗