Biomedical subjects
K L Jackson
Publications and source records attributed to K L Jackson.
Frequency of phobic disorder in a community sample of young adolescents.
OBJECTIVE: To investigate the frequency and phenomenology of clinical, subsyndromal, and subthreshold phobias in young adolescents. METHODS: A two-stage epidemiological study originally designed to investigate adolescent depression was conducted between 1986 and 1988 in the southeastern United States. In the first stage, a self-report depressive symptom questionnaire was administered to a community sample of 3,283 adolescents. In the diagnostic stage, the Schedule for Affective Disorders and Schizophrenia for School-Age Children and the Children's Global Assessment Scale were administered to 487 mother-child pairs. RESULTS: Prevalence rates of clinical, subsyndromal, and subthreshold phobia were 2.3%, 14.5%, and 22.2%, respectively. One-year incidence rates were 0.4%, 8.0%, and 16.9%, with 43.0% of phobic subjects categorized at the same or a more severe level after a year. Females, blacks, subjects not living with both biological parents, and older adolescents were more likely to meet the diagnostic criteria for clinical phobia. The majority (77%) of subjects with clinical phobia experienced multiple phobias. Subsyndromal (52%) and subthreshold (74%) phobics were more likely to experience simple phobias only. CONCLUSIONS: Phobic symptoms are relatively common at a moderate level and in the majority of adolescents are somewhat transitory in nature. Characteristic symptomatology and comorbidity may facilitate earlier identification of subjects at risk of persistent symptomatology and in need of treatment.
Confidence intervals for weighted proportions.
We investigate methods for the construction of confidence intervals for a proportion in a stratified two-stage sampling design with few events occurring in a small number of large, unequal size strata. The critical aspect is the incorporation of the weighting scheme into the construction of a single overall confidence interval. With small numbers of events, the binomial based methods may be inadequate since the normal approximation is not valid. Computer simulations compare coverage probability and bias for five methods of obtaining confidence intervals for proportions by combining: (1) binomial variances; (2) confidence intervals based on the F-distribution approximation to the cumulative binomial; (3) the binomial variance method with exact confidence limits when a zero prevalence occurs in any stratum; (4) confidence intervals based on the F-distribution using a rescaling factor; and (5) the binomial variance method with exact confidence limits using a rescaling factor. The method that performs best in terms of coverage probability is the combination of stratum specific confidence intervals based on the F-distribution using a rescaling factor. The methods involving the binomial variance tend to be negatively biased and the methods based on the F-distribution tend to be positively biased. Application of these methods with data from a study of adolescent depression that employs a stratified two-stage sampling design is consistent with these results.
Safety hazards in households with young children.
Interviewed 230 mothers of young children concerning in-home observations of safety hazards related to burns, poisoning, and falls, and self-reported measures of maternal supervision, locus of control, social support, and safety attitudes. These were supplemented by measures of mothers' risk perceptions, stress and coping, their child's previous injury experience, and indicators of the family's socioeconomic status (SES) collected by telephone survey. SES was an important predictor of observed home hazards. Child-related variables, risk perceptions, and domain-specific attitudes had little influence on home hazards. Maternal supervisory style, rated on dimensions of protectiveness, was an important correlate of all types of household hazards. Results suggest that residential injury prevention strategies for young children should stress active as well as passive countermeasures.
Mother-adolescent agreement on the symptoms and diagnoses of adolescent depression and conduct disorders.
OBJECTIVE: To determine rates and correlates of mother-adolescent agreement on the symptoms and diagnoses of depression and conduct disorders. METHOD: The Schedule for Affective Disorders and Schizophrenia in School Age Children was administered to a community sample of 460 adolescents and their mothers. Race, gender, family adaptability and cohesion, and living arrangement were evaluated as predictors of agreement. RESULTS: Mother-adolescent agreement was low (kappa < 0.40) for all diagnoses and symptoms with these exceptions: feeling tired (kappa = 0.40), inattention (kappa = 0.50), vandalism (kappa = 0.50), and chronic violation of rules (kappa = 0.72). Cohesion and adaptability were associated with mother-adolescent agreement on the symptoms and diagnosis of depression. This association was not demonstrated as consistently for agreement on the symptoms and diagnosis of conduct disorders. CONCLUSION: Study findings underscore the necessity of collecting data from both a parent and the adolescent when assessing an adolescent's psychological status.
Radiation hepatology of the rat: time-dependent recovery.
In situ recovery kinetics of gamma-irradiated rat livers was investigated. To measure short-term repair, surgically exposed livers were irradiated with a 12.5-Gy priming dose. At various times (0-24 h) the liver was re-exposed surgically to 10 Gy. To measure long-term recovery, rats were exposed to a 10-Gy priming dose to the upper abdomen to irradiate the whole liver. The liver was then re-exposed surgically and given graded test doses 0 to 56 days after the first exposure. Repair as a function of interfraction interval (1-12 h) between eight fractions of 3 Gy to the upper abdomen followed 2 weeks later by an 10-Gy top-up dose to the exposed liver was also investigated. Approximately 3 months after the last exposure plasma aspartate aminotransferase, retention of intravenously injected rose bengal, liver weight, and hydroxyproline content were measured to determine hepatic necrosis, function, mass, and fibrosis, respectively. A 15-Gy single-exposure threshold dose was needed to produce detectable hepatic injury. Exceeding this threshold dose resulted in a dose-dependent increase in liver injury as measured by all four end points. Split-dose irradiation with a 10-Gy priming dose and an interfraction interval of 1 day increased the isoeffect dose by 3.9 to 5.8 Gy. Increasing the interfraction interval from 1 to 56 days did not further increase the isoeffect dose. Exposing the liver to eight fractions of 3 Gy with an interfraction interval of 3 h or longer resulted in a dose recovery of approximately 80% (i.e., 19 Gy). A substantial portion of this recovery was evident with interfraction intervals of 1 h. A fluctuating repair pattern with increasing time (0 to 24 h) between 12.5 and 10.0 Gy liver irradiation was observed. This repair was characterized by a 1-h delay after irradiation, followed by near complete repair during the next 3 h, followed by sensitization during the next 2 h and a second wave of repair between 8 and 24 h. Repair was not completed until 21 h after irradiation. It is concluded that the liver's capacity to repair injury within 24 h is similar to that of other late-responding tissues. However, there is no additional repair after 24 h, indicating an absence of slow repair.
Amelioration of radiation nephropathy in rats by dexamethasone treatment after irradiation.
The effect of 20 Gy intraoperative bilateral local kidney irradiation was compared in rats treated after irradiation with dexamethasone and untreated rats. Ninety days after irradiation, body weights, WBC, RBC, hematocrit, and renal function (plasma urea nitrogen concentration and retention of ethylenediaminetetraacetic acid) were measured. The animals were then sacrificed and the kidneys were analyzed for water and hydroxyproline content and examined histologically. Local kidney irradiation reduced animal growth, prevented renal growth, decreased renal mass and renal function, and increased the water and hydroxyproline content of the kidneys. Histopathological examination revealed glomerular damage (atrophy, decreased RBC and endothelial cells, increased mesangial matrix), tubular damage (epithelial denudation, congestion with hyalin casts), and increased concentration of interstitial cells. Dexamethasone treatment significantly ameliorated the effects of kidney irradiation on body weights, renal mass, renal function, and the development of anemia. Dexamethasone had no effect on radiation-induced edema or fibrosis as measured by the water and hydroxyproline content of the kidneys. Dexamethasone-treated irradiated kidneys had significantly less damage to the glomeruli and tubules. The results suggest that dexamethasone is cytoprotective and prevents the destruction of the nephron.
Effect of adrenalectomy on the latency of radiation myelopathy in rats.
The effect of adrenalectomy on the development of radiation myelopathy was studied. A 1-cm section of cervical cord of adrenalectomized and intact animals was exposed to graded doses (18 to 30 Gy) of gamma rays. The radiation tolerance, the latent period from exposure to paralysis, plasma corticosterone levels at the time of paralysis, and histopathology of the cord were evaluated. Adrenalectomy essentially eliminated endogenous production of corticosterone and significantly shortened the mean latent period between irradiation (24 to 30 Gy) and paralysis by more than 10 weeks. This reduced latent period was not reversed by the administration of the exogenous glucocorticoid, dexamethasone, and corticosterone, although prolonged administration of dexamethasone resulted in the development of Cushingoid features, indicating hypercorticoidism. Histopathological examinations indicated that adrenalectomized paretic animals had multiple hemorrhages in both the gray and the white matter, but less white matter necrosis than normally observed in intact paretic animals irradiated similarly. Possible mechanisms for the shortened latent period in adrenalectomized animals are discussed.
Major depressive disorder and dysthymia in young adolescents.
A two-stage epidemiologic study conducted between 1986 and 1988 in the southeastern United States investigated the frequency of major depressive disorder and dysthymia in 12-14 year olds. In stage one, the Center for Epidemiologic Studies Depression Scale, a life event schedule, and a family cohesion scale were administered to a community sample of 3,283 adolescents. In stage two, 488 mother-child pairs were interviewed utilizing the Schedule for Schizophrenia and Affective Disorders in School Age Children. Although mean Center for Epidemiologic Studies Depression Scale scores were significantly higher in females (25.60) than in males (19.50), prevalence estimates based on a summary of mother and child symptom reports for Diagnostic and Statistical Manual of Mental Disorders, Third Edition, major depressive disorder were similar: 9.04% in males and 8.90% in females. The prevalences of dysthymia were 7.98% in males and 5.00% in females. Previous investigations have reported lower rates and a female preponderance of major depression. Disagreement between mothers and children regarding the presence of symptoms may explain this contradiction. Significant odds ratios were found between major depression and not living with both natural parents (odds ratio (OR) = 3.89), undesirable life events (OR = 1.09), and perceived family cohesion (OR = 0.96). Not living with both natural parents (OR = 14.67) and socioeconomic status (OR = 0.44) were significant correlates of dysthymia.
Effects of dexamethasone on the development of radiation nephropathy in the rat.
Low-dose, chronic administration of the synthetic glucocorticoid, dexamethasone, to male CD-I rats in the drinking water or by osmotic minipumps implanted subcutaneously after supralethal irradiation of the kidneys (20 Gy) was studied. The effectiveness of treatment with dexamethasone in the drinking water at concentrations of 23 micrograms/l to 188 micrograms/l and treatment times varying from 33 to 166 days was evaluated. At monthly intervals kidney function was assayed by measuring the clearance of 51Cr-ethylenediaminetetraacetic acid. All dexamethasone treatment regimens increased survival times significantly and delayed the development of kidney dysfunction. The most effective combination of concentration of dexamethasone in drinking water and treatment interval after irradiation with respect to survival was 94 micrograms/l and 88 days. However, a slightly longer survival and a better functional result was obtained if an equivalent amount of dexamethasone was administered by minipumps. Shielding the adrenal glands during kidney irradiation did not prolong survival. This shows that the beneficial effect of dexamethasone is not due to compensation for reduced adrenal glucocorticoid production resulting from concomitant exposures of these glands during kidney irradiation.
Effects of dexamethasone on late radiation injury following partial-body and local organ exposures.
Dexamethasone was evaluated as a treatment for radiation-induced lung, kidney, liver, and spinal cord injuries in rats. One experimental group was partial-body-irradiated (22.5 Gy) with the head, femur, and exteriorized intestine shielded to prevent acute mortality. Other animals received local irradiation to the kidney (20 Gy), liver (25 Gy), or a 1-cm segment of cervical spinal cord (18 to 40 Gy). Following irradiation half of the animals in each radiation group were given drinking water containing 188 micrograms/liter of dexamethasone. Tests were done to assess kidney function (hematocrit, plasma urea nitrogen, ethylenediaminetetraacetic acid clearance), liver function (rose bengal clearance, plasma glutamic oxaloacetic acid transaminase), or spinal cord injury (paralysis). The effectiveness of dexamethasone in preventing radiation injury was tissue specific. Dexamethasone eliminated lethal pleural fluid accumulation after partial-body irradiation and delayed development of kidney dysfunction after local kidney irradiation. As a result, dexamethasone increased the median survival time from 63 to 150 days after partial-body irradiation and from 126 to 175 days after local kidney irradiation. After whole-liver irradiation, development of hepatic functional injury was retarded by dexamethasone treatment but without significantly changing survival time. Dexamethasone had no effect on spinal cord tolerance but significantly shortened the latent period between radiation and paralysis.
Radiation hepatology of the rat: microvascular fibrosis and enhancement of liver dysfunction by diet and drugs.
Prior to whole-liver irradiation (0, 15, 25 Gy) rats were not treated, placed on a protein-deficient diet for 2 weeks, administered cyclophosphamide, and/or depleted of intracellular glutathione by injection with buthionine sulfoximide and diethyl maleate. At various times (0 to 84 days) after 0- and 25-Gy liver irradiation, liver function, liver mass, and hydroxyproline content were measured in nontreated animals. Liver function was measured in all other preirradiation regimens 2 to 3 months postirradiation. Histology and/or India ink perfusion of the liver were done on ascitic and jaundiced animals from all treatment groups. Approximately 20% of the 25-Gy whole-liver-irradiated animals in each preirradiation treatment group developed clinical signs of acute hepatitis (ascites, jaundice, and elevated liver enzymes in the plasma) 70 to 100 days after irradiation. Twenty-five-gray whole-liver irradiation also resulted in significant liver fibrosis that preceded the onset of liver dysfunction. Fibrotic changes were most dramatic in and around hepatic veins, sometimes resulting in complete or partial occlusion that disrupted intrahepatic blood flow and diminished liver function. In addition, a substantial accumulation of fluid in the liver of 25-Gy-irradiated livers occurred, resulting in a lower dry/wet liver weight ratio. Functional hepatic injury was enhanced by preirradiation treatment with a protein-deficient diet, cyclophosphamide, and/or depletion of intracellular glutathione. This enhancement of functional injury was pronounced after 15-Gy whole-liver irradiation when injury from radiation alone was minimal.
Suicidal behaviors in young adolescents.
A two-stage epidemiologic study investigated the frequency of suicidal behavior in children 12-14 years of age. In the first stage, the Center for Epidemiologic Studies Depression Scale, a three-item suicide scale, a life-event schedule, and a family environment scale were administered during 1986 to a southeastern US community sample of 1,542 seventh and eighth grade students. In the second stage, 226 mother-child pairs were interviewed utilizing the Schedule for Schizophrenia and Affective Disorders in School Age Children (K-SADS). Subjects interviewed included students with high depression scores and a random sample of the remaining students. Prevalence estimates for moderate to severe suicidal ideation (K-SADS score greater than or equal to 4) were 4.0% (95% confidence interval (CI) 0.6-16.4%) in males and 8.7% (95% CI 2.4-23.3%) in females. The prevalences of suicide attempts were 1.9% (95% CI 0.0-13.2%) in males and 1.5% (95% CI 0.6-12.7%) in females. Significant relations were found between major depression and both suicide ideation (odds ratio = 6.19, 95% CI 1.53-24.94) and suicide attempts (odds ratio = 9.80, 95% CI 1.89-50.86). The undesirable life-events score was also a significant predictor of suicide ideation and suicide attempts.
A longitudinal study of suicidal ideation in young adolescents.
As part of a longitudinal study of depression and suicidal ideation in adolescents, a three-item suicide screen was administered to 1,073 students for 3 consecutive years starting at the beginning of the 7th or 8th grades. Each year over 70% of respondents reported no suicidal thoughts, and less than 5.5% attained high suicide ideation scores. Blacks and females had higher scores, respectively, than did whites and males. The individual students' suicide scores were less stable than the overall distributions with 1- and 2-year correlations reaching 0.35 and 0.28, respectively. Only one student received a high score all 3 years. The best predictors of a given year's suicide score was the previous years' depression scores. Gender, undesirable life events, family adaptability, and family cohesion were significant but less consistent predictors.
The CES-D as a screen for depression and other psychiatric disorders in adolescents.
The performance of the Center for Epidemiologic Studies Depression Scale (CES-D) as a screen for depression was explored in a two-stage epidemiological study of adolescents. The study consisted of a CES-D screening stage completed by a school sample of 2,465 young adolescents and a structured psychiatric interview stage completed by 332 mother-adolescent pairs. Adolescents with interview validated depression had elevated screening scores (mean = 31.10, SD = 11.30) compared with individuals with no disorder (mean = 21.01, SD = 11.77). Using receiver operating characteristic curves, a cut point of 12 for males produced the best overall screening characteristics (sensitivity = 0.85, specificity = 0.49), while for females, a cut point of 22 was optimal (sensitivity = 0.83, specificity = 0.77).
Hepatic radiation injury in the rat.
The whole livers of rats were exposed intraoperatively to graded doses (0 to 75 Gy) of 137Cs gamma radiation. At various times (0 to 155 days) after liver irradiation, minimally invasive, nondestructive tests (rose bengal retention and plasma alkaline phosphatase, glutamic-oxaloacetic acid transaminase, glutamic-pyruvic transaminase) were performed on at least half the surviving animals in each dose group to assess developing liver injury. Liver histology was done on animals sacrificed 96 to 100 days after irradiation. Radiation damage to the stomach killed approximately 50% of the animals 30 to 60 days after exposure to doses of 25 Gy or higher. These deaths were significantly reduced when care was taken to shield the stomach during irradiation. Stomach injury did not, however, appreciably affect liver function as measured by rose bengal retention. Whole-liver irradiation to 15 Gy resulted in reduced liver size and minimal histological changes, but did not result in increased rose bengal retention or plasma alkaline phosphatase concentration. The next highest dose group studied (25 Gy) showed significant histological abnormalities and liver injury as measured by increased rose bengal retention and liver enzymes. The latent period for development of hepatic injury, as measured by increased rose bengal retention, was 35 to 42 days and was relatively invariant over the 25- to 75-Gy dose range. Hepatic vein lesions and cellular necrosis were the most prominent histological lesions observed in 25-Gy-irradiated liver.
Exercise and the incidence of upper respiratory tract infections.
We examined illness patterns in a cohort of 530 male and female runners who completed a monthly log for 12 months. The average number of upper respiratory tract infections (URTIs) per person per year for the cohort was 1.2. An upper respiratory tract infection was indicated by the report of any of the following symptoms; runny nose, sore throat, or cough. Using a multiple logistic regression model, the following factors were found to be associated with having one or more URTIs in the follow-up period: living alone (odds ratio = 2.27, 95% CI = 1.01, 5.09), running mileage (486-865 miles, odds ratio = 2.00, 95% CI = 1.01, 2.78; 866-1388 miles, odds ratio = 3.50, 95% CI = 1.52, 4.44; greater than 1388 miles, odds ratio = 2.96, 95% CI = 1.30, 3.68), body mass index greater than the 75th percentile (odds ratio = 0.58, 95% CI = 0.35, 0.94), and male gender (odds ratio = 0.14, 95% CI = 0.03, 0.68). A significant interaction was found to exist between gender and alcohol use, with the association between alcohol use and upper respiratory tract infections being positive in males and negative in females. These results suggest that running dosage (mileage) is a significant risk factor for upper respiratory tract infections in this group of exercisers.
Patterns of non-response to a mail survey.
This paper describes a basic investigation of possible non-response bias in a mail survey. We compare characteristics of responders and non-responders to a mail survey of health outcomes among participants of a longitudinal study of physical activity, physical fitness, and health. Results indicate that, at the first clinic visit, the responders were essentially the same as the non-responders on personal health history and laboratory measurements, while reporting significantly more family history of specific chronic diseases (cardiovascular disease, hypertension, stroke). The male responders were younger and reported more positive health behaviors as well as better weight and treadmill times at the first clinic visit. These results suggest that both response groups were equally healthy at entry, and that individuals who had family members with certain chronic conditions and who had positive health behaviors were more likely to respond (participate) in this health-related survey. Differences of this type could affect interpretation of future analyses. This work illustrates the importance of incorporating methods to examine non-response into any epidemiologic study.