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PubMedDate not supplied

Childhood longitudinal melanonychia: case reports and review of the literature.

"Longitudinal melanonychia" refers to a brown or brown-black longitudinal band on a fingernail or toenail. A number of conditions can cause longitudinal melanonychia, but its main importance is that, in some patients, it may indicate the presence of a subungual malignant melanoma. Hyperpigmented nail bands are not uncommon in African-American, Latino and Asian patients, especially those over sixty years of age, and are often multiple in these groups. Longitudinal melanonychia is most worrisome when there is a solitary, dark, broad longitudinal band with pigment extending over the proximal nail fold (Hutchinson's sign). Such findings are considered to be a strong indication for biopsy of the nail matrix to rule out melanoma. Since nail matrix biopsy sometimes results in permanent nail deformity, and since the incidence of malignant melanoma is quite small in the pediatric age group, there is some controversy as to whether this procedure should routinely be performed in children. We report two cases of dramatic longitudinal melanonychia in toddlers and review the current literature on the management of this striking condition in the pediatric age group.

Adolescent↗
PubMed1976

A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. III. The longitudinal anal muscle: anatomy and role in anal sphincter mechanism.

A study of the longitudinal anal muscle was performed in 16 cadaveric specimens. The study comprised dissection and microscopic examination. The bundles of the longitudinal were found arranged in three layers: medial, intermediate, and lateral; each has a different origin and is separated from the other by a fascial septum. Four fascial septa related to the longitudinal muscle could be identified. They split and decussate below the lower end of the longitudinal muscle to form the "central tendon." The central tendon lies between the base loop of the external anal sphincter and the longitudinal muscle. It gives rise to multiple small fibrous septa in different directions; those which penetrate the base loop split and decussate to form the corrugator ani cutis. A mechanism of action of the corrugator is presented. The role of the longitudinal muscle in the anal sphincter mechanism and during defecation is discussed. The muscle plays its major role during defecation. The part played by the muscle in anal fixation is considered. It helps to fix the anal canal to the side wall of the pelvis during defecation, thus preventing anal prolapse.

Adult↗
PubMed1992

Residues in the longitudinal, hydrophobic strip-of-helix relate to terminations and crossings of alpha-helices.

An alpha-helix terminates when the virtual extension of its most hydrophobic, longitudinal strip containing Leu, Ile, Val, Phe, and Met lacks those residues. In each of 247 helices a template was fitted to maximize the mean hydrophobicity of positions forming a longitudinal strip-of-helix. The template was then extended into sequences beyond the ends of the helices. Leu, Ile, Val, Phe, and Met occurred in positions in the longitudinal strip-of-helix at an increased frequency (p less than 0.001), but in the first and second positions beyond either end of each true helix, they occurred at the same frequency as for their empirical distribution over all the proteins. Excesses of Asp and Glu were found in the N-terminal loop, and of Arg, His, and Lys in specific positions about the C terminus of helices. The longitudinal hydrophobic strip, the smallest amino acid in that strip, and charged amino acids in that strip, related to rotational and longitudinal orientation of alpha-helices in 15 proteins. Adjacent helices generally crossed through their longitudinal hydrophobic strips. They usually crossed through the smallest residue in the strip. Charged residues, when they occurred in the strips, were excluded from the crossing regions.

Amino Acid Sequence↗
PubMed1990

[Difference in the action of prostaglandin E2 (PGE2) on longitudinal circular muscle contractions of the colon. Experimental study in dogs].

The effect of prostaglandin E2 (PgE2) on the circular and longitudinal contractions of the canine colon was studied in chronic conditions. A mechanical transducer developed in our laboratory and implanted on the canine colon collected simultaneously and separately the variations of length in two perpendicular directions. The recordings started at the 6 postoperative day. The colonic motility was recorded two hours before (as control period) and two hours after the intravenous injection of PgE2 at three different doses: 0.1-1.0 and 10 micrograms/kg. PgE2, at the three doses, induced, progressively over time, a significant decrease in duration and amplitude of the circular contractions, while the amplitude of longitudinal contractions remained unchanged. 10 micrograms/kg of PgE2 immediately induced a significant increase in the duration of longitudinal contractions followed by a decrease in this value during the 2nd hour after PgE2 administration. Each dose of PgE2 shortened the period of recurrence of longitudinal contractions, inducing rapid or immediate bursts of contractions. This effect was moderate or absent for the circular contractions. It is concluded, that PgE2 has different actions on circular and longitudinal contractions of the colon. According to the dose used, it induces hypokinesia (relaxation) in the circular muscle and premature strong contractions in the longitudinal motor activity.

Animals↗
PubMed1989

Interactions of neurogenic responses of longitudinal and circular muscle in the guinea-pig ileum.

The relationship between neurogenic responses of longitudinal and circular muscle was studied by measuring contractions and EMG or nonadrenergic, non-cholinergic (NANC) relaxations and NANC inhibitory junction potentials in different preparations of the guinea-pig ileum. NANC relaxation of longitudinal muscle was observed also without any preceding or concomitant circular muscle contraction ruling out the possibility that the latter might be the cause of the NANC relaxation. Circular muscle twitches or powerful contractions were absent if there was no preceding neurogenic or myogenic excitation of longitudinal muscle; in preparations with myenteric plexus-longitudinal muscle layers removed only small residual responses were seen although still under neurogenic influences. Thus excitation of longitudinal muscle seemed a prerequisite for synchronized and powerful contractions of circular muscle to occur. Cholinergic contraction and NANC relaxation of longitudinal muscle evoked by field stimulation were partly inhibited if the submucous plexus was also present suggesting the involvement of a more complex neuronal circuitry in these responses.

Adenosine Triphosphate↗
PubMed1988

Contraction mediated by Ca++ release in circular and Ca++ influx in longitudinal intestinal muscle cells.

The source of Ca++ responsible for contraction was examined in muscle cells isolated separately from the circular and longitudinal muscle layers of guinea pig and human intestine. Contraction was measured by scanning micrometry and cytosolic-free Ca++ ([Ca++]i) with the fluorescent indicator, quin2. In both species, contraction induced in circular muscle cells by cholecystokinin-8 (CCK-8) and acetylcholine was not affected by withdrawal of Ca++ from the medium or addition of the Ca++ channel blocker, methoxyverapamil, whereas contraction induced by both agonists in longitudinal muscle cells and by depolarizing concentrations of K+ in both cell types was abolished. Depletion of intracellular Ca++ stores with caffeine in Ca++-free medium abolished the response in circular muscle cells. Readdition of Ca++ to the medium for 30 sec restored the response in longitudinal but not circular muscle cells. [Ca++]i, measured in guinea pig muscle cells, increased 3- to 4-fold above resting levels (circular, 70.8 +/- 8.1 nM; longitudinal, 77.4 +/- 9.7 nM) in response to all three contractile agents. The increase in [Ca++]i induced by CCK-8 and acetylcholine in circular muscle cells was not affected by withdrawal of Ca++ from the medium or addition of methoxyverapamil, whereas the response to both agonists in longitudinal muscle cells and to 20 mM K+ in both cell types was abolished. It was concluded that cells from adjacent muscle layers of the intestine mobilize Ca++ differently during agonist-induced contraction, i.e., by Ca++ release in circular and Ca++ influx in longitudinal muscle cells.

Animals↗
PubMed1987

The effect of nifedipine on the contractile responses of the longitudinal and circular muscle of the isolated guinea-pig ileum to various agonists.

We investigated the inhibitory effect of nifedipine on contractile responses of the longitudinal and circular muscle of the isolated guinea-pig ileum. Nifedipine in very low concentrations, ranging from picomolar to nanomolar, inhibits the phasic and the tonic contractile responses of the longitudinal muscle induced by various agonists (histamine, acetylcholine, prostaglandin E2, serotonin and potassium chloride) in a concentration-dependent manner. Nifedipine produces a stronger inhibition of the tonic than of the phasic component of contractions induced by used spasmogens. The tonic contractile responses evoked by histamine and acetylcholine exhibited the highest degree of sensitivity to the inhibitory action of nifedipine. The calculated values of mean effective concentrations (ED50) indicate that the phasic responses of agonists are less sensitive to nifedipine. For obtaining a similar degree of inhibition of phasic contractions much higher concentrations of nifedipine are necessary. Our findings that nifedipine inhibits more strongly the tonic than the phasic contractile responses produced by different agonists, support the hypothesis of the existence of various types of calcium channels in the guinea-pig longitudinal muscle. Also, nifedipine reduced the contractile responses of the ileal circular muscle induced by histamine, acetylcholine, prostaglandin E2, serotonin and potassium chloride, in a concentration-dependent manner. The contractions induced by histamine are most sensitive to the inhibitory action of nifedipine. It should be pointed out that the phasic responses of the longitudinal muscle and contractions of the circular muscle are approximately equally sensitive to nifedipine. It can be speculated that some inherent similarity exists in contractile processes of the phasic responses of the longitudinal muscle and contractions of the circular muscle, or that agonists act via the same (or similar) population of calcium channels. Enhancing the calcium concentration in the bathing fluid did not reverse the inhibitory effect of nifedipine on contractions of the longitudinal and circular muscle, induced by various agonists.

Acetylcholine↗
PubMed1997

Differences between longitudinal and circular smooth muscle in beta-adrenergic control of motility of isolated equine ileum.

OBJECTIVE: To identify beta-adrenoceptor subtypes involved in motility inhibition of circular and longitudinal smooth muscle layers of equine ileum. SAMPLE POPULATION: Isolated strips of equine ileum circular smooth muscle and membrane preparations from circular and longitudinal muscle layers. PROCEDURE: Functional assays of circular muscle preparations and radioligand binding assays and measurements of cAMP production in smooth muscle membranes from circular and longitudinal layers. RESULTS: Selective beta-adrenergic agonists exerted inhibitory effects on circular muscle preparations. Binding studies of cell membranes indicated that the density and distribution of 3 beta-adrenoceptor subtypes did not differ between longitudinal and circular muscle layers. Measurement of cAMP production in membrane preparations of longitudinal and circular muscle after selective beta-stimulation confirmed presence of the 3 adenylate cyclase-coupled beta-adrenoceptor subtypes; however, preparations from the 2 layers had differing cAMP production efficacy. CONCLUSIONS: The data may partly explain the differing functional responses between circular and longitudinal muscle preparations. CLINICAL RELEVANCE: Findings support the important role of beta-atypical adrenoceptors in the inhibitory regulation of equine ileum motility.

Adrenergic Agonists↗
PubMed2003

Stability and change in adult personality over 6 years: findings from the Victoria Longitudinal Study.

Data from the Victoria Longitudinal Study were used to examine the 6-year longitudinal stability of personality in older adults. Personality was measured with the NEO Personality Inventory. The longitudinal sample consisted of 223 adults initially ranging from 55 to 85 years of age. Longitudinal confirmatory factor analyses were used to examine the stability of individual differences in change over time, and the stability of the longitudinal factor structure. The results indicated both substantial stability at the level of individual differences in change, as well as significant individual differences in change that were related to age and gender. Finally, the factor structure of personality was invariant over time but did not approximate simple structure for the five dimensions of personality. Our study of 6-year personality development provided both (a). a confirmation of early significant stability findings and (b). unique evidence for significant individual differences in late adulthood.

Aged↗
PubMed2004

High body mass index after age 20 and diabetes mellitus are independent risk factors for ossification of the posterior longitudinal ligament of the spine in Japanese subjects: a case-control study in multiple hospitals.

STUDY DESIGN: A sex- and age-matched case-control study was carried out. OBJECTIVES: To facilitate early prediction, prevention, and treatment of ossification of the posterior longitudinal ligament of the spine, the authors analyzed histories of past illness, past body mass indexes, and body pliableness by nature, adjusted for other factors considered to be risk factors. SUMMARY OF BACKGROUND DATA: The cause of ossification of the posterior longitudinal ligament of the spine has not yet been elucidated in detail, although many possible causative factors have been suggested, including gender, diabetes mellitus, trauma, hormonal imbalance, and dietary habits. METHODS: A self-administered questionnaire was obtained from 69 patients with ossification of the posterior longitudinal ligament of the spine and 138 sex- and age-matched control participants who were free of spinal disease, randomly selected from participants in a health checkup in a town. After univariate analysis, a stepwise method was applied to select significant factors in multivariate analysis. RESULTS: A multivariate analysis revealed that the following three indicators were independent potent risk factors for ossification of the posterior longitudinal ligament of the spine: history of diabetes mellitus, history of lumbago, and maximum body mass index before manifestation > or =25, after adjustment for other possible lifestyle risk factors. CONCLUSION: Excessive weight gain between 20 and 40 years of age, diabetes mellitus, and lumbago were found to be independent risk factors for ossification of the posterior longitudinal ligament of the spine. Follow-up studies, including the addition of hospital-based control participants and analysis of genetic polymorphisms, will be needed in the future.

Adult↗
PubMed2002

Mechanisms behind the failure of residents' longitudinal primary care to promote disclosure and discussion of psychosocial issues.

CONTEXT: Longitudinality (care by a single physician over time) and continuity (receipt of most care from a single physician) are believed to enhance patient-physician relationships and facilitate disclosure of emotional distress, but some studies suggest this potential goes unrealized. OBJECTIVES: To determine whether care in a pediatric residents' continuity clinic promotes, over time, increased discussion, disclosure, and detection of parents' social and emotional distress and to understand physicians' communication behaviors underlying changes with time. DESIGN: Longitudinal, observational study of parent-physician interaction over the course of 1 year. PARTICIPANTS: One hundred ninety parents (90% African American) and their infants' primary care physicians (31 [4 Asians and 27 whites] first- and second-year pediatric residents). MAIN OUTCOME MEASURES: Frequency with which parents and physicians raised topics related to parental mood and family or social functioning; proportion of distressed parents discussing mood or functioning; and physicians' detection of parent distress. RESULTS: Physician initiation of psychosocial topics fell in the course of longitudinal relationships (odds of initiation in visits > or =6 vs odds of initiation in visits 1-5 = 0.46 [95% confidence limits, 0.31%, 0.67%]); parent initiation did not change over time nor was it increased by greater levels of continuity. Length of relationship was not associated with increased physician detection of parental distress or with increased rates of disclosure by distressed parents. Physicians' positively framed leading questions, and their avoidant responses to prior parental disclosures were significantly associated with decreased odds of problem disclosure. In contrast, visits in which parents or physicians raised psychosocial topics were characterized, on average, by 40% higher levels of physicians' "patient-centeredness" (increases of about 100 utterances per visit [95% confidence limits, 65.7%, 133.9%]). CONCLUSIONS: Longitudinal relationships between residents and patients may not be sufficient to promote the discussion, disclosure, and detection of psychosocial issues. Training in communication skills may help residents achieve the potential and goals of longitudinal care.

Adult↗
PubMed2003

Longitudinal care improves disclosure of psychosocial information.

BACKGROUND: While longitudinal primary care is thought to promote patient rapport and trust, it is not known if longitudinality helps overcome barriers to communication that may occur when the patient and physician are of different ethnicities and/or sexes. OBJECTIVE: To examine if longitudinal pediatric care ameliorates disparities in parent disclosure of psychosocial information associated with ethnic and gender discordance between parent and physician. DESIGN: Longitudinal, observational study of parent-physician interaction at early visits and over the course of 1 year. PARTICIPANTS: Parents (90% African American and 10% white mothers or female guardians) and their infant's assigned primary care physician (white first- and second-year pediatric residents). MAIN OUTCOME MEASURE: Parents' psychosocial information giving measured by the Roter Interaction Analysis System. RESULTS: Sex- and race-related barriers to disclosure of psychosocial information were evident early in the parent-physician relationship. At early visits, African American mothers made 26% fewer psychosocial statements than white mothers; this discrepancy was not affected by physician sex. At early visits, white mothers made twice as many psychosocial statements when seeing white female compared with white male physicians. CONCLUSIONS: Patient-centeredness is an important factor promoting psychosocial information giving for African American and white mothers, regardless of physician sex. Longitudinal relationships facilitate mothers' disclosure to physicians of a different ethnicity or sex, but only if physicians remain patient-centered.

Adolescent↗
PubMed1999

Longitudinal data analysis (repeated measures) in clinical trials.

Longitudinal data is often collected in clinical trials to examine the effect of treatment on the disease process over time. This paper reviews and summarizes much of the methodological research on longitudinal data analysis from the perspective of clinical trials. We discuss methodology for analysing Gaussian and discrete longitudinal data and show how these methods can be applied to clinical trials data. We illustrate these methods with five examples of clinical trials with longitudinal outcomes. We also discuss issues of particular concern in clinical trials including sequential monitoring and adjustments for missing data. A review of current software for analysing longitudinal data is also provided. Published in 1999 by John Wiley & Sons, Ltd. This article is a US Government work and is the public domain in the United States.

Clinical Trials as Topic↗
PubMed1999

Analysis of binary outcomes in longitudinal studies using weighted estimating equations and discrete-time survival methods: prevalence and incidence of smoking in an adolescent cohort.

Longitudinal studies are increasingly popular in epidemiology. In this tutorial we provide a detailed review of methods used by us in the analysis of a longitudinal (multiwave or panel) study of adolescent health, focusing on smoking behaviour. This example is explored in detail with the principal aim of providing an introduction to the analysis of longitudinal binary data, at a level suited to statisticians familiar with logistic regression and survival analysis but not necessarily experienced in longitudinal analysis or estimating equation methods. We describe recent advances in statistical methodology that can play a practical role in applications and are available with standard software. Our approach emphasizes the importance of stating clear research questions, and for binary outcomes we suggest these are best organized around the key epidemiological concepts of prevalence and incidence. For prevalence questions, we show how unbiased estimating equations and information-sandwich variance estimates may be used to produce a valid and robust analysis, as long as sample size is reasonably large. We also show how the estimating equation approach readily extends to accommodate adjustments for missing data and complex survey design. A detailed discussion of gender-related differences over time in our smoking outcome is used to emphasize the need for great care in separating longitudinal from cross-sectional information. We show how incidence questions may be addressed using a discrete-time version of the proportional hazards regression model. This approach has the advantages of providing estimates of relative risks, being feasible with standard software, and also allowing robust information-sandwich variance estimates.

Adolescent↗
PubMed2000

Modern statistical techniques for the analysis of longitudinal data in biomedical research.

Longitudinal study designs in biomedical research are motivated by the need or desire of a researcher to assess the change over time of an outcome and what risk factors may be associated with the outcome. The outcome is measured repeatedly over time for every individual in the study, and risk factors may be measured repeatedly over time or they may be static. For example, many clinical studies involving chronic obstructive pulmonary disease (COPD) use pulmonary function as a primary outcome and measure it repeatedly over time for each individual. There are many issues, both practical and theoretical, which make the analysis of longitudinal data complicated. Fortunately, advances in statistical theory and computer technology over the past two decades have made techniques for the analysis of longitudinal data more readily available for data analysts. The aim of this paper is to provide a discussion of the important features of longitudinal data and review two popular modern statistical techniques used in biomedical research for the analysis of longitudinal data: the general linear mixed model, and generalized estimating equations. Examples are provided, using the study of pulmonary function in cystic fibrosis research.

Biometry↗
PubMed2006

Analysis of longitudinal multinomial outcome data.

Analysis of categorical outcomes in a longitudinal study has been an important statistical issue. Continuous outcome in a similar study design is commonly handled by the mixed effects model. The longitudinal binary or Poisson-like outcome analysis is often handled by the generalized estimation equation (GEE) method. Neither method is appropriate for analyzing a multinomial outcome in a longitudinal study, although the cross-sectional multinomial outcome is often analyzed by generalized linear models. One reason that these methods are not used is that the correlation structure of two multinomial variables can not be easily specified. In addition, methods that rely upon GEE or mixed effects models are unsuitable in instances when the focus of a longitudinal study is on the rate of moving from one category to another. In this research, a longitudinal model that has three categories in the outcome variable will be examined. A continuous-time Markov chain model will be used to examine the transition from one category to another. This model permits an unbalanced number of measurements collected on individuals and an uneven duration between pairs of consecutive measurements. In this study, the explicit expression for the transition probability is derived that provides an algebraic form of the likelihood function and hence allows the implementation of the maximum likelihood method. Using this approach, the instantaneous transition rate that is assumed to be a function of the linear combination of independent variables can be estimated. For a comparison between two groups, the odds ratios of occurrence at a particular category and their confidence intervals can be calculated. Empirical studies will be performed to compare the goodness of fit of the proposed method with other available methods. An example will also be used to demonstrate the application of this method.

Biometry↗
PubMed1993

Precision of dual-energy x-ray absorptiometry: development of quality control rules and their application in longitudinal studies.

In research settings, longitudinal measurements of bone mineral density have become an integral part of the assessment of patients with metabolic skeletal disorders. To adequately utilize longitudinal measures, confidence in the long-term precision of the measurement technique must be very high. Dual-energy x-ray absorptiometry (DXA) has become commonly utilized in this context, and to better understand its long-term precision and to develop quality assurance protocols for its use, we examined the performance of eight DXA machines over a 3 year period. Anthropomorphic spine phantoms were measured frequently on each machine during the period of observation, and precision was estimated from the consistency of these determinations. Overall precision was excellent (mean longitudinal coefficient of variation, 0.4%). Nevertheless, by using a series of objective quality control criteria, small alterations in the performance of each machine were identified (mean number of changes, 4.6 in 3 years; mean magnitude, 0.0039 g/cm2, or 0.4%). The cumulative effects of those changes were sufficient to cause a significant (albeit minor) change in the regression slopes (phantom mineral density versus time) of most machines. The same quality control rules were also used to quantitate the magnitude of change and to adjust retrospectively machine performance during the period of observation, such that alterations were minimal and regression slopes were not significantly different from zero. Although the precision of DXA is excellent, alterations in machine function must be anticipated during longitudinal use. The development of quality control protocols provides the means to detect change objectively and to adjust for alterations in performance during the course of longitudinal evaluations.

Absorptiometry, Photon↗
PubMed1994

Aging, vertebral density, and disc degeneration alter the tensile stress-strain characteristics of the human anterior longitudinal ligament.

The mechanical properties of the human lumbar anterior longitudinal ligament were investigated, and the influence of aging, disc degeneration, and vertebral bone density on these properties was determined. Tensile mechanical properties of the vertebra-anterior longitudinal ligament-vertebra complex were determined for 16 segments from cadavera of individuals who had been 21-79 years old (mean, 52.1 years) at the time of death. Regional strain patterns associated with three sites across the width and three sites along the length of the anterior longitudinal ligament were measured with use of a video-based motion analysis system. In the young, normal anterior longitudinal ligament, the elastic moduli of the insertion and substance regions of the ligament were similar (approximately 500 MPa). During aging (21-79 years), the elastic modulus of the substance region increased 2-fold, whereas the elastic modulus of the insertion decreased 3-fold; this resulted in an approximately 5-fold difference in elastic modulus between these regions in the older spine. The strength of the bone-ligament complex decreased approximately 2-fold (from 29 to 13 MPa) over this same age range. The outer portion of the anterior longitudinal ligament consistently had the highest peak tensile strains (11.8 +/- 2.7%) in all of the specimens examined. Preparations with nondegenerated discs and high bone density were significantly stronger (66%) and failed in the ligament substance; in contrast, segments from older individuals with degenerated discs and lower bone density failed in the ligament insertion regions.

Adult↗