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C M Owens

Publications and source records attributed to C M Owens.

9 recordsLinked to original sources
PubMed1992

Changes in the response states of primate spinothalamic tract cells caused by mechanical damage of the skin or activation of descending controls.

1. The responses of a population of 318 spinothalamic tract (STT) cells to mechanical stimulation of the skin were recorded in anesthetized macaque monkeys by several teams of investigators. The responses were subjected to k-means cluster analysis, a multivariate statistical procedure. 2. For an analysis that pertained to the responsiveness of the neurons, the mean responses to four standard mechanical stimuli (Brush, Pressure, Pinch, and Squeeze) were used. Although no true clusters were found, the cells could be partitioned into four groups (called clusters a, b, c, and d) that responded progressively more vigorously to the stimuli. 3. For an analysis that pertained to the selectivity of the cells for various stimulus intensities, from innocuous to highly noxious, the data were normalized by taking the ratio of the mean response evoked by each stimulus to the sum of the responses and multiplying by 100. This procedure does not have a bias toward selection of any particular number of clusters and resulted in three clusters of STT cells. 4. Cluster 1 STT cells responded best to Brush. Cluster 2 cells responded weakly to Brush and Pressure and maximally to Pinch. Cluster 3 cells responded weakly to Brush, Pressure, and Pinch and maximally to Squeeze. 5. The response states of STT cells with respect to mechanical stimulation of the skin can be defined by their cluster assignments on the basis of the responsiveness (clusters a-d) and selectivity (clusters 1-3) of the cells. The response states of newly recorded STT cells can be determined by discriminant analysis from the nearest centroids of the two types of clusters in the reference population of STT cells. 6. No consistent changes in response state were detected when a second series of mechanical stimuli was applied 1 cm from the site stimulated initially or when the stimulus series was alternately repeated at the initial site and at progressively more proximal sites. However, when the stimulus series was applied five times to the initial site, the response state of five of eight cells tested showed a change. Although a change in response state required repetitive damage, even a single stimulus series increased background activity and responses to Brush at undamaged sites. 7. The background activity and responses to Brush and Pressure of all five STT cells recorded in the superficial laminae increased after repeated testing. The background activity of five STT cells recorded in the nucleus proprius also increased, but the responses of only three of the cells to Brush and Pressure increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Case report: splenic infarction and acute splenic sequestration in adults with hemoglobin SC disease.

While acute splenic sequestration and splenic infarction are commonly observed in infants and young children with sickle cell anemia, they are rarely experienced by adult hemoglobin S homozygotes because the recurrent splenic infarction that takes place during childhood is typically followed by scarring, atrophy, and splenic fibrosis. Both acute splenic sequestration and splenic infarction do remain relatively common in adults with the other sickle hemoglobinopathies. These episodes are almost certainly a consequence of the persistently enlarged and distensible spleens that often remain present in these conditions. In this report, the authors describe two adult patients with hemoglobin SC disease: one who developed acute splenic sequestration and one with splenic infarction. In neither case was there a history of recent air travel or exposure to altitude. The clinical course of these two syndromes is presented, and the hematologic, radiologic, and pathologic manifestations are discussed. Because they can sometimes be difficult to distinguish from one another, and because a failure to identify acute splenic sequestration can be catastrophic, these two entities must be included in the differential diagnosis for any hemoglobin SC patient who present with an unexplained fall in hemoglobin, left upper quadrant pain, unexplained fever, or symptomatic splenomegaly.

Acute Disease↗
PubMed1991

Intracellular study of electrophysiological features of primate spinothalamic tract neurons and their responses to afferent inputs.

1. Intracellular recordings were made from 43 spinothalamic (STT) neurons in the lumbosacral region of the spinal cord in anesthetized macaque monkeys. The antidromic responses of these neurons to electrical stimulation of the ventral posterior lateral (VPL) nucleus of the thalamus were examined, and orthodromic responses to electrical stimulation of the sural nerve or to mechanical stimulation of hindlimb skin were recorded to study the electrophysiological features of these neurons and their responses to afferent inputs. 2. The resting membrane potential of the neurons ranged from -26 to -70 mV and the antidromic latency from 2.3 to 9.1 ms. Three of the neurons were located in lamina 1 and were recorded so briefly that only antidromic and spontaneous activity could be studied. The rest of the neurons were located in laminae III-V and were of the wide-dynamic-range (WDR) type. 3. The antidromic action potentials recorded in the somas of STT neurons typically showed a fast rising phase and a short initial segment-somadendritic (IS-SD) delay. After repetitive antidromic stimulation, a progressive elongation of the IS-SD delay, widening of the spike, and failure of the SD spike were observed. 4. The afterpotential of the antidromic action potential consisted of a fast afterhyperpolarization (AHPf) and sometimes a delayed depolarization (DD) and a slow afterhyperpolarization (AHPs). The amplitude and the duration of the AHPs were progressively increased when longer trains of stimuli were used. When the membrane potential was hyperpolarized, the amplitude of the AHPs decreased, suggesting an involvement of K+ and/or Cl- ions. However, the AHPs completely disappeared when the strength of stimulation was adjusted to a level just below the threshold for the axon, suggesting that it was unlikely that recurrent inhibition contributed to the AHPs. 5. The background activity of 32 STT neurons was analyzed. The membrane potential at which spikes were triggered in these neurons was around -42 mV. The width and the rise time of the spontaneous spikes were shorter than those of antidromic action potentials, although the maximum rate of rise was similar. The heights of the spontaneous spikes were slightly shorter than those of antidromic action potentials. 6. Three types of background activity have been observed. One type had a very low average spontaneous rate with a bursting firing pattern, consisting of a few spikes superimposed on a depolarization. This type of activity was seen mostly in lamina I neurons. The second type of activity had a moderate to high spontaneous rate with a fairly constant interval between spikes.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

Two forms of inhibition of spinothalamic tract neurons produced by stimulation of the periaqueductal gray and the cerebral cortex.

1. Recordings were made from the lumbosacral spinal cord in anesthetized macaque monkeys. The inhibitory effects of electrical stimulation of the periaqueductal gray (PAG) and the cerebral cortex or cerebral peduncle (CP) were tested and compared by recording 1) cord dorsum potentials evoked by stimulation of the sural nerve, 2) discharges recorded extracellularly, and 3) membrane potentials recorded intracellularly from spinothalamic tract (STT) neurons at rest (background activity) or in response to stimulation of the sural nerve. 2. Stimulation of the cortex or in the CP preferentially reduced the amplitude of the N1 and N2 waves of the cord dorsum potential evoked by stimulation of the sural nerve, without affecting the N3 wave. Stimulation of the PAG, on the other hand, reduced the amplitude of the N3 wave with little effect on the N1 and N2 waves. 3. The activity of 62 STT neurons was recorded extracellularly. Stimulation of the PAG or the cortex/CP inhibited nonpreferentially the responses of the neurons in the superficial laminae to all afferent inputs. On the other hand, stimulation of the PAG or the cortex/CP inhibited preferentially the responses of most STT neurons in deep layers of the dorsal horn to the small or large afferent input, respectively. 4. Thirty-five neurons were recorded intracellularly. The membrane potential of the neurons averaged -45.5 +/- 10.1 (SD) mV. All neurons were recorded in laminae III-VI; the neurons were of the wide-dynamic-range (WDR) type and had background activity. 5. The inhibitory effects of stimulation of the PAG were tested on all 35 neurons. In 32 of the neurons, stimulation of the PAG evoked a hyperpolarization. The background activity of the neurons was reduced (generally it completely ceased) by the hyperpolarization. In three neurons stimulation of the PAG did not evoke a hyperpolarization and the background activity of the neurons did not change. Nevertheless, the responses of these three neurons to afferent input were inhibited by stimulation in the PAG. 6. The inhibitory effects of stimulating the cortex and/or the CP were tested in 26 of the 35 neurons. Stimulation of the cortex and/or the CP evoked a hyperpolarization in all the neurons, although, in 10 of the 26 neurons, stimulation of the CP also evoked a depolarization. The hyperpolarization generally blocked the background activity of the neurons. 7. The effective stimuli in the PAG and the cortex/CP to evoke a hyperpolarization in STT neurons were short, high-frequency trains of pulses.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Sarcoidosis and lymphoma: an unusual association.

The coexistence of sarcoidosis and malignant lymphoma is uncommon. Here we report four patients with histologically proven sarcoidosis; one developed Hodgkin's Lymphoma of the pleura; another, B cell lymphoma involving the cervical nodes; the third Gastric B cell lymphoma, and the last an aggressive widespread B cell lymphoma.

Adolescent↗
PubMed1986

Integrated substrate utilization by perinatal lung.

The aims of this study were to examine the pattern and relative utilization of exogenously supplied substrates by the perinatal rat lung and to study their functional relationship at a key period of lung maturation (3 days before birth until one day after birth). Maximal incorporation of 14C-labeled substrates (glucose, lactate, glycerol, and beta-hydroxybutyrate) from the media into lung lipids occurred one day before birth and corresponded to maximal incorporation of 14C-choline into disaturated phosphatidylcholine (DSPC) (63 n moles X hr-1 X g-1), and to maximal increase in tissue DSPC concentration. Whereas, 14C-palmitate utilization for phospholipid synthesis was refractory to changes in DSPC synthesis. Lactate was shown to be a key substrate in fetal lung. When lactate and glucose were supplied at physiological concentrations, lactate: 1) provided 60% of the carbons for de novo fatty acid synthesis compared to only 9% from glucose, 2) produced 5 times more CO2 than glucose (23.9 vs. 4.9 u moles CO2 X hr-1 X g-1) and 3) altered the major fate of glucose incorporated into lung lipid from the fatty acid moiety to the glycerol moiety. Glycerol and palmitate were relatively unimportant energy fuels in the perinatal lung.

3-Hydroxybutyric Acid↗