Biomedical subjects
Publications and source records attributed to S Brem.
A patient with a 4-month history of unexplained nausea and vomiting is reported. The only abnormality found initially was severe gastroparesis found by gastric emptying scan. Subsequently, a posterior fossa tumor was found. The pathogenesis of this unusual presentation and the role of the gastric emptying scan is discussed.
Calcium antagonists are currently under investigation as potential beneficial drugs in the prevention of cerebral vasospasm. However, some calcium antagonists have the propensity to inhibit platelet aggregation. This study investigated the danger posed by the administration of calcium antagonists for recurrent hemorrhage in a simulated rat model of subarachnoid hemorrhage. We found that verapamil, a calcium antagonist with antiplatelet activity, lowers clot resistance and may promote rebleeding.
The authors describe a technique by which a properly demarcated regional cerebral exposure may be performed rapidly and safely. The method involves a linear scalp incision of varying length and orientation and a circumferential craniotomy of variable size and shape centered about a single burr hole. While providing for rapid exposure with reduced blood loss, the vascular integrity of the wound is also better preserved, allowing for rapid healing of the scalp. This technique provides satisfactory unilateral exposures of most cerebral sites not located in the vicinity of the frontal sinus or the sphenoid wing.
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AspCNU and SarCNU are two amino acid amide congeners (L-asparaginamide and sarcosinamide congeners) of chloroethylnitrosoureas. The in vitro myelotoxicity of these agents compared with BCNU at 1-8 micrograms/ml was determined in bone marrow cells from normal volunteers in the CFU-C assay. AspCNU and SarCNU were significantly (P less than 0.05) less myelotoxic than BCNU at equivalent microgram concentrations. SarCNU or AspCNU at 3 micrograms/ml demonstrate equivalent in vitro myelotoxicity to BCNU 1 microgram/ml. We used the human tumor stem cell assay (HTSCA) to investigate in vitro antitumor activity. We obtained four specimens of malignant glioma and one specimen of meningioma from patients not previously treated with chemotherapy. AspCNU and SarCNU were significantly (P less than 0.05) more active than BCNU at 1-3 micrograms/ml concentrations in the HTSCA in all four malignant glioma specimens. In the one meningioma specimen, BCNU was significantly (P less than 0.05) more active than either AspCNU or SarCNU at all concentrations studied. These results suggest that AspCNU or SarCNU at doses that should produce less myelotoxicity than BCNU may be more active than BCNU against gliomas.
A Cryptococcus neoformans strain which in 1983 caused an infection of the central nervous system (CNS) in a wildlife fox with rabies-like symptoms was tested for its strain-specific brown colour effect (BCE) on Guizotia abyssinica creatinine agar and for its ability to assimilate creatinine. Both reactions were found to be positive. These results were found to be largely identical with those of 2 out of 3 strains having caused fatal cryptococcosis in 1970, 1979 and 1983 in persons living in the area where the fox had been found (radius 40-100 km). Some theoretical aspects of the epidemiology and pathogenesis of cryptococcosis in the wildlife fox and rodents are discussed. For further epidemiological investigations into the prevalence of Cr. neoformans in man and animals in this area, the two reactions for detecting and typing, i.e. the BCE on Guizotia abyssinica creatinine agar and the creatinine assimilation are proposed.
Serine and phosphoglyceric acid are the classical marker intermediates of photorespiration and reductive carbon assimilation in C(3) plants. The present paper introduces a new and fast method for the determination of (14)C distribution in these compounds by selective elimination of C-3 (NaIO(4)) or C-1 (ninhydrin/ceric sulfate). Reproducibility of the procedure was found to be better than +/-1% upon degradation of [U-(14)C]serine and [U-(14)C]glycerate standards.Determination of labeling patterns in (dephosphorylated) phosphoglycerate and serine, extracted from grape leaf discs (Vitis vinifera L.) after administration of (14)CO(2) for 1 minute showed that (14)C distribution in serine changes considerably with changing assimilatory conditions. Interpretations of data basing on unusual labeling patterns of serine must therefore be accepted with caution.
The time course of intramolecular isotope distribution in phosphoglyceric acid and serine was determined after exposure of grape leaf discs (Vitis vinifera L.) to (14)CO(2) (1000 microliters per liter) for variable metabolic periods, and the labeling patterns were compared with the respective isotope distribution in the C(1-3) fragment of malic acid. The results clearly support the classical concept of a close precursor-product relationship between photosynthetic phosphoglycerate and malic acid. Under the assimilatory conditions used in this study, there was no indication of an immediate carbon transfer from serine to malate as has been suggested for C(3) plants (Kent et al. 1974 Plant Physiol 53: 491-495) because of a coincident labeling of these compounds in Vicia faba. According to our data, previous evidence in favor of this hypothetical pathway is based largely on an unusual (14)C distribution in serine, due to an extreme suppression of photorespiration, as well as on arbitrary comparisons between compounds of divergent kinetic characteristics and consequently different degrees of metabolic label randomization.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Tumor cells introduced into the rabbit vitreous produced a form of retinal neovascularization, but only when the tumor cells were in direct contact with the vascularized retina. This contrasted with the production of neovascularization at a distance of several millimeters in other angiogenesis models. An extract of adult rabbit vitreous was found to inhibit the growth of limbal neovascularization induced by tumors implanted in the rabbit corneal stroma. The experimental model of retrolental fibroplasia provides a bioassay to investigate further the apparent inhibitory substances in the vitreous.
Adult rabbit retinal vessels underwent neovascularization in response to tumor implantation within the vitreous body. The neovascular response was presumably elicited by the tumor angiogenesis factor (TAF). The response of adult retinal vessels to an angiogenic stimulus raises the possibility that a similar substance may cause retinal neovascularization in humans, and that in normal conditions the vitreous may be able to suppress angiogenic activity.
The widespread use of phototherapy for the prevention and treatment of neonatal hyperbilirubinemia has generated some conxern as physiologic substances other than bilirubin may be photoactivated. Little information is available on the long term toxicity of these photodecomposition products. Recent observations of the in vitro DNA-modifying activity of phototherapy lights has encouraged us to develop laboratory procedures which can identify and quantitate these light-induced alterations. The purpose of the present study was to develop a technique capable of detecting photochemical changes in the genetic material of human cells in tissue culture. The results demonstrate that the antinucleoside peroxidase staining procedure is capable of detecting changes in the DNA of human cells exposed to physiologic (riboflavin) and nonphysiologic (methylene blue) photosensitizing agents in the presence of light with a fluence rate (450 nm) of 141 muW-cm2.
The formation of new blood vessels, i.e., angiogenesis, is a critical step in the evolution of a brain tumor from the earliest avascular phase to the clinically overt, vascular stage. For cerebral astrocytomas, intense capillary proliferation is a poor prognostic sign, associated with rapidly growing tumors. The in vivo production of a vasoformative substance can be demonstrated by transplanting human and experimental gliomas to the rabbit cornea. Intense neovascularization is elicited by the tumor and not by control tissues. If the same tumor is transplanted to the vitreous, thereby interrupting the vasoformative signal, the tumor remains in a dormant state for a prolonged period of time, despite its malignant potential. Inhibition of angiogenesis would be an important adjunct to the surgical treatment of gliomas.
Tumors release a diffusible substance that stimulates neovascularization. To study the neovascularization that occurs in diabetic retinopathy, we implanted V2 carcinomas and mouse ependymoblastomas into the vitreous of experimental animals. In the vitreous, unlike previous sites, the tumors failed to stimulate neovascularization. They grew for weeks as small, unvascularized, three-dimensional aggregates of cells. Explosive growth into a large, vascularized mass occurred when the avascular tumors reached the retinal surface. The vitreous proved to be a valuable model for observing the in vivo growth of small, solid tumors. Xenografts survived for months without evidence of immune rejection. The consequence of the prolonged avascular state is the restriction of tumor size. The normal vitreous may act to inhibit capillary proliferation. An understanding of the mechanism for maintaining the avascular state may lead to therapeutic blockade of neovascularization. This would be important in the management of diabetic retinopathy and neoplasia.