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D Nyberg

Publications and source records attributed to D Nyberg.

16 recordsLinked to original sources
PubMed1999

Growth Rates of Marine Ciliates on Diverse Organisms Reveal Ecological Specializations within Morphospecies.

Abstract The growth rate of 31 stocks of Euplotes, a cosmopolitan, marine, unicellular protist, on six food species representing two different food types, microalgae and bacteria, has been determined. The 31 stocks represented nine reproductively isolated groups (biological species?) based on breeding relationships. Three morphospecies, E. vannus, E. crassus, and E. minuta, each with both autogamous and cross-breeding breeding groups, were included. The mean number of fissions completed in 5 days of a breeding group growing on one of the six food species varied from zero to 17.06. There is a strong interaction between morphospecies and food type. The largest morphospecies, E. vannus, translates the nutritional content of algae into growth better than it translates that of bacteria, while the reverse is true for E. minuta, the smallest morphospecies. Autogamous breeding groups grow more rapidly on algae than on bacteria when compared to cross-breeding groups in the same morphospecies. Two breeding groups cannot grow on Escherichia coli. ANOVA of fissions completed in 5 days revealed significant main effects and interactions between many hierarchical levels of stocks and food species. These significant interactions indicate that genetically determined ecologically important information is present at all taxonomic levels-morphospecies, breeding system, breeding group, and stock. As all these levels are biologically meaningful, measuring biodiversity in the E. vannus-crassus-minuta complex solely on morphospecies will inadequately represent the ecological diversity present in the organisms and their environment.

Journal Article↗
PubMed1995

Laboratory and bedside evaluation of portable glucose meters.

A two-phase, laboratory and bedside, evaluation of blood glucose meters was conducted in this study. Four meters, the AccuData Easy (Boehringer-Mannheim, Indianapolis, IN), HemoCue Glucose (HemoCue, Mission Viejo, CA), LifeScan One Touch II (LifeScan, Milpitas, CA), and Miles Encore QA (Miles, Elkhart, IN) systems, were compared to the Nova Stat Profile 5 (Nova, Waltham, MA) as the laboratory reference. Precision, linearity, correlation to the laboratory method, interference from hematocrit, data management, and operator preference were examined. None of the meters were found to satisfy all of the study's evaluation criteria. Therefore, institutions must weigh which criteria are most important to their individual settings. Although the HemoCue Glucose was found to be technically superior, this meter had no data management capabilities. The Encore QA had greater variance and low bias, whereas the AccuData Easy had bias affected by hematocrit and glucose concentration, and the One Touch II had a negative hematocrit bias and limited linear range when compared to the Nova. Only meters meeting both minimal analytical performance and computerization requirements, the One Touch II and AccuData Easy, were selected for further evaluation. At the bedside, the One Touch II demonstrated performance consistent with the lab evaluation, whereas the AccuData Easy showed greater imprecision in the low glucose range and a correlation that varied with sample type: capillary, venous, or arterial blood. This evaluation indicates that the clinician must interpret near-patient glucose results with respect to meter limitations. FDA approval and marketing statistics, alone, are insufficient to judge the performance of the meters in routine institutional use. Independent method validation, under actual operating conditions, is a better means of predicting future performance of the meters.

Blood Glucose↗
PubMed1992

Development of sexual maturity in the ciliate Euplotes crassus: sources of variation in the timing of maturity.

The life styles of ciliated protists are particularly suitable for experimental analyses of certain aspects of developmental and genetic biology. The progression from sexual immaturity to maturity to senescence represents one of the most intriguing aspects of developmental programs. The extent to which progeny clones, their subclones, and testers used in the assay result in different lengths of immaturity has been investigated in Euplotes crassus. Six subclones from each of 12 progeny clones from a cross between stocks EC1 and EC2 were tested for maturity with stocks EC3, EC4, and EC5 on every transfer. Analysis of variance was used to partition the total variation in fissions to maturity into parts due to clones, subclones, and testers and the interactions between these levels. The error, interaction of subclones and testers, corresponds to a standard deviation of only 4.1 fissions, while the within clone within tester means range from 15.2 to 46.7 fissions; all levels except testers contribute significantly to the total variation. Most of the variability is attributable to clones (66%), the next most to error (16%), the next most to interaction of clones by testers (13%), and the least to subclones (5%). An a posteriori analysis examined whether the differences among clones were due to the cytoplasm of the clone ancestor (exconjugant), its mat (mating-type) locus genotype, or the mated pair it came from. None of these characteristics was able to interpret simply the large variability among clones. These results provide evidence that the transition from immaturity to maturity is quantitative and complex rather than a jump from one well-defined state to another.

Analysis of Variance↗
PubMed1988

Vitamin E supplementation and intense selection increase clonal life span in Paramecium tetraurelia.

Vitamin E added to standard Cerophyl medium at 0.025 mg/ml significantly increased the mean clonal life span of 32 lines of Paramecium tetraurelia from 52.5 days and 187 fissions to 59.9 days and 209 fissions (p less than .05) when compared to unsupplemented, paired controls. The age-specific death rates increased exponentially. Regression analyses found a significantly lower rate of increasing mortality for the supplemented lines compared to controls. Weekly fission rates of supplemented lines declined linearly; more slowly than controls, but not significantly so. A second experiment tested two higher levels of supplemental vitamin E (0.10 and 1.00 mg/ml). Sublines receiving 1.00 mg/ml of supplemental vitamin E had higher rates of mortality and lower fission rates initially, but the mortality rates increased and the fission rates decreased more slowly than in sublines receiving 0.10 mg/ml supplemental vitamin E, resulting in maximum clonal life spans of 141 days and 330 fissions (1.00 mg/ml sublines), compared to 74 days and 271 fissions (0.10 mg/ml sublines). Survivorship of the last individual cells (nondividing) of each clone followed an exponential decline, with a significant increase in mean survival time for supplemented compared to unsupplemented cells (p less than .05).

Animals↗
PubMed1986

Cytoplasmic inheritance of temperature sensitivity in a wild stock of Paramecium primaurelia.

One stock, GBC, has a maximum temperature of growth about 5 degrees C lower than other recently collected stocks of Paramecium primaurelia. The resistant stocks (R) are able to grow continuously at 35 degrees C while the sensitive stock (S) cells die within 48 h. The F1s of R X S crosses exhibited a cytoplasmic pattern of inheritance and all F2-by-autogamy lines derived from the S cytoplasmic parent are sensitive. The F2-by-autogamy lines cytoplasmically descended from the R parent were predominantly (93%) R in the initial assay. Upon reinvestigation one year later, only 64% of these lines were R, 9% were S, and 27% had a new phenotype, weak (W), intermediate between R and S. Backcrosses of W lines to both R and S strongly suggest that the W lines have normal cytoplasm (i.e. R) but also have nuclear gene(s) for temperature sensitivity that are derived from the original S stock. The delayed manifestation of the W phenotype is not understood.

Animals↗
PubMed1986

Limb-body wall complex: in utero sonographic diagnosis of a complicated fetal malformation.

Limb-Body Wall Complex is a complicated fetal malformation with the essential features of neural-tube defects, body-wall disruption, and limb abnormalities. This complex should be distinguished from other body-wall defects including omphalocele and gastroschisis since the prognosis for limb-body wall complex is uniformly poor. For 13 cases of this unusual fetal anomaly, sonographic, radiologic, and pathologic findings were correlated. Thoracic or abdominal body-wall defects, neural-tube abnormalities, severe scoliosis, positional deformities, and abnormalities of fetal membranes were consistently demonstrated on in utero sonograms. Results show that the diagnosis of limb-body wall complex can be made by prenatal sonography.

Abdominal Muscles↗
PubMed1983

Tissue distribution of cadmium and metallothionein as a function of time of day and dosage.

Cadmium-109 chloride (1 mg or 48 ng Cd2+/kg body wt) was administered intraperitoneally to rats at one of eight selected times of day. Exactly 48 hr later each animal was sacrificed, and the cadmium content of the blood, brain, heart, kidney, liver, and testes was determined. Metallothionein levels in the liver and kidney were also measured. Distribution and retention of cadmium was very different at the different dose levels. Approximately 60% of the higher dose of cadmium was retained in the six tissues examined, while only 11.5% of the lower dose could be accounted for in these six tissues. The liver retained the largest percentage of the administered cadmium at both dose levels, but the magnitude of the retention differed by a factor of 6 (57.3% of the higher dose and 9.6% of the lower dose). The pattern of cadmium distribution among the other tissues was also different. At the 1-mg Cd2+/kg body wt level, the kidneys accumulated the second largest fraction of cadmium, followed by the blood, heart, testes, and brain. In the 48-ng Cd2+/kg body wt groups the order was kidney, testes, blood, heart, and brain. Only in the testes of animals receiving the low dose of cadmium was there an effect of time of day, and here the effect was marked. When cadmium was administered during the dark phase of the daily cycle, the testes contained an average of six times more cadmium than when cadmium was given during the light phase. Similarly, levels of metallothionein in the kidney were significantly higher when cadmium was administered during the dark phase. A trend toward higher metallothionein levels in the liver during the dark phase was also observed, but this trend was not statistically significant.

Animals↗
PubMed1979

The effect of temperature on copper tolerance of Paramecium.

The copper tolerance of paramecium tetraurelia decreases with increased temperatures over the range of 12 C to 34 C. The relationship is linear and the correlation = - 0.98. The regression equation has an intercept of 16 micro M Cu++ at O C, and tolerance is reduced by 0.33 micro M for each degree increase in temperature.

Animals↗
PubMed1975

Genetic analysis of copper resistance in Paramecium aurelia syngen 4.

Measurement of the median tolerance limit to cupric ion of 28 wild stocks of Paramecium aurelia syngen 4 revealed a phenotypic polymorphism: two stocks showed a much greater resistance than the others. Genetic analysis showed the resistant phenotype was produced by a recessive allele, cur, identical in both resistant wild stocks. No modification of the phenotypic expression of this allele could be detected after backcrossing into different genetic backgrounds. The results are interpreted to support the importance of mutational adaptation in this inbreeding species. Possible patterns of internal genetic organization of species which rely on mutation for adaptation are discussed.

Animals↗
PubMed1975

Limits to the advantage of recombination in increasing the rate of incorporation of favorable mutants.

The advantage of recombination in increasing the rate of incorporation of favorable mutants is shown to disappear for large NU if substitution is occurring at only two loci. Recombination will, on the average, destroy all double favorable individuals in a haploid population until the product of the frequencies of the single favorable mutants exceeds 1/N. As NU increases there is an increasing probability of the occurrence of the double favorable my mutation alone. Recombination provides a significant advantage in the rate of incorporation of favorable mutants only if 2s/InN less than NU less than 2c when substitution is occurring at only two loci. If substitution is occurring at more than two loci the recombining population apparently has a substantial advantage for large NU.

Haploidy↗
PubMedDate not supplied

Fertility is not a function of geographic distance in Tetrahymena.

The fertility of crosses between wild stocks of Tetrahymena americanis (n = 93) and T. hegewischi (n = 52) was not significantly related to the square root of the distance separating the parental stocks. Much of the death was probably caused by age-related damage to the micronucleus. Despite the confounding age-related death, the conclusion that neither species has detectably isolated local populations is supported.

Animals↗