Polyandry increases offspring viability and mother productivity but does not decrease mother survival in Drosophila pseudoobscura.

Polyandrous mating is common, but the benefits for females of polyandry remain controversial. To test whether mating with multiple males affects female fitness, we compared lifetime components of fitness of three experimental sets of Drosophila pseudoobscura females: monogamous females allowed to copulate one time (MOC); monogamous females held with a male over her entire life and experiencing many copulations (MMC); and polyandrous females with a different male over each day of their lives and also experiencing many copulations (PMC). Consistent with previous studies in this species, females in treatments in which multiple copulations occurred, MMC and PMC, had offspring with significantly higher egg-to-adult survival (i.e., offspring viability) and higher numbers of adult offspring (i.e., productivity) than MOC females, showing that multiple inseminations enhance offspring and mother fitness. In addition, although MMC females laid significantly more eggs than polyandrous (PMC) females, percent egg-to-adult survival and number of adult offspring were higher for PMC than MMC females, showing that polyandrous mating enhances the fitness of females more than multiply mating with only one male. Inconsistent with the cost of reproduction, lifespan was not significantly longer for MOC females than for MMC or PMC females. To our knowledge, this is the first study to examine simultaneously in outbred WT Drosophila pseudoobscura the lifetime costs and benefits to females of polyandry, monogamy with a single copulation, and monogamy with repeat copulations.

Diamond-anvil cell for radial x-ray diffraction.

We have designed a new diamond-anvil cell capable of radial x-ray diffraction to pressures of a few hundred GPa. The diffraction geometry allows access to multiple angles of Ψ, which is the angle between each reciprocal lattice vector g(hkl) and the compression axis of the cell. At the 'magic angle', Ψ≈54.7°, the effects of deviatoric stresses on the interplanar spacings, d(hkl), are significantly reduced. Because the systematic errors, which are different for each d(hkl), are significantly reduced, the crystal structures and the derived equations of state can be determined reliably. At other values of Ψ, the effects of deviatoric stresses on the diffraction pattern could eventually be used to determine elastic constants.

Evolutionary rearrangement of the amylase genomic regions between Drosophila melanogaster and Drosophila pseudoobscura.

Two Drosophila pseudoobscura genomic clones have sequence similarity to the Drosophila melanogaster amylase region that maps to the 53CD region on the D. melanogaster cytogenetic map. The two clones with similarity to amylase map to sections 73A and 78C of the D. pseudoobscura third chromosome cytogenetic map. The complete sequences of both the 73A and 78C regions were compared to the D. melanogaster genome to determine if the coding region for amylase is present in both regions and to determine the evolutionary mechanism responsible for the observed distribution of the amylase gene or genes. The D. pseudoobscura 73A and 78C linkage groups are conserved with the D. melanogaster 41E and 53CD regions, respectively. The amylase gene, however, has not maintained its conserved linkage between the two species. These data indicate that amylase has moved via a transposition event in the D. melanogaster or D. pseudoobscura lineage. The predicted genes within the 73A and 78C regions show patterns of molecular evolution in synonymous and nonsynonymous sites that are consistent with previous studies of these two species.

Equation of state measurements in liquid deuterium to 70 GPa.

Using intense magnetic pressure, a method was developed to launch flyer plates to velocities in excess of 20 km/s. This technique was used to perform plate-impact, shock wave experiments on cryogenic liquid deuterium ( L-D(2)) to examine its high-pressure equation of state. Using an impedance matching method, Hugoniot measurements were obtained in the pressure range of 30-70 GPa. The results of these experiments disagree with previously reported Hugoniot measurements of L-D(2) in the pressure range above approximately 40 GPa, but are in good agreement with first principles, ab initio models for hydrogen and its isotopes.

Mathematical modelling of non-stationary fluctuation analysis for studying channel properties of synaptic AMPA receptors.

1. The molecular properties of synaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are an important factor determining excitatory synaptic transmission in the brain. Changes in the number (N) or single-channel conductance (gamma) of functional AMPA receptors may underlie synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). These parameters have been estimated using non-stationary fluctuation analysis (NSFA). 2. The validity of NSFA for studying the channel properties of synaptic AMPA receptors was assessed using a cable model with dendritic spines and a microscopic kinetic description of AMPA receptors. Electrotonic, geometric and kinetic parameters were altered in order to determine their effects on estimates of the underlying gamma. 3. Estimates of gamma were very sensitive to the access resistance of the recording (R(A)) and the mean open time of AMPA channels. Estimates of gamma were less sensitive to the distance between the electrode and the synaptic site, the electrotonic properties of dendritic structures, recording electrode capacitance and background noise. Estimates of gamma were insensitive to changes in spine morphology, synaptic glutamate concentration and the peak open probability (P(o)) of AMPA receptors. 4. The results obtained using the model agree with biological data, obtained from 91 dendritic recordings from rat CA1 pyramidal cells. A correlation analysis showed that R(A) resulted in a slowing of the decay time constant of excitatory postsynaptic currents (EPSCs) by approximately 150 %, from an estimated value of 3.1 ms. R(A) also greatly attenuated the absolute estimate of gamma by approximately 50-70 %. 5. When other parameters remain constant, the model demonstrates that NSFA of dendritic recordings can readily discriminate between changes in gamma vs. changes in N or P(o). Neither background noise nor asynchronous activation of multiple synapses prevented reliable discrimination between changes in gamma and changes in either N or P(o). 6. The model (available online) can be used to predict how changes in the different properties of AMPA receptors may influence synaptic transmission and plasticity.

The LTP Program: a data acquisition program for on-line analysis of long-term potentiation and other synaptic events.

The LTP Program is a stimulation, acquisition and on-line analysis program for studying long-term potentiation (LTP), long-term depression (LTD), and stimulus-evoked synaptic responses in general. The program is freely available from the website: www.ltp-program.com. It is a 32-bit DOS program that runs on Windows 3/95/98 computers having a Pico Technologies ADC-42, Axon Instruments' Digidata 1200, or Scientific Solution's Labmaster acquisition board. The program records two channels of activity in extracellular, current- or voltage clamp modes. It acquires < or =1,000,000 samples per sweep, and has extracellular dual pathway stimulation and epoch-like intracellular stimulation. Basic protocols include slow alternating dual pathway stimulation. LTP is induced by single train, theta burst, or primed burst stimulation. LTD is induced using fast repetitive 1 pulse sweeps (< or =2 Hz). The program analyzes all stimulus-evoked synaptic responses in both acquisition channels. Analyzes include: slope, peak amplitude/latency, population spike amplitude/latency, average amplitude, duration, area, rise time, decay time, coastline, cell resistance and patch electrode series resistance. Sweeps can be averaged and digitally filtered. Trains can be analyzed by measuring the responses of all pulses relative to the baseline of the first pulse. Stimulus artifacts can be automatically removed for accurate determination of synaptic areas and peaks during a train.

Synaptic plasticity in the hippocampal slice preparation.

Synaptic plasticity is the process by which the brain alters the strength of its synaptic connections, a fundamental function of the brain that enables individuals to learn from experience. The study of synaptic plasticity often involves the application of standard in vitro electrophysiological techniques to hippocampal slice preparations. This unit discusses many of the special considerations that are applicable for the optimal study of synaptic plasticity in this system. Most of these principles also apply to the study of synaptic plasticity in other brain slice preparations.

The frequency of heteroplasmy in the HVII region of mtDNA differs across tissue types and increases with age.

An immobilized sequence-specific oligonucleotide (SSO) probe system consisting of 16 SSO probes that detect sequence polymorphisms within five regions of the mtDNA control region was used to investigate the frequency of heteroplasmy in human mtDNA. Five regions of hypervariable region II (HVII) of the control region were studied in blood-, muscle-, heart-, and brain-tissue samples collected from 43 individuals during autopsy. An initial search for heteroplasmy was conducted by use of the SSO probe system. Samples in which multiple probe signals were detected within a region were sequenced for the HVII region, to verify the typing-strip results. The frequency of heteroplasmy was 5 of 43 individuals, or 11.6%. The frequency of heteroplasmy differed across tissue types, being higher in muscle tissue. The difference in the frequency of heteroplasmy across different age groups was statistically significant, which suggests that heteroplasmy increases with age. As a test for contamination and to confirm heteroplasmy, the samples were sequenced for the HVI region and were typed by use of a panel of five polymorphic nuclear markers. Portions of the tissues that appeared to be heteroplasmic were extracted at least one additional time; all gave identical results. The results from these tests indicate that the multiple sequences present in individual samples result from heteroplasmy and not from contamination.

An investigation of the expression mechanism of LTP of AMPA receptor-mediated synaptic transmission at hippocampal CA1 synapses using failures analysis and dendritic recordings.

There is considerable controversy surrounding the mechanism of expression of long-term potentiation of AMPA receptor-mediated synaptic transmission in the CA1 region of the hippocampus, a process thought to be important for learning and memory in the mammalian CNS. We have re-examined the expression mechanism of this form of synaptic plasticity using whole-cell dendritic recordings, minimal stimulation to activate one or a few synapses, and failures analysis. Dendritic recordings provide improved resolution of small synaptic events, as compared to previous studies using somatic recordings, because there is less dendritic filtering of signals. We find that long-term potentiation (LTP) is associated with changes in the size of synaptic responses when they occur (potency) in all cells and this is accompanied by significant decreases in failure rate in approximately 60% of the experiments. This suggests that in some cells an increase in quantal amplitude is the sole expression mechanism for LTP and, in the cells where failure rate decreased, there is an additional mechanism causing a change in quantal content.

Preliminary findings from a teleultrasound study in Alberta.

BACKGROUND AND OBJECTIVES: Ultrasound practice in Alberta requires direct supervision by an ultrasound-accredited specialist physician (sonologist). This requirement limits access to ultrasound examinations in many rural communities. A prospective study was performed to evaluate the adequacy of teleultrasound service in High Level, Alberta, with remote sonologist supervision from Edmonton, Alberta. METHODS: A total of 146 patients were evaluated in two groups. Group A (72 patients) was evaluated by both an on-site radiologist in High Level and a remote supervising radiologist in Edmonton. Group B (74 patients) was evaluated only by the remote supervising radiologist in Edmonton. The teleultrasound service included digital store-and-forward capabilities using a commercially available teleradiology system, with videoconferencing review for real-time scanning. RESULTS: The teleultrasound service was helpful to the referring physician. It made transfer unnecessary in 42% of patients, and the results of the ultrasound assessment influenced management in 59% of patients. The sonographer on site and the remote radiologists agreed on the quality of the images. The information required for diagnosis was available from the sonographer's study in the majority of cases, with second-look scanning by the on-site radiologist or videoconferencing by the remote radiologist providing a major new diagnosis in only 1% of patients. CONCLUSION: Teleultrasound service to High Level could be provided reliably with remote supervision, comparable to direct on-site supervision.

A demographic approach to selection.

The concepts of demography provide a means of combining the ecological approach to population growth with the genetical approach to natural selection. We have utilized the demographic theory of natural selection developed by Norton and Charlesworth to analyze life history schedules of births and deaths for populations of genotypes in Drosophila pseudoobscura. Our populations illustrate a stable genetic equilibrium, an unstable genetic equilibrium, and a case of no equilibrium. We have estimated population growth rates and Darwinian fitnesses of the genotypes and have explored the role of population growth in determining natural selection. The age-specific rates of births and deaths provide insights into components of selection. Both viability and fertility are important components in our populations.

Mitochondrial gene divergence of Colombian Drosophila pseudoobscura.

Isolated populations of drosophila pseudoobscura, separated from North American populations by about 2,400 km, were found in Colombia in 1960. We compared for sequences of the small ribosomal RNA (srRNA) gene on the mitochondria between North American and Colombian D. pseudoobscura in order to clarify the age of the Colombian isolates. The North American populations were not genetically different from each other but were genetically different from the Colombian populations. The Mexican strains represent the area from which the Colombian founders might have come. The estimated net nucleotide divergence between Mexican and Colombian D. pseudoobscura indicates that the Colombian population is not an ancient lineage. Phylogenies using both distance and parsimony methodologies reinforced this conclusion. The Colombian samples group together with both methods but, according to the bootstrap analysis, not significantly. It appears that the populations have not been separated long enough for their DNA sequences to show much divergence.

The evolutionary history of the amylase multigene family in Drosophila pseudoobscura.

In Drosophila pseudoobscura, the amylase (Amy) multigene family is contained within a series of inversions, or gene arrangements, on the third chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL) inversions are central to the phylogeny of arrangements, and have clusters of other arrangements derived from them. The gene arrangements belonging to each of these three clusters have a characteristic number of Amy genes, ranging from three in ST to two in SC to one in TL. This distribution pattern can reflect a history of either duplications or deletions, although the data available in the past did not permit a decision between these alternatives. We provide unambiguous evidence that three Amy genes were present before the divergence of the ST, SC, and TL arrangements. Thus, the current status of the Amy multigene family is the result of deletions in the TL and SC arrangements, which created three new pseudogenes: TL Amy2-psi, TL Amy3-psi, and SC Amy3-psi. Analysis of pseudogene sequences revealed that, in the SC and ST arrangements, pseudogene evolution has been retarded, most likely due to the homogenization effect of gene conversion. Finally, by determining the original copy number, we have reconstructed the evolutionary history of the Amy multigene family and linked it with the evolution of the central gene arrangements.

Relative effects of female fecundity and male mating success on fertility selection in Drosophila pseudoobscura.

The fertility component of natural selection acting on chromosomal inversions in two experimental populations of Drosophila pseudoobscura was subdivided into the effects of female fecundity and male mating success. The offspring of the three female genotypes could be distinguished by their mitochondrial DNA haplotypes, thus permitting a direct measurement of the relative fecundities of the female genotype. The effects of male mating success on inversion frequency were measured by comparing inversion frequencies in parents and their offspring. Selection by fertility caused significant changes in inversion frequency in both populations. In one population, the changes in inversion frequency due to female fecundity and to male mating success were comparable. In the other population, however, the changes in inversion frequency due to male mating success were considerably larger than those due to female fecundity. The difference between the two populations underscores the intrinsic variability of the fertility component of fitness.

Molecular evolution of the Sex-Ratio inversion complex in Drosophila pseudoobscura: analysis of the Esterase-5 gene region.

The Sex-Ratio chromosome in Drosophila pseudoobscura is subject to meiotic drive. It is associated with a series of three nonoverlapping paracentric inversions on the right arm of the X chromosome. The esterase-5 gene region has been localized to section 23 within the subbasal inversion of the Sex-Ratio inversion complex, making esterase-5 a convenient locus for molecular evolutionary analyses of the Sex-Ratio inversion complex and the associated drive system. A 504-bp fragment of noncoding, intergenic DNA from the esterase-5 gene region was amplified and sequenced from 14 Sex-Ratio and 14 Standard X chromosomes of D. pseudoobscura, and from 9 X chromosomes of its two sibling species, Drosophila persimilis and Drosophila miranda. There is extensive sequence differentiation between the Sex-Ratio and Standard chromosomal types. The common Standard chromosome is highly polymorphic, while, as expected from either the neutral mutation theory or the selective sweep hypothesis, the rarer Sex-Ratio chromosome has much less within-chromosome nucleotide polymorphism. We estimate that the Standard and Sex-Ratio chromosomes in D. pseudoobscura diverged between 700,000 and 1.3 Mya, or at least 2 million generations ago. The clustering of D. pseudoobscura Sex-Ratio chromosomes in a neighbor-joining phylogeny indicates a fairly old, monophyletic origin in this species. It appears from these data that Sex-Ratio genes were present prior to the divergence of D. pseudoobscura and D. persimilis and that both the Standard and Sex-Ratio chromosomes of D. persimilis were derived from the Standard chromosome of D. pseudoobscura after the inversion events that isolated the D. pseudoobscura Sex-Ratio chromosome.

Cytoplasmic incompatibility and mating preference in Colombian Drosophila pseudoobscura.

MACRAE and ANDERSON observed a large frequency change of mitochondrial DNA (mtDNA) haplotypes in a population initiated with two allopatric strains of Drosophila pseudoobscura, BogER from Colombia and AH162 from California. They concluded that mtDNA haplotypes in D. pseudoobscura are not always selectively neutral. NIGRO and PROUT suggested, however, that a maternally transmitted incompatibility system, similar to the one they observed in two strains of D. simulans from Italy, could account for the observed mtDNA frequency changes. SINGH and HALE postulated that a mating preference between the strains BogER and AH162 in MACRAF and ANDERSON's experiment, in the form of negative assortative mating, could also account for the mtDNA frequency changes. We report two experiments designed to test the hypotheses: that a maternally transmitted cytoplasmic incompatibility system exists between D. pseudoobscura strains BogER and AH162; and, that BogER females mate preferentially with AH162 males. Our results do not support either hypothesis.

Interchromosomal exchange of genetic information between gene arrangements on the third chromosome of Drosophila pseudoobscura.

During the last 60 years, the inversion polymorphism on the third chromosome of Drosophila pseudoobscura has become a case study of the evolution of linked blocks of genes, isolated from each other by the suppression of recombination in heterozygotes for different inversions. Due to its location within inverted regions in most gene arrangements, the amylase (Amy) gene region can be used to elucidate the molecular pattern of evolution in these inversions. We studied this region in the Tree Line phylad of gene arrangements, with regard to both restriction site polymorphisms (RSP) and nucleotide sequences. The analysis of restriction maps, encompassing 26 kb, corroborates the cytogenetic phylogeny established on the basis of inversion breakpoints. However, we found that the 2.7 kb of nucleotide sequences of the AmyI gene are identical in both Estes Park and Hidalgo arrangements, despite the fact that these inversions arose independently from Tree Line. These contrasting results suggest that a homogenizing force, most likely gene conversion, is able to bring about localized exchanges between otherwise isolated gene arrangements.

Evidence for gene conversion in the amylase multigene family of Drosophila pseudoobscura.

The alpha-amylase (Amy) multigene family in Drosophila pseudoobscura is located on the third chromosome, which is polymorphic for more than 40 inverted gene arrangements. The number of copies in this family ranges from one to three, depending on the arrangement in question. A previous study of the three Amy genes from the Standard (ST) arrangement suggested either that duplicated copies (Amy2 and Amy3) are functionally constrained or that they are undergoing gene conversion with Amy1. In order to elucidate further the pattern of molecular evolution in this family, we cloned and sequenced four additional Amy genes, two from the Santa Cruz (SC) and two from the Chiricahua (CH) gene arrangement. Of the two alternatives, only the hypothesis of gene conversion is supported by the sequence analysis. The homogenization effect of gene conversion has been strongest in SC, whose copies differ by only two nucleotides, less noticeable in ST, and negligible in the CH. Furthermore, the action of gene conversion is apparently localized, occurring only in the coding region. Interestingly, these results concur with the findings of other workers for the duplicated Amy genes in the Drosophila melanogaster group. Thus, the occurrence of gene conversion in the Amy multigene family seems to be a common feature in the Drosophila species studied so far.