局部缓释IUdR治疗恶性星形细胞瘤实验研究

目的研究脑局部缓释125碘标记的 5-碘脱氧尿苷(I U dR)的作用.方法为了控制释放125碘-IUdR,合成了25 μCi的羧基苯氧丙烷:癸二酸(PCPP:SA)(20:80)125碘-IUdR聚合体.体外将合成的三聚体缓释剂(10 mg PCPP:SA) 置于37℃磷酸盐缓冲溶液(PBS)中孵育不同时间后移出溶剂并置换为新的PBS,将移出液于放射计数器上测量数值.在体研究采用雄性裸鼠(6周)颅内接种U251人恶性星形细胞瘤及皮下接种对比研究.将颅内荷瘤鼠瘤腔内及皮下接种肿瘤组织内分别应用三聚体缓释剂及空白缓释剂,于不同时间分别测量动物头颅及皮下结节的放射活性,间接定量研究缓释状况;采血了解全身代谢情况.对于多聚磷酸酯(PPE)缓释剂研究采用皮下肿瘤结节内局部应用并测量其缓释的方法,放射自显影研究及全身不同器官缓释剂的吸收代谢研究采用接种后2、4和8 d收集标本,分别行切片放射自显影和器官放射活性测定.结果体内和体外研究均显示PCPP:SA缓释剂对125碘-IUdR的控制性释放作用,尤其在体研究分别显示颅内和皮下接种的肿瘤组织对标记的IUdR的释放程度存有极大的差异,提示颅内局部应用的优越性.放射自显影定性研究显示了随距离的增加被标记的IUdR的递减趋势,为确定缓释剂施放部位和间距提供了参考数据.各主要脏器放射性测定的结果显示早期小肠内放射性较高,其次为脾脏,提示IUdR主要的代谢渠道,为处理应用其而可能引发的其他脏器损害或作用提供了线索.结论放射标记的IUdR缓释剂主要集中在接种部位且缓释作用确切.     

Maternal germ-line transmission of mutant mtDNAs from embryonic stem cell-derived chimeric mice

We report a method for introducing mtDNA mutations into the mouse female germ line by means of embryonic stem (ES) cell cybrids. Mitochondria were recovered from the brain of a NZB mouse by fusion of synaptosomes to a mtDNA-deficient (rho degrees ) cell line. These cybrids were enucleated and the cytoplasts were electrofused to rhodamine-6G (R-6G)-treated female ES cells. The resulting ES cell cybrids permitted transmission of the NZB mtDNAs through the mouse maternal lineage for three generations. Similarly, mtDNAs from a partially respiratory-deficient chloramphenicol-resistant (CAP(R)) cell line also were introduced into female chimeric mice and were transmitted to the progeny. CAP(R) chimeric mice developed a variety of ocular abnormalities, including congenital cataracts, decreased retinal function, and hamaratomas of the optic nerve. The germ-line transmission of the CAP(R) mutation resulted in animals with growth retardation, myopathy, dilated cardiomyopathy, and perinatal or in utero lethality. Skeletal and heart muscle mitochondria of the CAP(R) mice were enlarged and atypical with inclusions. This mouse ES cell-cybrid approach now provides the means to generate a wide variety of mouse models of mitochondrial disease.     

Starch grains on human teeth reveal early broad crop diet in northern Peru

Previous research indicates that the Ñanchoc Valley in northern Peru was an important locus of early and middle Holocene human settlement, and that between 9200 and 5500 ¹⁴C yr B.P. the valley inhabitants adopted major crop plants such as squash (Cucurbita moschata), peanuts (Arachis sp.), and cotton (Gossypium barbadense). We report here an examination of starch grains preserved in the calculus of human teeth from these sites that provides direct evidence for the early consumption of cultivated squash and peanuts along with two other major food plants not previously detected. Starch from the seeds of Phaseolus and Inga feuillei, the flesh of Cucurbita moschata fruits, and the nuts of Arachis was routinely present on numerous teeth that date to between 8210 and 6970 ¹⁴C yr B.P. Early plant diets appear to have been diverse and stable through time and were rich in cultivated foods typical of later Andean agriculture. Our data provide early archaeological evidence for Phaseolus beans and I. feuillei, an important tree crop, and indicate that effective food production systems that contributed significant dietary inputs were present in the Ñanchoc region by 8000 ¹⁴C yr B.P. Starch grain studies of dental remains document plants and edible parts of them not normally preserved in archaeological records and can assume primary roles as direct indicators of ancient human diets and agriculture.     

Errors in the determination of left ventricular functional parameters

Gated blood-pool scans of the left ventricle are routinely employed for determination of the left ventricular ejection fraction. Recently, attempts have been made to evaluate other left ventricular functional parameters. These values include peak emptying rate (PER), time to peak emptying rate (TPER), peak filling rate (PFR), and time to peak filling rate (TPFR). In studying these parameters clinically, we identified many software errors and assumptions that impact on these values. These errors may also affect the determination of left ventricular ejection fraction (EF). We conclude that before any serious investigation of left ventricular functional parameters is undertaken, a detailed evaluation and standardization of the acquisition and edge detection algorithms must be performed.     

Colonic cell proliferation and aberrant crypt foci formation are inhibited by dairy glycosphingolipids in 1, 2-dimethylhydrazine-treated CF1 mice

Dietary sphingomyelin (SM) inhibits early stages of colon cancer (appearance of aberrant crypt foci, ACF) and decreases the proportion of adenocarcinomas vs. adenomas in 1,2-dimethylhydrazine (DMH)-treated CF1 mice. To elucidate the structural specificity of this inhibition, the effects of the other major sphingolipids in milk (glycosphingolipids) were determined. Glucosylceramide (GluCer), lactosylceramide (LacCer) and ganglioside G(D3) were fed individually to DMH-treated (six doses of 30 mg/kg body weight) female CF1 mice at 0.025 or 0.1 g/100 g of the diet for 4 wk. All reduced the number of ACF by > 40% (P < 0.001), which is comparable to the reduction by SM in earlier studies. Immunohistochemical analysis of the colons revealed that sphingolipid feeding also reduced proliferation, with the most profound effect (up to 80%; P < 0.001) in the upper half of the crypts. Since the bioactive backbones of the glycosphingolipids (i.e., ceramide and other metabolites) are the likely mediators of these effects, the susceptibility of these complex sphingolipids to digestion in the colon was examined by incubating 500 microgram of each sphingolipid with colonic segments from mice and analysis of substrate disappearance and product formation by tandem mass spectrometry. All of the sphingolipids (including SM) disappeared over time with a substantial portion appearing as ceramide. Partially hydrolyzed intermediates (such as GluCer from LacCer or G(D3)) were not detected, which suggests that the cleavage involves colonic (or microflora) endoglycosidases. In summary, consumption of dairy SM and glycosphingolipids suppresses colonic cell proliferation and ACF formation in DMH-treated mice; hence, many categories of sphingolipids affect these key events in colon carcinogenesis.     

Inhibition of Moloney murine lymphoma and sarcoma growth in vivo by dietary retinoids

The effects of dietary retinoids on the growth of Moloney lymphoma (LSTRA) and sarcoma (MSC) in BALB/c mice were evaluated. Transplantable syngeneic Moloney lymphoma and sarcoma tumors are immunogenic. Preimmunization with LSTRA cells provides protection against subsequent challenge and sarcomas spontaneously regress following injection of an appropriate inoculum of MSC cells. In normal mice fed varying concentrations of all-trans-retinoic acid (RA) and given injections of 10(3) LSTRA cells, RA caused a dose-dependent increase in the number of survivors; 50% of the mice fed RA at 50 mg/kg of diet were long-term survivors. All animals died that were fed a control diet and challenged with 10(3) LSTRA cells. Athymic (nu/nu) mice fed RA were not protected against lymphoma growth, whereas euthymic (nu/+) mice were; therefore, the antitumor effect of RA was thymus dependent. Primary immunization with irradiated LSTRA in the presence of RA caused a significant increase in cell-mediated cytotoxicity by spleen cells at 4 days after immunization. However, challenge of animals preimmunized with LSTRA in the presence of dietary RA revealed a dose-dependent inhibition of memory. A significant reduction in MSC growth was also observed in normal mice fed 13-cis-retinoic acid (cRA). A comparison of the primary antilymphoma effect of dietary RA, cRA, N-(all-trans-retinoyl)-DL-leucine (RL), and N-(4-hydroxyphenyl)retinamide (4-HPR) revealed an efficacy hierarchy of RL greater than RA greater than cRA greater than 4-HPR with RL producing 70% long-term survivors at 115 days after challenge with 10(3) LSTRA cells. These studies indicate that retinoids can inhibit the growth of transplantable, retroviral-induced, immunogenic tumors by thymus-dependent mechanisms and that a newly synthesized retinoylamino acid (RL) is more potent than RA at inhibiting Moloney lymphoma growth.     

Disruption of p53 in human cancer cells alters the responses to therapeutic agents

We have examined the effects of commonly used chemotherapeutic agents on human colon cancer cell lines in which the p53 pathway has been specifically disrupted by targeted homologous recombination. We found that p53 had profound effects on drug responses, and these effects varied dramatically depending on the drug. The p53-deficient cells were sensitized to the effects of DNA-damaging agents as a result of the failure to induce expression of the cyclin-dependent kinase inhibitor p21. In contrast, p53 disruption rendered cells strikingly resistant to the effects of the antimetabolite 5-fluorouracil (5-FU), the mainstay of adjuvant therapy for colorectal cancer. The effects on 5-FU sensitivity were observed both in vitro and in vivo, were independent of p21, and appeared to be the result of perturbations in RNA, rather than DNA, metabolism. These results have significant implications for future efforts to maximize therapeutic efficacy in patients with defined genetic alterations.