Human Islet Morphology Revisited: Human and Rodent Islets Are Not So Different After All

There has been great interest in understanding how human islets differ from rodent islets. Three major issues about human islet morphology have remained controversial over recent decades: 1) the proportion of the islet made up of β-cells; 2) whether islet cell types have a non-random mantle-core pattern, as seen in rodents, or are randomly scattered throughout the islet; 3) the relation of the different cell types to the blood vessels within the islet, which has implications for intraislet function. We re-examined these issues on immunostained sections of non-diabetic adult human pancreas. The composition of the islets can vary by the analysis method (number vs volume) and by the sampling of islets by size. The majority of adult human islets have clear, non-random clustering of β-cells and blood vessels that penetrate into the β-cell cores. We conclude that although there is far more variability in islet composition both within each human pancreas and among different human pancreas than in rodent pancreas, the islet architecture is not so different between the species. The intrapancreatic variability raises important questions about how islets evolve and function throughout life and how this might relate to the pathogenesis of diabetes.     

Telomere Length Profiles in Humans: All Ends are Not Equal

Telomere length is an important parameter of telomere function since it determines number of aspects controlling chromosome stability and cell division. Since telomeres shorten with age in humans and premature aging syndromes are often associated with the presence of short telomeres, it has been proposed that telomere length is also an important parameter for organismal aging. How mean telomere lengths are determined in humans remains puzzling, but it is clear that genetic and epigenetic factors appear to be of great importance. Experimental evidence obtained from many different organisms has provided the basis for a widely accepted counting mechanism based on a negative feedback loop for telomerase activity at the level of individual telomeres. In addition, recent studies in both normal and pathological contexts point to the existence of chromosome-specific mechanisms of telomere length regulation determining a telomere length profile, which is inherited and maintained throughout life. In this review, we recapitulate the available data, propose a synthetic view of telomere length control mechanisms in humans and suggest new approaches to test current hypotheses.     

It's Not All Sex and Violence: Integrated Anthropology and the Role of Cooperation and Social Complexity in Human Evolution

Social scientists, especially anthropologists, have long endeavored to understand the evolution of "human nature." This investigation frequently focuses on the relative importance of competition versus cooperation in human evolutionary trajectories and usually results in a primary emphasis on competition, aggression, and even war in attempting to understand humanity. This perspective conflicts with long-standing perspectives in anthropology and some emerging trends and theory in evolutionary biology and ecology. Cooperation and competition are not mutually exclusive in an evolutionary context. As anthropologists, we have demonstrated that humans can–and usually do–get along. Evolution is complex with multiple processes and patterns, not all of which involve competition and conflict. In this article, I summarize elements of modern ecological and evolutionary theory in the context of human cooperative patterns in an attempt to illustrate the valuable role of evolutionary theory and cooperative patterns in integrative anthropological approaches to the human condition.     

Gene-Centromere Mapping in Rainbow Trout: High Interference over Long Map Distances

Ten enzyme loci were mapped in relation to their centromeres in gynogenetic diploid rainbow trout. Gene-centromere map distances, calculated under the assumption of complete interference, range from 1.1 cM for Ldh4 to 50 cM for Sod1. The Idh2 and Est1 loci are linked on the same chromosome arm.—The observation of close to 100% heterozygous gynogenetic diploids for the Sod1 and Mdh3,4 loci suggests that near-complete interference occurs on the chromosome arms carrying these loci. The high interference observed in this study and in several other species of fish may be related to the small size of fish chromosome arms.—Comparisons of map locations for the Ldh3 and Ldh4 and the Mdh3 and Mdh4 loci, which were duplicated by a tetraploid event in the evolution of salmonid fish, reveal that they are located at similar distances from their centromeres. Comparative mapping of loci duplicated longer ago shows more variation in map location.—The high proportion of heterozygotes for some loci after gynogenesis involving second polar body retention demonstrates that this is not a practical method for producing homozygous inbred lines in rainbow trout; treatments suppressing the first cell division are more promising for this purpose.     

Continuous Intragastric Milk Feeds in Infants of Low Birth Weight

In a feeding trial 66 infants of low birth weight received continuous intragastric milk feeds from the fourth hour of life, starting with 60 ml/kg/24 hr and reaching a maximum of 300 ml/kg/24 hr on the ninth day. Each infant received only full-strength milk, which was either expressed human breast milk or SMA-S26 (a proprietary low-protein adapted cows'' milk) or half-cream Regal milk (partly-skimmed evaporated cows'' milk). For various reasons 10 babies had to be withdrawn, and the final assessment was made on the 56 who completed the trial successfully.Persistent vomiting was a problem in only four infants. In two of them the trial was continued after gastric lavage and in the other two vomiting stopped when the volume was reduced. Despite a careful search no evidence was found of aspiration of feeds in any infant. Continuous intragastric milk infusion was shown to be a safe method of feeding infants of low birth weight and SMA-S26 was almost as well tolerated as human milk. Because of the high-protein content of half-cream cows'' milk preparations and the resultant high plasma amino-acid levels when they are given in these large volumes they should be avoided for this type of feeding although they produce better weight gains in the first week of life.     

Not All Is Lost: Old Adults Retain Flexibility in Motor Behaviour during Sit-to-Stand

Sit-to-stand is a fundamental activity of daily living, which becomes increasingly difficult with advancing age. Due to severe loss of leg strength old adults are required to change the way they rise from a chair and maintain stability. Here we examine whether old compared to young adults differently prioritize task-important performance variables and whether there are age-related differences in the use of available motor flexibility. We applied the uncontrolled manifold analysis to decompose trial-to-trial variability in joint kinematics into variability that stabilizes and destabilizes task-important performance variables. Comparing the amount of variability stabilizing and destabilizing task-important variables enabled us to identify the variable of primary importance for the task. We measured maximal isometric voluntary force of three muscle groups in the right leg. Independent of age and muscle strength, old and young adults similarly prioritized stability of the ground reaction force vector during sit-to-stand. Old compared to young adults employed greater motor flexibility, stabilizing ground reaction forces during sit-to-sand. We concluded that freeing those degrees of freedom that stabilize task-important variables is a strategy used by the aging neuromuscular system to compensate for strength deficits.     

Dendrochronology and Human Dimensions Issues in Global Change

This introduction briefly outlines the context for global change, the origin of this volume and presents a brief summary of its contents.     

The Human Dimensions of Geomorphological Work in Britain

The transfer of materials from the natural environment to the urban and industrially built environment produces two broad impacts on the landscape: a removal of materials from the earth's surface (a change in geomorphology) and the accumulation of a stock of concrete and other materials elsewhere in cities and industrial zones (a change in urban morphology). Thus, industrial activity transforms natural landscapes and, in doing so, has to be considered to be a geological and geomorphological agent. On the global scale, the deliberate shift of around 57,000 Mt (megatons)/yr of materials through mineral extraction processes exceeds the annual transport of sediment to the oceans by rivers (some 22,000 Mt/yr) by almost a factor of three. On the island of Britain, the total deliberate shift of earth-surface materials is between 688 and 972 Mt/yr, depending on whether or not the replacement of overburden in opencast coal mining is taken into account. The export of sediment to the oceans by rivers is only 10 Mt/yr whereas the export of materials in solution is about 40 Mt/yr, making the deliberate materials shift nearly 14 times larger than the shift caused by natural processes. Processes examined by industrial ecology, such as direct excavation, urban development, and waste dumping are those most driving changes in the shape of the British landscape today. These transformations pose added costs. Industrial ecology will produce an understanding of the hidden costs associated with these transformations. Such an understanding will help in planning and encouraging the reuse of materials everywhere and in identifying the key areas for intervention to reduce off-site geomorphological impacts and costs.