Aristotle on the infallibility of normal observation

Whereas it is well established that Aristotle allowed the possibility of error in some observations, it is often held that he was an infallibilist with respect to normal observational beliefs. We shall argue against this interpretation of Aristotle, and in particular show that it is not implicit in his view that observation is the ‘ultimate arbiter of truth’.     

Purification of the vascular plasminogen activator]

We have isolated a purified preparation of the vascular plasminogen activator. Plasma obtained from post occlusion venous blood has been chromatographed with low and high ionic strength buffers. The purified protein has a relative molecular weight of 71,000.     

Electron microscopic observation of bacteria growing on the skin surface

Résumé Des observations au microscope électronique ont été faites sur des bacteries se développant à la surface de la peau. En utilisant la technique de fixation deRyter-Kellenberger, les auteurs ont obtenu bonne préservation des microorganismes, ce qui a permis l'étude de leur fine structure.

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Supported in part by grants from the Eli Lilly Co., Indianapolis, Indiana and the Upjohn Co., Kalamazoo, Michigan. — We are indebted to Drs.S. H. Black, E. Kellenberger andR. P. Williams for their valuable suggestions. — We are also grateful to MissS. Martin, MissN. Moreland and Mr.G. Adams for their technical assistance.     

The effect of the anabolic steroid stanozolol on tissue plasminogen activator activity and plasmin inhibition in the rat

Summary The anabolic steroid stanozolol administered orally in male Sprague-Dawley rats induced a dose- and time-dependent increase in tissue plasminogen activator activity. The increase was highest in lung, lowest in heart, and intermediate in aorta and kidney. A slight increase in plasmin inhibition was noted only in the heart.This study was partially supported by a grant from the Atherosclerosis and Thrombosis Research Committee of the Austrian Academy of Sciences.     

Cellular and secreted tumor plasminogen activator: the effects of NaCl

Plasminogen activator, secreted by metastatic tumor cells, was strongly inhibited in buffer or tissue culture medium containing physiological concentrations of NaCl. Intact cells, however, expressed strong activity under similar conditions. Thus, if plasminogen activator is involved in invasion and metastasis, the cellular activity, acting as an ectoenzyme, may be more important than secreted enzyme under physiological conditions.     

Adsorption of hageman factor (factor XII) on collagen

Résumé Nous avons trouvé que le facteur Hageman (factor XII), contenu dans le plasma humain citraté, pauvre en plaquettes, est adsorbé presque sélectivement par le collagène. Il est également possible d'éluer ce facteur au pH alcalin.     

Ultrastructural observation on the tips of growing vascular cords in the rat cerebral cortex

Summary The distal ends of the vascular cord in the cerebral cortex are investigated electron microscopically in rats at the 13th postnatal day. The tip of the vascular cord consists of central cuboidal cells (primitive endothelial cells) and surrounding flat cells (primitive pericytes), and has no lumen. The primitive endothelial cells (tip cells) possess several long tentacles which contain only fibrous structures and extend through the neuropile.This study was supported in part by a grant in aid for Scientific Research from the Ministry of Education of Japan (No. 448085).     

Interferon-beta can induce the production of plasminogen activator by cultured human cancer cells

Three cultured human cell lines, renal cancer cells (ACHN), bladder cancer cells (EJ), and fibroblasts transformed in culture by Co-60 gamma rays (KMST-6), when treated with interferon-beta, produced 1.5 to 4 times as much plasminogen activator as the untreated control cultures. This enhanced production of PA was inhibited by cycloheximide or actinomycin D.     

A potent actomyosin ATPase activator from the Okinawan marine spongeAgelas cf.nemoechinata

Summary A bromine-containing alkaloid, oxysceptrin, has been isolated as a potent actomyosin ATPase activator from the Okinawan marine spongeAgelas cf.nemoechinata, and the structure elucidated to be1 on the basis of the 2D NMR spectral data.Acknowledgments. We thank Mr Z. Nagahama for his help in sponge collecting and Ms M. Takamatsu for her technical assistance.     

Experimental data on the neurotoxicity of methyl-ethyl-ketone (MEK).

A severe potentiating effects of methyl-ethyl-ketone (MEK) on the peripheral and central neurotoxicity of n-hexane could be demonstrated in a chronic inhalation study in rats.     

Experimental data on the neurotoxicity of methyl-ethyl-ketone (MEK)

Summary A severe potentiating effect of methyl-ethyl-ketone (MEK) on the peripheral and central neurotoxicity of n-hexane could be demonstrated in a chronic inhalation study in rats.