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At least 19 recordsLinked to original sources
PubMed1992

Relationship of total viable and culturable cells in epiphytic populations of Pseudomonas syringae.

The direct viable count method, used to detect viable but nonculturable bacteria in aquatic systems, was modified to examine epiphytic populations of Pseudomonas syringae. Viable-population sizes determined from the number of cells that elongated when incubated with yeast extract and nalidixic acid were compared with those determined by the conventional plate count method. The plate count method accurately determined the number of viable cells in epiphytic P. syringae populations in a state of active growth under conditions of high relative humidity. The plate count method also accurately determined the number of viable cells in P. syringae inoculum, or a growing P. syringae population, subject to desiccation stress under conditions of low relative humidity. In epiphytic populations of P. syringae older than 80 h, however, the plate count underestimated the viable-population size by about two- to fourfold, suggesting that up to 75% of the P. syringae population was nonculturable. These nonculturable cells may have entered a starvation-survival state, induced by low nutrient availability in the phyllosphere environment. Epiphytic P. syringae populations undergoing rapid size changes due to growth and death under fluctuating environmental conditions in the field should be accurately enumerated by the plate count method. However, the possible underestimation of viable-population size under some circumstances should be considered in epidemiological studies of phytopathogenic bacteria and when genetically engineered microorganisms in terrestrial ecosystems are monitored.

Colony Count, Microbial↗
PubMed1989

Sample size determination for confidence intervals on the population mean and on the difference between two population means.

Sample size determination is usually based on the premise that a hypothesis test is to be used. A confidence interval can sometimes serve better than a hypothesis test. In this paper a method is presented for sample size determination based on the premise that a confidence interval for a simple mean, or for the difference between two means, with normally distributed data is to be used. For this purpose, a concept of power relevant to confidence intervals is given. Some useful tables giving required sample size using this method are also presented.

Biometry↗
PubMed1985

[Restriction map of maxicircle kinetoplastic DNA of Leishmania gymnodactyli].

Kinetoplast DNA (kDNA) of Leishmania gymnodactyli, as in other Trypanosoma species, is a complicated associate consisting of mini- and maxicircular molecules. Minicircular DNA are presented by the homogeneous in size and heterogeneous in base sequence population. Their size determined by the agarose electrophoretic mobility in gel is 920 pairs of nucleotides. Maxicircular molecules of DNA are homogeneous and contains about 38 thou pairs of nucleotides. The restriction map of maxicircular kDNA molecule of L. gymnodactyli has been made up on the basis of the cleavage data of the whole associate kDNA by restrictases.

Animals↗
PubMed1968

Efficient filtration and sizing of viruses with membrane filters.

Untreated membrane filters retain viruses by adsorption, as well as by physical restriction which occurs when the pore diameter of the filter is smaller than that of the virus particle. As originally recommended by Elford, membranes had to be pretreated with proteinaceous material to preclude virus adsorption. However, coating materials that prevent adsorption of certain viruses do not necessarily prevent adsorption of other viruses. In contrast to proteins, salts enhance virus adsorption. Viruses treated with sodium lauryl sulfate to reduce the surface tension, or purified viruses in distilled water, are not adsorbed to membranes. A procedure is recommended by which viruses may be passed through membranes with a porosity twice the diameter of the virus. Such filtrates, which contain 50 to 100% of the initial virus concentration, should be used for sizing viruses by subsequent filtration through smaller pores. The determination of virus size would then be based on the major population of particles in the virus suspension. In the past, as little as 0.1 to 0.001% of the initial virus population was the basis for size determination, because more than 99.9% of the virus was often lost by adsorption to membranes during the clarifying procedures.

Adsorption↗
PubMed1975

The counting and sizing of spermatozoa from ten animal species using a Coulter counter.

Accurately calibrated Coulter Counters, Models ZB Industrial and F, were used to count and size spermatozoa before and after Zaponin treatment which lyses accompanying debris, droplets and peripheral sperm cytoplasm. Sperm specimens from the cauda epididymis of the rabbit, Guinea pig, hamster, rat and mouse were without accompanying particles and could be sized without Zaponin treatment. The large acrosome cap of the guinea pig swelled rapidly when the spermatozoa were released into an isotonic solution and measurement was only possible after equilibrium had been reached. Zaponin treatment completely dissolved rat and hamster spermatozoa within a few seconds and about 50% of the mouse spermatozoa. Spermatozoa form the cauda epididymis of the bull were accompanied by some unspecific debris which made size determination without Zaponin treatment difficult. A separate population of cytoplasmic droplets was not present and the amount of accompanying cytoplasm, as shown by its removal with Zaponin, was the least for the species examined. The size of spermatozoa in ejaculated specimens from the dog varied considerably according to whether the cytoplasmis droplet was still present, but after Zaponin treatment all specimens were about the same size. Ejaculated specimens from the European wild boar contained a separate population of small droplets which were sufficiently different in size from the spermatozoa to allow separate counting and sizing without Zaponin treatment. Ejaculated specimens from the Rhesus monkey required incubation to release the spermatozoa from the clot before they could be counted and sized. Their size tended to vary slightly according to the length of incubation. Ejaculated specimens from the rabbit and from man were so heavily contaminated with debris that counting and sizing was not possible without Zaponin treatment. The relationship between the amount of debris and the numbers of spermatozoa was extremely variable. The debris in human specimens was separated from the spermatozoa by downward fractionation of the motile spermatozoa into increasing concentrations of bovine serum albumin, so allowing measurement of untreated spermatozoa for the first time. The sperm size distribution curves for all the ten species examined, both before and after Zaponin treatment, were positively skewed. The peaks were broader and flatter when Zaponin was not used. Sperm sizes, in terms of total volume and of the diameter of a sphere of that volume, are given for all the species at both the mode and the mean of the size distribution curves. After Zaponin treatment the mean size was between a volume of 15 and 50 mum3 or an equivalent spherical diameter of 3-5 mum. Before Zaponin treatment all the sperm types were greater than 20% larger by volume and the mean volume was between 25 and 190 mum3.

Animals↗
PubMedDate not supplied

Statistical sampling approaches.

This article describes basic sampling principles and the application of statistical sampling techniques to specific problems encountered in the Food and Drug Administration (FDA). Concepts are emphasized, and theory is minimized. The basic principles of sampling from a normal and binomial population, including confidence interval calculation and sample size determination, are briefly reviewed. Stratified, random, systematic, and judgment sampling are explained. Operating characteristic curves for attribute (and perhaps variable) sampling for acceptance of lots are derived and applied to specific FDA problems. The advantages and disadvantages of single and multiple sampling plans and plans which address multiple classes of criteria such as major and minor defects are discussed. Sampling schedules such as MIL-STD-105D and Canada's Government Specifications Board CGSB-105-GP-1 are reviewed to familiarize readers with the principles involved in these plans and to give them an idea of how they could be applied to FDA problems.

Chemistry Techniques, Analytical↗
PubMed1992

Power of the independent samples t test under a prevalent psychometric measure distribution.

Studies in psychology often have low power because of inadequate sample size. Thus, recent articles in this journal have suggested making sample size determinations through readily available tables that are based on population normality. Questions have been raised on the use of these power tables because prevalent psychometric distributions, such as the discrete mass at zero with gap that occurs with first use or onset variables, are radically nonnormal. In addition to demonstrating the robustness of the independent samples t test with respect to type I error, the major finding of this study shows that researchers may use these power tables without modification for this radically nonnormal distribution.

Adolescent↗
PubMed1991

Acute phase reaction, infarct size and in-hospital morbidity in myocardial infarction patients treated with streptokinase or recombinant tissue type plasminogen activator.

We examined the acute phase reaction in myocardial infarction after thrombolytic treatment by streptokinase or tissue plasminogen activator. The magnitude of the acute phase reaction as determined by measurements of serum C-reactive protein and amyloid-A protein did not correlate with infarct size (determined by serial measurements of creatine kinase-MB) in this patient population. On the other hand, the development of acute cardiac failure was more closely associated with the magnitude of the acute phase reaction than with infarct size. The peak serum values of C-reactive protein in patients with and without acute cardiac failure were 128 mg/l (95% confidence intervals 85-170) and 60 mg/l (30-89); P less than 0.01 and concentration time integrals 578 mg/l x days (368-787) and 205 mg/l x days (62-350); P less than 0.01. The corresponding creatine kinase-MB values were 310 U/l (191-429) and 207 U/l (125-289) not significant; and 319 U/l x days (201-437) and 204 U/l x days (124-286) not significant; respectively. Patients requiring medication for cardiac failure on discharge from hospital had higher C-reactive protein and serum amyloid A protein values than those who did not, although the difference did not quite reach statistical significance. The infarct sizes were similar whether the patients needed medication for cardiac failure at discharge or not. Subjectively felt morbidity due to myocardial infarction was linearly associated with serum C-reactive protein peak values (P less than 0.05) and concentration time integrals (P less than 0.05), but not with infarct size. We conclude that thrombolytic treatment of myocardial infarction may reduce hospital inpatient morbidity independently of the limitation of infarct size. This diminished morbidity seems to be associated with modest or low acute phase reaction.

Acute-Phase Reaction↗
PubMed1985

Sample size determination in case-control studies: the influence of the distribution of exposure.

In the design of case-control studies, the determination of the required number of cases and controls is based on consideration of the strength of the relationship between the disease and exposure to the putative cause, the variability in exposure within the population under study, and the desired size and power of the statistical test. This paper derives sample size equations for studies with a continuous exposure which allow the investigator to specify the strength of the relationship between disease and exposure in terms of relative risk, etiologic fraction or the slope of an exposure response relationship. With these formulations it becomes apparent that the size of the sample increases with decreasing variability in exposure in the population under study, a finding not apparent in the use of conventional methods of sample size determination for continuous data. The ability of a case-control study to detect a significant association between disease and exposure therefore depends critically on the distribution of exposure which exists in the community to be studied. Implications of these findings for studies of diet and cancer are discussed.

Canada↗
PubMed1984

The SCE test as a tool for cytogenetic monitoring of human exposure to occupational and environmental mutagens.

The sister chromatid exchange (SCE) test system using human peripheral lymphocytes is proposed as a valuable tool for the cytogenetic monitoring of exposure to potential chemical mutagens in the occupational environment. We examined the SCE frequencies in organic solvent-exposed workers and reviewed the effects of occupational and environmental chemicals on SCE frequencies. The results obtained in these exposed populations are rather contradictory, which may be related to confounding factors, such as personal life style (smoking, drinking, and drugs) of the examinees, tissue culture conditions and the number of subjects examined. We discussed some practical problems for exposure estimation and sample size determination and are led to the following conclusions. 1) The possible combined effects of potential mutagens and cigarette smoking should be taken into consideration when using the SCE test system. 2) Cell cycle kinetic analysis by differential chromatid staining would provide valuable information as a biological indicator for the monitoring of the workers exposed to xenobiotics. 3) By appropriately setting the number of examinees, monitoring would become more efficient in detecting an increased SCE frequency in the exposed populations. Further studies are also required to enhance the sensitivity of the SCE test system for monitoring purposes.

Benzene↗
PubMed1986

Fluid filtration and protein clearances through large and small pore populations in dog lung capillaries.

Solvent drag reflection coefficients (sigma f) for six protein fractions with hydrodynamic radii ranging from 37 to 120 A were determined using dog lung lymph CL/CP data over a range of lung lymph flows (QL). Two equivalent pore populations with effective radii of 75-85 A and 200-325 A were determined for the pulmonary capillaries over a range of mean lymph flows for 1.8 to 6.3 times control. Fractional fluid clearance through the large pore population was observed to decrease from 0.28 to 0.16 as QL increased. These data indicate that lymph flow (filtration) increased primarily by an increased filtration through small pores with relatively little increase in filtration through the large pore population. The shift to small pore filtration at high filtration rates accounts for the dependence of the homoporous estimate of total protein sigma f on lymph flow previously observed using lung lymph (Parker et al., 1981). If capillary membrane heteroporosity is present then there should be a net convective clearance of protein across the capillary caused by a volume circulation between large and small pore populations. Minimal estimates of 6-10% of protein clearance are attributed to this mechanism even in the absence of net fluid movement across the capillary. The optimal solute radius for clearance due to volume circulation is about 60 A, based on the membrane pore sizes determined for lung capillaries. Although convective transport of macromolecules is generally acknowledged to account for most transcapillary protein clearance at high filtration rates, the inclusion of a volume circulation component suggests that convection may also be the dominant mode of macromolecular transport at low filtration rates.

Animals↗
PubMed1989

The human locus coeruleus complex: an immunohistochemical and three dimensional reconstruction study.

The CA (catecholamine/catecholaminergic) cell populations of the locus coeruleus (LC) and subcoeruleus (SubC) were studied using serial sections of the human brainstem immunostained with an antibody against tyrosine hydroxylase. The tyrosine hydroxylase-immunoreactive (TH-IR) neurons were plotted in a computer reconstruction system and their number and soma size determined. Serial section computer analysis was then used to create a three dimensional reconstruction of the LC complex. The number of cells containing neuromelanin pigment was also determined and compared with the number of TH-IR cells. In our sample there were 53,900 TH-IR cells in the LC and a further 6260 cells in the SubC. These numbers were very similar to our estimates of the number of cells containing neuromelanin pigment and we concluded that virtually all of these cells were also tyrosine hydroxylase positive. The average soma size of the TH-IR cells of the LC was 37 microns and in the SubC 34 microns. In addition to these quantitative observations the morphology of the TH-IR and the Nissl stained cells is described in some detail. We also compared the groups of immunoreactive cells in the human pons with the noradrenergic groups A5-A7 described in the rat. Although in the human these groups are contiguous, A5 is not part of the LC complex. However we did find that the A7 group is equivalent to the rostroventral part of SubC while the remainder of SubC is formed by ventral A6.

Humans↗
PubMed1984

Introns excised from immunoglobulin pre-mRNAs exist as discrete species.

We have discovered a new class of transcripts of immunoglobulin kappa genes in RNA from B-lineage cells. These transcripts have the properties predicted of free introns excised from kappa mRNA precursors. RNA extracted from populations of normal mouse spleen cells polyclonally activated with B-cell mitogens contains four such transcripts; their electrophoretic mobilities correspond to the distances between the intron-exon boundary of the C kappa region and the four useable J kappa elements, and their relative abundance reflects the relative usage of those J segments. Analysis of RNA from monoclonal kappa-expressing cell lines reveals that one active locus produces one free intron, its size determined by which J element is used in that locus. Apart from their distinctive size, free introns are identified by their lack of polyadenylic acid and their ability to hybridize to cloned probes containing intron sequences, but not to the adjacent V or C exonic sequences. They have a characteristic subcellular distribution, being extractable from nuclei by treatment with nonionic detergent; nuclei thus treated retain most of the primary mRNA precursors, but few of the free introns. A high level of kappa gene expression is not a prerequisite of a cell containing detectable free kappa introns; the lymphoma 38c has only 5% or less of the amount of kappa mRNA that the plasmacytoma MCP-11 contains, yet the ratio of free intron to mRNA precursor is about the same in both cell lines. When analyzed by electrophoretic separation of sufficient resolving power, the free introns due to a single kappa locus resolve into two discrete species. We consider that this most likely reflects the existence of two conformers of the intron, one presumably a covalently intact circle and the other linear molecule.

Animals↗
PubMed1977

Optical properties of normal and injured cells. Application of cytographic analysis to cell viability and volume studies.

A cell spectrophotometer (Cytograf Model 6300 A, Bio/Physics Systems, Inc.) was tested in a cytotoxic assay using Ehrlich ascites tumor cells as a model system. Several cellular conditions associated with volume expansion, staining of cellular components and fixation of cells were applied and the magnitude of the scattering and extinction signals were tested in these diverse cellular conditions. The magnitude of the scattering pulse of a cell spectrophotometer was found to be greatly dependent on the staining color and intensity of cellular components with vital dyes or following osmium tetroxide fixation. When the absorption wavelength of the vital dye was close to the wavelength used in the cell spectrophotometer (about 630 nm), dead stained and living nonstained cell populations were completely separated from each other. The magnitude of the extinction pulse was greatly dependent on the state (normal, injured cells) and staining intensity (vital dye staining, osmium fixation) of cellular components. The magnitude of the extinction pulse was reduced from that in normal cells when cells were treated with p-chloromercuribenzene sulfonic acid or in a hypotonic solution that caused a marked volume expansion of injured cells. When cells were fixed with a mixture containing glutaraldehyde and osmium tetroxide the cellular components of normal and injured cells turned black and in these conditions the magnitude of the extinction signal was in a linear correlation to the cross-sectional area of cells. In the present study, the cell spectrophotometer proved to be an efficient method for estimation of cellular viability, based on different scattering properties of cells, offering the advantages of high speed and precision. Demonstration of the use of a variety of vital dyes having diverse extinction properties with capabilities to differentiate between living and dead cells has indicated the potential use of the cell spectrophotometer in cytotoxic assay. Modification of the magnitude of the extinction signal in the cell spectrophotometer also shows great promise for accurate automated size determination of both normal and injured cells. Previously, determination of the size of injured cells has been beset with methodologic errors.

4-Chloromercuribenzenesulfonate↗
PubMed1990

Thyroid size determined by ultrasound. Influence of physiological factors and non-thyroidal disease.

Grading of goitre size according to WHO or the palpatory estimation of thyroid volume does not allow a quantitative estimation of thyroid size or an objective follow-up during treatment with e.g. radioiodine. The present and other studies have demonstrated that the ultrasonic evaluation of thyroid volume is both accurate and precise. In addition, it is non-invasive, rapid, inexpensive and without discomfort to the patient. Using this technique it was demonstrated that thyroid volume increases with increasing age and body weight in both sexes, with weight having the most pronounced influence. The relationship between thyroid volume, body weight and age in non-goitrous healthy subjects can be described using a formula that allows the calculation of normal thyroid size for a population: Thyroid volume (ml) = 1.97 + 0.21 x bodyweight (kg) + 0.06 x age (years). Cigarette smoking is associated with an approximately 10-fold increase in goitre frequency probably due to a combination of an increased sympathetic stimulation of the thyroid and an iodine deficiency state caused by inhalation of thiocyanate. Although no seasonal alteration in serum TSH level could be demonstrated thyroid volume is 23% higher in the winter than in the summer. Cyclic alterations of thyroid volume possibly related to TSH alterations have been found with a 50% difference between minimum values in the first half and maximum values in the second half of the menstrual cycle. Nonthyroidal illnesses are associated with marked alterations in thyroid volume. Thus, chronic renal disease and acute hepatic disease demonstrate significant increases in thyroid volume although the precise mechanisms have not been clarified. Chronic hepatic disease per se and chronic nonrenal nonhepatic disease does not seem to influence thyroid volume. Chronic alcoholism, however, with or without liver cirrhosis is associated with a marked decrease in thyroid volume and an increase in the amount of fibrosis probably related to a direct toxic effect of alcohol on the thyroid. All these factors should be kept in mind when goitre frequency, goitrogenic action of drugs and goitre treatment effects are evaluated.

Age Factors↗