Showing papers by "Johns Hopkins University School of Medicine published in 1978"

In situ injection of kainic acid: A new method for selectively lesioning neuronal cell bodies while sparing axons of passage

Abstract: The morphologic sequelae following stereotaxic injection into the rat striatum of kainic acid, a conformationally restricted analogue of glutamate, were examined by means of bright fields, histofluorescence and electron microscopic techniques. The neuropathologic response to kainate injection occurs in two distinct phases. Fist, the intrinsic neurons of the striatum undergo a rapid degeneration during the first 48 hours after injection; this is characterized by the sequential loss of cytoplasmic Nissl-substance (chromatolysis), shrinkage of the perikarya, clumping of the nuclear chromatin and finally disruption of the nuclear membrane. Between one and three weeks after injection, a marked proliferation of astrocytes in the gray matter formerly populated by neurons characterizes the second phase. The region of several neuronal loss in the kainate injected stratum is approximately spherical in shape, and its extent is non-linearly related to the amount of kainate injected. The neuropil of the injected striatum is markedly disrupted due to the death of intrinsic neurons and loss of their processes. Yet, histofluoresence microscopy demonstrates that the dopaminergic axons projecting from the substantia nigra do not degenerate in the kainate injected striatum; electron microscopic studies indicate that corticofugal fibers traversing the striatum also unaffected by kainate. Many presynaptic boutons, presumably of extrinsic origin, are intact up to ten days after injection; osmophilic vestiges of postsynaptic elements remain adherent to these boutons. Numerous phagocytic astrocytes are observed throughout the lesioned area. These morphologic studies provide (direct) evidence that in situ injection of kainic acid in brain causes a selective degeneration of neurons with cell bodies in the area of the injection but spares axons that arise from perikarya outside the region but pass through or terminate in the injected area. Thus, in situ injection of kainic acid is a new technique for making selective brain lesions that will be useful for examining neuronal connectivity.

Preparation and characterization of mitochondria and submitochondrial particles of rat liver and liver-derived tissues.

Abstract: Publisher Summary This chapter discusses techniques for the preparation and characterization of mitochondrial and submitochondrial fractions from liver and liver-derived tissues. The chapter represents the most detailed account of preparative procedures available for mitochondria and submitochondrial particles of rat liver. The chapter initially summarizes several methods for isolating rat liver mitochondria. Some of these methods yield type-1 mitochondria (partially purified but intact), and some yield type-2 mitochondria (highly purified). The two most common tests used to determine the quality of mitochondrial and submitochondrial preparations involve an examination of their respiratory characteristics in a small chamber equipped with an oxygen electrode, and an examination of their structural and morphological features under the electron microscope. The chapter presents flow diagrams that include many of the methods to obtain an overall view of a given procedure. The methodology involved in preparing mitochondria for evaluation in the electron microscope is summarized here, together with a few statements about what each step involves and why it is carried out.

Sodium-dependent, high affinity choline uptake

Abstract: MANY experiments in a variety of systems have revealed that the rate of synthesis of ACh adjusts to changes in the rate of release of ACh. From this follows the universal belief that the synthesis of ACh is regulated by some biochemical mechanism. All of the factors in the regulation of synthesis of ACh are not understood Most models of regulation deal with ChAc and/or the supply of acetylCoA and choline. Important questions dealing with choline have been formulated. What are the sources of choline? How is it utilized? What is the fate of choline derived from released ACh? All of these questions cannot be answered here for practical reasons, and there are several recent reviews dealing with the sources of choline for ACh synthesis and with overall aspects of its acetylation in neuronal tissue (HEBB, 1972; WHITTAKER et al., 1972; FONNUM, 1973, 1975; BROWNING, 1976; FREEMAN & JENDEN, 1976; HAUBRKH & CHIPPENDALE, 1977). This review will focus on choline transport into cholinergic neurons, especially by means of the sodium-dependent, high affinity choline uptake system (SDHACU) which appears to be involved in ACh synthesis and its regulation. Transport of choline through the blood-brain barrier has been discussed elsewhere (PARDRIDGE & OLDENWRF, 1977).

Dopamine receptors localised on cerebral cortical afferents to rat corpus striatum

Abstract: STRIATAL dopamine receptors, monitored by dopamine-sensitive adenylate cyclase activity1,2 or binding of 3H-haloperidol3–5 apparently represent distinct entities because of differences in drug sensitivity and the pattern of their ontogenetic development6,7. Dopamine also elicits both excitatory and inhibitory effects on striatal neurones8,9. We have examined the effects of selective degeneration of striatal intrinsic neurones with the neurotoxin. kainic acid10–12, and elimination of cortico-striate afferents by cortical ablation13 on the dopamine receptors in rat striatum. We present evidence that a substantial portion of striatal 3H-haloperidol receptor sites are localised to axons of cerebral cortical afferents whereas dopamine-sensitive adenylate cyclase is confined to neurones intrinsic to the striatum.

Slow axonal transport of neurofilament proteins: impairment of beta,beta'-iminodipropionitrile administration

Abstract: beta,beta'-Iminodipropionitrile (IDPN) administration prevented normal slow axonal transport of [35S]methionine- or [3H]leucine-labeled proteins in rat sciatic motor axons. Ultrastructural and electrophoretic studies showed that the neurofilament triplet proteins in particular were retained within the initial 5 millimeters of the axons, resulting in neurofilament-filled axonal swellings. Fast anterograde and retrograde axonal transport were not affected. The IDPN thus selectively impaired slow axonal transport. The neurofibrillary pathology in this model is the result of the defective slow transport of neurofilaments.

Tricyclic antidepressants: therapeutic properties and affinity for alpha-noradrenergic receptor binding sites in the brain.

Abstract: Tricyclic antidepressants vary in their capacity to cause psychomotor activation, to relieve agitated depressive states, and to cause sedation and hypotension. We have quantified relative potencies of tricyclic antidepressants in competing for the binding of 3H-labeled WB-4101 to alpha-noradrenergic receptor sites in rat brain membranes. Affinities of tricyclic drugs for alpha-noradrenergic receptor sites in the brain correlate well with the capacity of these agents to relieve psychomotor agitation and to induce sedation and hypotension; these affinities also correlate inversely with tendencies to elicit psychomotor activation.

The distribution and orientation of noradrenergic fibers in neocortex of the rat: an immunofluorescence study.

Abstract: A homologous antiserum directed against rat dopamine-β-hydroxylase (DBH) was employed in the indirect immunofluorescence technique of Coons ('58) to describe the distribution and orientation of noradrenergic (NA) axons in the cerebral neocortex of the adult albino rat. DBH is the terminal enzyme in the biosynthesis of noradrenaline and is a sensitive anatomic marker for NA neurons and their processes. Cryostat sections in three standard planes (coronal, sagittal and tangential) taken from four cortical fields (somatosensory, motor, visual and anterior cingulate) were processed for immunofluorescence, and adjacent sections were stained with a Nissl method to relate the pattern of NA axons to specific cortical laminae. Noradrenaline levels and DBH activity were measured in the same cortical fields by radioenzymatic assays. A rich network of DBH immunoreactive axons was observed throughout all cortical layers in each of the areas examined. The pattern of NA distribution is not diffuse, but is characterized by a geometric orderliness that is uniform throughout the neocortex, with only minor regional variations. In layer I the DBH-positive fibers are predominantly parallel to the pial surface and thus form a tangential grid-like pattern. Layers II and III are characterized by straight, radial fibers that rarely extend through layer IV to the infragranular layers. There appears to be a NA terminal field in layers IV and V where there is a network of short, oblique or tortuous axon segments, especially prominent in lateral neocortex. Layer VI is unique in that the prevailing orientation of NA fibers is in the anterior-posterior direction. This band of fibers does not extend into the sub-cortical white matter, where very few NA fibers are seen. The strong tangential projection of the NA neurons, particularly in layers I and VI, emerges as a dominant feature of this afferent system and appears to be superimposed on the predominantly vertical organization of the cortex. This tangential pattern of organization may allow the locus coeruleus to modulate the activity of adjacent columns synchronously over a vast expanse of cerebral cortex.

Neomycin-sorbitol and lactulose in the treatment of acute portal-systemic encephalopathy. A controlled, double-blind clinical trial.

Abstract: In a double-blind, randomized study the efficacy of lactulose was compared with neomycin-sorbitol in 45 episodes of acute nitrogenous portal-systemic encephalopathy (PSE) induced by dietary protein, azotemia, or gastrointestinal hemorrhage All patients had underlying cirrhosis, and at the time of randomization had encephalopathy of at least grade 2 severity and arterial ammonia concentrations greater than 150 microgram/100 ml Two thirds of the patients in each group returned to normal mental status and more than 80% in each group showed at least one grade improvement in mental state In addition, there was equivalent improvement in asterixis, in the performance of the Number Connection Test, in the electroencephalographic pattern, and in arterial ammonia concentration The principal difference between the two groups was a greater reduction in stool pH after lactulose therapy than after neomycin-sorbitol therapy One patient randomized to neomycin-sorbitol had to be withdrawn from the study because of persistent vomiting related to the administration of the medication Otherwise there were no complications attributable to therapy in either group These data suggest that neomycin-sorbitol and lactulose are equally effective in the treatment of acute nitrogenous portal-systemic encephalopathy

Brain mechanisms for directed attention.

Abstract: In his inaugural address of this series in 1957, Lord Adrian (Adrian 1957) elucidated the general conceptual approach used by Sherrington in his analysis of the function of the nervous system, and showed how in his long and productive scientific career Sherrington established the science of neurophysiology as we know it in the English-speaking world. Later lecturers (Denny-Brown 1962, Granit 1968, Whitteridge 1972) have illustrated through their own discoveries the continuing influence of Sherrington's ideas upon contemporary neuroscience. You will see from that which follows that I have taken a somewhat different approach in my research of recent years (Mountcastle et 0/. 1975, Mountcastle 1976, Lynch et 01. 1977). Nevertheless, I like to believe that Sherrington would have found something of interest in it. The experiments I shall describe have their conceptual origin in part in the studies of parietal lobe function in humans, particularly those studies of Holmes (1918, 1936), Critchley (1953) and Denny-Brown & Chambers (1958), and those of similarly perceptive neurologists who have followed them. Their clinical studies have led to the proposition that the parietal lobe of the cerebrum, together with its system connections, contains a neural apparatus which generates an internal neural image of the body position within the immediately surrounding behavioural space and the gravitational field, of the spatial relation between the body parts, of the direction of gaze and of visual attention, and of dynamic changes in these postural and attitudinal sets. It is the major theme of my lecture that this parietal lobe mechanism also receives signals concerning the internal state of the organism in terms of needs and interests, and from time to time generates commands for action, for selective and directed visual attention into the immediate behavioural surround, for the visual grasping ofobjects, and for skilled coordinated actions of hand and eye. On the afferent side this apparatus appears to be linked to the 'second' visual system, that which projects via the superior colliculus and pretectum to the dorsal thalamus and the parietal lobe, as well as to a relayed and convergent input from the geniculostriate system via the dorsal thalamus. This command apparatus of the parietal lobe appears to function less automatically than do more familiar ones linking input to output directly. It is conditional in nature, and depends for action upon the outcome of a matching function between the neural signals of the nature of objects quality, location, novelty and those of central drive states.

Progressive-ratio performance maintained by drug infusions: comparison of cocaine, diethylpropion, chlorphentermine, and fenfluramine.

Abstract: Cocaine, diethylpropion, chlorphentermine, and fenfluramine were compared on a drug-maintained progressive-ratio procedure in baboons. Intravenous infusions of drug were contingent on completion of a fixed-ratio response requirement (fixed number of lever-press responses) with a 3-h time-out period following each infusion. Prior to testing each dose of drug, stable self-infusion performance was first established with 0.4 mg/kg cocaine when the fixed-ratio requirement was 160. Subsequently, a test dose of drug was substituted for the standard dose of cocaine. If the dose of drug maintained a criterion level of self-infusion performance (six or more infusions per day for 2 days), the ratio requirement was systematically increased every day until the ‘breaking point’ at which the self-infusion performance fell below a criterion level (one or zero infusionsper day). Fenfluramine did not maintain criterion self-infusion performance at any dose tested (0.02–5.0 mg/kg). The dose ranges of the other drugs that maintained maximum breaking points were 1.0–5.6 mg/kg for chlorphentermine, 1.0–3.0 mg/kg for diethylpropion, and 0.1–0.4 mg/kg for cocaine. Within-animal comparison of the maximum breaking points indicated that cocaine maintained the highest breaking points, followed in order by diethylpropion, chlorphentermine, and fenfluramine. The rank ordering of these drugs with the breaking point measure corresponds well with both the results of other animal experiments on measurement of reinforcing efficacy of these drugs and with the clinical information about the human subjective effects and abuse of these drugs.

A new scale for assessing patients' psychosocial adjustment to medical illness

Abstract: The Psychosocial Adjustment to Illness Scale (PAIS) was administered to 37 Hodgkin's disease patients and 38 parents of children with Hodgkin's disease or solid tumour, and the scores were analysed for inter-rater reliability as well as construct and criterion validity. A significant inter-rater reliability coefficient was obtained for the total scale score, and also for 6 of the 7 subscale scores. The 7 subscale scores were shown to be relatively independent of each other, with 5 contributing strongly to the total score. Subscales analysed for criterion validity were shown to correlate significantly with independent assessments of their domains of adjustment. Results indicate that the PAIS can be administered by a diverse group of interviewers with an acceptable degree of reliability and with initial confidence in its validity.

Psychiatric disturbances in neurological patients: detection, recognition, and hospital course.

Abstract: The Mini-Mental State and General Health Questionnaire were used to detect cognitive defects and emotional disturbances, respectively, in 126 consecutively admitted neurological patients. The Mini-Mental State was revalidated in this sample as a measure related to cerebral disorder. Sixty-seven percent of the patients tested had cognitive defect, emotional disturbance, or both. Thirty percent of the patients with psychiatric disturbance were not recognized by their physician. The majority of psychiatric disturbances persisted at the time of discharge. Since psychiatric disturbances are common among neurological inpatients and are frequently unrecognized, further evaluation of the psychiatric training of neurologists is needed. Simple screening tests may help to increase the recognition of psychiatric disturbance. It is concluded that the Board requirement for neurologists to know psychiatry accurately reflects "the nature of their case material."

Quantitation by gas chromatography-chemical ionization mass spectrometry of cyclophosphamide, phosphoramide mustard, and nornitrogen mustard in the plasma and urine of patients receiving cyclophosphamide therapy.

Abstract: Cyclophosphamide, the widely used antitumour drug, is not itself toxic, but must be converted by microsomal metabolism to active metabolites. Despite an early understanding of the requirement for metabolic activation, the drug was used clinically for more than 10 years before the structures of any of its hepatic metabolites were elucidated. When the metabolites were finally isolated and identified, their characterisation rested heavily on mass spectral analysis (Bakke, Feil and Zaylskie, 1971; Colvin, Padgett and Fenselau, 1973; Struck et al., 1971). Subsequently mass spectrometry has been used in conjunction with stable-isotope labels to study the mechanism of alkylation of cytotoxic metabolites (Colvin et al., 1976) and for experiments with metabolic switching (Jarman et al., this volume pp. 85–95). Methodology has also been reported for assaying these cytotoxic metabolites using stable-isotope-labelled internal standards (Jardine et al., 1975, 1976; Jarman et al., 1975). In this report we will review the application of this methodology to assays of cyclophosphamide, phosphoramide mustard and nornitrogen mustard in blood and urine of patients, as well as in decomposition and protein-binding studies.

Long-term prognosis and followup in schizophrenia.

Abstract: The long-term course or natural history of schizophrenia is correlated with differing diagnostic criteria and commonly agreed upon prognostic variables. A review of 38 long-term followup studies of hospitalized schizophrenics reveals that unspecified or Kraepelinian-type schizophrenia has a much worse prognosis than atypical schizophrenia, schizoaffective psychosis, reactive psychosis, or other good premorbid types. Diagnoses based on longitudinal as well as cross-reactional data are more predictive of outcome than cross-sectionally based diagnoses. Drug and psychosocial treatment results must be evaluated in terms of prognostic variables, many of which are incorporated in some currently employed diagnostic criteria. There is no firm evidence that maintenance medication is indicated in some good prognosis patients. The paucity of long-range followups, the inadequacies of outcome assessments, and diagnostic disagreements limit our understanding of the effects of drug treatment, a treatment which is not without dangerous neurological side effects in many patients.

Survival of sucrose-loaded erythrocytes in the circulation

Abstract: IN an attempt to clarify the mechanism of cell lysis under intense electric fields1–5, we have found that aqueous pores are introduced into human erthrocyte membranes when an isotonic suspension of red cells is exposed to an electric field of a few kV cm−1 for a duration in μS range. These pores are formed when the transmembrane potential induced by the externally applied field exceeds a critical value of 1 V. The effective radius of the pores is several A, and can be varied by the adjustment of field intensity, field duration, and the ionic strength of the medium. The pores remain open at low temperatures but close completely on incubation at 37 °C. In a proper medium, the resealing of perforated cells takes place without haemolysis, allowing us to prepare erythrocytes (not ghosts) of altered intracellular composition. In particular, foreign molecules such as sucrose have successfully been incorporated into resealed erythrocytes, which were apparently intact at least in terms of cell volume, cell shape, glucose transport, and Na–K pump activity4. Thus we have suggested that erythrocytes loaded with a drug by this technique might serve as intravenous drug reservoirs which slowly release the drug molecules into the circulation. Here we demonstrate that erythrocytes loaded with sucrose survive in the circulation with a lifetime almost indistinguishable from that of normal cells, and that the sucrose remains entrapped within the cells. For drugs that slowly permeate the erythrocyte membranes, therefore, our technique offers a means of sustaining a low plasma level for a long period of time, and this could be advantageous in clinical and other situations.