The dual phases of the response to neonatal exposure to a VH family-restricted staphylococcal B cell superantigen

In vitro studies of several naturally occurring proteins have characterized VH family-specific B lymphocyte binding and stimulatory properties that appear analogous to those of T cell superantigens. To examine the in vivo consequences of exposure to a putative B cell superantigen, we treated neonatal BALB/c mice with a form of staphylococcal protein A (MS) devoid of Fcgamma binding activity, which retains the clan VHIII Fab binding specificity. In naive adults, about 5% of peripheral B cells and >13% of splenic IgM-secreting cells display MS binding activity, in association with high IgM and low IgG circulating anti-MS Ab titers. Neonatal exposure to MS elicited two distinct temporal phases of immune responsiveness. The early phase, representing the first approximately 5 wk of life, was associated with MS-specific B cell and T cell tolerance. Microfluorometric assays revealed that exposure caused a dramatic MS-specific B cell clonal loss in bone marrow and spleen, but levels normalized by about 3 wk of life. The late phase (>6 wk of age) was associated with spontaneous priming for MS-specific T cell responses and production of MS-specific IgG1 Abs despite long term persistently depressed in vivo and in vitro MS-specific IgM responses. In vivo challenge during the late phase induced high frequencies of MS-specific IgG-secreting cells, indicating recruitment of highly focused Ab responses that were predominantly encoded by rearrangements of the S107 family, a member of the VHIII clan. These studies document the immunodominance of the VH-restricted Fab binding site on staphylococcal protein A and demonstrate the diverse effects of a B cell superantigen on the emerging peripheral B cell compartment.     

Covalent modifications of aminophospholipids by 4-hydroxynonenal

Lipid oxidation is implicated in a wide range of pathophysiological disorders, which leads to reactive compounds such as aldehydes. Among them 4-hydroxynonenal (4-HNE) reacts strongly with the NH2 groups of amino acids and forms mainly Michael adducts and minor Schiff-base adducts. Such reactions occur also with compounds containing thiol groups. No data are available describing 4-HNE interactions with amino-phospholipids. To investigate such a possibility, 4-HNE was incubated with either phosphatidylethanolamine (PE) or phosphatidylserine (PS) in an aqueous-organic biphasic system and the resulting products were identified by liquid chromatography-mass spectrometry (LC-MS). Our study points out the potential capacity of 4-HNE to react with phospholipids containing amino groups and particularly PE. The main resulting compounds found were a Michael adduct plus a minor Schiff base adduct, which was partly cyclized as a pyrrole derivative via a loss of water. Its stabilization as a pyrrole derivative allows to differentiate 4-HNE from the other aldehydes generated via lipid oxidation (e.g., malondialdehyde, 2-nonenal) that lack the 4-hydroxyl group. Their formation seems not to be affected when the pH varies from 6.5 to 8.5. Surprisingly, PS reacted poorly producing only a small amount of Michael adduct, the Schiff-base adduct being nondetectable. We conclude that such adducts, if they are formed in cell membranes, could alter the phospholipase-dependent cell signaling.     

1,4-Cyclohexanecarboxylates: potent and selective inhibitors of phosophodiesterase 4 for the treatment of asthma

Evaluation of a variety of PDE4 inhibitors in a series of cellular and in vivo assays suggested a strategy to improve the therapeutic index of PDE4 inhibitors by increasing their selectivity for the ability to inhibit PDE4 catalytic activity versus the ability to compete for high affinity [3H]rolipram-binding sites in the central nervous system. Use of this strategy led ultimately to the identification of cis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxyl ic acid (1, SB 207499, Ariflo), a potent second-generation inhibitor of PDE4 with a decreased potential for side effects versus the archetypic first generation inhibitor, (R)-rolipram.     

The impact of maternal personality on individuation during adolescence.

The role of the mother in the resolution of the rapprochement crisis as it continues into adolescence is examined through the analyses of a 14-year-old boy and his mother. The symptoms of the adolescent were anxiety, poor school performance, and drug abuse. The mother sought treatment for intense anxiety and overwhelming dread when contemplating her future and that of her son. The dynamics of the mother, the nature of the symbiotic bond, and their impact on the inability of the adolescent to effectively disengage from anaclitic parental ties are discussed. The importance of understanding parental dynamics in the analysis of adolescents is stressed from theoretical and clinical viewpoints. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The membrane-cytoplasm interface of integrin alpha subunits is critical for receptor latency

Localization of integrin receptors to focal contact sites occurs upon ligand binding. This activity is latent, since unoccupied integrin receptors do not localize to focal contacts. Deletion analysis has revealed that the alpha cytoplasmic domains is required for the maintenance of integrin receptor latency. Our current hypothesis for the mechanism of integrin post-ligand binding events is that there is a change in relationship of alpha and beta cytoplasmic domains, which overcomes receptor latency. One possible mechanism for such a change would involve the amino acid residues at the membrane-cytoplasm interface. To test this hypothesis, we have produced point mutations in the human integrin alpha 1 subunit. These mutations had no effect on the adhesion via alpha 1 beta 1 to its ligand, collagen IV. However, receptor latency is lost in one of these mutants, leading to constitutive focal contact localization. This effect did not occur in receptors with an exchange of intracellular domains, suggesting that the mechanism of loss of latency involves a relative motion of the integrin chains. These results suggest a model in which post-ligand binding events in integrin receptors are associated with changes in the position of the alpha and beta cytoplasmic domains.     

Energy requirements of middle-aged men are modifiable by physical activity

BACKGROUND: Energy requirements for weight maintenance decrease with age. Often, this decline is not proportionately matched by reduced energy intake, resulting in weight gain. OBJECTIVE: We hypothesized that energy requirements for total daily weight maintenance in healthy, sedentary, middle-aged men would increase after regular aerobic exercise or aerobic exercise plus weight loss to levels comparable with those in middle-aged athletes. DESIGN: Weight-maintenance energy requirements were determined during weight stability (+/- 0.25 kg) in 14 lean, sedentary (LS) men; 18 obese, sedentary (OS) men; and 10 male athletes of comparable ages (x +/- SEM: 58 +/- 1 y). Studies were done at baseline and after 6 mo of aerobic exercise (LS men) or aerobic exercise plus weight loss (OS men) or 3 mo of deconditioning (athletes). RESULTS: The interventions raised maximal oxygen uptake (VO2max) by 15% in the LS men and by 13% in the OS men and decreased it by 14% in athletes (all P < 0.01), eliminating the differences among groups at baseline. Body fat was reduced significantly in LS and OS men; fat-free mass decreased in OS men. Average daily energy requirements increased by 8% in LS men and by 5% in OS men (both P < 0.01) to levels comparable with the baseline requirements of athletes and correlated with VO2max (r2 = 0.22, P < 0.0001) and fat-free mass (r2 = 0.05, P < 0.02) across the range of VO2max achieved by all subjects. CONCLUSIONS: Under free-living conditions, aerobic exercise eliminated the difference in weight-maintenance energy requirements between middle-aged sedentary and athletic men, suggesting that energy requirements of healthy, middle-aged men are modifiable by regular physical activity.     

Acute effects of nifedipine in renal transplant recipients treated with cyclosporine or azathioprine

Cyclosporine (CsA) impairs renal function, probably by preglomerular vasoconstriction. Vasodilating substances may therefore be of benefit to ameliorate CsA-induced renal dysfunction. We studied the acute effects on blood pressure and renal function of the dihydropyridine calcium antagonist nifedipine (10 mg orally) in 20 CsA-treated renal transplant patients. In addition, we compared the effects of nifedipine when given immediately before and 4 weeks after elective conversion from CsA to azathioprine. Compared with placebo (n = 14), administration of nifedipine led to a significant decrease in blood pressure and a strong natriuretic and diuretic response. Despite the reduction in blood pressure, glomerular filtration rate improved from 60 +/- 20 (mean +/- SD) to 69 +/- 24 mL/min/1.73 m2 (P < 0.001) and renal plasma flow (RPF) increased from 260 +/- 87 to 338 +/- 120 mL/min/1.73 m2 (P < 0.001). The combination of a decreased blood pressure with an increased RPF was reflected in a sharp decrease in renal vascular resistance (0.34 +/- 0.18 units v 0.23 +/- 0.10 units; P < 0.001). The conversion from CsA to azathioprine by itself led to significant increases in glomerular filtration rate (62 +/- 15 mL/min/1.73 m2 v 76 +/- 18 mL/min/1.73 m2; P < 0.05) and RPF (280 +/- 86 mL/min/1.73 m2 v 334 +/- 66 mL/min/1.73 m2; P < 0.05). During treatment with azathioprine an effect of nifedipine on glomerular filtration rate and RPF was no longer observed, although the natriuretic effect was similar on both occasions. The decrease in renal vascular resistance was larger during treatment with CsA than during treatment with azathioprine (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inactivation of pyridoxal phosphate dependent enzymes by mono- and polyhaloalanines

beta,beta-Dichloro- and beta,beta,beta-trifluoroalanine irreversibly inactivate a number of pyridoxal phosphate dependent enzymes which catalyze beta- or gamma-elimination reactions. The inactivation is time dependent and the rate of inactivation is first order in enzyme concentration. This suggests that inactivation is due to covalent modification of the enzyme by a species generated at the active site from the polyhaloalanine (i.e., suicide inactivation). Monohaloalanines are substrates and do not inactivate. For gamma-cystathionase, covalent and stoichiometric attachment of [1-14C]beta,beta,beta-trifluoroalanine was shown. It is proposed that the mechanism of inactivation involves Schiff base formation between inactivator and enzyme-bound pyridoxal and subsequent elimination of HC1 from dichloroalanine or HF from trifluoroalanine. This results in the formation of a beta-halo-alpha,beta unsaturated imine, an activated Michael acceptor. Michael addition of a nucleophile at the active site leads to covalent labeling of the enzyme and inactivation. Alanine racemase is also inactivated by the two polyhaloalanines. Glutamate-pyruvate and gultamate-oxaloacetate transaminase are inactivated by monohaloalanines but not by polyhaloalanines.     

Endoscopic visualization of induced colonic tumors in rats

The visualization of induced colonic tumors in rats was investigated using either a rigid or flexible endoscope. There was 89% agreement between presence or absence of at least one tumor as visualized at endoscopy and necropsy. The agreement was 83% (p < 0.01) when the exact number of tumors was compared. Neither carcinogens (1,2-dimethylhydrazine or N-methylnitrosourea) nor dietary supplements affected the results.