Analysis of the structure and expression of the c-myc oncogene in cervical tumor and in cervical tumor-derived cell lines

The structure of the c-myc oncogene in 17 cervical tumors and patient-matched nontumor tissues from Chinese patients residing in Taiwan was analysed. In contrast to recent reports on Mexican patients, none of the samples showed rearrangements and sequence amplification in the c-myc gene. The discrepancy may be explained by different carcinogenesis mechanisms being in operation in different geographic regions. Although no structural alterations in the c-myc gene were found in seven cervical carcinoma cell lines analysed, Northern blot analysis indicated different levels of c-myc gene expression which may be related to the presence of human papillomavirus (HPV) sequence in the cell and suggests a possible c-myc-hpv interaction in some stages of the transformation process.     

Prophylactic immunization against experimental leishmaniasis. IV. Subcutaneous immunization prevents the induction of protective immunity against fatal Leishmania major infection

Durable immunity against fatal L. major infection in genetically susceptible mice can be induced by immunization with 150,000-rad irradiated or heat-killed promastigotes administered i.v. or to a lesser extent i.p. Conversely, subcutaneous (s.c.) and intramuscular (i.m.) injections are not only totally ineffective but generally increase susceptibility to and enhance the progression of the disease, leading to earlier mortality. This detrimental effect is particularly evident with lower infecting challenge doses. Disease exacerbation is apparent in mice given 4 X s.c. injections of as few as 2 X 10(4) irradiated promastigotes, but it appears most potent after doses of 2 X 10(7). When mice given 4 X s.c. injections were subsequently immunized i.v. with 2 X 10(7) irradiated promastigotes, they failed to develop any evidence of protection against infection with 2 X 10(5) promastigotes, whereas mice given i.v. immunization alone were strongly protected. Thus, s.c. injections are capable of blocking the prophylactic effect of i.v. immunization with irradiated parasites. This inhibitory effect can be achieved with a single s.c. injection, although rather less potently than with four, and is even effective against four repeated weekly i.v. immunizations. Once induced, the effect persists undiminished after 100 days. A weaker effect is also inducible by s.c. injection given after i.v. immunization. The blocking effect of s.c. injection is not dependent on continuing viability of the promastigotes, as it can be induced equally readily with heat-killed, formalin-fixed, or sonicated parasites. The phenomenon extends to mouse strains genetically resistant as well as susceptible to L. major infection and, in congenic mice of BALB background, is independent of the major histocompatibility (H-2) gene complex.     

Prophylactic immunization against experimental leishmaniasis. V. Mechanism of the anti-protective blocking effect induced by subcutaneous immunization against Leishmania major infection

The responsiveness of BALB/c mice to protective i.v. immunization with 150,000-rad irradiated or heat-killed Leishmania major promastigotes can be totally suppressed by prior subcutaneous (s.c.) injection of the same "vaccine." Induction of this effect is leishmania specific for although prevention of protection against L. major infection can be obtained with either homologous or Leishmania donovani promastigotes, it does not follow s.c. administration of an immunogenic Trypanosoma cruzi epimastigote preparation. Multiple s.c. injections of irradiated L. major promastigotes do not inhibit the subsequent antibody response of any major isotype to i.v. immunization, but rather induce some priming. The same s.c. injections induced delayed-type hypersensitivity (DTH) reactivity that could be transferred locally or systemically, although it was weaker than in mice with cured infections. Parallel cell-mediated immunity (CMI) responses were also reflected in vitro in specific lymphocyte transformation assays. Despite this evidence of a DTH/helper type of T cell response, transfer of 5 X 10(7) viable T cell-enriched spleen cells from 4 X s.c. immunized donors to normal recipients completely abrogated the protective response to i.v. immunization. Conversely, T cell-depleted (anti-Thy-1.2 + C treated) cells were without effect. The inhibitory T cells were defined by monoclonal antibody pretreatment as possessing an Lyt-1+2-,L3T4+ phenotype. T cells from s.c. immunized donors were also shown, by mixed transfer experiments, to counteract completely the protective effect of T cells from i.v. immunized donors in 550-rad irradiated recipients. They were as potent as suppressor T cells from donors with progressive disease both in this capacity and in abrogating the prophylactic effect of sublethal irradiation itself. The similarities and differences between suppressor and immune effector T cells induced by s.c. or i.v. immunization and those arising in response to leishmanial infection itself are discussed.     

Enhancement of macrophage IL-1 production by Leishmania major infection in vitro and its inhibition by IFN-gamma

Peritoneal cells from highly susceptible BALB/c mice were infected with Leishmania major and cultured for various times in vitro. The culture supernatants contained significant levels of IL-1 which were consistently higher than those in the cell cultures stimulated with an optimal concentration of LPS. This finding extends to a macrophage cell line, P388D1, and peritoneal exudate cells stimulated with starch in vivo. However, the level of IL-1 produced was significantly reduced when the cells were preincubated with a lymphokine preparation (supernatant of Con A-stimulated rat spleen cells). The level of IL-1 produced seems to be directly correlated with the degree of parasitization of the macrophages. A similar and dose-dependent reduction in IL-1 production by infected macrophages could also be obtained when the cells were preincubated with IFN-gamma. This finding is in direct contrast to that of visceral leishmaniasis in which peritoneal macrophages from BALB/c mice infected with Leishmania donovani not only fail to produce IL-1 but also lose the capacity to produce IL-1. This apparent discrepancy is discussed in terms of a possible difference in the induction of cell-mediated immunity between the two leishmanial diseases.     

嗜盐耐盐微生物抗盐胁迫相关离子转运蛋白研究进展

离子转运蛋白在维持细胞内pH稳态、离子动态平衡等方面发挥着重要作用。钠离子转运体和钾离子转运体在嗜盐耐盐微生物中广泛存在,其"保钾排钠"机制是微生物抗盐胁迫的两大策略之一。近年来,嗜盐耐盐微生物中许多新型钠、钾离子转运体被陆续发现,如RDD蛋白、UPF0118蛋白、DUF蛋白和KimA蛋白等;Fe³⁺、Mg²⁺等其他金属离子的转运蛋白也被证实可通过影响微生物胞内相容性溶质的合成起到渗透调节的作用。本文综述了嗜盐耐盐微生物中抗盐胁迫相关的各类离子转运蛋白,分析其分子结构和工作机理,并对这些蛋白在农业方面的应用进行了展望。继续发现新的离子转运蛋白,探究抗盐胁迫相关离子转运蛋白的结构和机理,解析各转运系统的协同作用及分子调控机制,将进一步加深对嗜盐耐盐微生物抗盐胁迫调控的认识,并为盐碱地农作物的改良等提供新的思路。     

Stabilized bubbles in the body: pressure-radius relationships and the limits to stabilization

Van Liew, Hugh D., and Soumya Raychaudhuri. Stabilizedbubbles in the body: pressure-radius relationships and the limits tostabilization. J. Appl. Physiol.82(6): 2045-2053, 1997.We previously outlined the fundamentalprinciples that govern behavior of stabilized bubbles, such as themicrobubbles being put forward as ultrasound contrast agents. Ourpresent goals are to develop the idea that there are limits to thestabilization and to provide a conceptual framework for comparison ofbubbles stabilized by different mechanisms. Gases diffuse in or out ofstabilized bubbles in a limited and reversible manner in response tochanges in the environment, but strong growth influences will cause thebubbles to cross a threshold into uncontrolled growth. Also, bubblesstabilized by mechanical structures will be destroyed if outsideinfluences bring them below a critical small size. The in vivo behaviorof different kinds of stabilized bubbles can be compared by using plotsof bubble radius as a function of forces that affect diffusion of gasesin or out of the bubble. The two ends of the plot are the limits forunstabilized growth and destruction; these and the curve's slopepredict the bubble's practical usefulness for ultrasonic imaging orO₂ carriage to tissues.

     

丁酸钠和pH值对离体蚕豆花药中小孢子有丝分裂的影响

含单核中后期至后期花粉的蚕豆离体花药,经过2mM丁酸钠24小时预处理后,再漂浮培养于pH5.8或7.0的液体培养基。以不经预处理的作为对照。结果如下: 1.培养后9天内,丁酸钠预处理和培养基pH值并不明显影响花粉退化百分率。2.培养初期,pH7.0显著促进小孢子不等分裂。3.丁酸钠预处理抑制培养初期的小孢子有丝分裂,而后又显著增加小孢子均等分裂百分率。4.丁酸钠预处理导致小孢子有丝分裂类型的趋向改变。本文还对丁酸钠导致有丝分裂类型趋向改变的可能原因,进行了讨论。