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R A Baker

Publications and source records attributed to R A Baker.

At least 55 records · Page 3Linked to original sources
PubMed1997

Gastrin-releasing peptide stimulates possum gallbladder contractility in vitro.

Reports of the action of gastrin-releasing peptide (GRP) on gallbladder contraction are limited to a few species. We compared the action of GRP, acetyl gastrin-releasing peptide 20-27 (GRP 20-27), and cholecystokinin-octapeptide (CCK-8) on gallbladder contractility with and without pretreatment with the neural inhibitor tetrodotoxin (TTX) and the bombesin antagonist [D-Phe 6, Des-Met 14]-bombesin 6-14 ethylamide (BBS 6-14 E). Full-thickness muscle strips were prepared and suspended in organ baths. The maximum GRP, GRP 20-27, and CCK-8 responses were 54.2 +/- 4.2%, 74.6 +/- 6.4%, and 69.3 +/- 6.9% of that of carbachol, respectively. Pretreatment with TTX influenced the action of GRP 20-27, and pretreatment with BBS 6-14 E influenced that of GRP and GRP 20-27. These studies show that GRP and GRP 20-27 are potent agonists of gallbladder contractility, acting via GRP-preferring receptors, and that GRP 20-27 also acts via a neural component.

Animals↗
PubMed1996

Galanin modulates sphincter of Oddi function in the Australian brush-tailed possum.

The neuropeptide galantin (GAL) is found in neurons in the biliary tract of several species. We mapped the distribution of GAL-like immunoreactive nerve (GAL-LI) fibers in the sphincter of Oddi of the Australian brush-tailed possum by immunohistochemistry. The pharmacological effects of GAL in vitro and in vivo were studied by measuring sphincter of Oddi muscle strip contractility and transsphincteric flow, respectively. Muscle layers, and ganglionated and perivascular plexuses, contained GAL-LI nerve fibers. Exogenous GAL caused a concentration-dependent (10(9)-10(-6)M) increase in the spontaneous longitudinal but not circular muscle contractions. At 10(-6) M GAL, contractile activity was elevated two- to fourfold. This response was tetrodotoxin insensitive but competitively inhibited by galantide (10(-8)-10(-7) M). In vivo, intra-arterial bolus injections of GAL (1001000 ng/kg), decreased transsphincteric flow, with a maximum reduction to 80.2 +/- 6.8% of control. In conclusion, GAL appears to selectively stimulate longitudinally oriented sphincter of Oddi smooth muscle via a direct mechanism, which results in a modest reduction in transsphincteric flow.

Animals↗
PubMed1996

Effects of long-term treatment with antidepressant drugs on proopiomelanocortin and neuropeptide Y mRNA expression in the hypothalamic arcuate nucleus of rats.

Antidepressant drugs have in common a delayed onset of clinical efficacy. In rats, long-term, daily administration of four different types of clinically effective antidepressant drugs results in decreased corticotropin releasing hormone (CRH) mRNA expression levels in the hypothalamic paraventricular nucleus (PVN). Because a subpopulation of neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons in the hypothalamic arcuate nucleus (Arc) projects to the PVN, we measured NPY and POMC mRNA expression in the Arc using in situ hybridization histochemistry at several time points following daily administration of four different antidepressant drugs. After 14 and 56 days of imipramine treatment, Arc NPY mRNA levels are decreased to 85% and 75% of control levels, but are unchanged compared to control after one or five days of treatment. Arc POMC mRNA levels are unchanged compared to controls at 1, 5, 14, or 56 days following imipramine treatment. Unlike after imipramine, Arc NPY and POMC mRNA levels are increased significantly to 134-172% of control following 56-day treatment with the antidepressant drugs fluoxetine, phenelzine, or idazoxan. The divergent effects of imipramine vs the other 3 antidepressant drugs on Arc NPY mRNA expression are similar to the pattern of changes in tyrosine hydroxylase (TH) mRNA expression levels in the locus coeruleus (LC) using the same experimental paradigm, but are different from the unidirectional depressive effects of all four drugs on CRH mRNA expression in the PVN. Thus, the Arc NPY and LC noradrenergic systems may act coordinately in mediating antidepressant effects. The present data are consistent with the delayed onset of clinical efficacy for antidepressant drugs, and suggest that Arc NPY and POMC neurotransmitter systems play a role in the pathophysiology of depression.

Adrenergic alpha-Antagonists↗
PubMed1996

Coordination of biliary and upper gastrointestinal motility in the fasted conscious pig.

A chronic pig model was developed which permits the simultaneous measurement of integrated biliary motility as resistance to flow (CBD inflow), gallbladder, duodenal and gastric motility in addition to collection of venous blood samples for gut hormones estimations. Animals displayed a duodenal interdigestive cycle of 55.4 +/- 3.4 min (mean +/- SEM, n = 6), consisting of phase I, II and III (21.2 +/- 2.1, 70.5 +/- 2.0, 8.7 +/- 0.5% of the cycle, respectively). A gastric interdigestive cycle of 60.2 +/- 6.5 min (n = 4) was similarly demonstrated consisting of three phases which corresponded to the three duodenal phases. The gastric phases I, II and III comprised 26.3 +/- 3.0, 71.2 +/- 2.7 and 2.5 +/- 0.8% of the cycle, respectively. The gastric phase III immediately preceded the onset of the duodenal phase III. The gallbladder likewise displayed an interdigestive cycle of 54.5 +/- 7.2 min (n = 6) consisting of a quiescent period (37.2 +/- 3.7% of the cycle) corresponding temporally to duodenal phase III and phase I. This quiescent phase was followed by a period of rhythmic contractions (64.5 +/- 4.1% of the cycle) which corresponded temporally to duodenal phase II. The onset of the gallbladder quiescent period coincided with the onset of duodenal phase III. The CBD inflow similarly demonstrated an interdigestive cycle of 53.4 +/- 9.6 min (n = 4) duration, consisting of three phases. The initial phase was evident as a period of rapid inflow, the onset of which coincided with the onset of duodenal phase III and the gallbladder quiescent period, and occupied 12.0 +/- 0.8% of the cycle. The second phase which occupied 18.0 +/- 7.4% of the cycle, was typified as a period of declining inflow which reached a relatively stable level at a time corresponding to the end of duodenal phase I. The third phase consisted of the maintenance of the inflow rate achieved at the end of the previous phase (60% of maximum inflow), corresponding in onset and duration with duodenal phase II and occupied 70.0 +/- 8.6% of the cycle. Plasma motilin levels fluctuated in relation to the duodenal interdigestive cycle, peaking during phase III relative to phase I (36.9 +/- 8.5 vs 25.4 +/- 7.7 pg mL-1, respectively, n = 5, P < 0.05). Cholecystokinin levels did not fluctuate, remaining low (2.3 +/- 2.1 pM cholecystokinin octapeptide equivalents, n = 5) throughout the duodenal interdigestive cycle, but increased about two fold after ingestion of solid food. Feeding disrupted the gastric, duodenal, gallbladder and CBD inflow cycles.

Animals↗
PubMed1996

Gingival fluid tetracycline release from bioerodible gels.

Intracrevicular antimicrobial therapy is consistent with the site-specific nature of periodontitis. Considerable research has focused on the use of nonresorbable fibers. However, a bioerodible system is desirable. The purpose of this study was to assess tetracycline release and safety following a single application of a syringable 35% tetracycline hydrochloride in a lactic-glycolic acid gel. 31 generally healthy adult volunteers (mean age = 59 years) were enrolled in and completed this randomized, double-blind eight day study. 2, 6-10 mm non-adjacent interproximal pockets that bled on pocket probing were chosen as experimental sites in each subject. I experimental site and the surrounding gingival crevice received small particle size tetracycline in gel while the other site received larger particle size tetracycline in gel. Gingival crevicular fluid (GCF) was collected prior to treatment and 15 min, 1, 2, 3, 4 and 8 days post-treatment. GCF tetracyline concentrations were determined by agar diffusion bioassay and GCF volume measurements. 61% and 71% of sites had > or = 100 micrograms/ml tetracycline 3 days following application of large (mean concentration = 430 +/- 92 micrograms/ml) and small particle gels (mean concentration = 418 +/- 70 micrograms/ml), respectively. 37% and 55% of sites had measurable tetracycline 8 days after placement of large (mean concentration = 86 +/- 31 micrograms/ml) and small particle gels (mean concentration = 293 +/- 79 micrograms/ml), respectively. The most common adverse event was "bitter taste" (10% of subjects). Based upon the reduction in probing depths and % of sites bleeding on probing at 8 days relative to pretreatment, and the absence of any serious adverse events, it is concluded that these bioerodible gels are safe, and since the bacteriostatic range for most putative periodontopathogens is in the 2-10 micrograms/ml range, the tetracycline levels observed at days 3 and 8 likely represent significant antimicrobial efficacy.

Adult↗
PubMed1996

A binding-lipoprotein-dependent oligopeptide transport system in Streptococcus gordonii essential for uptake of hexa- and heptapeptides.

Cells of the oral bacterium Streptococcus gordonii express three cytoplasmic membrane-bound lipoproteins with apparent molecular masses of 76 to 78 kDa that are the products of three genes (designated hppA, hppG, and hppH). The lipoproteins are immunologically cross-reactive, contain 60% or more identical amino acid residues, and are highly similar to the AmiA, AliA (PlpA), and AliB substrate-binding protein components of an oligopeptide permease in Streptococcus pneumoniae. Insertional inactivation of the hppA or hppH gene resulted in loss of the ability of S. gordonii cells to utilize specific peptides of five to seven amino acid residues for growth. An insertion within the COOH-terminal coding region of hppG that caused apparent truncation of the HppG polypeptide had a similar effect; however, S. gordonii mutants in which HppG polypeptide production was abolished were still able to grow on all oligopeptides tested. Inactivation of hppA gene (but not inactivation of the hppG or hppH gene) caused reduced growth rate of cells in complex medium, slowed the rate of development of competence for transformation, reduced the efficiency of transformation, and increased the resistance of cells to aminopterin. These results suggest that the formation of a solute-binding-protein complex consisting of at least the HppA and the HppH lipopolypeptides is necessary for binding and subsequent uptake of primarily hexa- or heptapeptides by a Hpp (Hexa-heptapeptide permease) system in S. gordonii. In addition, Hpp may play a role in the control of metabolic functions associated with the growth of streptococcal cells on complex nitrogen sources and with the development of competence.

Amino Acid Sequence↗
PubMed1996

Quanticalc assessment of the clinical scaling benefits provided by pyrophosphate dentifrices with and without triclosan.

The Quanticalc (QC) dental scaler permits a quantitative assessment of the work used by professionals in calculus removal through the measurement of force dynamics and scaling strokes applied in calculus debridement. The purpose of this study was to use the QC to compare the clinical effects of two 5% pyrophosphate dentifrices on dental calculus in subjects following six-months' product use. Three-hundred forty-six subjects participated in a six-month, double-blind tartar control clinical trial involving traditional Volpe-Manhold Index (VMI) evaluations. Following the six-month VMI examinations, the subjects had a QC prophylaxis (scaling force measurements). The three dentifrice treatment groups included a control dentifrice (NaF only, Crest); NaF dentifrice containing 5.0% pyrophosphate (Crest Tartar Control); and NaF dentifrice containing 5.0% pyrophosphate plus 0.28% triclosan (antimicrobial). Subjects were balanced by baseline (pretest) VMI scores at the start of the trial. QC examinations revealed statistically significant reductions in total force and stroke number used by the therapist to scale the six anterior VMI teeth for subjects using the pyrophosphate tartar control dentifrices as compared to control dentifrice. The reduction in scaling effort amounted to almost 3 kg per scaling for subjects. QC results paralleled VMI reductions of calculus on the teeth and demonstrated that the use of 5% pyrophosphate dentifrices, with or without triclosan antimicrobial, results in significant reductions in the total (developed) force and strokes required by therapists in regular calculus debridement at a six-month interval. The clinical benefits of tartar control toothpastes may not only include reductions in cosmetically objectionable supragingival calculus, but in reducing professional effort in calculus debridement during regular prophylaxis.

Analysis of Variance↗
PubMed1995

Arcuate nucleus neurons that project to the hypothalamic paraventricular nucleus: neuropeptidergic identity and consequences of adrenalectomy on mRNA levels in the rat.

The possible role that the hypothalamic arcuate nucleus might play in mediating the increase in paraventricular nucleus corticotropin-releasing hormone mRNA levels following adrenalectomy was investigated in two series of experiments. In the first series in situ hybridization histochemistry was used to quantify levels of eight accurate nucleus neuropeptide and neurotransmitter mRNAs in neurons that potentially relay adrenal steroid feedback to the paraventricular nucleus. In the second series of experiments, arcuate neuropeptidergic projections to the hypothalamic paraventricular nucleus were characterized using retrograde tracing in combination with in situ hybridization histochemistry. Despite an increase in paraventricular nucleus corticotropin-releasing hormone (60%) and pituitary proopiomelanocortin mRNA levels (sixfold), arcuate mRNA levels for proopiomelanocortin, neuropeptide Y, somatostatin, galanin, dynorphin, tyrosine hydroxylase, glutamate decarboxylase, and the glucocorticoid receptor were unchanged 14 days following adrenalectomy. Neuropeptidergic characterization of arcuatoparaventricular projections was achieved by injection of the retrograde tracer fluorogold into the paraventricular nucleus; retrogradely labeled neurons were characterized with polyclonal antisera against fluorogold in combination with oligonucleotide probes directed against neuropeptide Y, proopiomelanocortin, or somatostatin. Out of these three arcuate neuropeptide Y mRNA was contained in 18% of the fluorogold-positive neurons in the arcuate, proopiomelanocortin mRNA was contained in 8%, and somatostatin mRNA was contained in 6%. Overall, the results from both experiments suggest that the arcuatoparaventricular neuropeptide Y, proopiomelanocortin, and somatostatin projections are not sensitive to a chronic (14 day) lack of adrenal steroids. These projections as well as the other arcuate neurotransmitter and neuropeptide systems appear not to contribute to the persistent elevations in paraventricular nucleus corticotropin-releasing hormone mRNA levels or pituitary proopiomelanocortin mRNA levels found in 14 day adrenalectomized rats.

Adrenal Glands↗
PubMed1995

Use of edible coatings to preserve quality of lightly (and slightly) processed products.

Lightly processed agricultural products present a special problem to the food industry and to scientists involved in postharvest and food technology research. Light or minimal processing includes cutting, slicing, coring, peeling, trimming, or sectioning of agricultural produce. These products have an active metabolism that can result in deteriorative changes, such as increased respiration and ethylene production. If not controlled, these changes can lead to rapid senescence and general deterioration of the product. In addition, the surface water activity of cut fruits and vegetables is generally quite high, inviting microbial attack, which further reduces product stability. Methods for control of these changes are numerous and can include the use of edible coatings. Also mentioned in this review are coating of nut products, and dried, dehydrated, and freeze-dried fruits. Technically, these are not considered to be minimally processed, but many of the problems and benefits of coating these products are similar to coating lightly processed products. Generally, the potential benefits of edible coatings for processed or lightly processed produce is to stabilize the product and thereby extend product shelf life. More specifically, coatings have the potential to reduce moisture loss, restrict oxygen entrance, lower respiration, retard ethylene production, seal in flavor volatiles, and carry additives that retard discoloration and microbial growth.

Food Handling↗
PubMed1995

Effect of prenatal ethanol and stress on levels of beta-endorphin in different brain regions of the rat.

The combination of prenatal ethanol exposure and footshock stress was investigated for its effects on brain beta-endorphin levels. Subjects were offspring of rats that received 1 of 3 prenatal dietary treatments: an ethanol-containing liquid diet, a identical liquid diet with ethanol substituted isocalorically with maltose-dextrin (pair-fed group), and standard laboratory rat chow (chow-fed group). Two different stress paradigms were used: a short (30-sec) footshock stress paradigm and a prolonged (180-sec) footshock stress paradigm. Levels of beta-endorphin were measured with radioimmunoassay in eight brain regions of unstressed (baseline) rats, and of stressed rats at 3 and 30 min following termination of the stress. Seven brain regions containing high densities of beta-endorphin axons and terminals were chosen, as well as the arcuate region of the hypothalamus, the only brain region where both beta-endorphin perikarya and terminals are located. Following the short footshock stress paradigm, there were no changes in beta-endorphin levels, except for a trend toward increased levels in the pair-fed group. After the prolonged stress paradigm, levels of beta-endorphin in both the pair-fed and chow-fed groups tended to be decreased in several brain regions, including the arcuate region, at 3 min after termination of the stress. In contrast, for the prenatally ethanol-exposed group, beta-endorphin levels were increased significantly in the arcuate region, and moderately increased in the septal/preoptic region and medulla/pons at 3 min after the prolonged stress paradigm.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗
PubMed1994

Intramural neural pathways between the duodenum and sphincter of Oddi in the Australian brush-tailed possum in vivo.

1. Balloon distension of the duodenum 2 cm oral or anal to the sphincter of Oddi-duodenal junction elevated the amplitude of spontaneous sphincter of Oddi phasic contractions by 37.7 +/- 8.5 or 120.1 +/- 79.8%, respectively (mean +/- S.E.M., both n = 6, P < 0.05, Wilcoxon test). To further investigate this response, this study aimed to determine if: (i) electrical field stimulation (EFS) of the duodenum influences sphincter of Oddi activity; (ii) intramural nerves mediate the response; and (iii) nicotinic and/or muscarinic receptors are involved. 2. Electrical field stimulation (70 V, 0.5 ms; 5-60 Hz, 10-20 s) of the duodenal anterior serosal surface 2-4 cm oral or anal to the sphincter of Oddi-duodenal junction, produced excitatory responses in the sphincter of Oddi in anaesthetized Australian brush-tailed possums (n = 45). 3. These responses were frequency dependent, maximal at 30 Hz (n = 4) and abolished by tetrodotoxin (9 micrograms kg-1 I.A.; n = 6), or by crushing the duodenum (n = 3). Hexamethonium bromide (30 mg kg-1 I.V.) did not significantly alter the response to duodenal EFS either oral (n = 6) or anal (n = 8) to the sphincter of Oddi-duodenal junction. Atropine sulphate (30 micrograms kg-1 I.V.) reduced the response to duodenal EFS oral and anal to the sphincter of Oddi-duodenal junction to 11.2 +/- 5.8 (n = 6) and 45.0 +/- 26.8% (n = 8), respectively (both P < 0.05). 4. Bilateral cervical vagotomy and guanethidine infusion (10 mg kg-1 over 15 min I.V.) did not significantly alter the responses to duodenal EFS (n = 7). 5. Excitatory intramural neural pathways between the sphincter of Oddi and the segment of duodenum 4 cm oral and anal to the sphincter of Oddi-duodenal junction have been demonstrated. These postganglionic pathways may involve muscarinic receptors.

Animals↗
PubMed1994

The value of serum carcinoembryonic antigen in predicting recurrent disease following curative resection of colorectal cancer.

UNLABELLED: Carcinoembryonic antigen (CEA) estimations are used to facilitate early diagnosis of recurrent disease after treatment for colorectal cancer. PURPOSE: This study was designed to determine the natural history of patients with normal and abnormal levels of CEA. METHODS: Patients undergoing potential curative resection of colorectal tumors (Dukes Stage A-C) entered a prospective, randomized trial comparing two follow-up regimens (to be reported separately) had CEA levels measured every 3 months for two years; then every 6 months for the next three years. In the study protocol, a rise in CEA was not an indication for investigation to determine recurrence unless there was also other evidence of recurrent disease. RESULTS: Three hundred eleven patients were followed for a median of 4.5 (range, 2-5) years. Recurrent disease developed in 98 (32 percent) patients, 57 of whom had an elevated CEA (sensitivity 58 percent), with a median lead time of six (range, 1-30) months from first abnormal CEA to diagnosis of recurrent disease by other means. The specificity, positive predictive value, and negative predictive value of CEA as an indicator of subsequent recurrent disease was 93 percent, 79 percent, and 83 percent, respectively. The sensitivity of CEA for predicting hepatic metastases was 80 percent, with a median lead time of eight (range, 1-30) months, compared with only 46 percent for sites of recurrent disease other than the liver. CONCLUSIONS: CEA was the first indicator of recurrent disease in 58 percent of all patients and in 80 percent of patients with liver metastases. The diagnosis of recurrent disease may be made several months earlier by investigating the first abnormal CEA level, although any benefit in terms of survival remains to be proven.

Aftercare↗
PubMed1993

Projections of nerve cells from the duodenum to the sphincter of Oddi and gallbladder of the Australian possum.

BACKGROUND: This study investigated the existence of direct neural connections between the duodenum and the biliary tract in the Australian possum. METHODS: Retrogradely transported neuronal dyes, Fast Blue and Dil, were injected into the wall of the gallbladder and the sphincter of Oddi. The duodenum, biliary tract, and sympathetic and sensory ganglia were examined for the presence of labeled cell bodies. RESULTS: Two to 3 weeks after gallbladder injection, labeled nerve cell bodies were found in the myenteric plexus of the proximal duodenum but were rare in the duodenum distal to the sphincter of Oddi. No neurons were found in the submucous plexus. Labeled nerve cells were also found in the sphincter of Oddi. After injection of the sphincter, labeled neurons were in both the submucous and myenteric plexuses of the duodenum, on either side. Approximately one third of labeled myenteric neurons were immunoreactive for enkephalin. Labeled cell bodies were also in the coeliaco-mesenteric, nodose, and dorsal root ganglia after both gallbladder and sphincter injection. After a myotomy on the proximal duodenum, no neurons were labeled on the pyloric side of the lesion by subsequent sphincter injection of dye. CONCLUSIONS: Direct neural pathways connect the duodenum with the gallbladder and the sphincter of Oddi, and the sphincter with the gallbladder; this implies that enteric nerve circuits participate in coordinating duodenal and biliary functions.

Animals↗
PubMed1993

Nitric oxide mediates nonadrenergic, noncholinergic neural relaxation in the Australian possum.

BACKGROUND: Nitric oxide has been shown to play an important role in neurally mediated relaxations of gastrointestinal smooth muscle. The aim of this study was to determine whether NO may be the inhibitory transmitter to circular smooth muscle from the sphincter of Oddi of the Australian brush-tailed possum (Trichosurus vulpecula). METHODS: The effects of drugs on relaxations evoked by electrical-field stimulation of circular muscle strips precontracted with either erythromycin or carbachol were studied. Preparations were also processed histochemically to determine the presence of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reactivity in the tissue. RESULTS: NG-nitro-L-arginine methyl ester reduced the amplitude of relaxations; this effect could be partially reversed by millimolar concentrations of L-arginine but not by D-arginine. Oxyhemoglobin also reduced the amplitude of the relaxations, and sodium nitroprusside mimicked the relaxations in precontracted strips. Histochemical processing revealed the presence of nerve cell bodies and nerve fibers associated with the circular muscle layer, which are reactive for NADPH-diaphorase and are thus likely to contain NO synthase. CONCLUSIONS: These results are all consistent with NO released from nerve cells mediating a significant part of the nonadrenergic, noncholinergic relaxation of the circular muscle layer of the sphincter of Oddi.

Animals↗
PubMed1993

Maxon is an optimal suture for bile duct anastomoses in pigs.

BACKGROUND: Three commonly used sutures were tested in a pig model of bile duct anastomosis to assess their relative contributions to inflammation and scarring. METHODS: Thirty pigs were randomised to bile duct division and anastomosis with either polyglyconate (Maxon), polyglactin 910 (Vicryl) or polypropylene (Prolene). Half the animals were sacrificed at two weeks and the remainder at 23 weeks. Anastomoses were assessed by cholangiography, scanning electron microscopy and light microscopy. RESULTS: There was less short term histological reaction with the two monofilament materials, Prolene and Maxon, compared to the braided suture Vicryl. Maxon was associated with less long term inflammation than Prolene, was found to handle better, and has an advantage over Prolene by being absorbable. CONCLUSION: Maxon is an optimal suture for bile duct anastomoses. Its long term absorption characteristics make it suitable for situations where bile duct healing may be delayed.

Anastomosis, Surgical↗
PubMed1993

Structure and innervation of the extrahepatic biliary system in the Australian possum, Trichosurus vulpecula.

The morphology, microanatomy and innervation of the biliary tree of the Australian possum, Trichosurus vulpecula, was examined. The gross morphology of the gallbladder, hepatic and cystic ducts, and the course of the common bile duct, conforms to those of other species. The sphincter of Oddi has an extraduodenal segment that extends 15mm from the duodenal wall; within this segment the pancreatic and common bile ducts are ensheathed together by sphincter muscle. Their lumens unite to form a common channel within the terminal intraduodenal segment. Nerve cell bodies of the gallbladder were found in an inter-connecting network of ganglia that were located in the serosa, muscularis and mucosa. Nerve fibres innervated the muscle, arterioles and the mucosa. Few ganglia were found along the supra sphincteric portion of the common bile duct. Nerve trunks followed the duct and a dense nerve fibre plexus was found in the mucosa. In the sphincter most ganglia were located in two plexuses, the first between the layers of the external sphincter muscle, which was continuous with the external muscle of the duodenum, and the second was associated with the internal sphincter muscle. Nerve fibres were numerous in the sphincter muscle, and were also found in the subepithelial and periglandular plexuses of both the pancreatic and common bile ducts.

Animals↗
PubMed1993

Effects of halothane anesthesia on the motility of the sphincter of Oddi and transsphincteric flow in Australian brush-tailed possums.

We evaluated the effect of halothane anesthesia on the motility of the sphincter of Oddi and simultaneous transsphincteric flow in Australian Brush-tailed possums (Trichosurus vulpecula). Halothane levels in the range of 0.25 to 2% were administered and decreased transsphincteric flow in a dose-dependent manner. Sphincter of Oddi basal pressure was higher than normal, but not in a dose-dependent manner. Additionally, halothane anesthesia influenced the sphincter of Oddi motility by decreasing the motility index (mean amplitude multiplied by frequency of contractions). This decrease was dose dependent. These findings indicate that sphincter of Oddi basal pressure is a major component of sphincter of Oddi motility responsible for regulating transsphincteric flow in this species. For studies of the sphincter of Oddi motility in anesthetized Australian Brush-tailed possums, we recommend anesthetic induction with ketamine (50 mg/kg, i.m.) and the inspired halothane level should not exceed 0.75% during the study period, as the effects we have demonstrated were most evident at levels greater than 0.75%. If higher halothane levels are required to maintain satisfactory anesthesia, an alternative anesthetic agent should be considered.

Animals↗