Spacer Acquisition Rates Determine the Immunological Diversity of the Type II CRISPR-Cas Immune Response

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Disintegration of Dung Pats from Cattle Treated with the Ivermectin Anthelmintic Bolus,or the Biocontrol Agent Duddingtonia flagrans

An experiment was performed during the grazing seasons of 1998, 1999 and 2000 to study the influence of the antiparasitic drug ivermectin and the nematophagous fungus Duddingtonia flagrans on cattle dung disintegration. The faeces originated from groups of animals that were part of a separate grazing experiment where different control strategies for nematode parasite infections were investigated. Each group consisted of 10 first-season grazing cattle that were either untreated, treated with the ivermectin sustained-release bolus, or fed chlamydospores of D. flagrans. Faeces were collected monthly on 4 occasions and out of pooled faeces from each group, 4 artificial 1 kg dung pats were prepared and deposited on nylon mesh on an enclosed pasture and protected from birds. The position of the new set of pats was repeated throughout the 3 years of the study. Each year, the dung pats were weighed 4, 6, 8 and 10 weeks after deposition and immediately afterwards replaced to their initial positions.

Results showed that there was no difference in faecal pat disintegration between groups. However, the time-lag between deposition and complete disintegration of the faeces varied significantly between deposition occasions. Dung pats disappeared within 2 weeks (visual observation) when subjected to heavy rainfall early after deposition, whereas an extended dry period coincided with faeces still remaining 12 months after deposition.

     

Blood pressure response to chronic episodic hypoxia: role of the sympathetic nervous system

Bao, Gang, Naira Metreveli, Rena Li, Addison Taylor, andEugene C. Fletcher. Blood pressure response to chronic episodic hypoxia: role of the sympathetic nervous system. J. Appl. Physiol. 83(1): 95-101, 1997.Previousstudies in several strains of rats have demonstrated that 35 consecutive days of recurrent episodic hypoxia (7 h/day) cause an 8- to13-mmHg persistent increase in diurnal systemic blood pressure (BP).Carotid chemoreceptors and the sympathetic nervous system have beenshown to be necessary for development of this BP increase. The presentstudy was undertaken to further define the role of renal arterysympathetic nerves and the adrenal medulla in this BPincrease. Male Sprague-Dawley rats had either adrenalmedullectomy, bilateral renal artery denervation, or sham surgery. Ratsfrom each of these groups were subjected to episodic hypoxia for 35 days. Control groups received either compressed air or were leftunhandled. Adrenal demedullation or renal artery denervation eliminatedthe chronic diurnal mean BP response (measured intra-arterially) toepisodic hypoxia, whereas sham-operated controls continued to showedpersistent elevation of systemic BP. Plasma and renal tissuecatecholamine levels at the end of the experiment confirmed successfuladrenal demedullation or renal denervation in the respectiveanimals. The chronic episodic hypoxia-mediated increase indiurnal BP requires both intact renal artery nerves as well as anintact adrenal medulla.

     

Isolation and characterization of plasma membranes from strains of Neurospora crassa with wild type morphology

A variety of commercially available cell wall hydrolytic enzyme preparations were screened alone and in various combinations for their ability to degrade the cell wall of Neurospora crassa wild type strain 1A. A combination was found which causes complete conversion of the normally filamentous germinated conidia to spherical structures in about 1.5 h. Examination of these spheroplasts by scanning electron microscopy indicated that, although they are spherical, they retain a smooth coat that can only be removed upon prolonged incubation in the enzyme mixture (about 10 h). The 10-h incubation in the enzyme mixture appears to have no obvious detrimental effects on the integrity of the plasma membrane since the activity and regulatory properties of the glucose active transport system in 10-h spheroplasts are essentially unimpaired. Importantly, plasma membranes can be isolated from the 10-h spheroplasts by an adaptation of the concanavalin A method developed previously in this laboratory for cells of the cell wall-less sl strain, which is not the case for the 1.5-h spheroplasts. The yield of plasma membrane vesicles isolated by this procedure is 18-36% as indicated by surface labeling with diazotized [125I]iodosulfanilic acid, and the preparation is less than 1% contaminated with mitochondrial protein. The chemical composition of the wild type plasma membranes is similar to that previously reported for membranes of the sl strain of Neurospora. The isolated wild type plasma membrane vesicles also exhibit all of the functional properties that have previously been demonstrated for the sl plasma membrane vesicles. The wild type vesicles catalyze MgATP-dependent electrogenic proton translocation as indicated by the concentrative uptake of [14C]SCN- and [14C]imidazole under the appropriate conditions, which indicates that they contain the plasma membrane H+-ATPase previously shown to exist in the sl plasma membranes and that they possess permeability barrier function as well. The vesicles also contain a Ca2+/H+ antiporter as evidenced by their ability to catalyze protonophore-inhibited MgATP-dependent 45Ca2+ accumulation. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analyses of the isolated vesicles indicate that the protein composition of the wild type vesicles is roughly similar to that of the sl plasma membranes with the H+-ATPase present as a major band of Mr approximately 105,000. The wild type plasma membrane ATPase forms a phosphorylated intermediate similar to that of the sl ATPase, and the specific activity of the H+-ATPase in both wild type and sl membranes is approximately 3 mumol of Pi released/mg of protein/min.(ABSTRACT TRUNCATED AT 400 WORDS)     

Separation of triglycerides and free fatty acids on Sephadex LH-20

Free fatty acids and triglycerides have been separated by elution with chloroform or chloroform + 0.2% ($\text{v}\text{v}$) acetic acid from columns of Sephadex LH-20. Loads of up to 10 mg/gm dry weight Sephadex were used, and recovery of artificial and natural mixtures was generally better than 95%.