PubMed Health⌕ Search

Biomedical subjects

D Zheng

Publications and source records attributed to D Zheng.

At least 91 records · Page 5Linked to original sources
PubMed1997

gp120-directed antibody-dependent cellular cytotoxicity as a major determinant of the rate of decline in CD4 percentage in HIV-1 disease.

OBJECTIVE: To determine the relationship between the rate of CD4 percentage decline and two factors postulated to be associated with CD4 cell destruction: circulating HIV-1 viral load and gp120-directed antibody-dependent cellular cytotoxicity (ADCC). DESIGN: Four women and 16 men had serial determinations of CD4 percentage gp120-directed ADCC activity [using the cell-mediated cytotoxicity (CMC) assay] natural killer (NK) cell number, spontaneous NK lytic function, and plasma HIV-1 RNA. METHODS: The rate of decline in CD4 percentage was modeled as a function of gp120-directed ADCC activity and circulating HIV-1 RNA using Pearson correlation and multiple regression analyses. RESULTS: All individuals had at least four CMC assays performed and two HIV-1 RNA polymerase chain reaction measurements over a median follow-up of 27 months. Although the rate of CD4 percentage decline was associated with either CMC activity (r = -0.53, P = 0.02) or circulating HIV-1 RNA (r = -0.42, P = 0.07), it was strongly correlated with an interaction between CMC and HIV-1 RNA (r = -0.76, P < 0.0001). Mean CMC activity was associated with both mean percentage of circulating NK cells and mean spontaneous NK cell lysis. CONCLUSIONS: The ability of cells from HIV-infected individuals to mediate gp120-directed ADCC, together with a sufficient circulating viral load, define conditions under which rapid CD4 cell destruction may occur. This relationship between viral load and an HIV-1-specific immune response lends important insights into the central causes of immunodeficiency in AIDS and suggests additional avenues for therapeutic intervention.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1997

The effects of short intravenous infusions of thiopentone on myocardial function, blood flow and oxygen consumption in sheep.

The cardiovascular effects of slow (over two minutes) intravenous infusions of thiopentone 750 mg in conscious instrumented sheep breathing 100% oxygen were examined for 30 minutes following the start of the infusion. The maximum rate of rise of left ventricular pressure (an index of myocardial contractility) decreased significantly from 1 to 10 minutes, to a minimum of 45% of baseline. Heart rate increased by up to 33% above baseline from 0.5 min onwards. Both mean arterial pressure and cardiac output were decreased from between 1 and 7 min. Left ventricular minute work was transiently decreased, but left coronary blood flow and myocardial oxygen consumption showed little or no change from baseline. We conclude that in vivo, thiopentone administered at a relatively slow rate caused large reductions in myocardial contractility, and therefore cardiac reserve, in the absence of significant changes in myocardial blood flow or oxygen consumption.

Anesthetics, Intravenous↗
PubMed1997

[Influences of terraazaindene on absorption spec tra and fluorescence spectra of sensitizing dyes].

This study is about the influences of tetraazaindene (TAI) on absorption spectra and the fluorescence spectra of three kinds of sensitizing dyes. The absorption of all peaks of the dyes enhance with increasing TAI, among which the absorption of J-aggregate has even marked enhancement. At certain value of TAI, the absorption of monomolecule of dye enhances much more rapidly as well as the absorption of H-aggegte decreasing because of H-aggregate dissociating into monomolecules. The results obtained also show that the fluorescence emissions of the dyes enhance with increasing TAI. The mechnisms of the observed phenomena are discussed in detail.

English Abstract↗
PubMed1997

Self-reported prevalence of diabetes and preventive health care practices among people with diabetes in South Carolina.

In conclusion, South Carolina has a higher prevalence of diabetes compared to the national average. Age is a major factor associated with increased prevalence. African Americans had a disproportionately higher prevalence of diabetes relative to white Americans in South Carolina. Compared to the standards of diabetes care recommended by the ADA, health care practice by people with diabetes and health professionals still needs to be improved. Diabetes communication programs, including diabetes education for people with diabetes and health professional education, continue to be necessary for the improvement of diabetes care.

Adolescent↗
PubMed1997

Immunoreactive growth hormone in human peripheral T lymphocytes: encoding sequence of cDNA identical to that of the pituitary human growth hormone.

OBJECTIVE: To detect the cDNA sequence of immunoreactive growth hormone (irGH) in human lymphocytes and to compare it with that of human growth hormone (hGH) in the pituitary. METHODS: The mRNA of irGH in human peripheral blood mononuclear cells (PBMC) was detected by Northern blot analysis. The cDNA of irGH was obtained by reverse-transcriptase and polymerase chain reaction amplification and obtained by screening from a cDNA library of human T lymphocytes. The sequence of irGH cDNA was determined and compared with that of the pituitary hGH. RESULTS: Very low level of irGH mRNA was detected in human PBMCs by Northern blot analysis. The cDNA sequence of the entire open reading frame of human irGH was 651 bp, which is identical to that of pituitary hGH. CONCLUSIONS: The same hGH molecule can be produced by human pituitary somatotrophic cells and human peripheral lymphocytes.

Amino Acid Sequence↗
PubMed1997

[Spectral analysis of R-R intervals in adolesent persons during mental stress].

In this study, power spectrum analysis of the autoregressive model was used to quantitatively estimate the power spectrum of R-R intervals in adolesent during the state of the mental stress. The power spectrum density of the lower frequency (HF: 0.05-0.15 Hz) and the high frequency (HF: 0.15-0.5 Hz) component were acquired. The results showed that during the mental stress the HF component decreased significantly (P < 0.001) while the LF component increased relatively and the center frequency of the HF increased remarkably (P < 0.001). This suggests that the spectral analysis of heart rate variability (R-R interval) offers an efficient non-invasive method to assess the autonomic nerve activity of cardiovascular system during the stress condition.

Adult↗
PubMed1996

The effect of exercise on ob gene expression.

Expression of the ob gene is subject to nutritional as well as hormonal regulation to control fat storage. In the present study we investigated the effect of acute exercise and long-term exercise training on ob mRNA levels in rat adipose tissue. Northern blot analysis showed that a single bout of exercise significantly decreased ob mRNA levels approximately 30% immediately and 3 hr after exercise. After 4 weeks of exercise training the ob mRNA level was significantly decreased approximately 48% at 2 hr after the last training session compared to the control group. These data demonstrated that exercise has a transient effect on ob gene expression and suggest that regulation of ob gene expression may help control energy balance following exercise.

Adipose Tissue↗
PubMed1996

Differential expression of ob mRNA in rat adipose tissues in response to insulin.

The recently cloned obese (ob) gene encodes a fat-specific mRNA and a protein which is believed to regulate satiety and metabolic rate so as to control fat storage. In the present study we investigated rat ob mRNA levels in different fat depots and the effects of insulin infusion on ob mRNA expression. Northern blot analysis showed the abdominal fat (epididymal and perirenal fat pads) had higher ob mRNA levels than subcutaneous fat. After a 2.5-hr infusion of insulin into fasted rats, ob mRNA levels were increased by 3.0 and 1.9-fold in epididymal and perirenal fat pads, respectively. However, no change of ob mRNA level was observed in the subcutaneous fat depot. These data demonstrate adipose depot site-specific expression of ob mRNA and support the hypothesis that insulin plays an important role in the expression of ob mRNA.

Adipose Tissue↗
PubMed1996

Characterization of universal small-subunit rRNA hybridization probes for quantitative molecular microbial ecology studies.

Universal oligonucleotide hybridization probes targeting the small-subunit rRNA are commonly used to quantify total microbial representation in environmental samples. Universal probes also serve to normalize results obtained with probes targeting specific phylogenetic groups of microorganisms. In this study, six universal probes were evaluated for stability of probe-target duplexes by using rRNA from nine organisms representing the three domains of Bacteria, Archaea, and Eucarya. Domain-specific variations in dissociation temperatures were observed for all probes. This could lead to a significant bias when these probes are used to quantify microbial populations in environmental samples. We suggest lowering the posthybridization wash stringency for two of the universal probes (S-*-Univ-1390-a-A-18 and S-*-Univ-1392-a-A-15) examined. These two probes were evaluated with traditional and modified hybridization conditions to characterize defined mixtures of rRNAs extracted from pure cultures and rRNA samples obtained from anaerobic digester samples. Probe S-*-Univ-1390-a-A-18 provided excellent estimations of domain-level community composition of these samples and is recommended for future use in microbial ecology studies.

Archaea↗
PubMed1996

[Detecting immunoreactive GH mRNA in human peripheral blood lymphocytes].

The present study demonstrats that immunoreactive GH mRNA is expressed at low level in normal human peripheral blood lymphocytes by RT-PCR amplification and hybridization. Northern blot analysis of total RNA from lymphocytes with a pituitary hGH cDNA probe revealed a faint transcript migrating almost coincident with pituitary hGH menssenger RNA. Reverse transcription-polymerase chain reaction from total RNA of lymphocytes by using hGH specific primers generated a predicted 702 base pair band with almost the same size as pituitary and also hybridized with pituitary hGH cDNA probe specifically in Southern blot analysis, which indicates a low level expression of GH-like mRNA in human peripheral blood lymphocytes.

Adenoma↗
PubMed1995

Impairment of synaptic vesicle clustering and of synaptic transmission, and increased seizure propensity, in synapsin I-deficient mice.

Synapsin I has been proposed to be involved in the modulation of neurotransmitter release by controlling the availability of synaptic vesicles for exocytosis. To further understand the role of synapsin I in the function of adult nerve terminals, we studied synapsin I-deficient mice generated by homologous recombination. The organization of synaptic vesicles at presynaptic terminals of synapsin I-deficient mice was markedly altered: densely packed vesicles were only present in a narrow rim at active zones, whereas the majority of vesicles were dispersed throughout the terminal area. This was in contrast to the organized vesicle clusters present in terminals of wild-type animals. Release of glutamate from nerve endings, induced by K+,4-aminopyridine, or a Ca2+ ionophore, was markedly decreased in synapsin I mutant mice. The recovery of synaptic transmission after depletion of neurotransmitter by high-frequency stimulation was greatly delayed. Finally, synapsin I-deficient mice exhibited a strikingly increased response to electrical stimulation, as measured by electrographic and behavioral seizures. These results provide strong support for the hypothesis that synapsin I plays a key role in the regulation of nerve terminal function in mature synapses.

Animals↗
PubMed1995

Effects of increased neural activity on brain growth.

We have measured the effects of regionally increased metabolic activity--and by inference electrical activity--on cortical growth in the developing rat brain. Cortical growth is significantly and specifically greater in regions of chronically increased activity. This effect of activity on cortical growth may help explain the permanent storage of early experience in the developing nervous system.

Aging↗
PubMed1995

Isolation and characterization of an in vitro DNA replication system from maize mitochondria.

An in vitro DNA replication system from maize mitochondria has been isolated and characterized. Maize mtDNA polymerase activity was purified about 1100-fold through DEAE cellulose and Heparin-Sepharose columns. In addition to the DNA polymerase activity, this in vitro replication system also contained topoisomerase I, DNA primase and RNA polymerase activities. Optimal conditions for enzyme activity, preferred templates and inhibitors were determined in order to further characterize this in vitro replication system; this system was devoid of any detectable extramitochondrial activity as determined by: a) the mt origin of the DNA polymerase activity as evidenced by studies using different templates and inhibitors, b) absence of chloroplast or nuclear DNA, glucose -6-P-dehydrogenase (known to be present only in the cytosol and chloroplasts) and photosynthetic pigments in the mitochondrial fraction and c) the ability of maize mt topoisomerase I to relax positively supercoiled DNA.

Chromatography, Affinity↗
PubMed1995

Characterization of microbial communities in anaerobic bioreactors using molecular probes.

The microbial community structure of twenty-one single-phase and one two-phase full-scale anaerobic sewage sludge digesters was evaluated using oligonucleotide probes complementary to conserved tracts of the 16S rRNAs of phylogenetically defined groups of methanogens and sulfate-reducing bacteria. These probe results were interpreted in combination with results from traditional chemical analyses and metabolic activity assays. It was determined that methanogens in "healthy" mesophilic, single-phase sewage sludge digesters accounted for approximately 8-12% of the total community and that Methanosarcinales and Methanomicrobiales constituted the majority of the total methanogen population. Methanobacteriales and Methanococcales played a relatively minor role in the digesters. Phylogenetic groups of mesophilic, Gram-negative sulfate-reducing bacteria were consistently present at significant levels: Desulfovibrio and Desulfobulbus spp. were the dominant sulfate-reducing populations, Desulfobacter and Desulfobacterium spp. were present at lower levels, and Desulfosarcina, Desulfococcus, and Desulfobotulus spp. were absent. Sulfate reduction by one or more of these populations played a significant role in all digesters evaluated in this study. In addition, sulfate-reducing bacteria played a role in favoring methanogenesis by providing their substrates. The analysis of the two-phase digester indicated that true phase separation was not accomplished: significant levels of active methanogens were present in the first phase. It was determined that the dominant populations in the second phase were different from those in the single-phase digesters.

Bacteria, Anaerobic↗
PubMed1995

The influence of aging on muscle strength and muscle fiber characteristics with special reference to eccentric strength.

It is well established that aging seriously reduces isometric and concentric muscle strength due to atrophy, deterioration of mechanical properties, and motor unit loss. However, there is limited information on the impact of aging on eccentric strength despite the fact that such forces play an equally important role during daily activities. The purpose of this study was to examine the influence of aging on three expressions of muscle strength (isometric, concentric, and eccentric) in relation to muscle fiber characteristics, with special emphasis on eccentric force. Sedentary but healthy men (age range 18-80 years, n = 60) and women (20-74 years, n = 30) were tested for maximal effort isometric, concentric, and eccentric (1.05, 2.09, 3.14 rads.s-1) quadriceps strength, body composition, and muscle fiber characteristics of the vastus lateralis (men only). There was a significant (p < .05) approximately 30 N per decade decline in isometric and concentric forces, but only 9 N per decade reduction in eccentric strength. There was a significant reduction in Type II muscle fiber area with aging (p < .05). Isometric, eccentric, and concentric force correlated r = .33, r = .32 (p < .05), and r = .12 (p > .05) with Type II muscle fiber area, respectively. The correlation between age and fat-free mass/force ratio ranged from r = .39 to .43 in men and r = .27 to .50 in women. The data suggest a relative preservation of eccentric strength with aging in men and women that seems to be independent of muscle mass or muscle fiber type or size.

Adolescent↗
PubMed1995

Over-expression of CD3 epsilon transgenes blocks T lymphocyte development.

We have reported previously that mice carrying > 30 copies of the human CD3 epsilon transgene completely lose their T lymphocytes and NK cells (36). Here we demonstrate by immunohistology that in the most severely immunodeficient mouse, tg epsilon 26, the thymus is very small, has sizeable vacuoles and does not contain recognizable T lymphocytes except for a small percentage of Thy-1+ cells and B cells. Cell surface phenotyping and TCR alpha and -beta rearrangement studies confirm that the arrest in T lymphocyte development precedes the arrest in rag-1null, rag-2null and TCR beta nuli mice. Since the T cell progenitors in which the arrest occurred were absent in the transgenic mice, indirect approaches were taken to examine the causes of the block in T cell development. Analyses of 12 independently established mutant mouse lines, generated with five different transgenic constructs, revealed that the severity of the abrogation in T cell development was dependent on the number of copies of transgenes. Since the number of transgene copies generally correlated with the levels of expression of the transgenic CD3 epsilon proteins, we concluded that over-expression of the CD3 epsilon protein was the likely cause of the block in T lymphocyte development. The T cell immunodeficiency was caused by either the human or the murine CD3 epsilon protein. Since transgene coded mRNAs were found in significantly higher quantities than endogenous CD3 epsilon mRNAs in fetal thymi on days 13 and 14 of gestation, over-expression took place very early in development, probably prematurely. Over-expression of the CD3 epsilon transgene in thymocyte precursors may therefore affect T lymphocyte development in the absence of TCR and possibly in the absence of the other CD3 proteins. More importantly, over-expression of the CD3 epsilon protein in thymocytes of mice with a low copy number of transgenes had a significant effect on late thymic development. Over-expression of the CD3 epsilon protein in immature thymocytes mimicked the effects caused by exposure of CD4- CD8- thymocytes to anti-CD3 epsilon treatment: apoptosis and lack of TCR beta expression. We therefore speculate that in the homozygous tg epsilon 26 animals the arrest in T cell development was caused by excessive signal transduction events rather than by a toxic effect of the transgenic protein.

Amino Acid Sequence↗