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Biomedical subjects

M Burke

Publications and source records attributed to M Burke.

At least 325 records · Page 18Linked to original sources
PubMed1985

W value measurements for protons in tissue-equivalent gas and its constituent gases.

Values of W (the mean energy required to create an ion pair when a charged particle is stopped in a gas) are needed in radiation dosimetry to convert ionisation chamber current readings to absorbed dose. For neutron dosimetry the most important W values are those for protons, and this paper describes absolute measurements for protons with energies between 1.2 and 3.5 MeV for methane-based tissue-equivalent gas and its constituent gases, i.e. methane, carbon dioxide and nitrogen. An ionisation chamber with a parallel-plate arrangement was used to determine the integrated charge created by a measured number of protons, and W values were determined with an estimated uncertainty of about +/- 0.5%. The results are presented and compared with previous measurements. In general the present data tend to be somewhat lower than previously reported values. Finally the accuracy of a formula for predicting W values for gas mixtures from the values for the individual constituents is investigated.

Animals↗
PubMed1985

W value measurements for 241Am alpha particles in various gases.

Measurements of W, the mean energy expended per ion pair formed, have been performed for 241Am alpha particles stopping in a number of the gases commonly used in ionisation chambers. Both absolute and relative measurements were made with nitrogen used as the reference gas for the relative measurements. The absolute method entailed a simultaneous measurement of a quantity of charge and the number of alpha particles which produced that charge, whilst the relative approach simply required a determination of the ratio of ion currents. Results were obtained for methane-based tissue-equivalent gas, for its constituents, i.e. methane, carbon dioxide and nitrogen, for argon, and also for a gas mixture with a composition approximately equivalent to A-150 plastic.

Americium↗
PubMed1985

Comparison of weight, depth, and diagnostic adequacy of specimens obtained with 16 different biopsy forceps designed for upper gastrointestinal endoscopy.

The influence of endoscopic forceps variables (size, design, and make) on biopsy specimen weight, depth, and diagnostic adequacy has been studied in vitro on normal human stomach, and in vivo at endoscopy in dog and in patients. Greater pressure during the biopsy procedure yielded significantly heavier, deeper, and histologically more acceptable specimens. Standard sized forceps (diameter 2.4 mm) and those with ellipsoid cups consistently produced larger specimens than the smaller 'paediatric' forceps (1.8 mm) and those with round cups. Deeper specimens were also obtained using the standard forceps. In vitro and in vivo in the dog, the standard sized forceps also produced specimens of greater diagnostic adequacy than the paediatric forceps. At endoscopy in patients, however, we could not detect any influence of the size, shape, and presence of forceps spike or fenestration on the diagnostic adequacy of the specimens.

Animals↗
PubMed1985

Breast lesions examined by digital angiography. Work in progress.

Differentiation of benign from malignant lesions in screening for breast cancer is usually arrived at via surgical biopsy, an invasive and costly procedure. Digital subtraction angiography (DSA) of the breast is a less invasive procedure. DSA imaging patterns from 22 patients with malignant and benign lesions were compared with surgical biopsy findings. DSA examinations were performed with the breast in an immobilization device and contrast medium was injected into the superior vena cava. Images were produced with a low kilovoltage (50 kVp) to enhance contrast, and a technique yielding an average dose to the breast of less than 2 rad (0.02 Gy) was used. Preliminary clinical results demonstrate the potential of DSA for differentiation of benign and malignant lesions and justify further investigations of its use as an alternative to surgical biopsy.

Angiography↗
PubMed1985

Campylobacter colitis: differentiation from acute inflammatory bowel disease.

We describe 10 patients with campylobacter colitis who gave a characteristic history of an acute diarrhoeal illness, rectal bleeding and colicky abdominal pain. For the majority of patients the clinical and sigmoidoscopic features differentiated campylobacter colitis from acute inflammatory bowel disease. Where doubt remained, evidence of a specific antibody response to campylobacter enabled a presumptive clinical diagnosis to be confirmed.

Adult↗
PubMed1984

Hepatic granuloma in polymyalgia rheumatica.

Hepatic granuloma occurs rarely in the polymyalgia rheumatica syndrome. A case was presented of a 62-year-old woman with polymyalgia rheumatica, elevated concentrations of hepatic enzymes, and granuloma of the liver. Low doses of corticosteroids produced a marked improvement in the patient's condition and a return of liver function tests to normal. This is apparently the first case of polymyalgia rheumatica associated with liver granuloma that has been reported in Israel.

Female↗
PubMed1984

'Essential' hypertension with hypokalemia. Caused by aldosterone-secreting adrenal adenoma.

Primary aldosteronism is a potentially curable cause of hypertension; it occurs in about 1% of hypertensive patients. In the case reported here, persistent hypokalemia developed in a 72-year-old man who had been treated for 13 years for essential hypertension. Investigation revealed elevated aldosterone level and reduced plasma renin activity. Computed tomography and selective angiography showed a tumor in the right adrenal gland. Aldosterone-secreting adenoma of the adrenal gland was diagnosed, and right adrenalectomy was performed. At a six-month follow-up examination, the patient's blood pressure and potassium level were normal.

Adenoma↗
PubMed1983

On the mode of the alkali light chain association to the heavy chain of myosin subfragment 1. Evidence for the involvement of the carboxyl-terminal region of the heavy chain.

Evidence is presented that the removal of the alkali light chain subunit from myosin subfragment 1 results in the exposure of a site (or sites) at the carboxyl-terminal region of the heavy chain that is rapidly digested by both trypsin and alpha-chymotrypsin. In the case of trypsin digestion, cleavage at this site proceeds at a much higher rate than cleavage at the two other sensitive regions located in the interior of the primary structure of this chain. This initial cleavage is responsible for the generation, on further digestion with trypsin, of a carboxyl-terminal fragment about 3000 daltons smaller than the corresponding fragment formed by digestion of subfragment 1. The ability of the heavy chain to reassociate with alkali light chain at 4 degrees C in the presence of MgATP is essentially abolished by cleavage at this exposed site by either trypsin or chymotrypsin. These observations indicate that the alkali light chain is binding to, or is capable of perturbing, a region of the heavy chain adjacent to the subfragment 1/subfragment 2 "hinge" region and support recent proposals that both the DTNB light chain and the alkali light chain may be interacting and may be modulating this flexible region of the cross bridge.

Actins↗
PubMed1983

Primary actinomycotic empyema.

We have presented a rare case of massive primary actinomycotic empyema, which resolved after combined cefazolin therapy and continuous pleural drainage. Poor dental hygiene and heavy smoking are proposed as predisposing factors.

Actinomycosis↗
PubMed1983

The effect of mismatching for HLA-DR in recipients of renal allografts sharing one HLA-ABC haplotype with related donors.

The effects of mismatching for DR antigens on renal allograft survival rates have largely been restricted to analyses of cadaver transplant results. Analyses of HLA matching in recipients of transplants from related donors have focused on the number of haplotypes shared between the recipients without regard to DR, or on the total number of HLA antigens mismatched, or on the degree of MLC responsiveness of the recipient to the donor. Most related donor-recipient pairs sharing only one HLA haplotype will be mismatched for DR at the other haplotype, but because there are a limited number of DR alleles, sharing of DR antigens on the mismatched haplotypes occurs relatively frequently. To determine the influence of mismatching for DR on the fate of renal allografts from related donors, we analyzed the results of 172 kidney transplants from related donors who shared one HLA-ABC haplotype with the recipient. There were 156 primary grafts and 16 retransplants; 147 donor-recipient pairs were satisfactory typed for DR antigens. Because genotyping was not usually done, we performed two analyses under two different assumptions. The first assumption was that individuals expressing less than or equal to 1 DR antigen had null antigens, or were homozygous for DR; the alternative assumption was that blanks were true antigens and individuals with blanks were heterozygous. The first assumption is more likely to be correct, and is the assumption used in most analyses of the effect of DR antigen mismatches on the results of cadaveric transplantation. Under the first assumption, of the 147 related donor-recipient pairs in whom DR typing was satisfactory, 33% were mismatched for 0, 64% for 1, and 3% for 2 DR antigens. The one-year absolute graft survival rates in recipients of kidneys from donors with 0 mismatches for DR was 92% (n = 49); in those with one mismatch for DR it was 82% (n = 94); and from those with two mismatches it was 50% (n = 4). The one-year graft survival rate in 25 donor-recipient pairs in which one or both members could not be satisfactorily DR typed was 76%. Differences in graft survival rates between the 0 and 1 and the 1 and 2 DR-mismatched groups were not statistically significant.(ABSTRACT TRUNCATED AT 400 WORDS)

Graft Rejection↗