Trudy Owens

Regional variations in the extent and pattern of grey matter demyelination in Multiple Sclerosis: a comparison between the cerebral cortex, cerebellar cortex, deep grey matter nuclei and the spinal cord

Background: Substantial grey matter (GM) demyelination occurs in both the cerebral cortex and spinal cord in multiple sclerosis (MS). GM demyelination also occurs in the cerebellar cortex and the deep GM nuclei of the brain. However, no study has made a direct “within subject” comparison of the extent of GM pathology between these regions. Aim: To examine the extent and pattern of GM demyelination in the motor cortex, cingulate gyrus, cerebellum, thalamus and spinal cord in MS. Methods: Postmortem study using material from 14 MS cases and three controls. Sections were taken from the five predetermined areas and stained for proteolipid protein. The extent of GM and white matter (WM) demyelination was assessed in each region. Results and conclusion: Overall, 28.8% of the GM was demyelinated compared with 15.6% of the WM (p<0.001), with demyelination being greater in the GM than in the WM at each of the anatomical sites. There was substantial variation in the extent of demyelination between the different CNS regions. GM demyelination was most extensive in the spinal cord and cerebellum while WM demyelination was most prominent in the spinal cord.

The impact of agricultural extension on farm production in resettlement areas of Zimbabwe

In this paper, we revisit the contested issue of the impact of agricultural extension on farm production. We exploit two features of the data available to us: its longitudinal nature and explicit measures of farmer ability. We find that after controlling for innate productivity characteristics and farmer ability either using household fixed effects estimation, or by including a measure of farmer ability and village fixed effects, access to agricultural extension services, defined as receiving one or two visits per agricultural year, raises the value of crop production by about 15 per cent. This parameter estimate is statistically significant. However, we also find variability in these parameter estimates across individual crop years, with the impact being markedly different in drought and non-drought years. Collectively, these results suggest that although access to farm-level extension visits does increase productivity even after controlling for innate productivity characteristics and farmer ability, results from single-year cross-sectional studies should be treated with caution

Ultra-high-field imaging distinguishes MS lesions from asymptomatic white matter lesions

Objectives: To investigate whether multiple sclerosis (MS) and non-MS white matter brain lesions can be distinguished by their appearance on 7 T T2*-weighted MRI. Methods: This was an observational study of 28 patients with MS and 17 patients with cerebral white matter lesions who did not have MS. Subjects were imaged using 7 T T2*-weighted imaging. White matter lesions were identified and analyzed for volume, location, and perivenous appearance. Results: Out of 901 lesions identified in patients with MS, 80% were perivenous. In comparison, 19% of 428 lesions identified in patients without MS had a perivenous appearance. Seven-Tesla T2*-weighted MRI reliably distinguished all patients with clinically definite MS (>40% lesions appeared perivenous) from those without clinical MS (<40% lesions appeared perivenous). Perivenous lesion appearance was more predictive of MS (odds ratio [OR] 14, p < 0.001) than subcortical or periventricular lesion location (OR 4.5, p < 0.001, and OR 2.4, p = 0.009). Perivenous lesion appearance was observed with a similar frequency in patients with clinically isolated syndrome of demyelination and in early (gadolinium-enhancing) MS lesions. Conclusion: Perivenous lesion location on 7 T T2*-weighted imaging is predictive of the presence of demyelination. Optimization of this imaging technique at lower magnetic resonance field strengths would offer benefit for the diagnosis of MS.

Spinal cord gray matter demyelination in multiple sclerosis : A novel pattern of residual plaque morphology

The extent and pattern of gray matter (GM) demyelination in the spinal cord in multiple sclerosis (MS) has not been examined in detail. Human autopsy material was obtained from 36 MS cases and 12 controls. Transverse sections were taken from five levels of the spinal cord (upper cervical, lower cervical, upper thoracic, lower thoracic and lumbar levels) and the extent of GM and white matter (WM) demyelination evaluated using proteolipid protein immunohistochemistry (IHC). The proportion of the GM that was demyelinated (33%) was significantly greater than the proportion of demyelinated WM (20%) (P < 0.0001). Similarly, demyelination was more extensive in the GM than in the WM at each of the five cord levels. The extent of GM demyelination was not significantly different between the five cord levels while WM demyelination was greatest at the upper cervical level. Morphologically, the borders of a proportion of the GM plaques show a strict respect for the GM/WM boundary. We demonstrate that extensive demyelination occurs in the GM of the spinal cord in MS. Myelin protein IHC reveals a novel pattern of residual plaque morphology challenging previous work suggesting that MS plaques display a total disregard for anatomical boundaries.

Revisiting forever gained: Income dynamics in the resettlement areas of Zimbabwe, 1983–96

This study examines income dynamics for a panel of households resettled on former white‐owned farms in the aftermath of Zimbabwes independence. There are four core findings: (i) over a 13‐year period (1983–96) there has been an impressive accumulation of assets and a dramatic increase of crop incomes; (ii) the rise of crop incomes is partly due to asset accumulation but largely to increased asset returns; (Hi) differences between households in initial conditions, such as previous farming experience, have few persistent effects; and (iv) income growth has been widely shared, income inequality has fallen sharply and the largest percentage increases in incomes are recorded by households that initially had the lowest incomes.

Clinico-pathological evidence that axonal loss underlies disability in progressive multiple sclerosis

Growing evidence suggests that axonal degeneration rather than demyelination is the pathological substrate underlying chronic, irreversible disability in multiple sclerosis. However, direct evidence linking clinical disability measured in vivo with corresponding post-mortem measures of axonal pathology is lacking. Our objective in this study was to investigate the relationship between motor disability accumulated by patients with multiple sclerosis during life and the degree of axonal loss observed in their descending motor tracts after death. Human spinal cord derived at autopsy from 45 patients with multiple sclerosis was investigated. The medical records of each patient were reviewed by a multiple sclerosis neurologist to determine the degree of motor disability reached before death. Spinal cord sections were stained immunohistochemically. The degree of demyelination and the number of surviving corticospinal tract axons were measured in each patient. Patients who had accumulated higher levels of motor disability prior to death demonstrated fewer surviving corticospinal axons. Motor disability did not correlate with degree of demyelination. This study provides for the first time, direct clinico-pathological evidence that axonal loss is the pathological substrate of established disability in multiple sclerosis.

Export-oriented industrialization through primary processing?

Abstract Recent research suggests that East Asias manufactured export success is not replicable in other developing countries, with lower skill/land ratios. This conclusion, however, is based on a narrow definition of manufactured exports. The present paper asks whether the chances of export-oriented industrialization in countries with low skill/land ratios seem better when the definition of manufactures is broadened to include processed primary products. The answer from its crosscountry econometric analysis is “yes” for countries with moderately skilled labor forces (as in Latin America), but “no” for countries where levels of skill are low (as in Africa).

Spinal Cord Neuronal Pathology in Multiple Sclerosis

The objective of this study was to assess neuronal pathology in the spinal cord in multiple sclerosis (MS), both within myelinated and demyelinated tissue. Autopsy material was obtained from 38 MS cases and 21 controls. Transverse sections were taken from three spinal cord levels and stained using Luxol Fast Blue/Cresyl Violet and myelin protein immunohistochemistry. Measurements of neuronal number and size were made for all neurons within the anterior horns of the gray matter. Neurons were classified as motoneurons or interneurons according to size criteria. In comparison with controls, both motoneuron and interneuron number were reduced in MS cases at the upper cervical (interneuron P = 0.0549; motoneuron P = 0.0073) and upper thoracic (interneuron P = 0.0507; motoneuron P = 0.0144), but not the lumbar level. Interneuron cross‐sectional area was reduced in MS cases at all levels (upper cervical, P = 0.0000; upper thoracic, P = 0.0002; lumbar, P = 0.0337). Neuronal loss appears to be predominantly related to local gray matter plaques, whereas interneuron atrophy occurs in both myelinated and demyelinated areas.

Greater loss of axons in primary progressive multiple sclerosis plaques compared to secondary progressive disease

The pathological substrate of progressive disability in multiple sclerosis is hypothesized to be axonal loss. Differences in the demographic, pathological and radiological features of patients with primary progressive compared with secondary progressive multiple sclerosis raise the question as to whether they actually represent separate clinical entities. So far, large pathological studies comparing axonal damage between primary progressive and secondary progressive multiple sclerosis have not been reported. In this clinico-pathological study we examined the cervical spinal cord in patients with primary and secondary progressive multiple sclerosis. Human cervical spinal cord was derived at autopsy from 54 patients (17 primary progressive, 30 secondary progressive and 7 controls). Tissue was stained immunohistochemically and examined to determine: (i) the number of surviving corticospinal tract axons; (ii) the extent of grey and white matter demyelination; (iii) the degree of inflammation inside and outside of lesions; and (iv) the relationship between demyelination and axonal loss. Associated clinical data was used to calculate expanded disability status scale for each patient preceding death. Motor disability in the primary progressive and secondary progressive groups was similar preceding death. Secondary progressive multiple sclerosis patients showed considerably more extensive demyelination of both the white and grey matter of the cervical spinal cord. The total number of corticospinal axons was equally low in primary progressive and secondary progressive multiple sclerosis groups versus controls. The reduction of axonal density in demyelinated regions compared to normal appearing white matter was significantly more extensive in primary progressive versus secondary progressive patients (33% reduction versus 16% reduction, P < 0.001). These findings suggest axonal loss is the pathological substrate of progressive disability in both primary progressive and secondary progressive multiple sclerosis with a common plaque-centred mechanism. More extensive axonal loss within areas of demyelination in primary progressive multiple sclerosis could explain high levels of axonal loss observed in these patients despite low levels of demyelination.

Ex-ante actions and ex-post public responses to drought shocks: Evidence and Simulations from Zimbabwe

Abstract The study examines the consequences of alternative public responses to drought shocks. It does so by drawing on household data from resettlement areas of rural Zimbabwe from 1992–93 to 1995–96 and the estimation of four behavioral relations: the determinants of crop income; the determinants of investment in livestock; the determinants of investment in agricultural capital stock; and the determinants of private transfers. This information is used to construct a series of simulations in which drought relief received in the aftermath of the 1994–95––the ex-post response––is made available to households in the form of agricultural capital stock and extension advice––an ex-ante action. Doing so is found to raise household welfare in nondrought years, but provides only limited protection in the aftermath of drought.