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Biomedical subjects

Y X Yu

Publications and source records attributed to Y X Yu.

At least 37 records · Page 2Linked to original sources
PubMed1992

Systemic tocainide relieves mechanical hypersensitivity and normalizes the responses of hyperexcitable dorsal horn wide-dynamic-range neurons after transient spinal cord ischemia in rats.

In the present study we examined the effect of systemic tocainide on sensory hypersensitivity in rats after spinal cord ischemia induced by a photochemical technique. After induction of spinal cord ischemia the rats exhibited a sensory disturbance which was mainly expressed as vocalization to innocuous cutaneous mechanical stimuli (allodynia) in the flank area during the following several days. Tocainide at 75 mg/kg i.p., but not 50 mg/kg i.p., significantly increased the vocalization threshold to mechanical pressure for 2 h. The effect of intraarterial (i.a.) tocainide on the responses of dorsal horn wide-dynamic-range (WDR) neurons to suprathreshold electrical stimulation of their receptive fields was also examined in normal rats and after transient spinal cord ischemia, at a time when the animals exhibited typical behavioral allodynia in the dermatomes innervated by the ischemic spinal segments. In normal rats, tocainide (50 mg/kg i.a.) strongly suppressed the responses of WDR neurons to C fiber input with lesser effect on A fiber input. In allodynic rats, tocainide suppressed the augmented A and C fiber mediated responses of WDR neurons to the extent that their responses were similar to those seen in normal rats without tocainide. There was no difference in the overall depression of A and C fiber mediated input by tocainide between normal and allodynic rats. The present results demonstrated the analgesic effect of systemic tocainide in relieving allodynia in rats and indicated that systemic local anesthetics, at doses that do not block nerve conduction, can be effective in suppressing dorsal horn WDR neuronal activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Antigenic characterization of the live attenuated Japanese encephalitis vaccine virus SA14-14-2: a comparison with isolates of the virus covering a wide geographic area.

In China, a live attenuated Japanese encephalitis (JE) vaccine, based on strain SA14-14-2, has been derived from the wild-type strain SA14 as an alternative to the current inactivated vaccines such as Nakayama-NIH and P-3. SA14-14-2 has been characterized using monoclonal antibodies derived in mice, using HAI and neutralization tests, and compared with other Chinese live vaccine clones and 14 wild-type strains of JE virus. Wild-type strain SA14 was found to be a poor immunogen and antigenically distant from all other viruses examined. The vaccine derivatives SA14-5-3 was more immunogenic than its wild-type parent, while SA14-14-2 (derived from SA14-5-3) was more immunogenic than SA14-5-3 and elicited a cross neutralizing antibody response. Our studies indicated that JE virus strain Nakayama elicited as good a neutralizing antibody response in hyperimmunized mice as the SA14-14-2 vaccine clones grown in either primary hamster kidney (PHK) or primary dog kidney (PDK) cells. A single dose of live SA14-14-2 (PHK) also elicited a good antibody response. Antigenic variation between wild-type and vaccine clones of JE virus were detected but were not considered significant in terms of controlling JE virus infections by vaccination.

Animals↗
PubMed1992

Transient spinal cord ischemia induces temporary hypersensitivity of dorsal horn wide dynamic range neurons to myelinated, but not unmyelinated, fiber input.

1. The activity of 197 single dorsal horn neurons was recorded extracellularly in the spinal cord of decerebrate, spinalized, unanesthetized rats. The response properties of 174 wide dynamic range (WDR) neurons to electrical, mechanical, and thermal stimulation in three groups of rats were studied:normal, 1-4 days after transient spinal cord ischemia induced photochemically by laser irradiation when the rats exhibited behavioral hypersensitivity to mechanical stimuli (allodynia), and 10-20 days after spinal ischemia when the allodynia had ceased. 2. In normal rats, the responses of dorsal horn WDR neurons to suprathreshold electrical stimulation of their receptive fields consisted of a short-latency (A) and a long-latency (C) response. In 77% of the neurons (57/74), there was a separation between the A- and C-fiber responses. The response threshold (defined as 20% increase in neuronal discharges above background activity) to mechanical stimulation applied with calibrated von Frey hairs was 13.8 g, and the discharges of these neurons to graded stimulation increased linearly. 3. In 68% of WDR neurons in allodynic rats (38/56), the response to suprathreshold electrical stimuli was a single burst with no separation between A- and C-fiber responses. The magnitude and duration of the response were significantly increased compared with those recorded in normal rats. The sensitivity of these neurons to mechanical stimulation was also greatly increased, expressed by a lowered threshold (2.1 +/- 0.3 g, mean +/- SE) and a shift to the left of the nonlinear stimulus-response curve. The background activity of the neurons and the size of the receptive fields were, however, unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Baclofen reverses the hypersensitivity of dorsal horn wide dynamic range neurons to mechanical stimulation after transient spinal cord ischemia; implications for a tonic GABAergic inhibitory control of myelinated fiber input.

1. In the companion paper, we described a state of hypersensitivity that developed in dorsal horn wide dynamic range (WDR) neurons in rats after transient spinal cord ischemia. Thus the WDR neurons exhibited lower threshold and increased responses to low-intensity mechanical stimuli. The response pattern of these neurons to suprathreshold electrical stimulation was also changed. Notably, the response to A-fiber input was increased. No change in response to thermal stimulation was found before and after spinal cord ischemia. 2. In normal rats, the gamma-aminobutyric acid (GABA)B agonist baclofen (0.1 mg/kg ip) administered 1-3 h before neuronal recording suppressed the responses of WDR neurons to high-intensity mechanical pressure without influencing the threshold and the responses to lower-intensity stimuli. 3. In allodynic rats, similar pretreatment with baclofen totally reversed the hypersensitivity of the WDR neurons to mechanical stimuli and normalized the response pattern of neurons to electrical stimulation. 4. The GABAA receptor agonist muscimol (1 mg/kg ip) did not influence the response of WDR neurons in either normal or allodynic animals. 5. The present results demonstrated that the GABAB agonist baclofen is effective in reversing the hypersensitivity of dorsal horn WDR neurons to low-intensity mechanical stimulation after transient spinal cord ischemia, indicating that dysfunction of the GABAergic inhibitory system may be responsible for the development of neuronal hypersensitivity. 6. It is suggested that GABAergic interneurons exert a tonic presynaptic inhibitory control, through baclofen-sensitive B-type GABA receptors, on input from low-threshold mechanical afferents, and that disruption of this control may result in painful reaction to innocuous stimuli (allodynia).

Animals↗
PubMed1992

[A study on virus localization and microcirculation in the liver in patients with epidemic hemorrhagic fever].

The findings in our clinical study was consistent with those reported by others that a temporary elevation of serum alanine aminotransferase activity is associated with epidemic hemorrhagic fever (EHF). However, the pathogenesis of the concomitant changes in liver function tests is still not clear. To clarify whether EHF virus is cytopathic or not for the liver, percutaneous liver biopsy was done in 19 patients with EHF within 3-12 days after the onset of symptoms. These liver biopsy specimens were examined with immunofluorescence assay and cell cultural technique, showing the presence of active viral replication in liver cells. Electron microscopy observation of the infected liver cells showed that ultrastructural distortions was accompanied by the existence of inclusion bodies of EHF virus in vacuoles of rough endoplasmic reticulum, endotheliocyte and microvilli. These findings strongly suggest that EHF virus may play a causative role in liver injury in patients suffering from EHF and hepatic microcirculation disturbance may be involved in the pathogenesis of EHF-related liver dysfunction as well.

Adolescent↗
PubMed1991

Hypersensitivity of dorsal horn wide dynamic range neurons to cutaneous mechanical stimuli after transient spinal cord ischemia in the rat.

The responsiveness of dorsal horn wide dynamic range (WDR) neurons to cutaneous mechanical stimuli was studied in decerebrate, spinalized, unanesthetized rats before and after transient photochemically induced spinal cord ischemia. In normal rats, the discharges of dorsal horn WDR neurons to the graded mechanical stimuli applied with calibrated von Frey hairs increase linearly. One to four days after spinal ischemia, when the rats exhibit a strong allodynia-like behavioral reaction to cutaneous stimuli, the sensitivity of dorsal horn WDR neurons to mechanical pressure is greatly increased. There is a significant decrease in the threshold pressure to evoke neuronal discharges and the exponential stimulus-response curve is shifted to the left. Thus, transient ischemia of the spinal cord results in hyperexcitability of dorsal horn WDR neurons, which may underly the allodynia-like sensory abnormalities observed in behaving animals. The present results may contribute to understanding the mechanism of the development of chronic central pain in patients after central nervous system injury involving ischemia.

Animals↗
PubMed1991

Identification of mutations that occurred on the genome of Japanese encephalitis virus during the attenuation process.

The total nucleotide sequences of the genomes of two Japanese encephalitis virus (JEV) strains, the attenuated vaccine strain SA14-14-2 and its parental virulent strain SA14, were determined by using the molecular cloning technique. The sequence analysis revealed that both virion RNA molecules were 10,976 nucleotides long with 95 and 585 flanking bases at the 5' and 3' untranslated sequences, respectively. A single, long open reading frame spanning 10,296 nucleotides was observed to encode a polyprotein of 3432 amino acid residues. When these sequences were compared with each other, 57 nucleotide substitutions were found to be scattered all over the genome. Of these, 24 resulted in amino acid changes within viral proteins. Structural proteins C and E contain one and eight amino acid changes, respectively. Of the nonstructural proteins, NS1 contains three, NS2a two, NS2b two, NS3 four, NS4a one, NS4b one, and NS5 two amino acid substitutions. The 5'- and 3'-terminal untranslated regions contain one- and two- point mutations, respectively. These data and comparative studies with other JEV strain genomes provide a molecular basis for investigating attenuation mechanisms of JEV.

Amino Acid Sequence↗
PubMed1991

Spinal evoked potential P2 wave elicited by C fiber input and depressed by analgesic factors.

Spinal cord potentials were recorded from the surface of the spinal cord of rats. The effects of various treatments on a positive wave following the original P wave, which was evoked by strong electrical stimulation and named the P2 wave, were investigated. The results of this study demonstrate that capsaicin applied on to the sciatic nerve, intrathecal injection of morphine, electroacupuncture and noxious heat applied to the hindpaw contralateral to the recording side could suppress the P2 wave. These data suggest that P2 is mediated by C afferents and might be useful as a new indicator of spinal nociception.

Analgesia↗
PubMed1991

[Clinical study of 63 patients with aplastic anemia by using in vitro culture of BFU-E, CFU-E, CFU-GM and of the relation between pathogenesis and treatment].

63 patients with aplastic anemia were studied by using in vitro assay for committed erythroid and granulomonocytic progenitors from the bone marrow. The T cell-mediated effects of suppression of normal hematopoiesis were observed by PBMNC of the patients when cocultured with normal bone marrow. The stimulated effects of androgen on BFU-E and CFU-E with methyl testosterone were also studied. The results showed that the PBMNC of 44.4% of the 63 patients suppressed normal hematopoiesis. 41.3% of the patients responded to methyl testosterone (MT) and 14.3% of the patients had very obvious decrease or absence of BFU-E, CFU-E and CFU-GM without evidence of immunological effects or response to androgen. According to these findings, it may be useful for clinicians to choose better therapeutic regimens for aplastic anemia. Such as BMT for the patients with hematopoietic stem cells deficiency; immuno-suppression treatment or splenectomy may be of benefit for those who suffered from immune mediated aplastic anemia (IMAA) and androstenones chosen for those sensitive to MT in vitro. There were 15 patients with IMAA treated with immuno-suppressive agents and 19 patients sensitive to MT treated with androgens. All of them had satisfactory results.

Adolescent↗
PubMed1990

[Micellar chromatographic study of amines].

Aqueous solutions of the cationic surfactant, hexadecyl-trimethyl ammonium bromide (CTAB), and the anionic surfactant, sodium dodecylsulfate (SDS) were used as mobile phase in HPLC to study the micellar chromatographic retention mechanism of seven amines and weak organic acids with various distribution coefficients and to study the influence of different pH values mobile phase on the solute retention. An exponential model equation for micellar chromatographic retention mechanism was put forward, which gives a reasonable explanation of the effects of electrostatic interaction and hydrophobic interaction between the solute and the three phases (micelle phase, surfactant modified stationary phase and bulk water phase). This equation can be used to estimate the micellar chromatographic retention pattern of the solute.

Amines↗
PubMed1989

Human papillomavirus-35-positive bowenoid papulosis of the anogenital area and concurrent human papillomavirus-35-positive verruca with bowenoid dysplasia of the periungual area.

We describe a 42-year-old woman with human papillomavirus (HPV)-35-positive bowenoid papulosis in her anogenital region and HPV-35-positive verruca with bowenoid dysplasia on her right ring finger. The anogenital lesions were diagnosed 11 years before the lesion on her finger developed. We were not able to cure her bowenoid papulosis, since new lesion formation occurred continuously. As pruritus of the anogenital area was always present, scratching may have resulted in autoinoculation. The fact that a "mucosal-type" HPV, which was cloned from a cancer of the uterine cervix, was detected in a dysplastic periungual lesion seems noteworthy. Viral copy numbers appeared to be much higher in the periungual lesion, indicating that in our patient HPV-35 was able to replicate well outside the anogenital area. There are as yet insufficient data on the epidemiology of HPV-35 to conclude how common extragenital infection with HPV-35 is.

Adult↗
PubMed1989

A double-stranded RNA-inducible fish gene homologous to the murine influenza virus resistance gene Mx.

We cloned and sequenced a 2.35-kilobase EcoRI fragment of genomic DNA from a local freshwater fish (Perca fluviatilis) that strongly hybridized to probes derived from the murine influenza virus resistance gene Mx. The cloned fish DNA contained blocks of sequences related to Mx gene exons 3 to 8, which appeared to represent exons of a bona fide fish gene because they were separated by intron sequences flanked by consensus splice acceptor and donor sites. Injection of double-stranded RNA into the peritoneal cavity of trouts resulted in 5- to 10-fold elevated levels of two liver mRNAs of about 2.0 to 2.5 kilobases in length that hybridized to the cloned genomic DNA. High sequence similarity between this fish gene and the murine Mx gene, identical exon lengths, and similar inducibilities in vivo by double-stranded RNA indicate that we isolated a fragment of a fish Mx gene.

Amino Acid Sequence↗
PubMed1989

[Experience of valve replacement in 16 cases of heart enlargement].

From July 1985 to 1988 Feb. 16 patients with large heart (C-T ratio 65-85%) underwent valve replacements with mechanical valve. Isolated mitral valve replacement was performed in 15 cases and combined aortic and mitral valve replacement in 1. The valvular lesions was rheumatic in origin. The heart function (NYHA) was grade III in 5 cases (32.5%), and IV in 11 (67.5%), 60% of the cases were suffered from moderate or severe pulmonary hypertension. 1 patient died postoperatively. In the survivals the cardiac function was improved and the heart-size reduced distinctly. Some points about the operative results, selection of the time for operation and the postoperative management were discussed.

Adolescent↗
PubMed1989

[Surgical treatment of patient ductus arteriosus associated with pulmonary hypertension under cardiopulmonary bypass].

From July 1985 through December 1987, 30 patients with PDA and pulmonary hypertension were treated surgically under cardiopulmonary bypass. 17 cases underwent closure of PDA through transpulmonary arterial incision and 13 cases by ligation of PDA. The operative mortality was 3.3% and there was no late death. Follow-up study from 6 months to 3 years after operation showed satisfactory results.

Adolescent↗
PubMed1989

Treatment of esophageal achalasia (cardiospasm) with diaphragmatic graft. Twenty-five years' experience.

Long-term results are presented in 60 patients (4 to 50 years old) who underwent a diaphragmatic graft procedure for relief of cardiospasm (achalasia) from 1962 through 1987. The operative technique involves construction of a pedicle flap of diaphragm. The muscular defect on the lower segment of the esophagus and the transplanted diaphragmatic pedicle that is sutured to the defect must be the same size. Immediate operative results were good. Only one complication developed, a case of pneumonia that was cured. The patients were followed up from 11 months to 25 years. Two patients were lost to follow-up, 55 had excellent results, and three patients still had nausea and heartburn but were better than before the operation. This procedure has three advantages: (1) It prevents the development of fistulas and diverticula at the site of the esophageal muscular defect; (2) it effectively eliminates both restenosis resulting from scar tissue and reflux esophagitis; and (3) it allows the cardia to recover its normal function and the esophagus to return to normal size at the site of the operation.

Adolescent↗
PubMed1988

Japanese encephalitis virus live-attenuated vaccine, Chinese strain SA14-14-2; adaptation to primary canine kidney cell cultures and preparation of a vaccine for human use.

The Japanese encephalitis (JE) live-attenuated vaccine virus clone SA14-14-2 was adapted to grow in primary canine kidney (PCK) cell culture, and vaccine seeds and a first lot of vaccine were prepared in these cells. Characterization of the PCK-grown virus by various laboratory and animal tests indicated that passage in PCK did not result in detectable phenotypic or genome changes for this virus clone. Markers of attenuation included small plaque size, lack of intracerebral virulence for weanling mice, minimal neurovirulence for rhesus monkeys and a distinct nucleotide pattern compared to the parent SA14 non-attenuated virus. In addition, the seeds and vaccine were free of any detectable adventitious microbial agents that would render these materials unsafe for human immunization. Small-scale clinical trials of the JE SA14-14-2 PCK vaccine can now proceed to test the human safety of this product.

Animals↗