Biomedical subjects

V D Douglas

Publications and source records attributed to V D Douglas.

7 recordsLinked to original sources

PubMed1999

Measurement of urinary N-acetyl-beta-D-glucosaminidase to assess renal ischemia during laparoscopic operations.

BACKGROUND: Oliguria during laparoscopy is a well-documented phenomenon of unknown etiology. Experimental evidence suggests that renal perfusion is reduced during pneumoperitoneum. N-acetyl-beta-D-glucosaminidase (NAG), which is present in renal tubular cells, is released into the urine in response to tubular insults. In this study, urinary NAG was measured before and after procedures to assess for ischemic renal injury. METHODS: A total of 31 patients underwent laparoscopic procedures while 28 patients had conventional surgery. Urine was obtained first at the time of preoperative Foley catheter placement and later during the recovery room stay. NAG levels were measured and indexed to urinary creatinine. RESULTS: Operative time for the laparoscopy group was 105 min (range, 15-255); for the conventional group, it was 179 min (range, 75-385) (P < 0.05). No differences were noted between pre- and postoperative NAG levels or between the groups. There was no correlation between urinary NAG levels and operative time. CONCLUSION: Pneumoperitoneum is not associated with a change in the urinary concentration of NAG. This finding suggests that there is no significant renal tubular injury associated with laparoscopic surgery.

Acetylglucosaminidase↗

PubMed1998

Propriospinal neurons in the C1-C2 spinal segments project to the L5-S1 segments of the rat spinal cord.

Physiological studies indicate that neurons in the upper cervical spinal cord have descending projections to the lumbosacral spinal cord and mediate inhibition of dorsal horn neurons activated from afferent input. In the present study, retrograde tracing techniques were used to examine the distribution of propriospinal neurons in C1-C2 spinal segments that project to lumbosacral spinal segments. Fluorogold or horseradish peroxidase were injected unilaterally or bilaterally into the L5-S1 spinal segments. After 2-4 days, rats were perfused with fixative and C1-C2 spinal segments were processed for retrograde labeling. Numerous neurons were found in the C1-C2 segments. In unilaterally and bilaterally injected rats, retrogradely labeled neurons were located on both the ipsilateral and contralateral sides. Retrogradely labeled neurons were located in the following locations: lateral cervical and spinal nuclei, nucleus proprius, ventral horn and the central gray region (area X). These studies demonstrate a descending projection from C1-C2 segments to the lower lumbar and sacral spinal cord. We hypothesize that many of these C1-C2 propriospinal neurons are important in modulating responses of spinal neurons at lower segmental levels to various peripheral stimuli.

Animals↗

PubMed1993

Glutaminase immunoreactive neurons in the rat dorsal root ganglion contain calcitonin gene-related peptide (CGRP).

The co-localization of glutaminase and calcitonin gene-related peptide (CGRP) was examined with immunohistochemistry in the rat dorsal root ganglion (DRG). The majority of the DRG neurons were immunoreactive for glutaminase and all DRG neurons that contained CGRP also contained glutaminase. These results indicate that some DRG neurons release glutamate and CGRP from the same axon terminals in the spinal cord. Co-release of glutamate and CGRP from primary afferents may have multiple effects including fast and slow neurotransmission of sensory information in the spinal cord.

Animals↗

PubMed1991

Relationships between sensory responsiveness and premovement activity of quickly adapting neurons in areas 3b and 1 of monkey primary somatosensory cortex.

When monkeys make wrist movements in response to vibration of their hands, primary somatosensory (SI) cortical neurons that adapt quickly to the vibratory stimulus often exhibit two temporally separate types of activity. Initially, these neurons respond to the stimulus. They then cease discharging, only to resume firing prior to the movement. This activation, cessation and reactivation occurs even though the sensory stimulus remains on until after the movement is begun. The first change in activity is most likely related to sensory input. The second, which has been called premovement activity, may have a sensory component as well as one related to the upcoming movement. We wanted to test the hypothesis that the premovement activity exhibited when vibration is present represents both a reactivation of a neuron's vibratory response and the premovement activity that normally occurs when vibration is absent. We also wanted to determine if area 3b and 1 quickly adapting (QA) neurons show similar or different activity patterns during the initiation and execution of sensory triggered wrist movements. Four monkeys were trained to make wrist flexion and extension movements in response to vibratory stimuli delivered to the handle which the animals used to control the behavioral paradigm. Two fo the four monkeys also made similar wrist movements following visual cues. We found that the premovement activity of QA neurons located in area 1 (but not area 3b) is comprised of a sensory-related component as well as a movement-related component. The magnitude of these individual components differs in relationship to a neuron's receptive field type, the movement direction and the external force imposed on the stimulated forelimb. Premovement activity of area 3b and area 1 QA neurons occurs at the same time prior to movement, regardless of whether visual or vibratory cues are used to trigger wrist movements. This activity occurs at about the same time as others have observed elevations in the threshold for tactile perception, suggesting that premovement activity and changes in sensory responsiveness before movement may be related. These and previous findings are used to construct a model which may predict the firing patterns of SI QA neurons during behavioral tasks. These findings also suggest that areas 3b and 1 may have different roles in processing task-related somatosensory information.

Animals↗

PubMed1991

Sensory response enhancement and suppression of monkey primary somatosensory cortical neurons.

Vibratory stimulus-related responses were recorded from monkey primary somatosensory cortical (SI) neurons while animals performed two tasks. In the movement task, vibratory stimuli served as the go-cue for wrist flexion or extension. In the no-movement task, movements normally made in response to vibratory stimuli were extinguished. Area 3a, 3b, and 1 neurons with deep receptive fields (RFs) exhibited greater stimulus-related activity during the movement task than during the no-movement task. Area 3b neurons with cutaneous RFs were similarly enhanced during the movement task, whereas area 1 neurons with cutaneous RFs were less responsive to vibratory stimuli during the movement task. These results suggest that motor-set and/or selective attention may modulate the responsiveness of SI neurons to peripheral stimuli and that changes in sensory responsiveness in SI neurons differ as a function of their cortical location and RF type.

Animals↗

PubMed1990

Reaction times for hand movements made in response to visual versus vibratory cues.

Reaction times were determined for monkeys and humans who made wrist flexion and extension movements in response to vibratory and visual cues. Humans initiated movements approximately 50 msec sooner in response to vibratory as compared to visual cues. For monkeys, this difference was approximately 100 msec. Mean daily reaction times for monkeys and humans improved with practice until they reached a steady level of performance. Increased differences between vibratory and visual reaction times were weakly correlated with increased age of humans. The increase in the differences appeared to result from decreased reaction times by older subjects for vibratory-cued movements; reaction times for visually cued movements did not consistently vary across the age range of subjects tested (19-36 years). The results obtained using this novel paradigm suggest that it may be a useful tool for simultaneously testing behavioral performance or neurological function during somatosensorimotor and visuomotor tasks.

Adult↗

PubMed1989

Changes in premovement activity in primary somatosensory cortex differ when monkeys make hand movements in response to visual vs vibratory cues.

Rhesus monkeys were taught to make identical wrist flexion and extension movements in response to either a visual cue or to vibratory cues. Changes in firing rates that were not stimulus-associated but preceded the movements were measured for each primary somatosensory cortical neuron recorded under the two stimulus cued conditions. The onset of the premovement activity changes and the magnitude of these changes differed when visually cued trials were compared with vibratory cued trials that resulted in the same behavioral response. In general, the magnitudes of premovement activity changes were less and the onset of these changes occurred earlier for vibratory cued trials than for the corresponding trials triggered by the visual stimulus. These findings support the hypothesis that centrally generated modulatory influences arriving at primary somatosensory cortical neurons prior to movement onset may differ, depending upon the modality of the stimulus which signals that a movement may be initiated.

Animals↗