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Biomedical subjects

J Tang

Publications and source records attributed to J Tang.

At least 379 records · Page 21Linked to original sources
PubMed1995

The Simulium damnosum species complex: phylogenetic analysis and molecular identification based upon mitochondrially encoded gene sequences.

The DNA sequence of portions of the 16s rRNA and the NADH dehydrogenase subunit 4 (ND4) genes were used to determine phylogenetic relationships in the Simulium damnosum s.l. species complex. Results suggested that at least two major clades existed in the S. damnosum species complex, and that members of the S. damnosum s.l. species complex were not closely related to North American Simulium species. The sequence variability of the ND4 gene was exploited to develop a method to distinguish the sibling species of the S. damnosum s.l. species complex, based on directed heteroduplex analysis of PCR products derived from the ND4 gene. This method was capable of classifying the six sibling species into at least five groups.

Animals↗
PubMed1995

Vocal efficiency as a function of vocal intensity: a study of children, women, and men.

The effect of vocal intensity on vocal efficiency (VE) for children as compared to adults is investigated, leading to the conclusion that children have different VE values than adults. Vocal efficiency was measured using a logarithmic form of the ratio of the acoustical power radiated from the lips to the aerodynamic power supplied to the glottis for voice production. Sixty subjects participated in this study, including 20 subjects with 10 males and 10 females in each of the three age groups: 4-year-olds, 8-year-olds, and adults. The speech tasks were produced at soft, comfortable, and loud levels, and the VE measurements were mathematically adjusted to account for the sound-pressure level variations within each intensity level among the subject groups. The VE values were compared for age, intensity, and gender differences. The results indicate that 4-year-olds and 8-year-olds have lower VE values than adults. Vocal efficiency increased with vocal intensity for all the age groups, and no significant differences were found for females as compared to males. Factors influencing VE such as maturation of the vocal ligament, amplitude of vocal fold vibration, fundamental frequency, tracheal pressure, as well as the source spectra are discussed.

Adult↗
PubMed1995

Prevention of diabetes does not completely prevent insulin secretory defects in the ZDF rat.

The rapid insulin secretory pulses that occur in the perfused rat pancreas can be entrained by an oscillatory glucose concentration in pancreata from nondiabetic rats but not from X diabetic Zucker diabetic fatty (ZDF) rats. To investigate whether this defect is present in prediabetic ZDF rats and whether treatment with either pioglitazone or acarbose can prevent or reverse this defect, 39 ZDF and 5 lean ZDF control rats were studied. The ZDF rats were divided into six groups depending on age, form of therapy used, and the time at which pioglitazone was started in relation to the onset of diabetes. The pancreas was isolated and perfused using a sine wave-shaped glucose concentration (mean 7 mM, period 10 min, amplitude 10%). The results, assessed by spectral analysis, revealed that in prediabetic animals and in controls, entrainment of pulsatile insulin secretion was normal. Initiation of pioglitazone therapy in ZDF rats at the time of weaning or before diabetes onset prevented hyperglycemia. However, entrainment was only partially retained. Thus, in these two groups, the spectral power at 10 min was greater than in untreated animals but lower than in prediabetic and control animals. Treatment with acarbose before or with pioglitazone after diabetes onset improved but did not normalize glucose levels, and it did not improve entrainment. The results demonstrate the presence of insulin secretory defects in 13-wk-old ZDF rats in which hyperglycemia was prevented.

Acarbose↗
PubMed1995

Identification of human growth hormone-releasing hormone receptor splicing variants.

The expression pattern of the receptor for human GHRH (hGHRHr) was investigated in normal human tissues and in pituitary and ovarian tumors by reverse transcription-polymerase chain reaction. Three transcriptional variant forms of the hGHRHr were found to be expressed in the normal pituitary and in GH-secreting pituitary tumors. Form a is identical to the previously reported hGHRHr, whereas forms b and c are not described in the literature. Form b and c are predicted to be transcribed into two truncated proteins. We amplified genomic DNA using primers designed from the complementary DNA of hGHRHr. A 2-kilobase genomic DNA fragment was cloned that contains part of the hGHRHr gene consisting of two exons, e864 and e934, separated by three introns, i863, i933, and i1025. Alternative splicing of i1025 was responsible for three variant forms of hGHRHr. Nonsecreting pituitary tumors showed an abnormal expression of the hGHRHr, probably due to alternative usage of exons at the 5'-end of the gene, although they also expressed the three variant forms. No hGHRHr expression was identified in a human mammosomatotroph cell line insensitive to GHRH, in normal human liver or ovary, or in various human ovarian tumors.

Alternative Splicing↗
PubMed1995

Pharmacokinetics of antisense oligonucleotides.

Antisense oligonucleotides are promising therapeutic agents for the treatment of life-threatening diseases. Intravenous injection of phosphodiester oligonucleotide analogue (P-oligonucleotide) in monkeys shows that the oligonucleotide is degraded rapidly in the plasma with a half-life of about 5 minutes. Administration of a single dose of the phosphorothioate (S-oligonucleotide) in animals by the intravenous route reveals biphasic plasma elimination. An initial short half-life (0.53 to 0.83 hours) represents distribution out of the plasma compartment and a second long half-life (35 to 50 hours) represents elimination from the body. This elimination half-life was similar when the oligonucleotide was administered subcutaneously. In contrast, methylphosphonate oligonucleotides have an elimination half-life of 17 minutes in mice. S-Oligonucleotide was distributed into most of organs of rats and mice. Liver and kidney were the 2 organs with highest uptake of the oligonucleotide. The S-oligonucleotide was primarily excreted in urine. Up to 30% was excreted in the first 24 hours. Repeated daily intravenous injections of a 25-mer S-oligonucleotide into rats showed that the concentrations in the plasma are at steady-state during the 8 days' administration. The data represented here support the potential utility of phosphorothioate and methylphosphonate oligonucleotides as therapeutic agents in vivo.

Animals↗
PubMed1995

Evolution of beta-cell dysfunction in the male Zucker diabetic fatty rat.

The molecular basis for the beta-cell dysfunction that characterizes non-insulin-dependent diabetes mellitus (NIDDM) is unknown. The Zucker diabetic fatty (ZDF) male rat is a rodent model of NIDDM with a predictable progression from the prediabetic to the diabetic state. We are using this model to study beta-cell function during the development of diabetes with the goal of identifying genes that play a key role in regulating insulin secretion and, thus, may be potential targets for therapeutic intervention aimed at preserving or improving beta-cell function. As a first step, we have characterized morphology, insulin secretion, and pattern of gene expression in islets from prediabetic and diabetic ZDF rats. The development of diabetes was associated with changes in islet morphology, and the islets of diabetic animals were markedly hypertrophic with multiple irregular projections into the surrounding exocrine pancreas. In addition, there were multiple defects in the normal pattern of insulin secretion. The islets of prediabetic ZDF rats secreted significantly more insulin at each glucose concentration tested and showed a leftward shift in the dose-response curve relating glucose concentration and insulin secretion. Islets of prediabetic animals also demonstrated defects in the normal oscillatory pattern of insulin secretion, indicating the presence of impairment of the normal feedback control between glucose and insulin secretion. The islets from diabetic animals showed further impairment in the ability to respond to a glucose stimulus. Changes in gene expression were also evident in islets from prediabetic and diabetic ZDF rats compared with age-matched control animals. In prediabetic animals, there was no change in insulin mRNA levels. However, there was a significant 30-70% reduction in the levels of a large number of other islet mRNAs including glucokinase, mitochondrial glycerol-3-phosphate dehydrogenase, voltage-dependent Ca2+ and K+ channels, Ca(2+)-ATPase, and transcription factor Islet-1 mRNAs. In addition, there was a 40-50% increase in the levels of glucose-6-phosphatase and 12-lipoxygenase mRNAs. There were further changes in gene expression in the islets from diabetic ZDF rats, including a decrease in insulin mRNA levels that was associated with reduced islet insulin levels. Our results indicate that multiple defects in beta-cell function can be detected in islets of prediabetic animals well before the development of hyperglycemia and suggest that changes in the normal pattern of gene expression contribute to the development of beta-cell dysfunction.

Animals↗
PubMed1995

Nucleotide sequence of the region between crr and cysM in Salmonella typhimurium: five novel ORFs including one encoding a putative transcriptional regulator of the phosphotransferase system.

A 4471 bp region between crr and cysM on the Salmonella typhimurium chromosome (49.5 min) has been sequenced. Five ORFs were found within this region, one of which is likely to be the putative regulatory gene, ptsJ, that corresponds in map position to a gene which when mutated allows expression of a cryptic Enzyme I of the phosphotransferase system. The deduced amino acid sequence of the encoded protein is similar to those of several open reading frames (ORFs) including ORFT2 of Rhodobacter spheroides with which it is 28% identical throughout most of its length (comparison score of 21 S.D.). PtsJ exhibits a putative, N-terminal, helix-turn-helix, DNA binding domain that is similar in sequence to those in members of the GntR family of transcriptional regulators. Analyses of the sequences of the ORFs encoded within this region are presented.

Amino Acid Sequence↗
PubMed1995

Regulation of human B cell lymphopoiesis by adhesion molecules and cytokines.

Recent advances in the ability to culture normal human B cell precursors have emphasized the supportive relationship between these cells and stromal cells in the bone marrow microenvironment. It is now possible to examine the role of adhesion molecules and cytokines in the regulation of different stages of human lymphopoiesis using these culture systems. Direct cell-cell adhesion mediated by the integrin adhesion molecule VLA-4 plays a critical role in supporting stromal dependent proliferation of human B cell precursors. In addition, human B precursor cell lines migrate underneath the stromal layer. This transmigration is VLA-4 dependent but not inhibitable by antibody to known VLA-4 ligands. IL-7 is secreted by the stromal layer, and is necessary for stromal-dependent proliferation of early human B cell precursors. Proliferation of early human B cell precursors or mature B cells. Since the bone marrow stroma is a source of cytokines with B cell precursor growth stimulatory activity, it is possible that adhesion interactions may play a co-stimulatory role with respect to cytokine secretion or response. As the cytokine requirements for human B cell lymphopoiesis become more completely defined, it will be important to uncover the cell-cell signals that regulate lymphopoiesis either directly or through modulation of cytokine secretion by supporting cells in the bone marrow microenvironment. The dependent relationship between human B cell precursors and the bone marrow microenvironment provides a model system for these cell-cell interactions which may be applicable to progenitor development in other lineages.

Animals↗
PubMed1995

[Observation on hypotensive action of adrenomedullin and its distribution in tissues].

The effect of adrenomedullin (AM) on blood pressure and tension of aortic rings were studied in normal and in either spontaneous or renal hypertensive rats (SHR/RHR). The distribution characteristics of AM in viscera was also investigated. It was found that the hypotensive action of AM was far more prominent in hypertensive than in normotensive rats. The tension lowering action on the aortic rings is dose dependent and requires the presence of endothelium. Immunohistochemistry reactivity of AM of different degrees were also found in lung, kidney and myocardium, in addition to cells of pheochromocytoma and adrenomedulla. It was suggested that AM may play an important role in the regulation of blood pressure and visceral blood circulation.

Adrenal Medulla↗
PubMed1995

Enhanced adeno-associated virus vector expression by adenovirus protein-cationic liposome complex. A novel and high efficient way to introduce foreign DNA into endothelial cells.

Adeno-associated virus vector (AAV), a non-pathogenic integrating vector, can integrate on chromosome 19 in humans. But its gene transfer efficiency is quite low. In this study we combined adenovirus (Adv-5) capsid protein or the Fiber protein of Adv with liposome, termed adenosome (adenovirus protein-cationic liposome complex). This complex can bring AAV/CMV-LacZ to the endothelial cells, and improve the efficiency of gene transfer. It may be a novel, specific, stable and safe gene delivery system and will be widely used in human gene therapy.

Adenoviruses, Human↗
PubMed1995

Adenovirus mediated gene transfer of vascular smooth muscle cells and endothelial cells in vitro.

Introducing foreign gene(s) into vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) is the pre-requirement of gene therapy for cardiovascular diseases. We have explored the use of adenoviral vectors (Adv-CMV/LacZ) to transfer LacZ gene into cultured VSMCs and ECs. Our results demonstrated that adenoviral vectors transferred foreign gene into VSMCs and ECs high-efficiently with dose-dependent response pattern. The frequencies of transfection reached 100% at the viral titer of 10(9) pfu/ml. Comparing the sensitivities of VSMCs and ECs to adenoviral vectors, we found that ECs were more sensitive than VSMCs, of which the frequencies of transfection in ECs reached 80% while in VSMCs only 40% for 8 hrs after transfection. In addition, the transfection of ECs and VSMCs with adenoviral vectors was partly blocked by monoclonal antibodies to Fiber and Core protein of the adenoviral capsid, but not by monoclonal antibody to Hexon protein. It is suggested transfection of ECs and VSMCs with adenovirus vectors is mediated by Fiber or Core protein of adenoviral capsid proteins.

Adenoviruses, Human↗
PubMed1995

[A study on hypotensive mechanism of adrenomedullin (13-52)].

In the present study the hypotensive mechanism of AdM (13-52) was investigated in rats, both in vitro and in vivo. It was found that the hypotensive effect of AdM (13-52) could be partially inhibited by L-NG-nitro-arginine (LNNA), an inhibitor of nitric oxide synthase. The vasodilator effect of AdM (13-52) was dependent on vascular endothelium and inhibited by LNNA in a dose-dependent manner. This LNNA induced inhibitory effect could be reversed with L-Arginine. In addition, the vasodilator effect of AdM (13-52) disappeared with methylene blue (MB), which blocked cGMP formation. Using radioimmunoassay it was shown that LNNA lowered, but AdM (13-52) elevated the vascular cGMP content, while vascular cGMP content was not altered by co-application of AdM (13-52) and LNNA. The above results suggest that the vasodilator effect of AdM (13-52) might be mediated by nitric oxide.

Adrenomedullin↗
PubMed1995

[Study on hsp 70 gene level in cultured smooth muscle cells and aorta from SHR and WKY rats].

Using nucleic hybridization, we investigated hsp 70 gene level on: 1. aorta on spontaneous hypertension rats (SHR); 2. cultured SHR and WKY smooth muscle cells (SMCs) induced by heat shock; 3. cultured SHR and WKY SMCs in 6 weeks and 3 months. The results indicated that hsp 70 mRNA increased in aorta of SHR (6 weeks), in cultured SHR SMCs as compared with WKY SMCs induced by heat shock (42 degrees C, 15 minutes), and in cultured SHR SMCs (6 weeks) as compared with WKY SMCs (6 weeks). Meanwhile, hsp 70 mRNA of cultured SHR SMCs in 6 weeks was higher than that in 3 months. We postulated that overexpression of hsp 70 of cultured SMCs and aorta of SHR in 6 weeks might be related with cellular proliferation during the development of hypertension and that the cultured SHR SMCs might be sensitive to heat shock.

Animals↗
PubMed1995

[A clinical report of refractory carcinoma of ovary and fallopian tube treated with taxol].

From September 1993 through March 1994, 30 cases of refractory carcinoma of the ovary and Fallopian tube were treated with Taxol. Complete response was seen in 4 and partial response in 8 cases with a response rate of 40%. The average length of remission was 5 months in CR and 3.9 months in PR. The major toxic side effect was decrease in total white cell count and in neutrophil count. Apart from flushing of face during Taxol infusion in 6 patients, no other allergic reaction was observed. Gastrointestinal, neurologic, liver and renal toxicities were mild. Taxol is a drug of choice in the treatment of patients with cancer of the ovary and Fallopian tube who are resistant to conventional chemotherapy.

Adenocarcinoma↗
PubMed1995

GM1 antibody in Guillain-Barre syndrome after Campylobacter jejuni infection.

Fecal culture of Campylobacter jejuni was prepared by the method of Skirrow, and serum class specific antibodies (IgG, IgM and IgA) to Campylobacter jejuni and serum class specific antibodies (IgG IgM) to GM1 were prepared with solid phase enzyme linked immunasorbent assay in 16 cases of Guillain-Barre syndrome (GBS), 32 controls with other neurological diseases (disease controls) and 90 normal controls. The results showed that the incidence of Campylobacter jejuni infection, especially recent infections, in the group with Guillain-Barre syndrome was much higher than that in the two control groups, and that the positive rate of GM1 antibody was also much higher in the GBS group than in the two control groups. The results suggest that Campylobacter jejuni infection may be one of the important precipitating factors of Guillain-Barre syndrome and play an important role in the epidemiological pattern of Guillain-Barre syndrome in China. It damages the myelin of peripheral nerves through induction of GM1 antibody production.

Adult↗
PubMed1995

Phenotypes of Heligmosomoides polygyrus selected to survive protective immunity in quackenbush mice.

The survival of Heligmosomoides polygyrus phenotypes passaged selectively through naive (Hpn) and immune (Hpa) outbred Quackenbush (Q) mice was compared in Q mice immunized passively with normal (NMS) and immune mouse serum (IMS). IMS raised against Hpn(Q) worms (IMS-N) was 93% and 92% protective against Hpn(Q) and Hpa(Q) phenotypes, respectively; IMS against Hpa(Q) (IMS-A) conferred 93% protection against the Hpn(Q) phenotype but gave only 45% protection against the adapted Hpa(Q) parasites (P < 0.01). IMS-A had less anti-parasite IgG reactivity than did IMS-N (P < 0.05). A 34-kDa antigen from male Hpn(Q), but not Hpa(Q) worms, and an antigen at 56 kDa in male Hpa(Q), but not Hpn(Q) parasites, reacted on immunoblots with both sets of IMS. Thus, it appeared that Hpa(Q) worms endured higher levels of protective immunity than did Hpn(Q) worms and that Hpa(Q) and Hpn(Q) phenotypes had different antigens, which, however, did not lead to phenotype-specific immunity. This reflects the complexity of host-parasite interactions.

Adaptation, Biological↗
PubMed1995

High expression of synthetic human interferon-gamma cDNA in E. coli.

Human interferon-gamma (IFN-gamma) cDNA was synthesized, and it makes the usage of favorable codons in E. coli. The authors got 9 different expression plasmids which contain the synthetic IFN-gamma-cDNA and have different spaces between SD sequence and ATG. The free energies G0f298 in the formation of stable secondary structure in the translation initiation region (TIR) are different in various expression plasmids. One of them, pLY4-gamma 5, can highly yield INF-gamma which will be about 60%-80% of the total bacterial proteins, such a high expression was hardly noted in literature. The reasons of high expression in this work are optimal spaces between SD and ATC, favorable delta G0f298, favourable condons usage for E. coli.

Amino Acid Sequence↗