Biomedical subjects

C J Green

Publications and source records attributed to C J Green.

At least 19 recordsLinked to original sources

PubMed2006

Positive inotropic effects of carbon monoxide-releasing molecules (CO-RMs) in the isolated perfused rat heart.

BACKGROUND AND PURPOSE: Carbon monoxide (CO) generated by the enzyme haeme oxygenase-1 (HO-1) during the breakdown of haeme is known to mediate a number of biological effects. Here, we investigated whether CO liberated from two water soluble carbon monoxide-releasing molecules (CO-RMs) exerts inotropic effects on the myocardium. EXPERIMENTAL APPROACH: Rat isolated hearts perfused either at constant flow or constant pressure were used to test the effect of CO-RMs. KEY RESULTS: CORM-3, a fast CO releaser, produced a direct positive inotropic effect when cumulative doses (3, 10 and 30 microg min(-1)) or a single dose (5 microM) were infused at either constant coronary pressure (CCP) or constant coronary flow (CCF). The inotropic effect mediated by CORM-3 was abolished by blockade of soluble guanylate cyclase or Na(+)/H(+) exchanger, but not by inhibitors of L-type Ca(2+) channels and protein kinase C. CORM-3 also caused a slight reduction in heart rate but did not alter coronary flow. In contrast, the slow CO releaser CORM-A1 produced significant coronary vasodilatation when given at the highest concentration (30 mug min(-1)) but exerted no effect on myocardial contractility or heart rate. CONCLUSION AND IMPLICATIONS: A rapid CO release from CORM-3 exerts a direct positive inotropic effect on rat isolated perfused hearts, whereas CO slowly released by CORM-A1 had no effect on myocardial contractility but caused significant coronary vasodilatation. Both cGMP and Na(+)/H(+) exchange appear to be involved in this effect but further work is needed to determine the relative contribution of each pathway in CO-mediated inotropic effect.

Alkaloids↗

PubMed2006

Morphometric placental villous and vascular abnormalities in early- and late-onset pre-eclampsia with and without fetal growth restriction.

OBJECTIVE: To evaluate placental morphology in pregnancies complicated by early- and late-onset pre-eclampsia (PET) with and without fetal growth restriction (FGR) using stereological techniques. DESIGN: A total of 69 pregnant women were studied. Twenty women had pregnancies complicated by PET, 17 by FGR and 16 by both PET and FUR; the remaining 16 were from gestational-age-matched controls. Each group was further classified into early onset (<34 weeks) and late onsets (>34 weeks) based on gestational ages. SETTING: NPIMR at Northwick Park and St Marks Hospital. POPULATION: placentae from pregnant women. METHODS: Formalin-fixed, wax-embedded sections stained with anti-CD34 antibodies and counterstained with haematoxylin. MAIN OUTCOME MEASURES: Volumes, surface areas, lengths, diameters and shape factors of the villous tissues and fetal vasculature in the intermediate and terminal villi of all the groups studied. RESULTS: Terminal villi volume and surface area were compromised in early-onset PET cases, late-onset PET had no impact on peripheral villi or vasculature features. The morphology of the vascular and villous subcomponents in the intermediate and terminal villi was significantly influenced by late-onset FGR, whereas early-onset FGR caused a reduction in placental weight. Length estimates were not influenced by PET, FGR or age of onset. Intermediate arteriole shape factor was significantly reduced in late-onset FGR. CONCLUSIONS: Isolated early-onset PET was associated with abnormal placental morphology, but placentas from late-onset PET were morphologically similar to placentas from gestational-age-matched controls, confirming the existence of two subsets of this condition and supporting the hypothesis that late-onset PET is a maternal disorder and not a placental disease.

Adult↗

PubMed2006

Treatment with CO-RMs during cold storage improves renal function at reperfusion.

Low concentrations of carbon monoxide (CO) can protect tissues against ischemia-reperfusion (I-R) injury. We have recently identified a novel class of compounds, CO-releasing molecules (CO-RMs), which exert important pharmacological activities by carrying and delivering CO to biological systems. Here, we examined the possible beneficial effects of CO liberated from CO-RMs on the damage inflicted by cold storage and I-R in isolated perfused kidneys. Hemodynamic and biochemical parameters as well as mitochondrial respiration were measured in isolated perfused rabbit kidneys that were previously flushed with CO-RMs and stored at 4 degrees C for 24 h. Two water-soluble CO-RMs were tested: (1) sodium boranocarbonate (CORM-A1), a boron-containing carbonate that releases CO at a slow rate, and (2) tricarbonylchloro(glycinato)ruthenium(II) (CORM-3), a transition metal carbonyl that liberates CO very rapidly in solution. Kidneys flushed with Celsior solution supplemented with CO-RMs (50 microM) and stored at 4 degrees C for 24 h displayed at reperfusion a significantly higher perfusion flow rate (PFR), glomerular filtration rate, and sodium and glucose reabsorption rates compared to control kidneys flushed with Celsior solution alone. Addition of 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor, prevented the increase in PFR mediated by CO-RMs. The respiratory control index from kidney mitochondria treated with CO-RMs was also markedly increased. Notably, renal protection was lost when kidneys were flushed with Celsior containing an inactive compound (iCO-RM), which had been deliberately depleted of CO. CO-RMs are effective therapeutic agents that deliver CO during kidney cold preservation and can be used to ameliorate vascular activity, energy metabolism and renal function at reperfusion.

Animals↗

PubMed2005

Reviewing the use of carbon monoxide-releasing molecules (CO-RMs) in biology: implications in endotoxin-mediated vascular dysfunction.

The inducible stress protein heme oxygenase-1 (HO-1) has been linked to tissue and organ protection against the deleterious actions of many pathological conditions, including endotoxin challenge. Similar protection can be achieved by the main products of heme oxygenase activity, namely bilirubin and carbon monoxide (CO). Since the identification of novel chemical compounds that liberate CO in biological systems (CO-releasing molecules or CO-RMs), our group and others have had access to a convenient and simple pharmacological tool that enables to study the role of CO in physiological functions. This article will review the scientific literature published to date on CO-RMs, with emphasis on the in vitro, ex vivo and in vivo experimental models employed to determine the contribution of CO to cellular mechanisms. In addition, we will report on the effect of heme oxygenase-related substances, such as bilirubin, CORM-3 and hemin, in a model of endotoxin-induced hypotension. Among the three different approaches examined, CORM-3 proved the most effective agent in reducing the fall in blood pressure caused by endotoxin. Furthermore, heme oxygenase-related substances affected the endotoxin-stimulated induction and distribution of hepatic HO-1 and inducible nitric oxide synthase (iNOS). Thus, it emerges that CO-RMs could exert important biological actions in the context of endotoxic-mediated dysfunction.

Animals↗

PubMed2005

Carbon monoxide-releasing molecules (CO-RMs) modulate respiration in isolated mitochondria.

Emerging evidence reveals that heme oxygenase-1 (HO-1) and its product carbon monoxide (CO) can exert diverse biological and cytoprotective effects. Our group has recently identified a new class of compounds (CO-releasing molecules or CO-RMs) that can carry and deliver CO to biological systems and can be used to examine the physiological properties of CO. Here, we evaluated the influence of endogenously-generated CO (via HO-1 induction by hemin) and CO liberated from exogenously supplied CO-RMs on mitochondrial function. Renal mitochondria were isolated either from rats with increased HO-1 or from untreated animals, the latter being exposed to different concentrations of CO-RMs (10-100 microM). We found that mitochondrial oxygen uptake was significantly reduced in kidneys after HO-1 induction and, in a similar fashion, CO-RMs inhibited mitochondrial function in a concentration-dependent manner. Specifically, a marked depression of state 3 was observed resulting in a significant decrease in respiratory control index (RCI) values. When mitochondria were incubated with the inactive forms of CO-RMs, which are devoid of CO, the respiratory parameters remained unchanged. In summary, the results indicate that HO-1 induction and enhanced CO decrease renal oxygen consumption and alter mitochondrial function suggesting that CO could be a physiological regulator of mitochondrial oxidative phosphorylation.

Animals↗

PubMed2005

Pre-eclampsia and fetal growth restriction: how morphometrically different is the placenta?

Both pre-eclampsia (PET) and fetal growth restriction (FGR) pose a heavy burden on fetal and maternal health and may disrupt pregnancy outcome. Using design based stereological techniques, placental vascular and villous morphology were assessed to determine the individual role played by both PET and FGR on placental growth during the third trimester. The following placentas delivered between 25 and 41 weeks of gestation were included into the study; controls (n=16), PET (n=20), FGR (n=17) and PET-FGR (n=16). Each placenta was uniformly randomly sampled and the sampled tissue processed to paraffin. Sections were stained with a CD34 antibody and the following morphometric parameters estimated: volumes, surface areas, length, diameters and the shape factor of the villous (terminal and intermediate) and vascular placental features. For stereologically estimated parameters pure PET had an effect on IVS and terminal villi volume only. FGR alone or when coexisting with PET contributed towards significant reductions in volumetric and surface area terminal villous and vascular features. FGR factors also contributed towards a significant reduction in the lengths of all parameters estimated and in the terminal villi diameter. Additionally, FGR was associated with a significant difference in shape factor indices for both intermediate and terminal villi. This study has shown that PET on its own has limited influence on the placental morphology studied, since the vascular features estimated do not differ stereologically from age matched normal controls. However, placental morphology is different between PET and PET-FGR and between PET-FGR and FGR. PET and FGR may have a cumulative effect on placental villous and vascular morphology as seen in the PET-FGR but there is no synergistic effect. These morphological abnormalities may have major physiological implications in terms of placental function and fetal growth.

Adult↗

PubMed2005

Histological evaluation of Permacol as a subcutaneous implant over a 20-week period in the rat model.

This study assessed the suitability of Permacol (a porcine derived, isocyanate cross linked collagen based biomaterial) as an alternative to autologous tissue in soft tissue reconstruction. The Sprague-Dawley rat was used as a model for subcutaneous implantation over a 20 week period and comparison made with two other porcine biomaterials (small intestinal submucosa and glycerol treated-ethylene oxide sterilised porcine dermis). Implants were scored histometrically on the degree of acute inflammation, chronic inflammation, fibrosis and stromal response. The vascularity and percentage composition of collagen within Permacol were assessed by stereology and seescan image analysis, respectively. In general terms, Permacol was well tolerated as a subcutaneous implant, with only a minor chronic inflammatory response remaining after a 20 week period of implantation. There was evidence of collagen degradation during this period and vascular ingrowth into Permacol was limited. Permacol has the potential for a broad range of applications in plastic surgery, but may benefit from modification to promote a more rapid degree of vascularisation.

Acute Disease↗

PubMed2005

Do seasonal changes in metabolic rate facilitate changes in diving behaviour?

Macaroni penguins were implanted with data loggers to record heart rate (fH), abdominal temperature (Tab) and diving depth during their pre-moult trip (summer) and winter migration. The penguins showed substantial differences in diving behaviour between the seasons. During winter, mean and maximum dive duration and dive depth were significantly greater than during summer, but the proportion of dives within the calculated aerobic dive limit (cADL) did not change. Rates of oxygen consumption were estimated from fH. As winter progressed, the rate of oxygen consumption during dive cycles (sVO2DC)) declined significantly and mirrored the pattern of increase in maximum duration and depth. The decline in sVO2DC) was matched by a decline in minimum rate of oxygen consumption (sVO2min)). When sVO2min) was subtracted from sVO2DC), the net cost of diving was unchanged between summer and winter. We suggest that the increased diving capacity demonstrated during the winter was facilitated by the decrease in sVO2min). Abdominal temperature declined during winter but this was not sufficient to explain the decline in sVO2min). A simple model of the interactions between sVO2min), thermal conductance and water temperature shows how a change in the distribution of fat stores and therefore a change in insulation and/or a difference in foraging location during winter could account for the observed reduction in sVO2min) and hence sVO2DC).

Animals↗

PubMed2004

Evaluation of a porcine origin acellular dermal matrix and small intestinal submucosa as dermal replacements in preventing secondary skin graft contraction.

The degree to which a split thickness skin graft (STSG) contracts after application to its recipient bed is related in part to the proportion of the dermis harvested from the donor site. Harvesting thicker skin grafts may produce better cosmetic results in the recipient bed but result in increased donor site morbidity. The combination of an autologous ultra thin split thickness graft with an underlying non-autologous dermal component may reduce secondary skin graft contraction without further increasing donor site morbidity. This study was aimed at assessing the suitability of two porcine derived biomaterials (Permacol and small intestinal submucosa, SIS) for use in combination with skin grafts in a Sprague-Dawley rat model. Full thickness wounds (1 cm(2)) were created in Sprague-Dawley rats and grafted with skin in combination with Permacol or SIS either as a one-stage operation or following a 2-week-period of vascularisation of these dermal matrices before a second stage operation to cover with skin. Skin graft viability and wound area were assessed at weekly intervals until 4 weeks after graft application. Both Permacol and SIS were able to support an overlying skin graft but had no beneficial effect on skin graft contraction in this model compared to skin grafts alone.

Animals↗

PubMed2004

The diamond CO2 laser as a method of improving the vascularisation of a permanent collagen implant.

For a biomaterial to be considered as anything other than a simple filler material it must allow a certain degree of ingrowth from the surrounding host tissues. Permacol is a novel porcine derived biomaterial that is isocynate crosslinked to prevent its degradation in vivo, but while it appears to be biocompatible in terms of its histological tissue response, our early studies demonstrate only a limited degree of fibrovascular ingrowth. The aim of this study was to assess the effectiveness of both laser perforations and topically applied VEGF as methods of encouraging fibrovascular ingrowth. Treatment of Permacol with the diamond CO(2) laser significantly increased the porosity of the material as assessed by seescan image analysis. Fibrovascular ingrowth as assessed in the Sprague-dawley rat model was found to be limited to the pores themselves and not the surrounding native matrix. Pre-soaking of laser treated Permacol in vascular endothelial growth factor (VEGF) did not further increase fibrovascular ingrowth. Increasing the porosity of Permacol may allow its use as a dermal replacement in the support of an overlying skin graft or keratinocyte sheet; however using the laser may not be the optimal method of achieving this aim.

Animals↗

PubMed2004

Analyses of the potential oxygen transfer capability in placentae from infants succumbing to sudden infant death syndrome.

BACKGROUND: Morphometric oxygen diffusive conductance (Dp) was estimated to assess the potential efficiency of oxygen transfer across the materno-fetal interface in placentae obtained from victims of sudden infant death syndrome (SIDS). STUDY DESIGN: SIDS placentae were retrieved from archived storage and classified into normal birth weight (NBW, n=16), or small for gestational age (SGA, n=9) and compared against control placentae (n=40) or SGA (n=24) placentae. A combination of stereological techniques and physiological constants were used to estimate total Dp. RESULTS: SIDS NBW cases showed a crucial reduction in fetal capillary surface area when compared with control placentae. SIDS SGA showed a number of deficiencies in basic volumetric and surface area parameters. Values for total and specific Dp in placentae in both SIDS groups were maintained at levels comparable with control and SGA cases, respectively. CONCLUSION: Since more reductions were observed in SIDS SGA group, this suggests that factors responsible for these reductions maybe associated with SGA rather than being SIDS-specific factors.

Adult↗

PubMed2003

Ecological interference between fatal diseases.

An important issue in population biology is the dynamic interaction between pathogens. Interest has focused mainly on the indirect interaction of pathogen strains, mediated by cross immunity. However, a mechanism has recently been proposed for 'ecological interference' between pathogens through the removal of individuals from the susceptible pool after an acute infection. To explore this possibility, we have analysed and modelled historical measles and whooping cough records. Here we show that ecological interference is particularly strong when fatal infections permanently remove susceptibles. Disease interference has substantial dynamical consequences, making multi-annual outbreaks of different infections characteristically out of phase. So, when disease prevalence is high and is associated with significant mortality, it might be impossible to understand epidemic patterns by studying pathogens in isolation. This new ecological null model has important consequences for understanding the multi-strain dynamics of pathogens such as dengue and echoviruses.

Acute Disease↗

PubMed2003

Prefabricated skin flaps in a rat model based on a dermal replacement matrix Permacol.

The reconstruction of three-dimensional structures is one of the most challenging problems in plastic surgery. While shaped frameworks incorporated within soft tissue envelopes often lose their fine detail, the integration of a blood supply to a stable biomaterial scaffold allows skin graft cover and emphasis of fine detail. The aim of this study was to evaluate whether a porcine derived isocyanate crosslinked collagen tissue matrix (Permacol) could be vascularised from an isolated vascular pedicle and subsequently sustain an overlying skin graft as a pedicled prefabricated flap. A vascular induction technique was employed using the epigastric pedicles in Sprague-Dawley rats to vascularise 2 x 2 cm(2) pieces of Permacol of standard 0.75 and 1.5 mm thickness Permacol and laser treated Permacol of 0.4 and 0.75 mm thickness. Flaps were able to support overlying skin grafts as early as 2 weeks following vessel implantation and laser treated Permacol had an increased vascularity compared to standard Permacol with no evidence of degradation. The study showed that Permacol could be a useful matrix for use in tissue engineered flaps.

Animals↗

PubMed2003

Morphometric assessment of the oxygen diffusion conductance in placentae from pregnancies complicated by intra-uterine growth restriction.

The morphometric oxygen diffusive conductance (D(p)) of the placenta provides a measure of the efficiency of oxygen transfer between the mother and the developing fetus. Any change in the D(p)may point towards possible adaptation in the light of altered oxygen transfer. Placentae from normal (n=40) and small for gestational age SGA (n=24) pregnancies were analysed using stereological techniques. Each placenta was uniform randomly sampled and tissue samples processed to wax infiltration and embedding using conventional histological preparatory methods. A combination of stereological techniques and physiological constants were used to estimate the partial conductances across the five major tissue compartments involved in oxygen transfer. There was a significant reduction in both fetal birthweight and placental weight in the SGA group when compared with controls. A decrease in both chorionic (S(cv)) and fetal capillary (S(fc)) surface area was also observed in SGA placentae when compared with controls (P>0.001). Villous membrane harmonic thickness (T(vm)) was reduced in the SGA placentae (2.33 microm) when compared with controls (2.67 microm P=0.019). This resulted in a reduction in the minimum D(p)in SGA placentae when compared with controls (P=0.023). Adjusting for fetal weight resulted in no difference in the specific diffusive conductance. Changes in T(vm)in SGA placentae combined with changes in basic surface areas were insufficient to maintain overall D(p)values comparable with control placentae.

Adaptation, Physiological↗

PubMed2002

The role of human-derived fibrin sealant in the reduction of postoperative flexor tendon adhesion formation in rabbits.

This study assessed the role of a novel fibrin sealant (Vivostat in adhesion reduction after flexor tendon surgery. The deep flexor tendons of the 2nd and 4th digits of the left paw of 20 rabbits were exposed and a standard partial injury was performed on each. The rabbits were randomized to either immediate post-injury treatment with Vivostat or no treatment. In each case active movement of the 2nd digit was prevented while the 4th digit was allowed to move normally. The two groups were assessed at 14 days for adhesion formation with a tensiometer. The right paw acted as the unoperated control. Results showed that there was no significant difference in the force needed to remove the tendon from its sheath when comparing the two Vivostat((R))-treated groups to the unoperated controls. There was, however, a highly significant difference in this force between the non-Vivostat-treated groups and the unoperated controls. This suggests a beneficial effect of Vivostat in reducing post surgical tendon adhesion formation.

Animals↗

PubMed2002

Caffeic acid phenethyl ester and curcumin: a novel class of heme oxygenase-1 inducers.

Heme oxygenase-1 (HO-1) is a redox-sensitive inducible protein that provides efficient cytoprotection against oxidative stress. Curcumin, a polyphenolic natural compound that possesses anti-tumor and anti-inflammatory properties, has been reported recently to induce potently HO-1 expression in vascular endothelial cells (Free Rad Biol Med 28:1303-1312, 2000). Here, we extend our previous findings by showing that caffeic acid phenethyl ester (CAPE), another plant-derived phenolic agent, markedly increases heme oxygenase activity and HO-1 protein in astrocytes. The effect seems to be related to the peculiar chemical structures of curcumin and CAPE, because analogous antioxidants containing only portions of these two molecules were totally ineffective. At a final concentration of 30 microM, both curcumin and CAPE maximally up-regulated heme oxygenase activity while promoting marked cytotoxicity at higher concentrations (50-100 microM). Similar results were obtained with Curcumin-95, a mixture of curcuminoids commonly used as a dietary supplement. Incubation of astrocytes with curcumin or CAPE at concentrations that promoted maximal heme oxygenase activity resulted in an early increase in reduced glutathione followed by a significant elevation in oxidized glutathione contents. A curcumin-mediated increase in heme oxygenase activity was not affected by the glutathione precursor and thiol donor N-acetyl-L-cysteine. These data suggest that regulation of HO-1 expression by polyphenolic compounds is evoked by a distinctive mechanism which is not necessarily linked to changes in glutathione but might depend on redox signals sustained by specific and targeted sulfydryl groups. This study identifies a novel class of natural substances that could be used for therapeutic purposes as potent inducers of HO-1 in the protection of tissues against inflammatory and neurodegenerative conditions.

Acetylcysteine↗

PubMed2002

Interaction of heme with nitroxyl or nitric oxide amplifies heme oxygenase-1 induction: involvement of the transcription factor Nrf2.

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme, the expression of which is highly sensitive to induction by pro-oxidant stimuli including the substrate heme and reactive oxygen species. Conceptually, the perception that HO-1 plays a key role in response to oxidative damage is paralleled by evidence showing high expression of HO-1 in a variety of cell systems challenged with nitric oxide (NO) or NO-derivatives, thus revealing a potential biological function for HO-1 against nitrosative stress. In this study, we report that exposure of cardiac cells to hemin (5-20 microM) in combination with compounds that liberate nitroxyl (HNO/NO-) or release NO significantly potentiates HO-1 mRNA and protein expression leading to a remarkable increase in heme oxygenase activity under both normoxic and hypoxic conditions. The amplification of the heme oxygenase pathway appears to involve a direct interaction between heme and the NO groups, as the ability of both NO(-)- and NO-releasing agents to induce HO-1 is totally lost by their pre-incubation for 1 hr in complete medium prior to cell treatment but is highly preserved by addition of hemin during the preincubation step. In addition, we show that the redox-sensitive transcription factor Nrf2 is highly expressed in the nuclear fraction of cells exposed to the NO- generator and that this effect is totally abolished by the presence of N-acetyl-L-cysteine. Interestingly, the expression of Nrf2 is gradually intensified by treating cells with a combination of the NO- releaser and increasing concentrations of hemin. Thus, a strict parallelism exists between the extent of HO-1 induction and expression of Nrf2 elicited by the heme-NO interaction. We propose that modification of the iron protoporphyrin centers by NO groups to modulate HO-1 expression might be regarded as a molecular switch to maximize heme oxygenase enzymatic activity and consequently mitigate the redox imbalance imposed by oxidative and nitrosative stress.

Acetylcysteine↗

PubMed2001

Homocysteine attenuates endothelial haem oxygenase-1 induction by nitric oxide (NO) and hypoxia.

The disrupted metabolism of homocysteine (Hcy) causes hyperhomocysteinemia, a condition associated with the impairment of nitric oxide (NO) bio-availability, tissue hypoxia and increased risk of vascular disease. Here, we examined how Hcy modulates the induction of the stress protein haem oxygenase-1 (HO-1) evoked by NO releasing agents and hypoxia in vascular endothelial cells. We found that Hcy (0.5 mM) markedly reduced the increase in haem oxygenase activity and HO-1 protein expression induced by sodium nitroprusside (SNP, 0.5 mM) but did not affect HO-1 activation mediated by S-nitroso-N-acetyl-penicillamine. Cells pre-treated with Hcy followed by addition of fresh medium containing SNP still exhibited an augmented haem oxygenase activity. Interestingly, high levels of Hcy were also able to abolish hypoxia-mediated HO-1 expression in a concentration-dependent manner. These novel findings indicate that hyperhomocysteinemia interferes with crucial signaling pathways required by cells to respond and adapt to stressful conditions.

Animals↗