Per Kjellstrand

Effects of organic solvents on motor activity in mice

Groups of male mice were exposed via inhalation to methylene chloride, perchloroethylene, toluene, trichloroethylene or 1,1,1-trichloroethane. The exposures were started at 2300 h. Generation of vapor was stopped after 1 h. Motor activity of the animals during the exposures was measured with a Doppler radar. Several concentrations of each solvent were tested. Concentrations could be found for all solvents at which they initially increased the motor activity. When the generation of vapor was terminated and the concentration started to decline, a new phase of changes in motor activity was induced. At this phase, motor activity was in most cases influence in the opposite direction to that at the beginning of the exposure. Trichloroethylene concentrations could be found which gave no increase in activity at the start of exposure but a prominent decrease at termination. The lowest concentration at which effects could be seen was different for the different solvents. Perchloroethylene was more and 1,1,1-trichloroethane less potent than the other solvents in inducing motor activity. The time pattern of the motor activity alterations was specific for each solvent. Both the concentration and the rate of the concentration increase were responsible for the effects on motor activity. The differences between the solvents probably reflect differences in their site of action, their distribution and their biotransformation.

Exposure and removal of stainable groups during Feulgen acid hydrolysis of fixed chromatin at different temperatures

SummaryHyperdiploid Ehrliohs ascites tumour cells grown in male mice (strain NMRI) were labeled with radioactive nucleotides. The nucleic acids were extracted from fixed, air-dried smears by fractionated hydrolysis and their radioactivity measured by liquid scintillation. The experiments showed that the exposure of aldehydes through removal of purine bases and the elimination of these aldehydes through depolymerisation of DNA were the two main processes responsible for the Feulgen hydrolysis curve. They were shown to be independent and overlapping. The depurination can be described as a simple hydrolytic reaction, while the extraction of DNA depends on a number of different factors. This entails that, in the Feulgen acid hydrolysis procedure, the part of DNA measured is dependent upon the stability of the chromatin. It was found that it is possible accurately to determine the depolymerisation process and thereby roughly correct the measured amount of Feulgen DNA.

Toxicity of heat sterilized peritoneal dialysis fluids is derived from degradation of glucose.

Heat sterilization makes peritoneal dialysis (PD) solutions cytotoxic. Two compounds in the solutions, lactate and glucose, can be degraded by heat. This studys goal was to discover which of the compounds was responsible for the cytotoxicity. The influence of sterilization temperature on degradation of the compounds was also subjected to investigation. Solutions of glucose and lactate and a mixture of lactate and glucose were prepared. These were sterilized in glass ampules in an oil bath at different temperatures for varying times. Toxicity was determined as inhibition of cell growth with a fibroblast cell line (L929), and ultraviolet (UV) absorbance was measured at 284 nm. Lactate solutions did not show cytotoxicity after heat sterilization. Glucose solutions that were heat sterilized showed an increase in UV absorbance at 284 nm and were cytotoxic. The mixture of lactate and glucose exhibited the same cytotoxicity as glucose alone. Lower sterilization temperatures lead to increased cytotoxicity and an increase in UV absorbance at 284 nm. Results indicate that the toxic products formed during heat sterilization of PD fluids are derived from glucose.

Trichloroethylene: Effects on body and organ weights in mice, rats and gerbils

The influence of continuous inhalation of 150 ppm trichloroethylene (TCE) on body, liver, spleen, and kidney weights in rats, mice, and mongolian gerbils was tested. An age dependent decrease in body weight gain was observed in female rats exposed to TCE. All 3 species showed liver enlargement caused by the exposure. The effect was much more pronounced in mice, in which the increase was 60--80%, than in rats and gerbils where it was only 20--30%. After the end of the TCE-exposure the liver weights of the mice decreased rapidly. After 5 days of rehabilitation the weight was only 10--20% higher than that of the controls. This difference persisted for at least 25 days. The spleen weight appeared unaffected or somewhat smaller in TCE-exposed animals of all species. An increased kidney weight (15%) was observe din TCE-exposed gerbils. This effect was less pronounced in mice and rats. Effects on the liver have earlier been seen only after exposure to concentrations much higher than that used in the present study. This difference in results is proposed to be due to the different schedules used for the exposure.

Effects of trichloroethylene inhalation on proteins of the gerbil brain.

Inhalation exposure of adult Mongolian gerbils to 320 ppm of trichloroethylene (TCE) during 8 weeks causes a decrease of soluble proteins per wet weight in frontal cerebral cortex, cerebellar anterior part of the hemispheres and in the posterior part of vermis, as well as in hippocampus, although the levels of S 100, a glial cytoplasmic protein, showed an overgoing increase back to control levels, or a significant increase. In the sensory-motor cortex, an overgoing increase of soluble proteins, as well as of the S 100, were observed during the exposure period.One of the major soluble polypeptides (m.w. 50,000–52,000) of cerebral cortex, the cerebellar hemispheres and the brain stem, decreased at the end of the exposure period. Possible candidates for such a polypeptide are among others the subunit of microtubular protein or a subunit of (Na+K+)-ATPase.The results show that inhalation of TCE effect various brain areas differently. The observed biochemical changes could be interpreted as an adaptation and in some brain areas neuronal cells seem to be more sensitive than glial cells to TCE.

Brain lipid changes in rats exposed to xylene and toluene

Rats were continuously exposed to vapors of xylene (320 ppm) for 30 or 90 days, other groups were exposed to toluene (320 ppm) for 30 days. After termination of exposure, different brain regions were removed for the determination of their lipid contents and ethanolamine phosphoglyceride fatty acid patterns. The 2 solvents had different effects on the animals. Xylene exposure resulted in limited transient changes. After 30 days exposure an increase in the liver to body weight ratio and a decrease in linoleic acid of ethanolamine phosphoglyceride in the cerebral cortex were observed. These changes were normalized after 90 days exposure. Toluene exposure, on the other hand, resulted in decreased weights of the body, of the brain as a whole and of the cerebral cortex. Liver weights were unchanged. Total phospholipids were found to be reduced in the cerebral cortex where also a slight increase in phosphatidic acid was observed. In this brain region a minor fatty acid of ethanolamine phosphoglyceride, 22:5 (n-3), was decreased. No changes were observed in the brainstem. The data on brain weights and lipid composition after exposure to toluene indicates a breakdown of phospholipids resulting in a loss of gray matter. The mechanism for these changes is uncertain but may involve degradation of phospholipids by phospholipase D. The effective metabolism of xylene and toluene seem to protect from fatty acid changes of brain phospholipids previously observed after exposure to chlorinated ethylenes.

A study of DNA depolymerisation during feulgen acid hydrolysis

SummaryThe binding of Schiff dye molecules after acid hydrolysis (1 M HCl) for varying lengths of time was studied in ascites tumour cells. The amount of dye bound to the tumour cells closely followed the number of aldehyde groups, calculated from the extraction of radioactive nucleotides. This constant dye to aldehyde ratio did not change when the hydrolysis was performed at a lower acid concentration (0.3 M HCl). The conclusion drawn is that Feulgen dye measurements represent, in a constant way, the number of aldehydes on DNA at any given time during hydrolysis. The alteration of the hydrolysis pattern of chromatin fixed in formalin was found to be due to a slower extraction of DNA depolymerisation products, the purine liberation being unaffected. A similar explanation is offered for the extreme pattern obtained from hydrolysis of bull spermatozoa chromatin.

Mechanisms of the Feulgen acid hydrolysis.

Our present knowledge of the two main reactions responsible for the form of the Feulgen hydrolysis curve is summarized. A suggestion that hydrolysis slightly above room temperature and in 5 M HCl is preferable is made and discussed. A formula making it possible to calculate the appropriate hydrolysis time at any normally used acid concentration and temperature is presented.

Influence of acid concentration and temperature on fixed chromatin during Feulgen hydrolysis.

SummaryLabelled nucleic acid were extracted from fixed, air-dried smears of Ehrlichs ascites tumour cells by fractionated hydrolysis and measured by liquid scintillation. It was found that the rates of RNA and DNA depolymerisation and of DNA depurination depended on temperature in the same way. The DNA extraction patterns retained their form when the temperature was varied. When the hydrolysis was performed in decreasing acid concentrations, however, there was a concomitant change in the form of the depolymerisation pattern. This change affects the amount of aldehyde groups available for dye-binding with the Feulgen method after the optimal hydrolysis time. The alteration in shape of the Feulgen curve is discussed and supposed to be due to an increased interaction between DNA and other macromolecules. It is suggested that this interaction may be useful in detecting differences in chromatin stability between cells which differ in gene activity.

Fatty acid changes in rat brain ethanolamine phosphoglycerides during and following chronic exposure to trichloroethylene

Rats were exposed by continuous inhalation to a moderate level of trichloroethylene (1720 mg/m3). The fatty acid pattern of brain ethanolamine phosphoglycerides was examined during exposure and after an additional exposure-free period. Alterations in the fatty acid pattern were noted after 30 days of exposure. An increased ratio of linoleic acid-derived (n-6) to linolenic acid-derived (n-3) fatty acids was observed in the cerebral cortex, the hippocampus, and the brain stem. Of the major fatty acids, arachidonic acid (20:4(n-6)) was increased in the cerebral cortex and the brain stem, while docosahexenoic acid (22:6(n-3)) was decreased in the cerebral cortex and the hippocampus. A further change in these fatty acids was observed in the cerebral cortex following a longer exposure period of 90 days. The 22-carbon linoleic acid-derived fatty acids were also increased after 90 days of exposure. These findings imply that trichloroethylene affects the metabolism of ethanolamine phosphoglyceride fatty acids in the rat brain by inhibiting desaturation of the linolenic acid family and by increasing desaturation of the linoleic acid family. The effect of trichloroethylene was partially reversible, since a postexposure solvent-free period revealed a rapid partial normalization of 22:6(n-3), which is the most important fatty acid of the linolenic acid family in the rat brain. However, the precursor of this fatty acid, 22:5(n-3), was decreased during the first 10 exposure-free days. This suggests that desaturation over the first steps was still impaired. A complete normalization of the fatty acid pattern was not observed during the 30-day solvent-free period. The decreased number of double bonds and shorter chain lengths detected after solvent exposure is consistent with the idea of a compensatory remodeling of membrane lipid composition based on membrane stability with regard to phase preference.