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Biomedical subjects

H Reddi

Publications and source records attributed to H Reddi.

6 recordsLinked to original sources
PubMed1998

A monoclonal antibody against the X protein of hepatitis B virus: fine mapping of its epitope and application in a quantitative ELISA of the X protein in sera of hepatitis B patients.

A HBx-specific mouse monoclonal antibody was developed and its epitope mapped to a hydrophilic segment 94HKRTLGL100 using the multipin peptide synthesis technique. A sensitive ELISA with a threshold of 5 to 10 ng was developed to identify the HBx-positive hepatitis B cases and measure the levels of HBx in sera. The same patient sera were also analyzed for the presence of anti-HBx using the purified recombinant antigen. HBx was present in 23% of the cases (15/65) whereas only 14% of the cases (9/65) were positive for anti-HBx. The mean value of HBx in acute hepatitis sera was higher (522 ng/ml) than in cirrhosis cases (48 ng/ml). PCR amplification of the S gene showed that all 15 HBx-positive cases were also positive for the viral DNA.

Animals↗
PubMed1994

Osteogenin (bone morphogenic protein 3) inhibits proliferation and stimulates differentiation of osteoprogenitors in human bone marrow.

Treatment of human bone marrow osteoprogenitors with osteogenin (BMP-3; at 1, 2.5 and 10 ng/ml) caused dose- and time-dependent inhibition of DNA synthesis and cell proliferation. Simultaneously, osteogenin stimulated type I collagen synthesis and cAMP production. Addition of osteogenin to the cell culture increased intracellular alkaline phosphatase activity and osteocalcin synthesis, with maximal stimulation at 2.5 ng/ml. Simultaneous addition of 2.5 ng/ml osteogenin and 1,25 dihydroxy vitamin D3 (10(-8) M) enhanced the stimulation observed in osteocalcin synthesis. The experiments reported here demonstrate the significant "in vitro" influence of osteogenin in the stimulation of osteogenic phenotype in osteoprogenitor cells which have been isolated from human bone marrow and cloned. These results support a reciprocal relationship between cell growth inhibition and expression of osteoblast differentiation.

Adult↗
PubMed1991

Tissue transformation into bone in vivo. A potential practical application.

The transformation of mesenchymal tissue, such as muscle, into cartilage and bone can be induced by the recently purified osteoinductive factor, osteogenin, and by its parent substratum, demineralized bone matrix. We investigated the possibility of transforming readily available muscle flaps into vascularized bone grafts of various shapes that could be used as skeletal replacement parts. In a rat experimental model, thigh adductor muscle island flaps were placed inside bivalved silicone rubber molds. Prior to closure of the mold, 18 flaps were injected with osteogenin and coated with demineralized bone matrix. Five flaps served as controls and were injected with the vehicle only, and not coated with demineralized bone matrix. The molds were implanted subcutaneously in the rats' flanks and reopened 10 days later. The control flaps consisted of intact muscle without any evidence of tissue transformation, whereas the flaps treated with osteogenin and demineralized bone matrix were entirely transformed into cancellous bone that matched the exact shape of the mold. Using tissue transformation, we were able to generate in vivo, autogenous, well-perfused bones in the shapes of femoral heads and mandibles.

Animals↗
PubMed1987

Acceleration of cartilage and bone differentiation on collagenous substrata.

Chondroprogenitor cells of newborn murine mandibular condyles were cultured on top of collagen sponges for up to 18 days. After 24 h in culture, new chondroblasts developed which subsequently matured showing signs of hypertrophy, while the extracellular matrix revealed positive reactivity for type II collagen, cartilage proteoglycans and mineralization. Light and electron microscopy examinations showed signs of new osteoid formation, a feature that was preceded by positive immunohistochemical reaction for type I collagen, fibronectin and bone specific sialoprotein. A close temporal and spatial association was noted between the development of mature, mineralized cartilage and new osteoid. The differentiation of new cartilage and bone cells was linked to an increased activity of DNA synthesis and cellular proliferation. The de novo bone formation was accompanied by increasing rates of alkaline phosphatase activity and uptake of [45Ca] features that were found to be tightly correlated to each other. The collagen substrata appeared also to facilitate the migration of cells, their replication and their subsequent differentiation to their respective cellular lineage. Hence, collagen sponges in vitro appear to serve as a promising substrata for culture systems involved with the growth and differentiation of mineralizing tissues such as cartilage and bone.

Alkaline Phosphatase↗