Biomedical subjects

S M Levy

Publications and source records attributed to S M Levy.

At least 19 recordsLinked to original sources

PubMed2004

The larval midgut of Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae): light and electron microscopy studies of the epithelial cells.

The morphology of the midgut epithelium cells of Anticarsia gemmatalis (Hübner) larvae is described by light and transmission electron microscopy. The midgut of A. gemmatalis is the largest portion of the digestive tract, with three distinct regions: proximal, media and distal. Its wall is formed by pseudostratified columnar epithelial tissue having four cell types: columnar, goblet, regenerative, and endocrine cells. The columnar cells are numerous and long, with the apical portion showing many lengthy microvilli and the basal portion invaginations forming a basal labyrinth. The goblet cells have a large goblet-shaped central cavity delimited by cytoplasmic projections filled with mitochondria. The regenerative cells present electron-dense cytoplasm and few organelles. The endocrine cells are characterized by electron-dense secretory granules, usually concentrated in the cytoplasm basal region.

Animals↗

PubMed2002

Functional specialization within the cat red nucleus.

Magnocellular (RNm) and parvicellular (RNp) divisions of the cat red nucleus (RN) project to the cervical spinal cord. RNp projects more heavily to upper cervical levels and RNm projects more heavily to lower levels. The cells in RN are active during reaching and grasping, and the differences in termination suggest that the divisions influence different musculature during this behavior. However, the spinal termination may not reflect function because most rubrospinal terminations are to interneuronal regions, which can influence motor neurons at other spinal levels. To test for functional differences between RNm and RNp, we selectively stimulated RNm and RNp as well as the efferent fibers from each region. Electromyographic activity was recorded from seven muscles of the cat forelimb during reaching. The activity from each muscle was averaged over several thousand stimuli to detect influences of stimulation on muscle activity. Stimulation within the RN produced a characteristic pattern of poststimulus effects. The digit dorsiflexor, extensor digitorum communis (edc), was most likely to show facilitation, and several other muscles showed suppression. The pattern of activation did not differ between RNm and RNp. In contrast, stimulation of RNp fibers favored facilitation of shoulder muscles (spinodeltoideus and supraspinatus), and stimulation of RNm fibers favored facilitation of digit and wrist muscles (edc, palmaris longus, and extensor carpi ulnaris). Fiber stimulation produced few instances of poststimulus suppression. The results from fiber stimulation indicate that the physiological actions of RNm and RNp match their levels of spinal termination. The complex pattern of facilitation and suppression seen with RN stimulation may reflect synaptic actions within the nucleus.

Animals↗

PubMed2001

A prospective study of antibiotic use and associated infections in young children.

This study examines antibiotic usage and associated infections in infants and young children in Iowa. Longitudinal data were collected using a cohort recruited at birth from eight hospitals in eastern Iowa. Parents of recruited children were mailed questionnaires at 6 weeks, and 3, 6, 9, 12, 16, and 20 months of age. The cumulative incidence of antibiotic use and associated infections was determined using Kaplan-Meier survival analysis. There were data on 1,368 children. Antibiotic use was common in our cohort and increased with age. Beginning at age 3 months, approximately 50% of the cohort was exposed to an antibiotic during each reporting period. Otitis media was the most common indication and was responsible for 67.3% of antibiotic use. Children were most frequently treated with amoxicillin, followed by the cephalosporins and sulphonamides. By 12 and 20 months of age 79.0% and 92.5% of the children, respectively, had been treated with at least one course of antibiotics. Children received antibiotics for a median of 43 days by 20 months of age. Males were more likely to experience any antibiotic exposure than females (hazard ratio = 1.18) and showed a trend for more days of use (P = 0.052). There was a small but significant variation in antibiotic usage in the different recruitment communities (P = 0.02).

Anti-Bacterial Agents↗

PubMed2001

Patterns of fluoride intake from birth to 36 months.

OBJECTIVES: Dental fluorosis prevalence has increased in the United States, Canada, and other nations due to the widespread availability of fluoride in many forms, with fluoride ingestion during the first three years of life appearing most critical in fluorosis etiology. With few contemporary studies of fluoride ingestion in this age group, the purpose of this paper is to describe patterns of estimated fluoride ingestion from birth to 36 months of age from water, dentifrice, and dietary fluoride supplements and combined. METHODS: Repeated responses to separate series of questions about water intake, use of fluoride dentifrice, and use of fluoride supplements were collected by questionnaire as part of the longitudinal Iowa Fluoride Study and used to estimate fluoride intake. Estimated intake is reported by source and combined at different ages. Effects of subject age and other covariates on fluoride intake were assessed using regression methods appropriate for the analysis of correlated data. RESULTS: For most children, water fluoride intake was the predominant source, especially through age 12 months. Combined daily fluoride intake increased through 9 months, was lower at 12 and 16 months, and increased again thereafter. Mean intake per unit body weight (bw) was about 0.075 mg F/kg bw through 3 months of age, 0.06 mg F/kg bw at 6 and 9 months, 0.035 mg F/kg bw at 12 and 16 months, and 0.043 mg F/kg bw from 20-36 months. Depending on the threshold chosen (e.g., 0.05 or 0.07 mg F/kg bw), variable percentages of the children exceeded the levels, with percentages greatest during the first 9 months. Regression analyses showed fluoride intake (mg F/kg bw) from 1.5-9 months to decrease with increasing child's age, mother's age, and mother's education, with a complex three-way interaction among these factors. From 12-20 months, fluoride intake increased with increasing child age and decreased with increasing mother's age. No statistically significant relationships were found for fluoride intake from 24-36 months. CONCLUSIONS: There is considerable variation in fluoride intake across ages and among individuals. Longitudinal studies may be necessary to fully understand the relationships between fluoride ingestion over time and development of fluorosis.

Adult↗

PubMed2001

Prevalence of dental fluorosis in the primary dentition.

OBJECTIVES: This paper presents data on the prevalence of primary tooth fluorosis among children residing in Iowa, and the relationships between fluorosis prevalence and selected measures of fluoride exposures. METHODS: Children in the study cohort were followed prospectively during the first year of life. This study assessed their home water fluoride concentrations and use of fluoride dentifrice or dietary fluoride supplements. A total of 637 children (320 females and 317 males) were examined for fluorosis using a modification of the TSIF index at age 4 1/2 to 5 years, with 90.4 percent having intact primary dentitions. RESULTS: 74 children (11.6%) had fluorosis present on one or more of their primary teeth, and 71 children (11.1%) had two or more teeth affected. Nearly all fluorosis was mild, with the primary second molar teeth most commonly affected. Fluorosis was significantly associated with higher water fluoride concentration, but not with the use of dentifrice or fluoride supplements. CONCLUSIONS: The results of this study show that primary tooth fluorosis is relatively uncommon, but is most frequently seen on the posterior teeth, particularly the primary second molars, which form at later stages of development. This finding suggests that primary tooth fluorosis is mostly a postnatal phenomenon, and is associated with higher water fluoride levels.

Cariostatic Agents↗

PubMed2001

Physical activity and bone measures in young children: the Iowa bone development study.

OBJECTIVES: Physical activity has a beneficial effect on bone development in circumpubertal children, although its effect on younger children is uncertain. In this cross-sectional study, we examined associations between physical activity and bone measures in 368 preschool children (mean age: 5.2 years, range: 4-6 years). DESIGN: Physical activity was measured using 4-day accelerometry readings, parental report of children's usual physical activity, and parental report of children's hours of daily television viewing. Total body and site-specific bone mineral content and area bone mineral density (BMD) were measured by dual energy radiograph absorptiometry. RESULTS: After adjustment for age and body size, accelerometry measures of physical activity and parental report of usual physical activity were consistently and positively associated with bone mineral content and BMD in both boys and girls (r = 0.15-0.28). Television viewing was inversely associated with hip BMD in girls (r = -0.15). The proportion of variance in bone measures explained by physical activity in linear regression models ranged from r(2) = 1.5% to 9.0%. In all of these models except total body BMD, at least 1 and often several of the physical activity variables entered as independent predictors. Activity variables most likely to enter the regression models were vigorous physical activity (as determined by accelerometry) and parental ranking of child's usual physical activity. CONCLUSIONS: Findings indicate that there are statistically significant and, perhaps important, associations between physical activity and bone measures during early childhood, well ahead of the onset of peak bone mass. This would suggest that intervention strategies to increase physical activity in young children could contribute to optimal bone development.

Absorptiometry, Photon↗

PubMed2001

Patterns of dental caries following the cessation of water fluoridation.

OBJECTIVES: To compare prevalence and incidence of caries between fluoridation-ended and still-fluoridated communities in British Columbia, Canada, from a baseline survey and after three years. METHODS: At the baseline (1993/4 academic year) and follow-up (1996/7) surveys, children were examined at their schools. Data were collected on snacking, oral hygiene, exposure to fluoride technologies, and socio-economic level. These variables were used together with D1D2MFS indices in multiple regression models. RESULTS: The prevalence of caries (assessed in 5,927 children, grades 2, 3, 8, 9) decreased over time in the fluoridation-ended community while remaining unchanged in the fluoridated community. While numbers of filled surfaces did not vary between surveys, sealed surfaces increased at both study sites. Caries incidence (assessed in 2,994 life-long residents, grades 5, 6, 11, 12) expressed in terms of D1D2MFS was not different between the still-fluoridating and fluoridation-ended communities. There were, however, differences in caries experienced when D1D2MFS components and surfaces at risk were investigated in detail. Regression models did not identify specific variables markedly affecting changes in the incidence of dental decay. CONCLUSIONS: Our results suggest a complicated pattern of disease following cessation of fluoridation. Multiple sources of fluoride besides water fluoridation have made it more difficult to detect changes in the epidemiological profile of a population with generally low caries experience, and living in an affluent setting with widely accessible dental services. There are, however, subtle differences in caries and caries treatment experience between children living in fluoridated and fluoridation-ended areas.

Adolescent↗

PubMed2000

Factors related to decisions to extract or retain at-risk teeth.

OBJECTIVES: Decisions to extract a tooth may be among the most critical in dentistry. The aim of this study was to prospectively investigate both clinical and nonclinical factors related to decisions to extract or retain teeth in private general dental practice. METHODS: A convenience sample of 196 Iowa dentists in private general dental practice reported on 549 cases where decisions were made to extract or retain teeth as they occurred in their practices during a one-month period in May 1997. Bivariate and multivariate analyses were used to identify factors that differentiated between cases where a tooth (or teeth) was extracted and cases where an at-risk tooth was retained. RESULTS: Of the 549 cases, 67 percent involved extraction, while the remainder involved alternatives to extraction. In comparing extraction cases to alternative treatment cases, we excluded 150 extraction cases because dentists reported that no alternative to extraction was available. Using Generalized Estimating Equations (GEE), we identified cost of treatment, presence of tooth mobility, poor prognosis of alternative treatment, and presence of gross caries as significant factors associated with extraction, while previous treatment of the tooth and concerns with patients' health were significantly associated with alternatives to extraction. CONCLUSIONS: For teeth at risk for extraction, cost, substantial periodontal disease, and several clinical factors were predictive of extraction.

Analysis of Variance↗

PubMed2000

A comparison of sealant placement techniques and 12-month retention rates.

OBJECTIVE: This study compared time required and 12-month retention for two methods of sealant placement: traditional acid-etch technique and air-abrasion technique without acid etch. METHODS: Sealants were placed on the permanent first molars of 84 children in grades 1-4 who were randomly assigned to treatment groups. All sealants were placed in a school setting by the same clinician. Chair time required for sealant placement was recorded, and retention rates were determined for each technique 12 months after placement. RESULTS: Mean chair time for placement of sealants on four first molars using the air-abrasion technique was significantly less than for the acid-etch technique (7:36 minutes vs 10:56 minutes). Fifty-eight children were available at 12-month follow-up; an examiner not involved in sealant placement and masked as to the technique used determined retention. Rates of complete retention for occlusal surfaces were not significantly different for the two techniques, although the rate for acid etch was higher than that for air abrasion (95% vs 87%). The complete retention rates for the acid-etch technique were significantly higher than air abrasion for buccal and distolingual surfaces. These rates were 65 percent and 58 percent, respectively, for acid etch and 6 percent and 28 percent, respectively, for air abrasion. CONCLUSION: Although more research is needed to improve air-abrasion applications, it does not appear that air abrasion without acid etching offers a significant advantage over traditional sealant placement methods and, in fact, appears to be inferior to the acid-etch technique for use in public health settings.

Acid Etching, Dental↗

PubMed1999

A pilot study of dental students' esthetic perceptions of computer-generated mild dental fluorosis compared to other conditions.

OBJECTIVES: Few studies have considered people's opinions about the esthetics of dental fluorosis. Assessments of fluorosis esthetics can be confounded by differences in a number of clinical factors, including tooth shape, color, contour, and gingival status. This pilot study compared esthetic perceptions of mild fluorosis and other conditions using computer-generated images made from a base set of normal appearing teeth. METHODS: Entering dental students (n = 61) completed questionnaires about four sets of paired photographs. Three sets consisted of fluorotic teeth (very mild to mild) versus other conditions (diastema, isolated enamel opacity, "normal"/control) and the other pair compared two presentations of mild fluorosis (generalized versus limited to incisal one-third). Six questions, both qualitative and quantitative, were asked about each pair of photographs. RESULTS: Mild fluorosis was assessed less favorably than normal/control, midline diastema was less favorable than mild fluorosis, and mild fluorosis was less favorable than isolated opacity. CONCLUSIONS: This approach allows fluorosis to be better compared with other oral conditions because the images are standardized. Additional research with this method is warranted, including more variations in conditions, more comparisons, and other study populations.

Adult↗

PubMed1999

Total fluoride intake and implications for dietary fluoride supplementation.

This paper reviews the history and validity of recommended "optimal" levels of systemic fluoride intake and the available information on levels of fluoride intake in young children from foods and beverages (including water), dentifrices, dietary fluoride supplements, mouthrinses, and gels. Most of the studies emphasize the substantial variation in ingestion among individuals. Often, a substantial proportion of individuals received fluoride well beyond the mean exposure reported in the study. Limitations in the existing data make it difficult to determine the total distribution of fluoride intake from all sources. Therefore, hypothetical combinations of possible daily fluoride intake from the three main sources (diet, dentifrices, and supplements) are presented for those aged 6, 12, 24, and 36 months, with associated mean intake per kg body weight. Findings suggest that some children exceed the "optimal" level of fluoride intake from single sources alone, while others can from a combination of sources. Moreover, if current recommended "optimal" levels, which have been derived on an empirical basis, are actually lower than what has been quoted in the literature, then more children could be ingesting excessive amounts of fluoride, which could increase their risk of developing objectionable dental fluorosis. The variation and complexity of fluoride ingestion from all sources should be considered in the evaluation of recommendations for use of dietary fluoride supplements.

Adolescent↗

PubMed1999

Assessing fluoride levels of carbonated soft drinks.

BACKGROUND: Dental fluorosis occurs as a result of excessive total fluoride intake during tooth development. Some children may receive substantial intake from soft drinks, but few studies have reported fluoride levels in soft drinks. The authors examined the fluoride concentrations of 332 soft drinks. METHODS: Soft drinks were purchased from Iowa grocery stores. To identify production sites, the authors recorded product details and batch numbers. After decarbonating the drinks, the authors assayed samples for fluoride content using a fluoride ion-specific electrode, and reported the results in parts per million, or ppm, using appropriate standards and duplicate assessments. Descriptive statistics were used to summarize the findings. RESULTS: The fluoride levels of the products ranged from 0.02 to 1.28 ppm, with a mean level of 0.72 ppm. Fluoride levels exceeded 0.60 ppm for 71 percent of the products. Results varied substantially by production site, even within the same company and for the same product. There were no substantial differences between flavors or between diet and regular soft drinks. CONCLUSIONS: The majority of soft drinks had fluoride levels exceeding 0.60 ppm. Variation in fluoride levels probably is due largely to the different water sources used in production. CLINICAL IMPLICATIONS: With no fluoride levels marked on the soft drink products or easily available from the manufacturers, it is not possible for clinicians or consumers to directly estimate fluoride ingestion from carbonated beverages. Therefore, to reduce the risk of dental fluorosis, dental and medical practitioners should be cautious about prescribing dietary fluoride supplements to preschool-aged children in nonfluoridated areas who consume large quantities of carbonated soft drinks.

Carbonated Beverages↗

PubMed1999

Fluorosis of the primary dentition: what does it mean for permanent teeth?

BACKGROUND: The prevalence of fluorosis of the permanent teeth has increased during the past few decades in the United States and Canada. However, primary-tooth fluorosis has been largely overlooked, because it is often difficult to recognize. This article describes primary-tooth fluorosis, both as characterized in the literature and as seen clinically. METHODS: The authors review and summarize previous studies of primary-tooth fluorosis and discuss its etiology. In addition, the authors describe the condition, based on findings from the literature, and their own experiences in characterizing it as part of a longitudinal investigation of fluoride exposures, dental fluorosis and dental caries. RESULTS: Several studies indicate that primary-tooth fluorosis can be prevalent and severe in areas of very high water fluoride concentrations. In these areas, primary-tooth fluorosis is likely the result of both pre- and postnatal exposures. Studies have documented that primary-tooth fluorosis does occur in areas with optimal or suboptimal water fluoride concentrations, and that in these settings primary-tooth fluorosis is most likely caused by postnatal exposures and is seen most commonly in the primary molars. Primary-tooth fluorosis, however, is often more difficult to identify than fluorosis in permanent teeth, and clinicians may be unfamiliar with its characteristics and may not recognize its somewhat subtle appearance. CONCLUSIONS: Primary-tooth fluorosis may be related to occurrence of fluorosis in the permanent dentition, so that its recognition by the clinician should raise awareness of possible increased risk for the permanent dentition. CLINICAL IMPLICATIONS: The detection of primary-tooth fluorosis in a young child should prompt the clinician to carefully review the child's past fluoride exposures and current fluoride practices, as well as those of any younger siblings.

Child, Preschool↗

PubMed1999

Systemic fluoride. Sources, amounts, and effects of ingestion.

Fluoride may be ingested from a variety of sources, including many foods and beverages. Fluoride intake varies greatly among individuals and is dependent on dietary constituents and use of fluoride products. Although ingestion of toxic amounts of fluoride is rare, the prevalence of dental fluorosis has increased in North America, suggesting that the levels of fluoride ingestion need to be closely monitored. Care should be taken to avoid excessive ingestion of fluoride dentifrice by preschool-aged children by placement of a small, pea-sized quantity on the tooth-brush. Dietary fluoride supplements should be considered a targeted, preventive procedure only for those at elevated caries risk, and before prescribing them, careful consideration should be given to other fluoride sources, including home and child-care water supplies, foods, and beverages.

Administration, Oral↗

PubMed1998

Evaluation of urinary IL-1alpha and IL-1beta in gravid females and patients with bacterial cystitis and microscopic hematuria.

OBJECTIVES: to determine IL-1alpha and IL-1beta levels in patients with bacterial cystitis, microscopic hematuria, and gravid females relative to a control group of normal subjects. METHODS: enzyme immunoassays were used to measure concomitantly urinary IL-1alpha and IL-1beta in clean catch urine samples from normal subjects (n = 31) and study patients (n = 46). All normal subjects and patients underwent urinalysis, urine culture, and urine creatinine level determination. Since the IL-1alpha assay was developed for serum, the utility of the assay for urine specimens was unknown. The key parameters of urine collection, processing and sample storage for IL-1alpha were evaluated in detail. RESULTS: mean values +/- SEM (pg/mg) for IL-1alpha/ Cr and IL-1beta/Cr were control group (0.25 +/- 0.10 and 0.17 +/- 0.06), bacterial cystitis (9.97 +/- 1.15 and 42.45 +/- 1.86), and microscopic hematuria (2.81 +/- 0.65 and 2.82 +/- 0.70). Differences in cytokine levels between the control group and patients with either bacterial cystitis or microscopic hematuria were statistically significant for both IL-1alpha/Cr (P < 0.026; P < 0.007, respectively) and IL-1beta /Cr (P < 0.0004; P < 0.014, respectively). IL-1beta/Cr correlates better with pyuria than IL-1alpha/ Cr (P = 0.02 vs P = 0.44). In gravid females, only IL-1alpha was significantly elevated relative to non-pregnant females (IL-1beta elevation approached statistical significance). Gravid females with positive urine cultures could not be distinguished from those with negative cultures based on either interleukin (P > 0.05). CONCLUSIONS: Significant elevations of IL-1alpha and IL-1beta occur in patients with bacterial cystitis and microscopic hematuria. Correlation between pyuria and cytokine elevation was stronger for IL-1beta than for IL-1alpha. Changes in IL-1alpha may reflect changes in the bladder epithelium rather than in the inflammatory leukocytes. The ability of IL-1alpha and IL-1beta to serve as markers for bacterial cystitis in gravid females is diminished due to high basal levels during pregnancy.

Bacterial Infections↗

PubMed1998

Patterns of dietary fluoride supplement use during infancy.

OBJECTIVES: This paper reports on patterns of dietary fluoride supplement use during infancy. METHODS: Data were collected by mail for a birth cohort (n = 1,072) studied at 6 weeks and 3, 6, 9, and 12 months of age. RESULTS: Percentages using supplements were 13.7 at 6 weeks, 13.4 at 3 months, 16.5 at 6 months, 13.0 at 9 months, and 12.1 at 12 months. Among those receiving supplements, mean proportions of weeks that supplements were received during the different time periods varied from 0.59 to 0.80. Number of days per week receiving supplements averaged 4.8 to 5.0. Mean fluoride dosages when supplements were received were 0.22 mg to 0.24 mg. Estimated average daily fluoride ingestion per day (among those receiving supplements during that time period and factoring in those days and weeks that supplements were not received) was 0.11 mg at 6 weeks, 0.15 mg at 3 months, 0.12 mg at 6 months, 0.11 mg at 9 months, and 0.14 mg at 12 months. Among the subset of 129 children with complete data at all time points who used supplements sometime during their first year of life, mean annual daily supplement dosage was 0.07 mg fluoride, with 75 percent having less than or equal to 0.10 mg. Those infants with mothers and fathers with more education were more likely to receive supplements. CONCLUSIONS: Group average use of fluoride supplements was fairly consistent over the 12 months; however, individual patterns varied substantially. Estimated actual mean daily fluoride intake when including days that supplements were not received was substantially less than the recommended 0.25 mg per day.

Adult↗

PubMed1997

Fluoride concentrations of infant foods.

Infants who ingest high amounts of fluoride can be at risk of dental fluorosis. The authors analyzed the fluoride concentration of 238 commercially available infant foods. Fluoride concentrations ranged from 0.01 to 8.38 micrograms of fluoride per gram, with the highest fluoride concentrations found in infant foods containing chicken. Infant foods, especially those containing chicken, should be considered when determining total fluoride intake.

Edible Grain↗

PubMed1996

Antibiotic use during the first 200 days of life.

To examine the use of antibiotics by infants in eastern Iowa, longitudinal data were collected from a cohort recruited at birth from 8 hospitals. Parents of recruited children were mailed questionnaires 6 weeks, 3 months, and 6 months after birth. Cumulative rates of use were determined by means of life tables for any antibiotic as well as by type of antibiotic. Factors associated with antibiotic use and patterns of use were also determined. There were data for 789 children. Antibiotic use was common in our cohort and increased with age. At 50, 100, 150, and 200 days of life, 8.7%, 26.7%, 37.3%, and 70.5%, respectively, of the infants had used at least 1 antibiotic. Infants were most frequently treated with amoxicillin, followed by cephalosporins and sulfonamides. Otitis media was the illness that most commonly prompted the use of an antibiotic.

Acute Disease↗