Variation in space and time: a long-term examination of density-dependent dispersal in a woodland rodent.

Dispersal is a fundamental ecological process that can be affected by population density, yet studies report contrasting effects of density on propensity to disperse. In addition, the relationship between dispersal and density is seldom examined using densities measured at different spatial scales or over extensive time series. We used 51 years of trapping data to examine how dispersal by wild deer mice (Peromyscus maniculatus) was affected by changes in both local and regional population densities. We examined these patterns over both the entire time series and also in 10-year shifting windows to determine whether the nature and strength of the relationship changed through time. Probability of dispersal decreased with increased local and regional population density, and the negative effect of local density on dispersal was more pronounced in years with low regional densities. In addition, the strength of negative density-dependent dispersal changed through time, ranging from very strong in some decades to absent in other periods of the study. Finally, while females were less likely to disperse, female dispersal was more density-dependent than male dispersal. Our study shows that the relationship between density and dispersal is not temporally static and that investigations of density-dependent dispersal should consider both local and regional population densities.

Analysis of morphology of platelet aggregates formed on collagen under laminar blood flow.

In a focal injury model, platelets adhere and activate under flow on a collagen-coated surface, creating a field of individual platelet aggregates. These aggregates exhibit distinct structural characteristics that are linked to the local flow conditions. By combining image analysis techniques and epifluorescence microscopy, we developed a robust strategy for quantifying the characteristic instantaneous width and length of a growing platelet deposit. We have confirmed the technique using model images consisting of ellipsoid objects and quantified the shear rate-dependent nature of aggregate morphology. Venous wall shear rate conditions (100 s(-1)) generated small, circular platelet deposits, whereas elevated arterial shear rates (500 and 1000 s(-1)) generated platelet masses elongated twofold in the direction of flow. At 2000 s(-1), an important regime for von Willebrand Factor (vWF)-mediated recruitment, we observed sporadic platelet capture events on collagen that led to rapidly growing deposits. Furthermore, inter-donor differences were investigated with respect to aggregate growth rate. After perfusion at elevated shear rates (1000 s(-1)) for 5 min, we identified a twofold increase in aggregate size (81.5 ± 24.6 µm; p < 0.1) and a threefold increase in growth rate parallel to the flow (0.40 ± 0.09 µm/s; p < 0.01) for an individual donor. Suspecting a role for vWF, we found that this donor had a twofold increase in soluble vWF relative to the other donors and pooled plasma. Microfluidic devices in combination with automated morphology analysis offer new tools for characterizing clot development under flow.

Diagnostic value of immunocytochemistry in leptomeningeal tumor dissemination.

Differentiating chronic aseptic meningitis from leptomeningeal carcinomatosis or gliomatosis can be difficult, particularly when the differentiation is based solely on routine cytologic examination. The diagnosis of cerebrospinal fluid tumor dissemination in at-risk patients requires cytologic examination of cerebrospinal fluid and radiography of the leptomeninges. Routine cytologic examination alone has proven less than desirable, in most instances providing confirmation in as little as 50% of cases in the first lumbar puncture. This percentage increases to 85% to 90% after multiple lumbar punctures. We retrospectively reviewed 2 cases of leptomeningeal dissemination (one gliomatosis, the other carcinomatosis) with initial false-negative test results. However, after further examination of the cerebrospinal fluid by selected battery of immunocytochemical stains, both cases were identified as positive for malignancy (ie, false negatives). Immunocytochemistry can be useful in distinguishing chronic aseptic meningitis from leptomeningeal carcinomatosis or gliomatosis in patients at risk or when abnormal cells are seen on routine cerebrospinal fluid cytologic examination.

Protein-tyrosine kinase-dependent activation of STAT transcription factors in interleukin-2- or interleukin-4-stimulated T lymphocytes.

The proliferation of activated T lymphocytes is critically dependent on the binding of the T-cell growth factors, interleukin (IL)-2 and IL-4, to distinct but evolutionarily related cell surface receptors. Previous results suggest that the IL-2 receptor (IL-2R) and IL-4R are coupled to both overlapping and distinct intracellular signaling pathways in T lymphocytes. In this study, we demonstrate that activation of Janus tyrosine kinases (JAKs) and STAT transcription factors is rapidly induced by exposure of factor-dependent murine T-cell lines to IL-2 or IL-4. Both IL-2 and IL-4 stimulated the rapid activation of JAK1 and JAK3, whereas JAK2 activity was unaffected by either cytokine. These responses were accompanied by the appearance in cell nuclei of 3 DNA binding activities that recognized a high-affinity binding site for STAT factors. In transient transfection assays, this STAT factor target sequence conferred IL-2 and IL-4 inducibility on a synthetic luciferase reporter gene. Antibody supershifting experiments indicated that IL-2 induces the formation of STAT dimers containing STAT3 and STAT1 alpha. Although IL-4 also activated STAT1 alpha, the major IL4-induced STAT factor is not STAT3 and remains undefined. Pretreatment of the T-cells with the protein-tyrosine kinase inhibitor herbimycin A blocked both the nuclear translocation of STAT factors and STAT-dependent reporter gene transcription. Immunoblot analyses confirmed that cytoplasmic STAT3 was heavily phosphorylated on tyrosine in IL-2-stimulated cells, and that phosphorylated STAT3 appeared in the nuclei of these cells. These results indicate that identical JAKs and partially overlapping sets of STATs are activated by IL-2 and IL-4 in T lymphocytes.

Major trauma outcomes in the elderly.

OBJECTIVES: To study mortality and functional outcome in elderly patients suffering major trauma and to assess whether age affects prognosis. DESIGN AND SETTING: Retrospective identification of patients from the Royal North Shore Hospital, a level three trauma service and teaching hospital of the University of Sydney. The patients were followed up for an average of three years after admission. PATIENTS: One hundred and eighteen patients aged over 60 years, with injury severity scores over 15, admitted consecutively between May 1988 and July 1990. To determine the effects of age on outcome, patients were divided into two groups: those aged 61-70 years (67 patients) and over 70 years (51 patients). MAIN OUTCOME MEASURES: Death in hospital, late death after discharge, change in preinjury v. current accommodation and current functional ability, measured with the Barthel activities of daily living index. RESULTS: Thirty-six of the 118 patients died in hospital. Eighty-one of the remaining 82 patients were followed up. Twenty-five of these patients died during the study period: three in the 61-70 years age group, and 22 in the over 70 years age group (P < 0.0001). Among the long term survivors, 43 of 53 continued to live independently, and 41 of 54 scored maximum points in activities of daily living assessment. Only seven people required nursing home care. CONCLUSIONS: Age is an important factor in survival after major trauma, but those that do survive generally return to full activity and independence. Aggressive treatment for elderly trauma victims is warranted.

Traumatic thoracic aortic rupture: investigation determines outcome.

Blunt thoracic aortic rupture (TAR) initially presents with subtle signs but is usually fatal if not diagnosed and treated early. Does the diagnostic process affect outcome? The definitive test most widely promoted is thoracic (arch) aortography but is usually only available in major teaching hospitals. Thoracic computerized tomography (CT) scanning is more readily available but its role in diagnosis of TAR is unproven. A retrospective review of trauma databases and medical record indexes over a 7 year period identified 38 patients presenting with TAR at Westmead and Royal North Shore Hospitals in the period 1984-91. Thirteen patients (34%) were dead on arrival or died within 15 min of arrival at either hospital. Five patients (13%) who arrived in cardiac arrest (with suspected TAR) died after immediate thoracotomy (two in the Emergency Department and three in the operating room). Two patients (5%) died from severe head injuries and were not investigated for TAR. Eighteen patients (47%) remained alive long enough for investigation and were considered potentially salvageable. Nine of these survived. Only 13 patients had arch aortography. No patient survived without an aortogram. Five patients had a chest CT scan; aortography followed in four patients. Computerized tomography scans delayed aortography or were misinterpreted. Review of all trauma thoracic (arch) aortograms for the same period at Westmead Hospital revealed a diagnosis of TAR in 7.4%. Blind thoracotomy did not result in survival. Computerized tomography scanning of the chest was of no value in the management of this injury. Early suspicion of possible thoracic aortic rupture demands urgent arch aortography and this remains the diagnostic 'gold standard'.

Serum complement concentrations, nutritional status and the outcome of measles and measles pneumonia.

A prospective study of children with measles has shown a significant association between malnutrition and a poor prognosis. Levels of a number of complement components bore no relationship to the severity of the disease or to its prognosis. Some of the children with acute measles had depressed serum concentrations of factor D, Clq or C3, but complement deficiency does not appear to be implicated in the heightened susceptibility to secondary bacterial and viral infection so commonly found after acute measles.