Stable association of PYK2 and p130(Cas) in osteoclasts and their co-localization in the sealing zone

Bone resorption is initiated by osteoclast attachment to the mineralized matrix, cytoskeletal reorganization, cellular polarization, and the formation of the sealing zone. The present study examines the interaction between PYK2 and p130(Cas) (Crk-associated substrate), suggested to be part of the signaling pathway initiated by osteoclast adhesion. Using murine osteoclast-like cells (OCLs) and their mononuclear precursors (pOCs), generated in a co-culture of bone marrow and osteoblastic MB1.8 cells, we show that: 1) p130(Cas) is tyrosine-phosphorylated upon adhesion of pOCs to vitronectin or ligation of beta3 integrins; 2) p130(Cas) colocalizes with PYK2 and the cytoskeletal proteins F-actin, vinculin, and paxillin in the podosomal-rich ring-like structures of OCLs plated on glass and in the sealing zone in actively resorbing OCLs on bone; 3) p130(Cas) and PYK2 form a stable complex in pOCs, independent of tyrosine phosphorylation of either molecule, and this complex is present in Src (-/-) OCLs, in which neither protein is phosphorylated or associated with the osteoclast adhesion structure; 4) the association of p130(Cas) and PYK2 is mediated by the SH3 domain of p130(Cas) and the C-terminal domain of PYK2. These findings suggest that p130(Cas) and its association with PYK2 may play an important role in the adhesion-dependent signaling that leads to cytoskeletal reorganization and formation of the sealing zone during osteoclast activation.     

Cerebrospinal fluid selenium and chromium levels in patients with Parkinson's disease

We compared CSF and serum levels of selenium and chromium, measured by atomic absorption spectrophotometry, in 28 patients with Parkinson's disease (PD) and 43 matched controls. The CSF and serum levels of these trace metals did not differ significantly between PD patients and controls. CSF selenium and chromium levels were not correlated with age, age at onset, duration of the disease, scores of the Unified Parkinson Disease Rating Scale of the Hoehn and Yahr staging in the PD group. Although antiparkinsonian therapy did not influence significantly the CSF levels of selenium, PD patients not treated with levodopa had significantly higher CSF selenium levels than controls (p < 0.01). It is possible that increased CSF selenium levels could indicate an attempt of protection against oxidative stress. The normality of CSF and serum chromium levels suggest that these values are not related with the risk for PD.     

Computerized tomographic assessment of the composition of gallstones

We present the results of an in vitro study of biliary lithiasis (n = 106) with computerized tomography (CT). We analyzed the correlation between composition of gallstones (crystallographic analysis of thin sections and atomic absorption spectrophotometric analysis of total calcium content) with CT patterns (densitometry) and their corresponding attenuations. Six main CT patterns were distinguished: hypodense (homogeneous and heterogeneous), dense, homogeneous hyperdense, ringed hyperdense and irregular hyperdense. Statistically significant differences (p < 0.05) were found between attenuations for cholesterol (mixed and pure) and pigmentary stones. We found a good inverse correlation between attenuations and cholesterol content; the contents of pigment, inorganic calcic salts and total calcium content also showed significant direct correlations (p < or = 0.01). Of the samples classified as pure cholesterol type stones, 86.4% showed hypodense patterns, and the remaining 13.6% showed irregular hyperdense patterns. Of the pigmentary stones, 80% showed homogeneous hyperdense images. All stones that contained more than 3% calcium produced hyperdense patterns, whereas 72.4% of the stones that contained less calcium produced hypodense images. Tomodensitometric measurements provided more information than simple radiography, and made it possible to distinguish a greater variety of gallstone types based on structural complexity.     

The stability of children's physical activity as measured by accelerometry and self-report

The Computer Science Application (CSA) accelerometer uses integrated circuitry and memory to provide a continuous recording of minute-by-minute movement counts. It has been previously validated as an objective monitor of children's physical activity in field and laboratory settings. Our purpose was to derive accelerometry summary variables reflective of different physical activity intensity levels, evaluate the stability of these summary variables, and define the number of days needed to adequately measure usual physical activity. A secondary study purpose was to compare three self-report questionnaires to accelerometry. Thirty children (7-15 yr) wore accelerometers for 12 h.d-1 for 6 d. Daily summary variables of average movement count (total physical activity) and daily frequency of sedentary through vigorous activity were constructed. Intraclass correlation coefficients (R) and 95% confidence intervals (CI) were used to analyze the data. Accelerometry stability using 1 monitored day to represent usual physical activity was R = 0.42-0.47. When 6 d were used, stability increased to R = 0.81-0.84. Acceptable intraclass correlations and CI were achieved with 4 d of monitoring (R = 0.75-0.78, CI = 0.60-0.88). The self-report questionnaires were poorly to moderately correlated to accelerometry variables (r = -0.03-0.51). Data indicate that in field settings: 1) accelerometry can be used to assess the intensity of children's activity and 2) 4 or more days of activity monitoring are needed to achieve satisfactory reliability.     

Unfolding and inactivation of Penaeus penicillatus acid phosphatase during denaturation by guanidine hydrochloride

Neuromuscular terminals of a single motoneuron to four muscles (CPV7a, GM5a, CV2, and CV3) in the stomach of the blue crab Callinectes sapidus showed structural evidence for the exocytotic release of dense-core vesicles exclusively at synapses. The primary evidence was the appearance of dense cores in the synaptic cleft, accompanied by indentations of the presynaptic or postsynaptic membrane. In their simplest form, these consisted of an omega-shaped figure of the presynaptic membrane enclosing one dense core, denoting release of a single dense-core vesicle. A larger indentation of the presynaptic membrane enclosing several dense cores denoted multiple release. A more complex form of multiple release was where the presynaptic membrane was normal, but the postsynaptic membrane elaborated into a sac projecting into the granular sarcoplasm and filled with dense cores. The postsynaptic sac in some instances was compressed into a thin, fingerlike extension, which lacked dense cores and, at its distal end, separated into small cisternae, suggesting a mechanism for membrane recycling. Profiles depicting single and multiple releases of dense-core vesicles were found more frequently at neuromuscular terminals that release relatively large amounts of transmitter with a single stimulus, such as CV2 and CV3, compared to those releasing smaller amounts, such as CPV7a and GM5a. The disparity in release sites among the four muscles of this single motor unit and the fact that many of the multiple-release figures were closely adjacent to the active zones for transmitter release suggest a possible modulatory role for dense-core vesicles in synaptic transmission. Such modulation may be long lasting, as implied by the postsynaptic sacs, which may permit prolonged release of the contents of their dense cores into the synaptic cleft. This is in keeping with the functional role of these stomach muscles, which is to be continuously active for long periods of time.     

Hospital experience and hospital mortality following partial pancreaticoduodenectomy in The Netherlands

OBJECTIVE: To analyse the effect of hospital experience on mortality after subtotal pancreaticoduodenectomy in the Netherlands. DESIGN: Retrospective evaluation. METHOD: Information on hospital mortality and pancreatic resection in 1994 and 1995 in the Netherlands was obtained from the National Medical Register. Subanalysis was carried out of surgical mortality by age and hospital experience. RESULTS: Approximately 50% of the pancreaticoduodenectomies in the Netherlands were performed in hospitals with limited experience (< 5 procedures per year). Hospital mortality was higher in small-volume hospitals than in hospitals with experience (> 25 procedures per year): in 1994 17.2 and 0% and in 1995 14.6 and 2.9%, respectively (p < 0.05). Mortality was higher in patients older than 70 years compared with patients younger than 55 (p < 0.05). CONCLUSION: There was a correlation between mortality after pancreaticoduodenectomy and hospital experience. Therefore these procedures should be performed in centres with experience.