PubMed Health⌕ Search

Biomedical subjects

K Cao

Publications and source records attributed to K Cao.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Comparison of AutoSet with polysomnography in the diagnosis of sleep apnea syndrome].

OBJECTIVE: To evaluate the validation of the AutoSet system in the diagnosis of sleep apnea syndrome(SAS). METHODS: One hundred and twenty patients were studied simultaneously performed both with the AutoSet and the polysomnography(PSG). The apnea index(AI) and apneas + hypopneas index (AHI) were compared between the two methods by Bland and Altmen method. RESULTS: A significant correlation was found between the AHI assessed by the AutoSet and by the PSG (r = 0.92, P < 0.001). The respiratory irregularity index (RII) of the AutoSet was well correlated with the arousal index (Ai) from the PSG (r = 0.72, P < 0.001). The sensitivity and specificity of the AutoSet in diagnosing sleep apnea were 94% and 80% for AHI > or = 5/hour, 92% and 85% for AHI > or = 10/hour, 91% and 92% for AHI > or = 15/hour, 91% and 91% for AHI > or = 20/hour. CONCLUSIONS: The AutoSet system is a sensitive and valuable tool for identifying patients with sleep apnea and can make a diagnosis of sleep apnea for these patients with AHI > or = 30/hour, but has some limits especially for mild to moderate sleep apnea.

Adolescent↗
PubMed1999

[Vestibular potentials evoked by electrical stimulation].

OBJECTIVE: To identify the evoked potentials (VsEPs) by electrical stimulation were from vestibule. METHODS: The stimulating electrode was set on the round window of guinea pig. Constant current shocks of 0.05 ms (0.25-1.2 mA) were used to evoke VsEPs by means of vertex-pinna skin electrodes. RESULTS: These potentials were short latencies of (0.973 +/- 0.086) ms, (1.618 +/- 0.176) ms and (2.416 +/- 0.274) ms respectively, which reflected true potentials and were not from electrical stimulus artefacts. It was pure vestibular origin. As being masked with a continuous white noise (120 dB SPL) or removed ipsilateral auditory nerve, and even after facial neurectomy, waves were still existing, but disapeared after selective vestibular neurectomy. The twitching responses in the facial region had never been detected during the whole test. These potentials were bioelectric responses in the vestibular sensory pathway, characterized by threshold saturation, adaptability of excitation, dependent on intact vestibular nerve. CONCLUSIONS: We have set up animal model of recording VsEPs evoked by electrical stimulation on the round window of guinea pigs.

Animals↗
PubMed1999

[Rate discrimination and tone recognition in mandarin-speaking cochlear-implant listeners].

OBJECTIVE: To explore the relationship between the rate discrimination and the tone recognition with psychophysical method, and provide a basis for evaluating the results from mandarin-speaking cochlear implantees who used multi-channel cochlear implant and designing new speech coding strategies of the speech processor. METHODS: Four postlingually-deafened adults with cochlear implant participated in this study. We used the method of constant stimuli to measure the rate discrimination as a function of the standard rate at 50, 100, 200, 400 Hz on electrode pairs (E1, E3), (E7, E9), (E14, E16), and (E20, E22), respectively. We also measured tone recognition in 25 consonant-vowel syllables, each of which has four tonal variations, resulting in a total of 100 words. These words were recorded by a male talker and were presented five times each to the implant users via their speech processors. The tone recognition results were scored in overall percent correct and analyzed by error patterns in the confusion matrix and fundamental frequency. RESULTS: The rate discrimination thresholds, defined at the 75% correct level, varied greatly among individuals and ranged from several Hz to hundreds of Hz. A three-way ANOVA indicated significant effect (P < 0.05) on rate discrimination for the standard rate, electrode position, and patient variable. The tone recognition ranged from 40% to 80% and tones 1 and 3 were more easily identified than tones 2 and 4. Preliminary analysis using linear regression revealed highly significant correlation between rate discrimination and tone recognition. CONCLUSION: These results suggest that identification of tones relies on good rate discrimination in cochlear implant listeners. Clinical rehabilitation strategies in improving rate discrimination were discussed.

Adult↗
PubMed1998

Lack of anti-GOR antibody among subjects with GB virus C/hepatitis G virus RNA.

Homologies were sought between the putative amino acid sequences of GB virus C/hepatitis G virus (GBV-C/HGV) and the GOR epitope or the liver/kidney microsome-1 (LKM-1) epitope, which share partial sequence identity with the hepatitis C virus (HCV) polyprotein. Anti-GOR antibody (anti-GOR) was assayed among 100 subjects with GBV-C/HGV RNA. Twenty-one and 25 subjects were coinfected with hepatitis B virus (HBV) or HCV, respectively. Homologies were found between the NS5 or E2 polyproteins of GBV-C/HGV and the GOR epitope or the LKM-1 epitope, respectively. These segments of GBV-C/HGV polyproteins sharing identity with the GOR or the LKM-1 epitope were well conserved among three genotypes of GBV-C/HGV. However, only 1 of 55 subjects (1.8%) with GBV-C/HGV RNA, but not with HBV or HCV, was positive for anti-GOR. The positivity for anti-GOR among the group with GBV-C/HGV RNA alone was significantly lower than that among the groups with HCV RNA (P < 0.01 and P < 0.05, respectively). Only 2 of 55 subjects (3.6%) with GBV-C/HGV RNA alone exhibited elevation of alanine aminotransferase. The incidence of liver dysfunction among the group with GBV-C/HGV RNA alone was significantly lower than the incidence among the groups with GBV-C/HGV RNA and hepatitis B surface antigen (HBsAg) or HCV RNA (P< 0.01 and P< 0.01, respectively). These data indicate that 1) there is no association between GBV-C/HGV infection and the presence of anti-GOR, and 2) GBV-C/HGV infection is not related to chronic liver dysfunction.

Adult↗
PubMed1998

Mass spectrometric methods for distinguishing structural isomers of glutathione conjugates of estrone and estradiol.

Collisionally activated decompositions (CAD) of [M + H]+ ions from two sets (estrone and estradiol) of three isomeric glutathione (GSH) conjugates were studied by using five tandem mass spectrometric methods: (1) low energy (LE) CAD in an ion trap, (2) LE CAD in a triple quadrupole, (3) electrospray ionization (ESI)-source CAD in a tandem four sector, (4) high energy (HE) CAD of both ESI-produced and fast-atom bombardment (FAB)-produced ions in a tandem four-sector mass spectrometer, and (5) metastable-ion decompositions of FAB-produced ions. Four types of fragment ions are produced. The first type, formed from cleavage of the peptide backbone, gives rise to modified b2, modified y2, y2, and b1 ions. These fragments are observed with all the methods and show that the catechol estrogen attachment is at the cysteine moiety of the GSH. Internal fragment ions are the second type, and they also support that the modification is at cysteine. The third type involves fragmentation of the C-S bond to give an ion containing the steroid bonded to the sulfur. The fourth type of fragment ion is similar to the third but involves oxidation of the steroid ring and reduction of the GSH moiety; it is the most isomer specific of the four. The isomer-specific ions are of relatively low abundance in the product-ion spectra taken on the triple quadrupole and ion trap, but their abundances can be improved by increasing the collision energy. ESI source-CAD and the HE-CAD spectra of the isomers are the most distinctive because abundant product ions of all four types are seen in a single spectrum.

Estradiol↗
PubMed1998

Synthesis and structure elucidation of estrogen quinones conjugated with cysteine, N-acetylcysteine, and glutathione.

Catechol estrogen quinones (CE-Q) have been implicated as ultimate carcinogenic metabolites in estrogen-induced carcinogenesis. CE-Q may covalently bind to DNA to initiate cancer. These quinones can also be conjugated with glutathione, a reaction that prevents damage to DNA by CE-Q. The glutathione conjugates are then catabolized through mercapturic acid biosynthesis to cysteine and N-acetylcysteine conjugates. This may be the most important detoxification pathway of CE-Q. The chemical synthesis and characterization of these conjugates are the first essential steps to better understand their function in biological systems. Eighteen conjugates were synthesized by reaction of estrone-3,4-quinone (E1-3, 4-Q), estradiol-3,4-quinone (E2-3,4-Q), estrone-2,3-quinone (E1-2, 3-Q), or estradiol-2,3-quinone (E2-2,3-Q) with various sulfur nucleophiles, RSH, in which R is the cysteine, N-acetylcysteine, or glutathione moiety. Reactions of E1-3,4-Q and E2-3,4-Q produce regiospecifically 4-OHE1-2-SR and 4-OHE2-2-SR, respectively, in almost quantitative yield. E1-2,3-Q and E2-2,3-Q react regioselectively and quantitatively to form 2-OHE1(E2)-1-SR and 2-OHE1(E 2)-4-SR, in which the 1-isomers are always the major products. The ratio between 1 and 4 isomers is 3.5 for cysteine, 2.7 for N-acetylcysteine, and 2.5 for glutathione. The synthesized conjugates will be used as standards in the identification of these compounds formed in biological systems.

Acetylcysteine↗
PubMed1998

Covalent binding of catechol estrogens to glutathione catalyzed by horseradish peroxidase, lactoperoxidase, or rat liver microsomes.

Oxidation of catechol estrogens (CE) leads to the reactive electrophilic CE quinones. Reaction of CE-3,4-quinones with DNA has been implicated in tumor initiation. One pathway to prevent this reaction is conjugation of CE quinones with glutathione (GSH). Four CE, 4-hydroxy estrone (4-OHE1), 4-hydroxyestradiol (4-OHE2), 2-OHE1, and 2-OHE2, were conjugated with GSH after oxidation catalyzed by horseradish peroxidase (HRP), lactoperoxidase (LP), or rat liver microsomal cytochrome P450. This reaction is a free-radical chain autoxidation that produces very high yields of products. Six mono-GSH conjugates, 4-OHE1(E2)-2-SG, 2-OHE1(E2)-1-SG, and 2-OHE1(E2)-4-SG, and four di-GSH conjugates, 4-OHE1(E2)-1,2-bisSG and 2-OHE1(E2)-1,4-bisSG, were identified and quantified. These di-GSH conjugates were also obtained quantitatively from oxidation of mono-GSH conjugates by the same enzymes. HRP and LP gave very similar product profiles. Phenobarbital- and 3-methylcholanthrene-induced microsomes with either NADPH or cumene hydroperoxide as cofactor oxidized 4-OHE2 to form similar amounts of GSH conjugates. Enzymatic oxidation of 2-OHE1(E2) in the presence of GSH produced more 2-OHE1(E2)-4-SG than the 1-isomer. This contrasts with the direct reaction of E1(E2)-2,3-Q and GSH, in which the 1-isomer is formed more abundantly than the 4-isomer (Cao, K., Devanesan, P. D., Ramanathan, R., Gross, M. L., Rogan, E. G., and Cavalieri, E. L. (1998) Chem. Res. Toxicol. 11, 909-916). Competitive enzymatic oxidation of equimolar 4-OHE2 and 2-OHE2 in the presence of an equimolar amount of GSH yielded more 2-OHE2 conjugates than 4-OHE2 conjugates, despite E2-3,4-Q being more reactive with GSH than E2-2,3-Q. These results suggest that 2-OHE2 is a better substrate than 4-OHE2 in the catalytic oxidation to quinones, despite the greater reactivity of E2-3,4-Q, compared to E2-2,3-Q, with GSH.

Animals↗
PubMed1998

Major histocompatibility complex genotype is associated with disease progression and virus load levels in a cohort of human immunodeficiency virus type 1-infected Caucasians and African Americans.

To assess the influence of HLA on AIDS-free survival, human immunodeficiency virus load, and CD4 cell counts, 91 Caucasian and 48 African-American seroprevalent men were typed for HLA classes I and II and TAP alleles. HLA associations with these markers were assessed by assigning sum integer scores based on 7 class I allele-TAP variants (+1) and 13 class I-class II-TAP combinations (-1) with different AIDS-free survival times found in a prior study. Subjects in both racial groups and combined with positive sum scores were less likely to have CD4 cell decline (P=.0004), to have increased virus burden (P=.014), and to develop AIDS (P=.034) in the follow-up period than were Caucasians and African Americans with scores of 0 or -1. These results confirm the reported associations of specific major histocompatibility complex genes with AIDS-free survival time in Caucasians and specifically extend them to African Americans and to two established markers of disease progression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Typing of HLA-B*15 alleles using sequence-specific primers.

We have developed a DNA based typing method to detect 38 known B*15 alleles using sequence-specific primers (PCR-SSP). This method involves 38 primers and 39 PCR-SSP reactions with results that can be obtained in 3 hours. The method is easy, fast and suitable for clinical typing for bone marrow and organ transplantation. We have typed 106 HLA-B15 samples using this method. For homozygous HLA-B15 samples, some B*15 allele combinations need to be resolved by additional PCR reactions not included in this article. The method allows the detection of potential new alleles requiring sequencing for confirmation, and it is useful to resolve unusual serological reaction patterns for different HLA-B15 serological specificities. In addition, it could be used to resolve ambiguous PCR-SSOP typing results and for recognition of mismatches in serologically matched unrelated individuals.

Alleles↗
PubMed1998

The effect of octreotide on breathing and the ventilatory response to CO2 in conscious dogs.

It has been reported that injection of somatostatin into the brain-stem will lead to apnoea in animals. The aim of this study was to determine whether peripheral administration of octreotide, an analogue of somatostatin, could influence the control of breathing. We measured the tidal volume, respiratory rate and ventilatory response to CO2, before and after the intravenous injection of two dose levels of octreotide (0.1 mg and 0.5 mg) or saline in four conscious adult dogs. Injection of octreotide altered the breathing pattern with a mean decrease in the respiratory frequency of 23% (p<0.05) and an increase in the tidal volume by 16% (p<0.05), resulting in no net change in ventilation. The normal value of the ventilatory response to CO2 ranged between 1.0-3.2 L x min(-1) x mmHg(-1), with a minor variance within each dog but a significant difference amongst the four dogs (p<0.05). No significant change in the ventilatory response to CO2 was observed after octreotide. We conclude that intravenous octreotide alters the pattern of breathing but preserves minute ventilation; peripheral administration of octreotide does not influence the ventilatory response to CO2.

Animals↗
PubMed1998

[The effect of calcium ion in perilymphatic fluid on guinea pig's distortion product otoacoustic emissions].

OBJECTIVE: To study the mechanism of the production of distortion product otoacoustic emissions (DPOAE) by electromobility of out hair cell. METHODS: The changes of nine gninea pig's DPOAE by means of perfusion of artificial perilymphatic fluid with and without calcium ion were observed. RESULTS: The mean value of DPOAE decreased from 41.3 dB to 13.7 dB after perfusion of fluid devoid of calcium ion, it revived to 36.7 dB after reperfusion with normal perilymphatic fluid. The result supports Pickle's muscle theory for DPOAE's mobile mechanism and does not support Brownell's electromobility theory. CONCLUSION: A normal concentration of calcium ion in perilymphatic fluid is necessary for outer hair cell to produce DPOAE.

Animals↗
PubMed1998

[Spatial tuning curve recording in inferior colliculus during electrical stimulation of the cochlea].

OBJECTIVE: To explore the electrical activity mechanism of auditory center to intracochlear electrical stimulation and provide physiological foundation for spatial encoding of electrical stimulation in multiple channel cochlear implant. METHODS: The spatial tuning curves(STC) in the inferior colliculus(IC) to monopolar electrical stimulation, bipolar electrical stimulation and tone stimulation in cats were composed by using the single unit and the multi-units cluster recording method. RESULTS: The bipolar electrical stimulation excited the response in the specific region in IC, which was similar to the response induced by tone stimulation. The monopolar electrical stimulation excited an extensive response and could not provide the spatial encoding. CONCLUSION: Using the bipolar electrical stimulation, the stimulation region is the key point for improving the spatial encoding. The physiological results of spatial encoding of monopolar electrical stimulation contradicted the psychophysical conclusion and the clinical effect of CI patients. The explanation to this needs further studies.

Animals↗
PubMed1998

GB virus C/hepatitis G virus infection among patients with hepatocellular carcinoma in the inshore area of the Yangtze River, China.

To investigate the association between GB virus C/hepatitis G virus (GBV-C/HGV) infection and the development of hepatocellular carcinoma (HCC) in H city, in the inshore area of the Yangtze River, where high prevalence of HCC has been reported, we determined hepatitis B virus (HBV) and hepatitis C virus (HCV) markers, GBV-C/HGV-RNA and GBV-C/HGV E2 antibody (anti-HG E2) among 114 HCC patients and the same number of age- and sex-matched controls. There were no significant differences in the clinical and demographic characteristics between them, except for serum alanine aminotransferase level and history of liver diseases. There was a significant difference of hepatitis B virus surface antigen (HBsAg) prevalence between the HCC patients (75.4%) and the controls (20.2%; P<0.01). Hepatitis C virus antibody was detected in 4.4% of the HCC patients, compared with 1.7% of the controls. GB virus-C/HGV-RNA and anti-HG E2 were detected in 14.9 and 1.7% of the HCC patients, respectively, compared with 7.0 and 1.7% of the controls, respectively. Nucleotide sequences and molecular evolutionary analysis showed the strains of GBV-C/HGV-RNA were classified into genotype 2 and 3 (HG and ASIA type). An effect analysis showed an odds ratio (OR) for developing HCC from GBV-C/HGV infection among HBsAg-positive subjects was 14.9, with a 95% CI of 4.9-45.4. HBsAg infection alone was 13.83 (95% CI 7.4-25.9) and GBV-C/HGV infection alone, 3.74 (95% CI 1.1-13.1), respectively. These data indicate that HBV infection is considered to be one of the major risk factors in patients with HCC and although GBV-C/HGV infection was observed in both the HCC and the control groups, it might not play an important role in the development of HCC in this area.

Adult↗
PubMed1997

GB virus C/hepatitis G virus infection among Korean patients with liver diseases and general population.

GB virus C and hepatitis G virus (GBV-C/HGV) have been identified from the patients with acute or chronic liver diseases as possible agents of non-B, non-C hepatitis by two different groups, independently. To investigate whether GBV-C/HGV plays a role among Korean patients with liver diseases, GBV-C/HGV RNA were evaluated in 337 sera by the reverse transcription polymerase chain reaction (RT-PCR) using specific primers derived from 5'-noncoding region of GBV-C/HGV genome. GBV-C/HGV RNA was identified in 11/337 (3.3%). They consisted of 1/160 (0.6%) and 10/177 (3.3%) among the general population and patients with liver diseases, respectively (P < 0.01). Nucleotide sequences of all PCR amplicons were determined by the dideoxy chain termination method and analyzed by molecular evolutionary methods. The phylogenetic tree showed all sequences could be divided into three genotypes. These results indicate that: (1) GBV-C/HGV already exist in Korea; (2) GBV-C/HGV may play some role as an etiologic factor among the Korean patients with liver diseases; (3) GBV-C/HGV infection is rare among Korean general population; and (4) there are at least three different types of GBV-C/HGV in Korea.

Adolescent↗
PubMed1997

Prevalence of hepatitis C virus infection in Nanjing, southern China.

There is little information on the prevalence of hepatitis C virus (HCV) infection in China. The prevalence of HCV infection was determined in 998 subjects (398 with liver disease and 600 without) in the city of Nanjing in southern China. Subjects were tested for anti-HCV antibodies by a second generation assay. We also determined serological HCV genotypes and HCV RNA sequences. Among the 600 subjects without liver disease, 3 (0.5%) were seroreactive for anti-HCV. All were less than 12 years of age and had a history of transfusion. Of the 398 liver disease patients, 20 (5.0%) were seroreactive for anti-HCV. Of 16 patients in whom serological HCV genotype was determined, 10 (62.5%) were infected with HCV type 1, 5 (31.3%) with type 2 and 1 (6.3%) undetermined. HCV genomes sequenced from 2 patients belonged to genotype 2 and were closely related to strains in Beijing and Japan by molecular evolutionary analysis. These results suggest that HCV infection is rare and not a major cause of liver disease in southern China.

Adult↗