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Time-resolved studies were performed for tryptic proteolysis of β-casein in media containing 10-40 % (v/v) ethanol at 37 °C and pH 7.9. The peptide bond demasking, the process which implies the removal of steric obstacles shielding polypeptide sites against enzymatic attack, was quantitatively evaluated with fluorescence spectroscopy by monitoring the exposure of Trp residues to the aqueous polar medium. This process obeys a first-order kinetic law that allowed us the determination of the rate constants of demasking k. The fraction of initially masked bonds m, being able to convert during proteolysis to the demasked ones, and the fraction of unhydrolysable bonds n were calculated within the framework of a two-step model with consecutive demasking and hydrolysis steps. Parameters m and n were shown to decrease and increase, respectively, with the addition of ethanol. [ABSTRACT FROM AUTHOR]

omatase inhibitors (AIs) have become the standard adjuvant therapy of postmenopausal breast cancer survivors. AIs induce a reduction of bioavailable estrogens by inhibiting aromatase, which would be expected to induce alterations in body composition, more extensive than induced by menopause. The objectives are to examine the impact of AIs on (1) DXA-scan derived body composition and (2) gonadal hormone levels. This is a sub-analysis of a 2-year double-blind, placebo-controlled, randomized trial of 82 women with nonmetastatic breast cancer, newly menopausal following chemotherapy, who were randomized to risedronate (35 mg once weekly) versus placebo, and stratified for their usage of AI versus no AI. Outcomes included DXA-scan derived body composition and gonadal hormone levels. As a group, total body mass increased in women over 24 months. Women on AIs gained a significant amount of lean body mass compared to baseline as well as to no-AI users ( P < 0.05). Women not on an AI gained total body fat compared to baseline and AI users ( P < 0.05). Free testosterone significantly increased and sex hormone binding globulin (SHBG) significantly decreased in women on AIs compared to no AIs at 24 months ( P < 0.01) while total estradiol and testosterone levels remained stable. Independent of AI usage, chemotherapy-induced postmenopausal breast cancer patients demonstrated an increase of total body mass. AI users demonstrated maintenance of total body fat, an increase in lean body mass and free testosterone levels, and a decrease in SHBG levels compared to no-AI users. The mechanisms and implications of these changes need to be studied further. [ABSTRACT FROM AUTHOR]

Molecular shuttles based on microtubules propelled by motor proteins can be guided on surfaces by adsorbing motors in chemical patterns or by using open guiding channels. While chemical patterns can guide microtubules based on a Brownian ratchet mechanism, the rigidity of the microtubules limits guiding to features with dimensions on the order of their persistence length (5 mm). To achieve guiding on micron-scale dimensions, physical barriers are required which can exploit the forces exerted by multiple motors to bend tubules into tight radii of curvature. Microtubule guiding is illustrated for the case of a special ratchet pattern that is capable of sorting microtubules on the basis of the direction of their motion. [ABSTRACT FROM AUTHOR]

The origin of arterio-venous anastomoses, connecting the efferent filament artery (EFA) with the central venous sinus (CVS) of gill filaments can be well discerned by scanning electron microscopy in the rainbow trout. Corresponding vessels between the afferent filament artery and the CVS could not be detected with the techniques applied. AVA-specific endothelial cells are characterized by their bulky shape and their microvillous surface. The general morphology of AVA's in Salmo gairdneri is very similar to that of AVA's in Tilapia mossambica (Vogel et al., 1974) but they are much longer in the trout. No filament whorls have been encountered in AVA endothelia of Salmo gairdneri. [ABSTRACT FROM AUTHOR]

Arterio-venous anastomoses (AVA) in gill filaments of Tilapia mossambica exhibit a distinct polarity. Two different types of highly specialized endothelial cells, both of epitheloid shape, line these vessels: Type I cells, contacting the arterial lumen, are elongated and about two to three times as large as type II endothelial cells. Their surface is increased by tentacular protrusions which reach far into the arterial lumen. Filament whorls forming tubelike structures with centrally located glycogen granules are abundant in these cells. Type II endothelial cells are located proximal to the central venous sinus (CVS). Their less abundant and more electron dense cytoplasm is free of filament whorls. There are also intermediate cell forms at approximately the middle of each anastomosis. Short cell processes protrude from all endothelial cell types into the AVA lumen. Outside the indistinct vascular basement lamina, a layer of cover cells tightly envelopes the AVA. These cells are, however, absent around the part of the AVA adjacent to the CVS. Here the endothelial cells are in immediate contact with the interstitium. Endothelial cells sheathed by cover cells reach the interstitium through basal foot processes. Nerve fibre bundles regularly come into close contact with the AVAs. Possible functions of the AVAs, including osmoreception are discussed. [ABSTRACT FROM AUTHOR]

The non-respiratory vascular system of T. mossambica gill filaments was studied in serial longitudinal and cross sections. Comparatively few scattered vascular communications occur between the afferent filament artery and the central venous sinus (AVA). The efferent filament artery, however, is connected by regularly arranged anastomoses (AVA), directly, and sometimes indirectly via nutritive vessels, to the central sinus. These AVA are about as numerous as lamellae counted on one side of each filament, although they diminish slightly in number towards the filament base. The relation AVA to AVA was 17.6:1 in the distal and 17.8:1 in the basal filamental region, while in the tip region of 7 filaments 126 AVA but only 1 AVA were encountered. No direct connection between the lamellar lacunae and the central sinus was detected. According to these results, non-respiratory intrafilamental blood shunting appears unlikely. AVA are assumed to be the main route for blood entering the central venous sinus which would consequently flow into the branchial veins. [ABSTRACT FROM AUTHOR]

In fresh water, Fundulus heteroclitus produces copious hypotonic urine. After transferring the fish over a period of 7-8 hours from fresh to seawater, the urine becomes hypertonic (U P/osm up to 2.4) and remains so for 24 to 36 hours. Transferring F. heteroclitus to seawater over a period of 3 days results in its producing an iso-to hypotonic urine. The nephron of the fish has been reconstructed with the help of serial sectioning. Its anatomy does not defer from that of marine teleosts. [ABSTRACT FROM AUTHOR]

The catalytic effect of metmyoglobin on the back thermal cis → trans isomerization reaction of stilbazolium betaine M is reported. This reaction shows substantial acceleration in the presence of metmyoglobin in comparison to the same reaction without the protein or in the presence of metmyoglobin cyanide. It is suggested that the observed thermal reaction acceleration may arise from the coordination of the protonated stilbazolium betaine molecule to the sixth ligand position of the heme iron and subsequent chromophore deprotonation or from the low polarity of the heme pocket microenvironment. [ABSTRACT FROM AUTHOR]