Ultrastructure of the sperm and spermatogenesis and spermiogenesis of Dina lineata (hirudinea,erpobdellidae)

The mature sperm of Dina lineata is of the modified type. The sperm are 48 μm long and 0.3 μm wide. The sperm are filiform and helicoidal cells with a distinct head, a midpiece, and a tail. There are two distinct regions in the head: the acrosome and the posterior acrosome, each with its own characteristic morphology. The midpiece is the mitochondrial region and has a single mitochondrion. Two distinct portions can be observed in the tail: the axonematic region and the terminal piece. In the process of spermatogenesis the early spermatogonia divide to form a poliplast of 512 spermatic cells. In the spermiogenesis the following sequential stages can be distinguished: elongation of the flagellum; reciprocal migration of mitochondria and Golgi complex; condensation of chromatin and formation of the posterior acrosome; spiralization of nuclear and mitochondrial regions; and, finally, formation of the anterior acrosome. The extreme morphological complexity of the Dina spermatozoon is related to the peculiar hypodermal fertilization which characterizes the erpobdellid family. Correlation between sperm morphology and fertilization biology in the Annelida is revised.     

Occurrence of a capsule in Aeromonas salmonicida

Aeromonas salmonicida grown in a medium with excess glucose as carbon source produces both capsular and exocellular polysaccharides. The capsular polysaccharide is composed of glucose, mannose, rhamnose, N-acetylmannosamine and mannuronic acid in the molar ratios of approximately 5:3:0.75:2:1. The extracellular polysaccharide is similarly constituted, but in the molar ratios of approximately 4.75:10.5:1.5:2:1. The capsular and exocellular polysaccharides did not cross-react with monoclonal antibodies against the A-layer or the O-antigen lipopolysaccharide.     

Estimated acid dissociation constants of the Schiff base, Asp-85, and Arg-82 during the bacteriorhodopsin photocycle.

The pK(a) values of D85 in the wild-type and R82Q, as well as R82A recombinant bacteriorhodopsins, and the Schiff base in the D85N, D85T, and D85N/R82Q proteins, have been determined by spectroscopic titrations in the dark. They are used to estimate the coulombic interaction energies and the pK(a) values of the Schiff base, D85, and R82 during proton transfer from the Schiff base to D85, and the subsequent proton release to the bulk in the initial part of the photocycle. The pK(a) of the Schiff base before photoexcitation is calculated to be in effect only 5.3-5.7 pH units higher than that of D85; overcoming this to allow proton transfer to D85 requires about two thirds of the estimated excess free energy retained after absorption of a photon. The proton release on the extracellular surface is from an unidentified residue whose pK(a) is lowered to about 6 after deprotonation of the Schiff base (Zimanyi, L., G. Varo, M. Chang, B. Ni, R. Needleman, and J.K. Lanyi, 1992. Biochemistry. 31:8535-8543). We calculate that the pK(a) of the R82 is 13.8 before photoexcitation, and it is lowered after proton exchange between the Schiff base and D85 only by 1.5-2.3 pH units. Therefore, coulombic interactions alone do not appear to change the pK(a) of R82 as much and D85 only by 1.5-2.3 pH units. Therefore, coulombic interactions alone do not appear to change the pK(a) of R82 as much as required if it were the proton release group.     

Mechanism of the HDL2 stimulation of progesterone secretion in cultured placental trophoblast

Lipoprotein cholesterol (C) supports the high rate of progesterone production by the human placenta as endogenous cholesterol synthesis is low. To study underlying mechanisms whereby lipoproteins, including high density lipoprotein-2 (HDL2), stimulate progesterone secretion, trophoblast cells were isolated from human term placentas and maintained in primary tissue culture. Lipoproteins were added at several concentrations and medium progesterone secretion was determined. HDL2 (d 1.063-1.125 g/ml) as well as low density lipoproteins (LDL) (d 1.019-1.063 g/ml) but not HDL3 (d 1.125-1.21 g/ml) stimulated progesterone secretion in a dose-dependent manner, with HDL2 cholesterol entering the cell and serving as substrate for progesterone synthesis. Conversely, LDL and HDL2 produced a significant decrease in [2-14C]acetate incorporation into cell cholesterol. Cholesterol-depleted lipoproteins did not stimulate progesterone secretion. The stimulating effect of LDL was abolished by apolipoprotein modification by cyclohexanedione or reductive methylation and by the addition of anti-LDL receptor antibody or 10 microM chloroquine to the medium. [14C]acetate conversion into cholesterol was accelerated by these procedures. However, HDL2 stimulation of progesterone secretion and reduction of [14C]acetate incorporation into cholesterol was not blocked by chemical modification of apolipoproteins, anti-LDL receptor antibody, or chloroquine. Treatment of HDL2 with tetranitromethane or dimethylsuberimidate also did not block the stimulation of progesterone. To determine whether the capacity of HDL2 to deliver cholesterol to the trophoblast cells was restricted to subfractions differing in apoE content, HDL2 was chromatographed on heparin-Sepharose and three fractions (A, B, and C) were obtained. Fraction A was poorest in apoE and free cholesterol, fraction B contained the majority of cholesterol, and fraction C was the richest in apoE and free cholesterol. When added to trophoblast cells, fraction A stimulated little progesterone secretion, fraction B stimulated moderately, and fraction C did so greatly. Modification of these subfractions with cyclohexanedione or reductive methylation did not inhibit these effects. In conclusion, HDL2 stimulated progesterone secretion in human trophoblast cell culture. Contrary to LDL, the HDL effect was not mediated by apolipoproteins or the LDL receptor pathway. The ability of HDL2 to stimulate progesterone secretion is consistent with the passive transfer of free cholesterol to the cell membrane from a physicochemically specific subfraction of HDL. This mechanism may be an auxiliary source of cholesterol for human steroidogenic cells.     

Pharmacological and nutritional agents promoting browning of white adipose tissue

The role of brown adipose tissue in the regulation of energy balance and maintenance of body weight is well known in rodents. Recently, interest in this tissue has re-emerged due to the realization of active brown-like adipose tissue in adult humans and inducible brown-like adipocytes in white adipose tissue depots in response to appropriate stimuli (“browning process”). Brown-like adipocytes that appear in white fat depots have been called “brite” (from brown-in-white) or “beige” adipocytes and have characteristics similar to brown adipocytes, in particular the capacity for uncoupled respiration. There is controversy as to the origin of these brite/beige adipocytes, but regardless of this, induction of the browning of white fat represents an attractive potential strategy for the management and treatment of obesity and related complications. Here, the different physiological, pharmacological and dietary determinants that have been linked to white-to-brown fat remodeling and the molecular mechanisms involved are reviewed in detail. In the light of available data, interesting therapeutic perspectives can be expected from the use of specific drugs or food compounds able to induce a program of brown fat differentiation including uncoupling protein 1 expression and enhancing oxidative metabolism in white adipose cells. However, additional research is needed, mainly focused on the physiological relevance of browning and its dietary control, where the use of ferrets and other non-rodent animal models with a more similar adipose tissue organization and metabolism to humans could be of much help. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.     

No Major Host Genetic Risk Factor Contributed to A(H1N1)2009 Influenza Severity

While most patients affected by the influenza A(H1N1) pandemic experienced mild symptoms, a small fraction required hospitalization, often without concomitant factors that could explain such a severe course. We hypothesize that host genetic factors could contribute to aggravate the disease. To test this hypothesis, we compared the allele frequencies of 547,296 genome-wide single nucleotide polymorphisms (SNPs) between 49 severe and 107 mild confirmed influenza A cases, as well as against a general population sample of 549 individuals. When comparing severe vs. mild influenza A cases, only one SNP was close to the conventional p = 5×10⁻⁸. This SNP, rs28454025, sits in an intron of the GSK233 gene, which is involved in a neural development, but seems not to have any connections with immunological or inflammatory functions. Indirectly, a previous association reported with CD55 was replicated. Although sample sizes are low, we show that the statistical power in our design was sufficient to detect highly-penetrant, quasi-Mendelian genetic factors. Hence, and assuming that rs28454025 is likely to be a false positive, no major genetic factor was detected that could explain poor influenza A course.     

Development and mapping of peach candidate genes involved in fruit quality and their transferability and potential use in other Rosaceae species

The goal of the present study was to identify candidate genes (CGs) involved in fruit quality in peach that can be transferred to other Rosaceae species. Two cDNA libraries from fruit of the “Fantasia” peach cultivar, constructed at two stages of development, were used to generate a set of expressed sequence tag sequences. A total of 1,730 peach unigenes were obtained after clustering. Sequences and corresponding annotations were stored in a relational database and are available through a web interface. Fifty-nine CGs involved in fruit growth and development or fruit quality at maturity, focusing on sweetness, acidity, and phenolic compound content, were selected according to their annotation. Fifty-five primer pairs, designed from peach CG sequences and giving PCR products in peach, were tested in strawberry and 36 gave amplified products. Eight CGs were mapped in peach, 14 in strawberry, four in both species and confirmed the pattern of synteny already proposed using comparative mapping. In peach, the CGs are located in three linkage groups (3, 5, 7), and in strawberry they are distributed in all seven Fragaria linkage groups. Colocalization between some of these CGs and quantitative trait loci for fruit quality traits were identified and are awaiting confirmation in further analyses.