Physics of Nuclei: Key Role of an Emergent Symmetry.

We show through first-principles nuclear structure calculations that the special nature of the strong nuclear force determines highly regular patterns heretofore unrecognized in nuclei that can be tied to an emergent approximate symmetry. This symmetry is ubiquitous and mathematically tracks with a symplectic symmetry group. This, in turn, has important implications for understanding the physics of nuclei: we find that nuclei are made of only a few equilibrium shapes, deformed or not, with associated vibrations and rotations. It also opens the path for ab initio large-scale modeling of open-shell intermediate-mass nuclei without the need for renormalized interactions and effective charges.

Persistence and Retention of Porcine Reproductive and Respiratory Syndrome Virus in Stable Flies (Diptera: Muscidae).

We investigated the acquisition of porcine reproductive and respiratory syndrome (PRRS) virus by the stable fly (Diptera: Muscidae; Stomoxys calcitrans (L.)) through a bloodmeal, and virus persistence in the digestive organs of the fly using virus isolation and quantitative reverse-transcription PCR (qRT-PCR). Stable flies were fed blood containing live virus, modified live vaccine virus, chemically inactivated virus, or no virus. Stable flies acquired PRRSV from the bloodmeal and the amount of virus in the flies declined with time, indicating virus did not replicate in fly digestive tissues. Virus RNA was recovered from the flies fed live virus up to 24 h postfeeding using virus isolation techniques and 96 h using qRT-PCR. We further examined the fate of PRRSV in the hemolymph of the flies following intrathoracic injection to bypass the midgut barrier. PRRSV was detected in intrathoracically inoculated adult stable flies for 10 d using qRT-PCR. In contrast to what we observed in the digestive tract, detectable virus quantities in the intrathoracically inoculated stable flies followed an exponential decay curve. The amount of virus decreased fourfold in the first 3 d and remained stable thereafter, up to 10 d.

Assessment of Stomoxys calcitrans (Diptera: Muscidae) as a vector of porcine reproductive and respiratory syndrome virus.

Porcine Reproductive and respiratory syndrome (PRRS) is a globally significant swine disease caused by an arterivirus. The virus replicates in alveolar macrophages of infected pigs, resulting in pneumonia in growing pigs and late-term abortions in sows. Outbreaks occur on disparate farms within an area despite biosecurity measures, suggesting mechanical transport by arthropods. We investigated the vector potential of stable flies, Stomoxys calcitrans (L.) (Diptera: Muscidae), in the transmission of porcine reproductive and respiratory syndrome virus (family Arteriviridae, genus Arterivirus, PRRSV) under laboratory conditions. Stable flies were collected around PRRS-negative boar stud barns in North Carolina and tested for presence of the virus. Stable flies were collected on alsynite traps placed near the exhaust fan of the close-sided tunnel-ventilated buildings, suggesting blood seeking flies are attracted by olfactory cues. No flies were positive for PRRSV. We assessed transmission of the virus through an infective bite by feeding laboratory reared stable flies on blood containing virus and transferring them to naive pigs for subsequent bloodmeals. Transmission of the virus to naive pigs by infective bites failed in all attempts. The volume of blood contained within the closed mouthparts of the stable fly seems to be insufficient to deliver an infective dose of the virus. Stable flies are unlikely to transmit PRRSV from one pig to another while blood feeding. The fate of the virus after a bloodmeal remains to be determined.

Porcine circovirus type 2 (PCV2) vaccination is effective in reducing disease and PCV2 shedding in semen of boars concurrently infected with PCV2 and Mycoplasma hyopneumoniae.

The objectives were to determine whether the amount of porcine circovirus type 2 (PCV2) shed in semen increased in boars experimentally coinfected with Mycoplasma hyopneumoniae (MHYO), and whether PCV2 vaccination of boars prior to PCV2 exposure reduced PCV2 viremia and virus shedding in semen. Twelve specific-pathogen-free PCV2- and MHYO-naïve boars were randomly and equally assigned to one of four groups. Six boars were vaccinated against PCV2 (VAC) on Day 0; three PCV2 vaccinated and three non-vaccinated boars were inoculated with MHYO on Day 21, and all boars were challenged with PCV2 on Day 35. The four treatment groups included PCV2-Infected (I), VAC-PCV2-I, MHYO-PCV2-Coinfected (CoI), and VAC-MHYO-PCV2-CoI. Semen, blood swabs, feces, and serum samples were collected weekly until Day 70. All vaccinated boars had seroconverted to PCV2 by Day 35. Between Days 28 and 35, MHYO boars developed moderate respiratory disease, characterized by coughing, respiratory distress, mucopurulent nasal discharge and loss of body condition. One MHYO-PCV2-CoI boar died on Day 50. Boars in the PCV2-I and MHYO-PCV2-CoI groups had significantly higher PCV2 DNA loads in blood swabs than the remaining boars. Moreover, PCV2 vaccination significantly reduced the incidence and amount of PCV2 shedding in semen and feces. In summary, although concurrent MHYO infection did not influence PCV2 shedding patterns, coinfection of boars with PCV2 and MHYO resulted in severe clinical disease and viral shedding was significantly decreased by PCV2 vaccination.

Evaluation of the safety of four porcine circovirus type 2 tissue homogenate vaccines in a pig bioassay.

Ten four-week-old porcine circovirus type 2 (PCV-2) naive piglets were housed individually in a HEPA-filtered isolator and were randomly assigned to one of six treatment groups. Each of the two pigs in groups 1 to 4 received two intramuscular doses of 2 ml of one of four different autogenous tissue homogenate vaccines (THVs) 14 days apart, and the other two pigs received 2 ml of PCV-2 virus or sterile phosphate buffered saline. When the piglets were euthanased 14 days after the second dose, the injection sites were grossly and microscopically free of swelling, an inflammatory response or abscesses. The positive control pig, one of the two pigs in the THV-2 group and both pigs in the THV-3 group became viraemic. The PCV-2 DNA from the positive control pig and the pigs in the THV-3 group was identical to the PCV-2 DNA that they had been administered.

Detection of two porcine circovirus type 2 genotypic groups in United States swine herds.

In late 2005, sporadic cases of an acute onset disease of high mortality were observed in 10- to 16-week-old growing pigs among several swine herds of the United States. Tissues from the affected pigs in Kansas, Iowa, and North Carolina were examined, and porcine circovirus type 2 (PCV2) was detected consistently among these tissues. Phylogenetically, PCV2 can be divided into two major genotypic groups, PCV2-group 1 and PCV2-group 2. Whereas PCV2-group 1 isolates were detected in all the diseased animals, only two of the diseased animals harbored PCV2-group 2 isolates. This observation is important because PCV2-group 1 isolates had never been reported in the United States before (GenBank as of May 16, 2006), and they are closely related to the PCV2-group 1 isolates that have been described in Europe and Asia, previously. Our analysis revealed that each genotypic group contains a distinct stretch of nucleotide or amino acid sequence that may serve as a signature motif for PCV2-group 1 or PCV2-group 2 isolates.

Innervation of extraocular muscles in the rabbit.

The innervation of extraocular muscles in the rabbit was studied by using the methods of horseradish peroxidase (HRP) histochemistry, gross dissection, and quantitative morphology. Subdivisions of the oculomotor complex that innervate the superior rectus, inferior rectus, medial rectus, and inferior oblique and levator palpebrae are described, and our results are in agreement with previous accounts of the projections of this nucleus. Our analysis of the innervation of the lateral rectus and retractor bulbi muscles, however, differs from previous descriptions. The axons of approximately 80% of neurons in the abducens nucleus are in the VIth nerve and innervate the lateral rectus muscle, and approximately 15-20% are internuclear neurons both surrounding and intermingling with the motor neurons of the abducens nucleus. The interneurons project to the medial rectus subdivision of the contralateral oculomotor complex via the medial longitudinal fasciculus (MLF). Neurons in both the abducens and the accessory abducens nucleus innervate the retractor bulbi muscles via the VIth nerve. All neurons in the accessory abducens nucleus innervate the retractor bulbi muscles, but gross dissection revealed that the retractor bulbi is also innervated by the IIIrd nerve. The bases for differences between our data and previously published descriptions are discussed. The trochlear nucleus of the rabbit has not been previously studied by methods of axonal transport. The body of the nucleus, its caudal tail, the trajectories of axons entering the trochlear nerve, and soma size distributions are described. The trochlear nucleus contains approximately 900 neurons; most are motoneurons the axons of which travel in the trochlear nerve and decussate in the anterior medullary velum. Approximately 3% of trochlear motor neurons innervate the ipsilateral superior oblique muscle. Their soma size is significantly smaller than that of contralaterally projecting neurons. For comparative purposes, the innervation of extraocular muscles by the trochlear nerve was also investigated in several rodents and carnivores. In all animals studied, the percentage of trochlear neurons innervating the ipsilateral superior oblique muscle was strikingly uniform (2-4%). Gross dissection of the extraocular muscles revealed in the rabbit a muscle, innervated by the trochlear nerve, for which we propose the name "tensor trochleae." In the rabbit, this muscle is innervated by approximately one-third of the trochlear motor neurons.(ABSTRACT TRUNCATED AT 400 WORDS)