Autoradiographic localization of binding sites for follicle stimulating hormone (FSH) in the boar testis.

The tubular localization of binding sites for 125I-FSH is demonstrated in vitro by the autoradiography on frozen sections of boar-testis. The uniform distribution of silver grains throughout the seminiferous epithelium suggests the presence of receptors for FSH also in the adluminal compartment. Similar results have been obtained using rat testis.     

Effects of picric acid-formaldehyde fixation on the LH(HCG) receptors' binding activity in the rat testis. A histochemichal model for qualitative and quantitative studies.

PAF (picric acid-formaldehyde) fixation of rat testis for a short time at 0-4 degrees C was found to give satisfactory histological results and to preserve most of the specific binding activity of LH(HCG) receptors. Investigations of the characteristics of the hormone-receptor reaction after mild PAF fixation indicated that this reaction was not substantially affected in hormne receptor affinity and its own specificity; only the capacity of the receptors was lowered by about 20%. A histochemical model is presented whose main features are: fixation of testis tissue in PAF; freezing in liquid nitrogen and cutting in the cryostat; radiolabelled hormone-receptor binding reaction performed on the sections; autoradiography to reveal the binding reaction. The utility of the method for qualitative and quantitative receptor studies and its possible application to biopsy and surgical specimens, are discussed.     

Increasing temperatures affect multiyear life cycle of the outbreak bush-cricket Barbitistes vicetinus (Orthoptera,Tettigoniidae)

Although outbreaks of rare species are unusual, several insect species have become emerging pests probably due to the ongoing environmental changes. Barbitistes vicetinus was first described in 1993 as an endemic bush-cricket of north-east Italy and was considered rare until 2008, when it became an established pest, causing severe damages to forests and crops. The possible role of temperature in changing its life cycle has still to be fully understood. Here, we explored the effect of summer temperature on egg diapause and the effect of winter temperature on egg survival. Field observations showed that the proportion of embryos that can complete development at the end of summer ranged from zero to nearly 90% depending on summer temperatures. A substantial shift in the rate of development from 20% to nearly 80% occurred in a thermal range of about 1 °C. On the contrary, overwinter egg survival was high and constant (90%) across a wide range of winter temperatures that go well beyond both the cold and warm thermal limits of the current species range. Overall, the results suggest a potential key role of summer temperature warming on the outbreak propensity of this species that is able to switch from a multiyear to an annual life cycle with just a 1–2 °C warming.     

Inhibition of basal insulin secretion induces insulin resistance in normal man: evidence for a tonic effect of insulin on carbohydrate metabolism

Insulin resistance has been demonstrated both in insulin deficiency and insulin excess in man and in animals. This study was carried out in normal man to evaluate the role of insulinopenia in the pathogenesis of insulin resistance. Insulin suppression was obtained by 4 h somatostatin (SRIF) infusion. Insulin receptors on circulating monocytes were evaluated before and after SRIF infusion; an insulin tolerance test (ITT) was performed after SRIF, saline or SRIF and replacing basal insulin secretion. Insulin binding to circulating monocytes did not change after 4 h insulinopenia (2.19 +/- 0.30 vs. 2.35 +/- 0.80%), while insulin sensitivity appeared decreased after SRIF (KITT = 0.97 +/- 0.13) as compared with saline (KITT = 3.30 +/- 0.42), and this effect was prevented by insulin (KITT = 2.46 +/- 0.38). A relationship was detected between KITT and plasma insulin concentration before ITT (r = 0.85, p less than 0.01), suggesting that insulin deficiency is the main cause of the phenomenon observed. The present data suggest that basal insulin concentration plays an essential role in the control of insulin sensitivity. If insulin binding on monocytes mimics the behavior of major insulin target tissues, it is possible that the impaired insulin action after 4 h of insulin deficiency is related to a post binding effect.