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Biomedical subjects

D W Wheeler

Publications and source records attributed to D W Wheeler.

24 records · Page 2Linked to original sources
PubMed1996

Neurologic dysfunctions caused by a molecular clone of feline immunodeficiency virus, FIV-PPR.

FIV is a lentivirus of domestic cats that causes a spectrum of diseases that is remarkably similar to the clinical syndrome produced by HIV infection in people. Both HIV and FIV has been shown to cause neurologic dysfunction. Specific Pathogen-Free (SPF) cats were placed into one of three groups: FIV-PPR infected; DU-FIV-PPR (a dUTPase mutant of the FIV-PPR clone) infected; or an age-matched control group. In both infected groups, the general clinical signs of infection included lymphadenopathy, oral ulcerations, rough hair coat, and conjuntivitis. Specific neurological changes in the FIV-PPR infected cats included hind limb paresis; delayed righting and pupillary reflexes; behavioral changes; delayed visual and auditory evoked potentials; decreased spinal and peripheral nerve conduction velocities; and marked alterations in sleep patterns. Most of these changes were also observed in the DU-FIV-PPR infected cats. However, these cats tended to have a slightly less severe disease. In this study, we have demonstrated that an infectious molecular clone of FIV closely parallels the disease course of wild type FIV-infected cats. By using a knockout gene mutant of this clone, we were able to demonstrate that the dUTPase gene is not essential for neuropathogenesis. Further use of the FIV-PPR clone should prove useful in determining the essential viral elements that are important in the neuropathogenesis of lentiviral infections.

Animals↗
PubMed1994

An audit of selected patients with non-functioning pituitary adenoma treated by transsphenoidal surgery without irradiation.

OBJECTIVE: To determine whether the rate of tumour regrowth in patients with non-functioning pituitary tumour treated by transsphenoidal surgery and selected for observation without post-operative irradiation is acceptably low, and to identify a group of patients who could appropriately avoid pituitary irradiation. SUBJECTS: One hundred and thirty-two patients treated by transsphenoidal surgery, of whom 98 did not undergo post-operative irradiation. These 98 were selected as having had apparently complete surgical removal, and as lacking features of tumour invasion or rapid growth; 73 of them are being followed by serial pituitary imaging to detect tumour regrowth. RESULTS: Forty-two patients who have been imaged on two or more occasions or more than two years after operation have shown no sign of tumour regrowth; 25 of them have been imaged at 3 or more years after operation, 13 at more than 5 years, and 4 at more than 10 years. Eight patients have shown regrowth as judged by imaging, although only one had pressure symptoms at the time; 5 out of 6 of these recurrences were found within 5 years of operation (two cannot be timed). The unirradiated group of 73 patients showed 90% recurrence-free survival at 5 years (95% confidence limits 80-100%). CONCLUSIONS: Provided that careful surgery and meticulous recall mechanisms for imaging can be ensured, patients so selected may be given the information contained in these results and offered the choice of follow-up by imaging alone, without pre-emptive irradiation. We recommend that they should be imaged 6-8 weeks post-operatively, then at either 6 or 12 months depending on the appearance, and then every 3-5 years for at least 15 years. By this means, many patient-years of good health and relative medical independence can be gained, together with some financial saving.

Adenoma↗
PubMed1994

Sensory nerve conduction velocity of the caudal cutaneous sural and medial cutaneous antebrachial nerves of adult horses.

Maximal conduction velocities of compound action potentials evoked by stimuli of 2 times threshold in the caudal cutaneous sural (CCSN) and medial cutaneous antebrachial (MCAN) nerves were determined by averaging potentials evoked and recorded through percutaneous needle electrodes. Mean maximal conduction velocities of compound action potentials were: CCSN = 61.3 +/- 2.0 meters/second (m/s) and MCAN = 56.4 +/- 2.8 m/s. To confirm accuracy of our percutaneous recordings, compound action potentials were recorded through bipolar chlorided silver electrodes from the exposed surfaces of fascicles of the CCSN and the MCAN. The maximal conduction velocities of these potentials were in agreement with the conduction velocities of compound action potentials that were evoked and recorded through percutaneous needle electrodes. The specificity of stimulating and recording sites was verified by recording before and after section of the nerves. Stimuli from 3 to 5 times threshold evoked a second, longer latency, compound action potential that consisted of a variable number of components in the CCSN and MCAN. The configurations and conduction velocities of the shorter latency potentials were the same as those of the single compound action potentials evoked by stimuli of 2 times threshold. Mean conduction velocities of the longer latency potentials were: CCSN = 24.4 +/- 2.6 m/s and MCAN = 24.5 +/- 2.2 m/s. Needle electrode and direct stimulation of either the CCSN or the MCAN at 3 to 5 times threshold failed to evoke contractions of limb muscles. Therefore, action potentials that contributed to the evoked compound potentials recorded in these horses arose, most likely, from afferent nerve fibers.

Action Potentials↗
PubMed1988

Functional and structural alterations of the nervous system induced by avian retrovirus RAV-7.

Chickens infected as embryos with RAV-7 developed neurological signs including ataxia, lethargy, and imbalance. Evoked spinal cord potentials for RAV-7 infected SC chickens were considerably slower (64.8 m/s) than for uninfected SC (103.4 m/s), genetically hypothyroid (OS) (93.9 m/s) or special C (95.1 m/s) chickens. Conduction velocity measurements of sciatic nerves showed normal values for all the chickens examined in this study. Histopathological studies revealed non-suppurative meningoencephalomyelitis in RAV-7 infected SC chickens. The inflammatory infiltrate consisted of lymphocytes, macrophages, and occasional plasma cells. The cells in the infiltrate reacted with mouse monoclonal antibodies directed against la and T-cell antigens. Astrocytic hypertrophy and hyperplasia, demonstrated by the use of monoclonal antibody specific for glial fibrillary acidic protein (GFAP), was associated with the CNS lesions. The results of this investigation indicate that RAV-7 causes significant central nervous system lesions and functional impairment in the infected chicken. This system may serve as a useful model for studying retrovirus-induced neurological dysfunction.

Animals↗
PubMed1977

I-fibrinogen as an oncophilic radiodiagnostic agent: distribution kinetics in tumour-bearing mice.

Fibrinogen radioiodinated by the iodine monochloride method was tested as a tumour radiodiagnostic agent in mice. The I-fibrinogen cleared from the blood of tumour-bearing mice more rapidly than from that of normal mice, but it cleared from the whole body more slowly, suggesting it accumulated in a substantial tumour-related compartment in the abnormal mice. The tumour concentration steadily increased for 4 h after injection, at which time it reached a peak concentration of 11-4% of the injected dose/g. This concentration was higher than the peak concentration for Ga-citrate (not reached until 24 h) or any other oncophilic radiopharmaceutical tested in this tumour model. The early accumulation is consistent with the use of 123I as a tracer label for fibrinogen. A combination of the large tumour concentration of I-fibrinogen, an increased catabolic rate induced by chemical modification, and the exceptional nuclear properties of 123I for scintigraphic imaging, could lead to a very useful radiodiagnostic procedure for cancer.

Adenocarcinoma↗