On the Error of Counting with a Haemacytometer

Student,

doi:10.2307/2331633

Cited by 101 publications

(42 citation statements)

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“…The hemacytometer counts used for enumeration were very variable (28,47) due to small differences in pipetting, loading of the chamber, and specimen mixing. Alternatively, the turbidity due to organisms in suspension can be measured and compared with the turbidity of latex bead or barium sulfate McFarland standards.…”

Section: Discussionmentioning

confidence: 99%

A Spore Counting Method and Cell Culture Model for Chlorine Disinfection Studies of Encephalitozoon syn. Septata intestinalis

Wolk

Johnson

Rice

et al. 2000

Appl Environ Microbiol

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The microsporidia have recently been recognized as a group of pathogens that have potential for waterborne transmission; however, little is known about the effects of routine disinfection on microsporidian spore viability. In this study, in vitro growth of Encephalitozoon syn. Septata intestinalis, a microsporidium found in the human gut, was used as a model to assess the effect of chlorine on the infectivity and viability of microsporidian spores. Spore inoculum concentrations were determined by using spectrophotometric measurements (percent transmittance at 625 nm) and by traditional hemacytometer counting. To determine quantitative dose-response data for spore infectivity, we optimized a rabbit kidney cell culture system in 24-well plates, which facilitated calculation of a 50% tissue culture infective dose (TCID 50 ) and a minimal infective dose (MID) for E. intestinalis. The TCID 50 is a quantitative measure of infectivity and growth and is the number of organisms that must be present to infect 50% of the cell culture wells tested. The MID is as a measure of a system's permissiveness to infection and a measure of spore infectivity. A standardized MID and a standardized TCID 50 have not been reported previously for any microsporidian species. Both types of doses are reported in this paper, and the values were used to evaluate the effects of chlorine disinfection on the in vitro growth of microsporidia. Spores were treated with chlorine at concentrations of 0, 1, 2, 5, and 10 mg/liter. The exposure times ranged from 0 to 80 min at 25°C and pH 7. MID data for E. intestinalis were compared before and after chlorine disinfection. A 3-log reduction (99.9% inhibition) in the E. intestinalis MID was observed at a chlorine concentration of 2 mg/liter after a minimum exposure time of 16 min. The log 10 reduction results based on percent transmittance-derived spore counts were equivalent to the results based on hemacytometer-derived spore counts. Our data suggest that chlorine treatment may be an effective water treatment for E. intestinalis and that spectrophotometric methods may be substituted for labor-intensive hemacytometer methods when spores are counted in laboratory-based chlorine disinfection studies.

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Section: Discussionmentioning

confidence: 99%

A Spore Counting Method and Cell Culture Model for Chlorine Disinfection Studies of Encephalitozoon syn. Septata intestinalis

Wolk

Johnson

Rice

et al. 2000

Appl Environ Microbiol

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“…Indeed one of the classical works by the statistician W. S. Gosset, publishing under the well known synonym "Student" was to examine the distribution of yeast cells suspended in fluid using a haemocytometer (Student, 1907). The conclusion that Gosset reached was that random distribution of yeast cells in a fluid suspension is a Poisson process.…”

Section: Introductionmentioning

confidence: 99%

The contribution of simple random sampling to observed variations in faecal egg counts

Torgerson

Paul²,

Lewis

2012

Veterinary Parasitology

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It has been over 100 years since the classical paper published by Gosset in 1907, under the pseudonym "Student", demonstrated that yeast cells suspended in a fluid and measured by a haemocytometer conformed to a Poisson process. Similarly parasite eggs in a faecal suspension also conform to a Poisson process. Despite this there are common misconceptions how to analyse or interpret observations from the McMaster or similar quantitative parasitic diagnostic techniques, widely used for evaluating parasite eggs in faeces. The McMaster technique can easily be shown from a theoretical perspective to give variable results that inevitably arise from the random distribution of parasite eggs in a well mixed faecal sample. The Poisson processes that lead to this variability are described and illustrative examples of the potentially large confidence intervals that can arise from observed faecal eggs counts that are calculated from the observations on a McMaster slide. Attempts to modify the McMaster technique, or indeed other quantitative techniques, to ensure uniform egg counts are doomed to failure and belie ignorance of Poisson processes. A simple method to immediately identify excess variation/poor sampling from replicate counts is provided.

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“…The total number of GFP-expressing foci and whether they comprised single or multiple cells was recorded. Data from the controls and treatments were tested for significant differences by Student's t test (39).…”

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confidence: 99%

Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway

Gordon‐Kamm

Dilkes

Lowe

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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The genome of the Mastreviruses encodes a replication-associated protein (RepA) that interacts with members of the plant retinoblastoma-related protein family, which are putative cell cycle regulators. Expression of ZmRb1, a maize retinoblastoma-related gene, and RepA inhibited and stimulated, respectively, cell division in tobacco cell cultures. The effect of RepA was mitigated by over-expression of ZmRb1. RepA increased transformation frequency and callus growth rate of high type II maize germplasm. RepA-containing transgenic maize calli remained embryogenic, were readily regenerable, and produced fertile plants that transmitted transgene expression in a Mendelian fashion. In high type II, transformation frequency increased with the strength of the promoter driving RepA expression. When a construct in which RepA was expressed behind its native LIR promoter was used, primary transformation frequencies did not improve for two elite Pioneer maize inbreds. However, when LIR:RepA-containing transgenic embryos were used in subsequent rounds of transformation, frequencies were higher in the RepA؉ embryos. These data demonstrate that RepA can stimulate cell division and callus growth in culture, and improve maize transformation.

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On the Error of Counting with a Haemacytometer

Cited by 101 publications

References 0 publications

A Spore Counting Method and Cell Culture Model for Chlorine Disinfection Studies of Encephalitozoon syn. Septata intestinalis

A Spore Counting Method and Cell Culture Model for Chlorine Disinfection Studies of Encephalitozoon syn. Septata intestinalis

The contribution of simple random sampling to observed variations in faecal egg counts

Stimulation of the cell cycle and maize transformation by disruption of the plant retinoblastoma pathway

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