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Biomedical subjects

K C Lin

Publications and source records attributed to K C Lin.

At least 73 records · Page 4Linked to original sources
PubMed1993

AIDS in the Republic of China, 1992.

From May 1985 to December 1992, a total of 5,931,032 serum samples from eight population groups were tested for antibody to human immunodeficiency virus type 1 (HIV). Mandatory testing is carried out for blood donors, military recruits, immigrants, and prisoners. The other population groups were tested anonymously with consent. A total of 407 samples were seropositive. Of those HIV carriers, 63 developed AIDS: 37 were homosexuals, 6 were hemophiliacs, 1 was an intravenous drug user, 15 were heterosexuals, and 4 had no known risk factors. Although the prevalence of HIV infection and AIDS in Taiwan has remained low, the increase since 1988 has been rapid. Before 1987, all of the 48 persons with HIV infection were homosexuals or hemophiliacs. Thereafter, the risk groups diversified, with the main group shifting from homosexuals to heterosexuals and the number of intravenous drug users surpassing the number of hemophiliacs. Among the 63 patients with AIDS, 59 were male and only 4 were female; 53 have died (3 committed suicide).

Acquired Immunodeficiency Syndrome↗
PubMed1993

DNaseI footprinting studies of Escherichia coli biotin repressor-operator interactions.

Transcription of Escherichia coli biotin operon is repressed by biotin repressor in the presence of biotinyl-5'-adenylate as a corepressor. To determine precisely the site of action of biotin repressor on the operator sequence, DNaseI footprinting experiments were performed on the PCR-produced biotin operator and its mutants. The results indicate that the repressor binds to the wild-type operator as well as mutated operator sequence at +15 position or -15 position, and protects the 39-base region from nucleotide -19 to +20 of the upper strand, and the 40-base region from nucleotide -22 to +18 of the lower strand, with a few hypersensitive sites. This is consistent with previous speculation that the biotin operator is an approximately 40 bp imperfect palindromic DNA sequence capable of binding with two molecules of biotin repressor. However, the protection pattern of the mutant operator which lacks half of the palindromic structure is quite different from the corresponding region of the wild type. Though two repressor monomers bound to the mutant operator, as revealed by parallel binding studies [Lin, Shiuan, and Campbell (1991) Biochim. Biophys. Acta 1090, 317-325], only 12 to 13 bp on the DNA sequence was protected, suggesting that one monomer of the repressor dimer is hanging near the DNA backbone of the mutant operator even though the biotin repressor is functioning as a dimer.

Adenosine Monophosphate↗
PubMed1993

Extracellular cAMP is sufficient to restore developmental gene expression and morphogenesis in Dictyostelium cells lacking the aggregation adenylyl cyclase (ACA).

Cell movement and cell-type-specific gene expression during Dictyostelium development are regulated by cAMP, which functions both as an extracellular hormone-like signal and an intracellular second messenger. Previous data indicated that aca- mutants, which lack adenylyl cyclase activity, fail to aggregate and do not express cell-type-specific genes. We show here that overexpression of ACG, a constitutively active adenylyl cyclase, which in wild-type cells is only expressed during spore germination, partially restores the coordination of cell movement and completely restores developmental gene expression. The aca- cells can also be induced to develop into viable spores by synergy with wild-type cells and, furthermore, form small but normal fruiting bodies, after a developmentally relevant regimen of stimulation with nanomolar cAMP pulses followed by micromolar cAMP concentrations. 2'-Deoxy cAMP, a cAMP analog that activates the cell-surface cAMP receptors but not cAMP-dependent protein kinase (PKA), also induces fruiting body formation as well as expression of prespore-specific and prestalk-enriched genes in aca- cells. Intracellular cAMP levels were not altered in aca- cells after stimulation with 2'-deoxy cAMP. Our data indicate that ACA is not required to provide intracellular cAMP for PKA activation but is essential to produce extracellular cAMP for coordination of cell movement during all stages of development and for induction of developmental gene expression.

Adenylyl Cyclases↗
PubMed1992

Observation of the inverted hexagonal phase of lipids by scanning tunneling microscopy.

Scanning tunneling microscopy (STM) has been used in direct observations of the inverted hexagonal phase of several lipids, such as cardiolipin (CL) in the presence of Ca2+, soybean PE, DOPE and a binary system of CL and DMPC as well. Single tube-like structures, bundles of tubes and the cross-sectional view of the HII phase can clearly be seen at room temperature in a near natural state of these lipids. The success of this study shed some light on the applicability of STM in the investigation of lipid polymorphism and its role in the function of biological membranes.

Cardiolipins↗
PubMed1992

Structurally distinct and stage-specific adenylyl cyclase genes play different roles in Dictyostelium development.

We have isolated two adenylyl cyclase genes, designated ACA and ACG, from Dictyostelium. The proposed structure for ACA resembles that proposed for mammalian adenylyl cyclases: two large hydrophilic domains and two sets of six transmembrane spans. ACG has a novel structure, reminiscent of the membrane-bound guanylyl cyclases. An aca- mutant, created by gene disruption, has little detectable adenylyl cyclase activity and fails to aggregate, demonstrating that cAMP is required for cell-cell communication. cAMP is not required for motility, chemotaxis, growth, and cell division, which are unaffected. Constitutive expression in aca- cells of either ACA or ACG, which is normally expressed only during germination, restores aggregation and the ability to complete the developmental program. ACA expression restores receptor and guanine nucleotide-regulated adenylyl cyclase activity, while activity in cells expressing ACG is insensitive to these regulators. Although they lack ACA, which has a transporter-like structure, the cells expressing ACG secrete cAMP constitutively.

Adenylyl Cyclases↗
PubMed1992

Esterification of fatty acids by bovine intramuscular and subcutaneous adipose tissues.

Exogenous fatty acid esterification in intramuscular and subcutaneous adipose tissues from 72-hr fasted or ad libitum fed Angus cattle was investigated. Intramuscular (interfascicular) and subcutaneous adipose tissue snips were obtained from the longissimus dorsi muscle and were incubated with radioisotopically labeled fatty acids (palmitate, stearate, oleate, linoleate or linolenate) at three different concentrations (0.3 mM, 0.6 mM and 2.0 mM) to assess rates of fatty acid incorporation into glycerolipids. Rates of fatty acid esterification in vitro increased with fatty acid concentration in both intramuscular and subcutaneous adipose tissues. For all of the fatty acids investigated, triglycerides were the predominant products (60-85%). Subcutaneous adipose tissue had larger adipocytes and more actively (P less than 0.05) esterified fatty acids, with the exception of palmitate, than intramuscular adipose tissue. The rate of palmitate esterification was not different between tissues, although intramuscular adipose tissue esterified a greater proportion (P less than 0.10) of palmitate as triglyceride (85%) than did subcutaneous adipose tissue (75%). Relative rates of incorporation of fatty acids into lipids in intramuscular and subcutaneous adipose tissues were: palmitate greater than linolenate greater than linoleate greater than stearate. In general, 72-hr fasting did not significantly reduce the rates of fatty acid incorporation in bovine adipose tissues. Results of this study revealed that:i) rates of exogenous fatty acid incorporation into adipose tissue lipids were dependent on the medium fatty acid concentration and adipose tissue depot; and ii) the relative esterification rates of the various fatty acids in vitro did not necessarily reflect the proportion of these fatty acids in bovine adipose tissues.

Adipose Tissue↗
PubMed1992

Chromosome mapping of the owl monkey CSF1R and IL5 genes.

We mapped the owl monkey colony-stimulating factor 1 receptor (CSF1R) locus to the proximal region of chromosome 3q of karyotype VI(K-VI) and karyotype V(K-V) and the interleukin 5 (IL5) locus to the mid-region of chromosome 3q(K-VI) and 19q(K-IV) using a combination of Southern hybridization of somatic cells and in situ chromosomal hybridization methodologies. The findings support the proposed evolution of owl monkey chromosome 3(K-VI) from a fusion of two smaller structures, the homologs of chromosomes 6 and 19 (K-IV). The data also indicate genomic conservation of the HSA 5q23-q35 segment in the higher primates.

Animals↗
PubMed1992

Transesophageal color Doppler flow imaging in the evaluation of prosthetic cardiac valves.

To determine the value of transesophageal echocardiography in the assessment of prosthetic cardiac valves, 11 patients with clinically suspected cardiac prosthetic valve dysfunction were studied by transesophageal two-dimensional imaging, as well as by color Doppler flow mapping. Among these 11 patients, there were 10 with biological tissue valves and 3 with metallic valves (1 Bjork-Shiley, 2 St. Jude). Nine patients had replacement of mitral valves alone. The remaining two had received both mitral and aortic prostheses. The degree of mitral regurgitation was graded by transesophageal color Doppler according to the area of the regurgitant jet visualized. The degree of aortic regurgitation was graded by the jet height/left ventricular outflow height ratio method. All transesophageal studies were performed without complication and all were well tolerated. The pathological morphology of the cardiac prosthesis was clearly visualized by transesophageal two-dimensional imaging and subsequently proven at surgery. Of those tested, one patient was found to have a torn leaflet, one had a dislodged leaflet, one patient had paravalvular leakage, four had cusp vegetations, and five patients had prosthetic degeneration for other reasons. Mitral regurgitation was graded as absent in one patient, mild in two patients, moderate in two patients, and severe in six patients. Aortic regurgitation was graded as severe in both patients with aortic prostheses. We conclude that in patients with clinically suspected cardiac prosthetic dysfunction, transesophageal two-dimensional imaging combined with color Doppler can provide reliable information that corresponds to surgical findings.

Adult↗
PubMed1992

Acute pseudo-obstruction of the colon following partial splenic artery embolization: report of a case.

This is a case of a 45-year-old woman suffering from liver cirrhosis with hypersplenism who received a partial splenic artery embolization with gelfoam pieces. Thrombocytopenia and leukopenia improved immediately after treatment. Marked abdominal distention, metallic bowel sounds and combined small and large bowel distension with air-fluid levels as shown on a plain abdominal X ray were noted on the fifth day after the embolization procedure. Laparotomy was performed. No mechanical obstruction was found during surgery. Acute pseudo-obstruction of the colon (Ogilvie's syndrome) was diagnosed. This condition was considered to be a complication of the partial splenic artery embolization and has not hitherto been reported.

Acute Disease↗
PubMed1992

Status and trend of HIV-1 infection and AIDS in Taiwan, December, 1991.

From May 1, 1985 to December 31, 1991, a total of 4,962,707 serum samples from 8 population groups in Taiwan were tested for anti-human immunodeficiency virus type 1 (anti-HIV-1). In total, 256 samples were seropositive; of these individuals, 43 developed acquired immunodeficiency syndrome (AIDS): 29 were homosexuals; 5 were hemophiliacs; 8 were heterosexuals and 1 was of unknown risk. Although the prevalence of HIV-1 infection and AIDS remains low compared with other countries, since 1988 the increase has been rapid. Before 1977 the majority were homosexuals and hemophiliacs; thereafter the risk groups diversified, with a trend away from homosexuals and hemophiliacs towards heterosexuals and intravenous drug abusers (IVDAs). A few patients have caused serious social problems for the public, health care workers and families. Active community efforts are needed to achieve future success in the control of HIV-1 infection and AIDS in Taiwan.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Binding characteristics of Escherichia coli biotin repressor-operator complex.

The genes of the operon bioA.BFCD are transcribed divergently from a single regulatory region between the bioA and, bioB genes. Transcription in both directions is co-repressed by biotinyl-5'-adenylate and the biotin repressor. The multimeric state of the biotin repressor bound to DNA and how it affects transcription have not been fully characterized. Therefore, we isolated the BirA protein from a recombinant strain which overproduced the biotin repressor and studied the repressor-operator binding characteristics through restriction enzyme site protection experiments and the mobility shift assay. We also measured the stoichiometry of the biotin repressor-operator complex directly. The results of restriction enzyme site protection studies are consistent with the postulation that the biotin operator is approx. 40 bp long. Only one retarded DNA band appeared in the mobility shift experiments, suggesting that the repressor-operator binding could be a single step reaction. The repressor-operator binding stoichiometry determination revealed that two repressor monomers may occupy the wild type or half palindromic biotin operator sequences.

Base Sequence↗
PubMed1991

The role of aggregation of platelets in pregnancy-induced hypertension: a comprehensive and longitudinal study.

Plasma 6-keto-prostaglandin F 1 alpha and thromboxane B2, the metabolites of prostacyclin and thromboxane A2 respectively, were measured in 12 women with pregnancy-induced hypertension, 12 age-matched normotensive pregnant women and 8 non-pregnant women as controls. Pregnancy was divided into 3 stages, namely: 22-27, 28-32 and 33-39 weeks. The concentrations of thromboxane B2 in the plasma of women with pregnancy-induced hypertension was 1.4-1.7 times greater than normotensive pregnant subjects at the same gestational stage, and 2 times higher than controls. Plasma levels of 6-keto-prostaglandin F 1 alpha in normotensive pregnant women was 1.8 times greater than in those with pregnancy-induced hypertension at 28-32 and 33-39 weeks, and was significantly higher than control. The ratio of thromboxane B2 to 6-keto-prostaglandin F 1 alpha was markedly increased in the group of patients with pregnancy-induced hypertension at 28-32 and 33-39 weeks gestation. The ratio of the two metabolites in normotensive patients at each stage of gestation was similar to the control group. The ratio of circulating aggregated platelets in subjects with pregnancy-induced hypertension was significantly lower than in normotensive pregnant subjects at 33-39 weeks, implying increased turnover of platelets in pregnancy-induced hypertension. There was no significant difference in count of platelets, adenosine diphosphate threshold concentration and variables of platelet aggregation induced by adenosine diphosphate among the 3 groups.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Relationship of platelet specific proteins and other factors to atherosclerosis in various stages of hypertension.

There is considerable evidence from previous studies that platelets play an important role in the development and progression of atherosclerosis in hypertension, more so in relation to the stage of hypertension. Seventy one hypertensive patients (WHO stage I: 39, stage II: 23, stage III: 9) aged 19-84 (mean age: 56, 59 and 62 respectively for each stage) and 37 normal controls (aged 22-72 with a mean age of 52) were involved in this study. Hematocrit, beta-thromboglobulin (beta-TG), platelet factor 4 (PF4), beta-TG/PF4 ratio, total cholesterol (TC), low density lipoprotein-C, and triglycerides were higher in the hypertensive group while platelet count, circulating platelet aggregates, and high density lipoprotein-C were higher in the normotensive group. Among the hypertensives, stage III patients showed the highest beta-TG, PF4, beta-TG/PF4 ratio, triglycerides, and stage I with the least elevation. There were no significant differences noted in the ADP or epinephrine-induced platelet aggregation in both the normal and hypertensive patients. Other parameters such as heart rate, serum sodium, potassium, renal and liver function tests, plasma renin activity, aldosterone, fibrinogen thromboxane B2 and 6-Keto-PGF1 alpha, showed no significant differences in both groups. This study clearly showed that beta-TG/PF4 ratio and triglycerides are closely related to the stage of hypertension and are good indicators of in vivo platelet activation in hypertensives which may account for the acceleration of hypertensive vascular complications secondary to atherogenesis.

Adult↗
PubMed1990

Studies on the mechanisms of Ni2(+)-induced cell injury: I. Effects of Ni2+ on microtubules.

Cytoskeletal perturbations have been associated with exposures to a variety of toxic agents as well as a number of human pathological conditions. We have observed dramatic alterations in the organization of microtubules (MT), a major component of the cytoskeleton, in 3T3 cells exposed to Ni2+. Severe perinuclear bundling and aggregation of MT occurred in both a time- and dose-dependent fashion, and this MT damage was reversible upon removal of Ni2+ from the culture media. To understand the mechanism of the Ni2(+)-induced MT change, we investigated the effect of Ni2+ (0.01 to 3.0 mM) on in vitro tubulin polymerization. Ni2+ at lower concentrations (0.01 to 1.0 mM) had little or no significant effect on the kinetics of MT polymerization. In contrast, in the presence of 1.5 to 2.0 mM Ni2+, a significant promoting effect on both the rate and the final extent of polymerization was observed. However, at Ni2+ concentrations higher than 2.0 mM, such stimulatory effect on the rate and the final extent of tubulin polymerization declined. Furthermore, the promoting effects of Ni2+ on MT polymerization were accompanied by a significant decrease in the lag period. Electron microscopic examination of samples of the polymerization product showed that MT, polymerized in the presence of 2.0 mM Ni2+, appeared more numerous and shorter (1.10 +/- 1.02 microns) than those of control (3.81 +/- 2.29 microns; p less than 0.005). This was probably a direct result of an increase in the number of initiation centers in the presence of Ni2+ as a consequence of the decreased critical concentration (7%, p less than 0.05) necessary for polymerization to occur. Our results suggest that Ni2+ may exert its toxic effect on MT in cultured cells by altering the normal kinetics of MT polymerization.

Animals↗
PubMed1990

Characterization of filamentous bacteriophage phi Lf from Xanthomonas campestris pv. campestris.

A filamentous phage, phi Lf, which specifically infects Xanthomonas campestris pv. campestris was isolated. The phage particle measured 1,000 (+/- 200) x 8 nm. It formed turbid plaques of about 1 mm in diameter. During multiplication, the progeny virions extruded into the medium without retarding host cell growth. Stocks were stable for 6 months at 4 degrees C and survived treatment at 80 degrees C for 10 min. Treatment with chloroform, ethanol or acetone completely destroyed infectivity; ethyl ether and methanol inactivated 98 to 99% of the phage. SDS-polyacrylamide gel electrophoresis showed a major coat protein band of approximate Mr 4000 whereas an immunoprecipitation test detected the existence of two coat protein species. The phage genome was shown to be a single-stranded DNA molecule. A physical map was constructed and the DNA size was calculated to be 5.9 kb. Cells treated with Tris-HCl containing CaCl2 and polyethylene glycol 6000 were transfected by replicative form DNA at a frequency of 3.4 x 10(3) p.f.u./micrograms.

Bacteriophages↗
PubMed1990

Detection of dysfunctioning mitral prosthetic regurgitation: transesophageal echocardiography in comparison with transthoracic echocardiography and angiography.

Transesophageal echocardiography has been increasingly used in addition to the transthoracic approach. It not only allows an unobstructed window for viewing the left atrium, but also provides high-quality imaging to improve diagnosis of prosthetic valve dysfunction. To determine the value of transesophageal echocardiography in detection of dysfunctioning mitral prosthetic regurgitation, 11 patients clinically suspected of dysfunctioning mitral prosthesis were studies by transthoracic, transesophageal echocardiography and was documented by a left ventricular angiography. There were 7 biological tissue valves and 4 metallic Bjork-Shiley valves. Compared with a left ventricular angiography, the transthoracic approach to 8 patients made an underestimation of the grade of regurgitation. The angiographic grading confirmed the transesophageal approach in all patients except one who was graded as mild regurgitation by left ventricular angiography, moderate regurgitation by transesophageal echocardiography, but no regurgitation by transthoracic echocardiography. Our results indicated that in patients with suspected mitral prosthetic dysfunction, a transesophageal echocardiography is more sensitive than a transthoracic echocardiography in detecting mitral regurgitation.

Adult↗