Frans Van Meir

Age-dependent cognitive decline in the APP23 model precedes amyloid deposition.

Heterozygous APP23 mice, expressing human amyloid‐precursor protein with the Swedish double mutation and control littermates, were subjected to behavioral and neuromotor tasks at the age of 6–8 weeks, 3 and 6 months. A hidden‐platform Morris‐type water maze showed an age‐dependent decline of spatial memory capacities in the APP23 model. From the age of 3 months onwards, the APP23 mice displayed major learning and memory deficits as demonstrated by severely impaired learning curves during acquisition and impaired probe trial performance. In addition to the cognitive deficit, APP23 mice displayed disturbed activity patterns. Overnight cage‐activity recording showed hyperactivity in the transgenics for the three age groups tested. However, a short 2‐h recording during dusk phase demonstrated lower activity levels in 6‐month‐old APP23 mice as compared to controls. Moreover, at this age, APP23 mice differed from control littermates in exploration and activity levels in the open‐field paradigm. These findings are reminiscent of disturbances in circadian rhythms and activity observed in Alzheimer patients. Determination of plaque‐associated human amyloid‐β1–42 peptides in brain revealed a fivefold increase in heterozygous APP23 mice at 6 months as compared to younger transgenics. This increase coincided with the first appearance of plaques in hippocampus and neocortex. Spatial memory deficits preceded plaque formation and increase in plaque‐associated amyloid‐β1–42 peptides, but probe trial performance did correlate negatively with soluble amyloid‐β brain concentration in 3‐month‐old APP23 mutants. Detectable plaque formation is not the (only) causal factor contributing to memory defects in the APP23 model.

Temporal distribution of distinct mast cell phenotypes during intestinal schistosomiasis in mice

Mastocytosis is a common feature of helminth infection in most host species. We examined the temporal distribution and phenotype of mast cells during intestinal schistosomiasis in mice, using antibodies directed against histamine, a general mast cell marker, against mouse mast cell protease‐1 (MMCP‐1), a mucosal mast cell (MMC) marker, and against tryptase, a predominantly connective tissue mast cell (CTMC) marker. Ileal paraffin and/or cryosections of control, 8‐ and 15‐week‐infected mice were quantitatively analysed. In the intestinal wall of non‐ and unisexual infected mice, a few dispersed mast cells were detected. In infected mice, a transient increase of mast cells in the mucosa and a gradual increase in the outer muscle layer were observed. MMCP‐1 expressing MMCs were predominantly present in the mucosa during the acute phase [8 weeks postinfection (p.i.)], while tryptase and histamine immunoreactivity demonstrated that two subsets of CTMCs were predominantly present in the outer muscle layer at 15 weeks p.i. (chronic phase). In conclusion, these results reveal that, in mice, both MMCs and CTMCs are involved in the inflammatory response during schistosomiasis. The recruitment of each mast cell population is time‐dependent and occurs at different locations. These data suggest that mastocytosis is associated with motility‐related gastrointestinal symptoms and egg excretion.

Development of Alveolar Septa and Formation of Alveolar Pores during the Early Postnatal Period in the Rat Lung

In order to investigate the formation of alveolar pores, lungs of rats, after intratracheal perfusion of glutaraldehyde, are processed at postnatal days 1, 7, 14, 16 and 21 for light and transmission electron microscopy and at days 7 and 16 for scanning electron microscopy. The initial low secondary crests of day 1 rapidly elongate to pleats subdividing the primary saccules. The ledges of some pleats partly grow toward each other as ring like diaphragms, leaving openings whose boundary is composed of alveolar epithelium separated by a basal lamina from a connective tissue sheath with capillaries. At day 7, in scanning electron microscopy the lumina of some rudimentary alveoli communicate by apertures of different sizes, as a result of the outgrowth of curved alveolar pleats which narrow to a ring-like aperture. The interalveolar openings observed in scanning electron microscopy resemble those investigated by light and transmission electron microscopy. The number of interalveolar pores increases from day 7 on; they become more and more frequent at days 14, 16 and 21, respectively. It appears that alveolar multiplication in newborn rats proceeds not only by segmentation of terminal respiratory units but also by compoundment of septa. The difference between genuine pores and transsections of folds in transmission electron microscopy will be given closer attention in this study. Also, the incidence and location of type II pneumocytes during rapid enlargement of the alveolar surface area is discussed.

Stereologic description of the changing expression of constitutive nitric oxide synthase and heme oxygenase in the enteric plexuses of the pig small intestine during development.

The similarities between heme oxygenase‐2 (HO‐2) and nitric oxide synthase (nNOS) and the transient expression of nNOS during development led us to investigate whether both systems are similarly affected by changes that occur during development and by regional differences along the small intestine. By combining NADPH diaphorase histochemistry and HO‐2 immunohistochemistry on whole‐mount preparations and by using stereologic methods, a qualitative and quantitative description of HO‐2 and nNOS expression was obtained. Examinations were carried out on the small intestine of fetal, 1–2‐day and 5–6‐week‐old pigs. In all age groups, three enteric plexuses were distinguished. The presence of HO‐2‐immunoreactive (HO‐2‐IR) and NADPH diaphorase‐positive neurons corresponded to earlier morphological and physiological reports. Nevertheless, the total number of nitrergic neurons remained constant or decreased in the enteric plexuses, whereas the total number of HO‐2‐IR neurons displayed an overall increase. Changing concentrations of glucocorticoids, target‐derived signals, presynaptic input, and an effect of HO‐2 activity on nNOS synthesis are likely to play roles in the observed developmental changes. The numerical density of HO‐2‐IR neurons remained relatively constant along the intestinal tract; in contrast, the nitrergic neurons were most numerous in the inner submucous and myenteric plexus in the duodenum and ileum, respectively. It is believed that the duodenal nitrergic neurons in the inner submucous plexus could be involved in the regulation of duodenal secretion processes, whereas the region‐dependent density in the myenteric plexus possibly forms the morphological basis for a regionally different participation of NO in the relaxation of the small intestine. J. Comp. Neurol. 437:118–128, 2001.

Microwave Staining of Enteric Neurons Using Cuprolinic Blue (Quinolinic Phthalocyanin) Combined with Enzyme Histochemistry and Peroxidase Immunohistochemistry

Methods that visualize subsets as well as the entire enteric neuron population are not readily available or have proved to be unreliable. Therefore, we attempted to combine NADPH-d histochemistry, AChE histochemistry, and CGRP immunohistochemistry, techniques that mark subsets of enteric neurons, with a technique that appeared to visualize the entire enteric neuron population, the cuprolinic blue staining method. To guarantee representative staining results, the individual staining methods were modified by using microwaves. In addition, this preserved the characteristics of each of the individual techniques. The distribution of NADPH-d, AChE, and CGRP corresponded well with previous morphological and physiological reports. Consequently, the different combinations gave rise to rapid, useful, and ready-to-use double labeling techniques. Their main advantage is that they simultaneously visualize the total population as well as subsets of enteric neurons.

Microwave Staining of Intestinal Whole-mount Preparations with Cuprolinic Blue

Encouraged by the knowledge that microwaves have a beneficial effect on immunohistochemical reactions, the present study aimed to find out whether microwaves could improve the Cuprolinic Blue staining of enteric neurons as well as the actual method that has been developed for gastrointestinal whole-mount preparations. In addition to incorporating a microwave application in the method described by Holst and Powley (1995), some other modifications were made: two incubations before incubation in the staining solution and free-floating incubations. In the whole-mount preparations, most, if not all, enteric neurons were stained by Cuprolinic Blue. These neurons appeared as blue–green cells with non-reacting nuclei and neuronal processes. At higher magnification, the cytoplasm was characterized by a fine blue– green granulation, and the nucleolus in the nucleus appeared as a blue iridescent structure. Non-specific staining occurred in fibrocy tes and epithelial cells but, because of their location and appearance, they could easily be distinguished from neurons. The modified incubations and the incorporation of a microwave application into the conventional Cuprolinic Blue staining method turn the method into an easy-to-use one that seems to visualize most, if not all, enteric neurons in whole-mount preparations of the pig jejunum.

Microperoxisomes in type II pneumocytes and interstitial cells of postnatal rat lungs

Microperoxisomes in alveolar type II pneumocytes and lipid interstitial cells are visualized using the diaminobenzidine method for catalase. These organelles, with a diameter ranging from 100-800 nm, respectively 200-500 nm, and with no crystalline cores or densities, are in close relation with the endoplasmic reticulum. No luminal continuity between microperoxisomes and the endoplasmic reticulum is observed. Postfixation with unbuffered ferrocyanide-reduced osmiumtetroxide contributes to a better localization of microperoxisomes in both celltypes.

Stereological approach on macrophages from human bronchopulmonary lavage

STEREOLOGICAL APPROACH ON MACROPHAGES FROM HUMAN BRONCHOPULMONARY LAVAGE Frans VAN MEIR (I), Dietrich W. SCHEUERMANN (I), Marcel VAN DER STRAETEN (21, Romaln PAm¢ELS (21 and Marie H.A. DE GROODT-LASSEEL (1) . (11 I n s t i t u t e of H i s t o l o g y and Microscopic Anatomy, U n i v e r s i t y of Antwerp (RUCAI, GroenenborgerlBan 171, B-2020 Antwerpen (Belgium), and (21 Department of Pneumology, U n i v e r s i t y H o s p i t a l , S t a t e U n i v e r s i t y of Ghent, De P t n t e l a a n 185, B-9000 Ghent (Belgium) To c h a r a c t e r i z e the p o p u l a t i o n of a l v e o l a r maerophages in bronchopulmonary l a v a g e s , wi th normal d i f f e r e n t i a l c e l l coun t s , (about 90Z or more macrophages) o r i g i n a t i n g from p a t i e n t s wi th a d i f f e r e n t c l i n i c a l h i s t o r y , a morphometrie a n a l y s t s of the n u c l e o c y t o p l a s m t c r a t i o and of v a r i o u s c e l l e r g o h e l l a s i s performed. A f t e r f i x a t i o n in cold 2.5% Na-cacodyla te b u f f e r e d g l u t a r a l d e h y d e , p o s t f t x a t t o n in 2% b u f f e r e d osmtumtet roxide and b l o c k s t a i n t n g in 0.5% b u f f e r e d u r a n y l a c e t a t e , the p e l l e t i s embedded in durcupan-ACM r e s i n . A n u c l e a r b i a s e d sampling f o r macrophages i s used because in t h i s way d i f f e r e n c e s in the c e l l o r g a n e l l e s between the c e n t e r and p e r i p h e r y of the c e l l s a re minimized. N e v e r t h e l e s s , i n about h a l f of the c e l l s cu t th rough the nuc l eus , no Golgt appara tus i s t r a n s s e c t i o n n e d . P r o f i l e a r e a s of c e l l s , n u c l e i and d i f f e r e n t c e l l o r g a n e l l e s , i . e . m i tochondr i a , lysosomes and lysosome l i k e bod i e s , endoplasmtc r e t i c u l u m and Golgi a p p a r a t u s , a r e q u a n t i f i e d by po in t coun t ing methods a p p l i e d on p r o j e c t e d p o s i t i v e f i l m s of the macrophages a t a f i n a l m a g n i f i c a t i o n of 25000 t imes . Our measurements of c e l l and nuc leus p r o f i l e a r e a s p o i n t to a g r e a t v a r i e t y of c e l l forms in the macrophage popu l a t i on (87.8 + 36.9 sq ~m, r e sp . 14.2 + 6.6 sq ~m, nffi2481. To a s c e r t a i n whether t h e s e k inds of c e l l s are the e x p r e s s i o n of d i f f e r e n t macrophage p o p u l a t i o n s or a re on ly an i n d i c a t i o n of v a r i o u s s t a g e s of macrophage a c t i v i t y , s p e c i a l a t t e n t i o n has been paid to the presence of pr imary lysosomes and the v a c u o l a r s t r u c t u r e s t h a t are the s i t e of d i g e s t i v e a c t i v i t y (secondary lysosomes) . The f requency d i s t r i b u t i o n s of lysosomal a reas per c e l l may a l low to d i s t i n g u i s h between macrophages wi th l e s s phagccy t t c a c t i v i t y showing mainly pr imary lysosomes and macrophages which a f t e r an i n t e n s e phagocy t i c a c t i v i t y c o n t a i n obv ious ly more secondary lysosomes.