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Biomedical subjects

L Rappaport

Publications and source records attributed to L Rappaport.

At least 91 records · Page 5Linked to original sources
PubMed1987

Concurrence of congenital ocular motor apraxia and other motor problems: an expanded syndrome.

The records of all cases of congenital ocular motor apraxia diagnosed by the Ophthalmology Department at the Children's Hospital, Boston, over the past 25 years were reviewed to ascertain other problems with motor organization. There were eight boys and two girls, ranging in age from eight months to 2 1/2 years at diagnosis. Eight of the 10 had evidence of oral motor planning problems which significantly affected their speech output. Five had evidence of awkwardness or clumsiness, suggesting difficulties with gross motor organization as well. This concurrence of motor planning problems in at least two spheres, ocular motor and oral motor, suggests more general difficulties with motor organization in this syndrome. In all cases for whom data were available the ocular motor problems resolved but oral motor problems persisted.

Apraxias↗
PubMed1987

Microtubules and desmin filaments during onset of heart hypertrophy in rat: a double immunoelectron microscope study.

The distribution of tubulin and desmin, the constituent proteins of microtubules and intermediate filaments, respectively, were studied in normal and hypertrophied rat myocardium by high-resolution immunofluorescence and immunoelectron microscopy. Cardiac hypertrophy was induced in 25-day-old rats by aortic stenosis. In the normal heart, double immunolabelling of ultrathin frozen sections of papillary muscle using gold-labelled probes for tubulin and desmin showed that microtubules ran primarily in a longitudinal direction through the intermyofibrillar spaces, perpendicularly to the desmin filaments. Microtubules were present near nuclei, mitochondria, and plasma membranes, while desmin filaments formed transverse connections between adjacent Z disks. No tubulin was observed near the intercalated disks, which were rich in desmin filaments. In hypertrophied hearts, myocytes exhibited the typical morphological features of developing hypertrophy. While there was little difference in the distribution of the microtubules around mitochondria and at the plasma membrane, considerable increases were seen near the nuclei and along the myofibrils. Desmin labelling was distributed transversely as in the controls; however, sometimes it was longitudinally oriented either in the intermyofibrillar space linking 2 Z disks out of register or along digitations of the intercalated disks connecting neighboring desmosomes. The unique rearrangement of desmin and tubulin filaments in hypertrophied cardiac myocytes emphasizes their distinct role in myocyte organization. We suggest that, during the development of cardiac hypertrophy, desmin filaments are mainly involved in maintaining the myofibrils in register, whereas the degree of assembly of microtubules is correlated with the rate of protein synthesis and with myofibrillogenesis.

Animals↗
PubMed1987

Adaptational changes of sarcomere and sarcolemma during chronic cardiac overloading in rats and in humans.

In response to increasing demand, the cardiac muscle has developed several adaptational mechanisms. Gene expression is modified in a quantitative and a qualitative way since the heart hypertrophies and since its structure changes to improve the efficiency of the contraction. The sarcomere modifications are both species- and tissue-specific. An isoenzymic shift of myosin from high adenosine triphosphatase (ATPase) activity form V-1 to low activity form V-3 occurs in all conditions in which V-1 is initially predominant, i.e., in rat (and also rabbit) ventricles and the atria of other species, including humans. It was not observed in conditions in which V-3 was predominant, as in human ventricles (and also in those of cats and pigs). Another shift from creatine kinase (CK) monomer M to CK B, the form that predominates in the fetal heart, is also observed. The sarcolemma is also modified, at least in rats. The digitalis receptor was characterized by studying the inotropic effect of the drug on an isolated heart preparation and on a purified preparation of sarcolemma with a high Na+,K(+)-ATPase activity by binding [3H]ouabain and ouabain-induced inhibition of the enzymatic activity. In hypertrophied heart, both the recovery of normal contractility after ouabain infusion and the release of previously bound ouabain infusion and the release of previously bound ouabain were slowed, as for fetal hearts. Changes in other inotropic receptors have also been reported. From a practical point of view, this means that screening of new inotropic agents has to be done on hypertrophied hearts and not, as usual, on normal tissue.

Adult↗
PubMed1986

Isolation and localization of filamin in heart muscle.

High-molecular-mass protein was isolated from chicken heart muscle. The apparent molecular mass of a single polypeptide chain is similar to that of chicken gizzard filamin: 250-270 kDa. The protein interacts with antibodies against chicken gizzard filamin and induces F-actin gelation in a concentration-dependent manner. Immunofluorescent staining of cardiomyocytes and chicken heart sections with antifilamin antibody demonstrates two types of filamin localization: filamin was located on the sarcomere border in the periphery of the Z-disk; filamin was found in intercalated disks between cardiomyocytes.

Animals↗
PubMed1986

Locus of control as predictor of compliance and outcome in treatment of encopresis.

We examined the effectiveness of instruments that describe a child's locus of control and perceived self-competence as predictors of outcome in the treatment of encopresis. Fifty children 9 to 12 years of age completed such instruments prior to clinical interview. Clinicians were blind as to the results of these questionnaires and administered a standard encopresis protocol to all patients. Six to 17 months later, 45 (90%) of the patient's parents were interviewed to assess compliance and treatment outcome. Children who significantly improved had a more internal locus of control (P less than 0.05) and better compliance (P less than 0.05) as determined by two separate outcome variables. Locus of control and compliance were not, however, significantly correlated with each other; each appeared to have an independent association with outcome. There was no association between perceived self-competence and outcome. The positive association between locus of control and outcome was not mediated by socioeconomic status, age, duration of encopresis, severity of encopresis, gender, or time between initiation of treatment and follow-up. Measurement of locus of control in children with encopresis appears to be helpful in identifing a group at high risk for resistance of treatment.

Child↗
PubMed1986

Locus of control and self-esteem in children with encopresis.

Children with encopresis were compared to children with other "high prevalence low-severity" disorders on measures of locus of control and self-esteem. Children with encopresis tended to feel less in control of positive life events, had lower self-worth, and were more apt to want to change and be different than children with other chronic symptoms. Data tend to contradict traditional interpretations of encopresis as a system of unconscious motives involving independence and control. Also, this information adds to the clinical impression culled from experience that active intensive remediation is the appropriate clinical response when treating children with encopresis.

Child↗
PubMed1986

Transport of gibberellin a(1) in cowpea membrane vesicles.

The permeability properties of gibberellin A(1) (GA(1)) were examined in membrane vesicles isolated from cowpea hypocotyls. The rate of GA(1) uptake was progressively greater as pH decreased, indicating that the neutral molecule is more permeable than anionic GA(1). Membrane vesicles used in this study possessed a tonoplast-type H(+)-translocating ATPase as assayed by MgATP-dependent quenching of acridine orange fluorescence and methylamine uptake. However, GA(1) uptake was not stimulated by MgATP. At concentrations in excess of 1 micromolar, GA(1), GA(5), and GA, collapsed both MgATP-generated and artifically imposed pH gradients, apparently by shuttling H(+) across the membrane as neutral GA. The relatively high permeability of neutral GA and the potentially detrimental effects of GA in uncoupling pH gradients across intracellular membranes supports the view that GA(1) accumulation and compartmentation must occur by conversion of GA(1) to more polar metabolites.

Journal Article↗
PubMed1986

Differential effect of thyroxine on atrial and ventricular isomyosins in rats.

Two myosin heavy chains (MHCs), alpha and beta, which exhibit different levels of ATPase activity related to the different velocities of muscle shortening, are differentially expressed in rat cardiac ventricles, depending on the developmental stage and the thyroid status of the animals. In contrast, no changes have been reported concerning the expression of atrial MHCs in the same physiological and pathological conditions. We have now performed studies with sensitive techniques to test the hypothesis that the expression of alpha- and beta-MHCs can also be modulated in the rat atria, although at a low level. Atrial and ventricular isomyosin patterns of various groups of rats were examined by two-dimensional peptide mapping, immunofluorescence with specific anti-alpha- and anti-beta-MHC immunoglobulins, and electrophoresis under nondenaturing conditions. Normal ontogenic development of the atria is characterized by the disappearance of a small amount of beta-MHC, present at 19 days in utero. At 3 wk of age, atria and ventricles both contain only alpha-MHC. Severe hypothyroidism, produced either by methylthiouracil (MTU) treatment of pregnant females and of their litters or by hypophysectomy of adult animals, did not significantly deinduce atrial alpha-MHC but was characterized by a significant although slight accumulation of beta-MHC (less than 5% of total myosin). This latter effect was abolished by L-thyroxine restoration. It is concluded that alpha- and beta-MHC are developmentally and hormonally regulated both in atria and ventricles, although the extent of regulation is very different for the two tissues.

Animals↗
PubMed1986

Microtubule reorganization is related to rate of heart myocyte hypertrophy in rat.

Since stimulation of heart hypertrophy by pressure overload was previously shown to be accompanied by a densification of microtubule network in rat heart myocytes, we verified that similar process occurred during postnatal growth in euthyroid rats and in hypothyroid rats whose growth was stimulated by 4 micrograms/day L-thyroxine (T4). For this purpose, tubulin, the constituent protein of microtubules, was immunolabeled in myocytes isolated at various times after birth. Myocyte hypertrophy was evaluated by myocyte size, the number of nuclei per cell and isomyosin expression. In hypothyroid rats, the microtubule network, which was underdeveloped, was most dense around the nucleus. During the phase of fast myocyte hypertrophy observed in euthyroid rats during late postnatal development and in hypothyroid rats after T4 administration, transient microtubule densification occurred in a myocyte subpopulation in which size was mainly determined by the rate of myocyte hypertrophy. The densification process and its kinetics resembled those observed when heart hypertrophy was induced by pressure overload. It is concluded that in rat heart myocytes undergoing hypertrophy, microtubule densification might be related to fast sarcomerogenesis, whether the stimulus is mechanical (e.g., pressure overload) or hormonal (e.g., T4).

Aging↗
PubMed1986

Physiological adaptation of the heart to pathological overloading.

Chronic overloading of the rat heart induces a cascade of adaptational events that compensate for the increase in work. At the myocardial level there are two types of adaptational mechanisms: qualitative, represented by the isomyosin changes leading to an improved efficiency; and quantitative, the hypertrophy. We present new approaches exploring possible adaptational changes at other levels within the myocardial cell. Studies of heart overload were performed either in young rats with experimental aortic stenosis or in humans with chronic compensatory hypertrophy. By means of double immunofluorescence labeling of isolated myocytes with anti-V1 and anti-V3 myosin immunoglobulins, we showed that the shift from high- to low-ATPase isomyosins occurs rapidly after aortic stenosis (2-3 days). Cardiac myocytes were shown to be poor in tubulin but a microtubule pattern was clearly visualized by an immunofluorescence approach. Their role in the onset of adaptational processes after aortic stenosis in not yet clear. On the other hand, we showed that in humans, contrary to small rodents, the adaptational process at the isomyosin level is very small or nonexistent.

Animals↗
PubMed1985

Microtubules and desmin filaments during the onset of heart growth in the rat.

Microtubules and intermediate desmin filaments were visualized in rat cardiomyocytes during the onset of heart growth by double immunolabelling of isolated myocytes, with specific antibodies raised against tubulin and desmin. Heart growth was stimulated either by mechanical overloading induced by aortic stenosis, or by injection of thyroxine into hypothyroid rats. In both experimental models, alterations in the microtubule pattern were observed soon after stimulation of growth whereas desmin filament organization remained unchanged. Microtubules were redistributed in arrays parallel to the long axis of the myocytes and were more numerous around the nuclei. Microtubules therefore appeared to be involved in the cellular events occurring during stimulated heart growth irrespective of the nature of the stimulus.

Animals↗
PubMed1985

Myofibrillar organization and desmin in rat heart myocytes.

The distribution of desmin, and alpha-actinin was studied in vivo growing rat heart myocytes and in vitro cultured heart myocytes using double indirect immunofluorescence labelling. Myocytes growing in vivo exhibited a superimposable pattern of alpha-actinin and desmin at the level of the Z discs and intercalated discs. Cultured neonate rat heart myocytes concurrently exhibited changes in shape and a loss of myofibrillar register. Whereas alpha-actinin staining remained unchanged, that of desmin disappeared from the Z discs but persisted as cables and randomly oriented foci throughout the sarcoplasm. We conclude that desmin binding to the Z discs is correlated with the in register organization of myofibrils.

Actinin↗
PubMed1985

Pediatric management of severe treatment-resistant encopresis.

Chronic fecal soiling is a distressing condition that often is associated with inappropriate psychological symptoms. This case report illustrates that a medical approach focusing on intensive "demystification" of the symptom and careful follow-up can successfully treat a child who initially might have been referred for psychiatric or even surgical consultation.

Child↗
PubMed1984

Unchanged myosin kinase activity in hypertrophied rat heart.

The decrease in myosin ATPase activity observed in cardiac hypertrophy induced by cardiac overload has been related to an isoenzymic redistribution of myosin. To test the hypothesis of an additional regulation of myosin ATPase through light chain phosphorylation, we measured the myosin kinase activity together in sham-operated and 50% to 100% hypertrophied rat hearts. The myosin kinase were purified approximately 600 fold with 6% yield by ion exchange chromatography and calmodulin-affinity chromatography. The presence of very important levels of proteolytic activity in the rat heart resulted in a partial loss of the myosin kinase calmodulin-dependency. The major component from both myosin kinase purified fractions was a 63 kdaltons protein. The protein content was identical in myosin kinase purified fractions from sham-operated and hypertrophied hearts. The calmodulin-dependent activity of myosin kinase, assayed in the presence of 0.1 mM Ca2+ and 10(-6) M calmodulin (about 6.6 nmol P X min-1 X mg-1), was identical in sham-operated and 50% to 100% hypertrophied hearts. Thus, myosin kinase specific activity, in these conditions, was unchanged in rat heart chronic hypertrophy. This result suggests that no direct functional relationship exists between the enzymatic properties of myosin and myosin kinase during the chronic phase of cardiac hypertrophy.

Adenosine Triphosphatases↗
PubMed1984

Isomyosins, microtubules and desmin during the onset of cardiac hypertrophy in the rat.

Chronic overloading of the rat heart induces a cascade of adaptational events which compensate for the increase in work. Two of these have been extensively described: a qualitative event with an isomyosin change leading to an improved efficiency and a quantitative event resulting in cardiac hypertrophy. By means of immunofluorescence, we investigated if elements of the cytoskeleton, i.e. microtubules and intermediate filaments, could be triggers for these adaptational mechanisms. Studies of overloaded heart were performed in young rats with aortic stenosis or adult rats with aortic insufficiency. Cardiac myocytes were isolated and labelled by immunofluorescence with antibodies raised against V1 or V3 isomyosin, desmin or tubulin. The aim of the work was to visualize: when and where the shift in the expression of isomyosins occurs within the myocytes; the eventual changes in the pattern of intermediate filaments of desmin and/or of microtubules during the adaptation of myocytes to overload. We observed: that the shift from the high (V1) to low (V3) ATPase isomyosin occurred in a population of myocytes soon after stenosis; that changes in the pattern of microtubules occurred soon after induction of hypertrophy; no changes in the distribution or intensity of the staining of desmin.

Adenosine Triphosphatases↗
PubMed1984

A study of treatment resistance among children referred for encopresis.

This study reports on some of the distinguishing characteristics of children with persistent encopresis who have proven, at long-term follow-up, to be resistant to intensive pediatric-based treatment at a referral outpatient clinic. Resistant children differed from responsive children primarily in two respects: they tended to have less stool retention at initial presentation, and their accidents occurred at all hours of the day. Additional information suggested that early success or failure did not presage long-term resistance and that parents' attributions of the cause of their child's soiling were related to outcome. Discussion centered on enumerating important high-risk factors that signal the need for more intensive intervention and follow-up.

Child↗
PubMed1984

Different distributions of microtubules, desmin filaments and isomyosins during the onset of cardiac hypertrophy in the rat.

To elucidate the role of the cytoskeleton in the development of adult heart, microtubules and intermediate filaments of desmin were studied in young and adult rat heart myocytes during the onset of growth, after mechanical overloading induced by aortic stenosis. Such overloading is known to cause heart hypertrophy by stimulating overall protein synthesis, and to initiate a shift in myosin isozymes. For this study, we used double immunolabelling of isolated myocytes with specific antibodies raised against tubulin, desmin, and the two main isomyosins V1 and V3. Whereas desmin remained unchanged, tubulin was redistributed in arrays parallel to the long axis of the myocytes, and was densest around the nuclei. Alterations in the microtubule pattern were observed very early after aortic stenosis, during the onset of heart growth; they were transitory, and did not occur simultaneously in all myocytes. Chronological examination of myocytes labelling with both antitubulin and anti V3 myosin clearly suggested that the transitory alteration in the microtubule pattern was an early event preceding the change in the expression of the myosin gene. Results, observed in young rats, in which mitosis is stimulated by overloading, and in adult rats, exhibiting no mitosis, showed that microtubules are involved in the development of cells in which mitosis does not occur. This work provides the first evidence of a correlation in functional adult heart, between the reorganization of cytoplasmic microtubules and the onset of growth.

Animals↗