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PubMed1989

A semiautomatic image analyzer for cell counts in monolayers. III. Statistical considerations.

The image-analyzing system described in the companion paper (Thorén and Lanke, 1989) is considered from a statistical point of view. Special attention is given to the following applications: simple cell counts, viability estimation, and toxicity estimation. Different estimators are considered, their variances are discussed, and it is shown how to compute standard errors in different situations.

Analysis of Variance↗
PubMed1983

Application of the Laplace operator to scintigraphic images: comparison with conventional scintigraphy and digital filtering.

The curvature scintigram is an image, obtained by applying the Laplace operator to nuclear medicine images, that shows local variations of count rate density. Applications to liver scintigrams are described. The diagnostic quality of the curvature scintigram is compared with that of the conventional and digitally filtered scintigrams, using a series of patients who have been categorized by histology or by transmission computer tomography. From our results, the curvature scintigram demonstrates an improvement over the subjective findings of clinicians. It enables the detection of an increased number of true-positives and a reduced number of false-positives.

Carcinoma, Bronchogenic↗
PubMed1999

Impedance microbiology: applications in food hygiene.

Impedance microbiology is a rapid method that enables qualitative and quantitative tracing of microorganisms by measuring the change in the electrical conductivity. With direct impedance technology, the change in the conductivity of a liquid culture medium serves as a measuring parameter, whereas with indirect impediometry, the change in the electrical conductivity of a reaction solution, which occurs through the absorption of gases from the inoculated bacterial culture, is measured. Most investigations concerning the applicability of impediometry in food microbiology deal with the impedimetric detection or enumeration of Enterobacteriaceae, especially the detection of Salmonella. However, impediometry has been applied to other bacterial groups or species as well. Furthermore, a great number of published findings concern the impedimetric determination of the total bacterial count. The successful application of this fast method on further areas of food hygiene, such as tracing antibiotics and testing additives for their antimicrobiological effect, has also been described. In general the use of impediometry for the application areas stated has been judged positively. However, the time and expense required by the user to optimize the method, the deficits when testing slightly contaminated sample material or determining the bacterial count in those cases in which the microorganisms are sublethally damaged, and the necessity of performing individual calibration for each food category limit the applicability of impediometry.

Bacteria↗
PubMed1999

Changes in hair weight and hair count in men with androgenetic alopecia, after application of 5% and 2% topical minoxidil, placebo, or no treatment.

Quantitative estimation of hair growth using hair weight and number was recorded for 120 weeks in 4 groups of 9 men with androgenetic alopecia. Three double-blind groups applied either 2% or 5% minoxidil solution, or vehicle. The fourth group, unblinded, received no treatment. Measurements of hair weight and number were continued for 96 weeks, when treatment (if any) was stopped, though measurements were continued for another 24 weeks. Although not compared statistically, the placebo and untreated groups behaved in a similar fashion. In contrast, the 5% and 2% minoxidil treatment groups showed a statistically significant increase in mean percentage change in interval weight from baseline compared with placebo; results for number counts were usually less significant. Over 96 weeks, topical minoxidil induced and maintained an increase in interval weight over baseline of about 30%. After treatment was stopped, hair weight and number counts for the minoxidil groups returned to about the same levels as placebo in 24 weeks.

Administration, Topical↗
PubMed1999

Delay in the application of the cover glass is a potential source of error with the Makler Counting Chamber.

OBJECTIVE: To determine the effect of delaying the application of the cover glass of a Makler Counting Chamber (Sefi Medical Instruments, Haifa, Israel) on the apparent concentration of sperm or Dynabeads (Dynal Pty Ltd, Carlton, Victoria, Australia). DESIGN: Systematic alteration of the time taken to apply the cover glass. SETTING: Comprehensive infertility service. PATIENT(S): Fresh semen from a patient or washed sperm from a donor. INTERVENTION(S): For the Makler Counting Chamber, a 5-microL drop of the sperm or bead suspension was placed in the center of the lower platform and the cover glass was applied either immediately (0 seconds) or after a delay of 5, 10, or 30 seconds. MAIN OUTCOME MEASURE(S): The concentration of beads or sperm counted using an Improved Neubauer Hemocytometer or a Makler Counting Chamber. RESULT(S): There was a progressive increase in sperm concentration with a longer delay in applying the cover glass when sperm was suspended in either seminal plasma or culture medium. Repeating the experiments with Dynabeads resuspended in phosphate-buffered saline, serum, or seminal plasma showed the same trend, although the suspension of beads in serum seemed to settle the least over the first 10 seconds. CONCLUSION(S): Delay in the application of the cover glass is a potential source of error with the Makler Counting Chamber and should be avoided.

Female↗
PubMed1991

Neurogenesis in adult rat dorsal root ganglia: on counting and the count.

La Forte et al. (this issue) failed to find an increase in the numbers of dorsal root ganglion (DRG) neurons in rats of advancing age. However, their conclusion that our data (Devor and Govrin-Lippmann, 1985) to this effect were methodologically flawed is based on an incorrect application of our counting method. In fact, both their counting method and ours provide similar results when applied to the same tissue sections. We believe that the difference in results is biological. Specifically, DRG neurogenesis in adulthood occurs in animals in which growth continues throughout life (including the male Wistar-derived rats we used), but not in those whose body size stabilizes soon after sexual maturity (including the female Sprague-Dawley rats they used). With this caveat in mind, recent data of Schmalbruch (1987a,b) and others can be understood as corroborating our conclusions. However, an adequate, independent replication of our 1985 study has yet to be carried out.

Aging↗
PubMed1987

Evaluation of the phase contrast microscopy method for the detection of fibrous and other elongated mineral particulates by comparison with a STEM technique.

The USPHS/NIOSH Membrane Filter Method is used to monitor for asbestos in occupational and mining atmospheres, and employs the phase-contrast optical microscope (PCM) that under optimum conditions has a resolution of approximately 0.25 micron. While amphibole cleavage fragments are usually visible by PCM, asbestos fibers (such as amosite and chrysotile) have finer widths that may render them invisible by PCM. In this study, personal air-monitoring filters containing chrysotile, amosite and amphibole cleavage fragments from various sources have been analyzed by PCM in accordance with the USPHS/NIOSH Method and scanning transmission electron microscopy (STEM) to assess the effectiveness of the PCM technique. Each STEM specimen was prepared using a direct-transfer technique to ensure that particle size distribution and concentration were not altered. STEM results for chrysotile samples are highly variable, with 9% to 81% of regulatory particles having widths smaller than 0.25 micron--the resolution of the optical microscope. Amosite samples have 27% to 38% of regulatory particles with widths below microscope resolution, indicating that routine particle counts by PCM on these samples would underestimate true fiber content by approximately one-third. All amphibole cleavage fragment samples had regulatory particles that would be observed by PCM. Multiplication factors have been suggested for application to routine counts by PCM to more accurately assess true particle content for mineral particulates on personal air-monitoring filters.

Air Pollutants, Occupational↗
PubMed2001

Polymer composites in 2000: structure, performance, cost and compromise.

Polymer matrix composites are based on the combination of stiff, strong reinforcing fibres with either thermosetting or thermoplastic polymer matrices. Since their introduction in the early 1940s, the world market has increased to some 5 million tonnes per annum, and some composites may now be considered commodity materials. The spectrum of fibre-reinforced plastics ranges from very high-performance speciality materials costing more than $1000/kg to these commodity composites, with more modest properties, at less than $10/kg. The performance of composites is determined by the properties of the fibre, the fraction of fibre in the composite and the structure, or fibre architecture. Processing technologies have been developed which maximise fibre content and precisely control the fibre architecture allowing for the manufacture of components with mechanical properties tailored to service requirements. Many composites offer significant advantages in specific stiffness and/or specific strength over metals. This makes them attractive for applications where high mechanical performance and minimum weight are important. However, the wider acceptance of composites is based on their ability to offer a more cost-effective alternative. In particular, composites also allow a dramatic reduction in the parts count in many applications, which leads to significant manufacturing advantages and greater economy.

Journal Article↗
PubMed2004

Need for kidney transplantation in HIV-positive individuals: results of a survey in Italy.

It is well known that HIV+individuals can be affected by end-stage renal diseases (ESRD). Despite the availability of new effective antiretroviral therapies, HIV-infected people are generally excluded from kidney transplantation, the treatment of choice for ESRD. A small number of transplantations have been performed, with encouraging data in terms of graft and patient survival. To evaluate the need of kidney transplant for HIV+individuals, we designed a multicentre study which enabled the simulation of a virtual transplant waiting list for those on dialytic treatment. In 38 participating infectious disease units, 16 HIV+patients were selected for renal replacement treatment/dialytic treatment, and they were enrolled. Clinical data were collected in order to apply general exclusion criteria and evaluate HIV clinical status. Clinical data confirmed inclusion of 7/16 patients. After application of CD4+count and HIV viraemia for further selection, the number of subjects was significantly reduced. Six patients had CD4+count greater than 200/cmm (2/6 with undetectable HIV viraemia). Only 3 patients had CD4+higher than 350/cmm (1/3 with undetectable HIV viraemia). Our data represent the first evaluation of the need and eligibility for kidney transplantation for HIV+subjects with ESRD. Application of HIV infection related parameters as selection criteria has a great strength in reducing the waiting list of HIV+subjects suitable for kidney transplant and could be carefully considered when planning inclusion/exclusion criteria for experimental purposes.

Adult↗
PubMed2005

Joint modelling of bivariate longitudinal data with informative dropout and left-censoring, with application to the evolution of CD4+ cell count and HIV RNA viral load in response to treatment of HIV infection.

Several methodological issues occur in the context of the longitudinal study of HIV markers evolution. Three of them are of particular importance: (i) correlation between CD4+ T lymphocytes (CD4+) and plasma HIV RNA; (ii) left-censoring of HIV RNA due to a lower quantification limit; (iii) and potential informative dropout. We propose a likelihood inference for a parametric joint model including a bivariate linear mixed model for the two markers and a lognormal survival model for the time to drop out. We apply the model to data from patients starting antiretroviral treatment in the CASCADE collaboration where all of the three issues needed to be addressed.

Anti-HIV Agents↗
PubMed2000

Application of alpha/beta discrimination in liquid scintillation counting for the purity control of 99mTc medical solutions.

99mTc is a widely used nuclide in nuclear medicine for diagnosis. 99mTc solutions are eluted from 99Mo/99mTc generators as sodium chloride solutions. As the 99Mo source is a fission product extracted from the reprocessing of nuclear fuel, one might expect the presence of radioactive impurities. One point of special concern described in the 1997 European Pharmacopoeia (1996) is the possible contamination in alpha-impurities (U, Pu, Am, Cm, ...) which must be very low. In order to check this impurity concentration, we used liquid scintillation counting (LSC) with alpha/beta discrimination and a commercial extractive scintillator, Alphaex. We first made measurements using synthetic mixtures of alpha and beta-emitters and then using the real effluent. This paper describes the measurement procedure used with the optimum chemical conditions for a correct extraction of the alpha-emitting nuclides. The sensitivity of the method is also described from the measurements made using the real effluent with an addition of a quantitative amount of alpha particle contamination.

Biological Science Disciplines↗
PubMed1981

Application of a 'standardized factor' to egg counting techniques for better prediction of worm burdens.

The reliability of Stoll's dilution egg count technique, Beaver's direct smear technique and Katz's modified thick smear technique were evaluated on patients with ascariasis. Studies revealed that the modified thick smear technique appears to be more reliable and accurate. The use of these three techniques revealed a significant correlation between the number of eggs per gram (e.p.g.) and worm load. Following the introduction of a standardized factor in a study of 30 patients with worm infections, a highly significant correlation was obtained between the e.p.g. and the worm load for all three techniques. The use of a Standardized Factor is recommended for better prediction of the worm burden. The results of this study reveal that a female Ascaris lumbricoides lays an average of 218,094 (range 82.251-365,200) eggs daily. The ratio of male to female A. lumbricoides was 1 : 1.4.

Adolescent↗
PubMed1989

An improved retinal densitometer: design concepts and experimental applications.

A photon-counting retinal densitometer is described that has been designed optically and electronically for improved sensitivity and reliability. The device allows measurement of visual pigments through the undilated natural pupils of subjects at relatively low levels of measuring lights, and serves also as an adaptometer for direct comparisons between pigment bleaching or regeneration and light or dark adaptation. Instrumental control and data collection are by computer to permit rapid and simple data analysis and comparisons between subjects. The methods by which the sensitivity and reliability have been enhanced are described in detail, and some examples of experimental results are presented.

Dark Adaptation↗