Interferometric analysis of intrasection and intersection thickness variability associated with cryostat microtomy

Fundamental developments in infrared spectroscopic imaging for biomedical applications

Infrared chemical imaging is a rapidly emerging field with new advances in instrumentation, data acquisition and data analysis. These developments have had significant impact in biomedical applications and numerous studies have now shown that this technology offers great promise for the improved diagnosis of the diseased state. Relying on purely biochemical signatures rather than contrast from exogenous dyes and stains, infrared chemical imaging has the potential to revolutionise histopathology for improved disease diagnosis. In this review we discuss the recent advances in infrared spectroscopic imaging specifically related to spectral histopathology (SHP) and consider the current state of the field. Finally we consider the practical application of SHP for disease diagnosis and consider potential barriers to clinical translation highlighting current directions and the future outlook.

Comparison of transmission and transflectance mode FTIR imaging of biological tissue

FTIR microscopy is a powerful technique which has become popular due to its ability to provide complementary information during histopathological assessment of biomedical tissue samples. Recently however, questions have been raised on the suitability of the transflection mode of operation for clinical diagnosis due to the so called Electric Field Standing Wave (EFSW) effect. In this paper we compare chemical images measured in transmission and transflection from prostate tissue obtained from five different patients, and discuss the variability of the spectra acquired with each sampling modality. We find that spectra obtained in transflection undergo a non-linear distortion, i.e. non-linear variations in absorption band strength across the spectra, and that there are significant differences in spectra measured from the same area of tissue depending on the mode of operation. Principal Component Analysis (PCA) is used to highlight that poorer discrimination between benign and cancerous tissue is obtained in transflection mode. In addition we show that use of second derivatives, while qualitatively improves spectral discrimination, does not completely alleviate the underlying problem.

A novel quantitative approach for eliminating sample-to-sample variation using a hue saturation value analysis program

OBJECTIVES

As computing technology and image analysis techniques have advanced, the practice of histology has grown from a purely qualitative method to one that is highly quantified. Current image analysis software is imprecise and prone to wide variation due to common artifacts and histological limitations. In order to minimize the impact of these artifacts, a more robust method for quantitative image analysis is required.

METHODS AND RESULTS

Here we present a novel image analysis software, based on the hue saturation value color space, to be applied to a wide variety of histological stains and tissue types. By using hue, saturation, and value variables instead of the more common red, green, and blue variables, our software offers some distinct advantages over other commercially available programs. We tested the program by analyzing several common histological stains, performed on tissue sections that ranged from 4 µm to 10 µm in thickness, using both a red green blue color space and a hue saturation value color space.

CONCLUSION

We demonstrated that our new software is a simple method for quantitative analysis of histological sections, which is highly robust to variations in section thickness, sectioning artifacts, and stain quality, eliminating sample-to-sample variation.

Microfluidic processor allows rapid HER2 immunohistochemistry of breast carcinomas and significantly reduces ambiguous (2+) read-outs

Biomarker analysis is playing an essential role in cancer diagnosis, prognosis, and prediction. Quantitative assessment of immunohistochemical biomarker expression on tumor tissues is of clinical relevance when deciding targeted treatments for cancer patients. Here, we report a microfluidic tissue processor that permits accurate quantification of the expression of biomarkers on tissue sections, enabled by the ultra-rapid and uniform fluidic exchange of the device. An important clinical biomarker for invasive breast cancer is human epidermal growth factor receptor 2 [(HER2), also known as neu], a transmembrane tyrosine kinase that connotes adverse prognostic information for the patients concerned and serves as a target for personalized treatment using the humanized antibody trastuzumab. Unfortunately, when using state-of-the-art methods, the intensity of an immunohistochemical signal is not proportional to the extent of biomarker expression, causing ambiguous outcomes. Using our device, we performed tests on 76 invasive breast carcinoma cases expressing various levels of HER2. We eliminated more than 90% of the ambiguous results (n = 27), correctly assigning cases to the amplification status as assessed by in situ hybridization controls, whereas the concordance for HER2-negative (n = 31) and -positive (n = 18) cases was 100%. Our results demonstrate the clinical potential of microfluidics for accurate biomarker expression analysis. We anticipate our technique will be a diagnostic tool that will provide better and more reliable data, onto which future treatment regimes can be based.

Can you trust your cryostat? Reproducibility of cryostat section thickness

Reproducibility of cryostat section thickness is required for valid quantitative microscopy. This is generally pursued by motorized sectioning using a low but constant speed. The purpose of our study was to compare variation in section thickness between motorized and manual cryostat sectioning. Serial sections were cut from a frozen block of homogenized tissue on different days. Lactate dehydrogenase activity was histochemically detected and calibrated absorbance measurements were taken. The coefficients of variation of measurements was 9.7% for motorized sectioning and 3.3% for manual sectioning. In conclusion, section thickness is similarly reproducible after manual sectioning compared with motorized sectioning, if not better.

A new chamber method for mounting tissue sections

We describe a method for mounting tissue sections onto slides that is faster and especially useful for those sections too thin or too large to be mounted easily by conventional methods. We have devised a chamber system for mounting tissue sections onto slides under buffer solution. Because of the buoyancy of sections in the buffer solution and the elimination of fluid surface tension, it is easy to move, turn, unfold, and spread even quite large or thin tissue sections. In-solution-mounting in this chamber also greatly reduces the force of the brush tip used to maneuver sections onto the slide, thus resulting in less damage to the tissue sections. This chamber greatly facilitates mounting multiple tissue sections onto a single slide. The new method is applicable to protocols that stain tissue sections either before (e.g. cytochrome oxidase) or after (e.g. cresyl violet) section mounting.

Cytophotometric analysis of magnocellular azure B-RNA and Feulgen-DNA following chronic GABA infusion into the nucleus basalis of rats

This investigation was undertaken to examine possible cytopathic effects of GABA infusion on nucleus basalis (NBM) magnocellular neurons. Sixty-three male Long-Evans rats received unilateral, intra-NBM infusions of either GABA100 (100 micrograms/microliters/h), GABA10 (10 micrograms/microliters/h), or ultrafiltered saline (1 microliter/h) for a period of 24 hours. Rats from each of these groups were sacrificed at either 24 hours, 48 hours or 8 days following initiation of infusions. The sham operated hemisphere of each rat served as a control for the infused hemisphere. After stoichiometric azure B-RNA and Feulgen-DNA staining of brain sections, scanning-integrating microdensitometry was used to quantify GABA-induced alterations in these well established indices of neuronal toxicity. These results provide evidence that the neurotoxic effects of 24 hours of 100 micrograms/microliters-h GABA infusion are manifested within 48 hours post-initiation of infusions. Although 24 hours of 10 micrograms/microliters-h GABA infusion suppressed NBM neuronal metabolism, the lower magnitude and duration of this effect signified an impending recovery. GABA infusion resulted in little if any NBM neuronal chromatin template impairment (i.e., reduced Feulgen-DNA reactivity), irrespective of the dosage employed and the delay prior to sacrifice.

Cytophotometric assessment of Feulgen-DNA and coomassie-total cell protein in adrenocortical fasciculata cells of noise-exposed Wistar rats

The present investigation was undertaken to examine possible noise-induced alterations in adrenal fasciculata cell (AFC) metabolism, and also to determine if the magnitude of these changes differs in male versus female rats. Wistar rats approximately 3 months old were exposed to intense noise for 60 min (100 dB, re 2 x 10(-5) N(m2)-1, 350-20,000 Hz); control rats were housed under identical conditions, at an ambient noise level of 40-60 dB. Adrenal fasciculata cells (AFC) from each animal were examined for noise-induced alterations in Feulgen-DNA reactivity (as an indicator of chromatin template activity) and Coomassie-total cell protein levels using scanning-integrating cytophotometry. The results provide evidence that intense noise elicited a marked AFC metabolic enhancement in both male and female rats; the degree of this enhancement was more pronounced in males. This disparity may be due to pre-existing differences in male versus female AFC enzymatic capability and subsequent responsiveness to noise-induced activation.

Cytophotometric analysis of T-2 toxin induced alterations in chromatin condensation and neuronal nuclear volume of rat supraoptic-magnocellular neurons

Quantitative cytophotometry and ocular filar micrometry were used to monitor T-2 toxin induced alterations in chromatin and neuronal nuclear volume in supraoptic-magnocellular neurons of rat hypo-thalami. Thirty male Sprague-Dawley rats (200-220g) were given a single i.p. injection of T-2 toxin (0.5, 0.75, 1.0 and 1.5 X LD50), a trichothecene mycotoxin; rats were decapitated 8 hours post-dosing. After stoichiometric Feulgen-DNA staining of brain sections, scanning-integrating microdensitometry was used to quantify changes in the susceptibility of chromatin to Feulgen acid hydrolysis. Changes in neuronal nuclear volumes were also determined histometrically. Within the magnocellular neurons of the supraoptic nuclei, significant reductions in F-DNA reactivity were observed in the 0.5, 0.75, and 1.0 X LD50 groups (i.e. 3.7%, 4.4% and 2.5%, respectively); however, rats receiving 1.5 X LD50 T-2 toxin showed no difference in F-DNA reactivity compared to controls. In addition, ocular filar micrometry demonstrated increased neuronal nuclear volumes in all groups receiving T-2 toxin, and following an inverse trend to that seen with F-DNA stainability. Additional observations included pronounced polydipsia, polyphagia and horripilation in the experimental groups, independent of the dosages employed; these changes were evident within 1 hour post-injection. It is postulated that the T-2 toxin induced reduction in the susceptibility of chromatin to Feulgen acid hydrolysis and concomitant increases in neuronal nuclear volumes represent an early indication of impaired metabolic activity. Since these neurons are important sites of vasopressin (antidiuretic hormone) synthesis, these data suggest an impaired osmoregulatory ability. The pronounced polydipsia which occurred shortly after intoxication is further evidence of this impairment. Although these findings do not provide insight relating to the mechanism of osmoregulatory disruption, it is evident that an impaired ability to osmoregulate is among the earliest indications of acute T-2 toxin mycotoxicosis.

Cytophotometric assessment of T-2 toxin induced alterations in azure B-RNA and Coomassie-protein in supraoptic-magnocellular neurons of rat hypothalami

Quantitative cytophotometry was used to monitor T-2 toxin-induced alterations in azure B-RNA and Coomassie-total cell protein in supraoptic-magnocellular neurons of rat hypothalami. Thirty male Sprague-Dawley rats (200-220g) were given a single i.p. injection of T-2 toxin (0.5, 0.75, 1.00 and 1.50 x LD50), a trichothecene mycotoxin; rats were decapitated 8 hours post-dosing. After stoichiometric azure B-RNA and Coomassie-protein staining of brain sections, scanning-integrating microdensitometry was used to quantify toxin-induced alterations in these well established indices of neuronal toxicity. Within the magnocellular neurons of the supraoptic nuclei, significant reductions in azure B-RNA reactivity were observed in the 0.75, 1.00 and 1.50 x LD50 groups (i.e. 11%, 13% and 8%, respectively); no differences in RNA levels were observed between controls and the 0.50 x LD50 group. In addition, a decrease in Coomassie-total cell protein was seen in animals receiving 0.50, 0.75 and 1.50 x LD50 T-2 toxin (i.e. 33%, 21% and 12%, respectively); however, toxin administration did not alter protein levels in the 1.00 x LD50 group. Furthermore, a dose-dependent decrease in systolic blood pressure was observed at 8 hr. post-injections (i.e., approximately -39%, -52%, -66% and -64% for the 0.50, 0.75, 1.00 and 1.50 x LD50 groups, respectively). Additional observations include pronounced polydipsia, ascites, abdominal and subdural hemorrhage, and horripilation (piloerection) in experimental groups. It is postulated that the T-2 toxin-induced reductions in azure B-RNA and Coomassie-protein represent an early indication of impaired metabolic activity. Since these neurons are important sites of vasopressin (antidiuretic hormone) synthesis, these data suggest an impaired osmoregulatory ability. The pronounced polydipsia which occurred shortly after intoxication is further evidence of this impairment. Although these findings do not provide insight relating to the mechanism of osmoregulatory disruption, it is advanced that the supraoptic-magnocellular compartment represents an important site in T-2 toxin mycotoxicosis. Moreover, these findings support previous claims that T-2 toxin intoxication may critically impair the vasopressinergic response to toxin-induced cardiovascular collapse.

Quantitative enzyme histochemistry of rat foetal brain and trigeminal ganglion

The increasing concern and the efforts in determining neurological effects in offsprings resulting from maternal exposure to xenobiotics are faced with several difficulties in monitoring damage to the central nervous system. In this paper, the efficiency of several enzyme histochemical reactions for analysing the forebrain and the trigeminal ganglia of rat foetuses are reported. Brains of 20-day-old Sprague-Dawley rat foetuses were frozen and analysed for 18 enzymes that had previously been used to monitor initial injury caused by toxic compounds in liver and other organs. Eight enzymes appeared suitable as histochemical markers for the functional integrity of different areas in brain and ganglia of rats exposed to xenobiotics. They were lactate, malate, glycerophosphate (NAD-linked), succinate, aldehyde and glucose 6-phosphate dehydrogenases, alpha-glycerophosphate-menadione oxidoreductase and cytochrome c oxidase. The activities of the enzymes were determined by microphotometry and the arrangement of absorbances of the enzyme final reaction products into appropriate analytical tables is proposed as an efficient procedure for data analysis.

Effects of diazepam on soman-induced brain neuronal RNA depletion and lethality in rats

Studies were conducted to determine effects of the benzodiazepine anticonvulsant diazepam on soman induced brain neuronal RNA depletion and lethality in rats. Quantitative azure B-RNA cytophotometry was used to monitor RNA responses of cerebrocortical (layer V) and striatal neurons following dosages of 0.5, 0.9 and 1.5 LD50 soman (LD50 = 135 micrograms/kg, sc), whereas mean time of death and 24-h survival following 0.8, 1.2 and 1.5 LD50 were used to assess the antidotal efficacy of diazepam (2.2 mg/kg, im) pretreatment. Soman produced dose-dependent RNA depletion in both brain regions. This RNA impairment was almost completely prevented by diazepam, although neuronal RNA contents were generally slightly lower than corresponding control values. However, diazepam pretreatment was not associated with any change in mean time of death or in 24-h survival. The overall data suggest that excessive neural activity per se may underlie the genesis of soman-induced central metabolic impairments, but also appear to effectively dissociate epileptiform activity from lethal actions of soman.

Determination of correction factors of 3H-beta-self-absorption for quantitative evaluation of grain number in autoradiographic studies. Interferometric studies of different cell types in the mouse brain

Deparaffinized and Feulgen-stained sagittal sections of the mouse brain were studied interferometrically in order to measure optical path differences of euchromatin and heterochromatin of various cell types. Furthermore, the ratio eu-: heterochromatin of each cell type was determined. From these data mass densities of karyoplasm and, finally, correction factors of 3H-beta-self-absorption were calculated for comparing grain numbers of different cell types in quantitative autoradiographic studies after application of tritium-labelled substances. Remarkable differences of correction factors up to a factor of 2.18 were found. Furthermore, the actual section thickness was determined interferometrically. A reduction to about 0.60 of the microtome setting was measured in two different areas of the brain. Using mass densities together with actual section thickness correction factors for a thickness of 1 micron were calculated. This was done also for cell types outside the brain the data of which were taken from literature. Thus, differences in correction factors up to about a factor of 4 were found pointing out the importance of considering 3H-beta-self-absorption in quantitative autoradiographic studies.