SEARCH · PubMed Health

Results for “Compensatory 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.

106 records · Page 6Linked to original sources

PubMed1991

[The osmoregulatory and natriuretic functions of the kidneys in the early stages of the evolution of hypertension].

Overall 78 men were examined. Of these, 30 presented with borderline arterial hypertension (BAH), 30 with stage I essential hypertension (EH), and 18 healthy subjects served as control. To assess osmoregulating and natriuretic renal functions, water and water plus salt were administered (at a rate of 22 ml water or isotonic sodium chloride per kg bw). Use was made of classic approaches in this case, with the determination of K+, Na+ excretion, blood plasma and urine osmolarity, calculation of the concentration index, clearance of osmotic-active substances and free water, total reabsorption of Na in the distal parts of nephron and intensity of that process. Besides, flame photometry was employed to measure blood K+, Na+ concentration and RIA to examine plasma renin activity. The data obtained indicate the heterogeneity of the patients with BAH and stage I EN according to the response to water and water and salt administration. Approximately 1/3 of the patients showed a tendency towards water retention in the body as well, which is common to patients with the volume-dependent form of arterial hypertension. In that case the compensatory potentialities of modulating renin-angiotensin system activity were preserved.

Adult↗

PubMed1992

Protein restriction and progression of chronic renal failure.

The effect of protein restriction upon the rate of renal functional decline was studied in 7 patients with moderate chronic renal failure (CRF). The rate of progression of CRF was evaluated by the reciprocal of plasma creatinine concentration (1/Cr) in time method, every 1-3 months, during 12 months while on ad-libitum diet and 23-40 months thereafter while on protein restriction. While on ad-libitum diet, 4/7 patients showed a progressive disease and the other 3 showed a relatively stable evolution. Six months after protein restriction, patients with a previous progressive disease showed an amelioration in the decline in renal function, and those with stable CRF showed a worsening of the disease in two cases and an improvement in the other one. During the first six months on low protein diet, a transitory increase in plasma creatinine concentration was observed, being maximum at 2.7 months. Plasma urea concentration fell, after protein restriction, to values close to that predicted at the time of the prescription of the diet. Mean systolic and diastolic arterial blood pressure remained stable throughout the study and it was not necessary to change the pharmacological treatment. Our data show that protein restriction decreases the rate of progression of CRF in patients with previous progressive disease. This benefit may result from the suppression of compensatory hyperfiltration induced by low protein diet, as suggested by the increase in plasma creatinine concentration.

Adult↗

PubMed1994

Base pairing between Escherichia coli RNase P RNA and its substrate.

Base pairing between the substrate and the ribozyme has previously been shown to be essential for catalytic activity of most ribozymes, but not for RNase P RNA. By using compensatory mutations we have demonstrated the importance of Watson-Crick complementarity between two well-conserved residues in Escherichia coli RNase P RNA (M1 RNA), G292 and G293, and two residues in the substrate, +74C and +75C (the first and second C residues in CCA). We suggest that these nucleotides base pair (G292/+75C and G293/+74C) in the ribozyme-substrate complex and as a consequence the amino acid acceptor stem of the precursor is partly unfolded. Thus, a function of M1 RNA is to anchor the substrate through this base pairing, thereby exposing the cleavage site such that cleavage is accomplished at the correct position. Our data also suggest possible base pairing between U294 in M1 RNA and the discriminator base at position +73 of the precursor. Our findings are also discussed in terms of evolution.

Base Composition↗

PubMed1990

Nucleolin gene organization in rodents: highly conserved sequences within three of the 13 introns.

The complete nucleotide (nt) sequence of the rat nuc gene encoding nucleolin, the major nucleolar-specific protein in eukaryotic exponentially growing cells, is compared with the corresponding locus recently characterized in mouse. [Bourbon et al., J. Mol. Biol. 200 (1988) 627-638]. In both murine species the genomic organization has been strikingly conserved during evolution, i.e., the coding region extends over 9 kb and is split into 14 exons, encoding a 712-amino acid protein. Moreover, all the exon-intron junction positions were strictly maintained during evolution. More unexpectedly, this analysis revealed that several introns contain highly conserved sequence elements of about 120 nt. The nt sequence of the homologous locus isolated from a Chinese hamster genomic clone established that these regions were under unusually high selective constraints (84-96% identity between the hamster and murine nuc genes) and, although they do not contain open reading frames, they surprisingly appear to be more conserved than most of the exons, suggesting that they play an important role. Such an element of 130 nt presents features of known genes transcribed by RNA polymerase III. Furthermore, in the rat nuc pre-mRNA the 5'- and 3'-end regions of the last intron are fully complementary over 16 nt, and so are predicted to be included in a prominent stem structure. Moreover, an homologous RNA stem structure can be derived from the mouse sequence, including two compensatory nt changes. As the secondary structure would occlude the canonical sequences required for the proper excision of this intron in both murine species, this remarkable finding could be relevant to the regulation of the nuc gene expression at the RNA processing level.

Amino Acid Sequence↗

PubMed1989

[Various immune functions (with particular attention to NK cells) in young people with frequent episodes of pharyngitis].

In four girls, selected during three years of ambulatory observations, the evolution of repeated upper respiratory tract infection events, under the immunologic aspect, has been studied. The group of girls, with age between 13 and 16 years, practically formed a small casuistry, as an experimental recruitment. With the aim to find the causes of the told infectious events, firstly were checked numerous immune functions, successively were evaluated only the ones that had resulted altered (percentage number of "NK" cells, complement "C3" fraction and "T4" lymphocytes). Particularly significative variations, toward diminution, of the "NK" cells number related to the most compelling school attendance periods were recognized. What observed could let hypothesize that stress and emotions , correlated to scholastic events negatively influence some immune functions, peculiarly the number of "NK" cells. To the lowering of these cells could correspond a facilitation and higher frequency of upper respiratory tract infections (with pharynx as an epicenter), likely by viral aetiology. The subsequent vicarious and/or compensatory intervention by other immune functions could allow, however, the spontaneous recovery, without chemotherapeutic recourse, of the infectious events, that could arise with higher frequency but, most likely, with lower seriousness than could happen when "NK" cells normally act.

Adolescent↗

PubMed1986

The pathophysiology of renovascular hypertension.

In hypertension associated with renal artery stenosis, the evolution of the raised blood pressure can conveniently be considered in three phases. In the first phase, blood pressure is raised by the direct pressor action of elevated peripheral plasma angiotensin II. In the second phase, circulating angiotensin II may be more modestly raised, but probably is still important in pathogenesis. Occasionally in phase II there is rapidly advancing elevation of renin, angiotensin II and aldosterone and severe hypertension, with sodium and potassium depletion. In the much later third phase, angiotensin II is not elevated, and the renin system may no longer be concerned in the hypertension. In phases I and II, but not in phase III, relief of the stenosis, removal of the affected kidney, or lowering of angiotensin II with converting enzyme inhibitors, can correct the hypertension. In the affected kidney with renal artery stenosis, the intrarenal content of renin is raised and its distribution altered; these changes represent compensatory local actions. The affected kidney secretes both active and inactive renin, while there is suppression of renin secretion by the contralateral kidney which becomes a net extractor of angiotensin II.

Aldosterone↗

PubMed2016

Loss of neurogenesis in Hydra leads to compensatory regulation of neurogenic and neurotransmission genes in epithelial cells.

Hydra continuously differentiates a sophisticated nervous system made of mechanosensory cells (nematocytes) and sensory-motor and ganglionic neurons from interstitial stem cells. However, this dynamic adult neurogenesis is dispensable for morphogenesis. Indeed animals depleted of their interstitial stem cells and interstitial progenitors lose their active behaviours but maintain their developmental fitness, and regenerate and bud when force-fed. To characterize the impact of the loss of neurogenesis in Hydra, we first performed transcriptomic profiling at five positions along the body axis. We found neurogenic genes predominantly expressed along the central body column, which contains stem cells and progenitors, and neurotransmission genes predominantly expressed at the extremities, where the nervous system is dense. Next, we performed transcriptomics on animals depleted of their interstitial cells by hydroxyurea, colchicine or heat-shock treatment. By crossing these results with cell-type-specific transcriptomics, we identified epithelial genes up-regulated upon loss of neurogenesis: transcription factors (Dlx, Dlx1, DMBX1/Manacle, Ets1, Gli3, KLF11, LMX1A, ZNF436, Shox1), epitheliopeptides (Arminins, PW peptide), neurosignalling components (CAMK1D, DDCl2, Inx1), ligand-ion channel receptors (CHRNA1, NaC7), G-Protein Coupled Receptors and FMRFRL. Hence epitheliomuscular cells seemingly enhance their sensing ability when neurogenesis is compromised. This unsuspected plasticity might reflect the extended multifunctionality of epithelial-like cells in early eumetazoan evolution.

Animals↗

PubMed1991

A phylogenetic study of U4 snRNA reveals the existence of an evolutionarily conserved secondary structure corresponding to 'free' U4 snRNA.

The nucleotide sequence of Physarum polycephalum U4 snRNA*** was determined and compared to published U4 snRNA sequences. The primary structure of P polycephalum U4 snRNA is closer to that of plants and animals than to that of fungi. But, both fungi and P polycephalum U4 snRNAs are missing the 3' terminal hairpin and this may be a common feature of lower eucaryote U4 snRNAs. We found that the secondary structure model we previously proposed for 'free' U4 snRNA is compatible with the various U4 snRNA sequences published. The possibility to form this tetrahelix structure is preserved by several compensatory base substitutions and by compensatory nucleotide insertions and deletions. According to this finding, association between U4 and U6 snRNAs implies the disruption of 2 internal helical structures of U4 snRNA. One has a very low free energy, but the other, which represents one-half of the helical region of the 5' hairpin, requires 4 to 5 kcal to be open. The remaining part of the 5' hairpin is maintained in the U4/U6 complex and we observed the conservation, in all U4 snRNAs studied, of a U bulge residue at the limit between the helical region which has to be melted and that which is maintained. The 3' domain of U4 snRNA is less conserved in both size and primary structure than the 5' domain; its structure is also more compact in the RNA in solution. In this domain, only the Sm binding site and the presence of a bulge nucleotide in the hairpin on the 5' side of the Sm site are conserved throughout evolution.

Animal Population Groups↗

PubMed1989

Genetic segregation and the maintenance of sexual reproduction.

Sexual reproduction confronts evolutionary biology with a paradox: other things being equal, an asexual (all-female) population will have twice the reproductive potential of a competing sexual population and therefore should rapidly drive the sexual population to extinction. Thus, the persistence of sexual reproduction in most life forms implies a compensatory advantage to sexual reproduction. Work on this problem has emphasized the evolutionary advantages produced by the genetic recombination that accompanies sexual reproduction. Here we show that genetic segregation produces an advantage to sexual reproduction even in the absence of an advantage from recombination. Segregation in a diploid sexual population allows selection to carry a single advantageous mutation to a homozygous state, whereas two separate mutations are required in a parthenogenetic population. The complete fixation of advantageous mutations is thus delayed in a heterozygous state in asexual populations. Calculation of the selective load incurred suggests that it may offset the intrinsic twofold reproductive advantage of asexual reproduction and maintain sexual reproduction in diploid populations.

Animals↗

PubMed1992

Left ventricular hypertrophy as a risk factor in arterial hypertension.

Data on the evolution and prognostic implications of left ventricular hypertrophy (LVH) determined by ECG, chest X-ray and echocardiogram in the Framingham Study are reviewed. Echocardiographic examination provides the most sensitive and specific measure of left ventricular hypertrophy, providing a quantitative evaluation of the anatomical condition. Chest X-ray evaluation is also more sensitive than the ECG, but less specific than the echocardiogram. When ECG-LVH is present, X-ray and echocardiographic LVH are often found; but, when negative, the ECG clearly does not exclude anatomical LVH. The incidence of each variety of LVH increases with age, weight and blood pressure. Although it may also appear following coronary heart disease (CHD), valvular deformity and congenital cardiac defects, the former are the major determinants of LVH in the general population. Each contributes independently to the occurrence of LVH. LVH has emerged as a powerful non-invasive indicator of increased vulnerability to the occurrence of major cardiovascular disease outcomes in hypertension. It appears that X-ray and echocardiographic LVH measure anatomical hypertrophy, whereas the ECG variety is also indicative of ischaemic myocardial involvement when repolarization abnormality is present. Hypertension clearly predisposes to both anatomical and ECG-LVH which cannot be taken as an incidental compensatory feature since at any blood pressure those with ECG-LVH, X-ray or echo LVH are distinctly more prone to cardiovascular sequelae. ECG-LVH carries a greater risk than anatomical (X-ray) LVH. ECG-LVH with repolarization abnormality is more dangerous than that with voltage alone. The latter appears to reflect chiefly the severity and duration of accompanying hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗

PubMed1984

Xenopus laevis 28S ribosomal RNA: a secondary structure model and its evolutionary and functional implications.

Based upon the three experimentally derived models of E. coli 23S rRNA (1-3) and the partial model for yeast 26S rRNA (4), which was deduced by homology to E. coli, we derived a secondary structure model for Xenopus laevis 28S rRNA. This is the first complete model presented for eukaryotic 28S rRNA. Compensatory base changes support the general validity of our model and offer help to resolve which of the three E. coli models is correct in regions where they are different from one another. Eukaryotic rDNA is longer than prokaryotic rDNA by virtue of introns, expansion segments and transcribed spacers, all of which are discussed relative to our secondary structure model. Comments are made on the evolutionary origins of these three categories and the processing fates of their transcripts. Functionally important sites on our 28S rRNA secondary structure model are suggested by analogy for ribosomal protein binding, the GTPase center, the peptidyl transferase center, and for rRNA interaction with tRNA and 5S RNA. We discuss how RNA-RNA interactions may play a vital role in translocation.

Animals↗

PubMed1989

Evolution of left ventricular function after intracoronary thrombolysis for acute myocardial infarction.

The temporal evolution of left ventricular (LV) function after intracoronary streptokinase therapy for acute myocardial infarction (AMI) was assessed from the data of 264 patients who had complete occlusion of either the left anterior descending or the right coronary artery before treatment. Angiography was performed immediately, and at 3 days and 6 months after AMI in 91%, 71% and 47% of the study group, respectively. Wall motion was measured by the centerline method. In patients with sustained reperfusion, the ejection fraction decreased at 3 days (delta = -2.0 +/- 9.9%, n = 134, p = 0.02) and recovered later (from 54 +/- 12% acutely to 57 +/- 12% at 6 months, n = 82, p less than 0.05). These changes in global function were associated with a marked regression in hyperkinesis in the noninfarcted wall by 3 days, and delayed recovery of wall motion in the infarct region (delta = 0.2 +/- 0.9 at 3 days, p = 0.055; 1.0 +/- 1.2 at 6 months, p less than 0.001). Patients without reperfusion or with reocclusion had a more severe decrease in ejection fraction at 3 days, and little or no subsequent functional recovery. The length of the hypokinetic segment increased significantly by 3 days but subsequently diminished to slightly less than the acute value. It is concluded that full recovery of ischemically impaired myocardium takes greater than 3 days, but compensatory hyperkinesis regresses earlier so that global LV function deteriorates by the third day. Variability or deterioration of LV function early after AMI need not be due to infarct extension; it can reflect regression of hyperkinesis in the noninfarcted region.

Angiography↗

PubMed1990

Phylogenetic and genetic evidence for base-triples in the catalytic domain of group I introns.

Understanding the mechanisms by which ribozymes catalyse chemical reactions requires a detailed knowledge of their structure. The secondary structure of the group I introns has been confirmed by comparison of over 70 published sequences, by chemical protection studies, and by genetic experiments involving compensatory mutations. Phylogenetic data can also be used to identify tertiary interactions in RNA molecules. This was first done by Levitt, who predicted tertiary interactions in transfer RNA, which were subsequently confirmed by X-ray crystallography. More recently, sequence comparison data have been used to predict tertiary interactions in ribosomal RNA. We have searched a complete alignment of the core regions of group I introns for evolutionary covariations that could not be ascribed to classical Watson-Crick or wobble base pairings. Here we describe two examples of phylogenetic covariation that are most simply explained by postulating hydrogen-bonded base-triples similar to those found in tRNA. Genetic experiments with the Tetrahymena and sunY introns confirm the importance of these interactions for the structure of the ribozyme.

Animals↗

PubMed1995

Lilly Lecture 1994. The beta-cell in diabetes: from molecular genetics to clinical research.

Pancreatic insulin secretion rates can be accurately derived by mathematical deconvolution of peripheral C-peptide concentrations either by using individual C-peptide kinetic parameters obtained by analysis of the decay curve of biosynthetic human C-peptide or by using published group parameters with appropriate adjustments for age and degree of obesity. Since the cross-reactivity of proinsulin and related peptides is low (< 10%) in many C-peptide assays, this experimental approach avoids the spurious increase in insulin immunoreactivity resulting from cross-reactivity with proinsulin and related peptides in the insulin assay. Application of this technique has demonstrated that the phenotypic expression of beta-cell dysfunction differs in subjects with different genetic mechanisms of non-insulin-dependent diabetes mellitus (NIDDM). Subjects who have maturity-onset diabetes of the young (MODY) due to mutations in the glucokinase gene demonstrate different patterns of altered insulin secretion when compared with subjects who have mutations in the MODY1 gene on chromosome 20. Glucokinase mutations affect the ability of the beta-cell to detect and respond to small increases in glucose above the basal level. However, compensatory mechanisms operative in vivo, which include a priming effect of glucose on insulin secretion, limit the severity of the observed insulin secretory defect, resulting in a generally mild clinical course in these subjects. In contrast, mutations in the MODY1 gene are associated with an inability to increase insulin secretion as the plasma glucose concentration increases above 7-8 mmol/l and the normal priming effect of glucose on insulin secretion is lost. These characteristics of the dose-response relationships between glucose and insulin secretion result in a more severe degree of hyperglycemia than observed in subjects with glucokinase mutations, and these subjects more frequently need insulin treatment. These alterations are evident in prediabetic subjects with normal glucose levels who carry the MODY1 mutation, suggesting that defective beta-cell function is the primary pathogenetic defect in the diabetic syndrome in these subjects. Studies performed in the classic form of NIDDM demonstrate that subjects with mild glucose intolerance and normal fasting glucose concentrations and glycosylated hemoglobin levels consistently demonstrate defective beta-cell function. These results are consistent with studies in the Zucker diabetic fatty rat, an animal model of NIDDM in which prediabetic animals demonstrate extensive alterations in expression of multiple genes involved in the regulation of insulin secretion. It thus appears that abnormal beta-cell function is present at a relatively early stage in the evolution of NIDDM, even before the onset of overt hyperglycemia.

Adult↗

PubMed2025

Enrichment of G-to-U Substitution in SARS-CoV-2 Functional Regions and Its Compensation via Concurrent Mutations.

We surveyed single nucleotide variant (SNV) patterns from 5 903 647 complete SARS-CoV-2 genomes. Among 10 012 SNVs, APOBEC-mediated C-to-U (C > U) deamination was the most prevalent, followed by G > U and other RNA editing-related substitutions including (A > G, U > C, G > A). However, C > U mutations were less frequent in functional regions, for example, S protein, intrinsic disordered regions, and nonsynonymous mutations, where G > U were over-represented. Notably, G-loss substitutions rarely appeared together. Instead, G-gain mutations tended to more frequently co-occur with others, with a marked preference in the S protein, suggesting a compensatory mechanism for G loss in G > U mutations. The temporal patterns revealed C > U frequency declined until late 2021 then resurged in early 2022. Conversely, G > U steadily decreased, with a pronounced drop in January 2022, coinciding with reduced COVID-19 severity. Vaccinated individuals exhibited a slightly but significantly higher C > U frequency and a notably lower G > U frequency compared to the unvaccinated group. Additionally, cancer patients had higher G > U frequency than general patients during the same period. Interestingly, none of the C > U SNVs were uniquely identified in 2724 environmental samples. These findings suggest novel functional roles of G > U in COVID-19 symptoms, potentially linked to oxidative stress and reactive oxygen species, while C > U remains the dominant substitution, likely driven by host immune-mediated RNA editing.

SARS-CoV-2↗

PubMed1995

The transverse plane evolution of the most common adolescent idiopathic scoliosis deformities. A cross-sectional study of 181 patients.

STUDY DESIGN: The transverse plane evolution of the most common idiopathic deformities was studied using a cross-sectional database of 181 patients whose deformities were visualized by precise three-dimensional techniques. OBJECTIVE: The objective was to test the hypothesis that for all common idiopathic scoliosis deformities evolution occurs as a torsion, the apex vertebra translating away from the upper end vertebra and at the same time angulating in a clockwise arc for right apex deformities and a counterclockwise arc for left apex deformities. SUMMARY OF BACKGROUND DATA: Perdriolle and Vidal proposed this hypothesis in 1987, which explained observations we had made in 1983 and which was partially supported in thoracic curves in our 1992 study. METHODS: Deformities were characterized as single thoracic major, thoracic major and thoracolumbar or lumbar minor, double thoracic and thoracolumbar or lumbar major, and single thoracolumbar or lumbar major curves. The dependent variable studied was the coronal plane regional angular (Cobb) deformity. The independent variables studied were the lateral and anteroposterior translation of the apex vertebra in relation to the upper end vertebra, and the transverse plane translation and angulation of the apex vertebra in relation to the upper end vertebra. For the model or hypothesis to be true, the apex vertebra to upper end vertebra transverse plane translational distance and angular relationship should increase as the Cobb angle increases. RESULTS: In relation to the upper end vertebra, the apex vertebra always translated laterally, almost always was accompanied by transverse plane translation increase, and usually was accompanied by transverse plane angulation increase. Anteroposterior translation was minimal, but for thoracolumbar and lumbar curves it tended to be posterior. CONCLUSION: The theory that these deformities evolve as torsions, with the apex vertebra translating away from the upper end vertebra and at the same time following a clockwise angular pathway to the upper end vertebra of right apex curves and a counterclockwise angular pathway for left apex curves is supported. Compensatory thoracolumbar and lumbar curves evolve in the same manner as major curves.

Adolescent↗