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Biomedical subjects

S Yang

Publications and source records attributed to S Yang.

At least 613 records · Page 34Linked to original sources
PubMed1991

Antigenicity of hantavirus nucleocapsid proteins expressed in E. coli.

DNA clones representing the small genomic segment of Nephropathia epidemica virus strain Hällnäs B1 (NEV) and Hantaan virus strain 76-118 (HTV) encoding their nucleocapsid proteins were inserted into the E. coli vector pIN-III-ompA for secretion of proteins into the periplasmic space. The complete HTV and NEV nucleocapsid proteins and two truncated versions of the NEV nucleocapsid proteins were expressed as fusion proteins. Unexpectedly, all products accumulated as insoluble aggregates. Most of the ompA signal peptide remained uncleaved. However, nucleocapsid fusion proteins could be purified from the insoluble fraction by extraction with 8 M urea followed by separation on SDS-PAGE and electroelution. Rabbits were immunized with the eluted proteins and the resulting antibodies reacted specifically with authentic viral nucleocapsid proteins of HTV and NEV. The recombinant nucleocapsid proteins were found to react specifically with various hantavirus-immune sera, but not with human control sera, indicating their suitability as potential diagnostic antigens. This is the first report on the expression of a protein of a NEV serotype strain of hantaviruses by use of recombinant DNA techniques.

Antigens, Viral↗
PubMed1991

An experimental study on the laryngeal electromyography and visual observations in varying types of surgical injuries to the unilateral recurrent laryngeal nerve in the neck.

A series of varying types of surgical injuries to the recurrent laryngeal nerve, including half section, double crush, suture ligation, and complete section of the nerve, was investigated in dogs by correlating clinical and electromyographic findings. The state of recovery from palsy was evaluated by recording the electromyography from the affected laryngeal muscles as well as by observing the movements of the vocal cords. Six electromyography patterns were recorded from the affected muscles following injuries to the recurrent laryngeal nerve. There is a close relationship between the electromyography patterns and the types of nerve injuries. Within 3 months after injuries of the recurrent laryngeal nerve, the electromyography motor unit potentials in the involved intrinsic laryngeal muscles and vocal cord movements on the side of the nerve injury were back to normal in the groups of dogs in which the recurrent laryngeal nerves were partially sectioned and doubly crushed; the electromyography potentials and vocal cord motion on the affected side did not return to normal in the group of dogs in which the recurrent laryngeal nerves were permanently ligated with suture. In the group of dogs which had had a complete section of the recurrent laryngeal nerve, no recovery of both electromyography and vocal cord function on the affected side was observed 6 months after injury of the recurrent laryngeal nerve. This study showed that the frequency of the regenerated potentials recorded from the affected muscles is related to the types and degrees of injuries to the recurrent laryngeal nerve. Recovery from recurrent laryngeal nerve palsy is complete within 3 months after nerve impairment if over half of the nerve fibers of the impaired nerve are maintained intact without degeneration. Moreover, the period from onset to complete recovery from palsy was remarkably short, less than 2 months. The most appropriate time for the electromyography examination to evaluate the degrees of the nerve injury and to anticipate the prognosis of recurrent laryngeal nerve palsy was proposed.

Animals↗
PubMed1991

[Model of stimulus train-induced bursting in rat hippocampal slice and the effect of L-glutamate on it].

A train of pulses (60 Hz, pulse duration 100 microseconds, train duration 2s, 2-3 fold maximal intensity) were applied to the CA3 stratum radiatum fiber pathway in rat hippocampal slices in vitro. Recordings of the field potentials were made from the stratum of CA3 pyramidal cells in response to these pulses so that the model of stimulus train-induced bursting (STIB) could be studied. It was a new and valuable model of epileptiform activity in hippocampal slices in vitro and the effect of L-glutamate (Glu) on STIB was also studied. Results showed that: 1. The number of train stimulus for a stable STIB averaged 5.5 +/- 2.1; the induced number of population spikes (PS) increased with an average in 5.2; and the STIB activity was long-last, persisting for up to 3-4 hours following the last train. 2. Superfusions of Glu in concentrations of 1, 2, and 3 mmol/L in hippocampal slices produced inhibition of STIB in CA3, but the first antidromic PS was unaffected, suggesting the site of inhibition is postsynaptic. The mechanisms related to the genesis of STIB and its inhibition by superfusion of Glu were discussed.

Animals↗
PubMed1991

[Effect of sodium valproate on bicuculline-induced epileptiform activity in rat hippocampal slices in vitro].

Experiments were conducted on the rat hippocampal slices in vitro with the superfusion of bicuculline (Bcl, 10 mumol/L) and stimulation of Schaffer collaterals by single pulse to produce epileptiform activity of the pyramidal cells in CA1 area. In these experiments the effect of constant microinjection of sodium valproate onto the surface of slice on the epileptiform activity was studied. The results showed that the valproate, in concentration of 20, 30, 50 and 100 mmol/L, inhibited the Bcl-induced epileptiform activity in a manner of dose-dependence. It was deduced that the inhibition of epileptiform activity by the valproate is possibly related to the recovery of and increase in the inhibition mediated by GABAergic neurons and may be also to the non-synaptic mechanism of the valproate in rat hippocampus.

Animals↗
PubMed1991

[Study on morbidity and relative factors of postmenopausal osteoporosis in 340 women in Chengdu].

In this cross-sectional study, the radius bone mineral content (BMC) of 340 postmenopausal women (mean age: 53; mean years since menopause: 5.56) were assessed by single photon absorptiometry (SPA) for determining prevalence rate of postmenopausal osteoporosis in Chengdu, and some factors relative to BMC were investigated. Eighty-five of 340 postmenopausal women were diagnosed osteoporosis by SPA. The prevalence rate, which increases with year since menopause and age, is 25%. There is significant increase in prevalence after the age of 60 years or 5 years since menopause. Sixteen factors were analysed by STEPWISE REGRESSION. The variables selected were serum calcium(SCa), serum alkaline phosphatase (SAkP), urine calcium (UCa), urine hydroxypoline (UH), age, and Para. Fisher DISCRIMINANT ANALYSIS was used for diagnosis with these variables, the accuracy of diagnosis being 75.2%. Our study showed that postmenopausal osteoporosis is a common disease in Chengdu. High SCa, UH, age and low SAkP level may be risk factors of osteoporosis.

Adult↗
PubMed1991

[Determination of tetramethylpyrazine in traditional Chinese medicines by high performance liquid chromatography].

This paper reports a method for determining tetramethyl pyrazine in pilules, injections and extracts of Ligusticum chuanxiong by high performance liquid chromatography. The results showed the recovery rate to be higher than 97% and the coefficient of variation (CV) to be 1.39% (with in day) and 1.51% (day to day). The lowest detection amount was 0.005 micrograms. The method was easy, fast and accurate.

Chromatography, High Pressure Liquid↗
PubMed1991

[Studies on the thermostable L-lactate dehydrogenase from thermophilic bacteria].

About 200 strains of extreme thermophilic bacteria were isolated from hot springs in Guandong province. A strain, HG25, was found to produce thermostable intracellular L-lactate dehydrogenase (EC. 1.1.1.27). It has the characteristic of Thermus sp. The cells were gram-negative, non-sporulating, nonmotile, aerobic rods containing yellow pigment. The optimum temperature for growth was between 65 degrees C to 75 degrees C, the maximum 85 degrees C, and minimum 40 degrees C. The generation time at the optimum was about 80 min. Starch was not hydrolyzed. Acid was not produced from glucose. The G+C content in DNA was 62-65 mol% (Tm). As the properties of strain HG25 is similar to those of Thermus aquaticus and T. thermophilus HB 8 belonging to the genus Thermus. The thermostable L-lactate dehydrogenase was partially purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. For pyruvate reduction, the optimum temperature of the enzyme was 60 degrees C and pH 8.0. After incubation in 0.1 mol/L phosphate buffer pH 7.4 at 70 degrees C for 10 min, the enzyme retained about 85% of its original activity. The half-live time (t1/2) at 85 degrees C was 10 min.

L-Lactate Dehydrogenase↗
PubMed1991

[Vasoactive intestinal peptide (VIP) concentration in ischemic rat brain microvessels].

UNLABELLED: VIP is extensively localized in the brain, spinal cord and peripheral neurons, and is especially rich in the nerves innervating the cerebral vasculature. VIP is a potent vasodilator of cerebral vessels. The aim of this study was to investigate VIP contents in brain microvessels and their changes during incomplete brain ischemia. METHODS: (1) Bilateral carotid artery ligation was performed in Wistar rats under urethane anesthesia to produce cerebral ischemia, which was further aggravated by bleeding to hypotension with a mean arterial pressure of 50-60 mmHg. At 5, 15 and 30 min after ligation, the rats were decapitated to obtain brain tissue. A sham surgery group served as controls. In some rats cerebral ischemia was confirmed by EEG. (2) Brain microvessels were prepared by brain homogenization in HEPES-Ringer buffer and gradient centrifugation in 30% BSA, followed by filtration through a glass bead column. (3) VIP contents were determined by radioimmunoassay. The results were that VIP contents of 30 min ischemic rats were significantly higher than in the controls (P less than 0.01). VIP contents of cerebral microvessels were also measured in two groups of gerbils. It was found that VIP contents in ischemic gerbils were significantly higher than in the controls (P less than 0.01). These results indicate that: (1) VIP is present in rat and gerbil brain microvessels. (2) During brain injury by ischemia, the increase in VIP content in cerebral microvessels may induce vasodilation and cause an increase in cerebral blood flow. This may well be an autoregulatory response to protect the ischemic brain and may have important pathophysiological implications.

Animals↗
PubMed1991

Contrast sensitivity in amblyopia.

Contrast sensitivity function (CSF) for sinusoid gratings of varying spatial frequencies was determined for each eye of 21 cases with unilateral amblyopia. The CSF of all amblyopic eyes, except one, showed reduced sensitivity when compared with the non-amblyopic eye of the same person. The curve showed reduction more significantly at middle and high spatial frequencies. The cut-off frequency was shifted toward lower spatial frequencies. The relationship between CSF and various degree of amblyopia was also discussed.

Adolescent↗
PubMed1991

Relationship between corneal dellen and tearfilm breakup time.

The BUT of 51 strabismus patients were measured before and after operation. The average pre-op BUT was 28.75 seconds (10.96"-91.80"). The post-op BUT in all operated eyes were reduced significantly, no matter what procedures had been performed and whether dellen appeared or not (P < 0.01). The BUT in the group complicated dellen reduced from 23.22" (pre-op) to 8.61" (post-op). The incidence of dellen was 22.54% in this study. The incidence of dellen after rectus resection procedure (47.75%) was much higher than that after rectus recession (5.13%) (P < 0.01). This study showed that dellen was closely related to the BUT and occurred more often in the eyes on which resection procedure was performed. It is considered that excessive lacrimation and elevation of the bulbar conjunctiva near the limbus may disturb the stability of the precornea tearfilm and cause the tearfilm break up earlier. Local corneal dehydration and dellen formation may be caused by reduced BUT. The incidence of dellen after operation may be higher if the cornea was carefully observed.

Corneal Diseases↗
PubMed1991

[Intermittent exotropia associated with accommodative esotropia].

Intermittent exotropia associated with accommodative esotropia is a rare particular type of strabismus. 8 cases of XT-ET were presented here. The clinical features of them were summarized as follows: 1. The age of onset was early. 2. The initial symptom was esotropia, exotropia was observed by doctor. 3. The most patients (6/8) associated high or medium hyperopia. 4. The AC/A rate were normal or lower than normal. 5. The angle of deviation varied with the examination, exotropia 30 degrees-15 degrees<-->orthophoria<-->esotropia 15 degrees-30 degrees. 6. The esotropia can be corrected with spectacles. The visual-vestibular interaction examination for eye movement were examined in 3 cases, but have no regular expression yet. Finally, the incidence (0.4%, 8/21 58) and treatment for this disease were discussed.

Accommodation, Ocular↗