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Biomedical subjects

A J Fox

Publications and source records attributed to A J Fox.

At least 163 records · Page 9Linked to original sources
PubMed1991

An epidemiologically valuable typing method for Neisseria meningitidis by analysis of restriction fragment length polymorphisms.

A restriction fragment length polymorphism (RFLP) typing method was developed for Neisseria meningitidis. A cloned EcoRI fragment from a Neisseria meningitidis Group B serotype 15P1.16 sulphonamide-resistant strain was used to probe Southern blots of total chromosomal DNA restriction fragments (enzyme AvaI). A group of 75 apparently unrelated organisms gave rise to 26 different restriction fragment length patterns and two different groups of epidemiologically related strains had RFLP patterns that were distinct for each group. The technique was highly reproducible and discriminatory. The RFLP data were compared with the results of serotyping and subtyping and isoenzyme electrophoretotyping. The RFLP data were consistent with those from the alternative typing methods; clones defined by isoenzyme analysis were subdivided by this technique. The use of RFLP typing by cloned probes should be of considerable epidemiological value.

Blotting, Southern↗
PubMed1991

Socioeconomic differences in cancer survival.

STUDY OBJECTIVE: The aim was to investigate the relationship between socioeconomic status and cancer survival. DESIGN: This was a prospective study, linking census and vital registration records for an approximate 1% representative sample of those enumerated in England and Wales in the 1971 census. SETTING: The study population is nationwide. PARTICIPANTS: The study sample consists of 250,588 men and 262,484 women. During 1971-81, 17,844 cases of cancer were registered, and of those registered, 13,532 died during 1971-1983. MEASUREMENTS AND MAIN RESULTS: Socioeconomic status was assessed in terms of housing tenure. Council tenants, the low socioeconomic group, had poorer survival than owner occupiers, the high socioeconomic group, for the combined group of all neoplasms, and for 11 out of 13 neoplasms examined in males, and 12 out of 15 neoplasms examined in females. Differences were found irrespective of age, cause of death and prognosis of the cancer. Survival analysis by length of follow up indicated that council tenants were more likely to present at a later stage than owner occupiers. CONCLUSIONS: Wide survival differentials were observed between socioeconomic groups. Differences in survival for cancers of poor prognosis (eg, oesophagus, pancreas, lung) where treatment has little effect, cannot be attributed to socioeconomic differences in treatment. The survival differences for cancers of good prognosis (eg, corpus uteri, bladder, skin) could, in part, be due to differences in treatment. It is probable that delay in seeking care is one of the major contributing causes.

Adult↗
PubMed1991

Optic neuritis and orbital lesions: lipid-suppressed chemical shift MR imaging.

A derivative of the Dixon method, chopper fat suppression, was used in the magnetic resonance imaging evaluation of 40 patients: 37 with suspected optic nerve lesions, predominantly optic neuritis, and three with orbital lesions. In patients with optic neuritis, the technique was sensitive, allowing detection of 29 of 34 visual-evoked-response-confirmed lesions on T2-weighted lipid-suppressed images. There were no false-positive studies. Sensitivity for detection of optic neuritis was 89%; specificity, 100%; and accuracy, 86%. The technique was also useful for depicting inflammatory changes in the orbital apex due to fungal abscess and confirming the fatty nature of an extraconal dermoid tumor. A slight increase in noise and mild accentuation of susceptibility effects at interfaces of air, bone, and brain did not degrade images significantly. The chopper-based technique requires only standard imaging time and has usual spin-echo sensitivity. The results are comparable to short-inversion-time inversion-recovery imaging, without the constraints of sequence limitations or artifacts at fat and water interfaces.

Adipose Tissue↗
PubMed1990

Peptidase activity as a determinant of agonist potencies in some smooth muscle preparations.

The influence of degradation by peptidases on concentration-response relationships for peptide agonists of the tachykinin and bombesin-like families was investigated. The combined presence of three peptidase inhibitors, phosphoramidon (1 microM), captopril (1 microM) and bestatin (100 microM), had no significant effect on the onset rates or peak contractile responses to these peptides in the rat urinary bladder and guinea-pig taenia caeci preparations, or on their peak potentiation of the contractile response to field-stimulation in the guinea-pig vas deferens preparation. However, rates of offset of the response to tachykinins were markedly prolonged in tissues treated with peptidase inhibitors. In experiments designed to estimate clearance of applied peptide from the organ bath, there was an initial rate of loss with the guinea-pig vas deferens and taenia caeci which, measured over the first 5 min, had a half-time of 2-3 min which was then prolonged to 6-8 min in the presence of peptidase inhibitors. These results show that although peptide breakdown can be demonstrated in these systems, it seems not to be an important determinant of relative pharmacological activity measured in terms of peak response.

Animals↗
PubMed1990

A surface polysaccharide forms when gonococci are converted to serum resistance by cytidine 5'-monophospho-N-acetyl neuraminic acid.

A serum-susceptible, guinea-pig chamber-passaged, laboratory strain (BS4 (agar)) of Neisseria gonorrhoeae was converted to serum resistance by incubation with cytidine 5-monophospho-N-acetyl neuraminic acid (CMP-NANA) and examined by electron microscopy after staining with ruthenium-red. In contrast to serum susceptible gonococci incubated without CMP-NANA, the majority (60-70%) of the serum resistant organisms showed a surface accumulation of polysaccharide. This surface polysaccharide was enhanced on all the resistant gonococci after incubation with fresh human serum. Control susceptible gonococci were devoid of the polysaccharide after incubation with heated human serum. Identical results were obtained with a fresh gonococcal isolate which had lost serum resistance on subculture but which, in common with 3 other isolates, was restored to serum resistance by incubation with CMP-NANA.

Animals↗
PubMed1990

Diagnosis of cytomegalovirus infection in cyclosporin-treated renal allograft recipients.

The relative merits of antibody response and virus shedding as markers of cytomegalovirus (CMV) infection among cyclosporin-treated renal allograft recipients were analysed. CMV-specific antibody was assayed by IgG-specific radioimmunosorbent test (RIST) and by complement fixation test (CFT). CMV shedding was assayed by virus isolation and by the rapid test immediate early nuclear antigen detection (IENAD). RIST and CFT detected seroconversion in similar numbers of patients, but the former test was the more sensitive when CMV antibody was sought in pretransplant sera to differentiate primary from recurrent infection. IENAD detected or excluded CMV shedding for more urine specimens than virus isolation (462/515 [90%] vs. 366/515 [71%]), but the reverse applied to saliva specimens (33/57 [58%] vs. 54/57 [95%]). The high specificity of IENAD allowed positive results by IENAD to be accepted when virus isolation failed to provide a result. IENAD was, however, less sensitive than virus isolation even when specimens yielding CMV by IENAD, but no result by virus isolation, were included in the analysis (27/44 [61%] vs. 38/44 [86%]). Assays of both antibody response and virus shedding were required to maximise the diagnosis of recurrent CMV infections, but the former assay detected all primary CMV infections. The diagnostic implications of these results are discussed.

Antibodies, Viral↗
PubMed1990

Arteriovenous malformations of the brain: recent results of endovascular therapy.

Results of embolization and subsequent surgical resection were reviewed in 38 patients with arteriovenous malformations (AVMs) of the brain during the past 3 years. Advanced techniques were used for embolization, including real-time digital subtraction angiofluoroscopy; directable microcatheters; and a mixture of microfibrillar collagen, polyvinyl alcohol sponge microparticles, and ethanol, in addition to acrylic glue. Embolization caused a permanent deficit in four patients (10.5%) (quadrantanopia [n = 3], cerebellar ataxia [n = 1]). Thirty-two patients (84%) underwent surgery after embolization, and 28 (74%) were completely cured, as assessed with postsurgical angiography. Twenty-five patients (66%) had either no deficit or no change in deficit after treatment. Two patients had worsening of a previous deficit after postembolization resection, two patients had mild weakness not previously present, and five patients had visual field defects. One patient developed Gerstmann syndrome after resection, and one patient with ataxia after embolization also had ataxia after surgical resection. Two patients died of complications due to surgical resection. Most of the AVMs in this series were large and complex. Embolization used predominantly as a preoperative procedure enabled complete resection, as achieved in the majority of these cases.

Adolescent↗
PubMed1990

Socio-economic differences in mortality and morbidity.

In England and Wales interest in differences in health between different sectors of the community can be traced back to analyses of vital registration records in the 1840s. Increased attention in recent years to differences between socio-economic groups, in part in response to initiatives by the World Health Organisation, has again exposed the limitations of traditional data. National data on this topic are now based on the OPCS Longitudinal Study, a record linkage study as used in a number of countries. Such studies provide more reliable measures of differences, cover a wider range of social dimensions, and also allow different explanations of differences to be investigated. Analyses of differences in mortality are complemented by longitudinal analyses of differences in health and morbidity now deriving from other studies such as the birth cohort studies which provide a basis for investigating processes. The time is ripe for more effort to be put into international comparisons of differences.

Computer Communication Networks↗
PubMed1990

Rupture of aneurysms following balloon embolization.

Three cases of complex aneurysms are presented in which balloon embolization therapy was associated with subsequent aneurysmal rupture, causing subarachnoid hemorrhage in two cases and a carotid-cavernous fistula in one. Two of these patients were treated directly by balloon embolization following surgical exploration. The third patient developed the fistula during postembolization volume expansion and heparinization.

Arteriovenous Fistula↗
PubMed1990

Hyperdense middle cerebral artery sign on CT: efficacy in detecting middle cerebral artery thrombosis.

The hyperdense middle cerebral artery sign is a CT predictor of the development of a large cerebral infarct. The limits of detectability were tested in a blinded, then unblinded analysis of CT scans from 25 acute stroke patients. In the initial blinded analysis, sign detection exhibited the following mean values: sensitivity, 78.5%; specificity, 93.4%; positive predictive value, 66%; negative predictive value, 96.4%; accuracy, 91.3%. Kappa statistics analysis indicated poor interobserver agreement (k = .38). Results of unblinded analysis were as follows: sensitivity, 69%; specificity, 94.4%; positive predictive value, 82.8%; negative predictive value, 88.7%; accuracy, 87.3%. There was fair unblinded interobserver agreement (k = .53). Unblinded analysis had a lower false-positive frequency and did not increase the number of true-positive determinations. We conclude that detection of the hyperdense middle cerebral artery sign on CT scans by multiple observers is a sensitive, accurate, and predictive indicator of middle cerebral artery thromboembolism.

Acute Disease↗
PubMed1990

Adult myelography with iohexol.

An open, multicenter trial of adult myelography was carried out at six centers in 117 patients with iohexol (Omnipaque) 240 mg I/ml and 300 mg I/ml to determine whether there was a difference in visualization or side-effects when a lumbar or cervical approach was used to visualize the areas where disease was suspected. One hundred and thirteen myelograms were analysable. In over 85% of the myelograms with a lumbar approach, visualization of the area injected was excellent or good. Just over half of these were obtained with the intention of visualizing primarily the cervical area, and in 93% of these visualization was good or excellent at that site. In 100% of the cervically injected myelograms, visualization was excellent in the cervical area. Areas more distant from the injections were well visualized in the majority of patients. There was no significant difference overall in visualization with either of the two concentrations of iohexol used. There were 59 side-effects, mostly mild in nature; 40 of them occurred in 50 patients receiving the higher concentration and 19 in 63 patients receiving the lower concentration. The most common side-effect was headache (23 patients). Nystagmus was the only severe side-effect and occurred in only one patient having cervical myelography. The patient made a complete recovery within 36 hours.

Blood Chemical Analysis↗
PubMed1990

Vascular relationships of the vestibulocochlear nerve on magnetic resonance imaging.

Vascular compression of the vestibulocochlear (VIIIth) nerve may cause constant or recurrent positional vertigo, tinnitus, and/or hearing loss. At present the diagnosis is based upon history, physical findings, audiologic assessment, vestibular function testing, and auditory brainstem evoked responses. Delineation of the vascular and neural anatomy within the cerebellopontine angle (CPA) has not been part of the preoperative assessment. We recently treated a patient demonstrating the clinical features of this syndrome. A magnetic resonance imaging (MRI) study revealed a vascular loop of the anterior inferior cerebellar artery intimately associated with the VIIIth nerve at the porus acusticus. To better define the significance of this finding, we retrospectively reviewed the CPA neurovascular anatomy of 100 (200 sides) otherwise normal MRI scans performed for unrelated disorders. Vessels were identified on 59.9 percent of sides while nerves were seen on 40 percent of sides. Contact between vessel and nerve occurred on 12.5 percent of sides and when both nerve and vessels were seen concurrently, they were in contact 50 percent of the time. These findings may preclude the use of MRI as the definitive diagnostic test in the preoperative assessment of vascular VIIIth nerve compression.

Arteries↗
PubMed1989

Leukoaraiosis.

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Aged↗
PubMed1989

Motoneuron disease: a disorder secondary to solvent exposure?

There seems to be a statistically significant association between work in the leather industry and subsequent development of motoneuron disease. The reason for this association may be occupational exposure to solvents, which may damage motoneurons either directly or through activation of latent virus.

Adolescent↗