Temperature dependence of macroscopic L-type calcium channel currents in single guinea pig ventricular myocytes

INTRODUCTION: Lowering temperature greatly reduces calcium influx through calcium channels. Studies on a number of tissues demonstrate that the peak inward current, ICa, exhibits Q10 values ranging from 1.8 to 3.5; however, it remains unclear which component(s) of calcium channel gating may give rise to this large temperature sensitivity. Components of gating that may affect channel availability include phosphorylation and changes in [Ca2+]i, processes that vary in pertinence depending on the channel examined. This study addresses this problem by examining the temperature sensitivity (from 34 degrees to 14 degrees C) of cardiac ICa under control conditions, during attenuation or activation of protein kinase A (PKA) activity, and when intracellular [Ca2+] has been elevated. METHODS AND RESULTS: ICa was studied using the whole cell configuration of the patch champ technique. In control, lowering temperature from 34 degrees to 24 degrees C resulted in a shift in the potential for maximum slope (Va) and the peak current (Ymax) toward more positive membrane potentials. The Q10 values for the decrease in Ymax and the macroscopic slope conductance (Gmax), which reflects the number of available channels, were 3.15 +/- 0.19 and 2.57 +/- 0.13, respectively. At 0 mV the Ca2+ current decayed biexponentially, and the two time constants (tau 1 and tau 2) showed Q10 values of 1.79 +/- 0.21 and 2.06 +/- 0.38, while their contribution to the total current (I1 and I2) showed a Q10 of 5.99 +/- 0.83 and 1.61 +/- 0.22. In myocytes loaded with inhibitors of the PKA cycle sufficient to inhibit the increase of ICa to 1 microM isoprenaline, the Q10 values for some of the kinetic parameters were increased with the Q10 for I1 increasing to 17.06 +/- 3.48. Stimulation of ICa by exposing myocytes to 1 microM isoprenaline reduced the temperature sensitivity of Ymax, Gmax and I1, yielding respective values of 2.00 +/- 0.18, 1.85 +/- 0.07, and 2.04 +/- 0.15. Raising [Ca2+]i to enhance Ca2+i-dependent inactivation, while affecting inactivation and activation kinetics, affected temperature sensitivity little compared to control. The Q10 for time to peak changed little under experimental conditions (2.3 to 2.4) CONCLUSIONS: Increasing the phosphorylated states of calcium channels, but not Ca2+i-dependent inactivation, reduces temperature sensitivity of certain gating parameters. The data suggest that the rate of the transitions between the unavailable and also between the various closed states are changed in the opposite direction to that induced by PKA-dependent phosphorylation. Processes, e.g., inhibitory mechanisms, may be involved to maintain channels in unavailable or "unphosphorylated" states, and it may be these that contribute to the high Q10 of macroscopic channel currents.     

Recognition of depressed affect in hospitalized psychiatric patients: staff and patient perceptions

A comparison of self-report vs. observer rating of depressed mood in a heterogenous inpatient population revealed wide variations in concordance among diagnostic groups. Patients diagnosed as having Affective Psychosis and "Other' illnesses showed the highest correlation between four self-report scales and an observer rating scale. Patients with a diagnosis of depressive Neurosis showed only modest correlation, while Schizophrenics revealed no significant correlation, on these instruments, suggesting inconsistent communication of affect from Schizophrenic patients to observers. In contrast, when self-report scales were intercorrelated, patients in all four diagnostic categories showed highly significant correlations, indicating that they were consistently reporting their affective state on these instruments. The implications of these findings for future research as well as for practical clinical management are discussed.     

Apoptotic induction in transformed follicular lymphoma cells by Bcl-2 downregulation

The roles of Bcl-2 protein and the protein ratio of Bcl-2/Bax in regulating cell growth in various lymphoma cell lines were examined. A dose-dependent decrease in Bcl-2 protein expression was observed in the different lymphomas incubated with lipid-incorporated bcl-2 antisense oligonucleotides (L-bcl-2). Growth inhibition was observed in a transformed follicular lymphoma (FL) cell line, which has the t(14;18) translocation and Bcl-2 protein overexpression. One of the mechanisms by which L-bcl-2 growth inhibition is mediated in these transformed FL cells might be through apoptotic induction, because the treated cells had an increased apoptotic index and showed the typical DNA fragmentation. These studies indicate that Bcl-2 protein is critical in the growth regulation of transformed FL cells. L-bcl-2 did not induce growth inhibition in lymphoma cells not expressing Bcl-2 or Bax protein. Thus, the protein ratio of Bcl-2/Bax may also be important in regulating the growth of these lymphomas.     

Analysis and neural network modeling of the nonlinear correlates of habituation in the vestibulo-ocular reflex

Through the process of habituation, continued exposure to low-frequency (0.01 Hz) rotation in the dark produced suppression of the low-frequency response of the vestibulo-ocular reflex (VOR) in goldfish. The response did not decay gradually, as might be expected from an error-driven learning process, but displayed several nonlinear and nonstationary features. They included asymmetrical response suppression, magnitude-dependent suppression for lower- but not higher-magnitude head rotations, and abrupt-onset suppressions suggestive of a switching mechanism. Microinjection of lidocaine into the vestibulocerebellum of habituated goldfish resulted in a temporary dishabituation. This suggests that the vestibulocerebellum mediates habituation, presumably through Purkinje cell inhibition of vestibular nuclei neurons. The habituated VOR data were simulated with a feed-forward, nonlinear neural network model of the VOR in which only Purkinje cell inhibition of vestibular nuclei neurons was varied. The model suggests that Purkinje cell inhibition may switch in to introduce nonstationarities, and cause asymmetry and magnitude-dependency in the VOR to emerge from the essential nonlinearity of vestibular nuclei neurons.     

The coxsackievirus-adenovirus receptor protein can function as a cellular attachment protein for adenovirus serotypes from subgroups A, C, D, E, and F

Attachment of an adenovirus (Ad) to a cell is mediated by the capsid fiber protein. To date, only the cellular fiber receptor for subgroup C serotypes 2 and 5, the so-called coxsackievirus-adenovirus receptor (CAR) protein, has been identified and cloned. Previous data suggested that the fiber of the subgroup D serotype Ad9 also recognizes CAR, since Ad9 and Ad2 fiber knobs cross-blocked each other's cellular binding. Recombinant fiber knobs and 3H-labeled Ad virions from serotypes representing all six subgroups (A to F) were used to determine whether the knobs cross-blocked the binding of virions from different subgroups. With the exception of subgroup B, all subgroup representatives cross-competed, suggesting that they use CAR as a cellular fiber receptor as well. This result was confirmed by showing that CAR, produced in a soluble recombinant form (sCAR), bound to nitrocellulose-immobilized virions from the different subgroups except subgroup B. Similar results were found for blotted fiber knob proteins. The subgroup F virus Ad41 has both short and long fibers, but only the long fiber bound sCAR. The sCAR protein blocked the attachment of all virus serotypes that bound CAR. Moreover, CHO cells expressing human CAR, in contrast to untransformed CHO cells, all specifically bound the sCAR-binding serotypes. We conclude therefore that Ad serotypes from subgroups A, C, D, E, and F all use CAR as a cellular fiber receptor.     

Distributed associative memory for use in scene analysis

A distributed associative memory system which is ideal for scene analysis is described. Recall of associated patterns using incomplete originals is made possible by the use of a distributed storage mechanism and a novel recall procedure. The memory is shown to store associations between patterns more efficiently than a conventional file store. The paper describes the memory structure, the recall process and its storage abilities, as well as an example of its implementation in hardware.     

Hairline lowering during foreheadplasty

Many patients seeking rejuvenation of their foreheads have high hairlines and are troubled by the prospect that surgery will worsen the deformity. Hairline elevation occurs in both coronal and endoscopic foreheadplasty techniques and is at least part of the reason that many surgeons do not always recommend these procedures when otherwise indicated. Although a pretrichial "hairline" incision prevents hairline retro-displacement, it results in forehead shortening only and not true hairline lowering. When a pretrichial incision is used in combination with a posterior scalp advancement flap, however, true hairline lowering is possible. Experience with this technique encompasses 27 procedures performed over a 5-year period. Patients ranged in age from 35 to 71 years. A significant improvement was demonstrable in all cases and corresponded with a high degree of patient satisfaction. No serious complications were seen. A high hairline must be recognized as the source of both a disproportionate and aged appearance. The ability to lower the hairline and place it in a more proportionate, youthful relationship with the rest of the face adds a new dimension to foreheadplasty equal to or greater in importance to an overall improved appearance as other maneuvers typically performed during the procedure. For many patients, the benefits of hairline lowering far outweigh the trade-off of a more anteriorly situated, and possibly more visible, scar.     

Protein kinase C regulates a vesicular class of calcium channels in the bag cell neurons of aplysia

Protein kinase C (PKC) acutely increases calcium currents in Aplysia bag cell neurons by recruiting calcium channels different from those constitutively active in the plasma membrane. To study the mechanism of PKC regulation we previously identified two calcium channel alpha1-subunits expressed in bag cell neurons. One of these, BC-alpha1A, is localized to vesicles concentrated primarily in somata and growth cones. We used antibodies to BC-alpha1A to analyze its expression in the bag cell neurons of juvenile Aplysia at a developmental stage at which PKC-sensitive calcium currents have previously been shown to be low. We find that vesicular BC-alpha1A staining is generally reduced in juvenile bag cell neurons but that its expression level can vary among juvenile animals. In 17 bag cell clusters examined, the percentage of neurons that displayed punctate alphaBC-alpha1A staining ranged from 0 to 85%. Sampling of calcium currents from cells of the same clusters by whole cell patch-clamp techniques revealed that the PKC-sensitive calcium current density is significantly correlated with the degree of vesicular staining. In contrast, no correlation of basal calcium current levels with aBC-alpha1A staining was found. These results strongly suggest that BC-alpha1A, a member of the ABE-subfamily of calcium channels, carries the PKC-sensitive calcium current in bag cell neurons. They are consistent with a model in which PKC recruits channels from the vesicular pool to the plasma membrane.