Search PubMed⌕ Search

Biomedical subjects

A Tsang

Publications and source records attributed to A Tsang.

At least 55 records · Page 3Linked to original sources
PubMed1991

Biochemical and genetic characterization of a rapid-development strain in Dictyostelium discoideum.

We have examined the rates of development of six wild-type and rapid-development strains of Dictyostelium discoideum. Strains NC4 and HU1231, a derivative of V12, have very similar developmental profiles. In comparison to these two strains, amoebae of the rapid-development strain HT100 reach the aggregation stage about 6 h earlier. Also, intracellular cAMP levels in HT100 increase precociously during early development. Postaggregative morphogenesis of HT100 proceeds at the same rate as NC4 and HU1231. In addition we have assessed the progress of development by RNA hybridization blotting. The appearance in HT100 of mRNAs associated with aggregation is advanced by 6 h while the appearance of early gene products is not affected appreciably. These data suggest that HT100 differs from strains NC4 and HU1231 primarily in the process of aggregation. We have partially characterized the genetic background of strain HT100. Mating and cell fusion analyses suggest that HT100 is a derivative of V12. We constructed a growth-temperature-sensitive derivative of HT100, and fused it with HU1231 cells. The resulting diploids develop at the same rate as HT100, suggesting that the rapid-development phenotype in HT100 is dominant.

Animals↗
PubMed1990

Cloning and characterization of cDNAs encoding a novel cyclic AMP-binding protein in Dictyostelium discoideum.

The cellular slime mould, Dictyostelium discoideum, contains a novel cyclic AMP-binding protein, CABP1, which is composed of two subunits. Using anti-CABP1 monoclonal antibody as a probe, a cDNA clone was isolated from a lambda gt11 expression library. By hybrid selection of the complementary mRNA and its translation in vitro, we demonstrated that the cDNA hybridized to mRNAs encoding both CABP1 polypeptides. With the positive cDNA as a probe, we isolated a series of overlapping cDNA clones covering the coding region of both CABP1 mRNAs. Expression of the cloned cDNAs in bacteria and sequence analysis showed that the CABP1 subunits are identical in amino acid (aa) sequence, except that the small subunit is missing 37 aa near its N terminus. Genomic analysis suggested that the two CABP1 transcripts are derived from a single gene. The N-terminal half of each subunit is rich in proline, glutamine and glycine residues and contains a large block of aa repeats. The C-terminal half has an approx. 47% aa identity (86% with functionally conservative substitutions) with two polypeptides encoded by a plasmid determinant for tellurium anion resistance.

Amino Acid Sequence↗
PubMed1990

The molecular basis for alternative splicing of the CABP1 transcripts in Dictyostelium discoideum.

We have determined the nucleotide sequence of the CABP1 gene from Dictyostelium discoideum. Together with previous data on cDNA sequences, we establish that alternative splicing of transcripts derived from this gene is responsible for the production of the two CABP1 subunits. RNA blot analysis suggested that alternative splicing of the CABP1 transcripts occurs during growth and throughout development. In addition, we have compiled the intron sequences of Dictyostelium pre-mRNAs and observed that the GUAAGU hexanucleotide at the 5' splice site is highly conserved. The 5' splice site of CABP1 deviates from the consensus hexanucleotide in having a sequence of GUAAUA. To assess the role of the modified 5' splice on differential splicing, we have constructed an actin-CABP1 fusion gene and transformed it into Dictyostelium cells. Analysis by immunoprecipitation, with anti-CABP1 antibody and amplification of specific cDNAs by polymerase chain reaction show that the transcripts generated by the fusion gene are alternatively spliced. When the 5' splice site of the fusion gene is mutated to conform to the consensus sequence, the resulting transcripts are constitutively spliced. These observations suggest that changes in positions 5 and 6 of the donor splice site are involved in the alternative splicing of the CABP1 transcripts.

Actins↗
PubMed1990

Early controlled active mobilization with dynamic splintage for treatment of extensor tendon injuries.

Early controlled active mobilization with a dynamic splint for treatment of repaired extensor tendon injuries was studied prospectively. Postoperative dynamic splintage started on the third postoperative day and involved elastic band extension and active flexion of the digits. Mobilization of the digits within the splint was done immediately under supervision. Range of motion was stepped up progressively and splintage was stopped after 5 to 6 weeks. Thirty-eight patients with 48 digits were reviewed. The average follow-up was 6.7 months (range, 4 to 10 months). Injuries involving the fingers showed an average final total active motion of 229 degrees (range, 95 to 270 degrees), whereas injuries involving the thumb was 118 degrees (range, 78 to 150 degrees). Lesions distal to the knuckles (zones II, III, IV) showed the worst results with an average total active motion of only 188 degrees (range, 95 to 270 degrees). The duration out of work was 8.5 weeks (range, 4 to 25 weeks). There was no infection or acute tendon rupture. One patient required reconstruction of a persistent button-hole deformity; two required tenolysis and capsulotomy. Of the six unsatisfactory results with poor total active motion, four had injuries distal to the metacarpophalangeal joint, three of which were crushing injuries.

Adolescent↗
PubMed1988

Characterization of an unusual cAMP receptor and its related polypeptides in Dictyostelium discoideum.

Several lines of evidence indicate that cAMP modulates developmental gene activity via cell-surface receptors. We describe here a novel cAMP receptor, CABP1, whose properties are consistent with the idea that this protein is involved in gene regulation. Firstly, immunological techniques using anti-CABP1 antibodies as probes showed that this cAMP receptor can be detected on the surface of developing cells. Secondly, there is a steady migration of CABP1 to the nucleus during development. Thirdly, some genetic variants exhibiting an altered pattern of development are found to possess modified CABP1. We also showed that CABP1 co-purifies with at least seven other polypeptides which share common epitopes with CABP1. Interestingly, four of the CABP1-related polypeptides can be detected on the cell surface as well as in the nucleus.

Dictyostelium↗
PubMed1988

Therapeutic functional bracing in upper limb fracture-dislocations.

The authors utilized the principle of functional bracing in the management of 307 fractures and/or dislocations of the upper limb. There were 29 humeral fractures, 111 fracture-dislocations around the elbow, 32 fractures of the forearm, and 135 fractures of the distal radius. The average follow-up was 9 months. The results showed that more than 95% of the patients regained good range of motion and power. The details of the technique and the protocols are described. The conclusion drawn from an analysis of the results is that functional bracing is a safe and effective method in the management of upper limb fracture dislocations.

Adolescent↗
PubMed1986

Immunolocalization of elastase in human emphysematous lungs.

The current working hypothesis concerning the pathogenesis of human pulmonary emphysema proposes that neutrophils migrate through the alveolar interstitium and degranulate, releasing proteolytic enzymes into the interstitium. These enzymes, in particular elastase, can bind to and degrade interstitial elastin. This report describes an immunohistochemical, ultrastructural technique that utilizes polyclonal antibodies to localize neutrophil elastase in human lungs. Using both the immunoperoxidase and the immunogold methods on thin, embedded sections of surgically resected human emphysematous lung tissue, elastase was localized in neutrophils in the lung interstitium and extracellularly in association with interstitial elastic fibers in human lungs that showed local emphysema of varying severity. Quantitative morphometric data were obtained from the lungs of eight patients undergoing lobectomy for removal of pulmonary carcinomas. Patients had preoperative forced expiratory volume (FEV1)% levels ranging from 55 to 77. There was a correlation between a quantitative measure of the local distribution of neutrophil elastase in contact with alveolar interstitial elastin and the local presence of emphysematous change as determined by mean linear intercept of the various histologic sections. These data support the validity of the "protease-protease inhibitor balance hypothesis" as an explanation of the pathogenesis of human pulmonary emphysema.

Adult↗
PubMed1984

Secretion of elastin in the embryonic chick aorta as visualized by immunoelectron microscopy.

Recently, significant advances have been made in characterizing the pathway of elastin biosynthesis from the biochemical point of view and a 70,000 dalton protein, designated tropoelastin, appears to be the primary translation product and soluble intermediate of the insoluble elastin. However, relatively little is known concerning the intracellular secretory pathway of tropoelastin. We previously developed an electron microscopic technique using elastin-specific antibody and ferritin-conjugated secondary antibody to identify intracellular elastin and to identify, provisionally, intracellular vesicles containing elastin ( Damiano et al., Conn. Tiss . Res. 8: 185-188, 1981). However, the method did not permit localization of elastin in other intracellular organelles. We now describe an improved post-embedding technique using the peroxidase-antiperoxidase method to detect the primary elastin antibody and have localized elastin in both the endothelial and medial cells of the embryonic chick aorta. Specific staining was visualized in the cisternae of the endoplasmic reticulum, in the Golgi apparatus, and in vesicles forming on the trans side of the Golgi. Some of these smaller vesicles appeared to fuse, forming larger vesicles which may have a storage function. Both types of vesicles were seen fusing with the cell plasma membrane, suggesting that elastin is secreted by an exocytotic process. These results suggest that tropoelastin follows the classical pathway for protein secretion.

Animals↗
PubMed1981

Immuno electron microscopic studies on cells synthesizing elastin.

Embryonic chick and hamster aortas were examined in the electron microscope using ferritin-conjugated, elastin-specific antibodies after etching of the plastic, thin sections with a dilute solution of benzene, methanol and ethanol. Specific staining of intracellular vesicles was observed in both smooth muscle and endothelial cells in addition to extracellular elastin fibers. In the chick cells, these ferritin-stained vesicles had a lipid-laden appearance. In both species the vesicles appeared to fuse with the plasma membrane and discharge their contents into the extracellular space suggesting elastin is secreted via vesicular structures.

Animals↗
PubMed1979

Immunologic localization of elastin by electron microscopy.

Research on the pathogenesis of experimental emphysema has involved studies of the distribution of and destruction of elastin in the alveolar interstitium. The ill-defined organization of elastin in the alveolar interstitium makes it difficult to identify the elastin specifically by staining procedures ordinarily used for electron microscopy. This problem becomes more significant when the elastic tissue is fragmented during emphysema development and localization of the elastin fragments is essential. Therefore, a specific technique using high-titer antibodies against purified canine lung elastin was developed. The primary antibody was used on preembedded or etched postembedded sections. Localization of the antielastin IgG was accomplished with ferritin-labeled rabbit antisheep IgG as the secondary antibody. Treatment with the preimmune serum gave negligible ferritin background staining. The antielastin antibody did not react with lung connective tissue proteins such as the microfibrillar component of elastin or collagen or proteoglycan. The antielastin antibody appeared to be species specific. The method may be useful for studies of experimental emphysema.

Animals↗
PubMed1975

The incidence of urine cultures positive for Mycobacterium tuberculosis in a general tuberculosis patient population.

When urine specimens from a general tuberculosis patient population of 328 were submitted routinely for mycobacterial cultures, 33 patients (10 per cent) a positive turine cultures for Mycobacterium tuberculosis. In 22 patients (7 per cent) a positive urine culture for M. tuberculosis was unanticipated. Review of these 22 patients revealed that all had denied current genitourinary symptoms, 58 per cent had urinalyses within normal limits, and 58 per cent had normal intravenous pyelograms. Thus, lack of symptoms and normal tests do not necessarily exclude the possibility of genitourinary tuberculosis. Only 4.7 per cent of patients with pulmonary tuberculosis but 21 per cent of those with extrapulmonary tuberculosis had unanticipated positive urine cultures for M. tuberculosis. This suggests that routine submission of urine specimens for mycobacterial cultures can be a valuable adjunct to the bacteriologic confirmation of the diagnosis of extrapulmonary tuberculosis.

Bacteriological Techniques↗
PubMed1972

Human cartilage lysozyme.

The lysozyme content of human cartilage was measured by incubation of lyophilized, powdered cartilage in a variety of buffers and salt solutions, and the factors controlling the binding of lysozyme within cartilage were studied. Lysozyme was extracted from hyaline cartilage by buffers of pH greater than 9.0 by solutions 1 M in monovalent cations, and by solutions 0.12-0.40 M in divalent cations. The ability of cations to extract lysozyme from cartilage agreed with their known affinities for binding to chondroitin sulfate. The total extractable lysozyme content of five samples of human costal cartilage ranged from 1.45 to 3.36 mug lysozyme per mg of cartilage; for five samples of hyaline cartilage from peripheral joints the range was 0.80-3.03 mug lysozyme per mg of cartilage. Cartilage incubated in excess exogenous lysozyme could bind 0.053 equivalents of lysozyme per equivalent of chondroitin sulfate. Fibrocartilage and synovium from knee joints yielded no detectable lysozyme, despite the fact that synovium, a tissue rich in lysosomes, contained measurable quantities of beta-glucuronidase. Lysozyme extraction from cartilage was not augmented by incubation with streptolysin S. When incubation was carried out with mild extraction techniques, lysozyme extraction from cartilage tended to parallel uronic acid release, both as a function of time and from one specimen to another. The active material as lysozyme. Lysozyme occurs in human hyaline cartilage as a counterion to polyanionic glycosaminoglycans. Carextracted from cartilage met five criteria for identification tilage lysozyme appears to be extracellular and nonlysosomal. Degradation of cartilage may contribute to the increased serum and synovial fluid lysozyme levels often present in patients with rheumatoid arthritis.

Adult↗
PubMedDate not supplied

Accuracy of recall of dyspnea after exercise training sessions.

BACKGROUND: Although clinicians often rely on patients' retrospective reporting of dyspnea, it is not known if dyspnea scores recalled after exercise are equivalent to dyspnea scores during exercise. The objective of this study was to determine whether patients could accurately recall after exercise the maximum ratings of the intensity of dyspnea and the anxiety associated with it that they experienced during exercise. METHODS: Forty-nine patients with chronic obstructive pulmonary disease (COPD) (forced expiratory volume in 1 second 0.92 +/- 0.23 L) participating in a randomized clinical trial of the impact of coached versus monitored exercise training on dyspnea rated dyspnea intensity (shortness of breath [SOB]) and dyspnea-related anxiety (DA) on a visual analog scale every 2 minutes during treadmill exercise. After each of 12 training sessions each subject was asked to rate the worst level of the two sensations that they recalled having experienced during exercise. RESULTS: For the groups as a whole, actual maximum scores for SOB and DA during exercise were highly correlated with recalled maximum values after exercise (r > or = 0.85, P < 0.0001) and the average differences were small (0-10.9 mm on a 200-mm scale). However, individual variation was substantial, limiting predictability for individual ratings. CONCLUSIONS: After exercise, patients with COPD as a group can accurately recall the worst SOB and DA that they experienced during exercise. This finding supports the further study and use of retrospective symptom ratings as a method for dyspnea assessment during exercise training in pulmonary rehabilitation.

Aged↗