Diurnal patterns and sex differences in cortisol, 11-ketotestosterone, testosterone, and 17beta-estradiol in the bluebanded goby (Lythrypnus dalli).

The primary goals of this study were to evaluate diurnal patterns of and sex differences in the levels of cortisol, 11-ketotestosterone, testosterone, and 17beta-estradiol in the sex-changing bluebanded goby Lythrypnus dalli. Steroid hormones were collected from water samples and analyzed by enzyme immunoassay. During the breeding season, hormones were sampled from both males and females at seven time points between 0600 and 2000 h. When comparing each time point separately, there were significant overall time effects for cortisol and 17beta-estradiol. Cortisol concentrations were lowest at the 0800-1000 h sampling point and showed a qualitative peak in late morning (1000-1200 h). Concentrations of 17beta-estradiol were elevated at the last sampling point (1800-2000 h). Broader temporal trends were revealed for testosterone and 11-ketotestosterone concentrations, both of which were elevated in the morning. There were no sex differences in overall hormone concentrations or temporal profiles for cortisol, 11-ketotestosterone, or testosterone. Males and females showed similar diurnal patterns of 17beta-estradiol but females had significantly higher water-borne 17beta-estradiol levels than males. The results show the presence of diurnal changes in steroid hormone levels in male and female bluebanded gobies. The lack of sex differences in androgens suggests that males of this species, and perhaps other bi-directional sex-changing species in which males do not exhibit prominent secondary sexual characteristics, do not require persistent elevations in 11-ketotestosterone or testosterone to maintain the male phenotype. Although the role of 17beta-estradiol in maintaining sex differences in sexually plastic species is unclear, our results suggest that, of the hormones measured, 17beta-estradiol has the greatest potential for future studies interested in this question.

Academic and commercial development of open source applications in international health informatics. Opposite sides of the same coin?

Whilst covertly in the past many ideas developed in academic environments have made their way into commercial applications, there is growing acknowledgment that this model may be necessary for both funding academics and for project enrichment in private ventures. This paper seeks to explore and expound on the various pressures related to protocol development and the creation of a MAP (Multiphasic Algorithimic Protocol) Engine as a commercial venture based on an evolution from an academic environment, into a service oriented commercial product. It has been determined in a series of symposia that an Object Oriented; Open Source (OS) environment may best meet the needs for this endeavor. Numerous barriers and agreements remain, and explorations of these will, we believe, bring out the best of both sides of the coin - reflecting the strengths of both cultures.

Developmental changes in isolated rat type I carotid body cell K+ currents and their modulation by hypoxia.

1. Whole-cell patch-clamp recordings were used to investigate possible age-related changes in K+ currents of type 1 carotid body cells isolated from the rat. K+ current density increased with age, as measured in cells isolated from 4-day-old, 10-day-old and adult rats (> or = 5 weeks old). 2. The proportion of current reversibly inhibited by high [Mg2+] (6 mM), low [Ca2+] (0.1 mM) solutions, indicative of the proportion of current attributable to activation of Ca(2+) -sensitive K+ (KCa) channels, was significantly smaller in cells of 4-day-old rats compared with 10-day-old rats, despite inward Ca2+ current densities being similar in these two age groups. Inhibition of K+ currents by high [Mg2+], low [Ca2+] solutions was similar in 10-day-old and adult type 1 cells. 3. Hypoxia (PO2, 16-23 mmHg) caused reversible reductions in type I cells from rats of all age groups. However, reductions seen in cells of 4-day-old rats were significantly smaller than those seen in cells of 10-day-olds and adults. The degree of hypoxic inhibition in these latter two groups was not significantly different. 4. In the presence of high [Mg2+], low [Ca2+] solutions, hypoxia (PO2, 16-23 mmHg) was without significant effect on residual K+ currents in cells from all age groups. 5. These observations indicate that K+ current density increases with postnatal age in the rat. Between days 4 and 10, there appears to be a predominant enhancement of KCa channels, and over the same age range hypoxic sensitivity of K+ currents increases. Our findings demonstrate that this latter observation arises because hypoxia selectively inhibits KCa channels in cells at all ages studied. These results suggest an important role for KCa channels in postnatal maturation of hypoxic chemoreception in the rat carotid body.

Extracellular potassium and chemosensitivity in the rat carotid body, in vitro.

1. The effects of raising extracellular potassium concentration ([K+]o) from 3.0 to 5.3, 9.5 or 16.8 mM on chemoreceptor responses to hypoxia, hypercapnia and asphyxia were examined in a superfused in vitro rat carotid body preparation. 2. Single-exponential functions with offset were fitted to the chemoreceptor discharge responses to ramp decreases in Po2. Increasing [K+]o was without effect upon the rate constants of the fitted exponential functions (P > 0.20). Increasing [K+]o, significantly increased the horizontal asymptote (chemoreceptor discharge in hyperoxia) in a non-linear fashion when all levels of [K+]o were included in the analysis (P < 0.001) but not when a comparison was made only between 3.0 and 5.3 mM Ko+ (P > 0.40). The rightward position of the response curves, as quantified by the Po2 at 50% maximum discharge, was linearly related to [K+]o but only when all levels of [K+]o were included in the analysis (P < 0.03). Chemoreceptor sensitivity to [K+]o increased non-linearly as [K+]o was increased but this effect was not dependent upon the Po2 (P > 0.90). 4. Increasing PCO2 in hyperoxia increased chemoreceptor discharge linearly at all levels of [K+]o. Whilst discharge at any level of PCO2 was elevated by increased levels of [K+]o, raising [K+]o did not increase CO2 sensitivity (P > 0.20). Similarly, increasing PCO2 did not increase chemosensitivity to [K+]o. The lack of effect of [K+]o upon CO2 chemosensitivity was also observed as Po2 was decreased to hypoxic levels (P > 0.10). 5. Our data demonstrate that an elevation of [K+]o can increase chemoreceptor discharge in the in vitro carotid body in a PO2- and PCO2-independent manner, suggesting that the PO2-dependent effects of [K+]o, previously reported in vivo may be due to other indirect effects of [K+]o or hypoxia.

Postnatal development of CO2-O2 interaction in the rat carotid body in vitro.

1. The effect of PCO2 upon the discharge response to changes in PO2 (between ca 450 and 30 mmHg) was observed in adult (> 5 weeks old) and neonatal (5-7 days old) rat carotid body chemoreceptors using an in vitro, superfused preparation. 2. In both adult and neonatal rats, regression analysis revealed that increasing PCO2 was without effect upon the shape of the PO2-response curves (P > 0.30), but did cause an upward shift in the position of the curves, as indicated by a significant increase in the baseline chemoreceptor discharge during hyperoxia (0.22 +/- 0.02% maximum discharge per mmHg PCO2, P < 0.001, and 0.25 +/- 0.07% maximum discharge per mmHg PCO2, P < 0.005, respectively). However, whilst increasing PCO2 caused a significant rightward shift of the response curves in adults (0.75 +/- 0.23 mmHg PO2 per mmHg PCO2; P < 0.005), it was without effect in neonates (0.21 +/- 0.22 mmHg PO2 per mmHg PCO2; P > 0.200). Thus increasing levels of hypoxia increased CO2 chemosensitivity in adult but not in neonatal rats as shown by multiple regression analysis of the CO2-response curves which revealed a significant interaction between PCO2 and PO2 for adult (P < 0.010) but not for neonatal (P > 0.150) rats. 3. We suggest that the previously reported maturation of peripheral chemoreceptor hypoxic sensitivity (resetting) may be due to the postnatal emergence of a significant degree of interaction between PCO2 and PO2 at the level of the peripheral chemoreceptor and/or its afferent innervation.

Effect of chronic hypoxaemia from birth upon chemosensitivity in the adult rat carotid body in vitro.

1. The effect of chronic hypoxaemia upon in vitro carotid body chemosensitivity was observed in eight rats > 5 weeks of age born and reared in 12% oxygen. Comparisons were made with eight age-matched normoxic rats. 2. Single exponential functions with offset were fitted to the normalized (percentage of maximum) discharge responses to ramp decreases in PO2 at three steady levels of PCO2. CO2 sensitivity was derived from these functions. 3. Increasing hypercapnia increased the horizontal asymptote of the exponential functions in the normoxic (0.15 +/- 0.03% discharge per mmHg PCO2; P < 0.001) and chronically hypoxic (0.13 +/- 0.04% discharge per mmHg PCO2; P < 0.005) animals but was without effect upon the rate constants in both groups (-0.04 +/- 0.18 mmHg PO2 per mmHg PCO2, P > 0.50 and 0.63 +/- 0.48 mmHg PO2 per mmHg PCO2, P > 0.20, respectively). Rate constants were greater in the chronically hypoxic animals (P < 0.05) compared with the normoxic animals. 4. CO2 chemosensitivity increased with decreasing PO2 in normoxic (P < 0.05) but not in chronically hypoxic (P > 0.50) rats. 5. Our results show that chronic hypoxaemia from birth attenuates the maturation of CO2-O2 interaction at the carotid body.

A monoclonal antibody to the Ca2+-ATPase of cardiac sarcoplasmic reticulum cross-reacts with slow type I but not with fast type II canine skeletal muscle fibers: an immunocytochemical and immunochemical study.

Ca2+-ATPase of the sarcoplasmic reticulum was localized in cryostat sections from three different adult canine skeletal muscles (gracilis, extensor carpi radialis, and superficial digitalis flexor) by immunofluorescence labeling with monoclonal antibodies to the Ca2+-ATPase. Type I (slow) myofibers were strongly labeled for the Ca2+-ATPase with a monoclonal antibody (II D8) to the Ca2+-ATPase of canine cardiac sarcoplasmic reticulum; the type II (fast) myofibers were labeled at the level of the background with monoclonal antibody II D8. By contrast, type II (fast) myofibers were strongly labeled for Ca2+-ATPase of rabbit skeletal sarcoplasmic reticulum. The subcellular distribution of the immunolabeling in type I (slow) myofibers with monoclonal antibody II D8 corresponded to that of the sarcoplasmic reticulum as previously determined by electron microscopy. The structural similarity between the canine cardiac Ca2+-ATPase present in the sarcoplasmic reticulum of the canine slow skeletal muscle fibers was demonstrated by immunoblotting. Monoclonal antibody (II D8) to the cardiac Ca2+-ATPase binds to only one protein band present in the extract from either cardiac or type I (slow) skeletal muscle tissue. By contrast, monoclonal antibody (II H11) to the skeletal type II (fast) Ca2+-ATPase binds only one protein band in the extract from type II (fast) skeletal muscle tissue. These immunopositive proteins coelectrophoresed with the Ca2+-ATPase of the canine cardiac sarcoplasmic reticulum and showed an apparent Mr of 115,000. It is concluded that the Ca2+-ATPase of cardiac and type I (slow) skeletal sarcoplasmic reticulum have at least one epitope in common, which is not present on the Ca2+-ATPase of sarcoplasmic reticulum in type II (fast) skeletal myofibers. It is possible that this site is related to the assumed necessity of the Ca2+-ATPase of the sarcoplasmic reticulum in cardiac and type I (slow) skeletal myofibers to interact with phosphorylated phospholamban and thereby enhance the accumulation of Ca2+ in the lumen of the sarcoplasmic reticulum following beta-adrenergic stimulation.