Liver glycogen,glucose mobilization and freezing survival in chorus frogs,Pseudacris triseriata

We compared liver glycogen stores and glucose mobilization during freezing among winters in chorus frogs, Pseudacris triseriata, where populations varied in freezing survival. We also characterized tissue glycogen levels across the annual cycle. Frogs with low liver glycogen stores mobilized low amounts of glucose during freezing, and these were correlated with population variation in freezing survival. Moreover, liver glycogen stores were significantly and positively related to body mass. These data suggest that chorus frogs store liver glycogen in preparation for hibernation and that body size and glycogen stores must reach threshold levels for successful survival of freezing bouts during the winter.     

Glycogen storage and degradation during in vitro growth and differentiation of Giardia intestinalis

Giardia intestinalis is the causative agent of human giardiasis, a common diarrheal illness worldwide. Despite its global distribution and prevalence, many questions regarding its basic biology and metabolism remain unanswered. In this study, we examine the accumulation and degradation of glycogen, an important source of stored carbon and energy, during the in vitro growth and differentiation of G. intestinalis . We report that, as G. intestinalis progresses through its growth cycle, cultures of trophozoites accumulate glycogen during the lag and early logarithmic phases of growth and then utilize this compound during their remaining logarithmic growth. As cultures enter the stationary phase of growth, they re-accumulate glycogen stores. The activity of glycogen phosphorylase, an enzyme involved in glycogen metabolism, also varied throughout in vitro trophozoite growth. During the in vitro induction of trophozoite differentiation into water-resistant cyst forms, the cultures initially accumulated stores of glycogen which diminished throughout transition to the cyst form. This observation is suggestive of a role for glycogen in the differentiation process. These studies represent the first thorough analysis of changes in glycogen content and glycogen phosphorylase activity during G. intestinalis growth and differentiation.     

Population genetics of introduced bullfrogs, Rana (Lithobates) catesbeianus, in the Willamette Valley, Oregon, USA

The American bullfrog, Rana (Lithobates) catesbeianus, is endemic to eastern North America, but has been introduced to approximately 40 countries on four continents and is considered one of the hundred worst invasive alien species in the world. Here, we investigated the genetics of invasive bullfrogs in the Willamette Valley, Oregon, USA, where bullfrogs are widespread and abundant to determine: (1) the minimum number of bullfrog introductions; (2) the native source population(s); and (3) whether genetic variation is reduced compared to source populations. To answer these questions, we analyzed partial sequences of the mitochondrial cytochrome b gene for 251 bullfrogs from the Willamette Valley and the native range. We found that bullfrogs from the Mississippi River basin and Great Lakes region were introduced at least once to the Willamette Valley. Genetic variation measured as haplotype diversity (h) and nucleotide diversity (?? _n ) was not significantly different between Willamette Valley and source populations. Our results were in contrast to a recent genetic analysis of invasive bullfrog populations in Europe, which found that genetic variation in European bullfrog populations was much lower than in source populations. European bullfrogs also originated from different source populations than Willamette Valley bullfrogs. The difference in genetic composition between Willamette Valley and European bullfrogs is likely due to differences in their invasion histories and may have implications for the potential of bullfrogs in these different regions to adapt and expand.     

Improved cardiac function following hormonal therapy in brain dead pigs: relevance to organ donation

Deterioration of function in brain dead baboons is associated with depletion of both myocardial energy stores and certain circulating hormones, notably thyroxine, cortisol, and insulin. We have therefore investigated the effect of the administration of these three hormones to the brain dead pig; their value has been assessed on both the freshly excised and stored donor heart. Brain death was induced by ligation of the two arteries to the upper part of the body which arise from the aortic arch. Storage of selected hearts was by continuous hypothermic perfusion for 20 to 24 hr. Hearts were biopsied for estimation of adenosine triphosphate, creatine phosphate, lactate, and glycogen, and were subsequently functionally tested. Six groups of pigs were studied. Hearts were tested from control pigs which had not undergone brain death (A1), from brain dead pigs which had received intravenous fluid and inotropic support for 4 hr (B1), and from brain dead pigs which had in addition received 2 hr of hormonal therapy (thyroxine 2 micrograms cortisol 100 mg, and insulin 5-10 IU hourly) (C1). A further 3 groups (A2-C2) underwent management identical to A1-C1, but in addition the hearts were stored for 24 hr. Brain death in pigs was followed by a consumption of myocardial energy stores, despite anaerobic glycolysis; this was associated with reduced myocardial function. The administration of hormones to the brain dead pig led to some replenishment of myocardial energy and glycogen reserves and reduction in lactate, with associated improvement in hemodynamic function. A period of hypothermic perfusion storage appeared to reverse the anaerobic metabolism occurring in the heart in the nonhormonally treated brain dead animal, though not in the hormonally treated animal, and led to replenishment of glycogen reserves in nontreated animals. The observation that both better function and an increase in myocardial energy stores occurred in hormonally treated, stored hearts, even though perfusate lactate dehydrogenase rose to significantly higher levels during hypothermic perfusion storage, and tissue lactate levels remained high, suggests that thyroxine promotes both aerobic and anaerobic metabolism in brain dead animals.     

Evolution of glycogen and blood metabolites after controlled suckling at two periods of lactation in young rabbits

In natural conditions young rabbit nurses once a day and therefore ingests the whole of his daily caloric intake during a single meal. The present work investigates glucose homeostasis during perinatal period in young rabbit by assessing blood glucose and glycogen stores before and after one single meal. Ponderal data, glycogen and blood metabolites were determined in 1-4 day- and 17-21 day-old rabbits before suckling and at different times (1, 3, 6, 9, 24, 48, 72 h) after controlled suckling. In "young" and "old" rabbits hepatic glycogen stores were exhausted after 48 and 72 h of fast. Within the first hours following milk ingestion, muscle and carcass glycogen did not vary until 9 h in the "young" and until 24 h in the "old" without notable variation of glycemia. From 24 to 72 h young rabbits were in a fasting period with low hepatic glycogen and a decrease of muscle and carcass glycogen, but glycaemia decreased only slightly at 48 and 72 h in "young" and at 72 h in "old" As blood alanine was decreased, it appears that gluconeogenesis was effective and that alanine-glucose and Cori cycles were operating in these conditions.     

Effects of experimental stress on the glycogen content of Cepaea hortensis (Mollusca)

A method for measuring the glycogen content of the hepatopancreas of Cepaea hortensis is described. Glycogen content was determined for snails from field population cages and from a nearby natural population. Results showed that caged snails possessed lower levels of glycogen than did the natural population, while the lowest levels of glycogen were associated with higher snail densities in the cages. There is evidence for an increase in glycogen content of C. hortensis during the late summer in nature and in experimental populations. The results are discussed with regard to the selective effect that glycogen may have on Cepaea and to the interpretation of events occurring in populations of Cepaea that glycogen assay could provide.     

The relationship between glycogen synthesis, biofilm formation and virulence in salmonella enteritidis

Salmonella enteritidis accumulated large quantities of intracellular polysaccharide when grown in unrestricted nutrient conditions. Dense, abundant cytoplasmic granules were observed by electron microscopy in sections stained by the periodic acid-chlorite technique, indicating that the polysaccharide was of the glycogen type. When biofilm-producing S. enteritidis was pre-incubated in media containing increasing levels of glucose concentration, the levels of both cytoplasmic glycogen and biofilm rose correlatively to a point where a ceiling effect was observed. Studies carried out with activators and inhibitors of glycogen biosynthesis confirmed that biofilm was formed from glycogen cell stores. On the other hand, the virulence of the biofilm-producing strain in infected chickens increased proportionally to the amount of stored glycogen, suggesting a possible role of the glycogen depot in the virulence of S. enteritidis.     

浙江东部牛蛙的自然种群及潜在危害

牛蛙(Rana catesbeiana)的入侵已成为一些本地两栖类种群数量下降或灭绝的主要因素之一。1959年牛蛙被引入中国大陆,但直到1990年才开始在国内大范围饲养。牛蛙的自然种群在国内一直未见报道。我们于2003年9—11月调查了浙江省东部5区3县的牛蛙种群,发现在岱山、秀山、六横及佛渡岛上有牛蛙分布,共捕获23只牛蛙,包括4只成年个体,18个亚成体和1只蝌蚪。于2004年1月和2月在岱山捕获28只蝌蚪。结果显示：(1)牛蛙的蝌蚪能在当地越冬成活,说明牛蛙在上述4岛成功地建立了自然种群;(2)牛蛙主要分布于水库、池塘和溪流,牛蛙的生境与6种当地蛙有部分重叠;(3)养殖时管理不善造成的牛蛙逃逸,以及牛蛙价格过低而导致养殖户将牛蛙弃置野外可能是牛蛙入侵的主要原因。牛蛙对当地蛙的潜在威胁很大,开展牛蛙的分布、食性和种群动态研究是当务之急。     

Glycogen repletion following burst activity: a carbohydrate-sparing mechanism in animals adapted to arid environments?

The Western chestnut mouse (Pseudomys nanus ferculinus) is one of several native rodent species adapted to the arid environments of Australia. Since these environments are often associated with a paucity in dietary carbohydrate, the problem arises as to the mechanism whereby these rodents replete their stores of muscle glycogen when recovering from high intensity physical activity. This is an important issue since the maintenance of adequate stores of muscle glycogen is crucial to support the energy demands associated with 'flight or fight' responses. Whilst it is known that food ingestion post-exercise is required for the total repletion of muscle glycogen in rats and humans, our findings indicate that the Western chestnut mouse has the impressive capacity to replete completely its stores of muscle glycogen, even in the absence of food intake. Indeed during recovery from burst activity which results in the massive breakdown of the stores of muscle glycogen, the levels of glycogen return back to pre-exercise levels within only 50 minutes despite the absence of food intake. This capacity is important in the broader context of nutritional adaptation to arid/seasonally-arid regions since it allows muscles to replete their fuel stores even when food is not available. How common is this strategy among desert-adapted mammal species is a question yet to be answered.     

Carbohydrate balance in competitive runners during successive days of intense training

This study was designed to investigate the effect of intense training on muscle glycogen stores under conditions of controlled carbohydrate (CHO) intake. On two separate occasions, 10 highly trained distance runners increased their training load for 5 days (20 km/day, approximately 80% maximal O2 consumption) while eating a diet whose carbohydrate composition either equaled (EQ-CHO) or contained approximately 50% of the runner's estimated daily expenditure (LO-CHO). Total muscle glycogen levels were lower after the LO-CHO regimen. Photometric analysis of the glycogen content in individual fibers revealed that 27% type I and 17% type II fibers had optical densities less than 0.2 U after the LO-CHO regimen, whereas 7% type I and 0% type II were similarly depleted after the EQ-CHO diet. A linear relationship was observed between the histochemical and direct chemical analysis of muscle glycogen content. Treadmill O2 uptake measured at 185 and 238 m/min was higher during the LO-CHO than the EQ-CHO regimen. Ratings of perceived exertion were higher during the 238-m/min run for the LO-CHO regimen. After 3 days of rest, running economy and perception of effort returned to pretraining levels and muscle glycogen stores were approximately 85% of the pretraining values. Thus when CHO intake was only approximately 50% of the energy requirements there was a marked depletion of muscle glycogen stores, particularly in type I fibers, and a concomitant decrease in running economy and increased perception of fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preservation of metabolic reserves and function after storage of myocytes in hypothermic UW solution

Isolated rat myocytes coldstored anaerobically up to 24 h in University of Wisconsinsolution lost 95% of their ATP and 100% of their glycogen. Theyunderwent contracture when rewarmed in a Krebs-Henseleit (KH) mediumthat contained Ca unless Ca addition was delayed. In the latter case,cell function, measured by stimulation-induced cell shortening, wassurprisingly well retained. Aerobically stored cells were resistant toCa on rewarming, although 96% of glycogen was still lost, along with46% of ATP. Cells that were incubated for 48 h aerobically withthe substrates glucose and pyruvate at pH 6.2 retained 77% of theirATP and 59% of their glycogen, with good cell morphology. At pH 6.2, the demand for ATP was only 55% of that at pH 7.4. However, afterrewarming, these cells functioned no better than anaerobically storedcells, although their inotropic response to isoproterenol was improved.We conclude that 1) aerobic conditions with substrates atlow pH preserve myocyte metabolic reserves well for 48 h, partlyby reducing the demand for ATP; 2) rewarming conditions arecritical for anaerobically stored cells with metabolic stores that areseverely depleted; and 3) unloaded cell function issurprisingly insensitive to a period of severe metabolic deprivation.

     

Effects of Extracellular Potassium on Glycogen Stores of Astrocytes In Vitro

Astrocyte-enriched and meningeal cell cultures of the rat cerebral cortex were prepared, and their glycogen content was measured after 10-90 min under control (2.5 mM) concentrations of potassium after prefeeding with 20 mM glucose. No net change in glycogen level was noted in either culture over this period. Cell cultures were then exposed to increased concentrations of potassium (5, 10, and 15 mM), and their glycogen content was measured after 10-90 min. Both types of cell culture showed complex and variable changes in glycogen content. In general, increased potassium concentrations caused astrocyte glycogen stores to be reduced at physiological increases of potassium levels (from 2.5 to 5 mM and above), although a period of resynthesis was evident at all potassium concentrations. Meningeal cell glycogen levels were highly variable and only affected by high (10 and 15 mM) levels of potassium. These results are discussed with respect to the theory that changes in the external potassium concentration caused by neuronal activity might act as a signal controlling astrocyte glycogen stores.     

Determining factors for cryoprotectant accumulation in the freeze-tolerant earthworm, Dendrobaena octaedra

The freeze-tolerant earthworm Dendrobaena octaedra is found in most of the European forest and tundra, Siberia, North America and Greenland where it over-winters in the top soil and encounters winter frost. In response to freezing this earthworm rapidly synthesises glucose which acts as a cryoprotectant. Frost tolerance varies extensively between geographical populations, and of the populations studied so far, the Finnish worms are most and the Danish worms least frost tolerant. Little is known about the determining factors for glucose synthesis and this study therefore investigated possible roles of acclimation and the cues for synthesis of glucose, in Finnish and Danish worms. The Finnish population had significantly larger glycogen reserves than the Danish during acclimation and in all worms, glucose synthesis was the result of an almost stoichemical reduction in glycogen stores. Maximum glucose levels were reached after the onset of freezing and were significantly higher in Finnish worms where the sugar accounted for as much as 5% of the fresh weight. On average, both the total glycogen phosphorylase activity and the active enzyme pool increased during acclimation in the Finnish but not the Danish populations. However, the increase in this enzyme was only significant during the freezing process. In this study, we show contrary to previous theory that glucose synthesis is initiated before the onset of freezing and that in this species, cryoprotectant synthesis is sensitive to very small temperature changes below 0 degrees C without the presence of ice.     

Utilization of pre-existing energy stores of female Aedes aegypti mosquitoes during the first gonotrophic cycle

Pre-existing energy reserves may play an important role in regulating the utilization of blood meal proteins in female anautogenous mosquitoes. Determining the fate of reserves derived from the sugar meal and larval food during the first gonotrophic cycle would help to elucidate the relative contributions of larval and adult nutrition to survival and reproduction. We measured the allocation of pre-blood-meal reserves to egg production or energy production during the first gonotrophic cycle by using [14C]-labeled female Aedes aegypti mosquitoes. Feeding adults [3,4-14C]-glucose labeled the glycogen and sugar stores (approximately 50%), lipid stores (approximately 25%), and protein and amino acid stores (approximately 25%). During the first gonotrophic cycle, about 60% of the glycogen and sugar stores were metabolized and all were used for energy production. About 33% of the labeled protein and 72% of the labeled amino acid stores were metabolized, with about 9% being transferred to the eggs and the rest oxidized. About 30% of the lipid was metabolized, with about 65% being transferred to the eggs and the rest oxidized. Feeding [1-14C]-oleic acid to larvae effectively labeled adult lipid stores with about 75% of the label in lipid stores and 16% in proteins and 6% in glycogen. During the first gonotrophic cycle, about 35% of the labeled lipid stores were metabolized, with equal amounts being oxidized and transferred to the eggs. None of the other maternal stores labeled by fatty acid were metabolized during the first gonotrophic cycle. These results show that carbohydrate reserves are a critical source of energy during the first gonotrophic cycle, while lipid reserves are used equally for energy production and provisioning the eggs.     

Can captive-bred American bullfrogs learn to avoid a model avian predator?

Animals that are isolated from their natural predators may lose the ability to express antipredator behavior. The aim of this study was to test whether it would be possible to train captive-bred North American bullfrogs (Rana catesbeiana) to avoid a model avian predator and to measure their behavioral responses to this predator. We used 18 animals divided into two groups, trained (N?=?6) and control (N?=?12); these individuals were from a line that has been bred in captivity for at least 20 generations without predator contact. The trained group was exposed, individually, to 20 sequential antipredator training sessions, during which the presence of a model avian predator was paired with an aversive stimulus. The control group was exposed, individually, once only to the same model avian predator, but without the association of the aversive stimulus. Both groups were observed for 10 min after the presentation of the avian predator, during which their behavior was recorded using instantaneous recording of behavior. The results showed that, after only two training sessions, the trained bullfrogs started to express proper antipredator behavior: diving to the bottom of the tank, lying still, and eventually, learning to cover themselves in substrate (mud). However, continued training sessions provoked a varied response to antipredator training, which was undesirable as the effectiveness of their antipredator response varied. This study has shown that captive-bred bullfrogs were capable of learning antipredator behavior, despite having been bred for many generations in captivity with no predator contact.     

Glycogen resynthesis in the absence of food ingestion during recovery from moderate or high intensity physical activity: novel insights from rat and human studies

The finding that during recovery from high intensity exercise, rats have the capacity to replenish their muscle glycogen stores even in the absence of food intake has provided us with an experimental model of choice to explore further this process. Our objective here is to share those questions arising from research carried out by others and ourselves on rats and humans that are likely to be of interest to comparative biochemists/physiologists. On the basis of our findings and those of others, it is proposed that across vertebrate species: (1). the capacity of muscles to replenish their glycogen stores from endogenous carbon sources is dependent on the type of physical activity and animal species; (2). lactate and amino acids are the major endogenous carbon sources mobilized for the resynthesis of muscle glycogen during recovery from exercise, their relative contributions depending on the duration of recovery and type of exercise; (3). the relative contributions of lactate glyconeogenesis and hepatic/renal gluconeogenesis to muscle glycogen synthesis is species- and muscle fiber-dependent; and (4). glycogen synthase and phosphorylase play an important role in the control of the rate of glycogen synthesis post-exercise, with the role of glucose transport being species-dependent.     

Glycogen metabolism of the anammox bacterium “Candidatus Brocadia sinica”

Presence of glycogen granules in anaerobic ammonium-oxidizing (anammox) bacteria has been reported so far. However, very little is known about their glycogen metabolism and the exact roles. Here, we studied the glycogen metabolism in “Ca. Brocadia sinica” growing in continuous retentostat cultures with bicarbonate as a carbon source. The effect of the culture growth phase was investigated. During the growing phase, intracellular glycogen content increased up to 32.6 mg-glucose (g-biomass dry wt)⁻¹ while the specific growth rate and ATP/ADP ratio decreased. The accumulated glycogen begun to decrease at the onset of entering the near-zero growth phase and was consumed rapidly when substrates were depleted. This clearly indicates that glycogen was synthesized and utilized as an energy storage. The proteomic analysis revealed that “Ca. B. sinica” synthesized glycogen via three known glycogen biosynthesis pathways and simultaneously degraded during the progress of active anammox, implying that glycogen is being continuously recycled. When cells were starved, a part of stored glycogen was converted to trehalose, a potential stress protectant. This suggests that glycogen serves at least as a primary carbon source of trehalose synthesis for survival. This study provides the first physiological evidence of glycogen metabolism in anammox bacteria and its significance in survival under natural substrate-limited habitat.Subject terms: Applied microbiology, Water microbiology     

Ultrastructure of Enteromyxum leei (Diamant, Lom, & Dyková, 1994) (Myxozoa), an Enteric Parasite Infecting Gilthead Sea Bream (Sparus aurata) and Sharpsnout Sea Bream (Diplodus puntazzo)

ABSTRACT. The ultrastructure of the developmental stages of the myxozoan Enteromyxum leei parasitizing gilthead seabream ( Sparus aurata ) intestine and sharpsnout sea bream ( Diplodus puntazzo ) intestine and gallbladder are described. The earliest stage observed was a small dense trophozoite located among enterocytes. Proliferative stages, observed intercellularly in the epithelium of the intestine and gallbladder as well as in the lumen, possessed the typical cell-in-cell configuration throughout their development. Secondary cells were seen undergoing division within a common vacuolar membrane that also encompassed pairs of tertiary cells. Cytochemical studies showed that primary cells stored mainly lipids whereas secondary cells stored abundant β-glycogen granules. Sporogonic development resembled that described for other disporous myxozoans. Within sporogonic stages, nonsporogonic secondary cells were observed accompanying two developing spores. Mature spores had a binucleated sporoplasm in which glycogen stores were abundant and no sporoplasmosomes were found. Our observations are discussed in relation to our knowledge on other myxozoans of the genus Enteromyxum .