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Biomedical subjects

L Tang

Publications and source records attributed to L Tang.

At least 289 records · Page 16Linked to original sources
PubMed1988

Crystallization and preliminary X-ray diffraction analysis of 11 S acetylcholinesterase.

The 11 S form of acetylcholinesterase from Electrophorus electricus was purified by affinity chromatography. The protein was crystallized from polyethylene glycol solutions. One crystal form proved suitable for x-ray diffraction studies. Preliminary x-ray analysis demonstrates that the space group of this crystal is F222. The unit cell dimensions are a = 141.0 +/- 0.2, b = 202.4 +/- 0.2, and c = 237.4 +/- 0.1 A. The diffraction is anisotropic, extending to at least 3.5 A along the a* and b* axes, but becoming weak beyond about 6 A along the c* axis. Crystal density measurements suggest that one complete 11 S tetramer occupies the asymmetric unit of the crystal.

Acetylcholinesterase↗
PubMed1988

Comparison of the properties of tubulin from Nippostrongylus brasiliensis with mammalian brain tubulin.

Tubulin was estimated to account for 16.3% and 0.25% of protein in rat brain and Nippostrongylus brasiliensis supernatants, respectively. Tubulin from N. brasiliensis and rat brain have been partially purified using polylysine agarose chromatography and high performance liquid chromatography on a gel permeation column. Western blots with alpha- and beta-tubulin monoclonal antibodies confirmed the presence of tubulin in different fractions. The mobility of N. brasiliensis tubulin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was similar to that of rat brain tubulin. The isoelectric range for N. brasiliensis alpha- and beta-tubulin isoforms was pH 5.4-4.8 and pH 4.8-4.7, respectively. However, for rat brain the corresponding ranges were pH 5.4-4.9 and pH 5.0-4.6, respectively. Western blots with anti-tubulin monoclonal antibodies revealed 8 isoforms of alpha-tubulin and 3 isoforms of beta-tubulin for N. brasiliensis and 14-15 and 7-8 isoforms for rat brain alpha- and beta-tubulins, respectively. Different peptide maps were obtained for N. brasiliensis tubulin compared with rat brain tubulin.

Animals↗
PubMed1987

In vivo and in vitro modulation of growth hormone and prolactin of a mixed somatotropic-lactotropic pituitary microadenoma.

Both in vivo and in vitro responses of prolactin and growth hormone to stimuli were studied in an acromegalic, amenorrheic woman with a chromophobe adenoma of the pituitary gland. Preoperative testing revealed a prolactin rise after thyrotropin-releasing hormone and chlorpromazine and a decline after L-dopa and bromocriptine administration. During 3.5-hour incubations, cultured tumor cells produced significant increases of growth hormone and prolactin after dibutyryl adenosine 3',5'-cyclic monophosphate stimulation, while bromocriptine inhibited both hormones.

Adenoma, Chromophobe↗
PubMed1986

Neuroleptic drug-induced alterations on neonatal growth and development. I. Prenatal exposure influences birth size, mortality rate, and the neuroendocrine system.

Subcutaneous injection of codeine or phenobarbital, and feeding amphetamine to rats during gestation and lactation caused irregularities in mortality rates, growth, development, and associated neuroendocrine events within the newborns. Most striking was the subnormal birth size, increased mortality rate, and decreased hypothalamic growth hormone-releasing activity of neonates of mothers fed the highest dose of amphetamine.

Animals↗
PubMed1968

Slow turnover of manganese in active rheumatoid arthritis accelerated by prednisone.

Total body and area counts of intravenously injected (54)Mn were measured periodically in 29 in-patients. A heterogeneous group of 19 control patients showed fair reproducibility in the immediate distribution, and considerable individual variance in the subsequent loss of the isotope. Eight studies of the effects of feeding excesses of manganous sulfate to five patients showed acceleration of the rate of loss of the radioisotope from the whole body and the liver. These findings seem compatible with the presence of control mechanisms in man, operating to vary the metal's excretion, while tending to preserve constancy of its concentration in tissues. Slow turnover rates of the metal were demonstrated in seven out of eight patients with active rheumatoid arthritis, in one with hydralazine disease, but not in one arthritic undergoing an impressive, spontaneous remission. Statistically significant differences were encountered in the measurements of (54)Mn turnover of the total body, the thyroid, and the liver. Administration of prednisone induced clinical improvement and significant acceleration of these turnovers. Slow turnovers are characteristic of nutritional manganese deficiency. Therefore, serum and blood manganese determinations were performed by neutron activation analysis on 14 control patients, and on six patients with active rheumatoid arthritis. A statistically significant elevation of the red cell manganese concentration was encountered in patients with rheumatoid arthritis. This argued against the presence of classical tracemetal deficiency and called for an alternative explanation of these findings.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Genetic control of polyketide biosynthesis in the genus Streptomyces.

The genetic control of polyketide metabolite biosynthesis in Streptomyces sp. producing actinorhodin, daunorubicin, erythromycin, spiramycin, tetracenomycin and tylosin is reviewed. Several examples of positively-acting transcriptional regulators of polyketide metabolism are known, including some two-component sensor kinase-response regulator systems. Translational and posttranslational control mechanisms are only briefly mentioned since very little is known about either of these processes. Examples of how enzyme levels and substrate supply affect polyketide metabolism also are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Maintaining restored bone with bisphosphonate in the ovariectomized rat skeleton: dynamic histomorphometry of changes in bone mass.

This experiment contains the crucial data for the Lose, Restore and Maintain (LRM) concept, a practical approach for reversing existing osteoporosis. The LRM concept uses ovariectomy (ox) to lose bone, an anabolic agent to restore bone mass and then switches to an antiresorptive agent to maintain bone mass. We ox'd or sham-ox'd rats for 150 days (Loss Phase), treated them with 6 mg PGE2/kg/d for 75 days to restore lost cancellous bone mass (Restore Phase) and then stopped PGE2 treatment and began treatment with 1 or 5 micrograms/kg Risedronate, a bisphosphonate twice a week for 60 days (Maintain Phase). During the Loss Phase, cancellous bone volumes of the proximal tibial metaphysis (PTM) in the ox'd rat fell to 19% of initial controls. During the Restore Phase, the PTM bone volume in ox'd rats doubled. However, when PGE2 treatment was stopped, the PGE2-induced cancellous bone disappeared. In contrast, 5 micrograms of Risedronate inhibited the bone loss and maintained it at the PGE2 treatment level. The key dynamic histomorphometry value for the restore (R) and maintenance (M) phases was the ratio of bone formation to resorption rates. The ratio was elevated to 5.8 in the R phase and depressed to 0.4 for no and 1 microgram Risedronate treated M phase and to a ratio of near unity of 1.1 for the 5 micrograms Risedronate treatment. These findings indicate that we were successful in maintaining the new PTM bone induced by PGE2 after discontinuing PGE2 by administering enough Risedronate, a resorption inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Interactions of vancomycin resistant enterococci with biomaterial surfaces.

Enterococci are a frequent cause of nosocomial infections and are often found adherent to indwelling catheters. Concern about such device associated infections has increased with the appearance of vancomycin resistant (VR) enterococci. However, the possible influence of vancomycin resistance in the pathogenesis of biomaterial centered infection has not yet been assessed. Using polyethylene terephthalate (PET) disks as model surfaces, the authors evaluated possible differences in the adherence and persistence of vancomycin sensitive (VS) and VR strains of Enterococcus faecium and Enterococcus faecalis on biomaterial surfaces in vitro and in vivo. The results indicate that: 1) as expected, the clearance of free VR and VS organisms after intraperitoneal injection into normal mice is equally efficient. 2) In vitro, VR bacteria are roughly twice as adherent to plasma coated PET surfaces as are VS organisms. 3) However, in vivo persistence of VS organisms preadherent to biomaterial implants is 5- to 10-fold better than that of preadherent VR organisms. The authors now believe that a discrete change in bacterial cell wall composition between VR and VS enterococci may contribute to the substantial differences in bacterial adhesion and survival of adherent organisms.

Animals↗
PubMedDate not supplied

Determinants of BDNF-induced hippocampal synaptic plasticity: role of the Trk B receptor and the kinetics of neurotrophin delivery.

The neurotrophins are a class of signaling molecules known for their growth and survival-promoting activities during neuronal development. Recent studies suggest that the neurotrophins, including brain-derived neurotrophic factor (BDNF), can also dramatically influence synaptic transmission in the adult hippocampus. The experiments described in this paper indicate that ability of BDNF to potentiate synaptic transmission in the hippocampus relies on functional Trk B receptors. Moreover, the rate at which BDNF is applied to hippocampal synapses is also a potent determinant of whether synaptic potentiation will result. Hippocampal slices perfused with BDNF at a very slow flow rate (e.g., < or = 25 ml/hr) did not show synaptic potentiation. Increasing the rate of BDNF application resulted in synaptic potentiation in which the magnitude and onset kinetics of the potentiation were determined by the rate of BDNF delivery. Immunocytochemical analysis of BDNF detected with confocal microscopy confirmed these electrophysiological observations, indicating that the penetration of BDNF into hippocampal slices is influenced dramatically by the perfusion rate.

Animals↗
PubMedDate not supplied

A cdc2-like kinase associated with commitment to division in Paramecium tetraurelia.

Cell division in higher eukaryotes is mainly controlled by p34cdc2 or related kinases and by other components of these kinase complexes. We present evidence that cdc2-like kinases also occur in Paramecium. Two polypeptides reacted with an antibody directed against the perfectly conserved PSTAIR region found in cdc2 kinases in other eukaryotes. Only the less abundant peptide bound to p13suc1 from Schizosaccharomyces pombe. Using centrifugal elutriation to select cells on the basis of size, we isolated highly synchronous Paramecium G1 cells. With this procedure, we demonstrated that the p13suc1-associated cdc2-like histone H1 kinase was activated before cell division at the point of commitment to division in Paramecium. Further, we show that Paramecium cdc2-like proteins occurred principally as monomers and that these monomers were active as histone H1 kinases in vitro.

Amino Acid Sequence↗
PubMedDate not supplied

Regulation of p105wee1 and p34cdc2 during meiosis in Schizosaccharomyces pombe.

Temperature-sensitive pat1 mutants of the fission yeast Schizosaccharomyces pombe can be induced to undergo meiosis at the restrictive temperature, irrespective of the mat1 configuration and the nutritional conditions. Using a combination of exit from stationary phase and thermal inactivation of the 52-kilodalton protein kinase that is encoded by the pat1 (also called ran1) gene, highly synchronous meiotic cultures were obtained. Synthesis and tyrosyl phosphorylation of p34cdc2 was evident during meiotic G1 and S phases. During this period there was increased expression of p105wee1, a protein kinase implicated in the tyrosyl phosphorylation of p34cdc2. Following a relatively brief G2 period, during which a reduction in the steady-state level of p105wee1 occurred, there was an approximately 19-fold increase in the histone H1 phosphotransferase activity of p34cdc2. Only a single peak of histone H1 kinase activation was observed, which implies that unlike meiosis in amphibians and echinoderms, p34cdc2 is functional only during one of the meiotic divisions in S. pombe, presumably meiosis II. Stimulation of the kinase activity of p34cdc2 was associated with its tyrosyl dephosphorylation. This is analogous to mitotic M phase and suggests parallels in the mechanism of activation of p34cdc2 during mitosis and one of the meiotic divisions in S. pombe.

Amino Acid Sequence↗
PubMedDate not supplied

Changes in mucosal levels of transforming growth factor-alpha from the oxyntic region and ulcer site during duodenal ulcer healing with ranitidine or sucralfate.

Changes in the levels of transforming growth factor-alpha (TGF-alpha) in gastric mucosa during ulcer healing were studied in 24 patients with endoscopically confirmed duodenal ulcers, treated either with ranitidine (300 mg daily, at night) or with sucralfate (2 g twice daily). Endoscopic biopsies were taken from the gastric fundus and from the ulcer margin at baseline and after 7-10 days of treatment. TGF-alpha levels were determined by radioimmunoassay in paired samples from 22 patients (fundal) and 18 patients (duodenal). There were no significant changes in TGF-alpha levels in the fundus of the whole group or of either treatment group. At the ulcer site, however, there was a significant increase in TGF-alpha levels in the whole group (from 16.4 to 33 pg/mg protein (medians); P < 0.005), and an increasing trend was seen in both treatment groups but was statistically significantly only in the group treated with sucralfate (P < 0.03).

Adult↗
PubMedDate not supplied

An open-label, randomized, controlled, 4-week comparative clinical trial of barnidipine hydrochloride, a calcium-channel blocker, and benazepril, an angiotensin-converting enzyme inhibitor, in Chinese patients with renal parenchymal hypertension.

This study compared barnidipine, a calcium-channel blocker, and benazepril, an angiotensin-converting enzyme inhibitor, in 85 Chinese patients with renal parenchymal hypertension (diastolic blood pressure range 95 - 110 mmHg). Patients were randomly assigned to receive either 10 mg barnidipine or 10 mg benazepril orally daily for 4 weeks. In patients with diastolic blood pressure > 90 mmHg after 2 weeks of treatment, the dose of barnidipine or benazepril was increased by 5 or 10 mg, respectively. Both the barnidipine-treated group (n = 43) and the benazepril-treated group (n = 42) showed significant mean reductions from baseline in sitting systolic and diastolic blood pressures. The decrease in diastolic blood pressure with benazepril was significantly greater than with barnidipine treatment. Sitting heart rate was not changed by either drug. There was no significant difference in adverse events between the two groups. Barnidipine is similar to benazepril for the treatment of renal parenchymal hypertension.

Adolescent↗