Search PubMed⌕ Search

Biomedical subjects

A Peters

Publications and source records attributed to A Peters.

At least 271 records · Page 15Linked to original sources
PubMed1981

Synaptic termination of thalamic and callosal afferents in cingulate cortex of the rat.

The distribution of degenerating thalamic and callosal afferents to cingulate cortex in the rat is analyzed. Both light microscopic silver impregnation and quantitative electron microscopic techniques demonstrate differences in the form, number, and laminar distribution of these two afferents in anterior and posterior cingulate cortices. Afferents from the mediodorsal thalamic nucleus terminate in area 24. Most terminals are in layer IIIb, fewer in layer Ia-b, and least in layers V and VI. In contrast, callosal afferents terminate mainly in layers Ib-c, II, IIIa, V, and VI. Thus, thalamic and callosal afferents terminate in a complementary pattern except in layers Ib and IIIb where they overlap. Quantitative analysis of degenerating axon terminals in area 24 indicates that there may be as many as seven times more callosal than mediodorsal thalamic terminals in this cortex. Projections of the anterior thalamic nuclei terminate in areas 29b and 29c, primarily in layer Ia, with fewer in layers Ib-IV and least in layers V and VI. Callosal afferents end mainly in layers V and VI and less densely in layers I-IV, which results in some overlap of thalamic and callosal afferents in layers Ic, IV, and V. In addition, patterns of termination of callosal afferents in posterior cingulate cortex change at borders between previously defined cytoarchitectural areas. Anterior thalamic terminals in area 29c differ from other thalamocortical afferents described previously in that they form two types of terminals. One is large (2-4 micrometer in diameter) and occurs mainly in layer Ia, whereas the second type is smaller and is present in layers Ib-V. Both types of terminals form asymmetric synapses mainly with dendritic spines.

Afferent Pathways↗
PubMed1981

Bipolar neurons in rat visual cortex: a combined Golgi-electron microscope study.

Golgi-impregnated bipolar neurons in rat visual cortex have been examined by both light and electron microscopy. Bipolar neurons are encountered throughout layers II to V and are recognized by their spindle-shaped cell bodies and vertically elongate, narrow dendritic trees which may traverse the cortex from layer II to layer V. Although a single primary dendrite usually extends from each end of the cell body, two primary dendrites may extend from one pole, usually the lower one, and an additional short dendrite may emerge from one side. In the electron microscope gold-toned Golgi-impregnated neurons are seen to have folded nuclear envelopes and except at the poles of the cell body where the dendrites emerge, the nucleus is surrounded by only a thin rim of cytoplasm. Both the cell body and the dendrites form asymmetric and symmetric synapses. Usually the axon of a bipolar neuron arises from one of the primary dendrites and it soon assumes a vertical orientation, to either descend or ascend through the cortical neuropil. Some bipolar neurons have myelinated axons and only the initial portion is impregnated in Golgi preparations, but when they are unmyelinated the axons can be seen to form vertical plexuses and asymmetric synapses. Most commonly the terminals synapse with dendritic spines, some of which are derived from apical dendrites of pyramidal cells, but other terminals synapse with the shafts of apical dendrites, and with the cell bodies and dendrites of nonpyramidal cells. It is apparent that these bipolar neurons are the cells which others have shown to label specifically with antisera to vasoactive intestinal polypeptide (VIP), and it is suggested that the prime role of these cells in the cerebral cortex is to excite the clusters of pyramidal cells.

Animals↗
PubMed1981

The structure of neuritic plaque in the cerebral cortex of aged rats.

Discrete patches of spongiform degeneration have been found in the cerebral cortex of three rats, 28 and 30 months of age. Many of these patches have in their midst a central nonvacuolated region containing a star-shaped homogeneous core. Using Congo red stain, there is evidence for the presence of amyloid in this core. In the electron microscope, this central region is seen to be composed of degenerating and abnormal neuronal processes, reactive neuroglia, and extracellular filamentous material with the fine structural characteristics of amyloid. Microglial cells are uniquely modified to accommodate bundles of these extracellular filaments, which are often contained in furrows that deeply invaginate the surfaces of these cells. On the basis of its three main constituents, the central region is considered to be a form of neuritic plaque. The large complex clearings in the vacuolar region of each lesion appear to be formed by the coalescence of smaller vacuoles in the surrounding neuropil.

Aging↗
PubMed1981

IgE bound to mast cells in bronchial mucosa and skin in atopic subjects.

In immune reactions of the immediate type, IgE bound to the membrane of mast cells plays an important role. In 45 patients with allergy and 12 patients without allergy the IgE load on mast cells in bronchial mucosa and skin was measured by an immunofluorescent technique. In the allergic patients a positive score was found in 38 bronchial biopsies and 31 cutaneous biopsies. The difference is significant in favor of the positive score of the bronchus biopsy. A correlation between the titre of IgE, bound on mast cells and the number of mast cells was not found.

Adolescent↗
PubMed1980

The relationship of intraglandular colloid production to hormone synthesis.

The production of intraglandular colloid, brought about by the cyclic breakdown of intermediate lobe cells, is related to the synthesis of hormones in the hypophysis. By analyzing the 'shift' of the amino acid, cystine, during various phases of the gland's cycle it is apparent that hormones, as well as other protein determinants of immunological importance, are transported by way of the intraglandular cleft to the venous circulation and to the cerebrospinal fluid.

Animals↗
PubMed1980

The visualization of myosatellite cells in normal and denervated muscle: a new light microscopic staining technique.

A new light microscopic staining technique allows the visualization of satellite cells on the surface of myofibers. Either prior to or during fixation, whole frog sartorius muscles are bathed in an acidic buffered solution containing lead nitrate and subsequently exposed to ammonium sulfide. The staining of the satellite cells resulting from this procedure reveals their positions, and the outlines of their cell processes which occasionally branch. Electron microscopy shows that the staining is due to lead deposits localized between apposing membranes of satellite cells and associated myofibers. Prior exposure to N-ethyl-maleimide (NEM) does not alter the formation of the lead deposits on the satellite cell, but reduces the amount of Pb deposits on the muscle surface and connective tissue. This technique has been applied to determine the effects of denervation on the satellite cells of frog sartorius muscles. Four weeks after denervation, the number of satellite cells is essentially the same in both denervated muscles and the intact muscles of the contralateral side. However, denervation results in a subpopulation of satellite cells with altered shapes. They have elongated cytoplasmic processes which often branch. It is suggested that these supernumerary cytoplasmic processes represent an intermediate phase in the transition of satellite cells to myoblasts.

Animals↗
PubMed1980

Synaptic relationships between a multipolar stellate cell and a pyramidal neuron in the rat visual cortex. A combined Golgi-electron microscope study.

Two synapsing and impregnated neurons in the rat visual cortex have been examined by a combined Golgi-electron microscope technique in which the Golgi precipitate is replaced by gold particles. One of the neurons is a stellate cell with smooth dendrites and a well impregnated axon, while the other is a layer III pyramidal neuron. Light microscopy showed some boutons from the axonal plexus of the stellate cell closely apposed to the soma and dendrites of the pyramid and it was predicted that synapses were present at these sites. An electron microscopic examination of serial thin sections, in which the profiles of the impregnated neurons are marked by their content of gold particles, showed most of these predicted synapses to exist. Indeed, axon terminals of the stellate cell formed five symmetric synapses with the cell body of the pyramid, one with the apical dendritic shaft and three with basal dendrites. Reasons are given for believing these synapses to be inhibitory. In addition, it was found that one of the axon terminals of the stellate cell synapsed with one of that cell's own dendrites. The significance of this finding is discussed.

Animals↗
PubMed1980

Preservation of human erythrocytes in the liquid state: biological results with a new medium.

Red blood cells (RBC) were collected with citrate-phosphate-dextrose (CPD) in a blood-pack optimal additive system. After concentration to 90% hematocrit they were diluted with saline-adenine-glucose medium (SAG-RBC), and stored for 35 days. In this work the RBC were stored in the presence of leukocytes. The SAG medium allows RBC conservation during 35 days at +4 degrees C. The adenosine triphosphate (ATP) level of RBC is compatible with their survival. During the first 2 weeks, hemolysis of SAG-RBC was not greater than in CPD blood. Nevertheless, hemolysis reached 1.49% on day 35, and there was a marked increase in RBC osmotic fragility. Scanning electron-microscopic studies of 35-day RBC showed that the majority of them became echinocytes. After incubation in fresh frozen plasma, the RBC recovered satisfactory osmotic resistance and normal disc shape. The post-transfusion viability was normal with greater than 70% recovery after 48 h. The in vivo restoration of 2,3-diphosphoglycerate (2,3-DPG) was rapid in the transfused SAG-RBC, 50% of the initial 2,3-DPG level being restored in 1 h. The in vivo studies proved that the functional quality of these RBC was compatible with their use in transfusion. The most important problem concerns the supernatant hemoglobin level of the SAG-RBC to be used for massive transfusion.

Adenine↗
PubMed1980

Pituitary colloid--a non vascular secretion with immunoglobulin-like properties.

We show evidence of an internal holocrine secretion capable of distributing its immunoreactive substances to the cerebrospinal fluid (CSF) and to the venous circulation of the cavernous sinuses. The substances, covering a wide molecular weight range, appear on immunoelectrophoresis, to be similar to serum proteins. Double diffusion shows no identity to serum immunoglobulins or albumin even though antisera produced against serum components react positively. Of equal interest is their identification with pituitary hormones, which theoretically are secreted directly into the blood stream. There is a suggestion that elevated or suppressed levels of immunoglobulins and other serum components manifest by current methodology may, in fact, be due to changes in pituitary function. This paper proposes that we take a serious look at the intermediate lobe of the pituitary gland, and examine its unique and individual contributions to our biological chemistry.

Animals↗
PubMed1980

Low molecular weight protein in bovine anterior pituitary similar to immunoglobulin M.

Bovine pituitary IgM was isolated from anterior lobe material by molecular sieve and DEAE-cellulose chromatography. It was characterized using physico-chemical and immunochemical techniques. The molecular weight of the molecule was below 20 000, and immunoelectrophoretic and immunodiffusion analysis, demonstrated precipitin arcs for IgM. The small molecular weight protein may prove to be significant in continuing studies of IgM and the relationship of the pituitary gland to the immune system.

Animals↗
PubMed1979

A technique for estimating total spine numbers on Golgi-impregnated dendrites.

The functional significance of dendritic spines and their morphological sensitivity to a wide spectrum of experimental manipulations and pathological states have led to a number of studies in which counts of dendritic spine number have been carried out. These studies have, for the most part, involved the enumeration of only those spines which protrude from the opaque shafts of Golgi-impregnated dendrites into the clear zones flanking the dendrite. Such counts, limited to only those spines which are visible, underrepresent the true total number of spines borne by the dendrites. The magnitude of underrepresentation correlates positively with dendritic shaft diameter and negatively with spine length. This seriously restricts the usefulness of comparisons of spine density between dendrites, or even between segments of the same dendrite. In the present report, a geometrically based method is presented whereby total dendritic spine numbers can be estimated with reasonable accuracy, taking into account factors such as dendrite diameter and spine length. The technique entails the following principal steps: a determination, for a given length of dendrite over which spines are to be enumerated, of the volume of the flanking zones in which spines are visible and can be counted; a determination of the volume of the entire zone which encircles the dendritic shaft and which contains all spines, both visible and not visible; and a proportional extrapolation from the number of visible spines to obtain an estimate of the true total spine number. Tests of the predictive accuracy of the technique using dendrites of known total spine number suggest that estimates which deviate from true total spine numbers by less than 10% can be achieved.

Animals↗