bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the tryptophan residues of soybean agglutinin. Involvement in saccharide binding
Authors: Swamy Musti Joginadha , Surolia Avadhesha
Published: February 2005

Modification of tryptophan side chains of soybean agglutinin (SBA) with N-bromosuccinimide results in a loss of the hemagglutinating and carbohydrate binding activities of the protein. One residue/subunit is probably essential for the binding activity. Modification leads to a large decrease in the fluorescene of the protein accompained by a blue shift. Iodide ion quenching of the protein fluorescence shows that saccharide binding results in a decreased accessibility of some of the tryptophan side chains. These results strongly point towards the involvement of tryptophan residues in the active site of SBA.
Somatostatin concentration and binding in the rat hypothalamus and striatum during severe insulin-induced hypoglycemia
Authors: Rodriguez-Sanchez M. N. , Arilla E.
Published: February 2005

Hypoglycemia was induced by administration of insulin (40 I.U./kg) to 24 h fasted rats. Somatostatinlike immunoreactivity (SLI) and125I-Tyr11-somatostatin binding were measured in the striatum and hypothalamus at the onset of hypoglycemic coma (5–10 min). No significant changes in SLI concentration were detected in either site although the total number of specific somatostatin receptors in the striatum membranes, but not in the hypothalamus, decreased in insulin-injected rats when compared with the control group.
Changes in lipoprotein binding and uptake by hepatocytes during rat liver regeneration
Authors: Trentalance A. , Bruscalupi G. , Devirgiliis L. Conti , Leoni S. , Mangiantini M. T. , Rossini L. , Spagnuolo S. , Erickson S. K.
Published: February 2005

The binding and uptake of cholesterol enriched lipoproteins by isolated hepatocytes was decreased at 16 hours after partial hepatectomy, with a tendency to return to control values as the regeneration proceeds. The number of lipoprotein binding sites of total cellular membranes remained similar to control at 16 and 24 hours. The plasma lipoprotein pattern, determined by electrophoretic analysis, showed a lower per cent of very low density lipoproteins (VLDL) and a higher per cent of low density lipoproteins (LDL) at 16 and 24 hours post-partial hepatectomy. At these times, plasma lecithin: cholesterol acyltransferase (LCAT) activity was decreased. It is intriguing to suggest that the regenerating liver could regulated the blood lipoprotein pattern and the uptake of lipoproteins by modulating the surface expression of the receptors.
A comparison of bradykinin, angiotensin II and muscarinic stimulation of cultured bovine adrenal chromaffin cells
Authors: O'Sullivan A. J. , Burgoyne R. D.
Published: February 2005

Bradykinin, angiotensin II and a mascarnic agonist, acetyl-B-methacholine (methacholine) were all found to elict catecholamine release from cultured bovine adrenal chromaffin cells. Bradykinin was the most potent of these secretagogues and methacholine the weakest, with angiotenin II intermediate in efficacy. All three secretagogues were much less effective than nicotinic stimulation. The three secretagogues all produced a rise in cytoplasmic free calcium concentration ([Ca2+]i), measured with the fluorescent indicator fura2, which was partially independent of external calcium. In the case of bradykinin the full rise in ([Ca2+]i) may involve a component of calcium entry in addition to release of calcium from an internal store. Secretion was also found to be partially independent of external calcium. The different efficacies of the three secretagogues in elicting secretion were correlated with the rise in ([Ca2+]i) produced. The differeing efficacies of the three secretagogues may be due to the extent of release of calcium from an intracellular store which itself is less effective in eliciting secretion than a rise in [Ca2+]i following calcium entry due to nicotine. Bradykinin also stimulates calcium entry, and this may increase the efficacy of the initial rise in [Ca2+]i. Treatment with pertussis toxin resulted in an enhancement of secretion in response to all of the secretagogues.
Concentrations of endogenous free amino acids in rabbit reticulocyte lysates and the effect of incubation
Authors: Mezl Vasek A. , Wall Jane
Published: February 2005

Amino acid analyses show that while the free amino acids found in the rabbit reticulocyte translation system do not increase during nuclease treatment or during prolonged storage, the endogenous levels of many amino acids are so high that the choice of a radioactive; precursor for a translation should be based not only on the abundance of the amino acid in the translation product but also on its concentration in the lysate preparation. It is shown that the variation of amino acid concentrations between different lysates is sufficiently small to allow one to use the concentrations reported in this study to calculate the amount of radioactive amino acid necessary for satisfactory incorporation.
Differential down-regulation and induction responses of testicular steroidogenic cytochromes P-450(cscc) and P-450(C17α) to human choriogonadotropin
Authors: Kühn-Velten Nikolaus , Bos Dagmar , Staib Wolfgang
Published: February 2005

Evidence is presented that the regulation of the cytochrome P-450(C17α) of the steroid-17α-monooxygenase and of the cytochrome P-450(cscc) of the cholesterolmonooxygenase by human choriogonadotropin (hCG) in vivo is mediated by differential mechanisms in the adult rat testis. An initial down-regulation of the cytochrome P-450(C17α) but not of the P-450(cscc) can be demonstrated. Furthermore, induction of the cytochrome P-450(cscc) requires exposure to higher hCG doses (3270 of the maximal induction rate of 43.7 pmol/(testis x d) are achieved with 4 IU hCG/single dose) than induction of the P-450(C17α) (59% of the maximal induction rate of 48.4 pmol/(testis x d) with 4 IU hCG/single dose), Finally, induction ofcytochrome P-450(cscc) starts faster after initiation of hCG treatment than induction of P-450(C 17α).
Scrapie-associated fibrils (SAF) purification method yields amyloid proteins from systemic and cerebral amyloidosis
Authors: Kitamoto Tetsuyuki , Hikita Kohtaro , Tashima Takatoshi , Tateishi Jun , Sato Yuji
Published: February 2005

We identified fibrils from non-transmissible systemic and cerebral amyloidosis using the purification method of scrapie-associated fibrils (SAF). The fibrils possessed the same nature of congophilia, filamentous structures and molecular weights as amyloid fibrils, and were resistant to Proteinase K digestion. This SAF method makes for a rapid extraction from amyloid-laden tissues. The method, therefore, may purify nontransmissible amyloids alone or together with SAF proteins.
Assembly of DNA onto the histone octamer facilitates the B-to-Z transition
Authors: Miller F. D. , Rattner J. B. , van de Sande J. H.
Published: February 2005

Nucleosomal core particles containing the right- and left-handed conformations of DNA were examined for their ability to support the B→Z or Z→B transition. Nucleosomes were assembled onto the B- and Z-conformations of poly[d(Gm5C)] and the B-conformation of poly[d(GC)] as previously described (1). Absorbance and circular dichroic spectroscopy indicated that the DNA on all three core particle populations could undergo the conformational B↔Z transition. Further, the right- to left-handed transition for both poly[d(Gm5C)] and poly[d(GC)] appeared to be facilitated by the DNAs association with the histone octamer. The DNA remained associated with the protein core subsequent to the transition, and electron microscopy and sedimentation velocity analysis indicated that there were no gross changes in nucleosomal structure. However, a change in the sedimentation value of the poly[d(Gm5C)] core particles was detected when the conformation of the DNA was altered from B to Z, resulting in a lower S20,w value for the Z-form particles than for the corresponding B-form particles.
Time dependent effect of indomethacin on the stimulation of protein synthesis in isolated rabbit muscle by insulin
Authors: Palmer R. M. , Bain P. , Reeds P. J.
Published: February 2005

Insulin (100 μU/ml) stimulated protein synthesis and PGF2α release in isolated rabbit muscle, but had little effect on the rate of protein degradation. The effect of insulin persisted for at least 5 h after removal of the hormone. Indomethacin, added at the start of the incubation, inhibited the stimulatory effect of insulin on protein synthesis and PGF2α release, but did not block the binding of iodinated insulin. When added 2 h after insulin, indomethacin did not inhibit the stimulation of protein synthesis but completely inhibited the increase in PGF2α release. The results suggest that the stimulation of protein synthesis by insulin is mediated by metabolites of membrane phospholipids but that these changes are involved during the phase of response that immediately follows the binding of insulin to its receptor.
Intrinsic fluorescence studies on saccharide binding toArtocarpus integrifolialectin
Authors: Sastry M. V. Krishna , Surolia A.
Published: February 2005

The combining region of Artocarpus integrifolia lectin has been studied by using the ligand-induced changes in the fluorescence of the lectin. The saccharide binding properties of the lectin show that C-l, C-2, C-4, and C-6 hydroxyl groups of D-galactose are important loci for sugar binding. The α-anorner of galactose binds more strongly than its β-counterpart. Inversion in the configuration at C-4 as in glucose results in a loss of binding to the lectin. The C-6 hydroxyl group is also presumably involved in binding as D-fucose does not bind to the lectin.

The lectin binds to the Thomsen-Friedenreich antigen (Galβ(1→3)GalNAc) more strongly than the other disaccharides studied, viz. Gal/β (1→4) Gal and Galβ (1→3) GlcNAc, which are topographically similar to T-antigen. This observation suggests that the combining region of Artocarpus lectin is complementary to that of T-antigen.

Solvent accessibility of the protein fluorophores have been probed by the quenching of protein fluorescence by Iodide ion in the absence and presence of sugar. In the presence of sugar a slight inaccessibility of the fluorophores to the solvent has been observed.
Pinocytic capture and exocytosis of rat immunoglobulin IgG-N-(2-hydroxy-propyl)methacrylamide copolymer conjugates by rat visceral yolk sacs culturedin vitro
Authors: Duncan Ruth , Cable Hazel C. , Strohalm Jiri , Kopeček Jindřich
Published: February 2005

Rat immunoglobulin (IgG) was covalently bound to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers via glycylglycyl spacer. The resultant conjugate, free IgG and HPMA copolymer (containing a low percentage of tyrosinamide to facilitate radiolabelling) were radioiodinated, and their rates of pinocytic uptake, intracellular degradation and exocytic release by rat visceral yolk sacs cultured in vitro were determined. Free IgG was pinocytosed rapidly by the yolk sac and some IgG was subject to intracellular proteolysis. In comparison the IgG-HPMA copolymer conjugate was captured more slowly, but faster than unmodified HPMA. IgG was also exocytosed rapidly by the yolk sac following pinocytic capture and similarly IgG-HPMA copolymer had a much higher rate of release than unmodified H PMA. Measurement of tissue accumulation of125I-labelled IgG-H PMA copolymer in the presence of increasing concentrations of non-radiolabelled IgG showed competition for membrane binding sites between the free, and polymer-bound immunoglobulin. These experiments indicate that immunoglobulins can be covalently bound to a soluble polymer developed as a drug-carrier in such a way that they can still interact with specific membrane receptors and they are subsequently subjected to specific cellular transport mechanisms.
Proteoglycan-collagen interactions in intervertebral disc. A chondroitin sulphate proteoglycan associates with collagen fibrils in rabbit annulus fibrosus at the d-e bands
Authors: Scott J. E. , Haigh M.
Published: February 2005

Rabbit annulus fibrosus and nucleus pulposus were analysed for hydroxyproline, chondroitin sulphate, keratan sulphate and dermatan sulphate. Tissue proteoglycans were stained for electron microscopy with Cupromeronic blue, used in the critical electrolyte concentration mode, with and without prior digestion by chondroitinase AC or ABC, hyaluronidase or keratanase. Collagen bands, a—e were demonstrated with UO2++. A chondroitin sulphate proteoglycan was found orthogonally associated with loosely packed collagen fibrils in annulus fibrosus at the d and e bands. The close metabolic and structural analogies with the dermatan sulphate proteoglycans previously shown to be located at collagen d-e bands in tendon, skin, etc. (Scott and Haigh (1985) Biosci. Rep.5:71–81), are discussed. Tightly packed annulus collagen fibrils were surrounded by axially oriented proteoglycan filaments, mostly without specific locations.
External anions relieve DIDS inhibition of SO4 efflux from placental membrane vesicles
Authors: Shennan D. B. , Boyd C. A. R.
Published: February 2005

Sulphate efflux from human placental microvillus membrane vesicles was inhibited by external DIDS (KI≅10−6 M). This inhibition was partially reversed on addition of the translocated substrates sulphate or selenate to the external medium: selenite which is not translocated does not protect against DIDS inhibition. These findings show that the mechanism responsible for sulphate efflux can be modified by substrate in the external medium.
Characterization of a membrane-specific tubulin isoform by peptide mapping
Authors: Hargreaves Alan J. , Avila Jesus
Published: February 2005

A membrane-specific tubulin-like protein, found in preparations of synaptic plasma membranes and brain mitochondria, was analyzed by chemical and proteolytic peptide mapping to determine which part of the molecule was different from cytoplasmic tubulin. The membrane polypeptide was identical to alpha tubulin in the first two-thirds of the molecule containing the amino terminal, as found by peptide mapping. However, some differences were observed in the peptide maps of the carboxy terminal one third of the molecule which includes a domain that is important in the regulation of tubulin self-assembly.
Amino acid transport systems of lysosomes: Possible substitute utility of a surviving transport system for one congenitally defective or absent
Authors: Christensen Halvor N.
Published: February 2005

Ways in which other transport systems may compensate for one that is genetically defective are considered. Comparisons of the transport systems of organelles (here the lysosome) with the transport system at the plasma membrane has significant implications for chemotherapy.
Leishmania donovani: Superoxide dismutase level in infected macrophages
Authors: Mukherjee Subrata , Bandyapadhyay Rajyasree , Basu Mukul Kumar
Published: February 2005

Superoxide dismutase (SOD), a metal containing enzyme is present in parasite Leishmania donovani as well as in host macrophages both resident and activated in a detectable amount, although the level is much higher in the latter case. It is observed that at any particular protein concentration, the SOD activity is highest in the case of parasite infected macrophages and lowest in the case of normal resident macrophages; the SOD activity of thioglycolate activated macrophages lies in between the two. It is also noticed that formalin-killed Leishmania donovani neither attach to macrophages nor do they increase the SOD activity of the host. Thus, the processes, e.g. attachment of the parasite to the host membrane, subsequent membrane perturbation and thus activation of membrane bound enzyme NADPH oxidase leading to respiratory burst, may be responsible for an enormous increase in the SOD level in macrophages during infection. Moreover, the chemical nature of the SOD found in infected macrophages has been investigated by using an inhibitor, e.g. NaCN, which specifically inhibits Cu-Zn SOD but not Fe-SOD. A considerable inhibition of SOD activity by NaCN in infected macrophages confirms the chemical nature of the increased SOD to be of Cu-Zn type, usually found in host. Presumably, Cu-Zn SOD or host SOD plays a protective role at the time of parasite infection although the role of parasitic SOD or some other mechanisms for the survival of the parasite within the toxic phagolysosome environment, of the macrophage cannot be ruled out.
The half-lives of dolichol and dolichyl phosphate in rat liver
Authors: Edlund Conny , Brunk Ulf , Chojnacki Tadeusz , Dallner Gustav
Published: February 2005

Rat liver dolichol and dolichyl-P were labeled by injection of [3H]mevalonate into the portal vein and their rates of synthesis and breakdown determined. In the initial phase the radioactivity appeared in α-unsaturated polyprenols. Subsequent saturation required 90 min. The half-lives of dolichols in microsomes were between 80 and 118 h, and shorter dolichols had shorter values of T1/2. The half-lives of dolichols in lysosomes were between 115 and 137 h, while microsomal dolichyl-P exhibited a T1/2 of 32 h. Injected dolichol was recovered in the lysomes of hepatocytes and exhibited a rate of breakdown which was slower than that of the endogenous compound. These results indicate differences in the catabolism of dolichol at different subcellular locations, as well as differences between the catabolism of dolichol and dolichyl-P.
Proteolytic specificity of chicken cathepsin L on bovine β-casein
Authors: Dufour Eric , Ribadeau-Dumas Bruno
Published: February 2005

The proteolytic specificity of chicken cathepsin L was studied using bovine β-casein as substrate. The peptide mixtures obtained after various times of hydrolysis were separated by RP-HPLC and ten peptides were identified. Chicken cathepsin L accepts proline residues in all positions except P1′. Looking at the amino acid residues on the amino side of the scissile bond we found three times the Tyr-Pro pair at P1′–P2′ positions and that the S1′ subsite can interact with modified amino acids such as phosphoserine.
Do asparagine-linked carbohydrate chains in glycoproteins have a preference for β-bends?
Authors: Beintema Jaap J.
Published: February 2005

X-ray structures of the conformation of carbohydrate moieties and connected regions of glycoproteins are summarized. Evidence is presented that there is some preference for carbohydrate attachment at β-bends. Evolution may have favored glycosylation to occur at bends to ensure free mobility of the carbohydrate moieties.
Inhibition of muscle tropomyosin polymerization by DNAse I
Authors: Payne Michael R. , Rudnick Suzanne E.
Published: February 2005

Tropomyosin polymerization is inhibited by DNAse I, an endonuclease which also interacts with G-actin. A 1:4 molar ratio of DNAse I to adult chicken pectoralis muscle tropomyosin almost completely prevents the increased viscosity of tropomyosin under polymerizing ionic conditions. While G-actin binding to DNAse I inhibits the DNAse I hydrolysis of DNA, tropomyosin does not affect this enzymatic activity. G-actin-DNAse I interaction is also not altered by tropomyosin.
Interaction of thymic peptide thymosin α1 with vasoactive intestinal peptide (VIP) receptors
Authors: Calvo J. R. , Goberna R. , Guerrero J. M.
Published: February 2005

Thymic peptide thymosin α1 (10−9 to 3 × 1010−7 M) is shown to inhibit the specific binding of [125I]VIP to rat blood mononuclear cells and liver plasma membranes. Thymosin α1 was 160 and 6250 times less potent that VIP at inhibiting [125I]VIP binding to blood mononuclear cells and liver plasma membranes, respectively. Thymosin α1 (10−10 to 1010−7 M) was weak in stimulating adenylate cyclase activity. Its efficacy is about 25 % and 27 % that of native VIP in blood mononuclear cells and liver plasma membranes, respectively. Thymosin α1 may behave as a partial VIP agonist in rat.
Regulation of acyl CoA: Cholesterol acyl transferase (ACAT) activity by mevalonate and cholesterol in isolated rat hepatocytes during perinatal development
Authors: Bruscalupi G. , Devirgiliis L. Conti , Leoni S. , Piemonte F. , Trentalance A.
Published: February 2005

Acyl CoA: cholesterol acyl transferase (ACAT) activity presents marked oscillations and differential sensitivity to the “in vitro” stimulation of the kinase-phosphatase modulatory system in the perinatal rat liver.

The regulation of this enzyme activity by some modulators generally active in adulthood, such as cholesterol, lipoproteins and mevalonate, has been studied in hepatocytes isolated at different developmental stages. A lack of effect of mevalonate and a positive effort of lipoprotein cholesterol have been observed at the fetal and neonatal stages.

A differential prevalence is suggested of one of the two modulatory mechanisms (phosphorylation-dephosphorylation system, or substrate effect) at each developmental stage.
Rapid purification and properties of protein kinase C from bovine adrenal medulla
Authors: Brocklehurst Keith W. , Lee George , Pollard Harvey B.
Published: February 2005

Protein kinase C was purified from bovine adrenal medulla using a rapid procedure which resulted in an approximate 1500-fold increase in specific activity. The characteristics of the enzyme are reported and for the first time it is possible to compare the effects of TPA on secretion from intact and permeabilized cells with the effect of TPA on protein kinase C purified from the same secretory tissue.
Monoclonal antibodies to the two most basic papaya proteinases
Authors: Goodenough Peter W. , Kilshaw Peter J. , McEwan Fiona , Jane Owen A.
Published: February 2005

The proteinases from Carica papaya include papain, isoenzymes of chymopapain and two proteinases A and B distinguished by their unusually high pI. The identity of one of the most basic proteinases has been questioned. The present report describes the preparation and characterisation of two monoclonal antibodies that react specifically with papaya proteinases A and B respectively and a third that identifies a common structural feature found in papain and proteinase A.
The effect of streptozotocin-induced diabetes on hepatic hexose transport
Authors: Europe-Finner G. N.
Published: February 2005

3-O-methyl-D-glucose (which is not metabolized in isolated parenchymal cells) was used to characterize the hexose transport process in hepatocytes prepared from 24 h fasted rats. The Vmax and Km obtained were 161 ± 12 nmol/mg dry wt./min and 39 ± 4 mM respectively (Europe-Finner GN, 1984, Biosci. Rep. 4, 4833–489). Streptozotocin-induced diabetes decreased the Km of the system by 50% to a value of 19 ± 6 mM without causing any change in the Vmax, Short term insulin treatment of cells prepared from 24 h diabetic rats appeared to partially return the system to normal.
The amino acid sequence of human sperm protamine P1
Authors: McKay D. J. , Renaux B. S. , Dixon G. H.
Published: February 2005

Human sperm protamines have been extracted from spermatozoa pooled from several donors, converted to their S-pyridylethylated derivatives and resolved into two major components, P1 and PI, by Bio-Rex 70 chromatography. Protamine P1 was further purified by Bio-Gel P-10 chromatography and sequenced directly on a gas phase protein sequencer for 43 residues. To complete the sequence, P1 was cleaved at methionine 36 and the C-terminal tetradecapeptide was purified by h.p.i.c, and sequenced completely. The 50 residue sequence is: 10 20 30 40 ARYRC CRSQS RSRYY RQRQR SRRRR RRSCQ TRRRA MRCCR 50 PRYRP RCRRH. This sequence has a calculated molecular weight of 6674 and is homologous with four other published mammalian protamine sequences.
Shape transformation of erythrocyte ghosts depends on ion concentrations
Authors: Herrmann Andreas , Müller Peter , Glaser Roland
Published: February 2005

Resealed human erythrocyte ghosts undergo shape transformations similar to those of intact erythrocytes. The results indicate that the shape of these ghosts depends on the inner as well as on the outer NaCl concentration. A correlation between shape and calculated transmembrane potential was established similar to that for intact human erythrocytes.
Influence of the intracellular and extracellular cation concentration on monovalent cation efflux of resealed human erythrocyte ghosts
Authors: Müller Peter , Herrmann Andreas , Bernhardt Ingolf , Glaser Roland
Published: February 2005

Tracer efflux measurements (86Rb+ and2NaNa+) were performed on resealed human erythrocyte ghosts at different intra- and extracellular NaCI concentrations. Using a modified Goldman equation the observed alterations of the rate constants could be explained by taking into account the transmembrane and surface potentials, at constant permeability coefficient. These results emphasize the importance of membrane surface potentials in triggering ion transport across biological membranes.
Impaired muscle glucose metabolism in acute renal failure
Authors: Palmer T. Norman , Caldecourt Margaret A. , Gossain Savita , Mangat Sheila , Sugden C.
Published: February 2005

Renal failure is associated with peripheral insulin resistance and consequent carbohydrate intolerance. This report investigates carbohydrate metabolism in vitro in epitrochlearis and hemidiaphragm muscles taken from acutely uraemic and sham-operated rats. Muscles from acutely uraemic rats (compared to those from sham-operated rats) incubated with 5 mM glucose showed increased rates of basal and insulin-stimulated glycolysis and glycogen turnover, but pyruvate dehydro-genase and tricarboxylic acid – cycle flux was not increased in uraemia. Glycolysis (but not glycogen turnover) in muscles from acutely uraemic rats tended to show decreased responsiveness to stimulation by insulin. It is concluded that acute uraemia is associ-ated with a defect(s) in muscle that produces intrinsic insulin resistance and results in diversion of glucose (both in basal and insulin-stimulated states) from glycogen synthesis into glycolysis.
Cholesterol as a target for toxins
Authors: de Kruijff B.
Published: February 2005

A mechanism is proposed for the way in which cholesterol facilitates channel formation by polyene antibiotics and bacterial protein toxins. Central elements of the model are: (i) interactions between the ring system of the sterol and rigid elements of the polyene or toxin molecule, and (ii) the specific orientation of cholesterol within the membrane.
Partial purification of a boar sperm membrane protein inducing sperm agglutinating antibody
Authors: Adeyemo Oyewole , Okegbile E. O. , Olorunsogo O. O.
Published: February 2005

For the development of immunological contraception, attention is being concentrated on the possibility of using a sperm membrane antigen. Boar sperm membrane was extracted with triton-X 100 and fractionated by Sephadex G-150 column chromatography. The glycosylated and nonglycosylated portions of protein peaks from the gel filtration were obtained by fractionating on concanavalin A-Sepharose and eluting the bound protein with 0.3 M methyl mannoside. A glycosylated fraction was found to induce sperm agglutinating antibodies in rabbit. The partially purified protein has a molecular weight of 30 kilodaltons, as determined by sodium dodecyl polyaccyrlamide gel electrophoresis. Further work is planned on the histochemical determination of the origin of this protein and species cross-activity of the antibody.
Interaction of free fatty acids with the erythrocyte membrane as affected by hyperthermia and ionizing radiation
Authors: Rybczynska Maria , Csordas Adam
Published: February 2005

The interference of hyperthermia and ionizing radiation, respectively, with the effects of capric (10:0), lauric (12:0), myristic (14:0), oleic (cis-18:1) and elaidic (trans-18:1) acids on the osmotic resistance of human erythrocytes was investigated. The results are summarized as follows: (A) not only at 37°, but also at 42° and 47°C lauric acid (12:0) represents the minimum chain length for the biphasic behaviour of protecting against hypotonic hemolysis at a certain lower concentration range and hemolysis promotion at subsequent higher concentrations; (B) with increasing temperatures the protecting as well as the hemolytic effects occur at lower concentrations of the fatty acids; (C) the increase of temperature promotes the extent of hemolysis and reduces the extent of protection against hypotonic hemolysis; (D) Gamma-irradiation of erythrocytes selectively affects the concentration of oleic acid at which maximum protection against hypotonic hemolysis occurs, without altering the minimum concentration for 100% hemolysis.
Different effects of chlorpromazine on bleomycin-and epirubicin induced cytotoxicity
Authors: Grankvist Kjell , Bergström Per , Henriksson Roger
Published: February 2005

The effect of the antiemetic chlorpromazine on bleomycin- and epirubicin cytotoxicity was tested in vitro. Chlorpromazine (0.1 or 0.01 mg/l) enhanced epirubicin-induced toxicity to cultured Chinese fibroblasts whereas 0.01 mg/l chlorpromazine inhibited the cytotoxicity of bleomycin. The results encourage further studies on the effects of commonly used antiemetics on the cytotoxicity and antitumoral effects of anticancer chemotherapeutics.
Combined use of oligo(dt) and 28S cDNA probes for the quantitation of total mRNA in polyribosomes: Application to the castration-induced atrophy of the rat prostate
Authors: Boissonneault Guylain , Tremblay Roland R.
Published: February 2005

The castration-induced atrophy of the rat prostate was used as a model for the validation of a sensitive technique allowing the quantitation of total mRNA in polyribosomes. Electron micrographs of polyribosome samples showed a decrease in polyribosomes length 7 days after castration (GDX). Specificity of labeled oligo(dt) probe for poly(A) was demonstrated and the technique was successfully applied to demonstrate that GDX is associated with a decrease in poly(A) mRNA content of polyribosomes. Provided that normalization of the hybridization signal for mRNA is achieved with a rRNA cDNA probe, the assay therefore represents a suitable tool for further studies regarding the translational regulation of total and/or specific mRNAs.
Verapamil and cyclosporin a sensitize human kidney tumor cells to vincristine in absence of membrane P-glycoprotein and without apparent changes in the cytoplasmic free Ca2+ concentration
Authors: Nygren P. , Larsson R.
Published: February 2005

Vincristine (Vcr) dose dependently inhibited growth of the kidney adenocarcinoma cell line ACHN during 4 days of culture. Verapamil (Ver) at 10 μM and cyclosporin A (CsA) at 1 μg/ml had no effect on cell growth but significantly potentiated the action of Vcr, despite the absence of the multidrug resistance associated membrane P-glycoprotein (P-gp). Neither Ver nor CsA had any acute or long term effects on cytoplasmic free Ca2+ concentration (Ca2+i), except for a small Ver induced increase after 36 h of incubation. The results indicate that Ver and CsA may have a sensitizing effect on chemotherapeutic drug sensitivity also in absence of P-gp. However, these effects are probably not mediated by changes in Ca2+i.
Retroviruses and oncogenes II
Authors: Bishop J. Michael
Published: February 2005

The relationship between retroviral genes and oncogenes is described.
Heat shock proteins induce pores in membranes
Authors: Alder G. M. , Austen B. M. , Bashford C. L. , Mehlert A. , Pasternak C. A.
Published: February 2005

Human heat shock protein (hsp) 70 and bacterial protein groEL promote leakage of calcein from liposomes induced by human serum albumin signal peptide, by S. aureus α toxin or by diphtheria toxin. Hsp 70 and groEL, as well as two mycobacterial homologues hsp 71 and hsp 65, induce ion conducting pores across planar lipid bilayers at low or neutral pH. It is concluded that hsp induce pores in membranes and that this may contribute to their action within cells.
Nucleotide regulation of vasoactive intestinal peptide binding to bovine thyroid plasma membranes
Authors: Calvo Juan R. , Morales María F. , Mesa Juan C. , Goberna Raimundo
Published: February 2005

The specific binding of vasoactive intestinal peptide (VIP) to bovine thyroid plasma membranes is inhibited by guanine nucleotides. Guanosine 5′-triphosphate (GTP) and the non-hydrolyzable GTP analogs guanosine 5′-β,γ-imidotriphosphate (Gpp(NH)p) and guanosine 5′-O-(3-thiotriphosphate) (GTP-γ-S) inhibited markedly the binding of VIP to its receptors. This inhibition was higher with GTP than with Gpp(NH)p and GTP-γ-S and was due to an increase of the rate of dissociation of peptide bound to membranes. Other nucleotides did not show any effect.
Cationic and anionic amino acid transport studies in rat red blood cells
Authors: Felipe Antonio , Viñas Octavi , Remesar Xavier
Published: February 2005

The transport of L-proline, L-lysine and L-glutamate in rat red blood cells has been studied. L-proline and L-lysine uptake were Na+-independent. When the concentration dependence was studied both showed a non-saturable uptake assimilable to a difussion-like process, with high Kd values (0.718 and 0.191 min−1 for L-proline and L-lysine respectively). Rat red blood cells showed high impermeability to L-glutamate. No sodium dependence was observed and the Kd value was low (0.067 min−1). Our results show firstly, that rat red blood cells do not have amino acid transport systems for anionic and cationic amino acids and secondly that erythrocytes show no sodium-dependent L-proline transport, and that these cells are very permeable to this amino acid.
Modularity of osteoclast behaviour and “mode-specific” inhibition of osteoclast function
Authors: Zaidi Mone
Published: February 2005

This study is part of an attempt to understand the role of specific cellular activities in the bone resorptive process. Experiments were performed whereby known pharmacological agents were used to inhibit individual modes of osteoclastic activity, such as motility and secretion. The effects of such treatments on bone resorption were assessed by quantitative scanning electron microscopy. The compounds included colchicine, which was used to inhibit osteoclast motility; molybdate ions which were used to selectively inhibit the catalytic activity of secreted acid phosphatase, and omeprazole which was employed to inhibit the secretion of hydrogen ions. All compounds inhibited osteoclastic bone resorption, but singularly affected defined modes of activity. These findings suggest that each mode of osteoclastic activity is essential for the bone resorptive process, and that “mode-specific” inhibition may provide a means whereby excessive activity of the osteoclast can be regulated in disease.
Transglutaminase involvement in the secretion of insulin from electropermeabilised rat islets of langerhans
Authors: Lindsay Mark A. , Bungay Peter J. , Griffin Martin
Published: February 2005

Ca2+-Induced insulin release from electropermeabilised islets is inhibited by the transglutaminase inhibitors monodansylcadaverine, glycine methylester, methylamine and cystamine but not by the control compounds dimethyl monodansylcadaverine and sarcosine methylester which lack the primary amine group. Neither monodansylcadaverine nor glycine methylester inhibited insulin secretion induced by either cAMP or the phorbol ester PMA at basal levels (10 nM) of Ca2+. These data provide further evidence for the involvement of transglutaminase in Ca2+ induced insulin secretion, they also suggest that insulin secretion induced by either cAMP or PMA may act in part by a mechanism independent of that induced by Ca2+.
Further evidence for abnormal protein kinase C regulation of macromolecule secretion in fibroblasts from cystic fibrosis patients
Authors: Bertrand F. , Hermelin B. , Paul A. , Garcia I. , Capeau J. , Cherqui G. , Picard J.
Published: February 2005

In comparison to skin fibroblasts from normal subjects, those from patients with cystic fibrosis (CF): (1) bound [20-3H] phorbol 12,13-dibutyrate (PDBu) with a higher affinity (Kd=25.8 vs 12.8 nM respectively) but expressed a similar number of total phorbol ester binding sites (about 2.5 pmol PDBu bound/mg of protein); (2) exhibited a faster and higher response to 4?-phorbol 12?-myristate 13?-acetate (PMA) for the stimulation of [35S]-labelled glycoconjutate release, but were equally sensitive to the synergistic effect of A23187 on this process; and (3) secreted glycoconjugates with similar [35S]-sulfate and [14C]-leucine to [14C]-glucosamine labelling ratios. Taken together, these results provide further evidence for abnormal protein kinase C (PKC) regulation of macromolecule secretion in CF disease.
Oxygen-centred free radicals can efficiently degrade the polypeptide of proteoglycans in whole cartilage
Authors: Dean Roger T. , Roberts Clive R. , Forni Luigi G.
Published: February 2005

Bovine nasal cartilage slices, biosynthetically labelled in their proteoglycan with35SO4, were used as substrate for the attack of free radicals generated on exposure to a Co60 source (which allows study of single radical species), and by chemical and enzymatic means. Systems generating hydroxyl (OH•) and superoxide (02•-) radicals degraded the proteoglycan efficiently, while the hydroperoxy radical (HO2•) was less efficient; addition of appropriate radical scavengers inhibited degradation. The radioactive products were heterogeneous in molecular size, but with doses up to 3600 Gy were the same size range as intact chondroitin sulphate. They contained free amino groups, and more were liberated by aminopeptidase M digestion, implying that at least a small peptide was present. Thus a major site of radical attack may be the polypeptide chain. We suggest that free-radical fragmentation of polypeptides may be important both in extracellular catabolism and in intracellular proteolysis.
Antibodies to guanylic acid: Fractionation and specificities
Authors: Iswari S. , Jacob T. M.
Published: February 2005

Guanylic-acid-specific antibodies were elicited in rabbits) using as immunogen pG linked through 5′-phosphate to thyroglobulin. Specificity and affinity of antibodies to nucleotides) nucleosides, DNA, and RNA were studied by their binding to radioactive ligands and competition experiments. Guanylic-acid-specific antibodies do not bind to deoxyguanylic acid and have an average association constant of 107 M−1 at 4°C Binding of the antibodies to3H-RNA is G-specifiC. The antibodies do not bind to32P-ssDNA or32P-dsDNA. The pG-specific antibodies could be separated into different fractions by affinity chromatography. These fractions) though specific to pG) differ in their cross-reactivities to nucleosides and nucleotides.
Post-meiotic transcription in mouse testes detected with spermatid cDNA clones
Authors: Fujimoto Hirokazu , Erickson Robert P. , Quinto Marie , Rosenberg Michael P.
Published: February 2005

cDNA clones to poly(A)+ mRNA from spermatids have been obtained to study gene transcription in post-meiotic germ cells. Four cDNA clones detect mRNAs that increase in abundance in post-meiotic germ cells. One clone, pPM459, was shown to correspond to an mRNA that is transcribed after meiosis. Pulse-labelling experiments demonstrate transcription o5 the message in spermatids. These data constitute further evidence for post-meiotic gene transcription in spermatids.
Effects of actinomycin D and cycloheximide on the increase in tyrosinase activity of hamster amelanotic
Authors: Słomiñski A. , Bomirski A. , Ścisłowski P. W. D. , Żołnierowicz S.
Published: February 2005

Tyrosinase activity in the Ab hamster amelanotic melanoma ceils cultured in serum-free Eagle's MEM increased 3 times after 6 h of primary cell culture. This increase was inhibited completely by cycloheximide, while actinomycin D had no effect on this process. After 24 h of culture in MEM with calf serum, further increase of the tyrosinase activity was inhibited by both cycloheximide and actinomycin D. The data presented may indicate that the increase of tyrosinase activity in the primary cell culture of the Ab melanoma is due initially to the unblocking of translation and later to the activation of transcription of the gene controlling the enzyme.
The binding of insulin-like growth factor II to the erythroleukemia cell line K562
Authors: Tally Michael , Xin-Zhi Tang , Enberg Gösta , Hall Kerstin
Published: February 2005

The erythroleukemia cell line K562 was previously shown to have specific binding sites for insulin but not for insulin-like growth factor I (IGF-I). In this study the presence of specific receptors for insulin-like growth factor II (IGFqI) is established. Scatchard analysis of the competition curve for IGF-II disclosed a non-cooperative binding kinetic with a calculated affinity constant of 2.4 × 108 M−1 and a receptor number of 4.8 × 104 sites/cell. IGF-I displayed 10% crossreactivity over the IGF-II receptor but insulin did not crossreact at all. Instead insulin, present in high concentrations, enhanced the binding of IGF-II. The presence of IGF II but not IGF-I receptors makes the K562 cell line suitable for studying properties of the type-2 receptor.
Role of cyclic AMP in the action of dopaminergic D2 receptors of some endocrine glands in rats
Authors: Abu-Jayyab Abdulrahim , El-Denshary Ezz-Eddin S. M. , Ageel Abdulrahman M. , Dakkak Mohamed Rafik
Published: February 2005

Short-term and long-term effects of bromocriptine mesylate (10 mg/kg i.p.) on cyclic AMP contents of the liver and some endocrine glands have been investigated in the presence and absence of sulpiride (10 mg/kg i.p.). Results revealed that bromocriptine caused significant elevations in the cyclic AMP contents of the liver and reduction in its adrenocortical content. Bromocriptine effect on the adrenal cortex was antagonized by sulpiride, whereas its effect on the liver was not changed. Bromocriptine did not change the, cyclic AMP content in the thyroid gland or the ovary.
Can viral envelope proteins act as or induce proton channels?
Authors: Kempf C. , Michel M. R. , Kohler U. , Koblet H.
Published: February 2005

The mechanism of the process leading to cell-cell fusion induced by enveloped viruses at a mildly acidic pH is as yet unknown. In this report we demonstrate that the fusion events induced by three viruses of different families, namely Semliki Forest (togavirus), vesicular stomatitis (rhabdovirus) and influenza (orthomyxovirus), share common features. In all three systems a sudden drop of the intracellular pH—below the critical eextracellular pH required to trigger “fusion from within” (FFWI)—is observed. This influx of protons is specific and not due to a general leakiness of the plasma membrane, and therefore might be caused by the opening of a proton channel.
Evidence for the involvement of calmodulin in natural cytotoxicity using a range of calmodulin antagonists of varying potency and improved specificity
Authors: Rees Robert C. , Parker Simon , Platts Andrew , Blackburn Michael G. , MacNeil Sheila
Published: February 2005

The calmodulin antagonist W7 and 4 of its analogues were examined for their ability to inhibit human NK cell mediated cytotoxicity. With the exception of one of these compounds, which is extremely hydrophobic, there was a good correlation between the ability of drugs to inhibit human NK antitumour cytotoxicity and calmodulin-dependent phosphodiesterase activity in vitro. The most potent of the compounds, 5-iodo-l-C8, an analogue of W7, has an IC50 of 3 μM upon biological and biochemical assay. This particular compound is both more potent and specific than the parent compound W7, is non-toxic to cells over the range used and is also capable of inhibiting the biological activity of NK cells upon pre-treatment of the effector cells, inferring the mechanism of NK cytotoxicity to be calmodulin dependent.
The role of lysolecithin in the relaxation of vascular smooth muscle
Authors: Bing Richard J. , Saeed Maythem
Published: February 2005

The effect of lysolecithin (lysophosphatidylcholine) on the relaxation of rabbit aortic strip closely resembled that produced by acetylcholine (ACh) which releases the endothelium-derived relaxing factor (EDRF). Relaxation induced by lysolecithin depended on the presence of endothelium and was inhibited by hemoglobin and methylene blue. It appeared to be mediated by the second messenger, c-GMP. Lysolecithin induced relaxation was slower but more persistent than that resulting from the endothelium-derived relaxing factor (EDRF) produced by acetylcholine (ACh). Like lysolecithin, Triton X-100, a non-ionic detergent, also preferentially relaxed aortic strips with intact endothelium. The results demonstrate the importance of phospholipids derived from cell membranes in vascular smooth muscle relaxation. Endothelium-derived relaxing factors appear as a group of heterogeneous substances.
Characterization and age dependence of the stimulatory effect of VIP on cyclic AMP accumulation in rat Leydig cells
Authors: Hueso C. , Carmena M. J. , Prieto J. C.
Published: February 2005

The neuropeptide vasoactive intestinal peptide (VIP) has been shown to stimulate cyclic AMP accumulation in Leydig cells isolated from rat testis. The effect was dependent on time, temperature and cell concentration. At 15° half-maximal and maximal stimulation were observed at about 1 and 100 nM VIP, respectively. The interaction was specific since an order of potencies chicken VIP> rat VIP> secretin>glucagon and no effect of neurotensin and substance P were obtained. The efficiency of VIP was lower in pubertal rats and then increased in young-adult and adult animals. These results together with the known presence of VIP in the testis support the idea that VIP may be involved in the regulation and function of Leydig cells during development.
Myelin Basic Protein inhibits the calcium response to phytohaemagglutinin in human lymphocytes
Authors: Bellini Tiziana , Degani Diana , Matteuzzi Maurizio , Dallocchio Franco
Published: February 2005

Myelin Basic Protein, one of the major membrane protein component of the central nervous system, was used to probe the molecular mechanism of cellular activation by phytohaemagglutinin.

Pre-treatment of human lymphocytes with myelin basic protein results in a lower rising of cytosolic concentration of free calcium after stimulation with phytohaemagglutinin.

This effect is dependent on myelin basic protein concentration and on the preincubation time of the protein with the cells. It is not due to a interaction between myelin basic protein and phytohaemagglutinin, but appears to be a consequence of the binding of the protein to the cell surface.

The reduction of the rise of cytosolic calcium induced by phytohaemagglutinin is specific for the myelin basic protein because other proteins like albumin and protamine have no effect.
Effects of mitogenic agents upon glucocorticoid action in human tonsillar T-lymphocytes
Authors: Altiok S. , Bermek E.
Published: February 2005

The treatment of human tonsillar T-lymphocytes with 4-phorbol 12-myristate 13-acetate (PMA), resulted in about two fold increase in glucocorticoid receptor (GR) number, without any significant change in the receptor affinity. This increase disappeared in the presence of cycloheximide.

Alone, PMA and calcium inophore A23187 did not affect, but together stimulated, like phytohaemagglutinin (PHA), leucine and, in particular, thymidine incorporation. PMA enhanced slightly the stimulatory effect of PHA. Alone, these agents failed to alter the suppressive effect of dexamethasone on thymidine and leucine incorporation; however, PMA-A23187 and PMA-PHA combinations appeared to antagonize the supression by dexamethasone.