Biomedical subjects

M Petkó

Publications and source records attributed to M Petkó.

At least 19 recordsLinked to original sources

PubMed2000

Propriospinal afferent and efferent connections of the lateral and medial areas of the dorsal horn (laminae I-IV) in the rat lumbar spinal cord.

The different subdivisions along the mediolateral extent of the superficial dorsal horn of the spinal cord are generally regarded as identical structures that execute the function of sensory information processing without any significant communication with other regions of the spinal gray matter. In contrast to this standing, here we endeavor to show that neural assemblies along the mediolateral extent of laminae I-IV cannot be regarded as identical structures. After injecting Phaseolus vulgaris leucoagglutinin and biotinylated dextran amine into various areas of the superficial dorsal horn (laminae I-IV) at the level of the lumbar spinal cord in rats, we have demonstrated that the medial and lateral areas of the superficial dorsal horn show the following distinct features in their propriospinal afferent and efferent connections: 1) A 300- to 400-microm-long section of the medial aspects of laminae I-IV projects to and receives afferent fibers from a three segment long compartment of the spinal dorsal gray matter, whereas the same length of the lateral aspects of laminae I-IV projects to and receives afferent fibers from the entire rostrocaudal extent of the lumbar spinal cord. 2) The medial aspects of laminae I-IV project extensively to the lateral areas of the superficial dorsal horn. In contrast to this, the lateral areas of laminae I-IV, with the exception of a few fibers at the segmental level, do not project back to the medial territories. 3) There is a substantial direct commissural connection between the lateral aspects of laminae I-IV on the two sides of the lumbar spinal cord. The medial part of laminae I-IV, however, does not establish any direct connection with the gray matter on the opposite side. 4) The lateral aspects of laminae I-IV appear to be the primary source of fibers projecting to the ipsi- and contralateral ventral horns and supraspinal brain centers. Projecting fibers arise from the medial subdivision of laminae I-IV in a substantially lower number. The findings indicate that the medial and lateral areas of the superficial spinal dorsal horn of rats may play different roles in sensory information processing.

Afferent Pathways↗

PubMed1996

Direct evidence of an extensive GABAergic innervation of the spinal dorsal horn by fibres descending from the rostral ventromedial medulla.

A long line of studies emphasizes the contribution of serotonergic fibres descending from the rostral ventromedial medulla in the control of spinal nociceptive information processing. A growing body of evidence, however, suggests that the relative contribution of serotonin to the mediation of spinal neuronal activity from the rostral ventromedial medulla may require re-evaluation. It has recently been substantiated that, in addition to the serotonergic fibres, the spinal dorsal horn receives an abundant non-serotonergic projection from the rostral ventromedial medulla. Furthermore, stimulation in the rostral ventromedial medulla could result in a powerful inhibition of nociceptive spinothalamic tract cells without any detectable serotonin release in the dorsal horn. After labelling raphe-spinal axons and axon terminals in the rat by iontophoretic injections of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin into the central region of the rostral ventromedial medulla (nucleus raphe magnus) and revealing GABA and glycine immunoreactivities of the labelled raphe-spinal terminals and their postsynaptic targets by postembedding immunocytochemical methods, here we demonstrate an extensive GABAergic projection from the rostral ventromedial medulla to the spinal dorsal horn. We show that the majority of the labelled raphe-spinal terminals in laminae I-IIo and IV-V contain GABA and some of the GABA-immunoreactive terminals are also immunoreactive for glycine. We also disclose that GABA-immunoreactive raphe-spinal terminals establish synaptic contacts primarily with GABA- and glycine-negative, presumably excitatory, spinal neurons, including Calbindin-D28k- as well as parvalbumin-immunoreactive cells in both laminae I-IIo and IV-V. The results suggest that volleys in fibres descending from the rostral ventromedial medulla may evoke GABA release from raphe-spinal terminals, and the released GABA, in some cases probably acting together with glycine, might play a crucial, as yet mostly unidentified, role in the inhibition of nociceptive information processing in the dorsal horn of the spinal cord.

Animals↗

PubMed1996

Distribution of somatostatin-immunoreactive structures in the central nervous system of the frog, Rana esculenta.

The distribution of somatostatin-containing structures in the central nervous system of the frog, Rana esculenta, was studied using the peroxidase immunohistochemical method. Immunoreactive elements were widely distributed in several regions of the central nervous system. With the exception of the primordium hippocampi, where a few stained perikarya were revealed, the pallium were free of immunoreactivity. In subcortical regions of the telencephalon, immunoreactive varicose fibers were observed in the septum and the amygdala, thin fibers were found in the lateral forebrain bundle, and patchy distribution of immunoreactivity was revealed in the striatum. A large number of immunostained perikarya was observed in the hypothalamus, the thalamus, and the preoptic and suprachiasmatic nuclei. Intensely stained CSF-contracting neurones were present among the ependymal cells in the preoptic recess. In the midbrain, the optic tectum and tegmental nuclei contained immunoreactive cell bodies and fibers, and an elongated dense bundle of fibers was detected in the basal area along the midline. In the hindbrain, the subventricular gray matter was rich in strongly stained cell bodies and fibers, and the nucleus of solitary tract presented moderately stained neurons. At different levels of the spinal cord, immunoreactive cell bodies were revealed in lamina X dorsal to the central canal, and scattered nerve fibers were shown in the superficial dorsal horn.

Animals↗

PubMed1996

Distribution of cholecystokinin-8-like immunoreactivity in the frog brain and spinal cord.

The distribution of cholecystokinin-8 (CCK8) containing structures in the central nervous system of the frog (Rana esculenta) was investigated with the aid of the peroxidase immunohistochemical method. In the forebrain, immunoreactive perikarya were found in the main olfactory bulb, septum, amygdala, and ventromedial thalamic nuclei. Networks of immunoreactive varicose fibers were observed in the septum, the basal area, and the infundibulum, and fiber bundles were found in the marginal and axial optic tracts. In the midbrain, immunoreactive cell bodies were seen in the mesencephalic reticular nucleus, and networks of fibers were observed in the optic tectum and the tegmentum. In the hindbrain, immunoreactive neurons were found in the nucleus of the solitary tract, and varicose fibers were observed in the superior vestibular nucleus and the subventricular area. The gray matter of the spinal cord was interlaced by immunoreactive fibers, and a few intensely stained perikarya were seen in the base of the dorsal horn. These findings indicate that CCK8 is widely distributed in the central nervous system of the frog, like in mammals. The CCK8 immunoreactivity is particularly high in the limbic structures and some diencephalic and mesencephalic areas (infundibulum, optic tectum), whereas the pallium is devoid of this peptide in the frog.

Animals↗

PubMed1994

Combination of cobalt labelling with immunocytochemical reactions for electron microscopic investigations on frog spinal cord.

Cobalt staining of primary afferents in frog spinal cord was combined with peroxidase-antiperoxidase pre-embedding or immunogold post-embedding immunocytochemical labelling. Our results have shown that cobalt labelling can easily be distinguished from both of the immunoreaction end products. The protocol of cobalt labelling did not affect the immunoreactivity of structures. The morphology and synaptology of cobalt labelled and immunostained profiles in our sections were very similar to those reported in previous studies using different double labelling techniques. These results indicate that this new combined method could be used as an alternative double labelling technique in electron microscopic studies on nervous tissues.

Animals↗

PubMed1992

Distribution of calcitonin gene-related peptide immunoreactivity in the central nervous system of the frog, Rana esculenta.

The distribution of calcitonin gene-related peptide (CGRP), immunoreactive structures in the central nervous system of the frog, Rana esculenta, was studied using the peroxidase immunohistochemical method. Immunoreactive perikarya were found in all major parts of the brain. In the forebrain, neurons of the septohippocampal formation, the amygdala, the ventromedial and posterocentral thalamic nuclei, and the cerebrospinal fluid contacting neurons in the diencephalic periventricular organ showed immunoreactivity. The pear-shaped neurons of the optic tectum, and perikarya of the oculomotor nucleus in the midbrain were also immunoreactive. In the hindbrain, neurons of the cranial nerve motor nuclei, neurons of the superior vestibular nucleus, giant cells of the reticular formation, and preganglionic parasympathetic neurons of the superior salivatory nucleus were stained. Motoneurons presented immunostaining also in the spinal cord. Immunoreactive fibers were shown to occur in the olfactory tract, the striatum, the tegmentum and the basis mesencephali, the descending tract of the trigeminal nerve, the solitary tract, Lissauer's tract, and the dorsal horn of spinal cord. A comparison of the distribution of CGRP immunoreactivity in the mammalian and amphibian central nervous system revealed that, in relation to the size of the brain, CGRP is more extensively distributed in the amphibian than in the mammalian limbic system.

Animals↗

PubMed1990

Retrograde transport of the lectin Phaseolus vulgaris leucoagglutinin in frog central nervous system.

The transport properties of the lectin Phaseolus vulgaris leucoagglutinin (PHA-L) were tested in the frog central nervous system. After delivery of the lectin to the lower brainstem by iontophoresis, stained axons and axon terminals, as well as neurons with richly arborizing dendrites, were observed indifferent regions of the brain and spinal cord even far away from the site of application. The large number and the Golgi-like appearance of labeled neurons situated rostral and caudal to the site of PHA-L deposit indicate that PHA-L is transported equally in both the anterograde and the retrograde direction in the central nervous system of the frog. This is in contrast with the mammalian nervous system, in which PHA-L is transported predominantly in the anterograde direction and the retrograde transport is poor.

Animals↗

PubMed1989

Distribution of substance P, vasoactive intestinal polypeptide and serotonin immunoreactive structures in the central nervous system of the lizard, Lacerta agilis.

The distribution of substance P (SP), vasoactive intestinal polypeptide (VIP) and serotonin (5-HT) containing structures in the central nervous system of the lizard, Lacerta agilis, were investigated with the aid of the peroxidase-antiperoxidase immunohistochemical method. SP and 5-HT nerve fibers are found almost all over the brain, whereas VIP fibers are mainly observed in the limbic area, in the periventricular gray matter of the diencephalon and in the brain stem. The cells of origin are located in the telencephalon for the SP, in the mesencephalic tegmentum for the VIP, and in the midline and the basis of the brain stem for the 5-HT. In addition to the known paraventricular organ in the diencephalon VIP and 5-HT immunoreactive cells are found in the ependymal layer of the rostral part of the lateral ventricle.

Animals↗

PubMed1984

Experimental calcipenic osteopathy.

Calcipenic osteopathy was used as a model, in order to reveal the diagnostic value and capacity of the noninvasive radiological methods (microradioscopy, densitometry, and Roentgen-morphometry), in comparison with the results of histological, histomorphometrical, and atomic absorption methods. The study proved that calcipenic diet causes an osteoporosis in the experimental animals. The alterations observed meet both the histological and radiological criteria.

Animals↗

PubMed1981

Correlation between serum calcitonin and calcium levels and bone calcium contents in rats.

The serum calcium and calcitonin levels and the calcium content of femora were measured in rats from the time of birth till 1.5 years of age. The serum calcium level was within the normal range of variation all over the measuring period with a high on the 10th day and a low on the 50th day of age. The serum calcitonin level was the highest in newborn animals, the lowest in 50-day old animals and reached a steady level with a slow rise on 120th day of age. The bone mineralisation abruptly increased in young animals and reached a constant value on the 20th day of age. The correlation of these values with the number of C cells determined previously in different ages is discussed.

Aging↗

PubMed1981

Seasonal and sex differences in the serum calcitonin levels of the rat.

The serum levels of calcitonin, calcium and inorganic phosphate, and the urine concentrations of calcium and inorganic phosphate were measured in male and female rats in spring and in autumn. Significantly higher levels of serum calcitonin and calcium were found in spring than in autumn in both male and female rats. The calcium and inorganic phosphate contents of the urine were also significantly higher in spring than in autumn in both sexes. In addition to the seasonal variations, the serum level of calcitonin was higher in female than in male rats both in spring and in autumn.

Animals↗

PubMed1978

Seasonal variations of rat thyroid C cell population.

With the aid of argyrophilic and metachromatic reactions male rats' thyroid C cells were investigated in spring and autumn. Autumn C cells were found to be more swollen and richer in granules and showed a more pronounced metachromasia and argyrophilia than spring C cells. The area occupied by C cells in the central part of the thyroid lobe was large in autumn and reduced in spring. A study into the proportions of C cell: follicular cell: colloid: stroma indicated a significantly higher number of C cells in autumn than in spring.

Animals↗

PubMed1976

Quantitative changes of the C-cell population in the rat thyroid during postnatal ontogenesis.

The number and distribution of C-cells in the rat thyroid gland, have been investigated during postnatal ontogenesis from birth to 120 days of age. The argyrophilic and metachromatic properties of these cells were used to identify them. In the thyroid of newborn rats the C-cells do not exhibit argyrophilia and metachromasia. These reactions appear at 10 days and can be seen at all subsequent ages. The number of C-cells shows a parallel increase with age as demonstrated by the change in the proportion of C-cells: F-cells: colloid: stroma during development. A marked increase in C-cells was found at 50 days of age when the proportion of C-cells rose to 27.67% from the value of 16.78% at 30 days. At 70 days a decrease was noted (20.50%) which hardly changed until 120 days of age (22.20%). The numerical increase in C-cells occurs at the expense of the follicular epithelium and stroma. The C-cells occupy elongated islet-like region in the central part of the lells are present. The long axis of the C-cells area is parallel with the longitudinal axis of the lobe. The area of C-cells is largest at the centre of the lobe, corresponding to the territory of the peak of the Gaussian curve for the numerical distribution of C-cells.

Age Factors↗

PubMed1975

Trace elements in tissues of normal and vitamin D2-treated rats.

Comparative spectroscopic investigations were performed on 22 trace elements regarding their presence and quantitative relations in cartilages (costal cartilage, intervertebral disc) and in soft tissues most exposed to metastatic calcification (aorta, kidney) of normal, vitamin D2-treated and rachitic rats. The results revealed differences in concentration and distribution of trace elements between soft tissues and cartilages on the one hand, and untreated controls and vitamin D-treated rats on the other. On vitamin D treatment an increase in the Cr, Fe and Cu contents was noted in the soft tissues, whereas in cartilages a higher Zn content was shown. It is suggested that these trace elements may play an important role in the mechanism of calcification, some acting as challengers, others as adjuvants or inhibitors.

Animals↗

PubMed1975

Connective tissue alterations following neonatal thymectomy. VI. Calcium histochemical, growth-dynamical and thermoanalytical investigations on bone tissue of thymectomized rats.

Thymectomy was performed in newborn rats and the changes occurring in the epiphyseal cartilage and bone were investigated by Ca histochemical and thermoanalytical methods, one, two and six weeks following operation. Formation of Ca complexes was slowed down in the epiphyseal cartilage and the rate of growth decreased. At the same time the inorganic substance content decreased considerably in the bone tissue of operated rats as compared to the controls.

Age Factors↗

PubMed1975

Examination with x-ray diffraction of cartilaginous tissues of rats of different ages with and without vitamin D treatment.

X-ray diffraction examinations were performed on different cartilages (epiphysis, joint, rib, nose-cartilage and discus intervertebralis) of 10 young and 10 old rats. Half of the animals served as untreated control, the other half was treated daily with 40,000 U of vitamin D3 through a gastric tube for 14 days. The examinations were performed partly with a Philips diffractometer and partly in a Guinier chamber, in order to determine the quantitative and qualitative crystallite size. The results obtained are as follows: 1. Cartilage crystallites, except those of the epiphysis, are more rough-grained in the old than in the young animals. 2. A difference was found between cartilages of the same age but of different types. In epiphysial cartilage thin crystals of medium length are formed while thick ones can be seen in discus intervertebralis, joint and rib cartilage. 3. According to the data obtained with the method of X-ray diffraction the crystals in epiphysial cartilage and discus intervertebralis will be lengthened upon the effect of vitamin D, while those in the rib and nose-cartilage shortened and bulkier. It can be imagined that cartilage and bone cells as well as basal substance have an influence on the morphological picture of calcium phosphate. Thus different forms of crystal are formed in cartilages of different functional activity.

Aging↗

PubMed1975

Morphological and histochemical changes of ultimobranchial follicles of the rat thyroid in the course of postnatal life.

Morphological and histochemical changes of ultimobranchial follicles of thyroid have been investigated in rats from newborn to 18 months of age. The first well-delimited ultimobranchial follicles, though with no lumen, were detected in the thyroid gland of 10-day-old rats. At 30 days of age, follicles possessing regular lumina were present in the thyroid. With age, the follicles gradually increased in volume assuming extreme dimensions in adult age. The follicles displayed varying shapes from simple cysts to bizarre forms. From the age of 50 days the cells of the follicular wall are separated from the cell debris contained in the lumen. The latter gave a PAS positive reaction. The cells of the ultimobranchial follicles did not exhibit argyrophilia and metachromasia showing that they differ considerably from the C-cells likewise of ultimobranchial origin, which are known to give marked argyrophilic and metachromatic reactions.

Age Factors↗

PubMed1975

Effect of triiodothyronine (T3) thyroparathyroidectomy and mercaptoimidazole treatment on enchondral bone growth. II. Growth dynamics in the proximal growth organ of the tibia in young rats.

The 24 hour growth rate of the tibial proximal growth organ was investigated in triiodothyronine or mercaptoimidazole-treated, and in thyroidectomized male rats. Longitudinal growth of the tibia of the same period was also studied. After one week treatment, the 24 hour rate of growth in the triiodothyronine-treated rats was retarded as compared with the controls, whereas at the end of the 3rd and 5th weeks the growth rate of the treated animals exceeded that of the controls. The tibia was somewhat longer in the treated rats than in the untreated controls, though the difference was not significant. The growth rate in the growth organ of mercaptoimidazole-treated and thyroidectomized animals was generally higher than that measured in the controls. The length of the tibia was less than in the controls, but the difference was not significant. The phenomenon is attributed to the altered hormonal conditions.

Animals↗