Quantification of nanoparticles in biological systems (i.e., cells, tissues and organs) is becoming a vital part of nanotoxicological and nanomedical fields. Dose is a key parameter when assessing behavior and any potential risk of nanomaterials. Various techniques for nanoparticle quantification in cells and tissues already exist but will need further development in order to make measurements reliable, reproducible and intercomparable between different techniques. Microscopy allows detection and location of nanoparticles in cells and has been used extensively in recent years to characterize nanoparticles and their pathways in living systems. Besides microscopical techniques (light microscopy and electron microscopy mainly), analytical techniques such as mass spectrometry, an established technique in trace element analysis, have been used in nanoparticle research. Other techniques require 'labeled' particles, fluorescently, radioactively or magnetically. However, these techniques lack spatial resolution and subcellular localization is not possible. To date, only electron microscopy offers the resolving power to determine accumulation of nanoparticles in cells due to its ability to image particles individually. So-called super-resolution light microscopy techniques are emerging to provide sufficient resolution on the light microscopy level to image or 'see' particles as individual particles. Nevertheless, all microscopy techniques require statistically sound sampling strategies in order to provide quantitative results. Stereology is a well-known sampling technique in various areas and, in combination with electron microscopy, proves highly successful with regard to quantification of nanoparticle uptake by cells.

SummaryThe stereological estimation of second-order descriptors of spatial architecture appears to be inherently more timeconsuming and labour-intensive than the estimation of firstorder quantities (total quantities or ratios). Therefore, far fewer researchers tend to make use of second-order approaches in their stereological research projects. In this paper, we use a tutorial approach to illustrate how a desire for practical simplicity has provided us with a data collection method that can be used to simultaneously estimate both first-order and second-order properties of the microstructure of a defined anatomical feature of an organ. The approach does not rely on new results from theory, but nevertheless allows either isotropic uniform random or vertical uniform random sections to be used to make estimates of a comprehensive list of 10 microstructural parameters using relationships that are well known in the literature. The probe used in all cases is an isotropically distributed Ruler and the data collection protocol is easy to learn and apply. We illustrate the method on brain tissue but emphasize that the approach can also be applied to non-biological material.

No abstract

Stereological techniques were used to assess seasonal influences on morphometric characteristics of hair follicles, sweat and sebaceous glands in abattoir pelts of ponies (PN), thoroughbred (TB) and non-thoroughbred (NTB) horses. Volume density of sweat glands increased significantly from winter (0.061) to summer (0.098) in TB, and showed no change in NTB and a positive tendency in PN. There might be a body surface area : volume effect for sweat gland parameters as PN had smaller values than either TB or NTB, probably attributable to control of heat loss in winter. In summer, the skin remained thick and the volume density of sebaceous glands was increased in NTB, in contrast to TB where both were decreased. It is possible that in summer, sebum has a particular importance in NTB to enhance wicking of sweat through the pelt. TB showed significantly higher volume measurements of sebaceous glands than NTB and PN for winter: sebum has probably a special importance for water-proofing in TB in winter. PN showed no significant seasonal changes in sebaceous glands, but had a thinner summer skin. Winter values for hair follicle volume density between equine groups were similar (TB, NTB 0.066; PN 0.059), as was skin thickness (1.14-1.19 mm). The volume density lowered significantly in summer in TB and NTB. The volume of hair follicles under a unit area of skin surface decreased significantly in TB and nonsignificantly in NTB and PN. The seasonal adaptations of the skin shown here were most pronounced in TB and differed between breeds.

No abstract