Rachel Y. Reams

Mesial Temporal Lobe Epilepsy: Pathogenesis, Induced Rodent Models and Lesions

Mesial temporal lobe epilepsy (MTLE), the most common epilepsy in adults, is generally intractable and is suspected to be the result of recurrent excitation or inhibition circuitry. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. Of the animal models developed to investigate the pathogenesis of MTLE, post-status epilepticus models have received the greatest acceptance because they are characterized by a latency period, the development of spontaneous motor seizures, and a spectrum of lesions like those of MTLE. Among post-status epilepticus models, induction of systemic kainic acid or pilocarpine-induced epilepsy is less labor-intensive than electrical-stimulation models and these models mirror the clinicopathologic features of MTLE more closely than do kindling, tetanus toxin, hyperthermia, post-traumatic, and perinatal hypoxia/ischemia models. Unfortunately, spontaneous motor seizures do not develop in kindling or adult hyperthermia models and are not a consistent finding in tetanus toxin-induced or perinatal hypoxia/ischemia models. This review presents the mechanistic hypotheses for seizure induction, means of model induction, and associated pathology, especially as compared to MTLE patients. Animal models are valuable tools not only to study the pathogenesis of MTLE, but also to evaluate potential antiepileptogenic drugs.

Streptococclcs suis infection in swine: a retrospective study of 256 cases. Part II. Clinical signs, gross and microscopic lesions, and coexisting microorganisms

A retrospective study of 256 cases of naturally acquired Streptococcus suis infections in swine submitted to the Indiana Animal Disease Diagnostic Laboratory from 1985 to 1989 was undertaken to describe the clinical signs, lesions, and coexisting organisms associated with S. suis serotypes 1–8 and 1/2. Infected pigs generally had clinical signs and gross lesions referable to either the respiratory system or to the central nervous system (CNS), but not both. Neurologic signs were inversely related to gross lesions in the respiratory tract (R 2 = −0.19, P = 0.003), as were respiratory signs and gross lesions in the CNS (R 2 = −0.19, P = 0.003). Suppurative bronchopneumonia was the most common gross lesion observed (55.2%, overall). Fibrinous and/or suppurative pleuritis, epicarditis, pericarditis, arthritis, peritonitis, and polyserositis were also reported. In 68% of the pigs, other bacteria in addition to S. suis were isolated. Escherichia coli (35.0%) and Pasteurella multocida (30.0%) were the most commonly recovered bacterial agents. Mycoplasma and viral agents were identified less often, and their role in the development of streptococcosis was difficult to assess. In pigs infected with serotypes 2–5, 7, 8, and 1/2, suppurative meningitis with suppurative or nonsuppurative encephalitis, suppurative bronchopneumonia, fibrinopurulent epicarditis, multifocal myocarditis, and cardiac vasculitis were the most common microscopic lesions observed, whereas pigs infected with serotype 1 generally presented with suppurative meningitis and interstitial pneumonia. Microscopic lesions were morphologically similar among serotypes and were also similar to those reported with other pyogenic bacteria. The distribution of clinical signs and the gross and microscopic lesions in pigs infected with S. suis varied among serotypes. However, these differences were not statistically significant and could not be used to distinguish between the various serotypes. These findings suggest that in pigs infected with S. suis, suppurative or fibrinopurulent inflammation in brain, heart, lungs, and serosae predominates and that bacterial culture is needed to confirm a diagnosis of streptococcosis in swine and to differentiate this disease from those caused by other pyogenic bacteria.

A SUDDEN DEATH SYNDROME INDUCED IN POULTS AND CHICKS FED DIETS CONTAINING FUSARIUM FUJIKUROI WITH KNOWN CONCENTRATIONS OF MONILIFORMIN

A sudden death syndrome was induced in chicks and poults fed diets containing Fusarium fujikuroi, formulated to contain 0-330 mg/kg moniliformin (M) with or without the maximum recommended therapeutic concentration of monensin. Lesions of monensin toxicosis were not observed. Clinical signs were referable to cardiac dysfunction (sudden death, dyspnea, cyanosis, depression). Poults and chicks dying early in the study had no gross lesions or had lesions of right ventricular dilation. Treated poults and chicks dying late in the study or euthanatized at termination of the study had lesions of bilateral myocardial hypertrophy, usually concentric. Absolute heart weights and relative heart weights, expressed as a percentage of body weight, were significantly greater in treated birds than controls (P < 0.05), whereas body weights were significantly less (P < 0.05). Microscopically, lesions progressed from acute myocardial degeneration to necrosis, fibrosis, and hypertrophy. Ultrastructural findings were consistent with the gross and microscopic lesions. Serum pyruvate concentrations were a useful indicator of M-induced cardiotoxicosis. Concentrations of serum pyruvate increased with increased concentration of dietary M, but were not affected by addition of monensin to the diet. In chicks ingesting 40-300 mg/kg M, serum pyruvate concentrations were significantly greater (P > 0.05) than those in controls (controls, 0.28 +/- 0.08 mmol/liter; exposed 0.38 +/- 0.11-0.55 +/- 0.13 mmol/liter). Poults ingesting 80-330 mg/kg M had significantly greater serum pyruvate concentrations than controls (controls 0.33 +/- 0.09 mmol/liter; exposed 0.43 +/- 0.13-1.00 +/- 0.006 mmol/liter). The Vetronics System was used to evaluate electrocardiographic alterations in a limited number of chicks and poults surviving to the end of the feeding trial. Electrocardiographic alterations in poults and chicks fed diets containing > or = 40 mg/kg and > or = 160 mg/kg M, respectively, were consistent with ventricular hypertrophy, myocardial injury, and hypoxia. Electrocardiographic alterations were more striking in poults than in chicks. Altered myocardial metabolism due to M toxicosis, in conjunction with the unusual susceptibility of domestic poultry to altered cardiac metabolism, is believed to be the cause of the organ-specific lesions in these birds. These findings suggest that cardiac injury with subsequent alterations in cardiac electrical conductance may be a cause of the sudden deaths observed in poultry chronically intoxicated with dietary M.

Multiple serotypes and strains of Streptococcus suis in naturally infected swine herds.

We present a brief description of the epidemiology, clinical signs, and lesions in 21 accessions in which multiple serotypes of S. suis or multiple distinct isolates (strains) of the same capsular serotype of S. suis were identified. Isolates of the same capsular serotype that had different antibiogram profiles were considered to be distinct isolates or “strains” for the purposes of this study. Streptococcus suis isolates of the same capsular serotype and identical antibiogram profiles were considered to be identical organisms. These cases were selected to determine whether or not herds infected with multiple serotypes (or strains) of S. suis had unique features that might serve to distinguish these herds from those infected with a single serotype and strain of S. suis and to provide additional information on the development of this disease in swine. Selected cases were limited to those in which isolates were identified by capsular serotyping. Untypeable isolates of S. suis were not included in this study. Case selection criteria, data collection procedures, etc., were as previously described. 12 Of 277 accessions in which S. suis was identified, 21 accessions (7.6%) involving 37 pigs were cases in which 46 different isolates of S. suis were identified. The distribution of these isolates is shown in Tables 1 and 2. Because of the small sample size, statistical analyses were not performed. Although there was a slight increase in recovery of S. suis in the fall and winter months for all serotypes, S. suis was readily isolated throughout the year. In this study, there was a slight increase (approximately 5%) in the prevalence of serotypes 3, 7, and 8 and a decrease (approximately 10%) in the prevalence of serotype 2 from those reported previously. 12

Streptococcus Suis Infection in Swine: A Retrospective Study of 256 Cases. Part I. Epidemiologic Factors and Antibiotic Susceptibility Patterns

A retrospective study of 256 cases of naturally acquired Streptococcus suis infections in swine submitted to the Indiana Animal Disease Diagnostic Laboratory from 1985 to 1989 was performed to determine the epidemiologic factors and antibiotic susceptibility patterns associated with S. suis serotypes 1–8 and 1/2. A standardized computer form was used to record the history, signalment, and clinical signs obtained from the records of selected cases and the microscopic lesions identified after review of the histopathology slides for each case. A computer statistics package (SAP) was used to evaluate the data. Although the number of recovered S. suis isolates increased in the fall and winter months, most serotypes were readily isolated throughout the year; only serotypes 1, 4, 7, and 1/2 increased in frequency of isolation in the fall, winter, and spring months. The majority (6 1.1%) of infected pigs in this study were < 12 weeks of age. More than 75% of pigs infected with serotypes 1, 6, 7, and 1/2 were < 12 weeks of age. There was extensive overlap in the age distributions for pigs with each serotype, and statistically significant differences for most serotypes were not observed. Fifty percent of pigs infected with S. suis serotypes 1 and 1/2 were 3–10 weeks of age, 50% of pigs infected with serotype 2 were 6–14 weeks of age, and 50% of pigs infected with serotypes 3, 4, 5, 7, and 8 were 2–16 weeks of age. Isolates of S. suis were not uniformly susceptible to penicillin, and a large percentage of isolates were resistant to many antibiotics in common usage. The results of this study indicated that the various serotypes of S. suis could not be readily separated based on antibiograms, epidemiologic factors (herd size, breed, etc.), or geographic location.

Kainic Acid-induced F-344 Rat model of Mesial Temporal Lobe Epilepsy: Gene Expression and Canonical Pathways

Mesial temporal lobe epilepsy (MTLE) is a severe neurological condition of unknown pathogenesis for which several animal models have been developed. To obtain a better understanding of the underlying molecular mechanisms and identify potential biomarkers of lesion progression, we used a rat kainic acid (KA) treatment model of MTLE coupled with global gene expression analysis to examine temporal (four hours, days 3, 14, or 28) gene regulation relative to hippocampal histopathological changes. The authors recommend reviewing the companion histopathology paper (Sharma et al. 2008) to get a better understanding of the work presented here. Analysis of filtered gene expression data using Ingenuity Pathways Analysis (Ingenuity Systems, http://www.ingenuity.com) revealed that a number of genes pertaining to neuronal plasticity (RhoA, Rac1, Cdc42, BDNF, and Trk), neurodegeneration (Caspase3, Calpain 1, Bax, a Cytochrome c, and Smac/Diablo), and inflammation/immune-response pathways (TNF-α, CCL2, Cox2) were modulated in a temporal fashion after KA treatment. Expression changes for selected genes known to have a role in neuronal plasticity were subsequently validated by quantitative polymerase chain reaction (qPCR). Notably, canonical pathway analysis revealed that a number of genes within the axon guidance signaling canonical pathway were up-regulated from Days 3 to 28, which correlated with aberrant mossy fiber (MF) sprouting observed histologically beginning at Day 6. Importantly, analysis of the gene expression data also identified potential biomarkers for monitoring neurodegeneration (Cox2) and neuronal/synaptic plasticity (Kalrn).

Temporal Profile of Clinical Signs and Histopathologic Changes in an F-344 Rat Model of Kainic Acid-induced Mesial Temporal Lobe Epilepsy

Since there is limited information in the literature, the purpose of this study was to investigate clinical signs, morphology, and temporal progression of lesions from Days 3 to 168 in a kainic acid (KA)-induced Fischer-344 (F-344) rat model of mesial temporal lobe epilepsy (MTLE). Following a single KA subcutaneous dose of 9 mg/kg to young adult male rats, 95% survived, 93% exhibited status epilepticus, and 80% eventually developed spontaneous motor seizures. Histopathology included hematoxylin and eosin (H&E), autofluorescence, Fluoro-Jade B, Timm’s, ED-1/CD68, GFAP, doublecortin, and Ki-67. Neuronal degeneration occurred on Day 3 in the hippocampal CA1, CA3, and dentate hilar regions; amyg-daloid and thalamic nuclei; and frontoparietotemporal, entorhinal and piriform cortices. Degeneration severity peaked on Day 6 and decreased progressively until Day 168. Aberrant mossy fiber (MF) sprouting was present in the inner molecular layer of dentate gyrus on Days 6–168. Microliosis and astrogliosis peaked on Day 28 and generally colocalized with the distribution of neuronal degeneration. Important correlates to human MTLE included induction of spontaneous seizures, more severe neuronal damage of CA1 than CA3 (in contrast to other animal models but similar to humans), hilar neuronal loss, activated microgliosis and astrogliosis, aberrant MF sprouting, and dentate granule cell neurogenesis. Aberrant MF sprouting prior to spontaneous motor seizures and reduced seizure frequency with a decrease in aberrant MF sprouting support the hypothesis that MF sprouts are necessary for spontaneous seizure generation and maintenance.

Development of a Percutaneous Cerebrospinal Fluid Collection Technique in F-344 Rats and Evaluation of Cell Counts and Total Protein Concentrations

A simple technique for cerebrospinal fluid (CSF) collection was developed in F-344 rats. Cell counts and total protein concentrations were evaluated to assess sample quality. While the 50 to 70 μL samples of CSF collected on three different days showed a progressive decrease in the total erythrocyte and nucleated cell counts, no significant changes were observed in the total protein concentrations. Progressive decreases in the total erythrocyte count correlated positively with the decreases in volume of CSF collected. Our data suggest that collection of less than 50 μL of CSF will give a better quality of CSF in F-344 rats. This is the first report of cellular and protein parameters in the CSF of F-344 rats.

Development of an L6 myoblast in vitro model of moniliformin toxicosis

L6 myoblasts were used as an in vitro model to investigate the role of moniliformin and its interaction with monensin in turkey knockdown syndrome and sudden death syndromes in poultry. Cell viability and microscopic and ultrastructural alterations noted in L6 myoblasts cultured in the presence of moniliformin (0.0–0.3 μg/μl) were compared to those observed in parallel cultures also containing one of the following compounds: selenium (0–0.004 ng/μl), thiamine (0–0.3 μg/μl), or pyruvate (0–0.46 μg/μl). Marked dilation of the RER, membranous whorls, glycogen deposition, membrane-bound cytoplasmic inclusions and necrosis were observed in myoblasts exposed to 0.03/2-0.30 μg moniliformin/μl medium. Supplementation of medium with thiamine and pyruvate, or selenium, provided significant protection to cells exposed to 0.0–0.3 μg/μl or 0.0–0.15 μg moniliformin/μl, respectively. Dose-dependent differences in protein and ATP production were not detected. Myoblasts grown in medium containing 0–0.15 μg moniliformin/μl and 7.5–50.0 μM A23187, beauvericin or monensin had degrees of cytotoxicity similar to parallel cultures receiving only an ionophore. L6 myoblasts were a useful model of moniliformin toxicosis. The findings of this study suggest cytotoxicity due to moniliformin in L6 myoblasts may be due in part to oxidative damage and altered pyruvate metabolism, and that moniliformin does not predispose myoblasts to ionophore toxicosis. This study supports the results of in vivo investigations in poultry that moniliformin and monensin do not act synergistically to induce knockdown or monensin toxicosis.

Cycad (Zamia Puertoriquensis) Toxicosis in a Group of Dairy Heifers in Puerto Rico

tory parenchymal necrosis and lysis associated with groups of bacteria (probably secondary infection), with focal hemorrhages. Structurally distinct types of schizonts with slender merozoites (Fig. 14) or short stubby merozoites (Fig. 15) were seen. Intestinal coccidiosis was seen in echidna nos. 2, 4, and 5 (Figs. 16-20). Lesions were more severe in the small intestines of echidna nos. 2 and 5 and consisted of desquamation of epithelial cells of glands of Lieberkiihn and surface epithelium, hypertrophy of villous epithelium, and mononuclear cell infiltration in lamina propria. Gamonts and oocysts The intravascular schizonts in the lungs of the echidnas were structurally similar to schizonts of Sarcocystis, particularly of the Sarcocystis species in cattle, sheep, and goats. Some of the schizonts in the liver, lungs, and spleen were difficult to distinguish from tachyzoites of T. gondii. However, T. gondii tachyzoites always divide into 2 by endodyogeny, whereas the extraintestinal protozoa of the echidnas divided into many organisms by schizogony. Acknowledgements. We thank the staff of the Veterinary Research Institute in Melbourne who made 3 of the cases available for examination. were seen in all 3 echidnas. Oocysts were approximately 25 x 20 μm and were unsporulated (Figs. 18-20). Few schizonts were seen only in 1. echidna no. 2. A 45x 25-μm schizont with numerous tiny merozoites in the lamina propria of the small intestine is shown in Fig. 17. Protozoa in the lung and liver of echidna no. 1 did not 2. react to T. gondii, N, caninum, or S. cruzi antisera. Protozoa in extraintestinal tissues of echidnas were un3= identified. Protozoa in the intestines of echidnas in the present study appeared to be structurally similar to the intestinal 4.