Spectrophotometric analysis of RNA and DNA using cetyltrimethylammonium bromide

TaSPL13 regulates inflorescence architecture and development in transgenic wheat (Triticum aestivum L.)

The SQUAMOSA promoter-binding protein-like (SPL) proteins play vital roles in plant growth and development in rice (Oryza sative L.) and Arabidopsis thaliana (L.) Heynh. However, few studies regarding the SPL proteins have been reported in wheat. In this study, 56 TaSPLs were clustered into eight groups according to an OsSPL phylogenetic comparison analysis. The expression patterns of TaSPLs in different tissues were analysed by RNA-seq data, and partial results were confirmed by qRT-PCR. Based on the above results, genes such as TaSPL13 and TaSPL15 may be involved in spike or seed development in wheat. Multiple genes that regulate the inflorescence architecture of rice have been identified. Additionally, studies on the genes associated with spikelet development in wheat have been reported relatively rarely. Here, TaSPL13-2B was transferred into wheat cv. Bobwhite. Compared with the wild type, the transgenic lines showed significant increases in the number of florets and grains per spike, indicating that TaSPL13-2B could influence the floret development of wheat. TaSPL13-2B was transferred into rice cv. Nipponbare, which demonstrated that TaSPL13-2B can modify panicle architecture in transgenic rice, with significant increases in panicle length, the number and length of primary branches, and the number of secondary branches.

An investigation on interaction between 14mer DNA oligonucleotide and CTAB by fluorescence and fluorescence resonance energy transfer studies

Possible interaction mechanisms between oligonucleotide (DNA) of 14 base pairs with cetyl trimethyl ammonium bromide (CTAB) were postulated based on fluorescence and fluorescence resonance energy transfer (FRET) studies. Detailed FRET investigations were carried out by fluorometric titrations of the surfactant with various oligonucleotide duplexes with 5'-tagged fluorescein (donor) (D(D)), 5'-tagged TAMRA (acceptor) (D(A)) and both (D(DA)). In general, fluorescence spectra of the duplexes (D(D), D(A) and D(DA)) revealed a reduction in the fluorescence intensities of 5'-fluorescein as well as 5'-TAMRA and thereafter an attainment of saturation with increase in the surfactant concentration. The observed changes in the oligonucleotide fluorescence intensities for the duplexes under investigation could be attributed to the microenvironmental changes during the oligonucleotide-CTAB interaction. Considering together, it appeared that the interaction is a three-stage process, wherein the initial addition of surfactant caused neutralization of the 14mer at Z(+/-)(1) = 0.8, which is manifested by a slight reduction in fluorescence intensity. Further, addition of the surfactant molecules sharply reduced the fluorescence intensity of the oligonucleotide depicting oligonucleotide induced self-assembly until the second break point (Z(+/-)(2) = 1.7). From the second break point, a striking resonance energy transfer was observed from donor to acceptor, which revealed shortening of distance between 5' ends of the oligonucleotides that attained a saturation at Z(+/-)(3) = 2.5. Similar three-stage interaction of oligonucleotide with the surfactant has also been observed through fluorometric titrations in the presence of NaCl. However, in the presence of the salt, neutralization of oligonucleotide, surfactant aggregation and FRET occurred at higher charge ratios due to the screening effect of Na+ ions followed by an increase in critical association concentration (CAC) of the surfactant. Overall, investigations probe possible structural changes in the 14mer oligonucleotide-CTAB complex upon increase in the surfactant concentration.

CTAB precipitation of cestode DNA

DNA probes are proving extremely valuable in the characterization o f cestodes - as well as other parasites. In this article, Kok Wei Yap and Andrew Thompson discuss some of the problems of DNA isolation, stressing the need for a gentle and economical procedure such as CTAB precipitation.

Determination of DNA with cetyltrimethylammonium bromide by the measurement of Resonance Light Scattering

A simple assay of DNA was developed based on the measurements of enhanced signals of Resonance Light Scattering (RLS) of cetyltrimethylammonium bromide (CTMAB) by DNA. The enhanced RLS signals, measured by simultaneously scanning the excitation and emission monochromators of a common spectrofluorometer with lambda ex = lambda em, was optimized for the DNA assay with CTMAB. On the conditions of pH 2.21 and ionic strength 0.002, the enhanced RLS intensity at 470.0 nm, delta I, was found to be proportional to the concentration of DNA in the range 0-2.5 micrograms/ml if 1.5 x 10(-5) M CTMAB was used. Limits of determination for calf thymus DNA and fish sperm DNA were 4.9 ng/ml and 9.2 ng/ml, respectively. Synthetic samples were determined with the recovery ratio ranging from 93.2% to 105.1%, and the RSD is lower than 2.7%.

A domain of the hepadnavirus capsid protein is specifically required for DNA maturation and virus assembly

Mutations introduced into the capsid gene of duck hepatitis B virus (DHBV) were tested for their effects on viral DNA synthesis and assembly of enveloped viruses. Four classes of mutant phenotypes were observed among a series of deletions of covering the 3' end of the capsid open reading frame. Class I mutant capsids were able to support normal single-stranded and relaxed circular viral DNA synthesis; class II mutant capsids supported normal single-stranded DNA synthesis but not relaxed circular DNA synthesis; class III mutant capsids resembled class II capsids, but viral DNA synthesis was inhibited 5- to 10-fold; and class IV capsids were severely restricted in their ability to support viral DNA synthesis. Class I capsids were assembled into enveloped virions, but class II, III, and IV capsids were not. Viral DNA synthesized inside class II capsids was normal with respect to minus-strand DNA initiation, plus-strand DNA initiation, and circularization of the DNA, but plus strands failed to be elongated to mature 3-kb DNA. The results suggest that a function of the capsid protein specifically required for viral DNA maturation is also required for assembly of nucleocapsids into envelopes. Thus, class II mutants appear to be defective in the appearance of the "packaging signal" for virus assembly (J. Summers and W. Mason, Cell 29:403-415, 1982).

Measurement of microgram quantities of protein by a generally applicable turbidimetric procedure

A modified turbidimetric method for protein determination which involves the use of trichloroacetic acid as the precipitating agent is described. Maximal turbidity develops in less than 30 min and is stable for at least 120 min. A linear relationship between turbidity at 340 nm and protein concentration is observed between 2 and 40 micrograms protein. Sodium dodecyl sulfate is added to avoid the interference by nonionic and cationic detergents and lipids and to decrease the protein-to-protein variation. The use of cetyltrimethyl ammonium bromide provides a two-step procedure to correct for the contribution of contaminating nucleic acid. Many compounds which interfere with other protein quantitation methods have no effect on this system. The interference of commonly used reagents as sucrose and urea can be easily corrected. This procedure compared favorably with the most widely used protein quantitation methods in simplicity, sensitivity, and specificity.

Taenia hydatigena: isolation of mitochondrial DNA, molecular cloning, and physical mitochondrial genome mapping

Mitochondrial DNA was isolated from Taenia hydatigena, T. crassiceps, and Echinococcus granulosus using a cetyltrimethylammonium bromide precipitation technique. The technique is simple, rapid, reproducible, and does not require extensive high speed ultracentrifugation. The advantage of using mitochondrial DNA from taeniid cestodes for comparative restriction analysis was demonstrated. Mitochondrial DNA of T. hydatigena was isolated as covalently closed circular molecules. These were linearized by single digestion with BamHI and the molecular weight was estimated from the linear form of 17.6 kb. The mitochondrial DNA of T. hydatigena is therefore similar in size and structure to that of many other animal species. The entire mitochondrial genome was cloned into pBR322 in Escherichia coli and a restriction map of the recombinant molecule was constructed. The potential of using the cloned mitochondrial genome as a probe in speciation studies as well as for providing functional information on the role of the cestode mitochondrion is discussed.

Long day lengths increase brain weight and DNA content in the meadow vole, Microtus pennsylvanicus

Male voles reared in long (spring) day lengths had heavier brains with greater total DNA content than did males housed in short (fall) day lengths; these effects were not observed in female littermates kept in the two photoperiods. Male brains were heavier than female brains in long but not in short photoperiods. Day length affected brain mass during early postnatal development, but not when treatments were initiated in adulthood. Seasonal differences in brain development, including the numbers of neurons and glia, may reflect different metabolic and behavioral demands faced by males born in spring and fall, respectively.

Acute biological effects of commercial cresyl diphenyl phosphate in rats

A commercial cresyl diphenyl phosphate preparation was analyzed to contain approximately 35% of triphenyl phosphate, 45% of cresyl diphenyl phosphates, 18% of dicresyl phenyl phosphates and 2% of tricresyl phosphates. The product was almost free of the o-cresyl isomers as revealed by the analysis of its alkaline hydrolysis products. A single intraperitoneal injection (150 or 300 mg/kg) caused an induction of microsomal cytochrome P-450 in the liver of Wistar rats with a concomitant increase in the activities of mixed function monooxygenases and proliferation of smooth endoplasmic reticulum 24 h after the treatment. These effects were not detected in the kidneys. The morphological changes in hepatocytes included the enlargement of nuclei and mitochondria with increased cristae. The hepatic morphology returned to normal 2 weeks after the treatment. The activity of pseudocholine esterase in blood was inhibited 4 h and 24 h after the injection but the effect levelled off. The concentration of the organophosphates in blood and liver decreased rapidly with only traces detected in blood after 24 h. No effects on the activities of cerebral and muscle acetylcholine esterase were observed. The treatment (300 mg/kg) inhibited the brain--2',3'-cyclic nucleotide 3'-phosphohydrolase through the 2-week observation period associated with demyelination in peripheral nerves.

Role of polyamines in experience-dependent brain plasticity

Enriched experience increases brain growth, neuronal differentiation and learning abilities. Polyamines are modulators of growth and differentiation. We studied the effect of difluoromethylornithine (DFMO, an inhibitor of putrescine synthesis) on brain growth of rats exposed either to a complex or an impoverished environment. In both environmental conditions, DFMO decreased cortical putrescine by 50% and increased spermine by 13%; spermidine remained constant. Cortical RNA was not affected significantly by DFMO but DNA was decreased exclusively in rats exposed to the impoverished environment. Environmental complexity increased cortical weight, RNA and spermidine content. These differences were larger in DFMO-injected rats than in saline controls. Since stimulants such as amphetamines also enhance the environmental effects it was conceivable that DFMO might act as a stimulant. We have measured the effect of DFMO on rats' exploratory activity and found it decreased by the drug. Therefore the enhancing effect of DFMO cannot be explained by its behavioral activity. We propose that DFMO enhances the experience-dependent brain plasticity by facilitating differentiation of neurons.

Forty minutes of experience increase the weight and RNA content of cerebral cortex in periadolescent rats

The goal of this work was to determine the shortest period of exposure to environmental complexity (EC) that would produce measurable changes in brain weight or RNA content. This period varied with the age of subjects. In young adult rats, 3 months old, 4 days of exposure to EC increased the RNA concentration in the occipital cortex above the level of littermates kept in impoverished condition (IC). Cortical weight was not affected. Seven or one daily hrs of exposure to EC did not produce significant differences between rats in EC and IC. In periadolescent rats, 30- to 40-day-old, 1 daily hr of enrichment for 4 days increased both the weight of occipital cortex and its RNA content. Exposures of 7 or 24 hrs/day produced similar results. In another experiment with periadolescent rats 1 hr or even 10 min of exposure to EC per day, for 4 days, increased total cortical weight and RNA content. Thus, periadolescent rat brain display remarkably high plasticity. These very short exposure periods are comparable to the duration of learning sessions in simple formal trainings.

Studies with digitonin-treated rat hepatocytes (nude cells)

Isolated rat hepatocytes were treated with digitonin to strip the plasma membrane. The effect of digitonin concentration and exposure time on the recovery of marker enzymes for cell organelles was examined. Hepatocytes treated at room temperature for 1-2 min with 1 mg/ml of digitonin lose some 40% of their protein but retain over 95% of their intact mitochondria and peroxisomes, 90-95% of their endoplasmic reticulum, and about 80% of their lysosomal enzymes. There is little loss of the mitochondrial intermembrane content, and both oxygen uptake and phosphorylation are unimpaired by the treatment. Electron microscopy reveals a complete loss of the plasma membrane, in spite of limited loss of marker enzymes for this membrane. Scanning electron microscopy revealed the interior of the cells to be made up of a dense network of fibers and lamellae attached to the nucleus, mitochondria, and small organelles. The treated cells were stable for many hours when kept in 0.25 M sucrose containing 25 mM monovalent salts. In salt-free sucrose the cells broke up very rapidly into nuclei and other single organelles. Addition of 5 mM NaCl or KCl retards breakup, and 15-20 min were required for dissolution. Intermediate stages, illustrated by scanning electron micrographs, show structure and chains made up mainly of mitochondria held together by a lamellar network. The rapid breakdown occurred at a pH above 7.5 in an oxygen atmosphere and in the presence of phosphate and apparently is an energy-requiring process. It is slow below a pH of 7.2, and at a pH of 6.8 the treated cells remain completely stable in salt-free sucrose. Our results suggest that endoplastic reticulum is a major component of the cytostructure holding together nuclei and organelles.

Toxicity of polymethylmethacrylate thermodegradation products

Polymethylmethacrylate was thermally degraded in air at 300 degrees C and the volatile decomposition products studied with gas chromatography-mass spectrometry. The main product was monomeric methacrylate, although many other compounds existed among the products. Electron spin resonance spectroscopy revealed the presence of free radicals. Wistar rats were exposed to the fumes of the plastic (300 degrees C) and their lungs and brain studied for biochemical effects. In the lung, the activity of 7-ethoxycoumarin O-deethylase decreased and an initial inhibition of glutathione peroxidase and superoxide dismutase was observed. The contents of reduced nonprotein sulfhydryl groups were decreased in the lung and brain. The exposures enhanced the activities of acetylcholine esterase, creatine kinase and NADPH-diaphorase in the brain. Scanning electron microscopy of the exposed lungs showed disorganization of ciliated cells, and the epithelial serous cells (Clara cells) were damaged.

Burden and biochemical effects of extended tetrahydrofuran vapour inhalation of three concentration levels

Adult male rats exposed to tetrahydrofuran vapour at 8.2 (200 p.p.m.), 41 (1,000 p.p.m.) or 82 mumol/l (2,000 p.p.m.) for 2 to 18 weeks, five days a week, 6 hrs daily, showed dose-dependent brain and perirenal fat solvent burden linearly correlated to each other. After two weeks of exposure, the body burden of tetrahydrofuran seems to decrease. This might have been caused by increased oxidative metabolism as enhanced 7-ethoxycoumarin O-deethylase activity was detected in liver and kidneys in the 2nd week and onwards. The exposure also caused inhibition of alcohol and formaldehyde dehydrogenase activities in liver at the highest dose. Biochemical effects in the cerebellum were not detected while gluteal muscle specimens showed increased succinate dehydrogenase activity in a dose-related manner. This points to effects on the energy metabolism. Muscle acetylcholine esterase activity was also increased showing possible effects on the myoneural junctions.

Neurochemical effects of ethylhexyl nitrate in rats

Rats injected i.p. with 100 mg ethylhexyl nitrate/kg body wt excreted 0.3% of the dose in the urine within 24 h. No urinary nitrite was found within 5 postinjection hours while an output of 26.9 +/- 15.8 micrograms nitrite/h X kg body wt. was detected between 5-24 h. Cerebral glutathione concentration was below the control level after 1 day but returned to control value after 3 and 7 days postinjection. Brain acetylcholine esterase activity was marginally decreased after 1 day while RNA and succinate dehydrogenase assay excluded major structural damage. It seems that the mechanism of clinical symptoms experienced by exposed workers are comparable to those exposed to dynamite and are largely functional.

Effects of nutrition and environment on brain biochemistry and behavior

A factorial design was used to explore the influence of malnutrition and environmental enrichment on brain development and adult behavior. Malnutrition in suckling rats was produced by restricting the intake of their dams to 40% of normal food consumption. Environment was enriched using combined preweaning handling and a postweaning complex environment treatment. Malnutrition produced lasting effects upon brain biochemical composition and behavior. The environmental manipulation had no ameliorative effect on the brain parameters measured but it had pronounced effects on behavior, decreasing latency to move in the open field and increasing some measures of activity while it enhanced passive-avoidance performance. There was little evidence for any interaction between the nutritional and environmental variables, but all trends were in the direction of the environmental treatment having more effect on the well-nourished rats.

Nuclear testosterone receptors in the ovine testis

Nuclear [3H] testosterone-receptor complexes were demonstrated in hypophysectomized ram testis after in vitro direct labelling. The nuclear binding was maximal after a 45 min incubation of the tissue. The receptors are extractable by 0.4 M KC1 or NaSCN with a 25-30% efficiency. They migrate towards the anodic region during electrophoresis on agar gel. Nuclear androgen receptors were characterized in intact lamb testis by a testosterone exchange assay. After precipitation by protamine sulphate, the receptors were labelled with [3H]testosterone during a 12 h incubation at 4 degrees C. The exchange activity was linear between 0.1 and 0.9 mg of DNA per ml of incubation buffer. The receptors bind testosterone with a limited capacity (40-180 fmoles per mg DNA) and a dissociation constant Kd of 2 x 10(-9) M. Their relative affinities for steroids are dihydrotestosterone greater than testosterone greater than estradiol greater than progesterone greater than 5 alpha-androstanediol greater than cyproterone acute greater than R5020.

Replication of the genome of a hepatitis B--like virus by reverse transcription of an RNA intermediate

Duck hepatitis B virus, a DNA virus closely related to human hepatitis B virus, was studied in infected duck liver. Subviral particles resembling the viral nucleocapsid cores were isolated from persistently infected liver and shown to have a DNA polymerase activity that utilizes an endogenous template and synthesizes both plus- and minus-strand viral DNA. Synthesis of the viral minus-strand DNA utilized an RNA template that was degraded as it was copied. Viral plus-strand synthesis occurred on the completed minus-strand DNA. A pathway for the replication of the DNA genome of hepatitis B-like viruses by reverse transcription of an RNA intermediate is proposed.

Effects of extended peroral borate ingestion on rat liver and brain

2-Month-old male Wistar rats were given sodium tetraborate in drinking water (3 g/l). Cerebral succinate dehydrogenase activity increased after 10 and 14 weeks of exposure. Increased RNA concentration and increased acid proteinase activity in brain occurred after 14 weeks. NADPH-cytochrome c reductase activity and cytochrome b5 content decreased in the liver microsomal fraction after 10 and 14 weeks. A reduction in the cytochrome P-450 concentration was detected at 14 weeks. The results support the hypothesis that borate anion exerts its toxic action by interfering with flavin metabolism in flavoprotein-dependent pathways.

Changes in cecal composition with Eimeria tenella infection

In each of three trials, the wet and dry weights of Eimeria tenella infected ceca were significantly increased compared to the control. The percentage of moisture and lipid in the cecal tissue remained unchanged or slightly increased. These effects were observed for all parasite strains examined and were detectable as early as day 4 postinoculation. Analysis of cecal protein and DNA suggested a uniform increase in cecal tissue rather than the production of a specific protein or component in response to the infection. Histological measurements of infected ceca, compared with the control, showed a twofold increase in both mucosal thickness and muscular thickness.

Neurochemical effects of short-term inhalation exposure to vinyltoluene vapor

Male rats were exposed to vinyltoluene vapor after pretreatment with polychlorinated biphenyl (PCB). Brain and body solvent burdens were in a linear relationship to the exposure level although it changed between the two weeks while the solvent accumulated in the perirenal fat. The pretreatment caused a significantly smaller burden in the fat samples. Lysosomal acid proteinase was above the control range in the brain homogenate in the highest exposure, while glutathione peroxidase and 2',3'-cyclic nucleotide 3'-phosphohydrolase showed a dose-dependent decrease in the homogenate during the first week. Acid proteinase activity in the glial cells increased above the control range only in the PCB-pretreated rats in the first week. Azoreductase increased in the glial cells above the control range only in the first week, and the pretreatment augmented the increase very significantly. All biochemical effects were largely abolished within two weeks of solvent-free period with the exception of an increase in the cerebral RNA at the highest dose level. Vinyltoluene can cause more pronounced neurochemical effects compared to styrene, xylene, or toluene at similar exposure levels.

Dose-related effects of dichloromethane on rat brain in short-term inhalation exposure

Male Wistar rats were exposed to 500, 1000 or 100 ppm as time-weighted average (t.w.a.) concentrations of dichloromethane vapour. The 1000 (t.w.a.) ppm exposure consisted of two 1-h peak concentrations (2800 ppm) on a basal exposure of 100 ppm. All exposures lasted for 6 h, 5 days weekly and for 2 weeks. The solvent burdens were analyzed in the perirenal fat samples which showed a relation to the dose with the highest values in the 1000 (t.w.a.) ppm exposures. The solvent concentrations increased in the perirenal fat between the two weeks of exposure. Blood carbon monoxide concentrations did not accurately reflect the body solvent burdens. Neurochemical effects also displayed a dose relationship, and included decreased succinate dehydrogenase activity in the cerebellum at the two higher doses and increased acid proteinase activity at 1000 ppm in the cerebrum. Withdrawal of the animals for 7 days from the 2-week exposure showed that the biochemical changes were largely abolished with the exception of decreased succinate dehydrogenase activity at 1000 ppm (t.w.a.).

Dose-dependent effects of peroral dimethylformamide administration on rat brain

Three-month-old Wistar rats were given dimethylformamide in their drinking water at three concentrations. Succinate dehydrogenase activity decreased at the two higher doses in brain after 2 or 7 weeks. Decreased glutathione concentration occurred at the highest dose. Cerebral azoreductase activity was below the control range after 7 weeks at all doses. Glial cell succinate dehydrogenase activity was below the control range in all animals. No qualitative changes in the spinal cord axon protein composition were detected. It is postulated that formic acid generated in the dimethylformamide metabolism might have led to a significant derangement of cerebral energy metabolism.

Neurochemical and biotransformational enzyme responses to manganese exposure in rats

Adult male rats were exposed to 0.5% manganese as MnCl2 in their drinking water for 1, 4, or 6 weeks. Manganese content was measured in brain, liver, kidney, and intestine. Peak manganese concentrations were found in all tissues after one week exposure. Hepatic aryl hydrocarbon hydroxylase, ethoxycoumarin O-deethylase, and epoxide hydrase activities increased after one week manganese exposure, while intestinal and renal activities decreased. The activities returned nearly to the control level at six weeks of exposure. The UDPglucuronosyltransferase activity increased in the liver, kidney, and intestinal mucosa after one week exposure, decreasing thereafter nearly to the control level. In the brain, most significant changes were found after six weeks exposure when the succinate dehydrogenase activity decreased. The results suggest an adaptation to manganese absorption during continuous exposure. The biotransformation enzymes respond first to manganese exposure followed by neurochemical changes in the central nervous system.

Burden and dose-related neurochemical effects of intermittent cyclohexane vapour inhalation in rats

Intermittent daily inhalation exposure to 300, 1000 or 2000 ppm of cyclohexane vapour resulted in a dose-dependent solvent concentration in the perirenal fat in rats. The linear relationship changed between the first and second week of exposure as the body solvent burden decreased, despite the continued exposure: this was especially clear in the brain cyclohexane analyses. The salient feature in the brain was the reduction in the activity of azoreductase, while no change could be found in the RNA or glutathione content or in glutathione peroxidase activity. The azoreductase activity was somewhat below the control range after a 2-week withdrawal period, while no solvent could be found and other biochemical variables were within the control ranges.

Biochemical effects of carbon monoxide poisoning in rat brain with special reference to blood carboxyhemoglobin and cerebral cytochrome oxidase activity

Male Wistar rats exposed to 1000 ppm carbon monoxide for 3 h showed a rapid removal of carbon monoxide from the blood, and a cerebral cytochrome oxidase activity within the control range immediately after the end of the exposure. The cytochrome oxidase activity decreased while carboxyhemoglobin concentration diminished during the reoxygenation period. The effect might have been caused through a loss of mitochondria by increased lipid peroxidation as cerebral glutathione concentration decreased and lysosomal acid proteinase activity increased in glial cell fractions. The present results seem to indicate that the cerebral cytochrome oxidase may not be specifically inhibited in non-lethal carbon monoxide poisoning despite its proven interactions in vitro.

Dose-dependent neurochemical changes during short-term inhalation exposure to m-xylene

Male Wistar were exposed to m-xylene vapor at concentrations of 2.0, 16.1, and 30.3 mumol/1 for 2 weeks (5 days a week, 6 h daily). Xylene concentrations in brain and perirenal fat increased between weeks 1 and 2 of exposure, in proportion to the exposure concentrations. Increase in brain NADPH-diaphorase and azoreductase activities was seen after week 2 at the two higher exposure levels, while superoxide dismutase activity decreased in a dose-related manner at the same time. Biochemical analyses on rats withdrawn from exposure for 2 weeks indicated that the biochemical effects were largely abolished within that time, although cerebral RNA was above the control value at the two higher exposure levels.

Dose-dependent neurochemical effects of 1,1,2-trichloro-1,2,2-trifluoroethane inhalation exposure in rats

Male Wistar rats were exposed to 200, 1000 or 2000 ppm of 1,1,2-trichloro-1,2,2-trifluoroethane vapour for 2 weeks, 5 day/week, 6 h daily and showed a dose-dependent accumulation of the compound in perirenal fat and brain. In the first week increased NADPH-diaphorase activity was observed and there was decreased cerebral glutathione at the highest dose. During the second week these effects disappeared while RNA tended to increase, and glutathione peroxidase activity to decrease at the highest dose. After a withdrawal period of 7 days, no fluorohydrocarbon was detected and the neurochemical effects had disappeared except that brain RNA at the highest exposure was below the control range.

Behavioural and glial cell effects of inhalation exposure to styrene vapour with special reference to interactions of simultaneous peroral ethanol intake

Male Wistar rats were exposed to 300 p.p.m. of styrene vapour with simultaneous ethanol ingestion for 4 to 17 weeks. The effects on behaviour were analyzed after 4, 9 and 13 weeks of the experiment. The most manifest behavioural effects were found in rats exposed to the combination, and the changes included increased preening time at the 4th week and increased ambulation and rearing at the end of the exposure. The ethanol ingestion affected also the accumulation of the solvent burden by delaying the peak solvent concentration in the perirenal fat to the 8th week of exposure. The fat solvent concentration did not differ from each other in the two groups at the end of the experiment, and they were similar as compared the concentration found in phenobarbital-pretreated rats exposed for reference. The styrene exposure had almost no effects on cerebral glial cells whereas ethanol induced unexpectedly increased protein destruction in them throughout the experiment. Co-exposure to ethanol and styrene decreased the magnitude of protein destruction in the glial cells. Withdrawal of the rats after an 8-week exposure showed that the styrene effects were largely abolished in two weeks of exposure-free period as analyzed by the determination of brain RNA and acid proteinase activity. Brain RNA was lower than control after two weeks of ethanol deprivation. The present data indicate that marked metabolic interactions between ethanol and styrene take place in agreement with experience on other similar solvent combinations.

Neurochemical effects on rats of n-heptane inhalation exposure

Inhalation exposure of male rats at three dose levels (4.2, 21, 62 mol/L) to n-heptane vapor caused a dose-dependent brain and body solvent burden, which increased during two weeks of exposure. Initial neurochemical effects included reduced RNA concentration and increased NADPH-diaphorase in brain at the lowest dose. Increased proteolysis was detected in the cerebral samples in the second week at all doses, and the NADPH-diaphorase returned to the control range. Brain RNA content tended to be larger than in the controls. All biochemical effects were abolished after two weeks of withdrawal from the two-week exposure, with the exception of reduced glutathione at the lowest dose. None of the rats presented clinical signs of neuropathy, which indicates that heptane and its metabolites do not share the specific neurotoxicity of hexane and its metabolites.

Neurochemical and behavioural effects of long-term intermittent inhalation of xylene vapour and simultaneous ethanol intake

Two-month-old male Wistar rats were exposed to 300 p.p.m. of xylene vapour with simultaneous ethanol ingestion for 5 to 18 weeks. Neurochemical effects of mere vapour inhalation included an increase in microsomal superoxide dismutase activity in brain at the end of the experiment. Concomitant ethanol ingestion added significantly to the xylene-induced effects by causing increased proteolysis at the 9th and 14th week of exposure whereas cerebral superoxide dismutase failed to increase in these animals. Preening frequency decreased transiently in ethanol and in xylene groups at 6 and 9 to 12 weeks, respectively, whereas increased ambulation occurred only in the xylene--ethanol group after 12 and 14 weeks of exposure. The behavioural effects were therefore different in the combined exposure, and our biochemical and behavioural observations may point at significant interaction of both solvents although the biochemical mechanisms remain largely unexplained.

Biochemical and toxicological effects of short-term, intermittent xylene inhalation exposure and combined ethanol intake

Intermittent inhalation of 300 ppm of xylene vapour 6 h daily for 2 weeks caused a marked accumulation of the solvent in the perirenal fat. Simultaneous ethanol ingestion reduced the solvent load significantly although the perirenal xylene concentration increased in both test groups between the first and second week of exposure. Xylene inhalation enhanced hepatic and renal ethoxycoumarin 0-deethylase activity about 1.5-fold. The combination of inhaled xylene and peroral ethanol showed a markedly potentiated effect on microsomal ethoxycoumarin 0-deethylase activity especially in the kidneys. The enhanced monooxygenase activity was compatible with the decreased body solvent burden. Therefore, simultaneous ethanol intake might significantly modify the toxicological hazard in xylene exposure. Slightly increased proteolysis was detected in brain of animals in the xylene-ethanol experiment after the second week. Brain RNA content decreased after 2 weeks of exposure in the ethanol consuming animals. Xylene inhalation enhanced cerebral DT-diaphorase activity in both groups after 2 weeks of exposure. Ethanol intake also potentiated the behavioural effects caused by the solvent inhalation.

Social grouping cannot account for cerebral effects of enriched environments

Several experiments were conducted to test whether, as suggested by Welch et al. in this journal, mere group living (social stimulation) can account for the significant differences in measures of brain anatomy and brain chemistry that develop between rodents housed in groups in enriched environments and rodents housed singly in restricted environments; the alternative hypothesis was that features of the inanimate environment can significantly affect brain measures of animals living in a social group. Groups of 12 male rats were assigned for 30 days to several types of environment: (a) large cage without stimulus objects, (b) large cage containing varied stimulus objects, (c) large cage containing a maze whose pattern of barriers was changed daily, and (d) a seminatural outdoor environment; in each experiment, littermates of rats in the social conditions were housed in isolation in small colony cages. At the end of the 30-day period, measures were taken of weights of brain regions, RNA and DNA contents of regions of cerebral cortex, and acetylcholinesterase activities of brain regions. Although the number of rats housed together was constant for conditions a--d and cage size was constant for conditions a--c, the magnitudes of the cerebral measures varied significantly as a function of the inanimate stimulus conditions. The differences from isola;ion-housed littermates was greatest in condition d and smallest in condition a. Thus, social grouping alone is inadequate to explain the cerebral effects of enriched environments and the inanimate stimulus conditions must be taken into account.

Effects of long-term turpentine inhalation on rat brain protein metabolism

Chronic exposure of adult male rats to commercial turpentine resulted in an accumulation of the solvent in perinephric fat and brain. The body solvent content remained virtually stable during 8 weeks. Brain RNA content was below the control range initially and it increased to the control level at the 4th week of exposure. Serum non-specific cholinesterase activity was somewhat below the control range at the first and second week of exposure and it returned to the control level thereafter. The present data are in agreement with the small effects of turpentine exposure on human central nervous system in clinical follow-up studies.

Biochemical and toxicological effects of combined exposure to 1,1,1-trichloroethane and trichloroethylene on rat liver and brain

1. Inhalation exposure of adult male rats to a mixture of 1,1,1-trichloroethane (500 p.p.m.) and trichloroethylene (200 p.p.m.) for four days 6 h daily resulted in an accumulation of 1,1,1-trichloroethane in perirenal fat. Further exposure on the fifth day caused a rapid increase in various organ contents of both solvents with secondary depression of brain RNA. 2. The four-day exposure doubled the RNA content of liver and caused a slight decline in the concentrations of glutathione in liver. 3. The amount of cytochrome P-450 in liver was increased, as well as the overall mono-oxygenase activity, measured with styrene as substrate. During continuing treatment on the fifth day, styrene mono-oxygenase activity decreased, the activity after 6 h being only about 50% of that at the beginning of the fifth day of exposure. 4. UDP-glucuronosyl transferase activity (measured in digitonin-activated microsomes) was doubled by the four-day combined exposure to 1,1,1-trichloroethane and trichloroethylene. 5. The changes during the fifth day of exposure, e.g. rapid increase in the concentrations of solvents in organs, the detection of trichloroethylene in tissues and depression of mono-oxygenase activity, obviously also occurred during the exposures on days 1 to 4 and reverted during each post-exposure period.

Effects of chronic styrene inhalation on rat brain protein metabolism

Adult male rats were exposed to 7.9 mumol/1 (300 ppm) of styrene for 2--11 weeks 6 h daily excluding Saturdays and Sundays. The exposures caused a marked styrene accumulation in brain and perinephric fat, and the accumulation tended to increase upto the 4th week. The body styrene content decreased thereafter gradually towards the end of the experiment to reach half of the styrene content of the 4th week. Serum creatine kinase activity increased at the initial stage of the exposures while serum non-specific cholinesterase was below the control range at the same time. Earliest biochemical changes were detected at the 9th week of exposure, and they included increased activity of lysosomal acid proteinase. Increased enzyme activity prevailed to the end of the exposures. Simultaneous minor alterions could be detected in spinal cord axonal protein pattern whereas water-soluble protein composition in cerebellum did not change. Biochemical alterations in brain were not accompanied by significant changes in serum enzyme activities. It is concluded that marked metabolic adaptation to inhaled styrene takes place. Serum enzyme determinations may prove valuable in the adaptation period whereas they may not reflect beginning chronically neurotoxic effects.

Trichloroethylene and 1,1,1-trichloroethane: effects on brain and liver after five days intermittent inhalation

The inhalation exposure of adult male rats to 7.9 mumol/l (200 ppm) of trichloroethylene for 4 days 6 h each day led to an accumulation of the solvent in the perirenal fat 17 h after the last exposure. Exposures to 20 mumol/l (500 ppm) of 1,1,1-trichloroethane caused similar accumulation. The latter rats presented no changes in their behaviour in an open-field test whereas the motor behaviour of the animals exposed to trichloroethylene was more active in comparison to controls 1 h after the exposure on the 4th day. Trace effects of trichloroethylene on emotional behaviour of the same rats could be seen 17 h after the last exposure. Further exposures on the 5th day increased brain, liver, lung and blood contents of trichlorethylene and 1,1,1-trichloroethane. A slight decrease in brain RNA content was found in the 1,1,1-trichloroethane exposed rats while RNA decreased significantly after the fifth day of trichloroethylene inhalation. The exposure to 1,1,1-trichloroethane on the 5th day depressed also the microsomal cytochrome P-450 content in liver of rats whereas trichloroethylene increased the hemochrome content slightly at the same time.

Effects of glucocorticoids on casein gene expression in the rabbit

Milk protein synthesis is initiated by prolactin and a glucocorticoid. In the rabbit, prolactin alone is sufficient. However, glucocorticoids potentiate the action of prolactin. The stimulatory effect of glucocorticoids was evaluated after injections of hydrocortisone acetate alone or associated with prolactin by measurements of (a) the total RNA and DNA content of mammary glands, (b) the lactose synthetase activity, (c) casein synthesis, and (d) the concentration of casein mRNA in total cellular RNA and in polysomal RNA by hybridization with its cDNA. The glucocorticoid, totally inactive alone, proved to have a stimulatory effect proportional to the dose injected when prolactin was present. This effect was more evident with low doses of prolactin. Glucocorticoids proceeded by amplifying the capacity of prolactin to enhance the concentration of casein mRNA available for translation. A parallel effect of glucocorticoids on translation of casein mRNA was suspected. Glucocorticoids injected with low doses of prolactin were unable to mimic all the effects of high doses of prolactin alone.