Chromosome behavior at the base of the angiosperm radiation: karyology of Trithuria submersa (Hydatellaceae, Nymphaeales).

UNLABELLED: • PREMISE OF THE STUDY: Hydatellaceae are minute annual herbs with potential as a model system for studying early angiosperm evolution, but their karyology and ploidy levels are almost unknown. We investigated these aspects of Trithuria submersa, a widespread species that we show to be amenable to extended vegetative propagation.• METHODS: We cultivated plants of T. submersa in vitro after developing and optimizing culture conditions. We estimated genome size using flow cytometry, counted chromosome numbers using root-meristem squashes after Feulgen staining, and examined meiotic chromosome behavior using microsporocytes.• KEY RESULTS: We developed methods to reliably germinate seeds of T. submersa and to propagate them vegetatively in critical thermo- and photoperiod regimes on 1/2 Murashige-Skoog (MS) medium with vitamins and 2% sucrose solidified with 0.7% agar-agar. Seedling growth requires the medium be supplemented with activated charcoal. The mean nuclear DNA content of T. submersa sporophytes is 2C = 2.74 pg (∼2.68 Gbp). The sporophytic chromosome number is 2n = 56 with a bimodal complement, which may suggest an allopolyploid origin. Some of the largest chromosomes lack a recognizable constriction, which relates to a highly unusual and irregular chromosome behavior. Microsporocytes undergo reduced and asynchronous meioses that show a modified intermediate cell division with a nucleus division by fractional postreduction, indicating partially inverted microsporogenesis.• CONCLUSIONS: In vitro cultivation and karyological assessment of T. submersa open new opportunities for investigating early-divergent angiosperms. The remarkably different meiotic behavior exhibits new insights into a potentially ancestral microsporogenesis.

Impact of spatial constraints during seed germination on the evolution of angiosperm cotyledons: a case study from tropical Hydatellaceae (Nymphaeales).

PREMISE OF THE STUDY: A bipolar embryo with cotyledons is a characteristic feature that appeared early in the evolution of seed plants. Cotyledon number is an important character in angiosperm classification. We explore the links between functional aspects of seed germination and the number and location of the cotyledons, using as a model the early-divergent angiosperm family Hydatellaceae, in which seedlings are superficially monocot-like. • METHODS: Seedlings of two species of tropical Hydatellaceae were studied using light and scanning electron microscopy. • KEY RESULTS: Seedlings of Trithuria cowieana bear two free cotyledons. Each cotyledon possesses a green, filiform, vascularized blade that resembles subsequent leaves, and a basal, nonvascularized, haustorial outgrowth that remains in close contact with the endosperm. Seedlings of Trithuria konkanensis have two free cotyledonary haustoria inserted close to each other and a leaf blade probably belonging to one of the cotyledons. The cotyledonary node elongates between the haustoria and the leaf blade to form a mesocotyl. • CONCLUSIONS: To date, the absence or presence of a cotyledonary tube represents the only known qualitative morphological difference between the two major clades of Hydatellaceae. Cotyledons with a haustorium and leaf blade are unusual at the scale of seed plants and probably evolved due to homeosis. The mesocotyl of T. konkanensis resembles that of grasses and sedges. Seedling diversity in Hydatellaceae and other seed plants is linked with the principal physical and spatial constraint of their embryo structure, with the primary root and shoot apical meristems located at opposite poles, and haustorial cotyledon tips.

Homocysteine and folate plasma concentrations in mother and baby at delivery after pre-eclamptic or normotensive pregnancy: Influence of parity.

UNLABELLED: Pre-eclampsia affects between 2% and 7% of all pregnant women, contributing to perinatal and maternal morbidity. There are conflicting data on plasma homocysteine and folate in pre-eclampsia, and little about fetal concentrations. OBJECTIVES: Firstly, to compare the concentrations of homocysteine and folate in maternal and paired fetal (umbilical venous) plasma samples from normotensive or pre-eclamptic pregnancies at delivery; secondly, to identify any effect of parity on these concentrations. STUDY DESIGN: Hospital based cross-sectional study consisting of 24 normotensive and 16 pre-eclamptic pregnant White European women from whom maternal and fetal plasma samples were collected at delivery. MAIN OUTCOME MEASURES: Maternal and fetal plasma homocysteine and folate concentrations between normotensive and pre-eclamptic pregnancies with varying parity. RESULTS: There were no significant differences in either maternal or fetal plasma homocysteine or folate concentrations between normotensive and pre-eclamptic pregnancies, or between homocysteine and folate. In both the normotensive and pre-eclamptic women, plasma folate concentration was higher in paired fetal compared to maternal plasma (P<0.001 and P=0.047, respectively). With regards to homocysteine, only the normotensive samples had higher fetal concentrations (P=0.002). Both maternal and fetal plasma folate concentrations were lower in parous women (P=0.001 and P=0.017, respectively), the lowest concentrations being in pre-eclamptic parous women (P=0.004), but homocysteine concentrations were similar (P>0.4 for both). CONCLUSIONS: The low plasma folate in parous women is an interesting finding and, when intake is also low, may contribute to adverse pregnancy outcomes, particularly in relation to pre-eclampsia.

Seed fertilization, development, and germination in Hydatellaceae (Nymphaeales): Implications for endosperm evolution in early angiosperms.

New data on endosperm development in the early-divergent angiosperm Trithuria (Hydatellaceae) indicate that double fertilization results in formation of cellularized micropylar and unicellular chalazal domains with contrasting ontogenetic trajectories, as in waterlilies. The micropylar domain ultimately forms the cellular endosperm in the dispersed seed. The chalazal domain forms a single-celled haustorium with a large nucleus; this haustorium ultimately degenerates to form a space in the dispersed seed, similar to the chalazal endosperm haustorium of waterlilies. The endosperm condition in Trithuria and waterlilies resembles the helobial condition that characterizes some monocots, but contrasts with Amborella and Illicium, in which most of the mature endosperm is formed from the chalazal domain. The precise location of the primary endosperm nucleus governs the relative sizes of the chalazal and micropylar domains, but not their subsequent developmental trajectories. The unusual tissue layer surrounding the bilobed cotyledonary sheath in seedlings of some species of Trithuria is a belt of persistent endosperm, comparable with that of some other early-divergent angiosperms with a well-developed perisperm, such as Saururaceae and Piperaceae. The endosperm of Trithuria is limited in size and storage capacity but relatively persistent.

Reduced selenium concentrations and glutathione peroxidase activity in preeclamptic pregnancies.

Preeclampsia is pregnancy-specific, affecting 2% to 7% of women, and is a leading cause of perinatal and maternal morbidity and mortality. Preeclampsia may also predispose the fetus to increased risks of adult cardiovascular disease. Selenium, acting through the selenoprotein glutathione peroxidases, has critical roles in regulating antioxidant status. Recent reports implicate poor maternal selenium status as a nutritional factor predisposing the mother to preeclampsia but the fetus and placenta have not been studied in tandem. Measurement of selenium concentrations, expression, and activity levels of glutathione peroxidase and markers of oxidative stress were performed on maternal and umbilical venous blood samples or the placenta from 27 normal pregnant, 25 preeclamptic, and 22 healthy age-matched nonpregnant women. The results of this study revealed highly significant reductions in serum selenium concentrations and plasma glutathione peroxidase activity in pregnancy per se compared to nonpregnant controls. Moreover, these levels were further decreased in the preeclamptic mothers and babies compared to normal pregnancies. Umbilical venous selenium was particularly low (42.1+/-11.8 and 29.0+/-9.9 microg/L; mean+/-SD; P<0.05). Both mother and baby had significantly increased levels of markers for oxidative stress in the preeclamptic group. The placental glutathione peroxidase activity and immunohistochemical staining were also reduced in the preeclampsia placentae. Oxidative stress associated with preeclampsia may be a consequence of reduced antioxidant defense pathways specifically involving glutathione peroxidases, perhaps linked to reduced selenium availability. Reduced glutathione peroxidases could be associated with increased generation of toxic lipid peroxides contributing to the endothelial dysfunction and hypertension of preeclampsia.

Seedling diversity in Hydatellaceae: implications for the evolution of angiosperm cotyledons.

BACKGROUND AND AIMS: Cotyledon number has long been a primary morphological feature distinguishing monocots from other angiosperms. Recent placement of Hydatellaceae near the early-divergent angiosperm order Nymphaeales, rather than in the monocot order Poales, has prompted reassessment of seedling morphology in this poorly known family. METHODS: Seedlings of six species representing all eco-geographical groups of Hydatellaceae are described using light and scanning electron microscopy. KEY RESULTS: Two seedling types were discovered. Material examined of Trithuria submersa, T. bibracteata, T. austinensis and T. filamentosa possess a transparent bilobed sheathing structure that surrounds the main axis below the first foliage leaf. The seed coat is attached to the sheathing structure. Seedlings of Trithuria lanterna and T. konkanensis lack a sheathing structure, and the seed coat is attached to a short, narrow lateral outgrowth on the main axis of the seedling. CONCLUSIONS: The sheathing structure that is present in seedlings of some Hydatellaceae could be homologized with the two united cotyledons of water lilies. It also resembles the single cotyledon of some monocots, and hence demonstrates a possible pathway of the origin of a monocot-like embryo, though no homology is implied. The sheathing structure is reduced in Trithuria lanterna and T. konkanensis, and the short, narrow outgrowth of its seedling could represent a single cotyledon. This synapomorphy suggests that the only Indian species of Hydatellaceae, T. konkanensis, is closer to the northern Australian T. lanterna than to the south-western Australian T. bibracteata.

Abnormal arterial flows by a distributed model of the fetal circulation.

Modeling the propagation of blood pressure and flow along the fetoplacental arterial tree may improve interpretation of abnormal flow velocity waveforms in fetuses. The current models, however, either do not include a wide range of gestational ages or do not account for variation in anatomical, vascular, or rheological parameters. We developed a mathematical model of the pulsating fetoumbilical arterial circulation using Womersley's oscillatory flow theory and viscoelastic arterial wall properties. Arterial flow waves are calculated at different arterial locations from which the pulsatility index (PI) can be determined. We varied blood viscosity, placental and brain resistances, placental compliance, heart rate, stiffness of the arterial wall, and length of the umbilical arteries. The PI increases in the umbilical artery and decreases in the cerebral arteries, as a result of increasing placental resistance or decreasing brain resistance. Both changes in resistance decrease the flow through the placenta. An increased arterial stiffness increases the PIs in the entire fetoplacental circulation. Blood viscosity and peripheral bed compliance have limited influence on the flow profiles. Bradycardia and tachycardia increase and decrease the PI in all arteries, respectively. Umbilical arterial length has limited influence on the PI but affects the mean arterial pressure at the placental cord insertion. The model may improve the interpretation of arterial flow pulsations and thus may advance both the understanding of pathophysiological processes and clinical management.

Peri-implantation undernutrition programs blunted angiotensin II evoked baroreflex responses in young adult sheep.

An adverse environment around conception and implantation influences later fetal growth and development to term in humans and sheep. Indeed, preimplantation undernutrition of rats elevated the systolic blood pressure of the resultant adult offspring. In this study, adult cardiovascular function is examined in a slower growing, non-litter-bearing species after peri-implantation undernutrition. Eight ewes were fed to 50% equivalent food intake of 12 control ewes from 1 to 30 days (term approximately 147 days) only. Following consumption of an adequate diet to term, natural lambing, and then weaning, resting cardiovascular status and baroreflex function were examined in the resultant young adult offspring. Birth weight and postnatal growth to 1 year of age were unaffected by early undernutrition; however, nutrient-restricted sheep had increased pulse pressure, a reduced rate pressure product, and a leftward shift in their baroreflex function curve. Baroreflex sensitivity during angiotensin II infusion was also blunted in early nutrient-restricted sheep but the tachycardia following a reduction in central blood pressure appeared potentiated, relative to controls. The data suggest that peri-implantation undernutrition may program long-term cardiovascular dysfunction that ultimately increases the risk of hypertension later in life. An increase in regional angiotensin II activity during this critical early phase of development is a likely candidate mechanism for the effects observed. The data have broad implications for the health outcome of those offspring from mothers who were poorly nourished during early, often unknown pregnancy and for embryos artificially manipulated because of infertility treatment.

Warfarin dosage in postpartum women: a case-control study.

OBJECTIVE: To investigate the clinical suspicion that postpartum women are more difficult to anticoagulate with warfarin than non-pregnant women due to the physiological changes in coagulation proteins that persist into the postpartum period. DESIGN: A retrospective case-control study. SETTING: University Hospital, Nottingham, UK. SAMPLE: Twenty-three postpartum women discharged from the obstetric wards on warfarin and 23 age-matched control women discharged from the medical wards on warfarin were identified using hospital databases. METHODS: Warfarin doses and international normalised ratio values were recorded from day one to 35. The number of days and total warfarin dose to achieve therapeutic international normalised ratio were recorded. Doses were compared with those recommended by a dosing nomogram. RESULTS: The postpartum group took significantly longer and significantly larger doses of warfarin to reach therapeutic international normalised ratio (P < 0.05). The postpartum group required a persistently higher maintenance dose of warfarin. Comparing the warfarin dose given on day three with a standardised nomogram, 79% of women in the postpartum group compared with 57% in the control group were under-dosed. CONCLUSION: Postpartum women require larger doses of warfarin to reach therapeutic international normalised ratio than non-pregnant women. We would recommend the use of a dosing nomogram.

Fetal exposure to magnesium chloride-adenosine triphosphate (MgCl2-ATP) results in alterations in cerebral blood flow and a metabolic acidosis.

OBJECTIVE: Magnesium chloride-adenosine triphosphate (MgCl(2)-ATP), advocated as an adjunct treatment in shock resuscitation, might be useful for pregnant women who develop hypovolemia secondary to conditions such as placental abruption. The effects of this treatment on the fetus, however, have never been investigated. This study determined the direct, acute effects of MgCl(2)-ATP on fetal organ blood flow, hemodynamic measurements, and metabolic parameters before and after maternal hemorrhage. DESIGN: Experimental, randomized, nonblinded, control study. SETTING: Animal laboratory at a university research facility. SUBJECTS: This study was performed on 11 chronically instrumented, 123-day gestational age, pregnant ewes (term = 147 days) and their fetuses. INTERVENTIONS: Ewes were randomly allocated to either experimental (Expt, n = 5) or control (Cntl, n = 6) groups. After a 60-min baseline period, Expt fetuses received a 60-min iv infusion of MgCl(2)-ATP (150 &mgr;mole/hr each of MgCl(2) and ATP; at 3 mL/hr), and Cntl fetuses received an equivalent volume of 0.9% NaCl. After this infusion-only period, the infusion was continued, and ewes were intermittently bled over 1 hr for a total blood loss of 20 mL/kg (hemorrhage-plus-infusion period). After this, the infusions were continued, and ewes and fetuses were monitored for 1 additional hr (posthemorrhage period). Measurements: At the end of all periods, fetal and maternal blood pressures, blood gases, oxygen saturation, hemoglobin, serum electrolytes, and serum glucose concentrations were measured. At the end of the baseline, infusion-only, and hemorrhage-plus-infusion periods, fetal organ blood flows were determined using a fluorescent microsphere technique. Nonparametric statistics were used for comparisons (2-tailed, p