A glycosaminoglycan activator of lipoprotein lipase in human plasma

By use of ion exchange chromatography we have isolated two discrete classes of “free” glycosaminoglycans (GAG) from human plasma. The GAG fractions were tested for their effects on two lipoprotein lipase (LPL) enzyme systems containing an apolipo-protein C-II activated emulsion as the triglyceride substrate and bovine serum albumin as the free fatty acid acceptor. The low-charge GAG (Fraction I) had essentially no effect on the LPL reaction. The high-charge GAG (Fraction II) stimulated the LPL reaction 100 to 300%. The GAG composition of each fraction was investigated with chemical and enzymatic techniques. Fraction I consisted of low-charge chondroitin sulfate noncovalently bound to protein. Fraction II consisted of a mixture of high-charge GAG non-covalently bound to protein. Degradation with nitrous acid eliminated the ability of high-charge GAG to stimulate LPL. This and other evidence suggests that the high-charge GAG in human plasma responsible for LPL activation is heparan sulfate (HS). We suggest that plasma HS may modulate triglyceride clearance mechanisms $\text{in vivo}$ by its interaction with LPL.     

Prostaglandin D2 as a potential antithrombotic agent

Prostaglandin D₂ was found to be a potent inhibitor of platelet aggregation. Aggregation of human platelets by ADP, collagen and prostaglandin G₂ was inhibited more strongly by PGD₂ than by PGE₁. Although ADP-induced aggregation of rabbit platelets was inhibited more strongly by PGE₁ than by PGD₂ the latter prostaglandin gave a more long-lasting inhibitory effect on platelet aggregation following intravenous or oral administration. These results coupled with the finding that PGD₂ has less hypotensive effects on the cardiovascular system than PGE₁ suggest the possible use of PGD₂ as an antithrombotic agent.     

Simultaneous determination of d- and l-thyroxine in human serum by liquid chromatography with electrochemical detection

A method for the determination of d- and l-thyroxine in human serum is described. The method involves extraction of thyroxine from serum and the separation of thyroxine enantiomers on a reversed-phase, high-performance liquid chromatographic column by use of a chiral eluent containing l-proline and cupric sulfate. Satisfactory resolution of the enantiomers of thyroxine, triiodothyronine, and reverse triiodothyronine can be achieved in 12 min and, employing amperometric detection to monitor the separation, the detection limit for serum thyroxine is in the range of 1–3 ng per injected sample.     

Distinguishing Family from Friends

Kinship and friendship are key human relationships. Increasingly, data suggest that people are not less altruistic toward friends than close kin. Some accounts suggest that psychologically we do not distinguish between them; countering this is evidence that kinship provides a unique explanatory factor. Using the Implicit Association Test, we examined how people implicitly think about close friends versus close kin in three contexts. In Experiment 1, we examined generic attitudinal dispositions toward friends and family. In Experiment 2, attitude similarity as a marker of family and friends was examined, and in Experiments 3 and 4, strength of in-group membership for family and friends was examined. Findings show that differences exist in implicit cognitive associations toward family and friends. There is some evidence that people hold more positive general dispositions toward friends, associate attitude similarity more with friends, consider family as more representative of the in-group than friends, but see friends as more in-group than distant kin.     

Substrate Locking Promotes Dimer-Dimer Docking of an Enzyme Antibiotic Target

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Oral Antibiotic Treatment of Mice Exacerbates the Disease Severity of Multiple Flavivirus Infections

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Chromosomal localization, gene structure and transcription pattern of the ORFX gene, a homologue of the MHC-linked RING3 gene

We have mapped the human ORFX gene to chromosome 9q34 and determined its complete gene structure. Comparison with RING3, the human MHC-linked homologue on 6p21.3, shows the two gene structures to be highly conserved but with an approximate threefold expansion in the ORFX introns. RING3 and ORFX are found to be ubiquitously expressed in human adult and foetal tissues. Evidence suggests that the two genes may have arisen from an ancient duplication in a common ancestral chromosome.     

Seasonal variation in the resting metabolic rate of male wood mice Apodemus sylvaticus from two contrasting habitats 15 km apart

Diurnal and nocturnal resting metabolic rates of winter- and summer-acclimatized adult male wood mice Apodemus sylvaticus from two adjacent populations, 15 km apart, were measured. One population lived in deciduous woodland, and experienced a narrower daily range of temperatures than the second population, which inhabited maritime sand-dunes. Ambient temperature and body mass had significant effects on the resting metabolism of mice, excluding winter-acclimatized sand-dune animals where only temperature explained significant amounts of the observed variation. Only in this latter group could a thermoneutral zone be determined, with a lower critical temperature of ca. 25 °C and resting metabolism of 0.155 W. Nocturnal resting metabolic rates were significantly greater than diurnal levels. Winter acclimatization was associated with reductions in thermal conductance and resting metabolism, thus minimizing energy expenditure at rest. Site differences in thermoregulatory strategies were only found in winter, thermal conductances remained similar but mice from the sand-dunes had significantly lower metabolic rates than those from the woodland. Winter acclimatization in wood mice was influenced by factors in addition to photoperiod. Intra-specific and individual variations in resting metabolism, as shown in this study, potentially have a pronounced effect on the daily energy expenditure of a free-living animal. Accepted: 6 September 1996