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Biomedical subjects

G C Lantz

Publications and source records attributed to G C Lantz.

33 records · Page 2Linked to original sources
PubMed1988

Transsphenoidal hypophysectomy in the clinically normal dog.

Pituitary function and short-term clinical effects after transsphenoidal hypophysectomy were investigated in clinically normal dogs. In study I, 8 dogs were given polyionic fluids IV during the first 12 hours after surgery. In study II, 4 dogs were given polyionic fluids IV and glucocorticoid supplementation for 7 days. Pituitary function was assessed by evaluating basal ACTH concentrations and results of a growth hormone stimulation test before and 1 and 12 weeks after hypophysectomy, an ACTH stimulation test, a thyrotropin-releasing hormone-stimulation test, and a modified water deprivation/vasopressin response test before and 1, 4, 8, and 12 weeks after hypophysectomy. Gross and histologic evaluations of the surgery site, thyroid and adrenal glands, and skin were done at 12 weeks after surgery. Four dogs from study I died within 27 hours after hypophysectomy. Postmortem examinations of these dogs revealed liver and lung congestion compatible with circulatory collapse. None of the dogs in study II died. For the surviving dogs in both studies, diabetes insipidus developed immediately after hypophysectomy and resolved within 2 weeks. Hypernatremia also developed immediately after hypophysectomy and resolved by 1 week. Production of ACTH was evident at 1 and 12 weeks after hypophysectomy in all dogs, and results of ACTH stimulation tests after surgery were not notably different from results obtained before surgery. Results of thyrotropin-releasing hormone stimulation and growth hormone-stimulation tests supported the diagnosis of hypothyroidism and hyposomatotropism attributable to hypophysectomy. Histologic examination revealed thyroid atrophy, epidermal and dermal atrophy, and normal adrenal glands in all dogs and remnants of the hypophysis in 2 dogs from study I.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1987

Partial mandibulectomy for treatment of mandibular fractures in dogs: eight cases (1981-1984).

Partial mandibulectomy was performed in 8 dogs with open or infected mandibular fractures (3 second degree and 5 third degree) because of economic restriction, osteomyelitis, or severe bone and soft tissue injury. Six dogs ate voluntarily by the second day after surgery, and 2 dogs required pharyngostomy tube feeding for 2 to 6 days. Complications included oral wound dehiscence (3 dogs), shifting of the mandible toward the operated side (6 dogs), and drooping of the tongue (2 dogs). Slight malocclusion was of no consequence, and all dogs were eating normally at follow-up evaluations (10 days to 24 months; median, 13 months). Mandibular function was maintained in all dogs.

Animals↗
PubMed1987

Intermittent open-mouth locking of the temporomandibular joint in a cat.

Impingement of a mandibular coronoid process on the ipsilateral zygomatic arch resulted in intermittent open-mouth locking of the temporomandibular joint in a 3-year-old male cat. Radiographic evaluation of the temporomandibular joints did not reveal abnormalities. Locking could not be recreated by manipulation of the mandible in the anesthetized cat, but the left coronoid process briefly contacted the left zygomatic arch. Excision of the rostroventral portion of the left zygomatic arch failed to stop the locking episodes; however, later excision of the rostroventral portion of the right zygomatic arch did prevent recurrence of locking.

Animals↗
PubMed1986

Intermittent open-mouth lower jaw locking in five dogs.

Intermittent open-mouth lower jaw locking was documented in 5 dogs. In contrast to what has been reported in other cases, pronounced radiographic abnormalities in the temporomandibular joints were not observed. In 4 of the dogs, locking episodes started at a later age (35 to 83.5 months) than had been reported by others (6 to 22 months). Duration and frequency of locking were variable. Lateral shifting of the jaw and lack of neurologic deficits indicated a temporomandibular joint abnormality. Excision of the rostroventral portion of the involved zygomatic arch prevented locking in all cases. This syndrome involves variable severity of temporomandibular joint dysplasia, which could account for the variable age of onset and random frequency of locking episodes.

Animals↗
PubMed1984

Pharmacokinetics and comparative nephrotoxicity of fixed-dose versus fixed-interval reduction of gentamicin dosage in subtotal nephrectomized dogs.

There is presently no consensus as to the relative safety of fixed-interval/reduced dose (FI) vs fixed-dose/increased interval (FD) dosage adjustment regimens for use in renal insufficiency. This study compared their nephrotoxic potential using gentamicin in beagle dogs with renal insufficiency secondary to subtotal surgical nephrectomy. Pharmacokinetic analysis in six dogs showed that this surgical procedure resulted in a decreased total body clearance of drug and a marginally contracted volume of the central compartment. An allometric analysis of gentamicin disposition in different species was used to derive a human-equivalent maximum canine nontoxic dose of 9 mg kg-1 day-1. Nephrotoxicity was detected by histopathologic analysis and changes in the pre- and post-drug treatment, creatinine clearance, and daily drug elimination rate constants. This allometric dose did not produce clinical toxicity in a control group of six dogs with intact kidneys given drug for 14 days. Dosage adjustments within the FI and FD groups were based on serum creatinine concentrations 10 days after surgery. Statistical analysis of morphological and functional parameters indicated that the FD method was significantly less toxic than the FI regimen.

Analysis of Variance↗
PubMedDate not supplied

Elastic modulus of prepared canine jejunum, a new vascular graft material.

The submucosal connective tissue of the jejunum has been shown to be suitable for use as a vascular graft in preliminary dog studies. To partially characterize the mechanical properties of this new graft material, longitudinal stress (sigma)-strain (epsilon)-data were obtained on 13 specimens of canine jejunum, stripped of its mucosal and external smooth-muscle layers. The ratio of stress to strain is the modulus of elasticity (E). It was found that the stress sigma-strain epsilon-data fitted the expression sigma = K epsilon alpha very well. For a typical specimen sigma = 2.69 x 10(6) epsilon 2.33. The modulus of elasticity (E = sigma 1-1/alpha K1/alpha) was found to increase with increasing stress, ranging from about 2,000 to 9,000 mmHg. For the average specimen E = 573 sigma 0.57, where sigma is in mmHg, (1 mmHg = 133.3 Pascals).

Animals↗
PubMedDate not supplied

The effect of elevated intracranial pressure on the vibrational response of the ovine head.

Although potentially fatal increases in intracranial pressure (ICP) can occur in a number of pathological conditions, there is no reliable and noninvasive procedure to detect ICP elevation and quantitatively monitor changes over time. In this experimental study, the relationships between ICP elevation and the vibrational response of the head were determined. An ovine animal model was employed in which incremental increases in ICP were elicited and directly measured through intraventricular cannulae. At each ICP increment, a vibration source elicited a flexural response of the animal's head that was measured at four locations on the skull using accelerometers. Spectral analysis of the responses showed changes in proportion to ICP change up to roughly 20 cm H2O (15 mm Hg) above normal; a clinically significant range. Both magnitude and phase changes at frequencies between 4 and 7 kHz correlated well (gamma > 0.92) with ICP across the study group. These findings suggest that the vibrational response of the head can be used to monitor changes in ICP noninvasively.

Animals↗
PubMedDate not supplied

Effects of flunixin meglumine on dogs with experimental gastric dilatation-volvulus.

Gastric dilatation-volvulus (GDV) was created experimentally and maintained for 90 minutes in 16 anesthetized, mixed-breed dogs. After the GDV was corrected, normal saline solution (0.044 mL/kg intravenously [IV]) was administered to eight dogs (controls), and flunixin meglumine (2.2 mg/kg IV) was administered to eight dogs. Microspheres labeled with radioactive cobalt, scandium, tin, or niobium were injected intravenously at baseline (before GDV) and minutes 90, 100, and 270, respectively, to determine tissue blood flows. Plasma endotoxin and prostacyclin were measured at the same intervals. Electrocardiogram, mean arterial pressure, portal pressure, and cardiac output were recorded continuously. Dogs were euthanatized at minute 270 and necropsied. There was no significant difference between treatment groups for any measured variable at any time. Endotoxin levels increased significantly during GDV. Prostacyclin levels were lower in dogs treated with flunixin meglumine than in controls at minutes 210 and 270. Histopathologic findings were similar for all dogs and consistent with those associated with endotoxemia. Flunixin meglumine treatment did not alter cardiac indices or tissue blood flows significantly. However, elevation of prostacyclin was inhibited by flunixin meglumine, which suggested that continued effects of endotoxic damage might be attenuated or inhibited.

Animals↗
PubMedDate not supplied

Small intestinal submucosa as a vascular graft: a review.

Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventitia. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.

Animals↗
PubMedDate not supplied

Multiple risk factors for the gastric dilatation-volvulus syndrome in dogs: a practitioner/owner case-control study.

A study was conducted of 101 dogs (i.e., case dogs) that had acute episodes of gastric dilatation-volvulus (GDV) and 101 dogs (i.e., control dogs) with nonGDV-related problems. The control dogs were matched individually to case dogs by breed or size, and age. Predisposing factors that significantly (p less than 0.10) increased a dog's risk of GDV were male gender, being underweight, eating one meal daily, eating rapidly, and a fearful temperament. Predisposing factors that decreased the risk of GDV significantly were a "happy" temperament and inclusion of table foods in a usual diet consisting primarily of dry dog food. The only factor that appeared to precipitate an acute episode of GDV was stress.

Acute Disease↗
PubMedDate not supplied

A prospective study of survival and recurrence following the acute gastric dilatation-volvulus syndrome in 136 dogs.

Dogs (n = 136) with gastric dilatation-volvulus (GDV) syndrome were followed over time to measure recurrence and mortality rates and to identify prognostic factors. Thirty-three (24.3%) died or were euthanized during the first seven days. Of 85 cases that were followed for up to three years, nine (10.6%) cases each had a recurrence of GDV and seven (8.2%) cases died or were euthanized. The median survival times for cases that had gastropexies and those that did not were 547 and 188 days, respectively. Depressed or comatose cases on admission were three and 36 times, respectively, more likely to die than alert cases, while cases with gastric necrosis were 11 times more likely to die.

Acute Disease↗
PubMedDate not supplied

Penile prolapse and urethral obstruction secondary to lymphosarcoma of the penis in a dog.

A 5-year-old Chihuahua presented for clinical signs of dysuria and penile prolapse. Radiographic studies identified a urethral obstruction distal to the junction of the proximal and middle third of the os penis that appeared to be secondary to swelling of the penis. Penile resection combined with a scrotal urethrostomy was performed. Histopathological examinations of tissue samples of the body of the penis revealed lymphosarcoma. Lymphosarcoma of the penis is a rare finding in all species. It can occur as a primary tumor of the penis in dogs. Penile lymphosarcoma should be considered in the differential diagnosis of dogs affected with penile prolapse and dysuria.

Animals↗
PubMedDate not supplied

Mechanical remodeling of small-intestine submucosa small-diameter vascular grafts--a preliminary report.

Small-intestine submucosa (SIS) is cell-free, 100-mu-thick collagen derived from the small intestine. It has been used as a vascular graft and has the highly desirable ability to be remodeled to become histologically indistinguishable from native adjacent artery. To date there has been limited reporting of its preimplantation and explant mechanical properties as a vascular graft. In this study, compliance, elastic modulus, and burst pressure were measured on preimplant-tested 5- and 8-mm SIS grafts and two 60-day remodeled grafts. Seven prefabricated grafts were implanted in the carotid (n = 7) in dogs, which were sacrificed after 55-63 days. The animals (n = 4) weighed from 22 to 27 kg. One dog received a unilateral carotid graft, and 3 dogs received bilateral carotid grafts. The fabrication technique employed hand-suturing with either nonresorbable or resorbable sutures. None of the grafts had a patency failure. Angiograms taken at 1 month and just before explantation showed uniform flow and no dilation. At the time of explantation, all carotid grafts were found to be encased in fibrous tissue. The grafts made with nonresorbable sutures showed thicker tissue growth at the suture line compared with those made with the resorbable sutures. Along the suture line, the grafts made with resorbable sutures exhibited a more natural color than those sutured with nonresorbable sutures. When the explanted carotid grafts were slit open, the lumen was white, shiny, and glistening. The grafts sutured with nonresorbable sutures exhibited small areas of fibrin and red blood cells when the suture was within the lumen. The resorbable-sutured grafts did not exhibit this response. The mean compliance (percent diameter increase for a pressure rise from 80 to 120 mm Hg) was on average 4.6% (range, 2.9%-8.6%) for the 5-mm preimplant-tested grafts. For the 8-mm preimplant-tested grafts, the increase in diameter for the same pressure rise was 8.7%, on average (range, 7.2% to 9.5%). For comparison, the small-diameter SIS graft at the time of implantation was about one half as compliant as the adjacent dog carotid artery, about 4 times more compliant than a typical vein graft, and more than 10 times more compliant than synthetic vascular grafts. The compliance measured on two 60-day carotid grafts was 10.5% and 7.2%, respectively. This is midway between the original compliance value and the compliance of a typical canine carotid artery (14%), indicating that mechanical remodeling occurred. The modulus of elasticity (E) increased exponentially with increasing pressure according to E = E0e alpha P, where E0 is the zero-pressure modulus and alpha is the exponent that describes the rate of increase in E with pressure; the unit of measure for variables E, E0, and P is g/cm2. The mean value for E0 was 4106 gm/cm2 (range, 1348-5601). The mean value for alpha was 0.0059 (range, 0.0028-0.0125). At 100 mm Hg, the mean value for E was 8.03 x 10(6) dynes/cm2 (range, 4.95-15.7 x 10(6)). For a 60-day SIS graft implant, the elastic modulus at 100 mm Hg decreased from a high value at implant time to twice that of a typical native canine carotid artery. The mean burst pressure for 5.5-mm grafts was 3517 mm Hg (range, 2069-4654). The burst pressure of the remodeled carotid grafts averaged 5660 mm Hg. The burst pressure for a typical carotid artery is about 5000 mm Hg. The results of this preliminary study complement those of previous SIS-vascular-graft studies and add a new factor, namely that the mechanical properties of the remodeled graft approach those of the vessel it replaces.

Animals↗