Experimental Evidence that a Desert Parasitoid Keeps its Host Cool

The wasp parasitoid Pseudopompilus humboldti (Hymenoptera; Pompilidae) in the Negev desert of Israel stores its paralyzed host, the spider Stegodyphus lineatus (Araneae; Eresidae), at the entrance of the spider's nest. The spider is moved by the wasp from the depth of the nest to the entrance in spite of increased exposure to visually-searching predators, such as birds. We examined the hypothesis that this behaviour has evolved to prevent the wasp's host from overheating in this hot desert. Experimental manipulations of the position of the parasitized spiders demonstrated that spiders and wasp larvae could not survive the heat experienced deep in the spider's nest during summer. By contrast, in the cooler nest entrance, spiders and larvae survived, if they were overlooked by predators. This host-storing behaviour is an adaptive trade-off between thermoregulatory requirements and predation risk. This appears to be the first evidence that a parasitoid manipulates the temperature of its host, albeit for its own ultimate gain.     

Isolation and Characterization of Hardening-Induced Proteins in Chlorella vulgaris C-27: Identification of Late Embryogenesis Abundant Proteins

Hardening-induced soluble proteins of Chlorella vulgaris BeijerinkIAM C-27 (formerly Chlorella ellipsoidea Gerneck IAM C-27) wereisolated and purified by two-dimensional high-performance liquidchromatography (2D-HPLC) on an anion-exchange column, with subsequentreversed-phase chromatography. Some of the proteins were resolvedby SDS-PAGE, characterized by amino-terminal sequencing andidentified by searching for homologies in databases. Separationof the soluble proteins during the hardening of Chlorella bya combination of 2D-HPLC and SDS-PAGE revealed that at least31 proteins were induced or increased in abundance. Of particularinterest was the induction after 12 h of a 10-kDa protein withthe amino-terminal amino acid sequence AGNKPITEQISDAVGAAGQKVGand the induction after 6 h of a 14-kDa protein with the amino-terminalsequence ALGEESLGDKAKNAFEDAKDAVKDAAGNVKEAV. The amino-terminalsequences of these proteins indicated that they were homologousto late embryogenesis abundant (LEA) proteins. Furthermore,the level of a 22-kDa protein also increased after 12 h. Theamino-terminal sequence of this protein, AAPLVGGPAPDFTAAAVFD,indicated that it was homologous to thioredoxin peroxidase. (Received June 9, 1995; Accepted September 12, 1995)     

Characterization and immunocytochemical demonstration of glucocorticoid receptor using antisera specific to transformed receptor

Cytosolic and nuclear forms of the glucocorticoid receptor were characterized using immunochemical techniques. Antibodies were raised in rabbits to an M_r 58,000 fragment of the transformed (DNA-binding) glucocorticoid receptor purified from rat liver cytosol by DNA-cellulose chromatography and polyacrylamide gel electrophoresis. Antibodies reacted with the transformed receptor form in a radioimmunoassay for glucocorticoid receptor. Western blot analysis of antibody reactivity revealed a single M_r 185,000 receptor form in rat liver cytosol but a smaller M_r 85,000 form in nucleosol, indicating the M_r 85,000 form is the transformed receptor. Furthermore, western blot analysis indicates that the M_r 185,000 receptor undergoes proteolysis during receptor purification and in vitro transformation processes by generating immunochemically similar proteins of smaller molecular weights. An identical M_r 185,000 glucocorticoid receptor was detected in cytosols of four rat tissues; liver, brain, adrenal medulla, and thymus. The glucocorticoid receptor was localized to the cytoplasm and nucleus of rat adrenal medulla cells by immunohistochemistry, demonstrating the existence in vivo of the transformed receptor and translocation of the receptor from cytoplasm to nucleus.     

Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland

The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia.     

Transient electric birefringence of the bacteriophages T3 and T7

Electric birefringence measurements of suspensions of T3 and T7 bacteriophages in 10^?2 M phosphate buffer, pH 6.9, show that there is a difference in their rotational diffusion coefficient. The values corrected to 25°C and water viscosity are D_25,w = 4630 ± 130 sec^?1 and D_25,w = 5290 ± 260 sec^?1 for T3 and T7, respectively. The value obtained from shell model calculations (according to Filson and Bloomfield) is D_25,w = 4500 ± 600 sec^?1. The apparent permanent dipole moments are 4.5 × 10^?26 C·m and 1.7 × 10^?26 C·m for T3 and T7, respectively. For both phage particles the intrinsic optical anisotropy is +7.2 × 10^?3. It is shown that this anisotropy is mainly due to the DNA molecule inside the head of the phage. Its positive value means that there exists an excess orientation of the DNA helix perpendicular to the symmetry axis of the particle. For T7 an unexpectedly large increase of Δn_s and K_sp occurs at a glycerol concentration of about 30% (v/v). This increase is interpreted as being caused by a change of the shape of the particle and/or a change in the secondary structure of the DNA inside the head of the bacteriophage.     

Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.