Human hypoxanthine-guanine phosphoribosyltransferase

A mutant form of human hypoxanthine-guanine phosphoribosyltransferase (HPRTToronto) was isolated from erythrocytes of a male patient with gout due to a partial deficiency of enzyme activity. The tryptic peptides of HPRTToronto were mapped by reverse-phase high pressure liquid chromatography in an attempt to define the precise abnormality in its primary structure. Sequence analysis of the single aberrant peptide in HPRTToronto revealed an arginine to glycine amino acid substitution at position 50. A single nucleotide change in the codon for arginine 50 (CGA leads to GGA) could explain this substitution.     

A landscape of shifting-mosaic steady state in Lassen Volcanic National Park,California

It is generally perceived that landscape patterns or textures in a given protected area are spatially stationary. The findings of this study suggest that this common perception is only partially correct. Over the course of 52 years, equilibrium in landscape shifting was detected using digital data for the Lassen Volcanic National Park (USA). Vertical aerial photographs taken of the park in 1941 were geo-referenced with the digital orthophoto quarter quadrangle (DOQQ) images of the same area from 1993 to identify landscape compositions and to measure change. Spatial analysis was used to observe pattern changes over time. The results suggested that landscape development maintained equilibrium while patches were in various stages of a successional sequence. The total area of each landscape component held steady, although over time patches throughout the landscape changed—a shifting-mosaic steady state (SMSS). These findings reflect the limitations of contemporary environmental conservation theory. They also suggest the importance of considering landscape change in policies that currently govern park planning and management.     

The preparation and kinetics of lactate dehydrogenase attached to water-insoluble particles and sheets

1. The preparation of lactate dehydrogenase covalently attached to anion-exchange cellulose particles and sheets by use of a dichloro-sym-triazinyl dyestuff, Procion brilliant orange MGS, is described. 2. The stability and kinetic properties of these preparations were investigated. 3. An equation is derived to describe the change in concentration of a substrate when passed through a uniform bed of a substrate-inhibited enzyme. A number of theoretical curves are shown to illustrate the system. 4. A titrimetric assay for lactate dehydrogenase is described, and shown to be stoicheiometric over the range pH5.0-9.2. 5. The results are discussed in relation to previous work, and the effects of charged groups on the support, and of the diffusion film surrounding any particle in suspension, are treated qualitatively.     

Bats and frogs and animals in between: evidence for a common central timing mechanism to extract periodicity pitch

Widely divergent vertebrates share a common central temporal mechanism for representing periodicities of acoustic waveform events. In the auditory nerve, periodicities corresponding to frequencies or rates from about 10 Hz to over 1,000 Hz are extracted from pure tones, from low-frequency complex sounds (e.g., 1st harmonic in bullfrog calls), from mid-frequency sounds with low-frequency modulations (e.g., amplitude modulation rates in cat vocalizations), and from time intervals between high-frequency transients (e.g., pulse-echo delay in bat sonar). Time locking of neuronal responses to periodicities from about 50 ms down to 4 ms or less (about 20–300 Hz) is preserved in the auditory midbrain, where responses are dispersed across many neurons with different onset latencies from 4–5 to 20–50 ms. Midbrain latency distributions are wide enough to encompass two or more repetitions of successive acoustic events, so that responses to multiple, successive periods are ongoing simultaneously in different midbrain neurons. These latencies have a previously unnoticed periodic temporal pattern that determines the specific times for the dispersed on-responses.     

The stem and bulb eelworm, Anguillulina dipsaci (Kühn, 1858): the importance of collating evidence on the behaviour of biologic strains

The results of experiments on the infection of many different plants with seven biologic strains of known history of the nematode, Anguillulina dipsaci (Kühn), are given, together with the results obtained by other investigators. The technique by which the nematode was induced to infect other host plants is described in detail. The biologic strain theory in relation to A. dipsaci is discussed, together with the merits of the trinomial system of nomenclature in connexion with unspecialized races. The factors concerned with nematode outbreaks receive consideration. The relationship that exists between flower colour in herbaceous phloxes and the degree of infection by A. dipsaci is presented.