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Biomedical subjects

N Johnson

Publications and source records attributed to N Johnson.

At least 235 records · Page 13Linked to original sources
PubMed1990

An inhibitor of the toxicity of tumour necrosis factor in the serum of patients with sarcoidosis, tuberculosis and Crohn's disease.

The activated macrophages present in the T cell-dependent granulomata of sarcoidosis and tuberculosis are primed for enhanced release of cytokines including tumour necrosis factor (TNF or cachectin). Release of this cytokine can induce an acute-phase response, fever, and necrosis in suitably prepared sites of inflammation; if chronic, its presence may contribute to weight loss. These clinical features are characteristic of tuberculosis, but not of sarcoidosis, though alveolar macrophages from both diseases release large quantities of TNF in vitro. We therefore postulated the presence in sarcoidosis patients of an inhibitor of TNF. We have studied levels of TNF inhibitory activity by determining the quantity of TNF required to give 50% kill of L929 cells in the presence of 20% heat-inactivated serum derived from various disease states (37 sarcoidosis, 13 tuberculosis, 13 Crohn's disease, 17 healthy donors). Normal sera used in this way do not inhibit significantly, but inhibition of TNF toxicity is caused by most sera from both sarcoidosis and tuberculosis. Used at 20%, five out of 37 sarcoidosis sera and one out of 13 tuberculosis sera caused complete inhibition of TNF, even when the latter was added at 100 times the concentration required to give 50% kill in control wells. This inhibitor may have an important physiological role.

Acute-Phase Proteins↗
PubMed1990

Using Lamicel to expose high cervical lesions during colposcopic examinations.

Women with abnormal cervical cytology and an unsatisfactory colposcopic examination were offered Lamicel in an attempt to expose the entire transformation zone. The sponge, which softens, dilates and effaces the cervix, was passed intracervically in 41 patients in whom the entire squamocolumnar junction could not be seen. After 3-4 h the sponge was removed and colposcopy repeated. In 29 of the 41 patients the lesion and the squamocolumnar junction were now fully visible. Twenty-five of these patients were spared a cone biopsy.

Adult↗
PubMed1990

The effect of caput succedaneum on oxygen saturation measurements.

Advances in oximetry have allowed the obstetrician to measure oxygen saturation in the fetus with non-invasive transcutaneous techniques. The influence of caput succedaneum formation on the oxygen saturation results obtained with a pulse oximeter was studied in 30 newborn infants. Caput was associated with a reduced oxygen saturation reading (mean reduction of 15%; P less than 0.001). This effect is partly due to a true drop in local tissue oxygenation but is exacerbated by a systematic error intrinsic to the physics of spectrophotometry. If continuous intrapartum oximetry is ever to become a part of routine obstetric monitoring then probes that pass through the cervix beyond the caput of the presenting part will be required if erroneously low readings are to be avoided.

Edema↗
PubMed1990

The effect of meconium on neonatal and fetal reflectance pulse oximetry.

Reflectance probes are being developed for neonatal use and obstetricians are beginning to use reflectance pulse oximetry to monitor the fetus. When a reflectance probe was used to monitor the arterial oxygen saturation of a baby whose skin was stained with meconium an artificially low result was obtained. This is because meconium absorbs more red than infra-red light and acts as a red light filter between the vascular bed and the probe. This effect may be reproduced by interposing a red filter between a reflectance pulse oximetry probe and the skin. Obstetricians who use a pulse oximeter to assess the fetus through intact membranes will record an erroneously low result if they are stained with meconium. Similarly neonatologists should avoid placing a reflectance pulse oximetry probe on babies skin which is stained with meconium.

False Negative Reactions↗
PubMed1990

Histiocytosis X of the vulva: a case report and review of the literature.

Histiocytosis X of the female genital tract is unusual. Thirty-two cases have been reported to date in the world literature. An additional case is reported herein, presenting as a vulvar ulcer in a 2.5-year-old child with osteolytic lesions of the skull, splenomegaly, and otitis media. The diagnosis of histiocytosis X may be established by identifying the Langerhans histiocyte, characterized by nuclear grooves, immunoreactivity for S-100 protein, and pentalamellar cytoplasmic structures seen by electron microscopy. Prognosis is difficult to determine with certainty. However, age of less than 2 years at presentation, multi-organ involvement, and/or organ dysfunction appear to be associated with a less favorable prognosis. The patient presented herein is currently receiving vinblastine chemotherapy for recurrence of disease, manifested as an osteolytic lesion in the skull.

Bone Diseases↗
PubMed1989

Simulation of cervical changes in labour: reproducibility of expert assessment.

A carefully designed set of simulators showing cervical effacement and dilatation was used to assess the error within and between observers in a group of 36 midwives and 24 obstetricians. No observer was correct in every case. There was no significant difference between the obstetricians and the midwives in assessment of effacement or overall assessment of dilatation. However, midwives were significantly more likely than obstetricians to assess dilatation inaccurately by more than 1 cm. Inaccuracy was greatest in the simulators 5-7 cm dilated. These findings have implications for labour management and teaching.

Audiovisual Aids↗
PubMed1989

Fitness reduction associated with the deletion of a satellite DNA array.

Satellite DNA refers to a class of tandem repeats of very simple sequences, usually A + T or G + C rich, which form a satellite band on a CsCl gradient. Their ubiquity and abundance in higher eukaryotes have led to speculation about their functions. It has often been suggested that satellite DNAs are merely innocuous genetic parasites or comprise 'junk' DNA. The recent identification of an array of satellite DNA repeats as the Responder (Rsp) locus of Drosophila melanogaster provides a new perspective on these elements. Rsp is in the centromeric heterochromatin of most natural second chromosomes. It causes spermatids bearing it to degenerate after meiosis when the homologous second chromosome is a Segregation Distorter (SD) chromosome. That is, SD targets the Rsp locus on its homologue for destruction during spermatogenesis, causing meiotic drive. Why then does the Rsp locus, a large array of satellite repeats, exist at all? One plausible explanation is that its existence contributes to the fitness of flies bearing it, compensating for the loss through meiotic drive. A direct demonstration of the usefulness of any family of satellite DNA is to compare the fitnesses of individuals with and without it. Previously, such an experiment has been difficult because the absence of a characteristic phenotype has precluded an efficient selection of deletion mutations. In this report we attempt to demonstrate a fitness reduction associated with the deletion of Rsp satellite DNA as well as the life stages at which such a reduction occurs.

Animals↗
PubMed1989

A new surgical technique to treat refractory labial fusion in the elderly.

An elderly woman with refractory labial fusion was treated by labial separation. The subsequent raw area was covered by a rotational skin flap from the thigh. The flap was deroofed of epithelium proximally and tunnelled subcutaneously. The distal portion emerged to cover the raw clitoral area and this successfully prevented contraction and scarring.

Dyspareunia↗
PubMed1989

Steady-state arterial and hepatic venous plasma concentrations of 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine in animals--drugs which are subject to both splanchnic and extra-splanchnic elimination.

We have previously shown that 5-fluorouracil (FUra) in humans obeys Michaelis-Menten elimination kinetics. In this article we show that the related bromine and iodine-containing analogs in animals obey similar kinetics. Steady-state arterial (CssA) and hepatic venous plasma (CssV) concentrations of 5-bromo-2'-deoxyuridine (BrdUrd) are reported for 7 rabbits given 5 different infusion rates of BrdUrd and 5 dogs given 4 or 5 different infusion rates of BrdUrd. Steady-state arterial and hepatic venous plasma concentrations of 5-iodo-2'-deoxyuridine (IdUrd) are reported for 5 rabbits and 2 dogs given 5 different infusion rates of IdUrd. Each set of data could be fitted by a nonlinear least squares method to the equation: (equation; see text) where Vm/Q is the maximum difference, (CssA) - (CssV), and Km is the Michaelis constant. The estimated parameter Vm/Q and Km are compared for the two drugs and different species and also with the same parameters derived in the same manner from previously published data on fluorouracil in 8 cancer patients. The infusion rate needed to saturate the splanchnic elimination system (Rs in mumol/kg/min) was also estimated. For BrdUrd the mean value of Rs in the rabbit, namely 1.23, and in the dog, namely 1.25 mumol/kg/min are essentially the same.

Animals↗