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Biomedical subjects

M Spector

Publications and source records attributed to M Spector.

At least 37 records · Page 2Linked to original sources
PubMed1986

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↗
PubMed1985

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↗
PubMed1985

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↗
PubMed1984

Histological evaluation of porous titanium cardiac pacemaker electrode tips.

An investigation of the tissue reaction to five porous titanium alloy pacemaker electrode tips inserted in sheep hearts was made. Attachment of the electrode tips to the endocardial wall was facilitated by fibrous tissue ingrowth into the porous material. Vascularized fibrocollagenous tissue was found within the pores of the tips. One tip was found to be infected. The presence of occasional multinucleated foreign-body giant cells within the porosity was related to the particulate features of the porous tip. The electrode tips had a reduced sensing impedance compared with conventional solid platinum tips. The present findings are consistent with previous observations relating to porous cobalt-chromium alloy and porous platinum-iridium alloy tips and suggest that porous titanium alloy may be a suitable pacemaker electrode tip material.

Alloys↗
PubMed1983

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↗
PubMed1983

Histological investigation of bone induction by demineralized allogeneic bone matrix: a natural biomaterial for osseous reconstruction.

The objective of the study was to delineate the histological sequence of events associated with bone formation induced in extraosseous sites by implants of demineralized allogeneic bone matrix (DABM) in order to provide a more complete basis for the clinical use of the natural biomaterial for osseous reconstruction. The rat was the experimental animal model. Implants were prepared by demineralization of diaphyseal cortical rat bone in 0.6N HCl for 18-24 h. A total of 104 specimens, 4 mm square, were implanted both subcutaneously and intramuscularly in 26 rats for periods of 3 days to 22 weeks. Histological evaluation revealed a sequence of events that at 3 days displayed an inflammatory response to surgical trauma and after 6 weeks exhibited the formation of a mature lamellar ossicle with central marrow which was maintained through 22 weeks. Resorption of the DABM, first evident at 1 week, was accompanied by the appearance of chondroblast in vascular canals and in crevices in the implant. Osteoblastic activity, initially seen at 2 weeks, appeared to be associated with capillary and blood vessel formation around the implant and within enlarged resorptive cavities within the specimens. Calcification occurred in the cartilaginous matrix and osteoid and within the implanted matrix. The osteoinductive process comprises (1) the inflammation/granulation/scar formation processes elicited by implantation of a material, (2) the resorptive response elicited by DABM, and (3) the process of induction of nonosseous mesenchymal cells to differentiate to chondroblasts and osteoblasts. The results of the present study support previous investigations demonstrating the bone-inducing property of DABM and provide further evidence for the potential value of this natural biomaterial for use in osseous reconstruction.

Animals↗
PubMed1983

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↗
PubMed1983

Osteomyelitis of the foot.

A favorable outcome was obtained in the case of an infected diabetic ulcer that resulted from neglect. The importance of appropriate antibiotic therapy and the advantage of a newer generation cephalosporin, cefamandole nafate (Mandol), is discussed. Optimal diagnostic information relative to the presence of osteomyelitis may be obtained by concomitant use of conventional radiographic technique and bone scanning. The most complete information concerning the status of diabetic control is gained by evaluation of standard blood glucose levels in conjunction with glycosylated hemoglobin A1C.

Cephalosporins↗
PubMed1983

Porous polysulfone coatings for fixation of femoral stems by bony ingrowth.

Sixteen porous polysulfone-coated canine femoral stems were inserted into 14 dogs. Coatings were approximately 40% porous, with an average pore size of 125 or 250 microns. Bone was formed within at least about 30% of the surface pores of the implants. The tissue ingrowths filling the pores included marrow and fibrous tissue. Correlated roentgenographic and histologic observations revealed a trabecular "lamina dura" at the coating-bone interface and relatively dense trabeculae distal to the stem tip. These observations support the concept of coating femoral prostheses with porous material for cement-free stabilization.

Animals↗
PubMed1982

Effects of magnesium deficiency on intratubular calcium oxalate formation and crystalluria in hyperoxaluric rats.

Previous studies have shown that magnesium deficiency accelerates renal tubular calcium oxalate monohydrate deposition in rats on chronic hyperoxaluric, lithogenic protocols. The present study was conducted to investigate the effect of magnesium deficiency on intratubular calcium oxalate formation in rats from the 1st day of administration of a hyperoxaluric agent. The objectives were to delineate early ultrastructural features of the formation, mechanisms of retention, and development of renal tubular crystal deposits and to characterize the crystalluria in rats on the hyperoxaluric/hypomagnesuric protocol. Intratubular calcium oxalate monohydrate deposits were found in magnesium deficient rats after only 24 hours of ad libitum administration of 1 per cent ethylene glycol drinking water. Animals on regular food diet did not display renal tubular deposition after 11 days of ethylene glycol administration. Strand- and sheet-like organic material emanating from the luminal wall of the tubules was adherent to the crystals, thereby serving to immobilize them within the tubule. Calcium oxalate monohydrate crystals predominated in the urines of hyperoxaluric/hypomagnesuric animals with intratubular deposits while dihydrate crystals were the primary constituent of urines from rats administered ethylene glycol alone (no intratubular deposition). The results support the supposition that under certain conditions magnesium deficiency is a significant risk factor for intrarenal calcium oxalate deposition and stone formation. Furthermore the identification of calcium oxalate monohydrate crystalluria may be an important indicator of the propensity toward intranephronic calcium oxalate formation and urolithiasis.

Animals↗
PubMed1982

Intratubular calcium phosphate deposition in acute analgesic nephropathy in rabbits.

Earlier chronic studies using both animal and human autopsy material have suggested that the initial lesion of analgesic nephropathy is papillary necrosis with secondary cortical interstitial nephritis. The present study was designed to define ultrastructural changes in renal tubules exposed to high levels of analgesics. Female New Zealand White rabbits were given 5-7 g APC and sacrificed after periods of 6 to 36 hours. As early as 6 hours after treatment, hydroxyapatite crystallite aggregates were seen impacted in Segment III (straight segment) of the proximal tubule at the cortico-medullary junction. Ultrastructural changes included selective calcification of the brush border, mitochondrial calcification, and peroxisomal changes. It was concluded, on the basis of ultrastructural changes, that calcification of altered tubular cells may be an initial event in analgesic nephropathy.

Analgesics↗
PubMed1981

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↗