Case report: Electron microscopic evaluation of bone from a patient treated with cinacalcet hydrochloride, maxacalcitol, and alfacalcidol for hyperparathyroid bone disease with secondary hyperparathyroidism.

Evaluation of bone is of great importance in chronic kidney disease patients, as these patients are at an increased risk for fractures. We treated a hemodialysis patient suffering from hyperparathyroid bone disease with cinacalcet hydrochloride and concurrent administration of maxacalcitol and alfacalcidol for a year. Hyperparathyroid bone disease is characterized by cortical thinning, increased cortical porosity, reduced trabecular bone volume, and increased hypomineralized matrix volume, and there is little information to date about the effects of treatment with cinacalcet hydrochloride on the bone fragility in patients with hyperparathyroid bone disease. In the present study, histological and backscattered electron microscopic evaluation of this combination treatment revealed an excellent improvement of both bone volume and bone morphology. This treatment improved cortical thinning, cortical porosity, and trabecular thinning. Furthermore, the treatment also reduced hypomineralized matrix volume, indicative of improved mineralization by osteocytes. We speculate that the intermittent maxacalcitol administration may have effectively stimulated the vitamin D receptors expressed on osteocytes and osteoblasts, resulting in increased mineralization. Our approach for evaluating the bone in patients with chronic kidney disease by backscattered electron microscopy is novel.

Associations between the levels of sclerostin, phosphate, and fibroblast growth factor-23 and treatment with vitamin D in hemodialysis patients with low intact PTH level.

UNLABELLED: Serum sclerostin levels could be closely associated with serum phosphate and fibroblast growth factor-23 levels in hemodialysis patients with low intact parathyroid hormone (PTH) levels. Further study is required to indicate whether these close associations are present in patients with spontaneously low PTH levels without any vitamin D treatment. INTRODUCTION: Intact parathyroid hormone (iPTH) is involved in the interaction between sclerostin and phosphate/fibroblast growth factor-23 (FGF23) in animal models. However, their relationship in patients on hemodialysis (HD) is unclear. METHODS: Data of 102 HD patients were collected regarding clinical and laboratory parameters and mineral bone disorder medications. The patients were divided into subgroups according to the iPTH level (A, <70 pg/mL; B, 70-150 pg/mL; C, 150-300 pg/mL; and D, ≥ 300 pg/mL). RESULTS: The sclerostin level was significantly and positively correlated with phosphate and log of FGF23 levels in subgroups A, B, and combined A and B. Multiple linear regression analysis in the combined A and B subgroup revealed that male sex (t = 3.24, P = 0.01; 95% confidence interval [CI] 11.78 to 50.43) and phosphate level (t = 2.13, P = 0.04; 95% CI, 1.08 to 36.91) were independent factors for serum sclerostin level. The log of serum FGF23 level (t = 1.90, P = 0.06, 95% CI -1.85 to 63.50) appeared to be an important factor for serum sclerostin level. The frequency of patients using vitamin D treatment was not significantly different among subgroups A (93.1%), B (88.0%), C (85.2%), and D (90.5%). CONCLUSION: Serum sclerostin levels were associated with serum phosphate and FGF23 levels in patients with low iPTH levels. Further study is required to indicate whether these close associations are present in patients with spontaneously low iPTH levels without vitamin D treatment.

Structure and function of AvtR, a novel transcriptional regulator from a hyperthermophilic archaeal lipothrixvirus.

The structural and functional analysis of the protein AvtR encoded by Acidianus filamentous virus 6 (AFV6), which infects the archaeal genus Acidianus, revealed its unusual structure and involvement in transcriptional regulation of several viral genes. The crystal structure of AvtR (100 amino acids) at 2.6-Å resolution shows that it is constituted of a repeated ribbon-helix-helix (RHH) motif, which is found in a large family of bacterial transcriptional regulators. The known RHH proteins form dimers that interact with DNA using their ribbon to create a central ß-sheet. The repeated RHH motifs of AvtR superpose well on such dimers, but its central sheet contains an extra strand, suggesting either conformational changes or a different mode of DNA binding. Systematic evolution of ligands by exponential enrichment (SELEX) experiments combined with systematic mutational and computational analysis of the predicted site revealed 8 potential AvtR targets in the AFV6 genome. Two of these targets were studied in detail, and the complex role of AvtR in the transcriptional regulation of viral genes was established. Repressing transcription from its own gene, gp29, AvtR can also act as an activator of another gene, gp30. Its binding sites are distant from both genes' TATA boxes, and the mechanism of AvtR-dependent regulation appears to include protein oligomerization starting from the protein's initial binding sites. Many RHH transcriptional regulators of archaeal viruses could share this regulatory mechanism.

Sialyl-glycoconjugates in cholesterol-rich microdomains of P388 cells are the triggers for apoptosis induced by Rana catesbeiana oocyte ribonuclease.

SBL/RC-RNase was originally isolated from frog (Rana catesbeiana) oocytes and purified as a novel sialic acid-binding lectin (SBL) that displayed strong anti-cancer activity. SBL was later shown to be identical to a ribonuclease (RC-RNase) from oocytes of the same species. The administration of SBL/RC-RNase induced apoptosis (with nuclear condensation and DNA fragmentation) in mouse leukemia P388 cells but did not kill umbilical vein endothelial or fibroblast cells derived from normal tissues. The cytotoxic activity of SBL/RC-RNase was inhibited by desialylation of P388 cells and/or the co-presence of free bovine submaxillary mucin. FACS analysis showed that SBL/RC-RNase was incorporated into cells after attachment to cholesterol-rich microdomains. Addition of the cholesterol remover methyl-ß-cyclodextrin reduced SBL/RC-RNase-induced apoptosis. Apoptosis occurred through the caspase-3 pathway following activation of caspase-8 by SBL/RC-RNase. A heat shock cognate protein (Hsc70) and a heat shock protein (Hsp70) (each 70 kDa) on the cell membrane were shown to bind to SBL/RC-RNase by mass spectrometric and flow cytometric analyses. Quercetin, an inhibitor of Hsc70 and Hsp70, significantly reduced SBL/RC-RNase-induced apoptosis. Taken together, our findings suggest that sialyl-glycoconjugates present in cholesterol-rich microdomains form complexes with Hsc70 or Hsp70 that act as triggers for SBL/RC-RNase to induce apoptosis through a pathway involving the activation of caspase-3 and caspase-8.

Oxidised LDL/LDL-cholesterol ratio and coronary artery calcification in haemodialysis patients.

BACKGROUND AND AIMS: Serum malondialdehyde-modified low-density lipoprotein (MDA-LDL) and MDA-LDL/LDL-cholesterol (LDL-c) ratio are risk factors for arteriosclerosis and cardiovascular disease (CVD). However, no information is available on these parameters or their associations with coronary artery calcification (CAC) in haemodialysis (HD) patients. METHODS AND RESULTS: Fifty-seven HD patients and 26 control subjects were included in this cross-sectional study. Serum MDA-LDL concentrations and MDA-LDL/LDL-c ratios were examined. HD patients had significantly higher MDA-LDL/LDL-c ratios than the controls (105.1 ± 27.5 vs. 81.4 ± 18.9 mU/mg, P < 0.001); however, there was no significant difference in serum MDA-LDL levels between the 2 groups. CAC scores were examined only in HD patients and their possible associations with the clinical/laboratory data were analysed. Analysis of HD patients showed that MDA-LDL/LDL-c ratio has an association with presence of CVD, CAC score, HD duration, MDA-LDL, or haemoglobin A1C. In addition, the CAC score was positively correlated with serum MDA-LDL level (P = 0.048) and MDA-LDL/LDL-c ratio (P = 0.006). Furthermore, multivariate logistic regression analysis showed that MDA-LDL/LDL-c ratio (ß = 0.04, P = 0.003) and HD duration (ß = 0.16, P = 0.007) were independently associated with CAC score. CONCLUSION: The MDA-LDL/LDL-c ratio of HD patients was significantly higher than that of non-HD subjects and was independently associated with the CAC score. Therefore, this ratio could be an important risk factor for CAC in HD patients.

Visualization of BrdU-labelled DNA in cyanobacterial cells by Hilbert differential contrast transmission electron microscopy.

We have attempted to observe the native shape of DNA in rapidly frozen whole cyanobacterial cells through 5-bromo-2-deoxyuridine (BrdU) incorporation and visualization with a Hilbert differential contrast transmission electron microscopy (HDC TEM). The incorporation of BrdU into the DNA of Synechococcus elongatus PCC 7942 was confirmed with fluorescently labelled anti-BrdU antibodies and through EDX analysis of ultra-thin sections. HDC TEM observed cells that had incorporated BrdU into their DNA exhibited electron dense areas at the location corresponding to fluorescently labelled BrdU. Since various strings and strands were observed in high contrast with the HDC TEM, we conclude that the method promises to allow us to identify and understand bulk structural changes of the in vivo DNA and the nucleoid through observation at high resolution.

Successful therapeutic use of a single-dose of rituximab on relapse in adults with minimal change nephrotic syndrome.

Minimal change nephrotic syndrome (MCNS) usually is considered to have a good renal prognosis, but the frequency of relapses is a therapeutic challenge to physicians. The treatment of patients with multiple relapses remains a matter of controversy, because few controlled studies are available. We report the case of a 25-year-old man who experienced relapses of MCNS. Single-dose rituximab therapy (total dose 500 mg) was given during the fourth relapse. Complete remission occurred 10 days later, when no CD19/20-positive B cells were detected in the blood. This the first report of efficacy of single-dose rituximab therapy to treat multi-relapsing MCNS in an adult patient.

Purification and biochemical characterization of a D-galactose binding lectin from Japanese sea hare (Aplysia kurodai) eggs.

A lectin was purified from Japanese sea hare Aplysia kurodai by lactosyl-agarose affinity chromatography. The molecular mass of the lectin was determined to be 56 and 32 kDa by SDS-PAGE under non-reducing and reducing conditions, respectively. It was found to agglutinate trypsinized and glutaraldehyde-fixed rabbit and human erythrocytes in the absence of divalent cations. The lectin exhibited stable thermo-tolerance as it retained hemagglutinating activity for 1 h even at 80 degrees C and showed stability at pH 10. By contrast, it was very sensitive at pH less than 5 and in the presence of the sulfhydryl-group preserving reagent, beta-mercaptoethanol. The hemagglutinating activity by the lectin was specifically inhibited by D-galactose, galacturonic acid, methyl-alpha- and methyl-beta-D-galactopyranoside, lactose, melibiose, and asialofetuin. The association rate constant (k(ass)) and dissociation rate constant (k(diss)) were determined for the lectin to be 4.3 x 10(5) M(-1) x sec(-1) and 2.2 x 10(-3) sec(-1), respectively, using a surface plasmon resonance biosensor. The lectin moderately inhibited cell proliferation in the P388 cell line dose dependently. Interestingly, lectin-treated cells did not show a fragmented DNA ladder as is caused by apoptosis, suggesting that the cell proliferation inhibition was caused by another unknown mechanism.

Decreased tyrosine phosphorylation of nephrin in rat and human nephrosis.

Phosphorylation of tyrosine residue (Y1204) of rat nephrin by Fyn kinase allows Nck adaptor protein binding to nephrin motifs, which include the phosphorylated tyrosine. This phosphorylation-dependent switch induces actin polymerization in a cell culture system. Here, we generated an antibody recognizing phosphorylated nephrin at the Nck binding sites pY1204 and pY1228 to determine the phosphorylation status of nephrin using a rat model of puromycin aminonucleoside-induced nephrosis. Changes in globular actin (G-actin) and filamentous actin (F-actin) contents in isolated glomeruli were measured by western blot. Before experimental nephrosis, both Y1204 and Y1228 were phosphorylated, and most of the actin was filamentous. Before the onset of overt proteinuria, however, phosphorylation of both Y1204 and Y1228 rapidly decreased and became almost undetectable. During this period, the amount of F-actin in glomeruli began to decrease, whereas G-actin increased. Phosphorylation of nephrin at Y1228 in glomeruli of patients with minimal change nephrosis was significantly decreased compared with that in normal glomeruli. Our study suggests that tyrosine phosphorylation of nephrin by regulating F-actin formation may be important for the maintenance of normal podocyte morphology and function.

Localization and functional characterization of rat kidney-specific chloride channel, ClC-K1.

To investigate the physiological role of a kidney-specific chloride channel (ClC-K1), we sought to determine its exact localization by immunohistochemistry and its functional regulation using Xenopus oocyte expression system. The antiserum specifically recognized a 70-kD protein in SDS-PAGE of membrane protein from rat inner medulla and an in vitro translated ClC-K1 protein. Immunohistochemistry revealed that ClC-K1 was exclusively localized to the thin limb of Henle's loop in rat inner medulla. In comparison with the immunostaining with anti-aquaporin-CHIP antibody that only stains the descending thin limb of Henle's loop (tDL), ClC-K1 was found to be localized only in the ascending limb (tAL) which has the highest chloride permeability among nephron segments. Immunoelectron microscopy confirmed that the staining of ClC-K1 in tAL was observed in the region of both apical and basolateral plasma membranes. Expressed chloride current in Xenopus oocytes by ClC-K1 cRNA was regulated by extracellular pH and extracellular calcium. Furosemide inhibited the expressed current (Ki = 100 microM), whereas N-ethyl-maleimide stimulated the current. These functional characteristics were consistent with the in vitro perfusion studies of chloride transport in tAL. The localization and the functional characteristics described here indicate that ClC-K1 is responsible for the transepithelial chloride transport in tAL.

Glycaemic control boosts glucosylated nanocarrier crossing the BBB into the brain.

Recently, nanocarriers that transport bioactive substances to a target site in the body have attracted considerable attention and undergone rapid progression in terms of the state of the art. However, few nanocarriers can enter the brain via a systemic route through the blood-brain barrier (BBB) to efficiently reach neurons. Here we prepare a self-assembled supramolecular nanocarrier with a surface featuring properly configured glucose. The BBB crossing and brain accumulation of this nanocarrier are boosted by the rapid glycaemic increase after fasting and by the putative phenomenon of the highly expressed glucose transporter-1 (GLUT1) in brain capillary endothelial cells migrating from the luminal to the abluminal plasma membrane. The precisely controlled glucose density on the surface of the nanocarrier enables the regulation of its distribution within the brain, and thus is successfully optimized to increase the number of nanocarriers accumulating in neurons.There are only a few examples of nanocarriers that can transport bioactive substances across the blood-brain barrier. Here the authors show that by rapid glycaemic increase the accumulation of a glucosylated nanocarrier in the brain can be controlled.

Dispersion and dry and wet deposition of PAHs in an atmospheric environment.

The atmospheric concentration and dry and wet deposition were measured for particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) from August to December in Higashi-Hiroshima City, Japan. PM concentration of fine particles (0.6-7 microm) was 5.7-75.1 micro m(-3), and coarse particles (> 7 microm) was 2.2-22.3 microg m(-3). Total PAHs concentration of fine particles was 0.14-16.3 ng m(-3), and coarse particles was 0.01-0.77 ng m(-3). Their concentration increased on non-rainy days and decreased rapidly on rainy days. For seasonal fluctuations of PAHs, their concentrations decreased from summer to winter, and the rate of decrease was more distinct for fine particles. For total (dry + wet) depositions, the PM flux was 1.9-11.2 mg m(-2) d(-1), and the total PAHs flux was 1.9-97.2 ng m(-3) d(-1). From these measurements, the yearly total loading of PAHs was estimated for the particle phase. Total loading was 28 microg m(-2) y(-1) for the dry deposition and 52 mg m(-2) y(-1) for the wet deposition. The loading of the wet deposition was comparable to those of the dry deposition for all ring numbers.

Induction of murine tumors in adult mice by a combination of either avian sarcoma virus or human adenovirus and syngeneic mouse embryo cells.

Primary murine Rous sarcoma was produced in adult mice of seven strains, C57BL/6, DBA/2, BALB/c, C3H/He, CBAJ, AKR, and DDD, by s.c. inoculation of a mixture of 5 X 10(6) chicken tumor cells containing Schmidt-Ruppin Rous sarcoma virus and 9- to 12-day-old mouse embryo cells (MEC) (2 X 10(6) ) of the syngeneic strain. The sarcoma developed at the site of injection in almost all mice tested, but there were some differences in the latent period and the survival time among mouse strains. When the number of cells inoculated was reduced to 5 X 10(4) for chicken tumor cells induced by the Schmidt-Ruppin strain of Rous sarcoma virus (SR-CTC) and 2 X 10(4) for MEC, no tumor was produced in C3H/He mice. These tumors had strain specificity and the Schmidt-Ruppin strain of Rous sarcoma virus genome in masked form. The tumor at the site of injection originated in the embryo cells injected along with SR-CTC. This was confirmed by CBAT6/T6 marker chromosome analysis of the tumor cells of CBA mice induced with SR-CTC plus CBAT6/T6 MEC and also confirmed by transplantation of a C57BL/6 X C3H/He F1 tumor which had been induced with SR-CTC plus C3H/He or C57BL/6 MEC. Tumor induction in adult mouse by a mixture of virus and syngeneic 9- to 14-day-old embryo cells was tested for human adenovirus serotype 12 (Ad12) and simian virus 40. Primary Ad12 tumor was also induced in adult CBA, C3H/He, and DDD mice by 4 X 10(5 to 6) 50% tissue culture infective dose of Ad12 with 5 X 10(6) syngeneic embryo cells. This tumor contained Ad12 T-antigen-positive particles in cells. But in the case of simian virus 40, the tumor did not appear for about 300 days of observation.

Susceptibilities of normal and malignant human lung cells in culture to the cytocidal action of antitumor agents.

Cultured normal and malignant human lung cells were examined for their different sensitivities to the cytocidal action of nine antitumor and three non-antitumor agents. The malignant cells were killed preferentially at lower concentrations and in a shorter time with each antitumor agent, Adriamycin, neocarzinostatin, bleomycin, actinomycin D, mitomycin C, carboquone, 1-beta-D-arabinofuranosylcytosine, 5-fluorouracil, and 5-fluorodeoxyuridine. Among these, Adriamycin, 5-fluorouracil, and 5-fluoro-deoxyuridine exhibited a higher differential lethal action on the malignant cells than did the other antitumor agents. The two cell lines exhibited little difference in cytolytic sensitivity to non-antitumor cytotoxic agents such as amphotericin B, G-strophanthin, and alph-amanitin.

A murine B-cell lymphoma induced by Gross virus.

A B-lymphocyte tumor (MLB-MN line) was induced by Gross murine leukemia virus in Slc:ddY mice, successively passaged in normal adult mice, and adapted to tissue culture. The surface marker expression of MLB-MN was examined and found to include several markers that are known to occur in normal B-lymphocytes. The cells bore surface immunoglobulin M, detected by indirect immunofluorescence staining, and Fc receptors and complement receptors, detected by rosette formation. Thy 1 antigen and secretion of immunoglobulin were lacking. These results have led us to postulate that the origin of the MLB-MN tumor was a late differentiation stage of the B-lymphocyte.

Isolation and characterization of Rana catesbeiana lectin and demonstration of the lectin-binding glycoprotein of rodent and human tumor cell membranes.

A lectin isolated from Rana catesbeiana eggs preferentially agglutinates a large variety of human and animal tumor cells but not normal red blood cells, lymphocytes, or fibroblasts. The phenomenon correlates with a higher binding activity of the lectin with tumor cells. Chemical and physical analysis of the purified lectin indicates that the lectin is a low molecular weight basic polypeptide with five intrachain disulfide bonds. Its agglutination of tumor cells was abolished by blocking the amino group. The lectin strongly binds with a large variety of tumor cells but binds only minimally with fibroblasts, lymphocytes, and erythrocytes. Tumor cell agglutination induced by this lectin was strongly inhibited by submaxillary mucin, to a lesser degree by fetuin and keratan sulfate, and not at all by less-sialylated glycoproteins, such as transferrin. Inhibition by mucin or fetuin was greatly reduced by desialylation of glycoprotein with sialidase. Treatment of tumor cells with sialidase greatly reduced the lectin-dependent agglutination, and the sialidase-dependent reduction of tumor cell agglutination was inhibited by the sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid. However, tumor cell agglutination was not inhibited by chondroitin sulfates or hyaluronic acid. Thus, the lectin-dependent tumor cell agglutination is due to a high density of sialic acid at the cell surface. The receptor glycoprotein that interacts with this lectin was demonstrated in the detergent-insoluble fraction of a variety of tumor cells by sodium dodecyl sulfate:polyacrylamide gel electrophoresis, followed by Western blotting with lectin and anti-lectin antibodies. The presence of a common high molecular weight lectin-binding glycoprotein in various tumor cells was demonstrated.

Effect of heat shock on protein synthesis by normal and malignant human lung cells in tissue culture.

Heat shock proteins were found in cultured human lung cells by sodium dodecyl sulfate:gel electrophoresis and autoradiography using [35S]methionine. The synthesis of a M.W. 70,000 protein was markedly stimulated in normal, malignant, and SV40-transformed cells, and that of M.W. 90,000 and M.W. 100,000 proteins was stimulated only in malignant and SV40-transformed cells after heat shock treatment. In contrast, the synthesis of M.W. 200,000 and M.W. 250,000 proteins observed in the unheated normal cells was diminished after the same procedure. The heat shock proteins were induced within a given range of temperature and duration of treatment, the conditions for normal and malignant cells being clearly different, i.e., optima of 43 degrees for 1 hr in the normal cells and 41 degrees for 1 hr in the malignant cells. The results suggest that the analysis of heat shock protein is very useful for identifying the differential heat susceptibilities of normal and malignant cells and for elucidating their bases and mechanisms.

Dependence on chain length of antitumor activity of (1 leads to 3)-beta-D-glucan from Alcaligenes faecalis var. myxogenes, IFO 13140, and its acid-degraded products.

The well-defined (1 leads to 3)-beta-D-glucan with (DPn) 540, produced by cultivation of Alcaligenes faecalis var. Myxogenes (IFO 13140), a mutant of a soil bacterium, had marked inhibitory activity against the s.c.-implanted Sarcoma 180 at 5 to 50 mg/kg for 10 days. It also exhibited very high activity in doses of 60 and 100 mg/kg i.p. by a single injection at 7 days after the initial s.c. transplantation of Sarcoma 180. The inhibition ratios observed with Ehrlich carcinoma, NTF (Nakahara-Tokuzen-Fukuoka) reticulum cell sarcoma, and CCM adenocarcinoma were somewhat less but were still significant. On the other hand the treatment failed to inhibit the growth of ascites Sarcoma 180 or to induce prolongation of life span. The mechanism of action of this glucan was considered to be host mediated because of a lack of effect in vitro and also because of the effectiveness of pretreatment of animals by injection before transplantation of a tumor. The results from the bioassay study of the low-molecular-weight (1 leads to 3)-beta-D-glucans prepared from the glucan with number-average degrees of polymerization (DPn) 540 by hydrolysis with formic acid or sulfuric acid showed that the glucans with DPn greater than 50 inhibited the growth of Sarcoma 180 implanted s.c. in mice, whereas the result of the schedule-dependent effect was obtained in the pretreatment of animals by the glucan with DPn 50. By i.v. administration, even the glucan with DPn 16 showed a strong antitumor effect comparable to that of the glucan with DPn 540.

Antitumor activity of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothec in, a novel water-soluble derivative of camptothecin, against murine tumors.

The search for new water-soluble analogues of camptothecin (CPT) with higher activity and less toxicity has led to the development of a novel compound, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothecin (CPT-11), which showed significant antitumor activity against a broad spectrum of experimental tumor models by i.p., i.v., or oral administration. When its activity against L1210 was compared with that of CPT and known derivatives, CPT-11 was most effective, giving the highest maximum increase in life span (ILS) and showing good activity over a wide dose range. The antitumor activity of CPT-11 was shown against tumors not only in the ascites form but also in the solid form. Included among the more susceptible murine tumors are S180, Meth A fibrosarcoma, Lewis lung carcinoma, Ehrlich carcinoma, MH134 hepatoma, mammary carcinoma of C3H/HeN mice, L1210, and P388 leukemia. Probable cures of these tumors were induced frequently by CPT-11. The antitumor activity of CPT-11 against i.p.-implanted L1210 was superior to that of Adriamycin in maximum ILS, the number of cured mice, and the therapeutic ratio. CPT-11 at a dose of 100 mg/kg produced an ILS in excess of 300% with five of six mice surviving tumor free, and effected 100% tumor regression at 200 mg/kg, whereas the optimum dose of Adriamycin, 12.5-25 mg/kg, brought about 114-129% ILS with one of six mice surviving. The acute toxicity of CPT-11 was extremely low, particularly in the case of oral administration. CPT-11 is expected to be clinically useful.

Inhibition of cell proliferation by Rana catesbeiana and Rana japonica lectins belonging to the ribonuclease superfamily.

Two frog egg lectins [Rana catesbeiana lectin (SBL-C) and Rana japonica lectin] preferentially agglutinate a large variety of human and animal tumor cells but not blood cells, lymphocytes, or fibroblasts. These lectins belong to the superfamily of pyrimidine base-specific RNases. The two lectins bound to a heparin-Sepharose column and were eluted from the column by an increase of NaCl molarity. Both their tumor cell-agglutinating activity and RNase activity were inhibited by heparin, and also by polyamines, such as spermine. Both lectins inhibited P388 leukemia cell proliferation. The inhibitory activity of SBL-C was blocked by addition of heparin. SBL-C inhibited protein synthesis by P388 cells, but RNase A did not. No lectin-induced antiproliferative effect was observed after sialidase treatment of cells. The antiproliferative activity of SBL-C was also inhibited by ammonium chloride treatment. These results suggest that internalization of the lectins by lectin receptor (sialoglycoconjugate)-mediated endocytosis is followed by cell death due to inhibition of protein synthesis. Administration of SBL-C i.p. delayed time to death in mice receiving i.p. transplants of Sarcoma 180 and Mep II cells.