Experimental Biology and Medicine

Given the close relationship among neuroendocrine systems, it Is likely that there may be common signals that coordinate the acquisition of adult reproductive function with other homeo-static processes. In this review, we focus on central nervous system insulin-like growth factor-1 (IGF-1) as a signal controlling reproductive function, with possible links to somatic growth, particularly during puberty. In vertebrates, the appropriate neurosecretion of the decapeptide gonadotropin-releas-ing hormone (GnRH) plays a critical role in the progression of puberty. Gonadotropin-releasing hormone is released in pulses from neuroterminals in the median eminence (ME), and each GnRH pulse triggers the production of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These pituitary hormones in turn stimulate the synthesis and release of sex steroids by the gonads. Any factor that affects GnRH or gonadotropin pulsatility is important for puberty and reproductive function and, among these factors, the neurotrophic factor IGF-1 is a strong candidate. Although IGF-1 is most commonly studied as the tertiary peripheral hormone in the somatotropic axis via its synthesis in the liver, IGF-1 Is also synthesIzed in the brain, within neurons and glia. In neuroendocrine brain regions, central IGF-1 plays roles in the regulation of neuroendocrine functions, including direct actions on GnRH neurons. Moreover, GnRH neurons themselves co-express IGF-1 and the IGF-1 receptor, and this expression is developmentally regulated. Here, we examine the role of IGF-1 acting in the hypothalamus as a critical link between reproductive and other neuroendocrine functions.

Secretion occurs in all living cells and involves the delivery of intracellular products to the cell exterior. Secretory products are Packaged and stored in membranous sacs or vesicles within the cell. When the cell needs to secrete these products, the secretory vesicles containing them dock and fuse at plasma membrane-associated supramolecular structures, called poro-somes, to release their contents. Specialized cells for neurotransmission, enzyme secretion, or hormone release use a highly regulated secretory process. Similar to other fundamen-tal cellular processes, cell secretion is precisely regulated. During secretion, swelling of secretory vesicles results in a build-up of intravesicular pressure, allowing expulsion of vesicular contents. The extent of vesicle swelling dictates the amount of vesicular contents expelled. The discovery of the Porosome as the universal secretory machinery, its isolation, its structure and dynamics at nanometer resolution and in real time, and its biochemical composition and functional reconstitution into artificial lipid membrane have been determined. The Molecular mechanism of secretory vesicle swelling and the fusion of opposing bilayers, that is, the fusion of secretory vesicle membrane at the base of the porosome membrane, have also been resolved. These findings reveal, for the first time, the universal molecular machinery and mechanism of secretion in cells.

Copper (Cu) deficiency in rats reduces the relative concentration of duodenal hephaestin (Hp), reduces Iron (Fe) absorption, and causes anemia. An experiment was conducted to determine whether these effects could be reversed by dietary Cu repletion. Five groups of eight weanling male rats each were used. Group 1 was fed a Cu-adequate diet (5.0 mg Cu/kg; CuA) and Group 2 was fed a Cu-deflcient diet (0.25 mg Cu/kg; CuD) for 28 days. The rats were fed 1.0 g each of their respective diets labeled with ⁵⁹Fe (37 kBq/g), and the amount of label retained was measured one week later by whole-body-counting (WBC). Group 3 was fed a CuA diet and Groups 4 and 5 were fed a CuD diet for 28 days. Group 5 was then fed the CuA dlet for another week while Groups 3 and 4 continued on their previous regimens. Rats In Groups 3, 4, and 5 were fed 1.0 g of diet labeled with ⁵⁹Fe, and the amount of label retained was measured by WBC one week later. Rats were killed and duodenal enterocytes Isolated for Hp protein analysis, whole blood was analyzed for hematological parameters, and various organs for ⁵⁹Fe content. CuD rats absorbed less (P <0.05) Fe than CuA rats, the relative amount of duodenal Hp was less (P <0.05) In CuD rate, and the CuD rats developed anemia. After the CuD rats had been repleted with Cu for one week, Fe retention rose to values even higher (P <0.05) than those in CuA rats. After two weeks, the relative amount of duodenal Hp was higher (P <0.05) than normal, and most signs of anemia were reversed. Liver ⁵⁹Fe was elevated In CuD rats, but was restored to normal upon Cu repletion. These findings suggest a strong association between duodenal Hp abundance and Fe absorption In the CuD rat, and that reduced Fe absorption Is an important factor in the cause of anemia.

Prostaglandins (PGs) are known to modulate the proper cycllcity of bovine reproductive organs. The main luteolytlc agent in ruminants Is PGF_2α, whereas PGE₂ has luteotropic actions. Estradiol 17ß (E₂) regulates uterus function by influencing PG synthesis. Phytoestrogens structurally resemble E₂ and possess estrogenic activity; therefore, they may mimic the effects of E₂ on PG synthesis and influence the reproductive system. Using a cell-culture system of bovine epithelial and stromal cells, we determined cell-specific effects of phytoestrogens (i.e., daidzein, genistein), their metabolites (i.e., equol and para-ethyl-phenol, respectively), and E₂ on PGF_2α and PGE₂synthesis and examined the intracellular mechanisms of their actions. Both PGs produced by stromal and epithelial cells were significantly stimulated by phytoestrogens and their metabolites. However, PGF_2α synthesis by both kinds of cells was greater stimulated than PGE₂ synthesis. Moreover, epithelial cells treated with phytoestrogens synthesized more PGF_2α than stromal cells, increasing the PGF_2α, to PGE₂ ratio. The epithelial and stromal cells were prelncubated with an estrogen-receptor (ER) antagonist (i.e., ICI), a transiation inhibitor (i.e., actinomycin D), a protein kinase A inhibitor (i.e., staurosporin), and a phospholipase C inhibitor (i.e., U73122) for 0.5 hrs and then stimulated with equol, para-ethyl-phenol, or E_2- Although the action of E₂ on PGF_2α synthesis was blocked by all reagents, the stimulatory effect of phytoestrogens was blocked only by ICI and actinomycin D in both cell types. Moreover, in contrast to E₂action, phytoestrogens did not cause Intracellular calcium mobilization in either epithelial or stromal cells. Phytoestrogens stimulate both PGF_2α and PGE₂ in both cell types of bovine endometrium via an ER-dependent genomic pathway. However, because phytoestrogens preferentially stimulated PGF_2α synthesis in epithelial cells of bovine endometrium, they may disrupt uterus function by altering the PGF_2α to PGE₂ ratio.

This study examined the contribution of hypothalamic neuronal histamine (HA) to the anorectic and febrlle responses induced by lipopolysaccharide (LPS), an exogenous pyrogen, and the endogenous pyrogens interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Intraperitoneal (ip) Injection of LPS, IL-1β, or TNF-α suppressed 24-hr cumulative food intake and increased rectal temperature in rats.

To analyze the histamlnergic contribution, rats were pre-treated with intracerebroventricular (icv) injection of 2.44 mmol/ kg or ip injection of 244 mmol/kg of α-fluoromethylhistidine (FMH), a suicide inhibitor of histidine decarboxylase (HDC), to deplete Neural HA. The depletion of neural HA augmented the febrile response to ip Injection of LPS and IL-1ß and alleviated the anorectic response to ip injection of IL-1ß. However, the depletion of neural HA did not modify the LPS-lnduced anorectic response or TNF-α-induced febrile and anorectic responses. Consistent with these results, the rate of hypothalamic HA turnover, assessed by the accumulation of tele-methylhistamine (t-MH), was elevated with ip injections of LPS and IL-1ß, but unaffected by TNF-α at equivalent doses. This suggests that (I) LPS and IL-1ß activate hypothalamic neural HA turnover; (II) hypothalamic neural HA suppresses the LPS- and IL-1β-induced febrile responses and accelerates the IL-1ß-induced anorectic response; and (iii) TNF-α modulates the febrile and anorectic responses via a neural HA-independent pathway. Therefore, hypothalamic neural HA is Involved in the IL-1ß-dominant pathway, rather than the TNF-α-dominant pathway, preceding the systemic Inflammatory response induced by exogenous pyrogens, such as LPS. Further research on this is needed.

Transmissible spongiform encephalopathies are a group of infectious diseases typically associated with the accumulation of a protease-resistant and ß-sheet-rich prion protein, PrP^Sc, in affected brains. PrP^Sc is an altered isoform derived from the host-encoded glycoprotein, PrP^c. The expression of PrP^c is the highest in brain tissue, but it can also be detected at low levels in peripheral tissue. However, it is unclear whether a significant amount of PrP^c is released into body fluid and excreted into urine. We have developed a simple, rapid method for the reliable detection of PrP^c in urine from normal subjects by Western blotting. Our method can easily and reliably detect PrP^c in apparently healthy individuals using less than 1 ml of urine in which the amount of urinary PrP^c is estimated to be in the range of low micrograms/liter.