bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphomechanics of the humero‐ulnar joint: II. Concave incongruity determines the distribution of load and subchondral mineralization
Authors: Eckstein Felix , Merz Beat , Müller‐Gerbl Magdalena , Holzknecht Nikolaus , Pleier Markus , Putz Reinhard
Published: February 2005

Background: A deeper joint socket (concave incongruity) is found at most angles of flexion of the humero‐ulnar joint and maintained over a wide range of physiological loading. It is, however, unclear how far this incongruity affects the distribution of load and subchondral mineralization of this joint as compared with a congruous configuration.

Methods: Two nonlinear, axisymmetrical finite element models with two cartilage layers were constructed, one congruous and one incongruous, with a joint space of realistic magnitude. The distribution of subchondral mineralization was determined by computed tomography osteoabsorptiometry in the same six specimens that were investigated in the first part of the study, and compared with the biomechanical data obtained there and the predictions of the models.

Results: In the congruous case, the center of the socket is highly loaded, whereas the periphery does not experience mechanical stimulation. A central bone density maximum is predicted. With concave incongruity the position of the contact areas shifts from the joint margin towards the center as the load increases, and the peak stresses are considerably lower. A bicentric ventro‐dorsal distribution pattern of subchondral mineralization is predicted, and this is actually found in the six specimens.

Conclusions: Concave incongruity is shown to determine load transmission and subchondral mineralization of the humero‐ulnar joint. It is suggested that this shape leads to a more even distribution of stress, provides intermittent stimulation of the cartilaginous tissue, and has beneficial effects on the metabolism, nutrition, and lubrication of the articular cartilage during cyclic loading. © 1995 Wiley‐Liss, Inc.
Rainfall modeling for integrating radar information into hydrological model
Authors: Morin Efrat , Goodrich David C. , Maddox Robert A. , Gao Xiaogang , Gupta Hoshin V. , Sorooshian Soroosh
Published: February 2005

A spatial rainfall model was applied to radar data of air mass thunderstorms to yield a rainstorm representation as a set of convective rain cells. The modeled rainfall was used as input into hydrological model, instead of the standard radar‐grid data. This approach allows a comprehensive linkage between runoff responses and rainfall structures. Copyright © 2005 Royal Meteorological Society
Improving hexane removal by enhancing fungal development in a microbial consortium biofilter
Authors: Arriaga Sonia , Revah Sergio
Published: February 2005

The removal of hydrophobic pollutants in biofilters is often limited by gas liquid mass transfer to the biotic aqueous phase where biodegradation occurs. It has been proposed that the use of fungi may improve their removal efficiency. To confirm this, the uptake of hexane vapors was investigated in 2.6‐L perlite‐packed biofilters, inoculated with a mixed culture containing bacteria and fungi, which were operated under neutral or acid conditions. For a hexane inlet load of around 140 g.m−3.h−1, elimination capacities (EC) of 60 and 100 g.m−3.h−1 were respectively reached with the neutral and acid systems. Increasing the inlet hexane load showed that the maximum EC obtained in the acid biofilter (150 g.m−3.h−1) was twice greater than in the neutral filter. The addition of bacterial inhibitors had no significant effect on EC in the acid system. The biomass in the acid biofilter was 187 mg.g−1dry perlite without an important pressure drop (26.5 mm of water.m−1reactor). The greater efficiency obtained with the acid biofilter can be related to the hydrophobic aerial hyphae which are in direct contact with the gas and can absorb the hydrophobic compounds faster than the flat bacterial biofilms. Two fungi were isolated from the acid biofilter and were identified as Cladosporium and Fusarium spp. Hexane EC of 40 g.m−3.h−1 for Cladosporium sp. and 50 g.m−3.h−1 for Fusarium sp. were obtained in short time experiments in small biofilters (0.230 L). A biomass content around 30 mg.g−1dry perlite showed the potential for hexane biofiltration of the strains. © 2005 Wiley Periodicals, Inc.
Amino acid content of recombinant proteins influences the metabolic burden response
Authors: Bonomo Jeanne , Gill Ryan T.
Published: February 2005

Recombinant protein production in Escherichia coli often results in a dramatic cellular stress response best characterized by a decrease in overall cell fitness. We determined that the primary sequence (the amino acid sequence) of the recombinant protein alone plays an important role in mitigating this response. To do so, we created two polypeptides, modeled after the 39‐40 amino acid Defensin class of proteins, which contained exclusively the five least (PepAA; His, Trp, Tyr, Phe, Met), or most (PepCO: Ala, Glu, Gln, Asp, Asn) abundant amino acids in E. coli. We determined that overexpression of PepAA resulted in a drastic decrease in growth rate compared to overexpression of PepCO, our model Defensin protein MGD‐1, or the 26 amino acid polypeptide contained within the pET‐3d vector backbone. We further determined, using Affymetrix E. coli gene chips, that differences among the whole‐genome transcriptional responses of these model systems were best characterized by altered expression of genes whose products are involved in translation, transport, or metabolic functions as opposed to stress response genes. Based on these results, we confirmed that translation efficiency was significantly reduced in cells overexpressing PepAA compared with the other model polypeptides evaluated. © 2005 Wiley Periodicals, Inc.
Adding tuples to Java: a study in lightweight data structures
Authors: van Reeuwijk C. , Sips H. J.
Published: February 2005

Java classes are very flexible, but this comes at a price. The main cost is that every class instance must be dynamically allocated. Also, their access by reference introduces pointer de‐references and complicates program analysis. These costs are particularly burdensome for small, ubiquitous data structures such as coordinates and state vectors. For such data structures a lightweight representation is desirable, allowing such data to be handled directly, similar to primitive types. A number of proposals introduce restricted or mutated variants of standard Java classes that could serve as lightweight representation, but the impact of these proposals has never been studied. Since we have implemented a Java compiler with lightweight data structures we are in a good position to do this evaluation. Our lightweight data structures are tuples. As we will show, using tuples can result in significant performance gains: for a number of existing benchmark programs we gain more than 50% in performance relative to our own compiler, and more than 20% relative to Sun's Hotspot 1.4 compiler. We expect similar performance gains for other implementations of lightweight data structures. With respect to the expressiveness of Java, lightweight variants of standard Java classes have little impact. In contrast, tuples add a different language construct that, as we will show, can lead to substantially more concise program code. Copyright © 2005 John Wiley & Sons, Ltd.
UMM: an operational memory model specification framework with integrated model checking capability
Authors: Yang Yue , Gopalakrishnan Ganesh , Lindstrom Gary
Published: February 2005

Given the complicated nature of modern shared memory systems, it is vital to have a systematic approach to specifying and analyzing memory consistency requirements. In this paper, we present the UMM specification framework, which integrates two key features to support memory model verification: (i) it employs a simple and generic memory abstraction that can capture a large collection of memory models as guarded commands with a uniform notation, and (ii) it provides built‐in model checking capability to enable formal reasoning about thread behaviors. Using this framework, memory models can be specified in a parameterized style—designers can simply redefine a few bypassing rules and visibility ordering rules to obtain an executable specification of another memory model. We formalize several classical memory models, including Sequential Consistency, Coherence, and PRAM, to illustrate the general techniques of applying this framework. We then provide an alternative specification of the Java memory model, based on a proposal from Manson and Pugh, and demonstrate how to analyze Java thread semantics using model checking. We also compare our operational specification style with axiomatic specification styles and explore a mechanism that converts a memory model definition from one style to the other. Copyright © 2005 John Wiley & Sons, Ltd.
Jeeg: temporal constraints for the synchronization of concurrent objects
Authors: Milicia Giuseppe , Sassone Vladimiro
Published: February 2005

We introduce Jeeg, a dialect of Java based on a declarative replacement of the synchronization mechanisms of Java that results in a complete decoupling of the ‘business’ and the ‘synchronization’ code of classes. Synchronization constraints in Jeeg are expressed in a linear temporal logic, which allows one to effectively limit the occurrence of the inheritance anomaly that commonly affects concurrent object‐oriented languages. Jeeg is inspired by the current trend in aspect‐oriented languages. In a Jeeg program the sequential and concurrent aspects of object behaviors are decoupled: specified separately by the programmer, these are then weaved together by the Jeeg compiler. Copyright © 2005 John Wiley & Sons, Ltd.
Immutability specification and its applications
Authors: Pechtchanski Igor , Sarkar Vivek
Published: February 2005

A location is said to be immutable if its value and the values of selected locations reachable from it are guaranteed to remain unchanged during a specified time interval. We introduce a framework for immutability specification, and discuss its application to code optimization. Compared with a final declaration, an immutability assertion in our framework can express a richer set of immutability properties along three dimensions—lifetime, reachability and context. We present a framework for processing and verifying immutability annotations in Java, as well as extending optimizations so as to exploit immutability information. Preliminary experimental results show that a significant number (61%) of read accesses could potentially be classified as immutable in our framework. Further, use of immutability information yields substantial reductions (33–99%) in the number of dynamic read accesses, and also measurable speedups in the range of 5–10% for certain benchmark programs. Copyright © 2005 John Wiley & Sons, Ltd.
No acute effect of nateglinide on postprandial lipid and lipoprotein responses in subjects at risk for type 2 diabetes
Authors: Johanson E. H. , Jansson P.‐A. , Gustafson B. , Sandqvist M. , Taskinen M.‐R. , Smith U. , Axelsen M.
Published: February 2005

Background

To study the acute effect of nateglinide, an insulinotropic agent, on the postprandial triglyceride and lipoprotein responses in subjects at risk for type 2 diabetes.

Methods

Six women and 10 men, with at least one first‐degree relative with type 2 diabetes were included (Age: 48 ± 7 years, BMI: 27.5 ± 2.8 kg m−2, P‐triglycerides: 1.3 ± 0.4 mmol L−1, P‐cholesterol: 5.4 ± 0.6 mmol L−1, B‐glucose: 4.6 ± 0.3 mmol L−1). They each had two 8‐h meal tolerance tests with either nateglinide or placebo given 10 min prior to the meals in randomized order. Lipoprotein fractions were separated by density gradient ultracentrifugation. First‐phase insulin secretion was assessed by an intravenous glucose tolerance test (300 mg kg−1 body weight) and insulin sensitivity by a hyperinsulinaemic euglycaemic clamp (40 mU m−2 min−1).

Results

The 1‐h insulin levels during the meal tolerance test were significantly higher with nateglinide (577 ± 81 vs 376 ± 58 pmol L−1, p < 0.001), as well as the response during the first two hours (IAUC: 41 243 ± 5844 vs 29 956 ± 4662 pmol L−1 min, p < 0.01). Accordingly, nateglinide lowered the 8‐h postprandial glucose response by around 60% compared to placebo (p < 0.001). In contrast, no significant lowering was seen in the excursion of postprandial triglycerides in total plasma or lipoprotein fractions. Consistently, the concentration of exogenous (apoB‐48) and endogenous (apoB‐100) lipoproteins was not reduced by nateglinide.

Conclusions

Acute administration of nateglinide reduces, as expected, the postprandial glucose concentration, but no reduction in triglyceride or lipoprotein responses are seen in subjects at risk for type 2 diabetes. Copyright © 2005 John Wiley & Sons, Ltd.
TGF‐β‐treated microglia induce oligodendrocyte precursor cell chemotaxis through the HGF‐c‐Met pathway
Authors: Lalive Patrice H. , Paglinawan Rey , Biollaz Gregoire , Kappos Elisabeth A. , Leone Dino P. , Malipiero Ursula , Relvas Joao B. , Moransard Martijn , Suter Tobias , Fontana Adriano
Published: February 2005

In acute experimental autoimmune encephalomyelitis (EAE), demyelination is induced by myelin‐specific CD4+ T lymphocytes and myelin‐specific antibodies. Recovery from the disease is initiated by cytokines which suppress T cell expansion and the production of myelin‐toxic molecules by macrophages. Th2/3 cell‐derived signals may also be involved in central nervous system (CNS) repair. Remyelination is thought to be initiated by the recruitment and differentiation of oligodendrocyte precursor cells (OPC) in demyelinated CNS lesions. Here, we report that unlike Th1 cytokines (TNF‐α, IFN‐γ), the Th2/3 cytokine TGF‐β induces primary microglia from C57BL/6 mice to secrete a chemotactic factor for primary OPC. We identified this factor to be the hepatocyte growth factor (HGF). Our studies show that TGF‐β‐1‐2‐3 as well as IFN‐β induce HGF secretion by microglia and that antibodies to the HGF receptor c‐Met abrogate OPC chemotaxis induced by TGF‐β2‐treated microglia. In addition we show spinal cord lesions in EAE induced in SJL/J mice to contain both OPC and HGF producing macrophages in the recovery phase, but not in the acute stage of disease. Taken these findings, TGF‐β may play a pivotal role in remyelination by inducing microglia to release HGF which is both a chemotactic and differentiation factor for OPC.
Serum amyloid A activates NF‐κB and proinflammatory gene expression in human and murine intestinal epithelial cells
Authors: Jijon Humberto B. , Madsen Karen L. , Walker John W. , Allard Brigitte , Jobin Christian
Published: February 2005

Serum amyloid A (SAA) is an acute‐phase protein whose levels positively correlate with disease activity in inflammatory bowel diseases. In this study we investigated the impact of SAA on NF‐κB signaling and proinflammatory gene expression in intestinal epithelial cells (IEC). Human HT‐29 and Caco‐2 monolayers were stimulated with recombinant SAA and NF‐κB activation/NF‐κB‐dependent gene expression measured. Adenoviral dominant negative mutants IκB‐α (Ad5IκBAA) were utilized to determine the contribution of NF‐κB signaling pathway to SAA‐dependent gene expression. Intestinal explant and primary IEC derived from κB‐EGFP transgenic mice were exposed to SAA and NF‐κB‐dependent enhanced green fluorescent protein (EGFP) fluorescence measured. SAA induced IκB‐α degradation, RelA serine 536 (S536) phosphorylation, NF‐κB transcriptional activity, RelA recruitment to the IL‐8 gene promoter and endogenous gene expression (IL‐8, COX‐2) in HT‐29 cells. Further, Ad5IκBAA abrogated SAA‐induced RelA nuclear translocation, NF‐κB transcriptional activity and IL‐8 gene expression. SAA‐dependent IL‐8 gene expression required activation of the MAPK ERK, p38 and JNK in HT‐29 cells. Finally, SAA induced EGFP expression in intestinal explants isolated from κB‐EGFP transgenic mice and enhanced RelA and IκBα phosphorylation in primary IEC. This indicates that SAA potentially participate in the inflammatory process by virtue of its ability to activate proinflammatory signaling in IEC.
Ex vivo expansion of human cytomegalovirus‐specific cytotoxic T cells by recombinant polyepitope: implications for HCMV immunotherapy
Authors: Rist Michael , Cooper Leanne , Elkington Rebecca , Walker Susan , Fazou Chrysa , Tellam Judy , Crough Tania , Khanna Rajiv
Published: February 2005

Stem cell transplantation (SCT) remains the most effective curative therapy for the majority of hematopoietic malignancies. Unfortunately, SCT is limited by its toxicity and infectious complications that result from profound immunosuppression. In particular, acquisition of exogenous or reactivation of endogenous human cytomegalovirus (HCMV) is common after SCT. More recently, reconstitution of host immunity through augmentation of anti‐HCMV T cell responses has been proposed as an exciting candidate therapy to avoid the requirement for antiviral drug use. Here we have developed a novel antigen presentation system based on a replication‐deficient adenovirus that encodes multiple HLA class I‐restricted epitopes from eight different antigens of HCMV as a polyepitope (referred to as AdCMVpoly). Ex vivo stimulation of peripheral blood mononuclear cells with AdCMVpoly consistently showed rapid stimulation and expansion of multiple epitope‐specific T cells that recognized endogenously processed epitopes presented on virus‐infected cells. Interestingly, the AdCMVpoly expression system is capable of expanding antigen‐specific T cells even in the absence of CD4+ T cells. These studies show the effectiveness of a polyepitope antigen presentation system for reproducible expansion of antigen‐specific T cells from immunocompetent and immunocompromised settings.
Efficient homologous prime‐boost strategies for T cell vaccination based on virus‐like particles
Authors: Schwarz Katrin , Meijerink Edwin , Speiser Daniel E. , Tissot Alain C. , Cielens Indulis , Renhof Regina , Dishlers Andris , Pumpens Paul , Bachmann Martin F.
Published: February 2005

Induction of high frequencies of specific T cells by vaccination requires prime‐boost regimens. To reach optimal immune responses, it is necessary to use different vectors for priming and boosting as e.g. DNA vaccination followed by boosting with a recombinant viral vector. Here, we show that vaccines based on virus‐like particles (VLP) displaying peptide epitopes are equally effective to induce CTL responses if used in a homologous or heterologous prime‐boost setting. Strikingly, high frequencies (>20% of CD8+ cells) of protective CTL could be induced and maintained by weekly injection of VLP. Thus, the use of VLP may avoid the requirement for complicated heterologous prime‐boost regimens, facilitating the development of effective T cell‐based vaccines.
Inverse correlation between IL‐7 receptor expression and CD8 T cell exhaustion during persistent antigen stimulation
Authors: Lang Karl S. , Recher Mike , Navarini Alexander A. , Harris Nicola L. , Löhning Max , Junt Tobias , Probst Hans Christian , Hengartner Hans , Zinkernagel Rolf M.
Published: February 2005

Persistence is a hallmark of infection by viruses such as HIV, hepatitis B virus, hepatitis C virus and LCMV. In the case of LCMV, persistence may often be associated with exhaustion of CD8+ T cells. We demonstrate here that persistent antigen suppressed IL‐7Rα expression and this correlated with T cell exhaustion and reduced expression of the anti‐apoptotic molecule B cell leukemia/lymphoma 2 (Bcl‐2). In contrast, exposure to short‐lived antigen only temporarily suppressed IL‐7Rα expression, failed to induce T cell exhaustion, and primed T cells. Persistent antigen also suppressed IL‐7Rα expression on primed T cells and this correlated with exhaustion of a previously stable primed T cell population. These findings suggest that antigen longevity regulates T cell fate.
CoII Complexes of Triazine‐Based Tridentate Ligands with Positive and Attractive CoII/III Redox Couples
Authors: Medlycott Elaine A. , Theobald Isabelle , Hanan Garry S.
Published: February 2005

CoII complexes based on the triazine ligand 2,4‐di(2'‐pyridyl)‐6‐(p‐R‐C6H4)‐1,3,5‐triazine have been synthesized and characterized. Cyclic voltammetry shows that the CoII/III redox couple is more positive than previously described Co complexes of tridentate ligands. The CoII/III redox couple may be varied depending on the nature of the substituent on the phenyl ring of the triazine ligand. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Survival outcome of patients with nasopharyngeal carcinoma with first local failure: A study by the Hong Kong Nasopharyngeal Carcinoma Study Group
Authors: Yu Kwok Hung , Leung Sing Fai , Tung Stewart Yuk , Zee Benny , Chua Daniel T. T. , Sze Wai Man , Law Stephen C. K. , Kam Michael K. M. , Leung To Wai , Sham Jonathan S. T. , Lee Anne W. M. , Au Joseph S. K. , Hui Edwin P. , Sze Wing Kin , Cheng Ashley C. K. , Yau T. K. , Ngan Roger K. C. , Wong Frank C. S. , Au Gordon K. H. , Chan Anthony T. C.
Published: February 2005

Background.

The purpose of this article is to report the overall survival (OS) outcome of patients with nasopharyngeal carcinoma (NPC) with local failure who received salvage treatment and to identify prognostic factors for OS.

Methods.

Between January 1996 and December 2000, 2915 patients received primary radiotherapy (RT) with or without chemotherapy for nonmetastatic NPC. At a median follow‐up of 3.1 years, 319 patients had developed local failure as the first failure, with or without synchronous regional/distant failure. OS was calculated from the start of primary RT. Univariate and multivariate analyses were performed to identify prognostic factors for OS in patients with isolated local failure.

Results.

The T classification distribution of the local failure (rT classification) was as follows: 68 (21%) rT1 to T2a, 92 (29%) rT2b, 82 (26%) rT3, and 77 (24%) rT4. The rT classification was the same as the initial T classification in 82% of patients. Two hundred seventy‐five patients (86%) had isolated local failure, and 232 (84%) of them did not have any distant metastasis or regional failure develop during follow‐up. Salvage treatment was given to 200 patients (73%) with isolated local failure. One hundred fifty‐nine patients (80%) received reirradiation (108 external beam RT [EBRT], 44 brachytherapy, and seven EBRT plus brachytherapy), 22 patients (11%) underwent nasopharyngectomy with or without postoperative RT, and 19 patients (9%) were treated with chemotherapy alone. Four patients died of RT complications, and one died of chemotherapy toxicity in the absence of active NPC. The 3‐year actuarial OS for patients with isolated local failure was 74%. On multivariate analysis, advanced initial T classification (hazard ratio [HR], 1.44; p = .0006) and the use of salvage treatment (HR, 0.54; p = .0038) were independent prognostic factors. For the subgroups of patients who had the same recurrent and initial T classification, salvage treatment was associated with improved OS only in the subgroup with T1 to T2 local failure (n = 127; p = 0.0446), but not in the subgroups with T3 (n = 48) or T4 (n = 54) disease.

Conclusions.

Most patients with first local failure have localized disease. Salvage treatment is feasible in most of the patients with clinically isolated local failure. Patients who had early initial T classification have a more favorable prognosis. Subgroup analysis suggests that salvage treatment only prolongs survival in patients with T1 to T2 recurrent disease. © 2005 Wiley Periodicals, Inc. Head Neck 27: XXX–XXX, 2005
Dichloroacetate‐induced developmental toxicity and production of reactive oxygen species in zebrafish embryos
Authors: Hassoun Ezdihar , Kariya Chirag , Williams Frederick E.
Published: February 2005

Dichloroacetate (DCA) is one of the toxic by products that are formed during the chlorine disinfection process of drinking water. In this study, the developmental toxicity of DCA has been determined in zebrafish (Danio rerio) embryos. Embryos were exposed to different concentrations (4, 8, 16, and 32 mM) of the compound at the 4 h postfertilization (hpf) stage of development, and were observed for different developmental toxic effects at 8, 24, 32, 55, 80, and 144 hpf. Exposure of embryos to 8–32 mM of DCA resulted in significant increases in the heart rate and blood flow of the 55 and 80 hpf embryos that turned into significant decreases at the 144 hpf time point. At 144 hpf, malformations of mouth structure, notochord bending, yolk sac edema and behavioral effects including perturbed swimming and feeding behaviors were also observed. DCA was also found to produce time‐ and concentration‐dependent increases in embryonic levels of superoxide anion (O) and nitric oxide (NO), at various stages of development. The results of the study suggest that DCA‐induced developmental toxic effects in zebrafish embryos are associated with production of reactive oxygen species in those embryos. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:52–58, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20051
Abnormal kinetic behavior of uroporphyrinogen decarboxylase obtained from rats with hexachlorobenzene‐induced porphyria
Authors: Chaufan Gabriela , Corvi Maria M. , Viale Leonor C. San Martín de , Cárdenas María Luz , Molina María del Carmen Ríos de
Published: February 2005

Uroporphyrinogen decarboxylase is an essential enzyme in all organisms and functions in the heme biosynthetic pathway, catalyzing the decarboxylation of the four acetate groups of uroporphyrinogen to form coproporphyrinogen. This work examines whether the four sequential decarboxylations occur at the same active site, and explores whether hexachlorobenzene‐induced porphyria affects the behavior of the enzyme. For this purpose, kinetic competition studies were done with mixtures of uroporphyrinogen III and pentacarboxyporphyrinogen III. With the enzyme from normal rats, a constant velocity was obtained with all the mixtures, indicating that uroporphyrinogen and pentacarboxy‐porphyrinogen react at the same active site, i.e. the first and fourth decarboxylations occur at the same site. In contrast, in experiments with enzyme from rats with hexachlorobenzene‐induced porphyria, the total rate for mixtures was always lower than the reference rate; and a curve with a deep minimum was obtained, indicating that the two reactions occur at functionally different sites, but with cross‐inhibition. This suggests that the modifications induced in the enzyme by hexachlorobenzene cause the two active sites to become nonequivalent and functionally different. The question is discussed how the hexachlorobenzene treatment may produce this abnormal kinetic behavior, and alternative hypotheses are considered. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:19–24, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20055
Transmembrane electropotential changes in amphibian eggs at ovulation, activation and first cleavage
Authors: Morrill Gene A. , Watson Donald E.
Published: February 2005

Electropotential differences between the cell interior and the external medium have been studied with intracellular microelectrodes in ovarian oocytes, ovulated unfertilized eggs and fertilized eggs of R. pipiens. In ovarian oocytes the cytoplasm was 50 to 80 mV negative, relative to isotonic Ringer's solution. In contrast, electrode penetration of the oocyte nucleus in situ indicated that the nucleoplasm was about 25 mV positive, relative to the cytoplasm. After ovulation, the cortical cytoplasm became 20 to 50 mV positive with regard to an external solution of 0.1 strength Ringer's solution (ca. pond water). Penetration of the cytoplasm at levels from 0.3 to 0.6 mm below the egg surface revealed an inner zone with a potential which was about 15 mV negative, relative to the cortical cytoplasm. A slow hyperpolarization of the cortical membrane occurred at activation, with the potential returning to that of the ovulated unfertilized egg within ten minutes. After fertilization, the egg cytoplasm remained positive until the first cleavage. As division proceeded, the cytoplasm slowly depolarized and became 50 to 60 mV negative, relative to 0.1 strength Ringer's solution.
Membranes of animal cells. I. Methods of isolation of the surface membrane
Authors: Warren L. , Glick M. C. , Nass M. K.
Published: February 2005

Procedures have been devised for the isolation of the surface membranes of mouse fibroblasts (L cell) and a variety of other cells. The surface membranes are stabilized by various reagents in a hypotonic solution and are then removed intact or as large fragments with a Dounce homogenizer. The membranes are purified by differential centrifugation on solutions of sucrose or glycerol or on a column of fine glass beads. A trilaminar pattern can be seen in thin sections of the membrane in the electron microscope. Sufficient material can be conveniently obtained for chemical analyses.
Electrical activity and structural correlates of giant nerve fibers in Kuruma shrimp (Penaeus japonicus)
Authors: Kusano Kiyoshi
Published: February 2005

Morphology and recordings of electrical activity of Kuruma shrimp (Penaeus japonicus) giant medullated nerve fibers were carried out. A pair of giant fibers with external diameter of about 120 μ and 10 μ in myelin thickness were found in the ventral nerve cord. The diameter of the axon is about 10 μ. Thus there is a wide gap between the axon and the external myelin sheath. Each axon is doubly coated directly by Schwann cells and indirectly by the myelin sheath layer which is produced by those Schwann cells.

Impulse conduction velocities of these giant fibers showed a range between 90–210 m/sec at about 22°C. Large action potentials (up to 113 mV, rise time of 0.16–0.3 msec, maximum rate of rise of 650–1250 V/sec, half decay time of 0.2–0.3 msec, maximum rate of fall of 250–450 V/sec and total duration of less than 1.5 msec) could be obtained by inserting microelectrodes or by longitudinal insertion of 25 μ diameter capillary electrodes into the gap but no DC‐potential difference was observed across the myelin sheath. Transmyelin electrical parameters were very favorable for fast impulse conduction: myelin resistance of 3 × 104 Ω cm2; time constant of 0.38 msec; myelin capacitance of 1.35 × 10−8 F/cm2; gap fluid resistivity of 23 Ω cm. The existence of nodes of Ranvier could not be demonstrated morphologically, but electrophysiological evidence suggests that a type of saltatory conduction occurs in these giant fibers.
Enzyme activity during the growth and aging of human cells in vitro
Authors: Cristofalo V. J. , Parris N. , Kritchevsky David
Published: February 2005

Acid phosphatase, alkaline phosphatase, and lactic dehydrogenase activities have been compared in normal human diploid cell strains and in SV40‐transformed heteroploid cell lines derived from them. A higher level of acid phosphatase activity was observed in diploid cultures derived from adult lung than in cultures derived from fetal lung of similar passage levels. The alkaline phosphatase activity of normal diploid fibroblasts was significantly higher than that of SV40‐transformed cell lines derived from them. Generally, the lactic dehydrogenase activities of all these cell cultures were similar.

Human diploid cells in culture “age,” in the sense that their ability to proliferate decreases with time during serial subcultivation. Evaluation of the activities of these three enzymes during the “aging” process showed that, although alkaline phosphatase and lactic dehydrogenase activities were similar in “young” and “senescent” cells, acid phosphatase showed a small but significant increase in the senescent cells.
Correlation between cell enlargement and nucleic acid and protein content of hela cells in unbalanced growth produced by inhibitors of DNA synthesis
Authors: Cohen Larry S. , Studzinski George P.
Published: February 2005

HeLa cells in monolayer cultures were treated with the following inhibitors of DNA synthesis: mitomycin C, nitrogen mustard, fluorodeoxyuridine, hydroxyurea, arabinofuranosylcytosine and high concentrations of thymidine. The concentration of each inhibitor used was, in most cases, just sufficient to arrest cell multiplication and all produced unbalanced growth in the sense that the synthesis of RNA and protein were only partially inhibited while DNA synthesis stopped. This resulted in approximately 100% increases in RNA and protein content per cell in 48 hours and, since cell volume also increased by 100% during this time, the concentration of RNA and protein per unit cell volume remained constant. It was concluded that cell protein content may be used as an accurate index of variation in cell size in HeLa cells treated with inhibitors of DNA synthesis.
Osmotic regulation in hydra: Sodium and calcium localization and source of electrical potential
Authors: Macklin Martin
Published: February 2005

Ca45 and Na22 radioautographs using freeze‐substitution with 2‐ethoxyethanol have been prepared for hydra. They reveal a heavy accumulation of Ca and Na along the mesoglea. Microelectrode probes indicate that the positive resting potential in the hydra gut may be resolved into a series of three steps. These results in hydra epithelium suggest that hydra concentrate ions across the outer epidermal cell layer in much the same way that Na is transported across frog skin.
The effects of some ions on the membrane potential of the giant axon of Myxicola
Authors: Goldman L.
Published: February 2005

The effects of various ions on the resting membrane potential of the giant axons of Myxicola were determined. The mean resting potential in artificial sea water is 69 mv, inside negative. The membrane potential decreases with incresing external potassium concentrations, while changes in the sodium and chloride concentrations have little or no effect. For potassium concentrations greater than 50 mM/L the relation between membrane potential and concentration approximates that of a perfectly selective potassium electrode. The data for the whole range of concentrations examined can be well fitted by the equation:

It was pointed out that the Myxicola giant axons can be studied under space voltage clamp and can be made available in the laboratory for 12 months out of the year. Myxicola then should become a very useful preparation for the study of membrane phenomena.
RNA synthesis in synchronously growing populations of HeLa S3 cells. I. Rate of total RNA synthesis and its relationship to DNA synthesis
Authors: Pfeiffer S. E. , Tolmach L. J.
Published: February 2005

The rate of RNA synthesis in synchronously growing HeLa S3 cells was determined as a function of position in the cell generation cycle. Measurements throughout the cycle of both the rate of incorporation of radioactively‐labeled uridine and of the total amount of RNA indicate that (1) the rate of RNA synthesis is constant (or increases only slightly) during G1, approximately doubles during the first half of S, and then remains constant during the remainder of S and G2, and (2) cells attain the average G1 rate of RNA synthesis very early in G1, and maintain the average G2 rate until mitosis.

If the initiation of DNA synthesis is blocked, the acceleration of RNA synthesis is markedly reduced or eliminated. Further experiments in which DNA synthesis was inhibited at different times in S, or to varying degrees from the beginning of S, suggest that the extent to which RNA synthesis is accelerated depends on the amount of DNA duplicated. These data also indicate that duplication of the first half, and in particular the first few per cent, of the DNA complement results in a disproportionate acceleration of RNA synthesis.

The possibility that fluctuations in the sizes of precursor pools may lead to misinterpretation of labeled‐uridine incorporation data was examined. Experiments indicate that in this system pool fluctuations do not cause invalid measures of RNA synthesis.

It is concluded that RNA synthesis occurs throughout interphase, but undergoes a two‐fold increase in rate which is dependent on the duplication of DNA.
Contact regulation of cell division in an epithelial‐like cell line
Authors: Castor Laroy N.
Published: February 2005

The rate of cell division in an epithelial‐like cell line, 1S1, was examined by time‐lapse cinemicrography. When precautions were taken to insure a sufficient nutrient supply, the number of mitoses per unit time in any given area of a confluent monolayer remained constant. This “contact regulation of cell division” resulted in a steadily decreasing frequency of mitosis per cell as the culture became crowded. With the decrease was associated a gradual change in cell shape, from maximally flattened to maximally compact, due to contact inhibition of the movement of cells across one another.

When cells were removed along a line scraped on a dense culture, the cells at the edge of the scrape flattened, migrated into the vacant area, and subsequently increased their frequency of mitosis to that characteristic of non‐confluent cells. Inhibition of mitosis caused by a limitation on the nutrient supply was also reversed at a line‐scrape. These observations suggest that cell flattening promoted mitosis by causing the cell membrane to expand, thereby facilitating the uptake of nutrients. The cell membrane would thus function in the mechanism of contact regulation as a transducer, for converting the pressure of the surrounding cell population into a restraining force upon the metabolism of cell division.
Fluctuations of DNA‐dependent RNA polymerase and synthesis of macromolecules during the growth cycle of Novikoff rat hepatoma cells in suspension culture
Authors: Ward Gary A. , Plagemann Peter G. W.
Published: February 2005

The transition of suspension cultures of Novikoff rat hepatoma cells from the exponential to the stationary phase is accompanied by decreases of over 90% in the rates of synthesis of RNA, DNA and protein, a 90% loss of the apparent DNA‐dependent RNA polymerase activity of the cells, and a disaggregation of the polyribosomes with a concomitant accumulation of 80 S and 110 S ribosomal structures. The cells also attain a minimum content of DNA, RNA and protein and a minimum size. Upon dilution of stationary phase cultures with fresh medium, the rate of protein synthesis begins to increase immediately and this correlates with a rapid reformation of the polyribosomes. The initial re‐formation of polyribosomes is little affected by the presence of actinomycin D. RNA polymerase activity also begins to increase immediately after dilution and an increase in rate of RNA synthesis becomes apparent shortly thereafter. The increase in polymerase activity is inhibited by treating the cells with puromycin or actidione. Cell division commences only 9–13 hours after dilution and the rate of DNA synthesis begins to increase about midway through the lag period. During the lag period the average cellular content of protein increases about 80% and that of RNA and DNA about 30%. These increases are accompanied by a marked increase in the average size of the cells.

Upon continued incubation of stationary phase cultures, the cells become irreversibly damaged physiologically before gross morphological damage becomes apparent. The irreversible physiological damage is recognized by the fact that the cells fail to recover when suspended in fresh medium.
Genetics of somatic mammalian cells. IX. Quantitation of mutagenesis by physical and chemical agents
Authors: Kao Fa‐Ten , Puck Theodore T.
Published: February 2005

The system previously described for inducing single gene mutations in Chinese hamster cells has been extended to produce additional auxotrophic mutants. An improved method for quantitating the efficiency of single gene mutation to specific auxotrophies has been developed. Mutagenesis in the forward direction has been measured after treatment of these cells with ethyl methanesulfonate, N‐methyl‐N1‐nitro‐N‐nitrosoguanidine, hydroxylamine, an acridine mustard (ICR‐191), caffeine and ultraviolet‐ and X‐irradiation. For each agent, the single cell survival curve and the efficiency of chromatid breakage and rearrangement were measured. Similar measurements were also carried out with a water‐soluble carcinogen N‐nitrosomethylurea, which was shown to be effective in producing auxotrophic, somatic mutations. These results offer promise of illuminating the relationships between cell killing, chromosomal aberration, single gene mutations and carcinogenesis produced by various agents. The methods described can be used in routine testing of drugs, food additives, and environmental pollutants for mutagenic action in mammalian cells in vitro.
Human bone marrow colony growth in agar‐gel
Authors: Pike Beverley L. , Robinson William A.
Published: February 2005

A technique for growing human bone marrow cell colonies in agar‐gel medium is described. “Feeder layers” containing 1 × 106 normal human peripheral white blood cells are used as the stimulus for colony growth. Human bone marrow aspirates are collected in heparinized syringes and plated as 2 × 105 cells on “feeder layers.” Normal human bone marrow yields 32–102 colonies per 2 × 105 cells plated. Colonies are almost exclusively granulocytic. Growth rate of colonies is slower than with mouse bone marrow but colonies reach a comparable size (500–1500 cells) at days 12–16.
Inhibition of RNA synthesis by actinomycin D: Characteristic dose‐response of different RNA species
Authors: Perry Robert P. , Kelley Dawn E.
Published: February 2005

A quantitative dose‐response study was made of the inhibition by actinomycin D of the synthesis of various RNA species in cultured L cells. After a suitable preincubation with various concentrations of actinomycin, synthesis was measured by a brief incorporation of radioactive uridine. The 45S precursor of ribosomal RNA, 5S ribosomal RNA, transfer RNA and various sized fractions of heterogeneous nuclear RNA were extracted from the appropriate subcellular fractions and resolved by acrylamide gel electrophoresis. Polyribosomal messenger RNA was also studied. Over the range of actinomycin concentrations employed cellular uptake of the drug is proportional to external concentration, and maximal inhibition of RNA synthesis is generally achieved within one hour after exposure.

For most of the RNA species studied the dose‐response data appear to follow an exponential inactivation function with some “tailing” evident at the higher doses. Sensitivities, defined as the reciprocal of the dose necessary to reduce synthesis to 1/e of the control level, were compared and examined with respect to the molecular weight of the RNA species under consideration. Among the heterogeneous nuclear RNA's there is a good correlation between RNA size and sensitivity, such that the sensitivity per unit molecular weight is relatively constant. A similar relationship is roughly applicable to the ribosomal and transfer RNA's when taken as a group, although in this case the sensitivity per unit molecular weight is 50 to 100 fold greater.

A model is proposed in which this marked difference in actinomycin sensitivity arises as a consequence of the transcription of stretches of contiguous repetitive genes by RNA polymerase molecules which attach to the DNA only at a limited number of entry points, the highest probability of attachment being at the beginning of a stretch.
Mammalian cell fusion. IV. Regulation of chromosome formation from interphase nuclei by various chemical compounds
Authors: Rao Potu N. , Johnson Robert T.
Published: February 2005

Hybrid HeLa cells formed by the fusion of mitotic with interphase cells have been used as a test system to study the effects of various positively and negatively charged compounds on the induction of premature chromosome condensation (PCC) of the interphase nuclei. Among the various positively charged compounds tested, spermine, putrescine and Mg++ were specific in promoting the PCC induction while spermidine was unique in inhibiting this event. All the negatively charged compounds including estradiol‐17β were uniformly inhibitory. The inhibitory effect of estradiol was reversed by putrescine. The inhibition of PCC induction by estradiol seems to be due to its binding to interphase chromatin rather than to the PCC inducers. The differences between the polyamines in their effects on the PCC inducing system has been explained on the basis of their abilities to bind stereospecifically with chromatin.
Galactose metabolism of mammalian erythrocytes
Authors: Paniker N. V. , Iyer G. Y. N.
Published: February 2005

Galactose metabolism in the red cells shows marked interspecies and even intraspecies variations. Red cells of guinea pig, dog and a group of rabbits metabolize galactose to a higher extent than those of other species, including human. In the rabbit, the difference in red cell galactokinase activity could not be correlated to the overall utilization of this sugar in the body.
The roles of calcium and cyclic AMP in the stimulatory action of parathyroid hormone on thymic lymphocyte proliferation
Authors: Whitfield J. F. , MacManus J. P. , Youdale T. , Franks D. J.
Published: February 2005

Both the parathyroid hormone (PTH) and the calcium ion increase the cellular content of cyclic adenosine 3′,5′‐monophosphate (cyclic AMP), promote the initiation of deoxyribonucleic acid synthesis and stimulate the proliferation of rat thymocytes maintained in vitro. The ability of cyclic AMP to serve as the mediator of the mitogenic actions of both PTH and calcium is established by the fact that cyclic AMP itself stimulates cell proliferation in the absence of PTH and extracellular calcium. Neither PTH nor calcium appear to raise the cellular cyclic AMP level by increasing the nucleotide's synthesis by adenylate cyclase (formerly adenyl cyclase); PTH concentrations as high as 50 μg per ml of medium do not increase the enzyme's activity (in the presence or absence of calcium) and mitogenic calcium concentrations inhibit it. PTH also does not directly affect isolated thymocyte phosphodiesterase, but mitogenic calcium levels inhibit the enzyme's activity. Additional experiments show that it is calcium which raises the cyclic AMP level in cells treated with PTH, and some possible calcium‐mediated mechanisms by which the hormone could elevate the cellular cyclic AMP levels are discussed. Thus, the mitogenic action of PTH is primarily mediated by calcium while cyclic AMP is the ultimate implementor of the hormonal action. However, calcium has a dual role and evidence is presented which indicates that besides raising the cellular cyclic AMP level, it also controls the operation of cyclic AMP's mitogenic end‐reaction.
Membrane potentials of BHK (baby hamster kidney) cell line: Ionic and metabolic determinants
Authors: Sachs Howard G. , McDonald Terence F.
Published: February 2005

The transmembrane potential of cells from a continuous cell line (BHK‐21) has been investigated by a combination of electrophysiological and flame photometric techniques. The ratio of sodium permeability to potassium permeability (PNa/PK) determined from membrane potentials recorded at varying external potassium concentrations was 0.082; from membrane potential measurements and the intracellular sodium and potassium concentrations of cells in 6.8 mM K+ media the value was 0.075. The PNa/PK ratio was not temperature dependent. Dinitrophenol (1 mM) did not significantly alter the membrane potential of cells incubated for one hour with the inhibitor. However, iodoacetate (1 mM) and sodium fluoride (30 mM) caused a significant depolarization during a one‐hour incubation. Measurements of sodium and potassium concentrations during incubation at 4°C showed a decrease in internal potassium and an increase in internal sodium accompanied by a decreased membrane potential. Ion concentrations and membrane potentials were measured in cells recovering at 37°C following 24 hours at 4°C. Membrane potentials in excess of EK during the first ten minutes of recovery may indicate electrogenic pumping.