Search PubMed⌕ Search

Biomedical subjects

I Johnson

Publications and source records attributed to I Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1998

Fluorescent probes for living cells.

The functional characteristics of fluorescent probes used for imaging and measuring dynamic processes in living cells are reviewed. Initial consideration is given to general design requirements for delivery, targeting, detectability and fluorescence readout, and current technologies for attaining them. Discussion then proceeds to the more application-specific properties of intracellular ion indicators, membrane potential sensors, probes for proteins and lipids, and cell viability markers.

Animals↗
PubMed1998

Minority populations in the child welfare system: the visibility hypothesis reexamined.

This study tests the "visibility hypothesis," which suggests that there is a higher probability for minority children to be placed in foster care when living in geographic locations where their proportions in the population are relatively low, compared to areas where their proportions are high. Results support the hypothesis for African-American youth only. Explanations of the findings, and their implications for research and practice, are discussed.

Adolescent↗
PubMed1998

Quality of life after acoustic neuroma surgery.

OBJECTIVE: To assess how surgery affected the quality of life of patients with acoustic neuromas and to investigate possible predictors of the functional outcome following surgery. STUDY DESIGN: A questionnaire based on the Glasgow Benefit Inventory was completed by patients randomly selected following acoustic neuroma surgery. SETTING: Skull base surgery unit of a university teaching hospital (tertiary referral center). PATIENTS: Fifty-three patients with acoustic tumors (follow-up, 1 to 3 y). RESULTS: With regard to overall quality of life, nine patients (17.4%) reported that it became better, 28 patients (53.8%) worse, and 15 patients (28.8%) that it remained the same. Four patients (7.8%) became better off financially, 15 patients (29.4%) worse, and 32 (62.8%) remained unchanged. Forty-one patients (78.8%) did not change their occupation, and 11 (21.2%) had to change their occupation, mainly because of the adverse effects of the operation. With regard to the age at operation, older patients were found to have better overall quality of life. Moreover, younger patients had worse postoperative financial status and they were more likely to change their occupation after the operation. The tumor size did not significantly affect the overall postoperative quality, but it did affect the postoperative financial status (patients with larger tumors were more likely to have worse postoperative financial status). CONCLUSION: Acoustic neuroma surgery has a significant impact on patients' overall quality of life. Surgeons proposing to operate on small tumors should not assume that the impact on patients' life will be necessarily less than that following the removal of larger tumors. All patients, especially in the younger age group, should be prepared and thoroughly informed about the consequences of the operation on their quality of life.

Adult↗
PubMed1996

Genotoxic effects of crude juices from Brassica vegetables and juices and extracts from phytopharmaceutical preparations and spices of cruciferous plants origin in bacterial and mammalian cells.

Crude juices of eight Brassica vegetables as well as juices and extracts of spices and phytopharmaceutical preparations from cruciferous vegetables were tested for induction of point mutations in Salmonella TA98 and TA100, repairable DNA damage in E.coli K-12 cells and clastogenic effects in mammalian cells. In bacterial assays, all juices caused genotoxic effects in the absence of metabolic activation, the ranking order being: Brussels sprouts > white cabbage > cauliflower > green cabbage > kohlrabi > broccoli > turnip > black radish. In experiments with mammalian cells, six juices induced structural chromosome aberrations. Brussels sprouts, white and green cabbage caused the strongest effects (800 microliters of juice induced a 5-fold increase over the background). In sister chromatid exchange assays, positive results were measured as well, but the effects were less pronounced. With all juices the genotoxic effects seen in mammalian cells were paralleled by a pronounced decrease in cell viability. Column fractionation experiments showed that 70-80% of the total genotoxic activity of the juices is found in the fraction which contains isothiocyanates and other breakdown products of glucosinolates, whereas phenolics and flavonoids contributed to a lesser extent to the overall effects. On the basis of these findings, and considering the negative results obtained with non-cruciferous vegetables (tomato, carrot and green pepper), it seems likely that the genotoxic effects of the juices are due to specific constituents of cruciferous plants such as glucosinolates and/or their breakdown products, in particular, isothiocyanates, which we found previously to be potent genotoxins in bacterial and mammalian cells. Finally, spices (mustards and horse radish paste) and phytopharmaceutical preparations were tested in bacterial assays. Mustards and horse radish caused very weak effects while most of the pharmaceutical preparations gave negative results, except cabbage tablets, which caused a strong and dose dependent induction of his revertants in Salmonella TA100. The present findings clearly indicate that cruciferous vegetables contain DNA damaging constituents. These observations are in contrast to earlier findings, which emphasized the antimutagenic effects of vegetable juices and also raise the question whether greatly increased consumption of Brassica vegetables or their concentrated constituents as a means for cancer prevention is indeed recommendable.

Animals↗
PubMed1995

An assessment of the intrauterine sound intensity level during obstetric echo-planar magnetic resonance imaging.

In order to assess the sound level experienced by the fetal ear during obstetric magnetic resonance imaging, a fluid filled stomach was used as an experimental model of the gravid uterus. A better than 30 dB attenuation in intensity was recorded across the frequency band of interest for all patient orientations. This was enough to reduce acoustic sound pressure from a level close to the instantaneous damage threshold (120 dB), to an acceptable level (< 90 dB). Direct mechanical coupling through the patient table was also shown to increase uterine sound pressure levels by as much as 10 dB. Much higher peak pressures could be obtained by tapping of abdomen with the fingers.

Acoustics↗
PubMed1993

Birth weight from pregnancies dated by ultrasonography in a multicultural British population.

OBJECTIVE: To produce standard curves of birth weight according to gestational age validated by ultrasonography in the British population, with particular reference to the effects of ethnic origin. DESIGN: Retrospective analysis of computerised obstetric database. SETTING: Three large maternity units associated with Nottingham University with over 16,000 deliveries a year. PATIENTS: 41,718 women with ultrasound dated singleton pregnancies and delivery between 168 and 300 days' gestation. MAIN OUTCOME MEASURES: Length of gestation, ethnic origin, parity, maternal height and weight at booking, smoking during pregnancy; the effect of these variables on birth weight. RESULTS: Birth weights from ultrasound dated pregnancies have a higher population mean and show less flattening of the birthweight curve at term than those of pregnancies dated from menstrual history. Significant differences were observed in mean birth weights of babies of mothers of European origin (3357 g), of Afro-Caribbean origin (3173 g), and from the Indian subcontinent (3096 g). There were also significant interethnic differences in length of gestation, parity, maternal height, booking weight, and smoking habit which affected birth weight. The ethnic differences in birth weight were even greater when the effect of smoking was excluded. CONCLUSIONS: Birthweight standards require precise dating of pregnancy and should describe the population from which they were derived. In a heterogeneous maternity population the accurate assessment of an individual baby's weight needs to take the factors which affect birthweight standards into consideration.

Birth Weight↗
PubMed1993

Satisfaction and change: a survey of volunteers in a hospice organisation.

Volunteers and their voluntary work play an important role within the 'mixed economy' of health and welfare provision in the U.K. A survey of volunteers working in a hospice organisation in Leicestershire (LOROS) found that most of them were satisfied with their work experiences as volunteers, and felt that they were adequately supported and valued by the organisation and its paid staff. They had become volunteers mainly through contact with friends, and a substantial minority were motivated by their own personal experiences of death. Their contact with dying patients did not cause them any serious emotional difficulties. LOROS has grown from a small, tightly focused organisation, dependent on a relatively small group of committed volunteers, to a much larger, busier, more diverse and geographically dispersed organisation, dependent upon a large pool of volunteers. These changes in the organisation had affected the way in which some volunteers experienced their work, and although they were supportive of the expansion of the organisation their sense of intimacy and belonging had lessened. Given the increasing competition for voluntary workers, the sensitive management of change is seen as vital if LOROS is to maintain the commitment of its volunteers and maintain its attractiveness as an organisation which should be supported by voluntary work.

Adult↗
PubMed1991

Extradural hematoma in neonates.

Six neonates with extradural hematomas (EDH) diagnosed by ultrasound and confirmed by computed tomography scan were reviewed. EDH was seen in term male infants of primigravidas. Predisposing factors were coagulopathy and forceps extraction after prolonged labor. Clinical features were similar to other intracranial hemorrhages, but no deterioration in the level of consciousness was noted. Constant ultrasonographic features include a biconvex, echogenic, intracranial mass adjacent to the inner table of the skull. Ultrasonography was shown to be a reliable tool in establishing the diagnosis, monitoring progress, and detecting complications of EDH. Recovery with conservative management was noted.

Cerebral Hemorrhage↗