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Results for “Evolution of cooperation”

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PubMed2004

Sexual conflict and cooperation under naturally occurring male enforced monogamy.

An evolutionary conflict often exists between the sexes in regard to female mating patterns. Females can benefit from polyandry, whereas males mating with polyandrous females lose reproductive opportunities because of sperm competition. Where this conflict occurs, the evolution of mechanisms whereby males can control female remating, often at a fitness cost to the female, are expected to evolve. The fitness cost to the female will be increased in systems where a few high status males monopolise mating opportunities and thus have limited sperm supplies. Here we show that in the cockroach Nauphoeta cinerea, a species where males enforce female monogamy in the first reproductive cycle, males that have become sperm depleted continue to be able to manipulate female remating behaviour. Although the manipulation severely decreases fecundity in females mated to sperm-depleted males, males benefit, increasing their relative fitness by preventing other males from reproducing. Our results suggest that there is selection on maintaining the mechanism of manipulation rather than maintaining sperm numbers. Taken with previous research on sexual conflict in N. cinerea, this study suggests that the causes and consequences of sexual conflict are complex and can change across the life history of an individual.

Analysis of Variance↗

PubMed1991

Identification of cooperating oncogenes in E mu-myc transgenic mice by provirus tagging.

Mo-MLV infection of E mu-myc transgenic mice results in a dramatic acceleration of pre-B cell lymphomagenesis. We have used provirus tagging to identify genes that cooperate with the E mu-myc transgene in B cell transformation. Here we report on the identification of four loci, pim-1, bmi-1, pal-1, and bla-1, which are occupied by proviruses in 35%, 35%, 28%, and 14% of the tumors, respectively. bmi-1, pal-1, and bla-1 represent novel common proviral insertion sites. The bmi-1 gene encodes a 324 amino acid protein with a predominantly nuclear localization. bmi-1 is highly conserved in evolution and contains several motifs frequently found in transcriptional regulators, including a new putative zinc finger motif. No genes have yet been assigned to pal-1 and bla-1. The distribution of proviruses over the four common insertion sites suggests that provirus tagging can be used not only to identify the cooperating oncogenes but also to assign these genes to distinct complementation groups in tumorigenesis.

Amino Acid Sequence↗

PubMed2004

Collective Rabi oscillations and solitons in a time-dependent BCS pairing problem.

Motivated by recent efforts to achieve cold fermions pairing, we study the nonadiabatic regime of the Bardeen-Cooper-Schrieffer state formation. After the interaction is turned on, at times shorter than the quasiparticle energy relaxation time, the system oscillates between the superfluid and normal state. The collective nonlinear evolution of the BCS-Bogoliubov amplitudes u(p), v(p), along with the pairing function Delta, is shown to be an integrable dynamical problem which admits single soliton and soliton train solitons. We interpret the collective oscillations as Bloch precession of Anderson pseudospins, where each soliton causes a pseudospin 2pi Rabi rotation.

Journal Article↗

PubMedDate not supplied

Epigenetic events during the process of cell transformation induced by carcinogens (review).

Recent studies clearly demonstrate that several environmental carcinogens lack the ability to initially induce genetic damage. In that view, multistage chemical carcinogenesis may be processed under the control of a variety of epigenetic events in addition to genotoxic impacts. The understanding of this mechanism as reviewed in this report requires knowledge of early changes induced by carcinogens in target cells, biochemical, biological and molecular reactions closely related to both sides of the growth equation: cell proliferation and programmed death. Among several cell transformation models, the most suitable for carcinogen detection and mechanistic study is the Syrian hamster embryo (SHE) cell transformation assay. This closely mimics the multistage carcinogenesis and we can examine, in a relatively short time (8 days), the mechanisms by which genotoxic and non-genotoxic agents may increase the frequency of cell transformation as a preneoplastic end-point. The mode of action of hundred of compounds, carcinogens and non-carcinogens, has been explored so far using one-stage and two-stage treatment protocols. In general, with the two-stage protocol, all carcinogens, irrespective of their genotoxic or non-genotoxic potential, give unambiguous positive results. Since perturbations of cell proliferation and death are considered essential events in the process of carcinogenesis, studies have been conducted on the dysregulation of two specific parameters, the induction of ornithine decarboxylase (ODC) an enzyme related to cell proliferation, and the apoptosis rate, when SHE cells are exposed to carcinogens. In one-stage treatment (5 h-24 h), only the promoter TPA induces ODC activity, while other carcinogens do not increase this activity. Using the two-stage exposure protocol (1 h xenobiotic/5 h TPA), all carcinogens both genotoxic and non-genotoxic, are able to stimulate ODC activity above the level obtained with TPA alone. Based on the two-stage treatment with carcinogens a close relationship can be obtained between the ODC superinduction and the increase of morphological cell transformation frequency. In cancer development, it is postulated that the inhibition of apoptosis may help altered cells to escape cell death and acquire a tumorigenic phenotype. Two-stage treatment carcinogen/TPA, effectively decreases the apoptotic rate. This is accompanied by an upregulation of the Bcl-2 oncoprotein, a well-known apoptotic inhibitor. However, treatment with a non-carcinogen phthalic anhydride, also inhibits apoptosis while it does not superinduce ODC activity. Although inhibition of apoptosis is not specific to the carcinogenic compound, both superinduction of ODC activity and inhibition of apoptosis via Bcl-2 upregulation may cooperate during the early stages of the carcinogenic process. In a long-term stage transformation assay, the rate of transformed colonies is relatively low (2-8%) bringing about the slow evolution of tumoral disease in humans and tumoral induction in rodents. This could be the consequence of the activation of various cellular repair mechanisms during the exposure time. Experimental data reported so far point out that genotoxic and non-genotoxic carcinogens, thought to be more active in the initiation or in the promotion stage, must share the same stage pathway leading to cancer development.

Animals↗

PubMed1993

Ongoing progress in the treatment of childhood rhabdomyosarcoma.

During the past 2 decades, several different multidisciplinary treatment studies of childhood rhabdomyosarcoma have been conducted, some as single-institution protocols and others as multi-institution cooperative endeavors. Much of our current understanding of the natural history and histopathology, as well as response to treatment, is derived from these studies. This understanding has allowed for the continued evolution of treatment, which has already resulted in a dramatic increase in overall survival rates. Current treatment trials are aimed at maintaining high cure rates while reducing treatment-related morbidity, and exploring innovative regimens to improve the outlook of poor-risk patients. The improved outcome in children with rhabdomyosarcoma is a tribute to the multi-institutional, multidisciplinary approach to cancer research and treatment.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1989

[Serum demyelinating activity and Guillain-Barre syndrome: favorable effect of plasma exchange].

The present study was designed to determine whether plasma exchange has a beneficial effect on the activity of the demyelinating factor present in the serum of patients with the Guillain-Barre syndrome. The demyelinating activity was assessed electrophysiologically after subperineurial injection of 20 to 30 microliters of serum into the rat sciatic nerves Serum was obtained from 26 patients from the French Cooperative Trial, among whom 12 had plasma exchange. Sera were drawn at hospital admission (DO) and at D15, D30 and D60. They consistently produced conduction block in a large proportion of motor axons, measured by the ratio of amplitudes of the motor action potential elicited by stimulation at both proximal and distal sites of injection. The serum activity diminished during the time course of the illness earlier in patients receiving plasma exchange and even more in patients with the less severe clinical score at the plateau phase. Serum from patients without motor sequelae after one year evolution did not produce conduction block prior to D30, as compared to sera from patients with sequelae which were still very active. This work add biological data to the positive results of plasma exchange in Guillain-Barre syndrome obtained by the North American and French Cooperative Trials.

Adult↗

PubMed2004

Longitudinal evolution of unidentified bright objects in children with neurofibromatosis-1.

Neurofibromatosis type-1 (NF-1) is the most common autosomal dominant disorder affecting the central nervous system. Magnetic resonance imaging (MRI) has revealed distinctive T2-weighted hyperintense foci (termed unidentified bright objects, UBOs) which appear to represent spongiform changes in the white matter. Cross-sectional and longitudinal analyses suggest that UBOs disappear over time; however, none of these studies have examined comprehensively these foci. We conducted a quantitative MRI longitudinal study of number of affected regions, number of UBOs per region, and UBO volume per region, in a sample of 12 children with NF-1. We applied semi-automatic morphometric methods and comprehensive statistical approaches, within a detailed anatomical parcellation framework. Our data demonstrate that, despite a similar UBO regional distribution (e.g., prevalent globus pallidus/internal capsule (GP/IC) location), UBO evolution was more complex than previously reported. In some subjects, the total number of UBO-occupied locations demonstrated a decrease between approximately ages 7 and 12 years, followed by a progressive increase during adolescence. This pattern was also found for UBO number and/or volume for all regions, with the exception of the cerebellar hemispheres. This REGIONAL distinction may reflect differences in white matter structure between affected long tract fiber bundles and that of cerebral and cerebellar myelinated fibers. The findings are also discussed in the context of previous MR and behavioral studies. We conclude that studies like the present one, in association with other MR modalities, are necessary to characterize more completely the nature and evolution of UBOs and their role in the cognitive phenotype of NF-1.

Adolescent↗

PubMed1976

Production of yeast alcohol dehydrogenase isoenzymes by selection.

Mutants of yeast alcohol dehydrogenase have been produced that protect the cell against the poisonous aldehyde acrolein by increasing the NADH-NAD ratio. The altered properties include changes both in binding constants and in cooperativity. Such mutants may be useful in exploring the nature of adaptation at the molecular level.

Alcohol Oxidoreductases↗

PubMed2000

The Evolution of Intraspecific Brood Parasitism in Birds and Insects.

Many species of birds and insects engage in intraspecific brood parasitism (IBP), when a female lays eggs in the nest of a conspecific and leaves without providing parental care. These visiting females may also act to cooperate with a primary female, staying to provide parental care. Therefore, IBP and cooperative breeding can be considered extremes on a continuum of parental care provided by a secondary female. When a secondary female abandons a nest, she creates an asymmetry in parental care between herself and the host. While models of asymmetry in reproductive allocation have focused directly on relatedness between females, we lack an appropriate theoretical framework that addresses the effects of relatedness on parental care asymmetry. Here, I present an evolutionarily stable strategy (ESS) model that predicts the conditions under which IBP is favored over cooperation and solitary breeding. Intraspecific brood parasitism is less likely to evolve (relative to cooperation and solitary breeding) as the relatedness between a host and parasite increases. It can evolve, however, if parasites achieve a high overall fecundity relative to solitary females. Constraints on solitary breeding can further promote IBP under some circumstances. Cooperation is favored when relatedness is high and reproductive skew is low. This model makes several predictions regarding the conditions under which IBP may evolve, motivating a variety of experimental approaches.

birds↗

PubMed2003

The evolution of the international system of radiological protection: food for thought from the Nuclear Energy Agency Committee on Radiation Protection and Public Health.

From its inception, the Nuclear Energy Agency (NEA), which is part of the broader Organisation for Economic Co-operation and Development, has contributed to the development of international radiological protection norms and standards. This continues today, in the form of studies and workshops to assist radiological protection policy makers, regulators and practitioners to develop concepts and approaches to help the international system of radiological protection, as recommended by the International Commission on Radiological Protection (ICRP), to evolve to better serve societal needs. The NEA's Committee on Radiation Protection and Public Health (CRPPH), in providing this support, has collaborated closely with the ICRP and strongly supports the current ICRP recommendation development process. In particular, active dialogue with a broad range of stakeholders is contributing to the evolution of concepts towards consensus on new ICRP recommendations. The CRPPH, as a body of ICRP recommendation practitioners, feels that the public, workers and the environment are well protected by the current radiological protection system, but agrees that a new consolidation and clarification of ICRP recommendations would be of value. The intent of the CRPPH in collaborating with ICRP is to develop a system of radiological protection that is simplified, more coherent, firmly based upon science and more clearly presented than the current system. This paper summarises the more detailed views of the CRPPH on the evolution of the system of radiological protection.

Global Health↗

PubMed2001

Carcinosarcoma of the uterine cervix: a report of eight cases with immunohistochemical analysis and evaluation of human papillomavirus status.

Carcinosarcomas (malignant Müllerian mixed tumors [MMMTs]) of the uterine cervix are rare neoplasms. This report describes the morphology, immunohistochemical profiles, and human papillomavirus (HPV) status of eight cervical MMMTs. Patients' ages ranged from 32 to 93 years (mean, 61 years). Seven cases showed in situ squamous cell carcinoma (SCC). The invasive epithelial component (EC) was composed of combined adenoid basal carcinoma, basaloid SCC, and adenoid cystic carcinoma (ACC) in two cases. Keratinizing SCC, large cell nonkeratinizing SCC, undifferentiated carcinoma, and basaloid SCC predominated in the remaining tumors, one of which had admixed ACC. The sarcomatous component (SC) was homologous and spindled with admixed myxoid areas in three lesions. The ECs and SCs in six MMMTs showed dual immunostaining with epithelial membrane antigen and the pan-keratin marker, MNF116. The SC was vimentin-positive in seven cases. Five tumors had a vimentin-positive EC. The SC was positive for muscle specific actin and/or smooth muscle actin in seven lesions, of which four were desmin-positive. Polymerase chain reaction (PCR) using GP5+/GP6+ L1 consensus primers detected HPV DNA in all eight cases. Nonisotopic in situ hybridization with digoxigenin-labeled probes to HPV types 6, 11, 16, 18, 31 and 33 demonstrated integrated HPV 16 in three cases, not only in the EC, but also in nuclei of the SC. This is the first study to implicate HPV in the evolution of cervical MMMTs. The above observations lend support to a metaplastic theory of histogenesis.

Adult↗

PubMed2005

Acute intramural hematoma of the aorta: a mystery in evolution.

BACKGROUND: The definition, prevalence, outcomes, and appropriate treatment strategies for acute intramural hematoma (IMH) continue to be debated. METHODS AND RESULTS: We studied 1010 patients with acute aortic syndromes who were enrolled in the International Registry of Aortic Dissection (IRAD) to delineate the prevalence, presentation, management, and outcomes of acute IMH by comparing these patients with those with classic aortic dissection (AD). Fifty-eight (5.7%) patients had IMH, and this cohort tended to be older (68.7 versus 61.7 years; P<0.001) and more likely to have distal aortic involvement (60.3% versus 35.3%; P<0.001) compared with 952 patients with AD. Patients with IMH described more severe initial pain than did those with AD but were less likely to have ischemic leg pain, pulse deficits, or aortic valve insufficiency; moreover, they required a longer time to diagnosis and more diagnostic tests. Overall mortality of IMH was similar to that of classic AD (20.7% versus 23.9%; P=0.57), as was mortality in patients with IMH of the descending aorta (8.3% versus 13.1%; P=0.60) and the ascending aorta (39.1% versus 29.9%; P=0.34) compared with AD. IMH limited to the aortic arch was seen in 7 patients, with no deaths, despite medical therapy in only 6 of the 7 individuals. Among the 51 patients whose initial diagnostic study showed IMH only, 8 (16%) progressed to AD on a serial imaging study. CONCLUSIONS: The IRAD data demonstrate a 5.7% prevalence of IMH in patients with acute aortic syndromes. Like classic AD, IMH is a highly lethal condition when it involves the ascending aorta and surgical therapy should be considered, but this condition is less critical when limited to the arch or descending aorta. Fully 16% of patients have evidence of evolution to dissection on serial imaging.

Acute Disease↗

PubMed1997

A model of collaboration: the Academic Practice Council.

If the profession of nursing is to survive in the changing health care delivery system, new models of collaboration between nursing education and nursing practice must be developed. Nursing is both an academic discipline and a practice profession. The historic dissonance between education and practice has never served the profession of nursing; the pressing challenge is to blend one with the other now. In an effort to respond to the demands of the discipline and profession of nursing, an academic institution and a health care delivery system developed a model of interagency collaboration. This article addresses historical perspectives, and evolution, structure, activities, evaluation, and future plans to the Academic Practice Council.

Cooperative Behavior↗

PubMed2005

Functional specification in the Drosophila endoderm.

The discovery of homeobox gene clusters led us to realize that the mechanisms for body patterning and other developmental programs are evolutionally-conserved in vertebrates and invertebrates. The endoderm contributes to the lining of the gut and associated organs such as the liver and pancreas, which are critical for physiological functions. Our knowledge of endoderm development is limited; however, recent studies suggest that cooperation between the HNF3/Fork head and GATA transcription factors is crucial for endoderm specification. It is necessary to further understand the mechanism through which cells become functionally organized. Molecular genetic analyses of the Drosophila endoderm would provide insights into this issue. During proventriculus morphogenesis, a simple epithelial tube is folded into a functional multilayered structure, while two functions of midgut copper cells (i.e. copper absorption and acid secretion) can be easily visualized. The homeobox gene defective proventriculus (dve) plays key roles in these functional specifications.

Animals↗

PubMed1985

Quasi-stationary concentrations of fructose-2,6-bisphosphate in the phosphofructokinase-2/fructose-2,6-bisphosphatase cycle.

The cooperation of phosphofructokinase-2 and fructose-2,6-bisphosphatase is investigated. Experimentally derived rate laws of the kinase and bisphosphatase activities introduced into the respective differential equations permitted to describe the time evolution of fructose-2,6-bisphosphate to quasi-stationary levels. The two enzyme activities were found to exert strong temperature dependence. The quasi-stationary levels of fructose-2,6-bisphosphate, however, are independent on temperature.

Adenosine Triphosphate↗

PubMed2004

A biophysical characterisation of factors controlling dimerisation and selectivity in the NF-kappaB and NFAT families.

The Rel/NF-kappaB family of eukaryotic transcription factors bind DNA with high specificity and affinity as homo- or heterodimers to mediate a diverse range of biological processes. By comparison, the nuclear factor of activated T-cells (NFAT) family has been recognised as Rel homologues due to structural similarities between the DNA-binding domains, yet they bind DNA as lower-affinity monomers. The structural and functional overlap between the NF-kappaB and NFAT families suggests that they may be evolutionarily divergent from a common, monomeric ancestor but have evolved different mechanisms to achieve high-affinity binding to their target DNA sequences. In order to understand the origin of these mechanistic differences, we constructed two chimeric proteins, based on molecular modelling, comprising the DNA-binding domain of NFAT and the dimerisation domain of NF-kappaB p50, differing only in the position of the splice site. Biophysical characterisation of the wild-type and chimeric proteins revealed that one of the chimeras bound DNA as a high-affinity, NF-kappaB-like cooperative dimer, whilst the other bound as a lower-affinity, NFAT-like monomer, demonstrating the importance of the interdomain linker in controlling the intrinsic ability of NFATc to form dimers. In addition, we have studied the rate of exchange of monomers between preformed NF-kappaB dimers and have determined, for the first time, the intrinsic homodimerisation constant for NF-kappaB p50. These data support a model in which NF-kappaB proteins bind DNA both in vitro and in vivo as high-affinity preformed homo- or heterodimers, which in an unbound form can still exchange monomer units on a physiologically relevant timescale in vivo.

Amino Acid Sequence↗

PubMedDate not supplied

Cloning and sequence analysis of kappa and gamma cynomolgus monkey immunoglobulin cDNAs.

One gamma heavy chain and 10 kappa light chain cynomolgus monkey (Macaca fascicularis) immunoglobulin cDNAs have been cloned and sequenced. Comparisons of the variable (V) regions to human antibody sequences have revealed extensive identity, exhibiting 93% at the amino acid level for the VH framework regions, and 88-99% for the V kappa frameworks. Identification of very few cynomolgus monkey-specific framework region residues suggests a role for cynomolgus monkey antibodies as donators of variable regions to chimeric monoclonal antibodies for utilisation in human therapy with human constant (C) regions. The cynomolgus monkey C kappa region exhibited 83% amino acid identity to its human counterpart, and the C gamma region was 95, 93, 95, and 95% similar to the human C gamma 1, C gamma 2, C gamma 3, and C gamma 4 regions, respectively. Evolutionary analysis of the C gamma genes, using the silent molecular clock, suggests that the divergence between cynomolgus monkey and human occurred before the time at which the ancestral gamma gene diverged into the multiple isotypes observed in humans.

Amino Acid Sequence↗

PubMed2006

A spectrum of PCSK9 alleles contributes to plasma levels of low-density lipoprotein cholesterol.

Selected missense mutations in the proprotein convertase subtilisin/kexin type 9 serine protease gene (PCSK9) cause autosomal dominant hypercholesterolemia, whereas nonsense mutations in the same gene are associated with low plasma levels of low-density lipoprotein cholesterol (LDL-C). Here, DNA sequencing and chip-based oligonucleotide hybridization were used to determine whether other sequence variations in PCSK9 contribute to differences in LDL-C levels. The coding regions of PCSK9 were sequenced in the blacks and whites from the Dallas Heart Study (n=3,543) who had the lowest (<5th percentile) and highest (>95th percentile) plasma levels of LDL-C. Of the 17 missense variants identified, 3 (R46L, L253F, and A443T) were significantly and reproducibly associated with lower plasma levels of LDL-C (reductions ranging from 3.5% to 30%). None of the low-LDL-C variants were associated with increased hepatic triglyceride content, as measured by proton magnetic resonance spectroscopy. This finding is most consistent with the reduction in LDL-C being caused primarily by accelerating LDL clearance, rather than by reduced lipoprotein production. Association studies with 93 noncoding single-nucleotide polymorphisms (SNPs) at the PCSK9 locus identified 3 SNPs associated with modest differences in plasma LDL-C levels. Thus, a spectrum of sequence variations ranging in frequency (from 0.2% to 34%) and magnitude of effect (from a 3% increase to a 49% decrease) contribute to interindividual differences in LDL-C levels. These findings reveal that PCSK9 activity is a major determinant of plasma levels of LDL-C in humans and make it an attractive therapeutic target for LDL-C lowering.

Alleles↗