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Biomedical subjects

G M Heaton

Publications and source records attributed to G M Heaton.

12 recordsLinked to original sources
PubMed1992

Technical aspects of hemodynamic pressure monitoring.

Invasive hemodynamic pressure monitoring may be used in the care of the critically ill pregnant woman. The critical care obstetric nurse must have a thorough understanding of the indications for monitoring and interpretation of acquired data and must develop the skills necessary to operate and trouble-shoot the related equipment. This article provides a review of technical aspects of a hemodynamic pressure monitoring system.

Critical Care↗
PubMed1992

Principles of intracranial pressure monitoring.

Increased intracranial pressure (ICP) is a life-threatening condition that requires immediate recognition and therapeutic intervention. The obstetric nurse must have in-depth knowledge of the physiologic changes occurring during pregnancy, the relationship between these changes and cerebrovascular accidents, and the pathophysiology of increased intracranial pressure to provide the most comprehensive nursing care. This chapter describes fundamental principles of intracranial pressure monitoring.

Critical Care↗
PubMed1978

Brown-adipose-tissue mitochondria: photoaffinity labelling of the regulatory site of energy dissipation.

Brown-adipose-tissue mitochondria possess an energy-dissipating ion uniport which is inhibited by purine nucleotides. The regulatory nucleotides bind to a high-affinity site on the outer face of the inner membrane which is independent of the adenine nucleotide translocator. A direct correlation between affinity for the regulatory site and ability to inhibit the ion uniport is demonstrated for a number of nucleotide analogues. 8-Azido-adenosine 5'-triphosphate, a photoaffinity label, also competes with GDP for the binding site and induces respiratory control. 8-Azido-adenosine [gamma-32P]triphosphate was prepared and covalently bound to hamster brown-adipose-tissue mitochondria by near-ultraviolet irradiation. Two major radioactive bands were identified of apparent molecular weight 30000 and 32000, representing 6% and 10% of the inner membrane protein respectively. Selective labelling enabled the 30000-Mr protein to be identified as the carboxyatractylate binding component of the adenine-nucleotide translocator and the 32000-Mr protein to be identified as the regulatory site of the energy-dissipating ion uniport. The levels of the 32000-Mr protein in the inner membrane of guinea-pig brown-adipose-tissue mitochondria correlate with the degree of thermogenic adaptation of the animal.

Adenosine Triphosphate↗
PubMed1978

The identification of the component in the inner membrane of brown adipose tissue mitochondria responsible for regulating energy dissipation.

The proton conductance of the inner membrane of hamster brown adipose tissue mitochondria can be regulated in vitro by exogenous purine nucleotides, which bind to a component on the outer face of the inner membrane. This unique mechanism has been proposed to represent the molecular site of non-shivering thermogenesis in this tissue. Using a photo-affinity analogue of ATP, we have identified the nucleotide binding component as a protein of 32,000 daltons.

Adipose Tissue, Brown↗
PubMed1976

Hamster brown-adipose-tissue mitochondria. The role of fatty acids in the control of the proton conductance of the inner membrane.

The specific ability of fatty acids to increase the proton conductance of the inner membrane of mitochondria from the liver and brown adipose tissue of cold-adapted hamsters was compared. The liver and brown-adipose-tissue mitochondria had their effective proton conductances increased by respectively 0.028 and 0.94 nmol H+- min-1. (mV of proton electrochemical gradient)-1 for each nmol of palmitate bound. No difference could be detected between the abilities of liver and brown-adipose-tissue mitochondria to bind fatty acids. Purine nucleotides did not displace farry acids from the brown-adipase-tissue mitochondria. The endogenous fatty acid content of hamster brown-adipose-tissue mitochondria prepared in the absence of album was found to be equivalent to 17 +/- 7 nmol of palmitate/mg protein. The fatty acid content was reduced to 1 nmol/mg after preincubation of the mitochondria with CoA, ATP and carnitine. No inert pool of fatty acids could be detected. The endogenous fatty acids of hamster liver mitochondria were less than 4 nmol of palmitate equivalent/mg protein. Some of the fatty acid associated with the brown-adipose-tissue mitochondria originates during preparation of the mitochondria. In the light of these results, the physiological role of the fatty acids in controlling the proton conductance of the brown-adipose-tissue mitochondrial inner membrane, and hence- non-shivering thermogenesis, is re-evaluated.

Acclimatization↗
PubMed1976

The calcium conductance of the inner membrane of rat liver mitochondria and the determination of the calcium electrochemical gradient.

1. A method is described for establishing steady-state conditions of calcium transport across the inner membrane of rat liver mitochondria and for determining the current of Ca2+ flowing across the membrane, together with the Ca2+ electrochemical gradient across the native Ca2+ carrier. These parameters were used to quantify the apparent Ca2+ conductance of the native carrier. 2. At 23 degrees C and pH7.0, the apparent Ca2+ conductance of the carrier is close to 1 nmol of Ca2+-min-1-mg of protein-1 mV-1. Proton extrusion by the respiratory chain, rather than the Ca2+ carrier itself, may often be rate-limiting in studies of initial rates of Ca2+ uptake. 3. Under parallel conditions, the endogenous H+ conductance of the membrane is 0.3 nmol of H+-min-1-mg of protein-1-mV-1. 4. Ruthenium Red and La3+ both strongly inhibit the Ca2+ conductance of the carrier, but are without effect on the H+ conductance of the membrane. 5. The apparent Ca2+ conductance of the carrier shows a sigmoidal dependence on the activity of Ca2+ in the medium. At 23 degrees C and pH7.2, half-maximum conductance is obtained at a Ca2+ activity of 4.7 muM. 6. The apparent Ca2+ conductance and the H+ conductance of the inner membrane increase fourfold from 23 degrees to 38 degrees C. The apparent Arrhenius activation energy for Ca2+ transport is 69kJ/mol. The H+ electrochemical gradient maintained in the absence of Ca2+ transport does not vary significantly with temperature. 7. The apparent Ca2+ conductance increases fivefold on increasing the pH of the medium from 6.8 to 8.0. The H+ conductance of the membrane does not vary significantly with pH over this range. 8. Mg2+ has no effect on the apparent Ca2+ conductance when added at concentration up to 1 mM. 9. Results are compared with classical methods of studying Ca2+ transport across the mitochondrial inner membrane.

Animals↗