Secretion of metabolites of vitamin A and B-carotene in the bile of sheep     

J A Boling  G E Mitchell  C O Little  C L Fields  J L Call 《Journal of animal science》1969,29(3):504-508

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Preliminary Evaluation of a Unique Freezing Technology for Bovine Spermatozoa Cryopreservation     

PZ Cotter  HA Goolsby  SD Prien 《Reproduction in domestic animals》2005,40(2):98-99

Artificial insemination (AI) and semen cryopreservation has significantly improved the breeding potential of male animals. However, current freezing techniques commonly result in reduced semen quality. Ten years ago, a unique freezing technology (UFT) was developed for the freezing of foodstuffs and other materials. Previous work from this laboratory has demonstrated the UFT to be a superior method of freezing for a number of cell types. In a preliminary study, the UFT was compared with the conventional freezing methodology of bovine semen. Semen samples were collected from an angus (Bull A) and a gelbivich bull (Bull B), prepared using a conventional bovine cryoprotectant, and frozen in the UFT or in liquid nitrogen (LN) mist. The samples were stored in LN before being thawed and assessed for the semen parameters of motility and forward progression. Preliminary results suggest the UFT is equivalent to current techniques in the cryopreservation and recovery of bovine semen, and with modification, possibly a superior technique for semen freezing. Further studies using larger sample populations, and using a CASA system to evaluate motility, forward progression and linearity are merited.  相似文献   

Validation of a Field Based Chromatin Dispersion Assay to Assess Sperm DNA Fragmentation in the Bottlenose Dolphin (Tursiops truncatus)     

M‐J Sánchez‐Calabuig  C López‐Fernández  E Martínez‐Nevado  JF Pérez‐Gutiérrez  J de la Fuente  SD Johnston  D Blyde  K Harrison  J Gosálvez 《Reproduction in domestic animals》2014,49(5):761-768

Over the last two decades, there have been significant advances in the use of assisted reproductive technology for genetic and reproductive management of captive dolphin populations, including evaluation of sperm DNA quality. This study validated a customized sperm chromatin dispersion test (SCDt) for the bottlenose dolphin (Tursiops truncatus) as a means of assessing sperm DNA damage both in the field and in the laboratory. After performing the SCDt, two different sperm morphotypes were identified: (i) sperm with fragmented DNA showed large haloes of dispersed DNA fragments emerging from a compact sperm nucleoid core and (ii) sperm containing non‐fragmented DNA displayed small compact haloes surrounded by a dense core of non‐dispersed DNA and protein complex. Estimates of sperm DNA fragmentation by means of SCDt were directly comparable to results obtained following a two‐tailed comet assay and showed a significant degree of correlation (r = 0.961; p < 0.001). This investigation also revealed that the SCDt, with minor modifications to the standard protocol, can be successfully conducted in the field using a LED florescence microscopy obtaining a high correlation (r = 0.993; p = 0.01) between the data obtained in the laboratory and in the field.  相似文献   

NAD+-linked isocitrate dehydrogenase in fish tissues     

Dr. Kenneth B. Storey  Jeremy H. A. Fields 《Fish physiology and biochemistry》1988,5(1):1-8

NAD⁺-linked isocitrate dehydrogenase was found in the brain, heart, gills, kidney, liver and muscle of trout, and in the liver and muscle of eel. A complex homogenization buffer containing 1 mM ADP, 5 mM MgSO₄, 5 mM citrate and 40% glycerol is required for retrieval of significant amounts of stable enzyme. The highest activities were found in brain of trout and the lowest in white muscle of trout and eel. The enzyme was partially purified from frozen trout heart to a final activity of 0.04 M/min/mg protein, and the kinetic properties of this partially purified enzyme were studied. The enzyme requires either Mn²⁺ or Mg²⁺ for activity, higher activities being observed with Mn²⁺. Saturation kinetics for DL-isocitrate were sigmoidal, apparent S_0·5=8.2±0.6 mM and n_H=1.8±0.2, in the absence of ADP, changing to hyperbolic, apparent S_0·5=1.4±0.3 mM and n_H=1.0, with 1 mM ADP added. Citrate and Ca²⁺ were found to activate the enzyme to a small extent. NADH strongly inhibited the enzyme, I₅₀=3.7±0.5 M. ATP was also found to be an inhibitor, I₅₀=7.2±1.4 mM. These properties are consistent with the role of the enzyme as a major control site of the tricarboxylic acid cycle.  相似文献   

Spatial Response of Mammals to Late Quaternary Environmental Fluctuations     

RW Graham  EL Lundelius  MA Graham  EK Schroeder  RS Toomey  E Anderson  AD Barnosky  JA Burns  CS Churcher  DK Grayson  RD Guthrie  CR Harington  GT Jefferson  LD Martin  HG McDonald  RE Morlan  HA Semken  SD Webb  L Werdelin  MC Wilson 《Science (New York, N.Y.)》1996,272(5268):1601-1606

Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene.  相似文献   

Synaptic connections in vitro: modulation of number and efficacy by electrical activity   总被引：1，自引：0，他引：1  

P G Nelson  C Yu  R D Fields  E A Neale 《Science (New York, N.Y.)》1989,244(4904):585-587

The functional architecture of synaptic circuits is determined to a crucial degree by the patterns of electrical activity that occur during development. Studies with an in vitro preparation of mammalian sensory neurons projecting to ventral spinal cord neurons slow that electrical activity induces competitive processes that regulate synaptic efficacy so as to favor activated pathways over inactive convergent pathways. At the same time, electrical activity initiates noncompetitive processes that increase the number of axonal connections between these sensory and spinal cord neurons.  相似文献   

Ammonium chloride prevents lytic growth of reovirus and helps to establish persistent infection in mouse L cells   总被引：12，自引：0，他引：12  

W M Canning  B N Fields 《Science (New York, N.Y.)》1983,219(4587):987-988

Ammonium chloride, a lysosomotropic agent that raises intralysosomal pH, reduces the yield of reovirus during infection of mouse L cells. Subsequent removal of ammonium chloride results in the rapid establishment of a persistent infection.  相似文献   

Mass spectrometry and carbon-13 labeling     

Meyerson S  Fields EK 《Science (New York, N.Y.)》1969,166(3903):325-328

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Early maritime economy and El Nino events at quebrada tacahuay, peru     

DK Keefer  SD deFrance  ME Moseley  JB Richardson  DR Satterlee  A Day-Lewis 《Science (New York, N.Y.)》1998,281(5384):1833-1835

The archaeological site of Quebrada Tacahuay, Peru, dates to 12,700 to 12,500 calibrated years before the present (10,770 to 10,530 carbon-14 years before the present). It contains some of the oldest evidence of maritime-based economic activity in the New World. Recovered materials include a hearth, lithic cutting tools and flakes, and abundant processed marine fauna, primarily seabirds and fish. Sediments below and above the occupation layer were probably generated by El Nino events, indicating that El Nino was active during the Pleistocene as well as during the early and middle Holocene.  相似文献   

Predatory dinosaur remains from madagascar: implications for the cretaceous biogeography of gondwana   总被引：1，自引：0，他引：1  

SD Sampson  LM Witmer  CA Forster  DW Krause  PM O'Connor  P Dodson  F Ravoavy 《Science (New York, N.Y.)》1998,280(5366):1048-1051

Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis of a number of unique features. Fossil remains attributable to abelisaurids are restricted to three Gondwanan landmasses: South America, Madagascar, and the Indian subcontinent. This distribution is consistent with a revised paleogeographic reconstruction that posits prolonged links between these landmasses (via Antarctica), perhaps until late in the Late Cretaceous.  相似文献