PubMed Health⌕ Search

Biomedical subjects

J Dainat

Publications and source records attributed to J Dainat.

At least 19 recordsLinked to original sources
PubMed2001

SFRP2 expression in rabbit myogenic progenitor cells and in adult skeletal muscles.

Satellite cells derived from fast- and slow-twitch muscles have different properties in culture. We have used the differential display technique to retrieve genes differentially expressed in fast- and slow-twitch muscle satellite cell cultures. Amongst these genes we have identified, cloned, sequenced and studied the expression in muscle of rabbit secreted frizzled related protein 2 (SFRP2) mRNA, whose importance in cell fate determination has been well documented. It has been shown that SFRP2 is widely expressed in the developing embryo but its expression in the adult is much more restricted. We show that primary cultures of satellite cells from adult rabbit fast- and slow-twitch muscles strongly and differentially express SFRP2 mRNA. Embryonic rabbit muscle cell primary cultures also strongly express SFRP2 mRNA whereas the myoblast C2.7 cell line shows little expression. We also studied SFRP2 mRNA expression in growing, regenerating and denervated muscles. Embryonic rabbit muscles express SFRP2 mRNA but this rapidly falls off after birth. In adult rabbit muscles SFRP2 mRNA is detected within 1 day of either muscle damage or denervation. Thereafter the SFRP2 mRNA expression profiles are different for fast- and slow-twitch muscle. The function of SFRP2 in muscle is unknown but its putative activity as a Wnt antagonist and its precocious expression after muscle damage suggest a role in satellite cell activation.

Aging↗
PubMed1991

Effects of thyroid state alterations in ovo on the plasma levels of thyroid hormones and on the populations of fibers in the plantaris muscle of male and female chickens.

Propylthiouracil (PTU), thyroxine (T4) or thyreoliberin (TRH) were injected in ovo to modify the thyroid state of chicken embryos. Significant sexual differences were observed in the effects of these treatments on the plasma concentrations of thyroid hormones and on plantaris muscle characteristics (DNA, RNA, populations of muscle fibers) in 3- and 35-day old male and female chickens. The T4 plasma concentration is lower in control males; it is decreased in PTU treated females and in the T4 treated females at 35 days. The T3 plasma concentration is lowered at 3 days in all treated chickens and also at 35 days in the TRH treated animals. The slow (STnO) and the fast (FTOG) fibers of the plantaris are always more numerous in males. In controls, the number of FTOG fibers remains steady between 3 and 35 days; at the same time, the number of STnO fibers rises in males only. Both PTU and T4 treatments increase the number of the FTOG and the STnO fibers respectively before and after the 3rd day. TRH treatment increases the number of STnO fibers at 3 and 35 days in males, but reduces it at 3 days in females. Thus changes in the number of FTOG fibers can be induced during in ovo myogenesis, whereas the number of STnO fibers may increase after hatching.

Animals↗
PubMed1989

[Properties of skeletal muscle fibers. II. Hormonal influences].

The skeletal muscle contains fibers with various contractile and metabolic properties. These populations of muscle fibers differ in their sensitivity and their response to circulating hormones which also affect the muscular differentiation (multiplication and fusion of myoblasts into myotubes). This review deals with the regulations of energy metabolism and of protein synthesis in muscles by several hormones acting either directly, or in association with other hormones, or by induction of growth factors. In most cases, hormonal effects seem to depend on the type and level of activity of the constitutive muscle fibers. The muscle fiber types involved in the anabolic properties of estrogens have not yet been clearly described. In the case of growth hormone and insulin, the slow fiber type is mainly affected; their effects are partially mediated through an increased secretion of somatomedins (IGFs) or by interaction on IGF receptors. The other reported hormones or factors induce a shift toward a more potent fast contracting activity, ultimately increasing the percentage of fast glycolytic fibers. Androgens, catecholamines and beta-agonists are anabolic and produce an enlargement of these fibers, whereas thyroid hormones or glucocorticoids in excess increase their catabolism.

Animals↗
PubMed1988

Postnatal changes in insulin binding in slow and fast-twitch rabbit skeletal muscles.

Changes of insulin binding characteristics (number of receptors, Kd) were studied in the semimembranosus proprius (SMP) and psoas major (PM) muscle from birth to adult stage. The Kd was about 0.15 10(-9) M in both muscles and did not change with age. The numbers of receptors were similar in both muscles at birth and changed differently thereafter to reach 1.3 fmoles per mg of muscle in the PM and 5.6 in the SMP muscle.

Aging↗
PubMed1986

Ontogenesis of triiodothyronine nuclear receptors in three skeletal muscles in male and female chicks.

The ontogenesis of nuclear triiodothyronine receptors was determined in the pectoralis (alpha W fibers: fast contracting, glycolytic metabolism), adductor brevis (alpha R fibers: fast contracting, oxido-glycolytic metabolism) and adductor magnus (beta R fibers: slow contracting, oxidative metabolism), muscles of male and female chickens at 18 days in ovo and 0, 6, and 30 days ex ovo. In the fast muscles (adductor brevis and pectoralis major), the T3 receptor number decreases from the 18th day of incubation to hatching or the 6th day after hatching, respectively, and then increases. In the slow muscle (adductor magnus), the T3 receptor number increases from 18 days in ovo to hatching and then decreases. At 30 days after hatching, the number of T3 receptors was higher in the fast muscles than in the slow one. A comparison of the two fast muscles reveals that the number of T3 receptors was more elevated in the pectoralis (glycolytic) fibers than in the adductor brevis (oxido-glycolytic) fibers. An overall test of significance showed a higher number of T3 nuclear receptors in muscles from females than from males.

Animals↗
PubMed1984

Perinatal age and sex variations of the triiodothyronine nuclear receptors in the chick pectoralis major muscle.

The ontogenesis of the nuclear triiodothyronine receptors was determined in the pectoralis muscle of male and female chicken at 18 days in ovo and 0, 3, 6, 14 and 35 days ex ovo. Our results show the presence of putative T3 nuclear receptors with equilibrium dissociation constant values (Kd approximately 5.50 X 10(-10) M) in good agreement with these reported in other tissues. The T3 receptor numbers decrease from 18 days incubation to 6-day-old animals, then increase until 35 days of age. Compared to the already reported levels of thyroid hormone in plasma and tissues, the results seem to correspond to a down-regulation of the muscle T3 receptors. The nuclear binding capacity of T3 was higher in females than in males, which could be related to the known effects of various sex steroid hormones on the T4 to T3 tissue conversion.

Age Factors↗
PubMed1983

Autoradiographic study of neurogenesis in the duck olfactory bulb.

Neurogenesis was studied in the duck olfactory bulb by injection of tritiated thymidine into the eggs at 53 h and at the 3rd, 5th, 8th, 10th, 12th, 14th and 18th days of incubation. The large neurons appear before the small ones: the mitral cells arise between embryonic day 3 (E3) and E5, the tufted cells between E5 and E8 and the granular cells between E12 and E14. The periglomerular cells could be formed after E18. The order of appearance of this 4 main neurons of the duck olfactory bulb is the same as that in the mouse. All the neurons, except maybe for the periglomerular cells, are principally formed before the hatching of the duckling and the olfactory sense seems to have acquired most of its principal functional aptitudes at this moment.

Animals↗
PubMed1981

Quantitative study of synapse formation in the duck olfactory bulb.

Synaptic emergence and development in the duck olfactory bulb was quantitatively studied by electron microscopy from the 14th day of incubation (E 14) to the adult stage. Overall synaptic density in this bulb grew considerably during the last weeks of embryonic life and the first postnatal week. The pattern of synaptic density development was similar in the four main architectonic layers of the bulb. However, lower density values were observed in the mitral and inner granule cell layers. In the glomerular layer (GL), axodendritic synapse density was always higher than dendrodentritic synapse density. In the external plexiform layer, most synapses were dendrodendritic and were established between the gemmules of the granule cells (GC) and the dendrites of the mitral cells (MC) or tufted cells (TC). Synapses established by MC and TC on GC gemmules, or by GC on MC and TC dendrites had densities very similar to each other at all the stages studied. Reciprocal synapses already appeared at E 14; their density grew until a week after birth (P7) and thereafter remained stable. In the internal granular layer, the density of asymmetrical synapses was always higher than that of symmetrical synapses. Excitatory synapses formed earlier on MC and TC than inhibitory synapses. The ratio of inhibitory-to-excitatory synapses rose rapidly after birth, reaching 2.5 in the adult duck. The density of excitatory synapses received by granule cells was as high in the external plexiform layer as in the inner granule layer, at all stages of GC development. However, the ratio of received-to-formed synapses fell in these cells from 8.42 at E 14 to 2 after birth. These results are discussed as a function of the evolution of the different synaptic balances during olfactory bulb development. Synaptic development in the duck olfactory bulb at birth is relatively close to the adult state. It appears sufficiently advanced to enable the olfactory system to function in a way compatible with the relatively independent behavior displayed by the duckling.

Aging↗
PubMed1980

Cerebellar tRNA methyltransferases: a developmental study.

Developmental patterns of homologous and heterologous tRNA methylation by cerebellar tRNA methyltransferases are described. The study revealed that: (a) homologous tRNA methylation results in the predominant formation of N2-methylguanine and 1-methyladenine; (b) tRNA methyltransferase of bulk-isolated Purkinje and granule cells methylate E. coli tRNAglu2 in vitro in a characteristic manner, and (c) the methylation of 8-day-old cerebellar, cortical and hepatic tRNA in vivo yields tRNAs containing different proportions of methylated bases. The findings suggest that the presumably cell-specific populations of cerebellar tRNA methyltransferases continue to alter their substrate recognition characteristics up to and beyond the first month of post-natal life.

Aging↗
PubMed1979

Age-dependent changes in the specificity of tRNA methyltransferases in the cerebellum of the icteric and nonicteric Gunn rat.

The activity of tRNA methyltransferases present in the cerebellum of 6- and 21-day-old nonicteric and icteric Gunn rats was compared using purified E. coli tRNAs as substrates. At 6 days the tRNA methyltransferases of the icteric animals were significantly more effective in methylating tRNAGlu2 and tRNAPhe than were those of their nonicteric counterparts. This relationship reversed itself at 21 days. The action of the tRNA methyltransferases from the 6-day-old icteric animals led to higher proportions of 1-methyladenine in tRNAGlu2 and tRNAPhe than were obtained using the corresponding enzymes of the nonicteric animals. The proportion of N2-methylguanine was also higher, yet only in tRNAfMet and not in tRNAPhe. The study reveals much more extensive fluctuations in the activity and in the substrate recognition specificity among the cerebellar tRNA methyltransferases of the icteric than among those of the nonicteric controls during the crucial 6--21 day period of cerebellar development.

Aging↗
PubMed1978

[Effects of thyroid hormones and heat value restriction of food intake on the glial surrounding and soma development of Purkinje cell (author's transl)].

Hyper- and hypothyroidism repercussions on soma, nucleus and cytoplasm increases were studied by electron microscopy on 7-, 14-, 21-, and 35-day-old rats. Adult normal animals were compared with adult ones made hypothyroid until they were 35 days old. Also heat value restriction of food intake effects were compared with hypothyroid ones at 14 and 35 days. Hyperthyroidism accelerated the soma and cytoplasm size increase as early as 14 days, and the nucleus size increase as early as 21 days. It did not change the nucleo-cytoplasmic ratio (N/P) markedly, except that maximal value of this ratio was reached earlier than in normal animals. Heat value restriction of food intake led to a transitory soma size decrease at 14 days and a high nucleus size increase. This diet did not change markedly either cytoplasm size or N/P ratio value. Hypothyroidism slackened the rate of the soma, nucleus and cytoplasm size increase during the third postnatal week especially. Beyond, these structures went on increasing and their size became greater than normal in adult hypothyroid animals. N/P ratio was always superior to normal. Hypothyroidism led to a high volumetric and linear density of Purkinje cell soma glial surrounding. Hyperthyroidism caused a slight increase of these parameters which were not greatly changed by heat value restriction of food intake.

Animals↗
PubMed1978

Variations au cours de la journée de l'incorporation in vivo de la leucine tritiée dans les protéines du cervelet et du cerveau du jeune rat normal et hypothyroïdien. Daily variations of the in vivo [3H] leucine incorporation into the cerebellar and cerebral proteins of the normal and hypothyroid young rat [(author's transl)].

In the normal and hypothyroid 6-day-old rat, the specific radioactivity (RSA) and the relative RSA (ratio of the RSA to the [3H] lecine concentration of the acido soluble phase) of the cerebral and cerebellar proteins, changes during the day synchronally. They show a maximum at 15.00 h and a minimum at 0.300 h. At all stages studied, these values are significantly lower in the hyothyroid animals than in normal ones.

Animals↗
PubMed1978

Correction of the biochemical effects of neonatal hypothyroidism by daily low doses of thyroxine. Comparative effects of hyperthyroidism and these corrections.

The purpose of the present communication was to study the corrective effects of low daily thyroxine doses, on the cerebellum biochemical maturation in propylthiouracile (PTU)-treated rats during the early postnatal life. The corrected hypothyroid animals were compared to the normal, hypo- and hyperthyroid ones. The protein, RNA and DNA cerebellar contents were evaluated at 6, 10, 14, 18 and 35 days old animals. At all ages hypothyroidism and hyperthyroidism decreased cerebellar protein, RNA and DNA contents, except in 35-day-old hyperthyroid animals, where DNA content returned to normal level. In these two experimental groups, protein/DNA and RNA/DNA ratios were higher than those of controls at 10 days and lower at 35 days. In hypothyroid animals treated by corrective doses of T4, cerebellar protein, RNA and DNA contents and DNA concentration were not different from hyperthyroid animal values at all stages, while protein/DNA and RNA/DNA ratios were higher than those of hyperthyroid animals. Administration of physiological doses of T4 to hypothyroid animals led to the same effects as higher doses in normal animals. Thus, neonatal hypothyroidism seems to lower the sensitivity threshold of the cerebellum to thyroid hormone effects.

Age Factors↗
PubMed1977

[Repercussions of hyperthyroidism on the total cerebellar DNA contents in the rat at 6 and 35 days of age. Comparative effects of LT3 and DLT4 (author's transl)].

The total cerebellar proteins RNA and DNA contents from DLT4-and LT3-treated rats was studied at 6 and 35 days of age. The effect of injections of 5 microng/j of DLT4 is comparable to that of 25 microng of LT3 at birth, followed by 0.5 microng every 2 days. On the other hand, injection of 0.5 microng of LT3 every 3 days does not induce any significant modification of the total DNA contents in the cerebellum.

Aging↗
PubMed1976

[Quantitative ultrastructural study of the perikaryon of the Purkinje cell and of the adjacent area in normal and hypothyroid rats aged 21 days].

The effects of neonatal hypothyroidism on synaptic organization, glial surrounding and cytoplasmic structures of the Purkinje cell perikaryon of the 21 days old rat were studied by electron microscopy. Hypothyroidism decreases the size of the perikaryon but does not change the nucleo-cytoplasmic ratio of the cell. At 21 days the axonal endings that make synapse on the Purkinje cell perikaryon, already show the adult morphological features and hypothyroidism does not change these. The general synaptic density on the Purkinje perikaryon is not significantly altered, but the cells of hypothyroid animals still recieve 1/3 of their axo-somatic synapses on somatic spines, whereas euthyroid animals have practically no synapses on somatic spines. Hypothyroidism leads the disappearance of the synchronism which normally exists between the translocation or resorption of the Purkinje cell somatic spines and the establishment of the basket cell synapses. The basket cell axons of the normal animals form synapses only on the smooth surfaces of the Purkinje cell perikaryon while they also establish it on the somatic spines of the hypothyroid animals. The density of the axon terminals of basket cells is decreased, while that of the endings of Purkinje cell axon collaterals and of climbing fibers are increased. Hypothyroidism produces an increase in the size of the glial sheath around the Purkinje perikaryon. It does not alter the proportion of the cytoplasmic area occupied by mitochondria, but in thyroid deficiency there is an increase in the numbers of mitochondria which are reduced in average size. The Golgi apparatus is only slightly affected. Thyroid defiency does not alter the density of the cytoplasmic agreggates of free ribosomes but there is a decrease in density of the ergastoplasm and a disorganization of the Nissl bodies.

Animals↗