The form of vitamin C released by the rat adrenal

Effects of injectable vitamin C at weaning and prior to transit on growth performance of early-weaned beef steers

This study investigated the effects of injectable vitamin C (VC) at weaning and prior to transit on growth performance and immune function in early-weaned beef steers. On day 0, 91 Angus × Simmental steers (92 ± 4 kg) were weaned (65 ± 11 d of age), given vaccination boosters, blocked by age, and randomly assigned to weaning (WEAN) treatments: intramuscular injections (20 mL per steer) of VC (250-mg sodium ascorbate per mL; 5 g per steer) or saline (SAL). From days 0 to 48, steers were housed at the Dixon Springs Agricultural Center (Simpson, IL) in pens (six pens; N = 14 to 16 steers per pen) equipped with two to three Vytelle bunks to measure individual daily feed disappearance. On day 49, half of the steers in each WEAN treatment were randomly assigned to an additional injection treatment (20 mL per steer) of VC or SAL prior to transport (TRANS). After administering pretransit injections, all steers were loaded onto a commercial livestock trailer with equal representation of treatments across compartments. Steers were transported for 6 h (approximately 480 km) to the Illinois Beef and Sheep Field Laboratory (Urbana, IL). Upon arrival, steers were sorted into pens (six pens; N = 13 to 17 steers per pen) with 2 Vytelle bunks per pen. Steers were weighed on days 0, 1, 14, 48, 49, 64, 78, 106, and 107. Blood was collected (WEAN = 24 steers per treatment; TRANS = 12 steers per treatment) on days 0, 1, 2, 14, 49 (pre- and posttransit), 50, and 51. Data were analyzed using the MIXED procedure of SAS 9.4 with fixed effects of age block, WEAN, TRANS, and WEAN × TRANS. Plasma ascorbate concentrations were greater (WEAN × time P < 0.01) on days 1 and 2 for steers that received VC at weaning. Similarly, for steers that received VC on day 49 pretransit, ascorbate concentrations were greater (TRANS × time P = 0.04) on days 49 posttransit, 50, and 51. Treatments did not affect (P ≥ 0.13) body weight, average daily gain, or gain to feed throughout the trial. Serum Bovine Viral Diarrhea Virus type 1 and 2 antibody titers on days 14 and 51 were not affected (P ≥ 0.32) by treatment. Injectable VC administered to early-weaned beef steers at the time of weaning or pretransit increased plasma ascorbate concentrations but did not improve growth performance or antibody response to vaccination booster.

The Effect of Alkaline Water and Sodium Ascorbate on Glucose and Cortisol Levels During Acute Hyperthermic Stress in White Laboratory Rats

Stress can be a reason for some physiological and biological disorders in the body. The antioxidative defense system is necessary for the maintenance of redox homeostasis in the organisms. Alkaline water (AW) is in the focus of the scientific interest due to its antioxidative effect. The treatment with AW and sodium ascorbate (SA) is expected to have potential preventive effect on the organism to hyperthermic stress. The aim of this study was to investigate the effect of AW and SA on glucose and cortisol levels during acute hyperthermic stress, in white female Wistar laboratory rats. The rats were divided into three groups, each having 10 subjects. They were exposed in hyperthermic conditions (41˚C) for 80 min, in 21 consecutive days in order to induce oxidative stress. The first group received drinkable water (control group), the second AW, and the third, AW and SA. Plasma glucose levels were determined by colorimetric method. Cortisol level was measured by the enzyme-linked immunosorbent assay method (ELISA). The means were compared using the Tukey test. Differences were considered significant at a level of p<0.05. Our results showed that levels of glucose and cortisol were significantly higher in the group treated with AW on the 21st day after treatment (p<0.0001), but not on the 7th and 14th day as compared to the control group. Also, co-treatment of animals with AW and SA had significantly increased the levels of glucose and cortisol on the 21st day after treatment, indicating a synergistic effect. In conclusion, the individual action of AW or in synergism with SA caused a high protective effect on oxidative damage in white Wistar laboratory rats.

Vitamin C: an essential "stress hormone" during sepsis

The stress response is a preserved evolutionary response that functions to enhance the survival of the species. In mammals, the stress response is characterized by activation of the HPA axis and sympathoadrenal system (SAS) as well as the increased synthesis and secretion of vitamin C. Cortisol, catecholamines, and vitamin C act synergistically to increase hemodynamic reserve, maintain immune function and protect the host against excessive oxidant injury. Humans (and anthropoid apes) have lost the ability to synthesize vitamin C and therefore have an impaired stress response. The inability to produce vitamin C has serious implications in septic humans. Treatment with vitamin C appears to restore the stress response and improve the survival of stressed humans.

Hypoxia depletes ascorbate in the cat carotid body

Vitamin C or L-ascorbate is an effective endogenous reducing agent influencing the functions that are involved with the redox mechanism. Detection of oxygen tension changes by the carotid body chemoreceptors is one such function. In this study we investigated the hypothesis that the level of ascorbate, if present, could change in the carotid body as a result of ascorbate's interaction in the chemosensing process, which would be reflected in the production of the ascorbyl radical. We addressed this issue by examining changes of the ascorbyl radical, using the in vitro electron spin resonance spectroscopy (ESR), in the carotid bodies dissected from pentobarbitone anesthetized cats exposed in vivo to three eucapnic, breathing gas mixtures of different O2 concentration: normoxic, 21% O2; hypoxic, 7% O2; and hypoxic-reoxygenated, 7% O2 followed by 100% O2. Each group consisted of five cats, yielding five pairs of carotid bodies for the ESR signal recording. We found that the intensity of ESR signals, measured as peak-to-peak amplitude, was diminished by 39 and 43% in the hypoxic and hypoxic-reoxygenated groups, respectively, compared with that in normoxia. The study shows that ascorbate was present in the normoxic carotid body and was depleted by hypoxia. We conclude that ascorbate is part of free radical mechanisms operative in the carotid body in hypoxia.

Uptake and release of ascorbic acid by rat Leydig cells in vitro

The mechanism by which ascorbic acid is transported into rat Leydig cells in vitro was investigated. Transport of [14C]ascorbic acid was temperature-dependent and inhibited in the absence of sodium in the incubation medium. The uptake of [14C]ascorbic acid was saturable (apparent Km approximately equal to 33 microM, Vmax approximately equal to 20 pmol/10(6) cells/min) and stereospecific. Uptake was not affected by removing glucose from the incubation medium, indicating that no significant uptake was occurring via the glucose transport system. Transport of [14C]ascorbic acid into Leydig cells was not affected by testosterone concentrations up to 7 microM or by LH at a concentration that causes maximum androgen secretion. Leydig cells preloaded with [14C]ascorbic acid rapidly released radioactivity into the incubation medium, a process that was unaffected by the presence of LH. The results suggest that ascorbic acid uptake by Leydig cells is by an electroneutral, sodium-dependent co-transport mechanism as in some, but not all, other types of cells.

A new orthodontic force system of magnetic brackets

Tooth movement in orthodontic treatment is achieved by a combination of mechanical and physiologic forces acting on the teeth and their supporting structures to effect the biologic changes that cause teeth to move through bone. Traditional orthodontic appliances using wires, springs, and elastic forces inevitably cause some degree of discomfort and pain. In the present study, a new magnetized edgewise bracket was designed. The magnet works to move teeth mesiodistally and is not merely a mechanical force. It is well adapted to the biophysical system of tooth and bone interrelationships. Therefore, it works effectively, gives less discomfort, and produces less stress for the patient. The new magnetic appliance provides a force system that approaches the ideal orthodontic requirements.

Purification and characterization of avian dopamine beta-hydroxylase

Dopamine beta-hydroxylase (EC 1.14.17.1) has been purified from the chromaffin granules of avian adrenals. The enzyme has a molecular mass of approximately 320K daltons and consists of four apparently identical subunits joined in pairs by disulfide bonds. Analysis of the products formed from dopamine tritiated in the beta position indicated that 1.72 times as much tritium was retained in norepinephrine as was released as water. Ferrocyanide could serve as a reductant, but ascorbate at equal concentrations afforded higher rates. The enzyme had a pH optimum of 5-6 and was activated by either fumarate or acetate, with fumarate being far more effective. Kinetic experiments varying the concentrations of the substrates ascorbate and dopamine and those of the products dehydroascorbate and norepinephrine suggested that the mechanism was un-uni bi-uni ping pong. By this mechanism, the enzyme released dehydroascorbate after being irreversibly reduced by ascorbate and then sequentially bound oxygen and dopamine and released the product norepinephrine. The enzyme was inhibited by high but probably physiological concentrations of the substrate ascorbate and was activated by low concentrations of the product dehydroascorbate. Ascorbate inhibition was noncompetitive with dopamine, and dehydroascorbate activation was due to an increase in the enzyme's affinity for ascorbate with little or no change in its Vmax. Substrate inhibition by ascorbate and product activation by dehydroascorbate might together ensure that the rate of norepinephrine synthesis in vivo remains relatively unaffected by changes in the ratio of ascorbate to dehydroascorbate within chromaffin granules.

Inhibitory effect of ascorbic acid (vitamin C) on cortisol secretion following adrenal stimulation in children

Measurements of plasma cortisol values before and at 4 and 6 hours after intramuscular administration of a depot preparation of synthetic b1-24 corticotrophin were carried out in 12 healthy children (group B) before, as well as on the 5th day of continuous ascorbic acid (AA) administration (1 g t.i.d. orally). Comparison of the results in group B with those of 8 healthy children similarly treated with corticotrophin but not given AA (group A) showed that, on the 5th day of AA administration the mean cortisol values after ACTH were significantly lower than the corresponding values in group A (p less than 0.02), or the post-ACTH values in group B observed on the 1st experimental day, i.e., before AA administration (p less than 0.001). On the other hand, AA administration had no significant effect on the fasting plasma cortisol values. These data suggest that AA excess following adrenal stimulation with ACTH exerts an inhibitory effect on cortisol secretion and consequently it may be of no benefit in conditions of stress.