7. Causation and remoteness

This chapter examines the issues of causation and remoteness in negligence, which basically concern the links between breaches of duty and the consequences of those breaches and the strength of those links. The chapter considers in detail causation in fact, causation in law, and remoteness of damage. We find that courts have developed several important exceptions to the ordinary ‘but for’ test of factual causation, including the Fairchild principle. Fairchild can be considered as a departure from the normal requirement that the claimant must prove factual causation of damage. Legal causation is tested by looking for unexpected events called novi actus intervenientes. Remoteness is an issue of foreseeability of damage.

Phosphorylation-dependent inhibition of Cdc42 GEF Gef1 by 14-3-3 protein Rad24 spatially regulates Cdc42 GTPase activity and oscillatory dynamics during cell morphogenesis

Active Cdc42 GTPase, a key regulator of cell polarity, displays oscillatory dynamics that are anticorrelated at the two cell tips in fission yeast. Anticorrelation suggests competition for active Cdc42 or for its effectors. Here we show how 14-3-3 protein Rad24 associates with Cdc42 guanine exchange factor (GEF) Gef1, limiting Gef1 availability to promote Cdc42 activation. Phosphorylation of Gef1 by conserved NDR kinase Orb6 promotes Gef1 binding to Rad24. Loss of Rad24–Gef1 interaction increases Gef1 protein localization and Cdc42 activation at the cell tips and reduces the anticorrelation of active Cdc42 oscillations. Increased Cdc42 activation promotes precocious bipolar growth activation, bypassing the normal requirement for an intact microtubule cytoskeleton and for microtubule-dependent polarity landmark Tea4-PP1. Further, increased Cdc42 activation by Gef1 widens cell diameter and alters tip curvature, countering the effects of Cdc42 GTPase-activating protein Rga4. The respective levels of Gef1 and Rga4 proteins at the membrane define dynamically the growing area at each cell tip. Our findings show how the 14-3-3 protein Rad24 modulates the availability of Cdc42 GEF Gef1, a homologue of mammalian Cdc42 GEF DNMBP/TUBA, to spatially control Cdc42 GTPase activity and promote cell polarization and cell shape emergence.

Techno-economic assessment of biogas production from press mud in Bangladesh

To assess the potential of biogas generation, as a new and renewable source of energy, physico-chemical parameters of press mud have been determined. It has considerable amount of volatile matter (75-80%) and C/N ratio (13-15) is slightly lower than the normal requirement for biomethanation. The total gas yield was 0.18 L/g and it contained about 65% methane. Biogas generation was studied in a 150 cft plant in the field at solid concentrations of 6 to 8%. Acclimatization of the reactor has been done by initial start-up by cow dung and gradual mixing with press mud in order to generate biogas from press mud alone. The profitability of the considered plant has been assessed using the discounting and dynamic Net Present Value methods. The biogas and biofertilizer production from press mud was found to be economically feasible. DOI: http://dx.doi.org/10.3329/bjsir.v48i1.15414 Bangladesh J. Sci. Ind. Res. 48(1), 51-58, 2013

Evolutionary Adaptation of Factor V from the Venom of the Common Brown Snake into a Potent Procoagulant

Some of the most toxic snakes in the world are those from the Australian Elapid family, including the three most venomous land snakes Inland Taipan, Coastal Taipan, and Common Brown snake. Their venom is strongly procoagulant and they are the only species known to have acquired a powerful prothrombin activator in their venom, which consists of a factor Xa (FXa)-like and factor V (FV)-like component. Venom-derived FV (pt-FV) from the Common Brown snake P. textilis shares 44% sequence homology with mammalian FV and has a similar domain organization. Remarkably, the B domain length of pt-FV is dramatically shortened compared to human FV (46 vs. 836 aa). This adaptation provides a unique opportunity to gain new insight into the function of the B domain and to examine the mechanistic basis for the strong procoagulant nature of the venom-derived prothrombinase complex. Pt-FV was expressed in BHK cells, purified, and characterized in functional assays employing FXa purified from P. textilis venom (pt-FXa). SDS-PAGE analysis revealed that pt-FV migrated as a single chain protein (~180 kDa). Thrombin completely processed pt-FV to pt-FVa, yielding the characteristic heavy and light chains. Surprisingly, pt-FVa migrated as a single band on a non-reducing gel, indicating that the heavy and light chains are connected by a unique disulfide bond. Functional analysis of prothrombin and prethrombin-1 conversion using a purified component assay in the presence of pt-FXa and negatively charged phospholipids revealed that pt-FV exhibits kinetic parameters comparable to human prothrombinase. Proteolytic processing of single chain pt-FV to the heterodimer did not significantly increase cofactor activity, indicating that pt-FV is expressed as a constitutively active cofactor that has bypassed the normal requirement for proteolytic activation. These results were confirmed using an uncleavable variant, pt-FV-QQ. We speculate that the mechanistic basis for this constitutive cofactor activity is related to the absence of a key cluster of conserved B domain residues, which we have recently shown to play an important role in maintaining FV as an inactive procofactor (JBC2007;282:15033). Additional experiments revealed that the pt-FV–pt-FXa complex does not require a membrane surface to optimally function, as the kinetics of prethrombin-1 activation were equivalent in the presence or absence of membranes. Binding measurements indicated that this was due to the high affinity interaction (Kd ~8 nM) of pt-FV with pt-FXa in solution. Interestingly, human FVa did not bind soluble pt-FXa with high affinity, suggesting that pt-FXa binding involves unique molecular features on pt-FV. Additional studies revealed that pt-FV does not lose activity following incubation with high concentrations of activated protein C (APC), even though the pt-FV heavy chain was fully proteolyzed. Collectively, our findings provide new insights into FV structure/function as well as a biochemical rationale for the powerful procoagulant nature of the prothrombinase complex from P. textilis venom. Remarkably, pt-FV has acquired at least three gain of function elements: first, it is constitutively active and as such the first example of a naturally occurring active FV variant. Second, pt-FV has a unique conformation as it bypasses the normal requirement for a membrane surface to achieve high affinity FXa binding. Finally, pt-FV is functionally resistant to APC which could be due to its unique disulfide bond. Taken together, venom-derived P. textilis FV represents an exceptional example of a protein that has adapted into a potent biological weapon for host defense and to incapacitate prey. Uncovering the mechanistic details of these gain of function elements will provide a new level of understanding of FV/FVa function.

Current Assets Management: A Comparative Study of India, Singapore and Thailand

The management of current assets (CA) such as cash, marketable securities, inventory and debtors, etc. is a vital aspect of corporate finance. These assets must be managed efficiently in order to maintain the liquidity of the firm while also ensuring that they are not kept at high levels either. This paper presents an empirical study, based on the data of corporate enterprises of India, Singapore and Thailand. Comparative practices with regard to CA management of the three countries have been examined. It has been observed that Singapore companies carry excessive cash balances, much more than the normal requirement. As regards inventory levels, Indian and Thai companies hold on average about 40 per cent of CAs as inventory as against 25 per cent in Singapore. It is noteworthy that the debtor-to-CA ratio is almost the same (about 33%) in all the three countries.

A mushroom-inducing DNA sequence isolated from the Basidiomycete, Schizophyllum commune.

A DNA sequence capable of inducing the de novo development of fruiting bodies (mushrooms) when integrated into the genome of unmated, nonfruiting strains of the Basidiomycete Schizophyllum commune has been isolated and partially characterized. This sequence, designated FRT1, overrides the normal requirement of a mating interaction for fruiting in this organism. It has been shown to integrate stably in different chromosome locations and appears to be trans-acting. It also enhances the normal process of fruiting that occurs after mating. Additional DNA sequences with similarity to FRT1 were detected within the genome of the strain of origin by hybridization of labeled FRT1 DNA to blots of digested genomic DNAs. FRT1 and the genomic sequences similar to it were shown to be genetically linked. Southern hybridization experiments suggested sequence divergence at the FRT1 locus between different strains of S. commune. A testable model for how FRT1 may act as a key element in the pathway for the differentiation of fruiting bodies is presented as a working hypothesis for further investigation.

Expression of recombinant myelin-associated glycoprotein in primary Schwann cells promotes the initial investment of axons by myelinating Schwann cells.

Myelin-associated glycoprotein (MAG) is an integral membrane protein expressed by myelinating glial cells that occurs in two developmentally regulated forms with different carboxyterminal cytoplasmic domains (L-MAG and S-MAG). To investigate the role of MAG in myelination a recombinant retrovirus was used to introduce a MAG cDNA (L-MAG form) into primary Schwann cells in vitro. Stably infected populations of cells were obtained that constitutively expressed MAG at the cell surface without the normal requirement for neuronal contact to induce expression. Constitutive expression of L-MAG did not affect myelination. In long term co-culture with purified sensory neurons, the higher level of MAG expression on infected Schwann cells was reduced to control levels on cells that formed myelin. On the other hand, unlike normal Schwann cells, infected Schwann cells associated with nonmyelinated axons or undergoing Wallerian degeneration expressed high levels of MAG. This suggests that a posttranscriptional mechanism modulates MAG expression during myelination. Immunostaining myelinating cultures with an antibody specific to L-MAG showed that L-MAG was normally transiently expressed at the earliest stages of myelination. In short term co-culture with sensory neurons, infected Schwann cells expressing only L-MAG segregated and ensheathed larger axons after 4 d in culture provided that an exogenous basal lamina was supplied. Similar activity was rarely displayed by control Schwann cells correlating with the low level of MAG induction after 4 d. These data strongly suggest that L-MAG promotes the initial investment by Schwann cells of axons destined to be myelinated.

A Diploma in Clinical Psychiatry

The MRCPsych is now firmly established as the normal requirement for a career in psychiatry in this country. The need for other medical specialists to acquire psychiatric knowledge and skills raises the question of a possible demand for a second type of College examination. The Court of Electors have been considering some of the arguments for and against a College Diploma and would welcome further discussion in the College on this.

The Possibility of Producing Useful Proficiency Tests in English*

To begin at the beginning, proficiency tests, like paper, printing, and gunpowder, were invented by the Chinese. As early as 2200 B.C. the emperor of China was using tests to decide which of his officials should be promoted and which should be fired. A thousand years later the Chan dynasty had developed a series of examinations in which every candidate for public office demonstrated his competence in the five basic arts: music, archery, horsemanship, writing, and arithmetic. Tests for teachers arrived in the Western world with the establishment of the medieval universities. The probationary discourse was the essential step by which a student proved himself fit for membership in the tightly held guild of university professors. Today tests are a normal requirement for admission to the practice of law and medicine, not to mention barbering, the selling of real estate, and the calculation of insurance risks. Both the pervasiveness and the ancient lineage of proficiency tests argue for the possibility that they are producible and for the probability that they are useful.