Epidemic of adenovirus-induced respiratory illness among US military recruits: epidemiologic and immunologic risk factors in healthy, young adults

Adenovirus (Ad)-induced acute respiratory illnesses resurged among civilian adults and selected military training populations in the United States during the late 1990s. We examined the epidemiologic and immunologic correlates of Ad-induced respiratory illnesses during a large outbreak at an Army basic training installation in southeast United States during a 9-day period in November 1997. A total of 79 recruits hospitalized with acute respiratory illnesses were evaluated during the outbreak period; confirmation of Ad infection by isolation of Ad-like cytopathic agents from throat cultures was detected in 71 (90%) of these patients. Serotyping of 19 (27%) of these 71 isolates identified the etiologic agent to be Ad type 4 (Ad4). In addition, 30 (81%) of 37 patients in whom paired sera were collected demonstrated significant increases (i.e., 4-fold or higher) in serum anti-Ad4 neutralizing antibodies. Anti-Ad4 immunity in new recruits was found to be very low (15 to 22%). A case-control study involving 66 of the 79 hospitalized cases and 189 non-ill controls from the same units was conducted. A lower risk of hospitalization for acute respiratory illnesses was documented for female recruits (odds ratio[OR] = 0.47, P <.05) whereas, a higher risk was noted for smokers (OR = 1.89, P <.05). Unit (training company) attack rates as high as 8 to 10% per week were documented and the outbreak quickly subsided after live, oral Ad types 4 and 7 vaccination was resumed in November 1997. Re-establishment of a military Ad vaccination program is critical for control of Ad-induced acute respiratory illnesses.

Hyperglycemia-induced ascorbic acid deficiency promotes endothelial dysfunction and the development of atherosclerosis

Dehydroascorbic acid, the oxidized form of vitamin C, is transported into mammalian cells via facilitative glucose transporters and hyperglycemia inhibits this process by competitive inhibition. This inhibited transport may promote oxidative stress and contribute to the increase in atherosclerotic cardiovascular disease observed in patients with diabetes mellitus. This review explores the importance of this proposed mechanism in light of current research. For example, recent reports suggest that administration of antioxidants, such as vitamin C, may slow atherogenesis by improving endothelium-dependent vasodilation in individuals with abnormal glucose and lipid metabolism, perhaps by preventing the oxidation of nitric oxide, an important regulator of vasomotor tone. Endothelial dysfunction plays a key role in the development of atherosclerosis and endothelial cells may be particularly affected by hyperglycemia-induced ascorbic acid deficiency as they line the interior of blood vessels. In addition, we discuss evidence of several other mechanisms by which vitamin C status may affect the development of atherosclerotic cardiovascular disease, particularly its inverse relationship to multiple cardiovascular disease risk factors and indicators. Given these factors, vitamin C administration is recommended during periods of both acute and chronic hyperglycemia to help preserve endothelial function.

Novel approach for the determination of the redox status of homocysteine and other aminothiols in plasma from healthy subjects and patients with ischemic stroke

BACKGROUND

Plasma "redox" status can be assessed by measurements of reduced (r)-, free (f)-, oxidized (ox)-, and protein-bound (b)-homocysteine (Hcy) plus the related aminothiols cysteine, cysteinylglycine (CysGly), and glutathione (GSH), but sample collection has been complex. The redox status has not been determined in ischemic stroke patients and may provide increased understanding of its role in pathogenesis. We wished to examine the feasibility of this measurement in samples collected in readily available acidic sodium citrate.

METHODS

We measured aminothiols and their stability in stabilized protein-free filtrate using acidic sodium citrate (BioPool Stabilyte, pH 4.3) vs EDTA whole blood. Before analysis, plasma samples were also ultrafiltered to obtain a protein-free filtrate. The concentrations of total Hcy (tHcy), fHcy, and rHcy and their related aminothiols, cysteine, cysteinylglycine, and glutathione were simultaneously determined on acidic sodium-citrated blood using reversed-phase HPLC with fluorescence detection. Bound and oxidized aminothiols were calculated by difference using the concentrations of the total, free, and reduced fractions. Using this approach, we compared the redox status in newly diagnosed ischemic stroke patients (n = 20) and healthy age- and sex-matched subjects (n = 20).

RESULTS

tHcy, tCys, tCysGly, and tGSH concentrations in whole blood with Stabilyte were stable for 8 h; the reduced fraction of each aminothiol was stable for 4 h. Recovery in the protein-free filtrate was 90-100% for all reduced thiols in acidified sodium-citrated blood. Patients with ischemic stroke had higher plasma tHcy, fHcy, bHcy, rHcy, and oxHcy (P <0.0005) and higher plasma t-, f-, r-, and oxCys (P <0.05). t-, b-, and rCysGly concentrations were lower in the stroke patients (P <0.05), as were t-, b-, and oxGSH (P <0.005).

CONCLUSIONS

Collection of blood in acidic sodium citrate (BioPool Stabilyte) permits the determination of the redox status of Hcy and its related aminothiols, which may add to the understanding of their relationship to the etiology of cerebrovascular disease.

Energy metabolism increases and regional body fat decreases while regional muscle mass is spared in humans climbing Mt. Everest

The objectives of the study were to determine regional changes in body composition, energy expenditure by means of doubly labeled water, and net energy balance during exposure to high and extreme altitudes (5,300-8,848 m). This study focuses on a subset of subjects who consumed the doubly labeled water (three base camp personnel and seven climbers). Regional body composition was determined by measuring skinfold thicknesses and circumferences at 10 different sites on the body. Energy expenditure was measured by doubly labeled water excretion. Discrepancies between actual energy expenditure and data obtained from diet records and body weight changes suggested a chronic underreporting of dietary energy intake, especially by those subjects who reached the highest altitudes. This underreporting may be due in part to diminished cognition or to a preferential focus on survival, rather than on filling out diet records accurately. Mean adjusted dietary intakes were 10.50 +/- 0. 65 MJ/d (2510 +/- 155 kcal/d) for those who remained at base camp, and 20.63 +/- 6.56 MJ/d (4931 +/- 1568 kcal/d) for those who climbed above base camp. Energy expenditure averaged 2.5-3.0 times sea level resting energy expenditure. Differential changes in regional body composition suggested a preferential loss of fat mass and a relative sparing of muscle mass, despite insufficient energy intake to maintain body weight.

Intakes of high fat and high carbohydrate foods by humans increased with exposure to increasing altitude during an expedition to Mt. Everest

The objectives of the study were to determine total energy intakes, distribution of energy derived from the macronutrients, and the effects of increasing altitudes on energy and macronutrient consumption during exposure to high altitudes. High fat, low carbohydrate diets (35% and 50% of energy, respectively) or low fat, high carbohydrate diets (20% and 65% of energy, respectively) were provided to two groups of subjects for a 3-wk period. Groups then consumed the alternate diet for 3 wk, followed by a return to the original diet for the remaining 3 wk of the study. Free choice of individual items and amounts within each diet was permitted. Intake of food and fluid was determined by means of monitored entries in daily food records. Five subjects remained at Base Camp (5300 m) and 10 subjects climbed to altitudes up to and including the summit of Mt. Everest (8848 m). Subjects consumed an average of 10.22 +/- 4.57 MJ/d (2442 +/- 1092 kcal) energy while at Base Camp, with climbers consuming significantly more than Base Camp personnel [11.89 +/- 4. 88 vs. 7.87 +/- 2.98 MJ/d (2841 +/- 1167 vs. 1881 +/- 713 kcal/d), P </= 0.0001]. There was a significant decline in energy consumption at increasing altitudes (P = 0.022), but no shift in distribution of energy provided from fat, carbohydrate or protein (P > 0.05). Contrary to previous reports, subjects in this study did not shift their food selections away from the high fat items towards high carbohydrate items.

Use of the Mogen clamp for neonatal circumcision

Most newborn circumcisions performed in the United States are done with either a Gomco clamp or a Plastibell device. The Mogen clamp, devised by a jewish mohel, provides a quick and simple surgical alternative. The foreskin is freed from the glans by blunt dissection, but no dorsal slit is made. A dorsal hemostat is placed, and traction is applied to bring the foreskin forward. Placement of the Mogen clamp follows the angle of the corona to avoid removing excess skin ventrally and to obtain a superior cosmetic result. The clamp crushes the foreskin along a line that is 1 mm wide, and the foreskin is excised distal to the clamp. After removal of the clamp, the glans is liberated by pulling the crush line apart. The procedure usually takes three to four minutes and is virtually bloodless.

Homocysteine metabolism and risk of myocardial infarction: relation with vitamins B6, B12, and folate

Elevated plasma homocyst(e)ine levels are an independent risk factor for vascular disease. In a case-control study, the authors studied the associations of fasting plasma homocyst(e)ine and vitamins, which are important cofactors in homocysteine metabolism, with the risk of myocardial infarction. The cases were 130 Boston area patients hospitalized with a first myocardial infarction and 118 population controls, less than 76 years of age, enrolled in 1982 and 1983. Dietary intakes of vitamins B6, B12, and folate were estimated from a food frequency questionnaire. After adjusting for sex and age, the authors found that the geometric mean plasma homocyst(e)ine level was 11% higher in cases compared with controls (p = 0.006). There was no clear excess of cases with extremely elevated levels. The age- and sex-adjusted odds ratio for each 3-mumol/liter (approximately 1 standard deviation) increase in plasma homocyst(e)ine was 1.35 (95% confidence interval 1.05-1.75; p trend = 0/007). After further control for several risk factors, the odds ratio was not affected, but the confidence interval was wider and the p value for trend was less significant. Dietary and plasma levels of vitamin B6 and folate were lower in cases than in controls, and these vitamins were inversely associated with the risk of myocardial infarction, independently of other potential risk factors. Vitamin B12 showed no clear association with myocardial infarction, although methylmalonic acid levels were significantly higher in cases. Comparing the mean levels of several homocysteine metabolites among cases and controls, the authors found that impairment of remethylation of homocyst(e)ine (dependent of folate and vitamin B12 rather than on vitamin B6-dependent transsulfuration) was the predominant cause of high homocyst(e)ine levels in cases. Accordingly, plasma folate and, to a lesser extent, plasma vitamin B12, but not vitamin B6, correlated inversely with plasma homocyst(e)ine, even for concentrations at the high end of normal values. These data provide further evidence that plasma homocyst(e)ine is an independent risk factor for myocardial infarction. In this population, folate was the most important determinant of plasma homocyst(e)ine, even in subjects with apparently adequate nutritional status of this vitamin.

Hyperglycemia-induced latent scurvy and atherosclerosis: the scorbutic-metaplasia hypothesis

Latent scurvy is characterized by a reversible atherosclerosis that closely resembles the clinical form of this disease. Acute scurvy is characterized by microvascular complications such as widespread capillary hemorrhaging. Vitamin C (ascorbate) is required for the synthesis of collagen, the protein most critical in the maintenance of vascular integrity. We suggest that in latent scurvy, large blood vessels use modified LDL--in particular lipoprotein(a)--in addition to collagen to maintain macrovascular integrity. By this mechanism, collagen is spared for the maintenance of capillaries, the sites of gas and nutrient exchange. The foam-cell phenotype of atherosclerosis is identified as a mesenchymal genetic program, regulated by the availability of ascorbate. When vitamin C is limited, foam cells develop and induce oxidative modification of LDL, thereby stabilizing large blood vessels via the deposition of LDL. The structural similarity between vitamin C and glucose suggests that hyperglycemia will inhibit cellular uptake of ascorbate, inducing local vitamin C deficiency.

A family practice article filing system

An organized article filing system can be a timesaver for the busy clinician. A comprehensive, specialty-based filing system for the family physician is presented. The full system uses about 700 three-tab manila folders. Each major medical specialty heading is placed on an empty center-tab folder. Subfolders within each major heading are all right- or left-tab folders, alternating for each successive major heading. Topics that overlap specialty are cross-referenced. Additional major headings are included for presenting symptoms, procedures, practice management topics, society membership, licensure, etc. The resulting filing system is intuitive to use since articles are filed by the specialty to which the the topic is most closely related. Journal articles and associated patient education materials may be filed in the same folder for quick retrieval.

Intestinal perforation from trauma to an inguinal hernia

Inguinal hernias are most feared to result in incarceration and strangulation of intra-abdominal structures. Blunt abdominal blows have previously been reported to cause traumatic perforation of bowel that overlays the defect of any abdominal wall hernia. To my knowledge, this case report is the first to show that bowel perforation may be caused by direct trauma to an inguinal hernia that contains a loop of small bowel. It is proposed that the force of the blow first opposes the walls of the incoming and outgoing bowel, sealing the loop. Then, additional pressure that is applied will raise the loop's intraluminal pressure to the point that traumatic perforation occurs. A simple experiment on a necropsy specimen showed that the proposed mechanism is plausible. This case points out another risk of leaving an inguinal hernia unrepaired.

The 'Modified U' technique: a refined method of Norplant removal

Norplant removal has been much more difficult for many physicians than might have been anticipated. Dr Untung Praptohardjo of Indonesia recently developed the "U" technique, speeding the time required to remove the six Norplant implants to an average of 7 minutes. In his technique, a unique oval-ring-tipped forceps with an internal diameter of 2.2 mm is used to reach through a 4-mm incision to firmly grasp each of the implants. The incision is made parallel to the implants between the lower tips of implants 3 and 4. The "U" technique requires grasping the implant within 4 mm to 5 mm of its tip. This preliminary paper describes the "Modified U" technique, which allows the physician who is removing the implants to grasp them anywhere along their shaft, not just near the tip. The Modified U technique involves the use of an improved ring-tipped forceps with a circular tip rather than the oval tip used in the "U" technique. This instrument, called Norgrasp, is a modification of the vas deferens fixation forceps used in the no-scalpel vasectomy (NSV) technique. In another adaptation of NSV instruments, an NSV dissecting forceps (a sharpened, curved hemostat) is used to free the implants from their tissue envelope and quickly deliver them through the skin incision. Using the Modified U technique, the time required to remove Norplant implants in 20 patients in the United States has ranged from 8 to 13 minutes. Improperly placed implants are readily removed with this technique. The Modified U technique requires a minimal incision and offers both the physician and the patient a speedy, positive removal.

Nebulized bacteriostatic saline as a cause of bronchitis

BACKGROUND

The purpose of this study was to determine whether nebulized bacteriostatic saline, which contains the preservative benzyl alcohol, is an irritant to the tracheobronchial mucosa in healthy adults.

METHODS

A randomized, double-blind, placebo-controlled study was conducted with 10 healthy adults who inhaled 3 mL of either bacteriostatic saline or saline placebo by nebulizer four times a day for 2 weeks. Pulmonary function tests and bronchoscopy with biopsy were performed immediately before and after the 2-week nebulization period.

RESULTS

Nine of 10 volunteers were compliant with the study protocol. Four of five volunteers who used nebulized bacteriostatic saline developed bronchitic symptoms and had bronchoscopic evidence of bronchitis. The fifth remained healthy. Four volunteers used nebulized saline (placebo). Two of these four became ill, one with a much more severe bronchitis than any of the bacteriostatic saline volunteers, and one with pharyngitis. Bronchoscopic biopsies showed a lymphocytic mucosal infiltrate in those who became ill while using nebulized bacteriostatic saline and a polymorphonuclear mucosal infiltrate in those who became ill while using nebulized saline placebo.

CONCLUSIONS

Nebulization of bacteriostatic saline, containing benzyl alcohol as its preservative, causes bronchitis in healthy adults. Even nebulization of sterile saline may be associated with bronchitis and pharyngitis. Physicians who prescribe nebulized medications must pay close attention to the bronchodilator diluent.

Vas deferens occlusion during no-scalpel vasectomy

The increasing popularity of the no-scalpel vasectomy (NSV) technique in the United States is driven by patient demand for surgical procedures presumed to be less invasive and by the somewhat lower complication rate of the NSV technique. The NSV technique addresses vasal delivery but not vasal occlusion. Intraluminal red-hot wire cautery with sheath closure over the inguinal end of the cut vas (Schmidt's method) has the lowest failure rate of all reasonable vas occlusion methods. The anatomical relationships of scrotal layers can be unclear during the NSV technique. Accurate identification of the sheath layer is critical to sheath interruption if this method of occlusion is to be used. Placement of an absorbable purse-string suture for sheath interruption during the NSV procedure is described. Special attention must be given to placement of one suture bite in the deep (posterior) sheath wall. The vasal occlusion technique described in this paper blends a refined method of vasal delivery (NSV) with the most effective method of vasal occlusion (cautery with sheath interruption).

Plasma pyridoxal phosphate in anxiety disorders

One hundred and eighty-nine subjects with either generalized anxiety disorder, panic disorder, or obsessive-compulsive disorder were evaluated for plasma pyridoxal phosphate (PLP) levels and compared with normal controls. There was no difference in plasma PLP levels between the anxiety disorder groups and normal controls. Low levels of plasma PLP were found in 42% of the controls. Our results suggest that previous reports of low PLP levels in psychiatric patients are unlikely to be significant in the etiology of the psychiatric disorders.

Pyridoxal 5'-phosphate related changes in retention of 1,25-dihydroxy vitamin D-receptor ligands in rat intestinal mucosa cell nuclei

After feeding rats a vitamin B-6-deficient diet, we observed a decrease in pyridoxal 5'-phosphate concentrations in intestinal mucosa cells to 32 and 48% of control in cytoplasm and cell nuclei, respectively. Correlation analysis suggested that there were two pyridoxal 5'-phosphate pools in the nuclei: a "mobile" pool (equivalent to about 5% the concentration of the cytoplasmic pyridoxal 5'-phosphate), and a "stable" pool, which was independent of cytoplasmic fluctuations of pyridoxal 5'-phosphate (about 9 pmol pyridoxal 5'-phosphate/mg DNA). Reduction in pyridoxal 5'-phosphate content in the cells of vitamin B-6-deficient animals was accompanied by a substantial increase in 1,25-dihydroxyvitamin D-receptor ligand concentration in the cell nuclei (76.6 +/- 19.7 vs 762 +/- 291 fmol/mg DNA, mean +/- SEM). The degree of 1,25-dihydroxyvitamin D accumulation in the nuclei appeared to be an exponential function of the "mobile" nuclear pyridoxal 5'-phosphate concentration. Semilogarithmic transformation of the data yielded a straight line, representing an inverse correlation between the cytoplasm-related nuclear pool of pyridoxal 5'-phosphate and the logarithm of the 1,25-dihydroxyvitamin D concentration in the nuclei (r = -0.95). These data suggest that pyridoxal 5'-phosphate may be related to 1,25-dihydroxyvitamin D retention in the nuclei, possibly through interaction of the pyridoxal 5'-phosphate with the vitamin D receptor protein in the nuclei.

Vitamin supplements: current controversies

Supplemental use of vitamins to prevent disease constitutes a major commercial enterprise in the United States. The efficacy of such use, or even the need for intakes above that which can be supplied by means of diet alone, has been the source of considerable controversy in the medical and scientific fields. Recently published data have given strong support to several of the claims for major benefits of disease prevention, including that of cancer, cardiovascular disease, carpal tunnel syndrome, and neural tube defects, to name just a few. The purported benefits for supplemental vitamin usage are discussed for these diseases, along with a call for a re-evaluation of the underlying philosophy of the Recommended Dietary Allowances, or consideration of their abolition, based on newly emerging data.

Accurate dosing of pediatric medications

Dosing of pediatric medications must be accurate. Combining constants in the usual calculation for amoxicillin dosing derives the Rule of Six (6 mg/lb per dose) for dosing. This rule generalizes to most pediatric antibiotics. The Decimal Move Rule (0.1 mL/lb per dose) can be used to dose many over-the-counter cough and cold remedies, bronchodilators, and iron preparations. A number of helpful hints to improve compliance and three comprehensive dosing tables are presented.

Treatment of myelodysplastic syndromes with daily oral idarubicin. A phase I-II study

BACKGROUND

Idarubicin, a new anthracycline analogue, is available in an oral preparation, and responses have been observed using relatively aggressive therapy in patients with myelodysplastic syndromes (MDS). The authors studied whether a chronic low-dose schedule would be effective but less myelotoxic.

METHODS

Forty-two patients with MDS received daily low-dose oral idarubicin in 5-week courses that included 3 weeks of treatment, followed by a 2-week rest period. Doses were escalated when possible after the second course, and each patient was to receive six courses.

RESULTS

Only one partial response was observed. Although no patient had fatal bone marrow toxicity, only eight patients received the full six courses, primarily because of myelosuppression.

CONCLUSIONS

This schedule of oral idarubicin is relatively safe but produces fewer responses than are reported with the high-dose pulse regimens.

Vitamin B-6 deficiency alters rat enterocyte calcium homeostasis but not duodenal transport

Isolated enterocytes were used as differential transporting cells to examine calcium homeostasis in control and vitamin B-6-deficient rats. Kinetic analysis of calcium fluxes, as well as biochemical determinations, indicated that enterocytes from control animals had high concentrations of cytosol ionized calcium (318.5 +/- 22.4 nmol/L) and a large pool of exchangeable calcium (2.72 nmol/mg protein, or 86% of total cell calcium). Vitamin B-6 deficiency resulted in a 44% reduction in total cellular calcium (1.71 +/- 0.24 vs. 3.07 +/- 0.29 nmol/mg protein), a 69% reduction in total exchangeable calcium (0.85 vs. 2.72 nmol/mg protein) and a 56% reduction in cytosol ionized calcium concentration (141.4 +/- 13.5 vs. 318.5 +/- 22.4 nmol/L). Calcium fluxes between all cellular compartments were markedly diminished as a result of vitamin B-6 deficiency. However, vitamin B-6 deficiency did not affect the basic morphological or functional features of the enterocytes, such as cell viability, cell volume, membrane permeability and protein content. Moreover, intestinal calcium transport in vivo was not affected during vitamin B-6 deficiency, perhaps due to the greater paracellular ion movement compensating for the lower transcellular transport.

Consumption of a dehydrated ration for 31 days at moderate altitudes: status of zinc, copper, and vitamin B-6

Intake of energy zinc, copper, and vitamin B-6 and indexes of zinc, copper and vitamin B-6 status were determined for eight men who consumed a high-carbohydrate dehydrated ration for 31 days of high activity at moderate altitudes (2,400 to 4,300 m). Data were collected 2 months before exposure (PRE), four times during the month at moderate altitudes (ALT), and 1 month after return (RET). Mean (+/- standard error) energy intake was 2,725 +/- 215, 3,430 +/- 79, and 3,370 +/- 215 kcal/day during PRE, ALT, and RET, respectively. Zinc and copper intakes averaged 10.6 +/- 1.6 and 1.0 +/- 0.1 mg/day during PRE and increased significantly to 16.9 +/- 0.7 and 3.5 +/- 0.1 mg/day during ALT; zinc and copper intakes were 15.5 +/- 1.6 and 1.9 +/- 0.3 mg/day for RET, respectively. Similarly, vitamin B-6 intake was significantly higher during ALT (PRE = 2.2 +/- 0.5 mg/day; ALT = 4.2 +/- 0.4 mg/day; and RET = 2.6 +/- 0.4 mg/day) as compared with PRE and RET. No significant changes were noted for plasma zinc, copper, or their related proteins or plasma or erythrocyte pyridoxal-5'-phosphate. Finally, no changes in urinary excretion of zinc were observed. The results indicate that dehydrated rations provide zinc, copper, and vitamin B-6 in amounts above the Recommended Dietary Allowances. Such diets may be consumed for at least 1 month without compromising status for these nutrients.

Effects of ascorbic acid and pyridoxine supplementation on oxalate metabolism in peritoneal dialysis patients

We studied the effect of vitamin C and B6 supplementation on oxalate metabolism in seven patients receiving chronic peritoneal dialysis therapy. The study was divided into three phases, each lasting 4 weeks. Plasma oxalate, total ascorbic acid, and pyridoxal-5'-phosphate (PLP) were measured at the end of each phase. Twenty-four-hour urinary excretion and dialysate removal rates of oxalate were also obtained. At the end of phase I (supplement-free period), plasma oxalate levels were markedly elevated at 47.6 +/- 7.1 mumol/L (437 +/- 66 micrograms/dL) (normal, 3.4 +/- 0.4 mumol/L [30.3 +/- 1.6 micrograms/dL]). Plasma total ascorbic acid levels were 62 +/- 6 mumol/L (1.0 +/- 0.1 mg/dL) (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]), while plasma PLP levels were markedly reduced to 24 +/- 5 nmol/L (normal, 40 to 80 nmol/L). Daily supplements of 0.57 mmol (100 mg) ascorbic acid orally (phase II) resulted in a 19% increase in the plasma oxalate levels to 57.8 +/- 6.1 mumol/L (520 +/- 55 micrograms/dL) (P less than 0.03), with a concomitant 60% increase in the plasma ascorbate levels (91 +/- 6 mumol/L [1.6 +/- 0.1 mg/dL], P less than 0.01). Plasma PLP values remained low. Finally, during phase III (0.57 mmol or 100 mg ascorbic acid plus 59.6 mumol or 10 mg pyridoxine HCI orally daily), plasma oxalate levels declined by 17% to 47.9 +/- 5.2 mumol/L (431 +/- 47 micrograms/dL) (P greater than 0.05 v phase II).(ABSTRACT TRUNCATED AT 250 WORDS)

Altitude retinopathy on Mount Everest, 1989

The authors studied prospectively the incidence of and risk factors for high altitude retinal hemorrhages among 14 members of the 1989 American Everest Expedition. All subjects had comprehensive eye examinations and fundus photography performed at sea level before the expedition and again at the Mt. Everest Base Camp after 6 weeks of exposure to altitudes between 5300 and 8200 meters. Asymptomatic intraretinal hemorrhages were found in five eyes of four climbers. An additional eye of one of these climbers had a central retinal vein occlusion with vitreous hemorrhage, which reduced visual acuity to counting fingers. Higher baseline intraocular pressure and use of nonsteroidal anti-inflammatory drugs were found to be significant risk factors for development of altitude retinopathy.

Consumption of a dehydrated ration for 31 days at moderate altitudes: energy intakes and physical performance

Energy intake, body weight, maximal work capacity, and measures of muscle strength and endurance were obtained from eight men who consumed a high-carbohydrate (CHO) dehydrated ration during a 31-day period of high activity at moderate altitudes. Data were collected 2 months before exposure to moderate altitudes (PRE), multiple times during the month's expedition at moderate altitudes (ALT), and after return from the expedition (RET). Work capacity per kilogram of body weight increased significantly from the PRE phase to the ALT phase. Mean energy intake averaged 2,354 +/- 71, 3,430 +/- 79, and 3,384 +/- 117 kcal/day during PRE, ALT, and RET, respectively; mean CHO intake during ALT was 595 +/- 13 g/day. Mean weight loss and reduction in body fat were significant: 1.9 +/- 0.9 kg and 18.9 +/- 10.1%, respectively. Energy deficits calculated from changes in body weight and composition during ALT ranged from 473 to 963 kcal/day, whereas the energy deficit estimated from the Harris-Benedict equation was only 194 kcal/day. The rigorous physical activity and exposure to moderate altitudes necessitated a high energy intake, approximating 3,800 kcal/day. The results indicate that physical performance and nutritional status are maintained when a high-CHO diet, consisting primarily of commercially available dehydrated foods, is consumed over a 31-day period of rigorous activity. However, weight loss and gastrointestinal distress were noted. These events might be minimized when a dehydrated ration is consumed, if dietary fat is substituted for some of the CHO.

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)

Extremely low serum pyridoxal 5'-phosphate in children with familial hypophosphatemic rickets

The apparent vitamin B-6 status of 31 children with familial hypophosphatemic rickets (FHR) was determined. All children had alkaline phosphatase activity that was high-normal to elevated for their ages. A sensitive assay for pyridoxal 5'-phosphate (PLP) indicated that 15 of the 31 children had an undetectable (less than 0.2 nmol/L) concentration of the vitamer--the lowest values yet reported in human serum. The 16 remaining children had concentrations of the vitamer so low that they indicated a potential severe vitamin B-6 deficiency. However, none of the children had ever presented with any of the classical vitamin B-6-deficiency symptoms. Treatment of three additional FHR children with 100 mg pyridoxine.HCl/d resulted in a moderate and transient elevation of their serum PLP concentrations, a dramatic elevation of their erythrocyte PLP concentrations, and no improvement in clinical condition. Serum or plasma PLP concentrations are an inappropriate index for determining vitamin B-6 status in people with FHR and perhaps in others with elevated alkaline phosphatase activity.