Isolation and Identification of l-Deoxy-l-(L-asparagino)-D-fructose Formed in the Autoclaved Culture Medium

To elucidate the effect of nutrition during induction on peripheral muscle responsiveness to insulin, the incorporation of radiolabeled glucose to glycogen and the uptake of radiolabeled deoxyglucose were studied in isolated diaphragms from the fetuses of normal and diabetic pregnant rats in vitro. Basal- and insulin-stimulated incorporation of [1-¹⁴C]glucose into diaphragm glycogen were greater in the fetuses of diabetic mothers (IDM) than in normal fetuses, but there was no difference in the degree of stimulation by insulin of labeled glucose into glycogen between normal fetuses and IDM. Diaphragms from normal fetuses and IDM had the same basal uptake of 2-deoxy-[1-³H]glucose as well as insulin-stimulated uptake. Consequently the sensitivity of glucose uptake to insulin was similar both in normal fetuses and IDM. These data indicate that glucose utilization (incorporation of labeled glucose into glycogen) was increased in IDM, but that the response of glucose uptake and glycogenesis to insulin was not altered.     

Early developmental stages of a protozoan parasite, Marteilioides chungmuensis (Paramyxea), the causative agent of the ovary enlargement disease in the Pacific oyster, Crassostrea gigas

A paramyxea, Marteilioides chungmuensis, causes the irregular enlargement of the ovary in the Pacific oyster, Crassostrea gigas in Korea and Japan. The knowledge about the life cycle of the parasite has been limited to the sporulation stages within the oocyte of oysters. In this study, we used the parasite-specific DNA probes and electron microscopy to experimentally infected oysters in a field and successfully clarified early developmental stages of the parasite. The parasite invaded the oysters through the epithelial tissues of the gills, mantle and labial palps. Extrasporogony repeatedly occurred in the connective tissues by binary fusion. The inner cell of the extrasporogonic stage migrated into the gonadal epithelium, invaded the oocyte to start sporulation.     

Impact of seston characteristics on qualitative particle selection sites and efficiencies in the pseudolamellibranch bivalve Crassostrea gigas

To date, knowledge of the qualitative particle selection sites and conditions in the widely-distributed bivalve Crassostrea gigas is incomplete, having focussed either on heterogeneous particles, or on particles intentionally too large to enter the gill principal filament tracts. We used endoscope-directed sampling and the intact diatom-empty, cleaned frustule approach to unambiguously establish qualitative selection sites and the influence of seston quality (varying proportions of intact diatoms and empty, cleaned frustules) and quantity (particle loads) on the degree of qualitative selection. Normally-feeding oysters were presented test mixtures of the naturally-occurring Actinoptychus senarius (small enough to enter the gill principal filaments), and the potential selection sites (gill: dorsal and ventral collecting tracts; labial palps: anteriorly-deposited pseudofaeces), were sampled for comparison with the proportions and concentrations of the ambient medium. Qualitative selection was demonstrated at both the gills and labial palps. Gill selection efficiency was shown to be directly proportional to seston quality and quantity, using a technique independant of pseudofeces mucus content. The oyster gill is thus able to increase ingested food quality when environmental food quality is low and / or when seston concentrations are high, which is typical of oyster habitats. Palp selection efficiency was directly proportional to seston quality, but at the highest concentration tested, no qualitative selection was observed on the labial palps, probably due to overload on these smaller organs. The partial functional redundancy of these key processing organs in heterorhabdic species such as oysters and scallops may enhance their success in high-turbidity habitats.     

The effect of maintenance in vitro on glucose uptake and the incorporation of glucose into glycogen by adult Schistosoma mansoni

The effect of maintenance in vitro on glucose uptake and the incorporation of glucose into glycogen by adult Schistosoma mansoni. International Journal for Parasitology16: 253–261. Adult male Schistosoma mansoni rapidly depleted their glycogen reserves in vitro. Both sexes also exhibited a gradual reduction in glycogen content during prolonged maintenance. Paired and separated worms were incubated in [³H] glucose and rates of glucose uptake and incorporation into glycogen were determined following periods of maintenance in vitro. The glucose uptake rate declined during long-term maintenance and was higher for separated males and females than for equivalent paired worms. Increasing the medium glucose concentration also increased the rate of uptake. Glucose continued to be incorporated into glycogen throughout 10 days in vitro, with evidence from paired schistosomes suggesting that the rapid depletion of male glycogen could be due to a decrease in incorporation rate in vitro. The incubation of separated worms and the use of higher glucose concentrations in media both effected an increase in incorporation rate. These results are discussed in the light of observations of the depletion of schistosome glycogen in vitro.     

Ultra morphology of sensilla on the head and mouth parts of the earwig Anisolabis martima (Bonelli) (Dermaptera: Carcinophoridae)

The earwig Anisolabis maritima is a cosmopolitan insect with a worldwide distribution, omnivorous in feeding, eating the eggs of different insects. Recently recorded in Saudi Arabia as a beneficial predator on eggs and newly hatched larvae of the red palm weevil Rhyncophrous ferrugineus, scanning electron microscopy (SEM) observations revealed the presence of different kinds of receptor sensillae occurring on the head and mouth parts of A. maritime. The sensillae are the same, but differ in numbers on both sexes. The head surface bears three subtypes of trichoid sensillae, one type of ceoloconica. Labrum, labium, labial palps and maxillary palps, possess different kinds of sensillae. Three subtypes of trichoid have been identified on the labrum. The labium contained one type of tricoid and basiconic sensillae. There are great numbers and numerous sensillae cheatica differing in length distributed on the maxillary and the labial palps on all segments between other stutter spines. The last terminal segment of maxillary or labial palps bears the greatest number of the sensillae cheatica. Adult A. maritima may be introduced in the future as a beneficial predator of eggs of R. ferrugineus as a tool for integrated pest management.     

Characterization of a Monoclonal Antibody Directed against Mytilus spp Larvae Reveals an Antigen Involved in Shell Biomineralization

The M22.8 monoclonal antibody (mAb) developed against an antigen expressed at the mussel larval and postlarval stages of Mytilus galloprovincialis was studied on adult samples. Antigenic characterization by Western blot showed that the antigen MSP22.8 has a restricted distribution that includes mantle edge tissue, extrapallial fluid, extrapallial fluid hemocytes, and the shell organic matrix of adult samples. Other tissues such as central mantle, gonadal tissue, digestive gland, labial palps, foot, and byssal retractor muscle did not express the antigen. Immunohistochemistry assays identified MSP22.8 in cells located in the outer fold epithelium of the mantle edge up to the pallial line. Flow cytometry analysis showed that hemocytes from the extrapallial fluid also contain the antigen intracellularly. Furthermore, hemocytes from hemolymph have the ability to internalize the antigen when exposed to a cell-free extrapallial fluid solution. Our findings indicate that hemocytes could play an important role in the biomineralization process and, as a consequence, they have been included in a model of shell formation. This is the first report concerning a protein secreted by the mantle edge into the extrapallial space and how it becomes part of the shell matrix framework in M. galloprovincialis mussels.     

Influence of diet on pre-ingestive particle processing in bivalves: II. Residence time in the pallial cavity and handling time on the labial palps

Previous studies have demonstrated that bivalve molluscs respond to changing food conditions through processes such as preferential selection and ingestion of particulate matter. Little is known, however, about the underlying mechanisms accountable for these responses. To further explain feeding processes at the level of the pallial organs, we determined pallial cavity residence times, or the amount of time it took particles to travel from the inhalant aperture to the stomach, in two species of bivalves, Crassostrea virginica and Mytilus edulis, under conditions of differing particle quality, particle concentration, and temperature. From these residence times, particle-handling times on the labial palps were determined. Diets of three different qualities were tested, including Rhodomonas lens cells, particles prepared from ground Spartina sp. detritus, and a 50/50 mixture of both. Bivalves were delivered one of the three diets along with 10-μm fluorescent polystyrene beads (tracer), removed from feeding chambers at intervals from 30 s up to 20 min, and placed in liquid nitrogen to halt particle transport. Digestive systems of bivalves were then dissected and examined for the presence of tracer beads. Particle-residence times in the pallial cavity and handling times on the labial palps of C. virginica were significantly affected by changes in diet type. Particle-handling times on the palps decreased with increasing diet quality and ranged from 2.2 min (100% R. lens) to 22.8 min (100% ground Spartina sp.), accounting for 88% and 99%, respectively, of the total time particles spent in the pallial cavity. In contrast, diet quality had little effect on particle-residence times in the pallial cavity of M. edulis. However, residence times were affected by temperature and diet concentration. Temperature significantly affected residence times at particle concentrations of both 20 and 100 particles μl⁻¹, whereas particle concentration affected residence times at 20 °C, but not at 5 °C. Particle-handling times on the labial palps ranged from less than 1 to 5.5 min, depending on temperature and concentration, accounting for 50% to 82%, respectively, of the total time particles spent in the pallial cavity. We suggest that (1) observed interspecific differences in particle handling on the labial palps may be due to differences in palp morphology and function, and (2) particle sorting and selection on the labial palps is a rate-limiting step of pre-ingestive feeding processes in by bivalves.     

Functional validation of the carbon dioxide receptor in labial palps of Helicoverpa armigera moths

Adult moths possess an organ in their labial palps, the labial-palp pit organ, which is specialized for sensing carbon dioxide (CO₂). They use CO₂ as a cue to detect healthy plants and find food or lay eggs on them. The molecular bases of the CO₂ receptor in Drosophila melanogaster and Aedes aegypti have been reported, but the molecular mechanisms of the CO₂ receptor in Lepidoptera remains elusive. In this study, we first re-examined three putative Helicoverpa armigera CO₂ gustatory receptor genes (HarmGr1, HarmGr2, and HarmGr3), and then analyzed expression patterns of them. RT-PCR results verified they were predominantly expressed in the labial palps of H. armigera. Thus, we used in situ hybridization to localize the expression of three genes in the labial palps. We found that all three genes were co-expressed in the same cells of the labial palps. Next, we employed the Xenopus laevis oocyte expression system and the two-electrode voltage-clamp recording to study the function of the three genes. Results showed that only oocytes co-expressing HarmGr1 and HarmGr3 or co-expressing HarmGr1, HarmGr2 and HarmGr3 gave robust responses to NaHCO₃. Finally, we confirmed that the sensory cells in labial palps of both females and males show dose dependent responses to CO₂ stimuli by using single sensillum recording. Our work uncovers that HarmGr1 and HarmGr3 are indispensable and sufficient for CO₂ sensing in labial palps of H. armigera.     

Insulin stimulation of glucose transport and metabolism in a human Wilms' tumor-derived myoblast-like cell Line: Modulation of hormone effects by glucose deprivation

The effects of insulin and glucose on parameters of metabolism were investigated in myoblast-like (MBL) cells, a human myoblast-like cell line derived from a Wilms' tumor. Insulin responses were studied after 4 hr pre-incubation in serum free media, with or without 5 mM glucose. Insulin was added during the last 2 hr. Glucose starvation markedly increased basal glucose transport (measured as 2-deoxyglucose uptake) as well as the net uptake of [¹⁴C]glucose and [¹⁴C]glucose incorporation into glycogen. Insulin stimulated net glucose uptake and incorporation into glycogen in a dose-dependent manner in glucose-fed and starved cells. These insulin responses were markedly enhanced in glucose-starved cells. Insulin accelerated 2-deoxyglucose transport in glucose-fed cells but did not further stimulate basal glucose transport in glucose-deprived cells. Insulin increased the incorporation of [³H]leucine into protein in glucose-fed or -starved MBL cells equally. The dose of insulin required for half-maximal insulin responses was similar for all parameters studied. Cycloheximide did not prevent the increased basal glucose incorporation in glucose-starved cells, but markedly inhibited the insulin response, while in glucose-fed cells, cycloheximide stimulated basal glucose incorporation. We conclude that MBL cells resemble fibroblasts in their insulin-independent stimulation of glucose transport in response to glucose-deprivation; when provided with glucose, they respond to insulin like fibroblasts. However, after brief glucose-starvation, the stimulated glucose transport system is no longer insulin-responsive in MBL cells, while pathways leading to the synthesis of macromolecules demonstrate preserved or enhanced stimulation by insulin, suggesting that these cells may serve as models to study the regulation of receptor-response coupling by the metabolic milieu.     

Nutrient storage cells isolation from mantle tissue of Mytilus galloprovincialis: glucose release and glycogen content

A method for obtaining isolated mantle nutrient storage cells and purifying vesicular (VC) and adipogranular (ADG) cells from mantle tissue of Mytilus galloprovincialis is reported. Tissue digestion is partly mechanical (stirring) and partly enzymatic (collagenase + dispase). Purification is carried out through continuous and discontinuous Percoll gradients. VC appears in fraction 3 (d = 1.05-1.08 g/ml) and ADG in fraction 2 (d = 1.09 g/ml). Intracellular glycogen and free-glucose content in September-April period is studied. When glycogen is detectable it is always accompanied by intracellular free-glucose pool in a concentration relationship glycogen/glucose 10:1. Furthermore, a glucose releasing activity elicited by the Ca2(+)-ionophore A23187 was found in isolated cells, which reproduce the former behaviour found with mantle tissue fragments in our laboratory.     

Short-term bioaccumulation, circulation and metabolism of estradiol-17β in the oyster Crassostrea gigas

Steroids are active signal transmitters in Vertebrates. These roles have also been hypothesized in other Phyla and endocrine disrupting effects have been reported for different estrogen-like compounds in fishes and some marine invertebrates. As estradiol-17β has shown some physiological activities in the oyster and as estrogens or estrogen-like molecules can be present in water, we have investigated the bioaccumulation and metabolism of this estrogen in vivo in the oyster Crassostrea gigas. When dissolved in seawater, in less than 48 h estradiol-17β concentrated up to 31 times in the soft tissues of the suspension-feeder mollusc. Injected in the adductor muscle, estradiol-17β circulated from muscle to the gonad, the gills, the mantle, the labial palps, and to a lesser extent to the digestive gland. After 2 h, estradiol flow increased specifically towards this gland. Different hypotheses were raised concerning the circulation paths. However, in all cases estradiol metabolism primarily evidenced an in vivo transformation into estrone in the whole oyster and in its digestive gland. This strong 17β-hydroxysteroid-dehydrogenase activity confirms our previous in vitro results. In conclusion, it is proposed that oyster is able to take in charge estradiol as a potential contaminant in seawater. Therefore, its bioaccumulation and transformation into estrone could be studied as potential biomarkers of endocrine disruption. Furthermore, the experimental approach with dissolved steroids in the seawater combined to an anatomical screening appears as an interesting tool to investigate the bivalve endocrinology.     

Sexual dimorphism of adult labial palps of the peach fruit moth Carposina sasakii Matsumura (Lepidoptera: Carposinidae) with notes on their sensilla

The labial palps and their sensilla of the peach fruit moth Carposina sasakii Matsumura, a serious pest of pome fruits in eastern Asia, were investigated using light microscopy and scanning and transmission electron microscopy. The labial palps are three‐segmented and exhibit distinct sexual dimorphism in length: much longer in the female than in the male. Four types of sensilla were found on the labial palps: campaniform, squamiform, chaetic and flattened sensilla. The campaniform sensilla are present on the first segment alone. The squamiform sensilla are located on all the three segments. The chaetic sensilla are mainly present on the third segment. The flattened sensilla are grooved with wall pores and situated in a labial palp‐pit organ, which is located at the apex of the distal segment of the labial palp. The sexual dimorphism of the labial palp and the labial palp‐pit organ was briefly discussed.     

Hypoglycemic action of the pectin present in the juice of the inflorescence stalk of plantain (Musa sapientum)—Mechanism of action

The pectin isolated from the juice of the inflorescence stalk of plantain (Musa sapientum) has been found to show significant hypoglycemic effect both in normoglycemic and alloxan diabetic rats. After its administration at a dose of 20mg/100g body weight, there was increase in the concentration of hepatic glycogen, increased glycogenesis as evident from the increased activity of glycogen synthetase and in normoglycemic rats increased incorporation of labelled glucose into hepatic glycogen. Glycogenolysis and glyconeogenesis were lower as was evident from the decreased activity of glycogen phosphorylase and gluconeogenic enzymes.     

Gametic, morphometric, and physiological variables influencing clutch size in the Chilean oyster, Ostrea chilensis (Philippi, 1845)

A number of marine bivalve taxa, including species of the genus Ostrea, have adopted brooding of the young in the mantle cavity as a reproductive mechanism. In spite of the importance of brooding in the reproductive success of such species, little is known about the most important variables influencing the process, including those limiting clutch size. This study addresses the regulation of brood size in the hermaphroditic oyster Ostrea chilensis. During spawning, oysters released all their oocytes into the mantle cavity. No residual oocytes remained in the gonad, so a second spawning during the same brooding season was not possible. There was a weak correlation between the number of embryos incubated during the early phase of brooding and the dry tissue weight of the brooding oyster, and between the number incubated and the shell length of the brooding adult during the later phases of brooding. The number of embryos was also correlated with the area of the labial palps of the brooder during the later stages, suggesting that the loss of veligers observed at this time may be at least partially attributable to a limitation of space around the palps, which manipulate the larvae and with which the larvae are closely associated. The oxygen consumption rate of brooders incubating a normal clutch of embryos was not significantly different from that of oysters in which clutch size had been experimentally reduced by 50%. Experimental increase of the normal clutch size by 100% significantly increased the oxygen consumption of the brooder, suggesting that there is a physiological as well as a spatial limit to brood size. Thus the number of embryos brooded by an oyster is initially dependent on its production of oocytes and secondarily by the high metabolic costs of incubating large numbers of embryos. As development proceeds, space available for brooding apparently becomes a limiting factor as the larvae grow. The fate of the excess larvae is not known at present, but any larvae released prematurely cannot be competent to settle, since development is synchronous and there is a complete release of all pediveligers at the end of the brooding period.     

The metabolism of glucose in diaphragm muscle from normal rats, from streptozotocin-treated diabetic rats and from rats treated with anti-insulin serum

1. The metabolism of [U-¹⁴C]glucose by the isolated diaphragm muscle of normal rats, rats rendered diabetic with streptozotocin and rats with transitory insulin deficiency after an injection of anti-insulin serum was studied. 2. The incorporation of [¹⁴C]glucose into glycogen and oligosaccharides was significantly decreased in the diabetic diaphragm muscle and in the muscle from rats treated with anti-insulin serum. 3. Neither diabetes nor transitory insulin deficiency influenced the oxidation of glucose, or the formation of lactate and hexose phosphate esters from glucose. 4. Insulin fully restored the incorporation of glucose into glycogen and maltotetraose in the diabetic muscle, but the incorporation into oligosaccharides, although increased in the presence of insulin, was significantly lower than the values obtained with normal diaphragm in the presence of insulin.     

Ultrastructure of sensilla on the maxillary and labial palps of three species (Coleoptera: Staphylinidae: Staphylininae)

Most species of Staphylinidae are predators in an agroecosystem. They acquire prey information from their environment through receptors. In this study, the sensilla on maxillary and labial palps of Philonthus kailiensis, Philonthus lewisius and Quedius robustus were examined with scanning electron microscopy to identify and analyse the external morphology and distribution of the sensilla to enhance our knowledge of the sensilla of Staphylinidae and provide a rationale of taxonomical studies on the two genus. Results showed that the sensilla are classified into six types: Böhm bristles, sensilla chaetica, sensilla furcate, sensilla coeloconica, sensilla placodea and sensilla basiconica. No sexual dimorphism exists among the three species. The relationships and functions of sensilla on maxillary and labial palps were also speculated. There may be a certain correlation between the sensilla on maxillary and labial palps of the staphylinid and its habitat.     

Interrelationship of insulin and glucagon ratios on carbohydrate metabolism in isolated hepatocytes containing high glycogen.

The effect of physiological concentrations of glucagon and insulin on glycogenolysis was studied in the presence and absence of substrates in isolated hepatocytes containing high glycogen. In the absence of substrates glucagon stimulated glycogenolysis at 10^?14M concentration, and addition of 100 μunits of insulin partially inhibited glucagon stimulated glycogenolysis (10^?14M to 10^?11M). However, in the presence of substrates, insulin completely inhibited glucagon stimulated glycogenolysis (10^?14M to 10^?11M), indicating that molar glucagon and insulin ratios control carbohydrate metabolism in liver. Additional studies showed incorporation of amino acid into protein was linear for only 3 to 4 hr in cells containing low glycogen, whereas in cells containing high glycogen, incorporation was linear for 8 to 10 hr.