Jamie Morrison

T-Cell-Dependent Fibrosis in the mdx Dystrophic Mouse

In Duchenne muscular dystrophy patients, the pathological hallmark of the disease, namely, the chronic accumulation of sclerotic scar tissue in the interstitial space of skeletal muscle is attributed to manifestation of secondary pathological processes. Such anomalous generation of matrix protein is thought to be driven by the continuous degeneration and regeneration of muscle both in Duchenne Muscular Dystrophy and in the mdx mouse homolog. We examined mdx and the control strain C57bl/10 mice over a range of ages with respect to the amounts of collagen present in muscles and other organs, finding that the mdx have significantly higher collagen content at later time points in their kidney and lung as well as their muscles. Surprisingly, when we bred the mdx mice on the nu/nu background, the time course of fibrogenesis was modified depending on the tissue and the collagen content was significantly different in age-matched mice. Transplantation of normal thymic tissue into the mdx-nu/nu mice replenished their T-cells and concomitantly altered the collagen content in their tissues to levels comparable with those in immunocompetent mdx mice. This suggests that T-cells play a role in the onset of the fibrotic events that undermines the ability of dystrophic muscle to regenerate.

Agricultural development and pro-poor economic growth in sub-Saharan Africa: potential and policy

There is widespread concern at continuing and deepening poverty and food insecurity in sub‐Saharan Africa and the lack of broad‐based economic growth. There is also debate about agricultures role in driving pro‐poor economic growth, some arguing it has a critical role while others see it is as largely irrelevant. We suggest that both sets of arguments pay insufficient attention to important institutional issues, and that agriculture has a critical role to play, largely by default, as there are few other candidates with the same potential for supporting broad‐based pro‐poor growth. There are, however, immense challenges to agricultural growth. In considering the costs and benefits of investment in agricultural growth, however, regard must also be given to the economic and social costs of rural stagnation and to providing safety nets in situations of enduring poverty. Policy needs to focus more on agriculture, and recognize and address the diversity of institutional, trade, technological and governance challenges to poverty‐reducing growth in Africa.

Effects of T-lymphocyte depletion on muscle fibrosis in the mdx mouse

Duchenne muscular dystrophy was initially described as a myosclerosis because of the conspicuous progression of interstitial fibrosis. Using the mdx mouse homologue, we have shown previously that the accumulation of intramuscular collagen is profoundly influenced by the presence or absence of T lymphocytes. Here we have used thymectomy and antibody depletion to examine the effect of ablating CD4 or CD8 or both subsets of T lymphocytes on skeletal muscle fibrosis in mdx and C57BL10 (wild-type) mice. Depletion of either or both subsets at 4 weeks of age did not influence fibrosis in mdx mice, as determined by measuring hydroxyproline levels and collagen deposition in diaphragm. Additionally, expression of transforming growth factor-beta1, which is implicated in collagen deposition, either decreased (mdx mice) or increased (C57BL/10 mice) after double CD4/8 depletion. Our data suggest that depletion of lymphoid cells may affect the tight regulatory control of transforming growth factor-beta1, with possible pleiotropic effects, and more importantly, that the fibrotic process is self-sustaining from a very early stage.

The Expression of Free Oligosaccharides in Human Seminal Plasma

Human seminal plasma is a complex mixture of proteins, glycoproteins, peptides, glycopeptides, and prostaglandins secreted by organs of the male reproductive tract. The components of this fluid have been implicated in the suppression of immune response, agonistic effects on sperm-egg binding, and promotion of successful implantation of the human embryo. Fractionation followed by biophysical analyses revealed that free oligosaccharides constitute a major component of the total glycoconjugates within seminal plasma. Significant findings of our analyses include the following: (i) the concentration of free oligosaccharides is 0.3–0.4 mg/ml; (ii) mono- and difucosylated forms of the disaccharide lactose are major components; (iii) many of the remaining oligosaccharides are also rich in fucose and carry Lewisx and/or Lewisyepitopes; (iv) a subset of the oligosaccharides express the reducing end sequence (GlcNAcβ1–3/4Glc) not reported in human milk oligosaccharides; (v) oligosaccharides in seminal plasma exclusively express type 2 (Galβ1–4GlcNAc) but not the type 1 sequences (Galβ1–3GlcNAc) that predominate in human milk glycans; and (vi) the structural diversity of seminal plasma oligosaccharides is far less than human milk oligosaccharides. The agonistic effect of both fucose and fucosylated glycoconjugates on human sperm-egg binding in vitro suggests that fucosylated oligosaccharides may also promote fertilization in the female reproductive tract.

Stochastic biases in technical change in South African agriculture.

This paper examines biased technical change in South African agriculture using a system of share equations with unobserved components. Developing on the work of Lambert and Shonkwiler (1995), this paper generalises previous work by introducing independent unobserved components into each model using a regression-based approach. We find evidence of stochastic technical change, which is itself biased between the four factors of production: machinery, land, labour and fertiliser, and which closely reflects distinct phases of South African agricultural policy and development.

Heroes, villains and victims: agricultural subsidies and their impacts on food security and poverty reduction

Subsidies have been a pervasive feature of agricultural policy throughout history. This chapter describes different kinds of subsidies and their changing roles in different societies. It reviews evidence on the economic, food security and poverty impacts of different agricultural subsidies in developed and developing countries. The evidence suggests that different subsidy programmes have had in some contexts profoundly positive and in other contexts profoundly negative impacts on food security and on the livelihoods of poor people and poor societies. Discussions of the historical and potential roles of subsidies and their more recent use have, however, often been the victim of a narrow overemphasis by some on their negative effects and, paradoxically, of their misuse as a result of others’ exaggerated expectations of their benefits. The chapter concludes with recognition that more judicious, differentiated and new uses of subsidies for food production may (with complementary investments in technology, infrastructure and socioeconomic change) be crucial in both high- and low-income countries in promoting sustainable food security and poverty reduction in the face of growing national and global challenges in food production and access.

A comparison of proxy variable and stochastic latent variable approaches to the measurement of bias in technological change in south african agriculture

Technical change is inherently unobservable and has conventionally been represented by proxy variables, from simple time trends to more sophisticated knowledge stock variables. This paper follows Lambert and Shonkwiler (1995) in modelling technical change as a stochastic unobservable variable and tests this formulation against the alternative of using R&D and patent indices. This is done by fitting a system of share equations, derived from the dual profit function, to production data for South African agriculture. Each equation includes both unobserved technical change components and technical proxy variables. Variable deletion tests show that conventional proxy variables fail to explain the biases of technological change, while cointegration tests show that technical change is both stochastic and biased. The latent variables provide estimates of biases that are consistent with past studies and the historical record and can be explained by policy change in South Africa following WWII. The demonstration of high rates of return to R&D is not sufficient to justify R&D activity when biased technological change exacerbates input use and welfare distortions within and without the sector. * We thank the University of Pretoria for funding the study and the referees and delegates for many useful comments.