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At least 1,279 records · Page 71Linked to original sources
PubMed1998

Protein synthesis in Giardia lamblia may involve interaction between a downstream box (DB) in mRNA and an anti-DB in the 16S-like ribosomal RNA.

Giardia lamblia, a parasitic protozoan, has been regarded as one of the most conserved eukaryotes evolved from the prokaryotes. One of its unique features appears to be the unusually short 5'-untranslated regions (UTR) (1-6 nucleotides (nts)) and the apparent absence of 5'-cap structures from its mRNAs. Transfection of the Giardia trophozoites with luciferase-encoding chimeric transcripts, flanked by the 5'- and 3'-ends of giardiavirus (GLV) (+)-strand RNA, indicated that the translational efficiency was enhanced by 5000-fold when the 5'-viral sequence extended 264 nts into the capsid coding region and fused with the luciferase open reading frame (ORF). A 13-nt downstream box (DB) was identified within this region which complements a 15-nt sequence between nts # 1382 and 1396 near the 3'-end of the Giardia 16S-like ribosomal RNA (the anti-DB). Deletion or scrambling of this DB in the mRNA leads to a significant loss of the translational efficiency in Giardia. A Shine-Dalgarno (SD)-like element was also identified at 9-14 nts upstream from the initiation codon in the viral (+)-strand RNA, but alteration of its sequence led to no change in translation. Using the sequence complementary to ribosomal anti-DB to probe the Giardia mRNAs available in the databases, each mRNA was found to contain a putative DB with an average length from 8 to 13 nts. It is thus possible that initiation of translation in Giardia may involve a DB in the coding region of mRNA that may bind to a putative anti-DB in the small ribosomal RNA through base pairing. This mechanism of ribosome recruitment, which finds a potential parallel in Escherichia coli, could illustrate a relatively close distance between Giardia and prokaryotes in terms of translation initiation, and may provide a model for studying the evolution of translation machinery.

5' Untranslated Regions↗
PubMedDate not supplied

Biomedical simulation of heat transfer in a human heart.

Theory and practical experiences from numerical simulations of heat transfer in the field of medicine are presented in this paper. The cooling of a human heart during surgery was taken as an illustrative example. All phases of the simulation process are described starting with the construction of an irregularly shaped 3-dimensional model. The mathematical model is based on diffusion and Navier-Stokes equations. The system of partial differential equations is solved by finite difference approximation using an explicit time-stepping scheme to obtain the time evolution of the solution for the complete simulated interval, which is typically 1 h. A typical domain is composed of several million voxels; therefore, the program was parallelized to speed up the simulation. A speed-up of 8.2 was obtained on 16 processors in a Linux cluster.

Algorithms↗
PubMed2004

Breast cancer associated with idiopathic thrombocytopenic purpura: a single center series of 10 cases.

The aim of this study was to define the characteristics of patients with idiopathic thrombocytopenic purpura (ITP) and breast cancer and discuss the relationship between these two diseases. Ten patients treated for breast cancer and presenting with ITP were screened for this study. The diagnosis of breast cancer was confirmed by biopsy or surgical sample. The diagnosis of ITP was defined by 1) platelet count less than 140.10(9)/l with normal or increased number of megakaryocytes on bone marrow aspirate, 2) after exclusion of thrombocytopenia-induced medication or disorders, and 3) absence of splenomegaly. ITP was diagnosed before breast cancer in three cases, concomitantly in three, and after the diagnosis of breast cancer in four cases. Platelet count and breast cancer showed an independent course in seven cases, and appeared to be correlated in the other three patients. No correlation was found between the development of ITP and tumor characteristics. In contrast, the median platelet count was 15.10(9)/l (range 3-26) for the 3 patients with a correlation between the course of ITP and breast cancer evolution and 70.10(9)/l (range 20-90) for the other cases (p = 0.05, Mann-Whitney U test). Breast cancers are associated with ITP, with a parallel course of the two diseases in one third of cases. This may suggest tumor-induced immunologic thrombocytopenia.

Adult↗
PubMed2000

Vegetative and reproductive innovations of early land plants: implications for a unified phylogeny.

As the oldest extant lineages of land plants, bryophytes provide a living laboratory in which to evaluate morphological adaptations associated with early land existence. In this paper we examine reproductive and structural innovations in the gametophyte and sporophyte generations of hornworts, liverworts, mosses and basal pteridophytes. Reproductive features relating to spermatogenesis and the architecture of motile male gametes are overviewed and evaluated from an evolutionary perspective. Phylogenetic analyses of a data set derived from spermatogenesis and one derived from comprehensive morphogenetic data are compared with a molecular analysis of nuclear and mitochondrial small subunit rDNA sequences. Although relatively small because of a reliance on water for sexual reproduction, gametophytes of bryophytes are the most elaborate of those produced by any land plant. Phenotypic variability in gametophytic habit ranges from leafy to thalloid forms with the greatest diversity exhibited by hepatics. Appendages, including leaves, slime papillae and hairs, predominate in liverworts and mosses, while hornwort gametophytes are strictly thalloid with no organized external structures. Internalization of reproductive and vegetative structures within mucilage-filled spaces is an adaptive strategy exhibited by hornworts. The formative stages of gametangial development are similar in the three bryophyte groups, with the exception that in mosses apical growth is intercalated into early organogenesis, a feature echoed in moss sporophyte ontogeny. A monosporangiate, unbranched sporophyte typifies bryophytes, but developmental and structural innovations suggest the three bryophyte groups diverged prior to elaboration of this generation. Sporophyte morphogenesis in hornworts involves non-synchronized sporogenesis and the continued elongation of the single sporangium, features unique among archegoniates. In hepatics, elongation of the sporophyte seta and archegoniophore is rapid and requires instantaneous wall expandability and hydrostatic support. Unicellular, spiralled elaters and capsule dehiscence through the formation of four regular valves are autapomorphies of liverworts. Sporophytic sophistications in the moss clade include conducting tissue, stomata, an assimilative layer and an elaborate peristome for extended spore dispersal. Characters such as stomata and conducting cells that are shared among sporophvtes of mosses, hornworts and pteridophytes are interpreted as parallelisms and not homologies. Our phylogenetic analysis of three different data sets is the most comprehensive to date and points to a single phylogenetic solution for the evolution of basal embryophytes. Hornworts are supported as the earliest divergent embryophyte clade with a moss/liverwort clade sister to tracheophytes. Among pteridophytes, lycophytes are monophyletic and an assemblage containing ferns, Equisetum and psilophytes is sister to seed plants. Congruence between morphological and molecular hypotheses indicates that these data sets are tracking the same phylogenetic signal and reinforces our phylogenetic conclusions. It appears that total evidence approaches are valuable in resolving ancient radiations such as those characterizing the evolution of early embryophytes. More information on land plant phylogeny can be found at: http: //www.science.siu.edu/ landplants/index.html.

Biological Evolution↗
PubMed2000

Molecular characterization of a new variant of toxin-coregulated pilus protein (TcpA) in a toxigenic non-O1/Non-O139 strain of Vibrio cholerae.

A toxigenic non-O1/non-O139 strain of Vibrio cholerae (10259) was found to contain a new variant of the toxin-coregulated pilus (TCP) protein gene (tcpA) as determined by PCR and Southern hybridization experiments. Nucleotide sequence analysis data of the new tcpA gene in strain 10259 (O53) showed it to be about 74 and 72% identical to those of O1 classical and El Tor biotype strains, respectively. The predicted amino acid sequence of the 10259 TcpA protein shared about 81 and 78% identity with the corresponding sequences of classical and El Tor TcpA strains, respectively. An antiserum raised against the TCP of a classical strain, O395, although it recognized the TcpA protein of strain 10259 in an immunoblotting experiment, exhibited considerably less protection against 10259 challenge compared to that observed against the parent strain. Incidentally, the tcpA sequences of two other toxigenic non-O1/non-O139 strains (V2 and S7, both belonging to the serogroup O37) were determined to be almost identical to that of classical tcpA. Further, tcpA of another toxigenic non-O1/non-O139 strain V315-1 (O nontypeable) was closely related to that of El Tor tcpA. Analysis of these results with those already available in the literature suggests that there are at least four major variants of the tcpA gene in V. cholerae which probably evolved in parallel from a common ancestral gene. Existence of highly conserved as well as hypervariable regions within the sequence of the TcpA protein would also predict that such evolution is under the control of considerable selection pressure.

Amino Acid Sequence↗
PubMed1976

Role of arginine deiminase in growth of Mycoplasma hominis.

Arginine has been considered as the major energy source of nonglycolytic arginine-utilizing mycoplasmata. When three strains of Mycoplasma arginini, and one strain each of Mycoplasma arthritidis, Mycoplasma fermentans, Mycoplasma gallinarum, Mycoplasma gallisepticum and Mycoplasma hominis were grown in the medium with high arginine concentration (34 mM) compared with low arginine (4 mM), both the protein content of the organisms and the specific activity of arginine deiminase increased. M. fermentans, the one arginine-utilizing species included in the survey which is also glycolytic, showed an increase in protein content but no increase in specific activity of the enzyme. The glycolytic non-arginine-utilizing M. gallisepticum did not show an increase in either parameter. The Km for arginine deiminase from crude cell extracts was 1.66 X 10(-4)M. The enzyme demonstrated a hyperbolic activation curve subject to substrate inhibition and was not affected by the presence of L-histidine. When mycoplasmic protein and arginine deiminase were determined for M. hominis under aerobic and anaerobic conditions, aerobically grown cells exhibited no detectable enzymatic increases until late in log phase. Higher levels of arginine deiminase were observed earlier in the anaerobic growth cycle. The rate of 14CO2 evolution from [guanido-14C]arginine was not altered in arginine-supplemented cells compared with cells grown in low arginine. In addition, CO2 production did not parallel increased arginine deiminase activity. These observations argue that arginine is used only as an alternate energy source in these organisms.

Aerobiosis↗
PubMed1992

Preliminary clinical experience with calcium antagonists in atherosclerosis. Verapamil in Hypertension Atherosclerosis Study Investigators.

Animal experiments have shown that the administration of calcium antagonists can prevent or slow the progression of atherosclerosis by inhibiting calcium overload and interfering with lipid metabolism and deposition. These encouraging results have prompted clinical trials to evaluate the effects of calcium antagonists (dihydropyridines and diphenylalkylamines) on atherosclerotic plaque formation. In patients with coronary heart disease, several studies have already shown that calcium antagonists can have a positive effect on plaque evolution, while in hypertensive patients no such study has been published to date. The Verapamil in Hypertension Atherosclerosis Study is an ongoing multicentre randomised double-blind parallel group trial comparing the antihypertensive efficacy of verapamil SR 240 mg/day with that of chlorthalidone 25 mg/day in 1464 patients with essential hypertension aged 40 to 65 years. In a randomised subgroup of patients (n = 550), who will be followed up for 3 years, B-mode ultrasonography is being employed to evaluate the effects of the 2 drugs on carotid wall thickness and carotid plaque development. Ultrasonographic evaluations are performed at baseline, after 3 months, and 1, 2 and 3 years after a standardised protocol to determine intimal-medial thickness in 4 segments of the extracranial carotid tree. The most interesting result to date is the high incidence of carotid alterations, with plaques present in 35% and arterial wall thickening in 31.8% of the 311 asymptomatic hypertensive patients processed so far. A preliminary evaluation of the antihypertensive efficacy of the trial medications after 6 months of double-blind treatment indicates a 63.5% response rate to monotherapy and a 7.8% drop-out rate because of drug inefficacy or intolerance.

Adult↗
PubMed2002

Cyclophosphamide with low or high dose prednisolone for systemic sclerosis lung disease.

OBJECTIVE: To evaluate the safety and efficacy of monthly intravenous pulses of cyclophosphamide (CP) in combination with low or high doses of prednisolone in patients with systemic sclerosis (SSc) related interstitial lung disease (ILD) with FVC < 70% of predicted. METHODS: An open label, non-parallel arm study, performed in the rheumatology outpatient clinic of a university hospital. Twenty-eight patients with SSc related ILD were evaluated. Endpoint evaluations included the evolution of high resolution computed tomography, pulmonary function tests, skin involvement and dyspnea over 12 months. Patients were treated with monthly IV CP in combination with prednisolone at low (< 10 mg/day; n = 12) or high doses (1 mg/kg/day for 4 weeks, then reducing the prednisolone by 5 mg/day on alternating days each 2 weeks; n = 16). RESULTS: In the low dose steroid group, no improvement was seen for any endpoint at 6 and 12 months of followup. In the high dose steroid group, at 12 months there was significant improvement in the percentage of "ground glass" parenchymal lung involvement (-5.7%; p = 0.003), as well as in the percentage of predicted FVC (12.4%; p < 0.001), the percentage of predicted DLCO (7.3%; p = 0.029), the percentage of skin involvement (-5.4%; p = 0.01), and the severity of dyspnea (p = 0.012). Substantial improvement was seen as early as 6 months. One patient (low dose group) died from ILD. CONCLUSION: A combination of IV pulse CP with high doses of prednisolone shows promising efficacy in improving the clinical, physiological, and radiological evolution of SSc related ILD with reversal of the underlying alveolitis.

Ambulatory Care↗
PubMed2001

[The contribution of invertebrate study to the biology of nitric oxide].

After the identification of nitric oxide (NO) with the endothelium derived-relaxing factor, many signaling mechanisms involving NO were identified through experiments on Mammals. NO activates soluble guanylyl cyclase leading to the formation of cGMP, stimulates the ADP-ribosylation of GAPDH, altering the cell energy production and combines with superoxide, generating cytotoxic peroxynitrite. NO was then progressively established as a major messenger molecule in Mammals. It is implied in the regulation of blood vessel dilatation, immune function, development and neurotransmission in brain and peripheral nervous system. Later, parallel findings were observed in Invertebrates and then, NO appeared as a signaling molecule widely spread throughout the animal kingdom and whose functions were highly conserved during evolution. The purpose of this short review is to highlight the contribution of Invertebrate studies to the knowledge of NO biology.

Animals↗
PubMed1975

[Morphological and functional variations of the muscles of invertebrates].

The problem of muscle evolution among Invertebrates has been considered, mainly in obliquely strated fibers of Annelida and in trasversally striated fibers of Insecta. In both groups the morphological variations run parallel to the functional requirements; similar modulations, in fact, have been observed in fast and slow acting muscle fibers independently from the basic pattern of Insecta and Annelida fibers. Fast acting muscles are characterized by a lesser diameter of myosin filaments and a low thin-to-thick filament ratio. On the contrary, the slow acting muscles show a greater diameter of the myosin filaments and a higher thin-to-thick filament ratio. These observations agree with the hypothesis of a common origin of almost all muscular systems.

Animals↗
PubMed2003

The evolution of the cognitive map.

The hippocampal formation of mammals and birds mediates spatial orientation behaviors consistent with a map-like representation, which allows the navigator to construct a new route across unfamiliar terrain. This cognitive map thus appears to underlie long-distance navigation. Its mediation by the hippocampal formation and its presence in birds and mammals suggests that at least one function of the ancestral medial pallium was spatial navigation. Recent studies of the goldfish and certain reptile species have shown that the medial pallium homologue in these species can also play an important role in spatial orientation. It is not yet clear, however, whether one type of cognitive map is found in these groups or indeed in all vertebrates. To answer this question, we need a more precise definition of the map. The recently proposed parallel map theory of hippocampal function provides a new perspective on this question, by unpacking the mammalian cognitive map into two dissociable mapping processes, mediated by different hippocampal subfields. If the cognitive map of non-mammals is constructed in a similar manner, the parallel map theory may facilitate the analysis of homologies, both in behavior and in the function of medial pallium subareas.

Animals↗
PubMedDate not supplied

Pattern visual evoked potentials represent an early index for the evolution of optic chiasma syndrome of tumoral etiology.

The use of visual evoked potentials in the detection of optic chiasma syndrome of tumoral etiology has been controversial in the literature. In our study the pattern visual evoked potentials (PVEP) were recorded in 22 healthy free volunteers and in 32 patients with optic chiasma syndrome (OCS) produced by tumors of the hypothalamic-pituitary area, mainly pituitary adenomas with suprasellar extension, proved by CT scan. The PVEP were recorded bilateral after monocular photic stimulation of each atropinized eye, in parallel with a complete ophthalmologic exam consisting in visual field, visual acuity and optic fundus. The main results showed that the latencies P100 recorded bilateral were correlated (p < 0.01) with the types of visual field deficiency, in each hemifield. The changes in P100 latency are more sensitive than the evolution of visual field deficiency by campimetry. The same correlation was observed between the "W" form of P wave with the visual field defect. A significant decrease (p < 0.05) of the amplitude of P100 was observed only if the visual acuity was less than 1/2. It is suggested that the PVEP is a reliable index of diagnosis and evolution for the optic chiasma syndrome aside the usual ophthalmologic exam.

Adolescent↗
PubMed2003

Heritability of resistance against ectoparasitism in the Drosophila-Macrocheles system.

Ectoparasites are abundant in natural communities, can have pronounced deleterious fitness consequences to their host and are important vectors of transmissible parasitic disease. Yet very few studies have estimated the magnitude of heritable genetic variation underlying resistance against ectoparasitism, which significantly limits our ability to predict the evolution of this ecologically important character. The present paper reports results of artificial selection for increased resistance in Drosophila nigrospiracula against ectoparasitic, haematophagous mites, Macrocheles subbadius. In this system, which occurs naturally in the Sonoran Desert of North America, ectoparasitism significantly damages the expression of host fitness traits, including longevity, fecundity and male mating success. In the present study, resistance, which was modelled as a threshold trait, responded significantly to selection applied on either sex. Realized heritability, calculated as a mean across four replicates, was estimated to be 0.152 +/- 0.014 (SE). The heritability estimate from selection on males did not differ from that on females, but both estimates differed significantly from zero. This documented presence of additive genetic variation for resistance, coupled with knowledge of the fitness consequences of ectoparasitism, indicates that the host population possesses significant evolutionary potential. Selection was applied on the pre-attachment phase, thereby targeting behavioural forms of defence. This study therefore establishes parallels between insects and other animals in their ability to protect themselves and evolve behavioural defences against ectoparasites.

Animals↗
PubMed2006

Evolution of parasitic symbioses between plants and filamentous microorganisms.

Innate defense in wild plant populations is an invaluable resource for understanding how sustainable disease control can be achieved in crops through research that is rooted in molecular and evolutionary biology. Much progress has been made from molecular research into pathogen detection and defense induction. Bacterial pathology of the wild species Arabidopsis thaliana is at the forefront in revealing parallels with animal innate immunity against infectious diseases. In plants, unlike in animals, however, expansion in biodiversity has been mirrored by tremendous diversification in filamentous parasites. The fungal and oomycete pathology of Arabidopsis is exposing opportunities to investigate the molecular bases of compatibility, plant-driven speciation of parasites, and molecular epidemiology. Such research might reveal evidence that an arms race did occur in the evolution of plant-parasite symbioses.

Plant Diseases↗
PubMed2004

An evaluation of the effects of exogenous ethephon, an ethylene releasing compound, on photosynthesis of mustard (Brassica juncea) cultivars that differ in photosynthetic capacity.

BACKGROUND: The stimulatory effect of CO2 on ethylene evolution in plants is known, but the extent to which ethylene controls photosynthesis is not clear. Studies on the effects of ethylene on CO2 metabolism have shown conflicting results. Increase or inhibition of photosynthesis by ethylene has been reported. To understand the physiological processes responsible for ethylene-mediated changes in photosynthesis, stomatal and mesophyll effects on photosynthesis and ethylene biosynthesis in response to ethephon treatment in mustard (Brassica juncea) cultivars differing in photosynthetic capacity were studied. RESULTS: The effects of ethephon on photosynthetic rate (PN), stomatal conductance (gS), carbonic anhydrase (CA) activity, 1-aminocyclopropane carboxylic acid synthase (ACS) activity and ethylene evolution were similar in both the cultivars. Increasing ethephon concentration up to 1.5 mM increased PN, gS and CA maximally, whereas 3.0 mM ethephon proved inhibitory. ACS activity and ethylene evolution increased with increasing concentrations of ethephon. The corresponding changes in gs and CA activity suggest that the changes in photosynthesis in response to ethephon were triggered by altered stomatal and mesophyll processes. Stomatal conductance changed in parallel with changes in mesophyll photosynthetic properties. In both the cultivars ACS activity and ethylene increased up to 3.0 mM ethephon, but 1.5 mM ethephon caused maximum effects on photosynthetic parameters. CONCLUSION: These results suggest that ethephon affects foliar gas exchange responses. The changes in photosynthesis in response to ethephon were due to stomatal and mesophyll effects. The changes in gS were a response maintaining stable intercellular CO2 concentration (Ci) under the given treatment in both the cultivars. Also, the high photosynthetic capacity cultivar, Varuna responded less to ethephon than the low photosynthetic capacity cultivar, RH30. The photosynthetic capacity of RH30 increased with the increase in ethylene evolution due to 1.5 mM ethephon application.

Carbon Dioxide↗
PubMed1993

On the evolution of waking and sleeping.

1. The aim of this paper is to present a new hypothesis to explain the evolution of the sleeping and waking states. 2. We propose that the reptilian waking state and the mammalian slow wave sleep are homologous states. 3. We also propose that instead of looking at the polygraphic sleep as a new evolutive acquisition of mammals and birds, it seems more convenient to look at the full waking state; the "advanced wakefulness" as the true new evolutionary acquisition of these animals. 4. These conclusions are reached after examining some available reports of slow wave electroencephalogram in waking reptiles, some other reports showing signs of rapid eye movement sleep in this same group and the coevolution between sleep states and thermoregulation. Finally, a clear parallelism between sleep ontogeny and phylogeny is shown under the light of the proposed hypothesis.

Aging↗
PubMed1998

[Evolution of monoamine receptors and the origin of motivational and emotional systems in vertebrates].

The evolving vertebrate nervous system was accompanied by major gene duplication events generating novel organs and a sympathetic system. Vertebrate neural pathways synthesizing catecholamine neurotransmitters (dopamine and noradrenaline), were subsequently recruited to process increased information demands by mediating psychomotor functions such as selective attention/predictive reward and emotional drive via the activation of multiple G-protein linked catecholamine receptor subtypes. Here we show that the evolution of these receptor-mediated events were similarly driven by forces of gene duplication, at the cephalochordate/vertebrate transition. In the cephalochordate Amphioxus, a sister group to vertebrates, a single catecholamine receptor gene was found, which based on molecular phylogeny and functional analysis formed a monophyletic group with both vertebrate dopamine D1 and beta adrenergic receptor classes. In addition, the presence of dopamine but not of noradrenaline was assayed in Amphioxus. In contrast, two distinct genes homologous to jawed vertebrate dopamine D1 and beta adrenergic receptor genes were extant in representatives of the earliest craniates, lamprey and hagfish, paralleling high dopamine and noradrenaline content throughout the brain. These data suggest that a D1/beta receptor gene duplication was required to elaborate novel catecholamine psychomotor adaptive responses and that a noradrenergic system specifically emerged at the origin of vertebrate evolution.

Animals↗
PubMed2001

Optimization of metabolic stability as a goal of modern drug design.

Metabolism and other pharmacokinetic (PK) studies have always played a critical role in helping to optimize the bioavailability and duration of action of new drugs thereby increasing their success rate. With the advent of automated combinatorial synthesis, high-throughput pharmacological testing, and the ability to create extensive databases in the past decade, drug discovery has undergone an amazing evolution. With the increased throughput of drug discovery, metabolism and other PK studies have evolved to keep pace. Often called "early ADME" studies, these studies are characterized by parallel processing and higher throughput than before. This article focuses on a particular class of early ADME (absorption, distribution mechanism, and excretion) studies known as "metabolic stability" studies. The theoretical basis for metabolic stability and its relationship to the concept of metabolic intrinsic clearance is briefly presented. Some key relationships between structure and metabolism are summarized. Several case studies from recent medicinal chemistry literature are reviewed to exemplify how metabolic stability studies influenced drug design and led to improvements in bioavailability and half-life. Finally, future trends in drug metabolism and analytical chemistry and how they may influence metabolic stability studies are reviewed.

Amidohydrolases↗