A new method for the purification of the influenza A virus neuraminidase

A rapid new method for the purification of neuraminidase (NA) heads from influenza A virus is described. Virus was pelleted directly from allantoic fluid and was digested with pronase. The cores were removed by centrifugation, redigested and the released NA heads were pooled and concentrated. The NA was separated from all contaminating proteins in a single step on a Superose 12 column. The purified material was suitable for both crystallography and for the production of monospecific antisera.     

Germination of seeds from an irradiated forest: implications for waste disposal.

Jack pine (Pinus banksiana Lamb.) retain their seeds from year to year, so that in an irradiated forest, each tree receives a specific dose rate but has seeds that have accumulated a range of total doses. The Field Irradiator-Gamma facility in Pinawa, Manitoba, contains jack pine that have been irradiated longer and at lower dose rates than previously reported. Seed germination and germination rate were examined on seeds irradiated on the parent tree for up to 5 years. Germination rate was most sensitive and showed deleterious effects at 1.1 mGy hr-1. This is not much lower than results reported by others in shorter-term studies. Effects were related to dose rate rather than total dose. Hormesis, indicated by statistically significant increased germination rate, was evident at 0.6 mGy hr-1. To put these results into context, the concentrations of selected radionuclides that, through internal contamination, would deliver 1.1 mGy hr-1 to plants were estimated. For 99Tc and 129I, these concentrations are far above the chemical toxicity thresholds for plants. Clearly, as assessments of waste repositories begin to consider effects on organisms other than humans, such as plants, chemical toxicity will be an important feature.     

Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging

Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.     

Differential sensitivity to halothane anesthesia of the genioglossus, intercostals, and diaphragm in kittens.

Recent studies in humans and animals have indicated that different inspiratory muscles have different sensitivities to respiratory depressants. The sensitivity of inspiratory muscles during early growth and development relative to that in adults of the same species, however, has not been studied. We therefore studied the activity of the diaphragm, the external intercostals, and the genioglossus by means of electromyography and its moving time average with different concentrations of halothane in seven 2-mo-old kittens. The kittens spontaneously breathed 1.0%-2.0% halothane in oxygen while PaCO2 was maintained at about 60 mm Hg by adding CO2 to the inspired gas as needed. Muscle activity was evaluated in terms of the peak height of the moving time average. Activity at 1% halothane was used as the control measurement because measurements at zero inspired concentrations of halothane could not be obtained without sedation, which is known to depress respiratory muscle activity. Halothane anesthesia significantly (P less than 0.01) decreased phasic inspiratory activity of the inspiratory muscles in a dose-dependent fashion. Genioglossal activity was completely abolished at 1.5% and 2.0% halothane. By contrast, in our previous study in adult cats under nearly identical experimental conditions, the phasic genioglossal activity was depressed but present even at 3.0% halothane. The degree of depression at 1.5% and 2.0% halothane was least in the crural diaphragm (71.8% +/- 5.8%, 66.6% +/- 4.5% of control, respectively), intermediate in the intercostals (68.9% +/- 9.6%, 35.4% +/- 8.8%), and greatest in the genioglossus (0.0%, 0.0%).(ABSTRACT TRUNCATED AT 250 WORDS)