Effect of maternal nutrient restriction in early gestation on responses of the hypothalamic-pituitary-adrenal axis to acute isocapnic hypoxaemia in late gestation fetal sheep

Epidemiological and experimental evidence suggests that maternal undernutrition during pregnancy may alter development of fetal organ systems. We have demonstrated previously that fetal hypothalamic-pituitary-adrenal (HPA) axis responses to exogenous corticotropin-releasing hormone (CRH) + arginine vasopressin (AVP), or adrenocorticotrophin hormone (ACTH), are reduced in fetuses of mildly undernourished ewes. To examine these effects further we tested HPA axis responses to acute isocapnic hypoxaemia in fetal sheep at 114-129 days gestation (dGA), following 15% reduction in maternal nutritional intake between 0 and 70 dGA. Fetuses from control (C) and nutrient-restricted (R) ewes were chronically catheterised and plasma ACTH and cortisol responses were determined at 114-115, 120-123 and 126-129 dGA during hypoxaemia (1 h) induced by lowering the maternal inspired O2 fraction (FI,O2). Basal plasma cortisol concentrations and HPA axis responses at 114-115 and 120-123 dGA did not differ between C and R fetuses. At 126-129 dGA, both plasma ACTH (P < 0.01) and cortisol (P < 0.05) responses were smaller in R fetuses compared to C fetuses. Fetal blood gas status, fetal body weight, body proportions and organ weights did not differ between the groups. We conclude that mild maternal undernutrition alters development of the fetal HPA axis producing a reduction in pituitary and adrenal responsiveness to endogenous stimuli.     

Effect of feeding on the diurnal rhythm of plasma cortisol and adrenocorticotrophic hormone concentrations in the pregnant ewe and sheep fetus.

The effects of two different feeding regimes on the 24 h profiles of maternal and fetal plasma cortisol and adrenocorticotrophic hormone (ACTH) concentrations were studied in eight pregnant ewes between 123 and 144 days of gestation. Once daily-fed ewes (n = 4) received 1 kg of lucerne-chaff at 11.00 h, and multi-fed ewes (n = 4) received 100-200 g of lucerne-chaff at 09.00, 11.00 and 13.00 h and then 150 g until 09.00 h the following day. There were significant differences between the two feeding groups in the 24 h profile of maternal plasma osmolality; once daily feeding at 11.00 h was associated with a peak in maternal plasma osmolality at 15.00 h whereas maternal plasma osmolality reached plateau levels at around 17.00 h in the multi-fed group. There were also differences between the two feeding groups in the 24 h profiles of maternal and fetal plasma glucose. Maternal and fetal plasma glucose reached peak concentrations at 19.00 h in the once daily-fed ewes in contrast to the multi-fed group, where a plateau in maternal and fetal plasma glucose was reached between 19.00 h and 09.00 h the following day. A significant diurnal variation in the plasma concentrations of cortisol was present in the once daily-fed ewes from 123 days gestation and in their fetuses after, but not before, 135 days gestation. Plasma cortisol peaked at 11.00 h in the ewes and at 13.00 h in the fetuses of this group. In the once daily-fed group there was also a significant diurnal variation in maternal and fetal plasma ACTH; plasma ACTH concentrations were highest at 11.00 h in the ewes aged between 123 and 144 days and in fetuses after 135 days gestation. In the multi-fed group, whilst ACTH was highest at 09.00 h in the ewes and at 13.00 h in the fetuses, there was no significant diurnal variation in the plasma concentrations of cortisol in the ewes or fetuses of this group at any stage between 123 and 144 days gestation.     

用实时荧光定量PCR方法检测母血中的胎儿SRY基因

目的　从孕妇外周血浆中分离出胎儿DNA ,并加以鉴定 ,预防X连锁遗传病患儿的出生。方法　从孕早期、中期共 3 0 0名孕妇外周血浆中分离胎儿DNA ,用实时荧光定量聚合酶链反应 (fluorescencequantitativepolymerasechainreaction ,FQ PCR)的方法检测其中的Y性别决定区 (sex determiningregionY ,SRY)基因。结果　孕早期怀男胎的孕妇 82名 ,70名SRY基因阳性 ,其平均浓度为 ( 5 8.82± 2 0 .90 )拷贝 /ml,中位数为 5 8.5 0拷贝 /ml。孕中期怀男胎的孕妇 90名 ,SRY基因均为阳性 ,平均为 ( 15 2 .0 8± 62 61)拷贝 /ml,中位数为 14 9.3 5拷贝 /ml。怀女胎的孕妇均为阴性。结论　用实时荧光定量PCR的方法最早在孕42天的孕妇外周血浆中就可以检测到胎儿SRY基因 ,随孕周的增加 ,母血中胎儿DNA的量也在逐渐增加。实时荧光定量PCR技术在进行无创伤性产前性别诊断中有重要的价值。     

Effects of digitoxin and lithium, used as a marker of passive Na transport, on secretin-dependent bile flow in the pig

The present study was performed in anaesthetized pigs, and the first aim was to assess the role of Na,K-ATPase in secretin-dependent biliary HCO3 secretion (JbHCO3). Intra-arterial administration of the cardiac glycoside digitoxin (0.2 mg/kg-1) reduced hepatic Na K-ATPase activity, JbHCO3 and secretin-dependent bile flow by 24, 55 and 34% respectively. In the second part of this study lithium (Li) was used as a marker of passive Na transport to assess the electrochemical gradient for Na flux into bile duct lumen during secretin-stimulated bile flow and impeded biliary osmotic water flow by i.v. infusion of glucose. At plasma glucose 85 (73-96) mmol l-1, bile [Na] and [Li] exceeded their concentrations in plasma by 57 and 47% respectively. By using the Nernst equation, transepithelial potential difference (PD) during hyperglycaemia was estimated to be -6.2 (0 to -10.8) mV (ductal lumen negative), which corresponds to a [Li]bile/[Li]plasma ratio of 1.3 (1.0-1.5). The ratio was not significantly different from the observed [Li]bile/[Li]plasma ratio of 1.4 (1.3-1.5). It is concluded (1) that Na, K-ATPase is necessary for JbHCO3, probably by sustaining the cell membrane PD (cell interior negative) which is a driving force for apical electrogenic HCO3 secretion, and (2) transepithelial Li (and hence Na) flux is driven solely by the negative transcellular PD during secretin-stimulated bile flow in the pig.     

母体循环中胎儿游离DNA的定量分析

目的依据孕妇血浆中存在游离胎儿DNA的理论，从孕妇外周血浆中分离出胎儿DNA并加以鉴定，预防x连锁遗传病患儿的出生。方法从孕早期、中期共78名孕妇外周血浆中分离胎儿DNA，用实时荧光定量聚合酶链反应（fluorescence quantitative polymerase chain reaction，FQ—PCR）的方法检测其中的Y性别决定区（sex—determining region Y，SRY）基因。结果孕早期怀男胎的孕妇28名，25名SRY基因阳性，其平均浓度为（58．82±25．22）拷贝／ml；孕中期怀男胎的孕妇20名，SRY基因均为阳性，平均为（152．08±62．61）拷贝／ml；怀女胎的孕妇均为阴性。结论用实时荧光定量PCR的方法最早在孕62天的孕妇外周血浆中就可以检测到胎儿SRY基因，随孕周的增加，母血中胎儿DNA的量也在逐渐增加。实时荧光定量PCR技术在进行无创伤性产前性别诊断中有重要的价值。     

Temperature-sensitive activation of G-protein regulating the resting membrane conductance of Aplysia neurons

Raising the temperature from 22 to 32 degrees C induced a marked hyperpolarization (15-30 mV) associated with an increase in membrane conductance of Aplysia neurons, whereas lowering the temperature from 22 to 12 degrees C caused a significant depolarization (10-20 mV) with a decrease in conductance. These temperature effects were far greater than those expected from the Nernst equation. The reversal potentials of these temperature responses corresponded with the equilibrium potential of K+, suggesting these responses were produced by opening or closing of K+ channels. Ouabain (5 x 10(-4) M) did not affect these temperature responses though it depolarized all cells examined (5-25 mV). Intracellularly injected guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) selectively depressed the response to warming without affecting the response to cooling. Intracellular application of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) produced a gradual increase in K+ conductance of the resting membrane and apparently depressed the response to warming while it markedly augmented the response to cooling. These results suggest that GTP binding protein can be activated thermally to open K+ channels without receptor stimulation. It is significant that the resting membrane potential of the neuron in the central nervous system may be regulated not only by Na+ pump but also by spontaneous activation of a certain GTP-binding protein, at least in Aplysia.     

Calcium-dependent potassium conductance in rat supraoptic nucleus neurosecretory neurons

Intracellular recordings of rat supraoptic nucleus neurons were obtained from perfused hypothalamic explants. Individual action potentials were followed by hyperpolarizing afterpotentials (HAPs) having a mean amplitude of -7.4 +/- 0.8 mV (SD). The decay of the HAP was approximated by a single exponential function having a mean time constant of 17.5 +/- 6.1 ms. This considerably exceeded the cell time constant of the same neurons (9.5 +/- 0.8 ms), thus indicating that the ionic conductance underlying the HAP persisted briefly after each spike. The HAP had a reversal potential of -85 mV and was unaffected by intracellular Cl- ionophoresis of during exposure to elevated extracellular concentrations of Mg2+. In contrast, the peak amplitude of the HAP was proportional to the extracellular Ca2+ concentration and could be reversibly eliminated by replacing Ca2+ with Co2+, Mn2+, or EGTA in the perfusion fluid. During depolarizing current pulses, evoked action potential trains demonstrated a progressive increase in interspike intervals associated with a potentiation of successive HAPs. This spike frequency adaptation was reversibly abolished by replacing Ca2+ with Co2+, Mn2+, or EGTA. Bursts of action potentials were followed by a more prolonged afterhyperpolarization (AHP) whose magnitude was proportional to the number of impulses elicited (greater than 20 Hz) during a burst. Current injection revealed that the AHP was associated with a 20-60% decrease in input resistance and showed little voltage dependence in the range of -70 to -120 mV. The reversal potential of the AHP shifted with the extracellular concentration of K+ [( K+]o) with a mean slope of -50 mV/log[K+]o.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of sodium current in developing rat diencephalic neurons in serum-free culture.

1. Dissociated, synchronized (G1 phase of cell cycle), and birth-dated fetal rat diencephalic neurons were grown in a serum-free defined medium. The gigaseal whole-cell voltage-clamp technique was used to measure the inward Na+ currents (INa) from morphologically identified bipolar neurons. The earliest expressed somatic INa has been characterized and compared with that present at a later date. 2. The identity of the INa was established on the basis of its reversal potential and reversible blockade by tetrodotoxin (TTX). Close agreement between the measured reversal potentials (68.5 +/- 1.3 and 38.3 +/- 2.4 mV, mean +/- SE) and calculated Nernst equilibrium potentials (64.6 and 34.7 mV) at two different bath Na+ concentrations (120 and 35 mM, respectively) suggests that the channels are highly selective for Na+. 3. The peak INa density increased from 47.7 +/- 2.9 pA/pF in younger neurons (5-6 days in culture) to 93.9 +/- 6.4 pA/pF in older neurons (12-13 days in culture). The activation voltage and the voltage for peak current were also shifted by 10 mV in the hyperpolarizing direction, from -30 and +10 mV in younger neurons to -40 and 0 mV in older neurons, respectively. However, the reversal potential did not change (69.2 +/- 2.3 and 68.5 +/- 1.3 mV in younger and older neurons, respectively). 4. In older neurons the steady-state inactivation parameters (V1/2, the voltage at which inactivation was 50% of maximum, and kh, the voltage at which there is an e-fold change in inactivation) were significantly altered. V1/2 was shifted from -41.5 +/- 2.3 to -48.8 +/- 1.8 mV, and kh was increased from 6.2 +/- 0.5 to 8.9 +/- 0.4 mV. However, the time course of activation and the rates of inactivation and recovery from inactivation were unchanged. 5. In both groups, the INa decays were best described by a sum of two exponentials. The corresponding time constants were voltage dependent. Also, the amplitudes of the two components were differentially affected by membrane potential and niflumic acid. 6. The extrapolated amplitudes of both the fast and the slow components of INa were larger in older neurons, but the ratio of the amplitudes of the two components did not change with age. The voltage dependencies of the time constants of both components were altered. 7. We conclude that INa in fetal rat diencephalic neurons grown in a defined medium with only essential nutrients undergoes in vitro changes in current density and in some, but not all, kinetic parameters.(ABSTRACT TRUNCATED AT 250 WORDS)     

Voltage-clamp analysis of a Ca2+- and voltage-dependent chloride conductance in cultured mouse spinal neurons

Current and voltage-clamp recordings were made at room temperature from cultured mouse spinal neurons using conventional two-electrode voltage-clamp techniques and electrodes filled with either 3 M KCl, 3 M CsCl, or 3 M Cs2SO4. In the presence of tetraethylammonium and tetrodotoxin, "fast" (rapidly rising and falling) action potentials (FAP) of variable duration were recorded in most neurons. "Slow" (slowly rising and falling) depolarizing potentials (SDP) occurred in 23% of the cells, when using KCl-filled electrodes, and in 82% of the cells with CsCl-filled electrodes. The SDP was frequently preceded by an FAP, although in some cells activation of the SDP occurred before the FAP threshold was reached and in a graded fashion. Both the FAP and SDP were abolished by Cd2+ and other Ca2+ antagonists. In cells exhibiting SDPs, voltage-clamp analysis revealed a sustained (noninactivating) inward current (Isin) during depolarizing steps to potentials more positive than -45 mV. Repolarizing steps resulted in slowly decaying inward tail currents (Itail). Both Isin and Itail were abolished in solutions nominally free of Cao2+, or containing Ca2+-channel antagonists. Bao2+ did not support Isin. The data indicated a U-shaped activation curve for Isin, peaking at about -10 mV. Activation of Isin occurred exponentially with a time constant of approximately 140 ms at -23 mV, becoming faster at more depolarized potentials (ca. 50 ms at -2 mV). Deactivation was slow, giving rise to tail currents lasting seconds. In some cases deactivation could be described by a single exponential process, although frequently the kinetics were more complex. Deactivation was faster at hyperpolarized potentials and sensitive to extracellular ([Ca2+]o), duration of activating voltage steps, and the degree of activation of Isin. Using CsCl-filled electrodes, the reversal potential (Erev) for Isin was -1.7 mV (SEM 3.5 mV, n = 20). Erev always corresponded to the reversal potential for gamma-aminobutyric acid-evoked currents in the same cell. In experiments in which Cs2SO4-filled electrodes were used, Erev was estimated to be -44 mV (SEM 2.3 mV, n = 9). Neither complete substitution of Nao+ with choline ions nor elevation of [K+]o 10-fold significantly affected the estimated Erev. However, substitution of Cl0- with isethionate or methanesulphonate increased the amplitude of inward currents (recorded with CsCl-filled electrodes) and shifted Erev to more depolarized potentials. The results indicate that Cl- are the primary charge carriers for this current and that Cai2+ is required for its activation, leading us to identify it as ICl(Ca).(ABSTRACT TRUNCATED AT 400 WORDS)     

Metabolic component in the epithelial intracellular potential of rabbit cornea

Summary Effects of the change of external ionic composition and the addition of metabolic inhibitors on rabbit cornea were studied by recording the epithelial intracellular potential. High K and Li Ringer's solutions, applied to the corneal endothelial side, caused a marked depolarization of the epithelial cells, but no potential change was seen when applied to the epithelial side. Ouabain, MIAA and NaCN applied to the endothelial side reduced the epithelial potential, while those applied to the epithelial side did not change the potential. DNP and FDNB also had no effect when applied to the epithelial side only. The thermal dependence of the epithelial intracellular potentials of whole eye (0.85 mV/°C) and excised cornea (2.01 mV/°C) preparations were greater than about 0.2 mV/°C predicted by the Nernst equation. It is concluded that the epithelial cell layers of rabbit cornea act as a tight barrier against diffusion of K ion and metabolic inhibitors from the tear side to the epithelial basal cell. A high thermal dependence of the epithelial intracellular potential may depend greatly on the pump inhibition.     

Maternal corticotropin-releasing hormone and habituation in the human fetus

Elevated concentrations of maternal corticotrophin-releasing hormone (CRH) during the 2nd and early 3rd trimester of human pregnancy are associated with spontaneous preterm birth, but the effects of maternal CRH on the fetus are unknown. Maternal plasma was collected for analysis of CRH concentration, m = 156.24 +/- 130.91 pg/ml, from 33 pregnant women during Weeks 31-33 of gestation. Immediately after collection of plasma, fetal heart rate (FHR) measures were obtained in response to a challenge with a series of vibroacoustic stimuli. Fetuses of mothers with highly elevated CRH did not respond significantly to the presence of a novel stimulus in a repeated series, p = 0.016. These effects on the FHR response were not related to parity, fetal gender, medical (antepartum) risk, or eventual birth outcomes. Impaired dishabituation in these fetuses of mothers with high concentrations of CRH suggests that neurological systems rich with CRH receptors that support learning and memory, such as parahippocampal regions, may be targets for maternal/placental CRH, with implications for fetal neurological development.     

Teratogenicity of N-(4-hydroxyphenyl)-all-trans-retinamide in rats and rabbits

N-(4-hydroxyphenyl)-all-trans-retinamide (HPR) has potential efficacy in the treatment of dermatologic, arthritic, and neoplastic disorders. The teratogenicity of such a compound is of special concern in light of the known adverse effects of retinoids, in general, on the developing conceptus. In these studies, Sprague-Dawley rats and New Zealand White rabbits were treated orally from gestation days 6 to 15 and 6 to 18, respectively, with 0, 20, 125, or 800 mg/kg/day of HPR. In rat fetuses, low incidences of hydrocephaly (mid- and high-dosage groups) were observed. Fetal tissue (ng/g) and maternal plasma (ng/ml) concentrations of HPR, its major metabolite (N-[4-methoxyphenyl] retinamide [MPR]) and retinol were determined in separate groups of similarly-treated rats 3 h following the last dose on gestation day 15. Fetal tissue concentrations of HPR and MPR were approximately one-half maternal plasma concentrations. A dose related reduction in maternal plasma and fetal tissue concentrations of retinol were also observed. In mid- and high-dosage rabbit fetuses, a dose-related increase in the incidence of dome-shaped head was observed. Subsequent skeletal evaluation revealed delays in skull bone ossification and a widening of the frontal and frontoparietal sutures. Microphthalmia was also observed in two high-dosage fetuses. A dose-dependent and statistically significant reduction in maternal plasma retinol levels was observed across all dosage groups.     

Effects of acute maternal hyperglycaemia and hyperosmolality on maternofetal transfer of calcium and magnesium across the in situ perfused rat placenta.

The effects of acute maternal hyperglycaemia and hyperosmolality on maternofetal placental transfer of Ca, Mg and 51Cr-EDTA were investigated in the rat. On day 21 of gestation (term = 23 d) the fetal circulation of the in situ placenta of anaesthetised rats was perfused with a Mg-free Krebs Ringer solution and the unidirectional maternofetal fluxes of Ca (CaJmf) and Mg (MgJmf), and the unidirectional maternofetal clearance of 51Cr-EDTA ((EDTA)Kmf) were determined before and during maternal hyperglycaemia, hyperosmolality and volume expansion, attained by infusing 30% D-glucose, 25% mannitol and 0.9% saline solutions, respectively, into the maternal circulation. MgJmf was significantly reduced during glucose infusion (23.9 +/- 1.2 v 28.2 +/- 1.4 nmol min(-1) g(-1) placenta during control perfusion (mean +/- SEM); p < 0.005) and during mannitol infusion (28.2 +/- 1.0 v 33.5 +/- 1.5 nmol min(-1) g(-1) placenta; p < 0.001). CaJmf and (EDTA)Kmf were not significantly altered by maternal hyperglycaemia or hyperosmolality. There was no significant change in MgJmf during infusion of saline into the maternal circulation. Maternal plasma Na concentration was significantly reduced in both glucose and mannitol infusion experiments, whereas maternal plasma Mg concentration was significantly reduced only during glucose infusion. We postulate that the reduced maternal plasma Na concentration in the glucose and mannitol experiments might decrease MgJmf via alteration of placental Na+/Mg2+ exchange activity.     

Effect of maternal starvation on fetal tissue nucleic acid, plasma amino acid and growth hormone concentration in sheep

The measurement of nucleic acids in fetal tissues as well as plasma growth hormone and amino acids was used in conjunction with fractional protein synthetic rates to investigate the mechanism of reduced fetal protein synthesis following acute maternal starvation. The nucleic acid analysis of fetal tissues from fed and 48 h starved ewes (120-130 days gestation) demonstrated a significant reduction in kidney RNA and heart DNA concentration in the starved fetuses. The RNA synthetic capacity (RNA/protein) was also seen to decrease in the starved fetuses both for liver and kidney tissue as was the protein/DNA in the lung tissue. Most revealing, however, were the measurements of RNA and DNA activity or the extent to which the protein synthesizing capacity was realized (g protein/g RNA or DNA/day). Significant reductions were observed in liver and brain RNA activity as well as the DNA activity of liver, lung, kidney and muscle. Plasma aminograms demonstrated reductions in maternal histidine, methionine and isoleucine as well as reductions in fetal glutamate and phenylalanine following starvation. Conversely, the fetal growth hormone levels were seen to rise under the influence of maternal starvation. The impact of maternal nutrient deprivation during gestation on fetal metabolism appears to depend on the ontogenic stage of development of specific tissues at the time the deprivation occurs.     

Transplacental genotoxicity of triethylenemelamine, benzene, and vinblastine in mice.

Transplacental cytogenetic effects of triethylenemelamine (TEM), benzene, and vinblastine on maternal mice and their fetuses have been investigated using micronucleus and sister chromatid exchange (SCE) as genetic endpoints. CD-1 mice were treated on day 14 and 15 of gestation with TEM (0.125, 0.25, and 0.5 mg/kg), benzene (439,878, and 1,318 mg/kg), and vinblastine (0.5, 1, and 2 mg/kg) by intraperitoneal injection at 24 hr intervals, and sacrificed 40 hr after the first injection. Erythrocytic precursor cells in maternal bone marrow and fetal livers (2-4) from each pregnant mouse were used for the micronucleus and/or the SCE analyses. Significant dose-related increases in both micronuclei and SCE were found in maternal bone marrow and fetal liver following TEM treatment. Benzene at the highest dose (1,318 mg/kg) also caused a significant increase in micronuclei and SCE in both maternal bone marrow and fetal liver cells. The embryonic genotoxic effect of TEM was much higher than that of benzene for both genetic endpoints, and the frequency of micronuclei induced by benzene was higher in fetal liver than in maternal bone marrow cells. Vinblastine, a spindle poison, induced micronuclei but not SCE. Micronuclei induction by vinblastine was 7 fold greater in maternal bone marrow than in fetal liver cells. All three chemicals were cytotoxic in maternal bone marrow cells, but not in fetal liver cells except for TEM, which showed a weak cytotoxicity in fetal liver cells in the micronucleus assay. These results indicate that TEM, benzene, and vinblastine are transplacental genotoxicants in mice.     

Influences of pressure-injected cyclic AMP on the membrane current and characteristics of an identified neuron of Aplysia kurodai

The ionic mechanism of the effect of intracellularly injected adenosine 3',5'-cyclic monophosphate (cAMP) on the membrane of identified neuron L5 of Aplysia kurodai was investigated with conventional voltage-clamp and ion-substitution techniques. The intracellular elevation of cAMP caused an inward current (IcAMP), which was not accompanied by a significant change in membrane conductance at potentials more hyperpolarized than -60 mV. The current increased over the voltage range (-50 to -30 mV) associated with a conductance decrease and decreased at potentials more hyperpolarized than -60 mV. Elevated intracellular cAMP was found to enhance a region of negative slope resistance in steady-state I-V relations. Duration of the IcAMP was greatly prolonged by bath-applied isobutylmethylxanthine (50 microM), but imidazole (10 mM) had an opposite effect on the IcAMP. Tolbutamide (5 mM), a protein kinase inhibitor, reduced the IcAMP. The current was not affected by the presence of bath-applied TTX (50 microM), ouabain (50 microM), or triaminopyrimidine (5 mM). Reduction of [Na+]0 reversibly decreased the IcAMP. Li+ could largely substitute for Na+. Alterations of [K+]0, and bath application of 4-AP (5 mM) and TEA (30 mM) did not affect the IcAMP. In the presence of Na+, Cl-, and divalent cations such as Ca2+ and Ba2+ inhibited the IcAMP. These results suggest that fast elevation of intracellular cAMP induces a TTX-resistant slow Na+ inward current, and the current might be due to activation of cAMP-dependent protein kinase.     

Maternal serum alpha-fetoprotein and fetal trisomy-21 in women 35 years and older: implications for alpha-fetoprotein screening programs

A retrospective study of 3,411 women who underwent midtrimester amniocentesis for fetal chromosome analysis between June 1979 and August 1984 was performed to evaluate an association between low maternal serum alpha-fetoprotein (AFP) concentrations and Down syndrome (DS) pregnancies. A total of 71 pregnancies was found with abnormal fetal chromosomes; of these, 26 cases were trisomy-21 and 10 cases were trisomy-18. The maternal serum AFP in women with DS fetuses was relatively lower than levels in women with fetuses that had normal chromosomes. In addition, the AFP concentrations in amniotic fluid were decreased in cases involving DS fetuses. We have estimated the risks for DS pregnancy at all maternal ages and most serum AFP concentrations. Using these calculations, genetic counselors will be able to provide more accurate risk estimates for trisomy-21 following maternal serum AFP testing.     

Quinolinic acid promotes albumin deposition in Purkinje cell, astrocytic activation and lipid peroxidation in fetal brain

In high concentrations or after prolonged exposure, the N-methyl-D-aspartate receptor agonist quinolinic acid (QUIN) induces lipid peroxidation, oxidative stress, and cell death in the adult brain, and after i.c.v. injection induces seizures and increases blood-brain barrier permeability. As QUIN is substantially increased in plasma and brain of fetal sheep after endotoxin treatment or maternal tryptophan loading, we examined the effects of increasing plasma QUIN concentrations on the brain of late gestation fetal sheep. Continuous fetal infusion of QUIN (0.1 mmol/h i.v.; n=4) for 12 h increased plasma QUIN concentrations from 22.3+/-6.0-210.8+/-31.4 microM; the infusion of vehicle [normal saline] had no effect on QUIN concentrations (n=4). At 24 h after QUIN infusion glial fibrillary acidic protein immunoreactivity was significantly increased in cerebral gray matter and the granule cell layer of cerebellum, and the lipid peroxide product 4-hydroxynonenal-immunoreactivity and albumin-immunoreactivity were present throughout the cytoplasm of cerebellar Purkinje cells. Extravasation of albumin into the brain was not observed, indicating the cerebral microvasculature with respect to permeability to plasma proteins was normal at the time of analysis. We suggest that increased glial fibrillary acidic protein and 4-hydroxynonenal result from oxidative stress induced by QUIN, and that the increased intracellular albumin in cerebellar Purkinje cells may be an adaptive response.     

不同妊娠状态下孕妇外周血中游离胎儿DNA定量分析

目的对不同妊娠状态下孕妇外周血中游离胎儿DNA(f DNA)定量分析,确定其平均浓度及临床参考值范围,初步探讨在不同妊娠状态下母血中f DNA的浓度变化,为临床应用提供科学依据。方法从孕妇外周血浆中提取fDNA,用实时荧光定量聚合酶链反应(FQ-PCR)方法检测其中Y性别决定区的SRY基因。结果在正常早期的孕妇组38例血浆标本中有32例检测到SRY基因,其平均浓度149.25拷贝数/ml,参考值范围为33.28~265.22拷贝数/ml;在正常晚期的孕妇组32例血浆标本中全部检测到SRY基因,其平均浓度为212.14拷贝数/ml,参考值范围为142.76~281.52拷贝数/ml;在晚期患有子痫前期的孕妇30例血浆标本中全部检测到SRY基因,其平均浓度为678.70拷贝数/ml,参考值范围为595.01~726.40拷贝数/ml。实验数据用单因素方差分析,组间差异显著性检验用LSD-t检验。妊娠晚期孕妇血浆中f DNA的含量较妊娠早期升高,约为1.4倍,有统计学意义(P<0.01);晚期患子痫前期的孕妇血浆f DNA的水平是同期正常对照组的3.9倍,有统计学意义(P<0.01)。结论1.用FQ-PCR法最早在孕48天孕妇外周血中即可检测到fDNA。2.随着妊娠的进展孕妇血浆中f DNA的含量升高。3.晚期患子痫前期孕妇其血浆f DNA的水平是同期正常对照组的3.9倍,有统计学意义(P<0.01)。4.f DNA在进行无创伤性产前诊断中有重要价值。     

Distribution of ions and electrical potential differences between mother and foetus at different gestational ages in goats and sheep

1. Potential differences associated with the compartments of goat and sheep conceptuses have been measured in vivo and in vitro during the last half of gestation and the osmolarity, and the [Na(+)], [K(+)], and [Cl(-)] of maternal and foetal plasma and amniotic and allantoic fluid taken from these animals were determined.2. The potential difference (p.d.) patterns of both goats and sheep were the same.(a) The transplacental p.d. was about 71 mV (foetus negative) in the goat, and about 51 mV (foetus negative) in the sheep.(b) The amniotic fluid p.d. (i.e. the p.d. measured between the maternal extracellular fluid and the amniotic fluid) decreased as gestation advanced (from 110 to 70 mV in the goat, and 90 to 50 mV in the sheep) and was equal to the sum of the transplacental p.d. and a p.d. between the foetal blood and the amniotic fluid. The amniotic fluid was negative relative to both maternal and foetal blood.(c) An allantoic fluid p.d. (measured between the maternal extracellular fluid and the allantoic fluid) of about 107 mV in the goat, and about 96 mV in the sheep, was equal to the sum of the transplacental p.d. and a p.d. between the foetal blood and the allantoic fluid. The allantoic fluid was negative relative to both maternal and foetal blood.(d) The results suggest that p.d.s of the fluid sacs arise from activity between the foetal fluids and the blood perfusing the foetal membranes, and not from activity across the full thickness of the foetal membranes.3. The ionic concentrations were considered in relation to the electrochemical gradients found between the maternal and foetal fluid compartments to determine whether the ions were distributed according to electrochemical equilibrium.(a) It seems that ions in the amniotic fluid tend to equilibrate with foetal plasma, and not with maternal plasma or allantoic fluid, that changes in the [Na(+)] and [K(+)] of amniotic fluid can be accounted for largely in terms of passive factors, and that variations in the [Cl(-)] are associated with activity of an electrogenic Cl(-) pump directed from the foetal blood into the amniotic fluid.(b) It appears that ions in the allantoic fluid can exchange with those of both maternal and foetal plasma, that an electrogenic pump effects absorption of Na(+) from the allantoic fluid into the foetal blood, and that the [K(+)] and [Cl(-)] of allantoic fluid are maintained largely by passive exchange under the action of electrochemical gradients between maternal plasma and allantoic fluid, and between foetal plasma and allantoic fluid.4. The results considered in the context of Na(+) passage between mother and foetus call in question the general assumption that all Na(+) reaches the foetus by passing across the placenta.