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A quantitative theory is developed for the relationship between stimulus and the resulting blood oxygen level-dependent (BOLD) functional MRI signal. The relationship of stimuli to neuronal activity during evoked responses is inferred from recent physiology-based quantitative modeling of evoked response potentials (ERPs). A hemodynamic model is then used to calculate the BOLD response to neuronal activity having the form of an impulse, a sinusoid, or an ERP-like damped sinusoid. Using the resulting equations, the BOLD response is analyzed for different forms, frequencies, and amplitudes of stimuli, in contrast with previous research, which has mostly concentrated on sustained stimuli. The BOLD frequency response is found to be closely linear in the parameter ranges of interest, with the form of a low-pass filter with a weak resonance at approximately 0.07 Hz. An improved BOLD impulse response is systematically obtained which includes initial dip and post-stimulus undershoot for some parameter ranges. It is found that the BOLD response depends strongly on the precise temporal course of the evoked neuronal activity, not just its peak value or typical amplitude. Indeed, for short stimuli, the linear BOLD response is closely proportional to the time-integrated activity change evoked by the stimulus, regardless of amplitude. It is concluded that there can be widely differing proportionalities between BOLD and peak activity, that this is the likely reason for the low level of correspondence seen experimentally between ERP sources and BOLD measurements and that non-BOLD measurements, such as ERPs, can be used to correct for this effect to obtain improved activity estimates. Finally, stimulus sequences that optimize the signal-to-noise ratio in event-related BOLD fMRI (efMRI) experiments are derived using the hemodynamic transfer function.

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UNLABELLED: Long-acting neuroleptics have become the mainstay of the long-term treatment of schizophrenia, improving compliance and thus preventing relapse. Since schizophrenia is a common condition and treatment is usually long-term, this has important financial implications. OBJECTIVE: Generic substitution is an important cost-saving measure and generic psychopharmacological agents are also currently available in South Africa. There have been concerns about the quality of these products, but these often arise from anecdotal reports. This study was undertaken to compare the clinical efficacy of a generic substitute of fluphenazine decanoate with the original product. DESIGN AND SETTING: The study was a double-blind randomised trial involving two parallel groups--generic substitution v. original product. Chronic schizophrenics, aged between 18 and 65 years, who had been on a constant dose of fluphenazine decanoate for at least 3 months preceding the trial, all treated as outpatients in the community, were studied. The Positive and Negative Syndrome Scale (PANSS) (positive scale) was used as measuring scale and patients were evaluated at inclusion and then every 2 weeks for the next 12 weeks. RESULTS: Both groups had a median change of zero in PANSS scores over the 12-week period. No clinically significant differences between the change in PANSS score were found in respect of the two products. CONCLUSIONS: Generic substitution could play an important role in containing the costs of health care in South Africa. Concerns about the quality and efficacy of these drugs should be investigated. In this study, no significant differences in the efficacy of the two products were found.

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This retrospective study evaluated the prognostic significance of the radiological signs of bony involvement in children with acute lymphoblastic leukaemia (ALL). The skeletal surveys of 52 children with ALL were reviewed for evidence of leukaemic involvement. Radiolucent metaphyseal bands, osteolytic lesions and periosteal reaction were considered signs of leukaemic changes. Twenty eight children had evidence of skeletal involvement of whom 14 had changes at three or more areas. Known risk factors such as age < 2 years and > 10 years, mediastinal lymphadenopathy, splenomegaly > or = 5 cm below the costal margin, a white cell count of > or = 20 x 10(9)/l and leukaemic blast cells in the cerebrospinal fluid at diagnosis occurred with equal frequency in children with and without skeletal changes as well as those children with signs of involvement at > or = 3 sites. Event free survival (Kaplan Meier analysis) also did not differ in these three categories of children. We concluded that bone involvement in childhood ALL is not associated with other risk factors and does not predict outcome per se.

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A case of amoebic meningoencephalitis in a sheep, suspected of being caused by Acanthamoeba sp., is described. An adult ewe was necropsied 5 days after it had developed anorexia and nervous signs, which included ataxia and walking in circles. Significant gross lesions were restricted to the central nervous system and consisted of thickening of the meninges and extensive necrosis of the cerebrum and cerebellum. The cerebral changes were characterised microscopically by a multifocal to coalescent necrotising granulomatous meningoencephalitis as well as choroid plexitis, ventriculitis and diffuse vasculitis. Numerous amoebic trophozoites and a few encysted forms morphologically compatible with Acanthamoeba sp. were present in the affected areas, particularly in the walls of blood vessels and perivascular spaces.

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In bulls (n = 2,437) examined by preputial sheath washes, 7.1% were found to be positive for trichomoniasis. The incidence varied from one area to the other, as well as between breeds.

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Seventeen Merino sheep in the Springbokfontein region of the Orange Free State were found to harbour Strobiloestrus sp. larvae in cutaneous nodules in the flank and rump regions of their bodies. The life cycle, however, could apparently not be completed in the sheep as the larvae left the nodules without developing further. Mountain reedbuck, running with the sheep, were also infested and were a probable source of infestation for the sheep.

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If routine cytoloical examination of a cervical smear reveals an abnormality short of invasive carcinoma, colposcopic examination, plus directed biopsy of the cervix, is the procedure of choice. Cytological examination is a laboratory technique, whereas colposcopy is a clinical diagnostic method. When the latter is used, anaesthesia and hospital admission are not required, and the hazards and limitations of cone biopsy of the cervix are avoided. The technique of colposcopy is a significant advance in gynaecology, and training in this method should be part of the curriculum for a higher qualification in gynaecology.

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The lecithin/sphingomyelin (L/S) ratio and the foam test to determine fetal lung maturity in order to prevent hyaline membrane disease (HMD) were used in 800 patients at Tygerberg Hospital. The incidence of HMD in all neonates diminished from 3.25% in 1971, when the lung maturity test was not done, to 2.12% in 1975, the 4th year that such determinations were done. In the same period the incidence of respiratory distress syndrome (RDS) increased from 3.68% to 4.31%. Only 1% of fetuses in whom lung maturity was determined during the period 1972--1975 developed HMD. This reduced incidence of HMD is considered to be the result of prenatal determination of fetal lung maturity. No correlation was found between fetal lung maturity and length of gestation or physical condition of the neonate. The foam test results were compared with the L/S ratio, and a false positive figure of 8.3% and a false negative figure of 27.1% were found. It is recommended that the foam test be used for screening and the L/S determination be done only if the foam test is negative in high-risk patients.

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