Biomedical subjects

A G Robertson

Publications and source records attributed to A G Robertson.

At least 37 records · Page 2Linked to original sources

PubMed1998

Molecular characterization of benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase II of Acinetobacter calcoaceticus.

The nucleotide sequences of xylB and xylC from Acinetobacter calcoaceticus, the genes encoding benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase II, were determined. The complete nucleotide sequence indicates that these two genes form part of an operon and this was supported by heterologous expression and physiological studies. Benzaldehyde dehydrogenase II is a 51654 Da protein with 484 amino acids per subunit and it is typical of other prokaryotic and eukaryotic aldehyde dehydrogenases. Benzyl alcohol dehydrogenase has a subunit Mr of 38923 consisting of 370 amino acids, it stereospecifically transfers the proR hydride of NADH, and it is a member of the family of zinc-dependent long-chain alcohol dehydrogenases. The enzyme appears to be more similar to animal and higher-plant alcohol dehydrogenases than it is to most other microbial alcohol dehydrogenases. Residue His-51 of zinc-dependent alcohol dehydrogenases is thought to be necessary as a general base for catalysis in this category of alcohol dehydrogenases. However, this residue was found to be replaced in benzyl alcohol dehydrogenase from A. calcoaceticus by an isoleucine, and the introduction of a histidine residue in this position did not alter the kinetic coefficients, pH optimum or substrate specificity of the enzyme. Other workers have shown that His-51 is also absent from the TOL-plasmid-encoded benzyl alcohol dehydrogenase of Pseudomonas putida and so these two closely related enzymes presumably have a catalytic mechanism that differs from that of the archetypal zinc-dependent alcohol dehydrogenases.

Acinetobacter calcoaceticus↗

PubMed1998

Interstitial iridium-192 implantation combined with external radiotherapy in anal cancer: ten years experience.

PURPOSE: To report our experience in the use of interstitial iridium-192 implantation combined with external radiotherapy in anal cancer. METHODS AND MATERIALS: From 1984 to 1994, 79 patients with anal cancer were treated with radical intent using radiotherapy (plus chemotherapy) at Beatson Oncology Centre, Glasgow, Scotland. The mean and median age at presentation were 68 and 70 years, respectively (range 34-85) with a male-to-female ratio of 0.39. The histologic distribution was as follows: 48 squamous, 16 basaloid, 14 adenocarcinoma, and 1 basal cell carcinoma. The T stages were: 8 T1, 40 T2, 26 T3, and 5 T4 lesions. Twelve (15%) patients had nodal involvement at presentation. All patients underwent interstitial implantation using iridium-192 as part of the initial treatment. Seventy-six patients were treated with external radiotherapy followed by implant with a mean delay of 37 days after the end of radiotherapy. Twelve patients also received chemotherapy with 5-fluorouracil and mitomycin-C concurrently with external radiotherapy. Follow-up ranged from 6 to 123 months, with a median of 37 months. RESULTS: Seventy-nine patients were analyzed to assess local control, survival, and complications. A complete response rate of 91% (72 of 79) was achieved after planned radiation treatment. At the end of external radiotherapy, 29% (22 of 76) had achieved complete response, 58% (7 of 12) with chemotherapy and 23% (15 of 64) without it. Local control was achieved in 62 of 79 (78%) patients and 8 of 17 (47%) local failures were salvaged by abdominoperineal resection. Five patients developed inguinal node failure; four of these were salvaged. Overall, 10% of all patients developed distant metastasis as the first site of failure and 25% failed at any site after salvage therapy. Time to unsalvageable relapse was significantly different on comparing T stage (p = 0.005) and histology (p = 0.029) of tumor. Major complications requiring surgical intervention were seen in six (7.5%) patients. Anal function preservation with local control was possible in 56 of 79 (71%) patients. CONCLUSION: We report excellent results with radiotherapy in T1 and T2 lesions. The role of chemoradiotherapy as radical treatment of anal cancer should be defined in the context of locally advanced tumors.

Adenocarcinoma↗

PubMed1998

Similar decreases in local tumor control are calculated for treatment protraction and for interruptions in the radiotherapy of carcinoma of the larynx in four centers.

PURPOSE: Data on patients with cancer of the larynx are analyzed using statistical models to estimate the effect of gaps in the treatment time on the local control of the tumor. METHODS AND MATERIALS: Patients from four centers, Edinburgh, Glasgow, Manchester, and Toronto, with carcinoma of the larynx and treated by radiotherapy were followed up and the disease-free period recorded. In all centers the end point was control of the primary tumor after irradiation alone. The local control rates at > or = 2 years, Pc, were analyzed by log linear models, and Cox proportional hazard models were used to model the disease-free period. RESULTS: T stage, nodal involvement, and site of the tumor were important determinants of the disease-free interval, as was the radiation schedule used. Elongation of the treatment time by 1 day, or a gap of 1 day, was associated with a decrease in Pc of 0.68% per day for Pc = 0.80, with a 95% confidence interval of (0.28, 1.08)%. An increase of 5 days was associated with a 3.5% reduction in Pc from 0.80 to 0.77. At Pc = 0.60 an increase of 5 days was associated with an 7.9% decrease in Pc. The time factor in the Linear Quadratic model, gamma/alpha, was estimated as 0.89 Gy/day, 95% confidence interval (0.35, 1.43) Gy/day. CONCLUSIONS: Any gaps (public holidays are the majority) in the treatment schedule have the same deleterious effect on the disease free period as an increase in the prescribed treatment time. For a schedule, where dose and fraction number are specified, any gap in treatment is potentially damaging.

Carcinoma↗

PubMed1998

Behavior of radial forearm skin flaps transplanted into the oral cavity.

Radial forearm skin flaps transplanted into the oral cavity in patients undergoing treatment for intra-oral tumors frequently acquire a gross appearance resembling that of buccal mucosa. This article reports studies of biopsies of the flaps in 53 patients, of which 21 showed changes at some stage in the follow-up period. The project aims to determine whether 1) the change in the epithelium to a mucosal form is genuine or reactive, 2) a creeping replacement of epidermis results from the surrounding buccal epithelium, 3) alterations in the epidermis could be associated with changes in the dermis, 4) the change is caused by radiotherapy. Examination of the biopsies by resin histology and transmission electron microscopy shows that the changes may be reversible: it suggests that they are reactive in nature, and related to the degree of dermal inflammation, rather than to the effect of radiotherapy. The dermis persists as such and is not replaced by buccal lamina propria.

Adult↗

PubMed1998

Effect of gap length and position on results of treatment of cancer of the larynx in Scotland by radiotherapy: a linear quadratic analysis.

PURPOSE: This paper reports on the analysis of the effect of the length and position of unplanned gaps in radiotherapy treatment schedules. MATERIALS AND METHODS: Data from an audit of the treatment of carcinoma of the larynx are used. They represent all newly diagnosed cases of glottic node-negative carcinoma of the larynx between 1986 and 1990, inclusive, in Scotland that were referred to one of the five Scottish Oncology Centres for primary radical radiotherapy treatment. The end-points are local control of cancer of the larynx in 5 years and the length of the disease-free period. The local control rates at > or =5 years, Pc were analyzed by log linear models and Cox proportional hazard models were used to model the disease-free period. RESULTS: Unplanned gaps in treatment are associated with poorer local control rates and an increased hazard of a local recurrence through their effect on extending the treatment time. A gap of 1 day is potentially damaging but the greatest effect is at treatment extensions of 3 or more days, where the hazard of a failure of local control is increased by a factor of 1.75 (95% confidence interval 1.20-2.55) compared to no gap. The time factor for the actual time was imprecisely estimated at 2.7 Gy/day with a standard error of 13.2 Gy/day. Among those cases who had exactly one gap resulting in a treatment extension of 1 day, there is no evidence that gap position influences local control (P = 0.17). The treatment extension as a result of the gap is more important than the position of the gap in the schedule. CONCLUSIONS: Gaps in the treatment schedule have a detrimental effect on the disease-free period. A gap has a slightly greater effect than an increase in the prescribed treatment time. Any gap in treatment is potentially damaging. The position of the gap in the schedule was shown to be not important.

Appointments and Schedules↗

PubMed1998

Early closure of a randomized trial: surgery and postoperative radiotherapy versus radiotherapy in the management of intra-oral tumours.

Tumours of the oral cavity/oropharynx occur relatively infrequently in the UK. The management of such lesions, especially the squamous cell carcinomas, is still a little controversial. Some centres advocate radiotherapy while others adopt surgery and radiotherapy. In an attempt to resolve the question of which approach gives the better results, a multicentre randomized trial was established to compare surgery plus postoperative radiotherapy with radical radiotherapy alone. It was anticipated that 350 patients would be required to give a statistically significant result, but, after 35 patients had been entered, the trial was closed prematurely with a marked difference in overall survival in favour of the combination arm (P = 0.0006). At this analysis, carried out 23 months after trial closure, the survival difference between the two arms remains statistically significant for all causes of mortality (P = 0.001; relative death rate = 0.24; 95% CI 0.10-0.59).

Adult↗

PubMed1998

Bolus/infusional 5-fluorouracil and folinic acid. A report on two prospective, consecutive phase II studies with 5-fluorouracil dose escalation.

We have used a relatively new trial methodology, the group sequential design, to prospectively evaluate two dose levels of bolus/infusional 5-fluorouracil (5-FU) and folinic acid in 192 consecutive-patients with advanced colorectal carcinoma. On day 1, all patients received 200 mg m(-2) of folinic acid infusion over 2 h. Cohort A (n = 102 patients) received 500 mg m(-2) 5-FU by i.v. 15-min infusion followed by an infusion of 500 mg m(-2) 5-FU over 22 h. Treatment was repeated on day 2 and further cycles given 2-weekly. After sequential analysis excluded a response rate of over 40%, cohort B (n = 90 patients) received an increased dose of 600 mg m(-2) 5-FU bolus and infusion. Patients had received no prior 5-FU therapy and the two cohorts had similar demographic features. In 179 evaluable patients, the overall response rate was 18% (95% CI 12-24%) with CR of 6% and PR of 12%, with no difference between the two cohorts. Overall median survival was 34 weeks (95% CI 30-39) with no significant difference between cohorts (median survival 32 and 37 weeks in cohort A and B respectively; P = 0.27). On multivariate analysis, poor performance status, elevated initial WBC and alkaline phosphatase and low serum albumin were associated with reduced survival (P < 0.05), and initial raised WBC showed an association with reduced likelihood of response (P = 0.002). Overall toxicity was low with CTC grade 3 mucositis, diarrhoea, nausea or vomiting in < or = 6% of patients and no treatment-related deaths. Significant (grade 3 or above) leucopenia was more common in cohort B than in cohort A (9% and 1% respectively); there were more dose reductions, and the median administered dose intensity was lower in cohort B than in cohort A (89% and 97% respectively; P = 0.006). In this group of relatively unselected patients, we have confirmed a relatively low objective response rate and median survival of 7.8 months with this regimen. There was no significant difference in outcome between the two dose levels but the higher dose of 5-FU was associated with more dose reductions and greater toxicity.

Adult↗

PubMed1997

Reduced cholinergic function in normal and Alzheimer's disease brain is associated with apolipoprotein E4 genotype.

Apolipoprotein E (ApoE) is a potent risk factor for Alzheimer's disease. Since the loss of cholinergic function in Alzheimer's disease is known to occur at an early stage in the disease we have examined this function in normal subjects with an Apoepsilon4 allele to see if the deficit occurs in the absence of Alzheimer pathology or symptoms. We report that brain tissue obtained post-mortem from normal subjects and Alzheimer patients with an Apoepsilon4 allele has a lower cholinergic activity than tissue from those subjects without this allele. This has important significance for the interpretation of the cholinergic deficits found in Alzheimer's disease.

Aged↗

PubMed1997

Cerebral metastases of cutaneous melanoma.

Cerebral metastases of cutaneous melanoma carry a very poor prognosis. We report our experience of 31 patients who presented with cerebral metastasis of cutaneous melanoma in a 5-year period between mid-1991 and mid-1996. Cerebral metastases were diagnosed on computerized tomography (CT) scan after patients became symptomatic. The overall median survival in our series was 4 months. Seventeen patients (55%) received treatment with radiotherapy and dexamethasone with resolution of their symptoms, although median survival remained at 4 months. Six patients (19%) had surgery followed by whole brain radiotherapy, with median survival of 5 months. The remaining eight patients received dexamethasone alone. Data from patients surviving less than 2 months and over 6 months suggest that the poor prognostic factors are the presence of more than one cerebral metastasis and additional extracranial metastases.

Administration, Oral↗

PubMed1997

Immunoglobulin-like domains define the nerve growth factor binding site of the TrkA receptor.

Nerve growth factor (NGF) is involved in the development and maintenance of the nervous system. NGF binds with high affinity to the extracellular region of the tyrosine kinase receptor TrkA. This domain comprises leucine and cysteine rich motifs, followed by two immunoglobulin like (Ig-like) domains. We describe the expression and purification of recombinant Ig-like domains. Fluorescence and circular dichroism spectroscopy show that the protein is folded into a compact globular structure and contains mainly beta-sheet secondary structure. Recombinant protein binds to NGF and can inhibit NGF bioactivity both in vitro and in vivo.

Amino Acid Sequence↗

PubMed1996

A comparative study of the efficacy of fluconazole and amphotericin B in the treatment of oropharyngeal candidosis in patients undergoing radiotherapy for head and neck tumours.

Radiotherapy given during treatment of oral and pharyngeal malignancy is frequently associated with colonization of the oral mucosa by Candida species. Treatment of these infections has included topical and systemic agents. In the present study 73 patients with oropharyngeal candidosis were treated with either amphotericin B (10 mg lozenges, four times daily for 14 days, 36 patients) or fluconazole (50 mg daily for 7 days, 37 patients). The yeasts most frequently isolated were C albicans and C glabrata. Clinical signs and symptoms showed improvement at end of treatment in 72% of patients who received amphotericin B compared with 92% of patients who received fluconazole. Mycological cure at end of treatment was achieved in 31% of the amphotericin B group and 46% of patients who received fluconazole. For both treatments the cure rate was less in denture wearers than in non denture wearers.

Adult↗

PubMed1996

A modelled comparison of the effects of using different ways to compensate for missed treatment days in radiotherapy.

There is much evidence for the detrimental effect on tumour control of missed treatment days during radiotherapy, amounting for example to approximately a 1.6% absolute decrease in local control probability per day of treatment prolongation in the case of head and neck squamous cell cancer. Various methods to compensate for missed treatment days are compared quantitatively in this article, using the linear-quadratic formalism. The overall time and fraction size can be maintained by either treating on weekend days (the preferred way (Method 1a), although with unsocial hours and at extra cost) or using two fractions per day to "catch up' (Method 1b). The latter might incur a small loss of tolerance regarding late reactions, when intervals of 6-8 h are used rather than 24 h, and there may be logistical/scheduling difficulties with larger numbers of patients in some centres when using this method. A second type of strategy retains overall treatment time, and also one fraction per day, but the size of the dose per fraction is increased. For example, this may be done for the same number of "post-gap' days as gap days (Method 2). However, with this method, calculated isoeffect doses regarding late reactions indicate a probable decrease in tumour control rate (Method 2a). Otherwise, isoeffective doses regarding tumour control result in an increase in late reactions (Method 2b). In addition, this method is unsuitable for short regimens already using high doses per fraction. To reduce this problem, overall treatment time can also be retained by using fewer fractions, all of greater size in the case of planned gaps (statutory holidays), or larger remaining fractions after unplanned gaps (Method 2c). The problem also with this method is that equivalence for tumour control gives an increase in late reactions. The least satisfactory strategy (Method 3) is to accept the protraction caused by the missed treatment days, and give either the same prescribed number of (slightly larger) fractions or the planned treatment followed by one (or more) extra fraction to compensate for the gap. This would retain the expected local control rate, but there would be an increase in late reactions. An example of this, using average parameter values, is that a 3-day gap (necessitating four extra days to complete treatment with one fraction of 2.4 Gy) might maintain a 70% local control rate for glottic carcinoma, but severe reactions might rise from 1% to 4% and minor/moderate reactions from 37% to 50%. In this example, the inclusion of an extra weekend would increase the required extra dose and hence may further increase the morbidity rates. A final point is that the effect of treatment interruptions for an individual patient is expected to be greater than that for a group of patients because of interpatient heterogeneity tending to flatten dose-response curves. Calculations show that the above value of 1.6% loss of local control per day for a group of patients may reflect values for individual patients that range around a median value of as much as 5% per day, so stressing further the importance of gaps in treatment. It is concluded that, wherever possible, treatment days should not be missed. If they are missed, it is important to compensate for them, preferably by one of the first of the above methods (1a or 1b), in order to keep as close as possible to the original/standard prescription in terms of total dose, dose per fraction and overall time.

Brachytherapy↗

PubMed1996

Carboplatin, 5-fluorouracil and folinic acid: a 48-hour chemotherapy regimen in advanced and recurrent squamous carcinoma of the head and neck.

Eighty patients with advanced squamous carcinoma of the head and neck were entered into a study using a 2-day, inpatient, intravenous regimen. Folinic acid 200 mg/m2, 5-fluorouracil (5-FU) 500 mg/ m2 bolus followed by 5-FU 500 mg/m2 in a 22-hour infusion were given on days 1 and 2, with carboplatin 300 mg/m2 on day 2. The whole was repeated every 21 days. Forty-three patients had advanced disease with no prior treatment; 37 had recurred following radical treatment. Fifty-eight patients were male and the median age was 60 years. In total, 275 cycles of chemotherapy were given. The major toxicity was haematological, which delayed 65 cycles of chemotherapy and contributed to the death of two patients. Non-haematological toxicity was mild, with less than 8% of patients experiencing any toxicity greater than WHO grade 2. The patients who had had no previous treatment had a 65% response rate (95% confidence interval (95% CI) 48-80). Those who had been previously treated had a 37% response rate (95% CI 21-55). The overall response rate was 52% (95% CI 40-64), of whom 5% were complete responders. The median survival time was 36 weeks (95% CI 29-45), with the majority of patients dying with progressive disease. We conclude that this chemotherapy regimen was well tolerated and produced minimal toxicity, while maintaining an acceptable response rate of 52%.

Aged↗

PubMed1995

Site-directed mutagenesis of cysteine-195 in isocitrate lyase from Escherichia coli ML308.

Cysteine-195 was previously identified as a probable active site residue in isocitrate lyase (ICL) from Escherichia coli ML308 [Nimmo, Douglas, Kleanthous, Campbell and MacKintosh (1989) Biochem. J. 261, 431-435]. This residue was replaced with serine and alanine residues by site-directed mutagenesis. The mutated genes expressed proteins with low but finite ICL activity, which co-migrated with wild-type ICL on both SDS/ and native PAGE. The mutant proteins were purified and characterized. Fluorimetry and c.d. in both the near- and the far-u.v. regions showed no differences between the mutants and wild-type ICL, indicating that the conformations of the three enzymes were very similar. ICL C195A (Cys-195-->Ala) and C195S (Cys-195-->Ser) showed 8.4-fold and 3.6-fold increases in the Km for isocitrate, while their kcat. values showed 30- and 100-fold decreases respectively. The effect of pH on the kinetic properties of the wild-type and mutant ICLs was investigated. The results showed that the response of the mutant enzymes to pH was simpler than that of the wild-type. For the mutants, ionisation of a group with a pKa of approx. 7.8 affected the Km for isocitrate and kcat.. For the wild-type enzyme, these parameters were affected by the ionization of two or more groups, one of which is presumed to by cysteine-195. The results are consistent with the view that the previously identified group with a pKa of 7.1 whose ionization affects the reaction of ICL by iodoacetate is cysteine-195 itself.

Bacterial Proteins↗

PubMed1995

Changes in the incidence and mortality of testicular cancer in Scotland with particular reference to the outcome of older patients treated for non-seminomatous germ cell tumours.

This paper describes the temporal pattern of germ cell testicular cancer in Scotland between 1960 and 1990. The effect of age on the prognosis of patients with non-seminomatous germ cell tumours (NSGCT) has been assessed by studying all patients presenting in the West of Scotland between 1975 and 1989. Between 1960 and 1990, the number of testicular germ cell tumours registered has increased more than 2-fold; mortality rates have declined equally dramatically. Univariate and multivariate analysis of the data obtained on 440 patients with NSGCT showed age was not a prognostic factor influencing survival. 52 were patients over 40 years at presentation; their 5 years survival was 71% compared with 79% in the younger patients (n = 388). This small survival difference is probably explained by the higher proportion of older patients treated before 1980. Treatment for this older group should be approached with the same curative intent as for younger patients and the same expectation of success.

Adolescent↗

PubMed1995

Effect of oral clodronate on metastatic bone pain: a double-blind, placebo-controlled study.

PURPOSE: To study the effects of oral clodronate on bone pain in patients with advanced metastatic bone disease. PATIENTS AND METHODS: Fifty-five patients with progressing bone metastases were randomized to receive oral clodronate 1,600 mg/d (n = 27) or matching placebo (n = 28). The main outcome measures were bone pain (visual analog score), analgesic use, and compliance with therapy. RESULTS: Visual analog pain score (median [interquartile range]) decreased from the pretreatment value in the clodronate group (-0.9 [-2.6 to -0.4]), but increased in the placebo group (+0.4 [-1.0 to +4.0]) (P = .03 between groups). Analgesic use increased with disease progression to a similar extent in both groups (59% increased use in the clodronate group v 64% of placebo group; difference not significant). Ten patients (37%) in the clodronate group and 12 (46%) in the placebo group withdrew from the study prematurely, most often because of difficulty with swallowing the capsules. CONCLUSION: Clodronate improved control of bone pain to a modest degree in patients with advanced metastatic cancer, but did not reduce analgesic requirement significantly. Perhaps as a result of these factors, it proved difficult to maintain patients on therapy. Further studies will be needed to define the role of bisphosphonates such as clodronate in this situation, in comparison with established treatments such as radiotherapy and analgesics.

Administration, Oral↗

PubMed1995

From asps to allegations: biological warfare in history.

Biological warfare has been waged intermittently for nearly 2,500 years. The techniques of delivery and weaponization of biological warfare agents have gradually evolved from the catapulting of plague victims to the deliberate use of infected clothes, insect vectors, and specialized weapon systems. Despite advances in immunotherapy and chemotherapy, the threat of biological warfare is increasing, and military health personnel should be acquainted with this area. This paper reviews the history, often controversial, of biological warfare from the Scythian archers through the Russian offensive program in 1994.

Animals↗

PubMed1994

Flow cytometric analysis of DNA content in squamous carcinoma of the tongue: the relationship to host and tumour factors and survival.

Cellular DNA content has been found to be an important prognostic factor in many human tumours, yet within the head and neck region few studies have examined its effect on survival and in those that have, findings differ. Eighty-one consecutive patients with squamous carcinoma of the tongue mainly treated by surgery and post-operative radiotherapy were studied. The DNA content of archival paraffin embedded tumours was measured by flow cytometry. Fifty-seven tumours were diploid and 24 were aneuploid. There was no association between ploidy status and age, sex, tumour size or nodal status. Ploidy status was not related to survival. These findings indicate that analysis of tumour DNA content in squamous carcinoma of the tongue does not provide any additional prognostic information for the individual patient.

Aneuploidy↗