Oxytocin release and milk removal in ruminants

Before milking, less than 20% of the milk yielded by dairy cows is stored within the cistern, where it is immediately available for removal. Most of the milk is available for the milking machine only after milk ejection, which occurs in response to tactile teat stimulation and oxytocin release. For complete milk removal, milk ejection is necessary throughout the entire milking process. The continuation of stimulatory effect of the milking machine until the end of milking is, therefore, essential. Premilking teat stimulation causes induction of alveolar milk ejection before the start of milking. Thus, bimodal milk flow curves (i.e., interruption of milk flow after removal of the cisternal milk) are avoided. Continual ejection of milk is dependent on the presence of elevated oxytocin concentrations during the entire milking. Any interruption of the milk ejection process can disturb milk removal. Disruption of milk removal can be caused by peripheral inhibition of oxytocin effects on the mammary gland or by inhibition of oxytocin release by the central nervous system. Peripheral inhibition is induced by elevated concentrations of catecholamines through stimulation of alpha-adrenergic receptors in the mammary gland, likely via changes in ductal resistance. Inhibition of oxytocin release by the central nervous system has been observed in primiparous cows immediately after parturition, during peak estrus, and during milking in unfamiliar surroundings; concentrations of beta-endorphin and cortisol are elevated in this situation. However, the role of endogenous opioid peptides in the inhibition of oxytocin release in cows remains unclear. In conclusion, during machine-milking, the physiological requirements of the cows need to be considered, and, most importantly, stressors must be minimized.     

Sustainable helminth control of ruminants in developing countries

Widespread anthelmintic resistance, at least amongst the important nematode parasites of small ruminants, threatens the sustainability of these livestock industries throughout both the developed and developing world. The exacerbation of this problem over the last decade or so, has provided the impetus for research into non-chemotherapeutic parasite control alternatives, such as host genetic resistance, grazing management, worm vaccines and biological control. Although some of these options provide practical benefits if currently adopted, or exciting prospects for the future, collectively they are unlikely to dispense with the need for the timely intervention of effective anthelmintic treatment. The issue of sustainability of helminth control practices therefore rests with the preservation of anthelmintic effectiveness through the implementation of principles of integrated pest management. Herein lies the difficulty-putting the principles into practice. Much of the research into sustainable nematode parasite control of ruminants has been done in the developed rather than the developing world, and the efforts to transfer this information to livestock owners has also been commensurately greater in the former. However the need for research and technology transfer is much more urgent in the developing world because of the lack of scientific and financial resources, the greater dependence on livestock industries and the much greater severity of the problem of anthelmintic resistance. This will require a major philosophical change in the affluent western world to the funding of national and international aid organisations who are largely responsible for these activities.     

Ammonia-hyperproducing bacteria from New Zealand ruminants

Pasture-grazed dairy cows, deer, and sheep were tested for the presence of ammonia-hyperproducing (HAP) bacteria in roll tubes containing a medium in which tryptone and Casamino Acids were the sole nitrogen and energy sources. Colonies able to grow on this medium represented 5.2, 1.3, and 11.6% of the total bacterial counts of dairy cows, deer, and sheep, respectively. A total of 14 morphologically distinct colonies were purified and studied further. Restriction fragment length polymorphisms of 16S rRNA genes indicated that all isolates differed from the previously described HAP bacteria, Clostridium aminophilum, Clostridium sticklandii, and Peptostreptococcus anaerobius. Carbon source utilization experiments showed that five isolates (C2, D1, D4, D5, and S1) were unable to use any, or very few, of the carbon sources tested. Biochemical tests and phylogenetic analyses of 16S ribosomal DNA sequences indicated that all isolates were monensin sensitive; that D1 and S1 belonged to the genus Peptostreptococcus, that D4 and D5 belonged to the family Bacteroidaceae, where D4 was similar to Fusobacterium necrophorum; and that C2 was most similar to an unidentified species from the genus Eubacterium. Growth on liquid medium containing tryptone and Casamino Acids as the sole nitrogen and energy source showed that D1, D4, and S1 grew rapidly (specific growth rates of 0.40, 0.35, and 0.29 h-1, respectively), while C2 and D5 were slow growers (0.25 and 0.10 h-1, respectively). Ammonia production rates were highest in D1 and D4, which produced 945.5 and 748.3 nmol/min per mg of protein, respectively. Tests of individual nitrogen sources indicated that D1 and D4 grew best on tryptone, S1 grew equally well on Casamino Acids or tryptone, and C2 and D5 grew poorly on all nitrogen sources. The intact proteins casein and gelatin did not support significant growth of any of the isolates. These isolates extend the diversity of known HAP rumen bacteria and indicate the presence of significant HAP bacterial populations in pasture-grazed New Zealand ruminants.     

Some aspects of inhibited development of trichostrongylids in ruminants

Inhibited development is an important aspect of the biology of some gastrointestinal nematodes of ruminants, particularly species of the subfamily Ostertagiinae and Haemonchus spp. There is a seasonality in the occurrence of the phenomenon. It tends to occur predominantly during the unfavourable season for the free-living stages. Thus 'winter' and 'summer-dry season' patterns of inhibition can be observed. Furthermore, the phenomenon is influenced by immunity of the host and by management factors. Different studies show conflicting results on the phenomenon of inhibition. This is examplified by studies related to H. contortus in small ruminants. Other studies indicate that large differences in propensity for inhibition can indeed occur in a single region. However, it has to be stressed that inadequate necropsy techniques can easily result in underestimation of the proportion of inhibited larvae, particularly in Haemonchus spp. in cattle. The macrocyclic lactones are highly effective against inhibited larvae of gastrointestinal nematodes. Treatment may even prevent establishment of inhibited larvae of Ostertagia and Trichostrongylus axei up to 1 month after treatment. The efficacy of benzimidazoles seems to be lower in the middle of the 'inhibition' period than at the beginning or the end. Some studies indicated that the presence of inhibited stages may be important for the build up of immunity. However, removal of high inhibited O. ostertagi burdens at housing does not impair development of immunity. Very little progress has been made on the molecular mechanisms of inhibited development.     

Alternative pathway of complement in ruminants: role in infection

Besides being initiated by antigen-antibody complexes, the classical pathway also can be activated by two innate mechanisms: (1) A family of proteins called collectins, which resemble C1q, bypass the activation of C1q. (2) Acute phase proteins, belonging to the family of pentraxins, activate the classical pathway by binding to C1q. The term 'alternative' complement pathway is a misnomer. This system is a primary primitive immune mechanism. It is phylogenetically older than the classical pathway. Contrary to the classical pathway, it does not require development of a specific immune response before getting into action. It acts within minutes after the microorganism has entered the body. The alternative pathway is continually activated at a low controlled rate but amplified by the surface of intruding microorganisms. It has the capacity to distinguish between self and non-self. Many nonpathogenic microorganisms are killed by the alternative pathway of complement. Pathogens have developed evasion mechanisms to escape the killing effect of this pathway. The kinetics of the activation of the alternative pathway of ruminants differs from that of mouse and man. The difference might be mediated by conglutinin.     

Acute poisoning in children

This prospective study comprised 120 children brought to the hospital with the history of acute poisoning. Poisonings occurred accidentally in 116 cases (96.7%) and 78 cases (65%) were children aged 1-4 years. Medical aid was sought earliest in case of children with animal bite and in infants. Kerosene and medications accounted for 72 cases (60%) of poisoning exposures. None of the care-takers of children received any instruction regarding prevention of accidents and poisoning prior to the episode, in spite of multiple contacts with health-care providers. Role of health education and other preventive measures are stressed.     

Gc-globulin in paracetamol poisoning

Gc-globulin scavenges actin liberated from necrotic cells. We measured serum Gc-globulin and the degree of complexing with monomeric actin (complex ratio) in the initial phase of paracetamol (acetaminophen) intoxication and related this to the severity of liver necrosis and the clinical course. In eighteen patients with paracetamol intoxication serial measurements of serum Gc-globulin and complex ratio were determined from admission and every three hours thereafter. Eight patients developed hepatic encephalopathy (HE) and two of them died. On admission all patients had significantly reduced serum Gc-globulin levels compared to normal individuals, and patients with HE had significantly lower values than patients without HE. All patients with HE had at least three samples, where Gc-globulin was below 120 mg/l (35% of normal). Complex ratio on admission did not differ significantly in the patients with and those without HE. The peak complex ratio was higher in patients with HE than in patients without HE, and three of four patients with peak complex ratio above 75% had HE. In conclusion, Gc-globulin levels were found to be decreased in patients with paracetamol intoxication; this decrease correlated with the most severe sign of liver dysfunction, HE. Serum Gc-globulin below 120 mg/l and peak complex ratios above 75% may be critical values.     

Paracetamol poisoning in infancy

An eight-week old infant with alcohol embryopathy, weighing 3,700 g, was found to have abnormal liver functions (GPT 312 U/l, Quick value 25%) after surgical repair of a stenosis of the left ureter at its origin. The hospital notes indicated that the infant had been given a total of 1.6 g paracetamol over 60 hours for postoperative restlessness and pain. The serum paracetamol level was 60 mg/l 8 hours after the last dose of the drug. Blood exchange transfusion lowered the paracetamol level to 11 mg/l within 14 hours. After the exchange transfusion further signs of poisoning, namely renal impairment and a severe encephalopathy were noted, and Candida was demonstrated in urine, tracheal secretion and ascites. The renal and hepatic damage proved reversible under symptomatic treatment. But the child, now 1 year old, is severely retarded mentally and in its motor functions. These sequelae may be a residue of the paracetamol poisoning, complications of the clinical course or a combination of the two.