Short-term performance of mitral valve replacement with porcine bioprosthetic valves in dogs

Porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compound were newly developed for mitral valve replacement (MVR) in dogs. Five beagle dogs were performed a left thoracotomy and underwent MVR using the porcine bioprosthetic valves during cardiopulmonary bypass (CPB). A vein catheter inserted into right atrium and a vent catheter inserted into the right ventricle to drain. The hemodynamic conditions of CPB were excellent during surgery. The left atrial pressure was measured before and after MVR; there was no significant difference and it was normal. Thrombosis and the prosthetic valve regurgitation were not observed one week after MVR. Pressure half time (PHT) prolonged significantly (P<0.05) from 31.40 +/- 4.0 msec presurgery to 99.20 +/- 19.4 msec at seven days after MVR, although it indicated the normal range as the bioprosthetic valve. The symptom of the prosthetic valve failure was not observed. This study indicated that the MVR using porcine bioprosthetic valves under CPB might have been effective in dogs as a short-term evaluation.     

Efficacy of open patch-grafting under cardiopulmonary bypass for pulmonic stenosis in small dogs

Objective   To assess the efficacy of an open patch-graft technique under cardiopulmonary bypass (CPB) in small dogs.
Design and methods   A retrospective analysis of 10 dogs with pulmonic stenosis. Records between 1992 and 2002 were reviewed. The effect of surgical correction was evaluated and perioperative parameters were compared between survivors and non-survivors.
Results   The postoperative pulmonary pressure gradient was reduced in all seven surviving patients. Mean ± SE was 21.5 ± 7.4 mmHg (range 3.0–54.2 mmHg) and 6/7 dogs were < 40 mmHg at 3 months postoperatively. Comparing the data between those patients that survived and those that did not, the preoperative pressure gradient (P = 0.04) and volume of the Glucose-Insulin-Kalium solution used (P = 0.001) were significantly higher in those that did not survive.
Conclusion   Open patch-grafting can be performed in small-breed dogs and decreased the pulmonary pressure gradient in survivors at 3 months postoperatively. However, this technique is more invasive than balloon valvuloplasty and should be used cautiously in severely stenosed patients.     

An H9N2 influenza virus vaccine prepared from a non-pathogenic isolate from a migratory duck confers protective immunity in mice against challenge with an H9N2 virus isolated from a girl in Hong Kong

H9N2 influenza viruses circulate in wild birds and poultry in Eurasian countries, and have been isolated from pigs and humans in China. H9N2 viruses isolated from birds, pigs and humans have been classified into three sublineages based on antigenic and genetic features. Chicken antisera to H9N2 viruses of the Korean sublineage reacted with viruses of different sublineages by the hemagglutination-inhibition test. A test vaccine prepared from a non-pathogenic A/duck/Hokkaido/49/1998 (H9N2) strain of the Korean sublineage, obtained from our influenza virus library, induced immunity in mice to reduce the impact of disease caused by the challenge with A/Hong Kong/1073/1999 (H9N2), which is of a different sublineage. The present results indicate that an inactivated whole virus vaccine prepared from a non-pathogenic influenza virus from the library could be used as an emergency vaccine during the early stage of a pandemic caused by H9N2 infection.     

Daily Rhythms of Left Atrial Pressure in Beagle Dogs with Mitral Valve Regurgitation

Background: Mitral valve regurgitation (MR) causes increased left atrial pressure (LAP) and is associated with occurrence of clinical signs. It will be useful to understand diurnal variations of LAP for the management of MR.
Hypothesis: Circulatory parameters and diurnal rhythm are linked to clinical signs in cardiac diseases. LAP also exhibits a diurnal rhythm in dogs with MR.
Animals: Five healthy Beagle dogs weighing 9.8–12.8 kg (3 males and 2 females; aged 2 years) were used.
Methods: A radiotelemetry system for continuous measurement of LAP was used in this study. Rupture of the chordae tendineae was experimentally induced via left atriotomy, and a transmitter catheter was inserted into the left atrium. The body of the transmitter was implanted SC. After clinical condition was stabilized, the severity of MR was evaluated by echocardiography, and LAP was recorded for 72 consecutive hours for the analysis of diurnal variation.
Results: Abrupt increases in LAP, which averaged 16.7 mmHg, were observed at feeding periods. In contrast, strong diurnal LAP variations were found, with a significant but slight increase in daytime LAP compared with nighttime LAP.
Conclusions and Clinical Importance: Diurnal LAP is characterized by a slight but significant nocturnal decrease and abrupt increases in response to excitation. The latter seemed to be more important considering the relationship with clinical manifestations. The clinical relevance of exercise restriction in the management of MR was acknowledged.     

Development of vaccine strains of H5 and H7 influenza viruses

To establish vaccine strains of H5 and H7 influenza viruses, A/duck/Hokkaido/Vac-1/04 (H5N1) [Vac-1/04 (H5N1)], A/duck/Hokkaido/Vac-3/07 (H5N1) [Vac-3/07 (H5N1)], and A/duck/Hokkaido/ Vac-2/04 (H7N7) [Vac-2/04 (H7N7)] were generated from non-pathogenic avian influenza viruses isolated from migratory ducks. Vac-1/04 (H5N1) and Vac-3/07 (H5N1) were generated by genetic reassortment between H5N2 or H5N3 virus as an HA gene provider and H7N1 or H6N1 viruses as an NA gene provider. Vac-2/04 (H7N7) was a genetic reassortant obtained using H7N7 and H9 N2 viruses to give high growth character of the H9N2 virus in chicken embryonated eggs. The results of sequence analyses and experimental infections revealed that these H5N1 and H7N7 reassortant viruses were non-pathogenic in chickens and embryos, and had good growth potential in embryonated eggs. These viruses should be useful to develop vaccines against H5 and H7 highly pathogenic avian influenza viruses.     

Difference in Amounts and Composition of Dew from Different Types of Dew Collectors

Dew was collected using several kinds of collectors at the same time, and the composition was compared. The volumes per unit surface areas of dew formed were different based on the types of collectors. It is found that the amounts of the ions, which in part come from gaseous substances, such as organic acids, nitrous acid, etc., per unit area in dew increase with dew volume per unit surface area. On the other hand, chloride, nitrate, sodium, potassium and magnesium which come from only particles showed no variation with the dew volume per unit surface area. These results suggest that the composition of dew varied by the dew volume per unit surface area formed in the different collectors. Dew is usually collected on a polytetrafluoroethylene (PTFE) sheet. The above result suggests that the dew concentration on the PTFE sheet does not represent the real dew concentration on various materials, such as leaves, cars, roofs, road, etc. To determine the real concentration of dew on a material, the material itself has to be usedas a collector. The PTFE sheet could be used as a standard dew sampler forcomparison of dew formed at various places.     

A low pathogenic H5N2 influenza virus isolated in Taiwan acquired high pathogenicity by consecutive passages in chickens

H5N2 viruses were isolated from cloacal swab samples of apparently healthy chickens in Taiwan in 2003 and 2008 during surveillance of avian influenza. Each of the viruses was eradicated by stamping out. The official diagnosis report indicated that the Intravenous Pathogenicity Indexes (IVPIs) of the isolates were 0.00 and 0.89, respectively, indicating that these were low pathogenic strains, although the hemagglutinin of the strain isolated in 2008 (Taiwan08) had multibasic amino acid residues at the cleavage site (PQRKKR/G). In the present study, these H5N2 viruses were assessed for their intravenous and intranasal pathogenicity for chickens. It was examined whether Taiwan08 acquires pathogenicity through consecutive passages in chickens. Intravenous pathogenicity of Taiwan08 depended upon the age of the chickens used for the IVPI test; all of the eight-week-old chickens intravenously inoculated with Taiwan08 showed clinical signs but survived for ten days post inoculation (IVPI=0.68), whereas all the six-week-old chickens died (IVPI=1.86). Taiwan08-P8, which were passaged in chickens for eight times, killed all the eight-week-old chickens (IVPI=2.36). The four-week-old chickens died after intranasal inoculation of Taiwan08-P8, indicating that Taiwan08 must have become highly pathogenic during circulation in chicken flocks. These results emphasize the importance of a stamping out policy for avian influenza even if the IVPI of the causal virus is low.     

Effect of long-term administration of a prostacyclin analogue (beraprost sodium) on myocardial fibrosis in Dahl rats

Beraprost sodium (BPS) is an orally active prostacyclin analogue. The effects of BPS on the heart, including coronary circulation improvement, myocardial and vascular protection and anti-fibrosis effect on myocardium interstitium, have previously been demonstrated. However, the effects of BPS on hemodynamics, cardiac function and myocardial contractility in patients in the hypertrophic phase have not been clarified. Therefore, in the present study, the effects of BPS under long-term administration were investigated using the hypertension model of salt-sensitive Dahl rats. Six-week-old Dahl rats were divided into three groups, an 8% high salt diet group treated with BPS (BPS group), an untreated 8% high salt diet group (HHF group) and an untreated 0.3% low salt diet group (Control group), and observations were conducted until 17 weeks of age. In the BPS and HHF groups, the survival rates after 11 weeks of high salt diet intake were 87.5% and 47.1%, respectively (p<0.05). At 17 weeks of age, the atrial systolic peak velocity/early diastolic peak velocity and heart weight index of the BPS group decreased significantly compared with the HHF group (p<0.05). The HHF group exhibited significantly more severe myocardial fibrosis mainly in the endocardial layer of the left and right ventricles compared with the BPS and Control groups (p<0.05). In the present study, long-term BPS administration preserved diastolic function and prevented myocardial interstitial fibrosis in the non-compensatory phase. The results of the present study suggest that BPS is effective for treatment of hypertensive cardiac hypertrophy.     

Long-term clinical evaluation of mitral valve replacement with porcine bioprosthetic valves in dogs

This study evaluated the long-term clinical performance of newly developed porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compound for mitral valve replacement (MVR) in dogs. Five beagle dogs underwent MVR using the porcine bioprosthetic valves during cardiopulmonary bypass. Antithrombotic drugs were administered only for one month after MVR. Six months after MVR, transvalvular regurgitation was not observed in all dogs, paravalvular leakage was seen only in one dog. Twelve months after MVR, mild transvalvular regurgitations were observed in two dogs. Although diastolic atrioventricular pressure gradient was increased gradually, no significant differences were observed. Pressure half-time and valve area were within normal ranges as the bioprosthetic value. There was no clinical symptom of the thrombosis and the thrombogenesis was not observed in the porcine bioprosthetic valve and the annulus in all dogs for twelve months after MVR. The clinical findings suggest that antithrombogenicity of the valves were maintained, though the duability might not be enough in the long-term period.     

Surgical correction of pulmonic stenosis using transventricular pulmonic dilation valvuloplasty (Brock) in a dog

A two-month-old male long coated Chihuahua, which had symptoms including anorexia and decreased growth, was diagnosed with pulmonic valvular stenosis. Echocardiography showed the severe progression of pulmonary arterial velocity (6.29 m/s, Pressure gradient (PG); 158 mmHg). Transventricular pulmonic dilation valvuloplasty (Brock) was conducted, and stenosed valve was dilated by the oto forceps. Pleural effusion was observed postoperatively, however, it was diminished under the intensive care for five days after the surgery. The right ventricular systolic pressure was decreased to 60 mmHg in angiocardiography conducted two months postoperatively and the dog has kept a good general condition with recovered vigor and appetite.