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B Jones

Publications and source records attributed to B Jones.

At least 289 records · Page 16Linked to original sources
PubMed1994

A zebrafish retinoic acid receptor expressed in the regenerating caudal fin.

Retinoic acid (RA) is an important signalling molecule in vertebrate pattern formation both in developing and regenerating tissues. The effects of RA are due largely to regulation of gene transcription, mediated by retinoic acid receptors (RAR-alpha, RAR-beta, RAR-gamma) and retinoid X receptors (RXR-alpha, RXR-beta, RXR-gamma). We have been using zebrafish as a model of regeneration to study the role of retinoic acid and its receptors in vertebrate pattern formation. In this report, we describe the molecular cloning and characterization of one of the zebrafish RARs that is the predominant receptor in the regenerating caudal fin and corresponds most closely to the RAR-gamma subtype isolated from mouse and human and to RAR-delta from newt. Zebrafish RAR-gamma (zfRAR-gamma) exhibits both structural and functional conservation with its mammalian counterparts. Studies utilizing both normal and regenerating caudal fins of the zebrafish have indicated that it is the RAR-gamma subtype, compared to RAR-alpha or RAR-beta, which is expressed at the highest levels in the tail fin. To localize the expression pattern of RAR-gamma during fin regeneration, we have carried out whole-mount in situ hybridization. ZfRAR-gamma transcripts, during fin regeneration, are localized in the blastemal tissue formed at the distal ends of the bony rays following amputation. Treatment of fish with RA during fin regeneration induces a number of striking morphological effects on the regenerate. When amputations are performed distal to the branch points or dichotomies, where a single ray bifurcates to extend two individual 'daughter' rays, RA treatment causes a dichotomy reduction where the two 'daughter' rays fuse to once again form a single ray. The single ray subsequently bifurcates in a comparatively normal manner. Our data suggest that exogenous RA can respecify pattern in the regenerating caudal fin and identifies the blastemae as possible RA target tissues.

Animals↗
PubMed1994

Effect of overall time when radiotherapy includes teletherapy and brachytherapy: a mathematical model.

By expanding the linear quadratic equations to allow for the interval of time between teletherapy and brachytherapy in a model which assumes continual exponential tumour regression following teletherapy, the loge cell kill resulting from brachytherapy is found to depend on radiosensitivity, tumour regression rate (lambda) and tumour clonogen doubling time (Tp). When lambda is relatively small the precise timing of brachytherapy following teletherapy is shown to influence the tumour cure probabilities. The model predicts a reduction in tumour control if brachytherapy is delayed when lambda values are small and Tp values are short, but when Tp values are long, deferral of brachytherapy may be advantageous. By differential calculus the occurrence of a minimum value of log cell kill can be found. Application of these concepts may improve the results of clinical radiotherapy.

Brachytherapy↗
PubMed1994

Effect of tumour shrinkage on the biological effectiveness of permanent brachytherapy implants.

A tumour shrinkage factor is incorporated into previously derived linear-quadratic (LQ) formulae which allowed radiobiological assessment of the efficacy of permanently implanted radionuclides. The new formulations relate the biologically effective dose (BED) to radionuclide half-life, recovery half-life, tumour radiosensitivity, potential doubling time and linear shrinkage rate. Specific attention has been given to the following radionuclides: gold-198 (half-life, 2.7 days), palladium-103 (half-life, 17 days), ytterbium-169 (half-life, 32 days) and iodine-125 (half-life, 60 days). For each nuclide the log cell kill resulting from typically prescribed doses was calculated for a range of tumour clonogen doubling times at various radiosensitivities and linear shrinkage rates. It is shown that even relatively modest shrinkage rates are capable of enhancing the clinical potential of the longer-lived nuclides. However, even though the effect of tumour shrinkage is minimal in the case of gold-198, for fast growing and/or insensitive tumours there are fewer radiobiological uncertainties associated with the use of this nuclide. The revised equations may also have applications in certain types of biologically targeted radiotherapy.

Brachytherapy↗
PubMed1994

A mathematical model of intraluminal and intracavitary brachytherapy.

The adaptation of the linear-quadratic model to allow for the effect of tumour regression and clonogen repopulation between initial teletherapy and subsequent brachytherapy has been extended to include the geometrical conditions encountered in intraluminal and intracavitary brachytherapy. For a radiation line source placed at the centre of a lumen or cavity, regression of any endoluminal tumour towards its mural origin will not result in any change in the minimum brachytherapy-tumour dose with time. In contrast, regression of transmural tumour will cause a potentially advantageous increase in the minimum brachytherapy-tumour dose with time. The latter effect will be opposed by tumour clonogen repopulation. The log(e) cell kill due to brachytherapy has been calculated for tumours of diameters 2, 4 and 6 cm at completion of teletherapy. The centres of the tumours were assumed to be at distances of 0, 1 and 2 cm from the radiation source. Tumour linear regression rates (lambda) ranging from 0.025 to 0.25 per week and tumour clonogen doubling times (Tp) of 2.5, 5 and 15 days were used in the calculations. The results demonstrate the critical importance of the distance of the tumour centre from the line source as well as the influence of tumour diameter, lambda and Tp. In some instances, both maximum and minimum values of log(e) cell kill occur. Calculations of tumour cure probabilities reveal that these variations in log(e) cell kill predicted by the model can produce highly significant differences in tumour control rates. Where the relevant parameters can be assessed directly or estimated from previous experience, the model provides a basis for the design of future intraluminal or intracavitary brachytherapy protocols.

Brachytherapy↗
PubMed1994

Results of a questionnaire regarding the practice of radiotherapy for carcinoma of the cervix in the UK.

A questionnaire was sent to 50 departments of clinical oncology in the UK in September 1991. The aim was to determine the range of external beam and brachytherapy techniques employed at that time in the radical treatment of carcinoma of the cervix. Replies were received from 35 centres. This paper summarizes the preliminary findings of the study. Low dose rate (LDR) brachytherapy techniques predominated (34/35 = 97%) but 41% of departments (13/32) had future plans for the use of high dose rate (HDR) equipment. For low bulk (Stage I-II) carcinoma of the cervix, there was no detectable association between the total brachytherapy dose prescribed and the brachytherapy dose rate. In bulky (Stage I-II) carcinoma of the cervix treated by initial open teletherapy (without shielding), there was a statistically significant reduction in the prescribed brachytherapy dose with increasing dose rate. There was considerable variation between centres in the measurement or estimation of normal tissue doses during brachytherapy. The range of techniques used and the variation in expected complication rates should be closely monitored via medical audit and a further follow-up questionnaire may reveal important changes.

Brachytherapy↗
PubMed1994

Non-uniform dwell times in line source high dose rate brachytherapy: physical and radiobiological considerations.

The ability to vary source dwell times in high dose rate (HDR) brachytherapy allows for the use of non-uniform dwell times along a line source. This may have advantages in the radical treatment of tumours depending on individual tumour geometry. This study investigates the potential improvements in local tumour control relative to adjacent normal tissue isoeffects when intratumour source dwell times are increased along the central portion of a line source (technique A) in radiotherapy schedules which include a relatively small component of HDR brachytherapy. Such a technique is predicted to increase the local control for tumours of diameters ranging between 2 cm and 4 cm by up to 11% compared with a technique in which there are uniform dwell times along the line source (technique B). There is no difference in the local control rates for the two techniques when used to treat smaller tumours. Normal tissue doses are also modified by the technique used. Technique A produces higher normal tissue doses at points perpendicular to the centre of the line source and lower doses at points nearer the ends of the line source if the prescription point is not in the central plane of the line source. Alternatively, if the dose is prescribed at a point in the central plane of the line source, the dose at all the normal tissue points are lower when technique A is used.

Brachytherapy↗
PubMed1994

Respiratory dysrhythmias in patients with tardive dyskinesia.

Tardive dyskinesia (TD) is a disorder characterized by abnormal involuntary movements and associated with neuroleptic therapy. To determine whether the respiratory muscles are involved in this condition, we compared the breathing pattern of ten patients with TD with ten patients with chronic schizophrenia receiving neuroleptic therapy without evidence of TD, and ten age-matched normal control subjects during resting tidal breathing, forearm pronation-supination (a maneuver designed to elicit the abnormal movements of TD), and breathing to a set frequency. Breathing patterns were also assessed in seven patients with TD during a progressive incremental exercise test and an overnight polysomnogram. Patients with TD had an irregular tidal breathing pattern, with a greater variability in both tidal volume and time of the total respiratory cycle (TTOT). Both groups of patients receiving neuroleptic therapy had a rapid shallow breathing pattern when performing forearm pronation-supination compared with control subjects. There were no differences between any of the subject groups when breathing to a set frequency. The patients with TD had a normal response to progressive exercise and inspiratory time and TTOT values were less variable during non-rapid eye movement sleep compared with wakefulness. We conclude that patients with TD have irregular rapid shallow breathing which is less variable during sleep and does not limit their exercise performance.

Adult↗
PubMed1994

Guanabenz induced hypothermia in a poisoned elderly female.

Guanabenz (Wytensin Wyeth-Ayerst Laboratories, Philadelphia, PA) is a centrally acting alpha 2 adrenergic agonist. Guanabenz shares structural and pharmacologic properties with the more commonly known sympatholytic agent clonidine. Little is known about guanabenz in overdose. Eleven cases of guanabenz poisoning have been reported in the literature and to the manufacturer to date and followed a clinical course comparable to clonidine poisoning. We report this case of guanabenz poisoning in an elderly woman who sustained protracted hypothermia following overdose. Hypothermia has been commonly associated with clonidine toxicity but has not been previously reported with guanabenz. Postulated mechanisms of clonidine induced hypothermia are discussed.

Aged↗
PubMed1994

Ethics, morals and patient photography.

This article reports on an investigation into the ethical and moral aspects of patient photography in an attempt to raise awareness of these issues among medical photographers. A questionnaire was used to determine common practices and attitudes towards the photography of patients in medical illustration departments across the country. Some wider issues, including the photography of fetuses and perinatal deaths are also examined. The results of the survey indicate that the majority seem to act with the patients' best interests in mind, however there are still areas that could be improved upon.

Attitude of Health Personnel↗
PubMed1994

Chordoma with cutaneous metastasis.

Chordoma is a neoplasm arising from the primitive notochord. Even though many chordomas follow a progressive course with multiple recurrences and metastases and eventual death due to tumor, reports of skin metastases from chordoma are rare. This report describes a case of chordoma with metastasis to the scalp in a 67-year-old man with a primary lesion of the sacrococcygeal region.

Aged↗
PubMed1994

The pharynx. Disorders of function.

Disorders in the function of the mouth and pharynx are extremely common. This article discusses the normal and abnormal swallow in detail. Neurologic disorders that result in dysphagia and the effect of aging on swallowing function also are presented.

Deglutition↗
PubMed1994

Results of cancer information assessment of high school students in West Virginia.

The "Just Say KNOW To Cancer" education program was implemented in public high schools in Kanawha County, W.Va., to assess students' knowledge of cancer risk factors and to provide an educational program about cancer prevention. An anonymous questionnaire was completed in two urban and six suburban schools by 1,235 students in their classrooms. The responses revealed that only 35% and 10% of students were able to identify two or more risk factors and one American Cancer Society warning sign, respectively. Tobacco was the most commonly identified risk factor, being listed by 64% of urban students, compared to 50% of suburban respondents (p < .001). Although 84% of all students correctly answered the question regarding the medical complications of smokeless tobacco, only 39% correctly answered the question relating second-hand smoke as a cancer risk factor. The results of this study indicate the need for cancer education in the high school health curriculum.

Adolescent↗
PubMed1994

Equipment for the large-scale electromanipulation of plant protoplasts.

Electric fields are now used extensively for the genetic manipulation of plant cells through protoplast fusion and direct gene uptake. The cost of commercially available electrofusion and electroporation equipment remains prohibitive for many laboratories. This paper describes an electronic apparatus, suitable for the large-scale electrofusion and electroporation of plant protoplasts that is compatible in both function and cost with commercially available equipment.

Biomedical Engineering↗
PubMed1993

Craniosynostosis.

Explore the source record for details and available documents.

Craniosynostoses↗
PubMed1993

Expression of precursor and mature carnitine palmitoyltransferase II in Escherichia coli and in vitro: differential behaviour of rat and human isoforms.

cDNAs corresponding to the precursor and mature forms of rat carnitine palmitoyltransferase II (CPT II) were found to be readily expressed in Escherichia coli. In both cases, catalytically active immunoreactive protein was produced and became largely membrane-associated. The precursor form of the enzyme was not proteolytically processed. Removal of 126 bp from the 5' end of the cDNA coding region allowed expression of a truncated CPT II (lacking the N-terminal 17 residues of the mature protein), but this product was inactive. cDNAs encoding the precursor and mature forms of human CPT II resisted direct expression in E. coli. However, the impediment was overcome when the latter cDNA was ligated in-frame 3' to sequence encoding a glutathione S-transferase. This construct yielded abundant quantities of the corresponding fusion protein, a portion of which was soluble and catalytically active. In vitro transcription and translation of the various cDNAs established that the lower mobility on SDS/PAGE of rat CPT II compared with its human counterpart (despite their identical numbers of amino acids) is an intrinsic property of the primary sequences of the proteins themselves. Also, the human cDNA was found to contain an artifactual termination signal for T3 RNA polymerase that could be bypassed by the T7 polymerase. Thus rat CPT II can be expressed in active form in E. coli with characteristics similar to those of the enzyme in mitochondria, opening the way to future location of active sites within the molecule. An alternative expression system will be needed for similar studies on human CPT II.

Animals↗
PubMed1993

Primary lymphoma of the colon and rectum: CT and barium enema correlation.

This paper presents the computed tomographic (CT) and barium enema (BE) findings in seven patients with proven primary lymphoma of the colon and rectum. CT and BE examination are complimentary studies in the evaluation of primary lymphoma of the colorectum, and certain relevant findings may be missed when radiographic evaluation does not include both modalities. Both CT and barium studies are very accurate in detecting bulky endoexoenteric tumor masses, although CT may suggest features which can differentiate primary lymphoma from adenocarcinoma. The renal utility of obtaining both a CT and BE examination may lie more in diagnosing complications, such as fistula formation and in the evaluation of subtle infiltrative lesions. While CT is necessary for staging purposes, BE examination may be invaluable for detecting subtle mucosal filling defects which could be missed on CT.

Aged↗