Biomedical subjects

K Albus

Publications and source records attributed to K Albus.

At least 19 recordsLinked to original sources

PubMed2000

Activity-dependent development of spontaneous bioelectric activity in organotypic cultures of rat occipital cortex.

The development of spontaneous bioelectric activity (SBA) in organotypic tissue cultures (OTCs) from rat occipital cortex was studied by means of extracellular recording techniques in OTCs grown normally for 6-51 days in vitro (DIV), and in OTCs in which SBA had been silenced from DIV 4 on for 2 to 3 weeks by elevating the Mg(2+) levels in the growth medium. The proportions of spontaneously active neurones increased from about 25% at 6-14 DIV to more than 80% beyond the third week in vitro. Mature neurones discharged at shorter intervals and more vigorously than immature neurones; the developmental increase in firing rate was not significant, however. In OTCs 6-14 DIV the majority of spontaneously active neurones fired sluggishly in a regular manner. The remaining neurones fired action potentials in the form of discrete bursts resembling interictal activity in vivo. The proportions of these neurones increased from about 40% at 6-14 DIV to more than 80% beyond the third week in vitro. During development in vitro the mean burst duration increased from 3.5 s to about 8 s whereas the mean burst rate (between 0.7-1 bursts/min) remained constant. Activity-deprived neurons had low firing rates and fired action potentials in the form of discrete bursts with a mean burst rate of 0.4/min. The proportions of spontaneously active neurons, the variability of neuronal firing and the viability of the explants either were not altered by the activity blockade or had recovered to control values after 5-6 days in normal growth medium. We conclude that in OTCs of rat neocortex the absence of SBA during development in vitro delays the maturation of excitatory mechanisms responsible for the developmental increase in firing intensity. The development of burst firing modes is less affected by activity blockade.

Animals↗

PubMed2000

Neuropsychological deficits in pediatric patients with childhood-onset schizophrenia and psychotic disorder not otherwise specified.

OBJECTIVE: Children with transient psychotic symptoms and serious emotional disturbances who do not meet current criteria for schizophrenia or other presently recognized diagnostic categories commonly present diagnostic and treatment problems. Clarifying the connections between children with narrowly defined schizophrenia and children with a more broadly defined phenotype (i.e., Psychotic Disorder Not Otherwise Specified, PD-NOS) has implications for understanding the pathophysiology of schizophrenia. In this study, the neuropsychological test performance of a subgroup of children with atypical psychosis was compared with that of patients with childhood-onset schizophrenia (COS). METHOD: Cognitive function was assessed with neuropsychological test battery regimens in 51 neuroleptic-nonresponsive patients within the first 270 at NIMH testing (24 PD-NOS, 27 COS) were included in this analysis. Seventeen (39%) of 44 COS subjects were unavailable for this study as their IQ tested <70. The PD-NOS patients were younger than the COS patients at the time of testing (12.0+/-2.8 vs 14.4+/-1.8years, respectively, p<0.004). The test levels of these groups were compared with each other. RESULTS: The neuropsychological test results for the PD-NOS and COS patients were 1-2standard deviations below normative data across a broad array of cognitive functions. There were no overall differences in the test levels for the six summary scales (F=2.82, df=1, 36, p=0.10) or in the profile shape (F=1.70, df=5, 180, p=0.14) between the PD-NOS and COS groups. For the COS patients, there was a significant difference between their mean full-scale WISC IQ (84.7+/-16.2) and their average standard scores for both the spelling (97.7+/-16.1, n=23, t=4.0, p=0.001) and reading decoding subtests (97.7+/-13.7, n=23, t=3.7, p=0.001) of the Kaufman Test of Educational Achievement. CONCLUSIONS: Treatment-refractory PD-NOS and COS patients share a similar pattern of generalized cognitive deficits, including deficits in attention, learning and abstraction which are commonly observed in adult patients with schizophrenia. These data support a hypothesis that at least some of the PD-NOS cases belong within the schizophrenic spectrum, which is of importance for future genetic studies planned for this cohort.

Adolescent↗

PubMed1999

Formation of the corticopontine projection in a long-term culture system.

The reestablishment in vitro of the corticopontine projection was studied in organotypic co-cultures of cortex and pons of rats 0 (day of birth) - 3 days old. After 2-3 weeks in vitro, application of the lipophilic tracer DiI in the pontine explant retrogradely stained in layer V of the cortical explant pyramidal neurons which were characterized by large somata and spiny dendrites with an apical dendrite that reached upper cortical layers II/III. The projection developed only in co-cultures from rats 0-2 days old when the pontine explant was placed in close vicinity either to the white matter or the pial surface of the cortical explant. Control experiments demonstrated the specificity of the corticopontine projection in vitro by showing that the projections of the layer V pyramidal cells to the pons did not reflect a non-directed outgrowth pattern with subsequent survival of axons contacting the target explant. Our findings demonstrate that morphology and laminar position of corticopontine projection neurons in vitro are similar to those in vivo and thus support the "organotypic" nature of the explant co-culture system.

Animals↗

PubMed1997

Performance of real time separation of multi-neuron recordings with a DSP32C microprocessor.

The performance of a method for sorting of waveforms in multi-neuron data (Gädicke and Albus, 1995) is evaluated by using artificial spike patterns generated by the computer and by adding to these spikes noise or free running sine waves of varying frequency and amplitude to simulate EEG-waves. The DSP32C is capable of continuously processing spikes at 183.106 Hz. In addition to real-time sorting the DSP32C also performs a running average of the spikes sorted into each class and transfers data to the host computer. The ability of the system to analyse burst of activity is determined by the FIFO memory buffer (2048 samples, or 32.768 ms at 62.5 kHz sampling rate). Adding a 50 Hz sine wave discrimination worked correctly with sine wave amplitudes of up to 2.5 times that of the smallest spike. Combining spikes with noise revealed errors of inclusion and/or exclusion of less than 0.1% provided the models spikes were determined from noiseless spikes and the spike threshold was set above the noise peak level. When noisy spikes were used to define model spikes about 4% of the smallest amplitude spikes (signal to noise ratio 3.3) were incorrectly classified. For higher amplitude spikes (signal to noise ratio > or = 5) the classification error was on average less than 1%. The artificial patterns used for performance testing are exactly defined and could be used to standardize the comparison between different sorting techniques.

Electroencephalography↗

PubMed1997

Pubertal development and onset of psychosis in childhood onset schizophrenia.

In this study, pubertal development was examined for a sample of children and adolescents with childhood onset schizophrenia (COS) defined as psychosis by age 12. Developmental and psychiatric histories were obtained for 28 adolescents (mean age 14.5 +/- 2.3 years) with severe, treatment refractory COS (14 males, 14 females). Age of onset of psychosis was also examined in relation to menarche and development of secondary sex characteristics. Girls had a trend towards developing secondary sex characteristics earlier than boys (P = 0.06), consistent with North American norms. Males (N = 14) and females (N = 14) had similar age of onset of psychosis. The age of development of secondary sex characteristics was associated with onset of psychosis for girls, but this finding was driven by one outlier. There was no significant correlation between development of psychosis and menarche. Neither male nor female probands differed significantly from their well siblings or from North American norms in their age of onset of pubertal development. There was no evidence of early onset of secondary sex characteristics for this sample. Finally, there was an absence of a clear relationship between onset of psychosis and indices of sexual development for these very early onset cases.

Adolescent↗

PubMed1997

Neurons in the rat occipital cortex co-expressing the substance P-receptor and GABA: a comparison between in vivo and organotypic cultures.

The morphology and the distribution of neurons expressing the NK1-receptor (NK1R) and the co-expression of gamma-aminobutyric acid (GABA) in these neurons were studied in the rat occipital cortex and in organotypic cultures (OTCs) derived from this structure. By employing immunohistochemistry, we demonstrate that the NK1R-expressing neurons are non-pyramidal neurons and co-express GABA. Some differences were noted between in vivo and OTCs. NK1R-expressing neurons in OTCs had larger somata and longer dendrites and the proportion stained with an anti-GABA-antibody (approximately 50%) was smaller than in vivo (90%). The preferential location of NK1R-expressing neurons in layers II/III and VI, seen in vivo is not present in OTCs where these neurons distribute rather homogeneously through layers II-VI. Our findings imply that in contrast to the cat and monkey, in the rat occipital cortex the effects of substance P are almost exclusively mediated via inhibitory interneurons.

Animals↗

PubMed1996

Childhood-onset schizophrenia: brain MRI rescan after 2 years of clozapine maintenance treatment.

OBJECTIVE: The effect of clozapine on striatal morphology was examined in adolescents with childhood-onset schizophrenia. METHOD: Eight adolescent patients with onset of psychosis before age 12 and eight matched comparison subjects had initial and 2-year follow-up brain magnetic resonance imaging scans. Basal ganglia and lateral ventricle volumes were measured. The patients were on a clozapine regimen during the 2-year interim. RESULTS: Caudate volume was larger in the patients at the initial scanning, decreased in the patients between scans, and did not differ significantly between the patients and the comparison subjects at the second scanning. CONCLUSIONS: Caudate enlargement in patients with childhood-onset schizophrenia who are taking typical neuroleptics appears to be secondary to medication exposure. Rescanning to examine basal ganglia morphology is indicated for these patients when they are taking an atypical neuroleptic.

Adolescent↗

PubMed1995

Real-time separation of multineuron recordings with a DSP32C signal processor.

We have developed a hardware and software package for real-time discrimination of multiple-unit activities recorded simultaneously from multiple microelectrodes using a VME-Bus system. Compared with other systems cited in literature or commercially available, our system has the following advantages. (1) Each electrode is served by its own preprocessor (DSP32C); (2) On-line spike discrimination is performed independently for each electrode. (3) The VME-bus allows processing of data received from 16 electrodes. The digitized (62.5 kHz) spike form is itself used as the model spike; the algorithm allows for comparing and sorting complete wave forms in real time into 8 different models per electrode.

Action Potentials↗

PubMed1994

The topography of tangential inhibitory connections in the postnatally developing and mature striate cortex of the cat.

Clustered intrinsic connections in the striate cortex of kittens originate from an unclustered, diffusely organized pattern prevailing during the first postnatal week. In order to study the participation of inhibitory neurons in this reorganization of the connections, we determined the topography of the inhibitory tangenital connections in the striate cortex of cats ranging in age between 7 and 330 days by combining retrograde transport of fluorescent microspheres with GABA immunohistochemistry. After small intracortical injections of tracer, neurons containing either microspheres only (non-GABAergic neurons) or GABA-like immunoreactivity in addition to microspheres (GABAergic neurons) are labelled at various horizontal distances from the injection. At the end of the first postnatal week, both GABAergic and non-GABAergic neurons are distributed in the horizontal plane in an unclustered fashion. During the second postnatal week, the tangential connections rearrange rapidly to form clusters. The tendency of the cells to form clusters is much weaker, however, in GABAergic than in non-GABAergic neurons. In regions > 500 microns distant from the centre of injection approximately 90% of the non-GABAergic neurons (range 87.5-92.6%) but only 63% (range 57.1-72.3%) of the GABAergic neurons reside within the clusters formed by the non-GABAergic neurons. These proportions do not change systematically with age. In the regions outside the non-GABAergic clusters, GABAergic neurons appear to be evenly distributed and not to aggregate in clusters. From postnatal day 7 forward GABAergic neurons largely retain their overall distribution and density in the horizontal plane. When considering all cortical layers (including the superficial white matter) the lateral spread of the GABAergic neurons is more restricted than that of the non-GABAergic neurons. Systematic changes in the lateral spread of inhibitory connections according to postnatal age were not observed. We conclude that, like the non-GABAergic neurons, the GABAergic neurons have attained an adult-like topography in the horizontal plane by about the end of the second postnatal week. From that time until adulthood they display much weaker clustering, a higher relative occurrence of short axon collaterals and a more restricted lateral distribution than do the excitatory neurons.

Animals↗

PubMed1993

Distribution of neurons expressing substance P receptor messenger RNA in immature and adult cat visual cortex.

We have investigated the expression of messenger RNA (mRNA) encoding substance P receptor (SPR) in the visual cortex of adult cats and 17-day-old kittens, using in situ hybridization histochemistry with two digoxigenin-labeled oligodeoxynucleotides complementary to the SPR mRNA. In the adult cortex, a subset of large pyramidal neurons of layer V and layer III is heavily labeled. Other, mainly pyramidal neurons in layers II, III and V are less intensely labeled, but most neurons in these layers appear unlabeled. Neurons in layer IV and VI, and in the white matter do not show hybridization signals above background levels. In the 17-day-old kitten, SPR mRNA-expressing cells are confined to layer V and to the upper white matter (subplate zone), whereas supragranular neurons do not yet contain SPR mRNA. A few neurons in layer VI display moderate labeling. Astrocytes, identified with anti-glial fibrillary acid protein antibodies, did not express detectable levels of SPR mRNA in both adult and kitten visual cortex. These results indicate that SPR mRNA expression is transient in neurons of the white matter, and is developmentally regulated in supragranular layers. In addition, the localization of SPR mRNA in a subset of pyramidal cells suggests that substance P modulates the excitability of certain projection neurons which are the origin of extrinsic connections.

Aging↗

PubMed1993

Examination of the effects of cholecystokinin 26-33 and neuropeptide Y on responses of visual cortical neurons of the cat.

Extracellular recordings were made from 160 neurons in area 17 (n = 120) and area 18 (n = 40) of the visual cortex of anesthetized cats. Cells were classified according to their receptive field properties and their intracortical positions were evaluated histologically. Cholecystokinin 26-33, antagonists, (cholecystokinin 27-32, cholecystokinin 27-33 and proglumide), amino acids, neuropeptide Y and solvent vehicle (control), were administered to cells by microiontophoresis (cholecystokinin and neuropeptide Y) or by pressure (neuropeptide Y). The results of the tests with cholecystokinin 26-33 fell into four categories: enhancement (31%), suppression (24%), mixed, i.e. either biphasic responses or dose-related alterations in the direction of effect (20%), and no effect (25%). Enhancements of the visually elicited response were more prevalent in simple (43%) and unimodal/movement-sensitive (34%) cells than in complex (7%) cells. The converse was true for suppressions: 19% of simple cells, 24% of unimodal/movement-sensitive cells, and 31% of complex cells were suppressed. Thirty per cent of the unaffected cells were complex or unimodal/movement-sensitive; only 14% were simple. Cells in layers II-IV were more likely to have firing enhanced than suppressed by cholecystokinin 26-33. The converse was true for cells in layers V and VI, where 50% of responses were suppressed and only 22% were enhanced. Unaffected cells were found predominantly in layer III of areas 17, and the lower part of layer III and layer IV of area 18. Cholecystokinin 26-33 sometimes exerted delayed, response-suppressant effects; it also occasionally elevated responsiveness preferentially within the upper ranges (10-20 degrees/s) of velocity tuning curves. Cholecystokinin 26-33 altered the response-suppressant action of GABA in 11 of 19 visually sensitive cells. The peptide potentiated the visual responsiveness in half of the cells where cholecystokinin 26-33 diminished the GABA-induced suppressions (n = 8). The presumed antagonists either exerted no effect on firing or on cholecystokinin 26-33-induced effects, or had cholecystokinin 26-33-like actions themselves. There was a reversible partial antagonism of the effects of cholecystokinin 26-33 on only two of 11 cells tested. Neuropeptide Y injected by pressure or administered iontophoretically had variable and inconsistent effects on the visually evoked responses of 29 additional neurons from those described above. These effects were indistinguishable from those of the vehicle whether spontaneous activity, magnitude of the visually elicited response, spatial integrity of the RF substructure, orientation or velocity tuning was assessed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Rapid rearrangement of intrinsic tangential connections in the striate cortex of normal and dark-reared kittens: lack of exuberance beyond the second postnatal week.

Clustered intrinsic connections in the kitten striate cortex originate from an unclustered, diffusely organized pattern prevailing during the first postnatal week. We have studied the progress of this reorganization and its dependence on visual input by determining the topographies of the intrinsic tangential connections at various postnatal ages by means of axonal tracing methods. Neurons were labeled either by diffusion of the carbocyanin dye DiI in animals ranging in age between 1 day and 30 days, or by retrograde transport of fluorescent microspheres in animals ranging in age between 7 days and 11 months. Quantitative evaluation of retrogradely labeled neurons revealed that during the first postnatal week, intrinsic tangential connections are organized in an unclustered fashion. During the second postnatal week a rapid rearrangement of connections occurs and is complete around postnatal day 11. The main events taking place during the course of this rearrangement are a decrease in the density of tangential connections and an arrangement of them in a clustered fashion. Once the clusters have been formed, the periodicity of the clustered pattern of connections and the size and distinctness of the clusters do not change. This means that the system of clustered tangential connections is adult-like at the end of the second postnatal week. Dark rearing affects neither the rapid rearrangement of horizontal connections into an adult-like system of clusters, nor the integrity of this clustered topography until the end of the first postnatal month. The overall distribution and the lateral extent of the tangential connections remain about the same during the postnatal period and are not affected by dark rearing until the end of the first postnatal month. We conclude that the clustered system of tangential connections in the cat's striate cortex is determined innately.

Aging↗

PubMed1992

Widespread lateral processes of glial cells in the immature striate cortex of the cat.

The topographies of intrinsic tangential connections of cells in the striate cortex of cats were determined in animals ranging in age between 1 day and 30 days. Implants of the carbocyanin dye, DiI, were found to label cellular elements which are classified by morphological criteria as astrocytes, in addition to neurons. Labeled astrocytes are seen in all cortical layers and in the superficial and deep white matter. Most labeled astrocytes occur underneath the DiI implant, but a number of them are also located horizontally at various distances from the implant. The horizontal span of the glial processes is the same as that for neuronal processes; in contrast to neurons however, the laterally distributed astrocytes assume a flat and unclustered distribution in the horizontal plane. Our observations suggest that the program for determining the span of laterally directed projections in the cat striate cortex is likely to be the same for neurons and astrocyte-like neuroglia.

Animals↗

PubMed1992

Tachykinins preferentially excite certain complex cells in the infragranular layers of feline striate cortex.

Microiontophoretically administered substance P (SP) affected the visually evoked responses (VER) and the spontaneous firing of 22 (14%) of the 152 neurons recorded from the striate cortex of anaesthetised cats. Enhancing effects were seen in 14 neurons and suppressant actions in 8 neurons. Most of the cells excited by SP were located in infragranular layers and had complex receptive fields; a few belonged to the movement-sensitive class or responded only weakly to visual stimulation. Of the neurons recorded in layer V, about 70% were excited by SP; the respective proportions were 8% in layer VI, and 2% in layer IV. Cells suppressed by SP had either simple or unimodal receptive fields including hypercomplex varieties; most of them were located in layer IVc. The effects of other tachykinins (neurokinin A, neurokinin B) and of the NK-3 receptor agonist Senktide tested in 36 cells were identical to those of SP with respect to types, and intracortical locations, of cells affected. During the enhancement induced by the tachykinins functional parameters of the neurons such as orientation and direction sensitivity were not substantially affected. It seems likely therefore that the effect of tachykinins in the primary visual cortex is not a shaping of receptive field properties, but rather a modulation of the general excitability of neurons projecting to subcortical centers, in particular to the midbrain and pons.

Animals↗

PubMed1991

The contribution of GABA-ergic neurons to horizontal intrinsic connections in upper layers of the cat's striate cortex.

The contribution of neurons containing gamma-aminobutyric acid (GABA) to horizontal intrinsic projections in layers I-III of cat's striate cortex was investigated by combining GABA-immunohistochemistry with axonal tracing. After intracortical injections of Rhodamine-labelled latex microspheres Rhodamine-labelled neurons form patch- or bandlike aggregations (clusters) separated from each other by regions containing fewer, evenly distributed or no labelled neurons. Of the Rhodamine-labelled neurons about 5% display GABA-immunoreactive material (double labelled = DL-neurons). Approximately 70% of the DL-neurons occur at distances of less than 1 mm, and the remaining 30% at distances between 1 mm and 2.5 mm from the injection. About 60% of the DL-neurons reside within clusters and 40% are located in regions between clusters; the respective percentages of the Rhodamine labelled GABA-negative neurons are about 85 and 15. Considering their small number and their spatial distribution inhibitory interneurons seem to make only minor contributions to the clustered pattern of intrinsic connections. Our results demonstrate that the topographical organization of neurons giving origin to lateral inhibitory interactions in upper layers of cat's striate cortex is different from that of neurons mediating excitatory functions.

Animals↗

PubMed1989

The postnatal development of layer VI pyramidal neurons in the cat's striate cortex, as visualized by intracellular Lucifer yellow injections in aldehyde-fixed tissue.

The postnatal development of layer VI pyramidal neurons in the cat's striate cortex has been studied by means of intracellular injections of Lucifer yellow in aldehyde-fixed tissue (LYF technique). It is shown that the LYF technique gives results qualitatively and quantitatively similar to results obtained with other techniques (Golgi, marker-injections in viable tissue). Quantitative analysis demonstrated significant increases in soma diameter, number and length of basal dendrites, length of second order apical dendrites and, in particular, in number of spines/unit dendritic length, during the first postnatal month. Maturation of the basal dendritic tree and increase in number of spines continue in the second postnatal month. At later postnatal times soma diameter and number of spines decrease by about 20%. Dendritic varicosities are most frequent during the first postnatal week, and decrease in number steadily from thereon. The late maturation of layer VI pyramidal neurons suggests that these cells might be affected by early peripheral lesions and/or sensory deprivation to which the striate cortex of the cat has been shown to be most susceptible around the end of the first postnatal month.

Aging↗

PubMed1989

A long term study of axonal transport in the central visual system following eye enucleation in the adult cat.

The effect of the enucleation of one eye on anterograde and retrograde labelling in geniculo-cortical, cortico-geniculate and commissural projections was investigated in adult cats by means of horseradish peroxidase (HRP) and tritiated aminoacids. It was found that in addition to the immediate decrease of retrograde labelling with HRP in the cortical projections from the deafferented A-laminae of the dorsal part of the lateral geniculate nucleus (Singer et al. 1977) there is a further reduction which lasts up to 75 days after enucleation. At 146 and 363 days after enucleation a slight increase in the number of labelled neurones was noted in the deafferented lamina. Qualitative assessment did not reveal any changes of anterograde labelling with tritiated amino acids in geniculo-cortical, cortico-geniculate and commissural axones. In addition, the retrograde labelling with HRP in cortico-geniculate and commissural projections seemed to be unaffected by eye enucleation.

Amino Acids↗

PubMed1988

Phaclofen antagonizes baclofen-induced suppression of visually evoked responses in the cat's striate cortex.

The suppression of visually evoked responses (VER) in the cat's striate cortex by baclofen was reversibly antagonized by the phosphonic acid derivative of baclofen, phaclofen. The antagonistic effect of phaclofen was seen irrespective of whether it enhanced, suppressed or did not change VER on its own. The suppression of VER by gamma-aminobutyric acid (GABA) was not affected by phaclofen. Our findings support the notion (Kerr et al., Brain Research, 405 (1987) 150-154) that phaclofen is an effective baclofen antagonist in the central nervous system of mammals. Preliminary findings indicate that in spite of its possible action on GABAB receptors, phaclofen does not significantly alter functional properties of striate cortical neurons, in particular direction and orientation sensitivity.

Animals↗