Frequency and distribution of megakaryoblasts in FAB subtypes of ANLL: an immunocytochemical ultrastructural study.

BACKGROUND: Identification of early megakaryocyte (MK) precursors is difficult and conflicting. The prevalence of leukemias with a megakaryocytic component may be underestimated when conventional techniques are utilized. The recent development of immuno-ultrastructural procedures for simultaneous detection of platelet peroxidase reaction and specific platelet membrane antigens has increased our capability of recognizing blast cells of the megakaryocytic lineage. METHODS: In this study the occurrence and distribution of megakaryoblastic in the FAB subtypes of adult "de novo" acute myeloid leukemias was employed to detect megakaryocytic precursors. RESULTS: A megakaryoblastic proliferation was demonstrated in 8/42 cases (19%), with a much higher percentage than previously reported and an unusual distribution in the M2 subtype. CONCLUSIONS: These findings indicate that megakaryocytic involvement may be found rather frequently when an immunocytochemical ultrastructural method is applied to the characterization of leukemias.

Morphological development of the human placenta in normal and complicated gestation: a quantitative and ultrastructural study.

In order to evaluate the structural potentialities of the placenta, we analyzed placentas in the following conditions: normal full term gestation, hypertensive status, twin pregnancy and abortion at 8-12 weeks of gestation, comparing cell structures, surface organization and tissue reaction. We quantitatively evaluated (1) the arborization of the placental villous tree, and (2) the microvillous density per unit of surface area, paralleling these data with ultrastructural and immunohistochemical features. In early gestation (8-12 weeks of pregnancy) the limited degree of branching of placental villi parallels a reduced number of clefts per unit of surface area (0.7/1,000 microns2), if compared with controls (2.7/1,000 microns2). In the full term twin placenta, the number of furrows is 2.26/1,000 microns2: this value reflects a low arborization potentiality, testifying to a low placental maturity. On the contrary, a high branching of the placental villous tree is present at term in hypertension. In this gestational condition, the number of sulci of 3.1/1,000 microns2 reveals a compensatory attitude of the placenta, aiming to sustain the impaired fetal-maternal metabolic interchange. In all these cases, syncytiotrophoblastic microvilli are reduced in number in comparison with the normal placenta, and this is likely to be an expression of a low trophoblastic maturation degree. The placenta is a barrier with a highly specialized function that conditions fetal outgrowth, and microenvironmental modifications are promptly faced by this structure through morphofunctional modulations.

Biological activity of chitosan: ultrastructural study.

Reparative processes are reconstructive phenomena in which cellular elements and extracellular matrix glycoproteins interact to build the injured tissue. Biomaterials can be used to improve or stimulate reconstruction. In the present experimental investigation, tissue repair induced by chitosan, an 86.8% deacetylated poly(GlcNAc), was monitored by morphological analysis. To evaluate its biological role, chitosan was positioned in contact with dura mater or was used as a dura mater substitute. This polysaccharide, having structural characteristics similar to glycosaminoglycans, seems to mimic their functional behaviour. The inductive and stimulatory activity of chitosan on connective tissue-rebuilding is clearly demonstrated, and it is suggested that chitosan could be considered a primer on which a normal tissue architecture is organized.

Root curettage and gingival repair in periodontitis.

Twelve patients, aged 35 to 60, having adult periodontitis were treated with scaling and root planning performed with ultrasonic and hand scalers. Biopsies were taken, gingival crevicular fluid and clinical parameters were analyzed at different times, and the healing process was monitored. Findings showed a clear correlation between the amount of crevicular fluid and the histological inflammatory pattern, whereas no relationship between crevicular fluid and gingival pocket depth was apparent. In this study, no differences were found in the histological features of the repair process triggered by either type of scaler.

Cytoskeleton and extracellular matrix of cutaneous vessels in inflammatory processes: immunomorphological study.

In pathological conditions, vascular modifications occur in various stages involving both vessel structure and adjacent extracellular matrix. The relationships between vascular cells and surrounding microenvironmental stroma are mediated by cytoskeleton. Our investigation showed a high number of vimentin- and actin-positive cells in the vascular cutaneous bed, mainly related to reactive vascularization phenomena, whereas vessel cells with a desmin-positive reaction were barely detectable. Furthermore, in newly formed vessels ultrastructure showed that basement membrane synthesis strictly depends on close contact between the endothelium and extracellular matrix. Our data give structural evidence of the close morphofunctional interactions existing between vascular cells and extracellular matrix.

Different metastatic aggressiveness by murine TS/A clones: ultrastructure, extracellular glycoproteins and type IV collagenolytic activity.

Cell ultrastructure, extracellular matrix glycoproteins, and type IV collagenolytic activity have been examined in four murine TS/A clones characterized by different metastatic aggressiveness. In vitro, highly metastatic clones (E) exhibited slightly less differentiated ultrastructure, and high type IV collagenolytic activity, while low metastatic clones (F) showed a more differentiated cytotype, with either high and low collagenolytic activity. Type IV collagen, laminin, and fibronectin were expressed without correlation with the metastatic efficiency; keratin was slightly more evident in E than in F cells. The morphological differences between E and F clones were less evident in the tumors produced by subcutaneous injection, and markedly reduced in the relative metastases composed only of the less differentiated cytotype; differences were also reduced in cells cultured on extracellular-matrix-coated flasks. The present study shows that no general correlation is observed between the studied parameters and metastatic aggressiveness.

Immunohistochemical study of basement membrane antigens in bronchioloalveolar carcinoma.

Bronchioloalveolar carcinoma (BAC), not yet completely defined as a biologic entity, has recently been classified into two different types. Immunohistochemical investigations, aimed at characterizing basement membrane (BM) behavior in the two types of BAC, revealed different distribution patterns. The first (Type I BAC) showed a linear staining for laminin and Type IV collagen similar to normal lung. Fibronectin was widely present in the septal interstitium and patchily distributed along the BM. The second (Type II BAC) showed a variable reaction for Type IV collagen and fibronectin, whereas laminin was absent or appeared as short, interrupted tracts around the epithelial neoplastic population, similar to conventional adenocarcinoma of the lung. These results suggest that only Type I BAC shows structural characteristics different from those of conventional adenocarcinoma of the lung.

Fibronectin distribution during lymph node development in guinea pig: an immunohistochemical study.

We carried out an immunohistochemical study on mesenteric guinea pig lymph nodes, from the 10th day prepartum till the 26th day postpartum, to assess the role of fibronectin in their organization during development. This glycoprotein is diffusely distributed in embryonic lymph nodes, suggesting a primer function during organogenesis. After birth, in fact, it is less widespread and is mainly localized around sinuses and vessels. Our data, supporting the important role of this glycoprotein during lymph node organization, are in agreement with the results obtained in other tissues and organs.

Detection of extracellular matrix antigens (fibronectin, laminin, type IV in collagen) in paraffin embedded sections by avidin-biotin-peroxidase complex labelling.

An avidin-biotin-peroxidase labelling method was applied to frozen sections and to routine-fixed, paraffin-embedded sections, and compared with immunohistochemical results of stromal antigen detection (type IV collagen, laminin and fibronectin) obtained in parallel on different neoplasias. Lung, breast and gastrointestinal tract tumors were studied. Superimposable sections were obtained from cryostat and formalin-fixed, paraffin-embedded specimens (previously digested by pepsin). The data demonstrate the potential use of immunohistochemical investigation of paraffin-embedded tissues for histological analyses of tumors.

Sequential behaviour of extracellular matrix glycoproteins in an experimental model of hepatic fibrosis.

The behaviour of extracellular matrix glycoproteins (fibronectin, laminin, basement membrane heparan-sulphate proteoglycan, type III, IV and V collagens) has been investigated in a sequential model of experimental hepatic fibrosis, using an immunofluorescence technique. The presence of some basement membrane macromolecules (such as type IV and V collagens, laminin and basement membrane heparan-sulphate proteoglycan) is detectable only in the early stages of septa formation, while type III collagen and fibronectin persist in late septa. These data suggest that hepatic fibroplasia proceeds through different steps in which stromal glycoproteins are preferentially engaged, as happens during organogenesis.