Biomedical subjects

H J G Gundersen

Publications and source records attributed to H J G Gundersen.

7 recordsLinked to original sources

PubMed2005

Preparation and characterization of Boron carbide nanoparticles for use as a novel agent in T cell-guided boron neutron capture therapy.

Boron carbide nanoparticles are proposed as a system for T cell-guided boron neutron capture therapy. Nanoparticles were produced by ball milling in various atmospheres of commercially available boron carbide. The physical and chemical properties of the particles were investigated using transmission electron microscopy, photon correlation spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, vibrational spectroscopy, gel electrophoresis and chemical assays and reveal profound changes in surface chemistry and structural characteristics. In vitro thermal neutron irradiation of B16 melanoma cells incubated with sub-100 nm nanoparticles (381.5 microg/g (10)B) induces complete cell death. The nanoparticles alone induce no toxicity.

Animals↗

PubMed2004

Total number and mean size of alveoli in mammalian lung estimated using fractionator sampling and unbiased estimates of the Euler characteristic of alveolar openings.

Estimation of alveolar number in the lung has traditionally been done by assuming a geometric shape and counting alveolar profiles in single, independent sections. In this study, we used the unbiased disector principle to estimate the Euler characteristic (and thereby the number) of alveolar openings in rat lungs and rhesus monkey lung lobes and to obtain robust estimates of average alveolar volume. The estimator of total alveolar number was based on systematic, uniformly random sampling using the fractionator sampling design. The number of alveoli in the rat lung ranged from 17.3 x 10(6) to 24.6 x 10(6), with a mean of 20.1 x 10(6). The average number of alveoli in the two left lung lobes in the monkey ranged from 48.8 x 10(6) to 67.1 x 10(6) with a mean of 57.7 x 10(6). The coefficient of error due to stereological sampling was of the order of 0.06 in both rats and monkeys and the biological variation (coefficient of variance between individuals) was 0.15 in rat and 0.13 in monkey (left lobe, only). Between subdivisions (left/right in rat and cranial/caudal in monkey) there was an increase in variation, most markedly in the rat. With age (2-13 years) the alveolar volume increased 3-fold (as did parenchymal volume) in monkeys, but the alveolar number was unchanged. This study illustrates that use of the Euler characteristic and fractionator sampling is a robust and efficient, unbiased principle for the estimation of total alveolar number in the lung or in well-defined parts of it.

Age Factors↗

PubMed2004

No change in neuron numbers in the dentate nucleus of patients with schizophrenia estimated with a new stereological method--the smooth fractionator.

The dentate nucleus is phylogenetically the most recent nucleus in the cerebellum. Owing to its connections to the thalamus and the prefrontal cortex it may be involved in the symptomathology in schizophrenia and other psychiatric illnesses. In this stereological study we implemented the smooth fractionator, which combines the unbiased principles of the optical fractionator with a new and more efficient sampling strategy to the dentate nucleus. The smooth fractionator represents the most efficient sampling strategy described so far in stereology, in terms of reducing the sampling variance and thus increasing the efficiency. It is the first application of the smooth fractionator to human brain tissue and presents estimations of total number of neurons in the dentate nuclei of eight patients with schizophrenia compared to eight control persons. The total number of neurons in the dentate nucleus was estimated to 3.36 x 10(6) in subjects with schizophrenia, which was not statistically significant different from 3.65 x 10(6) in control subjects (P = 0.63). The advantages and disadvantages of the smooth fractionator method are discussed and its precision in practical application is estimated.

Adult↗

PubMed2004

Volume estimation from projections.

We describe a new estimator of the volume of axially convex objects from total vertical projections with known position of the vertical axis. The estimator combines the Cavalieri method with the known formula for area in terms of the support function of a convex body. We examine the accuracy of the proposed estimator for ellipsoidal objects having exactly known support function and volume. In addition, we illustrate practical problems of accuracy by implementing the method for some biological products.

Biology↗

PubMed2002

Stereological estimation of tubular length.

Very efficient and unbiased principles exist for estimating the total three-dimensional (3D), two-dimensional and zero-dimensional amounts of arbitrary structure in 3D space. The total one-dimensional length of real structure, in the ordinary sense, is an abstraction from the point of view of integral geometry. All stereological estimators of 'tubular length' are thus approximations. In addition, they are riddled by biases due to several types of artificial edges and other practical problems. This paper discusses several of these and proposes practical solutions of minimal biases.

Journal Article↗

PubMed2002

Stereological estimation of the total number of ECL cells and related parameters using the smooth, vertical fractionator in the rat oxyntic mucosa.

During the last 10 years many attempts have been made to estimate the number of enterochromaffin-like (ECL) cells in various animal studies. This is the first presentation of an unbiased stereological estimator of the total number of histamine-positive ECL cells per rat and linked to estimators of related parameters: total volume of the oxyntic mucosa, total oxyntic mucosal surface area, total oxyntic serosal surface area, surface amplification factor, average thickness of the oxyntic mucosa, total and mean volume of the ECL cells, total number of oxyntic glands and pits, mean number of ECL cells per gland, and mean number of ECL cells and glands per oxyntic serosal surface area. This study is the first application of the smooth fractionator and includes a description of all sources of sampling variance in the smooth fractionator design with newly developed predictors.

Animals↗

PubMed2002

The smooth fractionator.

A modification of the general fractionator sampling technique called the smooth fractionator is presented. It may be used in almost every situation in which sampling is performed from distinct items that are uniquely defined, often they are physically separated items or clusters like pieces, blocks, slabs, sections, etc. To each item is associated a 'guesstimate' or an associated variable with a more-or-less close--and possibly biased--relationship to the content of the item. The smooth fractionator is systematic sampling among the items arranged according to the guesstimates in a unique, symmetric sequence with one peak and minimal jumps. The smooth fractionator is both very simple to implement and so efficient that it should probably always be used unless the natural sequence of the sampling items is equally smooth. So far, there is no theory for the prediction of the efficiency of smooth fractionator designs in general, and their properties are therefore illustrated with a range of real and simulated examples. At the cost of a slightly more elaborate sampling scheme, it is, however, always possible to obtain an unbiased estimate of the real precision and of some of the variance components. The only real practical problem for always obtaining a high precision with the smooth fractionator is specimen inhomogeneity, but that is detectable at almost no extra cost. With careful designs and for sample sizes of about 10, the sampling variation for the primary, smooth fractionator sampling step may in practice often be small enough to be ignored.

Chemical Fractionation↗