Accuracy of conventional digital palpation and ultrasound of the cricothyroid membrane in obese women in labour.

Success of cricothyroidotomy depends on accurate identification of anatomical neck landmarks. Anaesthetists palpated the cricothyroid membrane of 28 obese and 28 non-obese women in labour (cut-off BMI 30 kg.m(-2) ) and marked the entry point for device insertion with an ultraviolet invisible pen. Ultrasonography was used to mark the midpoint of the cricothyroid membrane and the distance between the two marks was measured. The median (IQR [range]) distance between the two marks was significantly greater in the obese than the non-obese patients (5 (2-9.5 [0-34]) mm vs 1.8 (0.1-6 [0-15]) mm, respectively; p = 0.02). The cricothyroid membrane was accurately identified with digital palpation in only 39% (11/28) of obese compared with 71% (20/28) of non-obese patients (p = 0.03). Increased neck circumference in obese patients was significantly associated with inaccuracy in locating the cricothyroid membrane. Percutaneous identification of the cricothyroid membrane in obese women in labour was poor. Pre-procedural ultrasound may help improved the identification of neck landmarks for cricothyroidotomy.

Impaired bone marrow microenvironment and immune function in T cell protein tyrosine phosphatase-deficient mice.

The T cell protein tyrosine phosphatase (TC-PTP) is one of the most abundant mammalian tyrosine phosphatases in hematopoietic cells; however, its role in hematopoietic cell function remains unknown. In this report, we investigated the physiological function(s) of TC-PTP by generating TC-PTP-deficient mutant mice. The three genotypes (+/+, +/-, -/-) showed mendelian segregation at birth (1:2:1) demonstrating that the absence of TC-PTP was not lethal in utero, but all homozygous mutant mice died by 3-5 wk of age, displaying runting, splenomegaly, and lymphadenopathy. Homozygous mice exhibited specific defects in bone marrow (BM), B cell lymphopoiesis, and erythropoiesis, as well as impaired T and B cell functions. However, myeloid and macrophage development in the BM and T cell development in the thymus were not significantly affected. BM transplantation experiments showed that hematopoietic failure in TC-PTP -/- animals was not due to a stem cell defect, but rather to a stromal cell deficiency. This study demonstrates that TC-PTP plays a significant role in both hematopoiesis and immune function.

The role of endogenous glucocorticoids on host T cell populations in the peripheral lymphoid organs of mice with graft-versus-host disease.

Previously, we demonstrated that immature CD4+8+ and mature CD4+ thymocyte populations were selectively eliminated during murine graft-versus-host disease (GVHD) as a consequence of elevated levels of endogenous glucocorticoids. In this report, we investigated whether the marked reduction of CD4+8+ and CD4+ thymocyte populations would affect host CD4+ and CD8+ T cell populations in the spleens and lymph nodes (LN) of mice undergoing GVHD. GVHD was induced in (C57BL/6 x A)F1 (B6AF1) mice by injecting A strain parental lymphoid cells. Using an antibody against H2Kb antigens, labeled host B6AF1 cells were distinguished from unlabeled donor A cells. Our results demonstrated a marked deficiency of host CD4+ and CD8+ T cells in the spleens and LN of GVHD mice on day 21 after GVHD induction. The severe reduction of host T cell populations in the peripheral lymphoid organs did not appear to result from the elimination of CD4+8+ and CD4+ thymocyte populations. However, adrenalectomy before GVHD induction reversed the severe loss of both host CD4+ and CD8+ T cell populations in the LN of GVHD mice on day 21, whereas cortisone treatment of adrenalectomized (ADX) GVHD mice resulted in reduction of host LN CD4+ and CD8+ T cell populations similar to that observed in non-ADX GVHD animals on day 21. In addition, adrenalectomy markedly improved the proliferative response of LN T cells to mitogens when compared with immunosuppressed T cells from the LN of non-ADX GVHD mice. In contrast, adrenalectomy did not reverse splenic T cell immunosuppression and the marked reduction of splenic host T cell populations during GVHD. These results suggest that high levels of endogenous glucocorticoids during GVHD play a central role in mediating severe deficiency of host T cell populations and inducing severe T cell immunosuppression in the LN, but not in the spleen, of GVHD mice.

Increased expression of proopiomelanocortin (POMC) mRNA in adrenal glands of mice undergoing graft-versus-host disease (GVHD): association with persistent elevated plasma corticosterone levels.

GVHD in animal models induces severe thymic atrophy as a result of prolonged secretion of high concentrations of adrenal glucocorticoids. In this study we investigated the mechanism responsible for the persistent stimulation of the adrenal glands to secrete glucocorticoids in mice undergoing GVHD. GVHD was induced across the major and multiple minor histocompatibility antigen difference in unirradiated C57Bl/6 x AF1 hybrid mice by the intravenous injection of A strain parental lymphoid cells. Our results showed plasma corticosterone (CS) levels were elevated in association with high concentrations of corticotropin (ACTH) in both the GVHD and control syngeneic (SYN) groups on day 9. By days 16 and 24, plasma CS and ACTH in the SYN mice returned to basal levels. In contrast, plasma CS levels remained elevated in the GVHD animals on days 16 and 24 despite decreasing concentrations of plasma ACTH. Reverse transcription-polymerase chain reaction (RT-PCR) showed several-fold increase in POMC mRNA in the adrenal glands of GVHD mice compared with SYN animals. In addition, high mRNA levels for murine prohormone convertase 1, the enzyme that cleaves POMC into ACTH, were also detected in GVHD adrenals. Histological analysis of GVHD adrenals failed to show any sign of adrenalitis, and RT-PCR of GVHD adrenals also failed to detect mRNA for interferon-gamma (IFN-gamma), a cytokine expressed by activated T and natural killer (NK) cells. However, mRNA for IL-12, a cytokine produced by activated macrophages, was increased in GVHD adrenals, suggesting that resident adrenal macrophages were activated during GVHD. Our findings suggest that persistent elevated levels of plasma glucocorticoids during GVHD could be mediated by intra-adrenal ACTH produced by resident adrenal macrophages activated as a consequence of GVHD.

Induction of a glucocorticoid-sensitive F1-anti-parental mechanism that affects engraftment during graft-versus-host disease.

Studies have shown that graft-vs-host disease (GVHD) in animal models induces persistent elevated levels of circulating adrenal glucocorticoids. In this report, we investigated the effects of endogenous glucocorticoids on the outcome of GVHD by adrenalectomizing (ADX) unirradiated (C57BL/6 x A)F1 (B6AF1) mice before GVHD induction. GVHD was induced by injection of 20 x 10(6) A strain parental lymphoid cells into B6AF1 mice. Our results demonstrated that non-ADX recipient mice experienced features characteristic of GVHD on day 13, which became progressively more severe by days 18 to 21. The GVHD features included severe immunosuppression, reversal in the host splenic CD4+/CD8+ ratio, histopathologic lesions in different tissues, and high parental cell chimerism in the spleens and lymph nodes. In contrast, ADX F1 recipient mice experienced GVHD features on day 13 similar to their non-ADX counterparts; however, ADX animals recovered rapidly from GVHD by days 18 to 21. Flow cytometry showed that, although a relatively high frequency of parental cells was detected in the spleens and lymph nodes of ADX mice on day 13, nearly all of the parental cells in the peripheral lymphoid organs disappeared on days 18 to 21, the time of recovery from GVHD. The marked reduction of parental cells and recovery from GVHD were prevented by treating ADX F1 mice with either exogenous glucocorticoid, anti-asialoGM1, or anti-CD8, but not anti-NK1.1 Ab. These results suggest that a dramatic recovery from GVHD was induced by a cell-mediated, steroid-sensitive F1-anti-parental mechanism. The F1-anti-parental phenomenon described herein is different from classical hybrid resistance.

Levels of p56lck and p59fyn are reduced by a glucocorticoid-dependent mechanism in graft-versus-host reaction-induced T cell anergy.

The graft-versus-host reaction (GVHR) results in profound, long-lasting immunosuppression characterized by T cell unresponsiveness to antigenic and mitogenic stimuli. In this report, the roles of the protein tyrosine kinases p56lck and p59fyn in GVHR-induced T cell anergy were investigated. GVHR was induced by the intravenous transfer of parental lymphoid cells into F1 hybrid recipient mice. The levels of lck and fyn declined dramatically in splenic and lymph node T cells of mice undergoing GVHR as the reaction progressed and T cell immunosuppression developed. Adrenalectomy of the GVH-reactive mice prevented both the GVHR-induced reduction of lck and fyn and the long-term T cell unresponsiveness to mitogens, suggesting a glucocorticoid-mediated mechanism. Indeed, treatment with exogenous glucocorticoids induced lck and fyn down-regulation in the lymph node T cells of normal mice, and in cultured T cell clones. We propose that the increase in endogenous glucocorticoids during GVHR triggers a reduction in T cell lck and fyn, leading to the severe immunosuppression of GVHR; this may represent a general mechanism of glucocorticoid-mediated immune regulation.