Biomedical subjects

M Lin

Publications and source records attributed to M Lin.

At least 55 records · Page 3Linked to original sources

PubMed2000

cDNA cloning and expression of a human aldehyde dehydrogenase (ALDH) active with 9-cis-retinal and identification of a rat ortholog, ALDH12.

This report describes the isolation of a heretofore uncharacterized aldehyde dehydrogenase (ALDH) with retinal dehydrogenase activity from rat kidney and the cloning and expression of a cDNA that encodes its human ortholog, the previously unknown ALDH12. The human ALDH12 cDNA predicts a 487-residue protein with the 23 invariant amino acids, four conserved regions, cofactor binding motif (G(209)XGX(3)G), and active site cysteine residue (Cys(287)) that typify members of the ALDH superfamily. ALDH12 seems at least as efficient (V(m)/K(m)) in converting 9-cis-retinal into the retinoid X receptor ligand 9-cis-retinoic acid as two previously identified ALDHs with 9-cis-retinal dehydrogenase activity, rat retinal dehydrogenase (RALDH) 1 and RALDH2. ALDH12, however, has approximately 40-fold higher activity with 9-cis- retinal than with all-trans-retinal, whereas RALDH1 and RALDH2 have equivalent and approximately 4-fold less efficiencies for 9-cis-retinal versus all-trans-retinal, respectively. Therefore, ALDH12 is the first known ALDH to show a preference for 9-cis-retinal relative to all-trans-retinal. Evidence consistent with the possibility that ALDH12 could function in a pathway of 9-cis-retinoic acid biosynthesis in vivo includes biosynthesis of 9-cis-retinoic acid from 9-cis-retinol in cells co-transfected with cDNAs encoding ALDH12 and the 9-cis-retinol/androgen dehydrogenase, cis-retinoid/androgen dehydrogenase type 1. Intense ALDH12 mRNA expression in adult and fetal liver and kidney, two organs that reportedly have relatively high concentrations of 9-cis-retinol, reinforces this notion.

Aldehyde Dehydrogenase↗

PubMed2000

Functional roles of charged residues in the putative voltage sensor of the HCN2 pacemaker channel.

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels contribute to pacemaking activity in specialized neurons and cardiac myocytes. HCN channels have a structure similar to voltage-gated K(+) channels but have a much larger putative S4 transmembrane domain and open in response to membrane hyperpolarization instead of depolarization. As an initial attempt to define the structural basis of HCN channel gating, we have characterized the functional roles of the charged residues in the S2, S3, and S4 transmembrane domains. The nine basic residues and a single Ser in S4 were mutated individually to Gln, and the function of mutant channels was analyzed in Xenopus oocytes using two-microelectrode voltage clamp techniques. Surface membrane expression of hemagglutinin-epitope-tagged channel proteins was examined by chemiluminescence. Our results suggest that 1) Lys-291, Arg-294, Arg-297, and Arg-300 contribute to the voltage dependence of gating but not to channel folding or trafficking to the surface membrane; 2) Lys-303 and Ser-306 are essential for gating, but not for channel folding/trafficking; 3) Arg-312 is important for folding but not gating; and 4) Arg-309, Arg-315, and Arg-318 are crucial for normal protein folding/trafficking and may charge-pair with Asp residues located in the S2 and S3 domains.

Amino Acid Sequence↗

PubMed2000

A structural basis for drug-induced long QT syndrome.

Mutations in the HERG K(+) channel gene cause inherited long QT syndrome (LQT), a disorder of cardiac repolarization that predisposes affected individuals to lethal arrhythmias [Curran, M. E. , Splawski, I., Timothy, K. W., Vincent, G. M., Green, E. D. & Keating, M. T. (1995) Cell 80, 795-804]. Acquired LQT is far more common and is most often caused by block of cardiac HERG K(+) channels by commonly used medications [Roden, D. M., Lazzara, R., Rosen, M., Schwartz, P. J., Towbin, J. & Vincent, G. M. (1996) Circulation 94, 1996-2012]. It is unclear why so many structurally diverse compounds block HERG channels, but this undesirable side effect now is recognized as a major hurdle in the development of new and safe drugs. Here we use alanine-scanning mutagenesis to determine the structural basis for high-affinity drug block of HERG channels by MK-499, a methanesulfonanilide antiarrhythmic drug. The binding site, corroborated with homology modeling, is comprised of amino acids located on the S6 transmembrane domain (G648, Y652, and F656) and pore helix (T623 and V625) of the HERG channel subunit that face the cavity of the channel. Other compounds that are structurally unrelated to MK-499, but cause LQT, also were studied. The antihistamine terfenadine and a gastrointestinal prokinetic drug, cisapride, interact with Y652 and F656, but not with V625. The aromatic residues of the S6 domain that interact with these drugs (Y652 and F656) are unique to eag/erg K(+) channels. Other voltage-gated K(+) (Kv) channels have Ile and Val (Ile) in the equivalent positions. These findings suggest a possible structural explanation for how so many commonly used medications block HERG but not other Kv channels and should facilitate the rational design of drugs devoid of HERG channel binding activity.

Amino Acid Sequence↗

PubMed2000

Cholesteryl ester transfer protein and phospholipid transfer protein have nonoverlapping functions in vivo.

Plasma phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein (CETP) are homologous molecules that mediate neutral lipid and phospholipid exchange between plasma lipoproteins. Biochemical experiments suggest that only CETP can transfer neutral lipids but that there could be overlap in the ability of PLTP and CETP to transfer or exchange phospholipids. Recently developed PLTP gene knock-out (PLTP0) mice have complete deficiency of plasma phospholipid transfer activity and markedly reduced high density lipoprotein (HDL) levels. To see whether CETP can compensate for PLTP deficiency in vivo, we bred the CETP transgene (CETPTg) into the PLTP0 background. Using an in vivo assay to measure the transfer of [(3)H]PC from VLDL into HDL or an in vitro assay that determined [(3)H]PC transfer from vesicles into HDL, we could detect no phospholipid transfer activity in either PLTP0 or CETPTg/PLTP0 mice. On a chow diet, HDL-PL, HDL-CE, and HDL-apolipoprotein AI in CETPTg/PLTP0 mice were significantly lower than in PLTP0 mice (45 +/- 7 versus 79 +/- 9 mg/dl; 9 +/- 2 versus 16 +/- 5 mg/dl; and 51 +/- 6 versus 100 +/- 9, arbitrary units, respectively). Similar results were obtained on a high fat, high cholesterol diet. These results indicate 1) that there is no redundancy in function of PLTP and CETP in vivo and 2) that the combination of the CETP transgene with PLTP deficiency results in an additive lowering of HDL levels, suggesting that the phenotype of a human PLTP deficiency state would include reduced HDL levels.

Animals↗

PubMed2000

Human histo-blood group ABO glycosyltransferase genes: different enhancer structures with different transcriptional activities.

The enhancer element of the human histo-blood group ABO glycosyltransferase gene has been demonstrated to be located -3.7 kb upstream from the transcription start site and to be composed of four tandem repeats of a 43-bp unit. Recently we identified three different enhancer structures among the allelic A, B, and O glycosyltransferase genes. The enhancer structure with four 43-bp units is present in the B and O genes, but not in the A gene. The corresponding enhancer region of the A gene contains only one 43-bp unit, and within this unit a nucleotide substitution exists when compared with the consensus sequence. Through transient transfection assays, the transcriptional activity of the A-gene enhancer region was demonstrated to be less than 1% of that of the B-gene enhancer. The difference between the transcriptional activities of the two enhancers became more significant when acting in concert with the ABO-gene's native promoter. The different repeat numbers of the 43-bp unit possessed by the two allelic genes were shown to be the main reason for the vast difference in the transcriptional activities between the A-gene and B-gene enhancers.

ABO Blood-Group System↗

PubMed2000

Expression of human prostatic acid phosphatase gene is regulated by upstream negative and positive elements.

Human prostatic acid phosphatase (PAcP) is a prostate epithelium-specific differentiation antigen. To understand the regulation of expression of the PAcP gene, we studied the cis-regulatory elements of its promoter. A DNA fragment from -2899 to +87 base pairs (bp) of PAcP gene was fused to the chloramphenicol acetyltransferase (CAT) reporter gene and introduced into PC-3 and LNCaP human prostate cancer cells. The expression of the CAT gene driven by the PAcP promoter was assessed in transient expression assays. Sequential 5' deletions of the promoter were constructed and analyzed to reveal the positive and the negative regulatory elements that are involved in regulating the transcription of the PAcP gene. Our data showed that the proximal sequence -1305/+87 bp directs a high level of the CAT activity in both cell lines. Deletion of the region from -1305 to -779 resulted in approximately a 10- and three-fold decrease of the PAcP promoter activity in PC-3 and LNCaP cells, respectively. Interestingly, an inverse correlation of the CAT activity with the cell growth was observed when the reporter gene was driven by the -1305/+87 fragment, but not by the -779/+87 fragment. Two regions of transcriptional suppression were identified and located in positions from -2899 to -2583, and from -2583 to -1305 bp. Furthermore, the activity of the core promoter region from -779 to +87 bp can be activated by a SV-40 enhancer. The results, thus, clearly demonstrate the presence of positive and negative cis-elements in the promoter region of the PAcP gene.

Acid Phosphatase↗

PubMed2000

Obstructive sleep apnea syndrome in obese Singapore children.

We set out to determine the prevalence of obstructive sleep apnea syndrome (OSAS) among obese Singapore school children and identify risk factors for OSAS. This study was designed as a prospective study in three phases. Parents completed a questionnaire with regards to sleep and daytime symptoms in Phase 1. Children suspected to have OSAS based on the questionnaire and all with a percent ideal body weight (IBW) >/=180 were called for clinic visits in Phase 2. All whose percent IBW >/=180 and those in whom the physicians strongly suspected OSAS were subjected to a polysomnogram in phase 3. The children were recruited from the School Health Nutritional Clinic for obese children. The investigations were carried out at Tan Tock Seng Hospital. In all, 3,671 children were screened with the questionnaire. Of these, 146 were selected to undergo polysomnography. Twenty-six had abnormal sleep studies with apnea/hypoxia indices (AHIs) >5/hr. The significant clinical feature which correlated with OSAS was sleep sitting up (P = 0.005). The risk is higher in morbidly obese (IBW >/=180), with a prevalence of 13.3% (8/60), than in less obese children (IBW <180). One in eight (12.5%) of these children was asymptomatic and would have been missed based on the questionnaire. Presence of adenotonsillar hypertrophy led to increased risk of OSAS. The prevalence of OSAS was 0.7% (26/3,671) among the obese schoolchildren in Singapore, which is similar to the prevalence reported by others. Using discriminant analysis, the estimated prevalence increased to 5.7%. In the morbidly obese (IBW >/=180), the prevalence rate is higher at 13.3%.

Adenoids↗

PubMed2000

Fluorescence polarization immunoassay: detection of antibody to Brucella abortus.

Fluorescence polarization immunoassay (FPA) is a homogeneous immunoassay useful for rapid and accurate detection of antibody or antigen. The principle of the assay is that a fluorescent dye (attached to an antigen or an antibody fragment) can be excited by plane-polarized light at the appropriate wavelength. As a rule, a small molecule rotates faster when in solution than a larger molecule. The rotation rate may be assessed by measuring light intensity in the vertical and horizontal planes. Generally, the time it takes a molecule to rotate through a given angle is an indication of its size. When a small molecule that rotates rapidly is bound to a larger molecule, the rotation rate is decreased and this decrease is measured. Because it is a primary antigen-antibody interaction, the rate of reaction is very rapid and usually a result may be obtained in minutes. This technology was applied to the detection of antibody to Brucella abortus in serum and milk, providing for the first time a rapid primary binding assay that is cost effective for use in the field.

Animals↗

PubMed2000

The role of neutrophil activation in pathogenesis of preeclampsia.

To investigate the effect of neutrophil activation on pathogenesis of pre-eclampsia, neutrophil activation was examined by using flow cytometry to assess the CD11b expression and the levels of plasma endothelin-1 (ET-1) and serum NO2- were also measured by using non-equilibrium radioimmunoassay and by Griess assay in 29 pregnant women with pre-eclampsia and 31 normal pregnant women at third trimester. The expression of neutrophil CD11b was significantly elevated in women with pre-eclampsia as compared with that of normal pregnant women at third trimester. The mean fluorescence index of CD11b was 438.38 +/- 179.91 and 326.97 +/- 170.14 respectively (P < 0.05). The plasma ET-1 level and serum NO2- concentration in pre-eclampsic women (63.69 +/- 48.33 pg/ml and 20.03 +/- 4.77 mumol/L, respectively) were both significantly increased as compared with those in the normal pregnancy women (29.98 +/- 20.25 pg/ml and 15.47 +/- 5.47 mumol/L, respectively, P < 0.01). The neutrophil CD11b expression was significantly elevated in pre-eclampsia. The increased neutrophil activation may cause the damage of vascular endothelium and result in NO release compensatory increase in endothelial cells, suggesting that the neutrophil activation may play a key role in pathogenesis of pre-eclampsia.

Adult↗

PubMed2000

Stilbene dimers from the lianas of Gnetum hainanense.

Five stilbene dimers, gnetuhainins F-J, were isolated together with gnetulin, rhapontigenin, isorhapontigenin and gnetol from the lianas of Gnetum hainanense C. Y. Cheng. Their structures and stereochemistry have been established on the basis of spectral evidence, especially 2D NMR spectroscopic techniques.

Molecular Structure↗

PubMed2000

Sleep apnea treatment improves seizure control in children with neurodevelopmental disorders.

Seizure disorder and sleep apnea are common chronic disorders in children, but the relationship between sleep apnea and seizure control has not been studied in the pediatric population. This retrospective review included nine children with neurodevelopmental disorders who had well-documented sleep apneic episodes and seizure disorders. Seizure frequency was reduced in five patients (56%) in the first 12 months after sleep apnea treatment without changes in their antiepileptic medications. Sleep apnea can be one of the seizure precipitants in children with epilepsy. This study indicates the importance of identifying sleep apnea when treating children with intractable epilepsy, particularly in those who are at high risk.

Anticonvulsants↗

PubMed2000

Five new stilbene dimers from the lianas of Gnetum hainanense.

Five new stilbene dimers, gnetuhainins A-E (1-5), were isolated together with resveratrol trans-dehydrodimer (6), resveratrol, oxyresveratrol, and (-)-epsilon-viniferin from the lianas of Gnetum hainanense. Their structures and stereochemistry were determined on the basis of their chemical and spectral data. Compounds 1-5 are dimers formed by a resveratrol unit and an oxyresveratrol unit and belong to a new type of oligostilbenes polymerized from two different stilbene units.

Dimerization↗

PubMed2000

Heterogeneity of Taiwan's indigenous population: possible relation to prehistoric Mongoloid dispersals.

Taiwan's 9 indigenous tribes (Tsou, Bunun, Paiwan, Rukai, Atayal, Saisiat, Ami, Puyuma, Yami) are highly homogeneous within each tribe, but diversified among the different tribes due to long-term isolation, most probably since Taiwan became an island about 12,000 years ago. Homogeneity of each tribe is evidenced by many HLA-A,B,C alleles having the world's highest ever reported frequencies, e.g. A24 (86.3%), A26 (18.8%), Cw10 (36.8%), Cw7 (66%), Cw8 (32.1%), B13 (27.9%), B62 (37.4%), B75 (18%), B39 (53.5%), B60 (33.3%), and B48 (24%). Also, all of these tribes have HLA class I haplotype frequencies greater than 10%, with A24-Cw7-B39 in Saisiat (44.5%) being the highest, suggesting Taiwan's indigenous tribes are probably the most homogeneous ( the "purest") population in the world. A24-Cw8-B48, A24-Cw10-B60 and A24-Cw9-B61 found common to many Taiwan indigenous tribes, have also been observed in Maori, Papua New Guinea Highlanders, Orochons, Mongolians, Inuit, Japanese, Man, Buryat, Yakut, Tlingit, Tibetans and Thais. These findings suggest Taiwan's indigenous groups are more or less genetically related to both northern and southern Asians. Principal component analysis and the phylogenetic tree (using the neighbor-joining method) showed close relationship between the indigenous groups and Oceanians. This relationship supports the hypothesis that Taiwan was probably on the route of prehistoric Mongoloid dispersals that most likely took place along the coastal lowland of the Asian continent (which is under the sea today). Cultural anthropology also suggests a relationship between Taiwan's indigenous tribes and southern Asians and to a lesser extent, northern Asians. However, the indigenous groups show little genetic relationship to current southern and northern Han Chinese.

Alleles↗

PubMed2000

Spermiogenesis and spermiation in a monotreme mammal, the platypus, Ornithorhynchus anatinus.

Spermatogenesis in the platypus (Ornithorhynchus anatinus) is of considerable biological interest as the structure of its gametes more closely resemble that of reptiles and birds than marsupial or eutherian mammals. The ultrastructure of 16 steps of spermatid development is described and provides a basis for determining the kinetics of spermatogenesis. Steps 1-3 correspond to the Golgi phase of spermatid development, steps 4-8 correspond to the cap phase, steps 9-12 are the acrosomal phase, and steps 13-16 are the maturation phase. Acrosomal development follows the reptilian model and no acrosomal granule is formed. Most other features of spermiogenesis are similar to processes in reptiles and birds. However, some are unique to mammals. For example, a thin, lateral margin of the acrosome of platypus sperm expands over the nucleus as in other mammals, and more than in reptiles and birds. Also, a tubulobulbar complex develops around the spermatid head, a feature which appears to be unique to mammals. Further, during spermiation the residual body is released from the caudal end of the nucleus of platypus sperm leaving a cytoplasmic droplet located at the proximal end of the middle piece as in marsupial and eutherian mammals. Other features of spermiogenesis in platypus appear to be unique to monotremes. For example, nuclear condensation involves the formation of a layer of chromatin granules under the nucleolemma, and development of the fibrous sheath of the principal piece starts much later in the platypus than in birds or eutherian mammals.

Animals↗

PubMed2000

Effects of parenteral infusion with medium-chain triglycerides and safflower oil emulsions on hepatic lipids, plasma amino acids and inflammatory mediators in septic rats.

This study was designed to investigate the effects of preinfusion with total parenteral nutrition (TPN) using medium-chain triglycerides (MCT) versus safflower oil (SO) emulsion as fat sources on hepatic lipids, plasma amino acid profiles, and inflammatory-related mediators in septic rats. Normal rats, with internal jugular catheters, were divided into two groups and received TPN. TPN provided 300kcal/kg/day with 40% of the non-protein energy provided as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fat emulsion, which was made of SO or a mixture of MCT and soybean oil (9:1) (MO). After receiving TPN for 6 days, each group of rats was further divided into control and sepsis subgroups. Sepsis was induced by cecal ligation and puncture, whereas control rats received sham operation. All rats were classified into four groups as follows: MCT control group (MOC, n= 8), MCT sepsis group (MOS, n= 8), safflower oil control group (SOC, n= 8), and safflower oil sepsis group (SOS, n= 11). The results of the study demonstrated that the MOS group had lower hepatic lipids than did the SOS group. Plasma leucine and isoleucine levels were significantly lower in the SOS than in the SOC group, but no differences in these two amino acids were observed between the MOC and MOS groups. Plasma arginine levels were significantly lower in septic groups than in those without sepsis despite whether MCT or safflower oil was infused. Plasma glutamine and alanine levels, however, did not differ between septic and non-septic groups either in the SO or MO groups. No differences in interleukin-1b, interleukin-6, tumor necrosis factor-alpha, and leukotriene B(4)concentrations in peritoneal lavage fluid were observed between the two septic groups. These results suggest that catabolic reaction is septic rats preinfused MCT is not as obvious as those preinfused safflower oil. Compared with safflower oil, TPN with MCT administration has better effects on reducing sepsis-induced liver fat deposition. Preinfusion with MCT before sepsis, however, had no effect on inflammatory-related cytokines or leukotriene in peritoneal lavage fluid. In addition, plasma arginine appears to be a more sensitive indicator than glutamine for septic insult.

Amino Acids↗

PubMed2000

A new stilbene dimer--shegansu B from Belamcanda chinensis.

A new dimeric stilbene, named shegansu B (1) was isolated from the ethanolic extract of the roots of Belamtantida chinensis (L.) DC., along with the known compounds isorhapontigenin, resveratol, p-hydroxybenzoic acid, iridin, tectoridin, tectorigenin and daucosterol. The structures were elucidated by means of spectroscopic evidence including 2D-NMR studies.

Chromatography↗

PubMed2000

Smoking among ethnic Chinese patients and their recall of quit advice by Chinese-speaking general practitioners in Sydney.

OBJECTIVES: To collect smoking-related data from Chinese patients attending Chinese-speaking general practitioners (CSGPs), including self-reported smoking status, recall of a question about smoking status during the previous six months by their GP and, for smokers, their recall of quit advice in their most recent consultation. DESIGN: Descriptive research first involving self-administered waiting-room questionnaires and, afterwards, a second self-administered questionnaire to examine behaviour in that most recent consultation. SETTING: Surgeries of 24 CSGPs in Central Sydney. SUBJECTS: 1084 Chinese patients aged 18-70 years. RESULTS: Self-reported smoking prevalence was 25% (95% CI: 21%-29%) for men and 4% (95% CI: 2%-5%) for women. Of 103 smokers who had visited their regular GP during the previous 6 months, 42% recalled a question about smoking status and 38% quit advice. As elicited at follow-up, 72% recalled any discussion in their most recent consultation about smoking although effective techniques were rarely recalled. Patient's sex (OR: 1.78; 95% CI: 1.28-2.47) and smoking status (OR: 1.39; 2.38; 95% CI: 0.85-2.25, 1.49-3.81) independently predicted a question about smoking status. Among smokers, marital status was the only independent predictor of quit advice. As assessed by a stage-of-change scale, significantly more Chinese smokers were not ready to contemplate cessation, compared with Angio-Celtic community survey results. CONCLUSIONS: Our study provides unique information about smoking among ethnic Chinese patients attending CSGPs. Findings also suggest CSGPs need greater support to maximize their clinical opportunities to advise Chinese smokers to quit.

Adult↗

PubMed2000

Patients' perceptions of physicians' recommendations for comfort care differ by patient age and gender.

OBJECTIVE: To determine patient characteristics associated with patient and proxy perceptions of physicians' recommendations for life-prolonging care versus comfort care, and with acceptance of such recommendations. DESIGN: Cross-sectional. SETTING: Five teaching hospitals in Denver, Colo. PATIENTS: We studied 239 hospitalized adults believed by physicians to have a high likelihood of dying within 6 months. MEASUREMENTS AND MAIN RESULTS: Interviews with patients or proxies were conducted to determine perceptions of physicians' recommended goal of care and roles in decision making. RESULTS: Patients' mean age was 66.6 years; 44% were women. In adjusted analysis, age greater than 70 years and female gender were associated with a higher likelihood of believing that comfort care had been recommended by the physician (odds ratio [OR], 3.70; 95% confidence interval [CI], 1.89 to 7.24; OR, 1.99; 95% CI, 1.04 to 3. 84, respectively). Patients and proxies gave substantial decision-making authority to physicians: 29% responded that physicians dominate decision making, 55% that decision making is equally shared by physicians and patients, and only 16% that patients make decisions. Increasing age was associated with an increased likelihood of believing that physicians should dominate decision making (P <.005). CONCLUSIONS: Among patients with advanced illness, perceived comfort care recommendations were related to patient age and gender, raising concern about possible gender and age bias in physicians' recommendations. Although all patients and proxies gave significant decision-making authority to physicians, older individuals were more likely to give physicians decision-making authority, making them more vulnerable to possible physician bias.

Age Factors↗