Low natural killer cytotoxicity in major depression

Natural killer cell cytotoxicity was significantly lower in a group of hospitalized depressed men than in matched controls. The absolute number of neutrophils was increased in the depressed group, but the numbers of other cell types did not differ between groups. These findings further demonstrate that altered immunity is a biologic concomitant of affective disorders.     

Delayed rectifying and calcium-activated K+ channels and their significance for action potential repolarization in mouse pancreatic beta-cells

The contribution of Ca2(+)-activated and delayed rectifying K+ channels to the voltage-dependent outward current involved in spike repolarization in mouse pancreatic beta-cells (Rorsman, P., and G. Trube. 1986. J. Physiol. 374:531-550) was assessed using patch-clamp techniques. A Ca2(+)-dependent component could be identified by its rapid inactivation and sensitivity to the Ca2+ channel blocker Cd2+. This current showed the same voltage dependence as the voltage-activated (Cd2(+)-sensitive) Ca2+ current and contributed 10-20% to the total beta-cell delayed outward current. The single-channel events underlying the Ca2(+)-activated component were investigated in cell-attached patches. Increase of [Ca2+]i invariably induced a dramatic increase in the open state probability of a Ca2(+)-activated K+ channel. This channel had a single-channel conductance of 70 pS [( K+]o = 5.6 mM). The Ca2(+)-independent outward current (constituting greater than 80% of the total) reflected the activation of an 8 pS [( K+]o = 5.6 mM; [K+]i = 155 mM) K+ channel. This channel was the only type observed to be associated with action potentials in cell-attached patches. It is suggested that in mouse beta-cells spike repolarization results mainly from the opening of the 8-pS delayed rectifying K+ channel.     

The effect of cycloheximide upon polyribosome stability in two yeast mutants defective respectively in the initiation of polypeptide chains and in messenger RNA synthesis

Summary The effect of cycloheximide upon protein synthesis, RNA metabolism, and polyribosome stability was investigated in the parent and in two temperature-sensitive mutant yeast strains defective respectively in the initiation of polypeptide chains and in messenger RNA synthesis. Cycloheximide at high concentrations (100 g/ml) severely inhibits but does not completely stop protein synthesis (Fig. 1); the incorporation of ¹⁴C-amino acids into polyribosome-associated nascent polypeptide chains continues at a slow but measurable rate (Figs. 2 and 3). Polyribosome structures are stable in the parent strain at 36° whether or not cycloheximide is present (Fig. 5). However, in Mutant ts^- 136, a mutant defective in messenger as well as in stable RNA production, polyribosomes decay at the restrictive temperature (36° C) at the same rate whether or not cycloheximide is present (Fig. 5). Thus the maintenance of polyribosome structures is dependent upon the continued synthesis of messenger RNA even under conditions of extremely slow polypeptide chain elongation. In mutant ts^- 187, a mutant defective in the initiation of polypeptide chains, all of the polyribosomes decay to monoribosomes within 2 minutes after a shift to the restrictive temperature; cycloheximide completely prevents this decay demonstrating that this mutant is capable of continued messenger RNA synthesis at 36° C. Consistent with these observations is the fact that a newly synthesized heterogeneously sedimenting RNA fraction continues to enter polyribosomes in the presence of cycloheximide whereas the entrance of newly synthesized ribosomal RNA is severely inhibited (Figs. 7, 8, 9). The decay or lack of decay of polyribosomes at the restrictive temperature is, therefore, a rapid and discriminating test for the analysis of mutants defective in macromolecule synthesis. Mutants which exhibit a decay of polyribosomes in the presence of cycloheximide are likely to be defective directly or indirectly in the synthesis of messenger RNA whereas mutants in which decay is prevented or slowed by cycloheximide are likely to be defective in some factor required for the association of ribosomes and messenger RNA.     

The Herpesvirus capsid surface protein, VP26, and the majority of the tegument proteins are dispensable for capsid transport toward the nucleus

Upon entering a cell, alphaherpesvirus capsids are transported toward the minus ends of microtubules and ultimately deposit virus DNA within the host nucleus. The virus proteins that mediate this centripetal transport are unknown but are expected to be either viral tegument proteins, which are a group of capsid-associated proteins, or a surface component of the capsid itself. Starting with derivatives of pseudorabies virus that encode a fluorescent protein fused to a structural component of the virus, we have made a collection of 12 mutant viruses that lack either the VP26 capsid protein or an individual tegument protein. Using live-cell fluorescence microscopy, we tracked individual virus particles in axons following infection of primary sensory neurons. Quantitative analysis of the VP26-null virus indicates that this protein plays no observable role in capsid transport. Furthermore, viruses lacking tegument proteins that are nonessential for virus propagation in cell culture were also competent for axonal transport. These results indicate that a protein essential for viral propagation mediates transport of the capsid to the nucleus.     

In vitro modulation of antioxidant enzyme levels in normal hamster kidney and estrogen-induced hamster kidney tumor

Antioxidant enzyme (AE) activities were studied in normal hamster kidney proximal tubules and in estrogen-induced hamster kidney cancer. In vivo, kidney tumor had lower activities of manganese superoxide dismutase (MnSOD), copper, zinc superoxide dismutase, catalase, and glutathione peroxidase than kidney proximal tubules. Differences in AE activities were, in general, maintained in tissue culture, with AE activities remaining low in tumor cells compared to normal cells. Normal proximal tubular cells showed significant induction of MnSOD activity as a function of time in culture of following exposure to diethylstilbestrol, a synthetic estrogen, while MnSOD activity remained low in tumor cells under these conditions. Our results suggest that antioxidant enzymes, particularly MnSOD, are regulated differently in estrogen-induced hamster kidney tumor cells than in normal kidney proximal tubular cells, demonstrating that cancers arising from hormonal influence have similar AE profiles to those previously described in cancers arising from viral or chemical etiologies.     

Two independent conjugal transfer systems operating in Bacteroides fragilis V479-1.

Bacteroides fragilis V479-1 (also designated strain 92) has previously been shown to contain a conjugative plasmid, pBF4, that specifies resistance to clindamycin (Cc). A report of inducible tetracycline (Tc) resistance in this strain suggested that this phenotype was also plasmid associated (G. Privitera et al., Nature [London] 278:657-659, 1979) and prompted further investigation. Mating experiments with V469-1 and a Cc-sensitive derivative of V479-1, V598, showed that Tc resistance transfer occurred by a conjugation-like event which was insensitive to DNase, was not mediated by donor culture cell-free filtrates, and required cell-to-cell contact. Results from transfer experiments with V479-1 indicated that Tc and Cc resistance determinants were not linked and segregated independently in matings. Progeny recovered from matings with the V479-1 or V598 donor strain were able to transfer the Tc resistance marker in secondary crosses. Tc resistance transfer from V479-1 or V598 was greatly stimulated by pregrowth in the presence of Tc but not Cc. pBF4-mediated Cc resistance transfer was not affected by pregrowth in the presence of Cc or Tc. Filter blot DNA hybridization studies revealed that pBF4 sequences were not involved in either the Tc resistant phenotype or its associated conjugal transfer properties. The Tc resistance transfer element was not associated with pBF4 or any other extrachromosomal DNA element.     

Identification of an intracellular microdomain of the P2X7 receptor that is crucial in basolateral membrane targeting in epithelial cells

We investigated membrane targeting of the P2X₇ receptor (P2X₇R) in polarized epithelial cells using immunofluorescent confocal imaging. The wild-type receptor was targeted to the basolateral membrane, independently of adaptor protein μ1B. Deletion of the majority of the intracellular C-terminus, or the last 26 residues (P570-Y595), conferred targeting of the protein to the apical membrane. Alanine substitution in the microdomain P582-Q587 caused similar apical membrane targeting without major effect on the receptor function and surface expression. Our results show basolateral membrane targeting of the P2X₇R in epithelial cells and that the intracellular C-terminal microdomain P582-Q587 is crucial in this process.

Structured summary

MINT-8055849:Beta-catenin (uniprotkb:B6V8E6) and P2X7R (uniprotkb:Q64663) colocalize (MI:0403) by fluorescence microscopy (MI:0416)