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Biomedical subjects

B L Guthrie

Publications and source records attributed to B L Guthrie.

16 recordsLinked to original sources
PubMed1996

Resection of multiple pulmonary metastases from a recurrent intracranial meningioma.

Surgical resection of multiple pulmonary metastases from a recurrent intracranial meningioma in a 53-year-old woman is presented. The primary tumor was diagnosed in 1984 and partially excised in early 1985. The tumor recurred and was re-excised in 1989 and 1992. A fourth intracranial recurrence was noted in 1993, accompanied by multiple bilateral pulmonary metastases. The metastases were excised using staged thoracotomies in July and September 1994. The patient is surviving with cranial tumor residual.

Female↗
PubMed1994

Extraocular muscle proprioception functions in the control of ocular alignment and eye movement conjugacy.

1. The function of extraocular muscle proprioception in the control of eye movements is uncertain. We tested the hypothesis that proprioception contributes to the long-term regulation of ocular alignment and eye movement conjugacy. 2. Eye movements were recorded in monkeys with unilateral extraocular muscle palsies, before and after proprioceptive deafferentation of the paretic eye. Following deafferentation, ocular alignment and saccade conjugacy gradually worsened over several weeks. In contrast, disconjugate adaptation induced by habitual binocular viewing with a prism (disparity-mediated adaptation) occurred normally after deafferentation. 3. These results provide the first evidence that proprioception functions in the control of eye movements in primates, and indicate that proprioception contributes to the long-term adaptive mechanisms that regulate ocular alignment during fixation and saccades. The error signal used in this process may be derived from a mismatch between the efference copy and proprioceptive afference.

Afferent Pathways↗
PubMed1994

Lymphocytic hypophysitis: occurrence in two men.

Two men undergoing transsphenoidal exploration for pituitary adenoma were found to have lymphocytic hypophysitis. Both presented with frontal headaches, lethargy, and diminished libido. Laboratory investigations showed markedly depressed serum testosterone, and magnetic resonance imaging demonstrated pituitary enlargement, with optic chiasm involvement. Intraoperatively, the dura was adherent to the pituitary in each case. The resected glands were effaced by a dense lymphoplasmacytic infiltrate and fibrosis, without granulomas. Nonspecific peripheral enhancement on imaging suggested a diagnosis other than adenoma, but more experience with peripheral enhancement in lymphocytic hypophysitis is needed. The diagnosis was histological and required surgical intervention. Long-term pituitary replacement therapy is usually required.

Adenoma↗
PubMed1992

The role of stereotactic biopsy in the management of HIV-related focal brain lesions.

The criteria for brain biopsy in patients with acquired immunodeficiency syndrome (AIDS) remain unclear and without universal acceptance. In order to shed more light on this issue, the authors reviewed the records of 25 AIDS patients with focal cerebral lesions who consecutively underwent stereotactic biopsy between November 1988 and October 1990. The most frequently occurring diagnoses were lymphoma (36%), progressive multifocal leukoencephalopathy (24%), and toxoplasmosis (8%). Patients whose central nervous system disease resulted in their initial presentation (approximately 40%) survived a median of 37 weeks, as opposed to 6 weeks for those who had previous AIDS-related infections. The proportion of biopsies of contrast-enhancing lesions that were diagnostic and thereby contributed to the patients' therapeutic management was 87.5%. On the other hand, only 67% of the biopsies of nonenhancing lesions were diagnostic, and none of these lesions were treatable. All of the lymphoma patients had had AIDS for some time and, despite a reasonable preoperative Karnofsky score and postoperative radiation therapy, their median survival was only 6 weeks; however, biopsy was critical to their therapeutic management. Early brain biopsy, rather than empiric antitoxoplasmosis therapy, appears indicated for aggressive therapy of contrast-enhancing lesions in patients who have had previous manifestations of AIDS. The role for biopsy of nonenhancing lesions is less clear, but it may provide prognostic information.

AIDS Dementia Complex↗
PubMed1992

Computer-assisted preoperative planning, interactive surgery, and frameless stereotaxy.

Frame-based stereotactic systems provide valuable localization information for the performance of neurosurgical procedures. State-of-the-art systems provide for sophisticated preoperative planning and intraoperative interactive help with resection of predefined tissue volumes, providing assistance with resection of intrinsic brain tumors whose margins may not be readily visible at the time of surgery. There remain, however, a majority of neurosurgical procedures that would benefit from some form of localization but for which the application of a cumbersome frame and arc system is inconvenient. Frameless stereotactic localization or "cranial-based" localization provides a rapid and convenient means for computer-interactive localization and surgery for many of these cases. The stereotactic operating arm system is designed to complement frame-based stereotactic surgery, bringing standard neurosurgical procedures into the realm of computer-assisted interactive localization. The pace of progress is such that eventually, some form of computer interactive cranial localization will become a common neurosurgical tool. The concept of frameless localization is taken a step further in the frameless radiosurgical system described above. It is reasonable to think that this concept of "automated feature recognition," whether for recognizing scalp or bone contours, will ultimately become the foundation of procedures requiring cranial localization with reference to previously obtained digital images.

Adult↗
PubMed1990

Supratentorial low-grade gliomas.

Low-grade gliomas (grades I and II) are infiltrative lesions. Patients harboring these tumors follow extremely variable clinical courses. Review of current data suggests that in patients with large tumors, complete excision affords long-term survival, with or without radiation therapy. Partial excision should be followed by radiation therapy. The management of very small tumors in patients who are neurologically normal is controversial. Stereotactic technique is particularly useful in diagnosis, and often in tumor resection, in this group of patients.

Combined Modality Therapy↗
PubMed1989

Meningeal hemangiopericytoma: histopathological features, treatment, and long-term follow-up of 44 cases.

Forty-four cases of meningeal hemangiopericytoma that were treated between 1938 and 1987 are reviewed. Fifty-five percent of these tumors occurred in men. The average age of the patients at diagnosis was 42 years. The average duration of preoperative symptoms was 11 months. Symptoms were related to tumor location, which was similar to that of meningioma. The operative mortality was 9% overall, and has been zero since 1974 (18 patients). The average time before the first recurrence was 47 months, with the recurrence rates at 1, 5, and 10 years after surgery being 15, 65, and 76%, respectively. Ten patients have developed extraneural metastasis, mostly to lung and bone, at an average of 99 months after the first operation. The 10- and 15-year rates of metastasis were 33 and 64%, respectively. The average survival period has been 84 months, with survival rates at 5, 10, and 15 years after surgery of 67, 40, and 23%, respectively. The histological diagnosis of the tumor was not related to survival or recurrence and did not change with recurrence. Tentorial and posterior fossa tumors tended to be more lethal. Total tumor resection favorably affected recurrence and survival, as opposed to subtotal resection. Metastasis adversely affected survival, and was followed by death at an average of 24 months after its diagnosis. Radiation therapy after the first operation extended the average time before first recurrence from 34 to 75 months, and extended survival from 62 to 92 months.

Adolescent↗
PubMed1988

Baroreceptor responses derived from a fundamental concept.

A model is presented that relates the change in baroreceptor firing rate to a step change in blood pressure. This relationship is nonlinear since the alteration in rate of firing depends on the current rate of firing. It is shown that this simple relationship embodies all currently established baroreceptor response modes. The model needs refinement to allow for effects arising from the properties of the tissue matrix in which the receptors are embedded. Further analysis is precluded at present owing to paucity of quantitative experimental data.

Animals↗
PubMed1985

Selective retrograde transneuronal transport of wheat germ agglutinin-conjugated horseradish peroxidase in the oculomotor system.

The fate of wheat germ agglutinin-conjugated horseradish peroxidase (WGA/HRP) subsequent to its uptake and retrograde axonal transport in abducens motoneurons of the monkey was studied using histochemical localization of WGA/HRP reaction product and light microscopy. Injections of WGA/HRP into monkey lateral rectus muscles produced a pattern of labelled motoneurons like that obtained with native HRP. In contrast to the native HRP data, WGA/HRP injections consistently labelled additional neuronal populations in the ipsilateral medial vestibular nucleus and contralateral dorsal medullary reticular formation. These regions correspond to those containing neurons known to make inhibitory synaptic contact with abducens motoneurons. No labelled neurons were observed in regions which contain excitatory premotor neurons. These data are consistent with the notion of retrograde transneuronal transport of WGA/HRP to premotor neurons. The specificity of the transneuronal exchange is indicated by the finding that only certain populations of premotor neurons were labelled. The precise manner by which preferential transneuronal transport of WGA/HRP is attained remains to be determined.

Abducens Nerve↗
PubMed1983

Corollary discharge provides accurate eye position information to the oculomotor system.

The saccadic system accurately compensates for perturbations of eye position produced by microstimulation of the superior colliculus. This requires that information about the stimulation-induced change in eye position be provided by an extraretinal source--either proprioceptive endings in extraocular muscles or a centrally generated corollary discharge. It is shown that compensation remains intact after elimination of extraocular muscle proprioception, demonstrating that corollary discharge provides accurate eye position information.

Animals↗
PubMed1976

Size and distribution of movement fields in the monkey superior colliculus.

A gradient of response magnitude was observed across the movement fields (the range of eye movements which alter the discharge frequency of a nueron) of neurons in the intermediate and deeper layers of the superior colliculus. A vigorous discharge preceded movements with a particular direction and amplitude but reduced responses preceded movements which deviated from this direction and/or amplitude. Movement field size is a function of the amplitude of the optimal movement. Neurons discharging prior to small saccades have small and sharply tuned fields. Neurons discharging prior to large saccades have large movement fields and tuning is relatively coarse. Movement fields are topographically organized within the superior colliculus. Neurons discharging prior to small saccades are located anteriorly; neurons firing before large saccades are found caudally. Neurons near the midline discharge prior to up movements and neurons located laterally fire before downward movements. Movement fields of superior colliculus neurons are also characterized by a temporal gradient. The interval between spike discharge and the onset of a saccade is greater for movements near the center of the movement field than for movements to the periphery of the field. Results are interpreted as supporting the foveation hypothesis of superior colliculus function. It is suggested that precise saccadic movements are not produced by the discharge of a small population of finely tuned neurons but result from the weighted sum of the simultaneous movement tendencies produced by the activity of a large population of less finely tuned neurons.

Animals↗