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2. Cross-sectional area of the elephant corpus callosum: comparison to other eutherian mammals.

Author

Manger, P R, Hemingway, J, Haagensen, M, Gilissen, Emmanuel, Manger, P R, Hemingway, J, Haagensen, M, and Gilissen, Emmanuel

Abstract

The current study reports our findings of the relationship between cross-sectional area of the corpus callosum and brain mass in over 100 eutherian mammal species. We were specifically interested in determining whether the elephant had a corpus callosum the size that would be expected for eutherian mammal with a brain mass of approximately 5000 g, or whether a different morphology had evolved. To answer this question we first analysed data from primates, other eutherian mammals and cetaceans, finding that primates and other eutherian mammals showed a positive allometric relationship between the two variables, such that larger brains had a relatively larger corpus callosum. Interestingly, primates have a slightly larger corpus callosum than other eutherian mammals, but showed a similar allometric scaling to this group. The cetaceans had a both absolutely and relatively small corpus callosum compared to other mammals and showed isometric scaling with brain mass. The six elephants studied herein had the largest absolute corpus callosums recorded to date; however, relative to the mass of their brain, the size of the corpus callosum was what would be expected of a typical eutherian mammal with a brain mass of approximately 5000 g. The data for elephants hinted at sexual dimorphism in size of the corpus callosum, with female elephants having both an absolute and relatively larger callosum than the males. If this observation is supported in future studies, the elephants will be the first non-primate species to show sexual dimorphism in this neural character. The results are discussed in both an evolutionary and functional context., Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2010

4. Steatosis in South African women: How much and why?

Author

Naran NH, Haagensen M, and Crowther NJ

Subjects
Adipose Tissue diagnostic imaging, Adipose Tissue pathology, Adult, Anthropometry, Black People, Body Mass Index, Cross-Sectional Studies, Fatty Liver diagnostic imaging, Fatty Liver metabolism, Female, Humans, Insulin Resistance, Linear Models, Liver diagnostic imaging, Liver pathology, Metabolic Syndrome diagnostic imaging, Metabolic Syndrome metabolism, Metabolic Syndrome pathology, Middle Aged, South Africa, Subcutaneous Fat, Abdominal diagnostic imaging, Subcutaneous Fat, Abdominal pathology, Tomography, X-Ray Computed, White People, Young Adult, Fatty Liver pathology
Abstract

Background: Globally, steatosis is the commonest type of liver pathology and is closely associated with obesity and the metabolic syndrome. Obesity is common in urban African females but no data is available on hepatic fat content in this population group when compared to other ethnic groups. The aim of this study was therefore to compare hepatic fat content in woman from different ethnic groups in South Africa and to characterise the principle determinants of liver fat., Materials and Methods: A convenience sample of 106 (48 Indian, 29 African and 29 Caucasian) female volunteers aged 20-60 years and having no history of cardiometabolic disorders were recruited. Hepatic fat was determined from CT scans using the liver-spleen attenuation ratio (LAR), which decreases with increasing levels of hepatic fat. Anthropometric and cardiometabolic parameters were measured with insulin resistance determined using the HOMA index and dysglycaemia defined as fasting glucose ≥5.60 mmol/L., Results: The African subjects had significantly lower hepatic fat content (LAR as median [interquartile range]: 1.35 [1.28, 1.41]) than the Indian (1.22 [1.10, 1.35]; p<0.005) and Caucasian (1.27 [1.16, 1.33]; p<0.05) females even though they had significantly higher BMIs than both groups (p<0.0005 and p<0.05, respectively). Linear regression showed that: subcutaneous abdominal fat was a significant (unstandardised β = 0.007; p = 0.03) negative, whilst insulin resistance (β = -0.97; p = 0.01) and dysglycaemia (β = -3.58; p = 0.01) were significant positive determinants of liver fat; higher hepatic fat levels in subjects with the metabolic syndrome were explained by insulin resistance and dysglycaemia., Discussion: African ethnicity is associated with low liver fat content. Subcutaneous abdominal fat protects against steatosis, possibly by acting as a triglyceride reservoir. Insulin resistance and dysglycaemia lead to greater hepatic fat deposition and explain higher liver fat levels in subjects with the metabolic syndrome. These observations must be further investigated in longitudinal surveys.

Published
2018
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