PubMed Health⌕ Search

Biomedical subjects

C M O'Toole

Publications and source records attributed to C M O'Toole.

At least 19 recordsLinked to original sources
PubMed2004

Semiautomatic brain region extraction: a method of parcellating brain regions from structural magnetic resonance images.

Structural MR imaging has become essential to the evaluation of regional brain changes in both healthy aging and disease-related processes. Several methods have been developed to measure structure size and regional brain volumes, but many of these methods involve substantial manual tracing and/or landmark identification. We present a new technique, semiautomatic brain region extraction (SABRE), for the rapid and reliable parcellation of cortical and subcortical brain regions. We combine the SABRE parcellation with tissue compartment segmentation [NeuroImage 17 (2002) 1087] to produce measures of gray matter (GM), white matter (WM), ventricular CSF, and sulcal CSF for 26 brain regions. Because SABRE restricts user input to a few easily identified landmarks, inter-rater reliability is high for all volumes, with all coefficients between 0.91 and 0.99. To assess construct validity, we contrasted SABRE-derived volumetric data from healthy young and older adults. Results from the SABRE parcellation and tissue segmentation showed significant differences in multiple brain regions in keeping with regional atrophy described in the literature by researchers using lengthy manual tracing methods. Our findings show that SABRE is a reliable semiautomatic method for assessing regional tissue volumes that provides significant timesavings over purely manual methods, yet maintains information about individual cortical landmarks.

Adult↗
PubMed2000

Ca(2+) entry through store-operated channels in mouse sperm is initiated by egg ZP3 and drives the acrosome reaction.

Fertilization occurs after the completion of the sperm acrosome reaction, a secretory event that is triggered during gamete adhesion. ZP3, an egg zona pellucida glycoprotein, produces a sustained increase of the internal Ca(2+) concentration in mouse sperm, leading to acrosome reactions. Here we show that the sustained Ca(2+) concentration increase is due to the persistent activation of a Ca(2+) influx mechanism during the late stages of ZP3 signal transduction. These cells also possess a Ca(2+) store depletion-activated Ca(2+) entry pathway that is open after treatment with thapsigargin. Thapsigargin and ZP3 activate the same Ca(2+) permeation mechanism, as demonstrated by fluorescence quenching experiments and by channel antagonists. These studies show that ZP3 generates a sustained Ca(2+) influx through a store depletion-operated pathway and that this drives the exocytotic acrosome reaction.

Acrosome Reaction↗
PubMed1999

Comparison of IgE and IgG antibody-dependent cytotoxicity in vitro and in a SCID mouse xenograft model of ovarian carcinoma.

Allergic reactions are mediated by IgE antibodies bound to high-affinity receptors on mast cells in peripheral tissues and are characterized by their immediacy and hypersensitivity. These properties could also be advantageous in immunotherapy against cancer growth in peripheral tissues. We have constructed chimeric IgE and IgG1 antibodies with murine V regions and human C regions corresponding to the MOv18 monoclonal antibody against the human ovarian tumor-associated antigen, folate binding protein. The antibodies exhibited the expected binding affinities for antigen and Fc receptors, and effector activities with human basophils and platelets in vitro. The protective activities of MOv18-IgE and MOv18-IgG1 were compared in a SCID mouse xenograft model of ovarian carcinoma. The beneficial effects of MOv18-IgE were greater and of longer duration than those of MOv18-IgG1. Our results suggest that the allergic reaction could be harnessed for the suppression of ovarian tumors.

Animals↗
PubMed1996

Role for Ca2+ channels in the signal transduction pathway leading to acrosomal exocytosis in human spermatozoa.

Progesterone interaction with human spermatozoa promotes a rise in intracellular Ca2+ and can trigger acrosomal exocytosis in capacitated cells. We have used nifedipine, a 1,4-dihydropyridine Ca2+ channel antagonist, to investigate the possibility that Ca2+ channels play a role in the progesterone-stimulated exocytotic response. Cells were assessed biochemically for the generation of diacylglycerol (DAG) and microscopically for acrosome loss using chlortetracycline fluorescence. When motile cells were preincubated for 5 hr using culture conditions similar to those used for successful human in vitro fertilization, a short exposure to progesterone significantly stimulated DAG formation and acrosomal exocytosis. The addition of nifedipine (10 and 100 nM), either at time 0 or just prior to progesterone introduction, significantly inhibited both DAG formation and exocytosis, suggesting that Ca2+ channels are involved in the responses observed. Treatment of capacitated cells with a synthetic permeant DAG stimulated exocytosis irrespective of whether nifedipine was present, indicating that Ca2+ channels function prior to DAG generation. The possibility that an influx of Na+, as well as Ca2+, might be involved in the exocytotic pathway was investigated using the monovalent cation ionophores monensin and nigericin. Both significantly stimulated DAG generation and acrosome loss, but the prior inclusion of nifedipine significantly inhibited all responses. These results strongly suggest that the entry of Ca2+ through Ca2+ channels, with characteristics similar to those of L-type, voltage-sensitive Ca2+ channels found in cardiac and skeletal muscle, is a crucial step in the sequence of events leading to exocytosis in progesterone-stimulated human spermatozoa. An influx of Na+ also may play a role, but at a point prior to the opening of Ca2+ channels.

Acrosome↗
PubMed1996

Differential maturation of avidity of IgG antibodies to gp41, p24 and p17 following infection with HIV-1.

We have evaluated solid-phase ELISA IgG antibody avidity studies as a means of identifying cases of recent HIV-1 infection. Although separate studies on the avidity of anti-gp41 and anti-p24 antibodies in seroconvertors have been reported, a comparison of the ability of patients to simultaneously mature their immune response to more than one HIV antigen immediately following seroconversion appears to be lacking. We have demonstrated a maturation in anti-gp41 avidity which reflects the time since seroconversion in all cases. In contrast, however, only some patients produced high-avidity anti-p24 or anti-p17 antibodies during the same time span. While the avidity of anti-gp41 antibodies remained high in cases of non-recent HIV infection, even in the face of advanced disease, we have confirmed the findings of others that the avidity of anti-p24 falls before the onset of ARC or AIDS. Therefore, whilst the avidity of anti-gp41 antibodies could reliably be of value in identifying cases of recent HIV infection, the avidity of anti-p24 or anti-p17 antibodies could not, but may be of prognostic value, even at an early stage. The time taken to reach maximum anti-p17, anti-p24 and anti-gp41 titres was variable, but anti-gp41 titres, like anti-gp41 avidity, remained high. In contrast, anti-p24 titres fell, even during the early followup period in some seroconvertors. Anti-p24 antibody avidity, however, appeared to be a better predictor of disease progression in 'remote' cases than anti-p24 titre. The avidity and titres of these antibodies are presented in relation to the clinical details, p24 antigen status, CD4 and CD8 counts where these are known.

Adult↗
PubMed1996

Protein kinase C activation during progesterone-stimulated acrosomal exocytosis in human spermatozoa.

The involvement of protein kinase C (PKC) in exocytosis of the mammalian sperm acrosome is still a controversial issue. Work carried out thus far has failed to provide direct evidence for the activation of this enzyme upon stimulation with natural agonists of acrosomal exocytosis. We have therefore used progesterone stimulation of the acrosome reaction in human spermatozoa to clarify this issue. In spermatozoa preincubated under conditions known to support capacitation and fertilization in vitro, treatment with progesterone caused a time-dependent stimulation of phosphorylation of at least eight proteins ranging in size from approximately 20-220 kDa. The inclusion of the PKC inhibitors chelerythrine chloride or calphostin C reduced the observed phosphorylation in a concentration-dependent manner. Exogenously supplied phorbol 12-myristate-13-acetate (PMA) or the permeant diacylglycerol 1-oleoyl-2-acetyl-sn-glycerol (OAG), synthetic activators of PKC, also stimulated phosphorylation in preincubated spermatozoa, but inclusion of calphostin C diminished the response. Furthermore, the prior inclusion of the 1,4-dihydropyridine Ca2+ channel antagonist nifedipine also inhibited phosphorylation, suggesting that PKC is activated downstream of Ca2+ channel opening. Exocytosis triggered by progesterone was significantly inhibited by chelerythrine chloride or calphostin C. Both PMA and OAG triggered exocytosis, but the inclusion of chelerythrine chloride significantly inhibited the response; exocytotic responses were seen only in capacitated cells. These results provide the first direct evidence that PKC activation plays a role in the signal transduction pathway underlying acrosomal exocytosis in progesterone-stimulated capacitated spermatozoa.

Acrosome↗
PubMed1996

A role for diacylglycerol in human sperm acrosomal exocytosis.

Using human spermatozoa stimulated with either progesterone or the Ca2+ ionophore A23187 to undergo acrosomal exocytosis, we have investigated potential pathways for generation of diacylglycerol (DAG) and have examined the possibility that DAG plays an important role in the exocytotic response. Both treatments resulted in rapid and considerable generation of DAG, followed by a limited rise in phosphatidic acid (PA). Further experiments indicated that phospholipase C (PLC) activity is important in this generation of DAG, but phospholipase D activity probably is not. In addition, polyphosphoinositide-specific phosphoinositidase C activation and hydrolysis, of phosphatidylinositol 4,5-bisphosphate appears to be a necessary prerequisite for activation of the PLC pathway. Finally the DAG formed appears to be important in acrosomal exocytosis: (i) blocking DAG metabolism with a DAG kinase inhibitor resulted in both increased endogenous levels of DAG and a significantly increased exocytotic response in stimulated cells and (ii) exogenous DAG induced exocytosis in capacitated spermatozoa whereas PA did not. Taken together, these results suggest that DAG plays a key role in events leading to membrane fusion during human sperm acrosomal exocytosis stimulated by natural agonists.

Acrosome↗
PubMed1995

The affinity of IgG antibodies to gag p24 and p17 in HIV-1-infected patients correlates with disease progression.

The affinity of anti-gag antibody was studied for up to 9 years (1984-1993) in sera from 15 HIV-1+ patients with haemophilia. On the basis of their 1993 clinical status patients were divided into two groups: (i) patients who remained asymptomatic (n = 9); and (ii) those who progressed to AIDS between late 1987 and 1993. The affinity constants of antibody for p24 and p17 were determined by a double isotope fluid-phase radioimmunoassay; and the relationships between antibody affinity and titre, patient clinical course, CD4 cell counts and p24 antigenaemia were analysed. The affinity of p24- and p17-specific antibody was up to 100 times greater in asymptomatic patients than in patients who progressed to AIDS. Patients who developed AIDS either lost or failed to develop high-affinity antibodies early in the infection. Asymptomatic patients maintained high-affinity antibodies for several years; however, in some of these patients the affinity of anti-p24 and p17 antibodies subsequently fell later in the study period. The presence of low-affinity antibody and progressive reduction in the titre of specific antibody were earlier predictors of disease onset than CD4 cell counts. The failure to either develop or maintain high affinity gag-specific antibody suggests an early impairment of T helper function in individuals who progressed to AIDS. The presence of antibody of high affinity could be essential in controlling virus replication and the onset of AIDS.

Antibody Affinity↗
PubMed1993

A 7-year analysis of anti-Gag (p17 and p24) antibodies in HIV-1-seropositive patients with haemophilia: immunoglobulin G titre and avidity are early predictors of clinical course.

OBJECTIVE: To study the humoral immune response to HIV-1 p17 and p24 Gag proteins longitudinally and assess any prognostic value. DESIGN AND METHODS: Fifteen HIV-1 infected patients with haemophilia were asymptomatic at entry to the study in 1986. Each patient was monitored at 6- to 12-month intervals for up to 7 years for p17 and p24 immunoglobulin (Ig)G titres, p17 IgG avidity, total IgG, p24 antigenaemia and CD4 cell counts. Results were correlated with the clinical course. RESULTS: Between 1986 and 1993, six of the patients developed CD4 cell counts below 200 x 10(6)/l (AIDS patients) while nine retained counts above this level (asymptomatic patients). All AIDS patients were characterized by declining IgG titres to p17 and p24 from 1986-1987 onwards. A reduction in specific p17 and p24 IgG preceded, by at least 3-4 years, the onset of CD4 cell depletion (< 200 x 10(6)/l). These six patients also had significantly lower p17 IgG avidity than the asymptomatic patients throughout the study. CONCLUSION: Titres of p17 and p24 IgG appeared to alter in the same manner. A progressive reduction in IgG titres and a low p17 IgG avidity were earlier predictors of disease progression than CD4 cell counts or p24 antigenaemia.

Adult↗
PubMed1993

A longitudinal study of the IgG antibody response to HIV-1 p17 gag protein in HIV-1+ patients with haemophilia: titre and avidity.

The IgG response to HIV-1 p17 gag protein was studied for up to 6 years in 12 HIV-1-infected patients with haemophilia, who had seroconverted between 1982 and 1985. To assess any prognostic value, p17 IgG titres were compared with p24 IgG titres, CD4 cell counts and p24 antigenaemia. p17 IgG avidity index was also examined. A strong similarity was found between the IgG titre to HIV-1 p17 and that to p24. In patients who developed AIDS the decline in p17 IgG titres could precede by several years the drop in CD4 cells to under 200 cells/microliters; whereas some long-term asymptomatic patients (CDCII) had increasing p17 IgG titres and stable CD4 cell counts. Declining p17 and p24 IgG titres were not always associated with an increase in p24 antigenaemia. IgG titres were found to be better predictors of disease progression than CD4 cell counts or p24 antigenaemia. Patients who developed AIDS during the study were also characterized by a lower p17 IgG avidity than patients who remained asymptomatic. This result suggests that IgG avidity could have prognostic relevance and be of importance for host resistance to AIDS onset.

Adult↗
PubMed1992

Decline in CTL and antibody responses to HIV-1 p17 and p24 antigens in HIV-1-infected hemophiliacs irrespective of disease progression. A 5-year follow-up study.

CTL and antibody responses to HIV-1 p17 and p24 antigens were monitored from 1986-1991, in 4 hemophiliacs. The patients had been infected with HIV-1 between 1980 and 1984. Two patients have remained asymptomatic while two progressed to AIDS in 1990. CTL were boosted by culturing with peptides from p17 aa 86-115, or p24 aa 265-279; and aa 270-373 or PHA. Lysis was measured on autologous or allogeneic targets pulsed with peptides or infected with recombinant vaccinia virus carrying HIV-1 gag or influenza A matrix genes. Antibodies to p17 and p24 were tested by ELISA using peptides and by Western blotting. High levels of CTL activity to p17 and p24 antigens could be generated only with lymphocytes from the two asymptomatic patients between 1986 and 1989, but these responses were absent in 1990 and 1991. Antibodies to p17 peptides disappeared in parallel with CTL activity. Antibodies to some p24 peptides also declined but most patients retained activity to others. In all patients a > or = 3-fold increase in CD8+ cell numbers occurred over time and accompanied the decline of CTL and antibody responses. The loss of CTL and p17 antibodies occurred irrespective of whether patients remained asymptomatic or progressed to AIDS in the intervening two years.

Cell Line, Transformed↗
PubMed1992

Assessment of the relative cytotoxicity of Porphyromonas gingivalis cells, products, and components on human epithelial cell lines.

Established human cell lines derived from a transitional cell carcinoma (J82), a squamous carcinoma (SCaBER), and a normal urothelium (HCV-29) were used to assess the relative cytotoxicity and tissue specificity of putative virulence determinants of P. gingivalis W83. Intact cells of W83 had no effect on any of the cell lines, whereas disrupted cells caused extensive cytotoxicity particularly to monolayers of HCV-29 and J82. The purified cysteine proteinase, gingivain, caused marked disruption of the basement membrane of the SCaBER monolayers but had no cytotoxic effects. Use of the thiol-inhibitor, 2,2'-dipyridyl disulphide revealed that the effects observed with the vesicles and the culture supernatant were due to the presence of the cysteine proteinase. The attachment of vesicles to the SCaBER cells was evident in electron micrographs. Short-chain volatile fatty acids added in concentrations equivalent to those present in the culture supernatant had no effect on any of the cell lines tested. Culture supernatants obtained from high speed centrifugation (150,000 x g) showed no cytotoxic effects. This was in marked contrast to the supernatant obtained by lower sedimentation (18,000 x g), which damaged all monolayers tested. These results suggest that these cell lines are potentially useful for assessing putative virulence determinants of P. gingivalis and other periodontal pathogens.

2,2'-Dipyridyl↗
PubMed1985

Cytomegalovirus infection in cardiac transplant recipients associated with chronic T cell subset ratio inversion with expansion of a Leu-7+ TS-C+ subset.

Lymphocyte subsets were analysed in 18 patients during the first 3 years after cardiac transplantation. The patients received Cyclosporin A and prednisolone for maintenance immunosuppression. Serological evidence of active cytomegalovirus (CMV) infection was found in 13 cases (72%), and in 12 of these an inversion usually of the T helper/T suppressor-cytotoxic ratio (TH/TS-C) was detected. T subset inversion usually preceded the diagnostic rise in CMV antibody titre. In 69% of patients with CMV the TH/TS-C ratio remained inverted throughout follow-up (245-951 days). Persistent T subset inversion was not found in all five patients who lacked serological evidence of active CMV. Chronic inversion consisted of an average increase in TS-C of 152% and an average decline in TH cells of 31% as compared to CMV negative patients. The proportion of lymphoid cells reacting with a phenotypic marker for natural killer (NK) cells (Leu-7) was increased by 83%. These alterations were also reflected in the absolute numbers of cells with these markers. Two-colour immunofluorescence analysis revealed that the expanded TS-C population present during chronic inversion was predominantly Leu-7+. As TS-C+ Leu-7+ cells in healthy persons may be hyporesponsive NK cells, a sustained increase in this cell type in allograft recipients could further reduce immunocompetence, thereby predisposing to superinfection or malignancy.

Adult↗
PubMed1984

Immune responses in cardiac transplantation. I. Detection of activated TIa+ cells in the blood during herpes virus infections.

Lymphocyte subpopulations in the blood of cardiac transplant recipients were monitored by single and double marker rosetting tests; using monoclonal antibodies to monomorphic determinants on T cells and 'Ia' antigens. Elevated absolute numbers and percentages of TIa+ cells were found in association with primary cytomegalovirus (CMV), and reactivation of Epstein-Barr virus or Herpes simplex virus. Serial tests showed that in primary CMV TIa+ cells peaked before the maximal IgM and IgG anti-viral titres measured by ELISA. Infection related antiglobulin levels increased in parallel with anti-viral IgM in primary CMV infections. Intravenous methylprednisone and blood transfusions selectively depressed TIa+ cell levels without affecting antibody titres. These results show that patients on maintenance immunosuppression of cyclosporin A and steroids can successfully mount T cell and antibody responses to herpes virus infections.

Antibodies, Viral↗
PubMed1983

Identity of some human bladder cancer cell lines.

Recent reports on transfection of mouse cells with DNA from the established human urinary bladder cancer cell lines T24, J82 and EJ (MGH-U1), and the presence of an identical genetic modification in T24 and EJ cells have led us to examine the identity of these and other cultures of urothelial origin. By the criteria of HLA-A-B-C typing 7 and isozyme analysis, we conclude that EJ (MGH-U1) and some cultures of J82 are in fact T24 cells. However, five other bladder cancer cell lines, J82 (CO'T), RT4, RT112, TCCSuP and SCaBER, are clearly distinct from T24 by HLA typing (ref. 7) and/or isozyme patterns.

Acid Phosphatase↗