WILLIAM SPENCER CARTER 1869-1944     

Hendrix BM  Porter EL  Calvin DB  Leake CD 《Science (New York, N.Y.)》1944,100(2586):42-43

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Plasticity of motor behavior in monkeys with crossed forelimb nerves   总被引：1，自引：0，他引：1  

C Brinkman  R Porter  J Norman 《Science (New York, N.Y.)》1983,220(4595):438-440

Monkeys in which nerves innervating the flexor muscles of the forearm and hand (the ulnar or the median nerve) had been surgically cross-united with the nerve innervating the extensor muscles (the radial nerve), and vice versa, showed excellent (ulnar-radial crosses) to moderate (median-radial crosses) control of movement performance after regeneration. Antagonistic movement responses were seen occasionally, but these were corrected almost immediately. Stimulation of the crossed nerves showed that they had innervated the antagonistic muscle groups. The results reveal the capacity of the primate central nervous system to adapt to gross disturbances imposed on the execution of movements by changes in peripheral innervation.  相似文献   

Muscle relaxation: evidence for an intrafibrillar restoring force in vertebrate striated muscle   总被引：1，自引：0，他引：1  

C Parsons  K R Porter 《Science (New York, N.Y.)》1966,153(734):426-427

Observations of contracting muscle fibrils in cultured cells indicate that the force which restores the resting length of the sarcomere comes from the contractile elements themselves and not from external elasticity, as is now generally accepted. In light of biochemical studies on the contraction-relaxation cycle, it is postulated that the elongating force is one of internal elasticity in the sarcomere, which arises during contraction from the distortion of bonds between filaments and/or structural proteins. This mechanism of restoration may serve to establish optimal sarcomere length for production of maximum contractile force, and in cardiac muscle this mechanism may be a factor in ventricular filling.  相似文献   

Air containing nitrogen-15 ammonia: foliar absorption by corn seedlings   总被引：4，自引：0，他引：4  

L K Porter  F G Viets  G L Hutchinson 《Science (New York, N.Y.)》1972,175(23):759-761

Thirty-day-old corn seedlings, grown in the greenhouse with different concentrations of supplemental nitrate nitrogen, were moved to a constant-temperature growth chamber and sealed in a 560-liter tent made of polyvinyl chloride. The plants were exposed to air containing ammonia labeled with nitrogen-15 (1, 10, and 20 parts per million) for 24 hours and then harvested. The nitrogen-15 content of the tops and roots showed that at 1 part per million 43 percent of the ammonia was absorbed, whereas at 10 and 20 parts per million, 30 percent of the ammonia was absorbed. The results demonstrate that growing plants may be a natural sink for atmospheric ammonia.  相似文献   

Use of variations in natural nitrogen isotope abundance for environmental studies: a questionable approach   总被引：2，自引：0，他引：2  

R D Hauck  W V Bartholomew  J M Bremmer  F E Broadbent  H H Cheng  A P Edwards  D R Keeney  J O Legg  S R Olsen  L K Porter  D H Kohl  G B Shearer  B Commoner 《Science (New York, N.Y.)》1972,177(47):453-456

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Design and chemical synthesis of a homogeneous polymer-modified erythropoiesis protein     

Kochendoerfer GG  Chen SY  Mao F  Cressman S  Traviglia S  Shao H  Hunter CL  Low DW  Cagle EN  Carnevali M  Gueriguian V  Keogh PJ  Porter H  Stratton SM  Wiedeke MC  Wilken J  Tang J  Levy JJ  Miranda LP  Crnogorac MM  Kalbag S  Botti P  Schindler-Horvat J  Savatski L  Adamson JW  Kung A  Kent SB  Bradburne JA 《Science (New York, N.Y.)》2003,299(5608):884-887

We report the design and total chemical synthesis of "synthetic erythropoiesis protein" (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino-acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 +/-10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications.  相似文献   

Luteinizing hormone-releasing activity in hypophysial stalk blood and elevation by dopamine   总被引：2，自引：0，他引：2  

I A Kamberi  R S Mical  J C Porter 《Science (New York, N.Y.)》1969,166(903):388-390

Pituitary halves incubated in pituitary stalk plasma release more luteinizing hormone than their opposite halves incubated in plasma from peripheral blood. Glands incubated in stalk plasma from dopamine-treated rats release more luteinizing hormone than glands incubated in stalk plasma from untreated controls. Luteinizing hormone-releasing activity in stalk plasma may be due to the luteinizing hormone-releasing factor, and the secretion of luteinizing hormone-releasing factor may be controlled by a dopaminergic mechanism.  相似文献   

A NEW PRESIDENT FOR THE HARVARD APPARATUS COMPANY,INC     

Porter WT 《Science (New York, N.Y.)》1944,99(2580):471-472

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Evidence for biased gene conversion in concerted evolution of ribosomal DNA   总被引：31，自引：0，他引：31  

D M Hillis  C Moritz  C A Porter  R J Baker 《Science (New York, N.Y.)》1991,251(4991):308-310

Concerted evolution is the production and maintenance of homogeneity within repeated families of DNA. Two mechanisms--unequal crossing over and biased gene conversion--have been the principal explanations of concerted evolution. Concerted evolution of ribosomal DNA (rDNA) arrays is thought to be largely the result of unequal crossing over. However, concerted evolution of rDNA in parthenogenetic lizards of hybrid origin is strongly biased toward one of two parental sequences, which is consistent with biased gene conversion as the operative mechanism. The apparent gene conversions are independent of initial genome dosage and result in homogenization of rDNA arrays across all nucleolar organizer regions.  相似文献   

THE FIRST FREE-LIVING FRESHWATER JELLYFISH FROM SOUTH AMERICA     

Porter CE  Schmitt WL 《Science (New York, N.Y.)》1942,96(2501):515-516

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