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Biomedical subjects

A Jackson

Publications and source records attributed to A Jackson.

At least 271 records · Page 15Linked to original sources
PubMed1993

Effect of the benzodiazepine receptor agonist, zolpidem, on palatable fluid consumption in the rat.

Two experiments examined the effect of the benzodiazepine receptor agonist, zolpidem, on palatable fluid intake in water-deprived rats. In the first experiment, pretreatment with 3.0 or 10.0 mg/kg zolpidem IP was found to increase consumption of a novel glucose drink (3% d-glucose and 0.15 sodium saccharine w/v in water). The increase in fluid consumption induced with zolpidem was comparable to the increases observed with diazepam and the benzodiazepine partial agonist, FG 8205. Experiment 2 demonstrated that this zolpidem-induced increase in drinking could be observed in both naive rats and in rats that had been habituated to the glucose drink and the testing environment: pretreatment with 3.0 mg/kg PO of zolpidem was found to increase fluid consumption in rats that had received either 0 or 8 days pre-exposure to the testing conditions. Contrary to earlier reports, these results support the conclusion that zolpidem, like other benzodiazepine agonists, can directly modulate ingestive behaviour.

Animals↗
PubMed1993

Perspectives of multidimensional conformal radiation treatment.

We consider the present technological advancement that underlies the implementation of computer-controlled conformal radiotherapy. We also consider the developments in modern biology that may provide input to therapy planning. The concept of multidimensional conformal radiotherapy is advanced, which integrates geometrical precision and biological conformality, to optimize the treatment planning for individual patients, with a view to improve the overall success of radiotherapy.

Humans↗
PubMed1993

Probability of radiation-induced complications in normal tissues with parallel architecture under conditions of uniform whole or partial organ irradiation.

A biologically based model is developed for normal tissue complication probability as a function of dose and irradiated volume fraction for organs such as the kidney and the lung. The organ is assumed to be composed of functional subunits (FSUs) which are arranged in a parallel architecture. The complication is produced only if a sufficiently large fraction of the FSUs are inactivated by radiation and an FSU is inactivated only when all the clonogenic cells within it are killed. The linear-quadratic model is used for the dose-response of individual cells within an FSU. The predictions of this model are compared with those of an empirical power law function for uniform whole and partial organ irradiation.

Dose-Response Relationship, Radiation↗
PubMed1993

Azygos catheter placement as a cause of failure of dialysis.

Common complications of venous dialysis catheters include sepsis and accidental removal. Angiographic demonstration of dialysis lines is only rarely requested usually to confirm the presence of clot or stenosis as a cause for poor dialysis flow. Poor flow can also be due to inadvertent placement of the catheter in the azygos system. The use of dialysis catheters with a long venous limb which extends beyond the arterial port may predispose to such placement as their lumen is lateral to the central axis of the catheter. In those patients with poor venous access catheter placement under angiographic control may be helpful.

Aged↗
PubMed1993

Visualization of extradural blood patch for post lumbar puncture headache by magnetic resonance imaging.

We describe a case of post lumbar puncture headache treated by extradural blood patch. Magnetic resonance imaging (MRI) demonstrated a large extradural haematoma extending over four spinal segments and extending out through the neural outlet foramina. There was significant compression of the thecal sac, supporting the theory that extradural blood patch causes tamponade at the site of dural puncture. The spread of clot was predominantly upwards from the injection site and subarachnoid extension of blood was also demonstrated.

Adult↗
PubMed1993

Magnetic resonance imaging of extradural blood patches: appearances from 30 min to 18 h.

We have used magnetic resonance imaging to examine five patients treated with extradural blood patches for persistent post lumbar puncture headache. Images were obtained between 30 min and 18 h after patching. Extradural blood patch injection produced a focal haematoma mass around the injection site which initially compressed the thecal sac and nerve roots. The main bulk of the extradural clot extended only three to five spinal segments from the injection site, although small amounts of blood spread more distally. Spread from the injection site was principally cephalad. Mass effect was present at 30 min and 3 h, but clot resolution had occurred by 7 h, leaving a thick layer of mature clot over the dorsal part of the thecal sac. Eighteen hours after injection only small widely distributed clots, adherent to the thecal sac, were demonstrated. Extensive leakage of blood from the injection site into the subcutaneous tissues was present in all patients.

Adult↗
PubMed1993

Characterization of the alpha 1-adrenoceptors of the rat prostate gland.

The alpha 1-adrenoceptor-mediated responses of the rat prostate to phenylephrine have been examined in-vitro. Phenylephrine induced concentration-dependent contractions of the isolated prostate gland which were antagonized by WB4101 (1-30 nM). Schild plot analysis of the antagonism yielded a straight line with a slope not significantly different from unity. The pKB value of 9.2 was similar to that obtained for WB4101 on the rat vas deferens (9.4) but was greater than that obtained on the rat spleen (8.4). Chloroethylclonidine depressed responses to phenylephrine of the rat spleen but not the prostate or the vas deferens. These results indicate that the rat prostate gland possesses a typical alpha 1A-adrenoceptor similar to that found in the vas deferens.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1993

Absence of cystic fibrosis mutations in a large Asian population sample and occurrence of a homozygous S549N mutation in an inbred Pakistani family.

The occurrence of cystic fibrosis is very rare in the Asian population. Carriers of the mutations most commonly found in Caucasians were not detected in a large Asian population sample of almost 900 chromosomes. However, an affected Pakistani child born to consanguineous parents was further investigated and shown to be homozygous for the mutation S549N (G-->A). Molecular and clinical data are presented which may improve our understanding of the phenotypic effects of the S549N mutation in the CFTR gene.

Asia↗
PubMed1993

Imaging of dialysis access: a review of 67 failing fistulas investigated by intravenous digital subtraction angiography.

We have reviewed 67 failing haemodialysis fistulas imaged by intravenous digital subtraction angiography (IVDSA). Peripheral venous injection of non-ionic contrast was used in all examinations. No complications relating to peripheral injection, contrast dose or fluid load were experienced. Image quality was poor, owing to inadequate vascular opacification, in 1/67. Image quality was excellent (53/67), or good (13/67) in the remaining 66. 56/66 of these examinations were diagnostic. Diagnoses included abnormalities of feeding arteries, anastomoses, draining veins, and central veins. Multiple abnormalities were demonstrated in 10/56 examinations. Conventional arm venography was performed in addition to IVDSA in five cases where venous images were inadequate owing to anastomotic obstruction (3/5) or poor opacification (2/5). 5/66 examinations were non-diagnostic owing to failure to image the central veins where no cause for fistula failure had been demonstrated. A further 5/66 examinations were non-diagnostic owing to failure to obtain oblique projections of the shunt where vascular details was obscured by overlapping vessels. The authors recommended routine imaging of the dialysis shunt in two planes and central venous imaging in all cases. This would have resulted in reduction of the failure rate from 16% to 1.5% in this series. IVDSA using a peripheral injection technique is simple, free from complications, and provides good quality images of both arterial and venous components of the fistula. Images of vessels not directly involved in fistula formation are routinely obtained and aid the planning of fistula revision.

Angiography, Digital Subtraction↗
PubMed1993

Low-dose computed tomographic imaging in orbital trauma.

We review the findings in 75 computed tomographic (CT) examinations of 66 patients with orbital trauma who were imaged using a low-radiation-dose CT technique. Imaging was performed using a dynamic scan mode and exposure factors of 120 kVp and 80 mAs resulting in a skin dose of 11 mGy with an effective dose-equivalent of 0.22 mSv. Image quality was diagnostic in all cases and excellent in 73 examinations. Soft-tissue abnormalities within the orbit including muscle adhesions were well demonstrated both on primary axial and reconstructed multiplanar images. The benefits of multiplanar reconstructions are stressed and the contribution of soft-tissue injuries to symptomatic diplopia is examined.

Humans↗
PubMed1993

Immunisation of woodchucks with hepatitis delta antigen expressed by recombinant vaccinia and baculoviruses, controls HDV superinfection.

We report the investigation of the role of humoral and cell mediated immune responses on hepatitis delta virus (HDV) superinfection of woodchucks chronically infected with woodchuck hepatitis virus (WHV). The animals were immunised with baculovirus or vaccinia virus recombinant hepatitis delta antigen (HDAg) but none showed detectable anti-HD titres prior to challenge with HDV. Following infection, both immunised and control animals developed HD-antigenaemia first detected after 2-3 weeks and lasting for up to 8 weeks. In spite of the presence of HDAg, in immunised animals HDV-RNA could only be detected by nested PCR in contrast with the controls, which were positive by dot blot hybridisation. No serum HDAg or HDV-RNA was detected after the acute episode over the six month follow-up period but intrahepatic HDAg was reported in post-mortem biopsies carried out at six months. Our results demonstrate that immunisation of woodchucks with HDAg expressed by vaccinia or baculovirus does not elicit a humoral immune response. The finding of a marked antigenaemia in the absence of serum HDV-RNA indicates a significant reduction in the number of circulating infectious virions possibly due to a cytotoxic T-cell response.

Animals↗