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Biomedical subjects

M Davidoff

Publications and source records attributed to M Davidoff.

At least 37 records · Page 2Linked to original sources
PubMed1990

Effects of (MET-5) enkephalin on the electrically-evoked mechanical responses in longitudinal and circular strips of the cat terminal ileum.

In longitudinal and circular strips from cat terminal ileum field electrical stimulation at a frequency of 2 Hz evoked contractile responses. Stimulation at frequencies of 10 or 30 Hz elicited contractions of the longitudinal muscle and relaxations of the circular strips. (Met-5) enkephalin (1 nM) naloxone-dependently reduced the contractile and increased the inhibitory responses. Atropine (3 microM) converted the contractile responses to slight relaxations and potentiated the inhibitory responses. After atropine (3 microM) and guanethidine (50 microM) both longitudinal and circular strips responded to electrical stimulation with relaxations. In atropine-pretreated strips (Met-5) enkephalin was effective only in the circular strips, increasing the inhibitory responses. In contrast, after atropine and guanethidine (Met-5) enkephalin decreased these inhibitory responses. In unstimulated strips (Met-5) enkephalin failed to change the responses to acetylcholine and noradrenaline. It is concluded that (Met-5) enkephalin reduces the excitatory cholinergic components of the electrically-evoked responses in both longitudinal and circular strips as well as the excitatory adrenergic and the inhibitory non-adrenergic, non-cholinergic components of the responses in the circular strips by acting presynaptically. Demonstration of (Met-5) enkephalin-like immunoreactivity showed immunostaining in nerves of the myenteric plexus and in nerve fibers between the smooth muscle cells suggesting that (Met-5) enkephalin effects could be also of physiological significance.

Acetylcholine↗
PubMed1990

Histo- and immunohistochemical changes in acetylcholinesterase and choline acetyltransferase activities in the amygdaloid complex in aged rats.

Histo- and immunohistochemical distribution of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) in the amygdaloid nuclei of young adult (3 month old) and aged (26 month old) Wistar rats was compared. AChE staining and ChAT immunoreactivity showed the same regional variations in the amygdaloid nuclei of young adult rats. The density and staining of AChE- and ChAT-positive fibres, terminals, and nerve cells were reduced in aged rat amygdala. Moreover, heavily stained aberrant fibres and coarse terminals were located around the nerve cells, blood vessels, and occasionally in patches. In aged rats, atrophic AChE positive and ChAT immunoreactive nerve cells exhibited serpentine-like, thicker, and less extensively branched dendrites than those in young adult rats. These changes are similar to the age-related changes in the cholinergic enzymes in other brain regions which are targets to the basal forebrain.

Acetylcholinesterase↗
PubMed1990

Immuno- and histochemical data on changed GABA transmission in aged rat cerebellum.

The distribution of gamma-aminobutyric acid-immunoreactivity (GABA-I) and activity of GABA-transaminase (GABA-T) was compared in the cerebellum of young adult (3-month old) and aged (24-month old) Wistar rats. A decrease in the density and staining of GABA-immunoreactive and GABA-T positive nerve cells, fibers and puncta were observed in both cerebellar cortex and nuclei of aged rats as compared to those in young adult rats. In contrast, an increased number of Bergmann glia cell and astrocyte processes and bodies in aged rats were demonstrated in GABA immunostaining and histochemical GABA-T reaction. The changes in GABA-I and GABA-T activity provide evidence for altered GABA transmission during normal aging of rat cerebellum.

4-Aminobutyrate Transaminase↗
PubMed1989

Electron microscopical localization of guanylate cyclase activity in the neocortex of the guinea pig.

The localization of the guanylate cyclase (GC) activity has been established in the neocortex of adult guinea pigs by means of electron microscopical histochemistry [the DMSO-method of Fujimoto et al. (1981)]. Reaction product was deposited within a population of large- and medium-sized cortical neurons as well as in the cytoplasm of a part of the dendrites of variable size and in the cytoplasm and the nuclear membrane of a number of protoplasmic astrocytes. In the perikarya of the positive neurons, the reaction precipitate was mainly located within the cisterns of the rough endoplasmic reticulum and on the nuclear membrane. In the dendrites, the reaction product was usually distributed in close contact with microtubules, microfilaments, and beneath the postsynaptic membranes of a number of axodendritic synaptic contacts. The axons and all presynaptic boutons were negative. Thus, the localization of the GC could be determined as exclusively postsynaptic. The results obtained support the view for the probable participation of cyclic GMP in the cholinergic, glutaminergic or GABAergic, or peptidergic transmitter mechanisms in the central nervous system.

Animals↗
PubMed1989

Immunocytochemical demonstration of substance P in hamster Leydig cells during ontogenesis.

The cellular localization of substance P immunoreactivity was demonstrated at the light microscopical level in the hamster testis during fetal and postnatal development. A selective immunostaining was observed both of fetal and adult generation of Leydig cells. The comparison of the immunocytochemical findings with the ultrastructural characteristics of Leydig cells provided evidence that Leydig cells besides their androgen-producing capacity also had an neuropeptide producing function. The possible role of substance P in the local paracrine control of gametogenesis was discussed.

Animals↗
PubMed1989

Immuno- and histochemical evidence for changed neurotransmission in basal forebrain, hippocampal formation and neocortex of aged rats.

The distribution of choline acetyltransferase- and gamma-aminobutyric acid-immunoreactivity as well as acetylcholinesterase-, gamma-aminobutyrci acid-transaminase- and monoaminooxidase-positive structures in the basal forebrain, hippocampal formation and neocortex of young adult and aged rats was compared. The changes in the staining and density of the immuno- and histochemical positive nerve cells and fibers observed provide evidence for the involvement of different transmitters in normal ageing.

Aging↗
PubMed1989

[Acetylcholinesterase activity, choline acetyltransferase and GABA immunoreactivity in the ventral horn of the spinal cord of rats during chromatolysis].

A comparative study on the changes of the acetylcholinesterase activity (AChE) and of choline acetyltransferase (ChAT)- and GABA-like immunoreactivity (LI) has been performed in the ventral horn cells of the spinal cord of white rats 1, 2 and 3 weeks after transection of the right sciatic nerve. For the visualization of the AChE the method of Karnovsky and Roots (1964) was used. ChAT-LI was demonstrated by means of the avidin-biotin-peroxidase complex method (Hsu et al., 1981), whereas GABA-LI was localized using the PAP-method of Sternberger et al. (1970). In the control rats AChE-activity was observed on the cellular membrane, weaker in the cytoplasm of the perikarya and the proximal processes of the motoneurons; a pericellular localization of the reaction product was also established. ChAT-like immunoreactivity was mainly observed in the cytoplasm of the perikarya and the cellular processes, whereas GABA-like was most intensive in the nuclei of a number of motoneurons and in the more distal parts of their dendrites; the staining intensity of the perikaryal cytoplasm was weaker. During chromatolysis a progressive decrease of the staining intensity of the reactions for all the 3 substances was observed. In some neurons there was a total loss of the immunoreactivity. These results suggest that during chromatolysis: 1. the production of acetylcholine and GABA decreases; 2. the GABA which coexists within some cholinergic motoneurons may be expressed by these cells and 3. the AChE activity may also in the future be used as a marker of the cholinergic system of the anterior horn cells of the spinal cord.

Acetylcholinesterase↗
PubMed1988

Serotonin-like immunoreactivity in the cat trigeminal ganglion.

The immunohistochemical distribution of serotonin-like immunoreactivity (SER-LI) has been established in networks of fine nerve fibers which arborize and wind profusely between non-immunoreactive sensory neurons in the cat trigeminal ganglion. Some of the varicose nerve fibers surround occasional non-immunoreactive sensory neurons like a woven basket. None of the sensory neurons display SER-LI. An extrinsic origin of intraganglionic fine nerve fibers has been suggested.

Animals↗
PubMed1988

Immunocytochemical and electronmicroscopical data on the differentiation of somatostatin-containing endocrine cells in human large intestine.

The distribution and ultrastructure of the somatostatin-containing endocrine cells in the distal large intestine of fetuses, children and adults was investigated by silver impregnation, immunocytochemical and electron-microscopical techniques. Somatostatin-containing endocrine cells in 10-14-week-old fetuses were found to differentiate very intensively. In 19-25-week-old fetuses the frequency of occurrence began to decrease and this tendency was preserved during the subsequent stages of ontogenesis. Conversely, the frequency of occurrence of argyrophil endocrine cells increased. The change in the mean diameters of the secretory granules was also studied.

Adult↗
PubMed1986

Histochemical, immunocytochemical and ultrastructural data on the innervation of the smooth muscle of the large intestine in Hirschsprung's disease.

The frequency of occurrence of the adrenergic, cholinergic, 5-hydroxytryptamine (5-HT)-, substance P (SP)-, methionine-enkephalin (met-Enk)- and somatostatin (SOM)-immunoreactive fibres innervating the smooth muscle of the large intestine in Hirschsprung and control children was compared. It was observed a higher frequency of catecholamine-fluorescence, acetylcholinesterase-positive and SOM-immunoreactive fibres in the muscularis externa and muscularis mucosa of the aganglionic segment in Hirschsprung gut as compared to that in the sigmoid colon and rectum in controls. In contrast, the frequency of SP-, met-Enk- and 5-HT-immunoreactive fibres in the aganglionic segment in Hirschsprung gut was lower than that in the controls. Ultrastructurally the cholinergic and adrenergic fibres occurred more often in the aganglionic segment in Hirschsprung gut than in the controls. A treatment with 6-OHDA and a fixation by Tranzer and Richards technique was used to confirm the nature of the adrenergic fibres. The p-type fibres occurred infrequently in the aganglionic segment of Hirschsprung gut. The results suggest that the change in the frequency of the nerves containing inhibitory transmitters may play an important role in the pathogenesis of Hirschsprung's disease.

Adolescent↗
PubMed1986

Distribution of substance P-, methionine-enkephalin-, somatostatin- and serotonin-immunoreactive nerve elements of the large bowel in Hirschsprung's disease.

The distribution of substance P-, methionine-enkephalin-, somatostatin- and 5-hydroxytryptamine-immunoreactive nerve elements in Hirschsprung's disease was studied. It was compared to the distribution of the comparable nerve elements in the sigmoid colon and rectum of control children. A reduction of substance P-, methionine-enkephalin- and 5-hydroxytryptamine-immunoreactive fibers as well as a higher density of somatostatin-immunoreactive fibers were found in the aganglionic segment in Hirschsprung gut as compared to those in the ganglionic segment in Hirschsprung children and the large bowel in control children. The changes in the density of peptide- and 5-hydroxytryptamine-immunoreactive fibers suggest the participation of different transmitters or transmitter candidates in the pathogenesis of Hirschsprung's disease.

Child↗
PubMed1984

Immunocytochemical localization of substance P, methionine-enkephalin and somatostatin in the cat intestinal wall.

The localization of substance P-(SP-), methionine-enkephalin (met-Enk-) and somatostatin (SOM-)like immunoreactivity was studied in the cat pyloric sphincter, ileum, ileocecal sphincter and proximal colon. The enteric plexuses in all regions examined contained SP-, met-Enk- and SOM-like immunoreactive varicose nerve fibres. A large number of especially SP- and met-Enk-containing varicosities were often seen to encircle the nerve cell bodies and processes in the two ganglionic plexuses. The SOM-like immunoreactive perikarya were the only peptide-containing nerve cells, preferentially located in the submucous ganglia. The predominant localization of the SOM-like immunoreactive neurons in the two enteric plexuses of the ileum was the most pronounced regional difference in the distribution pattern of the peptides. Among the layers of the cat intestinal wall the circular muscle contained the most peptide-immunoreactive fibres in contrast to the longitudinal muscle. Evidence was obtained for the occurrence of single peptide-immunoreactive varicose nerve fibres in muscularis mucosae as well as around the glands and the blood vessels. Immunoreactive endocrine cells occurred mainly in the ileum mucosa.

Animals↗
PubMed1983

Neurotransmitted effect of prostaglandin F2 alpha in isolated cat jejunum.

Prostaglandin F2 alpha (PGF2 alpha) (1 nM-0.1 microM) increased the amplitude of the spontaneous phasic contractions and produced tonic contraction of the isolated longitudinal muscle from the cat jejunum. The amplitude of the electrically-induced contractions increased by PGF2 alpha (1 nM-10 nM) in a dose-dependent degree. PGF2 alpha decreased the inhibitory effect of indomethacin (30 microM) on the contractile response to electrical stimulation. Hexamethonium did not influence the PGF2 alpha effect on the electrically-induced contractions but inhibited the PGF2 alpha-produced tonic contractions. The contractile effect of PGF2 alpha depended on the number of impregnated nerve cells and terminals preserved in the preparations long after dissection. The data suggest that PGF2 alpha increases the acetylcholine release and that there is a "stepwise" action of PGF2 alpha on the transmitter release from the postganglionic or preganglionic cholinergic terminals depending on the PGF2 alpha concentration and leading to phasic or tonic smooth-muscle contractions.

Acetylcholine↗
PubMed1981

[Distribution of some hydrolases in the rat kidney (author's transl)].

Most of the available histochemical methods and techniques (azodye, metal salt and indigogenic methods, cryostat, free-floating and lyophilized section techniques) and different modifications of these methods (different substrate concentrations, pH, temperature, incubation time e.g.) were applied to study the distribution of acid phosphatase (AcPB = after Barka and Anderson; AcPG = after Gomori), beta-glucuronidase (beta-Glu), aryl sulfatase (AS), beta-N-acetylglucosaminidase (NAG), acid 5'-nucleotidase (a5-Nucl), non-specific esterase (NE) and alkaline phosphatase (AlP) in the kidneys of rats of both sexes. The optimal conditions for the demonstration of these enzymes were established. As most important proved: the incubation of free-floating sections cut from "standard"-fixed (2 h in formol-calcium continued for another 18-22 h in the same fixative plus 0.88 M sucrose at 4 degrees C) kidney slices - only for AcPB and NE material fixed after Holt had to be used; the incubation for AlP and NE at 4 degrees C; final pH of the incubation medium for AcPB 5.5, AcPG 5.0 and NE 6.5; the use of Fast Garnet GBC Salt as coupler in the NE azo-dye reaction. Sex differences and for the female rats an increased activity during oestrus were established for all hydrolases studied. In particular the following results were obtained: AcPB, a5-Nucl and A1P are more intensive in male and AcPG in female S1 segments of the juxtamedullary nephrons in relation to the nephrons of the other parts of the cortex. In the medullary rays the NE and the a5-Nucl show a higher activity in the S2 segments of female rats demonstrate a more intensive activity for NAG and NE. This is true for AcPG and A1P in male rats. In the inner medulla a stronger beta-Glu activity in male rats and a stronger NAG activity in female rats is observed. The AcPB activity of the cortical distal tubules is higher in male rats.

5'-Nucleotidase↗