Neuropathology of trimethyltin intoxication. III. Changes in the brain stem neurons

Neuroprotective Effect of Bean Phosphatidylserine on TMT-Induced Memory Deficits in a Rat Model

BACKGROUND

Trimethyltin (TMT) is a potent neurotoxin affecting various regions of the central nervous system, including the neocortex, the cerebellum, and the hippocampus. Phosphatidylserine (PS) is a membrane phospholipid, which is vital to brain cells. We analyzed the neuroprotective effects of soybean-derived phosphatidylserine (Bean-PS) on cognitive function, changes in the central cholinergic systems, and neural activity in TMT-induced memory deficits in a rat model.

METHODS

The rats were randomly divided into an untreated normal group, a TMT group (injected with TMT + vehicle), and a group injected with TMT + Bean-PS. The rats were treated with 10% hexane (TMT group) or TMT + Bean-PS (50 mg·kg-1, oral administration (p.o.)) daily for 21 days, following a single injection of TMT (8.0 mg/kg, intraperitoneally (i.p.)). The cognitive function of Bean-PS was assessed using the Morris water maze (MWM) test and a passive avoidance task (PAT). The expression of acetylcholine transferase (ChAT) and acetylcholinesterase (AchE) in the hippocampus was assessed via immunohistochemistry. A positron emission tomography (PET) scan was used to measure the glucose uptake in the rat brain.

RESULTS

Treatment with Bean-PS enhanced memory function in the Morris water maze (MWM) test. Consistent with the behavioral results, treatment with Bean-PS diminished the damage to cholinergic cells in the hippocampus, in contrast to those of the TMT group. The TMT+Bean-PS group showed elevated glucose uptake in the frontal lobe of the rat brain.

CONCLUSION

These results demonstrate that Bean-PS protects against TMT-induced learning and memory impairment. As such, Bean-PS represents a potential treatment for neurodegenerative disorders, such as Alzheimer's disease.

Low-Dose Ketamine Improves LPS-Induced Depression-like Behavior in Rats by Activating Cholinergic Anti-inflammatory Pathways

About 16% of the world's population has major depressive disorder. Traditional antidepressants have slow effect rates and low response rates. Many studies have shown that low doses of ketamine can produce rapid and effective antidepressant effects. However, its mechanism of action needs further exploration. Lipopolysaccharide (LPS) was used to establish a depression model in rats and PC12 nerve cells were used for in vitro experiments. (2,4)-Dimethoxybenzylidene anabaseine dihydrochloride (GTS-21), a specific agonist of α7 nicotinic acetylcholine receptors (α7 nAChRs), was used to compare the rapid antidepressant effect of ketamine. Different doses of α7 nAChR antagonist methyllycaconatine (MLA) and α7 nAChR-siRNA were used to interfere with the protective effects of ketamine on neuroinflammation in rats and PC12 cells, respectively. MLA intervention downregulated the anti-inflammatory effects of ketamine and decreased the effects of ketamine on behavior, synaptic plasticity, and Nissl bodies in the neuronal cells. Moreover, the dose of MLA was positively correlated with the inhibitory effect in rat hippocampi and the protective effects of GTS-21 were consistent with ketamine. These results demonstrated that low-dose ketamine could produce neuroprotective effects by activating the α7 nAChR-mediated cholinergic anti-inflammatory pathway (CAP) in depression, resulting in a rapid antidepressant effect.

Krill-Derived Phosphatidylserine Improves TMT-Induced Memory Impairment in the Rat

The present study examined the effects of krill-derived phosphatidylserine (Krill-PS) on the learning and memory function and the neural activity in rats with trimethyltin (TMT)-induced memory deficits. The rats were administered vehicle (medium-chain triglyceride: MCT) or Krill-PS (50, 100 mg/kg, p.o.) daily for 21 days. The cognitive improving efficacy of Krill-PS in TMT-induced amnesic rats was investigated by assessing the Morris water maze test and by performing choline acetyltransferase (ChAT), acetylcholinesterase (AChE) and cAMP responsive element binding protein (CREB) immunohistochemistry. The rats with TMT injection showed impaired learning and memory of the tasks and treatment with Krill-PS produced a significant improvement of the escape latency to find the platform in the Morris water maze at the 2^nd and 4^th day compared to that of the MCT group (p<0.05). In the retention test, the Krill-PS+MCT groups showed increased time spent around the platform compared to that of the MCT group. Consistent with the behavioral data, Krill-PS 50+MCT group significantly alleviated the loss of acetylcholinergic neurons in the hippocampus and medial septum compared to that of the MCT group. Treatment with Krill-PS significantly increased the CREB positive neurons in the hippocampal CA1 area as compared to that of the MCT group. These results suggest that Krill-PS may be useful for improving the cognitive function via regulation of cholinergic marker enzyme activity and neural activity.

Neuroprotective Effect of Lucium chinense Fruit on Trimethyltin-Induced Learning and Memory Deficits in the Rats

In order to the neuroprotective effect of Lycium chinense fruit (LCF), the present study examined the effects of Lycium chinense fruit on learning and memory in Morris water maze task and the choline acetyltransferase (ChAT) and cyclic adenosine monophosphate (cAMP) of rats with trimethyltin (TMT)-induced neuronal and cognitive impairments. The rats were randomly divided into the following groups: naïve rat (Normal), TMT injection+saline administered rat (control) and TMT injection+LCF administered rat (LCF). Rats were administered with saline or LCF (100 mg/kg, p.o.) daily for 2 weeks, followed by their training to the tasks. In the water maze test, the animals were trained to find a platform in a fixed position during 6d and then received 60s probe trial on the 7(th) day following removal of platform from the pool. Rats with TMT injection showed impaired learning and memory of the tasks and treatment with LCF (p<0.01) produced a significant improvement in escape latency to find the platform in the Morris water maze at the 2(nd) day. Consistent with behavioral data, treatment with LCF also slightly reduced the loss of ChAT and cAMP in the hippocampus compared to the control group. These results demonstrated that LCF has a protective effect against TMT-induced neuronal and cognitive impairments. The present study suggests that LCF might be useful in the treatment of TMT-induced learning and memory deficit.

Bone marrow clastogenicity of trimethyltin

Aqueous solutions of trimethyltin in four different concentrations were administered i.p. for three different treatment periods, to five Swiss albino male mice for each experimental set. Bone marrow cells were processed for somatic chromosome preparation after 6, 18 and 24 h following the usual protocol. Structural abnormalities including chromatid and chromosome breaks, dicentrics, rings and fragments were recorded. Critical assessment of the data with the one-tailed trend test revealed a significant positive trend of the dose effects in all three treatment periods. With the ANOVA test, significant variations in aberrations were observed between chemical concentrations and between treatment periods and their interaction (dose x time) was significant in aberrations and mitotic indices. Depression of mitotic index was dose- and duration-dependent.

Cytotoxicity of tin on human peripheral lymphocytes in vitro

The comparative effects of inorganic and organic tin compounds on chromosomes were assessed in human peripheral blood lymphocytes of healthy donors 20-40 years of age. The endpoints observed were chromosomal abnormalities, sister-chromatid exchanges (SCEs) and cell cycle kinetics. The maximum concentrations which reduced the replicative index by about 50%, of stannic chloride and trimethyltin chloride were 40 micrograms and 2 micrograms per culture respectively. The tested doses were 20 micrograms and 10 micrograms of stannic chloride and 1 microgram and 0.5 microgram of trimethyltin chloride. Both doses of stannic chloride induced a much higher frequency of chromosomal abnormalities (P less than 0.05-P less than 0.001) and a greater reduction of cell cycle kinetics than the corresponding relative doses of trimethyltin chloride. The frequencies of SCEs/cell induced by the latter were, however, slightly higher than those induced by the former.

Regional variations in nerve cell responses to trimethyltin intoxication in Mongolian gerbils and rats; further evidence for involvement of the Golgi apparatus

The different responses of neurons with distinctive variations in morphology and function, confirm earlier observations of the lack of uniformity in the reaction of nerve cells to trimethyltin. Thus, hippocampal pyramidal and cortical neurons in both rat and Mongolian gerbil (M. unguiculatus) show abundant lysosomal dense bodies and disorganisation of the protein-synthesising apparatus. Cerebellar Purkinje cells in gerbil, but not in rat, show striking increases in smooth membrane systems, while dense bodies are insignificant in both species; large motor-type neurons in brain stem and spinal cord in both species do not accumulate dense bodies, but their rough endoplasmic reticulum (RER) may undergo intense vacuolation with or without subsequent cell death; and by contrast, spinal ganglion cells of both species may form an excess of dense bodies and, in the gerbil, vacuolation of RER. In contrast with these varied responses to trimethyltin most neurons, large and small, in both species regularly undergo striking vacuolation of the Golgi apparatus in the earliest phase of the intoxication, a constant feature that probably reflects the site of the primary cytotoxic lesion; all other changes we consider are secondary to such damage to the Golgi apparatus, however this may come about. These observations are discussed in relation to earlier reports of the variable effects of trimethyltin and with the metabolic changes reported in trimethyltin intoxication that in general accord with these morphological conclusions.

Neurotoxicological effects of trimethyltin on the stellate ganglion

Hamsters treated with trimethyltin (TMT), 3 or 4 mg/kg IP, developed neurological symptoms, including tremor, within 24 hours. Postganglionic action potentials were recorded from isolated stellate ganglia of untreated hamsters (control ganglia) and TMT-treated hamsters (TMT ganglia). Compound action potentials (nicotinic transmission) of control and TMT ganglia were not significantly different. The afterdischarges induced by preganglionic stimulation at 30 Hz for 2 sec in the presence of 10(-3) M hexamethonium (muscarinic transmission) were significantly smaller in TMT ganglia than in control ganglia. The discharges induced by the muscarinic cholinoceptor agonist. McN-A-343, were also smaller in the TMT ganglia. Two other muscarinic processes, posttetanic potentiation and potentiation of the compound action potential by McN-A-343, were not significantly reduced in the TMT ganglia. Morphological studies of the ganglia revealed marked changes in the TMT ganglia with severe neuronal degeneration including vacuole formations and accumulations of lysosomes in the cytoplasm. These results demonstrate that TMT has marked anatomical effects on the stellate ganglion that may lead to the reduction in muscarinic cholinergic transmission.

Cytotoxic effects of trimethyltin chloride on human peripheral blood lymphocytes in vitro

Trimethyltin chloride was found to induce cytotoxic damage in vitro in human peripheral blood lymphocytes. Two concentrations (0.5 micrograms and 1.0 micrograms) were added to lymphocytes from male and female subjects in mitogen stimulated and serum supplemented culture medium for 72 h. A dose-related increase of inhibition of replication index (P less than 0.01) and cell division (P less than 0.001) was observed. The frequencies of abnormal cells and chromosomal aberrations such as chromatid and chromosome breaks, dicentrics, triradial and quadriradial configurations were increased significantly (P less than 0.001), as were micronucleus counts (P less than 0.001) and sister chromatid exchanges (P less than 0.001). Endoreduplication, an extremely rare spontaneous event in human lymphocytes, was observed in a few cases at all dose levels. The effects were more pronounced in lymphocytes obtained from habitual smokers.

Trimethyltin-induced neuronal damage in the rat brain: comparative studies using silver degeneration stains, immunocytochemistry and immunoassay for neuronotypic and gliotypic proteins

Trimethyltin is a neurotoxicant which produces a distinct pattern of neuronal cell death following peripheral administration of a single dose (8 mg/kg, i.p.) in rats. The cupric-silver degeneration stain was used to produce an atlas documenting the distribution and time course of trimethyltin-induced neuronal damage in adult, male Long-Evans rats. Animals were examined at survival times of 1, 2, 3, 4, 5, 7, 10 and 18 days after intoxication. The earliest degeneration was observed at day 1 in the intermediate and ventral divisions of the lateral septal nucleus, followed by development of degeneration on days 2-4 in neuron populations including the septohippocampal nucleus, septohypothalamic nucleus, anterior olfactory nucleus, bed nucleus of the stria terminalis, endopiriform nucleus, parafascicular nucleus, superior colliculus, interstitial nucleus of the posterior commissure, inferior colliculus, pontine nuclei, raphe nuclei, pars caudalis of the spinal trigeminal nucleus, the caudal aspect of nucleus tractus solitarius, dorsal vagal motor nucleus, granule cells in the dentate gyrus, pyramidal cells in CA fields of the hippocampus, and of neurons in the subiculum, pyriform cortex, entorhinal cortex and neocortex (mainly layer Vb and VI). This was followed by degenerative changes on days 5-7 in other structures, including the amygdaloid nuclei, the ventral posterolateral and ventral posteromedial thalamic nuclei and the periaqueductal gray. The distribution of terminal degeneration from these neurons indicate that specific pools of cells are affected in each structure, and the time course suggests somatofugal degeneration. The trimethyltin damage was also assessed with immunocytochemical visualization of a neuronotypic protein, protein-O-carboxyl methyltransferase and a radioimmunoassay for glial fibrillary acidic protein. Protein-O-carboxyl methyltransferase immunoreactivity was altered in neuronal populations damaged by trimethyltin, but did not appear to be either as sensitive or selective an assay of neuronal damage as the silver stain, especially at short survival times. Glial fibrillary acidic proteins were dramatically elevated 21 days after trimethyltin intoxication, particularly in areas of extensive damage. These studies revealed advantages and problems encountered in the use of each technique in assessing neurotoxic effects, forming a basis for discussion of the relative merits of using a battery of specific molecular probes for neurotoxicity evaluations.

Biological activity of organotin compounds--an overview

As a consequence of the rapid expansion of the uses and applications of the organotin compounds, the concern about their environmental and health effects is increasing. The main subject of this overview is the current understanding of the mammalian toxicity of the organotin compounds. Four different types of target organ toxicity, namely neurotoxicity, hepatoxicity, immunotoxicity, and cutaneous toxicity, are discussed in more detail. The effects of the organotin compounds on the mitochondrial and cellular level are summarized and discussed in relation to the mode of action of these compounds on the central nervous system, the liver and bile duct, the immune system, and the skin.

Possible pathogenic mechanisms on trimethyltin-induced lesions in the hippocampus of adult and neonatal rats : An overview

The extent of trimethyltin (TMT) induced lesions in the rat hippocampal formation was reviewed. Adult rats were treated with a single dose of 6.0 mg TMT/kg body wt and were sacrificed between 3-60 d following exposure. In the hippocampal formation, the granule cells of fascia dentata showed early changes, which subsided considerably at a later time of the intoxication. On the other hand, destruction of the pyramidal neurons in the Ammon's horn became more pronounced with time, resulting in an extensive destruction of this structure. It is interesting to note that the CA3 neurons in the septal portion of the Ammon's horn were more vulnerable than those located more temporally, whereas the reverse pattern was observed for the dentate granule cells as well as for the CA1,2 neurons of the Ammon's horn. Special stain for zinc (Timm's method) also revealed a progressive depletion of zinc in the mossy fibers. When neonatal rats were treated at various times with a single injection of TMT, rapid and progressive destruction of the Ammon's horn was observed in animals injected between postnatal day (PND) 5-15. The progression of neuronal involvement was CA3b →CA3a, b →CA3(a,b,c)→CA3+CA2→entire Ammon's horn (CA1,2,3). This pattern of pathological lesion was in good concert with morphological development and functional maturity of the hippocampal formation. Destruction of the Ammon's horn neurons was proposed to be the result of hyperexcitation of the dentate granule neurons under the influence of TMT. Other possible mechanisms are also discussed.

Effect of trimethyltin on ornithine decarboxylase in various regions of the mouse brain

Male C57B1/6N mice, 8-10 weeks old were given a single oral dose of 0, 1.0 or 3.0 mg/kg body weight of trimethyltin hydroxide (TMT). Levels of ornithine decarboxylase (ODC) activity were measured in several brain areas, 1, 2 and 7 days later. The lower dose of TMT produced a decrease of ODC in the caudate nucleus and hippocampus at all time points studied. Hypothalamus, cerebellum and brain stem levels of this enzyme were unaltered. At the higher dose of TMT, ODC activity in hippocampus, cerebellum and brain stem were increased relative to controls at 1 and 2 days after treatment, while other regions were not significantly affected. These elevated ODC levels returned to control values within 7 days. Thus, trimethyltin treatment causes changes in ODC activity in a region and dose-specific manner.

The toxicity and neuropathology of dimethylethyltin and methyldiethyltin in rats

Triethyltin causes an increase in brain water with vacuolation of myelin sheaths, whereas trimethyltin is selectively damaging to neurons, especially of the hippocampal formations, causing chromatolysis, accumulation of cytoplasmic dense bodies and often cell death. The effects on rats of the analogues, dimethylethyltin and methyldiethyltin (oral LD50 14 mg/kg and 7.5-10.0 mg/kg respectively) are now reported. The dimethylethyl compound produces functional changes resembling those caused by trimethyltin, while the methyldiethyl compound causes responses similar to those produced by triethyltin. Structurally, however, the dimethylethyl compound, while producing marked nerve cell changes of the trimethyltin type also causes moderate vacuolation of myelin sheaths. By contrast, methyldiethyltin causes marked vacuolation of myelin sheaths of the triethyltin type and relatively minor neuronal changes of the trimethyltin type. These findings are discussed in terms of the structure-activity relationships of trialkyltin compounds.

Diurnal patterns in homecage behavior of rats after acute exposure to triethyltin

Diurnal patterns of eating, drinking, locomotor activity, and rearing in male Fischer-344 rats were examined for 11 days after a single oral dose of triethyltin bromide (TET) at 0, 1.5, 3, or 5 mg/kg. The 5 mg/kg group exhibited a time-related drop in food consumption and body weight until 3 of 10 rats were sacrificed moribund 11 days after dosing. Doses of 1.5 and 3 mg/kg TET did not reduce body weight or consumption of food and water. In contrast, food consumption was significantly increased 7 and 11 days after 3 mg/kg TET, and diurnal patterns of eating and drinking were disrupted 7 days after 3 and 5 mg/kg TET. A phase shift in licking patterns was induced by the high dose. Unlike trimethyltin (TMT), TET did not affect efficiency of eating. Diurnal patterns of both horizontal and vertical activity were disrupted at all dose levels on Day 2 after dosing; by 16 days after dosing, recovery was evident in all rats including those surviving 5 mg/kg TET. These results show that a near-lethal dose of TET produced a reversible syndrome of hypoactivity, aphagia, and weight loss similar to that seen after acute TMT; in the absence of the above signs, diurnal patterns of behavior revealed effects of TET at doses as low as 1.5 mg/kg; the magnitude of the effect depended on the time of day at which the response was measured; and TET did not produce the same effects on ingestive behaviors (polydipsia and reduced feeding efficiency) that were previously observed after acute TMT.

Cholinergic and dopaminergic alterations in the mouse central nervous system following acute trimethyltin exposure

Male mice were given a single oral dose of 0, 1 or 3 mg/kg TMT-hydroxide and sacrificed 48 hrs, 1 and 2 weeks later. Brain areas were removed, dissected and frozen for later analysis of neurotransmitter receptor binding by filtration techniques and determination of concentrations of monoamines and their metabolites by HPLC/EC. Muscarinic cholinergic receptor binding was measured over a [3H]-quinuclidinyl benzilate (QNB) concentration range of 0.02 to 2.0 nM. Two days after TMT treatment, affinity of [3H]-QNB binding in frontal cortex increased. Gradual return to control binding affinity was seen over the next 2 weeks. The number of receptors decreased only at high dose after 1 week. In hippocampus, a similar increase was seen only at the 3 mg/kg dose after 1 and 2 weeks. Homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were significantly decreased in the caudate nucleus 2 weeks after TMT treatment; concentrations of serotonin (5-HT), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC) were unaltered, nor was there a change in dopamine receptors as measured by [3H]-spiroperidol binding in the caudate nucleus or frontal cortex. To determine if TMT altered monoamine turnover or metabolite efflux, mice were dosed with 0 or 3 mg/kg TMT; 2 weeks later, pargyline (75 mg/kg, intraperitoneally) was administered and the mice sacrificed 0, 30 and 60 min. later. Monoamines and their metabolites were measured in caudate nucleus. The HVA elimination rate was unchanged. The data suggests that the lower concentrations of dopamine metabolites observed 2 weeks after TMT treatment were due to a decrease in dopamine turnover. The decrease in muscarinic receptor affinity in frontal cortex and hippocampus and the decrease in the rate of dopamine turnover in the caudate nucleus indicate that these 2 systems are affected by TMT and may participate in the expression of its toxicity.

Peripheral and central nervous system lesions caused by triethyl- and trimethyltin salts in rats

Both trimethyltin and triethyltin salts are known to produce toxic lesions in the central nervous system. Triethyltin intoxication has been associated with central intramyelin edema, while trimethyltin has been shown to produce neuronal necrosis in selected limbic and sensory regions of the brain. Only scant attention has been paid to peripheral nerves of animals treated with alkyltins. In this study, we have treated rats with 6 or 8 mg/kg trimethyltin, and 1, 2, 4, 6, or 8 mg/kg triethyltin (single or multiple exposure), and evaluated in detail at the light microscope level both central and peripheral nervous system lesions. In addition to the central neuron necrosis or myelin edema described previously, both compounds produced peripheral axon degeneration and chromatolysis of large spinal cord and brain stem neurons. Chromatolysis was seen in reticular neurons of the brain stem and ventral horn or spinal cord in rats receiving high doses (6 or 8 mg/kg) of triethyltin, and in these same areas plus mesencephalic trigeminal nucleus in animals treated with trimethyltin. Wallerian-like degeneration of peripheral axons was seen in sciatic and tibial nerve and ventral roots of animals receiving 3 injections of 4 mg/kg or single or multiple injections of 6 or 8 mg/kg triethyltin. Axon degeneration was also seen in sciatic and tibial nerves 21 days after a single exposure to 8 mg/kg trimethyltin. Since myelin edema is believed to be reversible, the axonal changes described here may be of greater clinical significance in relation to human exposure.

Trimethyltin ototoxicity: evidence for a cochlear site of injury

The environmental contaminant, trimethyltin (TMT), produces a profound elevation in tone intensity necessary to inhibit the acoustic startle reflex in laboratory animals which recovers over a prolonged period except at very high frequencies. The recovery that is observed does not begin until 3 to 5 weeks after a single acute administration depending upon dosage. As opposed to the very temporary threshold shifts by the salicylates and loop diuretics or the permanent and progressive ototoxicity resulting from aminoglycoside antibiotics the time course for recovery of acoustic startle reflex inhibition after TMT appears to be an anomaly for a chemical ototoxicant. In terms of the duration of loss only, this pattern appears similar to that sometimes observed after noise exposure. The current investigation replicates the finding that recovery of acoustic startle reflex inhibition after TMT is frequency related in that only the highest frequency impairment appears to be permanent. While this frequency dependence suggests a cochlear locus of injury, both the known neurotoxic effects of TMT and the time course of the behavioral impairment suggest a more central locus of injury. Compound action potential and cochlear microphonic recordings made from the round window in the current study confirm a preferential high frequency effect of TMT and demonstrate a significant cochlear component to the ototoxic effects of this agent.

Acute trimethyltin intoxication in the monkey (Macaca fascicularis)

Adult cynomolgus monkeys were administered trimethyltin (TMT) iv in dosages ranging from 0.75 to 4.0 mg TMT/kg and observed for behavioral changes. Animals were subsequently killed for light and electron microscopic examination. TMT showed a dose-related toxicity, with high dose animals (4.0 and 3.0 mg/kg) dying within 24 hr, and low dose animals (0.75 mg/kg) surviving without morphological effects. Animals given 1.10 mg TMT/kg displayed a reproducible clinical course, characterized by tremor, hyperactivity, and ataxia which progressed to stupor and finally unconsciousness. By light microscopy, neuropathology was most pronounced in the CA-3 and CA-4 regions of Ammon's horn. Degenerating pyramidal neurons, micro- and astrogliosis, and neuronophagia were commonly observed. Mild degenerative changes were identified in amygdala, medulla, spinal cord, and Purkinje cells. The fascia dentata remained intact. Ultrastructurally, injured neurons contained accumulations of lysosomes and lysosome-like structures within perikarya and neurites. Demyelination or vascular damage was not observed. Data indicate the monkey to be highly sensitive to TMT, with morphological injury most severe in limbic structures.

Evolution of the intracellular changes in neurons caused by trimethyltin

Rats have been given a single dose of trimethyltin (10 mg/kg) and the intracellular events have been followed particularly in hippocampus, cerebral cortex, cerebellum and spinal ganglion cells. The earliest change visible occurs 12 h after this dose and is found to be dense membrane-bound bodies, probably derived from branching tubulo-vesicular smooth endoplasmic reticulum formations. These occur in close connection with rought endoplasmic reticulum and polyribosomes and appear also to have some association with the Golgi complex. At 24 h there is a general vacuolation of Golgi cisterns and SER membranes, and the membrane-bound dense body formation is greatly increased. SER abnormalities are particularly conspicuous in Purkinje cells. In spinal ganglion cells, while vacuolation of Golgi cisterns is intense, dense bodies are inconspicuous and are replaced by increased autophagosomes, often of great complexity. By 48 h vacuolation of Golgi cisterns has waned, but accumulation of dense bodies and secondary lysosomes has steadily increased. In spinal ganglion cells autophagosomes only are increased as the Golgi vacuolation declines. At later times steady increases of lysosomal dense bodies is seen generally accompanied in hippocampal pyramidal cells and dentate fascia cells by abundant cell death. The suggestion is put forward that the Golgi complex may be the seat of the critical metabolic lesion and disturbances to protein transfer and protein synthesis follow. No explanation for the selective loss of hippocampal h1-5 (CA1-CA4 except Sommer's sector) pyramidal cells and of small dentate fascia neurons can be derived from these conclusions.

Neuropathology of trimethyltin intoxication. IV. Changes in the spinal cord

Young C57BL/6N mice were injected (ip) with trimethyltin chloride at a dosage of 3.0 mg/kg body wt. Animals were sacrificed between 48 to 72 hr postinjection by means of intracardial perfusion of saline solution followed by 2.5% buffered glutaraldehyde. For light microscopy, the cords were further fixed in 10% buffered formalin and embedded in Paraplast. For electron microscopy, tissue samples were obtained from the cord levels at L1-L4, further fixed in glutaraldehyde and osmium tetroxide, and embedded in Epon. Chromatolytic and vacuolar changes involving neurons mainly in the medial and lateral motor nuclei of the anterior horns were observed. Electron microscopy revealed lysosomal accumulation and extensive dilatation of the cytoplasmic membrane systems (endoplasmic reticulum, Golgi complex). Large intraneuronal vacuoles were formed as a result of extensive intraneuronal edema. Progressive distention of the cytoplasmic membranes resulted in severe vacuolation, disintegration, and total breakdown of the neurons.

Behavioral effects of trimethyltin in two strains of mice. II. Multiple fixed ratio, fixed interval

Adult male C57BL/6N and BALB/c mice were trained to respond under a multiple fixed-ratio 30, fixed-interval 600-sec schedule of milk presentation. After performance had stabilized, each mouse received a single dose of trimethyltin X Cl (TMT) by ip administration. Three hours after administration, behavioral testing was started and continued at 24-hr intervals thereafter. The behavior of mice receiving 0.3 mg/kg was unaffected at 3, 27, and 51 hr after administration. Likewise, no effects were seen at 3 and 27 hr after 1 mg/kg. However, at 51 hr after administration there was a significant change in the temporal patterning of fixed-interval responding in the C57BL/6N strain, as shown by a decrease in the fixed-interval quarter-life. There was no significant change in the BALB/c strain at this dose. At 3 mg/kg the responding of both strains was greatly affected, and responding remained disrupted for at least 6 to 7 weeks. Neuropathological examination of the brains of both strains of mice showed no significant lesions (light microscopy) at 0.3 and 1 mg/kg. At 3 mg/kg, severe neuronal necrosis was observed in the fascia dentata region in both strains. Thus, in mice receiving TMT, the behavioral deficits were closely paralleled by the presence or absence of significant neuropathology.

Behavioral effects of trimethyltin in two strains of mice. I. Spontaneous motor activity

Adult male mice (C57BL/6N and BALB/c) were administered single doses of trimethyltin X Cl (TMT) by the ip route. The effects of TMT administration were determined on lethality (3-6 mg/kg), spontaneous motor activity (SMA), and the physical appearance of the mice (0.3-3 mg/kg). The effects of TMT on lethality were strain dependent in that a single dose of 3 mg/kg, ip, produced approximately 35% lethality in the C57BL/6N strain during the first 72 hr following administration. Less than 15% lethality was observed at this dose in the BALB/c strain. In both strains, 3.5 mg/kg, ip, produced more than 70% lethality during the first 144 hr after administration. Higher doses produced proportionally greater lethality. The SMA of both strains was not affected significantly at doses below 1 mg/kg, ip. At 1 mg/kg a small decrease in activity was observed during the first 24 hr. At 3 mg/kg, SMA was initially decreased in both strains. However, the decrease was of smaller magnitude in the C57BL strain and was followed by a large increase in SMA which did not return to control levels for approximately 1 week. An increase in SMA was observed in the BALB/c strain on the fifth day following TMT but returned to control values by Day 6. At 3 mg/kg, ip, the C57BL mice were observed to have severe whole body tremors and were hypersensitive to external stimuli. The whole body tremor was not as marked in the BALB/c strain. Neuropathological studies on the treated mice indicated that the behavioral studies paralleled the pathology produced by TMT. These data confirm the initial observation of greater sensitivity of the mouse to toxic effects of TMT compared to the rat.