Steroid-bovine serum albumin conjugates: molecular characterization and their interaction with androgen and estrogen receptors

Conjugates of testosterone-3-carboxymethyloxime (T-3-CMO), testosterone-17-hemisuccinate (T-17-HS), 17 beta-estradiol-6-carboxymethyloxime (E-6-CMO), or 17 beta-estradiol-17-hemisuccinate (E-17-HS) and bovine serum albumin (BSA) with varying steroid:protein ratios were prepared using the mixed anhydride method. Dialysis followed by molecular filtration yielded monomer steroid-BSA conjugates with a molecular weight of 70,000 dalton, and polymer conjugates with molecular weights of 140,000 dalton and higher. When conjugates were prepared with increasing initial steroid:BSA molar ratios the ratio of the obtained conjugates increased, in parallel with a decrease in the relative amount of monomers and an increase in the mean molecular size of polymers. The molecular properties of these conjugates were studied further by polyacrylamide gel electrophoresis (PAGE) in native and denaturing conditions. In native PAGE the monomer fractions showed one main band with a mobility slightly lower than BSA and a faint band corresponding with BSA-dimers. The polymer fractions consisted of a heterogeneous population of protein oligomers with molecular weights varying from 140,000 to over a million dalton. In the presence of sodium dodecylsulphate part of the polymers dissociated into monomers. In buffered aqueous solutions the bulk of the conjugate preparation retained its molecular size and composition, although the generated covalent bonds were found to be liable to spontaneous hydrolysis. Steroid-protein conjugates were shown to contain appreciable amounts of non protein-bound steroids. Binding of T-BSA to androgen receptors in rat ventral prostate cytosol was assayed using LH-20 chromatography and sucrose gradient centrifugation analysis. Binding of E-BSA to estrogen receptors was analysed with rat uterus cytosol using the dextran coated charcoal assay and the sucrose gradient centrifugation technique. Relative binding affinities (RBA) were analyzed in competition experiments using radiolabeled ligands. It was found that the molecular size of the conjugate does not influence its interaction with steroid receptors. Steroid coupled via the 17-position show a higher RBA to receptors than the T-3 or E-6 derivatives. The RBA of T-3-BSA, T-3-CMO, T-17-BSA and T-17-HS appeared to be very low, i.e. between 0.1 and 1.7% of the RBA of dihydrotestosterone. Consequently, high concentrations of conjugate are required to saturate androgen receptor binding sites. Under these conditions involvement of type II and eventually type III binding sites, which show less ligand specificity and lower affinity, may be anticipated preventing exclusive detection of androgen receptors.(ABSTRACT TRUNCATED AT 400 WORDS)     

Foraging-efficiency-predation-risk trade-off in the grey squirrel

Many animals must often respond to environmental patterns that simulatneously influence both foraging efficiency and predation risk. We noted that grey squirrels (Sciurus carolinensis) sometimes immediately consume food items in areas of relatively great exposure to predators, and at other times carry food items to the safety of a tree prior to consumption. We outlined a hypothesis that the squirrels were somehow trading-off energy intake rate against predation risk. A simple model shows that maximal energetic efficiency is associated with immediate consumption, whereas (under the field conditions studied) carrying items to the safety of trees provides for minimal exposure to predation. Our analysis of the model predicts that the tendency to carry a food item should decrease with distance of food from cover (travel time) and increase with item size (handling time). To test our predictions, we presented free-roaming grey squirrels with patches containing a fixed number of identical food items. We estimated the proportion of items carried to trees before consumption for 12 different combinations of distance to the nearest tree and item size. The results support our hypothesis and indicate that a simple behavioural criterion based solely on foraging rate or time exposed to predators is insufficient to explain the variation in the data.     

The isolation and genetic analysis of aCaenorhabditis elegants translocation (szT1) strain bearing an X-chromosome balancer

A single X-chromosome balancer-bearingCelegans ♂+, as a founder of a strain (AF1), was isolated directly from Fl progeny of irradiated+dpy-8unc-3/lon-2++ hermaphrodites on the basis of the absence of recombinant F2 categories. The balancer chromosome (Bal-X-1) suppresses recombination over a two-thirds section of the X chromosome (between genesdpy-8 andlet-2) and is associated with a reciprocal translocation between linkage groups (LG) X and I. Animals homozygous for the translocation (szT1(X:1)) are nonviable. Hermaphrodites heterozygous for the translocation segregate male selfprogeny at a frequency of 0.08-0.12.Bal-X-l carries the marker mutationlon-2(e678) and can be detected cytologically. This balancer chromosome proved useful for rnaimaininga number of X-linked lethal mutations and deficiencies inC. elegans.     

Studies of the cellulolytic system of Trichoderma reesei QM 9414. Reaction specificity and thermodynamics of interactions of small substrates and ligands with the 1,4-beta-glucan cellobiohydrolase II

The 1,4-beta-glucan cellobiohydrolase II (CBH II) from Trichoderma reesei QM 9414 catalyses the hydrolysis of the 4-methylumbelliferyl beta-D-glycosides derived from cellotriose, cellotetraose and cellopentaose [MeUmb(Glc)n; n = 3 - 5]. The reaction has been followed by quantitative high-performance liquid chromatography. Specific activity for cellobiose removal at apparent substrate saturation were determined as (0.8 +/- 0.2) min-1 for MeUmb(Glc)3 and (9 +/- 2) min-1 for MeUmb(Glc)4. The enzyme showed a deviant specificity with MeUmb(Glc)5 as substrate. Two chromophoric products were formed simultaneously [MeUmb(Glc)3 and MeUmb(Glc)2] with turn-over numbers (17 +/- 4) min-1 and (21 +/- 6) min-1, respectively. Methylumbelliferyl beta-glucoside (MeUmbGlc) and the corresponding cellobioside [MeUmb(Glc)2] were used in equilibrium binding experiments. Both ligands yielded one binding site per molecule of Mr = 54000 upon forced flow dialysis (diafiltration). The association constants found were in fair agreement with those determined from MeUmb fluorescence quenching titrations. Quenching was total at all temperatures investigated for MeUmb(Glc)2, whereas for MeUmbGlc it increased from 80% to 100% between 2 degrees C and 20 degrees C. The association constants fitted linear van't Hoff plots in both cases. MeUmb(Glc)2 and MeUmbGlc were also used as indicator ligands to determine the association constants and thermodynamic parameters of several non-chromophoric ligands of CBH II. The binding of glucose increased the affinity for MeUmb(Glc)2 whereas it displaced MeUmbGlc from its complex. A putative binding site of the CBH II containing four subsites can be proposed. The thermodynamic data for methyl beta-D-glucopyranoside and cellobiose as ligands also point at an extended binding site.     

Teratogenic and goitrogenic activity of propineb and propylenethiourea in the rat

The teratogenic and goitrogenic effects of Propineb, dithiocarbamate pesticide and Propylenthiourea (PLTU), its metabolite and degradation product have been studied. The aim of this study was to show the possible correlation between the two activities. Female Sprague-Dawley rats were treated with Propineb and PLTU starting from 6th to 16th day of pregnancy. The functional state of maternal and foetal thyroid, the toxicity of products versus dams and embryotoxic and teratogenic effects were examined. The observed goitrogenic effect may be compared to that reported in the previous studies of the authors, if considering time of sacrifice. In fact, the lesion quickly rises and as rapidly regresses when treatment is stopped. The foetal thyroid has not been affected by the product administered to the dams. PLTU showed a clear teratogenic activity at doses that did not show any maternal toxicity (45 and 90 mg/k).     

Release of dopamine, noradrenaline and dopamine B-hydroxylase from mouse neuroblastoma

The murine C1300 neuroblastoma tumor was found to secrete dopamine, noradrenaline and dopamine B-hydroxylase into the circulation of tumor-bearing A/J mice. The plasma levels of dopamine, noradrenaline and dopamine B-hydroxylase increased with the size of the tumor, and the increase in noradrenaline paralleled the increase in dopamine B-hydroxylase (r = 0.86). The vesicular storage of dopamine and noradrenaline in the tumor was evidenced by a decrease of the tissue content of dopamine and noradrenaline 24 hours after the administration of reserpine (5 micrograms/g) respectively to 17.6% and 7.8% of control values. A similar observation could be made for the levels of dopamine and noradrenaline in the plasma of reserpinized C1300 mice. The total activity of dopamine B-hydroxylase in the tumor and in plasma was unaffected by the reserpine treatment. Chronic administration of 6-hydroxydopamine (100 micrograms/g for 8 days) had no effect on the tissue contents of dopamine, noradrenaline or dopamine B-hydroxylase. The release of catecholamines and dopamine B-hydroxylase from the C1300 neuroblastoma was studied in vitro on superfused tumor slices. Stimulation of these slices with 56 mM KC1 or with 5.10(-5) M tyramine failed to induce the release of endogenous dopamine, noradrenaline or dopamine B-hydroxylase above the basal outflow levels. These results are suggestive for a non-exocytotic release of catecholamines and dopamine B-hydroxylase from the neuroblastoma tumor.     

Influence of carbohydrate side chains on activity of tissue-type plasminogen activator

When messenger RNA (mRNA) from both untreated and phorbol ester-treated melanoma cells is translated in simple reticulocyte lysates, tissue-type plasminogen activator can be immunoprecipitated by an affinity-purified antibody as a approximately 52,000 mol wt protein, with no detectable biological (plasminogen activating) activity. When the reticulocyte lysate system is supplemented with a preparation of microsomal membranes, biological activity becomes detectable and a 63,000 mol wt protein can be immunoprecipitated with the same antibody. Furthermore, when natural tissue-type plasminogen activator (mol wt approximately equal to 70,000) is incubated with different glycosidases, distinct alterations in the electrophoretic mobility of the molecules are observed, together with alterations in the level of biological activity. While treatment with neuraminidase and beta-galactosidase caused decreases in activity, alpha-mannosidase caused an increase. These results suggest that the carbohydrate part of the molecule can influence its biological behavior.     

IMP production and energy metabolism during exercise in rats in relation to age.

IMP production in and force exerted by rat quadriceps muscle in situ during various types of exercise were examined in relation to age. During continuous isometric exercise with constant stimulation time, the amount of IMP was linearly and inversely related to the age of the animals; a higher IMP concentration was found in intermittent isometric and dynamic exercise. No relationship was found between the total AMP deaminase activity and age. Exercise influenced neither the total activity nor the activity in the soluble fraction. From the results it is concluded that: the IMP concentration is linearly related to the free intracellular ATP4-/ADP3- ratio and the free AMP2- concentration; older animals are better able to maintain a high intramuscular ATP4-/ADP3- ratio and a low AMP2- concentration; IMP is produced in particular under conditions when the muscle has to work under extreme stress. IMP possibly exerts a feed-back control on the contraction system.