Investigation of the interaction force between Cryptosporidium parvum oocysts and solid surfaces.

Interaction force profiles between single Cryptosporidium parvum oocysts and positively charged, silane-coated silica particles were measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized for the measurements by entrapment in Millipore polycarbonate membranes with 3 microm pore size. Experiments were performed in both NaCl and CaCl2 solutions at ionic strengths ranging from 1 to 100 mM. For both electrolytes, the decay length of the repulsive force profile was found to be nearly independent of the ionic strength and always much larger than the theoretical Debye length of the system. In addition, the magnitude of the force was found to be essentially the same for both electrolytes, suggesting that the long-range repulsive forces are primarily steric in nature. These results support the theory that the interaction force between oocysts and surfaces is controlled by an outer, weakly charged or uncharged carbohydrate layer. Measurements were also performed with oocysts that had been deactivated using either chemical (formalin) or heat treatment. The force profiles obtained with formalin-treated oocysts appear to be essentially the same as for the untreated oocysts, whereas the profiles measured with the heat-treated oocysts show a much stronger dependence on solution ionic strength. With either the heat-treated or formalin-treated oocysts, adhesion was observed much more frequently than with untreated oocysts, which is consistent with the increased deposition rate observed with treated oocysts by Kuznar and Elimelech (Kuznar, Z. A.; Elimelech, M. Langmuir 2005, 21, 710-716). These results also suggest that treated oocysts, especially ones that have been inactivated by heating, may not be good surrogates for viable oocysts in laboratory studies.

Interaction force profiles between Cryptosporidium parvum oocysts and silica surfaces.

The interaction force profile between single Cryptosporidium parvum oocysts and silica particles was measured in aqueous solutions using an atomic force microscope. The oocysts were immobilized during the measurements by entrapment in Millipore polycarbonate membranes with a 3 microm pore size. Experiments were performed in both NaCl and CaCl2 solutions at ionic strengths ranging from 1 to 100 mM. For both electrolytes the decay length of the repulsive force profile, obtained via the slope of a plot of the logarithm of interaction force versus separation, was found to be essentially independent of the ionic strength and always much larger than the theoretical Debye length of the system. In addition, the magnitude of the force was found to be essentially the same for both electrolytes, suggesting that the long-range repulsive forces are primarily steric in nature. Fitting the force to an expression for the steric repulsive force between two grafted brush layers yields a layer thickness of approximately 115 nm. These results support the idea that the oocysts are covered by a relatively thick layer of uncharged (or weakly charged) carbohydrates, possibly mixed with a thinner layer of charged protein.

Attitudes and beliefs about environmental hazards in three diverse communities in Texas on the border with Mexico.

OBJECTIVE: Since communicating risk related to environmental hazards has consistently presented a challenge to government agencies and industries, our objective was to better understand the attitudes and beliefs of three communities, so as to help agencies and industries develop better risk communication interventions. METHODS: We explored attitudes and beliefs about environmental risks in three diverse communities in Texas on the border with Mexico, in the county of El Paso. During the summer of 1995, using a door-to-door survey, we interviewed 147 individuals, using a questionnaire based upon an existing instrument. Interviews were conducted in three very different areas of the county: semirural low-income, urban low-income, and suburban upper-income. We randomly selected specific sections in each of the three communities for inclusion in the sample. We assessed attitudes and beliefs about regulations and experts, risk and hazards, and how to address environmental issues. RESULTS: Attitudes and beliefs varied among the three communities, especially in the assessment of riskiness of various hazards. In general, there was mistrust of government agencies and of industries, a strong feeling that the environment can be improved, and a lack of understanding about what actions individuals might take to improve the environment. DISCUSSION: Agencies need to find ways to increase their credibility with the public, and they should assess communities in order to understand the attitudes of the residents.

Acculturation and breast-feeding intention and practice in Hispanic women on the US-Mexico border.

OBJECTIVES: To explore the extent to which acculturation indicators predict both breast-feeding history and intentions among Mexican-American mothers having their first births, and among those having subsequent births. DESIGN: Cross-sectional survey in a hospital post-partum unit. METHODS: 3,036 Hispanic women were interviewed post-partum in their hospital room. A survey was administered in English or Spanish, and included questions about prenatal care, diet, work exposures, contraceptive use, and breast-feeding history and intentions. For the purposes of this study, acculturation was measured using a series of indicators including language spoken at home, language ability, country of birth, and country in which last schooling was received. RESULTS: Previous breast-feeding was significantly associated with educational attainment, speaking both English and Spanish at home, having had prenatal care during the previous pregnancy, and with both country variables (country of birth and country where finished school). Women with less education, women who were single, and women who did not receive any prenatal care were less likely to intend to breast-feed than were women with a college education, women with a partner, and women who received any prenatal care. Women born in Mexico (for multiparous women), or having finished school in Mexico (for primiparous women), were more likely to intend to breast-feed. CONCLUSIONS: Acculturation is associated with breast-feeding history and intention to breast-feed. Acculturation is a complex construct and traditional measures of acculturation based on language preference may not be as useful on the US-Mexico border. It is recommended that further study be conducted to determine what factors prevent women from breast-feeding, even though they intend to do so, especially in multi-cultural communities like those around the US-Mexico border.

Health care professionals' skills, beliefs, and expectations about screening for domestic violence in a border community.

This article describes domestic violence education of health professionals and determines association between screening behavior and preparedness, outcome expectations, and beliefs about how and when to screen. A survey was mailed to all primary care physicians, dentists, and nurse practitioners in El Paso, Texas (n = 561). Return rate was 34.4%. Using linear regression, differences (p < 0.05) were found between dentists and others in percentage of patients screened, education, preparedness, and beliefs. Education had a positive association (p < 0.001) with preparedness, beliefs about when to screen, and outcome expectations, and a negative association with beliefs about how to screen. Preparedness, beliefs, and realistic outcome expectations had a positive association (p < 0.02) with percentage of female patients screened. Education about domestic violence is important in increasing preparedness and influencing beliefs about when to screen and what outcomes can be expected. Educational programs should include not only information, but also skills training to increase perceptions of preparedness.

Developing a video intervention to model effective patient-physician communication and health-related decision-making skills for a multiethnic audience.

The ENDOW study is a multisite, community-based project designed to improve decision-making and patient-physician communication skills for midlife African-American, white, and Hispanic women facing decisions about hysterectomy. Based on results of initial focus groups, a patient education video was developed in English and Spanish to serve as the centerpiece of various interventions. The video uses community women to model appropriate decision-making and patient-physician communication skills. Women in the target populations rated the video as useful to very useful and would recommend it to others. The use of theory-driven approaches and pilot testing of draft products resulted in the production of a well-accepted, useful video suitable for diverse populations in intervention sites in several states.

Initiation of prenatal care by low-income Hispanic women in Houston.

OBJECTIVE: To understand why many Hispanic women begin prenatal care in the later stages of pregnancy. METHODS: The authors compared the demographic profile, insurance status, and health beliefs--including the perceived benefits of and barriers to initiating prenatal care--of low-income Hispanic women who initiated prenatal care at different times during pregnancy or received no prenatal care. RESULTS: A perception of many barriers to care was associated with later initiation of care and non-use of care. Perceiving more benefits of care for the baby was associated with earlier initiation of care, as was having an eligibility card for hospital district services. Several barriers to care were mentioned by women on open-ended questioning, including long waiting times, embarrassment the physical examination, and lack of transportation. CONCLUSIONS: Recommendations for practice included decreasing the number of visits for women at low risk for poor pregnancy outcomes while increasing the time spent with the provider at each visit, decreasing the number of vaginal examinations for low risk women, increasing the use of midwives, training lay workers to do risk assessment, emphasizing specific messages about benefits to the baby, and increasing general health motivation to seek preventive care through community interventions.