The relationship between the microtitration serum agglutination and complement fixation tests in bovine brucellosis serology

The relationship between antibody titres in the microtitration serum agglutination test and the complement fixation test in bovine brucellosis is described. For low and high MSAT values there is good agreement between the 2 tests. This is not the case for MSAT values between 54 and 338 IU/ml. For practical reasons, results falling into this category cannot all be repeated. Repetitions are so structured that less than 4% of the tests need to be repeated. If the level of repetitions should show an increase above 4%, it is assumed that technical or human error has occurred.     

A sensitive microassay for the determination of hemolytic complement activity in bovine milk

A ⁵¹Cr release microhemolytic complement assay is described to detect hemolytic complement activity in bovine milk. ⁵¹Cr-labeled guinea-pig erythrocytes (GPRBC), which have been sensitized with a subagglutinating amount of rabbit anti-GPRBC, are placed in microtiter plates. Pooled bovine sera as source of complement to achieve about 50% of ⁵¹Cr release were added to each well prior to the addition of the samples on the test. Determination of CH100 titer was obtained by difference of counting between heated and unheated diluted whey samples from a standard linear regression. Comparative hemolytic values throughout lactation were established for the first time and confirmed the improved sensitivity of the assay.     

Hemolytic and bactericidal activities of bovine complement in mammary secretions of cows during the early nonlactating (dry) period

Hemolytic and bactericidal complement-dependent activities were measured in quarter mammary secretions obtained during the first 21 days of the nonlactating (dry) period from 8 Holstein-Friesian cows. We demonstrated an inhibition of hemolytic activity and bactericidal activity against a serum-sensitive Escherichia coli strain. Both hemolytic and inhibitory titers increased markedly during active involution. The bactericidal activity of dry secretions required a minimal threshold of complement and an inhibitory titer lower than the hemolytic titer.     

The relationship between the variants of the bovine MBL2 gene and milk production traits, mastitis, serum MBL-C levels and complement activity

Mannose-binding lectin (MBL), a calcium-dependent collagenous lectin, plays an important role in the host immune defence against a wide range of pathogens. There are MBL1 and MBL2 genes which encode the MBL-A and MBL-C proteins, respectively. This study was carried out to investigate the relationship between the variants of the bovine MBL2 gene and milk production traits, mastitis, serum MBL-C levels and hemolytic complement activity in both classical pathway (CH50) and alternative pathway (ACH50) in Chinese Holstein cattle. Four single-nucleotide polymorphisms (SNPs) in the exon 1 of the MBL2 gene in Chinese Holstein cattle and Luxi yellow cattle were identified by the direct sequencing method. The SNP g.201 G>A was identified as a non-synonymous mutation (codon 31, Arg>Gln) at the N-terminus cysteine-rich domain and the SNPs g.234 C>A and g.235 G>A (codon 42) made Pro to Gln at the 1st Gly-X-Y repeat of the collagen-like domain, while the SNP g.244 T>C (codon 45) was identified as a synonymous mutation (Asn>Asn) at the 2th Gly-X-Y repeat of the collagen-like domain. The SNP markers (g.201 G>A, and g.234 C>A) were significantly correlated with somatic cell score (SCS) (P<0.05). The concentration of MBL-C protein in serum ranges from 0.8 to 7.4μg/mL by enzyme-linked immunosorbent assay. Six combinations of different haplotypes from the four SNPs were identified in Chinese Holstein cattle. Statistical analysis revealed that cows with the haplotype combination H4H5 exhibited the lowest SCS. The CH50 value of H4H5 and H5H5 cow are significantly higher than H2H5 haplotype combination (P<0.05). The association analysis results showed that the haplotype combination H4H5 may be used as a tolerance haplotype combination for the bovine mastitis.     

The influence of extracellular and phagolysosomal pH changes on the bactericidal activity of bovine neutrophils against Staphylococcus aureus

The influence of the pH of suspending medium on bovine neutrophil (PMN) function was assessed in tests of phagocytosis and killing of Staphylococcus aureus. Intracellular killing was markedly inhibited by moderate extracellular acidification whereas phagocytosis was little affected, except at the lowest pH level (pH 5.0). The killing of S. aureus by extracts of isolated PMN lysosomal granules showed a similar pH dependence and was optimal at pH levels above neutrality. Survival of S. aureus within PMN from different cows varied significantly and the relative differences in PMN bactericidal efficiency were maintained at all pH levels. The acidification of extracellular medium during incubation which resulted from metabolic activity of the PMN themselves, increased with increasing ratios of bacteria:PMN and varied significantly among cows. Addition of methylamine (10 mM) to elevate phagolysosomal pH inhibited phagocytosis and had no effect on intracellular survival of S. aureus. However, a lower concentration (1.5 mM) did not affect phagocytosis, but reduced bacterial survival without altering the relative differences in efficiency of PMN from different cows. It is suggested that the acidity of the extracellular medium may both reflect and influence the pH changes occurring within PMN phagosomes and, thereby, modulate the efficiency of intracellular destruction of S. aureus.     

The effects of diet and age on serum complement system activity in goat kids

Thirty new born male kids were allotted into three groups to evaluate the effects of diet and age on complement system activity in serum. After the colostrum feeding period, the control group (C) received a commercial milk replacer; the CLA group received 20 g/kg milk replacer DM of conjugated linoleic acid; and the GMK group was fed with goat milk. The kids were fed colostrum for 2 days and then either milk replacer or goat milk from days 3 to 60. Blood samples were taken at 1, 10, 20, 30, 40, 50 and 60 days of age. The complement system activity was higher (P < 0.05) in the GMK group throughout the whole experiment through alternative pathway. C kids did not present complement activity at any time. CLA group complement activity was statistically higher than that of C kids from 30 to 60 days, through alternative pathways. In conclusion, the milk replacer formula should be reformulated because it did not induce any complement system activity in the first two months of life.     

The role of lysozyme in killing and lysis of coliform bacteria in the bovine animal 1. Serum and milk concentrations of lysozyme and susceptibility of coliform strains to its action

Concentrations of lysozyme were determined in 206 bovine sera and 37 bulk-tank milks. Detectable levels were not found in 46.6% or 96 sera, 38.3% (79 sera) had less than 2.5 μg/ml, 12.1% (25 sera) had concentrations of 2.5 to 25 μg/ml and 2.9% (6 sera) had concentrations greater than 25.0 μg/ml. Only one milk sample had any detectable lysozyme (0.5 μg/ml) by the method used.Lysis by bovine sera of washed coliform bacteria previously determined to be resistant or sensitive to killing by bovine serum was tested in various buffer systems. No correlation between killing by serum and sensitivity to lysis by lysozyme was found. EDTA markedly potentiated serum lysis in the presence of added lysozyme. Lysozyme itself was not lytic.Added lysozyme did not potentiate killing of the coliforms by bovine serum when tested by direct plate counts or by spectrophotometric growth assay.These in vitor results suggest that lysozyme may have limited importance as a protective agent against coliform bacteria in vivo.     

The activity of enzymes in serum and tissues of clinically normal sheep

Extract

Feline infectious peritonitis was first described as a distinct disease entity in 1966 in the United States (Wolfe and Griesemer, 1966), although it had been observed prior to that date (Holzworth, 1963). The disease is widespread in that country (Disque et al., 1968: Hardy and O'Reilly, 1969; Ward and Pederson, 1969; Colby and Low, 1970; Colgrove and Parker, 1971) and has been recorded in Canada (Stephenson et al., 1971), England (Ingram, 1970), Ireland (Hartigan and Wilson, 1972), Japan (Konishi et at., 1971), the Netherlands (Mieog and Richter, 1971), Switzerland (Stunzi and Grevel, 1973) and most recently in Australia (Watson et al., 1974; Jones and Hogg, 1974). Two cases of feline infectious .peritonitis have, been seen in New Zealand (R. C. Gumbrell, pers. comm.). One experimental cat inoculated with peritoneal fluid from this case developed clinical signs and lesions said to be consistent with feline infectious peritonitis.