Synthesis, characterization, and in vivo biodistribution of 125I-labeled Dex-g-PMAGGCONHTyr

Dextran graft poly (N-methacryloylglycylglycine) copolymer-tyrosine conjugates (dextran-g-PMAGGCONHTyr) were synthesized and characterized. Dynamic light scattering (DLS) results indicated that the graft copolymers are soluble in pH 7.4 PBS and 0.9% saline solutions. The graft copolymers were labeled with (125)I, and the labeling stability in 0.9% saline solution was investigated. Pharmacokinetics studies showed a rapid clearance of (125)I-labeled graft copolymers from the blood pool. Biodistribution images confirmed the preferable liver and spleen accumulation within 1 h after injection and rapid clearance from all the organs over time. The graft copolymer with molecular weight of 9.8 kDa was eliminated from the kidney significantly faster than those with higher molecular weight. The effect of the numbers of -COOH groups on the graft copolymers on the biodistribution was also investigated. It was found that the graft copolymers with the average number of -COOH groups per glucopyranose unit (DS(-COOH)) of 0.57 and 0.18 are mainly distributed in liver and spleen at 1 h after injection, whereas the graft copolymer with DS(-COOH) of 0.07 is mainly accumulated in kidney.     

Tissue Typing,Antilymphocyte Globulin,and Prophylactic Graft Irradiation in Cadaver Kidney Transplantation

In a series of 27 recipients of cadaver kidney grafts, 26 were at the time of writing alive, 3 to 25 months after transplantation, and 25 patients were alive with functioning first grafts. The one-year patient survival in 18 patients was 94% and the one-year graft survival was 89%. There was no beneficial correlation between tissue matching and the frequency of major early rejection episodes or graft function 12 or more months after transplantation. Antilymphocyte globulin administration was associated with a lower incidence of early rejection episodes, but this was not statistically significant. A combination of prophylactic graft irradiation and antilymphocyte globulin administration for at least the first two weeks was associated with a significantly reduced frequency of major early rejection episodes and appreciably better graft function at 12 months. This effect could not be ascribed to better tissue matching.     

Dynamic,Nondestructive Imaging of a Bioengineered Vascular Graft Endothelium

Bioengineering of vascular grafts holds great potential to address the shortcomings associated with autologous and conventional synthetic vascular grafts used for small diameter grafting procedures. Lumen endothelialization of bioengineered vascular grafts is essential to provide an antithrombogenic graft surface to ensure long-term patency after implantation. Conventional methods used to assess endothelialization in vitro typically involve periodic harvesting of the graft for histological sectioning and staining of the lumen. Endpoint testing methods such as these are effective but do not provide real-time information of endothelial cells in their intact microenvironment, rather only a single time point measurement of endothelium development. Therefore, nondestructive methods are needed to provide dynamic information of graft endothelialization and endothelium maturation in vitro. To address this need, we have developed a nondestructive fiber optic based (FOB) imaging method that is capable of dynamic assessment of graft endothelialization without disturbing the graft housed in a bioreactor. In this study we demonstrate the capability of the FOB imaging method to quantify electrospun vascular graft endothelialization, EC detachment, and apoptosis in a nondestructive manner. The electrospun scaffold fiber diameter of the graft lumen was systematically varied and the FOB imaging system was used to noninvasively quantify the affect of topography on graft endothelialization over a 7-day period. Additionally, results demonstrated that the FOB imaging method had a greater imaging penetration depth than that of two-photon microscopy. This imaging method is a powerful tool to optimize vascular grafts and bioreactor conditions in vitro, and can be further adapted to monitor endothelium maturation and response to fluid flow bioreactor preconditioning.     

Survival of skin allografts following embryonic limb bud transplants in the turtle,Chelydra serpentina

Allografts of skin were observed in Chelydra serpentina. The response to these grafts was modified by a previous transplantation of a limb bud at an early embryonic stage. When the same donor was used for all transplants, the first skin graft was accepted by the host. A second skin graft, however, was rejected at about the rate of a simple first set allograft of skin. The animals were conditioned by the embryonic limb graft; this embryonic graft can be undergoing rejection at the same time a first set skin graft from the same donor was being accepted. The tolerance induced by the embryonic graft was sepcific for its donor.     

Facial autologous soft-tissue contouring by adjunction of tissue cocktail injection (micrograft and minigraft mixture of dermis, fascia, and fat)

Facial aging is both a physiologic and anatomic process characterized by changes in the skin and supporting tissues. The aging process produces an outer envelope that gradually expands while its contents gradually involute and the underlying structure weakens. This process results in an excess of skin that tends to create folds, grooves, and deepening furrows. Contour augmentation and filling depressions with autologous tissue or heterogeneous materials are widely used in face rejuvenation as an adjunctive procedure. There is unanimous agreement on the advantages of autogenous tissue grafts over alloplastic materials and heterogeneous transplants. It is also well known that the revascularization of a small graft (fat, dermis, and/or composite graft) is better than a large graft. For this reason, fat injections consisting of small particles have recently become popular. According to different authors, a graft take may vary from 30 to 50 percent. Nevertheless, it has been thoroughly documented that a graft consisting of dermis or fascia is superior to a fat graft in both the graft take rate and quality of the tissue. Strips of dermal graft have been used successfully for several years to fill lip contour and nasolabial folds. However, the main disadvantage of this technique is that utilization is restricted only to certain areas where there is a need for a small incision. To overcome this obstacle, the author developed a simple technique to obtain an injectable mass from a mixture of dermis, muscle strips, fat tissue, and fascia to use in body contouring (especially in the facial region) in large areas. The author describes the use of the technique in 450 patients. Follow-up in these patients from 6 months to 10 years showed that the application of the "tissue cocktail" procedure in select patients improved the author's results and created a marked increase in the number of satisfied patients with no complaints. The take and durability of this kind of graft were superior to the author's results using fat grafts. The tissue cocktail graft remained stable for several years, as effectively seen in the chin region. The sole complication from the procedure was some bruising, which was resolved in several days. No single infection or inclusion cyst was observed in this series.     

Enhancement of nerve regeneration and orientation across a gap with a nerve graft within a vein conduit graft: a functional, stereological, and electrophysiological study

In this study, the right sciatic nerves of 40 rats were used to determine whether a nerve graft within a vein graft might accelerate and facilitate axonal regeneration, compared with a nerve graft alone. The animals were separated into four groups, as follows: group 1, sham control; group 2 (control), segmental nerve resection and no repair; group 3, segmental nerve resection and nerve grafting; group 4, segmental nerve resection and reconstruction with a nerve graft within a vein conduit graft. For all groups, sciatic functional indices were calculated before the operation and on postoperative days 7 and 90. On postoperative day 90, the sciatic nerves were reexposed and nerve conduction velocities were recorded. The sciatic nerves were harvested from all groups for counting of the myelinated axons with a stereological method. No statistically significant differences with respect to return of gait function, axon count, or nerve conduction were noted between groups 3 and 4 (p > 0.05). However, functional recovery in group 4 on postoperative day 90 was significant, compared with group 2 (p < 0.05); the recovery difference between groups 2 and 3 was not significant (p > 0.05). This study was not able to demonstrate any functional benefits with the use of a nerve graft within a vein graft, compared with standard nerve grafting.     

A prospective, blinded, randomized, controlled clinical trial of topical negative pressure use in skin grafting

Topical negative pressure has been demonstrated to improve graft take in a number of noncomparative studies. This study aimed to assess whether split-thickness skin graft take is improved qualitatively or quantitatively with topical negative pressure therapy compared with standard bolster dressings. A blinded, prospective, randomized trial was conducted of 22 adult inpatients of Liverpool Hospital between July of 2001 and July of 2002 who had wounds requiring skin grafting. After grafting, each wound half was randomized to receive either a standard bolster dressing or a topical negative pressure dressing. Skin graft assessment was performed at 2 weeks by a single observer blinded to the randomization. Two patients were lost to follow-up and were excluded from the study. There were 20 patients (12 men and eightwomen) in the study group. The median patient age was 64 years (range, 27 to 88 years), and the mean wound size was 128 cm2 (range, 35 to 450 cm2). The wound exposed subcutaneous fat in eight patients, muscle in six patients, paratenon in four patients, and deep fascia in two patients. At 2 weeks, wounds that received a topical negative pressure dressing had a greater degree of epithelialization in six cases (30 percent), the same degree of epithelialization in nine cases (45 percent), and less epithelialization in five cases (25 percent) compared with their respective control wounds. Graft quality following topical negative pressure therapy was subjectively determined to be better in 10 cases (50 percent), equivalent in seven cases (35 percent), and worse in three cases (15 percent). Although the quantitative graft take was not significant, the qualitative graft take was found to be significantly better with the use of topical negative pressure therapy (p < 0.05). Topical negative pressure significantly improved the qualitative appearance of split-thickness skin grafts as compared with standard bolster dressings.     

Establishment, graft union characteristics and growth of Prunus micrografts

A micrografting technique for use on shoots derived by shoot-tip culture is described. Autografts of Prunus domestica cv. Hauszwetsche as well as heterografts of several sour cherry cultivars ( Prunus cerasus L. cvs Schattenmorelle, Weiroot 158, Köröser) were established. Successful graft formation in vitro was confirmed by translation of ⁸⁶Rb⁺ from the stock root into growing scion tissues. A mechanically strong graft union was formed during the course of a 3-week subculture of micrografts in a liquid medium without the addition of growth regulators. In the case of graft rejection, ⁸⁶Rb⁺ was mainly attracted to new developing shoots from lateral meristems of the stock plant. Histological examination of the graft union revealed callus formation, cytodifferentiation and xylogenesis leading to the formation of vascular connections. Stem elongation after micrografting was related to vigour of the stock and scion genotypes. Early stem elongation could be used as a criterion for preselection of growth vigour in graft combinations. Micrografts were transferred to soil and grown in the greenhouse.     

Differential susceptibility of heart, skin, and islet allografts to T cell-mediated rejection

Although it is widely accepted that there is a hierarchy in the susceptibility of different allografts to rejection, the mechanisms responsible are unknown. We show that the increased susceptibility of H-2K(b+) skin and islet allografts to rejection is not based on their ability to activate more H-2K(b)-specific T cells in vivo; heart allografts stimulate the activation and proliferation of many more H-2K(b)-specific T cells than either skin or islet allografts. Rejection of all three types of graft generate memory cells by 25 days posttransplant. These data provide evidence that neither tissue-specific Ags nor, surprisingly, the number of APCs carried in the graft dictate their susceptibility to T cell-mediated rejection and suggest that the graft microenvironment and size may play a more important role in determining the susceptibility of an allograft to rejection and resistance to tolerance induction.     

Preparation, characterization, and self-assembled properties of biodegradable chitosan-poly(L-lactide) hybrid amphiphiles

Biodegradable chitosan-graft-poly(L-lactide) (CS-g-PLLA) hybrid amphiphiles were prepared through direct grafting of a PLLA precursor to the backbone of CS. The average number of PLLA grafts per CS could be adjusted by the feed ratio of PLLA to CS, and it varied from 1.3 to 16.8. Moreover, both the crystallization rate and degree of crystallization of PLLA grafts with these graft copolymers could be adjusted by the chain length of PLLA and the number of PLLA grafts per CS, respectively. Meanwhile, CS-g-PLLA exhibited good solubility in some nonpolar and polar organic solvents compared with the original CS. Furthermore, self-assembled nanoparticles could be generated by direct injection of these graft copolymer solutions into distilled water, and their critical aggregation concentration decreased with increasing number of PLLA grafts per CS. The average size of the nanoparticles (25-103 nm) could be adjusted through the graft copolymer composition and the graft copolymer concentration, which was very different from the observations in ordinary PLLA-b-poly(ethylene oxide) amphiphiles. Significantly, this will provide a convenient method not only to combine the bioactive functions of CS with the good mechanical properties of biodegradable polymers, but also to generate nanoparticles with adjustable sizes for targeted drug release.     

Surgical techniques for a deep concha, a pseudomeatus, and high projection in congenital microtia

Some modified surgical techniques are described for constructing a deep conchal cavity and pseudomeatus and obtaining high auricular projection in congenital microtia. At the primary operation, a rather small portion of the microtic vestige is utilized for the lobule by switching, sparing the skin for the concha, with no free skin graft used. For higher projection of the auricle, three-dimensional transposition of a retroinfraauricular flap together with cartilage pieces underneath is applied to the cephaloauricular sulcus. A deep conchal cavity is constructed by further removal of the soft tissue there, transplantation of a cartilage for building a high posterior wall of the concha. The external meatus is successfully imitated by transplantation of a cone-shaped composite graft taken from the cymba of the opposite ear. The retroinfraauricular flap, the reconstruction of a deep concha, and the composite graft technique were successfully used in 55, 16, and 11 ears, respectively.     

Combined computational study of mechanical behaviour and drug delivery from a porous, hydroxyapatite-based bone graft

This paper presents a numerical model of a porous, hydroxyapatite-based bone graft also suitable as a drug delivery device. The graft was positioned in different sites and with different porosities inside a human femur model. The structural analyses were carried out to verify the graft mechanical strength, using the Tsai–Wu criterion, and the maximum porosity at which static failure does not occur. A local stress shielding risk was also calculated as the ratio between the bone stress in the intact condition and the stress after implantation of the graft. Drug release kinetics was calculated by means of the finite element method. High porosity grafts were found to fail in all implantation sites. Lower porosity grafts showed to have adequate strength if implanted in some positions, while provided insufficient resistance for other implantation sites. Drug release kinetics was found to be strongly dependent both on the porosity of the graft and the bone density near the bone-graft interface.     

Stability of polarity in the epidermis of a beetle, Tenebrio molitor L.

Cell polarity in the insect epidermis may be coupled to the orientation of anisometric cuticle components. Rotation of squares of sternite epidermis in the larva results in a corresponding rotation in the highly ordered orientation of cuticle fibers in the adult “crossply” cuticle. The patterns of fiber orientation resulting from graft rotation can be explained by the presence of an axial gradient of positional information.The polarity of the rotated tissue is, however, not fixed. Interaction between the polarity of the graft and host tissue may result in a partial shift of graft polarity toward the axial polarity of the host tissue. This interaction is apparently restricted to a limited period of the cell cycle: cell division. In Tenebrio, the sternite epidermis proliferates only once during metamorphosis, 140–90 hr before pupation. Rotational grafts performed before, during, and after this period present a graded series of “relaxation” patterns in fiber orientation in the graft area. Maximal graft repolarization coincides with maximal cell division on the sternite. The epidermal gradient, or cell response to the gradient, appears to be nonlinear along the segment.If no cell division intervenes between graft rotation and fiber deposition, graft polarity remains stable. This stability necessitates a “memory” component in the epidermis. It is suggested that periodic assessment of tissue polarity occurs concomitant with a particular process of cell division.     

Xanthan-g-poly(acrylamide): Microwave-assisted synthesis,characterization and in vitro release behavior

Xanthan-g-poly(acrylamide) was synthesized employing microwave-assisted and ceric-induced graft copolymerization, and was characterized by FT-IR, DSC, XRD and SEM studies. Matrix tablets of diclofenac sodium were formulated using graft copolymer as the matrix by direct compression technique. Release behavior of the graft copolymer was evaluated using USP type-II dissolution apparatus in 900 ml of phosphate buffer (pH 6.8), maintained at 37 °C and at 50 rpm. Microwave-assisted grafting provided graft copolymer with higher % grafting in a shorter time in comparison to the ceric-induced grafting. The % grafting was found to increase with the increase in the power of microwave and/or time of exposure. The matrix tablets were found to release the drug by zero-order kinetics, and the faster release of drug was observed from the graft copolymer matrix as compared to the xanthan gum matrix. It was observed that grafting reduces the swelling, but increases the erosion of xanthan gum.     

Effects of mechanical loading patterns,bone graft,and proximity to periosteum on bone defect healing

The goal of this study is to elucidate whether mechanobiological factors, including mechanical loading patterns, presence of bone graft, and proximity to the periosteum, correlate to de novo tissue generation and healing in critical sized long bone defects, which are enveloped by periosteum in situ and are bridged at 16 weeks, in sheep femora. Quantitative histomorphometric measures of defect cross sections show that, along the axis least able to resist bending loads (minor centroidal axis, CA), bone laid down in the first two weeks after surgery exhibits more mineralization albeit less total area compared to bone along the axis most able to resist bending loads (major CA). Similarly, areas of the cross section along the minor CA show a higher degree of perfusion albeit less total area of perfusion compared to bone along the major CA. Furthermore, proximity to the periosteal niche, in conjunction with the presence of bone graft and predominant loading patterns, relates significantly to the radial distribution of early bone apposition and perfusion of bone at 16 weeks after surgery (linear regression with R²>0.80). In the absence of graft, early bone density is relatively evenly distributed in the defect zone, as is the intensity of perfused tissue. As measured by a steeper average slope in intensity of fluorochrome (new bone) distribution between the periosteum and the IM nail, the presence of bone graft retards initial bone formation in the defect zone and is associated with less evenly distributed tissue perfusion (steeper slope) persisting 16 weeks after surgery. Finally, although the mean area of bone resorption is not significantly different within or between groups defined by the presence of graft and/or mechanical loading patterns in the defect zone, the mean area of infilling resorption spaces is significantly higher in areas of the defect zone least able to resist bending (minor CA) but is not significantly related to the presence of bone graft. To our knowledge, the use of the major and minor centroidal axes to relate prevailing mechanical loading patterns to area and density of early bone generation in bone defects has not been reported prior to this study and may provide a new means to assess structure–function relationships in de novo bone generation and healing of bone defects.     

Clinical significance, angiographic characteristics, and short-term outcomes in 30 patients with early coronary artery graft failure

BackgroundDespite technical advances in coronary artery bypass grafting (CABG), early postoperative myocardial ischaemia still remains a challenging problem. The aim of this study was to determine the incidence, clinical features, angiographic characteristics, and management of early graft failure in the present CABG era. MethodsBetween January 1997 and December 2002, 1731 patients underwent CABG at our institution. Coronary angiography was performed in patients with clinical evidence of early postoperative ischaemia (≤3 months). Thirty of these patients with graft failure constituted the population of this study. ResultsOff-pump and on-pump CABG were almost evenly performed in these patients [n=16 (53%) and n=14 (47%) respectively]. Acute myocardial infarction and unstable angina were the leading indications for coronary angiography in the majority of patients [n=28 (93%)]. The most common cause of graft failure was occlusion / thrombosis [n=20 (67%)]. Percutaneous coronary intervention (PCI) was offered to the majority of patients [n=22 (73%)]. Of these patients, 14 underwent PCI to native coronary arteries, whereas eight underwent PCI to the culprit vessel. Three patients underwent reoperation, and five received medical management. Four patients (13%) died in hospital (two after redo CABG, one after unsuccessful PCI, and one patient managed medically). Two patients (7%) had nonfatal major complications (one non-ST-elevation myocardial infarction and one stroke). ConclusionEarly graft failure generally presents as acute coronary syndrome. Graft occlusion/ thrombosis is the leading cause of ischaemia. Patients with graft failure can undergo PCI with a relatively low risk, but the need for redo CABG in associated with a high mortality. (Neth Heart J 2009;17:13-7.)     

Synthesis, characterization and thermal sensitivity of chitosan-based graft copolymers

Novel chitosan-based graft copolymers (CECTS-g-PDMA) were synthesized through homogeneous graft copolymerization of (N,N-dimethylamino)ethyl methacrylate (DMA) onto N-carboxyethylchitosan (CECTS) in aqueous solution by using ammonium persulfate (APS) as the initiator. The effect of polymerization variables, including initiator concentration, monomer concentration, reaction time and temperature, on grafting percentage was studied. XRD, FTIR, DSC and TGA were used to characterize the graft copolymers. Surface-tension measurements, turbidity measurements and temperature-variable (1)H NMR analysis were combined to investigate the thermal sensitivity of CECTS-g-PDMAs in aqueous solution.     

Allogeneic cell interactions during graft rejection in Callyspongia diffusa (Porifera, Demospongia); a study with monoclonal antibodies

Many aspects of the cellular immune system in the marine sponge Callyspongia diffusa, have been defined by using artificially transplanted allogeneic tissues. Rejections show specificity of 'non-self' recognition, cytotoxic effector responses and short-term immunological memory. Histological investigations reveal a generalized mesohyl migration to the graft zone where archaeocytes line up at the allogeneic interface. Monoclonal antibodies (mAbs) raised to sponge cells have shown that little or no allogeneic cell mixing occurs at the graft interface and that certain mesohyl cell types do not appear to be directly involved in graft rejections. However, all mesohyl cell types are present in autograft fusion zones and in inflammatory responses to injury. The involvement of only some of the mesohyl cell types in graft rejections suggests specific interactions of an effector 'immunocyte'.     

Leg regeneration in the cockroach,Blattella germanica

The interactions occuring between graft and host leg epidermis at a congruent junction (non-rotated, homopleural combination of components cut perpendicular to the proximal-distal axis) were studied at the tibia level in the cockroach,Blattella germanica. Grafts were made between dark (Bl) and light (br) cuticle colour mutants.

Autoradiographic and electron microscopic studies of minced cardiac muscle regeneration in the adult newt, notophthalmus viridescens.

The regenerative response of minced cardiac muscle grafts in the adult newt was studied using autoradiography and electron microscopy. One-sixteenth to one-eighth of the newt ventricle was amputated, minced, and returned to the wounded ventricle. At five days after grafting, no reorganization of graft msucle pieces was apparent and there was degeneration of much of the muscle graft. Another, smaller population of 5-day myocytes had euchromatic nuclei and intact sarcolemmae. In 10- and 16-day grafts, continuity between ventricular and graft lumina was established and coalescence of graft pieces was apparent. Ultrastructurally, 10- and 16-day graft myocytes appeared to have fewer myofibrillae and increased amounts of rough endoplasmic reticulum, polyribosomes, Golig complexes, and dense bodies when compared to uninjured ventricular myocytes. The peak of proliferative activity of graft cells was observed at 16 days. Electron microscopic autoradiography revealed breadkdown of myofibrillar structure in labeled myocytes, whereas in myocytes in the later stages of mitosis only scattered myofilaments and no Z bands were present. By 30 days, grafts appeared as an integrated structure composed primarily of cardiac muscle. Myocytes of 30-day grafts were observed in various stages of myofibrillogenesis and contained numberous 10-nm filaments. Seventy-day graft mycoytes had numberous well organized myofibrillae and intercellular junctions similar to those seen in uninjured ventricular myocytes.