CXCL12-Abundant Reticular (CAR) Cells Direct Megakaryocyte Protrusions across the Bone Marrow Sinusoid Wall

Megakaryocytes (MKs) release platelets into the lumen of bone marrow (BM) sinusoids while remaining to reside within the BM. The morphogenetic events of this complex process are still not fully understood. We combined confocal laser scanning microscopy with transmission and serial block-face scanning electron microscopy followed by 3D-reconstruction on mouse BM tissue sections. These analyses revealed that MKs in close vicinity to BM sinusoid (BMS) wall first induce the lateral retraction of CXCL12-abundant reticular (CAR) cells (CAR), followed by basal lamina (BL) degradation enabling direct MK-sinusoidal endothelial cells (SECs) interaction. Subsequently, an endothelial engulfment starts that contains a large MK protrusion. Then, MK protrusions penetrate the SEC, transmigrate into the BMS lumen and form proplatelets that are in direct contact to the SEC surface. Furthermore, such processes are induced on several sites, as observed by 3D reconstructions. Our data demonstrate that MKs in interaction with CAR-cells actively induce BMS wall alterations, including CAR-cell retraction, BL degradation, and SEC engulfment containing a large MK protrusion. This results in SEC penetration enabling the migration of MK protrusion into the BMS lumen where proplatelets that are adherent to the luminal SEC surface are formed and contribute to platelet release into the blood circulation.

Structural organization of the bone marrow and its role in hematopoiesis

PURPOSE OF REVIEW

The bone marrow is the main site for hematopoiesis. It contains a unique microenvironment that provides niches that support self-renewal and differentiation of hematopoietic stem cells (HSC), multipotent progenitors (MPP), and lineage committed progenitors to produce the large number of blood cells required to sustain life. The bone marrow is notoriously difficult to image; because of this the anatomy of blood cell production -- and how local signals spatially organize hematopoiesis -- are not well defined. Here we review our current understanding of the spatial organization of the mouse bone marrow with a special focus in recent advances that are transforming our understanding of this tissue.

RECENT FINDINGS

Imaging studies of HSC and their interaction with candidate niches have relied on ex-vivo imaging of fixed tissue. Two recent manuscripts demonstrating live imaging of subsets of HSC in unperturbed bone marrow have revealed unexpected HSC behavior and open the door to examine HSC regulation, in situ, over time. We also discuss recent findings showing that the bone marrow contains distinct microenvironments, spatially organized, that regulate unique aspects of hematopoiesis.

SUMMARY

Defining the spatial architecture of hematopoiesis in the bone marrow is indispensable to understand how this tissue ensures stepwise, balanced, differentiation to meet organism demand; for deciphering alterations to hematopoiesis during disease; and for designing organ systems for blood cell production ex vivo.

Blast vacuolization in AML patients indicates adverse-risk AML and is associated with impaired survival after intensive induction chemotherapy

Introduction

Vacuolization is a frequently found morphological feature in acute myeloid leukemia (AML) blasts. Subcellular origin and biological function as well as prognostic impact are currently unknown. The aim of this study was to evaluate whether vacuolization correlates with clinically relevant AML features.

Materials & methods

Bone marrow smears of patients diagnosed with AML at the University Hospital Frankfurt between January 2011 and August 2013 were analyzed for blast vacuolization and correlated with clinically relevant AML features. Patients undergoing standard induction chemotherapy were further analyzed for molecular and cytogenetic features as well as treatment response and survival.

Results

14 of 100 patients diagnosed with AML receiving standard induction chemotherapy had evidence of blast vacuolization. Positivity for vacuolization correlated with a CD15 positive immunophenotype and with a higher incidence of high-risk AML according to the European LeukemiaNet risk stratification. AML patients with blast vacuolization had a poor blast clearance after standard induction chemotherapy and poor survival.

Discussion

In conclusion, our findings demonstrate that vacuolization can easily be determined in myeloid leukemia blasts and may be a useful biomarker to predict AML risk groups as well as early treatment response rates and survival.

Characterization of the bone marrow adipocyte niche with three-dimensional electron microscopy

Unlike white and brown adipose tissues, the bone marrow adipocyte (BMA) exists in a microenvironment containing unique populations of hematopoietic and skeletal cells. To study this microenvironment at the sub-cellular level, we performed a three-dimensional analysis of the ultrastructure of the BMA niche with focused ion beam scanning electron microscopy (FIB-SEM). This revealed that BMAs display hallmarks of metabolically active cells including polarized lipid deposits, a dense mitochondrial network, and areas of endoplasmic reticulum. The distinct orientations of the triacylglycerol droplets suggest that fatty acids are taken up and/or released in three key areas - at the endothelial interface, into the hematopoietic milieu, and at the bone surface. Near the sinusoidal vasculature, endothelial cells send finger-like projections into the surface of the BMA which terminate near regions of lipid within the BMA cytoplasm. In some regions, perivascular cells encase the BMA with their flattened cellular projections, limiting contacts with other cells in the niche. In the hematopoietic milieu, BMAT adipocytes of the proximal tibia interact extensively with maturing cells of the myeloid/granulocyte lineage. Associations with erythroblast islands are also prominent. At the bone surface, the BMA extends organelle and lipid-rich cytoplasmic regions toward areas of active osteoblasts. This suggests that the BMA may serve to partition nutrient utilization between diverse cellular compartments, serving as an energy-rich hub of the stromal-reticular network. Lastly, though immuno-EM, we've identified a subset of bone marrow adipocytes that are innervated by the sympathetic nervous system, providing an additional mechanism for regulation of the BMA. In summary, this work reveals that the bone marrow adipocyte is a dynamic cell with substantial capacity for interactions with the diverse components of its surrounding microenvironment. These local interactions likely contribute to its unique regulation relative to peripheral adipose tissues.

Hairy Cell Leukemia: Enzyme-histochemical and Ultrastructural Investigation of one Case

The investigation was carried out on blood smears, bone marrow aspirates, one lymph node biopsy, and the surgically removed spleen of a 53-year-old man with hairy cell leukemia. In the blood smears stained with May-Grünwald-Giemsa, 60 to 70 % of the hairy cells contained tubular inclusions that corresponded to the ribosome-lamella complexes demonstrated at electron microscopy. In blood smears, imprints and cryostatic sections of the lymph node and of the spleen, hairy cells revealed tartrate-resistant acid phosphatase, beta-glucuronidase and adenosine-triphosphatase activity. In the spleen neutral esterase and alkaline phosphatase demonstrated the numerical increase of the histiocytes, which ultrastructurally displayed phagocytic activity. The presence in the spleen of pseudosinuses lined by hairy cells was confirmed by electron microscopy as well as by cytoenzymology.

Ultrastructural Alterations of Megakaryocytes in Some Hematologic Disorders

Bone marrow and peripheral blood samples of patients affected by hematologic disorders involving the megakaryocytic line were examined at the electron microscope. While in idiopathic thrombocytopenic purpura the megakaryocytes appeared almost normal, in primary thrombocythemia there were various ultrastructural alterations interpreted as a counterpart of ineffective thrombocytopoiesis. In one patient with blastic chronic myeloid leukemia and in another with acute megakaryoblastic leukemia, the electron microscope study was very useful in the identification of immature megakaryocytes. In fact, analysis of various ultrastructural parameters allowed some blast cells to be attributed to the megakaryocytic series. Furthermore, platelet demarcation system abnormalities and alterations of the circulating thrombocytes confirm the hypothesis that there is a block in megakaryocytic maturation.

Osteogenesis in Marrow-Derived Mesenchymal Cell Porous Ceramic Composites Transplanted Subcutaneously: Effect of Fibronectin and Laminin on Cell Retention and Rate of Osteogenic Expression

Cultured-expanded rat marrow-derived mesenchymal cells differentiate into osteoblasts when combined with a porous calcium phosphate delivery vehicle and subsequently implanted in vivo. In this study, the effects of ceramic pretreatment with the cell-binding proteins fibronectin and laminin on the osteogenic expression of marrow-derived mesenchymal cells were assessed by scanning electron microscopy, [3H]-thymidine-labeled cell quantitation, and histological evaluation of bone formation. Scanning electron microscopic observations showed that marrow-derived mesenchymal cells rapidly spread and attach to both fibronectin- or laminin-adsorbed ceramic surfaces but retain a rounded morphology on untreated ceramic surfaces. Quantitation of [3H]-thymidine labeled cells demonstrated that laminin and fibronectin preadsorbed ceramics retain approximately double the number of marrow-derived mesenchymal cells than do untreated ceramics harvested 1 wk postimplantation. Histological observations indicate that the amount of time required to first detect osteogenesis was shortened significantly by pretreatment of the ceramic with either fibronectin or laminin. Fibronectin- and laminin-coated ceramic composite samples were observed to contain bone within 2 wk postimplantation, while in untreated ceramic the earliest observation of bone was at 4 wk postimplantation.

A comparison was made of the initial cell-loading, in vivo cell retention characteristics, and rate of osteogenesis initiation of marrow-derived mesenchymal cells on two types of ceramic with different pore structure and chemical composition, with and without preadsorption with fibronectin or laminin. “Biphasic” ceramics contain randomly distributed pores 200-400 μm in diameter, and “coral-based” ceramics have continuous pores of approximately 200 μm in diameter. Laminin or fibronectin preadsorption significantly increases the number of cells retained in all ceramic test groups by day 7 postimplantation. In addition, by day 7 postimplantation, the biphasic ceramics retain a significantly greater number of cells for all test groups than do coral-based ceramics. The biphasic ceramics consistently have more specimens positive for bone with the identical cell-loading conditions used throughout this study. These results indicate that the retention of cells within the ceramic is an important factor for optimization of marrow mesenchymal cell initiated bone formation. The retention of cells within ceramics is augmented by the adsorption of the cell-binding proteins laminin and fibronectin, but this effect varies depending on ceramic pore structure and/or chemical composition.

HISTOCHEMICAL DEMONSTRATION OF PHOSPHOLIPASE B (LYSOLECITHINASE) ACTIVITY IN RAT TISSUES

A method has been developed for the histochemical demonstration of phospholipase B (lysolecithinase) of rat tissues. The enzyme attacks lysolecithin with liberation of 1 mole of glycerylphosphorylcholine and 1 mole of fatty acid. The recommended procedure involves use of 6-10 µ frozen sections, fixed in cold calcium-formol and incubated at 37°C in Tris buffered medium at pH 6.6 containing 2.2 x 10–3 M lysolecithin and 1% cobalt acetate. The fatty acid liberated by enzymatic hydrolysis is trapped as a cobalt precipitate and is then converted to a blackbrown precipitate by treatment with dilute ammonium sulfide in cold isotonic saline. Equivalent amounts of fatty acid and glycerylphosphorylcholine are recovered by extraction and analysis of the incubated sections and of the incubation medium, thus proving that lysolecithin hydrolysis occurs under the proposed reaction conditions. Staining is reduced by treating the sections with copper ions, mercury compounds, alcohols, acetone and by heating at 60°C prior to incubation with substrate. Lowering of the pH of the incubation medium has similar effect. These findings are interpreted as evidence of the enzymatic nature of the reaction. Cells exhibiting a positive staining are found in the lamina propria of the intestinal villi and crypts, in the red pulp of the spleen and in the interstitial tissue of lung, liver and thymus. Similar elements are present in bone marrow smears and in leukocyte preparations obtained by peritoneal lavage. The morphologic and staining characteristics of these cells correspond to those of the eosinophilic leukocytes. Physical and chemical agents (x-irradiation corticosteroids) which sharply decrease the number of eosinophils also reduce the number of cells shown histochemically to hydrolyze lysolecithin. A correspondent. diminution of phospholipase B activity of homogenates of the same tissues can be shown in vitro. Differences in tissue distribution and chemical properties distinguish the phospholipase B from less specific esterases and lipases.

A Light and Electron Microscopic Study of Changes in Blood and Bone Marrow in Acute Hemorrhagic Trypanosoma vivax Infection in Calves

Eleven 6-month-old calves were tsetse fly challenged with a stock of Trypanosoma vivax (IL 2337) that causes hemorrhagic infection. The calves were randomly euthanatized every 4 to 6 days; two other calves served as controls. Peripheral blood changes included anemia, thrombocytopenia, and an initial leukopenia. Later in the course of infection, leukocytosis associated with lymphocytosis and neutropenia developed. Moderate reticulocytosis (highest mean count 3.6 ± 3.7%, maximum count 9.4%) accompanied the first wave of parasitemia, but poor response (highest mean 0.4 ± 0.0%) occurred during the second wave, despite the persistence of severe anemia. Light microscopic examination of bone marrow samples showed a drop in the myeloid: erythroid ratio with a decrease in granulocytes, particularly metamyelocytes, bands, and segmenters. Increase in lymphocyte counts corresponded with the appearance of lymphoid nodules within the marrow. Megakaryocyte volume increased significantly in infected animals, and some megakaryocytes showed emperipolesis of red cells, neutrophils, and lymphocytes. Transmission electron microscopic examination of the bone marrow revealed that trypanosomes had crossed the sinusoidal endothelium into the hematopoietic compartment as early as the second day of parasitemia. Macrophages proliferated in the bone marrow; and from the second day of parasitemia until the end of the experimental infection, on day 46, the macrophages had phagocytosed normoblasts, eosinophil and neutrophil myelocytes, metamyelocytes, bands, and segmenters, as well as reticulocytes, erythrocytes, and thrombocytes. Therefore, dyserythropoiesis and dysgranulocytopoiesis were responsible, in part, for the observed anemia and granulocytopenia, respectively.

Aberration correction during real time in vivo imaging of bone marrow with sensorless adaptive optics confocal microscope

We have demonstrated adaptive correction of specimen-induced aberration during in vivo imaging of mouse bone marrow vasculature with confocal fluorescence microscopy. Adaptive optics system was completed with wavefront sensorless correction scheme based on stochastic parallel gradient descent algorithm. Using image sharpness as the optimization metric, aberration correction was performed based upon Zernike polynomial modes. The experimental results revealed the improved signal and resolution leading to a substantially enhanced image contrast with aberration correction. The image quality of vessels at 38- and 75-μm depth increased three times and two times, respectively. The corrections allowed us to detect clearer bone marrow vasculature structures at greater contrast and improve the signal-to-noise ratio.

Ultrastructural characterization of the implant interface response to loading

Dynamic loading can affect the bone surrounding implants. For ultrastructural exploration of the peri-implant tissue response to dynamic loading, titanium implants were installed in rat tibiae, in which one implant was loaded while the contralateral served as the unloaded control. The loaded implants received stimulation either within 24 hrs after implantation (immediate loading) or after a 28-day healing period (delayed loading) for 4, 7, 14, 21, or 28 days. The samples were processed for histology and gene expression quantification. Compared with the unloaded control, bone-to-implant contact increased significantly by immediate loading for 28 days (p < .05), but not in case of delayed loading. No effect of loading was observed on the bone formation in the implant thread areas, on the blood vessel area, and on endosteal callus formation. Loading during healing (immediate) for 7 days induced, relative to the unloaded control, a 2.3-fold increase of Runx2 in peri-implant cortical bone (p < .01) without a change in the RANKL/Opg ratio. Loading after healing (delayed) for 7 days up-regulated Runx2 (4.3-fold, p < .01) as well as Opg (22.3-fold, p < .05) compared with the unloaded control, resulting in a significantly decreased RANKL/Opg ratio. These results indicate a stimulating effect of dynamic loading on implant osseointegration when applied during the healing phase. In addition, gene expression analyses revealed molecular adaptations favoring bone formation and, at the same time, affecting bone remodeling.

Osterix-cre labeled progenitor cells contribute to the formation and maintenance of the bone marrow stroma

We have carried out fate mapping studies using Osterix-EGFPCre and Osterix-CreERt animal models and found Cre reporter expression in many different cell types that make up the bone marrow stroma. Constitutive fate mapping resulted in the labeling of different cellular components located throughout the bone marrow, whereas temporal fate mapping at E14.5 resulted in the labeling of cells within a region of the bone marrow. The identity of cell types marked by constitutive and temporal fate mapping included osteoblasts, adipocytes, vascular smooth muscle, perineural, and stromal cells. Prolonged tracing of embryonic precursors labeled at E14.5dpc revealed the continued existence of their progeny up to 10 months of age, suggesting that fate mapped, labeled embryonic precursors gave rise to long lived bone marrow progenitor cells. To provide further evidence for the marking of bone marrow progenitors, bone marrow cultures derived from Osterix-EGFPCre/Ai9 mice showed that stromal cells retained Cre reporter expression and yielded a FACS sorted population that was able to differentiate into osteoblasts, adipocytes, and chondrocytes in vitro and into osteoblasts, adipocytes, and perivascular stromal cells after transplantation. Collectively, our studies reveal the developmental process by which Osterix-Cre labeled embryonic progenitors give rise to adult bone marrow progenitors which establish and maintain the bone marrow stroma.

Bee venom induced in vivo ultrastructural reactions of cells involved in the bone marrow erythropoiesis and of circulating red blood cells

Ultrastructural answer of bone marrow erythroid series and of red blood cells (RBCs) in Wistar rats to bee venom (BV) was analyzed by transmission and scanning electron microscopy, and corroborated with hematological data. A 5-day and a 30-day treatment with daily doses of 700 μg BV/kg and an acute-lethal treatment with a single dose of 62 mg BV/kg were performed. The 5-day treatment resulted in a reduced cellularity of the bone marrow, with necrosed proerythroblasts, polymorphous erythroblasts, and reticulocytes with cytoplasmic extensions, and a lower number of larger RBCs, with poikilocytosis (acanthocytosis) and anisocytosis, and reduced concentrations of hemoglobin. After the 30-day treatment, the bone marrow architecture was restored, but polymorphous erythroblasts and reticulocytes with thin extensions could still be observed, while the RBCs in higher number were smaller, many with abnormal shapes, especially acanthocytes. The acute treatment produced a partial depopulation of the bone marrow and ultrastructural changes of erythroblasts including abnormal mitochondrial cristae. The RBCs in lower number were bigger and crenated, with reduced concentrations of hemoglobin. Overall, BV was able to promote stress erythropoiesis in a time- and dose-related manner, mitochondrial cristae modification being a critical factor involved in the toxicity of the BV high doses.

When are apparently non-clonal abnormalities in bone marrow chromosome studies actually clonal?

The observation of an apparently non-clonal abnormal cell in a cytogenetic study for a hematologic neoplasm opens the possibility of a small, or slowly proliferating, abnormal clone. Many laboratories analyze additional cells or reflex to fluorescence in situ hybridization (FISH) to evaluate this possibility further. In a retrospective study of 500 cases with a non-clonal abnormal cell identified in a 20-cell analysis, we found that the benefit of additional metaphase analysis was limited to specific categories of abnormal karyotypes, including those with a complex karyotype or a classic abnormality known to be a recurring finding in hematologic neoplasms, and excluding all other categories.

Acceleration of neutrophil precursors' maturation and immunostimulation of CD3+, CD4+ lymphocytes by stanozolol in mice

The abuse of anabolic-androgenic steroids (AAS) for improved physical performance is associated with many deleterious effects. The present study aims to evaluate the short-term effect of an AAS compound stanozolol, on lipoprotein profile, granulopoiesis and immune response in adult female mice. The mice were assigned to five experimental groups and different doses of stanozolol (low - 0.05 mg, medium - 0.5 mg, high - 5 mg and highest dose - 7.5 mg/kg bwt or only vehicle respectively) were administered s.c. for 15 days. A decrease in high density lipoprotein cholesterol (HDL-c) as well as total cholesterol (TC) in all the stanozolol treated groups and an increase in low density lipoprotein (LDL-c) in high and the highest dose treated groups indicate that stanozolol alters serum lipoprotein profile. A significant increase in the percentage of myelocytes, metamyelocytes and neutrophils in all the treated mice unveils the stimulation of granulopoiesis through the acceleration of neutrophil precursors' maturation in the bone marrow of mice. The stimulation of erythropoiesis was also noted in all the treated groups. The flow cytometry analysis of lymphocyte subpopulations (CD3(+) and CD4(+)) revealed immunoenhancing response of stanozolol at optimum physiological dose, however, it is immunosuppressive at supraphysiologic level. We conclude that stanozolol accelerates granulopoiesis and stimulates immune response (at physiologic level only), though it alters the lipoprotein profile in mice.

Characterization of megakaryocyte development in the native bone marrow environment

Differentiation and maturation of megakaryocytes occur in close association with cellular and extracellular components in the bone marrow. Thus, direct examination of these processes in the native environment provides important information regarding the development of megakaryocytes. In this chapter, we present methods applied to mouse bone marrow to (1) examine the ultrastructure of megakaryocytes and their state of maturation in situ in fixed bone marrow sections and (2) study the dynamics of proplatelet formation by real-time observation of fresh bone marrow explants where megakaryocytes have matured in their natural physiological context. Combining these two approaches allows detailed investigation of in situ megakaryocyte differentiation, including proplatelet formation, which is the final maturation step before platelet release.

Assessment of genotoxicity induced by 7,12-dimethylbenz(a)anthracene or diethylnitrosamine in the Pig-a, micronucleus and Comet assays integrated into 28-day repeat dose studies

As part of the Stage 3 of the Pig-a international trial, we evaluated 7,12-dimethylbenz(a)anthracene (DMBA) for induction of Pig-a gene mutation using a 28-day repeat dose study design in Sprague-Dawley rats. In the same study, chromosomal damage in peripheral blood and primary DNA damage in liver were also investigated by the micronucleus (MN) assay and the Comet assay, respectively. In agreement with previously published data (Dertinger et al., [2010]: Toxicol Sci 115:401-411), DMBA induced dose-dependent increases of CD59-negative erythrocytes/reticulocytes and micronucleated reticulocytes (MN-RETs). However, there was no significant increase in DNA damage in the liver cells when tested up to 10 mg/kg/day, which appears to be below the maximum tolerated dose. When tested up to 200 mg/kg/day in a follow-up 3 dose study, DMBA was positive in the liver Comet assay. Additionally, we evaluated diethylnitrosamine (DEN), a known mutagen/hepatocarcinogen, for induction of Pig-a mutation, MN and DNA damage in a 28-day study. DEN produced negative results in both the Pig-a mutation assay and the MN assay, but induced dose-dependent increases of DNA damage in the liver and blood Comet assay. In summary, our results demonstrated that the Pig-a mutation assay can be effectively integrated into repeat dose studies and the data are highly reproducible between different laboratories. Also, integration of multiple genotoxicity endpoints into the same study not only provides a comprehensive evaluation of the genotoxic potential of test chemicals, but also reduces the number of animals needed for testing, especially when more than one in vivo genotoxicity tests are required.

Proplatelet formation deficit and megakaryocyte death contribute to thrombocytopenia in Myh9 knockout mice

BACKGROUND

 Inactivation of the mouse Myh9 gene (Myh9Δ) or its mutation in MYH9-related diseases leads to macrothrombocytopenia. Paradoxically, previous studies using in vitro differentiated megakaryocytes showed an increased capacity for proplatelet formation when myosin was absent or inhibited.

METHODS

 To explore the origin of the thrombocytopenia induced by myosin deficiency, we studied proplatelet formation using bone marrow explants of wild-type (WT) and Myh9Δ mouse where megakaryocytes have matured in their native environment.

RESULTS AND DISCUSSION

 A dramatic decrease in the number and complexity of proplatelets was observed in megakaryocytes from Myh9Δ mice, while inhibition of myosin activity by blebbistatin increased proplatelet formation from WT mature megakaryocytes. Moreover, Myh9Δ megakaryocytes had a smaller size than the WT cells. These data indicate that myosin deficiency acts negatively on proplatelet formation, probably by impairing in situ megakaryocyte maturation, while myosin activity is dispensable at the latest stage of proplatelet formation. In addition, ultrastructural examination of Myh9Δ bone marrow revealed an increased proportion of megakaryocytes exhibiting signs of non-apoptotic cell death as compared with the WT mice.

CONCLUSION

 These data indicate that thrombocytopenia in Myh9Δ mice results from defective development of megakaryocyte size, impaired proplatelet formation and increased cell death.

Imaging resin-cast osteocyte lacuno-canalicular system at bone-bioactive glass interface by scanning electron microscopy

The morphology of the osteocyte lacuno-canalicular system at the bone-biomaterial implant-interface has not been fully investigated. In this study, the resin-cast scanning electron microscopy technique was used, for the first time, to image the lacuno-canalicular network within neoformed bone around bioactive glass (BG) particles implanted in rat tibia bone marrow. The most salient finding was that the osteocyte canaliculi pass through the calcium-phosphorus layer formed at the bone-BG interface and reach the silica-rich layer of the reacted BG.

Primary and isolated anaplastic large cell lymphoma of the bone marrow

Anaplastic large cell lymphoma (ALCL) is a T-cell lymphoma in which the majority of patients present with advanced stage III or IV disease. Here we report a case of ALCL where bone marrow was the only site of disease, in a 60-year-old man with pyrexia and pancytopenia. The diagnosis of ALCL was made on detection of CD30-positive anaplastic cells in the bone marrow, together with prominent hemophagocytosis. Genetics confirmed the clonal nature of the disease and showed it to be anaplastic lymphoma kinase (ALK) negative. Primary isolated bone marrow ALCL should be considered in the diagnosis of pancytopenia associated with hemophagocytosis.

Amyloid deposits in bone marrow aspirates in primary amyloidosis

Amyloid deposits aspirated from the bone marrow have a characteristic appearance in May--Grünwald-Giemsa-stained smears, and almost specific fibrillar pattern when viewed in an electron microscope.

Ultrastructural study of erythrophagocytosis in the rat bone marrow. I. Red cell engulfment by reticulum cells

Previous light microscopic studies have revealed the erythroclastic potential of the rat bone marrow reticulum cells, and call for ultrastructural study of the finer details of this process. Electron microscopy of rat bone marrow which had been stimulated to increase its erythrophagic activity, either by splenectomy or by transfusion of heat denatured erythrocytes, confirmed the central reticulum cell of erythroblastic islands as the main phagocytic cell in bone marrow erythroclasia. The early digestive vacuoles, which are formed by the fusion of erythrophagic vacuoles with lysosomes, correspond to the acidophilic, globular structures which characterize erythrophagocytosis as observed by light microscopy. By forming intrasinusoidal protrusions, the bone marrow reticulum cells engulf circulating effete red cells. The engulfed red cells are then transported intracellularly across the sinusoidal wall for final disintegration in the intraparenchymal part of the reticulum cell. This transmural mode of erythrophagocytosis by reticulum cells most probably demonstrates the fundamental phagocytic mechanism of the bone marrow part of the reticulo-endothelial system. Transmural transport of reticulocytes adherent to reticulum cells during the formation of protrusions illustrates a possible mechanism for liberation of red cells from the bone marrow.

Ultrastructural study of erythrophagocytosis in the rat bone marrow II. Iron metabolism in reticulum cells following red cell digestion

Intracellular transport and storage of iron in bone marrow reticulum cells can be studied in the electron microscope by the recognition of iron macromolecules. Following artificially increased bone marrow erythrophagocytosis ferritin molecules accumulate both in the cell sap and in the lysosomes of erythroclastic reticulum cells. Persistent iron loading transforms lysossomes into siderosomes, after which haemosiderin may be formed by grandual transformation of ferritin. The bone marrow reticulum cell shows evidence suggestive of autophagy, a process which may allow for the transfer of cell sap ferritin into lysosomes, as documented for other types of iron storing cells.

Different composition of the eosinophilic bone marrow pool in reactive eosinophilia and eosinophilic leukaemia

The composition of the eosinophilic cell series in the bone marrow has been analysed in 10 patients with a pronounced reactive eosinophilia (RE) and in 2 with eosinophilic leukaemia (EL). An imparied differentiation of the eosinophils was found in the EL patients compared with the RE group. Thus the ratio of eosinophilic promyelocytestmyelocytes: segmented eosinophils was 9.2 and 9.1, respectively, in the patients with EL and 0.1--3.1 (average 1.3) in the RE patients. It is suggested that EL is characterized by an impaired differentiation of the eosinophilic bone marrow cells and that the recognition of this abnormality is of value in the diffential diagnosis between EL and RE.

Dyserythropoiesis in homozygous haemoglobin C disease

Electron microscope studies of the bone marrow of three patients with homozygous haemoglobin C (HbC) disease have shown marked ultrastructural abnormalities in several of the polychromatic erythroblasts and marrow reticulocytes and the presence of phagocytosed erythroblasts within the macrophages. Such abnormalities were not found in the bone marrow of three patients with sickle cell anaemia indicating that the abnormalities represented a feature of HbC disease rather than a disturbance secondary to peripheral haemolysis. The characteristic ultrastructural finding in the polychromatic erythroblasts in HbC disease was the presence of grossly-disorganized nuclei showing multiple intranuclear clefts, the loss of parts of the nuclear membrane, oozing of nuclear material into the cytoplasm and an alteration of the structure and stainability of the nuclear chromatin. It is proposed that both the dyserythropoiesis and ineffective erythropoiesis in HbC disease may have resulted from the formation in vivo of very small aggregates of HbC within erythropoietic cells.

Ultrastructure of the bone marrow in HIV infection: evidence of dyshaemopoiesis and stromal cell damage

The ultrastructure of bone marrow cells was studied in nine patients infected with the human immunodeficiency virus (HIV). Two of these (cases 1 and 3) were thrombocytopenic, had never suffered from opportunistic infections and had not received any drugs prior to the time of study. A number of ultrastructural abnormalities were found in a variable proportion of the affected cell types in all nine patients. These were: (a) an increased prevalence of multivesicular bodies within several cell types and of abnormalities of the nuclear membrane in neutrophil granulocytes, (b) an increase in the size of the Golgi apparatus and in the quantity of endoplasmic reticulum in neutrophil granulocytes, (c) dysplastic features, including multiple long intranuclear clefts and large cytoplasmic vacuoles in some erythroblasts and (d) vacuolation of the plasma cells. Other abnormalities seen in a proportion of the patients were: (a) cylindrical confronting cisternae (CCC) in some of the lymphocytes, macrophages (phagocytic reticular cells), non-phagocytic reticular cells (including adventitial cells) and endothelial cells of marrow sinusoids, (b) tubuloreticular structures (TRS) in some lymphocytes, plasma cells, monocytes and endothelial cells and (c) precipitates of protein within occasional erythroblasts and marrow reticulocytes. There was also a striking and hitherto undescribed abnormality of the structure of the nucleus in intersinusoidal and perisinusoidal non-phagocytic reticular cells. This was seen in six patients, including case 3, and was characterized by the extensive detachment of masses of abnormally electron-dense heterochromatin from the nuclear membrane, the presence of a uniformly thin layer of electron-dense material at the inner surface of the areas of nuclear membrane denuded of heterochromatin masses and an abnormal electron lucency of areas containing euchromatin. The CCC and TRS were found in the six patients with the lowest number of circulating CD4-positive T cells. The precipitation of protein within erythroid cells may have been caused by the oxidant effect of dapsone or high doses of co-trimoxazole. The abnormalities in the stromal cells and in particular the nuclear changes seen in the non-phagocytic reticular cells support the possibility that one of the mechanisms underlying the cytopenia in patients infected with HIV may be a disturbance of the microenvironmental regulation of haemopoiesis.

Evaluation of the micronucleus assay in bone marrow and peripheral blood of rats for the determination of cigarette mainstream-smoke activity

The mammalian in vivo micronucleus assay is widely used as part of the genotoxicity testing battery required during the development of new drugs. As such, the in vivo micronucleus assay has been used in a battery of assays for the assessment of cigarette ingredients or design modifications to help ensure that there is no increase in risk or any new risk introduced by these additions or modifications. The present series of studies was conducted to optimize and evaluate this assay for the assessment of the effects of mainstream smoke on the micronucleus frequency in the bone marrow and peripheral blood of rats. In a first experiment, the optimal conditions for performing the micronucleus assay in these tissues were determined. This was done by use of two compounds known for their micronucleus-inducing activity, i.e., the clastogen cyclophosphamide and the aneugen colchicine. In a second experiment, the effects of tube restraint on untreated control rats were investigated. In a third experiment, the optimal conditions were used to assess the clastogenic/aneugenic activity of cigarette smoke in Sprague-Dawley rats. The rat micronucleus assay in both bone marrow and peripheral blood is able to detect clastogenic and aneugenic activity. The flow cytometric determination of micronucleated cells in rat blood is at least as sensitive as determinations in bone marrow. No statistically significant differences were observed in micronucleus frequencies between rats with and without the additional stress of tube restraint; however, the cautious approach would be to use a fresh-air-exposed group (with tube restraint) as the negative control in inhalation experiments. Using the conditions identified as optimal in the above-mentioned experiments, the micronucleus assay was not able to detect effects induced by smoke from conventional cigarettes. Nevertheless, the micronucleus assay will remain a valuable tool as part of a testing battery used to investigate possible adverse effects related to product modifications.

Characteristics of soluble and membrane-bound forms of haemopoietic growth factor receptors: relationships to biological function

In order to understand how extracellular growth factors (colony-stimulating factors, CSFs) induce biological responses in haemopoietic cells it is necessary first to describe the primary binding characteristics of isolated receptors and then to determine how living cells modify these binding characteristics and process the ligand-receptor complexes. We have solubilized multi-CSF (interleukin 3) and granulocyte macrophage CSF (GM-CSF) receptors in 1% Triton X-100 and developed methods to study their binding characteristics in solution. Whilst the multi-CSF receptor exhibits the same binding characteristics in solution and in the cellular state, the GM-CSF receptor appears to be converted to a lower affinity form in solution. In intact cells at biological temperatures both types of receptor and ligand are internalized and degraded under steady-state conditions; the kinetic processes underlying the maintenance of the steady state are characteristic for each type of receptor and each type of cell. We have determined the kinetic constants for a variety of CSFs and cell types and correlated steady-state receptor occupancy with biological responses. The importance of CSF utilization rate by responsive cells has also been evaluated as a mechanism for limiting biological responses.

Ocimum sanctumLinn. (Holy Basil) Ethanolic Leaf Extract Protects Against 7,12-Dimethylbenz[a]Anthracene-Induced Genotoxicity, Oxidative Stress, and Imbalance in Xenobiotic-Metabolizing Enzymes

The present study was designed to evaluate the protective effects of ethanolic Ocimum sanctum leaf extract against 7,12-dimethylbenz[a]anthracene (DMBA)-induced genotoxicity, oxidative stress, and imbalance in xenobiotic-metabolizing enzymes. Four different concentrations of ethanolic O. sanctum leaf extract (100, 200, 300, and 400 mg/kg of body weight) were administered to Wistar rats by intragastric intubation for five consecutive days followed by intraperitoneal injection of DMBA (35 mg/kg of body weight) 90 minutes after the final dose of the extract. Administration of DMBA increased bone marrow micronuclei, phase I enzymes, lipid peroxidation, and protein carbonyl formation. This was accompanied by a significant decrease in the activities of phase II detoxification enzymes and antioxidants in the liver, erythrocytes, and bone marrow. Pretreatment with ethanolic O. sanctum leaf extract at a concentration of 300 mg/kg of body weight significantly reduced micronuclei formation and phase I enzymes as well as lipid and protein oxidation with enhanced antioxidant and phase II enzyme activities. The results of the present study suggest that ethanolic O. sanctum leaf extract inhibits DMBA-induced genotoxicity and oxidative stress by modulating xenobiotic-metabolizing enzymes, reducing the extent of lipid and protein oxidation and up-regulating antioxidant defenses.

Destination of titanium particles detached from titanium plasma sprayed implants

Small titanium particles may detach from titanium plasma sprayed (TPS) implants during implant insertion, when no preliminary tapping is used, probably for the frictional force between titanium coating and host bone. Aim of this study was to investigate the destination of these titanium particles observed in the peri-implant environment. Twenty-four TPS screws were implanted in tibiae of two sheep. Fourteen and 90 days after implantation the implants with the surrounding bone were removed and processed to be analyzed by light microscope and scanning electron microscope (secondary electron and back-scattered electron probes). Small titanium particles detached from the unloaded TPS implants were observed both in the newly-formed bone matrix and in marrow tissue. Histomorphometric analysis showed that both at 14 and 90 days after implantation the titanium particles appeared more concentrated in marrow tissue than in calcified bone matrix, decreasing by 66.4% over time. In particular, smaller particles (<250 microm(2)) decreased by 81.5%, whereas the larger ones (250-2000 microm(2)) did not show any significant variations over time, suggesting that most of the smaller particles may undergo to ionic dissolution, probably migrating into the peri-implant marrow lacunae. A slight migration of titanium particles from the implant surface towards the more distant peri-implant tissues was also demonstrated over time.

Protein-energy malnutrition alters histological and ultrastructural characteristics of the bone marrow and decreases haematopoiesis in adult mice

Protein-energy malnutrition (PEM) decreases resistance to infection by impairing a number of physiological processes, including haematopoiesis. The aim of this study was to evaluate the microanatomical aspects of bone marrow (BM) in mice that were subjected to PEM, in particular, with respect to the components of the local extracellular matrix and the proliferative activity of haematopoietic cells. For this, histological, histochemical, immunohistochemical and ultrastructural techniques were used. Two-month old male Swiss mice were fed with a low-protein diet containing 4% protein and control mice fed a 20% protein diet. When the experimental group had attained a 25% loss of their original body weight, we collected the different biological samples. Malnourished mice had presented severe BM atrophy as well as a reduction in proliferating cell nuclear antigen and gelatinous degeneration. The malnourished mice had more fibronectin accretion in paratrabecular and endosteal regions and more laminin deposition in perisinusal sites than controls. Endosteal cell activation and hyperplasia were found, suggesting their participation in the process. Additionally, we have observed a decrease in the capacity of malnourished haematopoietic stroma to support the growth of haematopoietic stem cells (CD34+) in vitro. These findings point to a structural impairment of the haematopoietic microenvironments in mice with PEM, possibly hampering the interactions between cells and cellular signalling.

Effect of constant strain rate, composed of varying amplitude and frequency, of early loading on peri-implant bone (re)modelling

AIM

Examine the effect of varying components of strain rate -- amplitude versus frequency -- while maintaining a constant strain rate of early controlled mechanical loading on implant stability, peri-implant bone mass and bone-to-implant contact.

MATERIAL AND METHODS

Three groups of guinea-pigs received TiO2 -blasted implants in both tibiae. One week after installation test implants were loaded 5 days/week during 4 weeks. The contra-lateral implants were the unloaded controls. Strain rate was kept constant (1600 micro epsilon/s), while amplitude and frequency were varied per group. Implant stability was followed by resonance frequency analysis. Animals were sacrificed, and ground sections were prepared to rate bone-to-implant contact and bone mass.

RESULTS

All implants (n=78) integrated uneventfully. A significant positive effect (p=0.03) of early loading on bone mass was observed in the distal medullar cavity. A significant difference in bone mass between test and control implants was evidenced between the groups (p=0.03 and 0.04). A significant increase in implant stability and bone-to-implant contact could not be shown.

CONCLUSIONS

Early controlled stimulation of peri-implant bone is related to amplitude/frequency and not to strain rate as such, considering a constant stimulation time. An increase of bone mass around early-loaded implants was shown. This cortical bone model is most sensitive to low-frequency/high-amplitude stimulation.

Ultrastructure of the Interface Between Titanium and Surrounding Tissue in Rat Tibiae ? A Comparison Study on Titanium-Coated and -Uncoated Plastic Implants

PURPOSES

The purposes of this study were to prepare experimental titanium-coated plastic implants suitable for electron microscopy examination of the titanium-bone interface and the response of tissue surrounding titanium, and to histologically compare surrounding tissue responses in coated and uncoated implants.

MATERIALS AND METHODS

Experimental plastic implants were prepared from a plastic rod coated with a thin film of titanium. Plastic implants without coatings were used as controls. The implants were placed into tibiae of 10-week-old male rats. The specimens with implants were harvested 4 weeks after placement and observed under a light microscope, a transmission electron microscope, and a scanning electron microscope.

RESULTS

In the transmission electron microscopy, the titanium layer of the experimental implant was a uniform layer that was approximately 150- to 250-nm wide. The new bone formation was observed around both titanium-coated implants and plastic implants. However, there was no direct bone contact with the plastic implant.

DISCUSSION

The responses of tissue surrounding the experimental implants varied. Under an electron microscope, the following areas were observed: (1) an area with a direct contact between the titanium and bone, (2) an area at the interface where an amorphous layer was observed, (3) an area with progressing calcification in the surrounding tissue where the cells were adjacent to the titanium surface, and (4) an area in which bone resorption and apposition were observed and remodeling was thought to be occurring.

CONCLUSION

The experimental titanium was homogenous and was considered to be highly useful in observing the responses of the surrounding tissue to the titanium surface.

Polycystic disease caused by deficiency in xylosyltransferase 2, an initiating enzyme of glycosaminoglycan biosynthesis

The basic biochemical mechanisms underlying many heritable human polycystic diseases are unknown despite evidence that most cases are caused by mutations in members of several protein families, the most prominent being the polycystin gene family, whose products are found on the primary cilia, or due to mutations in posttranslational processing and transport. Inherited polycystic kidney disease, the most prevalent polycystic disease, currently affects approximately 500,000 people in the United States. Decreases in proteoglycans (PGs) have been found in tissues and cultured cells from patients who suffer from autosomal dominant polycystic kidney disease, and this PG decrease has been hypothesized to be responsible for cystogenesis. This is possible because alterations in PG concentrations would be predicted to disrupt many homeostatic mechanisms of growth, development, and metabolism. To test this hypothesis, we have generated mice lacking xylosyltransferase 2 (XylT2), an enzyme involved in PG biosynthesis. Here we show that inactivation of XylT2 results in a substantial reduction in PGs and a phenotype characteristic of many aspects of polycystic liver and kidney disease, including biliary epithelial cysts, renal tubule dilation, organ fibrosis, and basement membrane abnormalities. Our findings demonstrate that alterations in PG concentrations can occur due to loss of XylT2, and that reduced PGs can induce cyst development.