Search PubMed⌕ Search

Biomedical subjects

T Jones

Publications and source records attributed to T Jones.

At least 469 records · Page 26Linked to original sources
PubMed1982

Thioproline: an inhibitor of chemical carcinogenesis.

Experimental DBA/1 mice were implanted with methylcholanthrene impregnated filterpaper disks. The disks were removed six weeks after implantation and median induction of fibrosarcomas occurred in 114.5 +/- 6 days. Two weeks pretreatment with thioproline, a reverse transformation drug, followed by maintenance throughout the duration of the experiment (27 weeks) reduced the tumor incidence to 60% that of controls. Pretreatment with thioproline and drug administration continued only through the six weeks post-implantation period failed to alter tumor incidence.

Animals↗
PubMed1982

A benzylidene mannopyranoside derivative with antitumor activity in the spontaneous mammary tumor system.

Methyl 2,3,4,6-di-O-benzylidene alpha-D-mannopyranoside (MeDBMP) was synthesized to evaluate its potential as a cytotoxic benzaldehyde liberating agent. MeDBMP was found to cause significant reductions in the sizes of spontaneous mouse mammary carcinomas and to produce long term alterations in their growth characteristics. It was nontoxic at all doses examined and possessed no mutagenic properties in the Ames Salmonella/mammalian-microsome test.

Animals↗
PubMed1981

Differentiating violent and nonviolent prison inmates by use of selected MMPI scales.

Used multivariate procedures to determine whether prisoners who committed violent acts while in prison could be differentiated from those who did not. Ss were 141 adult male inmates in maximum security prisons. Multiple variable profile analysis that employed 22 MMPI scales and four demographic items significantly differentiated between violet and nonviolent inmates. Discriminant analysis that used all 26 variables yielded a significant root that accounted for 34.9% of the variance between violent and nonviolent inmates. The MMPI scales that contributed most to prediction of group membership were F, PA, PT, and SC, all of which had discriminant load values above .40. Finally, a discriminant function prediction equation was derived to predict the criterion variable (violent or nonviolent behavior). Applying this equation without knowledge of the S's actual group membership correctly classified 72.9% of the violent and 80.6% of the nonviolent inmates.

Adolescent↗
PubMed1981

Measurement of CBF and CMRO2 using the continuous inhalation of C15O2 and 15O. Experimental validation using CO2 reactivity in the anaesthetised dog.

Experimental support for the steady state 15O inhalation technique, as used to measure cerebral blood flow (CBF) and oxygen utilisation (CMRO2), was obtained by describing the response of the cerebral vasculature to variations in arterial PCO2 in 6 anaesthetised dogs. Measurements were made using a positron emission tomography (ECAT II) and arterial blood sampling, during the sequential constant inhalation of C15O2 and 15O2. Values of CBF and CMRO2 were calculated for a mixture of white and grey matter, using the steady state tracer equations derived by Jones et al. (1976). The mean CMRO2 was 3.58 +/- 0.81 ml O2 . 100 ml-1 . min-1, whilst the mean CBF and OER (oxygen extraction ratio) values (for an arterial PCO2 of 40 mm Hg) were 39.9 ml . 100 ml-1 and 0.50 +/- 0.06, respectively. Arterial PCO2 was varied between 20 and 150 mm Hg. CBF was found to correlate closely with arterial PCO2, resulting in a mean slope (specific reactivity) of 1.52 +/- 0.38 ml . 10 ml-1. mm Hg-1. Pooling the flow data resulted in a linear relationship between CBF (% change) and arterial PCO2 in the range 20-70 mm Hg, with a slope (% reactivity) of 3.2% mm Hg-1 (2 P less than 0.001). The oxygen extraction ratio (OER) fell with increasing values of arterial PCO2 resulting in a stable CMRO2 throughout each study. There was no correlation between CMRO2 and artificially increased CBF. These results support and give confidence in the use of the 15O inhalation technique for measuring CBF, OER and CMRO2.

Animals↗
PubMed1981

Regional cerebral oxygen supply and utilization in dementia. A clinical and physiological study with oxygen-15 and positron tomography.

The cerebral blood flow, oxygen extraction and oxygen utilization has been measured regionally in 22 dements, and 14 aged normal volunteers. Ten demented patients were studied twice at a six-month interval from initial measurements. The use of a steady-state 15O technique and positron tomography for measuring regional cerebral blood flow, regional oxygen extraction fraction and mean cerebral oxygen utilization is discussed. The limitations of measurements are reviewed in the light of the present results and the current state of technological development in positron emission tomography is discussed. A decline in cerebral blood flow and mean cerebral oxygen utilization was correlated with increasing severity of dementia in both degenerative and vascular dements. The decline was coupled, both for the cerebral hemisphere as a whole and regionally. There was no increase in oxygen extraction ratio globally, and therefore no evidence to support the existence of a chronic ischaemic brain syndrome. Focal abnormalities in oxygen utilization were observed for both vascular and degenerative groups. In the vascular group, parietal defects were the most pronounced. Individual derangements of the regional pattern varied, reflecting the different unique patterns of ischaemic damage in these patients. In the degenerative group, parietal and temporal defects were seen in the less severe group, but a profound depression in the frontal regions with relative sparing of occipital area characterized the severe degenerative dements.

Aged↗
PubMed1981

A theoretical study of the steady-state model for measuring regional cerebral blood flow and oxygen utilisation using oxygen-15.

There is a growing interest in the tomographic measurement of regional cerebral blood flow and oxygen utilisation using continuous inhalation of C15O2 and 15O2. This paper examines the influence of certain assumptions in the underlying steady-state model. Estimations are made for possible errors in the actual measurement of these quantities in grey and white matter.

Blood Flow Velocity↗
PubMed1981

Quantitative measurement of regional extravascular lung density using positron emission and transmission tomography.

A technique has been developed to measure regional values of vascular and extravascular lung density using positron emission and transmission tomography. Quantitative values of lung density in a transaxial plane are obtained by recording transmission scans during the exposure of a ring source of positron emitting germanium/gallium-68, which encircles the subject in the plane of the scan. Values of blood density are obtained by scanning in the emission mode following the labeling of the subject's red blood cells with a quantity of C-carbon monoxide inhaled as a bolus. Subtraction of the normalised blood volume scan from the normalised lung density (transmission) scan provides regional values of extravascular lung density. The response of the transmission scan to changes in density was obtained by scanning different tissue equivalent materials in the density range 0.02 to 1.0 g cm-3. This resulted in a linear relationship between pixel counts and density. Density measurements made in vitro on simulated chest phantoms suggest that, at worst, random errors of 3.5% and systematic errors (due to the influence of the chest wall) of between 10 and 15% will be incurred when measurements are made in vivo on lungs of average normal density (0.3 g cm-3). The random error associated with the emission scan (arising from counting statistics alone) was found to be 1.2%. Measurements of lung density made on five normal subjects (supine) resulted in a mean density of 0.29 g cm-3 for a region in the lower (caudal) part of the lung, with a range of values between 0.26 and 0.32 g cm-3 from subject to subject. A pronounced anteroposterior gradient of both lung density and blood density was observed, while the gradient of extravascular lung density was quite small. The mean value of the ratio extravascular: vascular lung density for both caudal and cranial lung regions was 0.92 +/- 0.25.

Adult↗
PubMed1981

CMRO2 and CBF by the oxygen-15 inhalation technique. Results in normal volunteers and cerebrovascular patients.

The oxygen-15 inhalation technique has been applied to the quantitation of regional CBF, CMRO2 and OER with positron emission tomography. The introduction of corrections for gamma-ray attenuation, and for recirculation, has allowed us to obtain values for CBF, CMRO2 and OER in close agreement with values obtained using other techniques. In 27 normal volunteers mean CMRO2 shows values ranging from 4.98 to 3.79 ml/100/min, depending on the region evaluated. Mean CBF values range from 55.3 to 38.8 ml/100ml/min. Mean OER is more constant, ranging from 0.56 to 0.49, with a mean of 0.53 +/- 0.04, thus reflecting the close matching between metabolism and blood supply. We have further identified corrections for cerebral blood volume, which is measurable, and for water partition coefficient, which remains uncertain. In preliminary studies these corrections decrease the OER over the physiological range of flow by 10%, with a 15% lower CMRO2. The reproducibility of the results and the effects of aging have been studied. A series of 27 studies on acute ischaemic CVD are reported. The course of the clinical condition has been correlated with the quantitation of oxygen utilization and blood flow performed at different intervals from the onset of symptoms.

Adult↗
PubMed1981

Nutritional support of the critically ill patient.

Protein-calorie malnutrition is prominent among patients undergoing gastrointestinal tract operations who are admitted as an emergency measure to the intensive care unit. Immediate feedings postoperatively with an elemental diet through a jejunostomy catheter can provide an alternative method of nutritional support in these critically ill patients. In patients with extremely high metabolic demands, it may be necessary to combine enteral feeding with parenteral support to achieve positive nitrogen balance.

Aged↗
PubMed1981

Positron emission tomography: state of the art in neurology.

The initial clinical application of PET has demonstrated intriguing aspects in ischaemic cerebrovascular disease and epilepsy. A few observations on migraine have also been published, and studies on extrapyramidal disorders are currently underway at the UCLA and the Hammersmith Hospital. The development of PET centres in the USA and Europe will result in larger clinical studies. The capacity for accurate and reliable quantitation of physiological parameters now opens the door to serial measurements in individual patients. Quantitation in absolute units of flow or consumption of a metabolite means that correlations and comparisons can be made between patients, and between studies in individual patients. This means that the natural history of cerebral disease in pathophysiological terms is open to study and, in turn, the effects of therapeutic interventions can be monitored. In this way, with the formulation of appropriate clinical research questions, significant advances in the understanding of cerebral disease and its treatment can be expected. Though the clinical results from PET studies are as yet scanty or preliminary, sufficient data exists to indicate that PET is the most promising tool for the exploration of functional and metabolic processes in the central nervous system in vivo.

Brain Diseases↗
PubMed1981

Bacteremia in a small non-urban community hospital.

Forty-six episodes of bacteremia were observed during a three-year period at a small, non-urban community hospital. The incidence of bacteremia was 4.3 episodes per 1,000 admissions; this rate is similar to the incidence of bacteremia in large, urban community hospitals but lower than the incidence of bacteremia in municipal or academic hospitals. Eleven percent of bacteremias were hospital acquired, an incidence of 0.5 hospital acquired bacteremias per 1,000 admissions. The low incidence of hospital acquired bacteremia was a reflection of the low incidence of nosocomial, aerobic, gram-negative bacteremia (0.1 per 1,000 admissions). Thirteen percent of bacteremic patients died. The mortality in patients with community acquired bacteremia (10%) was lower than that reported from larger, urban hospitals; the mortality in patients with hospital acquired bacteremia (40%) was similar to that reported from larger, urban hospitals. The lower rates of bacteremia and associated mortality that were observed appear to be due to the lesser severity of underlying diseases in these patients.

Adult↗
PubMed1981

Relative mutagenicity of some urinary metabolites of the antitumor drug cyclophosphamide.

Four urinary metabolites of the cytostatic drug cyclophosphamide were tested for mutagenicity in the Ames Salmonella assay: nornitrogen mustard (NM), 4-ketocyclophosphamide, 3-(2-chloroethyl)oxazolidone (OZ), and N,N'-bis(2-chloroethyl)piperazine. All four acted as direct base substitution mutagens although 4-ketocyclophosphamide showed an increase in mutagenicity after metabolic activation with S-9 rat liver fraction. Of the four compounds tested, NM was the strongest mutagen while all the others had weak mutagenic activity, with OZ being the weakest. We observed that, under conditions which facilitate the conversion of NM to OZ (presence of HCO-3 at neutral pH), the former lost both mutagenic and alkylating activities. Our findings, taken together with other reports in the literature, indicate that NM could be a major cause of secondary bladder carcinoma since it is a potent mutagen ad seems to be present in high levels in the urine of cyclophosphamide-treated patients. The fact that it can be detoxified to the weak mutagen OZ in the presence of HCO-3 suggests the possibility that, by increasing the concentration of HCO-3 in the urine of patients, that undesirable side effect of cyclophosphamide treatment can be alleviated.

Bicarbonates↗
PubMed1980

A study of coordination of services: referrals.

This article reports a study of referrals among social service and mental health agencies. Staff from human service agencies were interviewed about the process of referring and asked to make simulated referrals using mock clients constructed for this study. Interview data show lack of communication and inappropriate referrals as the biggest problems with the referral system. Interjudge agreement about the simulated referral choices was found to be not significantly different from chance. The data also suggest that agency staff refer on the basis of "habits" as much or more than on the basis of client problems. The frequency of inappropriate simulated referrals was relatively high (15%) considering that agencies included in the sample are large public agencies with broad definitions of what clients are appropriate for their services. Implications of these findings are discussed in terms of existing incentives for agencies to cooperate or compete and need for methodology to evaluate service delivery systems or networks.

Child↗
PubMed1980

Stented xenograft valve insertion.

A simple holder and the associated technique for temporarily converting the stented xenograft type of valve into a Starr-Edwards configuration are described. With this technique, the struts are not caught by the sutures during insertion.

Bioprosthesis↗