Showing papers by "Mark D. Johnson published in 1994"

Inhibition of angiogenesis by tissue inhibitor of metalloproteinase.

Abstract: Matrix proteases play a critical role in cell invasion and migration, including the process of angiogenesis. The ability of specific factors to induce angiogenic responses correlates with their stimulation of matrix protease synthesis and release. Using an in vivo angiogenesis assay, the endothelial cell response to known angiogenic factors, basic fibroblast growth factor (bFGF) and adipocyte conditioned medium, was blocked by an inhibitor of matrix metalloproteinase activity, TIMP-1. The TIMP effect was mediated, at least in part, through the inhibition of endothelial cell migration, as determined by the ability of TIMP to block chemotaxis in a Boyden chamber assay. These results indicate that the inhibition of migration is a direct effect on the endothelial cells and does not require accessory cells. An additional observation was that the RNA levels for TIMP were significantly reduced in differentiated adipocytes, compared to undifferentiated F442A controls. Therefore, the acquisition of an angiogenic phenotype may involve not only the induction of positive factors, but also the suppression of angiogenesis inhibitors.

Targeted disruption of the Hexa gene results in mice with biochemical and pathologic features of Tay-Sachs disease.

Abstract: Tay-Sachs disease, the prototype of the GM2 gangliosidoses, is a catastrophic neurodegenerative disorder of infancy. The disease is caused by mutations in the HEXA gene resulting in an absence of the lysosomal enzyme, beta-hexosaminidase A. As a consequence of the enzyme deficiency, GM2 ganglioside accumulates progressively, beginning early in fetal life, to excessive amounts in the central nervous system. Rapid mental and motor deterioration starting in the first year of life leads to death by 2-4 years of age. Through the targeted disruption of the mouse Hexa gene in embryonic stem cells, we have produced mice with biochemical and neuropathologic features of Tay-Sachs disease. The mutant mice displayed < 1% of normal beta-hexosaminidase A activity and accumulated GM2 ganglioside in their central nervous system in an age-dependent manner. The accumulated ganglioside was stored in neurons as membranous cytoplasmic bodies characteristically found in the neurons of Tay-Sachs disease patients. At 3-5 months of age, the mutant mice showed no apparent defects in motor or memory function. These beta-hexosaminidase A-deficient mice should be useful for devising strategies to introduce functional enzyme and genes into the central nervous system. This model may also be valuable for studying the biochemical and pathologic changes occurring during the course of the disease.

Spin polarization of gold films via transported (invited)

Abstract: The spin injection technique has been adapted to a thin‐film geometry. Measurements of the spin‐coupled voltage Vs as a function of film thickness d result in a determination of the spin diffusion length δs =√DT1 with D the electron diffusion constant, in polycrystalline gold films. The conduction electron spin relaxation time T1 is found to be 4.6±2.5×10−11 s, for the temperature range 4 K

Effect of salmeterol on human nasal epithelial cell ciliary beating: inhibition of the ciliotoxin, pyocyanin

Abstract: 1. Patients with airway infection by Pseudomonas aeruginosa have impaired mucociliary clearance. Pyocyanin is a phenazine pigment produced by P. aeruginosa which is present in the sputum of colonized patients, slows human ciliary beat frequency (CBF) in vitro and slows mucociliary transport in vivo in the guinea-pig. 2. We have investigated the effect of salmeterol, a long-acting beta 2-adrenoceptor agonist, on pyocyanin-induced slowing of human CBF in vitro. Salmeterol (2 x 10(-7) M) was found to reduce pyocycanin (20 micrograms ml-1)-induced slowing of CBF by 53% and the fall in intracellular adenosine 3':5'-cyclic monophosphate (cyclic AMP) by 26% and ATP by 29%. 3. Another beta 2-adrenoceptor agonist, isoprenaline (2 x 10(-7) M), also inhibited pyocyanin-induced slowing of CBF by 39%. 4. The effects of salmeterol (30 min preincubation) persisted after washing the cells. 5. Propranolol (10(-7) M) and the beta 2-specific antagonist, ICI 118551 (10(-6) M) blocked the protective effects of salmeterol completely, but atenolol (10(-6) M) was less effective. These results suggested that the effects of salmeterol on pyocyanin-induced effects were mediated primarily via the stimulation of beta 2-adrenoceptors. 6. Pyocyanin-induced ciliary slowing is associated with a substantial fall in intracellular cyclic AMP and ATP. Salmeterol reversed the effects of pyocyanin on cyclic AMP and ATP. 7. Mucociliary clearance is an important defence mechanism of the airways against bacterial infection. Salmeterol may benefit patients colonized by P. aeruginosa, not only by its bronchodilator action, but also by protecting epithelial cells from pyocyanin-induced slowing of CBF.

Decrease in Norepinephrine Release from Cardiac Adrenergic Nerve Terminals after Ischemia and Reperfusion a

Abstract: Occlusion of the coronary arteries causes adrenergc denervation of the infarcted myocardium and surrounding regions.’ Little is known about the extent of functional decline in the surviving adrenergc nerve terminals in the ischemic and non-ischemic portions of the myocardium or about the ability of these nerves to eventually recover full function. Injury and recovery may also be influenced by age and gender. Therefore experiments were performed to assess changes in cardiac adrenergic function after ligation and reperfusion of the left anterior descending artery (LAD) in young (6 months old) and old (24 months old) male and female F344 rats. K+-induced 3H-norepinephrine (NE) release fiom cardiac synaptosomes (SYN) and coronary arteries prepared from these hearts was used to measure adrenergc function. Male and female F344 rats were maintained in separate rooms under barrier conditions. Myocardial ischemia and reperfusion (1-9 was induced by ligation of the LAD as described by Lefer et aL3 Under sodium pentobarbital anesthesia (40 mg/kg) the chest was opened, a suture with slip knot was placed around the LAD, and the chest was closed. Ischemia was maintained for 10 min and was followed by 60 min of reperfusion before removing the heart. SYN were prepared from the ischemic and nonischemic regions of the heart. SYN and segments of the LAD and left circumflex artery (LCX) were incubated with 300 nM 3H-NE and then placed in individual chambers in a superfusion system. Preparations were also obtained from decapitated, unanesthetized, and unoperated control rats of the same ages and gender. 3H-NE release was induced by changing the superfusion buffer fbr 2 min to a high K+ buffer (peak chamber concentration of 45 mM K+). Methods are described in detail in Snyder et aL2 In the control groups, gender and age differences were observed in the net fractional release of 3H-NE from rat coronary arteries and SYN (TABLE 1). Old males showed significant decreases in release from the LAD, LCX, and SYN when compared to young males. These results agree with our previous findings.2 In contrast, female rats showed no significant age-related changes in release from the LAD, LCX, or SYN.