Comparison of cellular strain with applied substrate strain in vitro

Strain magnitudes within tenocytes undergoing substrate tensile strain are not well defined. It was hypothesized that strain magnitudes at the cellular level would reflect those of the applied substrate (equibiaxial or uniaxial) strain. A vacuum-operated device was used to apply equibiaxial or uniaxial tension to a flexible substrate upon which tenocytes were cultured in monolayer. Images of tenocytes labeled with Fura-2, to detect free intracellular calcium ions, and MitoFluor Green, to detect mitochondria, were taken prior to strain and for 20 min during application of static strain. A custom-written, texture correlation program computed strain magnitudes in the cell based on the change in pixel pattern displacements between images of non-strained and strained cells. On average, cellular strain was approximately 37+/-8% and 63+/-11% of the applied equibiaxial and uniaxial substrate strain, respectively. The largest cell strains were detected in cells oriented parallel to the direction of applied uniaxial tensile strain. However, strain magnitudes within a cell were heterogeneous. The variance in strain magnitude within and among tenocytes is dependent on cell orientation, cell stiffness, cytoskeleton organization, subcellular organelles, or placement and type of cell-substrate contacts. Results of the present study indicate that cultured tenocytes experience a moderate fraction of the applied substrate strain.     

一株卡他布朗汉姆菌的重新鉴定

目的对中国医学细菌保藏管理中心库藏的一株卡他布朗汉姆菌CMCC(B)29103株进行重新鉴定。方法用营养琼脂培养基培养CMCC(B)29103株,对其进行形态观察、生理生化特性、脂肪酸组分、分子生物学等多相鉴定,同时与模式株DSM25388T相对照;分析CMCC(B)29103株的特征属性、进化位置以及与Acinetobacter indicus模式株DSM25388T的同源性。结果形态学特性、生理生化以及脂肪酸组分构成均与DSM25388T株十分相似,仅存在个别差异;16 S rRNA基因序列比对显示,CMCC(B)29103株与Acinetobacter(不动杆菌属)相近,与模式株DSM25388T相似性最高,为99.85%。基于Acinetobacter属所有成员的16 S rRNA和rpo B基因的系统进化分析均显示CMCC(B)29103与DSM25388T稳定聚类成一个独立分支,且二者的DNA-DNA同源性为78.3%。结论CMCC(B)29103株属于Acinetobacter indicus种,与模式株DSM25388T为不同的菌株,可将其更名为Acinetobacter i ndicus。     

Synergistic degradation of benzylpenicillin by aPseudomonas strain and aFusarium strain

APseudomonas sp. and aFusarium sp. were isolated from pasture soil. The organisms grew syntrophically on a mineral medium with benzylpenicillin as carbon and nitrogen source. During synergistic degradation of the antibiotic, benzylpenicilloic and benzylpenilloic acid were intermediates. Activities of both organisms were necessary for further decomposition, during which the phenylacetate side chain was degraded. 6-Aminopenicillanic acid did not occur. During syntrophic growth, a red pigment appeared in fungal hyphae growing through bacterial colonies.     

Clostridial strain degeneration

Abstract: Strain degeneration, the loss of the capacity to produce solvents and form spores, typically occurs when Clostridium acetobutylicum and related clostridia are repeatedly subcultured in batch culture or grown in continuous culture, as opposed to being grown from germinated, heat-treated spores. Several mechanisms for degeneration have been identified thus far. (i) Degeneration can be caused by excessive acidification of the culture during exponential growth. We present data interpreted to mean that C. beijerinckii (formerly C. acetobutylicum ) NCIMB 8052 cells ferment glucose to acetic and butyric acids at an uncontrolled rate, so that, during rapid growth, the rate of acid production can exceed the rate of induction of the solventogenic pathway enzymes. As a result, the medium pH drops to bactericical levels, and the cells cannot switch to solventogenesis and sporulation. The clostridia seem to be poised either to produce excess acids, or to initiate solventogenesis, depending on small differences in the rates of growth. (ii) We have isolated transposon-insertion mutants of C. beijerinckii NCIMB 8052 that are resistant to degeneration, suggesting the involvement of a regulatory region of the clostridial chromosome. (iii) Involvement of a global regulatory gene has been inferred in C. beijerinckii NCIMB 8052 which degenerates irreversibly in chemostat culture. (iv) Impairment of butanol formation due to a defect in NADH generation has been reported in an oligosporogenous strain which can revert to the non-degenerate phenotype. (v) In continuous culture, degenerate cells may be selected because they continue to divide, while the non-degenerate cells stop dividing and start differentiating.     

Ploidy level in Streptomyces cerevisiae strain 15B-P4 strain]

Hybridization analysis of seven clones of Saccaromyces cerevisiae 15B-P4 strain, which were obtained from different cultures, was carried out. Yeast strains taken from the Peterhoff breeding stocks were kept in the laboratory of genetics at Biological Institute of Irkutsk University from 1970. Increase in the number of prototrophic segregants was shown to by the result of aneuploidy (2n + 1) in the hybrids under study. Aneuploidy was revealed for the chromosomes I, III, IX, XII. Disomic clones of 15B-P4 strain were unstable.     

Variations in erythropoiesis throughout a lifetime. Studies in a high-leukaemic mouse strain, the AKR/O strain, and a non-leukaemic strain, the WLO strain

We have studied the development of some haematological variables: erythropoiesis stimulating factor(s) (ESF), investigated with an in vitro cell culture assay; and the content of bone marrow and spleen erythroid colony forming unit(s) (CFU-E) and erythroid burst forming unit(s) (BFU-E) throughout the lifetime of 2 different mouse strains: the high-leukaemic, retrovirus infected AKR/O strain, and the non-leukaemic WLO strain. During the recovery phase of the postnatal anaemia, a peak in plasma ESF occurs in both strains. In young adult mice of both strains another peak in plasma ESF occurs at 70-110 days of age, associated with an increased number of bone marrow CFU-E, in a period when packed cell volume (PCV) remains stable. As the animals grow older PCV decreases, whereas plasma ESF and bone marrow CFU-E concentration increase. These results, together with in vitro dose-response studies, suggest reduced sensitivity to erythropoietin (Epo) of the ageing erythron. Throughout, the AKR/O strain has higher levels of plasma ESF and bone marrow CFU-E concentrations than the WLO strain, indicating both a reduced Epo responsiveness and some degree of ineffective erythropoiesis in the AKR/O strain. At all ages the AKR/O strain has a high concentration of Epo independent bone marrow CFU-E, possibly caused by the virus infection of precursor cells.     

International strain data networks

Summary Microbial resources, in the form of preserved cultures and individual records of the properties of these, are very extensive. However, access to this mass of information is extremely limited and primarily a manual operation. In the last few years, computerized data bases describing microbial strains have been established in many service and research culture collections world-wide. Some of these are planned to become publicly accessible data banks. Active investigation of the possibility of combining some of these data banks into regional networks is underway in at least the Nordic Countries, the UK, the Common Market Countries, Japan and the USA. The United Nations Environment Programme (UNEP), initiated, with further support from the Commission of the European Communities (CEC), and the Fonds National de la Recherche Scientifique (FNRS) of Belgium, an international workshop in Brussels in November 1983 to explore the possibility and modus operandi of a world microbial strain data network. The workshop participants appointed a Working Group and the project has subsequently become sponsored by the Committee on Data for Science and Technology (CODATA) and the World Federation for Culture Collections (WFCC). Key recommendations included: (1) a world system should have the flexibility to include non-computerized as well as computerized information; (2) the system should be distributed rather than be a single centralized data bank, and (3) a number of committees would have to be constituted to implement the project.

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Resumen Los recursos microbiológicos son muy extensos, si como tales consideramos las colecciones de cultivos y los conocimientos sobre sus propiedades almacenados en ficheros individuales. Sin embargo el acceso a toda esta información esta extraordinariamente limitado y se realiza generalmente de forma manual. En estos últimos años se han establecido bancos de datos computarizados describiendo cepas microbianas en centros de investigación y de conservación de colecciones de cultivos en todo el mundo. Algunos de ellos han sido ya diseñados para su conversión a bancos de datos de acceso público. En los países Nórdicos, los países miembros del mercado común, U.K., Japón y U.S.A.; se esta estudiando la posibilidad de reunir algunos de estos bancos de datos para formar una red regional. UNEP, CEC y FNRS de Bélgica patrocinaron en Noviembre 1983 una Reunión Internacional que tuvo lugar en Bruselas, con el fin de explorar las posibilidades y el modus operandi de un banco mundial de datos sobre cepas microbianas. Los participantes de la Reunión nombraron un grupo de trabajo y el proyecto ha sido a partir de entonces patrocinado por CODATA y WFCC. Las recomendaciones clave incluyen: (1) un sistema mundial debe ser lo suficientemente flexible para poder incluir información tanto computerizada como no computerizada; (2) el sistema ha de ser descentralizado; y (3) hay que constituir un cierto número de comités para implementar el proyecto.

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Résumé Les ressources microbiologiques en matière de cultures et de données sur les propriétés individuelles des souches sont considérables. Toutefois, l'accès à cette masse d'informations est encore très limité et nécessite des opérations manuelles. Au cours des dernières années, des informations computorisées sur les souches microbiennes ont été enrégistrées dans le monde entier par beaucoup de collections de cultures, dont certaines s'apprêtent à devenir des banques de données publiquement accessibles. Des études sur la possibilité de combiner ces banques de données sur la base de réseaux régionaux ont été entreprises, notamment dans les pays nordiques, le Royaume Uni, la Communauté Européene, le Japon et les USA. L'UNEP, la Communauté Européenne et le FNRS belge ont tenu à Bruxelles, en novembre 1983, une réunion internationale afin d'explorer la possibilité et le mode de fonctionnement d'un réseau mondial de données sur les souches microbiennes. Les participants ont constitué un groupe de travail et le projet a été patronné par CODATA et WFCC. Il a été essentiellement recommandé: (1) qu'un tel système mondial devrait être assez souple pour inclure à la fois des informations computorisées et non-computorisées; (2) que le système devrait être décentralisé; et (3) qu'il convient d'instituer un certain nombre de comités pour mettre en oeuvre le projet.

     

Herpesvirus saimiri strain variability

Herpesvirus saimiri was isolated from 22 squirrel monkeys by cocultivation of peripheral lymphocytes with permissive owl monkey kidney monolayer cells. Comparison of virion DNA fragments produced from restriction endonuclease digestion was used as a sensitive measure of strain variability. Although all isolates contained similarities and common features, 19 of the 22 were readily distinguished. Three of the isolates, however, were indistinguishable and possibly were related epidemiologically. Distinct subtypes of H. saimiri were not evident by these criteria; Peruvian, Colombian, Guyanan, and Bolivian squirrel monkeys yielded isolates without characteristic features peculiar to the geographic region. Three of three colony-born squirrel monkeys that were tested yielded a strain of virus distinct from that obtained from the mother. In separate experiments, two of three animals chosen at random yielded a strain of virus different from that originally obtained 16 and 22 months previously; only one of the three animals examined yielded the same strain of virus 22 months after the original isolation. The degree of restriction endonuclease fragment variability among H. saimiri strains appeared to be greater than previously observed for other herpesviruses.     

The relative value of strain and strain rate for defining intrinsic myocardial function

It is well accepted that strain and strain rate deformation parameters are not only a measure of intrinsic myocardial contractility but are also influenced by changes in cardiac load and structure. To date, no information is available on the relative importance of these confounders. This study was designed to investigate how strain and strain rate, measured by Doppler echocardiography, relate to the individual factors that determine cardiac performance. Echocardiographic and conductance measurements were simultaneously performed in mice in which individual determinants of cardiac performance were mechanically and/or pharmacologically modulated. A multivariable analysis was performed with radial and circumferential strains and peak systolic radial and circumferential strain rates as dependent parameters and preload recruitable stroke work (PRSW), arterial elastance (E(a)), end-diastolic pressure, and left ventricular myocardial volume (LVMV) as independent factors representing myocardial contractility, afterload, preload, and myocardial volume, respectively. Radial strain was most influenced by E(a) (β = -0.58, R(2) = 0.34), whereas circumferential strain was strongly associated with E(a) and moderately with LVMV (β = 0.79 and -0.52, respectively, R(2) = 0.54). Radial strain rate was related to both PRSW and LVMV (β = 0.79 and -0.62, respectively, R(2) = 0.50), whereas circumferential strain rate showed a prominent correlation only with PRSW (β = -0.61, R(2) = 0.51). In conclusion, strain (both radial and circumferential) is not a good surrogate measure of intrinsic myocardial contractility unless the strong confounding influence of afterload is considered. Strain rate is a more robust measure of contractility that is less influenced by changes in cardiac load and structure. Thus, peak systolic strain rate is the more relevant parameter to assess myocardial contractile function noninvasively.     

Catabolite regulation in a diauxic strain and a nondiauxic strain of Streptococcus bovis

Streptococcus bovis JB1 utilized glucose preferentially to lactose and grew diauxically, but S. bovis 581AXY2 grew nondiauxically and used glucose preferentially only when the glucose concentration was very high (greater than 5 mM). As little as 0.1 mM glucose completely inhibited the lactose transport of JB1. The lactose transport system of 581AXY2 was at least tenfold less sensitive to glucose, and 1 mM glucose caused only a 50% inhibition of lactose transport. Both strains had phosphotransferase systems (PTSs) for glucose and lactose. The glucose PTSs were constitutive, but little lactose PTS activity was detected unless lactose was the energy source for growth. JB1 had approximately threefold more glucose PTS activity than 581AXY2 (1600 versus 600 nmol glucose (mg protein)⁻¹(min)⁻¹. The glucose PTS of JB1 showed normal Michaelis Menten kinetics, and the affinity constant (K _s ) was 0.12 mM. The glucose PTS of 581AXY2 was atypical, and the plot of velocity versus velocity/substrate was biphasic. The low capacity system had a K_s of 0.20 mM, but the K_s of the high capacity system was greater than 6 mM. On the basis of these results, diauxic growth is dependent on the affinity of glucose enzyme II and the velocity of glucose transport. Received: 22 January 1996 / Accepted: 18 March 1996     

Characterizing bone strain distributions in vivo using three triple rosette strain gages.

Three triple-element rosette strain gages were attached to the equine third metacarpal midshaft to record site-specific strains engendered by locomotion. The distribution of strains acting upon the midshaft cross section were characterized using a combined beam theory and finite element model analysis that did not presume the manner by which the bone was inertially loaded. A medium-speed trot (3.6 ms-1) was chosen as a representative speed and gait, with normal and shear strains, and strain energy density (SED) distributions determined throughout the stance and subsequent swing phase. Importantly, the sites of maximum compression (-2400 mu epsilon), tension (810 mu epsilon), shear (1500 mu epsilon), and SED (54 kPa) were not located at any of the gage attachment sites, emphasizing that a minimum of three rosette gages are necessary to resolve the peaks and locations of functionally induced normal and shear strains. Considering the nonuniform strain distributions across the cortex, we conclude that the third metacarpal is subject to a complex loading milieu comprised of bending, axial compression, end shear, and torsion. As this complex manner of loading was consistent through the entire stance phase, it would appear that, at least during the trot, specific sites within the same cross section are subject to vastly different magnitudes of strain stimulus.     

Competition by allelopathy proceeds in traveling waves: colicin-immune strain aids colicin-sensitive strain

Producing toxic chemicals to suppress both the growth and survivorship of local competitors is called allelopathy; some strains of the bacteria Escherichia coli produce a toxin (named colicin) which may kill colicin-sensitive neighbors while they themselves are immune. In a previous paper, the competitive outcome between colicin-producing and colicin-sensitive strains was shown to differ between a spatially structured and a completely mixed population. In this paper, we analyze the role of a third, "colicin-immune," strain, which does not produce colicin but is immune to it. Without spatial structure, the colicin-immune strain suppresses the colicin-producing strain and enables the colicin-sensitive strain to win. In a spatially structured population, modeled as a reaction-diffusion system, we examine the speed of boundaries between areas dominated by different strains in traveling waves and the events after the collision of two such boundaries. The colicin-immune strain passes through the area dominated by the colicin-sensitive strain and drives the colicin-producing strain to extinction. Subsequently the colicin-sensitive strain occupies the whole population.     

松花湖铜绿微囊藻无菌株和单藻株生长因素的研究

用毛细滴管洗净法从松花湖分离纯化出铜绿微囊藻(Microcystisaeruginosa)的单藻株和无菌株,研究了温度、照度、N、P、Fe各种因素对单藻株和无菌株生长的影响。结果表明,各种因素对单藻株和无菌株最大比增长率的影响差别不大,单藻株和无菌株分别在温度33℃,照度5000Lx(2000Lx)、NO3-N浓度1.2mg·L-1,PO43-P浓度0.06mg·L-1,柠檬酸铁铁浓度0.05mg·L-1(0.04mg·L-1)时,达到最大比增长率。在一定浓度范围内,随着N、P、Fe浓度的增加,单藻株比无菌株的最大增长量高得多,可见附着细菌的存在,能促进铜绿微囊藻的生长。从松花湖湖水中N、P和Fe含量以及温度和照度的情况看,松花湖的某些区域已经基本具备了水华发生的条件。     

Equibiaxial strain and strain rate stimulate early activation of G proteins in cardiac fibroblasts

Cardiacfibroblasts are responsible for the production of the extracellularmatrix of the heart, with alterations of fibroblast function implicatedin myocardial infarction and cardiac hypertrophy. Here the role ofheterotrimeric GTP-binding proteins (G proteins) in themechanotransduction of strain in rat cardiac fibroblasts wasinvestigated. Cells in an equibiaxial stretch device were incubatedwith the photoreactive GTP analog azidoanalido[-³²P]GTP (AAGTP)and were subjected to various regimens of strain. Autoradiographicanalysis showed a 42-kDa protein labeled for cells exposed to 12 cyclesof 3% strain or 6 cycles of 6% strain over 60 s (strain rate of1.2%/s), whereas 6 cycles of 3% strain (0.6%/s) elicited nomeasurable response. To further investigate the role of strain rate, asingle 6% cycle over 10 or 60 s (1.2% and 0.2%/s, respectively) wasapplied, with the more rapid cycle stimulating AAGTP binding, whereasthe lower strain rate showed no response. In cells subjected to asingle 6% cycle/10 s, immunoprecipitation identified the AAGTP-labeled42-kDa band as the G protein subunits G_q andG_i1. These results demonstratethat G protein activation represents one of the earlymechanotransduction events in cardiac fibroblasts subjected tomechanical strain, with the rate at which the strain is appliedmodulating this response.