Ecophysiology of Salt Excretion in Aeluropus litoralis (Graminae)

Various aspects of salt excretion from leaves of Aeluropus were investigated. Salt excretion exhibited an optimum-type of curve when measured against external salt concentration, while sodium content of the leaves increased linearly. The ‘relative excretion’, i.e. rate of excreted ions: change in leaf ion content, was maximal in the low salt concentration range, and decreased when external sodium chloride concentration increased. Concentration of the excreted droplets was higher than the external concentration when the leaves were exposed to low salt concentrations in the medium, but the reverse occurred when the external salt concentrations were high. The excretion process was sensitive to water-stress conditions, caused either by high external salt concentrations or by exposure to dry atmosphere. A considerable fraction of the leaf sodium content in salt-treated leaves was only slightly available for excretion. Salt excretion in Aeluropus was enhanced by light. Such enhancement was indirect and is attributed to the increase of salt transport via transpiration stream. Selectivity of the salt-excretion mechanism is in favour of sodium and against potassium. On the other hand, potassium has a high affinity for the accumulation systems within the leaves. The ecological significance of the results is discussed.     

The Increasing Adenine Nucleotide Concentration and the Maturation of Rat Liver Mitochondria during Neonatal Development

The levels of adenosine triphosphate, diphosphate, and monophosphate in liver and isolated liver mitochondria were examined in foetal, neonatal, and suckling rats. It was shown that while the total adenine nucleotide level in liver varied only slightly during development, there was a steady increase in the concentration of mitochondrial adenine nucleotides. This increase was most dramatic just after birth. Experiments using pups obtained by caesarean section one day prior to normal birth and kept in a humidicrib for up to two hours, showed that the mitochondrial adenine nucleotide level doubles during this period. This increase is associated with the maturation of the mitochondrial inner membrane as measured by the enhancement of respiratory control.
The results indicate that in addition to the adenine nucleotide translocator—which effects the exchange of adenosine triphosphate and diphosphate—there must be a second transport mechanism present, at least in perinatal mitochondria, which is responsible for the net uptake of adenine nucleotides.
The adenine nucleotides in this study were measured, using a modified luciferin—luciferase assay. In this method the preincubation of sample with appropriate enzymes to convert adenosine monophosphate and diphosphate to adenosine triphosphate, was carried out in the same scintillation vial as the final assay. This eliminated a second sampling step and thereby increased the convenience, speed, and accuracy of this very sensitive method.     

ASSOCIATION OF SYNTAXIN WITH SNAP 25 AND VAMP (SYNAPTOBREVIN) IN TORPEDO SYNAPTOSOMES

Two proteins of the presynaptic plasma membrane, syntaxin and SNAP 25, and VAMP/synaptobrevin, a synaptic vesicle membrane protein, form stable protein complexes which are involved in the docking and fusion of synaptic vesicles at the mammalian brain presynaptic membrane. Similar protein complexes were revealed in an homogeneous population of cholinergic synaptosomes purified from Torpedo electric organ by combining velocity sedimentation and immunoprecipitation experiments. After CHAPS solubilization, virtually all the nerve terminal syntaxin was found in the form of large 16 S complexes, in association with 65% of SNAP 25 and 15% of VAMP. Upon Triton X100 solubilization, syntaxin was still recovered in association with SNAP 25 and VAMP but in smaller 8 S complexes. A small (2–5%) percentage of the nerve terminal 15 kDa proteolipid subunit of the v-H⁺ ATPase and of mediatophore was copurified with syntaxin, using two different antisyntaxin monoclonal antibodies. The use of an homogeneous population of peripheral cholinergic nerve terminals allowed us to extend results on the composition of the brain presynaptic protein complexes to the Torpedo electric organ synapse, a model of the rapid neuromuscular synapses. Copyright © 1996 Elsevier Science Ltd     

Histopathological diagnosis of myocarditis in a dengue outbreak in Sri Lanka, 2009

Background

In 2009, an outbreak of dengue caused high fatality in Sri Lanka. We conducted 5 autopsies of clinically suspected myocarditis cases at the General Hospital, Peradeniya to describe the histopathology of the heart and other organs.

Methods

The diagnosis of dengue was confirmed with specific IgM and IgG ELISA, HAI and RT-PCR techniques. The histology was done in tissue sections stained with hematoxylin and eosin.

Results

Of the 319 cases of dengue fever, 166(52%) had severe infection. Of them, 149 patients (90%) had secondary dengue infection and in 5 patients, DEN-1 was identified as the causative serotype. The clinical diagnosis of myocarditis was considered in 45(27%) patients. The autopsies were done in 5 patients who succumbed to shock (3 females and 2 males) aged 13- 31 years. All had pleural effusions, ascites, bleeding patches in tissue planes and histological evidence of myocarditis. The main histological findings of the heart were interstitial oedema with inflammatory cell infiltration and necrosis of myocardial fibers. One patient had pericarditis. The concurrent pulmonary abnormalities were septal congestion, pulmonary haemorrhage and diffuse alveolar damage; one case showed massive necrosis of liver.

Conclusions

The histology supports occurrence of myocarditis in dengue infection.

     

MAPPING CELL WALL POLYSACCHARIDES OF LIVING MICROBIAL CELLS USING ATOMIC FORCE MICROSCOPY

Functionalized atomic force microscope tips were used to sense specific forces of interaction between ligand—receptor pairs and to map the positions of polysaccharides on a living microbial cell surface. Gold-coated tips were functionalized with concanavalin A using a cross-linker with a spacer arm of 15.6Å. It was possible to measure the binding force between concanavalin A and mannan polymers on the yeast (Saccharomyces cerevisiae) cell surface. This force ranged from 75 to 200pN. The shape of the force curve indicated that the polymers were pulled away from the cell surface for a fairly long distance that sometimes reached several hundred nanometres. The distribution of mannan on the cell surface was mapped by carrying out the force measurement in the force volume mode of atomic force microscopy (AFM). During the measurement, the maximum cantilever deflection after contact between the tip and the sample was kept constant at 10nm using trigger mode to keep the pressing force on the sample surface as gently as possible at a force of 180pN. This regime was used to minimize the non-specific adhesion between the tip and the cell surface. Specific molecular recognition events took place on specific areas of the cell surface that could be interpreted as reflecting a non-uniform distribution of mannan on the cell surface.     

Biochemical key to eight species of adult Egyptian mosquitoes

1. An electrophoretic key is described, based on enzyme relative mobility, to distinguish eight species of Egyptian mosquito adults. 2. Using horizontal starch gel electrophoresis, five different enzyme assays unambiguously separated Culex pipiens L., Cx antennatus (Becker), Cx pusillus Macquart, Aedes caspius (Pallas), Culiseta longiareolata (Macquart), Uranotaenia unguiculata Edwards, Anopheles multicolor Cambouliu and An.pharoensis Theobald. 3. Diagnostic loci between species were: Ak-2, G6pd, alpha-Gpd, Gpi and 6-Pgd; the probability of correct diagnosis in each case was at least 0.989.     

AN ECOPHYSIOLOGICAL STUDY OF THE SALT SECRETION OF FOUR HALOPHYTES

Plants of Spartina anglica, Limonium vulgare, Armeria maritima and Glaux maritima were collected in the field and grown on different concentrations of NaCl, KCl and CaCl₂. Salt secretion, ion content, water content and transpiration rates were determined. The highest sodium secretion was found in Spartina anglica , a species from the most saline habitat; and a somewhat lower secretion rate in Limonium vulgare. The lowest rates were found in Glaux maritima and Armeria maritima. The sodium secretion efficiency, i.e. the ability to maintain an unchanged internal sodium content, was highest in Spartina anglica. Spartina anglica is the most successful in the removal of excessively absorbed salt, since it secretes 60% of the absorbed sodium. The values for Limonium vulgare, Glaux maritima and Armeria maritima were 33, 20 and 4% respectively. The species studied differ in the preferential sequence of ion secretion as well as in secretion rate and efficiency. This preferential sequence of ion secretion seems to be similar in members of the same taxonomic group (Plumbaginaceae). The comparability of the secretion parameters is discussed with regard to morphological differences between the species.