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Biomedical subjects

R G Wiley

Publications and source records attributed to R G Wiley.

126 records · Page 7Linked to original sources
PubMed1986

Wheat germ agglutinin-ricin A-chain conjugate is neuronotoxic after vagal injection.

'Suicide transport' is a term coined to describe the use of retrogradely axonally transported toxin to produce anatomically selective neural lesions. As a first step in developing neuron type-selective, systemically non-toxic suicide transport agents, a prototype hybrid toxin consisting of ricin A-chain (RTA) disulfide coupled to wheat germ agglutinin (WGA) was synthesized by first derivatizing WGA by reaction with N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP) in the presence of N-acetylglucosamine and then formation of WGA-SS-RTA by mixing the derivatized WGA with reduced RTA. The ability of this conjugate to inhibit protein synthesis was tested on two cell lines in vitro; the ID50 was 0.2 nM using the K562 hematopoietic stem cell line and 0.02 nM for the 2a neuroblastoma cell line. Suicide transport activity was assessed by microinjection of hybrid into the cervical vagus nerve of rats. Intact WGA-SS-RTA, but not hybrid that was pretreated with dithiothreitol to uncouple RTA from the WGA carrier, reliably killed vagal motor neurons. Both intact and reduced hybrid killed vagal sensory neurons. Indirect peroxidase immunohistochemistry demonstrated transport of RTA to vagal sensory neurons and WGA to both vagal sensory and motor neurons. These results are the first evidence that a hybrid toxin can be active as a suicide transport agent.

Animals↗
PubMed1986

Anatomically selective peripheral nerve ablation using intraneural ricin injection.

Anatomically selective destruction of sensory and motor neurons based upon which nerve contains the corresponding axons can be accomplished by intraneural pressure microinjection of the toxic lectin, ricin. Ricin is taken up by axons at the injection site and axonally transported to perikarya resulting in destruction of the neurons. In the present report, we describe a reliable procedure for making such lesions using pressure microinjection of ricin into nerve trunks. Consistent, complete lesions restricted to the appropriate sensory and motor neurons are documented after injection of the vagus, hypoglossal, phrenic and sciatic nerves and the superior cervical ganglion. Complete vagal ablations could be achieved with 100 ng or less of ricin; whereas, 1-3 micrograms was required to obtain similar results with hypoglossal and sciatic nerves. Although most neurons are dead within 24 h after the injection, survival times of 10-14 days may be necessary for complete disappearance of poisoned neurons. This technique can be valuable in making highly selective lesions for anatomical, neurochemical and neurophysiological experiments.

Animals↗
PubMed1986

Studies on the cellular localization of spinal cord substance P receptors.

Substance P-immunoreactivity and specific substance P binding sites are present in the spinal cord. Receptor autoradiography showed the discrete localization of substance P binding sites in both sensory and motor regions of the spinal cord and functional studies suggested an important role for substance P receptor activation in autonomic outflow, nociception, respiration and somatic motor function. In the current studies, we investigated the cellular localization of substance P binding sites in rat spinal cord using light microscopic autoradiography combined with several lesioning techniques. Unilateral injections of the suicide transport agent, ricin, into the superior cervical ganglion reduced substance P binding and cholinesterase-stained preganglionic sympathetic neurons in the intermediolateral cell column. However, unilateral electrolytic lesions of ventral medullary substance P neurons which project to the intermediolateral cell column did not alter the density of substance P binding in the intermediolateral cell column. Likewise, 6-hydroxydopamine and 5,7-dihydroxytryptamine, which destroy noradrenergic and serotonergic nerve terminals, did not reduce the substance P binding in the intermediolateral cell column. It appears, therefore, that the substance P binding sites are located postsynaptically on preganglionic sympathetic neurons rather than presynaptically on substance P-immunoreactive processes (i.e. as autoreceptors) or on monoamine nerve terminals. Unilateral injections of ricin into the phrenic nerve resulted in the unilateral destruction of phrenic motor neurons in the cervical spinal cord and caused a marked reduction in the substance P binding in the nucleus. Likewise, sciatic nerve injections of ricin caused a loss of associated motor neurons in the lateral portion of the ventral horn of the lumbar spinal cord and a reduction in the substance P binding. Sciatic nerve injections of ricin also destroyed afferent nerves of the associated dorsal root ganglia and increased the density of substance P binding in the dorsal horn. Capsaicin, which destroys small diameter primary sensory neurons, similarly increased the substance P binding in the dorsal horn. These studies show that the cellular localization of substance P binding sites can be determined by analysis of changes in substance P binding to discrete regions of spinal cord after selective lesions of specific groups of neurons. The data show the presence of substance P binding sites on preganglionic sympathetic neurons in the intermediolateral cell column and on somatic motor neurons in the ventral horn, including the phrenic motor nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Suicide transport of ricin demonstrates the presence of substance P receptors on medullary somatic and autonomic motor neurons.

Suicide transport of the toxic lectin, ricin, by hypoglossal and vagus neurons resulted in motor neuron loss in the associated nuclei, and reduced the binding of the 125I-Bolton-Hunter labeled substance P in the same nuclei. These data show that substance P receptors are located on the cell bodies of medullary somatic and preganglionic motor neurons of the hypoglossal and vagus nerves, and that suicide transport is a useful technique to determine the cellular localization of binding sites within a nucleus.

Animals↗
PubMed1985

Axonally transported Shigella cytotoxin is neuronotoxic.

Shigella dysenteriae strains produce an exotoxin (SdT) which inhibits protein synthesis in susceptible cells and is neurotoxic in some species. Intraneural microinjection of highly purified SdT into the cervical vagus nerves of rats, mice, guinea pigs and rabbits produced cytopathic changes within 24 hours in vagal sensory but not motor neurons. These changes consisted of an initial loss of Nissl substance followed by progressive cell degeneration and resulted in permanent neuronal loss. Indirect immunoperoxidase staining demonstrated SdT in nodose ganglion sensory neurons but not in vagal motor neurons of the brainstem. In rats, fatal enterotoxicity was common after intraneural injection of SdT doses that were reliably neuronotoxic; in rabbits and mice, a fatal ascending paralysis occurred at similar doses. Cytopathic changes were noted rarely in nodose sensory neurons of the uninjected side in mice suggesting systemic distribution and neuronal uptake of toxin. Injection of SdT into the tongue muscles of rats and mice failed to affect hypoglossal motor neurons within 50 hours. We conclude SdT is taken up and retrogradely transported by vagal sensory neurons with a resultant destruction of these neurons. The relationship of these findings to the reported neurotoxicity of SdT is unclear. However, SdT may prove useful in making selective lesions or as a model for some forms of neuronal degeneration.

Animals↗
PubMed1984

Combined trabeculectomy, intracapsular cataract extraction, and lens implantation: a clinical series.

Twenty-two eyes from 17 patients underwent a combined surgical approach for cataracts and glaucoma, involving an intracapsular cataract extraction, trabeculectomy, and anterior chamber intraocular lens implantation with an average follow-up of one year. The surgical technique is described. The average intraocular pressure fell from 24.9 mm Hg to 16.7 mm Hg. Seventy-three percent of the patients required no medication postoperatively for control of their glaucoma. Ninety-six percent of the patients showed an improvement in visual acuity improvement. Complications of flat peripheral anterior chambers and hyphema formation did not affect post-operative pressures or visual acuity results. The results encourage further investigation of this procedure.

Aged↗
PubMed1983

Ricin transport distinguishes between central and peripheral neurons.

Ricin conjugated to horseradish peroxidase was retrogradely transported by peripheral neurons of the nodose ganglion after microinjection into the nucleus tractus solitarius but was not transported by central neurons projecting to the nucleus tractus solitarius. Similarly, ricin was not transported by central neurons projecting to the caudate nucleus. Differences in labeling of central and peripheral neurons with ricin may reflect differences in surface glycoconjugates on processes of these neurons.

Animals↗
PubMed1982

Neurotoxicity of the pyrimidine synthesis inhibitor N-phosphonoacetyl-L-aspartate.

PALA (N-phosphonoacetyl-L-aspartate) impairs de novo pyrimidine biosynthesis by inhibiting the enzyme aspartate transcarbamylase. During cancer chemotherapy trials the drug was given by weekly intravenous infusion. Seizures developed in 9 (11%) of the first 80 patients to receive a total dose of 9 gm/m2 or more. Seven of the affected patients had structural brain lesions; they developed seizures at a lower total dose (median of 16.4 gm/m2) than the 2 patients without clinically detectable brain lesions (115 to 130 gm/m2). Reversible encephalopathy was observed in 6 (7.5%) additional patients without clinically detectable cause other than PALA. Both seizures and encephalopathy began after the second dose of PALA or later. Experiments in rats demonstrated similar delayed-onset seizures after two or three combined systemic and intracerebral doses of PALA at 4-day intervals. Concurrent administration of uridine or carbamyl aspartate prevented the development of seizures in rats, indicating that pyrimidine starvation of the central nervous system was responsible for PALA neurotoxicity.

Adult↗
PubMed1979

The scintillating scotoma without headache.

Scintillating scotomas are frequently seen without an associated headache and in general should be considered a benign symptom. In this series of 10 patients with an age range from 25 to 72 years, there were 7 female and 3 male patients. With an average follow-up of 1 1/2 years there was no patient who subsequently developed migraine headaches or any persisting neurologic sequelae.

Adult↗
PubMed1974

Synaptic vesicle depletion and recovery in cat sympathetic ganglia electrically stimulated in vivo. Evidence for transmitter secretion by exocytosis.

This study examined the ultrastructure of presynaptic terminals after short periods of vigorous acetylcholine (ACh) secretion in the cat superior cervical ganglion in vivo. Experimental trunks of cats anesthetized with chloralose-urethane were stimulated supra-maximally for periods of 15-30 min and at several frequencies including the upper physiological range (5-10 Hz). Stimulated and contralateral control ganglia from each animal were fixed by intra-arterial aldehyde perfusion, processed simultaneously, and compared by electron microscopy. Stimulation produced an absolute decrease in the number of synaptic vesicles, an enlargement of axonal surface membrane, and distinct alterations in the shape of presynaptic terminals. Virtually complete recovery occurred within 1 h after stimulation at 10 Hz for 30 min. These results support the hypothesis that ACh release at mammalian axodendritic synapses occurs by exocytosis of synaptic vesicles resulting in the incorporation of vesicle membrane into the presynaptic membrane and that synaptic vesicles subsequently are reformed from plasma membrane.

Acetylcholine↗
PubMed1972

Morphologic alterations of synapses in electrically stimulated superior cervical ganglia of the cat.

Prolonged preganglionic stimulation produces marked ultrastructural changes in presynaptic endings, which develop larger zones of contact with post-synaptic dendrites. Profiles of such endings, compared to controls, have fewer synaptic vesicles, similar areas, and greater circumferences. These results are compatible with the hypothesis that synaptic vesicles become incorporated into the plasma membrane during stimulation.

Animals↗
PubMedDate not supplied

The behavioral functions of the cholinergic basal forebrain: lessons from 192 IgG-saporin.

Until recently our understanding of the functional neuroanatomy of the cholinergic basal forebrain (CBF) has been hindered by the lack of a lesioning technique that is truly selective. The development of the immunotoxin 192 IgG-saporin (192-sap) has greatly improved our ability to create specific lesions of the CBF. Rats with such lesions have been studied in a wide variety of behavioral paradigms of learning, memory, and attention. Complete or near-complete destruction of the CBF results in deficits in a variety of behavior paradigms including passive avoidance, spatial tasks (water and radial mazes), delayed matching to position/sample, and attentional tasks. However, interpretation of many experiments is hampered by incomplete lesions and/or concomitant damage to cerebellar Purkinje neurons. Future studies will need to address these issues. Recent development of a similar immunotoxin that is effective in primates should permit more sophisticated behavioral analysis of CBF function. Additionally, immunotoxins selective for other types of neurons, such as the noradrenergic selective anti-DBH-saporin, will permit analysis of the behavioral functions of other diffusely projecting systems and how these other systems may interact with the CBF.

Animals↗
PubMedDate not supplied

Neuronotoxicity of axonally transported toxic lectins, abrin, modeccin and volkensin in rat peripheral nervous system.

In an attempt to find new and more useful suicide transport agents, the cytotoxic lectins abrin, modeccin and volkensin were pressure microinjected into peripheral nerves (vagus, hypoglossal and sciatic) of adult rats. After 33 h-5 days survival, the brainstems, spinal cords and corresponding sensory ganglia were examined histologically. All three lectins produced profound chromatolysis, and destruction of sensory and motor neurons projecting axons through the injected nerves. Volkensin and modeccin were significantly more potent than any previously reported suicide transport agent. It is concluded that abrin, modeccin and volkensin are effective, unselective suicide transport agents in the rat peripheral nervous system but none is clearly superior to ricin for making restricted sensory and motor neuron ablations. However, modeccin and volkensin are fundamentally different from any previously reported suicide transport agents with respect to spread within the CNS which destroyed neurons adjacent to those initially taking up and transporting the toxin. Possibly this is due to the different oligosaccharide binding specificity of modeccin and volkensin compared to other suicide transport agents. Modeccin and/or volkensin may prove useful in making lesions of CNS interneurons using the suicide transport strategy.

Abrin↗