Detection of conglutinin in bovine serum by complement-dependent agglutination of Escherichia coli.

Agglutination of Escherichia coli (ECA) by normal bovine serum was shown to be prevented by heating serum to 56 degrees C for 30 min, but restored by normal horse, swine, rabbit or guinea pig sera. Further investigation of the ECA reaction using techniques to distinguish between conglutination and immunoconglutination indicated ECA to be a conglutination reaction. Testing of 264 sera obtained from 22 normal cattle over a period of 5 months did not show individual or seasonal variation in ECA. Changes in ECA and conglutination were detected in sera of periparturient cows. The ECA reaction is a simple technique for detecting conglutinin in bovine serum.

Complement, bacteriostatic, and enzymatic activities in sera from guinea pigs given aflatoxin and/or rubratoxin.

The relationship of serum complement activity and bacteriostatic activity was investigated in male guinea pigs given aflatoxin and/or rubratoxin. In experiment 1, guinea pigs were given 0.6 mg of aflatoxin/kg of body weight, PO, once. In experiment 2, guinea pigs were given 0.02 mg of aflatoxin/kg, PO, and/or 8 mg of rubratoxin, PO, 11 times. Aflatoxin (0.02 mg/kg) had no effect given alone, but potentiated the effect of rubratoxin. In both experiments, changes in complement activity were accompanied by similar but not always significant (P less than 0.05) changes in bacteriostatic activity of serum. Guinea pigs given 0.06 mg of aflatoxin/kg had significant (P less than 0.05) changes in complement titers and in serum alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase activities. Guinea pigs given repeated oral doses of aflatoxin and/or rubratoxin had changes in complement titers, bacteriostasis, and alkaline phosphatase and aspartate aminotransferase activities, but not in alanine aminotransferase activities. Significant differences were detected only when average values for all guinea pigs given rubratoxin or rubratoxin with aflatoxin were compared with average values for guinea pigs not given rubratoxin.

Decreased complement and bacteriostatic activities in the sera of cattle given single or multiple doses of aflatoxin.

Five steers given 1 dose of partially purified aflatoxin at concentrations sufficient to provide 0.2 mg to 0.8 mg of aflatoxin B1 equivalents/kg of body weight were compared with 4 steers given 14 daily doses of 0.25 mg of aflatoxin B1 equivalents/kg of body weight for complement activity and bacteriostasis. Complement activity was measured by hemolysis in gel, and bacteriostatic activity, by growth inhibition of Escherichia coli in liquid medium. In the single-dose group, complement activity and bacteriostatic activities decreased by 57 hours after dosing, and both returned to near base line by 168 hours. In the daily dose group, only bacteriostatic activity decreased, and the decrease persisted 2 weeks after the last dose of aflatoxin was given. Apparently, aflatoxin affects both complement-dependent and independent serum bacteriostatic activity.

Histopathologic and antibody responses of rabbits exposed to aerosols containing spores of Aspergillus fumigatus: comparison of single and multiple exposures.

Resistance to pulmonary aspergillosis was studied in groups of rabbits exposed to aerosolized spores of Aspergillus fumigatus for 15 minutes on successive days for a total of 10, 7, or 4 exposures or a single exposure. The results of the study demonstrated that exposure of rabbits to spores for 15 minutes on 10 successive days did not result in an accumulation of viable spores in excess of those present in the lungs of rabbits exposed a single time. The tissue response in the lungs of the rabbits exposed at multiple times was more intense than that in the rabbits exposed once, but resolution of the lesions occurred similarly in terms of time and completeness of resolution. The duration of the antibody response as determined by a passive hemagglutination test and by enzyme-linked immunosorbent assay correlated with the number of exposures to spores, in that rabbits exposed 10 or 7 times to aerosolized spores remained positive longer than did those exposed fewer times. The results of the precipitin tests in agar gel were negative in all the rabbits but one.

Cloning and overexpression of Moloney murine leukemia virus reverse transcriptase in Escherichia coli.

A pBR322-derived expression vector, plasmid pKD1, was constructed containing the strong leftward promoter (pL) of bacteriophage lambda, the ribosome-binding site (RBS) of the cII gene of lambda, and a unique downstream NdeI restriction site for construction of an ATG initiation codon. The section of the pol gene of Moloney murine leukemia virus (M-MLV) that codes for reverse transcriptase (RT) was cloned into the NdeI site of this vector generating the plasmid pRT103. Upon thermal induction, enzymatically active RT was expressed in Escherichia coli [pRT103]. The identity of this activity was confirmed by its template specificity and its sensitivity to inhibition by immunoglobulin G (IgG) prepared against authentic murine RT. RT represented 20% of the newly synthesized protein in these cells 20 min after induction.

Dispersed 5S RNA genes in N. crassa: structure, expression and evolution.

The 5S RNA genes (5S genes) in N. crassa are not tandemly arranged or tightly clustered as in other eucaryotes that have been examined. 55 RNA or cloned 5S DNA hybridizes to at least 30 different restriction fragments of Neurospora DNA. Of 34 5S DNA clones examined, each contains a single 5S gene. Saturation hybridization analyses indicate that there are about 100 copies of 5S genes in the genome of this organism. We have partially or completely sequenced the 5S region of 15 clones. Both identical and highly divergent 5S coding regions were found. Nine are of one type (alpha). The other six include four different types (beta, beta', gamma and delta) which differ from each other and from the alpha genes to various degrees. Eleven of 15 genes have distinct flanking regions. Analysis of Neurospora 5S RNA showed that it consists of one principal species which matches the alpha-type gene sequence. Additional 5S species corresponding to the less abundant 5S gene types were also detected. The pattern of nucleotide substitutions between the predicted Neurospora 5S RNAs and between these and S. cerevisiae 5S RNA suggests that a particular 5S RNA secondary structure occurs in vivo and is conserved.