Studies on ascorbic acid related to the genetic basis of scurvy

Cancer Therapy Challenge: It Is Time to Look in the "St. Patrick's Well" of the Nature

Cancer still remains a leading cause of death despite improvements in diagnosis, drug discovery and therapy approach. Therefore, there is a strong need to improve methodologies as well as to increase the number of approaches available. Natural compounds of different origins (i.e., from fungi, plants, microbes, etc.) represent an interesting approach for fighting cancer. In particular, synergistic strategies may represent an intriguing approach, combining natural compounds with classic chemotherapeutic drugs to increase therapeutic efficacy and lower the required drug concentrations. In this review, we focus primarily on those natural compounds utilized in synergistic approached to treating cancer, with particular attention to those compounds that have gained the most research interest.

What Does the Taste System Tell Us About the Nutritional Composition and Toxicity of Foods?

One of the distinctive features of the human taste system is that it categorizes food into a few taste qualities - e.g., sweet, salty, sour, bitter, and umami. Here, I examined the functional significance of these taste qualities by asking what they tell us about the nutritional composition and toxicity of foods. I collected published data on the composition of raw and unprocessed foods - i.e., fruits, endosperm tissues, starchy foods, mushrooms, and meats. Sweet taste is thought to help identify foods with a high caloric or micronutrient density. However, the sweetest foods (fruits) had a relatively modest caloric density and low micronutrient density, whereas the blandest foods (endosperm tissues and meats) had a relatively high caloric and high micronutrient density. Salty taste is thought to be a proxy for foods high in sodium. Sodium levels were higher in meats than in most plant materials, but raw meats lack a salient salty taste. Sour taste (a measure of acidity) is thought to signify dangerous or spoiled foods. While this may be the case, it is notable that most ripe fruits are acidic. Umami taste is thought to reflect the protein content of food. I found that free L-glutamate (the prototypical umami tastant) concentration varies independently of protein content in foods. Bitter taste is thought to help identify poisonous foods, but many nutritious plant materials taste bitter. Fat taste is thought to help identify triglyceride-rich foods, but the role of taste versus mouthfeel in the attraction to fatty foods is unresolved. These findings indicate that the taste system provides incomplete or, in some cases, misleading information about the nutritional content and toxicity of foods. This may explain why inputs from the taste system are merged with inputs from the other cephalic senses and intestinal nutrient-sensing systems. By doing so, we create a more complete sensory representation and nutritional evaluation of foods.

Tirilazad mesylate protects vitamins C and E in brain ischemia-reperfusion injury

Brain concentrations of the antioxidant vitamins C and E decreased following unilateral carotid occlusion and reperfusion for 2 or 24 h in gerbils. Administration of the 21-aminosteroid inhibitor of lipid peroxidation, tirilazad mesylate (U74006F), prevented the decrease in level of both of these vitamins following 2 h of reperfusion. After 24 h of reperfusion, however, alpha-tocopherol (vitamin E) continued to be protected, but ascorbic acid (vitamin C) showed a pronounced decrease in content. The changes in concentrations of these vitamins are consistent with U74006F acting to inhibit peroxidation in the CNS by scavenging of lipid peroxyl radicals and suggest that, in the presence of this agent, injury-induced depletion of ascorbic acid may occur without irreversible tissue damage.

Ascorbic acid supplements in patients receiving chronic peritoneal dialysis

Ascorbic acid supplements are commonly prescribed to patients with end-stage renal disease receiving peritoneal dialysis. To establish the need for ascorbic acid supplements, we evaluated seven chronic peritoneal dialysis patients during a supplement-free (phase I) period, and while receiving oral ascorbic acid (0.57 mmol/d [100 mg/d]) (phase II). Because of a proposed interaction with vitamin B6, patients were additionally supplemented with pyridoxine HCl (59.6 mumol/d [10 mg/d]) (phase III). Plasma levels and dialysate removal rates of total ascorbic acid and plasma pyridoxal-5-phosphate (PLP) were measured at the end of each phase. During phase I, plasma ascorbic acid levels (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]) declined slightly from 74 +/- 11 mumol/L (1.3 +/- 0.2 mg/dL) to 62 +/- 11 mumol/L (1.1 +/- 0.2 mg/dL) (P less than 0.02) at the end of the third week, and then remained stable to the end of the fourth week. Plasma ascorbic acid levels were no different in patients with or without residual renal function. With the addition of vitamin C supplements, plasma ascorbic acid levels increased by 45% of the baseline value at the end of phases II (P less than 0.001). The dialysate removal rate of ascorbic acid was 0.28 +/- 0.03 mmol/d (50 +/- 6 mg/d) at the end of phase I, and increased by 57% of the baseline value at the end of phases II (P less than 0.001). However, the peritoneal clearance of ascorbic acid remained unchanged during all phases the study. Pyridoxine depletion or repletion had no effect on plasma ascorbic acid levels (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro estimation of non-specific and specific amino acid decarboxylase activities in guinea-pigs treated with chlorpromazine

1. In vitro studies of non-specific histidine decarboxylase activity was low or absent in control guinea-pigs and unchanged 9 or 27 hr after chlorpromazine (CPZ) injection intraperitoneally. 2. However, specific histidine decarboxylase activity was found in the control tissues and was increased 9 hr but not 27 hr after CPZ injection.

Radioactive uptake of [14C]histamine by certain tissues in guinea-pigs treated and untreated with chlorpromazine

1. Oral administration of [14C]histamine induced the presence of small amounts of [14C]histamine in stomach and ileal tissues of control guinea-pigs. In contrast, much larger amounts were found after 8 h infusion. 2. Similar amounts of [14C]histamine were found in the tissues when [14C]histamine was given by intravenous infusion from 24-30 h after chlorpromazine injection.

The depletion effects of chlorpromazine, reserpine and ascorbic acid on tissue histamine of guinea-pigs

1. 30 mg kg-1 chlorpromazine (CPZ) depleted more than half of the tissue histamine from lungs, stomach, ileum and skin of the normal guinea-pigs. However, the drug increased the tissue histamine content in scorbutic animals. 2. In contrast, reserpine depleted histamine from the four tested tissues in both normal and scorbutic animals, except those in the lungs of the control animals. 3. Ascorbic acid only depleted histamine from the stomach and ileum. 4. A 24 hr period was the time limit for CPZ to deplete the histamine in all the four tested tissues. 5. Histamine partially or completely recovered in the tissues after the next 24 hr.

Ascorbic acid content of neotropical plant parts available to wild monkeys and bats

The ascorbic acid content of foliage available to wild primates and bats in Panama (in transition between wet and dry seasons) was lower than that of temperate zone foliage but higher than that of most fruits and vegetables. Intakes of ascorbic acid (mg/kg b.wt/day) by wild primates and frugivorous bats in Panama are much greater than that of most human populations.

Urate and ascorbate: their possible roles as antioxidants in determining longevity of mammalian species

Urate has been shown to be a major antioxidant in human serum and was postulated to have a biological role in protecting tissues against the toxic effects of oxygen radicals and in determining the longevity of primates. This possibility has been tested by determining if the maximum lifespan potentials of 22 primate and 17 non-primate mammalian species are positively correlated with the concentration of urate in serum and brain per specific metabolic rate. This analysis is based on the concept that the degree of protection a tissue has against oxygen radicals is proportional to antioxidant concentration per rate of oxygen metabolism of that tissue. Ascorbate, another potentially important antioxidant in determining longevity of mammalian species, was also investigated using this method. The results show a highly significant positive correlation of maximum lifespan potential with the concentration of urate in serum and brain per specific metabolic rate. No significant correlation was found for ascorbate. These results support the hypothesis that urate is biologically active as an antioxidant and is involved in determining the longevity of primate species, particularly for humans and the great apes. Ascorbate appears to have played little or no role as a longevity determinant in mammalian species.

Specifically decreased collagen biosynthesis in scurvy dissociated from an effect on proline hydroxylation and correlated with body weight loss. In vitro studies in guinea pig calvarial bones

The question whether ascorbate regulates collagen production solely through its direct role in proline hydroxylation was investigated. Proteins in calvarial bones from control and scorbutic weanling guinea pigs were labeled in short-term cultures with radioactive proline. Proteins were digested with purified bacterial collagenase to distinguish between effects on collagen polypeptide production and hydroxyproline formation. There was a preferential decrease in the absolute rate of collagen biosynthesis beginning after 2 wk of ascorbate deficiency, and this effect was temporally dissociated from decreased proline hydroxylation. There were no significant changes in the absolute rates of collagen degradation or noncollagen protein production. In vitro inhibition of proline hydroxylation in normal bone with alpha, alpha'-dipyridyl did not affect the relative rate of collagen synthesis, further dissociating these functions. Ascorbate added to scorbutic bone cultures reversed defective proline hydroxylation but not defective collagen synthesis, suggesting that the latter was an indirect effect of scurvy. There was a linear correlation between the extent of body weight lost during the 3rd and 4th wk of scurvy and the rate of collagen synthesis in scorbutic bone. This correlation also applied to control animals receiving ascorbate, but with weight loss induced by food restriction. These studies establish for the first time that ascorbate deficiency in guinea pigs leads to a specific decrease in collagen polypeptide synthesis and suggest that this decrease results from the reduced food intake and/or weight-loss characteristic of scurvy.

The relationship of pellagra to corn and the low availability of niacin in cereals

The poorest inhabitants of an area generally eat the narrowest range of foods, and one staple (which serves as a cheap source of calories) dominates. In turn, the specific type of malnutrition seen in that area depends upon that predominant staple and how it is processed before consumption. Corn, used here in the sense of "Indian corn" or maize, was brought to Europe from America, and over the period 1750-1850 became the typical peasant's staple in many of the areas bordering the Mediterranean. By the end of that period, it had also come to be recognized that pellagra had become a serious, chronic disease in these same countries, flaring up each spring amongst the poorest people living on diets containing much corn and very little animal food (i.e., meat, eggs or dairy products) or wine and being generally in a state of wretchedness. Nothing of the sort was seen in areas where wheat and rice were the staple foods, even when they were highly milled. Most scientists agreed on this association with corn, though not on what was the true cause-and-effect relationship. Research in the present century has shown that pellagra is primarily due to a dietary deficiency of niacin. However, the niacin content of different foods did not tie in well with their pellagra-preventive value. But then it was discovered that a second nutrient, tryptophan, could act as precursor of the vitamin with approximately one sixtieth of the activity of the actual vitamin. The "niacin equivalent" values of foods (calculated from their content of both nutrients) show a much better correlation with their pellagra-preventive value. Thus, mature corn is lower in niacin content than are wheat and rice; also the mixed proteins of corn are lower in their tryptophan content. What is not explained by the calculation of "niacin equivalent" is the general freedom from pellagra of the peasants in Mexico and Central America, where corn has been the staple for millenia and where poverty, the consequent lack of animal foods in the diet, and general misery, have been fully equal to the conditions in Europe. It has been known for 40 years that analytical values for the niacin content of foods depended greatly on the method of extraction used, with the highest values being obtained after treatment with alkali. We have confirmed with rat growth assays that the niacin in corn, wheat and rice is only about one-third available to this species, even after ordinary cooking at neutral pH.(ABSTRACT TRUNCATED AT 400 WORDS)