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Biomedical subjects

J Chin

Publications and source records attributed to J Chin.

At least 181 records · Page 10Linked to original sources
PubMed1981

An outbreak of congenital rubella.

A large outbreak of rubella occurred in the San Francisco Bay Area in early 1979. Later that year and in early 1980, 13 cases of confirmed or probable congenital rubella syndrome were reported. Results of a subsequent investigation strongly suggest that these two events were related in a causal manner and do not represent an indirect association based on changes in diagnostic or reporting thoroughness. To prevent such episodes in the future, renewed emphasis must be placed on routine immunization of young children of both sexes, rigorous enforcement of school-entry immunization laws and selective immunization of women of childbearing age.

Adolescent↗
PubMed1979

Honey and other environmental risk factors for infant botulism.

Infant botulism results from the in vivo production of toxin by Clostridium botulinum after it has colonized the infant's gut. Epidemiologic and laboratory investigations of this recently recognized disease were undertaken to identify risk factors and routes by which C. botulinum spores might reach susceptible infants. Clostridium botulinum organisms, but no preformed toxin, were identified in six different honey specimens fed to three California patients with infant botulism, as well as from 10% (9/90) of honey specimens studied. By food exposure history, honey was significantly associated with type B infant botulism (P = 0.005). In California, 29.2% (12/41) of hospitalized patients had been fed honey prior to onset of constipation; worldwide, honey exposure occurred in 34.7% (28/75) of hospitalized cases. Of all food items tested, only honey contained C. botulinum organisms. On household vacuum cleaner dust specimens and five soil specimens (three from case homes, two from control homes) contained Clostridium botulinum. The known ubiquitous distribution of C. botulinum implies that exposure to its spores is universal and that host factors contribute importantly to the pathogenesis of infant botulism. However, honey is now an identified and avoidable source of C. botulinum spores, and it therefore should not be fed to infants.

Botulism↗
PubMed1979

Statistics of flexible chain configurations.

When Monte Carlo methods are employed to study the statistical dimensions of flexible polymer chains, it is necessary that the sampling be statistically unbiased. One Monte Carlo procedure is the so-called "slithering snake" technique, which has proved to be very useful. A question arises, however, as to how long it takes for a "slithering snake" to be completely regenerated to avoid biasing the samples around a particular configuration. It is demonstrated theoretically and verified by Monte Carlo studies that the number of iterations required to completely regenerate a sample polymer is a quadratic function of the chain length. This verification applies to chains in dilute solution but may not hold for bulk polymers.

Journal Article↗
PubMed1979

Further observations on infections of guinea pigs with Venezuelan encephalitis virus strains.

Guinea pigs from a Guatemalan colony died after subcutaneous inoculating of moderately small doses of equine-benign strains of Venezuelan encephalitis (VE) virus of hemagglutination-inhibition subtype I-E from enzootic habitats in Mexico and Guatemala. Thus these guinea pigs were unlike English short hair and inbred 13 guinea pigs, which usually survive infections with equine-benign VE strains of subtype I-E. We therefore caution others that not all strains of guinea pigs can be used to evaluate the potential equine virulence of VE viruses.

Animals↗
PubMed1978

Intestinal infection and toxin production by Clostridium botulinum as one cause of sudden infant death syndrome.

The spontaneous production of botulinum toxin in the infant gut by ingested Clostridium botulinum organisms is the underlying cause of infant botulism, recognised as an infectious disease only in late 1976. Because of the recognition of the pathophysiology of this disease and because the known potency and action of botulinum toxin can lead to rapid respiratory arrest, it appeared possible that the in-vivo production of botulinum toxin could cause the sudden death of some infants. To test this hypothesis, serum, selected tissues, and bowel contents from 280 dead infants were examined for the presence of C. botulinum toxin and/or organsisms. We found C. botulinum organisms in 10 infants, all of whom died suddenly and unexpectedly. 9 of these deaths were classified by the forensic pathologist as sudden infant death syndrome (S.I.D.S. or crib death). In 2 of these 10 sudden deaths both C. botulinum organisms and botulinum toxin were identified, and from the spleen of 1, C. botulinum organisms were isolated. Faecal specimens from 160 age-matched healthy infants who served as controls in studies of inpatient infant botulism cases were negative for both C. botulinum organisms and toxin, except for one specimen that contained only C. botulinum type A organisms. The 9 S.I.D.S. cases with evidence of C. botulinum infection comprised 4.3% of the 211 S.I.D.S. cases examined over 12 months. These findings suggest that intestinal production of botulinum toxin by C. botulinum is one cause of S.I.D.S. The strikingly similar age-distribution of 62 inpatient infant botulism cases and the 211 S.I.D.S. cases is also consistent with this concept. The possibility that in-vivo production of botulinum toxin may account for a larger proportion of S.I.D.S. cases is discussed.

Botulinum Toxins↗
PubMed1978

Mammalian cell mutant requiring cholesterol and unsaturated fatty acid for growth.

A mutant requiring both cholesterol and oleate for growth has been isolated from mutagenized Chinese hamster ovary cells. By comparison with wild-type cells, sterol and unsaturated fatty acid biosynthetic activities in the mutant cells grown in fetal calf serum medium appear to be nearly intact. However, whole-cell radioactive acetate, mevalonate, dihydrolanosterol, and stearate incorporation studies show that sterol synthesis from acetate, lanosterol demethylation, and fatty acid desaturation are defective in the mutant cells grown in delipidated serum medium. In vitro enzyme assays with crude cell extracts demonstrated that beta-hydroxy-beta-methylglutaryl-coenzyme A reductase is not induced in the mutant. These experiments were substantiated by gas/liquid chromatographic analyses which showed the sterol content and the percentage unsaturated fatty acids in mutant cells to be drastically reduced when the cells are grown in delipidated serum medium. A spontaneous revertant exhibiting prototrophic growth in lipid-free medium has been isolated from 50 X 10(6) mutant cells. All three defects in this revertant reverted back in parallel, which suggests that these three biosynthetic activities may be controlled by a common regulatory mechanism.

Cell Division↗
PubMed1978

Co-circulation of two influenza A (H3N2) antigenic variants detected by virus surveillance in individual communities.

From March through June 1977 a total of 31 influenza A (H3N2) viruses were isolated from students with respiratory disease who were seen at the student health service on the Berkeley campus of the University of California, and 32 influenza A (H3N2) viruses were isolated from persons who participated in a city-wide febrile respiratory disease surveillance program in Seattle. The antigenic specificity of the hemagglutinin was determined for each isolate by hemagglutination inhibition testing with sera from ferrets infected with prototype strains A/Victoria/3/75 and A/Texas/1/77. In each of the three months, April, May and June, A/Victoria/3/75-like and A/Texas/1/77-like viruses were identified among isolates from both communities, and the numbers of isolates of the two antigenic variants from patients seen with influenza-like illnesses were similar. The findings emphasize the need to examine multiple isolates even from within single communities to determine the antigenic specificity of current strains of influenza virus.

Adolescent↗
PubMed1978

Testing of hypoxic cell radiosensitizers in vivo.

Use has been made of the transplantable KHT sarcoma in C3H mice to test the in vivo effectiveness of some 2-, 4-, and 5-nitroimidazoles as hypoxic cell radiosensitizers. A comparison of the in vivo versus the in vitro sensitizing ability of misonidazole and metronidazole indicates some differences, probably due to drug delivery problems in vivo. The relative sensitizing abilities of eight 2-nitroimidazoles, two 4-nigroimidazoles and two 5-nitroimidazoles are compared on the basis of the amount of drug injected and the plasma levels obtained.

Animals↗
PubMed1977

Infant botulism. Epidemiological, clinical, and laboratory aspects.

Clostridium botulinum organisms and toxin were identified in the feces of six infants, aged 5 to 20 weeks, who had illnesses clinically consistent with botulism. Five of the infants lived in California and became ill within a six-month period in 1976; one infant became ill in New Jersey in 1975. Three cases were type A botulism, and three were type B. No source of ingested botulinal toxin could be found in any case. However, one infant with type B botulism had ingested a food containing C botulinum type B organisms, and no toxin was found in it. The clinical findings in these cases include constipation, weak sucking and crying ability, pooled oral secretions, cranial nerve deficits, generalized weakness, and, on occasion, sudden apnea. A characteristic electromyographic pattern termed "brief, small, abundant, motor-unit action potentials" (BSAP) was observed. The sources of C botulinum toxin for these six infants is thought to have been in vivo (gastrointestinal) production following ingestion of C botulinum organisms. Studies are underway to determine the full clinical spectrum, incidence, and potential public health importance of this infectious disease newly recognized in infants.

Age Factors↗
PubMed1977

Responses of guinea pigs to infections with strains of Venezuelan encephalitis virus, and correlations with equine virulence.

Five equine-virulent strains of Venezuelan encephalitis (VE) virus consistently killed guinea pigs (strain English short hair) inoculated subcutaneously, whereas ten equine benign strains did not. Two enzootic eastern Panamanian and Colombian strains of hemagglutination-inhibition antigenic subtype I-D and of undetermined virulence for equine animals also killed guinea pigs. This subtype of VE virus may represent an excpetion to a positive correlation between equine virulence and guinea pig lethality since another strain of ts subtype has been reported to be benign in horses inoculated subcutaneously. Within the strains tested, viruses of subtypes I-ABC and I-D were lethal for guinea pigs, and viruses of other subtypes were benign. There was no correlation between guinea pig and human virulence of VE strains.

Animals↗
PubMed1974

Stimulation of erythroblast maturation in vitro by sphingolipids.

A lipid factor previously isolated from leukocytes and found to stimulate basophilic erythroblast formation in an in vitro system of incubated rabbit bone marrow cells has been analyzed by thin-layer chromatography, gas-liquid chromatography, and gas-liquid chromatography-mass spectrometry. The biologically active components are sphingosine ceramides of tetracosanoic and dehydrotetracosanoic acids. Tests of a series of related ceramides show a high degree of structural specificity for the C(24)-V-acyl compounds with significant but markedly lower activity of the C(22) analog. Commercially available sphingomyelin shows activity comparable to that of the tetracosanoic acid ceramide. Sphingosine and tetracosanic acid supplied in equimolar amounts have negligible activity. The results, in the context of other findings, suggest a possible supportive role of plasma ceramides and sphingomyelins in red cell maturation.

Animals↗
PubMed1974

The epidemiology of influenza in California, 1968-1973.

Influenza is one of the most common acute febrile respiratory diseases in adults. Epidemics caused by influenza viruses occur every few years. When such epidemics are in progress, the medical community, the general public and the news media seek information regarding the presence, spread and severity of influenza. The methods and findings of the Influenza Surveillance System in California for the years 1968 through 1973 should be of interest generally. This period spans the total California experience with the type A Hong Kong variant (A/Hong Kong/1/68 [H(3)N(2)]), and the first appearance of the English strain of type A influenza virus (A/England/42/72 [H(3)N(2)]). The surveillance of influenza during this period showed that there were major epidemics in Calfornia only during the state's first experience with the type A Hong Kong variant in 1968-69, and with the English strain in 1972-73. Problems and limitations in influenza surveillance do exist. Nonetheless, the major surveillance indices used (school absenteeism, laboratory data and deaths from pneumonia and influenza) are reliable and sensitive indicators of general trends of influenza virus activity. These indices are most useful in comparing the relative severity of influenza epidemics. However, since these indices usually lag several weeks behind the occurrence of disease, this lag must be considered in making estimates of current incidence trends based on these indices.

Adolescent↗
PubMed1973

Botulism--diagnosis, management and public health considerations.

Botulism is an uncommon but often fatal disease associated with ingestion of a potent neurotoxin present in improperly preserved foods. Exposures to commercially preserved foods with an odd or peculiar taste almost never represent exposure to botulism toxin. Improperly prepared home-canned products which are tasted or consumed without heating are more likely to be associated with botulism. The management of suspect and confirmed cases of botulism is presented by medical epidemiologists in the State Department of Public Health, Bureau of Communicable Disease Control, to provide physicians in California with a practical approach to this problem.

Botulism↗
PubMed1973

Epidemiology of viral hepatitis in California, 1950-1970.

Epidemiologic patterns of type A (infectious) and type B (serum) hepatitis in California from 1950 to 1970 are presented. During this period hepatitis incidence increased greatly among teenagers and young adults but no significant increase occurred in other age groups. Much of this age-specific increase is related to the increasing drug abuse problem during the last decade. Other factors which possibly contribute to the current pattern of hepatitis in California are the overcrowding and inadequate sanitary facilities among a portion of young people between the ages of 15 and 30. Until these factors change or effective vaccines are developed, viral hepatitis will continue to be a significant public health problem.

Adolescent↗