Surface behavior of axolemma monolayers: Physico-chemical characterization and use as supported planar membranes for cultured Schwann cells

The axolemma membrane forms a stable and reproducible monomolecular layer at the air-aqueous interface. The major lipids and proteins are present in this monolayer in molar ratios similar to the original membrane. Acetylcholinesterase and Na-K-ATPase activities are preserved in the monolayer to levels of 64% and 25%, respectively. The total lipid fraction forms a homogeneously mixed phase. The presence of proteins in the monolayer introduces surface inhomogeneties. Among other features, this is revealed by the presence of two values of lateral pressure at which the monolayer shows partial or total collapse: a broad partial collapse at surface pressures between 13 to 30 mN/m and a sharp collapse point at 46 mN/m. The average molecular areas, the broad collapse point, and the variation of the surface potential per molecule suggest the relocation of protein components at surface pressures between 13 to 30 mN/m. The behavior is consistent with the extrusion and exposure of proteins toward the aqueous medium that depends on the lateral pressure. Schwann cells grown on coverslips coated with axolemma monolayers at 13 mN/m (beginning of the broad collapse) and 34 mN/m (above the broad collapse) recognize the difference in the surface organization of axolemma caused by the lateral pressure which affects their proliferation, morphology, and spatial pattern of organization. Our results show for the first time that response of Schwann cells depends on the intermolecular organization of the axolemma surface with which they interact. These results suggest that the local expression of putative surface molecules of axolemma that may mediate membrane recognition and the signalling of morphological and proliferative changes can be modulated by long range supramolecular properties. © 1993 Wiley-Liss, Inc.     

Stress signaling through Ca2+/calmodulin-dependent protein phosphatase calcineurin mediates salt adaptation in plants

Calcineurin (CaN) is a Ca²⁺- and calmodulin-dependent protein phosphatase (PP2B) that, in yeast, is an integral intermediate of a salt-stress signal transduction pathway that effects NaCl tolerance through the regulation of Na⁺ influx and efflux. A truncated form of the catalytic subunit and the regulatory subunit of yeast CaN were coexpressed in transgenic tobacco plants to reconstitute a constitutively activated phosphatase in vivo. Several different transgenic lines that expressed activated CaN also exhibited substantial NaCl tolerance, and this trait was linked to the genetic inheritance of the CaN transgenes. Enhanced capacity of plants expressing CaN to survive NaCl shock was similar when evaluation was conducted on seedlings in tissue culture raft vessels or plants in hydroponic culture that were transpiring actively. Root growth was less perturbed than shoot growth by NaCl in plants expressing CaN. Also, NaCl stress survival of control shoots was enhanced substantially when grafted onto roots of plants expressing CaN, further implicating a significant function of the phosphatase in the preservation of root integrity during salt shock. Together, these results indicate that in plants, like in yeast, a Ca²⁺- and calmodulin-dependent CaN signal pathway regulates determinants of salt tolerance required for stress adaptation. Furthermore, modulation of this pathway by expression of an activated regulatory intermediate substantially enhanced salt tolerance.     

Metastatic Psammomatous Somatostatinoma of the Pancreas Causing Severe Ketoacidotic Diabetes Cured by Surgery

A case of somatostatin-producing pancreatic tumor associated with severe insulindependent diabetes mellitus and ketoacidotic coma is reported. The tumor, a 10-cm expansile mass arising from the pancreatic tail of a 70-yr-old woman, was first detected by ultrasonography, performed because of abdominal pain, and subsequently confirmed by computed tomography and fine-needle tumor aspiration. Pathologic investigation showed a predominatly solid-trabecular structure with scattered microacini and psammomatous bodies. A large proportion of tumor cells expressed somatostatin and/or calcitonin. Following resection of the primary tumor and three peripancreatic lymph nodes with metastases, the patient recovered rapidly from her diabetic syndrome and remained in substantially good health during a subsequent 8-yr follow-up period, without evidence of tumor recurrence.     

Inhibition of nitric oxide synthase dramatically potentiates seizures induced by kainic acid and pilocarpine in rats

We investigated whether the severity of convulsions evoked by kainic acid and pilocarpine is modified in nitric oxide synthase inhibitor-treated rats. We found that chronic treatment (4 days) withN_w-nitro-l-arginine greatly potentiates seizures induced by both convulsants suggesting a potential role for nitric oxide in mechanisms regulating seizure induction and propagation.     

Proficiency test in clinical mammography. Results of a consecutive series of 130 volunteer Italian radiologists

PURPOSE: We evaluated the results obtained by 130 Italian radiologists undergoing a proficiency test of clinical mammography. MATERIAL AND METHODS: Radiologists were invited to report a series of 100 mammograms (two views), including 32 cancers and 78 non-cancers, with limited information regarding age, subjective symptoms, and findings at palpation. Sensitivity and specificity were then calculated. The test was validated by a panel of experts, and standards for test sufficiency were established on that basis (sensitivity > 80%, specificity > 85%). The tested radiologists differed by mammographic practice (average = 5.7 years, range 0.5-18), total number of mammograms read (average = 8,784, range 300-50,000) and per year (average = 1,535 range 300-5,000). RESULTS: Sensitivity (standard > 80%, average 81.1%, range 39-100%) and specificity (standard > 85%, average 84.0%, range 38-98%) standards were reached by 79 (60.8%) and 81 (62.3%) radiologists, respectively. Overall, only 37 (28.5%) radiologists passed the test (reached both standards). Mammographic practice (years of experience) (chi 2 for trend 5.26, p = 0.02), total mammograms read (chi 2 5.86, p = 0.05), and mammograms read per year (chi 2 8.07, p = 0.01) significantly correlated with a sufficient test. DISCUSSION: The evaluated sample is rather large but not necessarily representative of Italian radiologists. Had the sample been selected, there is no way to know if the results would have been biased towards a better or worse figure with respect to the national average. A significant correlation was found with reading experience (the best results were obtained by operators with > 10,000 films read and with > 2,000 films read/year), as which is important because most Italian radiologists reporting mammography usually read a limited number of cases. CONCLUSIONS: These results on such a wide sample of radiologists, possibly representative of the national average, are disappointing, and suggest that the average quality of mammography reporting in Italy may not be up to standards. Thus, we suggest that quality control program for clinical mammography not only test the equipment but include training and accreditation of radiologists.