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Biomedical subjects

Y Hong

Publications and source records attributed to Y Hong.

At least 217 records · Page 12Linked to original sources
PubMed1994

[Studies on the effect of deltamethrin bath treatment of hamsters infected with Leishmania donovani for interrupting kala-azar transmission].

Phlebotomus chinensis were fed respectively on two groups of Cricetulus barabensis infected with Leishmania donovani, of which one group had received deltamethrin bath and the other was not treated with insecticide bath. The results showed that all the sandflies in the former group died within 24 hours, while those in the latter group had a high survival rate. Among the 165 sandflies examined, 114 (69.1%) became infected. The promastigotes not only developed well in the midgut, but also invaded esophagus, pharynx and proboscis. In the control group, the mortality of sandflies in 24 hours was 5.1% (3/59). According to the data obtained in the present study, the authors consider that insecticide bath treatment of infected domestic dogs in endemic villages could be used for interrupting kala-azar transmission.

Animals↗
PubMed1993

Sequence of the growth hormone (GH) gene from the silver carp (Hypophthalmichthys molitrix) and evolution of GH genes in vertebrates.

The silver carp (Hypophthalmichthys molitrix) growth hormone (GH) gene was isolated and sequenced following amplification from genomic DNA by the polymerase chain reaction. The gene spans a region of approx. 2.5 kb nucleotides (nt) and consists of five exons. The sequence predicts a polypeptide of 210 amino acids (aa) including a putative signal peptide of 22 hydrophobic aa residues. The arrangement of exons and introns is identical to the GH genes of common carp, grass carp, and very similar to mammals and birds, but quite different from that for the GH genes of tilapia and salmonids. The silver carp GH gene shares a high homology at the nt and aa levels with those of grass carp (95.3% nt, 99.5% aa) and of common carp (81% nt, 95.7% aa).

Amino Acid Sequence↗
PubMed1993

Distribution of immunoreactivity for enkephalin, substance P and vasoactive intestinal peptide in fibres surrounding splanchnic sympathetic preganglionic neurons in rats.

The distribution of substance P, enkephalin and vasoactive intestinal peptide in fibres and cells was examined in the autonomic nuclei of the lower thoracic and lumbar segments of the rat spinal cord. Attention was focussed on the location of the peptides in sympathetic preganglionic neurons contributing to the greater and lesser splanchnic nerves and in fibres surrounding these neurons. To identify splanchnic preganglionic neurons, Fluoro-Gold was applied to the left splanchnic nerve in anaesthetized rats and some of these animals received intrathecal administration of colchicine at thoracic segments 6, 9 and 12, 24-48 h before perfusion with fixative. Immunoreactivity for substance P, enkephalin and vasoactive intestinal peptide in fibres and cells of the sixth thoracic to second lumbar spinal cord was detected with fluorescent immunocytochemical techniques. Most retrogradely labelled cells (90%) were located in the intermediolateral nucleus and the rest were situated in the nucleus intercalatus and the central autonomic nucleus of the gray matter. Terminals of fibres containing immunoreactivity to all three peptides were found in all autonomic regions. Fibres immunoreactive for substance P and enkephalin were seen projecting in the white matter to the region of the intermediolateral nucleus and extending from this nucleus to the central autonomic nucleus. Terminals containing each of the three peptides were also found surrounding the retrogradely labelled cells in the intermediolateral nucleus. Approximately two cells immunoreactive for vasoactive intestinal peptide were found per section and 80% were located in the autonomic regions. Fewer cells immunoreactive for substance P and enkephalin were observed (approximately one per section) and 70% were outside laminae VII and X. Although cells immunoreactive for substance P, enkephalin and vasoactive intestinal peptide were located in all autonomic regions of the spinal cord, cells doubly labelled with retrograde dye and with the antisera to either of the peptides could not be identified. The data suggest that (i) substance P, enkephalin and vasoactive intestinal peptide are contained in fibres of neurons regulating preganglionic sympathetic control of the abdominal viscera and its vasculature; and (ii) these peptides may not be major transmitters within splanchnic preganglionic neurons.

Animals↗
PubMed1993

Antimicrotubule agents induce polyploidization of human leukaemic cell lines with megakaryocytic features.

In most eukaryotic cells the regular alternation of chromosome reduplication and cell division is controlled by interdependent relationships which prevent progression to the next cell-cycle phase unless the preceding phase has been completed. Megakaryocytes become polyploid by allowing many rounds of DNA replication without completion of intervening mitoses. To assess the role of cell-cycle dependencies in megakaryocytopoiesis we examined human cell lines which express megakaryocytic features for their ability to continue DNA synthesis and undergo polyploidization in the presence of mitotic poisons. Treatment of HEL cells with colcemid blocked cell division but not cellular DNA synthesis. DNA content distributions of cells treated with colcemid for 48 h showed a marked increase in the proportion of polyploid cells (57.6% +/- 9.9%, n = 16), an increase in cellular size and nuclear lobation. Identical effects were observed in HEL cells treated with colchicine, nocodazole or taxol but not with the inactive compound lumicolchicine. Induction of polyploidization by antimicrotubule agents was also observed in the megakaryoblastic cell lines MEG-01, DAMI and UT-7 but not in the T-cell line MOLT-4 or the promyelocytic cell line HL-60. These results suggest that dependency of DNA replication on completion of the previous mitosis is suppressed in the megakaryocytic lineage.

Cell Division↗
PubMed1993

A sensitive serodiagnostic test for onchocerciasis using a cocktail of recombinant antigens.

A specific serodiagnostic test for onchocerciasis has been a priority objective of the World Health Organization. Fragments of cDNA encoding Onchocerca volvulus antigens selected on the basis of their specificity for this parasite were subcloned into a protein purification and expression system. No individual recombinant antigen showed a high sensitivity in an enzyme-linked immunosorbent assay because of heterogeneity in the response of O. volvulus-infected individuals. However, a cocktail of three recombinant proteins showed 96% sensitivity with 100% specificity, compared with 99% sensitivity and only 59% specificity against a crude O. volvulus extract. The sensitivity of detection of individual antigens varied between sera taken from individuals from different geographic areas infected with O. volvulus, but when used as a cocktail, all but one of the microfilaria-positive individuals from all the geographic areas studied were detected. Recombinant probes provide a practical basis for specific diagnostic tests for helminth infections.

Africa↗
PubMed1993

Recent advances in the application of molecular biology in filariasis.

Monitoring of filarial parasites in the host and vector has traditionally depended on morphological identification. Recently, species-specific DNA probes have been developed for Brugia malayi, Brugia pahangi and Wuchereria bancrofti. Repeated DNA sequences are useful in developing DNA probes because they evolve more rapidly then coding sequences and their high copy number increases the sensitivity of detection. The Hhal repeated DNA family represents 12% of the total B. malayi DNA. This DNA family is present in species of Brugia (B. malayi, B. timori and B. pahangi) but not W. bancrofti. Sequence analysis of the repeated DNA in B. malayi and B. pahangi has allowed construction of two species-specific DNA probes. These probes were used in a double blind field study in Indonesia. Microfilariae (mf) from infected cats and humans were identified by classical morphological methods and DNA probes. Agreement was found in 98.6% of the 642 samples tested by the two different techniques. Besides mf identification DNA probes can be used to determine the species of infective larvae (L3s) in infected mosquitos. This is useful because the L3s have similar morphology. DNA probes for the identification of W. bancrofti have recently been developed and are in the initial stages of testing in China (Piessens, personal communication) and Egypt (Williams, personal communication). An alternative approach for identification of infected individuals is to detect specific parasite antigens in circulation. A WHO initiative to use either an antigen or antibody assay to replace night blood is presently underway. This approach, if successful would not require the presence of microfilariae, but could detect occult infections.

Animals↗
PubMed1993

Effects of multiple mutations at the conserved TATA sequence of bacteriophage SP6 promoter on transcription efficiency.

Mutations of A<==>T were introduced individually and multiple to TATA from -4 to -1 of the phage SP6 promoter and their effects on transcription initiation efficiency measured in vitro. All 15 mutants tested were less active than the wild type. Mutation at -4T nearly abolishes promoter activity independent of other changes, and alteration at -3A reduces promoter activity substantially. On the other hand, effects of mutations at -2T and -1A depend on other changes, suggesting their role should be associated with neighboring base pairs. These results suggest that -4T and -3A are involved in SP6 RNA polymerase binding and -2T and -1A are involved in DNA unwinding. This bipartite role of the SP6 promoter TATA contrasts with the single role of T7 promoter TATA on DNA unwinding. The polymerase binding region extends further downstream in the SP6 promoter than in the T7 promoter.

Bacteriophages↗
PubMed1993

Hyperselective posterior rhizotomy in treatment of spasticity of paralytic limbs.

One hundred and eight patients with spasticity of the paralytic limbs were treated successfully with hyperselective posterior rhizotomy (SPR). Of the 108 patients, 100 had cerebral palsy, 2 hemiplegia, 3 sequelae of cerebral injury, 2 paraplegia and 1 multiple sclerosis. Twelve patients received cervical SPR and 96 lumbosacral SPR. Laminectomy is performed to open the dura and to separate the posterior spinal root into several rootlets. The lower threshold rootlets were divided after electrical stimulation. Follow-up for 6 to 30 months showed that the effective rate of reducing spasticity was over 95% and functional improvement rate over 80%.

Adolescent↗
PubMed1992

Structure of the rainbow trout metallothionein A gene.

To investigate the regulation of metallothionein-encoding genes in fish, we have isolated and sequenced the rainbow trout metallothionein-A-encoding gene (tMT-A) by polymerase chain reaction. This gene spans about 1.1 kb, consists of three exons and two introns, and has an A+T-rich 5'-region which contains a TATAAA signal, and two metal responsive elements (MREs). The transcription start point is centered around an A residue 81 nt upstream of the ATG codon.

Amino Acid Sequence↗
PubMed1992

Intrathecal administration of non-NMDA receptor agonists increases arterial pressure and heart rate in the rat.

We have found that spinal NMDA receptors are involved in control of sympathetic output in pathways to the heart and vessels. The present study was done to determine whether spinal non-NMDA excitatory amino acid receptors participate in cardiovascular regulation. Experiments were done on urethane-anesthetized Sprague-Dawley rats, giving the non-NMDA receptor agonists, quisqualate and kainate, and the antagonist, kynurenate, intrathecally at the spinal T9 level. Both quisqualate (30 nmol; n = 7; to activate AMPA receptors) and kainate (2 nmol; n = 6; to activate K receptors) increased arterial pressure and heart rate. The responses were characterized by a rapid onset, achieving, in most cases, greater than 80% of the maximum response within 1-4 min, and a persistence throughout the remaining 20-24 min of the experiment. I.v. injection of hexamethonium (10 mg/kg) prevented the effects of intrathecal administration of quisqualate (n = 5) but not of kainate (n = 7). To determine whether the hexamethonium-resistant effects of kainate were due to a peripheral action, kainate was given i.v. (n = 6); it was found to be without effect on arterial pressure or heart rate. The increases in arterial pressure and heart rate produced by intrathecal administration of quisqualate (30 nmol; n = 6), kainate (2 nmol; n = 6), glutamate (1 mumol; n = 6) and NMDA (2 nmol; n = 6) but not carbachol (27.4 nmol; n = 6) were prevented by similar preadministration of kynurenate (125 nmol). Intrathecal administration of kynurenate (125 nmol; n = 6; 500 nmol; n = 7) decreased arterial pressure and/or heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

NMDA receptor antagonists block cardiovascular responses to intrathecal administration of D-baclofen in the rat.

In previous studies we found that D and L-baclofen have different effects on sympathetic output when administered intrathecally, yet the actions of both enantiomers are blocked by intrathecal administration of phaclofen. The present experiments were done to determine the mechanism by which D-baclofen expresses its effects. In urethane-anaesthetized Sprague-Dawley rats, when D-baclofen was given intrathecally at the T9 spinal level following pretreatment with 2 nmol of the NMDA receptor antagonist, DL-2-amino-5-phosphonovaleric acid (APV), it increased systolic and diastolic arterial pressures (n = 7), as in the previous studies. However, after intrathecal administration of 10 nmol of APV, administration of D-baclofen had no effect on these parameters (n = 7). Intravenous administration of ketamine (7.5 mg/kg), another NMDA receptor antagonist, also blocked the effect of D-baclofen (n = 6) but it had no effect on the pressor responses produced by intrathecal administration of carbachol (27.4 nmol; n = 6). In additional experiments, L-baclofen (70 nmol) had no effect on the increases in heart rate and arterial pressure produced by N-methyl-D-aspartic acid (NMDA) (2 nmol; n = 8). These results indicate that D-baclofen increases arterial pressure via an NMDA receptor-mediated mechanism, perhaps by provoking the release of an endogenous ligand which activates these receptors.

2-Amino-5-phosphonovalerate↗
PubMed1992

Short amino acid sequences derived from C1q receptor (C1q-R) show homology with the alpha chains of fibronectin and vitronectin receptors and collagen type IV.

The human C1q receptor (C1q-R) is a 65-70-kd, highly acidic, hydrophobic glycoprotein that is expressed on a wide variety of cell surfaces. Although the C1q-R itself appears to bind preferentially to C1q, the region of the ligand to which C1q-R binds is the primary binding site for several other molecules, including fibronectin, laminin, and C1q inhibitor (chondroitin 4-sulfate proteoglycan) as well as the complement C1r2C1s2 tetramer. In order to further characterize the C1q-R molecule with regard to its structure and function, highly purified C1q-R was obtained from Raji cells using DEAE-Sephacel and C1q-Sepharose CL-4B chromatography. Studies performed with 125I-labeled C1q-R demonstrated that whereas the C1q-R molecule binds poorly to a variety of human collagens including types II, III, and V, markedly enhanced binding is observed with type IV collagen and moderately enhanced binding with type I collagen. Amino acid composition studies show that the C1q-R molecule contains approximately 44% hydrophobic and 12.6% hydrophilic residues with a ratio of negatively charged to positively charged residues of about 2:1. Treatment of 125I-labeled C1q-R with endoglycosidase F lowers the apparent molecular size from 70 to 58 kd, whereas endoglycosidase H lowered the size to 64 kd. Treatment with neuraminidase, on the other hand, shifted the size of C1q-R to 60 kd. These results suggest the presence of several highly sialylated complex-type or high mannose-type N-linked oligosaccharide side chains. Because purified C1q-R has a blocked amino terminus, amino acid sequences representing internal fragments of the molecule were generated by electroblotting and in situ enzymatic digestion. When these short sequences were searched against the National Biomedical Research Foundation computer data base, a seven-amino-acid sequence, VSWQGQI, showed significant homology (100% and 80% in a five-amino-acid overlap, respectively) with the alpha chains of the human fibronectin (alpha 5 beta 1) and vitronectin (alpha v beta 3) receptors, and to a lesser degree with epidermal growth factor receptor and T cell receptor. A second sequence, ISEDNIR, showed homology with mouse collagen type IV (86% in a six-amino-acid overlap), calmodulin (60% in a seven-amino-acid overlap), and a Leishmania major surface antigen, gp63. These observations seem to predict that C1q-R has pockets of conserved sequences that are similar to those not only present in its ligand(s) but also in other cell surface receptors that may, in part, fulfill similar functions.

Amino Acid Sequence↗
PubMed1992

Trichinella spiralis: activation of complement by infective larvae, adults, and newborn larvae.

The ability of Trichinella spiralis to activate complement (C) has been addressed by several investigators. However, these investigators employed methods in which either detection of C fragments on the parasite surface or the adherence of leukocytes to the parasite was considered an indication of C activation. The present studies were undertaken to examine: (a) whether activation of C occurs via the classical and/or alternative pathway, (b) at which stage(s) of the parasite C activating capacity is acquired, and (c) what molecular entities of the epicuticle and/or cuticle are responsible for initiating C activation. Our studies indicate that T. spiralis activates C primarily via the alternative pathway (and weakly via the classical pathway) since incubation of parasites obtained from infected mice with either normal human serum (NHS) or Mg.EGTA-NHS, followed by incubation (1 hr, 37 degrees C) with antibody-sensitized sheep erythrocytes or rabbit erythrocytes, respectively, showed a time-and parasite number-dependent depletion of C. Although the three stages of T. spiralis, i.e., infective larvae, adults and newborn larvae, are capable of activating C, the newborn appears to be the most potent activator, especially when parasite number and size are taken into consideration. Further evidence of C activation is obtained from SDS-PAGE and Western blot analysis in which homogenates of parasites preincubated with NHS showed the presence of C3, C9, and C1q, whereas controls without serum were negative. Since isolated C1q was also capable of directly binding to the surface of adults and infective larvae, it is postulated that their cuticle and/or epicuticle may possess surface structures which serve as binding sites for C1q.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Acyloin formation by benzoylformate decarboxylase from Pseudomonas putida.

Whole cells and cell extracts of Pseudomonas putida grown in a medium containing ammonium mandelate have the capacity to produce the acyloin compound 2-hydroxypropiophenone when incubated with benzoylformate and acetaldehyde. Benzaldehyde and benzyl alcohol were formed as reaction by-products. The enantiomeric excess of the 2-hydroxypropiophenone product was found to be 91 to 92%. The absolute configuration of the enzymatically prepared product at the carbinol carbon was found to be S. The thiamine PPi-linked enzyme benzoylformate decarboxylase, purified to give a single protein band on polyacrylamide gel electrophoresis, was shown to be responsible for the catalysis of this novel condensation reaction.

Benzaldehydes↗
PubMed1992

[Effects of 3 Chinese medical prescriptions on alkaline reflux gastritis in rats].

The experimental alkaline reflux gastritis in rats was established after 9 weeks of anastomosis between stomach and jejunum. The experiment shows that xiangsha liujunzi decoction, xiaochaihu decoction and dahuang gancao decoction all help to inhibit edema, hyperamia and extravasted blood, as well as depress inflammatory infiltration and hyperplasia. The number of intestinal metaplasia in the group treated with xiangsha liujunzi decoction is decreased. All the three prescriptions are not able to lower the contents of bile acid in the stomach.

Animals↗
PubMed1992

In situ demonstration of proliferating cells in the rat central nervous system during experimental autoimmune encephalomyelitis. Evidence suggesting that most infiltrating T cells do not proliferate in the target organ.

Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats and the bromodeoxyuridine (BrdU)-incorporating cells were demonstrated immunohistochemically in lesions in the central nervous system (CNS) to assess the extent of T cell proliferation during EAE. In active EAE, BrdU+ cells were most numerous on day 12 postimmunization, when both clinical signs and inflammation detected by histologic examination were most severe; they declined thereafter although a considerable number of inflammatory foci remained in some rats. In passive EAE, BrdU+ cells were most numerous 2 days before the full-blown EAE and then rapidly decreased in number. On day 6 post-transfer, the CNS showed the most severe histologic changes but virtually no inflammatory cells in the lesions were labeled with BrdU. Double immunofluorescence staining with T cell (OX52) and macrophage/microglia (OX42) markers showed that about half of the BrdU+ cells were labeled with OX52 at the peak of EAE. The proportion of BrdU+OX52+ T cells at later stages was about 20%. BrdU+OX42+ cells ranged between 50 and 80% throughout the course of the disease. Furthermore, serial pulsing experiments during passive EAE revealed that inflammatory cells that had been labeled with BrdU outside the CNS and found later in the CNS were 15 times more numerous than those labeled in situ in the CNS. Taken together, these findings indicate that the majority of T cells involved in EAE undergo DNA synthesis outside the CNS and then infiltrate into the CNS, and that T cells labeled in situ in the CNS are few, and decrease rapidly in number. Since interleukin-2-receptor-positive cells detected by mAb OX39 outnumbered BrdU+ T cells at these later stages, we postulate that an unresponsive state instead of T-cell proliferation was induced in the CNS.

Animals↗