Biomedical subjects

A Bahoric

Publications and source records attributed to A Bahoric.

At least 19 recordsLinked to original sources

PubMed2001

Aerosolization of epidermal cells with fibrin glue for the epithelialization of porcine wounds with unfavorable topography.

Aerosolized epidermal cell suspension was previously found to be effective for the epithelialization of full-thickness wounds. This suspension is less expensive than and requires a shorter preparation time than the currently used cultured epithelial autografts. Still, convex and irregular wounds present unfavorable conditions for homogenous dispersion of the aerosolized cell suspension. The authors hypothesized that the addition of fibrin glue to the aerosol of cells would reduce cell movement and ensure homogenous dispersion of the cells, thereby promoting wound epithelialization. The objectives of the study were to evaluate the healing of wounds with unfavorable topography after autotransplantation of an epidermal cell aerosol with and without fibrin glue. Six Yorkshire piglets were studied. An epidermal suspension was made from full-thickness groin skin. Dispase was used to separate the epidermis from the dermis, and trypsin was used to separate the epidermal cells from one another. Twenty-four hours later, full-thickness wounds with unfavorable topography were created adjacent to the vertebral column of six pigs. Twelve wounds were treated with an aerosol of epidermal cell suspension mixed with fibrin glue (study group), and 12 wounds were treated with the same suspension without the fibrin glue (control group). The percentages of total wound contraction and the epithelialized and nonepithelialized areas were evaluated 1, 2, 3, and 4 weeks after aerosolization. The histologic characteristics of the newly formed skin were examined by light microscopy using slides stained with hematoxylin and eosin. Study wounds were characterized by central epithelialization, whereas control wounds were characterized by peripheral epithelialization. Study wounds contracted at a slower rate than control wounds, but wound size was the same in both groups after 4 weeks. The addition of fibrin glue facilitated epithelialization: Study wounds showed 75.5 +/- 22.4 percent (mean +/- SD) and 94.2 +/- 8.8 percent epithelialization after 3 and 4 weeks, respectively, compared with 46.3 +/- 9.5 percent and 47.9 +/- 13.1 percent epithelialization of the control wounds at the same times. These differences between the study and control groups were statistically significant (p < 0.001, paired t test). The addition of fibrin glue to an aerosol of epidermal cells significantly enhances the epithelialization of wounds with unfavorable topography in pigs.

Administration, Topical↗

PubMed1997

Experimental trial of balloon-expandable, metallic Palmaz stent in the trachea.

OBJECTIVE: To determine the effect of the Palmaz stent, which has been successfully used to relieve airway obstruction in a small group of children, on the normal and operated on animal trachea. DESIGN: In this experimental trial, stents were placed bronchoscopically in the thoracic tracheae of 4 groups of 50 anesthetized cats. The cats in group 1 (adults, n = 10) and group 2 (kittens, n = 10) had normal tracheae; the cats in group 3 (adults, n = 15) underwent horizontal tracheal incision and closure; and the cats in group 4 (adults, n = 15) underwent pericardial patch tracheoplasty. In group 3 and 4, the stents were inserted in 10 cats and 5 cats served as controls. Stents were inflated to a 15-mm diameter in group 1 and an 8-mm diameter in the other groups. Half of the animals with stents were killed 5 weeks after the procedure, and the others, 10 weeks after the procedure. SETTING: The Hospital for Sick Children, Toronto, Ontario. RESULTS: In group 1, 1 animal died of tracheal perforation. A mild cough was noted in 15 of the 39 cats with stents. In group 4, 3 cats had difficulty eating and lost weight. The results of esophagoscopy excluded esophageal inflammation or obstruction in these 3 animals. The results of bronchoscopy indicated a nonobstructing rim of granulation tissue at the end of the stent in 15 of 20 cats in groups 1 and 2 and 17 of 20 cats in groups 3 and 4 and at the repair site in all animals with stents from groups 3 and 4. The results of autopsy indicated the cross-sectional area at the site of the stent was greater than normal in group 1 (P < .003) and smaller than the normal trachea at the site of the tracheoplasty in group 4 controls without stents (P < .02); however, the cross-sectional area at the tracheoplasty site with the stent was not smaller (P < .13). The results of histologic examination indicated a mild inflammatory reaction, with granulation tissue in all animals with stents, but in group 1, with overexpanded stents, the reaction was more severe, with epithelial ulceration, fibrosis, and sealed-off perforations in most animals. In group 3, the tracheae with stents had significantly more inflammatory reaction, granulation tissue, and epithelial damage than the controls without stents. CONCLUSIONS: The Palmaz stent provokes an inflammatory reaction in the normal trachea and the trachea recently operated on. With the exception of the group 1 animals with overexpanded stents, this reaction is clinically insignificant. The Palmaz stent is able to maintain a normal lumen size after pericardial tracheoplasty in cats.

Angioplasty, Balloon↗

PubMed1994

Tracheoplasty without stent, using preshaped cryopreserved cartilage allografts in neonatal pigs.

The management of congenital and acquired laryngotracheal stenosis in children often includes tracheoplasty with different materials. Autologous cartilage is the most commonly described graft for tracheal reconstruction. In 12 1-week old piglets a tracheal defect was created and repaired using cryopreserved allografts sculpted before preservation into a newly designed shape. In half the animals (group 1), a free pericardial autograft was interposed on the luminal surface of the cartilage graft. A stent was not used in any animal. The animals grew normally and were killed after 2 months. The grafted tracheas showed maintenance of their structural support, and no evidence of narrowing of the grafted area in comparison to the trachea above the graft. The lumen was lined by ciliated respiratory epithelium. There was no identifiable pericardium at the time of sacrifice and no differences between the two groups. This study shows that in neonatal pigs, cartilage allografts, sculpted before cryopreservation, are a suitable alternative to autografts to cover tracheal defects and can be used without stenting. No advantages were identified when interposing a free pericardial graft.

Animals↗

PubMed1992

Repair of long tracheal defects with cryopreserved cartilaginous allografts.

Tracheoplasties with various autografts (cartilage, periosteum, pericardium) have been used in the treatment of long-segment tracheal stenosis. Previous studies have shown that cartilage allografts survive transplantation on a long-term basis in various sites of the body. In this study we set out to determine if cryopreserved cartilage and cryopreserved tracheal allografts would survive when used to cover tracheal defects in animals. A rectangular defect (2.8 +/- 0.3 cm long and incorporating 50% of tracheal circumference) was created in the thoracic trachea of 18 piglets. The defect was covered with the excised tracheal segment in 6 (group A, control group), with a cryopreserved tracheal allograft in 6 (group B), and with a cryopreserved cartilage allograft harvested from the scapula in 6 (group C). The allografts were cryopreserved, by a standard slow-freezing technique, at -80 degrees C for more than 21 days. All animals survived the grafting procedure and were killed after 2 months. None had signs of airway obstruction. Using the trachea above the defect as the standard, the mean sagittal narrowing of the airway in the repaired trachea was 0.4 mm in group A, 0.7 mm in group B, and 0.6 mm in group C; the coronal diameter in normal and grafted trachea was similar. The lumen of all grafts was lined by regenerating respiratory epithelium, and cilia were seen in many. Some cartilage was reabsorbed in group A and B but cartilage islands were present in all. In group A, reabsorption of cartilage was minimal. These findings suggest that segments of trachea or cartilage allografts can be cryopreserved, stored, and, subsequently, used when necessary for tracheoplasty.

Animals↗

PubMed1991

Successful tracheal autotransplantation with a vascularized omental flap.

A major problem in tracheal transplantation is the restoration of an adequate vascular supply to the transplanted trachea. In 12 piglets, a segment (6 rings) of thoracic trachea was removed and the excised segment was then sutured back in place. In 9 animals (group A), a vascularized omental flap was wrapped around the autotransplanted trachea. In the other 3 pigs (group B), the omentum was not used. Eight of 9 group A pigs were killed, 1 or 2 months later, having had no signs of airway obstruction; the 9th pig was killed after 14 days because of airway obstruction. The 3 pigs in group B were killed after 11 to 13 days because of progressive respiratory obstruction. In the 8 asymptomatic pigs in group A, the omental flap was viable and tracheal growth was normal with no differences in diameter between normal and autotransplanted trachea. Histologically intact cartilage was lined with respiratory epithelium. In the one group A pig who was killed early, the omental flap was necrotic. In this pig and in the 3 group B animals, extensive tracheal necrosis and nonviable cartilage were observed. These findings indicate that in the pig, a 6-ring segment of trachea can be transplanted with vascularization provided by an omental flap.

Animals↗

PubMed1990

Reduced tracheal growth after reconstruction with pericardium.

Four groups of piglets were used to test the use of pericardium and periosteum as free grafts in the repair of full thickness cervical tracheal defects. Pericardium provided an airtight, rapidly healing graft, but did not give sufficient structural rigidity to prevent narrowing and growth failure at the graft site. Composite grafts of pericardium and periosteum were also unsatisfactory, in that the periosteum failed to produce enough bone to prevent collapse of the graft. Since previous studies have shown that periosteal grafts result in good bone formation when applied alone or as an extramucosal support, it is concluded that the osteogenic potential is dependent on the available blood supply and speed of revascularization. It appears that the presence of pericardium in the composite grafts may have inhibited this property.

Animals↗

PubMed1989

Continuous flow peritoneal dialysis in pigs, using a silicone rubber double lumen catheter.

Continuous flow (CFPD) and intermittent (IPD) peritoneal dialysis were compared in pigs, using a double lumen silicone rubber peritoneal dialysis catheter. For CFPD, after instillation of 30 ml/kg into the peritoneal cavity, dialysate was continually infused and drained at approximately 25 ml/kg/h. A dwell volume of 30 ml/kg was also used for IPD. Similar length cycles of each technique were compared in Experiment 1. In Experiment 2 total solute clearance and ultrafiltration achieved over two consecutive IPD cycles were compared with CFPD of a similar duration. The catheter functioned well with few complications. In Experiment 1, CFPD produced greater ultrafiltration and significantly improved the clearance of urea, potassium and phosphate compared to IPD. No significant difference between the techniques was observed in Experiment 2. Our data suggest that for CFPD to retain its advantage over IPD intermittent complete drainage of the peritoneal cavity may be necessary.

Animals↗

PubMed1988

A new intratracheal stent for tracheobronchial reconstruction: experimental and clinical studies.

An intraluminal tracheal stent (ITS) was used experimentally in rabbits and piglets, as well as clinically in infants with tracheal stenosis, to facilitate airway reconstruction. The ITSs were constructed of stainless-steel springs covered with silicone rubber. They were implanted in seven piglets (6 to 8 kg), five rabbits (3 to 5 kg) and three infants. No animals developed severe respiratory distress and all appeared to tolerate the ITS. Postmortem examinations 1 to 8 weeks after surgery showed (1) loss of stent fixation (one pig), (2) increased tracheal secretions, (3) pneumonia (one pig, two rabbits), and (4) focal squamous metaplasia of tracheal mucosa. Stents used to treat three infants (2 to 5 months of age) with complex tracheobronchial stenosis were placed at the time of periosteal tracheoplasty in two. Recurrent stenosis necessitated a second tracheoplasty and stenting in one, and a long tracheostomy tube and balloon dilatations in the other. The third child had endoscopic stent insertion to alleviate severe airway collapse after esophageal tracheoplasty. The child died from progressive respiratory failure after stent dislodgment. Although the stents were well tolerated in animals and they enhanced critical ventilation of all pulmonary lobes in infants after tracheal reconstruction, certain modifications such as alternative methods of fixation, accommodation for tracheal growth, and reduction in tissue reactivity are necessary before further use of the ITS can be advocated.

Animals↗

PubMed1988

Congenital tracheal stenosis: a review of 22 patients from 1965 to 1987.

Twenty-two infants with congenital tracheal stenosis (CTS) were treated in our hospital between 1965 and 1987. Diagnosis was confirmed by endoscopic and radiographic methods. Patients had a spectrum of tracheobronchial lesions from localized stenosis to more complex deformities involving the carina and bronchi. Other anomalies were found in all patients with the occurrence of vascular slings or rings in 11 patients (50%). Six infants treated nonoperatively died from severe CTS and other lethal anomalies. Five of 16 patients (31%) treated surgically survived. Localized CTS in four cases was treated by dilatation, tracheostomy, or tracheal resection with primary anastomosis (two survivors, 2 non-survivors). Funnel-shaped deformities and extensive tracheobroncial stenosis were treated by tracheal reconstruction using a variety of autogenous tissue and prosthetic grafts (three survivors, nine non-survivors). The overall mortality was 77%. A new intratracheal stent was used in two patients. The stent was a flexible steel spring covered with a silicone rubber sheath. In one patient, it was placed within the trachea at the time of repair and removed later with the bronchoscope. A stent was used in a second patient with intermittent airway obstruction following an esophageal tracheoplasty. In this case, the device failed to alleviate the obstruction, and the infant expired from progressive respiratory failure. Issues of importance in the management of infants with CTS are: (1) adequate evaluation of the tracheobronchial tree, (2) awareness that tracheobronchography may precipitate further respiratory decompensation, (3) assessment of vascular and other anomalies requiring surgical correction, and (4) selection of an appropriate therapeutic approach.

Female↗

PubMed1987

Tracheomalacia: an experimental animal model for a new surgical approach.

Tracheomalacia was created by removing the posterior 50% of the circumference of eight cartilage rings (5-6 cm in length) from the intrathoracic trachea in each of 12 piglets while leaving the mucosa intact. In 6 animals an autologous, free tibial periosteal graft was applied over the defect (graft group). The remaining 6 piglets served as the control group. In all animals, a silastic stent was left in the trachea for 2 weeks to prevent immediate tracheal collapse. The presence of tracheomalacia was assessed 6-8 weeks after surgery. At bronchoscopy total tracheal collapse during coughing occurred only in the controls. As the animals went from quiet breathing to coughing, mean intrathoracic pressure increased from 5 to 80 cm H2O in both groups, and average sagittal tracheal diameter decreased by 10% in the graft group and 71% in the controls. During coughing, mean resistance to airflow across the defect increased by 0.005 +/- 0.002 cm H2O/liter/min in the graft group, by 0.083 +/- 0.96 cm H2O/liter/min in the controls (P less than 0.005), and by 0.027 cm H2O/liter/min at the same tracheal level in two normal pigs. At sacrifice 12 weeks postoperatively, bone and collagenized fibrous tissue had been produced by all grafts, without evidence of stricture. This study shows that experimentally induced tracheomalacia can be treated successfully by the application of an autologous periosteal tibial graft, which becomes incorporated into the weakened tracheal wall.

Airway Resistance↗

PubMed1987

Selective in situ pancreatic perfusion via chronic in vivo celiac artery catheterization.

A new technique to catheterize the celiac artery has been developed. This has opened the possibility for direct in vivo, in situ study of pancreatic endocrine cell function in a conscious experimental animal. The catheter is small, soft and placed without arterial ligation so that celiac artery, hepatic, splenic, and pancreatic blood flows were essentially not compromised. Arterial vessel integrity, absence of inflammation, and thrombosis as well as catheter patency were achieved for periods exceeding eight months. Metabolically and hormonally, the presence of the catheter had no effect on the fasting status. However, we found somewhat lower glucose levels and higher insulin levels in the response to oral glucose challenges after catheterization, but these differences were statistically not significant. Glucose loads of 50 mg/kg (0.75 g) administered directly to the pancreas via the celiac artery produced peak insulin levels similar to peripheral glucose loads some tenfold larger. We suggest that this technique may be useful to selectively study the first-pass pancreatic response to a variety of hormones, drugs or metabolic substrates.

Administration, Oral↗

PubMed1987

Long-term functional results of prosthetic airway splinting in tracheomalacia and bronchomalacia.

The long-term functional results of splinting a collapsing major airway with a silastic Marlex mesh prosthesis were assessed. Six patients in whom follow-up has been longer than 4 years (mean 5.3 years) were studied. The prosthetic semirigid splints had been implanted in five children with tracheomalacia and one with bronchomalacia. Mean age at the time of airway splinting was 4 years (range 6 months to 8 years). At their last clinical evaluation, all six children were leading normal active lives. Three had mild respiratory symptoms not related to the splinting. The only long-term complication was a serous effusion that developed around the splint and compressed the trachea in one child 2 years postoperatively. Tracheal fluoroscopy, barium swallow, and computed tomography scans of the trachea in five patients demonstrated satisfactory tracheal caliber without airway collapse during expiration and coughing. Pulmonary function testing showed a mild increase in airway resistance in one child who had had a tracheostomy. These results demonstrate that the application of composite synthetic graft to a segment of a malacic airway in young patients can provide long-term relief from airway collapse without compromising airway growth.

Airway Obstruction↗

PubMed1987

Physiological relationships between growth hormone level, glycemia and metabolic control in dogs.

This study was undertaken to explore the physiological relationships between fasting glycemia, antecedent glycemic control and fasting growth hormone levels in pancreatectomized dogs. In contrast to other studies, we used continuous intravenous infusions of insulin in an attempt not only to normalize fasting plasma glycemia but also to eliminate the characteristic fluctuations of diabetes usually encountered in the postprandial and postabsorptive periods. For comparison, a similar group of healthy animals served as normal controls. In the healthy dogs, fasting growth hormone (GH) levels were stable and well within normal limits for this species, demonstrating an overall mean +/- SD of 2.50 +/- 0.46 ng/ml. In the pancreatectomized group as a whole, the fasting GH levels were significantly elevated (4.63 +/- 2.42 ng/ml, P less than 0.01) and significantly (P less than 0.001) more variable than in the controls. Multiple regression and analysis of variance confirmed the expected significant positive correlation between fasting GH and fasting plasma glucose levels, but also elucidated a heretofore unknown direct relationship between fasting GH levels and the preceding instability of glycemic control.

Animals↗

PubMed1986

The metabolic and hormonal adaptations of normal dogs to long-term exogenous sulfated insulin infusions.

Hyperinsulinism frequently accompanies glucose normalization in type I diabetes but the long-term consequences of this exaggerated hormonal state are not known. To study this condition, normal dogs received constant exogenous sulfated insulin infusions for prolonged periods up to 43 weeks. During the interval and inspite of prevailing postabsorptive and fasting hypoglycemia, overt resistance to the infused insulin or loss of sensitivity did not occur. In counterring the imposed fasting hyperinsulinemia and the resulting hypoglycemia, fasting pancreatic glucagon levels rose while the fasting levels of several glucogenic precursors (lactate, pyruvate, and alanine) decreased. Fasting free fatty acid (FFA) levels were suppressed, but beta-hydroxybutyrate (beta-OHB) levels were unchanged. Body weight did not change. Most remarkably, all changes measured in the fasting levels of the hormones and metabolites reverted to normal following the cessation of exogenous sulfated insulin infusion. In addition to the hormonal and metabolite adaptations invoked by chronic exogenous hyperinsulinism in the fasting state of these normal dogs, there were interesting responses to their usual mixed meals. Of particular interest in this regard were the plasma glucose, insulin, and FFA diurnal profiles. First of all, a definite and unusual postprandial glycemic excursion occurred. Second, insulin levels were elevated some sixfold, and rather unresponsive to the meal in general. Inspite of the depressed fasting FFA levels and the absence of a postprandial rise in insulinemia, FFA showed a distinct fall after the meal. Whether the sulfated insulins infused were of the bovine or porcine species of origin made no discernible difference.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗

PubMed1986

A central venous (W-B-W) catheter for multipurpose vascular access in children.

A central venous (W-B-W) catheter has been developed for vascular access in children of all ages and sizes. The catheter design and implantation technique permit nonsurgical bedside adjustment of catheter position and ease of removal. Multiple possible uses include intravenous fluid administration, blood sampling, central venous pressure monitoring, and plasma exchange therapy in addition to hemodialysis. Twenty-seven W-B-W catheters were placed in 24 patients in a 12-month period. The catheter provided adequate blood flow for hemodialysis. Seven catheters were removed nonelectively in five patients. One episode of catheter-associated sepsis occurred after renal transplantation in a patient on immunosuppressive therapy. It is concluded that the W-B-W catheter is a relatively safe, multipurpose, pain-free acute vascular access for children, which may also suffice for chronic hemodialysis.

Adolescent↗

PubMed1986

Pumped intravenous insulin in experimental diabetes.

We infused experimentally diabetic animals continuously with exogenous insulin for periods of up to 324 days. Direct intravenous infusions from a prototype of an implantable device were used to explore whether this route can achieve repetitive control of fasting glycaemia within normal limits, here defined as being between 60 and 120 mg/dl. Fasting plasma glucose levels were controlled by simply adjusting the rate of exogenous insulin delivery when the observed level was outside the range of 100-120 mg/dl. An analysis of the results obtained indicated that 73% (427/591) of the fasting plasma glucose levels were within these normal limits. Remarkably, only 1% (6/591) of them were below 60 mg/dl, the lowest being 42 mg/dl. Hyperglycaemia above 150 mg/dl was seen in 11% (67/591) of the observations. However, all (6/6) of the hypoglycaemic episodes and most, 87% (58/67), of the hyperglycaemic episodes were of an accountable nature secondary to mechanical failures, electrical failures, methodologic or other problems encountered episodically during the long course of these studies. Two parallel control groups of experimentally diabetic animals received the same diet and were treated prospectively by daily subcutaneous injections for periods up to 224 days. The goal of this treatment was to attain metabolic control by either "conventional" or "intensified" injection methods. To these ends, fasting plasma glucose levels were measured on a daily basis (5 days/week) in both groups, and also at intervals postprandially in the intensively controlled group. These data were used to adjust insulin dosages. An analysis of the results indicated that only 24% (148/617) of the fasting plasma glucose levels were within the normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

A new model of tracheal stenosis and its repair with free periosteal grafts.

Stenosis of 50% to 80% of the cervical or thoracic tracheal lumen was created in 17 piglets by encircling the trachea with silicone rubber sheet for 3 to 19 days (median 14 days). In 13 animals thoracic tracheal stenosis was repaired by longitudinal incision and insertion of a free tibial periosteal graft into the defect. An omental pedicle graft was applied to the surface of the free periosteal graft to augment its blood supply in three of these animals. An endotracheal silicone rubber splint was left in place for 2 to 3 weeks after the operations. Four animals served as untreated controls. In 12 of 13 piglets respiratory obstruction was relieved. One repair failed because of graft necrosis. In two animals put to death 1 month and 2 months later, stenosis was absent and the grafts showed variable ossification. The luminal surface had epithelialized. In nine of 10 animals put to death 3 months after the operation, tracheal cross-sectional areas had doubled, stenosis and granulation tissue were absent, and all the grafts had ossified and epithelialized. A mild stenosis (24%) developed over a 2 mm length in one animal and the graft had not ossified. The omental pedicle graft did not improve vascularization of the free periosteal graft. These studies describe a model of tracheal stenosis that can be used to assess various methods of repair. The results indicate that tracheal stenosis can be successfully treated by incision and insertion of a free periosteal graft into the defect.

Animals↗

PubMed1985

The successful reconstruction of thoracic tracheal defects with free periosteal grafts.

A defect was created in the thoracic trachea in nine piglets (10 kg) by excising a segment from the entire thoracic trachea proximal to the right upper lobe bronchus (3 to 3.5 cm in length) and 30% of the circumference in width (1 to 1.5 cm). The defect was repaired with a free tibial periosteal graft (FPG) and in four piglets an omental pedicle graft (OPG) was applied to the surface of the FPG. An internal tracheal splint was inserted for 12 to 16 days to support the repair and prevent air leak. The splints were removed bronchoscopically. None of the pigs developed signs of airway obstruction at any stage following the repair. Eight were killed 3 months postoperatively when four to six times their original weight. One pig died on the 18th postoperative day of unknown cause. The tracheas were removed, x-rayed, and examined grossly and histologically. The results demonstrated normal tracheal growth with absence of either stenosis, collapse, or granulation tissue. All grafts were viable, bone formation was present, and the lumenal surfaces were lined with columnar and respiratory epithelium. The OPG did not improve vascularization of the FPG. This model suggests that tracheal stenosis in children may be surgically corrected by simply incising the stenotic segment longitudinally and enlarging the tracheal diameter by inserting a FPG into the defect.

Animals↗