P‐11THE IMPACT OF INTRODUCING LIQUID BASED CYTOLOGY INTO A ROUTINE SCREENING LABORATORY

Introduction: A glacial acetic acid wash performed retrospectively or prospectively on visibly bloodstained cervical ThinPrep® specimens can reduce the unsatisfactory rate and increase the number of diagnostic epithelial cells. This study was undertaken to determine which specimens are most likely to benefit from a prospective glacial acetic acid wash. Methods: Bloodstained ThinPrep® specimens selected for routine lysing prior to processing were macroscopically assessed and scored based on the level of blood present (+ to +++). Both unlysed and lysed slides were prepared from each specimen and microscopically examined. Results: Fifty‐eight specimens (32 scored +, 12 ++ and 14+++) were assessed. Three unlysed slides prepared from the ++ specimens and 12 from +++ specimens were evaluated as unsatisfactory due to excessive blood and inadequate numbers of squamous cells. In contrast, only one of the unlysed slides from the 32 + specimens was considered to be unsatisfactory. Almost all the lysed slides were satisfactory and generally more cellular than the unlysed slides. Abnormal cells were found in four cases (both unlysed and lysed paired slides). Discussion: Although the acetic acid wash increases cellularity of bloodstained ThinPrep® specimens, prospectively lysing all bloodstained specimens is an unnecessary procedure. Lysing only very heavily bloodstained specimens prior to processing will reduce laboratory workload, costs and the possibility of specimen mix up. Occasionally a retrospective wash may be required but screening staff should be aware that although blood may be present on an unlysed ThinPrep® slide, a lysed slide should not be requested unless there are insufficient numbers of squamous cells present.     

A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques

After disulphide bonds are reduced with dithiothreitol, trans-3- (α-bromomethyl)-3’-[α- (trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 μM carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[α-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules.     

干扰素研究及应用进展

1957年,英国科学家Isaacs和Lindenmann利用鸡胚绒毛尿囊研究流感干扰现象时,发现一种能够干扰病毒繁殖的物质,称之为干扰素（IFN）,由于干扰素对许多疾病有很好的治疗作用,一直是医学领域研究的重要物质之一。现在干扰素已成功地用于肝炎、肿瘤治疗等方面。为了充分发挥干扰素的作用,人们稍用基因工程的方法来对干扰素的产量及功效进行改进,已达到更好的应用,因此基因工程干扰素越来越多地成了研究的重点。     

人热休克蛋白gp96基因的克隆及其在大肠杆菌中的表达与纯化

热休克蛋白gp96是热休克蛋白90家族成员,能够引起非特异性和特异性免疫反应。得到大量高纯度的蛋白质是研究开发gp96的关键。然而重组的gp96容易在E．coli中降解,并在一定条件下形成多聚体。实验先将人gp96基因克隆到pET-30a载体上并在E．coli Blstar中表达,再经过亲和层析、阴离子交换、分子筛分别纯化gp96。最终去掉了大部分的降解片段和多聚体,得到一定量的可溶性gp96,为进一步研究其结构和功能打下一定的基础。     

Distribution in tissue homogenates,and the nature of the linkage of injected proteins to subcellular particles

Intravenously injected labeled proteins were recovered mostly in particulate fractions of rat liver homogenate. Distribution showed changes depending on the time elapsed from the injection. ¹³¹I-albumin undergoes an intraparticulate hydrolysis which shows the highest activity in the gradient fractions associated with the highest level of acid phosphatase. The labeled albumin-bearing particles separated at 27,000 g × 10 minutes released their radioactive protein at the same rate as acid phosphatase appeared in the medium, under the effect of such agents as distilled water, salts, homogenization, sonication and pH changes. The substitution of sucrose for distilled water or salts showed that the particles behave as an osmotic system as do lysosomes. These experiments prove that secondary lysosomes involved in the hydrolysis of foreign proteins, whose existence was shown by other authors only at the histochemical level, may survive the distrupting action of conventional homogenization and maintain many properties characteristic of primary lysosomes in addition to the ability of hydrolysing “in vitro” the engulfed material.     

Biodeterioration of Mayan buildings at uxmal and tulum,Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.