North Sea cod and climate change – modelling the effects of temperature on population dynamics

In order to examine the likely impacts of climate change on fish stocks, it is necessary to couple the output from large‐scale climate models to fisheries population simulations. Using projections of future North Sea surface temperatures for the period 2000–2050 from the Hadley General Circulation Model, we estimate the likely effects of climate change on the North Sea cod population. Output from the model suggests that increasing temperatures will lead to an increased rate of decline in the North Sea cod population compared with simulations that ignore environmental change. Although the simulation developed here is relatively simplistic, we demonstrate that inclusion of environmental factors in population models can markedly alter one's perception of how the population will behave. The development of simulations incorporating environment effects will become increasingly important as the impacts of climate change on the marine ecosystem become more pronounced.     

Regulation, replication, and integration functions of the Vibrio cholerae CTXφ are encoded by region RS2

CTXφ is a filamentous phage that encodes cholera toxin, one of the principal virulence factors of Vibrio cholerae . CTXφ is unusual among filamentous phages because it can either replicate as a plasmid or integrate into the V. cholerae chromosome at a specific site. The CTXφ genome has two regions, the 'core' and RS2. Integrated CTXφ is frequently flanked by an element known as RS1 which is related to RS2. The nucleotide sequences of RS2 and RS1 were determined. These related elements contain three nearly identical open reading frames (ORFs), which in RS2 were designated rstR , rstA2 and rstB2 . RS1 contains an additional ORF designated rstC . Functional analyses indicate that rstA2 is required for CTXφ replication and rstB2 is required for CTXφ integration. The amino terminus of RstR is similar to the amino termini of other phage-encoded repressors, and RstR represses the expression of rstA2 . Although genes with related functions are clustered in the genome of CTXφ in a way similar to those for other filamentous phages, the CTXφ RS2-encoded gene products mediating replication, integration and repression appear to be novel.     

Insulin activation of phosphatidylinositol 3-kinase in human skeletal muscle in vivo

Hickey, Matthew S., Charles J. Tanner, D. Sean O'Neill,Lydia J. Morgan, G. Lynis Dohm, and Joseph A. Houmard. Insulin activation of phosphatidylinositol 3-kinase in human skeletal muscle invivo. J. Appl. Physiol. 83(3):718-722, 1997.The purpose of this investigation was to determinewhether insulin-stimulated phosphatidylinositol 3-kinase (PI3-kinase)activity is detectable in needle biopsies of human skeletal muscle.Sixteen healthy nonobese males matched for age, percent fat, fastinginsulin, and fasting glucose participated in one of two experimentalprotocols. During an intravenous glucose tolerance test (IVGTT)protocol, insulin-stimulated PI3-kinase activity was determined frompercutaneous needle biopsies at 2, 5, and 15 min post-insulinadministration (0.025 U/kg). In the second group, a 2-h, 100 mU · m² · min¹euglycemic hyperinsulinemic clamp was performed, and biopsies wereobtained at 15, 60, and 120 min after insulin infusion was begun.Insulin stimulated PI3-kinase activity by 1.6 ± 0.2-, 2.2 ± 0.3-, and 2.2 ± 0.4-fold at 2, 5, and 15 min, respectively, duringthe IVGTT. During the clamp protocol, PI3-kinase was elevated by 5.3 ± 1.3-, 8.0 ± 2.6-, and 2.7 ± 1.4-fold abovebasal at 15, 60, and 120 min, respectively. Insulin-stimulatedPI3-kinase activity at 15 min post-insulin administration wassignificantly greater during the clamp protocol vs. the IVGTT(P < 0.05). These observations suggest that insulin-stimulated PI3-kinase activity is detectable inneedle biopsies of human skeletal muscle, and furthermore, that theeuglycemic, hyperinsulinemic clamp protocol may be a useful tool toassess insulin signaling in vivo.

     

Gas-chromatographic resolution of the enantiomers of 3-(3,4-dihydroxyphenyl)alanine and its α-methyl analog

Methylation of (R,S)-DOPA with diazomethane gave the trimethyl derivative in which the phenolic hydroxy groups and the carboxy group were methylated. N-Methylated side products were also formed. N-Acylation of the racemic trimethyl derivative with (S)-α-methoxy-α-trifluoromethylphenylacetyl chloride gave two diastereomeric amides which were resolved by gas chromatography, the diastereomer derived from (S)-(−)-DOPA cluting first. The procedure was also applied to α-methyl-DOPA.