Biomedical subjects

M Silbermann

Publications and source records attributed to M Silbermann.

At least 73 records · Page 4Linked to original sources

PubMed1989

Age-related bone loss in lumbar vertebrae of CW-1 female mice: a histomorphometric study.

Age-related changes in vertebral cortical and trabecular bone were quantitated in female CW-1 mice. Histomorphometric measurements involved the use of two different systems of image analysis: Olympus Cue 2 and Zeiss Morphomat 10. The peak of bone mass, both cortical and trabecular, was found in mice aged 13.5 months. Thereafter, there was a progressive decline in the area occupied by bone tissue and this became highly significant in elderly female and male mice. A loss of about 60% of bone tissue was encountered in both the trabecular and cortical bone, as determined by automated image analysis system. Hence, aging CW-1 mice reveal structural features consistent with vertebral osteopenia. Despite the fact that to date we lack the precise etiology for the above-mentioned phenomenon, it is suggested that the laboratory mouse might serve as an appropriate experimental model for investigations related to age-related bone loss.

Aging↗

PubMed1989

Correlation between alkaline and acid phosphatase activities and age-related osteopenia in murine vertebrae.

Lumbar vertebrae (L4) from CW-1 female mice were examined for age-related changes in alkaline and acid phosphatase activities from young to old age. Histochemically, both enzymes were encountered along the bony surfaces of both trabecular and cortical bones with no significant age-related changes in their distribution. Biochemical determinations of bone alkaline phosphatase (Alk'ase) activity revealed that for a given unit level of bone or the bone as a whole no significant changes took place, whereas acid phosphatase (Acid'ase) activity was found to have increased significantly with age. A high positive correlative relationship was noted between the calcium content and the trabecular bone volume of the same vertebrae. It may, therefore, be proposed that age-related bone loss in mice could be attributed to an enhanced resorption rather than to a substantial reduction in the formative potential of bone cells.

Acid Phosphatase↗

PubMed1989

Effects of different concentrations of serum on cartilage growth in an organ culture system.

The purpose of the present study was to examine the effects of various concentrations of serum on the behavior of neonatal condylar cartilage when cultured in an organ culture system. Mandibular condylar cartilages were obtained from newborn ICR mice, of which the zone of undifferentiated chondroprogenitor cells along with a few layers of young cartilage cells were cultivated at the medium-air interface. The incubation medium included fetal bovine serum at concentrations ranging from 0 to 10%, and the explants were kept in vitro up to 10 d. The serum-free medium maintained the chondrogenic expression, and the overall size of the cartilagenous portion of the explants increased with the decrease of the concentrations of serum in the medium. When explants were labeled with [3H]thymidine and were then processed for autoradiography, the peak of labeling was noticed at 48 h, a feature that recapitulated itself in all cultures (73, 140, 175, 201, and 129 labeled cells per chondroprogenitor zone in explants grown in 0, 1, 2.5, 5, and 10%, respectively). It can be concluded that serum-free medium maintains the chondrogenic phenotype of condylar cartilage in vitro.

Animals↗

PubMed1989

Age-related changes in the cholinergic components within the central nervous system of CW1 female mice. I. Structural analysis.

Histomorphometric analysis of age-related structural changes in the brain was performed in CW1 female mice, 3, 9, 24 and 32 months of age. Cholinergic regions, such as the hippocampus, NBM and the medial habenula (MH) were investigated in more detail focusing on morphological parameters. The thickness of the frontoparietal cortex (FPC), and the surface area of the dorsal hippocampus and the MH were found to decrease significantly from 9 to 24 months of age. Except for the unique appearance of pseudo-cysts within the FPC, the structural changes culminated by 24 months. Cells' degeneration, in the CA3 hippocampal subfield, was noted already by 9 months of age whereas in other regions the cells' surface area decreased only between 9 and 24 months. Lipofuscin accumulation was most pronounced in the large neurons of the cortex, hippocampus and NBM at 24 months of age.

Aging↗

PubMed1989

Alkaline phosphatase activity in striated muscle: the effect of aging and long-term training in female mice.

Alkaline pNPPase (Alk'ase) activity was measured in bicarbonate buffer and in Triton buffer of striated muscles of aging mice. Between young age (4-9 months) and middle age (13-15 months) the enzyme specific activity increased by 41.8% in the bicarbonate buffer and by 22.6% in the Triton extraction. Thereafter, between middle age and old age (32 months), a marked decrease in enzyme activity took place in both the bicarbonate and Triton extractions (23.5% and 31.4%, respectively). Alk'ase activity in muscles of old mice that had been exposed for prolonged training (12-18 months), did not differ from that of age-matched controls in both types of extracts. However, cysteine, an Alk'ase inhibitor, affected the enzymatic activity in the various samples tested differently: in the bicarbonate buffer its inhibitory effect increased with age and training, whereas in the Triton extraction its effect decreased with age and following training. Thus, it seems conceivable that with age and following long-term physical exercise an overall functional change is taking place in muscle which makes Alk'ase more vulnerable. The membranous Alk'ase, however, appears more resistant to external inhibitors in the form of endurance training and to the aging process.

Age Factors↗

PubMed1989

Effect of thyroid hormone and growth hormone on recovery from hypothyroidism of epiphyseal growth plate cartilage and its adjacent bone.

Hypothyroidism was induced in young female Sprague-Dawley rats by the addition of methimazole (0.67 mg/ml) to drinking water for a period of 7 weeks (7-14 weeks of age). The responses of the articular cartilage, epiphyseal growth plate cartilage, epiphyseal trabecular bone, and metaphyseal trabecular bone in the proximal tibia were assessed by structural parameters. In addition, replacement therapies were introduced for the last 2 weeks of the experimental period. These included 0.7 U/kg BW human GH (hGH), 15 micrograms/kg BW L-T4 (T4), and a combination of hGH and T4 at the same doses. In the hypothyroid rats, the width of epiphyseal growth plate cartilage decreased by 27%, that of articular cartilage by 35%, epiphyseal trabecular bone volume by 30%, and metaphyseal trabecular bone volume by 66% relative to those in age-matched control tissues. T4 treatment led to a full restoration of the epiphyseal trabecular bone and surpassed by 40% the control value. The magnitude of the articular cartilage and the epiphyseal trabecular bone volume returned to control values, while that of metaphyseal trabecular bone was 68% of control values. Treatment with hGH did not improve the epiphyseal growth plate cartilage or articular cartilage. It did restore epiphyseal trabecular bone to almost normal values, but metaphyseal trabecular bone improved to only a small though significant level (45% of control value). The combination of T4 and hGH resulted in an additional enlargement in the width of the epiphyseal growth plate cartilage and an increase in metaphyseal trabecular bone volume compared to those in the T4 group. Qualitative examinations indicated that it was only in the T4 and T4 plus hGH groups that the lowest chondrocytes in the epiphyseal growth plate cartilage resumed their normal hypertrophied size. These results suggest that the change in the hypothyroid state do not rely solely on the lack of pituitary GH synthesis and secretion, as replacement by exogenous GH did not restore normal epiphyseal growth plate cartilage morphology or its remodeling into metaphyseal trabecular bone. Treatment with T4 (which restored endogenous pituitary GH to 30% of control levels) results in full recovery of the epiphyseal growth plate cartilage morphology along with its associated metaphyseal trabecular bone. In addition, it can also be concluded that the decrease in epiphyseal trabecular bone volume observed in the hypothyroid animals was due solely to the GH-deficient state that accompanied hypothyroidism.

Animals↗

PubMed1989

Effects of sex steroids on the response of cultured rat pituitary cells to growth hormone-releasing hormone and somatostatin.

In the male rat, GH secretion is characterized by high amplitude pulses that appear at regular intervals of 3-4 h, with low basal levels between such pulses. In the female, the pulses are irregular and more frequent, with lower amplitudes, while basal secretion is higher. The present study was designed to exclude the indirect effects of sex steroids on the pituitary, enabling investigation of the direct effects of sex steroids on the pituitary. Rats were gonadectomized at 22 days of age, and 12 days later their anterior pituitaries were trypsinized for cell dispersion. Testosterone (T) or 17 beta-estradiol (E2), 5 nM, was added to the medium for 6 days, and subsequently, GRF or somatostatin was added for 4 h. In a perifusion system, the male-derived cell response to GRF was augmented after pretreatment with T, but not with E2. The female-derived cell response to GRF was augmented by E2, but not by T. T increased the sensitivity of the cells to GRF from 3.0-0.03 nM and increased the maximal potency of GH secretion 3-fold. E2 had no significant effect on the sensitivity, but lowered the potency. Somatostatin (1 nM) inhibited GH secretion by 44% in T-treated cells. In E2-treated cells, somatostatin was ineffective. GRF increased the total amount of GH (medium plus cells) in both T- and E2-treated cells, but not in control pituitary cells. It is suggested that T has direct effects on the male somatotroph. By increasing the pituitary cell responses to GRF and somatostatin, T contributes to the high amplitude peak/low baseline pattern of the male. By decreasing the pituitary cell responses to GRF and somatostatin, E2 contributes to the low amplitude peak/high baseline pattern of the female.

Animals↗

PubMed1989

Human growth hormone enhances chondrogenesis and osteogenesis in a tissue culture system of chondroprogenitor cells.

GH is a systemic promoter of skeletal growth which increases the synthesis of insulin-like growth factor I in parenchymal tissues as well as in peripheral tissues such as the liver and growing cartilage. The present study was designed to examine whether GH possesses a direct effect on cellular proliferation and differentiation in mouse condylar cartilage. Cartilage progenitor cells were cultured in the form of a tissue culture on top of collagen sponges in medium containing 10% fetal calf serum and were treated with 50 ng/ml GH for 6 days. Three-day incubation with GH caused a marked increase in DNA synthesis and in the size of the culture, which developed into a nodule of differentiated chondrocytes and a well developed perichondrial layer around it. The effect of GH was even more pronounced after 6 days in culture; at which time a distinct network of trabeculae was noted throughout the extracellular matrix. The trabeculae contained osteocyte-like cells and were in close contact with both osteoblast-like and osteoclast-like cells. Using antibodies against bone-specific antigens, i.e. osteocalcin and osteopontin, provided further support for the notion that the newly formed trabecular formation was comprised of bone matrical components. Untreated control cultures lacked such structures, but contained hyaline-like cartilage. It, therefore, seems reasonable to suggest that GH induces a strong stimulatory effect on progenitor cell proliferation, cartilage differentiation, and extracellular mineralization, which supports de novo bone formation in vitro.

Alkaline Phosphatase↗

PubMed1989

Growth hormone stimulates the growth of mouse neonatal condylar cartilage in vitro.

This study used an organ culture system of neonatal condylar cartilage to study the in vitro effects of recombinant human growth hormone on the growth of cartilage and its inherent cell populations: progenitor cells, chondroblasts and early hypertrophic chondrocytes. Growth hormone at a dose of 2.5 nmol/l enhanced the overall growth of cartilage explant and stimulated the differentiation of its cells. Hence, growth hormone-treated explants revealed a substantial increase in the number of chondroblasts and young hypertrophic chondrocytes. Along with its effects upon cartilage the hormone also stimulated new bone formation adjacent to mineralized hypertrophic chondrocytes. These results provide support to the notion that growth hormone stimulates cartilage growth which in turn is followed by endochondral ossification. In spite of its in vitro effect it is not as yet clear whether the effect of growth hormone is indeed a direct one or is mediated via the local production of IGF-I.

Age Factors↗

PubMed1989

Structural and compositional changes in aging bone: osteopenia in lumbar vertebrae of Wistar female rats.

Changes in vertebral bone mineral content and density during aging were quantified in female Wistar rats. This study represents a longitudinal follow up utilizing single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (QCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV) and bone cortical area (BCA). The above measurements were accompanied by biochemical assays of calcium concentrations in the respective bones. All aging animals experienced significant decreases in BMC, BMD, TBV, BCA and in the calcium content of their bones. The above features have been further emphasized through the use of scanning electron micrographs showing the age-related structural changes in a three-dimensional fashion. New, advanced technologies will enable the quantitation of 3-dimensional images that are currently obtained from the scanning electron micrograph; thus will provide new consideration as related to trabecular bone compactness (density). Energy dispersive x-ray spectroscopy indicated that the nature of crystals in aging bones does not differ markedly from that encountered in young specimens. Data are also provided with regard to the health of the animals, and it became apparent that aging rats undergo changes in their kidneys yet do not show any significant change in renal functional parameters as measured in both the serum and the urine. Hence, new noninvasive methodologies are currently available for longitudinal studies related to the skeleton in laboratory animals enabling reliable monitoring of age-related and hormonally induced changes in bones (spine and hip) of well defined experimental models.

Absorptiometry, Photon↗

PubMed1988

Growth and repair of cartilage: organ culture system utilizing chondroprogenitor cells of condylar cartilage in newborn mice.

The zone of progenitor cells of mandibular condyles of neonatal mice was kept in an organ culture system for up to 8 days. Qualitative and quantitative determinations indicated a pronounced proliferative activity during the initial phases of the culture followed by a differentiation phase and the acquisition of typical hyaline cartilage. The mature hypertrophic chondrocytes were found to be surrounded by cartilage-specific macromolecules such as type II collagen, cartilage proteoglycans, and cartilage anchorin. The extracellular mineralization proceeded along matrix vesicles as is usually noted in vivo. A unique finding in this study was the observation that explants comprising cartilage progenitor cells and their adjacent extracellular matrix succeeded in repairing the damaged condylar in vitro.

Animals↗

PubMed1988

Triamcinolone impairs the synthesis of collagen and noncollagen proteins in condylar cartilage of newborn mice.

The effects of triamcinolone hexacetonide (TH) on the synthesis of collagen and noncollagen proteins were tested in mandibular condylar cartilage of newborn mice. Four-day-old ICR mice received a single i.p. injection of TH at doses ranging from 0.4 to 4.0 mg/kg body weight. Hydrocortisone, deoxycorticosterone, dexamethasone, and progesterone were administered at a dose of 4.0 mg/kg. Test animals and nontreated and vehicle-treated controls were sacrificed after 24, 48, and 72 hours and were processed for electron microscopy. Additional animals were injected with 5 microCi of 3H-proline 2 hours before sacrifice. The specimens were extracted with 5% TCA containing 1 mM proline followed by 5% TCA, acetone, and ether, homogenized and digested with purified bacterial collagenase, and the amounts of radioactivity in collagenase digestible (CDP) and noncollagen proteins (NCP) were determined. The present results revealed that triamcinolone led to a significant dose-dependent decrease in the protein content of the tissue that lasted for 3 days (12-14% at the dose of 4 mg/kg). The incorporation of 3H-proline into CDP was reduced by 39, 57, and 42% at 24, 48, and 72 hours, respectively whereas the incorporation into NCP was reduced by 20, 35, and 23%, respectively. When compared with other steroids, dexamethasone revealed a similar inhibitory effect, whereas hydrocortisone and deoxycorticosterone had no significant effect. Progesterone, on the other hand, showed a transient (24 hours) stimulatory effect on the synthesis of collagen synthesis (21%, P less than 0.05). Electron microscopy showed an atypical arrangement of collagen fibers and accumulation of large aggregates of collagen that filled the entire matrical space between cartilage cells.

Adrenal Cortex Hormones↗

PubMed1988

Ability of different techniques of measuring bone mass to determine vertebral bone loss in aging female rats.

Changes in vertebral trabecular bone were quantified in female Wistar rats. This study utilized single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (QCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV). The above measurements were accompanied by biochemical assays of protein and calcium concentrations in the tissues. Also, the activity of bone alkaline and acid phosphatases was measured. Lumbar vertebrae (L4, L5) in old rats 27 months old, compared with those of young rats 7 months old, showed significant decreases in BMC, BMD, TBV, protein and calcium, and enzyme activity. A high degree of correlation was recorded between the above changes. The various changes were accompanied by a marked reduction in the overall wet weight of the vertebrae. Hence, new noninvasive methods to quantitate bone mass can be applied in vivo to small laboratory animals such as the rat. These methods are much more accurate than standard radiographs in quantitating bone loss and are, therefore, recommended for experimental longitudinal studies related to aging of the skeleton.

Acid Phosphatase↗

PubMed1988

Rat epiphyseal cells in culture: responsiveness to bone-seeking hormones.

Cell cultures derived from young rat epiphyseal cartilage were grown for approximately 2 wk in BGJb medium supplemented with 10% fetal bovine serum to reach confluence. These cells were identified as chondrocytes as checked by morphology, the presence of alkaline phosphatase, and a positive type II collagen antibody reaction. The cells also responded to different hormonal treatment. Parathyroid hormone (PTH) increased cyclic AMP production by 50% within 15 min of treatment, whereas prostaglandin E2 (PGE2) caused an increase of 160%. Calcitonin (CT) did not affect cAMP production in these cells. DNA synthesis 24 h after hormonal treatment was increased by PTH (2.5-fold) and PGE2 (2-fold), but not by CT. Among the vitamin D metabolites, 24,25(OH)2D3 increased significantly the [3H]thymidine incorporation into DNA, whereas 1,25(OH)2D3 effect was minimal. These results provide evidence for the use of these cell cultures as a model for cartilage in vitro when studying biological and hormonal responsiveness.

24,25-Dihydroxyvitamin D 3↗

PubMed1988

Differentiation of cartilage cells studied by quantitative [3H]thymidine autoradiography in vitro.

The apical segments of the mandibular condylar cartilage of newborn ICR mice, containing the intact zones of progenitor cells along with a few rows of chondroblasts were initially prelabelled in vitro with [3H]thymidine and were subsequently chased and cultured for as long as eight days. Such explants underwent a process of tissue regeneration, as after three days in culture they reconstituted the original structure of the organ, thus resembling the in vivo appearance of neonatal mandibular condylar cartilage. Cellular proliferation with subsequent differentiation in the regenerating tissue was followed by means of quantitative autoradiography. Immediately after labelling, the autoradiography-positive grains were confined exclusively to progenitor cells. The latter revealed a substantial ability to proliferate in vitro, a fact that was manifested by a progressive increase in the labelling index along the course of the culture. The latter process was followed by cellular differentiation thereby obtaining hypertrophic chondrocytes. The increase in the rate of labelling index and in the total number of [3H]thymidine-labelled cells was significantly correlated with the overall growth of the regenerating explants.

Animals↗

PubMed1988

Abnormalities of intramuscular nerves in old mice: an ultrastructural study.

Intramuscular branches of tibial nerves of 5- and 27-month-old mice were compared. Seventeen intramuscular nerve fascicles were studied in each group: 174 myelinated axons were evaluated in the young mice, and 136 in the aged mice. The old mice showed significant decreases in numbers of myelinated axons per nerve, and these had significant decreases in concentrations of mitochondria. Interaxonal collagen and numbers of collagen fibrils were increased, as was the concentration of unmyelinated axons. Myelinated axons of old mice demonstrated myelin disorganization, myelin nodules, degeneration of axoplasm and Schwann cells.

Aging↗

PubMed1988

Age and exercise-related changes in myocardial mitochondria in mice.

A quantitative histochemical and an ultrastructural study was performed on the left ventricular myocardium of C57BL/6J female mice to evaluate the effects of aging and running exercise on mitochondrial structure and SDH activity. A comparison was made between 6-month-old ("young") and 27-month-old ("old") sedentary mice with age-matched mice subjected to running schedules (10 or 30 min/d) for 6 weeks. In longer-term studies, 27-month-old mice were given similar daily running schedules over a 10 month period ("long term runners"). No significant differences were found in SDH activity during the normal course of aging in mice (6 to 27 months of age), however, the response to running differed markedly in young versus old mice. "Young" trained mice showed significant increase in SDH activity compared with age-matched sedentary mice, whereas "old" trained mice showed significantly reduced SDH activity. Electron microscopy showed ultrastructural changes in mitochondria associated with aging including the development of large aggregations of mitochondria in subsarcolemmal and paranuclear sites. Running schedules, especially in aged runners, caused an increase in interfibrillar mitochondria hypertrophy, loss of matrix and cristae, incorporation of lipid inclusions and the formation of giant mitochondria. These abnormal mitochondrial changes are interpreted as being degenerative and possibly contributing to the reduced SDH levels found in cardiac myocytes of aged runners. Our results indicate that whereas regular exercise in young animals enhanced SDH activity, in aged mice it may be detrimental rather than beneficial.

Aging↗

PubMed1988

Enhancing effects of fluoride-containing ceramic implants on bone formation in the dog femur.

This study examined the enhancing effects of newly constructed ceramic implants, consisting of unidirectional macroporous (200 micron in diameter) material, upon in vivo bone formation in dogs' femurs. The implants comprised calcium phosphate salts that included 0.5% fluoride. The latter were introduced into bone defects in healthy dogs and were followed thereafter for a period of 8 months. Radiological and histological examinations indicated new bone formation at the implantation sites concurrent with the disappearance of the original implanted material. The rate of in situ degradation of these implants correlated to the overall size of the inserted implant. It became evident that this new kind of ceramic (that included fluoride in its basic composition) possessed a remarkable stimulating potential upon bone morphogenesis.

Animals↗