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Biomedical subjects

K R Smith

Publications and source records attributed to K R Smith.

At least 145 records · Page 8Linked to original sources
PubMed1981

Case report. Aphasia in thalamic stroke: CT stereotactic localization.

We present a patient in whom dysphasia followed suddenly upon an apparently discrete thalamic infarct proven by computed tomography (CT). Detailed psychometric data of the patient's speech and memory disorder obtained during the acute and chronic stages were correlated with the evaluation of a focal thalamic lesion as demonstrated by serial CT. The findings and deductions drawn from selective reports in the literature form the basis of this presentation.

Aphasia↗
PubMed1980

Randomized comparisons of radiotherapy and nitrosoureas for the treatment of malignant glioma after surgery.

Within three weeks of definitive surgical intervention, 467 patients with histologically proved malignant glioma were randomized to receive one of four treatment regimens: semustine (MeCCNU), radiotherapy, carmustine (BCNU) plus radiotherapy, or semustine plus radiotherapy. We analyzed the data for the total randomized population and for the 358 patients in whom the initial protocol specifications were met (the valid study group). Observed toxicity included acceptable skin reactions secondary to radiotherapy and reversible leukopenia and thrombocytopenia due to chemotherapy. Radiotherapy used alone or in combination with a nitrosourea significantly improved survival in comparison with semustine alone. The group receiving carmustine plus radiotherapy had the best survival, but the difference in survival between the groups receiving carmustine plus radiotherapy and semustine plus radiotherapy was not statistically significant. The combination of carmustine plus radiotherapy produced a modest benefit in long-term (18-month) survival as compared with radiotherapy alone, although the difference between survival curves was not significiant at the 0.05 level. This study suggests that it is best to use radiotherapy in the post-surgical treatment of malignant glioma and to continue the search for an effective chemotherapeutic regimen to use in addition to radiotherapy.

Aged↗
PubMed1980

Hydrolytic enzyme activities of the nervous system.

The activities of five hydrolytic enzymes (acid and alkaline phosphatase, hexosaminidase [N-acetyl-beta-D-glucosaminidase], beta-galactosidase, and beta-glucorinidase) were measured in reconstituted homogenates of lyophilized human brain tissue and primary and metastatic tumors. The linearity of reaction, with respect to incubation time, and optimal pH of each enzyme and in tumor tissues were comparable to those in normal brain tissue. Total enzyme activities of hexosaminidase, beta-glucuronidase, and beta-galactosidase were significantly higher in tumors than in normal cerebral white matter. The ratio of hexosaminidase activity to beta-glucuronidase activity was significantly lower for metastatic than for primary tumors or normal white matter. When histological observations do not clearly establish if a brain tumor is primary or metastatic, this ratio may help. Alteration of hydrolytic enzyme activities as demonstrated here may be indicative of "ket enzymes" that are essential for maintaining the metabolic advantages of tumors.

Acetylglucosaminidase↗
PubMed1980

Ultrastructure of degenerating cerebellothalamic terminals in the ventral medial nucleus of the cat.

Terminal degeneration of cerebellar afferents in the ventral medial thalamic nucleus (VM) was studied in cats at the ultrastructural level after uni- or bilateral lesions in the brachium conjunctivum (BC). To achieve discrete lesions within the BC, a new very accurate stereotaxic technique was used. Numerous large terminals belonging to a population of so-called LR boutons were observed degenerating in the VM. The boutons displayed a wide variety of degenerative changes. Some revealed the features of the classical neurofilamentous type of degeneration. Others, although containing a slightly increased number of neurofilaments, featured much more prominently large numbers of coated vesicle shells and heavy accumulations of a flocculent electron-dense material. Degeneration in a third group of boutons similar to some extent to the light type of degeneration was characterized by tight clumping of enormously swollen or distorted synaptic vesicles within a light matrix. At later stages, however, all these boutons were believed to become shrunken and electron-dense since intermediate stages between the light- and dark-appearing boutons were observed. The degenerating cerebellar boutons formed asymmetrical synaptic contacts. Groups of 3 or 4 boutons terminated upon dendrites of projection neurons synapsing more frequently on spines than on dendritic stems. The synaptic contacts between cerebellar boutons and the vesicle-containing dendrites of local circuit neurons were encountered as often if not more than the contacts on projection neuron dendrites. Triads consisting of cerebellar boutons and dendrites of both types of neurons were observed very regularly. This synaptic arrangement provides the anatomical basis for the modification of cerebellar input in the VM by interneurons.

Afferent Pathways↗
PubMed1980

Hydrolytic enzymes in meningiomal subtypes.

Estimation of activity of five hydrolytic enzymes was made in foru histologically different types of human meningiomas derived from surgery. The hydrolytic enzymes examined in 13 tumors included four lysosomal enzymes: beta-glucuronidase, N-acetyl-beta-D-glucosaminidase (hexosaminidase), beta-galactosidase, and acid phosphatase. The fifth enzyme studied was alkaline phosphatase. The one papillary-type meningioma examined appeared to contain generally greater activities of the lysosomal enzymes than the other tumor types. Alkaline phosphatase was decidedly greater in transitional type meningiomas. The correlation of histological types with alkaline phosphatase activity is discussed with regard to previous observations.

Acid Phosphatase↗
PubMed1980

Stereotactic neurosurgery in experimental animals. Use of intracerebral landmarks and an atlas of the cat brain.

A stereotactic method, based on the correlation of intracerebral radiological and anatomical landmarks, was developed for application in experimental animals. To make possible the use of this method, particularly in the cat, a stereotactic atlas was developed with an intracerebral coordinate system, as all currently available stereotactic atlases of experimental animals are based on extracranial landmarks. Advantages of the proposed method compared to the classical Horsley-Clarke method are discussed.

Animals↗
PubMed1979

Consideration of benefits and costs: a conceptual framework for the health planner.

It is not possible to set forth "cookbook" formulae to which health planners can refer when considering various priorities and recommended actions in the development of an HSP and AIP. It is, however, possible to develop a general framework for health planners to use in considering priorities of goals and in selecting recommended actions.

Cost-Benefit Analysis↗
PubMed1978

A stereotaxic method based on ventricular radiography in the cat (with special reference to the stereotaxic topography of the substantia nigra).

A method based on an intracerebral coordinate system and contrast ventriculography was developed for stereotaxic surgery in the cat. The intercommissural (CA-CP) line was used as the principal reference because its length showed little variability in animals within a wide weight range. The stereotaxic coordinates of the substantia nigra (SN) in relation to the CA-CP line and the midline were evaluated in serail sections. Stereotaxic operations with the use of ventricular radiography were performed in different parts of the SN in 18 cats. Histological verification showed that the selected target regions within the SN were very accurately reached in all animals operated with this method. The precision of the stereotaxic method based on the intracerebral coordinate system compared to the Horsley-clarke method is discussed.

Animals↗
PubMed1978

Nigrothalamic pathway in the cat demonstrated by autoradiography and electron microscopy.

Light microscopic autoradiography and electron microscopy were used to trace the nigrothalamic projections and to study the sites of termination of this pathway in the cat. Injections of tritiated amino acids or electrolytic lesions were placed in the substantia nigra pars reticularis (SNr). An accumulation of radioactivity was found in the ventral medial nucleus and in the ventromedial part of the ventral anterior nucleus. At the ultrastructural level degenerating medium size synaptic boutons and medium size myelinated fibers were observed in these nuclei. The boutons contained clear pleomorphic veiscles and formed symmetrical type synaptic contacts with regular type dendrites and vesicel-containing dendrites. The present findings indicate that the ventral medial nucleus is the principal site of termination of nigrothalamic projections in the cat.

Animals↗
PubMed1978

Primary leptomeningeal melanoma: an ultrastructural study.

A primary leptomeningeal melanoma in a 19-year-old white women has been shown by electron microscopy to contain light and dark cells. The light cells fill the subarachnoid space, contain mature melanosomes and exhibit intracytoplasmic fine fibrils. The dark cells are found within the collagen network of pia-arachnoid. They possess a small rim of ribosomal-rich cytoplasms, occasional premelanosomes and no intracytoplasmic fibrils. The tumor cells appear to arise from these dark activated melanoblasts in the pia-arachnoid and proliferate into more differentiated light cells. A similar pattern of two types of cells has not been described in primary CNS melanomas. The possibility of differentiation from cutaneous melanoma is discussed.

Adult↗
PubMed1978

Diverticular disease of the colon: surgical management at a military hospital.

A recent review of the surgical management of diverticular disease of the colon included 73 patients. One-stage resections were accomplished in 67%, primarily in patients operated on electively for recurrent diverticulitis or fistula, and in the group of patients with cecal diverticulitis operated on for presumed appendicitis. Single-stage resection with ileorectal anastomosis is also preferred in patients with massive diverticular bleeding. For patients with large abscesses or diffuse peritonitis a two-stage procedure which removes the site of disease in the initial operation is recommended. There were no deaths and a lower incidence of complications in the group of patients who had elective operations for recurrent diverticulitis and fistula.

Adult↗
PubMed1977

The Haarscheibe.

The Haarscheibe is a specialized spot of epidermis containing many Merkel cell-neurite complexes. It is a highly sensitive, slowly adapting, modality-specific touch receptor occurring in all mammals. Its exact role in signaling sensation in human beings is undetermined, and the function of Merkel cells, with their distinctive cytoplasmic granules, in transducing mechanical force into neural action potentials remains to be determined.

Action Potentials↗