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Biomedical subjects

C J Green

Publications and source records attributed to C J Green.

At least 163 records · Page 9Linked to original sources
PubMed1992

Is early vascularization of nerve grafts necessary?

Revascularization and regeneration through vascularized and non-vascularized nerve grafts were compared on optimal and adverse graft beds in 76 rabbit sciatic nerves. A delay in revascularization of more than 14 days was found to occur in 30 mm long, non-vascularized nerve grafts placed on completely avascular graft graft beds. However, over a period of 44 weeks, this prolonged ischaemia did not adversely affect nerve regeneration. The vascularized nerve grafts did not differ significantly with respect to the rate of regeneration, motor conduction velocity, fibre diameter and thickness of myelin sheath. In rabbits, the provision of early vascularity does not appear to confer superior regeneration through nerve grafts. The clinical use of vascularized nerve grafts is discussed in the light of these results.

Angiography↗
PubMed1992

Metabolic effects of dobutamine in normal man.

1. Dobutamine in 5% (w/v) D-glucose was infused at sequential doses of 2, 5 and 10 micrograms min-1 kg-1, 45 min at each dose, into eight healthy male subjects, and the effects were compared with those produced by infusion of the corresponding volumes of 5% (w/v) D-glucose alone. 2. The energy expenditure increased and was 33% higher than control (P less than 0.001) at 10 micrograms of dobutamine min-1 kg-1. The respiratory exchange ratio decreased from 0.85 (SEM 0.02) before infusion to 0.80 (SEM 0.01) at 10 micrograms of dobutamine min-1 kg-1, but did not alter during the placebo infusion (P less than 0.001). 3. Plasma noradrenaline concentrations were lower during the dobutamine infusion compared with during the infusion of D-glucose alone (P less than 0.025). Plasma dopamine concentrations remained below 0.1 nmol/l throughout both infusions. 4. Compared with during the placebo infusion, the blood glucose concentration decreased (P less than 0.001), the plasma glycerol and free fatty acid concentrations increased by 150 and 225%, respectively (both P less than 0.001), and the plasma potassium concentration decreased from 3.8 (SEM 0.07) to 3.6 (SEM 0.04) mmol/l (P less than 0.01) during dobutamine infusion. The plasma insulin concentration increased at 2 and 5 micrograms of dobutamine min-1 kg-1 (P less than 0.001) with no further rise at 10 micrograms of dobutamine min-1 kg-1. 5. Compared with during the placebo infusion, the systolic and diastolic blood pressures and the heart rate increased during dobutamine infusion (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Ultrastructural changes and lipid peroxidation in rat adipomusculocutaneous flap isotransplants after normothermic storage and reperfusion.

Parallel in vivo, histological, and ultrastructural studies were carried out and markers of lipid peroxidation (Schiff's bases [SB] and thiobarbituric-acid-reactive material [TBAR]) were measured in rat adipomusculocutaneous flap isotransplants that had been stored for 0, 2, 4, 6, and 8 hr under normothermic (37 degrees C) conditions and reperfused for specific periods. Flaps stored for 4 hr and treated with intravenous desferrioxamine (DFX) or hypertonic citrate flush (HCA) were also evaluated. In vivo assessment was made after 7 days of reperfusion. Flaps stored for 4 hr eventually exhibited partial necrosis in vivo, and neither DFX or HCA flush increased the area of surviving skin. Electron microscopy revealed extensive storage damage in epidermal, follicle, fat, and smooth muscle cells and in endothelium. HCA significantly preserved fat cells (P = 0.0035) and DFX diminished smooth muscle damage. Reperfusion injury was seen in endothelial cells in the form of swelling that was not prevented by HCA or DFX. Ultrastructural alterations correlated with changes in susceptibility to lipid peroxidation in fat but not in skin. The results of these parallel studies indicate that both free radical-dependent and independent mechanisms operate in ischemia and reperfusion injury in flap tissue and that fat has a greater predisposition to free radical damage than skin.

Adipose Tissue↗
PubMed1992

A cluster of nine tRNA genes between ribosomal gene operons in Bacillus subtilis.

A cluster of nine tRNA genes located in the 1-kb region between ribosomal operons rrnJ and rrnW in Bacillus subtilis has been cloned and sequenced. This cluster contains the genes for tRNA(UACVal), tRNA(UGUThr), tRNA(UUULys), tRNA(UAGLeu). tRNA(GCCGly), tRNA(UAALeu), tRNA(ACGArg), tRNA(UGGPro), and tRNA(UGCAla). The newly discovered tRNA gene cluster combines features of the 3'-end of trnI, a cluster of 6 tRNA genes between ribosomal operons rrnI and rrnH, and of the 5'-end of trnB, a cluster of 21 tRNA genes found immediately 3' to rrnB. Neither the tRNA(UAGLeu) gene nor its product has been found previously in B. subtilis. With the discovery of this new set of tRNA genes, a total of 60 such genes have now been found in B. subtilis. These known genes account for almost all of the tRNA hybridizing restriction fragments of the B. subtilis genome. The 60 known tRNA genes of B. subtilis code for only 28 different anticodons, compared with a total of 41 different anticodons for 78 tRNA genes in Escherichia coli. This may indicate that B. subtilis does not need as many anticodons because of more flexible translation rules, similar to the situation in Mycoplasma capricolum.

Bacillus subtilis↗
PubMed1992

A chelator is required for microsomal lipid peroxidation following reductive ferritin-iron mobilisation.

In the past, antioxidant and chelator studies have implicated a role for iron-dependent oxidative damage in tissues subjected to ischaemia followed by reperfusion. As ferritin is a major source of iron in non-muscular organs and therefore a potential source of the iron required for oxygen radical chemistry, we have determined conditions under which ferritin iron reduction leads to the formation of a pool of iron which is capable of catalysing lipid peroxidation. Under anaerobic conditions and in the presence of rat liver microsomes, flavin mononucleotide (FMN) catalysed the reduction of ferritin iron as shown by both continuous spectrophotometric measurements of tris ferrozine-Fe(II) complex formation and post-reaction Fe(II) determination. The presence of either ferrozine or citrate was not found to alter the time course or extent of ferritin reduction. In contrast, the addition of air to the reactants after a 20 min period of anaerobic reduction resulted in peroxidation of the microsome suspension (as determined with the 2-thiobarbituric acid test) only in the presence of a chelator such as citrate, ADP or nitrilotriacetic acid. These results support the concept that reduced ferritin iron can mediate oxidative damage during reperfusion of previously ischaemic tissues, provided that chelating agents such as citrate or ADP are present.

Animals↗
PubMed1992

The pathology of rat lung isografts following 48 or 72-hour cold storage and subsequent reperfusion in vivo for up to 1 month.

Using a left lung orthotopic isograft model in adult male AS strain rats, the pathology of lungs which were stored for 48 or 72 hours using a simple organ flush technique followed by low temperature (0 degrees C) immersion has been investigated. Lungs were examined after cold storage alone and after storage followed by either brief (up to 1 hour) or extended (30 days) reperfusion with blood in vivo. Grafts were flushed with either isotonic saline (NaCl) or hypertonic citrate solution (HCA) alone, or with HCA containing either verapamil (a Ca(2+)-channel blocker) or prostacyclin (PGI2 which has both anti-platelet and vasodilator actions). Controls included fresh non-flushed lungs and fresh HCA-flushed lungs which were transplanted immediately after harvest. After prolonged (48 or 72-hour) cold ischaemia alone the only clear change in lung morphology was of nuclear swelling. Early reperfusion changes included: (i) oedema (interstitial and alveolar); (ii) vascular congestion; and (iii) intra-alveolar haemorrhage. Features (i) and (ii) were diffuse whilst haemorrhage was patchy. Lungs which remained in vivo for up to 30 days showed focal scarring and chronic inflammation with numerous macrophages containing haemosiderin; the extent of the changes observed in individual grafts tended to mirror the gross macroscopic outcome. Attempts to improve the cold ischaemic tolerance with added agents (verapamil and prostacyclin PGI2) failed to produce a clear advantage.

Animals↗
PubMed1991

Geometrical approach to the end-to-side anastomosis.

We analyzed the procedure of performing an arterio- or venotomy in rats and changed it from parallel to the long axis to perpendicular to the long axis. Simultaneously, geometrical analysis of the shape of an arterio- or venotomy led to a new approach for the end-to-side anastomosis in experimental free flap transplantation. This new method was applied in 268 anastomoses. It necessitated only six sutures and resulted in 100% arterial early and late patency and in 99% venous early and late patency.

Anastomosis, Surgical↗
PubMed1991

Necrotizing myopathy in critically-ill patients.

Skeletal muscle wasting is commonly observed in critically-ill patients and has been attributed to catabolic fibre atrophy and to neuropathy. This study describes the occurrence of a necrotizing myopathy in 15 out of 31 critically-ill patients who had percutaneous biopsies taken from the tibialis anterior muscles. While most cases showed necrosis of isolated fibres, 5 of the 12 patients who had serial biopsies showed progressive necrosis of up to 95 per cent of the fibres. One other case showed infarction and one case had staphylococcal vasculitis. Atrophy of type 1 and/or type 2 fibres was documented by morphometry in 12 cases. Myoglobin-containing casts were demonstrated immunohistochemically in renal tubules on either biopsy or necropsy material in 5 out of 7 cases. The presence of muscle necrosis was a clinically unexpected finding which may contribute to weakness, complicate the interpretation of tissue biochemistry and energy balance studies, and potentiate renal failure. The necrosis is probably multifactorial in origin, with ischaemia and sepsis contributing factors.

Acetaminophen↗
PubMed1991

Plasma and mucosal histamine after small bowel transplantation in rats.

During the course of a study on preservation of small bowel transplants in rats, the hypothesis that histamine may play a role in graft damage has been investigated. Plasma and mucosal histamine levels have been measured after storage and reperfusion of Lewis rat small bowel transplants which have received an intravascular flush of saline or of one of the tissue preservation media, hypertonic citrate or University of Wisconsin solution. Plasma histamine concentration was unchanged from a control value of 23.2 +/- 2.6 ng/ml 15 min after reperfusion of grafts, whether fresh or stored for 24 h or for 48 h. Mucosal histamine levels in the grafts fell, however, from a control value of 371.0 +/- 22.9 ng/g tissue, first on storage then further after 15 min reperfusion. No differences were found in these parameters of histamine release between any of the preservation media. It is suggested that histamine may play a role in storage and reperfusion damage to small bowel transplants.

Animals↗
PubMed1991

Reperfusion injury in rat adipomusculocutaneous flaps: an ultrastructural and microangiographic study.

Electron microscopy (EM), microangiography (MA) and histological studies were carried out to demonstrate the vascular basis of ischaemic and reperfusion injury in rat adipomusculocutaneous free flaps which had been stored under normothermic conditions (37 degrees C) for specific periods of time. MA revealed that areas destined to die reperfused for at least 6 h in this model. EM showed progressive endothelial damage as a result of both storage and reperfusion. The use of the iron chelator desferrioxamine (DFX) did not benefit the endothelium or improve salvage of ischaemic flaps.

Adipose Tissue↗
PubMed1991

Selectivity of distal reinnervation of regenerating mixed motor and sensory nerve fibres across muscle grafts in rats.

This study investigated target specificity during axonal regeneration of a mixed motor and sensory nerve towards respective targets. The femoral nerves in rats were divided and allowed to grow across a 6 mm gap interposed with frozen and thawed muscle grafts towards their distal motor and sensory nerve stumps. Fourteen weeks later the number of motoneurons projecting axons into the motor and sensory branches were determined by retrograde axonal tracing using horse-radish peroxidase. There were significantly higher numbers of motoneurons (p = 0.0034) projecting into the motor nerve than the sensory nerve. Efferent axons of a mixed nerve selectivity grew into motor branches when allowed to regenerate across a 6 mm gap interposed with muscle grafts. It is possible that a deliberately created 'structured gap' during repair of mixed nerves could improve axonal matching by allowing expression of neurotropism.

Animals↗
PubMed1991

Lack of topographical specificity in sensory nerve regeneration through muscle grafts in rats.

Regenerating sensory axons of each receptor class make new connections with similar denervated receptors. This study investigates to what extent these axons return to their original receptive field. The lateral cutaneous nerves of the thigh in rats were divided and allowed to regenerate across a 6 mm. gap interposed with frozen and thawed muscle graft towards their original distal nerve stump and a "foreign" sensory nerve, the saphenous nerve. 16 weeks later, myelinated axon counts of 26 pairs of distal nerves showed no preferential growth towards the original receptive field. Lack of topographic specificity during sensory nerve regeneration may explain the faulty localisation of sensation after nerve repair in clinical practice. Following sensory nerve regeneration, the somatosensory cortex receives accurate afferent information but from disparate skin sites; this probably alters the relationship of overlapping sensory fields and may be the cause of distorted pattern recognition.

Animals↗
PubMed1991

Function of single rat lung isografts after 48-hour cold storage. The effect of treatment with free radical antagonists and prostacyclin PGI2.

Single orthotopic rat lung isografts were carried out in adult male AS rats after 48-hour cold storage (0 degrees C). Grafts were preserved by simple organ flush followed by low-temperature immersion. Hypertonic citrate (HCA) without additives was evaluated as the basic flush solution. In other groups desferrioxamine (an iron chelator), verapamil (a calcium channel blocker) and prostacyclin (PGI2) were added separately to HCA and given intravenously to donor and recipient animals in an attempt to improve the preservation. Baseline controls were fresh HCA-flushed lungs grafted immediately after harvest. Negative controls to the HCA assessment were lungs flushed with isotonic saline (NaCl) stored for 48 hr at 0 degrees C. Functional studies were carried out at weekly intervals until sacrifice (in the fifth postoperative week) and included assessment of blood flow, aeration and gas transfer by perfusion scintigraphy, chest roentgenograms, and blood gas analysis. Of the baseline control animals, 10/10 survived to the end of the study period; all grafts appeared macroscopically normal and blood gas analysis showed good function. Of the animals grafted with HCA-flushed, 48-hr-stored lungs 2/10 died postoperatively; 7/10 grafts appeared macroscopically normal at the end of the study, and one was slightly reduced in size. Blood gas analysis of HCA-flushed, 48-hr-stored lungs showed function similar to that of baseline control grafts. NaCl-flushed lungs (negative controls) survived surprisingly well: 3/10 animals died postoperatively, 6/10 lungs appeared normal, and one was reduced in size. Assessment of graft function showed no significant benefit of HCA flush compared with NaCl. Treatment with desferrioxamine, verapamil or prostacyclin (PGI2) failed to improve the outcome after HCA flush; in fact desferrioxamine gave significantly poorer results. The study has shown that successful 48-hr preservation of rat lung isografts can be achieved by simple organ flush with HCA and storage at 0 degrees C. Contrary to expectation and experience with preservation of other organs, rat lungs were remarkably well preserved after flush with NaCl.

Animals↗
PubMed1990

The discovery of new intron-containing human tRNA genes using the polymerase chain reaction.

Introns in transfer RNA genes are rare in vertebrates. Until now, the only intron-containing human tRNA genes were believed to be those coding for tRNA(Tyr). All of these introns are inserted 3' to the anticodon position in these genes. We have designed polymerase chain reaction primers that can amplify all of the tRNA(Tyr) genes for cloning and sequencing by using the conserved portions of the gene coding for the structural part of the tRNA. Our preliminary results have revealed five tRNA(Tyr) genes, each of which contains a different intron. We used the same technique to amplify, clone, and sequence the human genes for tRNA(Leu)CAA. This has resulted in the discovery that this human tRNA gene family also has introns inserted 3' to the anticodon. This polymerase chain reaction technique is useful in detecting new families of intron-containing tRNA genes as well as identifying sequence variations in the introns of individual genes.

Base Sequence↗