Biomedical subjects
B Falck
Publications and source records attributed to B Falck.
Do visual evoked potentials give relevant information to the neuro-ophthalmological examination in optic nerve lesions?
The visual evoked potentials (VEPs) and neuro-ophthalmological examinations of 134 patients were compared. The VEPs were abnormal in 95% of the eyes with optic neuritis. Defective color vision was found in 99%, visual field defects in 88%, decreased vision in 66% and an afferent pupillary defect in 55%. 29 patients with optic neuritis were followed up with repeated tests. VEPs and color vision recovered more slowly than visual acuity and visual field. Abnormal VEPs were observed in 68% of 50 MS patients. An analysis of symptomatic and asymptomatic eyes showed that testing of color vision, visual field and red-free ophthalmoscopy were equally as useful diagnostic tools as VEPs. 4 (8%) of the MS patients had abnormal VEPs despite a normal neuro-ophthalmological examination; 94% of MS patients with symptoms and 47% of MS patients without visual symptoms had abnormal VEPs. VEPs were pathological in 59% of 24 patients with traumatic or compressive optic nerve diseases or optic atrophies of unknown etiology. The neuro-ophthalmological examination was more sensitive than VEPs in the diagnosis of these disorders. A neuro-ophthalmological examination is in most cases sufficient to diagnose optic nerve lesions. VEPs are of diagnostic aid especially in mild optic nerve lesions.
The firing rate of motor units in neuromuscular disorders.
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New fluorophore-forming reactions for histochemical visualization of N-acetylated and tertiary indolamines using glyoxylic acid, aluminum-formaldehyde and trifluoroacetic acid anhydride as reagents.
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Recent developments in aldehyde-induced monoamine fluorescence: the aluminum-formaldehyde (ALFA) method applied to immature and adult central nervous tissue.
In this review, the new aluminum-formaldehyde (ALFA) histofluorescence method for the highly sensitive visualization of monoamine-containing neurones in adult and immature central nervous tissue is summarized. Animals are first perfused with a buffer containing high concentrations of aluminum ions and the brains are then freeze-dried, reacted with formaldehyde vapour and further processed according to the Falck-Hillarp fluorescence method. The ALFA technique applied to adult brains visualizes all known catecholamine neurone systems with a sensitivity comparable to, and for certain noradrenergic systems higher than, that of the previously published glyoxylic acid-Vibratome method. The catecholamine systems in immature brains are demonstrated with a sensitivity clearly superior to that of any other available method. If the ALFA method is combined with systemic injections of alpha-methylnoradrenaline into young animals (less than one week old), there is a dramatic increase in the intensity and number of catecholaminergic fibres. Many catecholaminergic systems which have too low concentrations of transmitter to be visualized in the untreated animal even with the ALFA method, can be demonstrated after administration of alpha-methylnoradrenaline. The use of freeze-dried, paraffin-embedded tissue in the ALFA method makes possible convenient storage and parallel processing of many specimens. This mode of processing also allows en bloc reaction, which is the only way by which consistent and reproducible fluorescence yields can be obtained throughout large series of sections and parallel-processed specimens. In animals pretreated with L-tryptophan and monoamine oxidase-inhibitor, the technique is also useful for studies on central indolamine-containing systems.
[Hereditary pressure-sensitive neuropathy].
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New views on epidermis and its langerhans cells in the normal state and in contact dermatitis.
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Ventilatory effects of the pulse wave in the maxillary sinus.
The perostial ventilation of the human maxillary sinus is achieved via three main factors: diffusion, respiration wave and the mucosal pulse wave. The ventilatory factors have been studied with the help of a model sinus. The values used in the model are based upon in vivo human studies. Diffusion is responsible for the most important ventilatory effect in large ostia. Respiration has a ventilatory effect in all ostial sizes. The mucosal pulse has a ventilatory effect when the pulse volume exceeds the dead space of the ostium. When the ostial volume is diminished, the pulse-induced ventilation increases and keeps the total ventilation constant regardless of ostial size. In very small ostia, the mucosal pulse and respiration are the two important ventilatory factors.
A two-channel method for sampling, averaging and quantifying motor unit potentials.
A method is described for sampling and averaging individual motor unit potentials (MUPs), which is based on an averaging technique using a special EMG electrode. The needle has two separate electrode surfaces, a conventional coaxial electrode at the tip and a single-fiber electrode opposite the bevel of the tip. With this method it is possible to extract individual MUPs even from interference activity during a moderate or even high muscular effort. The averaging of MPUs gives a good signal-to-noise ratio, which makes the quantification of MPUs precise. Late components are easily identified. Additionally during the collection of MPUs information of single-fiber characteristics (jitter, blocking and fiber density) is also acquired.
New aspects on factors determining the sensitivity of the formaldehyde and glyoxylic acid fluorescence histochemical methods for monoamines.
The fluorophore and fluorescence yield from tryptamine and 3-methoxytyramine in histochemical protein models have been compared in the standard formaldehyde reaction, the acid-catalyzed formaldehyde reaction, the formaldehyde-ozone reaction, and the aluminum-formaldehyde reaction. In the standard formaldehyde reaction both the fluorophore and fluorescence yields are low. However, the other reactions give a dramatic increase in fluorescence intensity (18-20 times) from tryptamine and 3-methoxytyramine whereas only minor changes (up to 100% increase) in fluorophore yield are observed. It is concluded that the relative fluorescence intensity of each fluorophore molecule formed in the three modifications of the formaldehyde reaction is much higher than that of the molecules formed in the standard formaldehyde reaction. It has previously been demonstrated that the fluorophores formed from dopamine in the gaseous formaldehyde and glyoxylic acid reactions have a much higher (10 times) relative fluorescence intensity than the synthetic fluorophores. the prresent experiments show that if the histochemicl models are dissolved in buffer after the reaction and new models are made from this solution, the fluorescence intensity of the fluorophores formed in the reaction is drastically reduced and becomes comparable to that of the synthetic ones. The results of this and our previous studies indicate that hitherto unknown fluorescence enhancing mechanisms play a major role for the fluorescence yield, i.e. the sensitivity, in the various formaldehyde and glyoxylic acid methods. One possible explanation to the high relative fluorescence intensity of the fluorophores formed in the histochemical reactions could be an energy transfer between, e.g. the non-fluorescent intermediary reaction products (the tetrahydro derivatives) and the fluorophores (the dihydroisoquinolines and dihydro-beta-carbolines). Such an energy transfer is probably attenuated in the dissolved models, where th distances betweenm and orientations of the various molecules have been changed.
The aluminum-formaldehyde (ALFA) histofluorescence method for improved visualization of catecholamines and indoleamines. I. A detailed account of the methodology for central nervous tissue using paraffin, cryostat or Vibratome sections.
This present paper presents a new aluminum-formaldehyde (ALFA) histofluorescence method for highly sensitive visualization of central monoamine-containing neurons, based on perfusion with or immersion in buffers containing high concentrations of aluminum ions. Our previous studies have shown that perfusion or immersion of tissues with solutions containing high concentrations of magnesium results in an improvement in the visualization of intraneuronal catecholamines in the reaction with formaldehyde and glyoxylic acid. This study demonstrates that aluminum is considerably more efficient as a fluorescence-promoting agent, thus causing a further increase in the sensitivity of the formaldehyde method. Detailed protocols are given for the ALFA-method applied to paraffin sections of freeze-dried tissue, and to cryostat and Vibratome sections. The present ALFA technique applied to paraffin sections of freeze-dried tissue visualizes all known catecholamine neuron systems with a sensitivity comparable to, and for certain noradrenergic systems higher than, that of the previously published glyoxylic acid-Vibratome method. Furthermore, the use of freeze-dried, paraffin embedded tissue makes possible convenient storage and parallel processing of many specimens. This mode of processing also allows en bloc reaction, which is the only way by which consistent and reproducible fluorescence yields can be obtained throughout large series of sections and parallelly processed specimens. In animals pretreated with L-tryptophan and MAO-inhibitor the technique is also useful for studies on central indoleamine-containing systems in freeze-dried tissue. The ALFA procedure applied to cryostat and Vibratome sections gives a more sensitive and reproducible visualization of central catecholamine neurons than previous methods.
The aluminum-formaldehyde (ALFA) histofluorescence method for improved visualization of catecholamines and indoleamines. 2. Model experiments.
The fluorescence-promoting effects of sodium, magnesium and aluminum ions in the histochemical formaldehyde (FA) reaction with catecholamines and indoleamines have been studied in protein models. The positive effects of aluminum and magnesium salts on the monoamine fluorescence yields, seen in tissue, could partly be reproduced in a simple protein matrix. The fluorescence-promoting potency was greatest for aluminum, moderate for magnesium and small for sodium. The aluminum effect was markedly concentration-dependent, with an optimum at a concentration of 5-10 mM in the model solution. Optimum pH was around 3.8. Experiments with synthetic fluorophores indicate that the principal action of the metal ions is on the fluorescence properties of the monoamine fluorophores rather than on the yield of fluorophores in the reaction of the monoamines with FA. The presence of aluminum ions in the models thus causes both increases in the fluorescence efficiency of the fluorophores as well as changes in their spectral properties. The direct effects on the monoamine fluorophores cannot, however, account for all effects of the metal salts seen in tissue. It is suggested that aluminum and magnesium ions, in addition, can act as acid catalysts in the FA-monoamine reactions, and that the metal salts have a direct effect on the tissue environment, leading to a 'locking-in' of the intracellular monoamines.
Enzymes related to monoamine transmitter metabolism in brain microvessels.
The activities of tyrosine hydroxylase, aromatic L-aminoacid decarboxylase, monoamine oxidase, and catechol-O-methyltransferase were measured in microvessel (capillaries and venules), parenchymal arterioles, and pial vessels from rat brains, and the decarboxylase activity was compared in brain microvessels from rabbit, cat, dog, pig, cow, baboon, and man. Cranial sympathectomy was performed to estimate the neuronal contribution to the enzyme activities. All vascular regions had substantial activities of the various enzymes studied. The activity of aromatic L-aminoacid decarboxylase in cerebral microvessels was high in rat, dog, pig, cow, and man; intermediate in rabbit and cat; and low in baboon. In addition to this enzyme, cerebral microvessels also contained tyrosine hydroxylase and monoamine oxidase. Aromatic aminoacid decarboxylase and monoamine oxidase serve an enzymatic barrier function at the microvascular level, whereas the main function of tyrosine hydroxylase is probably to synthesize monoamines within nerve terminals that remain in close association with microvessels under the conditions used for preparation of the microvascular fraction. In larger intracerebral and pial vessels monoamine oxidase was present both in the wall itself and in perivascular sympathetic nerves; the remaining two enzymes had a primarily neuronal localization. The latter types of vessels also contained catechol-O-methyltransferase in their walls.
Application of the aluminum-formaldehyde (ALFA) histofluorescence method for demonstration of peripheral stores of catecholamines and indolamines in freeze-dried paraffin-embedded tissue, cryostat sections and whole-mounts.
This paper describes new procedures for highly sensitive visualization of monoamine stores in peripheral tissues, taking advantage of the recently introduced aluminum-catalysed formaldehyde (ALFA) reaction. The tissues are exposed to an aluminum sulphate solution (with or without formaldehyde fixation) in a perfusion and/or immersion step, followed by formaldehyde vapour treatment. Procedures are described for freeze-dried, paraffin embedded tissue, cryostat sections and whole mount preparations. For all these tissue preparations the ALFA method gives a highly sensitive and precise demonstration of catecholamine-containing neurons and 5-HT-containing cells in a variety of peripheral tissues. For freeze-dried tissue and cryostat sections the ALFA method represents an improvement in comparison with other available methods. This is particularly noticeable for the very delicate adrenergic nerves in such organs as the thyroid, ovary, pancreas and the gastrointestinal tract.
The functional importance of sympathetic nerves to the liver and endocrine pancreas.
Sympathetic noradrenergic nerves, with their wellknown cardiovascular effects, have recently been found to influence several metabolic and hormone-releasing processes. Morphological investigations in man have revealed a dense sympathetic innervation of the liver parenchyma as well as sympathetic fibers among the endocrine cells in the islets of Langerhans. Functional studies both in animals and man have shown that electrical or reflex activation of the hepatic and pancreatic sympathetic nerve fibers causes an increased output of glucose from the liver as well as a stimulation of glucagon and an inhibition of insulin release from the pancreas. From these results we conclude that damage to sympathetic nerves should be avoided in abdominal surgery.
Studies on the enzymatic blood-brain barrier: quantitative measurements of DOPA decarboxylase in the wall of microvessels as related to the parenchyma in various CNS regions.
The presence of DOPA decarboxylase in cerebral microvessels (capillaries and venules) impedes the passage of circulating amine precursors into the brain. The relative amount of DOPA decarboxylase in this trapping mechanism as compared to the parenchyma per se was estimated in various CNS regions, measuring the formation of dopamine from L-DOPA in vitro or in vivo in two experimental models on rats and rabbits: (1) On the basis of the treatment with a peripheral decarboxylase inhibitor (carbidopa, which inhibits also microvascular DOPA decarboxylase in the CNS) it could be calculated that the enzyme in the microvessels of the caudate nucleus (rich in catecholamine nerve terminals), cerebellum (poor in catecholamine nerves), and spinal cord comprised 25, 91 and 79 per cent, respectively, of the total enzyme activity. (2) Measurement of dopamine formation in the spinal cord following transection at the midthoracic level (which causes degeneration of the catecholamine neurons caudal to the lesion since they are all descending) indicated that a similar fraction as found in the carbidopa model, 71%, of the total tissue decarboxylase activity resided in the microvessel walls. The results show that a considerable portion of tissue decarboxylase in the CNS is present in the microvessel walls, where it represents part of an enzymatic blood-brain barrier mechanism.
A comparative study on the uptake and subsequent decarboxylation of monoamine precursors in cerebral microvessels.
The endothelial cells and pericytes of brain microvessels (capillaries and small veins) are equipped with an enzymatic barrier, impeding the passage of circulating amino acids, such as amine precursors, into the brain. The properties of this mechanism was studied in brain slices and isolated microvessels from various species including man and also fetal material, following incubation in dihydroxyphenylalanine (DOPA), 5-hydroxytryptophan (5-HTP) and dihydroxyphenylserine (DOPS). A stereospecific, energy-dependent uptake leading to accumulation in the brain microvessel walls was found in all species studied; this process was found to exist already prenatally. The capacity of decarboxylation, the second step in the trapping mechanism at the blood-brain interphase, showed considerable species variation. The enzyme was present also in fetal brain microvessels. Inhibition experiments provided support for the presence of monoamine oxidase, but absence of catechol-O-methyl transferase, in the microvessel walls.