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Biomedical subjects

C J Green

Publications and source records attributed to C J Green.

At least 145 records · Page 8Linked to original sources
PubMed1993

The effect of a synthetic hexadentate iron chelator (CP130) and desferrioxamine on rabbit kidneys exposed to cold and warm ischaemia.

The effect of CP130 (a synthetic hexadentate pyridinone iron chelator) on the formation of two markers of lipid peroxidation (TBA-reactive material and Schiff's bases) in rabbit kidneys following a 72 h period of cold (0-4 degrees C) ischaemia was investigated by either adding CP130 to the flush/storage solution (hypertonic citrate solution) or by administering the agent intravenously 15 min before removal of the organs. In both cases, CP130 blocked the adverse rises in lipid peroxidation caused by ischaemia and subsequent reoxygenation of the homogenates in vitro. Both CP130 and desferrioxamine (DFX) (administered intravenously 15 min before ischaemia and 5 min before reperfusion) were also found to significantly reduce post-ischaemic rates of in vitro lipid peroxidation in kidneys rendered warm ischaemic for 90 min followed by reperfusion for 5 or 60 min in situ. Kidneys exposed to warm ischaemia and reperfusion developed interstitial and intracellular oedema, congestion and haemorrhage. DFX administration had little effect on the histological outcome, whereas CP130 significantly reduced interstitial oedema (at 5 min reperfusion compared to the DFX-treated group), intracellular oedema (at 60 min reperfusion compared to the DFX-treated group) and congestion (at 5 min reperfusion compared with a control group not given any agent). It is concluded that while CP130 and DFX exhibited similar antioxidant properties, CP130 provided better protection from ischaemia/reperfusion injury at the histological level. Synthetic iron chelators may therefore be of benefit in clinical organ transplantation by protecting against tissue damage caused by prolonged ischaemia.

Animals↗
PubMed1993

Restoration of basement membrane structure in pigs following keratinocyte autografting.

The attachment of grafts of keratinocyte sheets is mediated in part by the presence and organisation of basement membrane components. The reappearance of basement membrane following keratinocyte autografting was examined in pigs. These studies showed that there was rapid expression of anchoring fibrils and hemidesmosomes, which reached normal numbers at 10 days. However, the length of hemidesmosomes did not reach normal size during the period of study. Weakness of attachment of keratinocyte autografted epidermis was found to lie between the basement membrane and the granulation tissue. This suggests that reported clinical problems with keratinocyte graft attachment may be mediated not only by delay in maturation of the basement membrane but also by its poor integration with collagen of the wound bed.

Animals↗
PubMed1993

A porcine model using skin graft chambers for studies on cultured keratinocytes.

In wound healing research, animal models permit an extensive tissue analysis which is not normally possible in clinical studies. A morphological comparison of human and porcine skin was made in order to identify those aspects of the wound healing process where a porcine model may help our understanding of clinical problems. We describe a porcine model for evaluating the growth of cultured keratinocytes on a variety of wound beds. Polytetrafluoroethylene skin graft chambers were used to isolate wounds and prevent epidermal healing from the skin edge. The chambers remained in situ for 5-7 weeks. We detail the surgical technique, the method of porcine keratinocyte culture and highlight some practical measures that were taken to optimise the "take" of the cultured keratinocyte grafts.

Animals↗
PubMed1993

Kerato-dermal grafts: the importance of dermis for the in vivo growth of cultured keratinocytes.

In a porcine model, we studied the benefit of dermis for the growth of cultured autologous keratinocytes (CAK) on full-thickness wounds isolated within skin graft chambers. Kerato-dermal grafts were prepared in a two stage process using autologous de-epidermalised dermis (DED) and CAK (Group 1). Control wounds were prepared by grafting either CAK only (Group 2) or DED only (Group 3). The median epidermal cover of 34 wounds in Group 1 was 47% and was significantly greater (p < 0.001) than the epidermal cover of 12 wounds in Group 2 (4%) and 14 wounds in Group 3 (12%). The epidermis in Group 1 was durable whereas it was fragile in the control wounds. Histologically rête ridges were present at 2 weeks in Group 1, but not in the control wounds. These data indicate that a dermal wound bed significantly improves the in vivo growth of cultured keratinocytes.

Animals↗
PubMed1993

Neovascularisation precedes neural changes in the rat groin skin flap following denervation: an immunohistochemical study.

We have employed immunohistochemical techniques to study neural and vascular changes in rat skin flaps. Following partial or total denervation, flaps were studied at 4, 7 or 12 days using antisera to PGP 9.5 (panneural marker), the neuropeptides CGRP (sensory nerves) and CPON (adrenergic nerves) and an endothelial marker VWF. In partially denervated flaps, moderate increases in PGP-immunoreactive (PGP-IR) and CGRP-IR nerves and a mild increase in CPON-IR nerves in immediate surrounding skin preceded smaller increases in similar nerves around the pedicle. Following total denervation, mild increases in all nerve types at these locations were accompanied by a marked increase of these nerves in distant surrounding skin, 1-2 cm from the suture line. A gradual increase in endothelial cell staining (VWF) of blood vessels was seen in surrounding skin, flap beds and pedicles. Angiogenesis preceded flap reinnervation which occurred initially from surrounding skin, and later from the base, with sensory fibres appearing first.

Animals↗
PubMed1993

The effect of backing materials on keratinocyte autograft take.

A porcine model has been established to study keratinocyte autografts as a model of human keratinocyte grafting. Keratinocyte autografts were placed on 104 full thickness wounds in 13 pigs and backed with 3 dressings which varied in their ability to maintain an occlusive environment. Sixteen control wounds were ungrafted. No take was found using a backing of woven viscose and cotton gauze. Take was 20% at day 16 using a backing of woven viscose and paraffin gauze. Serial biopsies showed that keratinocytes frequently attached to the interstices of the viscose dressing and difficulty in detaching the viscose caused loss of epidermis. Hydrogel sheet backing made assessment at day 10 difficult because of wound hydration but dressing removal, enabling exudate evaporation, produced 22% take at day 13. The development of improved dressing techniques is certainly necessary for improved graft take.

Animals↗
PubMed1993

Increased whole body protein breakdown predominates over increased whole body protein synthesis in multiple organ failure.

1. Whole body protein turnover was measured using a primed-constant infusion of L-[1-13C]leucine with measurement of breath 13CO2 production and plasma 13C alpha-ketoisocaproate enrichment. Ten fasting patients, requiring mechanical ventilation and suffering from multiple organ failure, and six healthy control subjects were studied. 2. Protein breakdown and leucine removal from the plasma for protein synthesis were significantly higher in the patients than in the control subjects (P < 0.01). In addition, leucine oxidation was almost 75% higher in the patients than in the healthy control subjects (P < 0.05). 3. Plasma concentrations of glucose, insulin and growth hormone were not different between the two groups, but those of glucagon (not significant), noradrenaline (P < 0.05) and cortisol (P < 0.01) were almost two- and three-fold higher in the patients than in the control subjects. 4. Mean energy expenditure, measured by indirect calorimetry, was 30% higher in the patients than in the healthy control subjects (P < 0.01). 5. Combining the data from both groups of subjects and using multiple regression analysis, cortisol was found to be the most significant predictor of (i) protein breakdown (48% of variance explained), (ii) leucine oxidation (69%) and (iii) hourly energy expenditure (54%). 6. The present investigation using [13C]leucine tracer methods demonstrated, in patients with multiple organ failure, that whole body protein breakdown and synthesis increased concomitantly and were twice as high as rates measured in healthy control subjects. Of the hormones measured in the present study, cortisol appears to have the most significant effect on whole body protein turnover.

Adult↗
PubMed1993

The benefit of a single-passage perfusion with a hypertonic citrate solution on the cold ischemia tolerance of epigastric free flaps in Dark-Agouty rats.

In this study the effectiveness of a single-passage perfusion with hypertonic citrate solution on the cold ischemia tolerance in epigastric free flaps in Dark-Agouty rats was investigated. In the control group a significant decline in survival percentage was observed when the storage time was extended from 72 hours to 96 hours. A single (pressure controlled) passage perfusion with hypertonic citrate solution was able to prevent this decline.

Animals↗
PubMed1993

Staphylococcus aureus has clustered tRNA genes.

The polymerase chain reaction (PCR) was used to detect large tRNA gene clusters in Bacillus subtilis, Bacillus badius, Bacillus megaterium, Lactobacillus brevis, Lactobacillus casei, and Staphylococcus aureus. The primers were based on conserved sequences of known gram-positive bacterial tRNA(Arg) and tRNA(Phe) genes. This PCR procedure detected an unusually large tRNA gene cluster in S. aureus. PCR-generated probes were used to identify a 4.5-kb EcoRI fragment that contained 27 tRNA genes immediately 3' to an rRNA operon. Some of these 27 tRNA genes are very similar, but only 1 is exactly repeated in the cluster. The 5' end of this cluster has a gene order similar to that found in the 9- and 21-tRNA gene clusters of B. subtilis. The 3' end of this S. aureus cluster exhibits more similarity to the 16-tRNA gene cluster of B. subtilis. The 24th, 25th, and 26th tRNA genes of this S. aureus tRNA gene cluster code for three similar, unusual Gly-tRNAs that may be used in the synthesis of the peptidoglycan in the cell wall but not in protein synthesis. Southern analysis of restriction digests of S. aureus DNA indicate that there are five to six rRNA operons in this bacterium's genome and that most or all may have large tRNA gene clusters at the 3' end.

Bacillus subtilis↗
PubMed1993

Pathology of warm ischaemia and reperfusion injury in adipomusculocutaneous flaps.

In-vivo assessment and histological analysis after 168 hours of reperfusion were used to determine the normothermic (37 degrees C) ischaemic tolerance of adipomusculocutaneous, free flap, isotransplants in inbred AS rats. Flaps stored for up to 2 hours under normothermic conditions survived; flaps stored for 4 hours partially survived but those which had been stored for more than 6 hours became totally necrotic. Neither treatment with the iron chelator desferrioxamine (DFX) nor hypertonic citrate (HCA) flush increased the ischaemic tolerance of flaps which had been stored for 4 hours since neither diminished the amount of necrosis. Treated and untreated flaps stored for 4 hours were also assessed 0, 0.5, 24, 48, 96 and 168 hours after isotransplantation. They were compared to control flaps which had not been stored prior to reperfusion and negative control flaps which were not stored but isotransplanted without a blood supply. Oedema reached a peak at 24 hours and there was progressive increase in general severe necrosis, reaching a plateau by 48 hours. Suture line epidermalization and thickening was established by 48 hours. Among flaps stored for 4 hours, those treated with DFX had the most necrosis. Adipose tissue and striated muscle proved the least tolerant to warm ischaemic stress. These experiments suggest reperfusion injury contributes to eventual flap necrosis, but the role of free radicals has not been established. The 4-hour stored flap is a useful model to study the effects of ischaemia both in flap tissue and at the suture line.

Adipose Tissue↗
PubMed1993

Ultrastructural changes in rat adipomusculocutaneous flaps during warm ischaemic storage and reperfusion.

Electron microscopy (EM) was used to evaluate ultrastructural changes in adipomusculocutaneous rat flaps which had been stored for 0, 2, 4, 6 and 8 hours under normothermic conditions (37 degrees C). The effects of treatment with desferrioxamine (DFX) or hypertonic citrate flush (HCA), prior to 4 hours of storage, were compared to untreated flaps which had been stored for 4 hours. Ultrastructural changes caused by 30 minutes of reperfusion, were also studied. Most ultrastructural alterations occurred between 2 and 4 hours of warm storage and there were further changes in some cells after short periods of reperfusion. DFX decreased smooth muscle damage and HCA protected adipocytes but neither of these agents preserved endothelial cells. These studies indicated that free radical-dependent and independent mechanisms were both involved in events which led to flap necrosis after periods of warm storage and reperfusion.

Adipose Tissue↗
PubMed1992

Ebselen. Antioxidant capacity in renal preservation.

Ebselen (PZ51) was tested for its ability to inhibit oxidative membrane damage and improve outcome of rabbit kidneys rendered cold ischaemic for 72 hr. In view of the rapid metabolism of ebselen, the antioxidant capacities of its two principal metabolites were first compared with that of the parent drug in an in vitro hepatic microsomal lipid peroxidation system initiated by NADPH/Fe(3+)-ADP. The potent antioxidant activity of ebselen was confirmed but metabolite I (2-glucuronylselenobenzanilide) exhibited no antioxidant potential up to a concentration of 50 microM; metabolite II (4-hydroxy-2-methyl-selenobenzanilide) did inhibit lipid peroxidation but was about 80 times less effective than the parent compound. The storage of rabbit kidneys in hypertonic citrate solution at 0 degrees for 72 hr of cold ischaemia resulted in greatly increased susceptibility to oxidative membrane damage in both the cortex and medulla as determined by the subsequent in vitro formation of two markers of lipid peroxidation (Schiff's bases and thiobarbituric acid-reactive material). Inclusion of ebselen (50 microM) in the flush and storage solution led to a highly significant reduction in these oxidative markers in both regions of the kidney. Intracellular and interstitial oedema was noted in organs subjected to 72 hr cold ischaemia and was reduced by ebselen (50 microM in the flush/storage solution). The rate of post-ischaemic lipid peroxidation was found to correlate well with the extent of oedema in the renal medulla (r = 0.84, P less than 0.001) but no such correlation was found in the cortex. Administration of ebselen (5.5 mg/kg i.v. and 100 microM in the flush/storage solution) did not improve the long-term survival of rabbits following autotransplantation of a single kidney stored for 48 or 72 hr. No protective effect of ebselen could be demonstrated either in terms of graded physiological function or histological outcome.

Animals↗
PubMed1992

Gastric pressure response to low dose dopamine infusion in normal man.

The gastric pressure response to distension was measured during intravenous infusion of dopamine at a rate of 2 mug min(-1)kg(-1) over 2h 50min in 5 normal volunteers to determine whether dopamine at this dose potentiated gastric adaptive relaxation, leading to a fall in gastric pressure and thus a potential delay in gastric emptying. This would be of obvious importance in patients being given dopamine at this dose to support renal function and at the same time being fed by nasogastric tube. The pressure response decreased during the first hour in all five subjects (p < 0.01). In 2 it recovered during the third hour to pre-infusion values, but in 2 it remained diminished; in 1 subject the results were equivocal. Circulating dopamine, noradrenaline and adrenaline concentrations all increased during dopamine (p < 0.05), but compared with control there was no difference in plasma free fatty acids, glycerol, cortisol or glucose concentrations. Dopamine at 2 mug min(-1) kg(-1) produced a transient fall in gastric pressure in all subjects, and a persistent fall in some. The changes in gastric pressures were seen at infusion rates that produced no metabolic or inotropic effects.

Journal Article↗