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Biomedical subjects

C Gajdusek

Publications and source records attributed to C Gajdusek.

At least 19 recordsLinked to original sources
PubMed2001

Early molecular changes in irradiated aortic endothelium.

Irradiated aortic endothelial cells (EC) exhibit distinct morphological, functional, and physiological responses to ionizing radiation (IR). However, the molecular basis for these responses has not been fully characterized. Cultured bovine and rat aortic endothelial cells were exposed to single fraction doses (0-30 Gy) of gamma radiation. IR caused dose-dependent DNA strand breaks which were repaired to near baseline levels within 30 min. A dose-dependent inhibition of cell growth was noted for IR greater than 1 Gy. At doses greater than 2.5 Gy, morphologic changes consistent with apoptosis and loss of cell viability were present beginning 12-16 h after radiation, with subsequent detachment of EC from the cell monolayer. By Western blot analysis, expression of p53, gadd45, p21, and bax protein increased in a time-and dose-dependent manner; p53 expression was maximal at 3 h after IR, and gadd45, bax and p21 levels peaked at 6 h. By Reverse Transcriptase Polymerase Chain Reaction (RT-PCR), levels of p53 mRNA were not significantly increased after IR, whereas gadd45 exhibited time- and dose-dependent increase in mRNA synthesis after IR. Activation of intracellular caspases, manifest by proteolytic poly (ADP-ribose) polymerase (PARP) and lamin B cleavage, was maximal at 15 h after IR, concident with other indices of EC apoptosis, including oligonucleosomal DNA degradation, TUNEL immunostaining, and morphologic changes. The tripeptide protease inhibitor z-Val-Ala-Asp (zVAD) prevented PARP and lamin cleavage, DNA fragmentation, morphological changes, and cell detachment in irradiated EC. The combined data suggested that gamma radiation induces a dose- and time-dependent sequence of early events in cultured EC with modulate growth arrest, apoptosis, and possibly premature senescence in surviving cells.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Expression of endothelial nitric oxide synthase after exposure to perivascular blood.

OBJECTIVE: Although nitric oxide (NO) has been implicated in the development of vasospasm after subarachnoid hemorrhage, little is known regarding the time course of NO synthesis in vessel wall after exposure to perivascular blood. This study measures temporal characteristics of changes in vessel wall NO synthesis. METHODS: Rat femoral arteries exposed to perivascular blood for 3, 5, or 7 days were assayed for the endothelial isoform of NO synthase (eNOS) by Western blot testing. Additionally, rat femoral arteries exposed to perivascular blood for intervals from 3 to 14 days were analyzed by means of immunohistochemistry for eNOS. RESULTS: Semiquantitative densitometry of femoral artery Western blots demonstrated a biphasic pattern of eNOS expression after exposure to perivascular blood. Compared with control arteries, eNOS expression increased at 3 days (53 +/- 36%), normalized at 5 days (-6 +/- 7%), and decreased by 7 days (-39 +/- 15%). Immunohistochemistry confirmed the changes in expression of immunoreactive eNOS in femoral endothelium during the first week after chronic perivascular blood exposure and apparent reduced eNOS immunostaining, which persisted up to 14 days after application of blood. CONCLUSION: The expression of endothelial-derived NO in rat femoral artery exposed to perivascular whole blood does not directly correlate with changes in vessel caliber during this interval. The biphasic expression of eNOS observed in these experiments highlights the complexity of processes occurring in the vicinity of the vessel wall during vasospasm and may be related to several mechanisms that modulate vessel tone and response to injury.

Animals↗
PubMed2000

Inhibition of rat smooth muscle proliferation by radiation after arterial injury: temporal characteristics in vivo and in vitro.

Although several studies have suggested that inhibition of arterial narrowing by radiation after angioplasty is dependent on both time and dose, little is known regarding the temporal aspects of this effect and the mechanisms by which radiation affects the response of smooth muscle cells to injury. To determine the time course of inhibition of intimal hyperplasia by radiation, 135 rats were given single-fraction external gamma irradiation (1-10 Gy) to one carotid artery at intervals from 5 days before to 5 days after bilateral carotid artery balloon catheter injury, and intimal cross-sectional area was determined from histological sections at 20 days after injury. There was a prominent time- and dose-dependent inhibition of intimal hyperplasia by radiation when it was administered before or after balloon injury, with the greatest effect noted within 24 h before or after injury. To investigate the effect of radiation on smooth muscle cell growth (by cell counting) and proliferation, cell cycle kinetics (by BrdU incorporation), and cell killing (by clonogenic assay), smooth muscle cell cultures derived from rat aortic explants were seeded in equine plasma to induce quiescence, and radiation (2.5-10 Gy) was administered at various intervals before or after synchronous growth stimulation by 10% whole blood serum. A similar time and dose dependence was noted in growth kinetics, BrdU incorporation and cell killing for smooth muscle cells irradiated in vitro; in each case, the effect was most prominent for radiation administered in temporal proximity to stimulation with whole blood serum. By Western blot analysis, cultured smooth muscle cells showed a rapid time-dependent increase in Cdkn1a (formerly known as p21) protein expression, followed by a delayed increase in Tp53 (formerly known as p53) expression after irradiation. Activation of intracellular caspases, manifest by proteolytic poly(ADP-ribose) polymerase (PARP) cleavage, was not detected in smooth muscle cell cultures after irradiation. These observations suggest that radiation limits intimal hyperplasia in vivo by a transient, reversible process. Although apparent cytotoxic injury occurs in vitro, apoptosis of smooth muscle cells is not apparent. Both inhibition of proliferation of smooth muscle cells and cell cycle delay may contribute to inhibition of intimal hyperplasia in vivo by radiation.

Animals↗
PubMed1996

Reduction of intracellular glutathione levels produces sustained arterial narrowing.

OBJECTIVE: Although lipid peroxidation and alterations in endogenous antioxidants have been hypothesized to contribute to cerebral vasospasm after subarachnoid hemorrhage, there has been no direct evidence demonstrating the relationship between oxidative stress and delayed arterial narrowing. To elaborate the role of the endogenous intracellular antioxidant and electron exchanger glutathione (GSH) in cerebral vasospasm, rat femoral arteries were treated with perivascular application of I-buthionine-(SR)-sulfoximine (BSO), which inhibits the synthesis of GSH. METHODS: To determine the dose-response relationship, BSO at doses of 10 to 100 mg/ml, in platelet-rich plasma, was applied for 7 days to rat femoral arteries in vivo. Vessels were then perfusion-fixed for morphometric analysis of luminal cross-sectional area. To determine the time course of arterial narrowing, BSO (75 mg/ml) was applied to femoral arteries for 1, 3, 7, or 21 days before histological analysis, as described above. With rats treated with 50 to 100 mg/ml BSO, exogenous GSH (100 mg/kg) was administered, by intraperitoneal injection, daily for 7 days. To demonstrate the mechanism of BSO effects in smooth muscle cells (SMCs), cultured rat aortic SMCs were treated with 1 mmol/l BSO for 24 hours and assayed for intracellular levels of GSH and two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal. RESULTS: Compared with control arteries treated with platelet-rich plasma alone, perivascularly administered BSO applied for periods of 1 to 21 days produced sustained and reversible narrowing of rat femoral arteries with a time course, severity, and histological appearance analogous to those observed after perivascular application of whole blood. BSO-induced arterial narrowing was dose-dependent, with 60% reductions in the luminal cross-sectional area being noted at 75 and 100 mg/ml (P < 0.005). Systemic administration of exogenous GSH slightly inhibited the effect of BSO on arterial narrowing, although the inhibition was not statistically significant. Cultured rat aortic SMCs exposed to BSO for 24 hours showed a 70% decrease in intracellular GSH levels (P = 0.03); levels of two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal, were increased by 25% (P = 0.24) and 38% (P = 0.09), respectively. CONCLUSION: These data support the hypothesis that diminished intracellular levels of GSH may produce delayed chronic arterial narrowing after subarachnoid hemorrhage. The specific mechanism by which GSH levels modulate vasoconstriction remains uncertain but may involve endogenous antioxidant capacity in SMCs.

Animals↗
PubMed1995

Antioxidant and iron-chelating agents in cerebral vasospasm.

Prior work in our laboratory showed that the perivascular application of deferoxamine (an antioxidant and iron-chelating agent) inhibited delayed arterial narrowing after chronic blood exposure in a rat femoral artery model of vasospasm. To determine which of these mechanisms was operant in vasospasm, we compared deferoxamine with two agents (ascorbic acid and U74389F) that have antioxidant but not iron-chelating capacity. For the systemic application of drugs in 23 rats, whole blood encased in a silastic cuff was applied to the right femoral artery of each rat; whole-blood serum (lacking erythrocytes) was similarly applied to the left femoral artery. Deferoxamine (30 mg/kg/d), ascorbic acid (1000 mg/kg/d), U74389F (30 mg/kg/d), or pH-matched control vehicle was administered three times daily by intraperitoneal injection for 7 days. After exposure to whole blood, arteries treated with intraperitoneal vehicle showed an 85% reduction in the lumen, compared with vessels exposed to erythrocyte-free serum (P < 0.001). Intraperitoneal ascorbic acid and U74389F produced moderate amelioration in arterial narrowing (53 and 61% decrease, respectively, in the lumen versus controls; P < 0.05 versus vehicle); deferoxamine had no significant effect when administered intraperitoneally. To test the efficacy of these agents by the perivascular application of drugs, whole blood was applied to both femoral arteries in each of 25 rats. Solutions of deferoxamine (10 mg/ml), ascorbic acid (50 or 100 mg/ml), or U74389F (15 or 30 mg/ml) were directly applied to the perivascular thrombus surrounding the femoral arteries, compared with vehicle applied to contralateral vessels. The perivascular application of 50 mg of ascorbic acid (36% reduction, P < 0.05), 100 mg of ascorbic acid (31% reduction, P < 0.01), or 10 mg of deferoxamine (41% reduction, P < 0.05) significantly inhibited arterial narrowing, compared with vehicle. The application of U74389F at a dose of 15 or 30 mg directly into the perivascular thrombus produced nonsignificant reduction in arterial narrowing. These data suggest that mechanisms other than direct iron toxicity, such as generation of cytotoxic free radicals, may play an important role in cerebral vasospasm. In addition, the route of administration and concentration of drugs in the perivascular region adjacent to the thrombus may be critical to their efficacy.

Animals↗
PubMed1995

Radiation inhibition of intimal hyperplasia after arterial injury.

To demonstrate the effect of gamma radiation on proliferating smooth muscle cells in vivo, a standardized bilateral carotid balloon catheter arterial injury was produced in 45 rats and doses from 0-20 Gy were delivered to the right carotid artery at 24 h after injury. At 20 days after injury, cross-sectional area of intima was determined from axial histological sections. Compared to contralateral, nonirradiated balloon-injured arteries, radiation produced a significant dose-dependent reduction in intimal cross-sectional area, with a 50% decrease at 5-7.5 Gy. To determine the effect of timing of irradiation on intimal hyperplasia, 30 rats with bilateral carotid injury received unilateral cervical irradiation at doses of 1, 5 or 10 Gy administered at either 1, 3 or 5 days after injury. The radiation dose (P = 0.0002), timing of irradiation (P = 0.003) and an interaction between timing and dose (P = 0.0278) were significantly associated with reduction in neointimal cross-sectional area. To determine the effects of radiation on intimal hyperplasia at later intervals, rats irradiated with 15 (n = 5) or 20 Gy (n = 5) were euthanized at 3 months after injury. A significant persistent reduction in intimal cross-sectional area for irradiated arteries at 3 months was associated with minimal apparent radiation effects upon adjacent tissue. These data suggest that external gamma irradiation at the single doses used effectively inhibits smooth muscle proliferation and intimal hyperplasia in the rat balloon catheter injury model in a time- and dose-dependent manner.

Angioplasty, Balloon↗
PubMed1990

Identification of a unique biological tumor marker in human breast cyst fluid and breast cancer tissue.

Breast cyst fluid from 35 women was stratified into risk groups based on personal and family history of breast cancer. Mitogenic activity in breast cyst fluid of women at highest risk to develop breast cancer was significantly higher than the activity in the lowest-risk group. There was a direct dose-dependent relationship between mitogenic activity and increased risk of developing breast cancer. Size-exclusion chromatography showed that breast cyst fluid from women at highest risk contained two peaks of growth factor activity: less than 6 kilodaltons (kd), identified as human EGF (epidermal growth factor), and 6 to 18 kd. Moderate-risk group samples demonstrated only the single less than 6 kd peak, whereas the lowest-risk group had insignificant growth-promoting activity. Breast cancer tissue analyzed in a similar manner revealed a predominant 6- to 14-kd peak of mitogenic activity demonstrating the same acid- and heat-stability found in breast cyst fluid.

Biomarkers, Tumor↗
PubMed1988

Immunological findings in neurological diseases associated with antibodies to HTLV-I: activated lymphocytes in tropical spastic paraparesis.

A retrovirus involvement in the etiology of certain neurological diseases is currently an area of intense interest. Tropical spastic paraparesis and other chronic progressive myelopathies have been clearly associated with increased serum and cerebrospinal fluid antibody titers to human T-lymphotropic virus type I; however, little is known about the cellular immune response. In the present study, activated T-lymphocytes were found in the peripheral blood of patients with this disorder. There were increased numbers of large CD3-positive cells that also expressed histocompatibility leukocyte Class II (DR) and interleukin 2-receptor molecules. In addition, a significantly elevated spontaneous lymphoproliferative response was demonstrated in all patients. This is consistent with the known in vitro effects of human T-lymphotropic virus type I. In one patient, a defect in the generation of measles virus-specific cytotoxic T cells was identified. These observations indicate abnormalities of the cellular immune response in tropical spastic paraparesis.

Antibodies, Viral↗
PubMed1986

[Creutzfeldt-Jakob disease in France. Value of familial forms. Is there a gene controlling the length of the incubation period?].

An extensive search for patients who died of Creutzfeld-Jakob disease in France between 1968 and 1982 resulted in the discovery of 327 cases, 233 of which were histologically proven and 29 transmitted to animals; 17 patients belonged to 6 families. Further investigations among members of these 6 families yielded 21 additional cases, i.e. a total of 38 familial cases. Studies among sibships suggested an autosomal dominant pattern of transmission but did not exclude lateral contamination infancy. The patients' age at death was 10 to 15 years lower than that of the total of French cases and seemed to be a characteristic of each individual family. This suggests that, as in scrapie, a gene may control the length of the incubation period.

Adult↗
PubMed1986

Activation of coagulation releases endothelial cell mitogens.

Recent studies have indicated that endothelial cell function includes elaboration of growth factors and regulation of coagulation. In this paper we demonstrate that activated coagulation Factor X (Factor Xa), a product of the coagulation mechanism generated before thrombin, induces enhanced release of endothelial cell mitogens, linking these two functions. Mitogenic activity generated by cultured bovine aortic endothelial cells in response to Factor Xa included platelet-derived growth-factor-like molecules based on a radioreceptor assay. Effective induction of mitogens by Factor Xa required the integrity of the enzyme's active center and the presence of the gamma-carboxyglutamic acid-containing domain of the molecule. Factor Xa-induced release of mitogens from endothelium occurred in serum-free medium and was not altered by hirudin or antibody to Factor V, indicating that it was a direct effect of Factor Xa and was not mediated by thrombin. Elaboration of mitogenic activity required only brief contact between Factor Xa and endothelium, and occurred in a time-dependent manner. Generation of enhanced mitogenic activity in response to Factor Xa was unaffected by the presence of actinomycin D and was not associated with increased hybridization of RNA from treated cells to a v-sis probe. Release of mitogenic activity was dependent on the dose of Factor Xa, being half-maximal at 0.5 nM and reaching a maximum by 5 nM. Radioligand binding studies demonstrated a class of endothelial cell sites half-maximally occupied at a Factor Xa concentration of 0.8 nM. The close correspondence between the parameters of Factor Xa-induced mitogen release and Factor Xa binding suggests these sites may be related. When Factor X was activated on the endothelial cell surface by Factors IXa and VIII, the Factor Xa formed resulted in the induction of enhanced release of mitogenic activity. These data suggest a mechanism by which the coagulation system can locally regulate endothelial cell function and vessel wall biology before thrombin-induced release of growth factors from platelets.

Animals↗
PubMed1982

Kuru with incubation periods exceeding two decades.

The clinical characteristics of kuru in 15 patients are described. All the patients had a history of joint pains preceding difficulty walking. The severity of the neurological dysfunction varied from mild truncal and limb ataxia necessitating the use of a stick for walking to terminal illness accompanied by marked ataxia, rigidity, spasticity, and dementia. All the patients with kuru in this study had a apprehensive, frightened facial expression. Most of the patients examined showed diminished or absent optokinetic nystagmus bilaterally. Apprehensive facies and diminished optokinetic nystagmus have not previously been described in kuru. The other clinical features of the current patients with kuru are similar to those recorded twenty years ago. Epidemiological surveillance, anamnesis, and missionary reports strongly suggest that all the patients described in this study were exposed to the kuru agent more than two decades ago through ritualistic cannibalism. Thus the incubation period or time interval from exposure to the onset of clinical illness exceeds two decades, while the duration of illness is two years or less. The cause of these extraordinarily long incubation periods is unknown but may result in part from exposure to small doses of the kuru agent through an inefficient oral route.

Adult↗
PubMed1982

Interactions of vascular wall cells with collagen gels.

Culture properties of bovine aortic endothelial cells and bovine aortic smooth muscle cells have been examined in relation to collagen gels. Endothelial cells grown on collagen maintain typical monolayer morphology not only in relationship to the overlying medium but also with respect to the collagen substrate. Endothelial cells placed within a collagen matrix assume a mycelial pattern resembling that of the microvasculature. Overlayment of confluent endothelial cells with collagen induces separation of the cells, changes in morphology, and reinitiation of growth. These shape changes do not require protein synthesis, appear to be independent of fibronectin, are not inhibited by cytochalasin D, but are inhibited by colchicine. Endothelial cell growth can be reinitiated by collagen. This phenomenon appears to be related to a change in cell shape and perhaps to separation of cells at the intercellular junction. In contrast, smooth muscle cells plated on collagen infiltrate the gels and assume a spindle-like, elongated morphologic appearance. Overlayment with collagen does not alter smooth muscle cell shape. Migration into the collagen gels is significantly enhanced when cells are cultured in medium containing platelet-released products, independent of growth stimulation itself. Migration is accompanied by collagen gel degradation. Release of labeled collagen into the medium by smooth muscle cells and appearance of TCA fragments in collagenase assay suggest secretion of collagenase. In summary, endothelial cells, but not smooth muscle cells, are restricted to the surface of collagen gels. The ability of the smooth muscle cells to invade is stimulated by platelet products and may be related to the synthesis of a smooth muscle collagenase.

Animals↗
PubMed1980

Descriptive epidemiology of Creutzfeldt-Jakob disease in Chile.

Descriptive epidemiological data are presented from a survey of 35 cases of Creutzfeldt-Jakob disease (CJD) that occurred in Chile in the period 1955 to 1977. The average mortality in Chile (0.31 deaths per 1 million) and in urban Santiago (0.73 deaths per 1 million) is compared with data reported from other countries. An increasing incidence in recent years is probably related to a greater awareness of the disease. The familial occurrence of CJD in nine patients from five affected families is described, and its analysis suggests a genetically determined susceptibility with incubation periods of more than 30 years. Horizontal transmission of the disease may have occurred in one patient in whom the disease developed 13 years after the patient married into a family with seven other affected members.

Adult↗
PubMed1980

Amyotrophic lateral sclerosis among Chamorro migrants from Guam.

Amyotrophic lateral sclerosis (ALS), which occurs in unusually high incidence among the Chamorro people on the island of Guam, has developed in 28 Chamorro migrants--24 of whom had onset in the United States, Japan, Germany, or Korea--after periods of absence from Guam of 1 to 34 years. Thus, the latency period for the disease, if caused by environmental factors on Guam, may be over three decades. Four further patients developed ALS within 1 to 14 years of their return to Guam after long-term residence in the continental United States. The minimum exposure time to environmental variables on Guam, based on age at migration, was 18 years, and all patients had spent their childhood and adolescence on Guam. Estimates of crude mortality rates for ALS from these data are considerably higher than for the United States population, and lower than the ALS mortality rates for nonmigrant Chamorros on Guam.

Adult↗
PubMed1980

An endothelial cell-derived growth factor.

Cell-free plasma-derived serum (PDS) is deficient in the platelet-derived growth factor and will not support the growth of 3T3 cells, fibroblasts, or smooth muscle cells. However, when PDS-containing medium is preincubated with endothelial cells, the medium becomes modified so that it will support growth. The activity produced by the endothelial cells results from a polypeptide of 10,000 to 30,000 daltons which has several features that differ from those of the platelet-derived growth factor, including heat instability and lack of adsorption to CM Sephadex.

Animals↗
PubMed1976

Genetic structure and heterozygosity in the kuru region, eastern highlands of New Guinea.

Genetic structure of 20 of the 37 linguistic groups in the Eastern Highlands of New Guinea including the kuru region is analyzed using information on blood groups and serum protein polymorphisms. The average individual is heterozygous at 28.6% of loci and the average number of alleles per locus is 1.234. Coefficients of kinship for linguistic groups range from 0.005 for the sweet potato cultivating North Fore to 0.075 for the isolated Pawaians whose dietary staple is sago and who depend more on hunting and gathering. As one selects linguistic groups with smaller and smaller population size and increasing isolation, one finds that kinship coefficients rise as much as tenfold, but there is no concomitant loss of heterozygosity or trend toward fixation of alleles. Genetic relationships established by genetic distance trees and by principal components analysis are comparable and are consistent with other anthropological observations.

Alleles↗