#BodyPositive? A critical exploration of the body positive movement within physical cultures taking an intersectionality approach

Feminist activists and critical sport scholars in the global north have advocated for more inclusive representation of bodies and more accessible physical cultures. Body positivity, a contentious movement and concept, has been taken up in various ways by different groups. Some scholars believe it holds power to liberate individuals from patriarchal, neoliberal, capitalist, and colonial ideologies of what constitutes a "good" body. On the contrary, critics assert this movement has been gentrified by white-centered politics. Intersectionality has a similar genealogy as body positivity, with a rich history in Black feminist thought but now considered by many as coopted and whitened. In this article, we trace the rich and divergent legacies of both movements and explore at the structural level how body positivity is represented within physical cultures on Instagram. We use a social-justice oriented intersectionality framework exploring #BodyPositivity and #BodyPositive across a total of 141 posts using reflexive thematic analysis. We organize our findings into four themes: 1) Disclosure-Privilege of Body-Related Journeys; 2) The Absent-Present; 3) Consuming Positivity; and 4) Disrupting Normative Body Positivity Posts. Overall, we found that only certain bodies (and transformations) were visible within the data: those of (now) lean, white, cis-gendered individuals, many of whom were engaged in bodybuilding, and who were sharing their bodily transformation. We observe a remarkable absence of BIPOC, 2S LGBTQAI+, fat/thick/thicc/curvy, older, gender-nonconforming, and/or disabled representations. We also note the myriad ways that body positivity has been commodified and packaged into a product or service for consumption. Lastly, we outline and celebrate the exceptions to this norm where a minority of posts align more closely with the original intentions of the body positivity movement. We conclude with our position on how to do intersectionality research, and call on researchers to honor Black feminist origins and rich social justice history in these movements.

Is a Picture Worth a Thousand Words? Using Photo-Elicitation to Study Body Image in Middle-to-Older Age Women With and Without Multiple Sclerosis

In this study, we explored how women with varying relationships to disability and aging used photographs to represent their body image experiences. Seven middle-aged and older adult women with and without multiple sclerosis were asked to provide up to 10 photographs that represented their body image and complete a one-on-one interview. We used reflexive thematic analysis to develop themes and interpret the findings. Overall, the women expressed not only complicated relationships with their bodies, represented through symbolism, scrutiny of body features (e.g., posture, varicose veins, and arthritis) but also deep reflection linked to positive body image and resilience. These findings revealed not only the nuanced experiences women have with aging, disability, and gender but also the commonly experienced ingrained views of body appearance as each participant illustrated a difficult negotiation with the aesthetic dimension of their body image. Finally, we provide important implications of the use of visual methods in body image research.

Exploring primary care providers' understandings of body image in patient care

Research has shown that healthcare providers lack confidence in having the knowledge needed to have conversations about body image with their patients. No research to date has explicitly explored how providers in primary healthcare understand body image, including its definition and how it impacts plans for care. Accordingly, the current study explored how primary healthcare providers define body image and how they see the concept of body image manifest in their practice. A total of 21 participants were interviewed, including 3 registered dietitians, 6 occupational therapists, 4 physiotherapists, 1 registered massage therapist, 1 kinesiologist, 4 family physicians, 1 nurse, and 1 social worker. Using thematic analysis, it was found that gaps in knowledge about body image were quite apparent as participants' understanding of body image was slippery (e.g., they struggled to articulate specifics about the concept within care and recognized body image is not something associated with a clinical guideline that would bring form to the concept). However, healthcare providers believed in the importance of body image in their patients' care in broad and far reaching ways. Future directions for bridging the knowledge gap with respect to body image among primary healthcare providers are discussed.

Difference-attuned witnessing: Risks and potentialities of arts-based research

In this paper, we interrogate notions of affect, vulnerability and difference-attuned empathy, and how they relate to bearing witness across difference—specifically, connecting through creativity, experiencing the risks and rewards of vulnerability, and witnessing the expression of difficult emotions and the recounting of affect-imbued events within an arts-based process called digital/multi-media storytelling (DST). Data for this paper consists of 63 process-oriented interviews conducted before and after participants engaged with DST in a research project focused on interrogating negative concepts of disability that create barriers to healthcare. These retrospective reflections on DST coalesce around experiences of vulnerability, relationality, and the risks associated with witnessing one’s own and others’ selective disclosures of difficult emotions and affect-laden aspects of experiences of difference. Through analysing findings from our process-oriented interviews, we offer a framework for understanding witnessing as a necessarily affective, difference-attuned act that carries both risk and transformative potential. Our analysis draws on feminist Indigenous (Maracle), Black (Nash) and affect (Ahmed) theories to frame emerging concepts of affective witnessing across difference, difference-attuned empathy, and asymmetrical vulnerability within the arts-based research process.

Barriers and facilitators to adhering to an anti-inflammatory diet for individuals with spinal cord injuries

The purpose of this study was to explore the barriers and facilitators of an anti-inflammatory diet in people with spinal cord injury. Six participants (age range of 23-68 years, three women and three men) who had previously completed an anti-inflammatory diet study were interviewed. Facilitators identified were family support, autonomy over meal choice, peer support, health benefits gained, and implementation of adherence strategies. The main barriers discussed were lack of motivation after study period ended, social events, diet expenses, and lack of knowledge about the diet. Several health benefits including reductions in pain, edema, and improvements in cognition and mobility were reported.

How do you define body image? Exploring conceptual gaps in understandings of body image at an exercise facility

The definition of body image has evolved within research; however, less is known about the layperson's understanding of the construct. This study explored how members and student trainees of an exercise facility (designed for older adults, people with physical disability, and those with cardiac complications) defined body image. Nineteen participants completed a one-on-one interview, and seven of those participants took part in six additional focus group meetings. The following main themes were found: stereotypical assumptions about body image (e.g., it is solely a person's weight or merely a woman's issue), body image continua for positive and negative body image, degree of complexity of body image dimensions, broad considerations of body image (e.g., it is self-esteem), and limited knowledge about body image. These findings suggest a need for knowledge translation between researchers and the general public which informs future body image program design.

Exploring the complexities of body image experiences in middle age and older adult women within an exercise context: The simultaneous existence of negative and positive body images

Despite many body changes that accompany the aging process, the extant research is limited on middle age and older adults' body image experiences. The purpose of the present study was to explore how body image is represented for middle age and older adult women. Using thematic analysis, 10 women over the age of 55 were interviewed within an exercise context. The following themes were found: body dissatisfaction, body satisfaction despite ageist stereotypes, neutral body image within cohort, and positive body image characteristics. Negative and positive body images were experienced simultaneously, with neutral experiences expressed as low levels of dissatisfaction. This supports the contention that negative and positive body images exist on separate continuums and neutral body image is likely on the same continuum as negative body image. Programs that foster a social support network to reduce negative body image and improve positive body image in older female populations are needed.

Managing the stigma: Exploring body image experiences and self-presentation among people with spinal cord injury

Using modified constructivist grounded theory, the purpose of this study was to explore body image experiences in people with spinal cord injury. Nine participants (five women, four men) varying in age (21–63 years), type of injury (C3-T7; complete and incomplete), and years post-injury (4–36 years) took part in semi-structured in-depth interviews. The following main categories were found: appearance, weight concerns, negative functional features, impact of others, body disconnection, hygiene and incontinence, and self-presentation. Findings have implications for the health and well-being of those living with a spinal cord injury.

"It's all about acceptance": A qualitative study exploring a model of positive body image for people with spinal cord injury

Using modified constructivist grounded theory, the purpose of the present study was to explore positive body image experiences in people with spinal cord injury. Nine participants (five women, four men) varying in age (21-63 years), type of injury (C3-T7; complete and incomplete), and years post-injury (4-36 years) were recruited. The following main categories were found: body acceptance, body appreciation and gratitude, social support, functional gains, independence, media literacy, broadly conceptualizing beauty, inner positivity influencing outer demeanour, finding others who have a positive body image, unconditional acceptance from others, religion/spirituality, listening to and taking care of the body, managing secondary complications, minimizing pain, and respect. Interestingly, there was consistency in positive body image characteristics reported in this study with those found in previous research, demonstrating universality of positive body image. However, unique characteristics (e.g., resilience, functional gains, independence) were also reported demonstrating the importance of exploring positive body image in diverse groups.

Gatekeepers of Gerontological Research

Gerontological studies note research noncompliance as a limitation of their results; however, few investigations focus on ways to minimize noncompliance. Additionally, older adults’ research participation is often controlled by other individuals such as the managers of retirement residences or community centers, where recruitment often occurs. These individuals are, in essence, the Gatekeepers of research participation among older adults. This pilot study explored ‘research participation’ through semistructured interviews with four managers. Analysis of the transcript data identified several important differences between managers of retirement residences and community center managers. Gerontologists interested in obtaining more representative samples may want to consider the contextual factors of the managerial systems and experiences that can facilitate or obstruct research participation of older adults.

p21(WAF1/CIP1) induction by 5-azacytosine nucleosides requires DNA damage

Decitabine (DAC) and 5-azacitidine have recently been approved for the treatment of myelodysplastic syndrome. The pharmacodynamic effects of DAC and 5-azacitidine outside their known activity as inhibitors of DNA methyltransferases (DNMTs) require further investigation. The purpose of this study was to investigate the effect of DAC on the expression of p21(WAF1/CIP1), a gene with a putative CpG island surrounding its promoter region. Promoter methylation analysis of p21(WAF1/CIP1) in leukemia cells revealed the absence of CpG methylation. However, DAC upregulated p21(WAF1/CIP1) expression in a dose-dependent manner (ED(50)=103.34 nM) and induced G2/M cell cycle arrest in leukemia cells. Sequential application of DAC followed by different histone deacetylase inhibitors induced expression of p21(WAF1/CIP1) synergistically. Upregulation of p21(WAF1/CIP1) paralleled DAC-induced apoptosis (ED(50)=153 nM). Low doses of DAC induced gamma-H2AX expression (ED(50)=16.5 nM) and upregulated p21(WAF1/CIP1) in congenic HCT 116 colon cancer cells in a DNMT-independent and p53-dependent fashion. Inhibition of p53 transactivation by pifithrin-alpha or the kinase activity of ATM by either the specific ATM inhibitor KU-5593 or caffeine abrogated p21(WAF1/CIP1) upregulation, indicating that DAC upregulation of p21(WAF1/CIP1) was p53- and ATM-dependent in leukemia cells. In conclusion, DAC upregulates p21(WAF1/CIP1) in DNMT-independent manner via the DNA damage/ATM/p53 axis.

Factors regulating the differentiation of neural precursors in the forebrain

Precursors from the neuroepithelium of the developing cortex and the adult subventricular zone can be cloned in vitro after stimulation with fibroblast growth factor 2 (FGF-2), and they have the potential to give rise to both neurons and glia. The generation of neurons from these clones can be stimulated by either a factor derived from an astrocyte precursor line, Ast-1, or FGF-1. We have shown that neuronal differentiation stimulated by FGF-1 can be inhibited by diacylglycerol lipase inhibitor and mimicked by arachidonic acid, suggesting that the neuronal differentiation is signalled through the phospholipase C gamma pathway. The sequential expression of FGF-2, followed by FGF within the developing forebrain neuroepithelium, fits with the different functions that the two FGFs play in precursor regulation. We have shown that the precursor response to FGF-1 is regulated by a heparan sulphate proteoglycan expressed within the developing neuroepithelium. Precursors restricted to the astrocyte cell lineage can be stimulated by epidermal growth factor or FGF-2F however, the differentiation into glial fibrillary acidic protein-positive astrocytes appears to require a cytokine acting through the leukaemia inhibitory factor-beta receptor.

Archaeal histones: structures, stability and DNA binding

Structures, stability and DNA-binding properties have been established for archaeal histones from mesophiles, thermophiles and hyperthermophiles. Most archaeal histones are simply histone folds that are stabilized by dimer formation. Archaeal histones and the histone folds of the eukaryotic nucleosome core histones share a common ancestry and bind and wrap DNA similarly using conserved residues. The histone-fold residues that stabilize dimer–dimer interactions within an archaeal histone core contribute to determining archaeal histone–DNA affinity.

Archaeal histone selection of nucleosome positioning sequences and the procaryotic origin of histone-dependent genome evolution

Archaeal histones and the eucaryal (eucaryotic) nucleosome core histones have almost identical histone folds. Here, we show that DNA molecules selectively incorporated by rHMfB (recombinant archaeal histone B from Methanothermus fervidus) into archaeal nucleosomes from a mixture of approximately 10(14) random sequence molecules contain sequence motifs shown previously to direct eucaryal nucleosome positioning. The dinucleotides GC, AA (=TT) and TA are repeated at approximately 10 bp intervals, with the GC harmonic displaced approximately 5 bp from the AA and TA harmonics [(GCN(3)AA or TA)(n)]. AT and CG were not strongly selected, indicating that TA not equalAT and GC not equalCG in terms of facilitating archaeal nucleosome assembly. The selected molecules have affinities for rHMfB ranging from approximately 9 to 18-fold higher than the level of affinity of the starting population, and direct the positioned assembly of archaeal nucleosomes. Fourier-transform analyses have revealed that AA dinucleotides are much enriched at approximately 10. 1 bp intervals, the helical repeat of DNA wrapped around a nucleosome, in the genomes of Eucarya and the histone-containing Euryarchaeota, but not in the genomes of Bacteria and Crenarchaeota, procaryotes that do not have histones. Facilitating histone packaging of genomic DNA has apparently therefore imposed constraints on genome sequence evolution, and since archaeal histones have no structure in addition to the histone fold, these constraints must result predominantly from histone fold-DNA contacts. Based on the three-domain universal phylogeny, histones and histone-dependent genome sequence evolution most likely evolved after the bacterial-archaeal divergence but before the archaeal-eucaryal divergence, and were subsequently lost in the Crenarchaeota. However, with lateral gene transfer, the first histone fold could alternatively have evolved after the archaeal-eucaryal divergence, early in either the euryarchaeal or eucaryal lineages.

DNA repeats and archaeal nucleosome positioning

Archaeal histones, homologs of the eucaryal nucleosome core histones, have been identified in the Euryarchaeota. They assemble as tetramers with dsDNA to form archaeal nucleosomes that resemble the central structure of the eucaryal nucleosome formed by the histone (H3-H4)2 tetramer. Eucaryal and archaeal nucleosomes assemble preferentially on DNA molecules that best accommodate the severe bends found within these structures, and here we discuss the relationships between archaeal and eucaryal nucleosomes, repeating DNA sequences, and nucleosome positioning.

Intracellular accumulation of detergent-soluble amyloidogenic A beta fragment of Alzheimer's disease precursor protein in the hippocampus of aged transgenic mice

To study amyloid beta-protein (A beta) production and aggregation in vivo, we created two transgenic (Tg) mouse lines expressing the C-terminal 100 amino acids of human amyloid precursor protein (APP): Tg C100.V717F and Tg C100.WT. Western blot analysis showed that human APP-C100 and A beta were produced in brain and some peripheral tissues and A beta was produced in serum. Using antibodies specific for the A beta C terminus we found that Tg C100.V717F produced a 1.6-fold increase in A beta42/A beta40 compared with Tg C100.WT. Approximately 30% of total brain A beta (approximately 122 ng/g of wet tissue) was water-soluble. The remaining 70% of A beta partitioned into the particulate fraction and was completely sodium dodecyl sulfate-soluble. In contrast, human Alzheimer's disease brain has predominantly sodium dodecyl sulfate-insoluble A beta. Immunohistochemistry with an A beta(5-8) antibody showed that A beta or A beta-containing fragments accumulated intracellularly in the hippocampus of aged Tg C100.V717F mice. The soluble A beta levels in Tg brain are similar to those in normal human brain, and this may explain the lack of microscopic amyloid deposits in the Tg mice. However, this mouse model provides a system to study the intracellular processing and accumulation of A beta or A beta-containing fragments and to screen for compounds directed at the gamma-secretase activity.

Histone stoichiometry and DNA circularization in archaeal nucleosomes

Recombinant (r)HMfB (archaealhistone B fromMethanothermusfervidus) formed complexes with increasing stability with DNA molecules increasing in length from 52 to 100 bp, but not with a 39 bp molecule. By using125I-labeled rHMfB-YY (an rHMfB variant with I31Y and M35Y replacements) and32P-labeled 100 bp DNA, these complexes, designated archaeal nucleosomes, have been shown to contain an archaeal histone tetramer. Consistent with DNA bending and wrapping, addition of DNA ligase to archaeal nucleosomes assembled with 88 and 128 bp DNAs resulted in covalently-closed monomeric circular DNAs which, following histone removal, were positively supercoiled based on their electrophoretic mobilities in the presence of ethidium bromide before and after relaxation by calf thymus topoisomerase I. Ligase addition to mixtures of rHMfB with 53 or 30 bp DNA molecules also resulted in circular DNAs but these were circular dimers and trimers. These short DNA molecules apparently had to be ligated into longer linear multimers for assembly into archaeal nucleosomes and ligation into circles. rHMfB assembled into archaeal nucleosomes at lower histone to DNA ratios with the supercoiled, circular ligation product than with the original 88 bp linear version of this molecule. Archaeal histones are most similar to the globular histone fold region of eukaryal histone H4, and the results reported are consistent with archaeal nucleosomes resembling the structure formed by eukaryal histone (H3+H4)2tetramers.

DNA binding and nuclease protection by the HMf histones from the hyperthermophilic archaeon Methanothermus fervidus

The DNA-binding and nuclease-protection properties of the HMf histones from the hyperthermophilic archaeon Methanothermus fervidus have been shown to be consistent with the formation of nucleosome-like structures (NLS). These proteins bind to DNA molecules as short as 20 bp and form complexes that protect DNA fragments from micrococcal nuclease (MNase) digestion that are 30 bp, approximately 60 bp and multiples of approximately 60 bp in length. The sequences of 49 of the approximately 60-bp DNA fragments protected from MNase digestion by HMfA have been determined and their intrinsic curvatures calculated. A circular permutation gel mobility-shift assay was used to determine directly the curvatures for five of these sequences. HMfA bound to intrinsically curved and noncurved DNAs, but exhibited a slight preference for the model curved DNA in binding competitions with a model noncurved DNA. The results obtained are consistent with the concept that the archaeal NLS is analogous, and possibly homologous, to the central core of the eukaryal nucleosome formed by a histone (H3 + H4)2 tetramer.

Regulation of neural precursor differentiation in the embryonic and adult forebrain

1. Precursors form the neuroepithelium of the developing cortex and also from the adult sub-ventricular zone, can be cloned in vitro after stimulation with fibroblast growth factor (FGF)-2 and have the potential to give rise to both neurons and glia. The generation of neurons from these clones can be stimulated by either a factor derived from an astrocyteprecursor line, Ast-1, or FGF-1. 2. Neuronal differentiation stimulated by FGF-1 can be inhibited by diacylglycerol-lipase inhibitor and mimicked by arachidonic acid, suggesting that the neuronal differentiation is signalled through the PCL gamma pathway. 3. The sequential expression of FGF-2 and FGF-1 within the developing forebrain neuroepithelium fits with the different functions the two FGF play in precursor regulation. 4. We have shown that the precursor response to FGF-1 is regulated by a heparan sulphate proteoglycan (HSPG) expressed within the developing neuroepithelium. Precursors restricted to the astrocyte cell lineage can be stimulated by epidermal growth factor or FGF-2; however, the differentiation into GFAP positive astrocytes appears to require a cytokine acting through the leukaemia inhibitory factor beta receptor.

Virulence of a Porphyromonas gingivalis W83 mutant defective in the prtH gene

In a previous study we cloned and determined the nucleotide sequence of the prtH gene from Porphyromonas gingivalis W83. This gene specifies a 97-kDa protease which is normally found in the membrane vesicles produced by P. gingivalis and which cleaves the C3 complement protein under defined conditions. We developed a novel ermF-ermAM antibiotic resistance gene cassette, which was used with the cloned prtH gene to prepare an insertionally inactivated allele of this gene. This genetic construct was introduced by electroporation into P. gingivalis W83 in order to create a protease-deficient mutant by recombinational allelic exchange. The mutant strain, designated V2296, was compared with the parent strain W83 for proteolytic activity and virulence. Extracellular protein preparations from V2296 showed decreased proteolytic activity compared with preparations from W83. Casein substrate zymography revealed that the 97-kDa proteolytic component as well as a 45-kDa protease was missing in the mutant. In in vivo experiments using a mouse model, V2296 was dramatically reduced in virulence compared with the wild-type W83 strain. A molecular survey of several clinical isolates of P. gingivalis using the prtH gene as a probe suggested that prtH gene sequences were conserved and that they may have been present in multiple copies. Two of 10 isolates did not hybridize with the prtH gene probe. These strains, like the V2296 mutant, also displayed decreased virulence in the mouse model. Taken together, these results suggest an important role for P. gingivalis proteases in soft tissue infections and specifically indicate that the prtH gene product is a virulence factor.

Neuronal progenitors identified by their inability to express class I histocompatibility antigens in response to interferon-gamma

Interferon-gamma (IFN-gamma) can induce class I major histocompatibility complex (MHC) antigen (H-2) expression on virtually all neuroepithelial cells isolated from embryonic day 9 (E9) mice. However, a subpopulation of cells become refractory to H-2 induction (H-21-) by E10 and the percentage of H-2 noninducible cells increases during development. Cell sorting, by flow cytometry or magnetic bead immunoselection, has shown that H-21- cells give rise exclusively to neuronal cells, and by E12, the majority of the neuronal progenitors are found within this population. It has also been found that 98% of the H-21- also express the neuron-associated marker, A2B5. Cells of the glial cell lineage retain the ability to express class I antigens throughout development. From these studies, it is clear that the neuroepithelium contains cells committed to the neuronal cell lineage as early as E10 in the mouse.

The pattern of diagnosed HIV infection in Australia, 1984-1992

OBJECTIVE

To describe the pattern of newly diagnosed HIV infection in Australia, between 1984 and 1992.

METHODS

State and Territory health authorities reported cases of newly diagnosed HIV infection to the national HIV surveillance centre. Information sought on each case included the State or Territory of diagnosis, the case identifying number, the sex, date of birth and postcode of residence of the person with newly diagnosed HIV infection, the source of exposure to HIV and the date of specimen collection for the diagnosis of infection.

RESULTS

By the end of December 1992, a total of 16,765 cases of newly diagnosed HIV infection had been reported in Australia. The annual number of cases declined between 1985 and 1992. Most diagnoses were among males, and exposure to HIV was attributed to male homosexual contact for more than 80% of cases for which information on exposure to HIV was available. Cases of HIV infection attributed to heterosexual contact represented an increasing proportion of the annual number of diagnoses over the period 1985-1992, among both men and women.

CONCLUSION

National surveillance for newly diagnosed HIV infection has complemented national surveillance for diagnoses of AIDS as a key mechanism for monitoring the course of the HIV epidemic in Australia. The pattern of newly diagnosed HIV infection was similar to the pattern of AIDS diagnoses, with the overwhelming majority of diagnoses of infection being in adult males whose exposure to HIV was attributed to homosexual contact. Limitations of HIV surveillance include the lack of information on HIV testing patterns, incomplete information on HIV exposure histories and duplication of reported diagnoses.

The acquired immunodeficiency syndrome in Australia: incidence 1982-1991

OBJECTIVE

To describe the incidence of the acquired immunodeficiency syndrome (AIDS) in Australia between 1982 and 1991.

DESIGN

State and Territory Health Departments notified new diagnoses of AIDS to the National AIDS Registry. Information reported for each case included sex, date of birth, date of AIDS diagnosis, presumed mode of exposure to the human immunodeficiency virus (HIV), and illness(es) on which the diagnosis of AIDS was based.

RESULTS

To the end of March 1992, 3,160 cases of AIDS were reported as having been diagnosed between 1982 and the end of 1991. The cumulative incidence per head of population was about twice as high in New South Wales as in Australia as a whole. Over 97% of cases were in men, of whom 91% were adults or adolescents reporting homosexual contact. In women, 40% of cases were acquired through receipt of blood, blood products or tissue. The annual incidence of AIDS rose sharply until about 1988, but the annual rates of increase slowed in subsequent years. This trend was also apparent in cases acquired through sexual contact between men. In other exposure groups, numbers of cases were much smaller and trends less apparent. However, there was no indication of a similar levelling in AIDS incidence, except among blood transfusion recipients, in whom incidence may be declining.

CONCLUSION

Transmission of HIV among people with AIDS in Australia has been overwhelmingly attributed to sexual contact between men. The annual incidence of cases attributed to sexual contact between men appears to be stabilising.

A method for the isolation of purified murine neuroepithelial cells from the developing mouse brain

The adult mammalian central nervous system develops from the pseudostratified neuroepithelium of the neural tube. In order to study, in vitro, the differentiation of the neuroepithelial cells in detail and to identify factors that may influence this process, an uncontaminated, viable population of neuroepithelial cells, that still retains full developmental potential, is required. In this paper we describe a highly efficient method, involving differential trypsinization and micro-dissection, to cleanly separate the neuroepithelium from surrounding mesenchyme and ectoderm. The purity of isolated neuroepithelium has been assessed by monitoring for the presence of endothelial cells using an anti-endothelial antibody, MTS-12, and found to contain no significant level of contamination. Neuroepithelial cells prepared by this method have been demonstrated to divide and differentiate in tissue culture, to act as target cells for immortalization by proto-oncogenes and to differentiate into neurons in neural transplantation studies.

What stimulates atrial natriuretic factor release during exercise?

Prior studies have shown that circulating atrial natriuretic factor (ANF) increases during short-term exercise, but the mechanism controlling ANF release, as well as the effect of exercise training on ANF release, remains unclear. Fifteen healthy mongrel dogs underwent short-term exercise testing before and after a 12-week period of exercise training (n = 8) or cage confinement (n = 7). ANF, norepinephrine, epinephrine, right atrial pressure, and heart rate were measured simultaneously at rest and during exercise at the time of each acute exercise study. Data were analyzed for all animals with normal baseline ANF values. Exercise training had no modulating effect on circulating ANF levels at rest or during exercise. Therefore, data before and after exercise training or cage confinement were grouped (n = 24) to determine the effects of short-term exercise. ANF levels increased from 49 +/- 2 pg/ml at rest to 60 +/- 4 pg/ml during exercise (p less than 0.05). Heart rate, norepinephrine, and epinephrine values also increased, but right atrial pressure actually decreased from 2.3 +/- 0.9 mm Hg at rest to -3.8 +/- 0.9 mm Hg during exercise (p less than 0.05). There was no correlation between ANF concentrations and levels of these other variables either at rest of during exercise. By demonstrating an increase in ANF with a simultaneous decrease in right atrial pressure, this study clearly shows that increased right atrial pressure is not the secretory stimulus for ANF release during exercise in the normal dog. The lack of correlation between ANF and right atrial pressure, heart rate, norepinephrine, and epinephrine levels suggests that factors other than these variables stimulate ANF release during short-term exercise.

Immortalization of mouse neural precursor cells by the c-myc oncogene

Immortalized cell lines have been generated from embryonic mouse neuroepithelium by infection with a retrovirus containing the c-myc oncogene. The morphology and the antigenic phenotype of the cloned cell lines are characteristic of normal neuroepithelium. Although the cell lines are stable and do not spontaneously differentiate, morphological changes can be induced with both acidic and basic fibroblast growth factor. Fibroblast growth factor at 5 ng/ml stimulates differentiation of the neuroepithelial cells, and it has been shown that the cloned cell line 2.3D can differentiate into astrocytes, containing glial fibrillary acidic protein, and neurons, expressing the A2B5 marker and neurofilaments. This indicates that some cells in the neuroepithelium at embryonic day 10 are multipotent and are not restricted to either the glial or neuronal cell lineage. The cell lines also can be induced with interferon gamma to express class I and class II histocompatibility antigens. The response of the c-myc-immortalized cell lines to these two factors is similar to that observed with freshly isolated neuroepithelium and suggests that such immortalized precursor populations are representative of the cells found in the developing neuroepithelium.

Family medicine in small communities

This article is an off-the-cuff commentary on one practice in a city of 40,000 people. This city is in a largely agricultural area. The article stresses the pluses: the continuity of care and the more interesting and variegated nature of family practice here. There are negatives, as well: the more limited social life and the problems relating to employment for one's spouse. Patient confidentiality is more difficult to maintain, as is one's own privacy. Generally it is a busier and more challenging life, which I heartily recommend.