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Spatial variation at the diallelic Me-2 locus in the Atlantic salmon, Salmo salar L., was analysed using data from 95 river basins. Gene diversity was apportioned as follows: 63% within samples, 20% between North America and Europe, 14% between regions within continents and 3% within and among rivers within regions. On both continents the variation between rivers was clinal with latitude and highly correlated with summer temperatures. The correlation was detectable within and between rivers. These correlations strongly suggest that variation at the locus is subject to the direct or indirect effects of natural selection, and that caution is required when interpreting between-location differentiation at the locus as evidence for distinct stocks.

The effect of natural selection on the mMEP-2* locus on measures of genetic divergence among Atlantic salmon populations was investigated by examining the pattern of change in the level of genetic differentiation (FST) averaged over loci when data on the mMEP-2* locus were either included or excluded. The level of FST among populations at various geographic scales was estimated from allele frequencies at up to four loci (sAAT-4*, IDDH-1*, IDHP-3*, and mMEP-2*). At smaller geographic scales (within river systems or limited geographic regions) levels of variance in mMEP-2* allele frequencies were reduced relative to mean levels. At larger geographic scales (across continents or the species range) variation in mMEP-2* allele frequencies was greater than mean levels. These results suggest an a priori hypothesis for the effect of selection on the mMEP-2* locus which may be applied in future studies on variation in protein coding or other (e.g. mini- and microsatellite) loci in the Atlantic salmon. It is recommended that estimates of gene flow among populations of the Atlantic salmon based on mean FST estimates which include data on the mMEP-2* locus should be viewed with caution.

At the Girnock Burn, a tributary of the River Dee in Scotland, a substantial part of the annual production of migrant juvenile salmon ( Salmo salar L.) leaves the stream in autumn rather than in spring. Previously, the status of the autumn migrants was uncertain because Carlin tagging indicated that they returned to the stream with a lower frequency than smolts tagged in spring. The difference was not attributable to the smolting of autumn migrants outside of the Girnock Burn and their homing to these new locations since adults tagged as autumn parr were also under-represented in fisheries distant from the home stream. Instead, the differences were probably artifactual and attributable to a seasonal effect of the Carlin tagging procedure itself. When juveniles were tagged instead with wire microtags, recapture rates were similar for autumn and spring migrants. This is consistent with the hypothesis that the autumn migration is an aspect of smolting. Microtagging of all juvenile migrants (paired with adipose fin clipping) indicated that the homing of adult spawners to the Girnock Burn was substantially accurate. Over the period of study 45% of fish of the sea-age classes that were expected to bear adipose fin clips did so.

The reproductive success of mature male Atlantic salmon parr (Salmo salar) under natural spawning conditions was estimated using the polymorphism at the MEP-2* locus as a genetic marker. The percentage of eggs per redd fertilized by parr varied considerably over the five redds examined (0·9–27.7%, mean 10·8%), but a gametic contribution from mature parr was detected in each case. Parr reproductive success has important implications for the population structure and evolution of the Atlantic salmon through its effect on gene flow.

The principal focus of this study was an examination of the relationship between diallelic variation at the MEP-2* locus and growth and survival in Atlantic salmon parr. In addition, patterns of growth and survival among genotypes at the AAT-I*, IDDH-I* and ZDHP-2* loci were also examined. Significant differences in growth were found among MEP-2* genotypes, with *100/ 100 homozygotes largest in one of two independent comparisons and the *125/I25 homozygotes largest in the other. No growth differences were observed among genotypes at any other locus. Although no significant differences were found in survival among genotypes at any locus, results of joint analysis of the patterns of growth and survival among MEP-2* genotypes were consistent with a model of positive size-selective mortality. The demonstration of growth differences among MEP-2* genotypes in parr and smolts may indicate an association between selection on this locus in fresh water and previously reported differences in sea-age at maturity among MEP-2* genotypes in Atlantic salmon.

Genetic variation at six enzyme loci was examined in named lines of Atlantic salmon in culture in Scotland. Twelve lines were examined in each of two years of study. Significant differences in allele frequencies were observed between the year classes of named lines and heterogeneity was present among lines in both years. Allele frequencies in farmed lines founded on fish taken from Scottish rivers or from Norwegian farmed populations differed significantly at most loci. In both cases allele frequencies differed from those in samples of wild fish taken from 18 rivers in Scotland. Most farmed lines based on the fish of single rivers also differed from wild fish in the specific rivers from which they had been derived. Genetic distances between farmed lines and their wild sources were of the same order as those between the salmon of different rivers in Scotland. No overall reduction in heterozygosity was detected in farmed lines. Most differences between the farmed lines and their wild sources appeared stochastic in origin.

We modified a previously described disposable rearing container consisting of a multicellular plastic tray and heat seal cover. A clear plastic tray that consisted of 32 individual rearing cells thermo-formed from 15-mil polyvinyl chloride plastic and a cover of 2-mil Mylar perforated with 25 pinholes/2.54 cm2 for gas exchange and coated on one side with a heat sensitive adhesive met our requirements. Experiments were conducted to compare larval developmental time, pupal size, and pupal production for southwestern corn borers, Diatraea grandiosella Dyar; fall armyworm, Spodoptera frugiperda (J. E. Smith); corn earworms, Heliothis zea (Boddie); and tobacco budworms, H. virescens (F.), reared on diet in 30-ml cups with paperboard caps with those reared in the trays. The number of days required for larvae to develop to pupae was the same for cups and trays. Southwestern corn borer and corn earworm pupae recovered from trays were 8-11% smaller than those recovered from cups. About 9% more fall armyworm and tobacco budworm pupae were collected from cups than from trays. Equal numbers of corn earworm and southwestern corn borer pupae were collected from the two containers. Procedures and equipment for using the trays in a medium-sized rearing program and advantages of their use are discussed.

The extent of evolutionary divergence of phenotypes between habitats is predominantly the result of the balance of differential natural selection and gene flow. Lava lizards (Microlophus albemarlensis) on the small island of Plaza Sur in the Galápagos archipelago inhabit contrasting habitats: dense vegetation on the western end of the island thins rapidly in a transitional area, before becoming absent on the eastern half. Associated with these habitats are phenotypic differences in traits linked to predator avoidance (increased wariness, sprint speed, and endurance in lizards from the sparsely vegetated habitat). This population provides an opportunity to test the hypothesis that reduced gene flow is necessary for phenotypic differentiation. There was no evidence of any differences among habitats in allele frequencies at six out of seven microsatellite loci examined, nor was there any indication of congruence between patterns of genetic variability and the change in vegetation regime. We infer that gene flow between the habitats on Plaza Sur must be sufficiently high to overcome genetic drift within habitats but that it does not preclude phenotypic differentiation.

The reproductive success of alternative mating behaviours may vary within and among populations in relation to environmental factors and demographic parameters. We used behavioural and genetic data to investigate how male density affects reproductive success of territoriality and sneaking in the European bitterling (Rhodeus sericeus, Cyprinidae), a freshwater fish that spawns on the gills of living freshwater mussels. Keeping the number of spawning sites constant, we manipulated male densities in laboratory and mesocosm experiments. We showed that sneaked fertilizations were common in R. sericeus, and that they increased significantly with male density. Territorial mating was almost 17 times more successful than sneaking at the lowest male density treatment, and still 2-3 times more successful at intermediate densities. However, both behaviours conferred the same fitness pay-off at the highest male density. While the success of territorial males declined with male density, the success of individual sneaking males remained constant across densities. Notably, the capacity of territorial males to outcompete sneakers by preoviposition sperm loading was the best predictor of male reproductive success, rather than aggression, body size or postoviposition ejaculation.

With the advent of protease inhibitors, the treatment of persons infected with the human immunodeficiency virus (HIV) has resulted in lower levels of the virus in the blood. The first of these protease inhibitors was saquinavir, which inhibits the HIV protease enzyme responsible for post-translational processing of Gag and Gag-Po1 poly protein precursors into their functional products. Studies have suggested that ketoconazole, given in combination with saquinavir, increases the bioavailability of saquinavir. This study compared the HIV viral load in patients treated with saquinavir alone and in combination with ketoconazole. Results showed that while all patients who received saquinavir exhibited a positive response, patients who also received ketoconazole had a greater drop in viral load levels. In addition, a greater number of patients had undetectable viral levels after 3 months on the ketoconazole/saquinavir regimen. These results indicate that the combination of saquinavir/ketoconazole for the treatment of HIV requires further study.

Cryptosporidium enteritis (CE) in patients with acquired immunodeficiency syndrome (AIDS) can be a life-threatening opportunistic infection. A retrospective review of 471 charts of patients with AIDS in our clinic, prior to the availability of clarithromycin for the treatment of Mycobacterium avium complex (MAC), revealed that seven patients with CD4 counts < 25/mm3 developed CE. The median survival period from diagnosis to death in these patients was 10.6 days. The incidence of CE in patients with CD4 counts < 50/mm3 treated with clarithromycin prophylaxis for MAC was compared with patients not receiving clarithromycin prophylaxis. Of 136 patients with AIDS, 63 received clarithromycin 500 mg twice daily, and 73 patients not treated with clarithromycin represented the control group. None of the patients who received clarithromycin developed CE compared with four patients who developed CE in the control group. All four patients in the control group who developed CE had CD4 counts < 25/mm3. All patients who received clarithromycin remained stool negative for Cryptosporidium. In a subsequent 2-year follow-up of an additional 217 AIDS patients with CD4 counts < 50/mm3 receiving clarithromycin 500 mg twice daily as MAC prophylaxis, no patient developed CE. These results provide strong evidence supporting the use of clarithromycin as prophylaxis against cryptosporidium enteritis in patients with AIDS.

In a recent criticality analysis for an array of water-moderated packages containing highly enriched uranium, the 123-group cross-section library in the SCALE system was observed to have a nonconservative discrepancy of approximately 3 to 3.5% when compared with more recently developed libraries. A simple representative system of UO{sub 2}F{sub 2}-H{sub 2}O was used to identify that the problem results from a lack of resonance data for {sup 235}U. Only a single set of self-shielded cross sections, most likely corresponding to a water-moderated infinite dilute system, was provided with the original data. The UO{sub 2}F{sub 2}-H{sub 2}O study indicates that this limitation may cause nonconservative discrepancies as high as 5.5% for some water-moderated, highly enriched uranium systems. Characteristics of the systems where the discrepancy is evident are identified and discussed.

Traditionally, nuclear data evaluations have been performed in support of the analysis and design of thermal and fast reactors. In general, the neutron spectra characteristic of the thermal and fast systems used for data testing are predominantly in the low- and high-energy range with a relatively small influence from the intermediate-energy range. In the area of nuclear criticality safety, nuclear systems arising from applications involving fissionable materials outside reactors can lead to situations very different from those most commonly found in reactor analysis and design. These systems are not limited to thermal or fast and may have significant influence from the intermediate energy range. The extension of the range of applicability of the nuclear data evaluation beyond thermal and fast systems is therefore needed to cover problems found in nuclear criticality safety. Before criticality safety calculations are performed, the bias and uncertainties of the codes and cross sections that are used must be determined. The most common sources of uncertainties, in general, are the calculational methodologies and the uncertainties related to the nuclear data, such as the microscopic cross sections, entering into the calculational procedure. The aim here is to focus on the evaluated nuclear data pertaining to applications inmore » nuclear criticality safety.« less

One hundred individuals confirmed to be infected with the human immunodeficiency virus (HIV), volunteered to participate in a pilot study comparing clinical status and enteric parasite burden with race, age, CD4 levels, risk factors and sexual practice. The prevalence of enteric parasites was 55 (55%) for Giardia lamblia, 6 (6%) for Cryptosporidium, 10 (10%) for Isospora belli and 3 (3%) for Entamoeba histolytica. There was no associations between demographic variables and the presence of parasites. The presence of giardia was significantly associated with anal-penile sex (P = .017), with an odds ratio of 2.9. A logistic regression model was used to explain the presence of any parasite by a number of sexual practices. The only practice found to be significant was anal-penile sex, which substantially increased the likelihood of the presence of the parasites. In this regression, 38.5% of pairs were concordant and 12.2% were discordant. These findings differed from surveys conducted in similar populations. The significance of this will be discussed in the context of medical service provision to this and similar populations.

Thirty-five human immunodeficiency virus (HIV)-positive patients were followed over a 2-year period. All agreed to abstain from sexual intercourse. This group had a low level of recurring infections. A comparison study of sexually active HIV males is underway.

A Nd-glass laser facility is described which is designed for studies of the laser-plasma interaction and for the development of special diagnostic instrumentation relevant to the problems of laserdriven fusion. The laser produces a 1-J, 200-psec pulse of 1.06-?m radiation which is focused into a 50--100-?m target spot to generate the plasma under study. An instrumentation package has been developed for performing x-ray diagnostic measurements to obtain information on plasma parameters. The package consists of a multichannel curved-crystal x-ray spectrograph (1 eV resolution at 1000 eV), calorimeters, and a fast x-ray diode (20-psec rise time) with a tenchannel single-shot sampler readout. This system records x-ray spectra, conversion efficiencies, and time histories of selected portions of the x-ray spectrum. With the integrated system, a complete set of data can be obtained on each laser shot.

We present the analysis of the x-ray spectrum between 9.5 and 17.0 A of a laser-produced iron plasma. Wavelengths and relative intensities for 96 lines are measured. For the strongest part of the spectrum, above 13 A, almost all of the observed lines are identified as radiation from Fe/sup XVII/, Fe/sup XVIII/, and Fe/sup XIX/ ions. Measurements were made with a curved-crystal spectrograph. Calculations were full intermediate coupling, Hartree-Fock with relativistic corrections. Coulomb-approximation oscillator strengths were used to help in the line identification. (AIP)

A method for measuring angular distributions of individual x‐ray line intensities from laser‐produced plasmas is described and applied to measure the strong angular dependence of lines from an aluminum plasma. The data are consistent with calculations made with a simple plasma model incorporating radiation reabsorption and transport in the plasma.

Twenty-one patients who presented to three sexually transmitted disease (STD) clinics in the south area of Los Angeles County were diagnosed to have anorectal or pharyngeal gonorrhea and gave a history of hypersensitivity of penicillin. Treatment with doxycycline, 300 mg initially, followed by 200 mg daily for six days was successful in all cases. None was found to have penicillinase producing gonorrhea (PPNG).

Over 950 patients in the southeast region and south area of Los Angeles County were treated with cefotaxime and the effectiveness of its treatment is reported herein.

A mean containment time τ of many seconds has been observed for a significant fraction of the energetic (≤ 2.2‐MeV) positrons emitted from Ne19 isotropically and uniformly in a mirror geometry with mirror ratio R in the range 1.1–3.7. Long‐time containment has been observed for particles that escape through a mirror at radial distances for which the particle orbits do not encircle the axis, as well as for those that escape on or near the axis. The dependence of τ on the Z of the scattering gas, the gas pressure, the positron energy, the coil current, and the diameter and separation of the coils has been investigated. Most of the data were obtained with the two mirror coils separated one coil mean diameter. For sufficiently small values of λ (the ratio of the maximum orbit diameter on axis to the coil mean diameter), τ is independent of λ and its dependence upon the above parameters agrees with the predictions of scattering theory. Also, the fraction of particles trapped as a function of the mirror ratio agrees with calculations based on the loss cone concept. These results demonstrate that the particles ``behave adiabatically'' if λ is less than about 1/10. For larger values of λ the observed τ's are shorter. Results obtained with probes are in agreement with the prediction that the intersections of particle drift surfaces with the plane midway between the mirror coils are concentric circles centered on the axis. In the cusped field resulting from opposite currents in two coils separated by one coil mean radius, containment times of several seconds have been observed at radial distances where the field is of sufficient strength that ``adiabatic behavior'' is expected. Near the axis, however, no long‐time (> 0.5‐sec) containment has been observed.

Drift surfaces of guiding centers in the Bumpy Torus static magnetic field have been located and analyzed for various torus parameters by making use of the transverse adiabatic invariant μ = p⊥2/B and the longitudinal adiabatic invariant J = ∮ p∥ dl. In addition, the drift equations (for which μ is an invariant) have been solved numerically to investigate limitations on the application of the invariance of J. In general, J is an invariant for the drift equations under adiabatic conditions; however, some special guiding‐center trajectories are presented for which the drift per longitudinal period is sufficiently large that the assumption of the invariance of J is not valid. Closed surfaces of constant U = ∮ B−1 dl have been found. These are also surfaces of constant plasma pressure under static equilibrium conditions at low β for a hydromagnetic model. The stability of the equilibrium is discussed.

The motion of a charged particle in an asymmetric mirror geometry has been studied. The asymmetric geometry for these studies is constructed by giving equal but opposite tilts to the two identical, coaxial coils of a symmetric geometry in which the coils are spaced about one coil mean diameter apart. (This is equivalent to one section of a ``bumpy torus.'') A model for describing a particle's motion in this geometry is presented. It is based on the guiding‐center drift surfaces determined theoretically from the longitudinal and transverse adiabatic invariants and the invariance of the magnitude of the momentum. The results of the experimental investigations are successfully interpreted in terms of the model.