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Biomedical subjects

F H Top

Publications and source records attributed to F H Top.

At least 37 records · Page 2Linked to original sources
PubMed1976

Virus-enhanced modulation of cell surface antigens: effect on immune lytic susceptibility.

Monkey kidney cells, upon progressive subculture, became refractory to complement (C)-dependent immune cytolysis by anti-cell serum. Arbovirus infection restored these cells to a state of lytic susceptibility. Similar results were also abtained with antibody-dependent cellular cytotoxicity (ADCC), which is C independent. Antibodies raised against different subcultures varied considerably in lytic efficiency, indicating changing patterns of host cell expression during continous subculture. Taken together with the fact that arbovirus infection festored the lytic efficiency of all antibody preparations to the same degree suggested some form of host cell antigen re-expression as a mechanism. The results obtained in several exploratory experiments indicated that the antigenic re-expression responsible for the restoration of lysis was probably a local or selective rather than a generalized phenomenon. Thus, the amount of host cell surface antigen, measured by the use of mouse anti-cell serum and 125I anti-mouse globulin, was identical in both uninfected lytic susceptible and refractory cells, and decreased in both functional states following infection. Further, the binding of 125I concanavalin A, used to quantify surface glycoproteins, was similar in both lytic refractory and susceptible cells, and in both cases declined folowing virus infection. This result was incompatible with gross "masking" of cell surface antigens by exuberant production of surface coat material in lytic resistant cells. Finally, brief trypsinization of lytic resistant cells yielded an 8-fold increase in immune lysis, a result further consistent with local rather than generalized surface changes. The data were discussed interms of modulation of cell surface antigens affected both by repeated subculture and arboviral infection, and as a possible in vitro correlate of altered self-reactivity.

Animals↗
PubMed1975

Subtypes of hepatitis B surface antigen in Southeast Asia.

The prevalences of hepatitis B surface antigen (HBs Ag) subtypes in Thais, Cambodians, and Vietnamese were compared with the prevalences in Americans residing in Southeast Asia. HBs Ag was found with approximately equal frequency in Thai (43 percent) and American (39 percent) patients with hepatitis. However, higher prevalences of HBs Ag were found in asympotomatic Thais (9.5 percent), Cambodians (11.9 percent), and Vietnamese (14.3 percent) than in asymptomatic Americans (0.7 percent). Among asymptomatic Thais, the ratio of HBs Ag/adr to HBs Ag/adw was approximately 10:1, with one exception: adw was not detected in a rural population of northern Thailand. The y determinant was not found in Thais. In contrast, both d and y determinants were found in Americans. These observations conform to a geographic pattern, with ad as the predominant combination in the Far East. In Southeast Asia determinants w and r are more useful epidemiologic markers than y and d.

Animals↗
PubMed1975

An epidemiologic study of hepatitis B virus in Bangkok, Thailand.

Residents of a randomly selected sample of households in a low-income housing project in Bangkok were studied between July 1971 and April 1972. Prevalence of hepatitis B antigen (HBs Ag) in July 1971 was 8.2% in 697 persons age one year and older and changed little with age. Prevalence of antibody to HBs Ag (anti-HBs) was much higher in all age groups and was 46% overall. The prevalence of HBs Ag was higher in males than females from ages 10-29 years and the prevalence of anti-HBs was higher in males up to age 60. The HBV (combined HBs Ag and anti-HBs) age prevalence distribution in July 1971 revealed that over 20% of the children 1-4 years of age had serologic evidence of infection and that the prevalence rose rapidly with age reaching a plateau between 60-70% after age 15. During the nine months of serologic surveillance 13% of individuals acquired either HBs Ag or anti-HBs and 7% lost serologic evidence of HBV infection. The study data suggest that most HBs Ag positive persons are long-term antigen carriers, that their numbers and spatial distribution may be sufficient to account for the wide-spread transmission of HBV in this population, that close person-to-person contact with carriers is probably the most important mode of HBV transmission, and that the susceptibility to becoming an HBs Ag carrier is probably genetically determined.

Adolescent↗
PubMed1975

Hepatitis B antigen in saliva, urine, and stool.

A survey of hepatitis B patients, asymptomatic hepatitis B antigen (HBsAg) carriers, and control subjects was conducted to determine the relationship between antigenemia and antigen excretion in saliva, urine, and stool. Radioimmunoassay was used to detect HBsAg. Specificity-confirmed HBsAg was detected in the saliva of 6 (30%) of 20 antigenemic patients, 1 (5%) of 20 nonantigenemic patients, 14 (34%) of 41 carriers, and 0 of 112 controls. HBsAg was detected in urine only after 100-fold concentration of first-morning specimens. Specificity-confirmed HBsAg was present in the urine of 7 (16%) of 43 carriers; unconfirmed HBsAg was found in the urine of 5 (13%) of 38 patients and 5 (5%) of 112 controls. Unconfirmed HBsAg was detected in concentrated stool specimens from 5 (46%) of 11 patients and 3 of 8 carriers and controls. Longitudinally collected specimens from antigenemic subjects showed no consistent patterns of antigen excretion.

Carrier State↗
PubMed1975

Control of adenovirus acute respiratory disease in U.S. Army trainees.

Although limited almost exclusively to military trainees, acute respiratory disease (ARD) caused by adenovirus types 4 and 7 had been the leading cause of hospitalization in U.S. Army personnel. This decrease which resembles influenza in clinical manifestations led to hospitalization of as many as 50% of military trainees in midwinter and imposed a heavy burden on military hospitals and training programs. In studies undertaken from 1965 to 1970, live adenovirus type 4 and subsequently type 7 vaccines were found to be safe and immunogenic and to confer protection against type specific adenovirus ARD. For the past 5 yr. military trainees have been immunized with both adenovirus vaccines during periods of expected adenovirus disease. Since 1966, use of adenovirus vaccines has been monitored through the adenovirus surveillance program which yields weekly data on incidence and etiology of ARD in basic combat trainees. Since 1973, stable adenovirus vaccines have resulted in excellent control of adenovirus ARD. Potential problems with this immunization program are discussed.

Adenoviridae↗
PubMed1975

Evaluation of the plasma kinin system in dengue hemorrhagic fever.

The role of the plasma kinin system in the pathogenesis of dengue hemorrhagic fever (DHF) ws explored by simultaneously measuring factor XLL (Hageman), prekallikrein, kallikrein inhibitors, bradykinin, and complement (C3) in the blood of Thai children with DHF and acute febrile illnesses other than dengue. Prekallikrein, factor XII, and C3 levels were significantly lower in DHF patients compared to fever control patients with the lowest mean levels found in dengue patients with shock. However, bradykinin concentrations were not elevated and mean activity levels of kallikrein inhibitors were not depressed in dengue patients. Two dengue patients first studies at least 2 days before onset of shock had falling C3 levels which were more closely related temporally to the onset of shock than were their rising levels of prekallikrein. The results fail to provide convincing evidence ofr activation of the plasma kinin system leading to free bradykinin or a significant role for bradykinin in the immunopathogenesis of DHF. By contrast, the results refocus attention on complement as a potentially important humoral mediator of the dengue shock syndrome.

Antigens, Viral↗
PubMed1972

Enteric immunization with live adenovirus type 21 vaccine. I. Tests for safety, infectivity, immunogenicity, and potency in volunteers.

Studies were undertaken in volunteers to determine whether living adenovirus type 21 (ADV-21) vaccine could be safely administered orally to susceptible young adults. In the first study, ten volunteers were fed 10(6.4) tissue culture infectious dose(50) (TCID(50)) of ADV-21 vaccine virus, and five received placebo tablets. Nine of ten infected volunteers shed ADV-21 in stools (mean duration, 10.1 days; range, 4 to 17 days). No pharyngeal excretion of ADV-21 was observed in any of these volunteers. Each of the nine developed type-specific neutralizing (N) antibodies to ADV-21. No evidence for person-to-person transmission of vaccine was observed. In a second study, volunteers were immunized with ADV-21 vaccines containing 10(6.8), 10(4.6), and 10(2.4) TCID(50). ADV-21 N antibody responses were detected in nine of eleven who received the highest dose, six of twelve who received the middle dose, and two of twelve who were fed the lowest dose. None of twelve susceptible volunteers receiving the placebo capsule developed ADV-21 N antibodies postimmunization. This study established that the human infectious dose(50) for these lots of ADV-21 vaccine was approximately 10(4.6) TCID(50) and that the dose response to ADV-21 vaccine was lower than those previously reported for live ADV-4 and ADV-7 enteric vaccines.

Adenoviridae↗