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Biomedical subjects

C L Wilson

Publications and source records attributed to C L Wilson.

At least 91 records · Page 5Linked to original sources
PubMed1991

Busulphan/cyclophosphamide conditioning for bone marrow transplantation may lead to failure of hair regrowth.

Following the introduction of bulsulphan and cyclophosphamide (BUCY) conditioning in our unit in 1987, a number of patients noted incomplete scalp hair regrowth following bone marrow transplantation (BMT). Between August 1987 and May 1989, 22 patients had undergone allogeneic or autologous BMT in our unit and we recalled for detailed assessment the 14 who were alive and well at least 6 months post grafting. Six patients had experienced incomplete hair regrowth of varying severity 7-27 months following BMT. All those affected had received BUCY conditioning and the four most severely affected were allogeneic BMT recipients. No patient had received any post-BMT chemotherapy or radiation. None of the patients had evidence of graft-versus-host disease. No laboratory test abnormalities distinguished the affected from the unaffected patients. Despite the relatively small number of patients, our results suggest that BUCY has caused permanent damage to the hair follicles of the affected patients. Prolonged alopecia may markedly impair the quality of life for long-term survivors of BMT and this unexpected complication also has significant medicolegal implications.

Adolescent↗
PubMed1990

Functional connections in the human temporal lobe. I. Analysis of limbic system pathways using neuronal responses evoked by electrical stimulation.

Connections in the human mesial temporal lobe were investigated using brief, single pulses of electrical stimulation to evoke field potential responses in limbic structures of 74 epileptic patients. Eight specific areas within these structures were stereotactically targeted for study, including amygdala, entorhinal cortex, presubiculum, the anterior, middle and posterior levels of hippocampus and the middle and posterior levels of parahippocampal gyrus. These sites were studied systematically in order to quantitatively assess the response characteristics and reliability of responses evoked during stimulation of pathways connecting the areas. Specific measures included response probability, amplitude, latency and conduction velocities. The results are assumed to be representative of typical human limbic pathways since all recordings were made interictally and response probabilities across sites were not found to differ significantly between non-epileptogenic vs. identified epileptogenic regions. Field potentials ranging in amplitude from less than 0.1 to greater than 6.0 mV were evoked ipsilaterally, with mean onset latencies and conduction velocities ranging from 4.4 ms and 3.64 m/s in the perforant pathway connecting entorhinal cortex to anterior hippocampus to 24.8 ms and 0.88 m/s in the pathway connecting the amygdala and middle hippocampus. Stimulation of presubiculum and entorhinal cortex were most effective in evoking widespread responses in adjacent limbic recording sites, whereas posterior parahippocampal gyrus appeared functionally separated from other limbic sites since its probability of influencing ipsilateral sites was significantly lower than any other area. It was particularly noteworthy that stimulation did not evoke responses in any sites in contralateral hippocampal formation; even though a large number of sites were tested with bilateral implantation of homotopic electrodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1990

Tufted folliculitis. A specific bacterial disease?

Residual groups of hair follicles and unusual "tufts" of multiple hairs emerging from single follicular openings have been described in scarring alopecia associated with staphylococcal infection. Various mechanisms have been proposed to explain these findings. Histological study of four cases suggests that retention of telogen hairs through several hair cycles may be responsible for this phenomenon.

Adult↗
PubMed1990

Matting of scalp hair during shampooing--a new look.

We present a new case of irreversible hair matting, a rare, but important and alarming, acquired hair disorder. This case was investigated to test the causal hypothesis proposed in 1984. At the same time four other specimens of matted hair from patients and tangles from normal individuals were also examined. Light and electron microscopy showed dramatic permanent twisting and bending of the hairs through 180 degrees. There was marked variation in the fibre width of hairs from matted samples, with some longitudinally split along a considerable length. This bending and entanglement of hairs of varying widths (felting) seemed to be the main reason for the hairs becoming so dramatically knotted together in four of the cases. In only one case was there any evidence of a viscous fluid binding the hair together. This finding suggests that there may be two different mechanisms involved in hair matting.

Adult↗
PubMed1990

Characterization and reclassification of yeasts used for biological control of postharvest diseases of fruits and vegetables.

In previous studies workers have shown that three yeast strains (strains US-7, 82, and 101) have biological control activity against various postharvest fungal pathogens of fruits and vegetables, including Penicillium rots of apples and citrus and Botrytis rot of apples. In these reports the researchers have described these strains as Debaryomyces hansenii (anamorph, Candida famata) or Candida sp. strains. In this study we performed additional physiological, DNA reassociation, and mannan characterization tests that clearly established a new taxonomic classification for these strains, Candida guilliermondii. We also propose amendment of the physiological test profile in the taxonomic description of C. guilliermondii.

Journal Article↗
PubMed1990

Multimodality imaging of brain structures for stereotactic surgery.

An image analysis system was developed for stereotactic neurosurgery that allows the simultaneous display of brain images from different imaging devices obtained in different orientations. The system is based on a stereotactic frame and a microcomputer and features an easy user interface together with point registration and region of interest analysis in three-dimensional space. A dynamic multi-image environment allows for simultaneous display of magnetic resonance, computed tomography, digital subtraction angiography, and positron emission tomography images in multiple windows, adjusted for common coordinates with reference to stereotactic frame fiducial markers. Linkages between images allow information interchange between different modalities and different views: Points and regions defined in one image can be transferred to others, and cursor coordinates in one image can be calculated and dynamically projected in other images. Phantom studies show that the system distortions are minor and that the system is suitable for clinical use. The system provides exceptional advantages over previous imaging procedures for stereotactic surgery.

Angiography, Digital Subtraction↗
PubMed1990

Accuracy of MR-guided stereotactic electrode implantation. 1. Preimplantation correlation with the Talairach system.

The accuracy of stereotactic electrode implantation using MR guidance and a computerized imaging system was compared to the conventional Talairach system, using ventriculography and a stereotactic atlas. A combined methodology of two stereotactic approaches was used, with a modified Leksell and a Todd-Wells frame. The coordinates of temporo-limbic structures and the length of the AC-PC line were measured prior to implantation in 10 epileptic patients undergoing the combined procedure. Relative differences in single and three-dimensional values were obtained for 68 targets within the temporal lobe. Lengths of AC-PC lines were measured in 9 patients. Statistical differences were found for all temporal coordinates, but the AC-PC line did not differ significantly.

Brain Mapping↗
PubMed1990

Stereotactic investigation of limbic epilepsy using a multimodal image analysis system. Technical note.

A methodology has been developed for stereotactic investigation of limbic epilepsy using an image-analysis system that simultaneously displays different structural and functional images of the brain. The validity and accuracy of this system were established with phantom studies. Surgical planning and electrode implantation are guided by stereotactic magnetic resonance imaging, digital subtraction angiography, and position emission tomography. This methodology provides the spatiotemporal relationship of cerebral structure and function necessary to identify seizure onset and propagation in human limbic system epilepsy.

Brain Mapping↗
PubMed1990

Temperature regulation of microtiter plates for enzyme assays.

To facilitate the use of microtiter plates as vessels for enzyme assays, an incubator has been designed to maintain the wells of the microtiter plates at the appropriate temperature. The temperature variation within a single well was +/- 0.02 degrees (standard error of the mean) at 25 degrees C and +/- 0.02 degrees at 37 degrees C. The temperature variation was the same for internal and peripheral wells within the plates, although the internal wells were approximately 0.14 degrees C warmer than the outer wells at 25 degrees C and 0.68 degrees C cooler at 37 degrees C. The overall uncertainty (95% confidence interval) of the well temperature in a typical plate was +/- 0.4 degrees C at 25 degrees C and +/- 0.7 degrees C at 37 degrees C. This uncertainty is realistic for routine enzyme determinations, as opposed to precise studies. The incubator was designed to allow access to the plates from above so that additions could be made during the incubation. To demonstrate the suitability of microtiter plates and the incubator for enzyme determinations, this method was used to measure the activity of myeloperoxidase and alpha-naphthylbutyryl esterase.

Animals↗
PubMed1989

Selective secretion of alternatively spliced fibronectin variants.

We demonstrate that the alternatively spliced variable (V) region of fibronectin (FN) is required for secretion of FN dimers during biosynthesis. Alternative splicing of the V segment of the rat FN transcript generates three subunit variants (V120, V95, V0) that differ by the inclusion or omission of an additional 120 or 95 amino acids. We are exploring the functions of this segment by expressing variant cDNAs in normal and transformed fibroblasts. Like FN itself, the cDNA-encoded polypeptides (deminectins [DNs]) containing the V120 or V95 segment are efficiently secreted as disulfide-bonded homodimers. However, few homodimers of DNs lacking this region, V0 DNs, are secreted. V0 homodimers do form inside the cell, as demonstrated by biosynthetic analyses of dimer formation and secretion using pulse-chase and time course experiments, but these dimers seldom reach the cell surface and are probably degraded intracellularly. Coexpression of V0 and V120 subunits results in intracellular formation of three types of dimers, V0-V0, V0-V120, and V120-V120, but only the V120-containing dimers are secreted. This selective retention of V0 homodimers indicates that the V region is required for formation and secretion of native FN dimers. In an analogous in vivo situation, we show that plasma FN also lacks V0-V0 dimers and consists of V0-V+ and V+-V+ combinations. Dissection of V region sequences by deletion mapping localizes the major site involved in DN dimer secretion to an 18-amino acid segment within V95. In addition, high levels of dimer secretion can be restored by insertion of V into a heterologous site 10 kD COOH terminal to its normal location. We discuss the potential role of intracellular protein-protein interactions in FN dimer formation.

Animals↗
PubMed1987

The effect of supercoil and temperature on the recognition of palindromic and non-palindromic regions in phi X174 replicative form DNA by S1 and Bal31.

The effect of supercoil and temperature on the topology of phi X174 replicative form (RF) DNA was studied using single-strand specific endonucleases S1 and Bal31 as probes for cruciform extrusion and other structural perturbations of the B-helix. Both enzymes were found to recognize specifically and reproducibly over 30 sites, most of which were cleaved by both enzymes independent of the superhelicity of the genome. A negative superhelical density exceeding 0.06 stabilized a transition in the DNA conformation that generated several new cleavage sites for Bal31. The underlying structures appeared to be only transiently stable and were lost from in vitro supercoiled DNA during brief incubation at 65 degrees C. They were generally absent from in vivo supercoiled RF DNA of equal superhelicity as a consequence of the extraction and storage procedure. Mapping of the cleavage sites suggested that they were preferentially located near the beginnings and ends of genes and that the structural basis for at least some of them was the extrusion of relatively small palindromes into the cruciform state. Insertion of a short synthetic palindromic sequence into the phi X174 genome generated a supercoil-dependent, temperature-sensitive secondary structure that was cleaved in the Bal31 but not the S1 reaction, further supporting the hypothesis that even small cruciforms with stem size of 7 or less base pairs may be transiently stable. Subjecting supercoiled RF DNA to the typical S1 reaction conditions induced a topological shift that diminished all but one of the supercoil-induced Bal31 recognition sites and promoted the formation of one major new site.

Bacteriophage phi X 174↗
PubMed1987

Firing patterns of human limbic neurons during stereoencephalography (SEEG) and clinical temporal lobe seizures.

Comparisons of the patterns of neuronal firing and stereoencephalography (SEEG) recorded from the same microelectrodes chronically implanted in the human limbic system were made in order to study neuronal electrogenesis at onset and during propagation of focal partial complex seizures. Alert or sleeping patients were monitored during spontaneous subclinical seizures (no alterations in consciousness detectable), during auras reported by the patients as typical, and during clinical seizures with loss of consciousness, movements and post-ictal confusion. During subclinical SEEG seizures (ipsilateral, normal consciousness), few neurons increased firing (estimated at only 7%) either at the focus or at propagated sites. During auras, with altered consciousness, there were relatively few neurons that increased firing, with the estimate about 14% or twice as many as during a subclinical seizure. During the onset of a clinical seizure that involved loss of consciousness, movements and post-ictal confusion, many neurons were recruited into increased firing, with an estimate of approximately 36%. During this increased electrogenesis, neurons fired briefly in association with high-frequency local SEEG; however, the bursts were shorter than the SEEG seizure pattern. Apparently, other local neurons were recruited to fire in bursts to sustain sufficient axonal driving for widespread propagation of the seizure. When the focal SEEG slowed, the units stopped firing, which suggested that the 'focal' seizure need not be sustained for more than several seconds because propagated seizure activity was self-sustaining at distant structures. The data lead to the conclusion that SEEG seizures can be generated focally by synchronous firing of fewer than 10% of neurons in the 'epileptic pool.' However, when greater percentages of neurons are recruited in the 'epileptic focus' there is greater propagation to widespread sites, especially contralaterally, which will produce clinical partial complex seizures.

Action Potentials↗
PubMed1987

Diversity in periodic pattern of firing in human hippocampal neurons.

Firing periodicity was examined in human hippocampal neurons using autocorrelation analysis. Extracellular single-unit activities were recorded from the anterior hippocampus through fine platinum microelectrodes, and the typical firing pattern in an entire recording period was reconstructed statistically in autocorrelograms (average number of firings analyzed: 5639.0 +/- 968.1 SE, range: 1158 to 31,203; number of single-unit trains was 57). Three types of periodic firing were identified as highly consistent. The first pattern consisted of a random recurrence of high-frequency action potentials (100 to 300 Hz) and was observed as an intermittent burst. In this burst, the first 10 to 30 ms after the onset of the burst was the patterned firing of several action potentials, suggesting that the generation of this stereotyped portion of the burst is primarily due to intrinsic membrane characteristics. The second pattern was the continuous rhythmical firing with a lower frequency ranging from 1 to 30 Hz. The third pattern was a clustered rhythmical firing in which a series of short rhythmical firings recurred with regular intervals; the frequency of short rhythmical firing varied from 6.7 to 17 Hz between neurons, and the interval of the regular recurrence of these rhythmical firings ranged from 0.5 to 10 s among neurons. These firing periodicities not only cover a cellular rhythm in the theta frequency reported in the lower mammalian hippocampus but also appear to be more diverse than those previously reported for hippocampal neurons in the animal literature.

Electric Stimulation↗
PubMed1987

Structurally stable burst and synchronized firing in human amygdala neurons: auto- and cross-correlation analyses in temporal lobe epilepsy.

Burst structure and synchronized firing of bursts were studied, in the interictal period, using auto- and cross-correlation analyses in human amygdala neurons in temporal lobe epilepsy patients diagnosed as having a unilateral limbic seizure focus in anterior hippocampus and/or amygdala. Satisfactory single unit recordings were obtained from chronically implanted microelectrodes in 51 amygdala neurons, and auto-correlation analysis identified 27 of 51 neurons where burst firings recurred with regular interspike interval structures (structurally stable burst: S-burst). This structural stability was characteristic only for a short burst, or at the beginning of a series of repetitive firings, involving 2-5 action potentials. In 'non-epileptic' amygdala neurons located contralateral to the seizure focus, the average duration of S-burst was 15 msec and the number of action potentials (spikes) in the S-burst was inversely related to the interspike intervals in the S-burst, suggesting that endogenous membrane characteristics of non-epileptic amygdala neurons determine the patterns of S-burst. In contrast, in the seizure focus amygdala ('epileptic'), the duration of the S-burst was prolonged among epileptic neurons, not because of the occurrence of more action potentials within the S-burst, but because of a prolonged interspike interval within the S-burst. Furthermore, there was no relationship between the interspike interval and the number of action potentials in the S-burst, suggesting that synaptic inputs and/or extracellular environmental factors may affect an intrinsic mechanism for generating stable S-burst in epileptic neurons. Cross-correlation analysis identified synchronized firings in epileptic neurons: when two epileptic neurons both exhibited S-bursts, when either epileptic neuron exhibited S-burst, but never when neither exhibited S-bursts. Conversely, non-epileptic neurons rarely fired synchronously; even though they showed S-bursts. The difference in the pattern of S-bursts between epileptic and non-epileptic amygdala neurons seems to be the degree of firing synchrony. Our results provide, for the first time, direct evidence that human epileptogenic amygdala neurons recorded in vivo have unique burst firing patterns and significant synchronous excitatory interactions, different from a burst pattern found in non-epileptogenic amygdala neurons during the interictal period.

Action Potentials↗
PubMed1987

Effect on gait of motor task learning acquired in a sitting position.

The purpose of this study was to ascertain the importance of learning a motor task in a sitting position and its influence on gait. Thirty-one healthy subjects, divided into three groups, were asked to learn a synchronous heel-up-heel-down rhythm task in a sitting position and to reproduce the rhythm during their gait cycle on three separate occasions over a three-day period. This study provided evidence that training of a subject in a sitting position produced a nonspecific influence during ambulation. The inability to obtain an exact transfer of learning from a sitting position to gait and its implication to the specificity principle of learning are discussed. Some subjects had difficulty maintaining their performance over the three-day period. This finding was attributed in part to the influence of proactive and retroactive inhibition. Mat activities, therefore, seem to have a very limited impact on modifying gait. The clinical implications of these findings are presented.

Adult↗
PubMed1986

The effect of limbic and extralimbic electrical stimulations upon prolactin secretion in humans.

The effect that extra-hypothalamic regions of the brain have upon prolactin secretion in humans was evaluated by performing electrical stimulations. Thirty-nine stimulations were performed, 22 to basolateral amygdala, 12 to hippocampus and 5 to orbitofrontal, supplementary motor and cingulate cortex. Only two stimulations causing high-frequency widespread limbic afterdischarges were followed by significant prolactin elevation. Four low-frequency afterdischarges involving amygdala and anterior hippocampus, one amygdala stimulus-dependent discharge and 19 amygdala, 8 hippocampal and 5 frontal sub-afterdischarge threshold stimulations had no prolactin elevation. These results fail to replicate earlier studies. We suggest that there is no evidence that the amygdala regulates serum prolactin within physiologic ranges, but that the regulation of prolactin may depend primarily upon other sub-cortical structures.

Amygdala↗
PubMed1985

Recall deficits produced by afterdischarges in the human hippocampal formation and amygdala.

The human amygdala, hippocampus and parahippocampal gyrus were stimulated in 3 epileptic patients with low-level electrical current during a paired associates learning task. Delayed recall of the response-words was severely impaired if, and only if, a unilateral afterdischarge was evoked. Stimulation at the same strength produced no deficit in immediate recall, nor in mental arithmetic, even when auras and afterdischarges were evoked. These data support the association of amnesia with medial temporal lobe paroxysms during complex partial seizures.

Amygdala↗