bluuebunny/crossref_metadata_2025 huggingface dataset:
Occlusion and stability of synthetic femoral canal plugs used in cemented hip arthroplasty
Authors: Johnson James A. , Johnston David , El Hawary Rani , Tan Stephen R. , Wong Lori A. , Gross Michael
Published: May 2005

The occlusion and stability of five synthetic plugs used to restrict the femoral canal prior to cemented arthroplasty was assessed. A model was employed consisting of a hollow wooden dowel to simulate the canal, with adapters fixed to both ends to accommodate cement insertion and pressurization, and to produce a closed distal cavity. Three different canal diameters within the range accommodated by the plug selected were employed to assess insertion force, distal pressure during both insertion and pressurization of acrylic cement, and plug migration and leakage for each device. There was a wide variation among plugs in the magnitudes of the force and distal pressure upon plug insertion. During cement pressurization, cement leakage and/or plug migration was noted in all trials, and either of these events resulted in pressure rises in the distal cavity. Most notably, differences of only 0.5 mm in the diameter of the canal resulted in marked changes in the occlusion and stability achieved. It is concluded that for the range of canal sizes anticipated intraoperatively, these synthetic plugs appear deficient to varying extents in their ability to occlude or remain stable in the intramedullary canal. © 1995 John Wiley & Sons, Inc.
Reduced adherence of Candida to silane‐treated silicone rubber
Authors: Price C. L. , Williams D. W. , Waters M. G. J. , Coulthwaite L. , Verran J. , Taylor R. L. , Stickler D. , Lewis M. A. O.
Published: May 2005

Silicone rubber is widely used in the construction of medical devices that can provide an essential role in the treatment of human illness. However, subsequent microbial colonization of silicone rubber can result in clinical infection or device failure. The objective of this study was to determine the effectiveness of a novel silane‐treated silicone rubber in inhibiting microbial adherence and material penetration. Test material was prepared by a combination of argon plasma discharge treatment and fluorinated silane coupling. Chemicophysical changes were then confirmed by X‐ray photoelectron spectroscopy, contact‐angle measurement, and atomic force microscopy. Two separate adherence assays and a material penetration assay assessed the performance of the new material against four strains of Candida species. Results showed a significant reduction (p < 0.01) of Candida albicans GDH 2346 adherence to silane‐treated silicone compared with untreated controls. This reduction was still evident after the incorporation of saliva into the assay. Adherence inhibition also occurred with Candida tropicalis MMU and Candida krusei NCYC, although this was assay dependent. Reduced penetration of silane‐treated silicone by Candida was evident when compared to untreated controls, plaster‐processed silicone, and acrylic‐processed silicone. To summarize, a novel silicone rubber material is described that inhibits both candidal adherence and material penetration. The clinical benefit and performance of this material remains to be determined. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Study of the influence of β‐radiation on the properties and mineralization of different starch‐based biomaterials
Authors: Oliveira A. L. , Mano J. F. , Román J. San , Reis R. L.
Published: May 2005

In this work, the effects of β‐radiation are assessed, for the first time, on starch‐based biodegradable polymers, with the aim of using it as an alternative sterilization process to the previously studied sterilization methods. Different doses of radiation were used in order to investigate the possibility of using this sterilization technique as a treatment to tailor the surface and bulk properties (namely mechanical) of these polymers. The as‐treated substrates were characterized by water‐uptake measurements and contact angle (θ) measurements. The mechanical properties of the materials were characterized by tensile tests by means of ultimate tensile strength (UTS) and strain at break (εr). The fracture of the surfaces was observed by scanning electron microscopy (SEM). Dynamic mechanical analysis (DMA) was also used to characterize the viscolelastic behavior of the irradiated materials. The main effect of sterilization with β‐radiation over the starch‐based polymers seems to be a surface modification by an increase of the hydrophilicity. Nevertheless, because β‐radiation did not significantly affect the mechanical properties, it can be regarded as an effective way of modifying the surface for applications were more hydrophilic surfaces are desirable. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Equipment for cultivation of fastidious micro‐organisms
Authors: Achorn G. B. , Bokesch E. R. , Dapper E. R. , Lebherz R. W. , Metcalfe S. N. , Rawson A. J. , Smith J. R. E. , Schwab J. L.
Published: May 2005

Equipment has been developed in which fermentation processes for fastidious, pathogenic micro‐organisms can be operated on a pilot‐plant scale. Experience has shown the need for the development of concepts, techniques, and equipment meeting more stringent requirements than those ordinarily encountered in the fermentation industry. A system has been developed for the preparation of pure cultures which may be used either for the development of processes or in the preparation of substantial quantities of pure cultures. The equipment includes specially designed valves, fermentors, piping arrangement, and requires special methods of operation in order to maintain pure cultures during growth of the organism. The number of cultures of pathogenic, fastidious micro‐organisms contaminated in the systems commonly used in industry is materially greater than the number of contaminated cultures produced in the system described.
The significance of surface electric charge on algae in water purification
Authors: Ives K. J.
Published: May 2005

The results of a study on the surface electric charge carried by fresh‐water planktonic algae are used to provide a theory for the flocculation of algae with chemical coagulants. Where it is desirable to remove algae from water, for example from lakes or reservoirs for water supply, or from sewage oxidation ponds, the theory indicates certain practices are desirable to obtain the best removal. It is planned to extend the theory and experimental work to cover the removal of untreated algae from water by filtration through porous granular media, believed to be an adsorptive effect. Separation of different species of algae employing their electrokinetic properties is also described.
Agitation effects in yeast propagation
Authors: West John M. , Garden Elmer L.
Published: May 2005

The influence of mechanical agitation in aerobic fermentations is felt mainly through increased aeration efficiency. For yeast propagations in which oxygen supply is abundant—and presumably not limiting to growth—a specific, but limited, effect of fluid agitation on growth rate has been demonstrated. The improved growth rate is attributed primarily to better mixing of the entire fluid mixture rather than to improved cell‐fluid mass transfer.
Continuous streptomycin fermentation
Authors: Sikyta Bohumil , Doskočil Jiří , Kašparová Jitka
Published: May 2005

A pilot plant unit for continuous cultivation of hyphaeforming micro‐organisms, providing for a uniform flow velocity in fermentations on suspension media with a massive growth of mycelium, is described. For the maintenance of aseptic conditions, over‐pressre of air is maintained in the whole equipment. This equipment has been used for studies of the continuous biosynthesis of streptomycin. A three‐stage fermentation proved the most advantageous. The first stage serves for multiplication of the inoculum; the second and third for the formation of the antibiotic. The system was maintained for 300–400 h with yields amounting to 2,000–2,500 u. of streptomycin/ml without any signs of contamination or degeneration of the growing culture.
A kinetic study of the lactic acid fermentation. Batch process at controlled pH
Authors: Luedeking Robert , Piret Edgar L.
Published: May 2005

Kinetic data are needed to develop basic understanding of fermentation processes and to permit rational design of continuous fermentation processes.

The kinetics of the fermentation of glucose to lactic acid have been studied at six constant pH levels between 4·5 and 6·0 by measuring the instantaneous rates of bacterial growth and of lactic acid formation throughout each fermentation.

It was found that the instantaneous rate of acid formation dP/dt, could be related to the instantaneous rate of bacterial growth dN/dt, and to the bacterial density N, throughout a fermentation at a given pH, by the expression

where the constants α and β are determined by the pH of the fermentation.
Equipment for the resuspension or redissolving of precipitates in continuous‐flow centrifuges
Authors: Vallet L.
Published: May 2005

Equipment has been developed for resuspending or redissolving protein precipitates separated in a continuous‐flow centrifuge without first removing them from the centrifuge bowl. All the components can be sterilised by autoclaving. The equipment has been used successfully in selected stages of a process for the preparation of human plasma fractions.
Oxygen transfer in fermentation systems—I. Use of gluconic acid fermentation for determination of instantaneous oxygen transfer rates
Authors: Tsao George T. , Kempe Lloyd L.
Published: May 2005

Oxygen transfer has been studied in the Pseudomonas ovalis fermentation that quantitatively converts glucose into gluconic acid. The rate of oxygen uptake by this system was correlated with aeration rates and agitator speeds over wide ranges of these variables, by the introduction of a liquid expansion term. The technique described provides a biological method for studying oxygen transfer in the P. ovalis system; its general principles can be applied to other fermentations.
Rheological examination of some fermentation broths
Authors: Deindoerfer F. H. , West John M.
Published: May 2005

The broths of four important industrial fermentations, namely nystatin, penicillin, and streptomycin fermentations, and a fermentation used for steroid hydroxylation, were examined rheologically. Considerable variation in rheological properties was demonstrated among these fermentations as well as throughout the course of the nystatin and streptomycin fermentations. These latter fermentations, employing Streptomyces strains, were mostly Newtonian in behaviour. Departures from this behaviour twice in the streptomycin fermentation resulted in plastic characteristics. The other two fermentations employing moulds were found to be markedly non‐Newtonian, either plastic or pseudo‐plastic in their behaviour.

Rheological properties of most fermentation broths change appreciably during the course of fermentation. These properties influence the nature of the fluid regime in fermentors and, as a consequence, are important factors when considering mass and heat transfer. Therefore, a knowledge of the rheological behaviour of fermentation broths is an important prerequisite for an intelligent understanding of these transport processes. This paper briefly reviews some of the mathematical flow models used to characterize fluids and reports the rheological examination and analysis of several industrially important fermentation broths containing filamentous micro‐organisms.
Population dynamics in suspension cultures of an animal cell strain
Authors: Merchant Donald J. , Kuchler Robertj. , Munyon William H.
Published: May 2005

A composite of several studies by the authors is presented in an attempt to illustrate the use of the suspension culture method to analyze population dynamics of an animal cell strain. On the basis of these studies the nature of the lag and plateau phases is discussed. More extensive discussions of the various studies in relation to the work of others appear elsewhere.
Studies and observations on the growth of mammalian cells in agitated fluid medium
Authors: Cherry William R. , Hull Robert N.
Published: May 2005

Fourteen mammalian cell strains were studied in the ‘stirrer culture’. Fair to excellent growth was obtained with twelve of these strains while two strains failed to show evidence of proliferation. Growth curves, maximal population densities, and recovery following subculture of various cell strains, cultivated in this system, were described. Factors effecting the growth of cells under these conditions were outlined. Growth of cells in methods other than the ‘stirrer culture’ were reported. The practical importance of fluid suspension culture of mammalian cells, the potentialities and the problems involved in scaling such cultures to industrial size were discussed.
Mass algal culture in space operations
Authors: Gafford Robert D. , Richardson D. E.
Published: May 2005

A system is described which uses photosynthesis to regenerate oxygen from exhaled carbon dioxide in sealed cabins in the absence of gravity. Design considerations as to choice of algal strain, illumination, nutrients and gas‐exchange methods are discussed. Details are given of such an apparatus, of laboratory size, used to evaluate selected semipermeable gas‐exchange membranes. Data is presented and extrapolated to estimate size and weight of a possible manned space system.
Pilot plant studies on parboiling of rice—I. Soaking and gelatinization
Authors: Mazumder A. C. , Bose A. N. , Ganguli N. C. , Guha B. C.
Published: May 2005

The conventional parboiling process used in the Orient consists of steeping paddy in cold or lukewarm water for 48–72 hours, steaming for 15–25 min and then drying in the sun. This process yields rice of a poor quality, and an attempt has been made to improve it by devising both batch and continuous processes in which the soaking and steaming are carried out in the same equipment. The processes developed give a larger throughput and also a product of a quality superior in appearance, flavour and thiamine content to that produced by the usual parboiling method.
A new press for the disruption of micro‐organisms and other cells
Authors: Edebo Lars
Published: May 2005

A new press (the X‐press) has been developed for the disintegration of cells in the frozen state (mostly at −25°C). By forcing the frozen cells contained in a cylinder through a hole much smaller than the diameter of the cylinder but much larger than the size of the cells, a satisfactory disintegration can be obtained.

By forcing the cells through the hole repeatedly rather than once, a higher degree of disintegration can be achieved. By making the receiver identical to the charge chamber, repeated operations are possible without uncoupling the press.

The disintegrated material is very easily recovered—it is simply taken out of the press in the form of a cylinder containing the frozen, disintegrated material which is then easily homogenized.

This principle has been found satisfactory for the disintegration of a large number of cells, viz. bacteria, yeasts, moulds, plant and animal cells and, with regard to biochemical questions, it has been found to be superior to existing methods which do not treat the bacteria in the frozen state. The mechanism of the disintegrating action is discussed.
Control of stock culture preservation and inoculum build‐up in bacterial fermentation
Authors: Lincoln Ralph E.
Published: May 2005

Control of product quality throughout repeated fermentations depends upon maintenance of genetic uniformity from the time of strain selection until the product is harvested. Genetic control, therefore, must be maintained for stock cultures, and during inoculum preparation and growth to produce the product. Theoretical and applied aspects of a procedure that will accomplish this control are discussed. A specific procedure adaptable to situations in which a ‘seed’ is repeatedly increased to produce a larger quantity of a final material is described. The procedure was tested by comparing the product of three bacterial species grown by a standard or usual vs. recommended or experimental procedure comparing product quality and uniformity. Use of the recommended procedure resulted in the high production of a uniform product based on the maintenance of the colony type of Bacillus anthracis, colony colour and type of Serratia marcescens, and uniformity and amount of toxin produced by Clostridium botulinum type A.
Rapid determination of 17‐α‐oxy‐11‐desoxy‐corticosterone in the course of biological fermentative oxidations
Authors: Mizsei Antal , Szabó Antal
Published: May 2005

A rapid analytical method has been developed to follow the biological oxidation of 17‐α‐oxy‐11‐desoxy‐corticosterone (Reichstein compound S) to hydrocortisone. Paper chromatography is too slow to follow the progress of a preparative microbiological steroid transformation. However, 17‐α‐oxy‐11‐desoxy‐corticosterone can be separated in a sufficiently pure state for photometric assay by a simple extraction from fermentation broths containing several steroids. This extraction, coupled with the formation of a sulphuric acid chromogen, permits estimation of the steroid in fermentation liquors. The steady decrease of the 17‐α‐oxy‐11‐desoxy‐compound thus estimated proved to be a true indication of the progress of the oxidation process, allowing it to be stopped at the most favourable time.
Production of polysaccharide with Xanthomonas campestris
Authors: Rogovin S. P. , Anderson R. F. , Cadmus M. C.
Published: May 2005

Industrially important polysaccharides are now primarily obtained from plant sources. One exception is the exocellular bacterial polysaccharide, dextran. A survey at the Northern Laboratory revealed that many other microbial polysaccharides could be synthesized by the action of micro‐organisms on starch‐derived saccharides. Previous publications from this laboratory describe the production of the microbial polymer, phosphomannan, synthesized by the yeast Hansenula holstii. This paper describes the production of another polysaccharide, synthesized by the bacterium Xanthomonas campestris NRRL B‐1459.

Fermentation of media containing 3 per cent dextrose, seeded with 5 per cent inoculum of X. campestris NRRL B‐1459 and cultured aerobically at 28°C, is complete in 96 h. A light tan polymer is recovered in yields of 50 per cent, based on commercial dextrose, from the viscous fermentation broth by precipitation with methanol in the presence of an electrolyte. The viscosities of aqueous re‐solutions containing 1 and 2 per cent of the polymer were 3,000 cP and 11,000 cP respectively.
Recovery of bacterial spores and vegetative cells with a miniature spray drier
Authors: Rhian Morris , Lynch Daniel C.
Published: May 2005

A laboratory spray drier with a gas flow of 2 to 3 ft3/min was used to dry suspensions containing spores of Bacillus anthracis or cells of Pasteurella tularensis. Dried material was collected in a 1/2‐in. diameter cyclone that retained about 97 per cent of the product from the drier. The particle size distributions of the powders varied with the nature of substances in the suspension to be dried; as much as 80 per cent of the mass in particles 5 μ or less in diameter was obtained only when egg yolk was added to the suspensions. Retention of viability was about 90 per cent for B. anthracis spores and these powders contained from 175 to 522 × 109 viable spores/gram. Retention of viability of P. tularensis cells was 0·6 per cent or greater only when the suspension contained a relatively high proportion of stabilizers. With sucrose‐skim milk‐thiourea stabilizer about 10 per cent recovery of viability was obtained when the proportion of stabilizer solids to other solids was 3 : 1 or 6 : 1. These powders contained 140 × 109 viable cells per gram and the mass median diameter was 6·0 μ. The properties of the powders suggest that spray dried vaccines may be prepared for use either in suspension or in aerosols.
Bacterial sulphide production from sulphate‐enriched spent distillery liquor—II
Authors: Basu S. K. , Ghose T. K.
Published: May 2005

Accumulation of volatile acids produced during anaerobic fermentation of distillery‐spent liquor decreased the activity of Desulphovibrio desulphuricans employed in previously communicated studies; this caused a decrease in the reduction of sulphates to sulphides. An enriched strain of Desulphovibrio rubentschikii made in a synthetic mineral medium (NH4Cl, 1·0 g; MgSO4·7H2O, 2·0 g; NaCl, 10·0 g; CaSO4, 1·0 g; calcium acetate, 1·0 g; K2HPO4, 0·5 g; Mohrs' salt, trace in 1 l.) using calcium acetate as the substrate and carbon from the tap‐water was gradually built up to a 3‐1. volume. The amount of hydrogen sulphide in this medium was found to be 225 mg/l. The fermentation was next carried out in a synthetic medium containing volatile acids from distillery‐spent liquor as the only substrate. A 3‐1. fermentation set up with diluted distillery‐spent liquor (300 ml or raw liquor in 3,000 ml of water), neutralized with NaOH to pH 7·2 and supplemented with calcium sulphate and 0·1 per cent urea, showed sulphide productions (calculated as milligrams of hydrogen sulphide per litre of raw distillery‐spent liquid) of 2,000, 4,000 and 6,000 with 0·1, 1·0 and 2·0 per cent calcium sulphate in the charge respectively. The volatile acid content, expressed as acetic acid, was 18,564 mg/litre of raw distillery‐spent liquor on an average throughout the study. The ratio of hydrogen sulphide produced per litre of raw distillery‐spent liquor to the amount of volatile acids developed expressed in milliequivalents per litre of raw liquor during fermentation increased gradually from 0·1367 to 0·5567 in the presence of 0·1 to 2·0 per cent of calcium sulphate in the charge.
Adsorption method for measuring the specific and average areas of cells
Authors: Borzani Walter
Published: May 2005

This paper presents a method for measuring the specific area (area/mass) of micro‐organisms and the average area of cells, based on the adsorption of dyes.
Neue apparatur zur Herstellung von Schüttelkulturen von Mikroorganismen
Authors: Meystre Ch. , Reusser P.
Published: May 2005

A simple apparatus for preparing shake cultures of microorganisms on a laboratory scale is described. Using a series of special shaking vessels, each of a capacity of 1–10 l., a total volume of 20–200 l. of culture can be produced in one run. The rate of aeration is similar to the one observed in shake flasks.
Continuous cultivation of micro‐organisms: A new approach and possibilities for its use
Authors: Slezák Josef , Sikyta Bohumil
Published: May 2005

When trying to turn a batch fermentation process into a continuous process, many important factors must be repected. A new approach is presented by means of which it is possible to reproduce in a continuous system those changes (both inside the cells and in the environment) which are functions of elapsed time (lag‐type changes, sudden changes occurring at a constant growth rate of the micro‐organisms, etc.). Special attention is paid to lag‐type changes. In the hitherto described apparatuses for continuous cultivation it was difficult to follow changes which are functions of time. The use of a multi‐stage apparatus is therefore suggested, and a method of cultivation, which through adjusting retention times in individual cultivation vessels allows a detailed study of such changes, is proposed. Basic equations concerning the growth of microorganisms in the described apparatus are derived and some examples of the possible practical use of the new approach are presented.
The disintegration of bacteria and other micro‐organisms by the M.S.E.‐Mullard Ultrasonic disintegrator
Authors: Hughes D. E.
Published: May 2005

Two commercially available ultrasonic instruments are described, in which micro‐organisms and other cells may be disintegrated.

Sound waves (20 kc/s) are generated in the cell suspension by means of titanium velocity transformers (probes) coupled to a magnetostriction transducer. One instrument operating at 500 W will disintegrate from 2 to 500 ml, the other operating at 50 W from 1 ml to 30 ml.

Yeast was used as a test organism but results on some other organisms are also given. Cell rupture is shown to be independent of sonically generated free radicals, but enzyme inactivation (alcohol dehydrogenase) is accelerated by free radicals. Increasing the viscosity, decreasing surface tension of the suspending medium, or the presence of CO2 decreases disintegration. The addition of solid nuclei such as powdered glass, as well as small air bubbles, increases disintegration.

This is consistent with disintegration being due to cavitation, but does not indicate the precise mechanism of cell rupture. Some effects of sonic disruption are compared with disruption by other methods.
Expression and regulation of pOb24 and lipoprotein lipase genes during adipose conversion
Authors: Dani C. , Amri E.‐Z. , Bertrand B. , Enerback S. , Bjursell G. , Grimaldi P. , Ailhaud G.
Published: May 2005

Lipoprotein lipase (LPL) and pOb24 mRNAs are known to be early markers of adipose cell differentiation. Comparative studies of the expression of pOb24 and LPL genes during adipose conversion of Ob1771 preadipocyte cells and in mouse adipose tissue have shown the following: (1) the expression of both genes takes place at confluence; this event can also be triggered by growth arrest of exponentially growing cells at the G1/S stage of the cell cycle; (2) In contrast to glycerol‐3°phosphate dehydrogenase mRNA, the emergence of pOb24 and lipoprotein lipase mRNAs requires neither growth hormone or tri‐iodothyronine as obligatory hormones nor insulin as a modulating hormone; (3) in mouse adipose tissue, pOb24 mRNA is present at a high level in stromal‐vascular cells and at a low level in mature adipocytes, and in contrast LPL mRNAs are preferentially expressed in mature adipocytes. Thus, these two genes do not appear to be regulated in a similar manner, as also shown by the differential inhibition of their expression by tumor necrosis factor (TNF) and transforming growth factor‐β (TGF‐β ).
Involvement of a highly polyvalent Glycan in the cell‐binding of the aggregation factor from the marine sponge Microciona prolifera
Authors: Misevic Gradimir N. , Burger Max M.
Published: May 2005

A proteoglycan‐like aggregation factor from the marine spongeMicrociona prolifera (MAF) mediates cell‐cell recognition via a cell‐binding and a self‐association domain. After repetitive and prolonged treatment of MAF with glycopeptide‐N‐glycosidase (PNGase) the specific binding of MAF to homotypic cells was decreased by 72%. Polyacrylamide gel electrophoresis and gel filtration analysis of such PNGase digests showed that: (1) the enzyme released a single glycan type of Mr = 6 × 1032 (G‐6) from MAF, (2) 1 mole of MAF contains at least 830 moles of N‐linked chains of G‐6 glycan. The correlation between the loss of the binding activity of MAF and the extent of the release of the repetitive G‐6 polysaccharide strongly suggests its involvement in MAF‐cell association via highly polyvalent interactions.
Differentiation of BC3H1 and primary skeletal muscle cells and the activity of their endogenous insulin‐degrading enzyme are inhibited by the same metalloendoprotease inhibitors
Authors: Kayalar Celik , Wong William T. , Hendrickson Lisa
Published: May 2005

Upon reduction of serum in their media, mouse BC3H1 muscle cells withdraw from the cell cycle and begin to differentiate. In differentiating cells, the induction of muscle‐specific genes is accompanied by a distinct morphological chance. However, differentiated BC3H1 cells do not fuse with each other; they remain mononucleated. Metalloendoprotease inhibitors selectively block the differentiation of BC3H1 cells while inhibitors of other protease types are ineffective. In these cells, the degradation of the internalized insulin is initiated by a 110 kDa, non‐lysosomal protease known as the insulin‐degrading enzyme. The same metalloendoprotease inhibitors that block BC3H1 differentiation also inhibit, with a similar specificity and potency, the in vitro and the in vivo degradation of insulin by the insulin‐degrading enzyme. When the serum in the medium is reduced, the activity of the insulin‐degrading enzyme in the cell cytoplasm increases rapidly. This increase precedes any detectable change in the differentiation state of these cells by about 12 hours. These results, together with very similar ones obtained with primary rat skeletal muscle cells, support our earlier proposal that the insulin‐degrading enzyme is the metalloendoprotease involved in the initiation of the morphological and biochemical differentiation of muscle cells in culture.
Characterization and partial purification of human epithelial transforming growth factor
Authors: Dunnington Damien J. , Scott Robert G. , Anzano Mario A. , Greig Russell
Published: May 2005

A polypeptide growth factor has been partially purified from medium conditioned by the human adrenocortical carcinoma cell line SW13. This factor, designated h‐TGFe, stimulates anchorage‐independent growth of the SW13 cells. Similar activity was observed in human milk, and in conditioned media from seven of 14 epithelial cell lines. The SW13‐derived activity is stable to low pH and 8M urea but labile to dithiothreitol and 2% sodium dodecyl sulfate. Human TGFe does not bind to heparin and fails to stimulate growth of endothelial cells in monolayer culture. The apparent molecular weight of h‐TGFe is 59k by size exclusion chromatography in the presence of 8M urea and the activity binds strongly to cation exchangers. The activity elutes at 15–30% acetonitrile from a C18 reversephase column and has been partially purified by using a four‐step chromatographic procedure. TGFe appears to be a novel growth factor produced by many epithelial cells and tissues.
Cellular senescence: A reflection of normal growth control, differentiation, or aging?
Authors: Peacocke Monica , Campisi Judith
Published: May 2005

Normal cells, with few exceptions, cannot proliferate indefinitely. Cell populations—in vivo and in culture—generally undergo only a limited number of doublings before proliferation invariably and irreversibly ceases. This process has been termed the finite lifespan phenotype or cellular senescence. There is long‐standing, albeit indirect, evidence that cellular senescence plays an important role in complex biological processes as diverse as normal growth control, differentiation, development, aging, and tumorigenesis. In recent years, it has been possible to develop a molecular framework for understanding some of the fundamental features of cellular senescence. This framework derives primarily from the physiology, genetics, and molecular biology of cells undergoing senescence in culture. Our understanding of senescence, and the mechanisms that control it, is still in its infancy. Nonetheless, recent data raise some intriguing possibilities regarding potential molecular bases for the links between senescence in culture and normal and abnormal growth control, differentiation, and aging.
GMP‐140: A receptor for neutrophils and monocytes on activated platelets and endothelium
Authors: McEver Rodger P.
Published: May 2005

GMP‐140 is a membrane glycoprotein located in secretory granules of platelets and endothelium. When these cells are activated by agonists such as thrombin, GMP‐140 is rapidly translocated to the plasma membrane. GMP‐140, along with ELAM‐1 and the peripheral lymph node homing receptor, defines the selectin family of structurally related molecules that regulate interactions of leukocytes with the blood vessel wall. Each of these molecules contains an N‐terminal lectin‐like domain, followed by an EGF‐like region, a series of consensus repeats related to those in complement‐binding proteins, a transmembrane domain, and a short cytoplasmic tail. The genomic structures of the selectins suggest that they arose by duplication and modification of exons encoding specific structural domains. GMP‐140 is a receptor for neutrophils and monocytes when it is expressed on activated platelets and endothelium. This property facilitates rapid adhesion of leukocytes to endothelium at regions of tissue injury as well as platelet‐leukocyte interactions at sites of inflammation and hemorrhage. Like other leukocyte adhesion molecules, GMP‐140 may also participate in pathologic inflammation, thrombosis, and tumor metastasis. Confirmation of such pathologic roles may lead to design of new drugs that block adhesive receptor function in human disease.
The specific protein phosphatase inhibitor okadaic acid differentially modulates insulin action
Authors: Hess Susan L. , Suchin Craig R. , Saltiel Alan R.
Published: May 2005

The pleiotropic nature of insulin action suggests diverse mechanisms of signal transduction for the hormone. The specific protein phosphatase inhibitor, okadaic acid, is utilized to differentiate metabolic pathways that may be regulated by phosphorylation or dephosphorylation of key enzymes. In H‐35 hepatoma cells, okadaic acid inhibits insulin‐stimulated glycogen synthesis with an IC50 of 400 nM. In contrast, activation of lipogenesis by insulin is inhibited with an IC50 of 50 nM okadaic acid. The toxin also inhibits stimulation of lipogenesis in these cells by the insulin‐sensitive inositol glycan enzyme modulator. In isolated rat adipocytes, insulin‐stimulated lipogenesis is also inhibited by okadaic acid with an IC50 of approximately 1,700 nM. The antilipolytic effect of insulin in these cells is more sensitive to okadaic acid, exhibiting an IC50 of 150 nM. Maximal activation of lipogenesis by insulin is dramatically reduced by okadaic acid with no effect on the concentration required for half‐maximal activation, whereas the sensitivity of insulin‐induced antilipolysis is attenuated by okadaic acid, with no apparent reduction in the maximal effect of the hormone. Taken together, these data suggest that specific phosphatases may be differentially involved in some of the metabolic pathways regulated by insulin.
Neutral metalloendopeptidase associated with the smooth muscle cells of pregnant rat uterus
Authors: Ottlecz Anna , Walker Susan , Conrad Matt , Starcher Barry
Published: May 2005

The pregnant rat uterus contains a membrane‐bound metalloendopeptidase that is biochemically and immunologically similar to kidney enkephalinase (E.C.3.4.24.11). The uterus enzyme readily cleaved specific neutral endopeptidase substrates and oxytocin as well as the synthetic elastase substrate, Suc(Ala)3‐pNA, yet did not digest native elastin. Using specific inhibitors, the uterus endopeptidase was identified as a metallopeptidase and not a serine protease, having an absolute requirement for zinc and perhaps calcium for maximal activity. The uterus endopeptidase cross‐reacted with polyclonal antiserum to kidney microvillar endopeptidase and a monoclonal antibody to common acute lymphocytic leukemia antigen. Immunohistochemical localization of the enzyme in a 17 day pregnant uterus indicated that the enzyme was localized on the smooth muscle bundles of the myometrium and the endometrial epithelium. Total enzyme activity was 25 times higher in the late‐term pregnant uterus (17th day of pregnancy) than in the nonpregnant uterus. Enzyme levels dropped rapidly prior to parturition and within 4 days after delivery the enzyme activity had returned to control levels. Inhibition of NEP in uterine strips with phosphoramidon resulted in a marked potentiation of oxytocin‐induced contractions. Our results suggest that the uterine endopeptidase may have an important role in regulating uterine smooth muscle cell contraction during the latter stages of pregnancy through its action on oxytocin and perhaps other biologically active peptides.
Na+‐dependent, active nucleoside transport in S49 mouse lymphoma cells and loss in AE‐1 mutant deficient in facilitated nucleoside transport
Authors: Plagemann Peter G. W.
Published: May 2005

S49 murine lymphoma cells were examined for expression of various nucleoside transport systems using a non‐metabolized nucleoside, formycin B, as substrate. Nitrobenzylthioinosine (NBTI)‐sensitive, facilitated transport was the primary nucleoside transport system of the cells. The cells also expressed very low levels of NBTI‐resistant, facilitated nucleoside transport as well as of Na+‐dependent, concentrative formycin B transport. Concentrative transport was specific for uridine and purine nucleosides, just as the concentrative nucleoside transporters of other mouse and rat cells. A nucleoside transport mutant of S49 cells, AE‐1, lacked both the NBTI‐sensitive, facilitated and Na+‐dependent, concentrative formycin B transport activity, but Na+‐dependent, concentrative transport of α‐aminoisobutyrate was not affected.
A new perspective on ornithine decarboxylase regulation: Prevention of polyamine toxicity is the overriding theme
Authors: Morris David R.
Published: May 2005

The polyamines are essential cellular components for growth. Control of a key regulated enzyme of polyamine biosynthesis, ornithine decarboxylase (ODC), as a function of growth, is an area of intense interest. A unique regulatory property of ODC is the short half‐life of the protein, which has been suggested to be an important factor in rapid activation of polyamine biosynthesis after cells are mitogenically stimulated. In this paper, it is argued that the biological significance of the short half‐life of ODC is unrelated to the rate of its induction to a new steady state by growth factors, which is in fact limited by the relatively long half‐life of the ODC mRNA. Instead, I suggest that the rapid turnover of ODC protein becomes of significance when cells cease growth and expeditious downregulation of the enzyme is important in preventing polyamine overproduction, which would result in cytotoxicity in the arrested cells. Although mitogenic activation of ODC expression has been studied extensively, there is very little known about the mechanisms controlling downregulation of polyamine biosynthesis during the arrest of animal cell growth. These considerations suggest that this would be a fertile area of future inquiry.
Mutational analysis of leucine 47 in human epidermal growth factor
Authors: Matsunami Risë K. , Yette Margaret L. , Stevens Audrey , Niyogi Salil K.
Published: May 2005

Seven site‐specific mutants (including changes to other hydrophobic, charged, and heterocyclic amino acids) of leucine 47 of human epidermal growth factor (EGF) were generated by protein engineering and characterized for their activity in three assays: radioreceptor competition binding in membrane fractions, the stimulation of the EGF receptor's tyrosine kinase activity, and the stimulation of thymidine uptake in tissue culture cells. K½ (concentration required for half maximum response) values for each of the mutants are reported in the three assays. The results show that the native leucine residue is quite important for EGF activity. Substitutions are tolerated to different degrees, depending upon hydrophobicity and size of the side chain. Substitution with ionic residues led to the most drastic reduction in activity. One‐dimensional nuclear magnetic resonance spectroscopy, at physiological pH, of several of the mutants did not detect any major structural perturbations which would account for the loss of activity. The results suggest that the side chain of leucine 47, because of its charge neutrality, size, and hydrophobicity, is highly important, although not absolutely essential for the interaction of EGF with its receptor. A striking finding was the lower (compared with wild type) Vmax values of the mutants in the tyrosine kinase reaction, but these low Vmax mutants, in cell culture experiments, were able to stimulate at high concentrations a growth response equivalent to wild type EGF.
PCR analysis of dystrophin gene mutation and expression
Authors: Chamberlain Jeffrey S. , Farwell Nancy J. , Chamberlain Joel R. , Cox Gregory A. , Caskey C. Thomas
Published: May 2005

Duchenne muscular dystrophy (DMD) is caused by mutations that impair normal production of dystrophin in muscle and brain tissues. The dystrophin gene is expressed at extremely low levels in both humans and mice, which makes analysis of the 14kb mRNA a difficult task. In addition, 30% of all cases of DMD (and the genetic lesion in all three known mdx mouse models for DMD) are thought to arise from single base mutations, yet methods are not available to routinely identify and analyze these mutations and their effects on disease progression. We have been using the polymerase chain reaction (PCR) to analyze the expression of the murine dystrophin gene. A simple assay is described that distinguishes the murine dystrophin transcripts expressed from either the muscle or brain promoter. In addition, amplification of overlapping segments from the 5′ end of the murine transcript has enabled the identification of DNA sequence variations between wild‐type and mdx mice. These results demonstrate that the mutation in the original strain of mdx mice is distinct from those in two newer mdx isolates and that three independently isolated mdx mutants are available for study of DMD.
Vascular permeability factor: A unique regulator of blood vessel function
Authors: Connolly Daniel T.
Published: May 2005

Vascular permeability factor (VPF), also known as vascular endothelial growth factor (VEGF), is a potent polypeptide regulator of blood vessel function. VPF promotes an array of responses in endothelium, including hyperpermeability, endothelial cell growth, angiogenesis, and enhanced glucose transport. VPF regulates the expression of tissue factor and the glucose transporter. All of the endothelial cell responses to VPF are evidently mediated by high affinity cell surface receptors. Thus, endothelial cells have a unique and specific spectrum of responses to VPF. Since each of the responses of endothelial cells to VPF are also elicited by agonists, such as bFGF, TNF, histamine and others, it remains a major challenge to determine how post‐receptor signalling pathways maintain both specificity and redundancy in cellular responses to various agonists.
Effect of phospholipases and proteases on the [3H]N6‐(R)‐phenylisopropyladenosine ([3H]R‐PIA) binding to A1 adenosine receptors from pig cerebral cortex
Authors: Casadó Vicent , Mallol Josefa , Lluis Carmen , Canela Enric I. , Franco Rafael
Published: May 2005

The effect of phospholipases and proteases on the membrane‐bound and solubilized A1 adenosine receptor has been studied. Phospholipids modulate the [3H]N6‐(R)‐phenylisopropyladenosine binding to A1 adenosine receptors in crude membranes and in soluble preparations, because changes in the phospholipid environment decrease both the binding capacity and the affinity for the ligand. It has become clear that (1) there is co‐solubilization of receptor and phospholipids; (2) the phospholipid requirements are different for the coupled and the uncoupled receptor; (3) a net charge in the polar head produced by phospholipase D prevents the agonist binding to the receptor‐G protein complex; alternatively, when the whole polar head is removed by phospholipase C the uncoupled receptor is altered; and (4) the protease action upon the receptor suggests that receptor coupled to G protein is more protected by the membrane than the uncoupled receptor. In kinetic experiments performed on membranes it was demonstrated that phospholipase C and trypsin increased the Kd value of the high‐affinity state by modifying both k1 and k−1. In contrast they only modified the dissociation constant of the low‐affinity state. In conclusion it should be noted that phospholipids play a key role for the binding of R‐PIA to A1 adenosine receptor. Also, a different disposition within the membrane of the coupled and uncoupled receptor is encountered.
Regulation of transcription‐factor activity during growth and differentiation: Involvement of the nuclear matrix in concentration and localization of promoter binding proteins
Authors: Stein Gary S. , Lian Jane B. , Dworetzky Steven I. , Owen Thomas A. , Bortell Rita , Bidwell Joseph P. , van Wijnen Andre J.
Published: May 2005

Several lines of evidence are presented which support involvement of the nuclear matrix in regulating the transcription of two genes, histone and osteocalcin, that are reciprocally expressed during development of the osteoblast phenotype. In the 5′ regulatory region of an H4 histone gene, which is expressed in proliferating osteoblasts early during the developmental/differentiation sequence, a dual role is proposed for the nuclear matrix binding domain designated NMP‐1 (−589 to −730 upstream from the transcription start site). In addition to functioning as a nuclear matrix attachment site, the sequences contribute to the upregulation of histone gene transcription, potentially facilitated by concentration and localization of an 84kD ATF DNA binding protein. A homologous nuclear matrix binding domain was identified in the promoter of the osteocalcin gene, which is expressed in mature osteoblasts in an extracellular matrix undergoing mineralization. The NMP binding domain in the osteocalcin gene promoter resides contiguous to the vitamin D responsive element. Together with gene and transcription factor localization, a model is proposed whereby nuclear matrix‐associated structural constraints on conformation of the osteocalcin gene promoter facilitates vitamin D responsiveness mediated by cooperativity at multiple regulatory elements.
Insulin receptor signaling through non‐tyrosine kinase pathways: Evidence from anti‐receptor antibodies and insulin receptor mutants
Authors: Sung Chin K.
Published: May 2005

Although there is general agreement that insulin receptor tyrosine kinase activity mediates many of the actions of insulin, two types of studies suggest that non‐tyrosine kinase dependent pathways may also exist. First, both monoclonal and polyclonal antibodies to the receptor have been shown to mediate many of insulin's actions with little or no stimulation of receptor kinase. Second, insulin receptor mutants, with reduced or no tyrosine kinase activity, have been shown to mediate several actions of insulin. Non‐tyrosine kinase pathways that could signal insulin effects through the insulin receptor include non‐covalent activation of G proteins, phospholipase Cs, or docking proteins such as IRS‐1. Further studies on the chemical structures of phospholipids and their hydrolysis products involved in insulin action will be required to sort out the underlying mechanisms of insulin action via non‐tyrosine kinase dependent pathways.
Alterations in glucose transporter expression and function in diabetes: Mechanisms for insulin resistance
Authors: Kahn Barbara B.
Published: May 2005

Insulin resistance is a major pathologic feature of human obesity and diabetes. Understanding the fundamental mechanisms underlying this insulin resistance has been advanced by the recent cloning of the genes encoding a family of facilitated diffusion glucose transporters which are expressed in characteristic patterns in mammalian tissues. Two of these transporters, GLUT1 and GLUT4, are present in muscle and adipose cells, tissues in which glucose transport is markedly stimulated by insulin. To understand the mechanisms underlying in vivo insulin resistance, regulation of these transporters is being investigated. Studies reveals divergent changes in the expression of GLUT1 and GLUT4 in a single cell type as well as tissue specific regulation. Importantly, alterations in glucose transport in rodent models of diabetes and in human obesity and diabetes cannot be entirely explained by changes in glucose transporter expression. This suggests that defects in glucose transporter function such as impaired translocation, fusion with the plasma membrane, or activation probably contribute importantly to in vivo insulin resistance.