Castration-induced apoptosis in the rat ventral prostate is associated with increased expression of genes encoding insulin-like growth factor binding proteins 2,3,4 and 5

Insulin-like growth factor binding proteins (IGFBPs) have recently been demonstrated to act as regulators of apoptosis in vitro in both prostate and breast cancer cell lines. We show here that gene expression of IGFBP-2,-3,-4 and -5 increase rapidly in the rat ventral prostate following castration. Increases in IGFBP mRNA levels were detectable by Northern blotting by 6 hours and reached 5 to 10 fold of control levels at 72 hours after castration. Apoptosis in the ventral prostate, as detected in situ by the TUNEL method, was also induced as early as 6 hours after castration. TRPM-2/clusterin, a gene known to be associated with involution of the prostate, was not detected in sham castrated controls but was expressed by 24 hours following androgen ablation. IGF-I mRNA levels increased to 160% of control values within 6 hours following castration, then decreased gradually over the next 72 hours to 35% of control. Affinity labelling experiments demonstrated that IGF-I receptor levels increased initially after castration with peak binding at 24 hours, then declined to levels lower than control. These results suggest that rapid induction of IGFBPs in the rat ventral prostate following androgen ablation may play a role in apoptosis and involution of the prostate gland.     

Effects of Corynebacterium bovis infection on susceptibility to major mastitis pathogens

Experimental challenge procedures were used to study infectivity and virulence of Corynebacterium bovis. Challenge procedures using Staphylococcus aureus (Newbould 305) and Streptococcus agalactiae (McDonald 44) were used to study effects of Corynebacterium bovis infections on superinfection with major pathogens. Rate of infection under experimental challenge conditions was significantly greater with Corynebacterium bovis than previously observed for Staphylococcus aureus or Streptococcus agalactiae. Principal location of Corynebacterium bovis colonization appeared to the teat canal region, although the organism was isolated from 75% of the teat cisterns by puncture technique. Quarters with Corynebacterium bovis infections were more resistant to infection by Staphylococcus aureus than bacteriologically negative quarters. Quarters infected with Corynebacterium bacterium bovis were approximately 8.5-fold more susceptible to Streptococcus agalactiae infection than negative quarters. Somatic cell counts were doubled in negative quarters that developed Corynebacterium bovis infections; the geometric mean was 2.4 X 10(5).     

Prevalence of mastitis in dairy heifers and effectiveness of antibiotic therapy

Dairy heifers were treated 0 to 90 d, 90 to 180 d, or 180 to 270 d prepartum with one of five different antibiotic products to determine the best time and with which product they should be treated prior to calving. Two hundred thirty-three heifers were included in the study. At the initial sampling, 56.5% of quarters were infected with some type of organism and 15.4% of quarters were infected with Staphylococcus aureus. Treatments included a cephapirin dry cow product, a penicillin-novobiocin dry cow product, a penicillin-streptomycin dry cow product, an experimental dry cow product containing tilmicosin, and a cephalonium dry cow product not available in the United States. Cure rates for the five antibiotic products indicated that all were equally effective against Staph. aureus and all were significantly more effective than the spontaneous cure rate observed in untreated control quarters. No differences in efficacy were observed due to the different treatment times prepartum. However, fewer new Staph. aureus infections occurred after treatment in the group treated at 180 to 270 d prepartum, indicating that treatment in the third trimester will reduce the chances of new intramammary infections occurring after treatment and persisting to calving.     

Effects of novel intramammary device models on incidence of mastitis after experimental challenge

First-calf heifers were fitted with five different intramammary device models prior to, or within 2 mo after parturition. Each model represented an increase in the weight of the device to be supported by the epithelial cells of the gland cistern. Each model was tested in four animals by placing devices in two quarters while remaining quarters served as controls. Foremilk and stripping quarter secretion samples were collected prior to device placement and weekly thereafter and analyzed for total and differential cell counts, bacteriologic status, and NAGase activity. During the prebacterial challenge treatment period, foremilk and stripping SCC as well as percentage of neutrophils and NAGase activity in most device-fitted quarters remained significantly elevated over controls. Frequency of naturally occurring intramammary infection during the prechallenge period was lowest in quarters fitted with Models 2, 4, and 5. Frequency of infection with coagulase-negative staphylococci also tended to be lower in quarters fitted with Models 2, 4, and 5. Approximately 4 mo after device placement, all quarters were challenged by intracisternal inoculation with about 565 cfu Streptococcus uberis. Results across all models combined showed that although mean foremilk and striping SCC and percentage of neutrophils were significantly elevated in device-fitted quarters immediately prior to bacterial challenge, only Model 4 showed a protective effect. Several models were superior to others in elevating SCC and percentage of neutrophils, but no differences in susceptibility to Strep. uberis infection were observed among models based on these cytological characteristics.     

A comparison of two commercially available Escherichia coli J5 vaccines against E. coli intramammary challenge

The efficacy of two commercially available Escherichia coli J5 bacterins was investigated. Jersey cows were randomly assigned to one of three treatment groups: 1) unvaccinated controls, 2) vaccinated with J.VAC (Merial Limited, Athens, GA), and 3) vaccinated with J5 bacterin. All cows were vaccinated at drying off and at 2 wk before anticipated calving. Cows that were vaccinated with the J5 bacterin also received a third immunization at calving. One quarter of each cow was challenged with approximately 64 cfu of E. coli at 14 to 30 d postcalving. Immunization by either vaccine did not influence the severity of coliform mastitis; however, the mean number of colony-forming units of E. coli recovered from challenged quarters was significantly lower for immunized cows than for control cows at 144 h postchallenge. Serum and mammary secretion immunoglobulin (Ig)G, IgG1, and IgG2 titers against E. coli J5 whole-cell antigens were enhanced in vaccinated cows. Serum and mammary secretion IgM were not different among treatment groups. Somatic cell counts in milk from challenged quarters, rectal temperatures, and the clinical status of cows following intramammary challenge were not different among treatment groups.     

Comparison of tilmicosin and cephapirin as therapeutics for Staphylococcus aureus mastitis at dry-off

Forty-four cows (26 Jerseys and 18 Holsteins) that had at least 1 mammary quarter that was naturally (n = 12) or experimentally (n = 84) infected with Staphylococcus aureus were allotted to three treatment groups of approximately equal number at the end of lactation. Cows were dried off by abrupt cessation of milking, and dry cow therapy was administered as an intramammary infusion of cephapirin benzathine at 10 ml per quarter, an intramammary infusion of tilmicosin (solution containing 300 mg/ml) at 5 ml per quarter, or a subcutaneous injection of tilmicosin at 5 mg/kg of body weight on the day of drying off and another injection 4 d later. Mammary secretions were monitored during the dry period and postpartum for antimicrobial residues, intramammary infection (IMI) status, and somatic cell counts. Results demonstrated the following percentage cures for IMI caused by Staph. aureus at 28 d postcalving based on individual mammary quarters: cephapirin benzathine, 78.1%; tilmicosin infused, 74.2%; and tilmicosin injected, 9.1%. During the first 4 wk after drying off, the mean concentration of tilmicosin in mammary secretions from cows infused with the antibiotic remained approximately 10-fold higher than that in secretions from cows injected with the antibiotic (3.43 vs. 0.32 ppm), and, by the time of calving, concentrations for cows treated with both methods were below the dilution limit of the assay (< 0.1 ppm). Results demonstrated that intramammary infusion of tilmicosin was equally as effective as cephapirin benzathine in curing IMI caused by Staph. aureus at drying off; however, the subcutaneous injection of tilmicosin at the dose used was not effective as a dry cow therapeutic against Staph. aureus.     

Effects of recombinant granulocyte colony-stimulating factor on Staphylococcus aureus mastitis in lactating dairy cows

The in vivo effects of recombinant human granulocyte colony-stimulating factor on blood and milk leukocytes in dairy cows was examined. A 2-fold increase in peripheral white blood cell counts was observed by d 5 of treatment and peaked on d 12 with values 3-fold those of controls. Counts remained elevated above pretreatment values during the treatment period, then returned to normal by d 23 of the trial. Differential white blood cell counts demonstrated that neutrophils predominated (73.8%) in treated cows versus controls (22.1%) during the treatment period. Immediately prior to experimental challenge with Staphylococcus aureus, milk SCC were 582 x 10(3) and 261 x 10(3)/ml, and percentages milk neutrophils were 64.4 and 45.3, respectively, in treated and control cows. After challenge, a 46.7% reduction in new infections was observed in quarters of treated cows compared with controls. Recombinant human granulocyte colony-stimulating factor was a granulopoietic growth and differentiation factor in the cow, and the resulting leukocytosis into the mammary gland may have been protective against experimental bacterial challenge.     

Mammary leukocyte response to drug therapy

The possibility exists that antibiotics and anti-inflammatory agents will be used indiscriminately in attempts to reduce leukocyte or somatic cell counts in mammary secretions to conform with Interstate Milk Shippers quality standards for raw milk to be implemented July 1, 1986. Recent in vivo studies evaluating the effect of intramammary drug injection on milk leukocytes confirmed previous in vitro investigations demonstrating that certain drugs have a significant effect on leukocyte antimicrobial activity. Antibiotics commonly included in commercial infusion products used in this country such as penicillin G, semisynthetic penicillins, the mycins, cephalosporins, and sulfonamides did not affect leukocyte function. However, some drugs were detrimental, notably chloramphenicol, tiamulin, tetracycline, gentamicin, rifampicin, amikacin, and nitrofurantoin. In vitro investigations on the use of anti-inflammatory agents demonstrated that methylprednisolone had a stabilizing effect on leukocytes by maintaining viability and reducing degranulation, whereas flumethasone was detrimental to cell viability. The nonsteroid agent, ibuprofen, decreased viability and increased degranulation but also increased phagocytosis and bacterial killing. Intramammary infusion of anti-inflammatory agents was generally ineffective in lowering somatic cell counts of endotoxin-infused quarters, but certain drugs may be advantageous in limiting milk production losses during udder inflammation.