Biomedical subjects

Y Cheng

Publications and source records attributed to Y Cheng.

At least 217 records · Page 12Linked to original sources

PubMed1997

Expression of HBsAg gene in transgenic goats under direction of bovine alpha-S1 casein control sequence.

An expressive construct combining hepatitis B surface antigen gene and bovine alpha-S1 casein control sequence (a 16-kb fragment), lambda 106, was made successfully using DNA recombination technology. The construct was then introduced into fertilized goat eggs with a transgenic technique. As the eggs developed into adults which, in turn, began to secrete milk after parturition, ELISA assay demonstrated HBsAg in the milk, thus showing successful expression of the construct in the mammary gland of the G0 transgenic goats and the secretion of the expression product into the milk.

Animals↗

PubMed1997

Effect of TNF-alpha and IFN-alpha on the proliferation and cytotoxicity of lymphokine-activated killer cells in patients with bladder cancer.

OBJECTIVE: To investigate the effects of interleukin-2 (IL-2) combined with either tumor necrosis factor-alpha (TNF-alpha) or alpha-interferon (IFN-alpha) on the proliferation and cytolysis to bladder tumor cells of lymphokine-activated killer (LAK) cells in patients with bladder cancer. METHODS: LAK cells were generated by ficoll-paque density-centrifugation from 21 patients with bladder cancer and cultured in medium containing IL-2. LAK cell proliferation was assayed in the presence of various concentrations of either TNF-alpha or IFN-alpha by cell count in 96-well plates. Bladder cancer cell lines BIU-87 and EJ were cultured as target cells and the cytotoxicity of LAK cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide (MTT) assay. RESULTS: The proliferation of LAK cells induced by IL-2 was enhanced by TNF-alpha in a dose-responsive fashion. The direct growth support for the LAK cells was also observed with IFN-alpha at the concentration of 1000 U/ml after 48 hours of culture. TNF-alpha (5000 U/ml) resulted in an increase in the cytotoxicity of LAK cells to BIU-87 and EJ cells. However, the change of cytotoxicity of LAK cells treated with IFN-alpha was not statistically significant. CONCLUSIONS: TNF-alpha and IFN-alpha enhance the proliferation and activation of LAK cells and influence their antitumor cytotoxicity in patients with bladder cancer.

Carcinoma, Transitional Cell↗

PubMed1997

[Acute fatty liver in pregnancy: a clinicopathologic study].

OBJECTIVE: To investigate the early recognition and management of milder cases of acute fatty liver in pregnancy (AFLP). METHODS: Twelve cases of AFLP treated in our hospital during the past two and half years were retrospectively studied with emphasis on symptoms, laboratory findings, liver biopsy and maternal complications. The 12 cases were classified into 2 groups. Group 1, 6 cases of advanced AFLP diagnosed clinically, were treated in the first year of the study. Group 2, 6 cases of milder AFLP diagnosed by postpartum liver biopsy, were treated during the last one and half years of the study. RESULTS: The mean gestational age at onset was 34 +/- 3 weeks. In the early stage, all cases had malaise, nausea, loss of appetite and epigastric distress followed by jaundice in the third trimester of pregnancy. Laboratory findings included raised transaminases (< or = 300 IU/L) and total serum bilirubin (32.5-510.8 micro mol/L) levels, hypoalbuminemia (18-30 g/L), hypofibrogenemia (< 2.4 g/L), prolonged prothrombin time and prolonged partial thromboplastin time. Maternal complications were frequent including hepatic encephalopathy (9), ascites (9), hypoglycemia (7), renal failure (3), hematemesis (4), preeclampsia (6), and postpartum hemorrhage (5). Cesarean sections were performed in 7 cases. In group 2, both mother and fetuses had 100% survival. However, the mortality of the mothers and fetuses in group 1 were both 50%. CONCLUSIONS: With increasing awareness, especially in the early recognition of AFLP cases and prompt progressive management, including early termination of pregnancy and large dose infusion of fresh frozen plasma, the prognosis of AFLP is obviously improved. Percutaneous liver biopsy should be done when the coagulation tests became normal and the amounts of ascites decreased after delivery.

Acute Disease↗

PubMed1996

Nonpolar interactions of thrombin and its inhibitors at the fibrinogen recognition exosite: thermodynamic analysis.

Nonpolar interactions play a major role in the association of the fibrinogen recognition exosite of thrombin with the C-terminal fragment (55-65), Asp-Phe-Glu-IIe-Pro-Glu-Glu-Tyr-Leu-Gln, of hirudin, which is a naturally occurring thrombin inhibitor. The thermodynamic details (free energy, enthalpy, entropy, and heat capacity) of the molecular recognition are studied by using five analogs of a synthetic bivalent thrombin inhibitor (P552), tert-butylbenzensulfonyl-Arg-(D-pipecolic acid)-(12-amino-dodecanoic acid)-(gamma-aminobutyric acid)-hirudin55-65. The residue of PheH56, IleH59, ProH60, TyrH63, or LeuH64 in hirudin 55-65 segment is substituted by Gly in each analog in order to elucidate the contributions of these nonpolar side chains. The results show that the interactions of these nonpolar side chains with thrombin are enthalpy-driven, except for the contribution of the PheH56 side chain which is entropy-driven. Interestingly, molecular modeling predicts a large conformational change due to the Gly substitution of PheH56. In analyzing the correlation among the thermodynamic and structural properties of the nonpolar interaction, a good correlation is observed between the binding free energy and the hydrophobicity of the molecular surface; i.e., tighter binding is observed as more nonpolar atoms are buried and more polar atoms are exposed upon molecular association.

Antithrombins↗

PubMed1996

A high-resolution physical map of human chromosome 11.

The development of a highly reliable physical map with landmark sites spaced an average of 100 kbp apart has been a central goal of the Human Genome Project. We have approached the physical mapping of human chromosome 11 with this goal as a primary target. We have focused on strategies that would utilize yeast artificial chromosome (YAC) technology, thus permitting long-range coverage of hundreds of kilobases of genomic DNA, yet we sought to minimize the ambiguities inherent in the use of this technology, particularly the occurrence of chimeric genomic DNA clones. This was achieved through the development of a chromosome 11-specific YAC library from a human somatic cell hybrid line that has retained chromosome 11 as its sole human component. To maximize the efficiency of YAC contig assembly and extension, we have employed an Alu-PCR-based hybridization screening system. This system eliminates many of the more costly and time-consuming steps associated with sequence tagged site content mapping such as sequencing, primer production, and hierarchical screening, resulting in greater efficiency with increased throughput and reduced cost. Using these approaches, we have achieved YAC coverage for >90% of human chromosome 11, with an average intermarker distance of <100 kbp. Cytogenetic localization has been determined for each contig by fluorescent in situ hybridization and/or sequence tagged site content. The YAC contigs that we have generated should provide a robust framework to move forward to sequence-ready templates for the sequencing efforts of the Human Genome Project as well as more focused positional cloning on chromosome 11.

Chimera↗

PubMed1996

Nerve growth factor protects the neonatal brain against hypoxic-ischemic injury.

Nerve growth factor (NGF) has been shown to protect specific neurons that express its signaling receptor, trkA, from a variety of insults. There are some data, in particular in the developing brain, indicating that NGF has neuroprotective actions that extend beyond cells expressing trkA. In this study, we asked whether NGF would protect against brain injury in a neonatal model of hypoxia-ischemia. Postnatal day (PD) 7 rat pups received a right carotid ligation and were then exposed to hypoxic conditions. Prior to carotid ligation and 48 hours later, pups received an intracerebroventricular injection of NGF or denatured NGF dissolved in vehicle or vehicle alone. Brains were then assessed at PD21. In vehicle- and denatured NGF-treated animals, there was significant damage (30-40% volume loss) to both the striatum and cortex ipsilateral to the carotid ligation. In contrast, little damage (10% volume loss) was observed in most NGF-treated animals. NGF injection studies revealed that NGF stimulated tyrosine phosphorylation of trkA in multiple brain regions. These results show that NGF appears globally neuroprotective to the developing brain in a neonatal model of hypoxia-ischemia and that there may be novel mechanisms in vivo through which NGF exerts its protective actions.

Animals↗

PubMed1996

RS-66271, a C-terminally substituted analog of human parathyroid hormone-related protein (1-34), increases trabecular and cortical bone in ovariectomized, osteopenic rats.

It was predicted from the amino acid sequence of the bone anabolic peptides, parathyroid hormone (PTH) (1-34) and PTH related protein (PTHrP) (1-34), that the C-terminal amino acids form an amphipathic alpha-helix. Therefore, we substituted a model amphipathic alpha-helical peptide (MAP) sequence in the C-terminal region of hPTHrP(1-34), obtaining RS-66271 ([MAP1-10]22-31 hPTHrP(1-34)-NH2). The anabolic activities of RS-66271 and hPTHrP(1-34) were evaluated in 3-month-old, ovariectomized (OVX) osteopenic rats. Subcutaneous injection of hPTHrP(1-34) at 80 micrograms/kg/day partially reversed estrogen depletion trabecular bone loss but was ineffective in the cortex. In contrast, RS-66271 dose-relatedly reversed loss at both sites and, at 80 micrograms/kg/day, returned both trabecular and cortical bone calcium to the level of sham-operated controls. Histomorphometric analysis showed significantly elevated bone formation rates over vehicle-treated OVX in both trabecular and cortical tibial bone following treatment with RS-66271. Electron microscopy showed an increase in the relative surface area of vertebral trabeculae covered by osteoblasts in animals treated with RS-66271. These studies demonstrate that the C-terminal amino acids of hPTHrP(1-34) can be replaced by a model amphipathic helix and that the new chemical entity has greater anabolic activity than the parent peptide. The results suggest that RS-66271 may be a candidate molecule for the treatment of human osteoporosis.

Amino Acid Sequence↗

PubMed1996

Unique and conserved features of Tula hantavirus M gene encoding envelope glycoproteins G1 and G2.

The sequence of the genomic M segment encoding the surface glycoproteins G1 and G2 of wild-type Tula hantavirus (TUL) has been determined. Analyses of M nucleotide sequences show that TUL is genetically distinct from other hantaviruses. Comparison to ten currently known hantavirus G1G2 amino acid sequences points out several, presumably functional, regions with substantial homology indicating a common ancestry and similar evolutionary pathways for all members of the Hantavirus genus.

Amino Acid Sequence↗

PubMed1996

Single-tube nested polymerase chain reaction assay based on Flagellin gene sequences for detection of Borrelia burgdorferi sensu lato.

An inherent drawback of nested PCR systems to increase sensitivity of PCR-based assays is that tubes must be opened after the first round of amplification in order to transfer template molecules to the second amplification reaction; this procedure introduces the risk of carry-over contamination of negative specimens. To obviate this disadvantage, a nested PCR assay for detection of Borrelia burgdorferi in which both amplifications are performed in a single tube that remains closed throughout the entire process was devised. The assay is based on flagellin gene sequences with previously determined species-wide and species-specific properties. The nested PCR system proved to be 1000 times more sensitive than the conventional assay. Using the nested PCR system, ten spirochaetes could be routinely detected by agarose gel electrophoresis alone, whereas the conventional PCR system could detect only 10(4) spirochaetes under these conditions. After Southern transfer on amplification products and hybridization with 320- or chemiluminescent-labeled probes, the nested PCR system could easily detect a single spirochaete by both means, whereas the sensitivity of the conventional PCR assay varied from 10(1) (32P) to 10(3) (chemiluminescence) spirochaetes. This single-tube nested PCR system should be a useful addition to the current range of diagnostic assays for Lyme borreliosis.

Base Sequence↗

PubMed1996

Molecular characterization of Borrelia burgdorferi sensu lato from Slovenia revealing significant differences between tick and human isolates.

One hundred twenty-nine Slovenian isolates of Borrelia burgdorferi sensu lato derived from patients (69 strains) or Ixodes ricinus ticks (60 strains) were characterized. All of the strains were first- or second-passage isolates obtained in 1992 and 1993 from the same endemic region. The techniques used for the molecular analysis of strains included species-specific polymerase chain reaction (PCR) typing, and pulsed-field gel electrophoretic separation of undigested and MluI-digested genomic DNA. Isolates were identified to the species level by large restriction fragment pattern (LRFP) analysis and the results compared with the species-specific PCR result. Fifty-two patient isolates (75%) were typed as Borrelia afzelii (LRFP MLa1), 6 (9%) as Borrelia garinii (LRFPs MLg1-4), and 11 (16%) as Borrelia burgdorferi sensu stricto. The latter included 9 isolates (13%) with a new LRFP that is not typical of Borrelia burgdorferi sensu stricto and for which the designation MLx is suggested. In contrast, only 32 of 60 (53%) tick isolates were typed as Borrelia afzelii, while 20 strains (33%) were typed as Borrelia garinii and 8 strains (13%) as Borrelia burgdorferi sensu stricto. Three new LRFPs were found among the Borrelia garinii (MLg5 and 6) and Borrelia burgdorferi sensu stricto (MLb15) tick isolates. Large restriction fragment pattern analysis identified new groups of Borrelia burgdorferi sensu lato and revealed an apparent difference in the isolation frequency of different species from patients and ticks in the same endemic region.

Animals↗

PubMed1996

Enhanced lipid peroxidation by extracellular ATP in PC12 cells.

Recently we have demonstrated that extracellular ATP acts as an excitatory neurotransmitter and enhances cell death in the presence of ferrous ions. By using a newly developed cis-parinaric acid fluorescence technique, we demonstrated that ATP, in a dose dependent manner, enhanced the increased membrane lipid peroxidation in PC12 cells when cells were incubated with micromolar FeCl2/DTP. P2 purinoceptor agonists, alpha,beta-methylene ATP and 2-methylthio-ATP, induced PC12 cell lipid peroxidation, but to a lesser extent than ATP. ATP-induced Ca(2+) influx via P2 purinoceptor activation significantly increased the intracellular Ca(2+)concentration, which may have triggered a free radical generating cascade(s), and led to membrane lipid peroxidation and cell death. Since oxidative stress has been implicated in certain neurodegenerative diseases such as aging, extracellular ATP may contribute to neuronal cell death by an oxidative mechanism involving lipid peroxidation.

Adenosine Triphosphate↗

PubMed1996

European Lyme borreliosis: 231 culture-confirmed cases involving patients with erythema migrans.

In 1994, we isolated Borrelia burgdorferi sensu lato from 231 patients with erythema migrans who presented to the University Medical Center in Ljubljana, Slovenia. Samples of erythema migrans-affected skin were placed in media to support the growth of Borrelia species and evaluated in Ljubljana and Chicago. Patients whose cultures were positive included 132 women and 99 men; 136 of these 231 patients recalled a tick bite. Patients noted a rash an average of 24 days after a bite and presented a mean of 34 days after the bite with erythema migrans (mean diameter. 16 cm). Itching (44%) burning (18%), and pain (11%) were the most common local symptoms. Systemic complaints (40%) included headache, fatigue, malaise, and arthralgia. Other than erythema migrans, findings on physical examination were minimal (< 5% had fever, and in < 10% local lymph nodes were affected). Serial serological studies using indirect immunofluorescence assay, ELISA, and Western blot methods were performed, and antibodies to B, burgdorferi sensu lato were detected in < 50% of samples from patients. This is the largest series reported to date of patients with culture-confirmed Lyme borreliosis. It highlights the deficiencies of serological tests in early disease, demonstrates the sensitivity of direct detection methods for evaluation of patients with erythema migrans, and suggests that patients with early Lyme borreliosis in Slovenia may suffer a milder illness than those in the United States.

Adolescent↗

PubMed1996

Identification and genetic analysis of wunen, a gene guiding Drosophila melanogaster germ cell migration.

We describe a novel genetic locus, wunen (wun), required for guidance of germ cell migration in early Drosophila development. Loss of wun function does not abolish movement but disrupts the orientation of the motion causing the germ cells to disperse even though their normal target, the somatic gonad, is well formed. We demonstrate that the product of this gene enables a signal to pass from the soma to the germ line and propose that the function of this signal is to selectively stabilize certain cytoplasmic extensions resulting in oriented movement. To characterize this guidance factor, we have mapped wun to within 100 kb of cloned DNA.

Alleles↗

PubMed1996

Patient isolates of Borrelia burgdorferi sensu lato with genotypic and phenotypic similarities of strain 25015.

Strain 25015 is an atypical tick isolate that belongs to a distinct genomic group (DN127) within the general taxon Borrelia burgdorferi sensu lato. Similarities between this strain and a white-footed mouse isolate from Illinois, strain CT39, have been reported. In the course of isolating B. burgdorferi sensu lato in culture from Slovenian patients, 9 isolates were identified with the same genetic profiles as strains 25015 and CT39, as evidenced by restriction enzyme MluI digestion patterns of genomic DNA. The aim of the present study was to molecularly characterize all 11 isolates to examine the extent of their genotypic and phenotypic similarity. The results of molecular studies suggest a close relationship between the patient isolates and strains 25015 and CT39. However, CT39 and several patient isolates possessed unique characteristics that reflect their discrete ontogeny.

Animals↗

PubMed1996

Isolation and characterization of Tula virus, a distinct serotype in the genus Hantavirus, family Bunyaviridae.

A Vero E6 cell culture isolate of Tula virus (TUL), a hantavirus first detected in European common voles (Microtus arvalis and M. rossiaemeridionalis) by RT-PCR was obtained after initial passaging of TUL-infected vole lung samples in laboratory-colonized M. arvalis. TUL was defined as a classical serotype by a cross-focus-reduction neutralization test (FRNT) and was also shown to be distinct from other hantaviruses by haemagglutination inhibition assay. The sequences of S, M and partial L genome segments of the isolate were determined: the S segment was 99.9% identical to the original rodent-derived sequence. Serological evidence for a previous TUL infection was obtained from the serum of a blood donor living near a TUL focus in Moravia, Czech Republic, showing at least a 16-fold higher FRNT titre to TUL as compared to Puumala or other hantaviruses.

Animals↗

PubMed1996

Inkoo and Tahyna, the European California serogroup bunyaviruses: sequence and phylogeny of the S RNA segment.

Inkoo (INK) and Tahyna (TAH) viruses, European representatives of the California serogroup (CAL), genus Bunyavirus, family Bunyaviridae, are transmitted by mosquitoes and frequently infect man. The S segments of INK and TAH prototype strains were amplified, cloned and sequenced. INK S consists of 986 and TAH S of 977 nucleotides (nt) coding for a nucleocapsid protein of 235 amino acids (aa) and, in an overlapping reading frame, for a nonstructural protein of 92 or 97 aa, respectively. By S segment sequences and phylogenetic analysis INK was seen to be most closely related to Jamestown Canyon virus, isolated in the USA (92.4% nt and 96.6% aa identity), which is currently classified in a different subcomplex within the CAL viruses. TAH was genetically closest to Lumbo virus, isolated in Mozambique (89.0% nt and 94.1% aa identity). The data suggest that genetic variation within the CAL viruses is less related to geographical distance than to similarity in ecological cycles.

Base Sequence↗

PubMed1996

Quasispecies in wild-type tula hantavirus populations.

Tula virus (TUL) is a recently detected hantavirus carried by European common voles. Reverse transcriptase PCR cloning was used to study TUL S segment/N protein quasispecies. Both the distribution and character of mutations observed in three mutant spectra indicated limited selection at the protein level. At least 8% of the mutations were neutral or well tolerated; fixation of such mutations may play a role in TUL evolution in its natural host.

Animals↗

PubMed1996

Mechanisms contributing to renal resistance to atrial natriuretic peptide in rats with common bile-duct ligation.

Blunted volume expansion (VE) natriuresis and renal resistance to atrial natriuretic peptide (ANP) characterize states of pathological sodium retention. This study examined rats 1 to 3 wk after common bile-duct ligation (CBDL), at which time they had hyperbilirubinemia and hypoalbuminemia. Sham-operated normal rats (Sham) showed an increased sodium excretion rate (UNaV) from 1.0 +/- 0.1 to 16.3 +/- 3.9 muEq/min in response to acute VE (iv saline, 2 mL/100 g body wt over 5 min), whereas CBDL rats had a blunted response that was apparent after 1 wk and became maximal at 2 and 3 wk (0.3 +/- 0.1 to 3.2 +/- 0.4 muEq/min at 3 wk, P < 0.01 versus Sham response). The peak urinary cGMP excretion rate (UcGMPV) was also blunted (37.9 +/- 3.6 versus 87.5 +/- 8.3 pmol/min, P < 0.01) despite an even greater increase in plasma ANP concentration (Sham, 9.6 +/- 0.4 pg/mL in hydropenia to 22.8 +/- 2.6 pg/mL after VE; CBDL, 15.3 +/- 2.3 to 41.8 +/- 6.8 pg/mL). ANP-dependent cGMP accumulation by isolated inner medullary collecting duct (IMCD) cells from both Sham and CBDL rat kidneys was dose-dependent; however, at higher concentrations of ANP (> 10(-8) M), accumulation by cells from CBDL rats was significantly blunted, indicating resistance to ANP. Binding of 125I-ANP to IMCD cells was not different in CBDL rats compared with Sham control rats. Renal denervation improved but did not completely reverse the blunted natriuresis, and ANP resistance persisted in IMCD cells from denervated kidneys of CBDL rats. Incubation of IMCD cells with the phosphodiesterase inhibitors isomethylbutylxanthine or Zaprinast (each at 10(-3) M) restored ANP responsiveness in both innervated and denervated kidneys from CBDL rats, and intrarenal infusion of Zaprinast (10 micrograms/min) corrected the blunted increase in UNaV and UcGMPV after VE in rats with CBDL. These results suggest that ANP resistance in a model of abnormal sodium metabolism devoid of intrinsic renal disease may be related to increased activity of phosphodiesterase in renal target cells for ANP as well as to heightened renal nerve activity.

1-Methyl-3-isobutylxanthine↗