Response of Whole Blood,Erythrocyte and Plasma Vitamin E Content to Dietary Vitamin E Intake in the Chick

Whole blood, red blood cells (RBC), and plasma vitamin E (VE) levels in chicks fed dietary VE (dl-α-tocopheryl acetate, dl-αTa) supplementation in steps of 0.0, 5.0, 10.0, 15.0, 20.0 and 30.0 mg/Kg were determined to examine their usefulness as an index of VE status. The increase in VE level was significant and linear in whole blood (r = 0.90), RBC (r = 0.89) and plasma (r = 0.93) in response to dietary VE intake. There was a close correlation between VE in plasma vs whole blood (r = 0.90), plasma vs RBC (r = 0.91) and whole blood vs RBC (r = 0.95). The plasma VE content was 1.2–1.8 times greater than that of whole blood, and 6.6–12.5 times greater than that of RBC. The plasma total lipids content was not affected by the dietary VE intake, whereas the level of VE in the plasma total lipids was significantly increased with increasing supplementation. Alpha tocopherol was the major isomer (ca 92 %) of VE in whole blood, RBC and plasma at hatching. The small proportions of β-tocopherol (ca 2 %), γ-tocopherol (ca 5 %) and α-tocotrienol (ca 1 %) observed at 1 day of age had decreased or totally disappeared by 7 days of age after feeding the VE-free basal diet. The data showed that in the chick, the whole blood and RBC levels of VE were as sensitive and reliable indexes of dietary VE status as was that of the plasma.     

Vitamin A Transport and the Transmembrane Pore in the Cell-Surface Receptor for Plasma Retinol Binding Protein

Vitamin A and its derivatives (retinoids) play diverse and crucial functions from embryogenesis to adulthood and are used as therapeutic agents in human medicine for eye and skin diseases, infections and cancer. Plasma retinol binding protein (RBP) is the principal and specific vitamin A carrier in the blood and binds vitamin A at 1∶1 ratio. STRA6 is the high-affinity membrane receptor for RBP and mediates cellular vitamin A uptake. STRA6 null mice have severely depleted vitamin A reserves for vision and consequently have vision loss, even under vitamin A sufficient conditions. STRA6 null humans have a wide range of severe pathological phenotypes in many organs including the eye, brain, heart and lung. Known membrane transport mechanisms involve transmembrane pores that regulate the transport of the substrate (e.g., the gating of ion channels). STRA6 represents a new type of membrane receptor. How this receptor interacts with its transport substrate vitamin A and the functions of its nine transmembrane domains are still completely unknown. These questions are critical to understanding the molecular basis of STRA6′s activities and its regulation. We employ acute chemical modification to introduce chemical side chains to STRA6 in a site-specific manner. We found that modifications with specific chemicals at specific positions in or near the transmembrane domains of this receptor can almost completely suppress its vitamin A transport activity. These experiments provide the first evidence for the existence of a transmembrane pore, analogous to the pore of ion channels, for this new type of cell-surface receptor.     

Vitamin E and the Peroxidizability of Erythrocyte Membranes in Neonates

We showed the increased susceptibility of neonatal biomembranes to oxidation by a kinetic analysis using an azo compound as a free-radical initiator and red blood cell (RBC) ghosts as a model membrane. When the RBC ghosts were oxidized, oxygen consumption was suppressed during the induction period in which membrane tocopherol was consumed at a constant rate, while increased oxygen uptake was observed after the tocopherol was exhausted. The total tocopherol content was similar in cord, maternal, and adult RBC ghosts, and there were no differences in the induction period (t/_inh) among the three types of ghosts. While the oxygen uptake rate during the induction period (R_inh) was similar in cord and adult ghosts, the rate in the subsequent phase (R_p) was considerably faster in the cord ghosts. Fatty acid analysis in the membrane lipids showed that the active bisallylic hydrogen (active H) content was greater in cord ghosts than in adult ghosts. The active H content closely correlated with the R_p, but did not with the R_inh. The kinetic chain length (KCL), i.e., the ratio of the rate of propagation to that of initiation, was calculated from R_p and tocopherol consumption rate and KCL values were higher in cord ghosts than in adult ghosts. The faster R_p and the higher KCL of the cord ghosts were attributable to a greater active H content rather than to the tocopherol content.     

Purification of Potato Leaf Plasma Membrane Protein pp34, a Protein Phosphorylated in Response to Oligogalacturonide Signals for Defense and Development

A potato (Solanum tuberosum L.) plasma membrane protein called pp34, the only known example of a plasma membrane protein that is phosphorylated specifically in response to defined Oligogalacturonide signals in plants, has been purified to apparent homogeneity. Polyclonal antibodies raised in rabbits against the purified pp34 protein immunoprecipitated a single thiophosphorylated protein species from potato plasma membranes, as analyzed by two-dimensional denaturing electrophoresis and fluorography. The pp34 antibodies also recognized a single protein in tomato (Lycopersicon esculentum L.) membranes that is thiophosphorylated in response to Oligogalacturonide elicitors, as demonstrated by western blotting and specific immunoprecipitation. These experiments confirm the identity of the tomato membrane protein as a pp34 homolog and establish the high monospecificity of the pp34 antibodies. This will permit further investigation of the role of protein phosphorylation in oligouronide signaling for defensive genes in potato and tomato plants.     

血清视黄醇结合蛋白-4同儿童肥胖和代谢综合征组分的关系

目的:探讨儿童血清视黄醇结合蛋白-4(retinol-binding protein4,RBP-4),视黄醇,甲状腺素运载蛋白(transthyretin,TTR)等维生素A相关指标与肥胖、胰岛素抵抗以及代谢综合征组分之间的关系。方法:分别随机选取本地区13-15岁体检学生,其中正常对照组和单纯性肥胖组儿童各50例,测定其血清RBP-4、视黄醇、TTR水平;利用空腹胰岛素和定量胰岛索敏感性检测指标评价其胰岛素抵抗;同时测定代谢综合征部分组分水平和亚临床炎症指标。结果:仅5%的青少年存在维生素A营养不足状态。排除年龄、性别、感染等因素的影响后,血清RBP-4水平、视黄醇、RBP-4/TTR摩尔比值以及RBP-4/视黄醇摩尔比值与体重指数、体脂含量以及体脂的中心分布(WHR)等密切相关;RBP-4与代谢综合征组分的甘油三酯水平则存在明显的正相关,而RBP-4/视黄醇摩尔比值则与空腹胰岛素水平存在显著的正相关。结论:RBP-4可能通过视黄醇依赖和/或非视黄醇依赖的方式参与肥胖和代谢综合征的病理过程。     

Evaluation of Vitamin D Repletion Regimens to Correct Vitamin D Status in Adults

ObjectiveTo determine the efficacy and safety of commonly prescribed regimens for the treatment of vitamin D insufficiency.MethodsWe performed a retrospective analysis of 306 consecutive patients who were prescribed ergocalciferol (vitamin D₂) for correction of vitamin D insufficiency at the Atlanta Veterans Affairs Medical Center between February 2003 and May 2006. Serum levels of parathyroid hormone, 25-hydroxyvitamin D (25-OHD), and calcium were compared before and after treatment with ergocalciferol. Patients who did not have a 25-OHD determination (n = 41) were excluded from analysis. Vitamin D deficiency, insufficiency, and sufficiency were defined as a serum 25-OHD level of < 20 ng/mL, 21 to 29 ng/mL, and > 30 ng/mL, respectively.ResultsWe identified 36 discrete prescribing regimens. The 3 most common regimens were ergocalciferol 50,000 IU once weekly for 4 weeks followed by 50,000 IU once monthly for 5 months (n = 48); ergocalciferol 50,000 IU once monthly for 6 months (n = 80); and ergocalciferol 50,000 IU 3 times weekly for 6 weeks (n = 27). Each of these 3 treatments significantly increased serum 25-OHD (P < .01), but vitamin D sufficiency was achieved in only 38%, 42%, and 82% of study subjects, respectively. Regimens with > 600,000 IU of ergocalciferol given for a mean of 60 ± 40 days achieved sufficiency in 64% of cases, without vitamin D toxicity.ConclusionIn this study, regimens that contained at least 600,000 IU of ergocalciferol appeared to be the most effective in achieving vitamin D sufficiency. Guidelines for the treatment of vitamin D insufficiency in healthy adults should be developed. (Endocr Pract. 2009;15:95-103)     

Administration of Vitamin K to newborns: implications and recommendations.

The review by Drs. Brousson and Klein (see pages 307 to 315 of this issue) identifies controversies surrounding the administration of vitamin K to babies shortly after birth. Controlled studies comparing the effect of oral and intramuscular administration are unlikely to be conducted because of the large number of subjects needed. The evidence presented in the review should dispel concerns that intramuscular administration may be associated with childhood cancer. Oral administration of a single dose of vitamin K soon after is associated with significant biochemical vitamin K deficiency by 1 month of age, but the relation of biochemical abnormality to clinical manifestations of late hemorrhagic disease of the newborn is less clear. Epidemiologic studies indicate a small, but significant, increase in the incidence rate of hemorrhagic disease after oral administration of vitamin K (1.0 to 6.4 incidents per 1000 000 infants), compared with the incidence rate after intramuscular administration (0.25 incidents per 100 000 infants). Although repeated oral doses of vitamin K may be and effective alternative regimen, there is no approved oral vitamin K formulation, there are concerns about patient compliance, and there has been limited investigation of such regimen. Therefore, intramuscular administration of a single dose of 1.0 mg of vitamin K shortly after birth is recommended.     

Preeclampsia and Retinopathy of Prematurity in Very-Low-Birth-Weight Infants: A Population-Based Study

Preeclampsia and retinopathy of prematurity (ROP) are associated with impaired angiogenesis. Previous studies on the relationship between preeclampsia and ROP have produced conflicting results. The goal of this study was to evaluate the association between maternal preeclampsia and ROP using a large population-based cohort of very-low-birth-weight (VLBW) infants from 21 neonatal departments registered in the database of the Premature Baby Foundation of Taiwan. Multivariable logistic regression analysis was used to estimate the adjusted odds ratios (OR) and 95% confidence intervals (CI) for preeclampsia with reference to ROP and severe ROP. A total of 5,718 VLBW infants (844 cases with maternal preeclampsia) were included for analysis. The overall incidences of mild and severe ROP were 36.0% and 12.2%, respectively. Univariable analysis showed lower GA and lower birth weight, vaginal delivery, non-SGA, RDS, PDA, sepsis, transfusion, and absence of maternal preeclampsia to be associated with mild and severe ROP development. However, OR (95% CI) adjusted for the variables that were significant according to univariable analysis showed the risks of developing any-stage ROP and severe ROP for maternal preeclampsia to be 1.00 (0.84–1.20) and 0.89 (0.63–1.25), respectively. The results remained unchanged in stratified analyses according to SGA status. Our data showed that maternal preeclampsia was not associated with the subsequent development of any stage or severe ROP in VLBW infants.     

Chronic Ethanol Administration Decreases Phosphorylation of Cyclic AMP Response Element-Binding Protein in Granule Cells of Rat Cerebellum

Abstract: To help define the molecular basis of ethanol's actions on the nervous system, we have in previous studies demonstrated that ethanol administration triggers a robust increase in cyclic AMP-response element-binding protein (CREB) phosphorylation in the cerebellum. The purpose of the present study was to compare the effects of acute and chronic ethanol exposure on the phosphorylation of CREB in rat cerebellum and to determine which cell types in the cerebellum display this response to ethanol. An acute ethanol challenge (3.0 g/kg of body weight) induced a rapid increase in content of the phosphorylated form of CREB, peaking at 30 min and declining to basal levels within 2 h. Immunocytochemical studies revealed prominent ethanol-induced changes in phosphoCREB in the granule cell layer, with little phosphoCREB apparent in Purkinje cells. Following chronic ethanol exposure (5 weeks), induction of CREB phosphorylation by a subsequent acute ethanol challenge was markedly attenuated. The attenuation in CREB phosphorylation was associated with a significant reduction in the levels of the catalytic unit of protein kinase A and calcium/calmodulin-dependent protein kinase IV. In summary, induction of CREB phosphorylation in cerebellum is most prominent in the granule cell layer. Neuroadaptation to chronic ethanol exposure includes a reduction in nuclear protein kinase A and calcium/calmodulin-dependent protein kinase IV levels, an event associated with impaired CREB phosphorylation.     

Sequential Substrate Removal in Response to Qualitative Shock Loading of Activated Sludge Systems

Heterogeneous populations acclimated to sorbitol or mannitol were subjected to shock loading with glucose during growth on the sugar alcohol. Under these severe shock-loading conditions, glucose caused immediate cessation of sorbitol or mannitol removal. Metabolism of these compounds was renewed subsequent to glucose exhaustion. Under similar shock-loading conditions, with the use of cells operationally defined as “old,” the sugar alcohols were removed concurrently with glucose. In the absence of a nitrogen source with old cells, the added glucose was removed slowly in the presence of sorbitol and not at all in the mannitol-acclimated system. These results indicate the potential variability in purification efficiency attributable to substrate interaction.     

Antidiuretic Response of Kidneys to Different Modes of Vasopressin Administration

The effect of vasopressin given simultaneously with a water load was studied in healthy human volunteers. During maximal water diuresis induced by oral water load of 20 ml water per kilogram body weight, the excreted water fraction was 12.4%, whereas the excretion of osmotically free water was 10.0 ± 1.8 ml/min per 1.73 m² of body surface area. These data suggest that the secretion of arginine vasopressin by the neurohypophysis was almost completely blocked. A water load simultaneously with 8 g sublingual or 0.2 mg oral desmopressin caused a strong and long-lasting antidiuretic response accompanied by a drastic increase in the reabsorption of osmotically free water in the kidneys. It was shown that the magnitude and the time course of the antidiuretic response to therapeutic doses of desmopressin depended on the mode of its administration.     

A Random Sequential Mechanism of Aminoglycoside Acetylation by Mycobacterium tuberculosis Eis Protein

An important cause of bacterial resistance to aminoglycoside antibiotics is the enzymatic acetylation of their amino groups by acetyltransferases, which abolishes their binding to and inhibition of the bacterial ribosome. Enhanced intracellular survival (Eis) protein from Mycobacterium tuberculosis (Mt) is one of such acetyltransferases, whose upregulation was recently established as a cause of resistance to aminoglycosides in clinical cases of drug-resistant tuberculosis. The mechanism of aminoglycoside acetylation by MtEis is not completely understood. A systematic analysis of steady-state kinetics of acetylation of kanamycin A and neomycin B by Eis as a function of concentrations of these aminoglycosides and the acetyl donor, acetyl coenzyme A, reveals that MtEis employs a random-sequential bisubstrate mechanism of acetylation and yields the values of the kinetic parameters of this mechanism. The implications of these mechanistic properties for the design of inhibitors of Eis and other aminoglycoside acetyltransferases are discussed.     

Sexual Dimorphism in the Response of the GABAergic System to Estrogen Administration

Abstract: Administration of estradiol benzoate to gonadectomized female rats results in up-regulation of CNS γ-aminobutyric acid (GABA) receptors. The increase of [³H]muscimol binding activity is observed in six of the seven brain areas examined. The same treatment, performed in castrated male or and rogenized female rats, induced an increase of [³H]muscimol binding only in the striatum. Evidence is provided suggesting that the dimorphic sensitivity of GABA receptor is not correlated with the difference in spontaneous motor activity reported between male and female rats.