Richard B. Lynn

Decreased cerebrospinal-fluid/serum leptin ratio in obesity: a possible mechanism for leptin resistance

BACKGROUND A receptor for leptin has been cloned from the choroid plexus, the site of cerebrospinal-fluid (CSF) production and the location of the blood/cerebrospinal-fluid barrier. Thus, this receptor might serve as a transporter for leptin. We have studied leptin concentrations in serum and (CSF). METHODS AND FINDINGS We demonstrated by radioimmunoassay and western blot the presence of leptin in human CSF. We then measured leptin in CSF and serum in 31 individuals with a wide range of bodyweight. Mean serum leptin was 318% higher in 8 obese (40.2 [SE 8.6] ng/mL) than in 23 lean individuals (9.6 [1.5] ng/mL, p < 0.0005). However, the CSF leptin concentration in obese individuals (0.337 [0.04] ng/mL) was only 30% higher than in lean people (0.259 [0.26] ng/mL, p < 0.1). Consequently, the leptin CSF/serum ratio in lean individuals (0.047 [0.010]) was 4.3-fold higher than that in obese individuals (0.011 [0.002], p < 0.05). The relation between CSF leptin and serum leptin was best described by a logarithmic function (r = 0 x 52, p < 0.01). INTERPRETATION Our data suggest that leptin enters the brain by a saturable transport system. The capacity of leptin transport is lower in obese individuals, and may provide a mechanism for leptin resistance.

Solitarial premotor neuron projections to the rat esophagus and pharynx: Implications for control of swallowing

BACKGROUND & AIMS The buccopharyngeal and esophageal phases of swallowing are controlled by distinct networks of premotor neurons localized in the nucleus tractus solitarius. The neuronal circuitry coordinating the two phases was investigated using a combination of central and peripheral tracing techniques. METHODS Using pseudorabies virus, a transsynaptic tracer, in anesthetized rats, third-order esophageal neurons (neurons projecting to premotor neurons) were identified. In a separate protocol that combined transsynaptic and retrograde fluorescent tracing, third-order esophageal neurons projecting to pharyngeal motoneurons (buccopharyngeal premotor neurons) were then identified. RESULTS Third-order esophageal neurons were identified in the interstitial and intermediate subnuclei of the nucleus tractus solitarius and in other medullary, pontine, midbrain, and forebrain nuclei. A subpopulation of these neurons (double labeled) in the interstitial and intermediate subnuclei were found to project to pharyngeal motoneurons (buccopharyngeal premotor neurons) and to be linked synaptically to esophageal premotor neurons. CONCLUSIONS The synaptic link between buccopharyngeal and esophageal premotor neurons provides an anatomic pathway for the central initiation of esophageal peristalsis and its coordination with the pharyngeal phase of swallowing. This neural circuitry within the nucleus tractus solitarius is consistent with a complex central control mechanism for the swallowing motor sequence that can function independently of afferent feedback.

Intermittent intravenous pantoprazole and continuous cimetidine infusion: effect on gastric pH control in critically ill patients at risk of developing stress-related mucosal disease.

BACKGROUND This study aimed to assess intermittent intravenous (IV) pantoprazole for control of gastric acid and the possible prevention of upper gastrointestinal (UGI) bleeding in intensive care units (ICU) patients. METHODS This was a multicenter, randomized, open-label, dose-ranging pilot study of IV pantoprazole (40 mg q24 hour; 40 mg q12 hour; 80 mg q24 hour; 80 mg q12 hour; 80 mg q8 hour) or continuously infused cimetidine (300 mg bolus; 50 mg/h) in patients at risk for UGI bleeding. The primary endpoint was percent time gastric pH >/=4.0. UGI bleeding and pneumonia were measured as secondary endpoints. RESULTS Two hundred two ICU patients were randomized. Gastric pH was well controlled by all treatments. Gastric pH control improved from day 1 to day 2 in all pantoprazole groups, whereas there was decreased pH control in the cimetidine group. There were no cases of protocol defined UGI bleeding in any treatment group. Adverse event frequency and pneumonia incidence were similar between pantoprazole and cimetidine treated patients. CONCLUSIONS This pilot study indicates that intermittent IV pantoprazole effectively controls gastric pH and may protect against UGI bleeding in high risk ICU patients without the development of tolerance.

Distribution of bombesin-like immunoreactivity in the nucleus of the solitary tract and dorsal motor nucleus of the rat and human: colocalization with tyrosine hydroxylase.

Bombesin is a peptide neurotransmitter/neuromodulator with important autonomic and behavioral effects that are mediated, at least in part, by bombesin‐containing neurons and nerve terminals in the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (DMV). The distribution of bombesin‐like immunoreactive nerve terminals/fibers and cell bodies in relation to a viscerotopically relevant subnuclear map of this region was studied by using an immunoperoxidase technique. In the rat, bombesin fiber/terminal staining was heavy in an area that included the medial subnucleus of the NTS and the DMV over their full rostral‐caudal extent. Distinctly void of staining were the gelatinous, central, and rostral commissural subnuclei and the periventricular area of the NTS, regions to which gastric, esophageal, cecal, and colonic primary afferents preferentially project. The caudal commissural and dorsal subnuclei had light bombesin fiber/terminal staining, as did the intermediate, interstitial, ventral, and ventrolateral subnuclei. With colchicine pretreatment, numerous cell bodies were stained in the medial and dorsal subnuclei, with fewer neurons in the caudal commissural, intermediate, interstitial, ventral, and ventrolateral subnuclei. Bombesin‐like immunoreactive neurons were found in numerous other areas of the brain, including the ventrolateral medulla, the parabrachial nucleus, and the medial geniculate body. In the human NTS/DMV complex, the distribution of bombesin fiber/terminal staining was very similar to the rat. In addition, occasional bombesin‐like immunoreactive neurons were labeled in a number of subnuclei, with clusters of neurons labeled in the dorsal and ventrolateral subnuclei. Double immunofluorescence studies in rat demonstrated that bombesin colocalizes with tyrosine hydroxylase in neurons in the dorsal subnucleus of the NTS. Bombesin does not colocalize with tyrosine hydroxylase in any other location in the brain. In conclusion, the distribution of bombesin in the NTS adheres to a viscerotopically relevant map. This is the anatomical substrate for the effects of bombesin on gastrointestinal function and satiety and its likely role in concluding a meal. The anatomic similarities between human and rat suggest that bombesin has similar functions in the visceral neuraxis of these two species. Bombesin coexists with catecholamines in neurons in the dorsal subnucleus, which likely mediate, in part, the cardiovascular effects of bombesin.

Colocalization of NADPH-diaphorase staining and VIP immunoreactivity in neurons in opossum internal anal sphincter.

Nitric oxide and vasoactive intestinal polypeptide (VIP) are important inhibitory neurotransmitters mediating relaxation of the internal anal sphincter. The location and coexistence of these two neurotransmitters in the internal anal sphincter has not been examined. We performed a double-labeling study to examine the coexistence of nitric oxide synthase and VIP in the oppossum internal anal sphincter using the NADPH-diaphorase technique which is a histochemical stain for nitric oxide synthase. In perfusion-fixed, frozen-sectioned tissue, VIP-immunoreactive neurons were labeled using immunofluorescence histochemistry. After photographing the VIP-immunoreactive neurons, nitric oxide synthase was labeled using the NADPH-diaphorase technique. Ganglia containing neuronal cell bodies were present in the myenteric plexus for the entire extent of the internal anal sphincter. VIP-immunoreactive and NADPH-diaphorase-positive neurons were present in ganglia in the myenteric as well as the submucosal plexuses. Most of the VIP-immunoreactive neurons were also NADPH-diaphorase positive. VIP and nitric oxide synthase are present and frequently coexist in neurons in the internal anal sphincter of the opossum. These neurons may be an important source of inhibitory innervation mediating the rectoanal reflex-induced relaxation of the sphincter. The demonstration of the coexistence of these two neurotransmitters will be of fundamental importance in unraveling their relationship and interaction in the internal anal sphincter as well as other systems.

Heme oxygenase activity in the internal anal sphincter: Effects of nonadrenergic, noncholinergic nerve stimulation

BACKGROUND & AIMS To date, the exact role of carbon monoxide (CO) in the nonadrenergic, noncholinergic (NANC) relaxation is not known. This is partly related to the lack of an appropriate method to measure heme oxygenase (HO) activity in the gastrointestinal tissues. METHODS HO activity of the opossum internal anal sphincter (IAS) smooth muscle was determined using a newly developed assay system that used radiolabeled hemin as a substrate. Enzyme activity of the IAS tissues was measured in the basal state, after electric field stimulation (EFS), ganglionic stimulant dimethyl diphenyl piperazinium iodide (DMPP), and neuropeptide vasoactive intestinal polypeptide (VIP). The presence and localization of HO was examined by Western blot analysis and immunocytochemistry. RESULTS NANC nerve stimulation of the IAS smooth muscle by EFS (0.25-5 Hz), DMPP, and VIP caused a significant increase in the HO activity of the IAS. The increase in HO activity by EFS was inhibited by the HO inhibitor Tin protoporphyrin (1 x 10(-4) mol/L). Both HO-1 and HO-2 were present in the IAS tissue extracts, and both enzymes were localized in the neurons of the myenteric plexus. The method for HO activity determination used in the present study was found to be reliable and reproducible. CONCLUSIONS The data suggest that the HO pathway may have a role in neurally mediated relaxation of the IAS. The exact site of involvement and the source of HO activity, however, remains to be determined.

Clinical Value of Esophageal Motility Testing

Esophageal motility testing is the method of choice in evaluating esophageal motor disorders. Some physicians, however, question the clinical utility of esophageal motility testing, since the results are often normal in symptomatic patients. The clinical utility of esophageal motility testing is reviewed for patients with a complaint of noncardiac chest pain, dysphagia or symptoms of gastroesophageal reflux disease. Esophageal motility testing is particularly useful for evaluating patients with dysphagia, but less so for gastroesophageal reflux disease patients, and has little clinical utility in patients with noncardiac chest pain.

Inhibition of pentagastrin-stimulated gastric acid secretion by pantoprazole and omeprazole in healthy adults

Our objective was to compare the onset and duration of a single dose of pantoprazole or omeprazole on maximally stimulated gastric acid secretion. This double-blind, randomized, placebo-controlled study involved 36 healthy adults and utilized continuous pentagastrin infusion to stimulate acid secretion after administration of pantoprazole, 40 mg, omeprazole, 20 mg, or placebo. Gastric aspirates were collected over 24 hr and analyzed for volume, pH, and hydrogen ion concentration, and gastric acid outputs (GAO) were calculated. Comparison between GAO and intragastric pH was performed. Pantoprazole resulted in significantly greater inhibition of GAO than omeprazole. Mean cumulative 24-hr GAO was 164 ± 130 mEq for pantoprazole versus 283 ± 159 mEq for omeprazole (P = 0.031). Pantoprazole patients reached and maintained GAO levels below the 10-mEq/hr threshold at 5.7 hr, whereas omeprazole patients never reached this threshold. We conclude that pantoprazole significantly suppressed gastric acid secretion compared to omeprazole. Comparisons between pH and GAO showed that GAO was a more appropriate measure of gastric acid secretion than intragastric pH.

Ultrastructure of bombesin-like immunoreactive nerve terminals in the nucleus of the solitary tract and the dorsal motor nucleus.

Bombesin (gastrin-releasing peptide 14-27) inhibits gastric function and feeding when microinjected into the nucleus of the solitary tract (NTS)/dorsal motor nucleus of the vagus (DMV) complex. We performed a preembedding immunoelectron microscopic study in rats to describe the bombesin containing nerve terminals and to characterize their postsynaptic structures. 228 bombesin-L1 nerve terminals which made synaptic contacts in the NTS/DMV complex were studied. Labeling was heaviest over dense core vesicles and lighter over small clear vesicles. The dense core vesicles were typically located along the plasmalemma away from the synaptic face, a finding that is typical of neuropeptide containing nerve terminals. The postsynaptic structures were most often medium sized dendrites (56%) and small sized dendrites (27%), with similar percentages in the NTS and DMV. In the DMV, synapses on cell bodies (8%) were more frequent than in the NTS (1%). In the NTS, synapses on dendritic spines (10%) were more frequent than in the DMV (4%). Only a single axo-axonal contact was identified. These findings add to the increasing body of evidence that bombesin is a neurotransmitter/neuromodulator in the NTS/DMV complex. Bombesin rarely makes presynaptic (axo-axonal) contacts that might inhibit the release of excitatory neurotransmitters, but rather makes postsynaptic contacts potentially effecting vagal motoneurons.

Manifestations of Crohn's Disease

Accessible online at: http://BioMedNet.com/karger Fig. 1. A 62-year-old female with a history of Graves’ disease and fistula in ano presented to the emergency room with a 1-month history of bloody diarrhea, fever, chills, night sweats, and fatigue. On physical examination she was febrile to 38.5°C and had multiple lingual (a), gingival (b) oral ulcers, and vulvar ulcers. Ophthalmologic examination showed no uveitis. Laboratory data were significant for a hematocrit of 26% (normal 35–45), a mean corpuscular volume of 71 (normal 80–96), and a white blood cell count of 8.7/mm3 (normal 3.2–9.8). Erythrocyte sedimentation rate was 1140 mm/h (normal 0–15). Stool studies showed numerous fecal leukocytes, but no ova or parasites. Stool culture was negative for Salmonella, Shigella, and Campylobacter. ANCA and FANA were both negative. Colonoscopy revealed colitis with deep ulcers from the rectum to the midtransverse colon. Therapy with 5-ASA and prednisone was initiated and resulted in prompt disappearance of the oral and vaginal ulcers. Because of failure to wean off the prednisone, azathioprine was added. One year later, she presented with recurrent urinary tract infections and fever, but denied pneumaturia or fecaluria. Physical examination revealed multiple perirectal abscesses and fistulous tracts. An abdominal computerized tomography scan revealed air in the bladder (c, arrow) and thickened sigmoid colon adjacent to the bladder which was suspicious of a fistula. A vesiculogram showed extraluminal contrast in communication with the rectosigmoid colon compatible with enterovesical fistula. Despite maximal therapy with immunosuppressives, steroids, 5-ASA, and antibiotics, the patient required a total abdominal colectomy with ileostomy and takedown of the fistula. Microscopic examination of the colonic specimen revealed fulminant active and chronic colitis with rare granulomas consistent with Crohn’s disease (d, !900). Now, several months after surgery, the patient is doing well with no recurrence of her fistula. b