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PubMedDate not supplied

Prediction equations for handgrip strength in healthy Indian male and female subjects encompassing a wide age range.

PRIMARY OBJECTIVE: Handgrip strength is a simple index of skeletal muscle function and a functional index of nutritional status. A major lacuna in the use of handgrip strength is the limited availability of normative data. The main objective of this paper was to develop prediction equations for handgrip strength in Indians covering a wide age range. METHODS: Handgrip strength and basic anthropometric parameters were measured in 1024 healthy Indian subjects of both genders (613 males, 411 females) between the ages of 5 and 67 years. The sample was randomly divided into two sets; one set (n = 677) was used to develop the prediction equations for handgrip strength and the other (n = 347) was used to validate the equations. Each data set was further divided into two subsets (adults > 18 years, sub-adults <or= 18 years), since separate equations were developed for adults and sub-adults. Simple models that included one of the following variables: height, forearm circumference and age as well as a full model that included all three variables were developed. Gender was included in all models. RESULTS: In general, all simple models predicted handgrip strength better in sub-adults (R(2) = 0.78-0.81) as compared to adults (R(2) = 0.52-0.57). The best simple model in sub-adults was that which included age and gender (R(2) = 0.81), while for adults it was that which included forearm circumference and gender (R(2) = 0.57). The full model explained a further 3.4-6.5% of the variance in handgrip strength in sub-adults and a further 6.3-13.3% in adults. CONCLUSIONS: The simple and full model equations for handgrip strength had high predictive power in the sub-adults, while they were less predictive in adults. The equations will be of particular use in physiological studies assessing muscle strength and in clinical investigations of patients with malnutrition and neuromuscular disorders.

Adolescent↗

PubMed1993

Predicting use of hearing protection: a preliminary study.

The National Institute of Occupational Safety and Health targeted noise-induced hearing loss as one of the top 10 occupational hazards. Research has been directed toward reducing noise exposure rather than identifying the factors associated with workers' decision consistently to use hearing protection. The long-term goal of this program of research is to develop a causal model explaining workers' use of hearing protection to guide development of nursing interventions. This study was a preliminary one to prepare for testing Pender's health-promotion model (HPM) as a causal model. Ninety-eight skilled tradesmen completed written questionnaires at their work site. Although 98% indicated they were supposed to wear protection, their reported use averaged 50.3% of the time. Reported use significantly and positively correlated with workers' perceptions of the benefits and self-efficacy of use, value of outcomes regarding keeping out noise and increased well-being, and health-promoting behaviors in the areas of self-actualization and stress management. Perceptions of barriers of use were significantly and negatively related to use. In regression analyses of use of hearing protection on components of the HPM and dimensions of health behavior and lifestyle, one component of the HPM (benefits) and two dimensions of health behavior and lifestyle (self-actualization and interpersonal support) significantly predicted use, accounting for 24% of the variance in use of protection. Knowledge of the predictors of hearing protection use will ultimately aid nurses in implementing interventions, increasing use, and decreasing hearing losses.

Adult↗

PubMed1995

Community risk indicators for dental caries in school children: an ecologic study.

A statewide survey of NC schoolchildren found wide variation in dental caries prevalence among sampled classrooms. This study examined factors associated with this variation using classrooms as a surrogate for the larger community, in order to identify community risk indicators (CRI). In all, 172 classrooms (3400 students) in Grades K-6 were available for analysis. Initially, 56 sociodemographic, environmental, health system, and clinical factors were evaluated for their association with caries prevalence (K-3: average dfs + DMFS; 4-6: average DMFS) using univariate and bivariate analyses. Of these, 21 factors met our criteria for evaluation using WLS multivariate regression. For Grades K-3 (n = 108), population density, parental education, and coastal residence were negatively associated with caries scores, while age, and medical and dental, Medicaid expenditures were positive. For Grades 4--6 (n = 64), age and fs:dfs ratio were positively associated with caries scores while population density, population:dentist ratio, and years of natural fluoride exposure were negative. CRIs for both models, when compared to individual models, explained a substantial portion of the variation in caries prevalence, 31% for Grades K-3 and 51% for Grades 4-6. Results suggest that a risk assessment model based on community rather than individual variables is feasible and further refinement may reveal factors useful in identifying high risk communities.

Adolescent↗

PubMed2003

Scaling behavior of VO2peak in trained wheelchair athletes.

PURPOSE: To examine the scaling behavior of peak oxygen uptake (VO2peak) in wheelchair athletes, adjusting for known covariates. METHODS: Body mass, VO2peak, and an estimate of adiposity (sum of four skinfolds) were determined in a sample of 45 highly trained wheelchair basketball and racing athletes. The participants were classified as possessing either "high" or "low" trunk stability and balance using recognized sporting classifications. A wheelchair ergometer was used to obtain the VO2peak measurements. The relationship between VO2peak and body mass was obtained via a nonlinear allometric model with the sum of four skinfolds, trunk stability and balance, and chronological age entered as covariates. RESULTS: The point estimate exponent for body mass was 0.82 (95% CI, 0.54-1.10). After controlling for the influence of body mass, adiposity, and age, the wheelchair athletes with greater trunk stability and balance had on average an 11% greater VO2peak. The regression model explained 54% of the sample variance in VO2peak. CONCLUSIONS: The obtained mass exponent of 0.82 is congruent with that predicted from the multiple-causes allometric cascade model and consideration of the physiological characteristics of spinal cord injured athletes. To compare the body size-independent VO2peak values of athletes within the study sample, the mass exponent of 0.82 may be adopted (i.e., mL x kg(-0.82) x min(-1)). The uncertainty in the point estimate, reflected in the relatively wide 95% CI, highlights the need for further research with larger samples to increase the precision of estimation.

Adolescent↗

PubMed2005

A regional-scale study on the crop uptake of cadmium from sandy soils: measurement and modeling.

Plant uptake is one of the major pathways by which cadmium (Cd) in soils enters the human food chain. This study was conducted to investigate the uptake of Cd by crops from soils within the wastewater irrigation area (WIA) of Braunschweig (Germany) and to develop a simple process-oriented model that is suited to predict Cd uptake at the regional scale. The sandy soils within the WIA (4300 ha) have received considerable loads of heavy metals by irrigation using municipal wastewater for up to 40 years. In 1998 and 1999, we sampled soil and plant material at 40 potato (Solanum tuberosum L.), 40 sugar beet (Beta vulgaris L.), and 32 winter wheat (Triticum aestivum L.) fields. In both years and for all three crops, we found close linear relationships between the Cd content of plant material and the Cd concentration in soil solution. For all three crops, we observed a trend of relatively increased Cd uptake in the year with the higher saturation deficit of the atmosphere. We interpret this to indicate that transpiration plays an important role in the Cd uptake of crops under the conditions of the WIA. In modeling the uptake of Cd by crops, we assume that uptake is proportional to mass flow, that is, the product of water transpired, Cd concentration in soil solution, and a plant-specific empirical parameter. The simulations agreed well with the observed Cd contents in crops. Our model explained between 66 and 87% of the observed variance.

Beta vulgaris↗

PubMed1979

Testing a causal model of environmental influences on the early drug involvement of inner city junior high school youths.

The present study examines a causal model explaining inner city youths' drug involvement using environmental variables which previously have been investigated singly or in various combinations and shown to influence drug use: the availability of drugs in the neighborhood and at school, a view of the neighborhood as tough, the esteem given to drug using, gang-involved persons by peers, friends' substance use, and participation in drug/street culture spare-time activities. The results show friends' use of alcohol and marijuana and participation in drug/street culture out-of-school activities have strong direct effects on personal drug involvement for the Black and Puerto Rican junior high school males and females who were studied; further, friends' use of alcohol and marijuana and the status peers give to drug using, gang-involved persons have respectable indirect effects on drug involvement for the four groups. In addition to these common features, a number of differences in the factors relating to drug involvement are found in the four groups. Implications of the results for alternative methods of drug abuse prevention and treatment are discussed, as is the necessity of utilizing an environmental, sociocultural view of drug use to adequately explain youth drug taking.

Adolescent↗

PubMed1993

A unified perspective on copper deficiency and cardiomyopathy.

Dietary copper restriction in rats results in cardiomyopathy. In rats fed copper-restricted diets from weaning for 5 to 8 weeks, a concentric hypertrophy is apparent, whereas postweaning copper restriction does produce cardiomyopathy without apparent hypertrophy. Both sets of circumstances appear to affect the integrity of the basal laminae of cardiac myocytes and capillaries. In rats fed copper-restricted diets from weaning, decreases in cytochrome c oxidase are related not only to copper's role as a coenzyme, but also to a marked decrease in the nuclear encoded subunits of the enzyme complex. Decreased levels of the delta-subunit of ATP synthase have been observed. However, such aberrations in mitochondrial enzymes, as well as morphologic alterations, apparently do not affect cardiac levels of ATP. This review suggests mechanisms of cardiac adaptation and initiation factors leading to cardiac hypertrophy. We present a hypothetical working model explaining the events leading to cardiac failure in the copper-deficient rat heart based on the present body of knowledge, and compare the pathology with other models of cardiomyopathies.

Animals↗

PubMed2002

Radiographic measurements, bone mineral density, and the Singh Index in the proximal femur of white and black postmenopausal women.

BACKGROUND: Radiographic measurements, bone mineral density (BMD), and the Singh Index were examined to assess ethnic differences in the architecture and trabecular patterns in the proximal femur. METHODS: We measured height (cm), weight (kg), and the following radiographic variables in 326 white and black postmenopausal women participating in the Women's Health Initiative at the Clinical Center in Detroit, MI: neck breadth, inferior neck cortical thickness, head diameter, subtrochanteric breadth, and subtrochanteric medial and lateral cortical thicknesses. Bone densitometry was performed by dual-energy x-ray absorptiometry (Hologic QDR 1000 plus; Hologic Inc, Bedford, MA) at 5 regional sites in the proximal femur. The Singh Index was read by its originator. RESULTS AND CONCLUSIONS: There was no significant ethnic difference in mean age, height, or body mass index, but weight and BMD was higher in the black group at all regional sites. The inferior neck cortical thickness was significantly greater in the black group. The Singh Index was found to be grade VI (normal) in 87%, grade V in 9%, and grades II-IV in 4% of all subjects. Multiple regression models explained 35% to 60% of the variance in the regional BMDs; the Singh Index, weight, and subtrochanteric cortical thicknesses were significant contributors to all regional hip BMD models. Although there were ethnic differences in BMD, there were no ethnic differences in the distribution of the Singh Index scores.

Absorptiometry, Photon↗

PubMedDate not supplied

[The use of phase diagrams in the crystallization of oligonucleotide duplexes. I. A model of crystallization of the (pGpT)n.(pApC)n + spermine system].

A set of experimental phase diagrams revealing the region of existence of microcrystals in mixture "(pGpT)n.(pApC)n+spermine", n = 2,3,4, was obtained. All diagrams are wedge-like with the slope of the upper branch and the level of the lower one depending on the oligonucleotidd length. The presence of MPD, MgCl2 and NaCl changes the form of the diagrams in a different manner. A model explaining the peculiar features of the diagrams for mixture "oligonucleotide duplex+spermine" is proposed. The analysis of the diagrams was carried out on the basis of this model and the values of the binding constants for binding of spermine and Mg2+ to duplexes were estimated. Some conclusions about the types of complexes, which may form microcrystals in different regions of diagrams were made.

Binding Sites↗

PubMed2002

Counter aggression and reconciliation in Assamese macaques (Macaca assamensis).

Patterns of aggressive and affiliative behavior, such as counter aggression and reconciliation, are said to covary in the genus Macaca; this is referred to as the systematic variation hypothesis. These behavior patterns constitute a species dominance style. Van Schaik's [1989] socioecological model explains dominance style in macaques in terms of within- and between-group contest competition. Dominance style is also said to correlate with phylogeny in macaques. The present study was undertaken to examine phylogenetic and socioecological explanations of dominance style, as well as the systematic variation hypothesis. We collected data on counter aggression and reconciliation from a habituated group of Assamese macaques (Macaca assamensis) at the Tukeswari Temple in Assam, India. The proportion of agonistic episodes that involved counter aggression was relatively low. Counter aggression, however, occurred more often among males than among females, and it was most common when females initiated aggression against males. The conciliatory tendency for this group of Assamese macaques was 11.2%. The frequency of reconciliation was low for fights among males and for fights among females, but reconciliation was particularly rare for opposite-sexed opponents. Female social relationships were consistent with the systematic variation hypothesis, and suggest a despotic dominance style. A despotic dominance style in Assamese macaques weakens the correlation between dominance style and phylogeny in macaques, but it is not inconsistent with the socioecological model. Male-female relationships were not well explained by the despotic-egalitarian framework, and males may well have more tolerant social relationships than do females. Sex differences need to be considered when categorizing species according to dominance style.

Aggression↗

PubMed2005

What makes ribosome-mediated transcriptional attenuation sensitive to amino acid limitation?

Ribosome-mediated transcriptional attenuation mechanisms are commonly used to control amino acid biosynthetic operons in bacteria. The mRNA leader of such an operon contains an open reading frame with "regulatory" codons, cognate to the amino acid that is synthesized by the enzymes encoded by the operon. When the amino acid is in short supply, translation of the regulatory codons is slow, which allows transcription to continue into the structural genes of the operon. When amino acid supply is in excess, translation of regulatory codons is rapid, which leads to termination of transcription. We use a discrete master equation approach to formulate a probabilistic model for the positioning of the RNA polymerase and the ribosome in the attenuator leader sequence. The model describes how the current rate of amino acid supply compared to the demand in protein synthesis (signal) determines the expression of the amino acid biosynthetic operon (response). The focus of our analysis is on the sensitivity of operon expression to a change in the amino acid supply. We show that attenuation of transcription can be hyper-sensitive for two main reasons. The first is that its response depends on the outcome of a race between two multi-step mechanisms with synchronized starts: transcription of the leader of the operon, and translation of its regulatory codons. The relative change in the probability that transcription is aborted (attenuated) can therefore be much larger than the relative change in the time it takes for the ribosome to read a regulatory codon. The second is that the general usage frequencies of codons of the type used in attenuation control are small. A small percentage decrease in the rate of supply of the controlled amino acid can therefore lead to a much larger percentage decrease in the rate of reading a regulatory codon. We show that high sensitivity further requires a particular choice of regulatory codon among several synonymous codons for the same amino acid. We demonstrate the importance of a high fraction of regulatory codons in the control region. Finally, our integrated model explains how differences in leader sequence design of the trp and his operons of Escherichia coli and Salmonella typhimurium lead to high basal expression and low sensitivity in the former case, and to large dynamic range and high sensitivity in the latter. The model clarifies how mechanistic and systems biological aspects of the attenuation mechanism contribute to its overall sensitivity. It also explains structural differences between the leader sequences of the trp and his operons in terms of their different functions.

Journal Article↗

PubMed2006

Geographic patterns of advanced breast cancer in Los Angeles: associations with biological and sociodemographic factors (United States).

OBJECTIVE: Examination of patterns of advanced breast cancer may provide evidence needed to direct health care resources to those communities or population groups in greatest need. We assessed to what degree biologic, ethnic, and sociodemographic factors could explain such patterns within Los Angeles County. METHODS: The proportion of cases of advanced disease among all breast cancer cases identified during 1992-1996 were analyzed using generalized linear mixed models with random census tract effects. Models included characteristics of the individual and her tumor, census tract of residence, and aggregated health districts. RESULTS: Approximately 6% of cases, ranging from 4% for Asian to 10% for Black women, were diagnosed as advanced, exhibiting striking geographic patterns. Tumor histology and hormone receptor status were most predictive of advanced disease. Sociodemographic variables such as marital status, median income, and distance to nearest mammography unit showed additional association with risk. CONCLUSIONS: These models explain most of the geographical patterns and eliminate differences between White and Hispanic but not Asian or Black women, identify subpopulations at high risk of advanced disease, and suggest cancer control opportunities.

Adult↗

PubMed1989

Cellular 'neoteny': a possible developmental basis for chromaffin cell plasticity.

Adrenal medullary chromaffin cells, SIF cells and sympathetic neurons are derived from the sympatho-adrenal sublineage of the neural crest, and represent a range of cellular phenotypes extending from endocrine to neuronal. It is suggested here that these cell types may represent different stages of developmental 'arrest' along a linear pathway whose endpoint is a cholinergic sympathetic neuron. This model explains the 'transdifferentiation' of mature cells seen in this system as simply a delayed realization of transitions that normally occur between these stages during development. Such a 'linear model' of phenotypic diversification may be applicable to other developing systems that generate closely related but distinct cell types.

Adrenal Medulla↗

PubMed2004

Predictors of substance use among homeless youth in San Diego.

This study examined the frequency of substance use among 14- to 24-year-old homeless youth (N=113) recruited from two community drop-in centers and explored the relationship between substance use and hypothesized psychosocial predictors. Audio-computer-assisted self-interviewing (A-CASI) was used for assessment. Including alcohol and tobacco, the mean number of different drugs used was 3.55 for lifetime and 2.34 for the last 3 months. A three-block hierarchical multiple regression was conducted to determine potential predictors of overall drug use (the sum of all different drugs used) during the last 3 months. Block 1 included demographic variables, Block 2 included a parental monitoring variable, and Block 3 included peer and environmental variables derived from learning theories. Parental monitoring (-) and peer variables (+) predicted overall 3-month drug use. The final model explained 36% of the variance in overall drug use. Results suggest that homeless adolescent drug use exists at high levels and is related to parental monitoring and peer modeling of other risk behaviors. These results may inform future prevention strategies for homeless youth and other high-risk populations.

Adolescent↗

PubMed2005

Evidence that sensory traps can evolve into honest signals.

Conventional models explaining extreme sexual ornaments propose that these reflect male genetic quality or are arbitrary results of genetic linkage between female preference and the ornament. The chase-away model emphasizes sexual conflict: male signals attract females because they exploit receiver biases. As males gain control of mating decisions, females may experience fitness costs through suboptimal mating rates or post-copulatory exploitation. Elaboration of male signals is expected if females increase their response threshold to resist such exploitation. If ornaments target otherwise adaptive biases such as feeding responses, selection on females might eventually separate sexual and non-sexual responses to the signal. Here we show that the terminal yellow band (TYB) of several Goodeinae species evokes both feeding and sexual responses; sexual responsiveness phylogenetically pre-dates the expression of the TYB in males and is comparable across taxa, yet feeding responsiveness decreases in species with more elaborated TYBs. Displaying a TYB is costly, and thus provides an example where a trait arose as a sensory trap but has evolved into an honest signal.

Animals↗

PubMed2000

A model of gamma-frequency network oscillations induced in the rat CA3 region by carbachol in vitro.

Carbachol (> 20 microM) and kainate (100 nM) induce, in the in vitro CA3 region, synchronized neuronal population oscillations at approximately 40 Hz having distinctive features: (i) the oscillations persist for hours; (ii) interneurons in kainate fire at 5-20 Hz and their firing is tightly locked to field potential maxima (recorded in s. radiatum); (iii) in contrast, pyramidal cells, in both carbachol and kainate, fire at frequencies as low as 2 Hz, and their firing is less tightly locked to field potentials; (iv) the oscillations require GABAA receptors, AMPA receptors and gap junctions. Using a network of 3072 pyramidal cells and 384 interneurons (each multicompartmental and containing a segment of unmyelinated axon), we employed computer simulations to examine conditions under which network oscillations might occur with the experimentally determined properties. We found that such network oscillations could be generated, robustly, when gap junctions were located between pyramidal cell axons, as suggested to occur based on studies of spontaneous high-frequency (> 100 Hz) network oscillations in the in vitro hippocampus. In the model, pyramidal cell somatic firing was not essential for the oscillations. Critical components of the model are (i) the plexus of pyramidal cell axons, randomly and sparsely interconnected by gap junctions; (ii) glutamate synapses onto interneurons; (iii) synaptic inhibition between interneurons and onto pyramidal cell axons and somata; (iv) a sufficiently high rate of spontaneous action potentials generated in pyramidal cell axons. This model explains the dependence of network oscillations on GABA(A) and AMPA receptors, as well as on gap junctions. Besides the existence of axon-axon gap junctions, the model predicts that many of the pyramidal cell action potentials, during sustained gamma oscillations, are initiated in axons.

Action Potentials↗

PubMed2001

Structural model of the catalytic core of carnitine palmitoyltransferase I and carnitine octanoyltransferase (COT): mutation of CPT I histidine 473 and alanine 381 and COT alanine 238 impairs the catalytic activity.

Carnitine palmitoyltransferase I (CPT I) and carnitine octanoyltransferase (COT) catalyze the conversion of long- and medium-chain acyl-CoA to acylcarnitines in the presence of carnitine. We propose a common three-dimensional structural model for the catalytic domain of both, based on fold identification for 200 amino acids surrounding the active site through a threading approach. The model is based on the three-dimensional structure of the rat enoyl-CoA hydratase, established by x-ray diffraction analysis. The study shows that the structural model of 200 amino acids of the catalytic site is practically identical in CPT I and COT with identical distribution of 4 beta-sheets and 6 alpha-helices. Functional analysis of the model was done by site-directed mutagenesis. When the critical histidine residue 473 in CPT I (327 in COT), localized in the acyl-CoA pocket in the model, was mutated to alanine, the catalytic activity was abolished. Mutation of the conserved alanine residue to aspartic acid, A381D (in CPT I) and A238D (in COT), which are 92/89 amino acids far from the catalytic histidine, respectively (but very close to the acyl-CoA pocket in the structural model), decreased the activity by 86 and 80%, respectively. The K(m) for acyl-CoA increased 6-8-fold, whereas the K(m) for carnitine hardly changed. The inhibition of the mutant CPT I by malonyl-CoA was not altered. The structural model explains the loss of activity reported for the CPT I mutations R451A, W452A, D454G, W391A, del R395, P479L, and L484P, all of which occur in or near the modeled catalytic domain.

Alanine↗

PubMed2003

Test of a trust and confidence model in the applied context of electromagnetic field (EMF) risks.

Trust is an important factor in risk management. There is little agreement among researchers, however, on how trust in risk management should be studied. Based on a comprehensive review of the trust literature a "dual-mode model of social trust and confidence" is proposed. Trust and confidence are separate but, under some circumstances, interacting sources of cooperation. Trust is based on value similarity, and confidence is based on performance. According to our model, judging similarity between an observer's currently active values and the values attributed to others determines social trust. Thus, the basis for trust is a judgment that the person to be trusted would act as the trusting person would. Interpretation of the other's performance influences confidence. Both social trust and confidence have an impact on people's willingness to cooperate (e.g., accept electromagnetic fields or EMF in the neighborhood). The postulated model was tested in the applied context of EMF risks. Structural equation modeling procedures and data from a random sample of 1,313 Swiss citizens between 18 and 74 years old were used. Results indicated that after minor modifications the model explained the data very well. In the applied context of EMF risks, both trust and confidence had an impact on cooperation. Results suggest that the dual-mode model of social trust and confidence could be used as a common framework in the field of trust and risk management. Practical implications of the results are discussed.

Adolescent↗