Douglas C. Barnhart

Conservative management of mesenchymal hamartoma of the liver

The natural history of mesenchymal hamartoma of the liver is poorly understood. This case demonstrates the course of a biopsy-proven mesenchymal hamartoma using sequential computed tomography (CT) examinations. These CT scans show initial expansion of the lesion with subsequent involution. The spontaneous resolution in this patient suggests the possibility of conservative management of asymptomatic mesenchymal hamartomas. The case is presented, and the literature on mesenchymal hamartoma is reviewed.

Capacitative Ca2+ entry in enteric glia induced by thapsigargin and extracellular ATP

Mobilization of intracellular Ca2+ stores is coupled to Ca2+ influx across the plasma membrane, a process termed capacitative Ca2+ entry. Capacitative Ca2+ entry was examined in cultured guinea pig enteric glia exposed to 100 μM ATP, an inositol trisphosphate-mediated Ca2+-mobilizing agonist, and to 1 μM thapsigargin, an inhibitor of microsomal Ca2+ ATPase. Both agents caused mobilization of intracellular Ca2+stores followed by influx of extracellular Ca2+. This capacitative Ca2+ influx was inhibited by Ni2+ (88 ± 1%) and by La3+ (87 ± 1%) but was not affected by L- or N-type Ca2+channel blockers. Pretreatment of glia with 100 nM phorbol 12-myristate 13-acetate for 24 h decreased capacitative Ca2+ entry by 48 ± 2%. Chelerythrine (0.1-10 μM), a specific antagonist of protein kinase C (PKC), dose dependently inhibited capacitative Ca2+ entry. The nitric oxide synthase inhibitor N G-nitro-l-arginine (1 mM) decreased Ca2+ influx by 42 ± 1%. Capacitative Ca2+ entry was inhibited to a similar degree by the guanylate cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one). Capacitative Ca2+ entry occurs in enteric glial cells via lanthanum-inhibitable channels through a process regulated by PKC and nitric oxide.Mobilization of intracellular Ca2+ stores is coupled to Ca2+ influx across the plasma membrane, a process termed capacitative Ca2+ entry. Capacitative Ca2+ entry was examined in cultured guinea pig enteric glia exposed to 100 microM ATP, an inositol trisphosphate-mediated Ca2+-mobilizing agonist, and to 1 microM thapsigargin, an inhibitor of microsomal Ca2+ ATPase. Both agents caused mobilization of intracellular Ca2+ stores followed by influx of extracellular Ca2+. This capacitative Ca2+ influx was inhibited by Ni2+ (88 +/- 1%) and by La3+ (87 +/- 1%) but was not affected by L- or N-type Ca2+ channel blockers. Pretreatment of glia with 100 nM phorbol 12-myristate 13-acetate for 24 h decreased capacitative Ca2+ entry by 48 +/- 2%. Chelerythrine (0.1-10 microM), a specific antagonist of protein kinase C (PKC), dose dependently inhibited capacitative Ca2+ entry. The nitric oxide synthase inhibitor NG-nitro-L-arginine (1 mM) decreased Ca2+ influx by 42 +/- 1%. Capacitative Ca2+ entry was inhibited to a similar degree by the guanylate cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one). Capacitative Ca2+ entry occurs in enteric glial cells via lanthanum-inhibitable channels through a process regulated by PKC and nitric oxide.

Immediate and long-term results of surgical management of low imperforate anus in girls

BACKGROUND The majority of girls with imperforate anus are reported to have a malformation of the low variety. Despite this, much of the literature has focused on the more complex, high lesions. METHODS This study reviews our experience with 44 girls with low imperforate anus from a 22-year period. RESULTS The incidence of associated anomalies was 61%, which is higher than generally reported. All patients in the study had anal fistulae. Fifty-seven percent had perineal fistulae, 23% had fourchette fistulae, and 20% had vestibular fistulae. Cutback anoplasty was performed in 55%, Potts transfer anoplasty was used in 27%, and 18% of patients were treated with either limited posterior sagittal anorectoplasty or anterior sagittal anorectoplasty. Surgical complications were uncommon. Long-term follow-up was carried out by telephone survey. This showed 89% of the girls to be successfully toilet trained. However, 47% of patients experience at least occasional soilage or episodic fecal incontinence. CONCLUSIONS Low imperforate anus can be successfully treated using a variety of procedures without colostomy. Most girls with low imperforate anus are successfully toilet trained, but problems with continence persist in a significant number of these patients.

Endothelin-Stimulated Capacitative Calcium Entry in Enteric Glial Cells: Synergistic Effects of Protein Kinase C Activity and Nitric Oxide

Abstract: Depletion of intracellular calcium stores by agonist stimulation is coupled to calcium influx across the plasma membrane, a process termed capacitative calcium entry. Capacitative calcium entry was examined in cultured guinea pig enteric glial cells exposed to endothelin 3. Endothelin 3 (10 nM) caused mobilization of intracellular calcium stores followed by influx of extracellular calcium. This capacitative calcium influx was inhibited by Ni2+ (89 ± 2%) and by La3+ (78 ± 2%) but was not affected by L‐, N‐, or P‐type calcium channel blockers. Chelerythrine, a specific antagonist of protein kinase C, dose‐dependently inhibited capacitative calcium entry. The nitric oxide synthase inhibitor NG‐nitro‐l‐arginine decreased calcium influx in a dose‐dependent manner. The combination of chelerythrine and NG‐nitro‐l‐arginine produced synergistic inhibitory effects. Capacitative calcium entry occurs in enteric glial cells via lanthanum‐inhibitable channels through a process regulated by protein kinase C and nitric oxide.

PACAP-38 causes phospholipase C-dependent calcium signaling in rat acinar cell line

BACKGROUND Pituitary adenylate cyclase activating peptide (PACAP-38), a neuropeptide of the vasoactive intestinal peptide/secretin family, localizes to intrapancreatic neurons and stimulates exocrine secretion from the pancreas. PACAP-38 stimulates calcium signaling in the rat pancreatic cell line AR42J. The purpose of this study was to elucidate the mechanisms of PACAP-evoked calcium signaling in these cells. METHODS Continuous measurements of intracellular calcium were taken by fluorescent digital microscopy with the dye fura-2. Mechanisms of PACAP-38-evoked calcium signals were determined by a panel of inhibitors. Inositol phosphates production in response to PACAP-38 was measured. The ability of PACAP-38 to stimulate amylase release was used to determine a relevant dose range for these studies. RESULTS We have shown that (1) AR42J cells respond to PACAP-38 with biphasic increases in [Ca2+]i in a dose-dependent fashion; (2) PACAP-38 acts through phospholipase C to release inositol triphosphate (IP3)-sensitive Ca2+ stores with (3) a subsequent influx of extracellular Ca2+. CONCLUSIONS PACAP-38 activates calcium signaling through phospholipase C at concentrations that stimulate amylase release in AR42J cells.

Tachykinin Neuropeptide-Evoked Intracellular Calcium Transients In Cultured Guinea Pig Myenteric Neurons

Substance P and related tachykinins are present in the mammalian gut and act as neurotransmitters. Microfluorimetric measurement of intracellular calcium ([Ca2+]i) was used to study tachykinin-sensitive myenteric neurons. Substance P (0.001-10 microM) evoked concentration-dependent increases in percentage of neurons responding (6-75%) and delta [Ca2+]i (88 +/- 24 to 212 +/- 16 nM). Neurokinin A (0.001-1 microM) produced similar responses. Removal of extracellular Ca2+ abolished substance P-induced Ca2+ signals, as did the addition of the Ca2+ channel blockers lanthanum chloride (5 mM) and nickel chloride (2.5 mM). Both nifedipine (1-50 microM) and diltiazem (1-50 microM) inhibited substance P-evoked Ca2+ responses in a dose-dependent manner. Substance P and related tachykinins evoke Ca2+ signaling in cultured myenteric neurons by the influx of extracellular Ca2+ through L and N-type plasma membrane Ca2+ channels.

Calcium signaling induced by angiotensin II in the pancreatic acinar cell line AR42J

The purpose of this study was to characterize the nature and mechanisms of angiotensin II-evoked calcium signaling in AR42J cells. Cytosolic calcium concentrations were determined using fura-2-based microfluorimetry. Angiotensin II causes elevations in free cytosolic calcium ([Ca2+]i) in the rat pancreatic acinar cell line AR42J. The mechanisms of angiotensin II-evoked calcium signaling were examined using fura-2-based fluorescent digital microscopy. Angiotensin II caused dose-dependent increments in [Ca2+]i over a concentration range of 0.1-1,000 nM, with an average increment of 243 +/- 16 nM at an angiotensin II concentration of 1,000 nM. Dup753, an AT1-specific antagonist, inhibited angiotensin II-evoked signaling, whereas the AT2 antagonist PD123,319 had no effect. Preincubation with the phospholipase C inhibitor U73122 reduced the response in [Ca2+]i to 25% of that of the control. Thapsigargin abolished angiotensin II-evoked calcium signaling. The inositol 1,4,5-trisphosphate receptor antagonist heparin introduced by radiofrequency electroporation inhibited responses to 46 +/- 6% of controls. Angiotensin II-evoked signals were reduced in magnitude and duration by elimination of Ca2+ from the extracellular buffer. Preincubation with pertussis toxin (100 ng/ml) had no effect. Angiotensin II did not stimulate cyclic AMP or suppress vasoactive intestinal peptide stimulated cyclic AMP production over the concentration range that caused Ca2+ signaling.

Cholinergic Intrapancreatic Neurons Induce Ca2+ Signaling and Early-Response Gene Expression in Pancreatic Acinar Cells

Pancreatic exocrine function has been demonstrated to be under neuronal regulation. The pathways responsible forthis effect, and the long-term consequences of such interactions, are incompletely described. The effects of neuronal depolarization on pancreatic acinar cells were studied to determine whether calcium signaling and c-fos expression were activated. In pancreatic lobules, which contain both neurons and acinar cells, agonists that selectively stimulated neurons increased intracellular calcium in acinar cells. Depolarization also led to the expression of c-fos protein in 24% ±4% of the acinar cells. In AR42J pancreatic acinar cells, cholinergic stimulation demonstrated an average increase of 398 ±19 nmol/L in intracellular calcium levels, and induced c-fos expression that was time and dose dependent. The data indicate that intrapancreatic neurons induce Ca2+ signaling and early-response gene expression in pancreatic acinar cells.