The digestive performance of mammalian herbivores: why big may not be that much better

1. A traditional approach to the nutritional ecology of herbivores is that larger animals can tolerate a diet of lesser quality due to a higher digestive efficiency bestowed on them by comparatively long ingesta retention times and lower relative energy requirements. 2. There are important physiological disadvantages that larger animals must compensate for, namely a lower gut surface : gut volume ratio, larger ingesta particle size and greater losses of faecal bacterial material due to more fermentation. Compensating adaptations could include an increased surface enlargement in larger animals, increased absorption rates per unit of gut surface, and increased gut motility to enhance mixing of ingesta. 3. A lower surface : volume ratio, particularly in sacciform forestomach structures, could be a reason for the fact that methane production is of significant scope mainly in large herbivores and not in small herbivores with comparably long retention times; in the latter, the substrate for methanogenesis – the volatile fatty acids – could be absorbed faster due to a more favourable gut surface : volume ratio. 4. Existing data suggest that in herbivores, an increase in fibre digestibility is not necessarily accompanied by an increase in overall apparent dry matter digestibility. This indicates a comparative decrease of the apparent digestibility of non-fibre material, either due to a lesser utilization of non-fibre substrate or an increased loss of endogenous/bacterial substance. Quantitative research on these mechanisms is warranted in order to evaluate whether an increase in body size represents a net increase of digestive efficiency or just a shift of digestive focus.     

The evidence that the tree of life is not rooted within the Archaea is unreliable: a reply to Skophammer et al

Skophammer et al. [Skophammer, RG, Herbold, CW, Rivera, MC, Servin, JA, Lake, JA. 2006. Evidence that the root of the tree of life is not within the Archaea. Mol Biol Evol, 23, 1648-1651] report evidence suggesting that the tree of life cannot be rooted within the Archaea domain. I have observed that an alignment used in their analysis is not reliable and that, therefore, their conclusions are unjustified.     

Expression of a novel receptor tyrosine kinase gene and a paired-like homeobox gene provides evidence of differences in patterning at the oral and aboral ends of hydra

Axial patterning of the aboral end of the hydra body column was examined using expression data from two genes. One, shin guard, is a novel receptor protein-tyrosine kinase gene expressed in the ectoderm of the peduncle, the end of the body column adjacent to the basal disk. The other gene, manacle, is a paired-like homeobox gene expressed in differentiating basal disk ectoderm. During regeneration of the aboral end, expression of manacle precedes that of shin guard. This result is consistent with a requirement for induction of peduncle tissue by basal disk tissue. Our data contrast with data on regeneration of the oral end. During oral end regeneration, markers for tissue of the tentacles, which lie below the extreme oral end (the hypostome), are detected first. Later, markers for the hypostome itself appear at the regenerating tip, with tentacle markers displaced to the region below. Additional evidence that tissue can form basal disk without passing through a stage as peduncle tissue comes from LiCl-induced formation of patches of ectopic basal disk tissue. While manacle is ectopically expressed during formation of basal disk patches, shin guard is not. The genes examined also provide new information on development of the aboral end in buds. Although adult hydra are radially symmetrical, expression of both genes in the bud's aboral end is initially asymmetrical, appearing first on the side of the bud closest to the parent's basal disk. The asymmetry can be explained by differences in positional information in the body column tissue that evaginates to form a bud. As predicted by this hypothesis, grafts reversing the orientation of evaginating body column tissue also reverse the orientation of asymmetrical gene expression.     

Motility of dimeric ncd on a metal-chelating surfactant: evidence that ncd is not processive

The surface immobilization methods that allowed single-molecule motility experiments with native kinesin have not worked with the ncd motor protein and other kinesin-related motors. To solve this problem, a surfactant (Pluronic F108) was chemically modified with the metal-chelating group nitrilotriacetic acid (NTA) to allow surface immobilization of histidine-tagged microtubule motors. The chelating surfactant provided a convenient and effective method for immobilization and subsequent motility experiments with a dimeric H-tagged ncd protein (H-N195). In experiments with the absorption of H-N195 to polystyrene (PS) beads coated with F108-NTA, a monolayer of H-N195 bound in the presence of Ni2+, while in the absence of Ni2+, the extent of adsorption of H-N195 to PS beads was greatly reduced. In motility experiments with H-N195 immobilized on F108-NTA-coated surfaces, microtubules moved smoothly and consistently at an average speed of 0.16 +/- 0.01 micrometer/s in the presence of Ni2+, while without Ni2+, no microtubules landed on the F108-NTA-coated surfaces. Investigation of H-N195 motility on the F108-NTA surfaces provided several indications that ncd, unlike kinesin, is not processive. First, a critical H-N195 surface density for microtubule motility of approximately 250 molecules/micrometer(2) was observed. Second, microtubule landing rates as a function of H-N195 surface density in the presence of MgATP suggested that several H-N195 molecules must cooperate in microtubule landing. Third, the ATP KM in motility assays (235 microM) was substantially higher than the ATP KM of dimeric ncd in solution (23 microM) [Foster, K. A., Correia, J. J., and Gilbert, S. P. (1998) J. Biol. Chem. 273, 35307-35318].     

Phosphorylation of L-cell glucocorticoid receptors in immune complexes: evidence that the receptor is not a protein kinase

Two phosphoproteins are absorbed to protein A-Sepharose when cytosol from 32P-labeled L-cells is incubated with a monoclonal antibody against the glucocorticoid receptor: one is a 98K phosphoprotein that contains the steroid binding site, and the other is a 90K non-steroid-binding phosphoprotein that is associated with the molybdate-stabilized receptor [Housley, P. R., Sanchez, E. R., Westphal, H. M., Beato, M., & Pratt, W. B. (1985) J. Biol. Chem. 260, 13810-13817]. In this paper we have incubated L-cell cytosol with rabbit antiserum against the mouse glucocorticoid receptor and show that incubation of protein A-Sepharose-bound immune complexes with [gamma-32P]ATP and Mg2+ results in phosphorylation of the 98K steroid-binding protein but not of the 90K receptor-associated protein. Phosphorylation occurs regardless of whether the receptor is unoccupied or is present as the untransformed or transformed steroid-receptor complex. No phosphorylation occurs in the presence of Ca2+ instead of Mg2+. If protein A-Sepharose-bound immune complexes prepared with a monoclonal antibody against the receptor are incubated with [gamma-32P]ATP and Mg2+, neither protein is phosphorylated. If the protein A-Sepharose pellet is obtained from molybdate-stabilized cytosol that has been incubated both with monoclonal antibody to provide the 98K receptor and its 90K associated protein and with preimmune rabbit serum, which causes the nonspecific adsorption of an L-cell protein kinase, then incubation with [gamma-32P]ATP and Mg2+ causes receptor phosphorylation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The postanal tail of the enteropneust Saccoglossus kowalevskii is a ciliary creeping organ without distinct similarities to the chordate tail

Stach, T. and Kaul, S. 2011. The postanal tail of the enteropneust Saccoglossus kowalevskii is a ciliary creeping organ without distinct similarities to the chordate tail. —Acta Zoologica (Stockholm) 92 : 150–160. The postanal tail of chordates is one of the key characters in chordate evolution and it has been suggested to be homologous to the postanal tail of harrimaniid enteropneusts. We present electron microscopic data of the ontogeny of the postanal tail in the enteropneust Saccoglossus kowalevskii. The postanal tail develops as a ventral posterior allometric outgrowth with a ventral extension of the telotroch. Transmission electron microscopy of serial sections reveals the epidermal organization of the postanal tail with the exception of short, bilaterally symmetric extensions of the paired metacoels. The epidermis cells are connected by apical junctions, rest basally on the extracellular matrix surrounding the mesoderm, and possess a basiepidermal nerve net. The ventral cells in the postanal tail are multiciliated and used for creeping. Dorsal cells are monociliated with numerous microvilli. Two types of glandular cells are present among the epidermis cells. The mesoderm cells contain myofilaments. We were unable to detect anatomical structures similar to the ones present in the postanal locomotory tail of chordates, such as notochord, neural tube, or endodermal strand. Thus, results of our anatomical study do not support homology of the postanal chordate tail and the postanal tail of harrimaniid enteropneusts.     

Separation of cathepsin A-like enzyme and the proteasome: evidence that lactacystin/beta-lactone is not a specific inhibitor of the proteasome

Previous studies have described a human platelet cathepsin A-like enzyme with a number of similarities to the "acidic" and "neutral" chymotrypsin-like activities of the proteasome. This includes its strong inhibition by the highly specific proteasome inhibitor Lactacystin/beta-lactone, suggesting that either the Cbz-Phe-Ala-hydrolyzing activity attributed to cathepsin A was due to the chymotrypsin-like activity of the proteasome or that lactacystin was not a specific inhibitor of the proteasome. In the present study we discard the first possibility on the basis of the following findings: (a) human platelet cathepsin A, unlike proteasome, binds to concanavalin A, and does not bind to Heparin-Sepharose at pH 7.4; (b) neither the chymotrypsin-like activity of the proteasome, nor proteasome antigens are detected in the cathepsin A preparation; (c) purified proteasome does not exhibit Cbz-Phe-Ala-hydrolyzing activity; (d) Z-lle-Glu-(Ot-Bu)Ala-leucinal (PSI), a compound that selectively inhibits the chymotrypsin-like activity of the proteasome at a concentration of 10 microM has no inhibitory effect on the carboxypeptidase activity of cathepsin A; (e) cathepsin A, free of the proteasome, is completely inhibited by micromolar concentrations of lactacystin/beta-lactone. It is therefore concluded that lactacystin/beta-lactone is not a specific inhibitor of the proteasome.     

The synergid cell: attractor and acceptor of the pollen tube for double fertilization

In flowering plants, the egg cell is generally accompanied by two symmetrical cells, called synergid cells. As early as the 1870s, synergid cells were distinguished from egg cells and cooperation between synergid and egg cells was proposed; the term "synergid" is derived from the Greek "synergos," which means "working together." The accumulation of morphological and genetic data, and, more recently, the in vitro physiological analysis of the fertilization system of Torenia fournieri, have revealed that synergid cells work together with egg and central cells to accomplish double fertilization. This cooperation is of crucial importance in the attraction and acceptance of the pollen tube. In this review article, I focus on the physiological function and behavior of the synergid cell during the fertilization process. Received: December 20, 2001 / Accepted: December 27, 2001     

The structure and prophylactic role of the angiosperm embryo sac and its associated tissues:Zea mays as a model

Summary Various developmental phases can be distinguished in the definition of the archesporium and the early life of the embryo, takingZea mays (maize) as a model within the family Gramineae, and other families where pertinent: (1) the isolation of the megasporocyte and the functional spore derived from it; (2) the maturation of the specialized walls of the embryo sac, and their reinforcement by ensheathments derived from the contiguous nucellar cells during a sequence of phased genetic ablation; (3) the differentiation of the synergids, the associated flange, and the filiform apparatuses; (4) the blocking of the pollen tube pathway by secondary secretions in the micropylar region and the coagulation of the pollen tube cytoplasm within the filiform apparatuses during the process of fertilization; and finally (5) the development of a compound cutinized envelope of four fused layers (six where the outer integument is also involved) after fertilization. For the nascent haploid generation, the period of maximum vulnerability in respect to both pathogen invasion and the transition from diplophase control occurs during these phases. It is concluded that many of the protective features form a prophylactic shield and are key components of the angiosperms in general, which may have contributed to their evolutionary success as a group. Other physiological or biochemical adaptations or barriers may also supplement the mainly structural features described here.     

The long and the short of it: evidence that FGF5 is a major determinant of canine 'hair'-itability

Hair length in dogs has been known for many years to be primarily controlled by a limited number of genes, but none of the genes have been identified. One of these genes produces a recessively inherited long-haired phenotype that has been thought to explain the bulk of hair-length variation among many breeds. Sequence analysis of the FGF5 gene in short and long-haired corgis resulted in the identification of two coding region differences: a duplication in a relatively non-conserved region of the gene and a missense mutation, resulting in the substitution of Phe for Cys, in a highly conserved region. Genotyping of 218 dogs from three breeds fixed for long hair, eight breeds fixed for short hair and five breeds in which long hair is segregating provided evidence that the missense mutation is associated with the hair-length differences among these breeds.     

The embryo sac of Cynara cardunculus: ultrastructure of the development and localisation of the aspartic proteinase cardosin B

Cynara cardunculus is a native plant with flowers that are used traditionally in the manufacture of ewe’s cheese in the Iberian Peninsula. Milk clotting ability of the plant is attributed to the high concentrations of aspartic proteinases (APs), named cardosins, found in the flowers. Although these enzymes are well characterised on a molecular and biochemical basis, the biological role of the majority of plant APs is yet unassigned. We suspected APs play an important role in ovule function, and we characterised the maturation of the ovules of C. cardunculus and its Polygonum-type embryo sacs. The internal layer of the integument differentiates into an endothelium as described for other Asteraceae, with differentiation of two nucellar layers, a podium and a hypostase coinciding with the onset of pollen receptivity. In flowering plants, programmed cell death (PCD) events are essential for the success of nucellar maturation and consequent differentiation of a fully functional embryo sac. In C. cardunculus, nucellar PCD is integral to the maturation of the embryo sac, which in turn is closely correlated with the accumulation of the AP cardosin B specifically in the hypostase. The onset of cardosin B expression temporally coincides with the degeneration of nucellar cells. In fully mature embryo sacs, cardosin B is localised in both the hypostase and epistase, two regions that differentiate through PCD. Thus, cardosin B localisations closely correlate with events of PCD in the nucellus of C. cardunculus suggesting involvement in ovule and embryo sac development and further suggest the biological significance of APs like cardosin B, in this particular process. This work contributes new data to the plant AP research field and indicates an involvement of cardosin B in the PCD-dependent degeneration of the nucellus.     

Assembly of microtubules with ATP: evidence that only a fraction of the protein is assembly-competent

Chick brain microtubule protein can be assembled in vitro with ATP, although the extent of assembly is less than that with GTP. The ATP-induced assembly is not the result of generation of GTP by the co-purifying nucleoside diphosphate kinase. Neither an observed increase in the critical concentration nor the phosphorylation of MAP2 can account for the decreased extent of assembly. However, whereas microtubules are formed with both ATP and GTP, incubation with ATP yields additional filaments and polymorphic aggregates. The results demonstrate that of the total protein which can be assembled into microtubules by GTP, about 25-35% is assembled into other structural forms in the presence of ATP.     

The motif of SPARC that inhibits DNA synthesis is not a nuclear localization signal

SPARC (secreted protein acidic and rich in cysteine), although primarily known as a secreted, matricellular protein, has also been identified in urothelial cell nuclei. Many biological activities, including inhibition of cell adhesion and repression of DNA synthesis, have been ascribed to SPARC, but the influence of its intracellular localization on each of these activities is unknown. When exposed by epitope retrieval and nuclear matrix unmasking techniques, endogenous SPARC was found to localize strongly to the nuclei and the nuclear matrix of cultured urothelial cells. Live-cell time-lapse imaging revealed that exogenous fluorescently labeled recombinant (r) SPARC was taken up from medium over a 16 h period and accumulated inside cells. Two variants of rSPARC with alterations in its putative nuclear localization signal (NLS) were generated to investigate the existence and effects of the NLS. These variants demonstrated similar biophysical characteristics as the wild-type protein. Visualization by a variety of techniques, including live-cell imaging, deconvolution microscopy, and cell fractionation, all concurred that exogenous rSPARC was not able to localize to cell nuclei, but instead accumulated as perinuclear clusters. Localization of the rSPARC NLS variants was no different than wild-type, arguing against the presence of an active NLS in rSPARC. Imaging experiments showed that only permeabilized, dead cells avidly took up rSPARC into their nuclei. The rSPARC(no NLS) variant proved ineffective at inhibiting DNA synthesis, whereas the rSPARC(strong NLS) variant was a more potent inhibitor of DNA synthesis than was wild-type rSPARC. The motif of SPARC that inhibits the synthesis of urothelial cell DNA is therefore not a nuclear localization signal, but its manipulation holds therapeutic potential to generate a "Super-SPARC" that can quiesce proliferative tissues.     

Dimerization of ubiquilin is dependent upon the central region of the protein: evidence that the monomer, but not the dimer, is involved in binding presenilins

Ubiquilin proteins have been shown to interact with a wide variety of other cellular proteins, often regulating the stability and degradation of the interacting protein. Ubiquilin contains a UBL (ubiquitin-like) domain at the N-terminus and a UBA (ubiquitin-associated) domain at the C-terminus, separated by a central region containing Sti1-like repeats. Little is known about regulation of the interaction of ubiquilin with other proteins. In the present study, we show that ubiquilin is capable of forming dimers, and that dimerization requires the central region of ubiquilin, but not its UBL or the UBA domains. Furthermore, we provide evidence suggesting that monomeric ubiquilin is likely to be the active form that is involved in binding presenilin proteins. Our results provide new insight into the regulatory mechanism underlying the interaction of ubiquilin with presenilins.     

The digestive tract of the amberjack Seriola dumerili, Risso: a light and scanning electron microscope study

The histology of the digestive tract of the amberjack ( Seriola dumerili , Risso) was studied using light and scanning electron microscopy. The anterior oesophagus mucosa displays primary and secondary folds lined with a stratified squamous epithelium with fingerprint-like microridges which is substituted, on the top of the oesogaster folds, by a simple columnar epithelium with short microvilli. Only primary folds are present in the stomach. The anterior portion is rich in simple tubular glands, whereas the oesogaster and the pyloric region are devoid of them. Pyloric caeca and anterior and middle intestine mucosa display the same pattern of folding. The dominant cell type is the enterocyte, which exhibits larger and thinner microvilli in the caeca than in the intestine. The columnar epithelium of the rectum is replaced, in the anal sphincter, by a stratified flattened epithelium. Goblet cells are numerous throughout the whole length of the tract with the exception of the initial part of the oesophagus, the oesogaster, the stomach and the anal sphincter. Mucosubstances have been shown to vary in the different regions of the gut: acid mucines are found in the oesophagus, pyloric stomach, caeca, intestine and rectum, whereas neutral mucosubstances dominate in the anterior portion of the stomach. The muscularis is well developed throughout the length of the tract: two layers of striated muscle at the oesophageal level; two layers of smooth muscle in the stomach wall and three at the intestinal level.     

The presence of the brown bear Ursus arctos in Holocene Britain: a review of the evidence

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Two loci on chromosome 9 control bile acid composition: evidence that a strong candidate gene, Cyp8b1, is not the culprit

An intercross between C57BL/6J and CASA/Rk mice was used to study the genetics of biliary bile acid composition. In parental strains, male C57BL/6J mice had significantly higher cholic acid (CA; 14%) and lower beta-muricholic acid (betaMC; 27%) than CASA/Rk mice, whereas females did not differ. However, quantitative trait locus analysis of F2 mice revealed no significant chromosome 9 loci in males but loci in females on chromosome 9 for percentage CA (%CA) at 72 centimorgan (cM) [logarithm of the odds (LOD) 5.89] and %betaMC at 54 cM (LOD 4.09). Chromosome 9 congenic and subcongenic strains representing CASA/Rk intervals 38-73 cM (9KK) and 68-73 cM (9DKK) on the C57BL/6J background were made. In 9KK and 9DKK males, %CA was increased and %betaMC was unchanged, whereas in 9KK but not 9DKK females, %CA was increased and %betaMC was decreased. Sterol 12alpha-hydroxylase (Cyp8b1) channels bile acid precursors into CA and maps at chromosome 9 (73 cM). However, there was no significant difference in Cyp8b1 mRNA or enzymatic activity between parental mice, parental-congenic-subcongenic mice, or high-low biliary %CA F2 mice. In summary, two chromosome 9 loci control sexually dimorphic effects on biliary bile acid composition: a distal (68-73 cM) major determinant in males, and a more proximal (38-68 cM) major determinant in females. In this intercross, Cyp8b1, a strong candidate, does not appear to be responsible.     

DNA is present in the nucleomorph of cryptomonads: Further evidence that the chloroplast evolved from a eukaryotic endosymbiont

Summary The nucleomorph is a unique self-replicating organelle which is invariably present in the periplastidal compartment of cryptomonads. The nucleomorph ofCryptomonas abbreviata is located in a groove on the inner face of the pyrenoid. When JB-4-embedded sections ofC. abbreviata are stained with 4-6-diamidino-2-phenylindole (DAPI), the nucleomorph exhibits a blue fluorescence characteristic of DNA-DAPI complexes. This fluorescence is removed by DNase digestion, but not by RNase. When cells are prepared for electron microscopy by the method of Ryter and Kellenberger (Schreil 1964), a network of fine DNA-like fibrils is observed in the nucleomorph matrix. It is estimated that the nucleomorph contains between 10⁸ and 10⁹ daltons of DNA. The presence of DNA in nucleomorphs strongly supports the hypothesis that the nucleomorph is the vestigial nucleus of a eukaryotic endosymbiont. It is postulated that this eukaryotic symbiont was an ancestral red alga or an organism closely related to red algae. The cryptomonad host cell, on the other hand, is not evolutionarily close to any other group of algae.     

The endolymphatic duct and sac of the rat: a histological,ultrastructural, and immunocytochemical investigation

A study of the ultrastructure, vascularization, and innervation of the endolymphatic duct and sac of the rat has been performed by means of light- and electron-microscopic and immunocytochemical methods. Two different types of epithelial cells have been identified: the ribosome-rich cell and the mitochondria-rich cell. These two cell types make up the epithelium of the complete endolymphatic duct and sac, although differences in their quantitative distribution exist. The morphology of the ribosome-rich cells varies between the different parts of the endolymphatic duct and sac; the morphology of the mitochondria-rich cells remains constant. According to the epithelial composition, vascularization, and structural organization of the lamina propria, both duct and sac are subdivided into three different parts. A graphic reconstruction of the vascular network supplying the endolymphatic duct and sac shows that the vascular pattern varies among the different parts. In addition, the capillaries of the duct are of the continuous type, whereas those supplying the sac are of the fenestrated type. Nerve fibers do not occur within the epithelium of the endolymphatic duct and sac. A few nerve fibers regularly occur in the subepithelial compartment close to the blood vessels; these fibers have been demonstrated in whole-mount preparations by the application of the neuronal marker protein gene product 9.5. Single beaded fibers immunoreactive to substance P and calcitonin-gene related peptide are observed within the same compartment. Dopamine--hydroxylase-immunoreactive axons are restricted to the walls of arterioles. Morphological differences between the different portions of the endolymphatic duct and sac are discussed with regard to possible roles in fluid absorption and immunocompetence.Abbreviations CGRP Calcitonin gene-related peptide - DSP distal sac portion - DH dopamine--hydroxylase - ED endolymphatic duct - ES endolymphatic sac - EDP enlarged duct portion - IR immunoreactive - ISP intermediate sac portion - LIS lateral intercellular space - NDP narrow duct portion - PMA posterior meningeal artery - PVA posterior vestibular artery - PGP 9.5 protein gene product 9.5 - PSP proximal sac portion - SP substance P - TDP transitional duct portion - VVA vem of vestibular aqueduct