Aquatic vegetation and largemouth bass population responses to water-level variations in Lake Okeechobee,Florida (USA)

A five-year study examined the responses of submerged aquatic vegetation (SAV), emergent vegetation, and largemouth bass (Micropterus salmoides) to variations in water level in a large lake in Florida, USA. SAV was assessed using a combined transect survey/spatial mapping approach, emergent vegetation was quantified with aerial photography and GIS, and bass were surveyed by electro-shocking. During the period leading up to this study (1995–1999), water levels were high in the lake, and the SAV was reduced in spatial extent and biomass, compared to its condition in the early 1990s. Spatial extent of emergent vegetation also was low, and largemouth bass surveys indicated low densities and failure to recruit young fish into the population. This was attributed to the lack of critical vegetative habitat. In spring 2000, the lake was lowered by discharging water from major outlets, and this was followed by a regional drought. Water levels dropped by 1m, and there was widespread development of Chara lawns in shoreline areas, with coincident increases in water clarity. There was some germination of vascular SAV, but Chara was the extreme dominant, such that structural complexity remained low. There was no substantive improvement in bass recruitment. During 2001, water levels declined further, and emergent plants germinated in exposed areas of the lake bottom. SAV was restricted to sites farther offshore, and continued to be dominated by Chara. There again was no bass response. In 2002, conditions changed when water levels increased to a moderate depth, flooding shoreline habitat to 0.5m. Vascular SAV increased in biomass and spatial extent, such that the community developed a high structural complexity. At the same time, emergent aquatic plants developed dense stands along the western shoreline. Largemouth bass had a strong recruitment of young fish for the first time in 5years. Recruitment continued to be successful in 2003, when spatial extent of SAV was somewhat reduced by higher water but total biomass and diversity remained high. These results demonstrate an important effect of inter-annual variation in water depth on the population dynamics of aquatic plants and fish in a subtropical lake.     

Heritable variation in seed sex ratio of the stinging nettle (Urtica dioica)

Male and female flowering plants of the dioecious Urtica dioica occur in approximately equal numbers in our study area on the coastal sand dunes of Meijendel. The seed sex ratio (SSR, fraction of males) collected from female plants in the field varied between 0.05 and 0.76, and differed significantly between maternal parents. After one generation of selection for either high or low SSR, female plants produced seed batches with sex ratios as extreme as 0.08 and 0.73. Natural populations of U. dioica harbour considerable genetic variation in SSR.     

Effect of exogenous JHI on imaginal determination in Aeshna cyanea

Last instar larvae of Aeshna cyanea injected with 8 μg or more JHI before the end of the fourth ocular stage (day 7 or 8 of the instar) became perfect supernumerary larvae which indicates that adult determination does not occur before this time. When JHI is applied later (days 9–13) larval-adult intermediates are formed. It seems, therefore, that imaginal programming takes place at the end of the fourth ocular stage and might be correlated with the first ecdysone peak which occurs at the same time.     

Characterization of N alpha-acetyl methionyl human growth hormone formed during expression in Saccharomyces cerevisiae with liquid chromatography and mass spectrometry

We found a new variant of human growth hormone (hGH) from the recombinant hGH expression process in Saccharomyces cerevisiae. The variant was identified as N(alpha)-acetyl methionyl hGH which may be formed by N(alpha)-acetylation of met-hGH during the intracellular expression of hGH in S. cerevisiae. The variant was isolated from manufacturing process of LG Life Sciences' hGH product. The variant was subjected to trypsin digestion and RP-HPLC analysis, resulting in a delayed retention time and an increased mass (173 Da) of T1 tryptic peptide. The amino acid composition and amino acid sequence of the peptide showed the same result with T1 peptide of met-hGH except the N-terminal modification on methionine in the variant peptide. With collision induced dissociation (CID) experiments of the variant T1 tryptic peptide, we found the sequence and the a(1) fragment of N-terminal residue matched with those of acetyl-methionyl hGH. Within our production process, we produce the methionyl hGH first and then use the aminopeptidase to cut the N-terminal methionine. So the acetylation may inhibit the aminopeptidase to remove methionine and produces N(alpha)-acetyl methionyl hGH. And the biological activity of the variant was comparable to one of the unmodified hGH when tested by rat weight gain bioassay.     

Proteomics analysis of growth hormone isoforms in the human pituitary

In order to elucidate the roles of human growth hormone (hGH) in the normal (control) pituitary and in adenomas, the hGH isoforms in the human pituitary were analyzed with two-dimensional gel electrophoresis, immobilized metal affinity column (Ga(+3)) chromatography, mass spectrometry (MS), and bioinformatics. Twenty-four hGH-containing proteins, with significantly different expression proportions of their isoforms were found. The proportions of isoforms were as follows: isoform 1 (87.5%) > isoform 2 (8.1%) > isoform 3 (3.3%) > isoform 4 (1.1%). Deamidation of asparagine to aspartate was identified with matrix-assisted laser desorption/ionization-time of flight MS. Tandem mass spectrometry data demonstrated that hGH is a phosphoprotein (spot 6); phosphorylation was found at Ser-77 in the tryptic peptide (68)YSFLQNPQTSLCFSESIPTPSNR(90), at Ser-176 in the tryptic peptide (172)FDTNSHNDDALLK(184), and at Ser-132 in the peptide (126)SLVYGASDSNVYDLLK(141). The phosphorylation sites at Ser-77 and Ser-176 were consistent with computer-program predictions (NetPhos). These results provide novel clues for further studies of the functions, and mechanisms of action, of hGH in the human pituitary and in growth hormone-related diseases.     

Clutch size: a major sex ratio determinant in fig pollinating wasps?

Under local mate competition, sex ratio theory predicts that increasing numbers of ovipositing females (foundresses) on a site should lead to higher proportions of males in their broods. Fig pollinators have confirmed this prediction. It is also predicted that with decreasing clutch size, solitary foundresses should produce increasing proportions of sons. We show this to be true. Further, when several females compete, brood size decreases. As a result, the proportion of males increases, and this could provide a mechanistic explanation of sex ratio response to numbers of colonizing females. Therefore, sex ratio data on fig wasps need to be reassessed to determine whether females 'count' other foundresses, as is generally accepted, or whether they simply 'count' the number of eggs that they lay.     

Expression of insulin-like growth factor-1 and insulin-like growth factor-1 receptors in EL4 lymphoma cells overexpressing growth hormone

Almost all of the previous studies with growth hormone (GH) have been done with exogenously supplied GH and, therefore, involve actions of the hormone through its receptor. However, the actions of endogenous or lymphocyte GH are still unclear. In a previous study, we showed that overexpression of GH (GHo) in a lymphoid cell line resulted in protection of the cells to apoptosis mediated by nitric oxide (NO). In the present study, we show that the protection from apoptosis could be transferred to control cells with culture fluids obtained from GHo cells and blocked by antibodies to the insulin-like growth factor-1 (IGF-1) or antibodies to the IGF-1-receptor (IGF-1R). Northern and Western blot analysis detected significantly higher levels of IGF-1 in cells overexpressing GH. An increase in the expression of the IGF-1R in GHo cells was also detected by Western blot analysis, (125)I-IGF-1 binding and analysis of IGF-1R promoter luciferase constructs. Transfection of GHo cells with a dominant negative IGF-1R mutant construct blocked the generation of NO and activation of Akt seen in GHo cells compared to vector alone control EL4 cells. The results suggest that one of the consequences of the overexpression of GH, in cells lacking the GH receptor, is an increase in the expression of IGF-1 and the IGF-1R which mediate the protection of EL4 lymphoma cells from apoptosis.     

Hypercalcemia produced by parathyroid hormone suppresses experimental autoimmune encephalomyelitis in female but not male mice

Besides its role in regulating serum levels of calcium and phosphorus, 1alpha, 25-dihydroxyvitamin D3 (1,25-(OH)2D3) has potent effects on the immune system and suppresses disease in several animal models of autoimmune disorders including experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. While the amount of 1,25-(OH)2D3 needed to prevent EAE is dependent on the gender of the mouse and amount of calcium available in the diet, the minimum levels of 1,25-(OH)2D3 sufficient to prevent disease cause hypercalcemia. To test if hypercalcemia independent of high levels of 1,25-(OH)2D3 can suppress EAE, we used a 25-hydroxyvitamin D3-1alpha-hydroxylase (1alpha-hydroxylase) knockout mouse strain. Because these 1alpha-hydroxylase knockout mice lack the parathyroid hormone (PTH)-regulated enzyme that synthesizes 1,25-(OH)2D3, hypercalcemia from increased bone turnover was created by continuous administration of PTH without changing the circulating levels of 1,25-(OH)2D3. This PTH-mediated hypercalcemia generated after EAE induction prevented disease in female mice but not male mice. When hypercalcemia was prevented by diet manipulation, PTH administration no longer prevented EAE. We conclude that hypercalcemia is able to prevent EAE after disease induction in female mice.     

Microsomal triglyceride transfer protein expression in adipocytes: a new component in fat metabolism

Microsomal triglyceride transfer protein (MTP) is a carrier of triglyceride essential for the assembly of apolipoprotein (apo)B-containing lipoproteins by the liver and the small intestine. Its role in triglyceride transfer in tissues that do not secrete lipoproteins has not been explored. In particular, MTP would seem to be a candidate for a role in triglyceride metabolism within the adipocyte. To test this hypothesis, we probed adipocytes for the presence of MTP. Immunohistochemical and biochemical studies demonstrate MTP in adipocytes from brown and white fat depots of mice and human, as well as in 3T3-L1 cells. Confocal microscopy revealed MTP throughout 3T3 cells; however, MTP fluorescence was prominent in juxtanuclear areas. In differentiated 3T3 cells MTP fluorescence was very striking around lipid droplets. In vitro lipid transfer assays demonstrated the presence of triglyceride transfer activity within microsomal fractions isolated from rat adipose tissue. In addition, quantitative rtPCR studies showed that MTP expression in mouse white fat depots was approximately 1% of MTP expression in mouse liver. MTP mRNA in differentiated 3T3 cells was approximately 13% of liver expression. Our results provide unequivocal evidence for the presence of MTP in adipocytes and present new possibilities for defining the mechanisms by which triglyceride is stored and/or hydrolyzed and mobilized.