The role of anti-variable surface glycoprotein antibody responses in bovine trypanotolerance

It has been reported that some breeds of cattle such as the N'Dama mount a more effective antibody response to the variable surface glycoprotein coat of trypanosomes and that this may contribute to their ability to control the infection. Thus we have investigated antibody responses to surface exposed epitopes of the variable surface glycoprotein in Trypanosoma congolense -infected N'Dama (trypanotolerant) and Boran (susceptible) cattle. Similar titres and isotypes were found in both N'Damas and Borans indicating that trypanotolerance is not associated with superior antibody-mediated destruction of trypanosomes. However, significant differences in antibody responses to cryptic VSG epitopes and non-trypanosome antigens were identified. Trypanosusceptible Boran cattle had low IgG₁ responses to cryptic epitopes but high IgM responses to non-trypanosome antigens such as β-galactosidase. In contrast the N'Dama cattle had significantly higher IgG₁ responses to cryptic VSG epitopes and negligible responses to β-galactosidase. These results indicate differences in the induction of anti-trypanosome immune responses between trypanotolerant and susceptible cattle infected with T. congolense     

Epitopes of bovine leukemia virus glycoprotein gp51 recognized by sera of infected cattle and sheep

Sera of BLV-infected cattle and sheep are tested for their reactivity with different gp51 subregions by competition with radiolabeled monoclonal antibodies directed against 8 different gp51 epitopes. Sheep antisera are found to be very polyvalent, since they are able to displace the fixation of any of the mouse monoclonal antibodies to gp51. Bovine antisera do not display significant competition with monoclonal antibodies direct against 5 out of 8 gp51 epitopes. The bovine antibody response to gp51 is focused to a limited subregion of this molecule, bearing 3 epitopes (F, G and H) recognized by antibodies with virus-neutralizing activity. The differential reactivity of cattle and sheep antisera to BLV gp51 is discussed in relation to the pathology of BLV infection in these two species.     

Reconstitution of squid and cattle rhodopsin by the use of metaretinochrome in their respective membranes

Retinochrome is, even in membranes, converted to metaretinochrome by exposure to orange light. Upon incubation of metaretinochrome in membranes with cattle opsin in rod outer segment membranes, cattle rhodopsin is reconstituted in the dark. When opsin is present in molar excess to metaretinochrome, about 80% of the prosthetic retinal of retinochrome present initially is utilized for the reconstitution of cattle rhodopsin. One reason why all of the prosthetic retinal is not used for the rhodopsin reconstitution is that metaretinochrome transforms slowly to retinochrome during incubation in the dark and another is that metaretinochrome is in a photoequilibrium mixture with a trace of retinochrome after exposure to orange light.Squid rhodopsin is reconstituted when a mixture of metaretinochrome and squid opsin in their respective membranes is incubated in the dark. The reconstituted rhodopsin is converted to acid or alkaline metarhodopsin by exposure to orange light at neutral or alkaline pH, respectively.Three possible mechanisms for the transference of 11-cis retinal from metaretinochrome in a membrane to opsin in a different membrane were considered: (1) the migration of 11-cis retinal through an aqueous medium between the separate membranes, (2) the migration of 11-cis retinal from metaretinochrome to opsin in a fused membrane and (3) the transfer of retinal from membrane to membrane in close contact. In conclusion, the first two mechanisms were inapplicable and the third appeared to explain the present experimental findings.The possibility is discussed that the photoproduct of retinochrome may contribute to the rhodopsin synthesis as an effective donor of 11-cis retinal to opsin in the squid retina.     

Prolonged suppression of serum concentrations of melatonin in prepubertal heifers

Our objective was to suppress the daily surge of melatonin in serum of prepubertal dairy heifers by manipulating intensity of light (Experiment 1) and duration of exposure to light (Experiment 2). Heifers in Experiment 1 were exposed to either 12 hr of darkness (000 lux, control), or 400, 800, or 1,200 lux of light during the last 6 hr of their usual 12-hr nocturnal period. During this 6-hr exposure to various intensities of light, melatonin concentrations were similar to their respective daytime baseline values measured under 400 lux of light, but were 62% to 82% lower than melatonin concentrations during their nocturnal surge period. Suppression of melatonin concentrations was similar between 400 and 1,200 lux of light. In Experiment 2, heifers were exposed to LD 8:16, LD 16:8, LD 20:4, or LD 24:0 photoperiods (1,200 lux) for 4 months. Throughout treatment, concentrations and durations of the melatonin surge were suppressed in the LD 24:0 group and were greatest (during the nocturnal period) in the LD 8:16 group. Concentrations of prolactin in serum were elevated in animals under long days relative to LD 8:16 treatment and respective pretreatment periods. In conclusion, continuous light at an intensity of 1,200 lux suppressed the nocturnal surge of melatonin, but increased secretion of prolactin for at least 4 months in prepubertal heifers.     

RENIN AND PRORENIN IN REPRODUCTIVE TISSUES DURING GESTATION IN PIGS AND CATTLE

1. High concentrations of prorenin and active renin were previously found in ovarian follicular fluid from cattle but not from pigs. In the present study female reproductive tissues and fluids from cattle and pigs during gestation were investigated to clarify a possible species difference in active renin and prorenin concentrations. 2. Very high concentrations of active renin but no prorenin were found in corpus luteum from both species. 3. Relatively low concentrations of active renin, in the same order as in maternal blood plasma, were found in myometrium, endometrium, placenta and fetal membranes from both species. Prorenin was undetectable in these tissues except for bovine myometrium and porcine endometrium in some animals. 4. The concentrations of active renin and prorenin in amnionic fluid from both species were below the maternal plasma values. In allantoic fluid the concentrations were higher than in amnionic fluid. 5. The plasma concentrations of active renin and prorenin did not change during gestation in pigs. This finding is in contrast to the observations in humans and does not support a systemic effect of prorenin during gestation. 6. The presence of renin in the reproductive tissues, especially the very high concentrations in the corpus luteum, indicates a local function of the renin-angiotensin system during gestation.     

The molecular weight of hyaluronate in the aqueous humour and vitreous body of rabbit and cattle eyes

The molecular weight distribution of hyaluronate in the aqueous humour and vitreous body of rabbit and cattle has been determined by gel chromatography. The eluate from the column was monitored by a radioassay, whereby the molecular weight distribution of 15–20 μg samples could be analysed. Control experiments were carried out with radioactively-labelled hyaluronate added to bovine material to estimate the degradation of the polymer during handling of the ocular fluids. It was shown that in vitro degradation does not appreciably affect the results.The analyses show a considerable polydispersity of the hyaluronate preparations. There is also a marked variation in the degree of polymerization between the two species. Hyaluronate from rabbit vitreous has a weight-average molecular weight ($\text{M}{}_{\mathrm{<mtext>w</mtext>}}$) of 2–3 × 10⁶ while adult bovine vitreous displays a value of about 5–8 × 10⁵. The hyaluronate of bovine vitreous varies with age. In newborn calf, a value of 3 × 10⁶ was registered. This value dropped to about 5 × 10⁵ in old cattle.The hyaluronate in the aqueous humour of rabbit showed a considerably higher molecular weight than that of the vitreous indicating that part of the hyaluronate in the anterior segment originates elsewhere than the vitreous. The differences between hyaluronate from the aqueous humour of adult cattle and that from the vitreous were more complex. As with the rabbit, a relatively large proportion of hyaluronate in the aqueous humour was of high-molecular weight, but, in contrast, the aqueous humour also contained material which had a lower degree of polymerization than the hyaluronate in the vitreous. The proportion of high-molecular weight material in bovine aqueous humour seemed to be lower in the summer than in the winter.     

Clostridium difficile PCR ribotypes in calves, Canada

We investigated Clostridium difficile in calves and the similarity between bovine and human C. difficile PCR ribotypes by conducting a case-control study of calves from 102 dairy farms in Canada. Fecal samples from 144 calves with diarrhea and 134 control calves were cultured for C. difficile and tested with an ELISA for C. difficile toxins A and B. C. difficile was isolated from 31 of 278 calves: 11 (7.6%) of 144 with diarrhea and 20 (14.9%) of 134 controls (p = 0.009). Toxins were detected in calf feces from 58 (56.8%) of 102 farms, 57 (39.6%) of 144 calves with diarrhea, and 28 (20.9%) of 134 controls (p = 0.0002). PCR ribotyping of 31 isolates showed 8 distinct patterns; 7 have been identified in humans, 2 of which have been associated with outbreaks of severe disease (PCR types 017 and 027). C. difficile may be associated with calf diarrhea, and cattle may be reservoirs of C. difficile for humans.     

The Pathogenesis of Foot‐and‐Mouth Disease I: Viral Pathways in Cattle

In 1898, foot‐and‐mouth disease (FMD) earned a place in history as the first disease of animals shown to be caused by a virus. Yet, despite over a century of active investigation and elucidation of many aspects of FMD pathogenesis, critical knowledge about the virus–host interactions is still lacking. The aim of this review is to provide a comprehensive overview of FMD pathogenesis in cattle spanning from the earliest studies to recently acquired insights emphasizing works which describe animals infected by methodologies most closely resembling natural infection (predominantly aerosol or direct/indirect contact). The three basic phases of FMD pathogenesis in vivo will be dissected and characterized as: (i) pre‐viraemia characterized by infection and replication at the primary replication site(s), (ii) sustained viraemia with generalization and vesiculation at secondary infection sites and (iii) post‐viraemia/convalescence including resolution of clinical disease that may result in long‐term persistent infection. Critical evaluation of the current status of understanding will be used to identify knowledge gaps to guide future research efforts.     

牛肺表面活性物质治疗新生儿呼吸窘迫综合征临床观察与护理

[目的]观察牛肺表面活性物质(珂立苏)联合机械通气治疗新生儿呼吸窘迫综合征(NRDS)的疗效。[方法]对27例NRDS患儿在机械通气的同时,经气管导管滴入珂立苏,同时在NRDS患儿治疗过程给予保暖、保持呼吸道通畅、保证足够的营养和热量、严格无菌操作等护理。[结果]27例患儿治愈17例,明显好转6例,2例于刚撤机后家属要求回当地医院治疗,放弃治疗及病死各1例。23例NRDS患儿用药效果好,面色红润,血氧饱和度维持在87%~93%。[结论]珂立苏治疗NRDS疗效确切,早期足量应用珂立苏并给予积极有效的护理是治疗NRDS成功的有效方法。     

Protecting babies: vaccine strategies to prevent foetopathy in Neospora caninum-infected cattle

Neospora caninum is an apicomplexan protozoan parasite that is a significant infectious abortifacient agent in cattle. Despite the fact that it is a member of a well described taxonomic group, it is a relatively newly discovered parasite and its biology is not yet fully understood. Cattle become infected either congenitally via transplacental transmission or post-natally by ingesting oocysts derived from the definitive host; dogs and coyotes are the only definitive hosts that have been described to date. It is not known which of these two forms of transmission occurs most frequently and which is the most likely to result in abortion; there are no drugs available to treat infected cattle, so current control strategies rely on prevention of infection by management methods and strict hygiene; an effective vaccine would be a great advantage in its control. Neospora caninum is an economically important veterinary pathogen, but we can also draw analogies between its foetopathic effects and those of human pathogens such as Toxoplasma gondii, Chlamydophila abortus and Plasmodium falciparum. Understanding the immune response and the materno-foetal relationship in N. caninum-infected cattle may help us to design vaccination strategies, not only for neosporosis but also for other foetopathic agents.