Amniotic sac reference interval in early pregnancy between 7 and 10 weeks' gestation.

OBJECTIVE: To establish a normal reference interval for amniotic sac measurements between 7 and 10 weeks of gestation and its relative size in relation to the gestational sac and the embryo. METHOD: This was a prospective, cross-sectional study of consecutive women presenting to UCLH Early Pregnancy Unit between August 2022 to June 2023. We included live, normally sited, singleton pregnancies with a normal 20-week anomaly scan. We collected 120 cases per gestational week totaling 360 cases. We performed an inter and intra-observer variability assessment in the measurement of mean ASD in 30 patients. Regression analyses were used to establish reference intervals for GSD to CRL, ASD to CRL, GSD to ASD and GSD:ASD ratio to CRL. The fitted regression line was calculated, along with a 90% prediction interval and the R2 value. RESULTS: There was good interobserver agreement (difference 0.007mm ± 1.105 (95%CI -2.160 to 2.174)) and good intra-observer agreement between Observer A (0.007 ± 1.105 (-2.160 to 2.174)) and Observer B (-0.014 ± 0.919 (-1.814 to 1.786)) in the measurement of mean ASD in 30 patients. Regression analyses showed a highly statistically significant association between each pair of values (all p-values <0.001). There were significant quadratic associations between mean GSD and CRL (R2 = 56%) and mean GSD and ASD (R2 = 60), significant cubic association between ASD and CRL (R2 = 90%) and significant quadratic association between GSD to ASD ratio and CRL (R2 = 68%). The regression equations were used to quantify the values of ASD and GSD to ASD ratios for a range of CRL values and gestational age in days. CONCLUSION: Our study has produced comprehensive reference intervals for amniotic sac size in early pregnancy which could be used in routine clinical practice. This article is protected by copyright. All rights reserved.

Ultrasound study of natural progression of ovarian endometriomas.

OBJECTIVES: The aim of this study was to determine the natural history of ovarian endometriomas in women who are managed expectantly. METHODS: This was a retrospective cohort study of 83 women with evidence of ovarian endometriomas, who were managed expectantly between April 2007 to May 2022. The study was conducted in the Department of Women's Health, University College London Hospitals and The Gynecology Ultrasound Centre, London, UK. We searched our ultrasound clinic databases to identify women aged 18 years or older with evidence of ovarian endometriomas that were managed expectantly for ≥ 6 months. All women attended for a minimum of two ultrasound scans by a single expert ultrasound operator. In addition to patient demographics, we recorded the number, mean diameter and location of each cyst. The cyst growth rate was expressed as annual change in the mean diameter. RESULTS: 1,922 women attended our gynecology clinic during the study period who were found to have evidence of moderate or severe endometriosis on pelvic ultrasound examination. A total of 83 women had evidence of ovarian endometriomas and were managed expectantly. The median age of women was 39 (range 26 - 51). Each woman had at least two ultrasound scans performed by a single expert operator at a minimum interval of ≥6 months. 50/83 (60%, 95% CI 49-71) women had single cysts and the remainder had multiple cysts. The median number of endometriomas per patient was 1 (range 1 - 5) and the median follow up time was 634 days (range 187 - 2984). 39/83 (47%, 95% CI 36 - 58) women experienced an overall reduction in size of cysts, in 18/83 (22%, 95% CI 13 - 32) the cysts increased in size and in 26/83 (31% 95% CI 22 - 42) women, no meaningful change was observed. The median change in mean diameter of cysts per woman during the study period was -2.7 mm (-57.7 - +39.3), with an annual growth rate of -1.7 mm/year/woman (-24.6 - +42.0). Overall, cysts were smaller at the follow up visit [median diameter 22.3mm (6.7 - 77) vs. 18.5mm (5 - 72) p = 0.009]. We did not identify any clinical characteristics that could reliably predict the chance of endometrioma progression. CONCLUSION: In the majority of women with ultrasound diagnosis of ovarian endometriomas, the cysts do not increase in size significantly over time and they could be managed expectantly. This evidence may help clinicians when counselling asymptomatic or minimally symptomatic women about the options to manage their ovarian endometriomas. This article is protected by copyright. All rights reserved.

Imaging in gynecological disease (25): clinical and ultrasound characteristics of intramural pregnancy.

OBJECTIVE: To describe the clinical and sonographic characteristics of intramural pregnancy, as well as the available management options and treatment outcomes. METHODS: This was a retrospective single-center study of consecutive patients with a sonographic diagnosis of intramural pregnancy between November 2008 and November 2022. An intramural pregnancy was diagnosed on ultrasound when a pregnancy was implanted within the uterine corpus, above the level of the internal cervical os and separate from the interstitial section of the Fallopian tube, and extended beyond the decidual-myometrial junction. Clinical, ultrasound, relevant surgical and histological information and outcomes were retrieved from each patient's record and analyzed. RESULTS: Eighteen patients were diagnosed with an intramural pregnancy during the study period. Their median age was 35 (range, 28-43) years and the median gestational age at diagnosis was 8 + 1 (range, 5 + 5 to 12 + 0) weeks. Vaginal bleeding with or without abdominal pain was the most common presenting symptom, recorded in eight patients. Nine (50%) patients had a partial and nine (50%) had a complete intramural pregnancy. Embryonic cardiac activity was present in eight (44%) pregnancies. The majority of pregnancies (n = 10 (56%)) were initially managed conservatively, including expectant management in eight (44%) cases, local injection of methotrexate in one (6%) and embryocide in one (6%). Conservative management was successful in nine of the 10 (90%) pregnancies, with a median time to serum human chorionic gonadotropin resolution of 71 (range, 35-143) days. One patient with an ongoing live pregnancy had an emergency hysterectomy for a major vaginal bleed at 20 weeks' gestation. No other patient managed conservatively experienced any significant complication. The remaining eight (44%) patients had primary surgical treatment, comprising transcervical suction curettage in seven (88%) of these cases, while one patient presented with uterine rupture and underwent emergency laparoscopy and repair. CONCLUSIONS: We describe the ultrasound features of partial and complete intramural pregnancy, demonstrating key diagnostic features. Our series suggests that, when intramural pregnancy is diagnosed before 12 weeks' gestation, it can be managed either conservatively or by surgery, with preservation of reproductive function in most women. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Threats to reliability risk erroneous conclusions: a survey of prospective registration and sample sizes of randomised trials in women's health.

OBJECTIVE: Prospective registration of clinical trials has been required since 2005. We aimed to assess concordance between registered and reported sample sizes among prospectively registered randomised controlled trials (RCTs) in obstetrics and gynaecology. DESIGN: Analysis of prospectively registered and published data. SETTING: Women's health. SAMPLE: Obstetrics and gynaecology RCTs published in eight journals in 2015. METHODS: Specialist (Acta Obstet Gynecol Scand, BJOG, Obstet Gynecol and Am J Obstet Gynecol) and general (BMJ, N Engl J Med, JAMA and Lancet) journals were searched from 1 January to 31 December 2015 for main reports of obstetrics and gynaecology RCTs. Their corresponding registries and protocols were sought and data were extracted. Proportions and 95% CI were calculated using exact methods. MAIN OUTCOME MEASURES: Prospective registration of RCT and sample size concordance between RCTs and their registries within those where registration took place before patients were recruited. RESULTS: Of the 75 relevant RCTs, 51 (68%, 95% CI 56-78%, P < 0.001 using a null hypothesis requiring 100% compliance) were prospectively registered, a feature found to be more common in general journals versus specialist journals (21/22 versus 30/53, 95% versus 57%, P = 0.001). Of the 51 prospectively registered RCTs, 31 (61%, 95% CI 46-74%, P = 0.003 using a null hypothesis requiring 40% of studies to achieve their stated sample size) did not reach the target sample size. CONCLUSIONS: There are gaps in universal adoption of the prospective trial registration rule. Inability to meet target sample size risks deficiencies in statistical power with unreliability in results. TWEETABLE ABSTRACT: Only two-thirds of RCTs in women's health are prospectively registered, and over half fail to achieve target sample sizes.

Participation in clinical trials improves outcomes in women's health: a systematic review and meta-analysis.

BACKGROUND: Previous reviews examining the effect of participation in trials on outcomes have not consistently shown benefit. Obstetrics and gynaecology is a unique disease area posing challenges for both researchers and patients. OBJECTIVES: To determine whether participation in randomised controlled trials (RCTs), compared with non-participation, has a beneficial effect on women's health. SEARCH STRATEGY: Medline, Embase, the Cochrane Library, and PsycInfo were searched up to December 2015. SELECTION CRITERIA: We selected studies that reported the same clinical outcomes for participants in a women's health RCT and a comparable non-participant cohort. DATA COLLECTION AND ANALYSIS: Data were extracted on quality, characteristics and study results. Outcomes were compared using logistic regression. MAIN RESULTS: There were 21 relevant studies (20 160 women, 4759 outcome events). Trial participants, compared with non-participants, had 25% better odds of improved outcomes on average (OR 0.75; 95% CI 0.64-0.87; I2  = 64.3%). The beneficial effect of participating in a trial was larger in comparisons where: RCTs were of high quality (OR 0.62; 95% CI 0.50-0.76) versus low (OR 0.92; 95% CI 0.74-1.16); and RCT intervention was not available to non-participants (OR 0.57; 95% CI 0.47-0.69) versus when it was (OR 1.13; 95% CI 0.89-1.44). The effect of trial participation was not influenced by effect size within the RCT (P = 0.48), whether funding was received or not (P = 0.13), whether non-participants received any treatment or not (P = 0.49), and the quality of the comparison of RCT participants with non-participants (P = 0.88). CONCLUSIONS: Women participating in RCTs on average experienced better outcomes compared with those outside trials. TWEETABLE ABSTRACT: Participants in obstetric and gynaecology RCTs experience better outcomes compared with non-participants.

Entry demographics and pharmacological treatment of migraine patients referred to a tertiary care pain clinic.

The aim was to examine pharmacological treatment of migraine patients admitted to a tertiary care pain clinic. A retrospective review of 100 consecutive migraine patients admitted to The Wasser Pain Management Centre was conducted. Patients included met the 2nd Edition of the International Classification of Headache Disorders criteria for diagnosis of migraine. Data were collected with regard to nicotine and alcohol consumption, family history of migraine headaches, other pain diagnoses and pharmacological treatment. Twenty-two per cent of these patients were male as opposed to 78% female. The mean age of patients admitted for migraine was 43.4 years. Of the patients admitted, 48% had tried at least one triptan in the past and only 31% were actively using triptan(s). The most commonly used triptan in the past had been sumatriptan, whereas the most common triptan used on admission was rizatriptan. Opiate use was much more prevalent; 72% of admitted patients were using an opiate and 27% used multiple opiates. A significant number of patients had not yet been tried on a triptan despite meeting the diagnostic criteria for migraine and having significant disability. More education of the general medical community may be beneficial in implementing a stratified care approach to migraine management.

Notch receptor expression in adult human liver: a possible role in bile duct formation and hepatic neovascularization.

Notch signaling is an evolutionarily conserved mechanism, used to regulate cell fate decisions. Four Notch receptors have been identified in man (Notch-1 to -4). In this study, semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry were used to examine the expression pattern of Notch receptor genes in whole adult human liver and isolated liver cell preparations. All 4 receptors were expressed in the adult liver, with no significant differences in the levels of Notch-1, -2, and -4 messenger RNA (mRNA) between normal and diseased liver. However, Notch-3 expression appeared to be increased in diseased tissue. The distribution of Notch-1 and -4 in normal tissue was similar, with Notch-1 also detectable at low levels in the sinusoidal endothelium. Notch-2 expression was more widely distributed, and detectable in hepatocytes, medium-sized bile ducts, and the sinusoidal endothelium. Notch-3 expression was seen on hepatocytes, with weaker expression detectable in portal veins, hepatic arteries, and the sinusoids. In normal liver tissue Notch-1, -2, and -3 were found to be coexpressed on bile duct epithelium; however, with the exception of Notch-3 in primary sclerosing cholangitis (PSC) livers, expression was absent on proliferating ductules in all disease states examined. Interestingly, the expression of Notch-2 and -3 was associated with numerous small vessels within the portal tract septa of diseased tissue. The absence of Notch receptor expression on proliferating bile ductules and its presence on neovessels suggests that Notch signaling may be important for normal bile duct formation and the aberrant neovascularization seen in diseased liver tissue.

Tie-2 is expressed on thyroid follicular cells, is increased in goiter, and is regulated by thyrotropin through cyclic adenosine 3',5'-monophosphate.

Angiogenesis is coordinated with follicular cell growth in goitrogenesis. The angiopoietins, Ang-1 and Ang-2, are angiogenic growth factors acting through Tie-2, a tyrosine kinase receptor. We have examined the expression and regulation of the angiopoietins and Tie-2 in human and rat thyroids. In human goiters there was increased Tie-2 immunostaining, compared with that in normal thyroids, on both follicular and endothelial cells. In an induced goiter in rats, in situ hybridization showed increased expression of messenger ribonucleic acids (mRNAs) for Tie-2 and Ang-1 in follicular cells. As Tie-2 has previously been believed to be restricted to cells of endothelial lineage in adults, we examined its expression further in isolated follicular cells. Tie-2 and Ang-1 mRNA expression in human thyrocytes was confirmed by ribonuclease protection assay. Ang-2 mRNA was not detected in human cultures or rat thyroids. In both human follicular cell cultures and FRTL-5 cells, immunoblotting showed that Tie-2 expression was increased by TSH and agents that increased intracellular cAMP. In conclusion, we have demonstrated the expression of Tie-2 and Ang-1 in thyroid epithelial and endothelial cells, and have shown the regulation of Tie-2 by TSH and cAMP in follicular cells. Tie-2 expression is increased in goiter in both humans and rats, consistent with a role in goitrogenesis.

Xenopus Enhancer of Zeste (XEZ); an anteriorly restricted polycomb gene with a role in neural patterning.

We have identified the Xenopus homologue of Drosophila Enhancer of Zeste using a differential display strategy designed to identify genes involved in early anterior neural differentiation. XEZ codes for a protein of 748 amino acids that is very highly conserved in evolution and is 96% identical to both human and mouse EZ(H)2. In common with most other Xenopus Pc-G genes and unlike mammalian Pc-G genes, XEZ is anteriorly restricted. Zygotic expression of XEZ commences during gastrulation, much earlier than other anteriorly localized Pc-G genes; expression is restricted to the anterior neural plate and is confined later to the forebrain, eyes and branchial arches. XEZ is induced in animal caps overexpressing noggin; up-regulation of XEZ therefore represents a response to inhibition of BMP signalling in ectodermal cells. We show that the midbrain/hindbrain junction marker En-2,and hindbrain marker Krox-20, are target genes of XEZ and that XEZ functions to repress these anteroposterior marker genes. Conversely, XEZ does not repress the forebrain marker Otx-2. XEZ overexpression results in a greatly thickened floor of the forebrain. These results implicate an important role for XEZ in the patterning of the nervous system.

Domoic acid-induced neurodegeneration resulting in memory loss is mediated by Ca2+ overload and inhibition of Ca2+ + calmodulin-stimulated adenylate cyclase in rat brain (review).

Domoic acid is a shellfish toxin which produces neurodegeneration and CNS dysfunction, notably a loss of short-term memory. This toxin was found in blue mussels (Mytilus edulis) cultivated in river water in the east coast of Prince Edward Island in Canada and caused human poisoning. The toxin was localized in the stomach of blue mussels, which was engorged with algae, Nitzschia pungens, that were filtered from the surrounding water. The toxin was isolated from contaminated mussels or phytoplankton, and identified chemically as domoic acid (DOM) which is a tricarboxylic amino acid. Due to its structural resemblance to glutamic, aspartic and kainic acids, DOM was considered to produce excitotoxicity by similar mechanism(s). However, the latest evidence indicates differences in its mode of action from these excitatory agonists. We propose that DOM induces toxicity via changes in intracellular concentration of Ca2+ ([Ca2+]i). Results of our studies demonstrate that DOM elevated [Ca2+]i in brain slices. Glucose deprivation and removal of Na+ from the Krebs-bicarbonate medium further elevated [Ca2+]i, suggesting a relationship between glucose metabolism (cell energy), Na+ and Ca2+ transfer across neuronal membrane. DOM-induced rise in [Ca2+]i was due to enhanced Ca2+ influx and its mobilization from the endoplasmic reticulum. In addition, diminished Ca2+-ATPase activity due to lack of ATP, and variable amounts and expression of calcium binding proteins (CaBP) appear to contribute to an elevation in [Ca2+]i in response to DOM. Most interestingly, DOM inhibited Ca2+ and calmodulin-stimulated adenylate cyclase activity in brain membranes, resulting in reduced level of cyclic AMP. Cyclic AMP is known to activate protein kinase A to enhance phosphorylation of Ca2+ channels, thereby, reducing Ca2+ influx to prevent the development of Ca2+ overload which is detrimental to neuronal cell function (neuroprotection). However, DOM reduced cyclic AMP level, diminishing the feedback control of cyclic AMP on Ca2+ influx via Ca2+ channels, thereby, allowing continuing enhanced Ca2+ influx, resulting in Ca2+ overload which adversely affects many intracellular processes to induce toxicity. Ca2+ and CaM-stimulated adenylate cyclase activity in brain is highly correlated with the acquisition and retention of memory in different organisms. Calcium binding proteins bind Ca2+ reversibly and provide intracellular Ca2+ buffering, thereby, protecting neuronal cell from damage by Ca2+ overload in response to DOM. DOM appears to interfere with the cross talk between Ca2+ and cyclic AMP which is necessary for neuronal cell function. We have also demonstrated that DOM stimulates GLU release from synaptosomes and may produce some of its toxic effects via excess GLU in the neuronal synapse. In conclusion, DOM-induced neurodegeneration resulting in a loss of memory is mediated by Ca2+ overload, inhibition of Ca2+ and CaM-stimulated adenylate cyclase activity, and/or by the enhanced GLU release in rat brain.

Induction of placental heme oxygenase-1 is protective against TNFalpha-induced cytotoxicity and promotes vessel relaxation.

BACKGROUND: Pregnancy is characterized by an inflammatory-like process and this may be exacerbated in preeclampsia. The heme oxygenase (HO) enzymes generate carbon monoxide (CO) that induces blood vessel relaxation and biliverdin that acts as an endogenous antioxidant. MATERIALS AND METHODS: We examined the expression and localization of HO-1 and HO-2 in normal and preeclamptic placenta using reverse transcription polymerase chain reaction (RT-PCR), RNase protection assay, immunoblotting and immunohistochemistry. In addition, the effect of HO activation on tumor necrosis factor-alpha (TNFalpha) induced placental damage and on feto-placental circulation was studied. RESULTS: We provide the first evidence for the role of HO as an endogenous placental factor involved with cytoprotection and placental blood vessel relaxation. HO-1 was significantly higher at term, compared with first trimester placentae indicating its role in placental vascular development and regulation. HO-1 predominantly localized in the extravascular connective tissue that forms the perivascular contractile sheath around the developing blood vessels. HO-2 was localized in the capillaries, as well as the villous stroma, with weak staining of trophoblast. Induction of HO-1 caused a significant attenuation of TNFalpha-mediated cellular damage in placental villous explants, as assessed by lactate dehydrogenase leakage (p < 0.01). HO-1 protein was significantly reduced in placentae from pregnancies complicated with preeclampsia, compared with gestationally matched normal pregnancies. This suggests that the impairment of HO-1 activation may compromise the compensatory mechanism and predispose the placenta to cellular injury and subsequent maternal endothelial cell activation. Isometric contractility studies showed that hemin reduced vascular tension by 61% in U46619-preconstricted placental arteries. Hemin-induced vessel relaxation and CO production was inhibited by HO inhibitor, tin protoporphyrin IX. CONCLUSIONS: Our findings establish HO-1 as an endogenous system that offers protection against cytotoxic damage in the placenta, identifies the HO-CO pathway to regulate feto-placental circulation and provides a new approach to study the disease of preeclampsia.

Angiopoietin-1 and angiopoietin-2 activate trophoblast Tie-2 to promote growth and migration during placental development.

Human placental development involves coordinated angiogenesis and trophoblast outgrowth that are compromised in intrauterine growth restriction (IUGR). As Tie-2((-/-)) mice exhibit growth retardation and vascular network malformation, the expression of Tie-2 and its ligands, angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), were investigated in human placenta from normal pregnancies and those complicated by severe IUGR. Ribonucleotide protection assays showed no significant change in the expression of Ang-2 mRNA between gestationally matched normal and IUGR placentas; however, immunoblots revealed that Ang-2 protein was significantly decreased in IUGR, suggesting that this may contribute to the abnormal development of the villous vasculature. In situ hybridization studies showed that Ang-1 and Tie-2 were detected in the cyto/syncytiotrophoblast bilayer in first-trimester placenta, whereas Ang-2 mRNA was restricted to the cytotrophoblast, suggesting their role in trophoblast function. At term, Ang-1 mRNA and immunoreactive protein were restricted to the paravascular tissues of the primary stem villi, supporting its role in vessel maturation. In contrast, Ang-2 was expressed throughout the term villous core, perhaps to permit the developing placental vascular network to remain in a state of fluidity. As these studies also revealed that trophoblast, in addition to endothelial cells, expressed Tie-2 receptors, we investigated the potential role of Ang-1/Ang-2 on trophoblast proliferation, migration, and the release of NO. Using spontaneously transformed first-trimester trophoblast cell lines that exhibit cytotrophoblast-like (ED(27)) and extravillous trophoblast-like (ED(77)) properties, we show that the addition of Ang-2 (250 ng/ml) stimulated DNA synthesis in ED(27) trophoblast cells and triggered the release of NO. Ang-1 stimulated trophoblast (ED(77)) migration in a dose-dependent manner that was inhibited by recombinant Tie-2-FC. These data thus imply, for the first time, a specific role for angiopoietins as regulators of trophoblast behavior in the development of the utero/fetoplacental circulation, an action independent of their well-established roles in vascular endothelium.

The specification and growth factor inducibility of the pronephric glomus in Xenopus laevis.

We report a study on the specification of the glomus, the filtration device of the amphibian pronephric kidney, using an explant culturing strategy in Xenopus laevis. Explants of presumptive pronephric mesoderm were dissected from embryos of mid-gastrula to swimming tadpole stages. These explants were cultured within ectodermal wraps and analysed by RT-PCR for the presence of the Wilm's Tumour-1 gene, xWT1, a marker specific for the glomus at the stages analysed, together with other mesodermal markers. We show that the glomus is specified at stage 12.5, the same stage at which pronephric tubules are specified. We have previously shown that pronephric duct is specified somewhat later, at stage 14. Furthermore, we have analysed the growth factor inducibility of the glomus in the presence or absence of retinoic acid (RA) by RT-PCR. We define for the first time the conditions under which these growth factors induce glomus tissue in animal cap tissue. Activin together with high concentrations of RA can induce glomus tissue from animal cap ectoderm. Unlike the pronephric tubules, the glomus can also be induced by FGF and RA.

The specification of the pronephric tubules and duct in Xenopus laevis.

We have examined the timing of specification of the pronephric tubules and duct in Xenopus laevis by explanting the presumptive pronephric rudiments into blastula ectodermal wraps. We have established the time point of specification using the monoclonal antibody markers 3G8 and 4A6 which recognize antigens in pronephric tubule and duct, respectively. We show that, by experimental analysis in explants, kidney tubules are specified by stage 12.5 in the pronephric anlagen whereas pronephric duct is specified later between stages 13 and 14. Furthermore we show that signals involved in tubulogenesis of the pronephric tubules are normally received between stage 12.5 and 13. These experiments unambiguously pinpoint the timing of pronephros specification analyzed by explant experimentation to a developmental stage prior to that demonstrated for urodele amphibia, and provide an essential biological backdrop to a search for the molecular nature of pronephric inducers.

Over-expression of GATA-6 in Xenopus embryos blocks differentiation of heart precursors.

Xenopus GATA-6 transcripts are first detected at the beginning of gastrulation in the mesoderm, and subsequent domains of expression include the field of cells shown to have heart-forming potential. In this region, GATA-6 expression continues only in those cells that go on to form the heart; however, a decrease occurs prior to terminal differentiation. Artificial elevation of GATA-6, but not GATA-1, prevents expression of both cardiac actin and heart-specific myosin light chain. This effect is heart-specific because cardiac actin expression is unaffected in somites. Expression of the earlier marker XNkx-2.5 was unaffected and morphological development of the heart was initiated independently of the establishment of the contractile machinery. We conclude that a reduction in the level of GATA-6 is important for the progression of the cardiomyogenic differentiation programme and that GATA-6 may act to maintain heart cells in the precursor state. At later stages, when the elevated GATA-6 levels had decayed, differentiation ensued but the number of cells contributing to the myocardium had increased, suggesting either that the blocked cells had proliferated or that additional cells had been recruited.

Structure-function relationship in heart sarcolemma.

Dependence on the membrane lipids of sarcolemmal structure as well as functions was examined by incubating isolated rat heart sarcolemma with phospholipase A, C, or D. Conventional as well as negatively stained electron microscope preparations of the treated membranes revealed structural changes. Ca2+ binding and Na+, K+-ATPase activity were depressed following treatment of the membranes with any of the phospholipases whereas Ca2+-ATPase activity was not affected. Adenylate cyclase activity was increased by low concentration (25 micrograms/mg of protein) of phospholipase A, and a definite inhibition of the enzyme was noticed when the concentration of the phospholipase A was increased to 250 micrograms/mg of protein. Phospholipases C and D had no significant effect on the adenylate cyclase activity. Percentage of phospholipids hydrolyzed was more after phospholipase A treatments. These results provide evidence regarding the involvement of lipids in the membrane structure and functions.