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Biomedical subjects

A Peters

Publications and source records attributed to A Peters.

At least 217 records · Page 12Linked to original sources
PubMed1988

[Bursa iliopectinea--size and morphology].

The size of the iliopsoas bursa is usually larger than its size described in textbooks of anatomy. Proximally the synovial bursa lies on the pectineal eminence of the superior pubic ramus, passes across the front of the capsule of the hip joint and extends distally downwards almost as far as to the lesser trochanter. Only the tendon of the psoas major muscle is normally an immediate relation to the bursa. In 13% of all cases the iliopsoas bursa is partly separated by a septum into 2 cavities. Here the tendon of the psoas major muscle passes over the medial chamber and the tendon of the iliac muscle runs over the lateral chamber. With regard to modern diagnostic techniques (computer tomography, magnetic resonance-tomography) the results are significant for the differential diagnosis of inflammatory processes in hip joints.

Aged↗
PubMed1987

GABA immunoreactive neurons in rat visual cortex.

An antiserum to gamma-aminobutyric acid (GABA) was used in a light and electron microscopic immunocytochemical study to determine the morphology and distribution of GABA-containing neurons in the rat visual cortex and to ascertain whether all classes of nonpyramidal neurons in this cortex are GABAergic. The visual cortex used for light microscopy was prepared in such a way that the antibody penetrated completely through tissue sections, and in these sections large numbers of GABA immunoreactive neurons were apparent. The labeled neurons could be identified as being either multipolar, bitufted, bipolar, or horizontal neurons. In layers II through VIa, GABA immunostained cells were distributed uniformly and accounted for approximately 15% of all neurons, but in layer I all neurons appeared to be immunostained. Electron microscopy of GABA immunostained visual cortex prepared to ensure good fine structural preservation confirmed the presence in layers II through VIa of numerous immunoreactive bipolar neurons, both small and large varieties, as well as multipolar and bitufted neurons. Additionally, electron microscopy reveals that astrocytes are frequently GABA immunoreactive. From a correlated light and electron microscopic evaluation of neurons in GABA immunostained visual cortex, it was possible to confirm which kinds of neurons are GABAergic and what proportion of the neuronal population they represent. Thus, from an analysis of some 950 neurons, it was found that pyramidal neurons were never immunoreactive and that except for 20% of the bipolar cell population, all examples of other types of nonpyramidal neurons encountered in this material were GABA immunoreactive.

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PubMed1987

The neuronal composition of area 17 of rat visual cortex. IV. The organization of pyramidal cells.

In area 17 of the rat visual cortex, most of the apical dendrites of the large layer V pyramidal cells aggregate into oriented clusters, each containing three or more such dendrites. These clusters are not randomly distributed, but have a basic hexagonal packing distribution in which the mean center-to-center spacing is 55-60 microns. The majority of medium-size pyramidal cells of layer V also add their apical dendrites to the clusters. As these clusters pass through layer IV they remain intact, and successively layer III and finally layer II pyramids add their apical dendrites to them. Perhaps because the pyramidal cells in layer II/III are so numerous, some of their apical dendrites form independent groups. Apical dendrites of the small pyramidal neurons in layers VIa and IV seem not to specifically add to the clusters. Instead, apical dendrites of layer VIa pyramids form into contiguous fascicles and sheets, which pass around the groups of layer V pyramidal cell bodies to ascend to layer IV, where most of them form their apical tufts. Layer IV pyramidal cell apical dendrites behave somewhat similarly. These apical dendrites have to pass between the cell bodies of the lower layer III pyramidal cells. To do this, some join the clusters, but others form independent bundles. It is suggested that the pyramidal cells whose apical dendrites are clustered represent vertically oriented neuronal modules whose activity is synchronized, and that different combinations of these modules are excited by afferents to the cortex to provide the bases for the various kinds of functional columns.

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PubMed1987

Vasoactive intestinal polypeptide immunoreactive neurons in the primary visual cortex of the cat.

When cat visual cortex (area 17) is reacted with an antibody to vasoactive intestinal polypeptide (VIP) a variety of neuronal types is labelled. Many of the labelled neurons are bipolar in form and are most common in layers II and III, although significant numbers of bipolar neurons are also encountered in layer V. Multipolar cells are also labelled. These are most frequent in layer IV and have a variety of shapes. In layer I, the labelled cells are of three varieties, i.e. horizontal bipolar cells, horizontal bitufted cells and multipolar neurons, while in layer VI the few VIP-positive neurons are horizontal bipolar cells. This suggests that all of the VIP-labelled neurons in cat area 17 are non-pyramidal in form, and this has been confirmed by electron microscopy. In these preparations, axon terminals are also labelled and under the light microscope it can be seen that these terminals occur both within the neuropil and around the cell bodies of some neurons, particularly neurons in layers II and III. Electron microscopy has shown that all of the labelled axon terminals form symmetric synapses and that those in the neuropil synapse with the shafts of smooth dendrites. These axodendritic synapses account for about 90% of the synapses formed by the labelled axon terminals. The remainder of the labelled axon terminals synapse with the cell bodies of pyramidal neurons. Parallels are drawn between these results and those previously obtained by examining those neuronal elements labelled with VIP antibodies in rat visual cortex.

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PubMed1987

Preclinical studies of a panel of 12 monoclonal antibodies in view of bone marrow purging in acute lymphoblastic leukemia.

We analysed the optimal conditions for autologous bone marrow purging using complement binding monoclonal antibodies (mAbs). Twelve mAbs belonging to four clusters (CD9, CD10, CD19, CD24), alone or combined were evaluated by using direct cytotoxicity and clonogenic assays. We observed the following data: (1) optimal cytotoxicity was reached with doses of 1-10 micrograms mAbs for 10(7) cells, (2) the concentration of the cell suspension had to be below 3 X 10(7)/ml, (3) combinations of mAbs were more effective than a single mAb treatment, (4) in the case of an IgM isotype, there seems to be a clear dissociation between the amount needed for optimal toxicity and that for antigenic saturation measured by cytofluorometry.

Antibodies, Monoclonal↗
PubMed1986

Somatostatin immunoreactive neurons in rat visual cortex: a light and electron microscopic study.

Somatostatin immunoreactive neurons in rat visual cortex were examined in the light and electron microscopes using an antibody to the tetradecapeptide form of somatostatin. Somatostatin immunoreactive neurons were found to belong only to non-pyramidal classes. They are of five main types: multipolar neurons with either thin or thick dendrites; small and large bipolar neurons; bitufted neurons; horizontal neurons; and neurons in the subcortical white matter. Of the immunoreactive neurons, multipolar neurons are the most common and account for 30% of the population, while bipolar and bitufted neurons make up 25% and 15% of the immunoreactive population, respectively; the least common somatostatin immunoreactive neurons are the horizontal and subcortical white matter neurons. Occasional multipolar neurons with thick dendrites have a prominent ascending dendrite so that they resemble pyramidal cells in the light microscope, but electron microscopic examination confirms that, like all other somatostatin-positive cells, they are non-pyramidal neurons, for they have both symmetric and asymmetric synapses on their cell bodies. Somatostatin-positive neurons are distributed among all the cortical layers and the subcortical white matter but they are more common in two laminae, one coinciding with layer II/III and the other with layers V and VI. The multipolar and bipolar neurons are distributed in similar proportions in these upper and lower cortical laminae, while bitufted neurons are more common in upper laminae and horizontal neurons are predominantly located in layer VI.

Animals↗
PubMed1986

Laser-Doppler examinations in persons with healthy vasculature and in patients with peripheral arterial occlusive disease.

Recently, a new procedure for noninvasive measurement of the microcirculation has been developed in the form of a helium-neon-laser Doppler apparatus with which the total erythrocyte flow through a cubic millimeter of skin is quantifiable. The authors used the procedure to examine 17 persons with healthy vessels, 36 patients with a degenerative occlusive disease of the peripheral arteries in Fontaine stages II-IV, and 5 patients with endangiitis obliterans. It is concluded that single measurements do not permit an assessment of microcirculatory conditions but that provocative tests (which are described), especially occlusion tests, make possible valid and reproducible statements and have a high selectivity with respect to the different stages of disease. By repeated measurements followed by calculation of mean values, a further reduction in intraindividual variability among the measurement results can be obtained. Laser-Doppler examinations of the skin constitute a new procedure with which quantitative statements on the blood flow through skin are feasible and from which interesting results can be expected, especially when used as an acute test.

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PubMed1985

The neuronal composition of area 17 of rat visual cortex. III. Numerical considerations.

The neuronal population of area 17 of rat visual cortex has been examined by using tissue from brains fixed by perfusion. The tissue was osmicated and embedded in plastic so that the same neurons could be examined by both light and electron microscopy. In these preparations area 17 was 1.49 mm thick and by stereological procedures it was calculated that there are about 120,000 neurons beneath 1 mm2 of cortical surface. If one assumes area 17 in each hemisphere of the rat to occupy between 7.1 and 9.4 mm2 of cortical surface, then in each hemisphere the area contains between 850,000 and 1,128,000 neurons. Of these neurons 85% are pyramidal cells and 15% are nonpyramidal cells. About one-third of the nonpyramidal cells occur in layers I and VIb, both of which contain only this kind of neuron. The remaining two-thirds of the nonpyramidal cells are in layers II-VIa. Within these layers it has been possible to differentiate bipolar cells from other types of nonpyramidal cells and in each of these two nonpyramidal cell groups to recognize both small and large neurons. The greatest concentration of nonpyramidal cells occurs in layer II/III. To confirm the validity of the stereologically derived data direct counts were made of the medium and large pyramidal cells in layer V.

Animals↗
PubMed1985

The neuronal composition of area 17 of rat visual cortex. I. The pyramidal cells.

The pyramidal cells in area 17 of rat visual cortex have been examined by light microscopy using Golgi preparations and semithin plastic sections, and by electron microscopy. Pyramidal cells have cell bodies in layers II-VIa. The pyramidal cells in the lower portion of layer II/III are typical examples of this neuronal type in that they have pyramidal-shaped cell bodies, apical dendrites which ascend to layer I, and a skirt of basal dendrites. The pyramidal cells in upper layer II/III are similar in form but have shorter apical dendrites, while the most superficial pyramidal cells lack apical dendrites and instead have two or more primary dendrites that emanate from the upper surface of their somata. In layer V the pyramidal cells are of two sizes, medium and large, and both have a typical morphology, although the larger neurons have thicker apical dendrites and better-developed axon hillocks than the medium-sized pyramids. The medium-sized pyramidal cells of layer V outnumber the large ones to a ratio of 2.5:1. In layer IV a few typical medium-sized pyramidal cells are present, but the majority are small and can be regarded as star pyramids for they have dendrites radiating in all directions. No clearly identified spiny stellate cells have been encountered in layer IV. The pyramidal cells of layer VIa are also small, and most of them have apical dendrites which only ascend as far as layer IV. In addition to these varieties, both inverted and horizontally inclined pyramidal cells have been encountered. In electron micrographs it is apparent that although all of the pyramidal cells have symmetric axosomatic synapses, the frequency with which these synapses occur varies. The cell bodies of the various forms of pyramidal cells do not show a standard cytology. The medium-sized pyramidal cells of layer II/III usually have rounded nuclei, while the nuclei of the small pyramidal cells of layers IV and VIa are somewhat more irregular, and the large pyramidal cells of layer V have deeply indented nuclear envelopes. The appearance of the perikaryal cytoplasm also varies. The larger pyramidal cells have numerous mitochondria and well-developed Nissl bodies in their perikaryal cytoplasm, but the smaller cells have much-less-pronounced mitochondria and their rough endoplasmic reticulum is only organized into stacks at the bases of dendrites. Pyramidal cells account for about 87% of profiles of neuronal cell bodies with nuclei in layer II/III, 90% in layer IV, 89% in layer V, and 97% in layer VIa.

Animals↗
PubMed1985

The neuronal composition of area 17 of rat visual cortex. II. The nonpyramidal cells.

In the preceding article the characteristics of the various types of pyramidal cells present in area 17 of rat visual cortex were described (Peters and Kara, '85). In the present article the nonpyramidal cell population of this cortex is considered. It is known from Golgi preparations that in layers II-VIa there are bipolar cells, smooth or sparsely spinous multipolar and bitufted cells with either unmyelinated local plexus or myelinated axons, and chandelier cells. Each of these cell types has been previously examined in Golgi-electron microscopic preparations. The question now being asked is whether the information about the characteristics of these different types of nonpyramidal cells derived from the Golgi-electron microscopic studies can be used to identify the cell bodies of nonpyramidal cells in tissue prepared for conventional electron microscopy. If this can be done then the neuronal composition of area 17 can be determined. It has been found that the cell bodies of bipolar cells can be readily identified because they are elongate and have nuclei with a vertical infolding and few axosomatic synapses, which are of both the symmetric and asymmetric varieties. Evidence is presented to show that there are two types of bipolar cells, small ones and large ones, the large ones being distinguished by their well-developed endoplasmic reticulum in which the cisternae are arranged parallel to the cell surface. Bipolar cells account for 6% of the neuronal profiles in layer II/III, 3% in layer IV, 5% in layer V, and 2% in layer VIa. The cell bodies of other types of nonpyramidal cells in layers II-VIa cannot be distinguished from each other in thin sections, because recognition of the different cell types depends upon the characteristics and distribution of their dendrites and axons. However, it is evident that in this group of neurons there are some with small cell bodies and others with large cell bodies, and in both size groups there are varieties of neurons which can be recognized from the characteristics of their perikaryal cytoplasm. All of these neurons have both symmetric and asymmetric axosomatic synapses. The greatest number of these nonpyramidal cells which are not bipolar in form is found within layer II/III, where they account for 7% of all neuronal profiles. These neurons comprise 4% of all neuronal profiles in layer IV, 6% in layer V, and 2% in layer VIa. Layers I and VIb contain only nonpyramidal cells, but these are different from the ones in layers II-VIa.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

The morphology and synaptic connections of spiny stellate neurons in monkey visual cortex (area 17): a Golgi-electron microscopic study.

Based on a gold-toning, Golgi-electron microscope examination of 12 small and medium-sized spiny stellate neurons in laminae 4A, 4B, and 4C of the monkey visual cortex (area 17), the ultrastructure of the cell somata, dendrites, and axons of these neurons is described. Particular attention is paid to the synapses involving the surface of different parts of these neurons. Only symmetric synapses occur on the somata of spiny stellate neurons, and these occur with a frequency of 11.0-15.9 synapses/100 microns2 perikaryal surface. Symmetric synapses also occur on dendritic shafts and, occasionally, on dendritic spines. Asymmetric synapses are occasionally present along the dendritic shafts of spiny stellate neurons, but the majority of asymmetric synapses (75-95%) occur on their dendritic spines. The initial axon segments of the smallest spiny stellate neurons possess no axo-axonal synapses, but several symmetric synapses are present along the initial segment of a medium-sized, spiny stellate neuron in layer 4B. Fifty-three synapses made by boutons of the axons of these spiny stellate neurons have been identified, and all are asymmetric. Sixty per cent of the synapses are formed by boutons en passant and the remainder by the terminal swellings of spine-like axonal appendages, boutons terminaux. Of the synapses formed by the axons of spiny stellate cells, axo-spinous synapses outnumber axo-dendritic synapses two to one, and axo-dendritic synapses involve both spinous and aspinous dendrites. Evidence is presented which suggests that many of the axon terminals forming asymmetric synapses with the dendritic shafts and spines of spiny stellate neurons are derived from other spiny stellate neurons.

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