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Biomedical subjects

S Yang

Publications and source records attributed to S Yang.

At least 433 records · Page 24Linked to original sources
PubMed1996

Short-term canine implantation of a glucose monitoring-telemetry device.

In this study we report the development and short-term in vivo evaluation of an integrated implantable device consisting of an amperometric glucose biosensor, a miniature potentiostat, a FM signal transmitter, and power supply. The device (dimensions: 5.0 x 7.0 x 1.5 cm) was implanted under the skin of medium-size anaesthetized dog. The experimental set-up included several methods for data collection: analog recording via wired X-T chart recorders; data collection by wearable microprocessor--data logger, and remote data collection via antenna and receiver linked to a computer-based data acquisition system. The device (sensor) performance was evaluated in vitro prior to implantation, using different model solutions simulating the physiological environment. A linear response to glucose concentration was obtained up to 25 mM glucose, with a sensitivity of 0.5 microA/mM. The results of short-term subcutaneous implantation of the integrated device reveal adequate monitoring of an artificially-induced glycaemia. The delay-time was 3-7 minutes. These tests demonstrate the feasibility of data transmission by the telemetry system through the skin of a medium-sized dog and allow the commencement of chronic in vivo experimentation.

Animals↗
PubMed1996

Acute haemodynamic responses and inhibition of tumour necrosis factor-alpha by pentoxifylline in rats with cirrhosis.

1. Although pentoxifylline has been shown to reduce portal hypertension, the mechanism for this is unclear. Since pentoxifylline decreases tumour necrosis factor-alpha production and since this cytokine may induce vasodilatation per se, a pentoxifylline-induced decrease in tumour necrosis factor-alpha production may limit arterial vasodilatation and decrease portal pressure. The aim of the present study was to examine the effects of pentoxifylline administration on plasma tumour necrosis factor-alpha concentration and haemodynamics in normal and cirrhotic rats. 2. In both groups, systemic and splanchnic haemodynamics and plasma tumour necrosis factor-alpha concentrations were measured before and 120 min after the administration of saline or pentoxifylline (20 mg/kg intravenous bolus). 3. In cirrhotic rats, pentoxifylline significantly decreased portal pressure (24 +/- 13%) and tributary blood flow (33 +/- 30%). On the other hand, pentoxifylline significantly increased vascular resistance in portal and hepatic arterial territories. Systemic haemodynamics were not altered. In normal rats, pentoxifylline significantly decreased portal pressure but induced no other significant changes in splanchnic or systemic haemodynamics. In cirrhotic rats, plasma tumour necrosis factor-alpha concentrations were significantly reduced after pentoxifylline administration but not after saline administration. No significant correlations were found between pentoxifylline-induced changes in tumour necrosis factor-alpha levels and changes in splanchnic haemodynamics. In normal rats, plasma tumour necrosis factor-alpha concentrations significantly decreased after pentoxifylline or saline administration. 4. This study shows that in rats with cirrhosis, pentoxifylline induces a decrease in both portal pressure and plasma tumour necrosis factor-alpha concentrations. These reductions were not correlated however.

Animals↗
PubMed1996

Laboratory investigation of ecological factors influencing the environmental presence of Burkholderia pseudomallei.

Factors like temperature, pH value, water content in soil, and ultraviolet rays that might have influence on the survival of environmental Burkholderia pseudomallei strains were evaluated. Data showed that the optimal temperature and pH value for B. pseudomallei were 24 C to 32 C and 5 to 8, respectively. Water content in soil of less than 10% brought about the death of the bacteria within 70 days, while water content of more than 40% maintained bacteria life for 726 days. The bacteria were easily killed by ultraviolet rays at 465 mu W/cm2 for 7.75 min while other permanent soil bacteria were killed at 1,860 mu W/cm2 for 31 min. From these results, it could be concluded that proper temperature, enough water in soil, and suitable soil pH might be the three major ecological conditions governing the environmental presence of B. pseudomallei.

Burkholderia pseudomallei↗
PubMed1996

Evidence for a discrete UTP receptor in cardiac endothelial cells.

1. We have examined the effects of various purine and pyrimidine nucleotides upon cells cultured from guinea-pig cardiac endothelium (CEC), and find the P2Y-agonist 2-methylthioadenosine triphosphate (2MeSATP) to be a potent (EC50 = 85 +/- 10.2 nM) stimulator of increase in intracellular calcium concentrations, while uridine 5'-triphosphate (UTP) and adenosine 5'-triphosphate (ATP) are less potent but equipotent with one another (EC50s = 2.1 +/- 0.3 and 1.8 +/- 0.2 microM, respectively). 2. While the P2Y receptor exhibited rapid homologous desensitization, this had no effect upon subsequent responsiveness of CEC to either ATP or UTP. Effects of maximal concentrations of ATP and UTP were not only additive, but did not cross-desensitize. Responses to UTP (but not to ATP or 2MeSATP) were blocked by treatment with pertussis toxin (PTX); all three nucleotides appeared to liberate calcium from an intracellular pool. 3. Suramin (30 microM) significantly (P < 0.05) increased the EC50 for ATP-dependent increases in intracellular calcium (5.3 +/- 2.2 microM vs. 2.0 +/- 0.9 microM in the absence of suramin), while it completely blocked the response to 2MeSATP. Suramin had no effect upon responses to UTP at concentrations of 100 microM. 4. We conclude that in addition to the P2Y and P2U subtypes of the ATP receptor, an additional receptor responsive to UTP but exhibiting no affinity for purine nucleotides is present in CEC; this "pyrimidine receptor' liberates intracellular calcium via a G-protein, and may partly mediate the contractile response to UTP in the coronary vasculature.

Adenosine Triphosphate↗
PubMed1996

Mapping of the H7-serospecific domain of Escherichia coli flagellin.

The amino acid sequences responsible for H7 and H23 flagellum serology have been identified by using a genetic approach. The H7-specific domain was located between amino acids 352 and 374 of the H7 flagellin. The sequencing data also demonstrated that the difference between the H7 and H23 flagellins in this region results from a single substitution at amino acid 366 (Ser-->Thr). The common epitopes for H7 and H23 were located between amino acids 284 and 366.

Amino Acid Sequence↗
PubMed1996

Primary structure of the variable region of monoclonal antibody 2B10, capable of inducing anti-idiotypic antibodies that recognize the C-terminal region of MSA-1 of Plasmodium falciparum.

Previously, we reported on the properties of a monoclonal antibody, 2B10, which has the same determinant on the human erythrocyte as MSA-1 of Plasmodium falciparum (FCR3 strain); the binding of both ligands to erythrocyte receptors was totally sialic acid dependent. In this work, rabbit anti-2B10 idiopathic antibodies were generated. The anti-idiotypic antibodies recognized both the erythrocyte binding site of 2B10 and the C-terminal region of MSA-1 (amino acids 1047 to 1640); they were able to inhibit 2B10 and MSA-1 binding to erythrocytes and partially prevent P. falciparum merozoites from invading erythrocytes. The utility of 2B10 in the study of the interaction between MSA-1 and human erythrocytes prompted us to determine the nucleotide and deduced amino acid sequences of its VH and VL regions. The data show that the 2B10 VH region is part of the J558 family and is especially homologous to BALB/c anti-nitrophenyl monoclonal antibody 21.1.43; the VL region belongs to the VK1 subgroup and comes from the same genomic locus as (NZB x W)F1 anti-DNA and C57BL anti-dextran monoclonal antibodies BXW-14 and 42.48.12.2, respectively. Most of the differences among the VH and VL segments are located in CDR1 and -3. The binding site of 2B10 contains both negatively and positively charged amino acid residues. The amino acid sequences of the 2B10 VH region and a region of MSA-1 from the Wellcome strain of P. falciparum (amino acids 1002 to 1115) share 43% similarity, and the amino acid sequences between the 2B10 VL region and another segment of the same MSA-1 (amino acids 1247 to 1394) share 48% similarity. We conclude that the interactions between erythrocyte receptors and their ligands, 2B10 and MSA-1, are related and that the C-terminal region of MSA-1 is the erythrocyte binding domain.

Agglutination Tests↗
PubMed1996

Complete development of Cryptosporidium parvum in bovine fallopian tube epithelial cells.

Cryptosporidium parvum is a coccidian parasite responsible for causing protracted and life-threatening diarrheal illness in immunocompromised humans, especially patients with AIDS. The lack of medications effective in treating people suffering from cryptosporidiosis has prompted the development of in vivo and in vitro models for this disease. This study is the first to demonstrate that C. parvum can complete its entire life cycle (from sporozoite to infective oocyst) in a primary culture of bovine fallopian tube epithelial (BFTE) cells. Scanning and transmission electron photomicrographs were used to detail the ultrastructure of individual parasitic stages. Successful infections were produced by inoculating cell cultures with either oocysts or purified sporozoites. Infection of BFTE cells with C. parvum close paralleled in vivo infections with regard to host cell location and chronology of parasite development. Infecting BFTE cells with sporulated oocysts provided a reproducible and quantitative cultivation system with significantly (P < or = 0.001) higher infection rates than in Madin-Darby canine kidney cells. Oocysts produced in BFTE cells were infective for immunosuppressed adult C57BL/6N mice. Cultivation of C. parvum in BFTE cells will facilitate the study of interactions between parasites and host cells as well as provide a reliable system for evaluating anticryptosporidial compound efficacy.

Animals↗
PubMed1996

Altered contractility of urinary bladder in diabetic rabbits: relationship to reduced Na+ pump activity.

We studied the effect of alloxan-induced diabetes on Na+ pump activity in isolated rabbit bladder strips. In addition, the effects of diabetes and the Na+ pump inhibitor ouabain on contractions induced by carbachol (CCh) and KCl were studied. In bladder strips from diabetic rabbits, ouabain-sensitive 86Rb+ uptake (a measure of Na+ pump activity) was approximately 50% less compared with strips from normal bladder. Diabetes also reduced the maximum contractions induced by CCh and KCl. Treatment of bladder strips with ouabain alone caused an acute concentration-dependent increase in tone. In contrast, longer incubation with ouabain inhibited CCh- and KCl-induced contractions in normal and diabetic bladders. Furthermore, differences in agonist-mediated contractions observed between normal and diabetic bladders were abolished in the presence of the maximally effective concentration of ouabain (10 microM). The ability of CCh to cause contraction in normal and diabetic rabbit bladders was also significantly inhibited by the Na+ ionophore monensin but not by the Ca2+ ionophore A-23187 or by depolarization with KCl. Monensin also inhibited KCl-induced contractions in normal bladder strips. These results indicate that 1) Na+ pump activity is an important modulator of bladder smooth muscle tone, 2) diabetes diminishes Na+ pump activity and inhibits agonist-induced contractions in bladder, and 3) an increase in intracellular Na+ concentration, secondary to inhibition of bladder smooth muscle Na+ pump activity, is associated with reduced responsiveness to contractile agonists. Diminished Na+ pump activity in diabetes may, in part, contribute to the development of bladder cystopathy.

Animals↗
PubMed1996

Sexual dimorphism in secretion of hypothalamic gonadotropin-releasing hormone and norepinephrine after coitus in rabbits.

Coital activation of the hypothalamo-hypophyseal ovarian axis (HOA) is well documented in rabbits, but coital excitation of the hypothalamo-hypophyseal testicular axis (HTA) is less well described. We and others have postulated that the response of the HOA to coitus, as characterized by a dramatic release of hypothalamic GnRH, may be mediated by an increase in norepinephrine (NE) neuronal activity. Herein, we studied selective HOA and HTA responses in New Zealand White rabbits before, during, and after coitus. Firstly, we determined the effects of microdialysis (mu D) and blood-sampling methods on plasma LH and testosterone (T) patterns in male rabbits during sexual performance. Subsequently, we compared the patterns of release in GnRH and norepinephrine (NE) from the arcuate nucleus-median eminence (AME) at 10-min intervals with changes in plasma LH levels in copulating male and female rabbits. Lastly, in 2.5-min AME mu D samples from females immediately after coitus, we measured NE and GnRH concentrations to determine whether NE release precedes that of GnRH. Tethered, freely moving rabbits were exposed to their partners for 10 min at the end of the third (10-min sampling for 5-7 h) or second (2.5-min sampling for 4 h) hour. Data from individuals that did not mate during the 10-min of pairing in the 3- to 7-h sampling trials were included as a control group (sham-mated). The results showed no changes (P > 0.05) in plasma LH and T in either mated (LH: pre, 0.13 +/- 0.08 ng/ml; post, 0.15 +/- 0.03 ng/ml; T: pre, 2.39 +/- 1.20 ng/ml; post, 0.85 +/- 0.26 ng/ml) or sham-mated males (LH: pre, 0.21 +/- 0.08; post, 0.25 +/- 0.10 ng/ml; T: pre, 1.46 +/- 0.51 ng/ml; post, 1.40 +/- 0.38 ng/ml). Likewise, coitus did not alter patterns of AME-NE (pre, 0.47 +/- 0.25; post, 0.56 +/- 0.25 ng/ml) and GnRH (pre, 0.61 +/- 0.45; post, 0.74 +/- 0.32 pg/ml) in mated or sham-mated males. The constant HTA activity during coitus in males appears to be independent of experimental manipulation per se because LH and T levels between mu D (0.18 +/- 0.05 and 1.72 +/- 0.85 ng/ml, respectively) and non-mu D (0.16 +/- 0.05 and 1.52 +/- 0.36 ng/ml, respectively) rabbits were not different (P > 0.05). In contrast to males, females displayed unambiguous and simultaneous increases in NE (P < 0.05) and GnRH (P < 0.01) release from the AME within 10-20 min after coitus; these elevated concentrations in mu D samples lasted for 3-4 h. Microdialysis NE levels averaged 0.02 +/- 0.01 ng/ml before mating, whereas postcoital values averaged 0.09 +/- 0.01 ng/ml. GnRH levels were 1.04 +/- 0.56 and 11.78 +/- 5.06 pg/ml before and after coitus, respectively. Concomitant increases in plasma LH levels were also observed after coitus in these female rabbits. Moreover, measurements of NE and GnRH in 2.5-min mu D samples revealed that the postcoital increase in NE preceded that in GnRH by 2.5-7.5 min (P < 0.05). The results suggest that neuroendocrine circuits in the two sexes of the New Zealand White rabbit respond differently to genital stimulation. In male rabbits, coitus does not alter patterns of AME NE or GnRH secretion, nor does it change the circulating levels of plasma LH or T. Conversely, in females, coitus induces the rapid release of hypothalamic NE, GnRH, and pituitary LH. The increase in coitally induced NE occurs before the rise in GnRH, which supports the hypothesis that NE is a critical neurochemical in coital activation of GnRH neurons.

Analysis of Variance↗
PubMed1996

Effect of melittin on electrophysiological parameters in the frog cornea epithelium.

The effect of melittin on electrophysiological parameters of the bullfrog cornea was studied using an in vitro preparation. Epithelial cells of corneas were impaled with microelectrodes. Experiments were done under short-circuit current (Isc) conditions. Melittin was added in concentrations of 10(-5)M to the stromal or 10(-6)M to the tear solution. The effects of melittin were as follows: (i) stromal side, a decrease in Isc; an increase in the apical membrane fractional resistance, fRo; no change in the transepithelial conductance, gt; and a depolarization of the intracellular potential, Vo; (ii) tear side, an initial (first 10 min) increase and then a decrease in Isc; a decrease in fRo; an initial (first 10 min) increase with subsequent small decrease in gt; and a depolarization of Vo. Changes in tear Na+, but not in tear K+, with melittin present in tear solution, induced changes in some electrical parameters. The effects on the tear side may be explained by opening of nonspecific channels in the apical membrane with some specificity for Na+ channel. The subsequent effects on the tear and the effects on the stromal side may be explained by an inhibition of the primary transport system, that is, of the Na+/K+ -ATPase pump located in the basolateral membrane. In these experiments, there was no evidence of opening of channels in the basolateral membrane.

Animals↗
PubMed1996

Reservoir competence of the southeastern five-lined skink (Eumeces inexpectatus) and the green anole (Anolis carolinensis) for Borrelia burgdorferi.

The reservoir competence of two lizard species, the southeastern five-lined skink (Eumeces inexpectatus) and the green anole (Anolis carolinesis), for Borrelia burgdorferi was evaluated. Skinks and anoles were exposed by needle inoculation or tick bite to B. burgdorferi. Xenodiagnosis with larval Ixodes scapularis and culture of tissues were used to asses infection and the ability of infected lizards to infect attached ticks. Both lizard species were susceptible to B. burgdorferi by both routes of exposure. Xenodiagnostic ticks acquired spirochetes while feeding on both species. One tick that dropped from a skink on the ninth day after exposure was infected. The remainder of xenodiagnostic ticks that acquired spirochetes fed three weeks after exposure of the lizards to the spirochete. Lizards remained infectious to attached ticks for at least five weeks. Overall, more than 20% of xenodiagnostic larvae fed on southeastern five-lined skinks acquired spirochetes. Individual skinks infected up to 34% of attached ticks. A smaller proportion of ticks feeding on green anoles became infected. Borrelia burgdorferi recovered from infected lizards retained their infectivity for mammalian hosts. The ability of the lizards to sustain a Borrelia infection and infect attached ticks suggests that they may play a role in the maintenance of spirochete transmission.

Animals↗
PubMed1996

Primary and secondary infections with Cryptosporidium parvum in immunosuppressed adult mice.

The present study was undertaken to determine if infection of immunocompetent adult C57BL/6N mice with Cryptosporidium parvum would render them more resistant to a challenge infection following immunosuppression with dexamethasone (DEX). Fecal oocyst shedding and parasite colonization of the terminal ilea were greater in immunosuppressed mice than in nonimmunosuppressed mice. Secondary infections with C. parvum resulted in decreased oocyst shedding and reduced parasite colonization compared with primary infections. Flow cytometry revealed fewer splenic B cells but more splenic total T, CD4+ T, CD8+ T cells and macrophages in immunosuppressed mice than in nonimmunosuppressed mice. The CD4+ to CD8+ T cell ratios and blastogenic responses to lipopolysaccharide (LPS), but not to concanavalin A, were decreased in immunosuppressed mice compared with nonimmunosuppressed mice. Blastogenic responses to LPS and percentages of splenic total B cells and macrophages were increased in secondary infections compared to primary infections. Enhanced susceptibility to C. parvum infection in immunosuppressed mice revealed DEX-mediated effects on both cell-mediated and humoral immunity. Our results suggest that increased resistance in immunosuppressed mice to secondary infections with C. parvum may involve increases in B cells and macrophages.

Animals↗
PubMed1996

Interaction of the human serine protease inhibitor alpha-1-antitrypsin with Cryptosporidium parvum.

The protozoan parasite Cryptosporidium parvum was studied for interaction with a human serine protease inhibitor (serpin), alpha-1-antitrypsin (AAT). A C. parvum homogenate (CPH) prepared from oocysts was incubated with purified human AAT and complexes formed between the serpin and CPH were detected using an enzyme-linked immunosorbent assay (ELISA). The optical density read at 450 nm of AAT:CPH reactivity was significantly increased (P < 0.001) relative to CPH in the absence of AAT treatment. Additionally, ELISA reactivity was blocked by incubating AAT with a cognate target enzyme, porcine pancreatic elastase (PPE), prior to treatment of the CPH. Incubation of a partially excysted sample of C. parvum with AAT (37 C x 60 min) demonstrated preferential fluorescence labeling of sporozoites by indirect immunofluorescence assay; AAT complexes were not detected on intact oocysts. Localization of AAT interactions with C. parvum sporozoites was visualized by transmission immunoelectron microscopy. Collectively, these data suggest that C. parvum sporozoites express a protease-like component that is recognized by human AAT. The ability to block ELISA reactivity with PPE suggests that the AAT interactions we detected are functionally similar to the serpin-enzyme complex AAT forms with a protease target.

Animals↗
PubMed1996

Efficacy of serine protease inhibitors against Cryptosporidium parvum infection in a bovine fallopian tube epithelial cell culture system.

The anticryptosporidial potential of the protease inhibitors alpha-1-antitrypsin (AAT), antipain, aprotinin, leupeptin, methoxysuccinyl-ala-ala-pro-valine chloromethylketone (MAAPVCK), soybean trypsin inhibitor (SBTI), and phenylmethylsulfonyl fluoride (PMSF) was evaluated in a bovine fallopian tube epithelial (BFTE) cell culture system. Protease inhibitor concentrations of 5, 10, 50, 100, and 500 micrograms/ ml (PMSF at 1, 2, and 3 mM) in RPMI medium were mixed with Cryptosporidium parvum oocysts and used to inoculate BFTE cell monolayers. At 24 hr postinoculation (candlejar/37 C), cells were rinsed with RPMI medium, fixed in methanol, and stained with Giemsa. Parasites were enumerated in cell monolayers by brightfield microscopy. The mean number of parasites counted in each protease inhibitor treatment group was expressed as a percentage of the mean number of parasites counted in an infection control group. Leupeptin and SBTI reduced parasite numbers to 40-50% of the control mean at 500 micrograms/ml: AAT, antipain, and aprotinin reduced parasite numbers to 10-15% at the same concentration. PMSF reduced parasite numbers to 40% of the control mean at 3 mM. MAAPVCK did not significantly inhibit cryptosporidial infection. These findings suggest that a protease component of C. parvum may be essential for host cell infection.

Amino Acid Chloromethyl Ketones↗
PubMed1996

[Experimental study on "three-dimensional" culture of scar-derived fibroblasts].

Based on the monolayer cell culture system, we resuspended the scar-derived fibroblasts in a solution of polymerizing collagen to develop a "three-dimensional" cell culture system. In this system, cells, extracellular matrices and various modulating factors were associated to form an organic entity, in which the fibroblasts express their biologic characteristics similar to that in living body. With the three-dimensional system, we could study not only the morphology, proliferation and metabolism of fibroblasts, but also their cytophysiology, such as the role on connective tissue contraction. We recommend this culture system as a better model in the research of wound healing and scar formation.

Adolescent↗
PubMed1996

[Determination of chlorogenic acid in Epimedium koreanum Nakai by HPLC].

The chlorogenic acid content in Epimedium koreanum was determined by HPLC. The result shows that this method is simple, specific and accurate. The recovery was 97.5% and relative standard deviation was 1.4%. With good reproducibility and wide response linearity, the method can be used for the quality control of this herbal medicine.

Chlorogenic Acid↗