Density dependent recruitment in the reef fish Chaetodon miliaris

Synopsis Recruitment of reef fish has generally been found to be unrelated to or positively related to adult densities. This paper reports an inverse relationship between the number of recruits of Chaetodon miliaris and the density of conspecific adults. C. miliaris are non-territorial, planktivorous butterflyfish. The study populations occurred on the flanks of patch reefs of about 30 m in diameter. At their peak densities populations consisted of 300–400 C. miliaris. Recruitment (the appearance in the stock of fish less than 3.5cm in total length) occurred primarily from April to June and corresponded to the new moon period in these months. Populations generally showed a steady decline in numbers during months of the year when recruitment was not occurring: the finite rate of decline was approximately 30% per month. Populations varied in the density of adults at the start of the spring-summer period of recruitment, and the magnitude of recruitment to a reef was inversely related to the density of these conspecific adults. Reduction of the densities of adult C. miliaris through trap fishing, resulted in increased recruitment to the fished stock. These results provide evidence that in some. species of reef fish, benthic processes may play an important role in determining the magnitude of recruitment to an adult stock, in contrast to the widely held view that recruitment is in large part a result of chance events in the plankton or that recruitment is directly related to adult densities.     

Determination of molecular weights by differential cryoscopy on small volumes of dilute solutions of oligopeptides

A differential cryoscope of the equilibrium type is described. It requires only 1 ml of sample for a molecular-weight determination of a solute in a solvent that freezes below room temperature. The instrument is sensitive to +/- 0.0002 degrees C, which corresponds to +/- 0.0001 mol of solute per 1000 g of water. The apparatus was evaluated by measuring the freezing point depressions of 0.015 M urea and 0.01 M alanine in water, the measured molecular weights being accurate to within +/- 5%. The molecular weights of the following oligopeptides were then measured to determine their states of aggregation in the cited solvents: Ac-Asn-Pro-Tyr-NHMe in H2O and dimethyl sulfoxide and cyclo(L-alanyl-L-alanyl-epsilon-aminocaproyl), cyclo(L-alanyl-D-alanyl-epsilon-aminocaproyl), cyclo(L-alanyl-L-analyl-omega-capryl), cyclo(L-alanyl-D-alanyl-omega-capryl), and Ac-Tyr-Pro-Asn-NHMe in dimethyl sulfoxide.     

Carbohydrate binding module recognition of xyloglucan defined by polar contacts with branching xyloses and CH‐Π interactions

Engineering of novel carbohydrate‐binding proteins that can be utilized in various biochemical and biotechnical applications would benefit from a deeper understanding of the biochemical interactions that determine protein‐carbohydrate specificity. In an effort to understand further the basis for specificity we present the crystal structure of the multi‐specific carbohydrate‐binding module (CBM) X‐2 L110F bound to a branched oligomer of xyloglucan (XXXG). X‐2 L110F is an engineered CBM that can recognize xyloglucan, xylans and β‐glucans. The structural observations of the present study compared with previously reported structures of X‐2 L110F in complex with linear oligomers, show that the π‐surface of a phenylalanine, F110, allows for interactions with hydrogen atoms on both linear (xylopentaose and cellopentaose) and branched ligands (XXXG). Furthermore, X‐2 L110F is shown to have a relatively flexible binding cleft, as illustrated in binding to XXXG. This branched ligand requires a set of reorientations of protein side chains Q72, N31, and R142, although these residues have previously been determined as important for binding to xylose oligomers by mediating polar contacts. The loss of these polar contacts is compensated for in binding to XXXG by polar interactions mediated by other protein residues, T74, R115, and Y149, which interact mainly with the branching xyloses of the xyloglucan oligomer. Taken together, the present study illustrates in structural detail how CH‐π interactions can influence binding specificity and that flexibility is a key feature for the multi‐specificity displayed by X‐2 L110F, allowing for the accommodation of branched ligands. Proteins 2014; 82:3466–3475. © 2014 Wiley Periodicals, Inc.     

Characterization of the substitution pattern of cellulose derivatives using carbohydrate-binding modules

Background

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most prevalent pathogens responsible for nosocomial infections throughout the world. As clinical MRSA diagnosis is concerned, current diagnostic methodologies are restricted by significant drawbacks and novel methods are required for MRSA detection. This study aimed at developing a simple loop-mediated isothermal amplification (LAMP) assay targeting on orfX for the rapid detection of methicillin-resistance Staphylococcus aureus (MRSA).

Results

The protocol was designed by targeting orfX, a highly conserved open reading frame in S. aureus. One hundred and sixteen reference strains, including 52 Gram-positive and 64 Gram-negative isolates, were included for evaluation and optimization of the orfX-LAMP assay. This assay had been further performed on 667 Staphylococcus (566 MRSA, 25 MSSA, 53 MRCNS and 23 MSCNS) strains and were comparatively validated by PCR assay using primers F3 and B3, with rapid template DNA processing, simple equipments (water bath) and direct result determination (both naked eye and under UV light) applied. The indispensability of each primer had been confirmed, and the optimal amplification was obtained under 65°C for 45 min. The 25 μl reactant was found to be the most cost-efficient volume, and the detection limit was determined to be 10 DNA copies and 10 CFU/reaction. High specificity was observed when orfX-LAMP assay was subjected to 116 reference strains. For application, 557 (98.4%, 557/566) and 519 (91.7%, 519/566) tested strains had been detected positive by LAMP and PCR assays. The detection rate, positive predictive value (PPV) and negative predictive value (NPV) of orfX-LAMP were 98.4%, 100% and 92.7% respectively.

Conclusions

The established orfX-LAMP assay had been demonstrated to be a valid and rapid detection method on MRSA.     

Effects of Proportions of Dietary Macronutrients on Glucocorticoid Metabolism in Diet-Induced Obesity in Rats

Tissue glucocorticoid levels in the liver and adipose tissue are regulated by regeneration of inactive glucocorticoid by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and inactivation by 5α- and 5β-reductases. A low carbohydrate diet increases hepatic 11β-HSD1 and reduces glucocorticoid metabolism during weight loss in obese humans. We hypothesized that similar variations in macronutrient proportions regulate glucocorticoid metabolism in obese rats. Male Lister Hooded rats were fed an obesity-inducing ad libitum ‘Western’ diet (37% fat, n = 36) for 22 weeks, then randomised to continue this diet (n = 12) or to switch to either a low carbohydrate (n = 12) or a moderate carbohydrate (n = 12) diet for the final 8 weeks. A parallel lean control group were fed an ad libitum control diet (10% fat, n = 12) throughout. The low and moderate carbohydrate diets decreased hepatic 11β-HSD1 mRNA compared with the Western diet (both 0.7±0.0 vs 0.9±0.1 AU; p<0.01), but did not alter 11β-HSD1 in adipose tissue. 5α-Reductase mRNA was increased on the low carbohydrate compared with the moderate carbohydrate diet. Compared with lean controls, the Western diet decreased 11β-HSD1 activity (1.6±0.1 vs 2.8±0.1 nmol/mcg protein/hr; p<0.001) and increased 5α-reductase and 5β-reductase mRNAs (1.9±0.3 vs 1.0±0.2 and 1.6±0.1 vs 1.0±0.1 AU respectively; p<0.01) in the liver, and reduced 11β-HSD1 mRNA and activity (both p<0.01) in adipose tissue. Although an obesity-inducing high fat diet in rats recapitulates the abnormal glucocorticoid metabolism associated with human obesity in liver (but not in adipose tissue), a low carbohydrate diet does not increase hepatic 11β-HSD1 in obese rats as occurs in humans.