Biomedical subjects
Publications and source records attributed to N Dwyer.
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All vertebrate eggs have extracellular matrices, referred to as the zona pellucida in Mus musculus and the vitelline envelope in Xenopus laevis. The mouse zona, composed of three sulfated glycoproteins (ZP1, ZP2, ZP3), is critical for fertilization and early development, and mice lacking a zona pellucida produce no live offspring. The primary structures of mouse ZP1 (623 amino acids), ZP2 (713 amino acids) and ZP3 (424 amino acids) have been deduced from full-length cDNAs, but posttranslational modifications result in mature zona proteins with molecular masses of 200-180 kDa, 140-120 kDa, and 83 kDa, respectively. The vitelline envelope forms a similar structure around Xenopus eggs and contains three glycoproteins that are structurally related (39-48% amino acid similarity) to the three mouse zona proteins. To investigate whether the structural semblances are sufficient to allow incorporation of the mouse zona proteins into the Xenopus vitelline envelope, capped synthetic mRNAs encoding ZP1, ZP2, and ZP3 proteins were injected into the cytoplasm of stage VI Xenopus oocytes. After 20 h of incubation the oocytes were harvested, and posttranslationally modified zona proteins were detected with monoclonal antibodies specific to mouse ZP1, ZP2, and ZP3. The oocytes were imaged with confocal microscopy to detect individual zona proteins in the extracellular matrix of the oocytes, and this localization was confirmed biochemically. Thus the mouse zona proteins appear to have been sufficiently conserved through 350 million years of evolution to be incorporated into the extracellular envelope surrounding Xenopus eggs.
The pathophysiology of sickle cell anemia is primarily explained in terms of the oxygen-dependent polymerization of sickle hemoglobin (HbS) followed by sickling of erythrocytes. Since the rate and extent of HbS polymerization depend on its intracellular concentration, it has been generally assumed that sickling occurs primarily in mature erythrocytes with their high intracellular hemoglobin concentration. In the present study, we investigated the propensity of nucleated erythroid precursors to undergo sickling; both cultured and fresh marrow-derived erythroid precursors from patients with homozygous sickle cell anemia were studied. The results revealed that upon deoxygenation cultured erythroblasts underwent characteristic morphological deformation in the form of fine, fragile, elongated spicules. Ultrastructural analysis demonstrated highly organized and tightly aligned hemoglobin fibers in the protruded regions. Bone marrow cells examined under partial or complete deoxygenated conditions displayed similar morphological changes. When cultured SS erythroid precursors were exposed to hydroxyurea or butyrate, drugs that may increase fetal hemoglobin (HbF) and inhibit intracellular polymerization, a significant decrease was observed in the propensity of these precursors to undergo sickling, accompanied by a three- to fivefold increase in HbF. These results suggest that, in addition to mature erythrocytes, nucleated erythroid precursors in the bone marrow have the capacity to undergo characteristic sickling as a result of HbS polymerization and may be involved in several aspects of the pathophysiology of sickle cell anemia. Treatment with HbF-stimulating drugs may benefit patients with this disease by inhibiting polymerization-induced sickling of erythroid precursors in the marrow as well as mature erythrocytes in the peripheral blood.
OBJECTIVE: To compare the impact of endometrial resection and abdominal hysterectomy on a range of health outcomes and health service costs, based on longer term follow up of patients randomised to a clinical trial. DESIGN: A parallel group of randomised control trial. SETTING: The gynaecology department of a teaching hospital. PARTICIPANTS: 196 women requiring surgical treatment for menorrhagia were randomised and received surgery (88 underwent resection and 97 hysterectomy). Longer term follow up was undertaken using a postal questionnaire sent to all 196 women. MAIN OUTCOME MEASURES: Longer term assessment was on the basis of menstrual symptoms, health related quality of life using the Short Form 36 (SF36) and the EuroQol visual analogue scale, patient satisfaction and health service resource cost. RESULTS: Of 196 women who were sent a questionnaire, 155 (79%) responded at an average interval of 2.8 years after initial surgery. All aspects of health outcomes were as good or better in patients randomised to hysterectomy. Among patients randomised to resection, 57% had experienced no improvement in premenstrual symptoms following surgery and 23% had taken time off work due to menstrual problems; among hysterectomy patients, these rates were 23% and 4%, respectively. Women randomised to hysterectomy had better mean scores on seven of the eight dimensions of the SF36 health related quality of life instrument, with the greatest difference being on the pain dimension (P = 0.01). Women randomised to hysterectomy were generally more satisfied with treatment (P = 0.002). By two years after initial surgery, women randomised to resection had a 12% probability of having had a repeat resection and a 16% chance of having had a hysterectomy. As a percentage of the mean total cost associated with women randomised to hysterectomy, the mean total cost of resection was 53% based on four months follow up; this proportion had increased to 71%, based on an average overall follow up of 2.2 years. CONCLUSIONS: These results show that, at an average follow up of 2.8 years among responders to a questionnaire, women randomised to hysterectomy experienced more of an improvement in menstrual symptoms and higher rates of satisfaction with treatment. There is also some evidence of superior health related quality of life amongst hysterectomy patients. However, the health service cost of endometrial resection remains lower than that of hysterectomy. An assessment of the relative cost effectiveness of the two procedures awaits further research.
Mammalian oocytes synthesize and secrete a zona pellucida that surrounds the growing oocytes, ovulated eggs and preimplantation embryos. The extracellular zona matrix is composed of three glycoproteins (ZP1, ZP2, ZP3) that are involved in folliculogenesis, species-specific fertilization, and passage of the early embryo down the oviduct. We have established a mouse line in which Zp3 has been inactivated by homologous recombination with an insertional mutation. Neither Zp3 transcripts nor ZP3 protein was detected in female mice homozygous for the mutation (Zp3-/-), whereas both ZP1 and ZP2 were present in mutant oocytes. Homozygous mutant Zp3-/- mice had follicles with germinal-vesicle-intact oocytes but that lacked a zona pellucida matrix and had a disorganized corona radiata. Although mutant oocytes underwent germinal vesicle breakdown (GVBD) prior to ovulation, the cumulus-oocyte complex was markedly disrupted and the oocytes were often separate from the cumulus cells. After hormone-induced ovulation, cumulus masses were present in the oviducts of homozygous mutant mice, but zona-free eggs were observed in only half of the females and, in these, less than 10% of the normal number [correction of mumber] of eggs were detected. No zona-free 2-cell embryos were recovered from homozygous mutant Zp3-/- female mice after mating with males proven to be fertile, and none became visibly pregnant or produced offspring. These results demonstrate that a genetic defect in a zona pellucida gene causes infertility and, given the conserved nature of the zona pellucida, a similar phenotype is expected in other mammals.
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The small soil nematode Caenorhabditis elegans has only 302 neurons in its entire nervous system, so it is possible to analyse the functions of individual neurons in the animal's behaviour. We are using behavioural, cellular and genetic analyses of chemotactic responses to find out how olfactory behaviour patterns are generated and regulated. Single chemosensory neurons in C. elegans can recognize several different attractive odorants that are distinguished by the animal. Distinct sets of chemosensory neurons detect high and low concentrations of a single odorant. Odorant responses adapt after prolonged exposure to an odorant; this adaptation is odorant specific and reversible. Mutants with defects in odorant responses have been identified. Some genes appear to be necessary for the development or function of particular kinds of sensory neurons. Other genes have effects that suggest that they participate in odorant reception or signal transduction.
OBJECTIVE: To evaluate the effectiveness of endometrial resection as a surgical treatment for menorrhagia. DESIGN: Randomised controlled trial. SETTING: Gynaecology department at a teaching hospital. SUBJECTS: Two hundred women needing surgical treatment for menorrhagia between January 1990 and May 1991. After withdrawal of four women 97 underwent hysterectomy and 99 underwent endometrial resection. MAIN OUTCOME MEASURES: Patient satisfaction 4 months after surgery; post-operative complications; length of hospital stay; duration of time before return to work, normal daily activities and sexual intercourse; change in premenstrual symptoms. RESULTS: The difference in patient satisfaction between endometrial resection (84 out of 99) and abdominal hysterectomy (89 out of 95) just reached statistical significance in favour of abdominal hysterectomy at 4 months after surgery (difference = 9%, 95% confidence intervals (CI) 1.1%-17.5%). Post-operative morbidity, length of hospital stay and time taken to return to work, normal daily activities and sexual intercourse were significantly less in the endometrial resection group. However, the premenstrual symptoms of dysmenorrhoea, bloating and breast tenderness were less frequent after hysterectomy. CONCLUSION: In the short term, endometrial resection was almost as satisfactory as abdominal hysterectomy for the surgical treatment of menorrhagia, and was associated with less morbidity. However, even at 4 months after surgery, there was a failure rate of at least 10% in those in whom endometrial resection appeared complete. Longer term comparative studies are necessary before the widespread introduction of endometrial resection as an alternative to abdominal hysterectomy for the surgical treatment of menorrhagia.
OBJECTIVE: To evaluate the relative health service cost of endometrial resection versus abdominal hysterectomy for the treatment of menorrhagia and the value women attach to their health state before and after surgery. DESIGN: A prospective economic evaluation running alongside a randomised controlled trial. SETTING: The gynaecology department of a teaching hospital. SUBJECTS: 200 women requiring surgical treatment of menorrhagia between January 1990 and May 1991; after withdrawals, 97 women underwent hysterectomy and 99 underwent endometrial resection. MAIN OUTCOME MEASURES: The total health service cost of managing women in the two arms of the trial until 4 months after their operation. The change in women's valuation of their health state a fortnight after and a minimum of 4 months after surgery relative to that 1 month prior to their operation. RESULTS: Total health service costs are significantly higher amongst abdominal hysterectomy patients (mean 1059.73 pounds) than amongst endometrial resection patients with a mean difference of 499.68 pounds (95% CI 432 pounds-567 pounds). This significant difference exists under alternative assumptions about the difference in lengths of stay in hospital between the two treatment groups and the hotel cost per in-patient day. On a scale of 0 to 100, relative to a month before surgery, there is a statistically significant difference in favour of endometrial resection between the two groups in the increase in value women attach to their health state at a fortnight after surgery (mean difference 11.2; 95% CI 0.6-21.7), but not at a minimum of 4 months after surgery (mean difference 7; 95% CI -17.4 to 3.4). CONCLUSIONS: On the basis of health service resource cost up to 4 months after surgery, endometrial resection has a cost advantage over abdominal hysterectomy. However, given the fact that a subgroup of women requires retreatment due to resection failure and that this study considers a relatively short period of follow up, the long term costs and benefits of endometrial resection need to be evaluated before widespread diffusion is justified.
All new interventions and procedures must be properly assessed in comparison to the currently accepted method(s). It is unethical not to do so. The optimum method is by Randomised Controlled Trial (RCT). This is ideally suited to the testing of drugs because the trial can usually be double blind and placebo controlled. RCTs are less commonly used for the evaluation of new surgical techniques. There are valid and invalid reasons for this and these are discussed.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
A method--"fracture label"--is described for the cytochemical labeling of the membrane faces produced by freeze-fracture. Human erythrocytes embedded in a crosslinked matrix are frozen, fractured in liquid nitrogen, thawed, labeled, and cut into thin sections. Electron microscope observation of the fracture faces shows preferential partition of concanavalin A binding sites with the inner half of the membrane. This signifies that, during freeze-fracture, binding sites are dragged from the outer surface across the outer ("exoplasmic") half of the membrane and retained on the protoplasmic fracture face (face P). The fracture process results in exposure of new anionic sites on face P. Fracture-label can be applied to the cytochemical characterization of the cellular components exposed by freeze-fracture of isolated cells and tissues.
Experimental details of a new method for the cytochemical characterization of the membrane faces and cytoplasm produced by freeze-fracture of isolated cells and tissues are presented. This new method-"fracture-label"-involves grinding of frozen samples immersed in liquid nitrogen, thawing, cytochemical labeling of the fractured faces, and processing for thin section electron microscopy. Cationized ferritin (at pH. 7.5 and 4.0), colloidal iron, as well as concanavalin A are used to label the fractures faces of leukocytes and Hela cells embedded in a cross-linked matrix of bovine serum albumin and of liver and spleen tissues. Our results show the presence of numerous anionic binding sites on the fracture faces of all plasma and cytoplasmic membranes, and of concanavalin A binding sites preferentially associated to the exoplasmic fracture faces of plasma and nuclear envelope membranes. A proportion of the anionic sites appears to be revealed by, or during, the freeze-fracture process. Colloidal iron labeling also shows preferential association with the chromatin areas of cross-fractured nuclei. The results show that "fracture-label", i.e., the combined application of freeze-fracture and cytochemical labeling techniques, can be used to study the surface chemistry of the fractures faces of biological membranes as well as of cross-fractured cytoplasm.
A modified procedure for the isolation of a nuclear pore complex-lamina fraction from rat liver nuclei is described. Evidence is provided that the isolated lamina, a 150-A thick, proteinaceous structure, apposes the inner nuclear envelope membrane, connecting nuclear pore complexes and surrounding the entire nucleus.