Rim Of Cytoplasm Research Articles

Domains of high Ca2+ beneath the plasma membrane of living A7r5 cells.

Theoretical models and indirect experimental observations predict that Ca2+ concentrations at the inner surface of the plasma membrane may reach, upon stimulation, values much higher than those of the bulk cytosol. In the past few years, we have shown that the Ca2+-sensitive photoprotein aequorin can be intracellularly targeted and utilized for specifically monitoring the [Ca2+] of various organelles. In this work, we extend this approach to the study of the cytoplasmic rim beneath the plasma membrane. We have constructed a new aequorin chimera by fusing the photoprotein with SNAP-25, a neuronal protein which is recruited to the plasma membrane after the post-translational addition of a lipid anchor. The SNAP-25-aequorin chimera, expressed in the rat aortic smooth muscle cell line A7r5, appears correctly sorted as revealed by immunocytochemistry. Using this probe, we demonstrate that the mean [Ca2+] of this cytoplasmic region ([Ca2+]pm) can reach values >10-fold higher than those of the bulk cytosol ([Ca2+]c) upon activation of Ca2+ influx through plasma membrane channels. In unstimulated cells, the mean [Ca2+]pm appears also to be higher than the bulk cytosol, presumably reflecting the existence of microdomains of high [Ca2+].

The onychomatricoma: an electron microscopic study.

The electron microscopic findings in the onychomatricoma are described. In the proximal zone of the onychomatricoma, basal cells have various aspects, some being lacunar while others have only a limited cytoplasmic rim containing mitochondria and tonofilaments. In the parakeratotic cell columns the cells elongate and homogenized tonofilaments appear. Around the lacunae the cells are poorly differentiated and their cytoplasm is granular. It can be concluded that in an onychomatricoma the basal cells have a decreased amount of tonofilaments and desmosomes and that their evolution is not uniform. The tumour can be considered as being the result of a disturbed differentiation of nail matrix cells.

Open neural tube defects: Immunocytochemical demonstration of neuroepithelial cells in amniotic fluid

Cytologic evaluation of second trimester amniotic fluid (AF) is a rapid, inexpensive adjunct to prenatal diagnosis of open neural tube defects (ONTDs). Our goal was to determine whether the neural-appearing cells and/or large foamy macrophages in the AF of anencephalics are indeed of neural and/or glial origin. In two second trimester patients with elevated serum alpha-fetoprotein (AFP) and polyhydramnios, fetal sonogram studies showed anencephaly; amniocentesis was performed for AF-AFP, cytogenetic, and cytologic studies. AF sediment smears were initially Papanicolaou-stained; next, the same smears were immunoperoxidase (IP)-stained for glial fibrillary acidic protein (GFAP). If GFAP negative, slides were restained for synaptophysin (SYN) and neuron-specific enolase (NSE). Both AFs contained small neural-appearing cells (5–10 μm) singly and in clusters, with dense, round, homogeneous nuclei, an occasional nucleolus, and scant cytoplasmic rim. These were GFAP negative and SYN and NSE positive; the large vacuolated, lipid-laden macrophages (20–40 μm) were negative for all three IP stains. In conclusion, positive IP staining for SYN and NSE supports the morphologic impression that small dark cells in AF are of neural origin, while negative IP staining of large foamy macrophages suggests nonneural, nonglial origin. Diagn. Cytopathol. 16:143–144, 1997. © 1997 Wiley-Liss, Inc.

Open neural tube defects: immunocytochemical demonstration of neuroepithelial cells in amniotic fluid.

Cytologic evaluation of second trimester amniotic fluid (AF) is a rapid, inexpensive adjunct to prenatal diagnosis of open neural tube defects (ONTDs). Our goal was to determine whether the neural-appearing cells and/or large foamy macrophages in the AF of anencephalics are indeed of neural and/or glial origin. In two second trimester patients with elevated serum alpha-fetoprotein (AFP) and polyhydramnios, fetal sonogram studies showed anencephaly; amniocentesis was performed for AF-AFP, cytogenetic, and cytologic studies. AF sediment smears were initially Papanicolaou-stained; next, the same smears were immunoperoxidase (IP)-stained for glial fibrillary acidic protein (GFAP). If GFAP negative, slides were restained for synaptophysin (SYN) and neuron-specific enolase (NSE). Both AFs contained small neural-appearing cells (5-10 microns) singly and in clusters, with dense, round, homogeneous nuclei, an occasional nucleolus, and scant cytoplasmic rim. These were GFAP negative and SYN and NSE positive; the large vacuolated, lipid-laden macrophages (20-40 microns) were negative for all three IP stains. In conclusion, positive IP staining for SYN and NSE supports the morphologic impression that small dark cells in AF are of neural origin, while negative IP staining of large foamy macrophages suggests nonneural, nonglial origin.

Immunological aspects of kaolin-induced hydrocephalus

Adult female Sprague Dawley rats were administrated 0.1 ml Kaolin (250 mg/ml) into cisterna magna. One, 4 and 8 weeks later, brains were analyzed using antibodies against MHC class I (0X18), MHC class II (0×6), CD4 (0×38), CD8 (0×8), 0×42, EDI, NF, GFAP, AChE and TH. Remarkably high numbers of T lymphocytes, and 0×42- and EDI-positive macrophages were found aggregated in subarachnoid spaces, and in the third and fourth ventricles. Marked aggregations of ED1-positive reactive microglial cells were also found in paraventricular structures, medial septum, retrosplenic cortex and commissural structures. However, no such cells were found in hippocampus. ED1-positive areas were also positive for round cells with a rim of MHC I fluorescent cytoplasm as well as for OX42-positive cells and MHC II positive microglial cells. At week 1, in ventro-frontal areas of cortex, CD8-positive cells and MHC I positive astroglial fibers were detected. At week 1, MHC I positive ramified microglial cells were also recognized in almost the entire brain. These positive cells gradually decreased with time and finally remained rounded with a rim of fluorescent cytoplasm. In addition, EDI positive partly ramified microglial cells could be recognized in corpus callosum, probably representing cells in transition between ramified and reactive microglia. CD8+ cells entered ventral brain structures, and were found in the horizontal diagonal band at week 4, and had disappeared at week 8. Finally in cortex, EDI positive microglial cells could be identified only in the retrosplenic cortex, and there were also “dark shrunken neurons” in light microscopic stainings. However, there was only a moderate GFAP positive gliosis. In conclusion, kaolin-induced hydrocephalus leads to immune reactions in several defined areas such as cholinergic systems, corpus callosum, circumventricular organs, pontine cerebellar peduncles and the vestibular nucleus.

Hepatosplenic T-Cell Lymphoma: A Distinct Clinicopathologic Entity of Cytotoxic γδ T-Cell Origin

AbstractWe identified eight cases of T-cell lymphoma with evidence of a γδ phenotype over a 13-year period. Seven of these cases conformed to a distinct clinicopathologic entity of hepatosplenic γδ T-cell lymphoma. Nearly all of these patients were young adult males (five of seven), with a median age at presentation of 20 years. They presented with marked hepatosplenomegaly, without lymphadenopathy or significant peripheral blood lymphocytosis. Thrombocytopenia was seen in all patients, and five of seven were mildly anemic. The clinical course was aggressive, and despite multiagent chemotherapy, the median survival duration was less than 1 year. The morphologic findings were uniform; a monomorphic population of medium-sized lymphoid cells with moderately clumped chromatin and a rim of pale cytoplasm infiltrated the sinusoids of the spleen, liver, and bone marrow. The cells had a characteristic immunophenotype; CD2+, CD3+, CD4−, CD5−, CD7+, CD16+, CD57−, CD25−, T-cell receptor (TCR)δ+, βF1−. CD8 was positive in four of seven cases tested, and CD56 was positive in five of six. All cases expressed the cytotoxic granule-associated protein, TIA1, but perforin was detected in only one case. All cases with assessable DNA had a TCR γ gene rearrangement, and lacked Epstein-Barr virus sequences. Isochromosome 7q was identified in two cases with cytogenetic information. The one case of cutaneous γδ T-cell lymphoma differed in its clinical manifestations, histologic appearance, and immunophenotype. We conclude that hepatosplenic γδ T-cell lymphoma is a distinct clinicopathologic entity derived from cytotoxic γδ T cells, and should be distinguished from other lymphomas of T-cell and natural-killer cell (NK)-like T-cell derivation. This is a US government work. There are no restrictions on its use.

Hepatosplenic T-cell lymphoma: a distinct clinicopathologic entity of cytotoxic gamma delta T-cell origin

We identified eight cases of T-cell lymphoma with evidence of a gamma delta phenotype over a 13-year period. Seven of these cases conformed to a distinct clinicopathologic entity of hepatosplenic gamma delta T- cell lymphoma. Nearly all of these patients were young adult males (five of seven), with a median age at presentation of 20 years. They presented with marked hepatosplenomegaly, without lymphadenopathy or significant peripheral blood lymphocytosis. Thrombocytopenia was seen in all patients, and five of seven were mildly anemic. The clinical course was aggressive, and despite multiagent chemotherapy, the median survival duration was less than 1 year. The morphologic findings were uniform; a monomorphic population of medium-sized lymphoid cells with moderately clumped chromatin and a rim of pale cytoplasm infiltrated the sinusoids of the spleen, liver, and bone marrow. The cells had a characteristic immunophenotype: CD2+, CD3+, CD4-, CD5-, CD7+, CD16+, CD57-, CD25-, T-cell receptor (TCR)delta +, beta F1-. CD8 was positive in four of seven cases tested, and CD56 was positive in five of six. All cases expressed the cytotoxic granule-associated protein, TIA1, but perforin was detected in only one case. All cases with assessable DNA had a TCR gamma gene rearrangement, and lacked Epstein-Barr virus sequences. Isochromosome 7q was identified in two cases with cytogenetic information. The one case of cutaneous gamma delta T-cell lymphoma differed in its clinical manifestations, histologic appearance, and immunophenotype. We conclude that hepatosplenic gamma delta T-cell lymphoma is a distinct clinicopathologic entity derived from cytotoxic gamma delta T cells, and should be distinguished from other lymphomas of T-cell and natural-killer cell (NK)-like T-cell derivation.

Fine Structure of the Nuclei of the Karyorelictean Ciliate Tracheloraphis flexuosus from the Japan Sea

Summary The nuclear apparatus of the Japan sea population of Tracheloraphis flexuosus RAIKOV et KOVALEVA 1968 consists of a longitudinal row of 20–30 macronuclei and 10–15 micronuclei usually arranged into groups of two macronuclei and one micronucleus in each. The nuclear groups lie in a voluminous perinuclear lacuna, the proximal membrane of which tightly applies to the nuclei leaving around them only a thin rim of ground cytoplasm. This membrane encircles each nuclear group separately and apparently holds the nuclei together. The micronuclei are filled with spongy condensed chromatin and limited by a conventional envelope with pores. The micronuclear chromatin is resistant to bleaching with BERNHARD's EDTA. Young macronuclei occur in some groups and contain small scattered chromocentres but no nucleoli; the chromocentres are readily bleached with EDT A. Adult macronuclei contain several nucleoli of usual structure (fibrillar core, granular cortex), several chromocentres and rarely a small sphere. The chromocentres are heterogenous: each one shows a dense cap. They become bleached with EDTA even after short exposure whereas nucleoli and the sphere retain contrast. The nuclei of Tracheloraphis flexuosus are smaller than those of T. dogieli, the similar European form.

Selective Absence of Cone Outer Segment β 3-Transducin Immunoreactivity in Hereditary Cone Degeneration ( cd)

We have used immunocytochemistry and in situ hybridization to examine the expression of photoreceptor specific genes in retinas of normal dogs and those affected with hereditary cone degeneration ( cd), a rare autosomal recessive disorder that selectively affects cones. In the cdretina, cone disease begins early in life; cones are lost by extrusion of the nucleus into the inner segment, and later, by displacement of the nucleus, surrounded by a thin rim of cytoplasm, into the interphotoreceptor space. Two micrometer sections from the superior and inferior retinal meridians, extending from the optic disk to the ora serrata, were used for in situ hybridization with a bovine rod opsin and human red/green cone opsin cRNA probes, or were reacted with antibodies directed against photoreceptor-specific proteins and visualized with appropriate biotinylated antibodies. Antibodies against the following proteins were used: α- and β 3-transducins, phosducin, α/β- and γ-phosphodiesterases, COS-1, and OS-2, opsin, S-antigen and IRBP. Immunoreactivity or hybridization labeling was evaluated in unstained sections; cone pathology was judged in adjacent Toluidine Blue-stained sections. With these methods it was possible to evaluate immunoreactivity or hybridization labeling and cone pathology at the single cell level. Both middle- (COS-1) and short-(OS-2) wavelength-sensitive cones were present in controls and cdaffected retinae at 2.2 months, and distinct transcripts of the red/green cone pigment gene were identified in the majority of cones in both normal and affected retinas at this age. However, β 3-transducin immunoreactivity was completely absent from cd-affected cone outer segments. Both cone types were present but in reduced numbers in older animals (11.5 and 17 months), and no reactivity to β 3-transducin was noted. No differences were found with the other antibodies used. The specific absence of β 3-transducin immunoreactivity from the cone outer segments suggests a potential involvement of the β 3-transducin gene or gene product in the disease process.

Ultrastructural localization of acetylcholinesterase and choline acetyltransferase in oligodendrocytes, glioblasts and vascular endothelial cells in the external cuneate nucleus of the gerbil.

This study reports the reactivities of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) in some of the nonneuronal elements in the external cuneate nucleus (ECN) of gerbils. AChE reaction products were localized in some oligodendrocytes in their cisternae of rough endoplasmic reticulum, nuclear envelope and Golgi saccules. The basal lamina lining the capillary endothelia also displayed AChE reactivity. In ChAT immunocytochemistry, the reaction products were found to be associated with the vascular basal lamina as well as the endothelial plasma membrane facing the lumen. The most remarkable finding was the localization of ChAT immunoreactivity in some oligodendrocytes and occasional glioblasts (small glial precursor cells containing a thin rim of cytoplasm surrounding an irregular nucleus with homogeneous chromatin materials). The ChAT-positive oligodendrocytes consisted of two types, medium-dense and dark cells, either associated with blood vessels or ChAT-stained neuronal elements. It is suggested from these new findings that at least some of the oligodendrocytes and glioblasts in the ECN of gerbils may be involved in the synthesis, storage, release and degradation of acetylcholine.

Characterization of Peripheral Blood Stem Cells in Mice

Peripheral blood stem cells (PBSCs) were mobilized in mice by treatment with cytosine-arabinoside on day 0, followed by the administration by injection of granulocyte colony-stimulating factor for 4 days. There were remarkable increases in the numbers of cells with lineage-negative (Lin-) c-kit+ markers, cells with colony-forming unit-cell (CFU-C) and colony-forming unit-spleen (CFU-S) activities, and cells with marrow-repopulating ability (MRA) in the extramedullary sites (the spleen, peripheral blood, and liver) on day 5, whereas the number of these immature hematopoietic cells decreased in the bone marrow (BM) on day 5. This finding suggests the mobilization of immature hematopoietic cells from the BM to the extramedullary sites. Three-color flow cytometric analyses showed that CD4 antigen was not expressed on the Lin-Sca-1+ cells in the mobilized PB cells (PBCs), although CD4lo cells were found in those of normal BM cells. Lin-c-kit+ cells in the mobilized PBCs contained more cells with immature phenotypes (Sca-1+, Thy1.2lo, CD71-, and Rh123dull) than in normal BMCs, indicating an alteration of the hierarchical composition of the Lin-c-kit+ cells. The Lin-c-kit+Sca-1+ cells in the mobilized PBCs had similar CFU-C and CFU-S activities to those in normal BMCs. Electron microscopic studies of these cells in the mobilized PBCs showed that only 10% to 20% of these cells had a thin rim of cytoplasm with poorly developed organelles. Allogeneic transplantation [B6 --> C3H] of PBSCs showed long-term reconstituting activity across the major histocompatibility complex barrier 24 weeks after transplantation, although longer observation is necessary.

‘Undifferentiated progenitor cells’ in focal nodular hyperplasia of the liver

Focal nodular hyperplasia is a tumour like lesion, characterized by a central fibrous scar with irradiating fibrous septa that surround hyperplastic nodules and contain multiple bile ductules. The origin of the bile ductular structures is not clear. Recently, we found evidence for the existence of human counterparts of rat oval cells (potential stem cells) that have the ability of differentiating towards both bile duct cells and hepatocytes. These cells were found in regenerating human liver as well as in chronic cholestatic conditions. Because cholestatic features are seen in focal nodular hyperplasia, we initiated an immunohistochemical study on 23 surgical specimens using antibodies specific for cytokeratins 7 and 19 (bile duct type cytokeratins), OV6 (rat oval cell marker), chromogranin-A (shown to be positive in reactive bile ductules and human oval-like cells) and neural cell adhesion molecule--NCAM (shown to be positive in reactive bile ductules) to investigate whether 'undifferentiated progenitor cells' are also present in focal nodular hyperplasia. Electronmicroscopy was applied in five cases. Bile ductules invariably showed immunoreactivity for CK7 and 19, OV6, chromogranin-A and NCAM. In addition, small individual cells with an oval nucleus and a small rim of cytoplasm, in the vicinity of the septa, were immunoreactive for chromogranin-A, CK7 and 19 and OV6. These cells were hardly recognizable on routine light microscopy. Clusters of periseptal hepatocytes, seemingly in continuity with bile ductular structures, had a transitional phenotype: they stained positive for chromogranin-A, CK7 and OV6 and sometimes formed liver cell rosettes. The number of OV6-positive hepatocytes was greater than the number of chromogranin-A and CK7 positive hepatocytes. This indicates that, in human liver, OV-6 is not purely a marker of progenitor cells. Ultrastructurally, small immature cells, highly resembling rat oval cells, were recognized in the vicinity of septa. In addition, transitional cells displaying characteristics both of hepatocytes and bile duct cells were also present. These results confirm the presence of 'undifferentiated progenitor cells' in focal nodular hyperplasia and suggest that the ductular reaction in these lesions results, at least partly, from activation of these cells.

Axon-glial relationships in the anterior medullary velum of the adult rat

The anterior medullary velum is a thin sheet of CNS tissue which roofs the rostral part of the IVth ventricle and contains fascicles of myelinated fibres which, in part, arise from the nucleus of the IVth cranial nerve. This study used histochemical, immunohistochemical, and intracellular dye-injection techniques to describe cellular interrelationships in the velum in whole-mounts and in sections. Rip antibody-stained whole mounts provided a unique description of both oligodendrocyte units (defined as an oligodendrocyte and the complement of myelinated internodal segments it forms), and consecutive myelin sheaths along the same axon. A broad range of unit morphologies was categorised into four arbitrary groups, according to classical criteria, which comprised small cells supporting the short, thin myelin sheaths of 15-30 small diameter axons (Type I), through intermediate types (II & III), to the largest cells forming the long, thick myelin sheaths of 1-3 large diameter axons. Rip antibody and ferric ion-ferrocyanide staining, together with intracellular dye injection, revealed oligodendrocyte process branching patterns and their mode of engagement of myelin sheaths, nodes of Ranvier, and the spatial disposition of the outer cytoplasmic rims of myelin sheaths. The latter formed a conspicuous spiral ridge on the exterior surface of myelin sheaths which connected with the paranodal loops at each heminode. Large bundles of axons decussated through the velum, the bulk of which were IVth nerve fibres which constituted the IVth nerve rootlet. The PNS/CNS transitional zone of the IVth nerve was located 0.25-0.50 mm along the root, where astrocytic end-feet defined an abrupt margin, convex towards the periphery, where the heminodes of central and peripheral myelin were apposed, and where the basal lamina tubes of the Schwann cell units were discontinued. The basal processes of ependymal cells lining the ventricular wall of the velum, passed between axon bundles before abutting on the basal lamina of the pia. Many of these processes branched and ran along the axonal bundles. A monolayer of microglia occupied a subependymal stratum in which the non-overlapping dendritic territories of each cell formed a regular mosaic throughout the velum without any obvious interaction with either axons or other glial cells. Astrocytes were also uniformly distributed; their fine processes made up a dense lattice amongst axons, often running parallel and within the fibre bundles; stouter ones had terminal end-feet which undercoated the basal lamina of both the glia limitans externa and the blood vessels in the velum.

Cytoarchitecture of the substantia nigra pars lateralis in the opossum (Didelphis virginiana): a correlated light and electron microscopic study.

The substantia nigra has been divided into three subdivisions. However, the cytoarchitecture of one of these subdivisions, the pars lateralis (SNl), has not been previously examined in detail at the light and electron microscopic levels in any species. In the adult opossum, the three nigral subdivisions can be easily distinguished as distinct, rostrocaudally oriented cell groups separated by neuron-free zones. Thus it was possible to determine the boundaries of the SNl unambiguously. This report covers the results of an examination of the morphology and organization of the SNl in the opossum. Material from 13 opossums was used for this study. Eight of the animals had been previously stained for Nissl substance (n = 4) or impregnated by the Golgi technique (n = 4). The remaining five animals were prepared for electron microscopic studies using standard procedures. Two cell types were identified on the basis of morphological differences, small and medium-large neurons. Small neurons (10-18 microns long axis) have large nuclei with moderate amounts of heterochromatin and a thin rim of cytoplasm. They have long (up to 500 microns), spine-free dendrites. Medium-large neurons (18-54 microns long axis) have rounded nuclei with electron-lucent nucleoplasm. Few indentations of the nuclear envelope were observed. The surrounding cytoplasm has dense arrays of organelles. Nissl bodies are particularly prominent in the form of pyramids with their bases at juxtanuclear positions and their apices directed toward emerging dendrites. Dendrites of medium-large neurons are long (some > 1 mm in length), are primarily oriented in the frontal plane, and extend along the dorsal surface of or into the cerebral peduncle. Some cells have dendrites that are moderately spinous, whereas other neurons possess sparsely spinous dendrites. Relatively few synaptic profiles are observed to contact somata and proximal dendrites. This report provides added morphological support for the idea that the SNl is a distinct subdivision of the substantia nigra, a distinction previously made on the basis of the physiologically characterized relationship between the lateral substantia nigra and orienting behaviors and seizure-related function.

Detection of metrial gland cells in rat cervix after delivery by smear method.

It has been reported that the metrial glands, which form yellowish-white masses on the mesometrial triangle after pregnancy, coincide with the number of implants in the rat. In this study, the migration of the metrial gland cells (MGC) from the metrial glands to the endometrium after placental desquamation was investigated by the smear method. In smeared specimens, MGC appeared as large round cells with an unstained nucleus (a large binucleate cell was frequently seen), surrounded by a pinkish rim of cytoplasm, with PAS-staining; or appeared as a large reddish violet nucleus surrounded by dark violet cytoplasm with Giemsa staining. Numerous MGC were observed on the endometrium on the mesometrial side after artificial desquamation of the placenta on day 20 of pregnancy and day 0 of delivery. Further, MGC were observed on the endometrium on the antimesometrial side or in the cervix (including the internal and external orifice of the uterus) on day 0 of delivery, but no MGC could be detected in the cervix or on the antimesometrial side either during the period of placental signs (days 11-13) or on day 20 of pregnancy. Although MGC disappeared rapidly after delivery, slight traces of MGC remained on the mesometrial side until day 3 after delivery. In the case of abortion, MGC were observed in the cervix on the day of vaginal bleeding. In view of these results, it is considered that confirmation of MGC on the endometrium or the cervix provides evidence of abortion or delivery.

The Nuclear Complexes (“Composite Nuclei”) in the Genus Tracheloraphis: a Comparative Ultrastructural Study

Summary: Five most typical species of marine psammobiotic ciliates of the genus Tracheloraphis show the union of their entire nuclear apparatus, which consists of several or many macronuclei of the paradiploid never-dividing type and several to many micronuclei, into one or several nuclear complexes (“nuclear capsules”, “composite” or “complex” nuclei). Each of these complexes consists of four to 22 macronuclei in peripheral position and two to six micronuclei in central position. However, true fusion of the nuclei never occurs, the envelopes of each individual macro- and micronucleus remaining intact and separate from each other. The nuclei are united with a system of agranular endoplasmic reticulum cisternae that occur between the nuclei. From the outside, each nuclear complex is covered by a single additional agranular membrane which passes from one macronucleus onto another and represents the proximal membrane of the voluminous perinuclear cisterna of the smooth endoplasmic reticulum. Only a thin rim of ground cytoplasm occurs between this membrane and the envelopes of the outermost nuclei but more of it is present between the macronuclei and around the micronuclei. The macronuclei of representatives of this genus typically contain nuclear bodies in form of protein crystalloids in addition to chromocentres and nucleoli; the micronuclei contain compact, usually spongy chromatin andno nucleoli.

3 Morphology and cytochemistry of acute lymphoblastic leukaemia

ALL is characterized by small to medium sized leukaemic blasts with a rather low grade of cell-to-cell variability. The nucleocytoplasmic ratio is high with just a small cytoplasmic rim in many cases. The cytoplasm tends to be moderately basophilic. Usually, though not in each instance, it is agranular and free of vacuoles. The chromatin is more condensed than in AML and the nucleoli tend to be indistinct. The FAB classification of haematological malignancies separates ALL into three categories: ALL L1, L2, and L3. However, just the identification of the L3 variant is of major importance. The L3 cells are medium sized to large and are characterized by intensely basophilic and moderately abundant cytoplasm with prominent cytoplasmic vacuolation in the bone marrow but not necessarily in the peripheral blood. According to our experience there is a high but not universal correlation of the L3 phenotype as defined by morphology with the immunologically defined B-ALL with surface expression of immunoglobulins. Until recently, acute leukaemias proving negative for all cytochemical tests especially for the PAS reaction and for the focal type of acid phosphatase, were termed 'acute undifferentiated leukaemia' (AUL). However, this morphological/cytochemical diagnosis may be confused with the immunological diagnosis of unclassifiable leukaemia. Since almost any of these cases can be recognized as ALL or AML by immunology, the term AUL should be reserved for cases which can be classified neither by morphology/cytochemistry nor by immunology. The morphological and cytochemical distinction of ALL from poorly differentiated AML remains a problem, especially if the FAB criteria for distinguishing ALL from AML by cytochemistry (3% of the blasts positive for peroxidase) are applied rigidly. A small but significant percentage of poorly differentiated leukaemias have less than 3% of the blasts positive for peroxidase and the myeloid nature of the leukaemia can be identified by cytochemistry. The absence of blasts being positive for peroxidase is no reliable indicator for the lymphatic nature of a leukaemia, even if the PAS reaction is typical for ALL. The morphological diagnosis of ALL needs confirmation by immunology in each instance.

Microvascular lesions in reflux oesophagitis and Barrett's oesophagus

In 30 patients with reflux oesophagitis, the mucosal microvessels have been studied by transmission electron microscopy. The aim of the study was to test the hypothesis that a microvascular injury is involved in reflux oesophagitis, and to clarify if the epithelial metaplasia is correlated with a contemporaneous modification of the microvasculature in Barrett's oesophagus. In squamous epithelium-lined mucosa, signs of microangiopathy were found in all patients and capillaries regularly showed an interrupted, duplicated, or thickened basal lamina. In areas of columnar metaplasia, capillaries showed an ectatic lumen and a thin basal lamina without duplications or interruptions; endothelial cells had a thin rim of cytoplasm with many fenestrations. These findings demonstrate that microangiopathy is associated with epithelial damage in reflux oesophagitis.

M‐cells are damaged and increased in number in inflamed human ileal mucosa

Ileocolonoscopy and biopsies of patients with spondylarthropathy reveal gut inflammation in 62% of cases. In order to better understand the pathogenetic mechanisms of spondylarthropathy-related gut inflammation, the follicle-associated epithelium was examined. Biopsies from nine controls and 18 patients with spondylarthropathy were studied by electronmicroscopy. Membranous (M) cells were investigated in normal and inflamed ileum. In normal mucosa, M-cells were scarce whereas in inflamed mucosa their number was increased (up to 24% of follicle-associated epithelial cells). They showed a thin rim of cytoplasm covering groups of lymphocytes. In chronic ileitis, necrotic M-cells, rupture of M-cells and lymphocytes entering the gut lumen were observed. The bursting of M-cells at the top of the lymphoid follicles leads to interruption of the gut epithelial lining and gives the luminal content access to the lymphoid tissue. This pathogenetic mechanism may cause aphthoid ulcers.

Calretinin immunoreactivity in the monkey hippocampal formation—I. Light and electron microscopic characteristics and co-localization with other calcium-binding proteins

Calretinin-containing neurons were visualized by immunocytochemistry in the monkey hippocampal formation, subicular complex, and entorhinal cortex. Calretinin-immunoreactivity was present exclusively in non-granule cells of the dentate gyrus and in non-pyramidal cells of Ammon's horn, subiculum and entorhinal cortex. Most frequently, calretinin-positive neurons were found at the hilar border of the dentate granule cell layer and in the stratum radiatum of CA1–3 areas. In the subicular complex, immunoreactive neurons were evenly distributed in all layers, whereas in the entorhinal cortex, they were accumulated in external layers above the lamina dissecans. Distinct bands of calretinin-positive fibers occupied the supragranular zone of the molecular layer in dentate gyrus, the pyramidal cell layer of the CA2 area in Ammon's horn and the upper two layers of presubiculum. The majority of calretinin-immunoreactive neurons were small, bipolar or fusiform neurons with a dendritic tree oriented parallel to the dendrites of principal cells (granule cells in dentate gyrus and pyramidal neurons elsewhere). Dendrites were smooth or sparsely spiny, displaying small spines of conventional type. Co-existence studies showed that these neurons were completely devoid of other calcium-binding proteins, parvalbumin and calbindin. Electron microscopic analysis revealed somata of immunoreactive neurons which contained a large nucleus and a small cytoplasmic rim, which contained only few organelles. The nucleus displayed deep infoldings and intranuclear rods. Input synapses of immunoreactive neurons were rare both on somata and dendrites and large surface areas were frequently apposed by glial processes. This was very prominent in the dentate gyrus and Ammon's horn. Axons of calretinin-positive neurons were thin, arborized in all layers and had small varicosities. Their terminals formed symmetric synaptic contacts mainly with dendrites and less frequently with somata of principal cells. Axon terminals of calretinin-immunoreactive fiber bundles in the supragranular layer, as well as in the pyramidal layer of the CA2 area, formed asymmetric synaptic contacts with dendritic shafts. In addition, they established asymmetric axospinous and axosomatic synaptic contacts with granule cells of the dentate gyrus. In the presubiculum, the calretinin-positive axon bundle included a large number of immunoreactive myelinated axons, as well as axon terminals. The characteristic location and features of synapses suggests that these fibers derive from extra-hippocampal afferents (Nitsch, R. and Leranth C. (1993) Neuroscience 55, 797–812) and not from the calretinin-immunoreactive neurons of the hippocampal formation.