Incorporation of35S-sulphate in chick blastoderms during elongation and during shortening of the primitive streak

Summary Chick blastoderms were cultured for 2 h in the presence of³⁵S-sulphate. The distribution of the grains after light microscope autoradiography was compared in blastoderms during the elongation and during the shortening of the primitive streak. A uniform labeling was observed over the cells in both groups. Accumulation of grains was present in both groups at the ventral side of the upper layer, where transmission electron microscope studies have revealed a basal lamina. An additional accumulation of grains occurred over the cells and in the extracellular spaces of the head process and of the rostral part of blastoderms with shortening primitive streaks. This positivity could be correlated with the presence of ingressing and recently ingressed notochordal cells. Treatment of the sections with chondroitinase ABC and/or HNO₂ before dipping in the nuclear emulsion demonstrated that at least chondroitin sulphate and N-sulphated heparan sulphate were present.     

Age-related changes in responsiveness of rat Leydig cells to hCG

The responsiveness of decapsulated testes and isolated Leydig cell preparations from rats (30-80 days of age) to a constant dose of 3 ng hCG/2 ml was assessed by comparison of the production of testosterone and "total 17beta-hydroxy androgen" (17beta-HA). When testosterone secretion was used as the index of response, there was a marked increase in the production with age by decapsulated testes and also by equal numbers of Leydig cells. When 17beta-HA was taken as the response parameter this increase was only marginal for the decapsulated testes and there was an age-dependent decrease when expressed per 10(6) cells. These differences probably reflect changes in the metabolism of testosterone to 5alpha-reduced products with increasing age because 80% of androgen secreted at 30 days is 3alpha-androstanediol and 86% is secreted as testosterone at 80 days. We conclude that for studies on hCG responsiveness and the steroidogenic capacity of immature rat Leydig cells (a) testosterone is an inappropriate response parameter and (b) this response undergoes a decrease rather than an increase during prepubertal development.     

Effects of bleomycin on the epidermal content of growth-regulatory substances (chalones).

Hairless male mice were given 2 mg Bleomycin i.p. on two successive days. At different time intervals from 1 to 10 days after the last Bleomycin injection, groups of animals were killed and water extracts of hemogenized skin were made. These extracts, supposed to contain the epidermal G1 and G2 chalones, were injected into female hairless mice, and their growth inhibitory potency determined by two methods. 5 mg of lyophilized crude skin extract were injected i.p. together with Colcemid, and the animals killed 4 hr later. The number of Colcemid-arrested mitoses was determined, and was considered to be a measure of the G2 inhibitor present in the skin extracts. 10 mg of the same extracts were injected i.p., and these animals also got 3H-TdR i.p. 12 hr later, and were killed after a subsequent 30 min. The epidermal LI was determined, and was considered to be a measure of the epidermal G1 factor in the skin extracts. The results obtained were compared to the effect of Bleomycin alone and to the effects of skin extracts from non-Bleomycin-treated animals. The results show that Bleomycin provoked slight alterations in the growth-inhibitory potency of the G1 chalone, whereas significant effects were seen in the G2 chalone, There was an increased amount of growth-inhibiting factors on days 2 and 3, and on days 8-10. The results are discussed and it is concluded that the most probable hypothesis is that Bleomycin, in addition to its known inhibition by accumulation of cells with high growth inhibitory potency. An initial, additional direct effect of Bleomycin on the chalone system cammot be excluded.     

Estimation of levels of IgG to multiple sclerosis specific brain antigens in the cerebrospinal fluid of MS patients

The binding of partially purified multiple sclerosis (MS) specific brain antigens (MSG2) and of the corresponding antigens of non-MS brains (KG2) to cerebrospinal fluid IgG of patients with MS and other neurological diseases was assayed employing sandwich enzyme linked immunosorbent assay (ELISA). Assay of the antigen-antibody binding revealed that the concentration of MSG2 required for the optimum binding to IgG in the undiluted MS CSFs was lower than that of KG2 in all cases. The index for IgG binding capacity of an antigen (IgBC) was expressed as a ratio of the optical density of the enzymic products in ELISA at the optimal antigen-antibody binding to the lowest concentration of the antigen required for the optimal binding. The IgBC of MSG2 was found to be linearly correlated with the IgG concentration in the CSF of MS patients. These results indicate that IgG with specificity to MSG2 may be present in the CSF of MS patients.     

Resistance in tomato to the greenhouse whitefly: analysis of population dynamics

Life history parameters including longevity, developmental time, and reproduction were determined for whiteflies, Trialeurodes vaporariorum (Westwood), kept in clip-on cages on susceptible parent, Lycopersicon esculentum, resistant parent, L. hirsutum glabratum, and intermediate breeding lines of tomato. Using the Lewontin triangular reproductive function, the intrinsic rate of increase (r_m) was calculated for each genotype. This is an elegant tool for detecting resistance, as it incorporates all salient factors of life history. Comparing r_m to the other parameters measured, selection criteria were chosen. Developmental time is not a suitable selection criterion as it varies very little even between the most susceptible and the most resistant genotypes. Additionally, developmental time of T. vaporariorum offspring was found to be highly significantly correlated to parental age on all tomato genotypes except L. hirsutum glabratum. Total reproduction, truncated population counts, and longevity appear good criteria for selection. This test, focusing on antibiotic factors, shows large differences between the resistant and susceptible parent genotypes, but much smaller differences between the breeding lines and the susceptible parent. Earlier screenings relying on a variety of tests appear to have maintained antixenotic rather than antibiotic properties in the breeding lines.     

Electrogenic bicarbonate secretion in the turtle bladder: Apical membrane conductance characteristics

Summary We have recently shown that stimulation of electrogenic HCO ₃ ^– secretion is accompanied by a simultaneous increase in short-circuit current (I _sc, equivalent to HCO ₃ ^– secretion rate under these conditions), apical membrane capacitance (C _a , proportional to membrane area), and apical membrane conductance (G _a , proportional to membrane ionic permeability). The current experiments were undertaken to explore the ionic basis for the increase inG _a and the possibility that the rate of electrogenic HCO ₃ ^– secretion is regulated by changes inG _a . Membrane electrical parameters were measured using impedance-analysis techniques before and after stimulation of electrogenic HCO ₃ ^– secretion with cAMP in three solutions which contained different chloride concentrations. In another series of experiments, the effects of an anion channel blocker, anthracene-9-carboxylic acid (9-AA), were measured after stimulation of electrogenic HCO ₃ ^– secretion with cAMP. The major conclusions are: (i) a measurable apical Cl^– conductance exists in control hemibladders; (ii) the transport-associated increase inG _a includes a Cl^–-conductive component; (iii)G _a also appears to reflect a HCO ₃ ^– conductance; (iv) the relative magnitudes of the apical membrane conductances to Cl^– and HCO ₃ ^– are similar; (v) 9-AA reducesG _a andI _sc appear cAMP-stimulated hemibladders; and (vi) alterations inI _sc appear to be mediated by changes inG _a .     

A major stress-inducible Mr-42000 wall glycoprotein of French bean (Phaseolus vulgaris L.)

A major wall protein of suspension-cultured cells of French bean has been isolated and characterised. It can be prepared from walls or the culture filtrate and in composition it is particularly rich in proline, valine and glutamic acid/glutamine and contains appreciable amounts of hydroxyproline. The N-terminus shows some glycosylation, while following chemical deglycosylation the first 38 residues were found to be identical to those of proline-rich proteins from soybean. However, the composition of the highly purified M_r-42000 bean protein differs considerably from the soybean proteins and must contain its own specific domains. An antibody was raised and used to demonstrate the inducibility of the M_r-42000 bean protein in response to elicitor action. The protein was found to be mainly localised in the intercellular spaces of the cortical cells of bean hypocotyls and at the wall-plasmalemma interface of xylem vessels, another potentially accessible compartment for pathogens. Following wounding, the protein was found to be generally distributed in the wall of epidermal and cortical cells of the hypocotyls. The M_r-42000 protein is cross reactive with antibodies raised to glycoproteins of the Rhizobium infection thread and the chitin-binding hydroxyproline-rich glycoprotein, potato lectin. These common epitopes together with the previously demonstrated chitin-binding properties of the bean protein indicate a role in host-microbial interactions. Furthermore, the M_r-42000 protein itself bound to the growing hyphal tips of the bean pathogen, Colletotrichum lindemuthianum.Abbreviations FITC fluorescein isothiocyanate - IgG immunoglobulin G - PAL phenylalanine ammonia-lyase We thank Dr Nick Brewin for advice on interpretation of immunolocalisations and for the gift of MCA 265. We thank Dudley Fernandino for carrying out the confocal microscopy. GPB thanks the Science and Engineering Research Council for funding.     

Effects of excess selenomethionine on selenium status indicators in pregnant long-tailed macaques (Macaca fascicularis)

Forty pregnant long-tailed macaques were treated daily for 30 d with 0, 25, 150 or 300 μg selenium as L-selenomethionine/kg body weight. Erythrocyte and plasma selenium and glutathione peroxidase specific activities, hair and fecal selenium, and urinary selenium excretion were increased by and were linearly related to L-selenomethionine dose. Hair selenium was most sensitive to L-selenomethionine dose, with an 84-fold increase in the 300 μg selenium/(kg-d) group relative to controls (r=0.917). Daily urinary selenium excretion (80-fold,r=0.958), plasma selenium (22-fold,r=0.885), erythrocyte selenium (24-fold,r=0.920), and fecal selenium (18-fold,r=0.911) also responded strongly to L-selenomethionine. Erythrocyte and plasma glutathione peroxidase specific activities increased 154% and 69% over controls, respectively. Toxicity was associated with erythrocyte selenium >2.3 μg/mL, plasma selenium >2.8 μg/mL, and hair selenium >27 μg/g. Plasma, erythrocyte, and hair selenium concentrations may be useful for monitoring and preventing the toxicity of L-selenomethionine administered to humans in cancer chemoprevention trials.     

Description of the oöcysts of two new species of Eimeria (Apicomplexa: Eimeriidae) from the rough earth snake Virginia striatula (Serpentes: Colubridae) in Texas and Arkansas

Coccidian oöcysts recovered from the faeces of rough earth snakes Virginia striatula (Serpentes: Colubridae) were found to represent two previously unreported eimerians. Oöcysts of Eimeria desotoensis n. sp. were found in 5/32 (16%) of the snakes and were spherical to ellipsoidal, 18.4 × 17.2 (15–21.5 × 15–19.5) μm, with a thin, single-layered wall; their shape-index (length/width) was 1.07 (1.00–1.23). A micropyle and oöcyst residuum were absent; polar granule were present in 33% of the oöcysts. The sporocysts were ovoidal, 11.5 × 7.6 (10.5–13 × 7–8) μm, with a Stieda body; their shape-index was 1.51 (1.30–1.68). The sporocyst residuum was moderate in size and composed of a cluster of granules. Oöcysts of Eimeria hobartsmithi n. sp. were found in 2/32 (6%) of the snakes and were subspherical to ellipsoidal, 18.0 × 15.7 (16–20 × 15–17) μm, with a thin, single-layered wall; their shape-index was 1.15 (1.02–1.32). A micropyle, oöcyst residuum and polar granule were absent. The sporocysts were elongate, 13.2 × 6.3 (12–14.5 × 6–6.5) μm, with a Stieda body; their shape-index was 2.10 (1.88–2.34). A large sporocyst residuum was present in each sporocyst, often obscuring the sporozoites. In addition to the two new species, oöcysts of E. striatula Upton & McAllister, 1990 were observed in 38% of the snakes.