Inhibition of palmitate‐induced GADD34 expression augments apoptosis in mouse insulinoma cells (MIN6)

Saturated fatty acids like palmitate induce endoplasmic reticulum (ER) stress in pancreatic beta‐cells, an event linked to apoptotic loss of β‐cells in type 2 diabetes. Sustained activation of the ER stress response leads to expression of growth arrest and DNA damage‐inducible protein 34 (GADD34), a regulatory subunit of protein phosphatase 1. In the present study, we have used small interfering RNA in order to knockdown GADD34 expression in insulin‐producing MIN6 cells prior to induction of ER stress by palmitate and evaluated its consequences on RNA‐activated protein kinase‐like ER‐localized eIF2alpha kinase (PERK) signalling and apoptosis. Salubrinal, a specific inhibitor of eukaryotic initiation factor 2α (eIF2α) dephosphorylation, was used as a comparison. Salubrinal treatment augmented palmitate‐induced ER stress and increased GADD34 levels. Both GADD34 knockdown and salubrinal treatment potentiated the cytotoxic effects of palmitate as evidenced by increased DNA fragmentation and activation of caspase 3, with the fundamental difference that the former did not involve enhanced levels of GADD34. The data from this study suggest that sustained activation of PERK signalling and eIF2α phosphorylation sensitizes insulin‐producing MIN6 cells to lipoapoptosis independently of GADD34 expression levels. Copyright © 2014 John Wiley & Sons, Ltd.     

WFS1 and non-syndromic low-frequency sensorineural hearing loss: A novel mutation in a Portuguese case

Low-frequency sensorineural hearing loss (LFSNHL) is an unusual type of HL in which frequencies at 2000 Hz and below are predominantly affected. Most of the families with LFSNHL carry missense mutations in WFS1 gene, coding for wolframin.     

On Connectedness of a Two-way Elimination of Heterogeneity Design

For some subclass of a two-way elimination of heterogeneity design, necessary and sufficient conditions are established for row-connectedness and column-connectedness of a design to imply its connectedness.     

Central Place Foraging in Nonpatchy Habitats

This paper deal with a model of optimal foraging in a habitat with arbitrary food distribution. It takes into account an arbitrary risk cost related to the distance to the animal's nest. Food acquisition and risk cost are accounted for in common units of fitness. The resulting problem is solved in the context of Calculus of Variations. The optimal duration of absence from the nest and the optimal spatial allocation of foraging time are obtained: the optimal strategy leads to separate the habitat into a region to exploit and a region to ignore. The definition of these two distinct regions depends on the relative importance of risk and food availability. With realistic risk costs, the resulting strategy indicates a highly selective behaviour when far from the nest, as observed in field studies. The model is also extended to take account of the need of returning to the nest to guard it or to feed the young.     

Effects of starvation and sucrose feeding on corpora allata of last instar larvae of Manduca sexta: in vitro activity, size, and cell number

Abstract Larvae of the tobacco hornworm moth Manduca sexta starved for the first 3 days of the last (fifth) stadium undergo a supernumerary moult. If they are provided with sucrose during the starvation period, they develop into normal pupae although pupation is delayed. The activities of the corpora allata (CA) from normal, starved, and sucrose fed larvae were followed through the fifth stadium with a radiochemical assay for Juvenile Hormone (JH) biosynthesis. An attempt was made to correlate CA-activity with CA cell number, size, and protein content.
In CA of normally fed larvae the rate of JH synthesis declined to undetectable levels by day 4 which was also the time of exposure of the dorsal vessel. In CA of starved larvae, the rate of JH synthesis at first decreased but began to increase on day 3 and reached a peak value by day 7 , at which time head capsule slippage occurred. In CA of sucrose fed larvae, the rate of biosynthesis declined as in normal larvae but the decline was extended over a longer period. Exposure of the dorsal vessel was delayed in the same manner and occurred on days 7–9. The major JH in all cases was JH-II.
The CA comprise c. 150 cells in the early fifth stadium, and this number remained constant during the fifth stadium in all three feeding regimens. In normal larvae, CA size and protein content increased several-fold during the stadium whereas in starved and sucrose-fed larvae they increased slowly and in agreement with the altered timing of developmental events. In none of the groups was the CA activity pattern correlated with morphometric changes of the CA. The rates of JH biosynthesis were not closely correlated with published JH titre curves. The in vivo mechanisms for regulation of JH production remain to be elucidated.     

A One Year Audit of Fine Needle Aspiration Cytology For the Pre-Operative Diagnosis of Breast Disease

In 1988, 985 patients presenting with breast disease, most with a palpable abnormality, were investigated by the triple approach (clinical examination, imaging and fine needle aspiration cytology [FNAC]). Using FNAC, 28% of patients were diagnosed as having carcinoma, 45% benign disease, 4% had suspicious cytology and 3% equivocal cytology. The remaining 20% had inadequate aspirates. Two false positive diagnoses of carcinoma were made (a false positive rate of 0.7%); one was a case of high grade non-Hodgkin's lymphoma and the other a papillary lesion with epithelial atypia. The false negative rate was 6.4%. Of these 49 patients, six had carcinoma-in-situ and 19 had low grade tumours. The absolute and complete sensitivities for the diagnosis of carcinoma in this series were 84.7% and 91.9% respectively and the absolute and complete specificities 99.7% and 98.3%, respectively. These figures compare favourably with those from other centres and confirm the efficacy of FNAC as part of the triple approach to the diagnosis of breast disease. The use of FNAC has resulted in a reduction in the number of Trucut and frozen section biopsies performed. Eighty three per cent of the patients with benign disease diagnosed by the triple approach have avoided excision biopsy, none of whom have subsequently been found to have carcinoma. Eighty patients with advanced breast carcinoma were spared operative intervention.     

Reversible and time-dependent inhibition of the hepatic cytochrome P450 steroidal hydroxylases by the proestrogenic pesticide methoxychlor in rat and human

Methoxychlor, a currently used pesticide, is demethylated and hydroxylated by several hepatic microsomal cytochrome P450 enzymes. Also, methoxychlor undergoes metabolic activation, yielding a reactive intermediate (M*) that binds irreversibly and apparently covalently to microsomal proteins. The study investigated whether methoxychlor could inhibit or inactivate certain liver microsomal P450 enzymes. The regioselective and stereoselective hydrox-ylation of testosterone and the 2-hydroxylation of estradiol (E₂) were utilized as markers of the P450 enzymes inhibited by methoxychlor. Both reversible and time-dependent inhibition were examined. Coincubation of methoxychlor and testosterone with liver microsomes from phenobarbital treated (PB-microsomes) male rats, yielded marked diminution of 2α- and 16α-testosterone hydroxylation, indicating strong inhibition of P4502C11 (P450h). Methoxychlor moderately inhibited 2β-, 7α-, 15α-, 15β-, and 16β-hydroxylation and androstenedi-one formation. There was only a weak inhibition of 6β-ydroxylation of testosterone. The methox-ychlor-mediated inhibition of 6β-hydroxylation was competitive. By contrast, when methoxychlor was permitted to be metabolized by PB-microsomes or by liver microsomes from pregnenolone-16α-car-bonitrile treated rats (PCN-microsomes) prior to addition of testosterone, a pronounced time-dependent inhibition of 6β-hydroxylation was observed, suggesting that methoxychlor inactivates the P450 3A isozyme(s). The di-demethylated methoxychlor (bis-OH-M) and the tris-hydroxy (ca-techol) methoxychlor metabolite (tris-OH-M) inhibited 6β-hydroxylation in PB-microsomes competitively and noncompetitively, respectively; however, these methoxychlor metabolites did not exhibit a time-dependent inhibition. Methoxychlor inhibited competitively the formation of 7α-hydroxytestosterone (7α-OH-T) and 16α-hydroxy-testosterone (16α-OH-T) but exhibited little or no time-dependent inhibition of generation of these metabolites, indicating that P450s 2A1, 2B1/B2, and 2C11 were inhibited but not inactivated. Methoxychlor inhibited in a time-dependent fashion the 2-hydroxylation of E2 in PB-microsomes. However, bis-OH-M exhibited solely reversible inhibition of the 2-hydroxylation, supporting our conclusion that the inactivation of P450s does not involve participation of the demethylated metabolites. Both competitive inhibition and time-dependent inactivation of human liver P450 3A (6β-hydroxylase) by methoxychlor, was observed. As with rat liver microsomes, the human 6β-hydroxylase was inhibited by bis-OH-M and tris-OH-M competitively and noncompetitively, respectively. Testosterone and estradiol strongly inhibited the irreversible binding of methoxychlor to microsomal proteins. This might explain the “clean” competitive inhibition by methoxychlor of the 6β-OH-T formation when the compounds were coin-cubated. Glutathione (GSH) has been shown to interfere with the irreversible binding of methoxychlor to PB-microsomal proteins. The finding that the coincubation of GSH with methoxychlor partially diminishes the time-dependent inhibition of 6β-hydroxylation provides supportive evidence that the inactivation of P450 3A isozymes by methoxychlor is related to the formation of M*.     

Spatial clumping of food increases its monopolization and defense by convict cichlids, Cichlasoma nigrofasciatum

The hypothesis that resource monopolization and defense increaseas the spatial clumping of resources increases was tested usinggroups of three convict cichlids competing for 120 Daphnia magnaprey. Spatial clumping was manipulated by varying the distance(3, 20, or 40 cm) between three tubes through which the preyappeared. As predicted, monopolization of prey (percentage eatenby the dominant fish) and frequency of aggression (chases perminute) by dominant fish increased significantly as the distancebetween the tubes decreased. However, there was no evidenceof individual flexibility in the aggressiveness (percentageof conspecifics chased) of dominant fish across treatments.Differences among dominant fish in aggressiveness were positivelycorrelated with their ability to monopolize prey, but the strengthof the correlation decreased as the distance between the tubesincreased. Aggression appears to be a more effective mechanismof interference competition when resources are clumped thanwhen resources are dispersed.     

Amino acid sequence of photosystem I subunit IV from the cyanobacterium Synechocystis PCC 6803

We describe here the complete amino acid sequence of photosystem I subunit IV from Synechocystis 6803. The molecular mass of 8.0 kDa is lower than in higher plants and Chlamydomonas, due to the lack of a characteristic, proline-rich, N-terminal sequence. The remaining sequence exhibits a good conservation, with a hydrophilic and strongly basic N-tenninal head followed by two hydrophobic domains. There is no possibility of classical membrane-spanning alpha helices. This component is likely to be one of the most stroma accessible subunits of photosystem I.