Sieve-plate pores in tobacco and bean

Tobacco and bean plants were wilted and then fixed as whole plants with formaldehyde-glutaraldehyde for electron microscopy. In some tobacco plants the sieve-plate pores were large, with little callose. Light slime plugs were present, but there was no compaction of P-protein in the pores. Some pores in wilted bean plants were also unplugged. In other plants of both tobacco and bean the sieve-plate pores were plugged. The pores in unwilted control plants of both tobacco and bean were invariably plugged. Tobacco plants were also cut into thin slices and then immediately fixed. In specimens prepared in this way there was little callose in the pores, and many of the pores were not plugged with P-protein. These observations provide additional evidence that sieve-plate pores may be unplugged in vivo.

Phenylketonuria-the guthrie screening test-a method of quantitation, observations on reliability and suggestions for improvement

The Guthrie bacterial inhibition assay method of screening neonatal infants for phenylketonuria (pku) initiated mass screening for inborn errors of metabolism. It is a simple, cheap procedure admirably suited to private local use as against private or public central use. However, using parallel fluorometric determinations as a basis for comparison, and 4 mg per 100 ml serum phenylalanine as a presumptive positive threshhold, the Guthrie test yielded 53 per cent "false negatives." Extrapolating from a combination of our data and reported phenylalanine levels at three days of age or less in proved pku patients, it is estimated the Guthrie test might fail to detect one of 25 pku patients screened at three days of age or less. Means to diminish this risk are considered.

Survey of serologic evidence for syphilis among the Masai of Tanzania

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Electricity in Volcanic Clouds

In November of 1963 an oceanic volcano produced an island, Surtsey, just off the southern coast of Iceland. The volcanic crater was often flooded with sea water. Vigorous eruptions of steam and tephra were accompanied by an enhancement of the normal fine-weather potential gradient, and lightning was often observed. Measurements of atmospheric electricity and visual and photographic observations lead us to believe that the electrical activity is caused by the ejection from the volcano into the atmosphere of material carrying a large positive charge. The concentration of charge in the eruption plume as it issued from the orifice of the volcano is estimated to be of the order of 10(5) or 10(6) elementary charges per cubic centimeter.