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Biomedical subjects

R B Gordon

Publications and source records attributed to R B Gordon.

At least 55 records · Page 3Linked to original sources
PubMed1987

Molecular studies of hypoxanthine-guanine phosphoribosyltransferase mutations in six Australian families.

Genomic deoxyribonucleic acid (DNA) was isolated from six hemizygotes and five heterozygotes from unrelated families exhibiting the full clinical spectrum of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency. The DNA was digested with the restriction endonucleases, Bam H1, Pst 1 and Taq 1, previously found to be useful in demonstrating restriction fragment length polymorphism (RFLP) at the HPRT locus of the X-chromosome. DNA blotting experiments using a full length HPRT-cDNA probe, have revealed RFLPs in three families which may prove useful for the diagnosis of HPRT deficiency and the determination of heterozygosity. Total ribonucleic acid (RNA) was also extracted from our 11 subjects and analysed by Northern blotting for the presence of HPRT-messenger (mRNA). Apparently normal HPRT-mRNA was demonstrated in all the hemizygotes and heterozygotes for partial HPRT deficiency. In the families with complete HPRT deficiency (Lesch-Nyhan syndrome), the heterozygotes had normal HPRT-mRNA. However, one hemizygote had a complete absence of message for HPRT, while the other hemizygote had considerably reduced amounts of this message.

DNA↗
PubMed1987

Cecal diverticulitis: evaluation with CT.

The findings of computed tomographic (CT) examinations in seven patients with cecal diverticulitis are described and correlated with those of barium studies. The CT findings were linear and streaky densities in the pericecal fat compatible with pericecal inflammation (seven cases), intramural abscess (one case), thickening of the cecal wall (two cases), and cecal diverticulum (one case). Barium studies, available in four patients, led to a correct diagnoses of diverticulitis in two cases. CT scanning is a sensitive means by which to detect cecal diverticulitis. The radiographic appearance of the disease, however, mimics that of appendicitis, unless more specific findings such as cecal diverticula or intramural abscess with adjacent inflammation is detected. CT and barium study are complementary methods of examination that improve our ability to diagnose cecal diverticulitis and its complications.

Adult↗
PubMed1987

Perforated colorectal neoplasms: correlation of clinical, contrast enema, and CT examinations.

Results of clinical, contrast enema (CE), and computed tomographic (CT) examinations in 39 patients with perforated colorectal neoplasms were retrospectively reviewed. Twenty patients were toxemic at initial presentation, but in only four patients was the diagnosis of perforated colorectal neoplasm initially suspected clinically. CE study was performed in 22 patients and enabled the diagnosis of perforated neoplasm in 11 cases, neoplasm alone in eight, and neither neoplasm nor perforation in three. CT was performed in 38 patients and enabled the diagnosis of perforated neoplasm in 36; pericolic phlegmon but no mass lesion was evident in two. In 16 patients, CT also demonstrated metastatic disease. Because of its reliability in establishing the diagnosis and staging the extent of the inflammatory and neoplastic disease, CT is indicated in cases of suspected or proved perforated colorectal neoplasm and in cases in which CE study findings are indeterminate or suggestive of perforated neoplasm.

Adenocarcinoma↗
PubMed1986

CT of appendicitis.

The CT findings of 38 consecutive patients with acute appendicitis are analyzed, described, and illustrated. CT showed intraabdominal disease in 92% of patients and made a specific diagnosis of appendicitis in 79% of cases. The most common CT findings were pericecal inflammation (68%), abscess (55%), calcified appendicolith (23%), and an abnormal appendix (18%). CT had a sensitivity similar to that of contrast enema examinations, but it correlated much better with the surgical findings in detecting the precise nature, extent, and location of the disease process. Normal CT does not exclude appendicitis, since mild forms without periappendiceal disease may escape detection.

Acute Disease↗
PubMed1985

Xanthine-containing calculi during allopurinol therapy.

We report a case of urate overproduction owing to the Lesch-Nyhan syndrome (deficiency of hypoxanthine-guanine phosphoribosyltransferase). Urate crystalluria was controlled by allopurinol therapy but renal calculi developed, which contained a variety of purines, particularly the relatively insoluble xanthine, as well as oxypurinol and hypoxanthine. The potential hazard from the increased amounts of xanthine that are produced during allopurinol therapy for urate overproduction is stressed, as well as the importance of maintaining a high urine flow rate even during such therapy.

Adult↗
PubMed1984

Renal failure in infancy due to over-production of urate.

This report concerns a three month old infant who was failing to thrive. Renal insufficiency was demonstrated and attributed to aortic coarctation. However, surgical correction of the coarctation failed to correct the renal insufficiency completely and disproportionate hyperuricemia was noted. Excessive urinary excretion of uric acid was found and a moderate deficiency (6% of normal) of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) was demonstrated. When the urate over-production was corrected with allopurinol, renal function returned to normal and the child became well. The importance of over-production of urate and the resultant excessive urinary excretion of uric acid as a treatable cause of acute or persistent renal insufficiency is stressed.

Allopurinol↗
PubMed1982

Purine synthesis de novo in lymphocytes from patients with gout.

1. Variables that affect the measurement of purine synthesis de novo in human lymphocytes were studied and a reliable method of measurement of purine synthetic activity in these cells was established. 2. Purine synthesis de novo was measured as the rate of incorporation of [14C] formate into alpha-N-formylglycinamide ribonucleotide when further steps in the biosynthetic pathway had been blocked by azaserine. Incubation was carried out in a synthetic medium with a high phosphate concentration (25 mmol/l). 3. Purine synthesis de novo was measured in lymphocytes obtained on several occasions both from control subjects and from patients with gout, particularly those who tended to overproduce urate as suggested by high values of urinary urate. 4. Lymphocytes obtained from each individual on different occasions showed considerable variations in purine biosynthetic activity. This variation was such that there was no difference between the mean values obtained for the gouty subjects and the control subjects. 5. No correlation was obtained between the mean purine synthetic activity de novo in lymphocytes and either the serum urate concentration or the 24 h urinary urate excretion on a purine-free diet. 6 Apart from those with recognized enzyme mutations, no subgroup of the gouty population has been demonstrated in whom isolated lymphocytes demonstrate an intrinsic abnormality of purine synthesis de novo.

Adult↗
PubMed1981

Changes in intraocular pressure during acute exercise.

The effect of vigorous physical activity on intraocular pressure has been well documented. Other studies have only focused on pretest and posttest measurements of intraocular pressure. This study presents a continuous evaluation of intraocular pressure during exercise and correlates changes in intraocular pressure with changes in heart rate through time. A total of 17 adult male and female subjects were submaximally tested on a bicycle ergometer using the Astrand-Rhyming protocol. The results of this test were used to design an individualized four-stage workload that would proportionally take each subject to 85% of a predicted maximum heart rate. During this test, intraocular pressure was measured at the end of each stage and through 15 min of recovery with an American Optical non-contact tonometer. A statistically significant decrease (p less than 0.05) in intraocular pressure was noted at the end of the fourth stage and during 1, 5, and 10 min of recovery; however, no trend was found to indicate a significant correlation between heart rate and intraocular pressure.

Adolescent↗
PubMed1979

Regulation of purine de novo synthesis in cultured human fibroblasts: the role of P-ribose-PP.

Procedures for assaying the rate of purine de novo synthesis in cultured fibroblast cells have been compared. These were (i) the incorporation of [(14)C]-glycine or [(14)C]formate in alpha-N-formylglycinamide ribonucleotide (an intermediate in the purine synthetic pathway) and (ii) the incorporation of [(14)C]-formate into newly synthesised cellular purines and purines excreted by the cell into the medium. Fibroblast cells, derived from patients with a deficiency of hypoxanthine phosphoribosyltransferase (HPRT-) (EC 2.4.2.8) and increased rates of purine de novo synthesis, were compared with fibroblasts from healthy subjects (HPRT+). Fetal calf serum, which was used to supplement the assay and cell growth medium, was found to contain sufficient quantities of the purine base hypoxanthine to inhibit purine de novo synthesis in HPRT+ cells. This inhibition was the basis of differentiation between HPRT- and HPRT+ cells. In the absence of added purine base, both cell types had similar capacities for purine de novo synthesis. This result contrasts with the increased rates of purine de novo synthesis reported for a number of human HPRT- cells in culture but conforms recent studies made on human HPRT- lymphoblast cells. The intracellular concentration and utilisation of 5-phosphoribosyl-1-pyrophosphate (P-Rib-PP), a substrate and potential controlling factor for purine de novo synthesis, were determined in HPRT- and HPRT+ cells. The rate of utilisation of P-Rib-PP in the salvage of free purine bases was far greater than that in purine de novo synthesis. Although HPRT- cells had a 3-fold increase in P-Rib-PP content, the rate of P-Rib-PP generation was similar to HPRT+ cells. Thus, in fibroblasts, the concentration of P-Rib-PP appears to be critical in the control of de novo purine synthesis and its preferential utilisation in the HPRT reaction limits its availability for purine de novo synthesis. In vivo, HPRT+ cells, in contrast to HPRT- cells, may be operating purine de novo synthesis at a reduced rate because of their ability to reutilise hypoxanthine.

Adenine↗
PubMed1977

Hypoxanthine-guanine phosphoribosyltransferase: a simple spectrophotometric assay.

A simple spectrophotometric assay is described based on the conversion of hypoxanthine to inosine monophosphate and precipitation of both the reaction product and protein with lanthanum phosphate. The extent of conversion is determined by the fall in absorbance of hypoxanthine at 249 nm. The assay is suitable for screening red cell lysates for hypoxanthine-guanine phosphoribosyltransferase deficiency.

Erythrocytes↗
PubMed1977

Hypoxanthine-guanine phosphoribosyltransferase activity in individual erythrocytes: autoradiographic studies in heterozygotes.

Heterozygotes for the Lesch-Nyhan syndrome have normal hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity in their erythrocyte lysates. However, HGPRT activity in lysates from heterozygotes for the partial HGPRT deficiency states is often between that seen in the affected hemizygote and the normal. An autoradiographic technique was developed which demonstrated the HGPRT activity in individual erythrocytes in vitro. This technique revealed that heterozygotes for the Lesch-Nyhan syndrome had erythrocytes that contained normal HGPRT activity but heterozygotes for the partial deficiency had two populations of erythrocytes, one with normal HGPRT activity and the other with the reduced HGPRT activity characteristic of the hemizygote. With these latter heterozygotes, the proportion of HGPRT-deficient erythrocytes agreed with that calculated on the basis of enzyme activity in erythrocyte lysates.

Autoradiography↗