Biomedical subjects

S D Simon

Publications and source records attributed to S D Simon.

At least 19 recordsLinked to original sources

PubMed2001

Normal urinary calcium/creatinine ratios in African-American and Caucasian children.

A random urine calcium/creatinine ratio (UCa/Cr) is of practical use in screening for hypercalciuria. However, due to worldwide variations, reference values for the pediatric population are not yet well established. Furthermore, no study has been conducted to establish normal UCa/Cr values in young African-American (AA) children. It has also been previously reported that an elevated UCa/Cr is related to a high urine Na/K ratio (UNa/K). The objectives of the present study were: (1) to set normal values of random UCa/Cr by age and race in the pediatric population of Metropolitan Kansas City, (2) to identify potential racial differences in UCa/Cr between Caucasian (CS) and AA children, and (3) to determine the relationship between UCa/Cr and UNa/K in healthy children. A total of 368 healthy children of both genders were enrolled in the study. They were divided into four age groups as follows: (1) <7 months, (2) 8-18 months, (3) 19 months to 6 years, and (4) 7-16 years. Each group was subdivided into AA and CS. A non-fasting random urine specimen from each subject was analyzed for Ca, Na, K and creatinine. The median UCa/Cr values for AA were: (1) 0.13, (2) 0.09, (3) 0.06, and (4) 0.04 and for CS they were (1) 0.26, (2) 0.11, (3) 0.10, and (4) 0.09. The data showed a strong inverse relationship between UCa/Cr and age, the youngest children demonstrating the highest UCa/Cr. In each age group, UCa/Cr in CS exceeded the corresponding value in AA. The age-dependent 95th percentiles of UCa/Cr values for CS were (1) 0.70, (2) 0.50, (3) 0.28, and (4) 0.20 and for AA they were (1) 0.38 and (3) 0.24. Due to outliers, the 95th percentile could not be established for the other two AA subgroups. The relationship between UCa/Cr and UNa/K was found to be extremely weak in both AA (r2=0.00005) and CS (r2=0.02). On the other hand, a strong linear correlation was observed between UNa/K and age (CS r2=0.23, P<0.001, AA r2=0.19, P<0.001), explaining in part the lack of correlation between UNa/K and UCa/Cr. We conclude that the child's age, ethnicity and geographic location should be taken into consideration when assessing UCa/Cr ratio. Contrary to what has previously been reported in hypercalciuric children, no significant relationship was found between UCa/Cr and UNa/K in healthy children.

Adolescent↗

PubMed2001

Creatinine excretion rates for renal clearance studies.

A total of 637 timed-urine collections for creatinine excretion rates obtained from 295 children over 14 years have been analyzed. The children ranged in age from 2.8 to 21.7 years at the time of the clearance study. The data analyzed included only one study from a child during any 6-month period. The objective is to provide data defining the expected range of creatinine excretion for renal clearance studies. One hundred forty-two studies were conducted on children not pretreated with cimetidine and 495 on those pretreated with cimetidine. Analysis showed that pretreatment with cimetidine for creatinine clearance studies does not alter creatinine excretion rates (P=0.080; 95% CI -0.03 to 1.61). Creatinine excretion rates in urine collections obtained at home (roughly 24-h collections) were compared with 2-h supervised collections in the Children's Kidney Center. The supervised urine collections resulted in creatinine excretion rates 1.38 mg/kg/24 h greater than home collections (P=0.001; 95% CI 0.76-2.00). Using regression equations for creatinine excretion rate with age, tables have been prepared showing the expected rate of creatinine excretion for renal clearance studies in children 3-21 years of age.

Adolescent↗

PubMed2001

Should all infertile males undergo urologic evaluation before assisted reproductive technologies? Two cases of testicular cancer presenting with infertility.

OBJECTIVE: To report two cases of testicular cancer in patients presenting with infertility. DESIGN: Case reports. SETTING: University-affiliated urology practice. PATIENT(S): Two men presenting with infertility. INTERVENTION(S): Complete history and physical, hormonal assays, semen analysis, scrotal ultrasound, radical orchiectomy. MAIN OUTCOME MEASURE(S): Testicular pathology specimens. RESULT(S): Testicular cancer was diagnosed in two men sent to a urology clinic for infertility treatment. CONCLUSION(S): A thorough evaluation should be completed in all males in couples presenting with infertility.

Adult↗

PubMed2000

Semen quality and hormone levels among radiofrequency heater operators.

Approximately 9,000,000 US workers are occupationally exposed to radiofrequency (RF) radiation; over 250,000 operate RF dielectric heaters. Our purpose was to determine whether male RF heater operators experience increased adverse reproductive effects reflected in reduced semen quality or altered hormone levels. We measured incident RF heater radiation exposures and RF-induced foot currents at four companies. For 12 male heater operators and a comparison group of 34 RF-unexposed men, we measured 33 parameters of semen quality and four serum hormones. Despite wide variation in individual exposure levels, near field strengths and induced foot currents did not exceed current standard levels and guidelines. We observed minor semen quality and hormonal differences between the groups, including a slightly higher mean follicle-stimulating hormone level for exposed operators (7.6 vs 5.8 mIU/mL). Further occupational studies of RF-exposed men may be warranted.

Adult↗

PubMed2000

Factors influencing infant visits to emergency departments.

OBJECTIVES: To follow the 1995 birth cohort of infants, born in the State of Missouri, through their first birthday to: 1) examine their rates of visits to emergency departments (EDs), 2) identify predictors of any ED visit, 3) examine rates of nonurgent ED visits, and 4) identify predictors of nonurgent visits. METHODS: This was a retrospective population cohort study. Using deterministic linkage procedures, 2 databases at the Missouri Department of Health (DOH; (the patient abstract database and the birth registry database) were linked by DOH personnel. International Classification of Diseases, Ninth Revision-Clinical Modification codes for ED visits were classified as emergent, urgent, or nonurgent by 2 researchers. Eight newborn characteristics were chosen for analysis. Negative binomial regression was used to examine the rates and predictors of both total and nonurgent ED visits. RESULTS: There were 935 total ED visits and 153 nonurgent ED visits per 1000 infant years. The average number of visits was.94, with 59% of infants having no visits, 21% having 1 ED visit, and 20% having 2 or more visits. Factors associated with increases in both total and nonurgent ED visits were Medicaid, self-pay, black race, rural region, presence of birth defects, and a nursery stay of >2 days. Significant interactions were found between Medicaid and race and Medicaid and rural regions on rates of ED use and nonurgent use. The highest rate of ED use, 1.8 per person year, was seen in white, rural infants on Medicaid, and the lowest rate (.4 per person year) was seen in urban white infants not on Medicaid. The highest rates of nonurgent use,.3 per person year, were among urban and rural Medicaid infants of both races and among black infants on commercial insurance. The lowest nonurgent rate,.04 per person year, was seen in white urban infants on commercial insurance. CONCLUSION: Infants in the State of Missouri have high rates of ED visits. Nonurgent visits are only a small portion of ED visits and cannot explain large variations in ED usage. Increased ED use by Medicaid patients may reflect continuing difficulties in accessing primary care.

Age Factors↗

PubMed1999

High incidence of focal segmental glomerulosclerosis in nephrotic syndrome of childhood.

In recent adult literature, there have been reports of an increasing incidence of focal segmental glomerulosclerosis (FSGS) among patients with nephrotic syndrome. To examine whether this observation is also relevant to the pediatric population we utilized our hospital computerized database to analyze the data on children with primary nephrotic syndrome seen first between the years 1984 and 1995. A questionnaire was also sent to all metropolitan Kansas City pediatricians to identify possible patients outside the database. The inclusion criteria were clinical nephrotic syndrome or proteinuria with a kidney biopsy. A total of 148 patients (group A) were identified; 86 of them from metropolitan Kansas City (group B). In group A the incidence of minimal change disease (MCD) and FSGS was 52.7% [95% confidence interval (CI) 44%-60%] and 23.0% (95% CI 16-29%), respectively and in group B 54.7% (95% CI 44%-65%) and 24.5% (95% CI 15%-33%), respectively. Those numbers were significantly different from the International Study of Kidney Disease in Children (IS-KDC) reported incidence of 76.4% for MCD and 6.9% for FSGS. Similar to the ISKDC, in our population children over 6 years had a higher incidence of FSGS than younger children (32.8% vs. 16.7%, P = 0.028). The annual incidence rate for nephrotic syndrome in group B was 2.2 cases/10(5) children per year, of which MCD comprised 1.22 cases/10(5) children per year and FSGS 0.5 cases/10(5) children per year. The annual incidence rates of both primary nephrotic syndrome (3.6) and FSGS (1.6) were significantly higher in African-Americans, than Caucasians (1.8 and 0.3 cases/10(5) children per year, respectively). Our study indicates nearly no change in the annual incidence of pediatric primary nephrotic syndrome, but a higher incidence of FSGS with reciprocal decline in the incidence of MCD. The possibility of primary nephrotic syndrome being caused by a non-MCD entity is further raised among African-American and in children over 6 years. We conclude that our perception of primary nephrotic syndrome of childhood as a benign condition has to be carefully reexamined and a more-guarded prognostic approach adopted in our geographic area.

Adolescent↗

PubMed1999

Optimization of cytochrome P4502D6 (CYP2D6) phenotype assignment using a genotyping algorithm based on allele frequency data.

Cytochrome P4502D6 (CYP2D6) is a highly polymorphic gene locus with > 50 variant alleles which lead to a wide range in enzymatic activity. So called poor metabolizers are carriers of any two non-functional alleles of the CYP2D6 gene. CYP2D6 genotyping is cumbersome and the question of how much genotyping is necessary for an accurate phenotype prediction is still debated. The goal of this study was to determine the optimum amount of genotyping required to accurately predict the phenotype at a reasonable cost in a white North American population. To address this issue, we designed a polymerase chain reaction (PCR)/restriction fragment length polymorphism-based genotyping strategy to detect 'key' mutations linked to extensive metabolizer or poor metabolizer associated alleles in combination with extra-long PCR (XL-PCR). All mutations with the exception of gene deletions and duplications are detectable by simple restriction digestion analysis and agarose gel electrophoresis. In addition, we utilized a genotyping algorithm based on our own and published allele frequency data and phenotype analysis to calculate the probability of a correct genotype (and thus, phenotype) assignment. As little as one XL-PCR reaction followed by a maximum of six reamplification reactions allows an accurate prediction of an individual's genotype to 99.15%. As few as four reamplification reactions identify 97.9% of poor metabolizer individuals. We evaluated our model in 208 white North Americans by testing for the presence of 'key' mutations linked to CYP2D6*2, *3, *4, *6, *7, *8, *9, *10, *11, *12, *15, *17 and *18 alleles and the *5, *13 and *16 gene deletions. For all individuals, the correct phenotype has been predicted. Discordant phenotype assignment occurred in only two individuals which subsequently was attributed to CYP2D6 inhibition by concomitant drug therapy.

Algorithms↗

PubMed1996

Capitation: selecting the method, determining the rates. Can providers share risk without excessive financial exposure?

Healthcare providers in markets with a high degree of managed care penetration, such as western states, are aggressively pursuing capitated contracts that are comprehensive in scope and that assume a significant amount of risk sharing. Providers in other parts of the country, however, still are determining how much risk they can assume safely. Integral to this assessment is consideration of two factors: the form of the capitated payment and the capitation rate. Providers must understand the two forms of capitated payment--per member per month and percent of premium--and how each is affected by changes in market levels before they can choose the one best suited to the amount of risk they can assume. Findings from a study of capitation rates utilized by 10 large national or multiregional HMOs may serve as a point of reference for providers.

Capitation Fee↗

PubMed1994

Primary methotrexate, vinblastine, doxorubicin and cisplatin chemotherapy and bladder preservation in locally invasive bladder cancer: a 5-year followup.

A phase 2 protocol was designed for conservative treatment of muscle invasive transitional cell carcinoma of the bladder and consisted of primary methotrexate, vinblastine, doxorubicin and cisplatin chemotherapy followed by bladder sparing surgical reevaluation and surveillance. Of 36 patients 30 completed the protocol and were followed for at least 5 years. Initial complete response to chemotherapy was noted in 14 patients (47%, 95% confidence interval 30 to 64%) and complete responses were more common with low stage tumors. After chemotherapy the bladder was preserved in 18 patients (60%) but at 5 years only 6 (20%, 95% confidence interval 6 to 34%) were alive with the bladder intact. Bladder preservation was possible only in the complete response group. The long-term followup showed that after 5 years 16 patients (53%) were alive and 15 (50%, 95% confidence interval 32 to 68%) were disease-free. When patients were stratified according to the type of response to chemotherapy, the 5-year disease-free survival was 79% versus 25% for the complete response and the partial or no response groups, respectively (p < 0.01). According to these results and considering the highly selective nature of our study, primary methotrexate, vinblastine, doxorubicin and cisplatin chemotherapy compared to standard treatments does not improve the overall survival rate, nor does it allow for bladder preservation in most cases of locally invasive transitional cell carcinoma of the bladder. This approach seems only to segregate patients with a greater chance for long-term survival in the complete response group and a poor outcome for partial/no response patients regardless of early salvage bladder extirpation.

Actuarial Analysis↗

PubMed1994

Is your organization ready to share financial risk with HMOs?

Of growing importance in healthcare delivery is the issue of how the risk of providing services to healthcare maintenance organizations (HMOs) enrollees should be shared by the provider and the HMO. Understanding and monitoring risk-sharing arrangements and how they are developing is critical. This article reviews the trends in managed care and risk sharing and examines regulation of capitation and risk sharing as it varies form state to state.

Capitation Fee↗

PubMed1993

Measuring male reproductive hormones for occupational field studies.

As part of our longitudinal study of unexposed workers, we drew blood samples and analyzed the individual endocrine profiles for 45 men. The blood collection was between 8 AM and 8 PM, and three blood samples were drawn 20 minutes apart on three occasions during the course of the study (June, October, and February). Serum concentrations of follicle-stimulating hormone, luteinizing hormone, testosterone, and prolactin were determined. A component of variance model was used to estimate variability between the 20-minute blood draws. Statistical power analysis using this component showed that three blood draws provide a marginal improvement over a single blood draw in detecting population shifts. Also, if the prospect of three blood draws reduces subject participation by 10 to 20%, the increase in power would be negated.

Adult↗

PubMed1992

Pulmonary reactivity to vanadium pentoxide following subchronic inhalation exposure in a non-human primate animal model.

An experimental study was conducted to evaluate changes in pulmonary reactivity resulting from repeated vanadium pentoxide (V2O5) dust inhalation. The study assessed pulmonary reactivity to V2O5 through the use of provocation challenges, and compared V2O5 reactivity before and after subchronic V2O5 exposure. A total of 24 adult, male cynomolgus monkeys (Macaca fascicularis) were exposed by inhalation for 6 h per day, 5 days per week, for 26 weeks. Two V2O5-exposed groups (n = 8 each) received equal weekly V2O5 exposures (concentration x time) with different exposure profiles. One V2O5-exposed group received 0.1 mg V2O5 m-3 on Mondays, Wednesday and Fridays, with a twice-weekly peak exposure of 1.1 mg V2O5 m-3 on Tuesdays and Thursdays, and was included to investigate the influence of an exposure regimen with peaks on the development of pulmonary hyper-reactivity. The other V2O5-exposed group received a constant daily concentration of 0.5 mg V2O5 m-3. A control group (n = 8) received filtered, conditioned air. Pre-exposure challenges with V2O5 produced a concentration-dependent impairment in pulmonary function, characterized by airway obstructive changes (increased resistance and decreased flow). Analysis of respiratory cells recovered from the lung by bronchoalveolar lavage demonstrated that airway obstruction was accompanied by a significant influx of inflammatory cells into the lung. Subchronic V2O5 inhalation did not produce an increase in V2O5 reactivity in comparison to the control group, and cytological, immunological and skin test results indicate the absence of allergic sensitization. Instead, a trend toward decreased pulmonary reactivity was found following subchronic V2O5 inhalation.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗

PubMed1992

The classification of asbestos fibres by scanning electron microscopy and computer-digitizing tablet.

Because of the need to completely and accurately size asbestos bulk samples for toxicity studies, a method was developed to classify asbestos fibres using enlarged micrographs originally produced on the scanning electron microscope (SEM). Individual fibre length and width measurements were performed on a computer-assisted, digitizing tablet. This method, though time consuming, permitted the sizing of all fibres (length and width) and particles (area) in selected fields of view at SEM magnifications of x100 and x2500. Final enlargement of the micrographs permitted sizing magnifications of x10,000. Seven distinct asbestos samples were classified including five chrysotile and two crocidolite samples. Statistical analyses showed good interfilter fibre size correlation for all types of asbestos. In addition, it was determined that a representative sizing of all fibres and non-fibrous particles on a filter preparation could be performed using five sets of micrographs taken at a magnification of x2500 and enlarged to x10,000: an inverse square root transformation (-0.5 power) is needed to normalize the distributions of length and width.

Analysis of Variance↗

PubMed1991

Strongyloides hyperinfection in two patients with lymphoma, purulent meningitis, and sepsis.

Strongyloides stercoralis hyperinfection syndrome is a rare complication of strongyloidiasis that occurs in immunosuppressed patients. It is caused by increasing autoinfection of the host by the nematode, leading to serious superimposed enterobacterial sepsis. Once established, it has a high fatality rate. Two cases are reported of Strongyloides hyperinfection in patients with lymphoma who presented with purulent meningitis. Both were receiving combination chemotherapy that included high-dose corticosteroids, and neither was granulocytopenic at infectious onset. The patients had respiratory insufficiency that required mechanical ventilation and serious septic episodes. Both were treated with thiabendazole, and one survived with clearance of the larvae. These cases illustrate the possibility of strongyloidiasis hyperinfection as an underlying diagnosis of purulent meningitis and serious septic episodes in lymphomatous patients. It may occur even without granulocytopenia.

Escherichia coli Infections↗

PubMed1991

Phase II trial of etoposide (V), adriamycin (A), and cisplatinum (P) in patients with metastatic gastric cancer.

The efficacy and toxicity of a combination of etoposide (100 mg/m2 i.v. on days 1 to 3), Adriamycin (20 mg/m2 i.v. on days 1 and 8) and cisplatinum (40 mg/m2 i.v. on days 2 and 8) repeated every 4 weeks as an outpatient regimen were assessed in 29 consecutive patients with metastatic gastric cancer with measurable disease. Five of these patients were refractory to 5-Fluorouracil, Adriamycin, and Mitomycin C. Three of these previously treated patients responded to the etoposide. Adriamycin, cisplatinum (VAP) therapy. An overall objective response rate of 72.5% was achieved, including 14% that were complete responses. The median duration of response was 6.0 months; median overall survival was 7.2 months, overall one-year survival was 34.4%. Hematologic toxicity was intense, particularly among patients with lower performance status. Three patients died as a consequence of nadir sepsis episodes.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1991

Lung particulate burdens of subjects from the Cincinnati, Ohio urban area.

Because of the relatively small data base existing for lung particulate burdens of subjects with no overt pneumoconioses, the total exogenous lung particulate concentrations of 91 subjects from the Cincinnati, Ohio urban area were determined using an automated scanning electron microscope-energy dispersive x-ray analysis-image analysis system. Four of these subjects were foundry workers and had the highest exogenous particle concentrations seen in the 91 lungs, ranging from 1860 to 2990 x 10(6) particles per gram of dry lung (ppg). The average exogenous particle concentration for the remaining 87 subjects was 476 +/- 380 x 10(6) ppg with a range of 71 to 1860 x 10(6) ppg. The median size of the exogenous particles in the 87 lungs was narrow, ranging from 0.37 to 1.02 microns. The geometric mean particle size over all 87 lungs was 0.60 microns with a geometric standard deviation (sigma g) of 2.35. The total exogenous particle levels were elevated for the male subjects compared to females (p=0.015), and were positively associated with age (p=0.021). However, no correlation was seen between total particle concentration and race or smoking history.

Adult↗

PubMed1990

In vivo percutaneous absorption studies of volatile organic solvents in hairless mice. II. Toluene, ethylbenzene and aniline.

Percutaneous absorption studies were conducted with three single-ring, radiolabeled aromatic solvents (benzene derivatives) using a recently described direct method for studying volatile chemicals in hairless mice. Total absorption, determined from the sums of radioactivity found in the excreta, expired breath and carcass, was 2.1+, 3.4% and 4.7% of the nominal dose for toluene, ethylbenzene and aniline, respectively. Breath decay curves indicated that absorption of toluene and ethylbenzene was complete by 15 min after application and that by this time the excretion rate of aniline exceeded the absorption rate. Evaporation rates were used to derive estimated contact times, and these in turn were used in conjunction with the absorbed doses to estimate percutaneous absorption rates. Equivalent dermal exposures (cm2.min) that would yield body burdens equivalent to those expected following 8-h inhalations at existing US permissible exposure limits during light work were calculated. The data indicate that dermal absorption of these compounds could approach or exceed that from inhalation under some work conditions. Correlations between absorption and various physical properties were evaluated using Spearman's correlation coefficients. The physical properties evaluated included volatility, solubility, octanol/water partition coefficients and melting points. For this limited series of benzene derivatives, two measures of volatility, i.e. vapor pressure and boiling point, were the only physical properties significantly correlated with percutaneous absorption.

Aniline Compounds↗

PubMed1990

Duration of breast-feeding patterns established in the hospital. Influencing factors. Results from a national survey.

Data from a national survey of new mothers were analyzed to determine the effect that demographic characteristics, breast-feeding instructions, and infant formula discharge kits had on breast-feeding patterns established in the hospital. Results indicated that mothers who exclusively breast-fed their infant were more likely to be affluent, college educated, and not working outside the home. Mothers who exclusively breast-fed their infants in the hospital and subsequently practiced partial breast-feeding or formula, or cow's milk feeding were more likely to return to the work force within the first 6 postpartum months. Mothers who partially breast-fed their infants in the hospital were more likely to have a low-birth-weight neonate. Stepwise logistic regression analysis indicated that greater total family income, a better education, and having more than one child had positive significant effects on exclusive breast-feeding by the first and fourth month. Women who received a formula discharge kit compared with those who did not had a slightly higher probability of initiating partial breast-feeding (10 vs. 7% by the first month; 27 vs. 25% by the fourth month). Maternal employment had a large impact on duration of exclusive breast-feeding. By the fourth month, mothers who were employed had a higher probability of initiating partial breast-feeding (43 vs. 19%) compared with mothers who were not in the work force.

Animals↗