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Biomedical subjects

M Silbermann

Publications and source records attributed to M Silbermann.

At least 55 records · Page 3Linked to original sources
PubMed1991

Activity of alkaline phosphatase in rat skeletal muscle localized along the sarcolemma and endothelial cell membranes.

Alkaline phosphatase (AP), a membrane-associated glycoprotein which enhances the hydrolysis of monophosphate esters at alkaline pH, is widely distributed in animal tissues. AP activity is increased in a variety of muscle disorders, i.e., myopathies and denervation. Established histochemical methods at the light microscopy level failed to demonstrate AP in skeletal muscles. In the present study we applied the Gomori lead nitrate method for ultrastructural examination of AP in rat gastrocnemius muscles and showed that the enzyme was linked to the sarcolemma of the striated muscle and to the membranes of endothelial cells in adjacent capillaries. In comparison with ATPase activity, AP activity was inhibited by both levamisole and a pH of 7.2, but not by ouabain. Hence, it appears that in skeletal muscles AP is active at a high pH and is bound to cell membranes.

Alkaline Phosphatase↗
PubMed1990

Age-related structural changes in the rat hippocampus: correlation with working memory deficiency.

Age-related histopathological changes in the hippocampal formation were correlated with cognitive performance, evaluated in rats at the 8-arm radial maze. Experiments were conducted using young (3 months), mature (12 months), middle-aged (17 months) and aged (24 months) Wistar rats. Significant memory impairments were already observed at the age of 12 months in all the measured parameters (correct choices, percent errors and total time). No further decline was observed between 12 and 17 months of age, while at 24 months additional decline was monitored mainly in the percent errors parameter. Morphometric analysis revealed a decrease in the area of cells within the hippocampus and the number of cells in the CA3 subfield. This pattern of morphological changes with age corresponded well with the cognitive impairments, with high correlation especially to lesions at the CA3 subfield. It had also been confirmed in this study that lipofuscin appeared to be a good histochemical marker for CNS cell degeneration. It is concluded that 12-month-old Wistar rats may serve as the animal model of choice for the study of specific age-related behavioral deficits and that the hippocampal CA3 region might play a major role in the age-dependent cognitive decline.

Aging↗
PubMed1990

Growth and differentiation of murine cartilage cells in vitro following a short-term exposure to triamcinolone acetonide.

Measurements of 3H-thymidine incorporation, quantitative autoradiography and morphometry were used to evaluate cell behavior during the recovery of mandibular condylar cartilage cultures following short-term exposure to a corticosteroid hormone in vitro. Apical segments of mandibular condyles of newborn mice were initially incubated in the presence of the hormone triamcinolone acetonide (10(-6) M) for 24 h and were thereafter cultured for additional 6 days in hormone-free medium. The present results indicated that the treatment led to a decrease in the rate of incorporation of 3H-thymidine, a feature that lasted for 48 h following the removal of the hormone. Quantitative 3H-thymidine autoradiography of explants that were labeled in the presence of the hormone further substantiated the initial suppressive effect of the hormone on cellular proliferation, a feature that was followed by a recovery. Differences were noted in the pattern of distribution of labeled cells: in control explants, labeled cells progressively moved from the chondroprogenitor compartment into the differentiated portion of the cartilage; in hormone-treated explants, 3H-thymidine labeled cells were confined to the progenitor layer up to 5 days after the treatment and only then appeared in the chondrocytic compartment. The hormone's adverse effect upon differentiation was manifested by both morphology, and by causing a significant increase in the size of the progenitor layer (up to 50.5% on 4th post-treatment day) along with a 70.5% reduction in the size of chondroblastic layer. We conclude that a short-term exposure to a glucocorticoid hormone in vitro interferes with proliferation of chondroprogenitor cells and their subsequent differentiative pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Long-term physical exercise retards trabecular bone loss in lumbar vertebrae of aging female mice.

The present study examined the effect of long-term, moderate physical exercise on trabecular bone volume (TBV), calcium content, 3H-proline uptake, and the activities of alkaline and acid phosphatases in lumbar vertebrae of aging and senescent mice. It became apparent that if physical activity starts at an early stage of life, i.e., prior to middle age and is extended until old age, it exerts beneficial effects on trabecular bone mass and mineralization. Such a positive effect is not obtained if the training program is initiated after middle age. The training-induced reduction in bone loss was accompanied by a significant decrease in acid phosphatase activity whereas no changes took place with regard to the activity of alkaline phosphatase. Long-term physical exercise also enhanced the uptake of 3H-proline by lining cells along the bone trabecules. In spite of its moderate nature, the endured training program served as a stress factor for the involved animals, a fact that was manifested by an increase in the serum levels of corticosterone. Thus, it seems that whereas young animals respond favorably to such a stimulatory stress, older animals lose this ability of adaptation.

Acid Phosphatase↗
PubMed1990

Cellular enzymatic activities in the articular cartilage of osteoarthritic and osteoporotic hip joints of humans: a quantitative cytochemical study.

Quantitative cytochemical methods were applied to measure the activity of several oxidative enzymes in human articular cartilage of the femoral head obtained from osteoarthritic patients (OA) and from patients with fractured femoral neck (OP) due to primary osteoporosis. In both conditions, lactate dehydrogenase (LDH) was found to be the most active one followed by two additional cytosolic enzymes: glyceraldehyde 3-phosphate dehydrogenase (GAPD) and glucose 6-phosphate dehydrogenase (G6PD). On the other hand, the activity of mitochondrial enzymes such as succinate dehydrogenase (SDH) and beta-hydroxyacyl dehydrogenase (HOAD), appeared much lower in degree. Except for HOAD, all the other enzymes exhibited a high degree of activity along the inner zone in the cartilage, i.e., zone 3b, indicative of an apparently more active metabolism in the osteochondral junction. G6PD activity was significantly higher (p less than 0.01) in OP than in OA patients. By contrast, SDH appeared more active in specimens obtained from OA patients. The remaining enzymes showed no appreciable activity differences between cartilages of OP and OA patients. These findings suggest that oxidative enzyme activity in chondrocytes involved in osteoarthritis does not differ substantially from that in cartilage of OP patients.

Aged↗
PubMed1990

Age-related changes in the cholinergic components within the central nervous system. II. Working memory impairment and its relation to hippocampal muscarinic receptors.

Cognitive performance in aging Wistar rats was monitored using the radial arm maze and the latter was correlated with the density of muscarinic receptors in the CNS, using quantitative in vitro receptor autoradiography. Significant working memory deficits were observed in 12, 17 and 24-month-old rats as compared to 3-month-old animals. In addition, the number of the muscarinic receptors declined significantly with age (from 27 to 42% depending on the brain region sampled) utilising [3H]QNB and [3H]PZ receptor binding assays. The above trend became evident already at the age of 12 months. The present findings support the association of central cholinergic activity with memory processes.

Age Factors↗
PubMed1990

The activity of 2,5-oligoadenylate synthetase, an interferon-induced enzyme, is coupled to the differentiation state of mouse condylar cartilage.

The enzyme 2,5-oligoadenylate synthetase (2-5A synthetase) is associated with the interferon system, with special reference to the differentiation process of various cell types. The present study investigated whether 2-5A synthetase is also involved in the differentiation of neocartilage in perinatal mice. The cartilage of the mandibular condyle, a secondary type of cartilage, develops relatively late in prenatal life; and consequently it was possible to obtain a relatively embryonic cartilage at a developmental stage that could be manipulated enzymatically, in order to separate and thereby obtain its undifferentiated, proliferative portion along with its more mature fraction. Immunohistochemical studies using antibodies against type I and type II collagen and cartilage-specific proteoglycans could have determined the differentiation status of various portions of the developing condyle. However, the above methodology lacks the necessary precision and accuracy to indicate subtle changes in cellular differentiation. It became evident that the activity of 2-5A synthetase was indeed different in cellular compartments that were at different stages of differentiation. In the neonatal condyle the highest level of activity was encountered in proliferating and as yet undifferentiated prechondrocytes, whereas fully differentiated chondrocytes showed a marked decrease in the activity of this enzyme.

2',5'-Oligoadenylate Synthetase↗
PubMed1990

Histochemical study of matrical components in the mandibular condyle of the neonatal mouse.

In the mandibular condyle of the newborn mouse the chondroprogenitor (CP) zone is the only layer that incorporates 3H-thymidine thus serving the source for cells of the cartilage lineage. Ultrastructurally these cells have a mesenchymal appearance surrounded by collagen fibrils as well as by additional filaments that become apparent following fixation with ferrocyanide-reduced OsO4. In addition, electron-dense particles indicative of proteoglycans are scattered throughout the matrix in the CP zone as well as in the chondroblastic and hypertrophic zones. Following labeling with 35S-sulfate the CP zone as well as the other compartments revealed a substantial number of grains following processing for autoradiography. The number of grains per cell was highest in the hypertrophic zone. Indirect immunofluorescence indicated the presence of fibronectin in the articular surface, CP zone and in the hypertrophic zone. The immunogold method localized fibronectin intracellularly in CP cells and extracellularly in the hypertrophic zone. Therefore, in the mandibular condyle the CP cells which are capable for DNA synthesis are also involved in the synthesis of macromolecules of which some are specific for the cartilage phenotype, while others are associated with other functions of connective tissue cells.

Animals↗
PubMed1990

Effects of parathyroid hormone fragments on the growth of murine mandibular condylar cartilage in vitro.

The present study showed that the fragment hPTH (1-34) is mitogenic in organ cultures of neonatal mandibular condylar cartilage, and even more so in late fetal condyles. Three fragments of hPTH were used to clarify which part of the molecule possesses a mitogenic effect alike that of the native hormone: hPTH (1-34), (28-48) and (53-84). [3H]thymidine incorporation into trichloracetic acid insoluble material and quantitative autoradiography were employed in a serum-free medium to assess the effects of these fragments while light and electron microscopy studies served for morphological evaluations. It became evident that the fragment hPTH (1-34) enhanced the incorporation of [3H]thymidine, a fact that could be noted only in serum-free medium. The putative target cells for the effects of hPTH (1-34) were the chondroporogenitor cells which also appeared to have experienced a blockage in their differentiation into chondroblasts. Ultrastructurally, the latter cells responded in the formation of adherent profiles of plasma membranes, whereas the differentiated zone of the cartilage reduced its size. Using serum-free medium, hPTH (1-34) also brought about an inhibition in alkaline phosphatase activity, a fact that was not encountered in medium containing serum. By contrast, hPTH (28-48) had no mitogenic effect, although treated specimens revealed morphological changes in the chondroprogenitor cell zone along with an enhancement of cartilage cells hypertrophy. No significant effects on either mitogenecity or morphology could be noted in hPTH (53-84)-treated cultures.

Animals↗
PubMed1990

Changes in growth patterns in mouse condylar cartilage associated with skeletal maturation and senescence.

The squamoso-mandibular joint (SMJ) represents one of the most active joints in the mouse. In the young animal the main function of condylar cartilage in the SMJ is to serve as a growth center for the developing mandible. This first phase of skeletal growth lasts up to the age of 6-8 weeks, and is manifested by appositional growth of cartilage followed by endochondral ossification. Thereafter, the condylar cartilage gradually changes its function and serves mainly as an articulating surface for the joint. Consequently, the cartilage changes from a calcifying hyaline cartilage to a fibrous non-calcifying cartilage. The latter phase lasts through the stage of maturation (6 months of age) and it is manifested by a combination of appositional and interstitial patterns of cellular growth. Thereafter, the third phase develops which is characterized by degenerative changes that typify the aging process. In vivo autoradiography with [3H]-thymidine indicated that in the very young animal labeled cells are confined to the chondroprogenitor (proliferative) zone of the condylar cartilage. With maturation, the dimension of this zone as well as the number of labeled cells decrease, so that by 3 months of age the labeling index decreases by 30%. By the age of 6, 12 and 18 months, almost no cells take up the radioisotope while the total number of cells declines. During senescence only a very limited interstitial growth is taking place, a feature that might be associated with the repair processes that accompany the onset of osteoarthritic lesions.

Aging↗
PubMed1990

An immunohistochemical study of the distribution of matrical proteins in the mandibular condyle of neonatal mice. I. Collagens.

This study provides new information concerning the distribution of cartilage collagens in neonatal mammalian condylar cartilage. It became apparent that young cartilage cells contain pro-Type I collagen as well as pro-Type II collagen. The mature molecule of Type I collagen appears only in the extracellular matrix of the mineralisation zone close to the ossification front. Type II collagen, on the other hand, is apparent throughout the extracellular matrix as soon as the chondroprogenitor cells have differentiated into chondroblasts. In addition, Type II collagen is noticed in the core of the newly formed bone trabeculae within the primary spongiosa. Type IX collagen was found to be co-distributed with Type II collagen in cartilage and bone. Hypertrophic chondrocytes within the mineralisation zone, but in no other zone, demonstrate an intense reactivity for Type X collagen. Mild reactivity throughout the condylar process is encountered with regard to Type VI collagen. Perichondrium but not cartilage reacts positively for Type III collagen.

Animals↗
PubMed1990

An immunohistochemical study of the distribution of matrical proteins in the mandibular condyle of neonatal mice. II. Non-collagenous proteins.

This study has illustrated the localisation of several non-collagenous proteins in the extracellular matrix of neonatal condylar cartilage (chondrocalcin, proteoglycans and a 100 kDa protein). Also, it has been shown that chondrocytes synthesise laminin and anchorin CII. The bone trabeculae in the primary spongiosa reacted positively for chondrocalcin, osteopontin and BMP. The cartilaginous wealth of collagens (Type I, II, VI, IX, X and XI), together with the various non-collagenous proteins, are considered to possess an important role in the maintenance of chondrogenic expression as well as in the regulation of cartilage differentiation by means of an interaction with the undifferentiated precursor cells.

Animals↗
PubMed1990

In vitro systems for inducers of cartilage and bone development.

Murine condylar cartilages of perinatal mice were cultured in the form of organ or tissue cultures on top of collagen sponges in medium containing 10% fetal calf serum. Cultures were treated with increasing concentrations of recombinant human growth hormone, recombinant IGF-I, insulin, TGF beta-1, FGF and recombinant fragments of human parathyroid hormone. All the above agents [except for the fragments rPTH (28-48) and (53-84)] were found to be mitogenic as they accelerated the proliferative activity of the condylar stem cells. IGF-I and insulin also stimulated the synthesis of cartilage proteoglycans. Growth hormone also supported de novo osteogenesis in vitro.

Animals↗
PubMed1989

The effects of long-term lead intoxication on the nervous system of the chicken.

In order to study the possible etiologic role of lead in human motor neuron disease we produced chronic lead intoxication in the chicken by daily administration of lead acetate. Control animals received sodium acetate. During life, periodic measurements were made of motor function, motor nerve conduction velocity and response amplitude. After sacrifice, histologic analysis was performed on spinal cord, peripheral nerve and muscle. A syndrome was produced characterized by a fall in motor response amplitude, spinal motor neuron degeneration, motor axonal loss and atrophy of muscle, similar to that seen in human motor neuron diseases.

Animals↗
PubMed1989

Articular chondrocytes lose their proliferative activity with aging yet can be restimulated by PTH-(1-84), PGE1, and dexamethasone.

Mouse mandibular condyles develop spontaneous degenerative changes by 6 months of age, hence providing a good in vivo model for studies related to processes associated with the onset and progression of age-related osteoarthritis. Further, this joint provides an appropriate system to investigate the potential of articular cartilage to respond to hormones and local growth factors in old age. The present study examined (1) the age-related changes in [3H]thymidine incorporation by articular chondrocytes in the mouse mandibular condyle, and (2) the effect of systemic and local factors upon the tissue's ability to resume DNA synthesis. Condyles of female CW-1 mice ranging from 3 to 18 months of age were cultured in the presence of PTH-(1-84) (2 micrograms/ml), PGE1 (20 micrograms/ml), dexamethasone (10(-7) M), and MSA (5 micrograms/ml) and were concomitantly labeled with [3H]thymidine. Autoradiographs were analyzed quantitatively and revealed (1) a significant (p less than 0.01) age-related decrease (-80%) in the labeling index of the articular cartilage, and (2) the ability of old tissues to resume DNA synthesis following in vitro treatment with PTH-(1-84), PGE1, and dexamethasone. Concomitant quantitative incorporation studies further substantiated the autoradiographic findings. Hence, these factors possess a direct stimulatory effect upon senescent chondrocytes involved in an advanced stage of spontaneous osteoarthritis.

Aging↗
PubMed1989

Biochemical characterization of a virus-induced osteosarcoma-like osseous lesion in vitro.

Chondroprogenitor cells present in the apical and lateral parts of the mandibular condyle from neonatal mice differentiate towards the osteoblastic lineage and form bone within 7 days in culture. Infection of condylar explants with the FBR osteosarcoma virus (FBR MSV) results in the transformation of cells in the progenitor zone, previously identified as the target for the virus, and the formation of a transplantable osteosarcoma-like lesion. Morphological and biochemical changes in this system were investigated in the course of tumor development. Virus infection was followed by a significant increase in cell density and 3H-thymidine incorporation within the progenitor zone at the early stage of culture. In later stages, cell density and 3H-thymidine incorporation were lower than in control tissue. The 3H-thymidine labeling index gave similar results in infected and control tissues until day 7. Then, a significantly higher labeling index was found in the progenitor zone of infected condyles. At this stage, the proliferative effect of the virus even affected the cartilagenous core of the tissue. Quantitative alkaline phosphatase activity increased between day 3 and day 7 and was particularly high in the zone of infected cells. In addition, infected tissues consistently revealed a higher uptake of 45Ca, and deposition of the radioisotope along irregularly formed bone trabecules in the transformed tissue. The results suggest that there is an enhancement of tissue maturation following infection with the FBR osteosarcoma virus. Although biochemical investigations of whole condyles showed few differences in the total values of alkaline phosphatase activity, 3H-thymidine incorporation, DNA content, and 45Ca uptake, the histochemical assays revealed clear differences in the distributional pattern of these parameters within infected and control condyles.

Alkaline Phosphatase↗
PubMed1989

Effects of leukemogenic retroviruses on condylar cartilage in vitro: an ultrastructural study.

Mandibular condyles of late embryonic NMRI mice were used in an in vitro organ culture system to study the effect of bone tumor-derived murine leukemia viruses OS-5 MuLV and OA MuLV known to induce osteopetrosis and osteomas. Skeletal precursor cells present in the condylar tissue normally undergo rapid differentiation in vitro which results in new bone formation. The infection of condyles with either OS-5 MuLV or OA MuLV markedly interfered with the normal developmental pattern of the organ leading to the formation of an atypical, heavily mineralized tissue. Many spindlelike cells and pleomorphic cells were encountered, whereas fibroblastlike cells were found to penetrate an underlying collagen substratum. These observations indicate that bone tumor-inducing leukemogenic retroviruses directly affect cartilage and/or bone precursor cells resulting in pathologic developments in the skeleton.

Animals↗