Amália Turner Giannico

Proven cardiac changes during death-feigning (tonic immobility) in rabbits ( Oryctolagus cuniculus )

Tonic immobility (TI) is a response to fear or threat by remaining motionless, principally when attacked by predators from which there is no possibility of escape. Thus, here we demonstrate a way of easily reproducing this phenomenon in a laboratory setting and characterize the cardiac electromechanical alterations during TI. We observed a significant decrease in heart rate (HR) and changes of rhythm in electrocardiogram during TI in rabbits. Echocardiogram showed a significant increase in the left ventricle chamber diameter during systole and a consequent decrease in fractional shortening and ejection fraction, in addition to the HR and rhythm changes. There was also a significant decrease in aortic and pulmonary artery blood flow. Diastolic functional changes included a significant decrease of the peak atrial contraction velocity (A peak) and consequent increase in the ratio of peak early diastolic velocity to A peak and increased isovolumetric relaxation time. We were able to prove that TI changes the cardiac function considerably. Although the “fight-or-flight” response is the most common response to fear, which is characterized by the action of sympathetic nervous system with tachycardia and increased physical activity, TI is an alternative anti-predator behavior causing cardiac changes opposite to the “fight-or-flight” phenomenon.

Use of B-mode ultrasonography for fetal sex determination in dogs.

Ultrasonographic determination of fetal sex in dogs has not previously been reported. The aim of this study was to describe a method for determination of intrauterine fetal sex using ultrasound. A cohort study was conducted in pregnant bitches to perform ultrasound examination of the fetal genitalia between the eighth and ninth week of gestation. Fetal sex was determined in utero by consensus agreement of two sonographers. Eighteen pregnant bitches were included in this study, and a total of 39 fetuses were evaluated. The accuracy of ultrasonography to determine the sex with a 95% confidence interval was 62.24% to female fetuses and 65.48% to male fetuses. The sonographic accuracy in determining fetal sex can be achieved at 100% when there are up to two fetuses in the litter; however, the accuracy of the technique reduces (66.7%) when more than three fetuses are present. This study describes the sonographic appearance of the external genitalia in canine fetuses in utero associated with a specific position of the fetus and reports that sex determination is possible between 55 and 58 days of gestation.

The use of Doppler evaluation of the canine umbilical artery in prediction of delivery time and fetal distress.

The aim of this study was to describe changes in umbilical artery blood flow in the later stages of canine pregnancy. Seventeen pregnant bitches were examined sonographically to evaluate umbilical artery blood flow at the following antepartum times: 120-96, 96-72, 72-48, 48-24, 24-12, 12-6 and 6-1h. The peak systolic velocity and end diastolic velocity were measured to calculate the resistive index (RI). Bitches were classified into two groups according to delivery method: normal delivery (Group 1, n=11) and Cesarean section, due to fetal distress, (Group 2, n=6). During the study, the RI of the umbilical artery in bitches in Group 1 significantly declined in the time periods 72-48, 24-12, 12-6 and 6-1h before delivery when compared to the reference RI (120-96h antepartum period), with values ​​below 0.7 in the 12-6 and 6-1h periods. In Group 2, the RI decreased significantly in the antepartum periods 96-72, 72-48, 48-24h with respect to the period 120-96h, and increased in the periods from 24-12, 12-6 and 6-1h (being significantly higher in this last period) until the time of Cesarean section. Therefore monitoring of changes in umbilical artery RI in the pre-partum period may provide information about time of delivery in bitches and also assist in the diagnosis of possible dystocia and fetal distress.

Effects of prostaglandin analogs on blood flow velocity and resistance in the ophthalmic artery of rabbits

PURPOSE The aim of this study was to investigate the effects of prostaglandin analogs on blood flow in the ophthalmic artery of clinically healthy rabbits. METHODS Fifty-five clinically healthy New Zealand white rabbits were divided into six groups, and the left eyes were treated for four weeks with the preservative benzalkonium chloride (BAK) only or a topical formulation of different prostaglandin analogs (bimatoprost BAK, tafluprost BAK-free, travoprost BAK, travoprost POLYQUAD, and latanoprost BAK). Color Doppler imaging was performed before and after the treatments. The mean values of the peak systolic velocity (PSV) and end diastolic velocity and the resistive index (RI) were calculated. Statistical analysis was performed to compare the differences pre- and post-treatment for each drug and post-treatment among the drugs. RESULTS The prostaglandin analogs did not affect PSV. Bimatoprost BAK, travoprost POLYQUAD, and latanoprost BAK did not change RI. Tafluprost BAK-free and travoprost BAK therapy resulted in similar reductions in RI. No significant differences pre- and post-treatment were found when BAK was administered alone. CONCLUSION The prostaglandin analogs tafluprost BAK-free and travoprost BAK improved blood flow in the ophthalmic artery in healthy New Zealand white rabbits, which suggests that these drugs enhance the prevention of the progression the progression of glaucoma.

Characterization of the oculocardiac reflex during compression of the globe in Beagle dogs and rabbits

OBJECTIVE This investigation characterizes the occurrence of oculocardiac reflex (OCR) in conscious rabbits and dogs by observing the effect of an ocular compression stimulus on heart rate (HR). ANIMALS STUDIED Thirty-four clinically healthy adult rabbits and 15 clinically healthy adult Beagle dogs were studied. PROCEDURES An electrocardiogram was used to record the heart rhythm and HR continuously. Digital pressure was exerted over the eyelid on right eye, left eye and both eyes together for 1 min, with one-minute intervals between each compression. Variations in HR were observed in each minute by counting complexes on the electrocardiographs. RESULTS There were no differences in HR between stages without ocular compressions both in dogs and in rabbits. HR reduction caused by ocular compression was statistically significant in rabbits only when both eyes were compressed in contrast with all stages without compression. In dogs, a statistically significant reduction in HR was seen during compression of just the right eye or the left eye compared with the baseline HR, and when both the right and left eyes were compressed together compared with baseline or after compression of the right eye. In dogs, compression of individual eyes produced a change similar to that seen during compression of both eyes. CONCLUSIONS This study shows that OCR can occur during experimental ocular compression in conscious rabbits and Beagle dogs and characterizes the reduction in HR. Knowledge of this physiological response is important for veterinary anesthetists and ophthalmologists during ophthalmic surgery or eye manipulations.

Eyelash growth induced by topical prostaglandin analogues, bimatoprost, tafluprost, travoprost, and latanoprost in rabbits.

PURPOSE Prostaglandin analogues (PGA) are ocular hypotensive agents used for the treatment of glaucoma. Hypertrichosis of the eyelashes has been reported in humans as a side effect. Eyelash growth was investigated with clinical trials in people using bimatoprost. Scattered reports of eyelash growth during the treatment of glaucoma with other PGA are also found in the literature. We investigated the effect of 4 different topical PGA on eyelash length. METHODS Forty New Zealand white rabbits were divided into 4 groups and received daily topical application of bimatoprost, tafluprost, travoprost, and latanoprost in the left eye for 4 weeks. The right eye received no treatment. Eyelash length was measured in both eyes before and after treatment using a stainless steel digital caliper. RESULTS Bimatoprost and tafluprost groups had significant increases in eyelash length. We did not observe significant eyelash growth in rabbits receiving travoprost and latanoprost after 1 month of treatment. CONCLUSIONS Today, only bimatoprost is approved for growing eyelashes, and our research shows that tafluprost could be further explored by the cosmetic and pharmaceutical industry. Additional research using travoprost and latanoprost as agents for eyelash growth should be performed in the future using prolonged treatment periods to determine whether or not these PGA induce eyelash growth, and investigate other possible side effects.

Hemodynamics of the pectinis oculi artery in American pekin ducks (Anas platyrhynchos domestica).

OBJECTIVE To measure blood velocity parameters of the main detectable branch of the pectinis oculi artery and compare with values found in other arteries in other species to form a hypothesis of the function of the pecten oculi in birds. METHODS Eleven American pekin ducks (Anas platyrhynchos domestica) without ocular diseases were examined with ocular Doppler ultrasonography. The pectinate artery resistive index (RI) and pulsatility index (PI) were calculated. RESULTS The mean of RI and PI values resulted, respectively, in: left eye (0.43 ± 0.07; 0.58 ± 0.13), right eye (0.37 ± 0.09; 0.47 ± 0.14), and both eyes (0.40 ± 0.08; 0.53 ± 0.14). DISCUSSION The low RI and PI values found in the main branch of the pectinis oculi artery compared with other arteries in other tissues suggest a high metabolic activity in the pecten oculi, and it could indicate a nutritional function and/or intraocular pressure regulation.

Valores eletrocardiográficos em saguis-de-tufo-preto (Callithrix penicillata)

O conhecimento de parâmetros cardiacos em animais modelo experimentais e essencial para a investigacao medica comparativa. Nosso estudo teve como objetivo estabelecer parâmetros eletrocardiograficos e valores de referencia para saguis-de-tufo-preto (Callithrix penicillata). Dezenove saguis-de-tufo-preto adultos saudaveis foram utilizados. Uma combinacao de tiletamina e zolazepam foi empregada para contencao quimica antes da realizacao do exame eletrocardiografico (ECG). Foi utilizado para o exame de ECG um equipamento computadorizado. Os valores dos parâmetros do ECG encontrados foram frequencia cardiaca media de 264±74 bpm, uma variacao do eixo cardiaco medio entre 60° e -90°, a duracao da onda P media de 34±6ms e amplitude de 0,132±0,051mV, um intervalo PR com duracao de 56±11ms, duracao media do complexo QRS de 35±7ms e amplitude de 0,273±0,269mV, duracao do intervalo QT de 130±26ms, segmento ST isoeletrico (13 animais) e com supradesnivel (seis animais) e uma amplitude de onda T de 0,19±0,083mV e com polaridade positiva. Nao houve diferenca significativa entre machos e femeas. Os parâmetros eletrocardiograficos obtidos em nosso estudo em saguis-de-tufo-preto podem ser utilizados como referencia em outras pesquisas futuras, oferecendo aos pesquisadores parâmetros eletrocardiograficos que contribuem com a literatura.

Assessment of umbilical artery flow and fetal heart rate to predict delivery time in bitches

The aim of this study was to quantitatively investigate the oscillation of the fetal heart rate (HR) in advance of normal delivery and whether this index could be used to indicate impending delivery. In addition, fetal HR oscillation and umbilical artery resistive index (RI) were correlated to determine if the combination of these parameters provided a more accurate prediction of the time of delivery. Sonographic evaluation was performed in 11 pregnant bitches to evaluate the fetal HR and umbilical artery RI at the following antepartum times: 120 to 96 hours, 72 to 48 hours, 24 to 12 hours, and 12 to 1 hours. Statistical analysis indicated a correlation between the oscillation of fetal HR and the umbilical artery RI. As delivery approached a considerable reduction in the umbilical artery RI was documented and greater oscillations between maximum and minimum HRs occurred. We conclude that the quantitative analysis of fetal HR oscillations may be used to predict the time of delivery in bitches. The combination of fetal HR and umbilical artery RI together may provide more accurate predictions of time of delivery.