Blubber and flipper heat transfer in harp seals

The trunk of marine mammals is encased in a blubber layer which provides thermal insulation that can be changed by circulatory adjustments. The extremities, on the other hand, are poorly insulated but have vascular arrangements constructed for prevention or promotion of heat loss, depending on the thermal state of the animal. We have studied the importance of different body parts as sites for heat dissipation and also assessed the effect of circulatory adjustments on heat transfer through blubber, by combining direct measurements of heat flux from the flippers and trunk with simultaneous recordings of temperature gradients through the blubber and metabolic rates of harp seals (Phoca groenlandica) subjected to water temperatures between 1 and 24 °C. We also determined the thermal conductivity of blubber samples from the same animals after death, and compared this with the insulative properties of live blubber. At the lowest water temperatures, the insulative properties of live blubber were similar to those of dead blubber, and heat loss from the flippers only accounted for 2–6% of the metabolic heat production. As heat load increased with increasing water temperatures, the fraction of heat lost from the flippers increased, to 19–48% at 24 °C, while the fraction lost from the trunk decreased, despite an increase in the convective (circulatory) heat transfer through the blubber layer.     

Energetics of Cooperative Transitions of N‐Vinylcaprolactam Polymers in Aqueous Solutions

Summary: Phase and conformational behavior of poly(N‐vinylcaprolactam) was studied as a function of polymer concentration, concentration of NaCl, and concentration of sodium dodecyl sulfate (SDS). Precise measurements of the partial heat capacity of the polymer were first carried out within the temperature range 10–125 °C. Thermodynamic parameters of the phase separation transition (transition temperature, enthalpy, and heat capacity increment) do not change with variations in polymer concentration. In the presence of salt the transition temperature decreases, the enthalpy increases, and the heat capacity increment does not vary significantly. Beginning with the SDS concentration of 0.005 M , the phase separation is suppressed and the heat capacity peak splits into two peaks. Upon further increase in surfactant concentration the amplitude of the low‐temperature peak increases while that of the high‐temperature peak vanishes. Phase separation transition in aqueous solutions of N‐vinylcaprolactam‐methacrylic acid copolymers of different compositions were studied at different polymer concentrations and pH (4–12). The transition parameters do not depend on polymer concentration and pH.

“Macroglobule” formed spontaneously as a result of the phase separation of a poly(N‐vinylcaprolactam) solution.     

Postsacral Vertebral Morphology in Relation to Tail Length Among Primates and Other Mammals

Tail reduction/loss independently evolved in a number of mammalian lineages, including hominoid primates. One prerequisite to appropriately contextualizing its occurrence and understanding its significance is the ability to track evolutionary changes in tail length throughout the fossil record. However, to date, the bony correlates of tail length variation among living taxa have not been comprehensively examined. This study quantifies postsacral vertebral morphology among living primates and other mammals known to differ in relative tail length (RTL). Linear and angular measurements with known biomechanical significance were collected on the first, mid‐, and transition proximal postsacral vertebrae, and their relationship with RTL was assessed using phylogenetic generalized least‐squares regression methods. Compared to shorter‐tailed primates, longer‐tailed primates possess a greater number of postsacral vertebral features associated with increased proximal tail flexibility (e.g., craniocaudally longer vertebral bodies), increased intervertebral body joint range of motion (e.g., more circularly shaped cranial articular surfaces), and increased leverage of tail musculature (e.g., longer spinous processes). These observations are corroborated by the comparative mammalian sample, which shows that distantly related short‐tailed (e.g., Phascolarctos, Lynx) and long‐tailed (e.g., Dendrolagus, Acinonyx) nonprimate mammals morphologically converge with short‐tailed (e.g., Macaca tonkeana) and long‐tailed (e.g., Macaca fascicularis) primates, respectively. Multivariate models demonstrate that the variables examined account for 70% (all mammals) to 94% (only primates) of the variance in RTL. Results of this study may be used to infer the tail lengths of extinct primates and other mammals, thereby improving our understanding about the evolution of tail reduction/loss. Anat Rec, 298:354–375, 2015. © 2014 Wiley Periodicals, Inc.     

Anatomy of Shoulder Girdle Muscle Modifications and Walking Adaptation in the Scaly Chinese Pangolin (Manis Pentadactyla Pentadactyla: Pholidota) Compared with the Partially Osteoderm‐Clad Armadillos (Dasypodidae)

Because pangolins are unique mammals with a body and limbs almost entirely sheathed in hard keratinous overlapping scales and with digging and climbing abilities, the shoulder girdle muscles may differ significantly from those of other mammals including the partially osteoderm‐clad armadillos. Therefore, we conducted a functional anatomical study of the shoulder girdle muscles in Chinese pangolins (Manis pentadactyla pentadactyla, Pholidota) and some armadillo species (Dasypodidae). Our CT scans revealed that the pangolin's overlapping scales are hard structures completely encasing the limbs. The armadillo's limbs, however, are covered with small relatively soft non‐overlapping scales embedded in the skin, and articulate completely free of the hard osteodermal carapace. The attachments of some shoulder girdle muscles in the pangolin have moved from the surrounding edges of the scapula to the spine, and they, therefore, fully cover the scapula. In addition, some pangolin shoulder girdle muscles cross the shoulder joint to insert on the distal humerus, but this does not occur in armadillos. We cannot rule out the possibility that these muscle modifications represent adaptations for digging and/or climbing in pangolins. Our results and previous literature do not establish specific links between them and locomotive modes. However, we propose that the Chinese pangolin may use its derived muscular features when walking to move its armor‐restricted forelimbs more effectively by swinging its head from side to side. Anat Rec, 298:1217–1236, 2015. © 2015 Wiley Periodicals, Inc.     

Quantitative Computed Tomography of Humpback Whale (Megaptera novaeangliae) Mandibles: Mechanical Implications for Rorqual Lunge‐Feeding

Rorqual whales (Balaenopteridae) lunge at high speed with mouth open to nearly 90 degrees to engulf large volumes of prey‐laden water. This feeding process is enabled by extremely large skulls and mandibles that increase mouth area, thereby facilitating the flux of water into the mouth. When these mandibles are lowered during lunge‐feeding, they are exposed to high drag, and therefore, may be subject to significant bending forces. We hypothesized that these mandibles exhibited a mechanical design (shape and density distribution) that enables these bones to accommodate high loads during lunge‐feeding without exceeding their breaking strength. We used quantitative computed tomography (QCT) to determine the three‐dimensional geometry and density distribution of a pair of subadult humpback whale (Megaptera novaeangliae) mandibles (length = 2.10 m). QCT data indicated highest bone density and cross‐sectional area, and therefore, high resistance to bending and deflection, from the coronoid process to the middle of the dentary, which then decreased towards the anterior end of the mandible. These results differ from the caudorostral trends of increasing mandibular bone density in mammals, such as humans and the right whale, Eubalaena glacialis, indicating that adaptive bone remodeling is a significant contributing factor in establishing mandibular bone density distributions in rorquals. Anat Rec 293:1240–1247, 2010. © 2010 Wiley‐Liss, Inc.     

Tooth‐On‐Tooth Interlocking Occlusion Suggests Macrophagy in the Mesozoic Marine Crocodylomorph Dakosaurus

Metriorhynchidae was a peculiar but long‐lived group of marine Mesozoic crocodylomorphs adapted to a pelagic lifestyle. Recent discoveries show that metriorhynchids evolved a wide range of craniodental morphotypes and inferred feeding strategies. One genus, Dakosaurus, is arguably the most aberrant marine crocodylomorph due to its large, robust, ziphodont teeth; very low tooth count; and brevirostrine/oreinirostral snout. We here report an additional unusual feature of Dakosaurus that is unique among marine crocodylomorphs: tightly fitting tooth‐to‐tooth occlusion, whose inference is supported by reception pits along the upper and lower tooth rows, indicative of vertically orientated crowns that were in close contact during occlusion, and three distinct types of dental wear. These include irregular spalled surfaces near the apex (probably caused by tooth‐food contact), semi‐circular wear near the base, and elongate surfaces extending along the mesial and distal margins of the teeth, obliterating the carinae (including the denticles). Scanning electron micrographs show that these latter surfaces are marked by parallel apicobasal striations, which in extant mammals reflect tooth–tooth contact. As such, we interpret the carinal wear facets in Dakosaurus as being formed by repeated tooth–tooth contact between the mesial and distal margins of the teeth of the upper and lower jaw. We posit that this increased the available shearing surface on their high crowns. Together, these wear patterns suggest that occlusion in Dakosaurus was specialized for cutting large and abrasive prey items into portions small enough to swallow, making it a prime example of an aquatic reptile with macrophagous feeding habits. Anat Rec, 2012. © 2012 Wiley‐Periodicals, Inc.     

Comparative Jaw Muscle Anatomy in Kangaroos,Wallabies, and Rat‐Kangaroos (Marsupialia: Macropodoidea)

The jaw muscles were studied in seven genera of macropodoid marsupials with diets ranging from mainly fungi in Potorous to grass in Macropus. Relative size, attachments, and lamination within the jaw adductor muscles varied between macropodoid species. Among macropodine species, the jaw adductor muscle proportions vary with feeding type. The relative mass of the masseter is roughly consistent, but grazers and mixed‐feeders (Macropus and Lagostrophus) had relatively larger medial pterygoids and smaller temporalis muscles than the browsers (Dendrolagus, Dorcopsulus, and Setonix). Grazing macropods show similar jaw muscle proportions to “ungulate‐grinding” type placental mammals. The internal architecture of the jaw muscles also varies between grazing and browsing macropods, most significantly, the anatomy of the medial pterygoid muscle. Potoroines have distinctly different jaw muscle proportions to macropodines. The masseter muscle group, in particular, the superficial masseter is enlarged, while the temporalis group is relatively reduced. Lagostrophus fasciatus is anatomically distinct from other macropods with respect to its masticatory muscle anatomy, including enlarged superficial medial pterygoid and deep temporalis muscles, an anteriorly inflected masseteric process, and the shape of the mandibular condyle. The enlarged triangular pterygoid process of the sphenoid bone, in particular, is distinctive of Lagsotrophus. Anat Rec, 292:875–884, 2009. © 2009 Wiley‐Liss, Inc.     

MicroRNA miR‐7 contributes to the control of Drosophila wing growth

Background : The control of organ growth is critical for correct animal development. From flies to mammals, the mechanisms regulating growth are conserved and the role of microRNAs in this process is emerging. The conserved miR‐7 has been described to control several aspects of development. Results: Here, we have analyzed the function of miR‐7 during Drosophila wing development. We found that loss of miR‐7 function results in a reduction of wing size and produces wing cells that are smaller than wild type cells. We also found that loss of miR‐7 function interferes with the cell cycle by affecting the G1 to S phase transition. Further, we present evidence that miR‐7 is expressed in the wing imaginal discs and that the inactivation of miR‐7 increases the expression of Cut and Senseless proteins in wing discs. Finally, our results show that the simultaneous inactivation of miR‐7 and either cut, Notch, or dacapo rescues miR‐7 loss of function wing size reduction phenotype. Conclusions: The results from this work reveal, for the first time, that miR‐7 functions to regulate Drosophila wing growth by controlling cell cycle phasing and cell mass through its regulation of the expression of dacapo and the Notch signaling pathway. Developmental Dynamics 244:21–30, 2015. © 2014 Wiley Periodicals, Inc.     

Shearing Mechanics and the Influence of a Flexible Symphysis During Oral Food Processing in Sphenodon (Lepidosauria: Rhynchocephalia)

The New Zealand tuatara, Sphenodon, has a specialized feeding system in which the teeth of the lower jaw close between two upper tooth rows before sliding forward to slice food apart like a draw cut saw. This shearing action is unique amongst living amniotes but has been compared with the chewing power stroke of mammals. We investigated details of the jaw movement using multibody dynamics analysis of an anatomically accurate three‐dimensional computer model constructed from computed tomography scans. The model predicts that a flexible symphysis is necessary for changes in the intermandibular angle that permits prooral movement. Models with the greatest symphysial flexibility allow the articulation surface of the articular to follow the quadrate cotyle with the least restriction, and suggest that shearing is accompanied by a long axis rotation of the lower jaws. This promotes precise point loading between the cutting edges of particular teeth, enhancing the effectiveness of the shearing action. Given that Sphenodon is a relatively inactive reptile, we suggest that the link between oral food processing and endothermy has been overstated. Food processing improves feeding efficiency, a consideration of particular importance when food availability is unpredictable. Although this feeding mechanism is today limited to Sphenodon, a survey of fossil rhynchocephalians suggests that it was once more widespread. Anat Rec, 2012. © 2012 Wiley‐Periodicals, Inc.     

Uterine remodelling during pregnancy and pseudopregnancy in the brushtail possum (Trichosurus vulpecula; Phalangeridae)

The formation of a placenta is critical for successful mammalian pregnancy and requires remodelling of the uterine epithelium. In eutherian mammals, remodelling involves specific morphological changes that often correlate with the mode of embryonic attachment. Given the differences between marsupial and eutherian placentae, formation of a marsupial placenta may involve patterns of uterine remodelling that are different from those in eutherians. Here we present a detailed morphological study of the uterus of the brushtail possum (Trichosurus vulpecula; Phalangeridae) throughout pregnancy, using both scanning and transmission electron microscopy, to identify whether uterine changes in marsupials correlate with mode of embryonic attachment as they do in eutherian mammals. The uterine remodelling of T. vulpecula is similar to that of eutherian mammals with the same mode of embryonic attachment (non‐invasive, epitheliochorial placentation). The morphological similarities include development of large apical projections, and a decrease in the diffusion distance for haemotrophes around the period of embryonic attachment. Importantly, remodelling of the uterus in T. vulpecula during pregnancy differs from that of a marsupial species with non‐invasive attachment (Macropus eugenii; Macropodidae) but is similar to that of a marsupial with invasive attachment (Monodelphis domestica; Didelphidae). We conclude that modes of embryonic attachment may not be typified by a particular suite of uterine changes in marsupials, as is the case for eutherian mammals, and that uterine remodelling may instead reflect phylogenetic relationships between marsupial lineages.     

Effect of Reduced c‐Kit Signaling on Bone Marrow Adiposity

c‐Kit (CD117) is required for normal differentiation of osteoblasts from bone marrow stromal cells and for normal bone formation. Osteoblasts and adipocytes originate from a common progenitor cell, and a reciprocal relationship in differentiation of the two lineages is often observed. Therefore, the effects of abnormal c‐kit signaling on bone marrow adiposity and adipocyte precursor pool size were evaluated in mouse strains with loss of function mutations in kit receptor or kit ligand. Additionally, to determine whether short‐duration pharmacological disruption of kit signaling influences bone marrow adiposity, we administered the kit receptor antagonist gleevec (imatinib mesilate) for 1 week to middle aged (13‐month‐old) male rats known to have high levels of bone marrow fat. Compared to wild‐type littermates, adipocytes were absent and adipocyte precursors greatly reduced in bone marrow from kit receptor‐deficient Kit^W/W‐ν mice. Administration of secreted kit ligand to membrane‐associated kit ligand‐deficient Kit^Sl/Sl‐d mice was ineffective in inducing bone marrow adipogenesis. These findings suggest that activation of kit receptor by the membrane‐associated form of kit ligand is required for kit signaling to promote bone marrow adipogenesis in mice. Rats treated with gleevec had lower adipocyte density compared to age‐matched controls, suggesting that kit signaling is required to maintain normal bone marrow adiposity. Taken together, our results indicate that c‐Kit signaling plays an important but previously unsuspected role in regulating bone marrow adiposity. Anat Rec, , 2011. © 2011 Wiley‐Liss, Inc.     

Dielectric Relaxation of Poly(ester‐block‐amide) Multiblock Copolymers

A series of poly(ester‐block‐amide)s, composed of crystallized sequences of poly(butylene terephthalate) (PBT) and an amorphous, aliphatic oligoamide (PA 36.6) obtained by the reaction of diamines and dimerized fatty acids, has been synthesized by polycondensation in the melt. The dielectric properties of these multiblock copolymers have been investigated as a function of temperature and PBT/PA ratio in the frequency range from 5·10² to 10⁶ Hz. The melting and glass transition temperatures as well as the degree of crystallinity were characterized by means of DSC. The dielectric properties vary with temperature due to two relaxation processes: a) the β‐relaxation process, associated with the local motion of polar groups attached to the soft and hard segments of the copolymer chain, and b) the α‐relaxation process, associated with long‐range molecular motions near the glass‐transition temperature. This behaviour is discussed by means of the Havriliak‐Negami analysis.     

Physical training improves visceral adipose tissue health by remodelling extracellular matrix in rats with estrogen absence: a gene expression analysis

Adipose tissue development is associated with modifications involving extracellular matrix remodelling, and metalloproteinases play a significant role in this process. Reduced circulating sexual hormones cause impacts on the size, morphology and functions of the adipose tissue, increasing susceptibility to diseases. This study investigated whether exercise training may be an alternative strategy to combat the effects promoted by estrogen decay through modulation in gene expression patterns in the extracellular matrix (ECM) of visceral adipose tissue of ovariectomized rats. Nulliparous rats (n = 40) were randomly distributed into four groups (n = 10/group): sham sedentary (Sh‐S), sham resistance training (Sh‐Rt), ovariectomized sedentary (Ovx‐S) and ovariectomized resistance training (Ovx‐Rt). The Sh‐S animals did not have any type of training. The body mass and food intake, ECM gene expression, gelatinase MMP‐2 activity and adipocyte area were measured. A lack of estrogen promoted an increase in body mass, food intake and the visceral, parametrial and subcutaneous adipocyte areas. The ovariectomy upregulated the expression of MMP‐2, MMP‐9, TGF‐β, CTGF, VEGF‐A and MMP‐2 activity. On the other hand, resistance training decreased the body mass, food intake and the adipocyte area of the three fat depots analysed; upregulated TIMP‐1, VEGF‐A and MMP‐2 gene expression; downregulated MMP‐9, TGF‐β and CTGF gene expression; and decreased the MMP‐2 activity. We speculate that resistance training on a vertical ladder could play an important role in maintaining and remodelling ECM by modulation in the ECM gene expression and MMP‐2 activity, avoiding its destabilization which is impaired by the lack of estrogen.