Search PubMed⌕ Search

Biomedical subjects

Y Ma

Publications and source records attributed to Y Ma.

At least 523 records · Page 29Linked to original sources
PubMed1993

Fast minimicroassay of serum retinol (vitamin A) by capillary zone electrophoresis with laser-excited fluorescence detection.

In this paper, we present a fast minimicroassay of serum vitamin A by capillary zone electrophoresis with laser-excited fluorescence detection. A 60 cm x 50 microns I.D. fused-silica capillary was used for the separation, and the polymer coating was burned off 20 cm from the cathodic end to form a detection window. The buffer system consisted of 50 mM sodium phosphate plus 10 mM sodium chloride at pH 7.8. A helium-cadmium laser set at 325 nm was used for excitation, and the fluorescence of the vitamin A-retinol-binding protein complex was monitored at 465 nm using a photodiode. The stray and scattered radiation were removed by two special filters. Using this system, about 8 nl of serum sample were injected for direct analysis without any sample preparation. The analysis time for each sample was less than 6 min, and subfemtomole levels of vitamin A in human or animal blood could be easily detected. Therefore, the method is potentially useful for finger-prick vitamin A analysis, especially for babies and young children.

Buffers↗
PubMed1993

Determination of total polyamines in tumor cells by high-performance capillary zone electrophoresis with indirect photometric detection.

Tumor cells contain much higher levels of common polyamines such as putrescine, spermidine, and spermine than normal cells. Our previous work demonstrated that high-performance capillary zone electrophoresis with indirect photometric detection was suitable for the determination of underivatized free polyamines in tumor cells. We now report improved sensitivity (7-fold), greater quantitative reproducibility, and quantitation of both bound and free, underivatized polyamines in PC 12 tumor cells. 1,7-Diaminoheptane was used as an internal standard for quantification. Femtomoles of three polyamines and simple cations such as K+ and Na+ were easily separated in less than 10 min. The quantitations for total spermidine and spermine (bound and free) were found to be 2-fold higher than the quantitation for free, unbound polyamines using our previous method. The signal response was linear over 2 orders of magnitude. The method described here provides a fast and simple technique for quantitation of bound, unbound, and total polyamines for use in the study of the biological role of polyamines.

Adrenal Gland Neoplasms↗
PubMed1993

Molecular cloning of testicular 20 alpha-hydroxysteroid dehydrogenase: identity with aldose reductase.

Complementary DNA (cDNA) clones encoding bovine testicular 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) have been isolated from a bovine testicular lambda gt11 library using polyclonal antibodies against 20 alpha-HSD and DNA probe hybridization. Nucleotide sequencing of three independently isolated clones was used to establish a composite cDNA sequence that encodes the enzyme. It contains a coding sequence of 921 nucleotides, a stop codon, and a 264-nucleotide 3'-noncoding segment which allowed deduction of the amino acid sequence of the enzyme. A computer homology search of the 20 alpha-HSD cDNA performed against the GenBank DNA sequence database revealed it to be identical with bovine lens aldose reductase (alditol:NADPH oxidoreductase; EC 1.1.1.21), and a literature search reveals the deduced amino acid sequence to be identical with that reported for the bovine enzyme. Sequences obtained from the N-terminus of purified testicular 20 alpha-HSD and from random peptides obtained by treatment with endopeptidase Lys-C are all identical with regions of the deduced amino acid sequence of 20 alpha-HSD and/or the published sequence of aldose reductase. Further, the enzyme purified to homogeneity by following activity with 17-hydroxyprogesterone as a substrate was shown to reduce glucose, glyceraldehyde, and benzaldehyde (all classic aldose reductase substrates). Finally, 17-hydroxyprogesterone inhibited the reduction of benzaldehyde and glyceraldehyde. Because aldose reductase has been implicated in the etiology of diabetic complications, acceptance of steroid substrates may offer new implications for therapy.

20-Hydroxysteroid Dehydrogenases↗
PubMed1993

A study on the effect of lesions of area 7 of the parietal cortex on the short-term visual spatial memory of rhesus monkeys (Macaca mulatta).

This research is focused on the contribution of area 7 to the short-term visual spatial memory. Three rhesus monkeys (Macaca mulatta) were trained in the direct delayed response task in which 5 delay intervals were used in each session. When each monkey reached the criterion of 90% correct responses in 5 successive sessions, two monkeys underwent a surgery while the other one received a sham operation as a control. In the first stage of the surgery, bilateral areas 7a, 7b and 7ip of the parietal cortex of two monkeys were precisely lesioned. After 7 days of recuperation, the monkeys were required to do the same task. The average percentage of correct responses in the lesioned animals decreased from 94.7% to 89.3% and 93.3% to 82.0% respectively (no significance, P > 0.05, n = 2). In addition, the monkeys' complex movements were mildly impaired. The lesioned monkeys were found to have difficulty picking up food from the wells. In the second stage, bilateral area 7m was lesioned. In the 5 postoperative sessions, the average percentage of correct responses in one monkey, with a relatively precise 7m lesion, decreased from 94.7% to 92.2% (no significance, P > 0.05), while the other monkey, with widely spread necrosis of lateral parietal cortex, showed an obvious decline in performance, but still over the chance level. After 240 trials this monkey reattained the normal criterion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A novel combinational pH-PCO2 microelectrode.

A novel combinational pH-PCO2 microelectrode based on a neutral carrier hydrogen ion exchanger is described. It is easy to fabricate and allows pH and PCO2 to be measured simultaneously. The microelectrode has a 5-microns tip. The PCO2 microelectrode exhibits a linear response in the range 1.75 x 10(-5)-10(-2) mol/liter with a Nernstian slope of 57.0 mV/decade at 25 degrees C. The detection limit is 10(-5) mol/liter. The pH microelectrode exhibits a linear response in the range pH 4-12 with a Nernstian slope of 60.0 mV/decade at 25 degrees C. The 95% steady-state response time of the PCO2 microelectrode is about 2 min, while it is about 10 s for pH microelectrode. The electromotive force drift is 4.3 mV/h (PCO2) and 2.6 mV/h (pH), respectively. The lifetime is 3 to 4 days. The microelectrode can measure pH and PCO2 in body fluids simultaneously with satisfactory results. It is also a good basic electrode for enzyme microelectrolysis.

Animals↗
PubMed1993

Support for founder effect for two lipoprotein lipase (LPL) gene mutations in French Canadians by analysis of GT microsatellites flanking the LPL gene.

Mutations in the human lipoprotein lipase (LPL) gene are one of the major causes of familial chylomicronemia. We have characterized two polymorphic GT microsatellites flanking this gene. Two LPL mutations that are extremely frequent in French Canadians appear to be in complete linkage disequilibrium with specific LPL microsatellite haplotypes indicating a founder effect within this population.

Adult↗
PubMed1993

Gene expression in the developing cerebellum during perinatal hypo- and hyperthyroidism.

The intensity of p75NGFR receptor-like immunoreactivity and the mRNAs encoding p75NGFR, T alpha 1 alpha-tubulin, GAP-43 and the myelin proteins MBP and PLP were measured in the developing cerebellum to study the effects of perinatal thyroid hormone imbalance in rats. Results compared to age-matched controls provide in vivo evidence for differential gene regulation by thyroid hormone in the developing cerebellum. We found that p75NGFR immunoreactivity was strikingly elevated in hypothyroid rats, whereas p75NGFR mRNA content remained only twice as high as that of control levels on postnatal day 15 (P15). When p75NGFR immunoreactivity was still elevated in hypothyroid rats, Purkinje cells exhibited proximal axonal varicosities, axonal twisting and differences in axonal caliber. The mRNAs encoding proteins involved with neurite growth-promoting elements, T alpha 1 alpha-tubulin and GAP-43, were also increased in hypothyroidism, possibly reflecting a neuronal response to a deficiency in, or damage to, cerebellar neurons, or a general delay in their down regulation. Similar increases were not observed for the myelin specific genes. MBP and PLP mRNAs were first detected on P2 of hyperthyroid rats, and they increased with age. Hypo- or hyperthyroidism did not affect the initial onset of MBP and PLP expression, however, hyperthyroidism increased levels of PLP and MBP mRNAs between P2 and P10. By contrast, the most consistent decrease in MBP and PLP mRNAs in rats with thyroid hormone deficiency was observed only on P10. At later times (P15 and P30), the two mRNA levels were similar to controls in all groups. These results are consistent with a role for thyroid hormone in the earlier stages of cerebellar myelination. Hypothryoidism led to specific increases in T alpha 1 alpha-tubulin and GAP-43 mRNAs, and in the immunoreactivity and mRNA levels of p75NGFR receptor--all changes that may play a role in the observed abnormal neuronal outgrowth.

Animals↗
PubMed1993

The complete amino acid sequence for brain beta spectrin (beta fodrin): relationship to globin sequences.

The amino acid sequence of mouse brain beta spectrin (beta fodrin), deduced from the nucleotide sequence of complementary DNA clones, reveals that this non-erythroid beta spectrin comprises 2363 residues, with a molecular weight of 274,449 Da. Brain beta spectrin contains three structural domains and we suggest the position of several functional domains including f-actin, synapsin I, ankyrin and spectrin self association sites. Analysis of deduced amino acid sequences indicated striking homology and similar structural characteristics of brain beta spectrin repeats beta 11 and beta 12 to globins. In vitro analysis has demonstrated that heme is capable of specific attachment to brain spectrin, suggesting possible new functions in electron transfer, oxygen binding, nitric oxide binding or heme scavenging.

Actins↗
PubMed1993

Phenotypic variation of mutations in the human lipoprotein-lipase gene.

We have described a large number of different mutations in the LPL gene that result in completely catalytically defective LPL protein. More recently exonic polymorphisms in the LPL gene have been described that do not result in the catalytic activity of LPL being significantly impaired. Furthermore we have recently described a patient who is homozygous for a mutation in the LPL gene in a conserved region of exon 5 that results only in partial residual activity and a very mild clinical phenotype. This may suggest that the frequency of mutations in the LPL gene is greater than has been previously recognized. Recognition and selection of patients for analysis was based on the phenotype of chylomicronaemia. However, the existence of the Ser172-Cys mutation in the LPL gene that results in only moderate hypertriglyceridaemia in the absence of environmental factors might suggest that mutations in this gene are more frequent and could be seen in patients with a milder clinical phenotype. The clue to detecting these changes in the LPL gene might be to investigate patients who present with chylomicronaemia due to different environmental triggers while, in the absence of these environmental factors, they have only moderate hypertriglyceridaemia.

Genetic Variation↗
PubMed1993

Borrelia burgdorferi outer surface lipoproteins OspA and OspB possess B-cell mitogenic and cytokine-stimulatory properties.

Sonicated Borrelia burgdorferi was previously reported to possess both B-cell mitogenic and interleukin-6 (IL-6) stimulatory activities. In this report, two outer surface lipoproteins, OspA and OspB, were purified from B. burgdorferi and assessed for the presence of these functions. OspA was purified from two strains, an OspB-deficient variant of HB19 and N40, while OspB was purified from the N40 strain. All lipoprotein preparations were free of endotoxin contamination, and polymyxin B failed to inhibit responses, indicating that media contamination was not contributing to biological assays. All three preparations were able to stimulate proliferation of mononuclear cells from naive C3H/HeJ and BALB/c mice. Depletion experiments indicated that the responding cells were B lymphocytes and not T lymphocytes. Purified OspA and OspB stimulated immunoglobulin M production by splenocyte cultures from naive mice, a property also previously attributed to sonicated B. burgdorferi. OspA and OspB also stimulated the production of IL-6 and tumor necrosis factor alpha by bone marrow-derived macrophages from BALB/c and C3H/HeJ mice. Cytokine production was enhanced by the presence of gamma interferon in the cultures, indicating that the magnitude of responses to these lipoproteins may be modulated by cytokines in the microenvironment of infected tissues. Human endothelial cells produced IL-6 when incubated with OspA and OspB, indicating that non-hematopoietic lineage cells can respond to the lipoproteins. Purified OspA and OspB had approximately equal activity, with responses detected in the range of 10 ng of lipoprotein per ml to 1 microgram of lipoprotein per ml. Comparison with published dose responses for lipoproteins purified from Escherichia coli indicates that OspA and OspB purified from B. burgdorferi are much more potent. The high potency of the B. burgdorferi lipoproteins and the ability of the spirochete to invade tissues and persist argue that they could be important in the localized events contributing to the pathology of Lyme disease.

Animals↗
PubMed1993

Comparative analysis of the structure and function of adenovirus virus-associated RNAs.

The protein kinase DAI is an important component of the interferon-induced cellular defense mechanism. In cells infected by adenovirus type 2 (Ad2), activation of the kinase is prevented by the synthesis of a small, highly ordered virus-associated (VA) RNA, VA RNAI. The inhibitory function of this RNA depends on its structure, which has been partially elucidated by a combination of mutagenesis and RNase sensitivity analysis. To gain further insight into the structure and function of this regulatory RNA, we have compared the primary sequences, secondary structures, and functions of seven VA RNA species from five human and animal adenoviruses. The sequences exhibit variable degrees of homology, with a particularly close relationship between the VA RNAII species of Ad2 and Ad7 and notably divergent sequence for the avian (CELO) virus VA RNA. Apart from two pairs of mutually complementary tetranucleotides which are highly conserved, homologies are limited to transcription signals located within the RNA sequence and at its termini. Secondary structure analysis indicated that all seven RNAs conform to the model in which VA RNA possesses three main structural regions, a terminal stem, an apical stem-loop, and a central domain, although these elements vary in size and other details. The apical stem is implicated in binding to DAI, and the central domain is essential for inhibition of DAI activation. One of the pairs of conserved tetranucleotides (CCGG:C/UCGG) provides further evidence for the existence of the apical stem, but the other conserved pair (GGGU:ACCC) strongly suggests a revised structure for the central domain. In two functional assays conducted in vivo, the VA RNAI species of Ad2 and Ad7 were the most active, their corresponding VA RNAII species displayed little activity, and the single VA RNAs of Ad12 and simian adenovirus type 7 exhibited intermediate activity. Correlation of the structural and functional data suggests that the VA RNAII species adopt a structure different from those of the other VA RNA species and may play a different role in the life cycle of the virus.

Adenoviruses, Human↗
PubMed1993

Linkage of rhm, a recessive gene for resistance to southern corn leaf blight, to RFLP marker loci in maize (Zea mays) seedlings.

The recessive gene rhm confers chlorotic-lesion resistance to Bipolaris maydis race O, the southern corn leaf blight pathogen, in otherwise susceptible maize plants. Because of inconsistencies encountered in scoring the disease on mature plants in the field, an assay was developed to monitor the expression of this gene in maize seedlings under controlled conditions. One hundred and two related F3 families from the cross RH95rhm x B73 were inoculated with conidia of B. maydis race O, and the genotype at the rhm locus of each F2 parent was deduced from the reactions observed in the progeny seedlings. The F2 genomes were reconstituted by extracting DNA from leaf tissue pooled from 30-36 F3 progeny plants per family. The seedling disease ratings were analyzed together with the segregation scores for 14 single-copy DNA probes. Our results indicate that rhm is tightly linked to two restriction fragment length polymorphism (RFLP) marker loci (UMC85 and p144) that map to the short arm of chromosome 6. In addition, a rapid assay based on the polymerase chain reaction was used to confirm the linkage between rhm and the p144 RFLP marker locus in a second unrelated F2 population.

Ascomycota↗
PubMed1993

Gene-environment interaction in the conversion of a mild-to-severe phenotype in a patient homozygous for a Ser172-->Cys mutation in the lipoprotein lipase gene.

Normal pregnancy is associated with a two- to threefold increase in plasma triglyceride levels, particularly in the third trimester, due both to the overproduction of VLDLs and to the possible suppression of lipoprotein lipase (LPL) activity. Numerous mutations in the human LPL gene causing complete LPL deficiency have been described, but naturally occurring mutations that result in defective LPL with partial activity have not yet been reported. Here we describe a 30-yr-old woman who was first diagnosed with LPL deficiency during pregnancy after she developed pancreatitis. Her plasma triglyceride levels remained mildly elevated at approximately 300 mg/dl (3.4 mmol/liter) after the first pregnancy but rose significantly after she became pregnant again (1800 to 2000 mg/dl) (20.2 to 22.5 mmol/liter). DNA sequence analysis of the LPL gene showed that the patient is homozygous for a Ser172-->Cys missense mutation in exon 5. In vitro mutagenesis revealed that the Ser172-->Cys mutation caused a mutant LPL protein that had residual activity higher than that seen in all eight other missense mutations in patients with LPL deficiency identified in our laboratory. We propose that some mutations in the LPL gene produce a defective LPL with partial activity, which usually leads to mild hypertriglyceridemia.

Adult↗
PubMed1993

Antitumor protein-containing polysaccharides from a Chinese mushroom Fengweigu or Houbitake, Pleurotus sajor-caju (Fr.) Sings.

Protein-containing polysaccharides extracted from fruiting bodies of a Chinese fungus named Feng Wei Gu, were fractionated and purified, and their antitumor activities were tested, out of which the following active fractions were obtained. FIo-a: A protein-containing xyloglucan, MW 280,000, polysaccharide: protein = 76:24 (w/w), polysaccharide consisting of Man:Gal:Xyl:Glc = 2:12:42:42 (molar ratio). [alpha]D23 + 25.3 degrees. FA-2: A protein-containing mannogalactan, MW 120,000, polysaccharide: protein = 76:16 (w/w), consisting of Xyl:Man:Gal = 9:35:56 (molar ratio), [alpha]D23 + 98.5 degrees. FII-1: A Protein-containing xylan (62:21 w/w). MW 200,000, [alpha]D23 + 8.7 degrees. FIII-1a: A protein-containing glucoxylan (15:71 w/w), [alpha]D23 + 30.7 degrees, MW 90,000, consisting of Glc:Xyl = 40:44 (molar ratio). FIII-2a: A protein-containing xyloglucan, MW 70,000, polysaccharide:protein = 69:3 (w/w), polysaccharide consisting of Xyl:Glc = 36:62 (molar ratio). [alpha]D23 + 38.6 degrees.

Animals↗
PubMed1993

[Influences of acupuncture on gastroduodenal mucosal lesion and electrical changing induced by stress in rats].

Experiments were performed in 57 SD rats. The stress was induced by binding plus revolving (5.5 xg, 170 c/min, 10 min) or cold (0-4 degrees C, 30-60 min). Selected acupuncture points were "Zusanli" and "Weishu". Bipolar Ag-AgCl recording electrodes were respectively implanted on the serous membrane surface of the antrum, duodenum and on the abdominal skin corresponding to above areas. The results were as follows: (1) There are 63.2% individuals in the stress group which showed a large quantity of bleeding points spreading over the gastroduodenal mucosal membrane. The area density of lesion was 15.8-27.7%. Under microscope the signs emerged including mucosal blood vessel dilatation and hyperaemia, gland cell swelling, virlus broken and peeling off and lymph cell accumulating, etc. 84% individuals showed obvious inhibition of gastroduodenal electroactivities including that the amplitude of slow wave was lower, the frequency decreased even the rhythm was disordered, the number of fast wave reduced and the IDMEC III cycle was prolonged. (2) In the group of acupuncture plus stress only 16.7% individuals showed bleeding or hyperaemia, and the lesion area density was only 1.7%. Also the pathohistological changes were obviously decreased. Gastroduodenal electrical changes were hardly seen (27.2%) or the inhibitory state above were significantly reduced (54.5%) when compared with the stress group. There is strong reason to consider that acupuncture could effectively reduce the mucosal lesion and the electrical inhibition of stomach and duodenum induced by stress in rats.

Acupuncture Therapy↗