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Biomedical subjects

D R Jones

Publications and source records attributed to D R Jones.

At least 163 records · Page 9Linked to original sources
PubMed1995

Long-term storage of human fetal haematopoietic progenitor cells and their subsequent reconstitution. Implications for in utero transplantation.

Haematopoietic progenitor cells were isolated from human fetal liver, obtained between 6 and 15 weeks gestation. After preparation of a single cell suspension, the cells were stored using a stepwise freezing protocol; taking the cells from room temperature through -70 degrees C to liquid nitrogen. Viability (trypan blue exclusion), morphology (Leishman stain), identification of cell type (flow cytometry) and growth characteristics in semi-solid culture medium were assessed using the fresh cell suspension. We were able to confirm that the predominant cells in human fetal liver up to about 15 weeks gestation are those of the erythroid lineage. It was established that viability in excess of 75% was required to ensure adequate growth in culture after frozen storage and it was deemed important to ensure morphological integrity of the cell preparations. The colonies formed in culture were observed to be producing haemoglobin between 7 and 9 days after initial seeding. We have determined that cells can be stored in liquid nitrogen for up to 2 years without loss of (1) viability, (2) morphological features and (3) ability to form colonies and produce haemoglobin in culture. These findings offer encouragement for the implementation of a cell bank to support an in utero transplantation programme.

Cell Separation↗
PubMed1994

An enzyme-linked immunosorbent assay for complement regulatory proteins and membrane-bound immunoglobulins on intact red blood cells.

We have developed an ELISA technique to examine RBC-bound molecules in autoimmune disorders. In particular, the technique has enabled us to investigate the role of some complement regulatory proteins in immune complex transport and to suggest that decay accelerating factor (DAF) may be involved in this process. In both autoimmune haemolytic anaemia (AHA) and systemic lupus erythematosus (SLE) a sub-set of individuals was identified, on the basis of patterns of complement receptor 1 (CR1) expression on RBC. In these patients, CR1 identified using the monoclonal antibody E11 was low or absent whereas CR1 identified using a DAKO monoclonal antibody (C3RTo5) was present at normal levels.

Anemia, Hemolytic, Autoimmune↗
PubMed1994

Characterization of dextromethorphan N-demethylation by human liver microsomes. Contribution of the cytochrome P450 3A (CYP3A) subfamily.

In an effort to identify the human cytochromes P450 involved in the N-demethylation of dextromethorphan, the kinetics of 3-methoxymorphinan formation were studied in microsomal enzyme systems. Under initial rate conditions, 3-methoxymorphinan formation demonstrated single enzyme Michaelis-Menten kinetics using microsomes obtained from three human livers (Km: 0.52-0.71 mM; Vmax: 375-812 pmol/mg protein/min). B-lymphoblastoid cells expressing CYP3A4 incubated with 0.4 mM dextromethorphan catalyzed the formation of 3-methoxymorphinan at a rate of 22 pmol product/mg protein/min. Midazolam, a prototypic substrate for CYP3A4 and CYP3A5, competitively inhibited dextromethorphan N-demethylation by two human liver microsomal samples with Ki values of 46 +/- 10 and 63 +/- 8 microM. At a dextromethorphan concentration of 0.4 mM, gestodene (100 microM) inhibited 3-methoxymorphinan formation by approximately 50%. Immunoinhibition of dextromethorphan N-demethylation using rabbit anti-CYP3A4 antibodies resulted in a 60% decrease in 3-methoxymorphinan formation at a dextromethorphan concentration of 0.4 mM. Additional inhibition studies using furafylline, coumarin, sulfaphenazole, mephenytoin, quinidine, and diethyldithiocarbamic acid, which are selective inhibitors of CYP1A2, CYP2A6, CYP2C8/9, CYP2Cmp, CYP2D6, and CYP2E1, respectively, demonstrated no substantial inhibition of dextromethorphan N-demethylation. Correlation analysis was performed using the rate of 3-methoxymorphinan formation at a concentration of 1 mM dextromethorphan and immunoquantified levels of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 and their associated characteristic catalytic activities. A significant correlation was observed between dextromethorphan N-demethylase activity and midazolam 1'- and 4-hydroxylase activity (r2 = 0.77 and 0.69 respectively, N = 19, P < 0.01); the exclusion of those samples containing both CYP3A4 and CYP3A5 increased the correlation significantly (r2 = 0.87 and 0.91 respectively, N = 12, P < 0.01). In the absence of CYP3A5, a significant correlation was observed between 3-methoxymorphinan formation and the sample's erythromycin N-demethylase activity (r2 = 0.94, N = 12, P < 0.01), testosterone 6 beta-hydroxylase activity (r2 = 0.96, N = 7, P < 0.01) and relative immunoquantified levels of CYP3A4 (r2 = 0.96, N = 12, P < 0.01). Inclusion of those samples expressing CYP3A5 in addition to CYP3A4 reduced the magnitude of the observed correlation. No significant correlation between 3-methoxymorphinan formation and the sample's relative immunoquantified levels of or form-selective activity associated with CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19 (or CYP2Cmp), CYP2D6, and CYP2E1 was observed. In conclusion, dextromethorphan N-demethylation appears to be catalyzed primarily by CYP3A4 and to a lesser extent by CYP3A5 in vitro in humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Regioselective biotransformation of midazolam by members of the human cytochrome P450 3A (CYP3A) subfamily.

The capabilities of cytochrome P4503A4 (CYP3A4), CYP3A5, and fetal hepatic microsomes containing CYP3A7 to metabolize midazolam were investigated using human hepatic microsomes and purified CYP3A4 and CYP3A5. Under initial rate conditions and high substrate concentration (400 microM midazolam), variability among eighteen human liver microsomal samples was 30- and 16- fold for 1'- and 4-hydroxylation of midazolam, respectively. Exclusion of two samples isolated from patients previously administered barbiturates reduced the inter-individual variability to 10.5- and 6.0-fold for 1'- and 4-hydroxylation, respectively. Six fetal hepatic microsomal samples showed 10-fold variation in both 1'-hydroxymidazolam and 4-hydroxymidazolam formation rates. The rates of formation of 4-hydroxymidazolam and 1'-hydroxymidazolam from midazolam by adult samples containing only CYP3A4 and by fetal liver samples were highly correlated (r2 = 0.99 and 0.97, P < 0.01, respectively). The rates of formation of 1'-hydroxymidazolam and 4-hydroxymidazolam from midazolam (400 microM) by adult samples that contained only CYP3A4 were correlated significantly (P < 0.01) with the ability of the samples to N-demethylate erythromycin (r2 = 0.95 and 0.92, respectively). 6 beta-hydroxylate testosterone (r2 = 0.96 and 0.96, respectively), and the CYP3A4 content of the samples (r2 = 0.89 and 0.86, respectively). Microsomal samples containing CYP3A5 in addition to CYP3A4 exhibited a significantly greater ratio of 1'-hydroxymidazolam to 4-hydroxymidazolam compared with samples containing only CYP3A4 or CYP3A7 (P < 0.001). Purified CYP3A5 in a reconstituted system, consisting of dilauroylphosphatidylcholine, cytochrome b5, and NADPH-cytochrome P450 reductase, and an NADPH-regenerating system displayed a 2-fold greater rate of 1'-hydroxymidazolam formation and a similar rate of 4-hydroxymidazolam formation compared with a reconstituted system with CYP3A4. In conclusion, CYP3A4, CYP3A5, and fetal microsomes containing CYP3A7 catalyze 1'- and 4-hydroxylation of midazolam with the ratio of these metabolites indicative of the CYP3A form.

Biotransformation↗
PubMed1994

Safe use of heparin-coated bypass circuits incorporating a pump-oxygenator.

Durable, covalently bonded, heparin-coated cardiopulmonary bypass (CPB) circuits with oxygenators have been developed. Proposed advantages of heparin-coated CPB circuits include improved biocompatibility and thromboresistance. The purpose of this study was to evaluate our experience with heparin-coated CPB circuits in 20 patients. Heparin was given to maintain an activated clotting time equal to or greater than 200 seconds, while flow rates were kept equal to or greater than 2 L/min. Indications for use of this circuit included recent stroke, posttraumatic injuries, recent gastrointestinal bleeding, protamine allergies, combined cardiac and noncardiac procedures, and ventricular assist. Mean heparin dosage was 0.50 +/- 0.18 mg/kg and protamine dosage was 57.14 +/- 39.36 mg. Postoperative blood loss and transfusion requirements were minimal. Postoperative complement levels of C3a and C5a were normal, suggesting excellent biocompatibility. There were no deaths or perioperative complications. Heparin-coated CPB circuits using a pump oxygenator can be used safely with low-dose heparin administration in select patients requiring CPB.

Adolescent↗
PubMed1994

Potential application of p53 as an intermediate biomarker in Barrett's esophagus.

Diagnosis of the neoplastic progression in Barrett's esophagus using the histologic classification of dysplasia is frequently difficult. The tumor suppressor protein p53, when mutated, confers a promoter effect on cell growth. The purpose of this study was to evaluate the applicability of p53 as an intermediate biomarker of malignancy in Barrett's esophagus. Archival analysis of 100 biopsy specimens of Barrett's esophagus and 10 esophageal adenocarcinomas were compared with 35 chronic esophagitis biopsy specimens. Immunocytochemistry using an anti-p53 monoclonal antibody was performed and elevated immunoreactivity quantitated microscopically. Data were analyzed using a logistic regression model. Significant p53 immunoreactivity occurred as follows: chronic esophagitis (0%), Barrett's esophagus without dysplasia (10%), with low-grade dysplasia (60%), with high-grade dysplasia (100%), and adenocarcinoma (70%). All cases of Barrett's esophagus were significantly immunoreactive when compared with the chronic esophagitis cases (p = 0.001). There was an increase in p53 immunoreactivity as the histologic classification progressed toward adenocarcinoma (p = 0.001). Progression to high-grade dysplasia may be predicted based on p53 immunoreactivity. These findings suggest a role for p53 as an intermediate biomarker in Barrett's esophagus.

Adenocarcinoma↗
PubMed1994

Patients' experiences of health checks in general practice: a sample survey.

The 1990 contract for general practitioners in the UK offered incentives for them to organize health promotion clinics and required them to perform 'lifestyle' checkups of their patients every 3 years, despite uncertainty about the impact of such checks on patient health. To address this lack of appropriate evaluation, a follow-up study to assess benefits in terms of patient behaviour and health resulting from the introduction of lifestyle checkups in general practice in a sample of more than 7000 patients aged 30-70 from 18 practices in three FHSA areas (in south London, Surrey and Yorkshire) has been performed. Eighteen per cent of the random sample of patients reported having a health check in the previous year. A full health check comprising measurement of blood pressure, height and weight, urinalysis and questioning about smoking habits, alcohol consumption, exercise, diet and family illnesses had been given to 29% of respondents reporting a health check of any kind. Respondents in less privileged socioeconomic groups were more likely to have had a health check, but less likely to have had a 'full' check. Reactions to the checks were mainly positive; 81% regarded the check as helpful, and only 6% reported it to be worrying and 6% a waste of time. The implications for the new health promotion banding system in the UK are discussed.

Adult↗
PubMed1994

Patterns of respiration and heart rate during wakefulness and sleep in elephant seal pups.

Although breath holding during diving has been studied extensively in seals, the recent observation that these mammals also exhibit long-duration apnea while apparently sleeping has not been systematically examined. This project examined sleep apnea in northern elephant seal pups (Mirounga angustirostris). The animals exhibited a sequential sleep pattern of wakefulness-slow-wave sleep (SWS)-rapid eye movement (REM) sleep that resembled the normal pattern of mammalian sleep. The typical respiratory pattern during sleep in 4-mo-old pups consisted of short periods of continuous breathing separated by periods of apnea of up to 12 min. Several cycles of apnea and eupnea could occur during a single sleep episode. Breathing during a sleep cycle occurred only in SWS, never during REM sleep. The eupneic heart rate was characterized by significant sinus arrhythmia, and the apneic heart rate was similar to the minimum value during normal sinus arrhythmia. Patterns of change in breathing and heart rate associated with wakefulness and sleep were similar in seals sleeping underwater and on land. When sleeping underwater, the seals raised their heads to the surface to breathe without awakening. The changes in heart rate associated with normal sinus arrhythmia, sleep apnea, and diving apnea appear to be similar, suggesting regulation by a common homeostatic control mechanism.

Analysis of Variance↗
PubMed1994

Regional cerebral blood flow during submergence asphyxia in Pekin duck.

The cerebrovascular response to submergence asphyxia was studied in the Pekin duck (Anas platyrhynchos var.) by use of the cerebral blood flow (CBF) tracer [14C]isopropyliodoamphetamine and quantitative autoradiography. Blood flow of the whole brain was 158 +/- 14 (SE) ml.min-1 x 100 g-1 (n = 7) in control animals. There was a doubling of flow to 320 +/- 61 ml.min-1 x 100 g-1 (n = 6) during submergence asphyxia. The hypothesis that CBF is redistributed within the brain during asphyxia was not supported. There were no regional reductions in CBF during submergence asphyxia. Mean arterial blood pressure was similar (approximately 140 mmHg), but heart rate, arterial blood gas tensions, and arterial pH were significantly different in control and submerged ducks at the time CBF was measured. The differences in CBF among submerged animals correlated strongly with arterial PCO2 and mean arterial blood pressure. The smallest proportional difference in regional CBF between control and submerged ducks occurred in the ectostriatum (+141%) and the largest in the locus ceruleus (+241%). The largest absolute difference in regional CBF was in the nucleus ruber (+322 ml.min-1 x 100 g-1). These are the first measurements of blood flow in discrete nuclei and regions of the avian brain.

Amphetamines↗
PubMed1994

Relationship between intracellular pH, extracellular pH, and ventilation during dilution acidosis.

Previous experiments showed that acute hyperosmolality results in an extracellular acidosis that does not stimulate respiratory compensation (C.E. Kasserra, D. R. Jones, and M. R. Hughes. Respir. Physiol. 85: 383-393, 1991). The data suggested that development of the extracellular dilution acidosis would also result in a concomitant intracellular contraction alkalosis. The effects of acute hyperosmolality and lactacidosis on systemic intracellular pH (pHi) were studied in the conscious Pekin duck in an effort to separate the effects of pHi and extracellular pH (pHe) on ventilatory control. Brain pH was also measured during systemic hyperosmolality to determine the relationship between blood and brain pHi. Hyperosmolality caused a concurrent extracellular acidosis and intracellular alkalosis in pectoral muscle, whereas lactic acid infusion decreased both pHe and pHi. Ventilation was stimulated only during lactacidosis and did not change during hyperosmolality. Brain pHi did not show a consistent significant increase in response to systemic hyperosmolality over 1 h but did show a trend toward an alkalosis. Measurement of high-energy phosphate metabolites (phosphocreatine, ATP, and Pi) indicated an increase of metabolic rate during hyperosmolality. With the assumption that similar pHi changes were occurring in chemoreceptive cells, the results suggest that ventilation was responding to pHi changes and that much of the depressive response to acute hyperosmotic disturbance was peripherally generated.

Acidosis, Lactic↗
PubMed1994

Thoracoscopic resection of bilateral metastatic sarcomas causing spontaneous pneumothorax.

Pulmonary metastases from soft tissue sarcomas may present with spontaneous pneumothorax. Metastatectomy via thoracotomy or median sternotomy has been the procedure of choice. We present a patient with bilateral spontaneous pneumothorax secondary to metastatic angiosarcoma where staged video-assisted thoracic surgery using the thoracoscope was used to successfully resect the tumors.

Aged↗
PubMed1994

An overview of international issues in astronaut psychological selection.

The NASA Johnson Space Center Medical Sciences Division convened an In-House Working Group on Psychiatric and Psychological Selection of Astronauts in 1988. Working with the European Space Agency (ESA) and the National Space Development Agency (NASDA) of Japan, psychiatrists and psychologists experienced in selecting individuals for training as astronauts or analogous duties studied the development of appropriate criteria. Psychiatric criteria generally concern the detection of pathological conditions, and thus "select-out" applicants by disqualification. Psychological criteria may be used to identify specific affirmative criteria that make an individual particularly well-qualified for such duties, and thus concern "select-in" processes for operational crews. As space missions grow longer, and as crews become larger and more demographically diversified, the long-ignored questions, "What sort of healthy individuals should be selected for such missions," and "How do we know this?" will become more critical to the success of space exploration. The papers included in this Panel concern the results of these investigations, and represent long-needed quantification of these two selection processes, select-out and select-in, in several cultures.

Astronauts↗
PubMed1994

Computed tomographic diagnosis of acute blunt pancreatic transection.

Pancreatic injuries secondary to blunt trauma are challenging to diagnose. In many cases, the diagnosis is missed or delayed due to the subtle symptoms and signs of pancreatic injury. Blunt pancreatic injuries may evolve over a period of time and can be a source of extensive morbidity and mortality. Most radiologic and laboratory studies have been notoriously nonspecific in diagnosing pancreatic injuries. This article discusses three patients we treated with pancreatic transection secondary to blunt trauma, who underwent computed tomography (CT) of the abdomen on admission. The pertinent CT findings and utility of CT as a diagnostic tool in these three cases of blunt pancreatic injuries are reviewed. Abdominal CT scanning can accurately identify pancreatic injuries secondary to blunt trauma, allowing expeditious surgical intervention. A high index of suspicion for pancreatic injury combined with careful interpretation of abdominal CT scans can provide valuable information about pancreatic injury during the initial trauma assessment.

Accidents, Occupational↗