Computerized transaxial x-ray tomography of the human body.

The ACTA-Scanner has virtually unlimited potential in the evalution of any part of the body. The usefulness of the technique has already been shown in the appraisal of pathologies of the brain and cerebrospinal fluid cavities. The orbits and the eyeballs, the facial sinuses, and skull base lesions have also been elucidated. Tumors of the larynx, pharynx, thyroid, and parathyroid; lymphomas; and pathology of the spine and spinal cord are well within the reach of this new diagnostic methodology. Lung pathologies, such as emphysema, pneumonias, neoplasms, infarctions, pleural effusions and granulomatous diseases, and mediastinal pathology represent a challenging complex of lesions to be appraised by ACTA-scanning. For the heart, there is great potential for observing cardiac chamber size, hypertrophy of ventricular or atrial walls, and ventricular or aortic aneurysms, and possibly for recognizing the damaged myocardial tissue immediately after or some time after an infarction. The abdominal pathologies that can be studied are almost uncountable: gastric neoplasms, pancreatic cysts and stones, gallstones, neoplasms of the liver and pancreas, bowel tumors, abdominal aortic aneurysms, renal neoplasms and cysts, atrophy of the kidneys, bladder tumors, uterine tumors, ovarian cysts, and many more. Although bones and joints are adequately demonstrated by conventional x-ray techniques, there is no doubt that as the new technique is developed ACTA-grams will contribute significant information in the transverse plane, as well as in densitometric analyses. The impact of ACTA-scanning will not be limited to the diagnostic area, but will extend, at least indirectly, to general patient management and to some aspects of medical economics as well. Risk-laden, technically complex, and costly diagnostic procedures, sometimes requiring lengthy hospitalization, will in some cases be eliminated. The simple, innocuous, and noninvasive ACTA-scanning can be performed on an outpatient basis. Repeated follow-up examinations should be easily accepted by the patients, considering that this diagnostic test is carried out without discomfort. The entire field of diagnostic radiology is on the verge of revolutionary changes.

HIV associated pulmonary emphysema: a review of the literature and inquiry into its mechanism.

Chronic lung diseases are increasingly recognised complications of the human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). Of these, pulmonary emphysema, characterised by permanent destruction of the lung parenchyma distal to the terminal bronchioles accompanied by various degrees of inflammation, is emerging as a distinct source of morbidity for patients infected with HIV. Similarly, HIV is now frequently cited as a susceptibility factor for the development of emphysema, independent of cigarette smoking status. The presence of common coexistent confounding factors that may predispose patients to chronic lung injury such as drugs, opportunistic infections and malnutrition, limits the scope of studies of direct mechanisms involved in HIV associated emphysematous lung disease. We review the clinical studies supporting a direct association between HIV infection and emphysema. Recent developments in the basic understanding of HIV infection and emphysema are also reviewed, since they may aid in understanding the pathobiology of HIV associated emphysema. The authors emphasise how HIV infection may affect cytotoxic lymphocyte activation, lung capillary endothelial cell injury and apoptosis, sphingolipid imbalance and oxidative stress in the lung. A better understanding of the pathogenesis of HIV associated pulmonary emphysema may provide clues and therapeutic targets that have broader application in this disease, including cigarette smoke induced emphysema.

Impaired alveolar macrophage accessory cell function and reduced incidence of lymphocytic alveolitis in HIV-infected patients who smoke.

OBJECTIVE: To determine the effects of smoking on alveolar macrophage (AM) accessory cell (AC) function and the incidence of lymphocytic alveolitis in asymptomatic HIV-infected individuals. METHODS: AM AC function in smoking and nonsmoking HIV-positive volunteers was measured in concanavalin A and pokeweed mitogen assays. Mitogen-induced AM-T-cell adherence was determined. AM cytokine secretion was analyzed by interleukin (IL)-6 bioassay and IL-1 enzyme-linked immunosorbent assay (ELISA). The incidence of lymphocytic alveolitis in both groups was determined. RESULTS: AM from smokers were significantly poorer AC than AM from nonsmokers. Though AM-T-cell adherence was unaffected by smoking, IL-1 and IL-6 secretion was significantly impaired. Lymphocytic alveolitis was significantly less common in HIV-infected smokers. CONCLUSION: Smoking reduces AM AC function in HIV-infected individuals, probably by impairing secretion of cytokines important in T-cell proliferation. This may explain the decreased incidence of lymphocytic alveolitis in HIV-infected people who smoke.

Radiographic appearance of the thorax in systolic click-late systolic murmur syndrome.

The posteroanterior and lateral chest X-ray films of 64 consecutive patients with an isolated systolic click (55 patients) or a systolic click with a late systolic murmur (9 patients) showed a striking frequency of thoracic skeletal abnormalities. There were 50 female and 14 male subjects. The average age of the female subjects was 36.7 years (range 13 to 67), that of the male subjects 39.7 years (range 17 to 56). Seventy-two percent of the female and 78 percent of the male subjects had an anteroposterior/transverse thoracic ratio less than the mean ratio in a small population. Bony abnormalities such as pectus excavatum, straight thoracic spine and scoliosis occurred alone or in a combination in 31 of the 50 female patients (62 percent) and in 8 of the 14 male patients (57 percent). Overall, 39 of the 64 patients (61 percent) had at least one of the skeletal abnormalities. Scoliosis occurred in 25 subjects (39 percent) and was mild in 19. A "straight back" was found in 15 (23 percent) and pectus excavatum in 7 patients (11 percent). The explanation for these findings is not apparent. Thoracic cage abnormalities should be included as one of the nonauscultatory features of the systolic click-late systolic murmur syndrome.

B-lymphocytes in the lung: a topic to be revisited.

Humoral immunity is crucial to the immunologic homeostasis of the lung. Although having key roles in the clearance of infectious pathogens, humoral responses under certain condition may contribute to pathology in the lung. The regulation of local humoral immunity involves a highly complex network of antigen presenting cells, T and B-lymphocytes, as well as many membrane-bound and soluble signals. This review discusses B-lymphocyte function and immunoglogulin production in general, as well as the regulation and function of humoral immunity as it relates to the lung in health and disease.

Pulmonary host defenses.

The lung is constantly exposed to invading particulate matter and potential pathogens. To cope with this pressure, the lung has evolved a sophisticated, multitiered defense mechanism designed to clear offending agents while inducing a minimum amount of concomitant inflammation. Mechanical defense mechanisms first attempt to remove material physically from the tracheobronchial tree. Particulate matter and pathogens that circumvent this first line of defense are ingested by resident and recruited phagocytes in the lower respiratory tract and alveoli. If phagocytic defenses are impaired or overwhelmed, specific immune mechanisms become operational and lead to the generation of delayed-type hypersensitivity (granulomatous), cytotoxic, and humoral (antibody) responses. Congenital or acquired impairment of pulmonary host defenses can occur at any of these steps. Impairment of a particular component of pulmonary host defense is usually associated with a characteristic spectrum of infectious and noninfectious pulmonary complications. Thus, understanding all the components of pulmonary host defense and how to evaluate them will greatly aid the physician who cares for immunocompromised patients with lung disease.

High frequencies of polyfunctional HIV-specific T cells are associated with preservation of mucosal CD4 T cells in bronchoalveolar lavage.

The mechanisms underlying the massive gastrointestinal tract CD4 T-cell depletion in human immunodeficiency virus (HIV) infection are not well understood nor is it clear whether similar depletion is manifest at other mucosal surfaces. Studies of T-cell and virus dynamics in different anatomical sites have begun to illuminate the pathogenesis of HIV-associated disease. Here, we studied depletion and HIV infection frequencies of CD4 T cells from the gastrointestinal tract, bronchoalveolar lavage (BAL), and blood with the frequencies and functional profiles of HIV-specific T cells in these anatomically distinct sites in HIV-infected individuals. The major findings to emerge were as follows: (i) depletion of gastrointestinal CD4 T cells is associated with high frequencies of infected CD4 T cells; (ii) HIV-specific T cells are present at low frequencies in the gastrointestinal tract compared to blood; (iii) BAL CD4 T cells are not massively depleted during the chronic phase; (iv) infection frequencies of BAL CD4 T cells are similar to those in blood; (v) significantly higher frequencies and increased functionality of HIV-specific T cells were observed in BAL compared to blood. Taken together, these data suggest mechanisms for mucosal CD4 T-cell depletion and interventions that might circumvent global depletion of mucosal CD4 T cells.

Cigarette smoking decreases bioactive interleukin-6 secretion by alveolar macrophages.

Studies suggest smokers have decreased alveolar macrophage (AM) accessory cell (AC) function and a reduced incidence of immune-mediated lung diseases such as sarcoidosis. Impaired AM secretion of cytokines important in T-cell immune responses could explain this observation. We investigated production and secretion of interleukin-1 (IL-1) and interleukin-6 (IL-6) in smokers and nonsmokers. Lipopolysaccharide-induced AM IL-1 secretion in smokers was significantly reduced compared with nonsmoker AM. However, intracellular IL-1 in smoker AM was higher than in nonsmokers, suggesting that reduced IL-1 secretion was due to impaired release rather than reduced production. Smoker AM secreted significantly less bioactive IL-6 measured in a bioassay compared with nonsmoker AM. Intracellular IL-6 was virtually undetectable in both groups. In some smokers IL-6 production determined by immunoprecipitation was reduced. However, as a group antigenic IL-6 secretion determined by enzyme-linked immunoabsorbent assay was similar in smokers and nonsmokers, suggesting that smoker AM may cosecrete an inhibitor of IL-6 bioactivity. Indeed, AM supernatants from smokers inhibited B9 proliferation in response to maximal recombinant IL-6 stimulation, whereas supernatants from nonsmokers did not. We conclude that AM from smokers secrete less cytokines important in T-cell proliferation than AM from nonsmokers and suggest that for IL-6 this impairment is related to both decreased production of antigenic protein as well as cosecretion of an IL-6 inhibitor.

Role of alveolar macrophage-T cell adherence in accessory cell function in human immunodeficiency virus-infected individuals.

Previous work has shown that alveolar macrophages (AM) from human immunodeficiency virus (HIV)-infected patients are superior accessory cells (AC) and secrete greater amounts of T cell-stimulatory cytokines than do normal AM. We now examine the role of AM-T cell adherence in AM AC function by examining the ability of beta 2 integrins and intercellular adhesion molecule-1 (ICAM-1) to block adherence and lymphoproliferation. Mitogen-induced (concanavalin A, pokeweed mitogen) adhesion and proliferation were studied in the presence and absence of mAb directed against beta 2 integrins and ICAM-1. AM from normal subjects and HIV-positive patients were used as AC, and normal T cells were used as responders. Normal and HIV AM bound equal numbers of T cells under similar conditions. Adherence was blocked by antibodies to beta 2 integrins and ICAM-1 in both groups. Con A-induced lymphoproliferation was positively correlated with adherence in normal volunteers. In contrast, greater Con A-induced AM-T cell adherence in HIV-positive patients was associated with worse AC function. Antibodies that impaired AM-T cell adherence completely inhibited AC function in both groups when added at the beginning of mitogen assays, indicating that initial contact was required. However, the addition of antibodies after 4 h inhibited lymphoproliferation less in HIV-infected individuals than in normal volunteers, suggesting that prolonged AM-T cell adherence was less important for optimal AC function in these patients. Using these and previous results, we present a model for AM AC function in normal volunteers and HIV-infected individuals.

Measurement of IL-6 inhibitory activity in cultured cell supernatants and lysates.

Interleukin-6 (IL-6) participates in a variety of cellular activities including regulation of immune and inflammatory responses. We have previously reported a discrepancy between bioactive and antigenic IL-6 secretion by lipopolysaccharide-stimulated alveolar macrophages (AMs) from smokers and have speculated that this may be due to cosecretion of an IL-6 inhibitor. In this study we further define our methods for measuring IL-6 inhibitory activity by testing the ability of serially diluted, cultured cell supernatants and lysates to suppress proliferation of an IL-6-dependent cell line, B9, to optimal concentrations of rIL-6. AM secretion of the inhibitory factor was optimal when AMs were stimulated with 1 micrograms/ml lipopolysaccharide (LPS). AMs from smokers secreted significantly greater amounts of this factor than AMs from nonsmokers. It was crucial to remove IL-6 from test samples on an IL-6 immunoaffinity column before analyzing for IL-6 inhibitory activity because (1) B9 cell proliferation could be suppressed by excess amounts of IL-6 in test supernatants and (2) excess rIL-6 added to the inhibitor assay reduced inhibitory activity. The latter finding suggested that IL-6 inhibitory activity was due to a competitive inhibitor of IL-6. This factor was shown to be specific for IL-6, because no inhibitory activity was seen on IL-2- or IL-4-dependent cell lines. Finally, we demonstrated that monocytes could also secrete an inhibitor of IL-6 bioactivity. However, secretion appeared to be less than that observed by AMs, suggesting that differentiation of monocytes into macrophages upregulated production of this factor.

Role of cytokines in alveolar macrophage accessory cell function in HIV-infected individuals.

Mononuclear phagocytes, including alveolar macrophages (AM), can be chronically infected with HIV and thus serve as a reservoir for the virus. Acting as AC during the generation of an immune response, HIV-infected mononuclear phagocytes can facilitate viral T cell infection by several mechanisms, including direct contact of T cells with HIV-infected macrophages as well as cytokine-induced up-regulation of latent T cell infection. Our laboratory has shown that AM from HIV-infected individuals have enhanced AC function compared to normal AM. In this study we explored AM production and secretion of IL-1 beta and IL-6, two cytokines critical for optimal AC function, in normal volunteers and HIV-infected patients. Cultured AM supernatants and lysates were generated in the presence and absence of LPS and standard mitogens. In initial mixing experiments HIV AM supernatants enhanced mitogen-induced T cell proliferation using normal AM as AC significantly more than normal AM supernatants, suggesting that HIV AM secreted more T cell stimulatory factors than normal AM. Neither group could enhance T cell proliferation induced by HIV AM suggesting these cells already secreted optimal levels of these factors. AM from HIV+ individuals produced and secreted more IL-1 beta (measured by ELISA) and IL-6 (measured in a B9 bioassay and by immunoprecipitation) than normal AM both spontaneously and in the presence of low LPS concentrations and mitogens. In some cases depleting HIV AM supernatants of IL-1 beta and IL-6 on immunoaffinity columns abrogated their enhancement properties indicating that these cytokines were important in the observed enhancement. However, in other patients different factors must also be involved as depletion of IL-1 beta and IL-6 in their AM supernatants had no effect on enhancement function. These results show that HIV AM secretory products are important in the enhanced AC function demonstrated by these cells. However, although augmented IL-1 beta and IL-6 secretion likely contribute significantly to this enhancement, other AC secretory factors and/or functions must also be involved.

Modulation of accessory cell function and interleukin-6 production by the HIV-1 tat gene.

Manifestations of HIV-1 infection such as fever, hypergammaglobulinemia, and interstitial pneumonitis may be due to increased production of inflammatory cytokines such as interleukin-1 and interleukin-6 (IL-6). Monocytes/macrophages of HIV-1-infected individuals have been noted to produce increased amounts of IL-6, as well as to have enhanced accessory cell function. These studies examined the ability of HIV-1 tat, an important HIV-1 regulatory gene, to modulate monocyte/macrophage function. In these experiments, HIV-1 tat-transfected THP-1 cells, a monocytic cell line, enhanced THP-1 immune accessory cell function in the presence of pokeweed mitogen and concanavalin A. HIV-1 tat-transfected cells also increased production of lipopolysaccharide-stimulated IL-6 mRNA and IL-6 protein. The ability of monocytes/macrophages to support HIV-1 production while exhibiting little or no cytopathic effects allows these cells to serve as a reservoir for the virus. The ability of HIV-1 tat to regulate cellular function in monocytes/macrophages may play an important part in the pathogenesis of HIV-1 infection.

Radiographic diagnosis of tonsillar cyst presenting as dysphagia.

Tonsillar retention cysts are common and most often asymptomatic. The radiographic demonstration of a retention cyst in a symptomatic patient is reported. Emphasis should be placed on the oropharynx during barium swallow examinations in appropriately symptomatic patients. Tonsillar retention cysts should be included in the differential diagnosis of mass lesions in this area.

Perforated viscus presenting with gas in the soft tissues (subcutaneous emphysema).

We have reviewed the spectrum of gaseous densities in the soft tissues secondary to a perforated viscus. All patients presented late and most were elderly. The most common surgical procedure was diversion of the fecal stream proximal to the perforation. In our series 4 of 7 patients died in the immediate postoperative period. Knowledge of the mechanism and differential diagnosis of this entity will prevent overlooking this possibility, as occurs too frequently, particularly with subcutaneous emphysema of the leg.

Enhanced accessory cell function by alveolar macrophages from patients infected with the human immunodeficiency virus: potential role for depletion of CD4+ cells in the lung.

Mononuclear phagocytes, including alveolar macrophages (AM), can be infected by the human immunodeficiency virus (HIV). Acting as accessory cells (AC), AM could infect CD4 lymphocytes through cell-to-cell contact and by inducing T cell proliferation, which increases lymphocyte susceptibility to infection. Using normal allogeneic T cells as responders, AM from infected individuals demonstrated an enhanced ability to stimulate a Con A and pokeweed mitogen lymphocyte proliferation assay compared with normal AM. Exogenous IL 1 enhanced the stimulation of a mitogen response by normal AM, but not from HIV-positive individuals, suggesting increased levels of this cytokine may explain the observed enhancement. However, increased IL 1 secretion by AM from HIV-infected patients could not be demonstrated, either in a bioassay or antigenically using an ELISA for IL-1 beta. Syncytia formation was observed when AM from asymptomatic HIV-positive individuals were cultured with normal T cells, suggesting viral transmission was occurring. Finally, in individual patients the stimulation of a mitogen response was inversely correlated with the CD4/CD8 ratio and total CD4 count, suggesting that enhanced AC function and CD4 cell depletion may be related in vivo. These findings indicate that enhanced AM accessory cell function is seen in HIV-infected individuals and could be a potential mechanism for CD4 cell depletion in the lung.

Monocyte accessory cell function in patients infected with the human immunodeficiency virus.

Previous studies suggested that peripheral blood monocytes (Mo) from HIV-infected patients were poor accessory cells (AC), although most of these studies were limited by using autologous T cells as responders. Using allogeneic T cells from uninfected volunteers as responders, the current studies demonstrate that Mo from infected individuals were comparable to Mo from uninfected volunteers as AC in Con A and pokeweed mitogen-stimulated lymphocyte proliferation assays, but were inferior to normal Mo in stimulating a mixed leukocyte reaction. This deficiency was not explained by HIV Mo-induced suppression of lymphoproliferation or by death of responding CD4 lymphocytes induced by HIV transmission from infected Mo in 6-day MLR cultures. Mo from HIV-infected patients retained the ability to stimulate mumps-specific T cell lines in response to antigen, demonstrating that Mo from these individuals could process and display antigen on their cell surface in association with a functional DR molecule. Taken together these results suggest that Mo from HIV-infected patients (i) retain the ability to act as AC in T cell responses to mitogenic signals or to stimulate already activated antigen-specific T cells, but (ii) fail to stimulate resting and/or unprimed T cells in response to alloantigen and perhaps de novo antigen exposure. It is possible this Mo defect may have an adverse effect on the immune responsiveness of HIV-infected individuals.

Enhanced proliferation and IL-2 secretion by lung lymphocytes from HIV-infected subjects.

Human immunodeficiency virus (HIV)-positive patients frequently develop a CD3+/CD8+ cytotoxic T cell lymphocytic alveolitis. This could occur through in situ expansion of lung lymphocytes. We evaluated lung and blood lymphocyte proliferation in asymptomatic HIV-infected individuals by measuring spontaneous and cytokine-induced tritiated thymidine incorporation. Interleukin (IL)-2 and IL-4 secretion was determined with the use of enzyme-linked immunosorbent assay, Western blotting, and immunoprecipitation techniques. Spontaneous proliferation by lung lymphocytes from HIV-positive patients was significantly greater than that of normal volunteers. Proliferation was confined to the CD8+ lymphocyte subset. Over time, spontaneous proliferation declined unless autologous alveolar macrophages (AM) were added, suggesting AM were providing additional stimulatory signals to lung lymphocytes. Lung and blood lymphocytes proliferated in response to IL-2 but not IL-4. Lymphocytes in HIV-infected lung spontaneously produced and secreted more IL-2 than either normal lung lymphocytes or autologous blood lymphocytes. IL-4 production was not detectable in either group. These findings support the hypothesis that lymphocytic alveolitis in asymptomatic HIV-positive patients results from IL-2-dependent in situ proliferation of CD3+/CD8+ cytotoxic T cells.

Assessment of joint review of radiologic studies by a primary care physician and a radiologist.

OBJECTIVES: To assess whether the joint review of radiologic studies by the primary care physician and the radiologist affects patient care and health care costs. DESIGN: Prospective study. SETTING: Student health clinic at a university hospital. PATIENTS: University students seen during acute care visits. INTERVENTION: Joint weekly review of all radiologic studies ordered at the student health clinic between July 1992 and June 1993 by a staff radiologist and internist. MEASUREMENTS AND MAIN RESULTS: The outcome measures were: (1) change of radiologic diagnosis after review process and its effect on patient management; (2) expenses saved or incurred by the review process. Of 323 films ordered, 305 were reviewed, resulting in revisions of 23 (8%) of the initial readings. Sixteen revisions (5%) led to a change in patient management; the remainder were clinically insignificant. In these 16 cases, cancellation or simplification of further workup resulted in savings of $1,967. The cost for extra physician time was $5,499. Thus, the review process incurred a net cost of $3,532. Except for the reduction in diagnostic studies, no therapeutic benefit for the patients could be identified. Film readings in our radiology department were conservative, with a positive predictive value of 85% and a negative predictive value of 99.7%. CONCLUSIONS: Routinely reviewing every radiologic study did not affect patient outcome in an outpatient clinic with low prevalence of disease. Given our radiologists' conservative film-reading practice, a review of only abnormal studies may prove more cost-effective in a healthy population. This type of assessment has implications for improving the efficiency of a changing health care system.