Carsten Grøndahl

Jugular venous pooling during lowering of the head affects blood pressure of the anesthetized giraffe

How blood flow and pressure to the giraffes brain are regulated when drinking remains debated. We measured simultaneous blood flow, pressure, and cross-sectional area in the carotid artery and jugular vein of five anesthetized and spontaneously breathing giraffes. The giraffes were suspended in the upright position so that we could lower the head. In the upright position, mean arterial pressure (MAP) was 193 +/- 11 mmHg (mean +/- SE), carotid flow was 0.7 +/- 0.2 l/min, and carotid cross-sectional area was 0.85 +/- 0.04 cm(2). Central venous pressure (CVP) was 4 +/- 2 mmHg, jugular flow was 0.7 +/- 0.2 l/min, and jugular cross-sectional area was 0.14 +/- 0.04 cm(2) (n = 4). Carotid arterial and jugular venous pressures at head level were 118 +/- 9 and -7 +/- 4 mmHg, respectively. When the head was lowered, MAP decreased to 131 +/- 13 mmHg, while carotid cross-sectional area and flow remained unchanged. Cardiac output was reduced by 30%, CVP decreased to -1 +/- 2 mmHg (P < 0.01), and jugular flow ceased as the jugular cross-sectional area increased to 3.2 +/- 0.6 cm(2) (P < 0.01), corresponding to accumulation of approximately 1.2 l of blood in the veins. When the head was raised, the jugular veins collapsed and blood was returned to the central circulation, and CVP and cardiac output were restored. The results demonstrate that in the upright-positioned, anesthetized giraffe cerebral blood flow is governed by arterial pressure without support of a siphon mechanism and that when the head is lowered, blood accumulates in the vein, affecting MAP.

Identification of Acute Phase Proteins and Assays Applicable in Nondomesticated Mammals

Abstract The serum concentration of acute phase proteins (APPs) increases dramatically in response to inflammation and tissue injury. APPs are clinically useful in a range of domesticated mammals; however, knowledge is limited in nondomesticated mammals. The detective ability of two assays for each of three potential APPs—serum amyloid A (SAA), C-reactive protein (CRP), and haptoglobin (Hp)—was evaluated in eight species. For SAA, a turbidimetric immunoassay (TIA) demonstrated significant detective abilities in the Asian elephant (Elaphas maximus), impala (Aepyceros melampus), musk ox (Ovibos moschatus), and chimpanzee (Pan troglodytes), as did an SAA enzyme-linked immunosorbent assay (ELISA) in the impala. For CRP, both TIA and ELISA had significant detective abilities in the chimpanzee. For Hp, a colorimetric assay demonstrated significant detective abilities in impala, musk ox, sitatunga (Tragelaphus spekeii), and chimpanzee, as did the Hp ELISA in the impala, musk ox, and sitatunga. In conclusion, these results suggest that assays for detection of relevant APPs in several nondomesticated animals are available.

Protection against high intravascular pressure in giraffe legs

The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.

Meiotic studies in infertile domestic pig-babirusa hybrids.

Mating of a babirusa (Babyrousa babyrussa) boar and a domestic sow (Sus scrofa) resulted in the birth of 5 live domestic pig-babirusa hybrid piglets. Chromosome analysis of one of the surviving males confirmed that they were domestic pig-babirusa hybrids by revealing the presence of a complete haploid set of 19 porcine chromosomes as well as a complete haploid set of 19 babirusa chromosomes in the karyotype. None of the surviving piglets, two males and one female, had shown signs of sexual maturity at age 27 months. Histological examination of gonadal biopsies from the 2 males revealed that both were azoospermatic. Immunostaining revealed SCP3-positive axial elements in the nuclei of primary spermatocytes, indicating that they were progressing through leptotene and zygotene of meiotic prophase. However, the presence of multiple short stretches of axial elements in pachytene nuclei indicated that this phase was blocked, probably due to aberrant chromosome pairing. Histological examination of the ovaries revealed follicular structures, but oocytes within them were generally degenerated. We conclude that both male and female pig-babirusa hybrids were infertile, most likely due to germ cell death resulting from abnormalities of chromosome pairing during meiotic prophase.

Ungulate movement in an extreme seasonal environment: year-round movement patterns of high-arctic muskoxen

Detailed knowledge on movement behaviour of free-ranging muskoxen Ovibos moschatus is currently lacking. Quantifying variation in individual movement and the variables driving such patterns is important to understand how they meet their basic requirements and to inform management. Because muskoxen exist in nutrient-poor systems with extreme climatic and seasonal variability, individual movement patterns are expected to be largely dependent on environmental conditions and the seasonal variation therein. We analysed high-resolution location data of 14 adult female muskoxen roaming around Zackenberg in northeast Greenland (74°28′N, 20°34′W). We assessed the relative importance (Akaike variable weights) of multiple extrinsic conditions in explaining variation in hourly speed, turning angles, and activity. We found that time of day, ambient temperature, and land cover types were the most important covariates explaining variation in fine-scale movement and activity patterns throughout the year. Movement speeds were consistently lower in land cover types with more dense vegetation. Speed of movement was positively correlated with ambient temperature when the days were long, while negatively related with temperature in periods with few or no hours of daylight. Diurnal peaks in movement and activity patterns were observed most of the year (including mid-winter months with 24-h darkness), except during high-summer (24-h of daylight), when individual movement and activity remained continuously high. The topographic variation (elevation and slope) explained only a small part of the variation in muskox movement patterns in the areas where the muskoxen were observed. Analyses of displacement patterns revealed a mixture of movement behaviours. We conclude that muskoxen in high-arctic Greenland adopt a largely nomadic movement behaviour, but do so within a rather small geographical area (app. 5000 km2), and that their movement and activity patterns are largely directed at finding suitable foraging patches and avoiding cold-stress during harsh winter weather.

The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output

ABSTRACT Giraffes – the tallest extant animals on Earth – are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It thus remains unexplained how the normal-sized giraffe heart generates such massive arterial pressures. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4±1.4 l min−1, respectively. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg−1. Left ventricular circumferential wall stress was 7.83±1.76 kPa. We conclude that, relative to body mass, a small left ventricular cavity and a low stroke volume characterizes the giraffe heart. The adaptations result in typical mammalian left ventricular wall tensions, but produce a lowered cardiac output. Summary: A left ventricular cavity and low stroke volume characterise the giraffe heart, resulting in typical mammalian left ventricular wall tensions but lowered cardiac output.

Sensorimotor responsiveness and resolution in the giraffe

SUMMARY The ability of an animal to detect and respond to changes in the environment is crucial to its survival. However, two elements of sensorimotor control – the time required to respond to a stimulus (responsiveness) and the precision of stimulus detection and response production (resolution) – are inherently limited by a competition for space in peripheral nerves and muscles. These limitations only become more acute as animal size increases. In this paper, we investigated whether the physiology of giraffes has found unique solutions for maintaining sensorimotor performance in order to compensate for their extreme size. To examine responsiveness, we quantified three major sources of delay: nerve conduction delay, muscle electromechanical delay and force generation delay. To examine resolution, we quantified the number and size distribution of nerve fibers in the sciatic nerve. Rather than possessing a particularly unique sensorimotor system, we found that our measurements in giraffes were broadly comparable to size-dependent trends seen across other terrestrial mammals. Consequently, both giraffes and other large animals must contend with greater sensorimotor delays and lower innervation density in comparison to smaller animals. Because of their unconventional leg length, giraffes may experience even longer delays compared with other animals of the same mass when sensing distal stimuli. While there are certainly advantages to being tall, there appear to be challenges as well – our results suggest that giraffes are less able to precisely and accurately sense and respond to stimuli using feedback alone, particularly when moving quickly.

COMPARISON OF ETORPHINE-ACEPROMAZINE AND MEDETOMIDINE-KETAMINE ANESTHESIA IN CAPTIVE IMPALA (AEPYCEROS MELAMPUS)

Abstract:  Impala (Aepyceros melampus) are a notoriously difficult species to manage in captivity, and anesthesia is associated with a high risk of complications including mortality. The aim of this study was to compare an opioid-based protocol with an α-2 agonist-based protocol. Nine female impala were studied in a random cross-over design. Subjects received either an etorphine–acepromazine (EA) protocol: 15 μg/kg etorphine and 0.15 mg/kg acepromazine, or a medetomidine–ketamine (MK) protocol: 109 μg/kg medetomidine and 4.4 mg/kg ketamine on day 1. Anaesthesia was repeated 3 days later with the alternative protocol. Subjective assessments of the quality of induction, muscle relaxation, and recovery were made by a blinded observer. Objective monitoring included blood pressure, end-tidal CO2, regional tissue oxygenation, and blood gas analysis. EA provided a significantly quicker (mean EA, 7.17 mins; MK, 17.6 mins) and more-reliable (score range EA, 3–5; MK, 1–5) induction. Respiratory rates were lower for EA with higher end-tidal CO2, but no apnoea was observed. As expected, blood pressures with EA were lower, with higher heart rates; however, arterial oxygenation and tissue oxygenation were equal or higher than with the MK protocol. In conclusion, at these doses, EA provided superior induction and equivalent muscle relaxation and recovery with apparent improved oxygen tissue delivery when compared to MK.

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate

The tallest animal on earth, the giraffe (Giraffa camelopardalis) is endowed with a mean arterial blood pressure (MAP) twice that of other mammals. The kidneys reside at heart level and show no sign of hypertension‐related damage. We hypothesized that a species‐specific evolutionary adaption in the giraffe kidney allows normal for size renal haemodynamics and glomerular filtration rate (GFR) despite a MAP double that of other mammals.

Effects of Polar Bear and Killer Whale Derived Contaminant Cocktails on Marine Mammal Immunity

Most controlled toxicity studies use single chemical exposures that do not represent the real world situation of complex mixtures of known and unknown natural and anthropogenic substances. In the present study, complex contaminant cocktails derived from the blubber of polar bears (PB; Ursus maritimus) and killer whales (KW; Orcinus orca) were used for in vitro concentration-response experiments with PB, cetacean and seal spp. immune cells to evaluate the effect of realistic contaminant mixtures on various immune functions. Cytotoxic effects of the PB cocktail occurred at lower concentrations than the KW cocktail (1 vs 16 μg/mL), likely due to differences in contaminant profiles in the mixtures derived from the adipose of each species. Similarly, significant reduction of lymphocyte proliferation occurred at much lower exposures in the PB cocktail (EC50: 0.94 vs 6.06 μg/mL; P < 0.01), whereas the KW cocktail caused a much faster decline in proliferation (slope: 2.9 vs 1.7; P = 0.04). Only the KW cocktail modulated natural killer (NK) cell activity and neutrophil and monocyte phagocytosis in a concentration- and species-dependent manner. No clear sensitivity differences emerged when comparing cetaceans, seals and PB. Our results showing lower effect levels for complex mixtures relative to single compounds suggest that previous risk assessments underestimate the effects of real world contaminant exposure on immunity. Our results using blubber-derived contaminant cocktails add realism to in vitro exposure experiments and confirm the immunotoxic risk marine mammals face from exposure to complex mixtures of environmental contaminants.