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Biomedical subjects

R W Ryder

Publications and source records attributed to R W Ryder.

At least 73 records · Page 4Linked to original sources
PubMed1986

Age-related rate of seropositivity of antibody to Giardia lamblia in four diverse populations.

We used a solid-phase enzyme immunoassay to determine the age-specific rates of acquisition of antibody to Giardia lamblia in populations living in an inner city area of Baltimore, Md., on an Apache Indian reservation in Arizona, in a rural area of Panama, and in an urban area of Peru (Lima). Antibody to G. lamblia was found in a portion of the adults living in all of the study areas. Similar prevalence rates and quantitative levels of antibody were found in the adults living in Arizona (44%), Panama (48%), and Peru (46%). However, a significantly lower (P less than 0.05) percentage of the adults living in Baltimore (18%) displayed serological evidence of infection. Different patterns of age-associated acquisition of antibody were noted in the study populations. In the United States, children living in Baltimore had low levels of seropositivity throughout childhood, whereas children living on the Arizona Indian reservation showed a progressive acquisition of antibody early in childhood, with adult levels achieved by 8 years of age. In Latin America, children living in Panama attained adult levels of seropositivity between 9 and 20 years of age, whereas children in Peru displayed adult levels of seropositivity in the first 6 months of life. Our findings documented the widespread occurrence of G. lamblia infections in diverse populations. Children living in different areas and under different environmental conditions displayed widely differing rates of acquisition of antibody to G. lamblia, possibly resulting from different levels of sanitation, water contamination, and person-to-person contact. Our studies indicate that quantitative solid-phase immunoassays can be used to study the epidemiology of parasitic infections such as those caused by G. lamblia.

Adolescent↗
PubMed1985

Evidence of immunity induced by naturally acquired rotavirus and Norwalk virus infection on two remote Panamanian islands.

For better understanding of the role of humoral immunity in ameliorating infections with rotavirus (RV) and Norwalk virus (NW), 305 Cuna Indians living on two isolated islands located off Panama's Carribean coast were surveyed daily for diarrhea over a seven-month period. Nine (8%) of 108 persons with a baseline RV antibody titer of greater than 1:4 developed RV infection compared with 70 (46%) of 151 persons with a baseline RV antibody titer of less than 1:4 (P less than .001). Thirty-eight (25%) of 151 persons of all ages with baseline RV antibody titer of less than 1:4 had at least one episode of RV diarrhea compared with 6 (6%) of 108 persons who had baseline RV antibody titers of greater than 1:4 (P less than .001). Thirty-two (47%) of 68 persons of all ages who had a baseline NW antibody titer of less than 1:100 developed NW infection compared with 30 (13%) of 237 persons with a baseline NW titer of greater than 1:100 (P less than .001). The high NW and RV infection rates and the excellent levels of protection provided by specific preexisting humoral antibody to these agents should promote activities aimed at developing vaccines for preventing these infections.

Age Factors↗
PubMed1985

Risk factors for fatal childhood diarrhea: a case-control study from two remote Panamanian islands.

Between September 1979 and March 1980, distinguishing features between fatal and nonfatal cases of diarrhea caused by the same etiologic agents were sought in a case-control investigation of Cuna Indian children living on the San Blas Islands located off Panama's Caribbean coast. The eight fatal cases of diarrhea (four associated with rotavirus, one with Giardia lamblia, and three without identifiable pathogens), which occurred in a cohort of 186 children aged less than five years who were followed for seven months, were matched with 24 contemporaneously occurring nonfatal cases of diarrhea. Weight-for-length measurements falling below the 90th percentile of the reference standard, reliance on traditional rather than equally as available Western medicine, and failure to receive oral rehydration solution were significantly more common among fatal than nonfatal cases. Incorporating traditional medicine men with their long-standing village-wide authority into expanded community health education programs that emphasize the importance of early treatment of diarrhea with oral rehydration solution would probably reduce mortality associated with diarrheal illness in this population.

Child, Preschool↗
PubMed1985

The childhood health effects of an improved water supply system on a remote Panamanian island.

The incidence of diarrhea, respiratory disease, and skin infections was prospectively determined after the introduction of a system which distributed unlimited quantities of high quality fresh water to each of the 150 housing units on Tupile, an island devoid of fresh water located off Panama's Caribbean coast and inhabited by 1,500 Cuna Indians. Tupile residents used 7.1 liters of water/person/day compared to the 2.3 usage rate of inhabitants on Achutupo, the control island. Despite ready availability of water in each household, Tupile residents continued to store water in contaminated vessels prior to use. Forty percent of stored water samples tested on Tupile and 45% on Achutupo were contaminated with E. coli organisms. There were 4.7 episodes/child year (E/Y) of acute diarrhea on Tupile compared with the 3.5 rate on Achutupo. The rotavirus infection rate on Tupile was 0.8 E/Y compared with 0.2 E/Y on Achutupo. Infection rates for Norwalk virus, respiratory syncytial virus and Coxsackie B 1-6 viruses were similar on both islands. Respiratory disease rates were high on both islands (2.2 E/Y on Tupile, 2.7 E/Y on Achutupo). Achutupo had much higher rates of impetigo and scabies (0.6 E/Y and 2.5 E/Y, respectively) than Tupile (0.2 E/Y and 1.4 E/Y). Provision of the water distribution system had a beneficial effect on the incidence of water-washed diseases (impetigo and scabies), but at best had no effect on diarrheal disease.

Child↗
PubMed1984

Screening for hepatitis B virus markers is not justified in West African transfusion centres.

62 severely anaemic Gambian children who were transfused with whole blood not screened for hepatitis B surface antigen (HBsAg) were followed for evidence of hepatitis B virus (HBV) infection over six months. 89% of donors and 44% of recipients before their transfusion had at least one HBV marker. Of the 54 recipient children surviving for the follow-up period, only 1 had a transient rise in liver enzymes. In 13 (37%) of 35 previously uninfected children HBV infection developed within twelve weeks of transfusion. Only 1 of these 13 children followed up at one year had become a persistent HBsAg carrier. The rate at which this cohort acquired persistent HBV infection or clinically important hepatitis was no greater than that in a cohort of similarly aged, nontransfused, children not admitted to hospital. In sub-Saharan Black Africa, where 15% of children have persistent HBV infection by the age of 10 years, HBV screening programmes in transfusion centres cannot at present be justified.

Child↗
PubMed1984

An enzyme-linked immunosorbent procedure for assaying aflatoxin B1.

A polyclonal rabbit antibody preparation against aflatoxin B1 (AFB1), produced by immunization with a bovine serum albumin-AFB1 conjugate, has been used to develop an enzyme-linked immunosorbent assay (ELISA). AFB1-ovalbumin, obtained by reacting either AFB1-8,9-dichloride or -8,9-dibromide with ovalbumin, was used to coat each well of a polyvinyl microtitre dish. Rabbit antibody, diluted 1:100 000, was added to each well and left to attach for 90 min, then the excess was washed off with phosphate-buffered saline/Tween. Anti-rabbit IgG coupled to peroxidase was then added, left for 90 min and the excess washed away. Residual peroxidase activity was assayed using tetramethylbenzidine as substrate; the reaction was quenched at the end of the 15-min incubation period with 2 N sulfuric acid. Inhibitor studies to assay AFB1 and related compounds in urine involved prior incubation of the diluted anti-AFB1 antibody with inhibitor for 60 min at 37 degrees C, prior to dispensing into the multi-well plates. Inhibitor studies with AFB1 showed inhibition over a concentration range of 10(-1) to 10(-5) micrograms/ml. The minimum detectable concentration was approximately 10(-5) micrograms/ml (0.032 pmol/ml). Anti-AFB1 antibody was also inhibited by iro-AFB1-DNA, one of the forms of AFB1-DNA, as well as by AFB1-guanine. Undiluted urine from normal subjects inhibited antibody binding to plates; this inhibition could be prevented by either dilution or extraction procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxin B1↗
PubMed1983

Serum antibody response to toxins A and B of Clostridium difficile.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to toxins A and B of Clostridium difficile was developed. Serum samples from 340 patients were tested for determination of the age-related prevalence of antitoxin. Antibody to toxin A was present in 64% of patients more than two years old and antibody to toxin B in 66% of patients more than six months old. A strongly positive ELISA value correlated with the presence of cytotoxicity-neutralizing antibody (P less than 0.001). Strongly positive ELISA values were obtained more commonly in convalescent sera from 16 patients with C difficile-induced colitis than in sera from the control population (antibody to toxin A, P less than 0.05; antibody to toxin B, P less than 0.001). Testing of paired sera revealed significant increases in the titer of IgG antibody to toxin A or B. Ten of the 16 patients with colitis had IgM titers of greater than or equal to 1:160 to one or both toxins. The data presented suggest that antibodies to toxins A and B are present in the majority of older children and adults and that patients with C difficile-induced disease develop serologic responses to one or both toxins.

Adolescent↗
PubMed1982

Oral rehydration therapy of infantile diarrhea: a controlled study of well-nourished children hospitalized in the United States and Panama.

Although oral glucose-electrolyte solutions containing 90 mmol of sodium per liter have been widely used in the treatment of acute diarrhea among under-nourished children in the developing world, they have rarely been studied in well-nourished children. We therefore conducted a controlled randomized study among well-nourished children three months to two years who were hospitalized with acute diarrhea (52 in the United States, and 94 in Panama), to compare the efficacy of this solution with that of one containing 50 mmol of sodium per liter and with standard intravenous therapy. Oral rehydration with both solutions according to protocol was successful in 97 of 98 children (one required unscheduled intravenous therapy), and in 87 (89 per cent) no intravenous therapy was required. All of six children admitted with hypernatremia were successfully treated with oral therapy alone. We conclude that glucose-electrolyte oral solutions containing either 50 or 90 mmol of sodium per liter are effective and safe in the treatment of well-nourished children hospitalized with acute diarrhea, and that they may completely replace the intravenous fluids in the majority of such children.

Child, Preschool↗
PubMed1982

Seroepidemiology of heat-labile enterotoxigenic Escherichia coli and Norwalk virus infections in Panamanians, Canal Zone residents, Apache Indians, and United States Peace Corps volunteers.

Serum antibody titrations against the heat-labile enterotoxin (LT) of Escherichia coli were carried out on Panamanians, U.S. citizens resident in the Panama Canal Zone, Apache Indians living on the reservation in Whiteriver, Arizona, and Peace Corps volunteers before they traveled overseas. Antibody titers to Norwalk virus were also carried out on serum from Panamanian and Canal Zone residents. A high prevalence of low-titer LT antibodies was found in infants and adults from Panama, the Canal Zone, and Whiteriver. Panamanian children aged 1 to 5 years had the highest LT antibody titers. Peace Corps volunteers had a low prevalence and titer of LT antibodies. Prevalence and titer of antibodies to Norwalk virus were generally higher in Panamanians compared with Canal Zone residents of the same age. In the populations we studied, various modes of transmission and mechanisms of immunity likely explain the differences which we observed in antibody prevalence and titer to these two enteric pathogens.

Adolescent↗
PubMed1981

Travelers' diarrhea in panamanian tourists in Mexico.

To determine whether residents of developing countries are unlikely to acquire travelers' diarrhea, 64 Panamanians of widely divergent socioeconomic strata were studied during a 15-day tour through Mexico. Twenty-three (36%) tourists experienced 27 episodes of travelers' diarrhea that were caused by seven different pathogens. The most commonly identified etiologic agents were rotavirus (26%), Norwalk virus (15%), and Campylobacter fetus (11%), whereas enterotoxigenic Escherichia coli was not frequently associated with travelers' diarrhea. Acquisition of travelers' diarrhea was correlated directly with high socioeconomic status. Varying levels of immunity to enteropathogens that are endemic in Panama may explain the different isolation rates of pathogens.

Adolescent↗
PubMed1981

Traveler's diarrhea associated with rotavirus infection: analysis of virus-specific immunoglobulin classes.

An enzyme-linked immunosorbent assay for the detection of rotavirus-specific immunoglobulin G (IgG), IgM, and IgA antibodies was used in a serological study of Traveler's diarrhea. The antigenically related simian rotavirus (SA-11) was used as antigen in this study. Serum was obtained from two groups of volunteers before travel (pre-travel) and at various times after arrival at their destination (post-travel). One group consisted of 47 American Peace Corps volunteers who traveled to Honduras, and the second group consisted of 66 Panamanian travelers who visited Mexico. An association between rotavirus and Traveler's diarrhea was found in each group with 36% of American Peace Corps volunteers and 30% of Panamanians with diarrhea demonstrating a greater than or equal to 4-fold increase in rotavirus antibody titers in the post- as compared to the pre-travel specimens. While no rotavirus-specific IgM antibody was detected in any serum tested, increases in specific antibody were found in both the IgG and IgA immunoglobulin classes.

Adult↗
PubMed1980

Increase in antibiotic resistance among isolates of Salmonella in the United States, 1967-1975.

To study temporal changes in the antibiotic resistance of Salmonella in the United States, a study design similar to that of a 1967 study was used to determine the antibiotic sensitivity of 754 human nontyphoid Salmonella isolates sent to the Center for Disease Control, Atlanta, Georgia, in 1975. The frequency of resistance to one or more of the same nine antibiotics used in both studies increased significantly during the eight years in Salmonella typhimurium (40%-59%; P = 0.004), other serotypes (14%-23%; P = 0.001), and all serotypes combined (21%-31%; P < 0.001). The increase in frequency of resistance was significant for streptomycin (P = 0.022), sulfonamides (P < 0.001), ampicillin (P < 0.001), and kanamycin (P < 0.001). No chloramphenicol-resistant isolates were found in the 1967 study, whereas six isolates (0.8%) were resistant in 1975. The frequency of strains resistant to six or more antibiotics increased greatly (0.8%-5.0%; P < 0.001). These data document a continuing increase in antimicrobial resistance among Salmonella isolates.

Ampicillin↗
PubMed1980

Heat-labile enterotoxigenic Escherichia coli induced diarrhea aboard a Miami-based cruise ship.

Beginning in late December, 1975, almost one-third of the passengers on two successive cruises of a Miami-based cruise ship noted the onset of diarrheal illness while on board. A single serotype of Escherichia coli that produced heat-labile enterotoxin without producing heat-stable enterotoxin was recovered from the stool of most ill passengers cultured. Epidemiological investigation could not specifically define the mode of spread. The clinical picture presented was similar to the illness caused by enterotoxigenic E. coli that produce only heat-stable enterotoxin or that produce heat-stable and heat-labile enterotoxins.

Diarrhea↗
PubMed1980

Necrotizing enterocolitis: a prospective multicenter investigation.

Several pre- and post-natal factors possibly important in determining which infants will develop necrotizing enterocolitis (NEC) and which of these infants will die with this disease were prospectively studied in 1976 in 11 infants with radiographic or pathologic evidence of the disease from 12 institutions in the United States and 111 weight-matched, institution-matched control infants. By multivariant discriminant analysis, the authors idenfitied 10 independent significant determinants of NEC and 10 determinants predictive of a fatal outcome among case infants. Determinants of NEC were: Apgar score deterioration; presence of a patent ductus arteriosus; maternal receipt of anesthesia during delivery; infant not treated with parenteral gentamicin before the onset of disease; infant receipt of 10% dextrose solution; treatment of mother with antibiotics during pregnancy; hyperalimentation or gavage feedings; premature rupture of membranes. Important morbid events among cases included red blood cell transfusions, gas in the portal system, premature rupture of membranes, abdominal distension, isolation of Klebsiella organisms from the blood, surgery, prolonged perinatal oxygen requirement, and lower Apgar 2 score. Attempts to modify preventable risk factors may decrease the incidence (2.4 cases per 1000 live births) and case fatality (41%) documented in this study.

Anesthesia, Obstetrical↗
PubMed1979

Evidence for enterotoxin production by a classic enteropathogenic serotype of Escherichia coli.

Isolates of classic enteropathogenic Escherichia coli O:128 that had been implicated in an outbreak of diarrhea in a hospital nursery were found to produce heat-stable enterotoxin after storage for six years. This finding indicated that enteropathogenicity and the ability to produce enterotoxin may coincide in E. coli, and further study of enteropathogenic strains that produce enterotoxin may help in elucidation of the relationship between enteropathogenic and enterotoxigenic E. coli.

Diarrhea, Infantile↗
PubMed1978

Prevalence of antibody to the Norwalk agent by a newly developed immune adherence hemagglutination assay.

An immune adherence hemagglutination assay (IAHA) for the detection of antibody to the Norwalk agent of acute epidemic nonbacterial gastroenteritis was developed using as antigen virus purified from stool from an experimentally infected volunteer. The assay was sensitive and specific and was efficient for detecting Norwalk antibody seroresponses. The prevalence of Norwalk antibody in various groups in the United States was studied. Antibody to the Norwalk agent was acquired gradually, beginning slowly in childhood and accelerating in the adult period so that by the fifth decade 50% possessed antibody. This pattern of antibody acquisition contrasted sharply with that for the human rotavirus of infantile gastroenteritis. Rotavirus antibody was acquired during early childhood by almost all individuals in the pediatric groups studied. Antibody to the Norwalk agent was also found in rural Bangladesh; in a small prevalence survey of 39 children and adults 21% possessed Norwalk IAHA antibody, whereas 95% possessed antibody to the human rotavirus.

Adolescent↗