Ectopic atrial arrhythmias arising from canine thoracic veins during in vivo stellate ganglia stimulation

The purpose of the present study was to determine whether thoracic veins may act as ectopic pacemakers and whether nodelike cells and rich sympathetic innervation are present at the ectopic sites. We used a 1,792-electrode mapping system with 1-mm resolution to map ectopic atrial arrhythmias in eight normal dogs during in vivo right and left stellate ganglia (SG) stimulation before and after sinus node crushing. SG stimulation triggered significant elevations of transcardiac norepinephrine levels, sinus tachycardia in all dogs, and atrial tachycardia in two of eight dogs. Sinus node crushing resulted in a slow junctional rhythm (51 +/- 6 beats/min). Subsequent SG stimulation induced 20 episodes of ectopic beats in seven dogs and seven episodes of pulmonary vein tachycardia in three dogs (cycle length 273 +/- 35 ms, duration 16 +/- 4 s). The ectopic beats arose from the pulmonary vein (n = 11), right atrium (n = 5), left atrium (n = 2), and the vein of Marshall (n = 2). There was no difference in arrhythmogenic effects of left vs. right SG stimulation (13/29 vs. 16/29 episodes, P = nonsignificant). There was a greater density of periodic acid Schiff-positive cells (P < 0.05) and sympathetic nerves (P < 0.05) at the ectopic sites compared with other nonectopic atrial sites. We conclude that, in the absence of a sinus node, thoracic veins may function as subsidiary pacemakers under heightened sympathetic tone, becoming the dominant sites of initiation of focal atrial arrhythmias that arise from sites with abundant sympathetic nerves and periodic acid Schiff-positive cells.     

Suppression of circulating concentrations of FSH and LH by inhibin and estradiol during the initiation of follicle deviation in mares

The role of estradiol and inhibin in suppression of FSH and LH during the initiation of follicle deviation was examined in mares. In Experiment 1, the two largest follicles (F1, F2) were retained during a wave and the rest were ablated as they reached > or =10 mm. The largest follicle was left intact (control, n=12) or was ablated when it reached > or =20.0 mm (Day 0; expected beginning of deviation). The second largest follicle continued growing (n=9) or regressed (n=4) after F1 ablation. Circulating estradiol and total inhibin decreased after Day 0 in the F2-regressing group, whereas estradiol increased after Day 0.5 and inhibin was unaltered in the control and F2-growing groups. Circulating FSH decreased in the control group and increased in the F2-regressing group after Day 0. In the F2-growing group, FSH increased between Days 0 and 0.5 and then decreased. Circulating LH increased between Days 0 and 2 in the F2-regressing group and between Days 0 and 0.5 in the F2-growing group. In Experiment 2, 0 or 1 follicle was retained in a wave followed by administration of 0 or 1 mg of estradiol at the expected beginning of deviation (Hour 0; 2 x 2 factorial design, n=4-6/group). Circulating total inhibin was higher and FSH was lower at Hour 0 in the 1-follicle than in the 0-follicle groups. Follicle-stimulating hormone decreased after Hour 0 in the 1-mg but not in the 0-mg groups, and the decrease in the 0-follicle/1-mg group was not to the level of that in the 1-follicle/1-mg group. Circulating LH was not affected by follicle number but was reduced by estradiol. Results supported the hypotheses that F1 near the beginning of deviation produces inhibin and estradiol and that the increase in circulating estradiol at the beginning of deviation induces FSH suppression in combination with other follicle substances (presumably inhibin). Results also indicated that the increase in estradiol induces suppression of LH.     

Ultrasonographic and endocrine aspects of follicle deviation, and acquisition of ovulatory capacity in buffalo (Bubalus bubalis) heifers

The objectives of this study were to determine the interval from ovulation to deviation and the diameter of the dominant (DF) and largest subordinate (SF) follicles at deviation in buffalo (Bubalus bubalis) heifers. Two methods of evaluation (observed vs. calculated) were used. FSH and LH profiles encompassing follicle deviation (Experiment 1), and the follicular diameter when the DF acquired ovulatory capacity (Experiment 2) were also determined. The time of deviation and the diameter of the DF and the largest SF at deviation did not differ between observed and calculated methods. Overall, follicle deviation occurred 2.6 ± 0.2d (mean ± SEM) after ovulation, and the diameters of the DF and SF at deviation were 7.2 ± 0.2 and 6.4 ± 0.2mm, respectively. No changes in plasma levels of FSH or LH were observed (P=0.32 and P=0.96, respectively). Experiment 2 was conducted in two phases according to the diameter of the DF during the first wave of follicular development at the time of LH challenge (25mg of pLH). In the first phase, follicles ranging from 5.0 to 6.0mm (n=7), 6.1 to 7.0mm (n=11), or 7.1 to 8.0mm (n=9) were used, and in the second phase, follicles ranging from 7.0 to 8.4mm (n=10), 8.5 to 10.0mm (n=10), or 10.1 to 12.0mm (n=9) of diameter were used. After the pLH treatment, the DF was monitored by ultrasonography every 12h for 48h. No ovulations occurred in heifers in the first phase. However, in the second phase, an effect of follicular diameter was observed on ovulation rate [7.0-8.4mm (0.0%, 0/10), 8.5-10.0mm (50.0%, 5/10), and 10.0-12.0mm (55.6%, 5/9)]. In summary, follicle deviation occurred 2.6d after ovulation in buffalo (B. bubalis) heifers, when the diameters of the DF and SF were 7.2 and 6.4mm, respectively. No significant changes in plasma concentrations of FSH or LH were detected. Finally, the acquisition of ovulatory capacity occurred when the DF reached 8.5mm in diameter.     

Myocardial ischemia-reperfusion damage impacts occurrence of ventricular fibrillation in dogs

To define the relationship between ischemia-reperfusion-induced myocardial damage (IRD) and the occurrence of ventricular tachycardia (VT) and fibrillation (VF), we studied 23 dogs with a three-dimensional activation mapping system. Left anterior descending (LAD) coronary artery occlusion and reperfusion were performed while recording electrograms during VF and atrial pacing. Prior nonischemic sites showing IRD, defined as at least 10% loss of electrogram voltage after reperfusion, had the longest ventricular effective refractory periods (ERPs). IRD sites also occurred more frequently in dogs with reperfusion VF (44 +/- 2 sites, P < 0.01) compared with dogs with VT (18 +/- 5 sites) and no VT (16 +/- 3 sites). In dogs (n = 3) with 3 h of reperfusion, 95% of IRD sites still had lower voltage than those recorded during occlusion. Activation mapping of the first eight complexes of VF had Purkinje or endocardial focal origin in 57%, and complexes originated from IRD sites in 28%. In contrast, dogs with only reperfusion VT also had Purkinje or endocardial focal origin in 79%, but only 5% (P < 0.01 vs. VF dogs) of the sites of origin had IRD. Therefore, dogs with reperfusion VF had more IRD sites where the ERP was longest, and more focal ventricular complexes originated from IRD sites, indicating that IRD may be one important factor in the occurrence of VF during reperfusion.     

Prior exposure of maiden ewes to rams enhances their behavioural interactions with rams but is not a pre-requisite to their endocrine response to the ram effect

In this study, we tested whether prior experience with rams would modify the behavioural and endocrine responses of maiden ewes to rams. During mid-anoestrus, sexually na?ve, maiden ewes were exposed to rams for 7 days (ram experienced, RE; n=61) or isolated from rams (ram na?ve, RN; n=63). All ewes were subsequently isolated from rams. In Experiment 1, RE (n=55) and RN (n=57) ewes were introduced to rams during late anoestrus. RE ewes had more total and positive interactions with rams than RN ewes (P<0.001). RE ewes showed more ram seeking behaviour and spent more time in proximity of rams than RN ewes (at least; P<0.05). In Experiment 2, RE (n=6) and RN (n=6) ewes were introduced to rams midway through a frequent blood sampling regime in late anoestrus. Ram introduction stimulated an increase in LH pulse frequency and basal LH in both RE and RN ewes (at least P<0.05). RE ewes had an increase in mean LH concentrations (P<0.01) that failed to reach significance in RN ewes (P<0.1). There was no significant effect of prior experience with rams on LH pulse frequency, amplitude or whether ewes had an LH surge. In conclusion, prior experience with rams is important in developing appropriate ewe-ram interactions but is not a pre-requisite to the endocrine response to the ram effect.     

Calculated follicle deviation using segmented regression for modeling diameter differences in cattle

Segmented linear regression alone or in combination with simple linear regression was evaluated as an objective method to calculate the beginning of follicle deviation by modeling the sequential (Experiment 1) and non-sequential or single-point (Experiment 2) differences in diameter between the future dominant (F1) and largest subordinate (F2) follicles of Wave 1 in cattle. The segmented regression consisted of Segment 1 representing the common growth phase, Segment 2 representing the period of dominance, and a Join Point connecting the two segments and representing the end of the common growth phase and the beginning of deviation. The model was fit to the diameter differences for each heifer in Experiment 1 (n=15) and the group of heifers in Experiment 2 (n=40). The optimal Join Point value that corresponded to the maximum R(2) was designated the calculated hour (Experiment 1) or diameter of F1 (Experiment 2) at the beginning of deviation. In Experiment 1, simple linear regression was used to calculate the corresponding diameter of F1 at the beginning of deviation. Observed deviation was determined by inspection of the diameter profiles of F1 and F2 for comparison to calculated deviation. In Experiment 1, the observed method determined the beginning of deviation in 80% of the heifers, whereas, the regression method calculated deviation in 93% of the heifers including two of the three heifers in which observed deviation was not discernable (no significant difference between methods). The mean hours of deviation after wave emergence (Hour 0) and diameters of F1 at the corresponding hours were not significantly different between the observed (62 h and 8.4 mm) and calculated (61 h and 8.8 mm) methods. In Experiment 2, the diameter of F1 at the beginning of calculated deviation was 8.2 mm. The results indicated that the segmented regression model can provide an objective and more accurate alternative to estimate follicle deviation, especially when observed deviation is obscured by the complexity of follicle development in some waves.     

The effect of superoxide dismutase in the myocardium during reperfusion in the dog.

The aim of the study was to investigate the pathological role of free radicals during myocardial reperfusion. Low (0.5 mg/kg body weight) and high doses (5 mg/kg) of superoxide dismutase (SOD) were infused into the left atrium of mongrel dogs for 4 min starting 29 min after ligation and 1 min before reperfusion of the left anterior descending coronary artery (LAD). Arterial blood pressure, heart rate, electrocardiogram, and the regional contractile force of the left ventricle were monitored throughout the ligation (30 min) and reperfusion periods (20 min). Concentrations of creatine kinase (CK) and malondialdehyde (MDA) in the coronary sinus blood were determined before (0 min) and during ligation (15 and 25 min) and during reperfusion of the LAD (2, 7, and 20 min). In other groups of dogs, the effect of the two doses of SOD on epicardial blood flow was investigated during ligation and reperfusion by the measurement of epicardial temperature using a thermocardiograph. Experimental subjects were mongrel dogs of either sex (n = 25), weight 10-35 kg. Compared to controls (mean +/- SEM, 43.1 +/- 1.2; n = 7), the number of ventricular extrasystoles during the first 5 min of reperfusion was significantly (p < .001) decreased in dogs treated with the high dose (15.01 +/- 2.14; n = 5), but not in those receiving the low dose of the drug (34.6 +/- 5.66; n = 5). The concentrations of CK increased gradually until the end of reperfusion without differences among the different groups. Plasma MDA was the highest in control dogs 7 min after reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of naloxone on regional blood flow distribution in canine hemorrhagic shock

The opiate antagonist naloxone increases arterial pressure, maximal left ventricular dp/dt and cardiac output when administered to dogs subjected to hemorrhagic shock. The purpose of this study was to investigate regional blood flow changes associated with naloxone treatment in anesthetized hypovolemic and normovolemic dogs. Hypovolemic dogs (n = 10) were bled over 30 min (t = -30 to t = 0) to a pressure of 45 mm Hg which was maintained for 1 hr. At t = 60, five dogs received naloxone (2 mg/kg + 2 mg/kg X hr), and five received an equal volume of saline. Regional blood flows were determined at t = -30, 45, and 90 min using 15-micron microspheres. Normovolemic dogs (n = 10) were subjected to the same protocol except they were not bled. During hypovolemia, naloxone produced significant increases in myocardial, intestinal, hepatic, and adrenal blood flows whereas saline treatment did not. No significant changes in skin, muscle, fat, pancreatic, renal, or brain flows were detected. The increases in blood flow were not associated with significant changes in vascular resistance. Naloxone had no significant effects on any hemodynamic parameter during normovolemia. The beneficial effects of naloxone in hemorrhagic shock include increased blood flow to vital organs due to increased perfusion pressure which is secondary to improved cardiac performance.     

Follicle deviation and ovulatory capacity in Bos indicus heifers

The objectives of Experiment 1 were to determine the interval from ovulation to deviation, and diameter of the dominant follicle (DF) and largest subordinate follicle (SF) at deviation in Nelore (Bos indicus) heifers by two methods (observed and calculated). Heifers (n = 12) were examined ultrasonographically every 12 h from ovulation (Day 0) to Day 5. The time of deviation and diameter of the DF and largest SF at deviation did not differ (P>0.05) between observed and calculated methods. Overall, deviation occurred 2.5+/-0.2 d (mean +/- S.E.M.) after ovulation, and diameters for DF and largest SF at deviation were 6.2+/-0.2 and 5.9 +/- 0.2 mm, respectively. Experiment 2 was designed to determine the size at which the DF acquires ovulatory capacity in B. indicus heifers. Twenty-nine heifers were monitored every 24 h by ultrasonography, from ovulation until the DF reached diameters of 7.0-8.4 mm (n=9), 8.5-10.0 mm (n=10), or >10.0 mm (n=10). At that time, heifers were treated with 25 mg of pLH and monitored by ultrasonography every 12 h for 48 h. Ovulation occurred in 3 of 9, 8 of 10, and 9 of 10 heifers, respectively (P<0.05). In summary, there was no significant difference between observed and calculated methods of determining the beginning of follicle deviation. Deviation occurred 2.5 d after ovulation when the DF reached 6.2 mm, and ovulatory capacity was acquired by DF as small as 7.0 mm.     

Characterization of pulmonary vein reconnection post Cryoballoon ablation

BackgroundThe Arctic Front Cryoballoon System is a technology in which substrate alterations in patients with atrial fibrillation (AF) recurrence have not been well characterized. In this study, we evaluated sites of pulmonary vein (PV) reconnections and the accuracy of the Achieve? circular mapping catheter in detecting these reconnections after cryoablation.MethodsThis study included 15 patients undergoing redo AF ablation after a prior single cryoablation procedure. PV reconnection sites were determined by measuring PV signals and high output pacing from 4 vectors of the Achieve catheter. The results were compared with a roving mapping catheter guided by rotational intracardiac echocardiography (ICE) in the left atrium.ResultsAll patients had PV reconnections (2.1 ± 0.8 veins/patient). The left superior PV was most commonly reconnected (n = 11), whereas the right inferior PV was least likely (n = 3). Both carinas (left: n = 11; right: n = 7) and left atrial appendage ridge (n = 11) were also frequently reconnected. Mapping with the Achieve catheter showed a positive predictive value (PPV) 100% and negative predictive value (NPV) 96% when compared with ICE guided mapping. In 2 patients, right superior PV reconnection was not identified by the Achieve.ConclusionDuring redo AF ablation after index cryoablation, multiple PVs are usually reconnected, with both carinas and left atrial appendage ridge being common sites of reconnection. The Achieve mapping catheter was able to identify reconnection with high positive and negative predictive values.     

The effect of administering equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) post artificial insemination on fertility of lactating dairy cows

The objective was to evaluate the effect of equine chorionic gonadotropin (eCG) and hCG post artificial insemination (AI) on fertility of lactating dairy cows. In Experiment 1, cows were either treated with eCG on Day 22 post AI (400 IU; n = 80) or left untreated (n = 84). On Day 29, pregnant cows were either treated with hCG (2500 IU; n = 32) or left untreated (n = 36). Pregnancy and progesterone were evaluated on Days 29 and 45. In Experiment 2, cows (n = 28) were either treated with eCG on Day 22 (n = 13) or left untreated (n = 15) and either treated with hCG on Day 29 (n = 14) or left untreated (n = 14). Blood sampling and ultrasonography were conducted between Days 22 and 45. In Experiment 3, cows were either treated with eCG on Day 22 post AI (n = 229) or left untreated (n = 241). Pregnancy was evaluated on Days 36 and 85. In Experiment 1, eCG on Day 22 increased (P < 0.02) the number of pregnant cows on Day 29 (50.0 vs. 33.3%) and on Day 45, the increase was higher (P < 0.01) in cows with timed AI (41.2 vs. 6.5%) than in cows AI at detected estrus (50.0 vs. 37.8%). Pregnancy losses were reduced by eCG and hCG, but increased in cows that did not receive eCG but were given hCG (P < 0.01). Treatment with hCG tended (P < 0.06) to increase progesterone in control cows, but not in cows treated with eCG. In Experiment 2, hCG increased (P < 0.01) the number of accessory CLs on Day 35 (28.5 vs. 0.0%) and tended (P < 0.07) to increase progesterone. In Experiment 3, eCG increased the number of pregnant cows (P < 0.05) on Days 36 and 85, but only in cows with low body condition (eCG = 45.6 and 43.5%; Control = 22.9 and 22.9%). In conclusion, eCG at 22 days post insemination increased fertility, primarily in cows with low body condition and reduced pregnancy losses when given 7 days before hCG; hCG induced accessory CLs and slightly increased progesterone, but hCG given in the absence of a prior eCG treatment reduced fertility.     

Do Changes in the Pace of Events Affect One-Off Judgments of Duration?

Five experiments examined whether changes in the pace of external events influence people’s judgments of duration. In Experiments 1a–1c, participants heard pieces of music whose tempo accelerated, decelerated, or remained constant. In Experiment 2, participants completed a visuo-motor task in which the rate of stimulus presentation accelerated, decelerated, or remained constant. In Experiment 3, participants completed a reading task in which facts appeared on-screen at accelerating, decelerating, or constant rates. In all experiments, the physical duration of the to-be-judged interval was the same across conditions. We found no significant effects of temporal structure on duration judgments in any of the experiments, either when participants knew that a time estimate would be required (prospective judgments) or when they did not (retrospective judgments). These results provide a starting point for the investigation of how temporal structure affects one-off judgments of duration like those typically made in natural settings.     

Seroprevalence of canine herpesvirus in breeding kennels in the Gauteng Province of South Africa

Canine herpesvirus (CHV-1) causes neonatal deaths as well as infertility due to embryonal death, abortion and stillbirths in breeding kennels. The aim of this study was to determine the prevalence of antibodies against canine herpesvirus in the serum of dogs older than 1 year in breeding kennels in the Gauteng Province of South Africa. A serum neutralization test (SNT) and a newly developed enzyme linked immunosorbent assay (ELISA) were used to test the serum samples of 328 dogs in 38 breeding kennels. With SNT as well as ELISA, 22% of sera were positive (P>0.9). Seventeen kennels (45% of total kennels) each had at least one positive dog on SNT compared with twenty kennels (53% of total kennels) that each had at least one positive dog on ELISA (P=0.6). The prevalence of positive dogs in positive kennels was 42+/-26% (n=17 kennels) for SNT and 39+/-26% (n=20 kennels) for ELISA. Pairwise comparison of kennels showed that the prevalence of SNT positive dogs was similar to the prevalence of ELISA positive dogs (P=0.3, n=38 kennels). Seroprevalence was independent of age, gender or colony size. This study suggests that canine herpesvirus is sufficiently common in breeding dogs in the Gauteng Province of South Africa to pose a threat to neonatal survival and fertility.     

Oral administration of an anti-inflammatory does not compromise the efficacy of intra-testicular injection of zinc gluconate as a contraceptive for dogs

The objective was to determine whether the efficacy of zinc gluconate (Testoblock(?)) as a chemical contraceptive in male dogs was compromised in the presence of metamizole sodium (a nonsteroidal antiinflammatory/analgesic agent). Ten sexually mature mongrel dogs were assigned to two groups, a control group (n = 5) and a treated group (n = 5). Testoblock(?), a proprietary zinc-gluconate (13.1 mg zinc/ml) solution in a physiological vehicle, was injected into each testis (0.2-1.0 ml/testis, based on testis width). Half of the dogs (treated group) were also given metamizole sodium (also known as sodium dipyrone) orally (25mg/kg three times a day for 2 days), starting 2-3 h after testis injection. A physical examination and assessment of testis width, hematology, clinical chemistry (hepatic and renal function) and semen characteristics, were done immediately after treatment and then every 2 months for 180 days. There was no post-treatment scrotal biting or licking, although there was transient testicular swelling in both control and treated dogs during the first 3 days after injection. At 60 days after injection, all dogs were azoospermic. At 120 and 180 days, seven dogs had azoospermia and the remaining three (two control and one treated) had apparent aspermia (no ejaculate could be collected). There were no significant differences between groups for clinical findings or any aspect of hematology, renal, or hepatic function. In conclusion, giving metamizole sodium concurrent with an intra-testicular injection of a zinc-based solution did not interfere with chemical sterilization and it improved animal welfare.     

Changes in follicular blood flow and nitric oxide levels in follicular fluid during follicular deviation in cows

Two experiments were conducted to test the hypothesis that there are dynamic changes in follicular blood flow during follicular deviation and that nitric oxide (NO) in follicular fluid (FF) plays a role in regulation of follicular blood flow. In Experiment I, follicular blood flow of the two largest follicles was monitored by using Power Doppler ultrasonography during follicular deviation in sixteen follicular waves during eight estrous cycles in eight cows. Blood flow did not differ (P>0.05) between the dominant follicle (DF) and the largest subordinate follicle (SF) until the beginning of the deviation of the follicular size, but was higher (P<0.05) in DF than in the largest SF one and two days after the beginning of diameter deviation in ovulatory (n=5) and atretic (n=11) waves; respectively. In Experiment II, FF was aspirated from DF and the largest SF on the day of diameter deviation (DF, n=6; SF, n=6) and two days later (DF, n=12; SF, n=9). Nitric oxide did not differ (P>0.05) between DF and the largest SF on the day of diameter deviation but, one or two days after observed diameter deviation NO concentrations were lower (P<0.01) in DF compared to the largest SF. On the day of diameter deviation and two days later E2 levels in FF were higher (P<0.01) in DF than in the largest SF. P4 concentrations in FF were higher (P<0.05) in DF than in the largest SF on the day of diameter deviation, but did not (P>0.05) differ two days later. E2/P4 ratio in FF was the same (P>0.05) in DF and the largest SF on the day of diameter deviation, but was higher (P<0.01) in DF than in the largest SF one or two days later. In conclusion, area of follicular blood flow of DF and the largest SF increased in parallel with follicular size during follicular deviation. Furthermore, there were relationships between changes in follicular blood flow, NO concentrations and E2/P4 ratio in FF following the beginning of diameter deviation in cattle.     

The DC-Recorded Dog Electroretinogram in Ketamine -Medetomidine Anaesthesia

A new selective alpha 2-adre-noreceptor agonist, medetomidine hydrochloride was combined with low dosage ketamine hydrochloride and vecuronium bromide for d.c. (direct current) recordings of fast electroretinographic (ERG) components in nine ophthalmoscopically healthy dark adapted dogs. The dogs were tracheally intubated and manually ventilated. They were given full field single flash stimuli of different intensities starting with near b-wave threshold blue light (tests 1-3), followed by white light (tests 4-6) and 30 Hz photopic flicker (test 7). The a- and b-wave amplitudes and flicker responses were measured from the base line. The latencies were measured from the stimulus moment to the highest point of the different waves. Statistical analysis of results gave individual differencies which had a good constancy. This showed that the dogs had an individual ERG profile according to the standardized method. The latencies varied very little as expected, but the amplitudes differed individually and showed a good constancy as seen by reproducibility tests made nine to ten days later on three of the dogs’ ipsilateral eyes. The combination of drugs used in this study was considered suitable for short term (10-12 minutes) stable d.c.–ERG recordings in dogs as the rod and cone responses had higher amplitudes when compared to an identical examination made with other anaesthetic combinations on the same dogs. Involuntary eye movements and other involuntary muscular activity caused by ketamine in dogs were negligible when using medetomidine premedication and was completely absent when using vecuronium. The anaesthetic method described can be recommended for ambulatory ERG recordings in dogs because of the above mentioned advantages.     

Echocardiographic and Doppler assessment of maternal cardiovascular function in normal and abnormal canine pregnancies

The objective was to verify maternal hemodynamic differences between normal and abnormal pregnancies in dogs. Brucella-negative pregnant bitches (n = 31) were retrospectively classified into abnormal (which had either their pregnancy interrupted between Days 52 and 60 or perinatal death of more than 50% of the litter; n = 14) and normal (which had delivered healthy puppies at term; n = 17). These dogs were evaluated with echocardiography every 10 days from Days 0 to 60 of gestation (Day 0 = estimated day of LH peak). Systolic blood pressure was also assessed. At Day 50 of gestation, left ventricular free wall in systole increased in the normal but not in the abnormal group (P < 0.01). In contrast, end systolic stress (P < 0.01) and systolic blood pressure (P < 0.01) diminished only in normal animals. We concluded that signs of altered maternal cardiovascular adaptation to pregnancy may be predictors of obstetrical complications in dogs.     

Effect of carotid or aortic baroreceptor denervation on arterial pressure during hemorrhage in conscious dogs

We studied the effect of chronically denervating aortic baroreceptors (ABR; n = 6) or carotid baroreceptors (CBR; n = 7) on mean arterial pressure (MAP) and heart rate (HR) responses to hemorrhage in the dog. Neither denervation had a significant effect on basal MAP, the variability (standard deviation) of MAP, or resting HR. However, the breakpoint of MAP (defined as the volume of blood removed when MAP fell more than 10% below control and declined monotonically thereafter) was significantly reduced in dogs with only ABR functional (12.4 +/- 1.4 ml/kg) compared with the volume in the intact condition (18.9 +/- 1.8 ml/kg). In contrast, there was no difference in the breakpoint or the MAP at any time during hemorrhage in dogs with both CBR functional compared with their intact responses. In a different group of dogs (n = 6), responses were determined with both CBR operating and again after unilateral denervation, leaving only one CBR (1CBR) functional. Basal MAP and the variability of MAP were not altered in dogs with only 1CBR functional, but the breakpoint (11.7 +/- 1.4 ml/kg) during hemorrhage was significantly different compared with responses with two CBR (21.2 +/- 2.3 ml/kg), and MAP fell to much lower levels. These results indicate that the CBR can compensate fully for loss of ABR during hemorrhage but not vice versa; and bilateral CBR inputs are required for normal responses to hemorrhage.     

Part-Based and Configural Processing of Owner's Face in Dogs

Dogs exhibit characteristic looking patterns when looking at human faces but little is known about what the underlying cognitive mechanisms are and how much these are influenced by individual experience. In Experiment 1, seven dogs were trained in a simultaneous discrimination procedure to assess whether they could discriminate a) the owner''s face parts (eyes, nose or mouth) presented in isolation and b) whole faces where the same parts were covered. Dogs discriminated all the three parts of the owner''s face presented in isolation, but needed fewer sessions to reach the learning criterion for the eyes than for both nose and mouth. Moreover, covering the eyes region significantly disrupted face discriminability compared to the whole face condition while such difference was not found when the nose or mouth was hidden. In Experiment 2, dogs were presented with manipulated images of the owner''s face (inverted, blurred, scrambled, grey-scale) to test the relative contribution of part-based and configural processing in the discrimination of human faces. Furthermore, by comparing the dogs enrolled in the previous experiment and seven ‘naïve’ dogs we examined if the relative contribution of part-based and configural processing was affected by dogs'' experience with the face stimuli. Naïve dogs discriminated the owner only when configural information was provided, whereas expert dogs could discriminate the owner also when part-based processing was necessary. The present study provides the first evidence that dogs can discriminate isolated internal features of a human face and corroborate previous reports of salience of the eyes region for human face processing. Although the reliance on part-perception may be increased by specific experience, our findings suggest that human face discrimination by dogs relies mainly on configural rather than on part-based elaboration.     

Analysis of the inheritance of white spotting and the evaluation of KIT and EDNRB as spotting loci in Dutch boxer dogs

The genetic basis of the white spotting pattern in Dutch boxer dogs is not known. We studied whether the segregation of white spotting in boxers follows a Mendelian inheritance pattern. Blood samples were collected, along with digital photographs in standard directions of (grand)parents (n=16) and offspring (n=52) from eight litters of Dutch boxers. In order to select heterozygous parents, we selected nonuniform litters, in which at least one puppy was extreme white. On the basis of criteria for the location, the extent of white spotting, and the mean percentage of pigmented area of the foot soles, we classified 10 dogs as solid colored, 27 as flashy, and 15 as extreme white. This was not a significant deviation from the expected 1:2:1 ratio. Because the flashy phenotype seems to be an intermediate between the two homozygotes, white spotting in the Dutch boxer can be considered to be due to a single gene effect, with incomplete dominance. We have evaluated candidate genes c-KIT (KIT) and EDNRB for segregation with white spotting phenotype in these litters. Using polymorphic markers, very near the KIT and EDNRB genes, we found that segregation of the white spotting pattern did not coincide with segregation of these polymorphic markers. Thus neither KIT nor EDNRB are likely to be responsible for white spotting in the Dutch population of boxers.