Vanadium transport across placenta and milk of rats to the fetus and newborn

The transport of vanadium across placenta and milk rats was studied by iv injection of low doses of 48V-labeled pentavanadate (0.1 micrograms V/rat) to pregnant and nursing rats. Significant concentrations of vanadium were found in the liver, intestine, and kidneys of the fetuses, showing that vanadium is capable to pass the placental barrier and, thus, being metabolized in the fetuses. Two days after injection of 0.1 micrograms V/rat as 48V-labeled vanadate to nursing rats, 34 ng V/g milk were found, decreasing to 4 ng V/g at the d 12 after dosing. The corresponding suckling rats showed a significant absorption of vanadium taken up by the milk, as suggested by the presence in their intestine, where 48V is easily absorbed in form of low molecular weight components. Vanadium in milk may be transported in the form of a biocomplex with lactoferrin, since at 12 d after injection, the 48V in the rat milk was mainly found in fractions corresponding to proteins. In weanling rats, 7 d postlactation and 18 d after administration of vanadium to the mother, only very small amounts of 48V were still present in the organs. Excretion studies on weanling rats for 7 d showed that vanadium is rapidly released mainly via feces when earlier taken up by the milk of iv injected mothers and having the same elimination pattern as the milk, which lost about 80% of its vanadium concentration after 12 d.     

Glucose transfer across the intact guinea-pig placenta

Experiments were carried out in anaesthetized pregnant guinea-pigs. Following the maternal injection of a bolus containing 14C-hexose and 3H2O, blood was sampled from the fetal umbilical vein during a single circulatory transit. A placental transfer index was calculated from the ratio of the tracers in the fetal whole blood divided by that in maternal plasma. The transfer index for D-glucose, 0.66 +/- 0.03 (SEM), greatly exceeded that for L-glucose, 0.013 +/- 0.004. Elevation of the maternal plasma D-glucose concentration, with unlabelled D-glucose, resulted in saturation of D-glucose transfer with an apparent Km of 1.2 x 10(-2) mol/l mean maternal plasma D-glucose. Phlorizin at maternal plasma concentrations of approximately 10(-3) mol/l inhibited D-glucose transfer by 40%. Phloretin did not affect D-glucose transfer at levels estimated to be 10(-4) mol/l. Specificity studies with substituted D-glucose analogues showed that alpha-methyl-D-glucoside is not transported by a facilitated pathway; 2-deoxy-D-glucose and 3-O-methyl-D-glucose share the D-glucose carrier and D-galactose has a partial affinity for the D-glucose carrier.     

The transfer of fatty acids across the sheep placenta

Maternal and fetal plasma concentrations of free fatty acids, triacylglycerols and phospholipids and the profile of their fatty acids were measured in three catheterized and unanaesthetized sheep. Fetal concentrations of all three lipid fractions were low and did not correlate with maternal concentrations. There were no measurable umbilical venous-arterial differences. Linoleic acid concentrations were low in both mother and fetus. The fatty acid composition of fetal adipose tissue, liver, lung and cerebellum of five animals was analysed. Again linoleic acid levels were very low, but phospholipids contained 2-8% arachidonic acid. [14C] linoleic acid and [3H] palmitic acid were infused intravenously into three ewes. Only trace amounts of labelled fatty acids were found in fetal plasma and these were confined to the free fatty acids. 14C-label was incorporated into fetal tissue lipids, but most of this probably was due to fetal lipid synthesis from [14C] acetate or other water-soluble products of maternal [14C] linoleic acid catabolism. It is concluded that only trace amounts of fatty acids cross the sheep placenta. They are derived mainly from the maternal plasma free fatty acids and might just be sufficient to be the source of the small amounts of essential fatty acids found in the lamb fetus, but are insignificant in terms of energy supply or lipid storage.     

Factors affecting the resistance to heat transfer provided by clothing

1. 1. This paper discusses the factors that affect the insulation and evaporative resistance provided by clothing.

2. 2. These include: fabric thickness and density, the amount of body surface area covered by garments, the evenness of the distribution of fabrics over the body surface, the increase in surface area for heat loss due to clothing, the looseness or tightness of fit, a person's body position (seated vs standing), body motion and wind.

Counter-directed leucine gradient promotes amino acid transfer across the human placenta

The developing fetus is highly vulnerable to imbalances in the supply of essential amino acids (AA). Transplacental AA transfer depends on complex interactions between accumulative transporters, exchangers and facilitators, which maintain both intra-extracellular and materno-fetal substrate gradients. We determined physiological AA gradients between maternal and fetal blood and assessed their importance by studying maternal-fetal leucine transfer in human trophoblasts. Maternal-venous and corresponding fetal-arterial/fetal-venous sera were collected from 22 healthy patients at partum. The acquisition of the full AA spectra in serum was performed by ion exchange chromatography. Physiological materno-fetal AA levels were evaluated using paired two-way ANOVA with Tukey's correction. AA concentrations and gradients were tested for associations with anthropometric data by Spearman correlation analysis. Functional effects of a physiological leucine gradient versus equimolar concentrations were tested in BeWo cells using L-[³H]-leucine in conventional and Transwell-based uptake and transfer experiments. The LAT1/SLC7A5-specific inhibitor JPH203 was used to evaluate LAT1-transporter-mediated leucine transport. Maternal AA concentrations correlated with preconceptional and maternal weights at partum. Interestingly, low materno-fetal AA gradients were associated with maternal weight, BMI and gestational weight gain. Leucine uptake was promoted by increased extracellular substrate concentrations. Materno-fetal leucine transfer was significantly increased against a 137µM leucine gradient demonstrating that transplacental leucine transport is stimulated by a counter-directed gradient. Moreover, leucine transfer was inhibited by 10µM JPH203 confirming that Leu transport across the trophoblast monolayer is LAT1-dependent. This study demonstrates a currently underestimated effect of transplacental AA gradients on efficient leucine transfer which could severely affect fetal development.     

Factors affecting outcome in free-tissue transfer in the elderly

Free-tissue transfers have become the preferred surgical technique to treat complex reconstructive defects. Because these procedures typically require longer operative times and recovery periods, the applicability of free-flap reconstruction in the elderly continues to require ongoing review. The authors performed a retrospective analysis of 100 patients aged 65 years and older who underwent free-tissue transfers to determine preoperative and intraoperative predictors of surgical complications, medical complications, and reconstructive failures. The parameters studied included patient demographics, past medical history, American Society of Anesthesiology (ASA) status, site and cause of the defect, the free tissue transferred, operative time, and postoperative complications, including free-flap success or failure. The mean age of the patients was 72 years. A total of 46 patients underwent free-tissue transfer after head and neck ablation, 27 underwent lower extremity reconstruction in the setting of peripheral vascular disease, 10 had lower extremity traumatic wounds, nine had breast reconstructions, four had infected wounds, two had chronic wounds, and two underwent transfer for lower extremity tumor ablation. Two patients had an ASA status of 1, 49 patients had a status of 2, 45 patients had a status of 3, and four had a status of 4. A total of 104 flaps were transferred in these 100 patients. There were 49 radial forearm flaps, 34 rectus abdominis flaps, seven latissimus dorsi flaps, seven fibular osteocutaneous flaps, three omental flaps, three jejunal flaps, and one lateral arm flap. Four patients had planned double free flaps for their reconstruction. Mean operative time was 7.8 hours (range, 3.5 to 16.5 hours). The overall flap success rate was 97 percent, and the overall reconstructive success rate was 92 percent. There were six additional reconstructive failures related to flap loss, all of which occurred more than 1 month after surgery. Patients with a higher ASA designation experienced more medical complications (p = 0.03) but not surgical complications. Increased operative time resulted in more surgical complications (p = 0.019). All eight cases of reconstructive failure occurred in patients undergoing limb salvage surgery in the setting of peripheral vascular disease. Free-tissue transfer in the elderly population demonstrates similar success rates to those of the general population. Age alone should not be considered a contraindication or an independent risk factor for free-tissue transfer. ASA status and length of operative time are significant predictors of postoperative medical and surgical morbidity. The higher rate of reconstructive failure in the elderly peripheral vascular disease population compares favorably with other treatment modalities for this disease process.     

The role of the placenta in iron transfer from mother to fetus and the relationship between iron status and fetal outcome

During pregnancy, iron is transferred from the mother to the fetus across the placenta. The mechanism has been extensively studied. Altered iron metabolism changes transfer, but also has other consequences. In this review, we examine how the placenta adapts to altered iron supply, both in terms of changing cytokine expression and in relation to the proteins of iron transfer. Changing iron levels alters the levels of other metals, especially copper, and we review how this is related to changing function. There are also consequences to the placenta itself, to vascularisation and other aspects of the physiology. In turn, this has effects on the fetus and we review how growth and development are modified. Finally, we examine in more detail the efflux process, how it is regulated and, especially, the putative role of the placental Cu oxidase in the efflux process. As appropriate, we draw on data from humans, from animal models and from cell culture systems to illustrate the information.     

Factors affecting retrovirus-mediated gene transfer to human CD34+ cells

BACKGROUND: Retrovirus-mediated gene transfer is a useful technology in studying the biology of hematopoietic stem cells (HSCs) as well as in developing gene therapy products for a variety of human diseases. One of the most important factors determining the success of these studies is the number of HSCs receiving the gene of interest. METHODS: We tested various parameters for their influences on gene transfer efficiency to CD34+ cells derived from bone marrow. Based on a literature survey, three medium formulations of CD34+ cells have been compared for their effects on gene delivery efficiency and differentiation of them. We also tested whether FBS, used in the medium formulation, could be replaced with human serum or synthetic material. RESULTS: Formulation A, consisting of stem cell factor, Flt-3 ligand, thrombopoietin, and IL-3, provided optimum results in that it maintained the highest percentage of CD34+ cells during the culture as well as produced the highest gene delivery efficiency. It was found that the synthetic serum substitute containing bovine serum albumin, insulin and human transferrin could replace the fetal bovine serum present in the original formulation A without compromising gene transfer efficiency. When the transduction procedure was repeated three times, the gene could be delivered in up to 60% of the cell population. Gene delivery efficiency was comparable between CD34+ cells derived from bone marrow and mobilized peripheral blood. CONCLUSIONS: Our data could be useful in designing a procedure for stem cell gene therapy and providing a basis for further improving the conditions for gene transfer to various HSCs.     

Factors affecting the success of surgical and nonsurgical equine embryo transfer

Nonsurgical embryo recovery was attempted from light-horse and draft mares. Embryo recovery rates were not affected (P>.05) by technician or stallion but were lower (P<.05) from draft mares (44%) than light-horse mares (67%). Sham transfer of embryos on day 8 post-ovulation did not (P>.05) increase the number of mares returning to estrus by 22 days post-ovulation. Method of embryo transfer greatly affected pregnancy rates. Embryos transferred surgically during March–June resulted in 0 of 12 pregnancies versus 13 of 25 pregnancies obtained during July–September, This strongly suggests a seasonal influence on pregnancy rates. Technician influenced (P<.05) the success of nonsurgical transfer (46.2% vs. 7.7%). In addition, protection of the insemination rod with a sheath (guarded method) appeared to provide some advantage over an unguarded method of nonsurgical transfer (54% vs. 23%). Lastly, a preliminary experiment was conducted to evaluate transfer of embryos via flank incision. Four of 5 embryos transferred by this method resulted in a pregnancy at 50 days post estrus.     

Factors affecting chloride conductance in apical membrane vesicles from human placenta

Summary Apical membrane vesicles from human term placenta were isolated using a magnesium precipitation technique, and the purity of the vesicles was assessed morphologically using scanning and transmission electron microscopy, and biochemically, using marker enzymes. The vesicles were found to be morphologically intact and significantly enriched in enzymes associated with apical membranes. ³⁶Cl^– uptake into these vesicles was studied in the presence of an outwardly directed Cl^– gradient. This uptake was found to be time dependent, with an initial rapid uptake tending to peak between 10 and 20 min and thereafter decline. Uptake was found to be voltage dependent since 5 m valinomycin caused a decrease in uptake. The effects of N-phenylanthranilic acid (NPA) and 4,4-diisothiocyanostilbene-2,2-disulphonic acid (DIDS) and bumetanide on the initial rate of Cl^– were examined in the presence and absence of 5 m valinomycin. NPA and DIDS inhibited isotope uptake strongly with IC₅₀ values of 0.83±0.35 m and 3.43±0.37 m, respectively, in the absence of valinomycin. Although valinomycin reduced ³⁶Cl^– uptake by about 80% when added before the isotope, DIDS reduced the uptake which remained in a concentration-dependent fashion with an IC₅₀ of 5.6±2.1 m. Under these conditions, NPA was without effect at concentrations below 100 m. Bumetanide was without effect at the concentrations used in the absence of valinomycin. However, following valinomycin pretreatment, bumetanide reduced ³⁶Cl^– uptake significantly at 100 m concentration. Vesicle diameter, as assessed by flow cytometry, did not change under the conditions employed.The effects of some fatty acids were also investigated. Arachidonic acid and linoleic acid inhibited Cl^– uptake with IC₅₀ values of 37.6±14.9 m and 4.59±0.51 m, respectively. Arachidonyl alcohol and elaidic acid were found to be without effect. These studies show that human placental brush border membrane vesicles possess a chloride conductance channel, the activity of which can be measured in the presence of an outwardly directed Cl^– gradient and this channel is sensitive to Cl^– channel inhibitors, especially N-phenylanthranilic acid, and can be inhibited by unsaturated fatty acids such as arachidonic acid and linoleic acid.This work was supported in part by the Cystic Fibrosis Association of Ireland and Eolas, The Irish Science and Technology Agency. The technical assistance of Mr. Cormac O' Connell in the preparation of the electron micrographs and of Mr. Roddy Monks in the flow cytometric analysis is gratefully acknowledged.     

Factors affecting glucosyl and mannosyl transfer to dolichyl monophosphate by liver cell-free preparations

GDP-mannose and UDP-mannose (each at less than 1 micrometer) markedly inhibit glucosyl transfer from UDP-glucose (1.6 micrometer( to dolichyl phosphate in liver microsomal preparations. The biphasic response suggests the presence of two glucosyl transferases only one of which is inhibited. The inhibition appears to be a property of the intact nucleotide phosphate sugars and not due to competition for a limited pool of dolichyl phosphate. UDP-galactose and UDP-xylose cause a less marked inhibition of the same enzyme. The failure of UDP-glucose to inhibit mannosyl transfer suggests that the pool of dolichol monophosphate used by mannosyl transferase is not available to the glucosyl transferase. The relationship between the degree to which an exogenous prenol phosphate acts as an acceptor of mannose and the degree to which it inhibits mannosylation of endogenous dolichyl monophosphate varies among different prenyl phosphates. Mannosyl transferase exhibits two pH optima.