Immune memory in CD4+ CD45RA+ T cells

This study addresses the question of whether human peripheral CD4+ CD45RA+ T cells possess antigen-specific immune memory. CD4+ CD45RA+ T cells were isolated by a combination of positive and negative selection. Putative CD4+ CD45RA+ cells expressed CD45RA (98.9%) and contained < 0.1% CD4+ CD45RO+ and < 0.5% CD4+ CD45RA+ CD45RO+ cells. Putative CD45RO+ cells expressed CD45RO (90%) and contained 9% CD45RA+ CD45RO+ and < 0.1% CD4+ CD45RA+ cells. The responder frequency of Dermatophagoides pteronyssinus-stimulated CD4+ CD45RA+ and CD4+ CD45RO+ T cells was determined in two atopic donors and found to be 1:11,314 and 1:8031 for CD4+ CD45RA+ and 1:1463 and 1:1408 for CD4+ CD45RO+ T cells. The responder frequencies of CD4+ CD45RA+ and CD4+ CD45RO+ T cells from two non-atopic, but exposed, donors were 1:78031 and 1:176,903 for CD4+ CD45RA+ and 1:9136 and 1:13,136 for CD4+ CD45RO+ T cells. T cells specific for D. pteronyssinus were cloned at limiting dilution following 10 days of bulk culture with D. pteronyssinus antigen. Sixty-eight clones were obtained from CD4+ CD45RO+ and 24 from CD4+ CD45RA+ T cells. All clones were CD3+ CD4+ CD45RO+ and proliferated in response to D. pteronyssinus antigens. Of 40 clones tested, none responded to Tubercule bacillus purified protein derivative (PPD). No difference was seen in the pattern of interleukin-4 (IL-4) or interferon-gamma (IFN-gamma) producing clones derived from CD4+ CD45RA+ and CD4+ CD45RO+ precursors, although freshly isolated and polyclonally activated CD4+ CD45RA+ T cells produced 20-30-fold lower levels of IL-4 and IFN-gamma than their CD4+ CD45RO+ counterparts. Sixty per cent of the clones used the same pool of V beta genes. These data support the hypothesis that immune memory resides in CD4+ CD45RA+ as well as CD4+ CD45RO+ T cells during the chronic immune response to inhaled antigen.

The effect of R 15.7/HO, an anti-CD18 antibody, on the late airway response and airway hyperresponsiveness in an allergic rabbit model

1. The effects of a mouse (IgG1 fraction) anti-CD 18 neutralizing antibody (R15.7) on allergen-induced late airway response (LAR), airway hyperresponsiveness (AHR) and cellular recruitment were investigated in an allergic rabbit model. 2. Litter-matched NZW rabbits immunized within 24 h of birth with Alternaria tenuis (i.p.) and subsequently exposed to the allergen (i.p.) for the first 3 months of life were challenged with inhaled allergen as adult rabbits. Lung function in terms of dynamic compliance (Cdyn; ml cmH2O-1) and total lung resistance (RL; cmH2O-1 s-1) was monitored for 6 h following the allergen challenge. On day 16, separate groups of rabbits were pretreated with either control antibody (a non-binding mouse IgG1, 1 mg kg-1, i.v.) or R15.7 (1 mg kg-1, i.v.) and 1 h later all were challenged with Alternaria tenuis and lung function monitored thereafter. Airway responsiveness to inhaled histamine was assessed by measuring RL and Cdyn 24 h before and after allergen challenge and bronchoalveolar lavage (BAL) was also performed 24 h before and after allergen challenge. 3. Pretreatment of rabbits with the control antibody had no effect on the LAR as measured by AUC (Cdyn, 0-6 h). However, the magnitude of the LAR following treatment with R15.7 was significantly reduced when compared to LAR demonstrated on 1st challenge (P < 0.001) or to that of the control group on both challenges (P < 0.01). 4. In control antibody pretreated rabbits allergen induced a significant 3.4 fold reduction in the PC50 response to inhaled histamine in terms of RL changes (P < 0.05) and a significant 2.1 fold reduction in PC35 response to inhaled histamine in terms of Cdyn changes (P < 0.05). However, in anti-CD 18 antibody pretreated rabbits there was no significant change in responsiveness to histamine 24 h following allergen, as assessed by either RL PC50 or Cdyn PC35. 5. Allergen challenge induced a significant increase in eosinophil and neutrophil numbers (P < 0.05) in rabbits pre-treated with control antibody, whereas treatment with R15.7 significantly inhibited this increase in the numbers of both cell types. 6. This study demonstrates that the neutralization of CD-18 molecules reduces allergen-induced infiltration of both eosinophils and neutrophils into the airways and abolishes the accompanying LAR and AHR. These results provide evidence to support a role for CD-18 adhesion molecules in the transmigration of inflammatory cells into airways.

Human lung mast cells release small amounts of interleukin-4 and tumour necrosis factor-alpha in response to stimulation by anti-IgE and stem cell factor

Recent reports have suggested that mast cells are capable of producing and releasing a number of pro-inflammatory cytokines. However, these studies have mainly been carried out using murine tissue culture derived mast cells and it is known that these cells differ markedly in their functional properties from isolated human mast cells. It was therefore essential to study the release of cytokines from the latter cell type. On immunological stimulation with anti-immunoglobulin E (anti-IgE) or stem cell factor (SCF), purified human lung mast cells released, within 2-10 min, small amounts of tumour necrosis factor-alpha (10.5 +/- 2.9 pg/10(6) mast cells and 17.9 +/- 7.9 pg/10(6) mast cells, respectively) and interleukin-4 (5.3 +/- 2.5 pg/10(6) mast cells and 8.0 +/- 3.2 pg/10(6) mast cells, respectively). After longer periods of activation (30 min-4 h). the amounts of cytokines released from stimulated cells decreased to levels which were below those of the unstimulated cells. This possible degradation of cytokines by mast cells could not be prevented by the addition of protease inhibitors.

Effect of inhaled glucocorticoids on IL-1 beta and IL-1 receptor antagonist (IL-1 ra) expression in asthmatic bronchial epithelium

BACKGROUND

Accumulating evidence suggests that the cytokine network is central to the immunopathology of bronchial asthma and the existence of naturally occurring cytokine antagonists has added to this complexity. Upregulation of both interleukin 1 beta (IL-1 beta) and its naturally occurring receptor antagonist, interleukin 1 receptor antagonist (IL-1ra), has previously been observed on asthmatic bronchial epithelium compared with normal airways.

METHODS

The effect of inhaled beclomethasone dipropionate (BDP) on asthmatic bronchial epithelial expression of IL-1 beta and IL-1ra was studied. Frozen bronchial biopsy specimens from nine asthmatic subjects receiving 1000 micrograms BDP daily for eight weeks and from six asthmatic subjects receiving matching placebo were stained with anti-IL-1 beta and anti-IL-1ra antibodies. Hue-saturation-intensity (HSI) colour image analysis was used to quantify the brown immunoperoxidase reaction colour present on the bronchial epithelium.

RESULTS

There was a significant twofold decrease in the epithelial expression of IL-1 beta after treatment with BDP but no significant change was seen in IL-1ra (P = 0.175).

CONCLUSION

The selective inhibition of IL-1 beta, without effect on IL-1ra, provides a novel mechanism for the anti-inflammatory action of glucocorticosteroids.

Mechanisms of corticosteroid resistance in asthmatic patients

Corticosteroid-resistant (CR) asthma is associated with disease chronicity, a more frequent family history of asthma and impaired in vitro and in vivo responsiveness of peripheral blood mononuclear cells to the suppressive effects of glucocorticoids. CR asthma is associated with normal suppression of the hypothalamic-pituitary-adrenal axis and of biochemical indices of bone turnover by dexamethasone, indicating that the phenomenon of glucocorticoid resistance is specific to inflammatory leukocytes and that these patients are equally at risk of developing 'cushingoid' side effects. We have been unable to detect altered bioavailability of administered glucocorticoid, impaired ligand binding or nuclear translocation of the activated glucocorticoid receptor (GR) complex or structural abnormalities of the GR cDNA in our population of CR asthmatics. We have recently demonstrated that CR asthma is associated with decreased GR and increased AP-1 (Fos; Jun) DNA binding in peripheral blood mononuclear cells as compared to corticosteroid-sensitive asthma. These results highlight the central role of the AP-1/GR interactions in glucocorticoid action in CR asthma.

Prognostic value of cardiac troponin T after noncardiac surgery: 6-month follow-up data

OBJECTIVES

We sought to evaluate the prognostic significance of cardiac troponin T (TnT) serum levels after noncardiac surgery.

BACKGROUND

Cardiac TnT has been found to be marker for myocardial injury, but elevations of TnT are common in patients undergoing noncardiac surgery without clinical evidence of severe ischemia.

METHODS

We studied 772 patients who underwent major noncardiac procedures and did not have major cardiovascular complications during their inpatient course. Total serum creatine kinase (CK) and cardiac TnT were measured according to a protocol that included sampling in the recovery room and during the next 2 days. A 6-month follow-up interview was performed for 722 (94%) of the patients.

RESULTS

Elevated cardiac TnT and CK-MB results were detected for 92 (12%) and 211 (27%) patients, respectively. During the follow-up period, there were 19 (2.5%) major cardiac complications, including 14 cardiac deaths, 3 nonfatal myocardial infarctions and 2 admissions for unstable angina. Compared with patients with cardiac TnT values < 0.1 ng/ml, patients with elevated TnT had a relative risk for cardiac events of 5.4 (95% confidence interval: 2.2 to 13, p = 0.001), whereas CK-MB was not correlated with postdischarge cardiac events. In multivariate logistic regression analysis adjusting for preoperative clinical and CK-MB data, a cardiac TnT value > 0.1 ng/ml was in independent correlate of cardiac events (adjusted odds ratio 4.6, p < 0.05). This correlation was a function of the relation of elevated TnT levels with postoperative in-hospital congestive heart failure and new sustained arrhythmias, suggesting that elevated postoperative TnT levels detected myocardial ischemia during these clinical events.

CONCLUSIONS

We conclude that an abnormal TnT level in patients undergoing noncardiac surgery may be a useful marker of ischemic disease and a predictor of 6-month prognosis.

2',5'-Dihydroxychalcone as a potent chemical mediator and cyclooxygenase inhibitor

Eleven chalcone derivatives have been tested for their inhibitory effects on platelet aggregation in rabbit platelet suspension and the activation of mast cells and neutrophils. Arachidonic acid-induced platelet aggregation was potently inhibited by almost all the compounds and some also had a potent inhibitory effect on collagen-induced platelet aggregation and cyclooxygenase. Some hydroxychalcone derivatives showed strong inhibitory effects on the release of beta-glucuronidase and lysozyme, and on superoxide formation by rat neutrophils stimulated with the peptide fMet-Leu-Phe (fMLP). We found that the anti-inflammatory effect of 2',5'-dihydroxychalcone was greater than that of trifluoperazine. 2'5'-Dihydroxy and 2',3,4,5'-tetrahydroxyl chalcones, even at low concentration (50 microM), tested in platelet-rich plasma from man almost completely inhibited secondary aggregation induced by adrenaline. These results suggest that the anti-platelet effects of the chalcones are mainly a result of inhibition of thromboxane formation.

The effect of a novel orally active selective PDE4 isoenzyme inhibitor (CDP840) on allergen-induced responses in asthmatic subjects

Recent studies have suggested that theophylline, a nonspecific phospho-diesterase inhibitor, has useful anti-inflammatory actions in asthma. Phosphodiesterase 4 (PDE4) represents the predominant PDE isoenzyme present in inflammatory cells. PDE4 inhibitors might, therefore, have beneficial effects in asthma. Side-effects, specifically nausea, have limited the use of existing agents. CDP840 is an orally active, potent and selective PDE4 inhibitor. We have examined the effect of CDP840 on the allergen-induced asthmatic response, its possible modes of action, and its tolerability at therapeutic doses. A total of 54 patients were recruited to three double-blind, placebo-controlled studies. The first study examined the effect of CDP840 (15 mg b.i.d. for 9.5 days) on the allergen-induced asthmatic response in patients with known dual response to allergen. A second study examined the effect of CDP840 (15 mg b.i.d. for 9.5 days) on airway responsiveness to histamine. A third study examined whether single dose CDP840 (15 and 30 mg) had significant bronchodilatory effects. In all studies, CDP840 was well-tolerated, with no patients reporting nausea. CDP840 did not lead to changes in baseline forced expiratory volume in one second (FEV1) as compared to placebo. The late asthmatic response (LAR) to allergen, expressed as area under the curve at 3-8 h (AUC3-8h), was inhibited by 30% (p=0.016), an effect which persisted to the end of the observation period. The early asthmatic response (EAR) was unaffected, and there was no bronchodilatory effect at the doses used. Treatment with CDP840 did not affect bronchial hyperresponsiveness to histamine. In conclusion, CDP840 significantly attenuated the late asthmatic response to allergen challenge in the absence of any bronchodilatory or histamine antagonist effect. This suggests that CDP840 may exert its effects via an anti-inflammatory mechanism.

Conformational stability of a type II' beta-turn motif in human growth hormone [6-13] peptide analogues at hydrophobic surfaces

The interactive properties of several peptides related to human growth hormone (hGH) [6-13] containing a type II' beta-turn motif have been investigated using reversed-phase high-performance liquid chromatography (RP-HPLC). Various chromatographic parameters related to the hydrophobic interactive surface area and binding affinity were measured over the range of temperatures between 5 and 85 degrees C. Variations in these parameters were consistent with significant differences in the relative stability of the type II' beta-turn structures of these peptidomimetics. The effect of changes in peptide conformation were also investigated through the analysis of band-broadening behaviour during the chromatographic process. Significant variations in bandwidth observed at discrete temperatures were related to the rate of interconversion between the type II' beta-turn and more extended conformers. These investigations further document the potential of RP-HPLC for monitoring subtle changes in peptide secondary structure at hydrophobic interfaces.

Genetic variation within human immunodeficiency viruses generates rapid changes in tropism, virulence, and transmission

The human immunodeficiency viruses (HIV-1) undergo high rates of variation. Only a few point mutations in the envelope gene are required to switch the tropism of HIV-1 from a growth preference for monocytes to lymphocytes or to acquire lytic properties for rapid killing of infected T4 lymphocytes. Since heterosexual transmission efficiency is high for HIV-1's that are most prevalent in Africa or Asia, but low for HIV-1 B, which dominates in the US and western Europe, we asked whether African and Asian viruses had a particular tropism for cells of the reproductive tract. Langerhans' cells (LC), showed only minimal susceptibility to infection with HIV-1B from the US, but substantially greater sensitivity for infections by HIV-1 E and HIV-1 C, subtypes that predominate in Asia and Africa.

Immune localization of prolactin receptor in the mitochondria-rich cells of the euryhaline teleost (Oreochromis mossambicus) gill

The present work demonstrates, by Western blotting and immunofluorescent staining, the presence and localization of prolactin (PRL) receptor in tilapia (ti) Oreochromis mossambicus gills. Gill epithelial cells that reacted with PRL receptor antibody were found to be labelled concomitantly with Con A, a marker of the apical crypts in mitochondria-rich (MR) cells. No positive staining was observed in pavement cells or mucus cells with PRL receptor antibody. This indicates that PRL receptors are located specifically in the gill MR cells. Further, the tiPRL receptors were found only in the MR cells of seawater-adapted tilapia gills. The effects of salinity and ions on the expression of tiPRL receptors are discussed.

Body mass index as a correlate of postoperative complications and resource utilization

PURPOSE

To describe the relationship of body mass index (BMI) with postoperative complications and resource utilization.

PATIENTS AND METHODS

Two thousand nine hundred and sixty-four patients 50 years or older undergoing elective noncardiac surgery with an expected length of stay > or = 2 days were enrolled in a prospective cohort study to measure major cardiac complications, noncardiac complications, length of stay, and costs. The setting was an urban teaching hospital. A preoperative history, physical, electrocardiogram (ECG), and chart review were performed by study personnel. Postoperative complications were detected by ECGs, creatine kinase and creatine kinase MB levels, and daily chart review. Total costs were obtained from the hospital's computerized database.

RESULTS

Complication rates were not different among BMI groups (underweight < 20, normal 20 to 29, overweight 30 to 34, most overweight > 34), but patients with BMI 30 to 34 and > 34 who underwent abdominal or gynecologic procedures had significantly higher wound infection rates (11% each) than normal weight patients (4.7%) or the underweight (0%). After adjusting for age, race, gender, smoking history, comorbid diseases, procedure type, and insurance status, there were nonsignificant trends toward increased resource utilization by the most overweight patients (BMI > 34). These patients stayed 0.8 days longer (P = 0.13) and had total costs that were $843 higher (P = 0.17) than patients of normal weight (BMI 20 to 29). The underweight patients stayed 0.9 days longer (P = 0.23) and had total costs that were $3,150 higher (P = 0.04) than patients of normal weight. Quadratic models to test for a U-shaped relationship found no correlation between BMI and length of stay, but did find that BMI was significantly correlated with total costs (P = 0.04). This relationship persisted when patients who had complications were excluded from the analysis.

CONCLUSIONS

Overall, BMI was not significantly correlated with postoperative complications or length of stay. However, overweight patients who underwent abdominal or gynecologic procedures had higher wound infection rates, and patients with the highest and lowest BMIs had significantly higher adjusted total costs.

Echocardiographic prediction of complications in patients with chest pain

The optimal role of Doppler echocardiography in the evaluation of patients with acute chest pain syndromes is unclear. We prospectively studied a cohort of 466 patients admitted with acute chest pain syndromes to clarify the relation between echocardiographic data and the risk of serious predischarge complications, and to determine if echocardiographic data can provide incremental prognostic information beyond clinical and electrocardiographic variables. Doppler echocardiograms, performed an average of 21 hours after presentation, were independently analyzed by 2 echocardiographers for information on global left and right ventricular function and valvular disease. Regional function was assessed by a wall motion index (WMI). A composite complications end point was positive if significant recurrent myocardial ischemia, heart failure, or arrhythmia developed after the echocardiogram. In univariate analysis, left (odds ratio [OR] 2.9, 95% confidence interval [CI] 1.6, 5.1) and right (OR 2.7, 95% CI 1.2, 6.2) ventricular function, left ventricular end-diastolic (OR 1.6/cm, 95% CI 1.1, 2.3) and end-systolic (OR 1.4/cm, 95% CI 1.1, 1.9) dimensions, and WMI (OR 3.0, 95% CI 1.8, 4.8) predicted complications that developed after the echocardiogram. In multivariate analysis, WMI remained an incremental predictor of risk with an OR of 2.2/unit (95% CI 1.2, 3.9) scaled from 1 to 4. Even in the subset of 403 patients without acute myocardial infarction, WMI was associated with an OR of 1.9 (95% CI 1.0, 3.7). We conclude that early echocardiography provides incremental prognostic information concerning risk of subsequent complications in patients hospitalized with chest pain.

Apolipoprotein B gene regulatory factor-2 (BRF-2) is structurally and immunologically highly related to hepatitis B virus X associated protein-1 (XAP-1)

Hepatic cell-specific expression of the human apolipoprotein B (apoB) gene is controlled by at least four cis-acting elements located between positions -128 and +122 [Chuang, S. S., & Das, H. K. (1996) Biochem. Biophys. Res. Commun. 220, 553-562]. The distal element (-128 to -85) appears to be liver specific because it shows positive activity in HepG2 cells and negative activity in HeLa cells. ApoB gene regulatory factor-2 (BRF-2) interacts with the sequence (-104 to -85). BRF-2 has been purified from rat liver nuclear extract, and its molecular weight has been determined to be approximately 120 kDa [Zhuang et al. (1992) Mol. Cell. Biol. 12, 3183-3191]. In this paper we report the isolation of two isoforms of BRF-2 by further purification using high-performance liquid chromatography. Both isoforms produced a single approximately 120-kDa band in sodium dodecyl sulfate polyacrylamide gel electrophoresis detected by silver stain. The amino acid sequences of two tryptic peptides derived from HPLC-purified heavier BRF-2 isoform were determined to be YLAIAPPIIK and ALYYLQIHPQELR. These two peptides were found to share 100% sequence homology with human hepatitis B virus X associated protein-1 (XAP-1) and monkey UV-damaged DNA-binding protein (UV-DDB). Anti-peptide antisera raised against two synthetic peptides of XAP-1 recognized a approximately 120-kDa polypeptide band in both BRF-2 isoforms in a western blot analysis. By using apoB promoter fragments containing various internal deletions and a substitution mutation as templates for gel mobility shift assays, we identified the region between -104 and -85 as crucial for binding by the high-molecular weight form. In contrast, the lower molecular weight isoform bound to all apoB mutants tested. Anti-peptide 2 antiserum directed against XAP-1 was found to inhibit in vitro transcription of the apoB gene in rat liver nuclear extracts by 50%. These results suggest that BRF-2 and XAP-1 are structurally and immunologically highly related trans-activators of the apoB gene. We propose that BRF-2 exists both as a monomer (BRF-2M) and as a homooligomer. probably a homodimer (BRF-2D), in solution; oligomerization appears to be an essential step for imparting sequence-specificity to BRF-2 protein and thereby facilitating its role as a trans-activator of the apoB gene.

Differential effects of SCH 23390 on the apomorphine subsensitivity in the substantia nigra and ventral tegmental area 1 day following withdrawal from continuous or intermittent cocaine pretreatment

Using extracellular single-unit recordings in rats, the effects of chronic intermittent injections and continuous infusion of cocaine on single dopamine neurons were directly compared in the substantia nigra and ventral tegmental area. After 1-day withdrawal we determined: (1) the neuronal sensitivity to the mixed D1/D2 agonist apomorphine and (2) its modulation by the D1 antagonist SCH 23390. The nigral dopamine neurons exhibited subsensitivity to the impulse-inhibiting effects of apomorphine following both intermittent and continuous regimens. SCH 23390 selectively reversed the apomorphine subsensitivity in the intermittent group, while having minimal effects in the other group. Dopamine neurons in the ventral tegmental area, on the other hand, were sub- and normosensitive to apomorphine following intermittent and continuous dosing regimens, respectively. In contrast to the substantia nigra, SCH 23390 failed to alter the apomorphine sensitivity in either of the pretreatment groups. Possible mechanisms underlying these distinctive changes in the substantia nigra and ventral tegmental area following intermittent and continuous cocaine pretreatment regimens are discussed.

Diabetic neuropathy

Diabetic neuropathy affects up to 60 percent of the estimated 13 million Americans who have diabetes mellitus. Foot and ankle complications are responsible for more hospital admissions than all other complications of diabetes mellitus combined. Neuropathy is more likely to affect patients who have higher degrees of hyperglycemia and a longer history of diabetes, and those who are older, taller and male. Diabetic neuropathy is usually diagnosed by the loss of ankle reflexes and distal vibratory sensation, but these signs may not always be present. Electromyography is useful in establishing a diagnosis. Treatment is directed toward alleviating the symptoms and correcting the underlying pathogenesis. Strict glycemic control is key in the ultimate prevention of diabetic neuropathy. The family physician can play a significant role in preventing this complication by emphasizing the importance of strict glycemic control.

Nonoperative management of posterior tibial tendon dysfunction

Forty-nine patients with posterior tibial tendon dysfunction (4 patients had bilateral involvement) were treated with orthoses. Forty feet were treated with molded ankle-foot orthoses, and 13 feet were treated with University of California Biomechanics Laboratory shoe inserts with medial posting. A total of 37 women and 12 men were included in the study. The mean follow-up period was 20.3 months (range, 8-60 months). The average age of the patients was 66 years (range, 42-89 years). Sixty-seven percent of patients had good to excellent results, according to a functional scoring system based on pain, function, use of assistive device, distance of ambulation, and patient satisfaction. The average period of orthosis use was 14.9 months (range, 1.5-29 months), with an average length of daily orthosis wear of 12.3 hours. One patient elected to undergo surgical treatment rather than continuing with long-term orthosis use. Thirty-three percent of patients had discontinued using the orthosis at the time of follow-up evaluation. Three patients were unable to wear the orthosis because of concurrent medical conditions. Nine patients stopped wearing the orthosis after experiencing discomfort and inconvenience. Although these patients continued to exhibit signs and symptoms of posterior tibial tendon dysfunction, they were not disabled enough to consider further treatment. Four patients tolerated orthosis treatment poorly and were treated surgically. Patients with posterior tibial tendon dysfunction can be treated by aggressive nonoperative management using molded ankle-foot orthoses or University of California Biomechanics Laboratory shoe inserts with medial posting. Surgical treatment can be reserved for patients who fail to respond to an adequate trial of brace treatment. Nonoperative management using an orthosis is particularly useful for elderly patients with a sedentary lifestyle or for patients at high risk because of medical problems.

Effect of managed care on cardiovascular specialists: involvement, attitudes and practice adaptations

OBJECTIVES

This study was undertaken to determine the extent to which cardiovascular specialists are involved with and affected by managed care and to ascertain their attitudes toward it. This survey also served as the follow-up to an initial study on the subject performed by the American College of Cardiology in 1993.

BACKGROUND

The initial 1993 study was performed to address the lack of any comprehensive examination of the impact of managed care on cardiovascular specialists. In 1995, to reexplore this question and follow up the 1993 findings, the College conducted a survey of its membership in the following areas: 1) physician relationship with managed care plans; 2) number of managed care contracts; 3) breakdown of revenue by payment source; 4) changes in practice in response to managed care; and 5) physician attitudes toward managed care. To the extent feasible, the 1995 questionnaire paralleled the 1993 instrument to facilitate comparisons.

METHODS

A questionnaire was mailed to 5,147 practicing College members in the United States, who were categorized by specialty as pediatric cardiologists, adult cardiologists or cardiovascular surgeons. Mailings were sent to 1) all pediatric cardiologists and cardiovascular surgeons; 2) randomly selected adult cardiologists practicing in 10 states with high managed care penetration; and 3) randomly selected adult cardiologists in the nine U.S. census areas who were not practicing in the 10 states with high managed care penetration.

RESULTS

Usable surveys were returned by 1,236 respondents, for an overall response rate of 24%. Involvement with at least one type of managed care organization was reported by 89% of respondents, up from 76% in 1993. Although managed care relationships had increased across physician age, region, practice and specialty, respondents indicated that, on average, well below 50% of their practice revenues stem from managed care contracts. To adapt to the managed care environment, strategic practice changes, such as joining a cardiovascular network, implementing continuous quality improvement systems and adopting clinical pathways, were being instituted by most respondent practices of nine or more physicians. Smaller groups were less active. Most respondents involved with managed care disliked its effects, particularly in clinical matters. Their attitudes toward the assumption of risk, managed fee-for-service arrangements and a private versus single-payer system show that there is no uniformity of opinion regarding the best means to contain costs and promote efficiency.

CONCLUSIONS

Managed care has become an established part of cardiovascular specialist practice in the United States. Although this trend is viewed with some disfavor, most respondents are making practice changes to adapt to this new environment.

Mitochondria-rich cells in the branchial epithelium of the teleost,Oreochromis mossambicus, acclimated to various hypotonic environments

Branchial mitochondria-rich (MR) cells were examined on the afferent side of gill filaments in tilapia (Oreochromis mossambicus) acclimated to different hypotonic environments, local fresh water (LFW), hard fresh water (HFW) and 5‰ salt water (SW). Scanning electron micrographs (SEM) identified three types of apical surfaces of the MR cells, wavy convex, shallow basin and deep hole. In spite of the different types of apical surfaces, light microscopic (LM) and transmission electron microscopic (TEM) studies suggested that these cells were MR cells. The relative abundance of these 3 types of branchial MR cells varied with external hypotonic milieus. Wavy-convexed MR cells were dominant in the gills of fish adapted to HFW, whereas shallow-basined MR cells were evident in LFW-adapted fish. In SW-adapted fish, most of the MR cells were deep holes. Experiments on adaptation to various hypotonic milieus revealed that the changes of the branchial MR cells were reversible and occurred within 24 hours following transfer. The morphological alterations of the MR cells correlated with ionic changes in different milieus, indicating that these distinct types of MR cells may play key roles for osmoregulation in hypotonic media.