Derek Lobb - Academia.edu (original) (raw)

Papers by Derek Lobb

Psychological Reports, Oct 14, 2022

BMC Health Services Research

Background Midwives have long workdays and work many weeks on call. There is a concern that these... more Background Midwives have long workdays and work many weeks on call. There is a concern that these extended work schedules can negatively affect their intention to stay in the profession. Purpose This study provides evidence on Canadian midwives’ preferences for and experiences with policies and guidelines which limit the hours of work and weeks per year preferred to be on call, and examines the relationship between preferences and midwives’ intention to stay in the profession. Methods Data come from our 2018 pan-Canadian survey of midwives. Descriptive statistics of 720 midwives’ preferences and experiences are provided. In the correlations followed by the OLS regressions, 596 midwives’ data are used to test the associations between preferences and intention to stay in the profession. STATA (version 15) is used. A thematic analysis of 274 midwives’ responses to the open-ended survey question is conducted to give voice to midwives on what can be done for retention. Results Three quar...

Journal of Steroid Biochemistry, 1984

The metabolism of [3H]androstenedione in relation to estrogen formation was studied in incubation... more The metabolism of [3H]androstenedione in relation to estrogen formation was studied in incubations of Sertoli cell-enriched preparations (30-40% Sertoli cells) and purified Leydig cells (greater than 98%) from testes of mature male pigs. Radioactive metabolites were partitioned by countercurrent distribution (CCD) into unconjugated and 'conjugated' (water-soluble) fractions. Both unconjugated and solvolysed metabolites were separated into neutral and phenolic fractions by CCD with toluene and NaOH. The distribution of radioactivity was examined subsequently for each fraction by partition chromatography on celite columns. Major differences were noted in the products of metabolism from the two cell types. More than half of the radioactivity appeared in the conjugate fraction for Leydig cell incubations, but little or no conjugation occurred in Sertoli cell preparations. Metabolism of androstenedione to other neutral substances was extensive only for Leydig cells, with approx 2% remaining unchanged. No clear evidence of estrogen formation was observed with Sertoli cells; however, both unconjugated and conjugated phenolic for Leydig cell products showed radioactivity corresponding to estrone and estradiol-17 beta on chromatography. About 2-5% of androstenedione was converted to these two estrogens, whereas most of the phenolic material was present as compounds more polar than estradiol.

SSM - Qualitative Research in Health

Human Resources for Health

Background Midwifery students’ intention to stay in the profession can be influenced by how the i... more Background Midwifery students’ intention to stay in the profession can be influenced by how the interface of their work and personal life is affected by their clinical placement experience. The purpose of this study is to compare the intention to stay in the midwifery profession and its association with three work/personal life interface constructs among pre- and post-clinical placement midwifery students in Canada. The constructs investigated are work interference with personal life, personal life interference with work, and work/personal life enhancement. Methods Quantitative cross-sectional data were collected through two separate online surveys completed by pre- and post-clinical placement students. In total, 456 midwifery students attending six different midwifery education programs responded to the surveys. Results Compared to pre-clinical placement students, post-clinical placement students had significantly lower intention to stay in the profession. For pre-clinical placemen...

Academy of Management Proceedings

Soft robotics, Jan 9, 2018

Physical simulation systems are commonly used in training of midwifery and obstetrics students, b... more Physical simulation systems are commonly used in training of midwifery and obstetrics students, but none of these systems offers a dynamic compliance aspect that would make them more truly representative of cervix ripening. In this study, we introduce a unique soft robot phantom that simulates the cervix softening during the latent labor phase of birth. This proof-of-concept robotic phantom can be dilated by 1 cm and effaced by 35% through the application of a Foley catheter-like loading mechanism. Furthermore, psychophysics trials demonstrate how untrained subjects can identify hard and soft states of the phantom with specificities of 91% and 87%, respectively. Both results indicated the appropriateness for application of this soft robot technology to birth training simulators.

Journal of Assisted Reproduction and Genetics, Mar 1, 2006

To validate an expedited method for the removal of erythrocytes when preparing IVF granulosa-lute... more To validate an expedited method for the removal of erythrocytes when preparing IVF granulosa-luteal cells for culture. Granulosa cells were enriched for culturing from follicular aspirates by density gradient centrifugation and by hypo-osmotic lysis treatments. Cells prepared by either method showed the same cell viability and produced progesterone in similar quantities. Using hypo-osmotic lysis to remove erythrocytes does not impair granulosa cell viability or steroidogenesis. It avoids multiple density gradient centrifugations and washings, and yields IVF granulosa cells ready for culture efficiently.

Journal of Steroid Biochemistry, 1982

Growth Factors and the Ovary, 1989

British Journal of Midwifery, 2009

Fertility and sterility, 1987

Granulosa and thecal cells were isolated from follicles of ovaries removed from premenopausal wom... more Granulosa and thecal cells were isolated from follicles of ovaries removed from premenopausal women who underwent salpingo-oophorectomy. The electrophoretic profiles of the [35S]methionine-radiolabeled proteins secreted by the two cell types were quite distinct and showed different major proteins. Untreated granulosa cells secreted a major radiolabeled protein with a molecular weight of 220,000, identified as fibronectin by immunoprecipitation. This protein comprised 21% of the total secreted protein; however, the intensity of labeling was reduced after treatment with 0.5 mM dibutyryladenosine 3':5'-cyclic monophosphate ([Bu]2 cAMP). Fibronectin secretion by control cultures measured by a competitive enzyme-linked immunoadsorbant assay ranged from 15.1 to 16.8 micrograms/mg cellular protein/24 hours and was reduced to 30% after treatment with 0.5 mM (Bu)2 cAMP. In contrast, untreated thecal cells secreted only low levels of fibronectin and a 25,000-dalton protein contributed...

Molecular and cellular endocrinology, 1992

Relaxin mRNA concentrations in porcine corpora lutea were examined during the peri-implantation p... more Relaxin mRNA concentrations in porcine corpora lutea were examined during the peri-implantation period and throughout pregnancy using Northern and slot blot analysis. Total RNA was extracted from corpora lutea obtained from pigs of known breeding dates and pregnancy was confirmed by embryo recovery. A 32P-labelled porcine relaxin cDNA probe identified the 1.0 kilobase relaxin transcript. Slot blots were subsequently used to quantify relaxin mRNA concentrations. Relaxin mRNA was detectable in the corpus luteum of the regular cycle and was also present at similar low levels in corpora lutea of days 10, 11 and 12 of pregnancy. In corpora lutea from day 16 of pregnancy onwards 100-fold greater quantities of relaxin mRNA were observed. The intensity remained similar in samples between days 16 and 102 of pregnancy. These studies indicate that elevated relaxin gene expression commences very early in pregnancy and is first detectable in the peri-implantation period.

Journal of Steroid Biochemistry, 1987

In this paper we have examined the possibility that soluble factors produced by the thecal and gr... more In this paper we have examined the possibility that soluble factors produced by the thecal and granulosa cells may be essential local modulators of follicular development. The observations that insulin could influence both the growth and the differentiation of granulosa cells were important in establishing the concept that peptides could act as amplifiers of the actions of gonadotrophins. Insulin alone did not influence aromatase activity significantly but acted synergistically with FSH to augment aromatase activity in rat granulosa cells. Unlike aromatase activity, insulin alone was able to significantly stimulate 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity, the maximum level achieved approaching that obtained with high concentrations of FSH. To determine if insulin could influence other parameters of granulosa cell function in addition to steroidogenesis, we measured a component of extracellular matrix, fibronectin, previously shown to be inhibited by FSH. Treatment with insulin independently inhibited the increase in fibronectin secretion observed in control cultures. Also, insulin alone was able to stimulate quiescent bovine granulosa cells to incorporate [3H]thymidine into DNA under serum-conditions. The concentration of insulin required in these experiments was higher than physiological levels suggesting that other insulin-like growth factors may be involved. Our work and that of others has shown that IGF1 can mimic the actions of insulin and is effective at lower concentrations. A possible source of IGF1 production in the follicle was sought initially by collecting rat granulosa cell conditioned medium, and assessing biological activity and immunoreactivity. Conditioned medium augmented the actions of FSH on aromatase activity and alone stimulated 3 beta-HSD, indicating the presence of insulin-like bioactivity. A positive reaction on immunoblots using specific antiserum confirmed the presence of immunoreactive IGF1. Conditioned medium from thecal cells contained a growth-promoting activity (TcGF) that did not augment FSH-induced aromatase activity. The production of growth factors locally within the follicle may represent the self-amplifying mechanism that enables the dominant follicle to complete its developmental program and ovulate.

The Journal of Steroid Biochemistry and Molecular Biology, 2006

Progesterone is produced by granulosa cells under the influence of luteinizing hormone. Nuclear p... more Progesterone is produced by granulosa cells under the influence of luteinizing hormone. Nuclear progesterone receptors have been found in rat granulosa cells. Human granulosa-lutein cells rapidly respond to progesterone with an increase in intracellular calcium suggesting the existence of a nongenomic mechanism. This study was conducted to determine whether binding of progesterone to granulosa cells could occur at the membrane. Granulosa cells were obtained from an in vitro fertilization program and examined immunohistochemically with an antiserum to membrane progesterone receptors. Approximately 14-70% of freshly harvested or cultured granulosa cells of six patients showed a positive reaction to the antiserum, limited to the cell membrane. Western blot analysis of homogenates of granulosa cells and a granulosa cell tumour confirmed the presence of progesterone receptors A, B and C and low amounts of a putative membrane receptor. These results demonstrate that the plasma membranes of human granulosa cells possess binding components for progesterone which may be involved in its nongenomic mechanism of action.

Steroids, 1987

This study describes the effects of insulin, insulin-like growth factor

Reproduction, Fertility and Development, 1993

Transforming growth factor-alpha (TGF-alpha), a product of the thecal cells, has potent mitogenic... more Transforming growth factor-alpha (TGF-alpha), a product of the thecal cells, has potent mitogenic and steroidogenic influences on cells within the ovarian follicle. Whether TGF-alpha continues to be produced in those follicles that go on to ovulate and form a corpus luteum is currently under investigation. In the present study, TGF-alpha was localized in the bovine corpus luteum by means of immunoperoxidase staining using a monoclonal antibody for TGF-alpha that does not cross-react with epidermal growth factor. In corpora lutea from the mid-luteal phase of the cycle TGF-alpha staining was found predominantly in the large luteal cells. Northern blot analysis using a human TGF-alpha cDNA probe hybridized to the 4.5-4.8 kb TGF-alpha transcript in RNA from the corpus luteum. These studies provide new evidence that TGF-alpha, a potent paracrine regulator within the ovarian follicle, continues to be expressed in the corpus luteum.