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Biomedical subjects

S F Chang

Publications and source records attributed to S F Chang.

At least 73 records · Page 4Linked to original sources
PubMed1993

Cytomegalovirus recurrence in seropositive pregnant women attending obstetric clinics.

To understand reasons for cytomegalovirus (CMV) recurrence, a cohort of 350 CMV-seropositive pregnant women attending obstetric clinics in Taiwan was examined for cervical or urinary CMV shedding. Urine specimens were collected from 350 women and cervical secretion specimens were collected from 220 women. We measured the association of various factors with CMV recurrence, which was defined as viral shedding identified by the presence of a CMV-specific gene sequence amplified by the polymerase chain reaction in seropositive individuals. CMV recurrence status was independently associated with a sexual activity composite variable, which was defined by three sexual activity indicators: age at first sexual intercourse, total years of sexual experience, and average frequency of sexual intercourse prior to pregnancy. Pregnant women with a history of genital tract infection were more likely than women without such history to experience cervical CMV recurrence. Similarly, pregnant women with previous urinary tract infections were more likely to experience urinary CMV recurrence. The findings indicate that multiple exposure to CMV by sexual activity prior to pregnancy is an important determinant of CMV recurrence during pregnancy.

Antibodies, Viral↗
PubMed1993

Kinetics of absorption of a new once-a-day formulation of theophylline in the presence and absence of food.

Two three-way crossover studies were done to characterize the drug release characteristics of Monospan (3M Pharmaceuticals, St. Paul, MN) capsules, a new once-a-day theophylline formulation. In the first study, 22 healthy males received single 450-mg doses of Monospan in the presence and absence of a high-fat breakfast; the same dose of Somophyllin (Fisons, Rochester, NY) immediate-release liquid was given to fasted subjects as a reference. The second study involved 29 healthy males given a single dose of 900 mg of Monospan in the presence and absence of the same high-fat meal; Theo-24 (G. D. Searle and Co., Skokie, IL) capsules were given to fasted subjects as a reference. The results of both studies showed that food did not affect the absorption of theophylline from Monospan; peak concentration, to and area under the serum concentration-time curve were all unchanged. The absorption rates were similar with both strengths and dietary conditions and showed that theophylline was absorbed slowly from Monospan at a constant rate (approximately 3.2%/h) over 24 h. Absorption continued past 24 h, and the extent of absorption from Monospan compared with that from each reference averaged 88% or higher. A good correlation (r > 0.980) was observed for Monospan between the amount absorbed in vivo and the amount released in the in vitro dissolution test, a result that demonstrates the precise rate control of Monospan. We conclude that Monospan is a suitable once-a-day formulation that can be taken without regard to food.

Absorption↗
PubMed1993

High rate of concurrent genital infections with human cytomegalovirus and human papillomaviruses in cervical cancer patients.

A case-control study evaluated a possible association between infection with human papillomavirus (HPV) or cytomegalovirus (CMV) and cervical cancer. Seventy-eight patients with cervical cancer (cases) were compared with 55 age-compatible patients with uterine leiomyoma (controls). Genital CMV and HPV infections were diagnosed by polymerase chain reaction amplification of viral DNA in cervical tissues. Smoking, first coitus or pregnancy before age 20, multiple sex partners, history of multiple pregnancies, and frequent sexual intercourse were important factors associated with cervical cancer. Only 9% of the cases versus 29.1% of the controls did not have genital infection with either virus. Concurrent genital CMV and HPV infection was noted in 51.3% of the cases but in none of the controls. HPV infection alone occurred in 15.4% of the cases but in only 5.5% of the controls. CMV infection alone was associated with no increased risk for cervical cancer. These data suggest that a synergistic interaction may occur between these two viral infections in the oncogenesis of cervical cancer.

Adult↗
PubMed1993

Progressive alterations of cytokeratin expressions in the process of chronic arsenism.

Recent studies of an endemic occurrence of chronic arsenism in a limited area on the southwest coast of Taiwan are focusing on its cytokeratin analysis in hopes of tracing the disease's biochemical expression. Specimens were obtained from uninvolved skin and arsenical cancers including Bowen's disease, basal cell carcinoma, and squamous cell carcinoma. In this study, we used two-dimensional polyacrylamide gel electrophoresis to analyse cytokeratin expression. Progressive alterations in cytokeratin expression were found in various skin lesions. These include an expression of K16 in the uninvolved skin; K16 and K6 in Bowen's disease; and K16, K6 and K17 in squamous cell carcinoma and basal cell carcinoma. In addition, we found that the K1 isoelectric variants shifted to more acidic forms with the complete absence of K1 in basal cell carcinoma. K16 expression in uninvolved skin indicates that it is nevertheless in a hyperproliferative status. K17 was expressed in squamous cell carcinoma and basal cell carcinoma, but not in Bowen's disease. The progressive impairment of phosphorylation of K1 and K2 in the process of chronic arsenism provides us with a suitable model for studying the biological significance of phosphorylation in intermediate filaments during chemical carcinogenesis.

Arsenic Poisoning↗
PubMed1993

Cytomegalovirus excretion in pregnant and nonpregnant women.

Cervical and urinary excretion of cytomegalovirus by Taiwanese women was identified by the presence of a cytomegalovirus-specific immediate-early gene sequence amplified by the polymerase chain reaction. Excretion rates during the first trimester of pregnancy resembled rates for nonpregnant women. As pregnancy proceeded, the cervical excretion rate increased from 13 to 40% and the urinary excretion rate increased from 1 to 13%.

Adult↗
PubMed1993

[Epidemiological study of cerebrovascular disease in the Taiwan area: current status].

We reviewed the reported epidemiological studies on cerebrovascular disease in the Taiwan area and discussed the following advantages and drawbacks of different approaches to data acquisition and analysis of the results. 1) Analysis of the data from vital statistics is readily available, and gives adequate information for secular trends, but the reliability of death certificate and the accuracy of subtypes of cerebrovascular disease must be taken into consideration. 2) A series of patients based on hospital registration can provide detailed data about the clinical manifestation and subtypes of stroke; whereas selection bias among hospitals may distort some clinical profile, and patients who have not visited the hospital are not included. 3) A community survey can obtain representative distribution of diseases in a community, but it takes much manpower and cost. The diagnosis of stroke is not very reliable because of limited usage of computed tomography and insufficient participation by qualified neurologists. 4) A community based hospital study has the advantage of combining a hospital registry and a community survey. It is difficult to conduct this type of study in the current medical environment in Taiwan since the referral system has not been well established. 5) A study of the survivalship of stroke can provide valuable information about the natural course of cerebrovascular disease.

Cerebrovascular Disorders↗
PubMed1993

Characterization of R plasmids from Shigella sonnei in Taiwan.

Plasmids of 70MDa from 6 Shigella sonnei isolates originating in Kaohsiung, Taiwan were found. All of them encoded resistance to chloramphenicol and tetracycline. These plasmids belonged to the H II incompatibility group. The fertility inhibition property of plasmids was the fi- type. Restriction endonuclease analysis revealed the six plasmids all had identical restriction patterns with BamH I, Hind III and Nru I. All six plasmids carried the type I chloramphenicol acetyltransferase gene and the class B tetracycline resistance gene as determined by Southern hybridization with DNA probes of various antimicrobial resistance genes. The results demonstrated that S. sonnei isolates harboured the same R plasmid.

Chloramphenicol O-Acetyltransferase↗
PubMed1993

[Characterization of trimethoprim resistance in Shigella].

Ninety-seven Shigella strains from 1982 to 1987 were isolated. When these isolates were tested with minimal inhibitory concentrations of trimethoprim, twenty-two were found to be resistant. Among these, 10 were found to be S. flexneri, and 12 to be S. sonnei. In addition, all of these 22 isolates were found to have multiple drug resistance. In order to determine the type of dihydrofolate reductase (DHFR) genes in these 22 trimethoprim-resistant isolates, colony hybridization with probes representing types I, II, III and V DHFR, were used. The results revealed the presence of type I DHFR gene in all of these isolates. Further southern hybridization indicated that the type I DHFR gene was located on plasmids. In order to determine whether a trimethoprim resistant gene existed as a functional transposable element in these isolates, we used a specific probe to detect the prevalence of Tn7. However, no positive hybridization was found. The relationship between the trimethoprim resistant gene and integron is characterized by the fact that the integrase gene, in our study, was frequently found in all of the 22 resistant isolates. These results indicate that trimethoprim resistant genes might transfer among bacteria via site-specific integration.

Serotyping↗
PubMed1993

Cytomegalovirus transmission in special-care centers for mentally retarded children.

This study aimed to determine whether special-care centers for mentally retarded children are high-risk settings for cytomegalovirus (CMV) transmission. Serum and urine specimens obtained from 311 mentally retarded children aged 3 to 12 in three centers were compared for CMV seropositivity and CMV viruria with specimens from 360 normal children of the same ages. A seropositivity rate of 73.5% and a viruria rate of 8.7% were found among the children attending special-care centers. These rates were significantly higher than the 59.2% seropositivity and 1.7% viruria found among normal children. By logistic regression analysis, it was shown that the prevalence of CMV viruria in the class/center was one of the most important determinants for acquiring CMV infection. The data suggest that acquisition of CMV from playmates or classmates occurs frequently in special-care centers and that horizontal transmission of virus is the most plausible explanation for the higher prevalence of CMV infection among mentally retarded children.

Antibodies, Viral↗
PubMed1992

Seroepidemiology of cytomegalovirus infection among children between the ages of 4 and 12 years in Taiwan.

To determine risk factors responsible for primary cytomegalovirus (CMV) infection in Taiwan, samples of blood for antibody to CMV were obtained from 362 children aged 4 to 12 years: 58% were found to be positive for anti-CMV IgG antibody. Logistic regression analysis showed that seropositivity correlated with age, method of delivery, duration of breast feeding, and younger age of mother. Neither socioeconomic status nor crowded living conditions showed significant correlation with CMV seropositivity. Primary CMV infection in Taiwan appears to be less related to socioeconomic status shown in western countries, and, since the majority of pregnant women were seropositive in Taiwan, two of the major sources of primary CMV transmission are infected breast milk and the infected genital tract.

Adult↗
PubMed1992

Mutations adjacent to the dimple of the canine parvovirus capsid structure affect sialic acid binding.

The erythrocyte receptor on rhesus macaque erythrocytes used by canine parvovirus (CPV) for binding in hemagglutination (HA) was examined. Erythrocyte membrane proteins were electrophoresed and blotted to nitrocellulose and probed with [125I]-labeled CPV capsids, showing seven virus-binding proteins. Treatment of erythrocytes or isolated membranes with Clostridium perfringens neuraminidase virtually abolished virus binding. Binding was also affected by treatment with potassium periodate and inhibited by wheat germ agglutinin, but was not significantly affected by concanavalin A, peanut agglutinin, or soluble N-acetyl-neuraminlactose. A non-HA mutant of CPV failed to bind to erythrocytes or to blotted erythrocyte membrane proteins. The mutation was a single Arg-Lys difference of VP2 amino acid residue 377. The pH dependence of binding of the closely related feline panleukopenia virus was shown to result from a decreased binding in buffers with pH values of 6.8 or greater. The VP2 residues responsible for that difference have been shown to be 323 and 375. The sequences affecting binding were all adjacent to the dimple in the capsid, implicating that region of the capsid as the sialic acid binding site. The role of sialic acid in virus-host cell interactions was not defined, but the plaque sizes of the non-HA mutant and wild type CPV were indistinguishable.

Animals↗
PubMed1992

Drug resistance and plasmid profile of shigellae in Taiwan.

One hundred and twenty-eight shigella strains isolated from newborn and infant human faecal specimens at Kaohsiung Medical College Hospital in Taiwan were serogrouped, serotyped and examined for drug-resistance patterns and for the presence of plasmids. Forty-seven per cent of the isolates were found to belong to the Shigella sonnei serogroup, 41% to the S. flexneri group, 9% to the S. boydii group and 3% to the S. dysenteriae group. The serotype with the greatest number of strains was S. sonnei I. (29%) followed by S. flexneri 1 (27%). Each strain was tested for resistance to 11 antimicrobial agents. Eight-eight per cent of the strains were resistant to tetracycline, 87% to chloramphenicol, 84% to streptomycin, 52% to ampicillin, 25% to nalidixic acid, 29% to kanamycin, 11% to cephalothin, 11% to neomycin, 10% to cotrimoxazole, 1% to amikacin and none to gentamicin. The most prevalent resistance pattern was ApCmSmTc (28%). Clinical isolates demonstrating multiple resistance were found to harbour a large transmissible plasmid of 45-75 MDa while isolates without multiple resistance did not. Two large virulence plasmids of 123 and 110 MDa were found in 12 strains of S. flexneri and 4 strains of S. sonnei phase I. Small plasmids of 4.5, 4.2, 3.5, 2.8, 2.5. 2.0 and 1.5 MDa were also present in all strains. These small plasmids were species specific and can be used as marker plasmids to identify species.

Acute Disease↗
PubMed1992

The distribution of the DHFR genes in trimethoprim-resistant urinary tract isolates from Taiwan.

Between July 1987 and June 1989, 1054 urinary isolates of enterobacteria from Kaohsiung, Taiwan were studied for their trimethoprim resistance. Trimethoprim resistance was defined as MIC greater than 4 micrograms/ml and high-level resistance by MIC greater than 1000 micrograms/ml. The incidence of trimethoprim resistance increased from 33.6% in 1987 to 42.1% in 1989. Among the resistant strains studied, 90% were resistant to high levels of trimethoprim. An increase in the proportion of resistant strains (33.9-46.3%) exhibiting high-level non-transferable trimethoprim resistance was noted. The distribution of the dihydrofolate reductase (DHFR) genes by colony hybridization in 374 trimethoprim-resistant isolates revealed the presence of type I and type V DHFR genes in most of these isolates (45.4% and 10.4% respectively). Type I was predominant in Escherichia coli whereas type V was frequently seen in Enterobacter spp. None showed homology with the type II and type III DHFR probe DNA. In addition, transposon Tn7 was present in 7.8% of 374 trimethoprim-resistant enterobacteria.

DNA Transposable Elements↗
PubMed1992

Comparative absorption of atropine from a metered-dose inhaler and an intramuscular injection.

The inhalation of atropine sulfate from a pressurized metered-dose inhaler was investigated in a nonrandomized four-period rising-dose study. Eight healthy, nonsmoking subjects received 1.7, 3.4, and 5.2 mg of atropine sulfate by inhalation and 1.67 mg of atropine free base (equivalent to 2 mg of atropine sulfate) by intramuscular (i.m.) injection. Serum atropine sulfate concentrations were measured over a 24-h period by gas chromatography/mass spectrometry. Mean serum concentrations increased nonproportionally as the inhaled dose increased. Mean peak concentrations were 4.9, 6.1, and 7.9 ng/ml for the inhaled doses and 8.4 ng/ml for the i.m. dose. Typical anticholinergic effects were seen after all doses.

Absorption↗
PubMed1992

Characterization of an immortalized human cell line derived from neonatal foreskin diploid fibroblasts.

A new human skin cell line, designated as CCFS-1/KMC, immortalized from human neonatal foreskin diploid fibroblast cells, has been subcultured successfully in vitro for more than 500 passages. This anchorage-dependent cell line possesses many common features of transformation such as morphological and cytoskeletal changes, hypotriploidy, infinite lifespan, increasing plating efficiency and saturation density, and decreasing serum requirement and population doubling time. Human papillomavirus (HPV) type 18 DNA was detected in the cell line before and after immortalization by the polymerase chain reaction (PCR) method. Tumorigenicity, however, was not demonstrated in vivo. The isoenzyme activity of the cell line shows activation of a placental form of alkaline phosphatase and a changing lactate dehydrogenase isoenzyme pattern that is different from transformation by carcinogens. Class I HLA and class II HLA antigens are constitutively expressed on this skin cell line. Here we report that these immortalized human fibroblasts derived from neonatal HPV-18-DNA-contained diploid fibroblasts possess double minute chromosomes (DMs), a karyotypic aberration usually found in cancer cells.

Cell Division↗
PubMed1992

Molecular cloning and nucleotide sequencing of a novel aminoglycoside 6'-N-acetyltransferase gene from an R-plasmid of Salmonella typhimurium S24 isolated in Taiwan.

A conjugative aminoglycoside resistance plasmid pST2 has been isolated from Escherichia coli K-12 14R525, which was mated with a clinical isolate of Salmonella typhimurium S24. A novel resistance gene of aminoglycoside 6'-N-acetyltransferase[AAC(6')] was cloned from plasmid pST2 on a 1,393 kilobase (kb) of SphI-SalI fragment into vector pACYC184 and pUC18. This novel AAC(6') gene in plasmid pST2 acetylated kanamycin, amikacin, dibekacin, tobramycin, gentamicin, netilmicin, and sisomicin. The complete nucleotide sequence of the novel AAC(6') gene and its neighboring sequences were also determined. Minicell experiments detected only one protein of 24.7 kilodaltons (kDa) translated from an open reading frame of the 618 base pairs (bp) gene.

Acetyltransferases↗
PubMed1992

Multiple amino acids in the capsid structure of canine parvovirus coordinately determine the canine host range and specific antigenic and hemagglutination properties.

Canine parvovirus (CPV) and feline panleukopenia virus (FPV) are over 98% similar in DNA sequence but have specific host range, antigenic, and hemagglutination (HA) properties which were located within the capsid protein gene. In vitro mutagenesis and recombination were used to prepare 16 different recombinant genomic clones, and viruses derived from those clones were analyzed for their in vitro host range, antigenic, and HA properties. The region of CPV from 59 to 91 map units determined the ability to replicate in canine cells. A complex series of interactions was observed among the individual sequence differences between 59 and 73 map units. The canine host range required that VP2 amino acids (aa) 93 and 323 both be the CPV sequence, and those two CPV sequences introduced alone into FPV greatly increased viral replication in canine cells. Changing any one of aa 93, 103, or 323 of CPV to the FPV sequence either greatly decreased replication in canine cells or resulted in an inviable plasmid. The Asn-Lys difference of aa 93 alone was responsible for the CPV-specific epitope recognized by monoclonal antibodies. An FPV-specific epitope was affected by aa 323. Amino acids 323 and 375 together determined the pH dependence of HA. Amino acids involved in the various specific properties were all around the threefold spikes of the viral particle.

Amino Acid Sequence↗