Effect of butanedioic Acid mono (2,2-dimethylhydrazide) on the activity of membrane-bound succinate dehydrogenase

Mitochondria isolated from hypocotyls of five-day-old bean (Phaseolus vulgaris L. `Black Valentine') seedlings rapidly oxidized succinate, malate, and NADH. Oxidation rates, respiratory control, and ADP:O ratios obtained with saturating concentrations of all three substrates indicated that the mitochondria were tightly coupled. The mitochondrial preparation was then employed to investigate the respiration-inhibiting effects of butanedioic acid mono (2,2-dimethyl-hydrazide) (daminozide) a plant growth retardant having structural similarity to an endogenous respiratory substrate (succinate). Daminozide markedly inhibited the activity of membrane-bound succinate dehydrogenase. Inhibition was of the competitive type (apparent K_i, 20.2 millimolar) with respect to succinate. Although not excluding other hypotheses, the results support an active role for daminozide in the suppression of respiration as an important metabolic site of its action as a plant growth regulator.     

Clastogenic activity in urine of workers occupationally exposed to pesticides

Genotoxicity in the urine of orchardists occupationally exposed to pesticides was investigated. Urine samples were obtained during pre-spraying and spraying periods from 22 non-smoking orchardists who spray large amounts of pesticides during the fruit growing season. For comparison purposes, urine was collected from 11 non-smoking personnel at an agricultural research station located near the application site and from 21 non-smoking individuals (reference controls) in a non-agricultural area. Organic material was isolated from urine by preparative reversed-phase high-pressure liquid chromatography, and assayed for clastogenic activity using Chinese hamster ovary cells. Urine samples collected during the pre-spraying period showed no significant differences in clastogenic activity compared to that found for the reference control group. However, clastogenic activity of urine specimens collected during the spraying period was significantly elevated (p less than 0.001) for the highly-exposed orchardists, but not for the research station personnel. Clastogenicity of orchardists' urine was observed within 8 h of pesticide application.     

Hyperplasia of jejunal smooth muscle in the myenterically denervated rat

Summary Application of a cationic surfactant, benzalkonium chloride, to the serosa of rat jejunum results in an increase in thickness of both longitudinal and circular smooth muscle layers. The increase in thickness is due primarily to an increase in the number of smooth muscle cells (hyperplasia). Little cellular hypertrophy was observed. The time sequence of surfactant-induced effects on the muscle layers was determined. Within 24 h, total destruction of the longitudinal muscle and partial destruction of the circular muscle was evident. The myenteric plexus was also necrotic; however, the submucosal plexus remained intact. By 48 h after surfactant treatment, the smooth muscle cells remaining in the circular muscle layer had begun to divide, as indicated by the presence of mitotic figures and incorporation of ³H-thymidine. A repopulation of the longitudinal muscle layer began at this time, apparently the result of migration of cells arising in the circular muscle layer. By 5 days post-treatment, both muscle layers had regenerated to their original states. The myenteric plexus was totally absent. The denervated smooth muscle cells proceeded to divide until approximately day 15, resulting in hyperplasia of both muscle layers. Between 15 and 105 days, the number of muscle cells in the circular layer progressively declined, eventually returned to the value seen in control tissue. In contrast, the number of smooth muscle cells in the longitudinal layer remained elevated through the period of study (165 days). We hypothesize that the smooth muscle hyperplasia observed after serosal benzalkonium chloride application results from loss of the myenteric nerves.     

Congenital cataract linked to the Y chromosome]

A possible Y linked form of congenital cataract is reported, but an autosomal dominant mode of inheritance cannot be ruled out.     

A Pooled Response Strategy for Combining Multiple Lines of Evidence to Quantitatively Estimate Impact

The impacts of sediment contaminants can be evaluated by different lines of evidence, including toxicity tests and ecological community studies. Responses from 10 different toxicity assays/tests were combined to arrive at a “site score.” We employed a relatively simple summary measure, pooled P-values where we quantify a potential decrement in response in a contaminated site relative to nominally clean reference sites. The response-specific P-values were defined relative to a “null” distribution of responses in reference sites, and were then pooled using standard meta-analytic methods. Ecological community data were also evaluated using an analogous strategy. A distribution of distances of the reference sites from thecentroid of the reference sites was obtained. The distance from each of the test sites from the centroid of the reference sites was then calculated, and the proportion of reference distances that exceed the test site difference was used to define an empirical P-value for that test site. A plot of the toxicity P-value versus the community P-value was used to identify sites based on both alteration in community structure and toxicity, that is, by weight-of-evidence. This approach provides a useful strategy for examining multiple lines of evidence that should be accessible to the broader scientific community. The use of a large collection of reference sites to empirically define P-values is appealing in that parametric distribution assumptions are avoided, although this does come at the cost of assuming the reference sites provide an appropriate comparison group for test sites.     

A study of the localization of polynucleotide phosphorylase within rat liver cells and of its distribution among rat tissues and diverse animal species

1. Rat liver polynucleotide phosphorylase was localized in the mitochondrion, but may also occur in the nucleus. 2. The mitochondrial enzyme was found in rat heart, kidney, liver, muscle and spleen. 3. Mitochondrial polynucleotide phosphorylase is also present in calf, chicken, guinea-pig and rabbit liver and in goldfish muscle. 4. A possible physiological role for the enzyme in the control of the intramitochondrial ADP concentration is suggested.