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Background: The aim was to evaluate the relationship between the direction of the patent ductus arteriosus (PDA) shunt and the pre- and postductal gradient for arterial blood gas (ABG) parameters in a lamb model of meconium aspiration syndrome (MAS) with persistent pulmonary hypertension of the newborn (PPHN). Methods: PPHN was induced by intermittent umbilical cord occlusion and the aspiration of meconium through the tracheal tube. After delivery, 13 lambs were ventilated and simultaneous 129 pairs of pre- and postductal ABG were drawn (right carotid and umbilical artery, respectively) while recording the PDA and the carotid and pulmonary blood flow. Results: Meconium aspiration resulted in hypoxemia. The bidirectional ductal shunt had a lower postductal partial arterial oxygen tension ([PaO2] with lower PaO2/FiO2 ratio&mdash, 97 &plusmn, 36 vs. 130 &plusmn, 65 mmHg) and left pulmonary flow (81 &plusmn, 52 vs. 133 &plusmn, 82 mL/kg/min). However, 56% of the samples with a bidirectional shunt had a pre- and postductal saturation gradient of &lt, 3%. Conclusions: The presence of a bidirectional ductal shunt is associated with hypoxemia and low pulmonary blood flow. The absence of a pre- and postductal saturation difference is frequently observed with bidirectional right-to-left shunting through the PDA, and does not exclude a diagnosis of PPHN in this model.

Rationale: In heart failure, myofilament proteins display abnormal phosphorylation, which contributes to contractile dysfunction. The mechanisms underlying the dysregulation of protein phosphorylation on myofilaments is not clear. Objective: This study aims to understand the mechanisms underlying altered phosphorylation of myofilament proteins in heart failure. Methods and Results: We generate a novel genetically encoded protein kinase A (PKA) biosensor anchored onto the myofilaments in rabbit cardiac myocytes to examine PKA activity at the myofilaments in responses to adrenergic stimulation. We show that PKA activity is shifted from the sarcolemma to the myofilaments in hypertrophic failing rabbit myocytes. In particular, the increased PKA activity on the myofilaments is because of an enhanced β 2 adrenergic receptor signal selectively directed to the myofilaments together with a reduced phosphodiesterase activity associated with the myofibrils. Mechanistically, the enhanced PKA activity on the myofilaments is associated with downregulation of caveolin-3 in the hypertrophic failing rabbit myocytes. Reintroduction of caveolin-3 in the failing myocytes is able to normalize the distribution of β 2 adrenergic receptor signal by preventing PKA signal access to the myofilaments and to restore contractile response to adrenergic stimulation. Conclusions: In hypertrophic rabbit myocytes, selectively enhanced β 2 adrenergic receptor signaling toward the myofilaments contributes to elevated PKA activity and PKA phosphorylation of myofilament proteins. Reintroduction of caveolin-3 is able to confine β 2 adrenergic receptor signaling and restore myocyte contractility in response to β adrenergic stimulation.

We describe a case series of photoreceptor dysplasia with secondary retinal degeneration in juvenile Peregrine Falcons. Six Peregrine Falcons ( Falco peregrinus) and three Peregrine Falcon × Prairie Falcon ( Falco mexicanus) hybrids had early-life visual deficits. Eight birds had visual defects shortly after hatching, and one bird had visual deficits first noticed at 5 mo of age. Complete ophthalmic examinations were performed in each animal. Eight of the animals had electroretinograms, and nine of the animals had their eyes examined histologically after euthanasia. Ophthalmic examinations did not reveal consistent and potentially blinding abnormalities, including an absence of ophthalmoscopic retinal lesions. Electroretinographic findings included subnormal amplitudes (with rod responses more abnormal than cone responses), with a negative b-wave amplitude occurring in one bird. Histologically, a reduction in the number of photoreceptors was present with numerous degenerative changes to the remaining photoreceptors, including frequent blunting and disorganization of photoreceptor outer segments, decreased numbers of cells in the inner nuclear layer, decreased numbers of ganglion cells, decreased thickness of the nerve fiber layer, and decreased myelinated axons within the optic nerve. Ultrastructurally, only minor cone outer segment changes and occasional phagocytic cells were seen. Results strongly suggested a primary retinopathy, characterized by photoreceptor dysplasia and secondary retinal degeneration with loss of cellular elements throughout the retina. The presence of a similar spectrum of findings in related individuals, the early age of onset, and the relative lack of other environmental, ocular, or systemic abnormalities suggested possible heritability.

Background: Electrophysiological remodeling and increased susceptibility for cardiac arrhythmias are hallmarks of heart failure (HF). Ventricular action potential duration (APD) is typically prolonged in HF, with reduced repolarization reserve. However, underlying K + current changes are often measured in nonphysiological conditions (voltage clamp, low pacing rates, cytosolic Ca 2+ buffers). Methods and Results: We measured the major K + currents ( I Kr , I Ks , and I K1 ) and their Ca 2+ - and β-adrenergic dependence in rabbit ventricular myocytes in chronic pressure/volume overload–induced HF (versus age-matched controls). APD was significantly prolonged only at lower pacing rates (0.2–1 Hz) in HF under physiological ionic conditions and temperature. However, when cytosolic Ca 2+ was buffered, APD prolongation in HF was also significant at higher pacing rates. Beat-to-beat variability of APD was also significantly increased in HF. Both I Kr and I Ks were significantly upregulated in HF under action potential clamp, but only when cytosolic Ca 2+ was not buffered. CaMKII (Ca 2+ /calmodulin-dependent protein kinase II) inhibition abolished I Ks upregulation in HF, but it did not affect I Kr . I Ks response to β-adrenergic stimulation was also significantly diminished in HF. I K1 was also decreased in HF regardless of Ca 2+ buffering, CaMKII inhibition, or β-adrenergic stimulation. Conclusions: At baseline Ca 2+ -dependent upregulation of I Kr and I Ks in HF counterbalances the reduced I K1 , maintaining repolarization reserve (especially at higher heart rates) in physiological conditions, unlike conditions of strong cytosolic Ca 2+ buffering. However, under β-adrenergic stimulation, reduced I Ks responsiveness severely limits integrated repolarizing K + current and repolarization reserve in HF. This would increase arrhythmia propensity in HF, especially during adrenergic stress.

Telemetric physiological monitoring systems (TPMS) have enabled accurate continuous measurement of animal blood pressures and flows. However, few studies describe approaches for use of TPMS in the great vessels or inside the heart. We describe our initial experiences using two types of TPMSs. Twelve lambs (20-37 kg) underwent sternotomy. Two lambs were not instrumented and were killed at 14 days to confirm normal sternal wound healing (sham group, n = 2). Ten lambs underwent placement of either standard indwelling pressure-monitoring catheter and perivascular-flow-probe (CFP group, n = 3) or TPMS implantation (TPMS group, n = 7). The TPMS used were EG1-V3S2T-M2 (EG1, n = 5; Transonic Endogear Inc.) and Physio Tel Digital L21 (PTD, n = 2; Data Sciences Inc.). Two deaths because of respiratory problems occurred in TPMS group, attributed to lung compression by the implanted device. In TPMS group, more consistent trends of blood pressures and flows were recorded, and management of animals was easier and less labor-intensive. Comparing the two TPMSs, the initiation and renewal costs for each case was $28 K vs. $20 K and $1,700 vs. $0, (PTD versus EG1, respectively). In conclusion, TPMS implantation was feasible via median sternotomy in lambs. Telemetric physiological monitoring systems significantly improve reliability of hemodynamic monitoring in chronic survival animal study. EG1 was less costly than PTD.

Objective Fetal cardiac surgery is a potential innovative treatment for certain congenital heart defects that have significant mortality and morbidity in utero or after birth, but it has been limited by placental dysfunction after fetal cardiac bypass. We have used the TinyPump device for fetal cardiac bypass in sheep fetuses at 90 to 110 days gestation. Methods Ten mixed-breed pregnant ewes were used over a period of 6 months, and 10 fetuses were placed on bypass for 30 minutes. Five fetuses with a mean gestational age of 104 ± 4.5 days and mean weight of 1.4 ± 0.4 kg were placed on bypass using the TinyPump device, and 5 fetuses with a mean gestational age of 119 ± 4.5 days and mean weight of 3.4 ± 0.4 kg were placed on bypass using the roller head pump. The fetuses were monitored for up to 3 hours after bypass or until earlier demise. Results Progressive respiratory and metabolic acidosis developed in all fetuses. The TinyPump group had a lower gestational age and weight compared with the roller head pump group. However, the rate of postbypass deterioration in the TinyPump group, as measured with blood gases, was noted to be significantly slower compared with the roller head pump group. Conclusions We demonstrate the feasibility of the TinyPump device for fetal cardiac bypass in a fetal sheep model. The TinyPump group showed improved results compared with the roller head group despite more immature fetuses. The TinyPump device seems to be a promising device for future studies of fetal cardiac bypass in immature fetal sheep and in primates.

Fluorescence lifetime technique has demonstrated potential for analysis of atherosclerotic lesions and for complementing existing intravascular imaging modalities such as intravascular ultrasound (IVUS) in identifying lesions at high risk of rupture. This study presents a multimodal catheter system integrating a 40 MHz commercial IVUS and fluorescence lifetime imaging (FLIm) using fast helical motion scanning (400 rpm, 0.75 mm/s), able to acquire in vivo in pulsatile blood flow the autofluorescence emission of arterial vessels with high precision (5.08 ± 0.26 ns mean average lifetime over 13 scans). Co-registered FLIm and IVUS data allowed 3D visualization of both biochemical and morphological vessel properties. Current study supports the development of clinically compatible intravascular diagnostic system integrating FLIm and demonstrates, to our knowledge, the first in vivo intravascular application of a fluorescence lifetime imaging technique. Keywords: time resolved fluorescence spectroscopy, fluorescence lifetime imaging, intravascular ultrasound (IVUS), intravascular catheter, atherosclerosis 1. Introduction Coronary artery disease is the leading cause of death in western societies [1]. Although many diagnostic tools have been developed to help predict which patients will suffer cardiovascular complications, current diagnostic techniques have significant limitations [2]. New techniques, including intravascular methods, are needed in order to make a significant impact on this public health challenge. Point time-resolved fluorescence spectroscopy (TRFS) and fluorescence lifetime imaging microscopy (FLIM) have demonstrated ability to assess a plurality of diagnostic features associated with arterial wall pathologies including atherosclerotic plaques at risk of rupture [3]. However, the overall TRFS and FLIM potential for atherosclerotic plaques analysis was primarily evaluated ex-vivo in arterial tissue specimens with intima directly exposed to the fiberoptic probe interrogation. Practical intravascular application of these techniques requires development of TRFS systems and catheters capable of rapid acquisition of robust time-resolved fluorescence data in vivo from the luminal surface of the artery in the presence of pulsa-tile blood flow. A novel implementation of a TRFS apparatus with the ability to rapidly (

Single ventricle congenital heart defects are usually palliated with the end result of a Fontan circulation. Despite improving results, this circulation is still associated with long-term failure. We previously developed an animal model of mechanical cavopulmonary circulation support that was successful in the acute and mid-term period. In the current study, we evaluated longer support durations in five Western-breed sheep. Through a right thoracotomy we instituted mechanical support from the inferior vena cava to the pulmonary artery, using a Heartmate II axial flow pump (Thoratec Corp., Pleasanton, CA). Postoperatively, the animals were anticoagulated with heparin iv. Hemodynamics, pump flow, anticoagulation, and hepatic and renal function were monitored daily. All animals survived the operation. Signs of moderate liver and kidney injury in general reversed quickly. Two animals had a fatal pump thrombosis. When anticoagulation was effective, hemodynamics and pump flow were maintained to normal values. Effective anticoagulation was difficult to achieve because of the high variability in response to heparin. Survival up to 18 days was accomplished. This study is the longest reported survival of animals with a mechanically assisted cavopulmonary circulation. The performance of the Thoratec Heartmate II has been good, but the issue of effective anticoagulation has not yet been solved.

Congenital diaphragmatic hernia (CDH) is associated with significant neonatal morbidity and mortality. Although prenatal complete tracheal occlusion (cTO) causes hypoplastic CDH lungs to enlarge, improved lung function has not been demonstrated. Furthermore, cTO interferes with the dynamic pressure change and fluid flow associated with fetal breathing.The purpose of the study was to assess a novel dynamic tracheal occlusion (dTO) device that preserves pressure changes and fluid flow.In this pilot study, CDH was created in fetal lambs at 65 days of gestational age (GA). At 110 days GA, a cTO device (n = 3) or a dTO device (n = 4) was placed in the fetal trachea. At 135 days GA, lambs were delivered and resuscitated. Unoperated lamb co-twins (n = 5), sham thoracotomy lambs (n = 2), and untreated CDH lambs (n = 3) served as controls.Tracheal opening pressure, lung volume, lung fluid total protein, and phospholipid were significantly higher in the cTO group than in the dTO and unoperated control groups. Maximal oxygenation and lung compliance were significantly lower in the cTO group when compared with the unoperated control and dTO groups.Preliminary results suggest that in the fetal lamb CDH model, dTO restores normal lung morphometrics and function, whereas cTO leads to enlarged but less functional lungs.

Durable mechanical support in situations of physiologic single ventricle has been met with little success so far, particularly in small children. We created an animal model to investigate whether pulsatile or continuous flow would be superior. Three 1 month old sheep (10-16 kg) were instrumented. Via sternotomy and with cardiopulmonary bypass, a large ventricular septal defect and atrial septal defect were created. The left ventricle was cannulated using a Berlin Heart inflow cannula. This was connected sequentially to a continuous flow device (Thoratec HeartMate X, Pleasanton, CA) and to a pulsatile device (Berlin Heart Excor, The Woodlands, TX). Outflow was via a Y-graft to both aorta and pulmonary artery, striving for equal flow to both. Atrial filling pressures were controlled with volume infusions over a wide range. Under comparable loading conditions, significantly higher maximum flow was obtained by HeartMate X than by Excor (4.95 ± 1.27 L/min [range, 3.84-6.34 L/min] for HeartMate X vs. 1.80 ± 0.85 L/min [range, 1.01-2.7 L/min] for Excor; p < 0.05). Judging from this limited animal study, in single ventricle scenarios, continuous flow devices may achieve higher pump flows than pulsatile devices when provided with similar filling pressures. Their clinical use should be investigated. More extensive experimental studies are needed.

We report a scanning imaging system that enables high speed multispectral fluorescence lifetime imaging (FLIm) of coronary arteries. This system combines a custom low profile (3 Fr) imaging catheter using a 200 μm core side viewing UV-grade silica fiber optic, an acquisition system able to measure fluorescence decays over four spectral bands at 20 kHz and a fast data analysis and display module. In vivo use of the system has been optimized, with particular emphasis on clearing blood from the optical pathway. A short acquisition time (5 seconds for a 20 mm long coronary segment) enabled data acquisition during a bolus saline solution injection through the 7 Fr catheter guide. The injection parameters were precisely controlled using a power injector and optimized to provide good image quality while limiting the bolus injection duration and volume (12 cc/s, 80 cc total volume). The ability of the system to acquire data in vivo was validated in healthy swine by imaging different sections of the left anterior descending (LAD) coronary. A stent coated with fluorescent markers was placed in the LAD and imaged, demonstrating the ability of the system to discriminate in vivo different fluorescent features and structures from the vessel background fluorescence using spectral and lifetime information. Intensity en face images over the four bands of the instrument were available within seconds whereas lifetime images were computed in 2 minutes, providing efficient feedback during the procedure. This successful demonstration of FLIm in coronaries enables future study of atherosclerotic cardiovascular diseases.

We report an intravascular catheter system able to acquire multispectral time-resolved fluorescence images of coronary arteries in vivo in swine heart. Current results demonstrate the ability of this system to acquire robust fluorescence lifetime images in pulsatile blood flow.

STUDY DESIGN: Thermal energy was delivered in vivo to ovine cervical discs and the postheating response was monitored over time. OBJECTIVES: To determine the effects of two distinctly different thermal exposures on biologic remodeling: a "high-dose" regimen intended to produce both cellular necrosis and collagen denaturation and a "low-dose" regimen intended only to kill cells. SUMMARY OF BACKGROUND DATA: Thermal therapy is a minimally invasive technique that may ameliorate discogenic back pain. Potential therapeutic mechanisms include shrinkage of collagenous tissues, stimulation of biologic remodeling, and ablation of cytokine-producing cells and nociceptive fibers. METHODS: Intradiscal heating was performed using directional interstitial ultrasound applicators. Temperature and thermal dose distributions were characterized. The effects of high (>70 C, 10 minutes) and low (52 C-54 C, 10 minutes) temperature treatments on chronic biomechanical and architectural changes were compared with sham-treated and control discs at 7, 45, and 180 days. RESULTS: The high-dose treatment caused both an acute and chronic loss of proteoglycan staining and a degradation of biomechanical properties compared with low-dose and sham groups. Similar amounts of degradation were observed in the low-dose and sham-treated discs relative to the control discs at 180 days after treatment. CONCLUSIONS: While a high temperature thermal protocol had a detrimental effect on the disc, the effects of low temperature treatment were relatively minor. Thermal therapy did not stimulate significant biologic remodeling. Future studies should focus on the effects of low-dose therapy on tissue innervation and pro-inflammatory factor production.

Fluorescence lifetime technique has demonstrated potential for analysis of atherosclerotic lesions and for complementing existing intravascular imaging modalities such as intravascular ultrasound (IVUS) in identifying lesions at high risk of rupture. This study presents a multimodal catheter system integrating a 40 MHz commercial IVUS and fluorescence lifetime imaging (FLIm) using fast helical motion scanning (400 rpm, 0.75 mm/s), able to acquire in vivo in pulsatile blood flow the autofluorescence emission of arterial vessels with high precision (5.08 ± 0.26 ns mean average lifetime over 13 scans). Co-registered FLIm and IVUS data allowed 3D visualization of both biochemical and morphological vessel properties. Current study supports the development of clinically compatible intravascular diagnostic system integrating FLIm and demonstrates, to our knowledge, the first in vivo intravascular application of a fluorescence lifetime imaging technique.

Study design In vivo investigation of intradiscal ultrasound thermal therapy in ovine cervical spine model. Objective To evaluate the potential of interstitial ultrasound for selective heating of intradiscal tissue in vivo. Summary of background data Application of heat in the spine using resistive wire and radiofrequency current heating devices is currently being used clinically for minimally invasive treatment of discogenic low back pain. Treatment temperatures are representative of those required for thermal necrosis of ingrowing nociceptor nerve fibers and disc cellularity alone, or with coagulation and restructuring of anular collagen in the high temperature case. Methods Two interstitial ultrasound applicator design configurations with directional heating patterns were evaluated in vivo in ovine cervical intervertebral discs (n = 62), with up to 45-day survival periods. Two heating protocols were employed in which the temperature measured 5 mm away from the applicator was controlled to either 70 C (for coagulation of collagen) for a 10-minute treatment period. Transient and steady state temperature maps, calculated thermal doses (t43), and histology were used to assess the thermal treatments. Results These studies demonstrated the capability to control spatial temperature distributions within selected regions of the in vivo intervertebral disc and anular wall using interstitial ultrasound. Conclusions Ultrasound energy is capable of penetrating within the highly attenuating disc tissue to produce more extensive radial thermal penetration, lower maximum intradiscal temperature, and shorter treatment times than can be achieved with current clinical intradiscal heating technology. Thus, interstitial ultrasound offers potential as a more precise and faster heating modality for the clinical management of low back pain and studies of thermal effects on disc tissue in animal models.

Catheter‐based ultrasound is being investigated for the potential to deliver heat to disc tissue for the treatment of discogenic low back pain. Two ultrasound applicator design configurations were tested: an intradiscal (IDUS) applicator which can be implanted directly within the disc, and an extradiscal (EDUS) applicator which is placed adjacent to the disc. In vitro heating trials were performed in human lumbar cadaveric disc segments instrumented with 24 thermocouples to obtain detailed maps of the temperature distributions. A low temperature elevation heating protocol in which the maximum temperature measured 5 mm away from the applicator is controlled to 52° C for the treatment period, and a high temperature elevation protocol (maximum temperature controlled to >70° C) were evaluated in this study. In vivo experiments were performed in sheep cervical spine using both applicator configurations, and both heating protocols. Steady‐state temperature maps, and thermal doses (t43) calculated from the trans...

Superficial keratectomy was performed in a New Zealand White rabbit for a suspected limbic dermoid. Histology confirmed the diagnosis. Ocular dermoids have been reported in a variety of laboratory animals. This is the first report of a corneal dermoid in rabbits.

Semen from 15 turkeys was pooled and divided into two groups and diluted with glycerated freezing medium. One group contained naturally occurring levels of Mycoplasma meleagridis while the other was inoculated with a 24-hr culture of the organism. Both groups were frozen under identical conditions. Semen was evaluated for motility and live-dead analysis during various stages of cryopreservation. The number of viable mycoplasmas in both groups was determined prior to and at 1-, 2-, and 6-months frozen storage. The experiment was repeated twice. Semen motility and live-dead evaluation showed no apparent trends outside of the normal decline seen during various stages of cryopreservation. There was no significant decline in M. meleagridis levels in either treatment group in either trial when samples were tested at intervals up to 6 months. The naturally infected semen contained approximately 103 cfu/ml, while the inoculated semen had 105 cfu/ml. It was concluded that viable numbers of M. meleagridis do not substantially decline in turkey semen during cryopreservation and subsequent thawing. Consideration must be given to potential pathogens in turkey semen cryopreserved for long-term storage.