Objective—To determine the effect of histamine on
the contractile elements of the respiratory tract in
neonatal calves and young adult cattle.
Sample Population—Samples of trachealis muscle,
bronchi, and intrapulmonary arteries and veins dissected
from the respiratory tracts of healthy bovids (2
to 8 days and 16 to 20 months old).
Procedure—Histamine cumulative concentrationeffect
curves (10–8 to 10–3M) were constructed in duplicate
smooth muscle samples mounted in organ
baths. Contractile responses to histamine were compared
with reference contractions elicited by methacholine
(10–5M) for airways or KCl (127mM) for vessels.
Results—In young adult cattle, trachealis muscle had
a substantial contractile response to histamine (84%
of methacholine-induced contraction), whereas
bronchi reacted slightly (15 and 20% for large and
small bronchi, respectively). Although contractile
responses to KCl were comparable in arteries and
veins, histamine-induced contractions were greater
for intrapulmonary veins than for arteries (202 vs 48%
of KCl-induced contraction). In neonatal calves, histamine-
induced contraction of veins also exceeded that
of arteries (230 vs 54% of KCl-induced contraction);
however, unlike in young adult cattle, histamine produced
notable contraction of large and small bronchi
(48 and 60% of methacholine-induced contraction,
Conclusions and Clinical Relevance—Compared
with intrapulmonary arteries, intrapulmonary veins
have greater contractile responses to histamine in
neonatal and young adult cattle. Data suggest loss of
histamine responsiveness in bronchial smooth muscle
as neonatal calves grow to young adults.
Venodilation may be useful in treatment of lung
edema in cattle. (Am J Vet Res 2003;64:819–822)
Objective—To determine the contribution of MX dynamin, oligoadenylate synthetase (OAS), and double-stranded RNA-dependent protein kinase R (PKR) to the antiviral effects of type 1 interferons (IFNs) against bovine parainfluenza-3 virus (PI-3V) infection of Vero cells.
Sample Population—Vero cell cultures.
Procedures—PI-3V yield was first compared between control and transfected type 1 IFNs– incompetent Vero cells expressing recombinant OAS or MX proteins. Afterwards, phosphorylation of eukaryotic initiation factor 2 α (eIF2α) was used to scale the degree of PKR activation upon infection of Vero cells by PI-3V.
Results—Overexpression of OAS did not result in significantly decreased viral replication. Phosphorylated eIF2α forms, the hallmark of PKR activation, were not increased in IFNα-primed infected Vero cells. Although human MXA contributed to partial blockade of replication of bovine PI-3V, the antiviral effect was not as strong as that of IFNα.
Conclusions and Clinical Relevance—The powerful anti-Paramyxovirus activity of type 1 IFNs is mediated by noncanonic pathways.