Biaxial mechanical properties of the human thoracic and abdominal aorta,common carotid,subclavian, renal and common iliac arteries

The biomechanics of large- and medium-sized arteries influence the pathophysiology of arterial disease and the response to therapeutic interventions. However, a comprehensive comparative analysis of human arterial biaxial mechanical properties has not yet been reported. Planar biaxial extension was used to establish the passive mechanical properties of human thoracic (TA, \(n=8\) ) and abdominal (AA, \(n=7\) ) aorta, common carotid (CCA, \(n=21\) ), subclavian (SA, \(n=12\) ), renal (RA, \(n=13\) ) and common iliac (CIA, \(n=16\) ) arteries from 11 deceased subjects ( \(54\pm 21\)  years old). Histological evaluation determined the structure of each specimen. Experimental data were used to determine constitutive parameters for a structurally motivated nonlinear anisotropic constitutive model. All arteries demonstrated appreciable anisotropy and large nonlinear deformations. Most CCA, SA, TA, AA and CIA specimens were stiffer longitudinally, while most RAs were stiffer circumferentially. A switch in anisotropy was occasionally demonstrated for all arteries. The CCA was the most compliant, least anisotropic and least frequently diseased of all arteries, while the CIA and AA were the stiffest and the most diseased. The severity of atherosclerosis correlated with age, but was not affected by laterality. Elastin fibers in the aorta, SA and CCA were uniformly and mostly circumferentially distributed throughout the media, while in the RA and CIA, elastin was primarily axially aligned and concentrated in the external elastic lamina. Constitutive modeling provided good fits to the experimental data for most arteries. Biomechanical and architectural features of major arteries differ depending on location and functional environment. A better understanding of localized arterial mechanical properties may support the development of site-specific treatment modalities for arterial disease.     

ECA, the enterobacterial common antigen

Enterobacterial common antigen (ECA) is a family-specific surface antigen shared by all members of the Enterobacteriaceae and is restricted to this family. It is found in freshly isolated wild-type strains as well as in laboratory strains like Escherichia coli K-12. The family specificity of ECA can be used for taxonomic and diagnostic purposes. ECA is located in the outer leaflet of the outer membrane. It is a glycophospholipid built up by an aminosugar heteropolymer linked to an L-glycerophosphatidyl residue. In a few rough mutants, in addition, the sugar chain can be bound to the complete lipopolysaccharide (LPS) core. Recently, for Shigella sonnei a lipid-free cyclic form of ECA was reported. The genetical determination of ECA is closely related to that of lipopolysaccharide. For biosynthesis of ECA and LPS partly the same sugar precursors and the same carrier lipid is used.     

Globin-coupled sensors, protoglobins, and the last universal common ancestor

The strategy for detecting oxygen, carbon monoxide, nitric oxide, and sulfides is predominantly through heme-based sensors utilizing either a globin domain or a PAS domain. Whereas PAS domains bind various cofactors, globins bind only heme. Globin-coupled sensors (GCSs) were first described as regulators of the aerotactic responses in Bacillus subtilis and Halobacterium salinarum. GCSs were also identified in diverse microorganisms that appear to have roles in regulating gene expression. Functional and evolutionary analyses of the GCSs, their protoglobin ancestor, and their relationship to the last universal common ancestor (LUCA) are discussed in the context of globin-based signal transduction.     

Inbreeding, pedigree size, and the most recent common ancestor of humanity

How many generations ago did the common ancestor of all present-day individuals live, and how does inbreeding affect this estimate? The number of ancestors within family trees determines the timing of the most recent common ancestor of humanity. However, mating is often non-random and inbreeding is ubiquitous in natural populations. Rates of pedigree growth are found for multiple types of inbreeding. This data is then combined with models of global population structure to estimate biparental coalescence times. When pedigrees for regular systems of mating are constructed, the growth rates of inbred populations contain Fibonacci n-step constants. The timing of the most recent common ancestor depends on global population structure, the mean rate of pedigree growth, mean fitness, and current population size. Inbreeding reduces the number of ancestors in a pedigree, pushing back global common ancestry times. These results are consistent with the remarkable findings of previous studies: all humanity shares common ancestry in the recent past.     

Agglutinogens, White's 'Q' substance and the common proteins of Enterobacteriaceae

Reassessment of the antigens involved in the cross-relation of Enterobacteriaceae point to the common proteins first discovered by White (1932) and named substance Q. All the serological characteristics of substance Q, as described by White, are identical with those obtained with pure enterobacterial proteins.     

Development and keratinization of the epidermis in the common lizard, Anolis carolinensis

Epithelial-mesenchymal interactions play important roles in the development of the vertebrate integument with its diverse appendages. As a result of these interactions, specific morphogenetic events occur which result in the formation of distinct epidermal appendages. Following the early morphogenetic events involving cell proliferation and movement, other developmental events such as stratification, histotypic differentiation, and terminal cytodifferentiation occur in the epidermis. Using the common lizard Anolis carolinensis, we are seeking to obtain a better understanding of the relationship between the various developmental events and the expression of alpha and beta keratins, with the aim of eventually understanding the mechanisms by which tissue-specific keratinization patterns are established in the integument. As a first step, we have used immunoblot analyses and indirect immunofluorescence procedures with antisera specific for either alpha or beta keratins to determine the temporal and spatial appearance of these keratins at specific developmental stages. We have found that: 1) There are relatively low molecular weight alpha keratin polypeptides present in the epidermis early in development as morphogenesis is taking place. 2) After morphogenesis occurs and histogenesis is well under way, the alpha keratins which characterize the adult epidermis appear. 3) Only alpha keratins are found in the basal cells of all regions of the epidermis. 4) beta keratins are found only in the suprabasal layers of well-developed scales and show region-specific distribution in overlapping scales.     

Cloning and expression of apolipophorin-III from the common cutworm,Spodoptera litura

We have cloned apolipophorin-III (apoLp-III) cDNA from adult fat body of Spodoptera litura. The sequence encodes a 188 amino acid polypeptide including a 22 amino acid leader peptide. The circular dichroism spectrum from the purified apoLp-III indicated a considerable content of α-helix. Sequence alignment showed that S. Litura apoLp-III has a relatively high degree of sequence identity with the apoLps-III of lepidopteran, Manduca sexta (72%), Galleria mellonella (67%), Bombyx mori (60%). These alignments with four lepidopteran apoLps-III showed highly identical residues and conservative replacements at a degree of 86%. Levels of mRNA from last instar larval fat body and adult fat body were compared through Northern blot analysis using ³²P-labeled 704 bp apoLp-III cDNA probe. A 850 bp mRNA was detected in both stages and mRNA level of day 1 adult fat body was much higher than that of last instar larval fat body. The tissue-distribution of apoLp-III mRNA in adult ovary and testis was also examined and we confirmed the presence of apoLp-III mRNA in ovary and testis although apoLp-III was expressed in these tissues at very low levels compared with the adult fat body. Arch. Insect Biochem. Physiol. 39:166–173, 1998. © 1998 Wiley-Liss, Inc.     

Hyaluronan, a common thread

Hyaluronan, natures simplest, but still exceptionally versatile glycosaminoglycan, is currently the focus of attention across a wide front of research; from cell biology, morphogenesis, matrix organization, pathobiology to tissue engineering. This macromolecule has entangled me in a number of puzzling and challenging projects over the past 3 decades. These entertaining encounters are outlined in this retrospective.     

Weight loss,reproductive output,and the cost of reproduction in the common frog,Rana temporaria

Summary The consequences of reproduction for body weight, growth and survival were studied in a Swiss population of the explosive breeder, Rana temporaria. Males and females continuously loss weight in the range of 0.5% of total body weight per day from the breeding migration throughout May. Females also lost about 33% (1983) and 29% (1984) due to spawning. In addition to this significant year-to-year variation, there was also considerable individual variation in reproductive output. Skeletochronological techniques indicated that breeding male or female frogs experienced a growth reduction of several millimeters relative to non-breeding frogs of the same body size. There was no relationship between an individual female's reproductive output in consecutive years or with her subsequent growth or survival. It was concluded that weight loss is caused by a seasonally elevated metabolism in combination with a lack of feeding and represents a basic energetic cost of reproduction, resulting in lowered growth. Individual variation in relative reproductive output is mostly environmentally induced and is not an expression of different reproductive strategies. This may explain the lack of trade-offs that are predicted by the cost-of-reproduction-hypothesis.     

Comparative genomics, minimal gene-sets and the last universal common ancestor

Comparative genomics, using computational and experimental methods, enables the identification of a minimal set of genes that is necessary and sufficient for sustaining a functional cell. For most essential cellular functions, two or more unrelated or distantly related proteins have evolved; only about 60 proteins, primarily those involved in translation, are common to all cellular life. The reconstruction of ancestral life-forms is based on the principle of evolutionary parsimony, but the size and composition of the reconstructed ancestral gene-repertoires depend on relative rates of gene loss and horizontal gene-transfer. The present estimate suggests a simple last universal common ancestor with only 500-600 genes.