Group differences in mean intelligence for the Dutch and Third World immigrants.

Evidence from eleven samples indicates that the mean IQ of third world immigrants in the Netherlands is lower than the Dutch mean by approximately one standard deviation for Surinamese and Antillians, and by approximately one and a half standard deviations for Turks and Moroccans. Since IQ tests provide the best prediction of success in school and organizations, it could be that the immigrants' lower mean IQ is an important factor in their low status on the Dutch labour market. The IQs of second-generation immigrants are rising.     

Blood groups and natural selection by genetical environment

A survey is given of a number of investigations indicating the importance in natural selection of the genetical environment of populations and individuals.In the introduction it is observed that blood group frequency patterns are very stable, even in very small populations, and appear independent of environmental factors. They appear to be race-specific, maintained by a process of natural selection which is dependent of the racial genetical composition. Indications in favour of this hypothesis are obtained from several studies carried out in populations of mixed origin:The introduction on a small scale into the populations of New Guinea of foreign elements with some S genes may result in a population with relatively high S frequencies; the frequencies of certain of the blood group genes in the mixed negroid populations of Curaçao are not in agreement with the racial compositions of the mixtures as they have been calculated from the frequencies of other blood group genes, and the same appears to be the case in the populations of the Himalayas. The marked variation of MNSsHe frequencies in Africa may perhaps be explained by a powerful selective pressure exercized by the genetical backgrounds of the various populations, as is demonstrated by the absence of some expected genotypes among male Bush Negroes in Surinam.The effects of natural selection by genetical environment can also be demonstrated by family studies:In families with elliptocytosis Rhesus segregation shows some deviation from Mendelian laws, and the ratio of elliptocytosis-positive and-negative children appears to depend on the Rh genotype of the elliptocytosis-positive parent. From blood group studies in selected pedigrees and dizygotic twins it appears that twin pairs are more often doubly concordant for both MN and Rh than is to be expected.Some implications of the observed effects of natural selection in the study of human genetics and population dynamics are briefly discussed.     

Localization of HLA on the short arm of chromosome 6

Summary A detailed marker gene study in a large Dutch kindred segregating for a reciprocal translocation between the chromosomes 6 and 20, t(6;20) (p21;p13), revealed a close linkage between the HLA genes and the breakpoint on the short arm of 6. During this study an apparent peak lod score of 2.9 was obtained at a recombination value of 0.05 for a linkage between HLA and the breakpoint, indicating that the chromosomal region, carrying the HLA genes, is situated near the breakpoint in band 6p21 close to the transition to 6p22.     

Inhibition of nuclear T3 binding by fatty acids liberated from nuclear membranes via phospholipase C.

1. We have investigated whether phospholipase C (PLC) might act on phospholipids in the nuclear membrane of rat liver, resulting in inhibition of nuclear T3 binding (INB activity). 2. Incubation of intact nuclei with PLC caused a time- and dose-dependent increase of INB activity; this was correlated with a rise of the free fatty acid concentration in the nuclear ether extract. 3. Removal of the nuclear membrane resulted in a loss of INB activity of the nuclei. 4. Other compounds liberated by the action of PLC (such as diacylglycerols, IP3 and phosphoalcohols), had no INB activity. 5. We conclude that PLC can liberate fatty acids from the rat liver-nuclear membrane via further degradation of the direct product diacylglycerol. 6. These fatty acids display inhibition of nuclear T3 binding in vitro.     

Anaerobic biotransformation of hexachlorocyclohexane isomers by <Emphasis Type="Italic">Dehalococcoides</Emphasis> species and an enrichment culture

The biotransformation of hexachlorocyclohexane isomers (HCH) by two Dehalococcoides mccartyi strains (195 and BTF08) and an enrichment culture was investigated and compared to conversion by the obligate anaerobic strain Clostridium pasteurianum strain DSMZ 525. The D. mccartyi strains preferentially transformed γ-HCH over α-HCH and δ-HCH isomers while β-HCH biotransformation was not significant. In case of the enrichment culture, γ-HCH was preferentially transformed over the δ-HCH, β-HCH and α-HCH isomers. Major observed metabolites in both cases were tetrachlorocyclohexene and as end products monochlorobenzene (MCB) and benzene. Dechlorination of the γ-HCH isomer was linked to an increase in cell numbers for strain 195. γ-HCH transformation was linked to considerable carbon stable isotope fractionation with the enrichment factor ε_c?=???5.5?±?0.8‰ for D. mccartyi strain 195, ε_c?=???3.1?±?0.4‰ for the enrichment culture and ε_c?=???4.1?±?0.6‰ for co-metabolic transformation by C. pasteurianum.     

Conformation of the core sequence in melanocortin peptides directs selectivity for the melanocortin MC3 and MC4 receptors.

Melanocortin peptides regulate a variety of physiological processes. Five melanocortin receptors (MC-R) have been cloned and the MC3R and MC4R are the main brain MC receptors. The aim of this study was to identify structural requirements in both ligand and receptor that determine gamma-melanocyte-stimulating hormone (MSH) selectivity for the MC3R versus the MC4R. Substitution of Asp10 in [Nle4]Lys-gamma2-MSH for Gly10 from [Nle4]alpha-MSH, increased both activity and affinity for the MC4R while the MC3R remained unaffected. Analysis of chimeric MC3R/MC4Rs and mutant MC4Rs showed that Tyr268 of the MC4R mainly determined the low affinity for [Nle4]Lys-gamma2-MSH. The data demonstrate that Asp10 determines selectivity for the MC3R, however, not through direct side chain interactions, but probably by influencing how the melanocortin core sequence is presented to the receptor-binding pocket. This is supported by mutagenesis of Tyr268 to Ile in the MC4R which increased affinity and activity for [Nle4]Lys-gamma2-MSH, but decreased affinity for two peptides with constrained cyclic structure of the melanocortin core sequence, MT-II and [D-Tyr4]MT-II, that also displayed lower affinity for the MC3R. This study provides a general concept for peptide receptor selectivity, in which the major determinant for a selective receptor interaction is the conformational presentation of the core sequence in related peptides to the receptor-binding pocket.     

Microrheology of hyaluronan solutions: implications for the endothelial glycocalyx

The endothelial glycocalyx (EG) is a complex biopolymer network produced by vascular endothelial cells that forms a layer with multiple functions at the luminal side of blood vessels. The EG acts as an anti-adhesive protection layer, as a molecular sieve, as a chemical sensor site, and as a mechanotransducer of fluid shear stress to the underlying cell layer. A major component involved in these processes is the highly hydrated glycosaminoglycan (GAG) hyaluronan (HA). Here we used laser interferometry to measure the broadband mechanical response of reconstituted HA solutions at close to physiological conditions. HA showed rheological behavior consistent with that of a flexible polymer. The elastic behavior observed for entangled HA networks showed reptational relaxation with a large distribution of time scales, which disappeared quickly (15 min) with the addition of hyaluronidase (HAase). We conclude that the broadband mechanical probing of model systems (HA solutions) provides quantitative data that are crucial to understand the mechanical response of the EG in vivo and its role in mechanosensing.     

Rate of uptake of CO by hemoglobin in pig erythrocytes as a function of PO2

Te Nijenhuis, Francis C. A. M., Lydia Lin, Gerko H. Moens,Adrian Versprille, and Robert E. Forster. Rate of uptake of CO byhemoglobin in pig erythrocytes as a function ofPO₂. J. Appl.Physiol. 81(4): 1544-1549, 1996.This study wasinitiated to obtain data on the rate of carbon monoxide (CO) uptake(_CO) by hemoglobin in pigerythrocytes to derive, in a later study, the pulmonary capillary bloodvolume (Qc) in pigs from the Roughton-Forster relationship. Blood fromfive different female pigs was used. The_CO, the milliliters of CO takenup by 1 ml of whole blood per minute per Torr CO tension, wasdetermined on each blood sample with a continuous-flow rapid-mixingapparatus and double-beam spectrophotometry at 37°C and pH 7.4 atfour or five different PO₂ values.Because the individual regression lines of _CO vs.PO₂ were not significantly different,a common regression equation was calculated:1/_CO = 0.0084 PO₂ + 0.63. The slope of thisregression line is significantly steeper than the reported slopes ofthe regression lines for human and dog erythrocytes measured under thesame conditions. Our results revealed that calculation ofQc in pigs by using _CO valuesfor human or dog erythrocytes would result in an underestimation of 51 and 50%, respectively.