Magnetotactic bacteria at the geomagnetic equator     

Frankel RB  Blakemore RP  DE Araujo FF  Esquivel DM  Danon J 《Science (New York, N.Y.)》1981,212(4500):1269-1270

Magnetotactic bacteria are present in fresh water and marine sediments of Fortaleza, Brazil, situated close to the geomagnetic equator. Both South-seeking and North-seeking bacteria are present in roughly equal numbers in the same samples. This observation is consistent with the hypothesis that the vertical component of the geomagnetic field selects the predominant polarity type among magnetotactic bacteria in natural environments.  相似文献   

NUTRITIVE VALUE OF THE MEXICAN TORTILLA     

Cravioto RO  Anderson RK  Lockhart EE  DE P Miranda F  Harris RS 《Science (New York, N.Y.)》1945,102(2639):91-93

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The Name of America     

DE St Bris T 《Science (New York, N.Y.)》1888,12(283):12

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STUDIES ON THE FATE OF PLASMA PROTHROMBIN     

DE W Andrus W  Lord JW  Kauer JT 《Science (New York, N.Y.)》1940,91(2350):48-50

The level of the plasma prothrombin in the circulating blood is decreased during its passage through the pulmonary capillaries. In 85 per cent. of samples, plasma prothrombin has been found to be less in the blood of the left ventricle than in that from the right ventricle. This difference averaged 10.6 per cent. and ranged from 4 to 19 per cent. In no instance was the level in the right ventricle lower than that in the left. In samples of blood taken from the arterial and venous supply of the head, liver, spleen, intestine, kidney and hind limbs, no significant difference in plasma prothrombin levels was found. A possible explanation of this role of the lung in the loss of plasma prothrombin is thought to be the production of blood platelets in this organ, as demonstrated by Howell and Donahue. Platelets, as they undergo disintegration, initiate the first stage of the clotting process by releasing thromboplastin, which, in the presence of calcium, changes prothrombin to thrombin.  相似文献   

Racemization of Amino Acids in Dipeptides Shows COOH > NH2 for Non-Sterically Hindered Residues     

Smith GG  DE Sol BS 《Science (New York, N.Y.)》1980,207(4432):765-767

The relative rates of racemization for amino acid residues at the NH(2) and COOH ends of 37 different dipeptides were determined. In nine dipeptides containing alanine, leucine, phenylalanine, aspartic acid, and methionine, the amino acid residue racemized faster at the COOH-terminal position than at the NH(2)-terminal position (COOH > NH(2)). The sterically hindered amino acids isoleucine and valine showed NH(2) > COOH. Six proline dipeptides showed NH(2) > COOH. Intramolecular effects have been invoked to explain these surprising results.  相似文献   

Dorid nudibranch elaborates its own chemical defense     

Cimino G  DE Rosa S  DE Stefano S  Sodano G  Villani G 《Science (New York, N.Y.)》1983,219(4589):1237-1238

A biosynthetic experiment with mevalonic acid labeled with carbon-14 showed that the nudibranch Dendrodoris limbata elaborates polygodial, a sesquiterpenoid dialdehyde stored in the mantle, which constitutes its chemical defense against predators. Previously described nudibranchs drew defensive chemicals from their preys.  相似文献   

Influence of adrenalectomy and hypophysectomy on cerebral serotonin     

DE MAIO D 《Science (New York, N.Y.)》1959,129(3364):1678-1679

Diisopropylfluorophosphate inhibited all the sulfhydryl proteases studied in our tests. This inhibition was most pronounced at pH 6.0. By first blocking the sulfhydryl group with p-chloromercuribenzoate, inhibition could be prevented. Neither cysteine nor choline gave appreciable reactivation of diisopropylfluorophosphate-inhibited bromelain.  相似文献   

Release of autonomic mediators in cardiac tissue by suprathreshold stimulation     

FURCHGOTT RF  DE GUBAREFF T  GROSSMAN A 《Science (New York, N.Y.)》1959,129(3345):328-329

Pharmacological evidence is presented supporting the theory that the increase in contractile strength of isolated cardiac muscle under suprathreshold stimulation is due to the release of an adrenergic mediator (norepinephrine). However, release of this material does not account for changes in contractile strength associated with changes in frequency of stimulation at threshold levels.  相似文献   

COMPARISON OF SONOGRAPHIC FEATURES OF BENIGN AND NEOPLASTIC DEEP LYMPH NODES IN DOGS     

MARIE DE SWARTE  KATE ALEXANDER  BENOIT RANNOU  MARC‐ANDRE D'ANJOU  LAURENT BLOND  GUY BEAUCHAMP 《Veterinary radiology & ultrasound》2011,52(4):451-456

The differentiation of benign vs. neoplastic lymph nodes impacts patient management. Specific sonographic features are typically considered when assessing lymph nodes in dogs. However, the usefulness of these criteria in distinguishing benign vs. malignant lymph nodes remains largely unknown, especially for deep lymph nodes. Our aim was to compare sonographic features in benign and neoplastic deep lymph nodes with the hope of identifying predictive criteria. Thirty‐one deep lymph nodes (16 mesenteric, 10 medial iliac, three hepatic, one sternal, and one cranial mediastinal) in 31 dogs were examined prospectively with B‐mode and Color flow Doppler. Lymph nodes were aspirated using ultrasound‐guidance and final diagnosis were established based on cytologic and/or histopathologic interpretation. Prevalence of each sonographic feature and combinations of two features was calculated for each group and compared using a χ²‐test or Student's t‐test for unequal variances. Ten lymph nodes were benign (hyperplastic and/or inflammatory) and 21 were neoplastic. All were hypoechoic, except for one neoplastic lymph node. Maximal short‐axis diameter (P=0.0006) and long‐axis diameter (P=0.01), and SA/LA ratio (P=0.008) were increased significantly for neoplastic (2.8, 5.5 cm, and 0.50, respectively) vs. benign (1.2, 3.8 cm, and 0.34, respectively) lymph nodes. The prevalence of other features was similar between groups. Doppler evaluation was possible in 77% of lymph nodes, but there was no significant difference between groups. When any two ultrasound features were combined, the only difference between benign and neoplastic lymph nodes was for the combination of contour regularity and appearance of the perinodal fat (P=0.03).  相似文献   

Impact of the quality of organic amendments on size and composition of the weed seed bank     

B DE CAUWER  T D’HOSE  M COUGNON  B LEROY  R BULCKE  D REHEUL 《Weed Research》2011,51(3):250-260

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