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Biomedical subjects

W Stevens

Publications and source records attributed to W Stevens.

At least 73 records · Page 4Linked to original sources
PubMed1990

Development of a method to estimate thyroid dose from fallout radioiodine in a cohort study.

A cohort of 4831 persons aged 11-18 y in 1965 was identified among students in the schools of Washington County, UT; Lincoln County, NV; and Graham County, AZ. These children who had potentially been exposed to radioiodine from atomic weapons test fallout from the Nevada Test Site during 1951-1962 were selected for participation in a study of thyroid disease. The entire cohort was first examined during 1965-1968 for thyroid abnormalities. A total of 3,085 of these people were again reexamined during 1985-1986 to determine any subsequent occurrence of thyroid disease. In order to determine the relationship of the radiation dose to the thyroid with incidence of thyroid disease, we have developed a suite of models to calculate estimates of the internal dose received by the thyroid from fallout radioiodines. For completeness, the exposure to the thyroid from external radiation is also estimated. Dose estimates are made specific to each individual in the study using individual residential histories, the locality-specific exposure rate and radionuclide deposition, descriptions of dairy management for identified milk producers, and the subjects' sources of foods and intake rates of milk and leafy vegetables determined by interview. Other data such as the relationship of radioiodine deposition to measured exposure rate, environmental transfer parameters, and age-dependent factors for the conversion of radioiodine intake to thyroid dose were taken from work of other investigators. Dairy management information, milk distribution practices, the milk source for each study subject, as well as age-specific intake rates of milk and leafy vegetables, were determined by interview.

Adolescent↗
PubMed1990

Individual external exposures from Nevada Test Site fallout for Utah leukemia cases and controls.

External gamma-ray exposures from fallout originating at the Nevada Test Site (NTS) have been assigned to 6,507 individual subjects (1,177 leukemia cases and 5,330 control subjects) who died as Utah residents between 1952 and 1981. Leukemia cases were identified, confirmed, and classified by cell type from the Utah Cancer Registry, Utah State vital records, and medical records. Residential histories were obtained from the Deceased Membership File (DMF) of the Church of Jesus Christ of Latter-day Saints (LDS), supplemented by information from the LDS Church Census Records that were taken in 1950, 1955, and 1960-62. Control subjects were selected randomly within age strata from the DMF and were frequency-matched to the cases by age at death and for sex. Individual radiation exposures were assigned as a function of residence location and time interval for each residence during the fallout period (1951-1958) using geographic exposure data taken from the literature. Temporal distribution of exposure for subjects who resided in more than one locality or who were born or died during the fallout period was determined from data of other investigators. Calculated gamma-ray exposures for each place of residence were summed for each subject to yield the exposure to fallout from the NTS.

Case-Control Studies↗
PubMed1990

Cohort study of thyroid disease near the Nevada Test Site: a preliminary report.

The atmospheric testing of nuclear weapons in Nevada beginning in 1951 resulted in exposure of regions surrounding the Nevada Test Site (NTS) to fallout. A cohort of children born between 1947 and 1954 in two counties near the NTS, one in Utah and one in Nevada (UT/NV), were examined in 1965-1968 for thyroid abnormalities that might have been a result of exposure to radioiodine in fallout. The prevalence of thyroid abnormalities in these children (11-18 y) was compared to that in a control group selected from a county in Arizona (AZ) that was presumed to have received little or no fallout from the NTS. Thyroid nodules were found in 76 of the 4,819 children examined (15.8/1000). Of the 76 thyroid nodules, 22 were diagnosed as neoplasms. The rate of thyroid neoplasms among the UT/NV subjects was higher (5.6/1000) than among the AZ subjects (3.3/1000) (RR = 1.7), but because the number of neoplasms was small, the difference was statistically insignificant. In 1985-1986, 3,122 of the original study subjects were reexamined. In this reexamination, thyroid nodules were found in 125 individuals (44.2/1000). Of the 125 thyroid nodules detected during this later study period, 65 were considered to be thyroid neoplasms. Rates of thyroid neoplasms in UT/NV (24.6/1000) are again slightly higher than in AZ (20.2/1000) (RR = 1.2), but the difference is not significant (p = 0.65). Based on the rates of thyroid neoplasms in the two geographic locations, we conclude that living near the NTS in the 1950s has not resulted in a statistically significant increase of thyroid neoplasms in subjects from UT/NV when compared with subjects of the same age and gender living in AZ.

Adolescent↗
PubMed1989

Multiple regulatory elements of the murine gamma 2-crystallin promoter.

Crystallins are the major water-soluble proteins of the vertebrate eye lens. These lens-specific proteins are encoded by several multi-gene families whose expression is differentially regulated during development. Our previous studies showed that the mouse gamma 2-crystallin promoter is active on transfection into lens-explant cultures derived from 14-day-old chick embryos but not on transfection into a variety of non-lens cells. In this study, transient expression data show that a sequence of 226 nucleotides upstream from the transcription start site is sufficient for activity of this promoter in the chicken lens cells. This sequence can be further divided into two domains, A and B, both of which are required for promoter function. Domain A (nucleotide -68 to -18) contains the TATA box and sequence motifs that are conserved in all gamma-crystallin promoters. Domain B (-226 to -120) consists of three regions. One of these regions contains an element with dyad symmetry and a sequence similar to the octamer motif. The second region contains an enhancer core consensus sequence. Two "enhancer-like" activities have been detected, one in Domain B and a second in a more distal region (-392 to -278) that does not appear to be required for promoter activity in transfection assays.

Animals↗
PubMed1987

Serologic and immunologic studies in patients with AIDS in North America and Africa. The potential role of infectious agents as cofactors in human immunodeficiency virus infection.

Serologic and immunologic studies were performed in 38 African and 60 US patients with acquired immunodeficiency syndrome (AIDS), 100 African and 100 US heterosexual men and women, and 100 US homosexual men to examine the potential role of infectious agents in human immunodeficiency virus (HIV) infection. There were no significant differences in the prevalence of antibodies to cytomegalovirus, Epstein-Barr virus, hepatitis A and B viruses, herpes simplex virus, syphilis, and toxoplasmosis among the African and US patients with AIDS, African heterosexual controls, and US homosexual men. However, these four groups all demonstrated a significantly greater prevalence of antibodies to each of these infectious agents compared with US heterosexual men. Immunologic studies demonstrated a significant elevation of activated lymphocytes (HLA-DR and T3 positive) and immune complexes in both AIDS populations and African heterosexual and US homosexual populations, compared with the US heterosexual population. These data demonstrate that the immune systems of African heterosexuals, similar to those of US homosexual men, are in a chronically activated state associated with chronic viral and parasitic antigenic exposure, which may cause them to be particularly susceptible to HIV infection or disease progression.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Susceptibility of natural killer cell activity of old rats to stress.

We determined an in vivo response of NK cells in young and old rats towards the suppressive effect of stress. Stress was developed by isolating rats in separate cages, but control littermates were kept together. Animals were subjected to stress for 7 days, and alterations of NK cell activities were examined in the spleen, peripheral blood (PB) and bone marrow (BM). The results showed that old rats subjected to stress had a remarkable decrease in splenic and PB-NK activity compared to old control rats, concomitant with a highly increased level of NK cell activity in BM. Suppression of the lytic activity in the spleen of stressed old rats was correlated with a decrease in the percentage of conjugate formation between splenic NK cells and target tumour cells. In contrast, stressed young rats demonstrated relatively unchanged activity of NK cells examined in different tissues compared to age-matched controls. We concluded that old animals are more sensitive to the suppressive effect of stress compared to young ones, and the mechanism of this suppression is probably due to the migration of large granular lymphocytes (LGL) from spleen and PB to other sites such as BM.

Aging↗
PubMed1985

Evidence of functional cellular immune impairment in an adult Belgian with visceral leishmaniasis acquired in Spain.

An adult Belgian patient with visceral leishmaniasis acquired while on holiday in Spain is described. This patient's cellular immunity was assessed by skin testing using six different antigens and was normal just before leaving for Spain. During the leishmaniasis, skin tests with the same antigens showed complete anergy. Lymphocyte transformation tests to antigens and mitogens were severely impaired but normal T cell subsets determined by OKT monoclonal antibodies were found. Immune complexes, containing antibodies to Leishmania antigen were isolated during the patient's illness. It is most likely that visceral leishmaniasis caused the functional cellular immune impairment of the patient.

Antigen-Antibody Complex↗
PubMed1984

Acquired immunodeficiency syndrome in a heterosexual population in Zaire.

38 patients with the acquired immunodeficiency syndrome (AIDS) were identified in Kinshasa, Zaire, during a 3 week period in 1983. The male to female ratio was 1.1:1. The annual case rate for Kinshasa was estimated to be at least 17 per 100 000. Opportunistic infections were diagnosed in 32 (84%) patients, disseminated Kaposi's sarcoma (KS) with opportunistic infection in 5 (13%), and disseminated KS alone in 1 patient. Immunological characteristics of these patients were as reported for cases in the USA and Europe, but immunological abnormalities were also found in 6 controls with infectious diseases but no symptoms of AIDS. Female AIDS cases were younger than male patients with AIDS (mean ages 28.4 vs 41.1 years, respectively), and were more often single (14/18 vs 2/20). Homosexuality, intravenous drug abuse, and blood transfusion did not appear to be risk factors in these patients. The findings of this study strongly argue that the situation in central Africa represents a new epidemiological setting for this worldwide disease--that of significant transmission in a large heterosexual population. Two instances of clusters of AIDS (not included in the above series) involving males and females with frequent heterosexual contact further implicate heterosexual transmission.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Removal of Pu and am from beagles and mice by 3,4,3-LICAM(C) or 3,4,3-LICAM(S).

Decorporation of Pu and Am by tetrameric catechoylamide (CAM) ligands has been investigated in beagles and mice. Eight dogs were injected intravenously (iv) with 237 + 239Pu(IV) + 241Am(III) citrate, and 30 min later, pairs of dogs were injected iv with 30 mumole/kg of 3,4,3-LICAM(C) [N1,N5,N10,N14-tetrakis(2,3-dihydroxy-5-sulfobenzoyl)tetr aazatetradecane, tetrasodium salt], 3,4,3-LICAM(S) [N1,N5,N10,N14-tetrakis(2,3-dihydroxy-4-carboxybenzoyl)te traazatetradecane, tetrasodium salt], CaNa3-DTPA, or each of the latter two ligands. Blood was sampled, and excreta were collected for 7 days, at which time the dogs were sacrificed and nuclide retention in liver and nonliver tissue was measured. Groups of five mice were each given 238Pu(IV) or 241Am(III) citrate iv; 3 min later 30 mumole/kg of a CAM ligand was injected intraperitoneally, mice were killed at 24 hr, and separated excreta and tissues were analyzed. In the dogs, average retention at 7 days of the injected Pu and Am, respectively, was as follows: 12 and 70% after treatment with a CAM ligand alone; 30 and 20% after DTPA; 12 and 20% after LICAM(S) plus DTPA; 90 and 89% without a ligand. In the mice, mean retention of the injected Pu and Am, respectively, was as follows: 14 and 66% after treatment with LICAM(C); 21 and 54% after LICAM(S); 91 and 87% without a ligand. In both species, about 99% of net Pu excretion (excretion with ligand - excretion without ligand) promoted in 24 hr by DTPA or LICAM(S) was in the urine, whereas about 10% of net Pu excretion promoted by the less hydrophilic LICAM(C) was in feces. Delayed excretion of both Am and Pu was significant in all ligand-treated dogs. Comparison of the nuclide content of tissues of ligand-treated mice with those of mice killed 3 min after nuclide injection indicated that the CAM ligands chelated circulating Pu and Am and prevented further deposition. In addition, the CAM ligands removed much of the presumably loosely bound Pu present in liver and skeleton at the time of ligand injection. LICAM(C) was more effective in removing Pu from liver and LICAM(S) was more effective in the skeleton. Moderate to severe uremia and histological evidence of cell killing in the distal tubules of the kidney were observed in the four dogs injected once with 30 mumole/kg of LICAM(S).(ABSTRACT TRUNCATED AT 400 WORDS)

Americium↗
PubMed1984

Radiation dose rates to the proximal humerus of growing beagles injected with 239Pu.

The anatomical distribution of 239Pu in the proximal humerus was studied in four beagles injected at 90 days of age and sacrificed 7, 28, 56, and 128 days after injection, respectively. Initial deposition in each humerus was 3.1% of the injected Pu; 41% of that was retained with a net halftime of 248 days; for the remaining 59% no decrease was observed with time. Sixty-one percent of the initial deposit was concentrated in the proximal epiphysis and metaphysis. Average radiation dose rates to trabecular bone of the epiphysis, to those parts of the metaphysis that were formed before and/or after injection, and to the area corresponding to the primary and secondary spongiosa were determined by fission track autoradiography. Local dose rates within the range of 10 microns of the endosteal surface, to the marrow and to osseous tissue were calculated. Because of the rapid growth and modeling rate, surface deposits declined rapidly. In the metaphysis, bone formed after injection contained less than 1/2 the Pu concentration of bone which was present at the time of injection. At 100 days of age, bone mineralization as determined by the ash weight/wet weight ratio, and the fraction of bone volume occupied by mineralized tissue was 1/2 that seen in young adult beagles. The surface/volume ratio was twice as high as in young adult beagles. The possible effects of local radiation doses were correlated with areal densities of cells and types of cells at risk. Comparisons were made with corresponding sites from the humerus of beagles injected as young adults.

Aging↗
PubMed1983

Skeletal retention and distribution of 226Ra and 239Pu in beagles injected at ages ranging from 2 days to 5 years.

The age at exposure significantly affects the retention and distribution of 226Ra and 239Pu, both of which deposit in the skeleton although in somewhat different patterns. Beagles aged 2 days (neonates), 90 days (juveniles), 18 months (young adults), or 5 yrs (mature) received a single subacute injection of one of these nuclides and were sacrificed serially during a 2-yr interval. Nuclide concentrations in plasma, the skeleton, individual bones and bone sections were determined and retention equations were calculated. The microanatomical skeletal nuclide distribution was studied after fission track or conventional autoradiography. Elimination of 239Pu and its translocation from bone surfaces to the bone volume caused by bone growth and turnover processes were measured. Average radiation doses and dose rates as a function of age at exposure were determined. Initial uptake and retention, skeletal nuclide concentration, proliferative activity of local cell populations and residence time of the nuclide on skeletal surfaces were affected significantly by age at exposure. The effect of these parameters on tumor induction is discussed. This study has provided early retention and distribution data which together with data from a chronic toxicity study will be used to estimate the risk of Pu exposure relative to that of Ra to humans of all ages.

Aging↗
PubMed1982

Acute cardiovascular collapse after administration of suxamethonium.

The case is reported of an acute cardiovascular collapse immediately after the administration of suxamethonium to a 25-year-old woman undergoing a diagnostic laparoscopy under general anesthesia. Reintervention 14 days later--without the use of suxamethonium--was uneventful. A skin prik test with suxamethonium proved highly positive. A survey of the literature is given and an attempt is made to distinguish between true anaphylaxis and anaphylactoid reaction.

Adult↗