Lythrum hyssopifolia (lesser loosestrife) poisoning of sheep in Victoria

OBJECTIVE

To document an ovine disease attributed to the consumption of Lythrum hyssopifolia (lesser loosestrife).

PROCEDURES

Historical and histological review of field and experimental cases.

RESULTS

1-20% mortality occurred in sheep flocks grazing paddocks where L. hyssopifolia was the predominant green vegetation. Well-documented disease outbreaks occurred in summer on nine farms across Victoria between 1974 and 2002. Liver damage occurred in all nine outbreaks, with kidney damage in at least eight. Hepatocyte necrosis was usually zonal to midzonal (zone 2) in the liver samples from four farms and periacinar (zone 3) in those from three farms, but some livers showed only single-cell necrosis. Multinucleate hepatocytes near necrotic areas were a feature in six cases. Proximal tubular epithelium appeared to be the primary renal target and brown granules were often present in renal tubules. Biochemical and histological evidence of liver and kidney damage was obtained from two sheep experimentally pen-fed harvested L. hyssopifolia.

CONCLUSION

Chemicals in L. hyssopifolia are toxic to ovine hepatocytes and renal tubular epithelial cells.

The case for iron repletion as a promoter in testicular cancer

The incidence of testicular cancer has increased considerably in this century. Current hypotheses (most specifically, those concerning environmental estrogens) show inconsistencies with this increase, either in terms of time course or individual exposure to proposed promoters. This new hypothesis, which attributes the increased incidence in testicular cancer to our current more iron-replete dietary status, is devoid of these inconsistencies. Evidence to support this hypothesis includes the following: (a) the iron-related mechanism of drugs used in the treatment of testicular cancer, (b) dietary associations with disease frequency, (c) the similarity of time course between historic increases in testicular cancer incidence and dietary iron availability, and (d) potential genetic associations with hemochromatosis. The link between incidence of the cancer and cyptorchidism is also addressed. The article concludes with potential experimental approaches to test the hypothesis.

Reproductive organ morphology and carcass traits in unselected naturally mating female Bronze turkeys at onset of lay

A study was conducted examining the rates of development of components of the reproductive tract during sexual maturation in a flock of naturally mating Bronze turkeys. Birds were processed at 7-d intervals beginning at photostimulation (29.5 wk of age), for the following 5 wk, and following their first oviposition. The relatively low BW of this strain (6.6 kg) was associated with a very low lipid content (16.4%), abdominal fat pad weight (107 g), and breast muscle weight (1.15 kg). At sexual maturity the ovary contained 12.2 large yellow follicles with 59% of these follicles being in a multiple hierarchy arrangement. There was an average of 1.4 unreconciled POF (the remnant of the site of ovulation). The presence of unreconciled POF suggests that this may be a natural phenomenon in turkeys and not limited to modern fast growing strains. Birds that laid their first egg quickly were more likely to have ovulated several times prior to their first oviposition than birds commencing lay later (r = 0.64; P < 0.02). Regression analysis of reproductive tract development revealed that the oviduct reached its mature weight 3 d earlier than did the ovary (28.3 vs. 31.2 d) (r2 = 0.81; P < 0.0001). This strain resembled modern female line strains in regard to reproductive traits. Key words: Bronze Turkey, body weight, ovary morphology, reproductive disorders

Aerobic bacterial flora of addled raptor eggs in Saskatchewan

In south-central Saskatchewan, Canada, in 1986, 1987 and 1989, the aerobic bacterial flora was evaluated from 75 unhatched raptor eggs of three species: 42 of the Swainson's hawk (Buteo Swainsoni), 21 of the ferruginous hawk (Buteo regalis), and 12 of the great horned owl (Bubo virginianus). In addled Swainson's hawk eggs, the most common bacterial genera were Enterobacter (18 eggs), Escherichia (12), and Streptococcus (10). Seven great horned owl eggs and six ferruginous hawk eggs also contained Escherichia coli. Salmonella spp. were not isolated. These bacteria were interpreted as secondary contaminants and not the primary cause of reproductive failure.

Proposed role for a combination of citric acid and ascorbic acid in the production of dietary iron overload: a fundamental cause of disease

This paper presents a review of the significant body of literature liking dietary iron overload, not only to heart disease, but also to cancer, diabetes, osteoporosis, arthritis, and possibly other disorders. Following an analysis of our understanding of the mechanistic role iron plays in oxidative damage, an interpretation of the fact that plasma concentrations of several antioxidants are decreased in the presence of disease is offered. Evaluation of (1) age-related dietary trends over time and (2) factors involved in iron absorption leads to the hypothesis that the combination of citric acid and ascorbic acid (a synergistic pair of strong enhancers) is instrumental in causing a deleterious increase in iron load in aging populations. Iron overload may be the most important common etiologic factor in the development of the diseases mentioned; therefore, the synergistic combination of citric and ascorbic acids may play a major role in our worsening disease statistics. Evidence to support this hypothesis and possible experiments to test it are included. This combination needs further study, particularly because the iron overload produced may be correctable.

Efficient storage, computation, and exposure of computer-generated holograms by electron-beam lithography

An efficient storage format was developed for computer-generated holograms for use in electron-beam lithography. This method employs run-length encoding and Lempel-Ziv-Welch compression and succeeds in exposing holograms that were previously infeasible owing to the hologram's tremendous pattern-data file size. These holograms also require significant computation; thus the algorithm was implemented on a parallel computer, which improved performance by 2 orders of magnitude. The decompression algorithm was integrated into the Cambridge electron-beam machine's front-end processor.Although this provides much-needed ability, some hardware enhancements will be required in the future to overcome inadequacies in the current front-end processor that result in a lengthy exposure time.

Phenotypic, embryonic, and neonatal effects of a gene for sex-linked imperfect albinism (Sal-s) in chickens

Gross phenotypic observations, histology, and tissue culture showed that the gene for sex-linked imperfect albinism that occurred at the University of Saskatchewan (Sal-s), allows a small amount of melanin pigment to be deposited in eyes and feathers. Melanin pigment accumulates in retinal pigment epithelial and cultured neural crest cells, but neural crest cells pigmenting the feathers transfer their pigment as it is produced, and this is seen as a constant amount of color in successive generations of feathers. Despite differences from early reports, it would appear that the phenotype produced by Sal-s is essentially the same as that produced by other Sal mutations. Albinos have a high incidence of lesions in the regions of the navel, the hocks, and the nares, similar to those associated with other hypomelanic mutations in the chicken. Yolk contents appear to be used more slowly by albinos late in incubation. The increased size of the yolk sacs probably contributes directly to producing the navel lesions and indirectly to variation in hatch weight. Albinos have small bursae of Fabricius, reduced hatchability, and early growth.

Effects of imperfect albinism (sal-s) on egg production in two lines of chickens

Two trials were conducted with two different lines of chickens to determine whether a gene for sex-linked imperfect albinism (sal-s) affected various egg production traits. In a line with relatively good egg production, sexual maturity was delayed for albino compared with nonalbino hens, but overall egg production by albinos was higher. The increased production resulted in eggs with reduced yolk and shell weights. Albumen weights were not affected, and because the eggs from albinos were smaller, Haugh unit scores were higher. In another trial, sexual maturity of hens of a heavy line was not affected by the genotype, but these hens did not receive controlled lighting during the growing period. Egg production curves of these hens were very similar to those seen in the first trial. The laying house mortality rates were not affected by the sal-s gene, despite several periods of high environmental temperature. These trials suggest that sal-s could be used in a sex-linked cross of commercial layers or broiler breeders.

Effects of imperfect albinism (sal-s) on growth in a heavy line of chickens

Four trials compared growth, feed efficiency, and mortality of albino (sal-s) and nonalbino chickens under conditions approximating those used commercially for broilers. Early body weight reductions of albino chicks were substantial, but by a normal market age for broilers in North America, albinos weighed only 3 to 5% less than nonalbinos. The early mortality rate of albinos was elevated. Overall feed efficiency was not affected by the sal-s gene. An increased incidence of lesions of the navel, hocks, and nares was observed, but regression analyses showed them to be relatively unimportant in the determination of body weights. Heritability estimates showed that the lesions would be very difficult to eliminate through selective breeding. It is proposed that the gene could be used to sex either commercial broilers or their dams.

Quisqualate receptors in epileptic fowl: the absence of coupling between quisqualate and N-methyl-D-aspartate receptors

The ability of excitatory amino acid receptor agonists, AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and quisqualate to produce seizures was determined in 1-2 day old epileptic and non-epileptic (carrier) chicks. Both compounds produced prolonged clonic seizures in epileptic chicks at doses which were not convulsant in carrier chicks. Seizures produced in epileptics by AMPA were suppressed by the quisqualate antagonist CNQX (6-cyano-7-nitroquinoxaline-2,3-dione), but were not prevented by pretreatment with competitive (2-amino-7-phosphonoheptanoic acid, APH) or non-competitive (MK-801) NMDA (N-methyl-D-aspartate) receptor antagonists. These data do not support the hypothesis that NMDA receptors work in concert with quisqualate receptors. Binding sites for [3H]AMPA were characterized in cerebral hemispheres of both epileptic and carrier chicks. Analysis of the data revealed no significant alterations in the binding affinity (KD) or the number of binding sites (Bmax) of AMPA to tissue preparations from epileptic chickens when compared to carriers. The latter data does not explain the increased susceptibility of epileptic fowl to the convulsant effects of quisqualate and AMPA.

Attenuation of febrile seizures in epileptic chicks by N-methyl-D-aspartate receptor antagonists

Experimental febrile seizures can be evoked in epileptic chicks by elevation of their body temperature. Both competitive N-methyl-D-aspartate (NMDA) receptor antagonists [(3-(+/- )2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), DL-2-amino-7-phosphosphonoheptanoic acid (APH), DL-2-amino-5-phosphonovaleric acid (APV), D-alpha-aminoadipic acid (AAA), and DL-alpha, epsilon-diaminopimelic acid (DAP)] and the noncompetitive NMDA antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5, 10-imine maleate (MK-801) produced dose-dependent increases in latency to the onset of seizures. Of the drugs tested, MK-801 had the highest potency followed in order by CPP = APH greater than APV much greater than AAA greater than DAP. There was a high correlation (r = 0.995) between the dose capable of doubling seizure latency and the affinity of the competitive NMDA antagonists for the NMDA receptor as determined by in vitro binding assays. These data suggest that NMDA receptor mediated mechanisms may be involved in the production of seizures in response to hyperthermia.

Megalencephaly in the epileptic chicken: a morphometric study of the adult brain

The epileptic chicken is a genetic model of generalized epilepsy in which epilepsy is combined with megalencephaly. We have performed a morphometric study of the brains of adult epileptic hens, using heterozygous carrier hens as controls. There is no obvious disorder of cell form or of architectural arrangement in the megalencephalic brains. We have found that the enlargement of the epileptic brain is not uniform: it is most marked in the telencephalon, and is present to a lesser degree in the cerebellum, but neither the optic tectum nor the diencephalic nucleus rotundus shows a significant increase in size. The enlarged regions are characterized by a decrease in the packing density of neurons. There is an increase in the total neuron population in some of the enlarged areas (archistriatum), despite the lower density per unit volume, but in other enlarged areas (hippocampus) there is no difference in total neuron numbers. The glial cells, by contrast, show no significant alteration in packing density. These findings suggest that the megalencephaly of the epileptic chicken is due to an increase in neuron size, with a contribution from increased numbers of neurons and glial cells. The epileptic chicken may provide a valuable model for further dynamic studies of aberrant neuronal development, and of structural-functional relationships in epilepsy.

The relationship between anticonvulsant activity and receptor affinity of N-methyl-D-aspartate antagonists in epileptic fowl

The N-methyl-D-aspartate (NMDA) receptor antagonists [(3-(+/-)2-carboxypiperazin-4-yl)-propyl-l-phosphonic acid (CPP), +/- 2-amino-7-phosphonoheptanoic acid (2AP7), +/- 2-amino-5-phosphonovaleric acid (2AP5), D-alpha-aminoadipic acid (alpha AA), and +/- alpha, epsilon-diaminopimelic acid (DAP)] were tested for anticonvulsant activity in epileptic chickens. There was a high correlation between anticonvulsant potencies (ED50) and the affinity for the NMDA receptor measured by displacement of L-[3H]glutamate from synaptosomal membranes. The high seizure susceptibility is not due to abnormalities in the NMDA receptor as comparison of KD, Bmax and Ki values in synaptosomal preparations from epileptic and non-epileptic chickens indicated no differences in NMDA receptor binding receptor characteristics.

Use of interferometry in preschool children

Any procedure that can help to predict the outcome of treatment for a vision disorder is a desired clinical goal. Interferometry has shown such an ability for predicting the post-treatment visual acuities in amblyopia and other vision disorders. In this study, we investigated the effectiveness of using interferometry with preschool children, aged 3-5 years. We determined that they can be reliably tested in 5-10 minutes using a non-verbal, forced choice technique. Due to developmental differences, the 3-year-olds needed slightly more time to test and were more variable in their responses than the 4-years-olds. Overall, the prognostic value of interferometer visual acuity measures should be considered for use in preschool children with visual acuity disorders, e.g., amblyopia.

Protection by GABA agonists, gamma-hydroxybutyric acid, and valproic acid against seizures evoked in epileptic chicks by hyperthermia

With microwave diathermy, febrile seizures were produced in epileptic chicks aged 2-5 days. Drugs that enhance GABAergic activity (i.e., GABA, muscimol, and progabide), as well as valproic acid and gamma-hydroxybutyric acid, produced dose-dependent increases in latency to onset of seizures.

The cytogenetics of domestic geese

Hybrids were produced between an African male and several Pilgrim female domestic geese. Partial karyotypes revealed a difference in the fourth largest pair of autosomal chromosomes. This chromosome pair was metacentric in the African, submetacentric in the Pilgrim, and heteromorphic in the hybrids. A similar difference between the putative wild ancestors of the African and Pilgrim breeds has been reported by others. These findings provide cytological evidence to support the traditional opinion that the African breed was derived from the Asiatic swan goose (Anser cygnoides) and the Pilgrim breed was derived from the European greylag goose (Anser anser).

Benzodiazepine antagonist Ro 15-1788 (flumazepil) attenuates the anticonvulsant activity of diazepam in epileptic fowl

The ability of the imidazobenzodiazepine Ro 15-1788 to displace diazepam from brain membranes in vitro and to antagonize the anticonvulsant activity of diazepam in vivo was determined in epileptic fowl. At doses of 1.0 mg/kg and higher, Ro 15-1788 significantly attenuated the anticonvulsant action of diazepam (1.0 mg/kg) in epileptic chickens. Ro 15-1788 alone exerted no anticonvulsant activity even in doses as high as 10 mg/kg. Specific binding of 10 nM [3H]diazepam to whole homogenate fractions prepared from cerebral hemispheres of epileptic fowl was inhibited by Ro 15-1788 with an IC50 of 8.5 nM and the Ki was determined to be 4.25 nM. These results suggest that Ro 15-1788 competes directly with diazepam for a binding site involved in producing anticonvulsant activity.

Anatomical defects associated with a feathering mutant (Ottawa naked) in domestic fowl

An autosomal recessive mutation (Ottawa naked, nk) that causes abnormal feathering, fusion of the third and fourth toes, and low viability has been reported previously in the chicken. In the present study mutant individuals were examined from three different stocks: the original one in which the mutant was found and two outbred F2 stocks. Defects of the tail region were observed in all mutants from the original stock (20/20) and in 64% (16/25) of the mutants produced from the outcrossed stocks. The severity of the defects ranged from mild distortion and scoliosis of the coccygeal vertebrae to absence of all vertebrae from the lumbosacral level caudad. Forty percent (16/40) of the mutants from the original stock lacked caudal portions of the kidneys to varying degrees. Edematous areas were observed in 22% (15/67) of the embryos examined at 14 days of incubation. Other defects observed in the mutant embryos but not studied in detail are abnormal patterning or absence of scales, absence of the caudal spinal cord in embryos with severe rumplessness, and failure of the three metatarsal bones to fuse into a single element. Since all structures affected in the mutants differentiate primarily from or may be dependent upon the mesoderm, it is suggested that the site of gene action lies within this germ layer. A decrease was observed in both incidence and severity of the various defects following outcrossing, which suggests the presence of modifiers that influence the expression of the trait.

Integrated electromyographic measurement of abdominal motor blockade during bupivacaine epidural anesthesia for lower abdominal and pelvic surgery

The onset and regression of abdominal motor blockade was monitored with integrated electromyography in eighteen patients undergoing pelvic or lower abdominal surgery during lumbar epidural anesthesia using 0.75% bupivacaine with 1:200,000 epinephrine. The integrated electromyograph (EMG) was measured at the T-6, T-8, T-10 and T-12 dermatomes during a standardized head-raising test before anesthesia and at fixed time intervals thereafter for a minimum of four hours. Simultaneous measurements were made of abdominal sensory block (analgesia to Allis forceps pinch expressed in dermatomes) and lower limb motor blockade (Bromage scale). Motor block at a given dermatome level was defined as reduction of the integrated EMG amplitude to less than 20% of control. Mean maximum level of sensory block was T-4.2 +/- 0.6 (SEM) mean maximum level of motor block was T-8.8 +/- 0.5. The mean motor sensory differential varied between 4.5 +/- 0.6 and 5.3 +/- 0.9 segments over the 4-hr study period. Mean time to maximum abdominal sensory block was 28 +/- 3 min, and maximum abdominal motor block was 29 +/- 6 min. Mean time to two-segment regression of abdominal motor block was 94 +/- 18 min and to two-segment regression of abdominal sensory block, was 150 +/- 18 min.

Anticonvulsant effects of ivermectin in genetically-epileptic chickens

In genetically-photosensitive epileptic chickens, the anti-parasitic agent ivermectin, at 1.0 and 5.0 mg/kg, decreased or prevented seizures induced by intermittent photic stimulation without any side-effects on the central nervous system. The latency and duration of this anti-convulsant effect was dose-dependent. When combined with diazepam, ivermectin prolonged the anti-convulsant action of diazepam.

Evidence for the pharmacological relevance of benzodiazepine receptors to anticonvulsant activity

Each of a series of benzodiazepines was found to be effective in preventing convulsions evoked by intermittent photic stimulation of epileptic chickens. There was a high correlation between the anticonvulsant potencies (mean effective dosages) and the affinity of the agents for the putative benzodiazepine receptor as measured by displacement of [3H]diazepam from binding sites on chicken synaptosomal membranes. This correlation in a genetic model of epilepsy provides further evidence that benzodiazepines exert their anticonvulsant effects by interacting with the benzodiazepine receptor.

Experimental febrile convulsions in epileptic chickens: the anticonvulsant effect of elevated gamma-aminobutyric acid concentrations

The high seizure susceptibility in epileptic chickens is due to an autosomal recessive mutation. In 3-day-old chicks homozygous for the epilepsy gene (epileptics), elevation of body temperature using microwave diathermy evoked an initial febrile seizure resembling the clonic seizures evoked in epileptic chicks by photic stimulation. After complete recovery, this was followed by a clonic-tonic seizure. In nonepileptic heterozygote hatchmates (carriers) of the same age, only the latter seizure pattern was observed. In 16- to 17-day-old chicks of either phenotype, both seizure patterns were observed during hyperthermia. In all cases, the temperature at which seizures occurred was significantly lower in epileptic than in nonepileptic chicks, indicating a lower threshold for febrile seizures when there is an inherited predisposition to convulse. The occurrence of seizures was dependent on the body temperature and not on the rate of rise of temperature. Elevation of the brain gamma-aminobutyric acid (GABA) concentrations by administration of the GABA transaminase inhibitor gamma-vinyl GABA reduced the incidence of the initial febrile seizures and increased the latency in those birds that were not fully protected.

Benzodiazepine receptors and seizure susceptibility in epileptic fowl

Benzodiazepine binding to brain membrane preparations obtained from epileptic and nonepileptic carrier fowl was compared. [3H]Flunitrazepam binding to whole brain homogenates from 2-day-old chicks and [3H]diazepam binding to synaptosomal membranes and homogenates from adult chickens were determined. Scatchard analysis revealed no differences in either the number of receptors or their affinity for the ligands when the epileptics were sacrificed in the interictal state. Evoked seizures in adult epileptics had no effect on the number or affinity of binding sites using [3H]diazepam as the ligand. Moreover, the ability of gamma-aminobutyric acid to facilitate benzodiazepine binding was not different in epileptic fowl when compared with carriers.

Pharmacology of methyl- and propyl-beta-carbolines in a hereditary model of epilepsy

Intravenous administration of beta-carboline-3-carboxylate methyl ester (beta-CCM) produced convulsions at small doses (0.03 mg/kg) in adult chickens, homozygous for the epileptic gene. Nonepileptic heterozygote hatchmates (carriers) did not undergo seizures at doses of 1 mg/kg, and doses of 3-5 mg/kg produced only brief myoclonic responses. The convulsant effect of beta-CCM could be prevented by pretreatment with large doses of beta-carboline-3-carboxylate propyl ester (beta-CCP). beta-Carboline-3-carboxylate methyl ester displayed a higher affinity than diazepam in displacement studies on synaptosomal membrane preparations from brains of epileptic and carrier chickens.

Cyclic nucleotides and seizures in a hereditary model of epilepsy

The high seizure susceptibility in epileptic fowl is due to an autosomal recessive mutation. Cyclic AMP and cyclic GMP concentrations were determined in brains from two day old epileptic chicks (homozygotes) during an inter-ictal period as well as during and following a seizure evoked by stroboscopic stimulation. The data were compared to values obtained from non-epileptic carrier chicks (heterozygotes) sacrificed in an unstimulated state or subjected to the seizure evoking stimulus. During the inter-ictal state in epileptics no abnormalities were found in cyclic nucleotide concentrations indicating that the high seizure susceptibility is not related to abnormalities of these nucleotides. Although seizure activity in epileptics was associated with reduced cyclic AMP in the optic lobes this also occurred in carrier chicks subjected to the seizure evoking stimulus. The only significant changes in cyclic GMP levels, occurring as a result of seizures in epileptics, were an increase in cyclic GMP in the cerebral hemispheres during the seizure and a decrease in the optic lobes during the postictal period.

Febrile seizures in epileptic chicks: the effects of phenobarbital, phenytoin and valproate

Epileptic seizures can be evoked in chicks homozygous for the epileptic seizure gene (epi, epi) by elevating their body temperature using microwave diathermy. These seizures precede and differ in motor seizure pattern from a second clonic-tonic seizure produced by hyperthermia in both epileptic and carrier (heterozygote, Epi, epi) chicks. Hyperthermia did not evoke seizures in adult epileptic chickens. Phenobarbital delayed the onset of epileptiform seizures whereas phenytoin and valproate had no effect. These data suggest that epileptic chicks may provide a suitable model for studies on febrile convulsions.

Missing upper beak: a new lethal mutation in domestic fowl

A new condition affecting the facial structure of domestic fowl is described. It is controlled by an autosomal recessive gene having complete penetrance. The mutation has been named missing upper beak and the gene symbol mub is proposed. The condition is an obligate lethal. Mortality occurs on the twelfth day of incubation or during the hatching process. One chick hatched unaided and five were assisted from the shell; none of these survived beyond 11 days of age. They had partial vision and hearing, they could vocalize and had normal balance, but they were unable to eat. Major phenotypic effects of the mutation are absence of the upper beak and absence of eyelids. All or part of the upper eyelid is always missing; the lower eyelid and nictitating membrane may be present or absent. Premaxilla and nasal bones are greatly reduced causing the upper beak to be rudimentary. Other membranous bones of the head are reduced causing the face to be shortened. Cartilaginous bones appear not to be affected. It is postulated that the condition results from a defect in membrane formation during embryonic development.

Brain norepinephrine, dopamine, and 5-hydroxytryptamine concentration abnormalities and their role in the high seizure susceptibility of epileptic chickens

Norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine (5-HT) concentrations were determined in cerebral hemispheres, optic lobes, the midbrain pons–medulla, and cerebellum of adult homozygous recessive epileptic chickens during interictal periods and compared with concentrations in their nonepileptic heterozygous hatchmates. Cerebral hemispheres from epileptic fowl contained significantly lower concentrations of 5-HT and DA and higher concentrations of NE than nonepileptics. Elevation of 5-HT with phenelzine, tryptophan, or the combination of phenelzine plus tryptophan had no effect on seizure susceptibility or severity. Treatment with L-3,4-dihydroxyphenylalanine, which increased brain DA, also had no effect on the seizure incidence or severity. Administration of phenoxybenzamine, phentolamine, or propranolol to block adrenergic receptors did not reduce seizure susceptibility.

Epileptiform seizures in domestic fowl. IX. Implications of the absence of anticonvulsant activity of ethosuximide in a pharmacological model of epilepsy

Acute dose--response studies were conducted to determine if ethosuximide had anticonvulsant activity against seizures evoked by stroboscopic stimulation of epileptic fowl and to correlate the observed effects with the concentration of the drug in the plasma. Ethosuximide, in doses that produced mean plasma concentrations of 366 microgram/ml and signs of sedation, did not reduce seizure susceptibility. Twice daily administration of ethosuximide produced mean plasma concentrations of 430 microgram/ml after 36 h without affecting seizure susceptibility even in the presence of marked sedation. Previous studies have shown that epileptic fowl are sensitive to the anticonvulsant effects of phenobarbital, phenytoin, and primidone at plasma concentrations similar to those required in humans. Since ethosuximide has a high specificity against petit mal seizures in humans, the failure of ethosuximide to provide protection indicates that epileptic fowl represent a relatively specific pharmacological model for drugs effective against generalized tonic--clonic and focal cortical epilepsies in humans.

Epileptiform seizures in domestic fowl. VIII. Anticonvulsant activity of primidone and its metabolites, phenobarbital and phenylethylmalonamide

Primidone is an effective anticonvulsant against seizures induced in epileptic fowl by exposure to intermittent photic stimulation. Epileptic fowl metabolize primidone to phenobarbital. Pretreatment of epileptic fowl with SKF 525A to prevent the metabolism of primidone to phenobarbital indicated that primidone itself had anticonvulsant activity. Phenylethylmalonamide, a second metabolite of primidone, did not have anticonvulsant activity when administered at the same dose as primidone.

Inheritance of short coat and long coat in St. Bernard dogs

A popular belief among dog breeders is that long coat and short coat in certain dog breeds is controlled by a single pair of autosomal alleles, short coat being dominant to long coat. Data are presented for 221 litters and 1216 pups of the St. Bernard breed that support and verify this belief.

Epileptiform seizures in domestic fowl. VII. Plasma phenytoin concentrations and anticonvulsant activity

Acute dose-response studies with phenytoin were conducted to determine the relationship between plasma levels and anticonvulsant effect in epileptic chickens. Phenytoin produced statistically significant reductions in both the incidence and severity of seizures in photosensitive epileptic chickens when the plasma concentrations exceeded 8.15 +/- 0.89 microgram/ml. A high correlation exists between plasma phenytoin concentrations and both the reduction in incidence or severity of seizures. However, the appearance of plasma concentration dependent neurological toxicities resulted in a failure to achieve complete protection against intermittent photic stimulation induced seizures.

Epileptiform seizures in domestic fowl. VI. Plasma phenobarbital concentrations and anticonvulsant activity

The relationship between plasma phenobarbital concentrations and anticonvulsant activity was determined against seizures induced in epileptic chickens by intermittent photic stimulation (IPS). Intraperitoneally administered phenobarbital produced a plasma-concentration-dependent reduction in both the incidence and severity of seizures. Complete protection against IPS-induced seizures was observed for a period of 6 h after acute phenobarbital administration during which the mean plasma phenobarbital concentrations were between 16.2 +/- 0.91 and 13.6 +/- 1.0 microgram/lm. Plasma phenobarbital concentrations below 3.6 +/- 0.06 microgram/ml had no measurable effect.