Ruthenium tetroxide for fixing and staining cytoplasmic membranes.

Rat liver and kidney were fixed for electron microscopy with ruthenium tetroxide. When compared with tissues fixed with osmiun tetroxide, the membranes showed well without additional staining. The trilaminar structuire of the cytoplasmic membranes was clearly seen. In width the nuclear, mitochondrial, and cytoplasmic membranes investigated resembled the cell memnbrane.

Transcutaneous oxygen tension in legs and feet of diabetic patients.

Transcutaneous oxygen tension (tcPO2) of the legs and feet was measured at 37 and 44 degrees C in 21 patients with diabetes mellitus, 9 of whom had peripheral neuropathy. At 37 degrees C, tcPO2 in the legs and feet of diabetic patients with peripheral neuropathy was significantly higher (P less than .02) than in control subjects and diabetic patients without neuropathy. Whereas tcPO2 in the legs of control subjects and nonneuropathic diabetic patients was greater than in the feet (P less than .02), this leg-to-foot difference was absent in diabetic patients with neuropathy. After an increase in skin temperature to 44 degrees C, tcPO2 increased in the legs and feet of all three groups, but the increase was smallest in diabetic patients with neuropathy and greatest in control subjects. In neuropathic (P less than .02) and nonneuropathic (P less than .02) diabetic patients, tcPO2 was significantly lower than in control subjects. These data are consistent with a loss of vasoconstrictor tone in the blood vessels perfusing skin and subcutaneous tissue at 37 degrees C and an inability of these vessels to vasodilate and increase blood flow at 44 degrees C in diabetic patients in general and neuropathic diabetic patients in particular. This inability to increase tcPO2 after an increase in temperature and possibly other vasodilatory stimuli may contribute to the pathogenesis of nonhealing ulcers, protracted infections, and gangrene, which characterize the diabetic foot.

Surgical correction of venous incompetence restores normal skin blood flow and abolishes skin hypoxia during exercise.

Posture has long been recognized to be a crucial factor in the etiology of venous leg ulcers. Activation of the stretch receptors in the veins by venous distention induces reflex vasoconstriction and hypoxia. In patients with defective venous return, exercise fails to reduce venous pressure when the legs are dependent; therefore, hypoxia persists during exercise. Surgical treatment of venous incompetence abolishes the abnormal venous reflux and restores the normal vasodilator response to exercise, thereby correcting the sustained hypoxia observed in patients with venous leg ulcers.

The use of the Hellige Oxymonitor to study skin blood flow changes.

Transcutaneous oxygen tension is a flow related parameter. Detailed analysis of the physiology and physical chemistry of oxygen consumption and diffusion indicates that tcPO2 is not proportional to skin blood flow. Measurement of tcPO2 at 37 degrees C allows changes in skin blood flow to be clearly demonstrated and is of use in many areas of clinical medicine. Transcutaneous oxygen tension recorded using a polarographic oxygen electrode depends on skin blood flow, skin respiration, arterial oxygen concentration, temperature, skin and electrode permeability and the oxygen consumption of the electrode. Applying clearance principles, the relationship between blood flow, respiration and the difference between arterial and venous oxygen concentrations is well established. This has long been used to measure cardiac output, since the other three parameters are readily determined. Arterial saturation is normally greater than 95% of maximum in subjects without lung disease and it may thus be considered to be constant. Tissue respiration is independent of oxygen concentration when PO2 exceeds 2 mm Hg. If skin respiration is invariant at constant temperature, when the tissue oxygen tension exceeds 2 mm Hg, then blood flow is inversely proportional to the difference in concentration between arterial and venous blood. It has recently been directly shown that the inference that tissue respiration is independent of tissue blood flow is accurate. Correcting for the oxyhaemoglobin dissociation curve and for the deviation from zero order respiration kinetics when tissue PO2 less than 2 mm Hg, the relationship between venous oxygen tension and blood flow at 37 degrees C is shown when arterial oxygen concentration is constant (Figure 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Skin oxygen tension in venous insufficiency of the lower leg.

Tissue anoxia has for long been invoked as a cause of venous leg ulcers, and recently it has been suggested that pericapillary fibrin prevents the diffusion of oxygen in the skin. In the present study direct measurements of skin oxygen levels on the lower leg were made using a transcutaneous oxygen monitor. In the recumbent position mean oxygen tensions were higher in patients than in controls, thus disproving the existence of any block to oxygen diffusion. In both groups there was a fall in oxygen tension to low levels on standing as a result of the normal reflex vasoconstrictor response to increased venous pressure. Exercise produced a marked rise in skin oxygen tension in normal legs but not in those affected by venous insufficiency. In normal subjects exercise reduces venous pressure, thus removing the stimulus for reflex vasoconstriction. In patients with defective valves, the venous pressure remains high during exercise and reflex vasoconstriction persists. It is concluded from this study that the sustained low skin oxygen tension in the upright position even during exercise is responsible for leg ulcer formation associated with venous insufficiency. Normal legs are protected by a rise in skin oxygenation during exercise.

[Effect of long-chain polyunsaturated fatty acids on arachidonate and docosahexaeonic acid in healthy infants in the first four months of life]. / Hosszú szénláncú, többszörösen telítetlen zsírsavak hatása egészséges csecsemók arachidonsav-és dokozahexénsav-ellátottságára 92 eletelsonegy honapjaban.

Fatty acid compositions of plasma phospholipids (PL), triglycerides (TG) and sterol esters (STE) were measured by high resolution capillary gas-liquid chromatography in formula fed healthy infants at the ages of 5 days and 1, 2, 3 and 4 months. The infants were randomly assigned to receive either conventional infant formula (F, n = 10) without long-chain polyunsaturates (LCP) or the same formula supplemented with LCP (LCP-F, n = 12) in amounts and ratios similar to those characteristic to human milk. From the age of 1 month onwards, percentage contributions of the principal omega-6 LCP, arachidonic acid were significantly higher in plasma lipids of infants fed LCP-F than in those receiving conventional formula without dietary LCP. Values of the principal omega-3 LCP, docosahexaenoic acid were also significantly lower in the infants fed conventional formula than in those receiving LCP-F throughout the study. The data obtained indicate that from the formula supplemented with LCP both arachidonic and docosahexaenoic acids were effectively absorbed and incorporated into infantile plasma lipids. Recent data of the literature suggest that supplementation of infant formula with LCP may beneficially influence visual and psychomotor development also in healthy, term infants.

[Fatty acid levels in plasma phospholipids in the cord blood of Austrian and Hungarian newborn infants]. / Osztrák és magyar újszülöttek plazma foszfolipidjeinek zsírsavösszetétele a megszületéskor.

Fatty acid composition of plasma phospholipids in venous cord blood of 13 Austrian and 13 Hungarian infants was determined by high resolution capillary gas liquid chromatography. Values of linoleic acid and arachidonic acid [13.69 (12.57, 14.30) versus 19.79 (11.74, 22.83), % weight/weight, median (first and third quartile), Austrian versus Hungarian] did not differ between the two groups. Values of alpha-linolenic acid were slightly higher in Hungarian than in Austrian infants, whereas docosahexaenoic acid values did not differ [3.75 (2.80, 4.05)] versus 4.11 (1.55, 5.19)]. Neither saturated, nor cis monounsaturated fatty acid values differed between the two groups. Values of trans isometric fatty acids were significantly higher in Hungarian than in Austrian infants [total: 0.81 (0.70, 1.10) versus 1.19 (0.92, 1.46) p < 0.01]. Analysis of fatty acid composition of plasma phospholipids in venous cord blood of Austrian and Hungarian infants did not reveal major differences in the availability of essential and long-chain polyunsaturated fatty acids. Significantly higher contribution of trans isometric fatty acids to plasma phospholipids in Hungarian than in Austrian infants indicates higher dietary exposure of pregnant women to trans fatty acids in Hungary.