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M Hanani

Publications and source records attributed to M Hanani.

At least 55 records · Page 3Linked to original sources
PubMed1993

A simple and rapid method for staining the enteric ganglia: application for Hirschsprung's disease.

A simple and reliable method is described for staining the nerve plexuses of the human gastrointestinal tract in whole-mounts. The staining does not require fixation and consists of a single step of 6 to 10 minutes incubation in a solution of the fluorescent dye 4-(4-diethylaminostyryl)-methylpyridinium iodide. Aganglionic bowel specimens from 6 patients with Hirschsprung's disease were stained by this method and displayed the absence of ganglion cells and an abundance of nerve fibers in the myenteric and submucosal plexuses. This staining may be suitable for the diagnosis of Hirschsprung's disease.

Child, Preschool↗
PubMed1992

N-methylated analogs of Ac[Nle28,31]CCK(26-33): synthesis, activity, and receptor selectivity.

A series of singularly N-methylated analogs of Ac[Nle28,31]CCK(26-33) were synthesized by the solid-phase methodology, and their biological activity was tested in three different in vitro bioassays. The bioassays employed were the guinea pig gallbladder (GPGB), stomach (GPS), and ileum (GPI). All N-methyl analogs were agonists in all three bioassays. N-Methylation at either N- or C-terminals did not affect potency and selectivity, whereas N-methylation of internal residues [Nle28,(N-Me)Nle31]- and [Nle28,31,(N-Me)Trp30]CCK(26-33) in the sequence resulted in analogs which were 10-fold less potent than Ac[Nle28,31]CCK(26-33) in all three preparations. Different rank orders of potencies observed for [Nle28,31,Sar29]- and [Nle28,31,(N-Me)Asp32]CCK(26-33) analogs correspond to increased selectivity to either GPGB or GPS, respectively. We propose that systematic N-methylation of single amide bonds in a bioactive peptide should be conducted as an additional routine to probe structure-activity relationships.

Amino Acid Sequence↗
PubMed1992

Visualization of enteric and gallbladder ganglia with a vital fluorescent dye.

A method is described here for the vital staining of the nerve plexuses of the gastrointestinal tract with the fluorescent dye 4-(4-diethylaminostyryl)-methylpyridinium iodide (4-Di-2-ASP). This dye stained nerve fibers in the myenteric and submucosal plexuses and in the intramural ganglia of the gallbladder. In addition to staining the ganglia, the dye clearly revealed the secondary and the fine tertiary fibers of the myenteric plexus. In the submucosal plexus thin fibers innervating the blood vessels were also stained. This method proved to be effective in tissues that are relatively thick and in which the visualization of the nerves is quite difficult without staining--the myenteric plexus of rat small intestine, guinea-pig gallbladder and human large intestine. The staining did not fade within at least 6-8 h, or after long exposure to bright light. Intracellular recordings from myenteric neurons in the guinea pig ileum showed that cellular properties were not significantly altered after incubation in the dye solution. 4-Di-2-ASP thus appears to be suitable for rapid vital staining of nerves in whole mount from many parts of the gastrointestinal tract.

Animals↗
PubMed1992

Modulation of dye coupling among glial cells in the myenteric and submucosal plexuses of the guinea pig.

Dye coupling among glial cells in the ganglia of the myenteric and submucosal plexuses of the guinea-pig ileum was studied by intracellular injection of the dye Lucifer yellow (LY), which crosses gap junctions. The injection of a single glial cell with LY resulted in the staining of many glia. The mean number of cells coupled to the injected one was 87.0 +/- 7.9 in the myenteric plexus, and 20.7 +/- 5.6 in the submucosal plexus. As previously shown for myenteric plexus, injection of horseradish peroxidase into submucosal glia resulted in the staining of only a single cell. Dye coupling was significantly reduced in both plexuses by lowering intracellular pH, by replacing 100 mM of the chloride ions with propionate ions or by bubbling the solution with 100% CO2. Octanol (0.3 mM) also markedly diminished dye coupling in the two preparations. These treatments are known to block gap junctions in a variety of tissues. It is concluded that, like central glial cells, enteric glia are extensively coupled. This coupling is apparently mediated by gap junctions.

Action Potentials↗
PubMed1992

Corticotropin-releasing hormone excites myenteric neurons in the guinea-pig small intestine.

The electrophysiological actions of corticotropin-releasing hormone (CRH) on myenteric neurons from the guinea-pig ileum were studied by intracellular microelectrode recording. CRH, when applied by micropressure ejection or in the medium (0.2-20 nM) evoked prolonged depolarization in 21 of 42 S/type 1 neurons and in 28 of 40 AH/type 2 neurons. These responses were associated with increased input resistance and augmented excitability. The post-spike hyperpolarization in AH/type 2 cells was suppressed during the CRH-evoked responses. The reversal potential of the response to CRH was about -90 mV, consistent with the closure of potassium channels by the peptide. The CRH-induced depolarization was prevented by incubation in 10 microM 5'-N-ethylcarboxamidoadenosine (NECA, an adenosine analog) suggesting that the response was mediated by stimulation of adenylate cyclase and elevation of cAMP. CRH reduced the amplitude of fast nicotinic excitatory postsynaptic potentials. This appeared to be a postsynaptic action because the peptide also reduced the responses to exogenously applied acetylcholine. These results suggest that CRH can directly influence intestinal function by acting on myenteric neurons.

Animals↗
PubMed1991

Intracellular recordings from gallbladder ganglia of opossums.

Postganglionic parasympathetic neurons of the opossum gallbladder were studied using morphological and intracellular electrophysiological recording techniques. On average there were 17 ganglia/cm2 with 8 neurons/ganglion arranged as loosely or densely packed clusters. Intracellular injection of horseradish peroxidase identified two types of neurons. Most of the neurons (approximately 80%) had a single long process that extended beyond the ganglion border with few or no short additional neurites. The other type was multipolar, having several processes that did not appear to extend beyond the ganglion border. Gallbladder neurons had passive and active electrical properties similar to other parasympathetic ganglion cells. Most of neurons studied (71%) responded to intracellular injection of suprathreshold depolarizing current with a short burst of action potentials. The remaining neurons (29%) responded with only an initial action potential. Seventy percent of the neurons tested received nicotinic fast excitatory postsynaptic potentials (EPSPs). Nineteen percent of these neurons also exhibited a slow depolarizing response following repetitive orthodromic nerve stimulation. Cholecystokinin octapeptide sulfate (CCK-8, 0.1-500 nM) had no effect on resting membrane potential or membrane input resistance. However, CCK-8 increased the amplitude of fast EPSPs evoked by orthodromic nerve stimulation by facilitating release of acetylcholine because CCK-8 had no effect on the postsynaptic response to exogenously applied acetylcholine. These data suggest that the ganglionated plexus of the gallbladder may mediate some of the observed effects of CCK-8 on gallbladder motility.

Acetylcholinesterase↗
PubMed1990

Intercellular dye-coupling in intestinal smooth muscle. Are gap junctions required for intercellular coupling?

The dye Lucifer Yellow was injected into single smooth muscle cells in the guinea pig small intestine in order to study intercellular coupling. Dye-coupling was observed in both the circular and longitudinal muscle layers and was markedly reduced when the intercellular pH was lowered. These results suggest the presence of gap junctions among intestinal muscle cells, but are inconsistent with previous ultrastructural studies that failed to demonstrate such junctions in the longitudinal muscle.

Animals↗
PubMed1990

Rapid effects of MPTP in the mouse colon.

Mechanical responses of the mouse colon to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were measured in vitro. MPTP caused muscle relaxation with an onset time of about 10 s. This relaxation was inhibited by propranolol. Pretreatment of the animals with reserpine significantly reduced the MPTP-induced relaxation. These observations indicate that MPTP liberates a catecholamine (presumably noradrenaline) from nerve terminals in the colon wall. The mechanism underlying this effect is not yet clear but it appears that oxidation to 1-methyl-4-phenyl-pyridinium is not required.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1989

Glial cells in the guinea pig myenteric plexus are dye coupled.

Glial cells in the myenteric plexus of the guinea pig small intestine were stained intracellularly with Lucifer yellow and horseradish peroxidase. The cells were identified by both their electrophysiological characteristics and by their morphology. Injection of Lucifer yellow, which is known to cross gap junctions, resulted in the staining of many (up to about 100) glial cells. The staining pattern was comparable to the immunostaining of glia with an antiserum for S-100 protein. In contrast to Lucifer yellow, horseradish peroxidase (which does not cross these junctions), was confined to the injected cell. It is concluded that enteric glia are coupled, presumably by gap junctions. This finding indicates that in addition to structural and biochemical similarities, enteric glia may share certain physiological characteristics with central nervous system astrocytes.

Action Potentials↗
PubMed1988

The actions of receptor-selective substance P analogs on myenteric neurons: an electrophysiological investigation.

Intracellular recordings were made from myenteric neurons of the guinea-pig duodenum and the responses to local ejection of several substance P (SP) analogs were examined. It was found that senktide (succinyl-[Asp6,Me-Phe8]SP-(6-11)), a selective analog for the NK-3 (SP-N) receptor, was particularly effective in depolarizing the neurons. It was 20-100 times more potent than SP and about 1000-fold more potent than the selective analogs for the NK-1 (SP-P) receptor, which resides on muscle cells. The response to the peptides was prolonged (20-120 s), but in about 20% of the cells there was a fast, early depolarizing component (observed only with senktide). In most cases there was an increase in the input resistance of the cell during the slow depolarization. Together with the finding that the response reversed at about -90 mV, this indicates that the response is due to the closure of K+ channels. The results support the existence of an NK-3 (SP-N) receptor and provide direct information about the membrane mechanisms through which NK-3 agonists excite myenteric neurons.

Action Potentials↗
PubMed1987

The effect of meperidine on the guinea pig extrahepatic biliary tract.

The effect of meperidine on the mechanical activity of isolated guinea pig common bile duct (CBD) and gallbladder was studied in vitro. The effect was found to consist of inhibitory and excitatory phases. The inhibitory phase, characterized by a decrease in the response of the CBD and gallbladder to carbachol and electrical stimulation, was seen with concentrations of 10(-6) M or higher. The excitatory phase, seen at high concentrations of meperidine (5 X 10(-5)-10(-4) M), involved an increase in spontaneous contractions of CBD and in the tone of the gallbladder. Neither effect of meperidine was affected by 0.5 X 10(-5) M naloxone. These data indicate that meperidine acts on the biliary tract by a mechanism different from that associated with the effect of morphine.

Animals↗
PubMed1987

Effect of morphine on the mechanical activity of common bile duct isolated from the guinea pig.

The contractile response of isolated guinea pigs common bile ducts (CBD) to transmural electrical stimulation and the effects of morphine and naloxone was studied. Contractile responses increased as a function of stimulus frequency. In the absence of naloxone morphine inhibited the contractile response to electrical stimulation in a dose-dependent manner. Naloxone prevented the inhibitory effect of morphine on the contractile response to electrical stimulation. We conclude that smooth muscle of the CBD in guinea pig is functional and can contribute to biliary motility, and that opiate receptors exist in nerve elements in the CBD.

Animals↗
PubMed1986

Phenazine methosulfate induces a neurally-mediated contraction of the guinea-pig ileum.

Phenazine methosulfate (PMS) and related phenazines are widely used in biochemistry and histochemistry and act as anti-bacterial agents, however, there is little information on their pharmacological actions. In the present paper the guinea-pig ileum was used as a model for studying the effects of PMS on nerve cells. PMS was found to contract intestinal muscle. This action appeared to be mediated by the activation of muscarinic receptors since it was blocked by atropine. Neostigmine potentiated the response to PMS. The nerve blocker tetrodotoxin prevented the effect of PMS and it is concluded that PMS causes the release of acetylcholine from nerve elements. The action of PMS on nerves is not mediated by nicotinic receptors. Receptors for serotonin, substance P or cholecystokinin also appear not to be involved. Of all the phenazines tested PMS was found to be the most potent and reversible.

Acetylcholine↗
PubMed1986

The relation between sensitivity changes and response time scale in the barnacle photoreceptor.

Responses to brief light flashes were recorded intracellularly from the photoreceptors of the barnacle in order to study the relation between changes in sensitivity and latency. Conditioning lights either increased the response to a test flash (facilitation) or reduced it (desensitization). In both cases there was a shortening of the response latency. Similar observations were made when background illumination was used instead of conditioning lights. These effects were not qualitatively altered when the extracellular Ca2+ concentration was lowered. The results suggest that facilitation is not the result of a reduction of intracellular Ca2+ concentration; i.e. it is not the reverse of desensitization. Since during facilitation there is an increase in photoresponse associated with latency shortening it can be suggested that the underlying mechanism is an enhancement of the effective light intensity. The experiments do not provide quantitative evidence for this idea.

Adaptation, Ocular↗
PubMed1986

Nerve mediated responses to drugs and electrical stimulation in aganglionic muscle segments in Hirschsprung's disease.

The activity of isolated muscle strips from normal and aganglionic human large bowel was studied in vitro. The intrinsic nerves were stimulated electrically and by nicotinic agonists. The ganglionic preparations displayed a strong inhibitory response due to the release of both norepinephrine and a noncholinergic, nonadrenergic inhibitory neurotransmitter. In the aganglionic strips (obtained from patients with Hirschsprung's disease), nerve activation tended to evoke contraction, apparently due to enhancement in the release of acetylcholine. At the same time, the release of norepinephrine appeared to be less than normal. A particularly interesting finding in the aganglionic muscle strips was the presence of a substantial inhibitory response due to the release of a noncholinergic, nonadrenergic substance. These results provide further evidence for the importance of the innervation of the aganglionic segment in Hirschsprung's disease.

Child↗
PubMed1986

Effects of serotonin on the internal anal sphincter: in vivo manometric study in rats.

The effects of serotonin (5-hydroxytryptamine, 5-HT) on the internal anal sphincter were studied in anaesthesized rats. Serotonin induced a dose dependent relaxation of the internal anal sphincter. Methysergide blocked this relaxation, but did not affect the rectoanal reflex. Methysergide did not antagonise the actions of cholinergic and adrenergic agonists on the internal anal sphincter. Other 5-HT antagonists such as cyproheptadine, ketanserin, chlorpromazine, amitriptyline and ergotamine failed to reduce or block the internal anal sphincter relaxation due to 5-HT, nor did they alter the rectoanal reflex. Adrenergic and cholinergic antagonists had no effect on the 5-HT-induced relaxation of the internal anal sphincter, suggesting that 5-HT acts upon the internal anal sphincter via a non-adrenergic, non-cholinergic mechanism. Tetrodotoxin reduced or blocked the relaxation of the internal anal sphincter produced by 5-HT, implying that 5-HT acts through neural pathways rather than directly on the muscle. It is concluded that although 5-HT relaxes the internal anal sphincter, it does not participate in the rectoanal reflex.

Anal Canal↗
PubMed1985

The actions of substance P and serotonin on myenteric neurons in tissue culture.

Intracellular recordings were made from guinea-pig myenteric neurons in tissue culture. The responses to substance P (SP) and serotonin were compared. Putative transmitters were ejected by pressure from micropipettes. The response to SP was, in the majority of cases, a prolonged depolarization, with a latency of 1-5 s and a duration of 1-2 min. During the depolarization there was an increase in the input resistance of the cells, and the excitability was augmented. In two neurons the response to SP was hyperpolarization followed by depolarization. In about 30% of the cells the response to SP was relatively fast, with a duration of less than 10 s and a latency of less than 100 ms. These responses did not show desensitization. Serotonin induced relatively fast responses only, with durations of 0.3-3 s and latencies of 20-50 ms. These responses were usually depolarizing, but in 3 cells were hyperpolarizing. Two types of behaviour were observed during repetitive ejection of serotonin. Some cells showed strong desensitization while in others there was no desensitization and there was even summation. The actions of SP and serotonin were compared by their ejection in the same experiments. The same general properties described above were observed. It is concluded that the two putative transmitters act via distinct response mechanisms. The SP-induced depolarizations in tissue culture resemble in several respects the slow synaptic potentials recorded previously in myenteric neurons in freshly isolated preparations.

Animals↗