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Biomedical subjects

J H Barker

Publications and source records attributed to J H Barker.

At least 19 recordsLinked to original sources
PubMed1999

Antiphospholipid antibodies from antiphospholipid syndrome patients activate endothelial cells in vitro and in vivo.

BACKGROUND: Antiphospholipid (aPL) antibodies are associated with thrombosis in patients diagnosed with antiphospholipid syndrome (APS) and enhance thrombus formation in vivo in mice, but the mechanism of thrombosis by aPL is not completely understood. Although aPL antibodies have been shown to inhibit protein C activation and activate endothelial cells (ECs) in vitro, no study has examined whether these antibodies activate ECs in vivo. Therefore, human affinity-purified aPL (ap aPL) antibodies from APS patients were tested in a mouse model of microcirculation using the cremaster muscle that allows direct microscopic examination of thrombus formation and adhesion of white blood cells (WBCs) to ECs as an indication of EC activation in vivo. Adhesion molecule expression on human umbilical vein endothelial cells (HUVECs) after aPL exposure was performed to confirm EC activation in vitro. METHODS AND RESULTS: All 6 ap aPL antibodies significantly increased the expression of VCAM-1 (2.3- to 4.4-fold), with one of the antibodies also increasing the expression of E-selectin (1.6-fold) on HUVECs in vitro. In the in vivo experiments, each ap aPL antibody except for 1 preparation increased WBC sticking (mean number of WBCs ranged from 22.7 to 50.6) compared with control (14.4), which correlated with enhanced thrombus formation (mean thrombus size ranged from 1098 to 6476 versus 594 microm2 for control). CONCLUSIONS: Activation of ECs by aPL antibodies in vivo may create a prothrombotic state on ECs, which may be the first pathophysiological event of thrombosis in APS.

Adult↗
PubMed1999

Characterisation of genetic diversity in potential biomass willows (Salix spp.) by RAPD and AFLP analyses.

The genus Salix (willow) contains a number of species which have great potential value as biomass crops in short rotation coppice (SRC). Efforts to improve biomass willows by breeding are currently hampered by the limited information available on genetic diversity and on genetic relationships within and among species, clones, and hybrids in the gene pool. Hybridisation occurs commonly in nature and the relatedness of many clones is unclear. Molecular markers were used to assess genetic diversity in a reference set of willows maintained within the U.K. National Collection and 16 elite clones currently being evaluated in field trials at several European sites. The two marker systems tested, RAPDs and AFLPs, were equally informative for revealing relationships within the reference set of clones. No differences were observed when alternative similarity coefficients were compared or when analysis was restricted to the use of polymorphic bands only. Good agreement with available knowledge of the clonal origins was obtained and one instance of duplicate clones was identified. AFLPs revealed more genetic diversity and discriminated between closely related clones. A difference in the relationships revealed was observed with one AFLP primer combination. RAPDs were more problematic, both in terms of reproducibility and scorability.

DNA, Plant↗
PubMed1998

Long-term composite tissue allograft survival in a porcine model with cyclosporine/mycophenolate mofetil therapy.

BACKGROUND: Low-dose cyclosporine (CsA)/mycophenolate mofetil (MMF) therapy has significantly reduced the frequency of rejection and drug-induced side effects in rat hindlimb allograft recipients. With an eye toward direct clinical application, we developed a large-animal extremity composite tissue allograft model to assess the antirejection efficacy and systemic toxicity of combination CsA/MMF treatment. METHODS: Radial forelimb osteomyocutaneous flap transplants were performed between size-matched, outbred pigs assigned to one of two groups: 5 control pigs received no immunosuppression, and 10 pigs received a once-daily oral CsA/MMF/prednisone regimen. Rejection was assessed by visual inspection of flap skin and correlated with serial histopathologic examination of skin biopsies. RESULTS: In all control pigs, the flap was completely rejected on day 7. Of the 10 pigs receiving treatment, one died from pneumonia and an another from an anesthetic complication on days 19 and 30, respectively, without signs of rejection. Two flaps were lost on days 25 and 29 from severe rejection. Three pigs were free of rejection at the end of the 90-day follow-up period, and three had stable mild-to-moderate rejection at 90 days (P= 0.0007 vs. controls). White blood cell and platelet counts, serum creatinine values, and liver function tests remained normal in all animals receiving immunosuppressive therapy. CONCLUSIONS: Our results, to our knowledge, demonstrate for the first time that rejection can be significantly delayed in a large-animal composite tissue allograft model including skin using only orally administered agents dosed according to clinically relevant strategies without significant drug-specific systemic side effects.

Animals↗
PubMed1998

Do leukocytes contribute to impaired microvascular tissue perfusion after arterial repair?

Impaired capillary perfusion may result in flap failure. Platelet emboli, polymorphonuclear leukocytes (PMNs), and/or vasospasm have been identified as possible causes. This study investigates the role of PMNs in causing impaired capillary perfusion in a free flap model. PMN concentrations were depleted using antineutrophil serum. The cremaster muscles of 20 Sprague-Dawley rats were isolated on a single neurovascular pedicle and after a simulated technically poor arterial anastomosis upstream and reperfusion, capillary perfusion was measured each hour for 6 hours. Even though the number of PMNs was significantly reduced in the animals treated with antineutrophil serum, capillary perfusion was not changed compared with controls. These results demonstrate that depleting circulating PMNs does not protect capillary perfusion in our model. These findings suggest that reduced capillary perfusion downstream from an anastomotic repair is not mediated by the presence of PMNs in the microcirculation.

Anastomosis, Surgical↗
PubMed1998

Leukocyte behavior in a free-flap model following chemotherapy and application of granulocyte colony-stimulating factor (GCSF).

Free-flap reconstruction following tumor resection and chemotherapy is used increasingly in sarcoma patients. Granulocyte colony-stimulating factor (GCSF) is used to stimulate polymorphnuclear leukocytes (PMNs). In this study we used a free-flap model to investigate PMN behavior after chemotherapy and GCSF stimulation. Eighteen Lewis rats were divided into three groups: (1) chemotherapy + vehicle; (2) chemotherapy + GCSF; and (3) control. Group 1 received vinblastine; group 2 received vinblastine plus 300 microg rhGCSF. Blood was drawn for total white cell and PMN counts for 9 days. Free-flap surgery was simulated by isolating the cremaster muscle on its pedicle and anastomosing the artery. Leukocyte-endothelium interaction was assessed by observation of leukocytes rolling and sticking. Leukocyte sequestration was measured by counting leukocytes in the lungs and the abdomen. We found that leukocyte rolling and sticking were significantly increased, while sequestration was decreased in the chemotherapy + GCSF group. We conclude that leukocytes-endothelium interaction after chemotherapy and GCSF administration is increased in the microcirculation. This augments the risk of microvascular compromise and subsequent flap failure, as capillary flow may be altered.

Animals↗
PubMed1998

Effect of granulocytes on the microcirculation in free-flap surgery.

INTRODUCTION: Impaired capillary perfusion may result in flap failure. Platelet emboli, vasospasm and/or polymorphonuclear leukocytes (PMNs) have been identified as possible causes. This study investigates the role of PMNs in causing impaired capillary perfusion in a free-flap model. METHODS: Sprague-Dawley rats were injected with either anti-neutrophil serum or saline. Their cremaster muscle was isolated on its pedicle. After arterial repair and reperfusion, capillary perfusion was counted each hour for 6 h. RESULTS: The number of PMNs was significantly reduced in the animals treated with anti-neutrophil serum. However, capillary perfusion did not improve in this group. CONCLUSIONS: These results demonstrate that depleting circulating PMNs does not counterbalance the reduction of perfused capillaries, i.e., does not increase their number. It is suggested that reduced capillary perfusion downstream from an anastomotic repair is not mediated by the presence of PMNs in the microcirculation.

Anastomosis, Surgical↗
PubMed1998

Muscular urinary sphincter: electrically stimulated myoplasty for functional sphincter reconstruction.

PURPOSE: To reconstruct an electrically stimulated muscular urinary sphincter (MUS) using a tailored gracilis muscle free flap with intact nerve. MATERIALS AND METHODS: Unilateral surgically tailored gracilis muscle free flaps were transferred into the pelvis in eight dogs, leaving the obturator nerve intact. The muscle's pedicle vessels were anastomosed to the inferior epigastric artery and vein in the pelvis and the muscle was wrapped around the bladder neck. Electrodes were inserted into the MUS and connected to a programmable pulse generator. After 8 weeks of training the MUS, the pulse generator was programmed to be "on" for 4 hours and "off' for 15 minutes in a continuous cycle. Urodynamic studies were performed periodically, and at the end of the experiment the MUS and proximal urethra were harvested for histology. Three control dogs had sham operations. RESULTS: All MUS's functioned well following the procedure. Histology of the MUS/urethra complex showed no evidence of stricture. Except for one dog, all urethras were easily catheterized. CONCLUSIONS: This electrically stimulated innervated free-flap MUS technique effectively increases bladder outlet resistance without producing urethral obstruction.

Animals↗
PubMed1998

Electrically stimulated free-flap graciloplasty for urinary sphincter reconstruction: a new surgical procedure.

In electrically stimulated (dynamic) graciloplasty for urinary incontinence, the gracilis muscle is transposed into the pelvis, and the distal part is used to reconstruct a neosphincter. Clinical outcomes using this technique have been disappointing due to stricture of the urethra caused by ischemia in the distal part of the gracilis and limited gracilis length available for neosphincter construction. Furthermore, the urethra is twisted by the contracting gracilis, rather than circumferentially squeezed. The purpose of the present study was to test the anatomical and functional feasibility of a new surgical approach to reconstruct a urinary sphincter, using the gracilis muscle as a free flap. In 12 human cadavers, the anatomical feasibility for creating a neosphincter by using the gracilis free flap was determined. In all cases, transfer of the gracilis muscle into the pelvis as a free flap (with the nerve intact) was feasible, and ample muscle was available to construct a neosphincter around the bladder neck. Gracilis neosphincter function was studied in seven dogs. The left gracilis muscle was subjected to transfer into the pelvis as an innervated free flap to create a neosphincter around the urethra. The right (control) gracilis muscle was lifted as a single pedicle flap, remained in situ, and was wrapped around a stent to mimic the urethra. Function (expressed as peak pressure generation and fatigue rate) and surface perfusion were determined for all gracilis muscles. In each dog, both sides were compared using the paired Student's t test for statistical analysis, and no significant difference was measured for the two groups. In conclusion, an innervated gracilis free flap can be used to create a neosphincter around the bladder neck. In an acute study in dogs, function and perfusion of the innervated gracilis free flap are not compromised.

Animals↗
PubMed1998

Augmentation of skeletal muscle flap survival using platelet derived growth factor.

Distal muscle flap ischemia and necrosis is a recognized complication of acute elevation of large skeletal muscle flaps. The aim of this study was to investigate whether the angiogenic properties of platelet derived growth factor (PDGF) could be used to augment skeletal muscle flap survival through the induction of new blood vessel formation before flap elevation. We compared this form of flap augmentation with that achieved by subjecting the muscle to a bipedicled vascular delay procedure. The animal model used was the latissimus dorsi muscle of the male homozygous (hr/hr) hairless mouse. Four groups of animals were investigated in this study (n = 10 per group). Group 1 was the control group in which the entire muscle was elevated as a thoracodorsally based island flap. In group 2, the muscle was subjected to a bipedicled vascular delay procedure. In group 3, the muscle was treated with 500 microg of recombinant human platelet derived growth factor BB. In group 4, the muscle was treated with placebo. Ten days later the entire latissimus dorsi muscle was elevated as a thoracodorsally based island flap in groups 2, 3, and 4. Percentage muscle flap survival was quantitated in all groups 5 days after elevation of the entire muscle. Angiogenesis was then quantitated by analyzing capillary to muscle fiber ratios after alkaline phosphatase staining of representative latissimus dorsi muscle samples from the proximal, middle, and distal flap segments. Percentage muscle flap survival was significantly better in PDGF treated muscles when compared with the vascularly delayed muscles (p < 0.001). Histologic analysis of latissimus dorsi muscle flaps demonstrated a significantly greater number of capillaries in the middle (p < 0.001) and distal (p < 0.001) flap segments of PDGF-treated flaps when compared with the vascularly delayed flaps. Treatment of skeletal muscle with PDGF before flap creation resulted in survival of the entire muscle flap. Our results suggest that this survival may be secondary to PDGF-induced angiogenesis.

Animals↗
PubMed1998

Thrombogenic properties of antiphospholipid antibodies do not depend on their binding to beta2 glycoprotein 1 (beta2GP1) alone.

Immunization of mice with beta2glycoprotein 1 (beta2GP1) induces production of antiphospholipid (aPL) antibodies, which were shown to have thrombus enhancing properties in an experimental mouse model, indicating that these antibodies are thrombogenic in vivo. To determine whether the thrombogenic effect of murine antiphospholipid antibodies is due to their aPL or their anti-beta2GP1 activity, we injected mice with murine monoclonal anticardiolipin (aCL) and anti-beta2GP1 antibodies. Effects of these antibodies on thrombus formation, was evaluated utilizing a mouse model which enables kinetics of thrombus formation to be studied. The results of this study showed that the size of the thrombus in animals injected with murine aCL antibodies was larger than that in control groups. There was no difference in thrombus kinetics between anti-beta2GP1 injected mice and controls, suggesting that the thrombogenic effect of aPL antibodies is not related to their anti-beta2GP1 activity alone. Mice receiving monoclonal antibodies with both aCL and anti-beta2GP1 activity, also increase thrombus size when compared with controls. These data indicate that murine aCL, but not anti-beta2GP1, antibodies are thrombogenic in vivo.

Animals↗
PubMed1998

Modern therapy of chronic wounds with respect to radiation.

BACKGROUND: Descriptions of wound care techniques have been found in some of the oldest archeological findings and chronic wounds have been threaded man thousands of years. However, only in the last few decades substantial progress has been made in understanding the cellular and biochemical processes relevant in normal healing. PATHOPHYSIOLOGY: Wound healing is a complex process involving a variety of different cells, proteins, chemoattractants, proteinases and growth factors. The normal repair process is a coordinated cellular and biochemical event and can be characterized by 3 different healing phases (inflammatory, proliferative, and remodeling phase). Certain pathophysiologic conditions and metabolic disorders alter this preprogrammed course, leading to delayed healing or chronic non-healing wounds. DISTURBANCE OF WOUND HEALING AFTER RADIATION: Especially irradiation can complicate tissue repair and surgical wound healing. Therefore this article will review the basic understanding of the wound healing process and the knowledge of modern surgical and conservative wound therapy from a surgical point of view, which is essential to surpass pathophysiological situations and avoid chronic wounds.

Chronic Disease↗
PubMed1997

Hydroxychloroquine reverses thrombogenic properties of antiphospholipid antibodies in mice.

BACKGROUND: Previous studies have demonstrated that human monoclonal and polyclonal anticardiolipin antibodies have thrombogenic properties in vivo. Using such a model in which these antibodies have been shown to increase both the size of an induced thrombus and the duration of time in which such a clot lasts, we investigated whether hydroxychloroquine alters the dynamics of such thrombus formation. METHODS AND RESULTS: Three groups of nine mice were injected with purified immunoglobulin G (IgG) from a patient with the antiphospholipid syndrome (IgG-APS) and then fed with hydroxychloroquine at various doses (100, 6, and 3 mg/kg body wt). Three control groups of mice were also studied, including mice injected with IgG-APS and then fed with placebo, as well as two other groups injected with IgG from normal human serum and fed either hydroxychloroquine or placebo. A standardized thrombogenic injury was subsequently induced in the femoral vein of each mouse and the area (size) of thrombus measured as well as the total period of time that thrombus was present. Mice treated with hydroxychloroquine and IgG-APS showed significantly smaller thrombi that persisted for a shorter period of time compared with animals treated with IgG-APS and placebo. CONCLUSIONS: Hydroxychloroquine significantly diminished both thrombus size and total time of thrombus formation in mice previously injected with IgG-APS.

Animals↗
PubMed1997

Inhibition of wound contraction with locally injected lathyrogenic drugs.

BACKGROUND: Previous studies using systematically administered lathyrogens to inhibit wound contractures have produced inconsistent results. The purpose of this study was to investigate the effects of lathyrogenic drugs on wound contraction when injected locally. METHODS: Two symmetrical full-thickness wounds were made on the dorsum of either side of hairless (hr/hr) mice; thus, each animal served as its own control. Animals were divided into groups receiving daily local injections of beta-aminopropionitrile or D-penicillamine, or both beta-aminopropionitrile and D-penicillamine and normal saline vehicle (control side) for 5 or 10 days. The rate of contraction was determined by serial measurements of the surface area of each wound during the treatment period. At the end of the treatment period, the wounds were excised en bloc with the chest wall and prepared for blinded histological analysis. Granulation tissue thickness, number of fibroblasts in granulation tissue per unit area, number of inflammatory cells (neutrophils, lymphocytes, macrophages and mast cells) in subjacent muscle per unit area, and collagen deposition in subjacent muscle were determined. RESULTS: Wound contraction, granulation tissue thickness, and collagen deposition in subjacent muscle were decreased only in wounds treated with beta-aminopropionitrile plus D-penicillamine. Collagen deposition in subjacent muscle was also decreased in wounds treated with D-penicillamine alone. Neither drug alone nor the combination affected the number of inflammatory cells in subjacent muscle. Body weight was not affected by the experimental procedures. CONCLUSIONS: The combination of beta-aminopropionitrile and D-penicillamine is potentially useful for inhibiting contracture formation when injected locally.

Aminopropionitrile↗
PubMed1997

Vascular delay of the latissimus dorsi muscle: an essential component of cardiomyoplasty.

BACKGROUND: Cardiomyoplasty (CMP) uses the latissimus dorsi muscle (LDM) to assist the heart in cases of cardiac failure. Distal ischemia and necrosis of the LDM is a recognized complication of CMP that can reduce distal muscle function and the mechanical effectiveness of CMP. METHODS: Canine (n = 9) LDMs were subjected to a 10-day period of vascular delay followed by a simulated CMP. Two weeks after simulated CMP (corresponding to the healing delay between CMP and the onset of LDM stimulation used in the clinical setting), LDM perfusion was measured in the distal, middle, and proximal segments of the muscle, and circumferential (distal and middle squeezing muscle function) and longitudinal (proximal pulling muscle function) force generation and fatigue rates were measured. The results were compared with the contralateral nondelayed simulated CMP. RESULTS: Muscle perfusion was significantly (p < 0.05) greater in the distal and middle segments of vascular-delayed LDMs. Circumferential muscle force generation and fatigue rates were significantly (p < 0.05) improved in the vascular-delayed LDMs. CONCLUSIONS: Vascular delay can significantly improve LDM perfusion and function in a model that closely reflects clinical CMP, and the use of vascular delay may improve clinical outcomes in CMP.

Animals↗
PubMed1997

Platelet-derived thromboxane A2 decreases microvascular perfusion after arterial repair.

Previous work suggests that cod liver oil helps to protect the microcirculation from the consequence of thromboembolic events. The possibility that altered synthesis of thromboxane A2 accounts for the protective effects seen with cod liver oil was investigated in the present study. This was done using the combined thromboxane A2 synthetase inhibitor and thromboxane A2-prostaglandin H2 receptor blocker R68070 (Ridogrel). A standardized microvascular injury was inflicted on the right iliac artery of the rat to generate emboli. The downstream cremaster muscle was used to visualize the passage of the ensuing emboli and to assess the effects of this arterial injury on capillary perfusion and arteriole diameters. The number of visible emboli was not changed by either cod liver oil diet or Ridogrel administration. However, capillary perfusion was preserved by using cod liver oil (n = 7) and was significantly increased by using Ridogrel (n = 7) in comparison with untreated controls (n = 7) in which capillary perfusion was decreased because of the emboli. The administration of Ridogrel to cod liver oil-treated animals (n = 7) provided no additive benefit. The percentage change in A-2 vessel diameters in cod liver oil-treated (n = 7) animals was no different from the control group (n = 7). Ridogrel (n = 7), on the other hand, produced a significant increase in A-3 vessel (n = 21) diameters, but its effects were comparatively less in the cod liver oil-treated animals (n = 7). The formation of platelet aggregates (emboli) appears relatively independent of thromboxane A2 in the rat. Ridogrel is very effective in protecting the microcirculation, and these effects appear to be mediated by A-3 vasodilatation, which, therefore, is at least partially thromboxane A2-dependent. The positive effects of cod liver oil may be mediated by a mechanism that reduces thromboxane A2 synthesis, but further studies are necessary.

Animals↗
PubMed1997

Effect of low dose aspirin on thrombus formation at arterial and venous microanastomoses and on the tissue microcirculation.

In free flap/replantation surgery, failure is usually associated with thrombotic occlusion of a microvascular anastomosis (risk zone I) or, on occasion, flow impairment in the microcirculation of the transferred or replanted tissue (risk zone II). The objective of this study is to describe the effect of low dose aspirin on blood flow at both risk zones in microvascular surgery. Risk zone I: In rat femoral arteries and veins, thrombus formation was measured at the anastomoses using transillumination and videomicroscopy. Forty male Wistar rats were assigned in equal numbers to four groups: either arterial or venous injury with either aspirin (5 mg/kg systemically) or saline treatment. We found that aspirin significantly reduces thrombus formation at the venous anastomosis (p = 0.001). Risk zone II: In the isolated rat cremaster muscle downstream from an arterial anastomosis, we measured capillary perfusion, arteriolar diameters, and the appearance of platelet emboli for 6 hours in the muscle microcirculation. Sixteen male Wistar rats in two equal groups received either aspirin (5 mg/kg systemically) or saline. We found that in aspirin-treated animals, capillary perfusion is significantly (p = 0.002) improved, whereas arteriolar diameters and emboli only slightly increased. In conclusion, low dose aspirin inhibits anastomotic venous thrombosis and improves microcirculatory perfusion in our rat model. These studies provide quantitative data confirming and clarifying the beneficial effects of low dose aspirin in microvascular surgery.

Anastomosis, Surgical↗