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Biomedical subjects

X Pan

Publications and source records attributed to X Pan.

At least 145 records · Page 8Linked to original sources
PubMed1997

[The genetical effects of degUS gene in Bacillus subtilis Ki-2-132].

Using the methods of recombination and gene disruption, the effects of degUS gene in Bacillus subtilis Ki-2-132 were studied. The results showed that the gene could affect all protease-producing, competence formation, cell mobility and repression effects of glucose on protease-production. This implies that it is a pleitropic gene in Bacillus subtilis Ki-2-132. The disruption of the gene caused morphological changes and repressed the expression of aprE in vectors.

Bacillus subtilis↗
PubMed1997

[Molecular evolution of MHC DQA genes. II. Phylogenetic analysis based on nucleotide substitution and SCU bias].

Phylogenetics of 23 alleles at MHC DQA loci in 7 mammalian species was studied based on their nucleotide (NT) substitution and synonymous codon usage (SCU) bias. (1) It was demonstrated that the NT substitution rates are 1.0 x 10(-9) NT/site/yr for exon2 and 1.3 x 10(-9) NT/site/yr for exon2-4 in a large time scale, which is similar to other nuclear genes, while for mouse and rat the rates are nearly twice as high as above mentioned. (2) The DQA locus diversity and their interallelic diversity developed long after the radiation of mammalian 80Mya (million years ago). The bovine counterpart, of, and with the same recent ancestor of ovine DQA2, remains to be discovered. HLA-DQA2 locus split from HLA-DQA1 ancestor at the time between 12 approximately 20 Mya while allele diversity of HLA-DQA1 emerged and developed from 24 Mya to less than 1 Mya. (3) The phylogenetic trees based on SCU divergence reflect the phylogenetics of MHC DQA genes quite well generally in a new respect and reveal that HLA-DQA2 has a distinctive SCU bias different from all other MHC DQA locianalyzed. It indicates that SCU statistics plays an important and unique role in phylogenetic analysis of orthologous genes. The method to estimate the SCU divergence and SCU similarity was improved in this research.

Animals↗
PubMed1996

Origin and interstate spread of a New York City multidrug-resistant Mycobacterium tuberculosis clone family.

OBJECTIVE: To determine whether isolates of Mycobacterium tuberculosis from New York and elsewhere that are resistant to four or more primary antimicrobial agents and responsible for widespread disease in the 1990s represent a newly emerged clone or a heterogeneous array of unrelated organisms. SETTING: New York City area and selected locations in the United States. PATIENTS: M tuberculosis isolates from 1953 patients in New York and multidrug-resistant isolates from six patients from other US communities. DESIGN: Convenience sample of all M tuberculosis strains (M tuberculosis isolates resistant to rifampin, streptomycin, isoniazid, and ethambutol, and sometimes ethionamide, kanamycin, capreomycin, or ciprofloxacin) submitted to the Public Health Research Institute Tuberculosis Center since 1991 and samples submitted to the Centers for Disease Control and Prevention from throughout the United States. The samples submitted were representative of the New York City strains of M tuberculosis. MAIN OUTCOME MEASURE: Characterization of resistant M tuberculosis strains studied by IS6110 and polymorphic GC-rich repetitive sequence (PGRS) hybridization patterns, multiplex polymerase chain reaction (PCR) analysis, and automated DNA sequencing of genes containing mutations associated with resistance to rifampin (rpoB), isoniazid (katG and inhA locus), and streptomycin (strA and rrs). RESULTS: Multidrug-resistant M tuberculosis isolates were recovered from 253 New York City patients and had the same or closely allied IS6110 and PGRS patterns, multiplex PCR type, and gene mutations associated with resistance to rifampin, isoniazid, and streptomycin. Isolates with these same molecular characteristics were recovered from patients in Florida and Nevada, health care workers in Atlanta, Ga, and Miami, Fla, and an individual who recently moved from New York City to Denver, Colo, and caused disease or skin test conversion in at least 12 people in a nursing home environment. CONCLUSIONS: The results document the molecular origin and spread of progeny of a closely related family of multidrug-resistant M tuberculosis strains that have recently shared a common ancestor and undergone clonal expansion. The multidrug-resistant phenotype in these organisms arose by sequential acquisition of resistance-conferring mutations in several genes, most likely as a consequence of antibiotic selection of randomly occurring mutants in concert with inadequately treated infections. Dissemination of these difficult-to-treat bacteria throughout New York City and to at least four additional US cities has adverse implications for tuberculosis control in the 21st century.

Antitubercular Agents↗
PubMed1996

Hyperattenuating rim on noncontrast CT of the liver: probable peritumoral sparing of fatty infiltration.

CT scans showing a hyperattenuating rim within the liver were retrospectively evaluated in 10 patients to clarify the character, aetiology and clinical significance. All patients had hepatic tumours (7 cavernous haemangiomas in 6 patients, 3 metastatic tumours and 1 hepatocellular carcinoma) as well as fatty infiltration of the liver. Typical features of the hyperattenuating rim on noncontrast CT of the liver included (1) attenuation similar to that of the spleen, (2) a circular or semicircular shape, (3) a width of a few millimeters, (4) peritumoral localization and (5) loss of visualization with contrast enhancement. No such rims were noted around hepatic tumours unassociated with fatty infiltration. Peritumoral sparing of fatty infiltration was inferred. A hyperattenuating rim on noncontrast liver CT, although rare, suggests the presence of a hepatic tumour in fatty liver.

Adult↗
PubMed1996

Comparative antimycobacterial activities of rifampin, rifapentine, and KRM-1648 against a collection of rifampin-resistant Mycobacterium tuberculosis isolates with known rpoB mutations.

A collection of 24 rifampin-resistant clinical isolates of Mycobacterium tuberculosis with characterized RNA polymerase beta-subunit (rpoB) gene mutations was tested against the antimycobacterial agents rifampin, rifapentine, and KRM-1648 to correlate levels of resistance with specific rpoB genotypes. The results indicate that KRM-1648 is more active in vitro than rifampin and rifapentine, and its ability to overcome rifampin resistance in strains with four different genetic alterations may prove to be useful in understanding structure-function relationships.

Antibiotics, Antitubercular↗
PubMed1996

Characterization of rpsL and rrs mutations in streptomycin-resistant Mycobacterium tuberculosis isolates from diverse geographic localities.

Two genes (rpsL and rrs) with mutations associated with streptomycin resistance in Mycobacterium tuberculosis were characterized in 78 streptomycin-resistant and 61 streptomycin-susceptible isolates recovered from patients living in the United States, South America, Europe, Africa, and Asia. Fifty-four percent of the 78 resistant organisms had missense mutations in codon 43 of rpsL resulting in a K-43-->R substitution. Mutations in codon 88 of rpsL were also identified in four Asian isolates.

Antibiotics, Antitubercular↗
PubMed1996

Identification and subspecific differentiation of Mycobacterium scrofulaceum by automated sequencing of a region of the gene (hsp65) encoding a 65-kilodalton heat shock protein.

Mycobacterium scrofulaceum is most commonly recovered from children with cervical lymphadenitis, although it also accounts for approximately 2% of the mycobacterial infections in AIDS patients. Species assignment of M. scrofulaceum isolated by conventional techniques can be difficult and time-consuming. To develop a strategy for rapid species assignment of these organisms, a 360-bp region of the gene (hsp65) encoding a 65-kDa heat shock protein in 37 isolates from diverse sources was sequenced. Eight hsp65 alleles were identified, and these sequences formed phylogenetic clusters and lineages largely distinct from other Mycobacterium species. There was incomplete correlation between serovar designation and hsp65 allele assignment. The hsp65 data correlated strongly with the results of sequence analysis of the gene coding for 16S rRNA. Automated DNA sequencing of a 360-bp region of the hsp65 gene provides a rapid and unambiguous method for species assignment of these acid-fast organisms for diagnostic purposes.

Alleles↗
PubMed1996

Identification of a polymorphic nucleotide in oxyR specific for Mycobacterium bovis.

Automated sequence analysis of a 410-bp region of the axyR gene in 105 Mycobacterium tuberculosis complex isolates identified a polymorphic nucleotide that differentiated Mycobacterium bovis isolates from other complex members. All 29 M. bovis isolates sequenced had an adenine residue at nucleotide 285, whereas all 76 other complex isolates had a guanine residue. PCR-restriction fragment length polymorphism analysis of oxyR with restriction endonuclease AluI in an additional 255 complex isolates from widespread intercontinental sources confirmed and extended the unique association of adenine at position 285 with M. bovis isolates.

Adenosine↗
PubMed1996

Rat brain cannabinoid receptor modulates N-type Ca2+ channels in a neuronal expression system.

Modulation of neuronal ion channels by the cloned rat brain CB1 cannabinoid receptor was investigated with the use of a heterologous neuronal expression system. Transient expression of the rat brain CB1 cannabinoid receptor was accomplished through microinjection of in vitro transcribed cRNA into the cytoplasm of enzymatically dissociated adult rat superior cervical ganglion neurons. The cannabimimetic aminoalkylindole WIN 55,212-2 inhibited whole-cell Ca2+ currents in neurons injected 16-25 hr previously with rat brain CB1 cannabinoid receptor cRNA. Inhibition of the Ca2+ current was voltage and concentration dependent, with a maximal inhibition of 73% and an IC50 value of 47 nM. The synthetic cannabinoid analogue CP55,940 also inhibited Ca2+ currents, with a maximal inhibition of 38% and an IC50 value of 7 nM. Ca2+ current inhibition was blocked by inclusion of guanosine-5'-O-(2-thiodiphosphate) in the intracellular patch pipette solution or by pretreatment with pertussis toxin. Pretreatment with the N-type Ca2+ channel antagonist omega-conotoxin GVIA reduced the inhibition by 100 nM WIN 55,212-2 from 44% to 6%, indicating that N-type Ca2+ channels are a target of cannabinoid action. On washout of WIN 55,212-2, the Ca2+ current amplitude "overrecovered" in 47% of the neurons tested. Anandamide, the endogenous cannabimimetic compound, had an inconsistent effect on the voltage-dependent Ca2+ currents in the majority of neurons microinjected with cannabinoid receptor cRNA. Ca2+ channels were a specific effector target of the cannabinoid receptor, as two different K+ currents, the M current and the A current, were not modulated by the cannabimimetic WIN 55,212-2.

Animals↗
PubMed1996

Long-term blood pressure control in older Chinese patients with isolated systolic hypertension: a progress report on the Syst-China trial.

This report on the ongoing double-blind placebo-controlled Syst-China trial investigated whether antihypertensive drug treatment based mainly on a calcium entry blocker and a converting enzyme inhibitor, would be suitable for maintaining long-term blood pressure (BP) control in older Chinese patients (average age: 67 years) with isolated systolic hypertension (systolic pressure 160-219 mm Hg and diastolic pressure < 95 mm Hg). Active treatment consisted of nitrendipine (10- 40 mg/day) with the possible addition of captopril (12.5- 50 mg/day) and hydrochlorothiazide (12.5-50 mg/day), as necessary to reduce systolic pressure to a level of 150 mm Hg or lower and by at least 20 mm Hg. Matching placebos were used in the control group. This progress analysis was restricted to BP control up to 3 years of follow-up. The placebo (n = 1134) and active treatment n = 1245) groups had similar characteristics at enrolment. The sitting BP averaged 170/86 mm Hg. Systolic pressure fell (P < 0.001) on average 8 mm Hg more on active treatment than on placebo and diastolic pressure 3 mm Hg more. Fewer patients remained on monotherapy in the placebo than in the active treatment group (P < 0.001); on placebo the second and third line medications were started more frequently (P < 0.001). This progress report showed that significant BP reduction can be achieved and maintained in older Chinese patients treated with a calcium antagonist, associated with a converting-enzyme inhibitor and a thiazide, as necessary. Whether this BP reduction would result in a clinically meaningful decrease of cardiovascular complications is still under investigation.

Aged↗
PubMed1996

Prevalence and incidence of NIDDM in Daqing City.

OBJECTIVE: To investigate the prevalence and incidence of non-insulin dependent diabetes (NIDDM) in China by WHO criteria. METHODS: In the prevalence survey of NIDDM all 110660 participants (55391 men, 53269 women) were inhabitants of Daqing City, the largest oil center in northeast China, accounting for 87.3% of the 25 to 74 aged population in this city. They were screened by measuring two-hour plasma glucose concentrations (PG2 h) after a breakfast containing at least 80 g of carbohydrate, then a standard oral glucose tolerance test (OGTT, 75 g glucose load) was performed in 4209 subjects with PG2 h more than 6.67 mmol/L in this screen. NIDDM and impaired glucose tolerance (IGT) were diagnosed using WHO criteria. Incidence survey was made in 36471 non-diabetics identified in the prevalence survey. Two-hour urine-glucose after breakfast was determined during first screen. The urine-glucose trace or positive subjects were then followed by OGTT. Glucose was measured by glucose oxidation method. RESULTS AND CONCLUSIONS: In prevalence survey, 630 newly diagnosed NIDDM (296 males, 334 females) and 596 IGT (318 males, 278 females) were found in 110660 (male:female = 55391/53269) studied subjects in addition to 190 previously diagnosed NIDDM. Thus the total prevalence of NIDDM was 7.7/1000, and IGT was 5.5/1000. Standardized to the Chinese population in 1982, the prevalences are 12.6/1000 (95% CI = 12.0/1000-13.3/1000) and 7.7/1000 (95% CI = 7.16/1000-8.19/1000) respectively. In the incidence survey, 191 NIDDM (103 males, 88 females) were diagnosed in the 36471 (male:female = 18801/17670) non-diabetics from 1986 to 1990, thus the annual incidence of NIDDM was 131/100000 (137 males, 125 females). Standardized incidence is 131/100000 (95% CI = 94/100000-168/ 100000). It is estimated that there would be more than 700 thousand new diabetics per year in 24-74 years old Chinese if Chinese population were 1.3 billion in the early 21st century.

Adult↗
PubMed1996

[Chemical constituents of Aster albscens Hand.-Mazz].

Four compounds, stigmasterol, D-hurulon-14-en-3-ol, stigma-delta7.22-dien-3beta-palmitate and friedelin were isolated from the root of Aster albscens for the first time. Their structures were elucidated by spectral methods.

Asteraceae↗
PubMed1995

A lectin-like peptide isolated from the venom of the Chinese bird spider Selenocosmia huwena.

A peptide with haemagglutination activity was isolated from the venom of the Chinese bird spider Selenocosmia huwena by means of ion-exchange and reverse-phase high-performance liquid chromatography. This peptide, named SHLP-I, agglutinates human and mice erythrocytes at a minimum concentration of 125 micrograms/ml and 31 micrograms/ml, respectively. It consists of 32 amino acid residues including 3 Trp and 6 Cys residues, the latter of which form three disulfide bounds. The complete amino acid sequence was determined. The N-terminal and C-terminal residues were Gly and Trp, respectively. SHLP-I shows homology with a fragment of great nettle lectin and with huwentoxin-I from the venom of the same spider.

Amino Acid Sequence↗
PubMed1995

Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease.

Chromosomal diversity and relationships among 126 Streptococcus pyogenes strains expressing M1 protein from 13 countries on five continents were analyzed by multilocus enzyme electrophoresis and restriction fragment profiling by pulsed-field gel electrophoresis. All isolates were studied for the presence of the gene encoding streptococcal pyrogenic exotoxin A by PCR. Strain subsets were also examined by automated DNA sequencing for allelic polymorphism in genes encoding M protein (emm), streptococcal pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B (interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven distinct emm1 alleles that encode M proteins differing at one or more amino acids in the N-terminal variable region were identified. Although substantial levels of genetic diversity exist among M1-expressing organisms, most invasive disease episodes are caused by two subclones marked by distinctive multilocus enzyme electrophoretic profiles and pulsed-field gel electrophoresis restriction fragment length polymorphism (RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA gene and was recovered worldwide. Identity of speA, emm1, speB, and ska alleles in virtually all isolates of ET 1/RFLP type 1a means that these organisms share a common ancestor and that global dispersion of this M1-expressing subclone has occurred very recently. The occurrence of the same emm and ska alleles in strains that are well differentiated in overall chromosomal character demonstrates that horizontal transfer and recombination play a fundamental role in diversifying natural populations of S. pyogenes.

Amino Acid Sequence↗
PubMed1995

Detection of human papillomavirus types 16, 18 DNA related sequences in bronchogenic carcinoma by polymerase chain reaction.

In studying the relationship between human papillomavirus (HPV) and bronchogenic carcinoma, "high-risk" HPV 16, 18 DNA sequences were detected in samples from 50 lung cancer patients, 18 patients with benign pulmonary diseases and 4 fetal lung tissues by polymerase chain reaction (PCR) and dot-blot hybridization with biotin-labelled probes. The results showed that HPV 16, 18 DNA related sequences were found in 32% of lung cancer specimens, with 10 cases of HPV 16, 5 cases of HPV 18 and 1 case of both types. 48.15% (13/27) of squamous cell carcinomas were shown to be positive for HPV 16, 18 DNA. In addition, two adenocarcinomas and one small cell carcinoma were positive for HPV 16 DNA. No specimens from benign diseases tissues and fetal lung tissues showed positive results. These results suggest that primary bronchogenic carcinoma is related to HPV infection.

Adenocarcinoma↗
PubMed1995

[Effect of dietary and/or exercise intervention on incidence of diabetes in 530 subjects with impaired glucose tolerance from 1986-1992].

577 subjects with impaired glucose tolerance (IGT) aged from 25 to 74 were identified in Daqing in 1986. They were stratified according to BMI > or = 25 (352 cases) and BMI < 25 (225 cases) and subjects in each BMI group were randomly assigned to four groups: control, diet, exercise and diet plus exercise intervention groups (each group had similar age, BMI, fasting and 2-hour plasma glucose level). A six-year follow up study indicated that incidence of diabetes per 100-person-year was 15.7, 10.0, 8.3 and 9.6 in control, diet, exercise and diet plus exercise groups respectively. Proportional hazards regression analysis controlling for differences in baseline factors (age, sex, BMI and plasma glucose) showed that diet and/or exercise intervention were inversely related to the incidence of diabetes. The better the actual intervention, the less the incidence of diabetes. Therefore, the results strongly indicate that diet and/or exercise intervention treatment are effective methods to reduce the incidence of diabetes.

Adult↗