Noncemented hip implants. Factors augmenting or inhibiting biological fixation.
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Aging↗
Biomedical subjects
M Spector
Publications and source records attributed to M Spector.
Pancreatic calculi containing brushite: ultrastructure and pathogenesis.
Six pancreatic calculi were analyzed by X-ray powder diffraction and scanning electron microscopy. All were found to contain calcite; however, small amounts of two other morphologically distinct deposits containing only Ca were also detected in some of the stones. It is suggested that these substances may be vaterite and aragonite. In addition, significant deposits of brushite, CaHPO4 X 2H2O, were identified on the outer surfaces of three of the stones. This substance has not been previously reported as a constituent of pancreatic calculi, and its presence is surprising since physico-chemical factors such as phosphate concentration and fluid pH do not favor its deposition. We suggest that precipitation of calcite in the pancreatic duct occurs as the primary event in the formation of pancreatic calculi and that it may continue until the duct is completely occluded. Thereafter, further growth causes injury to the duct wall resulting in the calcite core being exposed to phosphate in the tissue fluid. Deposition of brushite follows.
Calcium Carbonate↗
The conical cartilage of the cat's middle ear.
The object of this study was to investigate the anatomy, histology, and possible function of a conical structure found in the middle ear of the cat. This conical structure lies across the dorso-caudal compartment of the middle ear. It is directly related to the course of the chorda tympani nerve in the middle ear. Its base is attached by fibrous tissue to the dorso-caudal segment of the tympanic bone adjacent to the tympanic membrane. Its apex rests on the promontory just rostral to the round window niche. Histologically, it is cartilaginous tissue enveloped by a mucous membrane with no trace of bone. Portions of some conical cartilage specimens display extensive calcification. A previous hypothesis suggests that this structure conducts high frequency sounds directly from the tympanic membrane to the round window membrane. This seems unlikely because its length is shorter than the distance between the tympanic membrane and round window membrane. The conical cartilage may be a vestigial remnant of the second arch bar (Reichert's cartilage).
Animals↗
Spaceflight results in formation of defective bone.
Growing rats were flown on 19 day spaceflights aboard Cosmos 782 and 936 biosatellites. Spaceflight resulted in a prominent skeletal defect at the periosteal surface of the tibia diaphysis. The defect, termed an arrest line, was approximately 3 micron across and separated the bone formed in space from that formed following spaceflight. The bone matrix at the arrest line region was abnormal in that collagen fibers were preferentially orientated parallel to the periosteal surface. In addition, the bone matrix was hypomineralized. The altered bone was inferior to normal bone in resistance to abrasion and may be partially responsible for the decrease in torsional strength observed after spaceflight.
Animals↗
Osteoinduction within porous polysulfone implants at extraosseous sites using demineralized allogeneic bone matrix.
The objective of this study was to determine if bone induction could occur in implants of porous polysulfone (PPSF) impregnated with particles of demineralized allogeneic bone matrix (DABM). DABM-PPSF composites were fabricated by inserting DABM particles into PPSF specimens. The porous implants were produced by sintering polysulfone particles (850-1180 micron in diameter). DABM particles were prepared by demineralizing rat cortical bone in 0.6N HCl at 4 degrees C for 18-24 h. A composite DABM-PPSF specimen and three "controls" were implanted subcutaneously at abdominal sites in 30 adult Sprague-Dawley rats. The three controls were whole DABM (4 X 4 X 1 mm), particulate DABM (1 X 1 X 1 mm), and porous polysulfone (5 X 5 X 1 mm). Microradiographic and histological evaluation of DABM-PPSF composites revealed chondrogenesis within the pores of the specimens at 10 days, followed by ossification and fatty marrow production at 21 and 43 days. This histological sequence was similar to that seen with DABM controls. The tissue response to porous polysulfone did not prevent the osteoinductive process. These results suggest that an osteoinductive material such as DABM may be useful in augmenting the implantation of porous implants at osseous sites in which the potential for bone regeneration is limited.
Animals↗
Tissue response to Plasti-Pore and Proplast otologic implants in the middle ears of cats.
Plasti-Pore (high density polyethylene) and Proplast (polytetrafluoroethylene-carbon fiber composite) are porous materials that have been employed for the fabrication of ossicular replacement prostheses. Despite many years of clinical experience with these otologic implants, questions remain regarding the tissue response elicited by these materials in the middle ear. The objective of this study was to evaluate histologically the tissue response to Plasti-Pore and Proplast implants in the middle ears of cats through one year of implantation. Plasti-Pore and Proplast total ossicular replacement prostheses, trimmed to "T" shapes, were inserted in fourteen cats, replacing the superstructure of the stapes. One Plasti-Pore and one Proplast implant were implanted in each animal. Cats were killed after two weeks, one, three, and six months, and one year. The histologic response to the Plasti-Pore and Proplast implants was similar. A fibrous capsule contained within a flattened epithelial cell sheath enveloped both types of implants. The mucosa enveloping the devices was continuous with the lining of the tympanic cavity and served to stabilize the implants. Fibrous tissue from the capsule infiltrated larger surface pores. Multinucleated giant cells and macrophages were the predominant cell types in the porosity of both types of implants. The relatively small pores of the devices did not appear to be able to accommodate both the phagocytic cells, which were responding to the particulate features of the materials, and fibrous tissue.
Animals↗
Warburg effect revisited: merger of biochemistry and molecular biology.
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Adenosine Triphosphatases↗
Stimulation of Ca2+ uptake and protein phosphorylation in tumor cells by fibronectin.
Suspensions derived from attached HeLa cells transported 45Ca2+ considerably faster than those derived from spinner cultures grown in liquid medium. Incubation of spinner cells with fibronectin or cold-insoluble globulin in the presence of 5% calf serum at 37 degrees C for 1 to 2 h greatly increased the rate of Ca2+ flux into the cells. Suspensions of cells transformed by Rous sarcoma virus transported Ca2+ much more slowly than cell suspensions of the parent strain of normal rat kidney. Incubation of the transformed cells or Ehrlich ascites tumor cells with fibronectin increased the rate of Ca2+ uptake, while no effect was seen on Ca2+ transport by this treatment of normal kidney cells grown in tissue cultures. A 45,500-dalton protein was found to interact firmly with Ca2+ that entered into attached HeLa cells or fibronectin-treated spinner cells. This Ca2+-associated protein was detected by lithium dodecyl sulfate gel electrophoresis at 0 degrees C after 30 s of exposure to radioactive Ca2+. In tumor cells without fibronectin treatment, the radioactive band was not seen under the same conditions, even after 10 min incubation with 45Ca2+. In fibronectin-treated tumor cells, addition of Ca2+ to buffered solutions resulted in increased phosphorylation of a protein in the 45,000-dalton region. The phosphorylated protein band which appears to be associated with the cytoskeleton can be resolved by isoelectric focusing into four polypeptide chains. The relation of these observations to the cascade of protein kinases involved in the phosphorylation of the beta-subunit of the (Na+-K+)-ATPase is discussed.
Animals↗
Regulation of phosphorylation of the beta-subunit of th Ehrlich ascites tumor Na+K+-ATPase by a protein kinase cascade.
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Animals↗
A mouse homolog to the avian sarcoma virus src protein is a member of a protein kinase cascade.
Recent work has identified a cascade of membrane bound protein kinases in Ehrlich ascites tumor cells. These enzymes, designated PKL, PKS and PKM, are present in both Ehrlich tumor and mouse brain, but the cascade is active only in the tumor tissue. We have now purified a fourth protein kinase, PKF, that is also associated with this cascade. Protein kinase F prosphorylates PKL and is phosphorylated by PKS. The position of this kinase in the cascade is as follows, where the arrows denote phosphorylation: [Formula: see text] The phosphorylation by PKF, like phosphorylation by the other kinases, is at a tyrosine residue and causes the substrate kinase (PKL) to become active. The role of the tyrosine phosphorylation in activating these kinases is described in detail elsewhere. One result of activation of the cascade is the phosphorylation of the beta subunit of the Na+K+-ATPase, which causes inefficient Na+ pumping and is at last in part responsible for the high aerobic glycolysis of Ehrlich ascites tumor cells. By several criteria protein kinase F from Ehrlich cells is homologous to the src gene product (pp60src) from avian sarcoma viruses. Antiserum raised against PKF and sera from rabbits bearing rous sarcoma virus (RSV)-induced tumors quantitatively precipitate the same 60 kd phosphoprotein from cell lysates of three different RSV-transformed cell lines. Both proteins phosphorylate PKL and a 130 kd cytoskeletal protein (vinculin). The tryptic maps of these proteins are closely similar. Both proteins bind specifically to PKL covalently coupled to Sepharose. We used this latter observation to facilitate the purification of pp60 src from RSV-transformed cells.
Amino Acids↗
Screening of solid and porous materials for pacemaker electrodes.
Several different materials, including one which was porous, were studied to assess their properties as pacemaker electrode tips. Leads were implanted in sheep for periods up to one year. Electrical measurements were made during the implant period and histopathological examination performed after sacrifice. Although titanium vapor-deposited carbon, and silver did not lower the chronic stimulation threshold below that of platinum, their electrical characteristics were within generally acceptable limits. Zinc evoked a severe tissue reactions and a high threshold. Porous titanium alloy electrodes demonstrated reduced dislodgement, more frequent attachment and a lower sensing impedance than other electrodes.
Alloys↗
Radionuclide bone imaging of femoral prostheses with porous coatings.
Radionuclide bone imaging can be of value in assessing the osseous changes around porous-coated femoral prostheses. Scintimetry appears to be a promising method for determining if radiodensities seen in radiographs of long-term prostheses are indicative of accelerated bone turnover or represent stable osseous structures. In dogs, the periosteal reaction which often occurs within two months of joint surgery masks endosteal-intramedullary osseous changes, including bone ingrowth into the porous coating.
Animals↗
Phosphorylation of the beta subunit of Na+K+-ATPase in Ehrlich ascites tumor by a membrane-bound protein kinase.
We have shown previously that proteoliposomes reconstituted with purified Na+K+-ATPase from Ehrlich ascites tumor cells, transport Na+ with low efficiency (Spector, M., O'Neal, S. and Racker, E. (1980) J. Biol. Chem., 255, 5504-5507). We now present evidence that this low efficiency (expressed in the ratio of Na+-transported/ATP-hydrolyzed) is caused by the phosphorylation of the beta subunit of the Na+K+-ATPase by an endogenous protein kinase. On addition of [gamma-32P]ATP, crude tumor plasma membrane preparations phosphorylated the beta subunit of the ATPase, whereas crude mouse brain plasma membranes did not. However, solubilized Na+K+-ATPase from either tumor or brain wre phosphorylated by purified protein kinase from the tumor plasma membrane and dephosphorylated by a phosphatase. In both cases, the phosphorylated enzyme was inefficient; the dephosphorylated enzyme was efficient after reconstitution into liposomes. During isolation of the Na+K+-ATPase from Ehrlich ascites tumor or mouse brain, an endogenous protease partially cleaved from the beta subunit a polypeptide of 29,000 daltons that contained the phosphorylation site. The proteolytic cleavage of the beta subunit was partially inhibited by phenylmethylsulfonyl fluoride and the major site of phosphorylation was then seen in the 53,000-dalton beta subunit of the enzyme. The isolated 29,000-dalton polypeptide from mouse brain ATPase was phosphorylated by tumor protein kinase with a stoichiometry of 1 mol of phosphate/mol of protein. When this 29,000-dalton polypeptide from mouse brain was incorporated into the tumor Na+K+-ATPase after mild proteolytic digestion, a marked increase in efficiency was observed after reconstitution of the Na+ pump.
Animals↗
Reconstitution of the Na+K+ pump of Ehrlich ascites tumor and enhancement of efficiency by quercetin.
Plasma membranes from Ehrlich ascites tumor cells were solubilized by octylglucoside in the presence of phospholipids. The Na+K+-ATPase was purified from this extract by adsorption and elution from thio-Seph-arose 4B. The enzyme (specific activity, 7 mumoles of ATP hydrolyzed min-1 mg of protein -1) was reconstituted into liposomes by the octyglucoside dilution procedure. An ATP-dependent Na+ influx with low efficiency was observed. On addition of appropriate amounts of quercetin, the Na+ flux/ATP hydrolysis ratio was increased from 0.4 to 1.4.
Animals↗
Brushite encrustation and lithiasis of the prostatic bed after transurethral resection of the prostate.
The first case of brushite encrustation and lithiasis of the prostatic bed is reported following transurethral resection of the prostate. Brushite crystals form on hydroxyapatite deposits exposed to the acidic urinary stream after transurethral resection of the prostate and serve to spawn brushite calculi.
Calcium Phosphates↗
Characteristics of tissue growth into Proplast and porous polyethylene implants in bone.
(1) Bone does not form within internal pores of undistorted Proplast implants because of the small interconnecting pore size of the material; (2) the nonosseous, fibrous tissue which exists in the pores of Proplast implants in bone is not attached to the surrounding bone (i.e., Sharpey's fibers are not present). The load-bearing support which can be afforded by Proplast implants is limited by the incomplete bone ingrowth along the margins of the material and the tensile strength of Proplast.
Absorptiometry, Photon↗
Porous titanium endosseous dental implants in Rhesus monkeys: microradiography and histological evaluation.
Artificial tooth roots with porous surface coatings were fabricated by sintering spherical powder of titanium alloy to solid cylindrical cores. The tooth roots were implanted subgingivally in healed mandibular premolar extraction sites of fifteen Rhesus monkeys. Supracrestal abutments were screwed into pretapped holes in the superior aspect of the primary subgingival stage four to eight weeks after implantation of the root. Clinical evaluations were performed monthly. Ten animals were sacrificed for histological evaluation of the functioning free standing implants. Of twenty-nine implants placed, three were lost and four were rated failures on the basis of histological evaluation. Postmortem evaluations revealed bone growth into the porous surface coating of the primary stage of all the implants. The most characteristic features which could be used to describe differences in the implant histology were the buccal and lingual crestal bone heights measured in relation to the root porosity. Twelve of sixteen implants had crestal bone heights within one millimeter of the superior aspect of the root. Four other implants displayed excessive bone recession, revealing as much as one half of the root porosity supracrestally. The four implant failures could be related to unfavorable features of recipient bone sites. The results demonstrate that the bone growth into the porous surface coatings of artificial tooth roots is an efficacious method of dental implant fixation.
Alloys↗