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J Westman

Publications and source records attributed to J Westman.

At least 91 records · Page 5Linked to original sources
PubMed1986

Ultrastructure of spinal efferents to the lateral reticular nucleus: an EM study using anterograde transport of WGA-HRP complex.

Anterograde transport of lectin-conjugated horseradish peroxidase and subsequent incubation with tetramethylbenzidine were employed to label the spinal terminals within the feline lateral reticular nucleus (NRL) for ultrastructural identification. Quantitative studies demonstrated that compared to the unlabelled terminals the spinal boutons were more than twice as large and contained fewer synaptic vesicles. Most of the synaptic contacts of the labelled terminals were located on dendritic shafts but contacts on dendritic spines as well as perikarya were also present. In four cases (all with cervical injections), the postsynaptic cells could be studied in the transversal sections of the medulla in the nuclear plane. The neurons were large and elongated with longest and shortest diameters of about 60 X 30 microns, belonging to the largest category of cells within the NRL. The observations were discussed and related to the findings made in other studies of the NRL.

Animals↗
PubMed1985

Light and electron microscopic study of neurones in the feline lateral cervical nucleus with a descending projection.

Nerve cells in the feline lateral cervical nucleus (LCN) with a descending projection were labelled by injections of horseradish peroxidase, in most cases conjugated to wheat germ agglutinin. After small injections into different spinal cord segments in 16 cats the labelled cells were found mainly in the rostral and ventral portions of the ipsilateral LCN, without a detectable topographic organization. Massive bilateral injections were made into the cervical or lumbar enlargement in 6 cats. Unilateral lesions of the dorsolateral funiculus rostral to the injections generally prevented labelling of LCN cells on the same side. The other side was used to calculate the total number of descending LCN neurones and it was estimated that approximately 500 cells projected down the spinal cord. Comparison with the number of labelled cells after the small injections revealed that the descending LCN neurones projected to an average of at least two spinal segments. Quantitative ultrastructural analyses were made of 17 descending neurones from 7 cats subjected to massive unilateral injections into the cervical or lumbar enlargement. The labelled cells constituted a fairly homogeneous population with respect to the investigated somatic and dendritic features. The morphology and relative frequency of the descending neurones indicate that they may constitute parts of the subpopulation of small LCN cells that have previously been assumed to consist of locally ramifying interneurones.

Animals↗
PubMed1985

Convergence on the same neurons in the feline ventrobasal thalamus of terminals from the dorsal column and the lateral cervical nuclei: an ultrastructural study combining orthograde degeneration and anterograde axonal transport of lectin conjugated horseradish peroxidase.

After electrocoagulation of the dorsal column nuclei (DCN) and injections of wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) into the lateral cervical nucleus (LCN), two kinds of changes in fibers and boutons were observed in the dorsolateral part of the thalamic ventroposterolateral nucleus (VPL). The axons and boutons from neurons in the DCN demonstrated dark degeneration, while the fibers and synaptic terminals from the LCN-neurons contained the characteristic needle-shaped peroxidase reaction products following incubation with tetramethylbenzidine (TMB). Occasionally dark degenerating boutons and boutons with TMB-positive reaction products showed synaptic contact with the same dendritic profiles. After consideration of the possibility of an axoaxonal transfer of the tracer it is concluded that the findings demonstrate convergence of synaptic input both from the DCN and from the LCN on the same postsynaptic VPL neurons. The present results are in accordance with earlier light microscopic and neurophysiological findings. It is also concluded that the ultrastructural technique employed in this study is well suited to reveal convergence of different afferent systems on the same postsynaptic neurons.

Afferent Pathways↗
PubMed1985

Immunocytochemical localization of glutamic acid decarboxylase and substance P in the lateral cervical nucleus: a light and electron microscopic study in the cat.

Using immunocytochemical technique, the light and electron microscopic localization of substance P and glutamic acid decarboxylase (GAD) immunoreactivity in the feline lateral cervical nucleus (LCN) has been investigated. A dense substance P labeling, confined mainly to boutons contacting dendritic profiles, was demonstrated in the ventromedial part of the LCN. GAD-positive boutons, frequently in contact with cell bodies, were found scattered throughout the nucleus. The results suggest that gamma-aminobutyric acid is an inhibitory transmitter in the LCN. The role of the substance P is unclear. Its distribution, however, supports the concept of a separate function of the ventromedial part of the LCN.

Animals↗
PubMed1985

Involvement of surface potential in regulation of polar membrane lipids in Acholeplasma laidlawii.

Upon induced variation of membrane lipid acyl chain unsaturation in Acholeplasma laidlawii, the cells strongly change in a characteristic manner the proportions of individual (charged and noncharged) polar lipids synthesized. Monolayer analysis of polar lipid extracts revealed different mean lateral molecular areas but similar surface charge densities. Microelectrophoresis of these lipids indicated an almost constant lipid membrane zeta-potential of about -35 mV. Simulation by the Gouy-Chapman-Stern (GCS) relations verified that the zeta (surface)-potentials remain constant. Exposing cells to increasing concentration of Na+ yielded a substantial increase in amounts of charged lipids synthesized. In model systems consisting of mixtures of A. laidlawii phosphatidylglycerol (anionic) and glucolipid (diglucosyldiglyceride, noncharged) microelectrophoresis showed; (i) increasing PG amounts resulted in an increased-, and (ii) increasing Na+ concentration resulted in a decreased zeta-potential, respectively, (iii) at physiological ionic strength and lipid surface charge densities the zeta-potential was approximately -35 mV, and (iv) simulation according to the GCS theory yielded an acceptable fit with experimental data. This behavior of the phosphatidylglycerol/diglucosyldiglyceride mixtures is very similar to that of phosphatidylserine/phosphatidylcholine mixtures. It is concluded that the changes in lipid surface charge densities (and surface potential) in A. laidlawii membranes brought by variation in lateral areas of lipid acyl chains and the concentration-dependent quenching of lipid charge by Na+, is compensated for by the cellular regulation of charged lipid amounts thereby maintaining a constant lipid surface potential.

Acholeplasma laidlawii↗
PubMed1985

Somatotopic termination of spinal afferents to the feline lateral cervical nucleus.

The labelling pattern of the feline lateral cervical nucleus (LCN) was investigated after pressure injections of lectin-conjugated horseradish peroxidase into cervical, thoracic or lumbar segments of the spinal cord. Sixteen cats received a 5-8 nl injection staining large parts of mainly the ipsilateral grey matter of a single segment. Light microscopic examination of frozen sections reacted with tetramethylbenzidine showed a somatotopic organization in the LCN. Rostral segments of the spinal cord projected mainly to rostroventral and medial parts of the ipsilateral LCN, while more caudally located segments projected to more dorsocaudal and lateral parts of the nucleus. Minor contralateral labelling with a similar somatotopic arrangement was seen in animals given cervical and lumbar injections. No significant labelling was found in the LCN of three control animals, the segmental injections of which were engaged mainly into the ipsilateral dorsal columns and the dorsolateral funiculus. Ultrastructural analysis in two animals which received multiple cervical or lumbar injections showed that about 70% of the peroxidase-positive structures in the LCN were boutons and the rest small myelinated axons. The precise termination pattern of ascending afferents to the LCN is compatible with the somatotopic organization of the other relay centres in the spino-cervico-thalamic pathway.

Afferent Pathways↗
PubMed1985

Synaptic terminals in the ventroposterolateral nucleus of the thalamus from neurons in the dorsal column and lateral cervical nuclei: an electron microscopic study in the cat.

The afferent fibres to the ventroposterolateral nucleus (VPL) of the contralateral thalamus from neurons in the dorsal column nuclei (DCN) and the lateral cervical nucleus (LCN) were labelled by anterograde transport of wheat germ agglutinin-horseradish peroxidase conjugate and subsequent histochemical processing with tetramethyl benzidine. In accordance with the results of previous light microscopical studies using the degeneration method or autoradiographic tracing technique, the distribution of the afferents from the DCN and LCN in the VPL differed considerably. Thus the DCN terminals, which were calculated to constitute about 7-8% of the total number of boutons in the VPL, were found throughout the entire VPL, whereas the LCN terminals were mainly located in its dorsal and dorsolateral parts, where they made up about 1% of the total number of boutons. However, the morphology and synaptic organization of the terminals from the DCN and LCN were virtually identical. Thus the synaptic terminals of the two afferent pathways seemed to be represented by large boutons of a similar type, which had large, slightly oval and loosely packed synaptic vesicles and contained numerous mitochondria. Both DCN and LCN terminals synapsed preferentially on medium-sized to large dendrites, but were also presynaptic to other vesicle-containing profiles, probably of internuncial origin, which in turn were in synaptic contact with the same dendrites as the labelled ones. It is suggested that the differences in physiological properties between the somatosensory information that is transmitted to the somatosensory cortex via the dorsal column-medial lemniscus pathway and the spino-cervico-thalamic tract do not seem to have a counterpart in differences in the synaptic organization of their relay in the VPL.

Afferent Pathways↗
PubMed1984

Light and electron microscopic localization of glutamic acid decarboxylase and substance P in the dorsal column nuclei of the cat.

Using immunocytochemical methods, glutamic acid decarboxylase (GAD)-immunoreactive boutons were demonstrated throughout the dorsal column nuclei of the cat brain. They were small and were generally presynaptic to larger unlabelled axon terminals, the latter probably originating from primary afferent fibres. The middle-ventral 'reticular' region of the cuneate nucleus also contained substance P-positive terminals, which were large and synapsed on dendritic profiles. The findings strongly indicate that gamma-aminobutyric acid (GABA) is the neurotransmitter that is responsible for the presynaptic inhibition in the dorsal column nuclei. The substance P-positive terminals probably originate from extrinsic fibers.

Animals↗
PubMed1984

Endogenous peroxidase-like activity in the feline dorsal column nuclei and spinal cord.

Endogenous peroxidase-like activity was investigated with a combined light and electron microscopical technique in 15 cats. The lateral cervical nucleus, the dorsal column nuclei, and segments C6 and L5 of the spinal cord were incubated with diaminobenzidine-tetrahydrochloride (DAB) or tetramethylbenzidine (TMB). After histochemical reaction with DAB a considerable amount of activity was found in nerve cells, astrocytes and pericytes. The neuronal labelling was mainly located in mitochondria of axon terminals and in dendrites whereas the astrocytic and pericytic activity was found in cytoplasmic dense bodies. The quantity of stained structures differed considerably between the animals. In TMB reacted tissue endogenous peroxidase-like activity was only sparsely seen. It was found mainly in frozen sections, in which the neuropil and perivascular structures sometimes contained granules and irregular filaments. The significance of the findings is discussed in relation to observations in tracer studies using horseradish peroxidase.

Animals↗
PubMed1984

Interaction of the cationic form of amphiphilic drugs with phosphatidylcholine model membranes. Competition with lanthanide ions.

Model membranes (liposomes) of egg yolk phosphatidylcholine were exposed to the charged (cationic) form of amphiphilic drugs (procaine, tetracaine, metroprolol, alprenolol and propranolol). Drug analysis by ultraviolet light absorption of the bulk solution after centrifugation separation was used to determine the amount of drug bound to the membranes. Microelectrophoresis was employed to measure the change in the zeta-potential after drug adsorption. Binding constants were derived by simulating the experimental curves with a theoretical model which considers the electrostatic effects (Gouy-Chapman theory). Analogous experiments were carried out for the adsorption of Eu3+. Metal analysis was made by three different methods. Good agreement between the centrifugation and electrophoresis experiments was obtained for reasonable positions of the plane of shear relative to the positional plane of the bound ions. Displacement of Eu3+ from vesicles upon addition of drug cations was followed by 31P-NMR. The competition experiments were numerically simulated. The Eu3+ binding was assumed to obey a mass action type equilibrium, whereas the drug binding was described by a Henry's law partition. The binding constants for the drugs in the competition experiments followed the same order as in the absence of Eu3+. However, the numerical values had to be reduced. The effect of anions was studied.

Journal Article↗
PubMed1983

Cation requirement for the reconstitution of oligomycin-sensitive ATPase by means of soluble F1-ATPase and F1-depleted submitochondrial particles.

Bovine heart submitochondrial particles depleted of F1 by treatment with urea ("F1-depleted particles') were incubated with soluble F1-ATPase. The binding of F1 to the particles and the concomitant conferral of oligomycin sensitivity on the ATPase activity required the presence of cations in the incubation medium. NH4+, K+, Rb+, Na+ and Li+ promoted reconstitution maximally at 40-74 mM, guanidinium+ and Tris+ at 20-30 mM, and Ca2+ and Mg2+ at 3-5 mM. The particles exhibited a negative zeta-potential, as determined by microelectrophoresis, and this was neutralized by mono- and divalent cations in the same concentration range as that needed to promote F1 binding and reconstitution of oligomycin-sensitive ATPase. It is concluded that the cations act by neutralizing negative charges on the membrane surface, mainly negatively charged phospholipids. These results are discussed in relation to earlier findings reported in the literature with F1-depleted thylakoid membranes and with submitochondrial particles depleted of both F1 and the coupling proteins F6 and oligomycin sensitivity-conferring protein.

Adenosine Triphosphatases↗
PubMed1982

Charge and pH dependent drug binding to model membranes. A 2H-NMR and light absorption study.

The binding of the local anesthetics tetracaine and procaine to model membranes of egg phosphatidylcholine and bovine phosphatidylserine has been studied by 2H-NMR and light absorption. Dispersions of drug-lipid mixtures in 0.1 M NaCl were centrifuged and the concentration of drug in the supernatant was measured by ultraviolet light absorption. Several freeze-thaw cycles of the sample were used before centrifugation to facilitate equilibration of the drug between the bilayers. Binding curves for the drug were obtained as a function of pH. The results were simulated by a theoretical model based on the Gouy-Chapman theory, in which both the charged and the uncharged forms of the drug, and the equilibrium between them, were included. Two deuterated forms of the drugs, [2H6] tetracaine and [2H4] procaine, were used for the 2H-NMR experiments. In most cases the 2H-NMR spectrum contained a broad central resonance and an underlying quadrupolar pattern. However, after five freeze-thaw cycles only a single broad resonance was observed under most conditions. Particle size measurements showed that freeze-thawing resulted in a more uniform population of liposomes of smaller average diameter than those obtained by simple vortex mixing. The single broad resonance observed in both cases is interpreted as due to rapid exchange of the anesthetic between lipid and bulk solution. In the absence of freeze-thawing, the quadrupolar pattern is attributed to anesthetic species in exchange with only a limited amount of water. The data suggest that a true equilibrium between lipid, water and anesthetic is only attained after freeze-thawing.

Animals↗
PubMed1981

Interaction of some charged amphiphilic drugs with phosphatidylcholine vesicles. A spin label study of surface potential effects.

Adsorptions of amphiphilic drugs (propranolol, alprenolol, metoprolol and tetracaine) to phosphalidylcholine vesicles in media of different pH and NaCl concentrations have been studied. A positively charged spin label amphiphile, N,N-di-methyl-N-nonyl-N-tempoylammoniumbromide, was used to follow the variation in the surface potential by ESR. Competition experiments between the probe molecule and the drugs were carried out. A spin-labeled analogue of propranolol was also employed. We have analysed the results in terms of the theory for the diffuse double layer (Gouy-Chapman) and treated various equilibrium models. A weak, specific adsorption of chloride ions was introduced. For the charged forms of the drugs simulations of the experiments by numerical solution of the system of equations in a satisfactory way furnished intrinsic binding constants, independent of surface potential effects. The common electrostatic surface potential is mainly ruling the competition, and not the number of surface vacancies.

Journal Article↗
PubMed1979

The interaction of various lanthanide ions and some anions with phosphatidylcholine vesicle membranes. A 31P NMR study of the surface potential effects.

The interaction of various lanthanide ions with vesicles of phosphatidylcholine from egg yolk has been followed by 31P NMR at 30 degrees C. From known magnetic properties of these ions, separation of the paramagnetic shift into a pure contact and a pseudo-contact part was carried out. Binding curves for the contact contribution (F curves) were obtained from vesicles in solutions of sodium salts with monovalent anions over a wide concentration range. These curves should be insensitive to any conformational effects due to ion binding. Indication of a conformational change in the lipid head group at low ion binding was obtained by studying the ratio between the contact and the pseudo-contact contributions. Besides the adsorption of lanthanide ions, specific anion binding to the surface was introduced to account for the enhanced chemical shifts (Cl- < Br- < NO3-). The results were analyzed in terms of the theory for the diffuse double layer (Gouy-Chapman-Grahame) with equilibrium conditions for the adsorbing cations and anions. Simulations of the titration curves furnished parameters for the ion-lipid interactions. The synergism between the cations and anions follows from the potential effects. Comparison of results with lanthanide ions and Ca2+ indicates that the anion adsorption probably depends on the nature of the adsorbed cation. Lanthanide ion binding to L-glycerophosphorylcholine is not influenced by sodium salts. The binding constant for this complex is weaker than with phosphatidylcholine. The chemical shifts for the lanthanide ion complexes with these two phosphorus compounds seem to be about the same.

Anions↗
PubMed1977

Arborization of initial axon collaterals of spinocervical tract cells stained intracellularly with horseradish peroxidase.

The initial axon collateral arborizations of two feline spinocervical tract cells have been analysed after intracellular staining with horseradish peroxidase. The images of the cells were reconstructed in the light microscope from transverse serial sections. The cell bodies were situated in laminae IV or III of the lumbar dorsal horn. Each cell exhibited one initial collateral. These emerged from the parent axons at distances of about 310 and 580 micron, respectively, from the cell body. The collaterals branched, mainly symmetrically, in laminae III-VI and IV-VI, respectively. The total collateral lengths were about 12,000 and 10,900 micron; altogether 329 and 274 stained terminals were found per collateral in laminae III-VI and IV-VI, respectively. The great majority of boutons were found in laminae IV and V. The terminals were distributed mainly in spherically arranged groups of 3-12 boutons, usually connected to each other by thin terminal axons. The light microscopically investigated sections were 're-embedded' and processed for electron microscopy. The ultrastructural investigation showed boutons with axo-dendritic, axo-somatic or axo-axonal synapses.

Animals↗
PubMed1977

Surface potential effects on metal ion binding to phosphatidylcholine membranes 31P NMR study of lanthanide and calcium ion binding to egg-yolk lecithin vesicles.

31P NMR of phosphatidylcholine (lecithin) from egg-yolk in sonicated vesicles has been measured in the presence of various ions. Addition of Ln3+ or Ca2+ shifted the 31P resonance of the phosphate groups of the outer surface of the vesicles. These shifts were measured at varied lanthanide or Ca2+ concentration at different ionic strengths obtained by addition of NaCl. The shifts induced by Tb3+ and Ca2+ have been analyzed using the theory of the diffuse double layer. Corrections were introduced for the effect of the ionic strength on the activities of the ions. The binding efficiency is shown to be controlled by the electrostatic potential produced by the bound cations at the membrane surface. This potential is slightly modified due to weak chloride binding. Binding constants have been derived.

Binding Sites↗
PubMed1977

Volume composition of the lateral cervical nucleus in the cat. I. A stereological and electron microscopical study of normal and deafferentated animals.

The neuropil of the lateral cervical nucleus (LCN) has been studied by means of ultrastructural stereological methods. Estimates of the fractional volumes of axons, glial cells (three types), extracellular space, boutons, bouton mitochondria, dendrites, dendritic mitochondria, neuronal somata and blood vessels were calculated for four normal cats and eight cats which had been subjected to spinal deafferentation 2, 4, 9, and 14 days before perfusion. 14 days after operation the fractional volume of boutons and dendrites in the nucleus was considerably lower on the operated side, corresponding to a reduction of 67% and 64% respectively. The bouton reduction was higher than could have been expected from findings in earlier qualitative studies. The reduction in dendritic volume, which was already present after 4 days, had not been detected in earlier studies of the LCN. Dark dendrites were found both in normal animals and on the normal and operated sides in operated animals. The variation from animal to animal was great but the figures for the deafferented sides were significantly higher. The general value of the stereological technique in ultrastructural neuroanatomical research is discussed and it is concluded that quantitative methods are more sensive to small and gradual changes and should give a better estimation of transneuronal effects and of the amount of degeneration than purely qualitative methods.

Afferent Pathways↗