Acute blood pressure elevation during repetitive hypocapnic and eucapnic hypoxia in rats

Bao, Gang, Preet M. Randhawa, and Eugene C. Fletcher.Acute blood pressure elevation during repetitive hypocapnic and eucapnic hypoxia in rats. J. Appl.Physiol. 82(4): 1071-1078, 1997.Using a ratmodel, we investigated whether episodic eucapnic hypoxia was a morepotent stimulus to acute blood pressure (BP) elevation and bradycardiathan episodic hypocapnic hypoxia. We also investigated therole of sympathetic and parasympathetic nervous system in thiscardiovascular response. Sprague-Dawley (SD) and Wistar Kyoto (WKY)rats were exposed to repetitive 30-s cycles of hypocapnic or eucapnichypoxia before and after intravenous injection of the₁-adrenergic blocker prazosin,₂-adrenergic blocker yohimbine,or atropine. Eucapnic hypoxia caused a threefold elevation in systolicBP from baseline (83.5 ± 3.5 mmHg in WKY, 70.6 ± 4.6 mmHg inSD) and greater bradycardia (178 ± 20 beats/min in WKY,178 ± 21 beats/min in SD) compared with hypocapnic hypoxia (29.8 ± 3.6 mmHg and 43 ± 15 beats/min in WKY,19.0 ± 4.1 mmHg and 45 ± 12 beats/min in SD). Afterprazosin, the BP increase from eucapnic hypoxia was blunted, yohimbineshowed no effect, and atropine blocked the bradycardia. Directmeasurement of sympathetic nerve activity confirmed that addingCO₂ to the hypoxic gas mixture caused a 61% increase in sympathetic nerve activity. WKY rats seemmore vulnerable than SD rats to both hypoxia exposures in terms of theelevation in BP. We conclude that, in the rat, eucapnic hypoxia is amore potent stimulus to acute BP elevation and bradycardia than ishypocapnic hypoxia. An increased sympathetic tone appears to beinvolved in the BP response to acute episodic hypoxia.

     

Blastomyces dermatitidis in India: first report of its isolation from clinical material

The isolation of Blastomyces dermatitidis in India is reported from the bronchial aspirate of a female asthmatic patient who had never travelled abroad. The patient was a resident of Rodhain, a small town in the District of Badaun (Uttar Pradesh), situated about 250 km south-east of Delhi. Apart from its demonstration by culture and direct microscopy of a bronchial aspirate, B. dermatitidis was seen microscopically on two occasions in KOH wet mounts and smears of sputum stained with periodic acid-Schiff's reagent. Anti-B. dermatitidis serum precipitins were shown by immunodiffusion in 3 of 4 serum samples from the patient. The identity of the fungus was based on its characteristic morphology in clinical specimens and in culture, conversion of the mold form to the yeast from in vitro and vice versa, and by verification of its pathogenicity in white mice. A detailed clinical and laboratory evaluation of the patient indicated that she had suffered from an episode of self-limited acute pulmonary blastomycosis that required no antifungal therapy. This is believed to be the first authentic report of the isolation of B. dermatitidis from clinical material in India.     

Application of Paraffin Bait Technique to the Isolation of Nocardia asteroides from Clinical Specimens

The principal findings of a study for further evaluating paraffin baiting as a routine laboratory diagnostic procedure in the isolation of Nocardia asteroides, the etiological agent of nocardiosis, are reported.     

Relation of growth and zinc uptake of rice to quantity,intensity and buffering capacity factors of zinc in soils

Adsorption of zinc in rice soils was studied to define the functional relationship between quantity, intensity and buffering capacity factors of soil zinc to the growth and zinc uptake of rice crop. A supply parameter integrating the quantity, intensity and buffering capacity factors into a single unifying term was computed from the data on Zn adsorption in these soils. A green house experiment was conducted with three soils providing a matrix of different values of supply parameter of Zn to determine the optimum value of this parameter for the proper growth and zinc nutrition of rice crop. Results indicated that a value of this parameter around unity is optimum for sustaining proper growth and zinc nutrition of rice in these soils. The variations in dry matter yield and zinc uptake of rice in different soils may be related to the differences in the physical and chemical properties of the soils.     

Cloning, sequencing, and characterization of Escherichia coli thioesterase II.

The gene (tesB) encoding Escherichia coli thioesterase II, a low-abundance enzyme of unknown physiological function which can hydrolyze a broad range of acyl-CoA thioesters, has been localized by transposon mutagenesis, cloned and sequenced. A two-cistron construct containing both the lac and tesB promoters was used successfully to overexpress the 286-residue polypeptide. The recombinant enzyme constituted up to 25% of the soluble proteins of E. coli and was readily purified to homogeneity as a tetramer of approximately 120,000 Da. Amino-terminal sequence analysis and electrospray ionization mass spectrometry confirmed the identity of the thioesterase and revealed that the amino-terminal formyl-methionine had been removed yielding a subunit species of average molecular mass 31,842 Da. The protein does not contain the GXSXG motif found characteristically in animal thioesterases which function as chain-terminating enzymes in fatty acid synthesis and exhibits no sequence similarity with these or any other known proteins. Activity of the recombinant enzyme was inhibited by iodoacetamide and diethylpyrocarbonate. The carboxamidomethylated residue was identified as histidine 58, and a role for this amino acid in catalysis is suggested. E. coli strains having a large deletion within the genomic tesB gene grew normally but retained a low level of thioesterase activity toward decanoyl-CoA. This residual activity indicates the presence of an additional decanoyl-CoA hydrolase in E. coli. Over-expression of the recombinant enzyme, under control of the lac promoter, did not alter the fatty acids synthesized by E. coli at any stage of cell growth and the physiological role of this enzyme remains an enigma.     

On the re-isolation and taxonomic study of Candida viswanathii Viswanathan et Randhawa 1959

Summary A detailed taxonomic study of a new isolate ofCandida viswanathii from sputum is reported.     

Targeted and efficient transfer of value-added genes into a wheat variety

With an objective to optimize an approach to transfer value-added genes to a wheat variety while maintaining and improving agronomic performance, two alleles (Als1 and Als2) with mutations in the acetolactate synthase (ALS) gene located on the long arm of wheat chromosomes 6B and 6D providing tolerance to imazamox herbicide were transferred to Eltan, a popular soft white common winter wheat cultivar in the Pacific Northwest (PNW), USA. Four-step marker-assisted background selection and marker assisted forward breeding approaches were used to develop a wheat variety carrying two genes (Als1 and Als2) for imazamox tolerance along with improvements in many other agronomic traits. Screening of 1600 BC₁ plants for imazamox tolerance identified 378 plants that were further screened with markers to identify seven plants that were used to make a population of 1400 BC₂ plants, and the selection cycle was repeated. Progeny of 17 selected BC₂F₁ plants was evaluated for various agronomic and quality parameters to select 12 plants that were increased for field testing. Field evaluation of these lines conducted over 58 location-years along with evaluation in the greenhouse/growth chamber led to the selection of a line “WA8143” carrying the two genes for imazamox tolerance that yielded >3% higher than Eltan did. With 96.8% similarity to the recurrent parent, WA8143 also showed a better disease resistance package and grain quality needed in a successful Pacific Northwest wheat variety and was subsequently released for cultivation under the name of “Curiosity CL+.”     

Benefits,costs and reactivity of inducible defences: an experimental test with rotifers

1. A key aspect of the ecology and evolution of adaptive prey responses to predator risk is the timing by which the former develop a defensive trait in response to inducing signals released by the latter. This property, called reactivity, has been shown to affect population stability and persistence. 2. Theoretically, the minimal predator density required by prey to exhibit induced defences is expected to increase with the effectiveness of the defence and decrease with its cost. Likewise, the time required for the prey population to exhibit an induced defence is expected to increase together with cost. 3. The freshwater rotifers Brachionus calyciflorus and B. havanaensis and their predator Asplanchna brightwelli were used to test the hypothesis that prey species exhibiting defences that offer a larger fitness benefit and lower fitness cost are more reactive to predator signals, in terms of requiring shorter exposure time and lower signal concentration to trigger a morphological defence reaction. 4. Our results showed that both prey species exhibited costly and effective defences after induction by predator infochemicals. Faster reactions were observed at higher levels of predator cues. Nevertheless, the observed relationship between reactivity and benefit/cost of defences did not agree with our expectations. 5. To our knowledge, this is the first study in which the timing of induction of morphological defences is experimentally assessed over a gradient of risk signals. We propose new research directions to disentangle the mechanisms and project the consequences of prey decisions at the morphological level.