Increased plasma cholestanol and 5 alpha-saturated plant sterol derivatives in subjects with sitosterolemia and xanthomatosis

We have measured plasma sterol composition in 14 subjects with sitosterolemia and xanthomatosis. In addition to elevated plasma phytosterol (campesterol 16 +/- 7 mg/dl and sitosterol 35 +/- 16 mg/dl) and normal to moderately high cholesterol levels (258 +/- 96 mg/dl), concentrations of 5 alpha-saturated stanols, cholestanol, 5 alpha-campestanol, and 5 alpha-sitostanol were at least 10 times greater than controls. Diets contained plentiful quantities of cholesterol and plant sterols, but only trace amounts of cholestanol (less than 2 mg/day) and no detectable 5 alpha-campestanol and 5 alpha-sitostanol, which indicated that the 5 alpha-saturated stanols were formed endogenously. Treatment with cholestyramine reduced plasma cholesterol and phytosterol levels by 45% and 5 alpha-saturated stanols by 55%. These results indicate that abnormally high plasma concentrations of cholestanol, 5 alpha-campestanol, and 5 alpha-sitostanol are found in subjects with sitosterolemia and xanthomatosis, and that treatment with cholestyramine effectively reduced elevated plasma sterol levels.     

Role of the antithrombin-binding pentasaccharide in heparin acceleration of antithrombin-proteinase reactions. Resolution of the antithrombin conformational change contribution to heparin rate enhancement.

The synthetic antithrombin-binding heparin pentasaccharide and a full-length heparin of approximately 26 saccharides containing this specific sequence have been compared with respect to their interactions with antithrombin and their ability to promote inhibition and substrate reactions of antithrombin with thrombin and factor Xa. The aim of these studies was to elucidate the pentasaccharide contribution to heparin's accelerating effect on antithrombin-proteinase reactions. Pentasaccharide and full-length heparins bound antithrombin with comparable high affinities (KD values of 36 +/- 11 and 10 +/- 3 nM, respectively, at I 0.15) and induced highly similar protein fluorescence, ultraviolet and circular dichroism changes in the inhibitor. Stopped-flow fluorescence kinetic studies of the heparin binding interactions at I 0.15 were consistent with a two-step binding process for both heparins, involving an initial weak encounter complex interaction formed with similar affinities (KD 20-30 microM), followed by an inhibitor conformational change with indistinguishable forward rate constants of 520-700 s-1 but dissimilar reverse rate constants of approximately 1 s-1 for the pentasaccharide and approximately 0.2 s-1 for the full-length heparin. Second order rate constants for antithrombin reactions with thrombin and factor Xa were maximally enhanced by the pentasaccharide only 1.7-fold for thrombin, but a substantial 270-fold for factor Xa, in an ionic strength-independent manner at saturating oligosaccharide. In contrast, the full-length heparin produced large ionic strength-dependent enhancements in second order rate constants for both antithrombin reactions of 4,300-fold for thrombin and 580-fold for factor Xa at I 0.15. These enhancements were resolvable into a nonionic component ascribable to the pentasaccharide and an ionic component responsible for the additional rate increase of the larger heparin. Stoichiometric titrations of thrombin and factor Xa inactivation by antithrombin, as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the products of these reactions, indicated that pentasaccharide and full-length heparins similarly promoted the formation of proteolytically modified inhibitor during the inactivation of factor Xa by antithrombin, whereas only the full-length heparin was effective in promoting this substrate reaction of antithrombin during the reaction with thrombin.(ABSTRACT TRUNCATED AT 400 WORDS)     

Central and local cholinergic components of histamine-induced bronchoconstriction in dogs

To determine the importance of central and local reflexes in the bronchoconstriction produced by inhaled aerosolized histamine, chloralose-urethan-anesthetized dogs were intubated with a double-lumen catheter, ventilated with a dual cylinder respirator, and instrumented for the measurements of pulmonary conductance (GL) and dynamic compliance (Cdyn) in each lung. In each dog, dose-response curves to inhaled aerosolized histamine were obtained in both lungs separately but synchronously. Four series of experiments were performed. In the first series (n = 10) the responses of the right and left lungs were compared and found to be approximately equal, indicating that one lung could be used as a control for the other. In the second and third series the dose-response curve of one lung that had either been treated with inhaled atropine sulfate (n = 6) (4 mg/ml) or vagotomized (n = 4) was compared with the contralateral control lung. At low concentrations of histamine, GL and Cdyn decreased more in the control lungs than in their atropine-treated or vagotomized counterparts, and approximately 40% of the bronchoconstriction induced was reflex in origin. At higher concentrations of histamine the responses of the control and atropine-treated or vagotomized lungs were not significantly different. In the fourth series of experiments (n = 6) histamine dose-response curves were obtained following combined bilateral vagotomy and unilateral delivery of inhaled aerosolized atropine. In these dogs GL, but not Cdyn, fell to a greater extent in the control than in the atropine-treated lung.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tachyphylaxis to inhaled aerosolized histamine in anesthetized dogs

Three consecutive dose-response curves to inhaled aerosolized histamine, separated by 1-h intervals, were obtained in 20 anesthetized mongrel dogs. In general, successive histamine dose-response curves shifted progressively rightward. Changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) in response to low concentrations of histamine were reproducible, but responses to high concentrations (sufficient to at least double RL or decrease Cdyn by at least 30%) decreased on successive dose-response curves. The concentration of histamine required to double RL increased significantly (P less than 0.05) from 1.01 mg/ml on the first to 1.62 and 2.02 mg/ml on the second and third dose-response curves. In contrast, consecutive methacholine dose-response curves were not significantly different. Indomethacin pretreatment (5 mg/kg iv) prevented histamine tachyphylaxis, whereas atropine (4 mg iv) did not. However, indomethacin did not alter base-line pulmonary mechanics or histamine responsiveness as measured on the first dose-response curve. We conclude that tachyphylaxis to inhaled aerosolized histamine occurs in anesthetized dogs. Our results are consistent with an important role for endogenous prostaglandins in modulating the airway responses to repeated histamine exposures.     

Glycolytic gene expression in amphibious Acorus calamus L. under natural conditions

Acorus calamus L is an amphibious plant, which is exposed to periods of flooding and consequently hypoxic conditions as a part of its natural life cycle. Previous experiments under laboratory conditions have shown that the plant can survive for two months in the complete absence of oxygen, and that during this period the expression of genes encoding the glycolytic enzymes fructose-1,6-bisphosphate aldolase (ALD), pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) is induced in leaves and rhizomes (Bucher and Kuhlemeier, 1993). Here we studied the expression of ALD and ADH through two years in the natural habitat of A. calamus. Under natural conditions roots and rhizomes were always submerged but newly grown leaves emerged in spring; in autumn the leaves senesced and the whole plant was submerged again. High Ald and Adh mRNA levels in leaf and rhizome were found only in winter when the leaves were entirely submerged. Upon leaf emergence in spring the mRNA levels rapidly declined. Under controlled experimental conditions expression of Ald and Adh was not induced by low temperature. The combination of laboratory and field experiments supports the hypothesis that oxygen deprivation rather than low temperature is a major regulator of glycolytic gene expression in A. calamus. The possible role of other environmental factors is also discussed.Abbreviations ADH alcohol dehydrogenase - Adh gene encoding ADH - ALD cytoplasmic fructose-1,6-bisphosphate aldolase - Ald gene encoding ALD - PDC pyruvate decarboxylase - Pdc gene encoding PDC     

FLORAL CORRELATES AND FITNESS CONSEQUENCES OF MATING-SYSTEM VARIATION IN TURNERA ULMIFOLIA

Outcrossing rates varied from 0% to 69% among Jamaican populations of Turnera ulmifolia. A correlation between increasing herkogamy and outcrossing rate occurred among populations. Predictions from sex-allocation theory were tested by estimating allocation to reproductive functions. Significant differences in allocation patterns occurred among populations, but they were not correlated with outcrossing rates. The fitness consequences of inbreeding were assessed in high- and low-density greenhouse experiments for nine populations with variable outcrossing rates. No evidence for inbreeding depression occurred in early portions of the life history, but multiplicative fitness functions provide evidence for inbreeding depression. We tested the prediction that selfing populations have lower levels of inbreeding depression than outcrossing populations but found no significant correlation.     

p28 Bap31, a Bcl-2/Bcl-XL- and Procaspase-8–associated Protein in the Endoplasmic Reticulum

We have identified a human Bcl-2–interacting protein, p28 Bap31. It is a 28-kD (p28) polytopic integral protein of the endoplasmic reticulum whose COOH-terminal cytosolic region contains overlapping predicted leucine zipper and weak death effector homology domains, flanked on either side by identical caspase recognition sites. In cotransfected 293T cells, p28 is part of a complex that includes Bcl-2/Bcl-X_L and procaspase-8 (pro-FLICE). Bax, a pro-apoptotic member of the Bcl-2 family, does not associate with the complex; however, it prevents Bcl-2 from doing so. In the absence (but not presence) of elevated Bcl-2 levels, apoptotic signaling by adenovirus E1A oncoproteins promote cleavage of p28 at the two caspase recognition sites. Purified caspase-8 (FLICE/MACH/Mch5) and caspase-1(ICE), but not caspase-3 (CPP32/apopain/ Yama), efficiently catalyze this reaction in vitro. The resulting NH₂-terminal p20 fragment induces apoptosis when expressed ectopically in otherwise normal cells. Taken together, the results suggest that p28 Bap31 is part of a complex in the endoplasmic reticulum that mechanically bridges an apoptosis-initiating caspase, like procaspase-8, with the anti-apoptotic regulator Bcl-2 or Bcl-X_L. This raises the possibility that the p28 complex contributes to the regulation of procaspase-8 or a related caspase in response to E1A, dependent on the status of the Bcl-2 setpoint within the complex.     

Genetic Sensitivity to 6-n-Propylthiouracil (PROP) and Hedonic Responses to Bitter and Sweet Tastes

Genetically mediated sensitivity to the bitter taste of 6-n-propylthiouracil(PROP) has been associated with greater acuity for bitter andfor some sweet tastes. Thus far, few studies have explored therelationship between PROP taste sensitivity and hedonic responsesto bitter and sweet. In this study, 87 normal-weight young womenwere divided into PROP non-tasters (n = 18), regular tasters(n = 49), and supertasters (n = 20), based on their PROP detectionthresholds and the scaling of five suprathreshold solutionsof PROP and NaCl. Non-tasters had thresholds >1.8 x 10^–4mol/l PROP. Supertasters had thresholds <3.2 x 10^–5mol/l PROP and PROP/NaCl ratios >1.70. As expected, dislikeof the bitter taste of PROP was determined by its perceivedintensity, which was greater among supertasters than among regulartasters or non-tasters. Significant correlations were observedbetween PROP taste thresholds and the sum of intensity ratings(r = –0.61) and between summed intensity and summed hedonicratings (r = –0.80). PROP taste sensitivity was weaklylinked to enhanced perception of sweet taste, but did not predicthedonic responses to sucrose or to saccharin solutions. Giventhat the dislike of PROP solutions is determined by their perceivedintensity, hedonic responses to PROP solutions may provide arapid way of screening for PROP taster status. Chem. Senses22: 27–37, 1997.