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Biomedical subjects

B D Moore

Publications and source records attributed to B D Moore.

At least 55 records · Page 3Linked to original sources
PubMed1988

Electrophysiological evidence of the neurotoxic effects of apamin on auditory function in the rat.

Brainstem auditory evoked potentials (BAEPs) were recorded from rats before and after injection with apamin, a polypeptide component of bee venom. Increased absolute and interpeak latencies were found in Peaks III-VII of the BAEP beginning about 30 minutes after apamin injection suggesting impaired auditory function. No change in BAEP was found when animals were injected with saline or during the baseline period before apamin administration. Results corroborate recent findings from our laboratories of decreased glucose metabolism in brainstem nuclei of the auditory system [3] after injection with the same dose of apamin.

Acoustic Stimulation↗
PubMed1988

Evidence for right-hemisphere involvement in recovery from aphasia.

Cortical evoked potentials and dichotic listening test scores were used to assess the extent of activation of the two cerebral hemispheres during various language tasks in a group of 21 recovering aphasics, 15 nonaphasic patients with right-hemisphere stroke, and 17 normal volunteers. In agreement with previous findings, both measures suggest greater right-hemisphere activation during language processing in the recovering aphasics than in nonaphasic patients and normal subjects. These data support the view that restitution of language entails reorganization of brain function with increased participation of the nondominant hemisphere.

Aphasia↗
PubMed1988

Dichotic-listening evidence of right-hemisphere involvement in recovery from aphasia following stroke.

A dichotic-listening procedure was used to investigate the role of the right hemisphere in recovery from aphasia following left-hemisphere stroke. Thirty-one stroke patients were divided into three groups: (a) patients who were recovering from aphasia (Aphasic group, n = 11), (b) patients who had experienced mild strokes with only transient dysarthria (Dysarthric group, n = 10), and (c) patients who had sustained right-hemisphere stroke with no language disturbance (Nonaphasic group, n = 10). In addition, a group of normal, healthy volunteers served as a control group (n = 11). Results show that, like the Control subjects, the Dysarthrics and Nonaphasics showed a strong right-ear advantage (REA) for dichotically presented consonant-vowel (CV) syllables. This is usually thought to be an indication of left-hemisphere dominance (Kimura, 1961). By contrast, the Aphasic group showed left-ear advantage (LEA) suggesting a shift in cerebral dominance for language. The possibility that the results were due to sensory degradation of the auditory messages (lesion effect) was explored. This idea was rejected in favor of an explanation based on increased right-hemisphere mediation of language following left-hemisphere aphasiogenic lesions.

Adult↗
PubMed1988

Photosynthesis in Flaveria brownii, a C(4)-Like Species: Leaf Anatomy, Characteristics of CO(2) Exchange, Compartmentation of Photosynthetic Enzymes, and Metabolism of CO(2).

Light microscopic examination of leaf cross-sections showed that Flaveria brownii A. M. Powell exhibits Kranz anatomy, in which distinct, chloroplast-containing bundle sheath cells are surrounded by two types of mesophyll cells. Smaller mesophyll cells containing many chloroplasts are arranged around the bundle sheath cells. Larger, spongy mesophyll cells, having fewer chloroplasts, are located between the smaller mesophyll cells and the epidermis. F. brownii has very low CO(2) compensation points at different O(2) levels, which is typical of C(4) plants, yet it does show about 4% inhibition of net photosynthesis by 21% O(2) at 30 degrees C. Protoplasts of the three photosynthetic leaf cell types were isolated according to relative differences in their buoyant densities. On a chlorophyll basis, the activities of phosphoenolpyruvate carboxylase and pyruvate, Pi dikinase (carboxylation phase of C(4) pathway) were highest in the larger mesophyll protoplasts, intermediate in the smaller mesophyll protoplasts, and lowest, but still present, in the bundle sheath protoplasts. In contrast, activities of ribulose 1,5-bisphosphate carboxylase, other C(3) cycle enzymes, and NADP-malic enzyme showed a reverse gradation, although there were significant activities of these enzymes in mesophyll cells. As indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the banding pattern of certain polypeptides of the total soluble proteins from the three cell types also supported the distribution pattern obtained by activity assays of these enzymes. Analysis of initial (14)C products in whole leaves and extrapolation of pulse-labeling curves to zero time indicated that about 80% of the CO(2) is fixed into C(4) acids (malate and aspartate), whereas about 20% of the CO(2) directly enters the C(3) cycle. This is consistent with the high activity of enzymes for CO(2) fixation by the C(4) pathway and the substantial activity of enzymes of the C(3) cycle in the mesophyll cells. Therefore, F. brownii appears to have some capacity for C(3) photosynthesis in the mesophyll cells and should be considered a C(4)-like species.

Journal Article↗
PubMed1988

The Influence of Leaf Age on C(4) Photosynthesis and the Accumulation of Inorganic Carbon in Flaveria trinervia, a C(4) Dicot.

Characteristics of C(4) photosynthesis were examined in young, mid-age, and mature leaves of Flaveria trinervia (an NADP-malic enzyme-type C(4) dicot). The turnover of [4-(14)C] (malate plus aspartate) following a pulse with (14)CO(2) was similar in leaves of different ages (apparent half-time of 18-25 seconds). However, the rate of (14)CO(2) incorporation in mid-age leaves was about 1.5-fold higher than in young leaves, and about 2.5-fold higher than in mature leaves. The rate of (14)CO(2) fixation was proportional to the total active pool of malate plus aspartate but was not correlated with the total photosynthetically derived inorganic carbon pool. The leaf's ability to concentrate inorganic carbon photosynthetically declined during leaf expansion, from 29 down to 7 nanomoles per milligram chlorophyll. Similarly, the active aspartate pool also declined during leaf expansion, from about 123 down to 20 nanomoles per milligram chlorophyll. Enhanced metabolism of aspartate to CO(2) and pyruvate in young leaves is suggested to facilitate the maintenance of high CO(2) levels in bundle sheath cells which are thought to have a higher conductance to CO(2).

Journal Article↗
PubMed1988

The relation between lorazepam-induced auditory amnesia and auditory evoked potentials.

We conducted a placebo-controlled double-blind investigation in 15 normal volunteers to study the time course of amnesia to auditory stimulation produced by lorazepam. We also studied the relationship between auditory amnesia and auditory evoked potentials to determine if long-latency auditory evoked potentials (LLAEPs) could be utilized as electrophysiologic predictors of memory. Amnesia was produced by administration of 0.05 mg/kg lorazepam intravenously. To separate the changes in LLAEPs due to generalized sedation from those associated with amnestic properties of a drug, a third group of subjects given 1.5 mg/kg secobarbital was included. Observed frequency and duration of amnesia to auditory stimulation after lorazepam was 58% and 3 hours, respectively (mean values), with marked diminuition of antirecall effect at 120 minutes. Administration of lorazepam increased the latency and decreased the amplitude of N1 and P3 components of LLAEPs. These changes appeared to be a result of generalized sedation rather than the amnestic properties of the drug. We failed to find a definite relationship between amnesia and changes in LLAEPs. We conclude that P3 component of LLAEPs cannot be utilized as an electrophysiologic predictor of amnesia in humans.

Adult↗
PubMed1987

Evoked potential correlates of right hemisphere involvement in language recovery following stroke.

A probe evoked potentials procedure was used to assess the relative engagement of both cerebral hemispheres during a language task in the following four groups of dextral adults: left hemisphere (LH)-damaged aphasics recovering from stroke, dysarthrics, right hemisphere (RH)-damaged nonaphasic patients, and normal control subjects. In agreement with previous findings using the probe procedure, the present results indicate greater task-specific RH activation in recovering aphasics and, to a lesser degree, dysarthric patients and greater LH activation in both nonaphasic, RH-damaged patients and normal control subjects. On the basis of these data, we suggest that increasing participation of the nondominant hemisphere may subserve restitution of language in adults sustaining LH lesions.

Adult↗
PubMed1987

Mensuration data in infant eyes with unilateral congenital cataracts.

The purpose of this study was to determine the size and shape of infant eyes having a unilateral congenital cataract. Fourteen infants presenting consecutively with a unilateral congenital cataract were studied. Ages ranged from 1.3 to 6 months (mean 3.7 months). Corneal curvature ranged from 43.00 to 49.50 D (mean 45.6 D). Refractive error at the corneal plane ranged from +23.50 to +34.00 D (mean +28.07 D). The axial length ranged from 16.49 to 20.09 mm (mean 18.41 mm). Microcornea was found in eight infants. There was rapid growth in eye size from normal neonatal dimensions. No significant relation was found among the following: corneal curvature and age; refractive error and age; axial length and age or presence of microcornea; and corneal curvature and refractive error. Corneal vault may be an important factor in fitting contact lenses to aphakic infants. Contact lenses for infants should be designed based on the dimensions of the infant eye.

Age Factors↗
PubMed1987

Photosynthetic Characteristics of the C(3)-C(4) Intermediate Parthenium hysterophorus.

The weedy species Parthenium hysterophorus (Asteraceae) possesses a Kranz-like leaf anatomy. The bundle sheath cells are thick-walled and contain numerous granal chloroplasts, prominent mitochondria, and peroxisomes, all largely arranged in a centripetal position. Both mesophyll and bundle sheath chloroplasts accumulate starch. P. hysterophorus exhibits reduced photorespiration as indicated by a moderately low CO(2) compensation concentration (20-25 microliters per liter at 30 degrees C and 21% O(2)) and by a reduced sensitivity of net photosynthesis to 21% O(2). In contrast, the related C(3) species P. incanum and P. argentatum (guayule) lack Kranz anatomy, have higher CO(2) compensation concentrations (about 55 microliters per liter), and show a greater inhibition of photosynthesis by 21% O(2). Furthermore, in P. hysterophorus the CO(2) compensation concentration is relatively less sensitive to changes in O(2) concentrations and shows a biphasic response to changing O(2), with a transition point at about 11% O(2). Based on these results, P. hysterophorus is classified as a C(3)-C(4) intermediate. The activities of diagnostic enzymes of C(4) photosynthesis in P. hysterophorus were very low, comparable to those observed in the C(3) species P. incanum (e.g. phosphoenolpyruvate carboxylase activity of 10-29 micromoles per milligram of chlorophyll per hour). Exposures of leaves of each species to (14)CO(2) (for 8 seconds) in the light resulted in 3-phosphoglycerate and sugar phosphates being the predominant initial (14)C products (77-84%), with </=4% of the (14)C-label in malate plus aspartate. These results indicate that in the C(3)-C(4) intermediate P. hysterophorus, the reduction in leaf photorespiration cannot be attributed to C(4) photosynthesis.

Journal Article↗
PubMed1986

Photosynthetic Induction in a C(4) Dicot, Flaveria trinervia: I. Initial Products of CO(2) Assimilation and Levels of Whole Leaf C(4) Metabolites.

Labeling patterns from (14)CO(2) pulses to leaves and whole leaf metabolite contents were examined during photosynthetic induction in Flaveria trinervia, a C(4) dicot of the NADP-malic enzyme subgroup. During the first one to two minutes of illumination, malate was the primary initial product of (14)CO(2) assimiltion (about 77% of total (14)C incorporated). After about 5 minutes of illumination, the proportion of initial label to aspartate increased from 16 to 66%, and then gradually declined during the following 7 to 10 minutes of illumination. Nutrition experiments showed that the increase in (14)CO(2) partitioning to aspartate was delayed about 2.5 minutes in plants grown with limiting N, and was highly dampened in plants previously treated 10 to 12 days with ammonia as the sole N source. Measurements of C(4) leaf metabolites revealed several transients in metabolite pools during the first few minutes of illumination, and subsequently, more gradual adjustments in pool sizes. These include a large initial decrease in malate (about 1.6 micromoles per milligram chlorophyll) and a small initial decrease in pyruvate. There was a transient increase in alanine levels after 1 minute of illumination, which was followed by a gradual, prolonged decrease during the remainder of the induction period. Total leaf aspartate decreased initially, but temporarily doubled in amount between 5 and 10 minutes of illumination (after its surge as a primary product). These results are discussed in terms of a plausible sequence of metabolic events which lead to the formation of the intercellular metabolite gradients required in C(4) photosynthesis.

Journal Article↗
PubMed1986

Photosynthetic Induction in a C(4) Dicot, Flaveria trinervia: II. Metabolism of Products of CO(2) Fixation after Different Illumination Times.

The metabolism of fixed (14)CO(2) and the utilization of the C-4 carboxyl of malate and aspartate were examined during photosynthetic induction in Flaveria trinervia, a C(4) dicot of the NADP-malic enzyme subgroup. Pulse/chase experiments indicated that both malate and aspartate appeared to function directly in the C(4) cycle at all times during the induction period (examined after 30 seconds, 5 minutes and 20 minutes illumination). However, the rate of loss of (14)C-label from the C-4 position of malate plus aspartate was relatively slow after 30 seconds of illumination, compared to treatments after 5 or 20 minutes of illumination. Similarly, the appearance of label in other photosynthetic products (e.g. 3-phosphoglycerate, sugar phosphates, alanine) during the chase periods was generally slower after only 30 seconds of leaf illumination, compared to that after 5 of 20 minutes illumination. This may be due to the lower rate of photosynthesis after 30 seconds illumination. The appearance of label in carbons 1-->3 of each C(4) acid during the chase periods was relatively slow after either 30 seconds or 5 minutes illumination, while there was a relatively rapid accumulation of label in carbons 1-->3 of both C(4) acids after 20 minutes illumination. Thus, while the turnover rate of the (14)C-4 label in both C(4) acids increased only during the first 5 minutes of the induction period, only later during induction is there an increased rate of appearance of label in other carbon atoms of the C(4) acids. The implied source of (14)C for labeling of the 1-->3 positions of the C(4) acids is an apparent carbon flux from 3-phosphoglycerate of the reductive pentose phosphate pathway to phosphoenolpyruvate of the C(4) cycle.

Journal Article↗
PubMed1985

Confirmation of brain death with portable isotope angiography: a review of 204 consecutive cases.

Intravenous isotope angiography is a rapid, safe, and specific bedside test for confirming brain death by demonstrating the lack of critical cerebral perfusion that occurs in this condition, regardless of etiology. A review of 204 consecutive cases of suspected brain death studied with isotope angiography has reaffirmed our confidence in the specificity of the technique and has convinced us to make less stringent our radiographic criteria for confirming brain death by this method. A technically satisfactory single flow study that shows arrest of the carotid circulation at the base of the skull and absence of the intracranial arterial circulation may be considered confirmatory of a carefully established clinical diagnosis of brain death, even though there may be some visualization of the intracranial venous sinuses. Arbitrary waiting periods, withdrawal of sedative drugs, and electrophysiological studies are not needed when this technique is used.

Adolescent↗
PubMed1984

Evoked potential correlates of posttraumatic amnesia after closed head injury.

The P-300 component of evoked potentials to a rare tone was measured in normal volunteers and in patients with closed head injuries who either were confused (in posttraumatic amnesia) or had recovered from posttraumatic amnesia and were oriented at the time of recording. The latency of this component, which reflects cortical processing of stimuli, varied reliably, with the degree of orientation being longest for confused patients and shortest for normal subjects. On the basis of these data, we suggest that the P-300 latency can be used as a physiological index of cognitive function in patients with closed head injury.

Adolescent↗
PubMed1983

Evoked potential indices of selective hemispheric engagement in affective and phonetic tasks.

Evoked potentials (EPs) to a probe click stimulus were recorded from left and right temporal areas of dextral adults engaged in phonetic and prosodic processing of an emotionally charged tape recorded conversation. Attenuation of the probe EP amplitudes was significantly greater in the left and right hemispheres during the phonetic and prosodic tasks, respectively, indicating lateral dominance shifts depending on selective processing of linguistic vs affective cues conveyed by the same speech signals.

Adult↗
PubMed1983

Cerebral activation patterns in an arithmetic and a visuospatial processing task.

Evoked potentials (EPs) to a probe tone stimulus were recorded simultaneously at the temporal and parietal areas of the left and right hemisphere of dextral adults engaged in either an arithmetic or a visuospatial task. The probe EP amplitude was attenuated in the left temporal area during the arithmetic task and in the left temporal and both parietal areas, but significantly more in the right, during the visuospatial task, indicating distinct patterns of regional cerebral engagement for the two types of cognitive activity.

Adult↗
PubMed1982

Electrophysiological response properties of spinoreticular neurons in the monkey.

Extracellular recordings were made from 29 spinoreticular cells in the spinal cords of anesthetized monkeys. The cells were in either the cervical or the lumbar enlargement, and they were identified by antidromic activation from the medial part of the pontomedullary reticular formation. More spinoreticular neurons were sampled in the cervical than in the lumbar cord. Most of the cells were contralateral to the side from which antidromic activation was observed, but a higher proportion of the spinoreticular neurons in the cervical enlargement than in the lumbar enlargement was ipsilateral to the antidromic stimulus. Three cells in the lumbar cord were antidromically activated not only from the reticular formation but also from the contralateral thalamus, confirming that some spinoreticular projections are formed by collaterals from spinothalamic cells. Most of the spinoreticular neurons were in the ventral horn in laminae VII and VIII, although a few were in laminae IV-VI. Nearly half of the spinoreticular cells in the sample could not be activated by any form of peripheral stimulation tested. The other cells could be activated by stimulation of receptive fields that varied from small to large, that were sometimes bilateral regions of the skin or deep tissues. Although some spinoreticular cells could be classified as low threshold or wide dynamic range, the largest proportion were high threshold, requiring noxious stimulation for their activation. Descending volleys resulting from stimulation in the reticular formation could often be shown to inhibit or to excite spinoreticular neurons. It can be concluded that at least some spinoreticular neurons may play a role in nociception.

Animals↗