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L Cabrera

Publications and source records attributed to L Cabrera.

At least 37 records · Page 2Linked to original sources
PubMed1996

Conjugation between cloned human NK cells (H7.8) and K562/MOLT4 tumor cell systems: saturability, binding parameters, and population distribution of conjugates.

Effector-target conjugation between cloned NK(H7.8)-K562 and NK(H7.8)-MOLT4 tumor cells has been studied from binding isotherms. Nonlinear and linear regression methods were used to calculate the maximum effector and target conjugate frequencies as well as the dissociation constant of the conjugates formed. The results obtained show there is an enhancement of the effector-target saturability and effector-target affinity in comparison with the values previously observed for polyclonal NK effector cells. Population distributions revealed that different types of conjugates were formed as the effector-to-target ratio was changed in the NK(H7.8)-K562 and NK(H7.8)-MOLT4 tumor cells. In both cases conjugates where one effector cell was bound to several target cells and conjugates with one target cell bound to several effector cells were found. At all values of R the prevailing conjugates were those with one effector cell bound to one target cell.

Cell Communication↗
PubMed1996

Computer simulation and data analysis of effector-target interactions: the extraction of binding parameters from effector and target conjugate frequencies data by using linear and nonlinear data-fitting transformations.

Binding isotherms for effector-target conjugation when effector conjugate frequencies are measured by holding constant the number of effector cells and by varying the number of target cells are characterized by two parameters, the maximum effector conjugate frequency, alpha max, and gamma, which is related to the dissociation constant of the conjugates formed, K d. The suitability of four linear transformations of these binding isotherms, as well as nonlinear data-fitting techniques, to provide estimates of alpha max and gamma is discussed. The strength and weakness of these procedures were investigated by calculating alpha max and gamma from different sets of 100 or 500 replicate "experiments," which were generated by using an algorithm that provides noise contributions to the conjugate frequencies with gaussian distributed errors. Both unweighted and weighted data points were used in these calculations. A similar analysis can also be performed for binding isotherms in which target conjugate frequencies are measured at different values of effector cells by holding constant the number of target cells. In this case, the binding isotherms are characterized by two parameters, the maximum target conjugate frequency, beta max, and delta, which is also related to K d. The results obtained demonstrate that if the experimental conditions are chosen properly, linear transformations and nonlinear fitting techniques provide reliable estimates for the binding parameters. Not all procedures, however, provide estimates with the same accuracy, and special emphasis to this fact must be given if the binding assays are performed at low values of the number of effector cells.

Algorithms↗
PubMed1996

Active surveillance for Vibrio cholerae O1 and vibriophages in sewage water as a potential tool to predict cholera outbreaks.

The 1991 Peruvian cholera epidemic has thus far been responsible for 600,000 cholera cases in Peru. In an attempt to design a cholera surveillance program in the capital city of Lima, weekly sewage samples were collected between August 1993 and May 1996 and examined for the presence of Vibrio cholerae O1 bacteria and V. cholerae O1 bacteriophages (i.e., vibriophages). During the 144 weeks of surveillance, 6,323 cases of clinically defined cholera were recorded in Lima. We arbitrarily defined an outbreak as five or more reported cases of cholera in a week. The odds of having an outbreak were 7.6 times greater when V. cholerae O1 was present in sewage water during the four previous weeks compared with when it was not (P < 0.001). Furthermore, the odds of having an outbreak increased as the number of V. cholerae O1 isolations during the previous 4 weeks increased (P < 0.001). The odds of having an outbreak were 2.4 times greater when vibriophages were present in sewage water during the four previous weeks compared with when they were not, but this increase was not statistically significant (P = 0.15). The odds of having an outbreak increased as the number of vibriophage isolations during the previous 4 weeks increased (P < 0.05). The signaling of a potential cholera outbreak 1 month in advance may be a valuable tool for implementation of preventive measures. In Peru, active surveillance for V. cholerae O1 and possibly vibriophages in sewage water appears to be a feasible and effective means of predicting and outbreak of cholera.

Bacteriophages↗
PubMed1995

The derivation of binding parameters from effector and target conjugate frequency data using linear and non-linear data-fitting transformations. Application of such transformations to the NK-MOLT4 and NK-K562 effector-target systems.

Effector-target conjugation is described quantitatively by binding isotherms which are characterized by three parameters, the maximum effector and target conjugate frequencies, alpha max and beta max, and the dissociation constant of the conjugates formed, KD. In this paper the application of non-linear data-fitting techniques, as well as linear transformations of the binding isotherms that permit us to use standard regression analysis, has been tested to calculate estimates of these parameters in the NK-MOLT4 and NK-K562 effector-target systems. Both unweighted and weighted data were used to calculate alpha max, beta max and KD for six different donors which were used as a source of NK cells. The results obtained have shown that these regression methods are useful for revealing potential disparities between binding efficiencies in effector-target systems.

Adult↗
PubMed1995

Community infection ratio as an indicator for tuberculosis control.

The epidemiology of tuberculosis remains poorly understood. We investigated the relative importance of within-household and community transmission of infection among children aged 6 months to 14 years living in a Peruvian shanty-town. The prevalence of Mycobacterium tuberculosis exposure among 175 contact children (sharing a household with a person who had confirmed pulmonary tuberculosis) and 382 control children (living in nearby households free of active tuberculosis) was defined as the proportion of children with a positive purified protein derivative (PPD) skin-test. 97 (55%) contact children and 129 (34%) controls were PPD positive. Living in a contact household (odds ratio 1.74, 95% CI 1.11-2.73) and age (1.11, 1.06-1.18) were significant risk factors for PPD positivity. We calculated the community infection ratio (CIR) as the odds ratio of PPD-positive controls to PPD-positive contacts: CIR = [formula: see text] A low CIR therefore suggests mainly household spread of infection, whereas a high value suggests frequent transmission outside the household. The adjusted odds ratio (for age, sex, within-household correlation, and household size) was 0.40 (95% CI 0.26-0.64), compared with values of 0.18-0.37 in studies elsewhere. Currently recommended tuberculosis control strategies are suitable for areas with low CIRs. Different strategies may be needed for areas, such as that we studied, with high values.

Adolescent↗
PubMed1995

Short report: a placebo-controlled study of Lactobacillus GG colonization in one-to-three-year-old Peruvian children.

A pilot, placebo-controlled study conducted in Peruvian toddlers in a periurban shanty-town community demonstrates that 1) a simple fluorescent antibody test performed on bacteria from colonies grown on solid culture media can be used as a presumptive screening tool for Lactobacillus GG, 2) Lactobacillus GG powder sprinkled on flavored gelatin as a nutritional supplement is well-accepted by infants and mothers in this population, and 3) daily doses of Lactobacillus GG result in efficient colonization of the gastrointestinal tract of Peruvian infants. This study demonstrates that Lactobacillus GG should be evaluated as an adjunct for diarrhea control programs at the community level as well as in hospital-based settings.

Animals↗
PubMed1994

Binding units (BU) and the area under binding isotherms (AUI). New indices of effector-target conjugation.

New methods for simplified quantitation of effector-target conjugation have been developed. The binding unit (BU) is defined as the number of target cells required to bind a specified percentage of effector cells. The number of binding units is determined from binding isotherms in which effector conjugate frequencies are measured by holding constant the number of effector cells and by varying the number of target cells. Alternately, a binding unit can be defined as the number of effector cells required to bind a specified percentage of target cells. In this case, BU is computed from binding isotherms in which target conjugate frequencies are measured at different values of effector cells by holding constant the number of target cells. Also, the area under the curve (AUI) of these isotherms is another index that can be used as an overall measure of the binding capacity in an effector-target system. The experimental values of BU and AUI determined from effector and target isotherms agree well with theoretical predictions based on our previously developed binding model (J. Immunol. Methods (1992) 155, 133-147). The relationship between BU and AUI, and procedures to determine these parameters are shown. The value of these indices to express effector-target conjugation quantitatively has been confirmed by determining the values of BU and AUI for the NK-K562 effector-target system.

Adult↗
PubMed1992

Effector-target interactions: saturability, affinity and binding isotherms. A study of such interactions in the human NK cell-K562 tumour cell system.

Effector-target interactions at the cell-to-cell level have been studied. This has revealed that saturability, i.e., the existence of a finite number of specific receptor sites, applies to both the effector and target cell populations and plays a key role in the formation of conjugates. As a result, two maximum conjugate frequencies, alpha max and beta max, are recognised for the effector and target cell populations, respectively. The dissociation constant of the conjugates formed, KD, characterizes effector-target affinity. This constant, together with the maximum conjugate frequencies, are the three parameters which make it possible to describe the binding process quantitatively. The existence of binding isotherms for effector-target interactions has been demonstrated. These isotherms contain all the relevant information necessary to interpret quantitatively the formation of conjugates. Quantitative procedures to determine the three binding parameters are described together with the modifications necessary to use Scatchard plots in the analysis of conjugate frequencies in these kinds of cell-to-cell interactions. A quantitative study of these interactions in the NK-K562 tumour cell system has been performed. For this purpose, nine different cell source donors were used to test the model proposed. Relationships with related phenomena--CMC and the adhesion process--are also discussed.

Adult↗
PubMed1991

Toxic effects of interleukin-2-activated lymphocytes on vascular endothelial cells.

IL-2-activated lymphocytes (LAK cells) show increased adherence to, and killing of, human vascular endothelial cells compared to resting lymphocytes. In the present work, we have found that supernatants from LAK cell cultures also are toxic to human umbilical vein endothelial cells (HUVEC) when tested for 48 h in a neutral red uptake assay. Recombinant TNF-alpha and IFN-gamma at high concentrations are also toxic under the same test conditions, and TNF-alpha was directly detected in LAK cell supernatants. An inconsistent inhibition of toxicity was found with anti-TNF-alpha whereas anti IFN-gamma antibodies had a partial inhibitory effect. The susceptibility of HUVEC to cellular killing by LAK cells could be up- and down-regulated with insulin-like growth factor I and IFN-gamma, respectively. It is concluded that damage to vascular endothelium during high dose IL-2 treatments may be partially related to an excessive production of lymphokines such as IFN-gamma and TNF-alpha. IFN-gamma may, in addition, be protective for HUVEC during cellular interactions with LAK cells.

Culture Media↗
PubMed1989

[Fat consumption in the autonomous community of Madrid].

The results, based on the study of total lipid and cholesterol intake in a representative population of the district of Madrid, reflect the unfavorable situation for this population in regards to the incidence of cardiovascular diseases when comparing our data with national data and that obtained in the district of Castilla-La Mancha. However, the results are similar to those from other developed countries. The consumption of total lipids and the percentage of energy obtained is greater in the district of Madrid than in the other two populations mentioned. The energy obtained from saturated fatty acids exceeds that recommended by the WHO. However, the consumption of polyunsaturated fatty acids and monounsaturated fatty acids was found satisfactory. Of the three populations, the district of Madrid has the highest cholesterol intake and, as in the other two groups, this substance comes from eggs.

Cholesterol↗
PubMed1983

Natural history of chagasic cardiopathy in Chile. Follow-up of 71 cases after 4 years.

As part of study of Chagasic cardiopathy in Chile we report a follow-up study of 100 cardiopathic patients from two endemic areas who had been diagnosed 4 years earlier during an epidemiological and clinical survey. The follow-up consisted of a clinical, serological and electrocardiographic examination, and a continuous ECG recording for 60 min to detect possible arrhythmias. From the original 100 cases, three had died: one of a gastric cancer and the other two due to probable chagasic cardiopathy. Twenty-six had migrated to other areas and were lost to our study. From the remaining 71 patients, 48 were asymptomatic and 23 had complaints including palpitations, dyspnoea and Stokes-Adams crisis. In most cases, seropositivity by indirect haemagglutination did not change, but in six cases the titres decreased, becoming negative in three of them. Xeno-diagnosis was positive in 19.3% of seropositive patients. The ECG had returned to normal in 18 cases (17%) but showed a higher degree of blockades in others, three of which reached complete A-V block. The 60 min ECG was very important as it showed alterations in 93% of the cases, revealing arrhythmias that the ECG alone did not show. This work demonstrates that chagasic cardiopathy in Chile is a slow, progressive disease, that attacks the heart as a whole, but with special damage to the conducting tissues.

Adult↗