Spatial Mapping of Hematopoietic Clones in Human Bone Marrow

Clonal hematopoiesis (CH) is the expansion of somatically mutated cells in the hematopoietic compartment of individuals without hematopoietic dysfunction. Large CH clones (i.e. >2% variant allele fraction) predispose to hematologic malignancy, but CH is detected at lower levels in nearly all middle-aged individuals. Prior work has extensively characterized CH in peripheral blood, but the spatial distribution of hematopoietic clones in human bone marrow is largely undescribed. To understand CH at this level, we developed a method for spatially aware somatic mutation profiling and characterized the bone marrow of a patient with polycythemia vera. We identified complex clonal distribution of somatic mutations in the hematopoietic compartment, restriction of somatic mutations to specific subpopulations of hematopoietic cells, and spatial constraints of these clones in the bone marrow. This proof-of-principle paves the way to answering fundamental questions regarding CH spatial organization and factors driving CH expansion and malignant transformation in the bone marrow.

IMC-Denoise: a content aware denoising pipeline to enhance Imaging Mass Cytometry

Imaging Mass Cytometry (IMC) is an emerging multiplexed imaging technology for analyzing complex microenvironments using more than 40 molecularly-specific channels. However, this modality has unique data processing requirements, particularly for patient tissue specimens where signal-to-noise ratios for markers can be low, despite optimization, and pixel intensity artifacts can deteriorate image quality and downstream analysis. Here we demonstrate an automated content-aware pipeline, IMC-Denoise, to restore IMC images deploying a differential intensity map-based restoration (DIMR) algorithm for removing hot pixels and a self-supervised deep learning algorithm for shot noise image filtering (DeepSNiF). IMC-Denoise outperforms existing methods for adaptive hot pixel and background noise removal, with significant image quality improvement in modeled data and datasets from multiple pathologies. This includes in technically challenging human bone marrow; we achieve noise level reduction of 87% for a 5.6-fold higher contrast-to-noise ratio, and more accurate background noise removal with approximately 2 × improved F1 score. Our approach enhances manual gating and automated phenotyping with cell-scale downstream analyses. Verified by manual annotations, spatial and density analysis for targeted cell groups reveal subtle but significant differences of cell populations in diseased bone marrow. We anticipate that IMC-Denoise will provide similar benefits across mass cytometric applications to more deeply characterize complex tissue microenvironments.

TCR-engineered adoptive cell therapy effectively treats intracranial murine glioblastoma

BACKGROUND

Adoptive cellular therapies with chimeric antigen receptor T cells have revolutionized the treatment of some malignancies but have shown limited efficacy in solid tumors such as glioblastoma and face a scarcity of safe therapeutic targets. As an alternative, T cell receptor (TCR)-engineered cellular therapy against tumor-specific neoantigens has generated significant excitement, but there exist no preclinical systems to rigorously model this approach in glioblastoma.

METHODS

We employed single-cell PCR to isolate a TCR specific for the Imp3D81N neoantigen (mImp3) previously identified within the murine glioblastoma model GL261. This TCR was used to generate the Mutant Imp3-Specific TCR TransgenIC (MISTIC) mouse in which all CD8 T cells are specific for mImp3. The therapeutic efficacy of neoantigen-specific T cells was assessed through a model of cellular therapy consisting of the transfer of activated MISTIC T cells and interleukin 2 into lymphodepleted tumor-bearing mice. We employed flow cytometry, single-cell RNA sequencing, and whole-exome and RNA sequencing to examine the factors underlying treatment response.

RESULTS

We isolated and characterized the 3×1.1C TCR that displayed a high affinity for mImp3 but no wild-type cross-reactivity. To provide a source of mImp3-specific T cells, we generated the MISTIC mouse. In a model of adoptive cellular therapy, the infusion of activated MISTIC T cells resulted in rapid intratumoral infiltration and profound antitumor effects with long-term cures in a majority of GL261-bearing mice. The subset of mice that did not respond to the adoptive cell therapy showed evidence of retained neoantigen expression but intratumoral MISTIC T cell dysfunction. The efficacy of MISTIC T cell therapy was lost in mice bearing a tumor with heterogeneous mImp3 expression, showcasing the barriers to targeted therapy in polyclonal human tumors.

CONCLUSIONS

We generated and characterized the first TCR transgenic against an endogenous neoantigen within a preclinical glioma model and demonstrated the therapeutic potential of adoptively transferred neoantigen-specific T cells. The MISTIC mouse provides a powerful novel platform for basic and translational studies of antitumor T-cell responses in glioblastoma.

Biochemistry and Immune Biomarkers Indicate Interacting Effects of Pre- and Postnatal Stressors in Pigs across Sexes

The effects of maternal immune activation (MIA) elicited by a prenatal stressor and postnatal metabolic or immune stressors on chemical and inflammatory biomarkers were studied in male and female pigs. Pigs exposed to MIA elicited by porcine reproductive and respiratory syndrome virus and matching controls were assigned at two months of age to fasting stress, immune stress, or a saline group. The serum levels of over 30 chemistry and immune analytes were studied. Significantly low levels of blood urea nitrogen were detected in females exposed to MIA, while the highest creatinine levels were identified in fasting females exposed to MIA. The levels of interferon gamma and interleukin 8 were highest in pigs exposed to postnatal immune challenge. The profiles suggest that MIA may sensitize pigs to postnatal stressors for some indicators while making them more tolerant of other stressors. Effectiveness of practices to ameliorate the impact of postnatal stressors on the physiology of the pig could be enhanced by considering the prenatal stress circumstances.

Transcriptional networks of progressive diabetic peripheral neuropathy in the db/db mouse model of type 2 diabetes: An inflammatory story

Diabetic peripheral neuropathy is the most common complication of diabetes and a source of considerable morbidity. Numerous molecular pathways are linked to neuropathic progression, but it is unclear whether these pathways are altered throughout the course of disease. Moreover, the methods by which these molecular pathways are analyzed can produce significantly different results; as such it is often unclear whether previously published pathways are viable targets for novel therapeutic approaches. In the current study we examine changes in gene expression patterns in the sciatic nerve (SCN) and dorsal root ganglia (DRG) of db/db diabetic mice at 8, 16, and 24 weeks of age using microarray analysis. Following the collection and verification of gene expression data, we utilized both self-organizing map (SOM) analysis and differentially expressed gene (DEG) analysis to detect pathways that were altered at all time points. Though there was some variability between SOM and DEG analyses, we consistently detected altered immune pathways in both the SCN and DRG over the course of disease. To support these results, we further used multiplex analysis to assess protein changes in the SCN of diabetic mice; we found that multiple immune molecules were upregulated at both early and later stages of disease. In particular, we found that matrix metalloproteinase-12 was highly upregulated in microarray and multiplex data sets suggesting it may play a role in disease progression.

Increased ratio of circulating neutrophils to monocytes in amyotrophic lateral sclerosis

Objective:

To elucidate amyotrophic lateral sclerosis (ALS) biomarkers and potential mechanisms of disease, we measured immune cell populations in whole blood from a large cohort of patients with ALS.

Methods:

Leukocytes were isolated from the blood of 44 control patients and 90 patients with ALS. The percentages and total numbers of each cell population were analyzed using flow cytometry and matched with patient ALS Functional Rating Scale–Revised (ALSFRS-R) score to correlate leukocyte metrics with disease progression.

Results:

We show a significant increase in the percentage of neutrophils and a significant decrease in the percentage of CD4 T cells and CD16⁻ monocytes in the blood of patients with ALS compared to controls; however, only CD16⁻ monocyte levels correlated with disease progression. We also examined the monocyte surface expression of CCRL2 and CCR3; CD16⁻ monocytes displayed decreased percentages and total numbers expressing CCR3, but these numbers did not correlate with ALSFRS-R score. We found that combining multiple disease metrics yielded the most accurate predictor of disease progression: the ratio of neutrophils to CD16⁻ monocytes (N:M ratio) is significantly increased in patients with ALS and better correlates with disease progression than any other single metric.

Conclusions:

These observations implicate neutrophils and monocytes as important factors in late disease progression.

Expression of microRNAs in human post-mortem amyotrophic lateral sclerosis spinal cords provides insight into disease mechanisms

Amyotrophic lateral sclerosis is a late-onset and terminal neurodegenerative disease. The majority of cases are sporadic with unknown causes and only a small number of cases are genetically linked. Recent evidence suggests that post-transcriptional regulation and epigenetic mechanisms, such as microRNAs, underlie the onset and progression of neurodegenerative disorders; therefore, altered microRNA expression may result in the dysregulation of key genes and biological pathways that contribute to the development of sporadic amyotrophic lateral sclerosis. Using systems biology analyses on postmortem human spinal cord tissue, we identified dysregulated mature microRNAs and their potential targets previously implicated in functional process and pathways associated with the pathogenesis of ALS. Furthermore, we report a global reduction of mature microRNAs, alterations in microRNA processing, and support for a role of the nucleotide binding protein, TAR DNA binding protein 43, in regulating sporadic amyotrophic lateral sclerosis-associated microRNAs, thereby offering a potential underlying mechanism for sporadic amyotrophic lateral sclerosis.

Neurogenic factor-induced Langerhans cell activation in diabetic mice with mechanical allodynia

Background

Langerhans cells (LCs) are antigen-presenting dendritic cells located in the skin. It has been reported that LC activation is associated with painful diabetic neuropathy (PDN); however, the mechanism of LC activation is still unclear.

Methods

The db/db mouse, a rodent model of PDN, was used to study the roles of LCs in the development of PDN in type 2 diabetes. Hind foot pads from db/db and control db/+ mice from 5 to 24 weeks of age (encompassing the period of mechanical allodynia development and its abatement) were collected and processed for immunohistochemistry studies. LCs were identified with immunohistochemistry using an antibody against CD207 (Langerin). The intraepidermal nerve fibers and subepidermal nerve plexus were identified by immunohistochemistry of protein gene product 9.5 (PGP 9.5) and tropomyosin-receptor kinase (Trk) A, the high affinity nerve growth factor receptor.

Results

CD207-positive LCs increased in the db/db mouse during the period of mechanical allodynia, from 8 to 10 weeks of age, in both the epidermis and subepidermal plexus. At 16 weeks of age, when mechanical allodynia diminishes, LC populations were reduced in the epidermis and subepidermal plexus. Epidermal LCs (ELCs) were positive for Trk A. Subepidermal LCs (SLCs) were positive for CD68, suggesting that they are immature LCs. Additionally, these SLCs were positive for the receptor of advanced glycation end products (RAGE) and were in direct contact with TNF-α-positive nerve fibers in the subepidermal nerve plexus during the period of mechanical allodynia. Intrathecal administration of SB203580, a p38 kinase inhibitor, significantly reduced mechanical allodynia, TNF-α expression in the subepidermal plexus, and increased both ELC and SLC populations during the period of mechanical allodynia.

Conclusions

Our data support the hypothesis that increased LC populations in PDN are activated by p38-dependent neurogenic factors and may be involved in the pathogenesis of PDN.

Identification of epigenetically altered genes in sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a terminal disease involving the progressive degeneration of motor neurons within the motor cortex, brainstem and spinal cord. Most cases are sporadic (sALS) with unknown causes suggesting that the etiology of sALS may not be limited to the genotype of patients, but may be influenced by exposure to environmental factors. Alterations in epigenetic modifications are likely to play a role in disease onset and progression in ALS, as aberrant epigenetic patterns may be acquired throughout life. The aim of this study was to identify epigenetic marks associated with sALS. We hypothesize that epigenetic modifications may alter the expression of pathogenesis-related genes leading to the onset and progression of sALS. Using ELISA assays, we observed alterations in global methylation (5 mC) and hydroxymethylation (5 HmC) in postmortem sALS spinal cord but not in whole blood. Loci-specific differentially methylated and expressed genes in sALS spinal cord were identified by genome-wide 5mC and expression profiling using high-throughput microarrays. Concordant direction, hyper- or hypo-5mC with parallel changes in gene expression (under- or over-expression), was observed in 112 genes highly associated with biological functions related to immune and inflammation response. Furthermore, literature-based analysis identified potential associations among the epigenes. Integration of methylomics and transcriptomics data successfully revealed methylation changes in sALS spinal cord. This study represents an initial identification of epigenetic regulatory mechanisms in sALS which may improve our understanding of sALS pathogenesis for the identification of biomarkers and new therapeutic targets.

Primary and secondary hemostatic functionalities of rehydrated, lyophilized platelets

BACKGROUND

The rehydrated, lyophilized (RL) platelet (PLT) is being developed as a hemostatic infusion agent for the control of active bleeding. The key to the method for preparing RL PLTs is a mild aldehyde stabilization that allows for freezing and lyophilizing without cellular rupture. RL PLTs have been shown to be effective at rapidly controlling bleeding in animal models of cardiopulmonary bypass induced PLT dysfunction and washout thrombocytopenia, yet the rehydrated cells have proved to be safe with respect to induction of pathologic intravascular coagulation.

STUDY DESIGN AND METHODS

In vitro and in vivo studies were performed to better understand the differential effect of the RL PLT manufacturing method on primary and secondary hemostatic processes. The functionality of the von Willebrand factor (VWF) receptor (glycoprotein Ib) complex, the PAR receptors, integrin-mediated aggregation (inside-out signaling), and surface membrane prothrombin to thrombin conversion systems were investigated.

RESULTS

RL PLTs were found to retain native VWF-mediated adhesion and surface thrombin generation functions. In contrast, the coupling of thrombin receptors to integrin inside-out signaling was largely inhibited.

CONCLUSION

These results suggest that RL PLTs may stop bleeding by forming primary hemostatic plugs and providing a localized source of thrombin for secondary hemostatic processes, yet do not build up occlusive pathologic clots possibly because integrin functions for forming PLT-PLT aggregates are partially inhibited.

Explaining the birth weight paradox: Latina immigrants' perceptions of resilience and risk

In the US, prenatal care is positively associated with improved birth outcomes. However, among Mexican-born Latinos, rates of low birth weight are lower than those of US-born counterparts despite the fact that recently arrived Latino immigrants are less likely to have received adequate prenatal care. The "birth weight paradox," identified through analysis of the HHANES, appears to hold constant across variations in age, marital status or educational attainment. The authors explore Latina immigrant's perceptions of resilience factors related to these better birth outcomes through focused group interviews, photonarratives, and documentation of local kin networks. The women's responses are grouped into five resilience factors and one risk complex that have the potential to further explain the HHANES findings. Women's responses, the stories of their photographs, and kin networks are presented. Knowledge of these protective and risk factors can be useful to health professionals and Latino advocacy groups in the design of community-based interventions that protect health status and promote the practice of protective health behaviors within immigrant families and communities.

Tell me what you mean by "sí": perceptions of quality of prenatal care among immigrant Latina women

Individual perceptions form the basis of many health research reports related to access, utilization, continuity, and quality. Many health care providers are not well equipped for designing studies or collecting data with immigrant populations. In this article, the authors examine issues in data collection on topics related to perceptions of quality of prenatal care among immigrant Latino populations. The conceptual model is Donabedian's framework for quality. Two instruments--a qualitative interview with photographs representing components of quality and a questionnaire--were used for data collection. Examples of narrative responses given by women in response to the photo-narrative prompts are presented and compared to shorter survey responses. The authors emphasize the importance of designing research instruments that reflect the perceptions of the research subjects rather than simply those of the investigators.

The influence of maternal intergenerational education on health behaviors of women in peri-urban Bolivia

The influence of maternal education on infant mortality has been demonstrated repeatedly in health and social science literature. Less explored is the influence of the education level of the mother's mother. In the present paper the authors examine the possible effect of grandmother's education on maternal behaviors. The relationship between intergenerational education and selected health behaviors, including utilization of health services for prenatal care, breast-feeding and family planning, are reported. The data were collected in peri-urban Santa Cruz, Bolivia among mothers of infants between 0 and 18 months of age. It appears that grandmother's education does exert an effect on health behaviors above and beyond the effect of maternal education. This effect is more pronounced for health services which fall clearly in the domain of the formal health care system. While the results are exploratory, the results suggest the worth of further study and consideration of the influence of mothers' mothers in the design of culturally sensitive quality health services.

From efficacy to effectiveness: selecting indicators for a community-based lactational amenorrhoea method promotion programme

This paper reviews the results of clinical trials and community studies of lactational amenorrhoea and its role as a contraceptive method (LAM). Indicators which are used in efficacy trials and effectiveness interventions are compared and sets of indicators of effectiveness appropriate to community-based LAM programmes are recommended. A five-tiered ecological framework is used to facilitate selection of indicators which range from individual to policy level outcomes. The indicator framework is intended as a tool for health practitioners in family planning and maternal and child health service delivery settings who are interested in designing programmatic interventions for the promotion of LAM, particularly among less well-educated women of lower socioeconomic communities.

Oral contraceptives and hormone replacement therapy do not increase the incidence of arterial thrombosis in a nonhuman primate model

Older oral contraceptive (OC) formulations containing high doses of potent synthetic estrogens and progestins are associated with increased risk of thrombosis. To examine the effects of current low-dose OC and hormone replacement therapy (HRT) regimens on arterial thrombosis, premenopausal and surgically postmenopausal cynomolgus monkeys were divided into four treatment groups. Premenopausal monkeys were given either no OCs or ethinyl estradiol and levonorgestrel as an OC at a dose equivalent to that currently given to women. Postmenopausal monkeys were given either no HRT or conjugated equine estrogens and medroxyprogesterone as an HRT at a dose equivalent to that currently given to women. The monkeys were fed an atherogenic diet containing these treatments for 27 to 30 months. At the end of this time, arterial thrombosis was evaluated with a standardized stenosis/injury procedure in the left carotid artery. Blood flow velocity was monitored for cyclic or permanent occlusive thrombosis. The current OC and HRT regimens did not increase the susceptibility of the artery wall to develop an occlusive thrombus following injury and stenosis. In fact, there was a reduction in the incidence of thrombosis in the OC animals compared with untreated controls. Increased amounts of atherosclerosis were associated with an increased incidence of occlusive arterial thrombosis. Several selected coagulation parameters [von Willebrand factor, protein C, lipoprotein(a), and platelet aggregation] did not appear to be associated with either the amount of atherosclerosis or incidence of arterial thrombosis.

The focus group as a tool for health research: issues in design and analysis

The focus group is a technique for eliciting information from specific population subgroups. Issues addressed may be little known or relatively well known to the researcher. The method is most effectively used when the objective of the investigation is to elicit points of view of client or consumer groups which may differ from those of providers. Despite the frequency with which focus groups are used, few published materials describe the practical application of the method. This paper presents a detailed methodology for the conduct of focus groups and analysis of focus-group data with the intention of improving its use among researchers and health-care professionals. Data from two studies, immunization compliance in West Africa, and barriers to use of prenatal-care services in Bolivia, are used as illustrative examples.

Infant feeding in Bolivia: a critique of the World Health Organization indicators applied to demographic and health survey data

Infant feeding is a multidimensional activity that can be described and analysed in many different ways. The World Health Organization (WHO) has recently issued recommended indicators for assessing infant feeding practices. This paper presents these indicators and demonstrates their applications using the 1989 Demographic and Health Survey (DHS) data for Bolivia. The results indicate that, although most Bolivian infants are breastfed and two-thirds are breastfed for > 1 year, supplementary feeding practices deviate considerably from international recommendations. Only 58% of infants < 4 months old are receiving breastmilk alone (the 'exclusive breastfeeding rate') and a similarly low percentage (54.7%) of 6-9 month olds are receiving the recommended combination of breast milk plus solid or semi-solid foods (the 'timely complementary feeding rate'). Furthermore, almost half of breastfed infants < 12 months old are also receiving bottle feeds. The infant feeding practices of city residents are least likely to conform to the infant feeding recommendations, while practices of mothers who have always lived in the country are most likely to be similar to the WHO guidelines. Mothers who have moved to the city since the age of 12 are most likely to be giving their infants other milks in addition to breast milk and to be bottle feeding their infants. The WHO infant feeding indicators provide a useful framework for quantifying infant feeding practices, and most of the indicators can readily be applied to DHS data. Nonetheless, improvements can be made in both the indicators themselves and the DHS questionnaire to improve reporting of internationally comparable infant feeding information.

Rural origin as a risk factor for maternal and child health in periurban Bolivia

Rapid migration in Latin America is settling rural women and their families next to those of urban origin in sprawling urban settings. Those born and reared in rural areas bring with them knowledge and skills learned and adapted to rural areas; those same skills may be maladaptive in urban areas. Hypothesized is that urban women of rural origin are more likely to have poorer health outcomes for themselves and their children than lifelong urban counterparts. Identification of specific risk factors affecting child and/or maternal health status in peri-urban barrios can assist health workers to target limited resources to those least likely to access available services.

Bacterial cell wall polymers (peptidoglycan-polysaccharide) cause reactivation of arthritis

Intraperitoneal (i.p.) injection of peptidoglycan-polysaccharide derived from group A streptococci (PG-APS) causes chronic arthritis with spontaneous remissions and exacerbations. We hypothesized that, following i.p. injection, PG-APS released from hepatic stores mediated spontaneous recurrences of arthritis. We tested whether transplanted livers with large amounts of PG-APS were able to reactivate quiescent arthritis. Saline-loaded (group 1) or PG-APS-loaded (group 2) livers were transplanted into rats which had been injected intra-articularly 10 days earlier with PG-APS in one joint and saline in the other. A comparison was made with the arthritis that occurred in rats injected i.p. with PG-APS which did not receive transplants (group 3). Arthritis was monitored by serial measurement of joint diameters. Transplantation of saline-loaded livers (group 1) caused no reactivation of arthritis. However, transplantation of PG-APS-loaded livers (group 2) reactivated arthritis (P < 0.0001). Injection of PG-APS i.p. (group 3) induced the most-severe arthritis. PG-APS levels in plasma decreased with time, and PG-APS accumulated in the spleen in groups 2 and 3. Plasma and hepatic levels of PG-APS in rats injected i.p. with PG-APS were greater than levels in rats transplanted with PG-APS-loaded livers, which in turn were greater than levels in rats with saline-loaded livers. Plasma tumor necrosis factor did not correlate with recurrence of arthritis. Transplantation with PG-APS-loaded livers induced reactivation of arthritis in preinjured joints. The extent of arthritis was proportional to hepatic PG-APS content. Reactivation of arthritis may be mediated by slow release of liver-sequestered PG-APS or cytokines (not tumor necrosis factor) released by the liver.

Validation of self-report of literacy among periurban women in Bolivia

Many surveys ask women to rate their literacy level, but the validity of these self-reports is not usually evaluated. In this study of infant health, conducted in Cochabamba, Bolivia, maternal literacy was assessed by the mother herself and by the interviewer, based on the mother's reading a short text aloud. The two ratings were highly correlated (P < 0.001). This finding suggests that maternal self-reports of literacy are very reliable.

Improving vaccination completion rates in liberia: evaluation of an intervention trial

Reported are findings from an evaluation of a community-based strategy employing local chiefs and traditional midwives as extenders of the Ministry vaccination team for the purpose of increasing vaccination completion in Liberia, West Africa. The intervention strategy-a training workshop and two subsequent supervisory visits-was selected from among those generated in Stage 1 of a three-stage operational research design. Evaluation of the intervention was carried out after an eight-month follow-up period. Visits to intervention and control villages, for the purpose of interviewing chiefs, traditional midwives (TMs) nand mothers of children under one year of age, were the means by which data were gathered. Both process and outcome indicators were identified as means of assessing the effectiveness of the strategy. Vaccination rosters and holding of a town meeting were used as evidence of the former. A vaccination coverage survey using a cluster sample methodology was used to evaluate differences in vaccination coverage. Results showed that knowledge about vaccination, treatment of side effects and the importance of the RTH Card was greater among chiefs/TMs and mothers in the intervention districts than in control districts. Coverage rates for fully immunized children were greater in the intervention districts (56% intervention vs. 45% control). When stratified by type of leadership, coverage rates were higher in intervention districts where TMs rather than chiefs served as vaccination team extenders, although chiefs were more effective than controls. As a result of this study, the Ministry of Health has decided to extend this activity into other counties and to add additional information on other PHC messages.

A review of dietary interventions aimed at controlling hypertension

Before planning programs to change dietary behavior in groups of individuals, evidence about the effectiveness of different interventions is needed. Articles published in the journals indexed by Index Medicus between the years 1975-84 were reviewed for evidence concerning the effectiveness of dietary modification programs in achieving dietary change. All program evaluations published in English and aimed at control of blood pressure levels in adults were eligible for review. Twenty-nine articles relevant to the synthesis contained sufficient information evaluating the contribution of dietary intervention. These 20 studies addressed changes in fat consumption, reduction in salt intake and reduction in calories consumed. The methods of intervention ranged from residential programs, through individual counseling and group discussion involving spouses, to audiovisual tapes. The studies had varying periods of follow-up; among those with one or more years of follow-up, a number of studies were able to demonstrate effectiveness using different outcome measures. For some dietary components, notably changes in fat intake and reduction in salt consumption, it has been possible to identify a minimal effective intervention, such as self-help materials or individual instruction, while changes in calorie intake or weight seem to require group counseling with family member involvement. The findings from this information synthesis should prove useful to those planning dietary interventions.

Bridging the gap: the village health worker as the cornerstone of the primary health care model

The Alma-Ata Conference in 1978 reiterated the goal of 'Health for All by the Year 2000' and declared primary health care (PHC) the vehicle through which this lofty goal was to be achieved. National governments were recognized as responsible agents for developing and implementing PHC plans. The emphasis on community-oriented delivery of care places great importance on the village health worker (VHW), the individual who serves as the 'interface' between the formal health care system and the community. Despite the acknowledged importance of the VHW role, the question of whether the PHC model, with the VHW as the cornerstone can be effectively implemented without a "fundamental shift of wealth and power" (Sidel) continues to be asked. This paper examines the evolution and current status of the VHW role in Costa Rica, Nicaragua and Columbia, three Latin American nations which have adopted the PHC model. The authors discuss the evolution of the PHC model in each country with particular reference to the occurrence or non-occurrence of fundamental changes in the society. The conclude that the primary determiner of successful implementation of PHC is a national commitment to PHC including recognition of the importance of community participation which is best achieved through reliance on the village health worker.