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PubMed2002

Human PTH (1-34) induces longitudinal bone growth in rats.

The growth plate is a specialized structure that is responsible for longitudinal bone growth (LGR). Growth plate organization is altered with loading in rats. Parathyroid hormone (PTH) is known to induce mitogenic effect on chondrocytes in vitro. Type I PTH/PTH related peptide (rP) receptor is expressed in growth plate cartilage in rats. We therefore investigated the effect of PTH administration on the organization and longitudinal growth rate of the growth plate in rats. We also investigated the effect of PTH on the changes induced by unloading in the organization and growth of the growth plate. Thirty 6-week-old and 30 15-week-old male Sprague-Dawley rats were randomly assigned to five groups (n = 6 per group), i.e., basal controls, control (i.e., normally loaded), PTH-treated control (i.e., PTH-treated under normal loading), unloaded, and PTH-treated under unloading. PTH-treated animals received human PTH (1-34) at a dose of 80 microg/kg per day five times per week for 3 weeks, for the duration of unloading. In young loaded rats treated with the systemic administration of PTH, growth plate thickness, chondrocyte number, and LGR were increased in the proximal tibiae compared with findings in young loaded rats without PTH administration. Hindlimb unloading induced a reduction in growth plate thickness, chondrocyte number, and LGR. In young rats, systemic administration of PTH partly prevented these changes induced by unloading. These preventive effects of PTH were observed only in young rats; not in adult rats. These results show that the systemic administration of PTH stimulates longitudinal bone growth, and diminishes the reduction in growth plate growth induced by unloading in young rats.

Animals↗
PubMed2006

Medical students' attitudes toward underserved patients: a longitudinal comparison of problem-based and traditional medical curricula.

Medical education has been shown to negatively influence student attitudes toward certain types of patient populations. Past research does not inform current educational practice because today's medical school environment is different from when most of the published research was conducted. There are more female students, curricular innovations such as problem-based learning have changed the framework for educational delivery, and longitudinal studies, which could inform when interventions may be needed, are uncommon. The purposes of this longitudinal, prospective cohort study were to compare the attitudes of Problem-based learning and Traditional curriculum students toward providing care for medically indigent patients as they progressed through the four-year undergraduate medical education curriculum, and to determine if gender differences were apparent and persisted over time. Attitudes of one cohort of students enrolled in separate curricula were studied. The outcome measure was the Medical Student Attitudes Toward the Underserved questionnaire, which was administered three times. A linear mixed effects regression analysis was performed to examine changes in factor scores over time and whether these changes differed between Problem-based and Traditional students, and males and females. Longitudinal findings revealed that commitment to caring for the medically underserved was greater when students entered medical school than when they graduated. Students in both curricula, as well as male and female students, experienced increasingly negative attitudes over the four year period. Decline in attitudes toward medically underserved patients was similar to previous research results. This study showed that attitudes of students were not influenced by the preclinical curriculum they experienced.

Adult↗
PubMed2006

Development of relative weight, overweight and obesity from childhood to young adulthood. A longitudinal analysis of individual change of height and weight.

BACKGROUND: To investigate individual longitudinal change of relative weight, overweight and obesity from age 5 to 25 years by gender. METHODS: A cohort was imbedded in four surveys conducted 1992/1993, 1995/1996, 1998/1999 and 2004/2005 in three areas in Germany. Twelve-year-follow-up of 2183 children initially aged 5-13 years at baseline. Main measurements are body mass index (BMI) and international obesity task force (IOTF)-cut point defined overweight and obesity. A special longitudinal random effects model for cohort data was applied, which uses age as meta-meter of follow-up time and takes age at study entry into account. RESULTS: BMI, overweight and obesity increases with linear and squared age. Girls have a significant higher growth rate than boys in BMI (BMI: 0.89 vs. 0.75 kg/m(2) per 1 year age increment), whereas there is no statistical significant gender difference for overweight [odds ratio (OR) = 1.08 per 1 year] or obesity (OR = 1.11 per 1 year). Longitudinal change rates of BMI vary substantially between individuals [95% reference range (beta +/- 1.96 x SD) for linear change per 1 year is -0.14 to 1.98 in females and -0.29 to 1.83 in males; the 95% range of quadratic change rates are -0.09 to 0.04 in females and -0.08 to 0.05 in males]. Moreover, a steeper increase in BMI over time is observed for children with a higher baseline relative weight. CONCLUSION: Increases in BMI and the propensity of overweight and obesity follow a quadratic growth curve with the steepest increase before and during puberty. However, the substantial variability of relative weight gain within individuals indicate, that more research in individual change patterns is needed.

Adolescent↗
PubMed1994

Effect of prednisone and hydroxychloroquine on coronary artery disease risk factors in systemic lupus erythematosus: a longitudinal data analysis.

PURPOSE: To determine the effect of prednisone dose and hydroxychloroquine dose on the coronary artery disease risk factors serum cholesterol level, mean arterial blood pressure, and weight in patients with systemic lupus erythematosus. PATIENTS AND METHODS: A longitudinal cohort study of 264 patients with systemic lupus erythematosus was conducted. For all patients in the cohort, serum cholesterol, mean arterial pressure, weight, prednisone dose, hydroxychloroquine dose, and other potential confounding variables were recorded at each visit. Regression analysis appropriate for longitudinal data was used to assess the effect of prednisone on serum cholesterol and mean arterial pressure. To assess the effect of prednisone on weight, patients' weights were compared 90 days before and after a 10-mg or 20-mg increase in prednisone. RESULTS: A total of 3,027 patient visits were analyzed. In the regression model for serum cholesterol, a change in prednisone dose of 10 mg was associated with a change in cholesterol of 7.5 +/- 1.46 (SE) mg% after adjustment for the other significant variables in the model, including sex, race, hydroxychloroquine dose, and proteinuria. In the regression model for hydroxychloroquine, the 200-mg and the 400-mg dose were both associated with lower serum cholesterol (8.9 +/- 3.44 SE mg%). In the regression model for mean arterial blood pressure, a 10-mg change in prednisone dose led to a change in mean arterial blood pressure of 1.1 mm Hg after adjustment for age, weight, and antihypertensive drug use. A 10-mg increase in prednisone dose was associated with a mean weight change of 5.50 +/- 1.23 (SE) lb. CONCLUSIONS: Changes in prednisone dose led to definable changes in risk factors for coronary artery disease, even after adjustment for other variables known to affect these risk factors. According to longitudinal regression analysis, hydroxychloroquine therapy was associated with lower serum cholesterol.

Adult↗
PubMed1987

The fibers which leave the Probst's longitudinal bundle seen in the brain of an acallosal mouse: a study with the horseradish peroxidase technique.

The congenital absence of the corpus callosum, a brain anomaly frequently noted in humans, has been recently found to occur in some mice of the ddN strain in our laboratory. In the brains of these mice, the Probst's longitudinal bundle is always present on both cerebral hemispheres and gives rise to some aberrant fibers toward the midline. In this research, the neuroanatomical features of these fibers were studied by iontophoretical injections of horseradish peroxidase (HRP) into the neocortex of acallosal mouse brains. The results revealed that the fibers which leave the Probst's longitudinal bundle are, at least, of 3 kinds: namely, the fibers that run out from the anterior portion of the bundle and take a U-turn ipsilaterally without crossing the midline through the septal tissue to go back again into the longitudinal bundle at the level where they have left it; the commissural fibers that leave the bundle from its middle portion and cross through a tiny bridge of tissue associated with the ventral hippocampal commissure to the opposite hemisphere; and the fibers that arise from the posterior portion of the bundle and accumulate as an anomalous fascicle below the cingulum. The observation that no labeled fibers were seen within the anterior commissure in the present HRP materials suggests that the axons from neocortex which are prevented from crossing the midline in mice with congenital absence of the corpus callosum cannot find an alternative pathway via the anterior commissure.

Agenesis of Corpus Callosum↗
PubMed1988

The fibers which course within the Probst's longitudinal bundle seen in the brain of a congenitally acallosal mouse: a study with the horseradish peroxidase technique.

The congenital absence of the corpus callosum, a brain anomaly frequently noted in humans, has been recently found to occur in some mice of the ddN strain in our laboratory. In the brains of these mice, the Probst's longitudinal bundle is always present on both cerebral hemispheres. In this research, the neuroanatomical features of the constituent fibers of this bundle were studied by iontophoretical injections of horseradish peroxidase into different loci in the neocortex of acallosal mouse brains. The results revealed that (1) certain cortical fibers of the Probst's bundle terminate in the ipsilateral neocortex; (2) some commissural fibers in the longitudinal bundle originate from the cells in the wide neocortical regions, and project to the opposite hemisphere in homotopic as well as heterotopic regions over the ventral hippocampal commissure; (3) the fibers from different cortical regions are arranged in a topographic manner within this bundle. The present data clearly demonstrate that a good portion of fibers in the Probst's longitudinal bundle seen in the congenitally acallosal mouse brain are corticocortical in nature, which indicates that this bundle has an ipsilateral neocortical association function.

Agenesis of Corpus Callosum↗
PubMed1978

Antagonism of cholinomimetics by troxypyrrolidinium in guinea-pig atria and longitudinal ileal muscle: comparison with hemicholinium-3.

The inhibitory effect of troxypyrrolidinium (trox) (10(-6) to 2 x 10(-3) M) on responses to carbachol (CCh) and acetylcholine (ACh) was investigated in the electrically stimulated left atrium and longitudinal ileal muscle of the guinea pig. In both tissues, trox exhibited antimuscarinic activity causing parallel shifts of the concentration--response curves to both agonists with no depression of maximum responses. Responses to CCh were inhibited by trox (5 x 10(-4) M) to a greater extent than responses to ACh and this difference was maintained following inhibition of cholinesterases with dyflos. In the guinea-pig atrium using CCh as agonist dose ratios produced by the higher concentrations of trox (greater than 5 x 10(-5) M) were less than expected resulting in a non-linear Arunlakshana--Schild (A-S) plot and this effect of trox was maintained in the presence of mecamylamine (2 x 10(-5) M). In longitudinal ileal muscle flattening of the A-S plot with high concentrations of trox did not occur. Although hemicholinium-3 (HC-3) produces a non-linear A-S plot for antimuscarinic activity in atria the A-S plot obtained with the longitudinal ileal strip using HC-3 (2 x 10(-5) to 2 x 10(-3) M) did not exhibit flattening at high concentrations. The dose ratios obtained with HC-3 (5 x 10(-4) M) using CCh as agonist were significantly greater than those obtained with ACh. It is suggested that trox, like HC-3, acts as a metaffinoid antagonist at the muscarinic receptor.

Animals↗
PubMed1986

Differentiation between myenteric plexus and longitudinal muscle of the rat jejunum as the site of action of putative enteric neurotransmitters.

The contribution of the myenteric plexus in the mechanical responses of rat jejunal longitudinal muscle produced by several enteric nerve substances was evaluated. The myenteric plexus of a segment of rat jejunum was destroyed by serosal application of benzalkonium chloride (BAC). Fifteen days after BAC treatment, both the BAC-treated and an orad control jejunal segment were removed and the mechanical responses of the longitudinal muscle produced by the following substances were examined: substance P, acetylcholine (ACh), 5-hydroxytryptamine (5-HT), cholecystokinin octapeptide (CCK-8), norepinephrine, vasoactive intestinal peptide (VIP), bombesin, [Leu5]enkephalin and somatostatin. Our results indicate that: substance P and norepinephrine produce their mechanical responses by acting predominantly on the longitudinal smooth muscle; 5-HT, CCK-8, ATP, VIP and neurotensin act predominantly through the myenteric plexus; ACh possesses both direct and indirect actions; and because the responses to [Leu5]enkephalin, bombesin and somatostatin were equivocal, a conclusion as to their site of action could not be made with this preparation.

Acetylcholine↗
PubMed1994

K+ channel openers relax longitudinal muscle of guinea pig ileum.

The plexus-free longitudinal muscle was used to investigate the muscle-relaxing effects of the known K+ channel openers, cromakalim, pinacidil and nicorandil, and compared with other known muscle relaxants, calcitonin gene-related peptide (CGRP) and isoprenaline. The three K+ channel openers all decreased basal tension and inhibited the tonic tension evoked by 30 mM KCl, 0.5 microM histamine or 0.1 microM oxotremorine in a dose-dependent manner. The order of potency is cromakalim > pinacidil > nicorandil in KCl or oxotremorine-precontracted muscle strip and nicorandil > cromakalim > pinacidil in histamine-precontracted muscle strip. Inhibition by cromakalim was completely reversed by glibenclamide, a blocker of ATP-sensitive K+ channels, while inhibition by nicorandil or pinacidil was only partially antagonized. The tonic tension evoked by KCl, histamine or oxotremorine was relaxed by CGRP or isoprenaline. Inhibition by neither of these compounds was relieved by glibenclamide. These results suggest that while ATP-sensitive K+ channels may be present in the longitudinal muscle cells, they may not be involved in the actions of CGRP or isoprenaline on the longitudinal muscle.

Animals↗
PubMed1984

Myocardial material mechanics: characteristic variation of the circumferential and longitudinal systolic moduli in left ventricular dysfunction.

Active systolic moduli for the circumferential (E theta) and longitudinal (E phi) axes of the left ventricle were determined along with circumferential and longitudinal contractile filament stress (sigma theta and sigma phi) and circumferential and longitudinal fiber strain (epsilon theta and epsilon phi). These material property parameters were determined at four points during cardiac systole. Thirty-nine patients comprising five clinical groups were evaluated using pressure and volume data acquired from single-plane cineangiography. The results indicate that the active moduli exponentially decrease during cardiac systole. Characteristic variations from normal differentiated the various pathological groups. With compensated volume overload, E theta was significantly reduced during the latter half of systole (p less than 0.25). With decompensated volume overload, both E theta and E phi were not significantly different from the normal group throughout cardiac systole. With compensated pressure overload, both E theta and E phi were significantly lower than the normal group at end-systole (p less than 0.005; p less than 0.005). With congestive cardiomyopathy, both E theta and E phi were significantly greater during the latter half of systole compared to the normal group (p less than 0.05 and p less than or equal to 0.025).

Adult↗
PubMed1996

Joint center longitudinal positions computed from a selected subset of Chandler's data.

Mathematical models of the human body are indispensable tools for studying the biomechanics of human movement. The geometrical centers of the 12 main joints (shoulders, elbows, wrists, hips, knees ankles), modeled as simple mechanical joints, are widely used as reference points for building mathematical models of the human body. These reference points, typically defined as "joint centers", are assumed to maintain a fixed 3D position relative to both the segments forming the joint, throughout the range of joint motion. No single point in a human joint perfectly meets this assumption, and no simple method is available for locating the points that are closest to meet it. Researchers often have recourse to subjective methods, based on their knowledge of anatomy. Objective estimates are easily attainable if the positions of a few bony landmarks can be measured on the subject, and the longitudinal distances of the joint centers from these landmarks are known. A subset of the anthropometric measurements performed by Chandler et al. (NTIS No. AD 710-622, 1975) on six cadavers was critically selected and utilized to compute the percent longitudinal distances of the 12 main joint centers from neighboring bony landmarks, relative to the lengths of the respective proximal and/or distal segments. Three-dimensional positions are attainable as well, by assuming joint centers lay on the respective segment longitudinal axes. The use of a method for accurately locating joint centers is recommended, particularly when they are used as reference points for defining a personalized geometrical model of a subject's body.

Anthropometry↗
PubMed1983

The effects of erythrosin B(FD & C Red No. 3) on the guinea-pig ileum myenteric plexus-longitudinal muscle preparation.

The responses of the guinea-pig ileum myenteric plexus-longitudinal muscle to the food, drug and cosmetic dye erythrosin B (FD & C Red No. 3) were examined in acetylcholine- and electrically-stimulated preparations. Erythrosin B (10(-6)-10(-4)) reduced the amplitude of the mechanical responses produced by both stimuli. The effects were not simply concentration- and time-dependent. Responses to field stimulation were more sensitive to inhibition by erythrosin B, inhibition increasing with both concentration of dye and time of exposure. Responses to acetylcholine were generally less sensitive to erythrosin B and inhibition at 90 min exposure was more evident at lower concentrations of the dye. Many preparations contracted briefly upon exposure to low concentrations of the dye. Erythrosin B did not significantly affect the specific binding of [3H]QNB to muscarinic receptors. Erythrosin B reduced resting K+ levels in the longitudinal muscle but Na+ concentrations were essentially unaffected. Muscarinic agonist-stimulated uptake of Na+ and release of K+ were inhibited by erythrosin B (10(-6)-10(-4)M); this effect was enhanced with increased time of exposure to the dye. The effects of erythrosin B on cellular ion concentrations were more evident at low than at high concentrations of the dye. Erythrosin B reduced the efflux of [3H]acetylcholine induced by field stimulation from the myenteric plexus longitudinal muscle preparation.

Acetylcholine↗
PubMed1980

Response of tracheal slowly adapting stretch receptors to longitudinal forces.

During breathing and various respiratory maneuvers the trachea sustains significant longitudinal stresses which could be sensed by its mechanoreceptors. In this study we have measured the longitudinal motion and elongation of the trachea in supine, anesthetized dogs during quiet breathing and with occlusion of the upper airways and recorded the response of tracheal stretch receptors in each of the two conditions. The respiratory modulation of intrathoracic tracheal stretch receptors is essentially absent during airway occlusion when the elongation of the trachea becomes greater than in a quiet breath. We have also measured the response of tracheal stretch receptors to transmural pressure at different tracheal length, both statically and dynamically. When the trachea is elongated the receptors decreased their activity at higher positive pressures and remained unaffected with lower distending pressures, at zero transmural pressure and with collapsing pressures. These results indicate that the longitudinal forces applied to the trachea are not capable of changing the transducing properties of its stretch receptors over most of its pressure-volume range, only toward its TLC position their response appear to become attenuated.

Animals↗
PubMed1982

Longitudinal mixing by the human larynx.

Both the characteristics of the velocity field and the longitudinal dispersion of helium, oxygen and sulfur hexafluoride in air flowing through a cast of a cadaveric human larynx have been studied. The larynx cast was mounted in the center of a 5 m long, 1.6 cm diameter tube through which air was admitted at 206, 425 or 775 ml/s, corresponding to fully-developed laminar (Reynolds number = 1110), transitional (2310), and fully-developed turbulent (4210) flow conditions, respectively. A significant enhancement of longitudinal mixing was detected immediately downstream of the glottis, presumably because of the jetting of air in the vicinity of the constriction. This enhancement did not depend upon the flow rate of air but was inversely related to the molecular diffusivity of the tracer gas; this indicates the importance of Taylor dispersion in the jet. The glottis also generated intense local turbulence which propagated as far as 110 cm from the constriction. This turbulence caused a flattening of the velocity profiles resulting in a reduction in the rate of downstream longitudinal mixing. The reduction was so great that, in spite of mixing enhancement in the jet, the overall mixing was less with the larynx in place than in the empty tube.

Biomechanical Phenomena↗
PubMed1983

Contractile effects of PGD2 and PGF2 alpha on mechanical and electrical activities in longitudinal and circular muscles of the guinea-pig colon.

Contractile effects of PGD2 and PGF2 alpha on mechanical and electrical activities were investigated in longitudinal and circular muscles of the guinea-pig isolated proximal colon. PGD2 and PGF2 alpha (1 microM)-induced contractions were reduced with a decrease in external Ca ion concentration and were prevented at zero Ca(EGTA 1 mM) in both muscles. In electrical activities recorded by the single sucrose gap method, PGD2 and PGF2 alpha (1 microM) increased the frequency of spike generation on the slow waves in both muscles. Verapamil (10 microM), a Ca antagonist, blocked spontaneous and PG-induced spike activities with little effect on the slow waves in both muscles. Verapamil markedly reduced the contractions to PGs in the longitudinal muscle, but not in the circular muscle. The results suggest that PGD2 and PGF2 alpha produced contractions which may depend largely on an increase in the inward Ca current of the spikes in longitudinal muscle, and may depend both on a release of Ca from the Ca sequestration in the cell, and on a spike-dependent Ca influx in circular muscle of the guinea-pig colon.

Animals↗
PubMed1989

Structure and mechanical properties of the longitudinal ligaments and ligamentum flavum of the spine.

Stress-strain curves were recorded from anterior and posterior longitudinal ligaments and ligamenta flava dissected from pig lumbar spines. Ligaments were examined during extension by light microscopy, to observe crimp structure, and by X-ray diffraction, to determine collagen fibril orientations. Scanning electron microscopy (SEM) was used to examine ligaments fixed at high and low strains. Initial stages of ligament extension involved alignment of collagen fibrils. Collagen fibrils in unstrained ligamentum flavum were much more disoriented than in the longitudinal ligaments. Thus, fibril alignment, and consequent stiffening, occurred at much higher strains than for longitudinal ligaments, allowing ligamentum flavum to exploit the extensibility of its elastin.

Animals↗
PubMed1993

Longitudinal transgastric echocardiographic views utilizing a single-plane probe: anatomic correlations and clinical applications.

In order to widen the diagnostic capability of single-plane transesophageal echocardiography, which has been so far confined to transverse imaging planes, we obtained four transgastric longitudinal echocardiographic views which have not been previously described. These views can image structures such as superior and inferior vena cava, the right ventricular inflow and outflow tract, the mitral apparatus and the ascending aorta, which are poorly visualized by transesophageal transverse single-plane echocardiography. Among 400 consecutive patients these scans gave relevant additional diagnostic information in 62 cases (15.5%) and provided the correct diagnosis in 37 (9.2%). There were no complications related to the longer gastric manipulation of the probe and the quality of the images was high. We conclude that longitudinal echotomographic scanning of the heart is not exclusively confined to the use of biplane or omniplane probes, but longitudinal views can be consistently obtained with a single-plane instrument.

Aorta↗
PubMed1982

Multiple unit activity recorded longitudinally in rats from pubescence to old age.

Longitudinal multiple unit activity (MUA) recordings of excellent quality over time periods as long as 26 months are described. The validity of the method was demonstrated by showing persistence of specific and idiosyncratic MUA responses to controlled sensory stimulation over these long time periods. This longitudinal MUA method was used to study level of localization neuronal activity as a function of aging. In agreement with deoxyglucose data from Sokoloff's laboratory, we found significant age-related declines in inferior and superior colliculi. In addition, our results showed the advantage of a longitudinal method over a cross-sectional one in following progressive changes into old age. The further declines in midbrain MUA level (though not in forebrain level) from middle age to old age that we observed were highly significant. The deoxyglucose method, on the other hand, had failed to show this kind of progression in those midbrain sites, probably because of a survival effect, a common sampling artifact in cross-sectional studies of aging.

Acoustic Stimulation↗