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Results for “Compensatory Evolution”

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PubMedDate not supplied

[Hemodynamics of the eyes in diabetes mellitus].

The authors present evidence on the state of hemodynamics of the eye in patients suffering from diabetes mellitus on the basis of rheoophthalmographic and ophthalmoscopic studies with the use of the method of fluorescent angiography of the retina. The volume circulation of the eye proved to be connected with the intraophthalmic pressure and depended on the degree of affection of the eye vessels. Its changes were two-stage in character and depended on the state of the venous outflow. Diabetic retinopathy of the II stage served as the stage during which there was a sharp reduction of compensatory possibilities of hemodynamics, and further progress of vascular disturbances were observed. Rheoophthalmography permits to assess indirectly the degree of compensation of hemodynamic disturbances and can be used to asses clinical evolution of diabetic retinopathy.

Adolescent↗

PubMed1989

Dinoflagellates in evolution. A molecular phylogenetic analysis of large subunit ribosomal RNA.

The sequence of the large subunit ribosomal RNA (LsuRNA) gene of the dinoflagellate Prorocentrum micans has been determined. The inferred rRNA sequence [3408 nucleotides (nt)] is presented in its most probable secondary structure based on compensatory mutations, energy, and conservation criteria. No introns have been found but a hidden break is present in the second variable domain, 690 nt from the 5' end, as judged by agarose gel electrophoresis and primer extension experiments. Prorocentrum micans LsuRNA length and G+C content are close to those of ciliates and yeast. The conserved portions of the molecule (1900 nt) have been aligned with corresponding sequences from various eukaryotes, including five protista, one metaphyta, and three metazoa. An extensive phylogenetic study was performed, comparing two phenetic methods (neighbor joining on difference matrix, and Fitch and Margoliash on Knuc values matrix) and one cladistic (parsimony). The three methods led to similar tree topologies, except for the emergence of yeast that groups with ciliates and dinoflagellates when phenetic methods are used, but emerges later in the most parsimonious tree. This discrepancy was checked by statistical analyses on reduced trees (limited to four species) inferred using parsimony and evolutionary parsimony methods. The data support the phenetic tree topologies and a close relationship between dinoflagellates, ciliates, and yeast.

Animals↗

PubMed1992

Evolutionary adaptation to different thermal environments via transcriptional regulation.

Populations of the teleost fish Fundulus heteroclitus are subjected to the clinical variation in environmental temperatures that occurs along the eastern seacoast of North America. In concordance with this change in temperature is the clinal variation in the enzyme concentration of the heart-type lactate dehydrogenase (LDH-B; E.C.1.1.1.27). Previously we have shown that the compensating change in the LDH-B enzyme concentration is due to a change in the amount of LDH-B mRNA, but we did not define whether this was due to differences in mRNA stability or to differences in rate of transcription. The results presented here help clarify the molecular mechanism responsible for the variation in Ldh-B gene expression: the rate of transcription from the Ldh-B locus is significantly different between populations, and this difference is responsible for the compensatory change in LDH-B enzyme concentration.

Adaptation, Biological↗

PubMed1975

Palatal epithelium of a monotreme and a marsupial.

The palatal epithelium of a monotreme, Tachyglossus aculeatus and a marsupial, Tarsipes spenserae were examined histologically and with the scanning electron microscope. Each animal possess keratinized palatal spines which although histologically similar, show significant differences in their external morphology. It is suggested that the spines in each case are highly differentiated filiform papillae which have developed as a compensatory mechanism of mastication, since both animals are in effect, edentulous. In the light of these findings and observations on the tongue of both animals, it is suggested that a degree of parallel evolution of the palate (as part of the masticatory apparatus) has occurred.

Animals↗

PubMed1992

Changes in contractile and non-contractile proteins, intracellular Ca2+ and ultrastructures during the development of right ventricular hypertrophy and failure in rats.

Whether cardiac hypertrophy is a compensatory response or a cause of decompensation has been an interesting and important controversy in cardiology. The purpose of this study is to assess qualitative and quantitative changes in biological factors involved in the evolution and the development of right ventricular hypertrophy (RVH) and right ventricular failure in response to pressure overload in rats with pulmonary hypertension induced by monocrotaline injection, and to clarify the process from compensation to deterioration in cardiac hypertrophy biochemically and morphologically. Significant RVH was produced in rats at 2 weeks after single subcutaneous injection of monocrotaline, and signs of right ventricular failure became obvious at 4 weeks as RVH became more severe. In the right ventricle of these rats, we found that: 1) myosin isoenzymes shifted from V1 to V3 both at 2 and 4 weeks; 2) total collagen content increased, and type III and type V collagens increased with a relative decrease in type I collagen at both 2 and 4 weeks; 3) intracellular Ca2+ transient recorded from isolated myocytes showed a lower peak and slower descent slope compared to those of control rats; 4) ultrastructural changes observed by scanning electron microscopy at 1 and 2 weeks disappeared gradually as heart failure developed, and degeneration or destruction of mitochondria or sarcoplasmic reticulum became remarkable at 3 and 4 weeks. These findings suggest that cardiac hypertrophy might be an ominous sign of cardiac failure rather than a benign adaptive process, at least in this model.

Animals↗

PubMed1986

Late modifications of residual parenchyma after splenic resections.

The increased experience in the field of splenic resections have brought up questions about the evolution of the residual parenchyma. Weight increase and the histologic structure of the splenic remnant were studied during a year following hemisplenectomy in rats. Histological studies show that the residual spleen presents a permanent compensatory hyperplasia rather than a true regeneration. This hyperplasia causes an increase in weight of the residual parenchyma which is moderate and only transitory. Indirect confirmation of findings obtained in rats comes from scintigraphic study of residual human splenic tissue after hemisplenectomy. The residual tissue keeps its original form without increase in volume, and the sectioned surface is always well identified one year after splenic resection.

Animals↗

PubMed1976

Temperature: a "shaping force' in protein evolution.

1. Comparisons of homologous enzymes from species adapted to widely different temperatures reveal that ligand-binding affinities are rigorously conserved. This is interpreted to mean that a critical relationship between ligand-binding ability and intracellular ligand concentrations must be maintained for proper enzymic regulation. 2. The catalytic efficiencies of enzyme homologues differ in temperature-compensatory manners. Activation free energies are proportional to adaptation temperature and, consequently, low-temperature-adapted enzymes have the highest substrate turnover numbers. 3. Temperature compensatory adjustments in catalytic efficiency may be achieved by altering the number of weak bonds that form or break during a catalytic conformational change. Support for this hypothesis comes from the finding that activation enthalpy and activation entropy values co-vary in a regular manner and by magnitudes consistent with different amounts of weak-bond formation/rupture during catalytic activation in differnt enzyme homologues. 4. Adaptive adjustments in ligand-binding energetics may also involve utilization of the energy changes that occur during conformational changes. This mechanism would permit enzymes with identical binding-site chemistries to display adaptively different ligand affinities. 5. The greater heat-stabilities of enzymes from warm-adapted species may cause these enzymes to be less efficient catalysts than cold-adapted heat-labile enzymes. Heat-stable enzymes may have to break more weak bonds during a catalytic conformational change than do cold-adapted enzymes. The requirements for thermal stability and high catalytic efficiency thus appear to force an adaptational 'compromise'.

Adaptation, Physiological↗

PubMed1990

An undecamer DNA sequence directs termination of human ribosomal gene transcription.

Previously we have shown that a repetitive 18 bp sequence motif, the Sal box (AGGTCGACCAGA/TT/ANTCCG), present in the 3' terminal spacer of mouse rDNA constitutes a termination signal for RNA polymerase I (pol I). Similar sequence elements which are functionally analogous to the murine terminator are present in the spacer of human rDNA. However, the human termination signal is shorter encompassing only 11 bp (GGGTCGACCAG) which correspond to the proximal part of the mouse sequence. Two out of the five human Sal box elements are functionally inactive due to natural point mutations which damage factor binding. A similar sequence motif with a 10 of 11 base identity with the downstream terminators is located upstream of the human transcription initiation site. The upstream element interacts with the same factor(s) as the downstream terminators and is also capable to stop elongating human RNA polymerase I. Despite the human and mouse factors exert different electrophoretic mobilities in gel retardation assays, UV-crosslinking and proteolytic clipping experiments indicate that both the sizes and the tertiary structure of the Sal box binding proteins of both species are very similar. When bound to DNA, both the human and the mouse factor terminate transcription of pol I from the heterologous species. The results implicate that changes in signal sequences necessary for termination have been accompanied by compensatory changes in the DNA binding domain of the protein(s) interacting with the termination signal. In contrast, the protein-protein interactions between the termination factor and the transcribing RNA polymerase I appear to have been conserved during evolution.

Animals↗

PubMed1992

Ventricular remodeling following myocardial infarction.

Ventricular remodeling denotes structural changes that occur in ventricular chamber size, wall thickness, and composition following myocardial damage. Following acute coronary occlusion, there are various factors to consider at different times that may contribute to subsequent ventricular dilation. Early infarct expansion and later healing may be accompanied by compensatory hypertrophy in the noninfarcted region and progressive global dilation, that may progress long term, the major stimulus being increased wall stress. The 2 major factors influencing ventricular remodeling following myocardial infarction are infarct artery patency and the ventricular loading conditions. Thrombolytic therapy may produce coronary reperfusion and limit infarct size. Patency of the infarct-related artery may also provide later benefits for ventricular remodeling. Following infarct evolution, pharmacologic intervention provides the potential to minimize the sequelae of infarct expansion and ventricular dilation. Clinical studies indicate that treatment of symptomless left ventricular dysfunction with angiotensin-converting enzyme inhibition at greater than or equal to 1 week following myocardial infarction may prevent further ventricular dilation and reduce the probability of progression to heart failure. Earlier intervention, at 24-48 hours following Q-wave myocardial infarction, is also practicable and effective. Even earlier intervention, in combination with or immediately following thrombolysis, is being assessed in other studies. The timing of treatment is of considerable importance because blockade of compensatory mechanisms activated at the time of infarction may not be desirable immediately, even though these mechanisms may be deleterious later. The results of large-scale mortality studies are awaited to indicate the benefit of this type of treatment in terms of heart failure prevention and survival long term.

Humans↗

PubMed1989

Sequence conservation in Alu evolution.

A statistical analysis of a set of genomic human Alu elements is based on a published alignment and a recent classification of these sequences. After separation of the Alu sequences into families, the consensus sequences of these families are determined, using the correct weighting of the unidirectional decay of CG-dinucleotides. For, the tenfold greater mutation rate at CG's requires separate consideration of an independent clock at every stage of analysis. The distributions of the substitutions with respect to the new consensus sequences, taking the CG and the non-CG-nucleotide positions separately, lie far closer to the expected distributions than the total diversity. Computer analysis of the folding of RNAs derived from these sequences indicates that RNA secondary structure is conserved among Alu families, suggesting its importance for Alu proliferation and/or function. The folding pattern, further substantiated by a number of compensatory mutations, includes secondary structure domains which are homologous to those observed in 7SL RNA and a defined region of interaction between the two Alu subunits. These results are consistent with a model in which a small number of conserved Alu master genes give rise via retroposition to the numerous copies of Alu pseudogenes, that then diversify by random substitution. The master genes appeared at different periods during evolution giving rise to different families of Alu sequences.

Base Composition↗

PubMed1990

Direct sequencing of the activation peptide and the catalytic domain of the factor IX gene in six species.

By means of RNA amplification with transcript sequencing (RAWTS) under low stringency conditions, sequence was obtained directly without cloning for the activation peptide and the catalytic domain of factor IX from six species--sheep, pig, rabbit, guinea pig, rat, and mouse. The data presented demonstrate that, by the appropriate design of oligonucleotides and by performance of a nested PCR under appropriate conditions, it is possible to obtain sequence on a battery of species with a minimum of oligonucleotide primers. A total of 5.2 kb of cross-species sequence was generated with RAWTS. The results indicate that (1) 69% of the amino acids in the catalytic domain, but only 23% of the amino acids in the activation peptide, are identical in humans and the six species; (2) the catalytic domain evolves at a slower rate, but the extent and pattern of conservation of amino acids in the activation peptide suggest that the peptide functions as more than a cleavage spacer that separates the heavy and light chains in the catalytically inactive zymogen; (3) 37% of the amino acids in the activation peptide and 34% of the amino acids in the catalytic domain are factor IX-specific; i.e., they are either identical or changed in a highly conservative fashion in factor IX, but not in other related coagulation proteases; (4) these conserved factor IX-specific amino acids fall into three clusters, which are candidates for involvement in the protein interactions specific to factor IX; (5) there is a human-specific deletion after lysine 142 and a rodent-specific insertion after alanine 161; (6) in guinea pig, the insertion is associated with a seven-amino-acid repeat that corresponds to a perfect repeat of a 21-bp sequence; (7) humans have lost a potential N-glycosylation site that is conserved in the other species; (8) in each species, a few nonconservative changes occur in amino acids that are otherwise completely conserved, suggesting that compensatory mutations may have occurred; and (9) when compared to that of mouse, the amino acid identity with guinea pig factor IX is no greater than that found for the non-rodent species, a result compatible with the postulated increased rate of evolution in rodents.

Amino Acid Sequence↗

PubMed1988

Evidence of natural selection to maintain a functional domain outside of the 'core' in a large subclass of group I introns.

Comparison of three closely-related, homologous Group I introns reveals conservation of RNA secondary structure and some primary sequence outside of the characteristic Group I core structure. Further examination of forty Group I introns showed that all can be placed into one of two categories based on the length of the "loop L5" region (subtended by the base-paired sequences P and Q): short (21 to 38 bases) or long (59 to 295 bases). Despite the large variation in size and sequence, all nineteen of the long L5 introns share a common structure whose features include an adenine-rich bulge at a fixed distance from the P-Q pairing. This bulge is flanked by base-paired regions of greater than or equal to 6 base pairs on the core-proximal side and greater than or equal to 3 base pairs on the distal side. In the core-proximal helix there are a large number and high proportion of deviations from the consensus sequence that maintain base-pairing. These naturally-occurring compensatory base substitutions provide compelling phylogenetic support for the existence of this pairing and indicate that the conserved structure has a function in vivo.

Aspergillus↗

PubMed1975

Growth hormone treatment in hypopituitary dwarfs: longitudinal psychological effects.

This is one of a series of studies on the psychological effects of medically induced growth in a group of hypopituitary dwarfs treated with Human Growth Hormone (HGH). Before treatment these dwarfs were found to be psychologically immature and hypoactive, without any manifestation of aggressive drives, and had an underlying low self-esteem when compared with the normal population. When compared with a matched group with constitutional growth delay the hypopituitary patients were found to use denial, whereas the control group used well-organized compensatory mechanisms (9). Immaturity was found in both groups. When the hypopituitary dwarfs reached adolescence they lacked the core attributes of masculinity or femininity and manifested some ambiguity or even inversion in their choice of gender role (10). This report deals with their psychological evolution in relation to physical growth.

Adolescent↗

PubMed2026

Balancing under constraint: Structural insights into norovirus evolution and antigenic innovation.

Norovirus is the leading cause of acute viral gastroenteritis worldwide. While genomic studies have revealed its diversity and evolutionary patterns, the structural mechanisms driving viral adaptation remain poorly understood. Here, we establish a comprehensive structural database of norovirus VP1 P-domains across nine genogroups (GI-GIX) through large-scale AlphaFold2 predictions. By integrating phylogenetic analysis of VP1 sequences and structures, we demonstrate that sequence and structural evolution show overall concordance under purifying selection, yet significant local discrepancies reveal distinct patterns of convergent evolution shaped by structural constraints and functional divergence. Focusing on the predominant GII.4 genotype, we found that compared to near-full-genome and nucleotide trees, only the VP1 amino acid tree reliably clustered GII.4 variants in chronological order as monophyletic groups. We further identify a hierarchical evolutionary strategy: positive selection may drive structural hypervariability in major antigenic epitopes D and C for immune escape, with epitope D exhibiting pronounced structural flexibility that complicates its structural characterization, whereas coevolutionary analysis uncovers a broad network of compensatory interactions spanning multiple epitopes, with striking enrichment in epitope A. These epitopes exhibited a pattern of "sequence plasticity with structural conservation", maintained by coevolutionary constraints that preserve conformational integrity. Together, these findings suggest that norovirus vaccine strategies targeting the structurally conserved conformations of epitopes A and G could overcome the limitations of traditional strain-specific approaches, offering a pathway toward broad protection against evolving viral diversity.

Norovirus↗

PubMed2026

Viral mimicry escape as a necessary feature of malignant transformation.

Malignant transformation is driven by disruption of pathways regulating proliferation and cell fate, but these same disruptions can create a collateral vulnerability: loss of transcriptional and epigenetic control over transposable elements and other normally silenced genomic regions. Consequently, emerging cancer cells can accumulate transposable element-derived and other endogenous immunogenic nucleic acids capable of triggering antiviral responses, a process termed viral mimicry. Increasing evidence indicates that viral mimicry can eliminate precancerous cells and shape tumour evolution, positioning it as an intrinsic tumour-suppressive mechanism. Here we highlight how cancer-associated changes in DNA methylation, histone modifications, splicing and RNA processing can lead to the presence of immunogenic nucleic acids that can activate viral mimicry pathways. We outline how cancer cells suppress viral mimicry, including compensatory epigenetic repression, RNA editing, nucleic acid decay and dampening of interferon signalling to enable cancer cell growth. Finally, we highlight the evidence suggesting that escaping viral mimicry is a fundamental process for cancer initiation and progression, and suggest that viral mimicry escape is necessary for cancer transformation and a therapeutic target in combination with immunotherapies. By framing viral mimicry escape as a necessary part of cancer transformation, this Review provides a unifying conceptual model for its translational exploitation.

Journal Article↗

PubMed1992

Interaction between verbal and gestural language in progressive aphasia: a longitudinal case study.

The objective of this longitudinal study is to investigate the on-line interaction between praxis and linguistic abilities in a progressive aphasia case. During 3 years of evolution, procedural discourse of a progressive aphasic patient was videotaped five times, allowing us to analyze the progression of both language and gestural production as well as the interaction between these two. We anticipated that, in the absence of apraxia, the patient would compensate for her speech deficit by producing progressively more and more meaningful gestures. Our compensatory hypothesis was confirmed but the compensation was not as efficient as one would expect given the absence of apraxia. With the progression of the speech deficit, the patient could not replace some verbs by pantomimes that were otherwise accompanying her discourse in the preceding testing sessions. We suggest that such a compensatory ability may constitute one important characteristic of the progressive aphasia syndrome.

Aphasia↗

PubMed1976

The differential development of the hominid pelvis.

The peculiarly shaped hominid pelvis represents the total response to the diverse forces which have moulded its structure, these being requirements for efficient bipedalism and parturition. In some respects the structural requirements of these unrelated functions have been in conflict. In these instances the morphological response to the dominant requirement, viz. bipedalism, is clearly discernible, while the changes subserving the needs of parturition are seen as compensatory modifications, the greater emphasis of which is responsible, in part, for pelvic sexual dimorphism in the female. Total pelvic architecture is thus a mosaic constituted by the aggregate of differential responses to different functional goals.

Adolescent↗

PubMed1987

Ecological compensation--a complication for testing life-history theory.

Mortality, growth and birth rates cannot vary independently in stable populations, environmental change of one variable must be accompanied by compensatory variation of another. Ecological compensation is recognized if the stable populations are genetically identical. Ecological compensation, if it operates, constrains the direction of evolutionary change, and predictions that ignore it may be in error.

Adaptation, Physiological↗