Biomedical subjects

H Tan

Publications and source records attributed to H Tan.

At least 109 records · Page 6Linked to original sources

PubMed1996

Electrically Conductive Crust in Southern Tibet from INDEPTH Magnetotelluric Surveying

The crust north of the Himalaya is generally electrically conductive below depths of 10 to 20 km. This conductive zone approaches the surface beneath the Kangmar dome (dipping north) and extends beneath the Zangbo suture. A profile crossing the northern Yadong-Gulu rift shows that the high conductivity region extends outside the rift, and its top within the rift coincides with a bright spot horizon imaged on the INDEPTH CMP (common midpoint) profiles. The high conductivity of the middle crust is atypical of stable continental regions and suggests that there is a regionally interconnected fluid phase in the crust of the region.

Journal Article↗

PubMed1996

SpHbox7, a new Abd-B class homeobox gene from the sea urchin Strongylocentrotus purpuratus: insights into the evolution of hox gene expression and function.

Hox genes, by virtue of their key functions in axial patterning, have long been thought to be pivotal players in the evolution of developmental mechanisms. Despite their potential importance in evolution, there is little information about Hox genes in animal groups that are most closely related to ancestral Chordates. Accordingly, we have taken the step of analyzing Hox gene expression and function in the sea urchin embryo, whose simple bilateral body plan is thought to resemble that of a stem organism in the Chordate lineage. Here we describe the isolation, sequences analysis and spatiotemporal expression pattern of a sea urchin (Strongylocentrotus purpuratus) Abd-B-like gene, designated SpHbox7. We show that this gene is one of at least two Abd-B-like genes in the S. purpuratus genome, a result that argues against the simple hypothesis that Hox gene duplications occurred only during the evolution of the chordates. SpHbox7 transcripts are first detectable in midblastula stage embryos, increase in amount during gastrulation, decline slightly by the pluteus stage, and are not detectable in any tissue of the adult. Whole mount in situ hybridization and antibody staining with an SpHbox7-specific antibody reveal that both SpHbox7 mRNA and protein are present throughout the embryo in the blastula. Subsequently, they are localized in the invaginating archenteron, secondary mesenchyme, and oral ectoderm. By the pluteus larva stage, SpHbox7 protein and mRNA are present in the gut, larval arms, and portions of the oral ectoderm. This complex and dynamic expression pattern suggests that SpHbox7 has a role in the patterning of the gut, the mesoderm, and the oral surface.

Aging↗

PubMed1996

Sequence of interleukin-2 isolated from human placental poly A+ RNA: possible role in maintenance of fetal allograft.

There are several cell types within the placenta that produce cytokines which can contribute to the regulatory mechanisms that ensure normal pregnancy. The immunological milieu at the maternofetal interface is considered to be crucial for survival of the fetus. Interleukin-2 (IL-2) is expressed by the syncytiotrophoblast, the cell layer between the mother and the fetus. IL-2 appears to be a key factor in maintenance of pregnancy. Therefore, it was important to determine the sequence of human placental interleukin-2. Direct sequencing of human placental IL-2 cDNA was determined for the coding region. Subclone sequencing was carried out for the 5'- and 3'-untranslated regions (5'-UTR and 3'-UTR). The 5'-UTR for human placental IL-2 cDNA is 294 bp, which is 247 nucleotides longer than that reported for cDNA IL-2 derived from T cells. The sequence of the coding region is identical to that reported for T cell IL-2, while sequence analysis of the polymerase chain reaction (PCR) product showed that the cDNA from the 3' end was the same as that reported for cDNA from T cells. Human placental IL-2 cDNA is 1,028 base pairs (excluding the poly A tail), which is 247 bp longer at the 5' end than that reported for IL-2 T cell cDNA. Therefore, the extended 5'-UTR of the placental IL-2 cDNA may be a consequence of alternative promoter utilization in the placenta.

Amino Acid Sequence↗

PubMed1996

[The clinical value of fetal congenital heart disease diagnosed by color Doppler echocardiography].

OBJECTIVE: To investigate the clinical value of color Doppler echocardiography for the diagnosis of fetal congenital heart disease (CHD). METHODS: 368 cases of high risk fetuses of CHD, aged from 20-40 gestational weeks, were examined by color Doppler echocardiography with Acuson 128 x P/10 color Doppler flow imaging system. The prenatal echocardiographic diagnosis were confirmed by fetal autopsy and echocardiographic examine after birth as well as follow-up. RESULTS: 11 cases of fetal CHD were detected by prenatal echocardiography, of those, 5 cases of CHD were confirmed by fetal autopsy after induction of labor and 5 cases of CHD were confirmed by color Doppler echocardiography after birth, 1 case of false-positive and 1 case of false-negative. CONCLUSIONS: The study suggests that four-chamber view is an important view for detecting fetal CHD by echocardiography, but multiple views are necessary for diagnosis of fetal complex CHD. Color Doppler echocardiography lists as the first choice for prenatal diagnosis of fetal CHD.

Adult↗

PubMed1996

[Hemoglobin A1c in diabetes related to pregnancy induced hypertension].

OBJECTIVE: To test the hypothesis that the poor control of diabetes during pregnancy is correlated with a high rate of pregnancy induced hypertension (PIH). METHODS: A retrospective analysis on 146 pregnant women with diabetes mellitus of White's class B to RF (gestational diabetes was excluded) diagnosed before pregnancy was carried out in Yale-New Haven hospital, U.S.A. RESULTS: 36.3% of the diabetic women developed PIH. Hemoglobin A1c (HbA1c) levels were higher than normal in 63.7% (93 cases) of the patients during their initial prenatal visits. In the group with HbA1c score > or = 6 and White's Class D-RF, more cases developed PIH than that in groups with HbA1c score < 6 and White's Class B and C (P < 0.01, P < 0.05). CONCLUSION: Diabetic women with high HbA1c score or advanced White's Class during pregnancy were at increased risk for PIH. Good control of blood glucose level throughout pregnancy may reduce the risk of PIH in diabetic women.

Female↗

PubMed1996

[Studies on distribution patterns of modulator CGRP in different motoneuron pools in rats].

Using retrograde labelling combined with calcitonin gene-related peptide (CGRP) immunocytochemistry technique, distribution patterns of the content of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) were studied in two different motoneuron (Mn) pools supplying soleus (SOL, slow-twitch muscle) and extensor digitorium longus (EDL, fast-twitch muscle) of hindlimbs in rats during development. The Mn pools were identified with a novel retrograde tracer, choleragen B subunit (CB) coupled with colloidal gold (CB-Au, 5 nm particle, prepared by ourselves), which was injected into EDL or SOL. After the silver intensification for visualizing colloidal gold particles, CGRP immunocytochemistry were processed. The CB-Au retrogradely identified Mns in each Mn pool were counted and CGRP-LI intensity of Mns was evaluated as strong, moderate, weak and negative. The double labelling revealed different distribution patterns of CGRP-LI content between SOL and EDL Mn pools during development. Comparing the level of CGRP expression between the two Mn pools, SOL Mn pool had a higher ratio of neurons lacking CGRP-LI/weak CGRP LI and a lower proportion of strongly CGRP-LI labelled ones. These results suggest that the difference in content of CGRP-LI in Mns is related to the type of muscular motor activity.

Animals↗

PubMed1995

Levels and alternative splicing of amyloid beta protein precursor (APP) transcripts in brains of APP transgenic mice and humans with Alzheimer's disease.

Abnormal expression of human amyloid precursor protein (hAPP) gene products may play a critical role in Alzheimer's disease (AD). Recently, a transgenic model was established in which platelet-derived growth factor (PDGF) promoter-driven neuronal expression of an alternatively spliced hAPP minigene resulted in prominent AD-type neuropathology (Games, D., Adams, D., Alessandrini, R., Barbour, R., Berthelette, P., Blackwell, C., Carr, T., Clemens, J., Donaldson, T., Gillespie, F., Guido, T., Hagopian, S., Johnson-Wood, K., Khan, K., Lee, M., Leibowitz, P., Lieberburg, I., Little, S., Masliah, E., McConlogue, L., Montoya-Zavala, M., Mucke, L., Paganini, L., and Penniman, E. (1995) Nature 373, 523-527). Here we compared the levels and alternative splicing of APP transcripts in brain tissue of hAPP transgenic and nontransgenic mice and of humans with and without AD. PDGF-hAPP mice showed severalfold higher levels of total APP mRNA than did nontransgenic mice or humans, whereas their endogenous mouse APP mRNA levels were decreased. This resulted in a high ratio of mRNAs encoding mutated hAPP versus wild-type mouse APP. Modifications of hAPP introns 6, 7, and 8 in the PDGF-hAPP construct resulted in a prominent change in alternative splice site selection with transcripts encoding hAPP770 or hAPP751 being expressed at substantially higher levels than hAPP695 mRNA. Frontal cortex of humans with AD showed a subtle increase in the relative abundance of hAPP751 mRNA compared with normal controls. These data identify specific intron sequences that may contribute to the normal neuronspecific alternative splicing of APP pre-mRNA in vivo and support a causal role of hAPP gene products in the development of AD-type brain alterations.

Aged↗

PubMed1995

Differential expression of a lipid transfer protein gene in cotton fiber.

A full-length cDNA clone, GH3, has been isolated from a cotton fiber cDNA library using a differential screening method. The nucleotide and derived amino acid sequence data show that GH3 encodes a lipid transfer protein (LTP) of 120 amino acids. The presence of a transmembrane signal peptide at the N-terminal of the protein would suggest its possible outer cellular location in fiber cells. Northern analysis indicates that the GH3 gene is developmentally regulated.

Amino Acid Sequence↗

PubMed1995

The effects of calcium channel blockers, verapamil, nifedipine and diltiazem, on metabolic control in diabetic rats.

The effects of calcium channel blockers (CCB)-verapamil, nifedipine, diltiazem on metabolic control in streptozotocin-induced long-term diabetes in rats were investigated. Diabetes mellitus was induced by single intravenous injection of streptozotocin (65 mg/kg body wt.). The animals were divided into five groups: a healthy control group, a diabetic group and three diabetic groups treated with one of the calcium channel blockers (verapamil, 25 mg/kg/day, nifedipine, 20 mg/kg/day, and diltiazem, 30 mg/kg/day, respectively). Body weight, glycemia, glycated hemoglobin and total serum protein levels of these animals were measured at the beginning and at the end (after 13 weeks) of the experiment. It was observed that diabetic animals who were not treated with CCB had lost weight at the end of the experiment (P < 0.01). The blood glucose and glycated hemoglobin levels were increased in the diabetic group in comparison to the healthy control group (P < 0.001). However, the calcium channel blockers seem to have beneficial effects on body weight, glycated hemoglobin and blood glucose levels.

Animals↗

PubMed1995

Depressed expression of the inducible form of HSP 70 (HSP 72) in brain and heart after in vivo heat shock.

The heat shock gene expression plays a role in the protection of cells from injury. In the present study, we have analyzed the expression of heat shock protein (HSP) 72 (the major inducible form of the HSP 70 family) in different rat organs after a total body hyperthermia. The content of HSP 72 was greatest in liver and colon. In contrast, accumulation of HSP 72 was low in heart and brain (3-5% and < 1% of the amount in liver, respectively). This low expression of HSP 72 in heart and brain could not be explained by a difference in the actual temperature within these organs. Analysis of cells in culture that resemble hepatocytes, myoblast, and neurons showed a pattern of HSP 72 expression similar to that observed in liver, heart, and brain in vivo after heat shock. These results suggest that this disparate expression of HSP 72 is due to intrinsic characteristics of the cell types rather than to physiological or environmental conditions. The differential expression of HSP 72 among different cell lines could be correlated with the different levels of protein synthesis protection.

Adaptation, Physiological↗

PubMed1995

Negative symptoms at discharge and outcome in schizophrenia.

BACKGROUND: The clinical significance in schizophrenia of positive and negative symptoms at discharge was assessed. METHOD: Of schizophrenic patients fulfilling DSM-III criteria, 113 were recruited for this study. Personal, social and psychopathological data were collected and all cases were followed up at one and two years after discharge. RESULTS: The presence of positive symptoms (64 cases), without concomitant negative symptoms, did not predict the follow-up social function and positive symptom score. Conversely, the presence of negative symptoms (31 cases) predicted worse social functioning (P < 0.05 to P < 0.005) and higher positive symptom scores (P < 0.01) at follow-up using MANOVA: Eighteen cases (15.9%) had neither positive nor negative symptoms and had the best clinical outcome. CONCLUSIONS: Negative, but not positive, symptoms assessed at discharge are an important predictor of poor outcome. In addition, negative symptoms may themselves expose a biological vulnerability to the presence of positive symptoms.

Adult↗

PubMed1995

[Induced expression of whiG, a gene crucial for sporulation of Streptomyces coelicolor].

whiG gene has been subcloned into Streptomyces expression vector pAK203 containing inducible promoter tipA. The expression of whiG gene promoted the spore formation of S. coelicolor J1501 and recovered the sporulation ability of whiG-deficient S. coelicolor C71. Increased amount of whiG gene product was detected by Western blot hybridization after induction of thiostrepton. It will be helpful for the future study of in vitro transcription of whiG-dependent promoters.

Gene Expression Regulation, Bacterial↗

PubMed1995

[Over-expression of glutathione S-transferase in Streptomyces].

mRNA was isolated and purified from human liver, and it was also used as templet for cDNA synthesis under the existence of reverse transcriptase. Two primers were designed and synthesized according to GST gene sequence which has been reported, GST gene was obtained using cDNA as templet and PCR technique. The sequencing result indicated that the GST gene is reliable, it was subcloned into NdeI and Bg1 II sites of plasmid pIJ6021, and then introduced into Streptomyces lividans TK54. Proteins were isolated from transformants (TK54/pIJ4486 and TK54/pIJ6021) respectively, SDS-PAGE result showed that the GST over-expressed and its yield is about 15% in soluble proteins in Streptomyces.

Glutathione Transferase↗

PubMed1995

[Chemical components of decoction of radix Paeoniae and radix Glycyrrhizae].

Eleven compounds were isolated from the water extract of the decoction of Radix Paeoniae and Radix Glycyrrhizae, namely benzoic acid, formononetin, isoliguiritigenin, liquiritigenin, 4',7-dihydroxyflavone, formononetin-7-glucoside, liquiritin, gallic acid, paeoniflorin, isoliquiritin and glycyrrhizin acid.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1994

Predominant localization of non-specific lipid-transfer protein of the yeast Candida tropicalis in the matrix of peroxisomes.

PXP-18 is a 14-kDa major peroxisomal protein of the yeast Candida tropicalis and a homologue of the non-specific lipid-transfer protein (nsLTP) of mammals. Mammalian nsLTP is thought to facilitate the contact of membranes, to stimulate lipid-transfer between them. If PXP-18 functions like nsLTP, it must be present on organelle membranes. Immunoelectron microscopy of C. tropicalis cells indicated that gold particles, which visualized PXP-18, localized exclusively in the matrix of peroxisomes. Subcellular fractionation followed by Western blotting revealed the association of PXP-18 with peroxisomes in C. tropicalis cells. An enzyme-linked immunosorbent assay revealed that almost all the PXP-18 associated with peroxisomes was detectable after the solubilization of the organelle but not before, implying the predominance of PXP-18 inside peroxisomes. This differential assay was applied to the intracellular import of the intact and truncated PXP-18s expressed in Saccharomyces cerevisiae cells. Most of the intact PXP-18 was shown to be imported into the matrix of host-cell peroxisomes, whereas the truncated PXP-18, which lacked the C-terminal tripeptide Pro-Lys-Leu, no longer targeted peroxisomes. These results are consistent with the view that PXP-18 is the matrix protein of peroxisomes and must function in a system other than that of lipid transfer.

Amino Acid Sequence↗

PubMed1994

Promoter analysis meets pattern formation: transcriptional regulatory genes in sea urchin embryogenesis.

Analyses of spatial and temporal gene control mechanisms in the sea urchin embryo have identified several important trans-regulatory factors, including some that are related to known developmental control genes of the fly and mouse. Recent advances in gene perturbation technologies, including the use of antisense oligonucleotides to target mRNAs in early-stage embryos, as well as the injection of mRNAs into zygotes to express genes ectopically, have made it possible to test the functions of such factors directly.

Animals↗

PubMed1994

Prognostic factors for the postoperative outcome of penile venous surgery for venogenic erectile dysfunction.

Since penile venous surgery is usually associated with a poor postoperative outcome, a study was done to evaluate possible prognostic factors for this procedure. A total of 77 patients with erectile dysfunction underwent ligation of all dorsal penile veins and resection of the deep dorsal penile vein for venous incompetence. In all patients a comprehensive evaluation was done preoperatively. All patients did not respond to pharmacotherapy and had a venous leak. After a followup of 6 months, patients were classified as having full spontaneous erections, failure and response to pharmacotherapy. Of the 77 patients 31 (40.3%) had full spontaneous erections, 8 (10.3%) were currently responding to pharmacotherapy and 38 (49.4%) failed. The maintenance flow was 75 +/- 45 ml. per minute in the group with spontaneous erections and 103 +/- 60 ml. per minute in the failure group (p = 0.20). Mean patient age was 49.8 +/- 11.7 and 49.1 +/- 10.2 years, respectively (p = 0.23). Of the 41 patients wih normal single potential analysis of cavernous electrical activity 28 had full erections postoperatively, 5 responded to pharmacotherapy and 8 failed, compared to 3, 3 and 30, respectively, of the 36 patients with abnormal single potential analysis of cavernous electrical activity. After a mean followup of 21 months (range 6 to 47 months), 4 patients with full erections at 6 months postoperatively currently require intracavernous pharmacotherapy. Our results indicate that single potential analysis of cavernous electrical activity seems to be an important prognostic factor for the postoperative outcome of penile venous surgery for venogenic impotence.

Adult↗

PubMed1994

A POU gene required for early cleavage and protein accumulation in the sea urchin embryo.

SpOct is a POU gene expressed during oogenesis and early embryogenesis of the sea urchin, Strongylocentrotus purpuratus. In the first use of antisense technology in the sea urchin embryo, we report that disruption of SpOct gene function in 1-cell zygotes by the injection of antisense oligodeoxynucleotides arrests development prior to the first cell division. We show that single-stranded antisense oligodeoxynucleotides specifically block cleavage, and that injection of SpOct mRNA overcomes this block. The accumulation of [35S]methionine into zygotically synthesized protein is significantly reduced in antisense-injected embryos. DNA synthesis is also reduced by the antisense regimen as expected from the antisense inhibition of protein accumulation. That protein accumulation prior to the first cleavage is retarded by antisense targeting of a transcription factor is very surprising in light of classical work showing that the activation of protein synthesis does not require zygotic transcription. We conclude that either some new transcription is obligate for the accumulation of new protein, or that the SpOct gene plays a novel, non-transcriptional role in this process.

Animals↗