Dynamics of follicular growth and atresia of large follicles during the ovarian cycle of the guinea pig: fate of the degenerating follicles, a quantitative study.

Background: A quantitative integrated study of healthy ovarian follicles of different sizes and their mitotic activity and of clearly defined atretic stages of involuting large growing follicles at different stages of the guinea pig ovarian cycle is not available in the literature. We considered that such a study would reveal new aspects of ovarian tissue dynamics and provide new information in an organ with a continuous phenotypic transformation of its cellular components.

Methods: Ovaries from guinea pigs were removed on days 1 (opening of the vagina), 3, 6, 9, 13, and 16 of the cycle, and the following were measured in serial sections: (1) total number of healthy follicles falling into categories based on the volume occupied by granulosa cells, (2) total number of atretic follicles falling into clearly defined morphological stages of the degenerative and involutionary process affecting medium to large follicles, and (3) proportion of metaphase-arrested granulosa cells, after colcemid injection, in healthy follicles of different size categories.

Prevention of spontaneous but not of adoptively transferred diabetes by injection of neonatal BB/hooded hybrid rats with splenocytes or concanavalin A blasts from diabetes-free strains.

Spontaneous diabetes was fully prevented in 65 BB/hooded (BB/h) highly diabetes-prone hybrid rats that were given five intraperitoneal injections (25 to 30 x 10(6) cells/injection) of fresh splenocytes or concanavalin A (ConA)-activated cultured splenocytes (blasts) from the diabetes-free Wistar-Furth or Long-Evans strains during the first 2 postnatal wk. Rats remained under observation for up to the age of 180-200 days. Of 70 littermate controls that received no cell injections, 63 developed overt diabetes before the age of 180 days.

Adoptive transfer of insulitis and diabetes in neonates of diabetes-prone and -resistant rats. Tissue localization of injected blasts.

Intravenous transfusion of concanavalin A-activated splenic cells from acutely diabetic BB or diabetic BB/hooded hybrid donor rats into 6- to 36-h-old neonate recipients of diabetes-prone and -resistant rat lines induced insulitis and in some severe diabetes. These effects were observed 10-20 days after the injection of the blasts. Focal lesions of insulitis were absent in neonates killed 1 and 3 days after the blast injection but were observed in neonates killed on the 5th and 8th day.

Hormonal and non-hormonal protein biosynthesis in the pancreatic beta cell of the intact rat after prolonged hyperglycaemia.

We examined the relative changes in the rates of biosynthesis of (pro)insulin and of non-hormonal beta cell proteins in rats with pronounced hyperglycaemia for up to several days. Labelling of pancreatic cells in vivo eliminated certain pitfalls that we encountered when isolated pancreatic islets from these rats were labelled in vitro. Rats were infused with glucose or buffer solutions for 24 and 72 h.

Complement-fixing islet cell antibodies in the spontaneously diabetic BB rat.

Fourteen rats of the spontaneously diabetic BB line were bled from the retroorbital sinus approximately every 10 days. Sera taken from an early age up to 20 days after the onset of overt diabetes were assayed for complement-fixing antibodies against antigens of the surface of islet cells (CFA). Dispersed islet cells from normal Wistar rats prelabeled with 3H-leucine were used as targets.

The onset and progression of pancreatic insulitis in the overt, spontaneously diabetic, young adult BB rat studied by pancreatic biopsy.

A specially developed clamping procedure permitted the easy, complication-free removal of splenic pancreas from rats. Using this biopsy procedure pancreatic tissue was removed from 50- to 90-day-old BB rats to study in a retrospective experimental design the time at which insulitis appears in BB rats, which develop acute, overt diabetes before the age of 120 days. Islets in biopsies taken 18-53 days before the onset of diabetes showed normal structure and were free from any mononuclear infiltrations.

Glucose stimulation of beta-cell DNA replication in the intact rat and in pancreatic islets in suspension culture. Effects of alpha-ketoisocaproic acid, dibutyryl cyclic AMP, and 3-isobutyl-1-methylxanthine in the in vitro system.

DNA replication in pancreatic beta-cells was compared in intact rats maintained hyperglycemic by continuous glucose infusion up to 10 days and in rat islets maintained in suspension culture in RPMI 1640 medium up to 12 days. Replicative activity was evaluated by counting the proportion of labeled beta-cell nuclei after injection or addition of [3H]thymidine. In both experimental systems, DNA replication initially was markedly stimulated by high glucose; then it subsided, even though high levels of glucose were maintained.

In vivo incorporation of [3H[ leucine and [3H] tryptophan into proinsulin-insulin and other islet cell proteins in normoglycemic, hyperglycemic, and hypoglycemic rats.

Rats were infused for brief periods with buffer, glucose, or insulin. L-[4,5-3H] leucine (2.5 mCi) or L-[2,3-3H]-tryptophan (0.

Biosynthesis of proinsulin and other islet cell proteins in pancreatic beta cells of the rat: a radioautographic evaluation of glucose effects in vitro.

Rat pancreatic islets were incubated in vitro with L-[4,5-3H]leucine or with L-[2,3-3H]tryptophan in Krebs-Ringer bicarbonate buffer, containing 0, 5, or 20 mM glucose. Incorporation of labeled amino acids in islet cells was evaluated quantitatively by a validated radioautographic procedure. Incorporation of labeled leucine into [3H]proinsulin and [3H]insulin was measured by immunoprecipitation and into other islet proteins by trichloroacetic acid precipitation.

Stimulation of proinsulin biosynthesis and insulin release by pyruvate and lactate.

Increasing concentrations of pyruvate failed to stimulate proinsulin biosynthesis and insulin release in freshly isolated islets. Glycolytic flux (3H2O from [5-3H]glucose) decreased by 80-85%, but decarboxylation of [1(-14)C]pyruvate was unaffected in islets tested immediately after alloxan exposure. This strongly suggested that in freshly isolated islets, beta-cells, in relation to other islet cells, hardly contribute to the decarboxylation of pyruvate.

Metabolic signals produced by purine ribonucleosides stimulate proinsulin biosynthesis and insulin secretion.

Inosine, guanosine and adenosine strongly stimulated proinsulin biosynthesis and insulin secretion in isolated mouse pancreatic islets. None of the purine ribonucleosides stimulated insulin secretion in rat islets, although as reported [jain & Logothetopoulos (1977) Endocrinilogy 100, 923-927] inosine and guanosine, but no adenosine, were potent stimulants of proinsulin biosynthesis in this species. The purine bases had no effect in either species.

Secretion of insulin in a perifusion system and conversion of proinsulin to insulin by pancreatic islets from hyperglycemic rats.

The secretory pattern of insulin and the rate of conversion of proinsulin to insulin were studied in isolated pancreatic islets from normoglycemic (buffer-infused for 24 hours) and hyperglycemic (glucose-infused for 24 hours) rats. The profiles of insulin secretion obtained during one hour of perifusion were markedly different in the two groups. The rate of insulin secretion by islets from the hyperglycemic rats was initially very high but progressively declined during the late period of the perifusion.

Stimulation of proinsulin biosynthesis by purine-ribonucleosides and D-ribose.

Inosine and guanosine were potent stimuli of proinsulin biosynthesis ([3H]leucine incorporation) in isolated pancreatic islets of the rat. The effect was nearly abolished by formycin B, an inhibitor of purine nucleoside phosphorylase, but not by D-mannoheptulose. The corresponding bases had no effect on the rate of proinsulin biosynthesis.

Proinsulin biosynthesis by pancreatic islets of the rat and the study of alloxan cytotoxicity in vitro.

Incorporation of L-[4,5-3H] leucine into proinsulin plus insulin by isolated pancreatic islets was shown to be severely inhibited by previous brief exposure to 1.25 mM alloxan, but incorporation into other islet proteins was not affected. The system proved valuable for the study of the prevention of alloxan cytotoxicity by various carbohydrates and carbohydrate derivatives.

The effects of D- and L-glyceraldehyde on glucose oxidation, insulin secretion and insulin biosynthesis by pancreatic islets of the rat.

D-glyceraldehyde stimulated insulin secretion from isolated rat pancreatic islets in static incubation and perifusion systems. At low concentrations (2-4 mM) D-glyceraldehyde was a more potent secretagogue than glucose. The insulinotropic action of 15 mM D-glyceraldehyde was not affected by D-mannoheptulose, was potentiated by cytochalasin B (5 mug/ml) and theophylline (4 mM), and was inhibited by both adrenalin (2 muM) and somatostatin (10 mug/ml).

Persisting enhanced proinsulin-insulin and protein biosynthesis (3H-leucine incorporation) by pancreatic islets of the rat after glucose exposure.

Pancreatic islets isolated from rats infused with glucose for twenty-four hours incorporated 3H-leucine into protein at higher rates than islets isolated from normoglycemic rats. Incorporation into proinsulin-insulin showed a thirteenfold increase. The effect on other islet proteins was fourfold.

A specific anti-proinsulin serum and the presence of proinsulin in calf serum.

A specific antibody against proinsulin has been obtained by adsorbing the original anti-proinsulin guinea pig serum with a solid immunosorbent of Sephadex-insulin. The specificity of the antibody against antigenic determinants of proinsulin was established by radioimmunoassay and by passive cutaneous anaphylaxis (PCA) tests. The presence of proinsulin in calf serum has been demonstrated by (a) gel filtration of an acid alcohol extract of the serum followed by immunoassays of the fractions using anti-insulin or the specific anti-proinsulin serum, and (b) direct assay of calf serum with the specific anti-proinsulin serum.