Stereological methods in cell biology: where are we--where are we going?

Sex-specific metabolic adaptations in transgenic mice overexpressing cytochrome b5 reductase-3

Cytochrome b5 reductase 3 (CYB5R3) activates respiratory metabolism in cellular systems and exerts a prolongevity action in transgenic mice overexpressing this enzyme, mimicking some of the beneficial effects of calorie restriction. The aim of our study was to investigate the role of sex on metabolic adaptations elicited by CYB5R3 overexpression, and how key markers related with mitochondrial function are modulated in skeletal muscle, one of the major contributors to resting energy expenditure. Young CYB5R3 transgenic mice did not exhibit the striking adaptations in carbon metabolism previously detected in older animals. CYB5R3 was efficiently overexpressed and targeted to mitochondria in skeletal muscle from transgenic mice regardless sex. Overexpression significantly elevated NADH in both sexes, although differences were not statistically significant for NAD+, and increased the abundance of cytochrome c and the fission protein DRP-1 in females but not in males. Moreover, while mitochondrial biogenesis and function markers (as TFAM, NRF-1 and cleaved SIRT3) were markedly upregulated by CYB5R3 overexpression in females, a downregulation was observed in males. Ultrastructural changes were also highlighted, with an increase in the number of mitochondria per surface unit, and in the size of intermyofibrillar mitochondria in transgenic females compared with their wild-type controls. Our results support that CYB5R3 overexpression upregulates markers consistent with enhanced mitochondrial biogenesis and function, and increases mitochondrial abundance in skeletal muscle, producing most of these potentially beneficial actions in females.

Mechanism of action and therapeutic route for a muscular dystrophy caused by a genetic defect in lipid metabolism

CHKB encodes one of two mammalian choline kinase enzymes that catalyze the first step in the synthesis of the membrane phospholipid phosphatidylcholine. In humans and mice, inactivation of the CHKB gene (Chkb in mice) causes a recessive rostral-to-caudal muscular dystrophy. Using Chkb knockout mice, we reveal that at no stage of the disease is phosphatidylcholine level significantly altered. We observe that in affected muscle a temporal change in lipid metabolism occurs with an initial inability to utilize fatty acids for energy via mitochondrial β-oxidation resulting in shunting of fatty acids into triacyglycerol as the disease progresses. There is a decrease in peroxisome proliferator-activated receptors and target gene expression specific to Chkb^−/− affected muscle. Treatment of Chkb^−/− myocytes with peroxisome proliferator-activated receptor agonists enables fatty acids to be used for β-oxidation and prevents triacyglyerol accumulation, while simultaneously increasing expression of the compensatory choline kinase alpha (Chka) isoform, preventing muscle cell injury.

Mutations in the CHKB gene cause muscular dystrophy. Here, the authors show that in mouse models of the disease changes in lipid metabolism are associated with decreased PPAR signaling, and show PPAR agonists can rescue expression of injury markers in myocytes in vitro.

A mouse model of inherited choline kinase β-deficiency presents with specific cardiac abnormalities and a predisposition to arrhythmia

The CHKB gene encodes choline kinase β, which catalyzes the first step in the biosynthetic pathway for the major phospholipid phosphatidylcholine. Homozygous loss-of-function variants in human CHKB are associated with a congenital muscular dystrophy. Dilated cardiomyopathy is present in some CHKB patients and can cause heart failure and death. Mechanisms underlying a cardiac phenotype due to decreased CHKB levels are not well characterized. We determined that there is cardiac hypertrophy in Chkb^−/− mice along with a decrease in left ventricle size, internal diameter, and stroke volume compared with wildtype and Chkb^+/− mice. Unlike wildtype mice, 60% of the Chkb^+/− and all Chkb^−/− mice tested displayed arrhythmic events when challenged with isoproterenol. Lipidomic analysis revealed that the major change in lipid level in Chkb^+/− and Chkb^−/− hearts was an increase in the arrhythmogenic lipid acylcarnitine. An increase in acylcarnitine level is also associated with a defect in the ability of mitochondria to use fatty acids for energy and we observed that mitochondria from Chkb^−/− hearts had abnormal cristae and inefficient electron transport chain activity. Atrial natriuretic peptide (ANP) is a hormone produced by the heart that protects against the development of heart failure including ventricular conduction defects. We determined that there was a decrease in expression of ANP, its receptor NPRA, as well as ventricular conduction system markers in Chkb^+/− and Chkb^−/− mice.

The Role of Mitochondrial Function in Peripheral Arterial Disease: Insights from Translational Studies

Recent evidence demonstrates an involvement of impaired mitochondrial function in peripheral arterial disease (PAD) development. Specific impairments have been assessed by different methodological in-vivo (near-infrared spectroscopy, ³¹P magnetic resonance spectroscopy), as well as in-vitro approaches (Western blotting of mitochondrial proteins and enzymes, assays of mitochondrial function and content). While effects differ with regard to disease severity, chronic malperfusion impacts subcellular energy homeostasis, and repeating cycles of ischemia and reperfusion contribute to PAD disease progression by increasing mitochondrial reactive oxygen species production and impairing mitochondrial function. With the leading clinical symptom of decreased walking capacity due to intermittent claudication, PAD patients suffer from a subsequent reduction of quality of life. Different treatment modalities, such as physical activity and revascularization procedures, can aid mitochondrial recovery. While the relevance of these modalities for mitochondrial functional recovery is still a matter of debate, recent research indicates the importance of revascularization procedures, with increased physical activity levels being a subordinate contributor, at least during mild stages of PAD. With an additional focus on the role of revascularization procedures on mitochondria and the identification of suitable mitochondrial markers in PAD, this review aims to critically evaluate the relevance of mitochondrial function in PAD development and progression.

Serial Block-Face Scanning Electron Microscopy (SBF-SEM) of Biological Tissue Samples

Serial block-face scanning electron microscopy (SBF-SEM) allows for the collection of hundreds to thousands of serially-registered ultrastructural images, offering an unprecedented three-dimensional view of tissue microanatomy. While SBF-SEM has seen an exponential increase in use in recent years, technical aspects such as proper tissue preparation and imaging parameters are paramount for the success of this imaging modality. This imaging system benefits from the automated nature of the device, allowing one to leave the microscope unattended during the imaging process, with the automated collection of hundreds of images possible in a single day. However, without appropriate tissue preparation cellular ultrastructure can be altered in such a way that incorrect or misleading conclusions might be drawn. Additionally, images are generated by scanning the block-face of a resin-embedded biological sample and this often presents challenges and considerations that must be addressed. The accumulation of electrons within the block during imaging, known as "tissue charging," can lead to a loss of contrast and an inability to appreciate cellular structure. Moreover, while increasing electron beam intensity/voltage or decreasing beam-scanning speed can increase image resolution, this can also have the unfortunate side effect of damaging the resin block and distorting subsequent images in the imaging series. Here we present a routine protocol for the preparation of biological tissue samples that preserves cellular ultrastructure and diminishes tissue charging. We also provide imaging considerations for the rapid acquisition of high-quality serial-images with minimal damage to the tissue block.

Serial block-face scanning electron microscopy reveals neuronal-epithelial cell fusion in the mouse cornea

The cornea is the most highly innervated tissue in the body. It is generally accepted that corneal stromal nerves penetrate the epithelial basal lamina giving rise to intra-epithelial nerves. During the course of a study wherein we imaged corneal nerves in mice, we observed a novel neuronal-epithelial cell interaction whereby nerves approaching the epithelium in the cornea fused with basal epithelial cells, such that their plasma membranes were continuous and the neuronal axoplasm freely abutted the epithelial cytoplasm. In this study we sought to determine the frequency, distribution, and morphological profile of neuronal-epithelial cell fusion events within the cornea. Serial electron microscopy images were obtained from the anterior stroma in the paralimbus and central cornea of 8–10 week old C57BL/6J mice. We found evidence of a novel alternative behavior involving a neuronal-epithelial interaction whereby 42.8% of central corneal nerve bundles approaching the epithelium contain axons that fuse with basal epithelial cells. The average surface-to-volume ratio of a penetrating nerve was 3.32, while the average fusing nerve was smaller at 1.39 (p ≤ 0.0001). Despite this, both neuronal-epithelial cell interactions involve similarly sized discontinuities in the basal lamina. In order to verify the plasma membrane continuity between fused neurons and epithelial cells we used the lipophilic membrane tracer DiI. The majority of corneal nerves were labeled with DiI after application to the trigeminal ganglion and, consistent with our ultrastructural observations, fusion sites recognized as DiI-labeled basal epithelial cells were located at points of stromal nerve termination. These studies provide evidence that neuronal-epithelial cell fusion is a cell-cell interaction that occurs primarily in the central cornea, and fusing nerve bundles are morphologically distinct from penetrating nerve bundles. This is, to our knowledge, the first description of neuronal-epithelial cell fusion in the literature adding a new level of complexity to the current understanding of corneal innervation.

Liver macrophages regulate systemic metabolism through non-inflammatory factors

Liver macrophages (LMs) have been proposed to contribute to metabolic disease through secretion of inflammatory cytokines. However, anti-inflammatory drugs lead to only modest improvements in systemic metabolism. Here we show that LMs do not undergo a proinflammatory phenotypic switch in obesity-induced insulin resistance in flies, mice and humans. Instead, we find that LMs produce non-inflammatory factors, such as insulin-like growth factor-binding protein 7 (IGFBP7), that directly regulate liver metabolism. IGFBP7 binds to the insulin receptor and induces lipogenesis and gluconeogenesis via activation of extracellular-signal-regulated kinase (ERK) signalling. We further show that IGFBP7 is subject to RNA editing at a higher frequency in insulin-resistant than in insulin-sensitive obese patients (90% versus 30%, respectively), resulting in an IGFBP7 isoform with potentially higher capacity to bind to the insulin receptor. Our study demonstrates that LMs can contribute to insulin resistance independently of their inflammatory status and indicates that non-inflammatory factors produced by macrophages might represent new drug targets for the treatment of metabolic diseases.

Low testosterone in ApoE/LDL receptor double-knockout mice is associated with rarefied testicular capillaries together with fewer and smaller Leydig cells

The testis as a site for atherosclerotic changes has so far attracted little attention. We used the apolipoprotein E (ApoE)/low density lipoprotein (LDL) receptor deficient mouse model (KO) for atherosclerosis (20, 40, 60 and 87-week-old) to investigate whether Leydig cells or the capillary network are responsible for reduced serum testosterone levels previously observed in extreme ages of this model. In KO mice, overall testosterone levels were reduced whereas the adrenal gland-specific corticosterone was increased excluding a general defect of steroid hormone production. In addition to micro-CT investigations for bigger vessels, stereology revealed a reduction of capillary length, volume and surface area suggesting capillary rarefaction as a factor for diminished testosterone. Stereological analyses of interstitial cells demonstrated significantly reduced Leydig cell numbers and size. These structural changes in the testis occurred on an inflammatory background revealed by qPCR. Reduced litter size of the KO mice suggests hypo- or infertility as a consequence of the testicular defects. Our data suggest reduced testosterone levels in this atherosclerosis model might be explained by both, rarefication of the capillary network and reduced Leydig cell number and size. Thus, this study calls for specific treatment of male infertility induced by microvascular damage through hypercholesterolemia and atherosclerosis.

Platelet recruitment promotes keratocyte repopulation following corneal epithelial abrasion in the mouse

Corneal abrasion not only damages the epithelium but also induces stromal keratocyte death at the site of injury. While a coordinated cascade of inflammatory cell recruitment facilitates epithelial restoration, it is unclear if this cascade is necessary for keratocyte recovery. Since platelet and neutrophil (PMN) recruitment after corneal abrasion is beneficial to epithelial wound healing, we wanted to determine if these cells play a role in regulating keratocyte repopulation after epithelial abrasion. A 2 mm diameter central epithelial region was removed from the corneas of C57BL/6 wildtype (WT), P-selectin deficient (P-sel^-/-), and CD18 hypomorphic (CD18^hypo) mice using the Algerbrush II. Corneas were studied at 6h intervals out to 48h post-injury to evaluate platelet and PMN cell numbers; additional corneas were studied at 1, 4, 14, and 28 days post injury to evaluate keratocyte numbers. In WT mice, epithelial abrasion induced a loss of anterior central keratocytes and keratocyte recovery was rapid and incomplete, reaching ~70% of uninjured baseline values by 4 days post-injury but no further improvement at 28 days post-injury. Consistent with a beneficial role for platelets and PMNs in wound healing, keratocyte recovery was significantly depressed at 4 days post-injury (~30% of uninjured baseline) in P-sel^-/- mice, which are known to have impaired platelet and PMN recruitment after corneal abrasion. Passive transfer of platelets from WT, but not P-sel^-/-, into P-sel^-/- mice prior to injury restored anterior central keratocyte numbers at 4 days post-injury to P-sel^-/- uninjured baseline levels. While PMN infiltration in injured CD18^hypo mice was similar to injured WT mice, platelet recruitment was markedly decreased and anterior central keratocyte recovery was significantly reduced (~50% of baseline) at 4–28 days post-injury. Collectively, the data suggest platelets and platelet P-selectin are critical for efficient keratocyte recovery after corneal epithelial abrasion.

Macrophages and Leydig cells in testicular biopsies of azoospermic men

A number of studies have indicated that testicular macrophages play an important role in regulating steroidogenesis of Leydig cells and maintain homeostasis within the testis. The current paper deals with macrophages (CD68 positive cells) and Leydig cells in patients with nonobstructive azoospermia (NOA). Methods employed included histological analysis on semi- and ultrathin sections, immunohistochemistry, morphometry, and hormone analysis in the blood serum. Histological analysis pointed out certain structural changes of macrophages and Leydig cells in NOA group of patients when compared to controls. In the testis interstitium, an increased presence of CD68 positive cells has been noted. Leydig cells in NOA patients displayed a kind of a mosaic picture across the same bioptic sample: both normal and damaged Leydig cells with pronounced vacuolisation and various intensity of expression of testosterone have been observed. Stereological analysis indicated a significant increase in volume density of both CD68 positive and vacuolated Leydig cells and a positive correlation between the volume densities of these cell types. The continuous gonadotropin overstimulation of Leydig cells, together with a negative paracrine action of macrophages, could result in the damage of steroidogenesis and deficit of testosterone in situ.

Magnetic resonance imaging for rapid screening for the nephrotoxic and hepatotoxic effects of microcystins

In vivo visualization of kidney and liver damage by Magnetic Resonance Imaging (MRI) may offer an advantage when there is a need for a simple, non-invasive and rapid method for screening of the effects of potential nephrotoxic and hepatotoxic substances in chronic experiments. Here, we used MRI for monitoring chronic intoxication with microcystins (MCs) in rat. Male adult Wistar rats were treated every other day for eight months, either with MC-LR (10 μg/kg i.p.) or MC-YR (10 μg/kg i.p.). Control groups were treated with vehicle solutions. T1-weighted MR-images were acquired before and at the end of the eight months experimental period. Kidney injury induced by the MCs presented with the increased intensity of T1-weighted MR-signal of the kidneys and liver as compared to these organs from the control animals treated for eight months, either with the vehicle solution or with saline. The intensification of the T1-weighted MR-signal correlated with the increased volume density of heavily injured tubuli (R2 = 0.77), with heavily damaged glomeruli (R2 = 0.84) and with volume density of connective tissue (R2 = 0.72). The changes in the MR signal intensity probably reflect the presence of an abundant proteinaceous material within the dilated nephrons and proliferation of the connective tissue. T1-weighted MRI-is a valuable method for the in vivo screening of kidney and liver damage in rat models of intoxication with hepatotoxic and nephrotoxic agents, such as microcystins.

Quantitative pathology in virtual microscopy: history, applications, perspectives

With the emerging success of commercially available personal computers and the rapid progress in the development of information technologies, morphometric analyses of static histological images have been introduced to improve our understanding of the biology of diseases such as cancer. First applications have been quantifications of immunohistochemical expression patterns. In addition to object counting and feature extraction, laws of thermodynamics have been applied in morphometric calculations termed syntactic structure analysis. Here, one has to consider that the information of an image can be calculated for separate hierarchical layers such as single pixels, cluster of pixels, segmented small objects, clusters of small objects, objects of higher order composed of several small objects. Using syntactic structure analysis in histological images, functional states can be extracted and efficiency of labor in tissues can be quantified. Image standardization procedures, such as shading correction and color normalization, can overcome artifacts blurring clear thresholds. Morphometric techniques are not only useful to learn more about biological features of growth patterns, they can also be helpful in routine diagnostic pathology. In such cases, entropy calculations are applied in analogy to theoretical considerations concerning information content. Thus, regions with high information content can automatically be highlighted. Analysis of the "regions of high diagnostic value" can deliver in the context of clinical information, site of involvement and patient data (e.g. age, sex), support in histopathological differential diagnoses. It can be expected that quantitative virtual microscopy will open new possibilities for automated histological support. Automated integrated quantification of histological slides also serves for quality assurance. The development and theoretical background of morphometric analyses in histopathology are reviewed, as well as their application and potential future implementation in virtual microscopy.

ICAM-1 mediates surface contact between neutrophils and keratocytes following corneal epithelial abrasion in the mouse

Corneal epithelial abrasion elicits an inflammatory response involving neutrophil (PMN) recruitment from the limbal vessels into the corneal stroma. These migrating PMNs make surface contact with collagen and stromal keratocytes. Using mice deficient in PMN integrin CD18, we previously showed that PMN contact with stromal keratocytes is CD18-dependent, while contact with collagen is CD18-independent. In the present study, we wished to extend these observations and determine if ICAM-1, a known ligand for CD18, mediates PMN contact with keratocytes during corneal wound healing. Uninjured and injured right corneas from C57Bl/6 wild type (WT) mice and ICAM-1(-/-) mice were processed for transmission electron microscopy and imaged for morphometric analysis. PMN migration, stromal thickness, and ICAM-1 staining were evaluated using light microscopy. Twelve hours after epithelial abrasion, PMN surface contact with paralimbal keratocytes in ICAM-1(-/-) corneas was reduced to  ˜ 50% of that observed in WT corneas; PMN surface contact with collagen was not affected. Stromal thickness (edema), keratocyte network surface area and keratocyte shape were similar in ICAM-1(-/-) and WT corneas. WT keratocyte ICAM-1 expression was detected at baseline and ICAM-1 staining intensity increased following injury. Since ICAM-1 is readily detected on mouse keratocytes and PMN-keratocyte surface contact in ICAM-1(-/-) mice is markedly reduced, the data suggest PMN adhesive interactions with keratocyte-stromal networks is in part regulated by keratocyte ICAM-1 expression.

Histopathological changes of the nasal mucosa induced by smoking

Changes in the histopathology of the respiratory epithelium in response to cigarette smoking have been studied in depth in the lungs, but data on the nasal lining are lacking. The aim of the present retrospective study was to investigate the histological changes that occur in the nasal mucosa of smokers compared with non-smokers. The study group included 47 patients who underwent partial resection of the inferior turbinates. Archival nasal tissue samples were collected and examined by light microscopy: the number of goblet cells was counted, and the degree of inflammation, congestion, and edema was graded as mild, moderate, or severe. Epithelial thickness was measured as well. Findings were compared between smokers (n = 21) and non-smokers (n = 26). On statistical analysis, significant differences were found between the smokers and non-smokers in mean number of goblet cells in the nasal epithelium, 43.43 +/- 16.80 vs. 16.23 +/- 5.65 respectively (p < 0.0001), mean edema grade, 2.43 +/- 0.75 vs. 1.12 +/- 0.33 respectively (p < 0.0001), and mean epithelial thickness, 111.9 +/- 25.8 microm vs. 60.4 +/- 18.4 microm respectively (p < 0.0001). The corresponding mean values of congestion were 2 +/- 0.71 and 1.27 +/- 0.67 (p < 0.001), and of inflammation, 1.81 +/- 0.60 and 1.81 +/- 0.85 (NS). In conclusion, the histopathological findings in the nasal mucosa of smokers resemble reported findings in the bronchial respiratory epithelium. The main differences from non-smokers are greater goblet cell hyperplasia and thicker epithelium.

Graft remodeling during growth following anterior cruciate ligament reconstruction in skeletally immature sheep

INTRODUCTION

Ruptures of the anterior cruciate ligament are being diagnosed with increasing frequency in skeletally immature individuals. It was our aim to investigate the graft remodelling process following an autologous, transphyseal reconstruction of the anterior cruciate ligament (ACL) in skeletally immature sheep. We hypothesized that the ligamentisation process in immature sheep is quicker and more complete when compared to adult sheep.

MATERIALS AND METHODS

Skeletally immature sheep with an age of 4 months underwent a fully transphyseal ACL reconstruction using an autologous tendon. The animals were subsequently sacrificed at 3, 6, 12 and 24 weeks following surgery. Each group was characterised histomorphometrically, by immunostaining (VEGF, SMA), by transmission electron microscopy (TEM) and biomechanically (UFS Roboter).

RESULTS

The histomorphometric analysis and presence of VEGF and SMA positive cells demonstrated a rapid return to a ligament like structure. The biomechanical analysis revealed an anteroposterior translation that was still increased even 6 months following surgery.

CONCLUSION

As in adult sheep models, the remodeling of a soft tissue graft used for ACL reconstruction results in a biomechanically inferior substitute. However, the immature tissue seems to remodel faster and more complete when compared to adults.

Does the use of recombinant AAV5 in pulmonary gene therapy lead to lung damage?

This study investigated whether repeated administration of recombinant adeno-associated virus type 5 (rAAV5) to the airways induces inflammatory processes in the lungs of BALB/c-mice, with mechanical and histologic changes. Saline was instilled intratracheally in the control group, and rAAV5-green fluorescence protein (GFP) (4x10(11)particles) in the virus group (VR). These groups were subdivided into four subgroups: one dose analyzed 3 weeks later (VR1d3w) and two doses analyzed 1 (VR2d1w), 2 (VR2d2w) and 3 weeks (VR2d3w) after the second dose. Lung morphometry, mechanical parameters, airway responsiveness, rAAV5-GFP transduction and the expression of inflammatory cytokines were investigated. No significant differences in lung mechanics, airway responsiveness, and morphometry were observed. Re-administration of rAAV5 vector resulted in a decrease in GFP mRNA expression in the VR2d3w group. There was no evidence of inflammatory response or apoptosis in any group. rAAV5 did not induce an inflammatory process, mechanical or morphometric changes in the lungs. AAV5 may be an appropriate vector for lung gene therapy.

Differential role of the nNOS gene in the development of behavioral sensitization to cocaine in adolescent and adult B6;129S mice

RATIONALE

Previous studies have suggested the involvement of neuronal nitric oxide synthase (nNOS) in the development of sensitization to psychostimulants. Ontogeny-dependent differences in the response to psychostimulants have been reported.

OBJECTIVE

The objectives were to investigate (a) the short- and long-term consequences of adolescent and adult cocaine exposure on behavioral sensitization and (b) the role of the nNOS gene in behavioral sensitization in adolescent and adult mice.

MATERIALS AND METHODS

Adolescent and adult wild type (WT) and nNOS knockout (KO) mice received saline or cocaine (20 mg/kg) for 5 days and then were challenged with cocaine (20 mg/kg) after a drug-free period of 10 or 30 days. Locomotor activity was recorded by infrared beam interruptions. nNOS immunoreactive (ir) neurons in the dorsal and ventral striatum were quantified 24 h after repeated administration of cocaine to adolescent and adult WT mice.

RESULTS

Repeated administration of cocaine to either WT or nNOS KO mice during adolescence resulted in locomotor sensitization, which persisted into adulthood. WT but not KO adult mice developed long-term sensitization to cocaine. Repeated cocaine administration resulted in a 96% increase in the expression of nNOS-ir neurons in the dorsal striatum of adult but not adolescent WT mice.

CONCLUSIONS

The nNOS gene is essential for the induction of behavioral sensitization to cocaine in adulthood but not in adolescence. The increased expression of nNOS-ir neurons in the dorsal striatum may underlie the induction of behavioral sensitization in adulthood. Thus, the NO-signaling pathway has an ontogeny-dependent role in the neuroplasticity underlying cocaine behavioral sensitization.

Quantitative and immunohistochemical analysis of neuronal types in the mouse caudal nucleus tractus solitarius: focus on GABAergic neurons

gamma-Aminobutyric acid-ergic (GABAergic) neurons are major inhibitory interneurons that are widely distributed in the central nervous system. The caudal nucleus tractus solitarius (cNTS), which plays a key role in respiratory, cardiovascular, and gastrointestinal function, contains GABAergic neurons for regulation of neuronal firing. In the present study, GABAergic neuronal organization was analyzed in relation to the location of subnuclei in the mouse cNTS. According to the differential expression of glutamate decarboxylase 67 (GAD67), vesicular glutamate transporter 2 (VGLUT2), calbindin, and tyrosine hydroxylase (TH) mRNAs, the cNTS was divided into four subnuclei: the subpostrema, dorsomedial, commissural, and medial subnuclei. The numerical density and size of soma in the four subnuclei were then quantified by an unbiased dissector analysis. Calbindin-positive cells constituted subpopulations of small non-GABAergic neurons preferentially localized in the subpostrema subnucleus. TH-positive cells constituted large neurons preferentially localized in the medial subnucleus. GABAergic neurons constituted a subpopulation of small neurons, preferentially localized in the commissural and medial subnuclei, which represented > or =50% of small cells in these subnuclei. Thus, the GABAergic small neurons were located around TH-positive large cells in the ventrolateral portion of the cNTS. This finding, in combination with results of previous studies in the rat cNTS showing that large cells originate efferents from the cNTS, suggests that GABAergic small neurons in the commissural and medial subnuclei might regulate output from the cNTS.

Adipokines oversecreted by omental adipose tissue in human obesity

Central-omental obesity plays a causative role in the pathogenesis of the metabolic syndrome. Adipokines are involved in the pathogenesis of this syndrome. However, adipokines secreted by omental adipose tissue (OAT) are still poorly characterized in human obesity. Therefore, we searched for novel adipokines abnormally secreted by OAT in obesity and examined their relationships with some features of metabolic syndrome and the respective contribution of adipocytes vs. stromal-vascular cells. OAT from obese and nonobese men was fractionated into adipocytes and SV cells, which were then cultured. Medium was screened by medium-scale protein arrays and ELISAs. Adipokine mRNA levels were measured by real-time RT-qPCR. We detected 16 cytokines secreted by each cellular fraction of lean and obese subjects. Of the 16 cytokines, six adipokines were newly identified as secretory products of OAT, which were dysregulated in obesity: three chemokines (growth-related oncogen factor, RANTES, macrophage inflammatory protein-1beta), one interleukin (IL-7), one tissue inhibitor of metalloproteinases (TIMP-1), and one growth factor (thrombopoietin). Their secretion and expression were enhanced in obesity, with a relatively similar contribution of the two fractions. The higher proportion of macrophages and endothelial cells in obesity may contribute to this enhanced production as well as changes in intrinsic properties of hypertrophied adipocytes. Accordingly, mRNA concentrations of most of these adipokines increased during adipocyte differentiation. Eventually, expression of the investigated adipokines did correlate with several features of the metabolic syndrome. In conclusion, six adipokines were newly identified as oversecreted by OAT in obesity. These adipokines may link obesity to its cardiovascular or metabolic comorbidities.

A brief update on lung stereology

Lung stereology has a long and successful tradition. From mice to men, the application of new stereological methods at several levels (alveoli, parenchymal cells, organelles, proteins) has led to new insights into normal lung architecture, parenchymal remodelling in emphysema-like pathology, alveolar type II cell hyperplasia and hypertrophy and intracellular surfactant alterations as well as distribution of surfactant proteins. The Euler number of the network of alveolar openings, estimated using physical disectors at the light microscopic level, is an unbiased and direct estimate of alveolar number. Surfactant-producing alveolar type II cells can be counted and sampled for local size estimation with physical disectors at a high magnification light microscopic level. The number of their surfactant storage organelles, lamellar bodies, can be estimated using physical disectors at the EM level. By immunoelectron microscopy, surfactant protein distribution can be analysed with the relative labelling index. Together with the well-established classical stereological methods, these design-based methods now allow for a complete quantitative phenotype analysis in lung development and disease, including the structural characterization of gene-manipulated mice, at the light and electron microscopic level.

Induction of adiponectin in skeletal muscle of type 2 diabetic mice: In vivo and in vitro studies

AIMS/HYPOTHESIS

Adiponectin is an adipokine that exhibits insulin-sensitising, fat-burning and anti-inflammatory properties as well as modulatory effects on oxidative stress. We examined whether adiponectin could be induced in a non-adipose tissue, skeletal muscle, in response to metabolic or oxidative aggression both in vivo (in a murine model of type 2 diabetes) and in vitro.

METHODS

Obese and diabetic ob/ob mice were used and compared with lean littermates. Some obese mice were treated with the antioxidant probucol for 3 weeks. At the end of the experiment, blood was sampled and tibialis anterior muscles were collected for mRNA measurement and immunohistochemistry. Additional in vitro experiments were performed on C2C12 myotubes cultured for up to 48 h.

RESULTS

In spite of hypoadiponectinaemia, Adipoq mRNA levels were markedly increased in the skeletal muscle of ob/ob mice and correlated with systemic oxidative stress. Adipoq upregulation was shown in laser-microdissected myocytes of obese mice. Concomitantly, immunoreactivity for adiponectin was enhanced in obese muscle fibres together with lipid infiltration and local markers of oxidative stress. In cultured C2C12 myotubes, a triglyceride mix and reactive oxygen species producers (H2O2 or a lipoperoxidation end-product) upregulated Adipoq expression and adiponectin production. This effect was reversed by an antioxidant. Finally, treatment of obese mice with probucol also attenuated upregulation in muscle.

CONCLUSIONS/INTERPRETATION

The paradoxical upregulation of adiponectin in muscle of obese and diabetic mice may result from lipotoxicity and related oxidative stress. This unexpected finding could be viewed as a local protection to counteract ectopic fat deposition and oxidative damage.

Transcriptional profiling of tissue plasticity: role of shifts in gene expression and technical limitations

Reprogramming of gene expression has been recognized as a main instructive modality for the adjustments of tissues to various kinds of stress. The recent application of gene expression profiling has provided a powerful tool to elucidate the molecular pathways underlying such tissue remodeling. However, the biological interpretations of expression profiling results critically depend on normalization of transcript signals to mRNA standards before statistical evaluation. A hypothesis is proposed whereby the “fluctuating nature” of gene expression represents an inherent limitation of the test system used to quantify RNA levels. Misinterpretation of gene expression data occurs when RNA quantities are normalized to a subset of mRNAs that are subject to strong regulation. The contention of contradictory biological outcomes using different RNA-normalization schemes is demonstrated in two models of skeletal muscle plasticity with data from custom-designed microarrays and biochemical and ultrastructural evidence for correspondingly altered RNA content and nucleolar activity. The prevalence of these biological constraints is underlined by a literature survey in different models of tissue plasticity with emphasis on the unique malleability of skeletal muscle. Finally, recommendations on the optimal experimental layout are given to control biological and technical variability in microarray and RT-PCR studies. It is proposed to approach normalization of transcript signals by measuring total RNA and DNA content per sample weight and by correcting for concurrently estimated endogenous standards such as major ribosomal RNAs and spiked RNA and DNA species. This allows for later conversion to diverse tissue-relevant references and should improve the physiological interpretations of phenotypic plasticity.

Evaluation of hypoxia in an experimental rat tumour model by [(18)F]fluoromisonidazole PET and immunohistochemistry

This study aimed to evaluate tumour hypoxia by comparing [¹⁸F]Fluoromisonidazole uptake measured using positron emission tomography ([¹⁸F]FMISO-PET) with immunohistochemical (IHC) staining techniques. Syngeneic rhabdomyosarcoma (R1) tumour pieces were transplanted subcutaneously in the flanks of WAG/Rij rats. Tumours were analysed at volumes between 0.9 and 7.3 cm³. Hypoxic volumes were defined using a 3D region of interest on 2 h postinjection [¹⁸F]FMISO-PET images, applying different thresholds (1.2–3.0). Monoclonal antibodies to pimonidazole (PIMO) and carbonic anhydrase IX (CA IX), exogenous and endogenous markers of hypoxia, respectively, were used for IHC staining. Marker-positive fractions were microscopically measured for each tumour, and hypoxic volumes were calculated. A heterogeneous distribution of hypoxia was observed both with histology and [¹⁸F]FMISO autoradiography. A statistically significant correlation (P<0.05) was obtained between the hypoxic volumes defined with [¹⁸F]FMISO-PET and the volumes derived from the PIMO-stained tumour sections (r=0.9066; P=0.0001), regardless of the selected threshold between 1.4 and 2.2. A similar observation was made with the CA IX staining (r=0.8636; P=0.0006). The relationship found between [¹⁸F]FMISO-PET and PIMO- and additionally CA IX-derived hypoxic volumes in rat rhabdomyosarcomas indicates the value of the noninvasive imaging method to measure hypoxia in whole tumours.

Lung morphometry and MMP-12 expression in rats treated with intraperitoneal nicotine

Nicotine, a toxic tobacco component, plays an important role in the development of cardiovascular and lung diseases in smokers. Our objective was to investigate the effects of the intraperitoneal (i.p.) nicotine treatment in lung morphology. Wistar male rats (3-4 months old) were divided in five groups, a control one, and other groups treated with nicotine (1 mg/kg/day) for 8 days and sacrificed after 24, 48, 96, and 192 h. Morphometry was used to estimate the lung alveolar parenchyme and septal elastic fibers changes, and immunohistochemistry was performed to detect macrophage metalloelastase (MMP-12) and quantify vessels by immunolabelling with alpha-smooth muscle cells. Thickening of the alveolar septa was present in all nicotine groups, and associated with mononuclear cell infiltration, angiogenesis, and irregular areas of collapse. After 96 h, rat lungs showed macrophage, expressing MMP-12, that was also present after 192 h of recovery. Pleural and parenchyma inflammation, fibrosis and macrophage were also seen after 192 h. Intraperitoneal nicotine treated rats exhibited an increase of the volume fraction of alveolar parenchyme, a reduction of volume and surface fraction septal elastic fibers, and an increase of the numerical fraction of microvasculature vessels compared to control ones. MMP-12 was detected in groups of macrophages Wistar rats lung exhibited a progressive morphological damage after 192 hours of recovery, after 8 daily doses of 1 mg/kg body weight on i.p. nicotine.

Seizures and proto-oncogene expression of fos in the brain of adult genetically epilepsy-prone rats

The mechanisms and brain circuitry that render genetically epilepsy-prone rats (GEPRs) susceptible to acoustically induced seizures are not completely known. The present study explores the neuroanatomy of acoustically induced seizures by immunohistochemical analysis of the proto-oncoprotein fos after intense acoustic stimulation (AS) with and without seizures. Acoustic stimulation induced tonic convulsions in GEPR-9s, but not in control rats. Locations of brain nuclei showing fos-like immunoreactive (FLI) neurons following AS with and without seizures were mapped. Semiquantitative methods were used to compare FLI neuron numerical densities in AS control rats and GEPRs. Many brain areas exhibited profound FLI in AS control rats and GEPRs. Unexpectedly, the cochlear nuclei and the central nucleus of the inferior colliculi (ICc), both of which are requisite for AGS initiation, exhibited a diminished fos expression in animals having seizures compared to AS controls. In contrast, GEPRs displayed a significant increase in FLI neurons within the dorsal cortex of the IC (ICd) compared to AS controls. This finding may suggest a seizure-related amplification of the auditory signal between the ICc and the ICd. Other nuclei, known to be involved in auditory transmission (i.e., superior olivary complex; trapezoid nucleus; dorsal nucleus of the lateral lemniscus, DNLL), did not show differential FLI densities between seizure and AS control animals. In contrast, seizure-induced FLI was observed in many nonauditory brain nuclei. Of particular interest was the identification of an intensely labeled nucleus in the GEPR. This nucleus resides in the most posterior and dorsal-lateral part of the pedunculopontine tegmental nucleus-pars compacta (PPTn-pc) immediately adjacent to the DNLL and extends posteriorly into the superior lateral subnucleus of the lateral parabrachial area (SLPBn). Therefore, we have tentatively termed this nucleus the PPSLPBn. The PPSLPBn lies in a region previously described as a mesencephalic locomotor region and a suspected functional involvement of this nucleus in display of seizure activity is under investigation. Other brain stem nuclei showing differential fos expression between GEPRs and AS control rats are also described.

Rapid and unbiased estimation of the volume of cutaneous malignant melanoma using Cavalieri's principle

The Cavalieri volume estimator has been employed to determine the macroscopic tumor volume of 34 cutaneous malignant melanomas. With this rapid and unbiased method using histological specimens from slabs of known thickness, tumor volumes between 3.9 mm3 and 841.5 mm3 were found. The coefficient of error (CE) for tumor volumes ranged between 0.028 and 0.141, with a combined group CE of 0.043. There was a remarkably good correlation between tumor volume and maximal vertical tumor thickness estimated according to Breslow, with a correlation coefficient of r = 0.86 for all tumors, and of r = 0.82, if the one extremely big tumor is omitted. Both inter- and intraobserver variability was very low, with only approximately 1-2% difference. Thus, the method described allows for the reproducible, rapid, and unbiased estimation of tumor volume independent of the shape of the tumor.

Volume estimation of multicellular colon carcinoma spheroids using Cavalieri's principle

Multicellular tumour-spheroids are regarded as suitable models for cancer research, similar to avascular tumour parts. As a size parameter of the spheroids, usually their maximum diameter is used, estimated on a section presumed to be equatorial or near equatorial. Estimation of the volume of spheroids is of interest for the detection of subtle changes in different kinds of investigations. Since spheroids are often not truly spherical, and because model-based methods for volume determination may be biased, Cavalieri's principle, rediscovered recently for stereology, was used to determine the volume of the spheroids. Here we report the results of the volume estimation of colon carcinoma spheroids, together with an outline of the basic stereological principle and formulas used. The spheroids investigated had a volume between 1.4 and 92.3 mm3 (mean 33.9). The volume fraction of necrotic to viable tissue cells was between 0.6:1 and 2.2:1. The coefficient of error (CE) was remarkably low with 3.7% for the volumes. Both inter- and intraobserver-variability were extremely low with correlation coefficients (r2) of 99%. Thus, the high precision of the stereological method, combined with a low workload, make it ideally suitable for routine volume estimation.

Age-related modification of average volume and anisotropy of vascular smooth muscle cells

The aim of this study was to determine what changes in the arterial wall are related to age. In two groups of rabbits, one young and one adult, the aorta and carotid were studied using a morphometric approach based on stereological axioms and planimetric morphometry. The problem of anisotropy of smooth muscle cells is discussed in detail. Two forms of anisotropy must be distinguished, that of single cell and that due to the histological pattern of the smooth muscle cells in the arterial wall. Our results show in adult animals, as compared to the young ones, statistically significant decrease in anisotropy of the cell pattern which tends to become more regular. Moreover, in aorta and carotid of young and adult animals there is an increment of 95.39% and 80% of the absolute cell volume, respectively. We suggest that there may be a direct relationship between aging and phenotypical modulation of the smooth muscle cells and that the modification of the architectural cell pattern with age may represent an adaptive event related to the change in forces acting upon the arterial wall.

Lipid accumulation in rabbit aortic intima 2 hours after bolus infusion of low density lipoprotein. A deep-etch and immunolocalization study of ultrarapidly frozen tissue

The intima from aortas of normal New Zealand White rabbits was studied 2 hours after infusion of 320 mg human low density lipoprotein (LDL), resulting in a plasma concentration of at least five times and maximally 20 times the values found in normal rabbit serum. The following techniques were used: 1) ultrarapid freezing without chemical fixation, followed by freeze-etching; 2) immunofluorescence microscopy; and 3) postembedding immunogold-labeling electron microscopy. In the latter two methods MB47, a murine monoclonal antibody against human apolipoprotein B, was used as the primary antibody. Control rabbits were infused with the same volume of buffer only. Rotary-shadowed replicas of samples from the LDL-injected rabbits showed the deposition of lipidlike particles in the subendothelial-intimal space that were the size of the injected LDL (23 nm). In focal areas of the intima, groups of 23-nm-sized lipidlike particles and larger lipidlike structures were found enmeshed in the extracellular matrix. Control replicas were essentially free of lipid deposition. Immunofluorescence microscopy of frozen aortic cross sections showed an overall increase in apolipoprotein B in the intima of the LDL-injected rabbits. The presence of apolipoprotein B in the intima was also confirmed by immunoelectron microscopy. These in vivo results show that clustering of LDL-sized particles occurs in the intima within 2 hours of excessive LDL uptake. It also demonstrates the interaction of these LDL-sized particles with the filaments of the extracellular matrix. The clustering of the LDL-sized particles supports the possibility that LDL self-aggregation may occur in vivo and that components of the extracellular matrix are involved in this process.

Ultrastructural morphometric analysis of cultured neonatal and adult rat ventricular cardiac muscle cells

Neonatal and adult rat ventricular cardiac muscle cells cultured on laminin differed from similar myocytes grown on plastic in the amount and distribution of their mitochondria and transverse tubules. Point-count morphometry was used at the electron microscopic level to quantify these differences. Adult myocytes grown on laminin contained more mitochondria per unit volume than adult myocytes grown on plastic. No significant differences were observed in the volume percent of myofibrils in either adult or neonatal ventricular myocytes when grown on laminin and compared to those grown on plastic. The transverse tubule system in neonatal and adult myocytes was reduced significantly when both groups were cultured on laminin. Furthermore, neonatal and adult myocytes cultured on laminin were flatter than those cultured on plastic. This may indicate a relationship between the surface/volume ratio and transverse tubule development in cultured myocytes. These studies establish that point-count morphometry can be used to quantify changes in the organelle volume densities of cultured cardiac muscle cells.

The intactness and orientation of acetylcholine receptor-rich membrane from Torpedo californica electric tissue

By a mild and highly reproducible fractionation of Torpedo californica electric tissue, we prepared membrane which was 30 times enriched in nicotinic acetylcholine receptor (AChR). This preparation was neither alkali-stripped nor reconstituted and consequently contained nu (43-kDa protein), which is associated with the cytoplasmic aspect of the receptor. We tested this membrane for the presence of sealed vesicles and determined the orientation of these vesicles by combining three methods. Two of these methods were based on the accessibilities, in the presence and absence of detergent, of the extracellular acetylcholine binding site to alpha-bungarotoxin and of the intracellular nu to trypsin. These two methods are specific for AChR-containing membrane. The third method was morphometry of electron micrographs, by which we estimated the proportion of sequestered membrane. These methods taken together indicated that approximately 45% of the AChR-containing membrane was in the form of leaky vesicles or sheets, 33% was sealed right-side-out vesicles, 11% was sealed inside-out vesicles, and 11% was sequestered within multilamellar or multivesicular vesicles. The complexity of this membrane needs to be taken into account in sidedness studies of the AChR.

Acidification and endosome-like compartments in the presynaptic terminals of frog retinal photoreceptors

By using the 'acidotropic' vital dye, Acridine Orange, we have found that the presynaptic terminals of rod and cone photoreceptors in retinas of Rana pipiens maintain a low pH relative to the surrounding medium through an energy dependent mechanism. When this pH is raised, by exposing the retinas to weak bases like ammonium chloride, the terminals exhibit large, membrane-delimited compartments, many of which accumulate endocytic tracers. This effect is partly reversed when the weak bases are removed. We infer that among the acidified structures within the terminals are endocytic compartments with at least some of the characteristics of the endosomes that participate in receptor-mediated endocytosis in other cell types. One role of these structures in the terminals may be in the recycling of synaptic vesicles.

Evaluation of the mitotic index of human colonic mucosa; results of two different observers

The mitotic index (M.I.) of the colonic mucosa was evaluated in 67 biopsies and divided into 6 groups. The M.I. was evaluated by one author twice at magnification X 1000 and by the other author once at magnification X 1000 and once at X 400, in order to assess the degree of intra- and interobserver agreement and the most suitable magnification for the evaluation of the M.I. of human colonic mucosa. The results indicate that the mean M.I. of a group of biopsies was similar between the two authors and may therefore be proposed as a valuable estimate of the mitotic activity of a group of patients during scientific investigations, provided that it is evaluated at sufficiently high magnification (X 1000, to our experience). On the contrary, there was only partial agreement (though highly significant) on the M.I. of each individual biopsy between the two authors and between different counts of the same author as well, thus indicating that the M.I. cannot be proposed as an accurate estimate of the mitotic activity of individual patients.

Observer reproducibility during computer-assisted planimetric measurements of nuclear features

To evaluate observer variance during microprocessor-assisted planimetry, nuclear features (area, perimeter, and form factor) were studied in a series of mammary ductal carcinomas. Fragments of formalin-fixed, paraffin-embedded tissue were re-embedded in plastic, sectioned at 1 micron, stained with methylene blue, and studied with a Zeiss-Kontron MOP-3 microprocessor-assisted planimeter. Both interobserver and intraobserver reproducibility were evaluated, the former among three different observers and the latter by two observers repeating their own measurements. Reproducibility was good for measurement of area, but deteriorated progressively for measurement of perimeter and form factor. Not only was observer correlation poor (identified via linear regression), but paired t-tests also showed consistent variation among observers. The major difficulty was in following the irregular nuclear contours that are characteristic of cancer cells. It is concluded that adequate demonstration of observer reproducibility remains an essential part of tissue investigation, even when the objective methods typical of morphometry are used.

Commercial image analysers and the characterization of microscopical images

This review surveys some of the current approaches to the characterization of microscopical images using commercially available image analysers. The role of image pre-processing and segmentation is considered, together with the characterization of images by optical density, as well as size and shape. The newer analysers are capable of investigating relationships between grey-levels in small areas of the image ('texture-analysis'); some of the descriptive approaches in this latter field are briefly outlined.

Automated techniques for the study of lung alveolar stereological parameters with the IBAS image analyser on optical microscopy sections

In the case of lung alveoli, the good contrast of the features allows the use of a fully automated image analysing procedure, yielding many of the desirable stereological parameters which can be estimated on optical microscopy slides: alveolar volume and surface densities, a form factor and average mean integral curvature. With our program, specially designed for the IBAS image analyser (Kontron Bildanalyse, Munich, B.R.D.), the whole automated process takes an average of 28 s per field. The image analyser-obtained stereological estimates compare well with those given by point and intersection counting methods. Some difficulties inherent in image analysers arise when measuring alveolar boundary lengths: a scheme is therefore proposed which eliminates the image-edge errors, with no sampling bias, by comparing three different frames inside each field. A solution to the problem of estimating automatically the positive and negative tangent counts, necessary for the curvature calculations, is also proposed. Our program has been applied routinely to the study of premature newborn rabbit lung alveoli, as part of a work dealing with an evaluation of the possibility of preventing the respiratory distress syndrome by the administration of heterologous surfactant.