Structure-function studies of the C3a-receptor: C-terminal serine and threonine residues which influence receptor internalization and signaling

The anaphylatoxic peptide C3a is a pro-inflammatory mediator generated during complement activation, whose specific G protein coupled receptor is expressed on granulocytes, monocytes, mast cells, activated lymphocytes, and in the nervous tissue. We have generated RBL-2H3 cell clones stably expressing mutants of the human C3a-receptor (C3aR) with combined alanine (Ala) substitutions of ten C-terminal serine (Ser) or threonine (Thr) residues, which may represent putative phosphorylation sites to characterize their role in ligand-induced C3aR internalization and signaling. Ser475/479 and Thr480/481 as well as Ser449 seemed not to be involved in ligand-induced receptor internalization. Either directly or by a conformational change they even "inhibit" C3aR internalization. In contrast, mutants with Ala substitutions at Ser465/470 and Thr463/466 were poorly internalized, and Thr463 seemed to be the most important C-terminal Thr or Ser residue directly effecting receptor internalization. However, it is likely that other C3aR regions additionally participate in this negative feed-back mechanism since even mutants with multiple Ala substitutions still internalized to a limited degree. Interestingly, in a mutant with a single exchange of Ser449 to Ala, the signal transduction assessed by a Ca(2+) assay and [(35)S]GTP gamma S-binding on HEK cells transiently co-transfected with G-alpha 16 or G-alpha O, respectively, was severely impaired, indicating that this residue of C3aR is involved in G protein coupling.     

The dual effect of L-proline on spreading depression in the chicken retina

Evidence was presented for a glutamate agonistic effect of L-proline which promotes K+-based spreading depressions (SD) in chick retinas at relatively high concentrations (5 mM), in addition to an antagonistic effect which inhibits glutamate-based SDs at lower (2 mM) concentrations. Together these effects explain the observed biphasic effect of L-proline on the incidence of SD in the retina.     

A biological context for the self-nonself discrimination and the regulation of effector class by the immune system

An effective immune response to an antigen requires two sets of decisions: Decision 1, the sorting of the repertoire, and Decision 2, the regulation of effector class. The repertoire, because it is somatically generated, large, and random, must be sorted by a somatic mechanism that subtracts those specificities (anti-self) that, if expressed, would debilitate the host, leaving a residue (anti-nonself) that, if not expressed, would result in the death of the host by infection. The self-nonself discrimination is the metaphor used to describe Decision 1, the sorting of the repertoire. In order to be functional, the sorted repertoire must be coupled to a set of biodestructive and ridding effector functions, such that the response to each antigen is treated in a coherent and independent manner. Although a reasonably complete framework for Decision 1 exists, Decision 2 lacks conceptualization. The questions that must be considered to arrive at a proper framework are posed. It should be emphasized that manipulation at the level of Decision 2 is where clinical applications are likely to be found.     

Cloning,sequencing and analysis of the yeastS. uvarum ERG10 gene encoding acetoacetyl CoA thiolase

Summary TheERG10 gene specific toS. uvarum, a brewing yeast, has been cloned by complementation of anS. cerevisiae erg10 mutant.S. uvarum contains two differentERG10 genes. One of these is similar to theS. cerevisiae ERG10 gene; they are structurally different, but functionally homologous. The clonedERG10 gene has been located on chromosome XVI, and we have shown that it is allelic to the previously isolatedtsm0115 mutants. Northern blot and sequence analysis indicate that theERG10 gene is highly expressed, and biochemical and genetic evidence show that it encodes the cytoplasmic acetoacetyl CoA thiolase.     

Description of Heart-Rate Variability Data in Accordance With a Physiological Model for the Genesis of Heartbeats

A survey is presented of techniques which transform heart-rate variability data into a signal that is both visually informative and accessible for analysis. The Instantaneous Heart-Rate (IHR) signal is introduced, i.e. the signal having the value of the heart rate (inverse interbeat interval) during the interval concerned. The IHR signal differs from the standard Delayed Heart-Rate (DHR) signal, which is always one beat late. The relationship is discussed between the different representation methods and the Integral Pulse Frequency Modulation (IPFM) model, the latter being a physiologically plausible model for the transformation of a continuous input signal (e.g., nervous influence on the cardiac pacemaker) into a series of events (heartbeats). It is shown that when the IHR signal is used as input of the IPFM model, the event series from which the signal was derived appears at the output. Hence, if the IPFM model is accepted as a model of the pacemaker, the IHR signal may be considered as an approximation of the neural (sympathetic and parasympathetic) influence on the pacemaker. In addition we show that the appearance of the IHR signal is less affected by trigger errors or extrasystoles than the standard DHR signal. It is concluded that the most attractive time-domain representation of physiological event series consists of the IHR signal, because this signal, being conceptually and computationally simple, is consistent with the IPFM model.     

Varied biologic functions of c-reactive protein

Our investigations of human C-reactive protein (CRP) and CRP transgenic mice have produced novel data that firmly establish this protein as an important host defense molecule. For example, we have learned that depending on the disease model, the beneficial effect of CRP can be direct, depend on the protein's ability to engage complement and Fcγreceptors, or rely on its ability to bridge innate and adaptive immunity. In addition, the degree of protection correlates with acute phase expression, but more important, also with the amount of CRP expressed constitutively. Furthermore, differences in baseline levels of CRP among healthy individuals and among patients can be attributed to a CRP gene polymorphism. In this article, we discuss these and other observations we have made during the last 5 yr and summarize our ongoing studies and future plans related to CRP biology.     

Technology evaluation in a US hospital: The role of clinical engineering

Appropriate deployment of technological innovation contributes to improvement in the quality of healthcare delivered, containment of cost, and an increased access to the healthcare system. Hospitals have been allocating a, significant portion of their resources to procuring and managing capital assets; they are continously faced with demands for new medical equipment and are, asked to manage existing inventory for which they are not well prepared. To objectively manage their investment, hospitals are developing medical technology management programmes that need pertinent information and methods for new equipment planning as well as for reduction in the ownership costs of existing equipment. Clinical engineers can identify new medical equipment, review their institution's technological position, develop equipment-selection criteria, supervise installations and monitor postprocurement performance to meet their hospital's programme's objectives. This programme, together with cost accounting analysis, will objectively guide the capital assets decisionmaking process. The result of systematic planning and execution, the programme will assure the lowest life-cycle costs at the best performance. The clinical engineer's skills and expertise are needed to facilitate the adoption of an objective methodology for implementing the programme, thus improving the match between the hospital's needs and budget projections, equipment performance and cost of ownership.