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At least 145 records · Page 8Linked to original sources
PubMed2002

Normal distribution of an intravascular ultrasound index of vessel remodeling.

BACKGROUND: As a consequence of plaque accumulation, coronary arteries may undergo both compensatory enlargement and paradoxical constriction. The aim of this study was to address the distribution of the different remodeling patterns in patients with obstructive coronary atherosclerosis. METHODS: Eighty-seven non-branching segments of native coronary arteries with de novo, focal, non-ostial lesions were imaged at intravascular ultrasound (IVUS). Images were acquired with a motorized pull-back at a speed of 0.5 mm/s. The cross-sectional area (CSA) circumscribed by the external elastic membrane (EEM), the plaque + media complex and the lumen area were measured at its narrowest site (CSA with the minimal lumen area) and in the reference segment (average of proximal and distal reference cross-sections, defined as the most normal looking sites). The IVUS index of vessel remodeling (VRI) was calculated using the following formula: (narrowest site EEM CSA--reference EEM CSA)/reference EEM CSA*100. The index was tested for normality using the Kolmogorov-Smirnov goodness-of-fit test. RESULTS: The frequency distribution of VRI was found to have a normal unimodal distribution (p = 0.60). VRI ranged from -60 to +164, with a mean of 9.3 +/- 28.0 and a median of 3.6. Frequency distribution of VRI slightly skewed towards right (skewness index 1.69). None of the analyzed clinical and morphological variables predicted the presence of compensatory enlargement as opposed to paradoxical constriction. CONCLUSIONS: The frequency distribution of the vascular remodeling of de novo coronary lesions is unimodal. Therefore, compensatory enlargement and paradoxical constriction represent the extremes of a continuous spectrum.

Coronary Artery Disease↗
PubMed1998

Normal distributions of thermal and vibration sensory thresholds.

The distributions of sensory thresholds were estimated in a healthy population while controlling for potential covariates. Using the method of levels and the two-alternative forced choice, thermal and vibration thresholds respectively were measured in the hand and foot of 148 subjects. Age was uniformly distributed between 20 and 86 years. Independent effects of age, gender, height, and skin temperature were estimated using multiple linear regression. Parametric and nonparametric methods were used to estimate the distributions of interest. Significant age-related increases were observed for all vibration thresholds (P < 0.0001), and for thermal thresholds in the foot (P < 0.0002). Percentiles were estimated for thermal thresholds in the hand and age-adjusted continuous distributions were calculated for all other thresholds. Height was positively associated with vibration thresholds in the foot (P < 0.003), and appropriate corrections were made. Our results provide reference values for thermal and vibration sensory thresholds in a healthy population, allowing for the accurate diagnosis of disordered sensory function.

Adult↗
PubMed1995

Issues in biomedical statistics: comparing means under normal distribution theory.

The test used most commonly in biomedical research to compare means when measurements have been made on a continuous scale is Student's t-test, followed closely by various forms of analysis of variance. These tests require that defined populations have been randomly sampled, but there are other assumptions about populations and samples that must be satisfied. These include: (i) normality of the population distributions; (ii) equal variance in those normal populations; and (iii) statistical independence of the samples. This review offers advice to investigators on how to recognize breaches of the assumptions of normality and equality of variance, and how to deal with them by modifying the usual t-test or by transforming the experimental data. The sample-size also has an important bearing on statistical inferences: (i) if it is too small, the risk of Type II error is inflated; and (ii) inequality of sample size exaggerates the effects of inequality of variance. The assumption of independence is breached if repeated measurements are made serially rather than in random order, but adjustments to analysis of variance can be made to correct for the inflated risk of Type I error. The review also considers the problem of making multiple comparisons of means, and recommends solutions.

Analysis of Variance↗
PubMed1978

The mucosa-associated microflora of the rat intestine: a study of normal distribution and magnesium sulphate induced diarrhoea.

Specimens of intestinal mucosa of rats were examined closely to determine the distribution of the mucosa-associated microbial flora. Six distinct zones were found along the length of the intestinal tract. The first zone, in the small intestine 50 cm or more from the ileocaecal junction, had no associated flora: however, each of the five other zones had different populations of microorganisms associated with the mucosa. Some of these organisms have not been reposted previously. Treatment of rats with oral doses of the purgative magnesium sulphate resulted in dramatic changes in the distribution of these mucosa-associated microorganisms. The normal flora of ileal and caecal crypts disappeared, while the organisms in colonic crypts were unchanged. Large numbers of mucosa-associated bacteria appeared in the stools of treated animals.

Animals↗
PubMed1986

Normal distribution of complement C3b receptor (CR1) numbers on erythrocytes in blood donors: low levels are associated with HLA-B27.

Blood donors were examined for C3b receptor (CR1) levels on erythrocytes by a microtiter plate enzyme-linked immunosorbent assay and for HLA-A, -B, and -C antigens, C3 phenotypes and blood groups. The CR1 levels among 150 donors varied in the range from 24 to 130% (mean +/- 1 SD = 69.9 +/- 22.9) of an erythrocyte standard, and in accordance with a polygenic model of inheritance the distribution of CR1 was well approximated by a normal curve (chi-square goodness-of-fit test nonsignificant, p = 0.66). Low CR1 levels were associated with HLA-B27 (n = 11, p = 0.05), which was confirmed by investigation of further 20 HLA-B27-positive donors (p = 0.05). The CR1 levels were not associated with a certain C3 phenotype. Possibly, the blood group phenotype M-M + S-s+ is associated with high and the S antigen with low CR1 numbers. The relation between low CR1 numbers and HLA-B27 might be important for the understanding of the association between HLA-B27 and certain inflammatory rheumatological diseases.

Blood Donors↗
PubMed1986

Mapping of the normal distribution of substance P-like immunoreactivity in the spinal trigeminal nucleus of the cat.

Although a recent preliminary report indicated a pattern of substance P-like immunoreactivity within the spinal trigeminal nucleus that is similar to the projection sites for dental afferent fibers, details of this substance P distribution are lacking. Our purpose was to describe in cats the complete normal pattern of this immunoreactivity within each of the spinal trigeminal subnuclei. Special emphasis was given to the distribution of substance P-like immunoreactive axons and terminals located in the rostral subnucleus caudalis and the periobex region of subnucleus interpolaris, as these are regions shown to receive dental afferent fibers. Careful mapping in normal cats showed, within the resolution of the light microscope, a consistent pattern of distribution that included only a portion of the previously identified dental relay sites, but was somewhat broader in certain levels and more restricted in others. The results are compared with those provided by others from regions such as the dorsal horn and subnucleus caudalis of the spinal trigeminal nucleus. The findings also provide an anatomical basis for a recent physiologic report on specific cell types associated with dental nociceptive afferent fibers. This study also provides a baseline control for future investigations of possible changes in substance P-like immunoreactivity that follows various peripheral, including dental and central, lesions.

Animals↗
PubMed2003

Interstitial cells of Cajal are normally distributed in both ganglionated and aganglionic bowel in Hirschsprung's disease.

Surgery for Hirschsprung's disease is often complicated by post-operative bowel motility disorders. The impact of intestinal neural histology on the surgical outcome has been previously studied, but no information is available concerning the influence of the distribution of interstitial cells of Cajal (ICC) on these complications. These cells are considered to be pacemakers in the gastrointestinal tract. The aim of this study was to assess the distribution of ICC in the proximal segment of resected bowel in Hirschsprung's disease and confront these results with the clinical outcome. Using immunohistochemistry for light microscopy, we compared the pattern of distribution of ICC in the proximal segment of resected bowel in Hirschsprung's disease with that in normal colon. We correlated these results with the corresponding neural intestinal histology determined by CD56 and the protein gene product 9.5 immunohistochemistry. The distribution of ICC in the proximal segment of resected bowel is identical to that of normal colon, regardless of normal or abnormal colon innervation. ICC distribution does not seem to contribute to post-operative bowel motility disorders in patients operated for Hirschsprung's disease

Child↗
PubMed1999

Transferrin is required for normal distribution of 59Fe and 54Mn in mouse brain.

Hypotransferrinemia (hpx/hpx) is a genetic defect in mice resulting in <1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. These mice provide a unique opportunity to examine the role of Tf in Fe and Mn transport in the brain. Twenty weanling wild-type BALB/cJ mice, 15 +/hpx mice, and 12 hpx/hpx mice of both sexes were injected i.v. with either 54MnCl(2) or 59FeCl(3) either 1 h or 1 week before killing at 12 weeks of age. Total brain counts of 54Mn and 59Fe were measured, and regional brain distributions were assessed by autoradiography. Hypotransferrinemia did not affect total brain Mn uptake. However, 1 week after i.v. injection, hpx/hpx mice had less 54Mn in forebrain structures including cerebral cortex, corpus callosum, striatum, and substantia nigra. The +/hpx mice had the highest total brain 59Fe accumulation 1 h after i.v. injection. A striking effect of regional distribution of 59Fe was noted 1 week after injection; in hpx/hpx mice, 59Fe was located primarily in choroid plexus, whereas in +/+ and +/hpx mice 59Fe was widely distributed, with relatively high amounts in cerebral cortex and cerebellum. We interpret these data to mean that Tf is necessary for the transport of Fe but not Mn across the blood-brain barrier, and that there is a Tf-independent uptake mechanism for iron in the choroid plexus. Additionally, these data suggest that endogenous synthesis of Tf is necessary for Fe transport from the choroid plexus.

Animals↗
PubMed1988

c-Ha-ras-1 polymorphism in human breast carcinomas: evidence for a normal distribution of alleles.

Analysis of the c-Ha-ras-1 locus for restriction fragment length polymorphism was determined by Southern blot hybridization in 112 specimens of primary breast carcinoma. Normal cell samples were lymphocytes obtained from 61 of these breast cancer patients and from 62 healthy donors. Our data indicate that the distribution of c-Ha-ras-1 alleles in breast carcinoma patients did not significantly differ from that found in normal individuals. In addition the loss of one allele detected in 5 tumor samples was not correlated to the aggressiveness of breast cancer. Consequently our data imply that hereditary predisposition to breast cancer is not associated with the c-Ha-ras-1 polymorphism as previously reported.

Alleles↗
PubMedDate not supplied

Normal distribution of lysozyme- and lactoferrin-secreting cells in the chinchilla tubotympanum.

The distribution of the antibacterial enzyme lysozyme- and lactoferrin-secreting cells in the tubotympanum of normal chinchillas was studied using an immunohistochemical technique. The middle ear mucosa contained lysozyme-secreting cells and lactoferrin-secreting cells. The former were localized primarily in the columnar epithelium area and the latter primarily in the cuboidal epithelium area (that contains serous cells) of the transitional zone. In the eustachian tube, the lysozyme was localized in goblet cells of the mucosal epithelium and mucous cells of the glands, while lactoferrin was localized in serous cells of the glands. Our results indicate that secretory lysozyme and lactoferrin are secreted by different cell types (mucous or serous), supporting the notion of heterogeneity of the secretory cells of the tubotympanum. This finding is consistent with the concept that antibacterial enzyme secretion is an integral part of the normal mucosal defense system in the tubotympanum.

Animals↗
PubMed1994

Normal distribution of alpha 2-adrenoceptors in the rat spinal cord and its modification after noradrenergic denervation: a quantitative autoradiographic study.

The distribution of alpha 2 (alpha 2)-adrenoceptors along cervical, thoracic, lumbar, and sacral segments of the spinal cord of normal rats has been studied by quantitative autoradiography using the specific alpha 2-antagonist [3H]rauwolscine as a ligand. In addition, the influence of noradrenergic (NA) denervation [obtained either by complete transection of the spinal cord at vertebrae level T8-T9 or by selective lesion of NA spinal cord system carried out by intracisternal injection of 6-hydroxydopamine (6-OHDA)] on eventual variations of alpha 2-adrenoceptor density at spinal cord target cells was studied in parallel. In control rats, the quantitative analysis of alpha 2-adrenoceptor densities revealed the presence of these receptors throughout the whole gray matter with a preferential location in the superficial dorsal horn. This pattern was the same at all rostro-caudal levels of the cord and appeared very well correlated with the distribution of NA terminals revealed by immunohistochemistry, particularly in the superficial layers of the dorsal horn. After total transection of the spinal cord (caudally to the section) and 6-OHDA-induced lesion, an increase of alpha 2-adrenoceptor density was mainly observed within the distal dorsal horn thus evidencing supersensitivity in this area, while modifications were not detectable in other regions of the spinal gray matter, except at the lumbar level where other dorsal, central, and intermediate zones were significantly enriched.

Animals↗
PubMed1985

Substance P in the interpeduncular nucleus of the rat: normal distribution and the effects of deafferentation.

The interpeduncular nucleus (IPN) is a midbrain structure that receives its major afferents from the medial habenulae via the fasciculi retroflexi. Among the axons projecting to the IPN is a population of substance P (SP)-containing axons. The IPN has been subdivided into the central, dorsal, intermediate, rostral, and lateral subnuclei using cytoarchitectonic criteria. The distribution of SP among these subnuclei was determined by using Sternberger's ('79) peroxidase-antiperoxidase technique. In the normal IPN the rostral subnucleus can be subdivided into two sectors on the basis of SP content. The ventral sector contains a moderate amount of SP and scattered SP positive perikarya. The dorsal cap of the rostral subnucleus contains denser SP than the ventral sector and it is continuous with the SP found in the dorsal subnucleus. The lateral subnuclei contain the densest SP found in the IPN and appear as laterally placed columns that expand in size caudally. The central and intermediate subnuclei contain very sparse SP. The fasciculus retroflexus was destroyed in 30 animals unilaterally or bilaterally and animals were perfused 4 days to 3 months postoperatively. After unilateral fascicular lesion, the SP in the rostral part of the ipsilateral lateral subnucleus is almost abolished, but caudally the decrease is confined to its lateral aspect. There is no visible decrease contralateral to the lesion. SP in the rostral part of the cap of the rostral subnucleus is decreased ipsilaterally but no loss is seen contralaterally or caudally. Animals with bilateral lesions show a great decrease in staining in the dorsal cap of the rostral subnucleus and the lateral subnuclei, with no decrease seen in the central, dorsal, or intermediate subnuclei. These results confirm that the origin of most of the SP in the IPN is fasciculus retroflexus fibers, but some of the SP arises from intrinsic SP perikarya located in the ventral sector of the rostral subnucleus and some may also arise from other sources. The areas of the IPN that receive bilateral SP projections from the fasciculus retroflexus (parts of the lateral and rostral subnuclei) show evidence for replacement of SP after lesion. This replacement implies sprouting or an increase in production of SP by remaining systems.

Afferent Pathways↗
PubMed1993

Normal distribution of alpha-1-adrenoceptors in the rat spinal cord and its modification after noradrenergic denervation: a quantitative autoradiographic study.

The distribution of alpha 1 (alpha 1)-adrenoceptors along the different segments of the spinal cord (cervical, thoracic, lumbar, and sacral) of normal rats has been studied by quantitative autoradiography using the specific alpha 1-antagonist [3H]Prazosin as a ligand. In addition, the influence of noradrenergic (NA) denervation [obtained either by complete transection of the spinal cord at vertebrae level T8-T9 or by selective lesion of NA spinal cord system carried out by intracisternal injection of 6-hydroxydopamine (6-OHDA)] on eventual variations of alpha 1-adrenoceptor density at spinal cord target cells was studied in parallel. In control rats, the quantitative analysis of alpha 1-adrenoceptor densities revealed a widespread distribution of these receptors along all segments of the spinal cord with a similar pattern in the various subregions of gray matter studied. This distribution of alpha 1-adrenoceptors was quite well correlated with the distribution of NA terminals, when referring to previous descriptions by immunohistochemistry. After 6-OHDA lesion, as well as caudally to the transection, a significant increase of alpha 1-adrenoceptor densities was observed in all spinal subregions thus evidencing supersensitivity. These results suggest that NA may act in the spinal cord, at least partly, via alpha 1-adrenoceptors and that the expression of these receptors could be influenced by NA dysfunction, as demonstrated here through the effects observed in lesioned animals.

Animals↗
PubMed2001

Measurement of the gadopentetate dimeglumine partition coefficient in human myocardium in vivo: normal distribution and elevation in acute and chronic infarction.

PURPOSE: To establish a method for measuring the partition coefficient (lambda) of gadopentetate dimeglumine in humans in vivo, evaluate the spatial and intersubject variation in the lambda of normal myocardium, and compare these values on a regional basis with lambda values of acute and chronic infarcted myocardium. MATERIALS AND METHODS: Twelve healthy subjects and patients with acute (n = 5) or chronic (n = 5) myocardial infarction underwent magnetic resonance imaging at 1.5 T. Look-Locker images were acquired at four short-axis levels to measure myocardial and blood longitudinal relaxation time at baseline and after a 30-40-minute infusion of gadopentetate dimeglumine. lambda was calculated as DeltaR1(M)/DeltaR1(B, )where M = myocardium, and B = blood. RESULTS: The magnitude of the estimated lambda in normal myocardium was uniform over the entire myocardium at 0.56 mL/g +/- 0.10 (SD). The lambda values in patients with acute (0.91 mL/g +/- 0.11, P <.001) or chronic (lambda = 0.78 mL/g +/- 0.09, P <.001) infarction were significantly elevated, as compared with those in healthy subjects. A 20% elevation in lambda, as compared with the mean value of a corresponding normal circumferential segment, allowed identification of chronically (sensitivity, 88%; specificity, 96%) or acutely (sensitivity, 100%; specificity, 98%) infarcted segments. CONCLUSION: Quantification of the lambda in vivo allows differentiation between normal and acutely or chronically infarcted myocardium, with high sensitivity and specificity.

Adult↗
PubMed1992

Multiple-trait restricted maximum likelihood for simulated measures of ovulation rate with underlying multivariate normal distributions.

A data set that was used to estimate covariance components with REML for an animal model with eight measures of ovulation rate treated as separate traits was used as a template to simulate data sets of eight multivariate normal traits that were then truncated to binomial traits. The model for simulation included eight measures on 610 animals with 1,071 animals in the numerator relationship matrix. Heritabilities were equal for the eight measures, and both genetic and phenotypic correlations among the measures were equal. Ten replications for each combination of heritability (.15, .25, and .35) and genetic correlation (.50, .66, and .90) were simulated on the normal scale. For each replicate, estimates of the eight heritabilities and 28 genetic correlations were obtained by multiple-trait REML. The usual transformation of heritability estimated on the binomial scale overestimated heritability on the normal scale. Genetic correlations on the binomial scale seriously underestimated the correlations on the normal scale. Standard errors of the estimates obtained by replication were somewhat larger than the approximate SE from REMLPK (the multi-trait REML program of K. Meyer). A final set of 10 simulated replications with heritability of .25 and genetic correlation of 1.00 resulted in average estimates of .18 for heritability and of .66 for genetic correlation that agree closely with those from the analysis of measures of ovulation at eight estrous cycles used as a template; averages for heritability of .16 and for genetic correlation of .66 were obtained.

Animals↗
PubMed1993

[Normal distribution curve for umbilical arterial flow velocimetry (S/D relation) measured by Doppler ultrasonography].

The umbilical artery flow is an important parameter for the management of obstetrical patients, specially those with retardation in intrauterine growth. A prospective study was carried out in 123 normal, pregnant women, from 20 to 40 weeks of gestation, with a reliable last menstruation date, who came for prenatal control to the Gyn-Ob Department at Hospital Central Militar, from June, 1991 to May 31, 1992. Umbilical artery velocimetry measurements, were done periodically, with S/D ratio determination, avoiding fetal respiratory movements, and at the chord site closest to the placenta. The equipment used was Toshiba Sonolayer SSA-270-A Doppler Duplex of pulsated wave; frequency of transmission-reception 3.5 Mhz and transductor fo 12 mm. diameter. All 123 products had a complete clinical examination, and determination of gestational age by Capurro at the time of birth, in order to exactly identify the gestational age of each ultrasonographic examination. With the obtained results four curves were made. One with average and standard error (EE +/- 1); another of simple lineal regression, obtaining confidence intervals of 95% with a correlation coefficient of r = 0.89; another one based on percentile 10, 50 and 90; and finally, one curve based of the confidence interval of 95%. The results are similar to the ones obtained by other authors, diminishing S/D ratio since week 20 to 40.

Adolescent↗
PubMed2001

Sensitivity of action potential triggering is normally distributed as a function of mean fractional receptor activation.

In 1968, Waud presented his general pharmacodynamic model consisting of two sub-functions that divide the pharmacodynamic cascade from drug concentration to cell effect/response into two successive steps: Step one (the internal function) characterizes the binding of agonist drug molecules to the post-synaptic receptors and the subsequent receptor activation, and step two (the external/effect function) characterizes the cell response induced by a critical receptor pool activation. According to Waud, the problem of determining the relation between drug concentration and cell response/effect reduces to the second step in the pharmacodynamic cascade. In this paper, we suggest a new external/effect-function, the cumulative Normal population-effect-function. It describes how muscle fibre excitability (all-or-none phenomenon) is distributed as a function of mean fractional receptor activation in a muscle fibre population. This function fits to empirical data and explains logically why the sigmoid muscle effect, from minimal to maximal, is seen in such a narrow range of antagonist concentrations and receptor occupancies.

Action Potentials↗