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PubMed2005

2-D homonuclear correlation and separated local field experiments for solids with strong homonuclear dipolar couplings.

An experiment for acquiring two-dimensional homonuclear correlation spectra of nuclei in solids in the presence of strong homonuclear dipolar couplings is described. The experiment utilizes a multiple-pulse homonuclear decoupling sequence with an effective precession axis parallel to the rotating frame z-axis during the evolution and detection periods. A multiple-pulse sequence that suppresses chemical shift and heteronuclear dipolar coupling evolution and scales the static homonuclear dipolar coupling is proposed for the mixing period. The evolution during the mixing period is analogous to the dynamics of the mixing period in solution-state TOCSY experiments, and can be interpreted as the oscillatory exchange of longitudinal magnetization between coupled spins. For nuclides with large gyromagnetic ratios, the static homonuclear dipolar interaction will be substantially larger than the mechanisms used to develop internuclear correlations in solution state 2-D experiments, which should make it possible to establish correlations over much longer distances and with significantly shorter mixing times. Extensions to separated local field experiments are discussed.

Algorithms↗

PubMed1998

HPLC determination of photosynthetic pigments during greening of etiolated barley leaves. Evidence for the biosynthesis of chlorophyll a'.

The temporal evolution of pigment composition during greening of etiolated barley leaves was investigated by reversed-phase HPLC with particular attention to chlorophyll (Chl) a' (C13(2) epimer of Chl a), which had been detected by ourselves in photosystem (PS) I particles. At early stages of greening, the Chl a'/Chl a molar ratio rapidly increased to a level more than twice that in mature leaves, then gradually leveled off, accompanied by a growth of the Chl b/Chl a ratio, to the mature level. After 3 h of illumination, the temporal evolution of the Chl a'/Chl a molar ratio nearly paralleled that of the P700/Chl a ratio with a stoichiometry Chl a'/P700 approximately equal to 2: this strongly suggests that Chl a' is biosynthesized as a constituent of the PS I reaction center complex.

Chlorophyll↗

PubMed1997

Central nervous system hemangiomatosis in early childhood.

Two cases of hemangiomatosis are reported, a girl of 3 years of age and a boy 2 years of age, both with central nervous system (CNS) involvement. In the first, the CNS lesions were asymptomatic; in the second, symptomatic. Magnetic resonance imaging was used both to identify the lesions and to follow their evolutions. In the first case, the CNS lesions involuted in parallel with those in skin and liver. In the second, while there was no obvious resolution of the CNS lesions, there was a decrease in the level of urine basic fibroblast growth factor, indicating the lesions were probably involuting. Serial magnetic resonance imaging studies and urine assays of basic fibroblastic growth factor have important roles to play in following CNS involvement in hemangiomatosis.

Brain↗

PubMed1996

Molecular cloning and expression of two novel avian cytochrome P450 1A enzymes induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Transcriptional regulation by the aryl hydrocarbon receptor, for which the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent ligand, leads in mammalian liver to the induction of genes for two distinct cytochrome P450 (CYP)1A enzymes, CYP1A1 and -1A2. Fish seem to have only one CYP1A enzyme. CYP1A enzymes have been regarded as injurious largely because of their ability to activate chemical carcinogens. We report here the cloning and sequencing of cDNAs for two catalytically distinct TCDD-induced CYP enzymes in chick embryo liver. One mediates classic CYP1A1 activities. The other has some -1A2-like activities and is also responsible for TCDD-induced arachidonic acid epoxygenation, a much more conspicuous effect in liver of chicks than of mammalian species. Amino acid sequence analysis shows that although each chick enzyme can be classified in the CYP1A family, both are more like CYP1A1 than -1A2, and neither can be said to be directly orthologous to CYP1A1 or -1A2. Phylogenetic analysis shows that the two chick enzymes form a separate branch in the CYP1A family tree distinct from mammalian CYP1A1 and -1A2 and from fish CYP1A enzymes. The findings suggest that CYP1A progenitors split into two CYP enzymes with some parallel functions independently in two evolutionary lines, evidence for convergent evolution in the CYP1A family. Northern analysis shows that the chick enzymes have a different tissue distribution from CYP1A1 and -1A2. Polymerase chain reaction and in situ hybridization data show that both chick enzymes are expressed in response to TCDD even before organ morphogenesis. The findings further suggest that beyond their role in activating carcinogens, CYP1A enzymes have conferred evolutionary and developmental advantages, perhaps as defenses in maintaining homeostatic responses to toxic chemicals.

Amino Acid Sequence↗

PubMed2001

Continuous renal replacement therapy in critically ill patients.

Acute renal failure is an evolving syndrome in which new pathogenetic mechanisms have recently been elucidated. The evolution of the field of haemodialysis has led to a parallel development in the therapeutic approach to patients suffering from this syndrome. In particular, acute renal failure is more frequently seen as part of a more complex syndrome, defined as multiple organ failure. In this clinical setting, patients are almost inevitably confined to intensive care units and sepsis is a frequent underlying mechanism of organ failure. The use of new devices and new machines, together with a better understanding of the underlying mechanisms of solute and water removal, have allowed us to achieve higher levels of efficiency and clinical tolerance during artificial renal replacement therapy. The first objective has been reached by increasing the automation of the extracorporeal circuits and the operational levels of the different techniques; the second has been achieved by means of a new generation of monitoring techniques and new machines equipped with specific interfaces and alarms. This progress has made continuous forms of renal replacement (CRRT) possible and easy to perform without major problems or complications. The most promising and effective options for treating acute renal failure in critically ill patients are today offered by continuous renal replacement therapies. Classic indications, but also alternative non-renal indications, have been proposed for these techniques. The most advanced indication is the multiple organ dysfunction occurring in septic patients. The possible removal of proinflammatory mediators may permit a blockade of the systemic inflammation, a modulation of the altered immune response in these patients, and it may lead to a partial or total restoration of the lost homeostasis.

Acute Kidney Injury↗

PubMed2001

Fluidlike behavior of dielectric permittivity in a wide range of temperature above and below the nematic-isotropic transition.

Singular behavior of the static dielectric permittivity of n-alkyloxycyanobiphenyls (CnH2n+1O-Ph-Ph-C [triple bond] N, n=6, 7) was studied above and below the nematic clearing point (T(I-N)). On approaching the clearing point, the evolution of principal components of the nematic permittivity tensor, epsilon(parallel) and epsilon(perpendicular), is described by the order parameter exponent beta approximately 0.25. The mean value of the nematic permittivity epsilon(mean)=(epsilon(parallel)+2epsilon(perpendicular))/3 exhibits a singular behavior similar to that observed in the isotropic phase and that for the diameter of the coexistence curve in binary mixtures. The derivative of experimental data d(epsilon)iso(T)/dT and d(epsilon)mean(T)/dT shows the specific-heat-like behavior with universal exponents alpha=alpha' approximately 0.5. Results obtained confirm the hypothesis of the fluidlike, pseudospinodal, and tricritical behavior of the isotropic to nematic phase transition. [A. Drozd-Rzoska, Phys. Rev. E 59, 5556 (1999)].

Journal Article↗

PubMed1966

Potentiation of photosynthetic oxygen evolution in red light by small quantities of monochromatic blue light.

Growth of the giant unicellular green alga, Acetabularia crenulata, stops in red light of broad spectral composition, but can be restored by the addition of small quantities of blue light. Long-term records of O(2) evolution indicate that the photosynthesis of Acetabularia responds in a parallel manner to blue light. Cells photosynthesizing at a light-limited rate in white light were given red light at an intensity that served to match or somewhat increase the instantaneous rate of O(2) production. A rapid decline in the rate commenced within 15 minutes and continued for 2 hours or more until it had fallen to 20 to 40% of the initial level. Very small doses of violet or blue radiation (<10(-8) Einstein/cm(2)) then affected a complete, though temporary, restoration of the original rate of photosynthesis. Responses began after a lag of 4 to 5 minutes, regardless of their magnitude, and in the most favorable instances persisted 4 to 6 hours after the stimulus. Blue light treatments were effective as flashes as brief as 2.5 seconds, given simultaneously or in sequence with the red measuring light, or as low-intensity continuous irradiations. Blue-light induction of the response was stable over at least 5 minutes of darkness. After a suitable red-light pretreatment, 2 other algae, Chlamydomonas reinhardi and Fucus vesiculosus, were shown to respond similarly to low-intensity irradiations with blue or blue-green light.Crude action spectra were determined for the response of Acetabularia to short wavelength irradiations given simultaneously or sequentially with the red measuring light. Two peaks of effectiveness were found, one near 450 mmu, and another, as yet ill defined, in the near UV. The data suggest a shoulder around 490 mmu. All wavelengths above 540 mmu were entirely ineffective.

Journal Article↗

PubMed2006

Cooperation between engulfment receptors: the case of ABCA1 and MEGF10.

The engulfment of dying cells is a specialized form of phagocytosis that is extremely conserved across evolution. In the worm, it is genetically controlled by two parallel pathways, which are only partially reconstituted in mammals. We focused on the recapitulation of the CED-1 defined pathway in mammalian systems. We first explored and validated MEGF10, a novel receptor bearing striking structural similarities to CED-1, as a bona fide functional ortholog in mammals and hence progressed toward the analysis of molecular interactions along the corresponding pathway. We ascertained that, in a system of forced expression by transfection, MEGF10 function can be modulated by the ATP binding cassette transporter ABCA1, ortholog to CED-7. Indeed, the coexpression of either a functional or a mutant ABCA1 exerted a transdominant positive or negative modulation on the MEGF10-dependent engulfment. The combined use of biochemical and biophysical approaches indicated that this functional cooperation relies on the alternate association of these receptors with a common partner, endogenously expressed in our cell system. We provide the first working model structuring in mammals the CED-1 dependent pathway.

ATP Binding Cassette Transporter 1↗

PubMedDate not supplied

[Reluctant partner: Canada's relationship with the Pan American Health Organization (PAHO)].

Despite a strong commitment to multilateralism and international health cooperation in the post World War II era, Canada refrained form joining the Pan American Health Organization - PAHO until 1971. Drawing on letters and memos sent between Canadian diplomats and government representatives, this paper explores official Canadian accounts of the factors that delayed Canada's membership in PAHO. These factors include the initial lack of official relations between Canada and Latin America, US hegemony in the region, and budgetary constraints. Canada's cautious position regarding PAHO is also placed within the context of Canada's overall foreign policy to the region, emphasizing the parallels between Canada's reluctant association with PAHO and the evolution of Canada's engagement with the region as a whole.

Canada↗

PubMed1992

AANA journal course: update for nurse anesthetists--current concepts in cardiopulmonary resuscitation.

Developmental strides in cardiopulmonary resuscitation were paralleled by acquired knowledge of pulmonary and cardiac physiology. The evolution of the current recommendations for cardiopulmonary resuscitation have evolved over the past 40 years as a result of human trial and error and have been authenticated through laboratory research and clinical experience. Current research efforts in cardiopulmonary resuscitation are examining the mechanisms of blood flow during external cardiac massage and techniques to optimize myocardial and cerebral perfusion during the resuscitative period. The restoration of circulation with preservation of myocardial and neurological function is the essential goal during the resuscitative effort. Prior to the 1950s, the occurrence of cardiac arrest was associated with the conduct of anesthesia and surgery. Although infrequent today by comparison, cardiac arrest continues to occur with the conduct of regional and general anesthesia. This course will review the etiology of cardiac arrest during anesthesia, detail the mechanisms of blood flow during resuscitation, and review the pharmacological importance of epinephrine for the preservation of myocardial and neurologic function.

Cardiopulmonary Resuscitation↗

PubMed2005

Teaching biochemistry to medical students in Singapore--from organic chemistry to problem-based learning.

The medical faculty in the National University of Singapore started in 1905 but the Chair in Biochemistry was only established in 1927. For many years the biochemistry course consisted of the teaching of the organic chemistry of substances of physiological importance, nutrition, metabolism and hormones. In 1961, clinical biochemistry was introduced and in the 1980s, genetics and molecular biology were included. By then, most of the organic chemistry content had been removed as greater emphasis was placed on clinical correlation. Laboratory classes consisted of mock glucose tolerance tests and the measurement of various enzymes. By the 1990s, students were no longer interested in such practical classes, so a bold decision was made around 1995 to remove laboratory classes from the curriculum. Unfortunately, this meant that the medical students who might have been interested in laboratory work could no longer do such work. However, the new curriculum in 1999 gave the department an opportunity to offer a laboratory course as an elective for interested students. This new curriculum adopted an integrated approach with Genetics being taught as part of Paediatrics, and a new module (Structural and Cell Biology) comprising aspects of cell biology and biochemistry was introduced. This module is currently taught by staff from Anatomy, Physiology and Biochemistry. Some biochemistry content is now incorporated into the clinical problem scenarios of problem-based learning such as jaundice, diabetes mellitus, anorexia nervosa, etc. So the evolution of teaching biochemistry to medical students in Singapore has paralleled worldwide trends and moved from the didactic teaching of organic chemistry of biomolecules to problem-based learning using clinical cases.

Biochemistry↗

PubMed1994

A reverse gyrase with an unusual structure. A type I DNA topoisomerase from the hyperthermophile Methanopyrus kandleri is a two-subunit protein.

Reverse gyrase, an ATP-dependent topoisomerase that positively supercoils DNA, has been purified to near-homogeneity from the hyperthermophile Methanopyrus kandleri. It migrates on SDS-polyacrylamide gel electrophoresis as two principal bands with apparent molecular masses of 150 and 50 kDa. Both proteins remain associated throughout all chromatographic steps. Transfer of a radioactive phosphate from DNA to the 50-kDa protein and gel retardation experiments indicate that this protein forms the covalent complex with DNA. A blot overlay assay identifies the 150-kDa protein as the potential ATPase. This is the first evidence that a reverse gyrase can be a topoisomerase consisting of two protomers. In analogy with the DNA gyrase A subunit (DNA breakage and reunion activity) and the B subunit (ATPase), the 50- and 150-kDa components of Mka reverse gyrase have been designated the A and B subunits, respectively. Methanopyrus reverse gyrase changes DNA linking number in steps of one and its A subunit covalently binds to the 5'-DNA phosphoryl group. It nicks DNA at sites that predominantly have a cytosine at the -4-position. The same rule was derived previously for monomeric reverse gyrase from sulfur-metabolizing hyperthermophiles and for topoisomerase I from mesophilic bacteria. Based on these results, Mka reverse gyrase is classified as belonging to group A of type I topoisomerases. The structural diversity of type I group A topoisomerases parallels the diversity of type II enzymes and suggests the evolution of an essential function by gene fusion.

Chromatography, Gel↗

PubMedDate not supplied

TGF-beta isoforms and fibroblast growth factor exhibit analogous indirect antioncogenic activity through triggering of intercellular induction of apoptosis.

TGF-beta-1 has recently been shown to trigger nontransformed effector cells to induce apoptosis specifically in transformed cells. This intercellular induction of apoptosis has been discussed as a potential control step in oncogenesis. Here we show that triggering of intercellular induction of apoptosis is not a non-specific growth factor effect, but is restricted to the TGF-beta and FGF family of growth factors. Within the TGF-beta family, all isoforms triggered the intercellular induction of apoptosis with the same efficiency. This finding illustrates that these effects observed have been conserved throughout evolution, which thus points to their potential biological significance. The parallel action of TGF-beta and FGF in the intercellular induction of apoptosis correlates with the role of both families of factors in the establishment and maintenance of the transformed state. Autocrine loops of either growth factor seem to be recognized by the surrounding nontransformed cells and to evoke an apoptosis- inducing effect which thus prevents the survival and outgrowth of potential tumor cells.

Animals↗

PubMed2006

Looking for a general for some modern major models.

Computer climate models are some of the most complex scientific structures ever conceived. Consisting of hundreds of thousands of equations and running on supercomputers capable of trillions of operations per second, they chart the evolution of past and future climates across thousands of years. These simulations are breathtaking in their qualitative detail and vastly ambitious in their quantitative exactitude. However, their progress has recently been challenged by the very size and complexity of the models, factors that are also paralleled in the communities of scientists that build them. This complex co-evolution of computers and scientific communities gives us insight into the promise and limits of sciences driven by exponential increases in computing power.

Climate↗

PubMed1983

Evolution of epitopes on human and nonhuman primate lymphocyte cell surface antigens.

The T- and B-cell surface polypeptides detected by an international workshop panel of 100 mouse monoclonal antibodies (M.Ab) were biochemically defined by radioimmunoprecipitation. Eight T-cell-associated molecules and eight B-cell-associated molecules were identified by multiple antibodies in the panel. Clusters of antibodies specific for the same polypeptide were then compared for their reactivity against peripheral blood mononuclear cells (PBMC) from 11 nonhuman primate species. All the major T- and B-cell antigens present in humans were also expressed in some nonhuman primates. M.Ab to the same antigen were found to react with distinct epitope groups that differed in their phylogenetic distribution. Some epitopes were highly conserved, while other epitopes on the same molecule were only expressed in hominoids and were not detected in old world and new world monkeys. Our detailed analysis of the phylogeny of 37 T-cell antigen epitopes on ten different molecules revealed there was no clear correspondence between the number of epitopes shared and evolutionary distance. Rather the data suggest that parallelism with back mutation may be a common mechanism in the evolution of T-cell antigens. The data also show that the tissue distribution of T-cell antigens can differ between primate species; for example, M.Ab to human Tp45 Tla-Qa-like antigens that did not react with human PBMC did react with PBMC from new world monkeys.

Animals↗

PubMed1985

Derived morphology of the wrist articulations and theories of hominoid evolution. Part I. The lorisine joints.

The claim that lorisines possess wrist joint specialisations that parallel those in hominoids is refuted. The cautious, quadrupedal climbing lorisines therefore do not provide an adequate model for the locomotion of emergent hominoids, as has been suggested. The notion that the Hominoidea possess unique wrist joint synapomorphies facilitating an increased range of forearm supination, and correlated thereby with a capacity for suspensory forelimb locomotion, seems to be sustained. The lorisines do possess their own derived characters at the wrist, largely centred on the midcarpal joint, which accommodate an exaggerated habitual movement comprising ulnar deviation with extension and rotation of the sense of pronation; this produces the powerful pincer-like split hand. Rather similar but more extreme specialisations are described in schizodactylous marsupials. In all these specialised hands the habitual movement at the midcarpal joint appears to be merely an exaggeration of that occurring in the clasping type of hand found in the primitive therian mammals. This movement, about an axis running from dorsally on the radial side of the carpus with an angulation proximally towards the volar aspect on the ulnar side, apparently provided for adjustments in angulation between forearm and manus in the semi-sprawling gait of primitive non-cursorial therian mammals.

Animals↗

PubMed1988

DNA content and genetic evolution of human colorectal adenocarcinoma. A study by flow cytometry and cytogenetic analysis.

We have conducted in parallel DNA flow cytometry (FCM) and cytogenetic (CG) analysis of a series of surgical specimens from 35 human colorectal adenocarcinomas. An excellent quantitative correlation was observed (r = 0.99) between modal peak values of FCM histograms and chromosome counts. This observation confirms that aneuploidy, as defined by FCM, accurately reflects the deviation from diploidy of the genomic DNA. FCM-derived DNA patterns have been analyzed in the context of the clonal chromosomal evolution determined by CG analysis. In the metaphases of a given tumor, even if karyotypes of different ploidy exist, the presence of identical marker chromosomes suggests a common origin for the multiple populations observed by FCM. Thus, heterogeneity in DNA content within a tumor, including the polyploidization step, would be indicative of genetic evolution.

Adenocarcinoma↗

PubMed1982

Fruit age and changes in abscisic Acid content, ethylene production, and abscission rate of cotton fruits.

The relationships of fruit age, abscisic acid (ABA) concentration, ethylene evolution, and abscission rates were studied in an effort to determine why cotton (Gossypium hirsutum L., cv. Deltapine 16) fruits rarely abscise more than 15 days after anthesis. Because abscission of cotton fruits is increased by conditions that limit photosynthesis, greenhouse-grown plants with fruits of various ages were placed in dim light for 3 days to induce high rates of fruit abscission. Abscission rates, ABA concentrations, and ethylene evolution rates were determined for fruits of various ages. Almost all of the young fruits abscised, but abscission rate declined with age until almost no abscission was observed in fruits that were 15 or more days past anthesis.Dim light increased the ABA concentrations of fruits that were 6 to 11 days old but did not increase ABA concentrations in fruits that were younger or older. The concentration of ABA declined with fruit age from peak values at 4 and 6 days after anthesis. Dim light also increased ethylene evolution from fruits up to 10 days old but had little effect on ethylene production or abscission of fruits more than 11 days old. Ethylene evolution declined with fruit age from peak values at 4 and 6 days after anthesis. Fruits of various ages (from plants not exposed to dim light) were sliced to induce high rates of wound ethylene production. The results indicated that the capacity for ethylene production declined with fruit age, parallel with a decline in abscission rate. Decreases in ABA concentration and ethylene evolution with fruit age indicate that change in the capacity to synthesize these hormones, especially in response to stress, is one cause of the decline in abscission rates as cotton fruits become older.

Journal Article↗