Visual reading of enzyme immunofluorescence assays for human cytomegalovirus antibodies

Enzyme immunofluorescence assays for cytomegalovirus antibodies could be read satisfactorily using a light box with ultraviolet illumination. Higher antibody titers were obtained with a fluorogenic substrate than with a color-producing substrate.

Carcinogenicity of tumor cell populations: origin of a putative H-2 isoantigenic loss variant tumor

The properties of an unusual mouse tumor capable of extremely rapid and widespread spontaneous metastatic growth were recently described; this tumor, called MDAY-D2, at first appeared to be an H-2Kk loss variant of an (A X DBA/2)F1 (H-2KkDd) sarcoma called MDAY and was obtained by serial ip passage of MDAY in DBA/2 (KdDd) mice. The studies described here were concerned with the analysis of the origin of MDAY-D2; i.e., was it a true variant or a newly induced DBA/2 tumor? Several approaches were used, most of which exploited defined cell surface alloantigenic systems as natural genetic markers. The results indicated that MDAY-D2 was indeed a newly induced DBA/2 tumor and, furthermore, that MDAY was a homozygous A-strain tumor, probably a T-cell lymphoma. Thus a) MDAY was found to be Ly-1.2+, Ly-2.2+, and Thy-1.2+, but Ly-6.2-, whereas the opposite pattern was observed with MDAY-D2; b) MDAY possessed the private and public H-2 specificities associated with H-2k and H-2Dd, but not H-2Dk [i.e., it typed as an A-strain (H-2a) tumor, not as (A X DBA/2)F1]; c) MDAY-D2 possessed private and public specificities associated with H-2Kd and H-2Dd and was found to be H-2Kk-negative [i.e., it typed as a DBA/2 (H-2d) tumor]; d) serial injection of clonally derived ouabain-resistant H-2Kk-positive MDAY cells into DBA/2 hosts led to the rapid development of an MDAY-D2 (H-2d-positive) tumor that was fully ouabain-sensitive. Several findings did not support a contaminant theory to explain induction of MDAY-D2. The rapid induction of a tumor after injection of allogeneic tumor cells may have importance in relation to oncogenesis, tumor variant formation, and tumor progression. The results showed that tumor cells themselves can be potent carcinogens.

Poly(A)-containing RNA in the livers of ethionine-treated rats

Ethionine intoxication in nonfasted rats leads to a rapid change in the levels of poly(A)+ RNA. Prolonged fasting causes a decrease in poly(A)+ RNA which is not aggravated further by ethionine. The size distribution of poly(A) tracts at the 3' end of mRNA is not affected by ethionine. However, ethionine induces a change in the metabolism of the poly(A) sequence relative to the remainder of the mRNA.

Poly(A) polymerase activity in ethionine-intoxicated rats: the relative effectiveness of disaggregated and intact polyribosomes as primers for poly(A) polymerase

Ethionine intoxication causes a change in the metabolism of poly(A) sequences on the 3' OH terminus of mRNA in rat liver in vivo. In an attempt to determine the factors responsible for these changes, nuclear and cytoplasmic poly(A) polymerase activities and the state of the primer were examined in vitro. Requirements for optimal enzyme activities were determined. The nuclear and cytoplasmic enzymes had different K+, Mn2+, and poly(A) primer optima. The levels of nuclear and cytoplasmic poly(A) polymerase activity were shown to decrease following ethionine intoxication. Poly(A)+ RNA isolated from the livers of saline- and ethionine-treated rats served equally well as primers for the cytoplasmic poly(A) polymerase. Disaggregated polysomes were seven times more effective as primers than were intact polysomes. The results suggest that the mRNP particle which is released from polysomes as a result of ethionine intoxication functions better as a poly(A) polymerase primer than does the intact polysome.

Fractionation and characterization of rat liver poly(A)-containing RNA

Three fractions of poly(A)-containing RNA were separated from total rat liver RNA using poly(U)-Sepharose 4B affinity chromatography. The poly(A)-containing RNA fractions were released by thermal elution. Fraction 1, eluted under the mildest conditions, and had poly(A) tracts of approx. 200 AMP units in length which appeared to be associated with poly(U) sequences of 20-50 UMP in length. Fraction 1 appeared to be present mainly in the nucleus and, its size distribution was similar to that of fractions 2 and 3. Fractions 2 and 3 eluted at higher temperatures and were associated mainly with polysomal and microsomal fractions. Poly(U) sequences were absent in fractions 2 and 3 while their poly(A) sequences had a size distribution characteristic of those reported in the mRNA of other organisms.

Antibody assays for varicella-zoster virus: comparison of enzyme immunoassay with neutralization, immune adherence hemagglutination, and complement fixation

An enzyme immunossay (EIA) was adapted for detection of antibody to varicella-zoster virus, and its sensitivity and specificity were compared with those of neutralization, immune adherence hemagglutination (IAHA), and complement fixation tests. Test sera showed little nonspecific reactivity in the EIA system, and valid results could usually be obtained at serum dilutions as low as 1:8. Demonstration of the presence or absence of varicella-zoster viral antibody by EIA showed 94% correlation with results obtained in neutralization tests, but EIA titers were 2- to 16-fold higher than neutralizing antibody titers. Results by IAHA showed 87% correlation with those obtained by neutralization. No false positive IAHA results were seen, but a number of false negative IAHA results were seen at the 1:8 serum dilution, particularly in older individuals. With increasing age (>40 years), and presumably increased time from varicella infection, neutralizing antibody levels generally declined to 1:8 or 1:16, EIA levels fell to 1:128 or 1:256, and IAHA and complement fixation antibody titers were usually <1:8 or 1:8. EIA and IAHA were as reliable as the neutralization and complement fixation tests for serodiagnosis of varicella and zoster infections. All tests demonstrated heterotypic varicella-zoster antibody titer rises in selected patients with initial herpes simplex virus infections, but fewer heterotypic responses were seen by EIA than by the other methods. EIA offers a rapid, sensitive, and specific method for varicella-zoster antibody assay that is applicable to use in a clinical setting.

Comparison of immunofluorescence and immunoperoxidase staining for identification of rubella virus isolates

To explore possible advantages which immunoperoxidase (IP) staining might have over immunofluorescence (IF) staining for identifying rubella virus isolates, direct comparative studies were done on the same coded clinical materials using the same rubella immune rabbit serum as the primary antiserum in both systems. The rubella immune rabbit serum and conjugated anti-rabbit immune globulins could be used more dilute in the IP system than in the IF system. Both IP and IF staining detected rubella antigen in all specimens which were positive by interference. IP staining also detected low levels of rubella antigen in a few additional specimens which had originally been positive for rubella virus, but which on retesting were negative by interference and IF staining. With second-cell-culture-passage material, IP and IF staining showed comparable specificity, and the few specimens which reacted nonspecifically generally did so in both systems. Cell cultures inoculated directly with urine specimens showed greater nonspecificity by IP than by IF, but this activity could be abolished by pretreatment with sodium azide and peroxide; other methods tried for inactivating endogenous peroxidase activity destroyed rubella antigen as well. The intensity of staining for positive specimens was comparable in the two systems. However, more antigen was demonstrable in both systems when BHK-21 cells were inoculated as a cell suspension and then permitted to grow into monolayers than when the same specimens were inoculated into preformed monolayers. IP staining was considered to be a highly satisfactory alternative to IF staining for identification of rubella virus isolates.

Complement-fixing reactivity of Varicella-Zoster virus subunit antigens with sera from homotypic infections and heterotypic Herpes simplex virus infections

Various subunit antigens of varicella-zoster (V-Z) virus were examined for complement-fixing (CF) activity with sera from homotypic infections and from herpes simplex virus (HSV) infections in which a CF antibody titer rise was demonstrated with crude V-Z antigen. The subunit antigens included nucleocapsids, envelopes, a soluble antigen produced from infected culture fluids by sucrose density gradient centrifugation, a soluble antigen produced by reducing the volume of clarified infected culture fluids, a soluble antigen derived from infected cell lysates, a "viral" antigen consisting largely of enveloped particles with a few nucleocapsids, and a cell membrane-associated antigen. None was more suitable than crude V-Z antigen for serodifferentiation of V-Z virus and HSV infections. The envelope antigen, cell membrane antigen, and the soluble antigen prepared by density gradient centrifugation showed little reactivity with sera from varicella and HSV infections, but gave high antibody titers with sera from zoster infections, suggesting that a secondary V-Z virus infection is required to produce an antibody response to these subunit antigens. Patients with varicella and zoster infections and the selected patients with HSV infections all showed significant CF antibody responses to the other V-Z subunit antigens.

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.

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.

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.

Templates for inoculation and microscopic observation of micro cell cultures

Simple, inexpensive plastic templates have been devised to aid in proper identification of cell cultures in microtiter plates during inoculation and microscopic observation. These have resulted in greater accuracy in performing and reading tests and in a saving of the microbiologists' time.

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.