Parasagittal Brain Research Articles

ANG II AT1 receptors induce depolarization and inward current in rat median preoptic neurons in vitro

To examine ANG II receptors in rat median preoptic (MnPO) neurons, we used patch-clamp whole cell recordings in a parasagittal brain slice preparation. Lucifer yellow-filled neurons displayed a simple morphology with two to three aspiny dendrites. Bath-applied ANG II (1-2,000 nM for 30 s) induced a response in 37 of 70 cells. In current-clamp recordings, cells displayed a prolonged (10- to 30-min) depolarizing plateau with action potential discharges and an associated reduction in postburst afterhyperpolarization and spike frequency adaptation. In voltage-clamp recordings (holding potential -65 mV), cells displayed tetrodotoxin-resistant inward currents of 7. 6 +/- 1.9 (n = 5), 9.9 +/- 1.9 (n = 9), and 9.2 +/- 2.2 pA (n = 6) at 10, 200, and 2,000 nM, respectively. Responses were blockable by pretreatment with losartan (2 microM; n = 6) but not by PD-123177 (20 microM; n = 3). Net ANG II-induced current revealed a 7.8 +/- 0. 9% reduction in membrane conductance, decreasing but not reversing at hyperpolarized levels. Neurons expressing a strong hyperpolarization-activated, time-independent inward rectification were more likely to respond to ANG II. There was no correlation between the response of a neuron to ANG II and its response to norepinephrine.

Primary intracranial malignant tumour mistaken for a postburn scalp Marjolin's ulcer

This report presents an apparent squamous cell carcinoma over a burn scar in the scalp (Marjolin's ulcer) that was resected and soft tissue expanders inserted in the hair-bearing scalp. In the postoperative period the patient developed neurological impairment with a CT scan showing a parasagittal brain tumour infiltrating the skin. The tumour was resected and the resultant skin and cranial defect were covered with an expanded scalp flap. Histological examination showed a malignant angioblastic meningioma. The tumour recurred aggressively, leading to the death of the patient. The case is considered very unusual, as a brain tumour does not seem to be a reasonable suspect in the differential diagnosis of a chronic ulcer over a burn-induced scalp scar.

Distribution of parvalbumin-containing interneurons in the hippocampus of the gerbil — a qualitative and quantitative statistical analysis

In the gerbil ( Meriones unguiculatus) hippocampal formation, the calcium-binding protein parvalbumin (PV) shows a unique species-specific distribution: it is present in the perforant path from the entorhinal cortex to the stratum moleculare of the dentate area and cornu ammonis. A possible relation of this to the seizure-sensitivity of gerbils has been suggested. In addition, as in other species, PV is contained in a subpopulation of GABAergic nerve cells of the gerbil hippocampus. The characteristics of these PV-containing neurons are here described. Distribution and shape of the PV-positive neurons in general agreed with the features described for rat hippocampus with two notable exceptions: in CA2 PV-containing perikarya were densely crowded and gave rise to an intense immunoreactive plexus around the pyramidal cells and, in CAI, the number of stained neurons was variable, often much lower than in rats and occasionally not a single PV-positive neuron was present. In parasagittal brain sections of the lateralities 1.0, 1.6 and 2.2 mm from the midline, obtained from 27 male gerbils, the number of PV-containing neurons was determined. The data set obtained in CA3 and dentate area resembled unimodal distributions, while in CAI a bimodal frequency distribution was present. Since parametric and non-parametric correlation tests rely on a unimodal distribution of the data set, they gave falsely significant values in CAI. The bimodal distribution suggests that, with respect to the PV-containing interneurons in CA1, two different populations of gerbils were included in our sample, those with many positive neurons and those with only a few. Since the nerve terminal staining is preserved also in those gerbils with only a few positive perikarya in CAI, it seems possible that an unknown factor influenced PV expression and storage in the soma. Sex, age, seasonal or circadian rhythm or quality of immunocytochemical staining did not influence the outcome of the quantitative analysis. However, a relation of the expression of the high affinity calcium buffering PV in interneurons and the individual seizure sensitivity of the gerbil is considered.

Contribution of neurons born during embryonic and adult life to the brain of adult canaries: Regional specificity and delayed birth of neurons in the song‐control nuclei

Neurogenesis occurs in adult song birds, which suggests that neurons born after hatching may contribute to histogenesis and plasticity of the avian brain. However, little is known about the overall contribution to the mature brain of neurons born in juveniles and adults, and how this process affects different regions of the avian brain. In fact, studies of the histogenesis of the avian forebrain have made the classical assumption that neuronal birth ends before hatching. Here we determined the contribution of neurons born before and after hatching to different regions throughout the adult canary brain. Male canaries were injected with [3H]-thymidine at different times during embryonic, juvenile, and adult life. The position of labeled neurons was mapped in parasagittal brain sections. Because all birds were killed as adults, results indicate the time of birth of neurons that survived to adulthood in different structures of the avian brain. Injection at embryonic day (E) 5 or E9 resulted in labeled neurons in all regions of the neuroaxis. The vast majority of neurons outside of the telencephalon were born before E9. One exception was a discrete region in the dorsal thalamus, a part of the song-control circuit, where neurons continued to be born after E9. Most regions of the telencephalon had a high proportion of its neurons labeled by the embryonic injections. In particular, archistriatum, anterior neostriatum, and the hippocampus had most of their neurons labeled before hatching. This indicates that many of the telencephalic neurons born in the embryo are long lived and are not replaced by other neurons that continue to be added to the telencephalon after hatching. Neurons labeled by [3H]-thymidine injections after hatching were restricted to the telencephalon and contributed importantly to many regions. In particular, the avian striatum (lobus parolfactorius, LPO) received a large number of its neurons during the first 20 days of life, but continued to incorporate new neurons throughout juvenile and adult life. Neurons continued to be added to the telencephalon of adults (even in 4-year-old birds). The distribution of labeled neurons after [3H]-thymidine injections in adults was similar to that observed in latter stages of juvenile development. The contribution of neurons born at different ages from embryonic development to adulthood varied among different anatomical subdivisions of the canary brain. this could, in part, explain differences in the cytoarchitecture and plasticity between brain regions. Neurogenesis after hatching may allow the modification of selected brain circuits as the bird matures and ages.

The electrotonic structure of regular-spiking neurons in the ventral cochlear nucleus may determine their response properties.

1. Intracellular recordings were obtained from neurons in parasagittal brain slices of the guinea pig ventral cochlear nucleus (VCN). The principal neurons of the VCN can be parceled into two categories. Regular-spiking (Type I) neurons have a linear current-voltage (I-V) relationship over a large range of intracellularly injected currents and fire tonically in response to suprathreshold depolarizing currents. Phasically spiking (Type II) neurons have a nonlinear I-V relationship and fire only phasically at the onset of a depolarizing current or offset of a hyperpolarizing current. Regular-spiking neurons have been shown to be of the stellate morphological type, whereas phasically spiking neurons have been shown to be bushy cells. 2. The electrotonic structure of regular-spiking neurons was studied by applying previously developed modeling techniques based on the somatic shunt model. In these techniques, physiological data are used to determine the set of parameters best describing the neuron. As predicted from previous theoretical investigations, the use of an anatomic constraint (somatic surface area) reduces the variance in estimates of model parameters, especially for the dendritic membrane time constant tau D. 3. Model representations of regular-spiking cells fall into two categories: those with (passive) somatic membrane properties that are nearly identical to those of the dendrite (8/15 cases), and those with a significant amount of somatic shunt (7/15). Estimates of tau D (mean = 7.7 ms) are lower than those often described in the literature. We argue that this low value of tau D may be related to the need of neurons in the auditory brainstem to operate at high firing rates and/or to encode audio-frequency temporal fluctuations. 4. Dendritic transfer functions were calculated as functions of synaptic location using somatic shunt representations of regular-spiking neurons. These transfer functions allow us to predict that mid-range auditory frequencies (approximately 1 kHz) are greatly attenuated, even for synapses near the soma. Thus it is suggested that the electrotonic architecture of regular-spiking cells creates sufficient low-pass filtering of synaptic inputs to reduce the synchronization of firing of these neurons to mid-frequency auditory stimuli.

Premonitory neurologic signs in a patient with an acute vertex epidural hematoma

A case of an acute vertex epidural hematoma with delayed neurologic deterioration is presented. Prior to the onset of signs of midbrain compression, the patient developed an excrutiating headache, a movement disorder, and upper motor neuron signs. A review of the literature and this case suggest that the presence of a severe, unrelenting headache and upper motor neuron signs in a victim of head trauma may be secondary to compression of the parasagittal brain region by a vertex hematoma.

The relation of corpus callosum connections to architectonic fields and body surface maps in sensorimotor cortex of new and old world monkeys.

Corpus callosum connections of parietal and motor cortex were studied in New World owl monkeys (Aotus trivirgatus) and Old World macaque monkeys (Macaca fascicularis) after multiple injections of 3H-proline and horseradish peroxidase, HRP, into one cerebral hemisphere, and extensive microelectrode mapping of architectonic Areas 3b, 1, and 2 of the other hemisphere. Results were obtained both from parasagittal brain sections cut orthogonal to the brain surface and from sections from flattened brains cut parallel to the brain surface. Cortical fields varied in density of callosal connections, and the density of connections varied according to body part within sensory representations. Thus, Area 3b had few, Area 1 had more, and Area 2 had relatively dense callosal connections. Within each of these fields, connections were much less dense for the representations of the glabrous hand and foot and much more dense for the representations of the face and trunk. For the representation of the hand, retrogradely labeled cells were extremely sparse in Area 3b, moderately sparse in Area 1, and moderate in Area 2. There were less dense callosal connections in the hand representations of Areas 3b, 1, and 2 in macaque as compared to owl monkeys. Label in posterior parietal cortex was uneven with zones of extremely dense connections. A large region of very dense callosal connections was noted in motor cortex just medial to the probable location of the hand representation. In all regions, callosally projecting cells appeared to be more broadly distributed than callosal terminations. In no region was the discontinuous arrangement of callosal connections obviously organized into an extensive pattern of mediolateral or rostrocaudal bands or strips.

Some perspectives on monoamine-opioid peptide interaction in rat central nervous system

Light microscopic immunocytochemistry was employed to investigate possible sites of interaction between the endogenous opioid peptides and monoamines in the rat central nervous system. The opioid and related peptides examined included beta-endorphin (β-END), alpha-MSH (α-MSH) and leucine-enkephalin (Leu-ENK). The monoamines were examined using antisera generated against tyrosine hydroxylase, dopamine-β-hydroxylase as well as serotonin. Due to the long-tract nature of the central monoamine projections as well as β-END/α-MSH fiber systems, serial section analyses were performed utilizing parasagittal brain sections. Many areas rich in both the monoamines as well as opioid peptides were investigated. These included several thalamic and hypothalamic nuclei, several limbic structures, mesencephalic periaqueductal gray, brain stem noradrenergic cell groups and their rostral projections, the dopaminergic nigrostriatal system, and the serotonergic raphe nuclei and their projections. The results suggest a more intimate linkage between the monoamines and the opioid peptides than previously realized. Some of the intricacies of monoamine-opioid peptide interaction, in particular those pertaining to their possible role in pain and analgesia, catalepsy, and neuroendocrine effects are also discussed.

ROENTGENOLOGIC FEATURES OF PROTRUDED THORACIC INTERVERTEBRAL DISKS.

In recent years the increased knowledge of thoracic disk protrusions and refinements in neurosurgical technics, which together have improved the surgical results, have encouraged neurologists, neurosurgeons, and neuroradiologists to suspect and seek such lesions in a large number of patients with unusual pain problems. The opinion of Cyriax (5), that the degree of patient disablement seldom warranted surgical intervention and that roentgen studies seldom afforded any help in the diagnosis, is no longer prevalent. Most authors (1–4, 6–15) now agree that early diagnosis and treatment of ruptured thoracic disk are desirable because the natural course of the disorder is one of progression and the results of treatment are more salutary if it is undertaken before the appearance of a severe neurologic deficit. Most would also agree that roentgenologic studies, especially myelography, are the most helpful and rewarding in arriving at the diagnosis. As in many other uncommon disorders, however, the condition must first be considered if the proper studies are to be performed. This communication is a report of the roentgen features in 43 cases of protruded thoracic intervertebral disk in which the diagnosis was surgically verified at the Mayo Clinic (Rochester, Minn.). Clinical Signs and Symptoms Some knowledge of the clinical features of protruded thoracic disk is necessary before one can intelligently conduct radiologic examinations to detect it. Love and Schorn (12) have recently reviewed these features in 61 cases seen at our institution. They found that protrusion of a thoracic intervertebral disk may occur at any level, but that one of the lower four dorsal interspaces was involved in two-thirds of their cases. Multiple (two) protrusions were found in only one case; in the remainder, a single disk was involved. The most common symptoms were pain, either radicular or of a dull, nagging type; paresthesias or numbness; motor weakness, usually involving the lower extremities; and visceral disturbances, affecting the urinary bladder or the bowel. Neurologic examination often revealed sensory loss, spastic paraparesis, hyper-reflexia, and positive Babinski signs, all of which indicate involvement of the spinal cord. The authors were unable, however, to formulate any clear-cut syndrome of thoracic intervertebral disk protrusion. Laboratory examination of the cerebrospinal fluid was of little help. In half the cases the results were normal, and in the remainder the changes noted were not specific or diagnostic. It is important to remember that a protruded thoracic disk may mimic other neurologic conditions in its symptoms and signs. Such conditions include demyelinizing diseases, intramedullary and extramedullary tumors of the spinal cord, protruded cervical or lumbar disks, herpes zoster, intercostal neuralgia, parasagittal brain tumors, cerebrovascular accidents, diseases of the various thoracic and abdominal viscera, and psychoneurosis. The correct diagnosis may be suspected only after extensive medical and surgical examinations.