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Biomedical subjects

L Zhou

Publications and source records attributed to L Zhou.

At least 523 records · Page 29Linked to original sources
PubMed1994

Isolation and expression of a cDNA encoding the precursor for a novel member (ACADSB) of the acyl-CoA dehydrogenase gene family.

The acyl-CoA dehydrogenases (ACDs) are a family of mitochondrial enzymes that oxidize straight chain or branched chain acyl-CoAs in the metabolism of fatty acids or branched chain amino acids. Deficiencies in members of this gene family are important causes of human disease. A cDNA encoding the human precursor for a novel member (gene symbol ACADSB) of the ACD gene family has been isolated and characterized. The open reading frame of 1.3 kb encodes a precursor protein of 431 amino acids, which is processed in vitro to yield a mature protein of 399 amino acids. The cDNA has significant sequence similarity to other members of the acyl-CoA dehydrogenase family, with the greatest homology (38%) to the short chain acyl-CoA dehydrogenase. The cDNA was expressed in eukaryotic (COS) and prokaryotic (Escherichia coli) cells, producing a protein of the expected size, with activity toward the short branched chain acyl-CoA derivatives ((S)-2-methylbutyryl-CoA, isobutyryl-CoA, and 2-methylhexanoyl-CoA), as well as toward the short straight chain acyl-CoAs (butyryl-CoA and hexanoyl-CoA).

Acyl-CoA Dehydrogenase↗
PubMed1994

The nucleotide sequence of the murine Hox-D3 (Hox-4.1) gene reveals extensive identity with the human protein.

We report the sequence of the murine Hox-D3 gene, formerly referred to as Hox-4, Hox-4.1 and Hox-4A. This gene is located on murine chromosome 2 in the Hox-D complex. The predicted Hox-D3 protein comprises 417 amino acids and displays 95% identity to the human protein. We have demonstrated that Hox-D3 is expressed in the skin, kidney and thymus, but not in lung, liver, spleen or stomach.

Amino Acid Sequence↗
PubMed1994

Differential ligand binding specificities of recombinant CD11b/CD18 integrin I-domain.

The alpha subunits of leukocyte CD11/CD18 integrins contain an approximately 200-amino acid "inserted" domain (I-domain) that may be important for multivalent adhesive recognitions. A recombinant form of the I-domain of CD11b/CD18 was generated and analyzed directly for interaction with complementary integrin ligands. CD11b I-domain bound the activation-dependent monoclonal antibody 7E3, and the functionally blocking anti-CD11b monoclonal antibodies OKM9, 60.1, and LM2/1, but not OKM1 or M1/70. Fibrinogen or soluble intercellular adhesion molecule-1 associated with CD11b I-domain in a concentration-dependent manner. Binding of 125I-fibrinogen to recombinant CD11b I-domain was saturable, governed by a Kd of approximately 0.22 +/- 0.06 microM, and fully inhibited by molar excess of unlabeled fibrinogen, or by the P1 peptide (KY)GWTVFQKRLDGSV (IC50 approximately 2.5-5 microM), duplicating the fibrinogen gamma chain sequence Gly190-Val202. In contrast, 125I-factor X binding to CD11b I-domain was only partially inhibited (50-60%) by a molar excess of unlabeled factor X, and entirely unaffected by functionally blocking anti-CD11b monoclonal antibodies or by factor X-derived synthetic peptidyl antagonists. We conclude that the I-domain of CD11b participates in qualitative mechanisms of receptor activation and contains the binding site(s) for the CD11b/CD18 ligands fibrinogen and intercellular adhesion molecule-1, while it is only minimally implicated in the recognition of factor X.

Amino Acid Sequence↗
PubMed1994

Probing the metal binding sites of Escherichia coli isoleucyl-tRNA synthetase.

The metal binding properties of isoleucyl-tRNA synthetase (IleRS) from Escherichia coli were studied by in vivo substitution of the enzyme-bound metals. Purified E. coli IleRS was shown to have two tightly bound zinc atoms per active site. Cobalt- and cadmium-substituted IleRS were also found to contain two tightly bound Co2+ and Cd2+ atoms per polypeptide chain, respectively. The d-d transitions in the low energy absorption spectrum of Co(2+)-substituted IleRS were characteristic of that expected for two tetrahedrally coordinated Co2+ metals. Apo-IleRS was found to be inactive in both the aminoacylation of tRNA(Ile) and in the isoleucine-dependent ATP-pyrophosphate exchange reactions. Both Co(2+)- and Cd(2+)-substituted IleRS were found to have kcat/Km values in the isoleucine-dependent ATP-pyrophosphate exchange assay approximately 5-fold lower than the native Zn2+ enzyme. A single enzyme-bound Zn2+ or Co2+ atom per polypeptide chain could be removed by dialysis of Zn(2+)- or Co(2+)-substituted IleRS against 1,10-phenanthroline. Removal of one of the two enzyme-bound Zn2+ atoms per polypeptide chain with 1,10-phenanthroline was found to decrease (kcat/Km)Ile by approximately 130-fold. The dependence of the kinetic parameters on the identity and number of enzyme-bound metals in the isoleucine-dependent ATP-pyrophosphate exchange reaction suggests that at least one enzyme-bound metal is indirectly involved in aminoacyladenylate formation. Metal substitution or removal of one of the two enzyme-bound metals in IleRS was found to have little effect on the Km value for tRNA(Ile) or the kcat value for aminoacylation of tRNA(Ile).(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1994

Intronless celB from the anaerobic fungus Neocallimastix patriciarum encodes a modular family A endoglucanase.

The cDNA designated celB from the anaerobic rumen fungus Neocallimastix patriciarum contained a single open reading frame of 1422 bp coding for a protein (CelB) of M(r) 53,070. CelB expressed by Escherichia coli harbouring the full-length gene hydrolysed carboxymethylcellulose in the manner of an endoglucanase, but was most active against barley beta-glucan. It also released reducing sugar from xylan and lichenan, but was inactive against crystalline cellulose, laminarin, mannan, galactan and arabinan. The rate of hydrolysis of cellulo-oligosaccharides by CelB increased with increasing chain length from cellotriose to cellopentaose. The predicted structure of CelB contained features indicative of modular structure. The first 360 residues of CelB constituted a fully functional catalytic domain that was homologous with bacterial endoglucanases belonging to cellulase family A, including five which originate from three different species of anaerobic rumen bacteria. Downstream from this domain, and linked to it by a serine/threonine-rich hinge, was a non-catalytic domain containing short tandem repeats, homologous to the C-terminal repeats contained in xylanase A from the same anaerobic fungus. Unlike previous fungal cellulases, genomic celB was devoid of introns. This lack of introns and the homology of its encoded product with rumen bacterial endoglucanases suggest that acquisition of celB by the fungus may at some stage have involved horizontal gene transfer from a prokaryote to N. particiarum.

Amino Acid Sequence↗
PubMed1994

Occurrence of specific sterols in Pneumocystis carinii.

We have examined the sterol composition and biosynthesis of rat Pneumocystis carinii. We found a number of lipid components among the nonsaponifiable fraction that appear unique to P. carinii. These lipids are present in P. carinii purified preparations and P. carinii-infected whole lungs but absent from control lungs. They show chromatographic properties typical of sterols on GC and HPLC; they are present in free and esterified sterol fractions isolated by thin layer chromatography, they are precipitated by digitonin and they are labeled upon incubation of purified P. carinii cell suspensions with [3H] mevalonate and [3H] squalene. The finding of these sterols opens new opportunities for the identification of chemotherapeutic targets against P. carinii.

Animals↗
PubMed1994

Gonadal steroid hormones and hypothalamic opioid circuitry.

Endogenous opioid peptides derived from several gene families are localized within hypothalamic regions known to be involved in the regulation of reproduction. For example, the proenkephalin gene products, met- and leu-enkephalin, and the proopiomelanocortin (POMC) gene product, beta-endorphin, are found in the rat medial preoptic area (MPOA). Moreover, the expression of these peptides and their receptors varies across the estrous cycle in the female rat. We have examined the gonadal steroid regulation of mu-opiate receptors and opioid peptides in the MPOA, and POMC mRNA expression in neurons that innervate the MPOA. mu-Opiate receptors in the MPOA are sexually dimorphic and gonadal steroid hormone-dependent. Hormonal priming of ovariectomized rats with estrogen and progesterone (P) upregulates MPOA mu-receptors 27, but not 3, hr after P treatment. Inhibition of protein synthesis during the first 6 hr after P prevents receptor upregulation. The density of beta-endorphin fibers in the MPOA also increases following hormone treatment, and POMC mRNA expression in neurons that innervate the MPOA is induced by hormone treatment beginning 13 hr after P treatment. This delayed response might be ubiquitous among POMC neurons, as those innervating the median eminence also exhibit increased POMC mRNA expression along a similar time course. The results suggest that hormonal feedback regulates opioid peptides which act at mu-receptors in the MPOA to influence reproductive behavior and cyclicity. These opioid functions represent an important component in the complex regulatory processes which control reproduction.

Animals↗
PubMed1994

Characterization of two density populations of feline calicivirus particles.

Feline calicivirus (FCV) F9 strain was propagated in Crandall-Reese feline kidney cells. Two density populations of viral particles were observed after equilibrium centrifugation in an isopyknic CsCl gradient. The buoyant density of the heavy particle (PH) is 1.33 g/ml. The light particle (PL), a previously undescribed form of feline calicivirus, has a buoyant density of 1.22 g/ml. The PH and PL presented a similar morphology by electron microscopy. Western blot showed that both PH and PL contained a major polypeptide of the typical FCV capsid protein with a molecular weight of 62,000. Infectivity assay and RNA isolation demonstrated that PH is the intact infectious virion while PL is FCV empty capsid.

Animals↗
PubMed1994

Clinical observation of treatment of hypertension with calcium.

The effect of oral calcium supplementation (1000 mg/day) on hypertension was studied in 57 borderline and mild-to-moderate hypertensive patients in a randomized, double-blind, placebo-controlled study for 14 weeks. Twenty-five patients from the above groups (11 from the calcium-treated group and 14 from the placebo group) were studied in a crossover fashion for 14 more weeks. The high calcium intake lowered systolic blood pressure by 17 mm Hg (P < .01), and diastolic blood pressure by 11 mm Hg (P < .01). Fifty percent of the calcium-treated patients showed a significant antihypertensive effect and were termed calcium responders. In the crossover study, serum sodium was lower after taking calcium than after placebo intake (P < .05). Pretreatment plasma free calcium content of the calcium-responsive patients was significantly lower (P < .05) than in the calcium nonresponsive patients, and was highly significantly increased (P < .01) after administering calcium. The result showed that oral calcium supplementation can lower blood pressure in a significant fraction of essential hypertensive subjects, and that the free calcium level in plasma may help identify calcium-responsive individuals. While the mechanism by which increased calcium intake lowers blood pressure in hypertension is still undetermined, these data support an underlying relationship between hypertension and calcium and possibly sodium metabolism.

Administration, Oral↗
PubMed1994

Comparison of dietary habits, physical activity and body size among Chinese in North America and China.

BACKGROUND: Chinese in North America have higher rates of many chronic diseases than do Chinese in Asia. However, there is a lack of data among comparisons of the environmental and lifestyle factors for Chinese in China and Chinese residing in North America. METHODS: We examined self-reported dietary nutrient intakes, physical activity patterns and body mass index of 2488 healthy Chinese men and women residing in North America (US and Canada) and in the People's Republic of China. RESULTS: On average, Chinese in China consumed more calories (males 2904 kcal in China, versus 2201 kcal in North America; females 2317 Kcal in China, versus 1795 Kcal in North America and more carbohydrate, but less fat (males 72.2 g in China versus 84.5 g in North America, females 56.6 g in China versus 70.8 g in North America), protein, vitamin A, beta-carotene and vitamin C than did Chinese in North America. Per cent calories from fat was 35% for Chinese in North America and 22% for Chinese in China. In contrast, the per cent of calories from carbohydrates was 62-68% in China and 48% in North America. Chinese in China reported spending more time in vigorous activity, sleeping and walking but less hours in sitting than Chinese in North America. Chinese in China weighted less and were leaner than North American Chinese. CONCLUSIONS: These differences in nutrient intakes, physical activity and body size of Chinese living on two different continents suggest possible explanations for observed differences in chronic disease rates in the two populations.

Asian People↗
PubMed1994

Use of a human skin-grafted nude mouse model for the evaluation of topical retinoic acid treatment.

Cultured human keratinocytes and artificial dermal equivalents maintained in vitro do not perfectly mimic the terminal differentiation patterns and response to drugs observed in intact human skin. We have made use of human skin grafted onto nude mice to demonstrate that such grafts maintain the pattern of pharmacologic responsiveness to all-trans retinoic acid previously reported in human subjects. The use of a quantitative polymerase chain reaction method to measure induction of a retinoic acid responsive gene, cytoplasmic retinoic acid binding protein II, has made it possible to generate objective data suitable for investigations of drug efficacy. This method of using grafted human skin has potential broad applicability for investigation of topical drugs in a number of therapeutic fields.

Administration, Topical↗
PubMed1994

Comparison of the neuralized genes of Drosophila virilis and D. melanogaster.

The neurogenic gene neuralized of Drosophila melanogaster is thought to play a role in the determination of cell fate in the embryonic nervous system as well as other tissues during development. To determine which sequences within the neuralized gene encode functionally important domains, we have initiated an interspecific comparison of the neuralized gene of D. virilis and D. melanogaster. In this study we show that several motifs that we have previously identified in the neuralized protein of D. melanogaster are conserved in D. virilis. These include a putative nuclear localization signal, a homeodomain similarity region, and a zinc finger motif. In contrast, a helix-turn-helix motif with structural similarity to those identified as DNA-binding regions of bacterial repressors is deleted. These results demonstrate that it is possible to identify key functional regions of the neuralized protein by an interspecific comparison.

Amino Acid Sequence↗