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Biomedical subjects

M F Charette

Publications and source records attributed to M F Charette.

11 recordsLinked to original sources
PubMed2000

Time window of intracisternal osteogenic protein-1 in enhancing functional recovery after stroke.

Osteogenic protein-1 (OP-1, BMP-7) is a member of the bone morphogenetic protein subfamily of the TGF-ss superfamily that selectively stimulates dendritic neuronal outgrowth. In previous studies, we found that the intracisternal injection of OP-1, starting at one day after stroke, enhanced sensorimotor recovery of the contralateral limbs following unilateral cerebral infarction in rats. In the current study, we further explored the time window during which intracisternal OP-1 enhances sensorimotor recovery, as assessed by limb placing tests. We found that intracisternal OP-1 (10 microg) given 1 and 3 days, or 3 and 5 days, but not 7 and 9 days after stroke, significantly enhanced recovery of forelimb and hindlimb placing. There was no difference in infarct volume between vehicle- and OP-1-treated animals. The mechanism of OP-1 action might be stimulation of new dendritic sprouting in the remaining uninjured brain.

Animals↗
PubMed1998

Potentiating interactions between morphogenetic protein and neurotrophic factors in developing neurons.

mRNA for bone morphogenetic protein receptor type II (BMPR-II) was mapped to different neurons in peripheral ganglia and spinal cord of the chicken embryo. The expression of this serine/threonine kinase receptor partially overlaps with that of tyrosine kinase receptors Trk and Ret. Biological activities of osteogenic protein-1 (OP-1), a documented ligand for BMPR-II, were tested in explanted embryonic chicken ganglia and dissociated ganglionic neurons. OP-1 had only a limited stimulatory effect on neuronal survival. However, OP-1 combined with either neurotrophin-3 (NT-3, a relative of nerve growth factor) or glial cell line-derived neurotrophic factor (GDNF) potentiated neuronal survival three- to fourfold. We also show that OP-1 strongly potentiates nerve fiber outgrowth from ganglia stimulated with NT-3 or GDNF. Signaling by BMPR-II in neurons may potentiate the tyrosine kinase pathway activated by NT-3 and GDNF. The data suggest that morphogenetic proteins may modulate neurotrophic activities during neuronal development and plasticity.

Amino Acid Sequence↗
PubMed1998

BMPR-II expression and OP-1 effects in developing chicken retinal explants.

Low-stringency PCR was used to isolate the chicken homologue of the human bone morphogenetic protein receptor type II (BMPR-II). In situ hybridization localized mRNA expression for this serine/threonine kinase receptor. It was weakly expressed in the vitreal side of the neural retina at E6. In the E7 chicken, fairly strong labelling was found in cells of the internal part of the neural retina. At E9, strong labelling was found in the region of the retinal ganglion cells. Explants of E6 retina exposed to osteogenic protein-1 (OP-1/BMP-7), exhibited dense retinal fibre outgrowth. This suggests that BMPR-II may form a signalling receptor complex important for retinal development. OP-1 and related ligands may serve functions supplementary to those of neurotrophins.

Amino Acid Sequence↗
PubMed1998

Osteogenic protein-1 mRNA expression is selectively modulated after acute ischemic renal injury.

Osteogenic protein-1 (OP-1) is a morphogenetic factor highly expressed in the kidney and involved in tissue repair and development. Homozygous OP-1-deficient mice die shortly after birth due mainly to arrest of renal growth and differentiation. Because postischemic injury involves several repair mechanisms, this study examined whether kidney OP-1 mRNA expression is modulated after ischemia. Acute ischemic renal injury was achieved in rats by unilateral clamping of the renal pedicle followed by reperfusion. Rats were killed at 3, 6, 12, 24, and 48 h and 7 d after reperfusion, and kidneys were microdissected and analyzed by histology and Northern and Western blots. Changes in OP-1 mRNA were determined by measuring the ratio of OP-1/glyceraldehyde 3-phosphate dehydrogenase signals for each OP-1 transcript (4.0 and 2.4 kb) from ischemic, opposite, and sham-operated rats. The OP-1 mRNA content for transcript 4.0 kb was fivefold lower in the whole ischemic kidney compared with that in sham animals 24 h after reperfusion. In the ischemic medulla, OP-1 mRNA was strikingly downregulated 20-fold when compared with the ischemic cortex. Results for transcript 2.4 kb and for the other time points were comparable. OP-1 mRNA expression was also affected in the opposite medulla compared with the sham medulla. However, only in the ischemic medulla was the relative OP-1 content significantly lower at all time points. Similar results were obtained when analyzing OP-1 protein by Western blot at 24 h after reperfusion. Seven days after reperfusion, the levels of OP-1 mRNA returned to baseline. In conclusion, kidney OP-1 mRNA and protein are selectively downregulated in the medulla after acute ischemic renal injury. OP-1 modulation may be a key element for kidney repair.

Animals↗
PubMed1993

Platelet-derived growth factor and dexamethasone combined with a collagen matrix induce regeneration of the periodontium in monkeys.

Platelet-derived growth factor (PDGF) and the glucocorticoid dexamethasone combined with a collagen carrier matrix (CM) induced regeneration of the periodontium in monkeys. Regeneration was stringently defined as: (1) new cementum, (2) new supra-crestal bone extending coronally from the residual alveolar interdental septum and (3) functionally-oriented periodontal ligament fibers attaching new cementum to new bone. A single application of PDGF/dexamethasone/CM or CM was placed in debrided lesions of experimental periodontitis displaying 3-5 mm of attachment loss associated with horizontal and angular bony defects. Regeneration, judged histologically by these criteria and quantified by computer assisted histomorphometry after 4 weeks, was present only in PDGF/dexamethasone/CM treated lesions and not in those treated with CM or debridement alone. PDGF/dexamethasone/CM induced 5-fold more new cementum and ligament, and 7-fold more supra-crestal bone than control treatments. The presence of substantial amounts of regenerated periodontium including increased height of the alveolar bone; fill of vertically resorbed interdental alveolar septa in PDGF/dexamethasone/CM treated lesions suggests that this combination may provide a new therapeutic agent for the regeneration of lesions of periodontitis associated with horizontal as well as angular bony defects.

Alveolar Process↗
PubMed1992

Synergistic effects of dexamethasone on platelet-derived growth factor mitogenesis in vitro.

Platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) interact to stimulate proliferation of fibroblasts in culture. Glucocorticoids variably effect the response of cultured fibroblasts to polypeptide growth factors. This study determined the effects of dexamethasone on growth-factor stimulation of gingival, periodontal ligament and pulp fibroblast proliferation in vitro. Cultures of quiescent, low-passage, human fibroblasts were treated for varying periods of time with transforming growth factor-beta 2 (TGF-beta 2), PDGF and IGF-I: (1) alone, (2) in combination with each other, (3) singly plus dexamethasone, (4) in combination plus dexamethasone. Combinations of human, recombinant PDGF and IGF-I (10-1000 ng/ml) induced significantly higher rates of cell proliferation than either factor alone. Dexamethasone at doses ranging from 10(-5) to 10(-8) M substantially enhanced cell proliferation induced by these combinations and by PDGF without IGF-I but not IGF-I alone. By 6 days after a single application, 2-3 times as many cells were present in the PDGF and dexamethasone cultures as compared to PDGF without IGF-I. TGF-beta 2 specifically blocked the effects of dexamethasone added to PDGF-stimulated cells. Collagen and non-collagenous protein synthesis was not affected by the addition of PDGF and IGF-I with or without dexamethasone. These data suggest that dexamethasone may substitute for IGF-I in PDGF stimulation of cell proliferation.

Cell Division↗
PubMed1992

Platelet-derived and insulin-like growth factors stimulate regeneration of periodontal attachment in monkeys.

Regeneration of cementum, ligament, bone and new attachment was achieved by introducing mixtures of recombinant human platelet-derived growth factor and insulin-like growth factor into debrided lesions of experimentally induced periodontitis in monkeys. This growth factor therapeutic regimen induced the regeneration of nearly 50% of the lost attachment within 4 weeks. New attachment in some cases included regeneration of horizontally resorbed interdental septa. These observations suggest that predictable, clinically significant gains in new attachment may be possible through the use of highly purified human recombinant growth factors delivered to debrided lesions of adult periodontitis in appropriate, inert carrier vehicles.

Alveolar Bone Loss↗
PubMed1986

Persistence of DNA synthesis arrest sites in the presence of T4 DNA polymerase and T4 gene 32, 44, 45 and 62 DNA polymerase accessory proteins.

DNA synthesis by phage T4 DNA polymerase is arrested at specific sequences in single-stranded DNA templates. To determine whether or not T4 DNA polymerase accessory proteins 32, 44, 45 and 62 eliminated recognition of these arrest sites, unique primer-templates were constructed in which DNA synthesis began at a DNA primer located at different distances from palindromic and nonpalindromic arrest sites. Nucleotide positions that caused polymerase to pause or leave the template were identified by sequence analysis of 5'-end labeled nascent DNA chains. Stable hairpin structures at palindromic sequences were confirmed by acetylation of single-stranded sequences with bromoacetaldehyde. Our results confirmed that these T4 DNA polymerase accessory proteins stimulated T4 DNA polymerase activity and processivity on natural as well as homopolymer primer-templates. However, they did not alter recognition of DNA synthesis arrest sites by T4 DNA polymerase. Extensive DNA synthesis resulted from an increased rate of translocation and/or processivity to the same extent over all DNA sequences.

DNA Replication↗
PubMed1984

DNA-stimulated ATPase activity on the lon (CapR) protein.

The gene product of the pleiotropic lon (also called capR) locus in Escherichia coli, the CapR protein, is an ATP hydrolysis-dependent protease and a nonspecific nucleic acid-binding protein. We demonstrated that it is also a DNA-stimulated adenosine triphosphatase (ATPase). This new activity is distinct from the protease-associated ATPase activity and occurs in the absence of proteolytic substrate. The reaction requires the presence of a divalent cation and has a pH optimum of 8.0. The products of the reaction are ADP and inorganic phosphate. No adenylation or phosphorylation of the DNA or proteins was detected. The maximum rate of ATP hydrolysis occurs in the presence of supercoiled (form I) DNA. Relaxed circles (form II), double-stranded DNA, and single-stranded DNA are less effective in promoting ATPase activity, whereas RNA is inactive. The DNA-stimulated ATPase activity is inhibited by a mutationally altered form of the CapR protein called the CapR9 protein. The interaction of the CapR and CapR9 subunits suggests that this enzymatic activity of the CapR protein is oligomeric in the presence of DNA. Our in vitro experiments indicate a possible role for nucleic acids in the regulation of all lon (capR) activity.

ATP-Dependent Proteases↗
PubMed1981

ATP hydrolysis-dependent protease activity of the lon (capR) protein of Escherichia coli K-12.

Mutations in the lon (capR) gene result in multiple phenotypes, one of which is the failure to degrade abnormal and normal proteins (Deg-). Previous work with partially purified preparations showed that the lon (capR) gene product is a 94,000-dalton polypeptide with an affinity for nucleic acids. The lon (capR) protein has now been highly purified and is demonstrated to have an ATP-dependent protease activity. The enzyme hydrolyzed 3H-labeled alpha-casein into trichloroacetic acid-soluble forms in Tris buffer containing Mg2+ and ATP. The reaction has a pH optimum of 8.5 and ATP was the preferred nucleotide. CTP and UTP could substitute for ATP (75% and 67%, respectively) but GTP, ADP, AMP, cyclic AMP, and PPi could not. Proteolysis by the lon (capR) protein required ATP hydrolysis. Nonhydrolyzable analogs of ATP and CTP did not promote casein cleavage. When low concentrations of ATP were used, proteolysis stopped as the ATP pool was depleted. Casein stimulated lon (capR) ATPase activity, and the products were ADP and inorganic phosphate in equimolar amounts. No protein kinase activity was detected. The DNA-binding activity, present in partially pure preparations, was retained in the purified protein. The gene product purified from a lon nonsense mutant that exhibits the Deg- phenotype (capR9), lacked both the ATP-dependent protease and ATPase activities, though it retained DNA-binding activity. Absence of an ATP-dependent protease activity could account for many of the pleiotropic effects observed in lon mutants.

ATP-Dependent Proteases↗