Milk fatty acid composition and cheese texture and appearance from cows fed hay or different grazing systems on upland pastures.

The objective of this work was to compare milk fatty acid (FA) profile and texture and appearance of Cantal cheeses obtained from cows grazing 2 different upland grasslands: a highly diversified pasture (74 species) of area 12.5 ha managed under continuous mode (C), and a weakly diversified pasture (31 species) of area 7.7 ha (an old temporary grassland) managed under rotational mode (R). A control group of cows fed a hay-based diet (indoors, I) was used. Three equivalent groups of 12 Montbéliarde cows underwent the 3 treatments from May to September 2008. The cheeses were manufactured during 3 consecutive days in early June, early July, and late August (27 cheeses in all). The texture, appearance, and chemical composition of the cheeses were determined after 12 wk of ripening. Concentrations of total saturated FA and monounsaturated FA were higher and lower, respectively, in I milks compared with pasture milks. The concentrations of trans-11-C18:1 and cis-9-C18:1, and polyunsaturated FA as well as yellowness decreased during the season in C-derived milk but remained constant in R-derived milk, through a combined effect of grass development stage and the cows' grazing selection. The I cheeses were, on average, firmer, less creamy, less elastic, and less yellow than the pasture cheeses. Decreasing and increasing trends in texture firmness during the season were observed for C and R cheeses, respectively. The rind of the pasture-fed cow cheese had fewer, less intensely colored, and less prominent spots than did that of I cheeses. This difference was probably due to greater migration of fat to the rind during pressing because of the lower fat melting point of the pasture-fed cow cheeses, which had higher unsaturated FA content. The greater amounts of fat deposited on the rind of the pasture-fed cow cheeses may have partially inhibited the microbial activity responsible for rind appearance. Our trial underlines the importance of the effects of grazing management associated with vegetation type on milk and cheese characteristics.

Conformational stability and in vitro bioactivity of porcine luteinizing hormone.

Temperature-dependent dissociation of porcine luteinizing hormone (pLH) and of two of its glycoforms was studied by a combination of SDS-PAGE and micro-scale size-exclusion HPLC in parallel with the study of co-operative folding by high-sensitivity differential scanning calorimetry (HS-DSC). The transition temperature of dissociation of pLH at pH 7.0 as quantified by SDS-PAGE, HPLC and residual activity in radioreceptor assay was found to match exactly the transition temperature of its unfolding as measured by HS-DSC. Free alpha- and beta-subunits did not exhibit any unfolding transition in the same conditions. The microcalorimetric data for two pLH isoforms exhibiting different glycosylations were identical to those of a preparation of non-separated isoforms. It is concluded that: (a) free subunits exhibit no co-operative folding (i.e. no stable three-dimensional structure) and co-operative folding occurs only in alphabeta heterodimers; (b) the co-operative folding is responsible for the stability of the association of subunits; and (c) the heterogeneity of carbohydrate chains does not affect the stability of folding and association of subunits. The fastening of the "seat-belt" of the beta-subunit embracing the alpha-subunit by the Cysbeta26-beta110 disulfide bridge had been postulated to play a role in the preservation of the dimeric structure of gonadotropins. The present work shows that dissociation of subunits is directly related to their loss of common co-operative folding.

Acute myocardial failure during Yersinia enterocolitica infection.

A case of severe cardiac failure during generalized Yersinia enterocolitica infection, in a previously healthy woman is described. It was possible to demonstrate the important role of coronary hypoperfusion in the late stages of septic shock. When beta stimulant drugs became ineffective, IABP improved cardiac function.

Left ventricular contractility using isovolumic phase indices during PEEP in ARDS patients.

The effects of incremental increases in PEEP during mechanical ventilation on left ventricular (LV) contractility before and after intravascular volume expansion (IVE) were studied in 10 patients treated for ARDS. A pulmonary artery (PA) catheter, a LV catheter-tip micromanometer, and an esophageal balloon catheter were inserted in these patients. We measured transmural right atrial and PA pressures, transmural LV end-diastolic and systemic arterial pressures, the first derivative of LV pressure (LV dP/dt), the ratio of LV dP/dt at transmural developed LV pressure (dP/dt/DPt) with DPt = 5, 10, 40 mm Hg, cardiac index (CI) at every level of PEEP and after IVE at the highest PEEP. Stepwise increases in PEEP (from 0-20 cm H2O) were associated with progressive fall in CI whereas heart rate remained unchanged. Transmural right atrial and PA pressures did not change; transmural LV end-diastolic and systemic arterial pressures and peak dP/dt decreased significantly with PEEP, except for dT/dt/dPt. IVE reversed this fall in CI and peak dP/dt. Whereas transmural LV end-diastolic pressure rose markedly. We conclude that the observed fall in LV performance during PEEP is not the result of a depressed LV contractility because PEEP does not induce a decrease in dP/dt/DPt, the least sensitive to change in preload isovolumic phase indices of contractility.