PubMed Health⌕ Search

Biomedical subjects

R M Helm

Publications and source records attributed to R M Helm.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of immune parameters in propanil-exposed farm families.

The rice herbicide propanil induces alterations in the mouse immune system, causing significant decreases in T cell-dependent and T cell-independent antibody responses. This postemergent herbicide is used extensively in rice production in the Mississippi River delta region of the southern United States. The aerial application and airborne drift of propanil may pose health concerns to exposed farm families living adjacent to sprayed rice fields. To determine if aerial spraying of propanil increases risks of altered immune responses in families bordering rice fields, immune parameters were assessed during a 2-year study. Families living within 100 yards of rice fields were compared in a case control study to farm families whose homes exceeded 1 mile from any rice field. Blood was analyzed in adults (n = 56) and children (n = 52) at three time intervals: (1) preseason, prior to propanil application; (2) 5-7 days after aerial application of propanil to rice fields; and (3) postseason, following harvest. Exposed adults and children were compared with controls for a number of immune parameters. Total cell count and the percentage of various lymphocytes (T cells, B cells, CD4+ helper cells, and CD8+ suppressor cells) and natural killer (NK) cells, mitogen-induced cell proliferation, cytokine (IL-2+) production, and NK cell function were assessed. A comparison of immune function between exposed and nonexposed farm families showed no significant differences, possibly related to propanil exposure. However, some immune test parameters changed as a function of season rather than propanil exposure. The data indicate that individuals living next to rice fields are not at increased risk of altered immune function due to propanil exposure.

Adolescent↗
PubMed2001

Certain immune markers are not good indicators of mild to moderate biotin deficiency in rats.

To assess the effects of marginal biotin deficiency on immune function and thereby evaluate immune function as a potential marker for impaired biotin status, we investigated immune function in a rat model during progression from sufficiency to moderate biotin deficiency. As immune function indicators, we assessed the IgG response to a vaccine and the cytokine responses and relative proportions of lymphocyte subpopulations in the immunocytes in blood, spleen and thymus. Neither phenotype nor organ redistribution of lymphocytes differed between biotin-deficient and biotin-sufficient rats. Assessment of immune function by mitogen T cell proliferation, mitogen-induced interferon-gamma and interleukin-4 levels, IgG antibody responses and natural killer cell activity were not significantly different in mild to moderately biotin-deficient rats compared with biotin-sufficient controls. The absence of effects on immune function was not attributable to failure to induce biotin deficiency; the rats exhibited unequivocal evidence of biotin deficiency, including reduced hepatic biotin and impaired leucine metabolism resulting from deficiency of the biotin-dependent enzyme methylcrotonyl-CoA carboxylase. We conclude that the immune markers examined are not promising candidates as indicators of mild to moderate deficiency in humans.

Animals↗
PubMed2001

In vivo biotin supplementation at a pharmacologic dose decreases proliferation rates of human peripheral blood mononuclear cells and cytokine release.

Theoretically, vitamin supplements may either enhance or reduce protein synthesis and proliferation in peripheral blood mononuclear cells (PBMC). In the present study, we determined whether administration of a pharmacologic dose of biotin affects proliferation rates of PBMC and cytokine release. Healthy adults (n = 5) ingested 3.1 micromol biotin/d for 14 d; blood and urine were collected pre- and postsupplementation. PBMC were isolated by density gradient and incubated with the mitogen concanavalin A for up to 3 d. At timed intervals during mitogen stimulation, we measured the following: 1) cellular uptake of [(3)H]thymidine to determine proliferation rates; 2) concentrations of various cytokines released into the medium; and 3) the percentages of PBMC subsets as judged by CD surface markers. Biotin supplementation caused a significant decrease of PBMC proliferation. At 2 d after mitogen stimulation, [(3)H]thymidine uptake by postsupplementation PBMC was 66 +/- 21% of the uptake by presupplementation PBMC (P < 0.05). Similarly, concentrations of interleukin-1beta (2 d after mitogen) and interleukin-2 (1 d after mitogen) in media from postsupplementation PBMC were 65 +/- 28% and 44 +/- 23%, respectively, of those for presupplementation PBMC (P < 0.01). Percentages of PBMC subsets were not affected by 14 d of biotin supplementation. Overall, this study provides evidence that administration of pharmacologic doses of biotin for 14 d decreases PBMC proliferation and synthesis of interleukin-1beta and interleukin-2.

Administration, Oral↗
PubMed2001

Food allergy: in-vivo diagnostics including challenge.

The diagnosis of food allergy related to IgE-mediated reactions is based on the establishment of the allergic origin of the symptoms and the identification of the causal allergen or allergens. The double-blind, placebo-controlled food challenge remains the 'gold standard' for the in-vivo diagnosis of specific food allergy. Valuable information can be obtained with both in-vitro and in-vivo diagnostic procedures; however, for the accurate prediction and diagnosis of food allergy, these methods must be standardized and correlated with a standardized double-blind, placebo-controlled food challenge procedure.

Colonoscopy↗
PubMed2000

Mutational analysis of the IgE-binding epitopes of P34/Gly m Bd 30K.

BACKGROUND: Peanuts and soybeans are 2 foods that have been shown to be responsible for many atopic disorders. Because of their nutritional benefit, soybean proteins are now being used increasingly in a number of food products. Previous studies have documented multiple allergens in soybean extracts, including glycinin, beta-conglycinin, and the P34/Gly m Bd 30K protein. OBJECTIVE: Our overall goal was to identify soybean-specific allergens to begin to understand molecular and immunochemical characteristics of legume proteins. The specific aim of the current investigation was to identify the essential amino acid residues necessary for IgE binding in the 5 distinct immunodominant epitopes of P34/Gly m Bd 30K. METHODS: Serum IgE from 6 clinically sensitive soybean-allergic individuals was used to identify P34/Gly m Bd 30K in the native and single amino acid substituted peptides with use of the SPOTS peptide synthesis technique to determine critical amino acids required for IgE binding. RESULTS: The intensity of IgE binding and epitope recognition by serum IgE from the individuals varied substantially. With use of serum from 6 clinically soybean-sensitive individuals, 2 of the 5 immunodominant epitopes could be mutagenized to non-IgE binding peptides. CONCLUSIONS: Single-site amino acid substitution of the 5 immunodominant epitopes of Gly m Bd 30K with alanine revealed that IgE binding could be reduced or eliminated in epitopes 6 and 16 in the serum obtained from 6 soybean-sensitive patients.

Allergens↗
PubMed2000

Mechanisms of food allergy.

The prevalence of food allergy continues to rise, particularly in 'westernized' societies; it has been linked to the 'hygiene hypothesis' and the increased diversity of food consumption worldwide. The pathogenic mechanisms and Th1/Th2 paradigm are being closely examined with respect to the occurrence of inflammatory and injury/repair responses at different mucosal sites. Genetically modified plants as potential food sources and allergenicity are current topics of controversy.

Animals↗
PubMed2000

A soybean G2 glycinin allergen. 1. Identification and characterization.

BACKGROUND: Multiple allergens have been documented in soybean extracts. IgE from individuals allergic to soybeans, but not to peanut, was shown by immunoblot analysis to bind to proteins with a molecular weight of approximately 21 kD. These findings suggested that unique proteins in soybeans might be responsible for soybean allergic reactivity. The objective of the present study was to identify unique proteins in soybean extracts that bind to specific IgE from soybean-sensitive individuals, and to characterize the allergen using physicochemical methods and IgE binding. METHODS: Two-dimensional and preparative SDS-PAGE/IgE immunoblot analysis was used to identify a 22-kD soybean-specific allergen from crude soybean extracts. N-terminal sequence analysis was used to determine the identification of the protein binding IgE from soybean-sensitive individuals. RESULTS: IgE immunoblot and amino acid sequence analysis identified the 22-kD protein as a member of the G2 glycinin soybean protein family. Further investigation revealed that the IgEs reacted with basic chains from each member of the glycinin family of soybean storage proteins. CONCLUSIONS: Each of the subunits from glycinin, the storage protein that is the most prevalent component of soybean, are major allergens.

Allergens↗
PubMed2000

A soybean G2 glycinin allergen. 2. Epitope mapping and three-dimensional modeling.

BACKGROUND: Multiple allergens have been documented in soybean extracts. IgE from individuals allergic to soybeans, but not to peanut, has been shown by immunoblot analysis to bind to proteins with a molecular weight of approximately 22 kD. These findings suggested that this unique protein fraction from soybean might be responsible, in part, for soybean allergic reactivity. The objective of the present study was to characterize specific B cell epitopes, to determine if any amino acid was critical to IgE binding and to model the 22-kD G2 soybean allergen to the three-dimensional (3-D) phaseolin molecule. METHODS: B cell epitopes were identified using SPOTs peptide analysis. Structural orientation of the IgE-binding regions was mapped to the 3-D phaseolin molecule using molecular modeling of the protein tertiary structure. RESULTS: Eleven linear epitopes, representing 15 amino acid peptide sequences, bound to IgE in the glycinin molecule. These epitopes were predicted to be distributed asymmetrically on the surface of G2 trimers. CONCLUSIONS: Only 1 epitope could be rendered non-IgE binding by alanine substitutions in the peptide. The nonrandom distribution of the IgE binding sites provides new insight into their organization in trimers in 11S complexes of the G2 glycinin allergen.

Alanine↗
PubMed1999

Common allergens in avian meats.

BACKGROUND: Reports of allergy to bird meats are uncommon, and most have been in patients with "bird-egg syndrome." OBJECTIVE: We sought to evaluate 3 patients who reported allergic reactions to several avian meats, but who denied allergic reactions to eating eggs. The patients required yellow fever vaccine for entry into the military. METHODS: Patients were skin tested with commercial extracts of chicken, turkey, and egg, as well as with crude extracts made from dove and quail meat, and with yellow fever vaccine. Immunoblots for IgE antibody were performed by using the same materials used for skin testing plus extracts of duck and goose meat. RESULTS: Skin tests were positive in all 3 patients to chicken, turkey, dove, quail, and yellow fever vaccine and negative to egg. This included some positive skin test responses to bird meats the patients denied ever having eaten. The vaccine was administered in graded doses. Immunoblots revealed IgE binding to several proteins of similar molecular weights in all of the avian meats but not to egg or yellow fever vaccine. Again, this included IgE antibody to some bird meats the patients denied ever having eaten. CONCLUSION: Patients allergic to one bird meat may be allergic to others, including game birds, probably because of cross-reacting allergens. Such patients may have to exercise caution even when eating bird meats they have not previously ingested. The relationship of this allergy to yellow fever vaccine, if any, remains to be determined.

Adolescent↗
PubMed1997

Identification and mutational analysis of the immunodominant IgE binding epitopes of the major peanut allergen Ara h 2.

A major peanut allergen, Ara h 2, is recognized by serum IgE from > 90% of patients with peanut hypersensitivity. Biochemical characterization of this allergen indicates that it is a glycoprotein of approximately 17.5 kDa. Using N-terminal amino acid sequence data from purified Ara h 2, oligonucleotide primers were synthesized and used to identify a clone (741 bp) from a peanut cDNA library. This clone was capable of encoding a 17.5-kDa protein with homology to the conglutin family of seed storage proteins. The major linear immunoglobulin E (IgE)-binding epitopes of this allergen were mapped using overlapping peptides synthesized on an activated cellulose membrane and pooled serum IgE from 15 peanut-sensitive patients. Ten IgE-binding epitopes were identified, distributed throughout the length of the Ara h 2 protein. Sixty-three percent of the amino acids represented in the epitopes were either polar uncharged or apolar residues. In an effort to determine which, if any, of the 10 epitopes were recognized by the majority of patients with peanut hypersensitivity, each set of 10 peptides was probed individually with serum IgE from 10 different patients. All of the patient sera tested recognized multiple epitopes. Three epitopes (aa27-36, aa57-66, and aa65-74) were recognized by all patients tested. In addition, these three peptides bound more IgE than all the other epitopes combined, indicating that they are the immunodominant epitopes of the Ara h 2 protein. Mutational analysis of the Ara h 2 epitopes indicate that single amino acid changes result in loss of IgE binding. Two epitopes in region aa57-74 contained the amino acid sequence DPYSP that appears to be necessary for IgE binding. These results may allow for the design of improved diagnostic and therapeutic approaches to peanut hypersensitivity.

2S Albumins, Plant↗
PubMed1997

Mapping and mutational analysis of the IgE-binding epitopes on Ara h 1, a legume vicilin protein and a major allergen in peanut hypersensitivity.

Peanut allergy is a significant health problem because of the prevelance and potential severity of the allergic reaction. Serum IgE from patients with documented peanut hypersensitivity reactions and overlapping peptides were used to identify the IgE-binding epitopes on the major peanut allergen, Ara h 1. At least twenty-three different linear IgE-binding epitopes, located throughout the length of the Ara h 1 protein, were identified. All of the epitopes were 6-10 amino acids in length, but there was no obvious sequence motif shared by all peptides. Four of the peptides appeared to be immunodominant IgE-binding epitopes in that they were recognized by serum from more than 80% of the patients tested and bound more IgE than any of the other Ara h 1 epitopes. Mutational analysis of the immunodominant epitopes revealed that single amino acid changes within these peptides had dramatic effects on IgE-binding characteristics. The identification and determination of the IgE-binding capabilities of core amino acids in epitopes on the Ara h 1 protein will make it possible to address the pathophysiologic and immunologic mechanisms regarding peanut hypersensitivity reactions specifically and food hypersensitivity in general.

Adult↗
PubMed1997

Wheat alpha-amylase inhibitor: a second route of allergic sensitization.

BACKGROUND: Low molecular weight allergens may be responsible for hypersensitivity reactions after the ingestion of wheat. OBJECTIVE: The purpose of this investigation was to identify relevant, low molecular weight allergens after the ingestion of wheat protein. METHODS: Serum samples were collected from seven children with wheat allergy and one adult with baker's asthma. Control serum samples were collected from wheat-tolerant patients. Wheat extracts were prepared and separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in 12.5% gels revealing numerous protein bands. IgE immunoblot analysis of crude wheat extracts identified multiple IgE-binding proteins. Wheat proteins were separated further with two-dimensional gel electrophoresis, which was followed by IgE immunoblotting investigations. RESULTS: Immunoblot analysis identified a 15 kd wheat protein that bound IgE from all five children with wheat allergy who were evaluated. No IgE binding to this wheat protein was demonstrated in any of the control subjects. Samples representing the 15 kd wheat protein (isoelective point, 5.85) were selected. The N-terminal peptide sequence of this protein (residues 1 to 20) matched to a wheat alpha-amylase inhibitor. CONCLUSION: These data demonstrate that wheat alpha-amylase inhibitor is a relevant allergen in patients experiencing hypersensitivity reactions after the ingestion of wheat protein. This wheat protein, which has been implicated as an important allergen in patients with baker's asthma, represents a sensitizing allergen after both ingestion and inhalation.

Adolescent↗
PubMed1997

Immune and clinical impact of Lactobacillus acidophilus on asthma.

BACKGROUND: Animal and human studies have suggested that yogurt containing live active bacteria leads to improved immune and clinical responses. Specific benefits of yogurt containing L. acidophilus on allergic asthma have been hypothesized but not studied. METHODS: In a crossover double-blinded design, the effect of live active yogurt (225 g twice daily) with or without L. acidophilus was studied in 15 adult patients with moderate asthma. Immune and clinical parameters were measured before and after the two 1-month crossover phases. RESULTS: No significant changes were noted in peripheral cell counts, IgE, IL-2, or IL-4 when comparing the two diets to each other. Concanvalin A-stimulated lymphocytes from patients who consumed yogurt containing L. acidophilus produced borderline elevated interferon gamma levels (P = .054). No differences were noted in mean daily peak flows or changes in spirometric values. Quality of life indices were unchanged when comparing the two groups. CONCLUSIONS: Yogurt containing L. acidophilus generated trends in the increase in interferon gamma and decreased eosinophilia; however, we were unable to detect changes in clinical parameters in asthma patients in association with these modest immune changes.

Adolescent↗
PubMed1997

Comparison of pediatric and adult IgE antibody binding to fish proteins.

BACKGROUND: Allergic reactions to fish are a common cause of food allergy. OBJECTIVE: We compared the binding of pediatric and adult fish-allergic patient IgE antibodies to fish proteins. METHODS: Clinical histories of fish allergy were confirmed by prick skin tests, RAST and if possible, with blinded oral food challenges. The patients included five children with severe allergic reactions to catfish (4/5), cod (1/5), and tuna (1/5) and five adults with severe allergic reactions to catfish (5/5), cod (2/5), snapper (3/5), and tuna (2/5). Extracted proteins from catfish, cod, snapper, and tuna were separated with SDS-PAGE. IgE immunoblots and immunoblot inhibition studies were performed using serum sample from these patients. RESULTS: Multiple fish proteins ranging from 12 to 45 kD from the four fish extracts were identified by SDS-PAGE. A major protein (12.5 kD) was present in all fish extracts except for raw tuna. Immunoblots using individual pediatric and adult serum samples revealed that the major IgE binding was to the 12.5-kD protein from catfish, cod, and snapper. The immunoblot with tuna using serum from a pediatric patient with isolated tuna anaphylaxis revealed an IgE binding protein band at 40 kD. Preincubation of serum samples from two separate fish-allergic patients with 1 mg of cod fish extract completely inhibited IgE binding to the 12.5-kD fish protein in subsequent immunoblots. CONCLUSIONS: Pediatric and adult fish-allergic patients have similar in vitro IgE binding to a 12.5-kD protein from fish extracts. This protein is immunochemically similar to Gad c I, the major allergen in cod.

Adult↗
PubMed1997

Impact of dietary yogurt on immune function.

Studies of the effects of yogurt on immunity and atopic diseases have suggested improvements in cytokine (interleukin-2 and interferon-gamma) responses and clinical scores in patients with allergic rhinitis. This study compares prospectively immune parameters of participants who received 16 oz of yogurt versus 16 oz of milk/day in a randomized cross-over design. Yogurt that contained live, active Lactobacillus bulgaricus and Streptococcus thermophilus or 2% milk was consumed for one month each. Twenty otherwise healthy adults with atopic histories documented by skin testing were enrolled. Immune studies were performed at the beginning and end of the two 1-month study phases, separated by a 2-week washout period. These studies included measurements of cellular, humoral, and phagocytic function. No adverse events were noted in either group. No significant improvements in any immune parameter were noted. The consumption of yogurt that contained the live active bacteria L bulgaricus and S thermophilus does not appear to enhance immune function in atopic individuals at the dosage and duration used in this study.

Adult↗