Comparison of gentamicin immunoassays using univariate and multivariate analyses

Gentamicin concentrations, pharmacokinetic parameters, and calculated doses from enzyme multiplied immunoassay (EMI) and fluorescence polarization immunoassay (FPIA) were compared in 79 samples from 39 patients. Associations between patient factors and the differences between assay results were also assessed. Concentrations were lower when measured by EMI than by FPIA in 71 of the 79 samples (p less than 0.001). Mean EMI values for elimination rate constant, volume of distribution, clearance, dose, and daily dose were 10-20% higher than mean FPIA values (p less than or equal to 0.01). Dosing intervals calculated from EMI and FPIA data were different in 20 pairs of intervals and varied depending on the length of calculated interval. Univariate and multivariate analyses revealed that renal function and the presence or absence of cardiovascular disease, cimetidine, or ranitidine, and heparin were related to differences between the assay results. EMI and FPIA yielded different results for gentamicin concentrations, pharmacokinetic parameters, and calculated daily doses in the clinical setting. Such differences could result in toxic or subtherapeutic doses being administered and may be related, in part, to various patient factors.     

Evaluating home environments of persons with dementia: interrater reliability and validity of the Home Environmental Assessment Protocol (HEAP)

PURPOSE: This article reports on an interrater reliability and preliminary validity study of an investigator-developed tool, the Home Environmental Assessment Protocol (HEAP) for use in homes of persons with dementia. METHOD: The HEAP consists of 192 items that are summed into separate indices representing the number of hazards, adaptations, and level of clutter and comfort in eight areas of the home. Interrater reliability was examined among four raters, two environmental experts and two non-experts, who observed 22 dementia households. RESULTS: The Kappa statistic was used to evaluate agreement level for each measured item and found that agreement ranged from slight to almost perfect. Intraclass correlations (ICCs), were used to evaluate agreement level for indices. The hazard index in each room ranged from fair (0.36) to moderate (0.66) for all raters. For the adaptation, clutter and comfort indices in each room, ICCs ranged from 0.51 to 0.90 for all raters. Agreement level between expert and non-expert raters differed minimally for all indices. Adaptations to dining rooms (r= -0.080, p = 0.001), kitchens (r = -0.52, p = 0.02) and bedrooms (r = -0.76, p = 0.001) were associated with patient deficits such that more adaptations were made in homes of dependent persons. Low Mini-Mental Status Examination scores were associated with fewer hazards, more adaptations, and less clutter. CONCLUSION: Findings show that both experts and non-expert raters use the HEAP consistently. Also, measured attributes are related to cognitive and functional status in the expected direction.     

Evidence for a causal role of parathyroid hormone-related protein in the pathogenesis of human breast cancer-mediated osteolysis.

Breast cancer almost invariably metastasizes to bone in patients with advanced disease and causes local osteolysis. Much of the morbidity of advanced breast cancer is a consequence of this process. Despite the importance of the problem, little is known of the pathophysiology of local osteolysis in the skeleton or its prevention and treatment. Observations in patients with bone metastases suggest that breast cancer cells in bone express parathyroid hormone-related protein (PTHrP) more frequently than in soft tissue sites of metastasis or in the primary tumor. Thus, the role of PTHrP in the causation of breast cancer metastases in bone was examined using human breast cancer cell lines. Four of eight established human breast cancer cell lines expressed PTHrP and one of these cell lines, MDA-MB-231, was studied in detail using an in vivo model of osteolytic metastases. Mice inoculated with MDA-MB-231 cells developed osteolytic bone metastasis without hypercalcemia or increased plasma PTHrP concentrations. PTHrP concentrations in bone marrow plasma from femurs affected with osteolytic lesions were increased 2.5-fold over corresponding plasma PTHrP concentrations. In a separate experiment, mice were treated with either a monoclonal antibody directed against PTHrP(1-34), control IgG, or nothing before tumor inoculation with MDA-MB-231 and twice per week for 26 d. Total area of osteolytic lesions was significantly lower in mice treated with PTHrP antibodies compared with mice receiving control IgG or no treatment. Histomorphometric analysis of bone revealed decreased osteoclast number per millimeter of tumor/bone interface and increased bone area, as well as decreased tumor area, in tumor-bearing animals treated with PTHrP antibodies compared with respective controls. These results indicate that tumor-produced PTHrP can cause local bone destruction in breast cancer metastatic to bone, even in the absence of hypercalcemia or increased circulating plasma concentrations of PTHrP. Thus, PTHrP may have an important pathogenetic role in the establishment of osteolytic bone lesions in breast cancer. Neutralizing antibodies to PTHrP may reduce the development of destructive bone lesions as well as the growth of tumor cells in bone.     

Requirement of pp60c-src expression for osteoclasts to form ruffled borders and resorb bone in mice.

Targeted disruption of the c-src proto-oncogene in mice has shown that src expression is required for normal bone resorption, since the src-deficient mutants develop osteopetrosis. To evaluate the mechanisms by which src-deficiency affects osteoclast function, we treated src-deficient mice with the stimulants of bone resorption, IL-1, parathyroid hormone, and parathyroid hormone-related protein, and analyzed the effects by quantitative bone histomorphometry and electron microscopy. Increased numbers of multinucleated cells with the morphological characteristics of osteoclasts appeared on bone surfaces, but these cells did not form ruffled borders or normal resorption lacunae. To confirm these in vivo findings, we cultured src-mutant bone marrow cells on dentine slices in the presence of 1,25 dihydroxyvitamin D3. Increased numbers of multinucleated cells were formed, but unlike normal murine bone marrow cells, they did not form resorption pits. These results indicate that osteoclasts appear in the absence of pp60c-src, but that pp60c-src expression is required for mature osteoclasts to form ruffled borders and resorb bone.     

Anticoagulant regimens in acute continuous hemodiafiltration: a comparative study

Objective To compare and contrast different heparin regimens for extracorporeal circuit anticoagulation in patients receiving acute continuous hemodiafiltration (ACHD).Design Prospective controlled randomized comparisons of the following regimens: 1) Low dose (500 IU/h) prefilter heparin versus regional anticoagulation in patients on continuous arteriovenous hemodiafiltration (CAVHD) via A-V shunt. 2) Low dose pre-filter heparin versus no anticoagulation in patients receiving CAVHD via femoral cannulae. 3) Low dose pre-filter heparin versus regional anticoagulation in patients on continuous veno-venous hemodiafiltration (CVVHD). 4) An assessment of the consequences of the use of no anticoagulant in patients predicted to be at high risk of hemorrhagic complications on treatment with CVVHD.Setting University Teaching Hospital ICU.Patients 64 ICU patients with acute renal failure.Measurements and main results Haemofilter survival during shunt CAVHD was significantly prolonged by the use of regional anticoagulation compared to the use of low dose heparin (mean filter survival: 57.1 h versus 42.9 h;p<0.05). In CAVHD using femoral cannulae, no significant differences in haemofilter survival were found between anticoagulation with low dose heparin and the use of no anticoagulant (mean filter survival: 55 h versus 52.5 h; NS). During CVVHD, regional anticoagulation compared to low dose heparin produced a trend towards prolonged filter life which was, however, not statistically significant (mean filter survival: 40.5 h versus 31.4 h; NS). In patients assessed to be at high risk of bleeding, CVVHD without anticoagulation provided a mean filter survival of 40.9 h (95% CI 27-54.8 h).Conclusions Regional anticoagulation leads to longer filter survival than low dose heparin in shunt CAVHD. A regimen of no anticoagulation during femoral CAVHD leads to a filter life similar to that of low dose heparinization. During CVVHD, regional anticoagulation and low dose heparin are associated with similar filter survival times. In patients assessed to be at high risk of bleeding, treatment with CVVHD without anticoagulation results in adequate filter survival.     

Fibrillation potentials following spinal cord injury: improvement with neurotrophins and exercise

Fibrillation potentials and positive sharp waves (spontaneous potentials) are the electrophysiological hallmark of denervated skeletal muscle, and their detection by intramuscular electromyography (EMG) is the clinical gold standard for diagnosing denervated skeletal muscle. Surprisingly, spontaneous potentials have been described following human and experimental spinal cord injury (SCI) in muscles innervated by spinal cord segments distal to the level of direct spinal injury. To determine whether electrophysiological abnormalities are improved by two therapeutic interventions for experimental SCI, neurotrophic factors and exercise training, we studied four representative hindlimb muscles in adult domestic short-hair cats following complete transection of the spinal cord at T11-T12. In untreated cats, electrophysiological abnormalities persisted unchanged for 12 weeks postinjury, the longest duration studied. In contrast, fibrillations and positive sharp waves largely resolved in animals that underwent weight-supported treadmill training or received grafts containing fibroblasts genetically modified to express brain-derived neurotrophic factor and neurotrophin-3. These findings suggest that neurotrophins and activity play an important role in the poorly understood phenomenon of fibrillations distal to SCI.     

Isolation,structural determination,synthesis and quantitative determination of impurities in Intron-A,leached from a silicone tubing

Investigation of unexpected levels of impurities in Intron product has revealed the presence of low levels of impurities leached from the silicone tubing (Rehau RAU-SIK) on the Bosch filling line. In order to investigate the effect of these compounds (1a, 1b and 2) on humans, they were isolated identified and synthesized. They were extracted from the tubing by stirring in Intron placebo at room temperature for 72 h and were enriched on a reverse phase CHP-20P column, eluting with gradient aqueous ACN and were separated by HPLC. Structural elucidation of 1a, 1b and 2 by MS and NMR studies demonstrated them to be halogenated biphenyl carboxylic acids. The structures were confirmed by independent synthesis. Levels of extractable impurities in first filled vials of actual production are estimated to be in the range of 0.01–0.55 μg/vial for each leached impurity. Potential toxicity of these extractables does not represent a risk for patients under the conditions of clinical use.     

Wild Felids as Hosts for Human Plague, Western United States

Plague seroprevalence was estimated in populations of pumas and bobcats in the western United States. High levels of exposure in plague-endemic regions indicate the need to consider the ecology and pathobiology of plague in nondomestic felid hosts to better understand the role of these species in disease persistence and transmission.