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

Does neurotransmission impairment accompany aluminium neurotoxicity?

Neurobehavioral disorders, except their most overt form, tend to lie beyond the reach of clinicians. Presently, the use of molecular data in the decision-making processes is limited. However, as details of the mechanisms of neurotoxic action of aluminium become clearer, a more complete picture of possible molecular targets of aluminium can be anticipated, which promises better prediction of the neurotoxicological potential of aluminium exposure. In practical terms, a critical analysis of current data on the effects of aluminium on neurotransmission can be of great benefit due to the rapidly expanding knowledge of the neurotoxicological potential of aluminium. This review concludes that impairment of neurotransmission is a strong predictor of outcome in neurobehavioral disorders. Key questions and challenges for future research into aluminium neurotoxicity are also identified.

Adrenergic innervation of the heart of the bat, Miniopterus schreibersii

The adrenergic innervation of the heart of the bat (Miniopterus schreibersii) was studied with a fluorescence histochemical technique. The appearance and distribution pattern of the terminal adrenergic nerve fibers demonstrated in the atria, sinoatrial and atrioventricular nodes, and ventricles is typically mammalian. Fine varicose adrenergic fibers run in and parallel to the ventricular muscle where they are common and uniformly distributed. Indian ink perfusion of the coronary vasculature demonstrates the high density of vessels in the ventricles, but obscures the terminal innervation of the ventricular muscle. This alone, or in combination with the apparent seasonal change in the terminal innervation of the ventricles, may explain the inability of previous workers to identify an adrenergic ventricular innervation in the bat Nyctalus noctula. The adrenergic ventricular innervation might be involved in the large increases in cardiac output associated with the commencement of flight and in the massive sympathetic activation that mediates arousal from torpor.

Alterations in gastric mucosal microvascular endothelium in a stressed condition--relevance to gastric ulcerogenesis

The present paper describes the morphological and functional alterations of the gastric mucosal microvascular endothelium under restraint-stressed condition. On the basis of the direct cholinergic innervation of capillaries and non-muscular venules in the gastric mucosa, these endothelial changes would be caused by the stress-induced overstimulation of the cholinergic nerves and modified by the degranulation of mast cells, contributing to the stress-induced ulcer formation as schematically illustrated in Fig. 10.

Clustering of intensely fluorescent sympathetic cells in embryonal and postnatal rats

A fluorescence microscopic study has been performed on the ontogenetic appearance of clusters of small intensely fluorescent (SIF) cells in the superior cervical ganglion of the rat. Small SIF cell clusters were observed after the 13th embryonal day. Postnatally, the number of clusters first reversibly decreased, while after the 2nd week, the adult level was reached. Since the total number of SIF cells greatly increased after the 3rd week, the mean size of the clusters increased. From the 1st postnatal week, SIF cell clusters were present also in the external carotid nerve, and from the 2nd postnatal week in the internal carotid nerve. In adult rats, SIF cell clusters were constantly observed in the main postganglionic nerve trunks or near their outlet. The fine structure of the SIF cell clusters in the ganglion and in the nerve trunks was essentially similar. Widened intercellular spaces between adjoining SIF cells, sometimes closed by mutual membrane thickenings, were separated from the pericapillary space often only by a basal lamina. Opening of coated pits into the intercellular spaces was a common occurrence, suggesting that catecholamines may be secreted by the SIF cells into intercellular canaliculi, possibly then diffusing into the pericapillary space. Coated pits were occasionally observed also in the immediate vicinity of synapsing nerve endings that contained small agranular vesicles, suggesting a reciprocal synaptic mechanism. Occurrence of presumable postganglionic axons and SIF cell processes within the same sheath cell enwrapment provides indirect evidence for the idea that the SIF cells may affect the axon, in addition to the cell soma, of the postganglionic neuron.

Evidence for the neurotransmitter role of norepinephrine in the ventral thalamic nucleus of the guinea pig: localization, uptake and release

The localization, uptake and release of norepinephrine (NE) by the isolated guinea pig ventral thalamic nucleus (VT) were studied to determine the possible neurotransmitter role of this catecholamine. The NE content in the VT was 356 +/- 24 ng/g wet weight and intraneuronal localization of NE was demonstrated in the VT by histofluorescence. [3H]NE accumulation into the VT slices was about 3 times that of [3H]NE (10(-7) M) in the medium 10 min after incubation. Kinetic analyses indicated 2 components of [3H]NE accumulation, one representing a high (Km1 4 X 10(-7) M and Vmax1 1.5 pmol/mg/10 min) and a low (Km2 1.8 X 10(-6) M and Vmax2 5 pmol/mg/10 min) affinity uptake system. Desmethylimipramine (10(-5) M) reduced the high affinity uptake of [3H]NE by 30% of the control value. Electrical stimulation of the slices increased the efflux of [3H]NE from tissues preloaded with [3H]NE, in a current- and frequency-dependent fashion. The release of [3H]NE induced by stimulation of up to 1 mA was inhibited by tetrodotoxin (10(-6) M) or Ca-free medium containing EGTA (10(-4) M). These findings provide strong evidence for the neurotransmitter role of NE in the VT.

The autonomic innervation of the vasa nervorum

Using catecholamine fluorescence and histochemical cholinesterase staining combined with quantitative image analysis a direct autonomic innervation of arteries, arterioles, venules, veins and arterio-venous anastomoses within peripheral nerves was demonstrated in normal as well as in chemically sympathectomized rats. The adrenergic nerves carry varicosities and were more diffused than acetylcholinesterase-containing nerves; the arteries and the arterio -venous anastomoses were more richly innervated. The findings that acetylcholinesterase-positive nerve fibres were unalterated by chemical sympathectomy and were revealed by short incubation times are indicative of a true cholinergic, and probably parasympathetic, innervation of the vasa nervorum. The possible importance of the autonomic innervation of the vasa nervorum in the pathogenesis of some diseases of peripheral nerves is discussed.

Indoleaminergic innervation of rat choroid plexus: a fluorescence histochemical study

Using a fluorescence histochemical technique we found that the precursor of serotonin, 5-hydroxytryptophan (5-HTP), is taken up by a population of nerve fiber-like structures, indoleaminergic in nature since selectively destroyed by the neurotoxin 6-hydroxytryptamine, within rat choroid plexus. Nerve fiber-like structures are localized within the wall of choroid blood vessels. More infrequently nerve fibers end in the stroma or in close relation to epithelial cells of the plexus. The electrolytic lesioning of raphe nuclei causes the disappearance of 5-HTP fluorescence, suggesting that these nerve fibers originate from raphe nuclei. These results suggest a direct influence of indoleaminergic pathways originating from the brainstem on the blood flow through choroid plexus as well as on the production of cerebrospinal fluid.

Histological appearances of the nerves of the bladder in patients with denervation of the bladder after excision of the rectum

Two groups of patients who developed denervation of the bladder after excision of the rectum for carcinoma have been studied by histological examination of bladder biopsies. The groups were compared with a group of control patients of a similar age. One group with denervation of the bladder was studied soon after (7 weeks) and the other group in the long term (10 months) after operation. Bladder biopsies were stained for acetylcholinesterase, catecholamines and connective tissue. Tissue was also processed for electron microscopy. In control patients, the ratio of cholinesterase positive nerves to the number of smooth muscle nuclei (24:100) was significantly greater than in patients with denervation of the bladder studied soon after operation (2.5: 100; P less than 0.01). Appearances consistent with degenerate nerve terminals were observed on electron microscopy in these patients. No increase in the density of adrenergic nerves was observed in either group of patients with denervation of the bladder. In the long term, a greater density of cholinergic innervation was noted compared with patients studied soon after operation (P less than 0.05). In addition, nerve terminals, similar in appearance to those of control patients, were observed on electron microscopy. The findings in patients with denervation of the bladder studied in the long term after operation are consistent with partial regeneration of autonomic nerves. They suggest that, whilst histological examination of bladder biopsies may be useful soon after excision of the rectum, they may be less sensitive in the long term.

Microspectrofluorometry in biogenic amine research

Microspectrofluorometry has played an important part in the development and understanding of fluorescence techniques for the demonstration of biogenic amines. This paper reviews briefly the techniques currently available for the characterization and localization of biogenic amines, and considers the basic design considerations applicable to the construction of a microspectrofluorometer, with special emphasis on the automated correction of spectral data. Spectral data for the commonly occurring biogenic amines dopamine, noradrenaline and 5-hydroxytryptamine have been summarized and the criteria applicable to the spectral analysis of the individual amines and their mixtures discussed. Discrepancies between spectral data derived from tissues and model systems are reviewed and emphasis is given to the importance of biochemical studies of amines prior to definitive microspectrofluorometric analysis. The conceptual basis of quantitative microspectrofluorometry is reviewed with a particular emphasis on the limitations of such studies. The analysis of terminal fields by scanning microspectrofluorometry and its application to the study of extracellular amine distribution is discussed.

Improved catecholamine histofluorescence in the developing brain based on the magnesium and aluminum (ALFA) perfusion techniques: methodology and anatomical observations

Detailed protocols for the application of two different metal salt perfusion procedures are described for the production of superior catecholamine histofluorescence in the brains of immature rats up to 2 weeks of age. As in the adult, both magnesium and aluminum salts are highly advantageous for catecholamine histofluorescence in developing animals, and yield marked increases in sensitivity. In the magnesium-perfusion technique, animals are perfused in a simple one-step process using a hand-held syringe with cold buffer containing magnesium sulphate, formaldehyde and glyoxylic acid. The aluminum-perfusion (ALFA) technique provides even greater sensitivity and richness of detail, but requires a controlled-pressure perfusion system and a two-step perfusion process. Animals are first perfused with a room-temperature buffer containing magnesium sulphate and procain (to prevent vasoconstriction) followed by cold buffer containing aluminum sulphate and formaldehyde. In both methods, tissue pieces are subsequently freeze-dried, reacted with formaldehyde vapour and paraffin-sectioned according to the standard Falck-Hillarp procedure. Tissue pieces can also be taken from aluminum-perfused brains for simultaneous catecholamine assay using radioenzymatic methods, thereby permitting correlated histochemical and neurochemical analyses on the same brains. Many catecholamine terminal systems can be visualized in the rat brain even at birth with the ALFA procedure following pargyline pretreatment. However, the endogenous intraaxonal catecholamine concentration is so low in immature brains that the full anatomical extent of these systems cannot be reliably seen without recourse to pre-loading with an exogenously administered amine. For this purpose systemic injections of alpha-methyl-noradrenaline were extensively investigated. In combination with the ALFA procedure, such pretreatment was found to cause a dramatic increase in both the intensity and number of terminal and preterminal fibers throughout the brain. Control experiments with 6-hydroxydopamine and the catecholamine uptake blocker, nomifensine, indicate that this loading is specific for catecholamine systems. This approach has indicated that certain of the forebrain noradrenergic and dopaminergic systems are very extensive at birth, and in some regions an intermediate stage of hyperinnervation is a normal feature of ontogeny. Some of these findings are illustrated here and will also be presented in greater detail in further reports.

Immunohistochemical demonstration of the distribution of serotonin neurons in the brainstem of the rat and cat

The morphological characteristics and distribution of the somata of serotonin-containing neurons in the brainstem of rats and cats were studied by use of the peroxidase-anti peroxidase (PAP) immunohistochemical method employing highly specific antibodies to serotonin. Antibodies were raised in rabbits against an antigen prepared by coupling serotonin to bovine thyroglobulin and using formaldehyde as the coupling reagent. The distribution pattern of serotonin neurons observed in the present material is essentially in agreement with that described by other investigators who used the Falck-Hillarp method. In addition, this immunohistochemical technique revealed serotonin-containing perikarya in the following regions: 1) the periaqueductal gray, especially lateral to the nucleus raphe dorsalis, 2) the nucleus interpeduncularis, 3) the nucleus parabrachialis ventralis and dorsalis, 4) the field of the lemniscus lateralis, and 5) the reticular formation of the pons and medulla oblongata. The described immunohistochemical procedure makes it possible to study central serotonin neurons in detail without pharmacological pretreatment. The wide distribution of serotonin neurons demonstrated in this study should be considered when interpreting experiments dealing with the serotonin system.

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.

Cholinergic nerves in the mesentery

The cholinergic innervation of extravascular portions of rat mesentery was studied in normal as well as 6-hydroxydopamine (7 OHDA) sympathectomized animals. We observed the presence of a cholinergic innervation unaltered by 6 OHDA treatment in extra-vascular portions of mesentery. Cholinergic nerve fibers coming from paravascular nerves forms loop]-like structures that innervate the mesentery proper. Also the islands of adipocytes of mesentery seem to be provided with a cholinergic innervation. The findings are discussed.

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.

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.