AN ACOUSTIC LINK BETWEEN BLUE WHALES IN THE EASTERN TROPICAL PACIFIC AND THE NORTHEAST PACIFIC1

Blue whale calls in the eastern North Pacific Ocean consist of a two-part call often termed the A-B call. This call has been described for regions offshore of Oregon, Washington, and California, USA and the Sea of Cortez, Mexico (reviewed in Rivers 1997). Data collected from moored hydrophones in the eastern tropical Pacific (ETP) indicate that the A-B pattern is common in this region as well. There is consistency in this call type throughout the eastern North Pacific and throughout the year. This acoustic evidence indicates continuity between blue whales in the ETP and those found west of North America. The acoustic data suggest that the population of blue whales generally referred to as the “Californi/Mexico” stock might better be termed the “northeast Pacific” stock of blue whales.     

Fluorescence microscopy of mycobacteria in pleural effusions

The diagnostic advantage of fluorescence microscopy (FM) of Papanicolaou-stained cytological specimens obtained by bronchoscopy has been described previously. This study was designed to evaluate the method's diagnostic benefit in cytological preparations of pleural effusions in cases of active pulmonary tuberculosis. In contrast to bronchial material there is no advantage in cytological evaluation of pleural effusions by FM.     

Detection of Vibrio parahaemolyticus in Penaeus chinensis using an indirect fluorescent antibody staining procedure

An indirect fluorescent antibody technique (iFAT) incorporating fluorescein-isothiocyanate conjugated anti-rabbit globulin goat serum, and rhodamine-isothiocyanate conjugated bovine serum albumin as background stain has been developed for the detection of Vibrio parahaemolyticus.     

银染技术在生殖细胞研究中的应用

新近对传统的银染技术作出改良,以氨银反应观察精子发生及受精过程中碱性蛋白的更替,以Ａｇ－Ａｓ反应观察精子发生过程中ＮＯＲ,嗜银细胞器,细胞骨架及其它嗜银成份的变化以及皮层皮应中嗜银成分的变化。     

Effect of palmitate on carbohydrate utilization and Na/K-ATPase activity in aortic vascular smooth muscle from diabetic rats

Immediately after bacterial endotoxin (LPS) enters the circulatory system there is increased production of free oxygen radicals by cells of the reticulo-endothelial system, followed by the release of cytokines considered as putative endogenous pyrogens. Fever originates by central nervous system activities, but neither exogenous nor endogenous pyrogens are able to cross the blood-brain barrier and the true signal which is transmitted to structures inside the blood-brain barrier is still unknown. To study the role of oxygen radicals in fever, we pretreated rats with methylene blue, an inhibitor of superoxide and hydroxyl radical production and investigated the febrile response to LPS in conscious rats by measuring malondialdehyde formation as an index of lipid peroxidation by oxygen radicals. Methylene blue lowered resting malondialdehyde levels to near detection level and significantly suppressed its rise which was regularly found following LPS in the untreated state. Pretreatment with methylene blue completely blocked the febrile response. Since fever is a central nervous system-mediated response these results indicate that the brain is able to sense oxidative stress and vicinal thiol groups of the redox-modulatory site of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor-channel complex could function as a possible receptive structure. To test this hypothesis we injected rabbits with the disulfide reducing agent dithiothreitol (DTT), known to penetrate the blood-brain barrier, and monitored its effect on normal and febrile body temperatures. DTT induced, independently of ambient temperature, within minutes and dose-dependently the full pattern of heat loss responses causing a fall of core temperature, indicative of a lowered thermoregulatory setpoint. Pretreatment with a bolus dose of 5 mg/kg DTT, followed by a continuous infusion of 5 mg/kg/h for 3 h completely prevented LPS-induced fever. A bolus dose of 20 mg/kg DTT, starting 30 min after LPS, immediately reversed the febrile cold defense pattern and lowered body temperature. We conclude that DTT reduces in the central nervous system oxidized vicinal thiol groups of NMDA receptors, thereby augmenting glutamate-induced nitric oxide synthase activation, and, thus, enhanced formation of NO, which, in turn, lowers the thermoregulatory setpoint. Reduction of other disulfide-containing molecules, especially oxidized glutathione and thiol-containing enzymes, by DTT by might additionally contribute to preventing fever.     

Viability staining of soybean suspension-cultured cells and a seedling stem cutting assay to evaluate phytotoxicity of Fusarium solani f. sp. glycines culture filtrates

The phytotoxicity of culture filtrates of Fusarium solani f. sp. glycines, the fungus causing sudden death syndrome (SDS) of soybean (Glycine max), was tested with a viability stain of soybean suspension-cultured cells and a stem cutting assay of soybean seedlings. Suspension-cultured cells from a SDS-susceptible soybean cultivar were exposed to cell-free culture filtrates of F. solani f. sp. glycines or other F. solani isolates for 2, 4, 6, and 8 days and then stained with 0.1% phenosafranin. The percentage of dead soybean suspension-cultured cells was greater (P<0.001) with filtrates prepared from F. solani f. sp. glycines than from other F. solani isolates, and dead cells increased over time and with higher concentrations of culture filtrate. Cuttings of soybean seedlings with their stems immersed in culture filtrates of F. solani f. sp. glycines isolates developed SDS-like foliar symptoms, but not when immersed in filtrates of other isolates. There was a positive correlation (r=0.94, P<0.001) between soybean foliar symptom severity and percentage of stained soybean suspension-cultured cells. Both methods were used to determine the phytotoxicity of fungal culture filtrates. Received: 9 December 1997 / Revision received: 10 August 1998 / Accepted: 28 August 1998     

Cell death in individual freshwater phytoplankton species: relationships with population dynamics and environmental factors

ABSTRACT

Understanding and predicting changes in phytoplankton populations requires knowledge of losses due not only to sedimentation and grazing, but also to intrinsic processes (here, collectively termed ‘cell death’). Cell death is poorly understood, especially in freshwater phytoplankton, but experiments in culture often suggest involvement of abiotic factors (e.g. temperature, light, nutrients). The occurrence of cell death was examined in a simple, natural environment: a small, well-mixed, temperate, urban pond during a period of phytoplankton growth, from mid-July to mid-November. Abundances of 18 phytoplankton taxa were measured weekly and fluorescence microscopy and staining was used to detect dead cells (using SYTOX which measures loss of membrane integrity) and cells undergoing cell death (using Annexin-V, which measures lipid inversions of membranes, an early signal of cell death). Dead and dying cells occurred in most phytoplankton taxa, but incidence and timing varied considerably, e.g. species like the chlorophyte Ankistrodesmus spiralis showed 20–30% of cells staining with SYTOX and Annexin in late autumn when the population was decreasing, while the dinoflagellate Peridinium sp. showed staining of up to 50% of cells with STYOX throughout the period, and the cyanobacterium Microcystis aeruginosa occasionally showed staining of 100% of cells with SYTOX. Overall, there was some association between cell death staining and growth phase with 10–15% of the total community showing SYTOX and Annexin staining in late autumn, when most populations were declining. Cell death could not be correlated with thresholds or rapid changes in abiotic conditions (e.g. temperature, irradiance) or with indicators of nutrient limitation (e.g. N:P ratios). While abiotic factors have been clearly implicated in cell death within unialgal culture experiments, in natural freshwater ecosystems interactions between biotic factors, such as pathogens or allelopathy, may play greater roles in losses related to cell death and be distinct for different taxa.     

Applying methods of hard tissues preparation for wood anatomy: Imaging polished samples embedded in polymethylmethacrylate

Cambial activity records short and long-term environmental signals in xylem anatomy, creating a permanent archive. Quantitative wood anatomy deciphers the relationship between cell structure and function in a spatiotemporal context. Obtaining high-resolution images of wood anatomical preparations is a critical stage in the process of decoding this information. Damage to cellular structures when sectioning by microtome is one of the main problems in the preparation of high-quality micro-sections. Cell damage leads to the occurrence of artifacts – most often related to broken cell walls – hindering the performance of image recognition programs, and increasing the time spent on the manual editing of images. In this work, we propose an alternative method to microtomy, based on embedding-polishing protocols established for hard tissue preparation. Wood samples are embedded in a transparent and non-reactive resin as polymethylmethacrylate (PMM) that is subsequently ground and polished. Being able to acquire images from the stained or unstained polished surfaces of the PMM-blocks and sections (thinner than 100 μm) by using a wide range of optical methods such as reflected polarizing microscopy, epifluorescence microscopy, bright-field microscopy with diffuse illumination and circularly polarizing microscopy. This embedding method improves the mechanical integrity and quality of wood anatomical preparations, eliminating the problem of broken cell walls. Furthermore, this technique allows the preparation and analysis of large tissue surfaces.     

Colorimetric detection of residual quaternary ammonium compounds on dry surfaces and prediction of antimicrobial activity using bromophenol blue

Controlling and monitoring the residual activity of quaternary ammonium compounds (QACs) are critical for maintaining safe yet effective levels of these agents in the environment. This study investigates the utility of bromophenol blue (BPB) as a safe, rapid and user-friendly indicator to detect in situ residual QACs dried on hard, non-porous surfaces, as well a means to assess their antimicrobial efficacy. At pH 7, BPB has a purple colour which turns blue upon its complexation with QACs such as didecyldimethylammonium chloride (DDAC). BPB itself has no antimicrobial properties up to 400 ppm. Within the range of 0–400 ppm, BPB colour change was tied to specific DDAC antimicrobial performances with a detection threshold of 100 ppm. BPB concentration and application volume could be adjusted such that a colour shift from purple to blue correlated with a set percent reduction (>99·9%) in test bacteria (Staphylococcus aureus and Klebsiella aerogenes). The BPB solutions developed in this study yielded similar colour shifts on polycarbonate and stainless steel surfaces and did not cross-react with chemical ingredients commonly found in sanitizers and disinfectant products. Overall, this study suggests that BPB provides a simple solution to safely monitor the post-application level and biocidal activity of residual dried QACs on surfaces.