Prosthodontic appliance for repair of an oronasal fistula in a cat

A 4.5-month-old Himalayan cat was evaluated because of a cleft secondary palate. Multiple surgical procedures failed to provide soft-tissue coverage of the defect. A 3-cm silastic nasal septal button was trimmed and placed in the oronasal fistula. This prosthodontic appliance provided obturation of the defect without the need for removal or cleaning. Food accumulation between the appliance and oral mucosa was minimal, avoiding the need for appliance manipulation. The owner reported clinical signs related to oronasal fistula or appliance complications were not evident 12 months after placement.

Inadvertent prostatectomy as a complication of cryptorchidectomy in four dogs

Inadvertent prostatectomy was identified as a complication of cryptorchidectomy in four dogs. Surgical correction of the resulting urethral trauma was attempted in each case. One case was euthanized due to a poor prognosis for recovery. Three cases survived without clinical evidence of urinary incontinence. Inadvertent prostatectomy during cryptorchidectomy may be avoided by adequate surgical exposure and proper identification of the abdominally retained testicle.

Image-guided spine surgery

Conventional imaging techniques are of limited usefulness in spinal navigation, due to their lack of a "three-dimensional perspective." An interactive image-guided approach has been developed that provides a three-dimensional image-space representation of surgical space, using a specially designed referencing system and computer workstation. The system is described and results from laboratory tests and clinical cases are reported. It is concluded that interactive image-guided stereotaxis can be a valuable tool in spinal localization because of its degree of precision and the increased margin of safety it can offer.

A novel histone H4 mutant defective in nuclear division and mitotic chromosome transmission

The histone proteins are essential for the assembly and function of th e eukaryotic chromosome. Here we report the first isolation of a temperature-sensitive lethal histone H4 mutant defective in mitotic chromosome transmission Saccharomyces cerevisiae. The mutant requires two amino acid substitutions in histone H4: a lethal Thr-to-Ile change at position 82, which lies within one of the DNA-binding surfaces of the protein, and a substitution of Ala to Val at position 89 that is an intragenic suppressor. Genetic and biochemical evidence shows that the mutant histone H4 is temperature sensitive for function but not for synthesis, deposition, or stability. The chromatin structure of 2 micrometer circle minichromosomes is temperature sensitive in vivo, consistent with a defect in H4-DNA interactions. The mutant also has defects in transcription, displaying weak Spt- phenotypes. At the restrictive temperature, mutant cells arrest in the cell cycle at nuclear division, with a large bud, a single nucleus with 2C DNA content, and a short bipolar spindle. At semipermissive temperatures, the frequency of chromosome loss is elevated 60-fold in the mutant while DNA recombination frequencies are unaffected. High-copy CSE4, encoding an H3 variant related to the mammalian CENP-A kinetochore antigen, was found to suppress the temperature sensitivity of the mutant without suppressing the Spt- transcription defect. These genetic, biochemical, and phenotypic results indicate that this novel histone H4 mutant defines one or more chromatin-dependent steps in chromosome segregation.

MR of recurrent high-grade astrocytomas after intralesional immunotherapy

PURPOSE

To describe the MR findings in six patients with recurrent cerebral astrocytomas before, immediately after, and 3 months after local immunotherapy with tumor-infiltrating lymphocytes and interleukin-2.

METHODS

Contrast-enhanced MR studies were obtained in six patients (three with anaplastic astrocytoma and three with glioblastoma multiforme) at the time of tumor recurrence, after a second resection and placement of an Ommaya catheter, at the end of immunotherapy, and thereafter at 3-month intervals. These MR studies were reviewed with special attention to pattern and degree of enhancement, edema, and mass effect.

RESULTS

In three patients, gross total removal of recurrent tumor was achieved and postimmunotherapy MR studies showed a flare phenomenon characterized by increased nodular enhancement, increased edema, and mass effect. On the 3-month follow-up examination, these findings had resolved, and no further tumor recurrence was seen during the following 12-month period. Neither of the two patients who had subtotal resection had a flare phenomenon. In one of these patients, the tumor was stable at the 12-month follow-up; the other patient had recurrent tumor at the 6-month follow-up. In the last patient, who also had subtotal tumor resection and progressive enhancement after immunotherapy, tumor progression was rapid.

CONCLUSION

After local immunotherapy, increased enhancement, edema, and mass effect are most likely the result of a flare phenomenon, but because rapid tumor progression may produce similar features, follow-up MR studies are indispensable. The flare phenomenon resolved by 3 months in all patients.

Use of a modified toggle pin for repair of coxofemoral luxation in dogs with multiple orthopedic injuries: 14 cases (1986-1994)

OBJECTIVE

To develop modifications of the toggle pin procedure for use as a ligament of the head of the femur (LHF) prosthesis and to assess outcomes when used for coxofemoral luxation (CFL) in dogs with multiple orthopedic injuries.

DESIGN

Retrospective case series.

SAMPLE POPULATION

14 dogs with CFL as a component of orthopedic polytrauma.

PROCEDURE

Modifications to previous descriptions of the technique for use of a toggle pin for LHF prosthesis included deletion of the osteotomy of the greater trochanter in 12 of 16 joints with CFL, drilling of the femoral tunnel from a distal-to-proximal direction, deletion of a second femoral bone tunnel for suture placement, and use of a 2-hole polypropylene button to secure the LHF prosthetic suture.

RESULTS

Mean age at time of injury, weight, and duration between injury and definitive surgery was 4.1 +/- 1.1 years, 19.7 +/- 2.8 kg, and 5.8 +/- 2.7 days, respectively. Weightbearing began 3.0 +/- 0.4 days after surgery. Mean postoperative follow-up period for dogs with maintained coxofemoral reduction of longer than 1 month (n = 13) was 19.5 +/- 6.1 months. Owners reported good or excellent clinical results, which were confirmed by semiquantitative assessment methods. Radiographic signs of degenerative joint disease were minimal. There was no significant difference between hind limbs when comparing mid-thigh limb circumference at the time of follow-up examination.

CLINICAL IMPLICATIONS

A modified toggle pin procedure for LHF prosthesis can maintain coxofemoral reduction and allow early weightbearing in dogs with coxofemoral luxation as a component of multiple orthopedic injuries.

Cannulated screws for odontoid screw fixation and atlantoaxial transarticular screw fixation. Technical note

Cannulated screw systems use thin Kirschner wires (K-wires) that have been drilled into the bone to direct screw trajectories accurately into small bone fragments. Use of the K-wires avoids overdrilling the pilot holes and allows fixation of adjacent bone fragments during screw insertion. Hollow tools and hollow screws are inserted into the bone over the K-wires. Cannulated screw fixation is useful in the cervical spine to stabilize odontoid fractures and to treat atlantoaxial instability. This report describes techniques for successful cannulated screw insertion and methods to minimize complications. Cannulated screws have several distinct advantages compared to noncannulated screws: 1) the K-wires guide the screw position into the bone; 2) the K-wire trajectory can be repositioned easily if the original trajectory was not ideal; 3) the K-wires allow continuous fixation of adjacent unstable bone fragments; and 4) the K-wires prevent migration of unstable bone fragments during screw insertion. Complications associated with the K-wire (breakage, repositioning, and advancement) can be minimized using precise operative techniques, a specialized tool system, and intraoperative fluoroscopic monitoring. A unique cannulated screw tool system was developed specifically for upper cervical fixation to allow percutaneous drilling using long tunneling devices, tissue sheaths, drill guides, and long K-wires. These tools allow delivery of cannulated fracture-fixation screws at a low angle to the spine through long soft-tissue trajectories. Cannulated screws have significant advantages compared to noncannulated screws for fixation of the unstable cervical spine.

Surgical approach for lymph node staging of oral and maxillofacial neoplasms in dogs

A single surgical approach was developed to provide exposure for excisional biopsy of lymph nodes with afferent drainage of the head. The procedure was performed in six, fresh, canine cadavers and three canine patients diagnosed with neoplasia of the head. The relatively short, oblique incision and subsequent deeper dissection allowed surgical access to the three principal lymphocentrums with afferents from the head. There was no clinical evidence of negative side effects in patients receiving this surgery for lymph node staging. Histopathological evidence of metastasis was observed in at least one of the three lymphocentrums evaluated. Interestingly, lymph nodes (parotid and medial retropharyngeal) which would have been considered difficult to evaluate by fine-needle aspiration provided useful diagnostic and prognostic information. Based on the results of this study, the ipsilateral parotid, mandibular, and medial retropharyngeal lymph nodes may be excised through a single incision in a safe and effective manner.

Cyclic AMP signaling is required for function of the N-terminal and CR1 domains of adenovirus E1A in Saccharomyces cerevisiae

We have constructed yeast vectors in which derivatives of the adenovirus E1A gene are expressed from the GAL1 promoter. Cells expressing E1A289 grow poorly and accumulate cells with a 1C DNA content. Using a series of E1A deletion mutants, we have identified three regions within the E1A protein that are necessary for the G1 growth phenotype; each deletion partially relieves the growth defect. These deletions span residues 4-25, 38-60 and 140-186, which fall within the N-terminal, CR1 and CR3 domains of E1A respectively. Expression of the first 82 residues of E1A, spanning just the N-terminal and CR1 domains, strongly inhibits yeast cell growth in G1 showing that these domains can function independently of other domains of E1A. Using this strong growth inhibition, we isolated a yeast mutant in the net1 gene that conferred resistance to the expression of E1A1-82. The mutant was insensitive to expression of both E1A1-82 and full length E1A, but remained sensitive to the toxicity caused by over-expression of a Gal4p-VP16 fusion. Finally, we found that the function of E1A in yeast depends on the cyclic AMP signaling pathway, providing a striking parallel with the action of E1A at the c-fos promoter in mammalian cells. These results suggest that a genetic analysis of the yeast model system will provide relevant new insights into mechanisms of gene regulation by E1A proteins.

Skull trauma and mandibular fractures

This article discusses the treatment of skull and mandibular fractures in small animals as well as fixation techniques, including interdental fixation, external skeletal fixation, intraoral splints, wiring, and pinning. Information is provided on the treatment of loose and damaged teeth in the fractured area. Management of temporomandibular joint luxation also is addressed.

Histone H4 and the maintenance of genome integrity

The normal progression of Saccharomyces cerevisiae through nuclear division requires the function of the amino-terminal domain of histone H4. Mutations that delete the domain, or alter 4 conserved lysine residues within the domain, cause a marked delay during the G2+M phases of the cell cycle. Site-directed mutagenesis of single and multiple lysine residues failed to map this phenotype to any particular site; the defect was only observed when all four lysines were mutated. Starting with a quadruple lysine-to-glutamine substitution allele, the insertion of a tripeptide containing a single extra lysine residue suppressed the G2+M cell cycle defect. Thus, the amino-terminal domain of histone H4 has novel genetic functions that depend on the presence of lysine per se, and not a specific primary peptide sequence. To determine the nature of this function, we examined H4 mutants that were also defective for G2/M checkpoint pathways. Disruption of the mitotic spindle checkpoint pathway had no effect on the phenotype of the histone amino-terminal domain mutant. However, disruption of RAD9, which is part of the pathway that monitors DNA integrity, caused precocious progression of the H4 mutant through nuclear division and increased cell death. These results indicate that the lysine-dependent function of histone H4 is required for the maintenance of genome integrity, and that DNA damage resulting from the loss of this function activates the RAD9-dependent G2/M checkpoint pathway.

Evaluation of three fixation techniques for repair of mandibular fractures in dogs

Bilateral midbody hemimandibular osteotomies were performed between premolars 3 and 4 in 18 adult dogs. Hemimandibles were repaired by use of monocortically applied bone plates (n = 6), an interdental fixator composed of an Erich arch bar and acrylic (n = 6), or a type I external skeletal fixator (n = 6). At the immediate postoperative evaluation, hemimandibles stabilized with interdental fixators had an osteotomy gap distance (mean +/- SEM, 1.6 +/- 0.2 mm) that was significantly (P < 0.05) greater than for hemimandibles stabilized with external skeletal fixators (1.2 +/- 0.3 mm). Osteotomy gap distance of hemimandibles stabilized with external skeletal fixators (1.5 +/- 0.2 mm) was significantly (P < 0.05) greater at weeks 4 (1.1 +/- 0.2 mm) and 8 (0.8 +/- 0.3 mm) after surgery than the osteotomy gap distance of hemimandibles stabilized by application of bone plates. By week 16, significant differences in osteotomy gap distance were not detected between groups. Immediately after surgery, mandibular alignment measurements were not significantly different for dogs with bone plates (0.3 +/- 0.1 mm), interdental fixators (0.3 +/- 0.1 mm), and external skeletal fixators (0.9 +/- 0.5 mm). Mandibular alignment scores were not significantly different between treatment groups during the remaining postoperative period. Occlusal measurements were not significantly different between evaluations performed before surgery and 16 weeks after surgery, regardless of treatment group. Radiographic evidence of healing in hemimandibles stabilized with external skeletal fixators was significantly (P < 0.05) less at 4 and 8 weeks, compared with hemimandibles stabilized with bone plates and interdental fixators; however, radiographic evidence of bone healing was not significantly different between fixation groups at 16 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of a mandibular periodontal interproximal defect with a bone graft in a dog

A 10-year-old German shepherd dog presented with a periodontal 10 mm interproximal defect between the left mandibular fourth premolar and first molar teeth. Bone graft removed from the caudoventral portion of the ipsilateral hemimandible was placed in the defect as a component of the periodontal treatment plan. The use of bone graft likely contributed to periodontal pocket reduction.

Voltage-gated calcium currents have two opposing effects on the secretion of aldosterone

Using Ca2+ channel blockers with different specificities for L- and T-type Ca2+ channels, we have investigated the roles of these two channel types in K(+)-induced aldosterone secretion. In whole cell voltage-clamp experiments, the spider toxin omega-agatoxin-IIIA (omega-Aga-IIIA) completely blocks L-type Ca2+ channels but has no effect on T-type Ca2+ channels. In contrast, Ni2+ and 1,4-dihydropyridines block both L- and T-type Ca2+ channels. Secretion induced by 7 mM extracellular K+ concentration ([K+]o) is unaffected by omega-Aga-IIIA but is strongly inhibited by Ni2+ or the 1,4-dihydropyridine, nitrendipine. This suggests that physiological increases in [K+]o stimulate aldosterone secretion primarily by enhancing Ca2+ entry through T-type Ca2+ channels. Surprisingly, secretion induced by 60 mM [K+]o is enhanced by omega-Aga-IIIA or Ni2+ and is inhibited by the L-type Ca2+ channel activator BAY K 8644. Nitrendipine (1 nM) also stimulates such secretion, although higher concentrations are inhibitory (concentration inhibiting 50% of maximal response approximately 30 nM). If extracellular Ca2+ concentration is reduced from 1.25 to 0.5 mM, secretion induced by 60 mM [K+]o is enhanced, and Ni2+ or low nitrendipine become inhibitory. Together, these results that L-type Ca2+ currents can reduce steroidogenesis and that the role of these currents was previously misconstrued because 1,4-dihydropyridines modify secretion by multiple mechanisms. Thus Ca2+ entry can function as a negative modulator of steroid secretion.

Rapid identification of highly active and selective substrates for stromelysin and matrilysin using bacteriophage peptide display libraries

The discovery of useful peptide substrates for proteases that recognize many amino acids in their active sites is often a slow process due to the lack of initial substrate data and the expense of analyzing large numbers of peptide substrates. To overcome these obstacles, we have made use of bacteriophage peptide display libraries. We prepared a random hexamer library in the fd-derived vector fAFF-1 and included a "tether" sequence that could be recognized by monoclonal antibodies. We chose the matrix metalloproteinases stromelysin and matrilysin as the targets for our studies, as they are known to require at least 6 amino acids in a peptide substrate for cleavage. The phage library was treated in solution with protease and cleaved phage separated from uncleaved phage using a mixture of tether-binding monoclonal antibodies and Protein A-bearing cells followed by precipitation. Clones were screened by the use of a rapid screening assay that identified phage encoding peptide sequences susceptible to cleavage by the enzymes. The nucleotide sequence of the random hexamer region of 43 such clones was determined for stromelysin and 23 for matrilysin. Synthetic peptides were prepared whose sequences were based on some of the positive clones, as well as consensus sequences built from the positive clones. Many of the peptides have kcat/KM values as good or better than those of previously reported substrates, and in fact, we were able to produce stromelysin and matrilysin substrates that are both the most active and smallest reported to date. In addition, the phage data predicted selectivity in the P2 and P'1 positions of the two enzymes that were supported by the kinetic analysis of the peptides. This work demonstrates that the phage selection techniques enable the rapid identification of highly active and selective protease substrates without making any a priori assumptions about the specificity or the "physiological substrate" of the protease under study.

Carbohydrate absorption from fruit juice in young children

OBJECTIVE

To compare carbohydrate absorption following ingestion of apple juice and white grape juice in 28 healthy children.

DESIGN

Randomized, double-blind crossover study.

SETTING

Outpatient pediatric clinic at Maimonides Medical Center.

PARTICIPANTS

A total of 18 healthy infants (mean age 6.3 months) and 10 toddlers (mean age 18.0 months), representing those ages when juice is first introduced (6 months) and when juice comprises a large portion of the diet (18 months).

METHODS

Breath hydrogen (H2) testing was performed after age-specific servings of white grape juice or apple juice, 4 and 8 ounces respectively, were consumed. These portions provided approximately 1 g of fructose per kg of body weight. Breath H2 responses of > 20 ppm were considered positive, indicating incomplete absorption of fruit juice carbohydrates.

RESULTS

In the combined age groups, carbohydrate malabsorption occurred more frequently after apple juice consumption (54%) than after white grape juice (19%; P < .001). Significant differences in area under the breath H2 curve (AUC) were also found between the two juices in both age groups. Among toddlers, the differences between the mean peak breath H2 responses were significant (48 ppm after apple juice consumption compared with 12 ppm after white grape juice; P < .001). These differences were not significant in the infant group. Significant differences (P < .05) were seen between the two age groups after consumption of apple juice; the toddlers exhibited a greater number of positive breath H2 responses and higher peak responses compared with the infants. Data from the children who drank both juices showed significant differences in peak breath H2 responses after consumption of apple juice compared with white grape juice (P < .005).

CONCLUSIONS

The study demonstrated less carbohydrate malabsorption following ingestion of white grape juice compared with apple juice in healthy 6- and 18-month-old children.

Evaluation of horizontal and vertical tracheotomy healing after short-duration tracheostomy in dogs

PURPOSE

The purpose of the study was to assess healing of horizontal and vertical tracheotomy after short-duration tracheostomy in dogs using clinical, radiographic, endoscopic, and histologic methods.

MATERIALS AND METHODS

Horizontal tracheotomy (n = 6) between the third and fourth tracheal rings or vertical tracheotomy (n = 6) across tracheal rings three through five was performed for airway management during laryngoplasty. Tracheostomy tubes were maintained for 6 hours with low-pressure cuff inflation time limited to the first 1.5 hours. Cervical radiographs and tracheoscopy were performed preoperatively and at postoperative weeks 2, 4, 8, and 12. Ten of the 12 dogs were killed 12 weeks after tracheostomy.

RESULTS

There was no significant difference in preoperative and postoperative tracheal diameter or change in endoscopic tracheal circumference at the tracheostomy site when dogs were compared based on type of tracheotomy. Three dogs with horizontal tracheotomies had evidence of scar (web) within the tracheal lumen 12 weeks after surgery. All vertical tracheotomies had a mild, ventral, triangular deformity. Histologic examination of vertical tracheotomy sites showed complete restoration of the pseudostratified columnar epithelium. Horizontal tracheotomies healed with a single layer of columnar epithelium. Intraluminal scar was composed primarily of loose connective tissue.

CONCLUSION

Based on the results of this study, vertical tracheotomy shows more consistent healing compared with horizontal tracheotomy after short-duration tracheostomy. No evidence was found to support the preferential recommendation of horizontal tracheotomy for short-duration tracheostomy airway management.

Contamination and infection of fractures resulting from gunshot trauma in dogs: 20 cases (1987-1992)

Medical records of 20 dogs with gunshot fractures were reviewed to determine the prevalence of preoperative contamination and postoperative osteomyelitis. Fractures were repaired primarily by application of a bone plate (n = 16) or external fixator (n = 2) in buttress fashion or application of interfragmentary screws and pins (n = 2). In 17 dogs, an autogenous bone graft was also used. Results of bacteriologic culture of swab specimens obtained intraoperatively for 15 of the 16 dogs that received antimicrobials preoperatively and for all 4 dogs that did not receive antimicrobials preoperatively were negative. Three dogs developed osteomyelitis at 6, 8, and 10 weeks following surgery; for all 3, results of bacteriologic culture of specimens obtained intraoperatively had been negative. Fracture healing was uncomplicated in the remaining dogs (mean follow-up time, 23 months; range, 2 to 58 months). Despite the potential for contamination associated with gunshot trauma, results indicated a low prevalence of preoperative fracture contamination and postoperative osteomyelitis. These results imply either a low contamination rate or treatable contamination of the perifracture area.

Updated management strategy for patients with cervical osteophytic dysphagia

Anterior cervical osteophytes impinging upon the pharynx or esophagus constitute a rare cause of dysphagia. In severe cases, surgical removal of these osteophytes can provide symptomatic relief. We describe a patient of this type who failed to improve postoperatively, only to be found subsequently to have a carcinoma of the base of the tongue. To assist other clinicians in evaluating similar patients, and also to emphasize the great utility of modern radiologic techniques in these cases, we propose a diagnostic algorithm that incorporates magnetic resonance or computerized tomographic imaging.

Acanthosis Nigricans among Native Americans: an indicator of high diabetes risk

Prevalence of the skin lesion acanthosis nigricans was determined in two tribal communities in Texas and Nebraska. Thirty-eight percent of the Alabama-Coushatta tribe of Texas had acanthosis nigricans. Nineteen percent of Omaha and Winnebago tribal children had the skin lesion; the youngest children had the least acanthosis nigricans. Among weight-matched Alabama-Coushatta, fasting insulin concentrations were twofold higher in subjects with the lesion. It was concluded that acanthosis nigricans is highly prevalent among Native Americans and that its presence suggests insulin resistance. Thus, it may identify those with the highest risk for non-insulin-dependent diabetes mellitus in this population.

Type III omega-agatoxins: a family of probes for similar binding sites on L- and N-type calcium channels

The peptide omega-agatoxin-IIIA (omega-Aga-IIIA) from venom of the funnel web spider Agelenopsis aperta is the only known agent that blocks L-type and N-type Ca channels with equal high potency (IC50 < or = 1 nM). From the same venom, we have purified and sequenced a family of peptides which are homologous to omega-Aga-IIIA but vary over 100-fold in their relative affinity for L-type versus N-type Ca channels. One of these, omega-Aga-IIIB, is 76 amino acids long and identical to omega-Aga-IIIA in 66 positions. We identified two other similar peptides, omega-Aga-IIIC and omega-Aga-IIID, as well as one single amino acid variant of omega-Aga-IIIA and two of omega-Aga-IIIB. The type III omega-agatoxins exhibit similar but distinct activities on voltage-gated Ca channels. omega-Aga-IIIA, omega-Aga-IIIB, and omega-Aga-IIID are nearly indistinguishable in their actions at the insect neuromuscular junction (no effect at 0.1 microM), on atrial T-type Ca channels (no effect at 0.5 microM), and in two assays for synaptosomal Ca channels: they are nearly equipotent inhibitors of 125I-omega-conotoxin GVIA binding to rat brain synaptic membranes (IC50 = 0.17-0.33 nM) and blockers of the K(+)-induced 45Ca2+ influx into chick brain synaptosomes (omega-Aga-IIIB, 1.2 nM; omega-Aga-IIIA, 2.4 nM). In contrast, omega-Aga-IIIA is a better blocker of locust Ca channels (IC50 approximately 10-50 nM) than is omega-Aga-IIIB. Finally, although omega-Aga-IIIA, omega-Aga-IIIB, and omega-Aga-IIID all block atrial L-type Ca channels, omega-Aga-IIIA is over 100-fold more potent. Thus, although type III omega-agatoxins appear to recognize a binding site common to L- and N-type Ca channels, omega-Aga-IIIB and omega-Aga-IIID identify differences between the two channels.