Mammalian adipose tissue and muscle are major sources of lipid transfer protein mRNA

The plasma cholesteryl ester transfer protein (CETP) catalyzes the transfer of cholesteryl esters from high density lipoproteins (HDL) to triglyceride-rich lipoproteins and plays a major role in the catabolism of HDL. Lipoprotein lipase (LPL) is the rate-limiting enzyme for hydrolysis of circulating triglyceride and is involved in HDL formation. We show that tissues containing LPL are major sources of CETP mRNA in several mammalian species, including some with low cholesteryl ester transfer activity in plasma. In hamsters, adipose tissue and heart were found to be the richest sources of both CETP and LPL mRNA; in situ hybridization studies showed that the same cell types (i.e. adipocytes or myocytes) contained CETP and LPL mRNA in these tissues. Isolated adipocytes synthesized active CETP. Dietary studies revealed a complex pattern of response of CETP mRNA levels in different tissues, which showed partial similarity to the changes in LPL mRNA abundance. However, high cholesterol diets resulted in increased CETP mRNA abundance in adipose tissue, heart, and skeletal muscle, without equivalent changes in LPL mRNA. Plasma HDL cholesteryl ester levels showed strong inverse correlations with CETP mRNA abundance in adipose tissue. The results suggest a conserved function of CETP in adipose tissue and heart, such as a co-ordinate action with LPL to enhance HDL turnover. Although there is considerable overlap in the tissue- and cell-specific pattern of CETP and LPL gene expression, dietary studies revealed only limited parallelism in response at the mRNA level. The increase in CETP mRNA in peripheral tissues in response to increased dietary cholesterol suggests that local induction of CETP synthesis may help to recycle cholesterol deposited in these tissues during lipolysis of dietary lipoproteins.     

Reduction of Visceral Adipose Tissue and Improvement of Metabolic Indices: Effect of Dexfenfluramine in NIDDM

Increased visceral adipose tissue is thought to contribute to impaired glucose tolerance. We studied 10 men with non-insulin dependent diabetes (NIDDM) before and after a 12-week intervention study using dexfenfluramine. Subjects had a mean body mass index (BMI) of 26.4 ± 1.7 kg\m² and had an abdominal distribution of body fatness (waist-to hip ratio >0.9). Anthropometric indices, biochemistry, macronutrient intake from 7-day food records as well as a euglycaemic glucose clamp and magnetic resonance imaging (MRI) were performed at week 0 and week 12. Abdominal adipose tissue area measured by MRI was reduced from 854 ± 270 cm² to 666 ± 231 cm² (p=0.003) due mainly to a selective 32% reduction in visceral fat area from 484 ± 230 cm² to 333 ± 72 cm² (p=0.002). Insulin sensitivity improved from 0.29 ± 0.13 [min^?1 (mU/L)] to 0.54 ± 0.21 [min^?1 (mU/L)] (p=0.01) and C-peptide levels reduced from 0.77 ± 0.24 μmol/L to 0.58 ± 0.15 μmol/L (p=0.002). The reductions in fasting glucose and glycated haemoglobin failed to achieve significance. Fasting total cholesterol and triglyceride levels significantly reduced (p=<0.001 and p=0.021 respectively). There was a reduction in total energy intake (p=0.005) due to a significant reduction in calories obtained from fat (p<0.001). Thus dexfenfluramine was shown to be a useful adjunct therapy for the reduction of visceral fat in abdominally-obese men with NIDDM with an associated improvement in insulin sensitivity.     

Studies on determining conformational order in n-alkanes and phospholipids from the 1130 cm−1 raman band

Conformational disorder in lipid bilayer systems is commonly measured with reference to the intensity of the 1130 cm^?1 Raman band. However, estimates of the concentration of gauche bonds may vary by a factor of six according to the model used to relate intensity and concentration. In an effort to narrow the wide range in these estimates, we have measured the intensity of the 1130 cm^?1 band of crystalline n-C₂₁H₄₄ in its orthorhombic and hexagonal phases. On transition to the hexagonal phase, the intensity of the 1130 cm^?1 band is much reduced. It is assumed that the observed intensity reduction results from the introduction of gauche bonds whose number can be independently estimated from other features in the Raman and infrared spectra. From these measurements we conclude that the intensity of the 1130 cm^?1 band is not linearly related to the concentration of gauche bonds and that a disproportionately large decrease in the 1130 cm^?1 band intensity results from the introduction of a low concentration of gauche bonds. Thus previous estimates of gauche bond concentrations based on the assumption of a linear relation have tended to greatly overestimate the gauche bond concentration. These results derived from experiment are in accord with those of Pink et al. (Pink, D.A., Green, T.J. and Chapman, D. (1980) Biochemistry 19, 349–356) derived from theory.     

Insertion of nonhomologous DNA into the yeast genome mediated by homologous recombination with a cotransforming plasmid

Bacterial plasmids containing no detectable homology with yeast DNA sequences were inserted into the yeast genome by cotransforming with a plasmid containing a yeast gene. Analysis of the yeast transformants confirmed that recombination events occurred between the prokaryotic sequences shared by the two plasmids and between the yeast sequences common to the cotransforming plasmid and to the genome. Multiple copies of the two plasmids, in both tandem and interspersed arrays, are inserted by this method. Populations of cells grown from individual transformants are heterogenous for the number of integrated sequences. The number of integrated bacterial sequences is greatly reduced after 100 generations of growth in the populations that initially contained large numbers of sequences, while it is stable in those populations that initially contained either a single or a small number of copies.     

Genetic studies in an exotic population of corn (Zea mays L.) grown under two plant densities

Summary Progenies of a Design II [Comstock and Robinson (1948)] using random S ₁ lines from an exotic population of corn (Zea mays L.) were evaluated in a randomized incomplete block design with two replications at two plant-population densities (1 7,222 plants/ha and 68,888 plants/ha) in 1970 and 1971, at Lincoln, Nebraska. Five traits were studied i.e. grain weight, number of ears, days to flower, plant height and ear height.Under both densities the estimates of additive genetic variance were much larger than those of dominance genetic variance for all traits. The ratio of dominance to additive genetic variance estimates was less than 0.5 suggesting that for the majority of loci controlling the traits, partial to complete dominance is likely.The estimates of additive genetic x year interaction variance were high and significantly different from zero under both densities, indicating that estimates of additive genetic variance in this population obtained from experiments conducted in only one year may be seriously biased. The estimates of dominance genetic x year interaction variance were not significant and most of them were negative.Under both densities high genetic inter-relationships were indicated between grain weight and number of ears, days to flower and plant height, days to flower and ear height, and plant height and ear height.Even though there was a large difference between the two densities used in the study, the differences between the estimates of genetic parameters were not significant in all cases.The sample size of S ₁ plants representing each S₀ parent in the crossing nursery used in the present study (11.75) caused a small upward bias in the estimates of additive genetic variance, but it caused an upward bias in the estimates of dominance genetic variance of 6–7% of the total genetic variance.It is suggested that a trait such as grain weight should be expressed on a unit area basis when genetic parameters (except for correlation and the ratio between two values) obtained from experiments with different plant-population densities are to be compared.Published as Paper Number 3542, Journal Series, Nebraska Agricultural Experimental Station. Part of a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph. D. degree.A. I. D. Participant.The work was supported in part by a grant from the Rockefeller Foundation.     

Intracellular formation and processing of the heterotrimeric gH-gL-gO (gCIII) glycoprotein envelope complex of human cytomegalovirus

The human cytomegalovirus (HCMV) gCIII complex contains glycoprotein H (gH; gpUL75), glycoprotein L (gL; gpUL115), and glycoprotein O (gO; gpUL74). To examine how gH, gL, and gO interact within HCMV-infected cells to assemble the tripartite complex, pulse-chase experiments were performed. These analyses demonstrated that gH and gL associate by the end of the pulse period to form a disulfide dependent gH-gL complex. Subsequently, the gH-gL complex interacts with a 100-kDa precursor form of gO to form a 220-kDa precursor of the mature gH-gL-gO complex that contains a 125-kDa form of gO. The 220-kDa precursor complex (pgCIII) was sensitive to treatment with endoglycosidase H (endo H), while the mature gCIII complex was essentially resistant to digestion with this enzyme, suggesting that formation of pgCIII complex occurs in the endoplasmic reticulum (ER) and is processed to mature gH-gL-gO (gCIII) in a post-ER compartment. While the N-linked glycans on the 100-kDa form of gO were modified to endo H-resistant states as the 125-kDa gO formed, additional posttranslational modifications were detected on gO. These processing alterations were non-N-linked oligosaccharide modifications that could not be accounted for by phosphorylation or by O-glycosylation of the type sensitive to O-glycanase. Of gH, gL, gO, and the various complexes that they form, only the mature form of the complex was detectable at the infected cell membrane, as judged by surface biotinylation studies.     

Northern hemisphere photosynthetic trends 1982–99

We examined trends in the averaged May–September AVHRR normalized difference vegetation index (NDVI) from 1982 to 1999 for the northern hemisphere. NDVI is closely related to the amount of absorbed photosynthetically active radiation; hence, trends in NDVI reflect trends in photosynthetic activity of land‐surface vegetation. Linear and nonlinear trend analysis techniques were applied to four differently processed and corrected Advanced Very High Resolution Radiometer (AVHRR) NDVI data sets. The results were compared in order to evaluate the effects of trends in NDVI unrelated to vegetation activity. We consistently found significant positive trends in averaged NDVI for latitude bands above 35°N in all but one data set; this one data set lacked corrections for sensor drift and instrument calibration. An impressive improvement in data quality was achieved by applying calibration and corrections for atmospheric effects. Conservative estimates of the trends over the 1982–99 period range from 0.0015 to 0.0045 NDVI units year^?1 for global latitude bands from 35 to 75°N, with trends generally higher in the 1990s than in the 1980s; trends in NDVI were larger than trends explained by artefacts. In the 1980s, North American and Eurasian trends were roughly comparable, whereas in the 1990s the North American trends were generally higher. A pixel‐level analysis shows the trends to be widespread, with large areas of Canada, Europe and northern Asia experiencing significant positive increases across all vegetated landcovers.