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Biomedical subjects

C J Green

Publications and source records attributed to C J Green.

At least 91 records · Page 5Linked to original sources
PubMed1996

A precursor of the nitric oxide donor SIN-1 modulates the stress protein heme oxygenase-1 in rat liver.

In this study the effect of increased nitric oxide (NO) production on the expression of rat liver heme oxygenase-1, an inducible stress protein responsible for the catalysis of heme to biliverdin and carbon monoxide, was investigated. Rats were injected intraperitoneally with molsidomine (SIN-10), a long acting drug that is enzymatically converted in the liver to yield the active NO-releasing agent 3-morpholinosydnonimine (SIN-1). Administration of SIN-10 resulted in a significant time- and dose-dependent increase in plasma levels of nitrite/nitrate, an index of NO release. A time course of heme oxygenase-1 mRNA levels in liver showed a gradual increase in the expression of the gene encoding for this protein, which was maximal at 4 hours and returned to normal levels by 6 hours after SIN-10 treatment. Heme oxygenase activity also increased by 50% at 4 hours and was maximal 12 hours after SIN-10 administration (63% increase over baseline). These results indicate a possible role for locally generated NO in the modulation of hepatic stress response in vivo suggesting that NO mediates cell adaptation to stress by activation of endogenous defensive mechanisms.

Animals↗
PubMed1996

Expression of the ATDC (ataxia telangiectasia group D-complementing) gene in A431 human squamous carcinoma cells.

The ATDC gene was originally identified by its ability to complement the radiosensitivity defect of an ataxia telangiectasia (AT) fibroblast cell line. Because hypersensitivity to ionizing radiation is an important feature of the AT phenotype, we reasoned that ATDC may function generally in the suppression of radiosensitivity. Previous work in our laboratory focused on radiosensitization mechanisms in human squamous carcinoma (SC) cells, especially A431 cells. To establish a basis for investigating the role of ATDC in radiation-responsive signaling pathways in human SC cells, we characterized ATDC message and protein expressions in A431 cells. ATDC message expression was also compared among human epidermoid cells (A431 cells, HaCaT spontaneously immortalized human keratinocytes and normal human epidermal keratinocytes) and a normal human fibroblast cell line (LM217). We made the following major observations: (i) the relative abundance of ATDC message is substantially higher in the epidermoid cells than in the fibroblast cell line, which has a message level comparable to those reported for other fibroblast lines; (ii) ATDC is constitutively phosphorylated on serine/threonine in A431 cells; (iii) in A431 cells, ATDC is a substrate for the serine/threonine protein kinase C (PKC) but not the epidermal growth factor (EGF) receptor tyrosine kinase; and (iv) EGF decreases ATDC message and protein expressions in A431 cells after a 24-hr exposure. The phosphorylation studies suggest that the ability of ATDC to modulate cellular radiosensitivity may be mediated in part through a PKC signaling pathway.

Ataxia Telangiectasia↗
PubMed1996

The catalytic core of RNase P.

A deletion mutant of the catalytic RNA component of Escherichia coli RNase P missing residues 87-241 retains the ability to interact with the protein component to form a functional catalyst. The deletion of this phylogenetically conserved region significantly increases the Km, indicating that the deleted structures may be important for binding to the precursor tRNA substrate but not for the cleavage reaction. Under some reaction conditions, this RNase P deletion mutant can become a relatively non-specific nuclease, indicating that this RNA's catalytic center may be more exposed. The catalytic core of the RNase P is formed by less than one third of the 377 residues of the RNase P RNA.

Bacillus subtilis↗
PubMed1996

Hemoglobin oxygenation kinetics and secondary ischemia in renal transplantation.

The significance of poor medullary reperfusion in the etiology of acute tubular necrosis during renal transplantation is poorly understood. Our objective was to determine the kinetics of renal hemoglobin oxygenation using near-infrared spectroscopy during renal transplantation, to provide a framework against which the timing of mitochondrial dysfunction could be considered. New Zealand White rabbit kidneys were flushed with hypertonic citrate solution (0-2 degrees C and autografted immediately (group 1) or stored at 0-2 degrees C for 72 hours before autografting (group 2). Changes in oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) were monitored by near-infrared spectroscopy for 3 hours of reperfusion. Intrarenal perfusion was evaluated separately by barium sulfate angiography. Reperfusion resulted in rapid increases in HbO2 within 1 minute in both groups. Group 1 HbO2 fell sharply to a minimum at 3 minutes but recovered by 20 minutes; group 2 changes were similar, but there was no recovery (P<0.05 by 10 minutes). Hb increased rapidly in both groups upon reperfusion but in group 2 was significantly greater after 10 minutes (P<0.05). Total hemoglobin levels were similar in both groups. Renal hemoglobin saturation was 69% at 1 minute in both groups; there was no significant change in group 1 but a profound desaturation in group 2 to 25% at 10 minute (P<0.005) and no recovery thereafter. Barium sulfate distribution was normal in all group 1 kidneys; cortical distribution was normal in all group 2 kidneys, but medullary perfusion was poor for the first 60 minutes. Renal hemoglobin oxygenation kinetics as determined here do not correlate with the timing of mitochondrial dysfunction previously reported (Thorniley et al., Kidney International, 1994; 45: 1489). We conclude that secondary ischemia during reflow is not the only mechanism leading to acute tubular necrosis.

Animals↗
PubMed1996

Experimental orthotopic small bowel transplantation: a revised model.

Small bowel transplantation is emerging as an alternative treatment for end-stage intestinal failure. To date, immunological and technical problems are still hampering clinical success. Functional experimental small bowel transplantation models have traditionally been plagued with a high technical complication rate. The purpose of this study was to describe in detail the harvesting and transplantation procedure in rats. In this paper the technical aspects of the one-stage, isogenic orthotopic partial small bowel transplantation model with systemic drainage are illustrated. Because of the achieved acceptable survival rate and the favourable functional outcome, the model is considered reliable and reproducible.

Animals↗
PubMed1996

Metabolic effects of cold storage on livers from euthermic and hibernating Columbian ground squirrels.

The current study was undertaken to investigate energy metabolism during hypoxia in the cold in livers from euthermic and hibernating Columbian ground squirrels. We hypothesized that the hibernating Columbian ground squirrel would be able to maintain liver energetics for a considerably longer time than euthermic animals. Particular reference was made to the function of glycolysis, which is the only mechanism for energy production under hypothermic ischemia. The transition from aerobic to anaerobic metabolism was apparent in both euthermic and hibernating animals as lactate levels rose within 1-3 h; total lactate accumulation was 2.5 micromol/g in both groups. In euthermic squirrels, liver ATP and ADP decreased considerably over the first 3-h storage; values dropped by 55% and 34%, respectively. Conversely, as the drain on high energy phosphate pools progressed, there was an increase in low energy adenylate, AMP. Between 10 and 24 h of storage, increases in AMP accounted for approximately 25-30% of total ATP + ADP decrease. The remainder of the drop in adenylates was accounted for by considerable decreases in total adenylate (TA) contents; by 24 h TA contents had decreased by 2.0 micromol/g. Livers from hibernating squirrels exhibited similar patterns of adenylate change and were not significantly higher than their euthermic counterparts. With respect to regulatory control of glycolysis, livers from euthermic squirrels exhibited no regulatory control at phosphofructokinase (PFK) or pyruvate kinase (PK). Livers from hibernating animals, however, showed an activation at PFK by 10 h of cold storage; levels of hexose phosphates, glucose-6-phosphate + fructose 6-phosphate (G6P + F6P), dropped and fructose 1, 6-biphosphate (F1,6P2), increased. Changes in metabolite levels (phosphoenolpyruvate and pyruvate) associated with another key suspect regulatory enzyme, PK, indicated no role in regulatory control of glycolysis during the 24-h period. The apparent increase in PFK responsiveness to declining energy stores may be a futile activation since there was no accompanying increase in anaerobic end product, lactate, and no maintenance of energetics.

Adenine Nucleotides↗
PubMed1996

Cold ischemia-induced damage to vascular endothelium results in permeability alterations in transplanted lungs.

UNLABELLED: Despite suggestions of a connection between endothelial damage and permeability alterations after ischemia and reperfusion in pulmonary tissue undergoing transplantation, no direct correlation between vascular endothelial discontinuity and parenchymal edema has yet been shown. METHODS: Forty-two rat lungs were harvested and stored for 48 or 72 hours under hypothermic and ischemic conditions. Stored pulmonary tissue was studied before transplantation and 5 minutes or 24 hours after transplantation by light microscopy and scanning electron microscopy of arterial vascular endothelium. RESULTS: Stored lungs not subjected to revascularization showed moderate perivascular edema, with small intercellular gaps in endothelial monolayers. Five minutes after transplantation, pulmonary tissue appeared congested, with perivascular and alveolar edema. Examination of vascular endothelium by scanning electron microscopy showed detachment of endothelial cells. Twenty-four hours after transplantation, edema, hemorrhage, and vascular congestion were found in all specimens. Arterial vascular endothelium showed weak intercellular connections, numerous intercellular gaps, and widespread cell detachment. Bronchial epithelial cells appeared damaged after storage, with loss of cilia, blebbing of apical cytoplasm, and cellular rounding. These changes were maintained 5 minutes after transplantation but appeared totally reversed after 24 hours in specimens stored 48 hours, whereas bronchial denudation was observed in 72-hour stored lungs. Statistically significant positive correlations (Kendall p < 0.001) between revascularization time and alveolar edema and hemorrhage were found for both storage periods. CONCLUSION: The results from this study demonstrate correlation between loss of endothelial monolayer continuity and histologic evidence of vascular permeability increases in pulmonary tissue before and after lung transplantation.

Adenosine↗
PubMed1996

Nerve growth factor enhances nerve regeneration through fibronectin grafts.

Soluble fibronectin and nerve growth factor (NGF) promote axonal regeneration when placed in silicone tubes. We investigated the ability of orientated fibronectin mats to bind and release bioactive NGF and the possibility of augmenting axonal regeneration following axotomy by using fibronectin conduits impregnated with NGF. The release of NGF was quantified using a fluorometric ELISA and bioactivity confirmed with a neuronal culture bioassay. Immunohistochemical techniques and computerized image analysis were used to assess the rate and volume of axonal and Schwann cell regeneration. The delivery of NGF to the site of injury produced an increase in the rate (P < or = 0.007) and volume (P < or = 0.004) of both axonal and Schwann cell regeneration when compared to conduits of plain fibronectin. We conclude that the local delivery of NGF by impregnated fibronectin conduits enhances axonal regeneration.

Animals↗
PubMed1996

Effects of depolarizing or non-depolarizing preservation solutions on human endothelial cells during cold hypoxia.

1. Hypothermic storage of whole organs flushed with a preservation solution is common practice in clinical transplantation. This procedure leaves vascular endothelial cells in direct contact with the preservation solution during the length of the cold ischaemic period. 2. Aiming to study the effects of organ preservation on vascular endothelium, we subjected cultures of human umbilical vein endothelial cells to hypoxic and hypothermic storage conditions in vitro for 3 or 16 h. Four preservation solutions with different levels of sodium and potassium were tested. Morphometric analysis and 51Cr leakage index were used to assess monolayer continuity, cell viability and membrane integrity. 3. Hypothermic storage resulted in severe changes in endothelial cell morphology with formation of intercellular gaps that destroyed monolayer continuity after only 3h. Cellular blebbing was a common feature in seriously damaged cells. 4. Morphometric analysis and 51Cr leakage results correlated well. No significant differences between the solutions tested were found after 3h of hypothermic hypoxic storage. After 16h, viability and monolayer continuity were significantly better preserved (Mann-Whitney, P < 0.01) in cells stored in lactobionate-based solutions than in hypertonic citrate solutions. No significant differences were found between endothelial cells stored in extracellular versus intracellular types of solutions for the lactobionate-based solutions. 5. The results of the present experiment showed that after a period of hypothermic hypoxic storage, vascular endothelial cells appeared morphologically deformed and poorly attached in vitro. Lactobionate-based preservation solutions were more effective in preserving viability and continuity. Protection of vascular endothelium under cold hypoxic conditions could be a critical factor in successfully preserving organs for transplantation.

Cell Hypoxia↗
PubMed1996

Non-invasive measurement of cardiac oxygenation and haemodynamics during transient episodes of coronary artery occlusion and reperfusion in the pig.

1. The non-invasive method of near-infrared spectroscopy was used to measure myocardial oxygenation and haemodynamics in response to left anterior descending coronary artery occlusion in a porcine model. 2. Near-infrared spectroscopy measures changes in haemoglobin (and myoglobin) oxygenation and blood volume to yield information on tissue perfusion and flow. It also measures the redox state of cytochrome aa3, thus providing information about intracellular oxygen utilization. 3. Left anterior descending coronary artery occlusion was induced to produce periods of ischaemia lasting between 24s and 13.5 min (n = 13). The changes in deoxyhaemoglobin, oxyhaemoglobin and cytochrome aa3 measured during occlusion were all highly significant compared with baseline variation. In all occlusions (n = 13) a rapid decrease in oxyhaemoglobin concentration (-75.83 +/- 3.27 mumol/l, mean +/- SEM) with a simultaneous increase in deoxyhaemoglobin of 9.27 +/- 1.69 mumol/l was measured. The total haemoglobin concentration also fell by -71.3 +/- 5.32 mumol/l. Cytochrome aa3 was also reduced during occlusion (-8.35 +/- 1.044) mumol/l. 4. Over the range 24-60s occlusion, the magnitude of the fall in total haemoglobin and oxyhaemoglobin correlated with the duration of occlusion (P < 0.003 and 0.013 respectively). For total haemoglobin only the magnitude of the fall correlated with the increase upon release of occlusion (r = 0.89, P < 0.003). 5. Release of occlusion (n = 8) resulted in an immediate increase in the concentration of deoxyhaemoglobin at 9.88 +/- 1.06s, then total haemoglobin at 13.62 +/- 1.23s and finally oxyhaemoglobin at 29.75 +/- 5.96s. The difference between the timing of the maxima after reperfusion is significant (P < 0.002 and P < 0.007 respectively). Moreover, the time for the deoxyhaemoglobin signal to reach maximum values was found to correlate with the duration of occlusion (P < 0.04). This could be indicative of the PO2 of the ischaemic tissues and an immediate off-loading of oxygen from oxyhaemoglobin. The results are reliable, reproducible and sensitive enough to detect the kinetics of haemoglobin oxygenation from a beating heart in situ.

Animals↗
PubMed1996

Long-term results of the use of cultured autologous epithelial cell grafting to mastoid cavities.

Thirty-nine patients (42 ears) who have had a cultured autologous epithelial cell graft technique to a continuously discharging mastoid cavity have been evaluated to determine the continued effectiveness of this procedure. A postal questionnaire indicated a 58% improvement in both the smell and quantity of discharge, and our conclusion is that this is a very effective measure to provide extended symptomatic improvement in this troublesome condition.

Adult↗
PubMed1996

Vitamin E concentrations in the human stomach and duodenum--correlation with Helicobacter pylori infection.

BACKGROUND: Vitamin E (alpha-tocopherol) is an important endogenous antioxidant and may also act as an anticarcinogen. AIM: To determine the vitamin E status of subjects with, and without, gastroduodenal inflammation and Helicobacter pylori infection. SUBJECTS: 36 patients undergoing routine gastroscopy for investigation of dyspepsia. METHODS: High performance liquid chromatography with fluorometric detection was used to determine alpha-tocopherol values. RESULTS: In H pylori negative subjects with normal gastroduodenal histology (n = 11) median alpha-tocopherol values (ng/mg tissue weight) were significantly higher in the corpus (16.4, interquartile range (IQR) 8.9-22.6) than in the antrum (3.0, IQR 2.6-6.7, p = 0.001) or duodenum (6.7, IQR 2.5-8.4, p = 0.001). H pylori infection (n = 19) was associated with a reduction in the corpus alpha-tocopherol values (median 8.3, IQR 4.9-13.7, p < 0.05) but there was no significant change in the antral concentrations although this was the main site of inflammation and neutrophil activity. Duodenal alpha-tocopherol values were not significantly changed in the presence of duodenitis or gastric H pylori infection. alpha-Tocopherol was not detected in the gastric juice of any of the subjects. Plasma alpha-tocopherol concentrations in the H pylori negative subjects (median 10.4 mg/l, IQR 7.2-11.9) were not significantly different to the values in the H pylori positive subjects (median 11.1 mg/l, IQR 7.6-12.7). CONCLUSIONS: Concentrations of alpha-tocopherol in H pylori negative subjects are higher in the corpus than in the antrum or duodenum. In the presence of predominantly antral H pylori infection and neutrophil activity the major change seen is a reduction in corpus alpha-tocopherol values while antral concentrations are maintained. These findings may reflect a mobilisation of antioxidant defences to the sites of maximal inflammation in the stomach.

Adult↗
PubMed1995

Targeted delivery of nerve growth factor via fibronectin conduits assists nerve regeneration in control and diabetic rats.

This study examined the influence of fibronectin conduits joining two halves of a sectioned sciatic nerve, with and without preimpregnation with nerve growth factor, on regeneration in rats with streptozotocin-induced diabetes mellitus. Regeneration, measured morphometrically in fibres containing immunoreactivity to calcitonin gene-related peptide (CGRP) and GAP-43, was significantly less (P < 0.0001 for all comparisons) in diabetic rats with fibronectin mat grafts without nerve growth factor compared to similarly treated controls. Regeneration distances in diabetic rats were reduced to 43% (CGRP-reactive fibres) and 44% (GAP-43-reactive fibres) of controls, and the total amounts of immunoreactivities in the conduits were also reduced, though by lesser amounts (55 and 61% of controls respectively). Impregnation of the conduits with nerve growth factor before implantation increased the distance and amounts of regenerating immunoreactivity in both control and diabetic rats for both CGRP and GAP-43, such that these regeneration parameters were similar in nerve growth factor-treated diabetic rats to those in control rats implanted with untreated fibronectin mat conduits. These findings implicate impaired neurotrophic support in the defective regeneration characteristic of diabetic. neuropathy.

Animals↗
PubMed1995

Stimulation of glycolysis by histidine buffers in mammalian liver during cold hypoxia.

This study was designed to address the reasons why glycolysis in mammalian liver is unable to function more efficiently during periods of cold hypoxia. Our hypothesis was that control of intracellular pH, by use of amino acid buffers with high pKa values, would allow prolonged flux through glycolysis and better maintenance of liver high-energy adenine nucleotide pool. The effects of two concentrations of histidine (90 and 180 mM) and one of carnosine (90 mM), a histidyl dipeptide, on energy metabolism and levels of glycolytic substrate (glucose) and anaerobic endproduct (lactate) were investigated during cold hypoxia using rat livers to model the mammalian system. The transition to anaerobic metabolism was apparent by an immediate rise in lactate levels upon entry into cold hypoxia. By 10-14 h hypoxia, contents of the endproduct had increased by 10, 13.5, and 14.5 mumol/g in buffers containing 90 and 180 mM histidine and 90 mM carnosine, respectively. As well, ATP, total adenylate contents, and "energy charge" ratios exhibited a rapid decline from initial values of 2.3-3.3 mumol/g, 4.3-5.5 mumol/g, and 0.64-0.75, respectively, over the first 2-4 h of cold hypoxia. With respect to efficacy, the 180 mM histidine buffer exhibited the most positive maintenance of adenylate levels, followed closely by 90 mM carnosine, and finally 90 mM histidine as the least effective of the three buffers. Nevertheless, all three buffers examined in this study showed positive effects compared to similarly treated livers stored in a solution of minor buffering capacity (a citrate-based solution) over the same time period. The data support the hypothesis that glycolytic flux and cellular energetics can be maintained by the inclusion of efficient buffering agents during periods of cold hypoxia.

Adenine Nucleotides↗
PubMed1995

Reinnervation and neovascularisation in prefabricated free muscle flaps.

In this study, immediate muscle reinnervation in flap prefabrication was investigated and compared with those flaps which were reinnervated after prefabrication. Using the flow-through wrap-around technique for neovascularisation, denervated external abdominal oblique random muscle flaps in Lewis rats were either immediately reinnervated by implantation of the epigastric nerve or reinnervated late after free transfer, following the prefabrication period of 15 days. Half of the flaps from each group were microsurgically transferred to isogeneic rats. Thirty days later, the flaps were harvested, and neovascularisation and reinnervation were studied with microangiography and immunohistochemistry using antibodies to protein gene peptide (PGP) 9.5, calcitonin gene-related peptide (CGRP), and von Willebrand factor (vWF). Microangiography and quantification of the vWF-stained vessels in the flaps confirmed increased neovascularisation over a longer time course. Reinnervation was found to have no influence over neovascularisation. Nerve sprouting was present 15 days after nerve implantation to the muscle and became widespread by 30 days. CGRP immunoreactivity, which is thought to have some role in trophic and regulatory processes, was observed only after 30 days of reinnervation. Regardless of the timing and extent of reinnervation, a considerable amount of muscle atrophy was observed in the flaps.

Animals↗