Ultrastructural investigation of the protective effects of propolis on bleomycin induced pulmonary fibrosis.

We investigated the antioxidant and anti-inflammatory effects of propolis on bleomycin induced lung fibrosis and compared these effects to prednisolone treatment. Forty rats were divided into four groups of ten: group 1 was treated with intratracheal infusion of 0.2 ml physiological saline followed by daily treatment with 0.5 ml physiological saline for 20 days. In the remaining groups (groups 2 - 4), 5 mg/kg bleomycin was given via the trachea. Rats in group 2 were given 0.5 ml physiological saline. Rats in group 3 were treated with 100 mg/kg propolis, and 10 mg/kg prednisolone was given to rats in group 4. The treatments for all groups were continued for 20 days. On postoperative day 21, blood and lung samples were taken for biochemistry, histopathology and electron microscopy evaluation. We compared oxidative stress parameters and found lower malondialdehyde and myeloperoxidase levels, and higher total sulfhydryl levels and catalase activities for the bleomycin + propolis group than for the bleomycin and bleomycin + prednisolone groups. The highest mean fibrosis score was detected in the bleomycin group. Although the mean fibrosis scores of the bleomycin + propolis and bleomycin + prednisolone groups were not significantly different, electron microscopy revealed that propolis diminished bleomycin induced lung fibrosis more effectively than prednisolone. The effects of propolis might be due to its potent antioxidant and anti-inflammatory properties.

Ultrastructural view of a promising anti TNF-α agent on hepatic ischaemia reperfusion injury.

BACKGROUND: Ischemia reperfusion causes injury to the liver cells during transplantation, trauma and emergency surgery. We investigated whether the anti TNF-α agent, etanercept, can reduce injury in an animal model of ischemia reperfusion owing to the fact that TNF-α plays a critical role in the process of inflammation. MATERIALS AND METHODS: Thirty rats were divided into three groups: sham (Group 1), control (Group 2), etanercept (5 mg/kg) treatment (Group 3). Ischemia-reperfusion model was carried out by clamping the hepatic pedicle for 45 min and then reperfusing the liver for 60 min. Etanercept (5 mg/kg) was injected intraperitoneally 5 min prior to reperfusion. At the end of the procedures, blood and liver tissue samples were obtained for biochemical and histopathological assessment. RESULTS: Control and treatment groups showed significant differences in hepatic function tests, plasma and tissue oxidative stress parameters. Samples in the control group histopathologically showed morphologic abnormalities specific to ischemia reperfusion. Histomorphologic findings in the treatment groups showed similar features as the sham group. CONCLUSIONS: Our evidence suggests that TNF-α plays a key role in liver ischemia reperfusion injury and etanercept may provide a novel therapeutic approach for patients undergoing liver surgical procedure (Tab. 3, Fig. 4, Ref. 22).

Effect of chemotherapy exposure prior to pregnancy on fetal brain tissue and the potential protective role of quercetin.

Cyclophosphamide (CYC) and doxorubicin (DOX) are among the most effective and widely used anticancer chemotherapeutic drugs. Potential chemopreventive and chemotherapeutic functions have recently been attributed to flavonoids. We hypothesized that Quercetin (QR) would protect against the toxic effects of chemotherapeutic agents applied prior to pregnancy. Rats were treated with the chemotherapeutic drugs CYC (27 mg/kg) and DOX (1.8 mg/kg) applied in a single intraperitoneal dose once every 3 weeks for 10 weeks. QR was administered at a dose of 10 mg/kg/day by oral gavage. 48 h following the experimental chemotherapy exposure, female rats were transferred to cages containing male rat for mating. Fetal brain tissues were removed from fetuses extracted by cesarean section on the 20th day of gestation for evaluation of antioxidant parameters. A significant increase in superoxide dismutase and malondialdehyde activity was observed in CYC and DOX treatment groups relative to the control group (p < 0.05). Similarly, carnitine acylcarnitine translocase and Glutathione activity was significantly reduced in the CYC and DOX groups relative to the control group (p < 0.05). Our results indicate that the use of chemotherapeutic drugs before pregnancy can result in oxidative damage to fetal brain tissue. Therefore, women who have been exposed to chemotherapy and may become pregnant should be treated with antioxidant compounds such as QR to reduce the risk of damage to fetal brain tissues.

Effects of organic apricot on liver regeneration after partial hepatectomy in rats.

BACKGROUND: The present study investigated the effects of (sun-dried organic apricot/SDOA) supplementation in chow on liver regeneration after partial hepatectomy/(PH) in rats. METHOD: In this study, 28 female rats were randomized into four groups. On the 7th day of the study, group 1 underwent laparoscopic intervention while a PH was performed on the other three cohorts. On day 28, all rats were humanely killed. Blood and liver tissue samples were subjected to biochemical determinations, histological examinations, and measurement of tissue oxidative stress enzyme activity. RESULTS: Serum levels of alanine transaminase (ALT), alkaline phosphatase (ALP), and liver tissue glutathione (GSH) activities were affected by PH and/or SDOA consumption (P < .05). Moderately staining cell counts in group 4 were significantly different from the other three groups (P < .05). However, no significant differences were detected among all groups in regard to aspartate aminotransferase (AST) serum levels or liver tissue superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT) or glutathione peroxidase (GSHpx) activities (P < .05). CONCLUSION: The 5% SDOA supplementation over a 21-day feeding period showed a beneficial effect on liver regeneration in rats, as reflects by Ki-67 finding although there was no change in ALT or ALP or in liver tissue GSH activity.

Comparison between the intraoperative use of polyvinyl chloride cover and surgical compresses for preventing postoperative adhesions.

BACKGROUND/PURPOSE: Surgical compresses used for retraction during major abdominal and pelvic procedures lead to postoperative adhesion formation resulting from damage to the visceral peritoneum. This study investigates whether polyvinyl chloride (PVC) covers cause less postsurgical adhesion and inflammation than surgical compresses in an animal model. METHODS: Female Wistar albino rats (n = 160) were divided into three groups (compress, PVC cover and control), which were then divided into 16 subgroups (n = 10/group). All animals underwent midline laparotomy and cecal abrasion. A metal retractor, which applies a constant force, was then placed on the small intestine for 2 h. In the control group, no material was placed under the retractor, whereas a surgical compress or PVC cover was placed in the experimental animals. Full-thickness small intestinal biopsies were obtained and examined by light and electron microscopy. The following parameters were evaluated: congestion, mesothelial proliferation, leukocyte migration and collagenization. Adhesions were scored according to the Nair, Knightly and Mazuji scoring systems. RESULTS: All inflammation scores were significantly higher in the compress group than in the other two groups. However, no significant difference was observed between the PVC cover and control groups. Adhesions were more frequent in the compress group than in the other two groups, regardless of the scoring system used. CONCLUSIONS: Surgical compresses used in abdominal and pelvic surgeries cause inflammation and adhesion. Contrary to surgical compresses, PVC covers do not cause inflammation and adhesion, which may considerably reduce adhesion-related complications in abdominopelvic surgeries.

Diosmin ameliorates intestinal injury induced by hepatic ischemia reperfusion in rats.

BACKGROUND: Hepatic ischemia-reperfusion causes histologic injury to the intestinal mucosa. We investigated the effects of diosmin, a phelobotrophic drug with antioxidant and antiinflammatory effects, on intestinal injury in the experimental liver ischemia-reperfusion model. MATERIALS AND METHODS: Fourty rats were divided into four groups: sham group (Group 1), control group (Group 2), perop diosmin group (50 mg/kg) treatment group (Group 3) and preop 10-day diosmin (50 mg/kg) treatment group (Group 4). Ischemia-reperfusion model was carried out by clamping the hepatic pedicle for 60 min and then reperfusing the liver for 90 min. At the end of procedures, blood and ileum tissue samples were obtained for biochemical and histopathological assessments. RESULTS: According to the results of liver function tests (AST, ALT and LDH) there was a significant difference between the control and other groups (p < 0.001 for all). According to the plasma and ileum oxidative stress parameters (MDA, GSH-Px and XO), there was a significant difference between the control and other groups (p < 0.05 for all). Histopathologically; the specimens in Group 2 showed specific morphological abnormalities (the epithelial lining of the apical surface of villi was degenerated and desquamated to the lumen). Group 3 and 4 showed ileal histomorphology similar to the sham group. Pathological scores were significantly different between Group 2 and other groups. CONCLUSIONS: Diosmin can be administered for protection from destructive effects of hepatic ischemia-reperfusion injury on intestine in both emergent and elective hepatic surgical operations in which the possible ischemic periods are expected (Tab. 4, Fig. 1, Ref. 39).

Adipocyte differentiation defect in mesenchymal stromal cells of patients with malignant infantile osteopetrosis.

BACKGROUND: Malignant infantile osteopetrosis (MIOP) is a disorder of osteoclasts characterized by defective bone resorption and death in infancy. The multipotent mesenchymal stromal cells (MSC) and their progeny (osteoblasts) are major components of the bone marrow (BM) microenvironment and are found in close contact with cells of hematopoietic origin, including osteoclasts. We hypothesized that MSC defects may be associated with osteoclast dysfunction and osteopetrosis phenotype. METHODS: BM MSC, obtained from six patients with MIOP, were expanded in vitro and characterized by morphology, plastic-adherence, immunophenotype and multilineage differentiation potential. RESULTS: Physical and immunophenotypic characteristics of patient MSC were similar to healthy age-matched controls. However, an isolated in vitro differentiation defect toward adipogenic lineage was demonstrated in patient MSC and confirmed by low or absent expression of adipogenic transcripts (peroxisome proliferator-activated receptor-gamma, adipophilin, stearoyl-CoA desaturase, leptin and adiponectin) upon induction of adipogenesis. Following BM transplantation, minimal improvement in adipogenic potency of MSC was demonstrated by Oil Red O staining. DISCUSSION: MIOP is associated in vitro with a failure of MSC to differentiate into an adipogenic lineage, suggesting a BM microenvironment defect. The defect may contribute to osteoclast dysfunction, or may be attributed to the effect of the osteopetrotic marrow environment. Further investigations should determine the pathophysiologic importance of this novel defect, and could perhaps contribute to consideration of MSC therapy in MIOP.

Effect of propolis on oxidative stress and histomorphology of liver tissue in experimental obstructive jaundice.

BACKGROUND: Propolis is a natural product collected by honey bees from various plant sources. We aimed to determine the possible effects of propolis on oxidative stress and hepatocyte apoptosis in experimental obstructive jaundice. METHODS: Thirty rats were divided into three groups: group I, sham-operated; group II, ligation and division of the common bile duct (BDL); group III, BDL followed by oral supplementation of propolis in a daily dose of 100 mg/kg. Liver samples were examined under the light microscope and transmission electron microscope. Hepatocyte apoptosis was quantitated using the transferase-mediated uridine nick end labeling (TUNEL) assay. Plasma and liver malondialdehyde (MDA) levels and glutathione peroxidase (GSH-Px) activities were measured. RESULTS: The plasma and liver levels of MDA were significantly lower in the propolis group than in the BDL group (p < 0.05 and 0.014, respectively). Although liver GSH-Px activities were significantly higher in the propolis group than in the BDL group (p < 0.001), there was no significant difference between the plasma GSH-Px activities of these groups (p > 0.05). In the propolis group, the enlargement of hepatocytes, dilatation of canaliculi and the edema regressed. The regenerating and normal hepatocytes were demonstrated. In the TUNEL assay, propolis administration reduced hepatocyte apoptosis. CONCLUSION: Propolis showed a significant hepatoprotective effect in this experimental obstructive jaundice model.

High cystine in platelets from patients with nephropathic cystinosis: a chemical, ultrastructural, and functional evaluation.

AIM: To investigate the morphology and function of platelets in nephropathic cystinosis (NC). METHODS: Seven patients (mean age, 6.5 years; SD, 20 months) with NC were investigated. Their platelets were examined by transmission electron microscopy (TEM) and the characteristics of the dense granules (DGs) were determined by mepacrine labelling and the uranaffin reaction. Bleeding time, turbidometric aggregation, and luminescence aggregation were studied and intraplatelet cystine was measured. RESULTS: Increased intraplatelet cystine, primary and secondary aggregation defects, and the absence of ATP release were demonstrated. TEM revealed DGs of various shapes and sizes and lamellary or amorphous cytoplasmic inclusions. Viscous material had been released into the vacuolar spaces and enlarged open canalicular system. Mepacrine labelling revealed that the numbers of DGs/platelet were comparable between the patients and the controls (mean, 2.9 (SD, 0.22) v 3.32 (0.18); p = 0.34). The uranaffin reaction revealed that the numbers of type 1, 3, and 4 DGs were comparable between the patients and the controls, but that there were fewer type 2 DGs in the patients (mean, 8.5 (SD, 1.95) v 17.22 (1.58); p = 0.01). TEM for platelet aggregation revealed a lack of induction and/or defective execution and/or delayed transmission. The patients' intraplatelet cystine concentrations were higher than the controls (mean, 1.56 (SD, 0.84) v 0.08 (0.01) nmol/mg protein; p = 0.009). CONCLUSIONS: This is the first report to demonstrate raised intraplatelet cystine, abnormal platelet ultrastructural findings, and defective aggregation in NC.

Effect of Candida albicans septicemia on the cardiovascular function of rabbits.

Candida albicans is an opportunistic pathogen that causes life-threatening systemic infection in immunocompromised host. However, little is known about the effects of yeast on the cardiovascular functions. This study examined the effects of C. albicans septicemia on the heart and vessel functions and nitric oxide (NO) production in infected rabbits. Anaesthetized animals were challenged with intravenous C. albicans (6 x 10(8)/kg) or saline and the blood pressure of rabbits were measured over 5 h. After that response of the isolated thoracic aorta, right atrium and left papillary muscle were recorded. Blood pressure significantly decreased in the infected rabbits during the septicemia but in the control animals it was stable. The blood nitrite levels and NO-synthases (eNOS, iNOS) expression and tissue nitrite levels in the heart and aorta were similar in the both groups. In the aorta isolated from C. albicans-infected rabbits, acetylcholine-induced endothelium-dependent relaxation was decreased, but contractions induced by phenylephrine were potentiated. The NOS inhibitor, L-N(G)-nitro-arginine methyl ester (L-NAME)-induced contraction increase in the right atrium was depressed by the yeast-infection. In the heart and aorta, microscopic examination revealed no tissue invasion of C. albicans. These results indicate the ability of C. albicans-induced septicemia to destroy NO-related responses of the heart and aorta and may have important implications for functional damage to endothelium and the regulation of cardiovascular functions. In addition, NOS induction and NO over-production are not stimulated by systemic C. albicans infection, which would alter the host immune reaction and homeostasis.

Ultrastructural analysis of TESE and semen sperm tails from patients exhibiting absolute immotility on the day of ICSI.

Sperm flagellar pathology was found to be the underlying cause of motility disorders that lead to male infertility. Conventional in vitro fertilization (IVF) procedures will fail when sperm show a total absence of motility. In such difficult cases intracytoplasmic sperm injection (ICSI) is the only available technique to fertilize an oocyte. Fertilization rates are low and may also be reduced when immotile sperm are used for ICSI from ejaculate of other than epididiymal or testicular origin. Presence of totally immotile sperm in the ejaculate on the day of ICSI if spermatogenesis is normal testicular sperm recovery can improve ICSI outcomes. But for patients having severe morphological or functional sperm defects embryos of lower quality tend to be produced when totally immotile sperm are used. In this study the 2 patients exhibiting totally immotile sperm in their ejaculates and TESE samples on the day of ICSI showed the same ultrastructural abnormalities. Peri-axonemal and axonemal abnormalities that were seen in association with sperm nucleus structural defects suggested that the source of sperm has no effect on morphologic characteristics and also reflects abnormality in both spermatogenesis and spermiogenesis. In this study the two patients who presented with oligoteratozoospermia with total immotility, using either ejaculate or TESE sperm fertilization and embryo development, can be obtained with ICSI, but no pregnancies were established after embryo transfers.

The contribution of vitamin C to healing of experimental fractures.

The benefits of various minerals and vitamins on fracture healing have been demonstrated in animal models. Vitamin C is an essential substance in fracture healing but has not been studied previously on an experimental basis. Sixteen rats were grouped randomly into control and vitamin C-supplemented groups. The right tibias of all rats were fractured by digital manipulation. One group received single high dose of vitamin C intramuscularly. On the 5th, 10th, 15th, and 20th days, two rats from each group were killed and the tibias examined under light microscopy. It was seen that the vitamin C-supplemented group went through the stages of fracture healing faster compared with the control group.

T-ALL with monoclonal gammopathy and hairy cell features.

The presented case is a boy with T-cell acute lymphoblastic leukemia (ALL) with hairy cell (HC) features and monoclonal gammopathy. The disease process had an acute onset and followed a rapid, progressive course. The patient had minimal splenomegaly and bicytopenia, but the bone marrow displayed increased numbers of reticulin fibers. The blasts were positive for tartrate-resistant acid phosphatase (TRAP) and CD11c. Molecular analysis revealed rearrangement of immunoglobulin heavy chain genes and a rearranged T-cell receptor (TcRbeta) beta gene. The patient responded to conventional ALL therapy. Acute T-cell ALL with HC features in childhood has not been reported previously, either alone or in association with monoclonal gammopathy. We propose "T-ALL with hairy cell features" to describe this case.

The effects of agonist stimulation and beta(2)-adrenergic receptor level on cellular distribution of gs(alpha) protein.

This study examines the effects of adrenergic ligands, cholera toxin, forskolin, and varying levels of beta(2) adrenergic receptors (beta(2)AR) on the cellular distribution of Gs(alpha) subunits in CHO cells. Localization of Gs(alpha) was evaluated by confocal microscopy and beta(2)AR-mediated signalling was assessed by adenylyl cyclase (AC) activity. In cells expressing 0.2 pmol/mg protein beta(2)ARs (WT18), the localization of Gs(alpha) subunit was restricted to the plasma membrane region. Isoproterenol (ISO), cholera toxin or forskolin elicited redistribution of cellular Gs(alpha) so that Gs(alpha) appeared as intense spots throughout the plasma membrane as well as the cytoplasm. Exposure to a neutral beta(2)AR antagonist, alprenolol, prevented the ISO-stimulated Gs(alpha) translocation from peripheral to inner cytoplasm. In cells expressing high level of beta(2)ARs (8.2 pmol/mg) (WT4), basal and ISO-stimulated AC activities were significantly elevated when compared to the values detected in WT18 clone, suggesting a positive correlation between receptor expression and receptor-mediated signalling. Basal Gs(alpha) distribution in this group was similar to that observed in ISO-, cholera toxin-, or forskolin-stimulated WT18 clone. ISO, cholera toxin, or forskolin did not change the distribution of Gs(alpha) significantly when tested in WT4 clone. No difference in the cellular level of Gs(alpha) protein between WT18 and WT4 clones was detected. Alprenolol did not affect the distribution of Gs(alpha) in WT4 clone. ICI 118,551, a negative beta(2)AR antagonist, altered Gs(alpha) distribution from a dispersed basal pattern to a membrane-confined pattern. The latter appearance was similar to that observed in unstimulated WT18 clone. Taken together, these data suggest that: (1) enhanced beta(2)AR-Gs(alpha) coupling induced by agonist stimulation or by increased expression of beta(2)ARs remodel the cellular distribution of Gs(alpha); (2) the alteration in Gs(alpha) distribution induced by beta(2)AR overexpression provides evidence for agonist-independent interaction of beta(2)AR and Gs(alpha), that can be inhibited by a negative antagonist but not by a neutral antagonist; and (3) forskolin influences the activity state of Gs(alpha) that displays a Gs(alpha) distribution pattern comparable to that observed when Gs(alpha) is activated via beta(2)AR stimulation or directly by cholera toxin.

Temporoparietal fascia: an anatomic and histologic reinvestigation with new potential clinical applications.

Temporoparietal fascia constitutes a very important structural unit from both an aesthetic and a reconstructive surgical point of view. A histologically supported anatomic study was conducted for the reappraisal of the anatomic relationships and clinical application potentials of the data obtained. Anatomy of the temporoparietal fascia was investigated on 20 sides from 10 cadavers. After dissections, necropsies were obtained to demonstrate histologic features of the temporoparietal fascia. The outer part of the temporoparietal fascia is continuous with the superficial musculoaponeurotic system (SMAS) in the inferior border and with orbicularis oculi and frontalis muscles in the anterior border. Therefore, plication of the temporoparietal fascia can increase tightness of the SMAS, orbicularis oculi, and frontalis muscle in rhytidectomy. The frontal branches of facial nerve were noted to course parallel to the frontal branch of the superficial temporal artery, lying deeper to the temporoparietal fascia within the innominate fascia. In the view of these findings, conventional subfascial dissection, which is performed to protect frontal branches of the facial nerve, is not reasonable during the temporal part of rhytidectomy. Careful subcutaneous dissection just under the hair follicles is more appropriate to avoid nerve injury and also provides excellent exposure of the temporoparietal fascia for plication in rhytidectomy with protection of the auriculotemporal nerve and the superficial temporal vessels. Furthermore, two layered structures of the temporoparietal fascia are very suitable to insert a framework into the temporoparietal fascia for ear reconstruction to eliminate some of the shortcomings of Brent's technique. A thin muscle layer was also noted within the outer part of the temporoparietal fascia below the temporal line; the term "temporoparietal myofascial flap" would, therefore, be more accurate than "temporoparietal fascial flap." Finally, the innominate fascia and the deep temporal fascia can be elevated with the two layers of the temporoparietal myofascial flap to obtain a well-vascularized, four-layered myofascial flap based on the superficial temporal vessels. This multilayered flap can be used to reconstruct all defects when fine, pliable, thin, multilayered flaps are required.

Effects of methylprednisolone on human myeloid leukemic cells in vitro.

We have demonstrated previously that high-dose methylprednisolone treatment induces differentiation and apoptosis of leukemic cells in patients with different morphological subtypes of acute myeloblastic leukemia (AML) in vivo. In the present study, we investigated the in vitro effects of high (10(-3) M) and low (10(-6) M) concentrations of methylprednisolone (MP) on freshly isolated bone marrow leukemic cells from nine newly diagnosed patients with AML by light and electron microscopy (EM) and agarose gel electrophoresis. A marked increase in MP-induced apoptosis of leukemic cells, with a maximum effect at 24 hr of exposure to both low and high concentrations of MP (10(-6) M and 10(-3) M), was demonstrated by light microscopy in cultures of four (three with AML-M1 and one with AML-M7) of the nine patients. In three cases, the increase in the number of apoptotic cells induced by high-concentration MP was approximately twice that observed when the lower concentration was used. A few apoptotic cells were detected in the cultures from the other five patients. However, a typical DNA ladder pattern of apoptosis was observed on gel electrophoresis of MP-treated leukemic cells from one patient (AML-M1) after 2 hr of incubation with both high- and low-MP concentrations. In two patients, a nonspecific DNA smear was observed only when high-concentration MP was used. The increase in differentiated leukemic cells induced by MP was also dose dependent, and was observed in cultures from all but one patient. Morphological features of apoptosis and differentiation were also confirmed by EM studies. The results of the present study, together with our previous clinical experience, suggest that MP, especially at high doses, could have a significant role in the treatment of some AML patients by inducing apoptosis and differentiation of leukemic cells.

Histological assessment of root cementum at periodontally healthy and diseased human teeth.

This study aimed to investigate and compare the lipid and polysaccharide content of the cemental surfaces of healthy and periodontally-involved teeth. Thirty periodontally-involved single-rooted teeth from fifteen patients with localized juvenile, adult and rapidly progressive periodontitis were included in the experimental group and 5 healthy teeth were assessed in the control group. Frozen serial sections were obtained and stained with hematoxylin-eosin for morphological assessment. Oil-Red-O and Alcian Blue-Periodic Acid Schiff stains were used to evaluate the presence of lipids, neutral and acidic polysaccharides using light microscopy. It was found that with hematoxylin-eosin staining in the experimental group, both the involved and uninvolved cementum surfaces of teeth, which belong to all periodontitis groups, showed generally irregular surfaces that contain some resorption areas. Alcian Blue-Periodic Acid Schiff positive staining was observed only superficially and at the areas associated with microbial dental plaque. However, Oil-Red-O staining was positive only superficially at 5 teeth that belonged to localized juvenile and rapidly progressive periodontitis groups. Apparent lipopolysaccharide staining into cementum was not seen in any of the diseased teeth. The results presented here suggest that endotoxin was only localized in superficial layers and associated with only microbial colonization.

Morphologic evidence of apoptosis in childhood acute myeloblastic leukemia treated with high-dose methylprednisolone.

We have previously demonstrated that various subtypes of AML children respond to high-dose methylprednisolone (HDMP; 20-30 mg/kg/day) which could induce in vivo differentiation of myeloid leukemic cells to mature granulocytes. In this study we have evaluated whether apoptosis occurs in AML cells of patients treated by HDMP using morphological criteria. For light and electron microscopic examination bone marrow aspirates were obtained four days and two weeks after methylprednisolone (30 mg/kg/day) treatment from two children with newly diagnosed AML (AML-M3 and AML-M4). In both patients maturation of leukemic cells has previously been reported four days (in patient with AML-M3) and two weeks (in patient with AML-M4) after HDMP treatment. Electron microscopy revealed the characteristic ultrastructural changes of various stages of apoptosis four days after HDMP treatment in a case with AML-M3. Morphologic evidence of apoptosis induced by HDMP were also detected on Wright-stained and toluidine blue stained semithin sections of BM preparations in a patient with AML-M4 and AML-M3 respectively. These findings suggest that HDMP which could induce in vivo terminal differentiation in myeloid leukemic cells is also able to induce apoptosis in patients with AML. The possibility of HDMP-induced apoptosis should be evaluated in a larger series of patients with AML and other types of malignant tumors.