Biomedical subjects

J C Lynch

Publications and source records attributed to J C Lynch.

14 recordsLinked to original sources

PubMed1992

Saccade initiation and latency deficits after combined lesions of the frontal and posterior eye fields in monkeys.

1. Monkeys were trained to perform horizontal visually guided saccades. Latency was measured before and after bilateral lesions of the frontal eye field (FEF) and after combined lesions of both the FEF and the posterior eye field. Destruction of either of these regions alone causes only modest deficits of eye movement, but destruction of both together produces profound oculomotor impairment. The results support the proposal that purposeful eye movements are controlled by a distributed corticocortical network that includes nodes in frontal and parieto-occipital regions.

Animals↗

PubMed1992

[Multiple intracranial aneurysms].

Thirty eight patients with multiple intracranial aneurysms were studied. They correspond to 19.4% of all aneurysms treated over a twelve year period in the Servidores do Estado Hospital. 89 aneurysms and 4 infundibuli were detected. In 71.0% of the patients, two aneurysms were found; in 18.4%, three aneurysms; and in 10.4%, 4 or 5 aneurysms were observed. Twenty-seven patients were women and 11 men, ranging in age from 16 to 72 (average 47 years old). Subarachnoid hemorrhage was found in 36 patients (86.8%). The operative mortality in this series was 3.5%. We concluded that patients with multiple intracranial aneurysms should have all aneurysms, that can bleed, clipped through standard micro-neurosurgery technics.

Adolescent↗

PubMed1991

Intravascular plastic catheters. How they potentiate tumor necrosis factor release and exacerbate complications associated with sepsis.

We tested the hypothesis that long-term intravascular cannulation exacerbates the harmful effects of an infectious challenge. Four groups of rats were initially studied: rats without intravascular catheters or infection (group 1), rats without catheters with a polymicrobial infection (group 2), rats with catheters but no infection (group 3), and rats with catheters and infection (group 4). Infected animals had an increased mortality and generated a significantly increased tumor necrosis factor response compared with noninfected animals. Animals with catheters and infection generated far less cardiac output than animals from the other three groups. No histologic changes differentiated the four groups. Therefore, the presence of a sterile intravascular catheter significantly increases cardiac dysfunction and mortality rates in rats with chronic bacteremia. These results suggest that intravascular plastic catheters potentiate the destructive cascade of events produced by the host in response to bacteremia.

Abscess↗

PubMed1991

Mediastinal bulk in Hodgkin disease. Method of measurement versus prognosis.

The presence of a large mediastinal mass (bulk disease) in patients with newly diagnosed Hodgkin disease is believed by many to predict a poorer prognosis and to warrant more aggressive treatment. These masses are formed by an aggregate of mediastinal lymph nodes. The determination of bulk disease is confusing, with at least 27 definitions having been proposed. This study seeks to determine the best definition, and determine the role of thoracic computed tomography (CT) versus chest radiographs in the evaluation of mediastinal bulk disease. One hundred seven consecutive newly diagnosed adult patients with Hodgkin disease were evaluated using 13 commonly used definitions of mediastinal bulk. Of the 76 patients with mediastinal disease, 73 had bulk disease as defined by at least one definition. Of the 16 patients who had recurrence of mediastinal disease, only the presence of bulk disease according to one definition (hilar adenopathy, greater than or equal to 2 cm) was statistically significant in its prediction (P = .05). No definition based on the size of the mediastinal nodal mass reliably predicted those patients with recurrence. No differences in our data were found for differing stages or disease cell types, the presence of extension, or with differing treatment regimens. This study highlights the confusion and controversy surrounding the use of bulk disease of the mediastinum as an adverse prognostic indicator. The numerous methods of measuring mediastinal bulk in patients with newly diagnosed Hodgkin disease are confusing, overlap, and are not statistically reliable in predicting recurrence. Efforts to create a standard or ideal definition were unsuccessful. Thoracic CT was useful in those patients whose bulk disease distorted only one side of the mediastinal silhouette on chest radiographs.

Adult↗

PubMed1991

Reported practice behaviors for medical care of patients with diabetes mellitus by primary-care physicians in Pennsylvania.

OBJECTIVE: To compare the American Diabetes Association standards for the medical care of diabetic patients with reported care patterns. RESEARCH DESIGN AND METHODS: These standards were compared with reported care patterns obtained from a stratified random telephone survey of general practitioners, family physicians, and general internists in Pennsylvania. A total of 610 physicians completed the survey for a response rate of 73%. RESULTS: All primary-care physicians reported measurement of glycosylated hemoglobin, routine referrals to eye doctors, and patient self-monitoring of blood glucose less than recommended. Nearly all physicians performed foot exams, but the exams were infrequent for many of the physicians. Significant and independent differences (P less than 0.05) were noted between different groups of physicians. Older physicians and general practitioners reported patterns of care most different from the recommended standards for referral to eye doctors, measurement of glycosylated hemoglobin, and use of patient self-monitoring of blood glucose. General practitioners reported the lowest frequency of foot exams. CONCLUSIONS: Educational programs on diabetes for primary-care physicians should focus on reported behaviors most different from recommended standards and may need to target subgroups of physicians to achieve a more uniform level of care for all diabetic patients.

Blood Glucose Self-Monitoring↗

PubMed1990

[Chronic subdural hematoma: surgical treatment and results in 96 patients].

Ninety-six patients with chronic subdural hematoma were treated surgically and their clinical features presented in detail. Carotid angiography gave the correct diagnosis in all patients. CT scan was performed in 38 and was diagnostic in 92.1% of the cases. The clots were removed through burr-holes or small trephines: 78 (81.3%) patients were cured, 6 (6.2%) had permanent disabilities and 12 (12.5%) died. Operative mortality was related to the degree of neurological impairment, advanced age and systemic diseases. Neurologic sequelae were mostly related to reoperations due to recurrence of the hematoma and bilateral clots, as well. Low intracranial pressure syndrome with brain collapse was seen in 3 cases and treated with lumbar injection of saline solution. The delay in diagnosis and operation as cause of bad outcome is stressed.

Adolescent↗

PubMed1990

The significance of necrotic mediastinal lymph nodes on CT in patients with newly diagnosed Hodgkin disease.

Necrosis in lymph nodes shown on CT in many patients with nodal metastases may indicate that the primary tumor is aggressive and has a high degree of malignancy. However, the significance of nodal necrosis in patients with mediastinal Hodgkin disease remains uncertain. We studied the thoracic CT scans of 76 patients who had newly diagnosed Hodgkin disease with mediastinal involvement with respect to the presence of necrosis (low attenuation, complex, fluidlike areas), the size and volume of the mass, the sites involved, extension ("E" disease), and the patients' clinical response to treatment. CT scans showed necrotic nodes in 16 patients (21%). The difference between these patients and those without necrotic nodes was not statistically significant with respect to sex, age, stage, distribution of disease, presence of E disease, cell type, mass diameter, or the presence of bulk disease (mass diameter/maximal thoracic diameter greater than or equal to 0.33). The mass volume as measured by CT was not significantly (p = .08) larger (1274 cm3) than the group without necrotic nodes (876 cm3). An analysis of the various mediastinal sites involved showed no difference between patients with and without necrotic nodes. Lastly, the presence of necrotic nodes had no significant impact on patients' clinical response to treatment or survival. The presence of mediastinal necrotic nodes appears to have little radiologic or prognostic significance in patients with newly diagnosed Hodgkin disease.

Adult↗

PubMed1990

The effects of sleep loss on cognitive performance of resident physicians.

Although the long hours worked by resident physicians have raised concern in the public, legislators, and members of the medical profession, the consequences of sleep loss on the ability of residents to perform in clinical settings is unknown. The present study examined the effects of various amounts of reported sleep on cognitive performance measured by the American Board of Family Practice in-training examination. A total of 353 family practice residents in 21 programs who took the examination in Pennsylvania in 1988 were studied. Linear regression analysis demonstrated a statistically significant (P less than .05) decline in composite test score with decreasing sleep on the night before the examination for residents in each year of training. Loss of one night's sleep resulted in changes in test scores that were approximately equivalent in magnitude to the change that occurred in test scores between residents in the first and third year of training. The results suggest that prolonged testing over several hours may be necessary to detect the subtle but significant differences in cognitive performance that are present with relatively mild degrees of sleep loss.

Cognition↗

PubMed1989

[Primary hematoma of the brain stem: considerations apropos of a case].

The case of a 48 year-old woman presenting with a primary pontine hematoma is reported. The clinical evolution simulated a brain stem tumor and the diagnosis of hematoma was not established before the operation. The preoperative neurological deficit improved except for a facial nerve palsy. These hematomas are thought to be due to rupture of "cryptic" arteriovenous malformations and should be differentiated from those secondary to systemic hypertension. The diagnosis of brain stem hematomas should be considered in any case of brain stem lesion, especially in young and normotensive patients.

Cerebral Hemorrhage↗

PubMed1979

Genetic variability and divergence in grayling, Thymallus arcticus.

In North America there are two disjunct forms of grayling, Montana and arctic, which have been separated for approximately 75,000 to 100,000 years. Electrophoretic analysis of thirty-six protein loci in these forms has revealed: (1) levels of gene duplication comparable to other salmonids, (2) a level of heterozygosity similar to other salmonids, (3) a fast and a slow evolving set of proteins, and (4) no obvious relationship between genetic variability and enzyme function. The genetic divergence between these populations may warrant subspecific designations for these two forms.

Animals↗

PubMed1977

Parietal lobe mechanisms for directed visual attention.

1. Experiments were made on the cortex of the inferior parietal lobule in 10 hemispheres of six alert, behaving monkeys. The electrical signs of the impulse discharges of single cortical cells were recorded as the monkeys executed tasks requiring them to fixate stationary visual targets, track those which moved slowly, and to make saccadic movements to foveate those which suddenly jumped from one locus to another within the field of view. A total of 907 neurons of area 7 were identified in terms of their physiological properties, particularly the correlation of their activity with the oculomotor components of these behavioral acts of directed visual attention; 480 of these were located by cytoarchitectural layer. Most identifiable cells of area 7 are visuomotor neurons, in a special and conditional sense. Their discharge frequencies increase before and during those steady fixations and movements of the eyes which secure and maintain foveation of objects, but only if the visual targets engaged are linked by a strong motivational drive; in our experiments, one between thirst and the light whose dimming the animal has learned to detect for liquid reward. We have identified and studied three major classes of neurons in area 7. 2. The visual fixation neurons (57%) accelerate discharge synchronously with fixation of a visual object the animal desires. The incremented discharge continues until reward, but then declines abruptly even when there is no immediate shift of the line of gaze. Fixation neurons are relatively inactive during those casual fixations by which the animal insepcts the surrounding environment. Mist fixation neurons subtend gaze fields limited to one quadrant or half of the total gaze field. The sum of the gaze fields of the fixation neurons in one hemisphere is weighted moderately toward the contralateral side. Fixation cells also discharge during slow pursuit movements in any direction so long as the movement stays within the gaze field of the neuron under study. About 40% of fixation cells are suppressed before and during saccadic movements of the eyes to a new target within the gaze field of the fixation cell. Those suppressed are located preferentially in layer V of the cortex. Suppression is maximal for saccades directed contralaterally to the hemisphere under study. 3. Visual tracking neurons are active during oculomotor pursuit of slowly moving visual objects, not during steady fixations. They show a marked directional but no laterality relation, and are suppressed before and during a visually evoked saccade superimposed on the smooth pursuit movement. The rate of discharge is a flat function of tracking speed so that these cells do not appear to emit signals which specify the speed of smooth pursuit movements. 4. The saccade neurons are active before and during visually evoked saccadic movements of the eyes but not before spontaneous saccades, no matter whether made in light or near darkness. The discharge of saccade neurons leads the eye movement by as much as 150 ms (mean, 73 ms)...

Action Potentials↗

PubMed1975

Posterior parietal association cortex of the monkey: command functions for operations within extrapersonal space.

Experiments were made on the posterior parietal association cortical areas 5 and in 17 hemispheres of 11 monkeys, 6 M. mulatta and 5 M. arctoides. The electrical signs of the activity of single cortical cells were recorded with microelectrodes in waking animals as they carried out certain behavioral acts in response to a series of sensory cues. The behavioral paradigms were one for detection alone, and a second for detection plus projection of the arm to contact a stationary or moving target placed at arm's length. Of the 125 microelectrode penetrations made, 1,451 neurons were identified in terms of the correlation of their activity with the behavioral acts and their sensitivity or lack of it to sensory stimuli delivered passively; 180 were studied quantitatively. The locations of cortical neurons were identified in serial sections; 94 penetrations and 1,058 neurons were located with certainty. About two-thirds of the neurons of area 5 were activated by passive rotation of the limbs at their joints; of these, 82% were related to single, contralateral joints, 10% to two or more contralateral joints, 6% to ipsilateral, and 2% to joints on both sides of the body. A few of the latter were active during complex bodily postures. A large proportion of area 5 neurons were relatively insensitive to passive joint rotations, as compared with similar neurons of the postcentral gyrus, but were driven to high rates of discharge when the same joint was rotated during an active movement of the animal...

Animals↗

PubMedDate not supplied

The spatial distribution of pulvinar neurons that project to two subregions of the inferior parietal lobule in the macaque.

The distribution of pulvinar neurons that project to the lateral intraparietal area (LIP) and area 7a, two subregions of the inferior parietal lobule in monkeys, was determined using small injections of retrogradely transported fluorescent dyes. Both LIP and 7a received the majority of their thalamic input from contiguous but distinct zones within the medial pulvinar nucleus. Thalamocortical cell bodies that projected to LIP were arranged in a dense, horizontally oriented cluster that was sandwiched between two similar clusters of neurons that projected to 7a. There was minimal overlap of the respective clusters. LIP also received an appreciable input from the dorsal half of the lateral pulvinar nucleus, but tracer placements in 7a resulted in only occasional labeled neurons in the lateral pulvinar.

Amidines↗

PubMedDate not supplied

Continuing medical education on diabetes by primary care physicians.

The actual and preferred methods of continuing medical education (CME) on diabetes were determined from a telephone survey of a stratified random sample of over 600 primary care physicians in Pennsylvania. A response rate of 73% was obtained. Journal articles were identified as the leading source of information that affected practice behavior related to diabetes. However, no single journal was read by a majority of physicians, and information provided in diabetes journals reached fewer than 10% of primary care physicians. Local educational programs and programs offered by hospitals were the preferred choices for continuing medical education. When reported patterns of care for diabetic patients were compared with published standards of care, no statistical differences were found between physicians who had and physicians who had not attended a CME course. To be most effective, CME courses should be intensive and may need to be presented locally to reach the widest possible audience.

Attitude of Health Personnel↗