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T Huang

Publications and source records attributed to T Huang.

At least 181 records · Page 10Linked to original sources
PubMed1988

Characterization of enkephalins in rat adrenal medullary explants.

In the rat, removal of depolarizing stimuli to the adrenal medulla by surgical denervation in vivo or by explanting adrenal medullae has been shown to dramatically increase preproenkephalin mRNA, and enkephalin-containing (EC) peptides. To further elucidate the cellular basis of these effects and the role of transsynaptic influences on post-translational processing, we have defined the time course, and characterized EC peptides in rat adrenal medullary explants in control and depolarized states. The rise in EC peptides begins after 1 day in culture and reaches a peak at 4-7 days. Although the onset of the increase in EC peptides in culture is delayed by 12-24 h compared to the changes seen in vivo, following surgical denervation, the time course of peak and duration is remarkably similar. Size exclusion chromatography (SEC) revealed that the major species of newly appearing EC peptides in explanted glands is a high molecular weight peptide of approximately 18,000 with a Met-/Leu-enkephalin ratio of approximately 6. These results suggest that proenkephalin, the initial precursor of the EC peptide family, is the major EC peptide that accumulates in rat adrenal medullary explants. A low-molecular weight EC peptide, found by high-performance liquid chromatography to be free Met-enkephalin, is a minor component of the culture induced increase in EC peptides. Culturing of medullae in the presence of depolarizing concentrations of K+ prevents the accumulation of the proenkephalin-like EC peptides and free enkephalins.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1988

Mapping and sequencing of the dihydrofolate reductase gene (DFR1) of Saccharomyces cerevisiae.

The dihydrofolate reductase gene (DFR1) from Saccharomyces cerevisiae has been mapped and sequenced. The gene was isolated on an 8.8-kb BamHI fragment from a yeast genomic library by screening of Escherichia coli transformants for resistance to trimethoprim. A 1.8-kb SalI-BamHI fragment which was able to confer methotrexate resistance in yeast also complemented an E. coli DHFR-deficient (folA) mutant. Nucleotide sequence analysis revealed that the yeast DFR1 gene encoded a polypeptide with a predicted Mr of 24230. The deduced sequence of 211 amino acid residues showed considerable homology with DHFRs from both bacterial and animal sources. The codon bias index of the DFR1 coding region is 0.0083, which indicates a random pattern of codon usage. The upstream region contains two consensus sequences required for binding of the yeast's positive regulatory factor, GCN4, suggesting that the DFR1 gene might be subject to the amino acid general control. Several potential 'TATA' boxes are located in the sequence 5' to the gene. Located in the 3' flanking region are homologies with several canonical sequences thought to be required for efficient transcription termination in yeast. We also mapped the DFR1 gene to a position 1.4 cM proximal to the MET7 locus on chromosome XV.

Amino Acid Sequence↗
PubMed1988

Retinol-regulated gene expression in human tracheobronchial epithelial cells. Enhanced expression of elongation factor EF-1 alpha.

Conducting airway epithelial cells requires vitamin A or its synthetic chemicals (retinoids) for their survival and for the expression of normal mucociliary functions. By using molecular cloning, we have shown that one of the effects of retinol on cultured human tracheobronchial epithelial (HTBE) cells is the enhancement (from 2- to 4-fold) of the mRNA encoding the elongation factor EF-1 alpha. Sequence analysis has shown that clone HT7, which was identified by differential hybridization procedures, contained a cDNA insert which encoded a protein closely resembling (81%) elongation factor EF-1 alpha from brine shrimp and completely identical to the published sequence of human elongation factor EF-1 alpha (Brands, H.H.G.M., Maassen, J.A., Van Hemert, F.J., Amons, R., and Moller, W. (1986) Eur. J. Biochem. 155, 167-171). Regions of homology of HT7 to EF-Tu from yeast mitochondria, plant chloroplasts, and Escherichia coli are also evident. A single RNA band at 1700 bases was observed for both untreated and retinol-treated HTBE cells, and for mouse liver and parotid glands when Northern transfer from denaturing agarose gel was probed with a 32P-labeled HT7 insert. An enhanced amino acid incorporation and increased protein content per cell for HTBE cells grown in the presence of retinol were observed. Results presented by these studies indicate that retinol may regulate the transcription of a factor required for translation.

Amino Acid Sequence↗
PubMed1988

Spontaneous fractures of the hip in the elderly.

The authors found 41 patients with 42 fractures of the hip who had no distinct history of trauma in the total of 1,449 hip fractures treated. They were all women ranging in age from 64 to 91 years. Most of the fractures were of intracapsular type. Three extracapsular fractures, however, were found. Fractures were randomly selected with clear history of trauma, which were matched to the patients with no trauma for age, sex, and type of fracture as a control group. The grades of osteoporosis of the femoral neck, estimated with the Singh index, and of the spine, estimated with the spinal score, were noted statistically significantly higher in the patients than those in the control group. Most of spontaneous fractures of the hip in the elderly are considered similar phenomena to the compression fractures of the dorsolumbar spine.

Aged↗
PubMed1988

Altered mRNA expression of basement membrane components in a murine model of polycystic kidney disease.

Basement membranes surround the renal tubules and have been shown to limit their distension in vitro. Therefore, it has been postulated that a defect in a basement membrane component(s) underlies the pathogenesis of polycystic kidney disease. Here we have studied a murine model of congenital polycystic kidney disease and found by immunohistology, that the components of the peri-cyst basement membrane appeared to diminish with time. We also measured mRNA levels for collagen IV and laminin, and found a different pattern than in the normal mouse kidney. In normal kidneys, mRNA levels for the B1 and B2 chains of laminin were maximal at birth, and at 1 week for the alpha 1(IV) chain of collagen IV. With all three chains, the levels then rapidly declined. In contrast, mRNA for the alpha 1(IV) chain in congenital polycystic kidneys was half normal 1 week after birth and then increased. Laminin B1 and B2 chain mRNA's were 80% of normal at 1 week but were maintained at that level. As a control, beta-actin mRNA was examined and found to remain constant in both normal and diseased kidneys. In situ hybridization of cRNA probes for the alpha 1(IV) chain confirmed that cells associated with cysts were the principal source of expression of these basement membrane mRNAs. Thus, there exists an abnormal regulation of basement membrane gene expression in congenital polycystic kidney disease. The first stage is characterized by reduced levels of expression. In the second stage, the levels are abnormally high, perhaps representing a compensatory synthesis of basement membrane as cysts enlarge.

Animals↗
PubMed1985

Effect of vasodilator treatment on the resolution of oleic acid injury in dogs.

Diffuse pulmonary injury is accompanied by reduction of blood flow to injured areas because of local pulmonary vasoconstriction, vascular thrombosis, and vascular obliteration. To assess whether reduced pulmonary arterial blood flow might produce relative ischemia in injured areas and consequent potentiation of the injury, we studied the effects of vasodilator treatment in a dog model of diffuse alveolar damage. Twenty-five awake dogs with arterial and pulmonary arterial catheters in place were given 0.08 ml/kg oleic acid, a dose that produces a diffuse lung injury that largely resolves over a 1-wk period. Ten of the animals were treated with minoxidil, a potent vasodilator and inhibitor of hypoxic pulmonary vasoconstriction. Observations were made for a total of 96 h. At 24 h, treated animals had lower pulmonary vascular resistance (207 +/- 85 versus 348 +/- 136 dyne X s X cm-5, p less than 0.01) but higher venous admixture (30 +/- 10% versus 18 +/- 12%, p less than 0.05) and thermodilution-measured lung water (17 +/- 8 ml/kg versus 9 +/- 2 ml/kg, p less than 0.05). However, by 96 h, there were no differences between the 2 groups in any measured parameters of hemodynamic status, gas exchange, or histologic examination. We conclude that pulmonary vasodilation increased blood flow to injured areas but did not affect eventual resolution of the injury.

Animals↗
PubMed1985

Pharmacokinetics and pharmacodynamics of subcutaneous morphine pellets in the rat.

The pharmacokinetics and drug release characteristics of a standard, widely available s.c. morphine pellet were examined in the rat, together with antinociceptive (tailflick) effects and physical dependence. Over a 72-hr implant period one, two or three 75-mg morphine pellets released 12.5, 22.6 and 27.6 mg of morphine, respectively. Mean plasma morphine concentration after two morphine pellets reached a peak at 4 to 6 hr, then declined to a mean apparent steady-state level of 210 ng/ml at 36 hr that was maintained until the pellets were removed at 72 hr. The antinociceptive action of two morphine pellets peaked at 4 to 6 hr and had returned to predrug base-line values by 36 hr. After pellet removal, the plasma elimination kinetics of morphine were biexponential with a terminal T1/2 of 8.3 hr. The plasma morphine concentration declined 85% before the onset of significant weight loss could be measured. Peak abstinence weight loss was dose-related and was significantly correlated with both plasma morphine levels just before withdrawal and total dose of morphine absorbed over the 72-hr implant. These studies indicate that the release of morphine from s.c. implanted pellets in the rat is characterized by an initially higher rate of release (dose dumping effect) over the first 24 hr followed by a very constant release from 36 to 72 hr after implantation. The pharmacodynamic consequences of these dosage characteristics are the rapid development of tolerance and maintenance of physical dependence during the period of the implant.

Animals↗
PubMed1983

Solid phase synthesis of polynucleotides. VIII. Synthesis of mixed oligodeoxyribonucleotides by the phosphotriester solid phase method.

A solid phase method for the simultaneous synthesis of mixed oligonucleotides using a phosphotriester approach has been developed. For this synthesis, a mixture of mono or dimeric coupling units is used, and a slight difference in the reactivity of those units is found. However, this difference does not hamper the simultaneous, mixed oligonucleotide synthesis, and the sequence analysis of a product demonstrates the existence of all desired sequences in the final mixture.

Base Sequence↗
PubMed1983

Effects of methylprednisolone on resolution of acid-aspiration pneumonitis.

We studied the effects of methylprednisolone sodium succinate on the pulmonary function of unanesthetized dogs for four days after aspiration of 1.5 to 2.0 mL/kg of 0.1N hydrochloric acid. Methylprednisolone sodium succinate (30 mg/kg) was administered to nine dogs at 2, 8, and 24 hours after acid aspiration. Nine animals were untreated after aspiration and served as controls. Acid aspiration caused significant increases in venous admixture and reductions in Pao2 in both groups of animals. These changes persisted for 96 hours after aspiration. There were no differences in cardiac output, venous admixture, and blood gas values between treated and untreated animals at any time. At death there were no differences between groups in amounts of lung water or histologic characteristics. We concluded that methylprednisolone administered after hydrochloric acid aspiration does not affect resolution of the injury.

Animals↗
PubMed1983

Does cell density correlate with red cell age?

We have examined age-related changes in red cells by employing a serial hypertransfusion protocol to generate populations of in vivo-aged mouse red cells. Studies of these old cells have revealed alterations in membrane components; namely, a conversion of band 4.1b to 4.1a and an increase in the amount of membrane-associated, Triton-insoluble globin. Furthermore, we have found that the erythrocyte does change in density, but only during the earliest stages of its life-span. As the cell continues to age, there is no longer a correlation between age and density.

Animals↗
PubMed1982

An alternate method for synthesis of double-stranded DNA segments.

Recent progress in the chemical synthesis of DNA has now made it possible to rapidly synthesize single-stranded DNAs over 40 bases in length. We have taken advantage of these longer DNAs in assembling and cloning a 132-base pair gene segment coding for amino acids 126 through the stop codon of human leukocyte interferon alpha 2. The method used involves DNA polymerase I-mediated repair synthesis of synthetic oligonucleotide substrates having short stretches of complementary sequence at their 3' termini. In the presence of DNA polymerase I and the four deoxyribonucleoside triphosphates, those primer-templates are converted to full length double-stranded DNAs. The economy in chemical synthesis using this approach is substantial with a greater than 40% reduction in the amount of chemical synthesis required as compared with the conventional approach. We describe in detail this methodology for the biochemical assembly of long gene segments from synthetic oligodeoxyribonucleotides.

Cloning, Molecular↗
PubMed1982

The effects of expiratory positive airway pressure on the resolution of oleic acid-induced lung injury in dogs.

It is not known whether positive end-expiratory pressure (PEEP) merely improves gas exchange in patients with the adult respiratory distress syndrome or also affects the resolution of their lung injury. We examined the effects of expiratory positive airway pressure (EPAP), a form of PEEP, on 13 pairs of spontaneously breathing mongrel dogs with permanent tracheostomies that were subjected to acute lung injury from oleic acid. One member of each pair was treated with 10 cm H2O EPAP by means of a special valve attached to its tracheostomy tube; the other member breathed through the tracheostomy tube alone. The EPAP was applied 3 h after an intravenous injection of 0.06 ml/kg oleic acid and continued for a total of 21 h. Functional residual capacity (FRC) was increased to preinjury values in the EPAP-treated dogs at 3, 12, and 24 h compared with that in the untreated dogs. The PaO2 was higher and the venous admixture (Qva/QT) was lower in the EPAP-treated dogs compared with that in the untreated dogs at 3 and at 12 h. However, over the 7 days after removal of EPAP no significant differences were noted between the 2 groups in FRC, PaO2, Qva/QT, inert gas elimination profiles, mortality, final lung compliance to initial lung compliance differences, lung water to dry lung weight ratios, or histologic features. We conclude that EPAP improves gas exchange during its administration but has no demonstrable effect on the resolution of lung injury induced by oleic acid in dogs.

Animals↗