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J R Wolff

Publications and source records attributed to J R Wolff.

At least 145 records · Page 8Linked to original sources
PubMed1980

Experimental studies of mechanisms involved in methods demonstrating axonal and terminal degeneration.

Factors influencing the consistency and specificity of the staining of neuronal degeneration products were studied in brain sections by varying systematically the composition of solutions used in the steps which are common to the degeneration methods. The formation of nuclei of metallic silver was determined either by physical development of 110Ag, after dissolving reducible silver by acetic acid. In degenerating axons metallic silver nucleic are formed by their own reducing groups in the first (acid) and in the second (alkaline) impregnating bath. The first impregnation turned out to be sufficient to produce complete staining of degenerating axons. The reducing capacity of normal axons and myelin can be suppressed by oxidation or by lowering the pH of the impregnating solution. Degenerating axon terminals are not able to reduce silver ions in either of the impregnating baths. Rather, the metallic silver nuclei initiating their staining are formed in the Nauta reducer by interaction of its reducing agent (formol) with silver ions which had been trapped in the tissue during the impregnation. Thus the nuclei are enlarged to microscopic visibility by a nonstandardized physical developer coming about from the Nauta reducer and the silver ions transferred with the sections. In this reaction catalytic sites in degenerating terminals as well as ammonium ions and the alkali reserve of the tissue play an important role. On the basis of the present results it was possible to stabilize the conditions for staining degenerating axons and degenerating axons terminals in two separate staining procedures detailed in following papers.

Animals↗
PubMed1980

A reliable method for demonstrating axonal degeneration shortly after axotomy.

A method has been elaborated by which degenerating axons can be selectively impregnated with silver. Based on reconsideration of the physicochemical mechanisms of the degeneration methods it takes advantage of physical developers over the chemical ones. The staining procedure is applied to frozen sections of brains fixed with formol. It consists of 6 steps: (1) pretreatment with alkaline hydroxylamine, (2) washing in acetic acid, (3) impregnation in silver nitrate in the presence of ferric ions, (4) washing in citric acid, (5) physical development, and (6) washing in acetic acid. By electron microscopy silver precipitates by this method are almost entirely restricted to the cytoplasm of dense, degenerating axons, sparing mitochondria and myelin sheaths. No special expertise is required to achieve reproducible results. Large numbers of sections treated simultaneously, and large sections, can be stained uniformly. Light microscopic criteria are described which help diagnose the source of possible failures. Low background staining allows dark field illumination and television image analysis to be applied. The method works at survival times of only 3 to 5 days after axotomy. Hence, degenerating axons and axon terminals can be stained in alternating sections from the same brain using this method and another being described separately, which, using different conditions, demonstrates degenerating axon terminals.

Animals↗
PubMed1980

A reliable and sensitive method to localize terminal degeneration and lysosomes in the central nervous system.

After reconsidering the physicochemical mechanisms involved in the so-called degeneration methods for the demonstration of axons and nerve terminals, the method of Eager was fundamentally modified in order to stabilize the staining process. This resulted in a simple and reliable method which stains degenerating terminals and lysosomes with a high degree of selectivity and sensitivity. Frozen sections 30 to 50 micrometers thick are prepared from material fixed with formaldehyde by cardiac perfusion. The staining procedure consists of 5 steps: 1) alkaline pretreatment (pH 13), 2) silver impregnation, 3) washing, 4) development at pH 5.0-5.5 monitored by an indicator, and 5) washing in acetic acid. Possible faults can be easily detected by their specific effects on the staining results. Primary submicroscopic silver precipitates are localized selectively in the osmiophilic parts of lysosomes and those degenerating presynaptic elements that are surrounded by glial processes. In degenerating axons, precipitates originating from mitochondria can usually be distinguished from terminal degeneration by their different size, shape, or characteristic arrangement. Nonspecific staining is restricted to glial fibrils, erythrocytes, and single cell nuclei. Dark field illumination can be applied routinely and television image analysis can be used for quantitative evaluation because of low background staining.

Animals↗
PubMed1979

Postnatal vascular growth in the neocortex of normal and protein-deprived rats. Morphometric studies.

The postnatal vascular growth in the neocortical area 18 of normal and pre- and postnatally protein-deprived rats was examined. For control rats the specific length, the specific surface and the volume fraction of vessels increased rapidly between 7 and 20 days of age. Thereafter, only a minor increase was seen. In protein-deprived rats there was no increase in the specific length of vessels between 7 and 10 days of age and this variable was still reduced at 30 days of age compared to controls. This reduction was due to a decrease in the specific length of thin vessels (luminal diameter less than 8.25 mu) whereas the specific length of wider vessels was not affected by the protein deprivation. There were no significant differences in the specific surface or volume fraction of vessels between control and protein-deprived rats. These findings indicate an adaptive increase in luminal diameter of vessels in the protein deprived rats during postnatal development. At 90 days of age no significant differences between vascular variables of control and protein-deprived rats were seen.

Age Factors↗
PubMed1979

Postnatal vascular growth in the cerebellar cortex of normal and protein-deprived rats. Morphometric studies.

The postnatal vascular growth in the cortex of vermis cerebelli folium IX of normal and pre- and postnatally protein-deprived rats was examined. The rate of increase in specific length of vessels seem to parallel the functional maturation of neurons in all cortical layers. From the first postnatal week there is a higher specific length of vessels in the Purkinje cell layer than in the adjoining parts of the molecular and granular layers. The results indicate that such differences are present also after the period of rapid vascular growth. Protein deprivation appears to affect the postnatal increase in specific length of vessels less in the Purkinje cell layer than in the granular and molecular layer where a significant reduction compared to controls was seen for the interval 7--20 days of age. At 90 days of age no significant differences were seen between control and protein-deprived rats.

Age Factors↗
PubMed1979

Induction and maintenance of free postsynaptic membrane thickenings in the adult superior cervical ganglion.

The superior cervical ganglion (SCG) of adult rats was exposed to GABA, either by long lasting microapplication (implantation of glass bulbs for 1-24 days) or in short term experiments (external application up to 6 h). Autoradiography showed that [3H] GABA accumulated selectively in satellite cells. The GABA produced the following effects: (1) Specialized membrane thickenings--similar in fine structural appearance to those seen as postsynaptic membrane thickenings at Gray type I synapses--were formed at the extrasynaptic dendritic surface of principal ganglion cells. (2) Morphometry revealed that the surface to volume ratio of dendrites increased significantly corresponding to an enlargement of their extrasynaptic surface as a result of the formation of spine-like projections. (3) Electrophysiology confirmed that, at least after short term application, the action potentials induced by preganglionic stimulation were heavily suppressed. These results suggest that, in the course of depressed ganglionic activity, so-called free postsynaptic membrane thickenings are generated and maintained in the SCG of adult rats even in the absence of significant axonal degeneration. The discussion focuses on two points: (1) possible similarities between the conditions of neurons after denervation and under the influence of GABA; (2) a possible role of GABA and other substances with inhibitory action in synaptogenesis.

Action Potentials↗
PubMed1978

Self-innervation of dendrites in the rat suprachiasmatic nucleus.

Golgi-Cox impregnantions of the rat suprachiasmatic nucleus show small dendritic side branches which appear to contact their neurons of origin. Electronmicroscopically a dendrite has been found forming a Gray-type-II synapse with one of its own branches. The arrangement is discussed as a general phenomenon of a feedback connection for temporal limitation of local excitation.

Animals↗
PubMed1978

Retinal afferents form Gray-type-I and type-II synapses in the suprachiasmatic nucleus (rat).

The synapses of optic nerve afferents in the suprachiasmatic nucleus (SCN) usually form Gray type I (asymmetrical) synapses, but about 13% show clear-cut Gray type II ( symmetrical) active zones. Some presynaptic elements form a Gray type I--active zone with one dendrite and a Gray type II-active zone with another postsynaptic element at the same time. It is discussed whether this variabilility is related to a simultaneous excitatory and inhibitory action, to a variable activity or efficiency of the synapses or to various stages of maturation.

Animals↗
PubMed1977

The distribution of degenerating axons after small lesions in the intact and isolated visual cortex of the cat.

The extent of the spread of axonal degeneration was investigated in the visual cortex of the cat after making small lesions restricted to the grey matter. Two series of experiments were undertaken. In the first, normal adult cats were used, and in the second, the cortex of the postlateral gyrus was isolated from its extrinsic afferents by surgical undercutting 3 months before making the lesions. The results were similar in the two series in most respects. 1. Horizontal fibres extended in considerable numbers for some 500 micrometer from the lesion, mainly in layers I, III/IV and V, a few reaching 2/3 mm. These fibres were better seen in the intact than in the isolated cortex. Their spread was usually asymmetrical, being greater posteromedially than anterolaterally. 2. Oblique axons ran downwards from the middle layers into layers V and VI, or upwards into layers I and II. 3. Axons arising from layers II to VI descended vertically into the white matter. Degeneration patterns after lesions in areas 17 and 18 were compared.

Afferent Pathways↗
PubMed1977

A device for dark field microphotography at low magnifications.

A simple illumination system is described that can be easily adapted to a laboratory stereomicroscope allowing for low power high contrast dark field surveying. The system uses commercially available fibre optic lamps, standard bright field objectives and produces a large, evenly illuminated field suitable for photography.

Animals↗