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Complete serial sectioning of the medulla oblongata in monkey, cat, guinea pig, and japanese dancing mouse and incubation for somatostatin-immunoreaction was carried out. Numerous regions of the medulla oblongata such as the nucleus reticularis gigantocellularis, nucleus cuneatus et gracillis, nucleus raphe magnus, nucleus tractus solitarius, nucleus vestibularis, and parts of the oliva contain dense networks of somatostatin-immunoreactive nerve fibers. Cell bodies were seen in the nucleus reticularis medullae oblongatae. In the spinal cord the sections from each segment were analyzed, showing the highest concentrations of somatostatinergic fibers in the substantia gelantinosa of the columna dorsalis. Cell bodies were seen in the zona intermedia centralis, especially in the upper cervical segments. Many positive fibers were also seen in the entire zona intermedia and the columna ventralis. Especially prominent was the immunoreactivity in the zona intermediolateralis of the thoracic segments and the columna ventralis of the lower lumbar and sacral segments.
A case of cavernous angioma of the medulla oblongata with clinical manifestations developing during the course of upper respiratory tract infection in a boy aged 16 years is described. In the first stage of the disease there were bulbar signs of gradually increasing intensity without changes in CSF. In the third week fatal haemorrhage to the medulla oblongata perforating into the cerebral ventricles and subarachnoid space occurred.
Morphological changes in blood vessels of the rabbit medulla oblongata were studied after successive effects of maximum-bearing gravitational overloadings of 10 units applied at different directions and hypokinesia of various duration. Blood system of 35 rabbits was injected with Gerota's mass, cleared horizontal sections of the medulla oblongata 120 mkm thick were stained with hematoxylin--eosin and after Van Gieson. The experiments demonstrated various, quantitative and qualitative, changes in the vessel structure of the medulla oblongata, prevalence of one of the factors applied--in one combination and successive application; total resulting effect of overloading and hypokinesia--in the other combination; peculiar morphological changes unusual to any of the two factors--in the third combination. It was also demonstrated that readaptation for 12 weeks resulted in a significant restoration of the blood vessel structure in the rabbit brains preliminarily subjected to a successive effect of hypokinesia for 4 weeks and overloading in cranio-caudal directions.
The influences of the vagal inhibitory and excitatory reflexes on the gastric motor centers in the dog's medulla oblongata were investigated. Dogs were anaesthetized with Nembutal, and supplemented Gallamine at need. The brain stem was transected on the level of inferior colliculi of midbrain, the spinal cord transected on the level of between C1 and C2. Bilateral splanchnic nerves were also severed. Electrical activities from the inhibitory and excitatory areas in medulla oblongata were recorded by using a concentric circle electrode which was inserted into medulla oblongata from the dorsal surface of it. Following results were obtaind. 1) Electrical activities of the gastric inhibitory areas were classifed into three types (see Table 1). Type I: The augmentation of electrical activities of the gastric inhibitory areas during theinhibitory reflex were associated with the diminution of them during the exictatory reflex. Type II: Although electrical activities of the gastric inhibitory areas were augmented during the inhibitory reflex, any changes of them were not obtained during the excitatory reflex. Type III: Any changes of electrical activities of the gastric inhibitory areas were not obtained during both inhibitory and excitatory reflexes. 2) Electrical activities of the gastric excitatory areas were classified into two types (see Table 2). Type I: The diminution of electrical activites of the gastric excitatory areas during the inhibitory reflex were associated with the augmentation of them during the excitatory reflex. Type II: Although any changes of electrical activities of the gastric excitatory areas were not observed during the inhibitory reflex, they were augmented during the excitatory reflex.
Application of acid cerebrospinal fluid at pH 6.8 to the ventral surface of the medulla oblongata in cats increased the arterial blood pressure and the activity of the vertebral nerve and enhanced respiratory modulation of the vertebral and cardiac nerves. Alkaline cerebrospinal fluid at pH 7.7 applied to the ventral surface of the medulla oblongata increased the arterial blood pressure without changes in the sympathetic nerve activity. When the spinal cord was superfussed with artificial acid cerebrospinal fluid at the Th1 level the activity of the vertebral nerve and cardiac nerve increased and the arterial blood pressure rose. The authors discuss the possibility of regulation of the activity of sympathetic neurons in the medulla and spinal cord by means of direct action of pH and pCO2 on the neurons, or through an indirect effect mediated by superficial chemoreceptors of the medulla oblongata. The role of local changes of the brain blood flow in the mechanism of these results is discussed as well.
The contribution deals with the distribution of alkaline phosphatase and 5-nucleotidase in the medulla oblongata of Taphozous melanopogon (a Microchiroptera), for the first time. The main highlights of the study are: (1) Cranial nerve nuclei demonstrate intense activity of alkaline phosphatase, whereas except nucleus tractus spinalis n. trigemini, rest of the nuclei show much variations of 5-nucleotidase distribution. (2) The vestibular nuclei are very intensely positive for 5-nucleotidase but exhibit variable activity of alkaline phosphatase. (3) Three subdivisions of nucleus olivaris inferior, i.e. nucleus olivaris accessorius medialis, nucleus olivaris accessorius dorsalis and nucleus olivaris inferior, which were not reported in the earlier neuroanatomical studies, have been identified. These nuclei show very intense alkaline phosphatase and relatively less intense 5-nucleotidase activities. (4) In general, the activity of alkaline phosphatase is stronger in neurons than in neuropil and that of 5-nucleotidase is stronger in neuropil than in neurons. (5) Blood capillaries are completely negative for alkaline phosphatase and intensely positive for 5-nucleotidase. A comparison is made between the distribution of these enzymes in the medulla oblongata of bat and other mammals so far studied.
The distribution of the Epinephrine forming enzyme (PNMT) activity and Epinephrine (E) levels was investigated in the medulla oblongata of spontaneous hypertensive rats (SH-rats) and in two normotensive strains, namely Wistar Kyoto rats (WK-rats) and Wistar rats. The PNMT activity increases progressively from the caudal to rostral parts in the C1 and C2 regions of the medulla oblongata. The enzyme activity and the E levels are in all parts of the C1 and C2 regions higher in Wistar rats than in WK-rats. The PNMT activity in all parts of the C2 region (with the exception of the caudal region), and in the middle part of the C1 region is higher in SH-rats than in WK-rats. The E levels in the SH-rats are higher than in WK-rats in the mediocaudal parts of the C2 and C1 regions.
The distribution of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) has been investigated in a series of sections passing through the medulla oblongata and pons of the squirrel brain. A comparison of the two enzymes has given an interesting picture of their selective localization in the different nuclei. Marked AChE activity has been observed in the cranial nerve nuclei. BChE activity in various nuclei of the medulla oblongata and pons is variable and occurs diffusely between the cells. Possible reasons pertaining to marked variation in AChE and BChE contents of various nuclei and fiber tracts have been discussed.
In the present study, acid phosphatase activity has been histochemically localized in the medulla oblongata (facialis part) of Streptopelia senegalensis and Uroloncha malabarica. It was noticed that the enzyme is present particularly in the motor nuclei and lysosomes of neuroglial cells of the medulla oblongata. However, enzymatic deposition appears to be somewhat more vigorous in S. senegalensis than in U. malabarica, thereby indicating their respective metabolic turnover and neuronal excitability. Simultaneously, the functional significance has been discussed in the light of differential localization.
The angioarchitectonic regions in the medulla oblongata and the midbrain of 14 grown-up guinea pigs are discribed. According to direction and number of the supplying arteries, three sections are distinguished. The medial part is supplied worst. It contains the medial row of the nuclei of the cranial nerves. The more lateral parts have always double or treble supplies. They are distinguished by a high capillary density. Those parts are associated with the medullar nuclei of the cranial nerves.
The central cardiovagal mechanism of the medulla oblongata was explored by stimulation and ablation techniques in the anesthetized cat. Insertion of an electrode into the nucleus solitarius (NS) occassionally evoked slight and transient bradycardia, but similar mechanical irritation to the nucleus ambiguus (NA) usually evoked prolonged and intense bradycardia. Electrical stimulation of the dorsal motor nucleus of the vagus (DNV) produced no or little bradycardia. Stimulation of NS and NA consistently produced cardiac slowing with a latency of less than 2 s and the effect was more prominent in the NA. Contralateral vagotomy did not significantly affect the bradycardia on the NS and NA stimulation but ipsilateral vagotomy caused a complete abolition. Lesions of the NA or DNV largely or completely abolished the bradycardia consequent to NS stimulation. Extensive destruction of the NS and/or DNV did not affect the bradycardia resulting from NA stimulation. Destruction of the ventral midline area partially reduced th bradycardia on NS STIMULATION BY 36-54%. The results suggest that the sequence of the three vagal nuclei for cardiac inhibition runs in the following order: NS, DNV, and NA. Synaptic connections are probably scanty in the DNV. Part of the vagal pathway passes through the ventral midline area before it reaches the NA. A scheme of the neural pathway for reflex bradycardia of vagal origin has been proposed.
In order to investigate foci of the electrical activity, studies have been made on the topography and form of total reactions to sound in the acoustico-lateral part of the medulla oblongata in the carp C. carpio. Two foci of the activity were found -- medical and ventral ones. Responses in the medial and ventral foci differ with respect to the form, latency (2.0--2.5 and 1.3--1.5 msec. respectively) and amplitude (200--600 and 50--200 microvolts respectively). It is suggested that total reactions in the medial focus reflect the activity of the nervous elements of the medulla oblongata, whereas the responses of the ventral focus reflect mainly microphonic reactions of sacculus of the inner ear of the carp.
The unit activity in the vagal lobe of medulla oblongata in response to stimulation of the mouth cavity and gills chemoreceptors with solutions of hydrochloric acid and sodium chloride was studied in immobilized carps and compared with those in the facial lobe in response to skin chemoreceptors stimulation. The firing rate in the vagal lobe is lower and the latent period is longer than in the facial lobe. The level of the chemical stimuli gradations analysis is different in two parts of the chemoreception primary centre. In the vagal lobe units responding to the impulses from both receptive fields as well as those responding selectively to stimulation either of the mouth cavity or the gills were found. Activity of a firing pattern was predominant in the vagal lobe units in response to stimulation with sodium chloride solutions.
The central noradrenaline (NA) and adrenaline (A) turnover in 15--16-week-old stroke prone, spontaneously hypertensive (sp-SH) female rats in an advanced stage of hypertension was found to differ from that of normotensive Wistar-Kyoto (WKy) control rats. The catecholamine (CA) levels were measured after inhibition of dopamine-beta-hydroxylase (DBH) or phenylethanolamine-N-methyltransferase (PNMT). in the hypertensive rats the dopamine (DA) and NA levels and the NA turnover were reduced in the hypothalamus, while in the dorsal part of the caudal medulla oblongata NA levels and A turnover were reduced. Changes in hypothalamic DA and NA mechanisms and in A mechanisms in medulla oblongata may therefore be of importance in the blood pressure regulation of sp-SH rats.
pH sensitivity of cells located at the ventral surface of the medulla oblongata was examined in a thin brain slice of the cat in vitro and the following results were obtained: (1) Transmembrane potential of the surface cells located in the area medial to the XIIth cranial nerve was reduced slightly by application of low pH solution; (2) In the rostral part of the area medial to the XIIth cranial nerve regular neuronal discharges could be observed extracellularly. The rate of firing of these cells was increased by lowering the external pH. These results were considered to support the idea the H+ receptor cells may exist in the surface layer of the ventral medulla.
The paper deals with the histological and histoenzymological studies of the medulla oblongata of Taphozous melanopogon Temminck (a microchiropteran bat). Three phosphatases, namely acid phosphatase (ACP), thiamine pyrophosphatase (TTP) and glucose-6-phosphatase (G-6-P) were studied. All the enzymes were seen in all the neurons. The large neurons of the different nuclei are more strongly positive for ACP than the small neurons. Further, the areas which contain dense populations of neurons are more strongly stained than the area containing scattered neurons. TPP and G-6-P distributions are almost parallel to that of ACP. The functions of these enzymes in synthesis and secretory processes were discussed.
1. Extracellular recordings have been made from proprio- and exteroceptive neurones in nucleus Z of the cat medulla oblongata. 2. Seventeen non-relay cells were excited by ipsilateral hind limb group I muscle afferents. Their functional were similar to those of the corresponding relay cells (Johansson & Silfvenius, 1977), i.e. activation by axon-collaterals of dorsolateral fascicle (DLF) fibres was observed, indicative of an input from the dorsal spinocerebellar tract (DSCT) to these neurones. The non-relay cells differed, however, from the relay cells in that a larger proportion of them were disynaptically connected to the spinal fibres. It is suggested that the non-relay cells by inhibition modulate the group I relay transmission in nucleus Z. 3. Fifteen cells were excited by ipsilateral hind limb low threshold skin afferents with their spinal fibres at the first cervical segment located either in the DLF or in the dorsal column (DC). Evidence for a cutaneous hind limb bulbothalamic path independent of that of the DC and of the spinocervicolemniscal path is presented. 4. Six cells were activated by ipsilateral hind limb joint afferents at low threshold. At the C1 level the spinal fibres were located either in the DLF or in the DC. No joint activated relay-cells were encountered. Axon-collateral activation of DLF-linked joint cells was observed during cerebellar stimulation, indicating that segmental DSCT cells mediated the joint input to nucleus Z. 5. The topographical organization within nucleus Z and its input relation to the DSCT is discussed.