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Biomedical subjects

Y S Lin

Publications and source records attributed to Y S Lin.

At least 127 records · Page 7Linked to original sources
PubMed1994

Variation in mitochondrial DNA and population structure of the Taipei treefrog Rhacophorus taipeianus in Taiwan.

Mitochondrial DNA (mtDNA) from 40 samples of the Taipei treefrog Rhacophorus taipeianus collected from seven populations in Taiwan were sequenced to document the DNA sequence variation in anuran mtDNA and to elucidate the phylogeographic population structure in the Taipei treefrog. Sequences of 722-764 bases in length, including a 108-bp segment of the cytochrome b gene and a 614-656-bp D-loop segment, were obtained by direct sequencing using polymerase chain reaction (PCR). The variation in length was due to a 40-bp region that tandemly repeated four to five times in the D-loop region. The first repeat is the most conserved one among the five repeats because there are no variable sites in this repeat. Besides the 40-bp length variation, 28 positions in the 764-bp sequences are variable and distributed evenly in the cytochrome b gene fragment and D-loop region. Variation in the D-loop of the Taipei treefrog is comparable to those of other vertebrates. Two well-differentiated lineages (northern and central) differing by mean sequence divergence of 1.7% are identified and concordant with their geographic distributions. The two lineages are inferred to have split from a common ancestral population in the early Pleistocene. However, the interpopulation divergence of the northern lineage (< 0.33%) is apparently lower than that of the central lineage (1.11%), implying that the two lineages evolved independently and had different demographic histories after divergence. This study reveals that anuran D-loop has potential as a genetic marker in phylogenetic and population genetic analyses of anurans.

Animals↗
PubMed1994

[Cyclocryotherapy for refractory glaucoma after penetrating keratoplasty].

Twenty-eight patients (28 eyes) with secondary glaucoma following penetrating keratoplasty and failed to respond to anti-glaucoma drugs and routine filtering procedures were performed with cyclocryotherapy by nitrogen monoxide. All patients were followed up for more than one year. The results showed intraocular pressure was well controlled in 89% of the eyes, graft remained clear in 85%, and visual functions are preserved in 82% of the patients. Our study suggests that precisely controlled temperature, time, and extent of cryotherapy, and post-operative anti-rejection agents be the key factor to success. Over-treatment, which may lead to atrophy of the eye, must be avoided. It should not be given up flowing under-treatment in the initial procedure.

Adolescent↗
PubMed1993

The effect of chronic and acute exercise on immunity in rats.

The effects of exercise training and acute exercise on the immune system were investigated in rats. For chronic exercise training, the rats ran on a drum exerciser at the intensity of about 60-70% of maximal oxygen consumption (VO2max) for 30 min and then extended up to 60 min per day, 5 days per week for 10 weeks. The rats were at rest for 3 days before sacrifice. The mitogenic activity of spleen lymphocytes to concanavalin A (Con A) and staphylococcal enterotoxin B (SEB) decreased as compared to the sedentary control, while proliferative response to lipopolysaccharide (LPS) increased. The interleukin-2 (IL-2) production in the training group was reduced. The immunomodulatory effect after acute exercise has also been investigated and it showed profound enhancement of cell proliferation to Con A, SEB and LPS in mild (50% VO2max for 10 min) and moderate (70% VO2max for 10 min) exercise groups. The enhancing activity was less prominent after severe exercise (> 75%) VO2max until exhaustion). The IL2 production increased in all of these acute exercise groups. Nevertheless, there was no significant variation between exercise and control groups in the cell number per spleen and the percentages of various lymphocyte populations, i.e., total T, CD4+, CD8+ and IL-2R+ T cells as well as B cells. In summary, this study indicates that chronic exercise training may cause the reduction of T cell activity while acute exercise manifests an enhancing effect. However, B cell proliferation was elevated in both chronic and acute exercise groups.

Animals↗
PubMed1993

The chromosomal DNA of Streptomyces lividans 66 is linear.

Two copies of a DNA sequence similar or identical to one end of the linear plasmid SLP2 were found on the Streptomyces lividans chromosome. Restriction mapping showed that these sequences represented free ends. Electrophoretic retardation and glass-binding studies indicated that the telomeres carry covalently bound proteins. Moreover, the chromosome migrated as an 8 Mb linear DNA in pulsed-field gel electrophoresis. A similar finding with the chromosomes of six other Streptomyces species suggested that a linear chromosome may be characteristic of the genus. The S. lividans chromosome can be circularized by joining the two ends by artificial targeted recombination or by spontaneous deletions spanning both telomeres. Thus the chromosome appears to be able to exist, in viable bacteria, as a linear or a circular molecule.

Bacterial Proteins↗
PubMed1993

The conjugative plasmid SLP2 of Streptomyces lividans is a 50 kb linear molecule.

The SLP2 plasmid had previously been demonstrated genetically to exist in Streptomyces lividans by its ability to promote conjugation and to elicit 'pocks' on recipient (SLP2-) cultures, but it had not been physically detected. Using pulsed-field gel electrophoresis, a 50 kb linear DNA was isolated from SLP2+ but not SLP2- strains of S. lividans, and from Streptomyces coelicolor and Streptomyces parvulus strains to which SLP2 had been transferred by conjugation or transformation. We conclude that this linear DNA is SLP2. The terminal fragments of SLP2 were cloned. The determined sequences revealed a 44bp imperfect terminal inverted repeat. The terminal 12bp sequence of SLP2 was identical to those of two other Streptomyces linear plasmids, pSLA2 and pSCL, and similar to the terminal sequences of another Streptomyces linear plasmid, SCP1. The termini of SLP2 DNA were resistant to digestion by lambda exonuclease and ExoIII. A truncated (probably crippled) copy of Tn4811 is present on the plasmid. While the SLP2 plasmid exists as a free form in the host, a 15.7 kb sequence corresponding to the segment of SLP2 from Tn4811 to the right terminus is also present (at a copy number similar to the free form) elsewhere in the genome of S. lividans. Furthermore, SLP2 is partially homologous to a newly discovered 650 kb linear plasmid in S. parvulus.

Base Sequence↗
PubMed1993

Chloride anion concentration as a determinant of renal vascular responsiveness to vasoconstrictor agents.

1. The role of chloride concentration in modulating vasoconstrictor responses of the rat isolated kidney, perfused with Krebs-Henseleit solution, to angiotensin II (AII), arginine vasopressin (AVP) and phenylephrine (PE) was investigated. 2. Reduction of perfusate chloride from a high (117 mM) to low (87 mM) concentration, by substitution of sodium chloride with a mixture of sodium salts of propionate, acetate and methanesulphonate, reduced responsiveness to all three vasoconstrictors, the change for AII being most pronounced. 3. For AII, reduced vasoactivity with low chloride was evident both in terms of the threshold dose and on the linear part of the dose-response curve but not for the maximum response. This attenuating effect of low chloride on the vasoconstrictor response to AII was reversed when perfusion with high chloride was reinstituted. Continuous perfusion with high chloride progressively increased the vasoconstrictor effect of low doses of AII for successive dose-response curves. 4. In addition to reducing responses on the linear part of the dose-response curve for both AVP and PE, low chloride also reduced the maximum vasoconstrictor response to PE, whereas the threshold dose for the two agonists was unchanged. In contrast to the enhanced pressor response to AII, during continuous perfusion with high chloride, tachyphylaxis occurred with AVP and PE. 5. The ability of chloride to modify renal responsiveness to vasoconstrictor agents may contribute to the increase in renal vascular resistance and decrease in glomerular filtration rate (GFR) which occurs during infusion of hyperchloremic solutions into the renal artery and explain the need for chloride as the anion accompanying sodium in salt-sensitive hypertensive models.

Angiotensin II↗
PubMed1993

Prediction of fetal macrosomia by single ultrasonic fetal biometry.

A total of 1,056 fetuses underwent single ultrasonographic measurement of fetal biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and estimated body weight within five days of delivery. The accuracy of these parameters and estimated body weight equations in the prediction of macrosomia (birth weight > or = 4,000 g) was evaluated. With the use of receiver operator characteristic curves, the optimal cutoff value for each parameter with the best sensitivity, specificity and accuracy was selected. BPDs > or = 9.4 cm had the best sensitivity (68.8%), specificity (74.3%), and accuracy (74.1%). ACs > or = 35 cm had the best sensitivity (81.3%), specificity (81.5%), and accuracy (81.5%). FLs > or = 7.0 cm had the best sensitivity (68.8%), specificity (74.5%), and accuracy (74.3%). The estimated body weight equations did not increase the prediction values whether or not FL was included. Both had the same prediction values at > or = 3,700 g, ie, sensitivity (71.9% vs 71.9%), specificity (92.1% vs 93.8%), and accuracy (91.5% vs 93.2%). The results showed AC to be the best single parameter for predicting macrosomia. Combinations of these parameters were better than a single parameter in the prediction of macrosomia.

Anthropometry↗
PubMed1993

Medical treatment of uterine myoma with long-acting gonadotropin-releasing hormone agonist prior to myomectomy.

A less bulky uterine myoma is technically easier to deal with during surgery. Recently gonadotropin-releasing hormone agonists (GnRH-a) have been used for the purpose of medical hypophysectomy, thereby reducing the size of uterine myomas. Ten premenopausal women with infertility and intramural-submucous myoma manifesting with menorrhagia and obstruction of the tubal ostia were recruited for this study. A long-acting depot GnRH-a, Decapeptyl, was given intramuscularly every four weeks for three months as an adjunct prior to myomectomy. Luteinizing hormone, follicular stimulating hormone and estradiol declined to the menopausal range following treatment. The size of the myoma decreased to a mean of 32.3 +/- 13.3% of the original volume. Myomectomy was performed in eight patients at the end of the study. Remarkably little blood loss was observed during the surgery. All of the patients had their uteri preserved, and six out of eight patients achieved pregnancy within 12 months after surgery. Our results indicate that monthly administration of long-acting GnRH-a significantly reduces the myoma volume and makes myomectomy technically easier to perform with the possibility of reduced complication rates and better preservation of future fertility.

Adult↗
PubMed1993

Renovascular actions of angiotensin II in the isolated kidney of the rat: relationship to lipoxygenases.

Several actions of angiotensin II have been linked to metabolism of arachidonic acid by lipoxygenases. To evaluate the importance of this interaction intrarenally we tested the effect of three different lipoxygenase inhibitors, BW755c (50 microM), a dual lipoxygenase-cyclooxygenase inhibitor, MK447 (200 microM), a nonselective lipoxygenase inhibitor which can stimulate cyclooxygenase, and baicalein (1 microM), a highly selective 12-lipoxygenase inhibitor, on angiotensin II-evoked hemodynamic changes in the rat isolated kidney, perfused with oncotic agents. Kidneys were pretreated with indomethacin (10 microM) to exclude participation of cyclooxygenase-dependent arachidonate products. Renal perfusion pressure was kept constant at 90 mm Hg by continuous adjustments in perfusate flow rate. Inhibition of cyclooxygenase alone produced a transient potentiation of the vasoconstrictor response to angiotensin II without altering GFR. On the other hand, the lipoxygenase inhibitors attenuated the angiotensin II-induced increase in renal vascular resistance by approximately 50% and promoted an increase in GFR above that of kidneys infused with angiotensin II in the presence of only indomethacin. Base-line values were essentially unchanged by lipoxygenase inhibition. Furthermore, the vasoconstrictor response to the thromboxane/endoperoxide agonist U46619 was unaffected. We conclude that products of the lipoxygenase pathway, arising within the kidney, contribute to the renal hemodynamic effects of angiotensin II.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

In vivo induction of apoptosis in immature thymocytes by staphylococcal enterotoxin B.

Staphylococcal enterotoxins are potent T cell mitogens. Recent studies have shown that the binding of these toxins to class II MHC molecules on accessory cells is essential for the stimulation of T cells which bear specific V beta segment of TCR. In the present study we show that i.v. administration of staphylococcal enterotoxin B (SEB) results in an enlargement of spleen and lymph nodes but causes thymus atrophy. Elimination of CD4+CD8+ cells predominantly accounted for the shrinkage of thymus, and the lowest level of this cell population was reached 4 days after SEB injection. Furthermore, this decrease in CD4+CD8+ cells was accompanied by a relative increase in the percentages of CD4+CD8-, CD4-CD8+ and CD4-CD8- cells, whereas their absolute numbers actually reduced on day 4. The thymus shrinkage involved apoptosis which was characterized by DNA fragmentation and morphologic changes. The depletion of Thy-1 high, TCR-alpha beta low and TCR-alpha beta intermediate cells also occurred with a kinetic correlated to the reduction of CD4+CD8+ cells. Our results further showed that the percentages of V beta 8+ cells reduced 12 h post SEB injection, increased after 2 days, and decreased again thereafter. SEB thus causes both apoptotic and stimulative effects in the thymus. Apparently, the tremendous loss of double-positive cells (greater than 90% in cell number on day 4) is not simply due to the reduction of V beta 8+ cells, the possible modulatory effect of other factors or hormones which may play a role in the cell death is discussed.

Animals↗
PubMed1992

Adsorption of complement proteins on surfaces with a hydrophobicity gradient.

Activation of the complement system is recognized as one of the major problems with respect to biocompatibility of biomaterials. The binding of C3 (central component of complement) and B (factor B, an activator of C3), and H (factor H, an inhibitor of C3 activation) plays a crucial role in the activation of the alternative pathway of complement on the surfaces of biomaterials during extracorporeal procedures. Here we report on the adsorption of C3, B or H on to the silica surface with a hydrophobicity gradient. The amount of native 125I-C3 bound to both hydrophilic and hydrophobic surfaces was very similar (0.8 and 0.9 micrograms/cm2; 4 x 10(-12) mol/cm2). Neither factor H nor factor B was able to displace already adsorbed 125I-C3 from either of the surfaces. The extent of binding of factors B and H to preadsorbed C3 was a function of the surface hydrophobicity: more 125I-B or 125I-H was bound to C3 adsorbed at the hydrophilic end than at the hydrophobic end of the gradient surface. The binding of 125I-B or 125I-H to preadsorbed C3 appeared to be influenced by the availability of their binding sites on adsorbed C3 molecules rather than by the amount of surface-bound C3. At the hydrophobic end of the gradient surface the molar binding ratio of B/C3 was considerably smaller than the molar binding ratio of H/C3. It can be speculated that the hydrophobicity of the surface determines orientation and/or conformation of adsorbed C3 molecule; when adsorbed at the hydrophobic end of the gradient, C3 molecule predominantly exposes the binding site to which only factor H can bind.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1992

Immunomodulatory activity of various fractions derived from Physalis angulata L extract.

The immunomodulatory effects of Physalis angulata L. extract fraction VII (PA-VII), PA-VII-A, PA-VII-B and PA-VII-C were investigated in this study. The results showed that PA-VII and PA-VII-C strongly enhanced blastogenesis response, PA-VII-B had moderate activity, and PA-VII-A exerted only slight effect on cell proliferation. A synergistic effect was observed when the suboptimal dosage of phytohemagglutinin (PHA) or lipopolysaccharide (LPS) was added to the culture. Furthermore, PA-VII and PA-VII-C possessed stimulatory activity on B cells and less effect on T cells. The antibody responses were also augmented by PA-VII, PA-VII-B and PA-VII-C, but not by PA-VII-A. The enhancement of antibody response could be observed both in BALB/c and C3H/HeJ mice.

Animals↗
PubMed1992

Comparison of umbilical blood gas and acid-base status of small-for-date and normal Chinese newborns.

A prospective study of umbilical arterial blood gas in appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) babies was performed at our hospital from August 1989 to July 1990. A total of of 512 cases were included, 432 cases in the AGA group and 80 cases in the SGA group, with gestational ages ranging from 26 to 42 weeks. Umbilical arterial blood was collected immediately after delivery of the newborns. Comparisons of maternal age, gestational age, birth body weight and body length of infants. Apgar scores at one minute and five minutes, cord arterial blood pH, pO2, pCO2, base excess, bicarbonate, total CO2, O2 saturation and O2 content between the AGA and SGA groups were taken into account. Our results demonstrated significant differences in birth body weight, birth body length, Apgar scores at one minute and five minutes and gestational age in the SGA group compared with those in the AGA group. The parameters of cord arterial blood gas were not correlated with gestational age in either group. The mean pH value in the AGA group (7.30 +/- 0.05) was higher than that in the SGA group (7.28 +/- 0.08). The same trend of difference was also noted between the AGA (7.30 +/- 0.04) and SGA (7.27 +/- 0.07) babies who were delivered by Cesarean section (p < 0.05). The latter results imply a more academic state in SGA babies which is independent of labor. Prepartum asphyxia plays an important role in determining the prognosis of SGA babies. We suggest routine umbilical cord blood gas and acid-base analysis at delivery to assess fetal asphyxia.

Acid-Base Equilibrium↗
PubMed1991

Utilization of methoxylated aromatic compounds by the acetogen Clostridium thermoaceticum: expression and specificity of the co-dependent O-demethylating activity.

The aromatic CO-dependent O-demethylating activity of Clostridium thermoaceticum was evaluated. Secondary aromatic substituent groups (-OH, -CO2H, -CH2OH, and -OCH3) were critical to O demethylation. O-demethylating activities and specificities were similar from cells grown at the expense of different methoxylated aromatic compounds; all O-methyl-grown cells catalyzed the same sequential O demethylation of multi-methoxylated compounds, suggesting that a broad specificity O demethylase was involved in O demethylation. In cell-fractionation studies, CO-dependent O demethylation was catalyzed by membrane-associated components.

Anisoles↗
PubMed1991

Binding of general transcription factor TFIIB to an acidic activating region.

A central issue in eukaryotic transcriptional regulation is the mechanism by which promoter-specific transcription factors (activators) stimulate transcription. Two lines of evidence indicate that the general transcription factor TFIIB is a pivotal component in the mechanism by which an acidic activator functions. First, during assembly of the preinitiation complex TFIIB binding is a rate-limiting step enhanced by an acidic activator. Second, the TFIIB activity in a HeLa cell nuclear extract is specifically retained on a column containing an acidic activating region. But because our previous study monitored only TFIIB activity, it remains possible that the interaction between TFIIB and the acidic activating region is mediated through additional proteins, for example, those designated as adaptors, coactivators or mediators. A complementary clone encoding TFIIB has recently been isolated and shown to encode a polypeptide of relative molecular mass 35,000. Here we report that TFIIB expressed in and purified from Escherichia coli (recombinant TFIIB) binds directly to the potent acidic activating region of the herpes simplex virus-1 VP16 protein.

Base Sequence↗
PubMed1991

Mechanism of action of an acidic transcriptional activator in vitro.

Transcription of a eukaryotic structural gene by RNA polymerase II requires the ordered assembly of general transcription factors on the promoter to form a pre-initiation complex. Here we analyze affinity-purified complexes at various stages of assembly to determine the mechanism of action of an acidic transcriptional activator. We show that the activator can function in the absence of ATP and stimulates transcription by increasing the number of functional preinitiation complexes. The activator effects this increase by recruiting the general transcription factor TFIIB to the promoter. Using protein affinity chromatography we demonstrate a specific interaction between an acidic activating region and TFIIB. Based on these combined results, we propose that TFIIB is a direct target of an acidic activator.

Cell Nucleus↗