Comparing physical activity questionnaires for youth: seasonal vs annual format

BACKGROUND

In large cohort studies of older children, self-report is the only practical way to assess physical activity. Assessing usual activity over the entire year is desirable, but children and adolescents may overestimate activities with high seasonal variability. Use of questionnaires in which individuals report each activity by season may improve accuracy.

METHODS

A total of 6782 girls and 5110 boys, aged 9-14 years in 1996, completed self-administered activity questionnaires in 1996 and in 1997. In 1996, participants reported the average time spent in each of 17 activities during the previous 12 months; in 1997, we also asked for the average time spent in the previous year, but within each of the four seasons.

RESULTS

Girls reported a median of 12.8 hours/week total activity in 1996 and 10.4 hours/week in 1997. For boys, the estimates were 15.5 hours/week and 13.4 hours/week, respectively. Girls and boys within 1-year age strata (e.g., comparison of 10-year olds in 1996 with 10-year olds in 1997) reported an average of 3.7 and 3.1 fewer hours per week, respectively, on the 1997 seasonal format versus the 1996 annual format questionnaire. In longitudinal analyses, the difference between the annual and the seasonal estimates was greater if participants did the activity in fewer seasons in 1997.

CONCLUSIONS

In comparison to an annual format questionnaire, a seasonal format questionnaire may improve accuracy of self-report of physical activity by reducing over-reporting of activities in which pre-adolescents and adolescents engage in fewer seasons.

Cost-effectiveness of screening for colorectal cancer in the general population

CONTEXT

A recent expert panel recommended that persons at average risk of colorectal cancer (CRC) begin screening for CRC at age 50 years using 1 of several strategies. However, many aspects of different CRC screening strategies remain uncertain.

OBJECTIVE

To assess the consequences, costs, and cost-effectiveness of CRC screening in average-risk individuals.

DESIGN

Cost-effectiveness analysis from a societal perspective using a Markov model.

SUBJECTS

Hypothetical subjects representative of the 50-year-old US population at average risk for CRC.

SETTING

Simulated clinical practice in the United States.

MAIN OUTCOME MEASURES

Discounted lifetime costs, life expectancy, and incremental cost-effectiveness (CE) ratio, compared used 22 different CRC screening strategies, including those recommended by the expert panel.

RESULTS

In 1 base-case analysis, compliance was assumed to be 60% with the initial screen and 80% with follow-up or surveillance colonoscopy. The most effective strategy for white men was annual rehydrated fecal occult blood testing (FOBT) plus sigmoidoscopy (followed by colonoscopy if either a low- or high-risk polyp was found) every 5 years from age 50 to 85 years, which resulted in a 60% reduction in cancer incidence and an 80% reduction in CRC mortality compared with no screening, and an incremental CE ratio of $92,900 per year of life gained compared with annual unrehydrated FOBT plus sigmoidoscopy every 5 years. In a base-case analysis in which compliance with screening and follow-up is assumed to be 100%, screening more often than every 10 years was prohibitively expensive; annual rehydrated FOBT plus sigmoidoscopy every 5 years had an incremental CE ratio of $489,900 per life-year gained compared with the same strategy every 10 years. Other strategies recommended by the expert panel were either less effective or cost more per year of life gained than the alternatives. Colonoscopy every 10 years was less effective than the combination of annual FOBT plus sigmoidoscopy every 5 years. However, a single colonoscopy at age 55 years achieves nearly half of the reduction in CRC mortality obtainable with colonoscopy every 10 years. Because of increased life expectancy among white women and increased cancer mortality among blacks, CRC screening was even more cost-effective in these groups than in white men.

CONCLUSIONS

Screening for CRC, even in the setting of imperfect compliance, significantly reduces CRC mortality at costs comparable to other cancer screening procedures. However, compliance rates significantly affect the incremental CE ratios. In this model of CRC, 60% compliance with an every 5-year schedule of screening was roughly equivalent to 100% compliance with an every 10-year schedule. Mathematical modeling used to inform clinical guidelines needs to take into account expected compliance rates. JAMA. 2000;284:1954-1961.

Relation of childhood diet and body size to menarche and adolescent growth in girls

Adolescent growth and development may be affected by factors such as dietary intake and body size from much earlier in childhood. In a longitudinal study of 67 Caucasian girls in Boston, Massachusetts, data were collected prospectively from birth during the 1930s and 1940s. Heights and weights were measured semiannually, and dietary history interviews were conducted with mothers. Stepwise linear regression methods were used to seek factors which best predicted age at menarche, adolescent peak height growth velocity, and the age at which peak growth velocity occurred. Girls who consumed more (energy-adjusted) animal protein and less vegetable protein at ages 3-5 years had earlier menarche, and girls aged 1-2 years with higher dietary fat intakes and girls aged 6-8 years with higher animal protein intakes became adolescents with earlier peak growth. Controlling for body size, girls who consumed more calories and animal protein 2 years before peak growth had higher peak growth velocity. These findings may have implications regarding adult diseases whose risks are associated with adolescent growth and development factors.

Association of adolescent cigar use with other high-risk behaviors

OBJECTIVES

To describe the association of cigar use with use of cigarettes, smokeless tobacco, and alcohol among adolescents; and to examine the association of self-esteem, physical activity, and use of tobacco promotional items with cigar use.

METHODS

A cross-sectional study of 7104 girls and 5499 boys 10 to 15 years of age in 1997. Data were collected from self-report questionnaires.

RESULTS

The prevalence of cigar use increased with age among both girls and boys. Among 11-year-olds, only 1% of girls and 3% of boys had used a cigar, whereas among 15-year-olds, 11% of girls and 25% of boys had used a cigar. Cigar users were much more likely than nonusers to have experimented with cigarettes (girls, odds ratio [OR]: 23.6; 95% confidence interval [CI]: 17.2-32.3; boys, OR: 21.3; 95% CI: 17.1-26.6), smokeless tobacco (girls, OR: 7.5; 95% CI: 4. 5-12.4; boys, OR: 13.0; 95% CI: 9.8-17.4), and alcohol (girls, OR: 6. 6; 95% CI: 4.8-9.1; boys, OR: 6.8; 95% CI: 5.3-8.8). There was a strong association between cigar use and binge drinking, especially among boys (girls, OR: 11.6; 95% CI: 7.9-16.9; boys, OR: 34.8; 95% CI: 19.4-62.3). Cigar users reported more hours of weekly physical activity than did nonusers. Additionally, cigar users were more likely to report high social self-esteem and to possess a tobacco promotional item.

CONCLUSIONS

Adolescents who use cigars are more likely to use other tobacco products and alcohol, to report high social self-esteem, and to possess tobacco promotional items. Health care professionals and teachers should include cigar use in discussions with adolescents addressing substance use.

Activity, dietary intake, and weight changes in a longitudinal study of preadolescent and adolescent boys and girls

OBJECTIVE

To examine the role of physical activity, inactivity, and dietary patterns on annual weight changes among preadolescents and adolescents, taking growth and development into account.

STUDY DESIGN

We studied a cohort of 6149 girls and 4620 boys from all over the United States who were 9 to 14 years old in 1996. All returned questionnaires in the fall of 1996 and a year later in 1997. Each child provided his or her current height and weight and a detailed assessment of typical past-year dietary intakes, physical activities, and recreational inactivities (TV, videos/VCR, and video/computer games).

METHODS

Our hypotheses were that physical activity and dietary fiber intake are negatively correlated with annual changes in adiposity and that recreational inactivity (TV/videos/games), caloric intake, and dietary fat intake are positively correlated with annual changes in adiposity. Separately for boys and girls, we performed regression analysis of 1-year change in body mass index (BMI; kg/m(2)). All hypothesized factors were in the model simultaneously with several adjustment factors.

RESULTS

Larger increases in BMI from 1996 to 1997 were among girls who reported higher caloric intakes (.0061 +/-.0026 kg/m(2) per 100 kcal/day; beta +/- standard error), less physical activity (-.0284 +/-.0142 kg/m(2)/hour/day) and more time with TV/videos/games (.0372 +/-.0106 kg/m(2)/hour/day) during the year between the 2 BMI assessments. Larger BMI increases were among boys who reported more time with TV/videos/games (.0384 +/-.0101) during the year. For both boys and girls, a larger rise in caloric intake from 1996 to 1997 predicted larger BMI increases (girls:.0059 +/-.0027 kg/m(2) per increase of 100 kcal/day; boys:.0082 +/-.0030). No significant associations were noted for energy-adjusted dietary fat or fiber.

CONCLUSIONS

For both boys and girls, a 1-year increase in BMI was larger in those who reported more time with TV/videos/games during the year between the 2 BMI measurements, and in those who reported that their caloric intakes increased more from 1 year to the next. Larger year-to-year increases in BMI were also seen among girls who reported higher caloric intakes and less physical activity during the year between the 2 BMI measurements. Although the magnitudes of these estimated effects were small, their cumulative effects, year after year during adolescence, would produce substantial gains in body weight. Strategies to prevent excessive caloric intakes, to decrease time with TV/videos/games, and to increase physical activity would be promising as a means to prevent obesity.

Family dinner and diet quality among older children and adolescents

CONTEXT

The proportion of children eating dinner with their families declines with age and has decreased over time. Few data exist concerning the nutritional effect of eating family dinner.

OBJECTIVE

To examine the associations between frequency of eating dinner with family and measures of diet quality.

DESIGN

Cross-sectional.

SETTING

A national convenience sample.

PARTICIPANTS

There were 8677 girls and 7525 boys in the study, aged 9 to 14 years, who were children of the participants in the ongoing Nurses' Health Study II.

MAIN OUTCOME MEASURES

We collected data from a self-administered mailed survey, including food and nutrient intakes from a validated semiquantitative food frequency questionnaire. Main outcome measures included servings per day of selected foods and food groups, daily intakes of selected macronutrients and micronutrients, and frequency of multivitamin use.

RESULTS

Approximately 17% of participants ate dinner with members of their family never or some days, 40% on most days, and 43% every day. More than half of the 9-year-olds ate family dinner every day, whereas only about one third of 14-year-olds did so. In age- and sex-adjusted logistic regression models, the odds ratios associated with a frequency of family dinner of most days compared with never or some days, or every day compared with most days, were as follows: for eating at least 5 servings per day of fruits and vegetables, 1.45 (95% confidence interval [CI], 1.37-1.53); for eating any fried foods away from home, 0.67 (95% CI, 0.64-0.70); and for drinking any soda, 0.73 (95% CI, 0.66-0.80). Multiple linear regression showed that an increased frequency of family dinner was also associated with substantially higher intake of several nutrients, including fiber, calcium, folate, iron, vitamins B6, B12, C, and E; lower glycemic load; and lower intake of saturated and trans fat as a percentage of energy. We observed little or no effect on intakes of whole dairy products, red meat, or snack foods. Patterns were similar for boys and girls.

CONCLUSIONS

Eating family dinner was associated with healthful dietary intake patterns, including more fruits and vegetables, less fried food and soda, less saturated and trans fat, lower glycemic load, more fiber and micronutrients from food, and no material differences in red meat or snack foods.

Reproducibility and validity of maternal recall of pregnancy-related events

We assessed the reproducibility and validity of a questionnaire that asks mothers to recall pregnancy-related events from thirty or more years ago. Among 146 women who completed the questionnaire twice, responses were highly reproducible for pre-pregnancy height and weight (r = 0.95), pregnancy complications (r = 0.74), substance use (r = 0.80), preterm delivery (r = 0.82), birthweight (r = 0.94), and breastfeeding (r = 0.89). Among 154 women whose questionnaire responses were compared to data collected during their pregnancies, recall was highly accurate for height (r = 0.90), pre-pregnancy weight (r = 0.86), birthweight (r = 0.91), and smoking (sensitivity = 0.86, specificity = 0.94). These findings suggest that long-term maternal recall is both reproducible and accurate for many factors related to pregnancy and delivery.

Weight concerns, weight control behaviors, and smoking initiation

OBJECTIVE

To examine the cross-sectional relationships between weight concerns, weight control behaviors, and initiation of tobacco use among youths.

STUDY DESIGN

Smoking status, weight concerns, and weight control behaviors were assessed in a cross-sectional sample of 16 862 children, 9 to 14 years of age, in 1996. Logistic regression was used to examine the relationship between weight concerns, weight control behaviors, and early stages of smoking initiation (precontemplation, contemplation, and experimentation). All analyses were adjusted for age, body mass index, and known predictors of initiation.

RESULTS

Approximately 9% of participants had experimented with cigarettes, and 6% were contemplating cigarette smoking. Contemplation of tobacco use was associated with misperception of being overweight (boys: odds ratio [OR], 1.65; 95% confidence interval [CI], 1.10-2.48), unhappiness with appearance (girls: OR, 2.05; 95% CI, 1.48-2.84; boys: OR, 1.60; 95% CI, 1.05-2. 42), and a tendency to change eating patterns around peers (girls: OR, 2.87; 95% CI, 2.28-3.62; boys: OR, 1.83; 95% CI, 1.25-2.66). Experimentation with cigarettes was associated with daily exercise to control weight among boys (OR, 1.92; 95% CI, 1.07-3.43) and with monthly purging (OR, 2.54; 95% CI, 1.27-5.07) and daily dieting among girls (OR, 1.79; 95% CI, 1.09-2.96).

CONCLUSIONS

Our findings suggest that, among both girls and boys, contemplation of smoking is positively related to weight concerns. Experimentation seems to be positively related to weight control behaviors. It is important for both pediatricians and comprehensive school health programs to address healthy methods of weight maintenance and to dispel the notion of tobacco use as a method of weight control.

Overweight, weight concerns, and bulimic behaviors among girls and boys

OBJECTIVE

To assess the prevalence rates and correlates of overweight, concern with weight, and bulimic behaviors.

METHOD

A survey was completed by a population-based sample of 16,114 boys and girls aged 9 to 14 years.

RESULTS

Although fewer girls (19%) than boys (26%) were overweight, more girls (25% versus 22%) perceived themselves as overweight (p < .001). The proportion of girls reporting trying to lose weight increased with age (p < .001). The prevalence of binge eating at least monthly increased with age among the girls, but remained stable among the boys. The prevalence of purging was low (< or = 1%) and comparable between genders until age 13. Among the 13- and 14-year-olds, girls were significantly more likely than boys to report using laxatives or vomiting to control weight (p < or = .001). Purging was independently positively associated with stage of pubertal development (girls: odds ratio [OR] = 2.1, 95% confidence interval [CI] 1.6-2.7; boys: OR = 1.5, 95% CI 1.0-2.2) and overweight (girls: OR = 1.9, 95% CI 1.2-3.0; boys: OR = 2.7, 95% CI 1.4-5.1).

CONCLUSIONS

Misperception of being overweight and concern with weight were common. Purging was a very rare behavior, but increased with pubertal development. Among the girls, the prevalence increased sharply around the onset of adolescence.

Adolescence and breast carcinoma risk

BACKGROUND

Breast carcinoma risk may be modified by early life factors, including physical growth and development, diet, and life-style factors of preadolescence and adolescence, as well as genetic factors.

METHODS

The authors tested their hypothesis that adolescent growth and development are related to breast carcinoma incidence by evaluating 65,140 women who participated in the Nurses' Health Study. During 16 years of follow-up, 806 women were diagnosed with breast carcinoma prior to menopause, and another 1485 were diagnosed after menopause. Because adolescent growth was not directly observed in this cohort, the peak height growth velocity for each participant was estimated by using a model from another longitudinal study. Finally, Cox proportional hazards regression models were used to study associations between breast carcinoma incidence and adolescent factors in the Nurses' Health Study.

RESULTS

Later menarche (relative risk [RR] = 0.52 for > or =15 vs. < or =11 years) and more body fatness at age 10 years (RR = 0.60 for fattest vs. leanest) were associated with a decreased risk of premenopausal breast carcinoma. The risk of postmenopausal breast carcinoma was lower for girls with later menarche (RR = 0.80), more body fat at age 10 years (RR = 0.72), and shorter adult height (RR = 1.29 for > or =67 vs. < or =62 inches). Higher peak height growth velocity, derived from these 3 variables, was associated with increased risk of both premenopausal (RR = 1.31 for highest vs. lowest quintile) and postmenopausal (RR = 1.40) breast carcinoma. These analyses controlled for birth cohort, other possible risk factors from the adolescent period, and family history. These associations persisted after controlling for age at the birth of a first child, parity, adult adiposity, and age at menopause. Post-hoc analyses suggested that, although childhood body fatness was associated with lower risk, increasing body fatness between ages 10 and 20 years was not protective against either premenopausal or postmenopausal breast carcinoma.

CONCLUSIONS

Earlier menarche, extremely lean body mass at age 10 years, and taller adult height were predictive of elevated breast carcinoma risk. The same three factors were also predictive of higher peak growth velocities during adolescence, lending credence to the hypothesis that more rapid adolescent growth may increase the risk of breast carcinoma development.

Identification and characterisation of a human calmodulin-stimulated phosphodiesterase PDE1B1

A cDNA encoding a calmodulin-stimulated 3',5'-cyclic nucleotide phosphodiesterase (PDE) was isolated from a human brain cDNA library. The cDNA, designated HSPDE1B1, encoded a protein of 536 amino acids that shared 96% sequence identity with the bovine "63 kDa" calmodulin-stimulated PDE. The recombinant protein had cyclic nucleotide phosphodiesterase activity that was stimulated approximately 2-fold by Ca2+/calmodulin and preferred cGMP as substrate. In addition, the enzymatic activity of HSPDE1B1 was inhibited by phosphodiesterase inhibitors with potencies similar to that displayed toward the bovine PDE1 enzymes: IBMX approximately equal to 8-methoxymethyl-IBMX > vinpocetine approximately equal to zaprinast > cilostamide > rolipram. HSPDE1B1 mRNA was found predominantly in the brain. Lower mRNA levels were found in heart and skeletal muscle. In situ hybridisation of brain revealed expression of HSPDE1B1 predominately in neuronal cells of the cerebellum, hippocampus and caudate. The HSPDE1B1 gene was mapped to human chromosome 12. A partial genomic sequence of HSPDE1B1 was isolated and shown to contain two splice junctions that are conserved in the rat PDE4 and the Drosophila dunce genes.

Validation of a youth/adolescent food frequency questionnaire

BACKGROUND

To address limited longitudinal nutrition data on children and adolescents, a self-administered food frequency questionnaire was designed for older children and adolescents. Initially, the Youth/Adolescent Questionnaire (YAQ) was developed and demonstrated to be reproducible. This study was conducted to evaluate its validity.

METHODS

The form was administered twice to a sample of 261 youths (ages 9 to 18) at an approximate interval of 1 year (1993-1994), and three 24-hr dietary recalls were collected during this period. Pearson correlation coefficients were calculated on nutrient data.

RESULTS

Validity was first evaluated by comparing the average of the three 24-hr recalls to the average of the two YAQs. Similar mean nutrients were found by both methods. Correlation coefficients between the mean energy-adjusted nutrients computed by the two methods ranged from 0.21 for sodium to 0.58 for folate. After correction for within-person error, the average correlation coefficient was 0.54, similar to that found among adults.

CONCLUSION

A simple self-administered questionnaire completed by older children and adolescents can provide nutritional information about this age group.

Physical activity and reduced risk of colon cancer: implications for prevention

This paper reviews the consistency of the relation between increased physical activity and reduced risk of colon cancer, estimates the potential prevention benefit from increasing population levels of physical activity, and considers social strategies to increase activity levels. The published literature was reviewed systematically and supplemented by MEDLINE searches through March 1997. Studies that reported a measure of physical activity and outcomes of colon cancer or colorectal cancer were included. We excluded the first report of a study that was expanded subsequently by extended follow-up, and any study that did not report the methods for measurement of physical activity. Data were extracted including details on study size, methods of classifying physical activity, and outcomes. A consistent inverse relation was observed such that increased physical activity was associated with reduced risk of colon cancer. About a 50 percent reduction in incidence was observed among those with the highest level of activity across numerous studies that used different measures of activity (occupational or leisure-time activity). This association persisted in studies using multivariate analyses to control for diet and other known or suspected risk factors for colon cancer. Risk reduction was attenuated in those studies that combined colon and rectal cancer. This review indicates that greater attention should be placed on social strategies to increase physical activity as a means of preventing colon cancer.

Treatment of endodermal sinus tumor in children using a regimen that lacks bleomycin

BACKGROUND

The EPO-VAC protocol was initiated to study 1) the efficacy of adding a cisplatin regimen (EPO) to VAC alone (the previous standard of care) and 2) the effect of replacing bleomycin with etoposide in the treatment of pediatric endodermal sinus tumors.

METHODS

The eligibility requirements for entry included age <21 years at diagnosis, diagnosis of a primary gonadal or extragonadal tumor (excluding central nervous system tumors and stage I testicular tumors), and histological confirmation of endodermal sinus tumor. Children who met the eligibility criteria were treated with four courses of EPO (etoposide, cisplatin, vincristine) alternating with three courses of VAC (vincristine, dactinomycin, and cyclophosphamide).

RESULTS

Eleven children were entered on the protocol. Six patients had extragonadal disease, five patients had ovarian primaries. Seven patients had low-stage tumor (I or II) and four had advanced-stage tumor (III or IV). Three of six evaluable patients attained a complete response at 21 weeks. Three patients with a residual soft tissue mass at restaging underwent further therapy. No patient has relapsed after a median of 51 (range 14-88) months of follow-up.

CONCLUSIONS

The results of this protocol suggests that a cisplatin-containing regimen that lacks bleomycin is active in childhood endodermal sinus tumors.

Reproducibility of recall of adolescent diet: Nurses' Health Study (United States)

Although diet and alcohol consumption at a younger age have been hypothesized to play an etiologic role in adult malignancy, few studies have addressed these relations and few data exist on the ability to measure recalled diet during adolescence. We undertook a study to determine whether the recall of diet during high school 22 to 47 years later was reproducible within a prospective cohort of women. In 1986, participants in the Nurses' Health Study (United States), aged 40 to 65 years, reported their diet during high school using a 24-item food frequency questionnaire (FFQ). On the 1988 questionnaire, the participants recorded their alcohol consumption between the ages of 18 and 22. In 1994, a random sample of 275 women were asked to record again their high school diet and alcohol consumption. The average of Spearman correlations between the two recalls of high school diet was r = 0.57 (range = 0.38 to 0.74). For alcohol intake, the correlation for the time period queried was 0.66. The correlation between the two recalls of high school diet was higher than the correlation between the first recall and current diet in 1986 (average r = 0.25). There was no effect of age on reproducibility of recall. These data suggest that recall of diet from the very distant past, during a distinct time period such as high school, is reasonably reproducible. Although further studies of validity are needed, such information may be sufficiently precise to assess the influence of remote diet in epidemiologic studies.

Models of breast cancer show that risk is set by events of early life: prevention efforts must shift focus

We have recently published a mathematical model of the etiology of breast cancer based on the data from the Nurses Health Study that extends the Pike model of breast cancer (see Appendix). The most salient feature of the model is that it identifies the years before the first birth of a child as the most crucial in establishing future risk of breast cancer. The extended model includes several additional details of reproductive risk factors, allowing us to quantify the relative importance of each of the reproductive risk factors and to estimate the effect of changes in key determinants of breast cancer. In this review, we present the evidence from both animal studies and epidemiological research that corroborate the critical importance of the exposures that occur before first birth. We argue that research and preventive interventions should now focus on youth. Population-wide prevention strategies are necessary because the inherited genetic risk for breast cancer accounts for no more than 10-15% of all breast cancer cases, leaving 85% of cases diagnosed among women who are not in this high-risk subgroup of the population. An example of a population-based intervention would be the promotion of increased physical activity among young girls that could result in the delay of menarche. An example of additional research that focuses on the importance of early life exposures would be an analysis of the relation between diet and other lifestyle factors during adolescence and the subsequent risk of breast cancer and studies of precursor lesions (atypical hyperplasia). Shifting the focus of breast cancer prevention to this age group is urgently needed.

Retrovirus-mediated transfer and long-term expression of HIV type 1 tat gene in murine hematopoietic tissues

Replication of the human immunodeficiency virus (HIV) is regulated tightly by the tat and rev genes. The tat gene of HIV is a potent trans-activator of virus gene expression. trans-Activation is mediated through the tat-responsive element (TAR). Tat also has been shown to affect transcription of cellular genes and to trans-activate other viral promoters. In transgenic animals, tat expression in skin was implicated in the development of lesions resembling Kaposi's sarcoma (KS). More recently, evidence has been presented that suggests that Tat might play a role in the maintenance of KS cells. To study the possible role(s) of Tat in pathogenesis and disease progression, we have developed a retroviral vector for the transfer of tat into murine bone marrow cells. We used this transduced bone marrow to repopulate recipient animals, which expressed the tat gene in peripheral blood 6 months after transplantation as determined by PCR amplification of first-strand cDNA. Analysis of the hematopoietic tissues of mice 6 months posttransplantation indicated persistence of the tat gene and its expression in thymus, lymph nodes, spleen, bone marrow, and peripheral blood. Although tat expression was sustained in all hematopoietic tissues, no gross abnormalities were observed. The presence of tat in all hematopoietic tissues strongly suggests transduction of stem or multipotential progenitor cells.

Specific suppression of human CD4 surface expression by Nef from the pathogenic simian immunodeficiency virus SIVmac239open

HIV-1 Nef down-modulates expression of human CD4, the human immunodeficiency virus (HIV) receptor, at the cell surface. Down-modulation of retrovirus receptors has been shown to be important in the survival of infected cells. To relate this observation to AIDS pathogenesis, we compared the ability of Nef from the SIVmac239open and HIV-1 SF2 isolates to suppress CD4 surface levels. We first obtained the simian immunodeficiency virus (SIV)nef gene by PCR and cloned it into the retroviral vector pLXSN. We then established high titer (1 x 10(6) CFU/ml) amphotropic retrovirus producer lines (PA317/LSnefSN). Using LSnefSN we obtained populations of CD4+ human and mouse T-cells, human B-cells, and mouse fibroblasts that expressed SIV or HIV Nef. In the two human cell lines, both HIV and SIV Nef expression correlated with a significant decrease in CD4 cell surface levels. However, Nef expression did not alter the cell surface levels of CD3, CD18, and MHC class I. Both Nef proteins also suppressed human CD4 surface expression in mouse fibroblasts. Interestingly, SIV Nef failed to suppress cell surface expression of mouse CD4 under conditions where HIV-1 Nef did. Human CD4 down-modulation is a conserved function of SIV and HIV Nef likely to be important for pathogenesis.

The interaction of signal transduction pathways in FRTL5 thyroid follicular cells: studies with stable expression of beta 2-adrenergic receptors

Multiple signal transduction pathways interact in FRTL5 cells to promote thyroid follicular cell differentiated function and cell proliferation. In these cells, TSH is a tissue-specific mitogen that promotes DNA synthesis primarily through activation of adenylate cyclase. To further test the role of adenylate cyclase in regulating cell growth and differentiated function we have introduced into FRTL5 the human beta 2-adrenergic receptor (BAR) complementary DNA and have studied the ability of isoproterenol, alone and in combination with insulin-like growth factor I (IGF-I), to stimulate cAMP accumulation, iodide transport, [3H]thymidine incorporation into DNA, and cell growth. Wild-type FRTL5 were infected with a PLJ retroviral construct containing the BAR in either a sense (FRTL BAR) or antisense (FRTL RBAR) orientation, and cell populations were selected on the basis of resistance to the antibiotic geneticin. FRTL BAR expressed approximately 1.3 x 10(5) high affinity binding sites per cell for the beta 2-specific ligand, CGP-12177, while neither FRTL5 wild-type nor RBAR cells demonstrated any specific binding. FRTL BAR had significantly higher levels of intracellular cAMP, [3H]thymidine incorporation, and iodide uptake in the absence of added isoproterenol than FRTL RBAR or wild-type cells. In FRTL BAR, but not RBAR cells, isoproterenol stimulated a dose-dependent accumulation of cAMP, iodide uptake, [3H]thymidine incorporation, and cell growth. FRTL BAR and RBAR cells were equally responsive to TSH and to IGF-I. Isoproterenol enhanced the ability of IGF-I to stimulate [3H]thymidine incorporation in BAR but not RBAR cells. Isoproterenol partially inhibited the ability of TSH to stimulate cAMP generation and DNA synthesis. These studies demonstrate that activation of adenylate cyclase through the BAR introduced into FRTL5 cells by retroviral infection reproduces the range of biological effects in these cells stimulated by TSH and suggest that activation of adenylate cyclase is sufficient to stimulate thyroid differentiated function and cell growth. FRTL BAR cells will provide an interesting model system with which to study the heterologous regulation of both TSH and BARs through activation of a common signal transduction pathway, adenylate cyclase.

Isolation of TSH and LH/CG receptor cDNAs from human thyroid: regulation by tissue specific splicing

A TSH receptor (TSH-R) cDNA has been isolated from a human thyroid lambda GT11 library. Unexpectedly, several cDNAs encoding the human LH/CG receptor (LH/CG-R), previously thought to be expressed solely in gonadal cells, were also isolated from the thyroid library. The receptors are structurally related, consisting of a signal sequence, a large extracellular amino terminal domain, seven membrane spanning domains, and a short carboxyl-terminal portion. The TSH-R is encoded by a single 4.2 kilobase mRNA specific to the thyroid. Introns were not present in any hTSH-R cDNAs examined, however, sequencing of several LH/CG-R cDNAs and RNase protection experiments demonstrated that the majority of hLH/CG-R mRNA in the thyroid is incompletely spliced. Consequently, tissue-specific splicing may be an important step in the regulation of the glycoprotein hormone receptor family.