Testicular Lesions in Rats Treated with a Sympatholytic Hypotensive Agent (Losulazine)

Groups of 25 male Sprague-Dawley rats were treated orally with losulazine at 0 (vehicle control), 4, 8, 16, or 32 mg/kg/day for 1 year. Daily clinical signs, weekly food consumption and body weight changes, and terminal hematologic and blood chemistry values were evaluated. Terminal urinalysis in 10 randomly selected rats from all groups and levels of serum luetinizing hormone, prolactin, and testosterone from control, low-, and high-dose groups were also evaluated. Fertility was determined in eight randomly selected rats from each group at 35–49 weeks. Reversibility of breeding performance was evaluated in 10 rats treated for 30 weeks and allowed to recover for 17 weeks. Selected organs were weighed and the testes and epididymides were microscopically evaluated in all rats that survived through the 1 year treatment period.

Rats treated with losulazine showed dosage-dependent ptosis, somnolence, fecal softening, and decreased food consumption with a corresponding retarded body weight gain. There were no biologically significant changes in hematologic, blood chemistry, or urinalysis values between treated and control rats. Relative spleen, heart, adrenal, and brain weights were increased in treated rats. There was a reversible dosage and time-dependent decreased fertility in rats treated with losulazine for 6–12 months. The incidence of testicular tubular atrophy/degeneration, usually confined to the subcapsular areas of the testes, and concentration of degenerate ge.minal cells in the epididymides, were increased in treated compared to vehicle control rats. Testicular lesions were not dosage related, were minimal to mild after 1 year of treatment, and were not attended by a decrease in relative testicular weights. Decreased fertility was not correlated with the apparently treatment-related testicular lesions. It could not be determined whether the minor testicular lesions seen in rats treated with losulazine were related to stressful conditions the rats were apparently under or to the effects of the drug on the hypothalamus-pituitary-gonadal axis or the sympathetic nervous system.

Intralobar nephroblastematosis: precursor lesions of nephroblastoma in the Sprague-Dawley rat

Precursor lesions of spontaneous nephroblastoma (NB) in rats are here characterized for the first time, with a description of the progression of the tumor in prenatal, postnatal, and adult Sprague-Dawley rats (Upj:TUC[SD]spf.nb), which are genetically predisposed to the tumor. NB in the rat starts as a focal or multifocal interstitial accumulation of intensely basophilic immature (blastema) cells, invariably located in the deep renal cortex. Precursor lesions of NB (designated intralobar nephroblastematosis) and the early tumor do not overtly disrupt the overall structural organization and integrity of the kidney. However, with increasing size and neoplastic transformation, these lesions trap, compress, and displace/replace the existing renal tubules. Nephroblastematous foci occurred in one or both kidneys in tumor-bearing or non-tumor-bearing kidneys and in young and old rats. Like the precursor lesions, the early tumors in rats as young as 6 weeks of age were located in the inner cortex. Well-developed NB was comprised of blastema cells arranged in dense sheets or in ductular structures surrounded by mantles of blastema cells supported by varying amounts of fibromatous stroma. The stroma in one rat was hemangiosarcomatous (triphasic Wilms' tumor). Tumor cells were slightly pleomorphic and had varying amounts of granular cytoplasm with sparse organelles and showed junctional complexes and basal laminae whose frequency apparently depended upon whether the blastema cell tended to differentiate to epithelial or mesenchymal cells. NB in the rat was morphologically similar to immature pre- and postnatal kidneys, regardless of whether it occurred in young or old rats. The deep cortical location and interstitial infiltrative characteristics of precursor lesions of NB in the rat were analogous to intralobar nephrogenic rests, a variant of the precursor to Wilms' tumor in children.

Venous irritation, pharmacokinetics, and tissue distribution of tirilazad in rats following intravenous administration of a novel supersaturated submicron lipid emulsion

PURPOSE

To compare the venous irritation, pharmacokinetics, and tissue distribution of tirilazad in rats after intravenous administration of a submicron lipid emulsion with that of an aqueous solution.

METHODS

Venous irritation was determined by microscopic evaluation of injury to the lateral tail veins of rats. Pharmacokinetic parameters were determined by following plasma concentrations of drug. Tissue distribution of [14C]-tirilazad was determined by quantitative whole body autoradiography.

RESULTS

Single dose injections of tirilazad as an emulsion at doses ranging from 1.52 mg to 13.5 mg were non-irritating whereas the solution was irritating at a dose of 1.3 mg. The pharmacokinetic parameters were not statistically different between the emulsion and the solution (p > 0.2) at doses of 6 mg/kg/day and 20 mg/kg/day. However, at 65 mg/kg/day dose, a higher AUC(0,6) (4-fold) and lower V(ss), (18-fold) and CL(5-fold) were observed for the lipid emulsion as compared to the solution (p < 0.05). Tissue distribution showed higher initial concentrations (two fold or more) in most tissues for the solution. These values, however, equilibrated by 4 h and AUC(0,4) differences were less than two fold in most tissues.

CONCLUSIONS

Formulating tirilazad in the lipid emulsion significantly reduces the venous irritation without changing the pharmacokinetics and tissue distribution at low doses.

Relationship between serum concentrations, hemodynamic effects, and cardiovascular lesions in dogs treated with minoxidil

The threshold hemodynamic changes associated with the cardiovascular (CV) toxicity of minoxidil (MNX) in the dog, characterized by subendocardial necrosis, right atrial hemorrhagic lesions, and coronary vascular medial hemorrhage and necrosis, have not been defined. To determine the relationship between serum concentration, hemodynamic effects [heart rate (HR) and mean arterial pressure (MAP)] and CV toxicity, groups of female Beagle dogs were treated with a continuous iv infusion of dextrose (control) or 0.05, 0.14, 0.43, 1.44, or 4.32 mg/kg/day of MNX for 3 days. Serum concentration of free MNX increased in a dose-related manner and reached steady state within 4 hr after the initiation of infusion. There was a time-dependent, apparently dose-related increase in HR at all doses. MAP was decreased at > or = 0.14 mg/kg/day in a time- and dose-related manner. The doses or steady-state serum concentrations of MNX that showed no significant hemodynamic effects and CV toxicity were approximately 0.05 mg/kg or 3.0 +/- 0.6 ng/ml and 0.14 mg/kg or 7.3 +/- 2.0 ng/ ml, respectively. CV toxicity occurred at a serum concentration of 16.6 +/- 1.9 ng/ml where HR was increased by 65 +/- 11 beats/min and MAP was decreased by 34 +/- 2 mm Hg. A serum concentration of 7.3 +/- 2 ng/ml of MNX that increased HR by 47 +/- 14 beats/min and decreased MAP by 17 +/- 8 mm Hg was not associated with CV toxicity. This study suggests that the threshold hemodynamic effects associated with the CV toxicity of MNX in the dog are a function of an increase in HR by at least 55 beats/min and a decrease in MAP by at least 30 mm Hg. In conclusion, the safety margin of drugs like MNX, where the mechanisms of toxicity are known to be related to their pharmacologic effects, should be based on the ratio of the pharmacokinetically and metabolically adjusted dose/serum concentration of the drug that evokes comparable pharmacologic effects in the animal model and humans rather than on the ratio of the nontoxic dose/serum concentration in animals to the efficacious dose in humans.

Heritable nephroblastoma (Wilms' tumor) in the Upjohn Sprague Dawley rat

There has been no satisfactory animal model for hereditary nephroblastoma (NB; Wilms' tumor), the most common malignant renal tumor in children. A rat subline with a high incidence of NB, designated Upj:TUC(SD)spf.nb, was established from tumor-bearing Upjohn Sprague Dawley (Upj:TUC[SD]spf) stock rats by inbreeding. Incidence of NB was increased from 2.2% (1/46) to 33.0% (4/12) in males and from 10.0% (5/50) to 58.3% (7/12) in females through four successive generations of sister-to-brother mating. The overall incidence of NB-6.5% (14/214) in males and 21.6% (49/227) in females-was over 150-fold higher than the incidence of the tumor in other strains of rats. Of the 63 tumors, 47 (75%) developed at 4 to 12 months of age, and 32 (51%) developed at 7 to 9 months of age. Twelve of the tumors (19%) were bilateral, and in four rats (6.3%) the tumor was triphasic Wilms' tumor. Five of the tumors invaded the adjoining abdominal organs; none metastasized to distant organs. The tumor was consistently transplanted to syngeneic rats through 10 successive passages. The transplanted tumor, as the primary tumor, was composed of blastemoepithelial cells. The Upj:TUC(SD) spf.nb rat with a high incidence of NB, established at the Upjohn Company and donated to the Cleveland Clinic, may be an appropriate animal model for NB (Wilms' tumor) in children.

The pharmacologic basis of the cardiovascular toxicity of minoxidil in the dog

Minoxidil (MNX), like several other vasoactive drugs, causes cardiovascular toxicity in dogs by undetermined mechanisms. We studied the mechanism of cardiovascular toxicity of MNX [an adenosine triphosphate (ATP)-sensitive potassium channel opener] by blocking its pharmacologic effects with glyburide (an ATP-sensitive potassium channel blocker) in groups of 5 female beagle dogs treated orally for 2 days with 1.0 mg/kg/day of MNX alone or with glyburide given in 5 or 6 divided doses of 300 mg/kg at 2 hr before and after each dose of MNX and at 3-6-hr intervals thereafter. A third group of 5 dogs received glyburide alone in the same dosing regimen as in the combination group. Mean arterial pressure (MAP), heart rate (HR), the pharmacokinetics of MNX, and gross and microscopic changes in the heart were evaluated. Glyburide did not influence the pharmacokinetics of MNX but prevented or markedly attenuated the MNX-induced cardiovascular lesions (right atrial hemorrhagic lesions, subendocardial necrosis, or coronary arteritis) occurred in dogs whose MNX-induced hemodynamic effects were effectively blocked by glyburide. In conclusion, the cardiovascular toxicity of MNX in dogs is not caused by a direct toxic effect of MNX on the heart but apparently is related to the exaggerated pharmacologic/profound hemodynamic effects it elicits in the dog.

Drug-induced hepatic microgranulomatosis in cynomolgus monkeys

This report discusses a unique drug-induced hepatotoxicity in cynomolgus monkeys treated orally with a novel potassium sparing experimental diuretic, [2,6-bis(4-chlorophenyl)-4-pyridinecarboxylic acid]. Groups of 6 adult male and female monkeys were treated orally with vehicle diluent, modified vehicle #122 or a suspension of the drug at 5.0, 12.5, or 32.0 mg/kg/day for 2 weeks. Another group of 5 monkeys were treated orally with 25.0 mg/kg/day of the drug for 2 weeks. Disposition of the drugs was evaluated in 2 monkeys in the later group that received 27.4 mg/kg of radiolabelled drug on the 1st and last day of dosing. Hepatic toxicity was characterized biochemically, light and electron microscopically, histochemically, immunocytochemically, and toxico-kinetically. Conjugated serum bilirubin, alanine transaminase, and aspartate transaminase levels were increased in monkeys treated with over 12.5 mg/kg/day of the diuretic. The periacinar hepatic plates of monkeys treated with 25.0 or 32.0 mg/kg/day were distorted by accumulation of PAS and oil red-O positive multinucleated Kupffer cells. The cytosol of these cells was expanded by phagolysosomes containing granular materials of varying electron densities. Granular electron dense materials were also in endothelial cells and bile canaliculi. Fatty change, cholestasis, and rare piecemeal hepatic necrosis were minimal. The drug was primarily excreted through urine. Plasma concentration and half life of the drug were increased with multiple dosing. The highest concentration of unexcreted parent drug was in the liver. Drug-induced noninflammatory hepatic microgranulomatosis, apparently caused by sequestered drug-lipid/mucopolysaccharide complex in the phagocytic cells of the liver, can occur in any species, including humans, if orally administered xenobiotics are presented to the liver in particulate form.

Pathologic changes in the accessory sex glands of rats treated with a sympatholytic hypotensive agent (losulazine)

Groups of 25 male Sprague-Dawley rats were treated by gastric intubation with either vehicle control (modified methylcellulose) or a suspension of losulazine at 4, 8, 16, or 32 mg/kg/day for 1 yr. Ten rats/group were killed after 6 months of treatment. Reversibility of drug-induced changes was evaluated in 8 rats/group treated for 6 months and held without treatment for 5 months. Daily clinical signs and weekly body weight changes were monitored. Seminal vesicle/coagulating glands were weighed in rats treated for 6 months. Gross and microscopic evaluation of the accessory sex glands (ampullary glands, prostate, seminal vesicles and coagulating glands) was conducted in all rats killed at 6 months, after the recovery period, and in rats that survived through the one-yr treatment period. Ptosis, somnolence, and fecal softening were detected in all groups treated with losulazine. There was a nonreversible body weight gain retardation in groups treated with 8 to 32 mg/kg/day of losulazine for 6 months or 1 yr. Absolute and relative weights of the seminal vesicle/coagulating glands of treated rats were not significantly different from those of control rats. The ventral prostate in a few rats in all treated groups had yellow to tan granular foci. Treatment, but not dose-related sperm granulomas or glandular impaction with inspissated secretion (formation of corpora amylacia) in the ampullary glands, enhanced cellular exudation into the acini of the ventral prostate, and impaction of the seminal vesicles with altered granular to globular secretion were found in rats treated with losulazine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis of cardiovascular alterations in dogs treated with minoxidil

Minoxidil and other potent vasodilators cause coronary arterial injury, right atrial hemorrhagic lesions, and subendocardial necrosis in dogs. This paper discusses the pathogenesis of coronary arterial and right atrial lesions associated with minoxidil in the dog. Acute coronary vascular injury characterized by segmental medial hemorrhage and necrosis and perivascular inflammation occurred only during the first few days of treatment, after which tolerance to further acute injury developed. At 30 d or more of treatment, coronary vascular injury was characterized by perivascular fibrosis rarely attended by medial distortion or hyperplasia and subintimal thickening, changes consistent with responses to previous injury. Right atrial hemorrhagic lesions, unlike coronary vascular injury, often became progressively more extensive with continued treatment. At 3 d, atrial hemorrhage and inflammation were confined to the subepicardium of the right atrium, evidently around affected subepicardial branches of the right coronary artery. At 30 d, fibrovascular proliferative right atrial lesions (granulation tissue with evidence of continual hemorrhage) extended from the epicardium to the myocardium, with eventual replacement of the atrial wall by mature connective tissue at 1 yr of treatment. Minoxidil-induced cardiovascular lesions were not prevented by treatment with a beta-blocker (propranolol), or an alpha-blocker (dibenzylene), or by sympathetic neural activity suppression (surgical sympathectomy or constant carotid sinus nerve stimulation), suggesting that the sympathetic response to the pharmacologic activity of minoxidil was not responsible for the induction of the cardiovascular lesions. Minoxidil-related vascular lesions were confined to the most pharmacologically responsive segment of the arterial system, the coronary arteries, suggesting that medial injury may have been associated with tensile changes in the arterial wall.

Cardiovascular complications of chronic catheterization of the jugular vein in the dog

Cardiovascular changes associated with indwelling catheters were evaluated in 51 adult beagle dogs catheterized for 4 to 9 weeks. Pathologic changes consistent with traumatic injury were in the vena cava and endocardium of the right atrium of 88% of cannulated dogs. Lesions were characterized by surface denudation and diffuse intimal thickening due to myointimal hyperplasia and deposition of extracellular matrix. Affected intima was lined by hyperplastic, poorly differentiated endothelial cells and contained round to oval cells with characteristics of smooth muscle cells. After 9 weeks, thickened intima was vascularized and composed of spindle-shaped cells and fibrillar stroma. Intimal sclerosis and localized proliferative papillary projections in the vena cava cranial to areas of myointimal hyperplasia occurred infrequently. Traumatic lesions, regardless of location or severity, did not extend below the internal elastic membrane. Inflammatory cellular responses, when present, were minimal. The location, distribution, and morphogenesis of catheter-related cardiovascular lesions distinguishes them from those induced by chemical toxicity or pharmacotoxicity.

Effects of losulazine on rat reproduction and development

Losulazine, a hypotensive agent, was given orally by gastric intubation to Sprague-Dawley rats in doses of 0, 2, 4, or 8 mg/kg/day in a study of fertility and general reproductive performance. Eighteen males per group were treated for 67 days before cohabitation, then daily until killed. Thirty-six females per group were treated for only 14 days because estrous cycles had been disrupted. Females remained untreated for 7 days before cohabitation; treatment was resumed after insemination was confirmed or when the cohabitation period ended. Males were cohabited on a 1:2 basis with females from the same treatment group for up to 14 days, then for 14 days with untreated females. The conception rate of both treated and untreated females was statistically significantly decreased as the dose increased. Mean body weights were statistically significantly greater and mean gestation periods were statistically significantly longer in losulazine-treated females than in females of the vehicle control group. Throughout the preweaning period mean body weights were significantly less in offspring from treated dams than in offspring of dams in the vehicle control group. This adverse effect on weight gain continued in male offspring until at least postpartum day 79. Functional development was significantly delayed in the offspring of losulazine-treated dams tested for pinna detachment, auditory startle, negative geotaxis, eye opening, and learning (swimming M-maze). Delays in development were generally greater in offspring of dams and sires treated with higher doses of losulazine. Fertility of male offspring from dams and sires treated with losulazine at 4 and 8 mg/kg/day was also affected adversely.

Reproductive and developmental effects on rats after prenatal, postnatal, or pre- and postnatal exposure to the hypotensive agent losulazine

Losulazine was administered orally to 21 bred Sprague-Dawley rats per group at 0, 4, and 8 mg/kg/day by three dosing schedules: gestation day 15 until term (prenatal section); postnatal days 1 to 21 (postnatal section); and gestation day 15 until postnatal day 21 (pre- and postnatal section). Dams were allowed to deliver and the number of live and dead pups recorded. Each pup was sexed and weighed on days 0, 4, and 21. Also, pinna detachment and eye opening were monitored. Randomly selected offspring were allowed to mature and then cohabited for assessment of reproductive performance. Dam body weight gain during dosing was reduced in the high dose group of the pre- and postnatal section. Treated dams in the postnatal and pre- and postnatal sections had litters with reduced body weight, delayed development, and decreased survival. In the F1 mating portion of the postnatal and pre- and postnatal sections, F1 offspring from losulazine-treated dams had reduced body weights over the entire study. A dose-related decrease was found for both the percentage of F1 males that bred and the conception rate of bred F1 females. All F1 females entered estrus at least once, and those that conceived delivered normal litters. Neither microscopic examination of F1 male reproductive organs nor analyses of serum prolactin, luteinizing hormone (LH), and testosterone levels indicated the cause of impaired fertility. Thus, although prenatal exposure only did not result in adverse effects, postnatal exposure to losulazine via lactation affected offspring growth, development, and reproductive capacity.

Cardiovascular alterations in dogs treated with hydralazine

Groups of 5 male beagle dogs were treated orally with hydralazine tablets in gelatin capsules at a dose of 12 or 24 mg/kg twice a day (6 hours apart) for 2 consecutive days. Five male dogs treated with empty gelatin capsules served as untreated controls. Clinical findings and heart rate changes during treatment and terminal body weight, hematology, and blood chemistry changes were evaluated. The heart, liver, kidneys, spleen, and thymus of each animal were examined microscopically. Dogs in the 12 mg/kg group ate less than control group. Dogs treated with 24 mg/kg did not eat and vomited. Heart rates in both of the treated groups increased by 60% to 80% within 2 hours of treatment and remained high during the entire treatment period. Significant hematologic change was confined to a slight increase in platelet number of dogs treated with 24 mg/kg. Serum glucose was increased in the hydralazine treated dogs. Conjugated serum bilirubin was increased and serum potassium, chloride and phosphorus were decreased in the 24 mg/kg group. Blood urea nitrogen and serum chloride were slightly increased in dogs treated with 12 mg/kg. Treatment-related pathologic alterations were confined to the heart. Two dogs from each of the hydralazine groups experienced acute localized hemorrhage into the epicardium and subepicardium of the right atrium. The media of the muscular branches of the coronary arteries, especially the left coronary artery, was hemorrhagic in 3 dogs from the 24 mg/kg group. Medial necrosis, when seen, tended to be proportional to the severity of medial hemorrhages. There was no necrosis in the papillary muscles of the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of anestrus in rats treated with an antihypertensive agent, losulazine hydrochloride

The mechanism of anestrus in rats treated with losulazine, a peripheral sympatholytic antihypertensive agent, was investigated by determining its effect on hypothalamic catecholamines and serum sex hormones and by evaluating the influence of bromocriptine on the reproductive functions of rats treated with losulazine. Groups of six female Upjohn Sprague-Dawley rats were treated orally with 10 mg/kg/day of losulazine and/or 18.75 mg/kg/day of bromocriptine for 15 or 27 days. Six rats were treated with losulazine plus 6.25 mg/kg/day of bromocriptine for 16 days followed by losulazine alone for 11 days. Rats treated with losulazine only were depleted of hypothalamic catecholamines, were hyperprolactinemic, and had interrupted estrous cycles and attenuated vaginal mucosa. Treatment with bromocriptine, a dopamine receptor agonist, resulted in suppression of serum prolactin and normal estrous cycles. Rats reverted back to hyperprolactinemia and anestrus shortly after bromocriptine withdrawal. These results suggest that hyperprolactinemia mediated through hypothalamic dopamine depletion is the mechanism of anestrus in rats treated with losulazine.

Horizontal transmission of pseudorabies virus in cattle

Pseudorabies virus (PRV) was not transmitted horizontally from 3 PRV-infected calves to 2 contact control calves during 4 days of comingling in experiment 1. Although these contact control calves developed clinical signs of pseudorabies when infected intranasally with PRV in experiment 2, they did not transmit PRV to a second pair of contact control calves. However, 1 of 2 pigs comingled with these 4 calves seroconverted. During both experiments, moderate amounts (10(2) to 10(5) TCID50) of PRV were present in the nasal secretions of the infected calves during the contact periods. All infected calves traumatized their nares or periorbital tissue. Infected calves developed a nonsuppurative meningoencephalitis mainly involving the brain stem. Four of the 5 infected calves had nonsuppurative ganglioneuritis and acute lymphoid necrosis of germinal centers. Virus could not be recovered from nasal and tonsillar swab samples from contact-control calves and pigs.

Induced latency in pseudorabies vaccinated pigs

A latent pseudorabies virus infection was established in pigs despite vaccination with a modified-live pseudorabies virus vaccine. Although the vaccinated pigs developed high concentrations of antibody, virus was recovered from the tonsils and lungs of pigs treated with dexamethasone three months after inoculation with virulent virus. These results may explain why vaccination programs have failed to eliminate the persistence and spread of virulent pseudorabies virus in infected herds.

A solitary plasmacytoma in a dog with progression to a disseminated myeloma

Solitary plasmacytomas are rare occurrences in dogs, consequently their potential for malignancy is undetermined. A solitary plasmacytoma was removed from the perianal region of a dog. The dog was clinically normal at that time, but was killed one year later as a result of hind limb stiffness and uremia. At the postmortem examination a disseminated myeloma was found, involving the vertebral column, liver, spleen, bone marrow and visceral lymph nodes.

Degenerative myelopathy in a cat

Degenerative myelopathy was diagnosed in a 6-year-old cat that had progressive ataxia, posterior paresis, and loss of conscious proprioception over a period of 8 months. Corticosteroid therapy did not alleviate clinical signs, and the cat was euthanatized. Microscopic examination of the spinal cord revealed diffuse degeneration of myelin attended by marked astrocytosis. The degenerative changes were most marked in the thoracolumbar segment. The cause of the degenerative lesions was not apparent.

Thymic dependence of immunity to Eimeria falciformis var. pragensis in mice

Athymic (nude) mice, their normal littermates, and Swiss white mice were infected with 750 oocysts of Eimeria falciformis var. pragensis and reinfected twice with 20,000 oocysts, 20 and 40 days after the primary infection. The prepatent and patent periods of the primary infection were similar in each group of mice; however, the athymic mice discharged more oocysts. The normal littermates and Swiss white mice developed immunity to the parasite after the first or second infection, whereas the athymic mice never developed immunity. Infection with E. falciformis var. pragensis induced the production of antibodies in the normal littermates and Swiss white mice, whereas antibody production was impaired in athymic mice. Passive administration of immune serum did not protect athymic mice from reinfection by the parasite. Immunity to the parasite was thymus dependent, and "effector" T-lymphocytes seemed to be required for protection.

Effects of acquired resistance on infection with Eimeria falciformis var. Pragensis in mice

Mice immunized with infections of 500, 5,000, or 20,000 oocysts of E. falciformis var. pragensis were reinfected with 20,000 and 100,000 oocysts at 20 and 38 days, respectively, after the initial infection. After the first challenge infection, none of the immunized mice showed clinical signs of coccidiosis; a few mice passed very low numbers of oocysts, and oocyst discharge seemed to correlate negatively with immunizing dose. None of the mice immunized twice passed oocysts after challenge. Mice immunized with three infections were completely immune to challenge for 4 months. The effect of the immune response on the life cycle of the coccidium was determined by histological examination of the intestines of immune and nonimmune mice infected with the parasite. In both the immune and nonimmune groups, sporozoites penetrated absorptive epithelial cells and migrated to crypt epithelial cells during the first 6 to 24 h postinfection. At 48 to 72 h postinfection, the sporozoites developed into mature first-generation schizonts in the nonimmune mice, whereas the developing first-generation schizonts degenerated within the crypt epithelial cells of the immune mice. In nonimmune mice, third-generation merozoites, inoculated intracecally, developed into mature fourth-generation schizonts, whereas in immune mice the developing fourth-generation schizonts degenerated before maturing. The possibility that a cellmediated immune mechanism is responsible for the arrest in schizogony is discussed.

The pathological changes caused by Eimeria falciformis var pragensis in mice

Groups of Swiss white mice weighing 25-28 grams were infected orally with 500, 2,000, 5,000 or 20,000 oocysts of Eimeria falciformis var pragensis. Depression, anorexia, weight loss, diarrhea or dysentery, and dehydration were most pronounced at eight to ten days postinfection. The highest mortality, 31%, occurred in mice infected with 20,000 oocysts. None of the mice infected with 500 oocysts died. The pathological findings were equally severe in mice infected with 5,000 and 20,000 oocysts. The enteric lesions, most pronounced at eight to ten days postinfection, were restricted mainly to the large intestine and consisted initially of both cryptal and absorptive epithelial cell destruction and submucosal edema. These changes were followed in 12 to 24 hours by a transient influx of neutrophils into the lamina propria followed by mononuclear cell infiltration which lasted for five to ten days. As the infective dose decreased, the inflammatory response occurred later and was less extensive. When seen, hemorrhage occurred seven to 11 days postinfection. In 50% of the mice infected with 5,000 and 20,000 oocysts, varying degrees of a nonselective mucosal necrosis were seen at eight to 12 days postinfection. In mice infected with 500 oocysts, mucosal destruction was restricted to the epithelium. Neutrophils predominated when necrosis was extensive, otherwise, mononuclear cells were the main inflammatory cells. Two to three days following necrosis, crypt hyperplasia was marked and mucosal integrity was restored. Ulcers, some of which extended into the submucosa, healed by days 14 to 20. Localized granulomatous colitis, induced by trapped oocysts within the lamina propria, was seen until the experiment was terminated at 25 days postinfection. Infection was followed by lymphoid hyperplasia in the lymph nodes and the spleen.

The life cycle of Eimeria falciformis var. pragensis (Sporozoa: Coccidia) in the mouse, Mus musculus

The life cycle of Eimeria falciformis var. pragensis, established from a single oocyst, is described in experimentally infected mice (Mus musculus). The coccidium had a prepatent period of 7 days and a patent period of 10--16 days. Oocysts were spherical to ellipsoidal in shape and measured 21.2 x 18.3 micron. Sporulation time was 3 to 3.5 days. Sporocysts measured 12.2 x 7.2 micron and contained a circular to avoid granular sporocyst residuum measuring 5.5 X 5.0 micron. One, 2 or 3 circular to rectangular polar granules were observed within each sporulated oocyst. The endogenous stages developed primarily in the cecum and colon and only occasionally in the lower ileum. Four generations of schizonts were found. Mature 1st-generation schizonts, first observed 48 hr postinfection (PI), measured 17.8 x 12.3 micron and had 12 merozoites that measured 13.3 x 2.0 micron. Mature 2nd-generation schizonts appeared 78 hr PI. They measured 10.2 x 9.3 micron and had 8 merozoites measuring 5.0 x 1.6 micron. Mature 3rd-generation schizonts appeared first at 114 hr PI and measured 17.5 x 10.2 micron and had 10 merozoites that measured 12.4 x 1.8 micron. Mature 4th-generation schizonts appeared first at 144 hr PI. They measured 18.2 x 15.3 micron and had 18 merozoites. The merozoites of the 4th-generation schizont were 4.5 x 1.2 micron. Mature macrogamonts and microgamonts developed simultaneously appearing at 156 hr PI. Macrogamonts measured 16 x 14.5 micron and microgamonts were 18.2 x 15.3 micron. In experimentally infected rats (Rattus norvegicus), development of E. falciformis var. pragensis progressed only as far as mature 1st-generation schizonts.

Atypical glycogen deposits in a plasmacytoma: an ultrastructural study

A solitary, benign plasmacytoma, arising from the gum of the lower jaw of a dog, was studied by light and electron microscopy. Some of the tumour cell nuclei showed the characteristic clockface or cartwheel pattern of heterochromatin distribution similar to that found in normal plasma cells. Like normal plasma cells the tumour cells were endowed with rough endoplasmic reticulum but this was invariably dilated or visiculated. Glycogen deposits were found within mitochondria and within the dilated and vesiculated rough endoplasmic reticulum. The idea that these deposits were derived secondarily from glycogen deposits in the cytoplasm seems untenable because no glycogen particles were found in the cytoplasmic matrix. It would therefore appear that most, perhaps all, stages of glycogen synthesis occurred within the mitochondria and rough endoplasmic reticulum of some of these tumour cells.

Duration of Brucella ovis infection in ewes

Twenty Romney Marsh ewes, some 5 to 40 days pregnant, were inoculated with a strain of Brucella ovis onto the scarified mucous membrane of the vagina. Establish of infection was ascertained by recovery of the organisms from blood; supramammary and inguinal lymph nodes; the vagina, after initial disappearance of the organism from this organ; and the complement fixation tests. The bacteremia was transitory or intermittent, but organisms could not be recovered from blood, or any other tissue examined, after 98 days of infection. Abortions or placentitis were not observed. It is recommended that in countries where sheep breeding is aseasonal a sexual rest of infected ewes for at least 4 months must be part of any program for the control and eradication of ram epididymitis.