Annular Field Research Articles

Factors affecting uredospore liberation in Puccinia antirrhini

Air sampling within an annular field plot of rusted snapdragons, and in a wind tunnel, has shown that uredospores of Puccinia antirrhini are readily liberated by wind shear at speeds = 2 m/sec. At constant temperature and wind speed, most uredospores are liberated in the light, mainly in the morning. Liberation in dry air is related logarithmically to wind speed; it is increased by the onset of rainfall or overhead sprinkling, and by bombarding sori with water droplets in the wind tunnel.

Decrease and increase in test-threshold luminance induced by a contiguous annular field.

The threshold luminance of the test field (0.6°) presented to the retinal region about 1°09′ below a fixation point was measured under various combinations of luminance and area of contiguous annular field, according to the method of limits. The following results for 2 Ss were obtained. (1) As the luminance of inducing field increased from −2.5 to 0.5 log mL, the test threshold, after once it became lower than the ones measured without inducing field, increased gradually. (2) It seemed to be dependent on the inducing-area where minimum value of threshold appears on the inducing luminance axis.

Lipogenesis in Human Skin. IV. In Vitro Rate Studies

In previous publications (1, 2) on the synthesis of squalene, cholesterol and fatty acids from acetate-1-C1 * by slices of human skin, the effects of various physical and chemical factors and of body site were evaluated. Freezing, and homogenization of skin completely inhibited lipogenesis. Procain and xylocain caused marked inhibition; an annular field block around a biopsy site was required. Epidermal slices synthesized cholesterol, but sebaceous glands carried the synthesis only as far as squalene. Cholesterol synthesis was constant in all body sites because of the nearly constant thickness of viable epidermis over the entire body. The activity of squalene synthesis was directly proportional to the number and size of sebaceous glands in different body sites.In this paper data have been presented to show the constancy of the rate of synthesis of these lipids in human skin during the 3 hour period of in vitro incubation. But the distribution pattern of the C14 label among individual fatty acids was different from the pattern of pre-formed fatty acids.METHODNormal human skin was obtained mostly from radical mastectomy specimens within an hour after the start of the operation. Skin from other body sites (abdomen) was supplied by general surgeons and (scalp) by plastic surgeons.Preparation of Skin SamplesExperiments with skin were conducted with 8 mm discs of whole skin cut from operative specimens with a cutaneous punch and trimmed of subcutaneous fat. In some experiments subcutaneous adipose tissue was studied separately. Gentleness in handling all specimens was empha-sized. Experiments were begun from 30 to 60 minutes after excision of specimens.Procedure for Incubation of Skin with Labeled Acetate and Recovery of LipidsThe details of this procedure have been reported (1). In brief, one to three discs of whole skin were shaken in one ml of phosphate buffer at 37°C in 100% oxygen for varying periods of time 0/2 to 3 hours). The buffer contained 25 micro-moles of acetate-1-C14 with a radioactivity of 10 or 50 microcuries.For subcutaneous adipose tissue, conditions were changed as follows: the buffer was glucose-bicarbonate, the gas phase 95% oxygen 5% carbon dioxide, and the incubation time 10 to 60 minutes.The labeled lipids were recovered from the tissue by hydrolysis in alcoholic KOH overnight, extraction by appropriate solvents and alumina chromatography. Squalene, sterols and fatty acids were isolated. Radioactivity measurements were made in a scintillation counter and expressed as m/u moles of acetate converted to lipid per gram wet tissue per hour.Gas-Liquid Chromatography of Fatty AcidsA Jarrell-Ash Model 700 Universal Gas Chro-matograph with an Argon Diode ionization detector whose source was tritium foil was used for most of the experiments. A Barber-Colman Series 5000 gas chromatograph with hydrogen flame detector and temperature programmer was available for the most recent experiments. Both instruments gave similar results, although the Barber-Colman produced a crjsper chromatogram because the design of the injection port facilitated direct on-column injection of the sample. Both instruments contained a 9:1 stream spliting device inserted between the column and the detector; only 10% of the column effluent passed through the detector, 90% being diverted to a heated exit port for collection.Satisfactory separation of methyl esters of fatty acids from human skin was obtained with either 15% diethylene glycol succinate on Ana-chrom ABS 100

Positive afterimage following brief high-intensity flashes.

The time course of the decay of the positive afterimage following high-intensity flashes was measured by monocular and binocular brightness matching. The comparison field luminance was adjusted by means of crossed neutral wedges driven by a reversible motor. Density of the wedges was continuously recorded and the afterimage was tracked up to seven minutes following the flashes. Flash durations of 0.24 to 1.4 msec were used with a flash luminance of 4×105 L. With a 10° monocular bipartite photometric field, the afterimage brightness 5 sec following a 3×107 td·sec flash was matched by a 105-td comparison field. Photometric matches made monocularly or binocularly with an annular afterimage, 10° o.d. and 5° i.d., concentric with a 2° centrally fixated comparison field required approximately 104 td. A 2° central afterimage matched with an annular comparison field showed no significant difference from the annular afterimage. The results for the first two minutes following the flashes for all conditions showed a linear relationship between the logarithm of the comparison field luminance and the logarithm of the time measured from the flash.