Biochemical basis of oxidative protein folding in the endoplasmic reticulum.

The endoplasmic reticulum (ER) supports disulfide bond formation by a poorly understood mechanism requiring protein disulfide isomerase (PDI) and ERO1. In yeast, Ero1p-mediated oxidative folding was shown to depend on cellular flavin adenine dinucleotide (FAD) levels but not on ubiquinone or heme, and Ero1p was shown to be a FAD-binding protein. We reconstituted efficient oxidative folding in vitro using FAD, PDI, and Ero1p. Disulfide formation proceeded by direct delivery of oxidizing equivalents from Ero1p to folding substrates via PDI. This kinetic shuttling of oxidizing equivalents could allow the ER to support rapid disulfide formation while maintaining the ability to reduce and rearrange incorrect disulfide bonds.

Reduced rate of disease development after HIV-2 infection as compared to HIV-1.

Human immunodeficiency virus type-2 (HIV-2) is a close relative of the prototype acquired immunodeficiency syndrome (AIDS) virus, HIV-1. HIV-2 is biologically similar to HIV-1, but information is lacking concerning clinical outcomes of HIV-2-infected individuals. From 1985 to 1993, a prospective clinical study was conducted in women with HIV-2 and HIV-1 infection to determine and compare rates of disease development. HIV-1-infected women had a 67% probability of AIDS-free survival 5 years after seroconversion in contrast with 100% for HIV-2-infected women. In addition to having significantly less HIV-related disease outcome in HIV-2 enrollees compared to HIV-1 enrollees, the rate of developing abnormal CD4+ lymphocyte counts with HIV-2 infection was also significantly reduced. This natural history study demonstrates that HIV-2 has a reduced virulence compared to HIV-1.

Natural protection against HIV-1 infection provided by HIV-2.

Significant differences have been observed in the rates of transmission and disease development in human immunodeficiency virus (HIV) types 1 and 2. Because many HIV-2-infected people remain asymptomatic for prolonged periods, the hypothesis that HIV-2 might protect against subsequent infection by HIV-1 was considered. During a 9-year period in Dakar, Senegal, the seroincidence of both HIV types was measured in a cohort of commercial sex workers. Despite a higher incidence of other sexually transmitted diseases (STDs), HIV-2-infected women had a lower incidence of HIV-1 than did HIV-seronegative women, with a relative risk of 0.32 (P = 0.008). An understanding of the cross-protective mechanisms involved may be directly relevant to HIV-1 vaccine development.

Human T-lymphotropic virus type 4 and the human immunodeficiency virus in West Africa.

A new human T-lymphotropic virus (HTLV-4) was recently described in healthy people from Senegal. This virus has many properties in common with members of the human T-lymphotropic viruses, particularly the human immunodeficiency virus or HIV, the etiologic agent of acquired immune deficiency syndrome (AIDS), but does not appear to be associated with immunodeficiency-related disorders. In the present study, serum samples were obtained from 4248 individuals from six West African countries, including Senegal, Guinea, Guinea Bissau, Mauritania, Burkina Faso, and Ivory Coast. These samples, collected during 1985-1987, were from people categorized as healthy control, sexually active risk, and disease populations. All samples were analyzed for reactivity to HTLV-4 and HIV by radioimmunoprecipitation-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. Evidence for HTLV-4 infection was found in five of the six countries. The seroprevalence varied markedly from country to country. Healthy sexually active individuals in the risk category had the highest levels of HTLV-4 infection compared to individuals in the healthy control category and the disease category, the latter including AIDS patients. The seroprevalence of HIV infection in most of these countries was quite low, although tightly associated with the rare cases of AIDS. The biology of HTLV-4 infection thus differs from that of HIV in Central Africa or the United States and Europe. The presence of these viruses and their different pathogenicities in several countries of West Africa indicate the necessity for serologic assays that will distinguish between them. Further studies of their origin and distribution as well as of their biology will be important in advancing our understanding of AIDS.

Association of Acute, High-dose Cadmium Exposure with Alterations in Vascular Endothelial Barrier Antigen Expression and Astrocyte Morphology in the Developing Rat Central Nervous System.

Clinical and experimental studies have demonstrated the neurotoxic and behavioural effects of cadmium. However, the exact pathophysiological mechanism(s) of cadmium neurotoxicity on the human central nervous system (CNS) is not completely understood. A rat blood-brain barrier (BBB) endothelial marker, the endothelial barrier antigen (EBA), has been identified and we have shown previously that an anti-EBA IgG1 antibody exclusively recognizes barrier-competent microvessels in the rat CNS and peripheral nervous system (PNS). Endothelial cells of peripheral tissues or brain regions possessing fenestrated microvascular endothelia do not display immunoreactivity for EBA. Here, we describe the application of sequential indirect immunofluorescence with anti-EBA, and an antibody directed against glial fibrillary acidic protein (GFAP), to evaluate the immunoreactivity patterns and morphological alterations in BBB microvessels and astrocytes, following a single, high dose of cadmium in normal, term-delivered young rats. We detected a moderate reduction in immunoreactivity and number of microvessels labelled by the anti-EBA in the forebrain, cerebellum and midbrain in cadmium-exposed rats compared with normal controls. We observed weakly GFAP-reactive astrocytes displaying cell bodies with ill-defined borders and blurred cytoplasm within the white and grey matter of cadmium-exposed brains. The astrocyte nuclei were markedly enlarged, intensely hyperchromatic and exhibited chromatin condensation with nuclear fragmentation. This study indicates for the first time that EBA is involved in, and could serve as a potentially useful marker for studying, cadmium neurotoxicity in the rat model system.

Cardiovascular abnormalities in transgenic mice with reduced brown fat: an animal model of human obesity.

BACKGROUND: A new model of murine obesity has recently been developed through transgenic ablation of brown adipose tissue that manifests typical metabolic complications of obesity, including insulin resistance and non-insulin-dependent diabetes mellitus. The cardiovascular phenotype has not been defined. METHODS AND RESULTS: Transthoracic echocardiography, aortic catheterization, isolated whole-heart studies, and morphometric histology defined cardiac structure and function in 30 transgenic mice with reduced brown fat and 30 matched wild-type controls. Obesity was indicated by a 77% increase in body weight and was accompanied by elevated systemic pressures (mean aortic blood pressure 85+/-1 versus 66+/-2 mm Hg; P<0.01), left ventricular dilation and hypertrophy (mass/body weight 4.0+/-0.2 versus 2.7+/-0.3 mg/g; P<0.01), and high cardiac output (cardiac index 3.2+/-0.4 versus 2.4+/-0.1 mL x kg(-1) x min(-1); P<0.01). Baseline functional parameters assessed in vitro were not different, but after imposition of zero-flow ischemia, significant relaxation impairment developed in obese mice. Although morphometrically determined myocyte diameters were similar, the percentage of interstitial fibrosis was significantly increased in transgenic mice compared with wild-type controls (7.5+/-2% versus 4. 2+/-0.2%; P<0.01). CONCLUSIONS: Transgenic ablation of brown adipose tissue is associated not only with obesity but also with systemic hypertension, left ventricular hypertrophy with eccentric remodeling and fibrosis, and high cardiac output, a unique constellation of findings strikingly similar to that seen in human obesity. Mice with reduced brown fat may serve as a new model for the cardiovascular morbid complications associated with obesity in humans.

Abnormal cardiac function in the streptozotocin-induced non-insulin-dependent diabetic rat: noninvasive assessment with doppler echocardiography and contribution of the nitric oxide pathway.

OBJECTIVES: We sought to evaluate in vivo and in vitro left ventricular (LV) geometry and function in streptozotocin-induced diabetic rats and the possible role of the nitric oxide (NO) pathway. BACKGROUND: Diabetes results in cardiac dysfunction; however, the specific abnormalities are unknown. Because decreased NO contributes to abnormal vascular function in diabetics, we hypothesized that NO pathway abnormalities may contribute to diabetic cardiomyopathy. METHODS: Control rats and those with non-insulin-dependent diabetes mellitus (NIDDM) underwent echocardiography, hemodynamic assessment, isolated heart perfusion and measurement of exhaled NO and LV endothelial constitutive nitric oxide synthase (ecNOS). RESULTS: Diabetic rats had increased LV mass (3.3 +/- 0.6 vs. 2.6 +/- 0.3 g/g body weight [BW], p < 0.001) and cavity dimensions (diastolic 2.0 +/- 0.1 vs. 1.8 +/- 0.2 cm/cm tibial length [TL], p < 0.05). Diabetic rats had prolonged isovolumic relaxation time (IVRT) (40 +/- 8 vs. 26 +/- 6 ms, p < 0.0001), increased atrial contribution to diastolic filling (0.47 +/- 0.09 vs. 0.30 +/- 0.08 m/s, p < 0.0001), and elevated in vivo LV end-diastolic pressure (7 +/- 6 vs. 2 +/- 1 mm Hg, p = 0.04). Diabetic rats had increased chamber stiffness. Shortening was similar in both groups, despite reduced meridional wall stress in diabetics, suggesting impaired systolic contractility. Exhaled NO was lower in diabetic rats (1.8 +/- 0.2 vs. 3.3 +/- 0.3 parts per billion, p < 0.01) and correlated with Doppler LV filling. The ecNOS was similar between the groups. CONCLUSIONS: Diabetic cardiomyopathy is characterized by LV systolic and diastolic dysfunction, the latter correlating with decreased exhaled NO. The NO pathway is intact, suggesting impaired availability of NO as contributor to cardiomyopathy.

Alterations in heart failure of cyclic AMP-dependent inotropic and lusitropic properties of cardiac and skeletal muscle.

A central working hypothesis in our laboratory is that deficient cellular cyclic AMP concentrations may be responsible, at least in part, for striated muscle dysfunction, both cardiac and skeletal, in heart failure. These results suggest that therapy aimed at restoring cyclic AMP to normal levels may be effective with regard to improving systolic and diastolic function in the heart and may decrease the development of fatigue in skeletal muscle of patients with failure. The use of cyclic AMP-dependent drugs in clinical practice has been limited by side effects associated with raising total cellular content of this cyclic nucleotide. However, evidence suggesting that separate pools of cyclic AMP may exist within the cell raises the possibility that those pools associated with excitation/contraction coupling could serve as more specific therapeutic targets.

Mechanisms of positive inotropic action of flosequinan, hydralazine, and milrinone on mammalian myocardium.

Flosequinan is an arterial and venous dilator that also has a positive inotropic effect at relatively higher doses. The purpose of this study was to determine the mechanism of this positive inotropic effect in ferret papillary muscles loaded with the Ca2+ indicator, aequorin. Over the range of doses from 10(-6) to 10(-3) M, flosequinan produced a 61 +/- 9% increase in peak tension that was accompanied by a corresponding increase in [Ca2+]i. This positive inotropic effect was not selectively blocked by addition to the perfusate of procaine 0.6 microM, tetrodotoxin 10(-6) M or by verapamil, 5 x 10(-8) M. In contrast, the positive inotropic effect of flosequinan, but not milrinone or hydralazine, was potentiated by prior addition of ouabain 3 nM to enhance intracellular Ca2+ via reduction of the Na+/Ca2+ exchange. Moreover, antagonists of Na+/Ca2+ exchange, including cadmium 10 microM, amiloride 600 microM and choline substitution for 1/3 Na+ in the perfusate, blocked the response to flosequinan but not hydralazine or milrinone. These results indicate that flosequinan produces a positive inotropic effect by reduction of Na+/Ca2+ exchange in mammalian myocardium. Moreover, flosequinan has the potential to interact synergistically with other positive inotropic agents such as digoxin that affect Na+/Ca2+ exchange by direct or indirect actions.

The social organization of nutritional inequities.

An institutional ethnography, a qualitative research methodology grounded in critical social science, was undertaken with the purpose of explicating the social organization of nutritional inequities among socially/economically disadvantaged women and their families living in an urban centre in Nova Scotia, Canada. Methods included participant observation of food and nutrition practices in the homes of five socially disadvantaged families and at a community drop-in center in a low-income neighborhood; in-depth individual interviews with family members; and group interviews with an additional 28 participants at the community center. Tape recordings and field observation notes were analyzed thematically, preserving the perspectives of the research participants. The explication began with the examination of the everyday household work of feeding the family which provided an entry point to broader social relations working outside of the households, but evident within them. At the household level, the gendered, 'invisible' nature of feeding work became readily apparent. The class context of feeding work became particularly evident upon examination of the practice of procuring food. The apparently simple act of buying groceries was complicated by limited access to inexpensive stores. The families developed innovative strategies to enhance their abilities to procure food within their limited means. However, because of inadequacies of subsistence welfare policies, they frequently were sufficiently short of funds to necessitate reliance on charity for food. Analysis of such social policy revealed that public and professional discourses organizing nutritional inequities were informed by individualistic ideology. Yet, individualistic discourses could not provide an adequate understanding of the experiences of the research participants. The impact of individualistic professional discourse included the irrelevance of nutrition education practices based upon information dissemination. In sum, the research revealed nutritional inequities as embedded within social constructs such as gender, class, commerce, policy and discourse. The educative nature of the participatory research process empowered study participants to initiate structural change in commercial pricing practices. Through making the analysis available to others, including policy makers, it may be possible to work toward changing the oppressive social organization which perpetuates inequities. The research calls for a reorientation in community educational practice from the dominant individual orientation to a social orientation.

The dragnet of children's feeding programs in Atlantic Canada.

Ivan Illich's 1976 prediction that medical dragnets will continue was correct. Now quasi-health dragnets are being established ostensibly to feed children perceived to be hungry. Our qualitative, multi-site case study found that programs justify their expansion to non-target group children as a means of reducing stigmatization, while reaching only an estimated one-third of targeted children. The dragnet continues as new services are added and franchising is proposed while the purpose of the program feeding healthy foods to children ultimately succumbs to drives for efficiency and the desire to maintain the program itself. In this field of social power relations, children become commodified through dialectical interplays among fundamental needs, manipulated needs, benevolence, and domination.

Associations between incisor and mandibular condylar movements during maximum mouth opening in humans.

This study evaluated the common clinical assumption that condylar translation and mouth opening at the incisor are closely related. The sample studied comprised 27 adult females (23-35 years), selected for normal temporomandibular function, occlusion, and skeletal patterns. Condylar and mandibular central incisor movements (straight-line distances and curvilinear pathways) were recorded in three dimensions (3D) for 20 s with an optoelectric (Optotrak(R)) jaw-tracking system while each participant performed multiple maximum opening cycles. Masticatory analysis and multilevel statistical programs computed the 3D movements of the incisors and condylar hinge axis during opening and closing. The incisor point moved an average straight-line distance of 46.6 mm during opening and 45.9 mm during closing; the lengths of the opening and closing curvilinear pathways were 48.6 and 47.7 mm, respectively. The condyles moved average straight-line distances of 11.9 and 12.2 mm during opening and closing, respectively. The condyles' curvilinear pathways during opening and closing were 14 and 14.6 mm, respectively. Ranges of condylar movement varied widely between individuals. The straight-line distances and curvilinear pathways were highly correlated for the incisors (R=0.98) and the condyles (R=0.98). Neither the straight-line distances nor curvilinear pathways of the incisors were correlated with those of the condyles. Incisor straight-line distances and curvilinear pathways were moderately correlated with mandibular rotation (R(between subjects)=0.82 and R(between repeats)=0.88). During repeated openings, both condylar and incisor excursions increased, but during repeated closings only incisor excursions increased. It is concluded that (1) maximum incisor opening does not provide reliable information about condylar translation and its use as a diagnostic indicator of condylar movement should be limited, (2) healthy individuals may perform normal opening with highly variable amounts of condylar translation, (3) the straight-line distances of the incisor and condyles provide adequate information about the length of the curvilinear pathway, and (4) variation in maximum incisor opening is largely explained by variation in the amount of mandibular rotation.

Incisor and mandibular condylar movements of young adult females during maximum protrusion and lateratrusion of the jaw.

This study evaluated the correlations between condylar translation and incisor movements during maximum protrusion and lateratrusion. The sample was 27 adult females (23--35 years old), selected for normal temporomandibular function, occlusion, and skeletal patterns. Condylar and mandibular central incisor movements [linear distances (LD) and curvilinear pathways (CP)] were recorded in three dimensions for 20 s with an optoelectric (Optotrak) jaw-tracking system while each participant performed multiple maximum protrusive and lateratrusive cycles. Masticatory analysis and multilevel statistical programs computed the three-dimensional movements of the incisors and condylar hinge axis during protrusion and lateratrusion. CP of the incisor point averaged 12.0 mm (9.3 mm LD) during protrusion, 13.0 mm (11.5 mm LD) during right excursion and 12.3 mm (11.0 mm LD) during left excursion. CP of the condyles averaged 11.9--12.9 (9.2--9.5 LD) mm during protrusion. During lateratrusion the contralateral condyles moved anteroinferiorly 11.6--14.1 mm (9.5--10.2 mm LD); the ipsilateral condyles moved posterolaterally 5.8-6.8 mm (2.3--2.5 mm LD). The left condyles demonstrated more movement than the right condyles during protrusion and than the contralateral condyles during laterotrusion. Relative variation, as measured by the coefficient of variation, was greater for the movements of the ipsilateral than contralateral condyles. Incisor movements were only moderately related to condylar movements between individuals and between replicates; LDs showed stronger correlations than CPs; and correlations were stronger for lateratrusion than protrusion. While incisor and condylar movements were not affected by repeated protrusion, incisor CP (approx. 0.2 mm/cycle) and LD (approx. 0.1 mm/cycle) increased significantly with repeated excursive movements to the left and right. It was concluded that (1) incisor protrusion and lateratrusion provide moderately reliable measures of condylar translation; (2) the linear distances that the incisors move during lateratrusion provide the best measure of contralateral condylar translation; and (3) condylar movements are not affected by repeated protrusion or lateratrusion.

Reducing inequities through participatory research and community empowerment.

Information dissemination for behavior change has been the mainstay of traditional health education practice, despite lack of demonstrated effectiveness in improving the public's health. Following a critique of traditional health education practice, an alternative orientation is proposed. Health education for social change, based on Paulo Freire's empowerment education and principles of participatory research, is examined theoretically within the context of the need to address inequities in health. The theoretical justification forms the basis for a description of a case study in reducing nutritional inequities. The case study analyzes how a process of participatory research and community organization was an empowering educational experience for a group of low-income urban women. The process of learning and social action is highlighted by chronicling changes associated with the experience. The realities and limitations of the project are also reflected upon. Implications for health education practice and future social change are highlighted.

Children's feeding programs in Atlantic Canada: reducing or reproducing inequities?

This study analyzed, through case studies of day-to-day observations and interviews with recipients and operators, the operations of nine children's feeding programs in Nova Scotia, New Brunswick, and Newfoundland. We found that children's feeding programs result in the stigmatization of participants and families, despite an ideology of equality. Most programs adopt a family substitution role in the lives of children they serve and function in a way that excludes parental participation. Programs also transmit a hidden curriculum to children that teaches them how to behave and how a 'proper' family functions. We found that the professionalization of food and nutrition, a desire for an expanded client base, and dependency creation through the provision of other material goods, permit programs to exert increasing institutional control over recipients, a process we, following Illich, call the dragnet. While these programs may be meeting some nutritional needs in a few poverty-stricken children, they ultimately reproduce, rather than reduce, inequities.

Homozygous familial hypercholesterolemia (HoFH) in Germany: an epidemiological survey.

INTRODUCTION: In Europe a disease is recognized as rare if less than 1 in 2000 people suffer from the specific disease. In patients with familial homozygous hypercholesterolemia (HoFH) the accumulation of low-density lipoprotein cholesterol (LDL-C) leads to generalized atherosclerosis due to an insufficient functioning of the LDL-C receptors. Patients die early sometimes even in the mid-30s, from myocardial infarction or stroke. For the German population, insufficient epidemiological evidence exists. METHODS: A systematic literature search in EMBASE and Medline was performed in conjunction with a targeted manual search for epidemiological HoFH studies. Additionally a nationwide survey was conducted in Germany in all identified apheresis- and lipid centers. The purpose of the survey was the validation of the systematic literature search results based on empirical (practice) data. RESULTS: In total 961 publications were found, 874 were excluded based on pre-defined exclusion criteria leaving only 87 for further review. After review of the identified abstracts (n = 87) 23 publications were identified as epidemiological studies. Only one publication was found which reported a prevalence of 1:1,000,000. The qualitative survey among 187 physicians in Germany also revealed a low prevalence: 95 HoFH patients were identified in 35 centers. CONCLUSION: The estimated frequency of homozygous familial hypercholesterolemia patients in Germany is around 95 (1:860,000) and the disease should be recognized as rare according to the definition of the European Medical Agency.