Short-term leaf elongation kinetics of maize in response to salinity are independent of the root.

The essentiality of roots to the short-term responses of leaf elongation to salinity was tested by removing the roots of maize (Zea mays L.) from the shoots and comparing the initial short-term response of leaf elongation to that with intact plants. Eightday-old seedlings growing in solution culture were treated with 80 millimolar NaCl and their leaf elongation rate (LER) was monitored with a linear variable differential transformer connected to a computerized data aquisition system. Initially, LER of intact plants was sharply reduced by salinity, then rose rapidly to reach a new steady-state rate about 1.5 hours after salinization. The new steady-state rate of salinized intact plants was about 80% of the control rate. When the roots of nonsalinized plants were excised under the surface of the nutrient solution, excision did not disturb the steady-state LER. When these shoots were salinized, they responded in a manner nearly identical to that of intact plants, indicating that roots are not essential for the modulation of short-term LER of salt-stressed plants.

Pineal gland free amino acids and indoles during postnatal development of the rat: correlations in individual glands.

Free amino acids and indoles were measured by HPLC in single pineal glands of 5-, 10- and 20-day-old rats sacrificed during mid-light and mid-dark at each age. Melatonin was detectable in neonates (5-day-old), but day vs night differences in indole constituents did not occur until 10 days of age. Free amino acid steady state levels were high in neonates and there was a tendency for reversal of day vs night differences coinciding with the onset of circadian rhythmicity in indole biosynthesis. High correlations (r greater than 0.85) existed for taurine vs. glutamate in individual glands regardless of age and time of sacrifice. These findings suggest that taurine and glutamate are biochemically interrelated and that developmental changes in amino acid metabolic pools reflect functional innervation of the gland.

Uptake and Assimilation of NO(3) and NH(4) by Nitrogen-Deficient Perennial Ryegrass Turf.

Assimilation of NO(3) (-) and NH(4) (+) by perennial ryegrass (Lolium perenne L.) turf, previously deprived of N for 7 days, was examined. Nitrogen uptake rate was increased up to four- to five-fold for both forms of N by N-deprivation as compared to N-sufficient controls, with the deficiency-enhanced N absorption persisting through a 48 hour uptake period. Nitrate, but not NH(4) (+), accumulated in the roots and to a lesser degree in shoots. By 48 hours, 53% of the absorbed NO(3) (-) had been reduced, whereas 97% of the NH(4) (+) had been assimilated. During the early stages (0 to 8 hours) of NO(3) (-) uptake by N-deficient turf, reduction occurred primarily in the roots. Between 8 and 16 hours, however, the site of reduction shifted to the shoots. Nitrogen form did not affect partitioning of the absorbed N between roots (40%) and shoots (60%) but did affect growth. Compared to NO(3) (-), NH(4) (+) uptake inhibited root, but not shoot, growth. Total soluble carbohydrates decreased in both roots and shoots during the uptake period, principally the result of fructan metabolism. Ammonium uptake resulted in greater total depletion of soluble carbohydrates in the root compared to NO(3) (-) uptake. The data indicate that N assimilation by ryegrass turf utilizes stored sugars but is also dependent on current photosynthate.

Intercellular bridges in ovaries of the newborn gerbil.

This study describes intercellular bridges in the ovaries of neonatal gerbils. Electron microscopy has revealed the presence of true intercellular bridges, connecting oogonia or oocytes, in ovaries of newborn gerbils. The cytoplasm of the intercellular channels is similar to that of the connected cells, with mitochondria, smooth and rough endoplasmic reticulum, and free ribosomes present. Lysosomes are also occasionally present in the intercellular bridges and they may be involved in early waves of oocyte atresia. An electron-dense substance, 350-500 A thick, is located immediately beneath the unit membrane of the intercellular bridges. Accumulation of electron-dense material increases the thickness of the walls of the intercellular bridges, supporting and maintaining the patency of the channels. It is suggested that the intercellular channels probably allow the interchange of nutrients, organelles, and possibly regulatory materials as well.

Effects of methyl methacrylate monomer vapors on respiration and circulation in unanesthetized rats.

A study was conducted in which two groups of female rats were exposed to vaporized MMA-m for a period of 20 minutes daily for 21 and 42 days, respectively. Systolic blood pressure, heart rate, respiration, and ECG were monitored for 5 minutes prior to MMA-m exposure and then during a 20-minute exposure to MMA-m. On the twenty-first and forty-second day, respectively, the aforementioned vectors were monitored again. During the first exposure 63% of the experimental animals displayed marked changes in respiration ranging from a modified Cheyne-Stokes type to periods of very shallow breathing followed by deep breathing. Thirty-eight percent showed ECG changes ranging from premature ventricular contractions and altered QRS complexes to markedly depressed T waves. Continued exposure resulted in an initial decrease followed by an increased systolic blood pressure with an increased respiratory and heart rate. At the final testing period all animals showed abnormal respiratory patterns and ECG changes and demonstrated a heart block pattern. In all animals systolic blood pressure increased the longer they were exposed to MMA-m.

Laboratory grouping based on previous courses.

In the human physiology course at Loyola University School of Dentistry, students (N = 761, second-year classes from 1971 to 1976) were divided into three laboratory groups according to prior experience with physiology courses and laboratories. To determine the effects of this grouping on academic performance, data were obtained on grades in the physiology course, National Board scores in physiology (combined with biochemistry from 1973 to 1976), predental GPA, and predental science GPA. Comparisons were made between the three groups using t-tests, and correlation coefficients were obtained for physiology grade and National Board score, predental GPA, and predental science GPA. The results indicated that there were no significant differences among the three groups in performance in the physiology course or on the National Board Examination. Significant correlations were found between course performance and the other three variables. The overall impression of the faculty and the students was that the grouping program has been successful in improving laboratory performance and participation in the conference sessions.

Temporary auditory threshold shift following sophomore operative technique laboratory.

Twenty sophomore dental students were studied for the "temporary threshold shift" (TTS) due to exposure to the noise of high-speed dental headpieces during technique laboratory sessions. TTS was experienced at all four frequencies tested--8000, 6000, 4000, and 3000 hertz, but tended to be greater and of longer duration at the higher frequencies. Approximately one-fourth of the students still had some hearing loss 15 minutes after leaving the laboratory.

Occlusal force discrimination by denture patients.

A study was conducted on subjects with conventional dentures and with overlay dentures to compare their abilities to discriminate between occlusal forces. Perpendicular forces were applied to the dynamic center of the occlusal table of the mandibular denture. Each subject's ability to distinguish differences in values of force was observed and recorded. All subjects with dentures showed sensory threshold values close to those reported for natural teeth. A graphic plotting showed that the responses of subjects with overlay-type dentures were more closely correlated with the psychophysical law as expressed by Stevens as a power function. Since this phenomenon holds true for natural teeth, the overlay denture more closely resembles natural teeth in this type of sensory function than does the conventional denture. In addition to recognized advantages, such as preservation of the ridge and improved retention and stability, the overlay denture provides more typical sensory function than is provided by the conventional denture. This advantage should further motivate dentists and patients to consider the retention and utilization of at least two suitable teeth in an overlay-type denture service.