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Biomedical subjects

Y Shi

Publications and source records attributed to Y Shi.

At least 667 records · Page 37Linked to original sources
PubMed1990

A comparison of maximum length and Legendre sequences for the derivation of brain-stem auditory-evoked responses at rapid rates of stimulation.

Experiments were performed in which brain-stem auditory-evoked responses (BAERs) were elicited by two types of pseudorandom pulse trains: maximum length sequences (MLS) and Legendre sequences (LGS). In experiment 1, each pulse sequence was presented at 50 dB nHL with minimum pulse intervals varying from 1 to 10 ms. Wave V latency increased and wave V amplitude decreased with decreasing minimum pulse intervals, with no significant effect of the type of sequence (MLS vs LGS), and no significant interaction between sequence and minimum pulse interval in terms of wave V amplitude or latency. In a second experiment, the minimum pulse interval was held constant at 4 ms, while MLS and LGS levels were varied from 20 to 60 dB nHL. With increasing click intensity, there is a decrease in wave V latency and an increase in wave V amplitude. There was no significant effect of type of sequence (LGS vs MLS) or interaction between type of sequence and stimulus intensity for wave V amplitude or latency. Despite the obvious violation of the assumptions (linearity and stationarity) underlying the application of maximum length sequence analysis and Legendre sequence analysis, both techniques produced reliable responses remarkably similar in morphology to evoked responses obtained by conventional averaging. The results of these experiments support the possibility that analysis methods based on pseudorandom pulse sequences may prove more efficient in data collection and provide a more thorough description of the electrophysiologic behavior of the auditory system compared to conventional averaging.

Adult↗
PubMed1990

Brain-stem auditory-evoked responses elicited by maximum length sequences: effect of simultaneous masking noise.

The effects of masking noise on wave V of the brain-stem auditory-evoked response (BAER) obtained to pseudorandom pulse sequences are evaluated in two experiments. In the first experiment, the level of broadband noise was covaried with minimum pulse interval (rate) using maximum length sequence analysis (MLSA). Both increasing noise level and decreasing minimum pulse interval decrease wave V amplitude and increase wave V latency. A nonadditivity of rate and noise level was observed such that, at the shortest interpulse intervals, simultaneous background noise produced virtually no latency change and minimal amplitude change, for the noise levels tested. In a second experiment, high-pass masking was performed to assess the feasibility of derived-band techniques using maximum length sequence analysis (MLSA) and to compare the frequency regions responsible for the BAER using MLSA versus conventional averaging. Results of experiment 2 showed that reliable responses across high-pass masker cutoff frequency could be obtained in normal-hearing listeners. The frequency specificity of the MLSA-based responses was nearly identical to that obtained by conventional averaging, although both amplitude and latency of wave V were affected by the high-pass masker cutoff and minimum pulse interval values. These studies suggest that the neuronal populations and frequency regions responsible for the BAER are virtually the same for MLSA and conventional averaging.

Adult↗
PubMed1990

[Effects of Ligusticum wallichii on the plasma and CSF levels of dynorphin A1-13 in rabbits under acute experimental cerebral ischemia].

By occluding the bilateral carotid arteries of rabbits to produce bilateral partial cerebral ischemia, and by using radioimmunoassays to measure the levels of dynorphin A1-13 like immunoreactivity (ir-Dyn A1-13) in plasma and cerebrospinal fluid (CSF), the authors find that the levels of ir-Dyn A1-13 in plasma and CSF have significantly increased (P less than 0.01) after cerebral ischemia appears. The result of the Ligusticum wallichii Franch (Ligusticum) pretreatment to the test-group shows a definite improvement of the changes of ir-Dyn A1-13 levels in plasma and CSF. The severity of brain ischemic damage and neurologic dysfunction in Ligusticum-treated animals is lighter than that of saline-treated group, too. In this study, some new approaches are explored to explain the pathophysiology of cerebral ischemia and the mechanisms by which Ligusticum prevents and treats cerebral ischemia.

Animals↗
PubMed1990

Pernicious anemia and type A atrophic gastritis in the Chinese.

Pernicious anemia has been considered a rare disease among the Chinese. But in recent years, by wide-spread use of gastroscopy, more cases of Type A atrophic gastritis associated with pernicious anemia have been discovered. Among 28 patients with Type A atrophic gastritis, we had identified 20 cases of pernicious anemia, 18 in frank form and 2 in latent form. This paper presented the results of our studies on clinical, endoscopic, and laboratory examinations of these patients. The findings suggest that pernicious anemia was not so rare among the Chinese. If we keep an alertness on this disease, more such cases could be diagnosed.

Adult↗
PubMed1990

Preliminary observations on the phenotypes of lymphoid cells in mycosis fungoides using anti-human-thymocyte monoclonal antibodies.

The phenotypes of lymphoid cells from twelve patients with mycosis fungoides (including 5 patients in the tumor stage and 7 in the pretumor stage) were determined immunohistochemically using anti-thymocyte monoclonal antibodies (HIT1, HIT2, and Leu 6). The results showed significant differences between the numbers of HIT1 and HIT2 positive cells in tumor and pretumor stage lesions, indicating that these two monoclonal antibodies may be of help in the staging of mycosis fungoides and in making a prognosis. Also, we found that some Leu 6 (+) cells in tumor stage lesions were round or oval in shape without dendritic processes, suggesting that they may be immature lymphocytes.

ADP-ribosyl Cyclase↗
PubMed1990

[A prevalence survey to gonorrhea in Jilin].

369 suspecious patients with gonorrhea from 6 general hospitals in Jilin between June and December, 1987, were examined clinically and bacteriologically. Gonococcus was found in 332 of 369 cases(90% positive rate) from their externalia excreta by Gram-staining technique. The period prevalence rate of gonorrhea was estimated at 27.8/100,000, ie, 332 from 1,199,445, the average population in Jilin, derived from Jilin Public Security Bureau. The population distribution survey to the patients shows more males than females, more married than unmarried, and more workers, salesmen, drivers and than others. Most of them received a middle-degree education. The cases were found mainly during July, August, and September. The result implies that gonorrhea trends to prevail in Jilin.

Adolescent↗
PubMed1989

Subfamily of submaxillary gland-specific Mup genes: chromosomal linkage and sequence comparison with liver-specific Mup genes.

Mouse major urinary proteins (MUPs) are encoded by a family of ca. 35 genes that are expressed in a tissue-specific manner in several secretory organs; in the liver, in the submaxillary, sublingual, parotid and lachrymal glands, and in the skin sebaceous glands. In this paper we describe the isolation of a Mup gene, Mup-1.5a, which is expressed predominantly in the submaxillary gland of BALB/c mice. We show that Mup-1.5a is a member of a subfamily consisting of two closely related genes, both of which are closely linked to the Mup-1 locus on mouse chromosome 4. Mup-1 is the locus of a class of Mup genes (Group 1) expressed in the liver. The complete nucleotide sequence of Mup-1.5a has been determined, and was compared to a previously sequenced Group 1 Mup gene. The comparison shows that the differentially expressed Mup genes are uniformly divergent in exons, introns and in their flanking sequences. The regions of homology extend at least 5 kb into the 5' flanking region of Mup genes.

Animals↗
PubMed1989

Silent genes in the mouse major urinary protein gene family.

To date, two classes of mouse major urinary protein (MUP)-encoding genes have been described, the expressed genes and the intervening-sequence-containing pseudogenes. The data presented in this paper define a third class, the silent Mup genes, which are potentially functional but appear not to be expressed under normal circumstances. We describe a MUP subfamily (Mup-1.5) containing two genes, Mup-1.5a and Mup-1.5b, that are nearly identical, differing at only three positions (greater than 99.9% identity) over the entire 4-kilobase (kb) transcription unit and approximately 1 kb of flanking DNA. The similarity between these two genes extends over greater than 35 kb. Using specific oligonucleotides, we have shown that the 5a gene is expressed in BALB/cByJ mice, primarily in the submaxillary gland, whereas the 5b gene is not expressed. However, we found that when a 9.4-kb DNA fragment containing the Mup-1.5b gene was introduced into the mouse germ line, mice in two of the four transgenic lines expressed this gene at a high level and with the tissue-specificity characteristic of the Mup-1.5a gene. These results suggest that the inactivity of the endogenous Mup-1.5b gene is due not to a lack of functional positive regulatory elements, but to long-range, inhibitory position effects.

Animals↗
PubMed1989

Adeno-associated virus P5 promoter contains an adenovirus E1A-inducible element and a binding site for the major late transcription factor.

Activity of the adeno-associated virus P5 transcriptional control region was found to be induced by adenovirus E1A gene products. A pair of adjacent sequence elements was found to mediate both basal and E1A-induced P5 activity. The first element is a binding site for the major late transcription factor (MLTF), a factor first identified on the basis of its binding to a specific sequence within the adenovirus major late promoter. The second element is a tandemly repeated 10-base-pair sequence whose relationship to previously described binding sites is unclear. Each element individually conferred E1A responsiveness on a heterologous promoter, and deletion analysis demonstrated that each contributed to the level of P5 activity in the presence of E1A products both in transfection- and infection-based assays. Although deletion of the MLTF binding site led to reduced P5 transcriptional activity in the presence of E1A proteins, the deletion generated enhanced P5 basal activity in the absence of the transcriptional activator. The negative effect of the MLTF binding site in the absence of activator and its positive effect in the presence of activator combine to enhance the magnitude of the response by the P5 control region to E1A gene products.

Adenovirus Early Proteins↗
PubMed1989

[Evoked otoacoustic emissions from normal-hearing young Chinese].

Evoked otoacoustic emissions (EOAE) were recorded in normal-hearing young Chinese. Incidences and thresholds of EOAE responses, interaural threshold differences and latencies were calculated. The results were compared with other reports in the literature. The average threshold of EOAEs evoked by 1 kHz bone-conducted tone-burst stimuli was found about 4.43 dB below the subjective thresholds for the stimuli. This result is quite different from that reported by Rossi in 1988. The cause of the result is yet not clear.

Acoustic Stimulation↗
PubMed1989

Effects of culture medium composition and temperature on hepatitis B surface antigen expression by recombinant yeast in fermentation processes.

Hepatitis B surface antigen (HBsAg, an exogenous protein) was produced by fermenting recombinant Saccharomyces cerevisiae containing the HBsAg gene. The relative HBsAg concentrations increased from 3.89 to 8.12 when glucose content was reduced and the culture medium was supplemented with glycerol and sucrose; specific activity also increased by a factor of 2.69. The temperature variation sequence for fermentation processes was established from experimental results. The amount of HBsAg gene expressed reached 13.51 in relative concentration terms. The stability of the recombinant plasmid containing the HBsAg gene was studied by the varying fermentation temperatures in a fed-batch process. There was a conversion activity distribution for the yeast containing the exogenous DNA, which affected HBsAg production by the genetically engineered yeast in fermentation processes.

Cloning, Molecular↗
PubMed1987

Expression of six mouse major urinary protein genes in the mammary, parotid, sublingual, submaxillary, and lachrymal glands and in the liver.

Mouse major urinary proteins (MUPs) are encoded by a family of about 35 to 40 highly conserved genes. In the preceding paper (K. Shahan, M. Gilmartin, and E. Derman, Mol. Cell. Biol. 7:1938-1946, 1987), we presented the sequences of the most abundant MUP mRNAs in the liver (MUP I, II, and III) and in the lachrymal (MUP IV) and submaxillary (MUP V) glands. We have shown that these five mRNAs are coded by five distinct genes, MUP I through V. In the present communication, we examine the expression of MUP genes in all of the six tissues in which MUP mRNAs are synthesized, the mammary, parotid, sublingual, lachrymal, and submaxillary glands and the liver. We show that gene MUP II is expressed in the liver and in the mammary gland, that gene MUP IV is expressed in the lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal glands. Furthermore, we present evidence that in addition to genes MUP I through V, another gene, MUP VI, is expressed in BALB/c mice in the parotid gland. The tissue-specific synthesis of MUP mRNAs is thus brought about by two major mechanisms: the expression, in different tissues, of different members of the family and the expression of a single gene at various levels in different tissues. When a particular MUP gene is expressed in several tissues, transcripts of this gene initiate at the same site and are spliced and polyadenylated in the same manner.

Age Factors↗
PubMed1987

Campylobacter-like organisms in chronic gastritis, peptic ulcer, and gastric carcinoma.

Biopsy samples were taken from the gastric mucosa of 209 patients endoscoped for dyspepsia symptoms. Campylobacter-like organisms (CLOs) were cultured from 74 of 179 (41.4%) cases and seen in sections from 110 of 209 (52.6%) cases and in smears from 119 of 209 (56.9%) cases; totally, 145 of 209 cases were positive, giving a rate of 69.4%. CLOs were positive in 45 of the 57 (78.9%) patients with superficial gastritis, in 52 of the 64 (81.3%) with atrophic gastritis, in 18 of the 21 (85.7%) with gastric ulcer, in 12 of the 14 (85.7%) with duodenal ulcer, and in 8 of the 10 (80.0%) with stump gastritis, whereas only a few CLOs were found in 3 of the 15 (20.0%) histologically normal subjects and in 7 of the 28 (25.0%) patients with gastric carcinoma. The organisms seem to live more frequently in diseased mucosa and are chiefly recognized through their characteristic morphology and habitat. A significant association between the presence of CLOs and chronic gastritis or peptic ulcer disease was noted, and the positive rate and the number of CLOs correlated highly with the activity of chronic gastritis. No such correlation was observed in gastric carcinoma. These findings support the view that CLOs may be etiologically related to chronic gastritis and peptic ulceration, even though their precise role still remains to be determined.

Adult↗
PubMed1986

Thermostability of double-stranded deoxyribonucleic acids: effects of covalent additions of a psoralen.

We have carried out a thermodynamic study on the effects of covalent additions of the psoralen derivative HMT, 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen, on the stability of double-stranded deoxyoligonucleotides. This was done with two systems. The first was a double-stranded DNA formed by two non-self-complementary oligonucleotides, 5'-GAAGCTACGAGC-3' and 5'-GCTCGTAGCTTC-3', where we site specifically placed an HMT molecule on the thymidine residue in oligonucleotide 5'-GAAGCTACGAGC-3' as either a furan-side monoadduct or a pyrone-side monoadduct. The second was a double-stranded DNA formed by a self-complementary oligonucleotide, 5'-GGGTACCC-3', where we placed an HMT molecule on the thymidine residue of each strand as a furan-side monoadduct or cross-linked the two strands with an HMT molecule linked to the two thymidines. We found that HMT cross-linking of the two strands stabilizes the double helix formed by 5'-GGGTACCC-3', as one might expect. Less predictable results were that the monoaddition of a psoralen stabilizes the double helix formed by the two non-self-complementary oligonucleotides by as much as 1.3 kcal/mol as a furan-side monoadduct and 0.7 kcal/mol as a pyrone-side monoadduct at 25 degrees C in 50 mM NaCl. In contrast, the monoaddition of a psoralen on each of the two thymidines in the double helix formed by 5'-GGGTACCC-3' destabilizes the helix by 1.8 kcal/mol at 25 degrees C in 1 M NaCl. This destabilization arises from an unfavorable enthalpy change (8.6 kcal/mol) and a favorable entropy change (23 cal/K X mol) due to the two HMT molecules at the centers of each strand.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗