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Biomedical subjects

P Johnson

Publications and source records attributed to P Johnson.

At least 397 records · Page 22Linked to original sources
PubMed1987

Spinal bone mineral after 5 weeks of bed rest.

Patients put at bedrest for medical reasons lose 1-2% of spinal bone mineral per week. Losses of this magnitude during even short-term space flights of a few months would pose a serious limitation and require countermeasures. The spinal bone mineral (L2-L4) was determined in 6 healthy males (precision = 2%) before and after 5 weeks of complete bed rest. Only one individual had a significant loss (3%) and the -0.9% mean change for the 6, was not significant (P = 0.06). The average negative calcium balance during the 5 weeks was 4 g or 0.36% of total body calcium, similar to that reported in other bed-rest studies. Spinal bone loss, however, in healthy bed-rested males is significantly less than reported for bed-rested patients, suggesting that a large loss of spinal bone mineral does not occur during space flight missions lasting 5 weeks or less.

Adult↗
PubMed1987

Effects of denervation on calpain and calpastatin in hamster skeletal muscles.

Three leg muscles (soleus, extensor digitorum longus, and plantaris) of adult male golden Syrian hamsters were denervated by bilateral transecting of the sciatic nerve. Eighteen days after denervation, wet weights, amounts of soluble protein, and activities of wide-specificity calpain II, intermediate filament protein-specific calpain I, and calpastatin were measured by protein determination and enzyme and immunological assays. In comparison with control (nondenervated) muscles and depending on the specific muscle and protein, the activities of the calpains increased 1.3 to 1.9 times the control values, whereas the calpastatin decreased to one-half and one-third of control values. The muscle which showed the greatest increase in both calpain activities and the largest decrease in calpastatin activity was the plantaris (a fast-twitch, oxidative glycolytic muscle). The extensor digitorum longus (fast-twitch glycolytic) showed increases in calpain II activity similar to those in the plantaris, but smaller changes in calpain I and calpastatin. The soleus (slow-twitch, oxidative) showed the smallest changes in calpain II and calpastatin activities, although an increase in the calpain I activity was seen after denervation. These results suggest a possible relationship between the presence of fast-twitch, oxidative glycolytic fibers in a muscle and increased potential for intracellular proteolysis following denervation.

Animals↗
PubMed1987

Obstetric factors associated with cord blood gas values at birth.

Values of pH, base deficit and Pco2 in 885 unselected samples of umbilical blood collected at birth were related to pregnancy and delivery details. An increase in acidosis in both umbilical vein and artery was associated with placental abruption, maternal pethidine, pre-eclampsia, primigravidity, vaginal operative delivery for fetal distress and a long second stage of labour. Increased acidosis in arterial, but not venous, blood occurred with cord entanglement, vaginal breech delivery, postmaturity, high birthweight and a long first stage of labour. The relationship between obstetric factors and the acid-base state of the neonate suggests a possible role for cord blood gas measurements in assessing the results of obstetric practice.

Abruptio Placentae↗
PubMed1987

Mass spectrometer system for continuous skin-surface and intravascular blood gas measurement of maternal-fetal respiration in labour.

This paper describes the performance characteristics of a dual-inlet mass spectrometer suitable for continuous monitoring of maternal and fetal blood gases using intra-arterial mass spectrometer catheters in the pregnant ewe and skin-surface mass spectrometer probes during human labour. Skin-surface measurements in newborn and adult sheep bore a close and easily interpretable relationship to intra-arterial measurements. The performance of the skin-surface mass spectrometer probe on the human forearm compared favourably with a commercially available transcutaneous electrochemical system for the measurement of oxygen and carbon dioxide but the mass spectrometer was capable of measuring additional gases such as nitrogen and argon.

Animals↗
PubMed1987

Characterization of calpains and calpastatins from hamster skeletal muscle.

1. Hamster skeletal muscle contains a wide-specificity calpain which was found to be a calpain II type and which is composed of a single Mr 80,000 polypeptide. 2. The muscle also contains a calpain I type enzyme which is specific for desmin degradation, and this enzyme consists of a single subunit of Mr 67,000. 3. Three calpastatins were detected in the tissue, one of which inhibited both calpains, whereas the other two appeared to be specific for the desmin-specific calpain. These calpastatins possessed the same inhibition properties when assayed with chicken gizzard calpains.

Animals↗
PubMed1987

Congenital ureteral valves in children: case report and review of the literature.

Congenital ureteral valves are a rare cause of ureteral obstruction. While only 17 pediatric cases have been reported in the literature, this condition should be considered in the differential diagnosis of the child with upper urinary tract obstruction. The pediatric cases are reviewed, and we present an additional case in which unilateral hydronephrosis caused by a ureteral valve was first detected by ultrasound in utero.

Female↗
PubMed1987

Marijuana testing--how good is it?

Testing for the use of marijuana necessitates one or more levels of assessment, depending on the clinical application of the test results. The EMIT-dau screening test with a sensitivity limit of 20 ng/ml is highly satisfactory for screening for the absence of marijuana in the urine. This test has a virtual 100% true-negative rate as long as an unadulterated urine specimen is analyzed. Positive results by the EMIT-dau procedure are presumptive because the test seems to produce false-positive results when applied to a random population of suspected drug users. In a population in a specific clinical environment such as in drug-treatment programs in which 20 of every 100 specimens will yield positive THC-COOH results by EMIT-dau screening, 3 (15%) of the 20 positive results will likely be false-positive. Our experience with the EMIT-dau suggests that of 100 test results, 3 will be false-positive, an overall 3% false-positive rate. If a positive test result will put the patient in considerable jeopardy and the screening result is the only evidence of drug use, confirmatory testing is imperative. Of the confirmatory tests, GC/MS seems to have the specificity necessary to provide a high level of confidence in the results. A combination of the EMIT procedure with a sensitivity level of 20 ng/ml and GC/MS confirmation yields virtually 100% accuracy in detection of marijuana abuse.

Cannabinoids↗
PubMed1987

Hepatic sarcomas in adults: a review of 25 cases.

Twenty-five patients with an apparently primary sarcoma of the liver are reviewed. Presenting complaints were non-specific, but hepatomegaly and abnormal liver function tests were usual. Use of the contraceptive pill (four of 11 women) was identified as a possible risk factor; one patient had previously been exposed to vinyl chloride monomer. Detailed investigation showed that the primary tumour was extrahepatic in nine of the 25 patients. Distinguishing features of the 15 patients with confirmed primary hepatic sarcoma included a lower incidence of multiple hepatic lesions and a shorter time from first symptoms to diagnosis, but the most valuable discriminator was histology. Angiosarcomas and undifferentiated tumours were all of hepatic origin, epithelioid haemangioendotheliomas (EHAE) occurred as primary and secondary lesions and all other differentiated tumours arose outside the liver. The retroperitoneum was the most common site of an occult primary tumour and its careful examination therefore crucial: computed tomography scanning was found least fallible in this respect in the present series. Where resection (or transplantation), the best treatment, was not possible, results of therapy were disappointing, prognosis being considerably worse for patients with primary hepatic tumours. Patients with EHAE had a better overall prognosis regardless of primary site.

Adolescent↗
PubMed1987

An endogenous peptide that stimulates lanthanum-resistant calcium uptake in vascular tissue.

A recent report has described the preparation of an extract from hemolyzed erythrocytes that has a stimulatory effect on lanthanum-resistant calcium uptake by vascular tissue in vitro and a hypertensive effect when injected into normotensive rats. The compound having a stimulatory effect on calcium uptake was further fractionated by molecular sieve and ion exchange chromatography, precipitation with CaCl2, high voltage paper electrophoresis, and high performance liquid chromatography (HPLC). HPLC yielded only a single fraction containing biological activity. This fraction was ninhydrin positive and acid labile. The amino acid composition was as follows: Asp/Asn (1.41), Ser (1.02), Glu/Gly (1.00), and Gly (2.00). Based on the assumption that the compound contains a single glutamic acid or glutamine residue, concentration-response data indicated that only nanomolar amounts of material were necessary to achieve significant stimulation. There was a marked increase in stimulatory activity of the resolubilized compound following calcium precipitation. The compound became inactive or showed a reduction in activity after being applied to a cation exchange column to remove calcium. Subsequent reprecipitation with CaCl2 and resolubilization restored the lost activity. Thus, we conclude that the compound is a small, acidic, calcium-dependent peptide that is extremely potent in stimulating lanthanum-resistant calcium uptake in vascular tissue.

Amino Acids↗
PubMed1987

Charting in the medical records: guidelines for child life workers.

Charting needs to be a primary tool for the child life worker as it is for other health care professionals. The foremost goal of charting is to communicate and to share information with other health care professionals in order to provide the most comprehensive and appropriate treatment possible. This paper discusses the purposes of charting and outlines basic charting formats and standards. A chart audit system is proposed as an important part of departmental quality assurance programs.

Child↗
PubMed1987

Parenting and schizophrenia: an Australian study of expressed emotion.

Parents of 66 schizophrenic Sydney patients were interviewed using the abbreviated Camberwell Family Interview (CFI). Using pre-established criteria, 71% of the mothers, 58% of the fathers and 74% of the households were categorised as being of high expressed emotion (EE) status. Comparison is made with published data on the CFI and on EE categorisation for similar groups studied in England, the United States and India. The Sydney families were described as 'vocal, ambitious and aggressive', and EE scale scores more resembled the Los Angeles families than the British families originally studied. A number of factors influencing high EE categorisation (e.g., family intactness, socio-demographic variables) are noted.

Adolescent↗
PubMed1987

Prophylactic effects of silver nitrate and erythromycin on Chlamydia psittaci conjunctivitis.

An animal model has been developed to study the effects of various prophylaxis agents on acquisition of chlamydial conjunctivitis. When Hartley strain newborn guinea pigs received ocular inoculations of Chlamydia psittaci followed by the instillation of various agents, 1% AgNO3 significantly lowered the risk of developing chlamydial conjunctivitis if it was administered within 15 min after the inoculation with C. psittaci. However, if the AgNO3 was administered at either 1 hr or 2 hr following inoculation, it did not have any prophylactic effect on the development of chlamydial conjunctivitis. Erythromycin ointment, 0.5%, was also found to prevent chlamydial conjunctivitis. The prophylactic effect was similar to placebo when the drug was given at 15 min; however, erythromycin ointment prophylaxis 1 hr or 2 hr after inoculation with C. psittaci was statistically superior to placebo.

Animals↗
PubMed1986

The calcium dependence of histamine, carbachol and potassium chloride-induced contraction in human airways in vitro.

The effect of depletion of calcium from the Krebs Henseleit (KH) solution and the addition of EDTA (1 mM) on contraction of human isolated bronchus by histamine, carbachol and potassium chloride (KCl) was examined. Contractions to histamine and carbachol were almost totally abolished in calcium free KH in the presence of 1 mM EDTA which only reduced KCl responses to 76% of control values. Verapamil (10(-6), 10(-5), 10(-4) M) decreased histamine and KCl contractile responses in a dose-related manner while having no significant effect on carbachol-induced tension. The intracellular calcium antagonist TMB8 10(-4) M caused a slight but significant decrease in histamine contraction but was without effect on the maximal response of the other two agonists. TMB8 decreased the potency of both histamine and carbachol. These results suggest that histamine, carbachol and KCl utilise different pools of calcium for contraction, that only part of the calcium entry for all agonists occurs via voltage-dependent calcium channels and that intracellular calcium stores may play a small role in contraction to these agonists.

Bronchi↗
PubMed1986

Complex genetic determinants of susceptibility to methylxanthine-induced locomotor activity changes.

The intent of this study was to investigate the role of inheritance in the determination of susceptibility to methylxanthine-induced behavioral changes. Two strains of inbred mice, SWR and CBA, which differ significantly in their response to caffeine- and theophylline-induced stimulation of locomotor activity, were used in classical genetic crosses to produce reciprocal F1 hybrids, reciprocal backcross progeny F2 progeny. Theophylline dose response curves in the reciprocal F1 hybrid strains were identical to each other and to their methylxanthine-responsive (CBA) parent. These results indicated that theophylline responsiveness behaved as a simple autosomal dominant trait. Behavioral responses of these F1 hybrid strains to caffeine showed the same maximal enhancement of locomotor activity as their CBA progenitor at a dose 10 mg/kg IP, but locomotor activity stimulation also occurred at 32 mg/kg IP, a dose which inhibited their CBA parent. These data suggest that the genes specifying caffeine responsiveness differ from those encoding theophylline responsiveness. For both caffeine and theophylline, behavioral phenotypes and their expected frequencies of occurrence among backcross and F2 progeny differed significantly from the segregation ratios expected for a trait determined by a single gene. These non-Mendelian segregation ratios suggest that locomotor activity stimulation by both of these methylxanthines is polygenically determined. It was anticipated that the same genetically encoded neurochemical mechanism would underlie the difference in behavioral response to the two methylxanthines. However, no significant correlation between caffeine-induced and theophylline-induced stimulation of locomotor activity was observed among progeny derived from backcrosses of F1 self-crosses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗