Nuss procedure: decrease in bar movement requiring reoperation with primary placement of two bars

BACKGROUND

The Nuss procedure, first reported in 1998, is currently the treatment of choice for pectus excavatum. The most significant bar-related complication documented is bar movement, requiring reoperation in 3.4%-27% of reports. Our report compares the initial placement of one Nuss bar versus two to prevent bar displacement.

SUBJECTS AND METHODS

An Institutional Review Board-approved, retrospective chart review was performed of all Nuss procedures performed from November 2000 through February 2010. Since November 2006, all initial Nuss procedures were started with the intent of placing two bars. Haller index, patient demographics, duration of surgery, length of stay, postoperative wound infections, and bar movement requiring reoperation were collected and compared for the one-bar versus two-bar patient populations.

RESULTS

In total, 85 Nuss procedures (58 with one-bar and 27 with two-bar primary Nuss procedures) were analyzed. Two attending pediatric surgeons performed all the procedures. Reoperation for bar movement when one bar was initially placed occurred in 9 patients (15.5%). No patients with initial placement of two bars required operative revision for a displaced Nuss bar (15.5% versus 0%, P=.05). Patient age and Haller index were not statistically different between groups.

CONCLUSIONS

Our data demonstrate improved bar stability with no reoperative intervention when pectus excavatum is initially repaired with two Nuss bars. Primary placement of two bars has now become standard practice in our institution for correction of pectus excavatum by the Nuss procedure and would be our recommendation for consideration by other centers.

Simultaneous carriage of multiple genotypes of Staphylococcus aureus in children

The co-existence of multiple genotypes in colonization by Staphylococcus aureus has not been fully investigated. The aim of this study was to evaluate the heterogeneity of S. aureus carriage in children. We evaluated 125 nasal and perianal swab samples that were positive for S. aureus from 76 children scheduled for elective surgery. For each sample, at least four colonies with the same or different morphotypes were selected for analysis. Multiple-locus variable-number tandem-repeat fingerprinting was used to determine the genetic relatedness and to characterize the clonality of the S. aureus strains. Of the 125 swabs, 91 (73 %) contained meticillin-sensitive S. aureus (MSSA), 8 (6 %) contained meticillin-resistant S. aureus (MRSA), and 26 (21 %) contained MSSA and MRSA simultaneously. A total of 738 S. aureus strains were evaluated with a mean of 6 colonies (range 4-15) picked from each culture. Of the 125 swabs, 32 (26 %) samples contained two genetically distinct S. aureus strains and 6 (5 %) contained three different genotypes. Multiple S. aureus strains simultaneously carried by individual children were genetically unrelated to each other. We concluded that the co-existence of multiple genotypes of S. aureus was common. The significance of multiple carriage is yet to be determined, but this intraspecies interplay could be important to pathogenicity and virulence in S. aureus.

Laparoscopic Ladd's procedure: treatment of choice for midgut malrotation in infants and children

INTRODUCTION

Rotational anomalies of the midgut encompass a broad spectrum of incomplete rotational events with malfixation of the intestines during fetal development. Ladd's procedure, as a correction of these anomalies, has traditionally been performed by laparotomy. In our institution, the laparoscopic Ladd's (LL) procedure was introduced in May 2004 and soon became the standard approach.

MATERIALS AND METHODS

A retrospective analysis of all Ladd's procedures in children in our institution between September 1998 and June 2008 was performed. Outcomes between the open (OL) and LL procedures were compared.

RESULTS

A total of 156 children underwent Ladd's procedure during the study period. There were 120 open and 36 laparoscopic procedures. Overall, 75% of patients in each group were symptomatic, most commonly with emesis and pain. Duration of surgery was similar in both groups. Time to starting feeds, and amount of time to attain full feeding, was significantly less in the LL group. Postoperative length of stay was significantly less in the patients having LL. Conversion rate to OL from LL was 8.3%.

CONCLUSIONS

LL can be performed safely in selected patients with no increase in complications. Short-term results are superior to OL and can be achieved without any increase in operative duration.

Transumbilical laparoscopically assisted appendectomy: an alternative minimally invasive technique in pediatric patients

INTRODUCTION

Transumbilical laparoscopically assisted appendectomy (TULAA) has been reported in the literature as an alternative to traditional three-port laparoscopic appendectomy (LA). Our study compares outcomes between LA and the one-trocar transumbilical technique in a single institution over a concurrent time frame for all cases of pediatric appendicitis.

METHODS

An Institutional Review Board-approved retrospective chart review of all appendectomies from July 2007 through June 2009 was performed. All appendectomies were performed either laparoscopically or transumbilically. One surgeon predominantly used the TULAA method, whereas the other 2 surgeons used strictly the LA method. No cases were converted to open. Categorization of specimens as normal, acute, or ruptured was based on pathology reports. Outcomes analyzed for each group included surgical duration, cost, length of stay, fever (>101.5F), wound infection, ileus, and postoperative abdominal-pelvic abscess.

RESULTS

A total of 131 appendectomies were performed by 3 surgeons, 83 were LA and 48 were TULAA. For all stages of appendicitis, outcomes differed significantly only for operating room cost, with the TULAA being significantly less expensive. All other outcomes were similar between the two techniques.

CONCLUSION

Our study suggests that TULAA is a reasonable alternative to the standard minimally invasive technique for appendicitis in both acute and ruptured situations. All analyzed complications were similar between the groups, suggesting that TULAA is an acceptable surgical method in pediatric patients for all stages of appendicitis.

Incision and loop drainage: a minimally invasive technique for subcutaneous abscess management in children

PURPOSE

The aim of the study was to evaluate outcomes after a minimally invasive approach to pediatric subcutaneous abscess management as a replacement for wide exposure, debridement, and repetitive packing.

METHODS

A retrospective study was performed of all children who underwent incision and loop drainage for subcutaneous abscesses between January 2002 and October 2007 at our institution.

TECHNIQUE

Two mini incisions, 4-5 mm each, were made on the abscess, as far apart as possible. Abscess was probed, and pus was drained. Abscess was irrigated with normal saline; a loop drain was passed through one incision, brought out through the other, and tied to itself. An absorbent dressing was applied over the loop and changed regularly.

RESULTS

One hundred fifteen patients underwent drainage procedures as described; 5 patients had multiple abscesses. Mean values (range) are as follows: age, 4.25 years (19 days to 20.5 years); duration of symptoms, 7.8 days (1-42 days); length of hospital stay, 3 days (1-39 days); duration of procedure, 10.8 minutes (4-43 minutes); drain duration, 10.4 days (3-24 days); and number of postoperative visits, 1.8 (1-17). Bacterial culture data were available for 101 patients. Of these, 50% had methicillin-resistant Staphylococcus aureus, 26% had methicillin-sensitive Staphylococcus aureus, and 9% streptococcal species. Of the 115 patients, 5 had pilonidal abscesses, 1 required reoperation for persistent drainage, and 1 had a planned staged excision. Of the remaining 110 patients, 6 (5.5%) required reoperation-4 with loop drains and 2 with incision and packing with complete healing.

CONCLUSION

The use of loop drains proved safe and effective in the treatment of subcutaneous abscesses in children. Eliminating the need for repetitive and cumbersome wound packing simplifies postoperative wound care. Furthermore, there is an expected cost savings with this technique given the decreased need for wound care materials and professional postoperative home health services. We recommend this minimally invasive technique as the treatment of choice for subcutaneous abscesses in children and consider it the standard of care in our facility.

A prospective study of methicillin-resistant Staphylococcus aureus colonization in children scheduled for elective surgery

BACKGROUND

Staphylococcus aureus is a major cause of surgical wound infections. To obtain contemporary data on S aureus, we performed a prospective study of colonization and infection in children scheduled for elective surgical procedures.

METHODS

A nasal swab and clinical information were obtained at the presurgical outpatient visit. At operation, nasal and perianal swabs were obtained. S aureus were isolated and characterized.

RESULTS

We enrolled 499 patients from June 2005 to April 2007. Wound classes were 1 (73%), 2 (22%), 3 (5%), and 4 (0.2%). Prophylactic antibiotics were administered for 153 (31%). Postoperative length of stay ranged from 0 (77%) to 6 days, with 19 (4%) staying 4 days or more. Screening cultures grew S aureus for 186 procedures (36.6%); of these, 141 were methicillin-resistant S aureus (MRSA) (76% of all staphylococcal cultures or 28% of all procedures). Most MRSA had Staphylococcal Chromosomal Cassette mec type II and resistance to clindamycin-typical for hospital-associated strains. There were 10 (2%) surgical site infections, including 4 methicillin-sensitive S aureus, 1 MRSA, 2 with no growth, and 2 with no cultures.

CONCLUSION

Methicillin-resistant S aureus colonization was common in asymptomatic children. Most strains appeared to be health care-associated and resistant to clindamycin. Wound infection rate remained low despite the high prevalence of staphylococcal colonization.

Complications associated with the Nuss procedure: continued evolution of the learning curve

BACKGROUND

We report unusual and/or significant complications encountered during and after the Nuss Procedure for pectus excavatum.

METHODS

This was a retrospective review that was approved by the institutional review board, with parental consent.

RESULTS

Seven patients had unique and/or significant complications as follows: (1) laceration of an internal mammary artery during bar placement requiring emergent minithoracotomy; (2) hemopericardium 10 weeks postoperatively after blunt chest trauma requiring exploration of the pericardium and clot evacuation; (3) almost complete recurrence of the pectus excavatum deformity immediately after bar removal; (4 and 5) immediate/early postoperative bar displacement requiring re-operation and placement of 2 bars each; and (6 and 7) almost complete neo-ossification of the Nuss bar, making removal challenging.

CONCLUSIONS

The Nuss procedure has met with near-universal acceptance. Complications are just being reported. We describe 7 events to add to the evolving literature as the entire pediatric surgery community participates in the initial learning curve.

Biliary dyskinesia: the most common indication for cholecystectomy in children

BACKGROUND

The purpose of this study is to examine the current indications for cholecystectomy in children and to evaluate the results after such surgery.

METHODS

Retrospective analysis of 107 consecutive cholecystectomies performed in children at the Children's Hospital of Illinois between October 1998 and September 2003. Hospital medical charts and outpatient clinic charts were reviewed. Patients' families were contacted by telephone to obtain longer-term follow-up. Results were analyzed with SPSS 12.0 for Windows (SPSS Inc, Chicago, Ill).

RESULTS

Biliary dyskinesia (BD) was the indication for surgery for 62 (58%) of the 107 children who underwent cholecystectomy during the study period. Gallbladder calculus (GC) disease was the next most common indication with 29 (27%) children. The duration of symptoms was longer for BD. The most common presenting symptom in both groups was abdominal pain. Food intolerance was reported by 45% of patients with BD, significantly higher than patients with GC. Mean length of stay after cholecystectomy was 17 hours and 45 hours for BD and GC, respectively. Short-term follow-up showed relief or improvement of symptoms in 85% of children with BD and in 97% with GC. There were no deaths. Two (1.9%) children of the total of 107 developed complications; both had intra-abdominal abscesses. Most patients had complete or considerable long-term improvement in symptoms.

CONCLUSIONS

Biliary dyskinesia was the most common indication for cholecystectomy in children in our study. More than half of the surgeries were performed on an outpatient basis. Morbidity was minimal and mortality was zero. We had satisfactory short- and long-term symptom resolution with long-term patient satisfaction reaching 95%.

Innervation and connexin isoform expression during diabetes-related bladder dysfunction: early structural vs. neuronal remodelling

Urinary bladder dysfunction is a major complication in diabetes mellitus and its mechanism has been attributed to altered neurological function (autonomic and/or peripheral neuropathy). Previous studies have demonstrated impaired nerve deficiencies, including either loss of nerve function and/or anatomical loss of neuromuscular nerve terminals. While the phenomenon of diabetes-related neurological injury is well recognised, its pathogenesis is not well understood. Using a well established rat model of diabetes (streptozotocin model), we investigated the prevalence of sympathetic and parasympathetic nerves and relative prevalence of connexin isoforms (gap junction proteins) during diabetes-related bladder dysfunction. Immunohistochemistry and digital image analysis was used to detect the prevalence of postsynaptic neuronal markers, NOS1 and connexin isoform expressions. Immunohistochemistry showed significant increases in tyrosine hydroxylase (marker of sympathetic innervation) and decreased vesicular acetylcholine transporter (marker of parasympathetic innervation), predominantly in the smooth muscle layer, 3 days after diabetes induction, when compared to age-matched controls. Time-dependent and cell-specific decreases in the connexin 43 isoform, but transient increases in connexin 32 and 26, were also observed in diabetic rats vs. controls (p<0.05). These data suggest that selective and time-dependent expression of gap junction proteins and altered prevalence of sympathetic/parasympathetic innervation are early events during diabetes-related bladder dysfunction and remodelling.

Perinatal management of gastroschisis: analysis of a newly established clinical pathway

PURPOSE

The authors developed a clinical pathway for optimal management after antenatal diagnosis of gastroschisis. This is the outcomes analysis of our first 30 consecutive patients.

METHOD

Antenatal counseling was provided for all families with in-utero diagnosis of gastroschisis. Bowel dilatation, thickness, motility, amniotic fluid volume, and fetal development were followed by ultrasonography every 4 weeks. Babies were delivered by cesarean section between 36 and 38 weeks gestation if the lungs were mature or earlier for bowel complications. Gastroschisis repair was scheduled 90 minutes after birth. Primary repair was attempted in all through the abdominal wall defect without an additional incision, resulting in an umbilicus with no abdominal scar.

RESULTS

Primary repair was achieved in 83%. Babies needed assisted ventilation for 3 days, reached full feeds by 19 days, and were discharged by 24 days (all medians). There were 3 (10%) deaths, all after staged repair.

CONCLUSIONS

Our new protocol of both scheduled elective cesarean section and early gastroschisis repair resulted in a higher proportion of primary repair, shorter duration of mechanical ventilation, earlier full feeds, and shorter length of stay. There was no increase in mortality or morbidity. The primary-repair babies had no mortality and had excellent cosmesis.

Differences in the outcome of surgically placed long-term central venous catheters in neonates: neck vs groin placement

BACKGROUND/PURPOSE

Long-term tunneled central venous catheters (CVC) are frequently used in the neonatal intensive care unit (NICU) babies. They are placed either in the neck or groin based primarily upon the surgeon's preference. There is meager published information available about the relative risks of these lines.

METHODS

This is a retrospective analysis of all the tunneled central venous catheters placed in NICU babies at a children's hospital over a nearly 5-year period. Single lumen Broviac catheters were used in all cases.

RESULTS

A total of 137 catheters were placed in 126 patients. There were 88 neck lines and 49 groin lines. Age, gestational maturity, and body weight were significantly lower for babies who underwent groin line placement. There was no significant difference in the number of days the catheters were live between the 2 groups. Total complication rates and catheter infection rates were significantly higher with neck lines. The accidental removal rate was higher with neck lines but did not reach statistical significance.

CONCLUSIONS

Broviac catheters placed in the groin of NICU babies are associated with significantly fewer complications compared with those placed in the neck.

The effect of pelvic osteotomy plate type on axial rotation of the acetabular segment in the triple pelvic osteotomy

OBJECTIVE

The purpose of this study is to evaluate the changes in structural anatomy of cadaver pelves, with specific emphasis on axial rotation, resulting from the application of TPO plates differing by type, angle and orientation.

SAMPLE POPULATION

Nine cadaver pelves procedure: The degree of axial rotation was determined for three different pelvic osteotomy plate types, four different plate angles and two different orientations of the same plate.

RESULTS

The observed degree of axial rotation was significantly different than the degree of axial rotation predicted by the plate angle for each group except the Rooks pelvic osteotomy plate.

CONCLUSIONS/CLINICAL RELEVANCE

In the triple pelvic osteotomy the final degree of axial rotation may be significantly different than the predetermined plate angle.

The effect of chicken, pigeon, and turkey demineralized bone matrix (DBM) implanted in ulnar defects fixed with the intramedullary-external skeletal fixator (IM-ESF) tie-in in pigeons (Columba livia): histological evaluations

Avian demineralized bone matrix (ADBM) powder prepared from chicken, pigeon, and turkey sources induced bone formation via endochondral and intramembranous processes, as in mammalian studies. There were no significant differences in percentage of new bone, percentage of cartilage, surface-forming osteoblast area, or osteoclast count between gaps treated with chicken, pigeon, and turkey DBM. However, there was a significantly (p<0.05) higher percentage of inflammatory area in gaps treated with chicken DBM than in gaps treated with pigeon DBM.

Laparoscopic appendectomy in children: technically feasible and safe in all stages of acute appendicitis

This is a retrospective outcomes analysis of pediatric open and laparoscopic appendectomy in a children's hospital. One hundred three children underwent appendectomy for appendicitis by two pediatric surgeons from August 1998 to December 2002. Patients were divided into two groups, laparoscopic appendectomy (LAP) and open appendectomy (OAP), and were further subdivided by diagnosis: normal (NL), acute (AA), and ruptured (RA). There were no differences in age, sex, race, or zip codes between groups. Median age was 10 years. In the acute phase, 28 patients underwent OAP and 65 underwent LAP whereas 10 patients underwent interval appendectomy (IA) 6 weeks after percutaneous drainage of established abscesses (eight were LAP vs two OAP). In the remaining patients, the appendix was normal in 17 (18.4%) and ruptured in 24 (25.8%) pathologically. LAP took longer to perform (57 minutes vs 34.5 minutes) at higher cost (3718 dollars vs 1858 dollars) than OAP. Overall complications were lower in the LAP group (17% vs 29%), and LAP for RA had significantly fewer total complications (25% vs 62.5%). Intra-abdominal abscess increased following LAP: 9.2 per cent versus 3.6 per cent. Length of stay was shorter for LAP versus OAP in both AA (2.0 vs 2.5 days) and RA (5.5 vs 7 days).

Laparoscopic Appendectomy in Children: Technically Feasible and Safe in All Stages of Acute Appendicitis

This is a retrospective outcomes analysis of pediatric open and laparoscopic appendectomy in a children's hospital. One hundred three children underwent appendectomy for appendicitis by two pediatric surgeons from August 1998 to December 2002. Patients were divided into two groups, laparoscopic appendectomy (LAP) and open appendectomy (OAP), and were further subdivided by diagnosis: normal (NL), acute (AA), and ruptured (RA). There were no differences in age, sex, race, or zip codes between groups. Median age was 10 years. In the acute phase, 28 patients underwent OAP and 65 underwent LAP whereas 10 patients underwent interval appendectomy (IA) 6 weeks after percutaneous drainage of established abscesses (eight were LAP vs two OAP). In the remaining patients, the appendix was normal in 17 (18.4%) and ruptured in 24 (25.8%) pathologically. LAP took longer to perform (57 minutes vs 34.5 minutes) at higher cost ($3718 vs $1858) than OAP. Overall complications were lower in the LAP group (17% vs 29%), and LAP for RA had significantly fewer total complications (25% vs 62.5%). Intra-abdominal abscess increased following LAP: 9.2 per cent versus 3.6 per cent. Length of stay was shorter for LAP versus OAP in both AA (2.0 vs 2.5 days) and RA (5.5 vs 7 days).

Time-dependent urinary bladder remodeling in the streptozotocin-induced diabetic rat model

Urinary bladder dysfunction and remodeling are well-recognized phenomena in diabetes but detailed assessments of tissue morphological changes have not been conducted. We studied time-dependent morphological changes in bladders from diabetic rats (streptozotocin model) and evaluated the usefulness of automated digital imaging technology as an unbiased, reproducible, and convenient method for the bladder morphometric analysis. Urinary bladders were isolated from diabetic (3 days, 2 weeks or 5 weeks after single injection of streptozotocin, 65 mg/kg) or control rats (0 or 5 weeks) and were processed for histochemical evaluations (hematoxylin/eosin and Mason's trichrome staining). Digital image analysis was used to quantify equatorial cross-sectional areas of bladder tissue and lumen, as well as relative prevalence of the three primary tissue components viz. smooth muscle, urothelium, and extracellular matrix. Digital imaging and color segmentation provided reliable and unbiased evaluations of the bladder tissue sections. Progressive increases in total bladder tissue and lumen area were observed in the diabetic animals relative to controls (p<0.05), demonstrating classic hypertrophy and dilation. Prevalence of smooth muscle and urothelium (% of total tissue) both increased significantly, but collagen content decreased. Average bladder wall thickness and urothelium thickness were unchanged. Bladder remodeling during experimental diabetes is associated with time-dependent chamber dilation and increased tissue mass. Changes in bladder wall composition also occurred in a time-dependent manner, most notably increased smooth muscle and urothelium and decreased collagen prevalence. Furthermore, automated digital imaging technologies provide an unbiased, reproducible, and convenient method for detailed morphometric analysis of bladder tissues.

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.

Fibrocartilaginous embolic myelopathy in miniature schnauzers

In large- and giant-breed dogs, fibrocartilaginous embolic myelopathy (FCEM) is a well-recognized syndrome of acute spinal cord infarction caused by embolization of fibrocartilage. The miniature schnauzer is reportedly the most frequently affected small breed, although clinical data from only six miniature schnauzers with FCEM is available in the literature. The purposes of this study were to determine the relative frequency of FCEM compared to other causes of myelopathy in miniature schnauzers, to characterize the clinicopathological features of FCEM in 38 miniature schnauzers, and to directly compare FCEM and intervertebral disk herniation in miniature schnauzers with respect to age at diagnosis; gender; neuroanatomical localization; and progression, asymmetry, and severity of neurological deficits. Fibrocartilaginous embolic myelopathy was the most common cause of myelopathy in miniature schnauzers. Age at diagnosis, asymmetry and severity of neurological deficits, and lack of progression of clinical signs after 24 hours assisted in distinguishing FCEM from intervertebral disk herniation. Fibrocartilaginous embolic myelopathy-related mortality in miniature schnauzers was significantly lower than mortality rates reported for affected large and giant breeds. Only 22% of miniature schnauzers were euthanized because of their disease, although the vast majority of survivors failed to achieve complete neurological recovery.

Free 3-nitrotyrosine causes striatal neurodegeneration in vivo

Peroxynitrite formation has been demonstrated in several neurodegenerative disorders; thus far, protein nitration and consequent alterations in protein function are implicated as mechanistic events. Free 3-nitrotyrosine (free-3NT) is also elevated in these settings; a neurotoxic role for this modified amino acid has not been investigated. We tested the hypothesis that free-3NT is neurotoxic in vivo, using a mouse model of striatal degeneration. The neurodegenerative effects of the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) (unilateral intrastriatal injection, 64 nmol) were compared with free-3NT (32 nmol) or free-tyrosine (free-TYR) (32 nmol). 6-OHDA-treated mice exhibited significant ipsilateral turning behavior after d-amphetamine challenge, indicative of unilateral striatal injury (ipsilateral-contralateral turning differential, 21.1 +/- 6.8). Significant turning behavior was also observed in free-3NT-treated mice but not in free-tyrosine-treated mice (free-3NT, 16.0 +/- 3.9; free-TYR, 1 +/- 2.7; p < 0.01). Immunohistochemistry was used to evaluate striatal tyrosine hydroxylase (TH) content. 6-OHDA or free-3NT treatment caused severe reductions in TH immunoreactivity in injected striata compared with the contralateral hemisphere (injected/contralateral immunoreactivity ratio: 6-OHDA, 0.23 +/- 0.07; free-3NT, 0.49 +/- 0.02). Free-tyrosine treatment had no effect (1.03 +/- 0.09). Turning behavior was correlated with striatal TH ratio (p < 0.01). Furthermore, we observed a striking unilateral reduction in TH-positive cell body counts in the substantia nigra pars compacta of 6-OHDA- and free-3NT-treated mice (injected/contralateral cell count ratio: 6-OHDA, 0.40 +/- 0.04; free-3NT, 0.59 +/- 0.02). Free-tyrosine treatment had no effect (1.05 +/- 0.04). No evidence for increased striatal protein incorporation of 3NT was observed in any treatment group. These data represent the first evidence that free-3NT can elicit neurodegenerative effects in vivo; free-3NT may have a causal role in neurodegenerative conditions.

NMDA antagonists block expression of sensitization of amphetamine- and apomorphine-induced stereotypy

We have been studying sensitization of psychostimulant-induced stereotyped behavior in mice using both single and multiple pretreatment paradigms. In the present study, we tested whether NMDA receptor antagonists and an inhibitor of nitric oxide synthesis inhibit expression of sensitization in either of these models. Male CF-1 mice were pretreated with a single dose or with three daily doses of amphetamine (14 mg/kg) or apomorphine (40 mg/kg). Two days following these pretreatments, mice were injected with ((+/-)3-(2-carboxypiperazine-4yl)-propyl-1-phosphonic acid (CPP, 20 mg/kg), dizocilpine maleate (MK-801, 0.1 mg/kg), 7-nitroindazole (25 mg/kg), or vehicle 30 min before receiving amphetamine (7 mg/kg) or apomorphine (3 mg/kg). The stereotyped behavioral response was enhanced in mice pretreated with amphetamine or apomorphine, indicating that sensitization had developed. CPP, MK-801, and 7-nitroindazole prevented the expression of the sensitized stereotyped response induced by either amphetamine or apomorphine in both paradigms. These drugs did not attenuate the stereotypy elicited by amphetamine and apomorphine in drug-naïve mice. The effect of 7-nitroindazole was reversed by pretreatment with 500 mg/kg of L-arginine but not by D-arginine. These results suggest that glutamatergic transmission and subsequent NMDA receptor activation and the production of nitric oxide play a critical role in the expression of the sensitized stereotyped behavioral response elicited by amphetamine or apomorphine.

NMDA glutamate receptor role in the development of context-dependent and independent sensitization of the induction of stereotypy by amphetamine or apomorphine

We have been studying sensitization of psychostimulant-induced stereotyped behavior in mice using both a context-dependent and a context-independent paradigm. In the present study, we tested whether N-methyl-D-aspartate (NMDA) receptor antagonists prevent development of sensitization in either of these models. Male CF-1 mice were pretreated with 20 mg/kg (+)3-(2-carboxypiperazine-4yl)-propyl-1-phosphonic acid (CPP), 0.1 mg/kg (+)5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohopten-5, 10-imine maleate (MK-801, dizocilpine maleate), or 25 mg/kg 7-nitroindazole 30 min before a single dose (context-dependent paradigm) or each of three daily doses (context-independent paradigm) of 14 mg/kg amphetamine or 40 mg/kg apomorphine. Two days following this pretreatment, mice were injected with 7 mg/kg amphetamine or 3 mg/kg apomorphine. The stereotyped behavioral response was enhanced in mice pretreated with amphetamine or apomorphine alone, indicating that sensitization had developed. Both CPP and MK-801 prevented the development of sensitization in the context-dependent model but not in the context-independent paradigm. 7-Nitroindazole did not attenuate development of sensitization in either model. The results suggest that activation of glutamatergic receptors is important in some sensitization paradigms but not others, indicating that glutamate can be important but is not always required for the development of sensitization.

Importance of environmental context in the development of amphetamine- or apomorphine-induced stereotyped behavior after single and multiple doses

The present study was designed to determine whether single and repeated pretreatment regimens with amphetamine or apomorphine differ in the context dependency of sensitization of stereotyped behavior. Male CF-1 mice that were pretreated with a single high dose of amphetamine (14 mg/kg, IP) or apomorphine (40 mg/kg, SC) only became sensitized to a lower test dose of amphetamine (7 mg/kg, IP) or apomorphine (3 mg/kg, SC) when placed in an environment that was the same as the pretreatment environment. However, animals pretreated with three high doses (24 h apart) of amphetamine (14 mg/kg, IP) or apomorphine (40 mg/kg, SC) did demonstrate sensitization to a lower test dose of amphetamine (7 mg/kg, IP) or apomorphine (3 mg/kg, SC) when placed in an environment that was different from the pretreatment environment. Context-dependent sensitization, but not context-independent sensitization, was extinguished by pairing the test environment with saline injections instead of drug injections. In addition, it was determined that neither sensitization model could be related to pharmacokinetic factors. Therefore, the results indicate that repeated exposure to amphetamine or apomorphine overcomes the context-dependent component of sensitization of amphetamine- or apomorphine-induced stereotyped behavior.

Importance of environmental context in the development of amphetamine- or apomorphine-induced stereotyped behavior after single and multiple doses

The present study was designed to determine whether single and repeated pretreatment regimens with amphetamine or apomorphine differ in the context-dependency of sensitization of stereotyped behavior. Male CF-1 mice that were pretreated with a single high dose of amphetamine (14 mg/kg intraperitoneally [IP]) or apomorphine (40 mg/kg subcutaneously [SC]) only became sensitized to a lower test dose of amphetamine (7 mg/kg IP) or apomorphine (3 mg/kg SC) when placed in an environment that was the same as the pretreatment environment. However, animals pretreated with 3 high doses (24-h apart) of amphetamine (14 mg/kg IP) or apomorphine (40 mg/kg SC) did demonstrate sensitization to a lower test dose of amphetamine (7 mg/kg IP) or apomorphine (3 mg/kg SC) when placed in an environment that was different from the pretreatment environment. Context-dependent sensitization, but not context-independent sensitization, was extinguished by pairing the test environment with saline injections instead of drug injections. In addition, it was determined that neither sensitization model could be related to pharmacokinetic factors. Therefore, the results indicate that repeated exposure to amphetamine or apomorphine overcomes the context-dependent component of sensitization of amphetamine- or apomorphine-induced stereotyped behavior.

Sensitization of apomorphine-induced stereotyped behavior in mice is context dependent

RATIONALE

The role of the environment in the sensitization of the stereotyped behavioral effects of apomorphine is unclear, since sensitization of this drug effect has either been difficult to demonstrate or has been shown to occur with a low but not a higher dose of apomorphine.

OBJECTIVES

The present study was designed to determine whether sensitization of the stereotyped behavioral effects induced by a single dose of apomorphine is dependent on environmental context.

METHODS

CF-1 mice were pretreated with apomorphine or vehicle under different environmental conditions and tested for stereotyped behavior after apomorphine challenge. Animals were scored positively for stereotyped behavior if they remained stationary and exhibited repetitive head and/or fore-limb movements, and data are reported as the percentage of mice rated as positive for stereotyped behavior.

RESULTS

When mice were pretreated with 40 mg/kg apomorphine and later tested in the same environment, the dose-response curve for stereotyped behavior elicited by apomorphine was shifted threefold to the left 48 h after pretreatment, and this sensitization persisted for at least 28 days after pretreatment. Mice pretreated with apomorphine did not have higher brain levels of apomorphine after administration of the test dose of apomorphine. When the pretreatment environment was different from the test environment, mice did not exhibit sensitization to apomorphine.

CONCLUSIONS

These results show that pre-exposure to a single high dose of apomorphine induces a long-lasting sensitization of apomorphine-induced stereotyped behavior that is context dependent. Since apomorphine directly activates dopamine receptors, these observations suggest that a mechanism located postsynaptic to dopamine neurons may be responsible for sensitization of stereotyped behavior.

Sensitization of stereotyped behavior to amphetamine is context and response dependent

The present study was designed to determine whether the environmental context in which amphetamine is administered plays a role in the development of sensitization to the stereotyped behavioral effects of amphetamine in mice. In male CF-1 mice, the dose-response curve for stereotyped behavior elicited by amphetamine was shifted 1.9-fold to the left 48 h after pretreatment with 14 mg/kg amphetamine. Behavioral sensitization only developed in mice that were pretreated in the same or a similar environment as that of the test environment. In addition, when mice were placed in an environment that attenuated the acute expression of stereotyped behavior elicited by the pretreatment dose of amphetamine, sensitization never developed. A further experiment showed that 96% of the mice that expressed stereotypy after the ED50 pretreatment dose of 10 mg/kg amphetamine showed a stereotyped behavioral response to the lesser dose of 7 mg/kg 48 h later, indicating sensitization. In contrast, mice that did not express stereotypy after the ED50 dose of amphetamine failed to show a significant stereotyped behavioral response to amphetamine challenge compared to vehicle-pretreated controls. Therefore, the results indicate that preexposure to a single high dose of amphetamine produces context- and response-dependent sensitization to amphetamine-induced stereotyped behavior.

Cervical vertebral fractures in 56 dogs: a retrospective study

The clinicopathological features of cervical fractures in 56 dogs were reviewed. "Hit by car" (HBC) was the most common inciting cause, and the axis and atlas were the vertebrae most frequently affected. Surgical treatment was associated with high (36%) perioperative mortality. However, all dogs that survived the perioperative period achieved functional recovery. Functional recovery was achieved in 25 (89%) of 28 nonsurgically treated dogs with adequate follow-up. Overall, severity of neurological deficits (nonambulatory status) and prolonged interval (five days or longer) from trauma to referral were associated with poorer outcome. Nonsurgical treatment is a viable therapeutic approach for many dogs with cervical fractures. Early neck immobilization and prompt referral are recommended, because delay in referral decreases the likelihood of functional recovery.

Sensitization elicited by directly and indirectly acting dopaminergic agonists: comparison using neural network analysis

The major aim of this work was to compare sensitized responses to amphetamine with those of apomorphine. This was done using both a univariant analysis of locomotor activity and a multivariant neural network analysis of five different behaviors. The neural network analysis compares the pattern of behaviors from a treated group to a set of patterns from control conditions and estimates the dose of drug in control conditions that best matches the pattern of behaviors of the treated group. Both methods indicated that repeated administration of 2.0 mg/kg amphetamine but not 0.5 mg/kg amphetamine resulted in sensitization to the administration of a 0.5 mg/kg amphetamine challenge given 10 days following the end of the sensitizing regimen. Both analyses indicated sensitization following repeated administration of 5 mg/kg apomorphine. Studies of cross sensitization were done using a neural network analysis that could distinguish patterns of behavior elicited by amphetamine from those elicited by apomorphine. Such studies indicated that apomorphine elicits an apomorphine-like response in animals sensitized to either apomorphine or amphetamine. In contrast, amphetamine produces an amphetamine-like response in animals sensitized to amphetamine and an apomorphine-like response in animals sensitized to apomorphine. The results indicate that neural network analysis may be a useful tool for analyzing drug effects on patterns of behavior.

Motor vehicle related injuries among American Indian and Alaskan Native youth, 1981-92: analysis of a national hospital discharge database

OBJECTIVE

To describe national trends in hospitalizations for motor vehicle related injuries among children and youth (0-24 years) of the United States Indian Health Service (IHS) from 1981-92.

DESIGN

Descriptive epidemiologic study of the E coded national hospital discharge database of the IHS.

RESULTS

From 1981 to 1992, the age standardized annual incidence of motor vehicle related injury hospitalizations (per 100,000 population) among American Indian and Alaskan Native (AI/AN) youth decreased more than 65% from 269 to 93. Substantial declines in hospitalization rates for all age and sex groups, all IHS areas, and most injury types were seen over this time. Injuries to vehicle occupants accounted for 78% of all motor vehicle related injury hospitalizations. The annual incidence of hospitalization (per 100,000 population) ranged from 291 in the Billings (Wyoming/Montana) and Aberdeen (the Dakotas) areas to 38 in the Portland area (Pacific Northwest).

CONCLUSIONS

National motor vehicle related injury hospitalization rates of AI/AN children and youth decreased significantly from 1981-92. This may be due to a reduction in the incidence of severe motor vehicle related trauma, changing patterns of medical practice, and changes in the use of services. Additional measures, such as passage and enforcement of tribal laws requiring the use of occupant restraints and stronger laws to prevent alcohol impaired driving, might further reduce the incidence of serious motor vehicle related injuries in this high risk population.

At risk in two worlds: injury mortality among indigenous people in the US and Australia, 1990-92

This paper outlines the commonalties and unique differences in injury experience among the indigenous people in the United States and Australia. Injury mortality rates among Indigenous people in the United States and Australia are approximately 2-3 times greater than rates for the non-Indigenous population in each country. Motor vehicle-related injuries accounted for one-third of the injury deaths for Native Americans and Australian Aboriginals. Suicide accounted for more deaths in Native Americans (15.5 per 100,000) than it did for Australian Aboriginals (11.1 per 100,000), whereas the injury death rate in Australian Aboriginals due to poisoning was almost twice that of Native Americans. Culturally appropriate interventions tailored to specific local settings and problems will be necessary to reduce injury mortality among Indigenous people.

Dopaminergic agonists administered into the nucleus accumbens: effects on extracellular glutamate and on locomotor activity

The hypothesis to be tested was that increased dopaminergic transmission induced by amphetamine in the nucleus accumbens results in increased glutamatergic neurotransmission in this brain area and that the increase in level of this neurotransmitter contributes to behavioral effects of psychostimulant drugs. Amphetamine (1 mg/kg, i. p.) increased the amount of extracellular glutamate in the accumbens, as measured by in vivo dialysis, and stimulated locomotor activity. Amphetamine (10 mM) infused into the accumbens by reverse dialysis through the probe produced a similar stimulation of locomotor activity as systemic amphetamine but a greater increase in extracellular glutamate levels. Both of these responses to amphetamine were attenuated by either the selective D1 antagonist SCH23390 or the selective D2 antagonist eticlopride. The combination of a D1 and D2 agonist, SKF38393 (20 mM) and quinpirole (50 mM), administered into the accumbens by reverse dialysis also increased extracellular glutamate and stimulated locomotor activity. Administration of a glutamate uptake inhibitor, threo-beta-hydroxy-aspartate (50 mM), increased extracellular glutamate but did not stimulate locomotor activity. Systemic administration of caffeine (15 mg/kg, i.p.) increased locomotor activity but did not increase extracellular levels of glutamate. These data suggest that activation of dopaminergic receptors in the nucleus accumbens results in stimulation of locomotor activity and in activation of glutamatergic transmission in this brain region. However, an increase in glutamate levels in the nucleus accumbens is neither sufficient nor necessary to produce a stimulation of locomotor activity.

Design and synthesis of enantiomers of 3,5-dinitro-o-tyrosine: alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA) receptor antagonists

The R- and S-isomers of 3,5-dinitro-o-tyrosine (6a,b) have been synthesized through the use of chemoenzymatic synthesis and shown to bind differentially with the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA, 3) receptors. The phenolic functional group of these o-tyrosine analogues was designed to act as a bioisostere of the gamma-carboxyl group of glutamate. The S-isomer of 3,5-dinitro-o-tyrosine (6b) was 6.5 times more potent than the R-isomer (6a) in inhibiting [3H]AMPA binding with IC50 values of 13 +/- 7 and 84 +/- 26 microM, respectively. The phenolic group was important for binding affinity since the methoxy compound 7 was less potent than the phenolic compound 6 in inhibiting the binding of AMPA. The free amino group was also shown to be important since the N-acetyl analogue 15 and the N-t-BOC compounds 16 and 17 exhibited very low affinity for the AMPA receptors. AMPA receptor functional tests showed that the o-tyrosine analogues are antagonists and that the S-isomer 6b (IC50 = 630 +/- 140 microM) was more potent than the racemate 6 (IC50 = 730 +/- 88 microM) while the R-isomer 6a was inactive up to 1 mM concentration, which is consistent with the S-isomer having higher binding affinity than the R-isomer.

1,4-dihydro-2,3-quinoxalinediones as potential flavin metabolites and excitatory amino acid receptor ligands. Part 1: Synthesis and pharmacological evaluation of the benzylic oxidation series of 1,4-dihydro-6,7-dimethyl-2,3-quinoxalinedione

A series of five 6,7-disubstituted 1,4-dihydro-2,3-quinoxalinediones was prepared, two of which are known microbial flavin metabolites and three of which are potential flavin metabolites. Four of the five compounds inhibited specific binding of [3H]-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid ([3H]AMPA), [3H]kainic acid, and [3H]6-cyano-1,4-dihydro-7-nitro-2,3-quinoxalinedione ([3H]CNQX) in rat brain homogenate fractions, with IC50 values in the low micromolar range (the fifth compound competed only with [3H]CNQX). Two of the compounds were moderately potent AMPA antagonists in an in vitro functional test.

Structure--activity studies for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid receptors: acidic hydroxyphenylalanines

Antagonists of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA) receptors may have therapeutic potential as psychotropic agents. A series of mononitro- and dinitro-2- and 3-hydroxyphenylalanines was prepared, and their activity compared with willardiine, 5-nitrowillardiine, AMPA, and 2,4,5-trihydroxyphenylalanine (6-hydroxydopa) as inhibitors of specific [3H]AMPA and [3H]kainate binding in rat brain homogenates. The most active compounds were highly acidic (pKa 3-4), namely, 2-hydroxy-3,5-dinitro-DL-phenylalanine (13; [3H]AMPA IC50 approximately equal to 25 microM) and 3-hydroxy-2,4-dinitro-DL-phenylalanine (19; [3H]AMPA IC50 approximately equal to 5 microM). Two other dinitro-3-hydroxyphenylalanines, and 3,5-dinitro-DL-tyrosine, were considerably less active. Various mononitrohydroxyphenylalanines, which are less acidic, were also less active or inactive, and 2- and 3-hydroxyphenylalanine (o- and m-tyrosine) were inactive. Compounds 13 and 19, DL-willardiine (pKa 9.3, [3H]AMPA IC50 = 2 microM), and 5-nitro-DL-willardiine (pKa 6.4, [3H]AMPA IC50 = 0.2 microM) displayed AMPA >> kainate selectivity in binding studies. Compound 19 was an AMPA-like agonist, but 13 was an antagonist in an AMPA-evoked norepinephrine release assay in rat hippocampal nerve endings. Also, compound 13 injected into the rat ventral pallidum antagonized the locomotor activity elicited by systemic amphetamine.

Differential effect of sensitizing regimen on induction of Fos-protein and locomotor activity elicited by apomorphine in rats

At doses that elicit behavioral activation, apomorphine does not induce Fos-protein in the nucleus accumbens of control animals but does under conditions of denervation supersensitivity. The purpose of this study was to determine whether apomorphine induces Fos-protein in animals sensitized by repeated treatment with apomorphine and whether the magnitude of such induction parallels the magnitude of behavioral response observed after different sensitizing paradigms. Apomorphine did induce Fos-protein expression in animals pretreated with apomorphine; however, the rats showing highest levels of induction were not those showing the largest behavioral responses.

Comparison of sensitization elicited by amphetamine and pertussis toxin: characterization of locomotor behavior and limbic dopamine release

1. Male, Sprague-Dawley rats were pretreated with one of several regimens of repeated, intermittent amphetamine or with a single-dose of intra-VTA pertussis toxin (PTX). 2. An amphetamine challenge dose (0.5 mg/kg, i.p.) produced increased locomotor activity in both amphetamine and pertussis toxin-pretreated rats. 3. The magnitude of activity in PTX pretreated rats exceeded 5-fold that of the amphetamine-pretreated rats. 4. There were no significant differences in the levels of sensitized behavior elicited by 4 distinct amphetamine pretreatment protocols. 5. Neither of the drug pretreatments caused significant changes in the ability of 10 microM amphetamine to promote dopamine efflux from nucleus accumbens or striatal tissue in vitro. 6. The sensitized behaviour cannot be explained by in vitro alterations in pre-synaptic dopamine release, which may suggest an up-regulation of post-synaptic activity.

Association between pelvic muscle mass and canine hip dysplasia

OBJECTIVE

To investigate the relationship between pelvic muscle mass and development and expression of canine hip dysplasia (CHD).

DESIGN

Prospective study.

ANIMALS

5 Greyhounds with anatomically normal hip joints, 59 German Shepherd Dogs (23 with CHD, 24 with near-normal hip joints, and 12 with normal hip joints), and 18 German Shepherd Dog-Greyhound crossbreeds (7 with CHD, 6 with near-normal hip joints, and 5 with normal hip joints) between 12 and 47 months old in which pelvic muscle mass was evaluated. Pectineal muscle and hip joint development were evaluated in 25 German Shepherd Dogs at 8 and 16 or 24 weeks of age.

PROCEDURES

For evaluation of pelvic muscle mass, individual pelvic muscles were weighed and hip joints were assigned a score on the basis of severity of degenerative changes. For evaluation of pectineal muscle development, muscle sections were stained and examined.

RESULTS

Pelvic muscle mass was greatest in Greyhounds, intermediate in crossbred dogs, and smallest in German Shepherd Dogs. Differences in pelvic muscle mass among breeds were attributable to differences in weights of individual muscles. Hip score was negatively correlated with pelvic muscle mass and weights of selected pelvic muscles. Dogs with pectineal hypotrophy at 8 weeks of age had type-2 muscle fiber paucity or muscle fiber-type grouping at 16 or 24 weeks of age. At 8 weeks of age, hip joints were composed of multiple centers of ossification, and the acetabulum was largely cartilaginous. By 24 weeks of age, the pelvic bones were largely, although incompletely, fused.

CLINICAL IMPLICATIONS

Diminished pelvic muscle mass in dogs with CHD and altered muscle fiber size and composition in 8-week-old dogs that subsequently develop CHD strongly suggest that abnormalities of pelvic musculature are associated with development of CHD. The complex development of the hip joint from multiple centers of ossification may make the joint susceptible to abnormal modeling forces that would result from abnormalities in pelvic muscle mass.

Clinical and radiographic evaluation of intertrochanteric osteotomy in dogs: a retrospective study of 18 dogs

OBJECTIVE

To determine whether intertrochanteric osteotomy (ITO) can prevent the progression of degenerative joint disease (DJD) in dysplastic hip joints.

STUDY DESIGN

The results of ITO were assessed retrospectively by using owner questionnaires, physical examination, and radiographic evaluation.

ANIMALS

Eighteen client-owned dogs (29 coxofemoral joints were evaluated).

METHODS

Lameness was scored according to a grading system. A scoring system was also developed to assess radiographically evident osteoarthritis on a ventrodorsal projection of the coxofemoral joints in extension.

RESULTS

Twenty-nine ITO were performed in 18 dogs with varying degrees of hip dysplasia. The dogs were lame on 19 of 29 rear limbs on physical examination before surgery. In 22 of the 29 hip joints, palpation caused signs of pain. The median age at the first and second surgical procedure was 14.5 months and 18 months, respectively. Follow-up evaluation was performed on average at 9.77 (FU I), 22.52 (FU II), and 47.50 months (FU III) after surgery. Based on the owners' evaluation, there was a tendency toward improvement after surgery. The results of the physical examination at the preoperative examination and at the three follow-up examinations did not differ significantly. The follow-up radiographic scores showed significantly worse DJD than the preoperative scores.

CONCLUSIONS

ITO does not prevent progression of DJD in the dysplastic hip.

CLINICAL RELEVANCE

Knowledge of the long-term effects of ITO is essential for surgeons trying to achieve improvement in dogs with hip dysplasia.

Robust sensitization to amphetamine following intra-VTA cholera toxin administration

Studies were conducted regarding the hypothesis that enhanced cAMP formation in the ventral tegmental area (VTA) affects the magnitude of the behavioral responses elicited by psychostimulant drugs. In the first paradigm, spontaneous and amphetamine-elicited locomotor activity was measured at various times following injection of cholera toxin (CTX), a known activator of adenylate cyclase, into the VTA. Adult male rats showed enhanced amphetamine-stimulated locomotor activity when tested 1 or 3 days after treatment with 0.5 microgram CTX into the VTA. Spontaneous activity was markedly increased 1 and 3 days following treatment with the higher dose of 1.0 microgram CTX into the VTA, and amphetamine was still capable of eliciting an increased level of locomotor activity above this high baseline. Using a paradigm in which repeated amphetamine injections were given on an intermittent schedule following injection of CTX into the VTA, it was observed that a single low dose of amphetamine (0.5 mg/kg) given 1 day after CTX (0.5 microgram) injection into the VTA led to a markedly potentiated locomotor activity response to subsequent treatment with amphetamine. Evaluation of this protocol (initial amphetamine dose 24 h after CTX injection, and challenge treatment of amphetamine at various times thereafter) showed that the sensitization was long-lasting and could be observed after an initial dose of amphetamine as low as 0.1 mg/kg. A sensitized response was also expressed when the challenge dose was given directly into the nucleus accumbens. These data suggest that injection of CTX into the VTA enhances the induction of locomotor sensitization to amphetamine.

Enhancement of the locomotor response to apomorphine in pertussis toxin-treated animals depends on the site of pertussis toxin injection into the ventral tegmental area

The locomotor stimulant response to either systemic or intra-accumbens amphetamine was enhanced 1-2 weeks after pre-treatment with pertussis toxin (PTX) into any of 3 different sites in the ventral tegmental area (VTA). An enhanced response to either systemic or intra-accumbens apomorphine occurred only after pre-treatment into the central VTA. Thus, enhanced sensitivity to drugs of either pre- or post-synaptic elements in the nucleus accumbens may develop depending on the site of the PTX pre-treatment within the VTA.

Amphetamine-induced sensitization and release of dopamine in slices from the ventral tegmental area of rats is enhanced following administration of cholera toxin into the ventral tegmental area

Administration of cholera toxin (CTX) into the ventral tegmental area (VTA) markedly potentiates the development of behavioral sensitization to amphetamine. Experiments were conducted to determine whether this phenomenon is associated with altered dopamine release from the VTA and nucleus accumbens (NAC). Adult, male rats received bilateral injections of CTX (0-1 microgram) or its vehicle into the VTA. Half of the animals then received four injections of amphetamine (0.5 mg/kg, i.p.) given every other day, while the other half received no additional treatments. In both groups, locomotor responses to amphetamine (0.5 mg/kg, i.p.) were measured on experimental day 18. One day later, amphetamine-induced [3H]dopamine release was measured in tissue slices of the VTA and NAC. Amphetamine-induced locomotor activity was augmented in rats receiving 0.5 or 1.0 microgram intra-VTA CTX pretreatment and the repeated amphetamine regimen. Amphetamine-induced [3H]dopamine release was increased from VTA but not NAC slices obtained from animals showing this behavioral sensitization. Thus, intra-VTA CTX treatment facilitates sensitization to low doses of repeated amphetamine which appears to be associated with the increased ability of this psychostimulant to release dopamine in the VTA.

Long-term results of treatment of traumatic coxofemoral joint dislocation in dogs: 64 cases (1973-1992)

OBJECTIVE

To determine long-term results of various treatments for traumatic coxofemoral joint dislocation in dogs.

DESIGN

Retrospective case series.

ANIMALS

64 dogs that underwent closed reduction and bandage stabilization, extracapsular suture stabilization, transacetabular pinning, toggle pinning, DeVita pinning, or femoral head and neck excision.

PROCEDURE

Follow-up evaluations included owner evaluation (64 dogs), physical evaluation (23), and radiography (19). Follow-up time ranged from 8 to 156 months.

RESULTS

Owner evaluation scores after closed reduction were significantly better than scores after DeVita pinning, extracapsular suture stabilization, and femoral head and neck excision. On physical examination, 6 of 23 dogs were lame on the side of the previous dislocation. Signs of pain and crepitation were evident during palpation of 12 and 8 of 25 joints, respectively. Thirteen of 21 joints had radiographic evidence of degenerative joint disease. There was a greater progression of degenerative joint disease in previously dislocated joints than in unaffected joints. There were not any significant differences between treatments in regard to results of physical and radiographic evaluation. Time between trauma and treatment and existence of concomitant injuries did not influence follow-up results, but there was a significant association between body weight and radiographic evaluation score.

CLINICAL IMPLICATIONS

Concomitant injuries do not appear to justify a worse prognosis in dogs with traumatic coxofemoral joint dislocation, nor does a delay in treatment of > 3 days. Gait abnormalities and degenerative joint disease might develop in the long term. Proper body weight should be maintained regardless of treatment.

Synthesis of chiral 1-(2'-amino-2'-carboxyethyl)-1,4-dihydro-6,7-quinoxaline-2,3-diones: alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor agonists and antagonists

Recently discovered 6,7-disubstituted quinoxaline-2,3-diones, 1, have been found to antagonize specific binding and functional responses to both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and kainic acid. Although a variety of studies have analyzed the activity of quinoxaline-2,3-diones with various substitutions at positions 6 and 7, there is little information regarding the effects of N-substitution. A racemic mixture of 1-(2'-amino-2'-carboxyethyl)-1,4-dihydroquinoxaline-2, 3-dione (QXAA, 2, R1 = R2 = H) has been synthesized from 1 (R1 = R2 = H). This compound inhibited specific [3H]AMPA binding but not [3H]kainate binding. IC50 values for QXAA, AMPA, and DNQX were 0.69, 0.012, and 0.74 microM, respectively. The R- and S-enantiomers were prepared by asymmetric synthesis. The S-isomer (2b) was 160-fold more potent in binding assays than the R-isomer (2d), with IC50 values of 0.23 and 38 microM, respectively. Both enantiomers were agonists in a functional assay, with the S-isomer having an EC50 value of 3 microM while that for the R-isomer was greater than 1 mM. Methyl substitutions at positions 6 and 7 (2a and 2c) resulted in antagonist compounds characterized by the S- and R-isomers being nearly equipotent, with IC50 values of 51 and 22 microM in the binding assay and EC50 values of 290 and 300 microM in the functional assay. AMPA had an EC50 value of 11 microM and DNQX an EC50 value of 30 microM in the functional assay. Analogs of quinoxalinediones with side chains other than an amino acid moiety on the nitrogen did not show good binding activities.

Magnetic resonance imaging and biological changes in injured intervertebral discs under normal and increased mechanical demands

STUDY DESIGN

An animal model was used to examine the short-term tissue response to changes in the mechanical environment after the structure (disc) is mechanically injured.

OBJECTIVES

To observe changes in an injured intervertebral disc and the corresponding motion segment when the mechanical demands of the disc were increased by fusion of the adjacent motion segments.

SUMMARY OF BACKGROUND DATA

Disc degeneration has been modeled in animals by producing a tear in the anulus via laminectomy, laparotomy, or posterolaterally. Methods of altering and quantifying the mechanics of the intervertebral joint by use of internal fixation and fusion in the canine have been developed.

METHODS

Eight dogs divided into two groups (a study and a control group) had anular stab wounds (L2-L3). The study group was surgically instrumented posteriorly from L3 to L7. Magnetic resonance imaging studies were conducted for all animals before and periodically after the surgical procedures. At the end of the study, the segments were processed histologically and biochemically.

RESULTS

Anular bulging was seen on magnetic resonance imaging in all control animals 4 months after injury and did not progress out until 6 months after injury. Similar changes were seen in study animals, but 75% were herniated by 6 months. Histologic changes correlated with magnetic resonance imaging changes. No significant difference in water or proteoglycan content of the disc tissue between groups was found.

CONCLUSIONS

Progression from the bulging of the anulus to herniation was not evident in damaged discs not subjected to adjacent fusions. No change in water or proteoglycan content as a function of altered mechanical state was found, suggesting the short-term effect of the altered mechanics is on the mechanical structure and not on the cells or extracellular matrix.

Induction of locomotor activity by the glutamate antagonist DNQX injected into the ventral tegmental area

DNQX, an antagonist of AMPA/kainate receptors, was injected into the ventral tegmental area (VTA) to test the hypothesis that AMPA/kainate receptors in this brain region might be involved in regulation of locomotor activity. Bilateral injection of 1 microgram DNQX into the VTA increased locomotor activity. In addition, unilateral injection of DNQX into this site produced contraversive turning, which was potentiated by coadministration of amphetamine (1 mg/kg, i.p.). These results suggest that a glutamatergic afferent to the VTA is tonically active in inhibiting locomotor activity. The locomotor stimulation produced by DNQX was not associated with a change in DOPAC/DA level in the nucleus accumbens or the striatum. However, the locomotor stimulation produced by DNQX was markedly attenuated following blockade of dopaminergic receptors by haloperidol (0.5 mg/kg, s.c.) or following dopamine depletion induced by reserpine plus alpha-methyl-para-tyrosine pretreatment. These results suggest that a basal activation of dopaminergic receptors is required for expression of the locomotor activity elicited by DNQX.

Kinematics of the canine lumbar intervertebral joint. An in vivo study before and after adjacent instrumentation

STUDY DESIGN

In vivo, canine lumbar spine intervertebral motion was measured before and after instrumentation of caudal segments. The three-dimensional kinematics of the intervertebral joint were described using helical axes and Fourier series.

OBJECTIVE

The in vivo three-dimensional kinematics of the intervertebral joint were measured and described. An animal model where intervertebral motion could be repeatedly changed was developed.

SUMMARY OF BACKGROUND DATA

The kinematics of intervertebral joints have been described from results of extensive in vitro testing, some limited in vivo testing, and clinically by evaluation of flexion/extension films. In the canine, in vivo intervertebral motion has been described previously, but the method possessed some measurement artifact.

METHODS

In vivo, four canines had motion data collected (L2-L3) while the animals walked on a treadmill. L3 To L7 were instrumented in all of the animals and motion testing was repeated 1 and 12 weeks later. Helical axes of motion were determined for each gait cycle. Fourier series were fit to the motion data, helical axis parameters, and Fourier coefficients were all statistically compared (pre- and postinstrumentation).

RESULTS

Vertebral rotations (coronal plane) and excursion of the L2/3 facet increased significantly (P < 0.01) after caudal instrumentation. Helical axes were oriented in a ventral direction and only the angle of rotation about the axis changed significantly (P < 0.05) after instrumentation of caudal segments. The Fourier coefficients (amplitudes) showed a significant (P < 0.05) increase in the coronal plane rotations only, after adjacent instrumentation.

CONCLUSION

The in vivo kinematics of the intervertebral joint have been completely defined in this study. Some motion characteristics compare very well to human motion. Since motion at an intervertebral joint now can be repeatedly altered, this animal model shows promise as a useful tool for investigation of tissue response to changes in motion at a joint.

DNQX in the nucleus accumbens inhibits cocaine-induced conditioned place preference

Several lines of evidence suggest that activation of both AMPA/kainate receptors and dopaminergic receptors in the nucleus accumbens may be required for psychostimulant drug induced reward. However, it has been reported that dopaminergic antagonists fail to block acquisition of conditioned place preference to cocaine. The goal of these experiments was to determine whether AMPA receptor antagonist injected into the nucleus accumbens could block conditioned place preference elicited by cocaine under conditions where dopaminergic antagonists do not inhibit acquisition of place preference. DNQX (1 microgram/0.5 microliter), injected into the nucleus accumbens just before systemic injections of cocaine (20 mg/kg i.p.) during the training sessions, attenuated the acquisition of place preference. This suggests that AMPA receptors are involved in acquisition of place preference to cocaine. By contrast, fluphenazine (2.5 micrograms/0.5 microliter), injected into the nucleus accumbens during training, did not alter cocaine-induced place preference. Analysis of locomotor activity showed that the ability of flyphenazine to inhibit cocaine-induced hyperactivity progressively decreased with each training session. These observations suggest that the failure of dopaminergic antagonists to block cocaine-induced place preference may be related to adaptations occurring following repeated exposure to these drugs. Both DNQX and fluphenazine blocked the expression of conditioned place preference in rats that had been previously trained with cocaine alone. This result suggests that both AMPA and dopaminergic receptors are involved in the expression of a conditioned place preference to cocaine.

Amphetamine induction of c-fos in the nucleus accumbens is not inhibited by glutamate antagonists

Systemic administration of relatively high doses of amphetamine or cocaine induces expression of c-fos in the rat striatum and nucleus accumbens. The doses of drugs used in such experiments are substantially higher than those needed to produce reward or sensitization. Therefore, it was determined if low doses of amphetamine capable of eliciting reward and sensitization increase levels of c-Fos protein in the nucleus accumbens. Amphetamine, 1 mg/kg, stimulated locomotor activity and increased the number of nucleus accumbens cells immunohistochemically positive for c-Fos protein to approximately 800 cells per section from a control of approximately 100 cells per section. Since glutamate antagonists modify various responses to amphetamine, it was then determined whether activation of glutamate receptors is involved in the induction of c-Fos protein by low doses of amphetamine. The NMDA receptor antagonist MK-801 by itself stimulated locomotor activity but did not alter baseline levels of c-Fos protein. When given before amphetamine, both locomotor activity and extent of c-fos induction were greater than from amphetamine alone. The AMPA receptor antagonist NBQX by itself had no effect on locomotor activity but increased slightly the number of cells positive for c-Fos protein in the nucleus accumbens. When given before amphetamine, locomotor activity was completely attenuated, and the extent of c-fos induction was greater than from amphetamine alone. We conclude that low doses of amphetamine do increase abundance of c-Fos protein in the nucleus accumbens. This action does not correlate with locomotor activity and is independent of activation of glutamate receptors.

Chronic bicipital tenosynovitis in dogs: 29 cases (1985-1992)

Medical records of 23 dogs with unilateral and 3 dogs with bilateral chronic bicipital tenosynovitis were reviewed. Mean age of affected dogs was 4.6 years (SD, 2.0 years), and mean body weight was 32.6 kg (SD, 14.5 kg). Neither a breed nor a gender predilection was detected. All dogs had a history of intermittent or progressive weight-bearing lameness that became worse after exercise. Mean duration of lameness prior to medical or surgical treatment was 6.5 months (range, 0.25 to 24 months). In all dogs, signs of pain were evident during palpation of the biceps tendon within the intertubercular groove. Radiography revealed sclerosis or osteophytosis of the intertubercular groove in all 29 shoulder joints. Mild degenerative joint disease was evident radiographically in 17. Arthrography was performed in 12 joints, and in 11 there were irregularities of or filling defects along the biceps tendon. Arthrocentesis was performed on 17 joints; 14 synovial fluid samples had cytologic abnormalities consistent with degenerative joint disease. Medical treatment, consisting of injection of methylprednisolone acetate into the biceps tendon and its synovial sheath, was attempted in 21 of the 29 affected shoulder joints. Surgery, which consisted of tenodesis of the biceps tendon, was attempted in 14 joints; 8 of these had not been treated medically; the remaining 6 had poor results following medical treatment. Gross and histologic findings consistent with chronic bicipital tenosynovitis were observed in all 14 joints in which surgery was performed. Seventeen of the medically treated shoulders were available for clinical evaluation, and results were excellent or good in 7.(ABSTRACT TRUNCATED AT 250 WORDS)