bluuebunny/crossref_metadata_2025 huggingface dataset:
On the involvement of cyclic AMP and extracellular Ca2+ in the regulation of hormone release from rat pituitary tumour (GH3) cells in culture
Authors: Sletholt Kjersti , Haug Egil , Gautvik Kaare M.
Published: February 2005

Thyroliberin (TRH), dibutyryl cyclic AMP (db-cAMP), and 3-isobutyl-l-methylxanthine (MIX) had a stimulatory effect on prolactin (PRL) and growth hormone (GH) release from GH 3 cells. Half-maximal and maximal effects were observed for TRH at 2.5 nM and 10 nM; for db-cAMP at 0.6 mM and 5 mM, respectively. MIX (0.1 mM-1 mM) induced a dose-dependent accumulation of cellular cyclic AMP, while the hormone release was already maximally stimulated at 0.1 mM MIX. The maximal effects on hormone release of TRH and db-cAMP, but not of TRH and MIX, were additive.

The Ca2+ channel blockers Co2+ (5 mM) and verapamil (100 μM) and the Ca2+ chelator EGTA (4 mM) abolished the stimulatory effect of TRH (1 μM) on hormone release. Co2+ and verapamil, but not EGTA, inhibited the stimulatory effect of db-cAMP (5 mM) on hormone release. The inhibitory effects of Co2+ and verapamil on GH release were counteracted by the combination of TRH and db-cAMP. For PRL release Co2+, but not verapamil, was able to inhibit the combined action of TRH and db-cAMP. Co2+, verapamil, and EGTA eliminated the stimulatory effect of MIX (1 mM) on PRL release while only Co2+ and EGTA affected the GH release. Hormone release in the presence of MIX plus verapamil or EGTA, but not Co2+, was increased by TRH.

The calmodulin antagonist trifluoperazine (TFP) at 30 μM inhibited basal hormone release and hormone release stimulated by TRH (1 μM), db-cAMP (5 mM), and MIX (1 mM). The Ca2+ ionophore A23187 (5 μM) had a stimulatory effect on basal hormone release which was abolished by 30 μM TFP.
Bisphosphoglycerate mutase and pyruvate kinase activities during maturation of reticulocytes and ageing of erythrocytes
Authors: Luque J. , Delgado M. D. , Rodriguez-Horche P. , Company M. T. , Pinilla M.
Published: February 2005

An increase in bisphosphoglycerate mutase (BPGM) and a decrease in pyruvate kinase (PK), i.e. a decrease in PK/BPGM ratio, was observed in red cell populations from anemic rats containing 95% down to 3% reticulocytes in blood. Such a ratio has been used to study the fractionation of recticulocytes, according to their degree of maturation, after counter-current distribution of those cell populations in dextrahpoly (ethylene glycol) two-phase systems. When applying this procedure to the fractionation according to age of erythrocytes from normal rats, the decrease of PK with cellular age was observed without a significant variation in BPGM activity.
Investigations on myelinogenesis in vitro: II. The occurrence and regulation of protein kinases by thyroid hormone in primary cultures of cells dissociated from embryonic mouse brain
Authors: Shanker G. , Pieringer R. A.
Published: February 2005

The occurrence and regulation by thyroid hormone of four protein kinases (cyclic AMP independent and dependent, calcium/calmodulin stimulated, and calcium/phosphatidyl serine stimulated protein kinases) was studied in primary cultures of cells dissociated from embryonic mouse brain. Serum from a thyroidectomized calf, which contained low levels of L-3,5,3′-triiodothyronine, T3 (<25 ng/100 ml), and thyroxine, T4 (<1 μg/100 ml) was used in the culture medium in place of normal calf-serum (T3, 130 ng/100 ml; T4 5.9 μg/100 ml) to render the cultures responsive to exogenously added T3. Cultures grown in hypothyroid calf-serum containing medium had less cAMP dependent and independent protein kinase activity than control cultures grown in normal calf-serum containing medium. However, this activity was restorable to a considerable degree if the cultures grown in hypothyroid calf serum containing medium were supplemented with L-3,5,3′-triiodothyronine (T3). The presence of calcium/calmodulin stimulated protein kinase was also distinctly observed. In comparison, the activity of calcium/phosphatidyl serine stimulated protein kinase was less than the other protein kinases.
Effect of 7-methylguanosine-5′-phosphate on the translation of rat milk-protein mRNAs in the wheat-germ cell-free system
Authors: Mezl Vasek A. , Lozano Andres
Published: February 2005

The translation of polyadenylated and of non-poly-adenylated RNA obtained from lactating rat mammary gland was almost totally inhibited by 0,5 mM 7-methylguanosine-5′-phosphate in the wheat-germ cell-free system, This inhibition was maintained during the preparation of the 9S whey-protein mRNA and of the 12S and ISS casein mRNAs, Chemical decapping of these mRNAs caused a similar reduction of their activity. Although a large fraction of milk-protein mRNAs have been reported to lack 3′-polyadenylation, these results show that the mRNAs in the mammary gland do contain a 5′-terminal 7-methylguanosine cap.
The immunity genes of colicins E2 and E8 are closely related
Authors: Lau Peter C. K. , Rowsome R. Wally , Watson Robert J. , Visentin Louis P.
Published: February 2005

We have determined the nucleotide sequence of the newly characterized colicin E8imm gene which exists in tandem with the colicin E3 imm gene in the: ColE3-CA38 plasmid. Comparison of these immunity structures reveals considerable sequence divergence) but the ColE8 imm gene is markedly homologous to the colicin E2 imm gene from the ColE2-P9 plasmid.
Inhibition of lipid peroxidation in muscle homogenates by phospholipase A2 inhibitors
Authors: Jackson M. J. , Jones D. A. , Harris E. J.
Published: February 2005

Chlorpromazine, mepacrine, tetracaine, dibucaine, chloroquine, and procaine have been shown to inhibit the iron- and ascorbate-induced lipid peroxidation of skeletal-muscle hornogenates in vitro. These compounds are known to be inhibitors of phospholipase activity, but they were also found to be effective in blocking free-radical-mediated damage to lipids in denatured homogenates, to linoleate suspensions, and to glutamic acid solutions where phospholipase activity was not a relevant factor. The inhibitory action did not appear to be related to any iron-binding activity of the compounds.
How do steroid hormones function to induce the transcription of specific genes?
Authors: Cato Andrew C. B.
Published: February 2005

On the whole, the question as to how steroid hormones act to induce the transcription of specified genes is not much more understood today than it was 15 years ago, but considerable progress has been made during this time to bring us a step closer to unravelling the mysteries surrounding the mechanism of hormonal gene activation. Hopefully, further studies in the three fields described (i.e. DNA/receptor binding experiments, gene-transfer experiments, and in vitro transcriptional studies) will bring in enough information for a complete story to be told one day. As to the questions asked in the introduction of this review, there appear to be sequences around inducible genes that render them sensitive to hormone administration. These sequences could be arranged in appropriate chromosomal structures flanking the gene region particularly at the 5′ end. As to whether these sequences bind the hormone/receptor complex, the experiments with the MMTV proviral DNA (17, 21–23) and the ovalbumin gene (27) appear to provide an affirmative answer. But the answer to whether this binding is responsible for the gene activation must await future experimentation. In vitro transcriptional studies specially designed with the hormone/receptor/DNA complex may be useful in answering this question.
A monoclonal antibody against human colonic adenoma recognizes difucosylated Type-2-blood-group chains
Authors: Brown A. , Feizi T. , Gooi H. C. , Embleton M. J. , Picard J. K. , Baldwin R. W.
Published: February 2005

A monoclonal antibody C14/1/46/10 showing preferential binding to membranes of human colorectal carcinomas over normal colon mucosae was obtained by immunization of mice with extra-nuclear membranes of a human colonic adenoma. Binding and inhibition of binding assays using blood cells or glycoproteins with known blood-group activities indicated that the antibody recognizes a carbohydrate antigen co-existing with the blood-group-H determinant: Fucα1→2Gal. Inhibition assays with structurally defined oligosaccharides showed that the antigenic determinant involves difucosylated Type-2-blood-group chains with the structure:
Tissue and subcellular distribution of enzymes inactivating leupeptin
Authors: Brown Catherine P. , Beynon Robert J.
Published: February 2005

Leupeptin, a proteinase inhibitor obtained from culture filtrates of Streptomyces sp., has been proposed as a valuable agent for the restriction of proteolysis in vivo. We have previously shown that mammalian tissues possess an enzymic system that is capable of inactivating leupeptin (Beynon R39 Brown CP & Butler PEr 1981, Acta. Biol. Med. Germ. 40, 1539–1546). This paper demonstrates the ubiquitous distribution of the inactivating system throughout mammalian tissues and provides evidence for the location of the enzyme(s) in the soluble fraction of the cell.
Rapid melanization of bomirski amelanotic melanoma cells in cell culture
Authors: Słominski A.
Published: February 2005

Transfer of Bomirski amelanotic melanoma ceils from in vivo to in vitro growth conditions results in occurrence of rapid melanization in their cytoplasm. The melanized ceils from primary cell culture initiate tumours in hamsters, which do not contain traces of melanin and resemble typical amelanotic melanoma.
Structural information from NMR secondary chemical shifts of peptide α C-H protons in proteins
Authors: Dalgarno D. C. , Levine B. A. , Williams R. J. P.
Published: February 2005

The secondary chemical shift experienced by the 1H-NMR resonances of the α C-H protons in proteins can be correlated with their backbone torsional angles ψ, which dictate the orientation of the α C-H proton to the adjacent carbonyl group. It is shown that α C-H protons present in β-sheet regions experience downfield secondary shifts, whereas those in α-helix regions experience upfield secondary shifts. The predictive use of this correlation in assignment studies is illustrated for the calcium-binding protein paravalbumin, for which a crystal structure is available, and troponin C, for which no crystallographic data are available.
Androgen-linked control of rat liver carbonic anhydrase III
Authors: Shiels A. , Jeffery S. , Phillips I. R. , Shephard E. A. , Wilson C. A. , Carter N. D.
Published: February 2005

The concentration of carbonic anhydrase IlI (CAIII) in male rat liver was found to be 30 times greater than that in the female. Castration of male rats led to marked reduction in liver CAIII concentrations which could be partially restored to control levels by testosterone replacement. Marked developmental and senescence changes in liver CAIII were also observed in male rats.
Liposome/white-cell interactions in vivo
Authors: Norman Palmer T. , Warner James P.
Published: February 2005

The purpose of this study was to establish whether liposomes administered via the intravenous route promote granulocyte aggregation and pulmonary leucostasis. White cells (labelled with [IIIln]tropolanate) and positively and negatively charged liposomes (containing entrapped [99mTc]DTPA) were administered i.v. to rats. The blood clearance and tissue distribution of IIIIn label was not altered by the administration of liposomes (and vice versa) and it is inferred that on intravenous liposome administration liposome/white-cell interactions are unlikely to compromise lung function.
Effect of reactive oxygen species on the erythrocyte calcium-pump function in protein-energy malnutrition
Authors: Okunade W. G. , Olorunsogo O. O.
Published: February 2005

The presence of detectagle amounts of non-heme iron in erythrocyte ghost membranes have been postulated to lead to the initiation of membrane lipid peroxidation and the attendant perturbation of membrane functions. We have investigated the presence of non-heme iron and endogenous products of lipid peroxidation in erythrocyte membranes of normal and kwashiorkor (KWA) subjects and assessed the susceptibility of the membranes to exogenously generated reactive oxygen species. The modulation of the basal and calmodulin-stimulated calcium-pumping activity of these membranes by reactive oxygen species was also assessed. The results show the presence of significant amounts of non-heme iron and endogenous free radical reaction products in the red cell membranes of KWA subjects compared with that of normal children. Estimation of the extent of lipid peroxidation in the presence of exogenously generated reactive oxygen species further revealed that erythrocyte ghost membranes of KWA subjects are more susceptible to oxidative stress than those of normal individuals. Although both the basal and calmodulin-stimulated activities of the membrane-bound Ca2+-pump enzyme in normal and KWA subjects were inhibited by oxygen-free radicals, the erythrocyte enzyme in KWA subjects showed higher susceptibility to inhibition by oxygen free radicals than that of normal individuals. We propose that the reduced erythrocyte calcium-pump function in KWA is not unconnected with excessive generation of reactive oxygen species.
The human placental transferrin receptor: Reconstitution into liposomes and electron microscopy
Authors: Demant Erland J. F. , Christiansen Kirsten , Tranum-Jensen Jørgen
Published: February 2005

Human transferrin receptor was isolated from Triton X-100 solubilized placental plasma membranes by a rapid one-step chromatographic procedure based on immunoadsorption of the receptortransferrin complex on anti-transferrin Sepharose and lectin-affinity on wheat germ agglutinin. Following exchange of Triton X-100 with CHAPS or n-octylglucoside, the purified receptor was incorporated into egg phosphatidylcholine liposomes upon, detergent removal by dialysis (lipid/protein ratio 15:1 to 45:1 (w/w) Reconstitution of the receptor was confirmed by trypsin cleavage to dissociate the large extracellular receptor domain from the liposomal membranes. Electron micrographs of the receptor-lipid recombinants negatively stained with sodium sillicotungstate, showed ographs of the receptor-lipid recombinants negatively stained with sodium sillicotungstate, showed that the receptor molecules distributed very inhomogeneously on the liposomes, most receptors being clustered. Single copies of the receptor were seen as elongate structures (5×10 nm) oriented with their long axis parallel to the liposome surface and separated from this by a 2–3 nm gap. This result provides evidence for a narrow connecting link between the globular extracellular receptor domain and the membrane spanning segment.
The use of biochemical parameters for a qualitative and quantitative assessment of ischemic damage to the small-intestinal mucosa
Authors: Filez Ludo , Stalmans Willy , Penninkx Freddy , Kerremans Raymond , Geboes Karel
Published: February 2005

Lactate dehydrogenase has been measured in the small-intestinal mucosa in order to assess its value as a marker for the effects of ischemia and of reperfusion. The decrease in specific activity of the enzyme illustrates the deleterious effect of reperfusion on the quality of the remaining epithelial cells. However, this parameter fails to detect the loss of epithelial cells, which is the major event during ischemia as well as during reperfusion. In contrast, the expression of enzyme activity per g protein of the underlying intestinal muscle allowed us, in addition, to assess quantitatively the loss of epithelial cells, in good agreement with the histological data.
Effect of a selective β2-adrenergic agonist (Cenbuterol) on energy balance and body composition in normal and protein deficient rats
Authors: Rothwell Nancy J. , Stock Michael J.
Published: February 2005

In rats fed a normal (22% protein) diet, injection of clenbuterol (1 mg/kg/d for 21 d) did not affect energy intake, energy expenditure or weight gain, but reduced energetic efficiency, and fat and energy gains and increased body protein content. Presenting a low-protein (8%) diet reduced energy intake, gain and efficiency, body protein content and the mass of the gastrocnemius muscle when compared to rats fed the control diet. Injection of the protein-deficient rats with clenbuterol (1 mg/kg/d for 21 d) caused hypophagia and reduced body weight and energy gains, energy expenditure and total body fat. However, the total body content of protein was not significantly reduced and the percentage of body protein in this protein deficient, clenbuterol-treated group was greater than that of untreated rats on both the high- and low-protein diets. The ratio of body protein to fat following clenbuterol treatment was increased by over 50% in both normal and protein-deficient rats. The results show that in protein deficient animals, clenbuterol treatment may help conserve body protein at the expense of fat, resulting in a smaller, but leaner body mass.
Phagocytic uptake of latex beads by rat peritoneal macrophages: Comparison of morphological and radiochemical assay methods
Authors: Pratten Margaret K. , Lloyd John B.
Published: February 2005

Contrary to previous reports, commercially available 1000-nm latex beads were found to be labelable with125I, yielding a product that retained its radiolabel on storage at 4°C and when incubated in tissue-culture media. This finding permitted a radiochemical method to measure phagocytic uptake of latex particles by rat peritoneal macrophages cultured in vitro, and a direct comparison with the established method of particle counting by light microscopy. The two methods yielded closely similar data, demonstrating that the (much more convenient) radiochemical method for quantitating phagocytic uptake is both feasible and reliable. The kinetics of phagocytic uptake of the latex particles and the effect of low temperature and metabolic inhibitors (sodium fluoride and 2,4-dinitrophenol) are described. Ongoing phagocytosis did not alter the rate of fluid-phase pinocytosis by macrophages.
Reduced lipogenesis in cafeteria-fed rats exhibiting diet-induced thermogenesis
Authors: Rothwell Nancy J. , Stock Michael J. , Trayhurn Paul
Published: February 2005

Fatty-acid synthesis has been measured in vivo with 3H2O in cafeteria-fed rats exhibiting diet-induced thermogenesis. Synthesis was decreased in brown adipose tissue, the liver, white adipose tissue, and the carcass of the cafeteria-fed animals compared to rats fed the normal stock diet. Whole-body synthesis was also decreased in the cafeteria-fed group. Diet-induced thermogenesis, in contrast to cold-induced non-shivering thermogenesis does not lead to increased fatty-acid synthesis and this is presumably due to the inhibitory effects on lipogenesis of the high dietary fat intake characteristic of cafeteria diets. The results also indicate that the energy cost of body fat deposition in cafeteria-fed rats is lower than in animals fed a low-fat/high-carbohydrate stock diet.
A membrane-bound human placental protein kinase activated by endogenous polypeptides
Authors: Abdel-Ghany Mossaad , Nakamura Shun , Navarro Javier , Racker Efraim
Published: February 2005

A protein kinase (PPdPK) was purified from plasma membranes of human placenta. Phosphorylation of casein, but not of phosvitin or lactalbumin, by [γ-32P]ATP in the presence of PPdPK was stimulated about 10-fold by naturally occurring polypeptides prepared from avariety of sources similar to the procedure of Roberts et al. (Proc. Natl. Acad. Sci. U.S.A. 77, 3494–3498, 1980). The amino acid phos-phorylated on casein was serine. According to gel exclusion chromatography the mol. wt, of PPdPK was 95 000. In autoradiograms, following polyacrylamide-gel electrophoresis, the autophosphorylation of PPdPK was greatly enhanced by the polypeptide activators.
In vitro inhibition of rat liver DNA polymerases α and β by β-blockers
Authors: Presta Marco , Mazzocchi Cecilia , Ziliani Silvia , Ragnotti Giovanni
Published: February 2005

The activity of DNA polymerases α and β, isolated from regenerating rat liver, is inhibited, in a dose-dependent fashion, by the oncogenic β-blocker DL-I-(2-nitro-3-methyl-phenoxy) - 3-tert-butylamino-propan-2-ol (ZAM[ 1305) and by non-oncogenic β-blockers DL-l-(2-nitro-5-methyl-phenoxy-3-tert-butylamino-propan-2-ol (ZAMI 1327) and DL-propranolol. The inhibition is due to a reversible interaction of the g-blockers with the two DNA polymerases. The interaction does not involve the template-DNA-binding site or the deoxynucleotide-binding site of the enzyme molecule. The degree of inhibition appears to be related to the hydrophobicity of the aromatic moiety and to the length and/or hydrophilicity of the aliphatic chain of the β-blocker molecule. These results may explain the transient in vivo inhibition of hepatic DNA synthesis observed in female rats treated with ZAMI 1305 or ZAMI 1327.
Phosphatidic acid regulates the activity of the channel-forming ionophores alamethicin, melittin, and nystatin: A1H-NMR study using phospholipid membranes
Authors: Hunt G. R. A. , Jones I. C. , Veiro J. A.
Published: February 2005

The regulation of ion channels by phosphatidic acid (a proposed active metabolite in the phosphatidylinositol effect) was investigated using1H-NMR spectroscopy and small unilamellar phospholipid vesicles. Transport across egg-yolk phosphatidylcholine (egg PC) and dipalmitoyl phosphatidylcholine (DPPC) vesicular membranes in the presence of the channel-forming ionophores alamethicin, melittin, and nystatin was monitored using the lanthanide probe ion Pr3+. In the absence of the ionophores, phosphatidic acid (PA) alone was found to have no ionophore properties, but in the presence of the ionophores the incorporation of 3 mol % phosphatidic acid in the bilayer markedly increased the rate of transport using melittin and nystatin, but decreased the rate using alamethicin, independent of the type of phosphatidylcholine used. The presence of PA in the bilayer also stimulated the production of lyric type channels, the extent of which were both ionophore- and lipid-dependent. These results are discussed in terms of possible molecular interactions between the PA, the individual ionophores, and type of lipid used.
Effect of pentylenetetrazol on the carbaryl-induced changes of serotonin metabolism in rat-brain hypothalamus
Authors: Ray S. K. , Poddar M. K.
Published: February 2005

Carbaryl (200 mg/kg or 400 mg/kg, p.o.) significantly elevated serotonin (5-HT) (57–109%) and 5-hydroxy-indoleacetic acid (5-HIAA) (60–78%) levels at 1.0 h in the hypothalamic region of adult male rat brain. Further, administration of carbaryl (200 mg/kg, p.o.) for different time intervals (0.5 h, 1.0 h, and 2.0 h) revealed that both 5-HT and 5-HIAA levels elevated maximally at 0.5 h in hypothalamus. These regional 5-HT and 5-HIAA levels were not significantly affected with pentylenetetrazol (PTZ) at any time after its treatment. But simultaneous administration of carbaryl (200 mg/kg, p.o.) and PTZ (60 mg/kg, s.c.) reduced the carbaryl-induced elevation of both 5-HT and 5-HIAA leveis. Measurement of (i) probenecid-induced (200 mg/kg, i.p.) accumulation and (ii) pargyline-induced (75 mg/kg, i.p.) depletion of hypothalamic 5-HIAA level in the absence or presence of carbaryl (200 mg/kg, p.o.) and/or PTZ (60 mg/kg, s.c.) revealed that (a) carbaryl enhanced the synthesis as well as the breakdown of 5-HT, (b) PTZ had no effect on either of these processes of 5-HT, and (c) carbaryl-induced increased catabolism of 5-HT became normal in the presence of PTZ.
Biochemical and immunological characterization of rice albumin
Authors: Mawal Yogesh R. , Mawal Madhumalti R. , Ranjekar P. K.
Published: February 2005

Rice albumin from Oryza sativa (Var. Basmati 370) accounts for about 5% of the total seed proteins. A major fraction of rice albumin has been found to be a glycoprotein which is a monomer of 60 kd having iso-electric point 6.54. When rice albumin is digested with trypsin, it shows the presence of 24 peptides as against 28 peptides which were estimated from its amino acid Composition. This indicates the presence of a few peptides which resemble each other in their charge and Rf values. Antibodies against Con A purified rice albumin were affinity purified and were used to quantitate the rice albumin levels during post-anthesis by RIA and ELISA. The latter experiments reveal that maximum albumin is present between 18 and 20 days post-anthesis.
The determination of alpha-adrenergic receptor concentration on rat pancreatic islet cells
Authors: Fyles J. M. , Cawthorne M. A. , Howell S. L.
Published: February 2005

The selective a2 adrenergic antagonist yohimbine has been shown to prevent the noradrenaline induced inhibition of insulin secretion from isolated rat islets of Langerhans, Binding studies utilizing [3H]yohimbine showed specific binding to dispersed rat islet cells with a Kd of 2.9 nM and receptor concentration of 645 fmols/mg protein. The use of chloroquine to inhibit receptor recycling did not affect binding of the ligand. Binding studies and secretion data are consistent with the suggestion that adrenergic receptors of the α2 sub-type may play a dominant role in the regulation of insulin secretion.
Propranolol apparently separates the physical and compositional characteristics of muscle growth induced by clenbuterol
Authors: Maltin C. A. , Delday M. I. , Hay S. M. , Smith F. G. , Reeds P. J.
Published: February 2005

The effect of propranolol on clenbuterol-induced changes in muscle fibre size and protein content were studied. Propranolol did not inhibit the ability of clenbuterol to stimulate protein accretion but reduced the increase in muscle fibre size. The compositional and physical characteristics of clenbuterol-induced muscle growth thus appeared to be separated by propranolol.
Reversible activation/inactivation of the deacylation/acylation cycle in rat liver microsomes
Authors: Hutson Julie L. , Higgins Joan A.
Published: February 2005

Rat liver microsomes incorporate [14C]palmitoyl CoA into membrane phospholipids via the deacylation/acylation cycle. This activity is reversibly inactivated/activated by treatment of the microsomes with ATP, MgCl2, and 105,000 g supernatant or with 105,000 g supernatant alone. These observations suggest that the acylation cycle is controlled by a mechanism involving phosphorylation/dephosphorylation. As the pool of lysolecithin in the membranes is not altered by conditions increasing incorporation of palmitoyl CoA into phospholipid, it is probable that the site of regulation of deacylation/acylation is at the acyltransferase rather than the phospholipase.
Mechanisms towards compensation of long-term haemopoietic injury in mice after 5 Gy irradiation: In vivo and in vitro enhancement of superoxide anion production by granulocytes
Authors: Gaitán Soledad , Cuenllas Elvira , Sancho Pilar , Bueren Juan A. , Tejero Concepción
Published: February 2005

This paper analyzes the long-term (6 and 12 months) function of mouse granulocytes after total body irradiation with a single dose (5 Gy) of X-rays. Superoxide anion production has been investigated in granulocytes from peripheral blood, and also in those harvested from long term bone marrow cultures, with the aim of correlating the environmental damage induced by radiation with the functional properties of granulocytes. An in vivo and in vitro enhancement of superoxide anion production and protein levels in granulocytes from irradiated mice is described. The presence of some colony stimulating factor in the supernatant of cultures from irradiated mice could play an important role in the priming of granulocytes.
A domain of the α-subunit of rabbit phosphorylase kinase shows homologies with regions of rabbit α-tropomyosin, human EGF receptor, and the α chain of bovine S-100 protein
Authors: Sotiroudis Theodore G. , Geladopoulos Taxiarchis P.
Published: February 2005

Sequence comparison of the α-subunit of phosphorylase kinase with α-tropomyosin revealed 32% identity, and 49% similarity, between the region of α-tropomyosin coded by exon 5 and a 39 amino acid segment of the kinase subunit. A subsequence of the α-subunit segment and a sequence overlapping the same α-subunit region are homologous with: (a) a region of the cytoplasmic domain of EGF receptor (50% identity) and (b) a Ca2+-binding domain of the α chain of S-100 protei (50% identity) respectively. Statistical analysis shows that these homologies are significant. The biological implication of the above similarities is discussed.
Studies on the subcellular localization and role of glutathione-insulin transhydrogenase in rat liver
Authors: Chowdhary Balvinder K. , Smith Geoffrey D. , Mahler Robert , Peters Timothy J.
Published: February 2005

125I-insulin was shown to be internalized in vivo to a discrete population of low-density membranes (ligandosomes), distinct from the Golgi, endoplasmic reticulum, plasma membrane, and lysosomes. However, analytical subcellular fractionation shows that glutathione-insulin transhydrogenase is localized to the endoplasmic reticulum. Measurement of the specific enzyme activity of glutathione-insulin transhydrogenase showed no differences between normal, diabetic, and hyperinsulinaemic rats. These results suggest that glutathione-insulin transhydrogenase is not directly involved in the subceltular processing of receptor-bound internalized insulin.
Membrane homeostasis: is there an optimum level of membrane cholesterol?
Authors: Sabine John R.
Published: February 2005

The hypothesis is proposed that the relationship between the level of cholesterol in a cellular or sub-cellular membrane and the activity of any membrane function affected by cholesterol is ogival in nature, i.e. there is an optimum level of membrane cholesterol at which functional activity is maximal, and above or below this level activity declines. Data already published from other laboratories, when analysed in this manner, show clearly that this hypothesis appears to hold true for at least several membrane-bound systems, in particular the microsomal enzyme cerebro side sulfotransferase and transmembrane ATP/ADP exchange and glucose transport.
Similarities in properties, content, and relative rates of synthesis of fructose-P2 aldolase in livers of fed and starved rats
Authors: Lebherz Herbert G. , Petell James K. , Shackelford Janis E.
Published: February 2005

The present work gives evidence that, in contrast to the situation reported by Pontremoli et al. for the rabbit (Proc. Natl. Acad. Sci. U.S.A. 76, 6323–6325, 1979; Arch. Biochem. Biophys. 203, 390–394, 1980; Proc. Natl. Acad. Sci. U.S.A., 79, 5194–5196, 1992), starvation for as long as 3 days does not cause intracellular covalent modification and inactivation of fructose-P2 aldolase molecules in rat liver cells. This conclusion is based on our observations that liver aldolase molecules isolated from fed and starved rats in the presence of proteolytic inhibitors were not distinguished on the basis of specific catalytic activity, electrophoretic mobility, subunit molecular weight, NH2-terminat structure, or COOH-terminal structure. Further, the approximate 40% loss in rat liver mass which occurred during the 3-day fast was not associated with appreciable changes in the content of aldolase and most other abundant cytosolic proteins per gram of rat liver, as judged by electrophoretic analysis of 100 000-g soluble fractions of liver extracts. Finally, a 3-day fast had no appreciable effect on the relative rates of synthesis of aldolase and most other abundant cytosolic proteins in rat liver. Our findings suggest that nutrient deprivation has no preferential effect on the concentration or metabolism of aldolase in rat liver cells.
It is possible to increase skeletal muscle fibre number in utero
Authors: Rehfeldt Ch. , Fiedler I. , Weikard R. , Kanitz E. , Ender K.
Published: February 2005

The administration of porcine somatotropin (pST) to pregnant sows during early gestation (day 10 to 24) induced the formation of significantly more muscle fibres in the semitendinosus muscle of the fetuses, representing a higher growth capacity of skeletal muscle. The pST-treatment during late pregnancy (day 80 to 94) accelerated the development of the fetus resulting in higher body weights and advanced stage of maturity at birth.
Comparison of the interaction of the anti-viral chemotherapeutic agents amantadine and tromantadine with model phospholipid membranes
Authors: Cheetham James J. , Epand Richard M.
Published: February 2005

Amantadine and tromantadine are agents used against influenza and herpes infections, respectively. Tromantadine raises the bilayer to hexagonal phase transition temperature of synthetic phosphatidylethanolamines and is less disruptive to phospholipid packing. Tromantadine acts similar to cyclosporin A, previously demonstrated to inhibit viral-induced cell-cell fusion. We suggest the balance between the hydrophobic and hydrophilic group sizes would allow tromantadine to prevent membrane fusion more than amantadine and thus inhibit infection by viruses such as Herpes, which fuse with the plasma membrane. Study of agents which stabilize the bilayer phase of membranes may lead to efficacious inhibitors of viral infections requiring cell fusion events.
A high-affinity folate binding protein in human semen
Authors: Holm Jan , Hansen Steen Ingemann , Høier-Madsen Mimi
Published: February 2005

The presence of a folate binding protein of high-affinity type (affinity constant 3.1010M−1, maximum folate binding 1.4 nM) in human semen was demonstrated in equilibrium dialysis experiments (37°C, pH 7.4) with the radioligand3H-folate. Radioligand dissociation from the binding protein was slow at pH 7.4, but rapid at pH 3.5. By use of rabbit antibodies against 25 kDa human milk folate binding protein we determined the concentration of folate binding protein in 16 speciments of human semen in an enzyme-linked immunosorbent assay. The concentration of immunoreactive folate binding protein was independent of the number of spermatozoa in individual specimens. Gel filtration showed that immunoreactive and radioligand bound folate binding protein coeluted in two peaks: a major one of 100 kDa and a minor one of 25 kDa.
Surface heterogeneity of bovine sperm revealed by aqueous two-phase partition
Authors: Cartwright Elizabeth J. , Cowin Allison , Sharpe Paul T.
Published: February 2005

Ejaculated, bovine sperm have been subjected to multiple partition in aqueous two-phase systems. This partition, carried out in a countercurrent fashion, reveals heterogeneity of the sperm population with respect to surface properties. The sperm, when partitioned in phase systems that detect non-change associated surface properties (change-insensitive) are largely distributed as two distinct populations. In charge-sensitive phase systems (which principally detect cell surface molecules carrying charge) the sperm do not show any obvious surface heterogeneity. Considerable heterogeneity is revealed in affinity-ligand phase systems containing palmitic acid coupled to one of the phase components-poly(ethylene glycol). There is a difference in surface heterogeneity between sperm which have been washed in buffer or left unwashed, direct from the ejaculate. This is indicative of weak adsorption of proteins to the sperm surface in seminal fluid. These results show that bovine ejaculated sperm is a heterogeneous cell population having unequal distributions of a number of different surface molecules.
Analysis of epidermal proteins for DNA-binding activity
Authors: Supakar Prakash C. , Misra Renuka , Bhatnagar Gopal M.
Published: February 2005

A group of DNA-binding proteins from the soluble extract of newborn rat epidermis have been separated by chromatography using DNA-cellulose columns. The electrophoretogram of the DNA-binding proteins eluted from a single stranded DNA-cellulose column shows five major proteins of molecular weights ranging between 25K to 40K. Both the epidermal protein filaggrin and most keratins, except two high molecular weight keratins, do not show in vitro DNA-binding activity.
Metabolic integrity and stability of isolated rat brown adipocytes
Authors: Van Voorhis Halina , Villa John J. , Otto David A.
Published: February 2005

Using rats previously anesthetized with pentobarbital and with subtle modifications to existing procedures, rat brown adipocytes of good yield, viability, and stability were consistently obtained. The metabolic integrity of the cells, indicated by an 8–11 fold norepinephrine-dependent stimulation of respiration, was reproducible between cell preparations and maintained even after 3–5 hours of cell storage at room temperature. The ATP content of freshly isolated and stored cells per mg DNA (using a modified DNA assay) closely reflected the in vivo content determined from freeze clamped tissue.
A study of selenate efflux from human placental microvillus membrane vesicles
Authors: Shennan D. B.
Published: February 2005

Selenate efflux from human placental brush border membrane vesicles was studied using an ion-exchange column assay. Selenate efflux was found to be mediated almost exclusively by a temperature dependent DIDS-sensitive pathway. Chromate markedly inhibited selenate efflux: in contrast medium selenate had no effect. It is concluded that selenate and sulphate share a common pathway for transport across the human placental microvillus membrane.
Increased glycolysis in ageing cultured human diploid fibroblasts
Authors: Bittles A. H. , Harper N.
Published: February 2005

With increasing population doubling in vitro, human diploid fibroblasts exhibited a highly significant increase in glucose uptake from the growth medium and a corresponding increase in lactate production. The switch to glycolysis occurred prior to the onset of changes in intracellular glucose and lactate concentrations or in the specific activity of the glycolytic regulatory enzyme, pyruvate kinase, it also preceded the morphological alterations held to be characteristic of cellular senescence.
Initiation of DNA synthesis in quiescent Swiss 3T3 and 3T6 cells by lanthanum
Authors: Smith Jeffrey Bingham , Smith Lucinda
Published: February 2005

La3+ stimulated quiescent Swiss 3T3 and 3T6 ceils to enter the DNA-synthesizing S phase of the cell cycle. La3+ and insulin interacted synergistically to increase DNA synthesis. A brief exposure of the cells to soluble LaCl3 optimally stimulated entry into S. La3+ was similar to Al3+ in its mitogenic properties (J. Cell. Physiol.118, 298, 1984), but La3+ was 10 times more potent than Al3+.
Common action of certain viruses, toxins, and activated complement: pore formation and its prevention by extracellular Ca2+
Authors: Bashford C. L. , Alder G. M. , Patel K. , Pasternak C. A.
Published: February 2005

Haemolysis by Sendal virus, α-toxin, and activated complement is inhibited by high concentrations of divalent cations. In Daudi cells, sublytic amounts of these agents induce the following changes: collapse of surface membrane potential, uptake of Na+ and loss of K+ from cells, and leakage of phosphorylated metabo-tites from cells. The changes induced by Sendal virus and complement are sensitive to physiological concentrations of extracellular Ca2+. It is concluded that fluctuations in plasma Ca2+ concentration may affect the damaging action of certain pore-forming agents on susceptible cells.
Cell surface effects of human immunodeficiency virus
Authors: Garry Robert F. , Gottlieb A. Arthur , Zuckerman Kenneth P. , Pace John R. , Frank Thomas W. , Bostick Denise A.
Published: February 2005

Cell killing by human immunodeficiency virus (HIV) is thought to contribute to many of the defects of the acquired immunodeficiency syndrome (AIDS). Two types of cytopathology are observed in HIV-infected cultured cells: cell-cell fusion and killing of single cells. Both killing processes appear to involve cell surface effects of HIV. A model is proposed for the HIV-mediated cell surface processes which could result in cell-cell fusion and single cell killing. The purpose of this model is to define the potential roles of individual viral envelope and cell surface molecules in cell killing processes and to identify alternative routes to the establishment of persistently-infected cells. Elucidation of HIV-induced cell surface effects may provide the basis for a rational approach to the design of antiviral agents which are selective for HIV-infected cells.
Are osmotic forces involved in influenza virus-cell fusion?
Authors: Pritzen Cornelia , Herrmann Andreas
Published: February 2005

The kinetics of the fusion process of unsealed and resealed erthyrocyte ghosts with influenza virus (A/PR8/34, A/Chile 1/83), were measured under hypotonic, isotonic and hypertonic conditions using a recently developed fluorescence assay (Hoekstra et al. (1984) Biochemistry23:5675–5681]. No correlation between the external osmotic pressure and kinetics and extent of fusion was observed. Influenza viruses fuse as effectively with unsealed ghosts as with resealed ghosts. It is concluded that osmotic forces as well as osmotic swelling of cells are not necessary for virus-cell membrane fusion.
Methyl gallate, methyl-3,4,5-trihydroxybenzoate, is a potent and highly specific inhibitor of herpes simplex virus in vitro. II. Antiviral activity of methyl gallate and its derivatives
Authors: Kane Cynthia J. M. , Menna Jay H. , Sung Ching-Ching , Yeh Yun-Chi
Published: February 2005

Methyl gallate (MG), methyl-3,4,5-trihydroxybenzoate, was highly active against herpes viruses as determined by plaque reduction assay. Herper simplex virus type 2, MS strain, was sensitive to MG at a mean 50% inhibitory concentration (IC50) of 0.224 μg/ml in monkey kidney cells. MG was specific for herpes viruses with the relative sensitivity HSV-2>HSV-1>CMV. Two RNA viruses tested were significantly less sensitive to MG. The structural components of MG which modulate the anti-herpetic activity were identified by analysis of chemical analogues. Our structural analyses indicated that three hydroxyl groups were required but were not sufficient for the anti-herpetic action of MG. The presence and chain length of the alkyl ester were also important to the anti-herpetic activity of MG. Methyl gallate may interact with virus proteins and alter the adsorption and penetration of the virion.
Foundations of vectorial metabolism and osmochemistry
Authors: Mitchell Peter
Published: February 2005

Chemical transformations, like osmotic translocations, are transport processes when looked at in detail. In chemiosmotic systems, the pathways of specific ligand conduction are spatially orientated through osmoenzymes and porters in which the actions of chemical group, electron and solute transfer occur as vectorial (or higher tensorial order) diffusion processes down gradients of total potential energy that represent real spatially-directed fields of force. Thus, it has been possible to describe classical bag-of-enzymes biochemistry as well as membrane biochemistry in terms of transport. But it would not have been possible to explain biological transport in terms of classical transformational biochemistry or chemistry. The recognition of this conceptual asymmetry in favour of transport has seemed to be upsetting to some biochemists and chemists; and they have resisted the shift towards thinking primarily in terms of the vectorial forces and co-linear displacements of ligands in place of their much less informative scalar products that correspond to the conventional scalar energies. Nevertheless, considerable progress has been made in establishing vectorial metabolism and osmochemistry as acceptable biochemical disciplines embracing transport and metabolism, and bioenergetics has been fundamentally transformed as a result.
Studies of translocation catalysis
Authors: Henderson Peter J. F.
Published: February 2005

There is a symbiotic relationship between the evolution of fundamental theory and the winning of experimentally-based knowledge. The impact of the General Chemiosmotic Theory on our understanding of the nature of membrane transport processes is described and discussed. The history of experimental studies on transport catalysed by ionophore antibiotics and the membrane proteins of mitochondria and bacteria are used to illustrate the evolution of knowledge and theory. Recent experimental approaches to understanding the lactose-H+ symport protein of Escherichia coli and other sugar porters are described to show that the lack of experimental knowledge of the three-dimensional structures of the proteins currently limits the development of theories about their molecular mechanism of translocation catalysis.
The effect of endurance-training on the maximum activities of hexokinase, 6-phosphofructokinase, citrate synthase, and oxoglutarate dehydrogenase in red and white muscles of the rat
Authors: Soar Paramjeet K. , Davies C. T. Mervyn , Fentem Peter H. , Newsholme Eric A.
Published: February 2005

Adult female rats were subjected to an eleven-week endurance-training programme, and, for the first time, the maximum activities of enzymes that can indicate the quantitative capacities of both anaerobic glycolysis and the Krebs cycle in muscle (viz. 6-phosphofructokinase and oxoglutarate dehydrogenase respectively) were measured in heart plus white and fast-oxidative skeletal muscle. No changes were observed in heart muscle. In fast-oxidative skeletal muscle, activities of hexokinase, citrate synthase, and oxoglutarate dehydrogenase were increased by 51, 26, and 33% respectively but there was no effect on 6-phosphofructokinase. These results demonstrate that in red muscle there is no effect of this training programme on the anaerobic capacity but that of the aerobic system is increased by one third. In white skeletal muscle, only the activity of citrate synthase was increased, which indicates that this activity may not provide even qualitative information about changes in capacity of the Krebs cycle.
A method to select cell populations with enhanced chemotatic activity
Authors: Albini Adriana , Müller Peter K. , Parodi Silvio
Published: February 2005

Virus-transformed and tumor ceils often show a higher chemotactic activity in comparison to normal cells. Here we show that the blind-well chamber assay is an easy and rapid procedure to select cell populations with enhanced chemotactic activity. Collagen-type-specific antibodies have been applied to analyze the efficiency of cell sorting by the chemotaxis assay.
Vasoactive intestinal peptide (VIP) binding to solubilized material from rat liver plasma membranes
Authors: Guerrero J. M. , Calvo J. R. , Garrido M. R. , Molinero P. , Osuna C. , Jiménez J. , Goberna R.
Published: February 2005

A non-ionic detergent such as Lubrol-PX extracts in soluble form the VIP-binding structures of rat liver plasma membranes. Detergent-solubitized proteins bind specifically [125I]VIP and the complex tracer-protein is identified by the use of Sepharose 6B columns. The interaction is only possible in the absence of detergent (below 0.001%) and is inhibited by native peptide. A molecular weight of about 80,000 was estimated for VIP-binding proteins by reference to a series of globular markers of proteins. Binding to VIP soluble proteins is specific and dependent on time as studied by the Hummel and Dreyer (Biochim. Biophys. Acta63:530–532, 1962) assay.
GERARD SCHURMANN IN INTERVIEW
Authors: Tomson Earl
Published: February 2005

Gerard Schurmann was born of Dutch parents in the former Dutch East Indies in 1924, but spent more than 40 years, including the most formative period of his musical life, in England before moving to the US in 1981. Even during his years in the Netherlands as orchestral conductor with the Dutch Radio in his early twenties, he maintained an apartment in London, sometimes commuting to his place of work in Hilversum. His experience was similar to Bernard van Dieren, another Dutch-born composer who lived in England, although not for as many years as Schurmann: Holland has made no particular move to claim either as a Dutch composer. It was in England that Schurmann developed his skills and persona as a musician, after arriving as a teenager in 1941.