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PubMed1983

Two Ca2+ functions are demonstrated by the substitution of specific divalent and lanthanide cations for the Ca2+ required by the aggregation factor complex from the marine sponge, Microciona prolifera.

Multivalent cations were tested for their ability to replace the Ca2+ requirements of aggregation factor (AF) complex in activity, stability, and integrity assays. The ability of each cation to replace the Ca2+ required for the cell aggregation-enhancing activity of AF was examined by replacing the usual 10 mM Ca2+ with the test cation at various concentrations in the serial dilution assay of the AF. The other alkaline earth cations, Mg2+, Sr2+, and Ba2+, could not replace Ca2+; two transition elements, Mn2+ and Cd2+, partially replaced calcium. All 15 of the available lanthanides (including La3+ and Y3+) produced normal activity but only at 10-400-fold lower cation concentrations than Ca2+. An AF preparation is stable and remains active for months in 1 mM Ca2+ but decays rapidly when Ca2+ is lowered. Sr2+ and Ba2+ at 20 mM but not at 1 mM could replace 1 mM Ca2+ and give long term stability. AF was not stable in the presence of Mg2+, even at 100 mM. High Mn2+ concentrations did not stabilize AF even though AF was partially active in Mn2+. Cd2+ gave full stability at 75 mM and La3+ at about 0.1 mM. When Ca2+ is chelated, the macromolecular subunits of the AF slowly dissociate. Permeation chromatography and analytical ultracentrifugation showed that the cations that stabilized activity maintained the integrity of AF complex while those that failed to stabilize activity allowed the complex to dissociate into subunits, indicating that these two Ca2+ requirements are related. The cation specificities for activity and for stability-integrity are different indicating that these are separate Ca2+-dependent functions.

Animals↗
PubMed1981

An alternative pathway for secretion of lipoprotein particles in rat liver.

Vesicles containing single lipoprotein particles were observed in the perisinusoidal cytoplasm of rat hepatocytes in the proximity of particle-containing rough-smooth endoplasmic reticulum transition elements. Single particle vesicles were observed also in stages interpreted as fusion with the plasma membrane. The putative smooth endoplasmic reticulum-derived vesicles were clearly different from the multiparticle secretory vesicles derived from the Golgi apparatus. The findings suggest the operation of two pathways of lipoprotein secretion in rat liver. One follows the orthodox smooth endoplasmic reticulum Golgi apparatus secretory vesicle plasma membrane export route. The second seems to proceed via smooth endoplasmic reticulum secretory vesicle plasma membrane in a manner that bypasses the Golgi apparatus.

Animals↗
PubMed1981

Kinetics of appearance of lipoprotein particles in perisinusoidal cisternae of smooth endoplasmic reticulum of isolated rat livers perfused with free fatty acid.

Vesicles containing single lipoprotein particles are found in the perisinusoidal cytoplasm of rat hepatocytes in the proximity of particle-containing rough-smooth endoplasmic reticulum transition elements. these lipoprotein particle-containing smooth endoplasmic reticulum elements provide an alternative to Golgi apparatus as a supplier of very low density lipoprotein particles to the circulation. To test this possibility, the kinetics of appearance of lipoprotein particles in these elements was determined for isolated rat livers first depleted of particles and then perfused with free fatty acid to restore particles. The results show that elements of the smooth endoplasmic reticulum in the perisinusoidal cytoplasm acquire lipoprotein particles in advance of elements of the conventional Golgi apparatus and that the particles contained within the perisinusoidal elements of smooth endoplasmic reticulum are not products of endocytotic uptake of particles from the circulation.

Animals↗
PubMed1962

Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements.

Woolfolk, C. A. (University of Washington, Seattle) and H. R. Whiteley. Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements. J. Bacteriol. 84:647-658. 1962.-Extracts of Micrococcus lactilyticus (Veillonella alcalescens) oxidize molecular hydrogen at the expense of certain compounds of arsenic, bismuth, selenium, tellurium, lead, thallium, vanadium, manganese, iron, copper, molybdenum, tungsten, osmium, ruthenium, gold, silver, and uranium, as well as molecular oxygen. Chemical and manometric data indicate that the following reductions are essentially quantitative: arsenate to arsenite, pentavalent and trivalent bismuth to the free element, selenite via elemental selenium to selenide, tellurate and tellurite to tellurium, lead dioxide and manganese dioxide to the divalent state, ferric to ferrous iron, osmium tetroxide to osmate ion, osmium dioxide and trivalent osmium to the metal, uranyl uranium to the tetravalent state, vanadate to the level of vanadyl, and polymolybdate ions to molybdenum blues with an average valence for molybdenum of +5. The results of a study of certain other hydrogenase-containing bacteria with respect to their ability to carry out some of the same reactions are also presented.

Arsenic↗
PubMedDate not supplied

Round spermatids show normal testis-specific H1t but reduced cAMP-responsive element modulator and transition protein 1 expression in men with round-spermatid maturation arrest.

During spermiogenesis, histones are replaced by transition proteins, which in turn are replaced by protamines. The TNP1 gene-encoding TP1 (transition protein 1) protein contains a cAMP-responsive element (CRE) that serves as binding site for the CRE modulator (CREM). To gain further insight into the complex regulation of nucleoprotein exchanges in haploid spermatids and its potential role for spermatogenic impairment, we studied the gene expression of testis-specific histone H1t, CREM, and TNP1 in testicular biopsies from men with normal spermatogenesis (n = 20) and with round spermatid maturation arrest (n = 16). During normal spermatogenesis, H1t messenger RNA (mRNA) was present in 86.2%+/-8.7% of pachytene spermatocytes (stages III-V), whereas H1t protein was synthesized in 83.5%+/-13.0% of pachytene spermatocytes (stages III-V) and persisted in 95.2%+/-3.1% of spermatids (steps 1-5). CREM mRNA was detectable in 74.2%+/-9.4% of pachytene spermatocytes (stages IV-V) and in 78.7%+/-10.0% of spermatids (steps 1-3). CREM protein was synthesized in 81.2%+/-14.2% of spermatids (steps 1-3). TNP1 mRNA was present in 80.0%+/-13.5% of spermatids (steps 2-4), whereas TP1 protein was synthesized in 89.7%+/-5.3% of spermatids (steps 3-4). In men with round spermatid maturation arrest, spermatids only develop to step 3 of differentiation. These spermatids were devoid of both CREM and TP1 but did contain H1t. These results indicate that TP1 is likely to be an important parameter in the histone-to-protamine exchange and in the initiation of spermatid elongation. CREM is involved in the regulation of TNP1 gene expression and consequently plays a vital role in the correct differentiation step from round spermatids to mature spermatozoa.

Chromosomal Proteins, Non-Histone↗
PubMedDate not supplied

[Elements for a theory of transition in health].

This article presents the basic elements for developing a theory of the health transition. Such elements include the definition of concepts, the specification of a framework on the determinants of health status, the analysis of the mechanisms through which changes in health occur in populations, the characterization of the attributes that allow us to identify different transition models, and the enumeration of the possible consequences of the transition. The propositions are presented with a sufficient level of generality as to make them applicable to different contexts; at the same time, an attempt is made to provide them with the necessary specificity to account for different national experiences, thus opening a space for future comparative research efforts. Through the systematization exercise presented in this paper, we hope to contribute to the progress of a topic that has gained growing importance during recent years. Such importance is due to the enormous potential that health transition theory has for understanding and transforming the growing complexity of our times.

Birth Rate↗
PubMed1996

Curious Consequences of Strong Coupling in NMR Experiments Involving Selective Pulses

This study is concerned with the effects of applying selective pulses to systems with strong second-order scalar couplings in isotropic phase, where different transitions (rs) are associated with different transition matrix elements F+(rs). Two unusual features can be distinguished: the nutation angle ("flip angle") depends on the matrix element of the irradiated transition (rs), and, in contrast to the behavior of an isolated spin-(1/2) system, the norm of the three single-transition operators [I(rs)x, I(rs)y, I(rs)z] associated with the fictitious spin-(1/2) space of the irradiated transition (rs) is generally not conserved. It is necessary to consider the single-transition operators [I(rp)x, I(rp)y, I(rp)z] and [I(sq)x, I(sq)y, I(sq)z] associated with all connected transitions (rp) and (sq) that share a common energy level r or s with the irradiated transition (rs). If the pulse applied to the (rs) transition is sufficiently selective, the transverse components I(rp)x, I(rp)y, I(sq)x, and I(sq)y, can be neglected, since their expectation values remain equal to zero after application of a selective pulse to the (rs) transition, but the longitudinal components I(rp)z and I(sq)z acquire nonvanishing expectation values. When the selective pulse affects several transitions simultaneously, the response varies from one transition to another, depending on the matrix elements and the connectivities. These effects manifest themselves in unusual amplitudes and phases of signals excited by selective pulses, in particular in selective two-dimensional correlation spectra.

Journal Article↗
PubMed1991

Elements for a theory of the health transition.

This article presents the basic elements for developing a theory of the health transition. Such elements include the definition of concepts, the specification of a framework on the determinants of health status, the analysis of the mechanisms through which health change occurs in populations, the characterization of the attributes that allow us to identify different transition models, and the enumeration of the possible consequences of the transition. The propositions are presented with a sufficient level of generality as to make them applicable to different contexts; at the same time, an attempt is made to provide them with the necessary specificity to account for different national experiences, thus opening a space for future comparative research efforts. Through the systematization exercise presented in this article, we hope to contribute to the progress of a topic that has grown in importance during recent years. Such importance is due to the enormous potential that health transition theory has for understanding and transforming the growing complexity of our times.

Demography↗
PubMed1990

Clonal analysis of a bladder cancer cell line: an experimental model of tumour heterogeneity.

The continuous cell line UCRU BL 17CL was derived from a human invasive bladder cancer and expresses elements of transitional, squamous and glandular differentiation. Nine clones of this line were established by limit dilution and have been extensively characterised. Only six of these clones grew subcutaneously in nude mice. Of these, three have exhibited local invasion, each in one of five implanted mice. Although all xenografts expressed transitional, squamous and glandular elements, different histological subtypes predominated within each clone. Only clones which grew in nude mice formed colonies in semi-solid medium, and each responded differently to the influence of medium that had been conditioned by the growth of UCRU BL 17CL, suggesting the possible secretion of a growth factor by these cells. The DNA content and lectin binding profiles of the clones also reflected the heterogeneity of the line. UCRU BL 17CL and the nine clones provide a unique model for the study of tumour heterogeneity, progression and differentiation, and the potential autocrine regulation of growth of bladder cancer.

Carcinoma, Transitional Cell↗
PubMed2006

The clc element of Pseudomonas sp. strain B13, a genomic island with various catabolic properties.

Pseudomonas sp. strain B13 is a bacterium known to degrade chloroaromatic compounds. The properties to use 3- and 4-chlorocatechol are determined by a self-transferable DNA element, the clc element, which normally resides at two locations in the cell's chromosome. Here we report the complete nucleotide sequence of the clc element, demonstrating the unique catabolic properties while showing its relatedness to genomic islands and integrative and conjugative elements rather than to other known catabolic plasmids. As far as catabolic functions, the clc element harbored, in addition to the genes for chlorocatechol degradation, a complete functional operon for 2-aminophenol degradation and genes for a putative aromatic compound transport protein and for a multicomponent aromatic ring dioxygenase similar to anthranilate hydroxylase. The genes for catabolic functions were inducible under various conditions, suggesting a network of catabolic pathway induction. For about half of the open reading frames (ORFs) on the clc element, no clear functional prediction could be given, although some indications were found for functions that were similar to plasmid conjugation. The region in which these ORFs were situated displayed a high overall conservation of nucleotide sequence and gene order to genomic regions in other recently completed bacterial genomes or to other genomic islands. Most notably, except for two discrete regions, the clc element was almost 100% identical over the whole length to a chromosomal region in Burkholderia xenovorans LB400. This indicates the dynamic evolution of this type of element and the continued transition between elements with a more pathogenic character and those with catabolic properties.

Aminophenols↗
PubMed2006

Adsorption of transition-metal atoms on boron nitride nanotube: a density-functional study.

Adsorption of transition atoms on a (8,0) zigzag single-walled boron nitride (BN) nanotube has been investigated using density-functional theory methods. Main focuses have been placed on configurations corresponding to the located minima of the adsorbates, the corresponding binding energies, and the modified electronic properties of the BN nanotubes due to the adsorbates. We have systemically studied a series of metal adsorbates including all 3d transition-metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and two group-VIIIA transition-metal elements (Pd and Pt). We found that many transition-metal atoms can be chemically adsorbed on the outer surface of the BN nanotubes and that the adsorption process is typically exothermic. Upon adsorption, the binding energies of the Sc, Ti, Ni, Pd, and Pt atoms are relatively high (>1.0 eV), while those of V, Fe, and Co atoms are modest, ranging from 0.62 to 0.92 eV. Mn atom forms a weak bond with the BN nanotube, while Zn atom cannot be chemically adsorbed on the BN nanotube. In most cases, the adsorption of transition-metal atoms can induce certain impurity states within the band gap of the pristine BN nanotube, thereby reducing the band gap. Most metal-adsorbed BN nanotubes exhibit nonzero magnetic moments, contributed largely by the transition-metal atoms.

Journal Article↗
PubMed2005

Memory retrieval tasks determine the serial position curves of linear orders with categorical structures.

I examined 2 different views on organization of linear order information in memory: the linear schema view and the hierarchical structure view. The linear schema view holds that there is a strong tendency in memory to organize an array of transitively related elements into a unidimensional order. The hierarchical structure view maintains that the transitively related elements are organized in memory in a hierarchy of items. I proposed an input structure and retrieval compatibility hypothesis as a coherent explanation for the contradictory views on the memory organization of serial elements. I argue that the organization of linear order information in memory is determined by the nature of the memory retrieval task used. For example, a comparative judgment task is more compatible with a unidimensional structure, whereas a sequential recall or serial position identification task is more compatible with a hierarchical organization. The input structure and retrieval compatibility concept can also explain why dichotomous categories imposed on a linear order play very little role in comparative judgments.

Analysis of Variance↗
PubMed2006

Transition: a literature review.

AIM: This paper reports a comprehensive literature review exploring how the term 'transition' has been used in the health literature. BACKGROUND: The meaning of transition has varied with the context in which the term has been used. The last 3 decades have seen altered understandings in the concept of transition in the social science and health disciplines, with nurses contributing to more recent understandings of the transition process as it relates to life and health. METHOD: The CINAHL, Medline, Sociofile and Psychlit databases were accessed and papers published between 1994 and 2004 were retrieved to answer the questions 'How is the word transition used?' and 'What is the concept of transition informing?' Transition theoretical frameworks were also explored. FINDINGS: Widespread use of the word 'transition' suggests that it is an important concept. Transitional definitions alter according to the disciplinary focus, but most agree that transition involves people's responses during a passage of change. Transition occurs over time and entails change and adaptation, for example developmental, personal, relational, situational, societal or environmental change, but not all change engages transition. Reconstruction of a valued self-identity is essential to transition. Time is an essential element in transition and therefore longitudinal studies are required to explore the initial phase, midcourse experience and outcome of the transition experience. CONCLUSION: Transition is the way people respond to change over time. People undergo transition when they need to adapt to new situations or circumstances in order to incorporate the change event into their lives. Transition is a concept that is important to nursing; however, to further develop understandings, research must extend beyond single events or single responses. Longitudinal comparative and longitudinal cross-sectional inquiries are required to further develop the concept.

Adaptation, Psychological↗