bluuebunny/crossref_metadata_2025 huggingface dataset:
Mevalonate-derived proteins in liver regeneration
Authors: Castellano Flavia , Bruscalupi Giovannella , Trentalance Anna
Published: February 2005

Sixteen hours after partial hepatectomy in the rat, the synthesis of mevalonate (MVA) is not committed to produce cholesterol and only partially utilized for dolichol formation. In order to investigate the fate of MVA in this replicative system, slices of the remaining liver were incubated with 5-3H-MVA. Labeled proteins from whole liver and purified nuclei were analyzed after extensive delipidation and separation by SDS-PAGE. Many MVA-derived proteins were identified at 16 hours, while only two labelled peptides were detectable at 24 hours. The radioactivity was localized in covalently bound lipid moieties. A highly labeled 26 kD peptide was detectable in the nucleus at 16 hours, suggesting its involvement in the cell cycle progression.
In situ optical spectroscopy of some systems of biological interest
Authors: Balasubramanian D.
Published: February 2005

Monitoring the optical absorption or emission spectrum of a condensed phase sample offers information about the supramolecular assembly, packing effects and other features characteristic of the phase that would be missed when one studies solution-state spectra. We have used the technique of photoacoustic spectroscopy to study intact biological specimens, such as algae, parasite cells and the eye lens. Such a study has offered information about the status of endogenous hemin in Plasmodium cells and the mode of interaction of antimalarial drugs of the chloroquine class therein. We have also attempted to do in situ fluorescence spectroscopy on isolated intact eye lenses, which has enabled us to follow the photochemistry and the status of the photoproduct of the oxidation of the trp residues of the crystallins of the lens.
The role of sophisticated instruments in biological research: Examples from nuclear magnetic resonance
Authors: Becker Edwin D.
Published: February 2005

The development of NMR is described to illustrate the importance of new methodologies to solve biological problems.
Regulation of cell division and malignant transformation
Authors: Bhargava Pushpa M. , Chandani Sushil A.
Published: February 2005

The problem of regulation of cell division is essentially a problem of understanding regulation of transition from the resting state of a cell to the dividing state and vice versa. In malignancy the ability to revert back to a normal resting state is impaired. A model is presented which attempts to explain the control of the above transitions through control of uptake of essential nutrients by a transport-inhibitory protein. Experimental evidence in favour of the model is given.
Neural networks and REM sleep
Authors: Crick Francis
Published: February 2005

The nature of certain forms of memory is discussed in relation to neural networks and REM sleep.
Plant transposable elements: Their role in evolution
Authors: Saedler Heinz
Published: February 2005

Transposable elements (TE) are natural constituents of plant genomes. However, their presence only becomes apparent if they become dislodged from their resident positions in the genome and transpore into another gene, thereby inducing a mutation. Such TE-induced mutations are somatically unstable because they revert to wild type and hence reconstitute the expression of the mutated gene. The frequent somatic excision of the TE results in a variegated phenotype. Since this instability is inherited in a Mendelian manner the variegated phenotype is nuclear determined. By this criterion TE have been shown to occur in more than 30 species belonging to different families and genera. Many questions arise when dealing with TE: their structure and functions, and the biological significance of the activity of elements in the differentiation of a normal plant or in the evolution of plant genes.
The major protein of bull seminal plasma: Biosynthesis and biological function
Authors: Scheit Karl Heinz , Kemme Michael , Aumüller Gerhard , Seitz Jürgen , Hagendorff Gerd , Zimmer Michael
Published: February 2005

We isolated the major protein of apparent Mr of 15,000–16,000 from seminal plasma as well as from seminal veiscle secretion of bull and proved by amino acid analysis and tryptic peptide mapping that the two proteins were identical. An antiserum against this major protein was employed to quantitate and identify the major protein in seminal plasma as well as seminal vesicle secretion. The antiserum did not cross-react with proteins from bovine or human plasma or follicular fluid respectively.

Cell-free translation of poly(A)RNA from seminal vesicle tissue and immunoprecipitation yielded one major species with apparent Mr of 18,000. Using the anti-major protein antiserum, this major species was specifically immuno absorbed. Cloning and sequencing of a major protein-specific cDNA led to the identification of clone pMP17, encoding a precursor of the major protein of 128 amino acid residues. We proved that the major protein is identical to protein PDC 109 (Esch et al., Biochem. Biophys. Res. Comm.113:861–867, 1983).

The seminal vesicles synthesize major protein in an androgen-dependent fashion. In addition to intraluminal secretion of the vas deferens, ampullary spermatozoa revealed an intense immunoreaction which was restricted to the neck region of the sperm head and the middle piece, while the principal piece of the tail as well as the sperm head were devoid of immunoreactive material. Epididymal epithelium (as well as calf seminal vesicle epithelium) showed no immunoreactivity with major protein antiserum. Immunoelectron microscopy demonstrated that only spermatozoa devoid of a plasma membrane around the middle piece were able to bind the antiserum against major protein. After removal of the plasma membrane from epididymal spermatozoa, binding of major protein to subplasmalemmal binding sites was visualised using gold-labeled MP.

Transblotting with gold-labeled MP demonstrated a protein of about 66 kDa which appears to represent the major protein-receptor. Binding of major protein to the receptor (after loss of the plasma membrane in the mid-piece region of the spermatozoa after contact with secretions from seminal vesicles) is interpreted as a phyisological process presumably related to the onset of sperm motility.
Isoproterenol induces a ribosomal modification in the heart and the skeletal muscle of hamsters
Authors: Noël Josette , Brakier-Gingras Léa
Published: February 2005

The protein synthesis activity of heart, skeletal muscle and liver polysomes from isoprotenerol-treated and control hamsters has been compared in an in vitro non-inititating translation system. Heart and skeletal muscle polysomes from treated hamsters were less active than controls and required a higher magnesium concentration for optimal protein synthesis. These results suggest that there is a conformational modification in heart and skeletal muscle ribosomes from isoprotenerol-treated hamsters. No such change was observed with ribosomes from the liver of isoproterenol-treated hamsters.
Effect of a cold stimulus on the synthesis of uncoupling protein in brown adipose tissue of rats and newborn rabbits
Authors: Arnold John , Patel Hasmukh V. , Ridley Robert G. , Freeman Karl B.
Published: February 2005

Rats are known to respond to a cold stimulus by increasing the activity and amount of the uncoupling protein in brown adipose tissue. A 48 h cold stimulus was found to increase the synthesis of uncoupling protein 3.g-fold in 4–5 week old rats whereas no change was observed with newborn rabbits. The lack of response in the latter case may reflect a difference between rabbits and rats or that synthesis is already maximal in newborn rabbits.
The carbohydrate specificities of the monoclonal antibodies 29.1, 445 and 3C1B12 to the epidermal growth factor receptor of A431 cells
Authors: Gool H. C. , Hounsell E. F. , Lax I. , Kris R. M. , Libermann T. A. , Schlessinger J. , Sato J. D. , Kawamoto T. , Mendelsohn J. , Feizi T.
Published: February 2005

Sixteen hybridoma-derived antibodies to the epidermal growth factor receptor of A431 ceils were studied with respect to their reactions with blood group-related carbohydrate structures. Twelve of these were assessed as recognizing carbohydrate determinants on the basis of their immunostaining of reference blood group substances on nitrocellulose paper. Three of these antibodies were further investigated by inhibition of binding assays with giycoproteins and structurally defined oligosaccharides or by haemagglutination of erythrocytes before and after treatment with endo-β-galactosidase. Two of the antibodies, 29.1 and 455, were shown to have blood group A-related specificities which differed from one another and from those of monocional anti-A antibodies described previously. The third antibody, 3CIB12, which was shown to recognize a determinant based on αl+3 fucosylated Type 2 chains on linear and branched backbone sequences, also differs from previously described monoclonal antibodies of 3-fucosyl-N-acetyllactosamine type, such as anti-SSEA-1 (anti-mouse embryo) and several antibodies to human myeloid ceils. While these antibodies are invaluable in providing structural information on the carbohydrate chains of the receptor glycoprotein and should help to elucidate their functions, their use as ‘anti-receptor’ reagents in cell biology will be influenced by the knowledge that the determinants they recognize are shared by other glycoproteins and glycolipids of diverse cell types.
Transglutaminase-catalyzed incorporation of [2,5-3H]histamine into a Mr 84000 particulate protein in pancreatic islets
Authors: Gomis Ramon , Casanovas Angeles , Malaisse Willy J.
Published: February 2005

Rat pancreatic islet homogenates catalyze the incorporation of [2,5−3-H]histamine into endogenous proteins recovered in both the stacking gel and a Mr 84000 protein separated by polyacrylamide electrophoresis. The labelling of these proteins represents a Ca2+-dependent process inhibited by glycine methylester, but not sarcosine methylester, and enhanced after preincubation of the islets at a high concentration of D-glucose. Although transglutaminase activity is found in both soluble and particlate subcelluler fractions, the endogenous transglutaminase substrates were located mainly in paarticulate, possibly membrane-associated, material.
Lateral diffusion of plasma membrane receptors labelled with either platelet-derived growth factor (PDGF) or wheat germ agglutinin (WGA) in human polymorphonuclear leukocytes and fibroblasts
Authors: Ljungquist Pia , Wasteson Åke , Magnusson Karl-Eric
Published: February 2005

The aims of the present investigation were (a) to compare the lateral mobility of membrane receptors of human fibroblasts and polymorphonuclear leukocytes (PMNL) labelled with either platelet-derived growth factor (PDGF), or the lectin wheat germ agglutinin (WGA), and (b) to study effects of serum or PDGF on the mobility of these receptor molecules in human fibroblasts. Human foreskin fibroblasts (AG 1523) were grown on coverslips either under standard (10%) or under serum-free conditions yielding “normal” and “starved” cells, respectively. The receptor mobility was studied in response to exposure to PDGF, or serum, in short time or prolonged incubations. Human polymorphonuclear leukocytes (PMNL) were adhered to microscope slides by clotting drops of blood. They were stained with rhodaminated PDGF or fluoresceinated WGA. The diffusion of labelled receptors was assessed with fluorescence recovery after photobleaching (FRAP). It was found that (a) fibroblasts grown at normal serum concentration had a lower diffusion coefficient (D=3×10−10 cm2 s−1) for the PDGF-receptor and a slightly lower mobile fraction (R=60%) than starved cells (D=5×10−10 cm2s−1 and R=73%), (b) addition of serum to starved cells increased both D and R for the PDGF receptor to 12×10−10 cm2 s−1 and 96%, respectively, (c) a similar pattern was obtained for WGA-labelled glycoconjugates indicating general membrane effects of serum-induced cell stimulation, and (d) in PMNL the PDGF receptor displayed motility characteristics (D=3–4×10−10 cm2 s−1 and R=59%) similar to those in fibroblasts, possibly suggesting equivalent anchorage mechanisms in the membrane.
ATP formation from deoxyadenosine in human erythrocytes: Evidence for a hitherto unidentified route involving adenine and S-adenosylhomocysteine hydrolase
Authors: Simmonds H. A. , Fairbanks L. D. , Duley J. A. , Morris G. S.
Published: February 2005

A novel route of ATP formation has been identified using erythrocytes from patients deficient in four different enzymes associated with ATP formation. It entails prior adenine production from deoxyadenosine (or adenosine) in a reaction involving S-adenosylhomocysteine hydrolase. The postulated route has been demonstrated in human erythrocytes which, unlike other human cells, cannot form ATP from IMP. It is based on studies by others using purified S-adenosylhomocysteine hydrolase preparations in vitro. The results provide the first confirmation that this reaction occurs in intact human cells in vitro and thus most probably in vivo. This adenine production is normally masked in intact cells by further metabolism to ATP. Clinical significance for such a route is suggested by the fact that some adenosine analogues with potent oncostatic and antiviral properties also release adenine (or analogues) in vitro.
Induction of hormone receptor formation in the unicellular tetrahymena
Authors: Kovács P. , Nozawa Y. , Csaba G.
Published: February 2005

Studies based on treatment with antibodies to thyrotropic hormone, luteotropic hormone, growth hormone or adrenocorticotropic hormone have shown that although the unicellular Tetrahymena does not possess sui generis receptors to all polypeptide hormones, such binding structures may arise, or become established in the membrane of the unicellular Tetrahymena in the presence of exogenous hormone. The Tetrahymena subjected to hormonal imprinting still contained an increased amount of hormone after six generation changes, which suggested that either hormone production had been induced by treatment, or the internalized hormone had not been degraded intracellularly. Thus the role of hormonal imprinting in receptor formation has also been substantiated by the immunocytochemical approach used in the present study.
A high-affinity folate binding protein in human urine. Radioligand binding characteristics, immunological properties and molecular size
Authors: Hansen Steen Ingemann , Holm Jan , Høier-Madsen Mimi
Published: February 2005

High-affinity binding of [3H]folate in human urine displayed characteristics, e.g. apparent positive cooperativity, which are typical of specific folate binding. By means of a two-site enzyme-linked immunosorbent assay (ELISA) with rabbit antibodies against the low molecular weight folate binding protein from human milk, we measured folate binding protein concentrations in the range of 0.51 to 4.13 nM in urine samples from 16 apparently healthy individuals. Ultrogel AcA 44 chromatography of the urine showed that immunoreactive and radioligand bound folate binding protein coeluted in one large peak (Mr∼25,000).
Effect of the β-adrenoceptor agonist BRL 26830 on fatty acid synthesis and on the activities of pyruvate dehydrogenase and acetyl-CoA carboxylase in adipose tissues of the rat
Authors: Wilson Shelagh
Published: February 2005

BRL 26830 is a thermogenic β-adrenoceptor agonist which stimulates lipolysis and fatty acid oxidation in vivo. It also stimulates insulin secretion, and hence promotes glucose utilisation in vivo. The effect of this agent on white and brown adipose tissue of the rat was investigated. BRL 26830 increased the rate of fatty acid synthesis in vivo in white adipose tissue by 135% but reduced the rate of fatty acid synthesis in vivo in brown adipose tissue by 78%. The increase was abolished in white adipose tissue of streptozotocin-diabetic rats, indicating that the effect involved a rise in circulating insulin levels. The reduction in fatty acid synthesis in brown adipose tissues was associated with a reduction in the activity of acetyl-CoA carboxylase in the tissue consistent with a direct β-adrenoceptor-mediated effect. BRL 26830 also increased the proportion of pyruvate dehydrogenase in its active form in vivo in brown adipose tissue and this increase was abolished in streptozotocin-diabetic rats. These findings illustrate different sensitivities of white and brown adipose tissues to combined β-adrenergic and insulin stimulation.
Monosialoganglioside GM1 increases survival of thymocytes
Authors: Ernström Ulf , Kölare Susanne
Published: February 2005

Gangliosides are normal constituents of the plasma membrane. Exogenous gangliosides can be incorporated into the membrane and extensive research in nervous tissue has demonstrated a beneficial effect of gangliosides on the functional recovery of lesioned neurons and protection against neurotoxins. This paper shows that the effect of gangliosides is not restricted to neurons. The monosialoganglioside GM1 efficiently increases the survival of thymocytes and protects them against both the lytic effect of the glucocorticoid prednisolone and the effect of a thymocytotoxic serum. The protective effect of GM1 was achieved both in vitro and in vivo.
Somatostatin promotes accumulation of phospholipids in regenerating liver tissue of rats
Authors: Milin Cedomila , Radosevic-Stasic Biserka , Kirigin Madena , Hinic Visnja , Rukavina Daniel , Berggren Per-Olof , Efendic Saud
Published: February 2005

Effects of somatostatin (SOM) on tissue contents of proteins, total lipids and phospholipids were investigated in regenerating and intact liver tissue of Y-59 rats. Whereas SOM inhibited protein accumulation in regenerating liver, the hormone evoked and increase in total lipids, and specially in phosphatidylcholine, phosphatidylethnolamine, phosphatidylserine (PS) and phosphatidylinositol (PI). Since the same effects were not seen when intact liver was analyzed, it is assumed that SOM acts primarily on tissue stimulated to rapid growth. The increase of PS+PI fractions indicates a specific effect of SOM on the metabolism of phosphatidylinositides. Such an effect might result from the interference of the hormone with the action of growth factors that accelerate phosphatidylinositol breakdown.
Effect of three organophosphates on respiration in rat brain and liver tissue
Authors: Nag Maitreyi , Nandi Namita
Published: February 2005

The effects of three organophosphate pesticides, i.e. monocrotophos, dichlorvos, and phosphamidon on respiration in rat brain and liver tissue slices have been studied. Among these pesticides dichlorvos causes significant inhibition of respiration both in brain and liver.
Antidepressants and brain respiration
Authors: Nag Maitreyi , Nandi Namita
Published: February 2005

Imipramine and clorgyline, at concentrations of 0.002 M, inhibit the respiration of brain tissue by 82 and 71 per cent respectively, while chloropromazine and tranylcypromine, at concentrations of 0.01 M, inhibit it about 25 per cent. Deprenyl and amphetamine at a concentration of 0.002 M inhibit brain tissue respiration by 12 and 18 per cent respectively. Respiration in brain is least affected by lithium chloride (only 5 per cent inhibition).
Characterization of the LDL receptor in rat promegakaryoblasts in culture
Authors: Budd Tracy J. , Hemming Frank W. , Middleton Bruce
Published: February 2005

Rat promegakaryoblasts (RPM, a precursor platelet cell line) in culture exhibited a capacity to bind, take up and degrade125I-LDL. The low density lipoprotein (LDL) binding showed the following characteristics: (a) high affinity, (b) saturability, (c) specificity, (d) down-regulation, after exposure to 25 hydroxycholesterol. Furthermore the proteolytic degradation of125I-LDL by RPMs was inhibited by chloroquine which interferes with the lysosomal degradation processes. These findings show LDL receptor cell biology of RPM to be of the classical type and to differ from that of platelets.
Functional and structural characterization of the secretin receptors in rat gastric glands: Desensitization and glycoprotein nature
Authors: Bawab Wafa , Chastre Eric , Gespach Christian
Published: February 2005

We have documented and characterized the down-regulation of the125I-secretin binding sites and the associated desensitization of the secretin receptor-cAMP system in rat gastric glands. Secretin induced a rapid decrease of the high-affinity125I-secretin binding sites with t1/2=30 min at 37°C. Half-maximal down-regulation and desensitization occurred at 10−9 M secretin, a physiological concentration corresponding to the half-maximal activation of the secretin receptor. The Scatchard parameters of the low-affinity125I-secretin binding sites were unaffected by the pretreatment. This desensitization is heterologous in view of the loss of responsiveness to the truncated glucagon-like peptide 1 (TGLP-1), and pharmacologically selective since the sectetin-related analogue VIP (10−7 M) does not alter the secretin-induced cAMP generation in rat gastric glands. The glycoprotein nature of the secretin receptor has also been demonstrated using WGA-agarose affinity chromatography of the solubilized125I-secretin receptor complex.
Amino acid composition of band 3 protein from red blood cells of normal and epileptic children
Authors: Benga Gheorghe , Pop Victor Ioan , Popescu Octavian , Benga Ileana , Ferdinand William
Published: February 2005

Amino acid analyses of the band 3 protein purified from erythrocyte membranes of control and epileptic children showed that no major structural abnormalities of this protein could be linked with the red blood cell membrane alterations previously described in child epilepsy and, consequently, the molecular basis of these alterations should be looked for elsewhere.
L-alanine transport in isolated cells of interscapular brown adipose tissue in rat
Authors: Rodríguez-Martín A. , Remesar X.
Published: February 2005

The pattern of L-alanine uptake in isolated cells of interscapular brown adipose tissue has been determined. The uptake can be divided into the diffusion component (Kd=0.55 min−1) and a saturable Na+-dependent transport (KM=0.87 mM and Vmax=155 nmol/min/106 cells). The saturable component can be subdivided into MeAIB-sensitive (KM=1.63 mM and Vmax=162 nmol/min/106 cells) and MeAIB-insensitive (KM=3.2 mM and Vmax=39.5 nmol/min/106 cells). This kinetic pattern could indicate the presence of transport system (s) that resemble the commonly described transport systems for alanine uptake in several tissues.
Amino acid composition of human liver mitochondrial membranes in normal and pathological conditions
Authors: Benga Gheorghe , Hodârnău Adriana , Tilinca Rozalia , Borza Victoria , Ferdinand William
Published: February 2005

The amino acid composition of proteins from liver mitochondrial membranes has been studied in patients with normal liver, with biliary diseases and fatty liver, with obstructive jaundice or liver cirrhosis. A characteristic pattern of the amino acid composition in patients with normal liver has been found. In the mitochondrial membranes of patients with fatty liver tryptophan and lysine were decreased while [aspartic acid plus asparagine] and [glutamic acid plus glutamine] were increased compared to their counterpart in the normal liver. In patients with obstructive jaundice of short duration (less than two months) only a slight decrease in methionine content was found, while in the case of liver cirrhosis amino acid composition was markedly changed.
Influence of lindane on the fluidity of the rat ventral prostate membranes
Authors: Senar S. , Gutierrez-Ocaña M. T. , Perez-Albarsanz M. A. , Recio M. N.
Published: February 2005

The influence of lindane upon the dynamic properties of plasma membranes from rat ventral prostate has been investigated using a fluorescence polarization technique. Preincubation with lindane decreased the fluorescence polarization in a dose dependent manner. This effect, which is associated with an increased membrane fluidity, occurred in a very short period of time.

Lindane also provoked a number of changes in lipid biosynthesis from acetate in the membrane. Less [1-14C]acetate was incorporated into cholesterol and more into phospholipids when this liposoluble toxicant was added to the preincubation medium. However, not all phospholipid classes were equally increased, because while the rate of acetate incorporation was greater into choline glycerophospholipids than into ethanolamine glycerophospholipids, both were higher than the rates of acetate incorporation into serine glycerophospholipids and sphingomyelin.
Identification of a mammalian growth factor as a ribofolate peptide
Authors: Ernström Ulf
Published: February 2005

Thymocyte growth peptide (TGP) promotes DNA synthesis of immature thymocytes. TGP has been purified from sheep, human and calf thymus and recently characterized as an N-terminally blocked nonapeptide. Evidence is presented here that the blocking moiety consists of a formylpteroyl group bound to the N-terminal glutamyl residue of the nonapeptide. The pterin part of the TGP molecule has a ribityl substituent in analogy with riboflavin, which explains the pronounced hydrophilic property of TGP in contrast to unsubstituted and unconjugated folates. The compound can be classified as a ribofolate peptide, a novel class of growth factor. Zn2+ counteracts degradation of the molecule and is required for full biological activity; mass spectrometric data confirm that native TGP contains zinc.
Role of Na+/K+-stimulated adenosine triphosphatase in the action of dopaminergic-D2 receptors of the liver in rats
Authors: Abu-Jayyab Abdulrahim , Mahgoub Ahmed
Published: February 2005

The dopamine receptor agonist, bromocriptine, in a dose of 10 mg/kg i.p. for 14 days, in rats caused a significant increase in liver Na+/K+-ATPase activity, whereas sulpiride, a dopamine receptor antagonist, in a dose of 10 mg/kg, i.p. for 14 days, in rats, caused a significant decrease in liver Na+/K+-ATPase activity. Injection of bromocriptine and sulpiride simultaneously in a group of rats, under the same conditions and using the same doses caused a complete block of both stimulatory activity of bromocriptine and inhibitory activity of sulpiride on liver Na+/K+-ATPase activity. It is suggested that Na+/K+-ATPase may have a role in the action of dopaminergic-D2 receptors.
Normal levels of serum corticosterone and hepatic glucocorticoid receptors in obese (fa/fa) rats
Authors: Shargill Narinder Singh , Al-Baker Ibtisam , York David A.
Published: February 2005

In an attempt to understand the hyper-responsiveness to glucocorticoids that is characteristic of genetically obese fa/fa rats, we have measured the levels of free corticosterone in serum from lean and obese rats as well as the number of “cytosolic” and “nuclear” binding sites in livers of these rats. Both the lean and obese rats had similar amounts of free corticosterone available for biological activity at 4 weeks and 10 weeks of age. Measurement of glucocorticoid binding to hepatic glucocorticoid receptors failed to show any differences between genotypes leading to the suggestion that the abnormal glucocorticoid response in obese rats may be due either to post-receptor defects or to a permissive action of the steroid in the expression of the fa/fa genotype.
In vitro labeling of peroxisomal cholesterol with radioactive precursors
Authors: Appelkvist Eeva-Liisa
Published: February 2005

Peroxisomes isolated from rat liver were incubated with [3H]squalene and [3H]mevalonate and the subsequent incorporation of radioactivity into cholesterol studied. The isolated lipids became labeled after incubation with both precursors. In contrast to findings with microsomes, trypsin and detergent treatment of peroxisomes did not influence the rate of cholesterol synthesis. In addition, the luminal content of peroxisomes could alone mediate this synthetic process. Upon treatment of rats with various inducers of peroxisomes and of the endoplasmic reticulum, as well as upon feeding with cholesterol and cholestyramine, large differences in the pattern of in vitro incorporation of [3H]mevalonate into the cholesterol of peroxisomes and microsomes were observed. Injection of this precursor also resulted in high initial labeling of peroxisomal cholesterol in vivo. These experiments indicate that cholesterol synthesis may also occur in peroxisomes.
Quantitative energy dispersive X-ray microanalysis of eight elements in pancreatic endocrine and exocrine cells after cryo-fixation
Authors: Norlund Robert , Roos Norbert , Täljedal Inge-Bert
Published: February 2005

Quantitative X-ray microanalysis of 8 elements was performed on ultrathin, freeze-dried sections of islets and pancreas pieces from non-inbred ob/ob-mice. Diffusion of elements was reduced to a minimum by rapidly freezing the tissue samples between nitrogen-cooled polished copper surfaces and avoiding the use of chemical fixatives and stains. The ultrastructural morphology was adequately maintained to allow measurements on secretory granules, mitochondria, cell nuclei, and cytoplasm free of these organelles. The distribution of the various elements between cellular compartments was similar in islet β-cells and exocrine pancreas cells. However, the insulin secretory granules were outstanding in exhibiting the highest concentrations of zinc and calcium. In comparison with cytoplasm in the β-cells, the insulin granules accumulated calcium 2-fold and zinc as much as 40-fold. As no correlation could be made for endoplasmic reticulum in the cytoplasmic measurements areas, the true accumulations above cytosol are likely to be even higher.
The effects of meal-feeding and the diurnal cycle on lipogenesis in brown adipose tissue of rats
Authors: Thompson Mary P. , Grigor Murray R.
Published: February 2005

A significant diurnal variation in the rates of lipogenesis in vivo in brown adipose tissue occurred in both virgin and lactating rats. On a meal-feeding regime of either a chow, high-sucrose, or high-lipid diet, there was a very large increase in BAT lipogenesis following the meal. The rates observed after the sucrose meal are the highest so far reported. There was no significant difference in BAT lipogenesis between lactating and virgin rats, contrary to previous reports by others. The pattern of stimulation of BAT lipogenesis by these feeding regimes was different from that for white adipose tissue and liver and was not correlated with plasma insulin levels.
Regulation of polyamine biosynthesis by antizyme and some recent developments relating the induction of polyamine biosynthesis to cell growth
Authors: Canellakis E. S. , Kyriakidis D. A. , Rinehart C. A. , Huang S.-C. , Panagiotidis C. , Fong W.-F.
Published: February 2005

This review considers the role of antizyme, of amino acids and of protein synthesis in the regulation of polyamine biosynthesis.

The ornithine decarboxylase of eukaryotic ceils and of Escherichia coli coli can be non-competitively inhibited by proteins, termed antizymes, which are induced by di-and poly- amines. Some antizymes have been purified to homogeneity and have been shown to be structurally unique to the cell of origin. Yet, the E. coli antizyme and the rat liver antizyme cross react and inhibit each other's biosynthetic decarboxylases. These results indicate that aspects of the control of polyamine biosynthesis have been highly conserved throughout evolution.

Evidence for the physiological role of the antizyme in mammalian cells rests upon its identification in normal uninduced cells, upon the inverse relationship that exists between antizyme and ornithine decarboxylase as well as upon the existence of the complex of ornithine decarboxylase and antizyme in vivo. Furthermore, the antizyme has been shown to be highly specific; its Keq for ornithine decarboxylase is 1.4 × 1011 M-1. In addition, mammalian ceils contain an anti-antizyme, a protein that specifically binds to the antizyme of an ornithine decarboxylase-antizyme complex and liberates free ornithine decarboxylase from the complex. In B. coli, in which polyamine biosynthesis is mediated both by ornithine decarboxylase and by arginine decarboxylase, three proteins (one acidic and two basic) have been purified, each of which inhibits both these enzymes. They do not inhibit the biodegradative ornithine and arginine decarboxylases nor lysine decarboxylase. The two basic inhibitors have been shown to correspond to the ribosomal proteins S20/L26 and L34, respectively. The relationship of the acidic antizyme to other known B. coli proteins remains to be determined.
Initiation of DNA synthesis in the liver and other tissues of adult mice by a growth factor (EACF) isolated from acellular fluid of the Ehrlich ascites carcinoma
Authors: Yeh Hsing-Wu , Burns E. Robert , Yeh Yun-Chi
Published: February 2005

The mitogenic effect of a new growth factor that we recently isolated from the acellular ascitic fluid of the Ehrlich ascites carcinoma grown in vivo was examined. We have called this factor EACF (Ehrlich ascites carcinoma factor). EACF caused initiation of DNA synthesis in the liver, submandibular gland, exorbital lacrimal gland and epithelium of the tongue of adult mice after i.p. injection at a protein concentration of 3 pg per 25 g of body weight. For all tissues examined, except the tongue, EACF initiated DNA synthesis at about 48 to 60 h after injection, with the maximum effect at approx. 85 h, and the stimulatory effect lasting approx. 60 h. The initiation of DNA synthesis in liver, which is normally characterized by only an occasional cell passing through the S phase by EACF is of particular interest. The initiation of DNA synthesis in the liver was not prevented by hypophysectomy. Evidence also indicates that a similar heat-labile growth promoting factor(s) is present in calf serum.
Assessment of the antidiabetic activity of epicatechin in streptozotocin-diabetic and spontaneously diabetic BB/E rats
Authors: bone A. J. , Hii C. S. T. , Brown D. , Smith W. , Howell S. L.
Published: February 2005

(−)-Epicatechin has previously been suggested to rapidly reverse alloxan diabetes in rats. We have assessed the therapeutic value of the compound in two further animal models of insulin-dependent diabetes mellitus, namely streptozotocin – diabetic rats and the spontaneously diabetic BB/E rat. There was no indication of a reversal of established diabetes in either the streptozotocin-diabetic or the spontaneously diabetic BB/E rats. Moreover, epicatechin also failed to halt the progression of the disease in prediabetic BB/E rats. Earlier claims of the potential use of epicatechin as an antidiabetic agent must therefore be treated with some caution.
Water exchange through erythrocyte membranes: p-choloromercuribenzene sulfonate inhibition of water diffusion in ghosts studied by a nuclear magnetic resonance technique
Authors: Benga Gheorghe , Popescu Octavian , Pop Victor I.
Published: February 2005

A comparison of water diffusion in human erythrocytes and ghosts revealed a longer relaxation time in ghosts, A comparison of water diffusion in human erythrocytes and ghosts revealed a longer relaxation time in ghosts, corresponding to a decreased exchange rate. However, the diffusional permeability of ghosts was not significantly different from that of erythrocytes. The changes in water diffusion following exposure to p-chloromercuribenzene sulfonate (PCMBS) have been studied on ghosts suspended in isotonic solutions. It was found that a significant inhibitory effect of PCMBS on water diffusion occurred only after several minutes of incubation at 37°C. No inhibition was noticed after short incubation at 0°C as previously used in some labelling experiments. This indicates the location in the membrane interior of the SH groups involved in water diffusion across human erythrocyte membranes. The nuclear magnetic resonance (n. m. r.) method appears as a useful tool for studying changes in water diffusiofl in erythrocyte ghosts with the aim of locating the water channel.
Short term regulation of acyl CoA: Cholesterol acyl transferase (ACAT) activity in the regenerating and perinatal liver
Authors: Bruscalupi G. , Leoni S. , Mangiantini M. T. , Piemonte F. , Spagnuolo S. , Trentalance A.
Published: February 2005

Acyl coenzyme A:cholesterol acyltransferase (ACAT), the enzyme catalyzing the hepatic cholesterol esterification could be involved in the modified availability of cholesterol detectable in proliferating systems. While no significant variations are detectable in the regenerating liver, the modified ACAT activity during liver development and its differential sensitivity to the in vitro stimulation of modulatory systems suggest an involvement of the enzyme in this proliferating process.
Aggregation and fusion of lipid vesicles induced by diphtheria toxin at low pH: Possible involvement of the P site and the NAD+ binding site
Authors: Cabiaux Veronique , Vandenbranden Michel , Falmagne Paul , Ruysschaert Jean-Marie
Published: February 2005

Model membranes have been used to study the interaction between diphtheria toxin and lipids. We report here on the ability of this toxin to induc% at low pH, fusion and aggregation of asolectin lipid vesicles. Resonance energy transfer experiments using lipid fluorescent probes make it possible to discriminate between these two processes.
In vitro establishment of human fibroblasts of lysosomal diseases, GM1-gangliosidosis and Sandhoff disease, by transformation with origin-minus SV40 DNA
Authors: Momoi Takashi , Furuya Tatsuko , Suzuki Yoshiyuki , Sato Hiroko , Yamaguchi Nubuo
Published: February 2005

The permanent human cell lines preserving defects of lysosomal enzymes, GM1-1019-SV and SA-1077-SV, were established from the respective fibroblasts from patients with GMl-gangliosidosis and Sandhoff disease by transfection with replication origin-minus simian virus 40 DNA. These ceils grow rapidly without entering senescence during more than 120 population doublings. The activity of β-galactosidase in GM1-1019-SV and of B-N-acetylhexosaminidase in SA-1077-SV was respectively 40- and 180-fold lower than that of normal fibroblasts.
High expression levels of ras p21 protein in normal mouse heart tissues
Authors: Spandidos Demetrios A. , Dimitrov Todor
Published: February 2005

We have investigated the levels of protein encoded by the rat oncogene in normal mouse tissues using an immunoblotting technique. We have found that heart from young or adult NIH or Balb C strains of mice contain high levels of rat protein as compared to lung, liver, spleen, kidney, brain and skeletal muscle tissues from the same animal. Our results indicate that cellular rat expression does not in every case correlate with cell proliferation.
Effects of noradrenaline on 45Ca2+ efflux from isolated rat islets of Langerhans
Authors: Morgan Noel G. , Rumford Gwyneth M. , Montague William
Published: February 2005

Noradrenaline caused a prompt but transient increase in the rate of45Ca2+ efflux from isolated rat islets of Langerhans perifused in Ca2+ depleted medium. The response was modest in size and was unaffected by isosmotic replacement of NaCl with choline chloride or by inclusion of 0.5 mM dibutyryl cAMP in the perifusion medium, suggesting that it was not mediated by Na+: Ca2+ exchange nor by lowered cAMP. Despite its effect on45Ca2+ efflux, noradrenaline treatment did not alter the kinetics of45Ca2+ efflux in response to the muscarinic agonist, carbamylcholine, nor did it change the magnitude of the response to this agent. Simultaneous introduction of 20 mM glucose with noradrenaline prevented a rise in45Ca2+ efflux and indeed resulted in inhibition of45Ca2+ efflux. The data suggest that noradrenaline does not directly activate the mechanisms which regulate Ca2+ extrusion from islets cells, and they do not support a primary role for the Ca2+ efflux response in mediating adrenergic inhibition of insulin secretion.
Rat carcinoma cells in long-term, serum-free culture provide a continuing supply of collagenase
Authors: Stevenson Geoffrey A. , Lyons J. Guy , Cameron David A. , O'Grady Robert L.
Published: February 2005

Neoplastic, epithelial cells derived from a spontaneously-arising rat mammary carcinoma have been cultured in a defined medium, in the absence of serum, continuously, for over 2 years. The medium is a mixture of Ham's F12 and Dulbecco's Modified Eagle's media supplemented with insulin, transferrin and bovine serum albumin. The cells have retained their potential to produce tumours and, in culture, a true vertebrate collagenase.

This system provides a continuing supply of vertebrate collagenase through the application of recently developed methods.
Inhibition by dicyclohexylcarbodiimide of ATP synthesis in isolated rat hepatocytes
Authors: Emami S. , Lodola A. , Partis M. , Sanadi D. R.
Published: February 2005

Dicyclohexylcarbodiimide (DCCD) inhibits, by 50%, ATP synthesis in isolated hepatocytes. This inhibition is associated with DCCD-binding to a proteolipid fraction present in submitochondrial particles.
Interactions of cannabinoids with bovine serum albumin
Authors: Haque S. J. , Poddar M. K.
Published: February 2005

There is no shift of emission maximum (F470nm) of bovine serum albumin (BSA)-l-anilino-8-naphthatene sulphonic acid (ANS) complex in the pesence of delta-9-tetrahydrocannabinol (delta-9-THC) alone and cannabidiol (CBD) or cannabinol (CBN) in the presence and absence of delta-9-THC. Delta-9-THC (1.66–13.33 μM) and CBD at higher concentrations (13.33–20.0 μM) produce a concentration-dependent significant quenching of fluorescence of BSA-ANS complex, but CBN (l.66–20.0 μM) as well as CBD at lower concentrations (1.66–6.66 μM) fails to produce any significant change in Iluorescence intensity under similar conditions. Furthermore, neither CBD nor CBN is able to affect the delta-9-THC-induced quenching of fluorescence intensity of BSA-ANS complex. These results indicate that the binding of cannabinoids to the ANS binding sites of BSA molecule are in the order detta-9-THC > CBr3 > CBN, and CBD or CBN does not have any influence on the binding of delta-9-THC to BSA molecules under these conditions.
Mode of organization of lipid aggregates: A conformational analysis
Authors: Brasseur Robert , de Kruijff Ben , Ruysschaert Jean-Marie
Published: February 2005

A computational approach is used to predict the mode of organization of lipid molecules. The calculated aggregate states are fully compatible with the lipid phase preference: bilayers for dipalmitoylphosphatidylcholine, micelles for palmitoyllysophosphatidylcholine, and inverted structures for protonated dioleoylphosphatidic acid. The minimal conformational energy of the isolated molecule is calculated as the sum of the contributions resulting from the Van der Waals interactions, the torsional potentials, the electrostatic interactions, and the transfer energy. Assembly of these structures in monolayers yields the most probable modes of organization of lipids. The described method may represent a useful toot to predict the phase preference of lipids and to give a molecular description of their mode of association.
High-mannose oligosaccharides from human Tamm-Horsfall glycoprotein
Authors: Serafini-Cessi Franca , Dall'olio Fabio , Malagolini Nadia
Published: February 2005

The present communication reports the occurrence of high-mannose oligosaccharides on Tamm-Horsfall glycoprotein prepared from human pooled urine. The Pronase digest of the glycoprotein was fractionated by gel filtration and a high-mannose glycopeptide species was separated from complex-type glycopeptides. When high-mannose glycopeptides were digested with endo-β-N-acetylglucosaminidase H, followed by reduction with [3H]KBH4, three oligosaccharides were resolved by thin-layer chromatography. On the basis of chromatographic mobility and exoglycosidase digestions the composition Man7-, Man6-, and Man5-GlcNAc was assigned to the three oligosaccharides. Man6GlcNAc is by far the major component.
Effects of insulin, pertussis toxin and cholera toxin on protein synthesis and diacylglycerol production in 3T3 fibroblasts: Evidence for a G-protein mediated activation of phospholipase C in the insulin signal mechanism
Authors: Hesketh John E. , Campbell Gillian P.
Published: February 2005

The rapid increase in protein synthesis that occurs on addition of insulin (1 mU/ml) to stepped-down 3T3 cells was blocked by pre-incubation of the cells with pertussis toxin. Cholera toxin on the other hand stimulated protein synthesis and this effect was insensitive to actinomycin D and inhibited by pro-treatment of the cells with phorbol dibutyrate to deplete cell protein kinase C. Insulin was found to cause a rapid and transient increase in diacylglycerol (DAG) synthesis. The insulin-induced increase in diacylglycerol was blocked by pertussis toxin. Exogenous DAG (10 μM) stimulated protein synthesis within 1 hour. The results suggest that insuIin stimulates ribosomal activity through a signal mechanism that involves a G-protein mediated activation of phospholipase C to increase DAG levels.
Effects of bromocriptine on cyclic-GMP contents of some endocrine glands and liver in rats
Authors: Abu-Jayyab Abdulrahim , El-Denshary Ezz-Eddin S. M. , El-Hakim Mohamed M.
Published: February 2005

Cyclic GMP contents of the thyroid gland and ovary were significantly increased in response to single and multiple treatments of bromocriptine, an effect which was antagonized by sulpiride. Liver and adrenocortical cyclic GMP levels have not been changed by bromocriptine although sulpiride alone induced a significant reduction. The data may indicate the presence of D2 receptors in ovary and thyroid gland that are related to cyclic GMP.
Isolation of riboflavin carrier proteins from pregnant human and umbilical cord serum: Similarities with chicken egg riboflavin carrier protein
Authors: Visweswariah Sandhya S. , Adiga P. Radhakantha
Published: February 2005

A riboflavin carrier protein has been purified from human pregnancy and umbilical cord sera by affinity chromatography and fast protein liquid chromatography. This protein has a similar molecular weight to the chicken egg riboflavin carrier protein and shares other physicochemical properties, such as pI and riboflavin binding characteristics, with the avian counterpart. A high degree of immunological cross-reactivity is observed between the human and avian riboflavin binding proteins indicating the extensive conservation of this protein throughout evolution.
Neutral mutations and repetitive DNA
Authors: Loomis William F. , Gilpin Michael E.
Published: February 2005

We have previously shown that computer simulations of processes that generate selectively advantageous changes together with random duplications and deletions give rise to genomes with many different genes embedded in a large amount of dispensable DNA sequence. We now explore the consequences of neutral changes on the evolution of genomes. We follow the consequences of sequence divergences that are neutral when they occur in dispensable sequences or extra copies of genes present in multigene families. We find that when divergence occurs at about the same frequency as duplication/deletion events, genomes carry repetitive sequences in proportion to their size. Inspection of the genomes as they evolved showed that multigene families were generated by relatively recent duplications of single genes and so would be expected to be highly homogeneous.
The purine path to chemotherapy
Authors: Elion Gertrude B.
Published: February 2005

Antimetabolites of purine metabolism have found a use as anti-leukaemic, antiprotozoal and antiviral drugs, in immunosuppression and transplantation, and in gout and hyperuricemia. Their mechanisms of action are reviewed.