Unpredictable mealtimes rather than social jetlag affects acquisition and retention of hippocampal dependent memory.

Some degree of circadian rhythm disruption is hard to avoid in today's society. Along, with many other deleterious effects, circadian rhythm disruption impairs memory. One way to study this is to expose rats to daylengths that are outside the range of entrainment. As a result, circadian processes and behaviors occur during phases of the light dark cycle in which they typically would not. Even brief exposures to these day lengths can impair hippocampal dependent memory. In a recent report, we created an unentrainable light dark cycle that was intended to resemble aspects of social jetlag. As predictable mealtime impacts circadian entrainment, in that report, we also created an unpredictable meal schedule with the idea that failure to entrain to a meal might afford a disadvantage in some instances. Both of these manipulations impaired retention in a spatial water plus-maze task. Using the same manipulations, the present study investigated their effects on acquisition in distributed and massed spatial water plus-maze paradigms. As in other reports with unentrainable daylengths, acquisition was not affected by our lighting manipulation. Conversely, in accordance with our past report, unpredictable mealtimes had a harmful effect on hippocampal dependent memory. Notably, impaired acquisition in the distributed version, and impaired retention in the massed version. In tandem, these data suggest that failure to consolidate or retrieve the information is the likely culprit. The unpredictable mealtime manipulation offers a unique opportunity to study the effects of circadian entrainment on memory.

Sustained stabilization of the resistive-wall mode by plasma rotation in the DIII-D tokamak.

Values of the normalized plasma pressure up to twice the free-boundary stability limit predicted by ideal magnetohydrodynamic (MHD) theory have been sustained in the DIII-D tokamak. Long-wavelength modes are stabilized by the resistive wall and rapid plasma toroidal rotation. High rotation speed is maintained by minimization of nonaxisymmetric magnetic fields, overcoming a long-standing impediment [E. J. Strait, Phys. Rev. Lett. 74, 2483 (1995)]]. The ideal-MHD pressure limit calculated with an ideal wall is observed as the operational limit to the normalized plasma pressure.

Pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in miniature donkeys.

OBJECTIVE: To describe the pharmacokinetics of phenylbutazone and oxyphenbutazone after IV administration in miniature donkeys. ANIMALS: 6 clinically normal miniature donkeys. PROCEDURE: Blood samples were collected before and 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300, 360, and 480 minutes after IV administration of phenylbutazone (4.4 mg/kg of body weight). Serum was analyzed in triplicate by use of high-performance liquid chromatography for determination of phenylbutazone and oxyphenbutazone concentrations. The serum concentration-time curve for each donkey was analyzed separately to estimate model-independent pharmacokinetic variables. RESULTS: Serum concentrations decreased rapidly after IV administration of phenylbutazone, and they reached undetectable concentrations within 4 hours. Values for mean residence time ranged from 0.5 to 3.0 hours (median, 1.1 hour), whereas total body clearance ranged from 4.2 to 7.5 ml/kg/min (mean, 5.8 ml/kg/min). Oxyphenbutazone appeared rapidly in the serum; time to peak concentration ranged from 13 to 41 minutes (mean, 26.4 minutes), and peak concentration in serum ranged from 2.8 to 4.0 mg/ml (mean, 3.5 microg/ml). CONCLUSION AND CLINICAL RELEVANCE: Clearance of phenylbutazone in miniature donkeys after injection of a single dose (4.4 mg/kg, IV) is rapid. Compared with horses, miniature donkeys may require more frequent administration of phenylbutazone to achieve therapeutic efficacy.

Techniques for evaluating selected reproductive disorders of stallions.

Numerous techniques may be used for evaluation of the different reproductive disorders of the stallion. Approaches may vary from real-time ultrasonography and biopsy for evaluating testicular tumors to use of special assays for evaluating sperm or plasma for presence of antisperm antibodies. This communication addresses techniques used to evaluate five relatively uncommon, but perplexing, disorders of breeding stallions: (1) seminal vesiculitis, (2) hemospermia associated with idiopathic urethral defects, (3) acrosomal dysfunction, (4) abnormal spermatozoal chromatin, and (5) azoospermia.

Paranasal sinus surgery through a frontonasal flap in sedated, standing horses.

OBJECTIVE: To report experience with paranasal sinus surgery through a frontonasal flap in sedated, standing horses. STUDY DESIGN: Treatment of 10 horses with naturally occurring paranasal sinus disease through a frontonasal bone flap created with the horses standing. ANIMALS: Ten adult horses. METHODS: After restraint and sedation, local anesthetic was injected subcutaneously along the proposed incision line over the conchofrontal sinus and was instilled into the sinuses through a small hole created in the frontal bone. A 3-sided, rectangular, cutaneous incision that extended through the periosteum was created over the frontal and nasal bones. The incision was extended into the conchofrontal sinus using a bone saw, and the base of the flap, on the midline of the face, was fractured. The sinuses were explored, and the horse was treated for the disease encountered. The flap was repositioned; subcutaneous tissue and skin were sutured separately. RESULTS: The horses had few signs of discomfort during creation of the bone flap and during disease treatment. Diseases encountered included inspissated exudate in the ventral conchal sinus (five horses), feed and exudate throughout the sinuses (one horse), occlusion of the nasomaxillary aperature (one horse), polyp (one horse), osteoma (one horse), and progressive ethmoidal hematoma (one horse). CONCLUSION: In selected cases, surgery of the paranasal sinuses can be performed safely on sedated and standing horses through a frontonasal bone flap. CLINICAL RELEVANCE: Performing surgery through a frontonasal bone flap with the horse standing and sedated, rather than anesthetized, eliminates risks and expense of general anesthesia.

Pharmacokinetics of flunixin meglumine in donkeys, mules, and horses.

OBJECTIVE: To compare serum disposition of flunixin meglumine after i.v. administration of a bolus to horses, donkeys, and mules. ANIMALS: 3 clinically normal horses, 5 clinically normal donkeys, and 5 clinically normal mules. PROCEDURE: Blood samples were collected at time zero (before) and 5, 10, 15, 30, and 45 minutes, and at 1, 1.25, 1.5, 1.75, 2, 2.5, 2.75, 3, 3.5, 4, 4.5, 5, 5.5, 6, and 8 hours after i.v. administration of a bolus of flunixin meglumine (1.1 mg/kg of body weight). Serum was analyzed in duplicate by the use of high-performance liquid chromatography for determination of flunixin meglumine concentrations. The serum concentration-time curve for each horse, donkey, and mule were analyzed separately to estimate noncompartmental pharmacokinetic variables RESULTS: Mean (+/-SD) area under the curve for donkeys (646 +/- 148 minute x microg/ml) was significantly less than for horses (976 +/- 168 minute x microg/ml) or for mules (860 +/- 343 minute x microg/ml). Mean residence time for donkeys (54.6 +/- 7 minutes) was significantly less than for horses (110 +/- 24 minutes) or for mules (93 +/- 30 minutes). Mean total body clearance for donkeys (1.78 +/- 0.5 ml/kg/h) was significantly different from that for horses (1.14 +/- 0.18 ml/kg/h) but not from that for mules (1.4 +/- 0.5 ml/kg/h). Significant differences were not found between horses and mules for any pharmacokinetic variable. CONCLUSION AND CLINICAL RELEVANCE: Significant differences exist with regard to serum disposition of flunixin meglumine in donkeys, compared with that for horses and mules. Consequently, flunixin meglumine dosing regimens used in horses may be inappropriate for use in donkeys.

Estrous cycle characteristics and response to estrus synchronization in mammoth asses (Equus asinus americanus).

Breeding records from a herd of mammoth asses (Equus asinus americanus) maintained on pasture in southeast Texas from 1990 to 1998 were reviewed. Jennies were pasture or hand mated, and estrus was either observed while the jennies were on pasture or when exposed to a jack after being penned. Eighty-one estrus periods and 43 diestrus intervals were recorded in 33 jennies over 4 seasons of the year (January-March, April-June, July-September, and October-December). Estrous cycle length and the duration of estrus were similar among seasons. Over all seasons, estrous cycle length was 23.3 +/- 2.6 d, duration of estrus was 5.9 +/- 2.1 d, and diestrus length was 17.4 +/- 2.6 d (mean +/- SD). During these same 9 yr, 58 injections of PGF2 alpha (5 mg, i.m.) were administered to 38 jennies without regard to stage of estrous cycle. Seventy-six percent (44/58) of the jennies showed signs of estrus after PGF2 alpha treatment, with an interval to estrus of 4.4 +/- 1.6 d and a duration of estrus of 5.6 +/- 1.7 d. Two estrus synchronization schemes were also assessed. Trial 1 was performed in October to November 1996, and Trial 2 was performed in February to March 1998. In Trial 1 (Group PE + PGF, n = 10), each jenny was injected intramuscularly once daily for 10 d with 150 mg progesterone and 10 mg estradiol-17 beta in sesame oil, and PGF2 alpha (10 mg) was injected intramuscularly on the last day of treatment. In Trial 2 (Group PGF-2X, n = 11), each jenny was injected intramuscularly twice, 16 d apart, with 10 mg PGF2 alpha. All Group PE + PGF jennies responded to treatment. One jenny in Group PGF-2X did not respond to either injection of PGF2 alpha, while 2 jennies responded to the first but not the second PGF2 alpha injection (8 of 11 jennies returned to estrus and ovulated after the second PGF2 alpha injection). Duration of estrus was 6.8 +/- 1.9 d for Group PE + PGF and 7.1 +/- 1.8 d for Group PGF-2X jennies. Interval to estrus and interval to ovulation following the last treatment were 9.0 +/- 0.9 d and 14.5 +/- 1.7 d, respectively, in Group PE + PGF jennies, and 4.5 +/- 0.9 d and 10.4 +/- 1.8 d, respectively, for Group PGF-2X jennies. In summary, estrous cycle characteristics of mammoth asses are similar to those reported for standard jennies, and estrus synchronization schemes used in horses are effective in mammoth asses.

Long-pulse narrow-linewidth dispersive solid-state dye-laser oscillator.

We report on narrow-linewidth long-pulse laser emission from a dispersive solid-state dye-laser oscillator. Output energy was ~0.4 mJ/pulse at laser linewidths of 650 MHz and pulse lengths of 105 ns FWHM. The solid-state gain medium utilized was Rhodamine 6G dye-doped 2-hydroxyethyl methacrylate:methyl methacrylate.

Tension band plating of an olecranon fracture in a bull.

A 1,018-kg (2,240-lb), 6-year-old bull was admitted for evaluation of a left forelimb lameness of 7 days' duration. Radiographic views of the proximal portion of the left forelimb revealed a type-III olecranon fracture that was minimally displaced. Conservative treatment, including stall confinement and administration of anti-inflammatory drugs, was attempted. Subsequent radiographic views, 27 days later, revealed displacement of the fracture with minimal callus formation. Open reduction and internal fixation was performed by placing a 4.5-mm, 10-hole broad dynamic-compression on the caudal surface of the olecranon. Good anatomic reduction was achieved, returning the bull to full weightbearing. Eight months following surgery the owners reported the bull was sound at a walk and able to breed cows.

Comparative pharmacokinetics of caffeine and three metabolites in clinically normal horses and donkeys.

OBJECTIVE: To determine whether clearance of capacity-limited drugs in horses differs from that in donkeys by comparing the serum disposition of caffeine and its metabolites, theophylline, theobromine, and paraxanthine after i.v. administration of caffeine to horses and donkeys. ANIMALS: 4 healthy horses and 5 healthy donkeys. PROCEDURE: Blood samples were collected from each animal at time 0 (before) and 5, 10, 15, 20, 30, and 45 minutes, and 1, 2, 3, 4, 6, 8, 12, 24, 30, 36, 48, 54, 60, 72, and 96 hours after IV administration of a bolus of caffeine. Serum was analyzed in triplicate by high-performance liquid chromatography to determine caffeine, theophylline, theobromine, and paraxanthine concentrations. The serum concentration-time curves for each animal were analyzed separately to estimate model-independent pharmacokinetic variables. RESULTS: Mean pharmacokinetic values for caffeine, theophylline, and paraxanthine did not differ significantly in horses, compared with donkeys. Mean peak serum concentration of theobromine was significantly higher in donkeys, compared with horses. CONCLUSION: Clearance of the capacity-limited drug caffeine does not appear to differ in horses, compared with donkeys. CLINICAL RELEVANCE: For some drugs that undergo hepatic metabolism, the dose and dose interval used for horses may be appropriate for use in donkeys.

Comparative pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in clinically normal horses and donkeys.

OBJECTIVE: To compare plasma disposition of phenylbutazone and its metabolite oxyphenbutazone after i.v. administration of phenylbutazone in horses and donkeys. ANIMALS: 4 clinically normal horses and 6 clinically normal donkeys. PROCEDURE: Blood samples were collected from each animal at time 0 (before) and 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300, 360, and 480 minutes after i.v. administration of a bolus dose of phenylbutazone. Serum was analyzed in triplicate by use of high-performance liquid chromatography for determination of phenylbutazone and oxyphenbutazone concentrations. The serum concentration-time curve for each horse and donkey was analyzed separately to estimate model-independent pharmacokinetic variables. RESULTS: Significant differences were found in several pharmacokinetic variables of phenylbutazone and oxyphenbutazone in horses, compared with donkeys. Mean total body clearance of phenylbutazone in horses was fivefold less than that in donkeys (29.3 and 170.3 ml/kg/h, respectively). Mean values for area under the curve and mean residence time in horses (118.3 micrograms/h/ml and 3.6 hours, respectively) were significantly greater than values in donkeys (28.3 micrograms/h/ml and 1.7 hours, respectively). Mean values for apparent volume of distribution at steady state were not significantly different between horses and donkeys. For oxyphenbutazone, mean time to peak concentration in donkeys was significantly less than that in horses (1.6 and 6.4 hours, respectively). CONCLUSION: Phenylbutazone clearance in donkeys was higher than that in horses, and appearance of the metabolite oxyphenbutazone in serum was more rapid in donkeys than in horses, indicating that hepatic metabolism of phenylbutazone is more rapid in donkeys than in horses. CLINICAL RELEVANCE: Because serum concentration of phenylbutazone after single i.v. bolus administration (4.4 mg/kg of body weight) decreases more rapidly in donkeys, compared with horses, phenylbutazone may require more frequent administration in donkeys to achieve therapeutic efficacy.

Pharmacokinetics and cardiopulmonary effects of guaifenesin in donkeys.

Five donkeys and three horses were given guaifenesin, intravenously, by gravity administration, until recumbency was produced. The time and dose required to produce recumbency, recovery time to sternal and standing were recorded. Blood samples were collected for guaifenesin assay at 10, 20, 30, 40, 50, 60 min, and 2, 3, 4 and 6 h after guaifenesin administration. Serum was analysed for guaifenesin using HPLC and pharmacokinetic values were calculated using a computer software package (RSTRIP). In donkeys, heart and respiratory rates and blood pressures were recorded before and at 5-min intervals during recumbency. Arterial blood samples were collected before and at 5 and 15 min intervals during recumbency for analysis of pH, CO2, and O2. ANOVA was used to evaluate dynamic data, while t-tests were used for kinetic values. Respiratory rate was decreased significantly during recumbency, but no other significant changes from baseline occurred. The mean (+/- SD) recumbency dose of guaifenesin was 131 mg/kg (27) for donkeys and 211 mg/kg (8) for horses. Recovery time to sternal (min) was 15 (SD, 11) for donkeys and 34 (SD, 1.4) for horses. Time to standing was 32 min for donkeys and 36 min for horses. Calculation of AUC (area under the concentration-time curve) microgram/mL) (dose-dependent variable) was 231 (SD, 33) for donkeys and 688 (SD, 110) for horses. The clearance (CL) (mL/h.kg) was 546 (SD, 73) for donkeys, which was significantly different from 313 (SD, 62) for horses. Mean residence time (MRT) (h) was 1.2 (SD, 0.1) for donkeys and 2.6 (SD, 0.5) for horses. Volume of distribution Vd(area) (mL/kg) was 678 (SD, 92) for donkeys and 794 (SD, 25) for horses. At the rate of administration used in this study, donkeys required less guaifenesin than horses to produce recumbency, but cleared it more rapidly.

Surgical repair of traumatically induced collapsing trachea in an ostrich.

A region of tracheal collapse was identified by endoscopy after surgical repair of a traumatic injury to the neck in an ostrich. During periods of excitation, the ostrich would become dyspneic and collapse. A tracheal split-ring prosthesis was placed surgically to support the collapsing trachea. This technique, which is frequently used in dogs, is applicable for use in birds with collapsing trachea.

Medical management of right dorsal colitis in 5 horses: a retrospective study (1987-1993).

Right dorsal colitis in horses has been associated with administration of phenylbutazone. Although reports of right dorsal colitis in this species have described surgical treatment associated with a poor prognosis, we have had success treating this condition medically. This report describes 5 horses with right dorsal colitis confirmed during celiotomy that were initially managed medically. All horses had a history of intermittent abdominal pain; weight loss was noted in only 1 horse. The doses (2.0 to 4.6 mg/kg PO bid) and duration (5 to 30 days) of administration of phenylbutazone were not unusually high relative to those recommended (4.4 mg/kg PO bid). Hypoproteinemia and hypoalbuminemia were observed in all horses at the time of admission; packed cell volume was low in 4 horses, and hypocalcemia was also observed in 4 horses. Three of 5 horses (60%) appeared to respond to dietary management and discontinuation of administration of nonsteroidal anti-inflammatory drugs. Dietary management consisted of feeding pelleted feed, and restricting or eliminating roughage for a period of at least 3 months. Two horses developed strictures of the right dorsal colon. One horse that developed a colonic stricture, possibly because its owners did not comply with recommendations for management, was subsequently treated surgically. The remaining horse that developed a stricture of the right dorsal colon was euthanized. These data indicate that some horses with right dorsal colitis can be successfully managed with medical treatment.

Permanent tracheostomy in standing horses: technique and results.

Permanent tracheal stomas were created in seven sedated, standing horses with severe upper airway obstruction. After local anesthesia, a 3-cm by 6-cm rectangle of skin was removed from the ventral surface of the neck, 3 cm distal to the cricoid cartilage. The sternothyrohyoideus muscles were clamped proximally and distally, then transected to expose the tracheal rings. The ventral third of four tracheal rings was dissected from the tracheal mucosa that was then incised in a double "Y." Two layers of suture were used to achieve mucocutaneous closure. Stomas healed without serious complications; two mares subsequently foaled, and three horses were used for riding.

Urinary surgery.

This article describes diagnosis, prognosis, pathophysiology, and methods to surgically correct abnormalities of the urinary system of ruminants. Surgery of the urinary system in ruminants most frequently is required to alleviate urethral obstruction or correct urinary bladder rupture. Several options for surgical management of those conditions are presented, but the prognosis for long-term survival or a return to reproductive function is poor if a urethrostomy is performed. Nephrectomy, translocation of ectopic ureters, removal of urachal remnants, and urethral extension to treat urovagina are performed less often in ruminants because animals requiring these procedures often are culled because of economic considerations or decreased productivity. Consequently, much of what has been described for ruminants is based on a limited number of cases or extrapolated from what has been learned from other species.