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Biomedical subjects

J Overgaard

Publications and source records attributed to J Overgaard.

At least 307 records · Page 17Linked to original sources
PubMed1977

Hyperthermic tumour-cell devitalization in vivo.

A review of the morphologic, biochemical and clinical effects of hyperthermia on malignant cells indicates the presence of two principally different heat-induced alterations. (1) A 'destructive' lysosomal dependent cytoplasmic reaction dominates the tumour-cell devitalization in vivo, probably influenced by the characteristic tumour cell environment. (2) 'Repressive' nuclear abnormalities may be observed, but seem to be secondary in the in vivo reaction. However, under certain conditions (combined treatment modalities) this nuclear effect may be of importance.

Animals↗
PubMed1976

Occurrence of paired cisternae in the cytoplasm of interphase murine mammary carcinoma cells.

The presence of paired cisternae in the cytoplasm interphase murine mammary carcinoma cells is described. The paired cisternae are composed of about 65A thin trilaminated membranes, about 65A in thickness, with ribosomes attached to the outer membranes, but with smooth adjacent membranes between the cisternae. The function and origin of these structures were not clarified, but it is suggested that they represent surplus fragments of nuclear envelope material.

Animals↗
PubMed1976

Cerebral blood flow in patients with intracranial pressure elevation due to traumatic brain edema.

The object of this study was to determine if traumatic brain edema (BE) and increased intracranial pressure (ICP) reduce cerebral blood flow (CBF). Two groups of patients were studied, one with slight BE and ICP less than 20 mm Hg., the other with pronounced BE and ICP over 20 mm Hg. Although ICP was higher and cerebral perfusion pressure lower in pronounced edema there was only a small and non-significant reduction in CBF and no difference in cerebro-vascular resistance. Since traumatic BE does not increase resistance to blood flow through the brain, cerebral perfusion can be maintained if an adequate perfusion pressure is established. This in turn, demands the monitoring and control of ICP.

Blood Pressure↗
PubMed1976

Influence of extracellular pH on the viability and morphology of tumor cells exposed to hyperthermia.

The influence of hyperthermia (42.5 degrees C) on the viability and morphology of L1A2 ascites cells incubated at various pH levels (6.4-7.2) was studied. In contrast to unheated cells, increased extracellular acidity in hyperthermically treated tumor cells was associated with markedly reduced viability of the tumor cells exposed to hyperthermia. The cells heated at neutral pH underwent ultrastructural nuclear changes; the most prominent were the appearance of filamentous bundles and increased perichromatin granules. The cells heated under more acid conditions had an increased lysosomal activity and intense cell lysis resulting in lethal damage to the entire cell population within 6 hours after treatment. The active mechanism was not clear, but cell membrane lesions combined with the increased lysosome activity seemed of major importance in the mechanism of heat-induced damage to tumor cells kept in an acid milieu.

Animals↗
PubMed1976

Cerebral circulation after head injury. Part 2: The effects of traumatic brain edema.

The authors have assessed the effects of subacute traumatic brain edema (BE) on cerebral circulation and metabolism, and on clinical outcome. Fifty-five severely injured, comatose, young patients who survived for more than 24 hours were studied on 78 occasions within 30 days of injury. After hematomas had been surgically evacuated, BE was diagnosed by radiological evidence of brain swelling, demonstrated by cerebral angiograms and ventriculograms. At identical levels of carbon dioxide pressure, intracranial pressure was significantly elevated in the Edema Group to twice the value in the No Edema Group (27.1 vs 14.1 torr). There were, however, no significant differences in cerebral perfusion pressure cerebral blood flow, resistance to blood flow, cerebral metabolic oxygen rate, ventricular cerebrospinal fluid acid-base, lactate, K+ or Na+ concentrations, or in clinical outcome. It is concluded that this type of subacute traumatic BE, which is significantly associated with surgical lesions, is not of major hemodynamic or clinical significance in intensively treated patients, and does not cause cerebral ischemia. Patient outcome is determined more by the severity of the initial diffuse cortical and subcortical injury than by the presence or absence of subacute BE.

Adolescent↗
PubMed1976

Ultrastructure of a murine mammary carcinoma exposed to hyperthermia in vivo.

The ultrastructural changes following local hyperthermic therapy was studied in a solid murine mammary carcinoma. A few hr after treatment, a pronounced lysosomal activity was observed in the cytoplasm of the tumor cells, together with mitochondrial destruction and disaggregation of the polyribosomes. Later, more destructive changes with intense cell shrinkage and cytoplasmic lysis occurred, and within 24 hr the entire cytoplasm of all the tumor cells was completely destroyed. In the nuclei shrinkage and condensation of heterochromatin were early features. The nucleoli were gradually degranulated, but with preservation of the fibrillary component. However, here, too, complete destruction occurred within the first few days after treatment. Cells in mitosis were also arrested and destroyed in the same way. The nonmalignant cells of the tumor tissue presented only minor reversible morphological changes, and within a few days the tumor area was replaced by ingrowth of fibroblasts and macrophages. The morphological changes are discussed in the light of our present knowledge of the hyperthermic effect on tumor cells. As regards the mechanism of hyperthermic destruction of solid tumors in vivo, the hypothesis is advanced that a primary, lysosomally conditioned, selective destruction of the malignant cells occurs and that this reaction is intensified by a high acidity in the tumor milieu.

Acid Phosphatase↗
PubMed1976

Combined adriamycin and hyperthermia treatment of a murine mammary carcinoma in vivo.

A study was made of the effect of combined adriamycin and hyperthermic treatment in a solid mouse mammary carcinoma in vivo. This study demonstrated: (a) that, when given separately, adriamycin and hyperthermia enhance the destruction of a solid mouse mammary carcinoma in vivo; hyperthermia (40.5-42.5 degreesy greatly increases tumor destruction and, in a number of cases, caused initial and long-time regression; (c) that whole-body hyperthermia in combination with adriamycin gives a significant delay in tumor growth as compared with the controls, but not to the same degree as the local combined therapy; and (d) that treatment with local hyperthermia and adriamycin gives a pronounced decrease in the lethal toxicitity of adriamycin. The effect of adriamycin and heat treatment may be due to hyperthermic cell destruction in the central area of the solid tumor, together with a synergistic effect of heat and adriamycin on the proliferating peripheral tumor cells. Furthermore, local heat application may increase the adriamycin concentration in the heated tumor area, which causes a high destructive effect and a less toxic influence on the nonheated normal tissue.

Animals↗
PubMed1975

rCBF in impending brain death.

Regional cerebral blood flow (rCBF) was measured in three patients after relief of elevated intracranial pressure and restoration of normal cerebral perfusion pressure. Two patients, studied within 4 hours after closed head injury were found to have marked impairment of cortical blood flow and elevation of cerebrovascular resistance. We suggest that this picture is indicative of impending brain death, and may be the result of a long period of severe cerebral ischemia. The third patient, who had a shorter period of intracranial hypertension occurring during anaesthetic induction, responded to reduction of ICP quite differently with a transient relative hyperaemia. The physiopathological explanations for these two different types of flow response and their possible clinical significance are discussed.

Accidents, Traffic↗
PubMed1975

Histologic and histochemical reactions in a mouse mammary carcinoma following exposure to combined heat-roentgen irradiation.

In mouse experiments a high curative effect on implanted tumours was obtained by successive application of low local heat and roentgen doses. Histologic and histochemical examinations of tumours so treated revealed a special reaction in the tissues. A total and rapid destruction of all hypoxic tumour tissue was observed and (in successful cases) a total blockade of all mitotic activity in euoxic tumour tissue was followed by a long-drawn necrobiotic decay of the existent tumour cells. The disturbances are electively bound to the tumour cells, only some normal tissues may secondarily be injured. A rapid and intensive lysosomal activity in all the tumour cells may probably be of importance in the reaction.

Animals↗
PubMed1974

Radiation sensitizing effect of heat.

The radiation sensitizing effect of heat is analysed. In an isologous mouse-tumour system a successive local exposition to heat and roentgen irradiation with doses of both components of a size expected separately to give no or a few cures only an evident rise in the curative results was obtained. The presence of a synergism of the factors applied is suggested. The effect obtained depends on the dose of both factors. It is independent of the sequence of the application of the two components and is not reduced by an interval of 24 h between the exposures.

Animals↗