SEARCH · PubMed Health

Results for “Continuous Evolution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources

PubMed1986

Diversity of neurohormonal release sites in insects: coexistence of two different (alpha and beta) types of neurohemal structure in the perisympathetic organs.

A comparative ultrastructural study of insects was made whose primitive perisympathetic organs consisted either of a single median neurohemal formation per segment (Periplaneta americana) or of two transverse formations (Carausius morosus), or again, of three--one median and two transverse--as in Locusta migratoria. The results showed that the perisympathetic organs always comprised two types of structure (alpha and beta), even when a single formation exists. In Periplaneta and Carausius, both types were seen to coexist in the same neurohemal formation. In Locusta, however, they were separated, the alpha structure constituting the median organ and the beta structure, the two transverse organs. Each of the two structures have special features: the beta structure displays the usual characteristics of a loose neurohemal organ, i.e., it is penetrated by sinuses and has neurosecretory endings devoid of a glial coat; the alpha structure, on the contrary, forms dense compact organs whose endings are covered with a continuous glial layer. During the evolution, this last structure gradually separated from the other neurohemal formations. It was observed to correspond to a single type of neurosecretory cell, distinct from all other cell types by the particular mode of its release. These results for primitive perisympathetic organs confirm earlier findings for advanced organs. They indicate that both the alpha and beta structures are generally present in insects, thus showing their importance in the physiology of these animals.

Animals↗

PubMed1987

Brain-stem monitoring. II. Preterminal BAEP changes observed until brain death in deeply comatose patients.

Preterminal BAEP changes were studied until brain death in 8 head-injured patients out of a series of 38 comas monitored by means of a system allowing high-rate sequential recording. Two different modalities of BAEP degradation were disclosed: (1) simultaneous latency increase of all components associated with a decrease of cerebral perfusion pressure (CPP), consistent with ongoing ischaemia of the posterior fossa; (2) deterioration of brain-stem components (waves III-V) with preserved or even enhanced wave I. The latter pattern was not consistently associated with any haemodynamic change and might be related to mechanical factors causing rostro-caudal deterioration of brain-stem function. The time course of BAEP degradation ranged from a few minutes to more than 10 h. In the case of slow preterminal evolution definitely pathological trends were identified even when individual BAEPs were still within normal limits. Such trends would have remained unnoticed in single BAEP records. Hypothermia and anaesthetic drugs were found to induce falsely alarming BAEP changes very similar to those seen during preterminal evolution. Our results suggest that continuous brain-stem monitoring could be helpful for management of comatose head-injured patients.

Blood Pressure↗

PubMed1994

Actin-bundling proteins.

Recent studies have greatly expanded our understanding of actin-bundling proteins. A new group of actin-bundling proteins, the fascins, has been recognized. An actin-bundling protein inhibits actin depolymerization even under conditions in which it cannot produce a gel, which suggests that bundling proteins may affect actin filament dynamics. A villin-like protein is present in Dictyostelium, shedding doubt on current ideas on the evolution of villin. Domain mapping continues to be a major thrust of research into most groups of bundling proteins.

Actinin↗

PubMed2005

[Bioabsorbable osteofixation devices].

There is continued interest in the development of new biomaterials. The application of new implantable biomaterials requires intense research and thorough evaluation. Much time and effort has been required to overcome the risks and problems associated with the bioabsorbable devices. For surgical bone fixation, these materials were investigated since the 1960's. Different polymer properties were explored to ensure adequate strength and biocompatibility. High-molecular-weight bioabsorbable polymers were initially used, followed by addition of reinforcement materials. The most recent materials are self-reinforced, small yet strong devices. The newer generations contain bioactive substances such as antibiotics and growth factors. Bioabsorbable materials are constantly changing as we try to adopt the principles of tissue engineering. Surgeons are using new techniques to exploit these polymers and their bioabsorbable properties. It is hoped that this multidisciplinary approach of surgery and research will continue to help the further evolution of biomaterial science.

Absorbable Implants↗

PubMed2026

Escape and survival: transposon adaptations in the face of insect host silencing.

Transposable elements (TEs) are mobile genetic sequences that have long resided within host genomes. Over this shared history, a continuous process of co-evolution has forged a diverse array of dynamic TE-host interactions. In an evolutionary arms race, hosts must silence TEs to protect genome integrity from deleterious mutations by TE insertions, while TEs must evade this silencing to survive. TE adaptations to host genomes have recently gained prominence, following many discoveries in eukaryotic genomes. Here, I discuss TE strategies to evade host silencing and ensure their long-term persistence within host genomes, focusing on insects as the primary model system. Furthermore, by describing host silencing, I postulate potential evasive mechanisms that may drive TE adaptation within host genomes.

Journal Article↗

PubMed2005

International trends in the treatment of cleft lip and palate.

This article presents a contemporary (2004) survey of the methods and timing used in the care of cleft patients. The results are compared, when possible, with those of a similar study published by the lead author in 1998 and with those of the Eurocleft Project that took place from 1996 to 2000. Although very little uniformity is seen in the care of cleft patients, this comparison demonstrates a significant degree of agreement on many aspects of cleft care and a continuing process of adaptation and evolution in the field of cleft lip and palate surgery.

Child↗

PubMed2005

Unenhanced CT and acute stroke physiology.

Unenhanced CT remains the most widely used imaging technique and is the standard of care for acute stroke evaluation. Early ischemic signs (EIS) within the first 3 to 6 hours of symptom onset (eg, parenchymal hypodensity, sulcal effacement, and dense vessel) have been advocated as a triage tool for thrombolytic therapy. Recent studies have challenged the relevance of these EIS within 3 hours of stroke onset, with advanced MR and CT methods increasingly competing with unenhanced CT as the primary imaging modality for acute ischemia. Nonetheless, the insights regarding acute stroke physiology provided by studying the CT evolution of early ischemic signs continue to be valuable for the informed interpretation of all stroke images. It is these insights that comprise the topic of this article.

Acute Disease↗

PubMed2004

Detoxification of the cruciferous phytoalexin brassinin in Sclerotinia sclerotiorum requires an inducible glucosyltransferase.

The phytoalexins, brassinin, 1-methoxybrassinin and cyclobrassinin, were metabolized by the stem rot fungus Sclerotinia sclerotiorum into their corresponding glucosyl derivatives displaying no detectable antifungal activity. Importantly, co-incubation of S. sclerotiorum with camalexins, various phytoalexin analogs, and brassinin indicated that a synthetic camalexin derivative could slow down substantially the rate of brassinin detoxification. Furthermore, inducible brassinin glucosyltransferase (BGT) activity was detected in crude cell-free extracts of S. sclerotiorum. BGT activity was induced by the phytoalexin camalexin, and the brassinin analogs methyl tryptamine dithiocarbamate and methyl 1-methyltryptamine dithiocarbamate. The overall results suggest that the fungus S. sclerotiorum in its continuous adaptation and co-evolution with brassinin producing plants, has acquired efficient glucosyltransferase(s) that can disarm some of the most active plant chemical defenses.

Antifungal Agents↗

PubMed1968

Renaturation and hybridization studies of mitochondrial DNA.

The products of the renaturation reaction of mitochondrial DNA from oocytes of Xenopus laevis have been studied by electron microscopy and CsCl equilibrium density gradient centrifugation. The reaction leads to the formation of intermediates containing single-stranded and double-stranded regions. Further reactions of these intermediates result in large complexes of interlinking double-stranded filaments. The formation of circular molecules of the same length as native circles of mitochondrial DNA was also observed. The formation of common high molecular weight complexes during joint reannealing of two DNA's with complementary sequences was used as a method to detect sequence homology in different DNA samples. Although this method does not produce quantitative data it offers several advantages in the present study. No homologies could be detected between the nuclear DNA and the mitochondrial DNA of X. laevis or of Rana pipiens. In interspecies comparisons homologies were found between the nuclear DNA's of X. laevis and the mouse and between the mitochondrial DNA's of X. laevis and the chick, but none between the mitochondrial DNA's of X. laevis and yeast. These results are interpreted as indicating the continuity of mitochondrial DNA during evolution.

Animals↗

PubMed1998

Unequal cross-over is involved in human alpha satellite DNA rearrangements on a border of the satellite domain.

It can be invoked from the theory of tandem repeat homogenization that DNA on a satellite/non-satellite border may carry sequence marks of molecular processes basic to satellite evolution. We have sequenced a continuous 17-kb alpha satellite fragment bordering the non-satellite in human chromosome 21, which is devoid of higher-order repeated structure, contains multiple rearrangements, and exhibits higher divergence of monomers towards the border, indicating the lack of efficient homogenization. Remarkably, monomers have been found with mutually supplementary deletions matching each other as reciprocal products of unequal recombination, which provide evidence for unequal cross-over as a mechanism generating deletions in satellite DNA.

Base Sequence↗

PubMed1998

Percutaneous interbody fusions.

Percutaneous interbody fusion procedures have evolved as a result of the need for precise and specific access corridors to facilitate the application of technology to perform these procedures. Endoscopic visualization has expanded minimally invasive capabilities, particularly in the thoracic and lumbar spine. Refinement of grafting concepts and structural composition continues. Based on the historical evolution of the described percutaneous interbody fusion procedures, the future of minimally invasive interbody arthrodesis shows promise through the ongoing definition of access corridors and the refinement of operative tools and techniques.

Humans↗

PubMed2003

A biogeochemical cycle for aluminium?

The elaboration of biogeochemical cycles for elements which are known to be essential for life has enabled a broad appreciation of the homeostatic mechanisms which underlie element essentiality. In particular they can be used effectively to identify any part played by human activities in element cycling and to predict how such activities might impact upon the lithospheric and biospheric availability of an element in the future. The same criteria were the driving force behind the construction of a biogeochemical cycle for aluminium, a non-essential element which is a known ecotoxicant and a suspected health risk in humans. The purpose of this exercise was to examine the concept of a biogeochemical cycle for aluminium and not to review the biogeochemistry of this element. The cycle as presented is rudimentary and qualitative though, even in this nascent form, it is informative and predictive and, for these reasons alone, it is deserving of future quantification. A fully fledged biogeochemical cycle for aluminium should explain the biospheric abundance of this element and whether we should expect its (continued) active involvement in biochemical evolution.

Aluminum↗

PubMed2001

Immunohistochemical localization and electrophysiological action of nociceptin/orphanin-FQ in the snail (Helix aspersa) neurons.

We report the existence and anatomical distribution to nociceptin/orphanin-FQ (N/O FQ)-like immunoreactivity in neurons and fibers in the perioesophageal ganglia of the snail (Helix aspersa). Intracellular recordings from perioesophageal ganglion neurons showed that the application of 10 microM N/O FQ produced an excitatory action in 22% of the neurons studied and an inhibitory action in 33% of the neurons regardless of their origin (cerebral or parietal ganglion). Our result provides evidence that N/O FQ-like peptide is located in whole perioesophageal ganglia (mainly in the cerebral one), and that it may serve as a neuromodulator of the neuronal spike discharge. These data support the idea that the N/O FQ opioid system has an early phylogenetic origin and a functional continuity during the course of evolution.

Action Potentials↗

PubMed2000

Merging clinical pathway programs as part of overall health system mergers: a ten-step guide. Spectrum Health.

BACKGROUND: Mergers, acquisitions, and reorganizations can be stressful and accompanied by ambivalence, confusion, and uncertainty. Providing clear and simple steps for merging clinical pathways may help organizations move through the transition process more smoothly. The ten steps according to which Spectrum Health merged its pathway program-conduct an inventory of previous efforts, plan for the ideal program, bring staff together early in the merger process, decide on a common format, standardize the development and revision process, standardize a reporting tool, create a clinical pathway manual, implement an educational plan, present the program to key customers, and appoint an advisory group-need not be done sequentially. The ten-step pathway merger program uses pathways as a means to improve the quality of the care provided, with a focus on multidisciplinary clinical pathway teamwork. Before the merger, the two hospital systems' pathway programs used different approaches to operations and pathway format. When the announcement to merge came in September 1997, steps to merge the clinical pathway programs began. DISCUSSION: More than two years into the merger, Spectrum Health continues to struggle with the evolution of the health system. Clinical pathways represent just one of the significant and extensive issues related to organizational mergers; organizational values, finances, vision, mission, customer relations, strategic priorities, and people issues are a few of the others. Focusing on merging programs such as clinical pathway programs can help put one large piece of the merger puzzle in place and reduce some of the ambiguity associated with all mergers. Executive support is critical to the success of the clinical pathway program.

Critical Pathways↗

PubMed2001

Effect of monochromatic UV-B radiation on electron transfer reactions of Photosystem II.

The adverse effect of low intensity, small band UV-B irradiation (lambda = 305 +/- 5 nm, I = 300 mW m(-2)) on PS II has been studied by comparative measurements of laser flash-induced changes of the absorption at 325 nm, DeltaA(325)(t), as an indicator of redox changes in Q(A), and of the relative fluorescence quantum yield, F(t)/F(o), in PS II membrane fragments. The properties of untreated control were compared with those of samples where the oxygen evolution rate under illumination with continuous saturating light was inhibited by up to 95%. The following results were obtained: a) the detectable initial amplitude (at a time resolution of 30 mus) of the 325 nm absorption changes, DeltaA(325), remained virtually invariant whereas the relaxation kinetics exhibit significant changes, b) the 300 mus kinetics of DeltaA(325) dominating the relaxation in UV-B treated samples was largely replaced by a 1.3 ms kinetics after addition of MnCl(2), c) the extent of the flash induced rise of the relative fluorescence quantum yield was severely diminished in UV-B treated PS II membrane fragments but the relaxation kinetics remain virtually unaffected. Based on these results the water oxidizing complex (WOC) is inferred to be the primary target of UV-B impairment of PS II while the formation of the 'stable' radical pair P680(+*)Q(A) (-) (*) is almost invariant to this UV-B treatment.

Journal Article↗

PubMed2000

Central serous chorioretinopathy following pigment epithelium detachment: fluorescein and indocyanine green angiography follow-up.

PURPOSE: To evaluate the evolution from idiopathic serous pigment epithelium detachment (PED) to central serous chorioretinopathy (CSC). METHODS: Fluorescein angiography (FA) and indocyanine green angiography (ICGA) were performed using the digital imaging system Topcon IMAGEnet H 1024. RESULTS: A leakage point which later became the typical smokestack image of a CSC was found in the upper margin of the persistent PED. Dilation of the choroidal vessels under the detached neuroepithelium was also seen. CONCLUSIONS: Clinical and angiographic evidence about the relation between the two entities can help us to understand CSC as a potential evolution of PED and to continue searching for the common injury of the pigment epithelium which probably is the primary event.

Choroid↗

PubMed2005

Rat liver betaine-homocysteine S-methyltransferase equilibrium unfolding: insights into intermediate structure through tryptophan substitutions.

Equilibrium folding of rat liver BHMT (betaine-homocysteine methyltransferase), a TIM (triosephosphate isomerase)-barrel tetrameric protein, has been studied using urea as denaturant. A combination of activity measurements, tryptophan fluorescence, CD and sedimentation-velocity studies suggested a multiphasic process including two intermediates, a tetramer (I4) and a monomer (J). Analysis of denaturation curves for single- and six-tryptophan mutants indicated that the main changes leading to the tetrameric intermediate are related to alterations in the helix alpha4 of the barrel, as well as in the dimerization arm. Further dissociation to intermediate J included changes in the loop connecting the C-terminal alpha-helix of contact between dimers, disruption of helix alpha4, and initial alterations in helix alpha7 of the barrel, as well as in the dimerization arm. Evolution of the monomeric intermediate continued through additional perturbations in helix alpha7 of the barrel and the C-terminal loop. Our data highlight the essential role of the C-terminal helix in dimer-dimer binding through its contribution to the increased stability shown by BHMT as compared with other TIM barrel proteins. The results are discussed in the light of the high sequence conservation shown by betaine-homocysteine methyltransferases and the knowledge available for other TIM-barrel proteins.

Amino Acid Substitution↗

PubMed2006

Microsporidian mitosomes retain elements of the general mitochondrial targeting system.

Microsporidia are intracellular parasites that infect a variety of animals, including humans. As highly specialized parasites, they are characterized by a number of unusual adaptations, many of which are manifested as extreme reduction at the molecular, biochemical, and cellular levels. One interesting aspect of reduction is the mitochondrion. Microsporidia were long considered to be amitochondriate, but recently a tiny mitochondrion-derived organelle called the mitosome was detected. The molecular function of this organelle remains poorly understood. The mitosome has no genome, so it must import all its proteins from the cytosol. In other fungi, the mitochondrial protein import machinery consists of a network series of heterooligomeric translocases and peptidases, but in microsporidia, only a few subunits of some of these complexes have been identified to date. Here, we look at targeting sequences of the microsporidian mitosomal import system and show that mitosomes do in some cases still use N-terminal and internal targeting sequences that are recognizable by import systems of mitochondria in yeast. Furthermore, we have examined the function of the inner membrane peptidase processing enzyme and demonstrate that mitosomal substrates of this enzyme are processed to mature proteins in one species with a simplified processing complex, Antonospora locustae. However, in Encephalitozoon cuniculi, the processing complex is lost altogether, and the preprotein substrate functions with the targeting leader still attached. This report provides direct evidence for presequencing processing in mitosomes and also shows how a complex molecular system has continued to degenerate throughout the evolution of microsporidia.

Amino Acid Sequence↗