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Biomedical subjects

D J Schaeffer

Publications and source records attributed to D J Schaeffer.

At least 37 records · Page 2Linked to original sources
PubMed1998

Fragment reconstruction and bone plate fixation versus bridging plate fixation for treating highly comminuted femoral fractures in dogs: 35 cases (1987-1997).

OBJECTIVE: To compare fragment reconstruction and bone plate fixation versus bridging plate fixation for treating highly comminuted (> 4 fragments) femoral fractures in dogs. DESIGN: Retrospective study. ANIMALS: 35 dogs with highly comminuted fractures of the femur. PROCEDURE: Medical records of all dogs included in this study were reviewed. Dogs had been treated with fragment reconstruction and bone plate application (n = 20) or major fragment alignment and bridging plate fixation (15). Postoperative and follow-up radiographs were evaluated. Operating and hospitalization times, bone alignment, bone healing, and complications were considered. RESULTS: There were no differences in hospitalization times, limb alignment, and complications between dogs with fractures treated with fragment reconstruction and dogs with fractures treated with bridging plate fixation. Dogs with fractures treated with bridging plate fixation had shorter operative times and faster times to radiographic evidence of bone healing. CLINICAL IMPLICATIONS: Bridging plate fixation is quicker to perform and results in faster healing than fragment reconstruction and bone plate fixation when used to treat comminuted femoral fractures.

Age Factors↗
PubMed1997

Open reduction and bone plate stabilization, compared with closed reduction and external fixation, for treatment of comminuted tibial fractures: 47 cases (1980-1995) in dogs.

OBJECTIVE: To compare open reduction and bone plate fixation with closed reduction and external skeletal fixation as treatment for severely comminuted fractures of the tibia. Limb alignment, fracture reduction, operating time, hospitalization time, postoperative care, time to unrestricted activity, bone healing, complications, and number of surgical procedures were considered. DESIGN: Retrospective case series. ANIMALS: 47 dogs with severely comminuted fractures of the tibia treated with open reduction and bone plate application (22 dogs) or closed reduction and external fixation (25 dogs). PROCEDURE: Medical records of all dogs included in this study were reviewed. Postoperative and follow-up radiographs were evaluated by 2 independent observers. RESULTS: Differences were not found in hospitalization time, time to unrestricted activity, or time to earliest radiographic evidence of bone healing between dogs with fractures treated with a bone plate and dogs with fractures treated with an external fixator. Fractures treated with an external fixator had more caudal malalignment, and fractures treated with a bone plate had more valgus malalignment. Malalignments were determined not to be related to clinical problems. Dogs with fractures treated with an external fixator had shorter surgery times and more recheck examinations. Dogs with fractures treated with a bone plate had more complications. CLINICAL IMPLICATIONS: Open reduction with bone plate fixation and closed reduction with external fixation were both effective for treatment of comminuted tibial fractures. External fixation was associated with shorter surgery time, but dogs required more extensive postoperative care. Bone plate fixation was associated with more complications.

Animals↗
PubMed1997

Risk factors associated with development of pelvic canal stenosis secondary to sacroiliac separation: 84 cases (1985-1995).

OBJECTIVE: To measure pelvic canal diameter in dogs from a ventrodorsal radiographic view of the pelvic region, to define a normal pelvic canal diameter, to evaluate risk factors associated with stenosis of the pelvic canal secondary to sacroiliac separation, and to determine clinical signs associated with pelvic canal stenosis. DESIGN: Retrospective case series. ANIMALS: 84 case-group and 46 control-group dogs. PROCEDURE: Medical records and radiographs of dogs with conditions unrelated to pelvic fracture (control group) and dogs with sacroiliac separation (case group) in which radiographs were obtained before surgery, after surgery, or after fracture healing were reviewed. Discriminant analysis was used to determine a normal pelvic canal diameter. An ANOVA and Dunnett's two-sided test were used to determine factors associated with pelvic canal stenosis. RESULTS: Pelvic canal diameter ratio determined from control-group dogs was > or = 1.1. Pelvic canal diameter ratios were significantly less for case-group dogs on radiographs obtained before surgery and after fracture healing than for control-group dogs, regardless of fracture type or treatment, except for dogs with ilial fractures treated conservatively. Pelvic canal diameter ratios did not differ for case-group dogs on radiographs obtained after surgery from those for control-group dogs, except when ilial fractures were surgically reduced. None of the dogs had clinical signs associated with pelvic canal stenosis. CLINICAL IMPLICATIONS: Pelvic canal diameter in dogs can be determined from a ventrodorsal radiographic view of the pelvic region. Dogs with pelvic fractures that have a normal pelvic canal diameter before surgery tend to have a normal pelvic canal diameter after fracture healing.

Animals↗
PubMed1997

The pharmacokinetics of cefadroxil over a range of oral doses and animal ages in the foal.

To evaluate the effect of foal age on the pharmacokinetics of cefadroxil, five foals were administered cefadroxil in a single intravenous dose (5 mg/kg) and a single oral dose (10 or 20 mg/kg) at ages of 0.5, 1, 2, 3 and 5 months. Pharmacokinetic parameters of terminal elimination rate constant (beta(po)), oral mean residence time (MRTpo), mean absorption time (MAT), rate constant for oral absorption (Ka), bioavailability F, peak serum concentrations (Cmax) and time of peak concentration (tmax), were evaluated in a repeated measures analysis over dose. Across animal ages, parameters for the intravenous dose did not change significantly over animal age (P > or = 0.05). Mean values +/- SEM were: beta(IV) = 0.633 +/- 0.038 h-1; Cl = 0.316 +/- 0.010 L/kg/h; Vc = 0.196 +/- 0.008 L/kg; Varea = 0.526 +/- 0.024 L/kg; VSS = 0.374 +/- 0.014 L/kg; MRTiv = 1.22 +/- 0.07 h; Kel = 1.67 +/- 0.08 h-1. Following oral administration, drug absorption became faster with age (P < 0.05), as reflected by MRTpo, MAT, Ka and tmax. However, oral bioavailability (+/- SE) declined significantly (P < 0.05) from 99.6 +/- 3.69% at 0.5 months to 14.5 +/- 1.40% at 5 months of age. To evaluate a dose effect on the pharmacokinetic parameters, a series of oral doses (5, 10, 20 and 40 mg/kg) were administered to these foals at 1 month of age. beta(po) (0.548 +/- 0.023 h-1) and F (68.26 +/- 2.43%) were not affected significantly by the size of the dose. Cmax was approximately doubled with each two-fold increase in dose: 3.15 +/- 0.15, 5.84 +/- 0.48, 12.17 +/- 0.93 and 19.71 +/- 2.19 micrograms/mL. Dose-dependent kinetics were observed in MRTpo, MAT, Ka and tmax.

Administration, Oral↗
PubMed1997

CCK-8 infusion increases plasma LMW alkaline phosphatase coincident with enterohepatic circulation of bile acids.

Bile acids may facilitate the release of liver alkaline phosphatase (ALP) from its hydrophobic membrane anchor. The purpose of this study was to determine whether such a facilitatory role could be observed during the enterohepatic circulation of bile acids in dogs. Increased hepatic ALP activity was induced in four dogs by daily injections of 4 mg.kg-1.day-1 of prednisone for 10 days. Intravenous infusions of cholecystokinin octapeptide (CCK-8) were given before treatment and on treatment days 3, 5, 7, and 10 to induce gallbladder emptying and the enterohepatic circulation of bile acids. Blood samples were taken hourly for 4 h before and for 4 h after CCK-8 infusion. These showed that plasma ALP activity increased significantly only after CCK-8 infusion. Gel exclusion chromatography, polyacrylamide gel electrophoresis, and octyl Sepharose phase separation showed that the increased ALP activity was a hydrophilic, low-molecular-weight (LMW) isoform, which is consistent with phospholipase release. Histochemical staining of endogenous ALP activity showed increased ALP activity over sinusoidal surfaces of prednisone-treated dogs. There was also an increased serum-to-tissue ratio of ALP activity in the prednisone-treated dogs, suggestive of increased release of ALP into blood. It was concluded that bile acids probably play a facilitatory role in the enzymatic release of ALP from the sinusoidal surface of hepatocytes, which may be accentuated by the presence of increased amounts of ALP on the sinusoidal surface in some disease states.

Alkaline Phosphatase↗
PubMed1997

Rehabilitation of dogs with surgically treated cranial cruciate ligament-deficient stifles by use of electrical stimulation of muscles.

OBJECTIVE: To determine effect of electrical muscle stimulation (EMS) on rate and degree of return to function of the limb and development of degenerative joint disease (DJD) after surgical creation and subsequent stabilization of the cranial cruciate ligament (CrCL)-deficient stifle. ANIMALS: 12 clinically normal adult large (19.5 to 31.5 kg) dogs. PROCEDURE: Dogs were anesthetized, and the right CrCL was severed via arthrotomy, destabilizing the stifle. After 3 weeks, the stifle was surgically stabilized. Three weeks later, 6 dogs were subjected to an EMS treatment protocol for the thigh muscles. At 5, 9, 13, and 19 weeks after stifle destabilization, treated (n = 6) and control (n = 6) dogs were evaluated for return of stifle function. Gross and histologic evaluations of the stifles were performed at 19 weeks after stifle destabilization. RESULTS: Treated dogs had significantly (P = 0.001) better lameness score than did control dogs. There was less palpable crepitation of the stifle in treated dogs (P = 0.06); treated dogs also had significantly (P = 0.01) fewer radiographic signs of bone changes. Thigh circumference was significantly (P = 0.02) larger in treated dogs. There was less gross cartilage damage (P = 0.07) in the EMS-treated dogs, but more medial meniscal damage (P = 0.058, cranial pole; P = 0.051, caudal pole). CONCLUSIONS: Improved lameness scores, larger thigh circumference, and decreased radiographically apparent bony changes observed for the treated group of dogs support the hypothesis that dogs treated by EMS after surgical stabilization of the CrCL-deficient stifle had improved limb function, with less DJD, than did dogs treated with the currently accepted clinical protocol of cage rest and slow return to normal activity. However, results of force plate evaluation did not support the hypothesis. Increased meniscal damage in dogs treated by EMS may be cause for concern.

Animals↗
PubMed1996

Closed reduction and type-II external fixation of comminuted fractures of the radius and tibia in dogs: 23 cases (1990-1994).

OBJECTIVE: To describe a technique for closed reduction of and application of a type-II external fixator to comminuted fractures of the radius and tibia in dogs and to evaluate outcome of the technique in a series of client-owned dogs. DESIGN: Retrospective case series. ANIMALS: 23 dogs that underwent closed reduction of severely comminuted (> or = 5 fragments); mid-diaphyseal radial (n = 9); and tibial (n = 14) fractures and stabilization with a type-II external fixator. PROCEDURE: Radiographs were made postoperatively and every 4 to 6 weeks until the fixator was removed. The effect of type of fracture (open vs closed), type of pins (threaded vs smooth), and number of fixation pins on surgery time, time between surgery and development of bridging callus, and time between surgery and removal of the fixator was evaluated using one-sided Student's t-tests. RESULTS: 21 fractures healed after a single surgery. Two dogs with radial fractures required a second procedure because of complications. All fractures healed with the original fixation device in place. Mean time between surgery and the development of bridging callus was 11.4 weeks (range, 4 to 22 weeks), and mean time between surgery and fixator removal was 14.7 weeks (range, 4 to 27 weeks). Type of fracture, type of pins, and number of fixation pins did not have a significant effect on surgery time, time to development of bridging callus, or time to fixator removal. CLINICAL IMPLICATIONS: Closed reduction and application of a type-II external fixator was an effective method of treating severely comminuted radial and tibial fractures.

Animals↗
PubMed1996

Use of orally administered succimer (meso-2,3-dimercaptosuccinic acid) for treatment of lead poisoning in dogs.

OBJECTIVE: To determine whether succimer (meso-2,3-dimercaptosuccinic acid) would be effective in reducing blood lead concentration in dogs with naturally acquired lead poisoning and whether treated dogs would develop clinically important adverse effects. DESIGN: Prospective case series. ANIMALS: 13 dogs with moderate-to-high blood lead concentrations (39 to 120 micrograms/dl) and clinical signs of lead poisoning. PROCEDURE: Dogs were treated with succimer (10 mg/kg of body weight, PO, q 8 h) for 10 days. Blood and urine samples were analyzed for lead concentration before, during, and after treatment with succimer. RESULTS: Mean blood lead concentrations on days 0, 3, 7, and 20 were 70.6, 32.7, 16.8, and 27.6 micrograms/dl, respectively. Mean blood lead concentrations decreased 53.6, 76.2, and 60.9% from pretreatment value on days 3, 7, and 20, respectively. Mean urine lead concentrations on days 0, 3, 7, and 20 were 70.0, 485.4, 254.3, and 28.3 micrograms/dl, respectively. CLINICAL IMPLICATIONS: In dogs with naturally acquired lead poisoning, succimer administered orally for 10 days effectively reduced blood lead concentrations and eliminated clinical signs of lead poisoning.

Administration, Oral↗
PubMed1996

Microcystin-LR and kinetics of cytoskeletal reorganization in hepatocytes, kidney cells, and fibroblasts.

Microcystin-LR (MCLR) is a cyanobacterial hepatotoxin that inhibits protein phosphatases 1 and 2A. To characterize cytoskeletal changes over time, hepatocytes were incubated with the toxin at 13.3 microM for 0, 2, 4, 6, 8, 16, 32, or 64 minutes. Changes in the hepatocytes were compared to those in cultured kidney cells and skin fibroblasts incubated with the toxin at 133 microM for 0, 2, 4, 8, 12, 16, or 24 hours. Cells were fixed and incubated with rhodamine-conjugated phalloidin, or primary antibodies against beta-tubulin and either vimentin or cytokeratin intermediate filaments (IFs), followed by fluorescein-conjugated secondary antibodies. The number of affected cells per 400 counted (NAC) with alterations in a specific cytoskeletal element were determined at each time point. In fibroblasts as well as kidney cells, changes occurred first in IFs, followed by microtubules (MTs), and later microfilaments (MFs). In some hepatocytes, IFs were affected first, but after 16 minutes, the NAC with altered MTs exceeded the NAC with alterations in other cytoskeletal elements. In both hepatocytes and non-hepatocytes, IFs and MTs condensed and collapsed around the nucleus. MFs similarly collapsed, but some of the actin radiated outward, producing a star-like appearance. The similarity of the cytoskeletal changes induced by MCLR in hepatocytes and non-hepatocytes suggests a common mechanism of action. Differences among cell types in sequential cytoskeletal alterations may be due to differences in phosphorylation of intracellular proteins.

Actin Cytoskeleton↗
PubMed1996

The effects of near ultraviolet radiation on the toxic effects of polycyclic aromatic hydrocarbons in animals and plants: a review.

Polycyclic aromatic hydrocarbons (PAHs) are common contaminants of terrestrial and aquatic ecosystems. Traditional, toxicological studies for defining the potential hazard of PAHs in wildlife have been conducted in the absence of UV radiation. However, recent toxicology studies particularly in the discipline of aquatic toxicology have presented evidence that PAHs may become toxic or substantially more toxic upon coexposure to UV light (300-400 nm). In this paper, a comprehensive review of the literature pertaining to the toxicological interaction of PAHs and UV light in aquatic and terrestrial organisms is presented. It is concluded that the acute phototoxic effects of PAHs should be considered when conducting environmental risk assessments; however, more research needs to be conducted to address the lack of data on the enhancement of UV-induced carcinogenesis by PAH compounds.

Animals↗
PubMed1996

Diagnosing ecosystem health.

In the past five years, international symposia, new journals, emergence of several new societies, redirection of environmental programs, and funding for new degree programs have heralded the birth of the science of "Ecosystem Health and Medicine." This paper develops the fundamental theory of diagnosis. As a medical science, a process for systematically developing an ecosystem "patient" history (anamnesis) is required. Taking a history implies that certain types of information, that are specifiable in advance, should be the focus of the preliminary examination. This paper identifies conceptual aspects of the preliminary examination and provides an initial anamnesis form. The primary emphasis of this paper is to present and illustrate a rigorous formal mathematical procedure for using the data to carry out the deductive process of health determination. As the process is carried out, deductive elimination of spurious signs and diseases will imply the types of detailed studies which are required to identify the combination of diseases (disease complex) occurring in a given ecological system.

Diagnosis↗
PubMed1995

Fixation and staining of planaria for histological study.

Fixation and staining of planaria can affect the interpretation of histopathological changes following their exposure to various agents. We assessed several fixation protocols with various stains in planaria to determine an optimal combination. Planaria were fixed in each of the following: 10% neutral buffered formalin, 2.5%, glutaraldehyde, Bouin's, Zenker's, 70% ethanol, and relaxant. In addition, planaria were fixed in relaxant and postfixed in each of the fixatives above. Paraffin embedded sections from each fixation protocol were stained with hematoxylin and eosin (H & E), toluidine blue, periodic acid-Schiff (PAS), or phosphotungstic acid-hematoxylin (PTAH). Relaxant fixed planaria were also stained with Steiner's, Holmes, trichrome, Giemsa, Grocott's methenamine silver (GMS) and antibodies for intermediate filaments (cytokeratin, vimentin and desmin). Relaxant and Zenker's gave the best fixation with minimal artifacts. Formalin, glutaraldehyde, and ethanol were unacceptable because they caused contortions of the body, crenation, and a darkly pigmented epidermis. Gastroderm could be differentiated from stroma best when stained with H & E, toluidine blue and PTAH. Other organ systems differentially stained included the epidermis, marginal adhesion gland, nervous tissue, and muscle. PAS, Steiner's, Holmes, trichrome and the intermediate filament stains were not useful for planaria staining. The most morphological information was obtained with relaxant fixative and a combination of sections stained with H & E and PTAH.

Animals↗
PubMed1995

Effects of animal and soy fats and proteins in the diet on fatty acid concentrations in the serum and skin of dogs.

Growing dogs were fed diets containing soy oil or poultry fat as the main fat source and soybean meal or meat meal as the main protein source to examine the effects of types of dietary fat and protein on fatty acid concentrations in serum and skin and on serum cholesterol concentrations. Dogs fed diets containing soy oil had higher serum linoleic acid concentrations and lower serum oleic acid, arachidonic acid, and cholesterol concentrations than dogs fed diets containing poultry fat. The type of dietary protein had marginal effects on fatty acid concentrations and did not affect serum cholesterol. Similar differences were found in cutaneous fatty acid concentrations, with soy oil-fed dogs having significantly (P < 0.05) higher linoleic acid and lower oleic acid concentrations in their skin than had poultry fat-fed dogs. This study suggested that dietary fat source influences serum and cutaneous fatty acid concentrations and serum cholesterol concentrations in dogs, irrespective of dietary protein source.

Animal Feed↗
PubMed1994

Surgeons' preferences in treating cranial cruciate ligament ruptures in dogs.

To characterize veterinary surgeons' preferences in diagnostic, surgical, and postoperative management of cranial cruciate ligament ruptures in dogs, 175 surgeons, including American College of Veterinary Surgeons diplomates, surgery specialty-practice veterinarians, university surgeons, and surgery residents, were surveyed. Their experience with stifle surgery was evenly distributed from 1 to > 21 years. Approximately 70% (118/175) of surgeons treated 3 to 9 dogs with cranial cruciate ligament rupture each month. In diagnosis, 98% (172/175) of the surgeons used a cranial drawer test with the stifle joint at 140 degrees of flexion. Stifle radiography was performed by 53% (93/175) of surgeons for acute and by 81% (141/175) of surgeons for chronic cases. In repair of cranial cruciate ligament ruptures, 32% (56/175) of surgeons did not use intra-articular procedures, whereas 8% (14/175) of surgeons did not use extra-articular procedures. Surgical preferences depended on dog size (P < 0.05). For small dogs (ie, < 11 kg), 80% (140/175) of surgeons used extra-articular methods, and 14% (24/175) used intra-articular methods. For medium dogs (ie, 11 to 29 kg), 52% (91/175) of surgeons used extra-articular and 43% (75/175) used intra-articular methods. For large dogs (ie, > 29 kg), surgeons' preferences depended on the injury's duration (P < 0.05). For large dogs with acute injuries, 39% (68/175) preferred extra-articular and 55% (96/175) preferred intra-articular, whereas in chronic cases, 52% (91/175) preferred extra-articular and 42% (73/175) preferred intra-articular. The most common extra-articular method was placement of a suture from the lateral fabella to a hole drilled in the tibial tuberosity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Phototoxicology. 1. Light-enhanced toxicity of TNT and some related compounds to Daphnia magna and Lytechinus variagatus embryos.

Many environmental pollutants interact with solar near-ultraviolet (nuv) light in a manner which greatly increases their toxic effects. The phenomenon of light-mediated toxicity (phototoxicity) is only now becoming generally recognized to any significant degree. Manufacture of, and loading munitions with, the explosive 2,4,6-trinitrotoluene (TNT) in past decades caused contamination of soils and sediments at levels exceeding 1000 ppm and of waters at levels near saturation (100 ppm). Manufacture of TNT produces numerous nitrated by-products, and most of these compounds, including TNT, can be metabolized by many species, including bacteria, fungi, plants, and mammals. This study investigated the phototoxicity of TNT, and 2,3-, 2,4-, 2,6-, and 3,4-dinitrotoluene (DNT) and -diaminotoluene (DAT), and the major metabolites 2-amino-4,6-dinitrotoluene (2A) and 4-amino-2,6-dinitrotoluene (4A), to Daphnia magna (acute toxicity) and Lytechinus variagatus (sea urchin) embryos (subacute, developmental toxicity). Most of the compounds were weakly toxic or nontoxic in the dark. All were phototoxic to sea urchins. In D. magna, 2,3- and 3,4-DNT/DAT and 4A were not toxic but were phototoxic, and 2A was toxic and phototoxic; the other isomers were not toxic or phototoxic to this species.

Animals↗