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Biomedical subjects

J Black

Publications and source records attributed to J Black.

At least 145 records · Page 8Linked to original sources
PubMed1995

Local and distant products from modularity.

In this study, the local and distant distribution of solid and soluble products of corrosion from the head and neck junction of modular femoral total hip prosthetic components were characterized. Particulate corrosion products from retrieved implants and surrounding tissues were analyzed. Serum transport and urinary excretion of metal was measured in correlation with the degree of corrosion at the head and neck junction. Particles of metal oxides, metal chlorides, and chromium phosphate corrosion products were identified on implants of 10 designs from 6 manufacturers. The most abundant solid corrosion product on the implant and within the periprosthetic tissues (size range, < 1-200 micrometers) was an amorphous chromium orthophosphate hydrate-rich material. Serum cobalt and urine chromium concentrations were elevated significantly in patients with implants that had moderate to severe corrosion in comparison with those with no to mild corrosion. Solid corrosion products from modular femoral stems may accelerate articular wear via a 3-body mechanism. Phagocytosable particles of these corrosion products may stimulate macrophage-mediated periprosthetic bone loss. Systemic dissemination of metallic corrosion products raises the issue of systemic toxicity; however, no overt evidence of metal toxicity was observed in this study.

Adult↗
PubMed1995

Carbon dioxide laser removal of polymethylmethacrylate.

Polymethylmethacrylate remains an excellent method of securing orthopaedic implants. However, revision surgery may be necessary when loosening of the prosthesis has occurred with symptomatology. Removal of polymethylmethacrylate during revision surgery can be difficult. Care must be taken to avoid damage to the remaining bone and surrounding soft tissue. This study was undertaken to characterize the efficacy of the carbon dioxide (CO2) laser for cement removal in vitro and in vivo. The CO2 laser did not damage adjacent bone or soft tissue via lateral heat transfer in vitro and in vivo. The maximum bone cortex temperature during CO2 laser removal was 56 degrees C. This was lower than the 60 degrees C temperature encountered during initial cement insertion and curing. The CO2 laser preferentially penetrates polymethylmethacrylate with absorption versus apparent relative reflection with bone. The products of vaporization from CO2 laser removal of polymethylmethacrylate were removed safely (to < 12.2 ppm) with a smoke evacuator without risk to the patient or operating room personnel. Removal of polymethylmethacrylate by CO2 laser was performed in 117 patients undergoing revision operations, including 78 total hip revisions, 33 total knee revisions, 3 total elbow revisions, and 3 spine revisions. No perforation or fracture of bone occurred with the use of the laser. There was no statistical difference in surgical time, blood loss, infection rate, or hospital stay when the CO2 laser was used. There were no cases of osteonecrosis or obvious soft tissue necrosis caused by the laser. The infection rate was 3.4% (4/117) when the laser was used for cement removal.

Body Temperature↗
PubMed1994

Polio eradication.

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Cost of Illness↗
PubMed1994

Simultaneous determination of primaquine and carboxyprimaquine in plasma using high-performance liquid chromatography with electrochemical detection.

A selective and sensitive high-performance liquid chromatographic method with electrochemical detection is described for the simultaneous quantitation of primaquine and carboxyprimaquine, its primary metabolite, in plasma. After addition of internal standard, plasma was deproteinized by addition of acetonitrile. Nitrogen-dried supernatants, resuspended in mobile phase were analyzed on a C8 reversed-phase column. Limits of detection for primaquine and carboxyprimaquine were 2 and 5 ng/ml with quantitation limits of 5 and 20 ng/ml, respectively. None of 47 tested antimicrobial agents interfered. In contrast to previously reported methods, the assay sensitivity and specificity are sufficient to permit quantitation of primaquine in plasma for pharmacokinetics following low dose (30 mg, base) oral administration of primaquine, typically used in the treatment of malaria and Pneumocystis carinii pneumonia.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Origins of the variations in long-term potentiation between synapses in the basal versus apical dendrites of hippocampal neurons.

Responses to theta pattern stimulation, and the long-term potentiation (LTP) they induce, were compared in the basal versus apical dendrites of neurons in field CA1 of hippocampus. A series of 10 theta bursts produced more than twice as much LTP in basal synapses as in their apical counterparts as measured with field EPSPs. This confirms earlier field potential studies showing that the maximum degree of potentiation (the LTP ceiling) is considerably greater in stratum oriens than stratum radiatum. Experiments with whole-cell clamp recording obtained similar results, indicating that synapses at different loci on the same neuron reach different LTP ceilings following prolonged theta burst stimulation. The basal synapses also required fewer theta bursts to reach their LTP ceiling than did the apical synapses. Tests with paired-pulse facilitation and an antagonist of the NMDA receptor gave no indication that the greater LTP in basal synapses was qualitatively different from the lesser effect obtained in apical contacts. Intracellular recording revealed significant differences between basal versus apical responses to single theta bursts and trains of bursts: the within-burst depolarization was greater and the between-burst hyperpolarization was smaller for the basal dendritic responses. These two variables have previously been proposed to influence the magnitude of LTP and the observed differences between basal versus apical synapses are in accord with this hypothesis. Together with recently described immunocytochemical results, the findings reported here suggest that variations in LTP across dendritic subfields of hippocampus reflect a differential distribution of a subclass of GABAergic interneurons.

Animals↗
PubMed1994

Macrophage/particle interactions: effect of size, composition and surface area.

Particulate wear-debris are detected in histiocytes/macrophages of granulomatous tissues adjacent to loose joint prostheses. Such cell-particle interactions have been simulated in vitro by challenging macrophages with particles dosed according to weight percent, volume percent, and number of particles. Each of these dosage methods has inherent shortcomings due to varying size and density of challenging particles of different compositions. In this study we challenged P388D1 macrophages with titania and polystyrene particles (< 2 microns), with dosage based on the ratio of the surface area of the particles to the surface area of the cells. The effect of size and composition on (1) the bone resorbing activity, (2) fibroblast proliferation, and (3) secretion of IL-1 and PGE2 was determined. Macrophage response to particulate debris appears to be dependent on particle size, composition, and dose as given by surface area ratio. P388D1 macrophages challenged with titania particles released IL-1, but did not stimulate fibroblasts. Inhibition of macrophage DNA synthesis at higher surface area ratios suggests cell damage or death. Particle-stimulated cells increased bone resorption up to 125% of controls but released only basal levels of PGE2. Macrophages stimulated by wear particles are expected to synthesize numerous factors affecting events in the bone-implant interface. Using the concept of surface area ratio allows us to study and compare such cellular responses to wear particles in a standardized manner.

Animals↗
PubMed1994

Cryopreservation of murine ovarian tissue.

To determine the feasibility of ovarian transplantation using cryopreserved tissue, ovaries were removed from anesthetized 12- to 20-week-old female mice. The controls consisted of a sham-operated group and an oophorectomized group, and the experimental groups were autologous transplants with and without cryopreservation. Ovaries for cryopreservation were suspended in 1.4 M dimethyl sulfoxide Tyrode's solution, at 22 degrees C for 5 min and cooled at a controlled rate (0.5 degrees C/min) to -55 degrees C. The ovaries were stored in liquid nitrogen for 1 to 30 days and then thawed at room temperature. Thawed ovarian tissue was washed free of dimethyl sulfoxide and transplanted. Subsequent daily examination of vaginal cytology indicated ovarian endocrine activity in all groups except those oophorectomized without transplants. Animals receiving ovarian tissue, fresh and cryopreserved, were euthanized at diestrus I, 6 weeks postoperatively, for ovarian histology; both groups demonstrated folliculogenesis. The histology and endocrine function of autotransplanted cryopreserved ovaries were similar to those of nonfrozen transplanted ovaries and of ovaries in sham-operated groups.

Animals↗
PubMed1994

Identification of four genes involved in the lysogenic pathway of the Salmonella newington bacterial virus epsilon 34.

A structure/function study has been initiated for the epsilon 34 bacteriophage proteins involved in lysogeny in Salmonella newington. Hydroxylamine and nitrosoguanidine mutagenesis of a wild type epsilon 34 phage was used to generate clear plaque variants. Complementation analysis was used to define four genes involved in the phage lysogenic pathway. A relative mapping order has been established. In addition, a virulent mutant, epsilon 34vir82, which defines a repressor binding site has been isolated.

Genes, Viral↗
PubMed1994

Prevention of relapse of histoplasmosis with fluconazole in patients with the acquired immunodeficiency syndrome.

OBJECTIVE: To assess the effectiveness of fluconazole for suppression of relapse of histoplasmosis in patients with acquired immunodeficiency syndrome (AIDS). DESIGN: Retrospective, nonrandomized, open trial. SETTING: Multicenter at two university referral centers and in five private practices. PATIENTS: Seventy-six patients with AIDS and disseminated histoplasmosis who completed induction treatment with amphotericin B, itraconazole, or fluconazole and maintained on treatment with fluconazole to prevent relapse. INTERVENTIONS: Fluconazole was given at dosages of 100 to 400 mg per day. Patients were followed by their primary physicians, who completed questionnaires collecting information about treatment and relapse status. Blood and urine specimens were submitted periodically for Histoplasma capsulatum var. capsulatum antigen determination. MEASUREMENTS AND MAIN RESULTS: Nine of the 76 patients relapsed during fluconazole therapy and another was removed from the study because of allergic rash. Survival after initiation of therapy for histoplasmosis was 94 weeks, ranging from 74 weeks for those who received less than 1 g of amphotericin B for induction and none for maintenance therapy to 156 weeks for those who received greater than 1 g for induction and additional amphotericin B for maintenance therapy before beginning fluconazole (P < 0.02). Antigen levels fell at rates of 0.05 units/week in urine and 0.02 units/week in serum in patients who were successfully maintained in remission and increased by > or = 2 units/week in 4 of 6 patients who relapsed. CONCLUSIONS: Fluconazole > or = 200 mg daily is a reasonable choice for chronic suppressive therapy of histoplasmosis in patients who cannot take itraconazole because of drug interactions, malabsorption, or side effects.

AIDS-Related Opportunistic Infections↗
PubMed1994

Neurotoxicity and haemostatic disturbances in patients envenomed by the Papuan black snake (Pseudechis papuanus).

Among 335 patients presenting with snakebites in Central Province, Papua New Guinea, nine were proved by enzyme immunoassay to have been bitten by Papuan black snakes (Pseudechis papuanus). Seven showed clinical evidence of envenoming. Early symptoms included vomiting and tender local lymph nodes. Five patients had neurotoxic signs and one required mechanical ventilation. Spontaneous systemic bleeding occurred in two patients. Coagulation studies in four patients showed thrombocytopenia, prolongation of prothrombin time, mild defibrination and depletion of other clotting factors with elevated fibrin(ogen) degradation products and other evidence of fibrinolysis. One patient developed mild renal dysfunction. There was no evidence of intravascular haemolysis or rhabdomyolysis. These clinical observations, which do not distinguish victims of P. papuanus from those of taipans (Oxyuranus scutellatus canni), suggest that the venom contains neurotoxic, haemorrhagic and mild procoagulant activities. Only two other cases of proven envenoming by this species have been reported. There appears to have been a decline in the abundance of this species, and hence its medical importance, over the last 25 years.

Adolescent↗
PubMed1994

Competitive binding of chromium, cobalt and nickel to serum proteins.

The competitive binding of chromium, cobalt and nickel chloride salts to murine serum proteins was studied in vitro. Individual metal salt solutions and combinations were incubated with 1:20 dilution of murine serum proteins for 24 h. Then free metal was removed by dialysis. The protein bound metal ions were analysed by graphite furnace atomic absorption spectroscopy. This study determined the saturation binding of cobalt and nickel to serum proteins. Murine serum is mostly saturated when cobalt or nickel is added at the concentration of 2 mol of metal to 1 mol of albumin. Chromium and cobalt have similar protein binding affinity, chromium and cobalt bind to protein in proportion to the added concentration ratio. However, nickel shows significant competition for chromium and cobalt binding moieties. This study provides a reference for future research on the biological role and properties of corrosion products.

Animals↗
PubMed1994

Survey of cell lines in the American Type Culture Collection for bovine viral diarrhea virus.

Cell lines originating from cattle, sheep, goat, deer, bison, swine, rabbit, hamster, cat, dog, monkey, human, and mosquito were obtained from the American Type Culture Collection and tested for contamination with bovine viral diarrhea virus (BVDV). Immunocytochemical procedures and polymerase chain reaction (PCR) amplification were used to detect viral antigen or viral RNA in 13 of 41 cell lines. The results of these procedures correlated exactly. Cell lines derived from cattle, sheep, goat, deer, bison, rabbit, and domestic cat were found contaminated with BVDV. Attempts were made to experimentally infect 14 swine, rabbit, hamster, cat, dog, monkey, and human cell lines that had been found free of virus. All swine cell lines, and most rabbit and cat cell lines, became infected with BVDV. Hamster, human, dog, and certain rabbit and cat cells were refractory to BVDV infection. Experimental infection of monkey cells produced variable results.

Animals↗