In vivo microscopy of a rat abdominal skin flap: A new model

This study describes a rat abdominal skin flap model of in vivo microscopy which provides a reliable, easy to perform system in which to examine the microcirculation of flaps. The island flap, which is based on the superficial inferior epigastric vessels caudally, and drained proximally by the lateral thoracic vein, can be mounted directly on a Perspex microscope stage. In vivo microscopy of the subdermal plexus of the flap allows detailed study of blood flow pattern, capillary flow, microvessel diameter, and margination of leucocytes, in a skin flap with versatile blood supply and innervation. © 1994 Wiley-Liss, Inc.     

Comparison of four methods to evaluate sperm DNA integrity between mouse caput and cauda epididymidis

It is well known that transit through the epididymis involves an increase in the compaction of sperm chromatin, which acquires fully condensed status at the caput epididymidis. The purpose of this study was to compare the terminal deoxyribonucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) assay, the comet assay, the sperm chromatin structure assay (SCSA) and the sperm chromatin dispersion (SCD) test by analysing spermatozoa from the caput and cauda epididymidis in order to demonstrate the ability of each technique to discriminate between different degrees of sperm maturity related to chromatin compaction and DNA fragmentation. Our results suggest that some populations of DNA-fragmented spermatozoa associated with immature sperm can only be identified using the comet assay and the SCSA but not with the SCD test or the TUNEL assay.     

A new method to evaluate the effects of shear on the skin

Currently, pressure ulcer preventive strategies focus mainly on pressure redistribution. Little attention is paid to reduce the harmful effects of shear‐force, because little is known about pathophysiological aspects of shear‐force. Even today, no method to measure the effects of shear‐force on the skin is available. Therefore, the aim of this study was to investigate the response to shear‐forces in terms of analyzing a noninvasive biomarker and reactive hyperemic parameter measured at the skin of healthy participants. A physical model was developed to produce a combination of pressure and shear or pressure alone on the skin. Ten healthy male participants were included and pressure (3.9 kPa) and a combined loading of pressure and shear (2.4 kPa + 14.5 N) was applied at the volar aspect of the forearms for 15 and 30 minutes. A Sebutape sample was used to collect IL‐1α and total protein (TP) noninvasively. The reactive hyperemic parameter was derived from a laser Doppler flowmeter. The increase in IL‐1α/TP‐ratio after a combined loading of pressure and shear for 30 minutes of 6.2 ± 2.5 was significantly higher compared with all other test conditions (p < 0.05). The increase in cutaneous blood cell flux was already significantly higher when a combined loading of pressure and shear was applied for 15 minutes compared with pressure alone. These results shows that the IL‐1α/TP‐ratio and cutaneous blood cell flux can be used as robust measures of the effect of shear‐force on skin in humans. Therefore, this model can be used to evaluate materials aimed at the reduction of shear.     

In vivo comparison of near infrared lasers for skin welding

The skin closure abilities of near infrared lasers and suturing were compared by histological examination and mechanical tensile tests during a 21-day healing period. One-centimeter incisions on the dorsal skin of Wistar rats were treated by one of the closing techniques: (a) soldering, using an 809 nm diode laser (0.5 W, 5 s) with 25% bovine serum albumin (BSA) and 2.5 mg/ml indocyanine green (ICG); (b) direct welding with a 980 nm diode laser (0.5 W, 5 s); (c) direct welding with a 1,070 nm fiber laser (0.5 W, 5 s); (d) suturing. Six spots (79.61 J/cm² for each spot) were applied through the incisions. Healing was inspected on the 1st, 4th, 7th, 14th, and 21st post-operative days. The closure index (CI), thermally altered area (TAA), granulation area (GA) and epidermal thickness (ET) were determined by histological examination. Tensile tests were performed at a 5 mm/min crosshead speed up to the first opening along the incision. Immediate superficial closure with high CI values was found for the laser-irradiated incisions at the early phase of recovery. Clear welds without thermal damage were observed for the group irradiated at 1,070 nm. For the sutured group, the incisions remained unclosed for the first day, and openings through the incision were observed. At the end of the 21-day recovery period, no differences between experimental groups were observed in terms of the CI, GA and ET values. However, the tensile strength of the groups irradiated at 980 nm and 1,070 nm was found to be higher than that of the sutured incisions. The laser welding techniques were found to be reliable in terms of immediate and mechanically strong closure compared with suturing. Of them, 1,070 nm laser welding yielded noticeably stronger bonds, with minimal scarring at the end of the 21-days of recovery.     

In vivo efficacy of a new autologous fibrin sealant

BACKGROUND: Fibrin-based sealants are commonly used to arrest bleeding following surgery. A new method has been developed for preparation of autologous fibrin sealant (FS) from protamine-precipitated fibrinogen concentrate. This FS has the potential to be a low-cost, safe, and convenient alternative to commercial sealants or cryoprecipitates usually prepared from patient or banked plasma. In this study, the efficacy of human FS was evaluated in a rat kidney model. MATERIALS AND METHODS: FS containing various fibrinogen concentrations (ranging from 15 to 60 mg/mL) were applied to controlled renal incisions, and bleeding time and blood loss were measured. Bleeding from the wounds was also predicted using a mathematical model based on tensile strength and adhesion strength of the sealants. RESULTS: The sealants, when applied under controlled conditions, reduced the blood loss and bleeding time more effectively than controls (where no sealant, plasma, or the commercial product Tisseel (Baxter Healthcare Corp., Westlake Village, CA) was applied). The sealant also significantly reduced bleeding time with a concomitant decrease in blood loss in rats that were anticoagulated with heparin. Bleeding times predicted by the mathematical model agreed well with experimental data and demonstrated that the ability of sealant to reduce bleeding time largely depended on its adhesion strength. CONCLUSION: The autologous fibrin sealant can be prepared with any volume (e.g., 5 to 500 mL) of patient's blood, within minutes, and exhibits equal or greater hemostatic efficacy compared with the leading commercial sealant.     

In vivo friction properties of human skin.

In vivo frictional properties of human skin and five materials, namely aluminium, nylon, silicone, cotton sock, Pelite, were investigated. Normal and untreated skin over six anatomic regions of ten normal subjects were measured under a controlled environment. The average coefficient of friction for all measurements is 0.46+/-0.15 (p<0.05). Among all measured sites, the palm of the hand has the highest coefficient of friction (0.62+/-0.22). For all the materials tested, silicone has the highest coefficient of friction (0.61+/-0.21), while nylon has the lowest friction (0.37+/-0.09).     

In vivo evaluations of a new thromboresistant polyurethane for artificial heart blood pumps

To reduce the risk of thromboembolic complications in prosthetic blood pumps, we have developed a new segmented polyurethane elastomer. This material is unique because its mechanical properties for long-term durability and surface properties for biocompatibility have been separated and developed in two distinct materials. Improved thromboresistance is then obtained by a 1% concentration of a new polymeric surface-modifying additive blended with the base polyurethane before fabrication of the blood pump. To evaluate this material in vivo, we performed 10 implants, in calves, of the Pierce-Donachy prosthetic ventricle with blood-pumping sacs and cannulas fabricated from the new surface-modifying additive copolymer blend (Thoratec's BPS-215M). In four control implants the blood sacs and cannulas were fabricated from Ethicon's Biomer segmented polyurethane, which is the present clinical standard for most artificial hearts and circulatory support devices. The blood pumps were connected from the apex of the left ventricle to the descending aorta in male Holstein calves weighing 82 to 108 kg and were driven pneumatically in the full-to-empty mode with flows averaging 5 to 6 L/min. Each calf was medicated with aspirin and dipyridamole throughout the study period and was electively put to death after 4 weeks for evaluation of explanted blood sacs and for examination of the kidneys for infarction. All 10 explanted blood sacs made with the surface-modifying additive copolymer blend were shiny and completely free of thrombus. Three of the four explanted Biomer blood sacs showed visible red thrombus, and all four showed small areas of white thrombus. The average surface area of the Biomer blood sacs covered with thrombus was 45 +/- 32 mm2. Use of a semiquantitative scale to assess renal infarction demonstrated that nine of 10 animals with a surface-modifying additive copolymer blend blood sac had infarction less severe than the mean infarct score of the animals with a Biomer sac. The surface-modifying additive copolymer blend has excellent mechanical and physical properties necessary for use in artificial heart blood pumps. From these experiments, we conclude that the surface-modified polyurethane blend is superior to Biomer polyurethane in blood compatibility and in freedom from thromboembolic risk. This material is now approved by the Food and Drug Administration for investigational device exemption studies in the Pierce-Donachy prosthetic ventricle.     

In vivo study of a new radioisotope-powered cardiac pacer.

A new radioisotopic pulse generator has been developed. It is 6 cm. long, 4.7 cm. high, 1.92 cm. wide, and weighs 61 Gm. (2 oz.). It is the smallest pulse generator made and has a life expectancy of over 20 years. The circuit is a conventional ventricular-inhibited (V.V.I.) type. In vitro testing has passed all Atomic Energy Commission requirements. The present study is concerned with in vivo testing of the complete pacemaker system, by means of both myocardial and endocranial electrodes, in 20 dogs with and without induced heart block. Extensive testing for electromagnetic compatability was carried out on 1 animal with induced heart block and a special, fast-rate pulse generator. Based on studies to date, the Atomic Energy Commission has issued a license for limited clinical trial which has already begun at the collaborating institutions.     

Google Maps offers a new way to evaluate claudication

Background

Accurate determination of walking capacity is important for the clinical diagnosis and management plan for patients with peripheral arterial disease. The current “gold standard” of measurement is walking distance on a treadmill. However, treadmill testing is not always reflective of the patient's natural walking conditions, and it may not be fully accessible in every vascular clinic. The objective of this study was to determine whether Google Maps, the readily available GPS-based mapping tool, offers an accurate and accessible method of evaluating walking distances in vascular claudication patients.

In vivo study of T-cell responses to skin alloantigens in Xenopus using a novel whole-mount immunohistology method

BACKGROUND: The African clawed frog, Xenopus, is a widely used comparative model for studying the immune response to transplantation antigens. METHODS: To better define the effector cells involved in the immune response to skin alloantigens of the frog Xenopus laevis, we have adapted a whole-mount immunohistology procedure used in mice that enables us to visualize leukocyte infiltration into unfixed transplanted skin tissues using fluorescent antibodies. We characterized the leukocyte populations present in donor skin at different times after transplantation using anti-class II and CD8 monoclonal antibodies. RESULTS: In autografts, only class II Langerhans or dendritic-like cells and very few CD8 T cells were detected. In contrast, major histocompatibility complex (MHC) disparate skin grafts at the peak of acute rejection (seven days posttransplantation, 50% rejection of pigment cells) were infiltrated with a large number of bright class II leukocytes, the majority of which were CD8 T cells. Most of these cells were located outside blood vessels and often near areas lacking pigmentation. Compared to MHC-disparate skin grafts, skin differing from the host only by minor histocompatibility antigens undergoes slower (i.e., chronic) rejection; interestingly, however, it was infiltrated by similar numbers of class II and CD8 T cell effectors, but with delayed kinetics (i.e., peaked around 15 days posttransplantation). CONCLUSIONS: Our data provide direct in vivo evidence of marked infiltration of effector leukocytes, a majority of which are CD8 T cells that occurs at the onset of tissue destruction of skin allografts.     

A simplified method to evaluate the loss of domain

Hernia - The treatment of giant incisional hernia (IH) with loss of domain (LOD, IHLD) is considerably challenging due to technical difficulties and subsequent post-operative complications. These...     

Novel methods to evaluate fracture risk models

Fracture prediction models help to identify individuals at high risk who may benefit from treatment. Area under the curve (AUC) is used to compare prediction models. However, the AUC has limitations and may miss important differences between models. Novel reclassification methods quantify how accurately models classify patients who benefit from treatment and the proportion of patients above/below treatment thresholds. We applied two reclassification methods, using the National Osteoporosis Foundation (NOF) treatment thresholds, to compare two risk models: femoral neck bone mineral density (BMD) and age (simple model) and FRAX (FRAX model). The Pepe method classifies based on case/noncase status and examines the proportion of each above and below thresholds. The Cook method examines fracture rates above and below thresholds. We applied these to the Study of Osteoporotic Fractures (SOF). There were 6036 (1037 fractures) and 6232 (389 fractures) participants with complete data for major osteoporotic and hip fracture, respectively. Both models for major osteoporotic fracture (0.68 versus 0.69) and hip fracture (0.75 versus 0.76) had similar AUCs. In contrast, using reclassification methods, each model classified a substantial number of women differently. Using the Pepe method, the FRAX model (versus the simple model) missed treating 70 (7%) cases of major osteoporotic fracture but avoided treating 285 (6%) noncases. For hip fracture, the FRAX model missed treating 31 (8%) cases but avoided treating 1026 (18%) noncases. The Cook method (both models, both fracture outcomes) had similar fracture rates above/below the treatment thresholds. Compared with the AUC, new methods provide more detailed information about how models classify patients. © 2011 American Society for Bone and Mineral Research     

In vitro and in vivo evaluation of a new dialyzer.

BACKGROUND: Recent dialyzer-related developments have concentrated upon the improvement of performance and biocompatibility. The focus of these developments was predominantly on the membrane itself. A newly developed high-flux dialyzer (FX60) with an advanced Fresenius Polysulfone) membrane (Helixone) overcomes this limitation and has several design-related advantages attributed to the redesign of the individual functional components. For the first time, polypropylene was selected as the material for the dialyzer housing. Both the fibre and the fibre-bundle geometry were refined with the aim of improving overall performance and to reduce dialysate consumption. METHODS: This study aims at investigating the in vitro and in vivo performance of the new FX60 dialyzer with the focus on dialysate flow distribution and dialysate consumption. A new method to analyse dialysate flow distribution, based on local clearances, is suggested. The effect of reducing dialysate flow from 500 to 300 ml/min is investigated in vivo. RESULTS: K(0)A(urea), a common measure to quantify device performance, is found to approach 1000 ml/min for the FX60 with a surface of only 1.4 m(2). Local clearance measurement shows equal performance of the Helixone fibre bundle over the entire cross-section. A dialysate flow reduction by 20% (in vivo) only results in a minor loss in clearance. CONCLUSIONS: The newly developed high-flux dialyzer (FX60) shows a remarkable performance (K(0)A(urea)). The excellent utilization of dialysate could be proven in vivo and is attributed to the superior dialysate flow distribution. A reduction of dialysate flow by 20% could lead to substantial economic savings.     

The bioengineering theory of the key modes of action of a cyanoacrylate liquid skin protectant

The objective of this article is to formulate a new bioengineering theoretical framework for modelling the biomechanical efficacy of cyanoacrylate skin protectants, with specific focus on the Marathon technology (Medline Industries, Inc., Northfield, Illinois) and its modes of action. This work details the bioengineering and mathematical formulations of the theory, which is based on the classic engineering theories of flexural stiffness of coated elements and deformation friction. Based on the relevant skin anatomy and physiology, this paper demonstrates: (a) the contribution of the polymerised cyanoacrylate coating to flexural skin stiffness, which facilitates protection from non‐axial (eg, compressive) localised mechanical forces; and (b) the contribution of the aforementioned coating to reduction in frictional forces and surface shear stresses applied by contacting objects such as medical devices. The present theoretical framework establishes that application of the cyanoacrylate coating provides considerable biomechanical protection to skin and subdermally, by shielding skin from both compressive and frictional (shearing) forces. Moreover, these analyses indicate that the prophylactic effects of the studied cyanoacrylate coating become particularly strong where the skin is thin or fragile (typically less than ~0.7 mm thick), which is characteristic to old age, post‐neural injuries, neuromuscular diseases, and in disuse‐induced tissue atrophy conditions.     

Fluorescence spectroscopy as a tool to detect and evaluate glucocorticoid-induced skin atrophy

Topical glucocorticoid (GC) therapy has been successfully used in the treatment of several common cutaneous diseases in clinical practice for a long time, and skin atrophy is one of the most typical cutaneous side effects of this therapy. The aim of this study was to evaluate the potential of noninvasive fluorescence spectroscopy (FS) technique in the detection and classification of GC-induced skin atrophy. A total of 20 male Wistar rats were used in the experimental protocol under controlled environmental conditions and with free access to food. One group received topical application of clobetasol propionate 0.05% for 14 days to induce cutaneous atrophy (atrophic group) and the other (control) group received only vehicle application following the same protocol and schedule. Histological analyses and FS measurements with laser excitation at both 532 nm and 408 nm were obtained on days 1 and 15. The FS results were classified as "normal" or "atrophic" according by histological analysis. Fluorescence spectra obtained with excitation at 408 nm allowed a clear distinction between the control and atrophic groups, and were more informative than the those obtained at 532 nm. Our results reveal that, if correctly applied, FS allows noninvasive evaluation of corticosteroid-induced skin atrophy, and thus represents an important step towards better monitoring of undesirable side effects of cutaneous therapy.     

In vivo fluorescence spectroscopy and imaging of human skin tumours

The feasibility of using in vivo autofluorescence for the diagnosis of skin cancer was evaluated. In vivo fluorescence measurements were performed on healthy human volunteers, and patients with different types of benign and malignant skin tumours. Fluorescence spectra as well as fluorescence images were acquired. The excitation-emission matrix of normal skin (n=3) showed a broad peak at the shortest excitation wavelength (365 nm) and at 440 nm fluorescence wavelength, smoothly decreasing towards longer excitation and fluorescence wavelengths. Non-melanoma skin tumours (n=31) and control skin excited with 375 nm showed a broad fluorescence band from 400 to 700 nm, peaking around 436 nm. No significant differences in measurements between tumours and the corresponding control sites were found. A large spatial variation in the fluorescence intensity was observed both in the tumours and in the control sites. Standard deviations found ranged from 0.15 to 1.5 times the mean fluorescence. Fluorescence images, excited with 375 nm and taken with an image intensified CCD camera, on eight malignant melanomas and eight benign pigmented lesions did not indicate any fluorescence intensity distribution specific to the malignancy of the lesion. Neither the shape of the fluorescence spectra, nor the spatial distribution of the fluorescence intensity showed any signature specific to the histopathological nature of the lesions investigated. Optical diagnostics of skin tumours using the autofluorescence does not seem to be feasible at the present time.