Digestive enzyme activities and their distribution in the alimentary canal of larvae of the three extant lamprey families     

Max H. Cake  Ian C. Potter  Glen W. Power  Mayamin Tajbakhsh 《Fish physiology and biochemistry》1992,10(1):1-10

The activities of trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), lipase (EC 3.1.1.3) and amylase (EC 3.2.1.1) were measured in different regions of the alimentary tract of ammocoetes from each of the three extant lamprey families. In the southern hemisphere speciesGeotria australis (Geotriidae), and even more particularlyMordacia mordax (Mordaciidae), enzymatic activity was almost entirely confined to prominent diverticular extensions which arise at the oesophageal-intestinal junction. However, in the holarcticLampetra richardsoni (Petromyzontidae), which does not possess a diverticulum, the enzymatic activity was highest in the upper anterior intestine. It is not clear whether the presence of significantly higher amylolytic and lower lipolytic activities in the diverticulum ofG. australis than in the exocrine tissue of the other two species reflects interspecific differences in the composition of their diets. The capacity of exocrine tissue extracts for chymotryptic and tryptic digestion was assayed before and afterin vitro exposure to trypsin and enteropeptidase, their respective catalytic activators. Prior to exposure to these exogenous activators, both proteolytic enzymes were fully active inL. richardsoni, partially active inG. australis and totally inactive inM. mordax. Maximal chymotryptic activity was greater inM. mordax than inL. richardsoni andG. australis. In contrast, maximal tryptic activity was greater inL. richardsoni than inG. australis and was very low inM. mordax. Since trypsin is the only known activator of chymotrypsinogen, the negligible activity of trypsin inM. mordax would appear anomalous unless a trypsin inhibitor is present in the protopancreas of this species. Differences in the distribution of enzymatic activity within the alimentary tract of the three species is discussed in relation to proposed phylogenetic relationships amongst the extant lamprey families.  相似文献   

Polyunsaturated fatty acids do not activate protein kinase C in the testis of the goldfish (Carassius auratus)     

Michael G. Wade  Patrice M. Jacobson  Glen Van Der Kraak 《Fish physiology and biochemistry》1994,13(1):49-57

Earlier studies have established that polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid and docosahexaenoic acid inhibit steroid production in the goldfish testis. As PUFA inhibit testicular steroidogenesis in the rat through activation of protein kinase C (PKC), the present studies were undertaken to characterize the properties of PKC in the goldfish testis and to test the effects of selected PUFA on PKC activity. PKC activity was quantified in goldfish testis homogenate following partial purification by DEAE-cellulose chromatography by determining the transfer of radiolabelled phosphate from [γ - ³²P]ATP to histone III-S. Testicular PKC activity was defined by the amount of protein phosphorylation in the presence of phosphatidylserine, phasphatidylcholine, Ca²⁺ ions and diolein (a 1,2-diacylglycerol analog) above that obtained in response to Ca²⁺ ions alone. Western blot analysis of a crude testis homogenate using an antibody specific to the α and β isoforms of mammalian PKC led to the identification a single band of protein (80 kD) that co-migrated with PKC from rabbit brain cytosol. Addition of arachidonic, eicosapentaenoic or docosahexaenoic acids failed to activate PKC. However, PKC activity stimulated by phospholipid, Ca²⁺ ions and diolein was inhibited in a dose related fashion by all of these fatty acids. These studies suggest that the inhibitory effects of EPA and DHA on testicular steroidogenesis are not mediated by activation of PKC. The lack of effect of PUFA on PKC activity in the goldfish testis suggests that either the distribution of PKC isoforms differs between the testis of mammals and fish or that PKC is not activated by PUFA in the goldfish.  相似文献   

Cortisol and liver metabolism of immature American eels,Anguilla rostrata (LeSueur)     

Glen D. Foster  Dr. T. W. Moon 《Fish physiology and biochemistry》1986,1(2):113-124

Plasma and liver composition, liver enzyme activities, and metabolite flux in isolated hepatocytes have been studied in immature American eels,Anguilla rostrata, injected daily IP with saline or cortisol (0.35 mg/kg eel). Plasma cortisol values were significantly increased above saline controls in those eels receiving cortisol at 3h and 6h following the final (tenth) injection. On day 6 and 10 of injection plasma cortisol levels were significantly below saline controls 24h following cortisol injection. Plasma glucose values were significantly depressed in the cortisol-injected eels at both 6 and 24h following the final (tenth) injection. At the 24h sampling time, plasma protein had significantly increased, but there was no change in either plasma amino acid or fatty acid levels. An increased hepatosomatic index was attributed to a major increase in total lipids, as both protein and glycogen contents were decreased. Of the liver enzymes assayed, significant activity changes occurred only for lactate dehydrogenase (decreased), mitochondrial citrate synthase (increased) and phosphoenolpyruvate carboxykinase (increased) 24h following the final (tenth) cortisol injection. Although enzyme activity changes implied increased liver gluconeogenesis, the absolute rate of lactate, alanine, and aspartate incorporation into glucose declined in viable hepatocytes isolated from cortisol-injected eels compared to the saline controls. Relative changes in metabolite flux did support a preferential increase in gluconeogenesis from amino acids. These results are consistent with the increase in amino acid gluconeogenesis as a result of cortisol administration implied in previous studies, but failed to show a definitive cortisol effect on this pathway in the eel liver. It is suggested that other hormones (e.g. thyroxine, catecholamines, glucagon) may interact in a complex way with cortisolin vivo to bring about the biochemical changes observed in this study. The rapid clearance of exogenously injected cortisol noted in this study makes causal relationships between the injected hormone and any observed metabolic effect in the intact animal difficult.  相似文献   

Zinc deficiency alters soybean susceptibility to pathogens and pests          下载免费PDF全文

Julian Helfenstein  Michelle L. Pawlowski  Curtis B. Hill  Jessica Stewart  Doris Lagos‐Kutz  Charles Roger Bowen  Emmanuel Frossard  Glen L. Hartman 《植物养料与土壤学杂志》2015,178(6):896-903

Inadequate plant nutrition and biotic stress are key threats to current and future crop yields. Zinc (Zn) deficiency and toxicity in major crop plants have been documented, but there is limited information on how pathogen and pest damage may be affected by differing plant Zn levels. In our study, we used soybean plants as a host, a soybean pest, and three soybean pathogens to determine whether plant Zn levels change pest and disease assessments. Two soybean cultivars were grown in sand culture with a soluble nutrient solution that ranged from Zn‐deficient to toxic. Detached leaves from these plants were either inoculated with Aphis glycines, the soybean aphid, Xanthomonas axonopodis pv. glycines, a bacterium that causes bacterial pustule, Sclerotinia sclerotiorum, the necrotrophic fungus responsible for stem rot, or Phakopsora pachyrhizi, a biotrophic obligate pathogen that causes soybean rust. There were significant (P < 5%) effects on aphid colonization, positive counts for bacterial pustule, S. sclerotiorum leaf area affected, and numbers of rust lesions associated with the Zn treatments. Plants grown with the physiologically optimal levels of Zn (2 µM) had less (P < 5%) soybean aphids cm^?2 leaflet than plants grown without Zn, at 0.1× Zn (0.2 µM), or at 100× Zn fertilization (200 µM). Plants grown with the normal fertilization of Zn or 100× Zn had fewer (P < 5%) positive counts for bacterial pustule and less lesion area affected by S. sclerotiorum than plants grown without Zn or fertilized with 0.1× Zn. For soybean rust, plants grown with the physiologically optimal fertilization of Zn or 100× Zn had higher (P < 5%) lesions cm^?2 on leaflets from plants grown without Zn or fertilized with 0.1× Zn. These results indicate different Zn nutrition levels in soybean significantly affected aphid and disease development.  相似文献   

Estimation of narrow-sense heritability for specific gravity in diploid potatoes (Solanum tuberosum subsp.phureja andstenotomum)     

Glen Ruttencutter  F. L. Haynes  R. H. Moll 《American Journal of Potato Research》1979,56(9):447-452

Narrow-sense heritability was estimated for specific gravity in diploid potatoes grown at two locations in North Carolina. Three methods used to estimate narrow-sense heritability were realized heritability, parent-offspring regression, and half-sib family analysis. Nine narrow-sense heritability estimates obtained ranged from 0.276 to 0.739. The three estimates least biased by genotype × environment interaction provided an average estimate of 0.428. The selected population was significantly different from the unselected population in specific gravity. Comparable genetic variances in selected and unselected populations suggest that further selection cycles should be effective in increasing specific gravity.  相似文献   

Barley genotype expressing “stay-green”-like characteristics maintains starch quality of the grain during water stress condition     

Peter W. Gous  Jovin Hasjim  Jerome Franckowiak  Glen P. Fox  Robert G. Gilbert 《Journal of Cereal Science》2013

The identification of “stay-green” in sorghum and its positive correlation with yield increases has encouraged attempts to incorporate “stay-green”-like traits into the genomes of other commercially important cereal crops. However, knowledge on the effects of “stay-green” expression on grain quality under extreme physiological stress is limited. This study examines impacts of “stay-green”-like expression on starch biosynthesis in barley (Hordeum vulgare L.) grain under mild, severe, and acute water stress conditions induced at anthesis. The proportions of long amylopectin branches and amylose branches in the grain of Flagship (a cultivar without “stay-green”-like characteristics) were higher at low water stress, suggesting that water stress affects starch biosynthesis in grain, probably due to early termination of grain fill. The changes in long branches can affect starch properties, such as the rates of enzymatic degradation, and hence its nutritional value. By contrast, grain from the “stay-green”-like cultivar (ND24260) did not show variation in starch molecular structure under the different water stress levels. The results indicate that the cultivar with “stay-green”-like traits has a greater potential to maintain starch biosynthesis and quality in grain during drought conditions, making the “stay-green”-like traits potentially useful in ensuring food security.  相似文献   

Determining photosynthetic responses of forest species to elevated [CO₂]: Alternatives to FACE     

E.A. Pinkard  C.L. Beadle  D.S. Mendham  J. Carter  M. Glen 《Forest Ecology and Management》2010

Free air CO₂ enrichment (FACE) experiments are considered the most reliable approach for quantifying our expectations of forest ecosystem responses to changing atmospheric CO₂ concentrations [CO₂]. Because very few Australian tree species have been studied in this way, or are likely to be studied in the near future because of the high installation and maintenance costs of FACE, there are no clear answers to questions such as: (1) which species will be the winners in Australia's natural forests and what are the implications for biodiversity and carbon (C) sequestration; and (2) which will be the most appropriate species or genotypes to ensure the sustainability of Australia's plantation forests.  相似文献   

Molecular diagnosis of Puccinia psidii (guava rust) – a quarantine threat to Australian eucalypt and Myrtaceae biodiversity     

S. R. H. Langrell †  M. Glen  A. C. Alfenas 《Plant pathology》2008,57(4):687-701

A species-specific, nested polymerase chain reaction (PCR)-based detection assay, using two primer sets designed from the rRNA ITS region, was developed for Puccinia psidii . Detection sensitivities of one urediniospore alone, or one or two urediniospores in the presence of pollen or leaf tissues, respectively, were observed. The assay reliably, accurately and sensitively detected the rust from naturally infected, geographically widespread eucalypt and fruit tree plantation and nursery species from diverse tissues types (e.g. leaves, flowers, fruits, pollen, seeds and woody material) including symptomless or cryptically contaminated plants or plant tissue. Independent testing in Brazil and Australia demonstrated the international inter-laboratory transferability of the P. psidii assay required for germplasm screening, disease monitoring and quarantine and incursion management, towards which the assay has already been employed.  相似文献   

Mating type ratios and pathogenicity in Diplodia shoot blight fungi populations: Comparative analysis     

Tania Manzanos  Glen R. Stanosz  Denise R. Smith  Jannes Muenchow  Patrick Schratz  Alexander Brenning  Ana Aragons  Eugenia Iturritxa 《Forest Pathology》2019,49(1)

Diplodia sapinea and Diplodia scrobiculata are opportunistic pathogens of Pinus species. Several studies about taxonomy, impact and epidemiology of these fungi have been conducted in previous years, which have provided useful information and have raised new issues. These diseases produce a considerable impact on plantations resulting in significant economic losses. The main aims of this study are to increase the knowledge of the potential of genetic exchange and the relative aggressiveness of these organisms that can persist in healthy tissues of asymptomatic trees. A collection of 250 isolates among which are 149 strains collected from Pinus radiata plantations in Basque Country (Spain) and 101 strains from different countries was included in this work. Mating type ratios were analysed and compared using the structure of the MAT locus (MAT1‐1‐1 and MAT1‐2‐1). Inoculations of Pinus radiata seedlings were performed in a biosafety greenhouse (P2) to confirm pathogenicity of isolates and compare their aggressiveness. The frequency of occurrence of both idiomorphs of D. sapinea in Basque Country isolates was close to 1:1, however, for collection of isolates of this fungus from around the world, the ratio was 1:2. Furthermore, the spatial distribution of the two mating types in the Basque Country was random. Despite no detection of a sexual state, these results could suggest sexual reproduction behaviour. The pathogenicity of all strains in the collection was confirmed. Although aggressiveness (in terms of lesion lengths resulting from inoculation) varied greatly, no statistically significant effects of MAT type or pathogen species were detected.  相似文献   

Use of an amplified ELISA technique for detection of a house dust mite allergen (Der f 1) in skin and coat dust samples from dogs     

Glass EV  Reid RA  Hillier A  Needham GR 《American journal of veterinary research》2003,64(2):162-165

OBJECTIVE: To use an amplified ELISA technique to document the presence and quantify the concentration of the house dust mite allergen, Der f 1, in skin and coat dust samples collected from dogs. ANIMALS: 29 pet dogs of various breeds. PROCEDURE: Dogs were weighed, and body surface area in square meters was determined. Skin and coat dust samples were obtained by vacuuming dogs. Collected dust was analyzed by use of standard and amplified ELISA techniques. RESULTS: By use of the standard ELISA technique, Der f 1 was detected in skin and coat dust samples from 6 of 29 (21%) dogs. Mean concentration of Der f 1 in the 6 samples with positive assay results was 16.16 ng/mL (range, 5.61 to 31.24 ng/mL). Samples with negative assay results were retested for dust mite allergen by use of an amplified ELISA technique; an additional 14 dogs had positive assay results. Mean concentration of allergen was 0.36 ng/mL (range, 0.19 to 2.20 ng/mL). Combining both techniques, 20 of 29 (69%) dogs had positive assay results for Der f 1. CONCLUSIONS AND CLINICAL RELEVANCE: Results of our study indicate that house dust mite allergens are present on the skin and in the coat of dogs, and this source of allergen may act as a reservoir for allergen exposure in hypersensitive dogs. Use of an amplified ELISA technique to determine environmental concentrations of house dust mite allergens in homes and on dogs will help to identify the relationship between immunologic findings and environmental exposures in dogs with atopic dermatitis.  相似文献