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1.
J Orthop ; 27: 79-83, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34588742

RESUMO

Following total knee arthroplasties patients using the X10 increased their quadriceps strength 120% at 30 days post-surgery compared to their pre-surgical baseline. This contrasts sharply with contrast studies outpatient physical therapy that show patients suffer a 50-60% quadriceps strength deficit at 30 days post-surgery. For X10 patients, the average range of motion at 30 days was 124° and at discharge it was 128° (mean 43 days). The trial involved a single surgeon and two groups. Group one (21 patients) used only the X10 for pre-habilitation and rehabilitation, while group two (20 patients) used X10 alone for pre-habilitation and then utilized the X10 plus home care plus outpatient physical therapy for rehabilitation. Adding home care and outpatient physical therapy did not improve outcomes compared to patients who utilized X10 alone. Our results show no significant difference between the two groups. Indicating that the X10 by itself is adequate to completely rehabilitation patients from total knee arthroplasties. Finally, we compared our results to those of Calatayud et al.1 who monitored two groups of patients, one group had only physical therapy for rehabilitation while the other group used physical therapy for both prehabilitation and rehabilitation. Our results were superior to Calatayud et al.1 for extension, flexion, and quadriceps strength; for each of these measures the X10 treatment groups improved over time, while the Calatayud et al.1 groups showed losses.

2.
Cutis ; 98(6): 393-398, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28099534

RESUMO

Cellulite is a cosmetic condition of subcutaneous fat herniation through fibrous connective tissue that results in a dimpled appearance of the skin. Occurring in approximately 85% to 90% of all women worldwide, cellulite has been well studied. The result has been the development of a plethora of treatment protocols yielding little to no success. We describe a noninvasive mechanical treatment for women with cellulite, evaluating the safety and effectiveness of a technique that utilizes a unique patented device for the reduction of the visible appearance of cellulite.


Assuntos
Tecido Adiposo/metabolismo , Celulite/terapia , Técnicas Cosméticas , Adulto , Idoso , Técnicas Cosméticas/efeitos adversos , Técnicas Cosméticas/instrumentação , Desenho de Equipamento , Feminino , Humanos , Pessoa de Meia-Idade , Resultado do Tratamento , Adulto Jovem
3.
Am J Bot ; 100(6): 1038-49, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23620206

RESUMO

PREMISE: The evolution of dioecy in plants is usually modeled as a consequence of self-fertilization. While increased seed and pollen production and dispersal patterns of specialized unisexuals have been examined, mating among relatives and interaction effects have been largely ignored. Here, we examine multiple variables simultaneously providing a more ecologically realistic set of conditions favoring the evolution of dioecy. • METHODS: We developed two complementary models to explore the evolution of dioecious plants. In both models, we examined the effects of inbreeding, compensation, and specialization on unisexual invasibility and were able to directly measure the influence of related matings on such a system. • KEY RESULTS: Our results support previous studies indicating dispersal specialization, consanguineous mating, and inbreeding depression facilitate the evolution of dioecy. However, our results suggest that it is the interaction effect of multiple forces acting simultaneously that allows for unisexual invasion at thresholds and frequencies witnessed in nature. Additionally, our results suggest that subdioecious populations often result, and depending on population conditions, dioecy evolves at different rates, lending importance to the ecological and life history conditions of the species. • CONCLUSION: Mating among relatives significantly enhances the invasibility of a unisexual mutant into a hermaphroditic population and lowers the levels of inbreeding depression required for invasion than previously reported conditions for unisexual invasion especially, if we consider multiple pressures simultaneously.


Assuntos
Evolução Biológica , Endogamia , Fenômenos Fisiológicos Vegetais/genética , Plantas/genética , Demografia , Ecossistema , Regulação da Expressão Gênica de Plantas , Modelos Biológicos , Processos de Determinação Sexual
4.
Commun Integr Biol ; 2(2): 141-3, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19704912

RESUMO

The growth and development of rice (Oryzae sativa) seedlings was shown to be regulated epigenetically by a fungal endophyte. In contrast to un-inoculated (nonsymbiotic) plants, endophyte colonized (symbiotic) plants preferentially allocated resources into root growth until root hairs were well established. During that time symbiotic roots expanded at five times the rate observed in nonsymbiotic plants. Endophytes also influenced sexual reproduction of mature big sagebrush (Artemisia tridentata) plants. Two spatially distinct big sagebrush subspecies and their hybrids were symbiotic with unique fungal endophytes, despite being separated by only 380 m distance and 60 m elevation. A double reciprocal transplant experiment of parental and hybrid plants, and soils across the hybrid zone showed that fungal endophytes interact with the soils and different plant genotypes to confer enhanced plant reproduction in soil native to the endophyte and reduced reproduction in soil alien to the endophyte. Moreover, the most prevalent endophyte of the hybrid zone reduced the fitness of both parental subspecies. Because these endophytes are passed to the next generation of plants on seed coats, this interaction provides a selective advantage, habitat specificity, and the means of restricting gene flow, thereby making the hybrid zone stable, narrow and potentially leading to speciation.

5.
J Biol Chem ; 283(41): 27810-27819, 2008 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-18678867

RESUMO

The life span of model organisms can be modulated by environmental conditions that influence cellular metabolism, oxidation, or DNA integrity. The yeast nicotinamidase gene pnc1 was identified as a key transcriptional target and mediator of calorie restriction and stress-induced life span extension. PNC1 is thought to exert its effect on yeast life span by modulating cellular nicotinamide and NAD levels, resulting in increased activity of Sir2 family class III histone deacetylases. In Caenorhabditis elegans, knockdown of a pnc1 homolog was shown recently to shorten the worm life span, whereas its overexpression increased survival under conditions of oxidative stress. The function and regulation of nicotinamidases in higher organisms has not been determined. Here, we report the identification and biochemical characterization of the Drosophila nicotinamidase, D-NAAM, and demonstrate that its overexpression significantly increases median and maximal fly life span. The life span extension was reversed in Sir2 mutant flies, suggesting Sir2 dependence. Testing for physiological effectors of D-NAAM in Drosophila S2 cells, we identified oxidative stress as a primary regulator, both at the transcription level and protein activity. In contrast to the yeast model, stress factors such as high osmolarity and heat shock, calorie restriction, or inhibitors of TOR and phosphatidylinositol 3-kinase pathways do not appear to regulate D-NAAM in S2 cells. Interestingly, the expression of D-NAAM in human neuronal cells conferred protection from oxidative stress-induced cell death in a sirtuin-dependent manner. Together, our findings establish a life span extending the ability of nicotinamidase in flies and offer a role for nicotinamide-modulating genes in oxidative stress regulated pathways influencing longevity and neuronal cell survival.


Assuntos
Longevidade/fisiologia , Modelos Biológicos , Neurônios/enzimologia , Nicotinamidase/biossíntese , Estresse Oxidativo/fisiologia , Transcrição Gênica/fisiologia , Animais , Células COS , Restrição Calórica , Sobrevivência Celular/fisiologia , Chlorocebus aethiops , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Resposta ao Choque Térmico/fisiologia , Histona Desacetilases/genética , Histona Desacetilases/metabolismo , Humanos , Mutação , Nicotinamidase/genética , Pressão Osmótica , Fosfatidilinositol 3-Quinases/genética , Fosfatidilinositol 3-Quinases/metabolismo , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Sirtuínas/genética , Sirtuínas/metabolismo
6.
Orthopedics ; 31(1): 75, 2008 01.
Artigo em Inglês | MEDLINE | ID: mdl-19292163

RESUMO

Proximal row carpectomy with capitate head resection and dorsal capsular interposition was performed in 8 patients with stage II and III scapholunate advanced collapse (SLAC). Mean patient age was 58.5 years (range, 50-79 years). One year postoperatively, range of motion and grip strength were not significantly changed from preoperative values. Mean postoperative Disabilities of the Arm, Shoulder, and Hand questionnaire score was 27. Pain improved from 8.8 preoperatively to 4.3 postoperatively on a scale of 0-10. Pain levels were highly inversely correlated with final range of motion (r=-0.94, P=.0004). Proximal row carpectomy with capitate leveling and capsular interposition for stage II and III SLAC wrist provides reasonable pain relief in 75% of patients. Patients should be counseled that 25% of cases may demonstrate progression of radiocapitate degeneration, necessitating further intervention.


Assuntos
Capitato/lesões , Capitato/cirurgia , Cápsula Articular/cirurgia , Osso Escafoide/lesões , Osso Escafoide/cirurgia , Ulna/lesões , Ulna/cirurgia , Traumatismos do Punho/cirurgia , Idoso , Artroplastia/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento
7.
Am J Bot ; 94(3): 425-36, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21636412

RESUMO

When addressing the nature of ecological adaptation and environmental factors limiting population ranges and contributing to speciation, it is important to consider not only the plant's genotype and its response to the environment, but also any close interactions that it has with other organisms, specifically, symbiotic microorganisms. To investigate this, soils and seedlings were reciprocally transplanted into common gardens of the big sagebrush hybrid zone in Salt Creek Canyon, Utah, to determine location and edaphic effects on the fitness of parental and hybrid plants. Endophytic symbionts and functional microbial diversity of indigenous and transplanted soils and sagebrush plants were also examined. Strong selection occurred against the parental genotypes in the middle hybrid zone garden in middle hybrid zone soil; F(1) hybrids had the highest fitness under these conditions. Neither of the parental genotypes had superior fitness in their indigenous soils and habitats; rather F(1) hybrids with the nonindigenous maternal parent were superiorly fit. Significant garden-by-soil type interactions indicate adaptation of both plant and soil microorganisms to their indigenous soils and habitats, most notably in the middle hybrid zone garden in middle hybrid zone soil. Contrasting performances of F(1) hybrids suggest asymmetrical gene flow with mountain, rather than basin, big sagebrush acting as the maternal parent. We showed that the microbial community impacted the performance of parental and hybrid plants in different soils, likely limiting the ranges of the different genotypes.

8.
J Hand Surg Am ; 31(3): 366-72, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16516729

RESUMO

PURPOSE: To report our experience using a fixed-angle volar plate in conjunction with a corrective osteotomy and cancellous bone graft for the treatment of distal radius malunions with dorsal angulation in 4 patients. METHODS: Four consecutive patients had a volarly based opening wedge osteotomy with a fixed angle volar plate and cancellous bone grafting for the treatment of a dorsally angulated distal radius malunion. Data collected retrospectively included a visual analog pain scale, grip strength, range of motion, radiographic parameters, and each patient's subjective functional outcomes as measured by the Disabilities of the Arm, Shoulder, and Hand questionnaire. Motion, strength, and radiographic values were compared with the contralateral arm for each patient. RESULTS: The average time from initial fracture to corrective osteotomy was 346 days. The average length of follow-up evaluation was 13.5 months. The flexion-extension arc of motion increased an average of 21 degrees to a value of 84% of the contralateral side; the pronation-supination arc of motion increased an average of 20 degrees to a value of 98% of the contralateral side. The average tilt of the radius improved from 26 degrees extension to 2 degrees extension; the average radial inclination improved from 22 degrees to 24 degrees; the average ulnar variance excluding the 1 patient who had a distal ulna resection improved from 5 mm to 1 mm. The average retrospective Disabilities of the Arm, Shoulder, and Hand score improved from 30 to 7; the average retrospective visual analog pain scale score improved from 4.5 to 1. The average grip strength increased from 20 to 29 kg, which corresponded to 73% of the contralateral extremity. CONCLUSIONS: The rigid characteristics of fixed angle volar plates can provide an alternative to the traditional techniques of distal radius osteotomy including structural bone grafting and dorsal plate fixation or external fixation. In addition these plates are strong enough to allow for early postoperative motion. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level IV.


Assuntos
Placas Ósseas , Fixação Interna de Fraturas/métodos , Fraturas Mal-Unidas/cirurgia , Fraturas do Rádio/cirurgia , Adolescente , Adulto , Idoso , Transplante Ósseo , Avaliação da Deficiência , Seguimentos , Fraturas Mal-Unidas/diagnóstico por imagem , Fraturas Mal-Unidas/fisiopatologia , Força da Mão/fisiologia , Humanos , Ílio/transplante , Masculino , Pessoa de Meia-Idade , Osteotomia , Medição da Dor , Pronação/fisiologia , Desenho de Prótese , Radiografia , Fraturas do Rádio/diagnóstico por imagem , Fraturas do Rádio/fisiopatologia , Amplitude de Movimento Articular/fisiologia , Supinação/fisiologia , Ulna/transplante
9.
Environ Mol Mutagen ; 45(2-3): 249-57, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-15657913

RESUMO

Chromosome breaks and rearrangements resulting from ionizing radiation can be much more complicated than many investigators thought possible some years ago. The realization that not all translocations are reciprocal, that multiway exchanges occur, and that some double-strand breaks are not repaired prior to mitosis have all contributed to the difficulty of knowing how best to identify, record, evaluate, and report chromosome translocations. Here we describe the results of a series of experiments in which blood from two normal healthy subjects was obtained, irradiated with 137Cs gamma-rays in vitro at doses ranging from 0 (controls) to 4 Gy, and cultured. Cells from each dose group and donor were harvested at days 2, 2.5, 3, 4, 5, and 7 and evaluated for chromosome damage by simultaneously painting chromosomes 1, 2, and 4 in red and 3, 5, and 6 in green. The persistence of dicentrics, fragments, rings, insertions, and PAINT translocations are reported separately by us in this issue. In this article, we focus on translocations, characterizing the various types in detail and comparing and contrasting their persistence across all dose groups for both donors. The results indicate that the persistence of all translocation types was sufficient to be used for retrospective dosimetry, although nonreciprocal translocations exhibited diminished persistence compared to the other types. We also characterize the kinetics of the radiation dose responses of the two donors who exhibited significant differences in the induction as well as the persistence of translocations. Based on the evidence presented here, we hypothesize that these individuals differ in the recognition and repair of radiation-induced damage as well as in cell cycle checkpoint control. Despite these differences, the temporal frequency of translocation losses at both the high and low doses was similar for both subjects.


Assuntos
Raios gama , Radiometria/métodos , Translocação Genética/efeitos da radiação , Adulto , Análise de Variância , Radioisótopos de Césio , Coloração Cromossômica/métodos , Relação Dose-Resposta à Radiação , Humanos , Cinética , Masculino , Pessoa de Meia-Idade , Fatores de Tempo
10.
Environ Mol Mutagen ; 45(2-3): 229-48, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-15657915

RESUMO

Chromosome translocations are used to estimate the doses of radiation received following occupational or accidental exposure. Biodosimetry relies on the assumption that translocations are not cell-lethal and persist with little or no loss over time. While translocations do exhibit substantially greater persistence than other aberration types (e.g., dicentrics), there is evidence that translocation frequencies also decline over time, at least following acute doses above 1 Gy. To the extent that translocation frequencies decline, the predicted absorbed doses will be underestimated. Yet unknown is whether translocations induced by ionizing radiation at doses below 1 Gy also show significant declines. Here we report on the persistence of translocations induced by 137Cs gamma-rays at acute doses ranging from 0.2 to 4 Gy using peripheral blood lymphocytes from two unrelated healthy male donors. Chromosome aberrations were evaluated by simultaneously painting chromosomes 1, 2, and 4 in red and 3, 5, and 6 in green in cells harvested 2-7 days following exposure and were scored using the PAINT system. Translocations were also enumerated using several other methods and these results are reported separately by us in this issue. For comparison, the persistence of dicentrics, rings, acentric fragments, and color junctions was also evaluated and showed rapid losses with time. The results from both donors provide evidence that translocation frequencies decline with time in a statistically significant manner at doses as low as 0.2-0.3 Gy. The frequency of translocations for all dose groups declined from day 2 to 7 by averages of 39% and 26% for donors 1 and 2, respectively. These data emphasize the importance of considering translocation loss in biological dosimetry long times after exposure.


Assuntos
Aberrações Cromossômicas/efeitos da radiação , Raios gama , Radiometria/métodos , Adulto , Análise de Variância , Radioisótopos de Césio , Coloração Cromossômica , Relação Dose-Resposta à Radiação , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Tempo
11.
Am J Sports Med ; 32(5): 1270-7, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15262653

RESUMO

BACKGROUND: Several shoulder function scores are used in research, with no universally adopted standard. This study compares 6 shoulder outcome scales. HYPOTHESIS: Correlations exist between shoulder outcome scales, allowing conversion between scales. Shoulder scales are correlated with age. STUDY DESIGN: Regression and correlation study. METHODS: Seventy subjects with shoulder pain completed 6 shoulder outcome scales. Pearson correlations were calculated between the total scores of the 6 instruments, between the components of the scales, and with age. Regression equations were calculated between scales. RESULTS: The range of r values for total scores was 0.495 < or = r < or = 0.770, P < or = .01. In general, a scale's components were themselves highly correlated and added little new information to the scale (0.260 < or = r < or = 0.705, P < or = .05). Most of the scale scores were highly correlated with age (0.291 < or = r < or = 0.582, P < or = .05). Constant's reported corrections for age reduced (from r = -0.582 to r = -0.250, P < .05) but did not eliminate age as a confounding variable. CONCLUSIONS: Correlations exist between shoulder outcome scales, but existing shoulder scales are not equivalent in their assessments of function; they contain redundant information and, in some cases, may reflect a patient's age better than his/her shoulder function. The utility of conversion equations is minimized as a result of low to moderate correlations between scales.


Assuntos
Avaliação de Resultados em Cuidados de Saúde/métodos , Medição da Dor/métodos , Dor de Ombro/reabilitação , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Amplitude de Movimento Articular/fisiologia , Articulação do Ombro/fisiopatologia , Estados Unidos
12.
J Orthop Res ; 22(4): 884-8, 2004 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15183450

RESUMO

INTRODUCTION: Shoulder strength is an integral component of shoulder function. In assessing shoulder function many functional scales rely on direct or indirect measures of strength. Strength, and thus these scales, is often highly correlated with age. We propose an allometric method for assessing shoulder strength. Allometric modeling has provided accurate predictions of biologic growth and physiologic function in both human and animal studies. Allometry utilizes the relationship between the two homologous structures on the left and right sides of the body, providing in effect an internal control and thus eliminating many confounding effects, e.g. age and level of activity. METHODS: Twenty patients with unilateral shoulder dysfunction underwent strength testing of their affected and unaffected shoulder. Strength testing of the bilateral shoulders was also assessed in twenty people without shoulder pain in order to delineate the effect of hand dominance on strength in those without shoulder pain. Absolute and predicted strength deficits of the involved shoulder were calculated via regression analysis. Pearson's correlation coefficients were computed between age and strength. RESULTS: Utilizing the contralateral extremity as an internal control eliminates age as a confounding variable in predicting strength outcomes (r = 0.093). CONCLUSION: Allometric concepts, applied to shoulder strength assessment, eliminates age as a confounding variable. Strength testing of both shoulders should be considered in the development of future shoulder outcome scales in order to eliminate the strong influence of age.


Assuntos
Biometria/métodos , Músculo Esquelético/fisiologia , Ortopedia/métodos , Dor de Ombro/reabilitação , Ombro/fisiologia , Adulto , Idoso , Teste de Esforço , Feminino , Humanos , Contração Isométrica/fisiologia , Masculino , Pessoa de Meia-Idade , Modelos Biológicos , Músculo Esquelético/fisiopatologia , Reprodutibilidade dos Testes , Ombro/fisiopatologia , Dor de Ombro/fisiopatologia , Resultado do Tratamento
13.
J Insect Sci ; 4: 30, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15861245

RESUMO

We examined habitat disturbance, species richness, equitability, and abundance of ants in the Fall-Line Sandhills, at Fort Benning, Georgia. We collected ants with pitfall traps, sweep nets, and by searching tree trunks. Disturbed areas were used for military training; tracked and wheeled vehicles damaged vegetation and soils. Highly disturbed sites had fewer trees, diminished ground cover, warmer soils in the summer, and more compacted soils with a shallower A-horizon. We collected 48 species of ants, in 23 genera (141,468 individuals), over four years of sampling. Highly disturbed areas had fewer species, and greater numbers of ants than did moderately or lightly disturbed areas. The ant communities in disturbed areas were also less equitable, and were dominated by Dorymyrmex smithi.


Assuntos
Formigas/fisiologia , Biodiversidade , Ecossistema , Animais , Formigas/classificação , Conservação dos Recursos Naturais , Georgia , Densidade Demográfica
14.
Oecologia ; 126(2): 239-246, 2001 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28547623

RESUMO

Several species of gall-forming insects specialize on big sagebrush (Artemisia tridentata), a species that shows much clinal and subspecific variation throughout its geographic range. Two of those subspecies, basin big sagebrush (A. t. ssp. tridentata) and mountain big sagebrush (A. t. ssp. vaseyana), form a narrow hybrid zone at Salt Creek, Utah. Reciprocal transplant experiments have shown that the hybrid big sagebrush at Salt Creek are more fit than either parental subspecies, but only in the hybrid zone. Do genotype and environment influence the density and distribution of galls on big sagebrush? We counted galls on parental and hybrid big sagebrush in three reciprocal transplant gardens at Salt Creek. Gardens were in each of the two parental zones and in the hybrid zone. Transplanted seedlings came from five source populations: two parental and three hybrid populations. We identified seven kinds of gall-forming flies (Rhopalomyia midges and Eutreta fruitflies) that produced identifiable galls. Densities of galls varied among the three gardens and five source populations, and there was also a significant garden by source interaction in gall density. In general, variation in gall density among gardens (i.e., environments) was much greater than the variation among source populations (i.e., genotypes). Nevertheless, significant genotype-environment interactions were observed for five of the seven kinds of galls. Overall density of galls, mostly due to Rhopalomyia ampullaria, was greatest in the high-elevation (mountain) garden and least in the low-elevation (basin) garden. To the best of our knowledge, this is the first reciprocal transplant experiment addressing herbivore richness in a hybrid zone.

15.
Chaos ; 8(3): 717-726, 1998 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12779777

RESUMO

Neo-Darwinian theory is highly successful at explaining the emergence of adaptive traits over successive generations. However, there are reasons to doubt its efficacy in explaining the observed, impressively detailed adaptive responses of organisms to day-to-day changes in their surroundings. Also, the theory lacks a clear mechanism to account for both plasticity and canalization. In effect, there is a growing sentiment that the neo-Darwinian paradigm is incomplete, that something more than genetic structure, mutation, genetic drift, and the action of natural selection is required to explain organismal behavior. In this paper we extend the view of organisms as complex self-organizing entities by arguing that basic physical laws, coupled with the acquisitive nature of organisms, makes adaptation all but tautological. That is, much adaptation is an unavoidable emergent property of organisms' complexity and, to some a significant degree, occurs quite independently of genomic changes wrought by natural selection. For reasons that will become obvious, we refer to this assertion as the attractor hypothesis. The arguments also clarify the concept of "adaptation." Adaptation across generations, by natural selection, equates to the (game theoretic) maximization of fitness (the success with which one individual produces more individuals), while self-organizing based adaptation, within generations, equates to energetic efficiency and the matching of intake and biosynthesis to need. Finally, we discuss implications of the attractor hypothesis for a wide variety of genetical and physiological phenomena, including genetic architecture, directed mutation, genetic imprinting, paramutation, hormesis, plasticity, optimality theory, genotype-phenotype linkage and puncuated equilibrium, and present suggestions for tests of the hypothesis. (c) 1998 American Institute of Physics.

16.
Evolution ; 51(1): 95-102, 1997 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28568779

RESUMO

Does endogenous or exogenous selection stabilize the big sagebrush (Artemisia tridentata) hybrid zone? After two years of study, our reciprocal transplant experiments showed significant genotype by environment interactions for a number of fitness components, including germination, growth, and reproduction. Hybrids were the most fit within the hybrid garden. In the parental gardens, the native parental taxon was more fit than either the alien parental or hybrids. These results are consistent with the bounded hybrid superiority model, which assumes exogenous selection, but are clearly at odds with the dynamic equilibrium model, which assumes endogenous selection and universal hybrid unfitness.

17.
Oecologia ; 93(4): 538-547, 1993 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28313823

RESUMO

The influence of environmental heterogeneity on components of male and female fitness is examined using Atriplex canescens growing on steep slopes and alluvium at the slope base as a model system. Female fitness is estimated as the grams of fruit produced per plant and the grams of fruit per gram leaf tissue. Male fitness is estimated as the grams of stamens produced, the number of pollen grains dispersed to a given distance, and the potential number of grams of fruit sired taking into consideration the number and distribution of mates and competing pollen donors. The influence of increased plant size on male and female fitness components, the cost of reproduction (as measured by biomass, joules and nitrogen) on a gross level and a per offspring basis are also examined. The results indicate that the female function is more limited on the slope than the male function. The efficiency of pollen dispersal (the number of pollen grains per unit donor plant volume dispersed to a given distance) is enhanced by growing on slopes. Males become less efficient at dispersing pollen as they increase in size, while the efficiency of female reproduction (grams of fruit per volume or gram leaf tissue) is unaffected by increasing plant size. The cost to a male of siring a gram of fruit is about the same as the cost to a female of producing the gram of fruit. Implications for the evolution of sexual lability and dioecy are discussed.

18.
Evolution ; 46(6): 1708-1721, 1992 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28567745

RESUMO

Prior studies have alternatively considered floral phenotypes in Atriplex canescens as trioecious (having three sexual genders) and/or dioecious and having a "leaky genetical switch." Clones transplanted from three populations and grown in common gardens reveal the existence of two distinctly different genetic controls regulating gender expression. In some clones gender is fixed as male (staminate) or female (pistillate), while in other clones gender varies, ranging from a mixture of male and female ramets to simultaneous hermaphrodites with various proportions of male and female flowers. For clones which vary their sex expression, variation occurs within irrigation treatments, between treatments and over time, as a consequence of the combined effects of genotype plus environment. The magnitude of sex change is also a product of the interaction of genetics and environment. Some clones have been repeatedly examined for 20 years.

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