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Biomedical subjects

A Crockard

Publications and source records attributed to A Crockard.

At least 19 recordsLinked to original sources
PubMed2005

Use of quantitative assessment scales in cervical spondylotic myelopathy--survey of clinician's attitudes.

BACKGROUND: There is considerable uncertainty regarding the selection criteria of patients and timing of surgery for cervical spondylotic myelopathy (CSM). Attempts have been made to quantify CSM severity using various assessment scales to provide an adjunct to clinical decision-making. The aim of the present study was to determine, by means of a 7-item questionnaire the attitudes of clinicians regarding the importance of quantitative assessment scales in the management of CSM, their actual use in clinical practice and how current scales fall short of the ideal. FINDINGS: Clinical history, examination, radiological imaging and quantitative functional assessment were regarded by 117 clinicians as being almost equally important in the management of CSM. However, only 22 (19%) of clinicians admitted to using an assessment scale in clinical practice and 4 (3%) believed there was a 'gold-standard' assessment scale. These clinicians also considered 'ease of use' to be the most important attribute of an ideal assessment scale, followed by 'reproducibility', 'sensitivity to change' and 'validity'. CONCLUSIONS: The discrepancy between the importance attached to quantitative measurement and its actual use suggests that current scales are under-utilised or unsuitable for clinical practice. A new easy-to use scale may be required that better reflects clinical requirements.

Cervical Vertebrae↗
PubMed2002

A white clover nodulin gene, dd23b, encoding a cysteine cluster protein, is expressed in roots during the very early stages of interaction with Rhizobium leguminosarumbiovar trifolii and after treatment with chitolipooligosaccharide Nod factors.

An early nodulin cDNA, dd23b, was isolated from white clover root tissue by differential display RT-PCR. Its full-length sequence of 340 nucleotides encodes a predicted 72-amino-acid protein of molecular mass 8.3 kDa, with a polypeptide region containing cysteine pairs spaced in the manner of a cysteine cluster protein. This feature, which is shared by some other late and early nodulins from pea and broad bean, suggests a role in metal ion binding and membrane transport. Temporal and spatial expression patterns were determined during infection and nodulation by the homologous microsymbiont. No expression was found in unchallenged root tissue over a 7-day sampling period. Expression was first detectable in roots by RT-PCR 6 h post-inoculation with Rhizobium leguminosarum biovar trifolii, placing dd23b among the earliest nodulins to be detected to date. In root nodules, expression occurred primarily in the central symbiotic zone, but also in some host cells within the infection zone. Addition of purified wild-type chitolipooligosaccharide Nod factor to axenic white clover roots induced dd23b expression, providing further evidence for the role of this gene in the early plant response to infection by rhizobia.

Journal Article↗
PubMed1999

Stereotactic radiosurgery. VI. Posterior displacement of the brainstem facilitates safer high dose radiosurgery for clival chordoma.

The current 'best treatment method' for clival chordoma is regarded as radical surgical resection followed by radiation therapy; radiosurgery usually plays a major part in the radiation therapy programme. From primate radiation biology studies and from clinical observations, the brainstem is known to be the most radiosensitive part of the central nervous system. The tolerance of the brainstem to high single radiosurgical doses of radiation is limited (all the more so in programmes such as our own where conventionally fractionated radiotherapy precedes radiosurgery or the patient has relapsed after conventional radiotherapy--as in the patient reported here). In this report we describe the operative displacement of the brainstem posteriorly at time of resection such that the proportion of the prescribed postoperative radiosurgical dose received by the brainstem is greatly reduced (by the order of 50%). The gains perceived to accrue from this technique are quantified from isodosimetric considerations not only in dose sparing to the brainstem, but importantly in that the dose to the clival chordoma may be highly significantly increased without exceeding current accepted tolerance brainstem dose limits. Two patients have received this joint surgical/radiosurgical approach to date; the second case is presented here in detail.

Brain Stem↗
PubMed1997

DNA denaturation sensitivity may invalidate bromodeoxyuridine--DNA flow cytometric analysis of potential doubling times in colorectal tumours.

BACKGROUND: Flow cytometric analysis of 5-bromo-2'-deoxyuridine (BrdU)-substituted DNA has been used to calculate tumour cell proliferation rate. In this methodology, DNA denaturation, commonly by hydrochloric acid, is essential to expose incorporated BrdU for quantification with monoclonal antibodies. This study was designed to establish the validity of this technique by examining the change in flow cytometric DNA profiles introduced by DNA denaturation procedures. METHODS: Four experiments were performed using suspensions of nuclei derived from human colorectal tumours exposed in vivo to 150 mg/m2 BrdU 8-11 h before sampling. RESULTS: After denaturation with hydrochloric acid 2 mol/l a significant decrease was observed in the DNA aneuploid G1 population (P < 0.001) with a concurrent increase in the DNA aneuploid S phase fraction (P < 0.05). These changes were independent of the washing-centrifugation step and were maximal at different hydrochloric acid concentrations for different tumours. CONCLUSION: Hydrochloric acid denaturation introduces a tumour-specific non-linear variation in the analysis of BrdU.

Aged↗
PubMed1994

Hydrochloric acid denaturation of colorectal tumour tissue infiltrated with bromodeoxyuridine.

The thymidine analogue, bromodeoxyuridine, is substituted into DNA during DNA synthesis and can be used to identify those cells which have passed through the S-phase of the cell cycle. Incorporated bromodeoxyuridine can be detected using anti-bromodeoxyuridine monoclonal antibodies which bind to the exposed bromodeoxyuridine in single-stranded DNA after a suitable denaturation step. Hydrochloric acid is the most commonly employed denaturation agent in bromodeoxyuridine monoclonal antibody methodologies. This preliminary study was to validate the hydrochloric acid denaturation step for colorectal tumour tissue infiltrated in vivo with bromodeoxyuridine. Standard immunohistochemistry and flow cytometric techniques using Bu20a were employed across a range of hydrochloric acid concentrations. Although high labelling indices were achieved using acid concentrations of 0.10 M HCl, the optimal hydrochloric acid concentration was not the same in all tumours. Sensitivity of DNA to hydrochloric acid denaturation should be carefully considered in bromodeoxyuridine methodologies using the monoclonal antibody Bu20a.

Antibodies, Monoclonal↗
PubMed1994

CD44 plays a role in adhesive interactions between glioma cells and extracellular matrix components.

Glioma invasion is a complex process involving interactions of tumour cells with host cells and extracellular matrix (ECM). The initial event in the process is recognition and attachment of glioma cells to specific ECM molecules prior to migration into proteolytically modified matrix. In comparison with other tissues, brain ECM is a relatively amorphous matrix which contains glycosaminoglycans including hyaluronan (HA). Recently CD44 which is a transmembrane adhesion molecule found on a wide variety of cells, has been suggested as the principal cell surface receptor for HA. In the present in vitro investigation we have analysed the role of CD44 in adhesive interactions between human gliomas and ECM. Our experimental procedures included immunocytochemistry, immunoblotting, in vitro adhesion assay and flow cytometry. CD44 was expressed on the surface of all gliomas analysed (9) and the level of expression showed no correlation with tumour grade. Eighty, 95 and 120 kDa isoforms were demonstrated by immunoblotting. In an adhesion blocking assay it was found that ligation of CD44 with specific antibody resulted in reduced adhesion to hyaluronan, chondroitin sulphate, fibronectin, laminin, collagen IV and Matrigel. We conclude that CD44 is involved in adhesion of glioma cells to a wide range of ECM components.

Brain Neoplasms↗
PubMed1994

Evaluation of spinal laminar fixation by a new, flexible stainless steel cable (Sof'wire): early results.

Segmental spinal stabilizations have been carried out in 72 patients (age, 5-79 yr) during the first 2 years of the availability of a new, flexible, multistranded stainless steel cable (Sof'wire, Hillway Surgical Ltd., London). A total of 519 sublaminar and occipital cables have been passed at 280 levels to fix an occipitocervical loop (36 patients) or contoured rectangle (14 patients). In 15 other patients, a Gallie fusion was combined with a C1-C2 lateral mass screw fixation; a cable-bone construct was used in five patients. Clinical and radiological follow-up at 1, 3, 6 (61 patients), 12 (48 patients), and 18 months (29 patients) and at 2 years (8 patients) has demonstrated no cable breakage or loosening. One postoperative death was due to inadequate transoral decompression before posterior fixation, and, in the 32 patients who underwent spinal monitoring, there were no major changes noted during surgery and no new postoperative neurological symptoms or signs. These preliminary observations are encouraging and merit further multicenter investigations.

Adolescent↗
PubMed1993

In vitro BrdUrd incorporation of colorectal tumour tissue.

This study describes a novel in vitro method for the incorporation of the thymidine analogue, bromodeoxyuridine (BrdUrd), in fresh colorectal tumour tissue. Disaggregation by pronase, collagenase and DNAse resulted in high cell yields of viable single cell suspensions, representative of the original tumour, which could be infiltrated with BrdUrd. A modified ELISA identified optimal incubation times and BrdUrd concentrations. This technique has been used in preliminary studies to investigate two important areas intrinsic in the analysis of BrdUrd colorectal cell proliferation data: 1) to determine the effects of the individual constituents of the cell culture media, in particular glutamine, on BrdUrd incorporation in suspensions of colorectal cells and 2) to examine the denaturation step. This method will have wide applicability in investigations of cell proliferation status in both normal and diseased tissue.

Bromodeoxyuridine↗
PubMed1993

The role of flow cytometry in carcinoma of the colon and rectum.

Flow cytometry was performed upon 312 patients with adenocarcinoma of the colon and rectum, satisfactory results being obtained with 275 (108 diploid, 130 aneuploid and 37 tetraploid). The proportion of nondiploid instances increased from 28 percent if one, to 80 percent when six specimens were assessed per patient. Reproducibility of the technique showed substantial agreement in the assessment of deoxyribonucleic acid ploidy (Kappa value equals 0.74). Increasing values of cells in the diving (G2/M) phase of the cell cycle were associated with little lymphocytic tumor infiltration (p = 0.0002) and extensive tumor fibrosis (p = 0.003). Univariate survival analysis revealed that, although diploid tumors tended to have a better prognosis than nondiploid tumors (p = 0.06), no flow cytometric variable was significantly related to survival. Flow cytometry similarly was not of prognostic value in instances without lymph node metastases or without distant metastases. Multivariate regression analysis of flow cytometric and clinicopathologic variables identified Dukes' stage, patient age and tumor differentiation as the combination of variables most closely related to survival. No flow cytometric variable could significantly improve on the prognostic model containing these three variables. It is concluded that conventional histologic variables remain the best predictors of prognosis in carcinoma of the colon and rectum.

Adenocarcinoma↗
PubMed1992

Oxygen saturation and cardiovascular changes during fibreoptic intubation under general anaesthesia.

Sixty patients who required fibreoptic nasotracheal intubation were studied. Arterial oxygen saturation, arterial blood pressure and heart rate were monitored continuously during fibreoptic intubation under deep halothane anaesthesia. There were significant decreases (p less than 0.001) in arterial blood pressure and heart rate despite administration of intravenous colloid and atropine. Almost one third of the patients (18 out of 60) suffered a decrease in arterial oxygen saturation below 90% during the intubation sequence and in five patients the saturation fell below 80%. The episodes of desaturation were not related to the induction-intubation time or to the grade of laryngeal visibility at direct laryngoscopy.

Adolescent↗