Biosynthesis of electroplax sodium channels in Electrophorus electrocytes and Xenopus oocytes

We have synthesized the eel electroplax sodium channel core polypeptide in both a cell-free and a frog oocyte system and report it does not possess the unusual electrophoretic properties of the mature, native sodium channel polypeptide isolated from electroplax membranes. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the mature channel polypeptide exhibits both a diffuse banding pattern (microheterogeneity) and an extremely high electrophoretic free mobility. In contrast, the core polypeptide synthesized in vitro or in vivo migrates as a sharp band with a near-normal electrophoretic free mobility (Mr 230,000). The microheterogeneity of the mature peptide has been inferred to result from varying degrees of glycosylation of the channel polypeptide [Miller, J.A., Agnew, W.S., & Levinson, S.R. (1983) Biochemistry 22, 462-470]. We present evidence here that the anomalously high electrophoretic free mobility is due to the binding of large amounts of sodium dodecyl sulfate to posttranslationally modified domains on the protein. In addition, we have followed the posttranslational processing of eel sodium channels in both the eel electrocyte and the frog oocyte. Using lectin binding and Ferguson analysis, we found that the channel was processed relatively rapidly to an intermediate form in the Golgi apparatus that apparently contained fewer carbohydrate and hydrophobic domains than the mature channel. The further addition of carbohydrate and hydrophobic domains, which are required before the channel acquires its characteristic physicochemical properties, proceeded relatively slowly in the electrocyte and appeared not to have occurred to the majority of intermediately processed channels in the frog oocyte.     

Parasite stress promotes homicide and child maltreatment

Researchers using the parasite-stress theory of human values have discovered many cross-cultural behavioural patterns that inform a range of scholarly disciplines. Here, we apply the theory to major categories of interpersonal violence, and the empirical findings are supportive. We hypothesize that the collectivism evoked by high parasite stress is a cause of adult-on-adult interpersonal violence. Across the US states, parasite stress and collectivism each positively predicts rates of men's and women's slaying of a romantic partner, as well as the rate of male-honour homicide and of the motivationally similar felony-related homicide. Of these four types of homicide, wealth inequality has an independent effect only on rates of male-honour and felony-related homicide. Parasite stress and collectivism also positively predict cross-national homicide rates. Child maltreatment by caretakers is caused, in part, by divestment in offspring of low phenotypic quality, and high parasite stress produces more such offspring than low parasite stress. Rates of each of two categories of the child maltreatment--lethal and non-lethal--across the US states are predicted positively by parasite stress, with wealth inequality and collectivism having limited effects. Parasite stress may be the strongest predictor of interpersonal violence to date.     

Exposing racial discrimination: implicit & explicit measures--the My Body, My Story study of 1005 US-born black & white community health center members

Background

To date, research on racial discrimination and health typically has employed explicit self-report measures, despite their potentially being affected by what people are able and willing to say. We accordingly employed an Implicit Association Test (IAT) for racial discrimination, first developed and used in two recent published studies, and measured associations of the explicit and implicit discrimination measures with each other, socioeconomic and psychosocial variables, and smoking.

Methodology/Principal Findings

Among the 504 black and 501 white US-born participants, age 35–64, randomly recruited in 2008–2010 from 4 community health centers in Boston, MA, black participants were over 1.5 times more likely (p<0.05) to be worse off economically (e.g., for poverty and low education) and have higher social desirability scores (43.8 vs. 28.2); their explicit discrimination exposure was also 2.5 to 3.7 times higher (p<0.05) depending on the measure used, with over 60% reporting exposure in 3 or more domains and within the last year. Higher IAT scores for target vs. perpetrator of discrimination occurred for the black versus white participants: for “black person vs. white person”: 0.26 vs. 0.13; and for “me vs. them”: 0.24 vs. 0.19. In both groups, only low non-significant correlations existed between the implicit and explicit discrimination measures; social desirability was significantly associated with the explicit but not implicit measures. Although neither the explicit nor implicit discrimination measures were associated with odds of being a current smoker, the excess risk for black participants (controlling for age and gender) rose in models that also controlled for the racial discrimination and psychosocial variables; additional control for socioeconomic position sharply reduced and rendered the association null.

Conclusions

Implicit and explicit measures of racial discrimination are not equivalent and both warrant use in research on racial discrimination and health, along with data on socioeconomic position and social desirability.     

Fight-or-flight: murine unilateral ureteral obstruction causes extensive proximal tubular degeneration, collecting duct dilatation, and minimal fibrosis

Unilateral ureteral obstruction (UUO) is the most widely used animal model of progressive renal disease. Although renal interstitial fibrosis is commonly used as an end point, recent studies reveal that obstructive injury to the glomerulotubular junction leads to the formation of atubular glomeruli. To quantitate the effects of UUO on the remainder of the nephron, renal tubular and interstitial responses were characterized in mice 7 and 14 days after UUO or sham operation under anesthesia. Fractional proximal tubular mass, cell proliferation, and cell death were measured by morphometry. Superoxide formation was identified by nitro blue tetrazolium, and oxidant injury was localized by 4-hydroxynonenol and 8-hydroxydeoxyguanosine. Fractional areas of renal vasculature, interstitial collagen, α-smooth muscle actin, and fibronectin were also measured. After 14 days of UUO, the obstructed kidney loses 19% of parenchymal mass, with a 65% reduction in proximal tubular mass. Superoxide formation is localized to proximal tubules, which undergo oxidant injury, apoptosis, necrosis, and autophagy, with widespread mitochondrial loss, resulting in tubular collapse. In contrast, mitosis and apoptosis increase in dilated collecting ducts, which remain patent through epithelial cell remodeling. Relative vascular volume fraction does not change, and interstitial matrix components do not exceed 15% of total volume fraction of the obstructed kidney. These unique proximal and distal nephron cellular responses reflect differential "fight-or-flight" responses to obstructive injury and provide earlier indexes of renal injury than do interstitial compartment responses. Therapies to prevent or retard progression of renal disease should include targeting proximal tubule injury as well as interstitial fibrosis.     

N-glycosylation promotes the cell surface expression of Kv1.3 potassium channels

The voltage-gated potassium channel Kv1.3 plays an essential role in modulating membrane excitability in many cell types. Kv1.3 is a heavily glycosylated membrane protein. Two successive N-glycosylation consensus sites, N228NS and N229ST, are present on the S1-S2 linker of rat Kv1.3. Our data suggest that Kv1.3 contains only one N-glycan and it is predominantly attached to N229 in the S1-S2 extracellular linker. Preventing N-glycosylation of Kv1.3 significantly decreased its surface protein level and surface conductance density level, which were ～?49% and ～?46% respectively of the level of wild type. Supplementation of N-acetylglucosamine (GlcNAc), l-fucose or N-acetylneuraminic acid to the culture medium promoted Kv1.3 surface protein expression, whereas supplementation of d-glucose, d-mannose or d-galactose did not. Among the three effective monosaccharides/derivatives, adding GlcNAc appeared to reduce sialic acid content and increase the degree of branching in the N-glycan of Kv1.3, suggesting that the N-glycan structure and composition had changed. Furthermore, the cell surface half-life of the Kv1.3 surface protein was increased upon GlcNAc supplementation, indicating that it had decreased internalization. The GlcNAc effect appears to apply mainly to membrane proteins containing complex type N-glycans. Thus, N-glycosylation promotes Kv1.3 cell surface expression; supplementation of GlcNAc increased Kv1.3 surface protein level and decreased its internalization, presumably by a combined effect of decreased branch size and increased branching of the N-glycan.     

Recent horizontal transfer of a mariner transposable element among and between Diptera and Neuroptera

Transposable elements of the mariner family are widespread among insects and other invertebrates, and initial analyses of their relationships indicated frequent occurrence of horizontal transfers between hosts. A specific PCR assay was used to screen for additional members of the irritans subfamily of mariners in more than 400 arthropod species. Phylogenetic analysis of cloned PCR fragments indicated that relatively recent horizontal transfers had occurred into the lineages of a fruit fly Drosophila ananassae, the horn fly Haematobia irritans, the African malaria vector mosquito Anopheles gambiae, and a green lacewing Chrysoperla plorabunda. Genomic dot-blot analysis revealed that the copy number in these species varies widely, from about 17,000 copies in the horn fly to three copies in D. ananassae. Multiple copies were sequenced from genomic clones from each of these species and four others with related elements. These sequences confirmed the PCR results, revealing extremely similar elements in each of these four species (greater than 88% DNA and 95% amino acid identity). In particular, the consensus sequence of the transposase gene of the horn fly elements differs by just two base pairs out of 1,044 from that of the lacewing elements. The mosquito lineage has diverged from the other Diptera for over 200 Myr, and the neuropteran last shared a common ancestor with them more than 265 Myr ago, so this high similarity implies that these transposons recently transferred horizontally into each lineage. Their presence in only the closest relatives in at least the lacewing lineage supports this hypothesis. Such horizontal transfers provide an explanation for the evolutionary persistence and widespread distribution of mariner transposons. We propose that the ability to transfer horizontally to new hosts before extinction by mutation in the current host constitutes the primary selective constraint maintaining the sequence conservation of mariners and perhaps other DNA-mediated elements.      

Contributions of the hippocampus and medial prefrontal cortex to energy and body weight regulation

The effects of selective ibotenate lesions of the complete hippocampus (CHip), the hippocampal ventral pole (VP), or the medial prefrontal cortex (mPFC) in male rats were assessed on several measures related to energy regulation (i.e., body weight gain, food intake, body adiposity, metabolic activity, general behavioral activity, conditioned appetitive responding). The testing conditions were designed to minimize the nonspecific debilitating effects of these surgeries on intake and body weight. Rats with CHip and VP lesions exhibited significantly greater weight gain and food intake compared with controls. Furthermore, CHip-lesioned rats, but not rats with VP lesions, showed elevated metabolic activity, general activity in the dark phase of the light-dark cycle, and greater conditioned appetitive behavior, compared with control rats without these brain lesions. In contrast, rats with mPFC lesions were not different from controls on any of these measures. These results indicate that hippocampal damage interferes with energy and body weight regulation, perhaps by disrupting higher-order learning and memory processes that contribute to the control of appetitive and consummatory behavior.     

Effects of anesthetics on cardiovascular responses of the marmot Marmota flaviventris

The effects of pentobarbital (30 mg/kg), urethan (2 g/kg), chloralose/urethan (50 mg/kg, 500 mg/kg), and thiobutabarbital (Inactin, 100 mg/kg) on the mean arterial pressure (BP) and heart period (HP) of Marmota flaviventris were examined. Anesthesia significantly decreased BP by 22-27 mm Hg and HP by 123-151 msec. In a series of paired studies with eight marmots it was found that pentobarbital increased the BP response to phenylephrine and almost abolished the baroreflex HP responses to phenylephrine and nitroglycerin. In another series of animals right carotid occlusion in unanesthetized animals produced greater changes in BP and HP than occlusion of the left carotid. Chloralose/urethan, urethan, or Inactin reduced the reflex BP response to unilateral carotid occlusion by 50% and the HP response by 96%. It was concluded that the anesthetic agents investigated depress baroreflex responses significantly by influencing efferent sympathetic and parasympathetic reflex responses. They, therefore, are not appropriate for cardiovascular studies in acute, anesthetized preparations of the marmot and, perhaps, other hibernating species.