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Results for “Continuous Evolution”

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PubMed1989

Review of invasive treatments of coronary artery disease.

Coronary artery disease is a difficult clinical entity to manage, and all forms of current therapy are palliative in nature. Results from the large randomized studies have clearly demonstrated the superiority of surgical versus medical therapy in subsets of patients previously described herein. As patients with severely compromised ventricles are demonstrated to fare better with bypass procedures, the number of patients that should be operated upon continues to grow. With refinements in operative and perioperative care and increased use of the internal mammary artery as the bypass conduit, it is inevitable that more subgroups will be determined to be best managed by surgical revascularization. For the present time, medical treatment is preferred for the vast majority of patients who were shown by randomized trials not to benefit significantly from surgical intervention. However, caution must be used in excluding patients based on trial results that used surgical techniques and conduits that are ten years old. The role of angioplasty in the invasive treatment of ischemic cardiac disease is still in evolution. Although not yet proved by vigorous trials, it is a procedure that most likely will continue to be used in many clinical applications. The high rate of restenosis after angioplasty, which is a formidable problem, may be a factor that will limit the application of angioplasty to patients with acute myocardial infarction or to those who do not desire surgical intervention. The answers to these and other complex problems of patient management must await well-designed prospective trials comparing angioplastic with surgical revascularization. Clinical use of some of the experimental procedures mentioned is certain; the efficacy and role of these procedures in the treatment of ischemic cardiac disease must also be defined with future studies.

Angioplasty, Balloon↗

PubMed2003

Density waves in traffic flow of two kinds of vehicles.

Through the car-following model, the traffic flow of two types of vehicles (cars and trucks) on a single-lane flow is studied, in which drivers on different vehicles have different sensitivities and the safety distance is assumed to be the same for all vehicles. The linear analysis is carried out to determine the condition of critical stability. With the nonlinear analysis, it proves that the small fluctuation of the vehicle density near the critical stable state satisfies the Korteweg-deVries equation and different sensitivities affect only the soliton evolution. When the headway in the critical state is more than the safety distance, the density around the soliton peak exceeds the density of the critical stable state, which can be explained as the formation of traffic jam. Contrarily, when the headway state is less than the safety distance, drivers will increase the headway to avoid the jam. The direct approach of the soliton perturbation shows that drivers' sensitivity will increase the soliton's amplitude continuously. Moreover, the increase of the number of trucks in the traffic flow will slow down the evolution of the amplitude.

Journal Article↗

PubMed1998

Evolution of the diverse antifreeze proteins.

Different types of ice-growth-inhibiting antifreeze proteins, first recognized in fish, have now been isolated from insects and plants, and the list continues to expand. Their structures are amazingly diverse; how they attain the same function are subjects of intense research. Evolutionary precursors of several members have been identified - divergent proteins of apparently unrelated function. The hybridization of information from structural and molecular evolution studies of these molecules provides a forum in which issues of selection, gene genealogy, adaptive evolution, and invention of a novel function can be coherently addressed.

Amino Acid Sequence↗

PubMed2002

Experimental conditions for the continuous subcutaneous infusion of four central analgesics in rats.

For the analysis of pharmacotherapeutic regimens for chronic pain in animals, it is important to establish delivery methods in which analgesics can be administered continuously and at a constant rate for a prolonged period of time. This allows for the assessment of how drug effects may vary over time in the presence of ongoing pain. The present study determined, for four analgesic compounds, the maximal doses that met all of the following criteria: (i) water-soluble, (ii) stable over 14 days at 38 degrees C, and (iii) devoid of undesirable side-effects in normal rats, as assessed by evolution of body weight and temperature after the subcutaneous implantation of an osmotic mini-pump that continuously infused the compounds over a 14-day period. The results showed the maximal doses to be 5 mg/rat/day for morphine hydrochloride, 2.5 mg/rat/day for imipramine hydrochloride, 20 mg/rat/day for ketamine hydrochloride, and 10 mg/rat/day for gabapentin. These doses were further found to be sufficient to express each compound's representative pharmacological activity. The conditions identified here appear appropriate for future studies of these four compounds in rat models of chronic pain and neuropathic allodynia.

Acetates↗

PubMed1995

Evolution of the cell cycle.

Cell proliferation involves duplication of all cell constituents and their more-or-less equal segregation to daughter cells. It seems probable that the performance of primitive cell-like structures would have been dogged by poor duplication and segregation fidelity, and by parasitism. This favoured evolution of the genome and with it the distinction between 'genomic' components like chromosomes whose synthesis is periodic and most other 'functional' components whose synthesis is continuous. Eukaryotic cells evolved from bacterial ancestors whose fused genome was replicated from a single origin and whose means of segregating sister chromatids depended on fixing their identity at replication. Evolution of an endo- or cytoskeleton, initially as means of consuming other bacteria, eventually enabled evolution of the mitotic spindle and a new means of segregating sister chromatids whose replication could be initiated from multiple origins. In this primitive eukaryotic cell, S and M phases might have been triggered by activation of a single cyclin-dependent kinase whose destruction along with that of other proteins would have triggered anaphase. Mitotic non-disjunction would have greatly facilitated genomic expansion, now possible due to multiple origins, and thereby accelerated the tempo of evolution when permitted by environmental conditions.

Archaea↗

PubMed2001

Evolution of IESs and scrambling in the actin I gene in hypotrichous ciliates.

Germ-line (micronuclear) genes in hypotrichous ciliates are interrupted by numerous, short, noncoding, AT-rich segments called internal eliminated segments, or IESs. IESs divide a gene into macronuclear destined segments, or MDSs. IESs are excised from micronuclear genes, and the MDSs are spliced when a micronuclear genome is processed into a macronuclear genome after cell mating. In the micronuclear version of the actin I gene intramolecular recombination between IESs during evolution has put MDSs into a scrambled disorder in some but not all hypotrichs. Studies using rDNA sequences to define phylogenetic relationships among eight hypotrichs suggests that evolution of the micronuclear actin I gene proceeds by successive addition of IESs in earlier diverging species, without MDS scrambling. Continued addition of IESs and recombination among IESs in later diverging species produced actin I genes with scrambled MDSs. Subsequent to MDS scrambling, additional IESs were inserted into the more recently evolved species. Thus, IES insertions and gene scrambling occur in a progressive manner during species evolution to produce micronuclear actin I genes of increasing structural complexity.

Actins↗

PubMed1986

Acute and chronic pulmonary thromboembolism: current perspectives. Part I: Glossary of terms, historic evolution and prevalence.

Despite considerable medical as well as surgical advances, the problem of pulmonary thromboembolism, both acute and chronic, continues to plague clinicians of all medical disciplines. Approximately 650,000 to 700,000 patients per year suffer from acute pulmonary thromboembolism in the United States. Of these, approximately 60,000-70,000 die as a direct result of it. Our knowledge of the etiology, pathology, pathogenesis of pulmonary infarction, pathophysiology, accurate diagnosis, proper management (including both primary and secondary prophylaxis) of deep vein thrombi and pulmonary thromboemboli has advanced considerably during the past 15 years. These advances, which have now been adopted in the clinical practice, have already begun to indicate that not only more cases of acute and chronic pulmonary thromboembolism are being recognized than before, but also the morbidity and mortality of this disease process is declining. This is likely to improve further as our quest for safe, accurate, noninvasive and inexpensive diagnostic methods continues. Medical thromboembolectomy using thrombolytic therapy is fast replacing the surgical thromboembolectomy for patients with acute massive pulmonary thromboembolism. Better thrombolytic agents, such as tissue plasminogen activator, which selectively lyses the thromboemboli without producing significant systemic lytic state and now undergoing clinical investigation, is likely to revolutionize the management of both acute and chronic pulmonary thromboembolism because of its propensity to dissolve plasminogen-bound thrombi of any age. The majority of the patients who suffer from acute pulmonary thromboembolism recover most of their lost lung function unless cardiopulmonary reserve was compromised prior to the onset of the acute episode.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1989

Exon-intron-like pattern of the first propagating molecule?

A biogeochemical scenario is proposed, according to which prebiotic self-replication of RNA-like molecules evolved gradually from domain propagation to entire strand replication. The hypothetical replicating entities that formed an evolutionary continuity in time, the prebioectons, were characterized by self-structuring, and started their evolution from strands possessing one or more templatable domains. The inherent self-structuring implies a very early coevolution of the replicating molecules with prebiotic peptides, in line with the cassette model of Cedergren and Grosjean (1987). The proposed approach can be partially tested in the laboratory.

Biological Evolution↗

PubMed2006

Encoding and processing biologically relevant temporal information in electrosensory systems.

Wave-type weakly electric fish are specialists in time-domain processing: behaviors in these animals are often tightly correlated with the temporal structure of electrosensory signals. Behavioral responses in these fish can be dependent on differences in the temporal structure of electrosensory signals alone. This feature has facilitated the study of temporal codes and processing in central nervous system circuits of these animals. The temporal encoding and mechanisms used to transform temporal codes in the brain have been identified and characterized in several species, including South American gymnotid species and in the African mormyrid genus Gymnarchus. These distantly related groups use similar strategies for neural computations of information on the order of microseconds, milliseconds, and seconds. Here, we describe a suite of mechanisms for behaviorally relevant computations of temporal information that have been elucidated in these systems. These results show the critical role that behavioral experiments continue to have in the study of the neural control of behavior and its evolution.

Action Potentials↗

PubMed1993

Bladder management in children with genitourinary sarcoma.

Between 1977 and 1991, 14 patients were treated for genitourinary sarcoma (mean age, 7.4 years). The primary site was bladder in six patients, prostate in five, and vagina in three. Histological study showed embryonal rhabdomyosarcoma in 12 and leiomyosarcoma in 2 children. Initial therapy included biopsy followed by chemotherapy in all patients. Subsequently, five patients had anterior exenteration, four underwent partial cystectomy, and one patient had a radical prostatectomy; four patients were treated with chemotherapy and external beam pelvic irradiation (4,000 to 6,000 rads) alone. Overall survival for the group is 100% (follow-up 6 to 168 months). Two of four patients undergoing partial cystectomy had bladder augmentation at the time of surgery. All patients having partial cystectomy had negative surgical margins, are tumor free, and have volitional voiding. Two of four patients (50%) initially treated with chemotherapy and radiotherapy alone have had significant bladder deterioration requiring bladder reconstruction. There has been an evolution toward less radical, initial surgical intervention in pediatric genitourinary sarcoma; however, surgical resection continues to be the primary curative modality. Partial cystectomy with or without primary reconstruction may be preferable to exenteration for selected patients. Primary reconstruction at the time of partial cystectomy leaves a functional bladder and excellent long-term results. Children treated with chemotherapy and radiotherapy protocols alone must be monitored for late bladder deterioration.

Adolescent↗

PubMed1991

Evolution of endoscopic urethropexy: seven-year experience with various techniques.

The surgical techniques for correction of stress urinary incontinence continues to evolve particularly those utilizing the endoscopic approach. Various forms of endoscopic urethropexy have been performed in 142 women with a minimum of one-year follow-up. The cure rate for the entire series was 94 percent. In the last two years the no-incision technique was used whenever feasible (31 patients) with an identical cure rate of 94 percent. Varying degrees of urinary retention occurred in 58 percent and was even more prevalent following the no-incision technique (68%). Owing to the high incidence of urinary retention a punch suprapubic cystostomy is now used in most patients. We conclude that endoscopic urethropexy is an effective means of correcting stress urinary incontinence. The no-incision technique is associated with even less morbidity and a reduction in hospital stay without compromising the outcome.

Adult↗

PubMed2005

[Herpetic neonatal hepatitis].

Herpes simplex virus (HSV) infection can affect various organs-systems in the neonatal period. Herpetic hepatitis was seldom reported in the literature. We report on 2 cases. Firstly, a 16 day-old newborn infant was admitted because of haemorrhagic syndrome and shock. Biological assessment showed a severe hepatic insufficiency. Antibiotic and aciclovir therapy was started as HSV infection was suspected. Five days later, the herpetic attack was confirmed by polymerase chain reaction (PCR) in blood and cerebrospinal fluid (CSF). The genotye of the virus in the CSF was HSV1. Treatment included aciclovir for 21 days intravenously and 2 months orally. At 10 months, the clinical and biological examinations were normal. Secondly, a 4 day-old newborn was hospitalised because of fever and polypnea. Pulmonary X rays showed heterogeneous opacities of the right base. Serum C reactive protein was 30 mg/l. Antibiotic therapy was started. Two days later, the fever persisted while a severe hepatic insufficiency developed. The diagnosis of herpetic hepatitis was evoked and the child was given aciclovir. Forty-eight hours later, the PCR confirmed a HSV in blood, while viral culture of a mouth swab found HSV 2. Evolution was favourable after 21 days of specific and symptomatic treatment. Aciclovir treatment was continued orally for six months. Herpetic hepatitis is rare in the neonatal period. Diagnosis must be evoked early when facing severe neonatal hepatic insufficiency. Provided specific treatment, prognosis is good.

Acyclovir↗

PubMed2003

[Musculoskeletal disorders of the upper extremity associated with work: from presentation to work maintenance].

The so called Musculo-Squeletal-Disorders in the upper extremity are frequent and are responsible for a significant cost. The increase in registered work-related affections has been quite impressive in the past few years. The type of social undertaking is determinant on the evolution and final outcome of the pathology. Our proposal for a "Passport to work continuation" follows two goals: facilitate and enhance the relations between medical and social workers concerned by the patient's course reduce the time off-work, improve prevention of work related pathologies, avoid dismissal for inaptitude, start earlier a vocational training, a rehabilitation or an adaptation of the work station.

Arm↗

PubMed2005

Hybridization as an invasion of the genome.

Hybridization between species is commonplace in plants, but is often seen as unnatural and unusual in animals. Here, I survey studies of natural interspecific hybridization in plants and a variety of animals. At least 25% of plant species and 10% of animal species, mostly the youngest species, are involved in hybridization and potential introgression with other species. Species in nature are often incompletely isolated for millions of years after their formation. Therefore, much evolution of eventual reproductive isolation can occur while nascent species are in gene-flow contact, in sympatry or parapatry, long after divergence begins. Although the relative importance of geographic isolation and gene flow in the origin of species is still unknown, many key processes involved in speciation, such as 'reinforcement' of post-mating isolation by the evolution of assortative mating, will have ample opportunity to occur in the presence of continuing gene flow. Today, DNA sequence data and other molecular methods are beginning to show that limited invasions of the genome are widespread, with potentially important consequences in evolutionary biology, speciation, biodiversity, and conservation.

Journal Article↗

PubMed1984

The influence of 15(R)-15 methyl PGE2, methyl ester, on Nd:YAG laser-induced gastric ulcers.

The effect of 15(R)-15 methyl PGE2 on the evolution of gastric ulcers induced by endoscopic Nd:YAG laser photocoagulation was studied. By continuous application of 50 to 70 watt power for 4 sec at a distance of 15 mm from the gastric mucosa, reproducible ulcers can be induced. The effect of the drug in nonantisecretory doses (10 micrograms/kg) on the acute ulcer formation and on the healing rate was evaluated in mongrel dogs by light microscopy. Local administration or oral pretreatment did not influence the size or depth of acute ulcers (7.4 mm in diameter) as compared to a control series (7.2 mm). Pretreatment for several days, however, had a marked beneficial effect on the healing rate of the ulcers (1.71 mm after 7 days compared to 2.76 mm for the control series). From these data it may be concluded that 15(R)-15 methyl PGE2 has a beneficial effect on ulcer healing, even in nonantisecretory doses.

Administration, Oral↗

PubMed1996

Development and applications of in vivo clinical magnetic resonance spectroscopy.

4.1 CURRENT STATUS. While an extensive clinical literature of MRS of muscle, brain, heart and liver has been achieved, the MRS technique is not considered essential for routine diagnosis because it is inherently insensitive and metabolic changes tend to be small. However, MRS techniques have proven to be of considerable value for prognosis in some circumstances, notably for predicting outcome following hypoxic-ischaemic injury in the newborn and also in predicting graft viability following organ transplantation. The chemical specificity of MRS has been illustrated, and exploiting the non-invasive nature of the technique, metabolic fingerprinting of pathophysiological processes throughout the natural history of a wide variety of diseases is now being accomplished. Particularly exciting are the applications of 13C MRS for measuring hepatic and muscle glycogen levels, for example in diabetics, and the use of hepatic 31P MRS for assessing liver function in cirrhosis. Other areas of excitement are the applications of 1H MRS in assessing neuronal function in epilepsy and stroke, and for measuring the evolution of lactate in stroke and hypoxic-ischaemic encephalopathy. Emphasis on technique development continues, and applications still tend to be technology-led. The availability of routine clinical MRI systems with spectroscopy capabilities has given MRS studies wider applicability. The recent improvements in spatial resolution have been impressive and the technique is slowly becoming more quantitative. 4.2. FUTURE PERSPECTIVES. Given the flexibility of clinical magnetic resonance techniques, particularly magnetic resonance imaging, it is likely that MRI will be the diagnostic tool of choice in a wider range of diseases, such as multiple sclerosis, stroke, neurodegenerative conditions, sports injuries and in staging malignancies. Since proton magnetic resonance spectroscopy packages have become a routine addition to many MRI systems, it is feasible to select the MRI sequences of most value in highlighting anatomical and pathological abnormalities and to incorporate specifically selected MRS sequences to emphasize biochemical differences. Improvements in technical methodologies are central to further developments. For example, use of internal coils, such as implantable or endoscopic coils, will enable small regions of tissue to be studied in considerable detail, which may otherwise be inaccessible to measurement. Chemical MRS studies have benefited from the use of higher magnetic fields, and the same may be expected for clinical MRS studies. Whole-body magnets up to 4 T have been used in a few centres, and certainly 3 T systems are becoming more widely available with the recent tremendous interest in functional imaging. Certainly, better control of artefacts can be expected; for example, improved definition of spectral changes due to voluntary or involuntary movements. Wider use of proton decoupling methods will improve the specificity of the spectra, by allowing definitive assignments of overlapping resonances, as well as the sensitivity. Comparing PET and MRS studies, it is becoming increasingly obvious that both will be required in parallel to explore parameters of brain metabolism and function. The ability to measure 13C MR signals in the brain has been demonstrated, which allows measurements of glutamate and glucose turnover. MRS measurements have the advantage of not requiring a radioactive isotope, as well as being insensitive to activity-related changes in regional cerebral blood flow. Also the study of cerebral glucose metabolism by MRS is very promising, allowing a resolution and sensitivity comparable to PET. A combination of MRS and PET studies will allow the pathogenesis of neuropsychiatric disorders to be better understood. (ABSTRACT TRUNCATED)

Biophysical Phenomena↗

PubMedDate not supplied

Interferon and ursodeoxycholic acid combined therapy in chronic viral C hepatitis: controlled randomized trial in 203 patients.

AIMS: This prospective randomized trial was carried out in order to determine whether the long-term administration of ursodeoxycholic acid after discontinuation of interferon had any beneficial effect on the clinical course of hepatitis C virus infection. METHODS: Enrolled in the study were 203 patients with chronic active hepatitis C. They were all given: interferon alpha-2a (3 MU subcutaneously thrice a week) and ursodeoxycholic acid (10 mg/kg/day) for 9 months. At month 9, biochemical responders only were randomized into ursodeoxycholic acid treatment or placebo for 12 additional months (double blind study). RESULTS: At the end of interferon therapy, 71 patients (37%) were virological responders and 107 (56%) patients were biochemical responders and were randomized: 54 into the ursodeoxycholic acid group and 53 into the placebo group. Sustained response was evaluated 12 months after withdrawal of interferon. Sustained biochemical and virological responses were, respectively, 30% and 22% in the ursodeoxycholic acid group and 46% and 32% in the placebo group, which did not significantly differ. Histological evolution of fibrosis and necrotic inflammatory activity were similar in the two groups. CONCLUSION: Continuation of ursodeoxycholic acid therapy after withdrawal of interferon in patients with end-of-treatment response did not result in any significant improvement either in the maintenance of response to interferon or in liver histology.

Adolescent↗

PubMed1995

The dynamics of a generalized Heisenberg ferromagnetic spin chain.

We introduce a generalized Heisenberg ferromagnetic spin chain with a four-dimensional target space, and investigate its continuous limit, the generalized continuous Heisenberg model (GCHM). We reduce the dynamics of the GCHM to a nonlinear evolution of space curves in four dimensions. The space curve evolution is expressed in terms of a system of coupled nonlinear equations for the three curvatures, k(1)(x),k(2)(x),k(3)(x), of a curve in R(4). Applying the Painleve analysis to the stationary equations, we conclude that GCHM, in general, is not integrable, unless k(1) is constant. We obtain explicit solutions of the resulting stationary system under the latter condition. (c) 1995 American Institute of Physics.

Journal Article↗