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Biomedical subjects

Y Cai

Publications and source records attributed to Y Cai.

At least 19 recordsLinked to original sources
PubMed1992

Rat pulmonary lipoxygenase: dioxygenase activity and role in xenobiotic metabolism.

1. Dioxygenase activity and the ability of pregnant rat lung lipoxygenase to oxidize xenobiotics were examined in vitro under a variety of experimental conditions. 2. More than 90% of the dioxygenase activity towards linoleic acid in the lung homogenate was found to be associated with the cytosolic fraction. The cytosolic enzyme exhibited pH optima at 6.5 and 9.5, the activity being two-fold greater at pH 9.5. To observe maximal dioxygenase activity (about 0.7 mumol of 13-hydroperoxylinoleic acid formed/min per mg protein) at pH 9.5, the presence of 6.0 mM linoleic acid was required. 3. Benzidine oxidation occurred at maximal rate of pH 6.5 when the reaction medium contained 1.0 mM benzidine and 13.5 mM linoleic acid. All eight xenobiotics tested were oxidized at significant rates by the lung cytosolic lipoxygenase. 4. Both dioxygenase activity and benzidine oxidation were inhibited by the inhibitors of lipoxygenase, viz. nordihydroguaiaretic acid, BHT, caffeic acid, esculetin, and gossypol, in a concentration-dependent manner. 5. The results suggest that oxidation of xenobiotics by lipoxygenase may be an important pathway of metabolism in the mammalian lung.

Animals↗
PubMed1992

Incidence of insulin-dependent diabetes mellitus in Colorado.

We examined the incidence of insulin-dependent diabetes mellitus in children 0-17 years of age in Colorado from 1978 to 1988. Cases were ascertained from a statewide registry based on physician surveillance. A total of 1,376 children were diagnosed during this interval in a population averaging 860,000 children. The degree of ascertainment was estimated to be 93.3%. The age-adjusted incidence rate of insulin-dependent diabetes mellitus was 14.8/100,000 person-years. The rate was lower in individuals of Spanish origin (Hispanics) (8.7/100,000 person-years) compared with non-Hispanic individuals (15.5/100,000 person-years) (incidence rate ratio = 0.6, 95% confidence interval = 0.4-0.8). Incidence rates were higher in winter and lower in summer for children 5-17 years old. Children diagnosed before the age of 5 years showed no significant seasonal pattern, although peak incidences were observed in autumn and spring. No temporal trend in diabetes incidence was observed overall or by ethnic group. The increasing insulin-dependent diabetes incidence reported by registries in Europe during this time period was not observed in Colorado.

Adolescent↗
PubMed1992

Synthesis of nitrogenase in mutants of the cyanobacterium Anabaena sp. strain PCC 7120 affected in heterocyst development or metabolism.

Mutants of Anabaena sp. strain PCC 7120 that are incapable of sustained growth with air as the sole source of nitrogen were generated by using Tn5-derived transposons. Nitrogenase was expressed only in mutants that showed obvious morphological signs of heterocyst differentiation. Even under rigorously anaerobic conditions, nitrogenase was not synthesized in filaments that were unable to develop heterocysts. These results suggest that competence to synthesize nitrogenase requires a process that leads to an early stage of visible heterocyst development and are consistent with the idea that synthesis of nitrogenase is under developmental control (J. Elhai and C. P. Wolk, EMBO J. 9:3379-3388, 1990). We isolated mutants in which differentiation was arrested at an intermediate stage of heterocyst formation, suggesting that differentiation proceeds in stages; those mutants, as well as mutants with aberrant heterocyst envelopes and a mutant with defective respiration, expressed active nitrogenase under anaerobic conditions only. These results support the idea that the heterocyst envelope and heterocyst respiration are required for protection of nitrogenase from inactivation by oxygen. In the presence of air, such mutants contained less nitrogenase than under anaerobic conditions, and the Fe-protein was present in a posttranslationally modified inactive form. We conclude that internal partial oxygen pressure sufficient to inactivate nitrogenase is insufficient to repress synthesis of the enzyme completely. Among mutants with an apparently intact heterocyst envelope and normal respiration, three had virtually undetectable levels of dinitrogenase reductase under all conditions employed. However, three others expressed oxygen-sensitive nitrogenase activity, suggesting that respiration and barrier to diffusion of gases may not suffice for oxygen protection of nitrogenase in these mutants; two of these mutants reduced acetylene to ethylene and ethane.

Anabaena↗
PubMed1992

Smokers with IDDM experience excess morbidity. The Colorado IDDM Registry.

OBJECTIVE--To determine whether there is an association between smoking and the self-reported morbidity of people with IDDM and to evaluate the nature of a possible interaction between smoking and IDDM in increasing the risk of morbidity among smokers with IDDM. RESEARCH DESIGN AND METHODS--Subjects were non-Hispanic whites aged 18-28 yr who participated in the Colorado IDDM Registry Follow-up Survey (case subjects, n = 24) or the 1985 NHIS (control subjects, n = 5876). Assessments of self-reported morbidity included any hospitalization in the past year; bed days, sick days, and limited-activity days in the past 2 wk; and ratings of poor health. The criteria outlined by Saracci were used to determine whether smoking was associated with greater morbidity among IDDM case compared to control subjects (smoking by IDDM interaction). RESULTS--Age- and sex-adjusted ORs, estimated from logistic regression, showed that people with IDDM reported excess morbidity compared with control subjects, regardless of smoking status. Smokers with IDDM reported morbidity 3-10 times as often as nonsmoking control subjects and were 2-3 times more likely to report morbidity than nonsmokers with IDDM. The smoking by IDDM interaction was more than multiplicative for all morbidity measures. Fifty to 75% of excess morbidity in young smokers with IDDM over simple additive effects was related to the interaction between smoking and IDDM. CONCLUSIONS--There was excess reported morbidity among people with IDDM who smoked, greater than that expected from the combined effects of smoking and IDDM. Smoking cessation in young people with IDDM may alleviate some of this excess, but more study is needed to determine whether smoking serves as an indicator of poor IDDM care practices or has a physiological impact that compounds the morbidity experienced by people with IDDM.

Adult↗
PubMed1992

[Flow cytometric analysis of surface antigens on liquid nitrogen-stored cells].

A high non-specific fluorescence background imposes serious interference on a flow cytometer in surface antigen assay for those cells stored in liquid nitrogen. The non-specific fluorescence comes from dead and dying cells, the permeability of whose membrane has been increased so that the fluorescence reagent can enter into the cells. To solve this problem, liquid nitrogen-stored PBMNC and Raji cells were screened on different gatings for surface antigen stained with fluorescence. It was observed that the high fluorescence background as well as debris can be gated out by means of gating on FALS, angle 90 degrees angle and PRFL. As a result, the percentage of surface antigen positive cells determined was close to that assayed in fresh samples.

Antigens, Surface↗
PubMed1992

Age-associated enhancement of diquat-induced lipid peroxidation and cytotoxicity in isolated rat hepatocytes.

The effect of age on the toxicity of diquat, a redox cycling compound, was investigated in hepatocytes isolated from mature (6 months) and old (24-29 months) male Fischer 344 rats. Hepatocytes of old rats were more sensitive than those of mature rats to diquat-induced cytotoxicity (lactate dehydrogenase release into the medium). Cell death was preceded by glutathione disappearance, and rates of glutathione depletion were similar in mature and old hepatocytes. In contrast, diquat-induced formation of thiobarbituric acid-reactive substances was much greater in the hepatocytes from old rats, suggesting that increased lipid peroxidation caused the enhanced cytotoxicity. Further experiments revealed that: 1) hepatocytes of mature and old rats were equally sensitive to iron-induced lipid peroxidation; 2) diquat-stimulated production of superoxide anion radical in liver microsomes did not increase with age, but decreased 43%; 3) superoxide dismutase activity was similar in hepatocytes of mature and old rats; 4) inhibition of catalase activity (which diminishes with age in male rats) did not increase diquat toxicity; and 5) malondialdehyde disappearance in intact hepatocytes decreased (33%) with age, but the toxicological significance of the decline in metabolism was uncertain. Thus, the results demonstrated that diquat-induced lipid peroxidation and cytotoxicity increase with age in male rat hepatocytes, but the enhanced sensitivity to diquat poisoning remains unexplained.

Aging↗
PubMed1992

[ELISA of serum isoferritin and its clinical application].

Serum isoferritin levels were detected by ELISA in 96 normal, 11 cases of hepatocellular carcinoma (HCC), 28 breast cancer (BC), 31 lung cancer (LC), 26 breast fibroma, 11 pneumonia and 11 tuberculosis. The results reveal significant differences of serum isoferritin levels between the normals and the patients, and between the malignant cases and benign cases (P < 0.01). Serum isoferritin demonstrates higher sensitivity in detecting HCC, LC and BC and thus is of great value in the differential diagnosis of these cancers.

Adult↗
PubMed1992

[Synthesis and cloning of the whole human erythropoietin (EPO) gene].

A 600 bp synthetic erythropoietin (EPO) gene encoding all 166 amino acids of the EPO protein and 27 amino acids of the signal peptide has been constructed. The whole gene was divided into three large fragments consisting of a total of 32 oligonucleotides. These oligonucleotides were synthesized by the solid-phase phosphor-amidite method and ligated into three large fragments. These latter three were separately cloned into vector M13mp19 and then transformed into E. coli JM 103. Positive clones were screened with 32P-labeled probes. The sequences of the fragments were confirmed by DNA sequencing, and the sequence of the whole synthetic EPO gene was confirmed by enzymatic digestion and sequencing. The results indicated that the nucleotide sequence of the synthetic EPO gene is identical to that of the original.

Cloning, Molecular↗
PubMed1992

[A 12-year clinical experience of cardiac valve replacement with domestic tilting disc valve prostheses in 1013 cases].

1013 patients with cardiac valve replacement during a 12-year period from 1978 to 1990 were reported. 566 cases were implanted with Shanghai-made tilting disc valve prostheses and 447 with Lanzhou-made (C-L valves). Mitral valve replacement (MVR) in 753 patients, aortic valve replacement (AVR) in 102 and double valves replacement (DVR) in 158. The overall early mortality rate was 6.2% with 4.9%, 7.8% and 11.3% after MVR, AVR and DVR respectively. Follow-up study was made in 3097.43 patient-year (mean 3.26 years). The late death rate was 1.6% patient-years and with 1.4, 1.8 and 3.2 after MVR, AVR and DVR respectively. The incidence of late valve-related complication (% patient-years) were: thromboembolism 0.39, anticoagulant-related hemorrhages 0.77, prostheses failure 0.22, prosthetic valve endocarditis 0.38, periprosthetic leak 0.12, and reoperations 0.38. The domestic tilting disc valve prostheses are considered to be qualified valves with low mortality and satisfactory results.

Adolescent↗
PubMed1992

The relationship between the changes in plasma atrial natriuretic peptide and renin angiotensin contents and hemodynamics in pulmonary hypertensive rats.

Pulmonary artery pressure (PAP) increased significantly in rats after hypobaric hypoxic exposure for 15 days (CH15) (P less than 0.001) and was maintained at the same level after prolonged hypoxic exposure for 40 days (CH40). There were no significant changes in carotid systolic and diastolic blood pressure in CH15 and CH40 rats. The contractility of the right and left ventricles of CH15 and CH40 rats showed no difference as compared with the control group. Plasma atrial natriuretic peptide (ANP) content in CH40 rats was obviously increased (P less than 0.001), while angiotensin II (AII) dropped markedly (P less than 0.05). Plasma renin activity was increased in both hypoxic groups (P less than 0.05 respectively). These results indicate that during chronic hypoxia, plasma ANP and the renin-angiotensin system (RAS) play an important role in the modulation of pulmonary as well as systemic hemodynamics. They may work cooperatively to limit the development of pulmonary hypertension and to maintain systemic blood pressure within the normal range.

Angiotensin II↗
PubMed1992

[Use of Cox's model in long-term survival analysis of cerebrovascular disease].

A long-term survival study on 885 cases of cerebrovascular disease was carried out. The results showed that after follow-up for 3, 5, and 8 years, the survival rates were 86.98%, 75.70% and 64.26% respectively, and all were lower obviously than that of the general population in the same district. The results of Cox's model analysis showed that recurrence, hypertension and age were the risk factors influencing the long-term survival of cerebrovascular disease, and the relative risks were 3.29, 2.17 and 1.65 respectively.

Adult↗
PubMed1992

A strategy for isolating differentiation-inducing complementary DNAs from human esophageal cancer cell line treated with retinoic acid.

Treatment of the human esophageal cancer cell line EC8712 with retinoic acid (RA) stopped the cell growth significantly and gave rise to terminal differentiation of the cells characterized by increased expression of involucrin gene. Two cDNA libraries were constructed from the parental and RA-treated cells respectively. Repeated subtractive hybridization of single-stranded plasmid DNA prepared from pooled colonies of cDNA library of the parental cells with cDNA probe generated from the RA-treated cells exhausted sequences common to both libraries of the cell. The unhybridized cDNA probe represented, therefore, the genes activated after RA-treatment. By using these enriched cDNAs as probe to screen the cDNA library constructed from the RA-treated cells thirty-nine positive colonies were obtained, of which two were specifically due to RA-induction. One of these two cDNA clones, designated as pRA538, has undergone further analysis and shown differentiation-inducing effect on parental cancer cells. A novel strategy for cloning genes involved in terminal differentiation of cancer cells is developed.

Carcinoma, Squamous Cell↗
PubMed1992

[Long-term prognosis following cerebrovascular disease].

A follow-up study on 885 cases of cerebrovascular disease who survived acute stage and were registered through prevalence survey in 1983, had been carried out for 5-8.5 years. The results shown that 34.58% died, 34.13% were independent and 31.29% needed help in various degrees. The older the age was, the worse the prognosis was. After 3, 5 and 8 years, the survival rates of the cases were 86.98%, 75.70% and 64.26% respectively, and all were lower than that in general population. The difference of survival rates between the ischemic cases and the hemorrhagic cases was not found.

Adult↗
PubMed1991

Chronic ethanol consumption depresses hypothalamic-pituitary-adrenal function in aged rats.

In separate experiments, nine (n = 20) and fifteen (n = 12) month old rats were treated with either 6% ethanol or 12% sucrose (to balance caloric intake) in the drinking water to examine the effect of chronic ethanol consumption on the hypothalamic-pituitary-adrenal axis of aged rats. Rats were maintained on these treatment regimens for thirty days and were killed by decapitation. Blood was collected and plasma concentrations of adrenocorticotropin (ACTH) and corticosterone were determined by radioimmunoassay. Adrenal glands were cleaned, quartered and used to test in vitro responsiveness to ACTH. Anterior pituitary glands from all 15 month old rats and one half of the nine month old rats were collected, frozen and extracted for measurement of tissue ACTH concentration. The remaining anterior pituitary glands from the nine month old rats were challenged with corticotropin releasing hormone (CRH) to test in vitro responsiveness. In nine month old rats, chronic ethanol consumption decreased plasma ACTH and corticosterone (P less than 0.05). Pituitary ACTH concentrations were unchanged in treated nine month old rats, but the amount of pituitary ACTH released in response to CRH was decreased (P less than 0.05) in rats consuming ethanol. In vitro responsiveness of the adrenal gland to ACTH in nine month old rats consuming ethanol was unchanged (P greater than 0.05). Plasma ACTH and corticosterone concentrations were also decreased in 15 month old rats chronically consuming ethanol (P less than 0.05). No differences were noted in responsiveness of the adrenal gland or in the amount of pituitary ACTH due to ethanol consumption in 15 month old rats (P greater than 0.05). The results of these experiments indicate that chronic ethanol consumption decreases hypothalamic-pituitary-adrenal function in aged rats.

Adrenocorticotropic Hormone↗
PubMed1991

Pathological changes of hyperphonated cat vocal folds.

To investigate the pathological changes of hyperphonated vocal folds 15 cats were used and over-cry was induced by mechanical stimuli. The longest experiment time was 15 weeks. All of the larynges were taken and the vocal folds were examined grossly and microscopically. The results were as follows: 1) liquid exudate accumulation beneath the epithelium developed in all of the experimental animals; 2) thickening of the epithelium was noticed in cats which had hyperphonated for more than 4 weeks; 3) acute laryngitis occurred in three cats.

Acute Disease↗
PubMed1991

Characterization of insertion sequence IS892 and related elements from the cyanobacterium Anabaena sp. strain PCC 7120.

IS892, one of the several insertion sequence (IS) elements discovered in Anabaena sp. strain PCC 7120 (Y. Cai and C. P. Wolk, J. Bacteriol. 172:3138-3145, 1990), is 1,675 bp with 24-bp near-perfect inverted terminal repeats and has two open reading frames (ORFs) that could code for proteins of 233 and 137 amino acids. Upon insertion into target sites, this IS generates an 8-bp directly repeated target duplication. A 32-bp sequence in the region between ORF1 and ORF2 is similar to the sequence of the inverted termini. Similar inverted repeats are found within each of those three segments, and the sequences of these repeats bear some similarity to the 11-bp direct repeats flanking the 11-kb insertion interrupting the nifD gene of this strain (J. W. Golden, S. J. Robinson, and R. Haselkorn, Nature [London] 314:419-423, 1985). A sequence similar to that of a binding site for the Escherichia coli integration host factor is found about 120 bp from the left end of IS892. Partial nucleotide sequences of active IS elements IS892N and IS892T, members of the IS892 family from the same Anabaena strain, were shown to be very similar to the sequence of IS892.

Amino Acid Sequence↗
PubMed1991

Characterization of the IS895 family of insertion sequences from the cyanobacterium Anabaena sp. strain PCC 7120.

A family of repetitive elements from the cyanobacterium Anabaena sp. strain PCC 7120 was identified through the proximity of one element to the psbAI gene. Four members of this seven-member family were isolated and shown to have structures characteristic of bacterial insertion sequences. Each element is approximately 1,200 bp in length, is delimited by a 30-bp inverted repeat, and contains two open reading frames in tandem on the same DNA strand. The four copies differ from each other by small insertions or deletions, some of which alter the open reading frames. By using a system designed to trap insertion elements, one of the elements, denoted IS895, was shown to be mobile. The target site was not duplicated upon insertion of the element. Two other filamentous cyanobacterial strains were also found to contain sequences homologous to IS895.

Amino Acid Sequence↗