Theoretical investigations of optical properties of FeF2.

Density functional theory has been employed to determine ground state properties and calculate the complex dielectric function of the FeF2 compound. The complex expression of magnetic permeability has been estimated using the formula of the magnetic permeability tensor. To interpret the optical transitions, densities of states and projected densities of states have been determined. Suitable expressions for treating contributions of electric permittivity and magnetic permeability to optical properties have been derived and applied. The absorption coefficient in the visible range is a result of the transitions from the top of the valence band to 4s bands of Fe2+ cations in the conduction band. In the far-infrared region, FeF2 is a perfect reflector. The estimated optical properties show good agreement with previous theoretical and experimental results in the literature.

Actin sliding velocity on pure myosin isoforms from hindlimb unloaded mice.

AIM: Notwithstanding the widely accepted idea that following disuse skeletal muscles become faster, an increase in shortening velocity was previously observed mostly in fibres containing type 1 myosin, whereas a decrease was generally found in fibres containing type 2B myosin. In this study, unloaded shortening velocity of pure type 1 and 2B fibres from hindlimb unloaded mice was determined and a decrease in type 2B fibres was found. METHODS: To clarify whether the decrease in shortening velocity could depend on alterations of myosin motor function, an in vitro motility assay approach was applied to study pure type 1 and pure type 2B myosin from hindlimb unloaded mice. The latter approach, assessing actin sliding velocity on isolated myosin in the absence of other myofibrillar proteins, enabled to directly investigate myosin motor function. RESULTS: Actin sliding velocity was significantly lower on type 2B myosin following unloading (2.70 ± 0.32 µm s(-1)) than in control conditions (4.11 ± 0.35 µm s(-1)), whereas actin sliding velocity of type 1 myosin was not different following unloading (0.89 ± 0.04 µm s(-1)) compared with control conditions (0.84 ± 0.17 µm s(-1)). Myosin light chain (MLC) isoform composition of type 2B myosin from hindlimb unloaded and control mice was not different. No oxidation of either type 1 or 2B myosin was observed. Higher phosphorylation of regulatory MLC in type 2B myosin after unloading was found. CONCLUSION: Results suggest that the observed lower shortening velocity of type 2B fibres following unloading could be related to slowing of acto-myosin kinetics in the presence of MLC phosphorylation.

Low incidence of hereditary nonpolyposis colorectal cancer syndrome in a selected area of the Lombardy Cancer Registry.

AIMS AND BACKGROUND: Epidemiological investigations on the frequency of hereditary nonpolyposis colorectal cancer (HNPCC) syndrome are few and have shown a variable worldwide incidence ranging from 1% to 7% of all colorectal cancers (CRCs). In Italy, relevant differences have been observed: 2.8-3% of all CRCs in northern regions and less than 1% in southern regions. The aim of the present study was to investigate the HNPCC incidence in a selected area of northern Italy belonging to the Lombardy Cancer Registry. METHODS AND STUDY DESIGN: We analyzed 197 consecutive patients with newly diagnosed CRCs, histologically verified, and resident in two areas of the Lombardy Cancer Registry. For each case, genetic counseling with at least three generations pedigree reconstruction, HNPCC classification according to Amsterdam criteria, molecular analysis for microsatellite instability and immunohistochemistry for hMLH1 and hMSH2 were performed. RESULTS: A very low frequency (0.5%) of HNPCC fulfilling the Amsterdam criteria was found in comparison to the other Italian areas. Such an incidence seems to be due to actual population differences and reflects a genetic heterogeneity. CONCLUSIONS: The data underline the importance of a precise knowledge of actual HNPCC incidence in different populations in order to optimize effectiveness and efficiency of screening programs for the disease.

Effect of blood flow rate and donor vessel diameter on the patency of carotid venous bypass grafts in dogs.

A saphenous vein graft was implanted from the right subclavian to the right common carotid artery in seven dogs (group I) and between the right and left common carotid arteries in another seven dogs (group II). The recipient artery was ligated proximally to augment blood flow through the graft. Immediately after the anastomoses were completed, the average blood flow through the graft was 32 +/- 25 mL/min in group I and 122 +/- 22 mL/min in group II. At sacrifice 30 days later, angiography showed that all grafts in group I were thrombosed, whereas six (87.5%) of seven grafts in group II were patent. These findings suggest that a larger donor vessel diameter and higher graft flow rates may improve patency in venous bypass grafts that are 3 to 5 mm in diameter.

Reversible middle cerebral artery occlusion without craniectomy in rats.

To develop a simple, relatively noninvasive small-animal model of reversible regional cerebral ischemia, we tested various methods of inducing infarction in the territory of the right middle cerebral artery (MCA) by extracranial vascular occlusion in rats. In preliminary studies, 60 rats were anesthetized with ketamine and different combinations of vessels were occluded; blood pressure and arterial blood gases were monitored. Neurologic deficit, mortality rate, gross pathology, and in some instances, electroencephalogram and histochemical staining results were evaluated in all surviving rats. The principal procedure consisted of introducing a 4-0 nylon intraluminal suture into the cervical internal carotid artery (ICA) and advancing it intracranially to block blood flow into the MCA; collateral blood flow was reduced by interrupting all branches of the external carotid artery (ECA) and all extracranial branches of the ICA. In some groups of rats, bilateral vertebral or contralateral carotid artery occlusion was also performed. India ink perfusion studies in 20 rats documented blockage of MCA blood flow in 14 rats subjected to permanent occlusion and the restoration of blood flow to the MCA territory in six rats after withdrawal of the suture from the ICA. The best method of MCA occlusion was then selected for further confirmatory studies, including histologic examination, in five additional groups of rats anesthetized with halothane. Seven of eight rats that underwent permanent occlusion of the MCA had resolving moderately severe neurologic deficits (Grade 2 of 4) and unilateral infarcts averaging 37.6 +/- 5.5% of the coronal sectional area at 72 hours after the onset of occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Scanning electron microscopy studies of needle and suture damage in rat carotid and femoral arteries.

Using the scanning electron microscope (SEM), we compared the areas of endothelial disruption 45 minutes after penetration of rat femoral and carotid artery walls with 75- and 100-mu taper point and taper cut microsurgical needles, with and without restoration of blood flow. Four experimental groups were designated: needle puncture only, single loose, suture loop, end-to-end anastomosis, and end-to-side anastomosis. The vessels were perfused with normal saline, immersed in 3% buffered glutaraldehyde, and mounted under slight tension to simulate physiological wall distention before SEM examination. Endothelial craters at vessel puncture sites were measured on SEM photomicrographs at 300 X magnification. All vessels were patent when examined. Crater diameters averaged less than double the needle size. Although taper cut needles produced craters that were 25% larger (P less than 0.05), vessel penetration was easier than with the taper point needle and bleeding times were the same. Suture loop produced craters that were 36% larger (P less than 0.05) than needle puncture alone. Craters were 20% larger when blood flow was restored and 50% larger in the femoral than in the carotid artery. Although craters seen after end-to-end anastomosis were not significantly larger than those after end-to-side anastomosis, interrupted sutures appeared to cause more endothelial damage than continuous sutures. These results suggest that the use of cutting needles, passage and tying of sutures, vessel distention by blood flow, and suturing of more muscular and less elastic vessel walls (femoral artery) may increase endothelial disruption but do not reduce patency.

Enfermedad de Chagas en Chile. Sectores urbanos. III - Frecuencia de la infeccion chagasica en madres y recien nacidos del Hospital de Copiapo (III Region, Chile). / Chagas' disease in Chile. Urban sections. III - Frequency of Chagas' infection in mothers and newborns from the Hospital of Copiapo (III Region, Chile)

III Region, Chile). /Chagas' disease in Chile. Urban sections. III - Frequency of chagasic infection in mothers and newborns from the Hospital of Copiapo (III Region, Chile)/.(III Region, Chile). /Chagas' disease in Chile. Urban sections. III - Frequency of chagasic infection in mothers and newborns from the Hospital of Copiapo (III Region, Chile)/.chagasic infection in mothers and newbors