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Dromedaries have been fundamental to the development of human societies in arid landscapes and for long-distance trade across hostile hot terrains for 3,000 y. Today they continue to be an important livestock resource in marginal agro-ecological zones. However, the history of dromedary domestication and the influence of ancient trading networks on their genetic structure have remained elusive. We combined ancient DNA sequences of wild and early-domesticated dromedary samples from arid regions with nuclear microsatellite and mitochondrial genotype information from 1,083 extant animals collected across the species’ range. We observe little phylogeographic signal in the modern population, indicative of extensive gene flow and virtually affecting all regions except East Africa, where dromedary populations have remained relatively isolated. In agreement with archaeological findings, we identify wild dromedaries from the southeast Arabian Peninsula among the founders of the domestic dromedary gene pool. Approximate Bayesian computations further support the “restocking from the wild” hypothesis, with an initial domestication followed by introgression from individuals from wild, now-extinct populations. Compared with other livestock, which show a long history of gene flow with their wild ancestors, we find a high initial diversity relative to the native distribution of the wild ancestor on the Arabian Peninsula and to the brief coexistence of early-domesticated and wild individuals. This study also demonstrates the potential to retrieve ancient DNA sequences from osseous remains excavated in hot and dry desert environments.

The autonomic response to acute emotional stress can be highly variable, and pathological responses are associated with increased risk of adverse cardiovascular events. We evaluated the autonomic response to stress reactivity of young healthy subjects and aging subjects with coronary artery disease to understand how the autonomic stress response differs with aging. Physiologic reactivity to arithmetic stress in a cohort of 25 young, healthy subjects (< 30 years) and another cohort of 25 older subjects (> 55 years) with CAD was evaluated using electrocardiography, impedance cardiography, and arterial pressure recordings. Stress-related changes in the pre-ejection period (PEP), which measures sympathetic activity, and high frequency heart rate variability (HF HRV), which measures parasympathetic activity, were analyzed as primary outcomes. Mental stress reduced PEP in both groups (p<0.01), although the decrease was 50% greater in the healthy group. Mean HF HRV decreased significantly in the aging group only (p = 0.01). PEP decreases with stress regardless of health and age status, implying increased sympathetic function. Its decline with stress may be attenuated in CAD. The HF HRV (parasympathetic) stress reactivity is more variable and attenuated in younger individuals; perhaps this is related to a protective parasympathetic reflex. ClinicalTrials.gov Identifier: NCT02657382.

A total of seven she-camels (3-4 years old) were slaughtered following the normal abattoir procedures in Khartoum state, Sudan. Longissimus thoracis (LT) muscle samples were aged for 1, 3, 5, and 7 days at 1-3° C. Chemical composition, muscle pH, drip loss (DL), water holding capacity (WHC), color, myosin heavy chain isoforms (MyHC) as well as lipid peroxidation (MDA) and vitamin E content were determined at the indicated times during ageing. Ageing time of LT muscle influenced significantly (P<0.001) chemical composition except ash. Dry matter and drip losses significantly increased while moisture and protein contents decreased during ageing, however, no differences were found in muscle pH, color, fat peroxidation and WHC although fat peroxidation tended to increase from 5 days of ageing onwards. Electrophoresis of MyHC isoforms indicated the presence of two muscle fiber types only: type I (64.1%) and type IIa (35.9 %), respectively. In conclusion, shelf life of camel meat could be extended in the presence of high levels of vitamin E which helps to maintain lipid stability. [PUBLICATION ABSTRACT]