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PubMedDate not supplied

The IQs of children with ADHD are normally distributed.

The purpose of this investigation was to determine whether or not attention-deficit/hyperactivity disorder (ADHD)-when there was an absence of reading problems-was associated with having a high IQ. The vocabulary and block design short forms of the Wechsler Intelligence Scale for Children-Third Edition were administered to 63 children with ADHD, 69 children with reading difficulties (RD), and 68 children with comorbid ADHD + RD. Results indicated that the distributions of estimated Full Scale IQs (FSIQ) for each of the three groups of children did not differ significantly from a normal distribution, with the majority of children (more than 50%) in each group scoring in the average range. The percentage of children with ADHD who scored in the above-average range for FSIQ was not significantly higher than the percentages of children in the other two groups. No significant group differences emerged for estimated FSIQ, vocabulary, or block design. It was concluded that children with ADHD are no more likely to have an above-average IQ than are other children.

Adolescent↗
PubMed1992

Estimation of direct formulation effect under log-normal distribution in bioavailability/bioequivalence studies.

This paper considers estimation of a measure of relative bioavailability of a test formulation to a reference formulation, on the original scale, under the assumption of a log-normal distribution for the data from a 2 x 2 crossover bioavailability/bioequivalence study. We propose the minimum variance unbiased estimator which is equal to the maximum likelihood estimator adjusted for bias by a correction factor. We also derive the variance of the minimum variance unbiased estimator and its unbiased estimator. We derive the biases and mean square errors of the maximum likelihood estimator, the ratio of the least square means, and the least squares mean of individual subject ratios, with respect to this measure, and compare them in a simulation study. Both theoretical and empirical results strongly suggest that one always consider the minimum variance unbiased estimator. A numerical example illustrates the proposed estimation procedure.

Bias↗
PubMed2006

Mixture of normal distributions in multivariate null intercept measurement error model.

In this paper we propose the use of a multivariate null intercept measurement error model, where the true unobserved value of the covariate follows a mixture of two normal distributions. The proposed model is applied to a dental clinical trial presented in Hadgu and Koch (1999). A Bayesian approach is considered and a Gibbs Sampler is used to perform the computations.

Algorithms↗
PubMed1993

Quantitative description of the absorption spectra of the coenzyme in glycogen phosphorylases based on log-normal distribution curves.

The absorption spectra of the coenzyme [pyridoxal 5'-phosphate (PLP)] in glycogen phosphorylase a (GPha), glycogen phosphorylase b (GPhb) and of the latter bound to various effectors and substrates were analysed on the basis of log-normal distribution curves. The results obtained showed that the ionization state of the PLP and GPha environment differs from that of GPhb. This divergence was interpreted in terms of tautomeric equilibria between some forms of the Schiff base of PLP and enzymic Lys-679. The ionic forms are slightly more predominant in GPha than they are in GPhb, so ionic and/or hydrogen-bonding interactions between the aromatic ring of PLP and GPha must be stronger than with GPhb. This confirms the purely structural role of the aromatic ring of the coenzyme. Binding of GPhb to AMP and Mg2+ results in the coenzyme adopting a similar state as in GPha. On the other hand, binding to IMP gives rise to no detectable changes in the tautomeric equilibrium of the coenzyme.

Animals↗
PubMed1991

Microglia in tadpoles of Xenopus laevis: normal distribution and the response to optic nerve injury.

We have studied the distribution of microglia in normal Xenopus tadpoles and after an optic nerve lesion, using a monoclonal antibody (5F4) raised against Xenopus retinas of which the optic nerves had been cut 10 days previously. The antibody 5F4 selectively recognizes macrophages and microglia in Xenopus. In normal animals microglia are sparsely but widely distributed throughout the retina, optic nerve, diencephalon and mesencephalon (other regions were not examined). After crush or cut of an optic nerve, or eye removal, there occurs an extensive microglial response along the affected optic pathway. Within 18 h an increase in the number of microglial cells in the optic tract and tectum can be detected. This response increases to peak at around 5 days after the lesion. At this time the nerve distal to the lesion contains many microglial cells; the entire optic tract is outlined by microglia, extended along the degenerating fibres; and the affected tectum shows a heavy concentration of microglia. This microglial response thereafter decreases and has mostly gone by 34 days. We conclude that the microglial response to optic nerve injury in Xenopus tadpoles starts early, peaks just before the regenerating optic nerve axons enter the brain, and is much diminished by the time the retinotectal projection is re-established. The timing is such that the microglial response could play a major role in facilitating regeneration.

Animals↗
PubMed2004

Consistent presence of two normally distributed sperm subpopulations within normozoospermic human semen: a kinematic study.

Sperm motion analysis was performed using computer-aided semen analysis (CASA) on nine normozoospermic human ejaculates following six fractionation schemes that included Percoll discontinuous gradient centrifugation, swim-up, hyper and hypo-osmotic stress in which 4600-13 400 tracks were analysed (depending on the scheme). In addition, the effect of ageing for 2 h in seminal plasma or re-addition of seminal plasma, on the kinematic properties was investigated. Analysis following sorting of the swimming velocity at 5 microm/sec intervals revealed the presence of two discrete normally distributed subpopulations selected on the basis of path velocity (VAP): these subpopulations were also present in the track speed (VCL) and progressive velocity (VSL) distributions. The validity of the two subpopulations was examined using a two-component normal mixture model and found to be highly statistically significant (p < 0.00001). The basis for the subpopulations was independent from the possession of midpiece vesicles or hyperactivation. Swim-up produced subpopulations of sperm that were significantly different from those obtained by Percoll separation. Compared with sperm in seminal plasma, swim-up and Percoll separation significantly increased the level of hyperactivated sperm at 2 h. Hyperactivation was inhibited by the re-addition of seminal plasma. Swim-up enhanced the proportion of sperm in the fast VAP subpopulation (independently of the level of hyperactivation) and whilst this altered distribution was maintained following the addition of homologous seminal plasma the mean velocity of the fast fraction was significantly decreased. Both swim-up and Percoll separation significantly increased the mean velocity of the fast subpopulation but the increase was greater with swim-up. This analysis highlights a way in which subpopulations may be detected and analysed. The procedure revealed fundamental differences in the kinematic properties of sperm processed by different methods that are used in assisted reproductive technology and showed that these were independent of hyperactivation.

Biomechanical Phenomena↗
PubMed1991

Evaluation of two assumptions: single straight line, and single normal distribution.

Using graphical and statistical approaches, Laszlo Endrenyi and Mayank Patel describe methods that answer two frequently asked questions: 'Can the data be characterized by a single straight line, or should a more complex model be invoked?' and 'Do the observations follow a single normal distribution, or is there evidence for deviations from this assumption, including the possibility of bimodality?" These methods complement those addressed in a recent Principles article by Dick Barlow.

Research Design↗
PubMedDate not supplied

Methods to estimate the optimal threshold for normally or log-normally distributed biological tests.

Putting a screening or a diagnostic test into everyday use requires the determination of its threshold. The authors present methods that yield a point and an interval estimation of the threshold that maximize the population utility whenever the test results are normally or log-normally distributed among healthy and among diseased subjects, with equal variances. These methods were assessed for bias, coverage probability, coverage symmetry, and confidence-interval width using simulation. They proved to be asymptotically nonbiased and to have a satisfactory coverage probability whenever the sample sizes of the healthy and the diseased subjects are equal to or greater than 50. The methods were next applied to determine an optimal threshold for the antibody load used to diagnose congenital toxoplasmosis at birth. The methods are easy to implement and impose few constraints; however, the sample sizes should be carefully determined according to the required accuracy.

Antibodies, Protozoan↗
PubMed1978

Amino acids in parenteral feeding. I. The normal distribution of serum amino acids in healthy subjects.

Questions as to the utilisation of intravenously supplied amino-acids are answerable by determining nitrogen balances and by ascertaining the pattern of amino-acids in the serum of plasma. In a first study, the normal distribution was established for the individual serum amino-acids in 150 fasting test persons with a healthy metabolism. Sex-specific differences in concentration became clearly evident for the majority of amino-acids present in the serum.

Adolescent↗
PubMed1994

Type IV collagen alpha 5 chain. Normal distribution and abnormalities in X-linked Alport syndrome revealed by monoclonal antibody.

Although the evidence indicates that mutation of the gene for the alpha 5 chain of type IV collagen, alpha 5-(IV), is the primary defect in X-linked Alport syndrome, protein data for the alpha 5(IV) chain with regard to its normal distribution and its distribution in patients with Alport syndrome is lacking. We produced a rat monoclonal antibody (H51) by immunizing rats with a synthetic peptide corresponding to the nonconsensus amino acid sequence of alpha 5(IV) NC1 domain. H51 reacted by Western blotting with 26-kd cationic monomers and associated dimers of human type IV collagen NC1 domain. Immunohistochemical studies demonstrated that in normal human kidney alpha 5(IV) was present in the glomerular basement membrane and basement membranes of the Bowman's capsule and in some tubules (collecting ducts). The alpha 5(IV) chain was also detected in the basement membranes of normal skin, eye, and lung. Male patients with X-linked Alport syndrome revealed no reactivity of renal and epidermal basement membranes with H51, whereas alpha 5(IV) staining was normal in the glomerular basement membrane of patients with other types of glomerular diseases, including benign familial hematuria. The staining was also normal in the skin of nonaffected males in X-linked Alport families. Female heterozygous for Alport syndrome exhibited a discontinuous or mosaic pattern in the immunofluorescent staining of the epidermal basement membrane. These findings confirm that in patients with X-linked Alport syndrome there are abnormalities in alpha 5(IV) in renal and epidermal basement membranes at the protein level. Immunofluorescent staining of skin biopsies with this antibody may be of value in making a diagnosis of Alport syndrome, and, furthermore, may aid in detecting carrier females in whom urinary abnormalities are often mild or silent.

Adolescent↗
PubMed1997

Normal distribution of collagen IV in renal basement membranes in Epstein's syndrome.

BACKGROUND: Epstein's syndrome is defined as a subtype of Alport's syndrome, and is distinguished from the other subtypes by accompanying macrothrombocytopenia. Mutations in collagen IV genes are known to be involved in the pathogenesis of typical Alport's syndrome. However, the presence of an underlying genetic defect has not been demonstrated in Epstein's syndrome. AIM: To clarify the involvement of collagen IV in Epstein's syndrome. METHODS: The distribution of the alpha(IV) chain was studied in renal specimens obtained from three patients with Epstein's syndrome using chain specific monoclonal antibodies and an antigen retrieval procedure. RESULTS: The patients showed a normal distribution of alpha(IV) chains: alpha 1(IV) and alpha 2(IV) were expressed ubiquitously, whereas expression of alpha 3(IV) through to alpha 6(IV) chains was limited to the glomerular basement membrane, Bowman's capsular basement membrane, and/or a portion of the tubular basement membrane. CONCLUSIONS: These results suggest that genes other than those encoding alpha(IV) chains are responsible for the pathogenesis of Epstein's syndrome.

Basement Membrane↗
PubMedDate not supplied

[The actually observed dependence of mortality on age--a consequence of the normal distribution of individuals in a cohort by the "vitality" criterion].

A mathematical model is elaborated to calculate mortality indices in a cohort under various conditions. It is based on experimental data on compensatory mortality, differences of character dispersions between males and females, linear time dependence of compensatory effects. Observed dependence of mortality on age may be obtained under provision of normal distribution of individuals by "vitality". 7 functional relations that describe variation of "vitality" dependently on time scale are considered. It is concluded that there must be obligatory longevity limit which is responsible for mortality dynamics: increased mortality in younger ages, its correspondence to Hompertz-Meykem low in middle age, and drastic retardation of mortality increasing in older age.

Adult↗
PubMed1994

Log-normal distribution of physiological parameters and the coherence of biological systems.

The well-known fact that biological parameters, randomly selected, are distributed according to log-normal frequency curves instead of normal ones, has been traced back to a 'multiplicative Gestaltungs-principle of nature'. A further analysis shows that the basis of this principle can be assigned to the optimization of connections in a network of circuit elements, or, even more profoundly, to the formation of coherent states in living systems. The diagnosis of patients based on physiological frequency distributions provides a new powerful tool of understanding sickness in terms of deviations from a basic regulation principle.

Animals↗
PubMed1996

Cornified cell envelope proteins and keratins are normally distributed in harlequin ichthyosis.

Long-term survivors of harlequin ichthyosis (HI) have raised a controversy over the differences between HI and lamellar ichthyosis (LI). Abnormal lamellar granules and the failure of conversion from profilaggrin to filaggrin have been reported in HI. On the other hand, malformation of the cornified cell envelope as a result of mutation of keratinocyte transglutaminase has been found in LI. In the present study, we analyzed the distribution of keratins, filaggrin/profilaggrin and cornified cell envelope proteins in the epidermis in HI. We studied a newborn Japanese male with typical clinical features of HI. Electron microscopic observation of a skin biopsy specimen taken from the trunk revealed the presence of lipid inclusions within the cornified cells, the absence of lamellar granules in the granular layer keratinocytes, and a lack of extracellular lamellar structures between the first cornified cell and the granular cell. Immunohistochemical labeling showed a normal distribution of keratins (keratins 1, 5, 10, and 14), filaggrin/profilaggrin and cornified cell envelope proteins (involucrin, small proline-rich proteins, and loricrin) in the epidermis of lesional skin. The present observations of the patient's skin verified that keratins and cornified cell envelope proteins are normally expressed in HI, thus demonstrating a different pathogenesis between HI and LI.

Epidermis↗
PubMed2002

The statistical merits of various methods of calculating transfer coefficients between environmental media--development of the ideal formula for data-sets with a log-normal distribution.

The statistical treatment of data-sets from environmental pollutant studies in which different measurements are combined to produce averages or comparative factors (e.g., transfer coefficients (TCs), input-output balance values) are considered here, with particular reference to the analysis of data from input-output balance studies of pollutants such as PCBs in animals and humans. Many methods of statistical analysis ignore the fact that all measurements are subject to error, and generally assume that the normal distribution applies to all data-sets, which is commonly inappropriate for environmental (and particularly biological system) data. Considerably different estimations can be obtained by applying different, commonly used, statistical methods, as shown in a simulation study presented here and when applied to data from an input-output balance study of PCBs in humans. Alternative average and combined factor estimators for the treatment of data from these types of studies that give considerable advantages in terms of bias and the ease of assessment of accuracy are proposed.

Animals↗
PubMed1981

On the Colton model for clinical trials with delayed observations -- normally-distributed responses.

The Colton model for the choice between two medical treatments is studied, with the additional assumption that there is a time lag between the administration of the treatments and the availability of the responses. Two simple procedures are suggested for dealing with patients who arrive during the waiting period, caused by the lag, between the trial and treatment stages of the model. The relative performance of the procedures in the Bayesian framework is discussed when the responses to the treatments are normally distributed with unknown means and a common known variance.

Bayes Theorem↗
PubMed1998

Deconvolution of chemiluminescent emission curve associated with phagocytosis into three logarithmic normal distributions.

The chemiluminescent emission reaction dependence on the activity of phagocytosis is well known. However, this method is not used to diagnostically in clinical assessment because the relationship between phagocytizing activity and chemiluminescent intensity has not been clearly established. Therefore, we attempted to analyze quantitatively the chemiluminescent emission curve by the phagocytosis of leukocytes. Mathematical assessment of the emission curve with respect to time was performed by fitting the curve to several regression models using the unweighed non-linear least squares method. A triple logarithmic normal distribution model provided a reasonable goodness of fit to the measured emission curve. The first component, about 5% of the calculated total counts, was assumed to arise from monocytes activity, the second component, about 20% from eosinocytes activity and the third component, up to 75%, from neutrophils activity. This method seems promising as a means for assaying whole blood without the need for pretreatment and for the providing a valid index that is independent of the technical differences between laboratories.

Data Interpretation, Statistical↗