Induction and evaluation of atherosclerosis in New Zealand white rabbits

Atherosclerosis was experimentally induced in New Zealand white rabbits by feeding a high cholesterol diet for 12 weeks for screening of drugs against atherosclerosis. After 12 weeks, blood was collected from ear vein for evaluation of total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL) and very low density lipoprotein (VLDL) levels, then the animals were sacrificed to collect the livers for estimation of cholesterol, and aorta for gross and histopathological evaluations. The elevated levels of serum and liver parameters accompanied by gross and histopathological changes like accumulation of foam cells, atheromatous plaque formation and replacement fibrosis supported the successful induction of atherosclerosis in New Zealand white rabbits.     

Nephrotoxicity of tiletamine in New Zealand white rabbits.

Tiletamine and zolazepam, the two constituents of Telazol, were evaluated independently to determine which agent was responsible for the nephrotoxicity caused by Telazol in New Zealand White rabbits. Five rabbits were injected i.m. with 32 mg/kg of tiletamine, four animals received 7.5 mg/kg of tiletamine, and five rabbits received 32 mg/kg of zolazepam. Urinalysis was performed and blood urea nitrogen and serum creatinine were monitored for 7 days postinjection. In all five rabbits injected with the high dose of tiletamine, blood urea nitrogen and creatinine rose by 3 days postinjection and increased steadily throughout the week. By 4 days postinjection, urine protein and glucose were elevated and cellular and protein casts were present. No serum chemistry or urine abnormalities were detected in rabbits receiving low doses of tiletamine, zolazepam, or in the four control rabbits. All animals were euthanized and necropsied at 7 days postinjection. Histopathology showed severe renal tubular necrosis in all five rabbits injected with 32 mg/kg tiletamine. Mild nephrosis was present in three of four rabbits injected with 7.5 mg/kg of tiletamine. No lesions were present in the zolazepam-injected or control rabbits. The results of this study show that tiletamine is the constituent responsible for the nephrotoxicity of Telazol in rabbits. They further demonstrate that doses commonly used for anesthetic induction or restraint can produce renal lesions in rabbits.     

Anesthetic and nephrotoxic effects of Telazol in New Zealand white rabbits.

Telazol was evaluated as an anesthetic for rabbits. Two groups of five rabbits each were injected intramuscularly with 32 or 64 mg/kg of Telazol, and the depth and duration of anesthesia period monitored. At both doses, the righting reflex was lost within 2 minutes postinjection. Animals in both groups responded to noxious stimuli for the duration of the anesthesia. Hematology and urinalyses were performed daily for 7 days postinjection. Hematologic parameters remained unchanged in both groups. In the high-dose group, blood urea nitrogen and serum creatinine levels increased 1 day postinjection and continued steadily throughout the week. Elevations in urine protein and the presence of casts correlated with this increase. In the low-dose group, blood urea nitrogen and creatinine levels increased and protein was present in the urine of four of five rabbits beginning approximately 5 days postinjection. Histologically, severe renal tubular necrosis was evident 7 days postinjection in all high-dose rabbits and in three rabbits in the low-dose group. Our results indicate that Telazol does not produce analgesia in rabbits and is nephrotoxic at both 32 and 64 mg/kg. We conclude that Telazol is contraindicated for use in rabbits.     

Effect of hypercholesterolemia on myocardial function in New Zealand white rabbits

Although hypercholesterolemia is a well-known risk factor for atherosclerosis, little is known about the effect of hypercholesterolemia on cardiac contractile function. The objective of this study was to examine the effect of hypercholesterolemia on myocardial contractility. Fifteen New Zealand white rabbits were fed standard chow (control group) and another 15 were fed a cholesterolenriched diet (HC group) for 12 weeks. The contractile response of ventricular muscle strips was measured in various extracellular calcium concentrations and at different pacing rates. The whole-cell calcium current recording, and mRNA and protein levels of cellular calcium-handling proteins were also analyzed. With 2 mM Ca²⁺ and stimulation at 3 Hz, the contractile force of HC strips was less than that of the controls (3.63±0.20 vs. 4.61±0.50 mN, p<0.05). The time to peak tension was longer for HC strips (93.3±2.16 vs. 82.2±2.81 ms, p < 0.05). The peak L-type calcium inward current density was slightly higher in HC myocytes but did not reach statistical significance (–14.90±0.94 vs. –12.44±0.84 pA/pF, p=0.15). The mRNA level of sarcoplasmic reticulum Ca²⁺-ATPase (SERCA), normalized to GAPDH, was significantly lower in the HC than that in the control group (2.85±0.14 vs. 7.67±0.67, p<0.05), as was the ryanodine receptor (RyR; 0.42±0.06 vs. 0.71±0.13, p<0.05). The mRNA of the Na⁺/Ca²⁺ exchanger (NCX) was statistically higher in the HC group (0.90±0.12 vs. 0.48±0.05, p<0.05). Western blot experiments revealed that protein expression of SERCA in the HC strips decreased, but that of the NCX increased. The protein expression of the dihydropyridine receptor was similar between these two groups. We concluded that hypercholesterolemia results in suppression of the maximal contractile function and in a longer systolic contractile time course. These changes may partially be mediated through a decrease in SERCA and RyR but an increase in NCX expression.     

Assessment of bacterial community composition within and among Acropora loripes colonies in the wild and in captivity

A growing number of studies have provided insights into the diversity of coral-associated bacteria and their function in the coral holobiont. Yet, information about spatial heterogeneity of bacteria within coral colonies is limited. Using 16S rRNA gene metabarcoding, we analyzed the bacterial community composition across four distinct locations in each of five wild Acropora loripes colonies. Considerable variation within and among colonies was present, which has implications for sampling strategies and data interpretation in coral microbiome research. Bacterial assemblages significantly differed in alpha and beta diversity among colonies, with all corals possessing a high relative abundance of Endozoicomonas. When the same A. loripes colonies were subsequently reared in aquaria over 4 weeks, the relative abundance of Marinobacter initially increased in all colonies. However, no significant alteration in bacterial community composition was observed over time and the colonies maintained distinct bacterial microbiomes.

     

The inheritance of skeletal muscle fibre composition in mice

Two inbred strains of mice C3H/HE and SWR, and generations produced by intercrossing, were studied to investigate the effect of heredity on muscle composition. The data were found to be consistent with a polygenic mode of inheritance. No simple effect of sex-linkage or maternal influence was evident. The heritability of fibre type percentage total fibre number and the relative size of Type I and Type II fibres were highly significant. Principal component analysis yielded a "genetic" vector which accounted for 57% of the variation in muscle fibre composition. Patterns of covariance of fibre type percentage, total fibre number and relative sizes of Type I and Type II fibres showed a single correlated response.     

Experimentally reducing corticosterone mitigates rapid captivity effects on behavior,but not body composition,in a wild bird

Wild animals and captives display physiological and behavioral differences, and it has been hypothesized, but rarely tested, that these differences are caused by sustained elevation of the hormone corticosterone. We used repeated computed tomography (CT) imaging to examine body composition changes in breeding male and female wild house sparrows (Passer domesticus; n = 20) in response to two weeks of captivity, and assessed behavioral changes using video recordings. Half of the birds received the drug mitotane, which significantly decreased stress-induced corticosterone titers compared to controls. Based on the CT images, fat volumes increased, and pectoralis muscle density and heart and testes volumes decreased, over the two weeks of captivity in both groups of birds. However, beak-wiping, a behavior that can indicate anxiety and aggression, showed increased occurrence in controls compared to mitotane-treated birds. While our results do not support the hypothesis that these body composition changes were primarily driven by stress-induced corticosterone, our data suggest that experimentally reducing stress-induced corticosterone may mitigate some captivity-induced behavioral changes. Broadly, our results emphasize that researchers should take behavioral and physiological differences between free-living animals and captives into consideration when designing studies and interpreting results. Further, time in captivity should be minimized when birds will be reintroduced back to the wild.     

Pathological study of Streptococcus faecalis antigen-induced arthritis in New Zealand white rabbits

The pathological examination of the rabbit knee joint with antigen-induced arthritis produced by heat-killed Streptococcus faecalis (Str. faec.) as antigen was carried out. Macroscopically, there were findings of acute inflammation about five hours after the injection. Histopathologically, very remarkable acute exudative inflammation was seen 48 hours later. This supported the picture of Arthus reaction. The Arthus reaction disappeared with time, and this supported the view of delayed-type hypersensitivity three weeks later. After that, an obvious chronic inflammation was admitted in 10 weeks. This resembled the histopathological feature of rheumatoid arthritis (RA) when these findings are summarized. It was suggested that arthritis produced by Str. faec. progresses from an acute condition to a one with time. As mentioned above, it thought that Arthus reaction of both immediate hypersensitivity and delayed-type hypersensitivity are necessary in the occurrence of this arthritis.     

Pathogenicity of Pasteurella multocida A:3 in Flemish giant and New Zealand white rabbits.

Pasteurella multocida A:3 was isolated during an outbreak of pasteurellosis in Flemish Giant (FG) rabbits. Since New Zealand White (NZW) rabbits housed in the same room were not as severely affected as FG rabbits, experimental inoculation was undertaken to determine if FG rabbits were more susceptible than NZW rabbits to pasteurellosis induced by this isolate. Rabbits of each breed were inoculated with P. multocida A:3 and observed for 3 weeks. Four of 5 FG rabbits developed severe clinical disease on days 6, 9, 12 and 14 after inoculation; whereas, the one affected NZW rabbit became ill 14 days after inoculation. All rabbits with clinical disease developed fibrinosuppurative pleuritis, pyothorax and pneumonia which was more severe in FG than NZW rabbits. At necropsy, P. multocida A:3 was isolated from multiple sites of the diseased rabbits. No significant difference (P = 0.099) in the prevalence of lesions between the two breeds was found; however, the score of pneumonia and pleuritis was 3 times greater in FG rabbits than NZW rabbits.     

Skeletal muscle and bone: effect of sex steroids and aging

Both estrogen and testosterone are present in males and females. Both hormones contribute to the well being of skeletal muscle and bone in men and women, and there is evidence that the loss of sex hormones is associated with the age-related decline in bone and skeletal muscle mass. Hormonal supplementation of older adults to restore estrogen and testosterone levels to those of young men and women is not without penalty.     

Aerosolized Bacillus anthracis infection in New Zealand white rabbits: natural history and intravenous levofloxacin treatment

The natural history for inhalational Bacillus anthracis (Ames strain) exposure in New Zealand white rabbits was investigated to better identify potential, early biomarkers of anthrax. Twelve SPF Bordetella-free rabbits were exposed to 150 LD(50) aerosolized B. anthracis spores, and clinical signs, body temperature, complete blood count, bacteremia, and presence of protective antigen in the blood (that is, antigenemia) were examined. The development of antigenemia and bacteremia coincided and preceded both pyrexia and inversion of the heterophil:lymphocyte ratio, an indicator of infection. Antigenemia was determined within 1 h by electrochemiluminescence immunoassay, compared with the 24-h traditional culture needed for bacteremia determination. Rabbits appeared clinically normal until shortly before succumbing to anthrax approximately 47 h after challenge or approximately 22 h after antigenemia, which suggests a relatively narrow therapeutic window of opportunity. To evaluate the therapeutic rabbit model, B. anthracis-exposed rabbits were treated (after determination of antigenemia and later confirmed to be bacteremic) intravenously with the fluoroquinolone antibiotic levofloxacin for 5 d at a total daily dose of 25 or 12.5 mg/kg, resulting in nearly 90% and 70% survival, respectively, to the study end (28 d after challenge). The peak level for 12.5 mg/kg was equivalent to that observed for a 500-mg daily levofloxacin dose in humans. These results suggest that intravenous levofloxacin is an effective therapeutic against inhalational anthrax. Taken together, our findings indicate that antigenemia is a viable and early biomarker for B. anthracis infection that can be used as a treatment trigger to allow for timely intervention against this highly pathogenic disease.     

Catarrhine juvenile mortality in captivity,under seminatural conditions,and in the wild

Juvenile mortality is an important problem in the development of captive populations. I compiled data from published literature on abortion, premature mortality, stillbirth, and death of unweaned young. Cumulative mortality incidences (CMI) during the first month in captive populations (CP) of Cercopithecoidea range between 13 and 51%, and CMI in the first year between 28 and 56%. Mortality rate during the first year ranges between <4 and 48% in free- ranging populations (FRP) and between 10 and 60% in wild populations (WP). Much of the juvenile mortality in CP appears to occur in the first month, whereas in FRP and WP mortality is more scattered throughout the juvenile period. High mortality rates occur in both CP and WP of nonhuman Hominoidea. Mortality rate during the first month in CP is between 12 and 36% for the Hylobatidae and between 18 and 31% for the Pongidae. If the entire juvenile period is considered, gorilla CP and WP have comparable CMI, while CMI is higher in WP than CP for chimpanzees. Most of the juvenile mortality in CP of chimpanzees occurs before the age of 1 year. Trauma, including infanticide and maternal inadequacy, seems to be a more important factor in infant mortality of Cercopithecoidea than infectious disease is. Relatively frequent reports of congenital, hereditary, and/or genetically determined malformations in the Cercopithecoidea may be related to the long use of animals in this group for laboratory purposes. Infectious disease is the most important cause of nonhuman hominoid juvenile mortality, followed by trauma and maternal disorders, particularly related aberrant maternal behavior. Cercopithecoid juvenile mortality risk factors most frequently mentioned in the literature are sex of the infant and rank of the mother: dominant females produce more female offspring, and juvenile males suffer higher mortality than females do. The female skewed sex ratio at birth in gorillas and chimpanzees could be explained by the local resource competition theory. Higher male mortality rates occur in nonhuman Hominoidea, except in two Hylobatesspp. and Pan paniscus,which have higher female mortality. Parity and rearing history of the mother are very important risk factors in nonhuman hominoid infant mortality.     

Cardiovascular reflexes during sustained handgrip exercise: role of muscle fibre composition, potassium and lactate

Six healthy men performed sustained static handgrip exercise for 2 min at 40% maximal voluntary contraction followed by a 6-min recovery period. Heart rate (fc), arterial blood pressures, and forearm blood flow were measured during rest, exercise, and recovery. Potassium ([K+]) and lactate concentrations in blood from a deep forearm vein were analysed at rest and during recovery. Mean arterial pressure (MAP) and fc declined immediately after exercise and had returned to control levels about 2 min into recovery. The time course of the changes in MAP observed during recovery closely paralleled the changes in [K+] (r = 0.800, P < 0.01), whereas the lactate concentration remained elevated throughout the recovery period. The close relationship between MAP and [K+] was also confirmed by experiments in which a 3-min arterial occlusion period was applied during recovery to the exercised arm by an upper arm cuff. The arterial occlusion affected MAP while fc recovered at almost the same rate as in the control experiment. Muscle biopsies were taken from the brachioradialis muscle and analysed for fibre composition and capillary supply. The MAP at the end of static contraction and the [K+] appearing in the effluent blood immediately after contraction were positively correlated to the relative content of fast twitch (% FT) fibres (r = 0.886 for MAP vs % FT fibres, P < 0.05 and r = 0.878 for [K+] vs % FT fibres, P < 0.05). Capillary to fibre ratio showed an inverse correlation to % FT fibres (r = -0.979, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of training on fibre composition in rat gastrocnemius muscle

Forty-eight adult Wistar rats were divided into four groups for experimentation. The group I was used as a control and groups II, III and IV underwent progressive treadmill training. Samples of the red and mixed portions of m. gastrocnemius (lateral head) were stained with the histochemical technique of m-ATPase to determine the percentage of type I, IIA and IIB fibres, and with NADH-TR, in order to quantify variations in "low-oxidative" fibre percentages. The results showed that progressive training did not lead to statistical variations in the percentage of type I fibres. However, the proportion of type IIA fibres rose, while that of IIB fibres fell, in both cases significantly. Variations were more marked in mixed than in red Gastrocnemius muscle. A clear decrease was noted in "low-oxidative" fibres, which were virtually absent from red portion. This decrease was more marked, and occurred more rapidly, than in type IIB fibres.     

Sexual behavior of male New Zealand white rabbits in an intensive production unit

Sexual behavior in the male white New Zealand rabbit in intensive production units is not fully documented. Therefore, the objective of this work was to provide further information about the sexual behavior of this species in intensive production systems. Fourteen 6- to 12-month-old rabbits were studied for 6 months (July/December) when housed individually under natural photoperiod (19 degrees latitude north). They were mated once a week. When mated they were exposed at 6-min intervals to five oestrous females. The number of mounts, time between mounts, time and number of ejaculations, time between ejaculations, and also enuresis, grasping and kicking were recorded. Mounts (n=222) were observed and recorded. Males mated one to five times during each evaluative session. Enuresis was present only in one observation. Sexual aggressiveness such as grasping and kicking was present during 142 and 133 matings. Time for mounting and ejaculation in accumulated means (minutes, seconds, tenths) from the first to the fifth mount were noted and an accumulative average of 4.20 min for the fifth mounting was noted. Minimum times for ejaculation and next mating was 00:17:00 min and maximum was 05:33:03 min. It was concluded that sexual behavior in white New Zealand male rabbits remained unchanged through the duration of the period of study.     

Red and white muscle fibre activity in swimming skipjack tuna, Katsuwonus pelamis (L.)

To test the hypothesis that white muscle fibre portions of the myotomes are used at sustainable swimming speeds, skipjack tuna, Katsuwonus pelamis , were forced to swim against various current velocities in a water tunnel while electrical activity of the red and white muscle fibres was simultaneously recorded. Eight fish were tested, five fish graded white muscle fibres into activity at swimming speeds above their minimum hydrostatic equilibrium speed, but well below the estimated maximum sustainable swimming speed of skipjack tuna. Three other fish showed white muscle fibre activity at minimum swimming speeds, a possibly abnormal condition.     

Skeletal muscle fiber type composition and performance during repeated bouts of maximal, concentric contractions

Force output and fatigue and recovery patterns were studied during intermittent short-term exercise. 27 men performed three bouts of 30 maximal unilateral knee extensions on 2 different occasions. Blood flow was maintained or occluded during recovery periods (60 s). Blood flow was restricted by inflating a pneumatic cuff placed around the proximal thigh. Muscle biopsies from vastus lateralis were analyzed for identification of fast twitch (FT) and slow twitch (ST) fibers and relative FT area. Peak torque decreased during each bout of exercise and more when blood flow was restricted during recovery. Initial peak torque (IPT) and average peak torque (APT) decreased over the three exercise bouts. This response was 3 fold greater without than with blood flow during recovery. IPT and APT decreased more in individuals with mainly FT fibers than in those with mainly ST fibers. It is suggested that performance during repeated bouts of maximal concentric contractions differs between individuals with different fiber type composition. Specifically, in high intensity, intermittent exercise with emphasis on anaerobic energy release a high FT composition may not necessarily be advantageous for performance.