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Biomedical subjects

J Dennis

Publications and source records attributed to J Dennis.

At least 91 records · Page 5Linked to original sources
PubMed1976

Plaque reduction neutralization test for human cytomegalovirus based upon enhanced uptake of neutral red by virus-infected cells.

Foci of cells infected with human cytomegalovirus were noted to stain more intensely than uninfected cells with neutral red, and this provided the basis for development of a plaque assay and plaque reduction neutralization test for cytomegalovirus. Plaques demonstrable by neutral red staining could be counted at 8 days after infection; thus, results could be obtained earlier than for plaque assay systems based upon the viral cytopathic effect, a fewer manipulations were required for staining cell monolayers to demonstrate plaques. Certain variables affecting plaque size and numbers and antibody titers were defined. Addition of fresh guinea pig complement to the reaction mixtures markedly enhanced cytomegalovirus-neutralizing antibody titers of hyperimmune animal sera, but titers of human sera were enhanced only two-or fourfold.

Animals↗
PubMed1976

Central hypoventilation during quiet sleep in two infants.

Expired ventilation (VE), tidal volume (VT), frequency (f), and alveolar PCO2 (PACO2) were examined in six normal infants at 41 to 52 weeks post-conceptional age and in two infants who were apneic at birth. Their response to breathing 5% carbon dioxide in air and to 100% oxygen in quiet sleep were compared to those in rapid eye movement (REM) sleep. VE in normal infants was 259 ml/kg/min in REM and 200.2 ml/kg/min in quiet sleep with the difference being due to decreased carbon dioxide production and to decreased dead space. VE increased 34.4 ml/kg/min/mm Hg of PCO2 elevation with 5% carbon dioxide breathing during REM and was not significantly different during quiet sleep. During oxygen breathing VE fell by 32.7% at 30 seconds before increasing again. In the affected infants, VE and PACO2 during REM at 1 and 4 months were normal. At 1 month, during quiet sleep, each infant became apneic and PACO2 rose 9 and 8 mm Hg/min respectively. At this time mechanical ventilation was begun. At 4 months, during quiet sleep, VE was 0.064 and 0.063 ml/kg/min at PACO2 of 66 mm Hg in each infant. The change was due entirely to a decrease in VT to 2.3 and 2.5 ml/kg. At this time 5% carbon dioxide breathing given during normal ventilation in REM produced an abrupt fall in VT to 2.0 and 2.2 ml/kg with no change in frequency. Oxygen breathing during REM at one month had no effect but at 4 months produced apnea requiring mechanical ventilation after one minute. The findings suggest that the ventilatory response to carbon dioxide is (1) important in initiation of extrauterine ventilation and (2) in sustaining ventilation particularly in quiet sleep. It is not necessary in sustaining ventilation awake or in REM sleep and it represents a balance between the stimulatory and depressant effects of carbon dioxide on the central nervous system.

Apnea↗
PubMed1975

A multi-purpose laboratory light box.

A multi-purpose, inexpensive laboratory light box is described which can be used for observing and photographing results of a diversity of laboratory tests using either white or ultraviolet light.

Lighting↗
PubMed1972

Modified hemagglutination-inhibition test for rubella employing human group O erythrocytes.

A hemagglutination-inhibition (HI) test for rubella is described which utilizes human group O, rather than 1-day-old chick, erythrocytes. The test was found to be as sensitive and reproducible for detection of rubella antibody as HI tests employing chick erythrocytes. Advantages to the use of human erythrocytes are (i) they are more available, (ii) it is unnecessary to absorb natural agglutinins from human test sera, and (iii) heparin-MnCl(2)-treated sera do not agglutinate human erythrocytes, as is sometimes the case with chick erythrocytes. Factors influencing the reliability of the test are discussed.

Agglutination Tests↗
PubMed1969

Enzymes produced by a Pseudomonas species which inactivate inhibitors of certain viral hemagglutinins. I. Identification and purification of a proteinase and phospholipase C.

Filtrates from cultures of a psychrophilic Pseudomonas species, which inactivate serum inhibitors of certain viral hemagglutinins, were shown to contain both lecithinase (phospholipase C) and a proteolytic enzyme with elastase activity. The bacterium was cultivated under conditions favoring production of the respective enzymes, and the enzymes were purified by ammonium sulfate precipitation followed by column chromatography or by gel filtration. The elastase was obtained in crystalline form and was recrystallized. It has properties similar to those of a number of other bacterial elastases but is more heat-labile than most. Although a high degree of purification was achieved for the lecithinase, as evidenced by an increase in specific activity, it was not obtained in crystalline form. Partially purified preparations of the lecithinase had extremely high activity compared to that of commercial preparations of phospholipase C from Clostridium welchii.

Chemical Precipitation↗