Biomedical subjects

J E Hoover

Publications and source records attributed to J E Hoover.

8 recordsLinked to original sources

PubMed1994

Input to the primate frontal eye field from the substantia nigra, superior colliculus, and dentate nucleus demonstrated by transneuronal transport.

The purpose of these experiments was to study the subcortical input to the frontal eye field (FEF) and to determine which subcortical structures might project to the FEF via pathways that contain only a single intervening synapse. We used retrograde transneuronal transport of herpes simplex virus type 1 (HSV-1) to label second-order neurons that send information to the FEF of cebus monkeys. The saccade region of the FEF was identified physiologically using intracortical stimulation and then injected with a strain of HSV-1 known to be transported transneuronally in the retrograde direction. Retrograde transport of virus labeled neurons was observed in all the thalamic sites known to innervate the FEF. In addition, we found neurons labeled by transneuronal transport in three subcortical sites: the pars reticulata of the substantia nigra, the optic and intermediate gray layers of the superior colliculus, and a posterior portion of the dentate nucleus of the cerebellum. Each of these sites has been shown in prior studies to project to thalamic regions that innervate the FEF. Moreover, the neurons labeled through transneuronal transport were located in a subregion of each subcortical site that is known to be involved in oculomotor control. These observations demonstrate that signals from the substantia nigra, superior colliculus and dentate nucleus can have a significant influence on the output of the FEF.

Animals↗

PubMed1993

Multiple output channels in the basal ganglia.

The neural circuits that link the basal ganglia with the cerebral cortex are critically involved in the generation and control of voluntary movement. Retrograde transneuronal transport of herpes simplex virus type 1 was used to examine the organization of connections in the cebus monkey between an output nucleus of the basal ganglia, the internal segment of the globus pallidus (GPi), and three cortical areas: the primary motor cortex, the supplementary motor ara, and the ventral premotor area. Spatially separate regions of the GPi were labeled after virus injections into each cortical area. The GPi projects to multiple cortical motor areas, and this pallidal output is organized into discrete channels. This information provides a new anatomical framework for examining the function of the basal ganglia in skeletomotor control.

Animals↗

PubMed1992

Retrograde labeling of lumbosacral interneurons following injections of red and green fluorescent microspheres into hindlimb motor nuclei of the cat.

In order to map the laminar and segmental positions of lumbosacral interneurons that project to L7 motor nuclei, red and green fluorescent latex microspheres ("beads") were pressure-injected through micropipettes into the deep peroneal or posterior biceps-semitendinosus motoneuron pools of cats. Micropipette tips were positioned by recording the antidromic field potentials evoked by electrical stimulation of the muscle nerves. Projecting interneurons were identified by the presence of retrogradely transported beads. Small bead injections labeled large numbers of neurons. These were observed in all the spinal segments examined, L1-S2, and were most densely concentrated within laminae VI and VII ipsilateral to the injections and lamina VIII contralaterally. In addition, significant numbers of labeled cells were observed in lateral lamina V ipsilaterally and in lamina X. A few cells with bilateral projections were double-labeled following injections of red and green beads on opposite sides of the cord. These were most often observed in midlumbar segments (L3-L5) in medial regions of the gray matter. The results suggest that the intermediate zone (laminae V-VIII and X) of the lumbosacral spinal cord is a major source of interneuronal projections to the L7 ventral horn. This is true for both lateral and medial areas of the intermediate zone, as the fluorescent microspheres labeled neurons in medial regions of the cord largely undetected in previous studies in which other methodologies were employed.

Animals↗

PubMed1991

Morphological relationships among extensor digitorum longus, tibialis anterior, and semitendinosus motor nuclei of the cat: an investigation employing the retrograde transport of multiple fluorescent tracers.

To determine the morphological relationships among extensor digitorum longus (EDL), tibialis anterior (TA), and semitendinosus (St) motor nuclei in the spinal cord of the cat, these nuclei were retrogradely labeled with three different fluorescent tracers. The fluorochromes--bisbenzimide, nuclear yellow, and propidium iodide--were applied by intramuscular injection or soaking the muscle nerve. The positions of the labeled motor nuclei were bilaterally symmetrical. The EDL and TA motoneurons were located in close proximity to one another, in the lateral regions of lamina IX in spinal segments L6 and L7. Although the boundaries of each nucleus were tightly opposed, the EDL and TA motor nuclei overlapped minimally, with the somata of EDL motoneurons positioned dorsal to those of TA. The St motor nucleus was located ventromedial to that of EDL and extended from the caudal portion of L6 through S1. Supplemental studies of the reflex effects evoked in EDL, TA, and St muscles by cutaneous nerve stimulation provided physiological observations that may be related to these anatomical results.

Animals↗

PubMed1989

Retention of a backward classically conditioned reflex response in spinal cat.

Retention of a backward classically conditioned reflex response was investigated in the spinal cat preparation. Facilitation of the flexion reflex was induced by the pairing of superficial peroneal nerve stimulation (30 Hz, 0.5 s), the US (unconditioned stimulus), with saphenous nerve stimulation (10 Hz, 1.5 s), the CS (conditioned stimulus). Both the US and CS were supramaximal for activation of A delta cutaneous afferent fibers. Experimental animals received 30 paired trials (US preceded CS by 0.25 s) with an intertrial interval (ITI) of three min. Control animals received the same stimuli but in an explicitly unpaired manner. Following acquisition, all animals received 30 additional CS-alone trials at five min intervals. This paradigm, which incorporated ITIs longer than those which had been used previously in backward conditioning studies, induced a long-lasting potentiation of the flexion reflex which appeared to be specific to spinal reflex pathways activated by A alpha cutaneous fibers. The relevancy of these results to a more specific understanding of backward and forward classical conditioning in the spinal cat is discussed.

Action Potentials↗

PubMed1979

Effects of urine from pregnant and lactating female house mice on sexual maturation of juvenile females.

The effects of urine from pregnant and lactating female/mice on puberty in young females were examined. In Experiment I urine from pregnant or lactating females painted daily on the external nares of young females led to earlier sexual maturation than treatment with water or urine from singly-caged, nonlactating, multiparous adult females. In Experiment II urine from either pregnant or lactating females, injected daily into perforated plastic capsules containing cotton, effected earlier maturation in female mice caged with these capsules than did the urine of singly-caged females or water. In Experiment III the effectiveness of these treatments on reproduction per se was confirmed: young females reaching maturity earlier as the result of urine treatments were in fact ovulating and were capable of conceiving and bearing young. One explanation for the presence of the urinary pheromone(s) involves changes in hormone levels during pregnancy and/or lactation and urinary excretion levels of hormones, hormone metabolites, or chemical compounds which are hormone dependent. The pheromone excretion, triggered by external factors, may be a general signal to other females that environmental and/or social conditions are favorable for reproductive activities.

Animals↗

PubMed1979

Effects of urine from pregnant and lactating female house mice on oestrous cycles of adult females.

It was demonstrated that mice treated with urine from pregnant or lactating females experienced longer periods of oestrus than did mice treated with water or urine from singly caged females. Application of urine by means of perforated capsules placed in the cage of the test mouse showed that the factor(s) responsible for the longer periods of oestrus was an airborne pheromone. The females experiencing longer oestrous periods ovulated (ova in oviducts), became pregnant and gave birth.

Animals↗

PubMedDate not supplied

Keeping abreast.

Explore the source record for details and available documents.

Periodicals as Topic↗