Plasma membrane cholesterol is a key molecule in shear stress-dependent activation of extracellular signal-regulated kinase

Shear stress, the dragging force generated by fluid flow, differentially activates extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) in bovine aortic endothelial cells (BAEC) (Jo, H., Sipos, K., Go, Y. M., Law, R., Rong, J., and McDonald, J. M. (1997) J. Biol. Chem. 272, 1395-1401). Here, we examine whether cholesterol-enriched compartments in the plasma membrane are responsible for such differential regulation. Pretreatment of BAEC with a cholesterol-binding antibiotic, filipin, did not inhibit shear-dependent activation of JNK. In contrast, filipin and other membrane-permeable cholesterol-binding agents (digitonin and nystatin), but not the lipid-binding agent xylazine, inhibited shear-dependent activation of ERK. The effect of cholesterol-binding drugs did not appear to be due to membrane permeabilization, since treatment of BAEC with a detergent, Triton X-100 which also permeabilizes membranes, did not inhibit shear-dependent activation of ERK. Furthermore, shear-dependent activation of ERK, but not JNK, was inhibited by cyclodextrin, a membrane-impermeable cholesterol-binding agent, which removes cell-surface cholesterol. Moreover, the effects of cyclodextrin were prevented by adding cholesterol during the incubation. These results indicate that cholesterol or cholesterol-sensitive compartments in the plasma membrane play a selective and essential role in activation of ERK, but not JNK, by shear stress. Although exposure to shear stress (1 h) increased the number of caveolae by 3-fold, treatment with filipin had no effect in either control or shear-exposed cells suggesting that caveolae density per se is not a crucial determinant in shear-dependent ERK activation. In summary, the current study suggests that cholesterol-sensitive microdomains in the plasma membrane, such as caveolae-like domains, play a critical role in differential activation of ERK and JNK by shear stress.     

Calretinin-immunoreactive neurons in the human thalamus

To identify plant defense components that are important in restricting the growth of virulent pathogens, we screened for Arabidopsis mutants in the accession Columbia (carrying the transgene BGL2-GUS) that display enhanced disease susceptibility to the virulent bacterial pathogen Pseudomonas syringae pv. maculicola (Psm) ES4326. Among six (out of a total of 11 isolated) enhanced disease susceptibility (eds) mutants that were studied in detail, we identified one allele of the previously described npr1/nim1/sai1 mutation, which is affected in mounting a systemic acquired resistance response, one allele of the previously identified EDS5 gene, and four EDS genes that have not been previously described. The six eds mutants studied in detail (npr1-4, eds5-2, eds10-1, eds11-1, eds12-1, and eds13-1) displayed different patterns of enhanced susceptibility to a variety of phytopathogenic bacteria and to the obligate biotrophic fungal pathogen Erysiphe orontii, suggesting that particular EDS genes have pathogen-specific roles in conferring resistance. All six eds mutants retained the ability to mount a hypersensitive response and to restrict the growth of the avirulent strain Psm ES4326/avrRpt2. With the exception of npr1-4, the mutants were able to initiate a systemic acquired resistance (SAR) response, although enhanced growth of Psm ES4326 was still detectable in leaves of SAR-induced plants. The data presented here indicate that eds genes define a variety of components involved in limiting pathogen growth, that many additional EDS genes remain to be discovered, and that direct screens for mutants with altered susceptibility to pathogens are helpful in the dissection of complex pathogen response pathways in plants.     

Mumps orchitis; review of 8 cases]

The occurrence of secondary hypogonadism is a common finding in males who seek help with erectile dysfunction, although the relationship to diminished testosterone is unclear. Two possibilities exist regarding both the genesis and maintenance of the hypogonadotropic hypogonadal state. First, a defect in hypothalamic function, resulting in downregulation as well as in alterations of anterior pituitary function; second, estradiol inhibition of gonadotropin release, both of which result in decreased testosterone production. As testosterone levels decrease and estradiol levels increase, the ratio of free testosterone to estradiol reaches a critical point and the estrogenic gonadotropin suppressive effects predominate. This ratio may signal the biological point of no return and could become one of the criteria for defining the separation of the transitional hypogonadal state from the final 'end stage' hypogonadotropic hypogonadal state. As the aging process continues, there is a relative accumulation of fatty tissue, and aromatization accelerates the conversion of testosterone to estradiol. This additional secondary estradiol inhibition results in the maintenance of the testosterone deficient state, and the aging process continues uncontested.     

Effect of pulmonary artery stenoses on the cardiopulmonary response to exercise following repair of tetralogy of Fallot

Data from exercise tests, echocardiograms, and lung perfusion scans were analyzed to determine whether the excessive minute ventilation (VE) often encountered among patients with tetralogy of Fallot is due to ventilation-perfusion mismatch secondary to branch pulmonary artery stenoses. Patients with branch PA stenoses had lower peak oxygen consumptions and higher VE during exercise than did patients without stenoses, and a strong correlation existed between the degree of pulmonary blood flow maldistribution on lung perfusion scan and the amount of excessive VE during exercise.     

Indomethacin inhibits the natriuretic effects of neuropeptide Y in anesthetized rats

Neuropeptide Y (NPY) is a unique modulator of renal function that enhances urine flow and sodium excretion despite marked reductions in renal blood flow. We investigated whether the cyclooxygenase inhibitor indomethacin alters the renal NPY effects in anesthetized rats. Treatment with 5 mg/kg indomethacin i.p. lowered urinary prostaglandin excretion by approximately 85%. Systemic infusion of NPY elevated mean arterial pressure by approximately 15 mm Hg and renovascular resistance by approximately 8.0 mm Hg/ml/min, whereas the related peptide YY3-36 (PYY3-36) did not. Nevertheless, both peptides enhanced urine flow rate by approximately 250 and approximately 100 microl/15 min, respectively, and sodium excretion by approximately 15 micromol/15 min. Treatment with indomethacin did not affect NPY- and PYY3-36-induced alterations of systemic and renovascular hemodynamics but completely abolished NPY- and PYY3-36-induced diuresis and natriuresis. Endogenous creatinine clearance was not affected by any treatment. We conclude that cyclooxygenase-derived arachidonic acid metabolites are not involved in the systemic or renal hemodynamic effects of NPY and PYY3-36 but mediate NPY- and PYY3-36-induced diuresis and natriuresis.     

Inhaled nitric oxide is not a myocardial depressant in a porcine model of heart failure

BACKGROUND: Inhaled nitric oxide has been shown to be a potent and selective pulmonary vasodilator. Reports of increases in left ventricular end-diastolic pressure and episodes of pulmonary edema during the clinical use of inhaled nitric oxide in patients with preexisting left ventricular dysfunction have raised concerns that this agent may have myocardial depressant effects. We therefore undertook a study of the effects of inhaled nitric oxide on myocardial contractility in a porcine model of ventricular failure and pulmonary hypertension. METHODS: After inducing heart failure in 10 pigs by rapid ventricular pacing, hemodynamic measurements and pressure-volume diagrams (by the conductance method) were obtained in six animals at baseline and during administration of inhaled nitric oxide at concentrations of 20 and 40 ppm. Myocardial contractile state was assessed by the end-systolic pressure-volume relationship and preload-recruitable stroke work, whereas diastolic function was measured in terms of the end-diastolic pressure-volume relationship and the pressure decay time constant T. RESULTS: Baseline hemodynamics reflected heart failure and pulmonary hypertension, and inhaled nitric oxide induced significant reductions in mean pulmonary artery pressure and pulmonary vascular resistance. Although left ventricular end-diastolic pressure increased during administration of inhaled nitric oxide, no changes were observed in measures of systolic or diastolic function. CONCLUSIONS: Inhaled nitric oxide reduced pulmonary vascular resistance but did not alter myocardial contractility or diastolic function. Increases in left ventricular end-diastolic pressure during inhaled nitric oxide therapy are therefore not due to myocardial depression and may be related to increases in volume delivery to the left side of the heart resulting from reduced pulmonary vascular resistance.     

Surface-specific electrical occlusal caries diagnosis: reproducibility, correlation with histological lesion depth, and tooth type dependence

We investigated the lipid metabolism in primary cultured hepatocytes to elucidate the causes of hyperlipidemia, increased cholesteryl esters, and decreased triglyceride levels in the livers of daunomycin-nephrotic rats. The incorporation of 14C-palmitate into phospholipids and triglycerides in primary cultured hepatocytes and medium was similar in daunomycin-nephrotic and control rats. The incorporation of 14C-acetate into phospholipids, triglycerides, cholesterol, cholesteryl esters, and total fatty acids in primary cultured hepatocytes was increased in daunomycin-nephrotic rats. The radioactivity of phospholipids, triglycerides, cholesterol, cholesteryl esters, and very-low-density lipoprotein lipids in medium was increased in the hepatocytes of daunomycin-nephrotic rats using 14C-acetate as a precursor. The increased cholesterogenesis and the increased secretion of triglycerides synthesized from acetate by hepatocytes may be due to an increased cholesteryl ester content and a decreased triglyceride content in the livers of daunomycin-nephrotic rats. The increased secretion of lipids synthesized from acetate by hepatocytes may be due to increased accumulation of lipids in serum and very-low-density lipoprotein in daunomycin-nephrotic rats.     

Effects of long-term testosterone, gonadotropin-releasing hormone agonist, and pimozide treatments on gonadotropin II levels and ovarian development in juvenile female striped bass (Morone saxatilis)

The ability of the juvenile female reproductive axis to respond to hormonal stimulation was investigated in a Perciform fish, the striped bass (Morone saxatilis) using various combinations of testosterone (T), GnRH agonist (GnRHa), and pimozide. A long-term treatment with T alone, or T in combination with GnRHa, increased pituitary gonadotropin II (GtH II) levels 2- and 3-fold, respectively, suggesting that T and GnRHa each stimulate GtH II accumulation. Release of the accumulated GtH II could be induced only by high doses of GnRHa in combination with T, indicating that GtH II synthesis and release require different levels of GnRH stimulation. The addition of the dopamine antagonist pimozide did not affect pituitary and plasma GtH II levels but, in response to an additional acute GnRHa challenge, inhibited the release of GtH II. Although ovarian development was slightly stimulated by a combined T and GnRHa treatment, vitellogenesis was generally not initiated. The present study demonstrated that the juvenile striped bass pituitary is responsive to hormonal stimulation, resulting in elevated levels of GtH II in the pituitary and plasma. However, increased plasma levels of GtH II did not result in precocious puberty, suggesting that additional factors are required for the initiation of ovarian development in this teleost.