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Biomedical subjects

T Davidson

Publications and source records attributed to T Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Putative determinants of the cellular response to hyperthermia.

Recently, it has been demonstrated that two different thermal resistant states found in Chinese hamster cells, one transient, associated with thermotolerance, and the other permanent, associated with the increased expression of the cognate member of the hsp 70 family, are characterized by faster recovery from heat-induced perturbations in several cellular processes (Laszlo 1992b). These processes include total cellular protein and RNA synthesis, the localization of hsp70, the organization of vimentin, and the protein composition of the nucleus. In the present study, the recovery from heat-induced perturbations in cellular physiology was extended further to two more types of Chinese hamster cells: permanently heat resistant cells in which thermoresistance is associated with the overexpression of hsp27 and heat-sensitive cell lines. When the heat-resistant hsp27 transfected cell lines were compared with the control wild-type cell line, the recovery of protein synthesis from heat-induced inhibition was similar in the normal and hsp27 transfected cells, while the recovery from heat-induced inhibition of total RNA synthesis and the recovery from heat-induced increased association of hsp70 with nuclei were both more rapid in the hsp27 transfected cell lines. In the permanently heat-sensitive cell lines, the kinetics of recovery from heat-induced inhibition of protein synthesis did not correlate with the heat sensitive state. However, delays in the recovery from heat-induced alterations in total cellular RNA synthesis and from heat-induced excess nuclear association of hsp70 were associated with the heat-sensitive state. Overall, these results suggest that the kinetics of recovery from heat-induced alterations in total cellular RNA synthesis and the localization of hsp 70 are putative candidates for being determinants of the cellular response to hyperthermia, and thus have the potential to form the basis of predictive assays for use in conjunction with clinical hyperthermia.

Adaptation, Physiological↗
PubMed1993

Preoperative drinking does not affect gastric contents.

We have compared the effect of allowing free clear fluids until the time of oral premedication with conventional preoperative fasting. In a prospective, randomized trial, the residual volume and pH of gastric contents after induction of anaesthesia were measured in 100 elective surgical patients allocated randomly to a group in whom the intake of free clear fluids up to the time of premedication was measured (mean 388 ml in 6 h before surgery) or a control group who were fasted for 6 h. Preoperative drinking did not affect either mean (SD) residual gastric volume (22 (21) ml in the study group vs 19 (16) ml in the control group) or pH (study group 2.64 (1.57) vs control group 2.26 (1.45)). The study group experienced less preoperative thirst. Problems with aspiration or regurgitation were not encountered. We believe that allowing elective surgical patients to drink clear fluids until 2 h before anaesthesia may enhance patient comfort without compromising safety.

Adult↗
PubMed1993

Interference from a hand held radiofrequency remote control causing discharge of an implantable defibrillator.

A 46-year-old man with a history of sustained monomorphic ventricular tachycardia underwent an implantation of a third generation multiprogrammable implantable cardioverter defibrillator. One year post implant, while manipulating a remote control to a radiofrequency modulated toy car, the patient experienced a defibrillator discharge not preceded by an arrhythmia prodrome. Subsequent interrogation of the defibrillator revealed that a 34-joule shock had been delivered and had been preceded by RR intervals ranging from 141-406 msec, consistent with sensing lead noise. The remote control utilizes a 12-volt battery and has a carrier frequency of 75.95 MHz and a modulating frequency of 50 Hz. Evaluation of the remote control and defibrillator interaction revealed that the remote control was able to trigger tachyarrhythmia sensing and reproduce the clinical episode. Interference was present only when the remote control was within 8 cm of the pulse generator and at specific angles relative to the device and only when the antenna length was > 45 cm. Interference was eliminated when a ground wire was attached to the antenna and when an aluminium shield was placed between the pulse generator and the remote control. This case report suggests that patients with third generation multiprogrammable defibrillators should be cautioned against close contact with potential sources of electromagnetic interference, such as remote control units.

Artifacts↗
PubMed1991

Emergency laparotomy in patients with AIDS.

The presentation, operative management and final diagnosis were reviewed in 28 patients with AIDS (27 men and one woman) who underwent emergency laparotomy. On clinical and radiological examination, six patients showed features of toxic megacolon, five patients had small bowel obstruction, six patients had localized peritonitis and three had perforated viscus with generalized peritonitis. The most common disease processes were acute colitis in seven patients (associated with cytomegalovirus (CMV) infection in six), intra-abdominal lymphoma in five patients, acute appendicitis in five patients (associated with CMV infection in two), and atypical mycobacterial (MAI) infection in four patients. Two perioperative deaths occurred; one in a patient with acute pancreatitis and a second with generalized peritonitis. Later deaths were due to progression of AIDS, and patient survival at 1 month, 3 months and 6 months was 89 per cent, 64 per cent and 48 per cent, respectively. Lower operative mortality than in previously reported series may be due to earlier intervention in CMV toxic megacolon. Surgery, however, conferred less benefit in patients with acute abdominal pain from MAI infection or lymphoma. With careful patient selection, emergency laparotomy may achieve worthwhile palliation in patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Psychological Profile and Outcome in Patients Undergoing Gastroplasty for Morbid Obesity.

Eighteen out of 22 consecutive patients undergoing vertical banded gastroplasty were reviewed with regard to preoperative psychological assessment and postoperative outcome. Each patient was initially evaluated by a consultant liaison psychiatrist with regard to previous or ongoing psychological disturbance, and suitability for bariatric surgery. Patients could be grouped into three broad categories: Group A (seven patients) those with no psychiatric abnormality; Group B (six patients) those with minor psychiatric disorders such as sociopathic teenage behavior, outpatient treatment for depression; and Group C (five patients) those with a history of major psychiatric disturbance such as depressive psychosis and drug dependency. Psychiatric morbidity had no adverse effect in terms of postoperative outcome or weight loss. Mean weight loss of 26%, 30% and 33% was recorded in groups A, B and C respectively after a mean follow-up period of 33 months following gastroplasty. The occurrence of postoperative psychiatric problems correlated closely with none of seven patients in group A but in four of the five patients in Group C requiring psychiatric management. Our findings indicate that psychiatric illness is not associated with poor outcome following surgery for morbid obesity and such patients should not be excluded if psychiatric support is available before and after surgery.

Journal Article↗
PubMed1990

Maintenance of the spinal nucleus of bulbocavernosus and perineal muscles in female Albino Swiss rats treated with perinatal dihydrotestosterone.

Female Albino Swiss rats were exposed to 5 alpha-dihydrotestosterone benzoate (DHTB) for the last 4 days of gestation, or for 4 days after birth, or both. Post-natal DHTB exposure (as well as pre-plus post-natal exposure) resulted in a 2-3-fold increase in the number of motor neurones forming the spinal nucleus of bulbocavernosus (SNB); numbers were intermediate between those found in normal females (approximately 40) and males (approximately 200). These DHTB-treated groups also possessed perineal muscles which were approximately 25% of the weight of those in normal males. Transverse sections of one of the muscles (levator ani) showed that it had approximately half the muscle fibres of normal males. Females exposed prenatally to DHTB showed a small (but significant) rise in SNB numbers, but had no recognizable perineal muscles.

Animals↗
PubMed1989

Inductively coupled plasma mass spectrometry and atomic emission spectrometry coupled to high-performance liquid chromatography for speciation and detection of organotin compounds.

Inductively coupled plasma mass spectrometry (ICP/MS) is utilized as a detector for several organotin species separated by high-performance liquid chromatography. Detection limits obtained by ICP/MS are 3 orders of magnitude lower than those obtained with inductively coupled plasma atomic emission spectrometry (ICP/AES) detection under the same chromatographic conditions. Chromatographic detection limits are higher than conventional solution nebulization for the same compound by a factor of 20. Ion-exchange chromatography yields linear response over 3 orders of magnitude, while ion pair chromatography gives a linear response of only 2 orders of magnitude as a result of poor resolution. The relative standard deviation for the injection of 20 ng of tin compounds is less than 10%.

Chromatography, High Pressure Liquid↗
PubMed1988

Intestinal obstruction in patients with gynaecological malignancies.

Bowel obstruction developing in patients with gynaecological malignancies may present as a therapeutic dilemma. The causes, and results of surgical and conservative management of 92 patients are analysed. The causes of obstruction in the 64 patients who were treated surgically were: tumour recurrence in 42, adhesions in 12, radiation stricture in 9 and pelvic abscess in 1. Surgical palliation was effective in 45 patients in this group, with another 12 patients being palliated initially but subsequently developing further obstructive symptoms. Surgical palliation was ineffective in 7. Conservative management was effective only in 12 of the 41 patients, and even in this group 8 developed further obstructive episodes within the first month of discharge. The median survival in the surgically treated group for benign and malignant causes is 57 and 10 weeks respectively; while it is 4 weeks for those treated conservatively.

Female↗
PubMed1987

Pre-operative assessment of soft tissue sarcomas by computed tomography.

The current trend towards limb-sparing surgery in patients with soft tissue sarcomas has increased the need for accurate pre-operative assessment of the primary tumour. Tumour site, extent and relationship to bone and neurovascular structures determine whether adequate radical surgery is feasible or whether more limited excision as a part of multimodality treatment is appropriate. Pre-operative computed tomography (CT) was compared with operative findings in 38 patients with soft tissue sarcomas. CT prediction of muscle group involvement by tumour was correct in 95 per cent and prediction of major artery or vein invasion was correct in 92 per cent and 97 per cent respectively. Assessment of tumour relationship to major peripheral nerve was accurate for thigh sarcomas but was not possible in upper limb tumours. While CT confirmed frank bony involvement in two patients, it failed to distinguish between tumours closely adjacent to periosteum and those with periosteal invasion. Detection of residual or recurrent tumour nodules is less reliable; CT is most accurate before any surgical intervention.

Adolescent↗
PubMed1987

Vulvo-vaginal melanoma--should radical surgery be abandoned?

A total of 32 patients presenting with melanoma of the vulva and vagina over a 20-year period was reviewed. Primary surgical treatment was by local excision in 14 patients, simple vulvectomy in seven patients and radical resection in 11 patients. Overall 5-year survival was 25% and only one patient was alive at 10 years. Comparison between the groups showed no benefit either in local control, disease-free interval or patient survival according to extent of primary resection. We suggest that, as in anorectal melanoma, radical resection of the primary lesion is unlikely to alter the extremely grave prognosis and its routine use should be abandoned.

Aged↗
PubMed1986

Radiation-induced soft-tissue sarcoma.

Twenty patients with soft-tissue sarcomas arising within previously irradiated fields have been analysed. The initial radiation dose ranged from 8.8 to 70 Gy, comprising either orthovoltage or megavoltage treatment. The latent interval following radiotherapy ranged from 7 to 45 years (mean 16.8 years). The commonest histological subtype was malignant fibrous histiocytoma. Four patients required forequarter amputation. The 5-year survival was only 14 per cent. The high morbidity and mortality accompanying post-radiation sarcomas must be borne in mind when the choice between therapeutic options for potentially curable cancers is finely balanced.

Adolescent↗
PubMed1986

The rabbit as an experimental model for regional chemotherapy. 1. Intra-arterial hindlimb infusion.

Regional delivery of chemotherapy to a tumour or tumour-bearing region has pharmacokinetic advantages over the systemic route. The applications of an animal model for regional drug delivery are outlined. The technique for intra-arterial infusion in the rabbit hindlimb is described. The use of the implantable VX2 rabbit carcinoma as a model for solid human tumours may be studied by this method. Pharmacokinetic data obtained with the model allow comparison between systemic and regional routes of delivery. The distribution of the cancerostatic plant toxin ricin following regional delivery has been investigated using this experimental model.

Animals↗