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Biomedical subjects

K Grant

Publications and source records attributed to K Grant.

At least 19 recordsLinked to original sources
PubMed1992

Sensory processing and corollary discharge effects in the mormyromast regions of the mormyrid electrosensory lobe. I. Field potentials, cellular activity in associated structures.

1. This is the first of a series of papers on the electrosensory lobe and closely associated structures in electric fish of the family Mormyridae. The study describes the neuronal responses to sensory stimuli and to corollary discharge signals associated with the motor command that drives the electric organ discharge (EOD). The study is focused on the regions of the electrosensory lobe where primary afferent fibers from mormyromast electroreceptors terminate. 2. This first paper of the series describes the field potentials in the caudal lobe of the cerebellum and in the electrosensory lobe. It also describes the different types of unit activity in the caudal lobe of the cerebellum. Granule cells of the caudal lobe of the cerebellum provide the parallel fibers for most of the molecular layer of the electrosensory lobe. Determination of the input and responses of these cells is therefore an important part of the effort to understand the electrosensory lobe. 3. Corollary discharge field potentials evoked by the EOD motor command are very prominent in the caudal lobe of the cerebellum and in the electrosensory lobe. The potentials indicate that corollary discharge excitation affects first the granule cells of the caudal lobe and then, a few milliseconds later, the deeper cellular layers of the electrosensory lobe. The prominence and complexity of the field potentials indicate that corollary discharge signals have an important and varied role in the processing of electrosensory information by the mormyrid electrosensory lobe. 4. The field potentials evoked by electrosensory stimuli suggest that direct primary afferent excitation is limited to the granule and intermediate layers of the electrosensory lobe, as is indicated also by anatomic studies. 5. Proprioceptive units are the most common type of unit recorded in the granule cell region of the caudal lobe of the cerebellum (eminentia granularis posterior). These units have a regular discharge rate that changes tonically in response to slight bending of the trunk, bending of the tail, or bending of individual fins. Proprioceptive input will have a strong effect on the molecular layer of the electrosensory lobe and will thus modulate the responses of electrosensory lobe cells to electrosensory stimuli. Such proprioceptive input to the electrosensory lobe would allow the expected effects of body position changes to be accounted for in the processing of electrosensory information. 6. Units with stereotyped, short-latency corollary discharge bursts to the EOD motor command were the next most common type of unit in the eminentia granularis posterior. These corollary discharge units were not affected by sensory stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

Sensory processing and corollary discharge effects in mormyromast regions of mormyrid electrosensory lobe. II. Cell types and corollary discharge plasticity.

1. This is the second of a series of papers on the electrosensory lobe and closely associated structures in electric fish of the family Mormyridae. The focus of the study is on the regions of the electrosensory lobe where primary afferent fibers from mormyromast electroreceptors terminate. 2. This second paper examines the responses of single cells in the mormyromast regions of the electrosensory lobe to electrosensory stimuli and to corollary discharge signals associated with the motor command that drives the electric organ to discharge. All recordings were extracellular. 3. Two major types of cells were identified: I cells, which were inhibited by electrosensory stimuli in the center of their receptive fields; and E cells, which were excited by such stimuli. 4. I cells and E cells shared a number of common features. Both types could have small receptive fields limited to only a few electroreceptors (3-5), and both types were markedly affected by the corollary discharge of the electric organ discharge (EOD) motor command. Cells of both types also showed clear plasticity in their responses to the corollary discharge or to the corollary discharge plus a stimulus. 5. I cells could be subdivided into three subtypes, I1, I2, and I3, on the basis of corollary discharge responses in the absence of sensory stimuli. I1 and I2 cells showed consistent corollary discharge bursts with little or no additional activity beyond the duration of the burst. The corollary discharge bursts of I1 cells were more stereotyped and of shorter latency than those of I2 cells. I3 cells had more spontaneous activity than I1 or I2 cells and minimal cells had more spontaneous activity than I1 or I2 cells and minimal corollary discharge responses in the absence of sensory stimuli. Field potentials indicated that all three subtypes of I cells were recorded in or near the ganglion layer of the electrosensory lobe. 6. Corollary discharge responses were plastic and depended on recent pairing of a sensory stimulus with the EOD motor command. Such plasticity was clearer in I2 and I3 cells than in I1 cells. Inhibitory sensory stimuli were paired with the EOD motor command for periods of a few seconds to several minutes. Such pairing resulted in a marked enhancement of the corollary discharge response in I2 cells, as shown by examining the effect of the motor command after turning off the stimulus. In I3 cells, such pairing resulted in a clear corollary burst to the command at the time of the previously paired inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Vasculitis with eosinophilia and digital gangrene in a patient with acquired immunodeficiency syndrome.

Fewer than 40 cases of vasculitis have been described in the setting of human immunodeficiency virus infection. We describe a patient with the acquired immunodeficiency syndrome (AIDS), a heavy smoker, who developed a syndrome of constitutional symptoms, eosinophilia and digital gangrene. Vasculitis of the digital arteries was documented by angiography. He responded to high dose corticosteroid therapy with arrest of the ischemic process. After steroids were discontinued, he suffered a relapse of the vasculitis documented by skin biopsy. In patients with AIDS with this serious, potentially steroid responsive condition, steroid therapy should be considered in spite of the preexisting immunodeficiency state.

Acquired Immunodeficiency Syndrome↗
PubMed1991

A randomized controlled trial of nursing home and long-stay geriatric ward care for elderly people.

This paper reports outcome data on mental and physical ability levels, mortality and accident rates, from a randomized controlled trial evaluating health authority funded nursing home and long-stay geriatric ward care in one inner London health district. There were no differences between settings in mortality rates, although respondents randomized to the nursing homes deteriorated more rapidly in overall, mental and functional ability levels. Previous analyses reported that they also experienced a higher accident rate than respondents in the wards. However, observational data from the evaluation clearly indicated that quality of life in the homes was superior to that in the wards. We conclude that the more rapid physical decline and greater risk of accident in the nursing homes have to be balanced against an inferior quality of life in the hospital, and that a judgement is not easy to make on behalf of other people.

Accidents↗
PubMed1979

[Oculomotor reflex evoked by vibrassae stimulation in the cat].

The oculomotor effects of vibrissae stimulation have been studied in the "encéphale isolé" non-anaesthetized Cat. Intracellular recording of lateral rectus motoneurones showed an excitatory projection via the ipsilateral infraorbital nerve to these motoneurones. The afferent fibers are type A alpha, recuited with a low threshold (0.2-0.5 mA) and convey information about vibrissae displacement.

Afferent Pathways↗
PubMed1979

[Interaction between the vestibulo-ocular and the oculomotor systems].

Optomotor nystagmic activity has been elicited in the "encéphale isolé" cat during repetitive electric stimulation of selective oculomotor regions of the frontal cortex and superior colliculus. These regions were nystagmogenic only when facilitated by a cortical arousal or a vestibular activation.

Animals↗
PubMed1979

Anatomical and electrophysiological identification of motoneurones supplying the cat retractor bulbi muscle.

Motoneurones innervating the retractor bulbi muscle in the cat have been identified by retrograde labelling with horseradish peroxidase, by intracellular recording and by intracellular staining with horseradish peroxidase. Their somata are found in an accessory abducens nucleus, analogous to that described in some other species, which consists of a narrow column of cells situated in the lateral tegmental reticular field, above the superior olive and medial to the facial nerve. The column of cells extends over approximately 1.5 mm from P 5.5 to P 7. The retractor bulbi motoneurones number from 80 to 120 and have large, elongated somata which give rise to five or six major dendrites. Their axons cross the reticular formation in a dorso-medial direction to pass through the principal abducens nucleus before turning to leave the brain stem in the 6th nerve. Antidromic latencies ranged from 0.4 to 0.7 ms. Some retractor bulbi motoneurones could also be activated antidromically by stimulation of the lateral rectus muscle nerve.

Abducens Nerve↗
PubMed1979

Morphological characteristics of lateral rectus motoneurones shown by intracellular injection of HRP.

The morphology of identified lateral rectus motoneurones is described after staining by intracellular iontophoresis of horseradish peroxidase. Soma vary in shape and size according to the number and orientation of primary dendrites. The basic pattern of arborisation shows short primary dendrites which branch close to the soma, forming a distal ramification extending over 600 to 1,200 micrometer from the soma. Distal dendrites extend into the ipsilateral medial vestibular nucleus, the reticular formation and amongst the fibres of the medial longitudinal fasciculus. This extension is greater than that previously seen in procion yellow and Golgi stained lateral rectus motoneurones. The axon originates from the perikarya or from the base of a primary dendrite. No axon collaterals have been observed.

Abducens Nerve↗
PubMed1978

Altered factor VIII complexes in patients with acute respiratory insufficiency.

Acute respiratory failure is an often-fatal syndrome of multiple etiologies in which altered factor VIII may be a marker of endothelial disease. 12 women with overwhelming viral pneumonia were studied with serial factor VIII antigen, procoagulant activity, and von Willebrand's factor assays. Antigen levels were elevated (range: 86--1644%) out of proportion to procoagulant activity (range: 35--521% by a one-stage assay), and factor VIII antigen to activity ratios were as high as 16:1. Von Willebrand's factor was normal but correlated best with procoagulant activity. All patients had abnormal antigen patterns on crossed immunoelectrophoresis, with increases in protein of both fast and slow mobility. These changes in factor VIII correlated with the patient's clinical courses.

Acute Disease↗
PubMed1978

Comparison of quinestrol and Tace for relief of postpartum breast discomfort.

A single 2-mg dose of quinestrol was demonstrated safe and effective for controlling postpartum lactation and for alleviating breast discomfort. A double-blind comparison to Tace 72 mg every 12 hours for 2 days, and to placebo, was made in 134 patients. The single oral dose of quinestrol showed efficacy equal to the 2-day regimen of Tace. Both were superior to placebo.

Adolescent↗
PubMed1978

A practical method of antimicrobial surveillance.

This antimicrobial surveillance program clearly relates inpatient antimicrobial usage to therapeutic or prophylactic indications. One nurse-epidemiologist gathers data for a medium-sized Veterans Administration hospital, in addition to carrying out infection surveillance and educational responsibilities, and reviews the data weekly with an infectious disease physician. Usage of antimicrobials for surgical prophylaxis is the area where violations of generally accepted criteria for usage can be most readily documented. Only 31% of usages were deemed appropriate. A similar percentage (about 65%) of antimicrobial usages were judged "appropriate" on the medical and surgical services in treatment of wound and urinary tract infection. Treatment of respiratory tract infection and sepsis was judge "appropriate" in over 85% of instances on the medical service. These categories contained too few cases to summarize on the surgical service.

Aminoglycosides↗
PubMed1976

Horizontal vestibular nystagmus. I. Identification of medial vestibular neurones.

1. The properities of inputs from the horizontal semi-circular canal to neurones of the medial vestibular nucleus have been studied intracellularly in the unanaesthetized encéphale isolé cat. 2. Secondary neurones of the bestibulo-abducens reflex arc were identified by their orthodromic response to labyrinthine stimulation and by antidromic excitation from the contralateral abducens nucleus. 3. The responses of medial vestibular cells receiving only labyrinthine in puts are also described. These were seen to be predominantly excitatory though IPSPs were observed in a few cases. 4. Identified vestibular neurones were intracellularly injected with procion yellow and showed different morphological characteristics correlated with function.

Abducens Nerve↗
PubMed1976

Horizontal vestibular nystagmus. II. Activity patterns of medial vestibular neurones during nystagmus.

1. Identified medial vestibular neurones were studied before, during and after nystagmogenic labyrinthine stimulation in the Encéphale isolé cat. Motor discharges were simultaneously recorded from the contralateral abducens nerve. 2. 87.9% of the recorded neurones showed changes in tonic firing frequency during repetitibe labyrinthine stimulation with no nystagmic modulation in behaviour. 3. The secondary vestibular neurones projecting monosynaptically to the contralateral abducens motoneurones were included in this non-rhythmic population. 4. Only 2% of the recorded population fired rhythmically both during nystagmogenic stimulation and poststimulation nystagmus. These neurones showed plasticity in behaviour regarding the phases of nystagmus recorded from the contralateral abducens nerve. 5. The remaining 10.1% of the medial vestibular neurones were excited or inhibited by repetitive stimulation of the labyrinth but showed burst firing pattersn correlated with poststimulation nystagmic discharges.

Abducens Nerve↗
PubMed1975

Effect of trimethoprim-sulfamethoxazole on blood insulin and glucose concentrations of diabetics.

Trimethoprim-sulfamethoxazole (TMP-SMX) caused no significant changes in the blood glucose or insulin concentrations of diabetic subjects treated by dietary measures alone or by insulin and diet. In only one of eight subjects receiving oral hypoglycemic agents for the control of diabetes did a significant immediate increase in immunoreactive insulin follow administration of TMP-SMX. In the same patient hypoglycemic symptoms were present after the agent had been taken for 14 days.

Administration, Oral↗