Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 757 records · Page 42Linked to original sources

PubMed1996

Effects of renin gene transfer on blood pressure and renin gene expression in a congenic strain of Dahl salt-resistant rats.

To investigate whether a BP-regulatory locus exists in the vicinity of the renin locus on rat chromosome 13, we transferred this chromosome segment from the Dahl salt-sensitive (S) rat onto the genetic background of the Dahl salt-resistant (R) rat. In congenic Dahl R rats carrying the S renin gene and fed an 8% salt diet, systolic BP was significantly lower than in progenitor Dahl R rats: 127 +/- 1 mmHg versus 138 +/- 4 mmHg, respectively (P < 0.05). Moreover, the decreased BP in the congenic Dahl R strain was associated with decreased kidney renin mRNA and decreased plasma renin concentration. These findings demonstrate that the Dahl S strain carries alleles in or near the renin locus that confer lower plasma renin concentration and lower BP than the corresponding alleles in the Dahl R strain, at least when studied on the genetic background of the Dahl R rat and in the environment of a high salt diet. The occurrence of coincident reductions in kidney renin mRNA, plasma renin concentration, and BP after interstrain transfer of naturally occurring renin gene variants strongly suggests that genetically determined variation in renin gene expression can affect BP.

Alleles↗

PubMed1996

Retinoic acid-induced embryopathy of the mouse inner ear.

Retinoic acid (RA) is an active metabolite of vitamin A that is teratogenic when present in excess during mammalian embryogenesis. We have investigated the effect of embryonic exposure to nonphysiological levels of all-trans RA on the development of the mouse inner ear. Dysmorphogenesis of both vestibular and auditory portions of the inner ear, and abnormal formation of the surrounding capsule are produced by exposure to teratogenic levels of RA at an embryonic age of 9 days (E9). There was no observable teratogenic effect of RA when administered at earlier (i.e., E7 or E8) or later (i.e., E10) stages of otic morphogenesis. We hypothesize that exposure to high levels of RA during a critical period of early otic morphogenesis interferes with the inductive tissue interactions required for inner ear development.

Abnormalities, Drug-Induced↗

PubMed1996

Neurotrophic effects of BDNF and CNTF, alone and in combination, on postnatal day 5 rat acoustic ganglion neurons.

The neuronal survival promoting ability of brain derived neurotrophic factor (BDNF), and ciliary neurotrophic factor (CNTF), individually and in combination, was evaluated in dissociated cell cultures of postnatal day 5 (P5) rat acoustic ganglia. The neuritogenic promoting effect of these same neurotrophic factors was examined in organotypic explants of P5 rat acoustic ganglia. The results showed that BDNF was maximally effective at a concentration of 10 ng/mL in promoting both survival and neuritogenesis of these postnatal auditory neurons in vitro. CNTF was maximally effective at a concentration of 0.01 ng/mL at promoting both survival and neuritogenesis in the acoustic ganglion cultures. BDNF had its strongest effect on neuronal survival while CNTF was most effective in stimulating neurite outgrowth. These two neurotrophic factors, when added together at their respective maximally effective concentrations, behave in an additive manner for promoting both survival and neuritic outgrowth by the auditory neurons.

Animals↗

PubMed1996

Avulsive amputations of the thumb: comparison of replantation techniques.

Twenty-five cases of avulsive amputation of the thumb are reported. Twenty-one of the 25 cases were categorized as Grade I avulsions (little or no skin defect) and four were categorized as Grade II avulsions complicated by a large skin defect. Three different replantation techniques were used and compared: (1) direct vessel anastomosis, (2) arterial anastomosis between the superficial branch of the radial artery and distal end of the thumb, and (3) arterial anastomosis after artery transfer from other digits. The authors concluded that direct vessel anastomosis was not the preferred method and that technique 2 could be used in any case but was especially suited to Grade II reconstructions. Technique 3 is mainly used in Grade I avulsions.

Amputation, Traumatic↗

PubMed1996

Glycohydrolases as markers of hepatic ischemia-reperfusion injury and recovery.

Advances in liver surgery and transplantation have lead to a steady increase in the number of these interventions. Prompt quantitative assessment of hepatic of hepatic function and a patient's subsequent morbidity and mortality following surgery remain difficult despite the currently utilized historic markers of hepatic parenchymal injury (e.g., aspartate transaminase [AST], lactate dehydrogenase [LDH] gamma-glutamyl transpeptidase [GGT]). Increases in serum glycohydrolase activities appear to provide sensitive and quantitative markers of hepatic ischemia/reperfusion injury. In 10 male swine (25 to 35 kg body weight) following 30, 45, and 90 minutes of acute hepatic ischemia, the systemic release of eight different glycohydrolases and lipid peroxides into serum were determined and compared with pre- and postischemic serum levels of LDH, GGT, and AST. The rapid release of glycohydrolases into serum was directly proportional to the length of the ischemic period from 30 to 90 minutes; e.g., beta-glucosidase, mean 1.9-fold increase at 30 minutes; 8.3-fold at 45 minutes; and 22.8-fold at 90 minutes; P < .002) and the activities peaked within the first 3 hours postischemia. In constrast, AST, LDH, and GGT were released slowly and peaked 20 to 30 hours after hepatic blood flow was restored. In swine with fatal outcomes (90 minutes of ischemia), all enzyme levels increased continuously during the final hours of life. However, in swine that survived hepatic ischemia/reperfusion injury (45 minutes of ischemia) the glycohydrolases, but not AST, LDH, and GGT, declined after 2 to 3 hours' postischemia and the serum lipid peroxide levels followed the same pattern. Serum beta-galactosidase and beta-glucosidase levels are sensitive markers that rise as quickly as traditional enzyme markers (AST, LDH, GGT) following hepatic ischemic injury; moreover, the glycohydrolases have the added value of serving as predictors of survival.

Acid Phosphatase↗

PubMed1996

Aqueous and vitreous penetration of ciprofloxacin following different modes of systemic administration.

The overall importance of the peak or the mean serum concentrations as predictors of ocular drug penetration is unknown. To address this fundamental question with an agent which shows promise as adjunctive therapy in the treatment of endophthalmitis, we studied the penetration of ciprofloxacin into the aqueous and vitreous humors following three different modes of systemic administration. New Zealand white rabbits received either a single bolus dose (40 mg kg-1), three intermittent doses of 13.33 mg kg-1 evenly spaced over an 8 hr period, or a continuous infusion of 40 mg kg-1 over an 8 hr period. Pharmacokinetic analysis was performed using RSTRIP II, a non-linear, least square regression model analysis program. The serum area under the concentration-time curve (AUC) values for each mode of drug administration were similar: 32.9 micrograms hr ml-1 for single dose, 31.9 micrograms hr ml-1 for intermittent dose, and 33.8 micrograms hr ml-1 for continuous infusion modes. The percentage penetration into the aqueous and vitreous were also similar; 30.5% and 6.5% for a single dose, 31.6% and 7.4% for intermittent doses and 30.0% and 7.5% for continuous infusion. The penetration into the aqueous and vitreous humors was not influenced by mode of administration. As with other quinolones we have studied, elimination rates were similar for the central and peripheral compartments in the post-distributive phase. Vitreous humor ciprofloxacin concentrations achieved were below that which inhibits most Staphylococcus epidermidis, the most common isolate in patients with post-operative endophthalmitis.

Animals↗

PubMed1996

Nitrate Nonutilizing Mutants and Vegetative Compatibility Groups in Fusarium poae

Nitrate nonutilizing (nit) mutants were recovered from 24 isolates of Fusarium poae and used to force heterokaryons between these isolates and to determine vegetative compatibility. Between 30 and 90% of the mycelial blocks, cultured on medium containing chlorate, produced nit mutants. The amount of chlorate in the medium altered the frequency and spectrum of nit mutants recovered. Most of the mutants (63%) had lesions at a nitrate reductase structural locus (nit1). Another 30% were mutants at one or more loci that control the production of a molybdenum-containing cofactor necessary for nitrate reductase activity (NitM). A few (6%) of the mutations occurred in a regulatory gene specific for the nitrate reduction pathway (nit3). Pairings between nit1 and NitM mutants were made on minimal medium containing nitrate as the sole nitrogen source. A mutant grows thinly unless it forms a complementary heterokaryon upon contact with another mutant. Heterokaryon formation was indicated by dense growth where the two mutant colonies touched. The 24 isolates could be divided into 13 nonoverlapping vegetative compatibility groups, suggesting that asexual exchange of genetic information within F. poae is subject to significant limitations.

Journal Article↗

PubMed1996

The preliminary research on the relationship between TNF- and egg-induced granuloma and hepatic fibrosis of schistosomiasis japonica.

The amount and distribution of tumor necrosis factor-alpha (TNF-alpha) in liver at various stages of Schistosomiasis japonicum-infected mice were immunohistochemically determined by SABC method. The results showed that the amount of TNF-alpha in liver began to increase at the 8th-12th week after infection, and reached a peak (9 mice reached 2+ grade or higher) 16 weeks after infection, which was higher than the levels 8 weeks after infection (P = 0.001) and was mainly scattered in and around egg granuloma. At the chronic stage of the infection, the amount of TNF-alpha in liver decrease not increase with an increased secretion of collagen in liver and development of hepatic fibrosis. On the contrary, FN, LN, type I and III collagen in liver began to rise 8-12 weeks after infection, and were linearly scattered around egg granuloma, reaching a peak (more than 70% of infected mice reached 3+(-)4+ grade) at the 20th and 24th week and they became wide, thick and retiform, and deposited around and in egg granuloma. After administration of recombinant TNF-alpha to the infected mice, the amount of FN and LN, the size and the inflammatory response of granuloma in liver showed no significant changes as compared with the untreated group at the same stage. However, the amount of type I collagen in liver increased, among which the amount of type I collagen was significantly higher than that in the untreated group at the same stage (P = 0.01), while similar changes were not observed when recombinant TNF-alpha was administrated to the healthy mice. It is suggested that TNF may play a role in stimulation of fibroblast in liver to proliferate and secrete collagen, but may need to cooperate with some factors.

Animals↗

PubMed1996

Immunoregulation of lupus-like NZB/W F1 mice by anti-murine IL-1 alpha, IL-6 antibodies.

Anti-murine IL-1 alpha, IL-6 antibodies were intra-peritoneally injected to the lupus-like NZB/W F1 mice of 4 months with the dosage of 10 micrograms per day for three days and then per month for three months. The mice were killed at the age of 11 months. The results showed that the treatment of the dosage could not absolutely prevent lupus nephritis--it could alleviate proteinuria, obviously reduce the levels of serum IL-1 alpha and inhibit the secretion of IL-1 alpha by celiac macrophage. As to the level of IL-6 and TNF-alpha no significant change was observed.

Animals↗

PubMed1996

Study of heat shock protein HSP90 alpha, HSP70, HSP27 mRNA expression in human acute leukemia cells.

The expression of three heat shock proteins (HSPs)-HSP90 alpha, HSP70, HSP27 in cells obtained from 22 patients with leukemia, K562 erythroleukemia cell line, and normal blood cells was observed by means of RNA dot blot analysis. The results showed that the expression of the HSP27 gene was enhanced in 4 cases of acute lymphoid leukemia (ALL), 7 cases of acute nonlymphoid leukemia (ANLL) and 2 cases of myelodysplastic syndrome (MDS) as compared with that of the normal blood cells, yet there was no significant difference in the HSP27 expression between the ALL and ANLL cells. The expression of HSP70 in all the 5 ALL and ANLL patients was much lower than that of the normal subjects, except 1 case of ALL and 1 case of MDS, in which the expression was obviously enhanced. All the cases including 11 ANLL, 5 ALL and 1 MDS had higher HSP90 alpha expression than the normal subjects. The enhanced expression of HSP90 alpha in leukemia cells may be associated with the active and indefinite proliferation of leukemia cells. Our results also suggest that the high expression of the HSP27 gene may not be confined to a specific type of acute leukemia.

HSP70 Heat-Shock Proteins↗

PubMed1996

Measurements of cerebral blood flow in post-asphyxiated newborns by color Doppler imaging (CDI).

Cerebral blood flow of 10 asphyxiated term newborns was continuously measured during the first 7 days of life and compared with that of 10 normal term infants by CDI. Frequency spectrum and blood flow variables in the anterior, middle and posterior cerebral arteries were studied. The results showed evidently lower systolic amplitude in patients than that in normal subjects. End diastolic amplitude was zero in part of vessels, and values of blood flow variables were all lower in day 1 of the life as compared with the control groups. Frequency spectrum recovered to normal patterns in 9 survived infants in day 2, but blood flow variables recovered to normal by day 7. Values of resistance index (RI) rose to 1 in some vessels of moderate hypoxic ischemic encephalopathy (HIE) infants and stayed at 1 in the severe HIE infants. It is concluded that low CBF plays a key role in brain damage of post-asphyxiated newborns and RI may be an important parameter in the evaluation prognosis.

Asphyxia Neonatorum↗

PubMed1996

The apolipoprotein B Q3405E polymorphism has no effect on its low-density-lipoprotein receptor binding affinity.

A better understanding of the apolipoprotein B100 (apoB100) sequences involved in binding to the low-density lipoprotein (LDL) receptor will be achieved by studying the effects of polymorphisms and rare mutations of apoB100. Upon re-examination of apoB100 DNA sequencing discrepancies, a charge-change polymorphism, Q3405E, was found in the putative LDL receptor binding domain of the protein. Positively charged lysine and arginine side chains of the protein have been demonstrated to participate in the ligand. This led us to propose that the presence of an additional negative charge in close proximity could have an impact on the binding affinity. The polymorphism is the result of a C-to-G transition at nucleotide 10422. Population screening revealed 20 of the less common glutamate alleles at an allele frequency of 0.9%. The effect of the presence of one glutamate allele on the binding affinity of LDL for the LDL receptor was investigated in seven heterozygous individuals by a competitive dual-label fibroblast binding assay. One individual who was homozygous for the glutamate allele was discovered and her LDL examined in a competitive displacement binding assay. The additional negative charge at residue 3405 had no detectable affect on the binding affinity.

Alleles↗

PubMed1996

On improving the accuracy of instrumented spatial linkage system.

Calibration is important for improving the accuracy of instrumented spatial linkage (ISL) in the application of biomechanical studies. The assumption of the linear performance of the potentiometer transducer has limited the improvement of the linkage accuracy. We present a non-linear numerical calibration procedure and double potentiometer design to improve the accuracy of ISL. Through the use of a three-degree-of-freedom linkage, the non-linear calibration procedure and the double potentiometer design were shown to be effective in reducing the ISL errors. The error, i.e. standard deviation for the angle decreased from +/-0.38 degree to +/-0.12 degree while the same for the translation decreased from +/-0.41 to +/-0.16 mm. A high-accuracy linkage system using low-cost potentiometers could be constructed by using our calibration method and double potentiometer design.

Calibration↗

PubMed1996

Down-regulation of vascular endothelial growth factor in human colon carcinoma cell lines by antisense transfection decreases endothelial cell proliferation.

BACKGROUND: Vascular endothelial growth factor (VEGF) is a potent paracrine angiogenic factor implicated in human colon cancer angiogenesis. This study determined whether regulation of VEGF expression by human colon cancer cell lines affects endothelial cell proliferation in an in vitro model of angiogenesis. METHODS: Human colon carcinoma cell lines were screened for VEGF mRNA expression. SW480 cells (low VEGF expresser) were transfected with the VEGF sense (VS) vector, and SW620 cells (high VEGF expresser) were transfected with the VEGF antisense (VAS) vector. Cells were transfected with the vector alone as control. Endothelial cells were grown in conditioned, serum-free medium produced from experimental cells, and proliferation was determined. RESULTS: SW480-VS transfectants exhibited a sixfold increase in VEGF secretion. SW620-VAS transfectants exhibited a 50% reduction in VEGF secretion. Endothelial cells grown in conditioned medium from SW480-VS cells exhibited a 1.5- to 2-fold increase in proliferation. Addition of conditioned medium from SW620-VAS cells resulted in a 25% to 50% decrease in endothelial cell proliferation. CONCLUSIONS: VEGF production by human colon cancer cells regulates endothelial cell proliferation. Antisense VEGF transfection can down-regulate VEGF secretion and biologic activity. Therapies to decrease VEGF expression may be a means of inhibiting angiogenesis in primary and metastatic colon cancer.

Alternative Splicing↗

PubMed1996

Effect of recombinant human growth hormone on the intestinal structure of rats receiving bowel resection and parenteral nutrition.

Recombinant human growth hormone (rHGH) can improve nitrogen balance and promotecell proliferation. Little is known about the relationship between rHGH and gastrointestinal mucosal structure and function after bowel resection and parenteral nutrition (PN). The aim of this study was to determine the effect of rHGH on bowel mucosal structure and barrier function in rats receiving 50% small intestinal resection and PN. Thirty Wistar rats with central vein catheterization plus 50% small bowel resection were divided into three groups: chow (chow), standard (STD) and rHGH (rHGH). The chow group received chow food; the STD group was given standard PN; the rHGH group received standard PN plus rHGH (4.8 mg/kg/day, subcutaneously). The groups were maintained on their respective diets for 8 days and then killed. Body weight, small intestinal mucosal thickness, villus height and Goblet cells in the villus were measured. Body weight loss in the STD group was significantly greater than that in the chow and rHGH groups (P< 0.01). The mucosal thickness and villus height of rHGH group were significantly greater than the STD and chow groups (mucosal thickness: 806 +/- 5.5 vs. 533 +/- 6.0 and 593 +/- 6.0 microm; Villus height: 506 +/- 6.0 vs. 295 +/- 5.5 gm and 400 +/- 6.7 lam, respectively) (P< 0.05). The number of Goblet cells in the STD group was significantly greater than the rHGH and chow groups (9.06 +/- 1.07 vs. 5.35 +/- 1.48 and 6.10 +/- 1.51/per villus) (P < 0.01). rHGH can maintain body weight and promote bowel mucosal cell growth and might improve the barrier function of the bowel in rats after 50% small intestinal resection and PN.

Journal Article↗

PubMed1996

A structural model for 30 Rh D epitopes based on serological and DNA sequence data from partial D phenotypes.

Both cDNA RHD sequences and reactivity with monoclonal anti-D have been reported in a number of partial D phenotypes, where parts (some epitopes) of the normal D antigen are missing, and anti-D of restricted specificity may be made in response to challenge with normal D positive blood. This paper analyses these reports together and proposes a model for the structure which comprise the epitopes of the Rh D antigen. Some epitopes are proposed to be comprised of continuous peptide sequence within one extracellular loop, whereas others require interactions between two or the extracellular peptide loops.

DNA↗

PubMed1996

Molecular biology of partial D phenotypes.

We have examined all DVI variant phenotypes submitted to the workshop by a combination of RT-PCR, multiplex RHD PCR and immunoblotting with Rh antipeptide sera. Our findings suggest that all DVI phenotypes arise through hybrid RHD-RHCE-RHD genes. Genomic DNA derived from all DVI samples were shown to be RHD intron 4 negative when analysed with an RHD intron 4/exon 10 multiplex assay. We assume therefore that all DVI phenotypes involve gene conversion events involving at least exons 4 and 5 of the RHD gene. Analysis of a novel D and E variant phenotype individual (ISBT49) by RT-PCR has allowed the identification of a hybrid Rh gene composed of exons 1-4 RHD: 5 RHCE/D and 6-10 RHD. We propose that the partial D & E phenotype observed arises through D & E expression on the hybrid RHD-RHCE-RHD protein: as no transcripts encoding Rh E could be found.

DNA↗

PubMed1996

Mutant fibrillin-1 monomers lacking EGF-like domains disrupt microfibril assembly and cause severe marfan syndrome.

Marfan syndrome (MFS), a heritable connective tissue disorder, is caused by mutations in the gene coding for fibrillin-1 (FBN1), an extracellular matrix protein. One of the three major categories of FBN1 mutations involves exon-skipping. To rapidly detect such mutations, we developed a long RT-PCR method. Either three segments covering the entire FBN1 coding sequence or a single 8.9 kb FBN1 coding segment were amplified from reverse-transcribed total fibroblast RNA. Restriction fragment patterns of these RT-PCR products were compared and abnormal fragments were directly sequenced. Six exon-skipping mutations were identified in a panel of 60 MFS probands. All skipped exons encode calcium binding epidermal growth factor (EGF)-like domains and maintain the reading frame. In five probands, exon-skipping was due to point mutations in splice site sequences, and one had a 6 bp deletion in a donor splice site. Pulse-chase analysis of labelled fibrillin protein revealed normal levels of synthesis but significantly reduced matrix deposition. This dominant-negative effect of the mutant monomers is considered in the light of current models of fibrillin assembly. Probands with this type of FBN1 mutation include the most severe forms of MFS, such as neonatally lethal presentations.

Epidermal Growth Factor↗