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M Hanani

Publications and source records attributed to M Hanani.

At least 37 records · Page 2Linked to original sources
PubMed1998

The three-dimensional structure of myenteric neurons in the guinea-pig ileum.

Myenteric neurons of the guinea-pig ileum were intracellularly filled with the fluorescent dye Lucifer Yellow, optically sectioned with a confocal microscope and volume reconstructed to recreate 3-D images of the cells. The resulting images provide information not evident from regular microscopy. The somata varied in cross-section from flat-oval to nearly circular, and their surface membranes were marked by invaginations and protrusions significantly increasing the surface area of the somatic membrane. The neurons could be divided into four morphological classes: Dogiel type I, Dogiel type II, filamentous, and intermediate. There was no clear correlation between cell class and the shape of the soma in cross-section. The dendritic processes of all the neurons studied extended in an orad-caudad or circumferential direction of the bowel wall. When the filled neurons were viewed edge-on, the spatial arrangement of the processes was confined to a plane that had a thickness less than the thickness of the parent soma. The broad, short dendrites of Dogiel type I neurons were oval or nearly circular in cross-section. Directly measured quantitative data were obtained for the volume and surface area of the somata and visible processes. The structural details reported herein are likely to have important implications regarding the functional properties of individual enteric ganglion neurons and circuits of enteric ganglion neurons.

Animals↗
PubMed1998

Visualization of interstitial cells of Cajal in the mouse colon by vital staining.

Interstitial cells of Cajal (ICCs) are believed to be a major element in generating the spontaneous rhythm of the gastrointestinal tract. A prominent problem in the study of these cells has been the difficulty in observing them in intact tissues. We used the lipophilic dye DiI to stain ICCs in the submucosal-circular muscle border of freshly dissected mouse colon. The placement of small DiI crystals in this area resulted in the labeling of ICC-like cells. Two main morphological cell types, viz., bipolar and multipolar, were noted. Bipolar cells had two primary processes emerging from the poles of an elongated soma. The mean length of these processes was 78.7 microm. These cells constituted 42.3% of the sample (n=105). Multipolar cells (54.3% of total) had a less elongated soma and extended 3-6 main processes whose mean length was 56.3 microm. These processes showed no preferred direction. The length of the primary processes of bipolar cells was 40% greater than that of multipolar cells (P<0.02). Three cells (2.9%) had only one primary process. The DiI stain could be converted into a stable electron-opaque product. Electron-microscopic observations showed that these cells had the typical appearance of ICCs reported in previous studies. This staining method should be useful for physiological investigations of ICCs in gastrointestinal tissues.

Animals↗
PubMed1998

Effects of erythromycin on contractility of isolated myometrium from pregnant rats.

OBJECTIVE: Erythromycin is a stimulant of motor activity in the stomach, but its effects on the uterus have not been studied and only its antibiotic properties have been considered in the treatment of idiopathic preterm labor. The objective of this study was to characterize in vitro the effect of erythromycin on the contractility of the pregnant rat uterus. STUDY DESIGN: Myometrial strips from pregnant rats were suspended in tissue baths Isometric contractions were monitored by force transducers in response to various agents that were added to the bath solution. RESULTS: Erythromycin exposure caused a sustained decrease in phasic contractions induced by oxytocin or carbachol. This effect started at 0.01 mmol/L. At 1 mmol/L erythromycin reduced the contractions amplitude to 22% of the control and the frequency was reduced to 38% of control. CONCLUSION: We conclude that erythromycin produces a decrease in the pregnant rat myometrial activity in vitro, independent of the stimulant.

Animals↗
PubMed1998

Bacterial wall lipopolysaccharide as a cause of intussusception in mice.

BACKGROUND: There is evidence that intussusception is associated with bacterial infection. It was hypothesized that a component of the bacterial wall may induce the intussusception. This study was intended to determine whether lipopolysaccharide from Escherichia coli or Salmonella can initiate intussusception in mice. METHODS: Lipopolysaccharide was injected intraperitoneally in mice, and the animals were examined for the presence of intussusception from 2 to 192 hours after injection. Gastrointestinal transit was assessed by measuring the passage of charcoal in the small intestine. Transit index was defined as the ratio between the distance traveled by charcoal and the total length of the small intestine. RESULTS: Intussusceptions were found in as much as 25.9% of lipopolysaccharide-injected animals, whereas in control animals, the incidence was zero. The threshold for the lipopolysaccharide effect was at 4 mg/kg and incidence reached a plateau at 8 mg/kg to 16 mg/kg. The incidence of intussusception peaked 6 hours after injection of lipopolysaccharide and declined to zero after 15 hours. To test the possibility that lipopolysaccharide induces intussusception by altering motility, its effect on transit index was measured. A dose of 12 mg/kg lipopolysaccharide reduced the transit index from 56.2+/-1.4% to 37.7+/-2.1% (p < 0.05). No microscopic histologic changes were found in the bowels with intussusception. CONCLUSIONS: Intraperitoneal bacterial wall lipopolysaccharide causes intussusception in mice by disturbing gastrointestinal motility.

Animals↗
PubMed1997

Phorbol esters alter the morphology of cultured guinea-pig myenteric glia via a protein kinase C-independent mechanism.

Cultures of myenteric ganglia from adult guinea-pigs were used to study the influence of neuroactive substances on glial cells by monitoring changes in their morphology. The following substances had no effect on glial morphology: adenosine, ATP, carbachol, glutamate, bradykinin, isoprenaline, prostaglandin E2, sodium nitroprusside and lipopolysaccharide. The only substances found to affect glial morphology were phorbol esters, and in particular phorbol 12-myrisate 13-acetate (PMA), which acted at the nM range. Glial cells, which were normally polygonal, assumed a stellate shape within 30-60 min after the addition of PMA. Protein kinase C (PKC) inhibitors did not block this effect, and PKC activators did not mimic it. The effect of PMA was also not mediated by changes in the intracellular concentrations of either Ca2+, H+ or cyclic AMP. Dye coupling among glial cells was blocked by PMA. The phorbol ester-mediated effect on glial structure may have profound influence on neuronal organization and function.

Animals↗
PubMed1997

The contribution of inflammatory mediators and nitric oxide to lipopolysaccharide-induced intussusception in mice.

Intussusception is a major cause for intestinal obstruction in children. Its etiology is unclear, but it is often associated with some kind of infection. We have developed a model for intussusception in mice using intraperitoneal (IP) injection of lipopolysaccharide (LPS). The objective of this study was to identify the putative mediators that participate in this LPS-induced intussusception. LPS (12 mg/kg) was injected into adult mice (N = 52) and 6 hr later, 25% of the animals demonstrated intussusception in the small or large intestine. We next tested whether nitric oxide (NO) or various inflammatory mediators contributed to this effect: Indomethacin (10 mg/kg) injected with LPS (12 mg/kg) completely prevented the effect of LPS (N = 20). The tumor necrosis factor (TNF) blocker pentoxifylline (200 mg/kg) significantly reduced the incidence of intussusception to 6.6% (N = 30). The platelet-activating factor (PAF) antagonist BN52021 (10 and 20 mg/kg) reduced the incidence of intussusception to 13.3% in both doses (N = 15 for each dose). Addition of 2% arginine (NO precursor) to the drinking water 36 hr before the injection of LPS increased the incidence of intussusception to 30.7% (N = 32). In mice injected with the NO synthase inhibitor L-NAME (20 mg/kg) only 3.8% developed intussusception (N = 26). Our results indicate that the induction of intussusception by LPS proceeds via parallel pathways involving cytokines, prostaglandins, and NO. Our previous pathological study showed that LPS did not cause any changes that may act as a lead point for the intussusception, suggesting that LPS induced intussusception by altering gut motility. We therefore propose that these mediators combine to induce disturbed gut motility that results in the formation of intussusception.

Animals↗
PubMed1997

Immunoreactivity for the Fas ligand in the mammalian enteric nervous system.

The Fas ligand induces apoptosis in activated immunocytes that express the Fas receptor. Fas-ligand transcripts have been found previously in murine intestine but the intestinal tissues that express Fas ligand have not been identified. We used immunohistochemistry to examine the expression of the Fas ligand in the enteric nervous system of rats, mice, guinea-pigs, ferrets and humans. Fas-ligand immunoreactivity was detectable in enteric nerve fibres and neurons in all species tested, representing 25%-50% of the neurons in rats, mice and guinea-pigs. An antigen of approximately 48 kDa was detected by Western blot analysis with Fas-ligand antiserum in the dissected enteric plexuses of duodenum from a C3H/HeJ mouse. In gld mice that harbour a Fas-ligand mutation, Fas-ligand immunoreactivity was slightly more intense in neurons and fibres and was also apparent in submucosal lymphocytes. In the myenteric plexuses of guinea-pig ileum and human colon, Fas-ligand immunoreactivity was not contained in neurons exhibiting nicotinamide-adenine dinucleotide phosphate-diaphorase activity. In the submucosal plexus of guinea-pig ileum, labelled neurons included some neuropeptide-Y-containing neurons but none with vasoactive intestinal polypeptide. We conclude that the Fas ligand is expressed by a large subset of enteric neurons and may provide the basis for cytotoxic neuroimmune interactions in the intestines.

Animals↗
PubMed1997

Synthesis and biological activity of novel backbone-bicyclic substance-P analogs containing lactam and disulfide bridges.

A biased library of 60 novel backbone-bicyclic Substance P analogs was prepared by the simultaneous multiple peptide synthesis method. The peptides, containing both a lactam and a disulfide ring, were synthesized by combined Boc and Fmoc chemistries, and were cyclized on the resin. Cleavage of the S-benzyl group and oxidation of the sulfhydryl groups was enabled by adaptation of the diphenylsulfoxidetrichloromethylsilane method to solid-phase synthesis. The peptides were screened for NK-1 and NK-3 activity, and were found to be weak agonists.

Animals↗
PubMed1997

Activity-dependent changes in intracellular calcium in myenteric neurons.

The spatial distribution and changes in intracellular calcium concentration ([Ca2+]i) in myenteric neurons were measured using fura 2 in the longitudinal muscle-myenteric plexus preparation from the guinea pig duodenum. These measurements were made simultaneously with intracellular voltage recordings. The generation of action potentials in the cell bodies of both S- and AH-type neurons increased [Ca2+]i in the processes and cell bodies. There was no measurable delay between the [Ca2+]i changes in the somata and the processes, indicating that these changes were caused by the spread of electrical signals and not by diffusion. The rate of Ca2+ removal was faster in the processes than in the somata, apparently due to the large surface-to-volume ratio in the former. In AH neurons, the [Ca2+]i transient was shorter than the duration of the after-spike hyperpolarization. It is concluded that the two main types of myenteric neurons possess voltage-gated Ca2+ channels in both somata and processes.

Action Potentials↗
PubMed1997

Microscopic analysis of pressure ejection of drugs from micropipettes.

Ejection of drugs from micropipettes by pressure is widely used for chemical stimulation of cells in electrophysiological experiments, but little is known about the dynamics of the processes involved. Several aspects of the formation of liquid droplets were studied by photographing them under a microscope using brief light flashes. The observations led to the following conclusions: 1. The characteristics of the micropipette tip strongly influence both the amount of liquid and the shape of the droplet. Micropipettes were divided according to their tip diameter. Those with a 3-8 microns diameter tip produce small droplets that remain near the tip; those with a tip diameter of 9-15 microns produce conical droplets that extent some distance from the tip; droplets ejected from micropipettes with tip diameter greater than 15 microns are mushroom-shaped and reach distances several hundred microns from the tip. 2. Back-flow of the bath medium, due to capillary force, diminishes the amount of the drug ejected from the micropipette. This effect is very prominent when brief (< 100 ms) pressure pulses are used, and to overcome it priming of the micropipettes several seconds before use is required. 3. Flow of the bath medium can divert the droplet from the expected trajectory. This point was verified during intracellular recordings of responses to pressure-ejected substance P in myenteric neurons. The recommended parameters for optimal use of pressure ejection are: tip diameter of 10-15 microns, pressure of 80-100 kPa, pulse pressure duration over 100 ms and priming by pressure pulse of 1-2 s duration; liquid column of about 5 cm can minimize back-flow.

Animals↗
PubMed1996

The actions of ketotifen on intestinal smooth muscles.

Ketotifen is a tricyclic drug with a wide spectrum of pharmacological effects. We studied the actions of ketotifen on the mechanical activity of isolated segments of guinea-pig ileum, guinea-pig colon and mouse colon. In the guinea-pig ileum ketotifen induced small contractions and inhibited the contractions induced by carbachol and by electric field stimulation. Responses to bradykinin (in the absence or in the presence of atropine 1 microM) were similarly inhibited by ketotifen, with an IC50 of 23 microM. In the guinea-pig colon ketotifen evoked non-cholinergic contractions with a pD2 of 4.5, but still it inhibited responses to bradykinin (IC50 = 75 microM). Ketotifen relaxed the unstimulated mouse colon with a pD2 of 4.2. This effect persisted in the presence of propranolol and phentolamine (each 10 microM). Incubation of the mouse colon with the nitric oxide synthase inhibitors NG-nitro-L-Arginine methyl ester hydrochloride (L-NAME), or L-NG-nitro-arginine (L-NNA) (100-500 microM) did not alter the inhibitory action of ketotifen. The histamine H1 receptor antagonist chlorpheniramine (5 microM) or the nerve blocker tetrodotoxin (1 microM) did not alter the inhibitory effects of ketotifen. It is concluded that the actions of ketotifen are mediated by a non-cholinergic, non-histaminergic mechanisms.

Animals↗
PubMed1996

Light, electron, and confocal microscopic study of the mouse superior mesenteric ganglion.

The superior mesenteric ganglion (S.m.g.), a sympathetic prevertebral ganglion, is an integrating center for gastrointestinal reflexes. Many details of its structure are still lacking. In the present study, mouse S.m.g. neurons were studied by light, electron, and confocal microscopy. Neurons had an average of 5-6 primary dendrites. Total dendritic length averaged 963 microns. Confocal microscopy and three-dimensional reconstructed images revealed cell body surface features, precise location where axons and dendrites emerged from it, cell body size, and extent of dendritic projection in three axes. Cell body diameter and dendritic projections were less in the dorsoventral than in the rostrocaudal or mediolateral axes. Cell body surface area and volume averaged 4,271 microns 2 and 4,908 microns 3, respectively. Dendritic surface areas and volumes were 5-6 times larger. Two main neuron types (projecting caudally or rostrally) were distinguished. The former were found throughout the S.m.g., whereas the latter were found only in the cephalad region, comprising about 40% of neurons found there. Rostrally projecting neurons had fewer primary dendrites, fewer total dendritic branches, and shorter total dendritic length than caudally projecting neurons. There were regional differences in percentage of neurons responding to electrical stimulation of left or right hypogastric, lumbar colonic, or left splanchnic nerves but not in nerve fibers connecting the S.m.g. and celiac ganglion. A greater percentage of caudally than rostrally projecting cephalad neurons responded to stimulation of any nerve trunk. These results indicate that the mouse S.m.g. contains at least two distinct types of neurons that differ in their morphology and their source of preganglionic synaptic input.

Animals↗
PubMed1995

Nitric oxide-containing nerves in bowel segments of patients with Hirschsprung's disease.

To assess the role of nerves that synthesize nitric oxide (NO) in Hirschsprung's Disease (HD), the authors studied the distribution of the enzyme NADPH diaphorase (NADPHd) in normal and diseased bowel segments. In the proximal (ganglionic) segment of the colon, NADPHd-positive neurons were present in both myenteric and submucosal plexuses. In the distal involved colonic segments from HD patients, the typical pattern of the neuronal network was completely missing in the regions of the two plexuses; instead, only disorganized NADPHd-positive nerve fibers were present and NADPHd-reactive neurons were absent. Mucosal NO synthase activity was 2.76 +/- 0.38 nmol/g/min in the proximal segment and only 0.83 +/- 0.49 nmol/g/min in the distal segment (P < .05, N = 3).

Adult↗
PubMed1995

Intracellular recordings from intramural neurons in the guinea pig urinary bladder.

1. Intracellular recordings were made from intramural neurons in the urinary bladder of guinea pigs. 2. The neurons were located in two types of ganglia: those where the cells were densely packed and those where the neurons were loosely packed. Staining of the cells by intracellular injections of markers showed that the cells had between one to three long processes and several short dendrites. 3. The resting potential measured in 230 neurons was -55.20 +/- 0.67 (SE) mV, and the input resistance was 58.37 +/- 1.78 M omega. 4. Injection of depolarizing currents from the recording electrode evoked two types of firing patterns. In 86.2% of the neurons, depolarizing currents evoked a prolonged firing of action potentials (tonic cells). In the rest of the neurons, a depolarization elicited one to three action potentials only (phasic cells). In all the cells tested, the action potentials were reversibly blocked by tetrodotoxin (TTX; 1 microM). In the presence of TTX. Ca2+ spikes were observed in 50% of the cases. 5. Single action potentials were followed by fast hyperpolarizations having mean duration of 92.7 +/- 6.0 ms and amplitude of 13.3 +/- 1.0 mV. In 62.5% of the cells repetitive firing of action potentials was followed by delayed, slow hyperpolarizations (duration 3.8 +/- 0.5 s), which were diminished by the K+ channel blocker 4-aminopyridine and in Ca+2-free high-Mg2+ medium. These results indicate that the prolonged after-spike hyperpolarizations were due to opening of Ca(2+)-induced K+ channels. 6. Electrical stimulation of nerve fiber tracts evoked fast excitatory synaptic potentials that were blocked by the nicotinic receptor antagonist hexamethonium (0.2 mM). Exogenous acetylcholine elicited depolarizations that were also blocked by hexamethonium. Nerve stimulation at frequencies of 0.1 Hz or higher caused strong facilitation of the synaptic potentials. Stimulation at 10-20 Hz did not evoke slow synaptic potentials.

Acetylcholine↗
PubMed1994

Morphology of horseradish peroxidase (HRP)-injected glial cells in the myenteric plexus of the guinea-pig.

Glial cells of the myenteric plexus from guinea pig small intestine were intracellularly filled with horseradish peroxidase (HRP), and histochemically stained. Camera lucida-like drawings of twenty cells were morphologically and morphometrically analyzed. The cells have very small ellipsoid somata (8.5 +/- 0.7 microns equivalent diameter, i.e., about 330 micron3 volume), and send up to 20 thin and short processes (less than 26 to about 110 microns in length). The morphology of the cells appears to depend on their location within the plexus. Glial cells located within the ganglia are similar to CNS protoplasmic astrocytes; they are star-shaped, and their very short processes are irregularly branched. In contrast, glial cells within the interganglionic fiber tracts resemble CNS fibrous astrocytes. They extend longer processes that are parallel to the fiber tracts, and show less tendency to branch. We propose that the morphology of enteric glia is determined by the structure of the microenvironment. Both cell types form several flat endfeet at a basal lamina either surrounding blood vessels or at the ganglionic border. Furthermore, the occurrence of "holes" in the glial cell processes suggests that particular neuronal cell processes may be enwrapped in a specific manner. Fractal analysis of camera lucida-like drawings of the cells showed that the cells have a highly complex surface structure, comparable to that of protoplasmic astrocytes in the brain. These tiny cells may possess a membrane surface area of approximately 2000 micron2, almost 90% of which are contributed by the cell processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Inhibition of gastrointestinal motility by MPTP via adrenergic and dopaminergic mechanisms.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was injected intraperitoneally in mice and caused an acute inhibition (of over 60%) of gastrointestinal motility, which was measured by the transit of charcoal. This inhibition was not related to conversion of MPTP to MPP+. Administration of the beta-adrenergic blocker propranolol significantly reduced, but did not completely block, the effect of MPTP. The dopaminergic blocker haloperidol also partly reversed the effects of MPTP. When these blockers were administered together, the action of MPTP was fully blocked. The results indicate that the toxin acted by releasing catecholamines (presumably norepinephrine and dopamine), thereby inhibiting motility.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

Enteric glial cells are major contributors to formation of cyclic AMP in myenteric plexus cultures from adult guinea-pig small intestine.

Cultures derived from ganglia isolated from the small intestine of adult guinea-pigs were used to determine relative contribution of neurons and glial cells to stimulation of cAMP formation by forskolin in myenteric ganglia. In untreated cultures (8-12 days), the ratio of glial cells to neurons was 5-fold higher than the ratio in intact myenteric plexus preparations. Treatment with cytosine arabinoside virtually eliminated the glia by the 12th day. Microelectrode recording of excitatory responses to forskolin in AH/Type 2 neurons confirmed the viability of cultured neurons in cytosine arabinoside. Forskolin elevated the cAMP content of cultures and cytosine arabinoside reduced this effect by 80-90%. This suggests that enteric glial cells are the major contributors to cAMP formation in the cultures and that glial cells contribute significantly to elevation of cAMP levels seen in intact myenteric ganglia.

Animals↗