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Biomedical subjects

R Waugh

Publications and source records attributed to R Waugh.

At least 127 records · Page 7Linked to original sources
PubMed1989

Decision-making in 100 patients referred to the Australian National Liver Transplantation Unit.

One hundred patients were referred to the Australian National Liver Transplantation Unit between January 1986 and August 1987. The commonest disorders for referral were chronic active hepatitis in adults (22 cases), fulminant hepatic failure (14), primary biliary cirrhosis (PBC) (12) and primary sclerosing cholangitis (PSC) (10). Of the 100 patients 31 were activated for transplantation while 35 were deferred and 34 were found to be unsuitable. The decision-making in these patients is discussed according to disease category. Timing of transplantation in PBC and PSC seemed clearcut, with 50% of referred patients being activated. However, major difficulties in timing of transplantation were found, particularly in patients with chronic active hepatitis (CAH) and fulminant hepatic failure (FHF). Of 36 patients with CAH (22) or FHF (14) only five were put on the active waiting list and only two were transplanted. Overall, 25 of the 31 patients underwent orthotopic liver transplantation, with 16 alive two-30 months later.

Adult↗
PubMed1986

Pleiotropic hydrogenase mutants of Escherichia coli K12: growth in the presence of nickel can restore hydrogenase activity.

Anaerobic growth in the presence of 0.6 mM NiCl2 was able to restore hydrogenase and benzyl-viologen-linked formate dehydrogenase activities to a mutant (FD12), which is normally defective in these activities. This mutant carries a mutation located near minute 58 in the genome. Hydrogenase isoenzyme I and II activities were restored along with the hydrogenase activity that forms part of the formate hydrogen lyase system. A plasmid (pRW1) was constructed, containing a 4.8 kb chromosomal DNA insert, which was able to complement the lesion in mutant FD12. Further mutants with mutations near 58 minutes on the chromosome, and which lacked hydrogenase and formate dehydrogenase activities were isolated. These mutants were divided into three groups. Class I mutants were restored to the wild-type phenotype either by growth with 0.6 mM NiCl2 or following transformation with pRW1. Class II mutants were also complemented by pRW1 but were unaffected by growth with NiCl2. Class III mutants were unaffected by both pRW1 and growth with NiCl2. The cloned 4.8 kb fragment of chromosomal DNA therefore encodes two genes essential for hydrogenase activity. Restriction analysis indicates that the cloned DNA is the same as a fragment that has previously been cloned and which complements the hydB locus (Sankar et al. (1985) J. Bacteriol., 162, 353-360). None of the three classes of mutants possess mutations in hydrogenase structural genes.

Anaerobiosis↗
PubMed1984

Radiologically-guided percutaneous fine needle aspiration biopsies of abdominal and osseous lesions.

The inductions, technique, complications and results of radiologically-guided percutaneous fine needle aspiration biopsy (FNAB) of abdominal and osseous sites performed over a four and a half year period at an Australian tertiary referral hospital are presented. FNAB provided a positive tissue diagnosis for malignancy in 79% of osseous and 78% of abdominal lesions with no false positive diagnoses in either series. Particular problems encountered and the methods employed to overcome them are discussed.

Abdominal Neoplasms↗
PubMed1984

Curative treatment of bleeding esophageal varices secondary to a splenic arterio-venous fistula.

A 59 year old female, who presented with abdominal pain, diarrhea, and ascites, developed major bleeding from esophageal varices. Celiac angiography demonstrated a splenic arterio-venous fistula with early filling of an enlarged splenic vein and esophageal varices (pre-sinusoidal extra hepatic portal hypertension). The patient underwent splenectomy and resection of the fistula with resultant disappearance of the varices and presenting symptoms.

Arteriovenous Fistula↗
PubMed1979

Thermoelasticity of red blood cell membrane.

The elastic properties of the human red blood cell membrane have been measured as functions of temperature. The area compressibility modulus and the elastic shear modulus, which together characterize the surface elastic behavior of the membrane, have been measured over the temperature range of 2-50 degrees C with micropipette aspiration of flaccid and osmotically swollen red cells. In addition, the fractional increase in membrane surface area from 2-50 degrees C has been measured to give a value for the thermal area expansivity. The value of the elastic shear modulus at 25 degrees C was measured to be 6.6 X 10(-3) dyne/cm. The change in the elastic shear modulus with temperature was -6 X 10(-5) dyne/cm degrees C. Fractional forces were shown to be only on the order of 10-15%. The area compressibility modulus at 25 degrees C was measured to be 450 dyne/cm. The change in the area compressibility modulus with temperature was -6 dyne/cm degrees C. The thermal area expansivity for red cell membrane was measured to be 1.2 X 10(-3)/degrees C. With this data and thermoelastic relations the heat of expansion is determined to be 110-200 ergs/cm2; the heat of extension is 2 X 10(-2) ergs/cm2 for unit extension of the red cell membrane. The heat of expansion is of the order anticipated for a lipid bilayer idealized as twice the behavior of a monolayer at an oil-water interface. The observation that the heat of extension is positive demonstrates that the entropy of the material increases with extension, and that the dominant mechanism of elastic energy storage is energetic. Assuming that the red cell membrane shear rigidity is associated with "spectrin," unit extension of the membrane increases the configurational entropy of spectrin by 500 cal/mol.

Elasticity↗
PubMed1977

Osmotic correction to elastic area compressibility measurements on red cell membrane.

In a recent article (Biophys. J. 16:585, 1976), we reported measurements of the elastic area compressibility modulus or red cell membranes using micropipette aspiration on osmotically preswollen red cells. Subsequently, we have analyzed the effects of osmotic and hydrostatic pressure driving forces across the cell membrane in conjuction with the mass conservation equation; we find that the change in cell volume due to the reversible movement of water out of the cell can produce one-third of the movement of the cell projection in the pipette tip. Since the actual volume changes is too small to measure directly (about 1% of the total cell volume), we have used an indirect experimental method to provide critical evaluation of the analysis of cell volume change versus applied pressure; this is based on the model that the change in cell volume is inversely proportional to the cellular osmotic strength. We have increased the cellular cation concentration with a drug, nystatin, and measured the elastic area compressibility modulus corrected for osmotic volume changes as a function of cellular osmotic strength. We find that the corrected elastic are compressibility modulus is independent of cellular osmotic strength, which supports the model and calculated correction for the osmotic effect. The elastic area compressibility modulus is 450 dyn/cm at 25 degrees C instead of 300 dyn/cm, determined previously.

Biological Transport↗
PubMed1976

Anaesthesia for separation of conjoined twins.

We have presented the anaesthetic technique used during the separation of two female pygopagus conjoined twins. The twins were three months old and weighed 9.2 kilograms on the day of the operation. The main problem during the operation was to evaluate blood volume lost by each patient and a close monitoring of all cardiovascular parameters was necessary to attain this aim. The little pygopagus recuperated well and left the hospital at six months old.

Anesthesia, Inhalation↗
PubMed1976

Elastic area compressibility modulus of red cell membrane.

Micropipette measurements of isotropic tension vs. area expansion in pre-swollen single human red cells gave a value of 288 +/- 50 SD dyn/cm for the elastic, area compressibility modulus of the total membrane at 25 degrees C. This elastic constant, characterizing the resistance to area expansion or compression, is about 4 X 10(4) times greater than the elastic modulus for shear rigidity; therefore, in situations where deformation of the membrane does not require large isotropic tensions (e.g., in passage through normal capillaries), the membrane can be treated by a simple constitutive relation for a two-dimensionally, incompressible material (i.e. fixed area). The tension was found to be linear and reversible for the range of area changes observed (within the experimental system resolution of 10%). The maximum fractional area expansion required to produce lysis was uniformly distributed between 2 and 4% with 3% average and 0.7% SD. By heating the cells to 50 degrees C, it appears that the structural matrix (responsible for the shear rigidity and most of the strength in isotropic tension) is disrupted and primarily the lipid bilayer resists lysis. Therefore, the relative contributions of the structural matrix and lipid bilayer to the elastic, area compressibility could be estimated. The maximum isotropic tension at 25 degrees C is 10-12 dyn/cm and at 50 degrees C is between 3 and 4 dyn/cm. From this data, the respective compressibilities are estimated at 193 dyn/cm and 95 dyn/cm for structural network and bilayer. The latter value correlates well with data on in vitro, monolayer surface pressure versus area curves at oil-water interfaces.

Cell Membrane↗
PubMed1976

Investigation of sound level conversion as a means of rating ear protector performance.

Sound level conversion, a single-number measure describing the noise reduction afforded by ear protectors, was calculated for 30 ear protectors in 615 industrial noise spectra. The results vindicate the utility of this measure for situations in which the noise hazard is characterised only by C- and A-weighted sound levels. A simple procedure for calculating SLC, accurate within +/- 1dB, is proposed. Minor adjustments of the calculation procedure enable wearer protection rates in the range 50% to 97% to be achieved.

Ear Protective Devices↗