Functional and biophysical analysis of the C-terminus of the CGRP-receptor; a family B GPCR

G-protein coupled receptors (GPCRs) typically have a functionally important C-terminus which, in the largest subfamily (family A), includes a membrane-parallel eighth helix. Mutations of this region are associated with several diseases. There are few C-terminal studies on the family B GPCRs and no data supporting the existence of a similar eighth helix in this second major subfamily, which has little or no sequence homology to family A GPCRs. Here we show that the C-terminus of a family B GPCR (CLR) has a disparate region from N400 to C436 required for CGRP-mediated internalization, and a proximal region of twelve residues (from G388 to W399), in a similar position to the family A eighth helix, required for receptor localization at the cell surface. A combination of circular and linear dichroism, fluorescence and modified waterLOGSY NMR spectroscopy (SALMON) demonstrated that a peptide mimetic of this domain readily forms a membrane-parallel helix anchored to the liposome by an interfacial tryptophan residue. The study reveals two key functions held within the C-terminus of a family B GPCR and presents support for an eighth helical region with striking topological similarity to the nonhomologous family A receptor. This helix structure appears to be found in most other family B GPCRs.

Editorial

This second issue of Knowledge Management Research & Practice (KMRP) continues the international nature of the first issue, with papers from authors based on four different continents. There are five regular papers, plus the first of what is intended to be an occasional series of 'position papers' from respected figures in the knowledge management field, who have specific issues they wish to raise from a personal standpoint. The first two regular papers are both based on case studies. The first is 'Aggressively pursuing knowledge management over two years: a case study a US government organization' by Jay Liebowitz. Liebowitz is well known to both academics and practictioners as an author on knowledge management and knowledge based systems. Government departments in many Western countries must soon face up to the problems that will occur as the 'baby boomer' generation reaches retirement age over the next decade. This paper describes how one particular US government organization has attempted to address this situation (and others) through the introduction of a knowledge management initiative. The second case study paper is 'Knowledge creation through the synthesizing capability of networked strategic communities: case study on new product development in Japan' by Mitsuru Kodama. This paper looks at the importance of strategic communities - communities that have strategic relevance and support - in knowledge management. Here, the case study organization is Nippon Telegraph and Telephone Corporation (NTT), a Japanese telecommunication firm. The third paper is 'Knowledge management and intellectual capital: an empirical examination of current practice in Australia' by Albert Zhou and Dieter Fink. This paper reports the results of a survey carried out in 2001, exploring the practices relating to knowledge management and intellectual capital in Australia and the relationship between them. The remaining two regular papers are conceptual in nature. The fourth is 'The enterprise knowledge dictionary' by Stuart Galup, Ronald Dattero and Richard Hicks. Galup, Dattero and Hicks propose the concept of an enterprise knowledge dictionary and its associated knowledge management system architecture as offering the appropriate form of information technology to support various different types of knowledge sources, while behaving as a single source from the user's viewpoint. The fifth and final regular paper is 'Community of practice and metacapabilities' by Geri Furlong and Leslie Johnson. This paper looks at the role of communities of practice in learning in organizations. Its emphasis is on metacapabilities - the properties required to learn, develop and apply skills. This discussion takes work on learning and core competences to a higher level. Finally, this issue includes a position paper 'Innovation as an objective of knowledge management. Part I: the landscape of management' by Dave Snowden. Snowden has been highly visible in the knowledge management community thanks to his role as the Director of IBM Global Services' Canolfan Cynefin Centre. He has helped many government and private sector organizations to consider their knowledge management problems and strategies. This, the first of two-part paper, is inspired by the notion of complexity. In it, Snowden calls for what he sees as a 20th century emphasis on designed systems for knowledge management to be consigned to history, and replaced by a 21st century emphasis on emergence. Letters to the editor on this, or any other topic related to knowledge management research and practice, are welcome. We trust that you will find the contributions stimulating, and again invite you to contribute your own paper(s) to future issues of KMRP.

Temperature effects on fatigue thresholds and structure sensitive crack growth in a nickel-base superalloy

Fatigue thresholds and slow crack growth rates have been measured in a powder formed nickel-base superalloy from room temperature to 600°C. Two grain sizes were investigated: 5-12 μm and 50 μm. It is shown that the threshold increases with grain size, and the difference is most pronounced at room temperature. Although crack growth rates increase with temperature in both microstructures, the threshold is only temperature dependent in the material with the larger grain size. It is also only in the latter that the room temperature threshold falls when the load ratio is increased from 0.1 to 0.5. At 600°C the higher load ratio causes a 20% reduction in the threshold irrespective of grain size. The results are discussed in terms of surface roughness and oxide-induced crack closure, the former being critically related to the type of crystallographic crack growth, which is in turn shown to be both temperature and stress intensity dependent. © 1983.

Effects of microstructure on long and short crack growth in nickel base superalloys

The use of engineering materials in critical applications necessitates the accurate prediction of component lifetime for inspection and renewal purposes. In fatigue limited situations, it is necessary to be able to predict the growth rates of cracks from initiation at a defect through to final fracture. To this end, fatigue crack growth data are presented for different microstructures of typical nickel base superalloys used in gas turbine engines. Crack growth behaviour throughout the life history of the crack, i.e. from the short crack through to the long crack propagation regime, is described for each microstructural condition and discussed in terms of current theories of fatigue crack propagation.

Effects of microstructure, temperature and R-ratio on fatigue crack propagation and threshold behaviour in two Ni-base alloys

Fatigue crack propagation and threshold data for two Ni-base alloys, Astroloy and Nimonic 901, are reported. At room temperature the effect which altering the load ratio (R-ratio) has on fatigue behaviour is strongly dependent on grain size. In the coarse grained microstructures crack growth rates increase and threshold values decrease markedly as R rises from 0. 1 to 0. 8, whereas only small changes in behaviour occur in fine grained material. In Astroloy, when strength level and gamma grain size are kept constant, there is very little effect of processing route and gamma prime distribution on room temperature threshold and crack propagation results. The dominant microstructural effect on this type of fatigue behaviour is the matrix ( gamma ) grain size itself.

Neurophysiological evaluation of convergent afferents innervating the human esophagus and area of referred pain on the anterior chest wall

Noxious stimuli in the esophagus cause pain that is referred to the anterior chest wall because of convergence of visceral and somatic afferents within the spinal cord. We sought to characterize the neurophysiological responses of these convergent spinal pain pathways in humans by studying 12 healthy subjects over three visits (V1, V2, and V3). Esophageal pain thresholds (Eso-PT) were assessed by electrical stimulation and anterior chest wall pain thresholds (ACW-PT) by use of a contact heat thermode. Esophageal evoked potentials (EEP) were recorded from the vertex following 200 electrical stimuli, and anterior chest wall evoked potentials (ACWEP) were recorded following 40 heat pulses. The fear of pain questionnaire (FPQ) was administered on V1. Statistical data are shown as point estimates of difference +/- 95% confidence interval. Pain thresholds increased between V1 and V3 [Eso-PT: V1-V3 = -17.9 mA (-27.9, -7.9) P < 0.001; ACW-PT: V1-V3 = -3.38 degrees C (-5.33, -1.42) P = 0.001]. The morphology of cortical responses from both sites was consistent and equivalent [P1, N1, P2, N2 complex, where P1 and P2 are is the first and second positive (downward) components of the CEP waveform, respectively, and N1 and N2 are the first and second negative (upward) components, respectively], indicating activation of similar cortical networks. For EEP, N1 and P2 latencies decreased between V1 and V3 [N1: V1-V3 = 13.7 (1.8, 25.4) P = 0.02; P2: V1-V3 = 32.5 (11.7, 53.2) P = 0.003], whereas amplitudes did not differ. For ACWEP, P2 latency increased between V1 and V3 [-35.9 (-60, -11.8) P = 0.005] and amplitudes decreased [P1-N1: V1-V3 = 5.4 (2.4, 8.4) P = 0.01; P2-N2: 6.8 (3.4, 10.3) P < 0.001]. The mean P1 latency of EEP over three visits was 126.6 ms and that of ACWEP was 101.6 ms, reflecting afferent transmission via Adelta fibers. There was a significant negative correlation between FPQ scores and Eso-PT on V1 (r = -0.57, P = 0.05). These data provide the first neurophysiological evidence of convergent esophageal and somatic pain pathways in humans.