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PubMed1999

Postsynaptic expression of long-term potentiation in the rat dentate gyrus demonstrated by variance-mean analysis.

1. Long-term potentiation (LTP) of synaptic transmission is the putative mechanism underlying learning and memory. Despite intensive study, it remains controversial whether LTP is expressed at a pre- or postsynaptic locus. A new approach was used to investigate this question at excitatory synapses from the medial perforant path (MPP) onto granule cells in the hippocampal dentate gyrus. The variance of the evoked synaptic amplitude was plotted against mean synaptic amplitude at several different Cd2+ concentrations. The slope of the variance-mean plot estimates the average amplitude of the response following the release of a single vesicle of transmitter (Qav). A presynaptic modulation should not affect Qav, but a postsynaptic modulation should alter it. 2. The variance-mean technique was tested by applying the analysis before and after three different synaptic modulations: (i) a reduction in Qav by the addition of the competitive antagonist CNQX; (ii) a reduction in the average probability of transmitter release (Pav) by the addition of baclofen; and (iii) an increase in the number of active synaptic terminals (N) by increasing the stimulus strength. CNQX reduced the average synaptic amplitude and Qav to the same extent, consistent with a postsynaptic action. In contrast, neither a change in N nor Pav altered Qav. This confirms that the variance-mean technique can distinguish between a pre- and a postsynaptic site of modulation. 3. Induction of LTP increased EPSC amplitude by 50 +/- 0.4 % (n = 5) and, in the same cells, increased Qav by 47 +/- 0.6 %. There was no significant difference between the increase in EPSC amplitude and the increase in Qav. Thus, LTP of the MPP input to dentate granule cells can be explained by an increase in the postsynaptic response to transmitter.

Algorithms↗
PubMed1995

[Current trends in the use of statistics in medicine. A study of original articles published in the Medicina Clínica (1991-1992)].

BACKGROUND: In recent years there has been a notable increase in the use of statistical techniques in biomedical journals. Furthermore, the complexity of statistical analysis has increased because of data processing. In this study statistical accessibility is quantified and the types of statistical analysis performed in all the articles published under the section of original articles in the journal Medicina Clínica from 1991 to 1992 (volumes 96 to 99). METHODS: One reviewer analyzed a total of 264 original articles. The statistical analyses were classified according to a list with 18 categories. The quantification of accessibility was obtained from the order of the 18 categories with bivariate statistics (up to simple regression), being used as the reference threshold. Intrareviewer concordance was 97%. RESULTS: Eighty-one percent of the 264 originals used categories of statistical analysis beyond that of descriptive statistics (inferential methods). The originals used bivariate tables (49.2%) and t and z tests (33.3%) most frequently. In 1992 the use of variance analysis and survival analysis increased notably (from 12.8% to 33.8% and 7.2% to 18.7%, respectively). More complex statistical techniques that models of simple regression (threshold reference) were used in 38.3% of the originals (31.2% in 1991 and 44.6% in 1992). CONCLUSIONS: The use of inferential statistics and the complexity of statistical analysis has increased suggesting a lower statistical accessibility in the originals of Medicina Clinica. The categories of variance analysis and survival analysis were those in which the greatest increase was observed in 1992 and were responsible for the increase in the complexity of 20% of the originals.

Analysis of Variance↗
PubMed2002

Test scores, measurement, and the use of analysis of variance: an historical overview.

In order to establish a firmer statistical foundation from which to draw inferences from factorial design study data, transformations of raw scores are occasionally employed in order to make their distributions more generally normal or to provide linearity. To date, few studies have been conducted to determine whether or not raw scores transformed or otherwise constitute measures for the purposes of statistical analysis. In this article, the historical development of the understanding of the term "measurement" by researchers in the social sciences is traced, and the development and use of One and Two-way ANOVA by researchers in the social sciences are presented and evaluated.

Analysis of Variance↗
PubMed1996

Association between drinking water disinfection and somatic parameters at birth.

We conducted an epidemiological study in Liguria, Italy, on the association between somatic parameters at birth and drinking water disinfection with chlorine dioxide and/or sodium hypochlorite. Over 2 years (1988-1989), 676 births at two public hospitals, one in Genoa (548 cases) and another in Chiavari (128 cases) were examined and data regarding both mother and child were obtained from hospital records. Results indicate a higher frequency of small body length (< or = 49.5 cm) and small cranial circumference (< or = 35 cm) in infants born to mothers who drank water treated with chlorine compounds. In particular, the statistical analysis (by simultaneous variance analysis and Scheffé test) indicated that there may be an association between infants with smaller body length and mothers who drank water treated with chlorine dioxide [adjusted odds radio (OR) = 2.0; 95% CI = 1.2-3.3] or sodium hypoclorite (adjusted OR = 2.3; 95% CI = 1.3-4.2) and between infants with smaller cranial circumference and mothers who drank water treated with chlorine dioxide (adjusted OR = 2.2; 95% CI = 1.4-3.9) or sodium hypochlorite (adjusted OR = 3.5; 95% CI = 2.1-8.5). The presence of neonatal jaundice is almost twice as likely (adjusted OR = 1.7; 95% CI = 1.1-3.1) in infants whose mothers drank water treated with chlorine dioxide.

Adult↗
PubMed1999

Polyploid evolution and biogeography in Chelone (Scrophulariaceae): morphological and isozyme evidence.

Chelone is a genus of perennial herbs comprising three diploid species (C. cuthbertii, C. glabra, and C. lyonii) and a fourth species (C. obliqua) that occurs as tetraploid and hexaploid races. To assess patterns of isozyme and morphological variation, and to test hypotheses of hybridization and allopolyploidy, we analyzed variation among 16 isozyme loci from 61 populations and 16 morphological characters from 33 populations representing all taxa and ploidy levels. Based on morphological analyses using clustering (unweighted pair group method using an arithmetic average) and ordination (principal components analysis and canonical variance analysis) methods, we recognize three diploid species without infraspecific taxa. Polyploids in the C. obliqua complex were most similar morphologically to diploid populations of C. glabra and C. lyonii. Patterns of isozyme variation among polyploids, which included fixed heterozygosity and recombinant profiles of alleles present in diploids, suggested polytopic origins of tetraploids and hexaploids. Our data indicate independent origins of polyploids in or near the southern Blue Ridge, Interior Highlands and Plains, and Atlantic Coastal Plain regions from progenitors most similar to C. glabra and C. lyonii. Extant tetraploids were not implicated in evolution of hexaploids, and plants similar to C. cuthbertii appeared unlikely as diploid progenitors for polyploids. We propose multiple differentiation and hybridization/polyploidization cycles in different geographic regions to explain the pattern of allopatry and inferred polytopic origins among polyploids.

Journal Article↗
PubMed2000

[Psychotic symptoms and Alzheimer's disease].

BACKGROUND: Psychotic symptoms appear during the course of Alzheimer's disease, but their frequency and intensity vary according to different studies and their nature remains unsettled. OBJECTIVES: To study the frequency and intensity of psychotic symptoms in two transversal series of patients with Alzheimer's disease and analyze its relationship with the duration of the disease and severity of cognitive impairment. PATIENTS AND METHODS: This study has been carried out in patients suffering from probable Alzheimer's disease (NINDS-ADRDA criteria). The stage of the disease was determined according to FAST, and the intensity of cognitive impairment in Mini Mental State Examination was classified as mild, moderate or severe. Frequency and intensity of psychotic symptoms (delusions, hallucinations and misidentifications) were determined by means of semistructured interviews (BEHAVE-AD 78 patients and CUSPAD 69 patients). The results obtained in these three groups of patients were compared through ANOVA variance analysis and mean contrast. Variance and covariance analysis were done to determine the relationship between psychotic symptoms and other variables (degree of cognitive impairment, length of evolution and stage of the disease). For this purpose, the patients with Alzheimer's disease but without psychotic symptoms were considered as control and compared to patients with psychotic symptoms. RESULTS: Nearly half the patients had psychotic symptoms. Delusions appeared earlier and were more frequent than hallucinations and misinterpretations. The more severe was the cognitive impairment, the more frequent and intense were psychotic symptoms, but the difference was significant only in cases with severe cognitive impairment. Hallucinations appeared mainly in patients with advanced dementia and were related firstly with the intensity of functional and cognitive impairment and secondly with the duration of the disease. CONCLUSIONS: Mild psychotic symptoms, especially delusions, appear early during the course of Alzheimer's disease. The frequency and intensity of these symptoms increase in parallel with the functional and cognitive impairments caused by the disease. Hallucinations, which appear mainly when the dementia is severe, can be considered as an evolutive marker of the process. Psychotic symptoms differ from those occurring in other disorders, either neurologic or psychiatric in nature.

Aged↗
PubMedDate not supplied

Electromyography study of the portions of the abdominal rectus muscle.

This study objective was to verify the behavior of three portions of the abdominal rectus muscle through a quantitative analysis of the electromyographic signal in different types of abdominal exercises. Ten young male between 16 and 27 years old were studied and they had no previous history of muscle and joint illness. They were well-trained and did seven abdominal exercises chosen considering the types of contraction (isotonic and isometric) as well as the muscle fixation points. The electric activity of the superior, medium (above umbilicus) and inferior (below umbilicus) portions at the left side of the abdominal rectus muscle was taken using Beckman type surface mini-electrodes. The registers were collected from computerized 8-channel Nicholet electromyography equipment, model Viking II. The signals were quantified using the MVA (Maximum Volunteer Activity) software, being considered for analysis the values of RMS (Root Mean Square). The obtained data were submitted to a parametric analysis using the variance analysis (F test) and also the Tukey test, besides a descriptive graphic analysis starting from the average RMS values of each muscle portion. This study results suggest that for the majority of the subjects, the functional activities of the abdominal rectus muscle are performed with electric activity differences among their portions, showing a tendency of producing more electric activity in the superior portion than in the medium and inferior portions. The experiment also demonstrated an absence of a common behavior pattern in the three portions of the ten tested subjects.

Adolescent↗
PubMed1990

[Study on the estimation theory of genetic parameters--the estimation method when the parents were relative].

By decomposing the expected mean squares in variance analysis, the estimation methods of genetic parameters are suggested in sib analysis when the parents of the sibs are relatives. Two estimation examples are also given. The results indicate that the estimation values are greater than those estimated by supposing that the parents are not relatives. The closer relative the parents are, the bigger the biased would be. The computer programme PARESTH and PARESTF made it easy to apply the methods. Furthermore, the methods can also be used in variance analysis when the relationships between the levels of each factors are determined.

Analysis of Variance↗
PubMed1988

Analysis of data in nephrology. III. Survival analysis and analysis of variance.

In this article discussion is continued of the case where the response variable is continuous and the explanatory variable is discrete. Two particular situations are covered: the response variable survival time and the explanatory variable dichotomous: and the response variable continuous (but not survival time) and the explanatory variable discrete (but not dichotomous).

Analysis of Variance↗
PubMed1989

[Evaluation of the intestinal absorption of iron orally administered as chondroitin sulfate in normal subjects].

The behaviour of sideremia has been studied in order to assess the intestinal absorption of iron of a new compound, ferric chondroitin sulfate after oral administration in 12 normal volunteers. After administration of 90 mg of iron as ferric chondroitin sulfate, sideremia rose from a basal value of 88 +/- 27 micrograms/dl to a value of 128 +/- 22 micrograms/dl at the third hour. Variance analysis showed that the increases were statistically significant (F = 27.7; p less than 0.00001). In the same subjects, the test was carried out in accordance with a randomised crossover design in two periods after administration of 91 mg of ferritin iron: sideremia rose from a basal value of 92 +/- 27 micrograms/dl to a value at the third hour of 97 +/- 28 micrograms/dl, moderate increases but statistically significant (F = 3.2; P = 0.0354). Variance analysis by repeated measurements showed that increases in sideremia were significantly higher after iron administration as ferric chondroitin sulfate than after administration of ferritin iron (F = 13.18; p = 0.0042). This study documents the good bioavailability of the iron contained in ferric chondroitin sulfate.

Administration, Oral↗
PubMed2003

Variance-mean analysis: a simple and reliable approach for investigating synaptic transmission and modulation.

The mechanisms underlying synaptic plasticity can be investigated by analyzing synaptic amplitude fluctuations before and after a synaptic modulation. However, many older fluctuation analysis techniques rely on models of synaptic transmission that incorporate unrealistic simplifying assumptions or have too many free parameters. As a result, these techniques have sometimes produced counterintuitive or contradictory results. In contrast, the variance-mean (V-M) technique requires fewer assumptions and is more robust than previous approaches. It achieves these improvements by focusing on two key parameters of synaptic transmission, the average probability that a vesicle is released from a synaptic terminal following a presynaptic stimulus (Pav), and the average amplitude of the postsynaptic response to a vesicle of transmitter (Qav). To apply V-M analysis, a fluctuating postsynaptic current (PSC) is recorded at several different extracellular Ca2+ or Cd2+ concentrations. The variance of the PSC amplitude is plotted against the mean amplitude at each concentration, forming a parabola. The degree of parabolic curvature estimates Pav, and the limiting slope under low release conditions estimates Qav. The shape of the V-M parabola changes in characteristic ways following each of the three standard forms of synaptic modulation: a change in Qav (postsynaptic), a change in Pav (presynaptic), or a change in the number of terminals (N). The approach does not require specialized software, and can even be implemented as a purely graphical technique. V-M analysis has been used to investigate the site of expression of long-term potentiation and the mechanisms underlying paired-pulse depression. This report presents a detailed mathematical development of the technique, and explores the limiting conditions under which it can confidently be applied. V-M analysis requires fewer than 100 PSC amplitude measurements to accurately estimate Pav and Qav, and it can reliably identify whether a synaptic modulation occurs at a pre- or postsynaptic site. In contrast to other techniques, V-M analysis is largely insensitive to recording noise, nonuniform modulation and intrinsic variability of the unitary synaptic amplitude.

Algorithms↗
PubMed1976

[On epidemiology of gastric cancer (author's transl)].

257 stomach cancer patients and 766 controls were interviewed using a standardized questionnaire for 35 variables. The two groups were compared by multivariate variance analysis. This analysis results in a combination of 20 variables significantly connected with gastric cancer. The rankorder of the most prominent variables is as follows: no food intolerance, higher alcohol consumption, living place near Berlin, occupation labourer, early loss of teeth, car driving, no gallstones, smoking and age. It can be assumed that these variables are of aetiological importance. In the aetiology of gastric cancer, exogenous cancerogens seem to play a more important role than endogenous factors. In two further multivariate variance analysis, control group is divided into persons with and persons without chronic gastritis verified by blind gastric biopsy and compared with gastric cancer patients, too. A fourth analysis is limited to female only. The results of the three last mentioned analysis are similar to those of the first one and also similar to results from other countries based on univariate analysis. The computed combination of variables was used for diagnosis of gastric cancer by discriminance analysis in the persons forming the material for this study. This diagnosis was correct in 71% of gastric cancer patients and in 72% of control persons.

Aged↗
PubMed1985

Guide for the interpretation of one-way analysis of variance.

In summary, one-way ANOVA for independent groups is used to test whether the group means for a specific dependent variable differ significantly after exposing each group to a unique level of a single factor or independent variable. You may recognize the preceding sentence. We hope it makes more sense to you now than when you first read it at the beginning of this article.

Analysis of Variance↗
PubMed1985

Post hoc tests following analysis of variance.

Review of nursing research literature revealed that post hoc comparisons of mean differences were not consistently reported, although their use was warranted. This paper describes the critical features of post hoc procedures and offers guidelines for selecting one method over another. Particular attention is given to how various procedures control Type 1 error. Selection of post hoc procedures considering the investigator's desire for control of Type 1 and Type 2 error also is presented.

Analysis of Variance↗
PubMed2000

Nonconjugate Bayesian analysis of variance component models.

We consider the usual normal linear mixed model for variance components from a Bayesian viewpoint. With conjugate priors and balanced data, Gibbs sampling is easy to implement; however, simulating from full conditionals can become difficult for the analysis of unbalanced data with possibly nonconjugate priors, thus leading one to consider alternative Markov chain Monte Carlo schemes. We propose and investigate a method for posterior simulation based on an independence chain. The method is customized to exploit the structure of the variance component model, and it works with arbitrary prior distributions. As a default reference prior, we use a version of Jeffreys' prior based on the integrated (restricted) likelihood. We demonstrate the ease of application and flexibility of this approach in familiar settings involving both balanced and unbalanced data.

Algorithms↗
PubMed1975

Randomization and the analysis of variance.

This paper attempts to strengthen faith in randomization, first by defining it in general and second by showing how it is the fundamental means, in many experiments, of generating the probability space. It is defined by the natural structure of the experimental units (E.U.'s) not by a particular experimental design imposed on that structure. Three examples are given, with the same design but different E.U. structures and randomizations, to show that models developed from experimental designs are superficial, but that their randomization is fundamental.

Analysis of Variance↗
PubMed1975

[Analysis of variance delimitation of factors influencing studies of acoustic evoked potentials].

The effect of the variables "stimulus intensity", "residual effect of previous stimulus intensity", "period effect" and "subject effect" on the amplitudes and on the peak latencies of the N1 and P1 components of the acoustical EEG evoked potentials was studied in human subjects with the use of an orthogonal experimental design. The stimulus intensity (30, 50 and 80 dB) accounts for the greatest part of the total variance of the amplitudes and of the peak latencies of N1.-The existence of a totalvariance component due to differences between the subjects is also statistically significant (P equals 5%), As far as the period effect (habituation effect) is concerned, only its effect on the amplitude of N1 - P2 is statistically significant. - The residual effect of the stimulus intensity used in the previous series was not significant.

Adult↗
PubMed1997

Clinical pathway management of total knee arthroplasty.

Using a retrospective cohort study design, the authors examined complications, readmissions, morbidity and mortality, and function scores in two groups of patients attended by the same surgeon for the year before and the year after the implementation of an outcomes management program with clinical pathways for patients undergoing total knee arthroplasty at an academic health center. The effectiveness of the pathway constantly was adjusted using variance analysis and continuous quality improvement techniques. This program reduced the length of stay by 57% from a premanagement value of 10.9 +/- 5.4 days in 1994 (Group 1) to 4.7 +/- 1.4 days in 1996 (Group 2). Hospital costs (based on an inflation adjusted cost to charge ratio) for all total knees were reduced 11% from $13,328 +/- $3905 in 1994 to $11,862 +/- $4763 in 1996. Preoperative and postoperative knee scores were 41.1 +/- 16.3 and 84.2 +/- 16.0 for Group 1 and 42.5 +/- 13.0 and 87.0 +/- 10.4 for Group 2, respectively. There was no statistically significant difference between the preoperative or the postoperative knee scores of Groups 1 and 2. The application of clinical pathways, variance analysis, and continuous quality improvement toward the treatment of patients who had total knee arthroplasty at an academic health center resulted in significant savings in length of stay without adversely affecting overall outcome.

Academic Medical Centers↗