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Biomedical subjects

D B Thomas

Publications and source records attributed to D B Thomas.

At least 37 records · Page 2Linked to original sources
PubMed2000

Tubal ligation and risk of cervical cancer. The World Health Organiztion Collaborative Study of Neoplasia and Steroid Contraceptives.

Data from a hospital-based case-control study collected in eight countries were analyzed to determine whether tubal ligation alters risk of invasive squamous-cell cervical cancer. Study subjects included 2339 cases aged 22 to 64 years with newly diagnosed squamous cell cervical cancer in 10 participating medical centers, and 13,506 hospitalized controls matched on age and place of residence to the cases. After adjustment for age, center, caesarian section, number of live births, number of marriages or other sexual relationships, age at first sexual relationship, and frequency of Pap smears, a small decrease in risk was observed during the first 5 postoperative years. Tubal ligation probably provides an opportunity for secondary prevention of cervical cancer.

Adult↗
PubMed2000

Tubal sterilization and use of an IUD and risk of cervical cancer.

The relationship of tubal sterilization and use of an intrauterine device (IUD) to the risk of invasive squamous cell cervical cancer was evaluated in a case-control study carried out in Shandong, China, from 1989 to 1991. Patients (cases) were 272 women aged 30-77 years with newly diagnosed invasive squamous cell cervical cancer in Shandong Province Tumor Hospital. Controls were 893 randomly selected screened women matched to the cases by age (within 2 years) and county. A decrease in risk was observed in uses of an IUD, especially in long-term users under age 33. A nonsignificant decrease in risk in women under age 33 who had had a tubal ligation was also observed, especially in the first 10 years since the procedure. Tubal ligation and IUD insertion and removal provide opportunities to screen women for cervical cancer and reduce the risk of invasive disease.

Adult↗
PubMed2000

Heating rate and induced thermotolerance in Mexican fruit fly (Diptera: Tephritidae) larvae, a quarantine pest of citrus and mangoes.

A bioassay and graduated temperature water baths were used to document the induction of thermotolerance in third-instar Mexican fruit fly, Anastrepha ludens (Loew). The 99% lethal time dose for larvae exposed to 44 degrees C core temperatures in artificial fruit is 61.5 min when a slow heating rate (120 min ramp) is applied, but only 41.9 min when a fast heating rate (15 min ramp) is applied. In electrophoretic profiles a heat inducible protein of molecular weight 32 kDa was detected in 76% of the larvae exposed to the slow ramp treatment, but only 42% of the larvae in the fast ramp treatment. Results from this research demonstrate that thermotolerance can be induced under conditions used to commercially disinfest fresh produce and highlight the necessity for specifying heating rates in quarantine treatment schedules.

Animals↗
PubMed2000

The decline in the mortality rates of cervical cancer and a plausible explanation in Shandong, China.

BACKGROUND: The aim of the present study is to describe the temporal trends in mortality rates of cervical cancer in Shandong Province, China, and to elucidate their likely explanations. METHODS: Three retrospective surveys of all causes of death in 1970-1974, 1985-1989 and 1990-1992 in Shandong were carried out. An age-period-cohort analysis based on similar survey data from Qixia, a county in Shandong, from 1970 to 1994 was performed. A correlation analysis between prevalence of syphilis and cervical cancer mortality rates three decades later was conducted. A cross-sectional survey of risk factors for cervical cancer was conducted in 1991 in one city and 12 villages in the province. RESULTS: A marked decline in cervical cancer mortality rates was observed from 1970 to 1992 and in successive birth cohorts from 1892 to 1927, and rates remained relatively constant in subsequent birth cohorts through that of 1952. The decline in these rates was strongly correlated with a decline in positive serological tests for syphilis 32 years previously. The percentages of women with selected risk factors were lower in younger women (30-54 years) than in older women (55-69 years) in both cities and rural areas. CONCLUSION: These trends are compatible with a decrease in risk of exposure to sexually transmitted factors at an early age after the founding of the People's Republic of China in 1949, and a decline in lifetime duration of exposure to possible co-factors in successive birth cohorts who reached sexual maturity before that time.

Adolescent↗
PubMed1999

Has the use of pap smears reduced the risk of invasive cervical cancer in Guadalajara, Mexico?

In Mexico, cervical cancer is the leading cause of death due to cancer among women 35 years of age and older. Although cytologic screening for cervical cancer was introduced as a national program 24 years ago, the mortality rate for this disease has been increasing. A case-control study was undertaken. Cases were women younger than 70, with newly diagnosed invasive cervical cancer (ICC), who had been residing for at least the past year in the metropolitan area of Guadalajara. They were selected from 5 hospitals belonging to the Mexican National Health System. Controls were women without cervical cancer who were treated in the same health center as the corresponding case. Analysis included 143 cases and 311 controls. Information on risk factors for cervical cancer and prior cervical cytologic screening was obtained through a standardized personal interview. Overall, 54% of the cases reported having had a cervical cytology compared with 82% of controls. When compared with unscreened women, those who had ever had a Pap smear had a significantly lower risk of cervical cancer (OR = 0.3, 95% CI 0.2-0.4), and the protective effect persisted for over 5 years. Utilization of Pap smears in the metropolitan area of Guadalajara exerted a protective effect on ICC. Of the 65 women who reported a negative history of Pap smears, 45 would not have contracted cancer if they had ever had a Pap smear.

Adult↗
PubMed1999

Breast conservation therapy in the United States following the 1990 National Institutes of Health Consensus Development Conference on the treatment of patients with early stage invasive breast carcinoma.

BACKGROUND: A National Institutes of Health (NIH) Consensus Development Conference on the treatment of patients with early stage invasive breast carcinoma, held in June 1990, recommended breast conservation therapy for the majority of women with Stage I or II breast carcinoma. The authors evaluated the national use of breast conservation therapy before and after the conference to determine whether the conference had had an impact on utilization. METHODS: Women with Stage I or II breast carcinoma (n = 109,880), diagnosed during the years 1983-1995, were identified via 9 population-based cancer registries of the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute. The likelihood of breast conservation surgery versus mastectomy and, among women who underwent breast conservation surgery, the likelihood of postoperative radiation therapy versus none, were assessed for 3 time periods (January 1983 to April 1985, May 1985 to June 1990, and July 1990 to December 1995). Associations between the use of breast conservation surgery or postoperative radiotherapy according to patient stage, age, race, and region were compared among women diagnosed before and after the NIH Consensus Development Conference. RESULTS: From 1985 (the year that the U.S. randomized controlled trial demonstrating equivalent efficacy between breast conservation therapy and mastectomy was published) through 1989, approximately 35% of women with Stage I and 19% of women with Stage II breast carcinoma underwent breast conservation surgery; these percentages remained constant throughout this period. Beginning in 1990, the year of the NIH Consensus Development Conference, the use of breast conservation surgery increased in each subsequent year; by 1995, 60% of women with Stage I and 39% of women with Stage II breast carcinoma received such treatment. However, regional variation in use was observed (Stage I, range 41.4-71.4% for 1995) and no registry reported breast conservation therapy for the majority of women with Stage II disease (range, 23.8-48.0%). The use of postoperative radiotherapy for women who underwent breast conservation surgery was similar in the periods before and after the conference. CONCLUSIONS: Although breast conservation therapy was performed more frequently following the NIH Consensus Development Conference, variation in use by region of the U.S. suggests the continued presence of barriers to widespread adoption of the recommendations formulated at the conference.

Adult↗
PubMed1999

The relationship between diet and breast cancer in men (United States).

OBJECTIVES: The purpose of this paper was to investigate the relationship between food and beverage consumption and the development of breast cancer in men. METHODS: Possible relationships of dietary factors to risk of breast cancer in men were assessed in a case-control study conducted between 1983 and 1986. Cases (N = 220) were ascertained from ten population-based cancer registries. Controls (N = 291) were selected by random-digit dialing (< age 65) and from Health Care Financing Administration Medicare beneficiary lists (> or = age 65). RESULTS: No trends in risk were observed with increasing intakes of specific foods, except for an increase in risk with citrus fruits. No increase in risk with increasing amounts of specific fats, vitamins, or minerals or with amounts of protein, fiber, carbohydrate, starches, nitrites, or alcohol consumed was observed, except for an increase in risk with dietary vitamin C consumption. A decreasing trend in risk with dietary niacin and with coffee and an increasing trend in risk with tea consumption were observed. No associations were found with use of any dietary supplements, including vitamin C. CONCLUSIONS: The observed associations are not consistent with findings from studies of breast cancer in women and probably do not represent causal relationships. Dietary factors are unlikely to be strong determinants of breast cancer in men.

Adult↗
PubMed1998

Novel diversity in Th1, Th2 type differentiation of hemagglutinin-specific T cell clones elicited by natural influenza virus infection in three major haplotypes (H-2b,d,k).

We report novel diversity in the lymphokine (LK) secretion profile of hemagglutinin-specific, CD4+ T cell clones elicited by influenza virus infection in three major haplotypes: I-Ad- or I-Ed-restricted T cell clones obtained from individual BALB/c donors, and specific for three distinct antigenic peptides (p56-76, or p186-205 or p177-199), were uniformly Th1 type, releasing only IFN-gamma on activation. In contrast, extensive diversity was evident for the C57BL/10 or CBA/Ca repertoire. Sibling T cell clones, established from the same C57BL/10 donor and expressing identical TCR beta-chains in their recognition of p186-205, released either (IFN-gamma and IL-5) or (IFN-gamma and IL-4 and IL-5) or (IL-4 and IL-5 and IL-10) following Ag-specific or nonspecific stimulation. Similarly, I-Ak-restricted T cell clones, specific for p120-139 secreted either (IFN-gamma only) or (IFN-gamma and IL-5) or (IFN-gamma and IL-2 and IL-5) on activation. Despite such phenotypic diversity within the individual's repertoire, all clones had been maintained under identical in vitro culture conditions. Moreover, sequence analyses of TCR beta gene usage indicated that in most instances clones from the same donor expressed identical (VDJ)beta rearrangements, indicative of a common progenitor cell. FACS analysis of cytoplasmic cytokine production confirmed that for the novel phenotype (IFN-gamma and IL-5), both LKs were synthesized at the single cell level. Sibling families of T cell clones, established from a common donor following viral infection but differing in LK secretion, may offer a suitable model system for further studies of signal transduction mechanisms that discriminate between Th1- and Th2-specific responses to a well defined protective Ag.

Animals↗
PubMed1998

Extra-tumoral breast tissue in breast-cancer patients: variations with a family history of breast cancer. WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

In order to study the relationship between benign breast changes, a family history of breast cancer and breast cancer, extratumoral breast tissue from 1259 breast-cancer patients in the WHO Collaborative Study of Neoplasia and Contraceptives was classified histologically. The occurrence of ductal hyperplasia, ductal atypia, sclerosing adenosis, adenosis, lobular atypia, lactational metaplasia, cysts, apocrine metaplasia, apocrine hyperplasia and atypia, duct ectasia and the epithelial-stromal ratio was evaluated as absent, mild, moderate or marked, along with registration of the quality and number of slides. Information on occurrence of cancer in the family was available for patients' mothers and grandmothers. Logistic-regression analyses showed that the prevalence odds ratios for lactational metaplasia, cysts, duct ectasia and calcification were significantly increased in patients with a family history of breast cancer. Apocrine metaplasia and hyperplasia were not significantly increased. The prevalence rates of ductal atypia (ductal carcinoma in situ and atypical ductal hyperplasia), ductal hyperplasia, sclerosing adenosis, adenosis and high epithelial-stromal ratio did not differ significantly among patients with or without a family history of breast cancer. A family history of other types of cancer did not influence the occurrence of any of the benign components. The findings in the present study are strikingly similar to those in our earlier comparison of extra-tumoral breast tissue in patients from countries with high and low risk of breast cancer. It is reasonable to conclude from this that a history of breast cancer in a woman's mother or grandmother and the factors leading to higher risk of breast cancer in some countries than in others have similar effects on the morphologic evolution of breast cancer through benign and pre-cancerous changes.

Breast Diseases↗
PubMed1998

The proliferative status of haematopoietic progenitor cells in the developing murine liver and adult bone marrow.

A class of primitive progenitor cells with high proliferative potential in vitro (HPP-CFC), has been identified in fetal liver and adult bone marrow both in murine and human systems. The kinetic properties of HPP-CFC2 and the more mature granulocyte-macrophage colony forming units (CFU-GM) derived from murine fetal liver on d13, d15 and d19 of gestation, newborn liver and neonatal liver on d3 and d8 postpartum have been evaluated and compared with the kinetic properties of these progenitor cell populations derived from adult bone marrow. The frequency of HPP-CFC2 in fetal liver was found to be greatest on d15 of gestation then subsequently declined in newborn and neonatal liver. Similarly, the highest proportion of HPP-CFC2 engaged in DNA synthesis (53+/-3%) was detected in d15 fetal liver. This proportion decreased to 13+/-2% in the liver 1 wk after birth, which is comparable to the number of HPP-CFC2 derived from adult BM which were in S-phase (10+/-1%). Production of CFU-GM was found to be greater in adult bone marrow than in either fetal or newborn liver. While the proportion of CFU-GM in S-phase was high all 3 tissue samples, the greatest proportion of cycling CFU-GM (50+/-2%) was detected in d15 fetal liver. These results suggest that HPP-CFC2 derived from fetal liver are actively cycling while HPP-CFC2 derived from adult bone marrow are relatively quiescent. In contrast, a high proportion of CFU-GM derived from fetal, newborn liver and adult bone marrow are engaged in DNA synthesis.

Analysis of Variance↗
PubMed1997

Extratumoral breast tissue in breast cancer patients: a multinational study of variations with age and country of residence in low- and high-risk countries. WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

With the aim of elucidating the relationships between breast cancer, risk factors and benign breast changes, extratumoral breast tissue in 1,506 women from the WHO Collaborative study of neoplasia and steroid contraceptives was studied histologically. Patients came from 3 countries with a high incidence of breast cancer (Israel, East Germany and Australia) and 6 low-risk countries (Thailand, China, Philippines, Mexico, Chile and Colombia). Ductal atypia, ductal hyperplasia, adenosis, lobular atypia, apocrine metaplasia, apocrine hyperplasia, apocrine atypia, cysts, duct ectasia, inflammatory reaction, calcification, lactational change and epithelial-stromal ratio were classified as absent/mild/moderate/marked. Prevalence odds ratios were calculated by logistic regression analyses. Increasing frequency with age was found for ductal hyperplasia, sclerosing adenosis, apocrine metaplasia and cysts, while adenosis, lactational change and the epithelial-stromal ratio decreased with age. No significant difference between high- and low-risk countries was found for ductal hyperplasia or sclerosing adenosis. Compared with cases from high-risk countries, those from low-risk countries had a significantly lower prevalence of apocrine metaplasia, apocrine hyperplasia and cysts, and a significantly higher prevalence of ductal atypia. When seen in conjunction with other studies, the results suggest that ductal hyperplasia and sclerosing adenosis have similar roles in cancer development in high- and low-risk countries and that the factors responsible for international differences in breast cancer may exert their effect by influencing the initial development of these changes. They also suggest a delayed progression from noninvasive to invasive carcinoma in low-risk countries.

Adult↗
PubMed1997

Randomized trial of breast self-examination in Shanghai: methodology and preliminary results.

BACKGROUND: The efficacy of breast self-examination in helping to reduce mortality from breast cancer has not been rigorously demonstrated. PURPOSE: To assess efficacy, a large, randomized trial was initiated in Shanghai, China. METHODS: From October 1989 to October 1991, 267040 current and retired female employees associated with 520 factories in the Shanghai Textile Industry Bureau were randomly assigned on the basis of factory to either a self-examination instruction group (133375 women) or a control group (133665 women). The women were born within the period from 1925 through 1958. Women in the instruction group were given intensive training in breast self-examination, including the use of silicone breast models and personalized instruction, plus two subsequent reinforcement sessions and multiple reminders to practice the technique. Women in the control group were asked to attend training sessions on the prevention of low back pain. All women have been followed for the development of breast diseases and for death from breast cancer. RESULTS: A high level of participation during the first 4-5 years of the trial was documented among women in the instruction group. Randomly sampled women in this group demonstrated greater proficiency in detecting lumps in breast models than did randomly sampled women in the control group. Approximately equal numbers of breast cancers were detected in the two groups (331 in the instruction group and 322 in the control group) through 1994, which is the last year for which case-finding efforts have been completed. The breast cancers detected in the instruction group were not diagnosed at an appreciably earlier stage or smaller size than those in the control group. More benign breast lesions were detected in the instruction group than in the control group (1457 versus 623, respectively), suggesting a higher index of suspicion for women who received training. Cumulative breast cancer mortality rates through 5 years from entry into the study were nearly equivalent for the two groups. CONCLUSIONS: Breast self-examination has not led to a reduction in mortality from breast cancer in this study cohort in the first several years since the trial began. A shift toward the diagnosis of disease at a less advanced stage in women given instruction has also not been demonstrated. Longer follow-up of participants in this trial is required before final assessment can be made of the efficacy of breast self-examination. IMPLICATIONS: At this time, there is insufficient evidence to recommend for or against the teaching of breast self-examination.

Adult↗
PubMed1997

Change in the use of breast-conserving surgery in western Washington after the 1990 NIH Consensus Development Conference.

OBJECTIVE: To evaluate the use of breast-conserving surgery in western Washington before and after the National Institutes of Health Consensus Development Conference (June 18-21, 1990) during which breast-conserving surgery was recommended for most women with early invasive breast cancer. DESIGN: Survey. SETTING: Population-based cancer registry in the Seattle-Puget Sound (Washington) region. PARTICIPANTS: The survey included 13541 women in whom American Joint Committee on Cancer stage I or II breast cancer was diagnosed between January 1, 1983, and December 31, 1993. MAIN OUTCOME MEASURE: Proportion of participants who underwent breast-conserving surgery. RESULTS: From April 1985, after results of a US randomized controlled trial showing equivalent survival in women undergoing mastectomy or breast-conserving surgery were published, to the time of the Conference, breast-conserving surgery was performed on 44.8% of women with stage I and 25.8% with stage II breast cancer. These percentages increased to 54.9% and 35.2%, respectively, during the post-Conference period. While women with stage II breast cancer were less likely than women with stage I breast cancer to undergo breast-conserving surgery before and after the Conference, trends for age and education were attenuated after the Conference. Differences in the use of breast-conserving surgery observed before the Conference between countries of residence and among hospital types were also reduced after the Conference. CONCLUSIONS: These findings suggest that the Conference recommendations had an effect on the adoption of breast-conserving surgery, particularly among groups who were previously least likely to undergo such surgery. Despite progress toward the Conference recommendation that the majority of women with early invasive breast cancer undergo breast-conserving surgery, the majority of women with stage II breast cancer undergo mastectomy.

Aged↗
PubMed1997

Risk of lung cancer among patients with head and neck cancer.

A cohort of 5180 patients with head and neck cancer, who were part of the tumor registry of the Surveillance, Epidemiology, and End Results area of western Washington State, was followed up for as many as 15 years to determine the risk of lung cancer. A sample of 522 patients from this cohort was interviewed to determine smoking history. Lung cancer developed in 356 (6.9%) of the 5180 patients. The overall annual incidence of lung cancer remained relatively constant between approximately 1.0% and 2.0% during the 15 years of follow-up. Men had an increased risk of lung cancer compared with women (relative risk (RR) = 1.56; 95% confidence interval (CI) = 1.18 to 2.03). Compared with patients with oral cavity cancer (RR = 1.00), the relative risk of lung cancer developing by the site of the index tumor was 0.63 (95% CI = 0.40 to 0.98) for lip, 1.12 (95% CI = 0.81 to 1.56) for intrinsic larynx, 1.73 (95% CI = 1.21 to 2.47) for oropharynx, 1.84 (95% CI = 1.16 to 2.92) for hypopharynx, and 2.28 (95% CI = 1.60 to 3.24) for extrinsic larynx. Among the 522 patients who were interviewed, men smoked more than women (p < 0.0001), and patients with laryngeal or pharyngeal cancer smoked more than patients with cancer of the lip or the oral cavity (p < 0.05). Among patients with head and neck cancer, the risk of lung cancer is highest for men and for patients with cancer of the pharynx or extrinsic larynx. These findings may be explained by differences in smoking consumption.

Adult↗
PubMed1997

Preferential adhesion of fetal liver derived primitive haemopoietic progenitor cells to bone marrow stroma.

The orderly transfer of haemopoiesis from the fetal liver to the medullary cavities during the ontogeny may result from a decrease in the capacity of the fetal liver to support haemopoiesis. Alternatively it could be facilitated by the preferential migration of primitive haemopoietic cells to the marrow. In this study we have compared the ability of high proliferative potential colony forming cells (HPP-CFC) derived from murine fetal liver (FL) on the 15th day of gestation and from murine adult bone marrow (BM) to adhere to either FL or BM derived stromal layers. Adhesion of FL HPP-CFC to bone marrow stromal layers was significantly greater than all other combinations tested. The remarkable affinity of HPP-CFC derived from FL for BM stromal layers is consistent with the preferential migration of haemopoietic cells from the fetal liver to the medullary cavities.

Animals↗
PubMed1997

Preferential selection of receptor-binding variants of influenza virus hemagglutinin by the neutralizing antibody repertoire of transgenic mice expressing a human immunoglobulin mu minigene.

An analysis was made of the neutralizing antibody repertoire, for influenza virus hemagglutinin (HA) of transgenic mice expressing a human immunoglobulin mu (IgH) minigene, by monoclonal antibody (MAb) selection and sequencing of the HA genes of X31 (H3N2 subtype) laboratory variants. Whereas previously reported laboratory variants, selected in ovo with high-affinity murine MAbs of the IgG class, differed from wild-type virus by a single amino acid residue change in one of the major antigenic sites, neutralizing MAbs from transgenic donors selected novel variant viruses with altered receptor-binding specificity and contained residue changes in both the receptor-binding pocket (HA1 225 or HA1 226) and an antigenic site (HA1 135, HA1 145, or HA1 158). Changes in receptor-binding specificities of the variant viruses were confirmed by their resistance to inhibition by horse serum glycoproteins and altered binding to neoglycoproteins. The residue changes in variant virus V-21.2 (HA1 135 G-->R, 225 G-->D) abrogated neutralization by each of the MAbs; nevertheless V-21.2 was recognized by its own selecting MAb in enzyme-linked immunosorbent assay and therefore qualified as an adsorptive mutant rather than an antigenic variant. We consider that a low-affinity neutralizing antibody response may preferentially select for receptor-binding variants of influenza virus HA.

Animals↗