Fatal herpesvirus encephalitis in a reticulated giraffe (Giraffa camelopardalis reticulata).

Fatal meningoencephalitis caused by equine herpesvirus-1 (EHV-1) was diagnosed in a reticulated giraffe (Giraffa camelopardalis reticulate). The giraffe died following a history of stumbling, incoordination, and abdominal pain. Gross examination of the brain revealed asymmetric edema and red-brown discoloration, predominantly within the telencephalon. Microscopically, there was perivascular lymphohistiocytic cuffing, multifocal gliosis, and neuronal necrosis in the cerebrum. Necrotic neurons contained acidophilic intranuclear inclusions. EHV-1 was isolated from the brain of the giraffe, and polymerase chain reaction was positive on sections of the brain. Immunohistochemistry using an EHV-1-specific antibody identified positive staining in neurons, astrocytes, and endothelial cells. The giraffe had been housed with a group of zebras that were serologically positive for EHV-1 and suspected as the source of infection. This raises concerns for cross-species transmission of EHV-1 when housing equids together with other species in zoologic collections.

Azithromycin versus ceftriaxone for the treatment of uncomplicated typhoid fever in children.

A total of 108 children aged 4-17 years were randomized to receive 7 days of azithromycin (10 mg/kg/day; maximum, 500 mg/day) or ceftriaxone (75 mg/kg/day; maximum, 2.5 g/day), to assess the efficacy of the agents for the treatment of uncomplicated typhoid fever. Salmonella typhi was isolated from the initial cultures of blood samples from 64 patients. A total of 31 (91%) of the 34 patients treated with azithromycin and 29 (97%) of the 30 patients treated with ceftriaxone were cured (P>.05). All 64 isolates were susceptible to azithromycin and ceftriaxone. Of the patients treated with ceftriaxone, 4 subsequently had relapse of their infection. No serious side effects occurred in any study subject. Oral azithromycin administered once daily appears to be effective for the treatment of uncomplicated typhoid fever in children. If these results are confirmed, the agent could be a convenient alternative for the treatment of typhoid fever, especially in individuals in developing countries where medical resources are scarce.

Unilateral cerebral necrosis resembling feline ischemic encephalopathy in an African lion (Panthera leo).

In November 1996, a 14-yr-old captive male African lion (Panthera leo) had sudden onset of left-sided hemiparesis and mydriasis of the left eye. After 24 hr of supportive care, the lion showed no improvement and was euthanized. At necropsy, the right cerebral hemisphere was diffusely and irregularly swollen and malacic. Histopathology revealed extensive acute necrosis and edema of the portion of the right cerebral hemisphere that received blood from the right middle cerebral artery. Gross and histopathologic cerebral findings resembled those of feline ischemic encephalopathy.

Fatal hepatic necrosis caused by disseminated type 5 adenovirus infection in a renal transplant recipient.

This is an unusual case of fatal hepatic necrosis caused by disseminated type 5 adenovirus in a renal transplant recipient. This adult patient may have been colonized at the time of transplantation with a kidney from a pediatric donor. The adenovirus became invasive when the host's cellular immune system was suppressed by high doses of corticosteroids given to reverse acute allograft rejection.

5-ethyl-5-phenylhydantoin N-glucuronide, the major urinary metabolite of 5-ethyl-5-phenylhydantoin (Nirvanol) in the dog.

A water-soluble metabolite, isolated from the urine of dogs given (S)-5-ethyl-5-phenylhydantoin [(S)-EPH], has been identified as 1-deoxy-1-[(5S)-5-ethyl-5-phenylhydantoin-3-yl] beta-D-glucopyranuronate [(S)-EPH N-glucuronide]. EPH N-glucuronide did not release the aglycone upon acid or beta-glucuronidase treatment, but incubation in alkaline solution (pH 12-13) readily formed 2-ethyl-2-phenylhydantoic acid (EPHA). The EPHA so formed could be quantitatively cyclized to EPH. With the knowledge of the conversion efficiency of EPH N-glucuronide to EPHA, a quantitative GLC assay for the metabolite was developed. EPH N-glucuronide was found to be the major urinary metabolite after administration to dogs of either (R)-, (S)-, or (RS)-EPH.

Stereochemical aspects of the metabolism of 5-ethyl-5-phenylhydantoin (Nirvanol) in the dog.

Enantiomers of 5-ethyl-5-phenylhydantoin (EPH) were administered to dogs, and urinary metabolites were quantitated. After administration of (R)-EPH, the urinary products included unchanged drug, 5-ethyl-5-(4-hydroxyphenyl)hydantoin (p-EHPH), 5-ethyl-5-(3-hydroxyphenyl)hydantoin (m-EHPH), and an N-glucuronide of EPH. Administration of (S)-EPH gave urinary products consisting of unchanged drug, p-EHPH, m-EHPH, an N-glucuronide of EPH, and a dihydrodiol metabolite, which has been isolated and identified as (5 S)-5-[(3R,4R)-3,4-dihydroxy-1,5-cyclohexadien-1-yl]-5-ethylhydantoin. The levorotatory isomers of p- and m-EHPH have been assigned the (R)-configuration. An unidentified metabolite of EPH has been detected through its reactivity under basic conditions to yield 2-ethyl-2-phenylhydantoic acid, which can be cyclized with acid to EPH. Quantitative studies of the disposition of single oral doses of (R)-, (S)-, and (RS)-EPH by these metabolic routes suggest that the metabolism of one enantiomer is unaffected by the presence of the other enantiomer. Stereoselectivities of metabolic pathways are discussed in relation to stereoselectivities observed for phenytoin metabolism in the dog.

Absolute configurations of the dihydrodiol metabolites of 5,5-diphenylhydantoin (phenytoin) from rat, dog, and human urine.

Dihydrodiol metabolites (DHD) of phenytoin (PHT) have been extracted from the urine of rats and dogs, and from that of a patient on chronic PHT therapy. The crystalline rat DHD was dehydrated to give a mixture of (S)-5-(4-hydroxyphenyl)-5-phenylhydantoin and (S)-5-(3-hydroxyphenyl)-5-phenylhydantoin. The absolute configuration of C5 of the hydantoin ring of the DHD can accordingly be assigned as (S). Circular dichroism studies allowed further assignment of absolute configuration to the crystalline rat DHD, the metabolite being identified as (5S)-5-[(3R,4R)-3,4-dihydroxy-1,5-cyclohexadien-1-yl]-5-phenylhydantoin, (5S)-DHD. The human DHD metabolite was identical with the (5S)-DHD. The DHD from dog urine was found to be a mixture of diastereoisomers; the major component was identified as (5R)-5-[(3R,4R)-3,4-dihydroxy-1,5-cyclohexadien-1-yl]-5-phenylhydantoin, (5R)-DHD, and the minor diastereoisomer was identified as (5S)-DHD. The ratio (5R)-DHD/(5S)-DHD was approximately 2. A comparison of the absolute configurations of phenolic metabolites of PHT and of the DHD's offered a basis for speculation as to stereochemical aspects of PHT metabolism in the rat, dog, and man.

Determination of 5-(3,4-Dihydroxy-1,5-cyclohexadien-1-yl)-5-phenylhydantoin (Dihydrodiol) and quantitative studies of phenytoin metabolism in man.

A routine gas chromatographic assay for urinary 5-(4-hydroxyphenyl)-5-phenylhydantoin (p-HPPH), the major metabolite of phenytoin (PHT) in man, was adapted to allow quantitation of 5-(3,4-dihydroxy-1,5-cyclohexadien-1-yl)-5-phenylhydantoin (Dihydrodiol, DHD) is based on the observation that acid-catalyzed dehydration of DHD quantitatively yields a mixture of p-HPPH and m-HPPH in a reproducible molar ratio of 56:44p-HPPH: m-HPPH and on the assumption that all m-HPPH found in urine after heating with acid has been derived from DHD. The urinary DHD content was verified by a "specific" method in which urine was incubated with beta-glucuronidase and the released phenolic metabolites completely removed by extraction. Subsequent acid-catalyzed dehydration of the remaining DHD yielded p-HPPH and m-HPPH, from the sum of which the original DHD concentration in urine could be calculated. In all of the urine samples from PHT patients examined to date, there was close agreement between the DHD values obtained by the "specific" method and those calculated from m-HPPH, in the simple acid-hydrolysis method. It can be inferred that much the greater part (greater than 90%) of m-HPPH found in human urine after acid treatment has been derived from DHD. All samples of urine after acid treatment has been derived from DHD. All samples of urine from PHT patients examined have shown detectable quantities of DHD. The methods described here may be useful in a survey of PHT patients to reveal unusual patterns of PHT metabolism and to permit recognition of possible associations between such unusual patterns and the occurrence of adverse reactions.

Absolute configuration of (+)-5-(o-hydroxyphenyl)-5-phenylhydantoin, the major metabolite of 5,5-diphenylhydantoin in the dog.

5-(3-Hydroxyphenyl)-5-phenylhydantoin (m-HPPH) has been resolved by crystallization of the brucine salts. The (+) enantiomer has been converted to (-)-5-cyclohexyl-5-phenylhydantoin, a compound previously demonstrated to have the R configuration. The R configuration can accordingly be assigned to (+)-m-HPPH, the principal metabolite of 5,5-diphenylhydantoin (phenytoin) in the dog.

Hydroxylation of 5,5-diphenylhydantoin (phenytoin) by dog liver microsomes.

Chang and Glazko in 1972 had reported failure to demonstrate any production from 5-5-diphenylhydantoin (phenytoin, DPH) by dog liver microsomes of either 5-(m-hydroxyphenyl-5-phenylhydantoin (m-HPPH) or 5-(P-hydroxyphenyl-5-phenylhydantoin (p-HPPH), metabolites of DPH produced by the dog in vivo. We have incubated DPH with 9,000 X g supermatants of dog liver homogenates and with suspensions of separated microsomes with added NADPH generating system, Mg(2+), and nicotinamide and have demonstrated the production of both m-HPPH and p-HPPH. Both metabolities were detected by thin-layer chromatography of extracts of the incubation mixtures. Detection and roughly quantitative measurement of m-HPPH were also accomplished with gas chromatography.

Studies of the metabolism of 5,5-diphenylhydantoin relating principally to the stereoselectivity of the hydroxylation reactions in man and the dog.

The hydroxylated metabolites of 5,5-diphenylhydantoin (DPH) in dog and human urine, after release by beta-glucuronidase, have been isolated and purified by procedures entailing only solvent partitioning without crystallization or any other procedure that could change the proportions of optical isomers. Dogs produced both the meta- and para-5-hydroxyphenyl-5-phenylhydantoins (m-HPPH and p-HPPH) from DPH, the former in approximately 6 times the amount of the latter. The m-HPPH from dog urine was dextrorotatory and had the properties of a pure optical isomer. The p-HPPH from dog urine was a mixture of optical isomers with approximately a 2:1 preponderance of the levorotatory isomer. When dog urine was heated with acid rather than treated with beta-glucuronidase, the isolated p-HPPH contained a small preponderance of the dextrorotatory isomer, probably owing to production of d-p-HPPH from the dihydrodiol metabolite. No o-HPPH was found in dog urine. When racemic p-HPPH and m-HPPH were administered to dogs, there was little if any preponderance of either optical isomer in the materials isolated from urine. Enzymatically released p-HPPH isolated from urine of human patients receiving DPH was a mixture of optical isomers with approximarely a 10:1 preponderance of the levorotatory isomer. Crystallization of this material readily yields pure l-p-HPPH. Human urine contained only very small amounts of m-HPPH, which was detectable by gas chromatography but insufficient in amount to permit isolation. Hypotheses are discussed that could account for the differences in the metabolism of DPH in man and dog. Small amounts of 2,2-diphenylhydantoic acid were found in urine of dogs but not of human patients receiving DPH.

Rabbit muscle triosephosphate isomerase: activity and inactivation by sulfhydryl reagents as affected by enzyme concentration.

Progressive increase of enzymatic activity with time occurs after dilution of a crystalline suspension of rabbit muscle TIM. The concentration of p-MB required to inhibit the enzyme is higher the greater the concentration of enzyme. With the lowest concentrations of mercurial that are ultimately inhibitory to the enzyme in dilute solution, there is a lag period before inactivation begins. With higher concentrations of mercurial, some degree of inactivation occurs almost immediately, and enzymatic activity thereafter decreases at a slower rate. With an enzyme concentration of 32 ng/ml, a low concentration of p-MB decreases Vmax without change KM. A higher concentration of mercurial also increases KM. With an enzyme concentration of 1 mg/ml, iodoace begins to inactivate it only after a lag period. In enzyme solutions containing 8 ng/ml, inactivation by iodoacetate progresses without significant initial lag. Discrepancies between the present work and that of other authors can probably be accounted for by differences in the concentrations of enzyme used. It is suggested that the conformation of rabbit muscle TIM in solution is dependent on its concentration. In more dilute solutions the enzyme assumes a conformation in which it is catalytically more active and in which its sulfhydryl groups are more accessible to chemical attack.