Invited review: effect of udder health management practices on herd somatic cell count.

A systematic review of the scientific literature on relationships between management practices used on dairy farms and herd somatic cell count (SCC) was undertaken to distinguish those management practices that have been consistently shown to be associated with herd SCC from those lacking evidence of association. Relevant literature was identified using a combination of database searches (PubMed, Medline, CAB, Agricola, and Web of Science) and iterative screening of references. To be included in the review, a manuscript had to be published after 1979 in French, English, or Dutch; study design had to be other than case report or case series; herds studied had to be composed of ≥ 40 milking cows producing on average ≥ 7,000kg of milk in 305 d; interventions studied had to be management practices applied at the herd level and used as udder health control strategies; and SCC had to be measured using electronic cell counting methods. The 36 manuscripts selected were mainly observational cross-sectional studies; 8 manuscripts dealt exclusively with automatic milking systems and 4 with management of calves and heifers and its effect on SCC in early lactation heifers. Most practices having consistent associations with SCC were related to milking procedures: wearing gloves during milking, using automatic take-offs, using postmilking teat dipping, milking problem cows last, yearly inspection of the milking system, and use of a technique to keep cows standing following milking; all were consistently associated with lower herd SCC. Other practices associated with lower SCC were the use of a freestall system, sand bedding, cleaning the calving pen after each calving, surveillance of dry-cow udders for mastitis, use of blanket dry-cow therapy, parenteral selenium supplementation, udder hair management, and frequent use of the California Mastitis Test. Regarding SCC of heifers, most of the consistent associations reported were related to interventions made during the peripartum period. Studies on automatic milking systems have frequently reported elevation of the herd SCC following transition to the new system. These elevations seemed to be mediated both by the lack of monitoring of chronically infected cows and by an elevated incidence of intramammary infections. By assembling the results reported in many different studies, this review generates a more comprehensive understanding of the management practices influencing SCC and highlights areas of SCC control knowledge that lack evidence of effectiveness.

Stun gun injury: a new presentation of the battered child syndrome.

Stun guns are self-protection devices that are increasingly available with few restrictions on their use and sale. We present a case of child abuse with a stun gun. The signs of such abuse are often subtle, and they may be underrecognized currently. The skin lesions that are often seen are hypopigmented circular macules, measuring approximately 0.5 cm in diameter. They may be raised slightly and erythematous if inflicted recently Most characteristic of stun gun assault is pairing of lesions approximately 5 cm apart. We discuss the design, operation, and effects of stun guns, and give an extensive differential of abusive and nonabusive circular lesions.

Sequential ADP-ribosylation pattern of nucleosomal histones. ADP-ribosylation of nucleosomal histones.

The pattern of nucleosomal histones poly(ADP-ribosyl)ation is changed under conditions which affect the poly(ADP-ribosyl)ation state of the enzyme. At low NAD concentrations the enzyme can poly(ADP-ribosyl)ate histones H1 and H1, H2A, A2A, and H2B. However at NAD concentrations above 10 microM the enzyme preferentially poly(ADP-ribosyl)ates histone H1 to a hyper ADP-ribosylated form. Furthermore we have observed hyper ADP-ribosylation of histone H2B at NAD concentrations of 10 microM suggesting that histone H2B can undergo the same type of ADP-ribosylation pattern as histone H1. Also at higher NAD concentrations an elongation of the polymer attached to the enzyme and other nuclear proteins takes place.

Nucleosomal poly(ADP-ribose) polymerase: properties and relaxation of the chromatin structure.

The properties of poly(ADP-ribose) polymerase associated to nucleosomes and nuclei were analyzed by measuring enzymatic activity, isolating poly(ADP-ribosylated) histones and by electron microscopy. The enzyme was found to be most active in tri- and tetranucleosomes. The presence of NaC1 (0 to 200 mM) in the incubation medium showed a very small inhibitory effect on the enzymatic activity of isolated nucleosomes; however, the enzyme activity of incubated nuclei showed a gradual reduction with increasing salt concentrations leading to an almost complete inhibition at 200 mM NaC1. In parallel, the histones H1 extracted from isolated nucleosomes incubated at 200 mM NaC1 were hyper(ADP-ribosylated), whereas the histones H1 extracted from nuclei chromatin showed no highly modified forms at 200 mM NaC1. The effect of ethidium bromide (EB) was also analyzed and was found to stimulate enzyme activity in tetranucleosomes and octanucleosomes but not in dinucleosomes and nucleosomes of 20 repeat units. Electron microscopic analysis of poly(ADP-ribosylated) nucleosomes does not show the presence of aggregates at low ionic strength. However at higher ionic strengths the presence of localized relaxed domains of chromatin is evidenced in condensed nucleosomes.

Correlation between endogenous nucleosomal hyper(ADP-ribosyl)ation of histone H1 and the induction of chromatin relaxation.

The effect of poly(ADP-ribose) synthesis on chromatin structure was investigated by velocity sedimentation and electron microscopy. We demonstrate that locally relaxed regions can be generated within polynucleosome chains by the activity of their intrinsic poly(ADP-ribose)polymerase. This relaxation phenomenon is also shown to be NAD dependent and to be correlated with the formation of hyper(ADP-ribosyl)ated forms of histone H1. Evidence is also presented which suggests that hyper(ADP-ribosyl)ated histone H1 is neither released from the relaxed chromatin, nor does it seem to participate in polynucleosomal aggregation.

Poly(ADP-ribosyl)ation of chromatin: kinetics of relaxation and its effect on chromatin solubility.

We have studied the kinetics of relaxation of poly(ADP-ribosyl)ated polynucleosomes produced by endogenous enzyme activity by comparing the generation of hyper(ADP-ribosyl)ated histone H1 and its effect on the chromatin structure as revealed by electron microscopy. A correlation can be established between the appearance of histone H1 modified forms and the localized relaxation of the chromatin. We have also noticed, in parallel, that poly(ADP-ribosyl)ated chromatin showed increased solubility in the presence of Mg2+ and 0.2 M NaCl. Electron microscopic examination of the solubilized chromatin produced by poly(ADP-ribosyl)ation shows polynucleosomes exhibiting more relaxed conformation, whereas an increasing amount of hyper(ADP-ribosyl)ated histone H1 is found in the pellet, as shown by acid-urea-polyacrylamide electrophoretic separation of histone extracts.