Ascorbic acid dynamics in the seriously ill and injured.

BACKGROUND: In addition to the known beneficial effects of ascorbic acid on wound healing and the immune response, it is also a potent extracellular antioxidant. Recent work in septic rats suggests that high-dose ascorbic acid total parenteral nutrition (TPN) supplementation may protect cells from free radical injury and improve survival. In this study, we determined ascorbic acid levels in the immediate post-injury/illness period and evaluated the ability of early short-term high levels of ascorbic acid in TPN to normalize plasma levels. MATERIALS AND METHODS: Ascorbic acid levels were determined in 12 critically injured patients and 2 patients with severe surgical infections. Each patient received TPN supplemented with increasing doses of ascorbic acid over a 6-day period. Therapeutic responses were determined by plasma and urine measurements using high-pressure liquid chromatography. RESULTS: The initial mean +/- SEM baseline plasma ascorbic acid concentration was depressed (0.11 +/- 0.03 mg/dl) and unresponsive following 2 days on 300 mg/day supplementation (0.14 +/- 0.03; P = 1.0) and only approached low normal plasma levels following 2 days on 1000 mg/day (0.32 +/- 0.08; P = 0.36). A significant increase was noted following 2 days on 3000 mg/day (1.2 +/- 0.03; P = 0.005). CONCLUSION: We confirmed extremely low plasma levels of ascorbic acid following trauma and infection. Maximal early repletion of this vitamin requires rapid pool filling early in the post-injury period using supraphysiologic doses for 3 or more days.

Gastric emptying in trauma patients.

BACKGROUND/AIM: The aim of this study was to obtain quantitative data on gastric emptying following trauma. METHODS: In order to assess gastric emptying for early enteral feeding, we evaluated the absorption of an amino acid, L-[1-(13)C]phenylalanine, within 24 h of admission and 7 days later in 14 trauma patients (injury severity score 36 +/- 2). Following nasogastric administration of 100 mg L-[1-(13)C]phenylalanine, the plasma L-[1-(13)C]phenylalanine enrichment at 30 and 60 min and the expired (13)CO(2) for 1 h in the breath were used to measure the degree of gastric emptying. RESULTS: The plasma L-[1-(13)C]phenylalanine enrichment concentration at 30 min was 0.53 +/- 0.23 mmol/l during the first study and 2.46 +/- 0. 62 mmol/l during the second study (p = 0.006, a fivefold increase). The L-[1-(13)C]phenylalanine plasma level in historic controls was 4. 57 +/- 1.48 mmol/l. The percent of the dose oxidized and expired as (13)CO(2) in 1 h was 0.51 +/- 0.17 during the first 24-hour study compared to the second study of 3.37 +/- 0.68 (p = 0.0008) 7 days later (an over sixfold increase). The percent of the dose oxidized in 1 h in 37 normal historic controls was 7.08 +/- 0.33. CONCLUSION: These data indicate delayed gastric emptying with limited recovery in 1 week. We conclude that gastric feeding should not be employed, and the route for early nutritional intervention should be transpyloric for the trauma patient.

Heparan sulfate proteoglycans mediate interleukin-7-dependent B lymphopoiesis.

Heparin/heparan sulfate proteoglycans (HSPGs) have the potential to bind and directly regulate the bioactivity of hematopoietic growth factors including interleukin-7 (IL-7), a cytokine critical for murine B-cell development. We examined the consequence of manipulating soluble heparin and cell-surface heparan sulfate to IL-7-dependent responses of B-cell precursors. Soluble heparin was found to inhibit production of lymphoid, but not myeloid, cells in long-term bone marrow cultures. Analysis of pro-B cells lacking plasma membrane HS suggests that this glycosaminoglycan is required for efficient binding and responsiveness to IL-7. By contrast, responses of hematopoietic cells to other cytokines were not influenced by heparin addition or HS removal. Therefore, HSPGs on B-lineage precursors may function as IL-7 receptor components similar to HSPGs known to be important for the bFGF receptor. Other experiments suggest that HSPGs on the surface of stromal cells provide a weakly associating docking site for IL-7, possibly controlling availability of this cytokine to B-cell precursors. Together these data demonstrate a direct role for heparinlike molecules in regulating the IL-7-dependent stages of murine B lymphopoiesis.

Cell interaction molecules utilized in bone marrow.

Many aspects of blood cell formation can now be modeled in culture and rapid progress is being made in understanding how blood cell precursors interact with unique components of their environment. This brief review considers some cell interaction molecules that may be important for controlling the position of cells within, as well as their egress from, bone marrow.

Blood cell precursors in context. Composition of the bone marrow microenvironment that supports B lymphopoiesis.

New molecular approaches are rapidly yielding information about the composition of bone marrow and culture studies suggest possible functions for many molecules in that organ. However, the marrow is extraordinarily complex with respect to interactions between cells and their behaviour may not be adequately modeled in culture. It is becoming apparent that post-translational modifications and function of proteins can be highly influenced by the cellular and extracellular environment. Therefore, in vivo studies will continue to be important for understanding this remarkable organ.

Stromal cell modulation of negative regulatory signals that influence apoptosis and proliferation of B lineage lymphocytes.

The bone marrow microenvironment influences whether a given B cell proliferates, differentiates, or undergoes apoptosis. In this report, we demonstrate that apoptosis of primary murine B lymphocyte precursors can be regulated either positively or negatively by stroma. Several stromal lines that support lymphocyte outgrowth suppressed the spontaneous apoptosis of pre-B cells by as much as 90%. Direct contact with stromal cells more effectively protected lymphocytes than did stromal cell-CM or a collection of recombinant cytokines. In contrast, one unique stromal cell clone actually induced lymphocyte apoptosis, and a second line appeared inert. A survey of adherent cell lines suggested that expression of life-sparing molecules is widespread but not ubiquitous. Experiments with neutralizing Abs to CD44, vascular cell adhesion molecule-1 (VCAM-1), CD9, intercellular adhesion molecule-1 (ICAM-1), or ICAM-2 suggested that these interaction molecules do not deliver short-term survival signals to B cell precursors. Of particular interest, direct interaction with lymphocyte-supportive stromal cells minimized the negative regulatory effects of IL-1alpha, and a glucocorticoid, but not IFN-beta or PGE2. These results demonstrate that the effect of negative regulators depends upon the context in which these signals are presented. As molecules that influence B lymphopoiesis are better defined, it will be important to consider the role of each in combination with other stimuli.

Nonprotective effects of extracellular metallothionein.

Metallothionein (MT) is a small, cysteine-rich protein that is readily induced by exposure to heavy metal cations. In previous work, we have demonstrated that MT has several significant immunomodulatory properties. MT decreases antigen-specific humoral responses in vivo and inhibits the ability of T cells to proliferate in response to antigen presented in vitro. To further characterize the mechanism by which this protein inhibits responsiveness to antigen, we have examined the effects of MT on cell viability in an antigen-presentation assay. MT (20 microM) caused substantial death to both lymphocytes and monocytes after 3 days of culture. The observed toxicity cannot be attributed to either increased superoxide radical generation or to production of tumor necrosis factor by MT-treated macrophages. Fractionation of supernatants from MT-treated cells suggests that the agent responsible for causing cytotoxicity is a soluble factor of at least 30 kDa. These results counter the perception that metallothionein uniformly plays a protective role in metal-stressed individuals.

Stress proteins as agents of immunological change: some lessons from metallothionein.

The stress response proteins each have somewhat unique characteristics that enable them to function under conditions of cellular stress, and to contribute to cellular survival in difficult times. The immune response is, by definition, a mechanism that often operates in times of cellular stress, and even creates stress during its operation. Cells called upon to respond to tissue damage caused by inflammation can have extraordinary demands placed upon them and surrounding tissue may suffer damaging conditions that were originally established to eliminate the source of the inflammation. Stress proteins may be released from some of these damaged cells as a programmed response to the stress, or as a simple consequence of excessive damage to the plasma membrane. In either instance, there is the opportunity for these stress proteins to interact with cells and proteins in the extracellular environment. It may be that those same characteristics that enable stress proteins to interact with structures within the cell also enable interactions outside the cell, but with dramatically different results. As has been found with MT, interference with these extracellular interactions may decrease the consequences of stress on the immune response, and may enable more effective immunity. It may also be possible to employ the various stress proteins to manipulate normal immune function.

Interactions of metallothionein with murine lymphocytes: plasma membrane binding and proliferation.

Metallothionein (MT) is a thiol rich protein that has been well characterized for its ability to bind and sequester heavy metal cations, free radicals and other reactive toxicants. In addition to induction by these stressors, MT gene expression is upregulated by several cytokines of the acute phase response. In previous work, we have shown that MT can alter aspects of lymphocyte function. MT alone induces modest proliferation of unfractionated splenocytes and acts synergistically with T cell- and B cell-specific mitogens. In contrast, MT inhibits humoral responsiveness in vivo and reduces in vitro T cell responses to processed antigen. In this report, we describe the effects of MT on specific lymphocyte subpopulations in order to further characterize the mechanism of MT-mediated alterations of immune activity. MT binds to the plasma membrane of both T and B lymphocytes, but, in the absence of a costimulatory agent, MT induces lymphoproliferation only in B cells. MT also enhances the capacity of naive B lymphocytes to differentiate into plasma cells. These results demonstrate differential immunomodulatory activities of MT and may explain some of the diverse immunoregulatory effects associated with exposure to environmental toxins.

Impact of enteral feeding of a glutamine-supplemented formula on the hypoaminoacidemic response in trauma patients.

Plasma amino acid concentrations were measured during fasting and after 3 days of enteral feeding in 16 trauma patients on a glutamine-supplemented diet and 14 patients on an isonitrogenous control diet. During fasting, total amino acids, including glutamine, were depressed by 50% and this was attributed to a reduction in both essential and nonessential amino acids. The essential amino acid concentrations increased in both groups after feeding. The nonessential amino acid concentrations also increased in the control group but not in the glutamine group during feeding. Repletion of the glutamine extracellular pool was not evident after an average intake of 27.1 g per day of glutamine for 3 days. Nitrogen balance was similar for the two groups during feeding. We conclude that in this study, enteral glutamine did not increase the glutamine plasma concentration. In addition, both formulas improved the hypoaminoacidemia of essential amino acids but only the control diet improved the nonessential amino acids plasma concentration.

Immunomodulatory activities of extracellular metallothionein. II. Effects on macrophage functions.

Metallothionein (MT) is a thiol-rich protein that is rapidly induced by exposure to heavy metal cations. We have previously demonstrated that exogenous MT stimulates murine splenocytes to proliferate, but inhibits humoral responses to antigen. These observations suggest that metallothionein released from cells has a complex role in heavy metal-mediated immune dysfunction. Here we examine one possible mechanism by which MT mediates suppression of humoral immunity. Exposure of macrophages to 20 microM MT did not affect their ability to engulf opsonized sheep erythrocytes, but in the presence of 20 microM MT, peritoneal macrophages were stimulated to produce increased levels of oxygen radicals. These results correlated with observations that while macrophage phagocytosis of opsonized Candida albicans was unaltered by the presence of exogenous MT, killing of the engulfed yeast cells was dramatically enhanced by 20 microM MT. Amounts of free cadmium and zinc equimolar to that added as Zn,Cd-MT had no effect on candidacidal activity. MT was also found to significantly decrease lymphocyte proliferation mediated by macrophage activity. Biotinylated MT (MT-b) bound specifically to the plasma membranes of these macrophages, suggesting that membrane-associated molecules of the macrophage may transduce a signal mediated by MT binding. These results demonstrate that macrophages are a sensitive target for MT-mediated immunomodulation and that some of the consequences of the MT interaction with macrophages may be alterations in the capacity to produce an effective immune response and increased extracellular exposure to damaging free radicals.

[Indicators of atherosclerosis risk. Evaluation with coronary angiography in non diabetic men with total cholesterol levels equal to or below 240 mg/dl]. / Indicadores de riesgo de ateroesclerosis. Evaluación mediante coronariografía en hombres no diabéticos con colesterol total igual o menor a 240 mg/dl.

We studied 90 male non diabetic patients aged between 40 and 65 years old with a total cholesterol of less than 240 mg/dl and not receiving cholesterol reducing drugs, that were subjected to elective coronary arteriography. Weight, height, blood pressure and smoking habits were recorded and a fasting blood sample was drawn to measure total and HDL cholesterol, triglycerides, apoproteins A1 and B, Lipoprotein(a) and plasma cholesteryl ester transfer activity. Arteriography disclosed coronary lesions in 54 patients. Compared to patients without lesions, the former had lower HDL cholesterol (34 +/- 9.8 vs 40.2 +/- 11.6 mg/dl) and higher total cholesterol/HDL cholesterol and apoB/apoA1 ratios. No differences were found for lipoprotein(a) and plasma cholesteryl ester transfer activity. Univariate analysis showed that low HDL cholesterol had the best predictive capacity for atherosclerosis.

Indicadores de riesgo de aterosclerosis: evaluación mediante coronariografía en hombres no diabéticos con colesterol total igual o menor a 240 mg/dl / Index of atherosclerosis risk: evaluation by coronariography in non diabetic males with total cholesterol same or less than 240 mg/dl

We studied 90 male non diabetic patients aged between 40 and 65 years old with a total cholesterol of less than 240 mg/dl and not receiving cholesterol reducing drugs, that were subjected to elective coronary arteriography. Weight, height, blood pressure and smoking habits were recorded and a fsting blood sample was drawn to mesure total and HDL cholesterol, triglycerides, apoproteins A! and B, Lipoprotein(a) and plasma cholesteryl ester transfer activity. Arteriography disclosed coronary lesions in 54 patients. Compared to patients without lesions, the former had lower HDL cholesterol (34 ñ 9.8 vs 40.2 ñ 11.6 mg/dl) and higher total cholesterol/HDL, cholesterol and apoB/apoA1 ratios. No differences were found for lipoprotein(a) and plasma cholesteryl ester transfer activity. Unvariate analysis showed that low HDL cholesterol had the best predictive capacity for atherosclerosis

Immunomodulatory activities of extracellular metallothionein. I. Metallothionein effects on antibody production.

Extracellular metallothionein (Zn,Cd-MT) has previously been shown to be a potent inducer of lymphocyte proliferation and to synergize with polyclonal activators in proliferation assays. In this report, the effects of metallothionein on the development of humoral responsiveness are examined. In vivo, the specific anti-ovalbumin (OVA) IgG response was diminished by co-injection of Zn, Cd-MT, while total IgG levels remained unchanged. A similar reduction was also observed when Zn,Cd-MT was administered during the development of an anti-sheep red blood cell (sRBC) humoral response. When amounts of Zn and Cd equimolar to that associated with the Zn, Cd-MT were co-injected with OVA, humoral responsiveness was enhanced, in contrast to the suppression seen with Zn, Cd-MT. Apothionein lacking the available thiols associated with native Zn, Cd-MT had no effect on the development of humoral immunity. These results point to the thiols associated with the protein as the important determinants in the observed immunosuppression and this is supported by the capacity of UC1MT, a new monoclonal anti-MT antibody, to reverse MT mediated immunosuppression. No evidence was found to suggest that Zn,Cd-MT was interacting directly with OVA. Finally, in vitro experiments with LPS-stimulated splenocyte production of IgM correlated with the in vivo observations of Zn,Cd-MT. These data provide evidence for a significant role for MT in the development of metal-mediated immunomodulation and suggest that MT may also possess immunomodulatory functions under circumstances where MT is synthesized in the absence of heavy metal stress. Furthermore, it may be possible to take advantage of this system to exogenously manipulate the development of the immune response.

Parenteral nutrition in hyperemesis gravidarum.

Hyperemesis gravidarum (HG) is a clinical condition that threatens fetal viability and even the mother's life when the severity of symptoms almost completely prevents the intake of food. Parenteral nutrition (PN) is a possible alternative. We present eight patients with HG. There were 10 PN treatments because two of the patients required the treatment twice. There were 9 central venous and 1 peripheral treatment delivery. The average age of the patients was 27.5 yr. Gestational ages varied from 8 to 19 wk. PN treatments were formulated as amino acid and glucose solutions (fat emulsions in 2 of the 8 cases) blended with vitamins and electrolytes. These treatments lasted 5-16 days. Before PN deliveries were initiated, five of the patients presented some degree of protein-calorie and/or visceral protein malnutrition. All of them showed minor liver dysfunction, which did not change during PN. Newborns were term deliveries, except for one case of missed abortion. Results show that PN constitutes a therapeutic alternative in cases of HG that do not respond to the standard treatment of parenteral hydration and antiemetics. In fact, symptoms disappear promptly, and no significant complications arise.

Gasto energético basal: variabilidad inter e intraindividual / Basal energy output: interindividual and intraindividual variability

La variabilidad intraindividual VI en el gasto energético basal medio GEM por calorimetría indirecta y la exactitud de las ecuaciones de Harris y Benedict, fue evaluada en 21 voluntarios adultos sanos. Se utilizó el método de circuito abierto con bolsa de Douglas y máscara facial con períodos de recolección de 5 minutos, con intervalos de 30 minutos, durante dos horas. El promedio de GEM fue de 19,5 ñ 2,6 y 22,4 ñ 3,9 kcal/kg/día en mujeres y varones, respectivamente. La VI del GEM, expresada como coeficiente de variación, fluctuó entre 6,2 y 14,7 por ciento en mujeres y entre 8,8 y 14,4 por ciento en hombres. La variación máxima entre dos mediciones del GEM fue de 27 por ciento en ambos grupos. La adecuación de Harris y Benedict sobreestimó el GEM en un 16,9 y 9,4 por ciento en mujeres y hombres, respectivamente, mostrando una precisión de ñ 16 por ciento en hombres y ñ 12 por ciento en mujeres. Se concluye que el gasto energético medido en condiciones basales presenta una importante variabilidad intraindividual, lo que obliga a efectuar más de una medición cuando se trabaja con este método

Situación en Chile de algunos tumores del tracto gastrointestinal: consideraciones nutricionales / Gastrointestinal tumors state in Chile: nutritional factors

La importancia de los factores ambientales, especialmente los dietéticos, en la génesis de los principales cánceres del tracto gastrointestinal, es de preocupación en la actualidad. El objetivo de este estudio fue verificar la evolución de la mortalidad por cáncer gástrico, de colon y vesícula, su distribución etárea, sexo y regiones geográficas, como primera etapa en la identificación de factores nutricionales que pudieran determinar estos tumores en población chilena. Con la información oficial se construyeron series temporales desde 1977 hasta 1989 y se compararon diferencias regionales entre las tasas del último trienio de la década de los 70 y el de los 80. La tasa de mortalidad por cáncer gástrico disminuyó hasta 1986, manteniéndose estable desde entonces. Es más prevalente en el sexo masculino, en los mayores de 45 años y en las regiones de mayor producción agrícola. El cáncer de colon ha mantenido tasas prácticamente constantes durante el período observado, tiene mayores tasas de mortalidad en mujeres, especialmente sobre los 65 años. Su distribución geográfica es homogénea, con excepción de las Regiones de Valparaíso y Magallanes que presentan mayores tasas. Las tasas de mortalidad por cáncer de vesícula ha presentado un aumento en el tiempo, es mayor en el sexo femenino y en los mayores de 65 años. Se ha verificado un aumento mayor de sus tasas en las mismas regiones donde el cáncer gástrico tiene mayor mortalidad. Se proponen hipótesis nutricionales sobre estas diferencias y se sugieren líneas de investigaciones futuras

[The effect of body weight change on cardiovascular risk factors]. / Efecto del cambio de peso corporal sobre los factores de riesgo cardiovascular.

Changes in cardiovascular risk factors and body weight were correlated in 568 professional males from 17 to 57 years of age. Measurements of weight, height, body mass index, blood pressure and fasting levels of blood sugar, triglycerides, total and HDL cholesterol were obtained in 1980 and again in 1985. A significant correlation was found between body mass index and blood pressure, total cholesterol, total/HDL cholesterol, HDL cholesterol (p < 0.005), triglycerides (p < 0.001) and blood sugar (p < 0.05). Changes in body weight during the study period were correlated to changes in total cholesterol (p < 0.001), triglycerides (p < 0.05) and diastolic blood pressure (p < 0.005). Thus, obesity is correlated to the presence of cardiovascular risk factors. Its modification may influence development of atherosclerotic cardiovascular disease.