Biomedical subjects

R Zhang

Publications and source records attributed to R Zhang.

At least 73 records · Page 4Linked to original sources

PubMed2001

Immunohistochemical and in situ hybridization studies of gonadotropin releasing hormone (GnRH) and its receptor in rat digestive tract.

GnRH(LH-RH) is first discovered in the hypothalamus and found to have a role in regulation of reproduction. With the study on it deepening, GnRH was demonnstrated that it also exists in a number of organs beyond the hypothalamus and acts on extrapituitary organs. To study whether digestive tract synthesizes GnRH and its receptor and, if it does, by what cells. In the experiment, the locallizations of GnRH and its receptors in rat digestive tract were studied using immunohistochemistry and in situ hybridization. The parietal cells of gastric gland, the villous and glandular epithelium in small and large intestine and parasympathetic ganglion cells of myenteric plexus showed GnRH immunoreactivity; GnRH mRNA hybridization signal was detected. The epithelium of gastric pit and the cells above in digestive tract showed GnRH receptor immunoreactivity; GnRH receptor mRNA hybridization signal was detected. The immunoreactive and signal materials distributed in cytoplasm of all positive cells, with nuclei being immunonegative and with no hybridization signal. These results suggested that the digestive tract can produce GnRH and express GnRH receptor; GnRH may also be a gastrointestinal hormone.

Animals↗

PubMed2001

Poly-L-proline type II peptide mimics based on the 3-azabicyclo[3.1.0]hexane system.

This paper describes conformational studies of proline-templated amino acids (PTAAs) based on the 3-azabicyclo[3.1.0]hexane system as well as conformational studies on short peptides composed of these PTAAs. NOE data, coupling constants, and molecular modeling are consistent with a flattened boat conformation for monomeric and oligomeric residues based on this bicyclic system. NMR studies on dimeric and trimeric oligomers are consistent with a populated poly-L-proline type II conformation in CDCl3 and D2O. Solution studies and molecular modeling predicts phi approximately -70 degrees, psi approximately 131 degrees, chi 1 approximately -57 degrees, and chi 2 approximately -158 degrees for oligomeric residues.

Bridged Bicyclo Compounds, Heterocyclic↗

PubMed2001

Engineering new bone tissue in vitro on highly porous poly(alpha-hydroxyl acids)/hydroxyapatite composite scaffolds.

Engineering new bone tissue with cells and a synthetic extracellular matrix (scaffolding) represents a new approach for the regeneration of mineralized tissues compared with the transplantation of bone (autografts or allografts). In the present work, highly porous poly(L-lactic acid) (PLLA) and PLLA/hydroxyapatite (HAP) composite scaffolds were prepared with a thermally induced phase separation technique. The scaffolds were seeded with osteoblastic cells and cultured in vitro. In the pure PLLA scaffolds, the osteoblasts attached primarily on the outer surface of the polymer. In contrast, the osteoblasts penetrated deep into the PLLA/HAP scaffolds and were uniformly distributed. The osteoblast survival percentage in the PLLA/HAP scaffolds was superior to that in the PLLA scaffolds. The osteoblasts proliferated in both types of the scaffolds, but the cell number was always higher in the PLLA/HAP composite scaffolds during 6 weeks of in vitro cultivation. Bone-specific markers (mRNAs encoding bone sialoprotein and osteocalcin) were expressed more abundantly in the PLLA/HAP composite scaffolds than in the PLLA scaffolds. The new tissue increased continuously in the PLLA/HAP composite scaffolds, whereas new tissue formed only near the surface of pure PLLA scaffolds. These results demonstrate that HAP imparts osteoconductivity and the highly porous PLLA/HAP composite scaffolds are superior to pure PLLA scaffolds for bone tissue engineering.

3T3 Cells↗

PubMed2001

A nitric oxide donor induces neurogenesis and reduces functional deficits after stroke in rats.

The adult rodent brain is capable of generating neuronal progenitor cells in the subventricular zone, and in the dentate gyrus of the hippocampus, throughout the life of the animal. Signals that regulate progenitor cell proliferation, differentiation, and migration are not well known. We report that administration of a nitric oxide donor, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) aminio]diazen-1-ium-1,2-diolate (DETA/NONOate), to young adult rats significantly increases cell proliferation and migration in the subventricular zone and the dentate gyrus. Treatment with DETA/ NONOate also increases neurogenesis in the dentate gyrus. Furthermore, administration of DETA/NONOate to rats subjected to embolic middle cerebral artery occlusion significantly increases cell proliferation and migration in the subventricular zone and the dentate gyrus, and these rats exhibit significant improvements of neurological outcome during recovery from ischemic stroke. Administration of DETA/NONOate significantly increases cortical levels of guanosine monophosphate both in ischemic and nonischemic rats, supporting the role of nitric oxide in promoting cell proliferation and neurogenesis. Thus, our data indicate that nitric oxide is involved in the regulation of progenitor cells and neurogenesis in the adult brain. This suggests that nitric oxide delivered to the brain well after stroke may have therapeutic benefits.

Animals↗

PubMed2001

Determination of Danshensu, a major active compound of Radix Salvia miltiorrhiza in dog plasma by HPLC with fluorescence detection.

A simple and sensitive high performance liquid chromatography method has been developed for the determination of Danshensu (3, 4-dihydroxyphenyllactic acid) in dog plasma. Plasma samples were extracted with ethyl acetate. Analysis of the extracts was performed on a reversed-phase column with an aqueous phosphate buffer-acetonitrile (93:7, v/v) mobile phase, and 4-hydroxybenzoic acid was used as the internal standard. Fluorescence detection at 285 nm (excitation) and 320 nm (emission) was employed. Standard curves were linear in the range from 0.125 to 11.3 microg/mL (regression coefficient r > 0.993) on three different days. Mean recovery was determined as 96.4% by analysis of plasma standard containing 0.63, 5.65 and 11.3 microg/mL of Danshensu. The inter-day precision (RSD) ranged from 3.4 to 8.6% at concentrations of 0.125, 1.88, 6.28 and 11.3 microg/mL, and the intra-day precision was better than 7.2%. The detection and quantitation limits were 0.063 and 0.125 microg/mL, respectively. This validated assay was applied to the determination of Danshensu concentration in dog plasma after oral administration of Radix Salvia miltiorrhiza extracts.

Administration, Oral↗

PubMed2001

Expression and purification of extracellular penicillin G acylase in Bacillus subtilis.

Penicillin G acylase (PGA) is one of the most important enzymes for the production of semisynthetic beta-lactam antibiotics and their key intermediates. To enhance its expression, the PGA gene from Bacillus megaterium was amplified by PCR and subcloned into an expression vector under the control of the P43 promoter. The resulting construct was transferred into Bacillus subtilis WB600 and the transformant producing the most PGA was selected and designated SIBAS205. In contrast to the parent cells, which have to be induced by phenylacetic acid and cultured at 28 and 25 degrees C successively to produce PGA, the recombinant cells needed neither induction nor thermoregulation during fermentation at 37 degrees C. PGA was secreted and reached an expression level of 40 U/mL under optimized conditions. The enzyme was separated by centrifugation and purified by Al(2)O(3) adsorption and phenyl-Sepharose CL-4B hydrophobic chromatography with a yield of 85%. The purified enzyme had a specific activity of 45 U/mg protein.

Bacillus megaterium↗

PubMed2001

Results of surgical resection of patients with primary lung cancer: a retrospective analysis of 1,905 cases.

BACKGROUND: Surgical resection, combined therapies, and lymphadenectomy are extensively utilized in the treatment of patients with lung cancer. In the present study, we summarized the clinical data of patients with primary lung cancer after surgical resection alone or combined with adjuvant therapy, and evaluate the main factors influencing long-term survival. METHODS: A retrospective review of 1,905 consecutive patients with primary lung cancer treated at the Cancer Institute of the Chinese Academy of Medical Sciences from March 1961 through December 1995 was performed. Statistical analysis was done using STATA software. The survival rate was estimated using the life-table method. Survival differences were performed using the log-rank test. The modified 1997 TNM staging system was used. RESULTS: There was a 12.28% morbidity rate and a 1.31% hospital mortality in our series. The 5-year survival rate for the complete resection was 49.5% and for the palliative resection 18.8% (p < 0.01). The 5-year survival rate was 72.0% in stage IA and 61.0% in stage IB (p < 0.05), 32.9% in stage IIA and 34.5% in stage IIB, 22.6% in stage IIIA and 15.9% in stage IIIB (p < 0.05), and 7.1% in stage IV. CONCLUSIONS: Multiple factors influence the long-term survival of patients with primary lung cancer after surgery. They include TNM staging, the extent of surgical resection (complete or palliative), resection margin (positive or negative), pathologic type of tumors, and type of resection.

Adult↗

PubMed2001

Prediction of programmed-temperature retention values of naphthas by wavelet neural networks.

The wavelet neural network (WNN) was used to predict the programmed-temperature retention values of naphthas. In WNN, a Morlet mother wavelet was used as a transfer function, and the convergence speed was faster than other neural networks. Sixty-four compounds (selected randomly from 94) were used as a training set, and the 30 remaining compounds were used as a test set. A very satisfactory result was obtained only after about 8000 training epochs. The other two methods, the artificial neural network (ANN) and the Simpson integral method, were also used for this study. The comparison of results obtained from three methods showed that the WNN is the most suitable tool in predicting programmed-temperature retention values of naphthas, consequently this method can be used to provide reliable data for the petrochemical industry.

Journal Article↗

PubMed2001

Prediction of enthalpy of alkanes by the use of radial basis function neural networks.

A new method for the prediction of enthalpy of alkanes between C6 and C10 from molecular structures has been proposed. Thirty five calculated descriptors were selected for the description of molecular structures. The first four scores of Principle Component Analysis on the calculated descriptors were used as inputs to predict the enthalpy of alkanes. Models relating relationships between molecular structure descriptors and enthalpy of alkanes were constructed by means of radial basis function neural networks. To get the best prediction results, some strategies were also employed to optimise the learning parameters of the radial basis function neural networks. For the test set, a predictive correlation coefficient of R = 0.9913 and root mean squared error of 0.5876 were obtained.

Journal Article↗

PubMed2001

Quantitative (stereological) study of placental structures in women with pregnancy iron-deficiency anemia.

OBJECTIVE: To determine the compensatory morphometric changes of placental structures in cases of maternal iron-deficiency anemia. METHODS: Placentas were obtained from a random sample of 26 full-term pregnant women, and methacrylate-embedded vertical sections were utilized to estimate parameters of placental structures with stereological methods. Materials were divided into three groups based on maternal hemoglobin levels: anemic (hemoglobin<100g/l), intermediate and non-anemic (hemoglobin>or=110g/l). RESULTS: Placental volume and absolute volume of the intervillous space or the chorionic villi per placenta significantly increased in the anemic group. There was a significant negative correlation between maternal hemoglobin level and absolute volume or surface area of the intervillous space or the villi. No significant difference, however, was found between the groups in the volume fraction or surface density of placental structures. CONCLUSION: Placental hypertrophy was associated with mild and moderate degree of maternal iron-deficiency anemia and the enlargement of placenta appeared to be a uniform (proportional) physiological compensatory growth.

Adult↗

PubMed2001

Compositional changes of cottonseed hull substrate during P. ostreatus growth and the effects on the feeding value of the spent substrate.

The dry matter and composition of cottonseed hull substrate for P. ostreatus cultivation were tested at different growth stages. As protein, cellulose, hemicellulose and lignin were used by P. ostreatus, the compositional profiles of the substrate were changed greatly, but their rates of change varied at different growing stages. The increase of protein content and the reduction of lignocellulose content contributed to the increase in the dry matter digestibility of the spent substrate, making it possibly acceptable as a potential ruminant feed. This could provide an alternative to environmentally sound use of P. ostreatus spent substrate.

Animal Feed↗

PubMed2001

Synthesis and quantitative structure-activity relationships of new 2,5-disubstituted-1,3,4-oxadiazoles.

Fourteen new 2,5-disubstituted-1,3,4-oxadiazoles, namely (i) six 2-[2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropyl]-5-substituted-1,3,4-oxadiazoles and (ii) eight 2-substituted-phenoxymethyl-5-substituted-aryl-1,3,4-oxadiazoles, were synthesized and evaluated for their insect growth regulatory activity against second-instar larvae of armyworm (Pseudaletia separata Walker). Two of these compounds (7 and 8) showed good insecticidal activities, with LC(50) values of 14.33 and 15.85 microg/mL, respectively. Steric parameters (e.g., the molecular length d and the ratio of the nonpolar surface area and polar surface area V(1)/V(2)) and semiempirical quantum parameters (e.g., the molecular total energy E(t) and the lowest unoccupied molecular orbital energy E(LUMO) and so on) of these compounds, as well as those of six other 2,5-disubstituted-1,3,4-oxadiazoles reported, were acquired by the molecular modeling method and the PM3-SCF-MO method, respectively. With the help of the synthons' activity contribution method based on the Free-Wilson approach in its Fujita-Ban variant, quantitative structure-activity relationships were studied by regressing half-lethal concentrations against the above parameters.

Animals↗

PubMed2001

Body mass index as a predictor of continued survival in older chronic dialysis patients.

OBJECTIVE: To investigate the contribution of body mass index (BMI) to mortality over 11 years of follow-up in a prevalent sample of dialysis patients aged 60+. DESIGN: Multivariate Cox proportional hazards regression analysis. SETTING: Multicenter stratified random sample of black and white older chronic dialysis patients in a southeastern state. SUBJECTS: 316 patients on hemodialysis (HD) and peritoneal dialysis (PD). MAIN OUTCOME MEASURE: Continued survival from baseline interview in 1988 to June 1999. RESULTS: Adjusting for age, primary diagnosis of diabetes, cardiovascular comorbidity, HD/PD therapy, and patient-reported functional impairment, the interaction of baseline BMI with race and gender was associated with older patients' risk of mortality. Black females, black males, and white males with higher BMI had a reduced risk of mortality, while no protective effect of higher BMI was found for white females. Patients with cardiovascular comorbidity and greater functional impairment at baseline had increased mortality risk. BMI was not significantly correlated with serum albumin or functional impairment. CONCLUSION: BMI, a simple anthropometric measure that provides a marker of nutritional status, interacts with race and gender to predict long-term survival in older dialysis patients. The association of survival with dialysis adequacy, nutritional indicators, and cardiovascular status in black and white dialysis patients is an important area of study.

Black or African American↗

PubMed2001

Acute tubulointerstitial nephritis after wasp stings.

A 61-year-old Caucasian man presented with acute renal failure after multiple wasp stings. The patient required dialysis support temporarily. Work-up failed to show rhabdomyolysis or hemolysis and a kidney biopsy revealed acute allergic interstitial nephritis. The patient's renal function recovered completely after a short course of steroid therapy. Acute renal failure after wasp stings is typically caused by acute tubular necrosis in the setting of hemolysis or rhabdomyolysis. Compared with previously reported cases of acute renal failure associated with bee stings, our patient is unique in that his renal failure was caused by a hypersensitivity reaction apparently to the wasp venom.

Animals↗

PubMed2001

A novel method to calculate the G+C content of genomic DNA sequences.

The base composition of a DNA fragment or genome is usually measured by the proportion of A+T or G+C in the sequence. The G+C content along genomic sequences is usually calculated using an overlapping or non-overlapping sliding window method. The result and accuracy of such an approach depends on the size of the window and the moving distance adopted. In this paper, a novel windowless technique to calculate the G+C content of genomic sequences is proposed. By this method, the G+C content can be calculated at different "resolution". In an extreme case, the G+C content may be computed at a specific point, rather than in a window of finite size. This is particularly useful to analyze the fine variation of base composition along genomic sequences. As the first example, the variation of G+C content along each of 16 yeast chromosomes is analyzed. The G+C-rich regions with length larger than 5 kb sequences are detected and listed in details. It is found that each chromosome consists of several G+C-rich and G+C-poor regions alternatively, i.e., a mosaic structure. Another example is to analyze the G+C content for each of the two chromosomes of the Vibrio cholerae genome. Based on the variations of the G+C content in each chromosome, it is shown that some fragments in the Vibrio cholerae genome may have been transferred from other species. Especially, the position and size of the large integron island on the smaller chromosome was precisely predicted. This method would be a useful tool for analyzing genomic sequences.

Base Composition↗

PubMed2001

Adenoviral-mediated gene therapy for thyroid carcinoma using thymidine kinase controlled by thyroglobulin promoter demonstrates high specificity and low toxicity.

A replication defective adenovirus transducing thymidine kinase (TK) gene under the control of the rat thyroglobulin (rTg) promoter (AdrTgtk) was developed to evaluate its cell-specific killing activity in gene therapy. We also developed adenoviruses containing the TK gene driven by the cytomegalovirus (CMV) promoter (AdCMVtk), and luciferase (Luc) gene driven by the rTg or CMV promoter (AdrTgLuc or AdCMVLuc). Luc activity in FRTL-5, HepG2, COS1, rMTC, hMTC, Hela, GH3, T98G, and CA77 cells was measured after infection with AdrTgLuc or AdCMVLuc. FRTL-5 cells produce thyroglobulin (Tg), whereas all other cells are non-Tg-producing cell lines. Transduction by AdCMVLuc caused high Luc activity in all cell lines. However, infection with AdrTgLuc induced Luc activity only in FRTL-5 cells. AdCMVtk or AdrTgtk was used to transduce various cell lines to evaluate the different killing effect. After infection with AdCMVtk vector followed by ganciclovir (GCV) treatment, cell growth was strongly suppressed in all cell lines compared both to noninfected cells and to cells infected by AdCMVLuc in the presence of GCV. When FRTL-5 cells were infected with AdrTgtk followed by GCV treatment, more than 90% were killed, but only a minimal effect was observed in other cell lines, indicating that the Tg promoter transduced TK expression only in Tg-producing cells. When adenovirus is given intravenously, liver and spleen are the major organs infected. A high Luc activity was found in liver and spleen of AdCMVLuc treated animals. No Luc activity was found in liver and spleen of AdrTgLuc-treated animals, indicating that rTg does not transduce Luc expression in non-Tg-producing tissues in vivo. No significant changes of the serum transaminase levels and histologic abnormalities were found in animals treated with AdrTgtk/GCV compared with control animals. High levels of serum transaminases, lymphocyte infiltration, some Kupffer's cell prominence, and extensive single cell hypatocyte death were found in AdCMVtk/GCV-treated animals, indicating severe liver damage induced, as expected, by a noncell-specific promoter. These results indicate that transfer of TK gene driven by the rTg promoter has thyroid cell-specific killing ability in the presence of GCV, little in vivo toxicity, and should be useful in the future for treating thyroid Tg-producing cancers.

Adenoviridae↗

PubMed2001

Race and restless sleep complaint in older chronic dialysis patients and nondialysis community controls.

There is mixed evidence about the relation of race to risk of sleep disturbance. We explored the relation of race to restless sleep complaint in survey data from a cohort of 311 older patients undergoing chronic renal dialysis and a similarly aged cohort of 354 nondialysis controls. Older dialysis patients were significantly more likely to report restless sleep. Restless sleep complaint was related to comorbidity, depressed mood, use of sleep medications, and perceived health status in both groups. Black patients in the dialysis cohort had decreased odds of restless sleep, but Black and White controls did not differ significantly in reporting restless sleep. Compared with their more socially advantaged White counterparts, older Black dialysis patients may perceive the chronic dialysis care environment more favorably. The findings are consistent with the view that sleep quality in late life is likely to reflect a delicate balance between psychological as well as physical well-being.

Black or African American↗

PubMed2001

Reduced de-etiolation of hypocotyl growth in a tomato mutant is associated with hypersensitivity to, and high endogenous levels of, abscisic acid.

A recessive single gene mutant, 7B-1, in tomato was originally selected for its photoperiod-dependent male sterility. The 7B-1 mutant also has some pleiotropic effects including reduced light-induced inhibition, i.e. de-etiolation, of the hypocotyl in long days (LD), increased seed size and weight, and reduced transpiration rate. These traits led us to investigate the sensitivity of 7B-1 to exogenous hormones and the interaction of these responses with daylength. In LD, but not in short days (SD), 7B-1 was more sensitive than wild-type (WT) to exogenous abscisic acid (ABA) for inhibition of seed germination, root elongation and transpiration rate. 7B-1 mutant also exhibited reduced responses to exogenous gibberellin (GA(3)) for hypocotyl elongation, and to inhibitors of GA biosynthesis for seed germination and root and hypocotyl elongation. 7B-1 hypocotyls contained a higher level of endogenous ABA than WT in both photoperiods, although ABA levels were higher in LD than in SD. In contrast, growth-active GAs, i.e. GA(1), GA(3) and GA(4), and IAA were low in the mutant hypocotyls. The 7B-1 mutant appears to be an ABA-overproducer, and the photoperiod-regulated ABA levels may be responsible for the hypersensitivity of the mutant to exogenous ABA.

Abscisic Acid↗