Search PubMed⌕ Search

Biomedical subjects

D Nugent

Publications and source records attributed to D Nugent.

At least 19 recordsLinked to original sources
PubMed1999

Low platelet alpha2beta1 levels in type I von Willebrand disease correlate with impaired platelet function in a high shear stress system.

Platelet adhesion to collagen-coated surfaces in whole blood under flow conditions is mediated by both von Willebrand factor (vWF)-dependent recruitment of the platelet glycoprotein Ib-IX receptor complex and collagen interaction with the integrin alpha2beta1. In type 1 von Willebrand disease (vWD), platelet adhesive functions are impaired due to the decrease in vWF levels in plasma and platelets. There are at least three alleles of the human alpha2 gene, distinguishable by a cluster of silent or noncoding sequence differences within a segment of the gene. Two alleles, associated with low receptor density can be distinguished by nucleotide 807C, while the third allele associated with high receptor density, expresses nucleotide 807T. Gene frequencies of these alleles in a normal population (n = 167) are 0.58 for 807C and 0.42 for 807T. We measured the frequencies of these alleles in symptomatic patients with five types of vWD (type 1, n = 78; type 2A, n = 25, type 2B, n = 14; type 2M, n = 10; and type 3, n = 20). Compared with the normal group, no significant difference in allele frequencies was observed among individuals with types 2A, 2B, 2M, or 3 vWD. However, the frequency of the 807C allele, associated with low collagen receptor density, among type 1 vWD patients (807C =.71; 807T =.29) was significantly higher than that of the normal population (P =.007). Also, in patients with vWD type 1 and borderline to normal ristocetin-cofactor (vWF:RCo) activity values, collagen receptor density correlates inversely with closure time in a high shear stress system (platelet function analyzer [PFA-100]). We propose that low platelet alpha2beta1 density results in less efficient primary platelet adhesion and may result in increased tendency to bleed, as evidenced by the high frequency of this polymorphism in patients with type 1 vWD compared with normal individuals. In addition, this may account for the variability between patients with similar levels of vWF antigen, but strikingly different bleeding histories.

Alleles↗
PubMed1999

A laparoscopic technique for obtaining ovarian cortical biopsy specimens for fertility conservation in patients with cancer.

OBJECTIVE: To evaluate the efficacy of a newly designed round biopter as a practical and safe method for collecting ovarian tissue for cryopreservation in young women with cancer before chemotherapy. DESIGN: Prospective study of young women volunteering for research (Leeds, United Kingdom) and patients with cancer (Jerusalem, Israel and Leeds, United Kingdom) undergoing laparoscopic ovarian cortical tissue biopsy and cryopreservation before administration of high-dose radiochemotherapy. SETTING: Two university-based tertiary referral centers of oncology and gynecology (Hadassah Medical Center, Israel; Leeds General Infirmary, United Kingdom). PATIENT(S): Twenty female volunteers undergoing routine laparoscopic gynecologic procedures (age, 25-34 years) and 20 young women (age, 11-30 years) with advanced cancer requiring potentially sterilizing radiochemotherapy. INTERVENTION(S): Cortical ovarian tissue biopsies performed under laparoscopy with use of the round biopter. RESULT(S): The laparoscopic sampling procedure was uncomplicated in all cases. In treated patients, five to six samples were obtained (5 mm in diameter; 2-3 mm in depth) using the round biopter, and radiochemotherapy was administered without delay. In volunteers, no adhesions were noted at repeat laparoscopy (9 patients). All biopsy specimens were cryopreserved, and histologic examination confirmed the presence of many primordial follicles. CONCLUSION(S): Laparoscopic ovarian biopsy performed with the round biopter is a safe and efficient method for collecting ovarian tissue for cryopreservation in patients with cancer.

Adolescent↗
PubMed1999

Subclinical depletion of primordial follicular reserve in mice treated with cyclophosphamide: clinical importance and proposed accurate investigative tool.

Studies have shown that ovarian failure is a common side-effect of chemotherapy treatment; however, continuation of regular menses post-treatment does not necessarily imply that the ovaries have escaped damage. This animal study measures directly the primordial follicle (PMF) loss following exposure to chemotherapy and evaluates reproductive outcome following significant destruction of the PMF population. Inbred Balb/c mice aged 5-6 weeks were administered different doses of an alkylating agent, cyclophosphamide, and the total number of PMF remaining in both ovaries was counted. Results show that cyclophosphamide causes PMF destruction in proportion to increasing dose (P = 0.0001). Reproductive performance was assessed after exposure to 75 mg/kg cyclophosphamide, a dose which destroys approximately 50% of PMF reserve, by evaluation of ovulation, mating and pregnancy rates. Reproductive potential of treated mice was not affected compared with controls despite the significant loss of PMF. Our results indicate that reproductive performance is not an accurate parameter for assessing ovarian injury. Rather, histological counting of PMF number more directly reflects the damage caused by chemotherapy to the ovary. This method can be used as a sensitive, inexpensive tool to gauge the damage to fertility caused by new chemotherapy agents or protocols.

Animals↗
PubMed1999

The influence of donated gametes on the incidence of hypertensive disorders of pregnancy.

Pregnancies achieved from oocyte, sperm or embryo donation are unique, since they have resulted from donor gametes that are immunologically foreign to the mother. Thus, studying the obstetric outcome of such pregnancies may shed some light on the pathophysiology of preeclampsia, particularly in women conceiving with donated embryos, since the entire fetal genome is allogenic in these pregnancies. In this retrospective cohort study, a total of 144 women were studied. Of these, 72 were infertility patients who had conceived as a result of sperm, ovum or embryo donation and the other 72 women were age- and parity-matched control patients who became pregnant with their own gametes, either spontaneously, or following intrauterine insemination with their partner's spermatozoa. Study patients were divided into three groups depending on the origin of the donated gametes. Group 1 consisted of pregnancies achieved by intrauterine insemination with washed donor spermatozoa (n = 33). Group 2 included women who conceived using donated oocytes (n = 27) and group 3 consisted of women who conceived as a result of embryo donation (n = 12). The incidence of pregnancy-induced hypertension in the donated gametes study group was 12.5% (9/72) compared with 2.8% (2/72) in the control group. In addition, pre-eclampsia was diagnosed in 18.1% (13/72) of the donated gametes study group compared to 1.4% (1/72) in the age- and parity-matched controls. The increased incidence of gestational hypertension in pregnancies resulting from donated gametes gives evidence for a maternal genetic component, with an equally strong fetal influence, in the complicated aetiology of gestational hypertension, and pre-eclampsia in particular.

Cohort Studies↗
PubMed1998

The relationship between follicular fluid aspirate volume and oocyte maturity in in-vitro fertilization cycles.

As a consequence of multiple follicular growth during ovarian stimulation for in-vitro fertilization (IVF), follicles of varying sizes often yield oocytes that vary in maturity and morphology of the oocyte-cumulus-corona complex. The objective of this prospective study was to explore the relationship between follicular fluid aspirate volume and the oocyte's developmental potential in an IVF treatment cycle. In total 9933 follicles were studied from 400 patients who underwent 535 consecutive IVF treatment cycles at St James's University Hospital, Leeds, UK, between February 1995 and February 1996. The volume of each individual follicle aspirated was recorded and related to the probability of obtaining an oocyte, its fertilizing capacity, the cleavage rate and the quality of embryos derived. We found no statistically significant difference in oocyte recovery rates between follicles with an aspirate volume < or = 1 ml and follicles with a volume > 1 ml. Although oocytes obtained from follicles with an aspirate volume > or = 1 ml showed a significantly lower fertilization rate, they went on to cleave at the same rate as oocytes obtained from larger follicles and resulted in embryos of comparable quality. Furthermore, there was no statistically significant difference in the implantation, clinical pregnancy or live birth rates per cycle between embryos derived from follicles with an aspirate volume < or = 1 ml and those derived from follicles with an aspirate volume > 1 ml. We conclude that follicular size and the oocyte's developmental potential in the stimulated ovary are not closely related and can be independent. This is in contrast to the Graafian follicle and the pre-ovulatory oocyte in the natural cycle.

Adult↗
PubMed1998

Protective effect of vitamin E on ischaemia-reperfusion injury in ovarian grafts.

Ovarian cortical tissue cryopreservation with subsequent autografting is a potential strategy for the preservation of fertility in patients undergoing systemic chemotherapy and pelvic radiotherapy. Non-vascular implants are first subjected to a period of ischaemia before revascularization and are, therefore, vulnerable to ischaemia-reperfusion injury from reactive oxygen species. Ischaemia-reperfusion injury was investigated during the first week after surgery in murine ovarian grafts and human ovarian xenografts in mice with severe combined immune deficiency (SCID) by measuring total lipid peroxides and malondialdehyde concentrations with a colorometric assay. The effects of administering an antioxidant, vitamin E, on these concentrations were also tested. Products of lipid peroxidation were higher in non-supplemented murine autografts compared with control ovaries (P < 0.05), and were significantly reduced on day 3 by vitamin E administration (P < 0.05). Similarly, in human xenografts, there was a significant reduction in lipid peroxidation with vitamin E administration. These results correspond to a significantly greater total follicle survival in the murine grafts of the supplemented group (45 versus 72%; P < 0.05). They suggest that antioxidant treatment improves the survival of follicles in ovarian grafts by reducing ischaemia-reperfusion injury.

Adult↗
PubMed1997

Isolation and characterization of primordial follicles from fresh and cryopreserved human ovarian tissue.

OBJECTIVE: To develop an efficient isolation technique for human primordial follicles. DESIGN: Prospective, experimental study of ovarian biopsies collected from healthy women undergoing elective cesarean section. Ovarian blocks either were fixed for histology and follicle counting or partially disaggregated with type 1A collagenase before or after cryopreservation. After partial disaggregation, follicles were isolated by microdissection. SETTING: Leeds General Infirmary. MAIN OUTCOME MEASURE(S): Follicle viability was assessed with live-dead stains using 5-(and 6-) carboxyfluorescein diacetate, succinimidyl ester and propidium iodide, respectively, and using electron microscopy. The numbers recovered were expressed as a percentage of the numbers of primordial follicles in comparable blocks of tissue and the viability of the whole follicle and oocyte were scored separately. RESULT(S): On average, 18.0 +/- 3.8 and 15.9 +/- 2.2 (mean +/- SEM) follicles per block were recovered from fresh and cryopreserved ovarian tissue, respectively, corresponding to recovery rates of 57.9% +/- 8.8% and 56.2% +/- 16.7%. In the fresh group, the percent viability of whole follicles and oocytes were 71.6% +/- 2.4% and 91.3% +/- 2% compared with 71.5% +/- 4.7% and 95% +/- 4.3% in the frozen-thawed group. Electron microscopy confirmed that the majority of the cells lacked ultrastructural signs of damage after isolation and cryopreservation. CONCLUSION(S): Primordial follicles can be isolated from fresh and cryopreserved human ovarian tissue with similar high efficiency and viability rates.

Adult↗
PubMed1993

Platelet-associated factor XIII as a marker of platelet activation in patients with peripheral vascular disease.

In the past several years, monoclonal antibodies have been developed that distinguish between resting and activated platelets in vitro. These antibodies recognize epitopes expressed on membrane proteins or soluble proteins, such as factor XIIIa and thrombospondin, that bind only to activated platelets. We have used fluorescence flow cytometry to determine whether three such antibodies can detect platelet activation in patients with severe peripheral vascular disease (PVD). Using two activation-specific monoclonal antibodies and a polyclonal antiserum to factor XIII a-chain, we have examined the platelets from PVD patients, age-matched control subjects who were free of detectable PVD, and unmatched control subjects. Cells analyzed as platelets were identified by their light-scatter profile and their reactivity with monoclonal anti-glycoprotein Ib. The platelets of patients with PVD showed no increase in binding of activation-dependent 1B3 (directed against a 180-kD membrane protein) compared with age-matched control subjects (p = 0.780). Similarly, there was no difference between PVD patients and control subjects in activation-dependent CD63 expression. Conversely, the binding of anti-factor XIII a-chain was significantly higher than in the control groups (p < 0.001). These data suggest that the detection of soluble factors that bind to activated but not resting platelets may be of use in the detection of pathological in vivo platelet activation.

Adult↗
PubMed1991

Multicenter study of superficial bladder cancer treated with intravesical bacillus Calmette-Guerin or adriamycin. Results of long-term follow-up.

We evaluated 158 cases of patients with superficial bladder cancers (Stages Ta, T1, and Tis). These cases were treated with either intravesical bacillus Calmette-Guerin (BCG) (Tice strain) or Adriamycin (ADR), in a multicenter, nonrandomized study. One hundred thirty-one of these patients were followed up; the results continue to show a higher percentage of initial complete remissions with BCG (68%) than with ADR (57%). With additional therapy, both BCG and ADR achieved complete remission in 83 percent of the patients. When 7 failures with patients taking ADR were switched to BCG and the disease cleared, the rate of complete remission for BCG rose to 85 percent. The recurrence rate per 100 patient-months was only slightly different for BCG (0.9) and ADR (0.8). The percentage of progressions continued to be higher for BCG (8%) than for ADR (5%). Cystectomies were performed in 2.5 percent of the BCG patients. Using the Cox regression model with covariates, we found drug treatment, tumor grade, and sex to be statistically significant in determining failures throughout the protocol. Although both BCG and ADR were effective over the course of the study, BCG is the drug of choice for residual tumor (Stages T1 and Tis).

Administration, Intravesical↗
PubMed1990

Multicenter study of superficial bladder cancer treated with intravesical bacillus Calmette-Guérin or adriamycin.

We evaluated 155 patients with superficial bladder cancers (Stages Ta, T1, and TIS) and treated them with either intravesical bacillus Calmette-Guérin (Tice strain) (BCG) or doxorubicin hydrochloride (Adriamycin), in a multicenter nonrandomized study. At present 140 of these patients in treatment Groups I and II are being followed up. With additional follow-up, BCG continued to produce a higher percentage of complete remissions (71%) than doxorubicin (54%). The percentage of incomplete remission with BCG (7%) was half that with doxorubicin (14%). Half of the patients whose initial therapy failed had complete remission after additional therapy. However, for patients with recurrence, additional follow-up shows a recurrence rate per 100 patient-months for BCG (1.0) only slightly lower than that for doxorubicin (1.1). The percentage of progressions continued to be higher with BCG (8.5%) than with doxorubicin (5%), but the difference between these results for the two drugs proved slightly less than we reported previously. Of the patients in this study, 2.5 percent (all treated with BCG) required cystectomy. A comparison of the results of our study with those of 13 other studies using BCG to treat bladder cancer indicates that therapy beyond an initial course of 6 weekly treatments increases the percentage of complete response. All of the studies showed that the greatest improvement in percentage of complete response occurred with the second course of treatment. The value of maintenance therapy cannot yet be determined, since few studies have used that protocol. The percentage of patients requiring cystectomy in studies with fewer than 20 treatments was 2.2 times higher than in studies with more than 20 treatments.

Administration, Intravesical↗
PubMed1988

Characterization of an antigen expressed on activated human T cells and platelets.

We have identified a protein complex on the surface of activated human T cells and platelets. This Ag, detected by the murine mAb 1B3, is not expressed on resting human T cells or platelets or on other hematopoeitic cells. The majority of T cells express the Ag after stimulation with PHA, Con A, or allogeneic cells. Platelets express the Ag after activation with 1 U/ml thrombin. Immunoprecipitation of 125I-labeled activated T cells with antibody 1B3 shows a heterodimer of 180,000 and 155,000 Mr. An additional protein of 130,000 Mr is very faintly seen depending on the cell type. On platelets, the 180,000 Mr protein is the predominant protein immunoprecipitated under both nonreducing and reducing conditions. Antibody 1B3 may prove useful in identification of activated T cells and platelets as well as definition of specific mechanisms of T cell and platelet activation.

Animals↗
PubMed1988

Superficial bladder cancer treated with intravesical bacillus Calmette-Guérin or adriamycin: follow-up report.

We evaluated 139 patients with superficial bladder cancer (Stages Ta, Tl, and TIS) and treated them with either intravesical bacillus Calmette-Guérin, Tice strain (BCG), or doxorubicin hydrochloride (Adriamycin [ADR]) in a nonrandomized, multicenter study. Our follow-up study comprises 135 of these patients. Of these patients, 78 tumors were completely resected, and 61 were incompletely resected. When a proportional-hazards model (Cox) was applied, there was a statistically significant difference between the recurrence rates for the two drugs. On the basis of recurrence rates per 100 patient-months, both BCG (1.2) and ADR (0.9) worked well with completely resected tumors. However, for incomplete resections, the recurrence rate for BCG (0.9) was less than half that for ADR (1.9). The overall recurrence rates were 1.1 and 1.3 for BCG and ADR, respectively. There have been 42 failures of treatment with either BCG or ADR. We defined failure as any recurrence of tumor; progression of the cancer in stage, grade, tumor number or size; or any residual tumor after 18 treatments (14 months of therapy). As to the failures in patients whom we followed up, and whose treatment was either switched from ADR to BCG or continued on further BCG treatment, 53 per cent have achieved complete remission. Complete remission for BCG and ADR were 76 per cent and 52 per cent, respectively. Of the various factors considered in the study, only tumor grade and treatment drug were statistically significant. The cystectomy rate was 1 per cent for BCG-treated patients and 0 for ADR-treated patients.

Administration, Intravesical↗
PubMed1987

Isolation and characterization of the alpha and beta chains of human platelet glycoprotein Ib.

Human platelet glycoprotein Ib has been purified in milligram amounts from platelets obtained by pheresis of thrombocytotic donors. Purification steps included lectin (wheat germ agglutinin) and immuno (murine monoclonal anti-glycoprotein Ib antibody)-affinity chromatography. The disulfide-linked individual alpha and beta chains of GPIb were separated and the amino-terminal amino acid sequence of each chain was determined. Rabbit polyclonal antibody directed against each individual chain was prepared by affinity chromatography and shown to be monospecific by western blot analysis using whole platelet lysate as antigen. These studies outline a useful approach to isolate and characterize the individual chains of GPIb.

Amino Acid Sequence↗
PubMed1987

Superficial bladder cancer treated by intravesical bacillus Calmette-Guerin or adriamycin: multicenter study interim report.

One hundred sixteen patients with superficial bladder cancers (Stages Ta, T1, and TIS) were evaluated and treated with either intravesical bacillus Calmette-Guerin [Tice strain] (BCG) or doxorubicin hydrochloride (Adriamycin [ADR]), in a multicenter study. One hundred nine of these patients currently have follow-up. Of these, 54 were completely resected and 55 incompletely resected. For complete resections, based on recurrence rates per 100 patient months, both BCG (0.22) and ADR (0.91) worked well, although BCG had a slightly lower recurrence rate. However, for incomplete resections, BCG (0.20) had a markedly lower recurrence rate than ADR (2.52). Eighteen patients failed initial treatment, with either BCG or ADR. All have been placed on long-term therapy schedules. Of the 12 failures who currently have follow-up, 11 (92%) have either partially or completely responded with additional intravesical therapy. No patients in this study have yet required cystectomies.

Administration, Intravesical↗