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Biomedical subjects

C Hong

Publications and source records attributed to C Hong.

At least 55 records · Page 3Linked to original sources
PubMed1997

Serotonin levels as a function of age in Aplysia californica.

The neurotransmitter serotonin (5-HT) plays an important role in a number of behaviors in Aplysia californica some of which have been shown to vary with age. We were thus interested in examining the age-dependence of 5-HT in A. californica. Because animals of the same age can have very different weights, and weight alone is reliably known for wild-caught animals, we also examined the variation of 5-HT with weight. Serotonin was measured in the ring and abdominal ganglia combined, in lab-reared animals from 3 to 12 months post-hatch across a wide weight range. Serotonin increased rapidly from 4 to 6 months, and more slowly from 6 to 13 months. Serotonin scaled by soluble ganglion protein increased from 3 to 6-7 months, reached a maximum, and then decreased again. Serotonin, but not scaled 5-HT, increased significantly with weight across the whole weight range. Animals of the same weight, but different ages, had different 5-HT levels, as did young animals of the same age but different weight. Serotonin varied significantly with both age and weight, with the age-dependence being the more significant.

Aging↗
PubMed1997

Roles of rDNA spacer and transcription unit-sequences in X-Y meiotic chromosome pairing in Drosophila melanogaster males.

Meiotic pairing of the X and Y chromosomes in Drosophila melanogaster males is mediated by the rDNA repeats, which are present in two tandem clusters, one in the centric X heterochromatin and the other near the base of the short arm of the Y chromosome. Deletion of the X chromosomal rDNA cluster disrupts X-Y pairing and causes high frequences of X-Y nondisjunction. Pairing can be partly restored by insertions of cloned complete rRNA genes or by rDNA fragments that include the intergenic spacer (IGS) region. A 240 bp repeated sequence in the IGS was shown to be effective in promoting pairing when present at copy numbers above five. This study further defines the rDNA sequences involved in mediating pairing. Germline insertions of a P element construct containing most of the rDNA transcription unit but no promoter or IGS region were obtained. Two single-copy insertions and four two-copy insertions proved unable to stimulate X-Y disjunction when located on an rDNA-deficient X chromosome. In addition, three insertions of a P element construct consisting of the IGS and promoter regions of the rDNA were characterized molecularly. These three insertions had previously been shown to range in pairing ability from very weak to quite strong. Molecular analysis revealed that the three insertions also vary in copy number of the 240 bp IGS repeat and that these structural differences correlate with the differences in pairing ability. These data indicate that 240 bp repeats are considerably more effective than other regions of the rDNA in stimulating chromosome pairing.

Animals↗
PubMed1997

Cytomegalovirus gB genotype distribution differs in human immunodeficiency virus-infected patients and immunocompromised allograft recipients.

Cytomegalovirus isolates can be grouped into 4 gB and 2 gH genotypes. gB genotypes were studied in patients infected with human immunodeficiency virus (HIV) and in allograft transplantation recipients. In allograft recipients, the distribution of gB 1, -2, -3, and -4 in leukocytes and urine, respectively, was 36%, 21%, 43%, and 0% and 39%, 30%, 17%, and 13%. However, in leukocytes of HIV-infected patients with <100/microL CD4 cells, gB1 was found significantly less often than in allograft recipients (11% vs. 36%) but gB2 was more frequent (56% vs. 21%; P < .05). The decreased incidence of gBl and increased incidence of gB2 compared with allograft recipients was also seen in urine of HIV-infected patients and reflected the distribution seen in leukocytes. gB4 was found significantly more often (P < .05) in semen than in leukocytes of HIV-infected patients with < 100/microL CD4 cells. gB1-4 genotypes were similar in patients with < 100/microL CD4 cells with or without retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Application of thrombin based fibrin glue and non-thrombin based batroxobin glue on intact human blood vessels: evidence for transmural thrombin activity.

An alternative method of uniting small diameter vessels to obtain tissue union while limiting the thrombogenic effect of suture placement at a vessel anastomosis involves the use of a thrombin based fibrin glue as a surgical sealant. This investigation addresses whether the in vitro application of a thrombin based glue (TG), or batroxobin glue (BG), a non-thrombin based glue made with the snake venom enzyme batroxobin, alters intravascular platelet deposition (PD) or cleaves blood fibrinogen, as measured by fibrinopeptide A (FPA) production, when the respective glue is applied to the external surface of an intact human placental artery or an artery with an anastomosis. When TG was applied to the adventitial surface of an intact vessel or an anastomosis (n = 7) of control and experimental vessels, there was a significant increase in intraluminal platelet deposition, an effect not realized with BG (n = 12, intact vessel TG p = 0.01, BG p = 0.66, anastomosis TG p <0.01, BG p <0.01). Both TG and BG significantly increased FPA levels when human whole blood was perfused through both intact vessels or vessels containing an anastomosis when compared to control vessels (intact vessel TG and BG p <0.01, anastomosis TG and BG p <0.01). Labelled thrombin studies document the rapid passage of thrombin through an intact vessel wall or vessels with an anastomosis when TG was applied to the adventitial surface of the vessel. The data suggest that TG and BG are drug delivery systems for their respective enzymes that either pass through or transfer a message across not only a surgically created anastomosis, but also an intact vessel wall.

Batroxobin↗
PubMed1996

Occurrence of anthelmintic resistant nematodes on sheep farms in England and goat farms in England and Wales.

A survey in 1992 showed that 44 per cent of the sheep farms tested in the south west and 15 per cent of those in the north east of England had parasitic nematode worm burdens which were resistant to benzimidazole anthelmintics, and that 65 per cent of the non-dairy goat farms tested in England and Wales had resistant worms. Ostertagia circumcincta was the main species in sheep and Haemonchus contortus in goats. The resistance to benzimidazoles was diagnosed by a combination of an egg hatch assay and a larval development test. A simplified faecal egg count reduction test was used to investigate sheep and goat farms for signs of ivermectin resistance but no positive cases were detected. The initial identification of levamisole resistance on one farm, both from a faecal egg count reduction test and a positive larval development test, was confirmed by a 'dose and slaughter' trial.

Animals↗
PubMed1996

Expression of IFN regulatory factor family proteins in lymphocytes. Induction of Stat-1 and IFN consensus sequence binding protein expression by T cell activation.

Interferon consensus sequence binding protein (ICSBP) is a transcription factor of the IFN regulatory factor (IRF) family. Evidence indicates that this family has a function in the immune system. Unlike other members of the family, ICSBP is expressed exclusively in the immune system. In this work, immunoblot analysis was performed to study expression of ICSBP and other members of the family in various murine lymphocytes. The results show that all IRF family members are expressed constitutively in B cells throughout development, and in resting and activated cells. In contrast, ICSBP expression was undetectable in thymocytes and resting T cells, while all other IRF proteins tested (IRF-1, IRF-2, and ISGF3-gamma) were detected in these cells. Induction of ICSBP (and weakly IRF-1, but not other members) was observed upon activation of T cells following anti-CD3 Ab binding or Con A stimulation. Once T cells were activated, ICSBP was expressed stably in both Th1 and Th2 cells. We show that Stat-1, which binds to the IFN-gamma-responsive element of the ICSBP promoter, was induced following anti-CD3 Ab and Con A stimulation. Stat-1 induction was found in T cells of IFN-gamma+/+, but not of IFN-gamma-/- mice, indicating that T cell activation stimulates the Stat pathway of transcription that is mediated through IFN-gamma. IFN-gamma-activated Stat-1 partly accounted for ICSBP induction in activated T cells, as levels of induction were lower in IFN-gamma-/- than in IFN+/+ T cells. Taken together, these results show that activation of ICSBP is coupled with T cell activation that is partly due to IFN-gamma-induced Stat-1.

Amino Acid Sequence↗
PubMed1996

VH gene usage is multiple myeloma: complete absence of the VH4.21 (VH4-34) gene.

The immunoglobin heavy chain variable region (VH) gene usage in multiple myeloma (MM) has not been reported, although a few studies have incidentally identified the VH gene rearranged in small cohorts of MM patients. We used a reverse transcriptase-polymerase chain reaction based technique to analyze the VH gene usage in MM. The VH sequences were obtained after amplification of bone marrow cDNA using the seven VH family-specific and constant region primers. The VH sequences of 72 patients were successfully identified. The frequency of VH family usage in decreasing order was VH3>VH4>VH1>VH5>VH2>VH6>VH7 and corresponded to the functional germline complexity of the VH families. Individual VH genes (VH1-69, VH3-9, VH3-23, and VH3-30) were overrepresented in our cohort of MM patients; some VH genes [VH3-49, VH3-53, and VH4.21 (VH4-34)], which are rearranged with increased frequency in normal circulating B cells, autoimmune diseases, and other B-cell malignancies, were not detected in any MM patient. Compared with germline sequences, an average of 8.8% (range, 2.7% to 16.5%) of the nucleotides had evidence of mutation within each VH sequence. Based on these results, we conclude that (1) the VH gene usage in MM is unique compared with other malignant and nonmalignant B-cell populations, (2) the physiologic process of clonal deletion functions to remove clones that have rearranged VH genes (VH4.21) capable of expressing antibodies, which recognize self-antigens, and (3) the complete lack of VH4.21 gene rearrangement may help to partially explain the paucity of autoimmune phenomena in MM.

Base Sequence↗
PubMed1996

Thrombin activity on dissected and anastomosed human arteries.

The mechanism of anastomotic thrombosis in microvascular surgery remains poorly understood. We hypothesized that thrombin activity at anastomoses plays a major role in this process. To study this, a surgically relevant human artery anastomosis model was used to (i) measure surface thrombin activity on anastomoses and on intact vessel, (ii) determine the inhibitability of surface thrombin by heparin and recombinant hirudin (r-hirudin), and (iii) determine the anastomotic and intact vessel binding capacity for additional thrombin. Human placental artery segments were placed in chambers in which 0.2 cm2 of luminal surface was exposed to citrated platelet-poor plasma for 10 min at 37 degrees C. The fibrinopeptide A (FPA) concentration (indicating the action of thrombin on fibrinogen) in the supernatant was then measured using an ELISA assay. Intact vessels and anastomoses expressed equivalent thrombin activity that could not be inhibited by heparin at a concentration (0.3 U/ml) that is sufficient to prolong the activated partial thromboplastin time two-fold. Conversely, the concentration of heparin routinely used in intraoperative vessel irrigation solutions (50 U/ml) was able to completely block thrombin activity at both sites. r-Hirudin (0.3 heparin equivalent anti-IIa U/ml) was able to inhibit nearly all of the thrombin activity on each site. Each site was able to bind and express the activity of additional thrombin, indicating the potential for increased vessel thrombogenicity after local clot has formed and has been removed. These data indicate the presence of thrombin on dissected human vessels and its presence in equal amounts on intact and anastomosed vessels when measurement is made before blood flow resumes. Furthermore, vessel-associated thrombin is resistant to a standard systemic concentration of heparin but is susceptible to the much higher heparin concentration that can be delivered locally by the surgeon during vessel irrigation.

Anastomosis, Surgical↗
PubMed1996

Tissue factor and its inhibition at the human microvascular anastomosis.

The surgically created vascular anastomosis is a thrombogenic zone of uncertain etiology. This study was designed to investigate the importance of tissue factor as a cause of human microvascular thrombogenicity. The ability of tissue factor pathway inhibitor (TFPI) to block the effect of tissue factor was also tested in this whole-vessel model system. Tissue factor activity in the presence of absence of TFPI was assayed on the luminal surface of dissected human placental arteries, on the advential surface, and also at the site of a microvascular anastomosis. Vessel wall thrombin activity was measured in the presence and absence of TFPI. Platelet deposition onto a vessel surface using a perfusion system was measured with and without TFPI. Tissue factor activity was greater on the adventitia (4.6 +/- 2.8 x 10(-4) units factor Xa generated/min) than on the endothelium (1.8 +/- 1.6 x 10(-4), P < 0.03) or at a surgically created anastomosis (2.1 +/- 1.2 x 10(-4), P < 0.04). TFPI reduced Xa generation to undetectable levels in 21 of 23 endothelial, adventitial, and anastomotic segments (P < 0.002). TFPI significantly reduced vessel wall thrombin activity in comparison to control anastomoses (control, 3.2 +/- 1.7 ng fibrinopeptide A (FPA)/(ml x min); TFPI, 1.4 +/- 1.2 ng FPA/(ml x min); P < 0.0001). TFPI reduced the platelet deposition on vessel segments with intact endothelium (no TFPI, 0.88 +/- 0.69 x 10(6) platelets/cm2; TFPI, 0.49 +/- 0.29 x 10(6) platelets/cm2; P < 0.06) and on vessel segments with anastomoses (no TFPI, 1.3 +/- 0.70 x 10(6) platelets/cm2; TFPI, 0.76 +/- 0.35 x 10(6) platelets/cm2; P < 0.02). This study demonstrates the importance of tissue factor as a thrombogenic element in a human whole-vessel model system. TFPI is effective in reducing this thrombogenicity.

Anastomosis, Surgical↗
PubMed1996

A recA-like gene in Drosophila melanogaster that is expressed at high levels in female but not male meiotic tissues.

The RecA protein is the central enzyme in prokaryotic recombination. It catalyzes pairing and strand exchange between homologous DNA molecules, and functions in both DNA repair and genetic recombination. The RecA-like proteins Rad51 and Dmc1 of yeast are both required for meiotic recombination and the former is also necessary for repair of double-strand breaks in vegetative cells. Genes encoding Rad51 homologs have been isolated recently from several higher eukaryotes. This paper describes the isolation and molecular characterization of a genomic DNA fragment from Drosophila melanogaster containing the coding sequence for a RecA-like protein. This protein exhibits strong sequence homology with the Rad51 proteins of budding yeast, fission yeast, chickens, mouse and humans, and slightly less (but still strong) homology with yeast Dmc1. Both in situ hybridization and Southern analysis indicate that the Rad51 gene is present only once per genome in Drosophila (at 99D on chromosome arm 3R). However, there are at least three other fragments that cross-hybridize strongly at low stringency. RNA blotting analysis detects a single transcript of about 1.35 kb that is present throughout development at low levels. Transcript levels are induced at least tenfold in ovaries, as measured by RNase protection analysis, suggestive of a role in female meiosis. Transcript levels are significantly lower in testes than in bulk RNA of adult males, however, indicating that Rad51 may be repressed in meiosis of Drosophila males.

Amino Acid Sequence↗
PubMed1996

Development of immunity to lungworm in vaccinated calves treated with an ivermectin sustained release bolus or an oxfendazole pulse release bolus at turnout.

The ivermectin sustained release bolus (IVSRB), when used at turnout as recommended, will provide season-long control of parasitic bronchitis, thus obviating the need for use of a lungworm vaccine. However, some concerns have been expressed that calves treated with an IVSRB will receive so little exposure to Dictyocaulus viviparus that it will compromise their immunity in subsequent grazing seasons, which would be of particular importance in dairy herds. Although there is evidence that IVSRB-treated calves can develop immunity to D. viviparus when exposed to pasture infection, it was considered worthwhile to evaluate the compatibility of the IVSRB and lungworm vaccination to allow veterinary surgeons the option of using these products concurrently when they have particular concerns about the long term immune status of replacement dairy heifers. Thirty-two dairy replacement heifers were vaccinated with two doses of lungworm vaccine and, at turnout, half the calves received an IVSRB and the remainder an oxfendazole pulse release bolus (OPRB). At the end of the grazing season four replicate bolus treated pairs and four parasite-naive calves were challenged with 1000 D. viviparus infective larvae. At slaughter there was a 95% and 93% reduction in D. viviparus burdens in the IVSRB and OPRB treated calves respectively, compared with the unvaccinated, untreated controls. These results indicate that where it is considered necessary to use lungworm vaccination in addition to an IVSRB or an OPRB, the compatibility of these products with lungworm vaccine will allow development of a protective level of immunity to D. viviparus.

Animals↗
PubMed1996

Potential for misinterpretation of the faecal egg count reduction test for levamisole resistance in gastrointestinal nematodes of sheep.

The faecal egg count reduction test (FECRT) is widely used to assess the presence or absence of levamisole resistance in gastrointestinal nematodes in sheep flocks. However, in a recent study the FECRT appeared to falsely indicate the presence of levamisole resistance. One possible explanation for this result could have been that the anthelmintic failed to completely remove all immature stages of levamisole-susceptible strains, which then developed into egg laying adults and gave misleading results in the FECRT. Artificial infection of lambs with levamisole-susceptible, benzimidazole-resistant strains of Ostertagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis was followed by treatment with levamisole when the infections were between 2 and 10 days old. Levamisole was 84%, 88% and 98% effective against these immature stages of three species, respectively. The positive control, ivermectin, was more than 99% effective against all three species. The percentage faecal egg count reduction on samples taken 11 and 20 days post-treatment with levamisole was 80% and 78%, respectively. These results demonstrate that, due to the maturation of immature stages, the FECRT based on faecal eggs counts taken 11 or more days after treatment may give results indicative of levamisole resistance despite the absence of levamisole resistant strains of gastrointestinal nematodes.

Animals↗
PubMed1996

Adjusting the evaluation limit for broad-band whole-body vibration.

The vibration levels of 87 axes in 29 conventional vehicles were measured, recorded, and analyzed. The mean deviation of the overall frequency-weighted vibration levels (Lw) and the greatest single one-third octave band frequency-weighted vibration levels (Lwi-max) in corresponding axes were statistically calculated. The results showed that the vehicle vibrations were broad-band vibrations. The mean deviation of Lw - Lwi-max is 6 dB. This article suggests a 6 dB value as an appropriate adjustment value for evaluating broad-band whole-body vibrations of vehicles when using the most sensitive limits given in International Organization for Standardization document 2631/1.

Acceleration↗
PubMed1996

Prostacyclin production at the human microvascular anastomosis: its effect on initial platelet deposition.

The human microvascular anastomosis represents a localized environment with strongly thrombotic tendencies. In previous studies, an increase in initial platelet deposition at a human ex vivo anastomosis was measured. It is postulated that this increase in anastomotic platelet deposition was due to a reduction in anastomotic prostacyclin production as a consequence of local endothelial cell injury or loss. Instead, in this study, an increase in anastomotic prostacyclin production over unsutured controls (control 1093 +/- 222 pg/ml of 6-keto prostaglandin F (PGF) 1-alpha, n=21; anastomosis 2494 +/- 414, n=21, mean +/- 1 SEM, p=0.005) is demonstrated. Anastomotic prostacyclin production was augmented by addition of arachidonic acid (0.1 mM) (39,000 +/- 11,300 pg/ml of 6-keto PGF 1-alpha, n=7, p<0.001) and suppressed by the preincubation of vessel segments with aspirin in a dose-dependent fashion (1mM) (83+/-22 pg/ml of 6-keto PGF 1-alpha, n=21, p<0.001); aspirin (0.1 mM) (312 +/- 56 pg/ml of 6-keto PGF 1-alpha, n=7, p<0.001). In further studies using a perfusion apparatus of human blood pumped through human placental artery segments, suppression of prostacyclin production did not augment initial platelet deposition (control anastomosis 4.9 +/- 2.2 x10(6) platelets per cm2, aspirin treatment 6.0 +/- 2.8 x 10(6) platelets per cm2, n=5, mean +/- 1 SEM, p>0.05). Suppression of platelet function with aspirin (0.1 mM) also did not decrease initial platelet deposition onto the anastomosis (5.8 +/- 2.8 x 10(6) platelets per cm2, n=r, p>0.05). In this model system, initial platelet deposition at the anastomosis may not be dependent upon cyclooxygenase pathways.

Anastomosis, Surgical↗
PubMed1996

Detection of Francisella tularensis by the polymerase chain reaction.

Francisella tularensis is the causative agent of tularaemia. Effective antibiotic treatment of tularaemia is now available, but the early diagnosis of tularaemia remains a problem. Four primers (three pairs) were designed to detect F. tularensis by the polymerase chain reaction (PCR), based on the previously published nucleotide sequence of T-cell epitopes of a F. tularensis membrane protein. Amplification of purified F. tularensis chromosomal DNA with the three pairs of primers resulted in three different products with sizes consistent with those predicted from sequence data (211 bp, 347 bp and 568 bp). The specificity of the PCR was confirmed as no amplification was detected with a range of other bacteria. The sensitivity of the PCR was determined with limiting dilution PCR and viable counts. The preliminary application of the PCR to the detection of F. tularensis in aerosols and experimentally infected mice was investigated. Comparison of the results with those from traditional culture indicated that PCR was more sensitive. The animal challenge test showed that, 24 h after inoculation with 15 cfu of F. tularensis, 38 (82.6%) of 46 blood samples were positive by PCR, whereas only 22 (47.8%) were positive by culture. The results showed that PCR is a helpful tool for the detection of F. tularensis in blood, liver and spleen which should enable the rapid confirmation of clinical diagnoses of tularaemia.

Aerosols↗
PubMed1996

Evaluation of pupillary block component in angle-closure glaucoma.

To evaluate the amount of the pupillary block component in primary angle-closure glaucoma, the dark-room prone-position test was carried out in 30 eyes of 20 primary angle-closure glaucoma patients, before and one month after argon laser iridotomy. The pupillary block component in the prone position (5.8 +/- 5.6 mmHg), which is the amount of reduction in IOP rise in the post-laser dark-room prone-position test, composed 67.8% of the IOP rise in the pre-laser dark-room prone-position test (8.6 +/- 5.6 mmHg). The amount of the pupillary block component correlated significantly with the IOP rise in the pre-laser dark-room prone-position test (r = 0.880, P < 0.001). The amount of the non-pupillary block component was relatively constant and correlated poorly with the IOP rise in the pre-laser dark-room prone-position test (r = 0.163, P = 0.386). The pupillary block component was significantly larger than the non-pupillary block component in the eyes with an IOP rise of > or = 7 mmHg in the pre-laser dark-room prone-position test (P < 0.01). The dark-room prone-position test could be useful in evaluating the pupillary block component in angle-closure glaucoma eyes and helpful in making a decision for laser iridotomy.

Adult↗
PubMed1996

Beta 2-glycoprotein I and anticardiolipin antibody binding to resting and activated cultured human endothelial cells.

OBJECTIVE: To examine beta 2-glycoprotein I (beta 2-GPI) binding and its ability to augment IgG anticardiolipin (aCL) antibody binding to resting and cytokine activated endothelial cells in vitro. To evaluate the ability of IgG aCL antibody positive sera to induce endothelial cell activation in vitro. METHODS: IgG with aCL activity was isolated by affinity purification from 6 patients with systemic lupus erythematosus (SLE) and 3 patients with primary antiphospholipid antibody syndrome (APS). Human umbilical vein endothelial cells (HUVEC) were cultured in serum-free conditions and examined in a resting state or after activation with tumor necrosis factor alpha (TNF-alpha). HUVEC were exposed to beta 2-GPI alone, IgG alone or IgG plus beta 2-GPI. Finally, we examined the ability of sera from the same patients with SLE and primary APS to activate HUVEC in culture. RESULTS: Neither beta 2-GPI, IgG aCL, nor IgG aCL plus beta 2-GPI bound to resting or cytokine activated endothelial cells. In addition, sera from the same patients did not induce in vitro activation of endothelial cells as assessed by enhanced surface expression of intercellular adhesion molecule, vascular cell adhesion molecule, and E-selectin. CONCLUSION: Results suggest that beta 2-GPI deposition on either resting or activated endothelial cells and modulation of its proposed in vivo anticoagulant activity through subsequent aCL antibody binding does not account for the thrombotic manifestations of APS.

Antibodies, Anticardiolipin↗