bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurements of the severity of fires involving private motor vehicles
Authors: Shipp Martin , Spearpoint Michael 
Published: December 2004

AbstractThis paper presents the results of full‐scale fires in two private motor vehicles conducted under insturmented calorimeter hoods for the Channel Tunnel Safety Unit, Department of Transport. Measurements of heat release rate, temperatures and other parameters of fire severity are given. The results were used for the assessment of the specification and design of the shuttle wagons and in the subsequent computer modelling calculations to analyse the impact of such a fire within a shuttle wagon. The fires were well ventilated and allowed to develop fully before firefighting intervention. Of the two tests the first burned for 17 min with the gas temperature in the rig reaching 1250°C and with a peak total heat output of at least 7½ MW before being extinguished. The other burned for 57 min, with gas temperatures reaching 1125°C and a pead heat output of 4½ MW.
Core substructure in cyanobacterial phycobilisomes
Authors: Gingrich Jeffrey C. , Lundell Daniel J. , Glazer Alexander N. 
Published: December 2004

AbstractThe tricylindrical core of Synechocystis 6701 phycobilisomes is made up of four types of allophycocyanin‐containing complexes: A, (αAP βAP)3; B, (αAP βAP)3 .10K; C, (ααβ).10K; D, (αAP βAP)2.18.5K.99K; where AP is allophycocyanin, APB is allophycocyanin B, and 10K, 18.5K, and 99K are polypeptides of 10,000, 18,500, and 99,000 daltons, respectively. The 18.5K polypeptide is a hitherto unrecognized biliprotein subunit with a single phycocyanobilin prosthetic group. The tricylindrical core is made up of 12 subcomplexes in the molar ratio of A:B:C:D: of 4:4:2:2. Complexes C and D act as terminal energy acceptors. From these results and previous analysis of the bicylindrical core of Synechococcus 6301 phycobilisomes [14,15] it is proposed that the two cylinders of the Synechocystis 6701 core, proximal to the thylakoid membrane, each have the composition ABCD, and that the distal cylinder has the composition A2B2.
Transport of hemolysin by Escherichia coli
Authors: Härtlein Michael , Schießl Sigrid , Wagner Wilma , Rdest Ursula , Kreft Jürgen , Goebel Werner 
Published: December 2004

AbstractThe hemolytic phenotype in Escherichia coli is determined by four genes. Two (hlyC and hlyA) determine the synthesis of a hemolytically active protein which is transported across the cytoplasmic membrane. The other two genes (hlyBa and hlyBb) encode two proteins which are located in the outer membrane and seem to form a specific transport system for hemolysin across the outer membrane. The primary product of gene hlyA is a protein (protein A) of 106,000 daltons which is nonhemolytic and which is not transported. No signal peptide can be recognized at its N‐terminus. In the presence of the hlyC gene product (protein C), the 106,000‐dalton protein is processed to the major proteolytic product of 58,000 daltons, which is hemolytically active and is transported across the cytoplasmic membrane. Several other proteolytic fragments of the 106,000‐dalton protein are also generated. During the transport of the 58,000‐dalton fragment (and possible other proteolytic fragments of hlyA gene product), the C protein remains in the cytoplasm. In the absence of hlyBa and hlyBb the entire hemolytic activity (mainly associated with the 58,000‐dalton protein) is located in the periplasm: Studies on the location of hcmolysin in hlyBa and hlyBb mutants suggest that the gene product of hlyBa (protein Ba) binds hemolysin and leads it through the outer membrane whereas the gene product of hlyBb (protein Bb) releases hemolysin from the outer membrane. This transport system is specific for E coli hemoiysin. Other periplasmic enzymes of E coli and heterologous hemolysin (cereolysin) are not transported.
Prolactin receptor expression in monolayer cultures of rabbit mammary epithelial cells: Pre‐ and postpartum [125I]‐prolactin binding activity
Authors: Soltysiak R. M. , Fellows R. E. 
Published: December 2004

AbstractExpression of specific [125I]‐prolactin‐binding sites under culture conditions has been investigated for isolated mammary epithelial cells from virgin, pregnant, and lactating rabbits. Primary monolayer cultures were obtained by sequential enzymatic dispersion of mammary tissue followed by 48 hr incubation in a medium selective for epithelial cells. Scatchard analyses of binding data obtained from these cultures indicated a single class of receptor sites, the affinity constant of which (2.5 × 109 M−1) did not vary significantly during mammary development. The number of prolactin receptors, however, expressed by virgin and early pregnant epithelial cells was significantly increased over those from late pregnancy or lactation. Less differentiated cells also respond to growth in pregnant rabbit serum with an increase in specific [125I]‐prolactin binding. The diminished receptor expression by cells obtained after 17 days of pregnancy coincides with the attainment of secretory capacity in the animal, and may reflect the influence of the low serum prolactin or high progesterone levels circulating during the last trimester in the rabbit, or be the cultural expression of secretory differentiation.
Reconstitution of the low density lipoprotein receptor
Authors: Schneider Wolfgang J. 
Published: December 2004

AbstractThe receptor for low density lipoprotein was purified from bovine adrenal cortex in the presence of the nonionic detergent octylglucoside. Receptors were incorporated into the bilayer of egg phosphatidylcholine vesicles by a detergent‐dialysis method. Reconstituted receptors were functional in that they bound low density lipoprotein as well as a monoclonal antibody directed against the receptor in a specific, saturable fashion. Binding activity of reconstituted receptors was measured by a gel chromatography assay. The orientation of the receptor molecule within the phospholipid bilayer was investigated by binding assays following proteolytic digestion. Reconstituted receptors showed an orientation that was functionally indistinguishable from that of low density lipoprotein receptors in the plasma membrane of intact human fibroblasts.
Isolation of PS II reaction centre and its relationship to the minor chlorophyll‐protein complexes
Authors: Camm Edith L. , Green Beverley R. 
Published: December 2004

AbstractEvidence is presented for the identification of the chlorophyll‐ protein complex CPa‐1 (CP 47) as the reaction centre of photosystem II (PS II). We have developed a simple, rapid method using octyl glucoside solubilization to obtain preparations from spinach and barley that are highly enriched in PS II reaction centre activity (measured as the light‐driven reduction of diphenylcarbazide by 2,6‐dichlorophen‐olindophenol). These preparations contain only the two minor chlorophyll‐protein complexes CPa‐1 and CPa‐2. During centrifugation on a sucrose density gradient, there is a partial separation of the two CPa complexes from each other, and a complete separation from other chlorophyll‐protein complexes. The PS II activity comigrates with CPa‐1 but not CPa‐2, strongly suggesting that the former is the reaction centre complex of PS II. Reaction centre preparations are sensitive to the herbicide 3(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), but only at much higher concentrations than those required to inhibit intact thylakoid membranes.A model of PS II incorporating our current knowledge of the chlorophyll‐protein complexes is presented. It is proposed that CPa‐2 and the chlorophyll a + b complex CP 29 may function as internal antenna complexes surrounding the reaction centre, with the addition of variable amounts of the major chlorophyll a+b light‐harvesting complex.
Effect of physiological concentrations of insulin and antidiabetic drugs on RNA release from isolated liver nuclei
Authors: Schumm Dorothy E. , Webb Thomas E. 
Published: December 2004

AbstractThe addition of 10−11M insulin to a cell‐free system from rat liver promotes the release of messengerlike RNA from isolated prelabeled nuclei. The stimulation was similar whether the nuclei were preincubatcd with insulin, or if insulin was added directly to the cell‐free system with or without a protease inhibitor. Dot blot hybridization using cloned cDNA for α2u‐globulin mRNA showed that this was one of the messages whose release was enhanced by insulin. Nuclei isolated from rats treated with either of the antidiabetics tolbutamide or tolazamide showed no increase in RNA release in the presence of insulin over the concentration range 10−5−10−14 M. Furthermore, these nuclei did not release detectable levels of α2u‐globulin mRNA.
Release and purification of trypanosoma brucei variant surface glycoprotein
Authors: Cross George A. M. 
Published: December 2004

AbstractConditions affecting the solubilization of variant surface glycoprotein (VSG) from Trypanosoma brucei have been investigated. The results obtained form the basis for a convenient and efficient method for VSG purification. VSG release from the cell surface was temperature‐dependent, following osmotic lysis at 0 °C, and was inhibited by low concentrations of Zn2+ but not by tosyl‐lysine chloromethyl‐ketone (TLCK), phenylmethylsulfonylfluoride (PMSF), or iodoacetamide. These and other results eliminated the possibility that release was due to proteolytic cleavage of the C‐terminal hydrophobic tail present on newly synthesized VSG. Bolton and Hunter reagent reacted with several components on living cells.
Synthesis, processing, and secretion of hepatic very low density lipoprotein
Authors: Janero David R. , Siuta‐Mangano Patricia , Miller Kurt W. , Lane M. Daniel 
Published: December 2004

AbstractVery low density lipoprotein (VLDL) is the major vehicle in the plasma which carries triacylglycerol synthesized in the liver to peripheral tissues for utilization. Estrogen‐induced chick parenchymal liver cells (hepatocytes) synthesize and secrete large amounts of VLDL. These cells, in a primary monolayer culture system developed in this laboratory, have been employed to study the operative and regulatory aspects of VLDL synthesis, assembly, and secretion. Some 10 min are required for the translation of the principle VLDL protein constituent, apolipoprotein B, and 30–35 min are required for the two newly translated chick VLDL apolipoproteins, apolipoprotein B and apolipoprotein II, to be secreted. Apolipoprotein B is synthesized on membrane‐bound polysomes as a contiguous polypeptide chain of 350K molecular weight (MW) and is not assembled posttranslationally from smaller‐peptide precursors. Translocation of puromycin‐discharged apolipoprotein B nascent chains into the endoplasmic reticulum lumen and their subsequent secretion are independent of both ongoing protein synthesis and the attachment of the nascent peptides to ribosomes. Apolipoprotein B nascent chains discharged by puromycin assemble with glycerolipid (mainly triacylglycerol) and are secreted as immunoprecipitable VLDL. Core oligosaccharides are added to the apolipoprotein B nascent chain co‐translationally in at least two stages, at molecular weights of ∼ 120K and ∼ 280K. Inhibition of N‐linked glycosylation of apolipoprotein B with tunicamycin affects neither the assembly of glycerolipids into VLDL nor the secretion of the VLDL particle, indicating that aglyco‐apolipoprotein B can serve as a functional component for VLDL assembly and secretion. Active synthesis of the VLDL apolipoproteins is required, however, for glycerolipid assembly into VLDL and secretion from the hepatocyte. The differential kinetics with which newly synthesized apolipoproteins and glycerolipids are secreted as VLDL and the timing of the effects of protein‐synthesis inhibitors on their secretion indicate that VLDL constituents are assembled sequentially in the intact liver cell. The bulk of the VLDL triacylglycerol and some VLDL phosphoglyceride is introduced early in the secretory pathway proximal, yet subsequent to apopeptide synthesis, while a significant fraction of VLDL phosphoglyceride associates with the resulting triacylglycerol‐rich lipid‐protein complexes just prior to their secretion as mature VLDL. Within the context of current models for VLDL structure, the late assembly of phosphoglyceride into VLDL is taken to represent a surface maturation of the nascent VLDL particle.
The natural heterogeneity of trypanosoma cruzi: Biological and medical implications
Authors: Dvorak James A. 
Published: December 2004

AbstractTrypanosoma cruzi is a heterogeneous group of parasites. The imposition of natural or artificial pressures can result in the selection of subsets of the population with concomitant changes in characteristics used to evaluate the group. In order to ascertain the extent of heterogeneity, stocks of single‐cell clones were prepared from various sources. Selected cell biological, biochemical, immunochemical, parasitological, and histopathological parameters of these clones have been studied. A ten‐fold difference in the rate of growth of the epimastigote stage of T cruzi clones has been observed. The extracellular growth rates of the clones correlate with the rate of growth of the obligate intracellular amastigote stage and consequently, the length of intracellular cycle of the parasite. A 40% difference in the amount of total DNA/parasite has been found between clones. Although the amount of DNA/kinetoplast and nucleus varies between clones, the major contribution to the differences in total DNA/parasite appears to be the nucleus. From 16 to 35 antigens have been demonstrated in the T cruzi clones assayed to date. Five to seven of these antigens are common to all of the stocks assayed. However, both isolate‐ and clone‐specific antigens have also been demonstrated. The susceptibility of inbred strains of mice to T cruzi clones varies with the clone of the parasite. These data imply that the genetics of the parasite as well as the host modulate both the course and outcome of a T cruzi infection. The influence of monosaccharides on the receptor‐mediated infection of vertebrate cells by trypomastigotes of T cruzi also varies between clones. The implications of these findings upon our concept and understanding of present and future problems in Chagas disease are discussed.
The in vitro trypanocidal activity of N‐substituted p‐benzoquinone imines: Assessment of biochemical structure‐activity relationships using the Hansch approach
Authors: Grady Robert W. , Blobstein Steven H. , Meshnick Steven R. , Ulrich Peter C. , Cerami Anthony , Amirmoazzami Jafargholi , Hodnett Ernest M. 
Published: December 2004

AbstractIt has previously been found that naphthoquinones can potentiate the rate of hydrogen peroxide production by mitochondrial preparations of Trypanosoma brucei brucei and that organisms treated with naphthoquinones are more susceptible to lysis, especially in the presence of compounds such as heme, which promote the homolytic cleavage of hydrogen peroxide. We have evaluated the lytic effect of various N‐substituted p‐benzoquinone imines both in vitro and in vivo and have attempted to correlate their structure with trypanocidal activity using the Hansch approach. While none of the compounds tested proved to be active in vivo, all caused the lysis of trypanosomes in vitro. The parameters that correlated best with trypanocidal activity were the conditional redox potential, the lipophilicity of the substituent attached to the nitrogen atom and the number of active hydrogens on the quinoncid ring. These findings suggest two possible modes of action, which may in fact be related. Conjugate nucleophilic addition and/or oxidative damage could be responsible for lysis of the parasites. These same compounds were previously found to be active against the ascitic sarcoma 180 in mice. The strong correlation between antineoplastic activity in vivo and trypanocidal activity in vitro suggests a similar mode of action in both cases. Further studies aimed at developing a quinonelike compound that will be active against trypanosomes in vivo are now in progress.
Phosphoproteins and the phosphoenolpyruvate: Sugar phosphotransferase system in salmonella typhimurium and escherichia coli: Evidence for IIIMannose, IIIFructose, IIIGlucitol, and the phosphorylation of enzyme IIMannitol and enzyme IIN‐acetylglucosamine
Authors: Waygood E. Bruce , Mattoo Roshan L. , Peri Krishna G. 
Published: December 2004

AbstractPhosphoproteins produced by the incubation of crude extracts of Salmonella typhimurium and Escherichia coli with either [32P]phosphoenolpyruvate or [γ32P]ATP have been resolved and detected using sodium dodecyl sulphate poly‐acrylamide gel electrophoresis and autoradiography. Simple techniques were found such that distinctions could be made between phosphoproteins containing acid‐labile or stable phosphoamino acids and between N1‐P‐histidine and N3‐P‐histidine. Phosphoproteins were found to be primarily formed from phosphoenolpyruvate, but because of an efficient phosphoexchange, ATP also led to the formation of the major phosphoenolpyruvate‐dependent phosphoproteins. These proteins had the following apparent subunit molecular weights: 65,000, 65,000, 62,000, 48,000, 40,000, 33,000, 25,000, 20,000, 14,000, 13,000, 9,000, 8,000. Major ATP‐dependent phosphoproteins were detected with apparent subunit molecular weights of 75,000, 46,000, 30,000, and 15,000. Other minor phosphoproteins were detected. The phosphorylation of the 48,000‐ and 25,000‐MW proteins by phos‐phoenolpyruvate was independent of the phosphoenolpyruvate:sugar phospho‐transferase system (PTS). The PTS phosphoproteins were identified as enzyme I (soluble; MW = 65,000); enzyme IIN‐acetylglucosamine (membrane bound; MW = 65,000); enzyme IImannitol (membrane bound; MW = 62,000); IIIfructose (soluble; MW = 40,000); IIImannose (partially membrane associated; MW = 33,000); IIIglucose (soluble; MW = 20,000); IIIglucitol (soluble; MW = 13‐14,000); HPr (soluble; MW = 9,000); FPr (fructose induced HPr‐like protein (soluble; MW = 8,000). HPr and FPr are phosphorylated on the N‐1 position of a histidyl residue while all the others appear to be phosphorylated on an N‐3 position of a histidyl residue. These studies identify some previously unknown proteins of the PTS and show the phosphorylation of others, which although previously known, had not been shown to be phosphoproteins.
Immunological comparison of desmosomal components from several bovine tissues
Authors: Giudice George J. , Cohen Stephen M. , Patel Nipam H. , Steinberg Malcolm S. 
Published: December 2004

AbstractA panel of monoclonal antibodies and conventional antisera directed against desmosomal proteins from bovine muzzle epidermis was used Io identify immunologically related proteins from two other bovine stratified squamous epithelia, cornea and esophagus. Desmosome‐enriched tissue fractions were prepared from epidermis, cornea, and esophagus. These tissue extracts were electrophoresed on sodium dodecyl sulfate (SDS)‐polyacrylamide gels, blotted onto nitrocellulose paper, and labeled using an indirect immunoperoxidase technique. Labeling with the conventional antisera demonstrates that each of the previously characterized epidermal desmosomal proteins or protein families has an immunologically cross‐reacting counterpart in cornea and esophagus. However, chemical differences between homologous desmosomal proteins in these three tissues have also been detected. The corresponding proteins in the different tissues have similar but not always identical apparent molecular weights. Moreover, tissue‐restricted antigenic determinants were detected in two of the desmosomal protein families using four monoclonal antibodies, each of which recognizes a distinct antigenic determinant.
Decreased activity of acetyl‐CoA carboxylase during chemically induced neutrophilic differentiation of human promyelocytic leukemia cells
Authors: Fischkoff Steven A. , Papuchis Gary C. , Nickols Wayne A. 
Published: December 2004

AbstractIn order to better understand the mechanism by which changes in the fatty acid composition of cellular lipids occur in leukemia cell lines induced to differentiate, the activity of the first enzyme of fatty acid biosynthesis, acetyl‐CoA carboxylase (EC 6.4.1.2) was measured in HL‐60 promyclocytic leukemia cells before, during and after treatment with compounds that induce these cells to mature to neutro‐phillike cells. After 24 h of exposure to dimethylsulfoxide, retinoic acid, or butyric acid, no morphological or biochemical (nitroblue tetrazolium reduction) evidence of differentiation occurred, but acetyl‐CoA carboxylase activity decreased 44, 44.5, and 49% respectively, compared to untreated cells. After 7 days of culture in the presence of these agents, 79, 83, and 72% of cells acquired the ability to reduce nitroblue tetrazolium (versus 15% of control cells) and enzyme activity decreased 92.7, 99.7, and 98%, compared to control cultures, with the three compounds respectively. Thus, some of the reported changes in fatty acid composition of leukemia cells with differentiation may arise, in part, from the depression of the de novo fatty acid biosynthetic pathway and the loss of acetyl‐CoA carboxylase activity may be a useful marker for neutrophilic differentiation in HL‐60 cells.
Protamine inhibits platelet derived growth factor receptor activity but not epidermal growth factor activity
Authors: Huang Jung San , Nishimura Junji , Huang Shuan Shian , Deuel Thomas F. , Deuel Thomas F. 
Published: December 2004

AbstractProtamine sulfate blocked 125I‐PDGF binding to its specific physiological receptor on Swiss mouse 3T3 cells. Reduced 125I‐PDGF binding in the presence of protamine sulfate correlated directly with a protamine sulfate dose‐dependent decrease in the PDGF‐dependent incorporation of [3H]‐thymidine into 3T3 cells and a decreased PDGF‐stimulated tyrosine‐specific protein kinase activity in isolated membrane preparations of 3T3 cells. Protamine sulfate blocked 125I‐PDGF binding to simian sarcoma virus transformed cells (SSV‐NIH 3T3 and SSV‐NPl cells) and to nontransformed cells in a manner qualitatively identical to unlabelled PDGF. In contrast, protamine sulfate enhanced the specific binding of 125I‐EGF by increasing the apparent number of EGF receptors on the cell surface. The increase in 125I‐EGF receptor binding was not prevented by cycloheximide nor by actinomycin D. Protamine sulfate did not affect 125I‐EGF binding to membranes from 3T3 cells or the EGF‐stimulated 3T3 cell membrane tyrbsinc specific protein kinase activity, suggesting that protamine sulfate may have exposed a population of cryptic EGF receptors otherwise not accessible. Protamine sulfate was fractionated into four active fractions by Sephadex G‐50 gel filtration columns; the half maximum inhibition concentration of 125I‐PDGF binding to 3T3 cells of protamines I and II (MW ∼ 11,000 daltons and 7,000 daltons, respectively) is ∼ 0.4 μM. Protamine II (MW ∼ 4,800 daltons) was equally active (half maximum inhibition concentration ∼ 0.4 μM); protamine IV (MW ∼ 3,300 daltons) was substantially less active (half maximum inhibition concentration ∼ 2.8 μM).These investigations have extended previous observations that protamine sulfate is a potent inhibitor of PDGF binding and establish that protamine sulfate blocks PDGF binding at the physiological receptor, preventing PDGF initiated biological activities. Protamine sulfate can be used as a reagent to separate the influence of PDGF and EGF on cells with high specificity and has been used to demonstrate that the receptors on simian sarcoma virus transformed 3T3 cells qualitatively respond identically to protamine sulfate as to unlabelled PDGF and are likely identical to those on nontransformed 3T3 cells.