bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional diversity of bioactive peptides in the nervous system itself: “How the brain may understand”
Authors: Chrétien Michel , Sikstrom Roy A. , Lazure Claude , Mbikay Majambu , Seidah Nabil G.
Published: February 2005

The interactions involving cells of the nervous system are a complex form of intercellular communication. Biosynthesis of peptide hormones or active neuropeptides is generally through a precursor which provides increased product choices as a function of the processing pathway. Proteolytic processing as well as other molecular modification lead to a wide range of mature products which may vary in different tissues even though they are derived from the same precursor. Also the same neuropeptide may exhibit different bioactivities for different target cells. Finally, by means of collective packaging in secretory organelles, a cell may be able by synergism to further broaden its biologic effects. In these ways, what is seen as added complication in the CNS, may be from the point of view of the cell, a successful attempt to increase its survival ability to adapt and influence its bioenvironment.
Characteristics of L-proline and sodium transport in renal brush border membranes isolated from 7-day-old and adult rats
Authors: Hsu Betty Y. L. , McNamara Pamela D. , Cariola Christina M. , Fenstermacher Elizabeth A. , Rea Claire T. , Reynolds Robert A. , Segal Stanton
Published: February 2005

To explore the nature of differences in uptake by renal brush border vesicles from animals of different ages, vesicles were isolated from 7-day old and adult rats by a Mg-aggregation method. A number of criteria were compared in vesicles from the young and mature animals. The vesicles isolated from animals of both ages appear similar on electron microscopy, in response to osmotic changes, and in uptake kinetics for L-glucose. Despite these parameters which indicate no basic differences between the membranes of young and mature kidney, differences in proline and sodium handling are seen. When compared to the uptake pattern seen in vesicles from adult animals, the height of the sodium gradient-stimulated proline overshoot is diminished and sodium entry is faster in vesicles of the 7-day old rats. These are the same differences which were found in vesicles prepared by differential centrifugation from 7-day old animals. In addition, although sodium efflux was faster from vesicles of immature kidney and mirrored the faster sodium entry, proline efflux was slower. The data indicate a dissociation of proline and sodium fluxes in brush borders of the young rat kidney.
Studies into hormonal imprinting in intact and transformed 3T3 fibroblast cell lines
Authors: Kovács P. , Okano Y. , Nozawa Y. , Csaba G.
Published: February 2005

The cells of the NIH 3T3 fibroblast line responded to primary interaction with insulin by a positive imprinting, i.e. by an increased binding capacity for the hormone on re-exposure. Positive imprinting, although to a lesser degree, was also induced by thyrotropin. However, oncogenic transformation by polyoma virus oncogens resulted in decreased imprinting in both the middle-T-antigen (MT3) and small-T-antigen-expressing (N4) cells.
Export of proteins across membranes: The helix reversion hypothesis
Authors: Shinde U. P. , Guru Row T. N. , Mawal Y. R.
Published: February 2005

A model is presented which explains the biological role of the leader peptide in protein export. Along the lines of this model, the conformational changes of a protein with environment serves as a general mechanism for translocation. The leader peptide in the cytoplasm takes a hairpin like conformation which reverts to an extended helix upon integration into the membrane. The essential features of this model are in accord with recent results of protein export.
Organization of mitochondrial UDP-glucose: Dolichylmonophosphate glucosyltransferase in the outer membrane
Authors: Gasnier F. , Lerme F. , Vaganay E. , Louisot P. , Gateau-Roesch O.
Published: February 2005

Previous studies have shown the existence of an autonomous mitochondrial UDP-glucose: dolichylmonophosphate glucosyltransferase, located in mitochondrial outer membrane of liver cells. To improve our knowledge about the topographical aspects of glycosylation in mitochondria, we have investigated the organization of this enzyme in intact mitochondria, using controlled proteolysis with trypsin and sensitivity towards amino-acid specific reagents.

Our data provides evidence:-for a mitochondrial glucosyltransferase facing the cytoplasmic side of the outer membrane-and for the involvement of histidine and tryptophan residues as well as sulfhydryl groups in the catalytic activity of the enzyme.
Localized energy coupling during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22
Authors: Hitchens G. Duncan , Kell Douglas B.
Published: February 2005

The principle of the dual inhibitor titration method for testing models of electron-transport phosphorylation is outlined, and the method is applied to the study of photophosphorylation in bacterial chromatophores. It is concluded that energy coupling is strictly localized in nature in this system, in the sense that free energy released by a particular electron-transport chain may be used only by a particular H+-ATP synthase. Dual inhibitor titrations using the uncoupler SF 6847 and the H+-ATP synthase inhibitor oligomycin indicate that uncouplers act by shuttling rapidly between the localized energy-coupling sites.
Evidence for the presence of a cell-surface ribonuclease in mechanically prepared rat-liver cells in suspension
Authors: Sirdeshmukh R. , Bhargava P. M.
Published: February 2005

Rat-liver parenchymal cells obtained in suspension by a mecahnical method are shown to contain a cell-surface nuclease(s) that rapidly degrades exogenously added total Escherichia coli RNA. However, no acid-soluble products are formed; all the degradation products in the incubation medium sediment in the 4–55 RNA region on a sucrose density gradient. A part of the degraded RNA seems to be taken up by the cells; the uptake of the degradation products, presumably derived from rRNAs, is more than that of purified 4–55 RNA. Most of the RNA taken up by the cell sediments in the 4–55 region; only a small proportion is degraded to acid-soluble material within the cell.
Cloning of metallothionein cDNA from neonatal rat liver
Authors: Mercer J. F. B. , Hudson P.
Published: February 2005

A metallothionein cDNA clone was isolated from a cDNA bank prepared from neonatal rat liver poly(A)-containing RNA by a colony screening procedure using [32P]cDNA probes prepared from mRNA of either metal-induced or uninduced rat livers. Nucleotide sequence analysis of this clone showed that it contained the entire 3′ untranslated region and 30% of the coding sequence for a rat metallothionein. The sequence is remarkably homologous with the mouse metallothionein-I gene.
The effects ofS-adenosylhomocysteine and S-adenosylmethionine on some purine- and pyrimidine-metabolizing systems
Authors: Tudball N.
Published: February 2005

The effects of S-adenosylhomocysteine and S-adenosyl-methionine on some purine- and pyrimidine-metabolizing systems have been examined. Both compounds were capable of acting as relatively good inhibitors of adenosine deaminase, nucleoside phosphorylase, and adenylate deaminase activities but as relatively poor inhibitors of myokinase and nucleoside monophosphate kinase. The inhibitory effects were freely reversible. 5′-Nucleotidase, orotidine 5′- phosphate, and phospho-diesterase were unaffected. Nucleoside phosphorylase was competitively inhibited by both compounds, whereas mixed inhibitory effects occurred with adenosine deaminase.
The effects of dexamethasone on α-fetoprotein and albumin synthesis in cultured hepatoma 7777 cells
Authors: Schwartz Charles E. , Burkhardt Anne L. , Huang Dao-Pei , Chiu Jen-Fu
Published: February 2005

Dexamethasone inhibits α-fetoprotein (AFP) synthesis, and stimulates albumin synthesis, in cultured hepatoma 7777 cells. These changes are due to a decrease in AFT-mRNA, and an increase in albumin-mRNA, in cells.
Characterization of two insulin-binding components of rat-liver plasma membranes
Authors: Baron M. D. , Sónksen P. H.
Published: February 2005

We have identified and isolated two forms of insulin receptor from rat-liver plasma membranes. The smaller (Mr = 90k) is a single polypeptide. The same poly-peptide appears to be the insulin-binding site of the largerMr = 280k). Only the larger, multisubunit, receptor shows high-affinity binding of insulin and negative cooperativity in its dissociation kinetics.
Regulation of protein synthesis in rabbit reticulocyte lysates: effect of of Ca2+, Mg2+, and Mn2+ on self-phosphorylation and heterophosphorylation catalyzed by the heme-regulated and double-stranded-RNA-activated protein kinases
Authors: Ranu Rajinder Singh
Published: February 2005

The influence of divalent cations Mg2+, Mn2+, and Ca2+ on the cyclic-AMP-independent protein kinases of the heine-regulated and double-stranded-RNA-activated translational inhibitory protein kinases on self-phosphorylation and heterophosphorylation of the substrate (the 38 000-dalton subunit of initiation factor eIF-2) has been examined, Results show that Mg2+, Mn2+, and Ca2+ affect the activities of these enzymes in the following fashion. Mg2+ supports both self-phosphorylation and heterophosphorylation efficiently. Mn2+ on the other hand supports self-phosphorylation but to a lesser degree the heterophosphorylation, Ca2+ promotes neither self-phosphorylation nor hetero-phosphorylation.
Lipolytic and adenyl-cyclase-stimulating activity of glucagon1–6: comparison with glucagon derivatives chemically modified in the 7–29 sequence
Authors: Jean-Baptiste Emile , Rizack Martin A. , Epand Richard M.
Published: February 2005

Glucagon1–6 has a maximum lipolytic activity (Lmax) in the rat adipocyte which is 66% of that of glucagon. The N∊-guanidyl derivative, modified at Lys12, has about the same Lmax as glucagon1–6. Modifying the carboxyl groups of glucagon with glycinamide or removing the COON-terminal residues with cyanogen bromide reduces Lmax to less than 25% of the level of glucagon. The potency of each of these analogs (A50) in μM is as follows: glucagon 6 × 10−3; glucagon1–6 2 × 10−2; N∊-guanidyl glucagon 9 × 10−3; glycinamide glucagon 10−2; cyanogen bromide peptide of glucagon 2 × 10−1. The ability of all of the glucagon analogs to stimulate adenyl cyclase was somewhat less than their tipolytic activities with the exception of the glycin-amide derivative and the cyanogen bromide peptide, which were slightly more active in stimulating adenyl cyclase than in lipolysis. Glucagon1–6 is much more potent in stimulating adipocyte than liver adenyl cyclase.
In vivo biosynthesis of the saturated isoprene unit of dolichyl phosphate
Authors: Vigo Carmen , Adair W. Lee
Published: February 2005

Reduction of the α-isoprene unit of polyprenols to form dolichols was studied in vivo using 3H-polyprenol derivatives as substrates and liposomes as carriers. Liposomes containing labeled polyprenol, polyprenyl phosphate, or polyprenyl pyrophosphate were injected through the portal vein into the livers of rats under anesthesia. Uptake and conversion of the labeled compounds to dolichol derivatives was studied at different intervals. The greatest conversion to dolichol derivatives was found with polyprenyl pyrophosphate and polyprenyl monophosphate, with 31% and 8% of the absorbed dose converted respectively. Less than 0.2% of the absorbed polyprenol was converted to dolichol derivatives. These results suggest that the substrate for the α-isoprene reductase involved in dolichol biosynthesis is either polyprenyl monophosphate or polyprenyl pyrophosphate, or both.
Isolation and expression of cDNA clones for a rat liver asialoglycoprotein receptor
Authors: Watts Colin
Published: February 2005

cDNA clones for the major rat liver asialoglycoprotein (ASGP) receptor were isolated from a phage λgtl 1 library using synthetic oligonucleotide probes corresponding to two regions of the protein sequence. The longest clone obtained encoded all but the first 11 codons of the receptor. The cDNA was completed with synthetic oligonucleotides and was used to direct the synthesis of mRNA for the receptor in vitro. Subsequent translation in a wheat germ lysate produced authentic ASGP receptor which assembled correctly into microsomal membranes.
Temperature effects on cholinesterases from rat brain capillaries
Authors: Catalan R. Edgardo , Hernandez Félix
Published: February 2005

The activities of acetylcholinesterase (ACHE) and butyrylcholinesterase (BuChE) in rat brain capillaries were measured as a function of temperature. Arrhenius plots of the data revealed that AChE exhibits a biphasic Arrhenius plot with a distinct break (transition temperature) at about 15.2 kcal/mol. In contrast, BuChE did not show evidence of discontinuity. BuChE showed an activation energy higher than that of AChE in the physiological range of temperature. These data suggest a lack of lipid-protein interaction in the case of BuChE. Although the possibility exists that BuChE is weakly anchored to the membranes, our results indicate that BuChE is not bound, at least significantly, to cellular membranes in brain capillaries as is ACHE.
Interaction of a bovine thymic peptide extract with vasoactive intestinal peptide (VIP) receptors
Authors: Guerrero J. M. , Goberna R. , Molinero P. , Jimenez J. , Calvo J. R.
Published: February 2005

Bovine t hymic peptide extract (1–100 μg/ml) is shown to completely inhibit the binding of [125I]VIP to rat blood mononuclear cells, lymphoid cells of spleen, and liver plasma membranes. In the three models, the bovine thymic peptide extract inhibits [125I]VIP binding with a potency that is 4000–7000 times lower than that of the native VIP, on a weight basis. In rat liver plasma membranes, the bovine thymic peptide extract stimulates adenylate cyclase with a maximal efficiency that is similar to that of VIP. At maximal doses, VIP and thymic peptide extract do not exert an additive effect on adenylate cyclase, suggesting that the activation of the enzyme by the bovine thymic peptide extract occurs through VIP receptors. Finally, no VIP-like immunoreactivity was detected in the thymic peptide extract using an antiserum raised against mammalian VIP. All these data suggest the presence in the bovine thymic peptide extract of a new substance which behaves as a VIP agonist in rat.
Isolation of glycoproteins of parainfluenza I (Sendai) by Helix pomatia Lectin column
Authors: Bartzatt Ronald , Martin Michael
Published: February 2005

Glycoproteins of Sendai virus were successfully isolated on a column of Helix pomatia Lectin-Sepharose 6MB following solubilization with Nonidet P-40. This technique can be used as a preparative step for the study of viral glycoproteins.
DNA sequences which influence the selection and efficient utilisation of transcriptional start sites of a eukaryotic gene by RNA polymerase II in vitro and in vivo
Authors: Kovacs Balazs J. , Butterworth Peter H. W.
Published: February 2005

Experiments are described which probe the relationship between three sequence elements which make up the eukaryotic RNA polymerase II promoter. A cloned eukaryotic gene, from which the TATA-box and 400 base pairs of Y-flanking sequence has been deleted, is still transcriptionally active in vivo (following its transfection into cultured mammalian cells) and in vitro. Deletion has appropriately positioned a cluster of five TATA box-like sequences upstream from multiple potential cap sites. Which cap sites are actually used can be predicted from the DNA sequence of TATA box-like sequences and their spatial relationship with respect to possible transcriptional start sites, although there appears to be some difference in cap site utilisation in vitro and in vivo. Data suggest that deletion has also removed “upstream” sequences which affect promoter function.
The relationship between the chromophore moiety and the cation binding sites in bacteriorhodopsin
Authors: Duñach Mireia , Seigneuret Michel , Rigaud Jean-Louis , Padrós Esteve
Published: February 2005

Bleaching of the purple membrane strongly reduces the number of divalent cation binding sites as well as their affinities. Conversely, deionization of the bleached membrane drastically inhibits the chromophore regeneration. Proteolysis experiments using bromelain show that the bleached membrane has an additional cleavage site probably located at the fifth loop, whereas in the blue membrane, the C-terminal tail is no longer susceptible to proteolysis. It is suggested that there exists a close relationship between the retinal environment and one or more of the cation binding sites.
Electrorotation of lymphocytes—The influence of membrane events and nucleus
Authors: Ziervogel Heiko , Glaser Roland , Schadow Dieter , Heymann Stephan
Published: February 2005

Electrorotation—the spin of cells in rotating high frequency electric fields—has been used to investigate properties of human peripheral blood lymphocytes. The rotation spectra of lymphocytes deviate from those of single shell spheres. The deviations are caused by the electrical properties of the nucleus in the cell interior.

Electrorotation allows the distinction between successfully stimulated lymphocytes and unstimulated cells after application of concanavalin A. Notwithstanding the fact that only a proportion of the cells will be mitogenically stimulated we detected an enhanced cell membrane conductivity for the whole cell population immediately after the addition of mitogen.
The metabolism of acetone in the pregnant rat
Authors: Peinado J. , López-Soriano F. J. , Argilés J. M.
Published: February 2005

The administration of a single dose of acetone (100 mg/kg bw) to virgin and 21-day pregnant rats resulted in the appearance of relatively high concentrations of 1,2-propanediol, acetol and methylglyoxal in plasma and liver. In the fetuses no methylglyoxal was detectable. The acetone metabolism curves tend to indicate that the capacity for acetone disposal may be enhanced in the 48 hr-fasted pregnant rat, thus enabling the animal to re-use acetone metabolically, possibly for accelerated gluconeogenesis.
Further evidence for a membrane potential-dependent shape transformation of the human erythrocyte membrane
Authors: Müller Peter , Herrmann Andreas , Glaser Roland
Published: February 2005

The influence of various factors (pH, temperature, sodium gluconate) on the ionic strength-dependent stomatocyte-discocyte-echinocyte transformation of the human erythrocyte membrane was investigated. The results give further evidence for a correlation between shape of erythrocyte membrane and the transmembrane potential of the cells.
Ionic strength-dependent alterations of membrane structure of red blood cells
Authors: Herrmann Andreas , Müller Peter
Published: February 2005

Electron paramagnetic resonance (EPR) measurements using various fatty acid spin labels were performed on membranes of intact human erythrocytes at physiological, and at low ionic strength. In the case of spin probes bearing the nitroxide near the polar head group, a less restricted motion at low ionic strength was seen than with those labels with a nitroxide deeper within the hydrophobic tail of the membrane. Although these data clearly show an influence of ionic strength on membrane structure, and possibly a modified protein-lipid interaction, they cannot be simply discussed in terms of an altered membrane fluidity.
Protein HMG1 is different from a DNA helix unwinding protein in calf thymus
Authors: Marekov L. N. , Demirov D. G. , Beltchev B. G.
Published: February 2005

A number of criteria were used—chromatography on columns with single-stranded and double-stranded DNA, electrophoresis, peptide analysis, immunological tests and thermal denaturation of DNA—to show that protein (high mobility group) HMG1 and an unwinding protein from calf thymus are two distinct, unrelated proteins. While both proteins are thought to be related to DNA replication this might involve different mechanisms of action.
Different patterns of protein turnover in skeletal and gastrointestinal smooth muscle and the production of Nτ-methylhistidine during fasting in the rat
Authors: Emery Peter W. , Cotellessa Laura , Holness Mark , Egan Christine , Rennie Michael J.
Published: February 2005

During four days of fasting in rats skeletal muscle protein synthesis fell pro-gressively, whereas skeletal muscle protein breakdown was unchanged until the third and fourth days when it rose dramatically. In contrast, the synthetic rate of smooth muscle protein was unchanged during three days of fasting despite a loss of protein content, indicating an abrupt rise in protein breakdown in this tissue on the first day of fasting which was sustained thereafter. Urinary excretion of Nτ-methylhistidine was significantly increased throughout fasting. The concentration of free Nτ-methylhistidine in plasma and in muscle tissue was elevated throughout the period of fasting. This elevation was not caused by reduced renal clearance, but appears to have been mainly the result of increased breakdown of Nτ-methylhistidine-containing proteins in tissues other than skeletal muscle.
Immunoperoxidase localization of type X collagen in chick tibiae
Authors: Kwan Alvin P. L. , Freemont Anthony J. , Grant Michael E.
Published: February 2005

Type X collagen was prepared from medium of long-term cultures of embryonic chick tibiotarsal chondrocytes. Antibodies to type X collagen were raised and used in immunoperoxidase localization studies with embryonic and growing chick tibiotarsus. Strong anti-type X collagen reactivity was detected mainly in the region of hypertrophic chondrocytes, and to a lesser extent in the zone of calcified cartilage. No reactivity was detected in the proliferative zone nor the superficial layer of the cartilage growth plate. These results suggest that type X collagen may play a key role in matrix calcification during growth and development of the skeletal system.
3-Ketoglutarate generation in pancreatic B-cell mitochondria regulates insulin secretory action of amino acids and 2-keto acids
Authors: Lenzen S. , Schmidt W. , Rustenbeck I. , Panten U.
Published: February 2005

The various neutral amino acids and aliphatic 2-keto acids exhibit differential effects on insulin secretion. The common denominator for all these effects is the 2-ketoglutarate generation in the pancreatic B-cell mitochondria. The neutral amino acids l-leucine and l-norvaline and the aliphatic ketomonocarboxylic acids 2-ketoisocaproate, 2-ketocaproate, 2-ketovalerate, and 2-keto-3-methylvalerate all stimulate insulin secretion and increase 2-ketoglutarate generation in pancreatic B-cell mitochondria through activation of glutamate dehydrogenase and transamination with l-glutamate and l-glutamine, respectively. The neutral amino acids l-valine, l-norleucine, and l-alanine and the aliphatic 2-keto acids 2-ketoisovalerate and pyruvate do not stimulate insulin secretion and do not increase 2-ketoglutarate generation in pancreatic B-cell mitochondria. Inhibition of 2-keto acid induced insulin secretion by l-valine and l-isoleucine is accompanied by reduced 2-ketoglutarate generation in pancreatic B-cell mitochondria. Thus intramitochondrial 2-ketoglutarate generation in pancreatic B-cells may regulate the insulin secretory potency of amino acids and 2-keto acids.
Galactosyltransferase activity is not localized to the brush border membrane of human small intestine
Authors: Boyle Frances , Snape Susan , Duane Paul , Cook Neil , Peters Timothy
Published: February 2005

A recent report [Roth et al. (1985) J. Cell Biol.100: 118–125], using immunocytochemical techniques, calimed that human duodenal galactosyltransferase is located predominantly on the external aspect of enterocyte brush border membranes. Analytical subcellular fractionation by sucrose density gradient centrifugation of human jejunum biopsy homogenates demonstrated that galactosyltransferase activity is localized to the Golgi fraction (equilibrium density of 1.14 g cm−3) and is not found in significant amounts in the brush border membrane (equilibrium density of 1.22 g cm−3).
A model for the asymmetric lipid distribution in the human erythrocyte membrane
Authors: Herrmann Andreas , Müller Peter
Published: February 2005

The asymmetric transverse distribution of phospholipids in the human erythrocyte membrane can be explained by differences between the rate constants of flip and flop motion of the lipids. A selective interaction between aminophospholipids and spectrin does not need to be assumed for creating and maintaining the asymmetric localization of these lipids. Shape transformation of red cells could be caused by alterations of the flip-flop rate constants leading to a change of the lipid distribution and, consequently, to a differential area expansion of the outer and inner membrane leaflet.
A study of the messenger RNA encoding pyruvate kinase of Neurospora crassa
Authors: Devchand M. , Kapoor M.
Published: February 2005

In Neurospora crassa, there is a single pyruvate kinase (PK) consisting of four identical subunits of ∼60k daltons. Northern and dot blot hybridization studies, using most of the yeast pyruvate kinase gene as a probe, suggest the presence of two distinct mRNA species for pyruvate kinase, separable on the basis of the length of their polyadenylated tails, by oligo(dT)cellulose chromatography. These messages are present in polysomes, immuno-precipitated by anti-PK antibodies, indicating probable translation in vivo. Fractions containing both messages were translated in vitro in the heterologous systems as well as in a homologous N. crassa lysate, the newly-synthesized PK being detected by immunoadsorption. Protection studies using S1-nuclease suggest no major structural differences in the 5′-untranslated and most of the coding regions of the two messages.
Effects of exposure to high potassium concentration on the longitudinal muscle-myenteric plexus preparation from guinea-pig
Authors: Aleixandre M. A. , Ayala E. , Garcia de Jalón P.
Published: February 2005

The effect of potassium on the longitudinal muscle-myenteric plexus (LM-MP) preparation from guinea-pig was studied. The strips were exposed to elevated K+ (30 m M, 60 m M, 90 m M, 120 m M or 150 m M). A phasic contraction of the LM-MP was caused by 10m M K+ or 15 m M K+ followed by an increase of the contractile activity probably due to the increase in acetylcholine release. A higher molarity of K+ produces more marked depolarization in the LM-MP and above 22m M K+ tetanizing effects were observed. We attempted to demonstrate that opiate-like material could be released when the tissue was exposed to more than 30 m M K+ even though several different neurotransmitters could be liberated by elevated K+ molarities.
Molecular mobility in the gap regions of type 1 collagen fibrils
Authors: Fraser R. D. B. , Trus B. L.
Published: February 2005

Recent studies of the structure of Type I collagen fibrils (Piez and Trus, Biosci. Rep.1:801–810, 1981; Fraser, MacRae, Miller and Suzuki, J. Mol. Biol.167:497–521, 1983) suggest that the segments of the collagen molecule which comprise the gap region are more mobile than those which comprise the overlap region. We have analyzed the distribution of amino acid residues and triplet types between the two regions, and find significantly non-uniform distributions for Ala, Gln, His, Hyp, Leu, Phe, and Tyr, and for triplets containing two imino acid residues. Taken together with the lower packing density in the gap region these observations provide a basis for understanding the greater mobility of the molecular segments in the gap region. In addition, we have examined the linear distribution of residue types in the two regions and also the hydropathy profile (Kyte and Doolittle, J. Mol. Biol.157: 105–113, 1982). These reveal a segment of the gap region comprising helical residues 165–173, 399–407, 633–641 and 867–975 which has the highest hydropathy index, is devoid of charged residues, and contains very high proportions of Ala, Hyp and Phe.
Detection of protein disulphide-isomerase in sheep pancreas fractions
Authors: Hillson David A. , Anderson Jacqueline
Published: February 2005

Conclusions

The use of diethylpyrocarbonate to inhibit endogenous ribonuclease in sheep pancreas allows the detection of protein-disulphide-isomerase activity in homogenates, at specific activities of up to 4 units/g. This is higher than the specific activity in sheep liver homogenates (about 2 units/g) or in homogenates of other sheep tissues (16). It is thus evident that high levels of protein-disulphide-isomerase activity are present in sheep pancreas. This is consistent both with the postulated general role of protein disulphide-isomerase in protein biosynthesis (10,11) and with the in vitro action of the enzyme on its conventional substrate scrambled ribonuclease, since pancreas is the major site of ribonuclease synthesis.
Molecular forms of the cholinesterases inside and outside muscle endplates
Authors: Jedrzejczyk Jolanta , Silman Israel , Lyles Joan M. , Barnard Eric A.
Published: February 2005

Individual endplates were micro-dissected from chicken fast-twitch muscle, and the molecular forms of acetylcholinesterase and of pseudocholinesterase therein, identified by their sedimentation coefficients, were analysed directly. The forms actually present at the endplate, and those that are non-synaptic9 were established. This analysis was also extended to muscle of the chicken with inherited muscular dystrophy, showing altered distributions of these forms.
Stimulation of Escherichia coli adenylate cyclase by lactose in strains carrying mutations in lactose permease
Authors: Peterkofsky Alan , Gazdar Celia
Published: February 2005

When a wild-type strain of Escherichia coli contains lactose permease, the accumulation of cyclic AMP (cAMP) by intact cells is inhibited by lactose. This inhibitory effect of lactose is observed in a strain with a mutant cAMP phosphodiesterase and therefore involves a regulation of adenylate cyctase activity. Some E. coli strains carrying mutations in lactose permease show an effect opposite to that of the wild-type strain; the accumulation of cAMP by intact cells is stimulated by lactose, but only when the mutant permease is present. Insertion of lactose permease into the membrane of ceils can produce a change in the specific activity of adenylate cycIase; induction of the wild-type transporter is correlated with a decrease in the specific activity, while implantation of a mutant form of lactose permease can lead to an increase in the specific activity. From these data, it is suggested that the state of the lactose transporter in the cell membrane influences the activity of adenytate cyclase.
The rapid transient stimulation of both cytoplasmic and mitochondrial ornithine decarboxylases in the liver of thyroidectomized rats by 3,5,3′-triiodo-L-thyronine
Authors: Palacios-Romero R. , Mowbray J.
Published: February 2005

Evidence is presented that liver from thyroidectomized rats has ornithine decarboxylase (ODC) in both mitochondrial and soluble fractions. The cytosolic activity was stimulated 7-fold and the mitochondrial activity 3-fold 15 min after the administration of triiodothyronine (T3). While the rapid transient stimulation of ODC could represent a direct intracellular response to T3, an incidental effect on a very-rapidly-turning-over enzyme seems more likely; this suggests that in vivo ODC may be controlled by a demand for polyamines.
Thiol proteins in chromatin
Authors: Ferraro Anna , Giartosio Anna , Eufemi Margherita , Barra Donatella , Altieri Fabio , Turano Carlo
Published: February 2005

Total half-cystine residues in proteins of pig liver chromatin have been measured. About half of them are present in the reduced state. Thiol groups of non-historic chromatin proteins, which amount to about 40 nmol/mg of protein, are preferentially located in chromatin fragments which are more easily solubilised either by DNAse I or by DNAse II. The data obtained are compatible with an involvement of SH and SS groups in chromatin structure and function.
Immunochemical recognition of phosphate ester derivatives of phenol rings is dependent upon the electronic charge of the ester group
Authors: Jones Jane A. , Wood Alison , Cushley William
Published: February 2005

The recognition of phosphate and sulphate esters of tyrosine residues has been studied employing antisera with specificity for tyrosine phosphate, and the enzymes aryl sulphatase, and acid and alkaline phosphatases. The ability of tyrosine phosphate, and of phosphate esters of phenol, to inhibit the antiserum was pH dependent. The capacity to effect inhibition appeared to correlate with alterations in the ionisation of the inhibitor. Moreover, the antisera with reactivity for tyrosine phosphate had no reactivity with tyrosine sulphate or sulphate esters of phenol at any pH value studied. The enzymes alkaline phosphatase, acid phosphatase, and aryl sulphatase were also studied. The phosphatases were found not to hydrolyse sulphate ester containing substrate analogues at any pH value in the range 5.0–9.0. In contrast, aryl sulphatase appeared to hydrolyse phosphate esters at pH 5.0 and 7.0, but not at pH 9.0.
Formation of myeloperoxidase compound II during aerobic stimulation of rat neutrophils
Authors: Edwards Steven W. , Lloyd David
Published: February 2005

We have made simultaneous spectrophotometric and O2 measurements on suspensions of rat neutrophils during activation of the respiratory burst. Under aerobic conditions an absorption increase attributable to myeloperoxidase compound II was observed in parallel with the rapid phase of O2 uptake. Identification of this compound was confirmed by analysis of a spectrum obtained with purified myeloperoxidase and H2O2. Whereas a second addition of stimulus did not increase O2 uptake any further, a second phase of myeloperoxidase release and compound II formation was observed. These results suggest that in vivo myeloperoxidase reacts with H2O2 generated via the respiratory burst to form compound II under conditions in which the chlorination reaction would be the expected major pathway.
Specific somatostatin-binding to cytosol of bovine gallbladder mucosa
Authors: Arilla E. , Colás B. , Prieto J. C.
Published: February 2005

The binding of somatostatin was studied in the cytosolic fraction of bovine gallbladder mucosa. The binding reaction depended on time, temperature and pH, and was reversible, saturable and specific. Stoichiometric data suggested the presence of two classes of binding sites: a class with high affinity (Kd=23.6 n M) and low capacity (3.7 pmol somatostatin/mg protein) and a class with low affinity (Kd=284.6 n M) and high capacity (85.0 pmol somatostatin/mg protein) at 37°C and pH 7.4. The binding sites were highly specific for somatostatin since peptides such as [Leu]enkephalin, neurotensin, vasoactive intestinal peptide and substance P showed practically no effect upon somatostatin binding. The presence of somatostatin-binding sites in the cytosolic fraction of gallbladder mucosa, together with the known occurrence of somatostatin nerve endings in the gallbladder strongly suggests that this peptide may be involved in the physiology and physiopathology of gallbladder mucosa.
The effect of a growth promoting drug, clenbuterol, on fibre frequency and area in hind limb muscles from young male rats
Authors: Maltin C. A. , Delday M. I. , Reeds P. J.
Published: February 2005

The effect of dietary administration of clenbuterol on soleus and extensor digitorum longus muscles was studied after 4 and 21 days. Both muscles showed an increase in wet weight with no significant change in total fibre number. After 4 days fibre cross-sectional areas were increased in soleus, but not in extensor digitorum longus, and after 21 days there was a change in fibre frequencies in extensor digitorum longus but not soleus muscles.
A comparison of topoisomerase I activity in normal and transformed cells
Authors: Colledge W. H. , Edge M. , Foulkes J. G.
Published: February 2005

Many viral oncogenes encode protein—yrosine kinase activities. However, important in vivo substrates of these enzymes have yet to be identified. Recently, type I topoisomerases were shown to be in vitro substrates for two tyrosine kinases. Following tyrosine phosphorylation, topoisomerase I activity was reduced 10-fold (Tse-Dinh et al. Nature312:785–786, 1984). To determine whether topoisomerase I activity was modulated by tyrosine phosphorylation in vivo, we have measured topoisomerase I activity in nuclear lysates prepared from both normal fibroblasts and cells transformed by two different viral oncogenes (v-abl, v-src). Under a variety of experimental conditions, we have found no evidence to support the notion that type I topoisomerase activity is modulated by tyrosine phosphorylation in vivo.
Dissociation of insulin binding from insulin stimulation of 2-deoxyglucose transport by ruthenium red
Authors: Williams P. F. , Plehwe W. E. , Turtle J. R.
Published: February 2005

Ruthenium red increased specific insulin binding to isolated adipocytes 5.4 fold and 2.6 fold over binding determined in the absence and presence of Ca2+ and Mg2+. The increase in insulin binding was not accompanied by an increase in insulin sensitivity. The lack of effect of ruthenium red on insulin action argued strongly against an increase in intracellular Ca2+ as a potential messenger/transducer of insulin action and suggested that the enhancing effect of Ca2+ on insulin action was a result of increased receptor affinity.
High liver lipoprotein lipase activity in hyperlipemic developing rats from undernourished pregnant mothers
Authors: López-Tejero D. , Llobera M. , Herrera E.
Published: February 2005

To study the potential relationship between circulating triacylglycerol (TAG) levels and lipoprotein lipase (LPL) activity in the newborn rat liver, pups from undernourished or normal control mothers were nursed by normal dams, and studied at 0, 1, 15 or 30 days of age. Plasma TAG levels and liver TAG concentration increased more in pups from undernourished mothers than they did in controls. At birth, liver LPL activity was similarly high in both groups but, whereas in controls it decreased progressively after birth, in pups from undernourished mothers it remained stable until 15 days of age. Results suggest that the hypertriglyceridemia present in pups from undernourished mothers may be responsible for the sustained high LPL activity in their liver which may enhance the hepatic uptake of circulating TAG.
Expression of herpes simplex virus glycoprotein D on antigen presenting cells infected with vaccinia recombinants and protective immunity
Authors: Wachsman M. , Aurelian L. , Hunter J. C. R. , Perkus M. E. , Paoletti E.
Published: February 2005

We studied the effect of the temporal regulation of herpes simplex virus (HSV) type 1 glycoprotein D (gD-1) expression in Ia+ epidermal cells (EC) and macrophages on virus specific immunity and protection from HSV-2 challenge. gD-1 was expressed on the surface of cells infected with a vaccinia recombinant containing gD-1 under the control of an early vaccinia virus promoter (VP176). It was not expressed in cells infected with a recombinant (VP254) in which gD-1 is controlled by a late vaccinia virus promoter. BALB/c mice immunized with both recombinants seroconverted to HSV-2 as determined by neutralization. However, HSV specific delayed type hypersensitivity (DTH) responses were significantly (p<0.025) higher in VP176 than VP254 immunized animals. Both VP176 and VP254 immunized mice were protected from severe neurological disease due to HSV-2 challenge at 14 days post immunization, but long term protection was observed only in VP176 immunized mice.
Several epitopes of p85 glycoprotein (CDw44) are dependent on intact disulphide bonds. Isolation of cDNA clones requires a polyclonal antibody raised against the reduced protein
Authors: Rogers Ian , D'Agostaro Giacomo , Vera Sonia , Letarte Michelle
Published: February 2005

Monoclonal antibodies 50B4 and 50E6 recognize two distinct epitopes of human p85 glycoprotein (CDw44). Both epitopes are destroyed by reduction of the purified gycoprotein as demonstrated by inhibition of cellular radioimmunoassay and Western blot analysis. Endoglycosidase F treated p85 glycoprotein, with an apparent molecular weight of 73,000 is still reactive with both monoclonal antibodies. Thus both epitopes are conformational determinats of the polypeptide chain. A rabbit antibody produced against purified native p85 glycoprotein also reacted only with the non-reduced form of p85. Repeated immunizations with SDS-dissociated and reduced p85 yielded a polyclonal antibody reactive by Western blot analysis with reduced and non-reduced forms of p85 glycoprotein. When a HOON leukemia cell line cDNA expression library was screened with this polyclonal antibody, two cDNA clones were isolated which reacted specifically with the antiserum and not with the control non-immune serum. Preliminary characterization of these clones indicates that they are p85-related.
Calcium binding protein changes of sarcoplasmic reticulum from rat denervated skeletal muscle
Authors: Loirat Marie-Jeanne , Lucas-Heron Brigitte , Ollivier Béatrice , Leoty Claude
Published: February 2005

Two Ca2+ sequestering proteins were studied in fast-twitch (EDL) and slow-twitch (soleus) muscle sarcoplasmic reticulum (SR) as a function of denervation time. Ca2+-ATPase activity measured in SR fractions of normal soleus represented 5% of that measure in SR fractions of normal EDL. Denervation caused a severe decrease in activity only in fast-twich muscle. Ca2+-ATPase and calsequestrin contents were affected differently by denervation. In EDL SR, Ca2+-ATPase content decreased progressively, whereas in soleus SR, no variation was observed. Calsequestrin showed a slight increase in both muscles as a function of denervation time correlated with increased45Ca-binding.

These results indicate first that Ca2+-ATPase activity in EDL was under neural control, and that because of low Ca2+-ATPase activity and content in slow-twitch muscle no variation could be detected, and secondly that greater calsequestrin content might represent a relative increasing of heavy vesicles or decreasing of light vesicles as a function of denervation time in the whole SR fraction isolated in both types of muscles.
Introduction of antibody (PL/IM 430) to a 100 kDa protein into permeabilised platelets inhibits intracellular sequestration of Ca2+
Authors: Hack Nashrudeen , Authi Kalwant Singh , Crawford Neville
Published: February 2005

A monoclonal antibody (PL/IM 430), previously found to inhibit the uptake of Ca2+ into highly purified platelet intracellular membrane vesicles (Hack, N., Wilkinson, J. M. and Crawford, N. 1988, Biochem. J.250, 355–361) has been introduced into saponin-permeabilised platelets. At a saponin concentration (20–25 μg/ml) commensurate with total LDH release, sequestration of Ca2+ into intracellular non-mitochondrial stores is inhibited by the antibody (~50% inhibition at 20 μg/ml IgG). At higher saponin concentrations when intracellular binding of125I-labelled mAb is maximum, inhibition of Ca2+ sequestration approaches 70%. The inhibition is specific, control studies with non-platelet directed mouse IgG and mAbs which immunoblot platelet antigens other than the 100 kDa protein did not affect the Ca2+ sequestration.

No effect of the antibody were observed against IP3-induced release of prestored Ca2+, either in permeabilised platelets or with isolated intracellular membrane vesicles. The mAb PL/IM 430 appears to bind only to the Ca2+ translocating channel protein associated with the intracellular membrane (Ca2++Mg2+) ATPase and not to Ca2+ channels responsive to IP3.
Heparin inhibits specific glycosyltransferase activities in interleukin 2 activated murine T cells
Authors: Schwarting Gerald A. , Gajewski Anna
Published: February 2005

In order to better understand the role of cell surface glycolipids in T lymphocyte activation, heparin was used to simultaneously modulate the expression of glycolipids and the lytic capacity of lymphocytes activated by interleukin-2. Results presented here show that heparin added at the start of a 3 day culture inhibited the formation of lymphokine activated killer cells by up to 50%. Heparin also has a profound effect on the synthesis of glycolipids during this three day period. Asialo GM1, a useful cell surface marker for subsets of murine cytotoxic cells, is reduced in amount, as are the other two major neutral glycolipids lactosylceramide and asialo GM2. In addition, the synthesis of some gangliosides is affected by heparin treatment. Comparison of the glycosyltrasferase activities of untreated and heparin-treated cells shows that the activities of a 2–3-sialyltransferase and a β1–3 galactosyltransferase are inhibited dramatically, while a third enzyme, N-acetyl-galactosaminyltransferase is unaffected. The two heparin inhibitable enzymes bind to heparin affinity columns but the galactosaminyltransferase does not. These studies suggest that the proper regulation of the activities of specific glycosyltransferases may be important events in lymphocyte activation.
Reactivation of apo horse liver alcohol dehydrogenase with the monovalent metal ion Ag(I)
Authors: Skjeldal Lars , Dahl Knut H. , McKinley-McKee John S.
Published: February 2005

Each subunit of the liver alcohol dehydrogenase dimer contains one catalytic and one structural Zn(II) atom. Enzyme with the catalytic metal atoms selectively removed is inactive but can be partly reactivated in the presence of Ag(I) ions. Reactivation results from Ag(1) ions entering the empty metal-binding site in the catalytic center. The specific activity of this silver enzyme reached 24% of the native enzyme. Atomic absorption analysis gave equal amounts of Ag(I) and Zn(II), corresponding to one mole of each metal per monomer. Metal-directed affinity labelling using bromo-imidazolyl propionate showed that the properties of the silver-reactivated enzyme were distinct from those of the native enzyme.
The serine codons UCX and AGY are not interchangeable in the mammalian mitochondrial genomes
Authors: Henaut A.
Published: February 2005

The study of silent substitutions in the mammalian mitochondrial genes shows that the probability that two species use the same codon is, as a general rule, equal to the product o5 the probabilities of use of this codon in the two species. The only appreciable exception is that of serine, for which the UCX and AGY codons are not interchangeable.
Columns of water molecules and chloride ions in hydrophobic channels in crystals of a potassium complex
Authors: Hanson I. R. , Truter Mary R.
Published: February 2005

The complex between potassium chloride and a macrobicyclic polyether (L) had been shown to crystallize as complex cations KL+ packed to form channels which contained ‘disordered’ water molecules and chloride ions. Here the arrangement of water molecules and chloride ions is described.
A unified matrix hypothesis of DNA-directed morphogenesis, protodynamism and growth control
Authors: Scherrer Klaus
Published: February 2005

A theoretical concept is proposed, in order to explain some enigmatic aspects of cellular and molecular biology of eukaryotic organisms. Among these are the C-value paradox of DNA redundancy, the correlation of DNA content and cell size, the disruption of genes at DNA level, the “Chromosome field” data of Lima de Faria (Hereditas93:1, 1980), the “quantal mitosis” proposition of Holtzer et al. (Curr. Top. Dev. Biol.7:229 1972), the inheritance of morphological patterns, the relations of DNA and chromosome organisation to cellular structure and function, the molecular basis of speciation, etc. The basic proposition of the “Unified Matrix Hypothesis” is that the nuclear DNA has a direct morphogenic function, in addition to its coding function in protein synthesis. This additional genetic information is thought to be largely contained in the non-protein coding transcribed DNA, and in the untranscribed part of the genome.