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PubMedDate not supplied

Projections from V1 to lateral suprasylvian cortex: an efferent pathway in the cat's visual cortex that originates preferentially from CO blob columns.

The patchy pattern of retrograde labeling produced by injections of anatomical tracers into the lateral suprasylvian (LS) visual area was compared to the cytochrome oxidase (CO) blobs in cat visual cortex. Following large injections of anatomical tracers in LS, retrograde labeling formed an irregular lattice of patches with a spacing of slightly less than 1 mm in area 17, and slightly greater than 1 mm in area 18. By comparing labeling in alternate serial sections, patches of LS-projecting cells in both areas were found to align with CO blobs. The conclusion of alignment between CO blob columns and patches of LS-projecting cells was confirmed by a quantitative analysis which showed a significant correlation between the local density of LS-projecting cells in reconstructions of charted cells and the intensity of CO staining in the CO-reacted sections. As for areas 17 and 18, labeling in other afferent areas of LS was also patchy with a spacing on the order of 1 mm except for area 19 where we found patches of LS-projecting cells with a larger spacing, roughly 2 mm. No matching fluctuations in CO density could be discerned in area 19, however. In conjunction with recent evidence that CO blob columns in cats receive strong input from Y-cells of the lateral geniculate nucleus (Boyd & Matsubara, 1996; Shoham, et al., 1996), these data support the hypothesis (Shipp & Grant, 1991) that the patches of LS-projecting cells correspond to Y-cell input columns. As a relationship between the CO architecture and certain classes of efferent cells has previously been shown in primates, these findings show new similarities between CO blobs in different mammalian species.

Animals↗
PubMed2005

Dissociable effects of lesions to the perirhinal cortex and the postrhinal cortex on memory for context and objects in rats.

Memory for the context in which an object appeared was investigated with a version of the spontaneous object recognition paradigm. Sham-operated rats explore familiar objects appearing in incongruent but familiar contexts more than those appearing in congruent contexts, revealing memory for the context in which an object previously appeared. At short delays, perirhinal cortex-lesioned rats were unimpaired on memory for object in context, whereas fornix-lesioned rats showed only a mild impairment. In contrast, postrhinal lesions resulted in severe deficits. However, in a comparable noncontextual object task, postrhinal and fornix lesions had no effect, whereas perirhinal-lesioned rats were severely impaired. Comparison of these tasks and other published data may shed light on the nature of the contextual processing involved.

Animals↗
PubMed1976

[Relationship between food protein quality and adrenal cortex function. 6. Interrelationship between aminotransferase activity (GPT1, GOT2) and the status of adrenal cortex function].

Growing male Albino rats were adrenalectomized and then treated with corticosterone in an attempt to determine the activity of amino transferases (GPT and GOT) in the liver and in the mucosa of the small intestine over a period during which the animals received dietary proteins of varying quality. However, statistically significant differences in the enzyme activity were established for only those groups in which the animals exhibited differences in the functional state of the adrenal cortex. Differences due to changes in the quality of the dietary protein were not observed. From this was concluded that the activity of the amino transferases in the tissues is largely dependent on the action of corticosteroids.

Adrenal Cortex↗
PubMed1976

[Relationship between food protein quality and adrenal cortex function. 7. Relationship between activity of selected liver and small intestine hydrolases and adrenal cortex function].

Male Wistar rats received 10% true digestible crude protein of varying quality (maize gluten (MK) = low protein quality; maize gluten + lysine, tryptophan, threonine, isoleucine (MK + AS) = high protein quality) for a period of three weeks. The trial was carried out to investigate the activity of the two enzymes leucine-arylamidase (LNA) and aminotripeptidase (TP) in the liver and the mucosa of the small intestine and that of alpha and gamma amylases and of total amylases in the mucosa of the small intestine in animals exhibiting differences in the functional state of their adrenal cortices (adrenalectomized animals (AE), normal rats (N) and animals receiving additional treatment with cortisol (KS). It was found that mucosal LNA and gamma amylase did not respond to functional changes in the adrenal cortex. Mucosal LNA had a higher activity if the dietary protein was of low quality and a lower activity if the protein quality was high. The level of liver LNA activity was significantly lower in N and KS animals than in AE animals. The highest activity of mucosal and liver TP was found in KS animals; it was lowest in N animals. Statistically significant differences brought about by changes in the quality of dietary proteins were only found to occur in the KS group. The activity of alpha amylase and total amylases was found to be lowest in N animals; it was significantly higher in animals of the AE and KS groups. Animals of the N and KS groups receiving MK + AS exhibited a significantly higher level in their alpha and total amylase activities than animals in the same group receiving MK. Here, the "permissive action" of glucocorticosteroids on metabolically active hydrolases is clearly evident. The pattern of mucosal LNA activity in the small intestine and that of gamma amylase may be regarded as further characteristic evidence for the digestive action of these enzymes. Liver LNA and liver TP as well as mucosal TP and alpha amylase acted like metabolic enzymes.

Adrenal Cortex↗
PubMed1976

Zonation of the adrenal cortex. II. Effect of BSA on coupling efficiency of mitochondria isolated from the zona glomerulosa of the bovine adrenal cortex.

Effect of bovine serum albumin on coupling efficiency of mitochondria isolated from the zona glomerulosa of the bovine adrenal cortex in various media was examined polarographically and electron microscopically. Albumin restored the coupling efficiency of mitochondria isolated from the zona glomerulosa regardless of isolation media when succinate or malate was oxidizable substrate. Respiratory controls greater than 5 were obtained. Albumin, however, had no effect when glutamate, beta-hydroxybutylate and pyruvate were the oxidizable substrates. The conditions have been found under which mitochondria of the zona glomerulosa stay in the orthodox configuration and yet coupled.

Adrenal Cortex↗
PubMed1998

Inhibitory influence of the ipsilateral motor cortex on responses to stimulation of the human cortex and pyramidal tract.

1. The ability of the primary motor cortex (M1) to modulate motor responses in ipsilateral hand muscles seems to be important for normal motor control and potentially also for recovery after brain lesions. It is not clear which pathways mediate this ipsilateral modulation. Transcallosal connections have been proposed, but are known to be sparse between cortical hand motor representations in primates. The present study was performed to determine whether descending ipsilateral modulation of motor responses might also be mediated below the cortical level in humans. 2. A paired-pulse protocol was used, in which motor-evoked potentials (MEPs) were produced by cortical transcranial magnetic stimulation (cTMS) or by electrical stimulation of the pyramidal tract at the level of the pyramidal decussation (pdTES), in both preactivated and relaxed hand muscles. Paired stimuli were applied at various interstimulus intervals (ISIs) between 2 and 100 ms. The conditioning stimulus (CS) was always magnetic, and delivered to the M1 ipsilateral to the target hand, prior to the test stimulus (TS). The magnetic TS was delivered to the M1 contralateral to the target hand; the electrical TS was applied through electrodes placed over the mastoid process bilaterally. Further experiments included cortical electrical stimulation and H-reflexes. The MEP amplitudes were averaged separately for each ISI and the control condition (no CS), and expressed as a percentage of the unconditioned response. 3. Conditioning stimulation of the ipsilateral M1 resulted in significant inhibition of magnetically evoked MEPs, and also of MEPs produced by pdTES. Inhibition occurred at ISIs between 6 and 50 ms, and was observed in preactivated and relaxed muscles. Higher CS intensities caused greater inhibition of both cTMS- and pdTES-evoked MEPs. 4. While the conditioning effects on magnetically evoked muscle responses could be explained by a transcallosal mechanism, the effects on pdTES-evoked MEPs cannot, because they are elicited subcortically and are therefore not susceptible to inhibitory mechanisms transmitted at the cortico-cortical level. 5. In conclusion, the present results provide novel evidence that the inhibitory influence of the human M1 on ipsilateral hand muscles is to a significant extent mediated below the cortical level, and not only through cortico-cortical transcallosal connections. They point to a concept of inhibitory interaction between the two primary motor cortices that is relayed at multiple levels along the neuroaxis, thus perhaps providing a structurally redundant system which may become important in case of lesions.

Adult↗
PubMed1992

Amino acid release from cerebral cortex in experimental acute liver failure, studied by in vivo cerebral cortex microdialysis.

Both increased gamma-aminobutyric acid (GABA)-ergic and decreased glutamatergic neurotransmission have been suggested relative to the pathophysiology of hepatic encephalopathy. This proposed disturbance in neurotransmitter balance, however, is based mainly on brain tissue analysis. Because the approach of whole tissue analysis is of limited value with regard to in vivo neurotransmission, we have studied the extracellular concentrations in the cerebral cortex of several neuroactive amino acids by application of the in vivo microdialysis technique. During acute hepatic encephalopathy induced in rats by complete liver ischemia, increased extracellular concentrations of the neuroactive amino acids glutamate, taurine, and glycine were observed, whereas extracellular concentrations of aspartate and GABA were unaltered and glutamine decreased. It is therefore suggested that hepatic encephalopathy is associated with glycine potentiated glutamate neurotoxicity rather than with a shortage of the neurotransmitter glutamate. In addition, increased extracellular concentration of taurine might contribute to the disturbed neurotransmitter balance. The observation of decreasing glutamine concentrations, after an initial increase, points to a possible astrocytic dysfunction involved in the pathophysiology of hepatic encephalopathy.

Acute Disease↗
PubMed1995

Information coding in the rodent prefrontal cortex. II. Ensemble activity in orbitofrontal cortex.

1. Neural activity was recorded from the orbitofrontal cortex (OF) of rats performing an eight-odor discrimination task that included predictable associations between particular odor pairs. A modified linear discriminant analysis was employed to characterize the population response in each trial of the task as a point in an N-dimensional activity space with the firing rate of each cell in the population represented on one of the N dimensions. The ability of the ensemble to discriminate among conditions of a variable was reflected in the tendency of population responses to cluster together in this activity space for repetitions of a given condition. We assessed coding of several variables describing the period of odor sampling, focusing on aspects of current, past, and future events reflected in single-neuron firing patterns, in ensembles composed of 22-138 cells active during the period when the rats sampled the discriminative stimulus in each trial. 2. OF ensembles performed well at discriminating variables with relevance to task demands represented in single-neuron firing patterns, specifically the physical attributes and assigned reward contingency of the current odor as well as the expectation of reward in the following trial that could be inferred from the predictable associations between particular pairs of odors. OF ensembles were able to correctly identify the identity and assigned reward contingency of the current odor in up to 52% (chance = 12.5%) and 99% (chance = 50%) of all trials, respectively, such that the observed behavioral performance required a population of 5,364 odor-responsive cells in the case of odor identity and only 40 cells in the case of valence. Expectations regarding upcoming rewards based on both assigned response contingency and associations between particular pairs of odors were correctly classified in up to 67% (chance = 20%) of all trials such that the observed level of behavioral performance required a population of 3,169 cells. 3. Other information represented in the single-neuron firing patterns, such as the identity and reward contingency of the preceding odor and specific odor-odor associations, was poorly encoded by OF ensembles. Thus neural ensembles in OF may represent only some of the information reflected in single-neuron activity. Stable coding of only the most useful and relevant information by the ensemble might emerge from the tuning properties of single neurons under the influence of the task at hand, producing in the well-trained animal the observed pattern of broad and diverse coding by single neurons and selective, task-relevant coding by neural ensembles in OF.

Animals↗
PubMedDate not supplied

Effects of a rostral motor cortex lesion on primary motor cortex hand representation topography in primates.

BACKGROUND: Small lesions to rostral versus caudal portions of the hand representation in the primary motor cortex (M1) produce different behavioral deficits. The goal of the present study was to determine if rehabilitative training has similar effects on functional topography of the spared M1 after rostral versus previously reported caudal M1 lesions. METHODS: Following a lesion to the rostral M1 hand area, monkeys were trained for 1 h/day for 30 days to retrieve food pellets from small wells using their impaired hand. Electrophysiological maps of the M1 were derived in anesthetized monkeys before infarct and after rehabilitative training using intracortical microstimulation. RESULTS: After a lesion to the rostral M1 and rehabilitative training, the size of the spared hand representation decreased 1.2%. This change is not statistically different from the 9% increase seen after caudal M1 lesion and rehabilitative training (P > 0.2). CONCLUSION: Postlesion training spares peri-infarct hand area regardless of whether the lesion is in the rostral or caudal M1.

Animals↗
PubMed1995

Effects of a peptide mixture with a high Fischer's ratio on serum and cerebral cortex amino acid levels and on cerebral cortex monoamine levels, compared with an amino acid mixture with a high Fischer's ratio.

Peptide mixtures with high and low Fischer's ratios (i.e., the ratio of branched-chain amino acids to aromatic amino acids), obtained from an enzymatic hydrolysate of casein, and the corresponding amino acid mixtures were intragastrically force-fed to rats. Cerebral cortex monoamines were more influenced by the ingestion of the peptide than that of the amino acid mixture.

Amino Acids↗
PubMed2004

Macaque ventral premotor cortex exerts powerful facilitation of motor cortex outputs to upper limb motoneurons.

The ventral premotor area (F5) is part of the cortical circuit controlling visuomotor grasp. F5 could influence hand motor function through at least two pathways: corticospinal projections and corticocortical projections to primary motor cortex (M1). We found that stimulation of macaque F5, which by itself evoked little or no detectable corticospinal output, could produce a robust modulation of motor outputs from M1. Arrays of fine microwires were implanted in F5 and M1. During terminal experiments under chloralose anesthesia, single stimuli delivered to M1 electrodes evoked direct (D) and indirect (I1,I2, and I3) corticospinal volleys. In contrast, single F5 shocks were ineffective; double shocks (3 msec separation) evoked small I waves but no D wave. However, when the test (T) M1 shock was conditioned (C) by single or double F5 shocks, there was strong facilitation of I2 and I3 waves from M1, with C-T intervals of <1 msec. Intracellular recordings from 79 arm and hand motoneurons (MNs) revealed no postsynaptic effects from single F5 shocks. In contrast, these stimuli produced a robust facilitation of I2 and I3 EPSPs evoked from M1 (60% of MNs); this was particularly marked in hand muscle MNs (92%). Muscimol injection in M1 reduced I waves from F5 and abolished the F5-induced facilitation of late I waves from M1, and of EPSPs associated with them. Thus, some motor effects evoked from F5 may be mediated by corticocortical inputs to M1 impinging on interneurons generating late corticospinal I waves. Similar mechanisms may allow F5 to modulate grasp-related outputs from M1.

Animals↗
PubMed2001

Focal ischemia in the cerebral cortex has an effect on the neurohypophysis. I. Ultrastructural changes in capillary vessels of the neurohypophysis after focal ischemia of the cerebral cortex.

OBJECTIVES: In our investigations we have reported that photochemical reaction leading to brain ischemia can also be precipitated with visible light from a non-coherent light source. It was revealed that focal cerebral ischemia after photochemical reaction cause the alterations in the capillaries ultrastructure and perivascular spaces of the barrier-competent regions of the brain. The purpose of this study is to first characterize the ultrastructural morphological consequences of photochemically induced ischemia in the cerebral cortex on the capillaries of neurohypophysis as the barrier-free region of the brain. METHOD: We used a model of ischemic brain damage due to obliteration of microvessels following the photochemical reaction. Rats were treated with an intravenous injection of rose bengal and irradiated from a halogen lamp source through an intact cranium to precipitate microvascular damage. Material for electron microscopic studies were sampled from the neurohypophysis 1 and 4 days after irradiation (4 animals in each group) in experimental group and 1 and 4 days after a rose bengal injection in control group. RESULTS: Investigations in transmission electron microscopy revealed platelet aggregation on the endothelium preceded by its early ultrastructural damage. In the capillaries of the neurohypophysis, one and four days after irradiation, numerous microthrombi adhering to the damaged endothelium were present. The capillary vessels contained a continuous, rather than a fenestrated endothelium. The basement membrane was thickened, blurred and locally multiplicated. CONCLUSION: Our results show that experimentally-induced thrombosis of cortical microvessels leads to alterations in the capillaries of neurohypophysis.

Animals↗
PubMed1976

Zonation of the adrenal cortex. III. Distribution of cytochrome P-450 in the zona glomerulosa of the bovine adrenal cortex.

A microsomal fraction was obtained from the zona glomerulosa of the bovine adrenal cortex. Glucose-6-phosphate activity of the fraction was found to be much lower than that of the liver. Contents of RNA and phospholipids, besides electron microscopic findings, of the fraction also indicate that it is rich in smooth-surfaced endoplasmic reticulum. Distribution of cytochrome P-450 in the zona glomerulosa was studied using various fractions including the microsomal fraction described above. The amount of cytochrome P-450 in mitochondria and that in microsomes were determined to be 0.73 and 0.32 nmoles/mg protein, respectively. The CO-difference spectrum was affected not only by the concentration of added deoxycholate but also by the incubation time after addition. Approximately 40-50% of cytochrome P-450 in the samples were converted to cytochrome P-420 within 20-30 seconds of incubation with deoxycholate.

Adrenal Cortex↗
PubMed1990

[The connections of the parietal cortex with the lateral suprasylvian gyrus (the Clare-Bishop field) and the auditory cortex in the cat].

It has been shown that a parietal projection to the Clare--Bishop area is moderate and organized in a topographic manner. Associative fibres of area 5 terminate in the anterior part of the Clare--Bishop area, which corresponds to the intermediate and anterior part of the posterior suprasylvian sulcus belt. Area 7 projects to the posterior part of the intermediate and posterior suprasylvian sulcus belt. Area 5 and 7 send a few fibres to the auditory cortex. Associative fibres of area 5 terminate in the middle ectosylvian and sylvian gyri: areas 22, 50. Area 7 is connected only with the superior extremity of the middle ectosylvian gyrus or of areas 22, 50.

Afferent Pathways↗
PubMedDate not supplied

[Effect of stimulation of interanalyzer association areas of rabbit cortex on evoked potentials and neuronal responses of the visual cortex].

The study was concerned with functional influences of associative cortical areas on EPs and neuronal responses to flashes in the visual projection zone of a rabbit. Stimulation of the anterior associative cortical parts leads to a prolongation of the inhibitory pause and to a decrease of late discharges in responses of visual cortical neurones which is manifested in a significant reduction of the secondary negative-positive EP complex. Stimulation of the posterior associative area causes a prolongation and a deepening of the inhibitory pause in the neuronal activity and an increase of late discharges in the neuronal response in the visual cortex with a corresponding significant enhancement of the secondary negative-positive EP complex. Different mechanisms of functional effects of the anterior and posterior interanalyser brain parts on the visual projection area are suggested.

Animals↗
PubMed1976

Zonation of the adrenal cortex. I. Isolation of mitochondria from the zona glomerulosa of the bovine adrenal cortex.

Isolation procedures for mitochondria from the zona glomerulosa of the bovine adrenal cortex are described in comparison to those isolated from the zona fasciculo-reticularis. The cristal membranes of mitochondria in the zona glomerulosa in situ are tubular or tubulo-vesicular, whereas those of mitochondria in the zona fasciculo-reticularis in situ are vesicular. When mitochondria are isolated from the former zone, they invariably showed a condensed configuration regardless of isolation media, whereas those isolated from the later zone in a ST medium showed an orthodox configuration. When Ca2+ was added to mitochondria isolated form either zone in an STE medium in the condensed configuration, transition from the condensed to the orthodox configuration took place; the cristel membrane of mitochondria from the zona glomerulosa became tubular or tubulo-vesicular and those of mitochondria from the zona fasciculo-reticularis became vesicular. Purity of mitochondria thus obtained from the zona glomerulosa was examined by electron microscope and marker enzymes. Coupling efficiency of mitochondria was found to be remarkably affected by temperature during the isolation procedures and a choice of substrates.

Adrenal Cortex↗