Effect of sodium nitroprusside on H+-ATPase activity and ATP concentration in Candida albicans

ATP hydrolysis by plasma membrane H+-ATPase from Candida albicans has been investigated in presence of nitric oxide and various nutrients (sugars and amino acids). Sodium nitroprusside (SNP) was used as nitric oxide donor. It was found that ATP concentration decreased in SNP treated cells which was more in presence of sugars like glucose, xylose and 2-deoxy-D-glucose and amino acids as compared to their respective controls. The activity of H+-ATPase from plasma membrane decreased by 70 % in SNP treated cells. Both in vivo and in vitro treatments of SNP showed almost similar effects of decrease in ATPase activity. Effect of SNP was more pronounced in presence of nutrients. Interestingly, it was observed that vanadate did not show any independent effect in presence of nitric oxide. Several workers have reported similar type of results with other P-type ATPases. For the first time, it was observed in the present study that in presence of nitric oxide, H+-ATPase activity decreased like other P-type ATPases. Our study indicated that NO had a significant effect on ATP synthesis and activity of H+- ATPase. In the presence of NO, the ATP concentration was decreased indicating it affected mitochondrial electron transport chain. It may be concluded that NO, not only affects (inhibit) mitochondrial electron transport chain but also interferes with H+- ATPase of plasma membrane by changing its conformation resulting in decreased activity.     

Enthalpy relaxation of gelatin in the glassy state

The enthalpy relaxation during the ageing of gelatin in the glassy state was studied for partially crystalline or amorphous materials at different water contents and ageing temperatures. The extent and rate of this relaxation associated with physical ageing were found to increase when the shifted temperature parameter (Ta-Tg) increased. This parameter was able to account for the effects of structure and water content (through Tg) and ageing temperature (Ta).     

Esthesioneuroblastoma metastatic to the breast in a young woman

BACKGROUND: Metastases to the breast are rare and can be missed without knowledge of the clinical history. We report an unusual breast metastasis originating in an olfactory neuroblastoma. CASE: A breast metastasis from esthesioneuroblastoma occurred in a 20-year-old woman 2 years after the onset of the disease. The aspirates were hypercellular and composed of cellular aggregates and single cells with a monomorphic appearance. The cytoplasm was scanty and inconspicuous. The nucleus was large, with granular, hyperchromatic chromatin. Mitoses and apoptotic bodies were numerous. Because we were unaware of the past history at the time of the cytologic analysis, a definitive diagnosis was made only after pathologic study. CONCLUSION: Esthesioneuroblastoma metastatic to the breast must be considered in the differential diagnosis of breast metastases. Fine needle aspiration, in conjunction with clinical information, can be effective in the diagnosis of esthesioneuroblastoma metastatic to the breast.     

Enthalpy relaxation of bovine serum albumin and implications for its storage in the glassy state

Two endothermic peaks could be observed for five commercial samples of bovine serum albumin (BSA). The smaller peak observed by differential scanning calorimetry (DSC) corresponded to enthalpy relaxation. This peak was followed on storage of BSA, in its glassy state, after it had been heated above its denaturation temperature. Enthalpy and peak temperature increased with duration of storage. On storage for one week at 60 degrees C, a sample at 8.3% moisture showed a peak at 100 degrees C with an energy value of approximately 2 J per g protein. BSA samples were heated within the DSC sufficiently to eliminate the lower enthalpy peak but without altering the denaturation enthotherm. The amount of physical aging shown by these BSA samples was similar to that of the heat-denatured samples. It was concluded that the heating endotherms of dry BSA reflect both the storage and thermal history of the sample. Possible implications of the enthalpy relaxation of BSA on the behavior of this important protein are considered.     

Nickel Uptake by Pseudomonas aeruginosa: Role of Modifying Factors

Pseudomonas aeruginosa cells growing in minimal medium were 40-fold more sensitive to Ni²⁺ than cells growing in enriched medium, suggesting a possible protective role of medium ingredients. Likewise, cells pre-grown in enriched medium showed a high K _m (6.15 mM) and increased Ni²⁺ uptake (950 nmol mg⁻¹ protein, 1h) over cells pre-sown in minimal medium (K _m , 0.48 mM; 146 nmol mg⁻¹ protein, 1 h). The overall pattern indicates that cells pre-grown in enriched medium were characterized by having lowered affinity towards Ni²⁺ than those with minimal medium background. The enhanced Ni²⁺ uptake by enriched medium-grown cells can be correlated with the improved metabolic state of the cells. Ni²⁺ uptake was optimum at neutrality (pH 7.0). A major Ni²⁺ transport system was competitively inhibited by Mg²⁺, Zn²⁺, Cd²⁺, or Co²⁺ (400 μM each). Noticeably, a minor Ni²⁺ transport pathway was still operative even in the higher concentration range of Mg²⁺ (4 mM and 40 mM). The stimulation of Ni²⁺ uptake monitored in the presence of different carbon sources (0.5% wt/vol, each) showed the sequence: glucose (1.6-fold) > phenol = gallic acid (1.5-fold). Succinate, in comparison, reduced Ni²⁺ uptake (0.5-fold) possibly because of its acting as a metal chelator as well. Sensitivity of Ni²⁺ transport towards methyl viologen, azide, 2-4 DNP, and DCCD suggested that transport was energy-linked. Received: 13 January 1998 / Accepted: 21 May 1998     

Assessment of Waterborne Amine-Coated Silver Nanoparticle (Ag-NP)-Induced Toxicity in <Emphasis Type="Italic">Labeo rohita</Emphasis> by Histological and Hematological Profiles

Silver nanoparticles (Ag-NPs) have wide applications in the medical field; however, the toxicological effects are still poorly studied. The study was aimed to determine the effects of 15.78 nm spherical and amine-coated Ag-NPs on hematology and histology of gills and liver tissues in 28 days treated Labeo rohita (L. rohita). It was found that Ag-NPs induced alterations in the hematological parameters in a dose dependent manner. The Ag-NPs also induced histological alterations in a dose-dependent manner. In gill tissues, it induced fusion of secondary lamellae, separation of gill epithelium, fusion and necrosis of lamellar cells, hyperplasia, deformed cartilaginous skeleton, separation and lifting of epithelium, and curling of lamellae in a dose dependent manner. In the liver, Ag-NPs produced abnormalities in hepatic tissues by reducing the size of hepatocytes and nuclei, and stimulated the production of necrotic and apoptotic bodies. It was concluded that Ag-NPs are toxic to aquatic organisms and induce hematotoxicity and histopathological conditions in exposed fish.     

Enhancement of Dynamic Sensitivity of Multiple Surface-plasmonic-polaritonic Sensor Using Silver Nanoparticles

Multiple surface plasmon-polariton (SPP) waves excited at the interface of a homogeneous isotropic metal and a chiral sculptured thin film (STF) impregnated with silver nanoparticles were theoretically assessed for the multiple-SPP-waves-based sensing of a fluid uniformly infiltrating the chiral STF. The Bruggemann homogenization formalism was used in two different modalities to determine the three principal relative permittivity scalars of the silver-nanoparticle-impregnated chiral STF infiltrated uniformly by the fluid. The dynamic sensitivity increased when silver nanoparticles were present, provided their volume fraction did not exceed about 1 %.     

Starch and sugar accumulation in Sulla carnosa leaves upon Mg2+ starvation

In the present work, magnesium deficiency effects were studied in Sulla carnosa plants grown in nutrient solution containing 1.50, 0.05, 0.01, and 0.00 mM Mg²⁺. After 5 weeks of treatment, fully expanded leaves were harvested to study their morphological and ultrastructural changes, as well as their carbohydrate, pigment, and Mg²⁺ concentrations. In control plants, leaves were well developed with remarkable green color. Down to 0.05 mM Mg²⁺, no chlorosis symptom was recorded, but below this concentration, mature leaves showed an appearance of interveinal chlorosis that was much more pronounced at 0.00 mM Mg²⁺ with the development of necrotic spots. Optima of chlorophyll a, chlorophyll b, and carotenoid concentrations were observed at 0.05 and 1.50 mM Mg²⁺; leaf magnesium concentration was severely reduced at 0.05 mM Mg²⁺. A significant decrease in pigment concentrations was noticed at 0.01 mM Mg²⁺, but the lowest values were recorded at 0.00 mM Mg²⁺. Enzymatic assays showed an increase in the accumulation of soluble sugars and starch with decreasing Mg²⁺ concentration. These results were in accordance with those of ultrastructural studies that revealed a marked alteration of chloroplasts in leaves of deficient plants. These chloroplasts were round and bigger as a result of a massive accumulation of oversized starch grains with disrupted thylakoids. As a whole, 1.50, 0.05, and 0.01 mM Mg²⁺ were found optimal, suboptimal, and deficient concentrations, respectively, the latter showing no significant difference with absolute Mg²⁺ absence (0.00 mM Mg²⁺).     

The Acidic C-terminal Tail of the GyrA Subunit Moderates the DNA Supercoiling Activity of Bacillus subtilis Gyrase

Gyrase is a type II DNA topoisomerase that introduces negative supercoils into DNA in an ATP-dependent reaction. It consists of a topoisomerase core, formed by the N-terminal domains of the two GyrA subunits and by the two GyrB subunits, that catalyzes double-stranded DNA cleavage and passage of a second double-stranded DNA through the gap in the first. The C-terminal domains (CTDs) of the GyrA subunits form a β-pinwheel and bind DNA around their positively charged perimeter. As a result, DNA is bound as a positive supercoil that is converted into a negative supercoil by strand passage. The CTDs contain a conserved 7-amino acid motif that connects blades 1 and 6 of the β-pinwheel and is a hallmark feature of gyrases. Deletion of this so-called GyrA-box abrogates DNA bending by the CTDs and DNA-induced narrowing of the N-gate, affects T-segment presentation, reduces the coupling of DNA binding to ATP hydrolysis, and leads to supercoiling deficiency. Recently, a severe loss of supercoiling activity of Escherichia coli gyrase upon deletion of the non-conserved acidic C-terminal tail (C-tail) of the CTDs has been reported. We show here that, in contrast to E. coli gyrase, the C-tail is a very moderate negative regulator of Bacillus subtilis gyrase activity. The C-tail reduces the degree of DNA bending by the CTDs but has no effect on DNA-induced conformational changes of gyrase that precede strand passage and reduces DNA-stimulated ATPase and DNA supercoiling activities only 2-fold. Our results are in agreement with species-specific, differential regulatory effects of the C-tail in gyrases from different organisms.