11q23 aberration is an additional chromosomal change in de novo acute leukemia after treatment with etoposide and mitoxantrone

We report on 2 patients with acute leukemia who had an 11q23 chromosomal aberration as an additional change after treatment with etoposide and mitoxantrone, agents that affect topoisomerase II (Topo II). One patient with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (L2) received chemotherapy, including 1,000 mg of etoposide and 75 mg of mitoxantrone. She relapsed 10 months later. Analysis at time of relapse showed a chromosomal aberration of del(11)(q23) as an additional cytogenetic change. The other patient was diagnosed with acute monoblastic leukemia (M5a) and received two autologous peripheral blood stem-cell transplantations. Her cumulative doses of etoposide and mitoxantrone were 6,000 mg and 42 mg, respectively. She also relapsed, and analysis at that time revealed del(11)(q23) as an additional chromosomal aberration. The mixed lineage leukemia/myeloid-lymphoid leukemia (MLL) gene was not rearranged in either case, making these cases distinct from previously described therapy-related leukemias caused by Topo II inhibitors. Based on these two cases, it may be that Topo II inhibitors can cause clonal evolution affecting chromosome band 11q23.

Inhibitory action of sulfatide, a putative ligand for L-selectin, on B cell proliferation and Ig production

The interaction of L-selectin and its ligand is widely accepted to mediate leukocyte rolling and adhesion on the endothelial surface. Although L-selectin is ubiqultously expressed on lymphoid cells, its role in execution of lymphocyte functions is unknown. By flow cytometric analysis using mAb specific for sulfatide, a putative ligand for L-selectin, we found that sulfatide was selectively expressed on B cells, but not on T cells. To elucidate the involvement of L-selectin and its ligand in B cell activation, the present study was undertaken to investigate effects of sulfatide on T cell-dependent and -independent Ig production by B cells. In pokeweed mitogen-stimulated cultures, addition of sulfatide resulted in almost complete inhibition of Ig production by B cells in the presence of memory CD4+ T cells, whether L-selectin-positive or -negative. A similar inhibition of Ig production by sulfatide was found when B cells were stimulated with Staphylococcus aureus Cowan I and IL-2. Unlike sulfatide, a desulfated form of sulfatide, galactosylaceramide, did not show any effects on Ig production by B cells. Maximal inhibition of Ig production was observed when sulfatide was added at the early period of culture. Sulfatide suppressed effectively proliferation of B cells, but not of T cells. Sulfatide competed the binding of anti-L-selectin mAb to B cells, suggesting it could interfere B cell activation by blocking L-selectin function. The results suggest a novel role of the L-selectin/its ligand system in the initiation of B cell activation.

Association of a mutation in thiazide-sensitive Na-Cl cotransporter with familial Gitelman's syndrome

Gitelman's syndrome is a variant of Bartter's syndrome, characterized by hypokalemia, hypomagnesemia, hypocalciuria, and hypovolemia. We have observed familial cases of Gitelman's syndrome, and a possible mutation in thiazide-sensitive Na-Cl cotransporter was investigated in this kindred. The proband was a 47-yr-old Japanese female, and her mother was also affected. Her parents and maternal grandparents are consanguineous. By using PCR-amplification and direct sequencing, we identified a novel non-conservative missense mutation at 623 amino acid position, which substitutes proline for leucine (L623P), and also creates an Nci I restriction site in the exon 15. The mutation was not detected in normal healthy subjects (n = 102). Nci I digestion of PCR-amplified exon 15 DNA fragments from individuals in the family indicated the autosomal recessive inheritance of the disorder. In conclusion, the L623P mutation in the thiazide-sensitive Na-Cl cotransporter gene is suggested to impair the transporter activity, and to underlie this familial Gitelman's syndrome; Gitelman's syndrome observed in this kindred has been inherited in an autosomal recessive fashion.

What influences social skills in patients with schizophrenia? Preliminary study using the role play test, WAIS-R and event-related potential

Persons with schizophrenia exhibit disabilities which profoundly affect their social and independent living skills, and social skills training is expected to be an effective treatment for reducing the level of severity of disabilities. Many factors may influence usage and learning of social skills; little is definitively known regarding which disabilities related to schizophrenia compromise social skills. The present report deals with factors affecting social skills. Twenty persons with schizophrenia (DSM-III-R) were tested using a Japanese version of the role play test, the reliability and validity of which were verified. Subjects were also tested using BPRS, auditory event-related potential (ERP) and WAIS-R. Nonverbal skills showed significant positive correlation with the amplitude of the N1 ERP component and age of onset, and 59% of the variance of nonverbal skills was accounted for by these factors using multiple regression analysis. Nonverbal skills are at least partially based on either automatic discriminating processes or selective attention, reflected in N1A. Information receiving and processing skills showed significant positive correlation with Performance IQ and Global Assessment of Functioning, and 61% of the variance of receiving and processing skills was accounted for by BPRS score, PIQ score and age. These skills are not directly related to elementary cognitive function as assessed by analyzing, for example, the ERP P3 component, but are based on more complex neuropsychological function.

Myocardial uptake of 99mTc-tetrofosmin, sestamibi, and 201Tl in a model of acute coronary reperfusion

BACKGROUND

To investigate whether tetrofosmin uptake is affected by myocardial viability as has been noted for 201Tl and sestamibi, we analyzed the initial and delayed distribution patterns of tetrofosmin in a rat coronary artery occlusion-reperfusion model.

METHODS AND RESULTS

Animals were intubated and ventilated, and their arterial pressures were monitored. A left thoracotomy was performed. After 1-hour occlusion and 1-hour reperfusion of a major branch of the circumflex artery, 201Tl and either tetrofosmin or sestamibi were injected intravenously. Radiolabeled microspheres were used to document the area at risk and reperfusion. Five minutes or 1 hour after administration of the diffusible tracers, the animals were killed. Tracer distribution was determined by use of segmental tissue analysis, and tissue viability was determined by use of histochemical staining. Both the initial and delayed retention of tetrofosmin were sensitive to myocardial viability, as shown by significantly lower uptake (30 +/- 14%) and retention (24 +/- 12%) of tetrofosmin in the nonviable segments compared with the viable segments. In addition, the initial myocardial distribution of tetrofosmin was similar to that noted for 201Tl, but after 1 hour of tracer circulation, the tetrofosmin tissue distribution appeared unchanged compared with the initial regional blood flow distribution. This is in direct contrast to our present observations of significant 201Tl redistribution and some changes in sestamibi distribution as well.

CONCLUSIONS

The clinical implication of these observations suggests that initial and delayed imaging after tetrofosmin administration would reflect both the initial regional blood flow pattern and myocardial viability.

Factors affecting rhythm after the maze procedure for atrial fibrillation

BACKGROUND

The maze procedure failed to abolish atrial fibrillation (AF) in 14% of patients with underlying organic cardiac lesions. Identification of contributing risk factors will improve results either by treatment of such factors or by avoidance of high-risk patients.

METHODS AND RESULTS

We analyzed 192 consecutive patients with AF undergoing three variations of the maze procedure performed simultaneously with correction of valvular diseases (n = 165), congenital anomalies (n = 19), isolated AF (n = 7), and ischemic disease (n = 1). Twenty-six preoperative factors and two postoperative cardiac size parameters were analyzed by multivariate analyses between patients with successfully ablated AF (n = 165) and those who remained in AF (n = 27) after the maze procedure. Among all factors, postoperative left atrial dimension was the most potent in predisposing patients to persistent AF. Duration of AF left atrial dimension, and cardiothoracic ratio were identified as preoperative risk factors, whereas modifications of the maze procedure and pathogenesis and location of underlying disease failed to have a significant prognostic impact on rhythm after surgery. Individual risk analysis using the three preoperative variables revealed that left atrial size reduction to normalize its dimension played a pivotal role in determining rhythm after the maze procedure.

CONCLUSIONS

Results favor earlier performance of the procedure before these risk factors develop, after which omission of the procedure or extensive left atrial plication may be appropriate. This requires further study.

Calcitonin-induced changes in the cytoskeleton are mediated by a signal pathway associated with protein kinase A in osteoclasts

Calcitonin is known to inhibit osteoclastic bone resorption through its receptor, which is abundantly expressed on the plasma membrane of osteoclasts. Recently, it was reported that calcitonin receptors were coupled to both cAMP-dependent protein kinase (PKA) and protein kinase C (PKC). To examine how the PKA and PKC pathways are involved in the effects of calcitonin, we focused on changes in the cytoskeleton of murine osteoclast-like multinucleated cells (OCLs) formed in vitro. When OCLs were cultured on dentine slices, they formed resorption pits and ringed structures of F-actin dots (actin rings). Elcatonin, a synthetic analogue of eel calcitonin, disrupted actin rings and inhibited pit formation in a dose-dependent manner. Forskolin and dibutyryl cAMP, both of which have the ability to activate PKA, mimicked the effects of elcatonin. Phorbol myristate acetate and phorbol 12,13-dibutyrate, both of which have the ability to activate PKC, also inhibited pit-forming activity, but little affected actin rings of OCLs. The inhibitory effects of elcatonin on the pit formation and actin ring formation were partially restored by the treatment with Rp-cAMPs, a cAMP antagonist. Elcatonin induced a rapid increase in PKA activity within a few minutes, and its activation by elcatonin occurred in a dose-dependent manner. The time- and dose-dependent profiles of elcatonin for the activation of PKA were similar to those for the disruption of actin rings. Moreover, microinjection of activated PKA into OCLs disrupted actin rings within 10 min on culture dishes. Actin rings were little affected by the microinjection of the PKA preincubated with a cAMP-dependent protein kinase inhibitor (IP-20) into OCLs. These results suggest that PKA activation, rather than PKC activation, is involved in mediating the effects of calcitonin, through the disruption of actin organization.

Mitral valve operation after percutaneous transvenous mitral commissurotomy (PTMC): an evaluation of PTMC indications based on intraoperative findings

Six patients underwent open heart surgery for mitral valve disease after percutaneous transvenous mitral commissurotomy (PTMC) because of recurrent mitral stenosis (MS) in 4, moderate mitral regurgitation (MR) in 1, and acute severe MR in 1. These 6 patients were the only such observed cases out of a total of 86 patients who presented with PTMC in our hospital between October 1989 and May 1995. The duration of the subjective symptoms related to heart failure was 24.1 +/- 11.6 years, ranging from 3 to 30 years. Four of the six patients had had a previous surgical commissurotomy [closed mitral commissurotomy (CMC) in 2 and open mitral commissurotomy (OMC) in 2] from 24 to 30 years earlier (mean 28 years). The intraoperative findings of the 4 with residual MS included severe thickening, calcification on anterior and posterior leaflets, and bilateral commissures. Five patients were noted to have shortening and adhesion in the mitral subvalvular apparatus. Two patients with moderate to severe tears on the anterior leaflets and another two patients with tears on the posterior leaflet were also noticed; however, these leaflets were not severely thickened. It was possible to split and repair the fused commissure in one patient, but the other five required MVR due to severe subvalvular lesions. Therefore, if a patient has bilateral commissural calcification or has less thickend leaflets with severe subvalvular thickening and fusion with a small MVA measuring less than 0.8 cm2 and a MS score of more than 8, the OMC procedure is considered to provide good long-term clinical results. The decision to perform either PTMC or OMC should only be made based on meticulous echo Doppler findings and a hemodynamic evaluation of the mitral valve.

Immunolocalization of rat thromboxane receptor in the kidney

Thromboxane (TX) is a vasoactive hormone which is known to be involved in renal physiology and pathophysiology. To identify the site of action of TX in the kidney, we examined the distribution of this receptor in the normal rat kidney using a polyclonal antibody against TX receptor we had raised. Western immunoblot of rat kidney membrane fractions with the antibody identified a single protein band at the predicted molecular mass of rat TX receptor protein. In the rat kidney, immunostainable TX receptor was observed in glomeruli, arterial walls, luminal membranes of thick ascending limbs of Henle's loop, the luminal and basolateral membranes of either distal convoluted tubules or connecting tubules, and the basolateral membranes of collecting tubules. The localization of TX receptor provides better understanding of the mechanism of previously reported effects of TX on glomerular and tubular functions leading to hypertension as well as renal parenchymal diseases.

The carbohydrate moiety of the bermuda grass antigen BG60. New oligosaccharides of plant origin

BG60 is an important allergen of Bermuda grass (Cynodon dactylon) pollen, which causes allergic responses in human. It was suggested that its carbohydrate moiety may be relevant to allergic reaction (Su, S. N., Lau, G. X., Shu, P., Yang, S. Y., Huang, S. W., and Lee, Y. C. (1996) J. Allergy Clin. Immunol., in press). Therefore, the structure of the carbohydrate moiety in BG60 was investigated. The N-linked oligosaccharides were released from the glycopeptides of BG60 by digesting with a glycoamidase from sweet almond and reductively aminated with a fluorescent reagent, 2-aminopyridine. The mixture of pyridylaminated oligosaccharides were separated by high-performance liquid chromatography (HPLC) using an octadecylsilyl (ODS) column. Five oligosaccharide fractions were isolated, and each fraction was found to be homogeneous by HPLC on an amide-silica column. The structure of each of the oligosaccharides was analyzed by the two-dimensional mapping technique (Tomiya, N., Awaya, J., Kurono, M., Endo, S., Arata, Y., and Takahashi, N. (1988) Anal. Biochem. 171, 73-90), in tandem with sequential exoglycosidase digestion. The two most abundant oligosaccharides, A and B, have an unusual structural feature, i.e. the presence of an L-Fuc alpha-(1,3)-linked to Asn-linked GlcNAc without a Xyl beta-(1,2)-linked to the branching Man (see below). To the best of our knowledge, these are the first such oligosaccharides found in plant glycoproteins.

Diastolic time during exercise-induced myocardial ischemia in patients with myocardial infarction

The relation between diastolic time and myocardial perfusion defect redistribution of the infarct-related region was studied during upright bicycle exercise with thallium-201 scintigraphy in 37 patients with recent anterior myocardial infarction. In addition to the higher incidence of residual stenosis of the infarct-related artery, a disproportionate shortening of diastolic time in patients with myocardial perfusion defect redistribution permitted further reduction of subendocardial blood flow during exercise.

Parathyroid hormone regulates osteoblast differentiation positively or negatively depending on the differentiation stages

The effects of parathyroid hormone (1-34) (PTH (1-34) on osteoblast differentiation were investigated using primary osteoblast-like cells isolated from newborn mouse calvaria. The osteoblast-like cells cultured at low cell densities, in which the cells remained in a subconfluent state at the end of culture, were exposed for 7 days to PTH. This stimulated alkaline phosphatase (ALP) activity in a dose-dependent manner. In contrast, PTH dose-dependently inhibited both ALP activity and osteocalcin production in cells inoculated at high cell densities, in which they had reached a confluent state before the end of culture. The changes of ALP activity by PTH were accompanied with the expression of ALP messenger RNA. PTH induced no changes of the hydroxyproline content in the cell layer when the cells were exposed to the hormone at a subconfluent state, but reduced the content at a postconfluent state. The stimulation of ALP activity by PTH at a preconfluent state was retained even after the removal of PTH from the culture media. The opposite effect of PTH, observed between the preconfluent and the postconfluent state, was reproduced by adding dibutyryl cyclic adenosine monophosphate (cAMP) or forskolin, but not by adding phorbol myristate acetate. In a colony-forming unit fibroblastic (CFU-F) assay, using bone marrow cells isolated from tibiae of 10-week-old mice, PTH induced no changes in the total number of CFU-Fs, but increased the proportion of ALP-positive colonies. These results indicate that PTH exerts opposite effects on the phenotypic expression of osteoblasts, depending on their differentiation stages of osteoblasts. PTH may preferentially stimulate osteoblast differentiation in immature osteoblasts but inhibit it in more mature cells.

[Investigation on 19 operated cases of intrathoracic thyroid tumors]

We investigated in this paper nineteen patients who had undergone removal of intrathoracic thyroid tumors. They were 4 males and 15 females, aged 22-73 years, on the pathological classification, 4 with follicular adenomas, 4 with adenomatous goiters, 6 with papillary carcinomas, 1 with follicular carcinoma, 3 with papillary and follicular mixed carcinomas and 1 with anaplastic carcinoma. A 10-year survival rate of carcinomas is 77.1%, and there were 4 cases that had long term interval (6-30 years) between removal of cervical thyroid carcinoma and finding out of intrathoracic thyroid carcinoma. One case of follicular adenomas gave rise to metastasis to lung after four years from removal of intrathoracic tumor, and so it is necessary to do a long term observation after removal of thyroid tumors.

Partial characterization of a 17 kDa acidic protein, EFP, induced by thiocarbamate in the early flowering phase in Asparagus seedlings

Asparagus officinalis seedlings treated with either thiocarbamates or carbamates are induced to flower within 2-3 weeks of application. SDS-PAGE and 2-D PAGE resolutions of total soluble proteins of treated seedlings showed the accumulation of an acidic 17 kDa polypeptide. Partial amino acid sequence of the acidic protein showed homology to the wound-responsive A. officinalis PR 1, AoPR1. We named this protein EFP, early flowering protein, owing to its advanced appearance during the early transition from vegetative to floral phase. Carbamates and thiocarbamates that induced more than 80% flowering rates corresponded with increased level of EFP while compounds that are weak flower inducers showed reduced amount of EFP. The observation thus defined the correlationship of EFP to variable flowering rates.

A new non-random chromosomal translocation t(3;6)(q27;p21.3) associated with BCL6 rearrangement in two patients with non-Hodgkin's lymphoma

We describe two cases of non-Hodgkin's lymphoma associated with t(3;6)(q27;p21.3) and BCL6 rearrangement. The first case was in a 78-year old woman, whose performance status (PS) was 1, the serum lactate dehydrogenase (LDH) level was elevated, and the Ann Arbor stage was IIIA with no extra nodal lymphomatous site. The pathological diagnosis from a biopsy of the inguinal lymph node was 'malignant lymphoma (ML), follicular, small cleaved' according to the Working Formulation. Complete remission was achieved. Although she had relapse in 1992, remission was obtained again. The second case was in a 62-year old man, whose PS was 1, the serum LDH was normal, and Ann Arbor stage was IVA with the involvement of the small intestine. Histological diagnosis of the cervical lymph node was 'ML, diffuse, large cell'. Complete remission was obtained without relapse. The 3q27 translocations, found in 20-30% of non-Hodgkin's lymphoma, are unique in having multiple chromosomal translocation partners. Chromosome band 6p21.3 is one of these partner sites that may be the site of a novel gene. The two cases presented here show that this translocation is a non-random chromosomal change involving 3q27 and BCL6. Since t(3;6) was the sole karyotypic abnormality in one case, this translocation may play a role in lymphomagenesis.

Hypoxia and hypoxia/reoxygenation activate Src family tyrosine kinases and p21ras in cultured rat cardiac myocytes

We previously reported that both hypoxia and hypoxia followed by reoxygenation (hypoxia/reoxygenation) rapidly and sequentially activate mitogen-activated protein kinase kinase kinase (MAPKKK) activity of Raf-1. This was followed by the sequential activation of MAP kinase kinase (MAPKK). MAP kinases (p42mopk and p44mopk), and S6 kinase (p90rsk). In this study, we demonstrated that both hypoxia and hypoxia/ reoxygenation caused rapid activation of Src family tyrosine kinases, p60c-src and p59c-fyn, which are upstream mediators of MAP kinase activation. This was followed by the activation of p21ras. Because Src family tyrosine kinases are known to be cell-surface-associated kinases and upstream regulators of p21ras, these results strongly suggested that activation of Src family tyrosine kinases plays a key role in triggering intracellular signaling cascades in cardiac myocytes in response to hypoxia and hypoxia/reoxygenation.

A new screening method for the selection of Lactobacillus acidophilus group lactic acid bacteria with high adhesion to human colonic mucosa

A hemagglutination (HA) assay was done for the screening of lectin-like components in surface layer protein (SLP) from Lactobacillus (L.) acidophilus A group strains. The new screening method, using polystyrene beads coated with rat-colonic mucin (RCM), which combines sugar chains similar to those of human colonic mucin, was also done. The results showed that the HA assay was not a good indicator for selecting strains having high adhesion to the human intestinal tract. The SLPs from 3 strains that strongly bound to RCM also bound well to carbohydrate portions of Carnoy's-fixed human colonic mucous layer. These results suggest that this method is a new promising screening technique for the L. acidophilus strains having high adhesion to the human intestinal tract.

Retinoylation of proteins in rat liver, kidney, and lung in vivo

Retinoylation (retinoic acylation) is a posttranslational modification of proteins occurring in a variety of cell types in vitro. This study was done to examine whether retinoylation occurs in vivo. We found that in retinol-deficient rats, radiolabeled retinol or retinoic acid was incorporated into the liver, kidney, and lung in a form that was not removed by extraction with CHCl3:CH3OH. About 98% of the radiolabeled retinoid was acid-soluble after digestion with proteinase K indicating that it was covalently bound to protein. About 50% of the retinoid covalently bound to liver and kidney protein was removed by mild hydrolysis with CH3OH-KOH. Methyl retinoate, all-trans-retinoic acid, and polar metabolites of retinoic acid accounted for essentially all of the retinoids released. We conclude that retinoylation of protein occurs in vivo primarily via the formation of an ester bond.

Role of the intrachain disulfide bond of ovalbumin during conversion into S-ovalbumin

Disulfide-reduced and carboxymethylated ovalbumin was treated at pH 9.9 and 55 degrees C for 24 h as a specific condition for preparation of S-ovalbumin. The stability and conformation of the product were investigated. Such alkaline treatment converted native protein to S-ovalbumin, but this modified ovalbumin was not stabilized, according to results of calorimetric analysis. Instead, it had lost its native like conformation; the magnitude of CD spectra decreased. The conformation after alkaline treatment was not clear, but the possibility of aggregation was excluded by electrophoretic analysis. These observations showed that the transformation of native ovalbumin into S-ovalbumin requires the presence of the disulfide bond.

Translocation (3;14)(q27;q11): a new variant translocation in a patient with non-Hodgkin's lymphoma of B-cell type with BCL6 rearrangement

We report a 65-year-old woman with non-Hodgkin's lymphoma (NHL) carrying a t(3;14)(q27;q11) and BCL6 rearrangement in the affected cells. She had generalized lymphadenopathy and the bone marrow was infiltrated by lymphoma cells at presentation. Histological diagnosis was "malignant lymphoma, diffuse, large cell" type according to an International Working Formulation. Chromosome analysis revealed a t(3;14)(q27;q11), which is a new variant translocation of t(3;14) (q27;q32). Southern blot analysis showed rearrangement of BCL6, JH, and TCR beta but not of TCR delta. Cosmid probe of BCL6 hybridized to 14q11 and 3q27 by fluorescence in situ hybridization (FISH). Although the band 14q11 is a locus of T-cell receptor alpha- and delta-chains (TCR alpha/delta), lymphoma cells expressed B-cell, IgGk phenotype. The findings suggest that a novel proto-oncogene in the vicinity of TCR alpha/delta is involved in this translocation.

[Reading ability of elementary school children: a componential analysis]

It was hypothesized that there are three independent levels of reading processing: Letter and word level, sentence level, and discourse level. Reading speed of 117 fifth-grade children were assessed, and clause length, position in each sentence, and position in passage were found to affect the speed independently. These features therefore must correspond respectively to the levels mentioned above. Since working memory capacity possibly determined the functioning of the three levels, reading span as the capacity was assessed in the study and incorporated into a multivariate path model, in order to predict ability in reading comprehension. The span and vocabulary explained the child's general reading ability. The ability together with domain specific knowledge explained the child's domain specific reading comprehension. Finally, the applicability of those findings to the programs to assist children who have difficulty in reading comprehension was discussed.

Pharmacokinetic analysis of protein-conjugated doxorubicin (DXR) and its degraded adducts in DXR-sensitive and -resistant rat hepatoma cells

After treatment of AH66DR cells with the multidrug resistance (MDR) phenotype with bovine serum albumin (BSA)-conjugated [14C]doxorubicin (DXR), accumulation of the drug in the secondary lysosomal fraction increased as a function of time up to 24 h without any significant increase of the drug in other organellae. By contrast, AH66P cells showed a marked increase in accumulation of the drug in the mitochondrial fraction, and a moderate increase in the lysosomal and nuclear fractions. The intracellular degradation of the internalized conjugate was assessed by HPLC gel filtration as molecular change of the drug. The initial molecular mass (M(r)) of BSA-conjugated [14C]DXR was estimated to be 70 kDa; however, the secondary lysosomal fraction contained mainly three peaks of [14C]compounds ranging from 3 to 70 kDa. The [14C]compound extracted from the nuclear and mitochondrial fractions showed only one peak, which was estimated to be smaller than 2 kDa. By contrast, the cytosolic fraction contained mainly two peaks of [14C]compounds, which were smaller than 2 kDa and larger than 500 kDa. These results indicated that the intracellular distribution of the administered drug, based probably on the drug-traffic mechanism in the cells, was quite different between the two cell lines, but some of the biochemical characteristics of the degraded compounds from each subcellular fraction were similar because the degradation processes in each fraction might be almost identical. The possibility of lysosomal degradation of the protein-conjugated DXR leading to expression of cytotoxicity was also confirmed by the fact that only lysosomal digestable poly-L-lysine-conjugated DXR exhibited dose-dependent cytotoxicity against both cell lines in marked contrast to the cells treated with poly-D-lysine-conjugated DXR. It was concluded that lysosomal breakdown of protein-conjugated DXR, which had been taken up by endocytosis, and the liberation of the degraded active adducts of the conjugate without efflux by the MDR pump mechanism must be an essential stage in the development of the cytotoxicity against tumor cells with or without the MDR phenotype.

Osteoclast function is activated by osteoblastic cells through a mechanism involving cell-to-cell contact

We have established a method for obtaining an enriched preparation of functionally active osteoclast-like multinucleated cells (enriched OCLs) from co-cultures of mouse primary osteoblasts and bone marrow cells. Using these enriched OCLs, the effect of osteoblastic cells on osteoclast function was examined in two assays: a pit formation assay and an assay for actin ring formation. The enriched OCLs cultured for 24 h on dentine slices formed only a few resorption pits. When various numbers of primary osteoblasts were added to the enriched OCLs, the areas of the resorption pits increased proportionally to the number of osteoblasts added. Like primary osteoblasts, the established cell lines of osteoblastic cell (MC3T3-E1 and KS-4) and bone marrow-derived stromal cells (MC3T3-G2/PA6 and ST2) potentiated the pit formation caused by enriched OCLs. In contrast, the fibroblastic cell lines (NIH3T3 and C3H10T1/2) and the myoblastic cell line (C2C12) failed to activate OCL function. When cell-to-cell contact between MC3T3-E1 cells and enriched OCLs was prevented, only a few resorption pits were formed. Pit formation by enriched rat osteoclasts placed on dentine slices was also stimulated by adding MC3T3-E1 cells. Actin ring formation and pit forming activity were well correlated in either culture of enriched mouse OCLs or authentic rat osteoclasts on dentine slices. These results indicate that osteoclast function is activated by osteoblastic cells-through a mechanism involving cell-to-cell and/or cell-to-matrix contact.