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Biomedical subjects

H Tan

Publications and source records attributed to H Tan.

At least 91 records · Page 5Linked to original sources
PubMed1998

[Local amyloidosis of stomach].

OBJECTIVE: To improve the diagnostic rate of local amyloidosis of stomach. METHOD: One case of local amyloidosis of stomach was reported and the literatures were reviewed on the etiopathology, clinical features, diagnosis, treatment and prognosis. RESULT: The patient was negative for family history and other chronic disease. Total gastrectomy was taken and was eventually found to have localized amyloidosis of stomach and regional lymph nodes. The amyloidosis was found to be of AA amyloidosis. Multiple biopsy specimens taken from esophagus, duodenum, rectum and bone marrow showed no amyloid deposition. CONCLUSION: Amyloidosis should be considered in the differential diagnosis of gastric tumors, and also should be removed by operation if complications are to be prevented.

Amyloidosis↗
PubMed1998

[Structure and function of saw1--a gene related to differentiation of Streptomyces ansochromogenes].

The DNA sequence of double strands of saw1 gene was determined by the method of chaintermination inhibitors. The result indicated that the 1500 bp of DNA fragment displayed a complete open reading frame (ORF), the encoding regions were located in 419 to 1252 bp positions, saw1 product has 89% identity to amino acids of sigma whiG of Streptomyces coelicolor. When recombinant plasmid containing a 1500 bp saw1 DNA fragment insert in plasmid pIJ702 was introduced into Streptomyces coelicolor C71, the sporulation deficient mutant C71 could form spore and produce grey pigment. The gene function was studied by using the method of gene disruption and the result showed that the saw1 played an important role in developmental changes from aerial hypha to spore formation of Streptomyces ansochromogenes.

Amino Acid Sequence↗
PubMed1997

Amyloid precursor protein processing and A beta42 deposition in a transgenic mouse model of Alzheimer disease.

The PDAPP transgenic mouse, which overexpresses human amyloid precursor protein (APP717V-->F), has been shown to develop much of the pathology associated with Alzheimer disease. In this report, levels of APP and its amyloidogenic metabolites were measured in brain regions of transgenic mice between 4 and 18 months of age. While absolute levels of APP expression likely contribute to the rate of amyloid beta-peptide (Abeta) deposition, regionally specific factors also seem important, as homozygotic mice express APP levels in pathologically unaffected regions in excess of that measured in certain amyloid plaque-prone regions of heterozygotic mice. Regional levels of APP and APP-beta were nearly constant at all ages, while A beta levels dramatically and predictably increased in brain regions undergoing histochemically confirmed amyloidosis, most notably in the cortex and hippocampus. In hippocampus, A beta concentrations increase 17-fold between the ages of 4 and 8 months, and by 18 months of age are over 500-fold that at 4 months, reaching an average level in excess of 20 nmol of A beta per g of tissue. A beta1-42 constitutes the vast majority of the depositing A beta species. The similarities observed between the PDAPP mouse and human Alzheimer disease with regard to A beta42 deposition occurring in a temporally and regionally specific fashion further validate the use of the model in understanding processes related to the disease.

Age Factors↗
PubMed1997

Cloning and characterization of a cotton lipid transfer protein gene specifically expressed in fiber cells.

A cotton genomic library was screened using a fiber-specific cDNA (GH3) encoding a lipid transfer protein (LTP). One genomic clone (1.7 kb DNA insert) containing the Ltp gene (Ltp6) was sequenced and characterized. The Ltp6 contains an open reading frame of 360 bp, which is interrupted by a single intron (136 bp) located in the region corresponding to the C-terminal of the protein. The derived amino-acid sequence of LTP6 is 64% homologous to that of GH3. Like the GH3 gene, the Ltp6 is specifically expressed in fiber cells in a temporal manner. However, its expression level is lower than that of GH3.

Amino Acid Sequence↗
PubMed1997

Characterization of dye-induced mobility shifts affecting DNA sequencing in poly(ethylene oxide) sieving matrix.

The influence of three classes of fluorescence labels including dipyrrometheneboron difluoride (BODIPY), energy transfer (ET) and conventional fluorescein and rhodamine (ABI), on DNA sequencing has been examined with laser-induced fluorescence detection and poly(ethylene oxide)-filled capillary electrophoresis. DNA sequencing fragments were generated by dye-labeled primer cycle-sequencing reactions in a hot-air thermal cycler. A parameter, relative-induced shift, was introduced to quantify the uniformity of electrophoretic mobilities of these fragments. BODIPY was found to have the smallest, but nonzero, effect for dye-induced nonuniformity. Although ET dyes provided the highest sensitivity due to their unique spectroscopic properties, they were found to lack photostability compared to BODIPY and ABI dyes. Characterization also brings out some important tips for selecting the suitable dye set for the two-channel ratio-based DNA base-calling method.

DNA Fragmentation↗
PubMed1997

Detection and analysis of the growth characteristics of Proteus vulgaris with a bulk acoustic wave ammonia sensor.

A bulk acoustic wave ammonia sensor to monitor the growth of Proteus vulgaris is described. The corresponding bacterial growth response equation was derived based on the basic growth characteristics of P. vulgaris, and was verified experimentally. The application of the equation to the estimation of kinetic parameters (such as the asymtote, the maximum specific growth rate and the lag time) was accomplished successfully. The generation time is 33.3 min at 37 degrees C. The influence of temperature on bacterial growth was also investigated and the activation energy of P. vulgaris growth was estimated. Furthermore, the initial bacterial concentrations were determined based on the linear relationship between the inflection time, ti, and the logarithm of the initial bacterial concentration in the range 10(2)-10(7) (cells ml-1). The results were in good agreement with those from the pour plate count method and the precision was better than that of the frequency detection time method.

Acoustics↗
PubMed1997

[Spinal segment distribution of neural innervation related houhai acupoint--studied by CB-HRP tracing method focused on observation of the dendrites of spinal motor neurons].

The spinal segment distribution of neural innervation related Houhai acupoint in rats has been investigted by using horseradish peroxidase conjugated cholera toxin B subunit (CB-HRP) tracing technique. Spinal motoneurons (Mn) in L6-S1 were labeled retrogradely by CB-HRP, and their features have been characterized: 1) their marginal plexus of the dendrites radially projected to the lateral and/or anterior funiculus and their distal portions forming subpial dendritic plexus; 2) the medial dendrites ran along the ventral margin of the gray commissure and their distal portions surrounded the central canal' forming a subependymal dendritic plexus. Both of them are Golgi-phobic. Some distal branches of dendrites penetrated to the contralateral gray matter. The dendritic arbors of the labeled motoneurons in the group of electro-acupuncture or group of acupoint-inoculation with sheep red blood cells contracted in comparison with that in the normal control group. The primary sensory transganglionic labeled fibers and preterminal fibers revealed by CB-HRP in the dorsal horn and dorsal commissural nucleus of the spinal cord (L5-S2) converged and overlaped with the dendrites of retrogradely labeled motoneurons. The results indicated there is a reflect circuit of afferent-integration-efferent neuro-network in the spinal cord related Houhai acupoint. The Mns retrogradely labeled by CB-HRP in the L6-S1 segments might be involved in Houhai acupuncture.

Acupuncture Points↗
PubMed1997

[Micrometastasis of colorectal carcinoma in bone marrow with immunohistochemical staining].

From April 1994 to April 1996, immunohistochemical technique was used to detect micrometastasis of patients with colorectal carcinoma with monoclonal antibody to epithelial membrane antigen (anti EMA). Positive cells were found in their bone marrow in 23 of 57 cases, including 14 in 34 patients with colonic carcinoma (positive rate 41%) and 9 in 23 patients with rectal carcinoma (positive rate 39.1%). The positive rate was 40.4%. Statistical analysis showed that the modified Dukes stage of the cancer, the pathological type of carcinoma and the age of the patients were correlated with the positive rate, but the primary locations of the cancer were not. This method can be used to identify the extent of the cancer and direct clinical comprehensive treatment for colorectal carcinoma.

Adenocarcinoma↗
PubMed1997

Serum lipids and their relationship with other coronary risk factors in healthy subjects in a city clinic.

Over a thousand subjects who visited a city private medical clinic for health screening and advice were examined for their lipid profile and other cardiovascular risk factors. The mean TC, TG, LDL-C and HDL-C were 5.43, 1.45, 3.61 and 1.15 mmol/l. Their derived ratios viz, TC:HDL-C and LDL:HDL-C were 5.11 and 3.43 respectively. The prevalence of hyperlipidaemia was moderately high. Of the subjects studied 58.5% had elevated serum cholesterol, 14.8% had raised triglycerides, 64.9% had raised LDL-C and 20.8% had low HDL-C. Male subjects generally showed higher mean values and abnormality frequency in TC, TG, LDL-C, TC:HDL-C and LDL:HDL-C as compared to female subjects. Although significant ethnic differences were not detected for certain lipid parameters (e.g. TC, TG and HDL-C), the Indians appeared to have higher mean lipid values (except HDL-C), and higher percentage abnormality for all the lipid parameters as compared to the Chinese and the Malays. In correlation studies, the following lipid parameters:- TC versus TG, LDL-C, TC:HDL-C; TG versus TC:HDL-C and LDL:HDL-C; LDL-C versus TC:HDL-C and LDL:HDL-C; were positively correlated. On the other hand, TC versus HDL-C, TG versus HDL-C, LDL-C and HDL-C, and HDL-C versus TC:HDL-C and LDL:HDL-C were negatively correlated. The coronary risk factors which generally showed positive correlations with lipid parameters were BMI and blood pressure. Positive correlations were also recorded between fasting blood glucose and TG; uric acid with TG, TC:HDL-C and LDL:HDL-C. In contrast, risk factors of negative correlations were observed between HDL-C and the coronary risk factors of BMI, diastolic blood pressure and uric acid. Smoking showed raised per cent lipid abnormality for TG, HDL-C, TC:HDL-C and LDL:HDL-C. Alcohol consumption also increased the mean level and abnormality frequency for TG. The implication of this investigation is discussed.

Adolescent↗
PubMed1997

Health status of senior civil servants in Kuala Lumpur.

733 senior civil servants comprising 520 males and 213 females with a mean age of 44 years (range 25-56 years) were screened for their health status. The sample population comprised of 67.9% Malays, 22.5% Chinese, 9.1% Indians and 0.4% other ethnic origins. The subjects' medical histories were recorded and a full medical examination including anthropometric measurements (weight, height, waist and hip circumference), blood biochemistry and urine analysis, chest X-ray and electrocardiograms were done. The results obtained showed that 36.0% of the study population were overweight with 6.5% being obese. Of this 32.0% had central obesity. 15.2% of the subjects had systolic hypertension (systolic BP > or = 140 mmHg) whilst 27.6% had diastolic hypertension (diastolic BP > or = 90 mmHg). Hyperlipidaemia was common, with 75.2% subjects having raised cholesterol, 19.9% raised triglycerides, 50.2% raised LDL-C, 74.6% raised TC:HDL-C and 26.6% raised LDL:HDL-C. An elevated blood glucose was found in 8.4% subjects, whilst urine sugar was detected in only 2.6%, and a raised uric acid was found in 2.8% subjects. The prevalence of hypertension, raised blood glucose and hyperlipidaemia increased with age with more males affected than females. Although hypercholesterolaemia appeared more frequently amongst the Malays, the Indians, by comparison had the highest prevalence for a raised LDL:HDL-C ratio, a reflection of the increase in LDL-C and a concomitant decrease in HDL-C. The latter findings indicate that the Indians are at greater risk for the development of coronary heart disease than the Chinese and Malays. In addition, the mean levels of serum cholesterol found in this study seemed to have exceeded the levels found in populations in the industrialised countries such as the USA. There is thus an urgent need for more public health campaigns aimed at the reduction and control of such coronary risk factors.

Adult↗
PubMed1997

[Cloning and restriction analysis of saw1--a key gene for differentiation of Streptomyces ansochromogenes].

saw1--a essential gene for sporulation of Streptomyces ansochromogenes was cloned, 7 kb of DNA fragment in Streptomyces plasmid pIJ702 could recover the sporulation of saw1-deficient strain W51 which could not form spore with white phenotype of aerial hyphae. The recombinant plasmid was deleted by some restriction enzymes, the result showed that 2.5 kb DNA fragment in pIJ702 still has function to recover sporulation of W51. The sequencing and expression of saw1 gene is carrying out at present.

Cloning, Molecular↗
PubMed1997

[Cloning and endonuclease digestion of lon gene from Streptomyces ansochromogenes].

Streptomyces ansochromogenes is a nikkomycin producer which has typical life cycle of Streptomyces differentiation on glucose asparagine medium. The lon gene product is an ATP-dependent serine proteinase. The lon gene might have some connection with physiological differentiation and also with the morphological differentiation in S. coelicolor. The lon-like gene of S. ansochromogenes was identified by hybridization and the lon-like gene in 4.6 kb PstI fragment was cloned. The physical map of this fragment and the localization of the target gene were preliminarily studied.

Cloning, Molecular↗
PubMed1997

Timing of the expression of enamel gene products during mouse tooth development.

In order to understand the mechanisms involved in tooth development it is important to define the timing for tissue-specific gene expression. A consequence of ameloblast cell differentiation is the sequential expression of tissue-specific genes whose products form the enamel extracellular matrix. The ameloblast phenotype has been characterized as consisting of two major classes of proteins: amelogenins and non-amelogenin proteins such as anionic enamel proteins (enamelins, tuft proteins, tuftelin, sulfated proteins) and enamel proteases. The postulated functions for the anionic enamel proteins are as nucleators for hydroxyapatite crystal formation while amelogenins control the crystal size, growth and orientation. While the amelogenins have been well characterized, detailed knowledge for anionic enamel proteins has been sparse. In the present study, we designed experiments to characterize one of the anionic enamel proteins from mouse molars, tuftelin, and to determine the timing of expression of this protein during molar tooth development. Our results showed the initial detection of tuftelin transcripts within proliferating inner enamel epithelial cells at very early stages of tooth development (13 days of embryonic development equivalent to the bud stage of tooth development). These data provide direct evidence that invalidates previous dogmas that enamel proteins were synthesized by polarized, non-dividing, fully differentiated ameloblast cells. In addition, tuftelin was found to be synthesized also by dental papilla mesenchyme cells suggesting that this protein is not enamel-specific. These data taken together open the possibility that the tuftelin present in the dentino-enamel junction could be secreted by both, preodontoblast cells and preameloblast cells. It might also suggest a possible different role for tuftelin than nucleator of hydroxyapatite crystals.

Amelogenin↗
PubMed1997

[Histochemical localization of nitric oxide synthase in the human placenta].

OBJECTIVES: To study localization, distribution and activity of nitric oxide synthase (NOS) in the human placenta and to speculate the action of nitric oxide (NO) during pregnancy. METHODS: NADPH-diaphorasc histochemical method was used to indicate the distribution, localization and activity of NOS in the placentae of normal term pregnancy (n = 21). Severe pregnancy induced hypertension (PIH) (n = 15), intrauterine growth retardation (IUGR) (n = 2) and villi of early pregnancy (n = 16). RESULTS: The NOS reactive product called blue formazan was found in most of syncytiotrophoblast (STr) and located in top of cells in severe PIH and IUGR placentae. In normal term placentae the blue formazan was found in STr and located in base of cells. The number of blue formazan was more than that of PIH and IUGR placentae. Endothelial cells of most capillaries of the terminal villi in severe PIH and IUGR placentae were found to be deposited with blue formazan, but in normal term pregnancy, blue formazan was found only on rare occasion. CONCLUSION: Distribution and localization of NOS in placentae of normal term pregnancy, severe PIH and IUGR cases and early villi are specific. The NOS activity of STr in severe PIH placentae and IUGR placentae are lower than that of normal term placentae. The distribution and localization of NOS within the STr in severe PIH placentae and IUGR placentae are different from those in normal term placentae. The low activity of NOS secreted by placenta may be relative to the pathogenesis of PIH and IUGR.

Adult↗
PubMed1996

Partially Molten Middle Crust Beneath Southern Tibet: Synthesis of Project INDEPTH Results

INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.

Journal Article↗