Oligomerized transferrin receptors are selectively retained by a lumenal sorting signal in a long-lived endocytic recycling compartment

Cross-linking of surface receptors results in altered receptor trafficking in the endocytic system. To better understand the cellular and molecular mechanisms by which receptor cross-linking affects the intracellular trafficking of both ligand and receptor, we studied the intracellular trafficking of the transferrin receptor (TfR) bound to multivalent-transferrin (Tf10) which was prepared by chemical cross-linking of transferrin (Tf). Tf10 was internalized about two times slower than Tf and was retained four times longer than Tf, without being degraded in CHO cells. The intracellular localization of Tf10 was investigated using fluorescence and electron microscopy. Tf10 was not delivered to the lysosomal pathway followed by low density lipoprotein but remained accessible to Tf in the pericentriolar endocytic recycling compartment for at least 60 min. The retained Tf10 was TfR-associated as demonstrated by a reduction in surface TfR number when cells were incubated with Tf10. The presence of Tf10 within the recycling compartment did not affect trafficking of subsequently endocytosed Tf. Retention of Tf10 within the recycling compartment did not require the cytoplasmic domain of the TfR since Tf10 exited cells with the same rate when bound to the wild-type TfR or a mutated receptor with only four amino acids in the cytoplasmic tail. Thus, cross-linking of surface receptors by a multivalent ligand acts as a lumenal retention signal within the recycling compartment. The data presented here show that the recycling compartment labeled by Tf10 is a long-lived organelle along the early endosome recycling pathway that remains fusion accessible to subsequently endocytosed Tf.     

Can active immunization redirect an anti-IgE immune response?

We used as a template a mouse monoclonal antibody against IgE to isolate peptides from random peptide phage display libraries. Thereby, two types of peptides were isolated that corresponded to two different epitopes on the human IgE molecule. These peptides, also called mimotopes, seem to be a suitable tool in conjunction with carriers to induce an autoimmune response with a beneficial effect in humans, because the originally used template antibody is capable of neutralizing IgE, is nonanaphylactogenic, and inhibits IgE synthesis. The vaccination approach is further supported by the fact that we were capable of isolating anti-idiotypic antibodies from antibody phage display libraries against the template antibody. These anti-idiotypic antibodies were inhibited by both of the isolated IgE mimotopes. Thus, active vaccination with defined IgE mimotopes may represent a follow-up drug for the presently used anti-IgE antibodies.     

Altered expression of myosin heavy chain in human skeletal muscle in chronic heart failure

To explore further alterations in skeletal muscle in chronic heart failure (CHF), we examined myosin heavy chain (MHC) isoforms from biopsies of the vastus lateralis in nine male patients with class II-III (CHF) (left ventricular ejection fraction (LVEF) 26 +/- 11%, peak oxygen consumption (peak VO2) 12.6 +/- 2 mL.kg-1.min-1) and nine age-matched sedentary normal males (NL). The relative content of MHC isoforms I, IIa, and IIx was determined by gel electrophoresis as follows: The normal sedentary group (NL) had a higher percent of MHC type I when compared with the patients (NL 48.4 +/- 7% vs CHF patients 24 +/- 21.6%, P < 0.05, no difference between MCH IIa (NL 45.1 +/- 10.5% vs CHF 56.0 +/- 12.5%), and CHF patients had a higher relative content of MHC type IIx than did the normal group (NL 6.5 +/- 9.6% vs CHF 20.0 +/- 12.9%, P < 0.05. Three of nine patients had no detectable MHC type I. In patients relative expression of MHC type I (%) was related to peak VO2 (r = 0.70, P < 0.05). Our results indicate that major alterations in MHC isoform expression are present in skeletal muscle in CHF. These alterations parallel previously reported changes in fiber typing that may affect contractile function i skeletal muscle and possibly exercise performance. The absence of MHC type I in some CHF patients suggests that skeletal muscle changes in this disorder are not solely a result of deconditioning, buy may reflect a specific skeletal muscle myopathy in this disorder.     

Mood and performance changes in women with premenstrual dysphoric disorder: acute effects of alprazolam

This study determined if women with premenstrual dysphoric disorder (PMS) showed impaired mood and performance when they were experiencing their premenstrual symptoms, and if the effects of alprazolam varied as a function of menstrual cycle phase. Under double-blind conditions, the acute effects of placebo and alprazolam (0.25, 0.50, 0.75 mg) were tested during both luteal and follicular phases. Women with confirmed PMS experienced substantial changes in mood as a function of menstrual cycle phase. However, under controlled laboratory conditions, acute doses of alprazolam did not improve negative premenstrual mood, but rather increased negative mood in the follicular phase. Alprazolam impaired task performance, although this impairment was generally similar in both phases when baseline phase differences were taken into consideration. Consistent with the failure of alprazolam to improve mood premenstrually, subjective measures indicative of abuse liability were not increased following alprazolam. Taken together, these data suggest that acute administration of alprazolam doses are not clinically useful for the treatment of PMS.     

Decreased heterogeneity of capillary plasma flow in the rat whisker-barrel cortex during functional hyperemia

The pattern of capillary plasma perfusion was investigated in the rat brain during functional activation. Functional hyperemia was induced in the left whisker-barrel cortex by deflection of the right mystacial vibrissae for 2 min at frequencies of 1-7 Hz. Rats were decapitated under anesthesia 3-4 s after i.v. bolus injection of Evans blue dye. The steep increase of the arterial dye concentration ensures that divergent capillary plasma transit times result in unequal intracapillary dye concentrations. Plasma perfusion heterogeneity was determined from the coefficient of variation (CV) of Evans blue concentrations measured in numerous single capillaries of the whisker-barrel cortex. Functional hyperemia was quantified from measurements of CBF using the [14C]-iodoantipyrine technique in a second experimental group. CBF in the left whisker-barrel cortex increased with the stimulation frequency and was maximal at 5 Hz compared to the right side. Conversely, plasma perfusion heterogeneity decreased with stimulation frequency in a reciprocal way, being minimal at 5 Hz. Results indicate a decrease in the microcirculatory flow heterogeneity during functional hyperemia in the brain.     

Interleukin-1 receptor antagonist in differential diagnosis of inflammatory bowel diseases

BACKGROUND: Immunoregulatory properties of cytokines may mediate disordered inflammatory events in inflammatory bowel diseases (IBDs). On the basis of data obtained in experimental colitis, the hypothesis has been advanced that in IBD the balance between interleukin-1 (IL-1) and the naturally occurring IL-1 receptor antagonist (IL-1ra) might influence disease expression. OBJECTIVE: We studied the profiles of IL-1ra and acute phase proteins produced by activated macrophages to determine whether the level of IL-1ra in peripheral blood is a marker of disease activity in IBD and a possible differential diagnostic marker. PATIENTS AND METHODS: Levels of IL-1ra, serum neopterin, urinary neopterin, alpha 1-glycoprotein and C-reactive protein (CRP) were measured in 80 patients with ulcerative colitis, Crohn's disease or infectious colitis. RESULTS: Levels of IL-1ra were markedly increased in patients with active ulcerative colitis or active Crohn's disease compared with those in patients with infectious colitis. Patients with active Crohn's disease had significantly higher serum IL-1ra levels than patients with active ulcerative colitis. Moreover, a positive correlation was found between levels of C-reactive protein, alpha 1-glycoprotein, and serum neopterin and the level of IL-1ra in active Crohn's disease but not in active ulcerative colitis, strongly suggesting that the pathogenesis of the two conditions differs. CONCLUSION: Levels of IL-1ra in the peripheral blood of patients with IBD are of clinical relevance, representing a potent marker of disease activity and a possible differential diagnostic marker.     

Perceived public stigma and the willingness to seek counseling: The mediating roles of self-stigma and attitudes toward counseling.

This study examined the mediating effects of the self-stigma associated with seeking counseling and attitudes toward seeking counseling on the link between perceived public stigma and willingness to seek counseling for psychological and interpersonal concerns. Structural equation modeling of data from 676 undergraduates indicated that the link between perceived public stigma and willingness to seek counseling was fully mediated by self-stigma and attitudes. Perceptions of public stigma contributed to the experience of self-stigma, which, in turn, influenced help-seeking attitudes and eventually help-seeking willingness. Furthermore, 57% of the variance in attitudes toward counseling and 34% of the variance in willingness to seek counseling for psychological and interpersonal concerns were accounted for in the proposed model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)