bluuebunny/crossref_metadata_2025 huggingface dataset:
Some aspects of glycosylation in rat liver during pregnancy
Authors: Marino M. , Leoni S. , Spagnuolo S. , Devirgiliis L. Conti , Mangiantini M. T.
Published: February 2005

The aim of the present report was to analyze the pattern of glycoprotein synthesis in rat liver on 19th and 22nd day of pregnancy by following the incorporation of14C-glucosamine and3H-galactose into isolated rat hepatocytes, the N-acetylglucosaminyl-1-P and galactosyl transferase activities, and the liver content of dolichol and dolichyl-phosphate.

The data obtained show a decrease of precursor incorporation into glycoproteins during the last period of pregnancy; this decrease is independent of enzyme activities. The dolichol content increases and the dolichyl-phosphate content, usually considered as rate limiting for glycosylation, decreases.

These results, present in other conditions of proliferation and differentiation of rat liver, could explain the differences in membrane organization, the increase of hepatic proteolysis and the alteration in secretory activity during the last phase of gestation.
Soe features of DNA fragments associated in vivo with the nuclear lamina
Authors: Christova R. , Yaneva J. , Galcheva-Gargova Z.
Published: February 2005

Ehrlich Ascites Tumour cells were irradiated with UV-light to crosslink DNA to proteins in vivo. The DNA fragments associated with the nuclear lamina were purified and characterized. The results of the Cot analysis and the hybridization experiments suggest that the DNA fragments attached to the nuclear lamina although containing the entire complexity of genomic DNA are enriched in some highly repeated sequences.
Enzyme regulation by biological disulfides
Authors: Ondarza Raul N.
Published: February 2005

More than a dozen enzymes have been found to be activated or inhibited in vitro by disulfide-exchange between the protein and small-molecule disulfides. Accordingly, thiol/disulfide ratio changes in vivo may be of great importance in the regulation of cellular metabolism. An awareness of this regulatory mechanism in both host cells and parasites, coupled with information on the presence or absence of key enzymes, may lead to rational drug design against certain diseases involving thiol intermediates, including trypanosomiasis.
Muscle wasting associated with endotoxemia in the rat: Modification by the β2-adrenoceptor agonist clenbuterol
Authors: Choo J. J. , Horan M. A. , Little R. A. , Rothwell N. J.
Published: February 2005

A single injection of endotoxin (1 mg/kg, sc) in rats caused significant fever, body weight loss and reduction in gastrocnemius muscle mass, none of which was mimicked by pair-feeding. Infusion of endotoxin via osmotic minipump over five days caused transient fever and suppression of growth. Recovery of body weight was significantly enhanced by the administration of the β2-adrenoceptor agonist clenbuterol (added to the diet at 4 mg/kg). In a separate experiment, injections of endotoxin (day 0 and day 2) caused significant reductions in body weight gain (42%), mass (9%) and protein content (13%) of gastrocnemius muscle over 3 days. Addition of clenbuterol to the diet reversed all of these effects but did not alter food intake or the febrile response to endotoxin. Clenbuterol caused large (20%) increases in the ratio of RNA to protein in muscle indicating that it may have stimulated protein synthesis. β2-adrenoceptor agonists may therefore be of value in preventing or inhibiting muscle atrophy associated with infection or injury.
Effect of transbilayer phospholipid distribution on erythrocyte fusion
Authors: Tullius Ellen K. , Williamson Patrick , Schlegel Robert A.
Published: February 2005

Phospholipid packing has been suggested as a relevant variable in the control of membrane fusion events. To test this possibility in a model system, a comparison was made of the fusability of erythrocytes with a normal asymmetric transbilayer distribution of plasma membrane phospholipids (tightly packed exterior lipids) and erythrocytes with a symmetric transbilayer distribution of phospholipids (more loosely packed exterior lipids), using polyethylene glycol as fusogen. Not only were lipid-symmetric cells more readily fused, but fusions of mixtures of lipid-symmetric and lipid-asymmetric cells indicated that both fusing partners must have a symmetric distribution for fusion to be enhanced. Lipid-symmetric cells may fuse more readily because loose packing of the exterior lipids enhances hydrophobic interactions between cells. Alternatively, enhanced membrane fluidity may facilitate intramembranous particle clustering, previously implicated as a potentiator of fusion. Finally, exposure of phosphatidylserine on the surface of lipid-symmetric erythrocytes may be responsible for their enhanced fusion.
Electrophoretic resolution of microheterogeneity in Vibrio cholerae lipopolysaccharide
Authors: Ghosh Souravi , Campbell Ailsa M.
Published: February 2005

Lipopolysaccharide (LPS) from Vibrio cholerae has been analysed by sodium dodecyl sulfate-potyacrylamide gel electrophoresis. Under normal conditions of electrophoresis which resolve Escherichia coli LPS, V. cholerae LPS shows two diffuse and unresolved bands. However, on long gels at low concentration it can be resolved into two major band types. There are at least 10 slow moving, discrete bands of regular periodicity and three fast moving bands. Comparison with LPS from E. coli indicates that the heterogeneity occurs over a much smaller range of molecular weight in V. cholerae LPS, with the entire spectrum of discrete bands being contained within the space of four E. coli repeating units.
Human placental tissue stimulates bovine capillary endothelial cell growth, migration and protease production
Authors: Presta M. , Mignatti P. , Mullins D. E. , Moscatelli D. A.
Published: February 2005

A crude extract of human placenta has been demonstrated to stimulate growth, motility and the production of the proteases plasminogen activator and collagenase in cultured bovine capillary endothelial cells. These data are in keeping with the presence of an angiogenic factor(s) in human placenta.
The primary structure of the fourth component of human complement (C4)-C-terminal peptides
Authors: Law S. K. Alex , Gagnon Jean
Published: February 2005

C-terminal CNBr peptides of the three polypeptide chains of C4 were obtained and sequenced. These results supplement previously obtained data, notably the protein sequence derived from cDNA sequencing of pro-C4 (Belt KT, Carroll MC & Porter RR (1984) Cell36, 907–914) and the N-terminal sequences of the three polypeptides (Gigli I, von Zabern I & Porter RR (1977) Biochem. J.165, 439–446), to define the complete primary structure of the plasma form of C4. The β (656 residues), α (748 residues), and γ (291 residues) chains are found in positions 1–656, 661–1408, and 1435–1725 in the pro-C4 molecule.
The subcellular localization of transglutaminase in normal liver and in glucagon-treated and partial hepatectomized rats
Authors: Bruce Sally E. , Peters Timothy J.
Published: February 2005

Rat liver was homogenized in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density-gradient centrifugation. Transglutaminase, when assayed with putrescine and dimethylcasein as substrates, showed three distinct localizations, cytosol (73%), plasma membrane (20%), and nuclei (7%). The distribution was unaffected by homogenization in the presence of potassium chloride, indicating that the particulate activity was not due to adsorbed cytosolic enzyme. The specific activity and subcellular distribution of transglutaminase in rats which had received intra-peritoneal glucagon, stimulating endocytosis; or which had been subjected to sub-total hepatectomy 2, 16, or 32 h previously, showed no significant difference from control animals.
In vitro degradation of leucine in muscle, adipose tissue, liver, and kidney of fed and starved sheep
Authors: Wijayasinghe M. S. , Milligan L. P. , Thompson J. R.
Published: February 2005

In vitro rates of conversion of [1-14C]leucine to 4-methyl-2-oxo[1-14C]pentanoate and of oxidation of [I-14C] and [U-14C]leucine were measured for tissues from fed and starved (5 days) sheep. Slices of liver and kidney and preparations of adipose tissue and of fibre bundles of external intercostal muscle (EIC) were used. Skeletal muscle is likely the major site of leucine catabolism in sheep although adipose tissue is capable of substantial metabolism. Muscle and adipose tissue from fed sheep released 17 and 5% of the [l-14C ]leucine transaminated as 4-methyl-2-oxo-[1-14C]pentanoate and upon starvation the proportions were increased (P<0.001) to 46 and 32%. Starvation reduced (P<0.01) leucine catabolism in all tissues except the kidney. The pattern of leucine catabolism in EIC muscle changed from extensive oxidation in the fed state to being limited essentially to transamination and decarboxylation in the starved state.
The effect of surface charges of liposomes in immunopotentiation
Authors: Latif Nahid , Bachhawat Bimal K.
Published: February 2005

The purpose of this study was to establish the effect of surface charges of liposomes on its adjuvant activity to an entrapped protein antigen. The immune responses of rabbits immunized subcutaneously with lysozyme entrapped in neutral negatively and positively charged liposomes and compared with complete Freund's adjuvant (CFA), showed positively charged liposomes to be a better adjuvant than neutral, negatively charged liposomes and even CFA. This was true for solid liposomes also. Interestingly, injection of positively charged liposomes led to the formation of granulomas at the sites of immunization, which was not observed with neutral and negatively charged liposomes.
A rapid and efficient method to enrich SAF-protein from scrapie brains of hamsters
Authors: Hilmert Horst , Diringer Heino
Published: February 2005

Scrapie hamster brains contain at least 5–10 μg of scrapie-associated fibrils (SAF) per brain as estimated by the amount of its major constituent, a protein of about 26 000 daltons (SAF-protein). It can be extracted efficiently by a 10% solution of sarkosyl and can be enriched by differentia] centrifugation and buffer extraction. Scrapie infectivity, SAF, and SAF-protein copurify.
Biosynthetic capacity of hepatocytes after storage at 4°C
Authors: Farrell Rosemary , Lund Patricia
Published: February 2005

Capacity to synthesize glucose, urea, and ketone bodies is well maintained in hepatocytes after storage for at least 24 h at 4°C. Substrates and albumin are the only requirements.
Phospholipid and protein analysis of pulmonary surfactant
Authors: Cottrell R. C. , Herod I. A. , Bayley D. , Purchase R. , Miller K.
Published: February 2005

Quantitative analysis of the phospholipid composition of pulmonary surfactant preparations has been achieved by a modification of the phosphorus-31 nuclear magnetic resonance method of E London and G Feigenson (3. Lipid Res. 20, 408–412, 1979). Resolution of the protein components by a 2-dimensional isoelectric-focussing - SDS/ polyacrylamide-gel-electrophoresis technique is reported for the first time.
Two (completely) rate-limiting steps in one metabolic pathway? The resolution of a paradox using bacteriorhodopsin liposomes and the control theory
Authors: Westerhoff Hans V. , Arents Jos C.
Published: February 2005

Proton pumping by bacteriorhodopsin and chargecompensating ion movement can both and simultaneously behave as the rate-limiting step in light-driven proton uptake into bacteriorhodopsin liposomes. This apparently excessive control exerted on the net proton influx is possible because of the negative (−1) ‘control coefficient” of the net proton influx with respect to the proton leaks. Furthermore, the property of bacteriorhodopsin that it is inhibited by the membrane potential is responsible for the transfer of part of the control on the net proton influx from the first, irreversible, step in the pathway (i.e. bacteriorhodopsin) to the second, reversible, step (i.e., charge-compensating ion movement).
Effect of polyethyleneglycols (PEG 600 and PEG 6000) and bovine serum albumin on myeloperoxidase-mediated release of [3H]-serotonin from rat peritoneal mast cells in vitro
Authors: Magnusson Karl-Eric , Stendahl Olle
Published: February 2005

Rat peritoneal mast cells in vitro released [3H]-serotonin in the presence of halide (I-), myeloperoxidase (MPO), and a H2O2-generating system. The degranulation was partly inhibited with low concentrations of bovine serum albumin (BSA; 0.1–l% w/v), or polyethyleneglycols (PEG 600 or PEG 6000, 0.1% w/v). Furthermore, PEG 600 and PEG 6000 enhanced the stabilization achieved with 0.1% BSA. The results may provide a new aspect on antigenicity of PEG-modified allergens, and on mast-cell response at an inflammatory site.
Monoclonal antibodies against plasma protease inhibitors: I. Production and characterization of 23 monoclonal antibodies against human α2
Authors: Herion P. , Siberdt D. , Soto G. Garduno , Urbain J. , Bollen A.
Published: February 2005

23 hybridomas secreting monoclonal antibodies against human α2, the fast-acting inhibitor of plasmin present in plasma, have been produced by the cell-fusion technique. Isotyping of the monoclonal antibodies has revealed that 14 monoclonal antibodies belong to the class IgG1, 6 to the class IgG2a, and 3 to the class tgG2b. All light chains belong to the κ group. The specificity and relative avidity of these monoclonals have been determined Using an indirect enzyme-linked immunosorbent assay. 13 monoclonals exhibit a relatively high avidity for α2, 5 are of intermediate avidity, and 5 of low avidity. The epitope specificity of these 23 rnonoclonal antibodies, originating from a single mouse, have been examined in inhibition experiments. A group of 10 monoclonal antibodies exhibit a very similar inhibition pattern. Partial inhibition effects displayed by 10 other antibodies define partially overlapping antigenic regions. The binding of these antibodies seems to produce a conformational change in the α2 molecule, reducing the binding of two other antibodies. The last antibody defines an independent epitope.
Isolation and patial sequence of bovine cDNA clones for the high-moility-group protein (HMG-1)
Authors: Pentecost Brian , Dixon Gordon H.
Published: February 2005

Several cloned ds cDNAs containing bovine HMG-1 sequences have been isolated from a ds cDNA library prepared from the poly(A)+ mRNA fraction of bovine testis using a pool of synthetic 17-rneric oligo-deoxyribonucleotides with the sequence α2 selected to be complementary to a region of the coding sequence corresponding to the relatively unambiguous amino acid sequence, Glu-Met-Trp-Asn-Asn-Thr. Determination of the DNA sequences in these clones indicates that they represent the 3′ half of the HMG-1 message and contain an unusually long putative 3′ untranslated region of 480 nucleotides. The sequence of the coding region corresponding to the 99 amino acids at the C-terminus of HMG-I has been determined and largely confirms the published primary sequence in this region (Walker 3M, (1982) in: The HMG Chromosomal Proteins, Academic Press, London & New York, pp. 69–88). In addition the cDNA sequence provides a complete sequence of the 30 residue polyacidic region and shows that the nucleotide sequence in this region is a repeating one and that the polyacidic domain comprises the C-terminus of the protein.
Effects of hyperthyroidism on stimulation of [1-14C]oleate oxidation to 14CO2 in isolated hepatocytes from fed rats by the catecholamines, vasopressin, and angiotensin II
Authors: Sugden Mary C. , El-Saadi Amal , Goode Anthony W. , Stewart Orr J.
Published: February 2005

Possible effects of adrenaline, noradrenaline, vasopressin, and angiotensin II to increase 14CO2 production from [1-14C]oleate were examined in hepatocytes from fed L-triiodothyronine(T3)-treated or control rats. Rates of 14CO2 production were decreased and rates of ketogenesis increased in hepatocytes from T3-treated rats. These changes were accompanied by a marked shift of the 3-hydroxybutyrate:acetoacetate concentration ratio towards acetoacetate. Rates of glucose and lactate release were decreased. Whereas the Ca2+-mobilizing hormones increased 14CO2 production from [1-14C]oleate by 64–84% with hepatocytes from control rats, they increased 14CO2 production from [1-14C]oleate by only 24–32% with hepatocytes from T3-treated rats. The magnitude of the response to the Ca2+-mobilizing hormones in hepatocytes from T3-treated rats was increased by the addition of 3-mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase, to the incubation medium (increases of 52–88%). In the presence of 3-mercaptopicolinate, the 3-hydroxybutyrate:acetoacetate concentration ratio in hepatocytes from fed, T3-treated rats was similar to that in hepatocytes from control rats in the absence of 3-mercaptopicolinate. The results demonstrate that hyperthyroidism per se does not lead to a loss of sensitivity, in terms of oleate oxidation, either to the catecholamines or to vasopressin and angiotensin II. The impaired ability of hepatocytes from T3-treated rats to respond to these hormones is a consequence of decreased net glycolytic flux or a more oxidized mitochondrial redox state.
Oligomeric forms of potato spindle tuber viroid (PSTV) and of its complementary RNA are present in nuclei isolated from viroid-infected potato cells
Authors: Spiesmacher Ellen , Mühlbach Hans-Peter , Schnólzer Martina , Haas Bernd , Sänger Heinz L.
Published: February 2005

Different oligomeric forms of PSTV are detected in nuclei isolated from PSTV-infected potato cells by means of molecular hybridization, using as probes synthetic oligodeoxyribonucleotides with sequence specificity for (+)PSTV and for (−)PSTV. In addition to several species of longer-than-unit-length (−)PSTV molecules, two oligomeric forms os (+)PSTV are detected, which correspond in size to RNA strands of approximately two and three times viroid unit-length. They must be considered as the precursors os the circular and linear (+)PSTV monomers accumulating in the cell nucleus.
Turnover of ribosomal 28S and 18S rRNA during rat liver regeneration
Authors: Nikolov Emil N. , Dabeva Mariane D.
Published: February 2005

The turnover of 28S and 18S rRNA was studied in the course of 12 d after partial hepatectomy, including the proliferative (1st to 5th d) and post-proliferative (6th to 12th d) phases of liver regeneration. Turnover data, as the day-to-day rates of synthesis and degradation of 28S and 18S rRNA, were obtained by employing a suitable experimental procedure for the estimation of the increase of the amount of rRNA in the regenerating liver. It was found that 28S and 18S rRNA are accumulated into the cytoplasm and degraded at identical rates both in the proliferative and post proliferative phases. The turnover of both rRNA moieties is markedly slower during the first 3 d of liver regeneration.
Stimulation of insulin secretion from isolated rat islets of Langerhans by melittin
Authors: Morgan Noel G. , Montague William
Published: February 2005

Melittin, an amphipathic polypeptide, stimulated the secretion of insulin from rat islets of Langerhans incubated in vitro. The secretory response was dose-dependent and saturable with half the maximal response elicited by a melittin concentration of 4 μg/ml. The response was rapid in onset, an increase in secretion occurring within 2 rain of exposure of the islets to melittin (2 μg/ml). An enhanced secretory rate could be maintained for at least 40 rain in the presence of melittin but declined steadily when the agent was removed. Stimulation of secretion by melittin occurred in the absence of glucose and in the presence of both 4 mM and 8 mM glucose but not in the presence of 20 mM glucose. The effect of melittin on secretion was dependent on the presence of extracellular calcium but was not inhibited by norepinephrine. The data suggest that melittin may be a valuable agent for further study of the role played by the B-cell plasma membrane in the regulation of insulin secretion.
Calcium, calmodulin, and the production of prostacyclin by cultured vascular endothelial cells
Authors: Seid J. M. , Macneil S. , Tomlinson S.
Published: February 2005

The production of prostacyclin (PGI2) by cultured porcine aortic endothelial cells, in response to serum and the calcium ionophore A23187, was inhibited by TMB-8, an antagonist of intracellular calcium mobilization. The calcium-channel blocker methoxyverapamil (D600) inhibited serum-induced PGI2 production in but had little effect on A23187-induced PGI2 production. Calmodulin activity was detected in endothelial-cell Jysates and was inhibited by the calmodulin antagonist W7, which also inhibited PGI2 production in response to both agonists. Calcium and calmodulin appear to play an important role in mediating PGI2 production by the vascular endothelium.
Monoclonal antibody reactive with the human epidermal-growth-factor receptor recognizes the blood-group-A antigen
Authors: Gool H. C. , Schlessinger J. , Lax I. , Yarden Y. , Libermann T. A. , Feizi T.
Published: February 2005

The hybridoma antibody TL5, which precipitates the EGF receptor from the human epidermoid carcinoma cell line A431, has been shown to recognize the blood-group-A carbohydrate structure. This conclusion has been reached from studies of (a) the binding of the antibody to glycoproteins and haemagglutination of erythrocytes with known blood-group-antigen activities and (b) the inhibition of binding of the antibody to a radiolabelled blood-group-A-active glycoprotein by structurally defined oligosaccharides.
Receptor-mediated phagocytosis of zymosan is unaffected by some conditions which reduce macrophage lysosomal enzyme secretion
Authors: Bodmer Judith L. , Dean Roger T.
Published: February 2005

We have previously shown that several agents which interfere with binding of Iigands to the mannose-glycoprotein receptor on macrophages can inhibit zymosan-induced lysosomal enzyme secretion. Here we show that mannose only reduces the association of zymosan with macrophages during the first hour of exposure; after longer periods of uptake no effect is detectable. We have previously shown that mannose reduces surface binding of zymosan, probably by interfering selectively with binding to the mannose receptor. The present inhibition of association of zymosan with macrophages during short exposures can be entirely explained by this reduction of binding. Macrophages must therefore internalize zymosan at sites in addition to the mannose receptor. In contrast to macrophages the routine macrophage-like cell line P388D1 is lacking the mannose-glycoprotein receptor. Accordingly we find that binding of zymosan to P388D1 is much slighter than to macrophages and is unaffected by mannose or mannose-6-phosphate. The spontaneous lysosomal enzyme secretion of P388D1 is also unaffected by mannose. The data on macrophages confirm our previous suggestion that agents interfering with the mannose receptor inhibit the induction of lysosomal enzyme secretion by acting directly on the receptor. The data on P388D1 ceils support this assertion by excluding effects at later steps in the secretory pathway.
Molecular mechanisms of membrane fusion: Steps during phospholipid and exocytotic membrane fusion
Authors: Zimmerberg Joshua
Published: February 2005

Exocytosis is considered as four separate steps: adhesion, fusion/pore formation, pore widening, and content discharge. Experiments on both synthetic and natural membranes are presented to show each of these steps. Major differences are seen in the two fusing systems. These differences are discussed in terms of molecular mechanisms of fusion.
Docking of chromaffin granules—A necessary step in exocytosis?
Authors: Schäfer Theo , Karli Urs O. , Schweizer Felix E. , Burger Max M.
Published: February 2005

Putative docking of secretory vesicles comprising recognition of and attachment to future fusion sites in the plasma membrane has been investigated in chromaffin cells of the bovine adrenal medulla and in rat phaeochromocytoma (PC 12) cells. Upon permeabilization with digitonin, secretion can be stimulated in both cell types by indreasing the free Ca2+-concentration to μM levels. Secretory activity can be elicited up to 1 hr after starting permeabilization and despite the loss of soluble cytoplasmic components indicating a stable attachment of granules to the plasma membrane awaiting the trigger for fusion. Docked granules can be observed in the electron microscope in permeabilized PC 12 cells which contain a large proportion of their granules aligned underneath the plasma membrane. The population of putatively docked granules in chromaffin cells cannot be as readily discerned due to the dispersal of granules throughout the cytoplasm. Further experiments comparing PC 12 and chromaffin cells suggest that active docking but not transport of granules can still be performed by permeabilized cells in the presence of Ca2+: a short (2 min) pulse of Ca2+ in PC 12 cells leads to the secretion of almost all releasable hormone over a 15 min observation period whereas, in chromaffin cells, with only a small proportion of granules docked, withdrawal of Ca2+ leads to an immediate halt in secretion. Transport of chromaffin granules from the Golgi to the plasma membrane docking sites seems to depend on a mechanism sensitive to permeabilization. This is shown by the difference in the amount of hormone released from the two permeabilized cell types, reflecting the contrast in the proportion of granules docked to the plasma membrane in PC 12 or chromaffin cells. Neither docking nor the docked state are influenced by cytochalasine B or colchicine. The permeabilized cell system is a valuable technique for the in vitro study of interaction between secretory vesicles and their target membrane.
Annexins—New family of Ca2+-regulated-phospholipid binding protein
Authors: Geisow Michael J. , Walker John H. , Boustead Catherine , Taylor Willie
Published: February 2005

Calcium and phospholipid binding proteins have been identified and localized by immunocytochemistry in a wide range of cells and tissues. Two of these proteins (calpactins) also bind F-actin and are substrates for tyrosine kinases. The similar membrane-binding properties of these molecules arise from conserved amino acid sequences and a model is proposed for the tertiary structure of a common calcium and phospholipid binding domain.
Effect of HDL1 infusion on biliary secretion in perfused rat liver
Authors: Rivabene Roberto , Cantafora Alfredo , Yan Chong Chao , Castellano Flavia , Bruscalupi Giovannella , Bravo Elena
Published: February 2005

The effects of HDL1 lipoprotein infusion on biliary lipid secretion were studied in the in vitro model of rat perfused liver. A strong increase in bile flow was observed during and after lipoprotein infusion. This caused a significant rise in cholesterol, phospholipid and bile salt secretions. However, only the percentage of cholesterol increased with respect to the other bile lipids. The changes observed in the cholesterol/phospholipid molar ratio values of liver membrane subfractions (i.e., liver plasma membrane, mitochondria plus lysosomes and microsomes) isolated from the perfused rat liver after HDL1 administration were not significant.
Diagnosis of nonsense mutations in Aspergillus nidulans
Authors: Martinelli S. D. , Roberts T. J.
Published: February 2005

Three genotypically suppressible alleles,alX4, alcA125, and niaD500, are phenotypically suppressed by aminoglycoside antibiotics. Unsuppressible alleles at these loci are unaffected as are known missense mutations at the yA and gdhA loci. This is consistent with the premise that the suppressible mutations are nonsense and that this highly-allele-specific phenotypic suppression can be used to distinguish nonsense from missense mutations of Aspergillus nidulans. Paromomycin and tobramycin are recommended for screening unknown mutations.
Sympathetic activation of brown-adipose-tissue thermogenesis in cachexia
Authors: Brooks S. L. , Neville A. M. , Rothwell N. J. , Stock M. J. , Wilson S.
Published: February 2005

Tumour-bearing mice spontaneously lose weight 8–9 weeks after implantation of a human hypernephroma, in spite of a normal food intake. Resting oxygen consumption was up to 40% higher in these animals than in sham-operated controls, but was significantly reduced by 8-adrenergic blockade with propranolol in the former group. The injection of noradrenaline caused a marked stimulation of the metabolic rate in all the animals, but the greatest response was seen in the cachectic mice. The brown-adipose-tissue mass was similar for both groups, but guanosine diphosphate binding to brownadipose-tissue mitochondria (an index of thermogenic capacity) was significantly increased in turnout-bearing mice, and the injection of noradrenaline 1 h prior to sacrifice caused the greatest stimulation of binding in the cachectic group. These data suggest that the rapid weight loss of tumour-bearing animals may be due to a high metabolic rate which results from sympathetic stimulation of brown-adipose-tissue metabolism. The relevance of these results to cancer-induced cachexia in man is discussed.
A novel form of host defence: Membrane protection by Ca2+ and Zn2+
Authors: Pasternak C. A.
Published: February 2005

This review focusses on two questions: (1) How can the intracellular toxicity of ions such as Ca2+ or Zn2+ be reconciled with their extracellular benefit? (2) Why is the dietary requirement for Zn2+ so high when its documented biological role is that of a tightly-bound prosthetic group of certain enzymes? An answer to both questions is provided by the observation that extracellular cations such as Ca2+ and Zn2+ protect the plasma membrane of cells against non-specific leakage, including an influx of Ca2+ or Zn2+. It is suggested that such protection, against leakage induced by microbial and other toxins, may contribute to the high dietary requirement for zinc. These arguments lead to the proposal that a previously unrecognized form of host defence is one of protection of the cell plasma membrane by divalent cations against damage induced by cytotoxic agents of environmental origin.
Surface-core correlations in serum lipoproteins
Authors: Herak J. N. , Pifat Greta , Brnjas-Kraljević Jasminka , Knipping Gabriele , Jürgens G.
Published: February 2005

It has been found that the capacity of lipoproteins for binding Mn(II) ions is dependent on the arrangement of the Iipoprotein core. A change in the molecular organization of the LDL core (thermotropic transition) is associated with the change on the lipoprotein surface. In HDL there is no thermotropic transition and no abrupt change of the binding capacity‥ The observed surface-core correlation might be an important link in understanding how dietary fat influences the lipoprotein metabolism.
Activation of mammalian skeletal-muscle carbonic anhydrase III by arginine modification
Authors: Tashian Richard E. , Johansen Jack T. , Christiansen Erik , Chegwidden W. Richard
Published: February 2005

Purified carbonic anhydrase isozymes I, II, and III (CA I, CA II, CA III) from various sources were treated with 2,3-butanedione and their bicarbonate dehydration reactions followed. The specific activities of human and bovine CA I and CA II and chicken CA III were not affected by the butanedione treatment, whereas the activities of human, gorilla, and bovine CA III were rapidly activated. These findings suggest that one, or both, of the two arginyl residues which appear to be unique to the active sites of the mammalian CA III isozymes are modified by butanedione.
The effect of tunicamycin on cell-surface changes associated with development and differentiation of Dictyostelium discoideum
Authors: Sharpe Paul T. , Watts D. J.
Published: February 2005

Developmental changes in surface properties of Dictyostelium discoideum cells have been detected by partitioning. Changes occurring between 0 and 6 h development were not affected by tunicamycin but subsequent changes associated with formation of presumptive spore cells were inhibited. It would seem that only the latter changes are dependent on glyco-protein synthesis.
Isolation and in vitro translation of a mammalian protamine mRNA
Authors: Krawetz S. A. , Dixon G. H.
Published: February 2005

mRNA was isolated from sexually mature rat, rabbit, and bovine testes. Poly(A+) and (A-) RNAs were prepared and hybridized to a rainbow-trout protamine probe. The bovine (A+) fraction showed significant hybridization compared to the other species and these related sequences were also found in total bovine DNA. Bovine mRNA programmed the in vitro synthesis of a basic protein that possessed protamine-like properties. The mRNA was fractionated by agarose-gel electro-phoresis and the fractions hybridized to the trout protamine probe. A significant hybridization signal was observed corresponding to a mRNA of approximately 400 nucleotides in length which coded for the protamine-like protein. The data support the view that we have isolated a mammalian (bovine) protamine mRNA.
Gramicidin a induces lysolecithin to form bilayers
Authors: Pasquali-Ronchetti I. , Spisni A. , Casali E. , Masotti L. , Urry D. W.
Published: February 2005

Heat-induced association of Gramicidin A with lyso-lecithin micelles results in the formation of lipid bilayer structures. The capacity of the Gramicidin A peptide to transform the lysolecithin lipid structure from micelle to bilayer is considered in terms of molecular packing mechanisms and relevance to membrane processes in general. The resulting lipid-bilayer-packaged channel system has particular usefulness in characterizing channel structure and mechanism.
Evidence for histidine residues in the immunoglobulin-binding site of human C1q
Authors: Easterbrook-Smith S. B.
Published: February 2005

The immunoglobulin-binding activity of subcomponent Clq of human complement is lost following treatment with diethylpyrocarbonate; the inactivation showed first-order kinetics with respect to time and modifier concentration. Soluble IgG oligomers protected Clq against diethylpyrocarbonate modification. Treatment of modified Clq with hydroxylamine resulted in an 85% recovery of its ability to bind to aggregated immuno-globulin. The inactivation process was associated with modification of 12.1±0.7 histidine residues per Clq molecule. These data are consistent with the presence of histidine residues in the immunoglobulin-binding sites of Clq; these residues may participate in ionic interactions with the carboxyl groups known to be in the Clq binding site of IgG.
Theoretical studies on capillary microviscometry of skeletal muscle actin
Authors: Masuhara Mitsuhiko , Yokoyama Hiroyuki , Tatsumi Noriyuki
Published: February 2005

For improving Ostwald's viscometry, which is time-consuming and requires a relatively large volume of specimen to determine viscosity, we developed a capillary microviscometric method with an appropriate mathematical model, and have compared this method with Ostwald's method.
The unwinding of circular DNA by intercalating agents as determined by gel electrophoresis
Authors: Dougherty Geoffrey
Published: February 2005

The conventional counting of electrophoretically resolvable topoisomers is an attractive technique for determining the number of superhelical turns in a closed circular DNA molecule. The method can be extended in order to determine the unwinding produced by a drug, if its binding constants are known under similar environmental conditions. Ethidium bromide was found to unwind a DNA molecule derived from the plasmid pBR322 by 26.0° in a magnesium-containing buffer. The method is convenient for investigating the possible effects of different environmental changes (such as ionic strength, ionic species, or temperature) on the unwinding angle produced by a particular drug. It can also give an early indication of multiple modes of binding.
Direct radioactive labelling of poly(ADP-ribose) in developing Xenopus laevis embryos
Authors: Williams Gwyn T. , Shall Sydney , Ford Christoper C.
Published: February 2005

It has not previously been possible to label the nuclear protein modification poly(ADP-ribose) directly from NAD because of the impermeability of the cell membrane. We have overcome this important problem by micro-injection of radioactively labelled NAD into xenopus laevis early embryos. The polymer was identified and then quantified by its insensitivity to DNAase, RNAase, and spleen phosphodiesterase and by the chromatographic mobility of the products of digestion with snake-venom phosphodiesterase. The quantity of poly(ADP-ribose) present after 25 h of development (129 ng/mg DNA) is lower than that found in fully differentiated tissue.
Suppressors suaC 109 and suaA 101 of Aspergillus nidulans alter the ribosomal phenotype in vitro
Authors: Zamir A. , Martinelli S. S.
Published: February 2005

A new homologous, cell-free system for protein synthesis has been devised for use with ribosomes and elongation factors from Aspergillus nidulans. Ribosome preparations from strains with either the suaAlO1 or suaCl09 mutations have a higher misreading ratio (non-cognate:cognate amino acid incorporation) in the presence of hygromycin than controls. They can be classed as fidelity mutants. These results also prove that the mutations must be in genes coding for ribosomal proteins or enzymes which modify ribosomal proteins post-translationally. Alternatively, the genes could code for translation factors.
MSH binding in bomirski amelanotic hamster melanoma cells is stimulated by L-tyrosine
Authors: Slominski Andrzej , Pawelek John
Published: February 2005

Bomirski Ab amelanotic melanoma cells have recently been shown to undergo striking phenotypic changes when precursors of the melanogenic pathway, L-tyrosine and L-dopa, are added to the culture medium. The changes include increased tyrosinase activity and de novo synthesis of melanosomes and melanin. L-tyrosine and L-dopa appeared to elicit these responses through separate but overlapping regulatory pathways. Here we show an additional effect of L-tyrosine: stimulation of MSH binding capacity. Cells cultured for 24–48 hours in the presence of 200 μM L-tyrosine display a 3–4 fold increase in their ability to bind125l-β-MSH. L-dopa did not stimulate MSH binding under the same conditions. In control experiments neither L-tyrosine nor L-dopa had any effect on insulin binding. The amelanotic cells respond to MSH with increased dendrite formation, increased tyrosinase activity without melanin production, and decreased growth rate.
Latent human leukocyte collagenase can be activated by gold thioglucose and gold sodium thiomalate, but not by auranofin
Authors: Sorsa Timo , Suomalainen Kimmo , Turto Heikki , Lindy Seppo
Published: February 2005

Gold thioglucose and gold sodium thiomalate were shown to be potent activators of latent human leukocyte collagenase. No activation by auranofin was noted. The activation may proceed through the action of gold on the essential sulfhydrylgroups of latent enzyme and, thereby, mimick the action of the known organomercurial activators.
Direct demonstration of increases in cytosolic free Ca2+ during stimulation of pancreatic enzyme secretion
Authors: Dormer R. L.
Published: February 2005

The Ca2+-activated photoprotein aequorin has been incorporated into intact, isolated rat pancreatic acini by a hypotonic swelling method. The isolated acini retained normal secretory responses after loading with aequorin. Increases in cytosolic Ca2+ concentration in response to a physiological secretagogue, carbamylcholine, and to divalent-cation ionophore A23187 have been demonstrated. Simultaneous measurement of the dynamics of enzyme secretion and changes in cytosolic Ca2+ concentration has been achieved using a newly developed apparatus.
Inhibition and recovery of DNA synthesis in PHA-stimulated u.v.-irradiated lymphocytes from patients with actinic keratosis
Authors: Abo-Darub J. M. , Mackie R. , Pitts J. D.
Published: February 2005

The recovery, after inhibition by u.v.-irradiation, of phytohaemagglutinin-stimulated DNA synthesis is impaired in lymphocytes from patients with multiple actinic keratoses (AK) compared to the recovery in lymphocytes from age-matched, control individuals. This shows that the reduced level (50%) of DNA repair activity in AK ceils is sufficiently different from that in normal cells to significantly affect cellular activity.
Studies of the growth of human bone-derived cells in culture using aqueous two-phase partition
Authors: Sharpe Paul T. , MacDonald B. R. , Gallagher J. A. , Treffry T. E. , Russell R. G. G.
Published: February 2005

Human bone cells, maintained in culture, have been subjected to partitioning in an aqueous two-phase system on a countercurrent distribution apparatus. A broad cell distribution was obtained indicating cell-surface heterogeneity. Two major cell populations were identified which appeared to be growing at different rates. The ‘fast’-growing cells had a less hydrophobic cell surface than the ‘slow’-growing cells. Possible relationships of these cell populations with osteoblast differentiation and the potential importance of this technique in studies of osteoblast differentiation are discussed.
Alterations in mammary-gland blood flow and glucose metabolism in the lactating rat induced by short-term starvation and refeeding
Authors: Jones Richard G. , Williamson Dermot H.
Published: February 2005

Six-hour starvation of lactating rats caused a 75% decrease in mammary-gland lipogenesis. The inhibition of lipogenesis was accompanied by a 45% decrease of blood flow to the mammary gland and a 60% decrease in glucose uptake. Within 2 h of refeeding, lipogenesis and glucose uptake by the gland increased to fed values though blood flow to the gland remained at only 63% of that in the fed state. It is concluded that blood flow, and hence substrate supply, is not a rate-limiting factor for lipogenesis by the lactating mammary gland in the rat.
Stimulation of flux through hepatic pyruvate dehydrogenase by 3-mercaptopicolinate
Authors: Myles David D. , Strong Peter , Stratton Garry D. , Skidmore Ian F. , Sugden Mary C.
Published: February 2005

Isolated hepatocytes from 24-h-starved rats were used to assess the possible effect of Ahe hypoglycaemic agent 3-mercaptopicolinate on flux through the hepatic pyruvate dehydrogenase complex. Increasing the extraceIIular pyruvate concentration from 1 mM to 2 mM or 5 mM resulted in an increase in flux through pyruvate dehydrogenase and the tricarboxylic acid cycle as measured by14CO2 evolution from [1-14C]pyruvate and [3-14C]pyruvate. Gluconeogenesis was inhibited by 3-mercaptopicolinate from both 1 mM and 2 mM pyruvate, but significant increases in malate and citrate concentrations only occurred in cells incubated with 1 mM pyruvate. Flux through pyruvate dehydrogenase was stimulated by 3-mercaptopicolinate with 1 mM pyruvate but was unaltered with 2 mM pyruvate. Dichloroacetate stimulated flux through pyruvate dehydrogenase with no effect on gluconeogenesis in the presence of I mM pyruvate. There was no effect of 3-mercaptopicolinate, administered in vivo, to 24-h-starved rats on the activity of pyruvate dehydrogenase in freeze-clamped heart or liver tissue, although the drug did decrease blood glucose concentration and increase the blood concentrations of lactate and alanine. Dichloroacetate, administered in vivo to 24-h-starved rats, increased the activity of pyruvate dehydrogenase in freeze-clamped heart and liver, and caused decreases in the blood concentrations of glucose, lactate, and alanine. The results suggest that 3-mercaptopicolinate increases flux through hepatocyte pyruvate dehydrogenase by an indirect mechanism.
Amino acid sequence and structural repeats in schistosome paramyosin match those of myosin
Authors: Cohen Carolyn , Lanar David E. , Parry David A. D.
Published: February 2005

The cDNA encoding about half of an antigenic non-surface schistosome parasite protein of Mr 97 K has recently been cloned and sequenced (Lanar, Pearce, James and Sher (1986) Science234:593–596). Analysis of this sequence, together with the properties of the native protein, reveals that this protein is paramyosin, the hitherto unsequenced core protein of myosin filaments in invertebrate muscle. In this report we analyze in more detail the partial amino acid sequence of schistosome paramyosin and describe electron microscope studies of the native protein and its aggregates. We show a close correspondence between the structures of paramyosin and the myosin rod that is required for these proteins to assemble together in muscle thick filaments.
Glutathione metabolism under the influence of hydroperoxides in the lactating mammary gland of the rat. Effect of glucose and extracellular ATP
Authors: Estrela José M. , Montoro Juan B. , Viña Juan R. , Viña José
Published: February 2005

Tert-butyl hydroperoxide decreases GSH and total free glutathione (GSH+2GSSG) contents of acini from lactating mammary glands. The decrease in total free glutathione can be explained by an increase in mixed disulfide formation and by excretion of GSS G to the extracellular medium, and subsequent degradation catalyzed by gamma-glutamyl transpeptidase. Low concentrations of glucose prevented the changes in glutathione levels induced by the peroxide. In the presence of extracellular ATP, glucose did not prevent these changes. However, incubations with the peroxide, did not alter the rate of other metabolic pathways by acini.
Proton microprobe analysis of 15 elements in pancreatic B cells and exocrine pancreas in diabetic Chinese hamsters
Authors: Juntti-Berggren Lisa , Lindh Ulf , Berggren Per-Olof , Frankel Barbara J.
Published: February 2005

Diabetes mellitus spontaneously develops in certain sublines of non-obese Chinese hamsters, and the diabetic L-subline is known for subnormal pancreatic insulin release in vitro. The cause of the secretory defect is unknown.

Freeze-dried pancreas sections from genetically diabetic Chinese hamsters and normal controls were subjected to proton bombardment and the concentration of 15 elements in B cells and acini was calculated from the X-rays emitted. Diabetic B cells contained significantly less Al (−61%) and significantly more Cu (+92 %), Mg (+6 %) and Rb (+13 %) than their normal counterparts. The diabetic acini showed similar, significant changes. The molar ratio between K and Na was about 10 in endocrine as well as exocrine pancreas from both groups of animals, implying that neither sample preparation nor irradiation had induced significant diffusive changes.

In conclusion, the high K/Na ratio suggests that the diabetic B cell has a well-functioning Na+/K+ pump. However, significant and parallel changes in Al-, Cu-, Mg- and Rb-levels were found in both the B cells and acinar portion of the diabetic pancreas. It is not clear whether these elemental changes cause the islet secretory defect or result from it.
The biological properties of bovine parathyroid hormone (1–41), a fragment generated from the native hormone by human leukocytes
Authors: Barling Peter M. , Lowe Carolyn
Published: February 2005

Native bovine parathyroid hormone (bPTH) was found to be readily cleaved with human leukocyte elastase to yield the fragments bPTH(1–41) and bPTH(42–84). These were then isolated by reverse-phase HPLC and characterised by gas-phase sequencing and amino acid analysis. The biological activities of these fragments were assessed in an adenylate cyclase bioassay using the rat osteosarcoma cell line UMR106. bPTH(1–41) was found to have approximately twice the molar potency of the native hormone from which it was derived, bPTH(42–84) had no biological activity and did not modulate the adenylate cyclase response to these cells to the native hormone. The possible physiological significance of these observations is discussed.