Triglycerides cross the blood-brain barrier and induce central leptin and insulin receptor resistance

OBJECTIVE

Resistance at the brain receptors for leptin and insulin has been associated with increased feeding, obesity and cognitive impairments. The causal agent for central resistance is unknown but could be derived from the blood. Here we postulate whether hypertriglyceridemia, the major dyslipidemia of the metabolic syndrome, could underlie central leptin and insulin resistance.

DESIGN

We used radioactively labeled triglycerides to measure blood-brain barrier (BBB) penetration, western blots to measure receptor activation, and feeding and cognitive tests to assess behavioral endpoints.

RESULTS

Human CSF was determined to contain triglycerides, a finding previously unclear. The radioactive triglyceride triolein readily crossed the BBB and centrally administered triolein and peripherally administered lipids induced in vivo leptin and/or insulin resistance at hypothalamic receptors. Central triolein blocked the satiety effect of centrally administered leptin. Decreasing serum triglycerides with gemfibrozil improved both learning and memory inversely proportionate to triglyceride levels.

CONCLUSIONS

Triglycerides cross the blood-brain barrier rapidly, are found in human cerebrospinal fluid, and induce central leptin and insulin receptor resistance, decreasing satiety and cognition.

Screening for Vitamin D Deficiency in Black Americans: Comparison of Total, Free, Bioavailable 25 Hydroxy Vitamin D Levels with Parathyroid Hormone Levels and Bone Mineral Density

OBJECTIVES

There is debate surrounding the adequacy of total and free 25 hydroxy vitamin D [25(OH)D] levels in black Americans who have inherently high bone mineral density [BMD] and low serum concentration of vitamin D binding proteins [VDBP].

DESIGN

Retrospective analysis of serum samples and BMD analyses from the African American Health Study [AAHS] cohort.

SETTING

The AAHS is a population-based longitudinal study initiated to examine issues of disability and frailty among urban-dwelling black Americans in the city of Saint Louis, Missouri.

PARTICIPANTS

122 men and 206 women, age 60.2 ± 4.3 years.

INTERVENTION

Retrospective analysis.

MEASUREMENTS

Total 25(OH)D, VDBP, PTH, and BMD of the lumbar spine and hip by dual energy x-ray photometry (DXA). Free and bioavailable vitamin D levels were calculated using serum concentrations and affinity constants for the VDBP (Gc1F and Gc1S) phenotypes.

RESULTS

Serum total 25(OH)D levels were 14.6 ± 8.9 ng/mL (36 ± 22 nmol/L). Vitamin D insufficiency was estimated by compensatory elevations of PTH above the normal range (> 65 pg/mL). PTH levels were within the normal reference range in > 95% of the samples at total 25(OH)D levels ≥ 20 ng/mL (≥50 nmol/L). There was no difference in the correlation of the reciprocal relationship of vitamin D vs parathyroid hormone between the VDBP phenotypes. Receiver operating characteristic curve analyses indicated that serum total 25(OH)D discriminated sufficiency from insufficiency at least as well as the calculated levels of the free and bioavailable vitamin D. Very low levels of total 25(OH)D (≤ 8 ng/mL, ≤20 nmol/L) were associated with decreased BMD (p=0.02), but higher levels of 25(OH)D did not show statistical differences in BMD.

CONCLUSION

Total 25(OH)D levels of ≤ 8ng/mL (≤20 nmol/L) are associated with clinically significant changes in BMD, whereas total 25(OH)D levels ≥ 20 ng/mL (≥50 nmol/L) suppressed PTH and were not associated with deficiencies in BMD. Lower levels of 25(OH)D may be acceptable for bone health in black than in white Americans.

Effect of LPS on the permeability of the blood-brain barrier to insulin

Insulin has emerged as an important neuropeptide. Central actions of insulin appear to oppose those in the periphery. Insulin is transported across the blood-brain barrier (BBB) by a saturable transport system. The permeability of the BBB to insulin is altered by various events, but no studies exist that have examined the permeability of the BBB to insulin during infection or inflammation, states which can induce peripheral insulin resistance. We looked at the effects of lipopolysaccharide (LPS), a bacterial endotoxin and a powerful cytokine releaser, on the permeability of the BBB to human insulin in CD-1 mice. Intraperitoneal injections of LPS significantly increased the uptake by the brain of 131I-insulin and disrupted the BBB to 125I-albumin. After subtraction of the brain/serum ratio for 125I-albumin, brain/serum ratios for insulin were increased: 10.38 +/- 0.70 microl/g (LPS) vs. 3.62 +/- 0.27 microl/g (no LPS), P<0.0001, showing that LPS increased the uptake of insulin independent of BBB disruption. This increase in insulin uptake was due to enhanced saturable transport. Pretreatment with indomethacin 10 min before LPS injections enhanced BBB disruption, but not insulin transport. Pretreatment with the nitric oxide (NO) synthase inhibitor aminoguanidine had no effect on insulin or albumin uptake, but pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) enhanced insulin transport, but not BBB disruption. We conclude that LPS increases the saturable transport of insulin across the BBB independent of disruption and prostaglandins with potentiation by NO inhibition. Such increased transport could potentiate the central effects of insulin and so contribute to the peripheral insulin resistance seen with infection and inflammation.

Effects of tetrodotoxin and OKY-046 in renal ischemia reperfusion

Ischemia reperfusion injury (IRI) contributes significantly to posttransplant graft dysfunction. An emphasis, therefore, has been directed toward the identification of novel renoprotective agents. In this study, the renoprotective effect of tetrodotoxin (TTX) alone, or in combination with a thromboxane synthetase inhibitor (OKY-046), was investigated in a 60-min warm ischemia, 72-h reperfusion, IRI rodent model. Unilateral nephrectomized rats were treated with the test vehicle alone, 1, 2, or 4 microgram/kg of TTX or 2 mg/kg of OKY-046 intravenously, either 15 min pre- or postischemia, or 2 microgram/kg TTX administered simultaneously with OKY-046 (2 mg/kg), following the ischemic interval. Baseline, 24, and 72 h mean plasma creatinine (Cr) and urea nitrogen (BUN) were compared. Maximal renoprotection was demonstrated by significantly improved 72-h Cr and BUN levels with the 2 microgram/kg of TTX or with 2 mg/kg of OKY-046, each administered after ischemia (ischemic control Cr = 8. 01 +/- 1.07 mg/dl vs TTX = 3.84 +/- 0.80 mg/dl, P = 0.008; vs OKY-046 = 4.0 +/- 1.5, P + 0.008; ischemic control BUN = 241.3 mg/dl +/- 32.8 vs TTX = 85.7 mg/dl +/- 18.7, P < 0.008; vs OKY-046 = 52.6 +/- 22.5, P = 0.008). The combination therapy utilizing TTX with OKY-046 resulted in reduced animal survival, demonstrating no renoprotection as measured with the biochemical parameters. These results support the renoprotective effects of TTX in a severe, rodent IRI model. The exact mechanism of action, as well as the therapeutic potential of TTX in preservation/transplantation, warrants further study.

Effect of octreotide on stimulated insulin release from pancreatic tissue slices

This study was designed to investigate a possible mechanism of action by which octreotide acetate causes insulin suppression in the denervated pancreas. Canine tissue slices were placed in a pH-adjusted medium with varying concentrations of glucose and octreotide acetate: Experiment 1, 30 min in basal medium with 0.6 mg/ml glucose; Experiment 2, addition of 6.0 mg/ml glucose; Experiment 3, addition of 4 microg octreotide acetate/70 ml (comparable to 100 microg/25 kg body weight); Experiment 4, addition of 16 microg octreotide acetate/70 ml; Experiment 5, incubation with 6.0 mg glucose/ml and 4 microg octreotide acetate/70 ml; Experiment 6, incubation with 6.0 mg glucose/ml and 16 microg octreotide acetate/70 ml; Experiment 7, preincubation with 4 microg octreotide acetate/70 ml, then with 6.0 mg glucose/ml; and Experiment 8, preincubation with 16 microg octreotide acetate/70 ml, then with 6.0 mg glucose/ml. Medium levels of insulin, glucagon, and amylase were collected at intervals during the incubation periods. There was an appropriate increase in the rate of insulin release to glucose stimulation in the high-glucose (6.0 mg/ml) group. There was no significant inhibition of basal or glucose-stimulated insulin release with either simultaneous or pretreatment of the canine pancreatic tissue slices with either concentration of octreotide acetate. These studies support an indirect mechanism by which octreotide acetate exerts its inhibitory effect on endocrine and exocrine function in the canine pancreas transplant model.

Evaluation of benzalkonium chloride chemoneurolytic proximal gastric vagotomy

BACKGROUND

Transmucosal chemoneurolytic injection of benzalkonium chloride (BAC) has previously been shown to duplicate operative proximal gastric vagotomy (PGV) in controlling gastric acid secretion. In this study, BAC was evaluated as to efficacious dose, methods of delivery, and systemic toxicities.

METHODS

Sham celiotomy, operative PGV controls, transmucosal injections through a gastrotomy, and transserosal injections of BAC (saline controls, 0. 625, 1.25, 2.5, 5.0, 10 mg BAC/kg body wt) were administered to Sprague-Dawley rats. After 3 months the rats underwent Congo red testing (CRT), horseradish peroxidase (HRP) neuronal staining, and necropsy. The color density change of the gastric mucosa from basic to acidic demonstrated by the CRT at the time of necropsy was used to calculate the residual anatomic acid-secreting area. Prior to necropsy, subserosal HRP injections into the anterior and posterior stomach walls assayed vagal neuronal viability via retrograde axonal flow. Results were compared by an ANOVA.

RESULTS

The results demonstrated that 1.25-10 mg/kg transmucosal BAC replicated the results of operative PGV; 2.5 mg/kg was found to be the most effective dose. All injection groups including saline controls demonstrated similar diminished vagal retrograde axonal flow by HRP testing consistent with local BAC chemoneurolytic effects. No systemic toxic symptoms were observed after tail vein intravenous BAC 1.25, 2.5, and 5.0 mg/kg.

CONCLUSIONS

These efficacy studies have demonstrated BAC's potential utility in the performance of endoscopic transmucosal chemoneurolytic PGV.

Renoprotective effects of the 21-aminosteroid U74389G in ischemia-reperfusion injury and cold storage preservation

Free radical mediated lipid peroxidation (LPO) has been implicated in the pathogenesis of ischemic-reperfusion injury (IRI). To address the renoprotective effect(s) of LPO inhibition, the efficacy of the 21 aminosteroid U74389G was evaluated in three IRI models. In Model 1 51 unilateral nephrectomized rats that underwent 60 min of warm ischemia followed by a 72-hr reperfusion interval were treated with the test vehicle only, or 3, 6, or 12 mg/kg of U74389G intravenously, 5 min pre- or postischemia. In Model 2 Sprague-Dawley rats underwent sham operation (n=9), or 45 min of warm ischemia and 10 min of reperfusion with U74389G (6 mg/kg; n=10) or test vehicle only (n=10) administered intravenously over 10 min beginning 5 min prior to clamp release. After reperfusion, LPO was determined by assay of snap frozen tissue for thiobarbituric acid (TBA) concentrations (nmol/g tissue weight). In Model 3 domestic lean maid pigs (14-18 kg) underwent left nephrectomy with 30 min of warm ischemia, Collins C-4 flush, and 24 hr of cold storage preservation. Heterotopic autotransplantation and immediate contralateral nephrectomy was then performed in Group A-nonischemic controls (n=4), Group B-ischemic controls (n=5), and Group C-U74389G (6 mg/kg) administered preischemia and at autotransplantation (n=5). In Model 1 maximal renoprotection was demonstrated with the 6 mg/kg dose of U74389G administered after ischemia (ischemic control 72-hr serum creatinine (Cr) = 8.01+/-1.1 mg% vs. 3.32+/-0.96 mg%; ischemic control creatinine clearance = 0.069+/-0.03 ml/min vs. 0.206+/-0.04 ml/min; P<0.05). In Model 2 TBA levels were significantly lower in U74389G treated animals (88.5+/-10.0 vs. ischemic controls = 296.8+/-81.4; P=0.02). In Model 3 graft survivals were 100%, 0%, and 60% respectively. Peak Cr and BUN (mg%) were significantly greater in Group C vs. Group A, (Group A Cr = 8.59+/-0.63 vs. Group C = 12.8+/-1.01; Group A BUN = 64.1+/-2.73 vs. Group C = 104.9+/-12.21)--however, by day 10, thee were no significant differences in renal function: (Group A Cr = 2.15+/-0.3 vs. Group C = 2.10+/-0.06; Group A BUN = 27.0+/-6.0 vs. Group C = 31.1+/-6.4). These results support the beneficial effects of LPO inhibitors in models of ischemia-reperfusion, as well as preservation/transplantation, and suggest that this renoprotection correlates with decreased membrane lipid peroxidation.

Effect of somatostatin and octreotide acetate on OP-CCK-stimulated exocrine secretion in the denervated canine pancreas

Somatostatin and its analogue, octreotide acetate (Sandostatin), have been demonstrated to suppress exocrine secretion in a denervated canine pancreatic autograft model. To help define this inhibitory mechanism, the effect of these agents on cholecystokinin (CCK)-stimulated acinar cell secretion was evaluated. In vitro assessment evaluated the effect of somatostatin on octapeptide (OP)-CCK-stimulated amylase release of pancreatic tissue slices. In vivo assessment employed animals with pancreatic autografts and pancreaticocystostomies, evaluating the effect of a bolus intravenous injection of 100 micrograms of octreotide acetate on the basal and OP-CCK-stimulated (125 ng/kg/h) secretion of urinary (autograft) amylase and bicarbonate. Incubation of tissue slices with 0.16, 0.24, or 0.32 microgram/ml somatostatin had no significant effect on in vitro OP-CCK-simulated amylase release. Intravenous octreotide acetate resulted in a significant decrease in the basal rate of amylase secretion but had no significant effect on OP-CCK-stimulated autograft amylase or bicarbonate release. These studies demonstrate that octreotide acetate has an in vivo inhibitory effect on basal amylase release of pancreatic autografts but cannot counteract maximal stimulation with exogenous OP-CCK. Also, somatostatin does not inhibit OP-CCK-stimulated acinar cell secretion of pancreatic tissue slices. These results indicate that the exocrine inhibition produced by somatostatin analogues in the grafted pancreas occurs via an indirect mechanism.

Effect of L-364,718 on pancreatic endocrine function following partial pancreatectomy

This study was designed to determine the effect of a potent cholecystokinin antagonist, L-364,718, on canine pancreatic endocrine function following partial pancreatectomy. Plasma glucose, insulin, and glucagon were determined over a 2-hr interval following an intravenous bolus of 0.5 g/kg glucose in a 50% solution. The following groups were established: normal animals (group A, n = 5), normal animals pretreated with 20 nmole/kg L-364,178 (group B, n = 5), partially pancreatectomized animals (group C, n = 5), and partially pancreatectomized animals pretreated with 20 nmole/kg L-364,178 (group D, n = 5). In contrast to animals with an intact pancreas, pretreatment with L-364,718 following partial pancreatectomy resulted in a significant decrease in peak insulin (group C = 132.8 +/- 13.0 microU/ml vs Group D = 90.4 +/- 16.1 microU/ml, P < 0.05) and the basal-to-peak insulin difference (group C = 111.9 +/- 11.5 microU/ml vs group D = 77.5 +/- 16.6 microU/ml, P < 0.05). Despite this, the rate of glucose utilization (K value) was significantly increased in the partially pancreatectomized animals given the antagonist (group C = -1.22 +/- 0.22%/min vs group D = -2.79 +/- 0.427%/min) and there were no significant differences in basal or peak glucose when comparing the groups given L-364,718 with the groups given placebo (group A vs B and group C vs D). Thus, the CCK antagonist L-364,718 significantly decreases peak insulin in partially pancreatectomized animals but not in nonoperative control animals. There is a paradoxical increase in the rate of glucose utilization but no effect on glucose homeostasis. The effect of this antagonist in other models of reduced islet cell reserve (i.e., pancreas transplantation) remains to be determined.

Evaluation of the thromboxane A2 synthetase inhibitor OKY-046 in a warm ischemia-reperfusion rat model

The pathophysiology of ischemia-reperfusion renal injury is mediated, in part, by the generation of the vasoconstricting prostanoid thromboxane A2 (TXA2). This study was undertaken to evaluate the renoprotective effects, as well as the optimal timing and dosage, of a selective thromboxane synthetase inhibitor, OKY-046, in a unilateral nephrectomized, 60 min ischemia, 72 hr reperfusion, rodent model. Forty-one rats were subjected to right nephrectomy only (group A), or right nephrectomy with 60 min of left renal ischemia and treatment with inactive vehicle only (group B), or 2 mg/kg or 4 mg/kg of OKY-046 administered intravenously before (groups C and D) or after (groups E and F) pedicle clamping. Outcome variables included animal survival; change in kidney weight; 0, 24, and 72 hr plasma creatinine (CR); urea nitrogen (BUN); thromboxane B2 (TXB2) and 6-keto prostaglandin F(1alpha) (6 kPGF(2alpha)) levels; creatinine clearance (CRCL); and histologic evidence of renal injury. Animal survival and postperfusion kidney weight were not significantly different among the groups. However, renal functional parameters were significantly improved with the 2 mg/kg dose of OKY-046 administered after renal ischemia. (group B 72 hr Cr= 8.01 +/- 1.1 mg% vs. group E=3.99 +/- 1.5 mg%, and group B 72 hr BUN=241.3 +/- 32.8 mg% vs. group E=52.6 +/- 22.5 mg%). The CRCL was also improved in group E vs. group B, although these results did not reach statistical significance (group B=0.069 ml/min vs. group E=0.194 ml/ min). The 24 hr TXB2 levels were significantly increased in group B (0 hr=754.1 +/- 219.4 pg/ml vs. 24 hr=2055.9 +/- 550.0 pg/ml), and pre- or posttreatment with OKY-046 abrogated this increase (group C 0 hr=517.1 +/- 80.9 pg/ml vs. 24 hr=384.7 +/- 251.5 pg/ml, and group E 0 hr=781.6 +/- 390.4 pg/ml vs. 24 hr=183.0 +/- 81.4 pg/ml). The 24 hr 6 kPGF(1alpha) levels decreased in all groups, whereas 72 hr 6 kPGF(1alpha) levels increased above baseline in groups A, C, and E, but not in group B. These data demonstrate the beneficial effects of thromboxane A2 synthesis inhibition in the setting of ischemia-reperfusion injury and suggest that this renoprotection correlates with late vasodilatory prostanoid synthesis.

Exocrine effects of the CCK antagonist L-364,718 in canine pancreatic autografts

This study evaluated the effect of the cholecystokinin antagonist L-364,718 on exocrine secretion in canine pancreatic autografts with pancreaticocystostomies. Urinary (autograft) amylase (U/min) and bicarbonate (mmole/min) secretion, over a 6 hr interval, were determined in the basal state (Group A), after a bolus injection of 20 nmoles/kg of L-364,718 (Group B), during a continuous cholecystokinin octapeptide (OP-CCK) infusion at 125 ng/kg/hr either alone (Group C), with a bolus injection of 20 nmoles/kg (Group D), or 30 nmoles/kg (Group E), of L-364,718 1 hr before initiating OP-CCK, or 20 nmoles/kg of L-364,718 1 hr after initiating OP-CCK (Group F). L-364,718 had no effect on basal or OP-CCK-stimulated secretion of bicarbonate. Basal amylase secretion was decreased 1 hr after L-364,718 and remained significantly lower than controls throughout the study interval. When compared to Group C (280.3 +/- 48.6), OP-CCK-stimulated amylase secretion was significantly lower for the first hour after L-364,718 in both Group D (157 +/- 46.7) and Group E (31.9 +/- 11.6). In Group E, 2, 3, and 4 hr post-L-364,718 amylase releases were 60.2 +/- 19.7, 77.7 +/- 25.1, and 87.2 +/- 28.3 compared to 335.5 +/- 85.9, 291.0 +/- 21.8, and 289.9 +/- 45.7 in Group C indicating a sustained significant inhibition of stimulated autograft amylase secretion with the higher L-364,718 dosage. In Group F, no significant change in amylase secretion was demonstrated, indicating that L-364,718 must be administered prior to CCK stimulation to be effective. These studies demonstrate that L-364,718 has a dose dependent, inhibitory effect on basal, and OP-CCK-stimulated amylase secretion in a denervated autograft model. The therapeutic potential of L-364,718 and other CCK receptor antagonists in pancreatic transplantation warrants further study.

The effect of octreotide acetate on meal-stimulated exocrine secretion in canine pancreatic autografts

Octreotide acetate (Sandostatin), a long-acting somatostatin analogue, has been demonstrated to have an inhibitory effect on exocrine secretion in the neurally intact pancreas. This study was designed to evaluate the effect of this agent on exocrine secretion in the denervated canine pancreas, utilizing animals with pancreatic autografts and functioning pancreaticocystostomies. The rates of secretion of urinary (autograft) amylase (units/min) and bicarbonate (mM/min), over a five-hr interval, were determined in the basal state (group A, n = 10), after a bolus injection of 400 micrograms of Sandostatin (group B, n = 5), after a standard meal (group C, n = 5), or a meal preceded by 400 micrograms of Sandostatin (group D, n = 5). Basal secretion of amylase was decreased for 4 hr following Sandostatin, although this decrease was not significant. Conversely, basal bicarbonate secretion was not inhibited by Sandostatin. When compared with group C (22.4 +/- 3.2), a significant inhibition of meal-stimulated amylase release was demonstrated in group D (5.4 +/- 0.21, P = 0.0006) during the first hour after Sandostatin was given. This inhibition remained significant at 2 hr (group C = 38.5 +/- 5.2 versus group D = 9.4 +/- 0.8; P = 0.0006) and 3 hr (group C = 38.6 +/- 6.3 versus group D = 17.5 +/- 0.9; P = 0.0108) after Sandostatin was given. In addition, meal-stimulated bicarbonate secretion was significantly inhibited for 2 hr following Sandostatin (group C = 0.19 +/- 0.03 versus group D = 0.07 +/- 0.02, P = 0.0096; and group C = 0.23 +/- 0.03 versus group D = 0.10 +/- 0.01, P = 0.0018, respectively). These studies demonstrate that Sandostatin has a profound inhibitory effect on meal-stimulated enzyme and bicarbonate release in a denervated canine autograft model. Although the site of action of this agent remains to be defined, Sandostatin may have therapeutic potential in clinical pancreas transplantation.

In search of an in vitro index of viability during pancreatic preservation

To determine an index of viability during pancreatic preservation, 15 dogs underwent segmental pancreatic autografting after 24 hr of pulsatile perfusion. These animals were divided into Group A (6) and Group B (9) on the basis of post-transplant normoglycemia or hyperglycemia. In each experiment, sequential perfusate amylase and arterial and venous blood gases were analyzed during preservation. In addition, sequential pancreatic tissue slices were obtained to determine in vitro insulin release. A comparison of perfusion parameters demonstrated no significant differences in pancreas weight (41 +/- 2.9 vs 38.3 +/- 1.5 mg), perfusate flow (0.24 +/- 0.2 vs 0.20 +/- 0.06 ml/min/g), diastolic (24.3 +/- 2.3 vs 26.9 +/- 1.6 mm Hg) or mean pressure (27.4 +/- 1.9 vs 30.1 +/- 1.5 mm Hg). Perfusate amylase levels (u/100 ml) and percentage change from baseline are as follows: (Table: see text). Perfusate amylase was significantly greater at 21 hr in Group A (P less than 0.005). In addition, a significantly greater rate of amylase release was evident in Group A at 1 hr (P less than 0.02), 3 hr (P less than 0.02), and 21 hr (P less than 0.01). Group B pancreata demonstrated significantly increased oxygen extraction at 1 hr (A-V O2 difference: Group A = -33, Group B = -68; P less than 0.05). In vitro insulin release of tissue slices obtained pre-harvest, post-flush, post-preservation, and 15 min post-transplantation was not significantly different in the two groups. In conclusion, sequential perfusate amylase and blood gas determinations may be useful in predicting pancreatic transplant function.

An in situ evaluation of distal splenic arteriovenous fistula on pancreas function in an isolated pancreas segment

To determine the effects of a distal splenic arteriovenous fistula on endocrine function and pancreatic blood flow, 25 dogs underwent proximal pancreatectomy with the pancreatic tail left in situ and free intraperitoneal drainage of the pancreatic duct. Group A served as controls. In groups B through E, ligation of all nonpancreatic splenic vessels was accomplished. In group B, no further manipulations were performed. In group C, an arteriovenous fistula was created. Groups D and E were identical to groups B and C, respectively, except for the induction of bile pancreatitis. During intravenous glucose tolerance testing, the mean (+/- SEM) basal-to-peak insulin difference was 10.1 +/- 3.5 microU/mL in group A, 16.3 +/- 3.6 microU/mL in group B, 14.8 +/- 5.1 microU/mL in group C, 16.4 +/- 3.1 microU/mL in group D, and 13.0 +/- 4.4 microU/mL in group E. Corresponding mean (+/- SEM) glucose clearance values were as follows: -0.907% +/- 0.24%/min, -0.867% +/- 0.14%/min, -1.056% +/- 0.21%/min, -1.365% +/- 0.26%/min, and -0.887% +/- 0.20%/min. These values were not significantly different. Ligation of all splenic arterial and venous branches resulted in a 64.8% to 78.3% reduction in splenic artery blood flow that was restored to 60.9% to 84.9% of basal flow by an arteriovenous fistula (groups C and E). In conclusion, the creation of a splenic arteriovenous fistula was not beneficial in this model and other factors (rejection or technical) should be considered in vascular thrombosis following segmental pancreatic transplantation.

Autoradiographic study of the right stellate ganglionic fibers to the cat heart

Autoradiographic techniques have been employed to demonstrate the distribution of the postganglionic sympathetic cardiac fibers originating from the right stellate ganglion in 3 cats. After exposing the ganglion through a right thoracotomy, a total of 500 muCi of tritiated leucine was injected into the right stellate ganglion of each cat. After 3 days the animals were sacrificed by vascular perfusion. The injected ganglia, the heart and great vessels were processed for autoradiography. The majority of the right stellate ganglionic fibers travelled between the trachea and aortic arch, and entered the cardiac fibers travelled between the trachea and aortic arch, and entered the cardiac plexus. Continuing through the plexus, these fibers coursed between the ascending aorta and the pulmonary arterial trunk to form a periarterial plexus around the left coronary artery and its branches. Most of the fibers followed the distribution of the ventral descending branch of the left coronary artery; a few followed the circumflex artery. A conspicuous subepicardial plexus was derived from the periarterial plexus and was most prominent in the cranial half of the left ventricle. Other fibers arising from the right stellate ganglion descended between the cranial vena cava and the right branch of the pulmonary artery. These ramified on the dorsolateral surface of the right atrium, and also formed a large bundle which passed caudally through the interatrial septum.

The orthograde labeling of postganglionic sympathetic cardiac nerves in the dog and cat as demonstrated by autoradiography

Previous functional and anatomical techniques have characterized the cardiac nerves and plexuses. They cannot, however, determine the course of fibers arising from a specific ganglion. This study has found that the intraaxonal orthograde labeling of axons can be used to determine the course of postganglionic sympathetic cardiac fibers in the dog and cat. The canine left caudal cervical ganglion and the feline right stellate ganglion were exposed through appropriate thoracotomies. Each ganglion received multiple injections of tritiated leucine (500 muCi/animal). Following a 3--14-day survival period the anesthetized animals were sacrificed by vascular perfusion. The injected ganglia, extracardiac nerves and selected portions of the heart were processed for autoradiography. Autoradiographs from the dog demonstrated labeled postganglionic sympathetic nerves in the extracardiac plexus, left atrial epicardium and the epicardium beneath the coronary sulcus. Labeled nerves in the cat heart were found within the epicardial layers and associated with blood vessels in the left ventricular myocardium. Neither myelinated fibers traveling through the injection site nor intrinsic cardiac ganglion cells were labeled, although the latter were often closely approximated to heavily labeled fibers.