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Biomedical subjects

C Johnson

Publications and source records attributed to C Johnson.

At least 19 recordsLinked to original sources
PubMed1992

Actions of the phorbol ester, PMA, on ATP-induced fluctuations in cytoplasmic calcium in single isolated bovine aortic endothelial cells.

Agonist-evoked rises in [Ca2+]i were recorded from single bovine aortic endothelial cells in the middle of confluent monolayers by dual-wavelength microspectrofluorimetry. Low doses of ATP (1-5 microM) induced a transient rise in [Ca2+]i followed by a maintained plateau phase upon which were superimposed irregular fluctuations in [Ca2+]i. The mechanism underlying these fluctuations is not known. Addition of the phorbol ester, phorbol 12-myristate 13-acetate (PMA), to single cells displaying ATP-induced fluctuations reduced the amplitude and frequency of these fluctuations but the maintained plateau phase was unaffected. Elevation of intracellular cAMP by activation of adenylate cyclase with forskolin, or application of dibutyryl cAMP did not affect the ATP-induced fluctuations. These results suggest a possible role for the diacylglycerol limb of the phosphoinositide hydrolysis pathway, via activation of protein kinase C, but not cAMP, in the mechanism responsible for generating ATP-induced fluctuations in [Ca2+]i.

Adenosine Triphosphate↗
PubMed1979

Trends in services for pregnant adolescents.

Because the rate of childbirth among adolescent girls in the United States is among the highest in the world, a pressing need exists for services for pregnant adolescents. After summarizing trends and indicating the complex problems in this area, the authors put forward recommendations for continued efforts.

Adolescent↗
PubMed1979

Severe right ventricular outflow tract obstruction caused by an intracavitary cardiac neurilemoma: succesful surgical removal and postoperative diagnosis.

A 32-year-old woman with a one-year history of progressive shortness of breath and chest pain was found to have a grade 4/6 systolic murmur at the base of the heart and left sternal border. Right ventricular enlargement was found by physical examination, ECG, and chest roentgenogram. Cardiac catheterization showed elevated right ventricular pressure, an intracavitary pressure gradient, and inability to enter the pulmonary artery. Angiography revealed a mass in the right ventricular outflow tract. Successful surgical removal of a large, well-encapsulated tumor mass was accomplished, and the tumor was interpreted as a benign neurilemoma. Postoperatively, the patient improved remarkably.

Adult↗
PubMed1979

Behaviour of human immunoregulatory cells in culture. I. Variables requiring consideration for clinical studies.

The suppressor function of lymphocytes stimulated with concanavalin A (Con A) provides a potential method for examining disorders of immunoregulation. Clinical application, however, requires definition of the culture conditions that influence the expression of normal suppressor cell activity. In the present studies culture conditions were modified until a sensitive assay for non-specific suppressor cell function was reproducible utilizing the response to varying doses of phytohaemagglutinin (PHA) as an indicator system. Practical conclusions included (1) that sensitivity was not lost if the suppressor cells and responder cells were allogenic; (2) that fresh responder cells were as sensitive as precultured responder cells; (3) that a wide range of Con A concentrations could induce suppressor activity; and (4) that the sensitivity of the assay was much enhanced by using suboptimal mitogen doses of PHA. Twelve percent of normal subjects gave false negative results but these could be avoided by studying cells at more than one time point after stimulation with Con A. Cells resting in culture for 7 days could be induced to suppress after stimulation with Con A and these suppressor cells were very sensitive to pharmacological doses of dexamethasone. Studies utilizing different times of cell pre-incubation before Con A stimulation and different periods of exposure to Con A revealed fluctuation in the induction of suppression that may represent alternating periods of suppression and amplifying activity among stimulated cells in vitro. Such variations will need to be taken into account in the application of this type of assay to clinical studies seeking disordered immunoregulation.

Cell Survival↗
PubMed1979

NCTR computer systems designed for toxicologic experimentation. V. Post-experiment information system.

The Post-Experiment Information System (PEIS) is an automated data collection and reporting system composed of three specialized subsystems: Pathology, Chemistry and Microbiology. These subsystems function either independently or collectively to construct and maintain a comprehensive data base of all experimental values derived from, or associated with, an animal carcass. All data are retrievable by the unique Carcass Identification (CID) number assigned at death, which is the correlative of the Unique Identification Number (UIN) assigned to the animal at birth and used throughout its lifespan. Elements processed under the PEIS include gross and microscopic pathological observations, organ weights, hematologic data, chemical data, and microbiological analyses. The ability of the system to integrate the post-experiment data with the information collected on an animal from birth (BIS) and during the experiment (EIS) provides a complete animal history to the Principal Investigator or other requestor.

Animals↗
PubMed1978

Observations on thyroid hormones in the blood of thoroughbreds.

During an investigation of a group of clinically well thoroughbreds housed in the same stable, it was noted that seven of the 14 had no detectable thyroxine in the plasma (less than 5 nmol/litre). An investigation of thoroughbreds in this stable over a five month period suggested that the thyroids were functioning normally and that the thyroxine was excreted in the urine. Thyroxine binding studies on the blood of these horses suggested that the major part of the circulating thyroxine was bound to albumin. The thyroxine had been displaced resulting in an apparent absence of plasma thyroxine since the limit of detection for normal radioimmunoassay is 5 nmol/litre. It is concluded that the measurement of plasma thyroxine as an indication of thyroid function in the thoroughbred can prove unreliable.

Animals↗
PubMed1977

Age-associated structural alterations in senescent mouse brain DNA.

The maintenance of structural integrity in the DNA of aging mice has been examined with the amin in view of determining whether changes in genome structure constitute the molecular basis of aging. Cell lysate DNA from brains of differently aged mice was subjected to alkaline sucrose gradient sedimentation. The results show that brain DNA from young mice sediments mondispersely while that from senescent mice exhibits polydisperse sedimentation patterns, bainding in four peaks corresponding to number-average molecular weights of 1.4-10(8), 70-10(6), 15-10(6) and 3-10(6). When treated with nuclease S1, it was the 30 month mouse DNA whose sedimentation shifted to the top of the gradient indicating a reduction in its molecular weight as a result of nuclease digestion. The apparent increase in single strand breaks implies that the rate of breakage in old mouse brain DNA is faster than that of repair replication. The conclusion is drawn that senescence could result from an accumulation of defects in the genome.

Aging↗
PubMed1977

Pseudomonas aeruginosa bacteremia in a dialysis unit. 11. Relationship to reuse of coils.

Blood for culture was obtained over a six week period from 17 patients undergoing long-term hemodialysis. Bacteremia was detected during 18 of 201 dialyses. Blood drawn during fifteen of these dialyses contained pseudomonas aeruginosa. Ten of the 17 patients (59 per cent) had a Pseudomonas bacteremia some time during the study. Only one patient was symptomatic. The frequency of positive cultures was related to reuse of coils. No cultures were positive until after the fifth use, but by the tenth use, 41 per cent of the dialyses were associated with bacteremia. All coils that were used repeatedly and 32 of 48 of those used only once, grew Ps. aeruginosa when filled with media and incubated. This suggests that the coils were inoculated during dialysis and that benzalkonium chloride, the sterilizing agent, was unable to eradicate this organism. With repeated uses, the number of residual bacteria in the coil became large enough to cause detectable bacteremia during dialysis.

Cross Infection↗
PubMed1977

On the birth of an infant with sickle cell anemia.

This is the first report in the English literature of the birth of an obligate SS infant whose parents both had sickle cell anemia. The young adult SS parents of this infant and their families did not wish to prevent the birth of this child but had, in fact, many positive reasons to continue the pregnancy to term even in the face of the increased personal risk of pregnancy for this mother. This unusual circumstance initiated a re-appraisal of the realistic expectations with respect to reproduction in patients with homozygous recessive genetic disorders. No definitive studies could be found which attempted to evaluate the influence of genetic counseling on reproductive behavior in patients with sickle cell anemia. The questions raised about the 'right to reproduce' and the realistic aims of genetic counseling in adult homozygote patients have been discussed. However, no conclusions seem warranted because of the paucity of available information.

Adult↗
PubMed1976

Raman pH profiles for nucleic acid constituents I. Cytidine and uridine ribonucleosides.

Raman spectra of aqueous solutions of uridine and cytidine have been recorded as a function of pH with the band intensities and vibrational frequencies monitored to determine bands which may be considered as diagnostic of the concentration of the various species. Quantitative band intensity measurements indicate that not all pH-sensitive bands can be considered as diagnostic of the pK value for the acid form of the nucleoside, and for the percent species in solution. Although the accuracy of the Raman band intensity method is inherently less than that of the titrimetric or visible-ultraviolet spectrophotometric methods, the pK values and percent species agree well with those obtained from these methods. The utility of the results obtained from the pH profiles for cytidine is discussed in terms of the effect of acidification on the structural and conformational characteristics of polycytidylic acid in solution.

Cytidine↗
PubMed1976

Raman ph profiles for nucleic acid constituents. II. 5'-AMP and 5'-GMP ribonucleotides.

Raman spectra of aqueous solutions of 5'-AMP and 5'-GMP have been recorded as a function of pH. Band intensities and frequencies have been monitored to determine bands which may be considered as diagnostic for the concentration and the pK of the solution species. Quantitative band intensity measurements indicate only a selected number of bands can be considered as diagnostic of the base or the secondary phosphate proton dissociation. The utility of the pH profiles derived from specific band intensity variations for 5'-AMP is discussed in terms of the effect of acidification on solution characteristics of polyadenylic acid.

Adenosine Monophosphate↗