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L Cisneros

Publications and source records attributed to L Cisneros.

12 recordsLinked to original sources
PubMed2002

Information transfer and nontrivial collective behavior in chaotic coupled map networks.

The emergence of nontrivial collective behavior in networks of coupled chaotic maps is investigated by means of a nonlinear mutual prediction method. The resulting prediction error is used to measure the amount of information that a local unit possesses about the collective dynamics. Applications to locally and globally coupled map systems are considered. The prediction error exhibits phase transitions at critical values of the coupling for the onset of ordered collective behavior in these networks. This information measure may be used as an order parameter for the characterization of complex behavior in extended chaotic systems.

Journal Article↗
PubMed1985

Case-control study to identify risk factors for paediatric endemic typhoid fever in Santiago, Chile.

Typhoid fever is an important endemic health problem in Santiago, Chile. Its incidence has more than doubled in recent years, during which access to potable water and sewage disposal in the home became almost universal in the city. A matched case-control study was carried out to identify risk factors and vehicles of transmission of paediatric typhoid fever; 81 children in the 3-14-years age group with typhoid fever were compared with controls, matched with respect to age, sex, and neighbourhood. It was found that case children more frequently bought lunch at school and shared food with classmates. Also, case children more often consumed flavoured ices bought outside the home; none of 41 other food items considered in the study was associated with a higher risk of typhoid fever. Only two food handlers for cases and one for controls were positive for Salmonella typhi, indicating that persons preparing food solely for their own family were not the main source of S. typhi infection. Rather, the risk factors identified in this study are consistent with the hypothesis that paediatric endemic typhoid fever in Santiago is largely spread by consumption of food-stuffs that are prepared outside the individual's home and are shared with or sold to children.

Adolescent↗
PubMed1982

The pathogenicity of nonenterotoxigenic Vibrio cholerae serogroup O1 biotype El Tor isolated from sewage water in Brazil.

Nonenterotoxigenic strains no. 1196-78 and no. 1074-78 of Vibrio cholerae serogroup O1 (biotype El Tor, serotype Ogawa) were isolated from sewage water in Brazil and fed to 20 volunteers. Neither strain caused diarrhea. None of the seven volunteers who ingested Ogawa strain no. 1074-78 (10(6) organisms) excreted the organism whereas eight of the 13 volunteers who ingested Ogawa strain no. 1196-78 (10(6) or 10(8) organisms) did excrete the organism in their stools. None of 114 stool-culture isolates yielded cholera enterotoxin, and none of the 20 volunteers had significant increases in serum titers of antitoxin as measured by enzyme-linked immunosorbent assay although six of the volunteers had slightly elevated vibriocidal antibody levels. Six volunteers used as controls and four volunteers who had stool cultures positive for strain no. 1196-78 of V. cholerae were challenged with pathogenic El Tor Ogawa strain no. E7946 (10(6) organisms) to determine if previous ingestion of the Brazilian strain would induce protective immunity. All 10 of the volunteers developed diarrhea, and the severity of the illness was similar in both groups.

Adult↗
PubMed1982

Evaluation of a phenotypic revertant of the A/Alaska/77-ts-1A2 reassortant virus in hamsters and in seronegative adult volunteers: further evidence that the temperature-sensitive phenotype is responsible for attenuation of ts-1A2 reassortant viruses.

In a previous study, a seronegative child to whom attenuated A/Alaska/77-ts-1A2 virus was administered (37 degrees C shutoff temperature for plaque formation) shed virus with an altered temperature-sensitive (ts) phenotype (40 degrees C shutoff temperature) (Murphy et al., Ann. N.Y. Acad. Sci. 354:172-182, 1980; Tolpin et al., Virology 112:505-517, 1981). This ts+ virus (FV1319) was evaluated for its level of replication in hamsters and for its virulence for humans. In hamsters, FV1319 ts+ virus replicated to the same level in the nasal turbinates as that of which the A/Alaska/77 wild-type virus replicated, but its replication in the lungs was reduced 40-fold. In contrast, the A/Alaska/77-ts-1A2 reassortant achieved a titer in hamster nasal turbinates that was significantly lower (P less than 0.005) than those achieved by the wild-type and the FV1319 viruses; the A/Alaska/77-ts-1A2 reassortant was not recoverable from the lungs. In seronegative adult volunteers, the pattern of replication of the FV1319 virus was similar to that of the A/Alaska/77 wild-type virus. The illness induced by the FV1319 ts+ virus was also similar to that caused by the wild-type virus. In contrast, the A/Alaska/77-ts-1A2 reassortant was satisfactorily attenuated in adult volunteers. These results suggest that attenuation of the A/Alaska/77-ts-1A2 reassortant virus in humans is a function of the ts phenotype: loss of this phenotype restored virulence. The ability of the A/Alaska/77-ts-1A2 reassortant to lose its ts phenotype and regain virulence during growth in a permissive host limits the usefulness of the ts-1A2 reassortants as vaccine viruses for humans.

Animals↗
PubMed1981

Duration of infection-derived immunity to cholera.

Four volunteers were rechallenged with Vibrio cholerae (10(6) classical Ogawa 395 organisms) 33-36 months after their initial induced cholera infection; none of the four veterans and four of five control volunteers developed diarrhea (P = 0.04). All control subjects, but only one veteran, had positive coprocultures. Three of the four veterans had significant levels of serum IgG antitoxin before challenge, but none had measurable intestinal levels of secretory IgA antitoxin. Significant rises in levels of serum vibriocidal and antitoxic antibody occurred in all control subjects and in two veterans, who also manifested rises in levels of intestinal secretory IgA antitoxin. The impressive duration of infection-derived immunity suggests that the most promising approach to development of cholera vaccines may be to mimic natural immunity with orally administered, attenuated strains of V. cholerae.

Antibodies, Bacterial↗
PubMed1980

Lack of person-to-person transmission of enterotoxigenic Escherichia coli despite close contact.

The scanty epidemiologic evidence available suggests that enterotoxigenic Escherichia coli (ETEC) are usually spread by contaminated food and water vehicles; little is known of the risk of secondary spread by contact transmission. Studies carried out in a 22-bed isolation Ward at the U. of Maryland Hospital gave the opportunity to determine whether individuals excreting ETEC, with and without diarrhea, would transmit the pathogen to controls living in close contact. In one combined study, seven volunteers who had ingested 10(8) virulent ETEC (strain H10407), were housed day and night for two weeks with eight other volunterrs participating in an intranasal attenuated influenza vaccine study. In a second study, four persons ingesting 10(8) ETEC (strain 214-4) lived with 13 who were inoculated with intranasal influenza vaccine. The individuals in the E. coli and influenza groups were randomly mixed in bedrooms and shared bathrooms, dining and recreation areas of the ward. Seven persons who ingested ETEC developed diarrhea; all 11 excreted the pathogen (10(7)-10(9) organisms/gm or ml of stool), and 10 had significant rises in anti-O or antitoxin antibody. In contrast, no influenza vaccinees, despite close sharing of facilities, developed diarrhea, excreted ETEC or had rises in antibody to E. coli antigens. These data suggest that ETEC are not readily transmitted to healthy adults by direct person-to-person contact. Precautions to prevent contamination of shared food sources would appear to be the most rational intervention to avoid secondary cases of ETEC diarrhea.

Adolescent↗
PubMed1979

Adsorption and growth of Vibrio cholerae on chitin.

Incubation of Vibrio cholerae of O-group serotype 1 with chitin particles resulted in adsorption of vibrios onto chitin; chitin-adsorbed V. cholerae survived exposure to acid better than nonadsorbed vibrios. V. cholerae multiplied in dialyzed chitin suspended in 4.2% NaCl, suggesting that adherence to ingested chitin of crustacea might be of epidemiological significance by providing a substrate for vibrio multiplication as well as protection from gastric acid during stomach transit.

Acids↗
PubMedDate not supplied

Treatment of experimentally induced enterotoxigenic Escherichia coli diarrhea with trimethoprim, trimethoprim-sulfamethoxazole, or placebo.

In a double-blind study of the treatment of disease caused by enterotoxigenic Escherichia coli (ETEC), diarrhea was induced in volunteers with a trimethoprim (TMP)- and sulfamethoxazole (SMZ)-susceptible strain of E. coli that produces both heat-stable and heat-labile toxin. III volunteers were then treated with TMP, TMP-SMZ, or placebo. Volunteers treated with both TMP alone and the TMP-SMZ combination showed a substantial decrease in the duration and severity of the illness, as compared with the placebo-treated controls. TMP-resistant (MIC, 3.1-12.5 micrograms/ml) ETEC were isolated from stool cultures of five of 10 TMP-treated volunteers and none of 10 TMP-SMZ-treated volunteers after 48 hr of therapy, and in two volunteers the appearance of resistant organisms was associated with a clinical relapse. These data suggest that the TMP-SMZ combination should be evaluated in field trials to determine its usefulness as an adjunct to replacement of fluid and electrolytes in the therapy of ETEC diarrhea.

Adult↗