Exon-intron structure of the human PTK6 gene demonstrates that PTK6 constitutes a distinct family of non-receptor tyrosine kinase

Partial PTK6 (also known as Brk) cDNA was initially isolated by reverse transcription-PCR of normal human melanocyte mRNAs and the full-length cDNA encodes a non-receptor protein tyrosine kinase with an SH3 domain, an SH2 domain, and a kinase catalytic domain. We have cloned the human PTK6 gene by screening human genomic lambda libraries using the full-length PTK6 cDNA as probe. The human PTK6 gene consists of 8 exons encompassing 8.8 kb and all the splicing junctions followed the conserved GT/AG rule. Coding sequence of the PTK6 gene was identical to that of the cDNA cloned from T-47D, human breast tumor cell line. Although the amino acid sequence of the PTK6 polypeptide showed the strongest homology to those of the Src family members of protein tyrosine kinases, exon-intron boundaries of the PTK6 gene were quite different from those of the Src family genes, which are evolutionarily conserved. The 813-bp 5'-flanking sequence of the PTK6 gene upstream of a luciferase reporter gene conferred significant promoter activity, at approximately 60% level of the SV40 promoter, in transient expression assays into MCF-7, human breast tumor cell line. PTK6 mRNA was expressed at very high level in colon and at high levels in small intestine and prostate, and at low levels in some tested fetal tissues. These results suggest that PTK6 constitutes an evolutionarily distinct family of non-receptor protein tyrosine kinases and may function as an intracellular signal transducer in specific tissues.

Microvascular decompression and percutaneous rhizotomy in trigeminal neuralgia

We analyzed 417 patients with trigeminal neuralgia who underwent microvascular decompression (MVD; n = 146) or percutaneous procedures, i.e. radiofrequency rhizotomy (RFR; n = 235) and glycerol rhizotomy (GR; n = 36) between March 1973 and December 1996. MVD and RFR showed the highest rates of initial pain relief (MVD 96.5%; RFR 92.3%; GR 82.8%). RFR and GR had 5.1 and 3.3% rates of facial dysesthesia, respectively, and MVD had the lowest rate (0.3%). Among 9 cases (8.6%) with recurrences after MVD, 8 cases underwent RFR and all of them obtained good long-term results (7.2 years on average). We concluded that MVD is the treatment of choice for tolerant younger patients and should be recommended for patients who desire no sensory deficit. We also determined that radiofrequency rhizotomy is the procedure of choice for patients in whom MVD failed.

MRI-guided stereotactic thalamotomy for cerebral palsy patients with mixed dyskinesia

The author has performed 108 stereotactic thalamotomies using MRI (MGSTs) without ventriculography in 77 cerebral palsy (CP) patients with dyskinesia(s) from January 1992 to January 1997. The clinical results were verified in terms of improvement of major preoperative symptom and patient's (or relative's) satisfaction using pre- and postoperative video recording and simple questionnaires. The results were as follows: excellent in 12 MGSTs, good in 69 and fair in 27. Postoperative morbidity was transient in all patients except for 2. Recurrences were noted in 6 MGSTs (5.6%). There was no death. MGST is thus a beneficial procedure for reducing dyskinetic symptom(s) of CP patients.

Anti-AIDS agents. 33. Synthesis and anti-HIV activity of mono-methyl substituted 3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (DCK) analogues

Four isomeric methyl substituted DCK analogues (2-5) were asymmetrically synthesized from different starting materials. 3-Methyl, 4-methyl, and 5-methyl-3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (2-4) all were extremely potent against HIV-1 replication in H9 lymphocyte cells with EC50 and therapeutic index values of < 4.23 x 10(-7) microM and > 3.72 x 10(8), respectively, which are much better than those of DCK and AZT in this assay.

Identification and characterization of the antimicrobial peptide corresponding to C-terminal beta-sheet domain of tenecin 1, an antibacterial protein of larvae of Tenebrio molitor

An active fragment was identified from tenecin 1, an antibacterial protein belonging to the insect defensin family, by synthesizing the peptides corresponding to the three regions of tenecin 1. Only the fragment corresponding to the C-terminal beta-sheet domain showed activity against fungi as well as Gram-positive and Gram-negative bacteria, whereas tenecin 1, the native protein, showed activity only against Gram-positive bacteria. CD spectra indicated that each fragment in a membrane-mimetic environment might adopt a secondary structure corresponding to its region in the protein. The leakage of dye from liposomes induced by this fragment suggested that this fragment acts on the membrane of pathogens as a primary mode of action. A comparison between the structure and the activity of each fragment indicated that a net positive charge was a prerequisite factor for activity. To the best of our knowledge this is the first report in which the fragment corresponding to the beta-sheet region in antibacterial proteins, which consists of alpha-helical and beta-sheet regions, has been identified as a primary active fragment.

Inhibitors of the proteasome block the myogenic differentiation of rat L6 myoblasts

Myogenesis is characterized by membrane fusion and accumulation of muscle specific proteins. We have previously shown that nitric oxide acts as a messenger for membrane fusion. Here we show that inhibitors of the proteasome, such as lactacystin, reversibly block both the fusion of L6 myoblasts and the accumulation of muscle specific proteins, such as myosin heavy chain (MHC). The inhibitors also reversibly prevented the induction of the NF-kappaB activity, which is required for the expression of nitric oxide synthase (NOS). Moreover, the inhibition of the NF-kappaB activity occurred in parallel with that of the NOS activity upon treatment with increasing concentrations of lactacystin. While pyrrolidine dithiocarbamate, an inhibitor of NF-kappaB, blocked both membrane fusion and accumulation of MHC, N(G)-monomethyl-L-arginine, a specific inhibitor of NOS, inhibited only the fusion. These results suggest that the proteasome plays an essential role in the regulation of myogenic differentiation through the activation of NF-kappaB and that the target of NF-kappaB for the expression of muscle specific proteins is distinct from that for myoblast fusion.

The position 4 nucleotide at the 3' end of the influenza virus neuraminidase vRNA is involved in temporal regulation of transcription and replication of neuraminidase RNAs and affects the repertoire of influenza virus surface antigens

Within the sequence motif conserved at the extreme ends of the influenza virus vRNAs, a unique natural variation, U or C, is observed at position 4 of the 3' end. To test the role of this nucleotide, two isogenic A/WSN/33 viruses, carrying either C4 or U4 nucleotide at the 3' end of the neuraminidase (NA) gene, were generated. Compared with the C4 virus, the U4 virus exhibited delayed synthesis of vRNA and stimulation of mRNA synthesis with prolonged accumulation in influenza virus-infected cells. The mRNA/ vRNA ratio was increased up to 20-fold by the C4 --> U4 substitution suggesting that the U4 nucleotide greatly stimulated transcription of the vRNA template. In isolated virion, the U4 virus had higher NA activity than the C4 virus. In MDBK cells, the U4 virus grew to lower haemagglutination (HA) titres but with higher infectivity than the C4 virus, with a corresponding increase in the ratio of p.f.u./HA units of about 10- to 40-fold. Western blot analysis of isolated virion showed that the ratio of two surface proteins, HA/NA, was greatly decreased in the U4 virus. This suggests that the position 4 nucleotide is a genetic determinant for the repertoire of surface antigens and their ratio could be changed without detrimental effects on virus growth. Results could be used to design genetically engineered influenza virus for vaccination. The observed down-regulation of transcription by C4 nucleotide is consistent with its potential role in segment-specific regulation of influenza virus gene expression, especially PB1, PB2 and PA proteins, during virus infection.

Induction of differentiation of the cultured rat mammary epithelial cells by triterpene acids

We investigated the effects of triterpene acids (TAs), ursolic acid (UA) and oleanolic acid (OA), on the induction of proliferation and differentiation of normal rat mammary epithelial cells (RMEC) or organoids cultured in Matrigel or primary culture system. To elucidate the effects, we tested their differentiation inducing activities with intercellular communication ability, cell cycle patterns, induction of apoptosis, and morphological differentiation in the three dimensional extracellular culture system. To study the changes of RMEC subpopulation in culture, the cultured cells were isolated, immunostained with peanut lectin (PNA) and anti-Thy-1.1 antibody and then analyzed with flow cytometry. Four different subpopulations, such as PNA and Thy-1.1 negative cells (B-), PNA positive cells (PNA+), Thy-1.1 positive cells (Thy-1.1+), PNA and Thy-1.1 positive cells (B+), were obtained and the size of each subpopulation was changed in culture with time in the presence of TAs. Intercellular communication was observed in culture for 7 days in TAs-treated cells, but not in culture for 4 days with scrape-loading dye transfer technique. G2/M phase cells and the number of apoptotic population were increased in TAs-treated groups in cell cycle analyses. S phase fractions were reduced and the change of G1 phase cells was not observed. The colonies with distinct multicellular structures, such as stellate, ductal, webbed, squamous, lobulo-ductal colonies, were observed in Matrigel culture and the frequencies of each colony were changed in the presence of TAs. These results suggest that UA and OA have differentiation inducing effects on rat mammary epithelial cells in primary or in Matrigel culture.

Stringent allele/epitope requirements for MART-1/Melan A immunodominance: implications for peptide-based immunotherapy

The exclusiveness of the relationship between peptide and HLA alleles, combined with their extensive polymorphism, emphasizes the need for immunization strategies based on endogenous processing of full length proteins (containing multiple epitopic determinants) for presentation to T cells. This could allow vaccination regardless of the patient's HLA phenotype, assuming that individual molecules can be efficient T cell Ags in association with various HLA alleles. An endogenous system of Ag presentation was developed using dendritic cells infected with recombinant viral vectors expressing the melanoma-associated Ag MART-1/Melan A. CD8+ T cells from melanoma patients were activated in vitro by coincubation with infected dendritic cells and tested for recognition of HLA-A-matched melanoma targets. This allowed the analysis of T cell induction in association with any HLA-A allele of a given patient's phenotype. In this system, MART-1/Melan A could not efficiently immunize in association with HLA-A alleles other than A*0201, including the one residue variant from A*0201: HLA-A*0226. Clonal analysis of MART-1/Melan A-specific CTL confirmed that MART-1/Melan A immunodominance is strongly restricted to the AAGIGILTV/HLA-A*0201 combination. The stringent epitope/allele requirements for MART-1/Melan A/TCR interactions were not associated with limitations in the TCR repertoire. In conclusion, autologous induction of MART-1/Melan A CTL by whole Ag processing and presentation is restricted to a unique allele/ligand combination and is excluded by minimal changes in HLA structure. Thus, whole protein vaccination for small m.w. Ags may provide no further advantage over a peptide-based approach.

Determination of cadmium and lead in urine by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry

Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) was applied to the determination of Cd and Pb in urine samples. The isotope ratios for each element in each analytical run were calculated from the peak areas of each isotope. A relatively low vaporization temperature was used, which separated the analyte from the major matrix components and improved the ion signals of Cd and Pb significantly. Various chemical modifiers were tested to obtain the best signal of Cd and Pb. After preliminary studies, 1% HNO3 was added to the samples as the chemical modifier. The ETV-ID-ICP-MS method was applied to the determination of Cd and Pb in freeze-dried urine reference material NIST SRM 2670 and several fresh urine samples. The results for NIST SRM 2670 agreed satisfactorily with the certified values. The results for other samples obtained by isotope dilution and the method of standard additions agreed satisfactorily. The detection limits were 0.02 and 0.005 ng ml-1 for Cd and Pb, respectively. The precision between sample replicates was better than 11% for all determinations.

Binding affinity of Cu(II)-VP-16 (etoposide) complex and its analogues to DNA and hydroxyl radical generation during DNA strand breaks

Conformational effects and affinities of VP-16 (etoposide) and its derivatives to DNA in the presence of Cu(II) ion were examined by circular dichroic (CD) spectra. The Cu(II)/Cu(I) redox kinetics and the hydroxyl radical (.OH) generation from the Cu(II)-complexes were estimated by the stopped-flow kinetics. Based on the results, DNA-cleaving activity of Cu(II)-complexes of VP-16 has been shown to be related with binding affinity of the complex to DNA, Cu(II)/Cu(I) redox and .OH generation, emphasising the mechanism of generated .OH attack to DNA.

[Inhibitory effect of methanol extract of Boschniakia rossica Fedtsch. et Flerov on rat hepatic preneoplastic lesions induced by diethylnitrosamine]

OBJECTIVE

To investigate the inhibitory effect of Boschniakia rossica(BR) on hepatocarcinogenesis in rats.

METHOD

Based on immunohistochemistry techniques, the expression of placental form glutathione S-transferase(GST-P), mutant p53 and p21 protein were investigated in hepatic preneoplastic lesions induced by Solt-Farber protocol in the liver of rats that had been treated with the above method, administered with BR extract and of control group.

RESULT

The extract of BR(500 mg/kg) has inhibitory effect on the formation of diethylnitrosamine-induced GST-P-positive foci in F344 rat and the expression of mutant p53 and p21 protein was lower than that of hepatic preneoplastic lesions, and the increasing gamma-glutamyltranspeptidase(gamma-GT) activity in rat liver treated with Solt-Farber protocol was decreased by the extract of BR.

CONCLUSION

These results indicate that BR has inhibitory effect on DEN induced hepatic preneoplastic lesions in F344 rat.

Gating provides improved accuracy for differentiating artifacts from true lesions in equivocal fixed defects on technetium 99m tetrofosmin perfusion SPECT

BACKGROUND

Because equivocal fixed perfusion defects on single photon emission computed tomography (SPECT) often cause a diagnostic dilemma in patients with suspected coronary artery disease (CAD), we used receiver-operating characteristic (ROC) curve analysis to evaluate the degree of increased accuracy provided by adding gated images for interpretation of such cases.

METHODS AND RESULTS

One hundred five (29%) of 365 consecutive patients undergoing technetium 99m tetrofosmin gated SPECT for evaluation of CAD demonstrated an equivocal fixed defect. Two independent observers graded the probability for true lesion with a 5-point system over 3 steps of interpretation: reviewing tomographic images alone (step 1), adding projection images (step 2), and adding gated cine images (step 3). Based on clinical criteria, 66 patients were categorized as disease negative and 25 as disease positive, while the final diagnosis was undetermined in 14 cases. Diagnostic performance was significantly higher at step 3 than at step 1 for both observers (p < 0.05 and < 0.0001) and at step 2 for observer B (p < 0.005). The maximum accuracy increased from 78.0% to 80.2% at step 2 to 84.6% to 86.8% at step 3. Moreover, the agreement of interpretation between the 2 observers was higher at step 3 (kappa = 0.53) than at step 1 (kappa = 0.29) or step 2 (kappa = 0.25).

CONCLUSION

In patients showing an equivocal fixed defect on 99mTc tetrofosmin SPECT, gated cine images provide improved differential accuracy and enhanced objectivity of interpretation by reducing interobserver variance.

Effect of silica on phospholipase D activity in rat alveolar macrophages

Silica may act as a stimulator of pulmonary inflammation and fibrosis. The effect of silica on phospholipase D (PLD) activity assayed as accumulation of [3H]phosphatidylethanol ([3H]PtdEt) was examined in [3H]palmitic acid-labeled primary cultures of rat alveolar macrophages. Silica induced a rapid accumulation of [3H]PtdEt in a time (0, 15, 30 and 45 min)- and concentration (0.5, 1.0, 2.5 and 5.0 mg/ml)-dependent manner indicating PLD activation. This silica-stimulated PLD activity was attenuated by the pretreatment with calcium chelator ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA) or/and 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid acetoxymethyl ester (BAPTA/AM) (EGTA: 54.3 +/- 8.6%, BAPTA/AM: 67.5 +/- 7.8% and EGTA + BAPTA/AM: 35.8 +/- 2.9, respectively). Also, silica-induced PLD activation was partially inhibited by the pretreatment with nonspecific phospholipase C (PLC) and PLD inhibitor (neomycin; 66.4 +/- 4.8%) or specific PLC inhibitor (U73122; 70.8 +/- 4.6%). Sphingosine as a protein kinase C (PKC) inhibitor did not change silica-induced PLD activity indicating that PKC might not play a role in PLD activation by silica. Based on these results, we concluded that a silica-stimulated phospholipase D activity is present in the rat alveolar macrophages and is predominantly regulated by PLC-mediated intracellular calcium.

Quantitation of taurine and selenium levels in human milk and estimated intake of taurine by breast-fed infants during the early periods of lactation

With these results we report the following: Taurine levels in human milk decreased slightly during the early lactation period. The concentration of taurine (406 +/- 174 nmol/ml) in colostrum was significantly higher than that (335 +/- 115 nmol/ml) in mature milk. Selenium content of human milk also decreased slightly during the early lactation period. The content of selenium (28.6 +/- 19.6 ng/ml) in colostrum was significantly higher than that (1 5.1 +/- 5.9 ng/ml) in mature milk. A correlation was not found between the taurine and selenium content of human milk. The intake of taurine and selenium by breast-fed infants progressively increased with days postpartum. These results were due to the significant increase in milk intake by infants. It is suggested that the taurine and selenium levels in colostrum are more concentrated than those in mature milk. However, the absolute intake of taurine and selenium by infants are higher in mature milk.

Determination of glycyrrhizic acid and 18-beta-glycyrrhetinic acid in biological fluids by micellar electrokinetic chromatography

A micellar electrokinetic chromatographic technique for determining acid (GZA) and 18 beta-glycyrrhetinic acid (GRA) in human plasma and urine was developed. Sample clean-up and analyte concentration were carried out by solid-phase extraction (with C18 sorbent). The buffer solution used for MEKC contained 20 mM sodium dihydrogenphosphate, 20 mM sodium tetraborate, 20 mM tetrabutylammonium bromide and 50 mM sodium dodecylsulphate, at a pH of 8.7. Good linearities for both GZA and GRA in plasma and urine were obtained. The recoveries of the method were in the range 86.5 to 107%. The detection limits for GZA in urine (0.5 ml) and plasma (1 ml) were 1.6 micrograms ml-1 and 0.8 micrograms ml-1, respectively, while for GRA in urine (0.5 ml) and plasma (1 ml) were 2 micrograms ml-1 and 1 micrograms ml-1, respectively.

Anti-AIDS agents. 31. Synthesis and anti-HIV activity of 4-substituted 3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (DCK) thiolactone analogs

Four DCK-thiolactone analogs (3-6) were synthesized asymmetrically and evaluated for anti-HIV activity against HIV-1 replication in H9 lymphocyte cells. Based on the functionality on the thiolactonecoumarin nucleus, activity was in the order: methyl > H > propyl > benzyl. 4-Methyl-3',4'-di-O-(-)-camphanoyl-(+)-cis-khelthiolactone (4) exhibited extremely potent anti-HIV activity with EC50 and therapeutic index values of 0.00718 microM and > 21,300, respectively.

Recent progress in the development of tubulin inhibitors as antimitotic antitumor agents

Tubulin protein is a major target of drug molecules, and consequently, tubulin inhibitors have attracted great attention as antimitotic antitumor agents for chemotherapeutic use. Hundreds of synthetic or semisynthetic tubulin inhibitors have been discovered and developed recently that are related to the natural products colchicine, vinblastine, and taxol. Representatives include allothiocolchicinoids, vinorelbine, and taxotere. This review will describe the recent progress being made in the development of novel antimitotic antitumor tubulin inhibitors. The emphasis has been placed on related research in the author's laboratory, including development of colchicine derivatives and other colchicine binding site drugs, such as flavonoids and quinolone derivatives. Syntheses and modifications of novel compounds, biological activity evaluation, and structural activity relationships will be discussed as well. Further research will undoubtedly lead to the discovery of additional tubulin inhibitors that have potential for use as anticancer drugs.

Phase I clinical trial: pharmacokinetics of a novel anthracycline, DA-125 and metabolites. Single dose study

Single dose of DA-125, 20 (n = 3), 40 (n = 3), 60 (n = 3), 80 (n = 6), or 100 (n = 6) mg/m2 body surface area, was administered intravenously in 5 min to 21 patients with various types of cancer as phase I clinical trial. The main side-effects of DA-125 were nausea, vomiting, leukopenia (especially neutropenia), and thrombocytopenia. Among those, hematological side-effects increased with increased doses of DA-125. No patient developed side-effects equal to or higher than grade III up to DA-125 dose of 60 mg/m2. However, at DA-125 dose of 80 mg/m2, 1 out of 3 patients developed grade III leukopenia and grade IV neutropenia. Therefore, 3 additional patients participated taking the dose of 80 mg/m2; no patient developed side-effects equal to or higher than grade III. Hence, DA-125 dose increased to 100 mg/m2. At DA-125 dose of 100 mg/m2, 2 out of 3 patients developed side-effects equal to or higher than grade III and, therefore, 3 additional patients participated taking this dose. Among the 3 additional patients, 1 patient developed both grade III leukopenia and neutropenia. Therefore, further accrual was stopped at this dose (100 mg/m2). The maximally tolerated dose (MTD) of DA-125 was determined to be 100 mg/m2, and the dose-limiting factor for DA-125 was bone marrow suppression. DA-125 dose of 80 mg/m2, 80% of MTD of DA-125, was recommended as the dose for phase II clinical trial. Cardiotoxicity was not observed in any of the 21 patients according to the ECG and RVG. Neither fever, stomatitis, diarrhea, and renal and nervous system toxicity, nor abnormality in blood coagulation was observed in any of the patients, and death or life-threatening side-effects due to DA-125 were also not observed. Antitumor effects of DA-125 were evaluated from the 21 patients; 6 progressive disease, 14 stable disease, and 1 partial response. Pharmacokinetic parameters of M1, such as AUC, t1/2, CL, VSS, and MRT, seemed to be independent of i.v. doses of DA- 125, 20-100 mg/m2 and less than 0.75% of M1 were excreted in 96 h urine when expressed in terms of DA-125 i.v. dose. M2 was the main metabolite of DA-125 among M1-M4 excreted in urine; 10.1 approximately 22.3% of M2 was excreted in 96 h urine when expressed in terms of DA-125 i.v. dose. Bile was collected via the T-tube in 1 additional patient at the dose of 100 mg/m2. Biliary excretion of M1 and M2 was negligible; less than 0.320 and 4.76% of M1 and M2, respectively, were excreted in 96 h bile when expressed in terms of DA-125 i.v. dose.

Impact of tumor necrosis factor alpha on mouse embryonic stem cells

Previous studies have shown the adverse impact of the cytokine tumor necrosis factor alpha (TNFalpha) on the development of the inner cell mass in mouse blastocysts. In the present study, two embryonic stem (ES) cell lines were used to further investigate the action of TNFalpha. The expression of TNFalpha receptors in ES cells was tested by reverse transcription-polymerase chain reaction and Northern blot analysis. Transcripts encoding the two distinct receptor isoforms were detected in these cells. Using different approaches, our data showed a TNFalpha dose-dependent decrease in the number of ES cells after 24 h of exposure. Simultaneous blocking of the two receptors with antagonist antibodies was needed to completely abrogate the inhibitory effect of the cytokine. Extensive DNA nicks (visualized by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling [TUNEL] method), but not nuclear fragmentation, was found with a higher incidence in ES cells exposed to TNFalpha. The possibility that TNFalpha may stimulate ES cell differentiation was investigated with a test based on the expression of alkaline phosphatase. The results indicated that TNFalpha cannot over-ride the negative control exerted by leukemia inhibitory factor on differentiation. The opposite possibility, that TNFalpha blocks differentiation, was tested in suspended medium drops. In this system, TNFalpha was found to decrease the ability of ES cells to differentiate into embryoid bodies. In addition, expression of Rex-1, a marker gene for undifferentiated ES cells, was increased in ES cells exposed to TNFalpha. Thus our data support the hypothesis that TNFalpha is a significant (negative) effector of proliferation and differentiation in inner cell mass-derived ES cells.

All-trans retinoic acid induced differentiation of rat mammary epithelial cells cultured in serum-free medium

Retinoids are applied to not only cancer prevention but also cancer chemotherapy by stimulating differentiation of cells. We studied differentiation inducing effect of all-trans retinoic acid (ATRA) by studying proportion of high dense fractions of stem-like cells and the size of S phase fraction in cell cycle. From mammary organoids obtained from 7- to 8-week old F344 female rat mammary gland, we cultured rat mammary epithelial cells (RMEC) and treated physiological doses of 10(-6), 10(-7), and 10(-8) M ATRA from the first day and then cultured for 4, 7, and 14 days. After that, immunostaining was performed using peanut agglutinin (PNA) and anti-Thy-1.1 monoclonal antibody (Thy-1.1) that can be used as markers of differentiation. We separated four different cell subpopulations by flow cytometry: cells negative to both reagents (B-), PNA-positive cells (PNA+), Thy-1.1-positive cells (Thy-1.1+), and cells positive to both reagents (B+). We observed continuous decreases of high dense fractions of stem-like cells (PNA+ subpopulations) for 14 days and as much decreases as high doses of ATRA, which were thought to be proportional to doses of ATRA. We labeled RMEC with bromodeoxyuridine and investigated cell cycle fractions that went through S phase. We observed a tendency of decrease of S phase fraction with time in culture, which is thought to be related to continuous decreases of PNA+ subpopulations and inhibitory role of ATRA on cell cycle. These results suggest that physiological doses of ATRA could stimulate differentiation of RMEC and convert stem-like RMEC to differentiated cells in SFM for a relatively long period of 14 days.

Localization of transferrin binding protein in relation to iron, ferritin, and transferrin receptors in the chicken cerebellum

We have demonstrated that transferrin binding protein (TfBP), ferritin, and iron, are specifically localized in Bergmann glia, while the transferrin receptor is confined to Purkinje cells in the chicken cerebellum. The results of this study suggest that Bergmann glia have previously undescribed functions related to iron regulation such as sequestration of iron and the maintenance of iron homeostasis in the cerebellum.

Antitumor agents. 185. Synthesis and biological evaluation of tridemethylthiocolchicine analogues as novel topoisomerase II inhibitors

Several 1,2,3-tridemethyldeacetylthiocolchicine derivatives have been synthesized and evaluated for cytotoxic activity against various human tumor cell lines and for their inhibitory effects on DNA topoisomerases in vitro. Exhaustive demethylation of thiocolchicine analogues completely changes their biological profiles. Instead of displaying antitubulin activity, most target compounds inhibited topoisomerase II activity. Only compounds with a larger side chain, such as 15a, 23a, and 24a, did not interfere with topoisomerase II enzymatic functions. The cytotoxicity of target compounds was reduced by 3 orders of magnitude compared to that of colchicine in most cell lines. The hydrophilicity of phenolic compounds might prevent drug passage through the cell plasma membrane and, thus, be responsible for the relatively weak cytotoxicity. To test this hypothesis, 27-30 were prepared from 16a by protecting all hydroxy groups with esters with an aim to facilitate drug transportation. In vitro cytotoxicity assays indicated that 27 was more potent than its parent compound in all tested tumor cell lines and showed tissue selective cytotoxicity with a significant inhibitory effect against KB cells (IC50 = 2.7 microg/mL). Therefore, we propose that 27 acts as a prodrug, liberating 16a to exert its antitopoisomerase activity and, finally, to cause cell death.

Anti-AIDS agents. 32. Synthesis and anti-HIV activity of betulin derivatives

Eleven betulin derivatives were prepared and evaluated for anti-HIV activity in H9 lymphocytes. Compound 4 was found to be the most active with EC50 and TI values of 0.00066 microM and 21,515, respectively.