A novel application of multi-event modeling to estimate class segregation in a highly migratory oceanic vertebrate

Spatial segregation of animals by class (i.e., maturity or sex) within a population due to differential rates of temporary emigration (TE) from study sites can be an important life history feature to consider in population assessment and management. However, such rates are poorly known; new quantitative approaches to address these knowledge gaps are needed. We present a novel application of multi-event models that takes advantage of two sources of detections to differentiate temporary emigration from apparent absence to quantify class segregation within a study population of double-marked (photo-identified and tagged with coded acoustic transmitters) white sharks (Carcharodon carcharias) in central California. We use this model to test if sex-specific patterns in TE result in disparate apparent capture probabilities (p^o ) between male and female white sharks, which can affect the observed sex ratio. The best-supported model showed a contrasting pattern of Pr(TE) from coastal aggregation sites between sexes (for males Pr[TE] = 0.015 [95% CI = 0.00, 0.31] and Pr[TE]= 0.57 [0.40, 0.72] for females), but not maturity classes. Additionally, by accounting for Pr(TE) and imperfect detection, we were able to estimate class-specific values of true capture probability (p^* ) for tagged and untagged sharks. The best-supported model identified differences between maturity classes but no difference between sexes or tagging impacts (tagged mature sharks p^*  = 0.55 (0.46-0.63) and sub-adult sharks p*  = 0.36 (0.25, 0.50); and untagged mature sharks p^*  = 0.50 (0.39-0.61) and sub-adults p^*  = 0.18 (0.10, 0.31). Estimated sex-based differences in p^o were linked to sex-specific differences in Pr(TE) but not in p^* ; once the Pr(TE) is accounted for, the p^* between sexes was not different. These results indicate that the observed sex ratio is not a consequence of unequal detectability and sex-specific values of Pr(TE) are important drivers of the observed male-dominated sex ratio. Our modeling approach reveals complex class-specific patterns in Pr(TE) and p^* in a mark-recapture data set, and highlights challenges for the population modeling and conservation of white sharks in central California. The model we develop here can be used to estimate rates of temporary emigration and class segregation when two detection methods are used.

Cardiac function in an endothermic fish: cellular mechanisms for overcoming acute thermal challenges during diving

Understanding the physiology of vertebrate thermal tolerance is critical for predicting how animals respond to climate change. Pacific bluefin tuna experience a wide range of ambient sea temperatures and occupy the largest geographical niche of all tunas. Their capacity to endure thermal challenge is due in part to enhanced expression and activity of key proteins involved in cardiac excitation-contraction coupling, which improve cardiomyocyte function and whole animal performance during temperature change. To define the cellular mechanisms that enable bluefin tuna hearts to function during acute temperature change, we investigated the performance of freshly isolated ventricular myocytes using confocal microscopy and electrophysiology. We demonstrate that acute cooling and warming (between 8 and 28°C) modulates the excitability of the cardiomyocyte by altering the action potential (AP) duration and the amplitude and kinetics of the cellular Ca(2+) transient. We then explored the interactions between temperature, adrenergic stimulation and contraction frequency, and show that when these stressors are combined in a physiologically relevant way, they alter AP characteristics to stabilize excitation-contraction coupling across an acute 20°C temperature range. This allows the tuna heart to maintain consistent contraction and relaxation cycles during acute thermal challenges. We hypothesize that this cardiac capacity plays a key role in the bluefin tunas' niche expansion across a broad thermal and geographical range.

Temperature dependence of cardiac sarcoplasmic reticulum Ca²⁺-ATPase from rainbow trout Oncorhynchus mykiss

In this work, the temperature dependence of the sarco-endoplasmic reticulum Ca(2+) -ATPase (SERCA2) activity from rainbow trout Oncorhynchus mykiss cardiac ventricles was measured and compared with the mammalian SERCA2 isoform. The rate of ATP-dependent Ca(2+) transport catalysed by O. mykiss vesicles was totally abolished by thapsigargin and the Ca(2+) ionophore A(23187) . At warm temperatures (25 and 30° C), the SERCA2 from O. mykiss ventricles displayed the same rate of Ca(2+) uptake. At 35° C, the activity of the O. mykiss enzyme decreased after 20 min of reaction time. The rate of Ca(2+) uptake catalysed by the mammalian SERCA2 was temperature dependent exhibiting its maximal activity at 35° C. In contrast to the rate of Ca(2+) uptake, the rate of ATP hydrolysis catalysed by O. mykiss SERCA2 was not significantly different at 25 and 35° C, but the rate of ATP hydrolysis catalysed by the rat Rattus norvegicus SERCA2 isoform at 35° C was two-fold higher than at 25° C. At low temperatures (5 to 20° C), the rate of Ca(2+) uptake from O. mykiss SR was less temperature dependent than the R. norvegicus isoform, being able to sustain a high activity even at 5° C. The mean ±s.e. Q(10) values calculated from 25 to 35° C for ATP hydrolysis were 1·112 ± 0·026 (n = 3) and 2·759 ± 0·240 (n = 5) for O. mykiss and R. norvegicus, respectively. Taken together, the results show that the O. mykiss SERCA2 was not temperature dependent over the 10 to 25° C temperature interval commonly experienced by the animal in vivo. The Q(10) value of SERCA2 was significantly lower in O. mykiss than R. norvegicus which may be key for cardiac function over the wide environmental temperatures experienced in this eurythermal fish.

Warm fish with cold hearts: thermal plasticity of excitation-contraction coupling in bluefin tuna

Bluefin tuna have a unique physiology. Elevated metabolic rates coupled with heat exchangers enable bluefin tunas to conserve heat in their locomotory muscle, viscera, eyes and brain, yet their hearts operate at ambient water temperature. This arrangement of a warm fish with a cold heart is unique among vertebrates and can result in a reduction in cardiac function in the cold despite the elevated metabolic demands of endothermic tissues. In this study, we used laser scanning confocal microscopy and electron microscopy to investigate how acute and chronic temperature change affects tuna cardiac function. We examined the temporal and spatial properties of the intracellular Ca2+ transient (Δ[Ca2+]i) in Pacific bluefin tuna (Thunnus orientalis) ventricular myocytes at the acclimation temperatures of 14°C and 24°C and at a common test temperature of 19°C. Acute (less than 5 min) warming and cooling accelerated and slowed the kinetics of Δ[Ca2+]i, indicating that temperature change limits cardiac myocyte performance. Importantly, we show that thermal acclimation offered partial compensation for these direct effects of temperature. Prolonged cold exposure (more than four weeks) increased the amplitude and kinetics of Δ[Ca2+]i by increasing intracellular Ca2+ cycling through the sarcoplasmic reticulum (SR). These functional findings are supported by electron microscopy, which revealed a greater volume fraction of ventricular SR in cold-acclimated tuna myocytes. The results indicate that SR function is crucial to the performance of the bluefin tuna heart in the cold. We suggest that SR Ca2+ cycling is the malleable unit of cellular Ca2+ flux, offering a mechanism for thermal plasticity in fish hearts. These findings have implications beyond endothermic fish and may help to delineate the key steps required to protect vertebrate cardiac function in the cold.

Effect of thermal acclimation on action potentials and sarcolemmal K+ channels from Pacific bluefin tuna cardiomyocytes

To sustain cardiac muscle contractility relatively independent of temperature, some fish species are capable of temporarily altering excitation-contraction coupling processes to meet the demands of their environment. The Pacific bluefin tuna, Thunnus orientalis, is a partially endothermic fish that inhabits a wide range of thermal niches. The present study examined the effects of temperature and thermal acclimation on sarcolemmal K(+) currents and their role in action potential (AP) generation in bluefin tuna cardiomyocytes. Atrial and ventricular myocytes were enzymatically isolated from cold (14 degrees C)- and warm (24 degrees C)-acclimated bluefin tuna. APs and current-voltage relations of K(+) channels were measured using the whole cell current and voltage clamp techniques, respectively. Data were collected either at the cardiomyocytes' respective acclimation temperature of 14 or 24 degrees C or at a common test temperature of 19 degrees C (to reveal the effects of acclimation). AP duration (APD) was prolonged in cold-acclimated (CA) cardiomyocytes tested at 14 degrees C compared with 19 degrees C and in warm-acclimated (WA) cardiomyocytes tested at 19 degrees C compared with 24 degrees C. This effect was mirrored by a decrease in the density of the delayed-rectifier current (I(Kr)), whereas the density of the background inward-rectifier current (I(K1)) was unchanged. When CA and WA cardiomyocytes were tested at a common temperature of 19 degrees C, no significant effects of temperature acclimation on AP shape or duration were observed, whereas I(Kr) density was markedly increased in CA cardiomyocytes. I(K1) density was unaffected in CA ventricular myocytes but was significantly reduced in CA atrial myocytes, resulting in a depolarization of atrial resting membrane potential. Our results indicate the bluefin AP is relatively short compared with other teleosts, which may allow the bluefin heart to function at cold temperatures without the necessity for thermal compensation of APD.

Habitat and behaviour of yellowfin tuna Thunnus albacares in the Gulf of Mexico determined using pop-up satellite archival tags

This study presents the first data on movement, habitat use and behaviour for yellowfin tuna Thunnus albacares in the Atlantic Basin. Six individuals were tracked in the Gulf of Mexico using pop-up satellite archival tags. Records up to 80 days in length were obtained, providing information on depth and temperature preferences as well as horizontal movements. Thunnus albacares in the Gulf of Mexico showed a strong preference for the mixed layer and thermocline, consistent with findings for this species in other ocean basins. Fish showed a diel pattern in depth distribution, remaining in surface and mixed layer waters at night and diving to deeper waters during the day. The vertical extent of T. albacares habitat appeared to be temperature limited, with fish generally avoiding waters that were >6 degrees C cooler than surface waters. The vertical and thermal habitat usage of T. albacares differs from that of bigeye Thunnus obesus and bluefin Thunnus thynnus, Thunnus orientalis and Thunnus maccoyii tunas. These results are consistent with the results of earlier studies conducted on T. albacares in other oceans.

Surface plasmon induced polarization rotation and optical vorticity in a single mode waveguide

The control and manipulation of the mode polarization state in a single mode dielectric waveguide is of considerable significance for optical information processing utilizing the polarization state to store digital information and integrated photonic devices used for high speed signaling. Here we report on an integrated on-chip mode polarization rotation based on short metal Cu electrodes placed in close proximity to the dielectric waveguide core. Polarization mode rotation with specific rotation of 10(4) degrees/mm is observed for offset metallic electrodes placed diagonally along a single mode dielectric waveguide. The mechanism for the polarization rotation is shown to be directional coupling into guided surface plasmon modes at the metal corners and coupling between the guided plasmon modes. This inter-plasmon coupling gives rise to giant polarization rotation and optical vorticity (helical power flow) in the waveguide.

Surface plasmon polarization filtering in a single mode dielectric waveguide

We demonstrate that metallic electrodes symmetrically placed about a single mode dielectric waveguide can effectively polarize the mode by excitation of surface plasmons. The transmission through the metal electrode waveguide structure is examined as a function of mode polarization and electrode spacing. It is found that modes polarized perpendicular to the metal surface can resonantly excite surface plasmons, extinguishing the mode in the waveguide core, while modes polarized parallel to metal surface only suffer mode attenuation due to the presence of the metal. The phase matching conditions for excitation of surface plasmons are examined and the polarization and insertion loss of the transmitted mode is experimentally verified.

Electrophysiological properties of the L-type Ca2+current in cardiomyocytes from bluefin tuna and Pacific mackerel

Tunas are capable of exceptionally high maximum metabolic rates; such capability requires rapid delivery of oxygen and metabolic substrate to the tissues. This requirement is met, in part, by exceptionally high maximum cardiac outputs, opening the possibility that myocardial Ca2+delivery is enhanced in myocytes from tuna compared with those from other fish. In this study, we investigated the electrophysiological properties of the cardiac L-type Ca2+channel current ( ICa) to test the hypothesis that Ca2+influx would be larger and have faster kinetics in cardiomyocytes from Pacific bluefin tuna ( Thunnus orientalis) than in those from its sister taxon, the Pacific mackerel ( Scomber japonicus). In accordance with this hypothesis, ICain atrial myocytes from bluefin tuna had significantly greater peak current amplitudes and faster fast inactivation kinetics (-4.4 ± 0.2 pA/pF and 25.9 ± 1.6 ms, respectively) than those from mackerel (-2.7 ± 0.5 pA/pF and 32.3 ± 3.8 ms, respectively). Steady-state activation, inactivation, and recovery from inactivation were also faster in atrial myocytes from tuna than from mackerel. In ventricular myocytes, current amplitude and activation and inactivation rates were similar in both species but elevated compared with those of other teleosts (Vornanen M. Am J Physiol Regul Integr Comp Physiol 272: R1432-R1440, 1997). These results indicate enhanced ICain atrial myocytes from bluefin tuna compared with Pacific mackerel; this enhanced ICamay be associated with elevated cardiac performance, because ICadelivers the majority of Ca2+involved in excitation-contraction coupling in most fish hearts. Similarly, ICais enhanced in the ventricle of both species compared with other teleosts and may play a role in the robust cardiac performance of fishes of the family Scombridae.

Migratory movements, depth preferences, and thermal biology of Atlantic bluefin tuna

The deployment of electronic data storage tags that are surgically implanted or satellite-linked provides marine researchers with new ways to examine the movements, environmental preferences, and physiology of pelagic vertebrates. We report the results obtained from tagging of Atlantic bluefin tuna with implantable archival and pop-up satellite archival tags. The electronic tagging data provide insights into the seasonal movements and environmental preferences of this species. Bluefin tuna dive to depths of >1000 meters and maintain a warm body temperature. Western-tagged bluefin tuna make trans-Atlantic migrations and they frequent spawning grounds in the Gulf of Mexico and eastern Mediterranean. These data are critical for the future management and conservation of bluefin tuna in the Atlantic.

Oxygen affinity and amino acid sequence of myoglobins from endothermic and ectothermic fish

Myoglobin (Mb) buffers intracellular O2 and facilitates diffusion of O2 through the cell. These functions of Mb will be most effective when intracellular PO2 is near the partial pressure of oxygen at which Mb is half saturated (P50) of the molecule. We test the hypothesis that Mb oxygen affinity has evolved such that it is conserved when adjusted for body temperature among closely related animals. We measure oxygen P50s tonometrically and oxygen dissociation rate constants with stopped flow and generate amino acid sequence from cDNA of Mbs from fish with different body temperatures. P50s for the endothermic bluefin tuna, skipjack tuna, and blue marlin at 20 degrees C were 0.62 +/- 0.02, 0.59 +/- 0.01, 0.58 +/- 0.04 mmHg, respectively, and were significantly lower than those for ectothermic bonito (1.03 +/- 0.07 mmHg) and mackerel (1.39 +/- 0.03 mmHg). Because the oxygen affinity of Mb decreases with increasing temperature, the above differences in oxygen affinity between endothermic and ectothermic fish are reduced when adjusted for the in vivo muscle temperature of the animal. Oxygen dissociation rate constants at 20 degrees C for the endothermic species ranged from 34.1 to 49.3 s(-1), whereas those for mackerel and bonito were 102 and 62 s(-1), respectively. Correlated with the low oxygen affinity and fast dissociation kinetics of mackerel Mb is a substitution of alanine for proline that would likely result in a more flexible mackerel protein.

The dance: essence of embodiment

An analysis of movement, and particularly of dance, helps us to see in an extraordinarily effective way the meaning of embodiment. This paper then looks through the eyes of dance theorists and at philosophers who consider dance and movement and their meaning of embodiment. A study of movement and dance encompasses the fullest meaning of embodiment: that the embodied way of being-in-the-world is also an embedded way of being in a world of others. Dance has critically important social ramifications. In our own and other cultures, dance plays an important role in healing and in health enhancement.

Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle

Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed in a fiber type-specific manner in fish skeletal muscle (11). In this study, we compare [(3)H]ryanodine binding and single channel activity of RyR1-slow from fish slow-twitch skeletal muscle with RyR1-fast and RyR3 isolated from fast-twitch skeletal muscle. Scatchard plots indicate that RyR1-slow has a lower affinity for [(3)H]ryanodine when compared with RyR1-fast. In single channel recordings, RyR1-slow and RyR1-fast had similar slope conductances. However, the maximum open probability (P(o)) of RyR1-slow was threefold less than the maximum P(o) of RyR1-fast. Single channel studies also revealed the presence of two populations of RyRs in tuna fast-twitch muscle (RyR1-fast and RyR3). RyR3 had the highest P(o) of all the RyR channels and displayed less inhibition at millimolar Ca(2+). The addition of 5 mM Mg-ATP or 2.5 mM beta, gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) to the channels increased the P(o) and [(3)H]ryanodine binding of both RyR1s but also caused a shift in the Ca(2+) dependency curve of RyR1-slow such that Ca(2+)-dependent inactivation was attenuated. [(3)H]ryanodine binding data also showed that Mg(2+)-dependent inhibition of RyR1-slow was reduced in the presence of AMP-PCP. These results indicate differences in the physiological properties of RyRs in fish slow- and fast-twitch skeletal muscle, which may contribute to differences in the way intracellular Ca(2+) is regulated in these muscle types.

Cloning of a neonatal calcium atpase isoform (SERCA 1B) from extraocular muscle of adult blue marlin (Makaira nigricans)

Complete cDNAs for the fast-twitch Ca2+ -ATPase isoform (SERCA 1) were cloned and sequenced from blue marlin (Makaira nigricans) extraocular muscle (EOM). Complete cDNAs for SERCA 1 were also cloned from fast-twitch skeletal muscle of the same species. The two sequences are identical over the coding region except for the last five codons on the carboxyl end; EOM SERCA 1 cDNA codes for 996 amino acids and the fast-twitch cDNAs code for 991 aa. Phylogenetic analysis revealed that EOM SERCA 1 clusters with an isoform of Ca2+ -ATPase normally expressed in early development of mammals (SERCA 1B). This is the first report of SERCA 1B in an adult vertebrate. RNA hybridization assays indicate that 1B expression is limited to extraocular muscles. Because EOM gives rise to the thermogenic heater organ in marlin, we investigated whether SERCA 1B may play a role in heat generation, or if 1B expression is common in EOM among vertebrates. Chicken also expresses SERCA 1B in EOM, but rat expresses SERCA 1A; because SERCA 1B is not specific to heater tissue we conclude it is unlikely that it plays a specific role in intracellular heat production. Comparative sequence analysis does reveal, however, several sites that may be the source of functional differences between fish and mammalian SERCAs.

Slow muscle function of Pacific bonito (Sarda chiliensis) during steady swimming

The Pacific bonito, Sarda chiliensis, is anatomically intermediate between mackerel and tuna. The specialisations exhibited by tuna are present in the bonito, but to a lesser degree. Slow-twitch muscle strain and activity patterns were determined during steady swimming (tailbeat frequency 1.2-3.2 Hz) at four locations on the body of Sarda chiliensis using sonomicrometry and electromyography. Both strain and the phase of electromygraphic activity were independent of tailbeat frequency. The strain of superficial slow-twitch muscle increased from +/−3.1 % l(0) at 0.35FL to +/−5.8 % l(0) at 0.65FL, where l(0) is muscle resting length and FL is the body length from snout to tail fork. Between 0.35 and 0.65FL, there was a negative phase shift of 16 degrees in the onset of electromygraphic activity in superficial slow-twitch muscle relative to the strain cycle. Muscle activity patterns are comparable with those of tuna. At 0.58FL, the onset of activity in deep slow-twitch muscle was approximately synchronous with the onset of activity in superficial muscle in the same myotome at 0.65FL. The distribution of slow-twitch muscle along the body of Sarda chiliensis and four additional fish species, Anguilla anguilla, Oncorhynchus mykiss, Scomber scombrus and Thunnus albacares, was also measured. Slow-twitch muscle appears to become more concentrated at approximately 0.5FL as swimming kinematics become more thunniform.

Toronto street youth and HIV/AIDS: prevalence, demographics, and risks

PURPOSE

The purposes of this study were: (a) to identify human immunodeficiency virus (HIV) prevalence in Toronto street youth through paired blood and saliva specimens; (b) to identify the HIV risk and prevention behaviors of street involved youth; and (c) to identify demographic or other factors that may contribute to the risk of street youth becoming infected with HIV/acquired immunodeficiency syndrome (AIDS) in the future.

METHODS

This was a cross-sectional convenience study of street-involved youth aged 14-25 years. The youth participated in interviews to identify HIV-related knowledge and personal risk and preventive behaviors. Following interviews, they were asked to provide a saliva sample, blood spot, or both. They could refuse one or both samples without jeopardizing their involvement or receiving an honorarium. Two males were the only participants who declined to provide a sample.

RESULTS

Fifteen of 695 (2.2%) youth tested positive for HIV infection. All were male, ranging in age from 18 to 25 years. Same and opposite sex, intravenous (IV) drug use, prostitution, and incarceration were risk factors associated with positive HIV test results. The rate of HIV infection was seven times greater for the group 20 years of age and older (20-25) compared to the younger group aged 14-9 years. The proportion testing positive for HIV from small cities, towns, and rural communities in Ontario was 40%; yet, they represented 21% of the study population. Most (57%) youth had been on their own for no more than 3 years and had moved frequently. Nearly two thirds (60%) had stayed in hostels or homeless shelters in the previous 6 months.

CONCLUSION

Street youth in Canada are at high risk of HIV infection with their risk increasing with age. Unprotected (same and opposite) sex, IV drug use, prostitution and incarceration were linked to their HIV infections. The high level of mobility identified by street youth challenges governments, communities, and public health officials to develop appropriate prevention strategies and to carefully monitor the spread of HIV infection in this vulnerable population.

Development of an acoustic telemetry tag for monitoring electromyograms in free-swimming fish

We report the development of an acoustic telemetry tag used to monitor electromyograms (EMGs) remotely from free-swimming marine fish. The device described amplifies and filters the EMG and then converts the electrical waveform into a frequency-modulated acoustic signal that is transmitted through water. The signal is then received, demodulated and recorded by the receiving system. The EMG tag described has been tested on a range of species, including toadfish Opsanus τ, spiny dogfish Squalus acanthias, yellowfin tuna Thunnus albacares and eastern Pacific bonito Sarda chiliensis, in different tank environments. In certain tanks the fidelity with which the system replicates the EMG is sufficient to quantify accurately the onset, offset, duration, the integrated area under the absolute value of the signal and the number of signal zero crossings. This EMG tag will expand the scope of questions that can be addressed about the behavior and physiology of free-swimming fish.

The sarcoplasmic reticulum plays a major role in isometric contraction in atrial muscle of yellowfin tuna

We used an isometric muscle preparation to test the hypothesis that yellowfin tuna Thunnus albacares utilize the intracellular Ca2+ storage sites of the sarcoplasmic reticulum (SR) during routine contractions. Ryanodine (a blocker of SR Ca2+ release) reduced the force of contraction by approximately 50 % and the rates of contraction and relaxation by 60 % in yellowfin tuna atrium. High levels of adrenaline were unable to ameliorate the effects of ryanodine. We conclude that the SR is active in contributing Ca2+ to force development at physiological contraction frequencies. Further, we suggest that, by using intracellular Ca2+ cycling, the yellowfin tuna is able to increase the maximum contraction frequency of its cardiac muscle beyond that of most other fishes.

A new satellite technology for tracking the movements of Atlantic bluefin tuna

The movements of Atlantic bluefin tuna (Thunnus thynnus thynnus) have captured the interest of scientists and fishers since the time of Aristotle. This tuna is unique among bony fish for maintaining elevated body temperatures (21 degrees C above ambient) and attaining large size (up to 750 kg). We describe here the use of a pop-off satellite tag, for investigating the Atlantic-wide movements and potential stock overlap of western and eastern Atlantic bluefin tuna. The tag also archives data on water temperatures. The objectives of this study were to evaluate the effectiveness of the technology, study the movements of Atlantic bluefin tuna, examine their thermal niche, and assess survivorship of tagged fish. The pop-off satellite technology provides data independent of commercial fisheries that, when deployed in sufficient quantity, should permit a critical test of the stock structure hypotheses for Atlantic bluefin tuna.

Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish

We have cloned a group of cDNAs that encodes the skeletal ryanodine receptor isoform (RyR1) of fish from a blue marlin extraocular muscle library. The cDNAs encode a protein of 5,081 amino acids with a calculated molecular mass of 576,302 Da. The deduced amino acid sequence shows strong sequence identity to previously characterized RyR1 isoforms. An RNA probe derived from a clone of the full-length marlin RyR1 isoform hybridizes to RNA preparations from extraocular muscle and slow-twitch skeletal muscle but not to RNA preparations from fast-twitch skeletal or cardiac muscle. We have also isolated a partial RyR clone from marlin and toadfish fast-twitch muscles that shares 80% sequence identity with the corresponding region of the full-length RyR1 isoform, and a RNA probe derived from this clone hybridizes to RNA preparations from fast-twitch muscle but not to slow-twitch muscle preparations. Western blot analysis of slow-twitch muscles in fish indicates the presence of only a single high-molecular-mass RyR protein corresponding to RyR1. [3H]ryanodine binding assays revealed the fish slow-twitch muscle RyR1 had a greater sensitivity for Ca2+ than the fast-twitch muscle RyR1. The results indicate that, in fish muscle, fiber type-specific RyR1 isoforms are expressed and the two proteins are physiologically distinct.

Efforts to improve the follow-up of patients with abnormal Papanicolaou test results

BACKGROUND

We describe and evaluate efforts to improve the follow-up care of patients with abnormal Papanicolaou test results at an academic family practice center at Shadyside Hospital in Pittsburgh.

METHODS

From 1994 to 1996, 1796 patients received Papanicolaou testing; 147 (8 percent) of the smears had abnormal findings--16 percent had atypia, 83 percent had dysplasia, and 1 percent had carcinoma in situ. Patients received follow-up care based on a formalized protocol using educational input, logistic aids, and automated prompting.

RESULTS

Overall follow-up success rates and colposcopy completion rates increased dramatically. Whereas 36 percent of patients with abnormal findings on Papanicolaou smears had been overdue for follow-up in 1990, only 13 percent were overdue in 1996 after our interventions. Patients assigned to Papanicolaou testing for follow-up of abnormal findings failed to receive a test in 9 of 45 (20 percent) cases, but those assigned to colposcopy follow-up failed to receive a test in only 10 of 102 (10 percent) of cases. Appointment failure rates at colposcopy clinic dropped from 56 percent in 1993 to 12 percent in 1996. Colposcopic biopsy was far superior to Papanicolaou test for detecting precursors of cervical cancer at follow-up.

CONCLUSIONS

Educational programs, formalized approaches to care, transportation assistance, and reminder systems are not only practical but also can dramatically improve the outcome of cervical cancer screening programs.

Histochemical and immunohistochemical studies on the origin of the blue marlin heater cell phenotype

The superior rectus muscle fibers of marlins, swordfish, sailfish and spearfish are modified for heat production at the expense of contractile ability. Although 'heater cells' are a muscle derivative (Block, 1986, 1991), the myoblast origin and developmental pathway of these thermogenic cells is unknown. To gain insight into heater cell origins, we characterized blue marlin superior rectus muscle and its heater tissue derivative with histochemical and immunological techniques. We specifically employed myosin ATPase and succinate dehydrogenase histochemical assays, and myosin heavy chain immunohistochemistry. Results revealed that marlin superior rectus muscles contain at least six distinct fiber types, and suggested the presence of both twitch and tonic fibers. Immunological results indicate that myosin is present within the thermogenic cells but not in myofibrillar lattices. The antibodies that recognized myosin in heater cells also labeled myosin in the twitch fibers of swimming muscle. In contrast, antibodies that labeled histologically defined tonic fibers did not label heater cells. These results suggest that heater cells and twitch fibers express the same myosin isoform, and establish a phenotypic connection between heater cells and twitch fibers. This conclusion is discussed in the context of the muscle-to-heater trajectory and the muscle fiber-type origin of heater cells.

Why do tuna maintain elevated slow muscle temperatures? Power output of muscle isolated from endothermic and ectothermic fish

It has been hypothesised that regional endothermy has evolved in the muscle of some tunas to enhance the locomotory performance of the fish by increasing muscle power output. Using the work loop technique, we have determined the relationship between cycle frequency and power output, over a range of temperatures, in isolated bundles of slow muscle fibres from the endothermic yellowfin tuna (Thunnus albacares) and its ectothermic relative the bonito (Sarda chiliensis). Power output in all preparations was highly temperature-dependent. A counter-current heat exchanger which could maintain a 10 degrees C temperature differential would typically double maximum muscle power output and the frequency at which maximum power is generated (fopt). The deep slow muscle of the tuna was able to operate at higher temperatures than slow muscle from the bonito, but was more sensitive to temperature change than more superficially located slow fibres from both tuna and bonito. This suggests that it has undergone some evolutionary specialisation for operation at higher, but relatively stable, temperatures. fopt of slow muscle was higher than the tailbeat frequency of undisturbed cruising tuna and, together with the high intrinsic power output of the slow muscle mass, suggests that cruising fish have a substantial slow muscle power reserve. This reserve should be sufficient to power significantly higher sustainable swimming speeds, presumably at lower energetic cost than if intrinsically less efficient fast fibres were recruited.

Effects of Ca2+ on oxidative phosphorylation in mitochondria from the thermogenic organ of marlin

Mitochondria from the muscle-derived thermogenic (heater) organ and oxidative red muscle of the blue marlin (Makaira nigricans) were studied in order to evaluate aspects of the mechanism of thermogenesis in heater tissue. We investigated whether short-term Ca(2+)-induced uncoupling of mitochondria contributes to the thermogenic cycle of the heater organ by enhancing the respiration rate. Specific electrodes were used to obtain simultaneous measurements of oxygen consumption and Ca2+ fluxes on isolated mitochondria, and the effects of various concentrations of Ca2+ on respiration rates and the ADP phosphorylated/atomic oxygen consumed (P/O) ratio were examined. Addition of Ca2+ in excess of 10 mumol l-1 to respiring heater organ or red muscle mitochondria partially inhibited state 3 respiration and reduced the P/O ratio, indicating that the mitochondria were partially uncoupled. These effects were blocked by 2 mumol l-1 Ruthenium Red. In heater organ mitochondria, state 3 respiration rate and the P/O ratio were not significantly reduced by 1 mumol l-1 free Ca2+, a concentration likely to be near the maximum achieved in a stimulated cell. This indicates that transient increases in cytosolic Ca2+ concentration may not significantly reduce the P/O ratio of heater organ mitochondria. The activity of 2-oxoglutarate dehydrogenase in heater organ mitochondria was stimulated by approximately 15% by Ca2+ concentrations between 0.2 and 1 mumol l-1. These results suggest that heater organ mitochondria are able to maintain a normal P/O ratio and should maintain ATP output during transient increases in Ca2+ concentration, supporting a model in which an ATP-consuming process drives thermogenesis. Activation of mitochondrial dehydrogenases by low levels of Ca2+ may also enhance respiration and contribute to thermogenesis.

Difficulties in evaluating abnormal lead screening results in children

BACKGROUND

This report chronicles efforts to provide follow-up care for children with abnormal whole blood lead concentrations using the 1991 Centers for Disease Control and Prevention (CDC) guidelines in the Family Health Center at Shadyside Hospital in Pittsburgh.

METHODS

An automated surveillance module found all children with abnormal lead concentrations obtained between January 1994 and July 1995 and singled out children who were overdue for follow-up. Automated physician reminders and nursing case management were used to improve care and documentation. Longitudinal case summaries were used to evaluate care.

RESULTS

All 99 children with a lead concentration of 10 micrograms/dL or greater had a documented follow-up plan. Twenty-nine children (47 percent) who had a lead concentration of 10 to 14 micrograms/dL, 23 (100 percent) who had a lead concentration of 15 to 19 micrograms/dL, and 8 (100 percent) who had a lead concentration of 20 micrograms/dL or greater had at least one follow-up lead concentration measurement by the end of the data collection in July 1995. Follow-up was incomplete in more than 70 percent of children. Nineteen children (19 percent) with initially abnormal lead concentrations had follow-up testing with persistently normal results. The yearly cost of follow-up was $15,888, with only 7 children requiring county health environmental intervention.

CONCLUSIONS

The nurse-centered, computer-aided system improved follow-up care of children with abnormal lead concentrations, but most patients still did not receive mandated follow-up testing because of logistic obstacles. The effort and cost associated with CDC-mandated follow-up of children with lead concentrations between 10 and 19 micrograms/dL provides no apparent benefit and might detract from the care of children at higher risk.

Influence of family functioning and income on vaccination in inner-city health centers

OBJECTIVES

To assess family functioning and consumer decision-making about vaccinations and to compare the results with age at vaccination.

DESIGN

Self-administered survey that was mailed to parents with comparison to vaccination records from chart audits.

SETTINGS

Two inner-city health centers in Pittsburgh, Pa, that receive free vaccine supplies.

PARTICIPANTS

Systematic sample from the billing computer records of parents whose children were aged 2 to 4 years as of July 2, 1993.

INTERVENTIONS

The survey used simplified versions of the Family Profile and the Triandis model of consumer decision-making that includes perceived consequences of vaccinations, attitude about vaccinations, social influences, and facilitating conditions (eg, ease of obtaining an appointment).

MAIN OUTCOME MEASURES

Variables associated with age at vaccination for third diphtheria and tetanus toxoids and pertussis vaccine immunization and first measles-mumps-rubella immunization.

RESULTS

Of 395 families, 167 responded. Higher family dysfunction scores and lower family concordance scores each were associated with receiving first measles-mumps-rubella vaccination (P < or = .02) and third diphtheria and tetanus toxoids and pertussis vaccination (P < = .02) at later ages. Many (30%-54%) of the respondents reported that they knew little about the risks and benefits of vaccination. However, knowledge about vaccines was not associated with vaccination status. Those respondents with an annual income of less than $10000 received the first measles-mumps-rubella vaccination later than those with an annual income $10000 or greater (P < .02) when the data were analyzed by age at vaccination but not when the data were analyzed as on-time vs late vaccinations.

CONCLUSIONS

To increase vaccination rates in innercity clinics, strategies need to consider family dysfunction and income and not merely focus on education. The use of age at vaccination as a continuous variable offers advantages over the dichotomy of immunized vs not immunized.

Expression of sarcoplasmic reticulum Ca(2+)-ATPase isoforms in marlin and swordfish muscle and heater cells

The superior rectus muscles of marlin, swordfish, sailfish, and spearfish are modified for generating heat rather than force. This study focuses on the sarcoplasmic reticulum calcium-adenosinetriphosphatase (SR Ca(2+)-ATPase) to gain further insight into the muscle fiber type origin of the billfish "heater cell." Direct sequencing and immunolocalization demonstrated that marlin and swordfish epaxial swimming muscles express two forms of the SR Ca(2+)-ATPase in a fiber type-specific manner; red slow-twitch skeletal and cardiac muscles express the same SERCA2 message, whereas white fast-twitch skeletal muscles express a SERCA1 message. Thus the expression pattern of the SR Ca2+ pump is similar in both billfish and tetrapod muscles. Molecular and immunological studies revealed that billfish heater tissue and superior rectus muscle express both fast and slow SR Ca2+ pump isoforms. Immunohistochemical results suggest that heater cells and most extraocular muscle fibers express the fast SR Ca2+ pump. Expression of the fast SR Ca(2+)-ATPase by heater cells has implications for heater cell origin and thermogenic control.

Physiological differences between the alpha and beta ryanodine receptors of fish skeletal muscle

Two isoforms of the sarcoplasmic reticulum Ca2+ release channel (ryanodine receptor or RYR) are expressed together in the skeletal muscles of most vertebrates. We have studied physiological properties of the two isoforms (alpha and beta) by comparing SR preparations from specialized fish muscles that express the alpha isoform alone to preparations from muscles containing both alpha and beta. Regulation of channel activity was assessed through [3H]ryanodine binding and reconstitution into planar lipid bilayers. Distinct differences were observed in the calcium-activation and -inactivation properties of the two isoforms. The fish alpha isoform, expressed alone in extraocular muscles, closely resembled the rabbit skeletal muscle RYR. Maximum [3H]ryanodine binding and maximum open probability (Po) of the alpha RYR were achieved from 1 to 10 microM free Ca2+. Millimolar Ca2+ reduced [3H]ryanodine binding and Po close to zero. The beta isoform more closely resembled the fish cardiac RYR in Ca2+ activation of [3H]ryanodine binding. The most prominent difference of the beta and cardiac isoforms from the alpha isoform was the lack of inactivation of [3H]ryanodine binding and Po by millimolar free Ca2+. Differences in activation of [3H]ryanodine binding by adenine nucleotides and inhibition by Mg2+ suggest that the beta and cardiac RYRs are not identical, however. [3H]ryanodine binding by the alpha RYR was selectively inhibited by 100 microM tetracaine, whereas cardiac and beta RYRs were much less affected. Tetracaine can thus be used to separate the properties of the alpha and beta RYRs in preparations in which both are present. The distinct physiological properties of the alpha and beta RYRs that are present together in most vertebrate muscles support models of EC coupling incorporating both directly coupled and Ca(2+)-coupled channels within a single triad junction.

Characterization of the sarcoplasmic reticulum proteins in the thermogenic muscles of fish

Marlins, sailfish, spearfishes, and swordfish have extraocular muscles that are modified into thermogenic organs beneath the brain. The modified muscle cells, called heater cells, lack organized myofibrils and are densely packed with sarcoplasmic reticulum (SR), transverse (T) tubules, and mitochondria. Thermogenesis in the modified extraocular muscle fibers is hypothesized to be associated with increased energy turnover due to Ca2+ cycling at the SR. In this study, the proteins associated with sequestering and releasing Ca2+ from the SR (ryanodine receptor, Ca2+ ATPase, calsequestrin) of striated muscle cells were characterized in the heater SR using immunoblot and immunofluorescent techniques. Immunoblot analysis with a monoclonal antibody that recognizes both isoforms of nonmammalian RYRs indicates that the fish heater cells express only the alpha RYR isoform. The calcium dependency of [3H]ryanodine binding to the RYR isoform expressed in heater indicates functional identity with the non-mammalian alpha RYR isoform. Fluorescent labeling demonstrates that the RYR is localized in an anastomosing network throughout the heater cell cytoplasm. Measurements of oxalate supported 45Ca2+ uptake, Ca2+ ATPase activity, and [32P]phosphoenzyme formation demonstrate that the SR contains a high capacity for Ca2+ uptake via an ATP dependent enzyme. Immunoblot analysis of calsequestrin revealed a significant amount of the Ca2+ binding protein in the heater cell SR. The present study provides the first direct evidence that the heater SR system contains the proteins necessary for Ca2+ release, re-uptake and sequestration, thus supporting the hypothesis that thermogenesis in the modified muscle cells is achieved via an ATP-dependent cycling of Ca2+ between the SR and cytosolic compartments.

The fastest contracting muscles of nonmammalian vertebrates express only one isoform of the ryanodine receptor

The skeletal muscles of chickens, frogs, and fish have been reported to express two isoforms (alpha and beta) of the sarcoplasmic reticulum calcium release channel (ryanodine receptor or RYR), while mammals express only one. We have studied patterns of RYR isoform expression in skeletal muscles from a variety of fish, reptiles, and birds with immunological techniques. Immunoblot analysis with a monoclonal antibody that recognizes both nonmammalian RYR isoforms and a polyclonal antibody specific to the alpha isoform show two key results: (a) two reptilian orders share with mammals the pattern of expressing only the alpha (skeletal) RYR isoform in skeletal muscle; and (b) certain functionally specialized muscles of fish and birds express only the alpha RYR isoforms. While both isoforms are expressed in the body musculature of fish and birds, the alpha isoform is expressed alone in extraocular muscles and swimbladder muscles. The appearance of the alpha RYR isoform alone in the extraocular muscles and a fast-contracting sonic muscle in fish (toadfish swimbladder muscle) provides evidence that this isoform is selectively expressed when rapid contraction is required. The functional and phylogenetic implications of expression of the alpha isoform alone are discussed in the context of the mechanism and evolution of excitation-contraction coupling.

Evolution of endothermy in fish: mapping physiological traits on a molecular phylogeny

Mackerels, tunas, and billfishes (suborder Scombroidei and Teleostei) provide an ideal taxonomic context in which to examine the evolution of endothermy. Multiple origins and diverse strategies for endothermy exist among these fish. Here a molecular phylogeny of the Scombroidei has been determined by direct sequencing of a portion of the mitochondrial cytochrome b gene. The distribution of endothermic species within this proposed genealogy indicates that the ability to warm the brain and retina arose independently in three lineages, each time in association with a movement into colder water. This suggests that the evolution of cranial endothermy in fish was selected in order to permit thermal niche expansion and not selected for increased aerobic capacity.

Development of a portable information system: connecting palmtop computers with medical records systems and clinical reference resources

The portability of palmtop computers makes them an ideal platform to maintain communication between busy physicians and medical information systems. In our academic FHC (Family Health Center) we have developed software that runs on a palmtop computer allowing access to information in the HIS (Hospital Information System) and our FHC's AAMRS (Automated Ambulatory Medical Record System). The resident physicians who staff the hospital and the FHC are frequently at home or otherwise off-site where terminal access is not available. Using a Hewlett-Packard 95LX palmtop computer as the base platform, custom software has been developed to access summary data on in-patients and out-patients. Data is downloaded into a database on a palmtop computer memory card. ASCII data from Medical Information Systems (MIS), is transformed into a database format readable on the palmtop. Our hospital MIS department transmits information daily on our in-patient service (20-30 patients). We also download, weekly, a patient summary on all of our active out-patients in our MUMPS-based AAMRS (2500-3000 patients). Each morning the resident in the Family Practice program updates his palmtop memory card at a central workstation. Palmtop computers with downloaded databases, can be valuable in care of patients when the physical or on-line chart is not easily accessible. They are particularly useful in multi-physician groups when the on-call physician provides care for the patients of other physicians. We have made the palmtop computer even more valuable to physicians by providing an integrated software package.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct sequencing of mitochondrial DNA detects highly divergent haplotypes in blue marlin (Makaira nigricans)

We were able to differentiate between species of billfish (Istiophoridae family) and to detect considerable intraspecific variation in the blue marlin (Makaira nigricans) by directly sequencing a polymerase chain reaction (PCR)-amplified, 612-bp fragment of the mitochondrial cytochrome b gene. Thirteen variable nucleotide sites separated blue marlin (n = 26) into 7 genotypes. On average, these genotypes differed by 5.7 base substitutions. A smaller sample of swordfish from an equally broad geographic distribution displayed relatively little intraspecific variation, with an average of 1.3 substitutions separating different genotypes. A cladistic analysis of blue marlin cytochrome b variants indicates two major divergent evolutionary lines within the species. The frequencies of these two major evolutionary lines differ significantly between Atlantic and Pacific ocean basins. This finding is important given that the Atlantic stocks of blue marlin are considered endangered. Migration from the Pacific can help replenish the numbers of blue marlin in the Atlantic, but the loss of certain mitochondrial DNA haplotypes in the Atlantic due to overfishing probably could not be remedied by an influx of Pacific fish because of their absence in the Pacific population. Fishery management strategies should attempt to preserve the genetic diversity within the species. The detection of DNA sequence polymorphism indicates the utility of PCR technology in pelagic fishery genetics.

Diagnosis and management of the paranoid patient

Patients with symptoms of paranoia often present to primary care physicians. The paranoia may range in severity from a mild and largely incidental finding to a psychotic symptom. In its more severe forms, paranoia may constitute the chief complaint or may interfere with the patient's ability to accept treatment for other medical conditions. After an assessment of the severity of the symptoms and consideration of an organic etiology, initial treatment is often begun with a supportive approach and the prescription of a neuroleptic medication.

Signing out patients for off-hours coverage: comparison of manual and computer-aided methods

This paper evaluates the communication of information to physicians who provide off-hours coverage to inpatients in two Family Practice residency programs.

METHOD

To describe the importance and accessibility of clinical information used by on-call residents in covering hospital patients, we administered a questionnaire. Then following the use of a new computerized sign-out system in one of the programs, residents filled out the same questionnaire again.

RESULTS

Residents felt that a "to do" list and information about the patient's "code status" were the most important data desired from sign-out sheets. However, 69% of residents in both programs felt that provision of this information was normally poor. Nearly all of the residents in Buffalo, using an entirely handwritten sign-out sheet, felt it was in need of improvement. Residents in Pittsburgh, using a summary aided by the hospital's computer print-out, felt this need much less acutely. After implementation of a new computerized sign-out sheet in Buffalo, residents indicated a slightly higher level of satisfaction. The work of data entry and re-entry into the computer was unpopular and inefficient.

CONCLUSION

The present method of transferring information at the end of a work day is not satisfactory for residents. Provision of data summaries from existing hospital information systems is a good first step in improving data transfer. A further study of more comprehensive automated sign-out systems is important, because of the increasing discontinuity of house officer care.

Activities of key metabolic enzymes in the heater organs of scombroid fishes

Maximal in vitro activities of key metabolic enzymes were measured in brain and eye heaters of five species of scombroid fishes. Istiophorid billfishes (blue marlin, striped marlin and Mediterranean spearfish), xiphiid billfishes (Pacific and Mediterranean stocks) and a scombrid fish (butterfly mackerel) were included in the analysis. Our main objectives were (1) to assess the maximum possible substrate flux in heater tissue, and (2) to determine what metabolic substrates could fuel heat production. Heater tissue of all scombroids examined showed extremely high oxidative capacity. Activities of citrate synthase, a commonly measured index of oxidative metabolism, included the highest value ever reported for vertebrate tissue. In most billfishes, citrate synthase activities were similar to or higher than those found for mammalian cardiac and avian flight muscle. Marker enzymes for aerobic carbohydrate metabolism (hexokinase) and fatty acid metabolism (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) also displayed extraordinarily high activities. Activities of carnitine palmitoyltransferase measured in heater organs were among the highest reported for vertebrates. These results indicate that heat production could be fueled aerobically by either lipid or carbohydrate metabolism. Inter- and intraspecifically, heater organs of fishes from the colder Mediterranean waters had a higher aerobic capacity and, hence, a greater heat-generating potential, than fishes from the warmer waters of the Pacific. This difference may be attributed to different thermal environments or it may result from allometry, since fishes caught in the Mediterranean were considerably smaller than those caught in the Pacific.

The interferon-induced Mx-homologous protein in people with symptomatic HIV-1 infection

Twenty-six people with symptomatic HIV-1 infection were screened for the presence of interferon (IFN) alpha and IFN alpha antibodies in their sera and the presence of the IFN-induced intracellular Mx-homologous protein in their peripheral blood leukocytes. Eleven people had measurable IFN alpha levels ranging from 1 to 40 IU/ml. None of the sera tested was positive for IFN alpha binding or IFN alpha neutralizing antibodies in the assays employed. Twenty-five of the 26 people had significant levels of the Mx-homologous protein in their peripheral mononuclear cells. The Mx concentrations varied from 0.3 to 6 U/ml in the people studied. IFN alpha-positive people had significantly higher levels of the Mx homolog than IFN alpha-negative people (P less than 0.03). Furthermore, the Mx homolog content in Walter-Reed class 2 people was significantly lower than in Walter-Reed class 5/6 people (P less than 0.01). Our results suggest that the IFN system is activated in more than 90% of the people with lymphadenopathy-associated syndrome, AIDS-related complex and AIDS. Since acid-labile IFN alpha can induce the Mx homolog in vitro endogenously produced IFN alpha seems likely to be responsible for the high Mx homolog levels detected.