Notch ligand-bearing thymic epithelial cells initiate and sustain Notch signaling in thymocytes independently of T cell receptor signaling

Thymic epithelial cells are specialized to play essential roles at multiple stages of T cell development in the thymus, yet the molecular basis of this specialization is largely unknown. Recently, the Notch family of transmembrane proteins has been implicated in thymocyte development. Such proteins interact with cell surface proteins of the Delta-like and Jagged families. It is known that Notch ligands are expressed intrathymically, and that Notch signaling is regulated by Notch ligands expressed on either the same or third-party cells. However, functional analysis of Notch ligand expression, and elucidation of the mechanism of Notch ligand signaling in thymocyte development, are unclear. Here, we find that Notch ligand expression in the thymus is compartmentalized, with MHC class II(+) thymic epithelium, but not thymocytes nor dendritic cells, expressing Jagged-1, Jagged-2 and Delta-like-1. We also provide evidence that contact with Notch ligands on thymic epithelium is necessary to activate and sustain Notch signaling in thymocytes, and that this can occur independently of positive selection induction. Our data suggest that Notch ligand expression by thymic epithelium may partly explain the specialization of these cells in supporting thymocyte development, by regulating Notch activation via an inductive signaling mechanism independently of signaling leading to positive selection.

Lymphostromal interactions in thymic development and function

The generation of a peripheral T-cell pool is essential for normal immune system function. CD4+ and CD8+ T cells are produced most efficiently in the thymus, which provides a complexity of discrete cellular microenvironments. Specialized stromal cells, that make up such microenvironments, influence each stage in the maturation programme of immature T-cell precursors. Progress has recently been made in elucidating events that regulate the development of intrathymic microenvironments, as well as mechanisms of thymocyte differentiation. It is becoming increasingly clear that the generation and maintenance of thymic environments that are capable of supporting efficient T-cell development, requires complex interplay between lymphoid and stromal compartments of the thymus.

Influence of insulin-like growth factor-I and its interaction with gonadotropins, estradiol, and fetal calf serum on in vitro maturation and parthenogenic development in equine oocytes

The effects of insulin-like growth factor-I (IGF-I) and its interaction with gonadotropins, estradiol, and fetal calf serum (FCS) on in vitro maturation (IVM) of equine oocytes were investigated in this study. We also examined the role of IGF-I in the presence or absence of gonadotropins, estradiol, and FCS in parthenogenic cleavage after oocyte activation with calcium ionophore combined with 6-dimethylaminopurine (6-DMAP), using cleavage rate as a measure of cytoplasmic maturation. Only equine cumulus-oocyte complexes with compact cumulus and homogenous ooplasm (n = 817) were used. In experiment 1, oocytes were cultured in TCM-199 supplemented with BSA, antibiotics, and IGF-I at 0 (control), 50, 100, 200 ng/ml, at 39 degrees C in air with 5% CO(2), 95% humidity for 36 or 48 h. In experiment 2, oocytes were cultured with FSH, LH, estradiol, and FCS with IGF-I at the concentration that promoted the highest nuclear maturation rate in experiment 1. In experiment 3, oocytes from the three experimental groups (IGF-I; hormones; and IGF-I + hormones) were chemically activated by exposure to calcium ionophore followed by culture in 6-DMAP. In experiment 1, IGF-I stimulated equine oocyte maturation in a dose-dependent manner with the highest nuclear maturation rate at a concentration of 200 ng/ml. No significant effect of IGF-I on nuclear maturation was observed in experiment 2. In experiment 3, a significant difference in cleavage rate was observed between the hormone + IGF-I group (15 of 33; 45.4%) compared with IGF-I (10 of 36; 27.8%) and hormone (4 of 31; 12.9%) alone (P < 0.05). These results demonstrated that IGF-I has a positive effect on nuclear maturation rate of equine oocytes in vitro. The addition of IGF-I to an IVM medium containing hormones and FCS did not increase nuclear maturation, but resulted in a positive effect on cytoplasmic maturation of equine oocytes measured by parthenogenic cleavage.

Protocols for high efficiency, stage-specific retroviral transduction of murine fetal thymocytes and thymic epithelial cells

Viral vectors have the potential to provide a fast and economic alternative to transgenic methods for manipulating gene expression in studies of immune system development and function. Although protocols exist for the infection of hematopoietic precursors and peripheral T cells in vitro, critical stages of T cell differentiation are strictly dependent upon a three-dimensional thymic architecture and their analysis poses unique technical challenges. Whole fetal thymic lobes have been used as targets for retroviral and adenoviral infection, both in situ and in vitro, but this approach does not allow for discrimination between lymphoid and stromal components. Isolated thymocytes have been infected by co-culture with viral producer cells, but under these conditions they rapidly lose their developmental potential. To overcome these problems we have combined a number of efficient techniques for retroviral production, concentration, and infection that allow us to rapidly achieve significant transduction rates of purified populations of double-negative (DN) and double-positive (DP) thymocytes, single-positive (SP) T lymphocytes, as well as fetal thymic MHC II(+) epithelial cells without the need for co-culture with viral producer cells. Reaggregate thymic organ culture (RTOC) techniques were used to assess the development and function of transduced cells in defined cellular environments. As a demonstration of the utility of these methods, CD80 (B7.1) was transduced into thymic epithelial cells and shown to allow them to mediate negative selection of DP thymocytes, and to act as antigen-presenting cells (APC) to mature T cells. The ability to genetically manipulate primary cells of a specified type and differentiation stage provides a powerful complement to RTOC techniques for the study of T cell development.

Are Fortune 100 companies responsive to chronically ill workers?

We conducted a survey of Fortune 100 companies to determine their response to the growing number of employees with chronic conditions. We found that although all companies cover some services that are particularly beneficial to persons with chronic conditions, gaps in coverage remain. We also found large variations in cost-sharing mechanisms, number of covered visits, and lifetime maximum benefit provisions, which are especially important to persons with chronic conditions. In general, for persons with chronic conditions the benefits offered by these Fortune 100 companies are superior to those offered by Medicare.

Ampicillin-resistant Escherichia coli in gestational pyelonephritis: increased occurrence and association with the colonization factor Dr adhesin

The pattern of ampicillin resistance and possible association with virulence factors of 78 Escherichia coli isolates taken from 78 pregnant women with pyelonephritis were evaluated. The current incidence of ampicillin resistance among pyelonephritis isolates (46%) was significantly higher than that reported in 1985 (22%). Resistance was found more frequently during the first (60%) and third (53%) trimesters than during the second trimester (33%). Of all dra(+) E. coli isolates, 75% were ampicillin resistant, whereas dra(+) isolates of O75 serotype E. coli accounted for 87% of ampicillin-resistant strains. The significant increase of ampicillin resistance among gestational pyelonephritis E. coli and the association with the dra gene cluster encoding colonization and invasive capacity may warrant further study involving obstetric and neonate wards, with the latter being at the higher risk for potential problems.

Relationship among plasma cortisol, catecholamines, neuropeptide Y, and human performance during exposure to uncontrollable stress

OBJECTIVE

Although many people are exposed to trauma, only some individuals develop posttraumatic stress disorder; most do not. It is possible that humans differ in the degree to which stress induces neurobiological perturbations of their threat response systems, which may result in a differential capacity to cope with aversive experiences. This study explored the idea that differences in the neurobiological responses of individuals exposed to threat are significantly related to psychological and behavioral indices.

METHODS

Individual differences in neurohormonal, psychological, and performance indices among 44 healthy subjects enrolled in US Army survival school were investigated. Subjects were examined before, during, and after exposure to uncontrollable stress.

RESULTS

Stress-induced release of cortisol, neuropeptide Y, and norepinephrine were positively correlated; cortisol release during stress accounted for 42% of the variance in neuropeptide Y release during stress. Cortisol also accounted for 22% of the variance in psychological symptoms of dissociation and 31% of the variance in military performance during stress.

CONCLUSIONS

Because dissociation, abnormalities in the hypothalamic-pituitary-adrenocortical axis, and catecholamine functioning have all been implicated in the development of stress disorders such as posttraumatic stress disorder, these data suggest that some biological differences may exist before index trauma exposure and before the development of stress-related illness. The data also imply a relationship among specific neurobiological factors and psychological dissociation. In addition, the data provide clues about the way in which individuals' psychobiological responses to threat differ from one another.

Comparing health system performance in OECD countries. Organization for Economic Cooperation and Development

We present data from the Organization for Economic Cooperation and Development and the World Health Organization on the performance of the health care systems in twenty-nine industrialized countries in 1998. We also compare the performance of the United States with the other industrialized countries for selected indicators in 1960, 1980, and 1998. On most indicators the U.S. relative performance declined since 1960; on none did it improve.

Specialty of principal care physician and Medicare expenditures in patients with coronary artery disease: impact of comorbidity and severity

OBJECTIVE

To explore differences in expenditures for elderly patients with acute and chronic coronary artery disease according to the specialty of the principal care physician.

STUDY DESIGN

Retrospective analysis of Medicare claims.

PATIENTS AND METHODS

A total of 250,514 patients with coronary artery disease (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] codes 410-414) were drawn from a national random sample of 1992 Medicare expenditures. Patients were classified by the physician type with the highest number of Medicare Part B outpatient claims into a cardiologist group and a generalist group. The outcome was mean total expenditures, stratifying (1) by comorbidity as measured by the modified Charlson Index and (2) by severity defined as the proportion of patients with acute myocardial infarction or unstable angina.

RESULTS

Those patients in the cardiologist group had lower comorbidity and higher severity than those in the generalist group. Overall mean expenditures were significantly higher for the cardiologist group than for the generalist group ($7658 vs $6047; P < .001). These differences in mean expenditures were evident at each level of comorbidity. However, when stratified by severity of diagnosis, differences were seen predominantly in those with acute diagnoses. For those with either acute myocardial infarction or unstable angina, the mean expenditures were higher for the cardiologist group than for the combined generalist group ($15,378 vs $12,260; P < .001); however, the mean expenditures for those with only chronic conditions were similar ($4856 vs $4745; P = .53).

CONCLUSION

Expenditures were higher when cardiologists were the principal care physicians treating patients with acute disease but not chronic disease.

Specialisation of thymic epithelial cells for positive selection of CD4+8+ thymocytes

Following their migration into the thymus, hemopoeitic stem cell precursors enter a complex developmental pathway involving proliferation, differentiation and alphabetaT-cell receptor (alphabetaTCR)-mediated selection procedures, in order to generate mature T-cell populations ready for export to the periphery. Thus, a critical stage during intrathymic T-cell development involves the generation of functionally mature CD4+8- and CD4-8+ cells from immature CD4+8- precursor thymocytes, a poorly understood process referred to as positive selection. While interactions between the alphabetaTCR and MHC-peptide complexes are known to be essential for the initiation of positive selection, additional unknown signals are also required. Using an in vitro reaggregate thymic organ culture system which allows comparison of the abilities of various cell types to induce maturation of CD4+8+ precursors, we provide evidence that both MHC-peptide complexes and specialised accessory molecules must be provided by thymic epithelium for efficient mediation of positive selection. Moreover, analysis of positive selection in the presence of thymic and non-thymic stromal cells expressing MHC class II molecules with the same limited peptide array suggests that this unique ability of thymic epithelium to mediate positive selection of CD4+8- cells is not solely due to presentation of a specialised peptide repertoire, but is dependent upon provision of specialised accessory interactions.

Congenital microvillous inclusion disease presenting as antenatal bowel obstruction

Prenatal ultrasound has led to confidence in the antenatal diagnosis of intestinal obstruction allowing counseling and birth planning. We describe a male infant of a diabetic mother who had an antenatal diagnosis of distal bowel obstruction. This baby was subsequently found not to have bowel obstruction, but a congenital enteropathy - microvillous inclusion disease. The antenatal scans had demonstrated polyhydramnios as well as multiple fluid-filled dilated loops of bowel in the fetal abdomen. To our knowledge, similar prenatal ultrasound findings have not been previously described in this condition. The baby was delivered in a pediatric surgical center and postnatally there was no evidence of bowel obstruction either clinically or on abdominal X-ray. This baby initially fed well, but became collapsed and acidotic on his third day, having lost 26% of his birth weight due to excessive stool loss. The diagnosis of microvillous inclusion disease was made by electron microscopy of a small bowel biopsy. Congenital microvillous inclusion disease is a very rare inherited enteropathy with high mortality and morbidity. This condition, and other enteropathies, should be considered in cases in which antenatally diagnosed bowel obstruction is not confirmed after birth.

Nonadherence with ACE inhibitors is common and can be detected in clinical practice by routine serum ACE activity

Our objective was to assess whether serum angiotensin-converting enzyme (ACE) activity during routine clinical practice accurately reflects patient adherence to ACE inhibitor treatment in chronic heart failure (CHF). During 1994-95, ACE was measured in 73 CHF patients who were routinely attending the heart failure clinic at Ninewells Hospital. At the same time, the Medicines Monitoring Unit collected data on whether and when prescriptions for ACE inhibitors were redeemed at community pharmacies, which enabled each patient's adherence over a prolonged period to be assessed. We then correlated whether an elevation in serum ACE was associated with poor adherence with ACE inhibitor treatment. In total, 18% of CHF patients appeared to exhibit less than 70% adherence with their ACE inhibitor treatment, with 34% exhibiting less than 85%adherence and 58% exhibiting less than 100% adherence. A serum ACE activity of more than 12 U/L gave 91% positive predictive accuracy that the patient was less than 100% adherent with his or her ACE inhibitor treatment. At the other extreme, a serum ACE less than 6.5 U/L gave 81% positive predictive accuracy that the patient was more than 85% adherent with ACE inhibitor treatment. Nonadherence with ACE inhibitor treatment, therefore, was found to be common in patients with CHF. The simple, inexpensive test of serum ACE activity can be used in CHF patients to identify many, although not all, nonadherent patients so that adherence-enhancing strategies can be targeted toward them. Further work is clearly required to explore the precise clinical utility of this promising test. (c)2001 by CHF, Inc.

Tramadol and seizures: a surveillance study in a managed care population

STUDY OBJECTIVE

To investigate the occurrence of tramadol-associated seizures.

DESIGN

Retrospective cohort and case-control studies.

SETTING

UnitedHealth Group-affiliated independent practice model health plans, from different regions of the United States, contracting with large networks of physicians.

INTERVENTION

Analysis of administrative data from a large U.S. managed care population.

PATIENTS

A cohort of 9218 adult tramadol users and 37,232 concurrent nonusers.

MEASUREMENTS AND MAIN RESULTS

Fewer than 1% of users (80) had a presumed incident seizure claim after the first tramadol prescription. Risk of seizure claim was increased 2- to 6-fold among users adjusted for selected comorbidities and concomitant drugs. Risk was highest among those aged 25-54 years, those with more than four tramadol prescriptions, and those with history of alcohol abuse, stroke, or head injury. A case-control study among users was conducted to validate incident seizure outcomes from medical records. Only eight cases were confirmed, and all had cofactors associated with increased seizure risk.

CONCLUSION

In a general population, risk of seizure may be associated with long-term therapy with tramadol or the presence of cofactors, or confined to a small sensitive population subset.

Intensive care unit telemedicine: alternate paradigm for providing continuous intensivist care

OBJECTIVE

Intensive care units (ICUs) account for an increasing percentage of hospital admissions and resource consumption. Adverse events are common in ICU patients and contribute to high mortality rates and costs. Although evidence demonstrates reduced complications and mortality when intensivists manage ICU patients, a dramatic national shortage of these specialists precludes most hospitals from implementing an around-the-clock, on-site intensivist care model. Alternate strategies are needed to bring expertise and proactive, continuous care to the critically ill. We evaluated the feasibility of using telemedicine as a means of achieving 24-hr intensivist oversight and improved clinical outcomes.

DESIGN

Observational time series triple cohort study.

SETTING

A ten-bed surgical ICU in an academic-affiliated community hospital.

PATIENTS

All patients whose entire ICU stay occurred within the study periods.

INTERVENTIONS

A 16-wk program of continuous intensivist oversight was instituted in a surgical ICU, where before the intervention, intensivist consultation was available but there were no on-site intensivists. Intensivists provided management during the intervention using remote monitoring methodologies (video conferencing and computer-based data transmission) to obtain clinical information and to communicate with on-site personnel. To assess the benefit of the remote management program, clinical and economic performance during the intervention were compared with two 16-wk periods within the year before the intervention.

MEASUREMENTS AND MAIN RESULTS

ICU and hospital mortality (observed and Acute Physiology and Chronic Health Evaluation III, severity-adjusted), ICU complications, ICU and hospital length-of-stay, and ICU and hospital costs were measured during the 3 study periods. Severity-adjusted ICU mortality decreased during the intervention period by 68% and 46%, compared with baseline periods one and two, respectively. Severity-adjusted hospital mortality decreased by 33% and 30%, and the incidence of ICU complications was decreased by 44% and 50%. ICU length of stay decreased by 34% and 30%, and ICU costs decreased by 33% and 36%, respectively. The cost savings were associated with a lower incidence of complications.

CONCLUSIONS

Technology-enabled remote care can be used to provide continuous ICU patient management and to achieve improved clinical and economic outcomes. This intervention's success suggests that remote care programs may provide a means of improving quality of care and reducing costs when on-site intensivist coverage is not available.

Hypertension and its treatment in postmenopausal women: baseline data from the Women's Health Initiative

Little is known about the patterns of treatment and adequacy of blood pressure control in older women. The Women's Health Initiative, a 40-center national study of risk factors and prevention of heart disease, breast and colorectal cancer, and osteoporosis in postmenopausal women, provides a unique opportunity to examine these issues in the largest, multiethnic, best-characterized such cohort. Baseline data from the initial 98 705 women, aged 50 to 79 years, enrolled were analyzed to relate prevalence, treatment, and control of hypertension to demographic, clinical, and risk-factor covariates, and logistic regression analyses were performed to estimate odds ratios after adjusting for multiple potential confounders. Overall, 37.8% of the women had hypertension, which is defined as systolic blood pressure >/=140 mm Hg and/or diastolic blood pressure >/=90 mm Hg or being on medication for high blood pressure; 64.3% were treated with drugs, and blood pressure was controlled in only 36.1% of the hypertensive women, with lower rates of control in the oldest group. After adjustment for multiple covariates, current hormone users had higher prevalence than did nonusers (odds ratio 1.25). Hypertensive women had more comorbid conditions than did nonhypertensive women, and women with comorbidities were more likely to be treated pharmacologically. Diuretics were used by 44.3% of hypertensives either as monotherapy or in combination with other drug classes. As monotherapy, calcium channel blockers were used in 16%, angiotensin-converting enzyme inhibitors in 14%, beta-blockers in 9%, and diuretics in 14% of the hypertensive women. Diuretics as monotherapy were associated with better blood pressure control than any of the other drug classes as monotherapy. In conclusion, hypertension in older women is not being treated aggressively enough because a large proportion, especially those most at risk for stroke and heart disease by virtue of age, does not have sufficient blood pressure control.

Microenvironmental regulation of T cell development in the thymus

T cell development in the thymus occurs through a series of events beginning with thymic colonization by migrant precursors and ending with the emigration of functionally competent CD4+ and CD8+ T cells to the periphery. It is well accepted that signals through the pre-T cell receptor (pre-TCR) and alpha-beta TCR (alphabetaTCR) complex play pivotal roles in the maturation of CD4-8- and CD4+8+ thymocytes, respectively. It is clear that stromal cells constituting the thymic microenvironment provide non-TCR-mediated interactions which are essential for several developmental events. Examples of such will be discussed here in relation to early and late events in T cell development.

Ovarian cancer tumor marker behavior in asymptomatic healthy women: implications for screening

Ovarian cancer screening protocols generally have been limited by inadequate recognition of the normal behavior of tumor markers in women at risk of ovarian cancer. We have characterized the behavior of five serum tumor markers in a large cohort of healthy women and examined the implications for screening. Serial measurements of CA125, HER-2/neu, urinary gonadotropin peptide, lipid-associated sialic acid, and Dianon marker 70/K were obtained during 6 years of follow-up of 1257 healthy women at high risk of ovarian cancer. We analyzed individual-specific tumor marker behavior and explored methods that can exploit this information to develop individual-specific screening rules. These five tumor markers behaved approximately independently. Substantial heterogeneity was observed among women in the behavior of each tumor marker, particularly CA125. Intraclass correlation (ICC), or the proportion of total variability that occurs between individuals, was approximately 0.6 for log-transformed CA125 and urinary gonadotropin peptide, and less than 0.4 for the other markers. This degree of tumor marker heterogeneity among healthy women, and the relative independence of these markers, has important implications for screening and diagnostic tests. Independence of markers results in the clinically useful fact that the combined false positive rate from screening with multiple markers may be estimated by the sum of individual false positive rates. Heterogeneity of tumor marker patterns in healthy women implies that a fixed screening cutoff level is suboptimal to a degree that depends strongly on ICC. Using information on longitudinal measurements and ICC, individual-specific screening rules may be developed with the potential to improve early detection of ovarian cancer.

An essential role for the IL-7 receptor during intrathymic expansion of the positively selected neonatal T cell repertoire

Intrathymic T cell development is a multistage process involving discrete phases of proliferation as well as differentiation. From studies on IL-7 or IL-7Ralpha-deficient mice, it is clear that the IL-7 receptor (IL-7R) plays a critical role during the initial stages of intrathymic CD4-8- precursor development. In contrast, the role of IL-7R in later stages of thymocyte development are unclear. Here, we have used various approaches to investigate directly the role of the IL-7R in thymocyte positive selection and the recently described phase of postselection proliferation. First, we show that positive selection involves selective up-regulation of IL-7Ralpha- and IL-7Rgamma-chains, with the majority of CD4+ and CD8+ cells being IL-7R+. Second, MHC class II+ thymic epithelium-which drives postselection proliferation-expresses IL-7 mRNA. Finally, analysis of positive selection and postselection proliferation in thymocytes from IL-7Ralpha-/- neonates shows that positive selection occurs normally, whereas postselection expansion is drastically reduced. Thus, our data provide the first evidence that, as well as playing a role during early phases of thymic development, IL-7R mediates intrathymic expansion of positively selected thymocytes, which may aid in establishment of the neonatal peripheral T cell pool.

MAM: a "new" high-incidence antigen found on multiple cell lines

BACKGROUND

Three women have been identified with an antibody to a "new" high-incidence antigen found on multiple cell lines.

CASE REPORTS

The proposita, M.A.M., presented during her third pregnancy with an antibody reacting with all RBCs tested except her own. She delivered a thrombocytopenic infant with a 3+ DAT, but without symptoms of HDN. The second example, A.N., presented during her third pregnancy with an antibody reacting with all RBCs tested except her own and those of M.A.M. She delivered a slightly thrombocytopenic but severely anemic infant. The third example, F.K., a sister of A.N., has an antibody reacting with all RBCs tested except her own and those of M.A.M. and A.N.

CONCLUSION

This "new" high-incidence antigen has been named MAM and assigned high-incidence antigen number 901016 by the International Society of Blood Transfusion. The corresponding antibody, anti-MAM, has been shown to cause HDN and has the potential to shorten RBC survival after the transfusion of incompatible RBC units, as determined by monocyte monolayer assay. Immunoblotting and flow cytometry show that this new antibody reacts with various WBC lines in addition to RBCs. This antibody also appears to react with platelets in some assays.