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Biomedical subjects

Z C Li

Publications and source records attributed to Z C Li.

At least 19 recordsLinked to original sources
PubMed1996

Effects of beta cell granule components on human islet amyloid polypeptide fibril formation.

Formation of amyloid-like fibrils in a solution of human islet amyloid polypeptide (hIAPP) with and without the presence of other beta-cell granule components was studied in vitro. Insulin at less than equimolar concentration strongly inhibited hIAPP fibrillogenesis. Proinsulin had a weaker inhibitory effect while C-peptide, Ca2+ and Zn2+ each individually enhanced fibril formation. C-peptide combined with Ca2+ had an inhibitory effect. Since IAPP was found almost exclusively in the halo fractions of isolated islet secretory granules, primarily the concentrations of C-peptide, Ca2+ and possibly proinsulin may be crucial for the native state of IAPP. It is concluded that an imbalance between fibril formation enhancers and inhibitors may be of importance in the pathogenesis of amyloid in the islets of Langerhans.

Amyloid↗
PubMed1996

Dietary cholesterol feeding suppresses human cholesterol synthesis measured by deuterium incorporation and urinary mevalonic acid levels.

The objective of this study was to measure the response of cholesterol biosynthesis in subjects to three different amounts of dietary cholesterol: 50 (low), 350 (medium), and 650 (high) mg cholesterol per 2800 kcal. Individuals with low (n = 7), normal (n = 12), and elevated (n = 11) plasma cholesterol concentrations consumed in random order solid-food test diets (15%, 55%, and 30% of energy as protein, carbohydrate, and fat, respectively) at each dietary cholesterol level. The three diets were consumed for 4 weeks each, and each dietary phase was separated by a 4-week washout period. During the final week of each diet, 0.7 g D2O was given per kilogram of body water and deuterium incorporation into the erythrocyte cholesterol pool was measured for 24 hours. Urinary mevalonate levels were also determined in samples obtained during two consecutive 24-hour periods. Both techniques provided measurements of whole-body cholesterol biosynthesis. In all subjects the cholesterol synthesis rate as measured by deuterium incorporation was significantly lower (P < .05) after the transition from low- to medium- and low- to high-cholesterol diets. Urinary mevalonate excretion decreased after the change from the medium- to high- (P < .05) and low- to high- (P < .01) cholesterol diets. Although correspondence between the two methods was poor, they both indicated some suppression of cholesterol synthesis by dietary cholesterol. The response of cholesterogenesis to different amounts of dietary cholesterol was related to the rate of synthesis under depressed conditions of the low-cholesterol diet. These findings indicate modest downregulation of synthesis in response to dietary cholesterol in humans, independent of plasma cholesterol levels.

Adult↗
PubMed1994

The measurement of DNA content in Wilms' tumor and its clinical significance.

DNA content analysis with paraffin-embedded tissue was performed by flow cytometry on extracted nuclei from 42 Wilms' tumors. DNA histograms showed diploid in 13, tetraploid in 12, and aneuploid in 17. The frequency of DNA aneuploid was 40.48%. The 2- and 5-year survival rates were 84% and 75.16%, respectively, for patients with the DNA diploid pattern; the 2- and 5-year DNA aneuploid survival rates were 47.06% and 41.18% (P < .03 and P < .05), respectively. The 2- and 5-year survival rates for DNA tetraploid were in between, both 55.90%. For patients with stage I and II, the difference in the 2- and 5-year survival rates between DNA diploid plus tetraploid and DNA aneuploid was even more significant (P < .004 and P < .002, respectively). Thus, DNA aneuploid is an important indicator of poor prognosis in Wilms' tumor, especially for stages I and II.

Child↗
PubMed1994

Comparative study on mortality patterns in Japan and China.

On the basis of the 1990 Chinese death notice data and 1990 Japanese populations vital statistical materials, the mortality patterns and proportions of individual causes of death in the two countries were compared. In both sexes, the mortality rates were the highest in almost all age groups in Chinese rural areas followed by urban areas and Japan. In Japan and in Chinese urban areas, malignant neoplasms cardiovascular diseases and cerebrovascular diseases were the major causes of death, with these three making up about 60% of the total. In Chinese rural areas, these three conditions were responsible for 43% of all deaths, a considerably lower figure as compared to those in the other two areas, and the mortality rates for infectious diseases and accident/suicide were higher than those in the other two areas. Of the three major adult diseases, cerebrovascular diseases were found to be especially frequent in both Chinese urban and rural areas. On the other hand, ischemic heart disease was found at comparable levels in Japan and China and the rate was lower than in other developed countries. Site-specific mortality rates for malignant neoplasms were characterized by high rates for lung, liver and esophageal cancers in China. The mortality rates for bronchitis in both Chinese urban and rural areas were markedly higher than those in Japan These differences in mortality rates and proportions of individual causes of death between China and Japan are thought to be attributable to the differences in medical services and the level of risk factors for each disease.

Adolescent↗
PubMed1993

Human cholesterol synthesis measurement using deuterated water. Theoretical and procedural considerations.

Human cholesterogenesis is measurable as the rate of incorporation of deuterium derived from deuterium oxide (D2O) within the body water pool into plasma or erythrocyte cholesterol pools. Oral D2O equilibrates across body water, thus enabling extracellular sampling of pools (such as urine) to serve as accurate indicators of intracellular deuterium enrichments at the point of synthesis. Required doses of D2O fall below the threshold associated with negative side effects. Deuterium/carbon incorporation ratios into cholesterol during biosynthesis have been established that are applicable in humans. Models using unconstrained and constrained curve fitting permit improved flexibility in interpretation of deuterium-uptake kinetics. However, sample-size restrictions presently limit the ability of the technique to examine the kinetics within individual lipoprotein species. Correction of enrichment data for proton exchange during combustion and reduction phases of sample preparation is an additional important procedural concern. In summary, the deuterated-water procedure is a useful tool in studies of human cholesterol synthesis that offers the advantages of short measurement interval, relative noninvasiveness, and provision of a direct index of synthesis in comparison with other available techniques.

Animals↗
PubMed1993

[Experimental study on the action of EDTA-liposome to remove mercury from the mice given methylmercury chloride].

It was reported that experimental study on the action of EDTA-Liposome to remove mercury from the mice given methylmercury chloride showed that elimination of methylmercury chloride from brain, testicle, liver, kidney and blood of mice treated by EDTA-Liposome was more significant than that of mice treated by EDTA alone. Mercury level in feces of EDTA-Liposome treated group increased significantly (P < 0.001). The advantages of treatment with EDTA-Liposome were discussed. Applying EDTA-Liposome is an efficient method in therapy of metal poisoning.

Animals↗
PubMed1992

Structural determinants in substrate recognition by proton-amino acid symports in plasma membrane vesicles isolated from sugar beet leaves.

Amino acids are actively transported across the plasma membrane of plant cells by proton-coupled symports. Previously, we identified four amino acid symports in isolated plasma membrane vesicles, including two porters for the neutral amino acids. Here we investigated the effect of amino acid analogues on neutral amino acid transport to identify structural features that are important in molecular recognition by Neutral System I (isoleucine) and Neutral System II (alanine and leucine). D-Isomers of alanine and isoleucine were not effective transport antagonists of the L-isomers. These data are characteristic of stereospecificity and suggest that the positional relationship between the alpha-amino and carboxyl groups is an important parameter in substrate recognition. This conclusion was supported by the observation that beta-alanine and analogues with methylation at the alpha-carbon, at the carboxyl group, or at the alpha-amino group were not effective transport inhibitors. Specific binding reactions were also implicated in these experiments because substitution of the alpha-amino group with a space filling methyl or hydroxyl group eliminated transport inhibition. In contrast, analogues with various substitutions at the distal end of the amino acid were potent antagonists. Moreover, the relative activity of several analogues was influenced by the location of sidechain branches and Neutral Systems I and II were resolved based on differential sensitivity to branching at the beta-carbon. The kinetics of azaserine and p-nitrophenylalanine inhibition of leucine transport were competitive. We conclude that the binding site for the carboxyl end of the amino acid is a well-defined space that is characterized by compact, asymmetric positional relationships and specific ligand interactions. Although the molecular interactions associated with the distal portion of the amino acid were less restrictive, this component of the enzyme-substrate complex is also important in substrate recognition because the neutral amino acid symports are able to discriminate between specific neutral amino acids and exclude the acidic and basic amino acids.

Alanine↗
PubMed1989

[A study on the retreatment of pulmonary tuberculosis by the addition of 654-2].

654-2 plus chemotherapy were used to retreat TB. After a full course of treatment, rates of negative sputum in the observation group and in the control group were 90.6% and 68.8% respectively (The difference in the rates was statistically significant P less than 0.05). The total rate of focus in the observation group was 46.9% and that in the control group was 21.9%. The difference was striking (P less than 0.05). The general efficacy for cavity alteration in the observation group was 42.3% and in control group was 16.0%. Comparing the two groups, there was an obvious difference (P less than 0.05). After ceasing medication, no relapse was observed through a period of one year in the treated group.

Adolescent↗
PubMed1988

Pial arteriolar vessel diameter and CO2 reactivity during prolonged hyperventilation in the rabbit.

Hyperventilation reduces intracranial pressure (ICP) acutely through vasoconstriction, but its long-term effect on vessel diameter is unknown. In seven rabbits with a cranial window implanted 3 weeks earlier, the effect of prolonged hyperventilation on vessel diameter was studied. Anesthesia was maintained for 54 hours with a pentobarbital drip (1 mg/kg/hr). The pH, CO2, and HCO3- levels were measured in arterial blood and cisterna magna cerebrospinal fluid (CSF). The diameter of 31 pial arterioles was measured with an image splitter. After baseline measurements, pCO2 was reduced from 38 to 25 mm Hg and allowed to return to 38 mm Hg for 10 minutes every 4 hours. There was an initial vasoconstriction of 13%, which progressively diminished by 3% every 4 hours. Thus, by the 20th hour, vessel diameters at a pCO2 of 25 mm Hg had returned to slightly above baseline values obtained at a pCO2 of 38 mm Hg. The temporary return of pCO2 to 38 mm Hg every 4 hours caused vasodilation: 12% at 4 hours, gradually increasing to 16% at 52 hours. Thus, at 52 hours, the vessel diameters were 105% of baseline at a pCO2 of 25 mm Hg and increased to 122% at a pCO2 of 38 mm Hg. Arterial pH had returned to baseline at 20 hours, and CSF pH had returned at 24 hours. Bicarbonate in blood and CSF remained decreased throughout the experiments. In three control experiments during which normocapnia was maintained, vessel diameter and pH and bicarbonate levels remained unaltered over the same period. The CO2 reactivity, tested by brief periods of hyperventilation every 4 hours, also did not change. These results indicate that hyperventilation is effective in reducing cerebral blood volume for less than 24 hours and that it should be used only during actual ICP elevations. If used preventively, its effect may have worn off by the time ICP starts to rise for other reasons, and further decreases in pCO2 cannot be obtained. Moreover, the reduction in buffer capacity with lower bicarbonate renders the vessels more sensitive to changes in PaCO2. This could lead to more pronounced elevations in ICP during transient rises in PaCO2, such as during endotracheal suctioning in head-injured patients.

Animals↗
PubMed1985

Successful separation of xiphoomphalopagus twins.

A pair of female xiphoomphalopagus twins were delivered by Caesarean section at 35th week of gestation on March 2, 1982, their combined weight being 4,800 g. Examinations revealed that they were conjoined from the xiphoid process down to the umbilicus. Infant A also had congenital heart defect (VSD). X-ray and echography showed that they had a fused liver and two independent biliary systems and alimentary tracts. After 6 weeks, the twins gained weight up to 7,000 g. The separation operation was performed at 1 1/2 months of age. During operation it was demonstrated that the xiphoid process and costal cartilages were fused together and the peritoneal cavities were of free communication above the umbilicus, and the livers merged into a single common liver. The large single liver was divided by electrocautery, resulting in a section surface of 8 X 7.5 cm. After separation, the closure of the abdominal wall in both infants presented some difficulties which were resolved by making relaxation incisions on either flanks. In the post operative period, the ventral wounds of both infants were disrupted for several centimetres and infant B had wound infection. The granulating area of skin defect on either relaxation incision of the flanks and ventral denuded wound were covered with full-thickness dead-foetus homografts. The wounds were well healed. Eventually both infants were discharged in good condition at 2 1/2 months after operation. Now they live well at 2 1/2 years of age.

Cesarean Section↗