Search

The mitogenic effect of elevated concentrations of zinc ions on human lymphocytes was found to be inhibited by the glucocorticoid hormone dexamethasone. The effect decreased progressively from complete block to partial inhibition when the culture period before the addition of dexamethasone was prolonged. In contrast, dexamethasone did not inhibit an induced formation of metallothionein in mononuclear cells. Furthermore, dexamethasone itself was found to induce small amounts of metallothionein. Apparently, the mitogenic effect and the induction of metallothionein by zinc ions in mononuclear cells occur by mutually independent mechanisms.

1. 1. The cytosolic binding of Cd, Cu, Zn and Ni in four polychaete species collected from metal-contaminated sediment was investigated by gel-filtration chromatography, affinity studies and atomic absorption spectrometry. 2. 2. There were no major species differences in the binding patterns of Zn and Ni in the four annelids. Zn was mainly associated with high molecular weight proteins (> 35 kDa), whereas Ni eluted with components of very low molecular weight ( 3. 3. Cd and Cu were associated with proteins of size 10–20 kDa in the detrivore Chaetozone setosa and the carnivorous Goniada maculata. In both species, these proteins had high affinity for 109Cd added in vitro. 4. 4. In the two sediment-feeding polychaetes, Pectinaria belgica and Orbinia norvegica, Cu, Zn and Ni were associated with components of either high or very low molecular weight. 5. 5. It is suggested that analysis for metallothionein-like proteins may not be satisfactory for monitoring purposes, and that other cytosolic components must be included in such studies.

1. 1. Low mol. wt proteins with high Cd-binding capacity were found to be induced by Zn in cultured monocytes and lymphocytes. 2. 2. In T cell cultures one protein was found to be induced by 125 μM Zn for 6 days, while in monocytes and B enriched cells under these conditions two proteins were found, of which the one with higher mol. wt had similar electrophoretic mobility to the T cell protein on polyacrylamide gels. 3. 3. Mol. wt criteria and crossreactivity towards anti-metallothionein (Mt) antibody identified these proteins to be Mts of about 23 and 27 kDa mol. wt. 4. 4. Metal binding studies indicated that monocyte and lymphocyte Mts had a higher affinity to Zn compared to Cd than rat liver Mt and Mts from Cd-resistant substrains of a human epithelial and a murine fibroblast cell line. 5. 5. The presence of the T cell mitogen phytohemagglutinin (PHA) was found not to be necessary for this Mt induction by Zn.

The use of a neural network model of a cerebral cortical area as an aid to understanding this area's function is reviewed. The basic model is a feedforward multilayer network that learns to transform the coordinates of a visual stimulus from a retinocentric to a craniocentric reference frame using backpropagation. An extension of the model to one that transforms retinal coordinates into body-centered ones predicts response properties that are confirmed by neurophysiological experiments. The simulation of electrical stimulation of the model predicts a pattern of effects similar to the one obtained by stimulation of a specific region of the parietal cortex. The study of the response properties of the model's units provides a simple explanation of how the parietal cortex might compute coordinate transformations and of why certain manipulations such as stimulation should produce the effects observed. >

Metallothionein (MT) is produced at high rates in isolated monocytes, and T and B lymphocytes during induction in vitro. At optimal concentrations, 125 microM for Zn and 10 microM for Cd and dexamethasone (dex), MT was demonstrated after only 2 h in some cases, and in all cell types substantial levels were measured after 1 day of exposure to all three inductors. With Cd, lower amounts of MT were found, but maximum levels were reached faster than with Zn. The same result was found for dex compared to Zn. Zn and dex in combination showed the same accumulation rate as Zn alone. If the inductors were used in lower concentrations than optimal, reduced accumulation rates occurred, particularly during the first part of the exposure period. No MT was found for concentrations below 5 microM Zn, 1 microM Cd or 0.5 microM dex. The constitutive levels of MT (mean +/- S.E.M.) were 0.11 +/- 0.05, 0.54 +/- 0.3, 0.06 +/- 0.05 and 0.15 +/- 0.08 nmol Cd bound/5 x 10(6) unseparated mononuclear cells (MNC), monocytes, T lymphocytes and B lymphocytes, respectively. Monocytes accumulated 19 times and B lymphocytes 6 times more MT than T lymphocytes after 2 days of exposure to 125 microM Zn. Despite these differences in accumulated amounts of MT, the fold accumulation values were rather similar between the cell types, reflecting corresponding variations in background MT levels. After exposure of unseparated MNC to 125 microM Zn for 2 days, removal of the metal caused constitutive MT levels to be reestablished in 5 days. Five different MT forms, all capable of Cd complexation, were demonstrated in these cells. These forms had kinetically different behaviour during Zn exposure among the cell types, and the response to Cd was different from the Zn response. The results indicate metals to be closely controlled in MNC and emphasize a role for multiple MT forms in the process of regulation.

1. 1. An antimetallothionein antibody, raised against Cd-carrying metallothionein, was applied in Western blotting of metallothionein. 2. 2. Treatment of the electroblotted nitrocellulose sheets with metals belonging to the periodic system transition groups Ib and IIb, or with Pb, Ni or Cr, considerably enhanced binding of anti-metallothionein. A similar effect was found when the electroblotted sheets were treated with the strong alkylator N-ethylmaleimide. 3. 3. It seems that the binding of metal to metallothionein modifies the configuration of the antibody binding sites by the formation of metal thiolate complexes. 4. 4. Metal treatment of the nitrocellulose sheets after electroblotting, but before application of the primary antibody, offers a convenient method for use in Western blotting to significantly potentiate the reaction between metallothionein and the antimetallothionein antibody.

1. The cholinesterase (ChE) of chicken brain cortex could be easily solubilized. About 10% was found to be soluble in 0.05 M phosphate buffer. After treatment of 0.25% (v/v) Triton X-100 alone, about 20% and in combination with 1 M NaCl not more than 5% of the total activity was left particle bound. NaCl by itself did not solubilize ChE. 2. Two isozymes of ChE could be separated by polyacrylamide gel electrophoresis, isoelectric focusing and sucrose gradient centrifugation. 3. The S values (and approximate molecular weights) of the two forms separated by sucrose gradient centrifugation were estimated to be 7.4 ± 0.44 (133,000 ± 12,000) and 11.2 ± 0.67 (247,000 ± 23,000). The molecular weights of these forms determined by electrophoresis in different polyacrylamide gel concentrations were found to be about twice as large, namely 223,000 ± 18,000 and 450,000 ± 22,000. 4. Substrate specificity, substrate inhibition, K m values and inhibition rates were examined without finding any significant differences between the forms of ChE separated by sucrose gradient centrifugation and isoelectric focusing. 5. The results were found to be in general accord with the suggestion that the multiple forms of brain ChE may be related to the aggregation of a single low molecular weight species.

1. Except for pH optimum, reactivation and “aging”, the results indicate that the ChE of Eisenia foetida is distinct from acetylcholinesterase and butyrylcholinesterase. 2. Propionylcholine was found to be a better substrate than acetylcholine, while butyrylcholine, benzoylcholine and acetyl-beta-methylcholine were found to be poor substrates for this ChE. 3. Little or no tendency towards substrate inhibition was seen. 4. The rate constants of inhibition by alkyl phosphates and carbamates favour the concept of this enzyme being a B-esterase, but different from the two main classes of ChE. 5. The buffer-soluble and membrane-bound ChE showed no differences in substrate specificity and Michaelis-Menten constants. 6. These enzymes separately also showed little or no tendency towards substrate inhibition. 7. Crude homogenate, membrane-bound, buffer-soluble and Triton X-100 solubilized ChE, as well as fractions from isoelectric focusing are acted upon by inhibitors at rather similar rates. 8. The presence of only one type of enzyme is therefore indicated. 9. The existence of isoenzymes is not clearly indicated either by isoelectric focusing, by gel electrophoresis technique or density gradient centrifugation. 10. The latter method indicated the molecular weight to be 108,000 ± 7000.

1. 1. Frog brain acetylcholinesterase (AChE) was more resistant to inhibition by organophosphorus compounds than chicken and rat brain AChE. The differences in inhibition rates were 2 times for soman, 10 times for sarin, tabun and Tx-60, 100 times for DFP, dimethylphosphorylfluoride and paraoxon and 1000 times for diethylphosphorylfluoride. 2. 2. Physostigmine and neostigmine inhibited chicken and rat brain AChE about 100 times faster than frog brain AChE. 3. 3. Chicken and rat brain AChE were inhibited only slightly faster by methylsulphonylfluoride than the frog brain AChE. The inhibition was accelerated by tetraethylammonium ions and retarded by tensilon in all cases. 4. 4. Tetraethylammonium ions, however, slightly retarded the inhibition rate of chicken and rat brain AChE by dimethylphosphorylfluoride. No significant effect was observed for the frog brain AChE. 5. 5. The species differences in inhibition rates were probably not due to differences in phosphorylation rates or conformational changes, but rather to the steric arrangement in the active site of the enzyme molecules.

1. The contractile behaviour of rabbit and man bronchial musculature has been tested in response to some commonly used substrates for cholinesterase, histamine and adrenaline by the kymograph technique. 2. The sensitivity of the smooth bronchial musculature from both rabbit and man was found to be highest for acetylcholine and acetyl-β-methylcholine (6.3 × 10 −8 M) and lowest for butyrylcholine (6.3 × 10 −6 M). 3. The smooth bronchial musculature of man was slightly more sensitive to histamine and adrenaline than that of the rabbit. 4. The results indicate that the contractile behaviour in the smooth bronchial musculature of rabbit and man is remarkably similar.

Radiolabelled paraquat (bis-N-(14C)methyl-4,4'-bipyridylium chloride) was administered intravenously to pregnant rats and guinea-pigs and examined by the whole body autoradiography method. Male rats were examined for comparison with the same method. The results showed that the radiolabelled compound was rapidly distributed throughout the tissues, with the highest concentrations in the cartilage, kidney, lung, spleen, salivary gland and skin. High concentrations were found in the placenta and throughout the fetuses 0.5 hr after the administration.

1. 1. Four groups of polychaete worms, differing in feeding habits, have been studied with respect to presence of metal-binding proteins. 2. 2. The presence of low molecular weight metal-binding proteins was clearly demonstrated in the species Lumbrineris fragilis as well as in Harmothoe sp. both being carnivorous animals. One of the proteins found in L. fragilis was similar to mammalian metallothionein (Mt).

Polychaetes normally comprise 70–90% of the total macrofauna in soft-bottom communities, both with regard to numbers and biomass. Many polychaete species are also of economic importance as food for benthic fish. The present study was undertaken to investigate the binding of metals in polychaetes and how it related to ambient metal levels. Polychaete and sediment samples were taken in a metal-contaminated coastal area close to Kristiansand, southern Norway. Crude extracts were prepared from each of the five selected polychaete species, and aliquots subsequently applied to a Sephadex G-75 column. The collected fractions were pooled according to molecular size (HMW, MT and LMW) and analyzed for Cu, Zn and Ni by atomic absorption spectrometry (AAS). Extracts from each of the species were also subjected to polyacrylamide electrophoresis (SDS-PAGE). Cu in the extracts was primarily associated with components of high and very low molecular weight (Mr), but also with proteins of size similar to mammalian metallothionein. Zn was mainly recovered in the HMW pool (> 35 kDa), whereas most of the Ni present eluted with very low molecular weight components (Mr

Movement in a centric diatom, Actinocyclus subtilis, is reported here for the first time. The movement is directional and strong circumstantial evidence from histochemistry and electron microscopy supports the proposal that motility is achieved by the production of mucopolysaccharides through the labiate processes.

1. 1. A low molecular weight metal-binding protein was found in the snail Nassarius reticulatus cytosol, which was induced in heavy metal contaminated environments. 2. 2. In our sodium dodecyl sulfate-mercaptoethanol polyacrylamide gel systems it behaved as a protein of 19 kDa mol. wt. 3. 3. Amino acid composition studies definitely established this protein not to be metallothionein (Mt) like, because it had a much lower level of cysteine and substantial amounts of aromatic amino acids and histidine. 4. 4. The metal-binding strength of this protein was concluded to be much weaker than that of Mt. 5. 5. In the crustacean Pagurus bernhardus L. such a protein could not be demonstrated. 6. 6. In both the snail and the crustacean Zn may inhibit the accumulation of Hg. The premise for studying the induction of the metal-binding Nassarius protein as a supplement to environmental metal monitoring purposes is briefly discussed.

1. 1. Studies have been performed on untreated and heavy metal treated Hydra attenuata in order to reveal the presence of low mol. wt metal-binding proteins. 2. 2. A prepared rat metallothionein (Mt) standard, gel permeation, polyacrylamide gel electrophoresis and autoradiographic techniques were used in the experiments. 3. 3. Our results indicate that H. attenuata , and three species of marine coelenterates, lack metallothionein (Mt) or other metal binding proteins.

1. Diisopropoxyphosphorylfluoride and soman caused rapid decline of the cholinesterase (ChE) activity levels in earthworm, chicken, guinea pig, mouse and rat tissues. 2. The onset of recovery of ChE activity was well established within 5 days in all species except for the earthworm whose whole body ChE activity level remained low for at least 15 days. 3. Plasma ChE of the rat recovered to the normal activity level already in 6 days. After that, however, the activity level still continued to increase. This overshoot effect was much more pronounced in females than in males. 4. In females the activity level reached 50% above normal values after about 7 days. The overshoot of plasma ChE in the female rat still persisted 15 days after inhibition. 5. The overshoot of ChE activity was also observed in mouse and rat liver after inhibition. In the chicken ChE overshoot was not found. 6. The recovery of erythrocyte and brain ChE activity of the rat was observed to be slower than that of plasma and liver. Likewise the recovery of brain ChE activity of the mouse seemed to be slower than that of liver. Similar results were obtained for the chicken. Generally soluble ChE seem to recover faster than membrane bound. 7. In the case of erythrocyte and brain ChE the results indicated a similar ChE turnover as generally observed for other proteins in brain tissue. 8. In brain and retina of chicken as well as in rat brain and in guinea pig iris two distinct forms of ChE were found with marked different molecular weights. 9. In the chicken the activity of the form with a low molecular weight was found to predominate during the early recovery stages following ChE inhibition. At later stages the activity of a heavy weight form dominated. 10. In rat brain and retina as well as in guinea pig iris the activity of the form with the higher molecular weight was always predominating. 11. The results may, however, be interpreted such that the synthesis of the form of ChE with the lower molecular weight proceeds the appearance of the higher molecular weight form. 12. Administration of l -anserine nitrate, l -homocarnosine sulphate, l -carnosine and thyrotropin releasing hormone to the rats as well as primobolan to the mouse did not affect the recovery of activity and molecular forms of ChE following irreversible ChE inhibition. In the rats hypophysectomy was not found to affect the recovery either.

Aqueous solutions of molecular oxygen, per se, or in combination with either pyrogallol or 6-azauracil increased tumorigenesis in Nicotiana suaveolens × Nicotiana langsdorffii seedlings relative to control seedlings. The biological activities of the organic chemicals were O 2 -dependent, because the substitution of N 2 or O 2 or the degassing of 0.1–1 mM solutions of the compounds eliminated or greatly reduced their tumorigenic effects. Rates of tumorigenesis exceeded 95% for 0.5 mM solutions of either pyrogallol or 6-azauracil solutions in the presence of 1 mM O 2 . Although tumors developed in 20% of seedlings in the presence of 1 mM O 2 , alone, 4–5 times more tumors were induced by the organic chemical-O 2 -H 2 O systems. Dinitrophenol and ascorbic acid, compounds which affect cellular respiration or redox systems, strongly inhibited the chemically-mediated tumorigenesis. Dinitrophenol was equally effective at one-tenth of the molar concentrations of ascorbic acid that were required for the suppressions of oncogenesis. Dehydroascorbic acid was much less inhibitory than ascorbic acid.

1. The high affinity uptake of GABA in optic tectum was found to be about 40% higher in frogs kept in complete darkness for 3 weeks, than in frogs in the normal condition. 2. No effects were obtained in uptake of glutamate and activity of GAD in the optic tectum. 3. The isoenzyme composition of cholinesterases in frog optic tectum and retina was not affected by dark adaptation either.

1. 1. Dexamethasone induced thionein in rat liver cross reacts with antibody made towards Cd-thionein from rat liver. 2. 2. Dex-thionein binds Cd. 3. 3. Compared to Cd-thionein, dex-thionein behaves differently on SDS polyacrylamide gels. 4. 4. On molecular filtration on Sephadex G-75 columns, dex-thionein elutes slightly more towards the low molecular weight region than Cd-thionein. 5. 5. Dex-thionein elutes in one peak with two shoulders after DEAE-Sephadex A-50 ion exchange chromatography, while Cd-thionein elutes in two peaks.

1. 1. Rat superoxide dismutase (SOD) prepared from the rat was not found by sedimentation in sucrose gradients or isolectric focusing to consist of more than one molecular form. On polyacrylamide gels, however, one major and one minor activity form could be demonstrated. 2. 2. The sedimentation constant and corresponding molecular weight of the enzyme determined by sucrose gradient centrifugation were found to be 3.0 ± 0.36 (34,300 ± 4023) and the isoelectric point 4.75. 3. 3. These characteristics were not found to differ for SOD prepared from different rat tissues and were not affected by a single dose of 40 mg/kg paraquat given subcutaneously 48 hr prior to sacrifice. 4. 4. The protein contents of various tissues based on both wet and dry weight were not found to deviate from normal during 5 days following a single exposure of paraquat up to 40 mg/kg. 5. 5. Experiments based on SOD activity measurements in different tissues as a function of time following single exposures of paraquat, revealed the presence of a very high induction capability of the SOD protein in the rat. The results have been correlated to autoradiographic studies. A correlation between SOD induction and tissues showing high paraquat retention could be demonstrated. This was especially expressed for the lung. 6. 6. Due to difference in the induction pattern following exposure to 5 and 10 mg/kg paraquat, respectively, it has been suggested that the ability of the rat to bear paraquat loads might be related to the SOD induction capability in various tissues.

A vascularly perfused phrenic nerve-hemidiaphragm preparation from the rat was developed to study effects of physostigmine and some organophosphate inhibitors on the synthesis and release of endogenous and deuterium-labelled (choline--D9) acetylcholine (ACh) as well as the presynaptic uptake of choline. Choline and ACh were determined by combined gas chromatography/mass spectrometry. Without stimulation the endogenous levels of ACh were 320 pmole/hemidiaphragm for unlabelled and less than 1 pmole/hemidiaphragm of deuterium-labelled ACh. After stimulation at 15 Hz for 1 hr, 460 pmole/hemidiaphragm of unlabelled and 15 pmole/hemidiaphragm of deuterium-labelled ACh were found. Without stimulation the release of unlabelled ACh was 6 pmole/min/hemidiaphragm and for deuterium-labelled 0.2 pmole/min/hemidiaphragm. Evoked release (15 Hz, 1 hr) was 22 pmole/min/hemidiaphragm for unlabelled and 1.8 pmole/min/hemidiaphragm for deuterium labelled ACh. During stimulation and treatment with high concentrations (10(-5)-10(-4) M) of soman, DFP and Vx the level of unlabelled endogenous ACh increased, but the level of deuterium labelled ACh decreased in the diaphragm. During stimulation and treatment with these inhibitors the release of both unlabelled and labelled ACh decreased. During treatment with high concentrations (10(-5)-10(-4) M) of sarin and physostigmine there were no changes in endogenous levels or release of unlabelled or deuterium labelled ACh. The different effects of cholinesterase inhibitors are probably linked to the synthesis and release mechanism of ACh rather than to the choline uptake mechanism.

1. 1. Brain cholinesterase (ChE) levels in Wistar rats from Mollegarden, Denmark (Mol: WIST) were found to be higher than in Wistar rats from Charles River, France (Cre: (WI)BR). 2. 2. Serum ChE levels were considerably higher in females than in males of both Wistar stocks. 3. 3. This difference disappeared after hypophysectomy such that male rat serum ChE levels increased while those in females decreased.

1. 1. The cholinesterase (ChE) of frog brain and retina could be easily solubilized. About 10% of the brain and 20% of the retina ChE were found to be soluble in 0.05 M phosphate buffer. After treatment with 0.5% (v/v) Triton X-100, about 30% of the total ChE activity of the brain and only 10% for retina was left particle bound. NaCl by itself did not solublize ChE. Use of higher NaCl concentrations in combination with Triton X-100 as well as higher detergent concentrations alone seemed to cause an inhibiting effect of the solubilized ChE from retina. 2. 2. The solubilized ChE from brain as well as retina were electrofocused as one main activity peak, corresponding to isoelectric points of pH 6.1 and 6.0, respectively. A second molecular form at pH 5.9 was distinguishable for the brain, but not for retina ChE. 3. 3. Sucrose gradient centrifugation indicated that the ChE solubilized from the brain and retina consists of two molecular forms exhibiting S values of 5.1 ± 0.24, 10.9 ± 0.33 and 6.1 ± 0.30, 10.9 ± 0.43, respectively. After solubilization by higher Triton X-100 concentrations the soluble extracts from brain and retina seemed to contain the activity of these forms in different proportions. 4. 4. Polyacrylamide gel electrophoresis separated three molecular forms of the brain ChE. One of these forms was found to have a molecular weight of 394,000 ± 20,000. The others were found to have an identical molecular weight of 550,000 ± 10,000. Two molecular forms exhibiting molecular weights of 292,000 ± 10,000 and 470,000 ± 10,000, could be separated for retina. The high as well as the low molecular weight form of brain and retina seemed to differ with respect to charge. 5. 5. The results found clearly indicate that the molecular forms of the frog ChE exhibit a high degree of lability. 6. 6. Substrate specificity, substrate inhibition, K m values and inhibition rates were examined without finding any significant differences between ChE solubilized from the brain and retina of the frog ( Rana temporaria ).

1. Frog serum ChE showed high substrate specificity towards ACh and AThCh. 2. Frog serum ChE was inhibited at higher substrate concentrations for ACh and AThCh, but not for higher homologe choline esters. 3. Frog serum ChE shows high resistance towards many inhibitors. 4. Substrate specificity and insensitivity towards inhibitors for the frog serum ChE did not differ much from that of the brain ChE. A smaller esteratic site, as proposed for the brain ChE, is therefore also probably present in the serum ChE. 5. Both frog and rat serum ChE were inhibited to the same extent by quaternary ammonium ions. 6. Substrate hydrolysis of chicken serum ChE was activated in the presence of quaternary ammonium ions. 7. Different electrophoretic mobilities were observed for brain and serum ChE from frog, chicken and rat.

Crystals of ((CH/sub 3/)/sub 3/SiC/sub 5/H/sub 4/)/sub 3/U are orthorhombic, Pbca, with a = 22.630(8), b = 29.177(10) and c = 8.428(3) A at 23/sup 0/C. For Z = 8 the calculated density is 1.551 g/cm/sup 3/. The structure was refined by full-matrix least-squares to a conventional R factor of 0.041 (2251 data, F/sup 2/ > 2 sigma(F/sup 2/)). The uranium atom is bonded to the three cyclopentadienyl rings in a pentahapto fashion and is in the plane of the ring centroids. The U to ring distances are 2.54, 2.47 and 2.51 A, and the average U-C distance is 2.78 +- 0.04 A. 7 refs., 1 fig., 3 tabs.

1. By use of our metallothionein (Mt) antibody in Western blotting and techniques for investigating protein metal-binding capacity, the form and content of Mt in bile, collected from cadmium (Cd) treated rats, were studied. 2. It was found that bile is an excretory pathway for Mt from the liver. 3. However, only immunoreactive proteins of higher molecular weight, probably representing polymerized forms of Mt or Mt bound to other proteins, were detected. 4. No monomeric Mt was found. 5. Excretion of Mt is probably not of importance in biliary metal transport.

Publisher Summary Four quaternary nitrogen compounds, one of them an irreversible cholinesterase inhibitor (2-MPAM-ES), the remaining three cholinesterase reactivators—namely,P2S, Tx 10, and Toxogonin— are used in this chapter, in a study of the permeability of the blood-brain barrier (BBB) and the blood-retinal barrier (BRB), the latter being, from an ontogenetic point of view, a part of the former. In contrast to other parts of the BBB, which have been found in earlier work to show slight mutual differences with regard to permeability, the BRB is found to be more permeable to the reactivators than was the BBB proper. Both the BBB and the BRB are impermeable to 2-MPAM-ES. This impermeability is not influenced by high X-ray doses (5,000 rad), nor by toxic doses of 2,4-dinitrophenol or ouabain. No marked differences are found among the cholinesterase reactivators with regard to penetration of either barrier.

A sensitive gas-liquid chromatographic method was developed for the quantitative measurement of l -phenylalanine ammonia-lyase activity in Nicotiana tabacum leaf by means of electron capture detection. l -Phenylalanine ammonia-lyase activity, measured by this method, was significantly higher in developing leaves of a “high-phenolic” tobacco variety than in similar leaves of a “low-phenolic” variety. The enzymatically produced trans-cinnamic acid was silyated and chromatographed on 10% OV-101 at a column temperature of 150°. The approximate lower limit of detection with an electron capture detector was 0.1 nmole trans-cinnamic acid.

1. 1. There are considerable differences between acetylcholinesterase (AChE) from different species with regard to their reactions with organophosphorous anticholinesterases. AChE from chicken brain was inhibited 20 times as fast with 2-MPAM-ES as rat and mouse brain AChE. In contrast AChE from frog brain was inhibited 1000 times slower with 2-MPAM-ES, 100 times slower with DFP and 10 times slower with 2-MPA-ES than rat brain AChE. 2. 2. The differences in inhibition rates were similar for membrane-bound enzymes and enzymes solubilized by Triton X-100. 3. 3. Both chicken and frog brain AChE were inhibited to the same extent by quaternary ammonium salts. 4. 4. There were only small species differences with regard to reactivation of DFP-inhibited enzymes by 2-PAM. 5. 5. When AChE from the different species were inhibited by DFP, the enzyme from frog brain “aged” 10 times slower than in the other enzymes. 6. 6. Substrate specificity studies showed that chicken brain enzyme exhibited its highest activity towards propionylcholine whereas frog enzyme had the highest activity towards acetylcholine.