Evidence for a free radical mechanism of N-demethylation of N,N-dimethylaniline and an analog by hemeprotein--H2O2 systems.

Horseradish peroxidase and metmyoglobin catalyze the H₂O₂-supported N-demethylation of N,N-dimethylaniline and N,N-dimethyl-p-toluidine. The catalytic activities of horseradish peroxidase are more than 100-fold larger than those of metmyoglobin or those previously reported for liver microsomal cytochrome P-450. Distinct free radical species of these N-methyl substrates were detected with both catalysts. These findings establish the general validity of a recently proposed free radical mechanism of oxidative N-demethylation (Griffin, B. W., and Ting, P. L., Biochemistry (1978), 2206–2211), which is quite different from that previously suggested for the analogous cytochrome P-450-dependent reactions.     

The audibility of frog choruses to migrating birds

Breeding choruses of Hyla crucifer and H. versicolor are loud enough to be audible to migrating birds up to at least 1 km from their source, both vertically and horizontally, provided that no large obstacles intervene. During May in south-eastern New York State sound pressure levels (A weighting) at altitudes of 200 to 965 m and slant ranges from the frogs of 225 to 1020 m varied from 28 to 52 dB SPL.     

Colonization of rye green manure and peanut fruit debris by Aspergillus falvus and Aspergillus niger group in field soils.

Aspergillus flavus and Aspergillus niger group colonization of deep-plowed, decomposing rye green manure cover crops in peanut field soils was studied in four fields during 1972 and 1973; colonization of decomposing peanut fruits was studied in 1972 in two fields. A. flavus colonization of rye and peanut fruits was greater in soils of heavy texture, and an A. flavus population as high as 165 propagules per g of soil was observed in soil adjacent to rye, whereas A. flavus populations in soils not associated with rye were 18 propagules per g of soil or lower. Highest A. flavus populations in soil adjacent to decomposing peanut fruits were usually comparable to populations associated with rye. Little decomposing rye or peanut fruit colonization was generally observed by the A. flavus competitor, A. niger group. A. flavus may maintain or increase its inoculum potential by colonization of these and other moribund plant tissues.     

Survey of aflatoxicosis in farm animals.

Over a 22-month period, 278 submissions of farm animals were made to the North Carolina Diagnostic Laboratory for suspected aflatoxicosis, and 94 cases were confirmed on the basis of finding aflatoxin in the feed and the occurrence of bile ductule proliferation. There was an annual variation in the incidence of aflatoxicosis, as well as a seasonal variation: the peak incidence occurred in the winter, and the minimum incidence occurred during the summer. The annual increase coincided with the corn harvest. All confirmed cases occurred on farms that raised and stored their own corn, and 88% were in swine. The cases were geographically localized in the eastern section of North Carolina (94% of the total cases) where 82% of the swine and 79% of the corn are produced. Mean concentration of aflatoxin in feed samples from the confirmed cases was 3,890 mug/kg, and the mean value for corn used in making the feed was 5,180 mug/kg. Only aflatoxin B1 was found in the samples. These data were interpreted to mean that the incidence and severity of aflatoxicosis is greater than previously suspected, that poor on-farm storage of corn is a primary contributing factor, that aflatoxin formation continues during and after the milling process, and that mycotoxicoses other than aflatoxicosis may cause equal or greater problems.     

Glycine-specific synapses in rat spinal cord. Identification by electron microscope autoradiography

Glycine, an inhibitory transmitter in spinal cord, is taken up into specific nerve terminals by means of a unique high-affinity uptake system. In this study, [3H]glycine was directly microinjected into rat ventral horn in vivo and electron microscope autoradiography used to localize the label in various anatomic compartments. Quantiative analysis showed that [3H]glycine labeled a high proportion of axosomatic and axodendritic synapses which presumably act to inhibit spinal motor neurons.     

Rapid Determination of the Amount of Cetylpyridinium Chloride Bound by Bacteria

A modification of the Colowick and Womack procedure for measuring ligand binding by macromolecules is described for drug binding by bacteria. This technique is based on the determination of drug concentration in the dialysate from a bacteria-drug mixture at equilibrium. The dialysis cell of the original procedure was replaced by a Minibeaker (Bio-Rad), which has a larger membrane surface area, and the dialysate was continuously monitored with a spectrophotometer equipped with a flow cell. With this system, only 3 min was required to determine the amount of cetylpyridinium chloride bound by Escherichia coli K-12 strain P678. Possible applications of the technique are discussed.     

The morphology of the Limulus visual system

An ocellus of the horseshoe crab, Limulus polyphemus, has been serially sectioned for light and electron microscopy, its sensory cells have been indexed, and the interconnections of a third of these traced. The ocellus contains 155 retinula cells and 26 arhabdomeric cells, which are secondary sensory neurons. Of these, 55 retinula cells constitute 7 quasi-ommatidial assemblages, each innervated by at least one and a total of 9 arhabdomeric cells. When known electrotonic coupling patterns are compared with gap-junctional connections, retinula cells sensitive to visible or ultraviolet light can be tentatively identified. Retinula cell axons contribute collaterals to a synaptic plexus, in which the arhabdomeric cells apparently do not participate.     

Sinks without borders: snowshoe hare dynamics in a complex landscape

A full understanding of population dynamics of wide-ranging animals should account for the effects that movement and habitat use have on individual contributions to population growth or decline. Quantifying the per-capita, habitat-specific contribution to population growth can clarify the value of different patch types, and help to differentiate population sources from population sinks. Snowshoe hares, Lepus americanus , routinely use various habitat types in the landscapes they inhabit in the contiguous US, where managing forests for high snowshoe hare density is a priority for conservation of Canada lynx, Lynx canadensis . We estimated density and demographic rates via mark–recapture live trapping and radio-telemetry within four forest stand structure (FSS) types at three study areas within heterogeneous managed forests in western Montana. We found support for known fate survival models with time-varying individual covariates representing the proportion of locations in each of the FSS types, with survival rates decreasing as use of open young and open mature FSS types increased. The per-capita contribution to overall population growth increased with use of the dense mature or dense young FSS types and decreased with use of the open young or open mature FSS types, and relatively high levels of immigration appear to be necessary to sustain hares in the open FSS types. Our results support a conceptual model for snowshoe hares in the southern range in which sink habitats (open areas) prevent the buildup of high hare densities. More broadly, we use this system to develop a novel approach to quantify demographic sources and sinks for animals making routine movements through complex fragmented landscapes.