Biomedical subjects
Publications and source records attributed to J G Stone.
A 14-yr-old boy was first found to have tracheal stenosis when anaesthesia was induced for extensive scoliosis surgery in the prone position. There are no guidelines for airway management under these conditions. We describe how we managed the problem and suggest some useful modifications.
Lobular carcinoma in situ (LCIS) is an unusual histological pattern of non-invasive neoplastic disease of the breast occurring predominantly in women aged between 40 and 50 years. LCIS is frequently multicentric and bilateral suggesting a genetic basis to the disease. The high frequency of microsatellite instability in lobular breast cancers, coupled with increased risk of breast cancer associated with germline mismatch repair gene mutations raises the possibility that mutations MSH2 or MLH1 might confer susceptibility to LCIS. To explore this possibility we have examined a series of 71 LCIS patients for germline MSH2 and MLH1 mutations. No mutations were detected in MSH2. Two sequence variants were identified in MLH1. The first was a CTT-->CAT substitution, codon 607 (exon 16) changing leucine to histidine. The other mutation detected in MLH1 was a TAC-->TAA substitution codon 750 (exon 19) creating a stop codon, predicted to generate a truncated protein. These findings suggest that mutations in MLH1 may underlie a subset of LCIS cases.
Colorectal cancers with DNA mismatch repair (MMR) gene mutations characteristically display a high rate of replication errors in simple repetitive sequences detectable as microsatellite instability (MSI). Most are the result of somatic MMR dysfunction; however, a subset are caused by germline mutations. The availability of commercial antibodies for MSH2 and MLH1 [corrected] offers an alternative strategy to molecular methods for identifying MMR deficient cancers. To evaluate immunohistochemistry, MLH1 and MSH2 expression was studied using monoclonal antibodies in formalin fixed, paraffin wax embedded cancers. The immunohistochemical staining patterns of 23 cancers displaying MSI, including four cases with germline mutations, were compared with 23 microsatellite stable (MSS) cancers. All MSS cancers exhibited staining with both antibodies. Twenty two of the MSI cases showed absent MMR expression with either anti-MSH2 or anti-MLH1 [corrected]. The high sensitivity and predictive value of immunohistochemistry in detecting MMR deficiency offers a method of discriminating between MSI and MSS cancers caused by MSH2 and MLH1 [corrected] dysfunction. The application and suitability of immunohistochemistry for the detection of MSI and as a strategy for prioritising the mutational analysis of MMR genes in routine clinical practice is discussed.
Approximately 13% of colorectal cancers display microsatellite instability (MSI), a form of replication error repair. Colorectal cancers developing in individuals with constitutional defects in the mismatch repair (MMR) genes hMLH1, hMSH2, hPMS1 and hPMS2 consistently show evidence of this phenomenon. Since MSI is indicative of MMR deficiency, testing colorectal cancers for MSI provides a method of refining the identification of carriers of germline MMR mutations. To assess which microsatellites represent the best reporters of replication error (RER) status we have examined 116 early onset colorectal cancers for MSI. MSI was assessed using eight dinucleotide- and two mononucleotide-repeat fluorescently labelled polymerase chain reaction (PCR) markers. The two mononucleotide repeat markers (BAT25 and BAT26) were highly sensitive and typing of either represents an efficient strategy for defining RER status of colorectal cancers and obviates the requirement of typing numerous microsatellite markers.
Lobular carcinoma in situ (LCIS) is an unusual histological pattern of non-invasive neoplastic disease of the breast occurring predominantly in women aged between 40 and 50 years. LCIS is frequently multicentric and bilateral, and there is evidence that it is associated with an elevated familial risk of breast cancer. Although women with LCIS suffer an increased risk of invasive breast disease, this risk is moderate suggesting that LCIS may result from mutation of a gene or genes conferring a high risk of LCIS, but a lower risk of invasive breast cancer. The high frequency of somatic mutations in E-cadherin in LCIS, coupled with recent reports that germline mutations in this gene can predispose to diffuse gastric cancer, raised the possibility that constitutional E-cadherin mutations may confer susceptibility to LCIS. In order to explore this possibility we have examined a series of 65 LCIS patients for germline E-cadherin mutations. Four polymorphisms were detected but no pathogenic mutations were identified. The results indicate that E-cadherin is unlikely to act as a susceptibility gene for LCIS.
The Li-Fraumeni syndrome (LFS) is a dominant disease whose hallmark is an increased risk of breast cancers, brain tumours, sarcomas, leukaemia and adrenal carcinoma. Some, but not all LFS and Li-Fraumeni-like (LFL) families are caused by TP53 mutations. Bcl10 is a recently identified tumour suppressor reported to be commonly mutated in a wide range of cancers. To investigate the possibility that Bcl10 is a susceptibility gene for LFS and LFL we have analysed 27 LFS/LFL families. No mutations were observed. This indicates that Bcl10 is unlikely to act as a susceptibility gene for LFS and LFL.
Bcl10 is a recently identified gene reported to be involved commonly in human malignancy (Willis et al (1999) Cell 96: 1-20). To investigate whether it is frequently mutated in colorectal cancer we have analysed a series of 132 colorectal cancers and eight colorectal cancer cell lines for mutations in Bcl10. One feature of the Bcl10 gene is that it harbours two polyadenine tracts. These repeating elements in genes can be prone to a high rate of mutation if there is defective mismatch repair. To examine the possibility that Bcl10 may be preferentially mutated in mismatch repair-deficient cancers, 49 of the tumours and cell lines were known to be replication error (RER)-positive and, of these, ten were from individuals harbouring germline mutations in hMLH1 or hMSH2. No pathogenic mutations were detected in the tumours and only one mutation was found in the colorectal cancer cell lines. These results indicate that Bcl10 is unlikely to be involved in the pathways of colorectal carcinogenesis.
Bcl10 is a cancer gene recently identified in B-cell lymphomas of mucosa-associated lymphoid tissues. It has been suggested as a target for mutation in multiple types of tumour including follicular lymphoma, T-cell acute lymphoblastic leukaemia and Sezary syndrome. To evaluate further the role of Bcl10 in human adult haematological cancers, we screened for mutations samples from 24 patients with B-cell chronic lymphocytic leukaemia (CLL) and 18 samples from patients with T-cell prolymphocytic leukaemia (T-PLL). No pathogenic mutations were detected in any of the samples analysed, strongly suggesting that Bcl10 is not involved in the development of CLL or T-PLL and that its involvement may be restricted to other haematological malignancies.
UNLABELLED: Patient-controlled analgesia (PCA) has become a standard modality for the management of postoperative pain, although anecdotal reports of excessive sedation and respiratory depression impugn its safety. To study the prevalence and severity of nocturnal hypoxemia, we measured arterial oxygen saturation (SpO2) continuously overnight in 32 postoperative patients who were receiving morphine via PCA. To evaluate the potential benefit of providing concurrent supplemental oxygen, the patients breathed oxygen-enriched air the night of surgery and room air the next night. Patients experienced more pain and consumed twice as much morphine the first night. However, breathing supplemental oxygen that night, the nocturnal mean SpO2 was 99%+/-1%, 94%+/-4% (P<0.001), and only four patients had periods of hemoglobin desaturation <90%. In contrast, breathing room air the subsequent night, the mean SpO2 was lower (94%+/-4%; P<0.001), and hypoxemia occurred more frequently and was more severe: 18 patients experienced episodes of SpO2 <90%, 7 patients experienced episodes of SpO2 <80%, and 3 patients experienced episodes of SpO2 <70%. One patient required resuscitation for profound bradypnea and cyanosis, but none suffered permanent sequelae. We conclude that when postoperative patients use PCA at night, hypoxemia can be substantial and oxygenation can be improved by providing supplemental oxygen. IMPLICATIONS: Oxygen saturation was measured postoperatively in patients using morphine patient-controlled analgesia. Substantial nocturnal hypoxemia occurred in half of the patients while they breathed room air. The severity of the hypoxemia was reduced when patients received supplemental oxygen.
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OBJECTIVE: Because hypothermia enhances human tolerance for cerebral ischemia, profound hypothermia is induced in many centers so that the circulation can be arrested while clips are applied to high-risk giant cerebral aneurysms. Brain temperature is measured directly with an intracerebral probe that avoids the uncertainty of surrogate monitoring. However, when there is a large thermal gradient between brain temperature and that of the operating room, even direct measurements can sometimes be misleading. This study was undertaken to determine how deeply a thermal sensor must be embedded in the cerebral parenchyma to ensure that the ambient environment does not distort the measurement of brain temperature. METHODS: Each of 39 normothermic patients had a thermocouple sensor inserted into a temporal lobe seizure focus just before its resection. Brain temperature was measured as the sensor was withdrawn in stages. RESULTS: At both 3 and 2 cm beneath the cortical surface, the temperature of the brain was essentially the same. However, when the sensor was withdrawn to 1 cm, recorded temperature decreased from 35.7 +/- 0.9 to 34.3 +/- 1.4 degrees C (P < 0.001) and irrigation in the vicinity caused major thermal change. At shallower depths, even lower brain temperatures were recorded. No morbidity was attributable to the temperature measurements. CONCLUSION: Direct intraoperative measurement of human brain temperature is feasible and safe, but accuracy requires that the temperature sensor be inserted at least 2 cm into the cerebral cortex.
The peptide endothelin 3 (EDN3) is essential for normal neural crest development in vivo, and is a potent mitogen for quail truncal crest cells in vitro. It is not known which subpopulations of crest cells are targets for this response, although it has been suggested that EDN3 is selective for melanoblasts. In the absence of cell markers for different precursor types in the quail crest, we have characterised EDN3-responsive cell types using in vitro colony assay and clonal analysis. Colonies were analysed for the presence of Schwann cells, melanocytes, adrenergic cells or sensory-like cells. We provide for the first time a description of the temporal pattern of lineage segregation in neural crest cultures. In the absence of exogenous EDN3, crest cells proliferate and then differentiate. Colony assay indicates that in these differentiated cultures few undifferentiated precursors remain and there is a low replating efficiency. By contrast, in the presence of 100 ng/ml EDN3 differentiation is inhibited and most of the cells maintain the ability to give rise to mixed colonies and clones containing neural crest derivatives. A high replating efficiency is maintained. In secondary culture there was a progressive decline in the number of cell types per colony in control medium. This loss of developmental potential was not seen when exogenous EDN3 was present. Cell type analysis suggests two novel cellular targets for EDN3 under these conditions. Contrary to expectations, one is a multipotent precursor whose descendants include melanocytes, adrenergic cells and sensory-like cells; the other can give rise to melanocytes and Schwann cells. Our data do not support previous claims that the action of EDN3 in neural crest culture is selective for cells in the melanocyte lineage.
BACKGROUND: Although low-flow cardiopulmonary bypass (CPB) has become a preferred technique for the surgical repair of complex cardiac lesions in children, the relative hypotension and decrease in cerebral blood flow (CBF) associated with low flow may contribute to the occurrence of postoperative neurologic injury. Therefore, it was determined whether phenylephrine administered to increase arterial blood pressure during low-flow CPB increases CBF. METHODS: Cardiopulmonary bypass was initiated in seven baboons during fentanyl, midazolam, and isoflurane anesthesia. Animals were cooled at a pump flow rate of 2.5 l.min-1.m-2 until esophageal temperature decreased to 20 degrees C. Cardiopulmonary bypass flow was then reduced to 0.5 l.min-1.m-2 (low flow). During low-flow CPB, arterial partial pressure of carbon dioxide (Pco2) and blood pressure were varied in random sequence to three conditions: (1) Pco2 30-39 mmHg (uncorrected for temperature), control blood pressure; (2) Pco2 50-60 mmHg, control blood pressure; and (3) Pco2 30-39 mmHg, blood pressure raised to twice control by phenylephrine infusion. Thereafter, CPB flow was increased to 2.5 l.min-1.m-2, and baboons were rewarmed to normal temperature. Cerebral blood flow was measured by washout of intraarterial 133Xe before and during CPB. RESULTS: Phenylephrine administered to increase mean blood pressure from 23 +/- 3 to 46 +/- 3 mmHg during low-flow CPB increased CBF from 14 +/- 3 to 31 +/- 9 ml.min-1.100 g-1, P < 0.05. Changes in arterial Pco2 alone during low flow bypass produced no changes in CBF. CONCLUSIONS: Although low-flow CPB resulted in a marked decrease in CBF compared with prebypass and full-flow bypass, phenylephrine administered to double arterial pressure during low-flow bypass produced a proportional increase in CBF.
BACKGROUND: Some patients who undergo cerebral aneurysm surgery require cardiopulmonary bypass and deep hypothermic circulatory arrest. During bypass, these patients often are given large doses of a supplemental anesthetic agent in the hope that additional cerebral protection will be provided. Pharmacologic brain protection, however, has been associated with undesirable side effects. These side effects were evaluated in patients who received large doses of propofol. METHODS: Thirteen neurosurgical patients underwent cardiopulmonary bypass and deep hypothermic circulatory arrest to facilitate clip application to a giant or otherwise high-risk cerebral aneurysm. Electroencephalographic burst suppression was established before bypass with an infusion of propofol, and the infusion was continued until the end of surgery. Hemodynamic and echocardiographic measurements were made before and during the prebypass propofol infusion and again after bypass. Emergence time also was determined. RESULTS: Prebypass propofol at 243 +/- 57 micrograms.kg-1.min-1 decreased vascular resistance from 34 +/- 8 to 27 +/- 8 units without changing heart rate, arterial or filling pressures, cardiac index, stroke volume, or ejection fraction. Propofol blood concentration was 8 +/- 2 micrograms/ml. Myocardial wall motion appeared hyperdynamic at the end of cardiopulmonary bypass, and all patients were weaned therefrom without inotropic support. After bypass, vascular resistance decreased further, and cardiovascular performance was improved compared to baseline values. Nine of the 13 patients emerged from anesthesia and were able to follow commands at 3.1 +/- 1.4 h. Three others had strokes and a fourth had cerebral swelling. CONCLUSIONS: Propofol infused at a rate sufficient to suppress the electroencephalogram does not depress the heart or excessively prolong emergence from anesthesia after cardiopulmonary bypass and deep hypothermic circulatory arrest.
OBJECTIVE: Hypothermia has been demonstrated to protect the brain from ischemic or traumatic injury. Previous efforts to induce cerebral hypothermia have relied on techniques requiring total body cooling that have resulted in serious cardiovascular derangements. A technique to selectively cool the brain, without systemic hypothermia, may have applications for the treatment of neurological disease. METHODS: After induction of general anesthesia in 12 baboons, the right common carotid artery and ipsilateral femoral artery were each occlusively cannulated and joined to a centrifugal pump. In a closed-circuit system, blood was continually withdrawn from the femoral artery, cooled by water bath, and infused through the common carotid artery with its external branches occluded. Pump flow was varied so that right carotid pressure approximated systemic blood pressure. In six animals, perfusate was cooled to decrease right cerebral temperature to < 19 degrees C for 30 minutes. In six animals, right cerebral temperature was decreased to < 25 degrees C for 3 hours. In those six animals, 133Xe was injected into the right carotid artery before, during, and after hypothermia. Peak radioactivity and washout curves were recorded from bilateral cranial detectors. Systemic warming was accomplished by convective air and warm water blankets. Esophageal, rectal, and bilateral cerebral temperatures were continuously recorded. RESULTS: In animals cooled to < 19 degrees C, right cerebral temperature decreased from 34 degrees C to 18.5 +/- 1.1 degrees C (mean +/- standard deviation), P < 0.01, in 26 +/- 13 minutes. Simultaneously, left cerebral temperature decreased to 20.7 +/- 1.6 degrees C. During 30 minutes of stable cerebral hypothermia, esophageal temperature decreased from 35.1 +/- 2.3 degrees C to 34.2 +/- 2.2 degrees C, P < 0.05. In animals cooled to < 25 degrees C, right cerebral temperature decreased from 34 degrees C to 24.5 +/- 0.6 degrees C in 12.0 +/- 6.0 minutes, P < 0.01. Simultaneously, left cerebral temperature decreased to 26.3 +/- 4.8 degrees C. After 3 hours of stable cerebral hypothermia, esophageal temperature was 34.4 +/- 0.5 degrees C, P < 0.05. Right hemispheric cerebral blood flow decreased during hypothermia (26 +/- 16 ml/min/100 g) compared to values before and after hypothermia (63 +/- 29 and 51 +/- 34 ml/min/100 g, respectively; P < 0.05). Furthermore, hypothermic perfusion resulted in a proportionally increased radioactivity peak detected in the left cerebral hemisphere after right carotid artery injection of 133Xe (0.8 +/- 0.2:1, left:right) compared to normothermia before and after hypothermia (0.3 +/- 2 and 0.3 +/- 1, respectively; P < 0.05). Normal heart rhythm, systemic arterial blood pressure, and arterial blood gas values were preserved during hypothermia in all animals. CONCLUSION: Bilateral cerebral deep or moderate hypothermia can be induced by selective perfusion of a single internal carotid artery, with minimal systemic cooling and without cardiovascular instability. This global brain hypothermia results from profoundly altered collateral cerebral circulation during artificial hypothermic perfusion. This technique may have clinical applications for neurosurgery, stroke, or traumatic brain injury.
Global cerebral hypothermia of 24 degrees C was induced without systemic cooling by means of selective hypothermic perfusion of a single internal carotid artery in four baboons. With a closed-circuit pump system, blood was withdrawn from the femoral artery, cooled in a water bath, and infused through an internal carotid artery catheter, which was positioned with fluoroscopic guidance. This endovascular technique may have applications in the treatment of neurologic disease in humans.
The aim of this study was to determine whether buccal mucosa would provide an alternate source of tissue for human biomonitoring. Samples of clinically normal oral biopsies were excised, and buccal mucosa were scraped or brushed from patients while they were undergoing surgery for the excision of intra-oral squamous cell carcinoma. Extracted DNA was 32P-postlabeled using the butanol enhancement method, and DNA adduct levels were quantified to compare the accuracy of adduct detection in buccal mucosa versus oral biopsies. For both tissues, tobacco smokers were found to have statistically significant higher levels of DNA damage than samples obtained from nonsmokers (P < 0.001). Mean relative adduct labeling in smokers was very similar for oral biopsies (6.16 x 10(-7)) and buccal mucosa (6.73 x 10(-7)). Likewise, mean relative adduct labeling values for nonsmokers were comparable in the two tissues (1.66 x 10(-7) for biopsies and 2.1 x 10(-7) for mucosa). Overall, an excellent correlation (r = 0.79; n = 32) was obtained between adduct levels in biopsies and mucosa for all classes of patient. These data indicate that buccal mucosa provides an additional tissue for monitoring human exposure to environmental genotoxins. The tissue is obtained rapidly in a noninvasive fashion when harvested by brushing. It can clearly be used to study components in cigarette smoke which cause DNA damage, and it is on the major route of exposure to many environmental genotoxins.
The duration of the antagonism to neuromuscular blockade produced by pyridostigmine is prolonged in elderly patients, and a pharmacokinetic explanation was sought. Ten elderly (71-85 yr) and 10 younger (21-51 yr) patients were anesthetized with thiopental, nitrous oxide, and isoflurane and paralyzed with a combination of d-tubocurarine and pancuronium. When twitch height returned to 5% of baseline, pyridostigmine 0.25 mg/kg was administered and blood samples were collected intermittently for 6 h. Pyridostigmine plasma concentrations were determined by radioimmunoassay and after an hour were always greater in the elderly than in the younger patients. In both groups, plasma pyridostigmine decrement curves were best described by triexponential equations. Pharmacokinetic analysis revealed that plasma clearance in the elderly group was significantly decreased compared to that in the younger group (6.7 +/- 2.2 vs 9.5 +/- 2.7 mL.kg-1.min-1, P < 0.05). Elimination half-lives and volumes of distribution were not significantly different between groups. We conclude that a possible explanation for the prolonged duration of action of pyridostigmine in the elderly is its slow plasma clearance.