Subdermal Connective Tissue Research Articles

Understanding the Interplay Between Skin, Fascia, and Muscles of the Midface in Facial Aging.

Surgical, minimally-invasive, and non-invasive aesthetic procedures try to ameliorate the signs of facial aging, but also focus on enhancing various individual features of beauty in each patient. Herein, the midface plays a central role due to its location but also its importance for the aesthetic perception and facial expression. To date, no study has investigated the interplay between facial muscles and its connecting subdermal architecture during facial aging to provide a more comprehensive understanding of the middle face. A total of 76 subjects, consisting of 30 males (39.5%) and 46 females (60.5%) with a mean age of 42.2 (18.7) years [range 19-80] and a mean BMI of 24.6 (3.7) kg/m2 [range 18-35], were enrolled in this investigation. Cutometry (skin aging), 3D skin displacement analyses (subdermal connective tissue aging), and sEMG (muscle aging) analyses were utilized. The results revealed that overall skin firmness increased, and skin elasticity decreased (p < 0.001), sEMG signal of the investigated muscles decreased (p < 0.001), whereas midfacial mobility remained unaltered (p = 0.722). The results of this study indicate that midfacial aging is a measurable effect when utilizing individual measurement modalities for assessing skin, subdermal fascia, and midfacial muscles. The function of midfacial muscles revealed a potential threshold effect, which is not reached during midfacial aging due to the unchanged soft tissue mobility at older age. However, to understand its clinical presentation all midfacial soft tissues need to be factored in and a holistic picture needs to be created. This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes review articles, book reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to authors www.springer.com/00266 .

Feasibility of Implanting a Foot-Ankle Endoprosthesis within Skin in a Rabbit Model of Transtibial Amputation.

Prosthetic limbs that are completely implanted within skin (i.e., endoprostheses) could permit direct, physical muscle–prosthesis attachment to restore more natural sensorimotor function to people with amputation. The objective of our study was to test, in a rabbit model, the feasibility of replacing the lost foot after hindlimb transtibial amputation by implanting a novel rigid foot–ankle endoprosthesis that is fully covered with skin. We first conducted a pilot, non-survival surgery in two rabbits to determine the maximum size of the skin flap that could be made from the biological foot–ankle. The skin flap size was used to determine the dimensions of the endoprosthesis foot segment. Rigid foot–ankle endoprosthesis prototypes were successfully implanted in three rabbits. The skin incisions healed over a period of approximately 1 month after surgery, with extensive fur regrowth by the pre-defined study endpoint of approximately 2 months post surgery. Upon gross inspection, the skin surrounding the endoprosthesis appeared normal, but a substantial subdermal fibrous capsule had formed around the endoprosthesis. Histology indicated that the structure and thickness of the skin layers (epidermis and dermis) were similar between the operated and non-operated limbs. A layer of subdermal connective tissue representing the fibrous capsule surrounded the endoprosthesis. In the operated limb of one rabbit, the subdermal connective tissue layer was approximately twice as thick as the skin on the medial (skin = 0.43 mm, subdermal = 0.84 mm), ventral (skin = 0.80 mm, subdermal = 1.47 mm), and lateral (skin = 0.76 mm, subdermal = 1.42 mm) aspects of the endoprosthesis. Our results successfully demonstrated the feasibility of implanting a fully skin-covered rigid foot–ankle endoprosthesis to replace the lost tibia–foot segment of the lower limb. Concerns include the fibrotic capsule which could limit the range of motion of jointed endoprostheses. Future studies include testing of endoprosthetics, as well as materials and pharmacologic agents that may suppress fibrous encapsulation.

Influence of immersion agents on optical parameters of bio-tissues during laser photothermal therapy of tumor: pilot study

Combined use of an immersion agent with low-intensity laser irradiation for optical clearing of skin before plasmon photothermal therapy (PPTT) procedure is offered. Pilot study results of influence of the immersion agents on optical parameters of skin, subdermal connective tissue and model tumor of rats in vivo at hyperthermia during PPTT are presented. Model of alveolar liver cancer --- cholangiocarcinoma, transplanted under the skin, was used as a model tumor. For PPTT the gold nanorods with absorption band in the area of diode laser radiation (808 nm) were introduced. Monitoring of light attenuation coefficient change in skin at optical clearing was performed using optical coherent tomography. Measurements of optical parameters of the complete tumor and its layers were performed using spectrometers in a wave length range of 350-2200 nm. Reduction of skin thermal damage during PPTT with preliminary optical clearing using immersion agent (mixture of 70% glycerol water solution and 10% DMSO) and low-intensity laser irradiation at wave length of 808 nm is observed. Keywords: gold nanorods, IR laser radiation, optical clearing, optical parameters, plasmon photothermal therapy.

Ultrasonic measurement of blubber thickness in right whales

The right whale population in the northwestern Atlantic appears to face the risk of extinction: ship and fishing gear trauma are significantmortality factors, but calving rates are also depressed compared to southern right whales. A major factor in calving success in many speciesis body condition. Knowledge of the dynamics of body condition is also important in studies of juvenile and sub-adult growth and seasonalchanges in adults. This paper describes a method to assess body condition in live right whales. To characterise the acoustic properties ofthe blubber/muscle interface we first studied samples of Atlantic white-sided dolphin and right whale in the laboratory. Tissue heterogeneitywas examined grossly and in histological sections. Acoustic echoes were strong from the sub-dermal connective tissue sheath(s). Echostrengths did not appear to vary with lipid content. We then used a 0.5MHz ultrasound transducer on a cantilevered 12m pole to touch theback of surfacing right whales briefly. Multiple laboratory and field measurements on individual animals suggest repeated measures ofblubber thickness at a single location are reasonably consistent. Data will be normalised to both sampling position on the body and to lengthof the animal, estimated by mensuration from stereo video images of the animal during sampling. In this way, using a long-term consistentdatabase of blubber thickness measurements, and catalogued reproductive histories from on-going photographic identification studies, weplan to assess the significance of changing body condition in right whale population dynamics.

Diet of whale sharks Rhincodon typus inferred from stomach content and signature fatty acid analyses

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 493:219-235 (2013) - DOI: https://doi.org/10.3354/meps10500 Diet of whale sharks Rhincodon typus inferred from stomach content and signature fatty acid analyses Christoph A. Rohner1,2,3,*, Lydie I. E. Couturier1,4, Anthony J. Richardson1,5, Simon J. Pierce3,6, Clare E. M. Prebble3, Mark J. Gibbons7, Peter D. Nichols8 1Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, EcoScience Precinct, GPO Box 2583, Brisbane, Queensland 4102, Australia 2Biophysical Oceanography Group, School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, Queensland 4072, Australia 3Manta Ray and Whale Shark Research Centre, Marine Megafauna Foundation, Praia do Tofo, Inhambane, Mozambique 4School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia 5Centre for Applications in Natural Resource Mathematics (CARM), School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia 6Wild Me, Praia do Tofo, Inhambane, Mozambique 7Department of Biodiversity & Conservation Biology, University of the Western Cape, Bellville 7535, South Africa 8Wealth from Oceans Flagship, CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, Tasmania 7000, Australia *Email: c.rohner1@uq.edu.au ABSTRACT: Whale sharks Rhincodon typus are large filter-feeders that are frequently observed feeding in surface zooplankton patches at their tropical and subtropical coastal aggregation sites. Using signature fatty acid (FA) analyses from their subdermal connective tissue and stomach content analysis, we tested whether whale sharks in Mozambique and South Africa predominantly feed on these prey and/or what other prey they target. Arachidonic acid (20:4ω6; mean ± SD = 17.8 ± 2.0% of total FA), 18:0 and 18:1ω9c were major FA of whale sharks, while in contrast, coastal epipelagic zooplankton collected near feeding whale sharks had 22:6ω3 (docosahexaenoic acid), 16:0 and 20:5ω3 (eicosapentaenoic acid) as major FA. Stomach contents of 3 stranded sharks were dominated by mysids (61 to 92% of prey items), another one by sergestids (56%), and a fifth stomach was empty. The dominant mysids (82% index of relative importance) were demersal zooplankton that migrate into the water column at night, suggesting night-time feeding by whale sharks. High levels of bacterial FA in whale sharks (5.3 ± 1.4% TFA), indicating a detrital link, potentially via demersal zooplankton, also support night-time foraging activity. High levels of oleic acid (16.0 ± 2.5%) in whale sharks and their similarity with FA profiles of shrimp, mysids, copepods and myctophid fishes from the meso- and bathypelagic zone suggest that whale sharks also forage in deep-water. Our findings suggest that, in the patchy food environment of tropical systems, whale sharks forage in coastal waters during the day and night, and in oceanic waters on deep-water zooplankton and fishes during their long-distance movements. KEY WORDS: Feeding ecology · Omega 6 fatty acids · Signature lipids · Mysida · Chondrichthyans · Fatty acid biomarkers Full text in pdf format PreviousNextCite this article as: Rohner CA, Couturier LIE, Richardson AJ, Pierce SJ, Prebble CEM, Gibbons MJ, Nichols PD (2013) Diet of whale sharks Rhincodon typus inferred from stomach content and signature fatty acid analyses. Mar Ecol Prog Ser 493:219-235. https://doi.org/10.3354/meps10500 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 493. Online publication date: November 20, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Histopathological study of cutaneous form of Avipoxvirus infection in Jungle crow Corvus macrorhynchos

Aim: A detailed histopathological examination of the samples collected from morbid jungle crow was performed to know the cause of death. Materials and Methods: Gross as well as histopathological examination was conducted. The suspected tissues get processed by formalin fixation and paraffin embedding technique. Result: On gross examination, dry pox lesions were seen on the external body surface whereas no internal lesions were observed. However on histopathological examination, the keratin layer of the epidermis was found to be intact and there was extensive proliferation of subdermal connective tissue infiltrated with polymorph mononuclear (PMN) cells. There was marked ballooning of keratinocytes. Swollen keratinocytes had enlarged pleomorphic and hyper-chromatic nuclei. Several keratinocytes also showed presence of eosinophilic intracytoplasmic inclusions (Bollinger bodies) which was considered confirmatory. Conclusion: Avipoxvirus infection was noticed in a jungle crow. On histopathological study, proliferation of subdermal connective tissue, swollen keratinocytes, pleomorphic and hyper-chromatic nucleus and eosinophilic intracytoplasmic inclusions were noticed.

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We report a case of medial meatal fibrosis, a rare external auditory canal condition, in which hearing improved postoperatively. A 60-year-old woman had undergone surgery and 6-month follow up. Extrinsic stimulus-induced fibrosis was attributed to her daily swimming. External auditory meatus inflammation was quite moderate, so the external ear canal skin was preserved, the removed thickened subdermal connective tissue removed, and the bony external ear canal drilled to enlarge the meatus diameter. We confirmed hearing improvement and no fibrosis recurrence. Medial meatal fibrosis may thus be treated satisfactorily with surgical intervention.

Cutaneous form of pox infection among captive peafowl (Pavo cristatus) chicks

The present study was carried out to investigate the epidemiology and lesions of avian pox in captive peafowl chicks. Overall values of morbidity, mortality and case fatality were 45.2%, 27.1% and 60.0%, respectively. The chicks of 9 to 12 weeks of age showed a significantly (P<0.001) higher prevalence rate than other age groups. The morbidity and mortality due to avian pox in peafowl chicks was significantly (P<0.001) reduced when kept in mosquito-proof cages and hatched under broody chicken hens. Morbidity due to poxvirus infection on the peafowl farm was 82%, 26% and 12% in successive years. This reduction might have been the result of the introduction of mosquito-proof nets after year 1, although this was not the subject of a controlled experiment. All of the peafowl chicks suffering from dry pox showed pustular and nodular lesions on eye lids, beak, legs and toes. Distribution of lesions in different body parts varied significantly (P<0.023). Lesion diameters were less than 1 cm (59.73%), 1 to 2 cm (23.75%) and more than 2 cm (16.87%). Histopathological studies revealed extensive proliferation of subdermal connective tissue and infiltration of heterophils and macrophages. The keratinocytes showed degenerative changes in the form of cytoplasmic vacuolation, ballooning and hyper-chromatic nuclei. Eosinophilic intracytoplasmic inclusions (Bollinger bodies) in keratinocytes were consistently present. It was concluded that avian pox rendered high morbidity, mortality and case fatality in peafowl chicks.

Analysis of the tight skin (Tsk1/+) mouse as a model for testing antifibrotic agents

The tight skin 1 (B6.CgFbn1Tsk+/+Pldnpa/J, henceforth referred to as Tsk1/+) mouse was first described as a spontaneously occurring mutant that resulted in hyperplasia of the subcutaneous loose connective tissue, and has subsequently been proposed to be a model of the human fibrotic disorder scleroderma. We have investigated the Tsk1/+ mouse as a model system for testing the efficacy of antifibrotic agents against skin fibrosis. We find that the tightness of the skin at the scruff of the neck leads to a measurably thicker skin pinch, but we suggest that this is due to hyperplasia of the subdermal loose connective tissue, which results in increased tethering of the skin to the underlying muscle layers. In contrast to previously published data, we do not find a significant difference in the dermal thickness or collagen content of the Tsk1/+ mouse skin compared with wild-type controls. In addition, expression profiling of Tsk1/+ mouse skin indicated that there are very few changes in gene expression, and that there is no evidence for upregulation of the transforming growth factor β signaling axis. Therefore, we conclude that this model is not suitable for testing the effect of antifibrotic agents on the dermis, and that changes potentially related to scleroderma may be confined to subdermal connective tissue.

The dinosaurian origin of feathers: perspectives from dolphin (Cetacea) collagen fibers.

The early origin of birds is a hotly disputed debate and may be broadly framed as a conflict between paleontologists and ornithologists. The paleontological emphasis has shifted from Archaeopteryx and its origins to recent finds of Cretaceous birds and "feathered" dinosaurs from China. The identification of alleged feathers has, however, relied principally on the visual image. Some workers have interpreted these integumentary structures as collagen fibers. To test the latter hypothesis, using light microscopy, collagen from the hypodermis (blubber) and subdermal connective tissue sheath was examined from a dolphin that had been buried for a year as part of an experiment. Within the blubber, toward the central thicker parts of the material, the collagen fibers had compacted and the three-dimensional latticework of normal blubber had more or less collapsed. Chromatographic analysis of the blubber revealed pronounced oxidation of the unsaturated lipids, probably accounting for the collapse of the latticework. Fibers normally bound together in bundles became separated into individual fibers or smaller bundles by degradation of the glue-like substance binding them together. These degraded collagen fibers show, in many instances, feather-like patterns, strikingly reminiscent of many of those identified as either "protofeathers" or "modern" feathers in dromaeosaurid dinosaurs. The findings throw serious doubt on the virtually complete reliance on visual image by supporters of the feathered dinosaur thesis and emphasize the need for more rigorous methods of identification using modern feathers as a frame of reference. Since collagen is the main fiber type found in most supporting tissues, the results have wide implications regarding the degradation and fossilization of vertebrate integument, such as that of the ichthyosaurs, dinosaurs and birds.

Expression of midkine in normal and burn sites of rat skin

Expression of midkine (MK), a retinoic acid-inducible heparin binding growth factor, was examined immunohistochemically in normal and burn sites of rat skin. In the normal skin, MK was localized in the epidermis and dermal appendages such as hair follicles and sebaceous glands. Mast cells in the subdermal connective tissue also accumulated MK. After burn injury, MK-positive cells began to infiltrate into subdermal connective tissue, and the number of MK-positive cells in the region increased to a maximum at postburn day two and then decreased gradually. Western blotting analysis of both normal and postburn skin revealed a 30 kDa band reactive with anti-MK antibody; this band was concluded to be a dimer of MK. These findings were discussed from the viewpoint of the possible role of MK in wound healing.

An exploratory investigation of the morphology and biochemistry of cellulite.

Dimpling of the skin of the thighs and buttocks is commonly referred to as cellulite, and it afflicts women much more frequently than men. Whereas many therapies that presume cellulite is caused by an abnormality of adipose tissue have gained recent popularity, the basic pathophysiology of cellulite has not been clearly identified. Theoretically, cellulite could reflect differences in adipose tissue biochemistry or connective tissue structure of affected versus unaffected individuals and/or of affected versus unaffected regions within an individual. We report here on direct experimental examination of these possibilities. Seven healthy adult subjects (five women, two men; four affected, three unaffected) underwent sonography of the thigh, measurement of regional in vivo subcutaneous adipose tissue metabolism (catecholaminergic responsiveness and blood flow) by microdialysis probe studies of the abdomen and the thigh, and full-thickness wedge biopsy of the thigh under local anesthesia. The presence of cellulite was defined as evidence of dimpling of the skin of the posterolateral thigh when the subject stood with the affected leg flexed to 90 degrees at the hip and knee. Any continuous area of skin at least 3 cm in diameter in which no dimpling was evident was designated as "unaffected." In all affected individuals, studies were performed to include both affected and unaffected areas of the thigh. In vitro pathologic examination of wedge biopsies and in vivo sonographic examination of the thigh both showed a diffuse pattern of extrusion of underlying adipose tissue into the reticular dermis in affected, but not unaffected, individuals. In vitro and in vivo studies also demonstrated that women had a diffuse pattern of irregular and discontinuous connective tissue immediately below the dermis, but this same layer of connective tissue was smooth and continuous in men. This connective tissue layer was more irregular and discontinuous in affected versus unaffected individuals. No significant differences were noted in subcutaneous adipose tissue morphology, lipolytic responsiveness, or regional blood flow between affected and unaffected sites within individuals. There is a sexual dimorphism in the structural characteristics of subdermal connective tissue that predisposes women to develop the irregular extrusion of adipose tissue into the dermis, which characterizes cellulite. These gender-related differences are diffuse and not localized only to affected areas. There is no evidence of any primary role for adipose tissue physiology, blood flow, or biochemistry in the etiology of cellulite, although the connective tissue of the female thigh is structured to accentuate differences in small subdermal adipose tissue depots.

Morphology of the subdermal connective tissue sheath of dolphins: a new fibre‐wound, thin‐walled, pressurized cylinder model for swimming vertebrates

The subdermal connective tissue sheath (SDS) of dolphins is a fibre‐reinforced membrane connected to other locomotor tissues, including blubber, axial muscles and tendons, and vertebral column. The complicated connections between the SDS and other locomotor tissues suggest that the SDS acts as a peripheral skeletal element for the axial locomotor muscles and as an anchor for a de novo dermal appendage, the dorsal fin. The morphology of the SDS suggests that the dolphin can be modelled as a fibre‐wound, thin‐walled, pressurized cylinder. Existing cylinder models predict that the SDS functions to resist torsional forces, prevent aneurysms, and limit wrinkling when the dolphin bends in locomotion. I present a new functional model that more accurately represents the morphology of the dolphin cylinder wrapped by the SDS. The new model predicts that the SDS: (1) acts as a retinaculum for the terminal tendons of the axial locomotor muscles; and (2) plays a role in maintaining the laterally flattened cross‐sectional shape of the caudal peduncle. The model is based on external morphological features of dolphins shared by other steady swimming aquatic vertebrates, such as carangiform and thunniform fishes. These features, which include a streamlined body shape and narrow necking of the caudal peduncle have been identified as adaptions to reduce drag. The new model offers insight into some of the structural features of the body wall required to maintain the hydrodynamicallytuned, external morphology of steady‐swimming vertebrates.

Caloric Restriction: Conservation of Cellular Replicative Capacity in Vitro Accompanies Life-Span Extension in Mice

We have tested whether life-long caloric restriction (CR) slows or delays the age-related loss of cellular replicative potential that occurs during normal aging in ad libitum (AL) fed mice. Both mean and maximum life spans of the restricted animals (60% of AL intake) were significantly extended 30-40% by CR treatment. Proliferative potential, measured by determining the fraction of cells capable of forming large clones in vitro, was compared in five cell types from six tissue sites from two strains of mice (Male (C57BL/6 × DBA/2)F1("B6D2F1") and female (C57B1/6 × C3H)F1("B6C3F1")). This included four nonhematopoietic organ sites: fibroblast cells from ear skin, tail skin, and subdermal connective tissue and epithelial cells from the medullary part of the kidney and two cell types, myofibroblasts and endothelial-like cells, from spleen and bone marrow. The proliferative potential of cells from AL mice decreased progressively with age in all tissues sites of both mouse strains. CR delayed or decreased the loss of proliferative potential in all situations, but the timing of this was tissue specific. For cells from the four nonhematopoietic tissue sites from female B6C3F1 female mice, CR delayed the onset of proliferative loss, such that the fraction of large clones was significantly greater for the CR 18- to 24-month-old mice than in AL controls at three of four sites (as determined by the fraction of large clones after 1 week of clonal growth). The proliferative loss in CR tissues then accelerated from 24 to 30 months, so that both CR and AL mice had similar fractions of large clones after 30 months of age. CR was also seen to delay loss of proliferative potential in cells from skin and kidney of B6D2F1 male mice at 23-24 months of age when cloned for 2 weeks. For fibroblast and endothelial-like cells from bone marrow and spleen stromal sites from both strains of mice, CR also significantly decreased loss of proliferative potential; furthermore, in these tissues the proliferative advantages remained or increased from 24 to over 30 months of age. In companion studies (N. S. Wolf et al., 1995. Exp. Cell. Res. 217, 000-000), CR was seen to decrease age-related losses in the maximal rates of cell replication in vivo in a panel of tissues from B6D2F1 male mice. The preservation of replicative potential by CR mice in all tissues tested, both in vitro and in vivo, indicates that CR preserves proliferative capacities in the cells and tissues of chronically restricted mice and may permit CR mice to better respond to proliferative stresses in old age.

Decrease in cellular replicative potential in "giant" mice transfected with the bovine growth hormone gene correlates to shortened life span.

Adult mice, (C57BL/6 x Sjl)F1 hybrids, transfected with the bovine growth hormone gene (bGH) grow to twice normal size, but have a mean life span less than 50% that of control siblings without the transgene. The replicative potentials of cells from six different tissue sites (tail skin and ear skin dermal fibroblasts, tail subdermal connective tissue fibroblasts, kidney medulla epithelial cells, bone marrow myofibroblasts, and spleen myofibroblasts) were assayed in vitro using clone size distribution analysis. Cells from all of the above bGH+ tissues produced a smaller fraction of large clones, relative to age-matched controls, in all of these cell types. The loss of replicative potential did not appear to be the result of negative conditioning of the cloning media by the bGH+ cells, and was tightly correlated to the period of accelerated growth in these animals (3-12 weeks), a time when additional GH receptors are expressed.

Intramuscular morphology and tendon geometry of the epaxial swimming muscles of dolphins

The dolphin upstroke is powered primarily by the m. multifidus and m. longissimus—robust muscles that insert serially along the vertebral column. Intramuscular and tendon morphology coupled with kinematic data are used to hypothesize regionally specific functions of these muscles. Both muscles develop equivalent forces (approximately 2kN) in the region of the thoraco‐lumbar spine, but transmit those forces to different regions of the vertebral column. The m. multifidus transmits the majority of its force locally to the thoraco‐lumar spine, a region of the body that undergoes no measurable bending. The action of the m. multifidus appears to be to stiffen its deep tendon of insertion, forming a temporary skeletal element for the m. longissimus. The m. longissimus transmits the majority of its force to the caudal spine, by way of a novel interaction between its insertional tendons and the subdermal connective tissue sheath. This insertional pattern confers torsional stiffness on the caudal peduncle, and allows the m. longissimus to do relatively more work (118 J) than if it had a typical mammalian insertional pattern. The caudal extension of the m. multifidus does 12 J of work on the caudal spine during an upstroke. The caudal extension of the m. longissimus transmits its force to the vertebrae in the caudal flukes and is the only epaxial muscle that acts to control the angle of attack of the fluke blade.

Dolphin swimming–a review

AbstractResearch into dolphin swimming has historically been guided by false assumptions of ‘effortless’, ‘high‐speed’ swimming. These assumptions have instigated the development of drag‐reduction hypotheses but tests of these hypotheses have generally had little success. The autecological approach has dominated recent efforts and has been more successful. In this review we summarize results of decades of research efforts to study these creatures. (1) Drag is minimized primarily by the streamlined shape of the body and appendages, with no known contributions from compliant dampening, dermal ridges, secretions, boundary layer heating, or skin folds. All indications are that the boundary layer is turbulent. (2) Muscles for the upstroke and downstroke of swimming dolphins provide approximately equal power. (3) Output force is enhanced by insertions occurring on the long processes of the vertebrae and on the subdermal connective tissue sheath. (4) Measured swimming speeds are lower than previously believed, with maximum reported routine speeds being approximately 3 m/s. (5) Porpoising behaviour appears to be the most energetically conservative manner in which to breathe when swimming at high speed. (6) Riding surf and wind waves involves the balance between the wave slope and the weight of the animal whereas riding the bow wave involves the interaction of the pressure wave in front of a ship and the drag of the dolphin.

Lack of Correlation between Mast Cell Response and Active Anaphylaxis in Mice

Mast cell-competent mice, sensitized to lysozyme, were examined for their mast cell and anaphylactic responses to determine whether anaphylactic shock could occur independent of mast cell participation. Tissues (cremaster muscle, subdermal connective tissue and mesentery), taken a short time after intravenous antigenic challenge, showed no evidence of mast cell degranulation above control tissues. Data obtained from a quantitative comparison of the onset and increase in local and systemic anaphylactic and mast cell sensitivities to the antigen provide strong support for the view that mast cells are not the major effector cells for systemic anaphylaxis in mice. The significant increase in blood pressure that occurred immediately after infusion with the antigen also indicates that other cells within the blood stream are involved.

Collagen types I, III, and V in human embryonic and fetal skin.

The dermis of human skin develops embryonically from lateral plate mesoderm and is established in an adult-like pattern by the end of the first trimester of gestation. In this study the structure, biochemistry, and immunocytochemistry of collagenous matrix in embryonic and fetal dermis during the period of 5 to 26 weeks of gestation was investigated. The dermis at five weeks contains fine, individual collagen fibrils draped over the surfaces of mesenchymal cells. With increasing age, collagen matrix increases in abundance in the extracellular space. The size of fibril diameters increases, and greater numbers of fibrils associate into fiber bundles. By 15 weeks, papillary and reticular regions are recognized. Larger-diameter fibrils, larger fibers, denser accumulations of collagen, and fewer cells distinguish the deeper reticular region from the finer, more cellular papillary region located beneath the epidermis. The distribution of collagen types I, III, and V were studied at the light microscope level by immunoperoxidase staining and at the ultrastructural level by transmission (TEM) and scanning electron microscopy (SEM) with immunogold labeling. By immunoperoxidase, types I and III were found to be evenly distributed, regardless of fetal age, throughout the dermal and subdermal connective tissue with an intensification of staining at the dermal-epidermal junction (DEJ). Staining for types III and V collagen was concentrated around blood vessels. Type V collagen was also localized in basal and periderm cells of the epidermis. By immuno-SEM, types I and III were found associated with collagen fibrils, and type V was localized to dermal cell surfaces and to a more limited extent with fibrils. The results of biochemical analyses for relative amounts of types I, III, and V collagen in fetal skin extracts were consistent with immunoperoxidase data. Type I collagen was 70-75%, type III collagen was 18-21%, and type V was 6-8% of the total of these collagens at all gestational ages tested, compared to 85-90% type I, 8-11% type III, and 2-4% type V in adult skin. The enrichment of both types III and V collagen in fetal skin may reflect in part the proportion of vessel- and nerve-associated collagen versus dermal fibrillar collagen. The accumulation of dermal fibrillar collagen with increasing age would enhance the estimated proportion of type I collagen, even though the ratios of type III to I in dermal collagen fibrils may be similar at all ages.

Effect of parathyroidectomy on plasma calcium levels in the seal salamander, Desmognathus monticola

The parathyroid glands of Desmognathus monticola are located in the subdermal connective tissue of the neck. Although they are smaller than previously described urodele parathyroid glands, their histological structure is similar. Parathyroidectomy caused a decrease in plasma calcium concentrations within 4 days following the operation. By Days 12 and 21, however, the plasma calcium levels of parathyroidectomized animals were not significantly different from those of sham-operated animals. Thus, the parathyroid gland of this species contains a hypercalcemic principle, but the recovery from hypocalcemia suggests that some hypercalcemic mechanism other than the parathyroid system must be involved in calcium homeostasis.