Somatic mutations in organisms with complex life histories.

A theoretical model is developed of the fate of mutations for organisms with such life-history characteristics as indeterminate growth and clonal reproduction. It focuses on how the fate of a particular mutant depends on whether it arises during mitotic cell division (somatic mutation) or during meiotic cell division (meiotic mutation). At gamete production, individuals carrying somatic mutations will produce some proportion of gametes reflecting the original, zygotic genotype and some proportion reflecting genotypes carrying the somatic mutation. Focusing on allele frequencies at gamete production allows the effects of growth and clonal reproduction to be summarized. The relative strengths of somatic and meiotic mutation can be determined, as well as the conditions under which the change in allele frequency due to one is greater than that due to the other. Examples from a published demographic study of clonal corals are used to compare somatic and meiotic mutation. When there is no selection acting on either type of mutation, only a few cell divisions per time unit on average are needed for the change in allele frequency due to somatic mutation to be greater, given empirically based mutation rates. When somatic selection is added, the most dramatic effect is seen with fairly strong negative selection acting against the somatic mutation within individuals. In this case, selection within organisms can effectively counteract the effects of somatic mutation, and the change in allele frequency due to somatic mutations will not be greater than that due to meiotic mutations for reasonable numbers of within-generation cell divisions. The majority of the mutation load, which would have been due to somatic mutation, is purged by selection within the individual organism.     

Genital and body allometry in two species of noctuid moths (Lepidoptera: Noctuidae)

One‐size‐fits‐all and related hypotheses predict that static allometry slopes for male genitalia will be consistently lower than 1.0 and lower than the slopes for most other body parts (somatic traits). We examined the allometry of genitalic and somatic morphological traits in males and females of two species of noctuid moths, Spodoptera exigua (Hübner, [1808]) and Helicoverpa armigera (Hübner, [1808]). The relationship between genitalic traits and body size was generally strongly negative‐allometric in males but with no significant differences from 1.00 in females of the two species examined. However, in females, the slope of genital traits was also lower than the slopes for somatic traits. The relationship between somatic traits and the body size indicator was approximately isometric in most cases in males, except in four traits in S. exigua, in which the slopes showed slight negative allometry, and the hind tibia in H. armigera, in which the slope had positive allometry. However, in females, some somatic traits showed isometric and some other showed negative allometry in both species. The coefficients of variation (CV) for all structures in the males were low, not exceeding 10%. Genitalic traits showed significantly lower CV than somatic traits in males. In females, somatic traits showed lower CV than genitalic traits but with no significant difference in the H. armigera. Our observations of strongly negative allometry for genitalic traits in males are consistent with stabilizing selection on genital size and we suggest that male performance in interactions with females is the source of selection on male genital allometry. The difference in the degree of phenotypic variation between genitalic and somatic traits in the two studied species is attributed to the different developmental‐genetic architectures of these traits. Female genitalia showed a similar trend to the males, although the difference between genital and somatic traits was not significant in females. This finding suggests that selection is acting differently on male and female genitalia. Positive allometry of hind tibia in H. armigera may be a result of secondary sexual function.     

Unstable ring Y chromosome in an aspermic male

Summary A ring Y chromosome was found in a male showing growth retardation and aspermia but normally developed external genitalia. The ring does not display either the characteristic brilliant Y fluorescence or the typical latereplicating heterochromatin.     

Simple Growth Patterns Can Create Complex Trajectories for the Ontogeny of Constitutive Chemical Defences in Seaweeds

All of the theory and most of the data on the ecology and evolution of chemical defences derive from terrestrial plants, which have considerable capacity for internal movement of resources. In contrast, most macroalgae – seaweeds – have no or very limited capacity for resource translocation, meaning that trade-offs between growth and defence, for example, should be localised rather than systemic. This may change the predictions of chemical defence theories for seaweeds. We developed a model that mimicked the simple growth pattern of the red seaweed Asparagopsis armata which is composed of repeating clusters of somatic cells and cells which contain deterrent secondary chemicals (gland cells). To do this we created a distinct growth curve for the somatic cells and another for the gland cells using empirical data. The somatic growth function was linked to the growth function for defence via differential equations modelling, which effectively generated a trade-off between growth and defence as these neighbouring cells develop. By treating growth and defence as separate functions we were also able to model a trade-off in growth of 2–3% under most circumstances. However, we found contrasting evidence for this trade-off in the empirical relationships between growth and defence, depending on the light level under which the alga was cultured. After developing a model that incorporated both branching and cell division rates, we formally demonstrated that positive correlations between growth and defence are predicted in many circumstances and also that allocation costs, if they exist, will be constrained by the intrinsic growth patterns of the seaweed. Growth patterns could therefore explain contrasting evidence for cost of constitutive chemical defence in many studies, highlighting the need to consider the fundamental biology and ontogeny of organisms when assessing the allocation theories for defence.     

The 48,XXXX/49,XXXXY/49,XXXX,i(Yq) mosaicism in a 3-year-old boy from a twin pregnancy

Summary A 3-year-old boy from twin pregnancy with the features of marked dystrophia from birth, deficient growth, considerable retardation of physical and mental development, numerous somatic defects, suspected congenital heart disease, and hypoplastic external genitalia, is reported. The 48,XXXX/49,XXXXY/49,XXXX,i(Yq) karyotype was diagnosed. The boy's brother, normally developed, had a 46,XY karyotype. It was found on the basis of serologic findings that the brothers were dizygotic twins.     

The Structure and Taxonomic Status of Toddia from the Cottonmouth Snake Agkistrodon piscivorus leucostoma*

SYNOPSIS. Of 163 cottonmouth snakes Agkistrodon piscivorus leucostoma from Louisiana, 4 (2.4%) were infected with Toddia França, 1911, an erythrocytic parasite said to be a protozoon. In the 4 blood films, Toddia had an average size of 1.65–1.98 μ with a total size range of 0.88–3.4 μ. In Giemsa-stained slides, the organisms were usually a round red-staining mass which was either homogeneous or sometimes contained granules. A pattern of growth was seen in which the organisms increased in size and in which there was development of an erythrocytic inclusion. The inclusion, which was not a part of the parasite, developed first as a spheroid and then became altered in shape to a crystalloid square, possibly a break-down product of the host cell hemoglobin. The first noticeable damage to the erythrocytes was to the nuclei, which became nearly round; later, when the crystalloid had formed, the host cell degenerated into a small mass containing a pycnotic nucleus, a remnant of cytoplasm and the Toddia. A review of the literature on Toddia and on Pirhemocyton Chatton & Blanc, 1914 leads to the conclusion that the organisms are closely related and that both are viruses of the DNA type.     

Copper and the biological evolution

Copper is contained in a number of enzymes and proteins. A remarkable feature is that except for the electron-carrying blue copper proteins (azurin and plastocyanin) and copper-containing cytochrome c oxidase found in some cyanobacteria and some aerobic bacteria, all copper enzymes and proteins are found only in eukaryotes. In the early and middle precambrian period when the stationary oxygen pressure in the atmosphere was quite low, copper existed as either metallic or cuprous sulfides which are very insoluble in aqueous media; thus copper might have been unavailable to organisms. The time when copper became Cu(II) upon rise of the atmospheric oxygen pressure and thus became available to organisms seems to be in the middle of Proteozoic era when first eukaryotic organisms seem to have appeared on earth. Thus copper may be considered to be an indicator element for the atmospheric evolution (switching from anoxygenic to oxygenic) and the evolution of higher organisms (eukaryotes).     

Tradeoffs between somatic and gonadal investments during development in the African clawed frog (Xenopus laevis)

Tradeoffs between time to and size at metamorphosis occur in many organisms with complex life histories. The ability to accelerate metamorphosis can increase survival to the next life stage, but the resulting smaller size at metamorphosis is often associated with lower post-metamorphic survival or reduced fecundity of adults. Reduced fecundity is thought to be because of reduced energy reserves, longer time to maturity, or reduced capacity to carry eggs or compete for mates. This pattern could also be explained by a shift in allocation to somatic growth that further retards the growth or development of reproductive tissues. The main goal of this study was to determine if the relationship between growth and development of somatic and gonadal tissues depends on environmental conditions. We address this question through two experiments in which we quantify the development and growth of the body and gonads of Xenopus laevis reared in different resource environments. First, tadpoles were reared communally and development and growth were evaluated over time. Restricted food reduced somatic and gonadal growth rate, but did not affect the developmental rate of either tissue type. Second, tadpoles were reared individually and evaluated at metamorphosis. Restricted food reduced somatic development and growth, but only influenced size, and not developmental stage of testes at metamorphosis. This work demonstrates that environmental conditions influence tradeoffs between growth and development of somatic and gonadal tissues, apparently in a sex-specific manner. These tradeoffs may contribute to phenotypic correlations between small size and reduced fitness.     

Extracellular proteins in embryogenic suspension cultures of Norway spruce (Picea abies)

Embryogenic cell lines of Norway spruce ( Picea abies ) varying in growth habit and morphology were compared as regards profiles of extracellular proteins. Similar proteins were detected in the culture medium by SDS PAGE and in vivo labeling experiments, indicating that the proteins were secreted. Approximately 20 protein bands could be detected in the medium of each cell line. Three of the bands represented glycosylated proteins, as revealed by Concanavalin A staining. Some of the secreted proteins were similar for all tested embryogenic lines of Norway spruce, others were either specific for a group of cell lines or for individual cell lines. A correlation was observed between the morphology of the somatic embryos in a cell line and the presence of secreted proteins. The embryogenic cell lines of Norway spruce can be divided into two main groups. A and B, where A is characterized by somatic embryos with dense embryoheads and B by somatic embryos with loosely aggregated cells in their embryoheads. When proteins secreted from a cell line belonging to group A were added to cell lines belonging to group B, the somatic embryos of the B type developed further and became more similar in morphology to A-type embryos. These observations indicate that cell lines belonging to group A secrete certain proteins to the culture medium that are essential for the development of somatic embryos of Norway spruce.     

In vitro cultivation of Fasciola hepatica metacercariae and of partially developed flukes recovered from mice

Attempts were made to culture the metacercariae of Fasciola hepatica under a wide variety of conditions. Of the media tested, the most successful was NCTC 135 plus 50% heat inactivated chick serum and sheep red blood cells at 37°–38°C. In this medium, somatic development of newly excysted juveniles was similar to that of flukes recovered from the liver of a mouse 11 days post-infection. There was, however, no corresponding development of the genital rudiment. Various supplements, such as liver extract, bile, yeast extract, embryo extract, egg products, monolayer cells and diphasic media were tested, but none enhanced development. The effects of various physical parameters on growth and development in vitro were examined. Cultured metacercariae appeared to be in a state of ‘suspended animation’; when injected intraperitoneally into mice they developed into egg-producing adults. Flukes recovered from the abdomen and liver of mice continued their somatic growth in vitro but their genitalia failed to develop further.     

Aneugenic effect of ionizing radiation in mammalian and human somatic cells

Aneuploidy is among the most serious impairments of hereditary material in somatic and germline cells of living organisms. Chromosome loss or the appearance of an extra homolog in the chromosome set can result in either cell death or the development of various neoplasms with high probability of malignancy. It was traditionally believed that ionizing radiation produces primarily a clastogenic effect. However, there is apparently an aneugenic component of radiation, with mechanism different from that of structural chromosome damage. The present review focuses on the evidence for the existence of the aneugenic effect of ionizing radiation in mammalian and human somatic cells.     

Female genitalia are moderately informative for phylogenetic inference and not concerted with male genitalia in Saprininae beetles (Coleoptera: Histeridae)

Our study – the first of its kind within Histeridae (Coleoptera) – deals with the female genitalia in the subfamily Saprininae, with respect to their variation and utility for phylogenetic reconstruction. Morphology of female genitalia (chiefly characters of the spermatheca, and variation of the gonocoxites, articulating sclerites and gonostyli) is herein described and depicted. We perform parsimony‐based morphological phylogenetic analyses of Saprininae using combined datasets that comprise somatic, male and female genitalia characters. We assess phylogenetic utility of female genital characters and test for their correlation with male genital characters. We found that female genitalia are generally moderately informative for phylogenetic reconstruction. The somatic and male genitalia characters (on average) possess higher phylogenetic signal; female genitalia provide better support and diagnoses for particular clades (emphasizing their importance for systematics), in which the evolution of female genitalia can be linked to environmental factors imposed by the mode of life. Regardless of the degree of informativeness, structures of female genitalia represent an additional interesting and important source of information for systematics and taxonomy. We did not find any evidence of correlated evolution between male and female genitalia.     

The concept of the organism in physiology

Summary The growth of physiology in the 19^th and 20^th centuries was accompanied by the development of disciplinary boundaries between physiology and other biological sciences. Physiology became the study of the mechanisms that underlie the functions of organisms and their component parts. Concern with the internal workings of organisms has led physiologists to focus on the maintenance of homeostasis in the internal environment rather than on the interactions of organisms with their external environments. Moreover, interest in the cellular or biochemical mechanisms that underlie organismal function has resulted in the use of inbred populations of laboratory animals in which these mechanisms can be most rigorously studied. Finally, emphasis on the function of fully developed or adult organisms has been accompanied by a relative neglect of developmental processes. Disregard for the environment, for variation, and for development has made possible major advances in our knowledge of physiological mechanisms but has led to an impoverished concept of organisms. Incorporation of evolutionary, ecological, and developmental perspectives into the study of organisms might help to unite physiology more closely with the other biological sciences and lead to a richer and fuller understanding of organisms.     

Somatic embryogenesis in peanut (Arachis hypogaea L.): stimulation of direct differentiation of somatic embryos by forchlorfenuron (CPPU)

Summary The ability of forchlorfenuron (CPPU), a substituted phenylurea compound, for inducing somatic embryogenesis in peanut (Arachis hypogaea L.) seedlings has been demonstrated. CPPU promoted somatic embryogenesis at a range of concentrations in all three peanut cultivars tested. Embryogenic response was dependent on applied CPPU concentrations. Exposure of seedlings for only two days to CPPU induced somatic embryogenesis, but the most effective treatment was to induce seed germination on media supplemented with either 2.5 or 4.0 M CPPU and to maintain the seedlings on the same medium. Number of somatic embryos and the frequency of embryogenesis was higher for younger seedlings (up to 9 days), regardless of the CPPU concentrations and seedlings older than 21 days failed to produce somatic embryos. Removal of cotyledons from the seeds drastically reduced the embryogenic potential of the seedlings. Somatic embryos developed into whole plants following their separation and subculture on a medium lacking growth regulators. The induction of somatic embryos using CPPU as a sole growth regulator may provide a useful system to study the role of this compound in plant morphogenesis.Abbreviations CPPU N-(2-chloro-4-pyridyl)-N'-phenylurea - DPU N,N'-diphenylurea - IAA Indole-3-acetic acid     

The Selection-Mutation-Drift Theory of Synonymous Codon Usage

It is argued that the bias in synonymous codon usage observed in unicellular organisms is due to a balance between the forces of selection and mutation in a finite population, with greater bias in highly expressed genes reflecting stronger selection for efficiency of translation. A population genetic model is developed taking into account population size and selective differences between synonymous codons. A biochemical model is then developed to predict the magnitude of selective differences between synonymous codons in unicellular organisms in which growth rate (or possibly growth yield) can be equated with fitness. Selection can arise from differences in either the speed or the accuracy of translation. A model for the effect of speed of translation on fitness is considered in detail, a similar model for accuracy more briefly. The model is successful in predicting a difference in the degree of bias at the beginning than in the rest of the gene under some circumstances, as observed in Escherichia coli, but grossly overestimates the amount of bias expected. Possible reasons for this discrepancy are discussed.     

Food utilization and metabolic efficiency in larval and adult house crickets

The most rapid growth of the fat body, ovaries and residual body occurred only at the time of maximal feeding, which was the time of highest metabolic rate. Larvae ceased feeding before the next moult and lost weight. Adult females did not cease feeding and never lost weight. Mated females maintained a high feeding rate that corresponded to a constant oviposition rate with no gonotrophic cycles. Virgin females maintained a lower feeding rate and maintained fully mature eggs in a viable state for life.Growth during the last larval stadium was entirely somatic and characterized by a great accumulation of a lipid rich (65%) fat body. Net growth during the first 10 days of adult life was entirely gonodal, because the small amount of residual body growth was matched by the amount of fat body loss. However, since the residual body was 60% protein and the fat body was 60% lipid, some of the somatic protein growth had to come from the diet and some of the fat body lipid went for ovarial growth.The 20% dietary protein was more than sufficient for all somatic and ovarial growth, and some protein was catabolized for energy. The amount of uric acid in larval faeces accounted for almost all protein catabolism, but in adult females half of the catabolized protein nitrogen did not appear in the faeces. With only 5% dietary lipid both larvae and adults had to synthesize additional lipids from carbohydrates to supplement absorbed lipids for growth demands. Almost all absorbed and synthesized lipids were used for somatic growth in the larvae and for ovarial growth in the adults, because the per cent of food calories used for growth greatly exceeded the per cent dry weight of food used for growth. Based on the calories and dry weight of available fuel, almost all energy production was based on carbohydrate oxidation. Some carbohydrate was used for lipid synthesis but very little was used for growth.Probably the absorption efficiency (72%) and growth efficiency (28%) was the same for both the last instar larvae and virgin females because they ate exactly the same food. However, the larval metabolic efficiency (42%) was higher than that of females (37%), which indicated that more of the absorbed food was converted to tissue during larval growth (somatic) than during adult growth (ovarial).Of the dry weight of food eaten during the last larval stadium, 30% was egested, 32% was oxidized, 28% appeared as growth, and 10% was condensed to lipid and became part of the 28% growth. Of the dry weight of food eaten during the first 10 days of adult life, 27% was egested, 41% was oxidized, 25% appeared as growth, and 6% was condensed to lipid.     

Was Lysenko (partly) right? Michurinist biology in the view of modern plant physiology and genetics.

Soviet Lysenkoism was the darkest period of modern science, and its main product--Michurinist biology--was a collection of absurd theories usually based on anecdotal observations or on a few badly designed experiments without proper controls and without any statistical evaluation of results. However, in the thirties and early forties, Lysenkoists also described (and misinterpreted) some interesting data and observations which could have been real and which might inspire modern biologists to construct testable hypotheses and suggest experiments that could extend our scientific knowledge. Here, I attempt to present an explanation in terms of modern biology of some of those phenomena, namely vegetative hybridization, wobbled heritability, heritability of environmentally induced adaptive modifications and effects of intravariety hybridization of self-fertilizing cultivars. The first two phenomena can be explained on the basis of visualization of hidden genetic and epigenetic polymorphism (originating from somatic mutations, somatic recombination and paramutations), the third phenomenon by the occurrence of intraindividual selection of somatic cell lines, and the fourth phenomenon by low heritability of phenotypic properties (and therefore also low capability to evolve) of outcrossing organisms (in comparison with self-fertilizing or asexual organisms), i.e., by a theory of frozen plasticity.     

Dissemination of Leishmanias to the organs of Syrian hamsters following intrasplenic inoculation of promastigotes

Four strains of leishmanial promastigotes were inoculated intrasplenically into male Syrian hamsters (Mesocricetus auratus). The dissemination of the parasites as amastigotes to various organs was followed at closely spaced intervals for 3.5 mo.An Israeli strain of Leishmania tropica and a strain isolated in Israel from a gerbil (Meriones shawi) displayed practically identical distribution patterns. Migration was outward from the spleen to the body surface, where intense multiplication of the amastigotes occurred, primarily in the ear pinnae and in the extremities of the limbs. A cryptic visceral infection persisted in the spleen, and most of the internal organs studied also developed cryptic infections. The bone marrow became rather heavily infected, and the epididymis, exceptionally heavily infected.An Indian strain of L. donovani led to a severe visceral infection in the spleen, liver, and bone marrow; and to mild to cryptic infections in most of the other visceral organs studied. However, no invasion of the genitalia occurred, nor did the body surface become infected.An Ethiopian strain of diffuse cutaneous leishmaniasis (DCL) was noninfective to Syrian hamsters, following either the intrasplenic or the intradermal inoculation of promastigotes.     

Somatic embryogenesis from immature embryos of redbud (Cercis canadensis)

Somatic embryos developed directly from 96 and 110 day post-anthesis Cercis canadensis L. (redbud) zygotic embryos from one of two trees sampled that were explanted onto modified Schenk and Hildebrandt medium amended with either 1, 2, 3 or 5 mg/1 2,4-D in combination with either 7.6 or 12. 6 mM ammonium ion. Although somatic embryogenesis was expressed on most media, the number of explants that produced somatic embryos and the mean number of embryos formed per explant were greatest on media that contained either 2 or 3 mg/1 2,4-D; 12.6 mM ammonium ion inhibited embryogenesis from 96 day post-anthesis explants. Zygotic embryos explanted 117 days after anthesis produced only callus and roots. Somatic embryos that were bottle-shaped or had distinct cotyledons organized roots on germination media, but only one embryo formed a shoot. No additional development occurred. Histological examination of somatic embryos showed that shoot apical meristems were poorly developed.Abbreviations 2,4-D 2, 4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - BAP 6-benzylaminopurine - FPA Formalin-propionic acid-ethanol (50%)