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Biomedical subjects

D J Dawson

Publications and source records attributed to D J Dawson.

At least 37 records · Page 2Linked to original sources
PubMed1993

Biochemical properties and fatty acid composition of Mycobacterium haemophilum: study of 16 isolates from Australian patients.

The biochemical properties and fatty acid compositions of 16 strains of Mycobacterium haemophilum from Australian patients were studied. The strains proved to be indistinguishable from each other but could readily be differentiated from other slowly growing mycobacteria with similar cultural features. Mycolic acid analyses revealed the presence of alpha-, methoxy-, and ketomycolates. The fatty acid composition supports the validity of the fact that M. haemophilum is a distinct species. The fatty acid composition was consistent among the 16 strains, but it was unusual in that there was some resemblance to the fatty acid composition of M. leprae. The wide range of pHs (5.4 to 7.4) that supported growth of M. haemophilum on artificial medium is in keeping with suggestions that M. haemophilum exists in an environmental habitat.

Australia↗
PubMed1992

Mycobacterium haemophilum causing perihilar or cervical lymphadenitis in healthy children.

We describe five apparently immunologically normal children with infection caused by Mycobacterium haemophilum and resulting in perihilar or cervical lymphadenitis. Clinical distinction from Mycobacterium tuberculosis infection could be made by culture only, because differential Mantoux test results suggested tuberculosis. Treatment of these children involved chemotherapy or surgery or both, and outcome in all cases has been excellent. We believe that M. haemophilum should be added to the list of non-tuberculosis mycobacteria known to cause lymphadenitis in otherwise healthy children.

Antitubercular Agents↗
PubMed1991

Medulloblastoma: long-term follow-up of patients treated with electron irradiation of the spinal field.

Thirty-two patients with posterior fossa medulloblastoma underwent treatment with electron irradiation to the spinal field. The 5- and 10-year actuarial survival rates were 57% and 50%, respectively. Late complications observed in the 15 patients followed up for more than 5 years were short stature (six patients), decreased sitting-standing height ratio (four patients), scoliosis (two patients), poor school performance (seven patients), xerostomia (one patient), esophageal stricture (one patient), pituitary dysfunction (four patients), primary hypothyroidism (one patient), bilateral eighth-nerve deafness (one patient), and carcinoma of the thyroid (one patient). Complications following treatment with electrons to a spinal field are compared with reported complications following treatment with photons to the spinal field. Although short-term reactions were minimal, the authors found no difference in late complications. More sophisticated treatment planning may show such a long-term benefit in the future.

Adolescent↗
PubMed1991

Characterization by restriction endonuclease analysis and seroagglutination of strains of Mycobacterium avium and Mycobacterium intracellulare obtained from farmed deer.

Restriction endonuclease analysis and seroagglutination were used to characterize strains of Mycobacterium avium and Mycobacterium intracellulare (collectively, MAI) recovered from 1 local herd and 2 imported shipments of red deer (Cervus elaphus) that developed sensitization to bovine tuberculin during skin testing. A total of 31 MAI strains were isolated from lymph node pools (head, thorax, abdomen, and peripheral regions) of 21 of 29 local deer. Similarly, 15 MAI strains were isolated from the lymph node pools of 12 deer from the 2 imported shipments. Mycobacterial strains were isolated from more than 1 of the lymph node pools of 9 local and 2 imported deer. Most of the strains (59% from local deer, 46% from imported deer) were recovered from the lymph nodes of the head region. After restriction endonuclease analysis of these isolates using the enzymes Bcl I, BstEII, and Pvu II, 26 of the strains from the local herd were separated into 3 groups, each consisting of strains with indistinguishable or closely related patterns. Seroagglutination results indicated that the first of these groups contained strains belonging to serotype 1, the second group contained strains belonging to serotype 8; and the third group of strains belonged to serotype 3 and 9. The 5 remaining strains from the local herd had unrelated restriction patterns. One of these belonged to serotype 3, whereas the remaining 4 could not be serotyped. Restriction analysis of the 15 strains from the imported deer identified 2 groups. Seroagglutination results indicated that 1 group contained strains belonging to serotype 2 and the other group contained strains belonging to serotype 8.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination Tests↗
PubMed1990

Infection with Mycobacterium avium complex in Australian patients with AIDS.

Data supplied by tuberculosis reference laboratories in Australia indicate that from mid-1985 to the end of 1988, 202 patients with the acquired immunodeficiency syndrome (AIDS) were diagnosed as having concomitant infection caused by organisms of the Mycobacterium avium complex. This figure represents 17.3% of all AIDS cases diagnosed. Serotyping showed that the majority of isolates were serovars of M. avium, namely serovars 1, 4 and 8. There is evidence of geographic differences in the dominant serovar. Of 45 patients with isolates from more than one site of the body, 17 (38%) were infected with at least two different serovars. The findings show the importance of disseminated atypical mycobacteriosis in patients with AIDS, and they provide data for use in defining the epidemiology and natural history of such infections.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Simultaneous assessment of intestinal permeability and lactose tolerance with orally administered raffinose, lactose and L-arabinose.

1. In order to develop an improved differential sugar absorption test for simultaneously assessing intestinal permeability and lactose intolerance, methods were established for determining raffinose, lactose and L-arabinose in human urine. Using NAD(P)H-coupled enzymatic assays and fluorimetry, each sugar was measurable over a concentration range of approximately 3-300 mumol/l in diluted urine specimens. 2. After an overnight fast, 40 normal volunteers drank an iso-osmotic solution containing raffinose, lactose and L-arabinose. The median 5 h urinary sugar excretion was 0.26% of the ingested raffinose, 0.05% of lactose and 17.5% of L-arabinose. 3. In 143 patients with gastrointestinal disease, excretion of both ingested raffinose and lactose was significantly increased in coeliac disease in relapse or in partial remission and in Crohn's disease, but not in the irritable bowel syndrome, coeliac disease in remission or ulcerative colitis. Excretion of lactose, but not raffinose, was increased in patients with mucosal lactase deficiency, whereas excretion of L-arabinose was reduced in all disease groups except ulcerative colitis. 4. Discrimination between diseases was poor when based on individual sugar recoveries, but improved dramatically when excretion was expressed relative to that of L-arabinose. The raffinose/L-arabinose excretion ratio, an index of intestinal permeability, was greater than 0.08 in 15/15 untreated coeliac patients but less than 0.06 in all normal subjects and in 9/9 lactase-deficient patients, 15/16 recovered coeliac patients, 5/6 patients with ulcerative colitis, 13/16 patients with Crohn's disease and 61/62 patients with irritable bowel syndrome.

Adolescent↗
PubMed1990

Identification of various serovar strains of Mycobacterium avium complex by using DNA probes specific for Mycobacterium avium and Mycobacterium intracellulare.

Reference strains of the Mycobacterium avium complex (MAC) belonging to serovars 1 to 28 were examined with DNA probes (Gen Probe Rapid Diagnostic System for the MAC; Gen Probe Inc., San Diego, Calif.) specific for either M. avium or Mycobacterium intracellulare. This study revealed that the earlier designations of the MAC serovars, in which serovars 1 to 3 and 4 to 28 were regarded as M. avium and M. intracellular, respectively, should be revised as follows. First M. avium includes serovars, 1 to 6, 8 to 11, and 21. Second, M. intracellulare includes serovars 7, 12 to 20, and 25. However, other serovars, such as serovars 22 to 24 and 26 to 28, involve M. intracellulare, Mycobacterium scrofulaceum, and MAC that are lacking in the reactivity with either DNA probe and that are too disordered to enable a conclusive description here, particularly concerning their taxonomic positions in the MAC.

Antigens, Bacterial↗
PubMed1990

Arylsulfatase activity for differentiating Mycobacterium avium and Mycobacterium intracellulare.

Arylsulfatase activities (96-h reaction) of various strains of Mycobacterium avium and M. intracellulare, as identified by a DNA probe test, were measured. The enzyme activities of M. avium strains were significantly lower [corrected] than those of M. intracellulare strains (P less than 0.005 to P less than 0.025). The enzyme activities did not vary with serovar; that is, the activities of serovars 1, 2, 8, and 9 (belonging to M. avium) were similar to each other, as were the activities of serovars 7, 12, 13, 14, and 16 (belonging to M. intracellulare). The results indicate the usefulness of the arylsulfatase test in distinguishing M. avium from M. intracellulare in an accurate manner.

Arylsulfatases↗
PubMed1988

Changes of the biotype of Mycobacterium avium-Mycobacterium intracellulare complex causing lung disease in Japan.

A survey was carried out on the biological and biochemical characteristics of 661 strains of Mycobacterium avium-M. intracellulare complex that caused lung disease in the period 1976 to 1986. The results showed that the proportion of strains which showed 2-week-arylsulphatase activity and that of those which were able to utilize glucose as sole carbon source in the presence of glutamate-nitrogen decreased markedly, and that the proportion of those which utilized neither n-butanol nor iso-butanol as sole carbon sources in the presence of ammoniacal nitrogen increased markedly over these 11 years. These findings indicate that the predominant biotype changed from M. intracellulare to M. avium during the period under study. This postulate is supported by a limited study of the serovars present among the isolates.

Arylsulfatases↗
PubMed1988

Changes in jejunal permeability and passive permeation of sugars in intestinal biopsies in coeliac disease and Crohn's disease.

1. The relative effects of changes in mucosal surface area and mucosal permeability on the passive uptakes of mannitol and raffinose have been studied in vitro using jejunal biopsies from 48 controls, 32 patients with coeliac disease and 11 patients with Crohn's disease. Total mucosal permeation was corrected for surface area measured morphometrically to provide an index of mucosal permeability. 2. In untreated coeliac disease, permeation of mannitol was reduced by 35% (P = 0.006) and that of raffinose was increased by 66% (P = 0.0095) compared with controls, whereas mucosal permeability to mannitol was increased twofold (P = 0.009) and to raffinose fivefold (P = 0.0001). Mucosal permeability was similar for each sugar. 3. In treated coeliac disease, permeation and permeability for mannitol were normal, but remained elevated for raffinose by 23% (P = 0.036) and 41% (P = 0.024), respectively. 4. In Crohn's disease, permeation of mannitol was reduced by 21%, but that of raffinose and mucosal permeability to both sugars were normal. 5. These findings suggest that surface area is quantitatively more important than mucosal permeability in determining the total permeation of mannitol, while the converse is true for raffinose. The findings are compatible with paracellular uptake of raffinose, but with both paracellular and transcellular uptake of mannitol. Both pathways are affected in coeliac disease, whereas only transcellular uptake is affected in Crohn's disease.

Adolescent↗
PubMed1988

Bacteremia caused by Mycobacterium neoaurum.

An immunocompromised patient with an indwelling Hickman catheter developed Mycobacterium neoaurum bacteremia. This rapidly growing mycobacterium was previously isolated from soil, dust, and water but has not been described as a human pathogen. The infection responded to therapy with cefoxitin and gentamicin. It was not necessary to remove the Hickman catheter.

Catheterization, Central Venous↗
PubMed1987

The kinetics of monosaccharide absorption by human jejunal biopsies: evidence for active and passive processes.

The kinetics of initial rates of uptake of glucose, galactose, arabinose and mannitol have been measured in jejunal biopsies from normal subjects in order to investigate the existence of multiple uptake systems. Glucose kinetics fitted best a model of a saturable uptake system (app Kt = 2.06 +/- 0.33 mM, app Jmax = 93.85 +/- 1.19 nmol/10 min/mg dry weight), together with a linear uptake indistinguishable from the passive uptake of arabinose and mannitol (app Kd = 0.80 +/- 0.05 nmol/10 min/mg dry weight/mM for glucose, 0.75 +/- 0.03 for arabinose, and 0.83 +/- 0.03 for mannitol). The saturable uptake, but not the linear uptake, was inhibited by phlorizin and by the absence of sodium. Cytochalasin B and phloretin had no effect on overall uptake. Galactose kinetics in the absence of inhibitors fitted best a model of a single saturable uptake system (app Kt = 11.05 +/- 0.12, app Jmax = 201.9 +/- 1.13) with no evidence of linear uptake. In the presence of phlorizin, or in the absence of sodium, uptake was predominantly linear with app Kds of 0.84 +/- 0.03 and 0.79 +/- 0.01, not significantly different from the linear component of glucose uptake. We conclude that hexose uptake in human jejunum in vitro occurs by both active and passive routes, and that the active uptake of galactose appears to be inhibited at high galactose concentration.

Adolescent↗
PubMed1986

Lactose digestion by human jejunal biopsies: the relationship between hydrolysis and absorption.

The relationship between lactose hydrolysis and absorption of released glucose was investigated by determining the kinetics of lactose digestion by jejunal biopsies incubated in vitro. Lactase activity in intact biopsies correlated with conventional assay of tissue homogenates (r = 0.85, p less than 0.001), and glucose uptake from 28 mM lactose was directly proportional to lactase activity (r = 0.95, p less than 0.001) in 21 subjects with normal lactase levels, six with hypolactasia (primary or secondary to coeliac disease) and two with lactose intolerance but normal lactase activity. Kinetic analysis at 0.56-56 mM lactose in five normal subjects showed saturable kinetics for hydrolysis (app Km = 33.9 +/- 2.2 mM; app Vmax = 26.5 +/- 1.1 nmol/min/mg dry weight) but glucose uptake could be fitted to a model either of saturable uptake (app Kt = 47.2 +/- 0.3 mM; app Jmax = 14.1 +/- 0.2 nmol/min/mg) or saturable uptake plus a linear component (app Kt = 21.3 +/- 1.15; app Jmax = 4.59 +/- 0.12; app Kd = 0.093 +/- 0.010 nmol/min/mg/mM). The proportion of glucose taken into the tissue did not significantly exceed 50% of the total released at any lactose concentration suggesting the lack of an efficient capture mechanism for the released glucose. The results suggest that lactose hydrolysis is the rate limiting step in the overall absorption of glucose from lactose in vitro, and that the relationship between hydrolysis and absorption is the same in normal subjects and in hypolactasic subjects.

Adolescent↗
PubMed1985

Detection of inflammatory bowel disease in adults and children: evaluation of a new isotopic technique.

The distribution of radioactivity after the oral administration of sucralfate labelled with technetium-99m was studied in 33 patients with Crohn's disease (13 adults, 20 children), 10 with ulcerative colitis (four adults), and 29 controls (23 with upper intestinal disease, four irritable bowel, one hypolactasia, and one malrotation of the gut). Positive scans were obtained in all patients with ulcerative colitis and 29 of 31 with active Crohn's disease. The scans of two patients with inactive Crohn's disease were negative. There were two false negative scans in patients with Crohn's colitis and one false positive scan. Overall, sensitivity was 95% and specificity 97%. Comparison with radiology in 39 patients showed similar distribution of disease in 24 and more extensive disease in 12. The scan was inexpensive, simple to perform, well tolerated, allowed small and large bowel to be visualised simultaneously, and used a lower dose of radiation than barium studies. It may prove useful as a screening test for inflammatory bowel disease and in the serial assessment of disease activity.

Administration, Oral↗