Histidine modulates the clastogenic effect of oxidative stress

The kinetics of the formation of single-strand breaks induced by H2O2 in DNA is more rapid in Eagle's Modified Minimal Essential Medium (MEM) than in phosphate-buffered saline (PBS). Among the components of MEM, we found that histidine increases the rate of degradation of DNA by H2O2 in PBS dose-dependently. In hamster lung fibroblasts histidine increases the cytotoxicity of H2O2, as well as the number of sister-chromatid exchanges and the frequency of micronuclei induced by hydrogen peroxide.     

Seasonal changes in the pigments, carbohydrates and growth of red spruce as affected by ozone

Two-year-old red spruce seedlings were exposed to various levels ot ozone, from 0.4 to 3 times ambient levels, in open-top chambers in Ithaca, NY, USA. Exposures, which varied with changes in day length, commenced on May 30, 1987 and continued until December 14, 1987. Seedling biomass, carbohydrate contents, pigment contents, and rate of electron transport were assessed twice monthly during the fumigation period. Orthogonal quadratic or cubic polynomials were used to model the response through time each variable measured. A one-way analysis of variance model was fitted to every regression coefficient in each polynomial model to test for ozone effects on seasonal physiological patterns. Ozone did not influence growth, foliar pigment content, foliar starch content, root carbohydrate content, or rate of electron transport. The seasonal change of needle raffinose content differed between exposed to low (0.4 ×, 1×) and high (2×, 3×) ozone levels. There was also a trend towards reduced total soluble sugar content foliage during late autumn in higher ozone treatments.     

The response of murine intestinal crypts to short-range promethium-147 beta irradiation: deductions concerning clonogenic cell numbers and positions

An exteriorized loop of mouse intestine was exposed to 147Pm low-energy electrons, where the dose rate decreased by a factor of 5 from the base of the crypt to the top of the proliferative zone. A crypt survival curve was obtained, expressed in terms of exposure time. The shape of the curve was interpreted in terms of survival parameters for colony-forming cells (clonogens) derived using 137Cs gamma rays and the depth-dose curve measured for 147Pm electrons. It is concluded that the shape of the crypt survival curve using 147Pm electrons is inconsistent with the notion of either the presence of a large number of clonogens or a small number near the top of the proliferative zone. A computer fitting procedure showed that the best agreement between predicted and observed curves was achieved with 2.7 +/- 0.5 clonogens at cell position 5.6 +/- 0.6, in the putative stem-cell zone.     

The dosage thresholds for disordered physical work capacity in mice and rats following irradiation

Physical efficiency of mice and rats at early times following irradiation with doses of 35 to 200 Gy was estimated by the muscle endurance and motor coordination indices. A threshold nature of the effects was exhibited at high doses. For instance, as large as 40 Gy was the dose threshold at which stability in the accomplishment of the known operations was impaired; at 70-100 Gy, the accomplishment decreased down to 50% of the initial level, by the 2nd hour after irradiation, with the subsequent partial restoration; 200 Gy was the threshold dose at which the disturbances were irreversible. These values were also similar to those of the threshold doses at which clinical picture of the affection was changed.     

Isolation of a natural cytotoxic IgM "antibody" in human serum sensitizing L cells to complement

An IgM fraction of human serum was isolated and purified. A portion of this fraction firmly attaches to L cells' surfaces, which sensitizes these cells to the lytic action of low concentrations of serum C. It contains the natural cytotoxic "antibody" to L cells.     

Central nervous system malformations induced by triamcinolone acetonide in nonhuman primates: pathology

Triamcinolone acetonide (TAC) was administered to pregnant macaques (Macaca mulatta [15] and M. radiata [7]) during gestational days (GD) 23 to 41 using various dosing schedules. A daily dose of 10 mg/kg is approximately equal to 100 x the human dose equivalent. The brains of the fetuses and infants were studied grossly and histologically. All cases displayed either the mild form of the TAC-induced syndrome (craniofacial dysmorphia, cranium bifidum occultum, meningocele, and mild distortion of the midbrain) or the more severe form (occipital encephalocele, hydrocephalus, severe distortion of the midbrain or midbrain "beaking," shunting of cerebrospinal fluid, and craniofacial malformations). The dysmorphology was dose-related, with severity increasing at higher doses or with increased numbers of treatments. Individual cases were assessed for the severity of the syndrome by comparison of like components between groups. The lesions observed were morphologically comparable to those described in spontaneous human cases; the TAC-induced occipital encephaloceles were associated with brainstem and cerebellar abnormalities, and, with the less severe form of the syndrome, brainstem abnormalities were occasionally present, with occipital meningoceles. Controversy exists concerning the significance and temporal development of the midbrain changes. However, the associated alteration in aqueduct conformation may have been responsible for functional compromise and ensuing hydrocephalus.     

A standardized x-ray examination of mandibular fractures

Proceeding from an x-ray examination of 143 patients with mandibular fractures, the most informative methods and projections as well as the order of their use with account of the site of a fracture, were determined. The most informative method in all fracture sites was orthopantomography; panoramic roentgenography was indicated only in fractures of the frontal part. If panoramic tomography cannot be done, roentgenography or electroroentgenography in the frontal-nasal projection is recommended. If panoramic roentgenography cannot be done, extraoral roentgenography is indicated in the diagnosis of fractures of the frontal part of the mandible.