Generation of third-order spherical and coma aberrations by use of radically symmetrical fourth-order lenses.

We have extended the method of Alvarez [J. Am. Optom. Assoc. 49, 24 (1978)] to generate a variable magnitude of third-order spherical and/or coma aberration by using a combination of fourth-order plates with a magnification system. The technique, based on the crossed-cylinder aberroscope, is used to measure the wave-front aberration generated by the plates. The method has been applied to correct the third-order spherical aberration generated by an artificial eye as well as the coma produced by a progressive addition ophthalmic lens. The simplicity of the method and its relatively low cost make it attractive for partial correction of the aberrations of the eye.

Seasonal profiles of melatonin in adult rams.

The objective of this study was to investigate the seasonal changes in melatonin profiles based on frequently collected samples in adult rams maintained under simulated natural photoperiod. In a group of six rams, the seasonal changes of melatonin were characterized in samples collected at 10-min intervals for an equal period before and after the median of the scotophase during the spring (March) and the autumn (September) equinoxes, and also during the summer (June) and the winter (December) solstices. In an additional two rams, the rapid changes in melatonin concentrations were investigated in samples drawn at 2-min intervals for a 2-hr period before and after the median of the scotophase, but only during the summer and the winter solstices. The results show that in adult rams there is a distinct seasonal variation in the nightly rise of melatonin (P less than 0.01). Mean concentrations in June and September were higher than in March or December (P less than 0.05). There was no difference between the means in June or September. However, the means in March were lower than in December (P less than 0.05). Rapid changes in melatonin concentrations occurred in samples collected either at 10-min or 2-min intervals. In rams sampled at 2-min intervals, mean melatonin values in June were also higher than in December (P less than 0.01). The results suggest that there are distinct seasonal changes in melatonin concentrations in the ram and that rapid changes in melatonin concentrations reflect pulsatile secretion.

Effects of heat stress on serum progesterone in cyclic ewes and on progesterone and cortisol response to ACTH in ovariectomized ewes.

The daily mean of serum progesterone in cyclic ewes (N = 5) as well as the profile characteristics of progesterone and cortisol in response to an acute single dose (5 i.u./kg liveweight 0.75) of adrenocorticotrophic hormone (ACTH) into ovariectomized ewes (N = 4) was investigated during exposure to a constant thermoneutral temperature of 18 +/- 1 degree C or to a daily cyclic heat stress temperature of 18 degrees C-35 degrees C-18 degrees C, in an environmental chamber. Serum collected daily from the cyclic ewes was assayed for progesterone, while serum collected more frequently for 10 h, on the 14th day of exposure to the respective temperature, from the ovariectomized ewes was assayed for progesterone and cortisol by RIAs. In cyclic ewes, heat stress increased the area under the daily progesterone curve (P less than 0.09) but had no effect on progesterone concentration after the regression of the CL. In ovariectomized ewes, ACTH significantly elevated the response of both cortisol and progesterone (r = 0.75, P less than 0.001) within 10-15 min of injection. In the ovariectomized ewes and during heat stress, the responses of progesterone and cortisol to ACTH were characterized by an initial acute rise, a transient drop, a steep elevation and a gradual but prolonged decline. During thermoneutral temperatures, this biphasic response pattern was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between periodontal health, salivary steroids, and Bacteroides intermedius in males, pregnant and non-pregnant women.

Relationships between four steroids, determined by radio-immunoassay of whole saliva, and clinical and bacteriological parameters were studied in 90 subjects: males, menstruating females, and pregnant females. Pocket depths and both plaque and gingival bleeding scores were recorded. Total counts and percentages of Gram-negative organisms Bacteroides and B. intermedius were determined from anaerobic cultures of subgingival plaque from 9-14 subjects in each group. None of the clinical parameters for the pregnant females differed significantly from those of non-pregnant females, nor did these parameters show any significant correlation with progression of pregnancy. No correlations were detected between bacterial and clinical parameters in the pregnant group. There were no statistically significant differences between the total bacterial counts from the three groups, yet males had significantly higher proportions of Gram-negative bacteria, Bacteroides, and B. intermedius, than did pregnant and non-pregnant females. Proportions of B. intermedius did not differ significantly between the two female groups, nor was there any correlation with progression of pregnancy. While some steroids appeared to affect some clinical or bacteriological parameters in some groups, no obvious patterns consistent with different steroid levels were detected. The results do not indicate that increased hormone levels cause more severe periodontal disease in pregnant women, nor that high salivary steroid levels result in increased recovery of B. intermedius from subgingival plaque.

A novel high-frequency visual acuity chart.

A high-frequency eye test chart using letters or figures of alternating black and white stripes (or dots) on a grey background was developed. Any cross-section of the letters has a Fourier transform with a zero frequency component equal to the luminance of the grey background. When the letters are out of focus, their image on the retina fades rapidly into the grey background, rendering them invisible rather than merely blurred as in a standard chart. The chart was calibrated by simulating refractive errors with defocusing lenses applied to a photographic camera and to subjects' eyes. No constant ratio was found between the size of the Snellen letters and the size of the high-frequency letters for equal visibility. The new chart requires letters for 20/200 acuity to be only 3.6 times larger than those for 20/20 vision. Results confirm the arbitrary nature of the Snellen fraction and warn about the accuracy of visual acuity determined by using charts of different letter types, calibrated by Snellen's system.

Changes in serum levels of LH, FSH, prolactin, testosterone, and cortisol associated with season and mating in male pygmy goats.

Four male pygmy goats were used in a study designed to determine the effects of season on serum hormone (luteinizing hormone, follicle stimulating hormone, prolactin, testosterone, and cortisol) levels, testis size and libido, and the effects of mating on serum hormone profiles. Seasonal peaks were observed for prolactin in July, luteinizing hormone and follicle stimulating hormone in September, and testosterone in October. Luteinizing hormone peak frequency was greatest in September and was increased by mating activity in the months immediately preceding the breeding season. Scrotal circumference did not vary with season and libido showed no consistent seasonal pattern. Mating appeared to raise all hormone levels except during the months when these hormones were seasonally elevated. When episodic releases of luteinizing hormone occurred, they were associated with subsequent rises in serum testosterone levels. On some mating days, when episodic releases of luteinizing hormone were absent, changes in testosterone levels were highly correlated with changes in cortisol levels. It was concluded that both season and mating influence reproductive hormone levels in male pygmy goats.

Seasonal changes in the endocrine responsiveness of the pituitary and tests of male sheep in relation to their patterns of gonadotropic hormone and testosterone secretion.

Pituitary and testicular endocrine responses to exogenous gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH), respectively, were assessed for adult rams in an investigation of the regulation of seasonal changes in the patterns of episodic LH and testosterone secretion. Concurrent variations in testis size and in circulating levels of follicle stimulating hormone (FSH) and prolactin (PRL) were also examined. On 10 occasions throughout the year, serum hormone levels were assessed over 6- to 8-h periods during which time rams were left untreated (day 1) or were injected (iv) with single doses of either 10 micrograms synthetic GnRH (day 2) or 30 micrograms NIH-LH-S18 (day 3); blood samples were collected from the jugular vein at 10- to 20-min intervals. Testicular redevelopment during the summer, as indicated by increasing testis diameter measurements, was associated with increases in mean FSH level and was preceded by a springtime rise in mean PRL level; "spontaneously" occurring LH pulses and those produced in response to GnRH treatment were relatively large during this period. Increases in the magnitude of testosterone elevations in response to both endogenously and exogenously produced LH pulses occurred in August. Mean testosterone levels were elevated fourfold in the fall as a consequence of relatively frequent and small LH pulses stimulating a more responsive testis to produce more frequent and larger testosterone elevations; endogenous LH pulses, however, did not appear to stimulate the testes maximally at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal changes in the secretion of gonadotropic hormones and in the endocrine response of the pituitary of male sheep in the absence of gonadal influence.

Circulating levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PRL) were assessed in four long-term castrate rams at monthly intervals for 1 year beginning in March. Each month, rams were bled from the jugular vein at 10-min intervals for an 8-h period; 10 micrograms synthetic gonadotropin releasing hormone (GnRH) was injected into the jugular vein following 6 h of sampling. Changes in natural daylength were associated with seasonal variations in mean serum levels of LH (r = 0.57, P less than 0.05) and PRL (r = 0.94, P less than 0.01). LH levels declined 55% between June and October as LH peaks became more frequent and progressively smaller in magnitude, and base-line levels decreased; these trends were reversed by December. In comparison, FSH levels increased 40% between June and September and then returned to relatively low values in October. Seasonal variations in the magnitude of endogenous LH pulses were not associated with definitive changes in the LH response of the pituitary to exogenous GnRH. Although LH and FSH levels in the castrate rams were typically high, many of the seasonal-directional changes in the secretory characteristics of these hormones (i.e., LH peak frequency and magnitude, and mean FSH level) were similar to those reported for the intact ram. Data indicate that photoperiodic regulation of hypothalamic function of rams is in part via direct or steroid-independent means.

Optics of photorefraction: orthogonal and isotropic methods.

Analysis of the optics of photorefractively computed ray tracing shows that, for short camera-to-subject distances, the function relating image size to defocus of the eye is not symmetrical for errors of focus in front of and behind the camera. This asymmetry is exploited in the new method of isotropic photorefraction, in which the supplementary cylinder lenses of the original orthogonal photorefractors are replaced by defocusing of the camera lens itself. By comparing photographs taken with the camera focused in front of and behind the subject, the sign of the eyes' defocus (myopic or hyperopic relative to the camera) can be determined. The axis of any astigmatism is readily apparent as the direction in which the photorefractive images are elongated. The method is well adapted for the refractive screening of infants and young children.

Saliva progesterone throughout the menstrual cycle and late pregnancy.

Whole saliva was collected daily by four women during one menstrual cycle and twice weekly by three women during their third trimester of pregnancy. Follicular-phase saliva progesterone concentrations, as measured by radioimmunoassay, generally remained below 50 pg/mL. However, progesterone rose to a peak of 400 +/- 107 pg/mL (mean +/- SE) between days 17 and 25, after which it declined to 143 +/- 67 pg/mL by one day prior to menses. The third trimester of pregnancy was characterized by steadily increasing concentrations of saliva progesterone until 1--3 weeks prior to parturition; concentrations following parturition were similar to those of the follicular phase.

Effect of glucoprivation induced by 2-deoxy-D-glucose on serum gonadotropin levels, pituitary response to GnRH and progesterone-induced release of luteinizing hormone in rats.

Intact (experiment 1) or castrated (experiment 2) male rats were either fed or fasted for 24 hours. Half of each group received 75 mg 2-deoxy-D-glucose/100 gm body weight, intraperitoneally. Assays of sera from blood samples obtained from intact rats 4 hr after the injection revealed that 2-deoxy-D-glucose suppressed serum testosterone levels (P < 0.05) while 2-deoxy-D-glucose plus fasting was most effective in suppressing LH and FSH. In castrates LH was suppressed by 2-deoxy-D-glucose and FSH by fasting (P < 0.01 and P < 0.05). Serum glucose was elevated 3-5 fold by 2-deoxy-D-glucose (P < 0.01). Experiments with female rats revealed that treatment with 2-deoxy-D-glucose had no effect on the rise in serum LH that followed GnRH treatment in ovariectomized, steroid-primed animals. However, progesterone-induced LH release in estrogen-primed ovariectomized rats was blocked by 2-deoxy-D-glucose. Collectively, these results suggest that glucoprivation impairs hypothalamic control of gonadotropin secretion.

Pituitary response to gonadotropin-releasing hormone in diabetic male rats.

The rise in serum lutenizing hormone concentration after treatment with gonadotropin-releasing hormone was less in diabetic castrated male rats than control castrates. In intact male rats, gonadotropin-releasing hormone treatment resulted in higher serum luteinizing hormone concentrations in diabetic than in control rats.

Effect of underfeeding on the inhibition of gonadotrophin secretion by testosterone propionate in rats.

Single (0 . 25 mg/100 g body wt) or multiple (5 x 20 microgram/100 g) injections of testosterone propionate were given to castrated male rats fed normally or restricted to a 50% intake. Serum FSH and LH levels were higher in the underfed rats and the effectiveness of testosterone propionate in suppressing serum levels of gonadotrophins was increased by underfeeding.