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Biomedical subjects

D Tang

Publications and source records attributed to D Tang.

At least 109 records · Page 6Linked to original sources
PubMed1997

Microbiologic and clinical value of primary broth cultures of wound specimens collected with swabs.

In order to assess the microbiologic and clinical value of primary broth culture of wound specimens collected with swabs and submitted to the laboratory in transport medium, we compared the results of primary agar culture with the results of a corresponding primary broth culture for 344 aerobic specimens and 176 anaerobic specimens. While 8.7% (45 of 520) of the specimens yielded organisms from the primary broth culture that were not recovered from the corresponding primary agar culture, only 5.0% (26 of 520) of the specimens yielded organisms from the primary broth culture other than Staphylococcus epidermidis, viridans group streptococci, and Corynebacterium spp. Moreover, the primary broth culture of only 0.6% (3 of 520) of the specimens yielded organisms not recovered from the primary agar culture that caused a change in the therapy of the patient. Our conclusion is that primary broth cultures are unnecessary for the processing of wound specimens properly collected with swabs.

Bacteria, Aerobic↗
PubMed1997

[The effect of recombinant human growth hormone on thyroid function in patients with growth hormone deficiency].

To evaluate the effect of growth hormone treatment on thyroid function of growth hormone deficient children, 19 (18M/1F) euthyroid children of growth hormone deficiency (GHD) were treated with Genotropin, a recombinant human growth hormone (rhGH) for 12 months. rhGH was injected subcutaneously with a daily dosage of 0.1 IU/kg. All the patients were diagnosed by two GH provocative stimulating tests with the serum GH peak level < 7 micrograms/L. During the treatment, blood was drawn before or 6 and 12 months after the initiation of therapy to measure serum T3, T4, FT3, FT4, rT3 and thyroid-stimulating hormone (TSH) levels. In the meantime, thyrotropin releasing hormone (TRH) stimulating test was performed by an i.v. injection of 200 micrograms synthetic TRH. The results showed that (1) the average serum levels of T4 and FT4 decreased significantly 6 at the 6th and 12th month (P < 0.001), while the serum FT3 level decreased only at the 6th month (P < 0.05). The serum T3, rT3 and TSH concentrations remained unchanged. (2) 8 euthyroid patients (45%) became subclinical hypothyroidism after 12 months' treatment with rhGH for their serum FT4 levels fell to below the normal range. The 19 patients were divided into thyroid function normal (n = 11) and subnormal group (n = 8) according to their posttreatment thyroid functions. (3) The TSH response to TRH was evaluated by the area under the curve (AUC) of serum TSH. The average AUC was greater in the subnormal group than in the normal group whether before or 6 and 12 months after the treatment. The greater TSH response to TRH among patients with decreased posttreatmental FT4 levels suggests that latent TRH deficiency has already existed, which may be the pathogenetic basis of the hypothyroidism developped after rhGH treatment. Thus the thyroid function of GHD patients should be monitored during rhGH treatment in order that the thyroxine replacement therapy can be given in time.

Child↗
PubMed1997

[A follow-up survey of results of lacrimal gland surgery of pleomorphic adenoma].

OBJECTIVE: To investigate the causes of recurrence and malignant change of pleomorphic adenoma (benign mixed tumour) of lacrimal gland. METHODS: 42 cases with the adenoma were followed postoperatively, the follow-up periods ranging from 0.5 to 17.0 years. RESULTS: In the follow-up, 34 cases had no recurrence or malignant change, and 8 cases had recurrences. Of the cases with recurrences, 7 cases had undergone several times of surgeries, because of incomplete resection of the tumor leading to recurrence. CONCLUSION: The key points to obtain success of the surgery and to decrease the rate of recurrence are complete removal of the tumor in its capsule in the initial surgery, and avoidance of aspiration or biopsy made before the operation.

Adenoma, Pleomorphic↗
PubMed1997

[Seasonal variation on reproductive cycle of the female Chinemys reevesii].

Seasonal variation in the reproductive cycle of female Chinese three-keeled pond turtles, Chinemys reevesii, was studied. Vitellogenesis began in early October and reached maximum level in early May (maximum follicle diameter was 19.2 mm). The first clutch was laid in June. Oviposition continued until August when follicular regression began. An ovarian quiescent period was evident in September. Two-three clutches are laid per year. Mean clutch size is 5. Annual reproductive potential ranges from 10 to 15 eggs. Age at maturity for females is six years.

Animals↗
PubMed1997

[Biologic characteristics and cultured methods of Palea steindachneri].

Palea steindachneri is a precious animal and its carapacial bones and plastral bones are expensive Chinese medicinal materials. This paper introduces the biologic characteristics and cultured methods of Palea steindachneri. It provides a valuable information for the culture of Palea steindachneri.

Animals↗
PubMed1997

[The expression of calponin in Oddi's sphincters and its actions during gallstone formation].

OBJECTIVES: To study on the expression of calponin in an animal model of gallstone disease and investigate the molecular mechanisms of gallstone formation. METHODS: After feeding a high-cholesterol diet to guinea pigs, Oddi's sphincters were disseced on day 30 and day 60 respectively. We used RT-PCR, western-blotting to evaluate expression level of calponin gene. RESULTS: Down-regulation of calponin gene expression was observed in animals with gallstone. The levels of both protein and mRNA expression for calponin on day 30 and day 60 were lower than those of control group with the level from day 60 lower than that from day 60, while myosin expressions were relatively stable. CONCLUSION: Our results indicated that the decrease of calponin could increase the pressure of sphincter of Oddi, aggravate the stasis of bile and promote the gallstone formation.

Animals↗
PubMed1996

Evidence for the existence of a sodium-dependent glutathione (GSH) transporter. Expression of bovine brain capillary mRNA and size fractions in Xenopus laevis oocytes and dissociation from gamma-glutamyltranspeptidase and facilitative GSH transporters.

Our laboratory previously has shown apparent carrier-mediated glutathione (GSH) uptake across the blood-brain barrier (BBB) in two animal models. In the present study, when Xenopus oocytes were injected with bovine brain capillary mRNA expression of intact GSH, uptake was observed after 3 days. When total mRNA was converted to cDNA and subfractionated with subsequent cRNA injection into oocytes, three distinct fractions (5, 7-8, and 11-12) expressed carrier-mediated intact GSH transport. Northern blot analysis established the presence of RcGshT, the previously cloned sodium-independent hepatic canalicular transporter, only in fraction 5. GSH transport activity in fraction 7 was significantly inhibited by replacement of NaCl with choline chloride and by sulfobromophthalein-GSH, neither of which affects RcGshT. The Na(+)-dependent GSH uptake kinetics exhibited high affinity (approximately 400 micron) and low affinity (approximately 10 mM) components. Fraction 11 expressed Na(+)-independent transport of intact GSH and also contained the GGT transcript. In conclusion, we have identified three distinct sized transcripts from bovine brain capillary mRNA which express GSH transport: one fraction expresses a novel Na(+)-dependent GSH uptake which can be dissociated unequivocally from both GGT and RcGshT for the first time and which may account for uptake of GSH against its electrochemical gradient at the BBB.

Animals↗
PubMed1996

Interaction of cyclin-dependent kinase 5 (Cdk5) and neuronal Cdk5 activator in bovine brain.

Neuronal cdc2-like kinase (Nclk) purified from bovine brain is a heterodimer of Cdk5 and an essential 25-kDa regulatory subunit (Lew, J., and Wang, J. H. (1995) Trends Biochem. Sci. 20, 33-37). The regulatory subunit is an N-terminal truncated derivative of a 35-kDa protein expressed specifically in brain, hence the name neuronal Cdk5 activator, p25/p35nck5a. In this study, we probe the relationship between the two different forms of Nck5a and their interaction with and activation of Cdk5 in bovine brain extract. Using protein fractionation procedures in combination with Western blot analysis and protein kinase assay, three forms of Cdk5 have been detected in bovine brain: a monomeric Cdk5 that can be activated by bacterially expressed GST-p21nck5a, a heterodimer of Cdk5 and p25nck5a that displays high kinase activity, and a Cdk5.p35nck5a complex that is inactive and refractory to GST-p21nck5a activation. Analysis of the Cdk5.p35nck5a complex by gel filtration chromatography indicated that the complex was part of a macromolecular structure with a molecular mass of approximately 670 kDa. When the macromolecular complex was subjected to gel filtration chromatography in the presence of 10% ethylene glycol, the fractions containing both p35nck5a and Cdk5, although eluting at the same position as control, displayed high kinase activity. The result is compatible with the suggestion that the macromolecular complex contained a kinase inhibitory factor that dissociated from the complex in 10% ethylene glycol.

Animals↗
PubMed1996

Binding capacity of alpha-crystallin to bovine lens lipids.

Three experiments were performed to determine the alpha-crystallin binding capacity of bovine lens lipid vesicles. In one experiment lipid was kept constant (2.5 mg ml-1) and the alpha-crystallin concentration was changed (0.5 to 3.0 mg ml-1). In another experiment, alpha-crystallin was kept constant (1 mg ml-1) and the concentration of lipid was varied (0.25 to 3 mg ml-1). We calculated the binding capacity of the lipid to be 0.33 +/- 0.05 (S.D.) mg alpha-crystallin (mg lens lipid)-1. This was confirmed by changes in the anisotropy and fluorescent intensity of a probe that partitions at the headgroup region of the lipid bilayer. Near 0.33 mg alpha-crystallin (mg lens lipid)-1 the fluorescence intensity and anisotropy of the probe increases and plateaus which indicates that concomitant with alpha-crystallin binding, water is excluded from the head group region of the bilayer and the headgroup region becomes less mobile. It is possible that alpha-crystallin binding could protect and stabilize the lipid bilayer and decrease membrane permeability.

Animals↗
PubMed1996

Cyclin-dependent kinase 5 (Cdk5) and neuron-specific Cdk5 activators.

While cyclin-dependent kinase 5 (Cdk5) is widely distributed in mammalian tissues and in cultured cell lines, Cdk5-associated kinase activity has been demonstrated only in mammalian brains. An active form of Cdk5, called neuronal cdc2-like kinase (Nclk) has been purified from mammalian brain and shown to be a heterodimer of Cdk5 and a 25 kDa protein, which is derived proteolytically from a 35 kDa brain and neuron-specific protein. The protein is essential for the kinase activity of Cdk5 and is therefore designated neuronal Cdk5 activator, p25/35Nck5a. Nclk appears to have important neuronal functions. The changes in Cdk5 and Nck5a expression appear to correlate with the terminal differentiation of neurons of the mouse embryonic brain. Transfection of cultured cortical neurons with dominant negative cdk5 mutants or Nck5a antisense DNA may reduce neurite growth, suggesting that Nclk plays an active role in neuron differentiation. A number of cytoskeletal proteins including neurofilament proteins, the neuron-specific microtubule associated protein tau, and the actin binding protein caldesmon are in vitro substrates of Nclk. Although Nck5a has cyclin-like activity, it shows minimal amino acid sequence identity to members of cyclin family proteins. The mechanism of activation of Cdk5 by Nck5a differs from that of cyclin activation of Cdks in that full Cdk5 kinase activity can be achieved in the absence of phosphorylation of Cdk5. An isoform of Nck5a, a 39 kDa protein has been cloned and shown to share extensive amino acid identity and the mechanism of Cdk5 activation with Nck5a. These proteins may represent a subfamily of Cdk activators distinct from cyclins.

Amino Acid Sequence↗
PubMed1996

Disulfide bonds of herpes simplex virus type 2 glycoprotein gB.

Glycoprotein B (gB) is the most highly conserved envelope glycoprotein of herpesviruses. The gB protein is required for virus infectivity and cell penetration. Recombinant forms of gB being used for the development of subunit vaccines are able to induce virus-neutralizing antibodies and protective efficacy in animal models. To gain structural information about the protein, we have determined the location of the disulfide bonds of a 696-amino-acid residue truncated, recombinant form of herpes simplex virus type 2 glycoprotein gB (HSV gB2t) produced by expression in Chinese hamster ovary cells. The purified protein, which contains virtually the entire extracellular domain of herpes simplex virus type 2 gB, was digested with trypsin under nonreducing conditions, and peptides were isolated by reversed-phase high-performance liquid chromatography (HPLC). The peptides were characterized by using mass spectrometry and amino acid sequence analysis. The conditions of cleavage (4 M urea, pH 7) induced partial carbamylation of the N termini of the peptides, and each disulfide peptide was found with two or three different HPLC retention times (peptides with and without carbamylation of either one or both N termini). The 10 cysteines of the molecule were found to be involved in disulfide bridges. These bonds were located between Cys-89 (C1) and Cys-548 (C8), Cys-106 (C2) and Cys-504 (C7), Cys-180 (C3) and Cys-244 (C4), Cys-337 (C5) and Cys-385 (C6), and Cys-571 (C9) and Cys-608 (C10). These disulfide bonds are anticipated to be similar in the corresponding gBs from other herpesviruses because the 10 cysteines listed above are always conserved in the corresponding protein sequences.

Amino Acid Sequence↗
PubMed1996

Evidence for a phosphorylation site in cytomegalovirus glycoprotein gB.

As part of our vaccine program, we have purified a recombinant form of human cytomegalovirus glycoprotein B that is able to induce high titers of virus-neutralizing antibodies. The isolated protein was found to be phosphorylated at a serine residue in position -7 from the C terminus of the protein. The corresponding synthetic peptide, HLKDSDEEENV, was an efficient in vitro substrate of casein kinase II.

Amino Acid Sequence↗
PubMed1996

Neuronal Cdc2-like kinase: from cell cycle to neuronal function.

Neuronal Cdc2-like kinase, Nclk, is a heterodimer of cyclin-dependent protein kinase 5 (Cdk5) and a 25-kDa essential regulatory subunit that is derived from a 35-kDa brain- and neuron-specific protein. This protein is called neuronal Cdk5 activator, p25/35nck5a. Nclk is one of the best characterized Cdc2 family kinases whose primary function is not cell cycle related. It has been suggested that this protein kinase plays important roles in neurocytoskeleton dynamics and its loss of regulation has been implicated in Alzheimer pathology. As a member of the Cdc2-like kinase family, Nclk shares many common properties with other members of the Cdc2-like kinase family. It also possesses unique characteristics that may be related to its distinct and noncell cycle related functions. The regulatory and functional properties of Nclk are reviewed in this communication.

Amino Acid Sequence↗
PubMed1996

Molecular epidemiology in environmental carcinogenesis.

Molecular epidemiology has significant potential in preventing cancer and other diseases caused by environmental exposures (related to lifestyle, occupation, or ambient pollution). This approach attempts to prevent cancer by incorporating laboratory methods to document the molecular dose and preclinical effects of carcinogens, as well as factors that increases individual susceptibility to carcinogens. Recently we have carried out validation studies of biologic markers such as carcinogen--DNA and carcinogen--protein adducts, gene and chromosomal mutations, alterations in target oncogenes or tumor suppressor genes, polymorphisms in putative susceptibility genes (individual P450s, glutathione transferase M1), and serum levels of micronutrients. This research involves adults, infants, and children exposed to varying levels of carcinogens, as well as cancer cases and controls. On a group level, dose-response relationships have frequently been seen between various biomarkers and environmental exposures such as polycyclic aromatic hydrocarbons, cigarette smoke (active and passive), and ambient indoor and workplace air pollution. However, there is significant interindividual variation in biomarkers that appears to reflect a modulating effect on biomarkers (hence potential risk) by genetic and acquired susceptibility factors. Ongoing retrospective and nested case-control studies of lung and breast cancer are examining the association between biomarkers and cancer risk. Results of these studies are encouraging; they suggest that biomarkers, once validated, can be useful in identifying populations and individuals at risk in time to intervene effectively.

Biomarkers, Tumor↗
PubMed1996

Identification of a novel, sodium-dependent, reduced glutathione transporter in the rat lens epithelium.

PURPOSE: To determine whether glutathione (GSH) transporter(s) other than the previously identified rat canalicular GSH transporter (RcGshT) is present in the lens. METHODS: Poly (A) +RNA isolated from rat and guinea pig lens cortex and epithelium was injected into Xenopus laevis oocytes. The effect of sodium removal was determined by measuring cell-associated radioactivity in lenticular epithelium or cortex mRNA injected oocytes (pretreated with acivicin to inhibit gamma glutamyltranspeptidase) after 1 hour of incubation in NaCl medium or choline chloride (Na(+)-free) medium containing tracer GSH (plus unlabeled GSH). The effect of 2 mM bromosulfophthalein-GSH (BSP-GSH) on GSH uptake in the lens epithelium and cortex in NaCl medium at two GSH concentrations also was determined. The molecular form of uptake of GSH in lens epithelial mRNA-injected oocytes was examined by high-performance liquid chromatography. Western blot analysis was performed to study the presence of RcGshT in the cortex and epithelium. RESULTS: Oocytes injected with mRNA from rat and guinea pig lens epithelium and cortex compartments expressed GSH transport. High-performance liquid chromatography confirmed that epithelial uptake was as intact GSH under conditions of inhibition of GSH synthesis with dl-buthionine sulfoximine. The mean GSH uptake (nmol/oocyte per hour) in epithelial mRNA-injected oocytes was significantly reduced (P < 0.01, n = 4 oocyte preparations) under Na(+)-free conditions compared to NaCl medium at 0.05 mM and 2 mM GSH in the medium. Uptake in cortical mRNA-injected oocytes was unaffected by Na+ removal. Lens epithelial uptake exhibited a strong inhibition by BSP-GSH at 0.05 mM (55%) and 2 mM (64%), whereas cortical uptake was unaffected by BSP-GSH. Western blot analysis identified RcGshT in the cortical and epithelial regions. CONCLUSIONS: Results from the current study provide strong evidence for the presence of a hitherto unreported Na(+)-dependent, BSP-GSH inhibitable GSH transporter in the lens epithelium, which may mediate concentrative, basolateral uptake of aqueous GSH consistent with in situ eye perfusion studies. The Na(+)-independent, BSP-GSH insensitive RcGshT may function as an apical GSH effluxer in lens epithelium and in mediating concentration gradient driven inward GSH movement by uptake-efflux in the lens cortex.

Animals↗
PubMed1995

An isoform of the neuronal cyclin-dependent kinase 5 (Cdk5) activator.

Neuronal Cdc2-like kinase is a heterodimer of Cdk5 and a 25-kDa subunit that is derived from a 35-kDa brain- and neuron-specific protein called the neuronal Cdk5 activator (p35/p25nck5a) (Lew, J., Huang, Q.-Q., Qi, Z., Winkfein, R. J., Aebersold, R., Hunt, T., and Wang, J. H. (1994) Nature 371, 423-426; Tsai, L. H., Delalle, I., Caviness, V. S., Jr., Chae, T., and Harlow, E. (1994) Nature 371, 419-423). Upon screening of a human hippocampus library with a bovien Nck5a cDNA, we uncovered a distinct clone encoding a 39-kDa isoform of Nck5a. The isoform, designated the neuronal Cdk5 activator isoform (p39nck5ai), showed a high degree of sequence similarity to p35nck5a with 57% amino acid identity. Northern blot analysis detected its mRNA transcript in bovine and rat cerebrum and cerebellum, but not in any other rat tissues examined. In situ hybridization showed that Nck5ai was enriched in CA1 to CA3 of the hippocampus, but absent in the fimbria of hippocampal formation. Among seven cell lines in proliferating cultures, only PC12 and N2A, two cell lines capable of differentiating into neuron-like cells, were found to contain Nck5ai mRNA. A 30-kDa truncated form of Nck5ai expressed as a glutathione S-transferase fusion protein in Escherichia coli] was found to associate with Cdk5 to form an active Cdk5 kinase. Thus, the isoform shares many common characteristics with p35nck5a, including Ckd5 activating activity and brain- and neuron-specific expression. Both proteins show limited sequence homology to cyclins, suggesting that they define a new family of cyclin-dependent kinase-activating proteins.

Amino Acid Sequence↗