A Comparative Mechanical Study of 3 External Fixator Clamps

OBJECTIVE: To compare external fixator clamps from Kirschner-Ehmer (K-E), Synthes, and Meynard with respect to 6 mechanical parameters. Study Design-A bench test of mechanical properties. METHODS: Specially designed fixtures were used to mechanically test 6 clamps of each type at 2.5, 5.0, and 7.5 Newton-Meters of clamp bolt-tightening torque. RESULTS: Components slipped axially and torsionally in the K-E clamp at higher forces for all parameters except for clamp bolt axis pivot. No bolt axis pivot occurred with the Synthes clamp. Instead, the clamp plastically deformed at the fixator-pin interface. This failure occurred at a higher applied torque than the pivot torque for other clamps. The Meynard clamp withstood significantly greater force than the K-E clamp when torsion was applied to the clamp bolt axis in the clockwise direction. Pivot forces for the K-E clamp were significantly higher than the Meynard clamp in the counterclockwise direction. CONCLUSIONS: Overall, the K-E clamp was able to resist higher axial and torsional forces before slipping than the Meynard clamp or the Synthes clamp. The Synthes clamp was best able to resist torsion around the clamp bolt axis. Torsional resistance at the clamp-fixator pin and clamp-connecting bar interface was the weakest parameter of clamp mechanics. CLINICAL RELEVANCE: The ability to resist motion within a clamp is related to fracture-reduction stability. Knowledge of the mechanical properties of fixator clamps will improve a clinician's ability to apply rigid fixation.     

Persistent Experimental Salmonella dublin Intramammary Infection in Dairy Cows

Experimental intramammary infections were induced in five post-parturient Holstein cows by inoculation of low numbers (5000 colony forming units) of virulent Salmonella dublin via the teat canal of mammary gland quarters. Rectal temperature, pulse and respiratory rates, milk yield, and milk quality as assessed by the California Mastitis Test (CMT) and somatic cell counts (SCC) were recorded every 12 hours at milking. Bacteriologic cultures of foremilk quarter samples and feces were obtained daily, as were complete blood counts. ELISA titers for IgG and IgM recognizing S. dublin lipopolysaccharide (LPS) were obtained weekly on serum and quarter milk samples. All cows excreted S. dublin intermittently from infected quarters, but no changes were detected in rectal temperature, appearance of the mammary gland or secretions, CBC, milk yield, and pulse and respiratory rates. Somatic cell counts were modestly increased in infected quarters as compared with uninfected quarters (P = .015, paired t test); however, CMT scores after infection remained low, and were not significantly different from pre-infection scores (P greater than .10, sign test). After infection, administration of dexamethasone resulted in signs of clinical mastitis and increased excretion of S. dublin from mammary quarters (P = .0004, paired t test). One cow had necrotizing mastitis and S. dublin septicemia and was euthanatized. In the four surviving cows, clinical improvement was observed after systemic gentamicin therapy and intramammary infusion with polymyxin B, but all cows continued to excrete S. dublin intermittently from one or more quarters and occasionally from feces for the remaining period of observation. All infected cows demonstrated a rise in IgG and IgM ELISA titers recognizing S. dublin LPS in serum and milk. At necropsy (13-25 weeks postinfection), S. dublin was recovered only from the mammary tissue or supramammary lymph nodes in three of four cows. In one cow, mammary gland and lymph-node samples were negative for S. dublin despite positive milk cultures. In all cows, histopathologic examination revealed multifocal areas of chronic active mastitis. These lesions were similar to histopathologic findings from mammary gland carriers with naturally acquired S. dublin infection.     

RETROSPECTIVE ANALYSIS OF BRAIN SCINTIGRAPHY IN 116 DOGS AND CATS

We performed a retrospective study of 100 dogs and 16 cats with planar brain scintigraphy and histopathologically established diagnoses from a total of 485 studies performed from 1976 to 1992. Necropsy (112) or surgical biopsies (4) diagnoses were categorized in two ways: first as focal brain disease, diffuse brain disease or normal; second as either neoplastic, non-neoplastic or normal. A radiologist reviewed brain scintigrams and categorized the studies as focal areas of increased accumulation, diffuse or poorly localized areas of increased accumulation, or normal. We calculated for this population of 116 animals that focal brain scintigrams had 75% sensitivity and 90% specificity for any focal brain disease. The sensitivity and specificity of a focal scintigraphic lesion for a brain tumor was 72% and 82% respectively. The sensitivity and specificity of a diffuse or poorly localized scintigraphic lesion as a test for diffuse brain disease was 40% and 88% respectively.     

Protein, energy and dry matter consumption by racing thoroughbreds: A field survey

A field survey involving 109 horses in 9 stables at a Detroit racetrack was conducted to determine feeding practices and to estimate crude protein (CP), digestible energy (DE), and dry matter (DM) consumption by racing Thoroughbreds, and to compare those intakes with 1989 recommendations of the National Research Council (NRC), "Nutrient Requirements of Horses." Trainers were interviewed regarding: 1) the age and sex of the homes; 2) their feeding practices; and 3) the horse's training and racing schedule. Only adult homes who were actively racing and continuously stabled at the track were included. Body weights (BW) were estimated using a chest girth measurement. The horses had an overall mean body condition score of 5 which indicated average body condition for a racing. Thoroughbred at this track. Feed samples of hay and concentrate from each stable were weighed and analyzed at a commercial laboratory to determine CP, DM, acid detergent fiber (ADF), and estimated energy density. A computer program calculated CP, DE, and DM values for each horse's ration based onamounts fed. The software program included with the 1989 NRC publication was used to compare estimated nutrient intakes with current NRC recommendations for a horse of a given BW. Trainers fed a variety of hays. Eight trainers fed oats and only one fed corn. All trainers fed commercial sweet feeds. The mean total amount of feed for all homes on an "as fed" basis was 13.7 kg. The mean estimated DM intake for all horses was 12.3 kg vs. NRC recommended 11.6 kg. The mean for percentage of roughage in the ration for all stables was 53% vs. a NRC recommendation of 35%. The mean CP% ona DM basis for all stables' rations was 13.8% vs. a NRC recommendation of 11.4%. The means for actual CP and DE intakes for all horses were 1678 g and 33.3 Meal compared with current NRC recommendations of 1324 g CP and 33.1 Meal DE. Protein amounts were above those recommended due to the common practice of feeding relatively higher CP% in the rations than necessary for racehorse performance. These data appear to be more consistent with the recommendations of NRC in 1989 than previous recommendations in 1978.     

Efficacy of Medroxyprogesterone Acetate in Suppression of Estrus in Cycling Mares

The effects of compounded medroxyprogesterone acetate (MPA) on follicular activity and estrous behavior were evaluated. Eighteen cycling mares were assigned to one of three treatment groups. Mares in the MPA group (n = 6) were injected intramuscularly with 1,600 mg MPA (week 1), then 400 mg weekly for the next 5 weeks. Saline mares (n = 6) were injected intramuscularly weekly for 6 weeks. Altrenogest mares (n = 6) received 10 mL orally daily for 7 weeks. Mares were teased daily for 60 days and categorized as displaying estrous, diestrous, or neutral behavior. Transrectal ultrasound examinations were performed three times weekly, or daily when a 30-mm follicle was identified, until ovulation. Blood samples were harvested weekly for analysis of progesterone concentration and daily from days 14 to 23 for analysis of luteinizing hormone (LH) concentration. Mares treated with saline or MPA showed normal intervals of diestrus and estrus during the study. All altrenogest mares showed behavioral diestrus during treatment. All mares in the saline and MPA groups showed normal follicular development and ovulations. No altrenogest mares ovulated during treatment; four mares returned to estrus and resumed normal follicular development after treatment ceased. Progesterone analyses agreed with transrectal ultrasonographic ovarian activity for all mares. LH levels were lower for altrenogest-treated mares compared with MPA-treated and saline-treated mares during the treatment period. In conclusion, compounded MPA at dose rates and intervals used in this study was not effective in suppression of estrus, follicular development, or LH secretion in mares.     

Effects of toe angle on hoof growth and contraction in the horse

The effects of toe angle on the growth of the unshod hooves of mature horses were measured over 126 days. The hooves of 4 horses were trimmed long in the toe and short in the heel (“LT”), with toe angles of 40° for the forelimb and 50° for the hind limb hooves; 4 others were trimmed short in the toe and long in the heel (“ST”), with toe angles of 50° for the forelimb and 55° for the hind limb hooves. Growth of the hoof wall at the toe ranged between .19 and .28 mm/day, and was slowest in the forelimb hooves trimmed ST. After 126 days, the hooves trimmed LT were 7% smaller in width than they had been at day 0. Narrowing of the hoof walls and frogs was accompanied by deformation of the angles of the walls (bending outward of their weightbearing surfaces). Frog lengths and sole areas were not affected by toe angle. Regardless of trimming method, all forelimb hooves tended to return to a toe angle of 45° between trimmings, while all hind limb hooves tended toward toe angles of 52° to 53°. The soles of all hooves were basically circular in shape, although the hooves trimmed LT tended to be skewed to the left, as viewed from above, after 126 days.     

Non-equivalence of canine tissue and intraluminal PCO2 responses at different sites during hemorrhage and during resuscitation

Objective: The purpose of this study was to measure and compare the hemorrhage and resuscitation partial pressure of CO₂ (PCO₂) responses at a variety of sites, predominantly intraluminal gastrointestinal, in the same dog and among different dogs. Design: Observational study. Setting: Association for Assessment and Accreditation of Laboratory Animal Care accredited research laboratory. Animals: Pound source mongrel dogs being used in 4 separate hemorrhage and resuscitation studies, the objectives of which were unaffected by the PCO₂ monitoring. Interventions: Fiber‐optic PCO₂ monitoring systems were used to simultaneously monitor subcutaneous (n=8), sublingual (n=8) PCO₂, and intraluminal esophageal (n=10), gastric (n=27), duodenal (n=16), jejunal (n=8), and ileal (n=7) PCO₂ of 28 dogs used in 4 hemorrhage and resuscitation studies. Measurements and main results: The tissue or intraluminal PCO₂ at all sites increased in response to hemorrhage. The rate and magnitude of esophageal, gastric, duodenal, jejeunal, and ileal intraluminal PCO₂ varied widely between dogs for the same site and between sites in the same dog. Different gastrointestinal sites also responded differently to resuscitation. The rate and magnitude of changes in subcutaneous and sublingual PCO₂ values were lower than those in the other tissues examined. The mean and maximum coefficients of variation for each site were as follows: subcutaneous 9%, 31%; sublingual 10%, 23%; esophageal 15%, 40%; gastric 26%, 90%; duodenal 25%, 70%; jejunal 25%, 95%; and ileal 34%, 87%. Conclusions: At different tissue sites, PCO₂ values do not respond equivalently to either hemorrhage or resuscitation. One site cannot, therefore, be reliably used to indicate the energy status of an alternate site.     

The effect of kefir on glutathione (GSH), malondialdehyde (MDA) and nitric oxide (NO) levels in mice with colonic abnormal crypt formation (ACF) induced by azoxymethane (AOM)

In this study we investigated the effect of kefir on the levels of glutathione (GSH), malondialdehyde (MDA), nitric oxide (NO) in the liver, stomach, spleen and colon of mice with colonic aberrant crypts formed by azoxymethane (AOM). Thirty 12 weeks old Swiss Albino mice averaging 31.5 g weight were used as experimental animals. The mice were separated into 3 groups. The first group was the control group, second group was the AOM and third group was the AOM+kefir group. We applied AOM to the second and third groups. Mice were fed ad libitum by laboratory rodent chow during the experiment period. Water was given to the first and second groups and third group received only kefir diluted with water (50%). AOM was injected subcutaneously to the second and third groups for 7 weeks (two times a week, 5 mg/kg). Six weeks after the final AOM treatment the animals were sacrificed and liver, stomach, spleen and colon samples were collected from all the groups. MDA level demonstrated an increase only in stomach for the third group (p < 0.001), while an elevation was observed for all of the four organs for the second group (spleen p < 0.001, liver p < 0.001, colon p < 0.01). GSH level showed an increase in the second group at stomach (p < 0.01) and colon (p < 0.001), while in the third group, a small increase was determined only at the colon (p < 0.05). NO level increased at all of the organs in the second group (spleen, liver, colon p < 0.001, stomach p < 0.05), but only at liver and colon in the third group 3 (p < 0.001). In conclusion these results showed that kefir plays an antioxidant role.