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Biomedical subjects

J Ma

Publications and source records attributed to J Ma.

At least 343 records · Page 19Linked to original sources
PubMed1998

Developmental regulation of heterochromatin-mediated gene silencing in Drosophila.

The roles of differentiation, mitotic activity and intrinsic promoter strength in the maintenance of heterochromatic silencing were investigated during development using an inducible lacZ gene as an in vivo probe. Heterochromatic silencing is initiated at the onset of gastrulation, approximately 1 hour after heterochromatin is first visible cytologically. A high degree of silencing is maintained in the mitotically active imaginal cells from mid-embryogenesis until early third instar larval stage, and extensive relaxation of silencing is tightly associated with the onset of differentiation. Relaxation of silencing can be triggered in vitro by ecdysone. In contrast, timing and extent of silencing at both the initiation and relaxation stages are insensitive to changes in cell cycle activity, and intrinsic promoter strength also does not influence the extent of silencing by heterochromatin. These data suggest that the silencing activity of heterochromatin is developmentally programmed.

Animals↗
PubMed1998

Mechanisms of the therapeutic effect of astragalus membranaceus on sodium and water retention in experimental heart failure.

OBJECTIVE: To investigate the therapeutic effect of Astragali on sodium and water retention in aortocaval fistula-caused experimental congestive heart failure and its involved mechanisms. METHODS: In aortocaval fistula-caused chronic (5 wk), heart failure rats treated with and without Astragali 1.0 g/day intraperitoneally, changes of cardiac and renal function, renal response to atrial natriuretic peptide (ANP) were examined. Dot blot analysis was used to determine the effect of Astragali on hypothalamic arginine vasopresin (AVP) mRNA expression, and mRNA expressions of aortic and renal AVP V1a receptor, renal AVP V2 receptor and aquaporin-2 (AQP2) were simultaneously detected by RT-PCR method. RESULTS: Rats with aortocaval fistula impaired cardiac and renal functions evidenced by higher right atrial pressure (RAP), left ventricular end-diastolic pressure (LVEDP), lower + dP/dtmax of left ventricle, glomerular filtration rate (GFR), renal plasma flow (RPF), urine volume (UV), urinary sodium excretion (UNaV) and free water clearance (CH2O) compared with sham-operated control (P < 0.05). There was no change in serum sodium, hematocrit and plasma osmolality. Astragali could remarkably improve the cardiac and renal functions. Dot blot analysis demonstrated upregulated hypothalamic AVP mRNA expression in this experimental heart failure. The AVP V1a receptor mRNA level of aortic arch and renal medulla were reduced, while in renal cortex it was elevated. The mRNA expressions of AVP V2 receptor and AQP2 were increased in renal cortex while decreased in medulla. Astragali could partially or completely correct those abnormal mRNA expressions. Analysis on plasma atrial natriuretic peptide (ANP), urinary cyclic guanidino monophosphate excretion (UcGMP V), urinary cyclic guanidino monophosphate excretion/plasma atrial natriuretic peptide (UcGMP V/pANP), and further correlation and linear regression analysis between UcGMP V and plasma ANP showed that there was blunted renal response to ANP in heart failure rat, and astragali could improve the renal reaction to ANP significantly. CONCLUSION: Chinese herb, astragali have therapeutic effects on sodium and water retention in aortocaval fistula-induced heart failure, the mechanisms of which might be the improvement of cardiac and renal functions, partly correction of abnormal mRNA expressions of AVP system and AQP2, and amelioration of blunted renal response to ANP.

Animals↗
PubMed1998

[Studies on immunization strategy against hepatitis A in a highly prevalent area].

OBJECTIVE: To explore a strategy for immunization against hepatitis A (HA) in highly prevalent areas. METHODS: Maternal antibodies against hepatitis A virus (anti-HAV) were detected for newly born infants and infection rate of HAV was monitored for children at various stages of epidemic of HA. RESULTS: Proportions of positive maternal anti-HAV in newly born infants decreased from 97.4% to 5.0% during their first 13 months of life in a logistic curve pattern. HAV infection increased with age after one and a half years old during non-epidemic period, and kept in less than 10% before two years old. The age of the increase in HAV infection shifted to an earlier dates and the rate of infection speeded up more for children during an epidemic period. The "window" phase converting maternal anti-HAV to natural infection for infants in the highly prevalent areas was in 12 to 24 months after birth, because the age starting to increase HA infection lagged behind that of infection. CONCLUSION: Based on the prevalence of HA and economic situation, the appropriate time for children's HAV immunization is 12 to 24 months of age.

Adult↗
PubMed1998

[Studies on infection of Helicobacter pylori and their subtypes cagA+ and hspA+ in population living in the areas with high and low incidence of gastric cancer].

OBJECTIVE: To explore the difference in infection of Helicobacter pylori (Hp) and their subtypes cagA+ and hspA+ in the residents living in the areas with high and low incidence of gastric cancer. METHODS: Immunoglobulin G and A antibodies against Hp and immunoglobulin G antibodies against cagA+ and hspA+ were detected for the residents in Linqu and Cangshan Counties of Shandong Province with enzyme-linked immunosorbent assay (ELISA). RESULTS: Rate of infection with Hp in the residents in Linqu County, an area with high incidence of gastric cancer, was 73.8 percent, significantly higher than that in Cangshan County (59.9%), an area with low incidence. Rates of infection with Hp cagA+ and hspA+ in the residents in Linqu County were 50.9 and 17.0 percent, respectively, also significantly higher than those in Cangshan County (34.0% and 13.2%, respectively). Sensitivities and specificities of the methods for detecting antibodies against Hp, cagA+ and hspA+ were 92.3, 63.2 and 21.9 percent and 71.0, 80.6 and 95.2 percent, respectively, evaluated with 13C-urea breath teat (13C-UBT). Rate of infection with Hp, especially with Hp cagA+, correlated significantly with the high incidence of gastric cancer. CONCLUSION: The methods for detecting antibodies against Hp and cagA+ subtype are more sensitive and can be used as better indicators in epidemiological studies on gastric cancer.

Adult↗
PubMed1998

[Association between levels of plasma lipid profile with apolipoprotein B gene polymorphism in 93 children].

OBJECTIVE: To study the relationship between levels of plasma lipid profile and variation of apolipoprotein (Apo) B gene. METHODS: The relationship between frequency of polymorphism genotype of Apo B gene Xba I locus and levels of plasma lipid profile was studied in 93 children aged eight to eleven years. RESULTS: The frequency of dominant X- allele (common allele) in Xba I locus was 0.967 in the children and that of uncommon X+ allele 0.033. Average levels of plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL-ch) in children with X- X+ genotype (4.59 and 2.98 mmol/L, respectively) were significantly higher than those with X-X- genotype (3.84 and 2.32 mmol/L, respectively). Levels of TC and/or LDL-ch in 4 of 6, cases of X-X+ genotype exceeded their the 90th percentile, indicating association between X+ allele and high plasma cholesterol level. CONCLUSION: To certain extent, there is association between polymorphism of Xba I locus of Apo B gene and levels of plasma lipid profile in children, which may be a genetic marker for abnormal level of plasma lipid profile during childhood.

Apolipoproteins B↗
PubMed1998

[Cellular sociological characteristics of osteoblasts].

There is a great hope to treat long bone defects with bioactive artificial bone constructed by osteoblasts and biomaterials, in which the key point is to provide an optimum environment for the normal function of osteoblasts. The cellular sociological characteristics of osteoblasts were summarized and it was suggested that the ideal bioactive artificial bone should be composed of inorganic and organic materials together with cellular components such as osteoblasts and vascular endothelial cells, and combined with control release of growth factors, following its implantation it could be vascularized very soon and merged with the host bone by bony consolidation.

Bone Substitutes↗
PubMed1998

[Solid adsorption and stability of essential oil from pericarp of Gaultheria yunnaensis (Franch.) Rehd].

Experiments have been made on the solid adsorption and stability of the essential oil extracted from Gaultheria yunnanensis. The results show that among the chemical constituents of the oil, methyl salicylate accounts for 99.66%. Grain adsorbents of aluminum hydroxide gel have been proved useful in obtaining higher release rates of the oil at required temperatures as well as keeping the oil stable at room temperature.

Adsorption↗
PubMed1998

[The long-term effect of double embolization of bronchial artery on patients with hemoptysis].

OBJECTIVE: To investigate the long-term effect of bronchial arterial embolization with different material and procedure on patients with hemoptysis. METHOD: Seventy two cases were divided into two groups, one received the double embolization of bronchial artery, the other group used single gelfoam embolization. In double embolization group, the mixture containing gelfoam microspheres (0.5 mm x 0.5 mm), erythromycin and high osmalality sodium chloride were firstly used to embolize the terminal vessels, the gelfoam particle (1 mm x 1 mm) was then used to embolize the main trunk of bronchial artery. RESULT: After 2-4.8 years following up, it turned out that the cure rate and general effectiveness were: the double embolization group 83%, 100% respectively, the single gelfoam embolization group 61%, 95%. By comparison, there were significant difference on cure rate between these two groups(P < 0.05). CONCLUSION: The bronchial arterial double embolization will increase the long-term effect obviously on patients with hemoptysis.

Adolescent↗
PubMed1998

[Tail-suspended rats with inguinal canal ligation and their myocardial function].

To examine the effect of testosterone level on myocardial contractility and to prevent the testis from sliding into abdominal cavity when subjected to tail-suspension, a new tail-suspended model of rat with its inguinal canal ligated was made. Rats suspended for 4 w without inguinal canal ligation (SUS) exhibited significant reduction in weight of testis (CON 1.70 +/- 0.19 g; SUS 0.60 +/- 0.16 g) and in serum testosterone level (CON 99.5 +/- 32.7 ng/dl; SUS 23.0 +/- 13.2 ng/dl) (P<0.01). Unexpectedly, 4 w tail-suspension of rats with inguinal canal ligation (ST) also showed significant changes in testis weight (1.21 +/-0.30 g) and serum testosterone level (40.7 +/- 32.6 ng/dl). A significant decrease of the developed tension of the papillary muscle of the left cardiac ventricle was observed in SUS and ST group as compared with controls (CON: 3.93 +/- 0.42 g/mm2, SUS: 2.54 +/- 0.85 g/mm2, ST: 2.60 +/- 0.73 g/mm2). There was no relationship between the developed tension and serum testosterone level. It suggests that the decrease of blood supply of the testis may result in an atrophy of the testis in ST group.

Animals↗
PubMed1998

Alteration of vasoreactivity of mesenteric arteries in rats after two-week simulated weightlessness.

To investigate the effects of simulated weightlessness on vasoreactivity of mesenteric arteries, rats were tail-suspended for two weeks, and vasoreactivity were studied in vitro using isolated mesenteric arterial ring. The results showed that maximal contractile responses to KCl (10-80 mmol/L) and phenylephrine (PE, 10(-10)-10(-4) mol/L) were attenuated in arterial rings isolated from tail-suspended rats. After constriction caused by 10(-7) mol/L PE, maximal dilatory responses induced by sodium nitroprusside (SNP, 10(-10)-10(-4) mol/L) were not different between tail-suspended and control groups. These data indicated that contractile ability of mesenteric artery was diminished by tail-suspension, whereas the dilatory capacity of arterial smooth muscle was not altered.

Animals↗
PubMed1998

[Synthesis and evaluation of restricted access stationary phases].

The restricted access stationary phase (RAS) are a new type of chromatographic packing material having a hydrophobic interior covered with a hydrophilic barrier. The RAS is used for direct injection in high-performance liquid chromatography for determination of drugs in biological fluids. These stationary phases include internal surface reverse phase, semipermeable surface, shielded hydrophobic phase and mixed functional phase (MFP). A kind of MFP packing material was synthesized from a porous silica gel-introduction of hydrophobic phenyl phase and introduction of hydrophilic diol phase. The MFP of RAS, on which proteins were eluted in the void volume, while the drugs were retained and separated, can be used for direct injection analysis of hydrophilic and hydrophobic drugs in serum and plasma. The recovery of the drugs in human serum was almost 100% with good reproducibility.

Blood Proteins↗
PubMed1998

[Investigation and manufacture of intellectualized tonometer bassed on the principle of linearly measuring the applanation area diameter of ocular cornea].

The design principle of intellectualized tonometer based theory of linearly measuring the applanation area diameter of ocular cornea has been mainly introduced, which inclueds optics and construction design principle, principle of hardware and software design of intellectualized instrument and the calculation method of ocular pressure etc. The method and result of calibration of the tonometer are also included.

Cornea↗
PubMed1998

Impact of selected medical conditions on self-reported lower-extremity function in Mexican-American elderly.

OBJECTIVE: To examine the independent impact of common medical conditions on lower-extremity function in Mexican-American elderly. DESIGN: Cross-sectional study using a probability sample of non-institutionalized Mexican Americans aged 65 or older. SETTING: The five Southwestern states, Texas, New Mexico, Arizona, Colorado and California. PARTICIPANTS: All subjects were interviewed in person (n = 2,873) or by proxy (n = 177) in their homes during late 1993 and early 1994. MAIN OUTCOME MEASURES: Respondents were asked whether they could perform four activities related to lower-extremity function without help: walking across a small room, getting from a bed to a chair, walking up and down stairs, and walking half a mile. A summary measure of lower body disability created from these four items was regressed on seven common medical conditions plus five control variables using multiple logistic regression. RESULTS: Adjusted Odds Ratios (OR) suggested that impaired lower-extremity function was associated with previous diagnosis of hip fracture (OR = 4.28), stroke (OR = 3.47), lower extremity arthritis (OR = 2.60), heart attack (OR = 2.29), diabetes (OR = 2.03) and obesity (OR = 1.50). Impaired lower-extremity function was significantly associated with older age (75+ years old), gender (female) and marital status (unmarried). In addition, there was a linear increase in the risk of function loss by number of medical conditions. CONCLUSIONS: It appears that Mexican-American elderly diagnosed with medical conditions, especially stroke and hip fracture, have a high risk for lower-extremity dysfunction. These findings have implications for efforts to prevent or reduce lower-extremity dysfunction, as well as for the provision of community-based long-term care services for Mexican-American elderly.

Activities of Daily Living↗
PubMed1998

Vitamin D receptor polymorphisms, circulating vitamin D metabolites, and risk of prostate cancer in United States physicians.

Prostatic cells express vitamin D receptor (VDR), which mediates the functions of 1,25-dihydroxyvitamin D. Two recent case-control studies suggested strong inverse associations between two VDR polymorphisms, TaqI and poly(A), and risk of prostate cancer. These two and a third polymorphism, BsmI, are closely linked. In a case-control study nested in the Physicians' Health Study, a randomized double-blind trial of aspirin and beta-carotene among 22,071 United States male physicians, we examined the associations between BsmI and TaqI and prostate cancer risk and whether the associations varied according to age and vitamin D metabolite levels among 372 incident cases and 591 controls. Among controls, the BB genotype was significantly associated with higher 1,25-dihydroxyvitamin D (median = 36.2 pg/ml for the BB versus 33.9 pg/ml for the bb genotype; P = 0.02), suggesting an association of the VDR polymorphisms with VDR function. Overall, we observed no significant associations of these VDR polymorphisms with prostate cancer risk: relative risk (RR) = 0.86 [95% confidence interval (CI) = 0.57-1.29] for the BB genotype and RR = 0.92 (95% CI = 0.69-1.22) for the Bb genotype, compared with the bb genotype (results were similar for the TaqI polymorphism). Stratification by age (< or = 61 and > 61 years) and tumor aggressiveness showed no significant associations. However, in an analysis restricted to men with plasma 25-hydroxyvitamin D below the median, we observed a 57% reduction (RR = 0.43, 95% CI = 0.19-0.98) in risk for those with the BB versus the bb genotype; the risk reduction was particularly marked among older men (RR = 0.18, 95% CI = 0.05-0.68). We did not observe this inverse association among men with 25-hydroxyvitamin D levels above the median, nor did we observe it among younger men.

Adult↗
PubMed1998

[Detection of the mutant phenylalanine hydroxylase gene by dideoxy fingerprinting].

OBJECTIVE: To establish a method with high efficiency in detecting phenylalanine hydroxylase (PHA) gene mutations and hence to rapidly diagnose prenatal fetals with phenylketonuria. METHODS: Dideoxy fingerprinting (ddF) was used. It is a hybrid method of dideoxy sequencing and single strand conformation polymorphism (SSCP); it can effectively detect the presence of mutant genes and would not be limited by the length of the amplified products, by ddF, the mutant genes Y165X, Y204C and Q355H of PAH genes were detected. RESULTS: Many bands showed altered migration, compared with the controls. Abnormal band migration in Y165X and Q355H was also detected by SSCP, but it was not detected in Y204C which had large amplified products. CONCLUSION: Compared with SSCP, ddF is a more sensitive method detecting gene mutations in large fragments, ddF is a practicable method for detecting gene mutations.

DNA Fingerprinting↗
PubMed1997

Ligand-induced conformational changes in ras p21: a normal mode and energy minimization analysis.

A normal mode and energy minimization of ras p21 is used to determine the flexibility of the protein and the origin of the conformational differences between GTP and GDP-bound forms. To preserve the integrity of the structures, a hydration shell of water molecules was included as part of the system. Certain low-frequency modes were found to have high involvement coefficients with the conformational transition between the GTP and GDP-bound structures; the involvement coefficients of some of the modes increase when the gamma-phosphate group is removed. Two unstable modes that appear in the GTP-bound structure upon deletion of the gamma-phosphate group were determined and shown to have dominant contributions in the regions of switch I and switch II; there was also a significant displacement of loop 1. The initial motion in these regions is predicted by the modes to be approximately perpendicular to the direction of the transition from the GTP-bound state to the GDP-bound state. The overall conformational change in the switch I and II regions involves rearrangements of the protein backbone within these regions, rather than rigid body motion. Differences in the low-frequency modes of the GTP and GDP-bound forms appear to play a role in ligand binding. A coupling between the helix alpha3 position and the deletion of the gamma-phosphate group may be involved in the interaction with GAP. The oncogenic mutation G12D leads to a global increase in the rigidity of the protein. Thus, the mutant is likely to have a higher barrier for the conformational change to the inactive form; this would slow the transition and could be related to its oncogenic properties.

Binding Sites↗