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Biomedical subjects

C S Johnston

Publications and source records attributed to C S Johnston.

15 recordsLinked to original sources

Antihistamine effect of supplemental ascorbic acid and neutrophil chemotaxis.

Renewed interest in the antihistamine action of ascorbic acid has emerged with the recently recognized immunosuppressive role of histamine. We examined the antihistamine effect of acute and chronic vitamin C (VC) administration and its effect on neutrophil chemotaxis in healthy men and women. In the chronic study, 10 subjects ingested a placebo during weeks 1, 2, 5 and 6, and 2 g/day of VC during weeks 3 and 4. Fasting blood samples were collected after the initial 2-week period (baseline) and at the end of weeks 4 and 6. Plasma ascorbate rose significantly following VC administration compared to baseline and withdrawal values. Neutrophil chemotaxis rose 19% (NS) during VC administration, and fell 30% after VC withdrawal, but these changes were not correlated to plasma ascorbate levels (r = 0.01). Chemotaxis was inversely correlated to blood histamine (r = -0.32, p = 0.045), and, compared to baseline and withdrawal values, histamine levels were depressed 38% following VC supplementation. Blood histamine and neutrophil chemotaxis did not change 4 hours following a single 2 g dose of ascorbic acid, although plasma ascorbate rose 150%. These data indicate that VC may indirectly enhance chemotaxis by detoxifying histamine in vivo.

Adult

Pregnancy weight gain in adolescents and young adults.

We examined whether adolescents required greater prenatal weight gains than nonadolescents to deliver equal weight babies following a low-risk pregnancy. Maternal characteristics and monthly weight gains were collected from medical records obtained from a private health maintenance organization (n = 423). Maternal weight gain, gestational age, parity, and cigarette use during pregnancy were significant predictors of infant birth weight in our regression models. Subjects were nonsmokers with a gestational age greater than 37 weeks and a parity equal to 0 who entered prenatal care during the first trimester of pregnancy. Mean total weight gains for the adolescents (16.2 +/- 4.8 kg; n = 51) and adults (15.2 +/- 5.4 kg; n = 65), and infant birth weights were similar. Mean infant birth weight was 3473 +/- 394 g for the adolescents and 3339 +/- 453 g for the young adults, whereas the optimal weight range for newborns is about 3500-3999 g. Modifiable risks are the important predictors of infant birth weight, and adolescents do not appear to require a greater weight gain than young adults to deliver similar weight babies.

Adolescent

Complement component C1q activity and ascorbic acid nutriture in guinea pigs.

When guinea pigs are fed tissue-saturating amounts of ascorbate, C1q concentrations are significantly higher than in those animals fed only enough ascorbate for adequate growth and for the prevention of scurvy. C1q is the recognition protein of the classical complement pathway, a system of blood proteins that constitutes an important part of host defense against pathogens. The observed effect of ascorbate nutriture on C1q concentrations is consistent with the known role of ascorbic acid in hydroxyproline biosynthesis. C1q is a hydroxyproline-containing protein with structural similarities to collagen.

Analysis of Variance

Effect of ascorbic acid nutriture on blood histamine and neutrophil chemotaxis in guinea pigs.

Histamine suppresses certain immune responses, including neutrophil chemotaxis. The present study examined whether the histamine-lowering effect of ascorbate was accompanied by enhanced chemotaxis in guinea pigs. Animals were fed low ascorbate, adequate or high ascorbate diets (0.5, 2.0 or 50 mg ascorbate.100 g body wt-1.d-1) for 4 wk. Mean liver ascorbate paralleled dietary intake, and these values differed significantly. Blood histamine was significantly depressed in the high ascorbate group compared to the adequate and low ascorbate groups, and liver ascorbate was inversely correlated to blood histamine levels (r = -0.64, P less than 0.001). The random migration of neutrophils was not significantly affected by vitamin dosage. Leukocyte chemotaxis was significantly impaired in low ascorbate animals compared to that of animals with adequate ascorbate nutriture. Leukocyte chemotaxis in high ascorbate animals did not differ significantly from that in the adequate or low ascorbate groups. Furthermore, chemotaxis was significantly lower when cells extracted from animals with adequate ascorbate nutriture were incubated in low ascorbate or high ascorbate serum rather than in autologous serum. These data suggest that the histamine-lowering effect of supplemental ascorbate does not appear to enhance leukocyte chemotaxis and that serum from guinea pigs fed low or high levels of ascorbate appears to contain factors that depress chemotaxis.

Animals

Menstrual function and eating behavior in female recreational weight lifters and competitive body builders.

A group of 103 female weight lifters (WL) and 92 control (C) women answered a survey concerning eating behavior and attitudes (including the Eating Disorder Inventory) and menstrual function. The incidence of menstrual dysfunction, defined as oligomenorrhea plus amenorrhea, was significantly higher for the WL (30%) than for the C (13%) not on contraceptive pills. Only 2% of the women had amenorrhea. The incidence of dysfunction was highest for the subset of 12 WL who had competed in at least one body building competition (COMP); 86% of the COMP not on birth control pills had menstrual dysfunction (P less than 0.05). More WL than C reported missing at least one menstrual period during the last year (P = 0.06). WL scored significantly higher than C on the Drive for Thinness subscale of the Eating Disorder Inventory (EDI). Fifteen percent of the WL and 9% of the C achieved the criteria on this subscale for being weight preoccupied (P greater than 0.05). Significantly more WL than C responded that they were terrified of becoming fat (WL 56%, C 38%), were obsessed with food (WL 47%, C 30%), used laxatives for weight control (WL 14%, C 1%), and claimed that they had been anorexic in the past (WL 17%, C 5%). Examination of the answers of COMP revealed several items that were significantly different from the remainder of the WL. For example, 42% used to be anorexic, 67% were terrified of becoming fat, and 50% experienced uncontrollable urges to eat.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue

Effect of a single oral dose of ascorbic acid on body temperature and trace mineral fluxes in healthy men and women.

Several metabolic changes characteristic of the acute-phase response were examined in healthy men and women following a single 1 g dose of ascorbic acid. Utilizing a placebo-controlled, double-blind protocol, oral body temperatures were recorded in rested, fasted subjects (0900 hr) prior to the consumption of 1 g L-ascorbic acid or placebo (n = 10/group). Temperatures were recorded hourly for the next 8 hours, and again the next morning in the rested, fasted state (0900 hr). Blood samples, collected at 0, 4, and 24 hours post-dose, were analyzed for plasma ascorbate, iron, and zinc. Mean oral body temperature was significantly elevated 2 hours post-dose in the experimental subjects compared to controls (+0.7 degrees F, p = 0.03). In the vitamin-dosed subjects, mean plasma ascorbate rose 32% over the control value after 4 hours (1.11 +/- 0.08 and 0.84 +/- 0.06 mg/100 ml, ns). Serum iron levels were similar in the two groups at 0 and 4 hours post-dose, but at 24 hours post-dose mean serum iron of the vitamin-dosed subjects fell to 73% of that recorded for the control subjects (77 +/- 8 and 105 +/- 10 micrograms/100 ml, p = 0.04). Plasma zinc levels were similar for both groups at 0, 4, and 24 hours post-dose. These data indicate that ascorbate administration, at a level commonly supplemented in the US diet, elicits several host metabolic responses similar to those observed following exposure to infectious or inflammatory agents. These metabolic changes are most likely due to the reducing potential of the vitamin and may factor in the reported prophylactic success of vitamin C supplementation.

Acute-Phase Reaction

Effect of single oral doses of ascorbic acid on body temperature in healthy guinea pigs.

A series of experiments were conducted to examine the effect of single oral doses of ascorbic acid on body temperature in healthy guinea pigs. Fifteen male guinea pigs (approximately 200 g) were fed a nonpurified diet designed for rabbits (a scorbutogenic diet) ad libitum and received orally 2 mg L-ascorbic acid/100 g body wt daily. After acclimation, rectal temperatures were recorded hourly following five separate ascorbate dosage treatments: 0 (control dosage), 2, 10 or 50 mg ascorbic acid/100 g body wt, or 50 mg ascorbic acid and 0.07 mg indomethacin/100 g body wt. Mean body temperature was significantly elevated (P less than 0.05) after 1 h in animals receiving either the 10 or 50 mg dosage (+ 0.27 +/- 0.05 and + 0.41 +/- 0.07 degree C, respectively) compared to that in animals receiving the 2 mg dosage (-0.07 +/- 0.05 degree C), the recommended daily intake for guinea pigs. Changes in body temperature of animals receiving the 50 mg dosage plus indomethacin did not differ significantly from those reported with the 2 mg dosage. Thus, a single oral dose of ascorbic acid at levels 5-25 times the recommended intake, can elevate body temperature significantly in healthy guinea pigs, a phenomenon which is inhibited by indomethacin administration.

Animals

The effect of vitamin C nutriture on complement component C1q concentrations in guinea pig plasma.

This study shows that guinea pigs fed 100 times the amount of vitamin C needed for growth and for prevention of scurvy have elevated levels of complement component C1q. C1q is a plasma protein rich in hydroxyproline, an amino acid whose biosynthesis requires ascorbate. C1q is essential for host defense against pathogens, both as a component of the classical complement pathway and as an opsonin in the phagocytosis process. We measured C1q in vitamin C-depleted guinea pigs that had been repleted for 4 wks with the following daily doses of ascorbate (mg/100 g body wt): 0.50 (suboptimal), 2.0 (adequate), 10 (ample) and 50 (tissue saturating). We measured C1q in three ways: indirectly by quantifying protein-bound hydroxyproline and directly by hemolytic assay and by immunodiffusion against anti-C1q. Regardless of the method, plasma C1q was 30-50% higher in animals fed tissue-saturating ascorbate than in those fed adequate or suboptimal amounts of the vitamin (p less than 0.05, one-way analysis of variance, least significant difference test). These data confirm and significantly extend earlier work that provided indirect evidence for a relationship between C1q and ascorbate nutriture in the guinea pig. They are consistent with a possible relationship between ascorbate nutriture and host defense.

Animals

Effect of ascorbic acid nutriture on protein-bound hydroxyproline in guinea pig plasma.

This paper provides indirect evidence that ascorbate nutriture affects plasma concentrations of complement component C1q in the guinea pig. C1q is a protein with a hydroxyproline-rich region similar in structure to collagen. It is essential for complement-mediated lysis of pathogens and may also facilitate phagocytic activity of macrophages and neutrophils. Since C1q is the only hydroxyproline-containing protein in the euglobulin fraction of plasma, it can be quantified indirectly by precipitating this fraction, hydrolyzing it and estimating hydroxyproline colorimetrically. We investigated the effect of ascorbate nutriture on protein-bound hydroxyproline (PBH) in the euglobulin fraction of plasma of young male guinea pigs. The animals had been depleted of ascorbate for 3 wk to produce scurvy and then repleted (6 wk) as follows: 0.5, 2.0 and 10.0 mg ascorbate/100 g body weight per d or 10 g ascorbate per liter of drinking water. PBH values were significantly correlated (P less than 0.001) with dietary ascorbate (+ 0.74) and with liver ascorbate (+ 0.75). Plasma PBH was significantly higher (P less than 0.01, Scheffé's test) in guinea pigs fed ample ascorbate (10.0 mg/100 g body weight per day) or tissue-saturating levels (10 g/L of drinking water) than in those fed adequate (2.0 mg/100 g body weight) or suboptimal (0.5 mg/100 g body weight) levels. These data are consistent with the known biochemical role of ascorbic acid in hydroxyproline biosynthesis and suggest a possible link between ascorbate and the immune response via C1q.

Animals