Biomedical subjects

C H Lin

Publications and source records attributed to C H Lin.

At least 199 records · Page 11Linked to original sources

PubMed1998

Technetium-99m-HMPAO brain SPECT in neonates with hypoglycemic encephalopathy.

Regional brain injury in three neonates with hypoglycemic encephalopathy are presented using serial 99mTc-hexamethyl propyleneamine oxime (HMPAO) SPECT and, for comparison, MRI. During the acute stage, both 99mTc-HMPAO SPECT and MRI reveal abnormalities in the posterior cerebrum. Technetium-99m-HMPAO SPECT reveals further areas of insult, for example the frontal lobes. The degree of hypoperfusion correlates with the clinical severity of hypoglycemia during the neonatal period and subsequent neurological sequelae. Follow-up with HMPAO SPECT several months after insult demonstrates persistent hypoperfusion in some areas, mainly in the occipital and posterior parietal regions. MRI can depict morphological changes with superior resolution. Because morphological change generally follows slowly after functional change, MRI is less sensitive than HMPAO SPECT in detecting and predicting the extent of hypoglycemic cerebral injury during the acute phase. HMPAO SPECT during the acute stage is a valuable tool for evaluating the extent and severity of brain injury in neonates with hypoglycemic encephalopathy.

Brain↗

PubMed1998

Neurodevelopment of surviving infants at age two years, with a birthweight less than 2000 g and cared for in neonatal intensive care units (NICU)--results from a population based longitudinal study in Taiwan.

All surviving infants from nine neonatal intensive care units (NICU) in a southern city and county of Taiwan were followed up and assessed at 2 y of age if they had a birthweight of less than 2000 g and were born between February 1, 1993 and January 31, 1994. The assessments included: neurological, growth and general health. A comparison group of normal birthweight and full-term infants without congenital anomalies, matched by birth month and sex to the NICU survivors was also studied with respect to the same outcome measures. A developmental delay (either a severe neurological deficit or Mental Development Index < 68 or Psychomotor Development Index < 68) was present in 21 (15.4%) of the cases, compared to 3 (2.5%) of the controls (P < 0.0004). Significant correlates of developmental outcome for the cases were birthweight, gestational age, and maternal education. The very low birthweight (VLBW) children (< 1500 g) in our study cohort had a comparatively higher incidence of severe neurological deficits (and cerebral palsy) than that reported by other similar studies in developed countries. The incidence of abnormal neurodevelopmental outcome remained high in the graduates of NICU at 2 y of age, compared to that in normal controls. The findings have important implications in future health policy making regarding postnatal management of the surviving infants of NICU in developing countries such as Taiwan.

Case-Control Studies↗

PubMed1998

Genetic analysis of interleukin-10 promoter region in patients with systemic lupus erythematosus in Taiwan.

Overproduction of interleukin-10 (IL-10) may play an important role in the development of systemic lupus erythematosus (SLE) or lupus nephritis. There is also a polymorphic dinucleotide repeat in the human IL-10 promoter region (IL-10PR). Our aim was to study whether or not the IL-10PR alleles contributed to the susceptibility to SLE or lupus nephritis. One hundred SLE patients and 103 healthy controls were studied for IL-10PR by PCR and electrophoretic analysis. The distribution of IL-10PR alleles, genotypes and the sum of both alleles (SBA) from different groups or subgroups were analyzed. SLE patients showed no difference in the distribution of IL-10PR alleles, genotypes and SBA, as compared to healthy controls. Lupus nephritis patients (N = 49) also showed no difference in IL-10PR alleles, genotypes and SBA, as compared to SLE patients without nephritis (N = 51). Of 49 lupus nephritis patients, ten developed end-stage renal disease (ESRD) and four of them were found to suffer from rapid progressive renal failure (RPRF). Patients with RPRF presented much smaller SBA than other ESRD patients (p = 0.005). Lupus nephritis patients carrying small SBA (< 18) suffered from a higher prevalence of RPRF than lupus nephritis patients without small SBA (50% V.S. 0%, p < 0.001, relative risk 82). Our data provide the first evidence of a strong association between IL-10PR and severe progression of lupus nephritis in human patients. In the future, a prospective genetic analysis of IL-10PR for patients with lupus nephritis is recommended. It might be helpful for physicians to identify the lupus nephritis subgroup with a high risk of developing RPRF early, because this might lead to a better therapy and prognosis for these patients.

Adult↗

PubMed1998

Lymphoepithelial cyst of the parotid gland--a case report.

The lymphoepithelial cyst has been commonly termed branchial cleft cyst or branchial cyst. Although many theories, including the branchial apparatus theory, thymic duct theory, and inclusion theory, have been put forward, the etiology is still controversial. Parotid lymphoepithelial cysts are rare and could be divided into two groups, AIDS-related and non-AIDS related, by the relationship with HIV infection. A non-AIDS related lymphoepithelial cyst of left parotid gland in an 81-year-old man presenting as a parotid tumor is described. A left partial parotidectomy was carried out to remove the lesion. There was no recurrence after 2 years. Lymphoepithelial cysts of the parotid gland are often misdiagnosed as other benign tumors in spite of detailed preoperative investigations. Thus a pathological proof is needed for precise diagnosis. In addition, we also need to take the possibility of HIV infection into consideration, although Taiwan is not an AIDS epidemic area.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Intradermal injection of tramadol has local anesthetic effect: a comparison with lidocaine.

BACKGROUND: We observed that intravenous retention of tramadol with a pneumatic tourniquet on the arm inflated to 70 mmHg for one minute could effectively reduce the subsequent propofol injection pain. Tramadol is a central-acting analgesic. The local analgesic effect of tramadol on reducing propofol injection pain is not well known. METHODS: To explore this problem we conducted a double-blind study on intradermal injections of tramadol 25 mg, lidocaine 5 mg and normal saline (all in 0.5 ml volume) which were given to each of the 10 healthy volunteers on the forearm at random. Pain on injections and the degree of local analgesia to pinprick, light touch and cold at each injection site were scored on a 0-4 scale at designated intervals. RESULTS: 5% tramadol, similar to 1% lidocaine, rendered loss of sensation to pin prick, light touch and cold for 30 min after intradermal injection as compared with normal saline (p < 0.01). CONCLUSIONS: We concluded that intradermal injection of tramadol or lidocaine can produce local anesthetic effect.

Adult↗

PubMed1997

Evidence for a glutathionyl-enzyme intermediate in the amidase activity of the bifunctional glutathionylspermidine synthetase/amidase from Escherichia coli.

Glutathionylspermidine (Gsp) is a metabolite common to Escherichia coli and protozoal parasites of the Trypanosoma family. Though its role in E. coli is unknown, Gsp is known to be an intermediate in the biosynthesis of N1,N8-bis(glutathionyl)spermidine (trypanothione), a metabolite unique to trypanosomatids that may allow the parasites to overcome oxidative stresses induced by host defense mechanisms. The bifunctional Gsp-synthetase/amidase from E. coli catalyzes both amide bond formation and breakdown between the N1-amine of spermidine [N-(3-aminopropyl)-1,4-diaminobutane] and the glycine carboxylate of glutathione (gamma-Glu-Cys-Gly), with net hydrolysis of ATP [Bollinger et al. (1995) J. Biol. Chem. 270 (23), 14031-14041]. Synthetase and amidase activities reside in separate domains of the protein, and liberation of the amidase domain from the synthetase domain activates the amidase activity as much as 70-fold in kcat/K(m) for a chromogenic substrate gamma-Glu-Ala-Gly-pNA [Kwon et al., (1997) J. Biol. Chem. 272 (4), 2429-2436]. When substrates for the Gsp-synthetase activity are present (GSH, ATP-Mg2+), Gsp-amidase is highly activated (15-fold). We provide kinetic and mutagenesis evidence suggesting that the amidase operates by a nucleophilic attack mechanism involving cysteine as the catalytic nucleophile. Stopped-flow studies on the 25 kDa Gsp-amidase fragment and the 70 kDa full-length Gsp-synthetase/amidase with gamma-Glu-Ala-Gly-ONp demonstrate burst kinetics characteristic of a covalent acyl-enzyme intermediate. Studies using various group-specific protease inhibitors, such as iodoacetamide, suggest an active-site cysteine or histidine as being relevant to amidase activity, and site-directed mutagenesis indicates that Cys-59 is essential for amidase activity.

Acylation↗

PubMed1997

Identification of the transcription start site for the spinach chloroplast serine tRNA gene.

Deleting part of the 3' end of the spinach chloroplast serine tRNA coding region, which destroyed the proper folding of its RNA transcript and resulted in the inhibition of tRNA processing, allowed the detection of a serine tRNA primary transcript. The transcription start site for this primary transcript, synthesized from the internal promoter, was mapped to -12 upstream from the mature tRNA coding region. Transcription analysis with various 5' deletion mutants suggested that the AT-rich region between -31 and -11, immediately upstream of the serine tRNA transcription start site, affects the transcription efficiency, and possibly the selection of transcription start site. Identification of the transcription start site for the spinach chloroplast serine tRNA gene in this study represents the first example of 5' end mapping of a tRNA precursor transcribed from chloroplast tRNA genes containing an internal promoter.

Base Sequence↗

PubMed1997

Insulin receptor substrate-2 (IRS-2) can mediate the action of insulin to stimulate translocation of GLUT4 to the cell surface in rat adipose cells.

Insulin receptor substrates-1 and -2 (IRS-1 and -2) are important substrates of the insulin receptor tyrosine kinase. Previous studies have focused upon the role of IRS-1 in mediating the actions of insulin. In the present study, we demonstrate that IRS-2 can mediate translocation of the insulin responsive glucose transporter GLUT4 in a physiologically relevant target cell for insulin action. Co-immunoprecipitation experiments performed on cell lysates derived from freshly isolated rat adipose cells incubated in the presence or absence of insulin indicated that twice as much phosphatidylinositol 3-kinase was associated with endogenous IRS-1 as with IRS-2 after insulin stimulation. When rat adipose cells in primary culture were transfected with expression vectors for IRS-1 or IRS-2, we observed 40-fold overexpression of human IRS-1 or murine IRS-2. In addition, anti-phosphotyrosine immunoblotting experiments confirmed that the recombinant substrates were phosphorylated in response to insulin stimulation. To examine the role of IRS-2 in insulin-stimulated translocation of GLUT4, we studied the effects of overexpression of IRS-1 and -2 on translocation of a co-transfected epitope-tagged GLUT4 (GLUT4-HA). Overexpression of IRS-1 or IRS-2 in adipose cells resulted in a significant increase in the basal level of cell surface GLUT4 (in the absence of insulin). Interestingly, at maximally effective concentrations of insulin (60 nM), the level of cell surface GLUT4 in cells overexpressing IRS-1 or -2 significantly exceeded the maximal recruitment observed in the control cells (160 and 135% of control, respectively; p < 0.003). Our data directly demonstrate that IRS-2, like IRS-1, is capable of participating in insulin signal transduction pathways leading to the recruitment of GLUT4. Thus, IRS-2 may provide an alternative pathway for critical metabolic actions of insulin.

Adipose Tissue↗

PubMed1997

Design, synthesis, and biochemical evaluation of phosphonate and phosphonamidate analogs of glutathionylspermidine as inhibitors of glutathionylspermidine synthetase/amidase from Escherichia coli.

Three phosphapeptides designed to mimic two distinct tetrahedral intermediates formed during either the synthesis or hydrolysis of glutathionylspermidine (Gsp) were synthesized and evaluated as inhibitors of the bifunctional enzyme Gsp synthetase/amidase. While the polyamine-containing phosphapeptides were determined to be potent and selective inhibitors, they selectively inhibit the synthetase activity over the amidase domain. A phosphonate-containing tetrahedral mimic is a reversible mixed-type inhibitor of Gsp synthetase with an inhibition constant of 6 microM for the inhibitor binding to the free enzyme (Ki) and 14 microM for the inhibitor binding to the enzyme-substrate complex (Ki'). The corresponding phosphonamidate is a slow-binding inhibitor with a Ki of 24 microM and a Ki* (isomerization inhibition constant) of 0.88 microM. A non-polyamine-containing phosphonamidate exhibits no significant inhibition of the synthetase or amidase activity.

Amide Synthases↗

PubMed1997

On roads not taken in the evolution of protein catalysts: antibody steroid isomerases that use an enamine mechanism.

Reactive immunization has emerged as a new tool for the study of biological catalysis. A powerful application resulted in catalytic antibodies that use an enamine mechanism akin to that used by the class I aldolases. With regard to the evolution of enzyme mechanisms, we investigated the utility of an enamine pathway for the allylic rearrangement exemplified by Delta5-3-ketosteroid isomerase (KSI; EC 5.3.3.1). Our aldolase antibodies were found to catalyze the isomerization of both steroid model compounds and steroids. The kinetic and chemical studies showed that the antibodies afforded rate accelerations up to a factor of 10(4) by means of an enamine mechanism in which imine formation was the rate-determining step. In light of our observations and the enzyme studies by other workers, we suggest that an enamine pathway could have been an early, viable KSI mechanism. Although this pathway is amenable to optimization for increased catalytic power, it appears that certain factors precluded its evolution in known KSI enzymes.

Antibodies, Catalytic↗

PubMed1997

Making chemistry selectable by linking it to infectivity.

The link between recognition and replication is fundamental to the operation of the immune system. In recent years, modeling this process in a format of phage-display combinatorial libraries has afforded a powerful tool for obtaining valuable antibodies. However, the ability to readily select and isolate rare catalysts would expand the scope of library technology. A technique in which phage infection controlled the link between recognition and replication was applied to show that chemistry is a selectable process. An antibody that operated by covalent catalysis to form an acyl intermediate restored phage infectivity and allowed selection from a library in which the catalyst constituted 1 in 10(5) members. Three different selection approaches were examined for their convenience and generality. Incorporating these protocols together with well known affinity labels and mechanism-based inactivators should allow the procurement of a wide range of novel catalytic antibodies.

Antibodies, Catalytic↗

PubMed1997

Application of capillary electrophoresis-fluorescence line-narrowing spectroscopy for on-line spectral characterization of closely related analytes.

Capillary electrophoresis (CE) interfaced with low-temperature (4.2 K) fluorescence line-narrowing spectroscopy (FLNS) is used for the separation and spectral characterization of closely related analytes. In this paper, the CE-FLNS system is applied to the analysis of a mixture of deuterated and protonated benzo[a]pyrene, a mixture of structurally similar benzo[a]pyrene and benzo[e]pyrene, and mixtures of dibenzo[a,l]pyrene-derived adenine DNA adducts. The CE-FLNS system provides on-line separation and high-resolution spectroscopic identification of CE-separated analytes, via fingerprint structure of vibrationally resolved FLN spectra at 4.2 K. The combination of the separation power of CE and the spectral selectivity of FLNS provide a methodology that has potential to become a powerful tool for molecular analyte characterization. The main applications of the CE-FLNS system, due to its selectivity, should be in the chemical analysis of structurally similar analytes and applications where analyte purity and detailed structural characterization are required.

Benzopyrenes↗

PubMed1997

Bacterial resistance to vancomycin: overproduction, purification, and characterization of VanC2 from Enterococcus casseliflavus as a D-Ala-D-Ser ligase.

The VanC phenotype for clinical resistance of enterococci to vancomycin is exhibited by Enterococcus gallinarum and Enterococcus casseliflavus. Based on the detection of the cell precursor UDP-N-acetylmuramic acid pentapeptide intermediate terminating in D-Ala-D-Ser instead of D-Ala-D-Ala, it has been predicted that the VanC ligase would be a D-Ala-D-Ser rather than a D-Ala-D-Ala ligase. Overproduction of the E. casseliflavus ATCC 25788 vanC2 gene in Escherichia coli and its purification to homogeneity allowed demonstration of ATP-dependent D-Ala-D-Ser ligase activity. The kcat/Km2 (Km2 = Km for D-Ser or C-terminal D-Ala) ratio for D-Ala-D-Ser/D-Ala-D-Ala dipeptide formation is 270/0.69 for a 400-fold selection against D-Ala in the C-terminal position. VanC2 also has substantial D-Ala-D-Asn ligase activity (kcat/Km2 = 74 mM-1min-1).

Bacterial Proteins↗

PubMed1997

Role of modified glutamic acid in the helical structure of conantokin-T.

Circular dichroism (CD) and 2-dimensional NMR were used to study the solution conformation of conantokin-T (Con-T), a small peptide toxin found in the venom of fish-hunting cone snails, and its Glu-substituted analog. Con-T lacks disulfide bonds but contains many gamma-carboxyglutamic acids (Gla), a post-translationally modified residue. Our results show that Con-T adopts an alpha-helical conformation in aqueous solution even in the absence of calcium. Glu replacements diminish both helicity and function of Con-T. The helical content of Con-T is higher than most natural helical peptides of this length in aqueous solution. The sequence of this small toxin incorporates several known elements that stabilize alpha-helical structure in peptides. Gla residues form several salt bridges that stabilize helical conformation of Con-T.

1-Carboxyglutamic Acid↗

PubMed1997

Transcription and processing of the gene for spinach chloroplast threonine tRNA in a homologous in vitro system.

An in vitro system was established to study the transcription and processing of threonine tRNA using spinach chloroplast enzyme extract. Experiments using a series of 5' deletion mutants demonstrated that the transcription of trnT gene required no 5' upstream promoter elements. Four plasmid DNA templates containing trnT were constructed for tRNA processing assay. The processing reaction was carried out either with exogenously added precursor-tRNAs made by T7 RNA polymerase or with RNAs synthesized by the transcription activity in the same processing enzyme extract. Both assays demonstrated that the 5' and 3' ends of mature tRNA were processed endonucleolytically and the processing of the 5' end preceded the maturation of the 3' end. The activity of nucleotidyl transferase that adds CCA nucleotides to the 3' end of tRNA was also observed. The use of a coupled transcription and processing system provides us with a better insight to the tRNA processing mechanism of the chloroplast.

Base Sequence↗

PubMed1997

Protein-tyrosine phosphatases PTP1B and syp are modulators of insulin-stimulated translocation of GLUT4 in transfected rat adipose cells.

The protein-tyrosine phosphatases PTP1B and Syp have both been implicated as modulators of the mitogenic actions of insulin. However, the roles of these protein-tyrosine phosphatases in the metabolic actions of insulin are not well characterized. In this study, we directly assessed the ability of PTP1B and Syp to modulate insulin-stimulated translocation of the insulin-responsive glucose transporter GLUT4 in a physiologically relevant insulin target cell. Primary cultures of rat adipose cells were transiently transfected with either wild-type PTP1B (PTP1B-WT), wild-type Syp (Syp-WT), or the catalytically inactive mutants PTP1B-C/S or Syp-C/S. The effects of overexpression of these constructs on insulin-stimulated translocation of a co-transfected epitope-tagged GLUT4 were studied. Cells overexpressing either PTP1B-C/S or Syp-WT had insulin dose-response curves similar to those obtained with control cells expressing only epitope-tagged GLUT4. In contrast, for cells overexpressing PTP1B-WT the level of GLUT4 on the cell surface at each insulin dose (ranging from 0 to 60 nM) was significantly lower than that observed in the control cells. Interestingly, cells overexpressing the dominant inhibitory mutant Syp-C/S also had a small but statistically significant impairment in insulin responsiveness. At a maximally stimulating concentration of insulin (60 nM), cell surface epitope-tagged GLUT4 was approximately 20% less than that of the control cells. It is possible that effects from high level overexpression of Syp and PTP1B constructs may not reflect what occurs under physiological conditions. Nevertheless, our data raise the possibility that PTP1B may be a negative regulator of insulin-stimulated glucose transport, while Syp may have a small role as a positive mediator of the metabolic actions of insulin.

Adipocytes↗

PubMed1997

Suppression of myelopoiesis and myeloid leukemia cell line proliferation by a novel bone marrow-derived factor, reptimed.

Bone marrow is the major site of hematopoiesis in the adult mammal. Bone marrow contains a highly organized microenvironment for the support of hematopoietic stem and progenitor cells, including the production of growth factors. Bone marrow cells also produce negative regulatory factors which may regulate hematopoiesis and inflammatory responses. In this paper we describe Reptimed, a unique bone marrow-derived factor with inhibitory activity for myelopoiesis and in vitro growth of myeloid cell lines. Reptimed was partially purified from bone marrow supernatants using a combination of solid-phase extraction and size exclusion chromatography. Reptimed is < 1000 Da MW and is water soluble. Reptimed inhibited growth of granulocyte-macrophage and macrophage colonies as well as proliferation of several myeloid leukemia cell lines. Reptimed may be part of a hemoregulatory circuit.

Animals↗

PubMed1997

Why is CMP-ketodeoxyoctonate highly unstable?

CMP-ketodeoxyoctonate (CMP-KDO) and analogs, including CMP-5-deoxy-5-fluoro-KDO, CMP-5-deoxy-KDO, and CMP-5-epi-KDO, were prepared from CTP and the corresponding KDO sugars catalyzed by CMP-KDO synthetase. These analogs were found to be much more stable than CMP-KDO (t1/2 = 0.57 h) yet less stable than CMP-sialic acid (t1/2 = 151 h). Fluorination at the 5-position of CMP-KDO has a 200-fold enhanced stability compared to the 156-fold enhancement for the 3R-fluoro analog, probably due to the loss of H-bonding interactions (for the 5-F derivative) and the cause of remote inductive effect (for the 3- and the 5-F analogs) on the glycosidic cleavage. Hydrolysis of CMP-KDO is perhaps facilitated by an intramolecular hydrogen bond from the 5-OH group with the phosphate oxygen as demonstrated by the 3-5-fold enhanced stability of CMP-5-epi-KDO and CMP-5-deoxy-KDO compared to CMP-KDO and by molecular modeling studies of water-solvated CMP-KDO. Hydrolysis of CMP-KDO also was found to be subject to a substantial solvent isotope effect (kH/kD = 2.7), which is significantly different from the reported solvent isotope effect for the hydrolysis of sialyglycosides (kH/kD = 0.86) and dependent on both buffer and magnesium ion concentrations. Considering these results and molecular modeling studies, it is proposed that the hydrolysis of CMP-KDO under neutral conditions proceeds through a glycosidic cleavage which occurs at the electronically favorable twist-boat conformation, facilitated by intramolecular H-bonding interaction of the 4-, 5- and 7- (or 8-) OH groups and the phosphate oxygen and by the leaving group magnesium ion complexation.

Buffers↗