Uptake and retrograde axonal transport of various exogenous macromolecules in normal and crushed hypoglossal nerves

Direct differentiation of whole blood for forensic serology analysis by thread spray mass spectrometry

Direct analysis of whole blood on bloodstained textiles is achieved with thread spray mass spectrometry (MS). This capability satisfies investigators' first priority in crime scene investigations, which is determining if a stain is blood. This thread spray method explores the use of evidentiary fabric threads for rapid determination of hemoglobin directly from whole blood within textiles without prior extraction steps. The multiplicity of information that can be derived from the thread spray MS method distinguishes it from the current presumptive Bluestar® method, by enabling the detection of hemoglobin (both α- and β-chains), the heme co-factor and lipids all from a single blood sample. Lipid composition was found to differ for blood samples originating from human, canine, and horse species. The robustness of the thread spray MS method as a forensic analytical platform was evaluated in three ways: (1) its successful applicability to samples previously tested by the Bluestar® presumptive method, offering a confirmatory test without prior sample pre-treatment, (2) successful detection of heme from previously washed fabrics, which demonstrated the unprecedented sensitivity of the thread spray method, and (3) the ability to analyze samples stored under ambient conditions for up to 30 days. These results attest to the potential capabilities of the thread spray MS platform in forensic serology, and its application for direct analysis of evidentiary garments, which confer the advantages of rapid analysis and the reduction of the false positive and negative identification rates for blood on textiles.

Insights into the binding behavior of native and non-native cytochromes to photosystem I from Thermosynechococcus elongatus

The binding of photosystem I (PS I) from Thermosynechococcus elongatus to the native cytochrome (cyt) c₆ and cyt c from horse heart (cyt c_HH) was analyzed by oxygen consumption measurements, isothermal titration calorimetry (ITC), and rigid body docking combined with electrostatic computations of binding energies. Although PS I has a higher affinity for cyt c_HH than for cyt c₆, the influence of ionic strength and pH on binding is different in the two cases. ITC and theoretical computations revealed the existence of unspecific binding sites for cyt c_HH besides one specific binding site close to P₇₀₀ Binding to PS I was found to be the same for reduced and oxidized cyt c_HH Based on this information, suitable conditions for cocrystallization of cyt c_HH with PS I were found, resulting in crystals with a PS I:cyt c_HH ratio of 1:1. A crystal structure at 3.4-Å resolution was obtained, but cyt c_HH cannot be identified in the electron density map because of unspecific binding sites and/or high flexibility at the specific binding site. Modeling the binding of cyt c₆ to PS I revealed a specific binding site where the distance and orientation of cyt c₆ relative to P₇₀₀ are comparable with cyt c₂ from purple bacteria relative to P₈₇₀ This work provides new insights into the binding modes of different cytochromes to PS I, thus facilitating steps toward solving the PS I-cyt c costructure and a more detailed understanding of natural electron transport processes.

A label-free phosphorescence sensing platform for trypsin based on Mn-ZnS QDs

A label-free phosphorescence strategy to determine trypsin was proposed using Mn-ZnS QDs as the phosphorescence probe with a better validity.

The aggregation of cytochrome C may be linked to its flexibility during refolding

Large-scale expression of biopharmaceutical proteins in cellular hosts results in production of large insoluble mass aggregates. In order to generate functional product, these aggregates require further processing through refolding with denaturant, a process in itself that can result in aggregation. Using a model folding protein, cytochrome C, we show how an increase in final denaturant concentration decreases the propensity of the protein to aggregate during refolding. Using polarised fluorescence anisotropy, we show how reduced levels of aggregation can be achieved by increasing the period of time the protein remains flexible during refolding, mediated through dilution ratios. This highlights the relationship between the flexibility of a protein and its propensity to aggregate. We attribute this behaviour to the preferential urea-residue interaction, over self-association between molecules.

Separating proteins with activated carbon

Activated carbon is applied to separate proteins based on differences in their size and effective charge. Three guidelines are suggested for the efficient separation of proteins with activated carbon. (1) Activated carbon can be used to efficiently remove smaller proteinaceous impurities from larger proteins. (2) Smaller proteinaceous impurities are most efficiently removed at a solution pH close to the impurity's isoelectric point, where they have a minimal effective charge. (3) The most efficient recovery of a small protein from activated carbon occurs at a solution pH further away from the protein's isoelectric point, where it is strongly charged. Studies measuring the binding capacities of individual polymers and proteins were used to develop these three guidelines, and they were then applied to the separation of several different protein mixtures. The ability of activated carbon to separate proteins was demonstrated to be broadly applicable with three different types of activated carbon by both static treatment and by flowing through a packed column of activated carbon.

Native SDS-PAGE: high resolution electrophoretic separation of proteins with retention of native properties including bound metal ions

Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is commonly used to obtain high resolution separation of complex mixtures of proteins. The method initially denatures the proteins that will undergo electrophoresis. Although covalent structural features of resolved proteins can be determined with SDS-PAGE, functional properties are destroyed, including the presence of non-covalently bound metal ions. To address this shortcoming, blue-native (BN)-PAGE has been introduced. This method retains functional properties but at the cost of protein resolving power. To address the need for a high resolution PAGE method that results in the separation of native proteins, experiments tested the impact of changing the conditions of SDS-PAGE on the quality of protein separation and retention of functional properties. Removal of SDS and EDTA from the sample buffer together with omission of a heating step had no effect on the results of PAGE. Reduction of SDS in the running buffer from 0.1% to 0.0375% together with deletion of EDTA also made little impact on the quality of the electrophoretograms of fractions of pig kidney (LLC-PK1) cell proteome in comparison with that achieved with the SDS-PAGE method. The modified conditions were called native (N)SDS-PAGE. Retention of Zn(2+) bound in proteomic samples increased from 26 to 98% upon shifting from standard to modified conditions. Moreover, seven of nine model enzymes, including four Zn(2+) proteins that were subjected to NSDS-PAGE retained activity. All nine were active in BN-PAGE, whereas all underwent denaturation during SDS-PAGE. Metal retention after electrophoresis was additionally confirmed using laser ablation-inductively coupled plasma-mass spectrometry and in-gel Zn-protein staining using the fluorophore TSQ.

The perforin pore facilitates the delivery of cationic cargos

Cytotoxic lymphocytes eliminate virally infected or neoplastic cells through the action of cytotoxic proteases (granzymes). The pore-forming protein perforin is essential for delivery of granzymes into the cytoplasm of target cells; however the mechanism of this delivery is incompletely understood. Perforin contains a membrane attack complex/perforin (MACPF) domain and oligomerizes to form an aqueous pore in the plasma membrane; therefore the simplest (and best supported) model suggests that granzymes passively diffuse through the perforin pore into the cytoplasm of the target cell. Here we demonstrate that perforin preferentially delivers cationic molecules while anionic and neutral cargoes are delivered inefficiently. Furthermore, another distantly related pore-forming MACPF protein, pleurotolysin (from the oyster mushroom), also favors the delivery of cationic molecules, and efficiently delivers human granzyme B. We propose that this facilitated diffusion is due to conserved features of oligomerized MACPF proteins, which may include an anionic lumen.

Advanced unidirectional photocurrent generation via cytochrome c as reaction partner for directed assembly of photosystem I

Engineering biohybrid photodiodes using surface-fixed cytochrome c as scaffold for efficiently connecting photosystem I with electrodes in 3D protein architectures.

A novel double-coating carrier produced by solid-in-oil and solid-in-water nanodispersion technology for delivery of genes and proteins into cells

A novel intracellular delivery method both for genes and proteins is one of the most coveted systems in the drug delivery field. In the present study, we developed a double-coating carrier loaded with gene and protein produced by solid-in-oil and solid-in-water nanodispersion technology. The double-coating carriers did not require electrostatic interactions during the preparation so were able to encapsulate plasmid DNA, ovalbumin (pI 4.5), horseradish peroxidase (pI 7.2), and cytochrome-c (pI 10.5) in a consistent manner. The carriers had practical encapsulation efficiencies and release profiles for genes and proteins. Furthermore, effective gene expression and cellular uptakes of both anionic and cationic proteins were achieved by modification of carriers with functional molecules. These findings indicate that the double-coating carrier has high potential for cellular delivery of various drugs and is a novel, superior method for both gene and protein delivery into cells.

High-efficiency protein extraction from polyacrylamide gels for molecular mass measurement by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry

A simple and fast method of protein extraction from Coomassie Brilliant Blue (CBB)-stained polyacrylamide gels suited for molecular mass measurement of proteins by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) is reported. Proteins in CBB-stained gel pieces were extracted by a 10-min soaking in 0.1 M NaOH at 25 degrees C. The recovery of this one-step extraction method was 34-73% for proteins <67 kDa. CBB adduction to proteins during mass spectrometric analysis was avoided by a destaining step before the alkaline extraction. The molecular mass values of the extracted proteins coincided with those of purified proteins within +/-0.01-0.10% deviation for all the proteins <36 kDa. Because of the high extraction recovery, mass measurement was possible for the proteins extracted from CBB-stained gels with loaded protein quantities as little as 34 ng for cytochrome c, alpha-lactalbumin, myoglobin, beta-lactoglobulin, trypsinogen, and carbonic anhydrase (12.4-29.0 kDa), 340 ng for glyceraldehyde-3-phosphate dehydrogenase (35.6 kDa) and albumin (66.3 kDa). This method provides a highly efficient approach to utilize CBB-stained one- or two-dimensional gels for whole protein analysis using MALDI-TOF-MS.

Nanotoxicology: an emerging discipline evolving from studies of ultrafine particles

Although humans have been exposed to airborne nanosized particles (NSPs; < 100 nm) throughout their evolutionary stages, such exposure has increased dramatically over the last century due to anthropogenic sources. The rapidly developing field of nanotechnology is likely to become yet another source through inhalation, ingestion, skin uptake, and injection of engineered nanomaterials. Information about safety and potential hazards is urgently needed. Results of older biokinetic studies with NSPs and newer epidemiologic and toxicologic studies with airborne ultrafine particles can be viewed as the basis for the expanding field of nanotoxicology, which can be defined as safety evaluation of engineered nanostructures and nanodevices. Collectively, some emerging concepts of nanotoxicology can be identified from the results of these studies. When inhaled, specific sizes of NSPs are efficiently deposited by diffusional mechanisms in all regions of the respiratory tract. The small size facilitates uptake into cells and transcytosis across epithelial and endothelial cells into the blood and lymph circulation to reach potentially sensitive target sites such as bone marrow, lymph nodes, spleen, and heart. Access to the central nervous system and ganglia via translocation along axons and dendrites of neurons has also been observed. NSPs penetrating the skin distribute via uptake into lymphatic channels. Endocytosis and biokinetics are largely dependent on NSP surface chemistry (coating) and in vivo surface modifications. The greater surface area per mass compared with larger-sized particles of the same chemistry renders NSPs more active biologically. This activity includes a potential for inflammatory and pro-oxidant, but also antioxidant, activity, which can explain early findings showing mixed results in terms of toxicity of NSPs to environmentally relevant species. Evidence of mitochondrial distribution and oxidative stress response after NSP endocytosis points to a need for basic research on their interactions with subcellular structures. Additional considerations for assessing safety of engineered NSPs include careful selections of appropriate and relevant doses/concentrations, the likelihood of increased effects in a compromised organism, and also the benefits of possible desirable effects. An interdisciplinary team approach (e.g., toxicology, materials science, medicine, molecular biology, and bioinformatics, to name a few) is mandatory for nanotoxicology research to arrive at an appropriate risk assessment.

Anterograde transport of tumor necrosis factor-alpha in the intact and injured rat sciatic nerve

Tumor necrosis factor-alpha (TNF) appears as a key player at both central and peripheral terminals in early degenerative pathology and pain behavior after peripheral nerve injury. Recent studies suggest that TNF may be axonally transported and thereby contribute to these central and peripheral actions. To characterize this transport, we used a double ligation (DL) procedure that distinguishes between anterograde and retrograde flow to visualize the axonal transport of endogenous TNF compared with the neurotrophin nerve growth factor (NGF) and to the neuropeptide calcitonin gene-related peptide (CGRP). In the intact nerve, TNF and CGRP immunoreactivity predominantly accumulated proximal to the DL (anterograde transport), whereas NGF displayed exclusive retrograde transport. At 20 hr after chronic constrictive injury (CCI), the anterograde transport of TNF and CGRP to the nerve injury site was dramatically increased. The results were corroborated by the analysis of axonal transport of exogenously applied 125I-TNF and 125I-NGF. After intraneural injection, 125I-TNF accumulated proximally to a DL, suggesting anterograde transport. In the unligated nerve, 125I-TNF was specifically transported anterogradely to the innervated muscle but not to skin. After CCI, 125I-TNF accumulated proximally to the peripheral nerve injury site, and endogenous TNF was exclusively increased in medium-sized and large dorsal root ganglion (DRG) neurons, suggesting that DRG neurons are a major contributing source of increased TNF traffic in the injured sciatic nerve. Our results suggest that anterograde transport of TNF plays a major role in the early neuronal response to peripheral nerve injury at sites distal to the cell body.

Increased stability of airflow following botulinum toxin injection

OBJECTIVES

The purpose of this study was to determine whether stability of airflow, as well as mean airflow, increased following botulinum toxin injection to laryngeal and extralaryngeal muscles in persons with spasmodic dysphonia (SD), some with associated vocal tremor (VT).

STUDY DESIGN

Aerodynamic data were collected from five subjects before and at 2, 4, and 8 weeks after they received treatment by each of two different arms in an injection protocol in a crossover study. One arm of the protocol involved treatment of the thyroarytenoid muscles only. The other arm involved treatment of both the thyroarytenoid muscles and the strap muscles.

METHODS

Measures of mean airflow and coefficient of variation (COV) of airflow during phonation were obtained. A decrease in the COV of airflow would indicate increased stability of phonatory airflow.

RESULTS

Before treatment, all subjects with SD/VT exhibited mean airflows that were similar to controls. The COV of airflow ranged from normal to substantially elevated. Following botulinum injection, mean airflow characteristically increased and COV of airflow decreased.

CONCLUSIONS

This finding suggests there is a change in the type, as well as the level, of activity in the muscles of speech production following botulinum toxin injection. The increase in airflow stability identified could be due to increased stability of the laryngeal system and possibly of the respiratory system as well.

Neuronal injury increases retrograde axonal transport of the neurotrophins to spinal sensory neurons and motor neurons via multiple receptor mechanisms

We investigated the retrograde axonal transport of 125I-labeled neurotrophins (NGF, BDNF, NT-3, and NT-4) from the sciatic nerve to dorsal root ganglion (DRG) sensory neurons and spinal motor neurons in normal rats or after neuronal injury. DRG neurons showed increased transport of all neurotrophins following crush injury to the sciatic nerve. This was maximal 1 day after sciatic nerve crush and returned to control levels after 7 days. 125I-BDNF transport from sciatic nerve was elevated with injection either proximal to the lesion or directly into the crush site and after transection of the dorsal roots. All neurotrophin transport was receptor-mediated and consistent with neurotrophin binding to the low-affinity neurotrophin receptor (LNR) or Trk receptors. However, transport of 125I-labeled wheat germ agglutinin also increased 1 day after sciatic nerve crush, showing that increased uptake and transport is a generalized response to injury in DRG sensory neurons. Spinal cord motor neurons also showed increased neurotrophin transport following sciatic nerve injury, although this was maximal after 3 days. The transport of 125I-NGF depended on the expression of LNR by injured motor neurons, as demonstrated by competition experiments with unlabeled neurotrophins. The absence of TrkA in normal motor neurons or after axotomy was confirmed by immunostaining and in situ hybridization. Thus, increased transport of neurotrophic factors after neuronal injury is due to multiple receptor-mediated mechanisms including general increases in axonal transport capacity.

A review of axonal transport of metals

Neurons have efficient mechanisms for the transport of organelles and chemical substances in axons to the nerve terminals and back to the cell bodies. Enzymes involved in transmitter synthesis, peptide transmitters and their precursors are examples of macromolecules that are transported down the axon, anterogradely. For final degradation and possible reuse, many constituents are transported back to the cell body, retrogradely. Retrograde transport is also a pathway by which certain toxins may bypass the blood-brain barrier and accumulate in neurons. In recent years, it has been shown that certain metals may accumulate in neurons following retrograde transport. The metals for which retrograde transport has been demonstrated include lead, cadmium and mercury. In this article recent findings regarding axonal transport of metals are reviewed. The putative mechanisms involved in the uptake of metals into the nerve terminal and the fate of metals in the cell body are outlined. Axonal transport of metals as a possible etiological factor in diseases of the human nervous system is discussed.

Anterograde neuroanatomical tract tracing with central nervous system injections of immunoglobulin G: a light and electron microscopic evaluation

Normal rabbit serum (NRS) was pressure injected into the forebrain of rats to be tested as an anterograde neuroanatomical tracing substance. Undiluted NRS was stereotaxically injected into the bed nucleus of the stria terminalis (BST) with a 1-microliter Hamilton syringe. Postinjection survival times ranged from 24 h to 14 days. An immunohistochemical method utilizing goat anti-rabbit IgG antibody was used to detect the rabbit IgG within vibratome sections. Visualization of the final reaction product (diaminobenzidine, DAB) was enhanced by a silver/gold postintensification (SGI) method. Rabbit IgG-containing neural structures were examined at both light and electron microscopic (EM) levels. At the injection site neuronal soma, dendrites and axons were filled homogeneously with the SGI-DAB at 24 h, 48 h, 7 days and 14 days indicating local neuronal uptake, storage and transport of rabbit IgG. In the hypothalamus many anterogradely filled axons were present and displayed short collateral branches and terminals. EM examination revealed synaptic terminals containing IgG, without signs of transsynaptic transport after 14 days. Signs of retrograde transport of IgG were never observed. A propensity of neurons to take up, sequester and anterogradely transport immunoglobulin G is indicated.

False-positive artifacts of tracer strategies distort autonomic connectivity maps

The widespread use of new axonal transport tracing techniques in the ANS has resulted in substantially revised and amended descriptions of ANS organization. The present review suggests, however, that at least some of the results on which proposed revisions of ANS anatomy have been based have incorporated artifacts and therefore should be cautiously interpreted. The peripheral nervous system and viscera are composed in part of connective and endothelial tissues that are porous or 'leaky' to solutes with appropriate chemical characteristics, including the major tracer compounds. As a result, several extra-axonal routes for redistribution of label from the application site into other tissues are present. These include (1) diffusion through tissue membranes to enter directly adjacent tissues and (2) leakage into extracellular fluids within the body cavity, vasculature, lymphatics, exocrine ducts, or organ lumens to migrate to more distant tissues. As a consequence of the extreme sensitivity of the methods used, such redistribution of even minute amounts of label can produce false positives. Review of autonomic neuroanatomy suggests additional mechanisms, including tracer uptake by fibers of passage, can produce artifactual staining. Based on these surveys of tissue composition, tracer characteristics and sources of artifact, experimental controls and criteria for identifying and avoiding labeling artifacts are described. Since no single procedure is foolproof for ANS experimentation, the routine application of multiple controls, particularly ones which restrict or prevent tracer diffusion, are needed.

Brainstem afferents to the basal forebrain in the rat

Brainstem afferents to various nuclei of the basal forebrain of the rat were examined using the retrograde transport of wheat germ agglutinin-horseradish peroxidase. These forebrain nuclei included the medial septum-vertical limb of the diagonal band nucleus, the lateral septum, the nucleus of the horizontal limb of the diagonal band, the medial preoptic area and the magnocellular preoptic nucleus/substantia innominata. Medial septal-vertical limb of the diagonal band injections produced dense cell labeling in: raphe obscurus, nucleus incertus, central gray-pars alpha, locus coeruleus, raphe pontis, median raphe, nucleus of Darkschewitsch, a compact cell group within the mesencephalic gray dorsolateral to the nucleus of Darkschewitsch and the supramammillary nucleus. Lateral septal injections produced the heaviest cell labeling in the A1 and A2 areas (of Dahlstrom and Fuxe), the lateral parabrachial nucleus, the Kolliker-Fuse nucleus, the ventral tegmental area and the supramammillary nucleus. There were considerably fewer labeled cells overall with lateral septal as compared with medial septal injections. Brainstem projections to the horizontal limb of the diagonal band were pronounced. The most heavily labeled nuclei were A1, locus coeruleus, laterodorsalis (dorsolateral tegmental nucleus of Castaldi), raphe pontis, median raphe, lateral parabrachial nucleus, ventral tegmental area, nucleus of Darkschewitsch and the supramammillary nucleus. Medial preoptic area injections produced pronounced labeling in: A1 and A2 areas, raphe magnus, locus coeruleus, laterodorsalis, lateral parabrachial nucleus, pedunculopontine nucleus, peripenduncular nucleus and the supramammillary nucleus. The pattern of brainstem labeling obtained with magnocellular preoptic/substantia innominata injections was considerably different from the patterns seen with the other injections. Specifically, relatively few cell groups, essentially confined to the upper brainstem (rostral pons and midbrain), were densely labeled following magnocellular preoptic/substantia innominata injections. These included the medial parabrachial nucleus, the pedunculopontine nucleus, the dorsal raphe nucleus, the ventral tegmental area and the supramammillary nucleus. With the exception of the supramammillary nucleus, each of these cell groups was more heavily labeled with magnocellular preoptic/substantia innominata injections than with others of this series. The above describes the major brainstem projections to each of the forebrain sites.(ABSTRACT TRUNCATED AT 400 WORDS)

Uptake and axonal transport of horseradish peroxidase isoenzymes by different neuronal types

The uptake and transport of basic and acidic horseradish peroxidase isoenzymes was compared in the neuromuscular, visual and olfactory systems of Xenopus larvae and postmetamorphic frogs. The concentration (w/v) of the two preparations was corrected to compensate for their difference in enzymatic activity (unit/w), which was seven-fold higher in basic horseradish peroxidase. Uptake and transport of horseradish peroxidase isoenzymes could be demonstrated with 7% basic horseradish peroxidase, but not with equal amounts of 49% acidic horseradish peroxidase in all systems investigated: retrograde transport from terminals of retinal ganglion cells, isthmotectal neurons and spinal motoneurons, as well as anterograde transganglionic transport along olfactory neurons. A very weak labelling of the same neuronal pathways by acidic horseradish peroxidase was obtained only after increasing the amount injected by approximately two-fold. Basic horseradish peroxidase isoenzymes were also preferentially taken up and transported retrogradely by broken axons of the optic nerve. When tested, similar results were obtained in both larvae and frogs suggesting that preferential uptake and transport of basic horseradish peroxidase is a general feature of all neurons and of all developmental stages. Electron microscopical analysis of the outer layers of the optic tectum revealed that, in the same experimental conditions producing no retrotrade labelling of optic axons, acidic horseradish peroxidase was rarely found to enter nerve terminals. It appears that interactions between horseradish peroxidase and neuronal membranes occur during uptake and transport and that molecular charge plays an important role, beyond non-specific fluid-phase endocytosis. We suggest that differences between horseradish peroxidase isoenzymes as neuronal tracers reflect a process of adsorptive endocytosis related to general characteristics of neuronal membranes (regardless of age) and not to specific receptor-mediated interactions characteristic of neuronal specificity.

Retrograde axonal transport of beta-adrenoreceptors in rat brain: effect of reserpine

Retrograde axonal transport of beta-adrenoreceptors was assessed by measuring the accumulation of binding sites for the beta-receptor ligand [125I]iodocyanopindolol [( 125I]ICP) distal to a unilateral 6-hydroxydopamine (6-OHDA) lesion placed in the ascending noradrenergic axons of the locus coeruleus. Accumulation of binding sites was linear over a 3 day period and was blocked by intracerebroventricular 6-OHDA given 1 day prior to sacrifice. A single dose of reserpine (5 mg/kg, i.p.) caused a long lasting (6-8 week) biphasic depletion of frontal cortex norepinephrine (NE) associated with increased frontal cortex binding of another beta-receptor ligand, [3H]dihydroalprenolol [( 3H]DHA), at 7-14 days, and again at 28 days post-reserpine. Unlike the changes in cortical beta-receptors, retrograde transport of [125I]ICP in presynaptic noradrenergic neurons was decreased or blocked completely at 7-14 days and at 6 weeks, and was increased to 470% and 240% of control at 21 days and 8 weeks after reserpine. Anterograde transport of [3H]DHA binding sites was measured by accumulation proximal to a 6-OHDA lesion in this pathway. This transport varied in a pattern similar to that seen for retrograde transport of [125I]ICP binding sites. These data and others suggest that presynaptic beta-receptors are regulated independently of frontal cortex beta-receptors, which appear to be located primarily on postsynaptic cells. On the other hand, the regulation of both anterograde and retrograde transport appears to be interrelated since both types of transport were altered in a similar way in the face of long-term NE depletion by reserpine.

A lectin horseradish peroxidase study of the origin of ascending fibers in the medial forebrain bundle of the rat. The lower brainstem

The origins of projections within the medial forebrain bundle from the lower brainstem were examined with the horseradish peroxidase technique. Labeled cells were found in at least 15 lower brainstem nuclei following injections of a conjugate or horseradish peroxidase and wheat germ agglutinin at various levels of the medial forebrain bundle. Dense labeling was observed in the following cell groups (from caudal to rostral): A1 (above the lateral reticular nucleus); A2 (mainly within the nucleus of the solitary tract); a distinct group of cell trailing ventrolaterally from the medial longitudinal fasciculus at the level of the rostral pole of the inferior olive; raphe magnus; nucleus incertus; dorsolateral tegmental nucleus (of Castaldi); locus coeruleus; nucleus subcoeruleus; caudal part of the dorsal (lateral) parabrachial nucleus; and raphe pontis. Distinct but light labeling was seen in raphe pallidus and obscurus, nucleus prepositus hypoglossi, nucleus gigantocellularis pars ventralis, and the ventral (medial) parabrachial nucleus. Sparse labeling was observed throughout the medullary and caudal pontine reticular formation. Several lower brainstem nuclei were found to send strong projections along the medial forebrain bundle to very anterior levels of the forebrain. They were: A1, A2, raphe magnus (rostral part), nucleus incertus, dorsolateral tegmental nucleus, raphe pontis and locus coeruleus. With the exception of the locus coeruleus, attention has only recently been directed to the ascending projections of most of the nuclei mentioned above. Evidence was reviewed indicating that fibers from lower brainstem nuclei with ascending medial forebrain bundle projections distribute to widespread regions of the forebrain. It is concluded from the present findings that several medullary cell groups are capable of exerting a direct effect on the forebrain and that the medial forebrain bundle is the major ascending link between the lower brainstem and the forebrain.

The permeability of the basal lamina at the neuromuscular junction. An ultrastructural study of rat skeletal muscle using particulate tracers

Various macromolecular substances, such as toxins and antibodies, may interfere with neuromuscular transmission. The neuromuscular junction is also known to be a site for the uptake of macromolecular substances into the axon for subsequent transport to the central nervous system. The synaptic cleft of the neuromuscular junction is separated from the rest of the extracellular compartment of muscle by the basal lamina, the permeability properties of which are not known. The penetration of macromolecular substances of varying size into the synaptic cleft of the neuromuscular junction has been studied in rats. Four different tracers: Imferon (an iron-dextran measuring 11 X 7 X 7 nm), ferritin (a spherical iron-protein 12 nm in diameter), Imposil (an iron-dextran measuring 21 X 12 X 12 nm) and colloidal gold-protein (20-25 nm in diameter) were injected into the palmaris longus muscle. Fifteen and 120 min after injection, the distribution of these particulate tracers was studied by electron microscopy. Imferon and ferritin penetrated rapidly through the basal lamina along the muscle fibres and also into the synaptic cleft of the neuromuscular junction. The larger Imposil and colloidal gold particles were restricted from penetrating the basal lamina even after 2 h, and these particles were traced only occasionally within the synaptic cleft. The results indicate that the basal lamina of muscle acts as a diffusion barrier to large macromolecules, preventing them from entering the synaptic cleft.

Maturation of the goldfish preoptic area: ultrastructural correlates of position and maturation of neurosecretory cells

A gradation of small rostral to larger caudal neurosecretory cells is found in the preoptic area of fish. Regional variations in ultrastructural features were assessed in this region of fish ranging widely in size (1.7-283.1 g), some of which had received intraperitoneal injections of horseradish peroxidase in order to label neurons projecting beyond the blood-brain barrier (i.e. neurosecretory cells). In small (less than or equal to 6.6 g) fish, neurosecretory cells of the caudal preoptic area were 10-15 microns in diameter and contained dense core vesicles. More rostral smaller cells had few or no dense core vesicles, but were labeled following intraperitoneal horseradish peroxidase injections. Cells in both areas were progressively larger, with larger nuclei and more granular reticulum in larger fish. In large fish, neurons that contained dense core vesicles ranged from 10 microns in diameter rostrally to 70 microns in diameter caudally. Some intermediate and large cells were extensively vacuolated and contained extremely convoluted and possibly multiple nuclei. Degenerating material was seen in apparently normal large fish. A few neurosecretory cells were extensively surrounded by perineuronal electron-dense glial cells. Most neurosecretory cells were involved in extensive soma-somatic apposition, which was especially pronounced in fish which were removed from cold water in late fall. Gap junctions were also clearly present on the somata of preoptic neurosecretory cells of these fall fish. These data imply that increased capacity for hormone secretion in large fish may be accomplished in part by neuronal hypertrophy. Maturational and seasonal variation in structure suggest that physiological characteristics are also variable in this nucleus.

Three-dimensional computer reconstruction of the distribution of neuromuscular junctions in the thyroarytenoid muscle

Microinjections of botulinum toxin have recently been shown to be effective in the treatment of strabismus, and it has also been suggested that microinjections of this myoneural blocking agent might be of value in the treatment of spastic dysphonia. The success of such a microinjection technique would rely on a precise knowledge of the distribution of myoneural junctions in the thyroarytenoid muscle. In view of this potential application as well as the need for such information in reinnervation procedures, we have used computer graphics to reconstruct the three-dimensional distribution of motor end-plates in the thyroarytenoid muscle. Three cat and one human (fresh autopsy specimen) larynges were frozen and sectioned on a cryostat. Serial sections were then processed for the histochemical localization of acetylcholinesterase activity to demarcate the neuromuscular junctions. An X-Y digitizer was used to reference the position of the motor end-plates in each serial section, and the three-dimensional distribution of the neuromuscular junctions was reconstructed on a computer graphics terminal. The results are discussed in regard to their applicability to clinical treatment of spastic dysphonia and other disorders of phonation.

Uptake of horseradish peroxidase by axons of passage and its modification by poly-L-ornithine and dimethylsulphoxide

It has been shown that transected axons of passage in the optic tract can take up horseradish peroxidase (HRP) and transport it back to the cell bodies. This effect is considerably reduced if the HRP is injected from a small-tipped micropipette 6-12 h after insertion into the injection site. HRP is not taken up by uninjured axons of passage. The use of poly-L-ornithine and dimethylsulphoxide dramatically increases the numbers of labeled cells. These numbers are undiminished after 6-12 h waiting periods. From this and from calculation it is clear that much of this effect must occur via uninjured axons. These substances should not be used in any situation where it is important not to label axons of passage. If other HRP conjugates and additives have the same effect as those described here, the results of experiments with these substances should be interpreted with caution.

Extensive labelling of injured insect neurons with seven different heme peptides

Seven different heme peptides were used in neuronal uptake and labelling experiments in flies. The peptides were: catalase, lactoperoxidase, hemoglobin, horseradish peroxidase (HRP), myoglobin, cytochrome c and microperoxidase. All of these peroxidase active peptides were taken up by lesioned neurons and the markers spread throughout the entire cells resulting in a detailed labelling of their processes and cell bodies. Only HRP was taken up by intact neurons. Attempts were made to block axonal transport of HRP with colchicine, vinblastine and 2,4-dinitrophenol. These attempts were unsuccessful and it is proposed that HRP and the other six heme peptides testes are non-selectively diffusing through lesioned or damaged nerve cells in flies.

Retrograde transport of doxorubicin (adriamycin) in peripheral nerves of mice

Doxorubicin (adriamycin) is a fluorescent compound which is widely used in the treatment of malignant tumors due to its capacity to bind and influence the DNA in the nucleus of cells. We have now observed that the compound after injection into a skeletal muscle of adult mice is transported to the corresponding nerve cell bodies, i.e. can be used as a retrograde tracer in neuroanatomical and neuropathological research. Six hours after injection into the tongue nerve cell nuclei were labeled in the hypoglossal nuclei of the brainstem. The fluorescent tracer had the same distribution as the chromatin. Glial nuclei in the vicinity of the hypoglossal neurons were also labeled presumably due to a transfer from the neurons to the glial cells during life or during the histochemical procedure. Since doxorubicin is also neurotoxic it might be a useful tool in neurobiological research, particularly if the labeled neurons later on will show toxic effects. In this way the compound could be used in models for experimental motor neuron disease and provide a means by which retrograde fluorescent tracing and a degeneration method can be combined for studies on various neuronal systems.

Ascending projections of the brain stem reticular formation in a nonmammalian vertebrate (the lizard Varanus exanthematicus), with notes on the afferent connections of the forebrain

In the present study an attempt has been made to analyze the ascending reticular projections in the lizard Varanus exanthematicus by means of the horseradish peroxidase (HRP) technique. Reticular projections ascending to the telencephalon were found to arise in the mesencephalon, but not caudal to the mesorhombencephalic border. HRP injections into the dorsal thalamus have demonstrated retrogradely labeled cells in the mesencephalic reticular formation, particularly at the level of the oculomotor nerve and in the medial magnocellular zone of the rhombencephalic reticular formation, predominantly rostrally. HRP infiltrations at the mesodiencephalic border damaged most of the fibers passing beyond this junction, resulting in the uptake of HRP by the damaged axons and subsequent labeling of the cell bodies or origin of ascending reticular projections to the diencephalon and telencephalon. From a comparison of cell-labeling patterns in cases of HRP injections of, respectively, the dorsal thalamus and the mesodiencephalic border, it seems likely that the nucleus reticularis medius and more sparsely the nucleus reticularis inferior project to ventral diencephalic structures (ventral thalamus and hypothalamus), whereas the midbrain reticular formation and the rostral parts of the rhombencephalic reticular formation (nuclei reticulares isthmi and superior) project to both the dorsal thalamus and more ventral diencephalic structures. Projections arising throughout the rhombencephalic reticular formation, but predominantly in the nucleus reticularis inferior, were found to ascend to the midbrain reticular formation. The present experimental data in the lizard Varanus exanthematicus are comparable to the findings in mammals, with the exception of the reticulo-oculomotor pathways which have not been analyzed so far in reptiles. In addition to the aforementioned ascending reticular projections, the present study has demonstrated projections ascending from monoamine cell groups, various diencephalic structures, as well as from neuronal groups involved in somatosensory, auditory, and gustatory systems. Projections were found from the locus coeruleus and the nucleus raphes superior to the telencephalon, as well as from the substantia nigra and the presumable reptilian homologue of the mammalian ventral tegmental area to the basal forebrain and the dorsal thalamus. Bilateral projections were demonstrated from the principal trigeminal nucleus to the telencephalon, reminiscent of the quintofrontal tract of birds. Ascending projections to the diencephalon were found to originate bilaterally in the descending trigeminal nucleus and the dorsal funicular nucleus. Auditory projections to the midbrain arise bilaterally in the superior olivary complex and in the cochlear nuclear complex. Finally, the ascending gustatory pathway arising in the nucleus of the solitary tract was found to project to the "parabrachial region," which in its turn has extensive projections to the forebrain.

Neuronal uptake of iron: somatopetal axonal transport and fate of cationized and native ferritin, and iron-dextran after intramuscular injections

Mice were injected into the muscles of the vibrissae with native ferritin (NF), cationized ferritin (CF) and iron-dextran. CF adsorbed on to the surface of the axon terminal at the neuromuscular junction, while NF did not. Both CF and NF were incorporated into vesicles and vacuoles at the synapse, but CF uptake was detected after injections at much lower concentrations than NF. In contrast to NF, CF was also found histochemically in cell bodies of facial neurones after a single i.m. injection, showing that the electrical charge of a molecule is one factor of importance for its potential to be incorporated in axons and transported somatopetally. Repeated i.m. injection of iron-dextran into suckling mice resulted in a marked iron load of Schwann cells and nerve cell bodies. This produced no signs of toxicity and the nerve fibre developed normally. Iron had disappeared from the nerve cell bodies after 25 days, while in Schwann cells it still persisted after 223 days.

Cytochrome c as a high resolution marker of neurons for light and electron microscopy

Cytochrome c is taken up by lesioned neurons in the central and peripheral nervous system of the house fly. The enzyme reaction product is evenly distributed in cell bodies, axons, dendrites and axon terminals after 3-6 h uptake. No uptake into undamaged neurons, nor any transneuronal uptake could be demonstrated. Pre- and postsynaptic relations of cytochrome c-labeled neurons can be resolved.

The uptake and retrograde transport of horseradish peroxidase--polylysine conjugate by ligated postganglionic sympathetic nerves in vitro

The uptake and retrograde transport of horseradish peroxidase (HRP) and horseradish peroxidase-poly-L-lysine conjugate (HRP-PL) were compared using a system comprising the guinea-pig inferior mesenteric ganglion (IMG) and ligated hypogastric hypogastric nerves maintained in vitro in a twin chamber apparatus. 0.5 mg of HRP-PL applied to the ligated nerves produced stronger retrograde labelling of neurons within the IMG than did 10 mg of HRP. This may have been due to the greater uptake of HRP-PL in a vesicular form by the axons immediately proximal to the ligation. The possible roles of large rounded vesicles and elongated cisternae in retrograde axoplasmic transport are discussed.

Axonal uptake of horseradish peroxidase isoenzymes during Wallerian degeneration

Horseradish peroxidase isoenzymes were applied around crushed mouse hypoglossal nerves to study the influence of electrical charge on the uptake and ultrastructural distribution of macromolecules in axons distal to an injury. Both isoenzymes tested (Sigma type IX, cationic and type VII, anionic) were readily taken up into axons and moved in a distal direction along the nerve. Samples taken 1-3 mm below the crush showed that reaction products from both enzymes covered the inner surface of the axonal plasma membrane and were attached to organelles, particularly microtubules and neurofilaments. However, reaction product in the Schwann cell basement lamina and in the endoneurial collagen was much more dense with cationic peroxidase than with the anionic isoenzyme. Our study shows that both cationic and anionic macromolecules can move into axons distal to a nerve lesion. It can be assumed that also other agents can be taken up into axons and that 'wound substances' in this way may influence the processes by which axons are destroyed during Wallerian degeneration.

Cells of origin of pathways descending to the spinal cord in some quadrupedal reptiles

The cells of origin of pathways descending to the spinal cord have been determined in several quadrupedal reptiles, viz., the turtle Pseudemys scripta elegans and Testudo hermanni and the lizards Tupinambis nigropunctatus and Varanus exanthematicus, following a technique introduced by Kuypers and Maisky ('75). This technique was very effective in producing retrograde transport of HRP to a great many neurons in the hypothalamus and in the brain stem. Projections from the hypothalamus (the nucleus paraventricularis and the nucleus periventricularis hypothalami), the interstitial nucleus of the film, the nucleus ruber, the nucleus of Edinger-Westphal, the locus coeruleus, the subcoeruleus area, a conspicuous cell group comparable to Kuypers and Maisky's (75, '77) lateral pontine area, the magnocellular reticular formation, the ventrolateral, ventromedial, and descending vestibular nuclei, the dorsal motor nucleus of the vagus, and the nucleus of the solitary tract, reach at least as far as the lumbar intumescence. Projections from two somatosensory nuclei, i.e., the nucleus descendens nervi trigemini and the nucleus funiculi dorsalis, as well as the laminar nucleus of the torus semicircularis, have been demonstrated to at least the ninth spinal segment. The two deep cerebellar nuclei, particularly the medial cerebellar nucleus, were found to project contralaterally to the spinal cord, in the lizard Varanus exanthematicus at least as far as the seventh segment; in the turtles studied so far, only projections as far caudal as the fourth spinal segment could be demonstrated. Data on the funicular trajectory of various descending pathways could also be obtained. It seems likely that in the reptiles studied, in addition to rubrospinal and reticulospinal pathways, projections from the hypothalamus, the nucleus of Edinger-Westphal, the cell group comparable to the mammalian lateral pontine area, the locus coeruleus, and subcoeruleus area, and the nucleus of the solitary tract pass via the lateral funiculus. The pathways descending from the hypothalamus and brain stem to the spinal cord in the quadrupedal reptiles studied appear to show remarkable similarities to pathway in mammals as regards their cells of origin as well as their funicular trajectory. It seems likely that some of the projections demonstrated, viz., from the locus coeruleus, at least part of the cell group comparable to the lateral pontine area, as well as the cells in and around the dorsal motor nucleus of the vagus, are noradrenergic pathways.

Delivery of antiviral chemotherapeutic agents to neurons by retrograde axonal transport

It may be possible to eliminate herpes simplex or zoster viruses from the neurons of carriers by treatment with an antiviral chemotherapeutic agent such as adenine arabinoside, ribavirin or acyclovir, coupled to a compound such as horseradish peroxidase that undergoes retrograde axonal transport.

Differences between the peripheral and the central nervous system in permeability to sodium fluorescein

Sodium fluorescein (SF) was used as a very small tracer (mol wt 376; 5 A diameter) to examine diffusion barriers in peripheral nerves and to compare them to those in other regions of the nervous system. The technique involved immobilization of the tracer by rapid freezing, followed by freeze-drying and vacuum embedding in paraffin. The localization of the SF was then determined in tissue secretions using fluorescence microscopy. Even at the highest doses of intravenously (IV) injected tracer, no extravasation could be detected in the cerebral cortex. On the other hand, SF penetrated very rapidly into peripheral ganglia and into the epineurium and perineurium of large peripheral nerves. The penetration of SF into the endoneurium of large nerves was, however, much more restricted with tracer detectable within the endoneurium only at high doses and long survival times. Even in such cases, the level of SF fluorescence was much lower within nerve fascicles than in the epineurium and the perineurium, and a sharp gradient in fluorescence intensity persisted at the inner border of the perineurium. The extent of extravasation into the endoneurium varied markedly betwen different fascicles of the same nerve and between different nerves in the same animal. Experiments involving injection of high doses of SF adjacent to the nerve indicated relatively little movement of SF across the perineurium, which indicates that the observed accumulation of tracer within the endoneurium was the result of direct extravasation of SF from the endoneural blood vessels. Small nerve branches (< 100 mu diameter) showed an earlier and more extensive penetration of SF into the endoneurium than large nerves like the sciatic, hypoglossal, or ventral tail nerve. This may be due to a diffusion of SF along the extracellular space of the endoneurium from nerve terminals where the perineurial barrier is open-ended. In experiments involving IV injection of a solution containing both green fluorescent SF and red fluorescent Evans Blue (Evans Blue-serum albumin conplex, EBA = mol wt. 69,000), the distribution of SF could be directly compared at various sites and sacrifice times to that of EBA, a much larger tracer. SF appeared more rapidly and extensively than EBA in the various compartments in ganglia and peripheral nerve. The distribution of EBA was the same as is typically seen when this tracer is injected alone, indicating that there was no change in vascular permeability associated with IV injection of SF. Since SF is of very small size, freely diffusible, nontoxic, and detectable at very low concentrations, it should be a useful complement to existing tracers. When tissues are processed according to the indicated procedure, one can obtain a very sensitive and reliable localization of this tracer which should be of value for studies in the nervous system concerning various pathological conditions associated with permeability alterations.