Recovering an endangered frog species through integrative reproductive technologies.

The establishment and management of ex situ breeding and assurance populations around the globe are meant to provide short-term solutions to the formidable loss of amphibian diversity presently occurring. Large multi-scaled facilities, such as zoos and aquariums, can provide the infrastructure to safeguard species and populations. However, often even large, economically viable facilities lack the knowledge to efficiently cater to the plethora of environmentally controlled physiological strategies that amphibians possess. Anurans present a class of amphibians that have often been viewed as easy to maintain ex situ. However, while adult survival may be relatively successful it is rarely accompanied by good reproductive output, health, and fitness. Even more conspicuous is the low survivorship of offspring produced ex situ once they are translocated back into the wild. The mountain yellow-legged frog (R. muscosa) ex situ breeding program EBP is a prime example of the challenges that amphibians EBPs face. Although more research is needed, the R. muscosa program has increased reproductive output and health of its colony by incorporating reproductive technologies and strategic genetic management in conjunction with a greater understanding of the species' natural history, to produce and translocate viable animals each year. This paper highlights the EBPs past decade of research featuring the program's contribution to building empirical, multidisciplinary approaches that boost the robustness of an endangered species, by safeguarding existing genetic diversity and maximizing fitness and survival outcomes.

Surgical learning activities for house officers: do they improve the surgical experience?

OBJECTIVE: To ascertain whether house officers (HOs) attain a more satisfactory surgical rotation experience when they perform basic surgical learning activities. We also sought to establish how many and which learning activities HOs achieve and the effect on their surgical experience. METHODOLOGY: A questionnaire listing 20 learning activities and questions regarding satisfaction with an overall experience was disseminated to HOs in the UK and Ireland who had completed ≥3 months of surgical rotations. Satisfaction with surgical experience was dichotomised in order to perform logistic regression using R Studio software v0.98. RESULTS: The survey was completed by 150 respondents, with 26 % completing at least 10 basic surgical learning activities during their surgical rotation. On multivariate analysis, the completion of these learning activities was significantly associated with a satisfactory rotation experience (p < 0.001). Furthermore, the use of a checklist of surgical activities provided to HOs was associated with a significant increase in the performance of learning activities (p = 0.003). CONCLUSION: Surgical HOs who were informed about potential basic surgical learning activities that can be performed during their rotations performed significantly more of these activities. And these activities were associated with a significantly greater satisfaction with surgical rotations. Therefore, we recommend facilitating HOs completion of these activities as this will ensure that basic surgical competencies are achieved and that HOs will be more satisfied with their surgical experience.

Effect of family support on the success of translocated black-tailed prairie dogs.

Translocation has become a widely used conservation tool but remains only marginally successful. High mortality is often attributed to predation, but for highly social species, founder group composition may also play a critical role in postrelease survival. I compared the fitness of black-tailed prairie dogs translocated with or without their family groups. Animals in the family translocated groups were individually marked and observed until coterie membership was determined. Nonfamily translocated animals were trapped without regard to family membership. I measured fitness by retrapping all marked animals remaining at release sites in the summer following release. Family translocated animals were five times more likely to survive and had significantly higher reproductive success than those translocated without families. Predation was an important impediment of translocation success, but family translocation significantly reduced the success of predators on newly established prairie dog colonies. Postrelease survival was also affected by the timing of release, but appeared to be more important for juveniles than adults. These results demonstrate the importance of considering familiarity when translocations are required. More broadly, these results illustrate the value of applying animal behavior to conservation efforts and suggest that other species dependent on social interactions for survival and reproduction may benefit substantially from the maintenance of social groups during translocations.

Maternal presence and rearing condition affect responses to a live predator in kangaroo rats (Dipodomys heermanni arenae).

Experiment 1 compared the responses of wild-caught adult and captive-born adult and juvenile kangaroo rats (Dipodomys heermanni arenae) to a live snake. Wild-caught adult rats were less active and monitored the snake more than during a control condition; captive-born juvenile rats did not behave differently during snake and control tests. Snake-naive adult rats behaved more like the wild-caught adult rats, but not on all measures. In Experiment 2, pups were tested at 25 and 50 days of age in 4 conditions: no-snake control, alone with the snake, with a sibling and the snake, and with the mother and the snake. Pups did not behave differently during control and snake tests, but during tests with the mother, pups faced the snake less and followed the mother. Younger pups were more often near the mother than a sibling and followed the mother more when the snake was present. Development of defensive behavior may depend on both predator experience and maternal influence.

Pressure diuresis and autonomic function in conscious dogs.

Pressure diuresis is thought to be a major long-term regulator of arterial blood pressure (AP). Previously, pressure diuresis has been characterized using pharmacological or surgical blockade of other mechanisms known to affect renal function. This study evaluated pressure diuresis in conscious dogs with minimal experimental interference. Dogs were chronically instrumented under pentobarbital anesthesia with aortic and urinary bladder catheters. AP was increased by 10% in resting dogs by exposure to increased light and sound intensity (arousal) for 90 min. During arousal, urine flow (UV) and Na+ excretion (UNa+ V) correlated with AP (UV vs. AP, r = 0.12, P less than 0.05; UNa+ V vs. AP, r = 0.19, P less than 0.005; 17 trials in 7 dogs). Arousal did not affect the plasma concentration of atrial natriuretic factor, suggesting that this hormone did not contribute to the correlations between UV or UNa+ V and AP. Because arousal may induce an autonomically mediated antidiuresis, studies were repeated during autonomic ganglionic blockade with hexamethonium. During autonomic blockade, the correlations between UV or UNa+ V and AP were increased (UV vs. AP, r = 0.72; UNa+ V vs. AP, r = 0.72, P less than 0.001; 6 trials in 4 dogs). We conclude that the effect of pressure diuresis on UV and UNa+ V can be detected in the intact animal, during normal operation of all the mechanisms that control renal function. Furthermore, when autonomic reflexes are blocked, the pressure-diuresis mechanism is a major determinant of UV and UNa+ V.

Production of renin, angiotensin II, and aldosterone by adrenal explant cultures: response to potassium and converting enzyme inhibition.

The existence of renin in a number of extrarenal tissues has been well documented, but the physiological role of extrarenal renin remains unknown. To study the physiological role of adrenal renin, we developed a serum-free culture system for adrenal capsular/zona glomrulosa explants. Explants showed good viability in culture (greater than 80%), and demonstrated net production of aldosterone, angiotensin II, and prorenin. Aldosterone production was consistently stimulated by an increase in potassium (6 mM) in the culture medium. Both aldosterone and angiotensin II production could be attenuated by adding the angiotensin converting enzyme inhibitor lisinopril to the culture medium (0.1 mM). These data suggest that rat adrenal explants are capable of producing all of the components of a functional renin-angiotensin-aldosterone system and that these components can interact in response to physiological stimuli. These findings support the hypothesis that a local adrenal renin system may play a physiological role in the control of adrenal aldosterone production.

Regulation of adrenal renin messenger ribonucleic acid by dietary sodium chloride.

Zona glomerulosa (ZG) and zona fasciculata (ZF/M) poly(A)+ RNA were isolated from the adrenals of bilaterally nephrectomized female Sprague-Dawley rats and hybridized to a full-length 32P-labeled 1423-base pair (bp) renin cDNA as well as a 698-bp renin cDNA KpnI segment (corresponding to amino acids 92-325) by the dot blot procedure using Bio-Rad Zeta Probe membranes. Extensive hybridization was observed with ZG mRNA, and only slight binding was seen with ZF/M mRNA. These results extend earlier reports from this laboratory indicating that the enzymic activity for renin is predominantly localized in ZG cells. Hence, high message levels account for the high enzymic activity. Adrenal ZG poly(A)+ RNA was also isolated from rats maintained on normal and sodium-deplete diets for 15 days and was hybridized to the radiolabeled 698-bp renin probe. Essentially twice the amount of probe was bound to the message from salt-deplete ZG tissue compared to message from normal ZG per microgram mRNA. Hybridization was proportional to the amount of poly(A)+ RNA employed over the range of 0-1 microgram, suggesting the applicability of this procedure for approximate quantitation purposes. The membranes were freed from the 32P-labeled renin cDNA and subsequently rehybridized with a 32P-radiolabeled 1200-bp beta-actin cDNA probe. It was observed that ZF/M poly(A)+ RNA contained more beta-actin message than ZG poly(A)+ RNA, indicating a greater transcription rate for beta-actin in ZF/M tissue in contrast to transcription of the renin gene.

Adrenal renin: a possible local hormonal regulator of aldosterone production.

The complete renin-angiotensin system is present in the adrenal cortex: prorenin, renin, angiotensinogen, angiotensin I and II, and converting enzyme. Most of the renin found is probably synthesized there since the renin concentration increases after nephrectomy, and the mRNA for renin is present. The renin-angiotensin system has the highest activity in the zona glomerulosa cells, the site of aldosterone formation. A low-sodium diet or a high-potassium diet, or nephrectomy markedly increases the adrenal renin concentration in the zona glomerulosa cells without any effect on the fasciculata-medullary cells. There is a close correlation between adrenal renin and aldosterone production. The adrenal renin angiotensin system may be a local regulator of aldosterone production.

Effect of atrial natriuretic factor on calcium fluxes in adrenal glomerulosa cells.

We studied the effect of atrial natriuretic factor (ANF) on calcium influx and efflux in rat adrenal glomerulosa cells stimulated by angiotensin II (Ang II) or potassium ion, and observed how ANF inhibits the initial and sustained phases of the aldosterone response to Ang II or K+ using a superfusion system of dispersed adrenal glomerulosa cells. K+ (8 mM) significantly increased Ca2+ influx rate compared with basal rate (0.91 +/- 0.10 vs 0.42 +/- 0.04 nmol/min/10(6) cells; p less than 0.01). ANF (10(-8) M) did not inhibit the K+-induced increase in Ca2+ influx rate (0.99 +/- 0.18 nmol/min/10(6) cells). Ang II (10(-9) and 10(-8) M) stimulated Ca2+ influx rate (10(-9) M Ang II, 0.62 +/- 0.02; 10(-8) M Ang II, 0.71 +/- 0.09 vs basal, 0.44 +/- 0.03 nmol/min/10(6) cells; p less than 0.05), while ANF (10(-8) M) did not change the Ca2+ influx rate increased by Ang II (ANF + 10(-9) M Ang II, 0.62 +/- 0.06; ANF + 10(-8) M Ang II, 0.69 +/- 0.14 nmol/min/10(6) cells). In the Ca2+ efflux study ANF (10(-8) M) was perfused through the cells 10 minutes before the start of perfusion with Ang II (10(-9) M) or K+ (12 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-stimulated drinking in marine fish.

Drinking rates in both marine and freshwater stenohaline fish were studied by measuring the ingestion of polyethylene glycol that had been added to the aquarium water. Two marine species, the long-horned sculpin and the flounder, and three freshwater species, the common goldfish, the mottled sculpin, and the common shiner, were used. Control drinking rates in freshwater fish averaged 0.03-0.1% body wt/h and in marine fish varied between 0.06 and 0.24% body wt/h. Intramuscular injections of angiotensin II (ANG II) stimulated drinking two- to threefold in the two marine species but had no effect on the drinking rate of the freshwater species. Hemorrhage (1-2% of body wt) also stimulated drinking in the two marine species (6- to 10-fold) but did not affect the drinking rate of two freshwater species. Thus exogenous ANG II and hemorrhage stimulate drinking in two marine stenohaline fish as they do in mammals. These responses were absent in the three freshwater fishes studied. However, injection of converting enzyme inhibitor (SQ 20881) or saralasin in order to block endogenous ANG II did not attenuate either basal or hemorrhage-stimulated drinking in the marine fish.

Alterations in renal vascular reactivity induced by chronic central administration of captopril in the spontaneously hypertensive rat.

We have previously demonstrated that chronic intracerebroventricular (ICV) administration of captopril attenuates the development of hypertension in young SHR in association with a depression in whole animal reactivity to vasoactive agents and an increased baroreflex sensitivity. In the present study we analyzed vascular reactivity in perfused kidneys from SHR treated with captopril or vehicle to determine whether the depression in reactivity was due to changes in baroreflex activity or an effect on the vasculature. Captopril (1.25 micrograms/hr) was infused (osmotic mini pumps) for 4 weeks. Vascular reactivity to norepinephrine, angiotensin and vasopressin was assessed in isolated kidneys perfused with an artificial medium at constant flow. SHR treated with ICV captopril showed a significantly lower arterial pressure and basal renal vascular resistance than SHR treated with ICV vehicle or IV captopril. In addition, these rats showed decreased vascular reactivity to all vasoactive agents tested as signified by a shift in the dose-response curves to the right with an increase in threshold (ED16) and ED50. Kidneys from WKY treated with ICV captopril also showed a decrease in vascular reactivity in comparison to WKY treated with ICV vehicle. Our data suggest that captopril, through a central action, attenuates the development of hypertension by decreasing vascular reactivity to vasoconstrictors.

Differential secretion and removal of multiple renin forms.

Hepatic clearance of renin in anesthetized dogs was measured during aortic constriction and after nephrectomy. Aortic constriction caused a transient increase in the hepatic extraction ratio for renin (ER) from 0.34 +/- 0.05 to 0.52 +/- 0.05, whereas nephrectomy caused the ER to decrease with time. Isoelectric focusing of plasma samples over an average pH gradient of 4.0-6.2 yielded several peaks of renin activity. Peaks focusing above pH 5.0 were combined and arbitrarily classified as basic renin, whereas peaks below pH 5.0 were classified as acidic renin. In each period the ER for basic renin was significantly greater than that for acidic renin. The proportion of basic renin was transiently increased at 10 min (59 +/- 4%) compared with control (41 +/- 4%). This contributed to the increased ER after constriction. The decreased ER after nephrectomy, however, was not solely due to differential removal of these forms. We conclude that hepatic clearance of renin is partly a function of the type of renin secreted by the kidney, which in turn may change with the duration of the secretory stimulus.

Optimal locations for a class of nonlinear, single-facility location problems on a network.

This paper investigates a class of single-facility location problems on an arbitrary network. Necessary and sufficient conditions are obtained for characterizing locally optimal locations with respect to a certain nonlinear objective function. This approach produces a number of new results for locating a facility on an arbitrary network, and in addition it unifies several known results for the special case of tree networks. It also suggests algorithmic procedures for obtaining such optimal locations.

Sensitivity of trends in geometric mean blood levels to random measurement errors.

A statistical model is investigated that expresses observations, such as blood lead levels, as an additive function of true levels and random measurement errors. Both empirical results (obtained from a series of computer simulation experiments) and theoretical results indicate how certain summary statistics for the observations vary in response to random measurement errors. Such results are applied to a very large data base of pediatric blood lead levels collected in New York City during 1970-1976, and they indicate that the observed trends in geometric mean blood lead levels are not significantly altered by the possible presence of measurement errors.

The renin angiotensin system in conscious Brattleboro strain rats.

Plasma renin activity (PRA) was measured in conscious Brattleboro strain, vasopressin (AVP)-deficient diabetes insipidus (DI) and heterozygous rats with the aid of chronically implanted catheters. Baseline, dehydration-stimulated, and hemorrhage-stimulated levels of PRA were elevated in DI rats, as compared to levels in heterozygous controls. Replacement therapy with either AVP or the nonpressor AVP analog dDAVP reduced PRA to control levels. The high level of PRA in DI rats was associated with the lack of endogenous antidiuretic activity per se and not the pressor activity associated with the vasopressin molecule. Thus, elevated PRA in the chronic absence of AVP (in DI rats) most probably results indirectly from the chronically reduced plasma volume reported associated with hypothalamic diabetes insipidus.

Relation of pediatric blood lead levels to lead in gasoline.

Analysis of a large data set of pediatric blood lead levels collected in New York City (1970-1976) shows a highly significant association between geometric mean blood lead levels and the amount of lead present in gasoline sold during the same period. This association was observed for all age and ethnic groups studied, and it suggests that possible exposure pathways other than ambient air should be considered. Even without detailed knowledge of the exact exposure pathways, sufficient information now exists for policy analysis and decisions relevant to controls and standards related to lead in gasoline and its effect on subsets of the population.

Player Aggregation in Noncooperative Games.

A condition is given, under which subsets of the players of a noncooperative game can be combined into "aggregate players" without changing the set of equilibrium-point solutions of the game. The condition is that an individual player's payoff does not depend on the strategy choices of the other players forming the same aggregate player. "Approximate" versions of this result are also formulated and proven.

Analysis of pediatric blood lead levels in New York City for 1970-1976.

A study was completed of more than 170,000 records of pediatric venous blood levels and supporting demographic information collected in New York City during 1970-1976. The geometric mean (GM) blood lead level shows a consistent cyclical variation superimposed on an overall decreasing trend with time for all ages and ethnic groups studied. The GM blood lead levels for blacks are significantly greater than those for either Hispanics or whites. Regression analysis indicates a significant statistical association between GM blood lead level and ambient air lead level, after appropriate adjustments are made for age and ethnic group. These highly significant statistical relationships provide extremely strong incentives and directions for research into casual factors related to blood lead levels in children.