Effects of age and body mass on development of diving capabilities of gray seal pups: costs and benefits of the postweaning fast.

Development of adequate diving capabilities is crucial for survival of seal pups and may depend on age and body size. We tracked the diving behavior of 20 gray seal pups during their first 3 mo at sea using satellite relay data loggers. We employed quantile analysis to track upper limits of dive duration and percentage time spent diving, and lower limits of surface intervals. When pups first left the breeding colony, extreme (ninety-fifth percentile) dive duration and percentage time spent diving were positively correlated with age, but not mass, at departure. Extreme dive durations and percentage time spent diving peaked at [Formula: see text] d of age at values comparable with those of adults, but were not sustained. Greater peaks in extreme percentage time spent diving occurred in pups that had higher initial values, were older at their peak, and were heavier at departure. Pups that were smaller and less capable divers when they left the colony improved extreme dive durations and percentage time spent diving more rapidly, once they were at sea. Minimum survival time correlated positively with departure mass. Pups that were heavier at weaning thus benefitted from being both larger and older at departure, but smaller pups faced a trade-off. While age at departure had a positive effect on early dive performance, departure mass impacted on peak percentage time spent diving and longer-term survival. We speculate that once small pups have attained a minimum degree of physiological development to support diving, they would benefit by leaving the colony when younger but larger to maximize limited fuel reserves, rather than undergoing further maturation on land away from potential food resources, because poor divers may be able to "catch up" once at sea.

Diurnal and seasonal variations in the duration and depth of the longest dives in southern elephant seals (Mirounga leonina): possible physiological and behavioural constraints.

This study seeks to understand how the physiological constraints of diving may change on a daily and seasonal basis. Dive data were obtained from southern elephant seals (Mirounga leonina) from South Georgia using satellite relay data loggers. We analysed the longest (95th percentile) dive durations as proxies for physiological dive limits. A strong, significant relationship existed between the duration of these dives and the time of day and week of year in which they were performed. The depth of the deepest dives also showed a significant, but far less consistent, relationship with local time of day and season. Changes in the duration of the longest dives occurred irrespective of their depth. Dives were longest in the morning (04:00-12:00 h) and shortest in the evening (16:00-00:00 h). The size of the fluctuation varied among animals from 4.0 to 20.0 min. The daily pattern in dive depth was phase-shifted in relation to the diurnal rhythm in dive duration. Dives were deeper at midday and shallower around midnight. Greater daily changes in duration occurred in seals feeding in the open ocean than in those foraging on the continental shelf. The seasonal peak in the duration of the longest dives coincided with austral midwinter. The size of the increase in dive duration from autumn/spring to winter ranged from 11.5 to 30.0 min. Changes in depth of the longest dives were not consistently associated with particular times of year. The substantial diurnal and seasonal fluctuations in maximum dive duration may be a result of changes in the physiological capacity to remain submerged, in addition to temporal changes in the ecological constraints on dive behaviour. We speculate about the role of melatonin as a hormonal mediator of diving capability.

Radionuclide diagnosis of diaphragmatic rupture with hepatic herniation.

Seven surgically proven cases of a traumatic rupture of the right hemidiaphragm with a hepatic herniation were preoperatively diagnosed by radionuclide liver-spleen imagings, and they were retrospectively analyzed. All injuries resulted from blunt traumatic injury including automobile accidents, and there were associated pelvic and rib fractures in five cases. All patients developed some degree of dyspnea in the relatively immediate phase. All chest radiographs showed an apparent elevation of right hemidiaphragm. Radionuclide liver-spleen imaging with 99mTc sulfur colloid characteristically demonstrated a distortion of liver configuration with superior and posterior displacement of the right lobe. Four patients had a large tear in the central tendon of the right hemidiaphragm, and none had a tear in the anterior part or in left lobe of the liver. The differential diagnosis of elevated right hemidiaphragm is briefly discussed. It is concluded that the correct preoperative diagnosis of the diaphragmatic rupture with liver hernia could be made with an awareness of this condition following trauma and radionuclide liver-spleen imaging.

133xe uptake in focal hepatic fat accumulation: CT correlation.

Irregular fatty infiltration of the liver appears as focal areas of decreased attenuation on computed tomography (CT) and often cannot be distinguished from other, clinically more significant space-occupying lesions. Six patients with CT and clinical findings suggestive of fatty infiltration had xenon-133 ventilation scans of the liver. Four of these patients showed uptake and retention of 133Xe in the corresponding area of the liver, confirming the presence of fatty infiltration. The two patients in whom there was no uptake or retention of xenon by the liver were subsequently proven to have liver abscess and metastatic adenocarcinoma, respectively.

Correlation of nonspecific immune monitoring with rejection or impaired function of renal allografts.

Two nonspecific immunological assays were combined with radionuclide scanning to monitor 113 patients thrice weekly following allotransplantation. The nonspecific immune assays included measurement of the percentage of active T rosette-forming cells (% A-T RFCs) and spontaneous blastogenesis (SB). An increase in SB and decrease in % A-T RFCs (greater than 1 sd of normal controls) constituted an immune event. The immune parameters were correlated with thrice weekly radionuclide studies which were computer analyzed for glomerular and tubular function. Alteration of the immunological and radionuclide parameters significantly correlated (P less than 0.001) with 90 rejection episodes displayed by 72 nonantithymocyte globulin (ATG)-treated renal allograft recipients during the first 30 postoperative days. In the absence of clinically defined rejection, changes in immune parameters correlated with (1) decline of radionuclide parameters and (2) alterations in weight, temperature, creatinine clearance, and serum creatinine, suggesting subclinical events. As a result of the effects of ATG on lymphocytes, a similar comparison could not be made for 41 other patients treated with this immunosuppressive drug. The incidence of false positive tests was 12.7%. Thus, the combination of two nonspecific immune parameters, % A-T RFCs and SB, with computerized analysis of radionuclide scans may afford a reliable index to diagnose early rejection or impaired function of renal allografts.

Radioisotope angiography in diagnosis of varicocele.

A varicocele, the most common surgically correctable cause of subfertility in men, is a manifestation of abnormal retrograde venous blood flow through the internal spermatic vein into the peritesticular pampiniform plexus. Methods of diagnosing the varicocele, including careful physical examination using a Valsalva maneuver as well as a Doppler stethoscope, remain somewhat subjective. Venography, while a reliable and objective technique, is invasive and not without morbidity. In the present study, 16 patients with clinically detectable varicoceles of various sizes were studied using a testicular radioisotope angiogram developed in our laboratory. Following the injection of 15 mg. of stannous pyrophosphate which results in tagging of the circulating red cell pool, 20 mCi. of 99m-technetium were administered in an intravenous bolus injection. The isotope binds to the pyrophosphate thus tagging the red blood cells and creating a blood-pooling agent with a relatively short half-life (six hours). Perfusion studies as well as static views of the scrotal contents, both in the supine and erect position, with and without Valsalva maneuver, were obtained using a gamma camera. The activity in each hemiscrotum then was quantitated using a digital computer. It is proposed that quantitation of this differential blood pool will make the identification of even subclinical varicoceles a potentially objective determination.