Categorization of humans in biomedical research: genes,race and disease

A debate has arisen regarding the validity of racial/ethnic categories for biomedical and genetic research. Some claim 'no biological basis for race' while others advocate a 'race-neutral' approach, using genetic clustering rather than self-identified ethnicity for human genetic categorization. We provide an epidemiologic perspective on the issue of human categorization in biomedical and genetic research that strongly supports the continued use of self-identified race and ethnicity.     

Muscarinic M2 receptors in acetylcholine-isoproterenol functional antagonism in human isolated bronchus

The muscarinic functional antagonism of isoproterenol relaxation and the contribution of muscarinic M2 receptors were examined in human isolated bronchus. In intact tissues, acetylcholine (ACh) precontraction decreased isoproterenol potency and maximal relaxation (-log EC50 shift = -1.49 +/- 0.16 and E(max) inhibition for 100 microM ACh = 30%) more than the same levels of histamine contraction. The M2 receptor-selective antagonist methoctramine (1 microM) reduced this antagonism in ACh- but not histamine-contracted tissues. Similar results were obtained for forskolin-induced relaxation. After selective inactivation of M3 receptors with 4-diphenylacetoxy-N-(2-chloroethyl)piperadine hydrochloric acid (30 nM), demonstrated by abolition of contractile and inositol phosphate responses to ACh, muscarinic recontractile responses were obtained in U-46619-precontracted tissues fully relaxed with isoproterenol. Methoctramine antagonized recontraction, with pK(B) (6.9) higher than in intact tissues (5.4), suggesting participation of M2 receptors. In M3-inactivated tissues, methoctramine augmented the isoproterenol relaxant potency in U-46619-contracted bronchus and reversed the ACh-induced inhibition of isoproterenol cAMP accumulation. These results indicate that M2 receptors cause indirect contraction of human bronchus by reversing sympathetically mediated relaxation and contribute to cholinergic functional antagonism.     

Changes in some innate defence parameters of seabream (Sparus aurata L.) induced by retinol acetate

The effects of high doses of dietary or intraperitoneally (i.p.) injected retinol acetate on the gilthead seabream (Sparus aurata L.) innate immune system were studied. Gilthead seabream specimens were fed a commercial non-supplemented diet containing 1.75 mg of vitamin A kg(-1) (as control) or the same diet supplemented with 50, 150 or 300 mg of retinol acetate kg(-1) (as vitamin A source). After 1, 2, 4 or 6 weeks, serum samples and head-kidney leucocytes were obtained from each fish. Serum lysozyme activity and myeloperoxidase (MPO) content were unaffected by the vitamin A diet content. The phagocytic and respiratory burst activities of head-kidney leucocytes were established, as well as their myeloperoxidase content. While phagocytosis was not enhanced by dietary vitamin A intake and was even slightly decreased after 2 weeks, respiratory burst activity was enhanced in specimens fed supplements of 150 and 300 mg retinol acetate kg(-1) diet for 1 or 2 weeks. Leucocyte MPO content was also enhanced when seabream were fed the highest vitamin A dose for 2 or 4 weeks and after being fed the 150 or 50 mg supplemented diets for 4 or 6 weeks, respectively. Three different groups of seabream were i.p. injected with 1 ml of phosphate buffer containing an amount of retinol acetate equivalent to the daily dietary supplements from the first experiment (0-control-, 0.05 or 0.30 mg 100 g(-1) biomass). Both injection doses of retinol acetate were toxic for the gilthead seabream which showed hypervitaminic effects. These data show that retinol acetate plays an important role in the gilthead seabream nonspecific cellular immune system due to its antioxidant properties. They also point to the importance of the way in which it is administered, by dietary uptake or intraperitoneal injection.     

On the systematic position of Ophiosacculus Macy, 1935 (digenea: Lecithodendriidae), with the erection of the Ophiosacculinae n. subfam

The phylogenetic relationships and systematic position of the digenean genus Ophiosacculus Macy, 1935 has been controversial and opinions of different authors on its systematic position and content are contradictory. Molecular analysis based on the partial sequences of the large subunit ribosomal DNA gene of the type and only valid species of the genus, Ophiosacculus mehelyi (Mödlinger, 1930), as well as previously published sequences of members of several families of Plagiorchiata (including the Allassogonoporidae, Lecithodendriidae and Pleurogenidae as potential relatives of Ophiosacculus) has shown that Ophiosacculus forms a clade with the typical representatives of the Lecithodendriidae from bats. Ophiosacculus is basal to the cluster containing Lecithodendrium, Prosthodendrium and Pycnoporus and has quite pronounced differences in the sequenced fragment compared to these genera. Based on the results of the molecular study, morphological characteristics of Ophiosacculus (in particular, possession of a seminal vesicle lying freely in parenchyma) and the fact that the type-specimen of Gyrabascus brevigastrus Macy, 1835 (type-species of the monotypic genus Gyrabascus and type-genus of the subfamily Gyrabascinae) belongs to Allassogonoporus, a new subfamily, the Ophiosacculinae, with Ophiosacculus as the type-genus, is established within the Lecithodendriidae. Molecular study did not support a close phylogenetic relationship between Allassogonoporus and Ophiosacculus, although several authors previously allocated both these genera to the Allassogonoporidae. Morphological study revealed the position of the genital pore in O. mehelyi to be at the posterior margin of the ventral sucker. An amended diagnosis of Ophiosacculus and a diagnosis of Ophiosacculinae n. subfam. are given.     

Bovine floor plate explants secrete SCO-spondin

SCO-spondin is a large-molecular mass glycoprotein, secreted by the subcommissural organ (SCO), which has been implicated in neuronal development during ontogeny of the central nervous system. The expression of SCO-spondin is not restricted to the SCO but it also occurs in the floor plate, a key structure participating in neuronal differentiation and patterning of the neural tube. It has been postulated that SCO-spondin detected in the floor plate is released into the lumen of the neural tube, but this new route of secretion of floor plate cells needs to be further substantiated. For this purpose, we standardized long-term organ culture of bovine floor plate and performed morphological, immunological, biochemical, and gene expression analyses. The study of floor plate explants and their conditioned media allowed us to demonstrate that: (1) organ-cultured floor plate cells are actively secretory for up to 25 days; (2) SCO-spondin gene is actively transcribed and translated by the cultured floor plate cells; (3) SCO-spondin is released into the culture medium via the apical cell pole; and (4) upon release, SCO-spondin does not aggregate in the conditioned medium but remains soluble. Furthermore, in the cultured floor plate cells, SCO-spondin may be secreted through a route bypassing the Golgi apparatus.     

Prostaglandin E(1) inhibits abnormal follicle rupture and restores ovulation in indomethacin-treated rats

In the presence of indomethacin, an inhibitor of prostaglandin (PG) synthesis, the gonadotropin surge induces abnormal follicle rupture at the basolateral follicle sides, thus preventing effective ovulation in rats. This study was undertaken to analyze whether exogenous prostaglandin administration can overcome the antiovulatory action of indomethacin. Cycling rats were treated with vehicle (olive oil) or indomethacin (1 mg/rat) on the morning of proestrus. Rats treated with indomethacin were injected with different doses (50, 250, or 500 micro g/rat) of PGE(1), PGE(2), PGF(2alpha), or vehicle (saline) at 1900 h in proestrus. The ovulatory response was analyzed on the morning of estrus by evaluating follicle rupture and the location of the oocytes in serially sectioned ovaries. The number of oocytes in the oviducts was also counted in rats treated with the highest prostaglandin doses. In indomethacin-treated rats, most newly formed corpora lutea showed abnormal follicle rupture at the basolateral sides. In addition, invasion of the ovarian stroma and blood and lymphatic vessels by granulosa cells and follicular fluid was observed. Prostaglandins of the E series, and especially PGE(1), inhibited abnormal follicle rupture and restored ovulation, although the number of oocytes in the oviducts were significantly decreased. PGF(2alpha) was only partially effective in inhibiting abnormal follicle rupture and restoring ovulation. These data suggest that prostaglandins of the E series, and particularly PGE(1), play a crucial role in ovulation by determining the targeting of follicle rupture at the apex, thus allowing release of oocytes to the periovarian space.     

The Haemophilus ducreyi cytolethal distending toxin induces DNA double-strand breaks and promotes ATM-dependent activation of RhoA

Among bacterial protein toxins, the cytolethal distending toxins (CDTs) are unique in their ability to activate the DNA damage checkpoint responses, causing cell cycle arrest or apoptosis in intoxicated cells. We provide direct evidence that natural intoxication of cells with the Haemophilus ducreyi CDT (HdCDT) holotoxin induces DNA double-strand breaks similarly to ionizing radiation. Upon DNA damage, epithelial cells and fibroblasts promote the formation of actin stress fibres via activation of the small GTPase RhoA. This phenomenon is not toxin specific, but is part of the ATM-induced cellular responses to genotoxic stresses, including ionizing radiation. Activation of RhoA is associated with prolonged cell survival, as HdCDT-treated epithelial cells expressing a dominant-negative form of RhoA detach and consequently die faster than cells expressing a functional RhoA. Our data highlight several novel aspects of CDT biology: (i) we show that a member of the CDT family causes DNA double-strand breaks in naturally intoxicated cells, acting as a true genotoxic agent; and (ii) we disclose the existence of a novel signalling pathway for intracellularly triggered activation of the RhoA GTPase via the ATM kinase in response to DNA damage, possibly required to prolong cell survival.     

GASP phenotype: presence in enterobacteria and independence of sigmaS in its acquisition

The appearance of growth advantage in stationary phase or GASP was originally detected in Escherichia coli. The presence of this phenotype in other enterobacteria such as Enterobacter cloacae, Salmonella typhimurium, Providencia stuartii and Shigella dysenteriae is described in this work. E. cloacae GASP strains presented lower levels of RpoS than the parental strain, although no mutation in the gene or its promoter was detected. This work offers evidence of GASP rpoS-independent pathways as GASP was also acquired in knock-out rpoS E. cloacae and E. coli strains.     

Homothorax switches function of Drosophila photoreceptors from color to polarized light sensors

Different classes of photoreceptors (PRs) allow animals to perceive various types of visual information. In the Drosophila eye, the outer PRs of each ommatidium are involved in motion detection while the inner PRs mediate color vision. In addition, flies use a specialized class of inner PRs in the "dorsal rim area" of the eye (DRA) to detect the e-vector of polarized light, allowing them to exploit skylight polarization for orientation. We show that homothorax is both necessary and sufficient for inner PRs to adopt the polarization-sensitive DRA fate instead of the color-sensitive default state. Homothorax increases rhabdomere size and uncouples R7-R8 communication to allow both cells to express the same opsin rather than different ones as required for color vision. Homothorax expression is induced by the iroquois complex and the wingless (wg) pathway. However, crucial wg pathway components are not required, suggesting that additional signals are involved.     

A mannose-receptor is possibly involved in the phagocytosis of Saccharomyces cerevisiae by seabream (Sparus aurata L.) leucocytes

In this paper the possible involvement of the mannose-receptor on the non-specific recognition and phagocytosis of heat killed yeast cells (Saccharomyces cerevisiae) by gilthead seabream (Sparus aurata L.) head-kidney leucocytes was established by studying the ability of different sugars to inhibit the uptake of the yeast cells by leucocytes. Leucocytes were preincubated for 30min with different concentrations of sugar (alpha-mannan, d-mannose, d-fucose, l-fucose, d-glucose, d-glucosamine and n-acetyl-glucosamine, all of them described as specific ligands of the vertebrate mannose-receptor) and afterwards incubated with FITC-labelled yeast cells for phagocytosis assays. The phagocytic ability (percentage of cells with one or more ingested yeast cells within the total cell population) and capacity (number of ingested yeast cells per cell) of leucocytes was analysed by flow cytometry. The results demonstrate the potential existence of a specific receptor-sugar or receptor-yeast cell binding process, which was saturable, specific and dose-dependent. More specifically, when leucocytes were preincubated with appropriate doses of d-mannose, d- or l-fucose, d-glucose or n-acetyl-glucosamine the phagocytosis of yeast cells by head-kidney leucocytes was partially blocked. Seabream leucocytes were also preincubated with chloroquine, a lysosomotropic drug which downregulates (in a nonspecific manner) the expression of mannose-receptors in mammals, before phagocytosis assays were performed. The results demonstrated that the phagocytosis of yeast was completely blocked by this substance. The overall results seem to corroborate the presence of the mannose-receptor in seabream phagocytes, which is involved in the non-specific binding and phagocytosis of yeast cells by head-kidney leucocytes.