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Biomedical subjects

D W Wheeler

Publications and source records attributed to D W Wheeler.

16 recordsLinked to original sources
PubMed2003

Palliative surgery for acute bowel obstruction caused by Kaposi's sarcoma in a patient with AIDS.

Patients with human immunodeficiency virus (HIV) infection or acquired immune deficiency syndrome (AIDS) can present with acute abdominal surgical problems, either with intra-abdominal opportunistic infection as a result of their immunosuppression, or with associated malignancies. We report a 39-year-old man who developed intermittent nausea and vomiting, which was originally thought to be a side-effect of the chemotherapy he was receiving for facial Kaposi's sarcoma. However, he was found to have intraperitoneal Kaposi's sarcoma causing small bowel obstruction, which was successfully excised at laparotomy. There were no perioperative complications despite AIDS-related respiratory disease. The patient remained free of abdominal symptoms until his death. HIV infections or AIDS alone should not be contraindications to surgery for such problems, as careful patient selection can yield good results and significantly improve quality of life.

Acquired Immunodeficiency Syndrome↗
PubMed2000

The effect of a heat and moisture exchanger on gas flow in a Mapleson F breathing system during inhalational induction.

Heat and moisture exchangers (HMEs) humidify, warm and filter inspired gas, protecting patients and apparatus during anaesthesia. Their incorporation into paediatric anaesthetic breathing systems is recommended. We experienced delays in inhalational induction whilst using a Mapleson F breathing system with an HME. We have demonstrated that the HME significantly alters gas flow within the breathing system. Approximately half of the fresh gas flow is delivered to the patient, the remainder being wasted into the expiratory limb of the breathing system. We suggest that the HME should be removed from the Mapleson F breathing system until inhalational induction is complete, or that the reservoir bag is completely occluded until an effective seal is obtained with the mask.

Anesthesia, Inhalation↗
PubMed2000

A model for pleiotropic muscarinic potentiation of fast synaptic transmission.

The predominant form of muscarinic excitation in the forebrain and in sympathetic ganglia arises from m1 receptors coupled to the G(q/11) signal transduction pathway. Functional components of this system have been most completely mapped in frog sympathetic B neurons. Presynaptic stimulation of the B neuron produces a dual-component muscarinic excitatory postsynaptic potential (EPSP) mediated by suppression of voltage-dependent M-type K(+) channels and activation of a voltage-insensitive cation current. Evidence from mammalian systems suggests that the cation current is mediated by cyclic GMP-gated channels. This paper describes the use of a computational model to analyze the consequences of pleiotropic muscarinic signaling for synaptic integration. The results show that the resting potential of B neurons is a logarithmic function of the leak conductance over a broad range of experimentally observable conditions. Small increases (<4 nS) in the muscarinically regulated cation conductance produce potent excitatory effects. Damage introduced by intracellular recording can mask the excitatory effect of the muscarinic leak current. Synaptic activation of the leak conductance combines synergistically with suppression of the M-conductance (40 --> 20 nS) to strengthen fast nicotinic transmission. Overall, this effect can more than double synaptic strength, as measured by the ability of a fast nicotinic EPSP to trigger an action potential. Pleiotropic muscarinic excitation can also double the temporal window of summation between subthreshold nicotinic EPSPs and thereby promote firing. Activation of a chloride leak or suppression of a K(+) leak can substitute for the cation conductance in producing excitatory muscarinic actions. The results are discussed in terms of their implications for synaptic integration in sympathetic ganglia and other circuits.

Action Potentials↗
PubMed1998

The incidence and Dukes' staging of colorectal cancer over 3 decades.

AIMS: Two previous studies (1966-1971 and 1979-1983) of patients with colorectal cancer (CRC) have been reported from our hospital. A large increase in the incidence of CRC was noted, and an improvement in Dukes' staging of tumours at treatment. We report a series of patients admitted with newly diagnosed CRC to evaluate this trend further. METHODS: A prospective study was made of all patients with newly diagnosed CRC admitted to the John Radcliffe Hospital, Oxford in 1995. Means of diagnosis and Dukes' staging were recorded. RESULTS: In 1 year 177 patients were admitted with newly diagnosed CRC. Previous studies had shown an increase from 52.8 to 103.4 patients per year. The number of patients diagnosed by colonoscopy doubled from 19.4% in 1979-1983 to 41% in 1995. No significant change in the proportion of patients with Dukes' A or B tumours was found. CONCLUSION: The number of patients treated annually with CRC in a stable population has more than trebled in the last 3 decades. A real increase in the incidence of CRC is likely as this rise cannot be explained solely by changing referral patterns or an ageing community. There are no significant changes in presentation patterns despite the availability of colonoscopy since 1975.

Aged↗
PubMed1997

A parallel licensing model of normal slips and phonemic paraphasias.

A model of phonological processing in speech production based on prosodic licensing can capture general patterns of errors found in both normal and aphasic speech. All segments must be licensed by some prosodic category (syllable, nucleus, or rime) in order to be produced. Constraints on licensing, including both phonotactic and binding constraints, ensure that only correct licensing associations are retained. A computer simulation of our model produces utterances in qualitative agreement with human speech error data. Phonemic puraphasias are claimed to arise from the same mechanisms as normal speech errors; the difference being only a matter of disturbance of the lexical retrieval and licensing processes. The fact that these errors, which can involve gross disruption of the segmental sequence, still produce phonotactically well-formed strings is a direct consequence of the syllabic licensing that forms the core of our theory of speech production.

Aphasia↗
PubMed1996

Adult coeliac disease and cigarette smoking.

BACKGROUND: Genetic predisposition and gliadin exposure are known to be crucial factors in the development of coeliac disease. Circumstantial evidence suggests that other unidentified environmental factors may also be of pathogenetic importance. AIM: To define the relation between cigarette smoking and the risk of development of symptomatic adult onset coeliac disease. SUBJECTS: Eighty six recently diagnosed adult coeliac disease patients and 172 controls matched for age and sex. METHOD: Matched case control study, using a simple questionnaire to determine smoking history, and in particular smoking status at the time of diagnosis of coeliac disease. RESULTS: At the time of diagnosis, the proportion of current smokers was 7% in the coeliac group, and 32.6% in the control group, giving a matched odds ratio of 0.15 (95% confidence intervals 0.06, 0.38). The difference could not be accounted for by social class, nor by coeliac patients giving up smoking after the onset of symptoms as most non-smokers in the coeliac group had never smoked. CONCLUSION: Cigarette smoking, or a factor closely linked to it, seems to exert a major protective effect against the development of symptomatic adult onset coeliac disease. The implication is that gliadin exposure is not the only important environmental factor involved in the pathogenesis of this condition.

Adolescent↗
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↗