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Biomedical subjects

J Schwartz

Publications and source records attributed to J Schwartz.

At least 127 records · Page 7Linked to original sources
PubMed1999

Heart rate variability associated with particulate air pollution.

BACKGROUND: Epidemiologic studies have linked fine particulate air pollution with cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown. Changes in heart rate variability (HRV) may reflect changes in cardiac autonomic function and risk of sudden cardiac death. This study evaluated changes in mean heart rate and HRV in human beings associated with changes in exposure to particulate air pollution. METHODS: Repeated ambulatory electrocardiographic monitoring was conducted on 7 subjects for a total of 29 person-days before, during, and after episodes of elevated pollution. Mean HR, the standard deviation of normal-to-normal (NN) intervals (SDNN), the standard deviation of the averages of NN intervals in all 5-minute segments of the recording (SDANN), and the square root of the mean of squared differences between adjacent NN intervals (r-MSSD) were calculated for 24-hour and 6-hour time segments. Associations of HRV with particulate pollution levels were evaluated with fixed-effects regression models. RESULTS: After controlling for differences across patients, elevated particulate levels were associated with (1) increased mean HR, (2) decreased SDNN, a measure of overall HRV, (3) decreased SDANN, a measure that corresponds to ultralow frequency variability, and (4) increased r-MSSD, a measure that corresponds to high-frequency variability. The associations between HRV and particulates were small but persisted even after controlling for mean HR. CONCLUSIONS: This study suggests that changes in cardiac autonomic function reflected by changes in mean HR and HRV may be part of the pathophysiologic mechanisms or pathways linking cardiovascular mortality and particulate air pollution.

Adult↗
PubMed1999

Maturation of cortisol responses to adrenocorticotropic hormone in twin fetal sheep in vivo.

OBJECTIVE: Adrenal steroidogenesis is important for maturation of fetal organ systems and plays a role in triggering parturition in ovine pregnancies. Studies have suggested a differential increase in baseline cortisol between twin gestations near term. Our aim was to further delineate the mechanisms responsible for the differences between the hypothalamic-pituitary-adrenal axes of twin fetuses in vivo. STUDY DESIGN: Surgery was performed on pregnant ewes (n = 6) with twin gestations to implant fetal vascular catheters. After recovery but while the subjects were resting, plasma cortisol concentrations were similar in both fetuses. Fetuses received, intravenously, boluses of adrenocorticotropic hormone at 2 doses, and plasma samples were obtained for analysis of the cortisol response. This stimulation by adrenocorticotropic hormone was then repeated in the same fetuses approximately 4 days later, after the increase of resting daily cortisol values in one but not the other fetus. RESULTS: Cortisol responses to adrenocorticotropic hormone before changes in daily resting cortisol concentrations were indistinguishable between twins. However, after separation of daily resting cortisol values, fetuses in group A (elevated resting cortisol concentration) demonstrated a significantly increased response to stimulation by adrenocorticotropic hormone. CONCLUSION: These results suggest a differential development in response to stimulation by adrenocorticotropic hormone between twin fetuses in vivo as the mechanism responsible for the asynchronous elevation of one twin's resting plasma cortisol concentration.

Adrenal Glands↗
PubMed1999

Detection of human papillomavirus type 10 DNA in eccrine syringofibroadenomatosis occurring in Clouston's syndrome.

Syringofibroadenomatosis is often associated with an underlying condition such as diabetes mellitus or hidrotic ectodermal dysplasia. By reason of these associations, a reactive or hamartomatous cause is suspected. We report a case of a 71-year-old woman with Clouston's syndrome in whom progressive multiple palmoplantar syringofibroadenomas developed over a 10-year period. The syringofibroadenomas formed flat-topped papules simulating verruca plana; the widespread distribution and chronic progressive course resembled epidermodysplasia verruciformis. Contiguous with the syringofibroadenoma's characteristic epithelial-stromal proliferation were epidermal changes of verruca plana. Evidence of human papillomavirus (HPV) infection was verified by immunolabeling with antibodies to bovine papillomavirus type 1 and detection of HPV 10 viral DNA by means of polymerase chain reaction. Rather than a hamartomatous process, these findings suggest that syringofibroadenomas occurring in the setting of Clouston's syndrome could represent an HPV-induced epithelial proliferation.

Aged↗
PubMed1999

Insulin-like growth factors and IGF-binding proteins in bovine seminal plasma.

Insulin-like growth factor-I (IGF-I) is an important factor for germ cell development and maturation of spermatozoa. Actions of IGFs are modulated by IGF-binding proteins (IGFBPs) that may, depending on their concentration and site of expression, inhibit or enhance effects of IGF-I. We characterized IGFs and IGFBPs in seminal plasma from bulls routinely used for artificial insemination (AI) and from bulls producing poor-quality semen (low mass and individual motility of spermatozoa). IGFs were measured by specific radioimmunoassay in 22 samples of seminal plasma from nine different AI bulls with high (> 76.8%), average (72.8-73.4%), or low (< 69.5%) nonreturn rate (NRR). IGF-I and IGF-II levels were 144 +/- 9 ng/ml (mean +/- SE; range, 79-238 ng/ml) and 144 +/- 10 ng/ml (range, 55-221 ng/ml), respectively, and did not correlate with NRRs. IGF-I concentrations in seminal plasma from bulls producing poor-quality semen (n = 10) were significantly (P < 0.05) greater (194 +/- 26 ng/ml; range, 94-370 ng/ml), whereas IGF-II levels were significantly (P < 0.05) lower (93 +/- 17 ng/ml; range, 38-183 ng/ml) than in AI bulls. Ligand blot analysis of seminal plasma for IGFBPs revealed the presence of a 38-/45-kDa doublet band and a 30-kDa IGFBP. These IGFBPs were identified as IGFBP-3 and IGFBP-5, respectively, by immunoprecipitation using specific antibodies. In addition, a low amount of IGFBP-4 was detected in bovine seminal plasma by immunoprecipitation. There was a marked difference in the activity of IGFBPs between individual bulls, with a relatively small within-bull variance. The differences in IGFBP activities did not correlate with the fertilization capacity of the bulls in vivo or in vitro nor with immunoreactive IGF-I and IGF-II levels in seminal plasma. Our results demonstrate the presence of IGFBPs in bovine seminal plasma. In contrast to human seminal plasma, high activity of IGFBP-3 was detected in seminal plasma of some bulls, suggesting species-specific regulation of IGFBP activity by proteases.

Animals↗
PubMed1999

Workday communication and ambulatory blood pressure: implications for the reactivity hypothesis.

Ambulatory blood pressure monitoring was used to investigate the cardiovascular correlates of naturally occurring interpersonal interactions. Participants were New York City traffic agents, who routinely engage in conflict-prone communication with the public under relatively fixed conditions. Talking with the public, supervisors, or coworkers was associated with levels of systolic and diastolic blood pressure and heart rate that exceeded a resting baseline. Blood pressure was higher when agents were talking to the public than when they were talking to coworkers or engaged in a noncommunicative work task. Systolic blood pressure response during communication was associated with the agent's mood. Blood pressure effects associated with communication appear to persist after the communication has ceased. Implications of these data for the reactivity hypothesis of the pathogenesis of cardiovascular disease are discussed.

Adult↗
PubMed1999

Medical hypnosis for hyperemesis gravidarum.

Hyperemesis gravidarum in pregnancy is a serious condition that is often resistant to conservative treatments. Medical hypnosis is a well-documented alternative treatment. This article reviews the empirical studies of medical hypnosis for treating hyperemesis gravidarum, explains basic concepts, and details the treatment mechanisms. The importance of a thorough differential diagnosis and appropriate referrals is stressed. The article presents three case studies to illustrate the efficacy of this treatment approach. It is suggested that medical hypnosis should be considered as an adjunctive treatment option for those women with hyperemesis gravidarum. It is also stressed that medical hypnosis can be used to treat common morning sickness that is experienced by up to 80 percent of pregnant women. Its use could allow a more comfortable pregnancy and healthier fetal development, and could prevent cases that might otherwise proceed to full-blown hyperemesis gravidarum.

Adult↗
PubMed1999

Leukemia inhibitory factor as an intrapituitary mediator of ACTH secretion.

In the normal anterior pituitary, intercellular interactions are important for the expression of hormones including adrenocorticotropin (ACTH). Leukemia inhibitory factor (LIF) is secreted by anterior pituitary cells and stimulates both basal and corticotropin-releasing hormone (CRH)-stimulated ACTH secretion in AtT20 cells. To determine the effects of LIF on normal pituitary cells, we measured the effects of LIF and an immunoneutralizing antiserum against LIF on ACTH secretion by cultured sheep anterior pituitary cells. In intact populations of anterior pituitary cells, LIF (10 nM) stimulated ACTH secretion (from 0.30 +/- 0.06 to 0.77 +/- 0.01 ng/well per 3 h) and antiserum to LIF (by itself) had no effect (0.29 +/- 0.05 ng/well per 3 h). In marked contrast, following pharmacological elimination of CRH-target cells, a condition known to disinhibit ACTH secretion, basal ACTH secretion was elevated (0.74 +/- 0.13 ng/well per 3 h); LIF produced no further stimulation (0.73 +/- 0.22 ng/well per 3 h) but immunoneutralization of LIF significantly reduced secretion to 0.50 +/- 0.10 ng/well per 3 h. Medium, conditioned by exposure to CRH-target-depleted cultures of anterior pituitary cells, increased net ACTH secretion (from 0.29 +/- 0.03 to 6.54 +/- 0.71 ng/well per 3 h), when added as a challenge to naive, cultured anterior pituitary cells. Inclusion of antiserum to LIF significantly attenuated (5.29 +/- 0.62 ng/well per 3 h) this response. The presence in and secretion of LIF by normal individual pituitary cells was detected using immunocytochemical methods. Seven to 8% of all cells stained positively for LIF, with 66 +/- 11% of those secreting detectable amounts of LIF under unstimulated conditions. LIF colocalized with TSH and LH in pituitary cells. Taken together, these data suggest that LIF can stimulate ACTH secretion by normal anterior pituitary cells, and potentially plays a role as an intrapituitary stimulator of ACTH secretion under certain conditions.

Adrenocorticotropic Hormone↗
PubMed1999

Oxygen saturation, pulse rate, and particulate air pollution: A daily time-series panel study.

Although epidemiological studies have linked particulate air pollution with cardiopulmonary mortality, underlying biological mechanisms remain largely unknown. Unexplored pathophysiological pathways include transient declines in blood oxygenation and/or changes in cardiac rhythm following particulate exposure. In this study, blood oxygen saturation using pulse oximetry (SpO2) and pulse rate were measured daily on a panel of 90 elderly subjects during the winter of 1995-1996 in Utah Valley. Associations of SpO2 and pulse rate with respirable particulate pollution (particles with an aerodynamic diameter </= a nominal 10 microm [PM10]) were evaluated. SpO2 was not consistently associated with PM10. Pulse rate and the odds of the pulse rate being elevated by 5 or 10 beats per minute (beats/min) were associated with PM10 on the previous 1 to 5 d. A 100 microg/m3 increase in previous-day PM10 was associated with an average increase of 0.8 beats/min and 29 and 95% increased odds of the pulse rate being elevated by 5 or 10 beats/min, respectively. Although there was little evidence of pollution-related hypoxia, alterations in pulse rate could reflect cardiac rhythm changes and may be part of the pathophysiology linking particles to cardiopulmonary mortality. The observed lag structure is consistent with particulate-induced pulmonary inflammation and cytokine release, but the biological relevance requires further study.

Aged↗
PubMed1999

Episodes of high coarse particle concentrations are not associated with increased mortality.

Fine particle concentration (i.e., particles <2.5 microm in aerodynamic diameter; PM2.5), but not coarse particle concentration, was associated with increased mortality in six U.S. cities. Others criticized this result, arguing that it could result from differences in measurement error between the two size ranges. Fine particles are primarily from combustion of fossil fuel, whereras coarse particles (i.e., particles between 2.5 and 10 microm in aerodynamic diameter) are all crustal material, i.e., dust. One way to determine if coarse particles are a risk for mortality is to identify episodes of high concentrations of coarse, but not fine, particles. Spokane, Washington, is located in an arid area and is subject to occasional dust storms after crops have been harvested. Between 1989 and 1995, we identified 17 dust storms in Spokane. The 24-hr mean PM10 concentration during those storms was 263 microg/m3. Using control dates that were the same day of the year in other years (but with no dust storm on that day) and that had a mean PM10 concentration of 42 microg/m3, we compared the rate of nonaccidental deaths on the episode versus nonepisode days. There was little evidence of any risk [relative risk (RR) = 1.00; 95% confidence interval (CI), 0.81-1.22] on the episode days. Defining episode deaths as those occurring on the same or following day as the dust storm produced similar results (RR = 1.01; CI, 0.87-1.17). Sensitivity analyses, which tested more extensive seasonal control, produced smaller estimates. We conclude that coarse particles from windblown dust are not associated with mortality risk.

Air Pollutants↗
PubMed1999

The independent contribution of bone and erythrocyte lead to urinary lead among middle-aged and elderly men: the normative aging study.

Plasma is the component of blood from which lead is free to cross cell membranes and cause organ toxicity. Plasma lead levels, however, are extremely low and difficult to measure. Urinary lead originates from plasma lead that has been filtered at the glomerular level; thus, urinary lead adjusted for glomerular filtration rate serves as a proxy for plasma lead levels. In this investigation we examined the interrelationships of lead levels in whole blood corrected by hematocrit [i.e., erythrocyte lead (EPb)], trabecular bone (TBoPb), cortical bone (CBoPb), and urine excreted over 24 hr (UPb); all samples were obtained from 71 middle-aged and elderly men with no known occupational lead exposures. Lead was measured by graphite furnace atomic absorption spectroscopy (blood), K-X-ray fluorescence (bone), and inductively coupled plasma mass spectroscopy (urine). Lead levels were generally low, with mean EPb, TBoPb, and CBoPb values of 13.8, 31.1, and 21.7 microg/g, respectively, and a median UPb value of 6.15 microg/day. In generalized additive models adjusted for body weight and creatinine clearance rate, both EPb and bone lead variables remained independently and significantly associated with UPb. This finding suggests that bone influences plasma lead in a manner that is independent of the influence of erythrocytic lead on plasma lead. Thus, the superiority of bone lead over blood lead in predicting some chronic forms of toxicity may be mediated through bone's influence on plasma lead. In addition, this study suggests that measurement of urinary lead might be useful as a proxy for plasma lead levels in studies of lead toxicity.

Aged↗
PubMed1999

A case-crossover analysis of air pollution and mortality in Philadelphia.

This study reassessed Schwartz and Dockery's analysis of daily mortality from nonexternal causes among residents of Philadelphia, Pennsylvania, over 8 years, from 1973 to 1980 [American Review of Respiratory Disease 145:600-604 (1992)]. A Poisson regression analysis using the same model found that a 100-microg/m(3) increment in the 48-hr mean concentration of total suspended particulates (TSP) was associated with increased all-cause mortality [rate ratio = 1.069; 95% confidence interval (CI), 1.043-1.096) after adjustment for quadratic trend, season, year, previous day's mean temperature, dew point, winter temperature, and indicators of hot (temperature > 80 degrees F) and humid days (dew point > 66 degrees F). Critics suggested that time-varying factors such as season and day of week were not sufficiently controlled in this analysis and subsequent studies in other locations. We used a conditional logistic regression analysis with a case-crossover design to reanalyze the data, with air pollution in the prior and subsequent weeks to the day of death serving as referent periods. The case-crossover approach controls for season and day of week by design rather than modeling. We found that a 100-microg/m(3) increment in the 48-hr mean level of TSP was associated with increased all-cause mortality [odds ratio (OR) = 1.056; CI, 1.027-1.086) after adjustment for the same weather variables as above. Similar associations were observed for deaths in individuals over 65 years of age (OR = 1.074; CI, 1. 037-1.111) and for deaths due to cardiovascular disease (OR = 1.063; CI, 1.021-1.107). The current case-crossover analysis confirms the general conclusion of the previous Poisson regression analysis of an association of TSP with daily mortality in Philadelphia, Pennsylvania.

Adolescent↗
PubMed1999

Reanalysis of the effects of air pollution on daily mortality in Seoul, Korea: A case-crossover design.

We used the case-crossover design to identify any increase in mortality in Seoul, Korea, when there were higher levels of ambient air pollution on case-days than would be expected solely as a result of chance. This empirical study showed that either unidirectional retrospective (selecting only control days prior to death) or prospective (selecting only control days after death) control sampling could cause risk estimates to be confounded by seasonal waves as well as time trends in air pollution levels. In bidirectional control sampling in which exposures at death were compared with exposures both before and after death, the estimated mortality was resistant to confounding by time patterns of air pollution. Using a bidirectional control sampling approach, the results from a conditional logistic regression model controlling for weather conditions showed that the nonaccidental mortality associated with a 50-ppb increment over a 3-day moving average of SO(2) concentrations, including the concurrent day and preceding 2 days, was 1.023 [95% confidence interval (CI), 1.016-1.084]. The relative risk of death was 1.023 (CI, 0.999-1.048) per 50 ppb for 1-hr maximum O(3) and 1.010 (CI, 0.988-1.032) per 100 microg/m(3 )or total suspended particulates. In conclusion, the findings of this study were 2-fold: given the consistency of the observed association between SO(2) and daily mortality across different analysis methods, the association reported here indicates that air pollution is a probable contributor to premature death; and bidirectional control sampling is needed in a case-crossover design applied to air pollution epidemiologic studies to control confounding by seasonal patterns of air pollution as well as time trends.

Adolescent↗
PubMed1999

GnRH and oxytocin have nonidentical effects on the cellular LH response by gonadotrophs at pro-oestrus.

For full fertility in the female ovulation is necessary, which is dependent on the production of a surge of LH. An understanding of the processes which result in the high levels of LH requires delineation of the activities of individual component cells. In this study the responses of gonadotrophs to two signalling hypothalamic peptides, GnRH and oxytocin, were investigated. A cell immunoblot method was used to identify and distinguish between cells which secrete LH and those which contain LH but do not secrete the glycohormone. Rats were killed on the morning of pro-oestrus, the pituitary collected and the cells dispersed onto a protein-binding membrane for study. Cells were then incubated with GnRH and oxytocin, after which the membranes including the attached cells were stained by immunocytochemistry for LH. GnRH increased the total number of immunopositive cells which were present in a concentration-dependent manner. The most prominent change after 2 h incubation was in the number of secreting cells, whereas after 4 h there was also a marked increase in numbers of nonsecreting cells. Oxytocin also increased the total number of immunopositive cells in a concentration-responsive manner, however the profile of action of oxytocin was different from that observed for GnRH. Oxytocin had a relatively greater effect on numbers of immunopositive nonsecreting cells. Thus, the results reveal the potential for gonadotrophs to be flexibly and appropriately modulated by selected hypothalamic peptides. When cells were preincubated with oxytocin prior to GnRH there was not an additive increase in the numbers of immunopositive cells, suggesting that the two agonists act, in a nonidentical manner, on similar cells. The increase in the total number of immunopositive cells implies that there was a production of LH or post-translational processing, induced by exposure to GnRH or oxytocin. The results confirmed the heterogeneity of gonadotrophs and the existence of functionally distinguishable subpopulations, and revealed a difference between the effects of GnRH and oxytocin on expression and secretion of LH.

Animals↗
PubMed1999

Daily changes in oxygen saturation and pulse rate associated with particulate air pollution and barometric pressure.

Epidemiologic studies have linked fine particulate air pollution with increases in morbidity and mortality rates from cardiopulmonary complications. Although the underlying biologic mechanisms responsible for this increase remain largely unknown, potential pathways include transient declines in blood oxygenation and changes in pulse rate following exposures to particulate air pollution episodes. This study evaluated potential associations between daily measures of respirable particulate matter (PM) with pulse rate and oxygen saturation of the blood. Pulse rate and oxygen saturation (Spo2) using pulse oximetry were measured daily in 90 elderly subjects living near air pollution monitors during the winter of 1995-96 in Utah Valley. We also evaluated potential associations of oxygen saturation and pulse rate with barometric pressure. Small but statistically significant positive associations between day-to-day changes in Spo2 and barometric pressure were observed. Pulse rate was inversely associated with barometric pressure. Exposure to particulate pollution was not significantly associated with Spo2 except in male participants 80 years of age or older. Increased daily pulse rate, as well as the odds of having a pulse rate 5 or 10 beats per minute (bpm) above normal (normal is defined as the individual's mean pulse rate throughout the study period), were significantly associated with exposure to particulate pollution on the previous 1 to 5 days. The medical or biologic relevance of these increases in pulse rate following exposure to particulate air pollution requires further study.

Aged↗
PubMed1999

Control for seasonal variation and time trend in case-crossover studies of acute effects of environmental exposures.

The case-crossover study design is used to study the triggers of acute outcomes in populations. It controls for all measured and unmeasured time-invariant confounders by design. Studies of environmental triggers of morbidity are potentially confounded by temporal trends in the outcome owing to omitted covariates. We conducted a simulation study of the case-crossover design's ability to control for temporal confounding patterns by design rather than through modeling. We compared five case-crossover control sampling strategies including the matched pair, a symmetric bi-directional, a total history approach, and two approaches proposed by Navidi (Biometrics 1998;54:596-605). We simulated true relative risks (RR) of 1.10 and 2.00 and induced confounding by seasonal patterns as well as linear and nonlinear long-term trends to yield estimated RR values as high as 3.18. The symmetric bi-directional approach was compared across four lag times and controlled for temporal confounding best when the lag was shortest. With a 1-week lag, it estimated the RR values as 1.10 and 2.01. The four other approaches failed to control for the temporal trends. Our simulations show that the symmetric bi-directional case-crossover design can substantially control for temporal confounding by design although it is not as efficient (66%) as Poisson regression analysis.

Computer Simulation↗
PubMed1999

Air pollution and hospital admissions for heart disease in eight U.S. counties.

This study examines the consistency of the association between particulate matter less than 10 microm in aerodynamic diameter (PM10), carbon monoxide (CO), and hospital admissions for cardiovascular disease across eight urban counties with different levels of correlation between pollutants and between the pollutants and weather. I fit Poisson regression models controlling for day-of-week effects and using nonparametric smoothing to control for season and weather. Daily variation in PM10 was associated with hospital admissions for heart disease in the elderly (2.48% increase, for an interquartile range increase in exposure; 95% confidence limits = 1.82%, 3.15%). Daily variation in CO was also associated with admissions (2.79% increase, for an interquartile range (1.75 parts per million) increase in exposure; 95% confidence limits = 1.89%, 3.68%). These associations held in both humid and dry locations and were independent of the correlation between the pollutants and weather or other pollutants. The effect size estimates for PM10 and CO likewise showed no association with their correlation in each location, as one would expect if one pollutant were merely a proxy for the other. The PM10 effects are consistent with recent animal data showing cardiovascular effects and with preliminary human data showing effects on heart rate variability and plasma viscosity. The CO results are consistent with literature on angina exacerbations.

Aged↗