Intermittent contact mode AFM investigation of native plasma membrane of Xenopus laevis oocyte.

Intermittent contact mode atomic force microscopy (AFM) was used to visualize the native plasma membrane of Xenopus laevis oocytes. Oocyte membranes were purified via ultracentrifugation on a sucrose gradient and adsorbed on mica leaves. AFM topographs and the corresponding phase images allowed for visualization and identification of both oocyte plasma membrane patches and pure lipid bilayer regions with a height of about 5 nm within membrane patches. The quantitative analysis showed a normal distribution for the lateral dimension and height of the protein complexes centered on 16.7 +/- 0.2 nm (mean +/- SE, n = 263) and 5.4 +/- 0.1 nm (n = 262), respectively. The phase signal, providing material-dependent information, allowed for the recognition of structural features observed in AFM topographs.

Adhesion and proliferation of fibroblasts on cluster-assembled nanostructured carbon films: the role of surface morphology.

We have investigated the influence on adhesion and proliferation of NIH 3T3 fibroblasts of the surface morphology of cluster assembled carbon films deposited by Supersonic Cluster Beam Deposition. Nanostructured carbon films exhibit a multi-scale morphology, which resembles the surface structure of the extracellular matrix, and possess a high specific area, while being relatively smooth at all scales. Correlations between measured morphological parameters and adaptive cell response have been brought out. High specific area and smoothness appear to conceivably favour both the early attachment of plated cells and the long-term survival of adherent cells. Moreover, nano-structured carbon films affect the cells morphology as well as the extension and the number of the focal contacts.

[Colon recanalization after Hartmann's procedure. A challenge for the surgeon or a strategy to be changed?]. / La ricanalizzazione del colon dopo l'intervento di Hartmann. Un impegno per il chirurgo o una strategia da cambiare?

AIM: Restoration of colorectal continuity is the second step of the procedure originally described by H. Hartmann for the treatment of sigmoid colon cancers. It is a safe, but complex procedure, that needs a meticulous surgical technique and is associated with a significant morbidity in as many as 40% of cases. For this reason, many patients are not submitted to reversal of the colostomy. METHODS: The authors report their experience: 32 patients underwent colostomy closure after Hartmann's procedure during the last 8 years. RESULTS: The mortality rate was nil, but post-operative complications occurred in 12 patients (37.5%), namely: wound infection (11 patients) and anastomotic leak (2 patients). CONCLUSION: In light of this, it could be wiser to perform, in the patients affected with benign pathology, and in those affected with limited malignant pathology (T3), resection of the diseased segment of colon and primary anastomosis with temporary ileostomy, reserving Hartmann's procedure to patients unsuitable to one step treatment because of their poor general and local conditions.

[Laparoscopic cholecystectomy. Our clinical experience from 1994 to 1996]. / La colecistectomia laparoscopica. La nostra esperienza clinica dal 1994 al 1996.

BACKGROUND AND AIM: Videolaparocholecystectomy is now regarded as the gold standard of treatment for lithiasis of the gallbladder. METHODS: The authors report a retrospective of 258 consecutive videolaparocholecystectomies performed by the Surgical Division of Valduce Hospital in Como between 1994 and 1996. The authors describe the indications for VLC, techniques for the induction of pneumoperitoneum and the realisation of VLC and the percentage and caused of conversion. RESULTS: During this period a steady reduction was noted in the number of laparotomic cholecystectomies and a parallel increase in cholecystectomies performed using a laparoscopic technique (69.2 vs. 30.8% in 1994; 76.4 vs. 23.2% in 1995; 91.1 vs. 8.9% in 1996). A gradual extension of the indications for laparoscopic surgery can be seen leading to the application of this technique in patients suffering from acute cholecystic infection, hydros or empyema of the gallbladder. Conversion were required in 25 cases in this series (9.7%). During the last year analysed there were a total of 9 conversions (7.9%) even though the percentage of acute cholecystitis accounted for 38.9% of all cases of cholecystectomy. CONCLUSIONS: In line with the experience of other centres, the authors, currently propose VLC as the treatment of choice for lithiasic pathologies of the cholecyst.

[Measurement of venous pressure by Doppler sonography: usefulness and limitations in saphenectomy]. / Misurazione della pressione venosa con la Doppler sonografia: utilità e limiti nell'intervento di safenectomia.

After a short mention on the many last methods for venous pressure measurement, the Authors presents a relatively new method of this measurement with the Doppler ultrasonography. They point out its utility with regard to safenectomy by a study on 42 patients whose, at the present, only 10 preliminary results are available. This results allow to verify the opportunity of to value preoperatory and precisely the pressure drop obtainable with the safenectomy.

Correction of a developmental defect in neutrophil activation and movement.

In order to more fully understand the mechanisms involved in the developmental defect in polymorphonuclear leukocyte (PMN) movement in human neonates, the authors have examined several events in the activation response sequence. Chemotactic factor receptor numbers have been found to be normal on the PMNs of neonates, but chemotactic factor-induced changes in membrane potential and cyclic adenosine monophosphate concentrations were markedly decreased to absent in the neonatal cells. Because the neonatal PMN lacks the ability to deform normally, we examined the effects of a methylxanthine derivative, pentoxifylline, on the responses of neonatal cells. This agent has been reported to increase cell deformability and improve cell movement. Pentoxifylline had an effect in improving chemotactic function in the PMNs of neonates, while correcting the abnormality in membrane potential. In addition, this agent was found to enhance the movement of cell surface concanavalin A receptors after colchicine treatment. These results suggest that this developmental defect in cell activation and movement may be an abnormality that can be corrected pharmacologically.

Complement-dependent bactericidal activity for E. coli K12 in serum of preterm newborn infants.

Complement-dependent serum bactericidal activity for E. coli K12 was assessed in 12 term infants and in 16 preterm infants. In both groups of newborns, at birth, bactericidal reaction by the classical pathway of complement activation was impaired with respect to normal controls at less than 0.001 level of significance (as estimated by Student's t-test). The serum bactericidal reaction by the alternative pathway of complement activation was significantly impaired only in preterm newborns, being normal in term infants. At a time corresponding to 40 weeks' gestational age also in preterm newborns alternative pathway mediated bactericidal activity for E. coli K12 was found normal. Classical pathway mediated bactericidal activity became normal only at an age corresponding to 52 weeks' gestational age.

Abnormality in actin polymerization associated with defective chemotaxis in neutrophils from neonates.

In an attempt to determine the mechanism of the profound defect in chemotaxis observed in the neutrophils of human neonates, we have examined the generation of polymerized or filamentous actin (F actin) following stimulation of the cells with chemotactic factors. We have also examined the changes in the intracellular levels of free calcium in neonatal neutrophils and compared the results with those in adult neutrophils. Following exposure to formyl-methionyl-leucyl-phenylalanine (FMLP) or zymosan-activated serum (ZyAS), neutrophils from adult donors showed an increase in intracellular free calcium, as determined by Quin 2/AM fluorescence, and in actin polymerization (45-55%), as measured by nitrobenzoxadiazole phallicidin fluorescence. These responses were abolished by preincubation with the calcium antagonist verapamil (0.1 mM), which inhibits both calcium influx and release from intracellular stores. In marked contrast to the results obtained with neutrophils from adults, neutrophils from newborn infants, which have defective chemotactic responses, failed to generate F actin following FMLP or ZyAS stimulation and developed significantly lower levels of free intracellular calcium.

Inhibition of lymphocyte and neutrophil chemotaxis by pertussis toxin.

The cells of the mammalian immune system possess special migratory properties within their in vivo environment, a surveillance characteristic that is thought to be important in the protection of the organism from transformants and exogenous pathogens. Pertussis toxin (PT) has been shown to disrupt the intensity of this process by seriously affecting lymphocyte recirculation in vivo. The mechanisms responsible for this inhibition were investigated by using the in vitro model systems of polymorphonuclear leukocyte and lymphocyte chemotaxis. The type of inhibition that was observed in these in vitro assay systems was quite similar to that observed in vivo, because PT could depress chemotaxis in vitro as well as the accumulation of radiolabeled lymphocytes and neutrophils within a peripheral site of inflammation in vivo. The alterations in neutrophil motility were found to be associated with a stimulus-specific inhibition of the triggering of superoxide anion generation and lysosomal secretion. Some inhibition of neutrophil adherence to plastic surfaces was also observed, most notably after augmentation of adherence with the chemoattractant fMLP. The observed alterations in cellular function after PT treatment occurred in the absence of defects in chemoattractant binding to the neutrophil cell surface, or of membrane potential changes stimulated by ligand binding. The effect of PT in this system was found to be associated with an abnormality in the regulation of intracellular free calcium, suggesting that the substrate for PT in neutrophils is involved in the regulation of calcium ion channels.