Advantages of sharp adventitial dissection for microvascular anastomoses

Adventitia is usually removed from arteries to simplify microvascular anastomoses. Some surgeons peel the adventitia away bluntly whereas others trim the adventitia sharply with scissors. We used a rat cremaster flap for intravital microscopy to evaluate these two techniques. Animals with unmanipulated vessels, without anastomosis or adventitial removal, served as controls. Fifty-four rats were studied in three groups of 18 rats. Functional capillary density, red blood cell velocity, diameter of the flap's feeding artery (A1), microthrombi formation, and neutrophilic activity were studied for 5 hours following anastomosis, and 24 and 72 hours later. Histological changes in blunt and sharply prepared arteries were compared with control vessels. After blunt preparation, capillary perfusion was reduced to 61% of control values (p < 0.05) and A1 diameter was reduced to 77% of control values (p < 0.05). Capillary perfusion and A1 diameter were unchanged in sharply prepared arteries. Architectural changes in the vessel wall were more profound, and neutrophilic activity was increased in bluntly prepared arteries. In this study, sharp preparation of small arteries was beneficial compared with blunt preparation.     

Segmental dilatation of the ileum

Three new cases of congenital segmental dilatation of the ileum are presented and added to 12 cases of segmental dilatation found in the literature. The aspect of the condition which is of particular interest is the presence in 3 of the dilated segments of heteroplastic foregut derivatives of unusual varieties. The etiology of the condition is discussed; it does not appear to be a single distinct pathological entity.     

Should long-term care residents be supplemented with vitamin D?

The Health Canada recommendation of 600 IU of vitamin D daily for those over age 70 may be inadequate to prevent deficiencies. A literature search was conducted to examine whether older people living in long-term care (LTC) facilities are at high risk for vitamin D deficiency and therefore should receive a minimum daily supplement of 800 IU. The search included the major databases; the search terms "elderly" and "vitamin D" were used. Articles primarily related to calcium were excluded. The results show that North American seniors generally consume a diet low in vitamin D and have limited sun exposure. The majority, particularly those living in LTC facilities, may have a vitamin D deficiency. Also contributing to deficiencies is an age-related decline in cutaneous production of vitamin D and altered metabolic processes responsible for converting vitamin D to its active form. In summary, research conducted in both Canada and the United States provides sufficient evidence to indicate that older people living in LTC facilities are at high risk for vitamin D deficiency and should receive a minimum daily supplement of 800 IU.     

Aglycone and glycoside specificity of apple skin flavonoid glycosyltransferase

O-Glycosyltransferase(s) extracted from apple (Malus pumila Mill) fruit skin showed activity towards a range of flavonols and anthocyanins. However, no glycosylating activity was shown towards a dihyroflavonol (dihydroquercetin), a flavanone (eriodictyol) or a flavone (luteolin). The enzyme preparation glycosylated those flavonoids normally present in apple skins (quercetin and cyanidin) and in addition several other related compounds (delphinidin, fisetin, isorhamnetin, kaempferol, myricetin and pelargonidin). This enzyme(s) specifically transferred the glycosyl moiety from sugar nucleotide donors to the 3-position of the flavonoid nucleus. Only flavonoid 3-glycosides occur naturally in apple skin. Activity with different sugar donors was in the order galactose>glucose>xylose, which reflected the ratios of cyanidin and quercetin glycosides found in apple fruit skin. There were slight differences in the relative UFGT activity with quercetin and the three different sugar donors between ‘Granny Smith’ and ‘Splendour’, and this was reflected by similar differences in the ratios of endogenous quercetin glycosides. ©1997 SCI     

Optimizing the Diffusion Welding Process for Alloy 800H: Thermodynamic,Diffusion Modeling,and Experimental Work

A research effort was made to evaluate the usefulness of modern thermodynamic and diffusion computational tools, Thermo-Calc and Dictra (Thermo_Calc Software, Inc., McMurray, PA), in optimizing the parameters for diffusion welding of Alloy 800H. This would achieve a substantial reduction in the overall number of experiments required to achieve optimal welding and post-weld heat treatment conditions. This problem is important because diffusion-welded components of Alloy 800H are being evaluated for use in assembling compact, micro-channel heat exchangers that are being proposed in the design of a high-temperature, gas-cooled reactor by the U.S. Department of Energy. The modeling was done in close contact with experimental work. The latter included using the Gleeble 3500 System (Dynamic Systems, Inc., Poestenkill, NY) for welding simulation, mechanical property measurement, and light optical and scanning electron microscopy. The modeling efforts suggested a temperature of 1423 K (1150 °C) for 1 hour with an applied pressure of 5 MPa using a 15-μm Ni foil as joint filler to reduce chromium oxidation on the welded surfaces. Good agreement between modeled and experimentally determined concentration gradients was achieved, and model refinements to account for the complexity of actual alloy materials are suggested.     

In situ measurement of corrosion of type 316L stainless steel in 553 K pure water via the electrical resistance of a thin wire

A system for the in situ monitoring of corrosion depth via electrical resistance measurements was applied to study the corrosion rate of type 316L stainless steel at 553 K in pure water. Corrosion depth was measured using a 50 μm diameter wire probe mounted axially in the tube. Measurements were in good agreement with literature data for both the hydrogen water chemistry (HWC) condition and the normal water chemistry (NWC) condition. Oxide film analyses by scanning electron microscopy and laser Raman spectroscopy on the wire probe and the tube showed no effects from shape of the test specimens or the application of electric current. Corrosion kinetics was evaluated by fitting equations to the measurements. Data for the HWC condition could be fitted by a two-step logarithmic–parabolic law. A single-step logarithmic law fitted data for the NWC condition. Changes in corrosion rate by the water chemistry changes were readily detected with the technique. Corrosion depth change could be observed for the water chemistry change from the NWC condition to the HWC condition with electrochemical corrosion potential (ECP) of ?0.56 V vs. standard hydrogen electrode, which is lower than the ECP that the phase of iron oxide changes from α-Fe₂O₃ to Fe₃O₄.