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Biomedical subjects

P Vigneron

Publications and source records attributed to P Vigneron.

At least 37 records · Page 2Linked to original sources
PubMed1986

Characterization of insulin binding to slices of slow and fast twitch skeletal muscles in the rabbit.

Insulin binding was studied in rabbit semimembranosus proprius and psoas major muscles composed of slow-twitch oxidative (SO) and fast-twitch glycolytic (FG) fibers, respectively. For this purpose, we developed a technique using cryostat microtome muscle slices. Degradation of 125(I)-insulin during the incubation period was prevented by the addition of 1 mM bacitracin in the buffer. Specific binding to muscle slices plateaued by the 24 hrs. of incubation at 4 degrees C. It increased as a function of the amount of muscle, with a maximum binding occurring at about 5 mg of muscle slices. Triton X-100 has been shown to increase specific binding from a critical concentration of 10(-4) M with a maximum effect occurring at 3.3 10(-4) M. Under this condition, the binding was specific since displacement studies showed no inhibition of 125(I)-insulin binding by GH, HCG, ACTH and glucagon, whereas half maximal inhibition was achieved using 5 10(-10) M insulin, 3 10(-9) M IGF1 and 2 10(-8) M proinsulin. The analysis of the binding data yielded curvilinear Scatchard plots. The number of high affinity insulin receptors was higher in the SO muscle than in the FG muscle (4.3 +/- 0.7 vs 0.7 +/- 0.2 fmol/mg fresh muscle; P less than 0.001) with similar high affinity dissociation constants (Kd = 1.5 10(-10) M). Analogous results were obtained using muscle microsomal fractions. The differences in insulin binding might be related to the more intense metabolism of SO fibres which contract more often than FG fibres in vivo.

Animals↗
PubMed1985

Retrograde effect of muscle on forms of acetylcholinesterase in peripheral nerves.

In the peripheral nerves of birds and mammals, acetylcholinesterase (AChE) exists in four main molecular forms (G1, G2, G4, and A12). The two heaviest forms (G4 and A12) are carried by rapid axoplasmic transport, whereas the two lightest forms (G1 and G2) are probably much more slowly transported. Here we report that nerves innervating fast-twitch (F nerves) and slow-twitch (S nerves) muscles of the rabbit differ both in their AChE molecular form patterns and in their anterograde and retrograde axonal transport parameters. Since we had previously shown a selective regulation of this enzyme in fast and slow parts of rabbit semimembranosus muscle, we wondered whether the differences observed in the nerve could be affected by the twitch properties of muscle. The results reported here show that in F nerves that reinnervate slow-twitch muscles, both the AChE molecular form patterns and axonal transport parameters turn into those of the S nerve. These data suggest the existence of a retrograde specific effect exerted by the muscles on their respective motoneurons.

Acetylcholinesterase↗
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↗
PubMed1980

Influence of experimental hypothyroidism on chick myogenesis.

The influence on chick myogenesis of hypothyroid status induced in ovo by methimazole was histologically (number and types of muscle fibers) and biochemically studied. A single injection of methimazole induced an hypothyroid status during embryogenesis, as shown by the plasma T4 levels which were separately assayed in male and female controls and treated embryos from day 12 of incubation to day 4 after hatching. In both sexes, control plasma T4 reached a peak on day 20 of incubation, but the female values were significantly higher; plasma T4 in the treated embryos remained at a low level independently of sex. Only methimazole-treated males showed a significant increase (P less than 0.01) in the total number of fibers of the two muscles (tibialis posterior and flexor digitorum) studied. Moreover, the histochemical results on succinate dehydrogenase and myofibrillar ATPase evidenced that, of the three fiber types (alpha R, alpha W and beta R) constituting the skeletal muscles, only the alpha fibers increased significantly. Aldolase (glycolytic) and NADP isocitrate dehydrogenase (tricarboxylic acid cycle) activities, measured on the adductor and pectoralis muscles, showed a similar developmental pattern in control and treated animals, but was retarded in the latter due to a 5-day delay in hatching. It is not known whether the tissular differences were related directly to the hypothyroid status, to alterations in nervous system differentiation or, as suggested by intersexual differences, to modifications in hormonal balance.

Animals↗
PubMed1979

[Sexual differences in the development of plasma thyroxine levels in the embryo and young chick].

Plasma thyroxine (T4) levels were separately ascertained in male and female embryo and young chicken from the 12th day of incubation till the 4th day after hatching by the thyroxine binding globulin technique. In both sexes, plasma T4 reach a peak the 20th day of incubation, but values are significantly higher in females. A sharp decrease occurred thereafter, plasma T4 tending toward adult values the 4th day after hatching.

Aging↗
PubMed1979

Nonfunctional and functional occlusal contacts: a review of the literature.

A review of the literature on occlusal contacts emphasizes the following points. 1. Contacts in centric occlusion do not correspond to any ideal occlusal diagram. 2. Canine protection and group function appear to correspond to two successive states of the evolving dentition under the effect of abrasion. In most lateral occlusions, two maxillary teeth, of which one is the canine, are involved. 3. During mastication, tooth contacts exist. They occur most often during a sliding movement in which the direction and the origin are variable. This justifies the concept of an occlusal field of mastication. 4. During unilateral mastication, the chewing of the food is performed by working as well as nonworking contact. This imposes the distinction between the chewing and nonchewing sides (functional) and the working and nonworking sides (kinematic). 5. Centric occlusion is the occlusion most often used during mastication. It is also the occlusion for which the masticatory forces are the greatest. 6. The bibliographic data concerning occlusal contracts during swallowing are largely contradictory. It nevertheless seems that the occlusal contacts obey laws nearly the same as those governing the occlusal contact during mastication (sliding on an occlusal field of deglutition, and the importance of centric occlusion).

Deglutition↗