Protein Reserves Research Articles

Coronary microembolization

Atherosclerotic plaque rupture is the key event in the pathogenesis of acute coronary syndromes and it also occurs during coronary interventions. Atherosclerotic plaque rupture does not always result in complete thrombotic occlusion of the epicardial coronary artery with subsequent impending myocardial infarction, but may in milder forms result in the embolization of atherosclerotic and thrombotic debris into the coronary microcirculation. This review summarizes the present experimental pathophysiology of coronary microembolization in animal models of acute coronary syndromes and highlights the main consequences of coronary microembolization--reduced coronary reserve, microinfarction, inflammation and oxidative modification of contractile proteins, contractile dysfunction and perfusion-contraction mismatch.Furthermore, the review presents the available clinical evidence for coronary microembolization in patients and compares the clinical observations with observations in the experimental model.

The effect of nutritional management of the dairy cow on reproductive efficiency

The cause of low fertility in dairy cows is multifactorial. Poor nutrition during the dry and early postpartum periods results in reduced glucose, insulin, insulin-like growth factor (IGF-I) and low LH pulse frequency with concomitant increases in β-hydroxy butyrate, non-esterified fatty acids (NEFA) and triacylglycerol. Cows must mobilize large lipid, but also some protein reserves, with a consequent increased incidence of such metabolic disorders as hypocalcaemia, acidosis, ketosis, fatty liver and displaced abomasums. The occurrence of milk fever and ketosis affects uterine contractions, delays calving and increases the risk of retained foetal membranes (RFM) and endometritis. The nutritional risk factors that cause RFM are hypocalcaemia, high body condition score (BCS) at calving and deficiencies in Vitamin E and selenium. The risk factors for endometritis are hypocalcaemia, RFM, high triacylglycerol and NEFA. Thus, metabolic disorders predispose cows to gynaecological disorders, thereby reducing reproductive efficiency. Cows that are overconditioned at calving or those that lose excess body weight are more likely to have a prolonged interval to first oestrus, thereby prolonging days open. Nutritionally induced postpartum anoestrus is characterized by turnover of dominant follicles incapable of producing sufficient oestradiol to induce ovulation due to reduced LH pulse frequency. High nutrition can also increase metabolic clearance rate of steroid hormones such as progesterone or oestradiol. Lower concentrations of oestradiol on the day of oestrus are highly correlated with the occurrence of suboestrus, thereby making the detection of oestrus in high yielding cows even more difficult. Nutrition also affects conception rate (CR) to AI. Cows that develop hypocalcaemia, ketosis, acidosis or displaced abomasums have lower CRs and take longer to become pregnant. Excessive loss of BCS and excess protein content of the ration can reduce CR while supplemental fats that attenuate the production of F2α can improve CR. The increased metabolic clearance rate of progesterone (P4), which decreases blood concentrations during early embryo cleavage up to the blastocyst stage is associated with decreased CRs. In conclusion, poor nutritional management of the dairy cow, particularly before and after calving, is a key driver of infertility.

Cancer-Associated Cachexia and Underlying Biological Mechanisms

Cancer metastases (spread to distant organs from the primary tumor site) signify systemic, progressive, and essentially incurable malignant disease. Anorexia and wasting develop continuously throughout the course of incurable cancer. Overall, in Westernized countries nearly exactly half of current cancer diagnoses end in cure and the other half end in death; thus, cancer-associated cachexia has a high prevalence. The pathophysiology of cancer-associated cachexia has two principal components: a failure of food intake and a systemic hypermetabolism/hypercatabolism syndrome. The superimposed metabolic changes result in a rate of depletion of physiological reserves of energy and protein that is greater than would be expected based on the prevailing level of food intake. These features indicate a need for nutritional support, metabolic management, and a clear appreciation of the context of life-limiting illness.

Lesser Scaup Spring Nutrient Reserve Dynamics on the Lower Great Lakes

The North American lesser scaup (Aythya affinis) population has declined since the mid-1980s. The acquisition of nutrient reserves during spring migration may play a role in explaining that trend. We studied nutrient-reserve dynamics of lesser scaup collected during spring at 3 major stopover sites and assessed whether reserves of birds on the lower Great Lakes (LGL) differed from those at other staging (or breeding) areas. At lakes Ontario and St. Clair, males had larger fat reserves than females, but no other substantial sex-related differences were observed in fat, protein, or mineral reserve levels of lesser scaup. Protein in males and mineral reserves of both sexes at lakes Erie and St. Clair did not change throughout spring. Male fat reserves remained constant at Lake Erie and increased at Lake St. Clair, whereas female fat and protein reserves increased at both stopover sites. Patterns of fat and protein dynamics in males partly may be due to energetic costs of courtship and pair-bond maintenance. However, maintenance and accumulation of fat reserves in both sexes while on the LGL is important for impending migration and subsequent reproduction. Female lesser scaup staging on the LGL had fat reserves comparable to, or slightly higher than, those reported in other studies of northern spring-staging and breeding birds. Fat reserves of LGL females, however, were much lower than those reported for birds at another midlatitude stopover site. These comparisons suggest that events occurring on Atlantic Flyway wintering areas or LGL staging areas are potential factors contributing to nutrient-reserve limitation and possibly to observed declines in scaup numbers in North America.

Vaccinia virus strain Western Reserve protein B14 is an intracellular virulence factor

A characterization of the B14R gene from Vaccinia virus (VACV) strain Western Reserve (WR) is presented. Computational analyses of the B14R gene indicated high conservation in orthopoxviruses but no orthologues outside the Poxviridae. To characterize the B14 protein, the B14R gene was expressed in Escherichia coli and recombinant protein was purified and used to generate a rabbit polyclonal antiserum. This antiserum recognized a 15 kDa cytoplasmic protein in mammalian cells that were transfected with the B14R gene or infected with VACV WR, but not from cells infected with a VACV mutant (vdeltaB14) from which the B14R gene was deleted. Compared to wild-type and revertant virus controls, vdeltaB14 had normal growth kinetics in cell culture. The virulence of vdeltaB14 was assessed in two in vivo models. Mice infected intranasally with vdeltaB14 had similar weight loss compared to the controls, but in C57BL/6 mice infected intradermally vdeltaB14 induced a smaller lesion size compared with controls. Moreover, intradermal infection with vdeltaB14 caused an increased infiltration of cells into the infected lesion despite the smaller lesion size. Therefore, B14 is an intracellular protein that is non-essential for virus replication in cell culture but contributes to virus virulence in vivo and affects the host response to infection.

Effects of larval nutrition on the endocrinology of mosquito egg development

Reproduction by female mosquitoes is dependent on energy resources but modulated by hormones. Our study focused on blood-meal-dependent, anautogenous Aedes aegypti and autogenous Ochlerotatus atropalpus that rely on larval-derived nutrient stores to develop eggs. To determine how larval nutrition affects the endocrinology of egg development in these females, we manipulated the quantity of larval food and measured in vitro production of juvenile hormone (JH) by corpora allata (CA) and ecdysteroids by ovaries. Newly emerged A. aegypti contain lower larval-derived protein reserves, and their CA produce high amounts of JH, in comparison with similarly staged Oc. atropalpus. Ecdysteroid production was initiated in newly emerged Oc. atropalpus females, which have higher protein reserves and which develop eggs without a blood meal, which is required by A. aegypti females to complete egg development.

Integration of amino acid metabolism during intense lactation

This review focuses on research from the author's laboratory and that of N.L. Trottier concerning protein and amino acid metabolism during intense lactation, a physiological state characterized by high rates of the net transfer of amino acids from physiological reserves in skeletal muscle to the mammary gland. These studies have broader interest for our understanding of the supply and distribution of amino acids towards key processes. The synthesis of milk protein occurs at a distinct anatomical location, such that arterio-venous differences may be employed to identify all amino acid inputs into the mammary gland. These approaches can be used to determine the relative contributions to the mammary amino acid supply of systemic amino acid availability, transport system regulation and blood flow. Milk protein synthesis is partly reliant on the mobilization of endogenously stored protein in skeletal muscle, and our ability to modulate the size of physiological protein reserves and their rate of mobilization in an experimental context can be used to clarify the regulatory events that underlie the access to and eventual depletion of skeletal muscle protein. Massive rates of milk production are achieved by increased mammary blood flow and amino acid extraction. Muscle protein mobilization is a key resource in the overall amino acid supply, and the absolute size of the protein reserve at parturition is a key factor in supporting lactation. The progressive depletion of muscle may ultimately provide insufficient substrate to support this process.

GENIC CAPTURE AND THE GENETIC BASIS OF SEXUALLY SELECTED TRAITS IN THE ZEBRA FINCH

The lek paradox, in which female choice erodes genetic variation in male sexually selected traits, is a fundamental issue in sexual selection. If females gain only genetic benefits from preferentially having their ova fertilized by males with particular traits, what maintains variation in these traits? Under strong directional selection mediated through mate choice, the alleles for beneficial male traits are expected to go to fixation and exhibit little variation. A theoretical solution to the lek paradox is the genic capture hypothesis which states that: costly male traits subject to female choice are condition dependent, that male condition is dependent on genes at many loci and exhibits additive genetic variance, and that positive genetic correlations exist between sexually selected traits and condition. Using a captive population of the zebra finch Taeniopygia guttata, we tested two key predictions from this model: (1) that genetic variance exists in beak color which is a sexually selected trait, but also in condition and immune function, and (2) that positive genetic correlations exist between condition and beak color, and between beak color, condition, and immune function. Genetic parameters were estimated from a large breeding experiment involving 81 sires, 972 offspring, a pedigree of 1526 individuals, using the animal model. We employed the following index of body condition: residuals from a log-log plot of body mass on tarsus length following a standardized and extended period of exercise, in which residual mass is known to reflect fat and protein reserves. Our results were broadly consistent with the genic capture hypothesis because we found (1) additive genetic variation in beak color and immune function and condition, and (2) positive genetic correlations between condition and beak color, and between condition, beak color, and several assays of immune responsiveness. However, both of these results need qualification. In the first case we identified an important general problem in estimating the coefficient of additive genetic variance (CVA) in body condition. In the second case, although most of the genetic correlations were positive as predicted, only some were statistically significant, possibly due to our relatively small sample sizes, because genetic correlations typically have large standard errors and therefore require very large samples to be statistically significant. The statistically significant, positive genetic correlations included those between beak color and immune function (response to tetanus), and between immune function (response to tetanus) and condition, both of which indicate that females gain good genes from mating with males in good condition and/or with a redder beak color. We discuss the implications of our results for devising more rigorous but pragmatic tests of the genic capture hypothesis.

Control of seed size in plants

Reproductive success in seed plants depends on a healthy seed set. The viability of the embryo is enhanced if a seed contains substantial reserves of starch and protein to nourish the seedling when it germinates months or years later in uncertain conditions. Increased reserves will generally result in an increased seed size, but large seeds are less efficiently dispersed, unless there is human or other intervention. Since the beginning of agriculture, food grains have been subjected to selection and breeding for size as well as for other qualities, and most of the grains consumed today have seeds far larger than their wild relatives. Although grain size has been much analyzed and used by plant breeders over the past century, it is only in the past decade that we have at last begun to identify the molecular regulators of seed size in plants, mainly from studies in the model plant Arabidopsis (reviewed in ref. 1). The article by Luo et al. (2) in a recent issue of PNAS marks another step toward understanding the nature of these controls. The life cycle of plants involves an alternation of generations between the haploid gametophyte and the diploid sporophyte. In angiosperms (flowering plants), seed development begins with double fertilization. Pollen grains (male gametophytes) carry two haploid sperm cells, which fertilize the egg cell and the central cell of the haploid embryo sac (female gametophyte) contained within the maternal tissues of the ovule. This event results in the formation of the diploid embryo and the triploid endosperm, respectively, the latter arising from the central cell that contains two identical haploid sets of chromosomes. Seed development is marked by the rapid growth of the endosperm and the embryo, until seed maturation, which is accompanied by desiccation. Simultaneously, the maternal ovule also undergoes regulated growth to accommodate …

Gonadal development and biochemical composition of female crayfish Cherax quadricarinatus (Decapoda: Parastacidae) in relation to the Gonadosomatic Index at first maturation

Gonadal development of female crayfish Cherax quadricarinatus at first maturation (25.5 ± 3.8 g) was investigated using morphological criteria (Gonadosomatic and Hepatosomatic Indices or GSI and HSI), biochemical composition (proteins, lipids, and carbohydrates) of the gonad and hepatopancreas, histological indicators (oocyte diameter, frequency of pre-vitellogenic, vitellogenic, and post-vitellogenic oocytes), and histochemical analyses (percentage coverage of lipid and carbohydrate reserves or LI and CI). There was a negative relation between GSI and HSI ( P < 0.01). Protein ( P < 0.01), lipid ( P < 0.01), and carbohydrate ( P < 0.01) contents in the gonad were dependent on GSI. At mature stages, higher concentrations of protein and lipid reserves were observed, while carbohydrates diminished. In hepatopancreas, the lipid content decreased in relation to GSI ( P < 0.05). There was no evidence that protein and carbohydrate components in the hepatopancreas varied in relation to GSI ( P > 0.05). High statistical power (> 0.99 for both contents) indicates that protein and carbohydrate concentration remains relatively constant throughout gonadal development. A significant decrease in the frequency of oogonia ( P < 0.01), pre-vitellogenic oocytes ( P < 0.01), and primary vitellogenic oocytes ( P < 0.01) was observed as maturation was reached. A mathematical inflexion point showed that there was a maximum frequency of secondary vitellogenic oocytes at 4.06 GSI. There were increases in diameter and nuclei of oocytes at all developmental stages ( P < 0.05). LI increased as oocytes developed ( P < 0.01). CI varied between stages ( P < 0.01) and peaked at the primary vitellogenic stage. The dynamics of biochemical composition of gonad and hepatopancreas of female C. quadricarinatus was in agreement with similar studies in decapods. The usefulness of the GSI as an indicator of reproduction stage and female broodstock management is addressed.

DIGITAL IMAGE ANALYSIS OF LIPID AND PROTEIN HISTOCHEMICAL MARKERS FOR MEASURING OOCYTE DEVELOPMENT AND QUALITY IN PEARL OYSTER PINCTADA MAZATLANICA (HANLEY, 1856)

Abstract We applied quantitative histochemical techniques and digital image analysis to study seasonal cycles of use of lipid and protein reserves during vitellogenesis in the pearl oyster Pinctada mazatlanica. Female gonad samples were collected seasonally during an annual cycle and processed histologically to characterize the gametogenic cycle, analyze variations in the frequency and size of vitellogenic and postvitellogenic oocytes and calculate the ooplasm:nucleoplasm ratio for both types of oocytes. Lipid and protein inclusions in each type of oocyte were identified using Sudan Black B and Schiff's ninhydrin stains. In both cases, quantification of lipid and protein components was performed through measuring variations in the color coverage area of the oocyte with a digital image analysis system. With this procedure, we calculated a lipid index and a protein index to refer oocyte quality. The lipid index was higher in winter, suggesting a strategy towards storage in the gonad. The protein index was h...

Compositional changes in seed and embryo axis of jojoba ( Simmondsia chinensis) during germination and seedling emergence

The dry weight, moisture, wax compositions, simmondsins content, protein and sugar content of germinating jojoba cotyledons and developing seedling were studied. During imbibition the seed absorbed water and the moisture content increased steadily during germination. Radicles emerged after 10–15 days of germination and only at that time compositional changes in wax, and simmondsins content were determined. Wax breakdown was the main source of carbon and energy for the developing seedling, while protein reserves were the nitrogen source. The profile of the fatty acids changed through germination and esters with 20:1 fatty acid were preferentially used. Simmondsin concentration increased at the time of radicle emergence and than decreased. Ferulate derivatives almost disappeared while didemethyl simmondsin concentration decreased more slowly. Simmondsins but not the ferulate derivatives were building up in the radicle and young shoots.

Embryo origin and development in Crocus sativus L. (Iridaceae)

Fruit and seed set were obtained in the triploid Crocus sativus (saffron) either by hand crossing with pollen of the diploid C. cartwrightianus or by free pollination. The morphology of the capsules and seeds was similar in both Crocus species. The embryo is comparatively small, whereas the endosperm is formed of numerous layers of cells with hemicellulose-thickened walls and a cytoplasm containing few lipid and protein reserves. Seed germination gave rise to a white prophyll from which a green leaf emerged. At the base of this leaf, a small corm without tunics developed, which, after leaf desiccation, became dormant. These corms sown separately in pots were again capable of growth and emitted a single long green leaf. Vegetative development of new corms was similar in the diploid and hybrid saffron plants. In sites of past saffron cultivation the beds were found to contain degenerated corms and corms at different development stages. The absence of fruit and seed set in emasculated and self- and out-pollinated plants suggests that saffron does not form apomictic embryos.

Diet quality affects egg size and number but does not reduce maternal antibody transmission in Japanese quail Coturnix japonica

Summary The ability to resist infection is an important component of survival and lifetime reproductive success. Mounting and maintaining an immunological defence is assumed to be energetically costly and nutritional resources expended on immune function may induce trade‐offs with other energetically expensive functions, including reproduction. Resource limitation may even have transgenerational effects on immune function during reproduction because mothers are the primary source of humoral immunity in young vertebrates. To determine whether protein restriction affects humoral immunity, either within or across generations, we fed adult Japanese quail Coturnix japonica isocaloric diets containing either the recommended protein content for reproducing adults (20%), or a low protein diet (12%). Females fed the low protein diet weighed less than control females and produced fewer eggs that were smaller in size. However, dietary treatment did not affect the antibody response to a novel antigen (SRBCs) or immunoglobulin concentration (IgG = IgY) in either females or their eggs. This suggests that the magnitude of the humoral immune response is either not constrained by protein availability or that birds can compensate for low dietary protein intake when fed ad libitum. Maternal protein reserves may be catabolized to support egg production and antibody formation under protein restriction such that only very severe malnutrition would affect immune function. Future work should address whether other resources mediate the trade‐off between immunity and reproduction or whether other components of the immune response are impacted by resource limitation.

Lessons from an estivating frog: sparing muscle protein despite starvation and disuse

Long (6- to 9-mo) bouts of estivation in green-striped burrowing frogs lead to 28% atrophy of cruralis oxidative fibers (P < 0.05) and some impairment of in vitro gastrocnemius endurance (P < 0.05) but no significant deficit in maximal twitch force production. These data suggest the preferential atrophy of oxidative fibers at a rate slower than, but comparable to, laboratory disuse models. We tested the hypothesis that the frog limits atrophy by modulating oxidative stress. We assayed various proteins at the transcript level and verified these results for antioxidant enzymes at the biochemical level. Transcript data for NADH ubiquinone oxidoreductase subunit 1 (71% downregulated, P < 0.05) and ATP synthase (67% downregulated, P < 0.05) are consistent with mitochondrial quiescence and reduced oxidant production. Meanwhile, uncoupling protein type 2 transcription (P = 0.31), which is thought to reduce mitochondrial leakage of reactive oxygen species, was maintained. Total antioxidant defense of water-soluble (22.3 +/- 1.7 and 23.8 +/- 1.5 microM/microg total protein in control and estivator, respectively, P = 0.53) and membrane-bound proteins (31.5 +/- 1.9 and 42.1 +/- 7.3 microM/microg total protein in control and estivator, respectively, P = 0.18) was maintained, equivalent to a bolstering of defense relative to oxygen insult. This probably decelerates muscle atrophy by preventing accumulation of oxidative damage in static protein reserves. Transcripts of the mitochondrially encoded antioxidant superoxide dismutase type 2 (67% downregulated, P < 0.05) paralleled mitochondrial activity, whereas nuclear-encoded catalase and glutathione peroxidase were maintained at control values (P = 0.42 and P = 0.231), suggesting a dissonance between mitochondrial and nuclear antioxidant expression. Pyruvate dehydrogenase kinase 4 transcription was fourfold lower in estivators (P = 0.11), implying that, in contrast to mammalian hibernators, this enzyme does not drive the combustion of lipids that helps spare hypometabolic muscle.

Biochemical, physiological, and immunological changes during starvation in juveniles of Litopenaeus vannamei

In an attempt to know how the protein level modulates catabolism and its effects on the immune response, we studied juvenile L. vannamei that had been starved for varying period after being conditioned on diet containing either maintenance or optimal dietary protein levels (DPL). The effect of dietary protein level on nutritional reserves management of shrimp and its relation with immune condition was also addressed. Juvenile shrimp were fed for 21 days on diets containing 5% and 40% dietary protein. Hemolymph metabolites (glucose, cholesterol, protein, acylglycerols, and lactate), hemocyanin, osmoregulatory capacity, digestive gland glycogen and lipids, and immune conditions (hemocytes characterization, phenoloxidase activity, respiratory burst: basal and activated) were evaluated and considered as initial condition. After that time, shrimp were starved for 21 days. During starvation time every 7 days nutritional, physiological and immunological condition were evaluated. A reduction in all physiological and immunological indicators was observed with starvation. The protein level of the conditioning diet had a significant effect on this response; generally, the effect was smaller with shrimp previously fed 40% dietary protein. In this sense the present results demonstrate that shrimp are well adapted to tolerate food deprivation for some time but that this tolerance is closely related to its previous nutritional condition. In the case of shrimp fed 40% DPL, wet weight, nutritional and immune condition was significantly affected after 14 days of starvation. In shrimp previously fed 5% DP, tolerance to starving condition was limited to only a few days (7 days) as a result of low reserves of circulatory and mussel proteins. All these results demonstrate that dietary protein levels can governor the immune condition of shrimp through the management reserves metabolism, indicating that a shrimp with a good nutritional condition can tolerate until 14 days without modifying the evaluated immune responses. In this sense it can be concluded that protein metabolism have a central role for shrimp.

Anatomy and ontogeny of Pterodon emarginatus (Fabaceae: Faboideae) seed

The aim of this study was to describe the anatomy and ontogeny of Pterodon emarginatus seed using the usual techniques. The ovules are campilotropous, crassinucelate, and bitegmic. The following processes occur during integument development: anticlinal divisions and phenolic compound accumulations in the exotesta, whose cells become palisade; predominantly periclinal divisions and cell expansion in the mesotesta, where the rapheal bundle differentiates; differentiation of the hourglass-cell layer adjacent to the palisade; fusion of outer and inner integuments, which remain individualized structures only at the micropylar end; and intense pectin impregnation in the mesotesta thicker walls with lignification restricted to the xylem. At the hilar pole, the Faboideae seed characteristic structure develops, with double palisade layer, subhilar parenchyma, and tracheid bar. The younger nucellus shows thicker pectic cell walls and is consumed during seed formation. The endosperm is nuclear and, after cellularization, shows peripheral cells with dense lipid content; the seeds are albuminous. The axial embryo shows fleshy cotyledons, which accumulate lipid and protein reserves; starch is rare. Although the seed structure is characteristic of the Fabaceae, the inner integument coalesces into the outer integument without being reabsorbed.

Chilling effects during seed filling on accumulation of seed reserves and yield of chickpea

AbstractChilling (&lt;15 °C) during the reproductive phase of chickpea leads to abortion of flowers and pods, infertile pods, smaller seeds and reduced seed yields. In the present study, effects of chilling during seed development were evaluated on accumulation of seed reserves and yield parameters in an extra early maturing chickpea genotype ICCV 96 029. Relative to control plants (17/28 °C mean minimum/maximum temperature), those subjected to cold stress (5/13 °C mean minimum/maximum temperature) showed a marked increase in electrolyte leakage, while cellular respiration (assessed as 2,3,5‐triphenyl tetrazolium chloride reduction activity), chlorophyll content, relative leaf water content and rate and duration of seed filling decreased significantly. In cold‐stressed plants, seed number per 100 pods, seed weight per plant, average seed weight and average seed size decreased by 35, 43, 41 and 24% respectively. Seed reserves of starch, protein and fat decreased by 34, 33 and 43% respectively, while total soluble sugars increased twofold. The accumulation of storage proteins such as globulins and albumins was inhibited to a greater extent than that of prolamins and glutelins. Most of the amino acids decreased as a result of stress, while some such as proline and glutamic acid increased significantly. Among the minerals examined, phosphorus content decreased more than calcium and iron contents. Copyright © 2005 Society of Chemical Industry

A role for phosphorylation in the regulation of the barley scutellar peptide transporter HvPTR1 by amino acids

Protein reserves in the cereal endosperm are sequentially degraded to small peptides and amino acids during germination and these are translocated across the scutellum to support growth of the embryo. Peptide transport in the germinating barley grain is mediated by specific carriers localized to the plasma membrane of the scutellar epithelium. In isolated barley embryos peptide transport is rapidly inhibited by amino acid concentrations comparable with those found in the post-germination barley grain. However, this inhibition of HvPTR1 activity is not effected at either the transcriptional or translational level. The protein phosphatase inhibitor okadaic acid repressed transport of Ala-[14C]Phe, but not [14C]Ala, into the barley scutellar epithelium. In vivo [32P]orthophosphate labelling studies of barley scutellar tissue in combination with immunoprecipitation studies using antiserum raised to HvPTR1 showed that HvPTR1 (66 kDa) is phosphorylated in the presence of amino acids. Immunopurified HvPTR1 was further demonstrated to be phosphorylated on serine residues. Digestion with the N-glycosidase enzyme PNGase F results in a shift in the molecular mass of the protein by 10 kDa, indicating that HvPTR1 is an N-linked glycoprotein. These results provide strong circumstantial evidence that HvPTR1 peptide transport activity in the germinating barley grain is regulated at the post-translational level by phosphorylation in response to rising levels of amino acids emanating from the endosperm as a result of storage protein breakdown and mobilization. This is potentially an important element in balancing the flux of organic nitrogen and carbon from the endosperm to embryo during germination and seedling establishment.

LIFETIME NUTRIENT DYNAMICS REVEAL SIMULTANEOUS CAPITAL AND INCOME BREEDING IN A PARASITOID

Models of host handling decisions and physiologically structured host–parasitoid population dynamics make diverging assumptions, untested as of this writing, about the allocation rules of nutrients to survival and reproduction. Our aim is to develop a data-rich multidimensional dynamical budget of nutrient acquisition and allocation in survival and reproduction in the host-feeding, synovigenic bruchid ectoparasitoid Eupelmus vuilletti (Hymenoptera: Eupelmidae) over the entire lifetime of the animal in order to address the above questions. We quantified sugar, glycogen, protein, and lipid reserves of single females at birth and death and their daily maintenance needs. We recorded each host-feeding and oviposition event over entire lifetimes and quantified the amounts acquired and invested in eggs using microcolorimetric techniques. We then built two nutrient budgets, with and without hosts, encompassing 20 measured biochemical parameters and tested their predictions using time of death. Carbohydrate reserves are burned at a high rate for maintenance and can be used to predict lifetime in absence of hosts. The model without hosts is adequate, but the one with hosts is not, as it predicts a continuous increase of proteins from the massive host-feeding intake, contrasting with the observed decline. A good prediction of time of death could be achieved in that model by assuming that the large amounts of ingested proteins and carbohydrates from host-feeding are used for maintenance, thereby enabling females to spare lipids for reproduction. We tested this assumption in a treatment with hosts and supplemental sugars, in which the maximal number of produced eggs is expected to be almost exclusively a function of lipids when other nutrients can be obtained to cover maintenance costs. Our results enable us to discriminate between competing hypotheses about nutrient allocation in models of parasitoid behavior and host–parasitoid population dynamics. They show that E. vuilletti is both a capital breeder for lipids and an income breeder for sugars, implying that this dichotomy is best superseded by a multidimensional and dynamical approach to nutrient acquisition and allocation.