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Biomedical subjects

G Dawson

Publications and source records attributed to G Dawson.

At least 73 records · Page 4Linked to original sources
PubMed1997

Anti-immunoglobulin-induced apoptosis in WEHI 231 cells involves the slow formation of ceramide from sphingomyelin and is blocked by bcl-XL.

Prolonged (>24 h) exposure to anti-IgM (an antigen surrogate that induces membrane cross-linking and apoptosis) induced a 3-fold increase in the mass of endogenous ceramide measured by 32P labeling by diacylglycerol kinase and a 4-fold increase in ceramide as measured by metabolic labeling with [3H]palmitate in a B-lymphocyte cell line, WEHI 231. This correlated with the induction of apoptosis. Shorter exposure times to anti-IgM (up to 8 h) failed to elicit apoptosis and did not elicit increased ceramide formation. After 8 h, apoptosis occurs concomitantly with ceramide formation over the next 40 h. Further, we showed that exogenous ceramide mimicked anti-IgM-induced apoptosis and that apoptosis was potentiated in serum-free media. Treatment of cells with an inhibitor of ceramide catabolism, N-oleoylethanolamine, increased both ceramide formation and apoptosis and accelerated apoptosis induced by anti-IgM. To examine further how ceramide metabolism is involved in apoptosis, we derived cell lines from a small population of cells resistant to N-oleoylethanolamine. These cell lines were selected based on an altered ceramide metabolic pathway, were resistant to apoptosis induced by anti-IgM, and showed no significant increase in ceramide when challenged with anti-IgM. The basis of this resistance was shown to be the failure to activate neutral sphingomyelinase activity following 24-h treatment with anti-IgM, in contrast to the 2-fold increase in neutral sphingomyelinase activity observed in wild type cells. We have shown previously that transfection of WEHI cells with bcl-xL conferred resistance to anti-IgM-induced apoptosis, whereas transfection with bcl-2 did not (Gottschalk, A., Boise, L., Thompson, C., and Quintans, J. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 7350-7354). In this study, these bcl-xL transfectants also displayed increased resistance to exogenous N-acetylsphingosine (C2-ceramide) or N-hexanoylsphingosine (C6-ceramide). However, when challenged with anti-IgM the bcl-xL transfectants produced levels of ceramide similar to wild type cells, suggesting that ceramide formation is upstream of bcl-xL and that it is a major determinant of B-cell death.

Amidohydrolases↗
PubMed1997

Completeness of case ascertainment in a Scottish regional cancer registry for the year 1992.

To assess completeness of case ascertainment by the Scottish Cancer Registry for the year 1992, we assembled a collection of databases containing potential registrations (excluding non-melanoma skin tumours and non-invasive neoplasms) from 14 separate sources relating to the population covered by one of the five regional registries. Apparently missed registrations were identified by linkage of these databases to cancer registration records. Their eligibility for registration was determined by reference in medical records, or when these were unavailable, by reference to the local Community Health Index (to establish residency at the time of diagnosis) in conjunction with the text of the original pathology report and/or the original death certificate. Misclassifications of site or incidence year were not regarded as missed cases. Of 517 apparently missed cancer registrations, 66 cases (3.5% of the revised total number of registrations of malignant neoplasms other than non-melanoma skin tumours for the study area in 1992) should have been registered as new independent primary malignant neoplasms, giving an overall estimate of completeness of 96.5%. The fact that so many apparently missed registrations were not eligible for registration illustrates the limitations of passive registration. Ascertainment of cases by the Scottish Cancer Registry appears to be high for most sites and compares favourably to the figures reported by registries outside Scotland.

Humans↗
PubMed1997

Infants of depressed and nondepressed mothers exhibit differences in frontal brain electrical activity during the expression of negative emotions.

Studies have shown that infants of depressed mothers express negative emotions more frequently than infants of nondepressed mothers. The present study examined electrical brain activity during expression of negative and positive emotions in infants of depressed and nondepressed mothers. Infants, 11 to 17 months of age, were exposed to conditions designed to elicit positive and negative emotions while electroencephalographic (EEG) activity was measured from left and right, frontal and parietal regions. EEG activity was analyzed when infants were displaying prototypic expressions of emotions. Compared with infants of nondepressed mothers, infants of depressed mothers exhibited increased EEG activation in the frontal but not parietal region when expressing negative emotions (unfelt smiles and anger). The two groups of infants did not show reliable differences is brain activation during the expression of positive emotions (happiness, surprise) or neutral expressions. Compared with infants of nondepressed mothers, infants of depressed mothers exhibit greater frontal EEG activation during the expression of negative emotions.

Anger↗
PubMed1997

Chronic exposure to kappa-opioids enhances the susceptibility of immortalized neurons (F-11kappa 7) to apoptosis-inducing drugs by a mechanism that may involve ceramide.

Chronic exposure of embryonic brain to opioids leads to microcephaly and developmental abnormalities. An immortalized mouse neuroblastoma x dorsal root ganglion hybrid cell line stably transfected to overexpress kappa-opioid receptors (F-11kappa7) showed complete loss of kappa-receptor binding to [3H]U69,593 after exposure to the kappa-agonist U69,593 for 24 h. U69,593 had no measurable effect on cell viability as determined by either cell viability or DNA fragmentation assays. However, when cell death (apoptosis) was induced by either staurosporine or the phosphatidylinositol 3-kinase inhibitors wortmannin and LY294002, cells pretreated with U69,593 for 24 h showed increased apoptosis compared with untreated cells. Thus, staurosporine (50 nM), wortmannin (4 microM), and LY294002 (30 microM) treatment for 24 h induced a 50% loss of cell viability and DNA fragmentation in 24 h. U69,593 pretreatment produced the same killing at lower concentrations, namely, 20 nM staurosporine, 2 microM wortmannin, and 14 microM LY294002, respectively. The effects of U69,593 were time-, dose-, and naloxone-reversible, suggesting that they are receptor-mediated. However, coaddition of U69,593 at the same time as staurosporine, wortmannin, or LY294002 did not enhance apoptosis. All three drugs that induced apoptosis were found to increase the level of ceramide, and pretreatment with U69,593 further increased the rate of formation of ceramide, a lipid that induces apoptosis in cells. We propose that chronic exposure to kappa-receptor agonists promotes increased vulnerability of neurons to apoptosis.

Analgesics↗
PubMed1997

Low molecular weight storage material in infantile ceroid lipofuscinosis (CLN1).

The identification of the genetic defect in CLN1 as a palmitoyl-protein thioesterase deficiency initiated a search for the lysosomal storage material. Pulse-chase labelling of fibroblasts and lymphoblastoid cell lines with [35S]cysteine revealed the presence of lipid [35S]cysteine material in CLN1 fibroblasts and not in controls, CLN2 or CLN3 patients or other patients with lipidosis. A single band comigrated with the acylcysteine standard and labelling with [3H]palmitate showed a band of material which eluted from the silicic acid column with the phospholipid fraction and which co-migrated with the lipid-[35S]cysteine band. The storage material is tentatively identified as palmitoylcysteine.

Adolescent↗
PubMed1997

The impact of gunshot wounds on an orthopaedic surgical service in an urban trauma center.

OBJECTIVE: To determine the prevalence of gunshot wound related orthopaedic injuries in an urban trauma center and outline the socioeconomic background of this patient population. DESIGN: Retrospective study conducted from January 1, 1994, through December 30, 1994. SETTING: University-affiliated level 1 trauma center. PATIENTS: Strict inclusion and exclusion criteria were established. INCLUSION CRITERIA: All patients were admitted through the emergency room with a gunshot wound for which the orthopaedic surgery service was consulted. The study group consisted of 284 patients. EXCLUSION CRITERIA: Those individuals excluded from the study were patients with an orthopaedic injury who died during or before attempts at resuscitation in the emergency room and patients treated on an outpatient basis. MAIN OUTCOME MEASURES: Orthopaedic and nonorthopaedic diagnoses, etiology, procedures performed, number of hours from admission to the first surgical procedure, average daily hospital census, drug and alcohol screen results, and patient financial status. RESULTS: The orthopaedic service was consulted on 284 patients admitted with gunshot wounds. This group comprised 24% of all orthopaedic admissions, 33% of the average daily orthopaedic census, and 14% of all orthopaedic surgery cases performed. Ninety-four percent were African American and 87% were male, with a mean age of 27 years. Approximately half were tested for alcohol and/or drugs, 45% of whom were positive for alcohol and 65% for drugs. Only 4% of the patients were privately insured. CONCLUSIONS: During the period of this study, gunshot wound injuries required more orthopaedic trauma resources than any other single diagnosis.

Adult↗
PubMed1997

Infants of depressed mothers exhibit atypical frontal brain activity: a replication and extension of previous findings.

The left frontal brain region is specialized for expression of positive emotions (e.g. joy) whereas the right frontal region is specialized for negative emotions (e.g. sadness). Depressed adults have been found to exhibit reduced left frontal electroencephalographic activity. In this study, baseline frontal and parietal EEG activity was measured in 13-15-month-old infants of depressed and nondepressed mothers who were of middle income with no other major psychiatric problems. Compared to infants of nondepressed mothers, infants of depressed mothers exhibited reduced left frontal EEG activity. Infants of mothers with major depression exhibited lower levels of left frontal EEG activity than those of mothers with subthreshold depression.

Adult↗
PubMed1996

Cell-specific regulation of the stably expressed serotonin 5-HT1A receptor and altered ganglioside synthesis.

Neurotransmission is dependent on the presence of neuronal receptors at the synapses, and important cell surface molecules such as gangliosides are pivotal in the maintenance of synaptic contacts. To study the interrelationship between these two classes of molecules, we achieved stable expression of the hippocampus- and CNS-localized serotonin 1A receptor (5-HT1A-R) in three 5-HT1A-R-deficient neuronal cell lines and also the control, non-neural CHO cells. A strong passage dependence of 5-HT1A-R expression, as measured by mRNA levels as well as membrane binding to the selective agonist [3H]8-OH-DPAT, was observed only in the HN2 (hippocampal) and NCB-20 (CNS) cells which are derived from tissues of natural occurrence of the 5-HT1A-R. A paradigm of stress was obtained by carrying out continuous culture of cells without feeding. During this time a dramatic increase in 5-HT1A-R mRNA and [3H]8-OH-DPAT binding was observed only in the neuronal cells after confluence and during decreased cell viability (days 10/11). This was not due to differentiation, since deliberate serum deprivation and differentiation of cells did not result in any dramatic increase in 5-HT1A-R expression. Analysis of ganglioside synthesis by pulse labeling of the transfected cells produced striking results. In the dorsal root of the ganglion (DRG) derived F-11 cells which show low but significant levels of complex gangliosides before transfection, the mere presence of the serotonin 1A receptor resulted in a dramatic increase in synthesis of gangliosides comigrating with GM2, GD1a, GD1b, and GT1b (20-fold by densitometry). In contrast, there was only a 2-fold increase in the overall content of complex gangliosides in the presence of the 5-HT1A-R. In the NCB-20 cells which contain only GD1a but no GD1b or GT1b before transfection, a decrease in GD1a synthesis was observed following transfection. Also agonist (8-OH-DPAT) binding to the serotonin 1A receptor in NCB-20 cells produced a 3-fold increase in synthesis of a ganglioside comigrating with GM3. Thus, our neuroblastoma transfectants help demonstrate stress-induced regulation of the 5-HT1A-R, which in turn exerts a strong and cell type-specific control over such essential cell-surface determinants like gangliosides.

Animals↗
PubMed1996

Programmed cell death in neurotumour cells involves the generation of ceramide.

Ceramide has been typically thought of as the membrane anchor for the carbohydrate in glycosphingolipids but many studies have suggested that it may cause apoptosis. Apoptosis or programmed cell death (PCD) is thought to be responsible for the death of one-half of neurons surviving the development of the nervous system. The potential involvement of the sphingomyelin-ceramide signaling process as an integral part of PCD was therefore examined in several neurotumour cell lines. We show that synthetic C2-ceramide (N-acetylsphingosine), a soluble ceramide analogue, can rapidly trigger PCD in these cells, characterized by: 1) classic DNA laddering on agarose gels; 2) DNA fragmentation as determined by Hoechst Dye; and 3) cell viability (mitochondrial function and intact nuclei) assays. We report that staurosporine can both activate PCD (by all three criteria above) in neurotumour cells and increase both the formation of ceramide and ceramide mass. Both ceramide formation and the induction of PCD were further enhanced by the co-addition of a ceramidase inhibitor oleoylethanolamine (25 microM). Staurosporine and oleoylethanolamine were similarly effective in inducing ceramide formation and PCD in immortalized hippocampal neurons (HN-2) and immortalized dorsal root ganglion cells (F-11). Our data suggests that formation of ceramide is a key event in the induction of PCD in neuronally derived neurotumour cells.

Adenosine Triphosphate↗
PubMed1996

Stable expression and heterologous coupling of the kappa opioid receptor in cell lines of neural and nonneural origin.

Signal transduction cascades initiated by the neuronal kappa opioid receptor were studied following transfection of a neuronal (hippocampal) line, HN2, and the non-neural CHOs. Retinoic-acid mediated differentiation resulted in intense staining of the HN2 cells with a neurofilament protein antibody SMI 33 but not with an antibody to GFAP, thus establishing neuronal characteristics of the HN2 cell line. The kappa opioid receptor was stably expressed in the two cell lines by electroporation mediated transfer of a Cytomegalovirus-promoter driven construct, pCMV-kappa, harboring the kappa-opioid receptor cDNA. Positive clones (HN2 kappa 24 and CHO kappa 18) from both lines showed high expression of the kappa opioid receptor, as identified by [3H] U-69,593 binding to membranes prepared from HN2 kappa 24 and CHO kappa 18. Scatchard analysis revealed the presence of high affinity kappa opioid receptors in both engineered cell lines (KD=1.3 nM for HN2 kappa 24 and 2.1 nM for CHO kappa 18). Functional coupling to adenylate cyclase was displayed by 1 microM U-69,593 mediated inhibition (55-63%) of prostaglandin E1-stimulated intracellular cAMP levels. A major difference between the two clones was observed in functional coupling of the expressed kappa opioid receptor to phospholipases C (PL-C) and D (PL-D). U-69,593 (1 microM) treatment stimulated PL-C, but not PL-D, in HN2 kappa 24 cells, whereas PL-D, but not PL-C, was stimulated following such treatment of CHO kappa 18 cells. Our results using the model neuronal system, HN2 kappa 24, demonstrate cell-type specific, positive coupling of the kappa opioid receptor to the major Ca2+ mobilizing system, the PL-C cascade, which regulates neuronal firing.

Adenylyl Cyclases↗
PubMed1996

Staurosporine induces programmed cell death in embryonic neurons and activation of the ceramide pathway.

We activated the death pathway in embryonic chick cerebral hemisphere neuron (E7CH) cultures with staurosporine (0.1-1.0 microM) and observed the meporphological changes, DNA laddering patterns, and DNA fragmentation (determined by Hoechst 33258 dye) associated with apoptosis. N-Acylsphingosine (C2-ceramide), a soluble ceramide analogue, was also able to induce apoptosis in these cells with the same characteristics and in the same time frame. We then observed that staurosporine was effective in inducing hydrolysis of sphingomyelin to ceramide as measured by a threefold increase in ceramide mass and increased incorporation of [3H]-palmitate into ceramide, concurrent with activating the cell death program. Furthermore, the coaddition of a specific ceramidase inhibitor, oleoylethanolamine (15 microM), enhanced the formation of ceramide as well as the degree of DNA fragmentation and cell death. Exogenous addition of sphingomyelinase activated the death pathway whereas ceramide glycanase did not, and inhibitors of sphingomyelin or protein synthesis failed to block this type of killing. Our data suggest that formation of ceramide from sphingomyelin is a key event in staurosporine-induced and potentially all programmed cell death.

Alkaloids↗
PubMed1996

Induction of the serotonin1A receptor in neuronal cells during prolonged stress and degeneration.

Neuronal migration in brain is followed by differentiation of committed neurons and simultaneous apoptosis of uncommitted preneuronal cells due to a limiting supply of trophic factors and nutrients. We have dissected differentiation and apoptosis by designing a simple in vitro model for this nutrient deprivation using engineered neuronal cell lines stably transfected with a promoterless segment (G-21) of the intronless human serotonin1A receptor (5-HT1A-R) gene. Despite the use of widely different heterologous promoters (cytomegalovirus and Rous sarcoma virus) for the stable expression of G-21, a dramatic increase in expression of the 5-HT(1A)-R (five- to 15-fold) and its mRNA was always observed during degeneration and apoptosis of nutrient-deprived neuronal cells. Involvement in this induction of a 170-bp 5'-end untranslated sequence (5'-UT) (tail end of the 500-bp natural promoter) of G-21 was confirmed by stable transfection of neuronal cells with an SV-40 promoter-driven construct harboring the 5'-UT and the reporter chloramphenicol acetyltransferase (CAT) cDNA. Presence of the 5'-UT resulted in a threefold increase in CAT expression during nutrient deprivation in randomly chosen clones. The induction was also observed in the endogenous 5-HT1A-R, expressed by embryonic day 16 mouse hippocampal neurons, subsequent to nutrient deprivation and onset of degeneration. A trophic role of the 5-HT1A-R has been suggested in earlier studies. Considering the example of protective heat shock proteins, which are induced during various types of stress, our results suggest that stressed neuronal cells undergoing degeneration and apoptosis synthesize increased levels of 5-HT1A-R as a final attempt to survive.

Animals↗
PubMed1996

Benefits and limitations of pathology databases to cancer registries.

In order to assess the benefits and limitations of pathology databases to cancer registries, computerised pathology records of malignant neoplasms diagnosed during 1992 were obtained for a defined area of Scotland for which pathology data were not routinely being used for cancer registration. Apparently 'missed' cancer registrations were identified by computerised probability matching with cancer registration records and their eligibility for registration was determined by reference to medical records, or when these were unavailable, by reference to the text of the original pathology report in conjunction with the local Community Health Index (to establish residency at the time of diagnosis). Misclassifications of site or incidence year were not regarded as 'missed' cases. Of 218 apparently 'missed' cancer registrations identified from computerised pathology records, 133 (5.7% of the revised total number of registrations for the study area in 1992) should have been registered. A further 14 cases were already registered but with misclassified site, morphology and/or behaviour codes. Ascertainment of cases by the Scottish Cancer Registration Scheme seems to be high for most sites. Pathology databases represent a useful additional source of cases but the fact that 71 apparently 'missed' cases were found to be ineligible for registration as independent primary malignant neoplasms suggests that unverified computerised pathology data should not be used uncritically nor independently for cancer registration purposes.

Databases, Factual↗