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Biomedical subjects

M Silbermann

Publications and source records attributed to M Silbermann.

At least 127 records · Page 7Linked to original sources
PubMed1983

Morphometric analysis of aging skeletal muscle following endurance training.

Aging of skeletal muscle in the hindleg of the mouse is accompanied by a progressive increase in the amount of the interstitial tissue and especially that of lipid cells and fibroblasts. Quantitative analysis indicates that there was a nonsignificant increase in the total number of muscle fibers per unit area, perhaps due to a splitting process. The proportion of high oxidative fibers was decreased to a nonsignificant degree, and the remaining high oxidative fibers underwent a significant compensatory hypertrophy. Concomitantly, the number of low oxidative fibers increased significantly. This study revealed that endurance training in young animals induced morphometric changes very similar to those noticed in intact aging animals (i.e., splitting phenomenon, hypertrophy of high oxidative fibers, and an increased proportion of low oxidative fibers). It also became apparent that the skeletal muscle of old animals lacks the capacity to respond to enforced training, except for a further increase in the proportion of low oxidative fibers. It appears that aging muscle is unable to adapt to changing environmental circumstances.

Aging↗
PubMed1983

Changes in the structure and chemical composition of the mandibular condylar cartilage of the neonatal mouse.

The cartilage of the mandibular condyle of growing mice was used to monitor changes in the content of protein, DNA, hydroxyproline, hydroxylysine, uronic acid, calcium and phosphate. Protein and DNA increased in a stepwise fashion with one spurt seen during the first 2 weeks of post-natal life a second immediately after weaning. Hydroxyproline increased during the entire growth period, i.e. until the 8th post-natal week. Hydroxylysine increased only until week 4. The content of the uronic acid fluctuated and showed highs and lows throughout the growth period. Both calcium and phosphate increased in an almost parallel fashion from birth until the stage of tissue maturation. Morphological studies indicated that the hyaline type of cartilage in the newborn is gradually replaced by a fibrous tissue, which reveals a markedly different structure and composition.

Animals↗
PubMed1983

The effects of enforced running on the gastrocnemius muscle in aging mice: an ultrastructural study.

C57BL/6J mice (6, 19 and 27 months old) were trained in an electrically driven treadmill for a total period of 10 weeks. The training program started with 5 min. run per day and reached a maximum of 30 min. per day. Light and electron microscopy examinations of the gastrocnemius muscle showed that in young animals endurance training did not evoke any appreciable changes. In contrast, both test animals and their controls in the old group revealed clear signs of muscle cell atrophy which for the most part was accompanied by focal loss of myofilaments, mitochondrial changes and an increase in the amount of endomyseal collagen fibrils. In the old-trained group, the most obvious abnormality comprised of multiplication of both the T-tubules and of the tubules of the sarcoplasmic reticulum. Consequently, most of these animals showed the formation of tubular aggregates in their gastrocnemius muscle. Hence, it appears that endurance training in old animals tends to enhance the regressive changes that accompany the aging process of mammalian skeletal muscle.

Aging↗
PubMed1983

Incorporation of bone graft covered with methylmethacrylate onto acetabular wall. An experimental study.

The acetabular model, as described in the present study, appears to serve as a promising experimental model for grafting procedures since it promotes the acceptance of autogenous grafts and the induction of new bone formation. Further, the biologic and mechanical properties of the femoro-acetabular joint appear permissive to the development of an efficient reparative system even when a foreign material such as methylmethacrylate cement is incorporated into the overall reconstructive procedure. Hence, it is hereby recommended to utilize the biological approach in the frame of replacement arthroplasty of severely damaged acetabulum.

Acetabulum↗
PubMed1983

The effect of 1,25-dihydroxyvitamin D3 on cartilage growth in neonatal mice.

The in vivo effects of 1,25(OH)2D3 on cell proliferation, tissue organization and matrix mineralization have been studied in condylar cartilage of neonatal mice. A relatively low dose of the metabolite, 50 ng/kg body weight, significantly reduced the incorporation of [3H]thymidine as well as the number of chondroblasts. The cartilage as a whole underwent a marked derangement in its organization, as many fibroblastlike cells appeared to occupy the zone of progenitor cells. There was a high degree of correlation observed between the effects of 1,25(OH)2D3 upon [3H]thymidine incorporation and the size of the condylar zone of chondroblasts. With increasing doses, enhanced mineralization was noted in the cartilaginous matrix, along with cartilage cell degeneration. These findings indicate that 1,25(OH)2D3 possesses an inhibitory effect upon both the proliferative activity of prechondroblasts and upon the capacity of those cells to differentiate into chondroblasts.

Animals↗
PubMed1983

Glucocorticoid hormone adversely affects the growth and differentiation of cartilage cells in neonatal mice.

Condylar cartilage of neonatal mice served as an experimental model to study the late in vivo effects of a single dose of a fluorinated synthetic analogue of cortisol on cartilage cell growth and development. Forty-eight hours after the administration of triamcinolone hexacetonide, the proliferative rate of chondroprogenitor cells decreased significantly. However, by the 6th day a marked recovery took place when the total number of 3H-thymidine labelled cells increased by 52.9%, and by 13 days hormone-treated condyles revealed an increase of 93.1% in the total number of labelled cells. At the same time, the magnitude of the chondroprogenitor zone increased by 194.4% and it was found to contain a large population of fibroblast-like cells. The latter were found to synthesize type I collagen and fibronectin, lacked any specific organization and occupied larger portions of the condylar head. Twenty days following the administration of the hormone the newly-formed mass of fibroblast-like cells penetrated the underlying cartilage, split it and formed a direct communication with the marrow cavity. Ultrastructural examination further substantiated the fibroblastic nature of the newly-formed cell population. Hence, it seems very possible that if a corticosteroid hormone is administered to newborn animals it possesses the capacity to affect the normal differentiative pathway of pre-chondroblasts and shift their developmental pathway toward the fibroblastic cell line.

Animals↗
PubMed1982

Landmarks in chondrocyte differentiation and maturation as envisaged by changes in the distribution of calcium complexes: an ultrastructural histochemical study.

Organ cultures of fetal condylar cartilages have been examined using the K-pyroantimonate-osmium fixation method to follow alterations in cellular calcium distribution in maturing cartilage. Special attention has been given to analyzing the temporal and spatial relationships among intracellular calcium accumulation, cell maturation, and matrix mineralization. The findings of this study suggest that concomitant with the change in cellular metabolism from aerobic respiration to glycolysis there is a distinctive change in the distribution of cellular and matrical calcium complexes. This ultrastructural histochemical method can thus be used to evaluate the maturational state of chondrocytes actively involved in endochondral ossification.

Animals↗
PubMed1982

Viability and osteogenicity of bone graft coated with methylmethacrylate cement.

The idea of utilizing bone grafts during hip arthroplasty has been discussed in the literature and clinical successes have been indicated. These communications, however, did not relate to long-term results. Thus, to date, we still lack sufficient understanding as to the fate of bone grafts when they are coated with methylmethacrylate. In order to elucidate the above issue further an experimental study has recently been initiated in an attempt to provide answers to the following questions: a) do bone grafts remain viable when they are held in place with methylmethacrylate bone cement? and b) do such grafts retain their osteogenic potential? In the present study osteotomies were made in the femora of dogs and cortico-cancellous strips of autogenous bone were placed around the osteotomy site. The grafts were then surrounded by polymethylmethacrylate bone cement. Mechanical examination and morphological studies, performed 3, 6 and 10 months following surgery, revealed the elaboration of fibro-osseous union. Our present findings tend to indicate that bone grafts, even if they are covered with methylmethacrylate bone cement, still retain their viability as well as their osteogenic potential.

Animals↗
PubMed1982

Studies on hormonal regulation of the growth of the craniofacial skeleton: II. Effects of a glucocorticoid hormone on sulfate incorporation by neonatal condylar cartilage.

Condylar cartilage of neonatal mice served as an experimental model to study the early in vivo effects of a single dose of a fluorinated synthetic analogue of cortisol on sulfate incorporation and matrix metachromasia. Twenty-four hours after the administration of triamcinolone hexacetonide condyles incorporated significantly less 35SO4, a feature that followed a dose-response relationship. Dexamethasone, another fluorinated synthetic analogue of cortisol, evoked a similar effect, as did triamcinolone. On the other hand, corticosterone, the natural glucocorticoid in rodents, induced a markedly milder effect, whereas hydrocortisone lacked it altogether. Progesterone, a nonglucocorticoid steroid hormone, induced a reverse effect as it was found to increase 35SO4 incorporation into condylar cartilage. The hormonal inhibitory effect upon 35SO4 incorporation persisted, for the most part, for 2 days, and thereafter the sulfation process appeared to have returned to normal values. Of interest was the finding that the latter response was not accompanied by distinct changes in the degree of matrix metachromasia when measured at the chrondroblastic zone. It, therefore, seems possible, though not as yet proved, that concomitant with the transient inhibitory effects on 35SO4 incorporation, the hormone also induced changes in the degradative processes within the cartilage matrix.

Animals↗
PubMed1981

Changes in gastric parietal cells during prolonged intermittent corticosteroid treatment.

Immature A/J mice were treated for up to 7 weeks with intermittent doses of triamcinolone hexacetonide and were thereafter allowed to recover for 7 weeks. Structural examinations and morphological measurements were performed on the parietal cells in the gastric mucosa. By the 3rd injection a significant decrease was noted in the number of the above cells - a feature that lasted throughout the experimental period. In contrast, the diameter of the parietal cells increased. However, following recovery, the latter returned to their normal size.

Animals↗
PubMed1981

Glucocorticoid-induced changes in the activity of cartilage alkaline phosphatase.

Glucocorticoid hormones are known to exert distinct inhibitory effects upon cartilage metabolism and endochondral bone growth. This study examined the influence of triamcinolone hexacetonide, a long-acting synthetic analogue off cortisol, on the activity of non-specific alkaline phosphatase i condylar cartilage of neonatal mice. Four-day-old mice received a single dose (10 mg/kg) of the hormone and the activity of beta-glycerophosphatase was assayed 3 and 6 days thereafter. Whereas no significant changes were noted in the enzyme's specific activity, distinct alterations were observed in the latter's distributional pattern. By 48 hours cells along both the proliferative and chondroblastic zones exhibited a significant enhancement of alkaline phosphatase activity. This increase in enzyme activity was most prominent along the cells' plasmalemma and within their adjacent matrix. Thus, glucocorticoid hormones possess a significant stimulatory effect upon alkaline phosphatase activity in very young cartilage cells which in turn might affect the mineralization process.

Alkaline Phosphatase↗
PubMed1981

Liver growth retardation in corticosteroid-treated neonatal mice.

This study examined the influence of triamcinolone hexacetonide on the growth and nucleic acid synthesis in the liver of neonatal mice. Following a single dose of the hormone the synthesis of DNA was significantly depressed, a feature that lasted for 72 hours. Thereafter an almost full recovery took place and by 144 hours no significant differences existed between hormone-treated livers and their nontreated controls. The above inhibitory effect was dose-dependent and was specific to steroids with glucocorticoid activity. A markedly different response was noted in regard to RNA synthesis. Hormone-treated livers revealed an initial increase in the uptake of 3H-uridine and RNa synthesis but later on revealed a significant decrease in the incorporation of uridine resulting in a marked reduction in the tissue's content of RNA. Concomitantly, the hormone increased significantly the protein content of the liver. It thus became clear that glucocorticoid hormones possess both a significant inhibitory effect upon the proliferative activity of neonatal hepatocytes and interfere with the latters' protein synthetic machinery, thereby affecting the normal growth of the liver at its critical period of growth and development.

Animals↗