Biomedical subjects

Justin Taylor

Publications and source records attributed to Justin Taylor.

6 recordsLinked to original sources

PubMed2006

Spiny mice (Acomys cahirinus) do not respond to thymus-independent type 2 antigens.

Analysis of the immune system of spiny mice (Acomys cahirinus) has been limited. Originally grouped with Mus, Acomys has recently been placed closer to Meriones (gerbils). This study compared immunity in Acomys, Mus, and Meriones. Lymphocytes from all rodents examined proliferated in response to mitogen and superantigen stimulation. Only Mus T cells responded to anti-CD3 stimulation. Acomys, like Meriones, and Mus that express xid, did not respond to thymus-independent type 2 antigens. Flow cytometric analyses revealed that T cell-specific MAbs did not bind Acomys or Meriones lymphocytes. The B cell-specific anti-CD45R (B220) MAb detected all rodent B cells and revealed the absence of a CD45R(lo) subset in the peritoneal cavity of Acomys and Meriones. Bone marrow from Acomys and Meriones failed to reconstitute B cell function in SCID mice. Thus, in terms of immunity, Acomys appears to be more similar to Meriones than Mus.

Animals↗

PubMed2004

Effects of exogenous and endogenous natriuretic peptides on forearm vascular function in chronic heart failure.

OBJECTIVE: Natriuretic peptides (NPs) reduce central venous pressure in patients with chronic heart failure (cHF) despite attenuation of arterial, renal, and humoral effects. This suggests a preserved venodilator response. This study had 4 aims: to compare the venodilator effects of human NPs in patients with cHF; to assess the contribution of basal ANP and BNP levels to regulation of forearm vascular volume (FVV); to test the hypothesis that venous ANP responsiveness is preserved in cHF; and to assess the involvement of endothelial nitric oxide-synthase (eNOS) in NP-induced vascular effects. METHODS AND RESULTS: Venous and arterial forearm vascular responses to incremental intra-arterial doses of ANP, Urodilatin, BNP, CNP, or the ANP receptor antagonist A71915 were studied in 53 patients and 11 controls. ANP receptor antagonism reduced FVV by 4.4%+/-1.2% (P<0.05). The forearm blood flow (FBF) response to ANP was significantly blunted in patients versus controls (P<0.01), whereas FVV increased similarly in both groups (maximum 14.7% and 13.4%, both P<0.001). The eNOS blockade reduced ANP-induced FBF changes in controls but not in patients (P<0.05), whereas similar reductions in FVV changes were seen in groups (both P<0.001). CONCLUSIONS: In cHF venous, but not arterial, ANP responsiveness is preserved. Arterial endothelial dysfunction may contribute to NP resistance.

Adult↗

PubMed2004

Mls presentation by peritoneal cavity B cells.

DBA/2J spleen and peritoneal cells were compared for their ability to present the minor lymphocyte stimulatory superantigen Mls-1a. Although capable of Mls presentation in vivo, peritoneal cells were less effective than spleen cells in vitro. This difference was not due to cell concentration or culture duration. Flow cytometric comparison of spleen and peritoneal B cells revealed no significant differences in cell surface markers needed for cognate interaction with T cells. Resolution of peritoneal B cell subsets by cell sorting revealed that even though B-1 cells were capable of Mls presentation, they were less effective than B-2 cells. Mixing experiments showed that B-1 cells did not inhibit B-2 cell presentation of Mls. In contrast, total peritoneal cells inhibited T cell responses to Mls presented by spleen cells. The peritoneal cavity harbors B cells that can present Mls as well as other cells that can suppress this response.

Animals↗

PubMed2004

Nonlymphoid peritoneal cells suppress the T cell response to Mls.

Comparative analyses of the ability of lymphoid tissue to present the minor lymphocyte stimulatory (Mls) superantigen Mls-1a in vitro revealed that all tissues containing mature B cells, except peritoneal cavity (PerC) cells, induced Mls-1a-specific T cell activation. Irradiation and mitomycin C treatment, addition of IL-2 and IL-12, and neutralization of IL-10 and TGF-beta did not restore Mls-1a antigen presentation by PerC cells. Co-culture studies revealed that PerC cells actively suppress the T cell response to Mls-1a. PerC cells from severe-combined immune-defective (SCID) mice also suppressed this response indicating that nonlymphoid cells mediate this effect. These results suggest that in addition to antigen processing and presentation, resident peritoneal cavity cells may temper lymphocyte activation.

Animals↗

PubMed2003

Atrial natriuretic peptide regulates regional vascular volume and venous tone in humans.

OBJECTIVE: To date, the contribution of basal atrial natriuretic peptide (ANP) levels to resting vascular function in humans is unknown. In the present study we sought to investigate the role of ANP in regulating regional vascular volume and venous tone in healthy subjects. METHODS AND RESULTS: We used radionuclide plethysmography to examine the effects of ANP and the ANP-receptor antagonist A71915 on forearm vascular volume. Creating pressure/volume relations, we determined changes in vascular volume, compliance, and tone. Performing dose-ranging studies, we additionally assessed the potency and specificity of A71915 in the forearm resistance vasculature. Equilibrium blood pool scintigraphy was then used to assess the effects of systemic administration of A71915 on regional intestinal vascular volume. Infusion of ANP increased forearm vascular volume in a dose-dependent manner (maximum 20%; P<0.001), exerting a maximum venodilating effect at plasma levels similar to that seen in heart failure. A71915 increased venous tone, thereby decreasing vascular volume by 9.6+/-1.1%, P<0.001 (forearm), and 2.6+/-0.5%, P=0.01 (intestinal beds). At an infusion ratio of 50:1, A71915 almost completely abolished the effects of ANP on forearm blood flow. CONCLUSIONS: ANP locally regulates regional vascular volume and tone without affecting compliance.

Adult↗

PubMed2002

Lack of rapid aldosterone effects on forearm resistance vasculature in health.

OBJECTIVES: Systemic infusions of aldosterone cause an acute increase in systemic vascular resistance (SVR) in healthy subjects. It is not clear whether this is due to a direct effect on the vasculature or the result of increased sympathetic tone. We investigated the short-term effects of locally infused aldosterone on the forearm resistance bed. METHODS: In this dose response study, we assessed the effects of incremental doses (10, 50, 100 ng/minute) of intrabrachial aldosterone on forearm blood flow (FBF), using conventional strain gauge plethysmography. Arterial blood pressure was monitored continuously, using finger photo- plethysmography. Forearm vascular resistance (FVR) was calculated. FBF and FVR were also measured in the non-infused arm. Changes in FBF and FVR in the infused arm were corrected for those occurring in the control arm. RESULTS: Plasma aldosterone levels in the venous effluent of the infused arm increased in a dose-dependent fashion, from 113.3+/-17.9 pg/ml at baseline to 297.8+/-51.8 pg/ml at 10 ng/minute (p=<0.01), 743.9+/-105.9 pg/ml at 50 ng/min (p=<0.001 vs. baseline) and 1230.6+/-73.7 pg/ml at 100 ng/min (p=<0.0005 vs. baseline). Plasma concentrations of aldosterone in the control arm did not change significantly vs. baseline. The corrected FBF (+4.1+/-10.3%) and corrected FVR (+4.3+/-11.3%) did not change significantly even at peak infusion rates. CONCLUSIONS: Local intra-arterial infusion of aldosterone had no acute effect on forearm resistance vessels in healthy male volunteers.

Adult↗