bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporation of 3-deoxy-3-fluoro-D-glucose into glycogen and trehalose in fat body and flight muscle in Locusta migratoria
Authors: Agbanyo Moses , Taylor Norman F.
Published: February 2005

Flight muscle and fat body extracts from Locusta migratoria were incubated with D-[U-14C]-glucose or D-[3-3H]-3-deoxy-3-fluoroglucose and the products were analyzed. In the case of the latter compound, radio-chromatographic analysis yielded glycogen and trehalose fractions that were shown by19F nuclear magnetic resonance to contain fluorine. Acid hydrolysis of these fractions liberated tritium labelled 3-deoxy-3-fluoro-D-glucose. In addition to the formation of “fluoroglycogen” and “fluorotrehalose” in these tissue extracts, there was an accumulation of tritium labelled fructose.
Immunochemical characterization of a new platelet specific monoclonal antibody and its use to demonstrate the cytoskeletal association of the platelet glycoprotein IIb-IIIa complex
Authors: Bird Christopher , Callus Marion , Trickett Lynne , Thorpe Robin
Published: February 2005

We describe the production and characterization of a monoclonal antibody specific for platelets. This antibody reacts strongly with human and primate platelets, but does not recognise human monocytes, polymorphonuclear leucocytes, lymphocytes, erythrocytes, leukaemic nor fibroblast cell lines, nor rodent platelets. Immunoprecipitation studies using radiolabelled platelet membrane proteins showed that the monoclonal antibody binds to the platelet membrane glycoprotein IIb-IIIa complex. Affinity chromatography using immobilized monoclonal antibody allows purification of the antigen, but also co-purifies the cytoskeletal proteins actin and myosin.

Our results demonstrate immunochemically that although the GP IIb-IIIa complex is an external structure, it is connected through the cell membrane to the microfilament system.
Collagen stability and cross-linking in normal and kyphoscoliotic mouse intervertebral discs
Authors: Venn Gillian , Sims Trevor , Mason Roger M.
Published: February 2005

Intervertebral discs of the cervical-thoracic region of the spine of BDL mice which are homozygous for the ky gene mutation undergo degeneration. Discs from these mice have a normal collagen content and undergo normal collagen cross linking prior to the appearance of degenerative changes. The major reducible collagen cross-link formed in discs of these mice and in normal CBA strain mice is hydroxylysino-5-ketonorleucine. These results and other previous results indicate that the discs in the ky mouse develop degenerative disease due to an extrinsic factor rather than to an intrinsic abnormality of their extracellular matrix. The extrinsic factor has been identified as spinal muscle atrophy.
Exocytosis reconstituted from the sea urchin egg is unaffected by calcium pretreatment of granules and plasma membrane
Authors: Whalley Tim , Whitaker Michael
Published: February 2005

Micromolar calcium ion concentrations stimulate exocytosis in a reconstituted system made by recombining in the plasma membrane and cortical secretory granules of the sea urchin egg. The isolated cortical granules are unaffected by calcium concentrations up to 1 mM, nor do granule aggregates undergo any mutual fusion at this concentration. Both isolated plasma membrane and cortical granules can be pretreated with 1 mM Ca before reconstitution without affecting the subsequent exocytosis of the reconstituted system in response to micromolar calcium concentrations. On reconstitution, aggregated cortical granules will fuse with one another in response to micromolar calcium provided that one of their number is in contact with the plasma membrane. If exocytosis involves the generation of lipid fusogens, then these results suggest that the calcium-stimulated production of a fusogen can occur only when contiguity exists between cortical granules and plasma membrane. They also suggest that a substance involved in exocytosis can diffuse and cause piggy-back fusion of secretory granules that are in contact with the plasma membrane. Our results are also consistent with a scheme in which calcium ions cause a reversible, allosteric activation of an exocytotic protein.
Central effects of TNF α on thermogenesis and fever in the rat
Authors: Rothwell Nancy J.
Published: February 2005

Intracerebroventricular (icv) injection of purified recombinant human tumour necrosis factor α (TNF α, 4–8μg) in conscious rats, produced increases in colonic temperature (1.0°C) and resting oxygen consumption (VO2, 14%) which were maximal after 80–90 minutes. Pretreatment with propranolol (10mg/kg s.c) significantly inhibited the rise in VO2, and prevented the increase in body temperature. Icv injection of an antagonist to corticotropin releasing factor (α-helical CRF 9–41, 25 μg), which prevents the pyrogenic and thermogenic actions of interleukin-1β, did not influence the effects of TNFα on temperature or VO2. Injection of a fragment of TNFα (113–130 amino acid sequence) did not affect body temperature or VO2. TNFα injection (icv) significantly increased brown adipose tissue (BAT) in vitro mitochondrial GDP binding, and this effect was slightly inhibited, but not prevented, by surgical denervation of the tissue, and was unaffected by pretreatment with α-helical CRF 9–41. These data indicate that TNFα can stimulate thermogenesis by a direct central action. The effects are largely, but not totally, dependent on the sympathetic nervous system but, unlike the thermogenic actions of interleukin they do not require release of CRF.
Differential phosphorylation of murine class I major histocompatibility antigens
Authors: Hong Wanjin , Le Anh Van , Doyle Darrell
Published: February 2005

Recent studies have shown that the H-2K and H-2D transplantation antigens are expressed differentially in different tissues of mouse. Our previous investigations also established that in thioglycolate-stimulated peritoneal macrophages the H-2Dk antigen exists in distinct cell surface and intracellular forms. These two forms are glycosylated differently. In this report, we have found that (1) H-2Dk antigen is phosphorylated whereas H-2Kk antigen is not, and (2) only the cell surface form of H-2Dk antigen is phosphorylated in thioglycolate-stimulated macrophages derived from C3H/Heha mice. This differential phosphorylation of H-2 antigens will provide a model system for further studies on the molecular mechanism and function of phosphrrylation of H-2 antigens.
Mammalian cells contain a DNA-recombining activity that can be dissociated from topoisomerase activity
Authors: Hamelin C. , Alain R. , Houde D. , Berthiaume L.
Published: February 2005

The role of the topoisomerase enzyme in DNA recombination was investigated by extracting chromosomal deoxyribonucleoproteins from a variety of cultured mammalian ceils and assaying for the formation of recombinant DNA structures. Although each of the crude deoxyribonucleoprotein preparations contained topoisomerase activity, they did not all contain DNA-recombining activity. A distinct, perhaps novel, enzyme may therefore promote DNA recombination in these cell-free systems.
Immunotoxins up to the present day
Authors: Drobniewski Francis A.
Published: February 2005

Immunotoxins consist of monoclonal or polyclonal antibodies conjugated to bacterial or plant toxins. The toxins used are typically of the A-B type in which a toxic A chain is coupled to a B chain responsible for cell binding and facilitation of A chain entry into the cytosol. Two broad strategies have been followed: coupling intact toxins, or A chains alone, to antibodies. This review examines current progress in in vitro and in vivo research, including recent clinical studies, concentrating principally on ricin or ricin A chain conjugates. The future role of conjugates using membrane-acting toxins, immunolysins, is also discussed.
The effects of experimental uremia in rats on duodenal VIP levels and the interaction of VIP with duodenal epithelial cells
Authors: Fernández-Moreno M. D. , Arilla E. , Prieto J. C.
Published: February 2005

The effects of experimental uremia on the concentration of vasoactive intestinal peptide (VIP) in duodenum as well as on the interaction of this neuropeptide with the corresponding epithelial cells were studied in rats. Duodenal VIP concentration was significantly decreased in uremic rats as compared to control animals. The specific binding of VIP to duodenal epithelial cells increased in rats with uremia due to an increase in the number of VIP receptors rather than a change in the binding affinity or in the extent of VIP degradation. On the other hand, the efficacy but not the potency of VIP upon cyclic AMP generation varied in parallel to that observed at the receptor level.
Insulin binding to rat intestinal epithelial cells following partial small-bowel resection
Authors: Fernandez-Moreno Maria-Dolores , Arilla Eduardo , Prieto Juan-Carlos
Published: February 2005

Partial (60%) resection of rat small bowel was performed in order to obtain a model of intestinal mucosal hyperplasia for studying specific insulin binding. The affinity, but not the binding capacity, of insulin receptors in the adaptive mucosa decreased three and seven days following enterectomy. This modification took place only in crypt cells but not in mature villous cells. Since plasma insulin levels were not altered by the surgical manipulation, the observed decrease of insulin binding could not be related to regulation by insulin concentration. These results do not support a trophic role of insulin on intestinal mucosa and appear to be more a consequence of the hyperactive status of proliferation and differentiation at the mucosat level.
Selective retention of organic phosphate esters and phosphonates on aluminium oxide
Authors: Coletti-Previero M-A. , Pugnière M. , Mattras H. , Nicolas J. C. , Previero A.
Published: February 2005

Compounds containing the −PO3H2 function, such as monoesters of phosphoric acid and phosphonic acids, specifically bind to aluminium oxide in aqueous solution under experimental conditions where non-phosphorylated compounds are completely desorbed. The bound organic phosphate can be specifically displaced by aqueous solution of inorganic phosphates thus allowing their separation or detection by a technique similar to that of affinity chromatography. The consequences of this finding for phosphate compound biochemistry are discussed.
Antigenic probes locate the myosin subfragment 1 interaction site on the N-terminal part of actin
Authors: Méjean C. , Boyer M. , Labbé J. P. , Derancourt J. , Benyamin Y. , Roustan C.
Published: February 2005

The interaction of two different anti-actin antibody populations with the myosin subfragment 1-F-actin rigor complex has been studied. In contrast with the 1–7 sequence, the 18–28 sequence appears to be strongly implicated in the contact area of the myosin head on the actin polypeptide chain.
Interaction of quercetin with DNA
Authors: Alvi N. K. , Rizvi R. Y. , Hadi S. M.
Published: February 2005

I n vitro experiments to study interaction of the mutagenic flavonoid quercetin with DNA are described. Calf thymus DNA treated with quercetin for various time periods was subjected to S1 nuclease hydrolysis. Thermal melting profles of treated DNA were also determined using St nuclease. The rate of DNA hydrolyzed after 1 hr of pre-treatment with quercetin was found to be only about 50% of that in its absence. However, after 10 and 24hrs of treatment with the drug, the rate of S1 nuclease hydrolysis was observed to be greater than that of native DNA. Thermal melting profiles of DNA, treated with quercetin for 10 and 24 hrs, indicated a slight decrease in melting temperatures. Gel filtration of native DNA, which had been digested with S1 nuclease after preincubation with quercetin for 24 hrs, indicated the production of various sized degraded molecules. The results suggest that the initial interaction of quercetin with DNA may have a stabilizing effect on its secondary structure, but prolonged treatment leads to an extensive disruption of the double helix.
Rabbit antibodies against the folate binding protein from cow's milk. Production, characterization and use for development of an enzyme-linked immunosorbent assay (ELISA)
Authors: Høier-Madsen Mimi , Hansen Steen Ingemann , Holm Jan
Published: February 2005

Rabbit antibodies to purified folate binding protein from cow's milk whey were used for development of a two-site enzyme-linked immunosorbent assay (ELISA) for quantitation of bovine folate binding proteins, The folate binding proteins in human milk and serum showed no cross-reactivity. A partial saturation of purified bovine folate binder with folate gave rise to an increased antigenicity probably due to a ligand (folate)-induced exposure of antigenic sites on the protein.
Interaction of alpha-sarcin and gelonin with Cibacron blue
Authors: Sperti Simonetta , Montanaro Lucio , Rambelli Fioretta , Zamboni Mariacristina
Published: February 2005

Alpha-sarcin and gelonin, two proteins which inactivate the 60S ribosomal subunit, interact with Cibacron blue and bind to blue dextran-Sepharose, from which they are partially desorbed by nucleoside triphosphates and, more efficiently, by homopolynucleotides. It is further shown that the two proteins bind to poly(U)-Sepharose and that homopolynucleotides protect dilute solutions of both inhibitors from inactivation. It is suggested that the presence of a polynucleotide site on alphasarcin is related to its ribonuclease activity. The existence of a similar site on gelonin might be a clue to its yet unknown mechanism of action.
Effect of garlic oil extract on glutathione reductase levels in rats fed on high sucrose and alcohol diets: A possible mechanism of the activity of the oil
Authors: Adoga Godwin I.
Published: February 2005

The effect on glutathione reductase activities of feeding garlic oil to white albino rats maintained on high sucrose and alcohol diets was studied. Whereas high sucrose and alcohol diets resulted in significant increases in the activity of glutathione reductase in liver, kidneys and serum, the presence of garlic oil restored the levels to near normal. It is proposed that the mechanism of this action of garlic oil involves the active principle, diallyl disulphide, which interacts in an exchange reaction with enzymes and substrates such as glutathione reductase and glutathione which contain thiol groups.
Nucleotide sequence of a cDNA coding for mitochondrial fumarase from human liver
Authors: Kinsella B. Therese , Doonan Shawn
Published: February 2005

The nucleotide sequence of a 1.46 kb cDNA, selected from a human liver library by the expression of fumarase antigenic determinants, was determined using the dideoxy chain termination method. The cDNA contained an open reading frame extending from the extreme 5′-base and coding for a protein with 468 amino acids. This protein, with the exception of an N-terminal methionine, was identified as mitochondrial fumarase. The protein showed a high degree of identity of structure with the fumarase from Bacillus subtilis (56.6 %) and a fumarase from Escherichia coli (product of the fumC gene, 59.3 %), and a lower degree of identity with the aspartase of E. coli (37.2 %).
An experiment in enzyme evolution studies with Pseudomonas aeruginosa amidase
Authors: Clarke Patricia H. , Drew Robert
Published: February 2005

The regulation of amidase synthesis in P. aeruginosa is under positive control. This review describes the experimental evolution of amidase and its regulator protein for the hydrolysis of novel substrates and experiments to elucidate the mechanism of the control system.
The influence of starvation and natural refeeding on the rate of triacylglycerol/fatty acid substrate cycling in brown adipose tissue and different white adipose sites of the rat in vivo. The role of insulin and the sympathetic nervous system
Authors: Mercer Stewart W. , Williamson Dermot H.
Published: February 2005

Triacylglycerol/fatty acid substrate cycling was measured in vivo in brown adipose tissue (BAT) and white adipose tissue (WAT) of fed, starved and refed rats. Starvation (24 h) significantly decreased the rate of cycling in BAT, and refeeding chow diet led to a rapid, 6-fold increase in cycling. Cycling rate in WAT was much lower than in BAT, and was not influenced by fasting or refeeding. Similar rates of cycling were found in epididymal, mesenteric, subcutaneous, and scapular WAT depots. Sympathetic denervation of interscapular BAT abolished the response of the tissue to refeeding, as did acute suppression of insulin secretion. Similarly, rats fasted for 3 days showed no acute increase in the activity of the cycle following refeeding.
Cartilage proteoglycan aggregate and fibronectin can modulate the expression of type X collagen by embryonic chick chondrocytes cultured in collagen gels
Authors: Terrig Thomas J. , Grant Michael E.
Published: February 2005

Chick embryo sternal chondrocytes from the caudal and cephalic regions were cultured within type I collagen gels and type I collagen/proteoglycan aggregate composite gels in normal serum. Caudal region chondrocytes were also cultured within type I collagen gels in the presence of fibronectindepleted serum. There was a marked stimulation of type X collagen synthesis by the caudal region chondrocytes after 9 days in the presence of fibronectin-depleted serum and after 14 days in the presence of proteoglycan aggregate. These results provide evidence for the ability of chondrocytes from a zone of permanent cartilage to synthesise type X collagen and for the involvement of extracellular matrix components in the control of type X collagen gene expression.
The synthetic precursor specific region of pre-pro-parathyroid hormone forms ion channels in lipid bilayers
Authors: Tosteson Magdalena T. , Caulfield Michael P. , Levy Jay J. , Rosenblatt Michael , Tosteson Daniel C.
Published: February 2005

We have used the chemically synthesized sequence of pre-pro-parathyroid hormone and several of its analogues to test the notion that the capacity of amphipathic peptides to aggregate in membranes and form ion-permeable channels correlates with their ability to function as signal sequences for secreted proteins. We found that pre-pro-parathyroid hormone (the signal sequence and pro-region of parathyroid hormone (M)), as well as some of its analogues, forms aggregates of monomers which are ion-permeable. The ion-permeable aggregates (2–3 monomers) formed by (M) are voltage-dependent and are more permeable for cations than for anions. The compounds which formed ion channels in bilayers also acted as potential signal sequences. We conclude that the ability of peptides to form ion-permeable pathways in bilayers may be correlated to their ability to function as signal peptides.
Colchicine, colcemide and cytochalasin B do not affect translocation of the glucocorticoid hormone-receptor in rat thymocytes or ehrlich ascites cells
Authors: Vorgias Constantine E. , Perides Georg A. , Traub Peter , Sekeris Constantine E.
Published: February 2005

The involvement of intracellular cytoskeletal elements in the translocation of the dexamethasone-receptor complex from the cytoplasm to the nucleus was studied using the cytoskeleton-disrupting agents colcemide, colchicine and cytochalasin B. These compounds did not affect the translocation of the hormone-receptor complex. We conclude that microfilaments and microtubules do not play a role in the translocation of the glucocorticoid hormone-receptor complex from the cytoplasm to the nucleus.
The role of high rates of glycolysis and glutamine utilization in rapidly dividing cells
Authors: Newsholme E. A. , Crabtree B. , Ardawi M. S. M.
Published: February 2005

The rates of utilization of both glucose and glutamine are high in rapidly dividing ceils such as enterocytes, lymphocytes, thymocytes, tumour cells; the oxidation of both glucose and glutamine is only partial, glucose to lactate and glutamine to glutamate, alanine or aspartate; and these partial processes are termed glycolysis and glutaminolysis respectively. Both processes generate energy and also provide precursors for important biosynthetic processes in such cells. However, the rates of utilization of precursors for macromolecular biosynthesis are very low in comparison to the rates oi partial oxidation, and energy generation per se may not be the correct explanation for high rates of glycolysis and glutaminolysis in these cells since oxidation is only partial and other fuels can be used to generate energy. Both the high fluxes and the metabolic characteristics of these two processes can be explained by application of quantitative principles of control as applied to branched metabolic pathway s (Crabtree & Newsholme, 1985). If the flux through one branch is greatly in excess of the other, then the sensitivity of the flux of the low-flux pathway to regulators is very high. Hence, it is suggested that, in rapidly dividing ceils, high rates of glycolysis and gtutaminolysis are required not for energy or precursor provision per se but for high sensitivity of the pathways involved in the use of precursors for macromolecular synthesis to specific regulators to permithigh rates of proliferation when required for example, in lymphocytes in response to a massive infection.
Kinetic studies of pyruvate kinase during in vitro differentiation of GM-CFC haemopoietic precursor and bone marrow cells in mice
Authors: Cuenllas Elvira , Gaitan Soledad , Bueren Juan A. , Tejero Concepcion
Published: February 2005

Pyruvate kinase studies in the granulocyte-macrophage lineage during in vitro differentiation have been performed using culture techniques on GM-CFC cells and a study has also been done in bone marrow cells.

The enzyme exhibits biphasic behaviour with respect to both of its substrates in cells derived from in vitro cultures at 5 and 7 days of incubation period. However in bone marrow cells these kinetics are only observed for ADP.

The different kinetic behaviour of pyruvate kinase toward Fru-1,6-P2, Ala, Phe and ATP in the three cellular populations allows us to conclude that the expression of pyruvate kinase is associated with the differentiation of these cells.
The mechanisms by which vasoactive intestinal peptide (VIP) and thyrotropin releasing hormone (TRH) stimulate prolactin release from pituitary cells
Authors: Bjøro Trine , Sand Olav , Østberg Bjørn Chr. , Gordeladze Jan O. , Torjesen Peter , Gautvik Kaare M. , Haug Egil
Published: February 2005

The effect of vasoactive intestinal peptide (VIP) on prolactin (PRL) secretion from pituitary cells is reviewed and compared to the effect of thyrotropin releasing hormone (TRH). These two peptides induced different secretion profiles from parafused lactotrophs in culture. TRH was found to increase PRL secretion within 4 s and induced a biphasic secretion pattern, while VIP induced a monophasic secretion pattern after a lag time of 45–60 s.

The secretion profiles are compared to changes in adenylate cyclase activity, production of inositol polyphosphates, changes in intracellular calcium concentrations and changes in electrophysiological properties of the cell membrane.
Chronic and endogenous regulation of insulin receptors by catecholamines in adipocytes from patients with a phaeochromocytoma
Authors: Carranza M. C. , Simón M. A. , Torres A. , Calle C.
Published: February 2005

Insulin binding in adipocytes from patients with a phaeochromocytoma (PH) approached that of the controls (C) at low and higher concentrations of unlabeled insulin. The apparent receptor affinity was unchanged (ED50: PH 0.50×10−9M and C0.60×10−9M). Scatchard analysis of the binding data using the negative cooperative model revealed a 46% decrease in the total number of receptors together with no changes in both K−e (PH 0.55×109M−1 and C 0.36×109M−1) and K−f (PH 0.13×109 M−1 and C 0.07×109 M−1). According to the two site model, an altered proportion in the two classes of insulin binding sites was detected. This was accompanied by a catecholamine-desensitization of the adipocytes to the antilipolytic action of insulin. These events could represent a final situation of a chronic and endogeneous regulation by high levels of catecholamines of insulin receptors in human adipose tissue.
Changes in glycine and leucine transport during red cell maturation in the rat
Authors: Felipe A. , Viñas O. , Remesar X.
Published: February 2005

Both glycine and leucine transport in rat red blood cells have been studied. The glycine uptake showed two different components, one sodium-dependent and another diffusion-like process. In contrast, leucine uptake was sodium independent. Both, Na+-dependent glycine and the overall leucine uptake in red blood cells showed a saturable pattern. Kinetic parameters in reticulocytes were: i) glycine: apparent Km 0.16 mM; Vmax 100.2 nmol/ml ICW/min; ii) leucine: apparent Km 2.11 mM; Vmax 3.88 μmol/ml ICW/min. The erythrocytes kinetic parameters were: i) glycine: apparent Km 0.17 mM; Vmax 9.47 nmol/ml ICW/min; leucine; apparent Km 4.77 mM; Vmax 7.42 μmol/ml ICW/min. The Kd values (sodium independent glycine uptake) were similar in both kind of cells, but the importance of this component in total glycine uptake in erythrocytes was much higher than in reticulocytes. Our results confirm that rat red blood cells have both saturable leucine and Na+-dependent glycine uptake, but some important changes occur during cell maturation.
Can the topological distribution of membrane spanning amino acid residues be responsible for the recognition of signal peptides by signal peptide peptidases?
Authors: Shinde Ujwal P.
Published: February 2005

Signal peptides are selectively recognized and degraded by membrane associated proteases called as signal peptide peptidases. The hydrolysis of the signal peptide occurs only after its cleavage from the precursor. The possible reasons for this selectivity have been investigated. The results indicate that in signal peptides, leucine residues are clustered to a large extent on the same side of the membrane spanning alpha helix as the polar residues, but are distinctly separated along the length of the axis. Such topological differences in the distribution of amino acids on the surface of the membrane spanning alpha helix may play a crucial role in selective degradation of signal peptides.
Hormonal modulation of hepatic plasma membrane lactate transport in cultured rat hepatocytes
Authors: Metcalfe H. K. , Cohen R. D. , Monson J. P.
Published: February 2005

Hormonal modulation of hepatic plasma membrane lactate transport was studied in primary cultures of isolated hepatocytes from fed rats to examine the mechanism for the known enhancement of lactate transport in starvation and diabetes. Total cellular lactate entry was increased by 14% in the presence of dexamethasone; this was accounted for by an approximately 40% increase in the carrier-mediated component of entry with no effect on diffusion. A trend of similar magnitude was evident with glucagon. The effects of dexamethasone and glucagon on lactate transport constitute an additional potential mechanism for enhancement of gluconeogenesis by these hormones.
Studies on the involvement of calcium and calmodulin in the action of growth-hormone-releasing factor
Authors: Merritt Janet E. , Dobson Pauline R. M. , Wojcikiewicz Richard J. H. , Baird John G. , Brown Barry L.
Published: February 2005

A possible role for Ca 2+ and calmodulin in the action of growth-hormone-releasing factor (GHRF) was investigated. Low extracellular Ca2+ (<100 μM), methoxyverapamil, flunarizine, cinnarizine, and Co2+ decreased both basal and GHRF-stimulated growth-hormone secretion, but did not totally inhibit GHRF-stimulation secretion. A calmodulin antagonist, W7, abolished GHRF-stimulated GH secretion, with no effect on basal secretion. It is suggested that GHRF may act primarily by elevating cellular cyclic AMP, which may then modulate calcium mobilization or flux; the increased intracellular Ca2+ concentrations may then activate calmodulin.
Arrhenius plot characteristics of adipocyte-plasma-membrane adenylate cyclase activity in lean and genetically obese (ob/ob) mice
Authors: French R. R. , York D. A.
Published: February 2005

Arrhenius plots of fluoride- and guanine-nucleotide-stimulated adenylate cyclase activity were linear in adipocyte plasma membranes from lean and obese (ob/ob) mice. Arrhenius plots of isoprenaline-stimulated adenylate cyclase activity in hepatic plasma membranes biphasic in both groups. The results were biphasic in membranes from Jean mice but linear in membranes from obese mice. In contrast, Arrhenius plots of glucagon-stimulated adenylate cyclase activity in hepatic plasma membranes were biphasic in both groups. The results suggest that the coupling between the β-receptor and the regulatory unit of adenylate cyclase, which has been observed to be defective in adipocyte plasma membranes from obese mice, is influenced by a different lipid environment in membranes from obese animals.
Immunological studies on lysosomal sphingomyelinase: Identification of a 28 000-Da component deficient in urine from patients with Niemann-Pick disease types A and B
Authors: Schram André W. , Dreissen Marianne , Bastiaannet Johan , Donker-Koopman Wilma E. , Brouwer-Kelder Elisabeth M. , Weitz Gabriele , Barranger John A. , Sandhoff Konrad , Tager Joseph M.
Published: February 2005

The immunoblotting technique was used to identify sphingomyeJinase protein in samples of tissue and urine after subjection to poIyacrylamide-gel etectrophoresis in the presence of sodium dodecyl sulphate. In a sphingomyelinase preparation purified from control urine a prominent band was seen with an Mr of 28 000 Da. Glycoprotein fractions from urine and placenta, a membrane extract from spleen, and a partially purified sphingomyelinase preparation from placenta contained the 28 000-Da band plus additional, higher-Mr bands. The 28 000-Da band was detectable in urine from a patient with Niemann-Pick disease type C, but not in urine from patients with Niemann-Pick disease types A and B. It is concluded that sphingomyeJinase is composed of at least one polypeptide with an Mr of 28 000 Da and that this polypeptide is deficient in the urine of patients with Niemann-Pick disease types A and B.
A small camel-milk protein rich in cysteine/half-cystine
Authors: Beg Obaid Ullah , von Bahr-Lindström Hedvig , Zaidi Zafar H. , Jörnvall Hans
Published: February 2005

A small protein (Mr about 14 000) rich in cysteine/half-cystine has been isolated from camel milk by exclusion chromatography and reverse-phase high-performance liquid chromatography. The N-terminal amino acid sequence shows a region with several positional identities with α and β-caseins, which however lack cysteine residues; postions 16–20 are identical and involve the serine residues that have been found to be phosphorylated in β-caseins.
Chronic and acute ethanol impair the in vivo glucose uptake by lactating rat mammary gland
Authors: Vilaró S. , Viñas O. , Herrera E. , Remesar X.
Published: February 2005

Chronic and acute ethanol treatments increased the 3-hydroxybutyrate uptake by lactating rat mammary gland as a consequence of its high afferent concentration, without changing its relative extraction. The uptake of glucose was inhibited in the ethanol treated animals due to intrinsic alterations in the mammary gland metabolism as indicated by the decreased relative extraction and unchanged afferent concentration. These results would suggest that the elevated uptake of ketone bodies in ethanol-treated rats can be responsible, at least in part, for the decrease in glucose uptake by lactating rat mammary gland, although other direct effects of ethanol may be implied.
In vitro and in vivo effect of organophosphate pesticides on monoamine oxidase activity in rat brain
Authors: Nag Maitreyi , Nandi Namita
Published: February 2005

The effects of some organophosphate pesticides, e.g. lebaycid, metacid and metasystox on the monoamine oxidase (MAO) activity in rat brain mitochondria have been studied. These pesticides cause significant inhibition of MAO activity in vitro but have negligible effects on its activity in vivo.
Partial sequence of hemoglobin from cobra (Naja naja naja)
Authors: Naqvi Sabira , Nadvi Iffat N. , Zaidi Zafar H.
Published: February 2005

Hemoglobin from the cobra snake, Naja naja naja, was isolated and its chains separated on a CM-cellulose column. The separation profile revealed an α and two β chains having the molar proportions of [α]2,[β1]1,[β2]1. The N-terminal amino acid sequence of the intact chains and of the CNBr peptides were carried out. The β2 chain was found to be heterogeneous comprising a minor component amounting to 11%. This later showed changes at two positions 9 and 14 in the first 30 residues sequenced.
Effect of haloperidol withdrawal on somatostatin level and binding in rat brain
Authors: Perez-Oso E. , Lopez-Ruiz M. P. , Arilla E.
Published: February 2005

The effects of withdrawal on the level and specific binding of somatostatin in the frontoparietal cortex and hippocampus of the rat after chronic haloperidol treatment were examined using125I-Tyr11 somatostatin as tracer. One week after haloperiodol withdrawal the number of specific somatostatin receptors in both brain areas returned to control values, after having decreased as the result of chronic administration. Neither administration of haloperidol nor withdrawal of it affected the levels of somatostatin-like immunoreactivity (SLI) in the two brain areas studied. The return of the somatostatin receptor number to control values after haloperidol withdrawal may be related to the motor side-effects that are clinically observed when the haloperidol treatment is terminated.
Evidence for the involvement of vicinal sulfhydryl groups in the insulin stimulation of intracellular glucose metabolism in Zajdela Hepatoma cells
Authors: Caron Martine , Cherqui Gisèle , Wicek Denise , Melin Brigitte , Reynet Christine , Capeau Jacqueline , Picard Jacques
Published: February 2005

Phenylarsine oxide (PhAsO), a dithiol reagent that blocks insulin stimulation of glucose transport in 3T3 L1 cells, also altered insulin stimulation of intracellular glucose metabolism in Zajdela Hepatoma cultured cells. PhAsO (2 μM) similarly inhibited the insulin-induced glycogen and lipid syntheses without modifying the basal level of these processes, cell viability or the ATP content. Prior incubation of the cells with PhAsO did not prevent insulin binding to the cells, or activation of the receptor tyrosine kinase, while it minimally (16%) altered receptor internalization. These results indicate that cellular dithiols located at a post-receptor step are involved in the transduction of the insulin signal to intracellular glucose metabolism.
The basal permeability to water of human red blood cells evaluated by a nuclear magnetic resonance technique
Authors: Benga Gheorghe , Pop Victor Ioan , Popescu Octavian , Borza Victoria
Published: February 2005

The characteristics of water diffusional permeability (P) of human red blood cells were studied on isolated erythrocytes by a doping nuclear magnetic resonance technique. In order to estimate the basal permeability the maximal inhibition of water diffusion was induced by exposure of red blood cells to p-chloromercuribenzene sulfonate (PCMBS) under various conditions (concentration, duration, temperature). The lowest values of P were around 0.7×10−3 cm s−1 at 10°C, 1.2×10−3 cm s−1 at 15°C, 1.4×10−3 cm s−1 at 20°C, 1.8×10−3 cm s−1 at 25°C, 2.1×10−3 cm s−1 at 30°C and 3.5×10−3 cm s−1 at 37°C. The mean value of the activation energy of water diffusion (Ea,d) was 25 kJ/mol for control and 43.7 kJ/mol for PCMBS-inhibited erythrocytes. The values of P and Ea,d obtained after induction of maximal inhibition of water diffusion by PCMBS can be taken as references for the basal permeability to water of the human red blood cell membrane.
Inhibitory action of estradiol on growth promoting activity in extract from uterine cancers
Authors: Imai Atsushi , Matsunami Kazutoshi , Iida Koji , Tamaya Teruhiko
Published: February 2005

Extracts from uterine cervical and body cancers, but not from benign tumor or intact tissues tested, were found to contain a growth-promoting activity which induced the proliferation of human endometrial fibroblasts. Exposure of cultured fibroblasts to the cancer extracts increased the rate of [3H]thymidine incorporation in a dose-dependent manner. The activity was heat-labile, and not inactivated by removal of lipid-soluble material suggesting that the activity is associated with a protein. When the fibroblasts were preincubated with estradiol for 12 hours, but not for 1 hour, the extract-induced fibroblast proliferation was suppressed. The inhibitory effect of estradiol was dose related (EC50: 10 nM) and non-competitive, suggesting that the steroid may reduce the sensitivity of fibroblasts to the extracts. This is the first report to provide direct evidence that estradiol may play an inhibitory role in the action of growth factor-like peptide produced from malignant tumors.
Evidence for the involvement of a 35-kDa membrane protein in the synthesis of glucosylphosphoryldolichol
Authors: Drake Rick , Palamarczyk Grazyna , Haley Boyd , Lennarz William J.
Published: February 2005

Photoactivatable (β-23P)5-azidoUDPGlc binds to two proteins in rat liver microsomes. As determined by SDS-PAGE electrophoresis, the molecular masses of the32P-labeled proteins were found to be 62-and 35-kDa. Binding of the photoprobe to both proteins was inhibited by addition of unlabeled UDPGlc. Labeling of the higher molecular weight protein occurred in the absence of photoactivation. In contrast, formation of the32P-labeled 35-kDa protein was dependent on exposure of the membranes to UV light (250nm). Moreover, labeling of the 35-kDa protein required the intact sugar nucleotide and divalent cations and was affected by the level of the endogenous and exogenous dolichylphosphate. All of these results are consistent with the possibility that the 35-kDa membrane protein is a component of glucosylphosphryldolichol synthase.
A high-affinity folate binding protein in human amniotic fluid. Radioligand binding characteristics, immunological properties and molecular size
Authors: Holm Jan , Hansen Steen Ingemann , Høier-Madsen Mimi
Published: February 2005

The presence of a folate binding protein of high-affinity type (affinity constant 5 · 109M−1, maximum folate binding 3 nM) in human amniotic fluid was demonstrated in equilibrium dialysis experiments (37°C, pH 7.4) with the radioligand3H-folate. Dissociation of3H-folate from the binding protein was slow at pH 7.4 but rapid at pH 3.5. By use of rabbit antibodies against low molecular weight folate binding protein from human milk we determined the concentration of folate binding protein in 5 amniotic fluids (range 1.5–2.3 nM) in an Enzyme-Linked Immunosorbent Assay (ELISA). ultrogel AcA 44 chromatography of amniotic fluid showed that immunoreactive and radioligand bound folate binding protein coeluted in two peaks: a major one (Mr~25 000) and a minor one (Mr~100 000).
Comparison of linoleate, palmitate and acetate metabolism in rat ventral prostate
Authors: del Hoyo N. , Pulido J. A. , Carretero M. T. , Pérez-Albarsanz M. A.
Published: February 2005

Rat ventral prostate incorporated (1-14C)acetate, (1-14C)palmitate and (1-14C)linoleate into different phospholipids in a time-dependent process. The rate of incorporation into total phospholipids was higher with linoleate (10.0 nmol/g) than with either palmitate (5.8 nmol/g) or acetate (4.7 nmol/g). Predominant labelling with all the radioactive substrates assayed was found in choline glycerophospholipids (PC). The radioactive profiles for linoleate in the other ventral prostate phospholipids differed from those obtained with palmitate and acetate. Specifically linoleate was incorporated into inositol glycerophospholipids plus lysoethanolamine glycerophospholipids (PI+LPE) and not into sphingomyelin (SM), while palmitate and acetate incorporated into SM but not into PI+LPE. Acetate showed the highest oxidation to CO2 whereas no differences were observed in the radioactivity incorporated into CO2 from a saturated (palmitate) or an essential unsaturated fatty acid (linoleate). These studies also show zinc-dependence by the acetate to CO2 oxidation.
Decreased insulin binding and antilipolytic response in adipocytes from patients with Cushing's syndrome
Authors: Calle C. , Carranza M. C. , Simón M. A. , Torres A. , Mayor P.
Published: February 2005

Human adipocytes from patients with chronic endogenous hypercortisolism (Cushing's syndrome) showed a statistically significant decrease in insulin binding at low unlabelled-insulin concentrations but no change in receptor numbers (Cushing's 180,000±48,000 (3) receptors/cell and controls 189,000±30,000 (7)) together with a fourfold decrease in apparent receptor affinity (ED50: Cushing's 2.25×10−9 M and controls 0.57×10−9 M) and a decreased sensitivity to the antilipolytic effect of insulin. These events could represent the final situation of a chronic and endogenous regulation by high levels of cortisol of insulin receptors in human adipose tissue.
Clonal heterogeneity of thymic muscle-cell precursors
Authors: Kamo Isao , Nonaka Ikuya , Furukawa Shoei , Satoyoshi Eijiro
Published: February 2005

Three myoid-cell clones were established from the thymuses of two Wistar rats; one thymus yielded two clones, RBISA and R615B2, and the other yielded one clone, R613Ad. The three clones were divided into two subtypes. Both subtypes were able to form myofibrils, expressed AChR on their cell-surface membrane, and contained myofibrillar ATPase characteristic of und ifferentiated type-2C fibers, but they differed from each other in morphology, expression of Thy 1 antigen, spontaneous contractility, and qualitative accumulation of AChR. Immunolocalization studies using antisera against the respective cell subtypes also indicated regional differences in their cellular origin. These results show that the thymus contains heterogenous myoid-cell precursors.
The development of insulin resistance in brown adipose tissue may impair the acute cold-induced activation of thermogenesis in genetically obese (ob/ob) mice
Authors: Mercer Stewart W. , Trayhurn Paul
Published: February 2005

Genetically obese (ob/ob) mice develop insulin resistance in brown adipose tissue during the fifth week of life. Prior to this, at 26 days of age, oh/oh mice show a substantial increase in GDP binding to brownadipose-tissue mitochondria during acute cold exposure. When insulin resistance in brown fat develops, by 35 days of age, the increase in GDP binding in response to cold is markedly reduced. Studies with 2-deoxyglucose suggest that insulin resistance in brown adipose tissue could impair thermogenic responsiveness during acute cold exposure by limiting the ability of the tissue to take up glucose.
The use of a prostacyclin analogue, [3H]iloprost, for studying prostacyclin-binding sites on human platelets and neuronal hybrid cells
Authors: Hall Jean M. , Strange Philip G.
Published: February 2005

The stable prostacyclin analogue [3H]iloprost has been used for labelling prostacyclin-binding sites on human platelets and NCB-20 neuronal hybrid cells. The ligand-binding properties of the sites have been determined and correlate well with stimulation of cAMP synthesis in NCB-20 cells and inhibition of aggregation in human platelets.
Studies of phosphorus metabolism by isolated nuclei. XII. Some fundamental properties of the incorporation of 32Pi into polyphosphate by rat liver nuclei
Authors: Penniall Ralph , Griffin James B.
Published: February 2005

Rat liver nuclei incubated in vitro catalyze a sustained incorporation of32Pi into polyphosphate. A preliminary estimate indicates a minimal rate of 10 moles of Pi incorporation into polyphosphates/h/mg protein. Polyphosphate is the predominant acid-insoluble product of nuclear phosphorylation; its formation is dependent on the presence of a divalent cation and is catalyzed by a system or systems as yet uncharacterized.
Effects of training and exhaustive exercise on the mitochondrial oxidative capacity of brown adipose tissue
Authors: Gohil K. , Henderson S. , Terblanche S. E. , Brooks G. A. , Packer L.
Published: February 2005

Oxidation of pyruvate, α-ketoglutarate, palmitoylcarnitine, succinate, and ferrocytochrome c by interscapular-brown-adipose-tissue (BAT) mitochondria of untrained and trained rats were measured at rest and alter running to exhaustion. At rest, BAT mitochondria from trained rats showed significantly lower activities (<50%) for the oxidation of all the substrates. In untrained rats the activities of the enzymes for the oxidation of all the substrates except pyruvate and succinate were lower at exhaustion compared to the resting state when expressed on a per-gram-fresh-Weight basis. In trained rats all of the enzyme activities increased as a result of exhaustive exercise. These differences between the two groups of rats in the post-exercise changes in oxidative capacities suggest that following an initial adaptation, resulting in a large decrease in mitochondrial oxidative activity, training protects the residual oxidative pathways against exercise-induced inactivation. These data show that unlike exposure to cold, or overfeeding, a physiological stimulus such as exercise reduces the oxidative capacity of BAT, and therefore may reduce the thermogenic activity of the tissue in endurance-trained rats as has been addressed in the scientific literature.
Loop diuretics may fail to inhibit (Na+, K+, Cl−) ‘cotransport’ in human red cells
Authors: Chipperfield A. R.
Published: February 2005

The inhibition of passive K+ influx into human red blood ceils (RBC) by loop diuretics was found to be dependent on the external Na+ concentration, In the absence of external Na+, there was minimal inhibition but the influx remained dependent on CI- ions. Thus, raising the external Na+ concentration increased the affinity of the putative (Na+, K+, Cl- cotransport system in human RBC for loop diuretics.
Partial purification of dopamine D2 receptors using lectin affinity columns
Authors: Abbott W. Mark , Strange Philip G.
Published: February 2005

Dopamine D2 receptors, detected by [3H]spiperone Dopamine D2 receptors, detected by [3H]spiperone binding, were solubilized from bovine caudate nucleus by cholate/sodium chloride and were found to bind to wheat germ agglutinin immobilized on agarose. Specific elution could be achieved with N-acetylglucosamine whereas other sugars tested were inactive in this regard. The eluted preparation was enriched in solubilized receptors about sevenfold. The pharmaco-logical properties of the preparation were essentially unchanged by the lectin affinity purification procedure. The D2 dopamine receptor is therefore a glycoprotein. binding, were solubilized from bovine caudate nucJeus by cholate/sodium chloride and were found to bind to wheat germ agglutinin immobilized on agarose. Specific elution could be achieved with N-acetylglucosamine whereas other sugars tested were inactive in this regard. The eluted preparation was enriched in solubilized receptors about sevenfold. The pharmacological properties of the preparation were essentially unchanged by the lectin affinity purification procedure. The D2 dopamine receptor is therefore a glycoprotein.
Preferential uptake of intravenously administered hyaluronidase (Hyalosidase) by damaged rat myocardium
Authors: Earnshaw Julia S. , Peh Kheng H. , Dodgson Kenneth S. , Olavesen Anthony H. , Gacesa Peter
Published: February 2005

The induction of myocardial infarction in rats by ligation of the left – anterior coronary artery was confirmed by measurement of increased plasma levels of creatine kinase, aspartate aminotransferase and lactate dehydrogenase. Using this model system it has been established that intravenous administration of 12SI-labelled hyaluronidase to rats resulted in a preferential uptake of the enzyme by damaged myocardium as compared to normal heart tissue.