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Biomedical subjects

M L Woodruff

Publications and source records attributed to M L Woodruff.

At least 19 recordsLinked to original sources
PubMed1992

Angiotensin II binding sites in the hamster brain: localization and subtype distribution.

This study was designed to characterize the distribution of angiotensin II (AII) binding sites in the hamster brain. Brain sections were incubated with [125I][sar1,ile8]-angiotensin II in the absence and presence of angiotensin II receptor subtype selective compounds, losartan (AT1 subtype) and PD123177 (AT2 subtype). Binding was quantified by densitometric analysis of autoradiograms and localized by comparison with adjacent thionein stained sections. The distribution of AII binding sites was similar to that found in the rat, with some exceptions. [125I][sar1,ile8]-angiotensin II binding was not evident in the subthalamic nucleus and thalamic regions, inferior olive, suprachiasmatic nucleus, and piriform cortex of the hamster, regions of prominent binding in the rat brain. However, intense binding was observed in the interpeduncular nucleus and the medial habenula of the hamster, nuclei void of binding in the rat brain. Competition with receptor subtype selective compounds revealed a similar AII receptor subtype profile in brain regions where binding is evident in both species. One notable exception is the medial geniculate nucleus, predominately AT1 binding sites in the hamster but AT2 in the rat. Generally, the AII binding site distribution in the hamster brain parallels that of the other species studied, particularly in brain regions associated with cardiovascular and dipsogenic functions. Functional correlates for AII binding sites have not been elucidated in the majority of brain regions and species mismatches might provide clues in this regard.

Angiotensin II↗
PubMed1992

Surface morphology of fetal neural transplants into the lateral ventricles after hippocampal lesions.

The surface morphology of transplants of rat fetal hippocampal tissue, and of cavities formed by aspiration lesion of the adult rat hippocampus and overlying neocortex into which the transplants were placed, was studied by scanning electron microscopy. The surface of lesion cavities was covered by a scar upon which occasional cellular profiles were found. The surface cells resembled supraependymal macrophages. Lesion cavities with a transplant showed similar scarring although the number of supraependymal structures was increased. Polymorphic cells and numerous fiber processes were observed both on the surface and embedded in the scar. Ependymal structures were seen on the non-damaged ventricular surfaces adjacent to the lesion site. These regions, however, also displayed increases in the number and types of supraependymal structures. Scanning electron microscopy demonstrated considerable variability in surface morphology of different transplants and over the surface of individual transplants. A transplant could show regions of scarring, areas covered by cells resembling ependymal cells, and regions covered by a dense matrix of fibers. In many regions the fibers coalesced to form a branching, web-like network over the transplant surface. Transmission electron microscopy indicated that the surface could be covered by ependymal cells or by the scar seen in scanning specimens. Some surface fibers were identified as axons. Cells on the surface of the transplants could be identified as neuronal, glial-like, and phagocytic. The cells and the possible effects of surface morphology on transplant function is discussed.

Animals↗
PubMed1992

Helix aspersa neurons maintain vigorous electrical activity when co-cultured with intact H. aspersa ganglia.

1. Identified neurons from the right parietal lobe of the circumoesophageal ganglion of adult land snails, Helix aspersa, were isolated and placed in primary cell culture. 2. The individual neurons were removed from the right parietal lobe by microdissection without the aid of exogenous enzymes and plated on poly-L-lysine coated coverslip in normal Helix Ringer's solution conditioned with Helix circumoesphageal ganglia. The neurons become firmly attached to the substrate and begin to extend processes within 6 hr. 3. The cells show a dramatic increase in electrical activity when they are co-cultured with intact Helix circumoesophageal ganglia (1 ganglion/ml). Co-cultured neurons have resting potentials between -45 and -110 mV, comparable to in situ, show spontaneous action potential firing and respond to putative neurotransmitters. Heat-treated conditioned media was inactive. 4. When dopamine or serotonin (5-HT) are added, right parietal beating neurons, F14-F16 and F29-F32, (i) show a suppression of action potentials occurrence; (ii) a decrease in action potential amplitude and duration, and (iii) an increase in after-hyperpolarization. 5. Right parietal bursting neuron F1 in culture fire action potentials only in a beating mode. Dopamine addition to F1 suppresses action potential occurrence and causes an increase in action potential after-hyperpolarization, but there is only a small decrease in duration of action potentials and no significant change in action potential amplitude. 5-HT addition to F1 increases the occurrence of action potentials with little or no change in action potential shape. 6. This primary cell culture method is an efficient system for doing biochemical and electrophysiological studies on individual, identified neurons.

Action Potentials↗
PubMed1992

Effects of transplantation of fetal hippocampal or hindbrain tissue into the brains of adult rats with hippocampal lesions on water maze acquisition.

Rats were given bilateral aspiration lesions of the hippocampus. Some of these rats then received bilateral transplants of fetal hippocampal or dorsal ventricular ridge tissue that was dissected from embryonic rat brains at 16 or 17 days of gestation. The remaining rats with hippocampal lesions did not receive fetal brain transplants. Rats with neocortical aspiration lesions, but without transplants, and rats without brain damage were also included in the study. All of the rats were trained to find a submerged platform in a Morris water maze. Rats with the fetal brain transplants were more impaired in some measures of maze learning than were rats with hippocampal lesions only. The results indicate that transplants of fetal brain tissue are not always associated with recovery of behavioral function after brain damage and may even increase a lesion-induced behavioral impairment in tasks that require complex cognitive functioning.

Animals↗
PubMed1991

Cobalt-dependent potentiation of net inward current density in Helix aspersa neurons.

A low concentration of transition metal ions Co2+ and Ni2+ increases the inward current density in neurons from the land snail Helix aspersa. The currents were measured using a single electrode voltage-clamp/internal perfusion method under conditions in which the external Na+ was replaced by Tris+, the predominant external current carrying cation was Ca2+, and the internal perfusate contained 120 mM Cs+/0 K+; 30 mM tetraethylammonium (TEA) was added externally to block K+ current. In the presence of Co2+ (3 mM) or Ni2+ (0.5 mM) inward Ca2+ currents were stimulated normally by voltage-dependent activation of Ca2+ channels. There was a 5-10% decrease in the rate of rise of the inward current. The principal effect of Co2+ and Ni2+ in increasing the current density seems to be a decrease in the rate at which the inward currents decline during a depolarizing voltage pulse. The results may be due to a decrease in a voltage-dependent or Ca(2+)-dependent outward current and/or an inhibition of Ca2+ channel inactivation. Outward current under these conditions (zero internal K+) was significant and most likely due to Cs+ efflux through the voltage-activated or Ca(2+)-activated nonspecific cation channels. Co2+ is an extremely effective blocker of this outward current. These results are not an artifact of internal perfusion or the special ionic conditions. Intracellular recording of unperfused neurons in normal Helix Ringer's solution showed that the Ca(2+)-dependent action potential duration was increased significantly by low concentrations of Co2+. This result is consistant with the Co(2+)-dependent increase in inward (depolarizing) current seen in voltage-clamp experiments.

Action Potentials↗
PubMed1991

Neurochemical anatomy of fetal hippocampus transplanted into large lesion cavities made in the adult rat brain.

The purpose of the present study was to determine whether neurochemicals normally found within neuron somata, fibers, and terminals of the hippocampal formation would also be present in transplanted hippocampal tissue that had developed in lesion cavities made in adult rat brains by aspiration of the hippocampus and overlying dorsolateral neocortex. Embryonic Day 15 or 16 rat brian tissue containing hippocampus with some medial pallial anlage was transplanted into the site of hippocampal aspiration lesions in adult male rats. One hundred ten to one hundred thirty-five days later the brains of these rats were sectioned and processed using the avidin-biotin-horseradish peroxidase immunocytochemical procedure to visualize choline acetyltransferase, met-enkephalin (MENK), neurotensin (NT), somatostatin, substance P, tyrosine hydroxylase (TH), or vasoactive intestinal polypeptide. Sections from two brains were stained using the thiocholine technique for visualization of acetylcholinesterase. All of these substances were found within cell bodies and/or fibers in the transplants. However, several abnormalities were noted. In addition to TH-immunoreactive fibers, TH-immunoreactive cell bodies were found in the transplants. Since TH is not expressed in mature hippocampal or cortical neurons this suggests that mechanisms for suppression of manufacture of this enzyme are lacking or inhibited in the transplants. Further, although all of the peptides were present either in fibers or in both cell bodies and fibers, the density of staining for NT and MENK was less than would be expected for normal hippocampus, and none of the cell bodies or fibers reacting for the peptides exhibited any apparent organization resembling that normally observed in hippocampus or cortex. However, some histological organization was present and the cholinergic markers were associated with this organization. These data suggest that some tropic and/or trophic factor such as nerve growth factor is present in the transplants to guide cholinergic innervation.

Animals↗
PubMed1991

Anatomical and behavioral sequelae of fetal brain transplants in rats with trimethyltin-induced neurodegeneration.

The effect of transplants of either fetal hippocampal or dorsal ventricular ridge (DVR) tissue into the brains of adult male rats exposed to TMT was determined for two behavioral tasks. Administration of TMT produced deficits in acquisition and performance of an operant differential reinforcement of low response rates (DRL) schedule and learning in the Morris water maze. The fetal transplants developed well within the TMT-damaged brains of the adult rats and numerous axons could be shown to cross the host-transplant interface. The transplants significantly reduced the DRL deficit produced by exposure to TMT. However, the TMT-induced deficit in water maze acquisition was made significantly worse by the hippocampal transplants. The improvement in DRL performance is attributed to the effect on the host brain of an unidentified trophic substance produced by the transplants. However, this positive effect may not protect the brain sufficiently to produce recovery in tasks demanding more complex neural computations than are required to withhold lever-press responses. The transplant-induced deficit observed in some aspects of water maze acquisition and performance may be attributable to either a tumor-like deleterious effect of the mass of the transplant or to abnormal neuronal activity transmitted from the transplant to the host brain. The results of the present study, and those from other similar studies, suggest that transplants of fetal tissue may be useful in producing changes in the brain of an animal exposed to an environmental neurotoxin, but that research should be focused upon development of transplant methodology that will minimize adverse effects of the grafts.

Animals↗
PubMed1990

The effects of stimulation of the A5 region on blood pressure and heart rate in rabbits.

The effects of stimulation of the A5 cell group of the caudal ventrolateral pons electrically or with L-glutamate on heart rate and blood pressure were determined in rabbits. Electrical stimulation caused blood pressure increases and reflex bradycardia. L-glutamate caused decreases in blood pressure and heart rate which were blocked by the L-glutamate antagonist aminophosphoheptanoic acid. Transection of the brainstem at the level of the midbrain did not alter the effects of either electrical or chemical stimulation. Lesions of the nucleus and tractus solitarius (NTS) attenuated the effects of L-glutamate, but did not change the effectiveness of electrical stimulation. Injections of 6-hydroxydopamine three to four weeks before the experiments blocked the effects of electrical stimulation but only reduced the effects of L-glutamate injection. The A5 group may have two functional subdivisions. Some A5 cells may produce blood pressure depressor and bradycardic effects by means of projections to the NTS and the spinal cord. Other A5 cells may produce blood pressure pressor effects by means of projections to the spinal cord.

Animals↗
PubMed1986

Inputs to the pontine A5 noradrenergic cell group: a horseradish peroxidase study.

The noradrenergic A5 cell group of the caudal ventrolateral pons has been implicated in regulation of cardiovascular activity. The efferent fibers from this cell group have been established, but the sources of afferents into the region have not. Horseradish peroxidase (HRP) was injected into the A5 region in rabbits, or into regions surrounding A5. The pattern of retrograde labeling indicated that several areas known to have a role in the control of cardiovascular function by the brain send projections to and/or through the A5 region.

Adrenergic Fibers↗
PubMed1979

Cerebellar nuclear lesions in rats: subsequent avoidance behavior and ascending anatomical connections.

Bilateral lesions of the rat cerebellar dentate and lateral interposed nuclei produced transient deficits in movement and posture, and facilitated acquisition of two-way active avoidance. Bilateral lesions of the fastigial and medial interposed nuclei of the rat cerebellum also produced transient deficits in movement and posture, but impaired acquisition of the avoidance task. Analysis of degeneration patterns after unilateral lesions to either the lateral or medial nuclear region indicated that the lateral area has a denser rostral projection than the medial area, while the medial nuclear region has a heavier caudal projection. It is suggested that these differences in anatomic connections may be related to the observed differences in lesion effect on two-way active avoidance.

Afferent Pathways↗
PubMed1979

Amplitude, kinetics, and reversibility of a light-induced decrease in guanosine 3',5'-cyclic monophosphate in frog photoreceptor membranes.

The concentration of guanosine 3',5'-cyclic monophosphate (cyclic GMP) has been examined in suspensions of freshly isolated frog rod outer segments using conditions which previously have been shown to maintain the ability of outer segments to perform a light-induced permeability change (presence of calf serum, anti-oxidant, and low calcium concentration). Illumination causes a rapid decrease in cyclic GMP levels which has a half-time approximately 125 ms. With light exposures that bleach less than 100 rhodopsin molecules in each rod outer segment, at least 10(4)-10(5) molecules of cyclic GMP are hydrolyzed for each rhodopsin molecule bleached. Half of the total cyclic GMP in each outer segment, approximately 2 X 10(7) molecules, is contained in the light-sensitive pool. If outer segments are exposed to continuous illumination, using intensities which bleach between 5.0 X 10(1) and 5.0 X 10(4) rhodopsin molecules/outer segment per second, cyclic GMP levels fall to a value characteristic for the intensity used. This suggests that a balance between synthesis and degradation of cyclic GMP is established. This constant level appears to be regulated by the rate of bleaching rhodopsin molecules (by the intensity of illumination), not the absolute number of rhodopsin molecules bleached...

Animals↗
PubMed1977

Epileptiform lesions in rat hippocampus and acquisition of two-way avoidance.

Three experiments were conducted to examine the effects on the acquisition of two-way active avoidance of implantation into the hippocampus of rats of two substances (aluminum hydroxide, penicillin) known to produce epileptogenic electrical discharges. In Experiment 1 bilateral deposits of aluminum hydroxide (ALOH) were placed in the hippocampus and the effects of this manipulation were compared to the effects of bilateral hippocampal aspiration. Sufficient postoperative time (130 days) was allowed such that epileptogenic discharges developed in the ALOH-implanted rats. Both bilateral hippocampal-ALOH deposits and bilateral hippocampal aspiration resulted in facilitated acquisition of the two-way avoidance. The results of Experiment 2 replicated this observation, but also indicated that bilateral hippocampal deposits of penicillin did not cause detectable effects on acquisition of the avoidance. Epileptiform activity produced by the penicillin was observed to disappear by postoperative Day 4. In Experiment 3 unilateral hippocampal aspiration was combined with contralateral implants of either ALOH or penicillin and avoidance training was begun 13 days postoperatively. Epileptiform activity was not observed in the ALOH-implanted rats and disappeared by postoperative Day 4 in the penicillin implanted rats. No significant changes were observed in the rate of acquisition of two-way active avoidance as a result of the manipulations done in Experiment 3. It is concluded that epileptiform discharge initiated focally within the hippocampus produces effects on the acquisition of two-way active avoidance which are similar to the effects produced by bilateral ablation.

Animals↗
PubMed1977

Guanosine 3',5'-cyclic monophosphate and the in vitro physiology of frog photoreceptor membranes.

Frog rod outer segments freshly detached from dark-adapted retinas contain approximately 1-2 molecules of guanosine 3',5'-cyclic monophosphate (cyclic GMP) for every 100 molecules of visual pigment present. This cyclic GMP decays to 5'-GMP, and the conversion is accelerated upon illumination of the outer segments. Bleaching one rhodopsin molecule can lead to the hydrolysis of 1,000-2,000 molecules of cyclic GMP within 100-300 ms. The decline in cyclic GMP concentration becomes larger as illumination increases, and varies with the logarithm of light intensity at levels which bleach between 5 X 10(2) and 5 X 10(5) rhodopsin molecules per outer segment-second. Light suppression of plasma membrane permeability, assayed in vitro as light suppression of outer segment swelling in a modified Ringer's solution, occurs over this same range of light intensity. The correlation between cyclic GMP and permeability or swelling is maintained in the presence of two pharmacological perturbations: papaverine, a phosphodiesterase inhibitor, increases both cyclic GMP levels and the dark permeability of the plasma membrane; and beta,gamma-methylene ATP increases the effectiveness of light in suppressing both permeability and cyclic GMP levels.

Animals↗
PubMed1976

Hyperemotionality and enhanced tonic immobility after septal lesions in the rabbit.

Large lesions of the septal region in the rabbit increased tonic immobility as measured by the number of successful inductions and by duration of immobility. Open field activity was also increased. Septally lesioned rabbits also exhibited increased emotionality, although the topography of the 'septal syndrome' in these rabbits was different from that described for rats. The septally lesioned rabbits exhibited increases in fear reactions such as thumping, escape responses and vocalization when caught, rather than increased aggressiveness. The results are discussed in terms of loss of inhibition of species-typical responses after septal damage.

Animals↗
PubMed1975

An economical operant space interface for the PDP-8 computer.

An inexpensive input/output transfer system between a PDP-8/1 Digital Equipment Corporation computer and two operant stations is described. An interrupt facility is included. Slight modification of this interface will also permit it to work with the newer PDP-8 series computers.

Animals↗