Phytoplankton community structure and the drawdown of nutrients and CO2 in the southern ocean     

KR Arrigo  DH Robinson  DL Worthen  RB Dunbar  GR DiTullio  M VanWoert  MP Lizotte 《Science (New York, N.Y.)》1999,283(5400):365-367

Data from recent oceanographic cruises show that phytoplankton community structure in the Ross Sea is related to mixed layer depth. Diatoms dominate in highly stratified waters, whereas Phaeocystis antarctica assemblages dominate where waters are more deeply mixed. The drawdown of both carbon dioxide (CO2) and nitrate per mole of phosphate and the rate of new production by diatoms are much lower than that measured for P. antarctica. Consequently, the capacity of the biological community to draw down atmospheric CO2 and transport it to the deep ocean could diminish dramatically if predicted increases in upper ocean stratification due to climate warming should occur.  相似文献   

Production, behaviour and fertility of Merino wethers, hemi-castrates with reduced testicular parenchyma and induced cryptorchids     

FM FOSTER  RB JACKSON†  DL HOPKINS‡ 《Australian veterinary journal》1993,70(8):289-293

Greasy wool production, body weight, behaviour and fertility of male, fine wool Merino sheep were studied from 10 to 21 months of age to assess their suitability for wool production. The males were either castrated (wethers), or were hemi-castrated with a vasectomy and reduction (either partially or in full) of the parenchyma of the retained testicle, or the testicles pushed up into the ingulnal canal and the scrotum shortened (induced cryptorchids). There were significant differences among all groups in body weight, with increases being associated with the larger amounts of testicular tissue present. Fertility was low in the induced cryptorchids at 19 months of age. The hemi-castrates with reduced testicular parenchyma were infertile. The hemi-castrates with reduced testicular parenchyma had significantly heavier greasy fleece weights than the wethers and induced cryptorchids, which had similar fleece weights. The wether group suffered a higher prevalence of posthitis in spring and autumn than the hemi-castrate or induced cryptorchid groups. Those hemi-castrates with the largest amount of testicular parenchyma retained and the induced cryptorchids exhibited masculine behaviour patterns and had an increased incidence of fly strike to the head. The principle of hemi-castration and reduction of the testicular parenchyma is shown to be applicable in wool producing flocks with the potential to increase greasy wool production while minimising the management and marketing limitations previously associated with induced cryptorchids.  相似文献   

Echinococcus granulosus infection of foxes in south-eastern New South Wales     

DL OBENDORF  MJ MATHESON  RCA THOMPSON 《Australian veterinary journal》1989,66(4):123-124

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The relationships among body weight, body composition, and intramuscular fat content in steers   总被引：1，自引：0，他引：1  

Bruns KW  Pritchard RH  Boggs DL 《Journal of animal science》2004,82(5):1315-1322

Angus steers of known age (265 +/- 17 d) and parentage were used in a 2-yr study (yr 1, n = 40; yr 2, n = 45) to evaluate the relationship between percentage of i.m. fat content of the longissimus dorsi at the 12th rib and carcass characteristics during growth of nonimplanted steers. Steers were sorted by age and EPD of paternal grandsire for marbling into high- and low-marbling groups so that steers with varying degrees of genetic potential for marbling were evenly distributed across slaughter groups. All steers were fed a 90% concentrate corn-based diet. Steers were allotted to five slaughter groups targeted to achieve hot carcass weights (HCW) of 204, 250, 295, 340, and 386 kg over the course of the feeding period. Data were analyzed as a completely random design with a factorial arrangement of treatments (year, marbling group, and slaughter group). Marbling group did not affect backfat, LM area, yield grade (YG), or marbling score. Regression equations were developed to quantify the change in carcass characteristics and composition over slaughter groups. Hot carcass weight increased in a linear fashion and differed (P < 0.01) among the slaughter groups as anticipated by design. Yield grade followed a quadratic upward pattern (P < 0.01) as HCW increased. Slaughter group affected the degree of marbling linearly (P < 0.01). There were no slaughter group x marbling group interactions, indicating that no differences occurred in the pattern of marbling attributable to paternal grandsire EPD. Carcasses expressed small degrees of marbling at 266 kg of HCW and obtained a YG of 3.0 at 291 kg of HCW. Fractional growth rates decelerated with increasing HCW. Greater advances in marbling relative to total carcass fatness occurred at HCW less than 300 kg. Management practices early in growth may influence final quality grade if compensatory i.m. fat content development does not occur.  相似文献   

Effects of pH, sodium bicarbonate, cryoprotectants and foetal bovine serum on the cryopreservation of European eel sperm.     

DL Garzón  DS Peñaranda  L Pérez  F Marco‐Jiménez  X Espert  T Müller  M Jover  JF Asturiano 《Reproduction in domestic animals》2008,43(1):99-105

The main objective of the present study was to evaluate the influence of pH and bicarbonate concentration in the activation or inhibition of European eel (Anguilla anguilla) spermatozoa and to evaluate the effect of different cryoprotectants: dimethyl sulphoxide (DMSO), acetamide, ethylene glycol, propanol, glycerol and methanol (MeOH). The effect of these factors was evaluated comparing the percentage of motile cells, the percentage of alive cells (by Hoechst staining) and the spermatozoa morphometry pre- and post-cryopreservation (by computer-assisted morphology analysis). Based on the above findings, three cryoprotectants (DMSO, MeOH and glycerol) were chosen and evaluated in two media (P1 and P1 modified) with different concentrations of NaHCO(3) and in the presence or absence of foetal bovine serum (FBS). The effect of these factors was evaluated comparing the percentage of alive and motile cells post-cryopreservation. DMSO was the cryoprotectant showing better results in relation to the percentage of spermatic alive cells post-freezing and caused a smaller modification of the head spermatozoa morphology. The combination of P1-modified medium with DMSO and containing FBS increased slightly but significantly the percentage of motile spermatozoa post-cryopreservation.  相似文献   

The rise of the mediocre forest: why chronically stressed trees may better survive extreme episodic climate variability     

Steven G. McNulty  Johnny L. Boggs  Ge Sun 《New Forests》2014,45(3):403-415

Anthropogenic climate change is a relatively new phenomenon, largely occurring over the past 150 years, and much of the discussion on climate change impacts to forests has focused on long-term shifts in temperature and precipitation. However, individual trees respond to the much shorter impacts of climate variability. Historically, fast growing, fully canopied, non-chronically stressed (NCS) trees (e.g., those with minimal insect or disease damage, growing on high nutrient, moist soils), have been considered the model of individual health, while slower growing, broken crown, chronically stressed (CS) trees growing on nutrient poor, or dry soils, were considered to be unhealthy and prone to stress related mortality. Over the coming years and decades, climate variability (e.g., extreme precipitation events, drought, heat waves) is expected to increase. We hypothesize that as the duration, severity and interaction of stress becomes more pronounced under increasing climate variability, seemingly less healthy, CS trees could begin to survive environmental stress better than their traditionally considered healthy, NCS tree counterparts. We further hypothesize that this shift in survivorship will be attributed to tree response to increasingly extreme climate variability at levels not previously observed in recorded history. While NCS trees can better survive historic episodic stress, we hypothesize that CS trees may be better suited to survive the combination of chronic low-level stress, and extreme episodic stress associated with anthropogenic climate change and increasing climate variability. Specifically, morphological differences such as increased root and reduced leaf mass, and physiological differences such as more oleoresin production, could make slower growing, CS forests more resilient to catastrophic episodic mortality compared to more NCS stands under certain circumstances. General circulation models suggest that climate variability will increase in the future. Therefore, the occurrence of slow growth, CS forest stands out surviving faster growing NCS less stressed stands may become more common place, and eventually lead to “The Age of the Mediocre Forest”. This paper addresses the type of environmental conditions that could create such an inverse in forest health conditions, and the implications that this shift might have in forest genetics and management.  相似文献   

Effect of Cryopreservation on Bovine Sperm Viability as Determined by Dual DNA Staining     

DL Garner  CA Thomas  CH Allen  PL Senger  RG Sasser 《Reproduction in domestic animals》1997,32(6):279-283

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Yellow traps as an aid in fish farming     

S. ERHARD  H. KRATOCHVIL  M. LÖDL 《Aquaculture Research》1993,24(1):129-131

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Bone marrow colonies: stimulation in vitro by supernatant from incubated human blood cells   总被引：12，自引：0，他引：12  

P A Chervenick  D R Boggs 《Science (New York, N.Y.)》1970,169(946):691-692

A substance which stimulates growth of granulocytic and mononuclear cell colonies from mouse and human bone marrow was produced by incubated human blood cells. It is resistant to heat and freezing and is not dialyzable. Intact irradiated and unirradiated cells had very little activity, and sonically disrupted cells had no activity. The addition of plasma or sonically disrupted cells to the cell supernatant decreased its activity.  相似文献   

Lunar surface magnetic fields and their interaction with the solar wind: results from lunar prospector   总被引：1，自引：0，他引：1  

RP Lin  DL Mitchell  DW Curtis  KA Anderson  CW Carlson  J McFadden  MH Acuna  LL Hood  A Binder 《Science (New York, N.Y.)》1998,281(5382):1480-1484

The magnetometer and electron reflectometer experiment on the Lunar Prospector spacecraft has obtained maps of lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic latitude (30 degreesS to 80 degreesS) and low ( approximately 100 kilometers) altitude. Electron reflection maps of the regions antipodal to the Imbrium and Serenitatis impact basins, extending to 80 degreesS latitude, show that crustal magnetic fields fill most of the antipodal zones of those basins. This finding provides further evidence for the hypothesis that basin-forming impacts result in magnetization of the lunar crust at their antipodes. The crustal magnetic fields of the Imbrium antipode region are strong enough to deflect the solar wind and form a miniature (100 to several hundred kilometers across) magnetosphere, magnetosheath, and bow shock system.  相似文献