Ultrastructure and Transport-Related Enzymes of the Gills and Coxal Gland of the Horseshoe Crab Limulus polyphemus

The horseshoe crab, Limulus polyphemus, may be unique among marine arthropods in that both its book gills and its coxal gland may serve as sites of ion transport. We have therefore examined the ultrastructure of these organs, as well as the distribution and relative levels of two major transport-related enzymes: the Na+ + K+ ATPase and carbonic anhydrase (CA). The ventral surface of the central region of each lamella shows the typical ultrastructural specializations for ion transport: 10 μm cell thickness, an extensive network of tubules originating from infoldings of the basal membrane, and a high density of mitochondria. This region also contains high levels of activity of the Na+ + K+ ATPase and CA. The distribution of ion transporting epithelium and transport enzymes is identical in each of the five gill books. The peripheral region of the lamellae of each gill book is specialized for passive gas exchange. The ultrastructural and biochemical profile of the coxal gland is similar to that of the central-ventral region of the gill. Limulus possesses the same general mechanism of ion regulation seen in euryhaline decapod crustaceans, but the structural and functional components are uniquely distributed.

Does post-laparoscopy pain relate to residual carbon dioxide?

We studied 20 day case gynaecological laparoscopy patients, who had an erect chest X ray taken before discharge. Patients were telephoned the next day for a semi-structured interview. Particular note was made of shoulder tip pain and pain relieved by changing posture. The X ray was analysed for measurements of the length of arc and height of the gas bubble under each hemi-diaphragm, from which an estimation of bubble volume was also made. We found statistically significant correlations between both the length of arc (p = 0.005) and volume of gas bubble (p = 0.008) on the right side, with the pain score. Residual gas can be a prominent cause of post-laparoscopy pain.

Toward a conceptual understanding of the flow experience in elite athletes

An in-depth investigation into flow state was conducted in order to understand how this optimal state is experienced by elite athletes. Twenty-eight elite-level athletes, representing 7 sports, were interviewed on their perceptions of flow state during performance of their sport. Csikszentmihalyi's (1990) model of the flow state was examined for its applicability to elite athletes. Correspondence was found between the dimensions of flow, as described by Csikszentmihalyi (1990), and the athletes' descriptions of their experience of flow; some dimensions received greater support through the qualitative analysis of the athletes' descriptions than did other dimensions. Those dimensions of flow most represented across the group's data were the autotelic experience of flow, total concentration on the task at hand, merging of action and awareness, and the paradox of control. The analyses provided a detailed, sport-specific picture of flow state in elite athletes.

Nuclear-cytoplasmic translocations of protein p26 during aerobic-anoxic transitions in embryos of Artemia franciscana

Embryos of the crustacean Artemia franciscana survive continuous anoxia for periods of years, during which their metabolism comes to a reversible stand-still. A question of some interest concerns the maintenance of cellular integrity in the absence of biosynthesis and an ongoing energy metabolism. The present paper continues previous work on an abundant protein (p26) that undergoes extensive intracellular translocation during aerobic-anoxic transitions, exhibits several characteristics of stress proteins, and might be involved in metabolic regulation during aerobic-anoxic transitions. Since it has been established that intracellular pH (pHi) plays a major role in aerobic-anoxic transitions in this system we examined the pH-dependence of nuclear-cytoplasmic translocations of p26. In unincubated and aerobic-incubated embryos (pHi > or = 7.9) p26 was located in the "soluble" fraction, whereas in anoxic embryos (pH about 6.3) roughly 50% was translocated into the nucleus as shown by immunocolloidal gold electron microscopy. These nuclear translocations also took place in vitro, simply by manipulating buffer pH in a physiologically appropriate fashion. Immunostaining of Western blots prepared after two-dimensional electrophoresis revealed several isoforms of native p26. The isoelectric point of the major isoform was 7.10 +/- 0.05, a value close to the pH at which p26 translocation into the nucleus was first initiated in vitro. 31P-NMR measurements indicated that pHi was maintained at acidic levels (about 6.3) during prolonged anoxia. We also found that pHi of hydrated (0 degree C) but otherwise unincubated embryos was alkaline, allowing for rapid resumption of metabolism under permissive conditions. The significance of these pH-dependent translocations of p26 is discussed.

Platelet GPIIb/IIIa receptor occupancy studies using a novel fluoresceinated cyclic Arg-Gly-Asp peptide

DMP 728 is a potent and specific platelet GPIIb/IIIa antagonist. Like all GPIIb/IIIa antagonists, DMP 728 has a steep dose-response relationship in inhibiting platelet aggregation. In this study the relationships between receptor occupancy, platelet aggregation and bleeding time was determined in anesthetized dogs after intravenous infusion of DMP 728 (0.01 and 0.1 mg/kg/2h). Receptor occupancy was determined by flow cytometry using XL086, a novel fluorescent cyclic RGD peptide that binds to GPIIb/IIIa with high specificity and affinity (kd approximately 55 nM). Mean number of GPIIb/IIIa as determined by flow cytometric assay was approximately 53,8000 and 79,000 on unactivated and ADP-activated platelets respectively. After DMP 728 intravenous infusion, there was a dose- and time-dependent increase in receptor occupancy, inhibition of platelet aggregation and bleeding time. The two methods of receptor occupancy determination correlate with each other with an r2 = 0.78. The present data suggest that blockade of only 40-60% (approximately 40,000 receptors) of the total platelet GPIIb/IIIa was required to achieve > 90% inhibition of platelet aggregation and > 15 min bleeding time. Our results showed the potential clinical utility of this approach in the study of GPIIb/IIIa dose-response relationship.

Multiple cavitating pulmonary lesions in non-Hodgkin's lymphoma

We report two patients with multiple cavitating lung lesions caused by large cell non-Hodgkin's lymphoma. This pattern of disease has rarely been reported in non-Hodgkin's lymphoma and is more commonly described in Hodgkin's disease. The patterns of pulmonary parenchymal involvement in non-Hodgkin's lymphoma are reviewed with particular reference to cavitary lesions.

Extensive intracellular translocations of a major protein accompany anoxia in embryos of Artemia franciscana

Cells of encysted gastrula embryos of the crustacean Artemia franciscana exhibit extraordinary stability during prolonged anoxia. We find that they contain an abundant protein (referred to as "26-kDa protein") that undergoes translocation to the nucleus during anoxia. The reverse translocation rapidly occurs when anoxic embryos are returned to aerobic conditions. A similar translocation appears to take place in embryos exposed to 42 degrees C aerobic heat shock and prolonged exposure to low temperature (0-2 degrees C), and in diapause embryos. Gel filtration and Western immunoblotting indicate that the 26-kDa protein is translocated to other cellular compartments and may also be associated with a wide variety of "soluble" proteins during anoxia. This protein makes up roughly 15% of the total nonyolk embryo protein and is, by far, most abundant in the encysted embryo stage of the life cycle. The hypothesis is advanced that the 26-kDa protein may play the role of a metabolic regulator and/or a protective molecular chaperone during prolonged anoxia and other forms of stress.

Coping strategies used by national champion figure skaters

This investigation had two purposes: (a) to identify and describe the coping strategies used by national champion figure skaters and (b) to examine the relationship between coping strategies and particular stress sources. Participants were 17 of 20 (85%) Senior U.S. National Champion figure skaters who won titles between 1985 and 1990. All skaters were interviewed, and the interview transcripts were content analyzed. General coping dimensions reported by at least 40% of the skaters included (a) rational thinking and self-talk, (b) positive focus and orientation, (c) social support (e.g., receiving support from coach, talking with friends and family), (d) time management and prioritization, (e) precompetitive mental preparation and anxiety management (e.g., relaxation, visualization), (f) training hard and smart, (g) isolation and deflection (e.g., not letting things get to me, avoiding/screening media), and (h) ignoring the stressor(s). It was also found that the skaters implemented different coping strategies depending on the specific stressors encountered.

High-resolution CT of the chest: radiation dose

OBJECTIVE

The purpose of this study was to compare the skin radiation dose to the chest produced by high-resolution CT (HRCT) with the radiation dose produced by conventional CT. Previous studies have reported that radiation doses with HRCT are equal to or higher than those with conventional CT. These results, however, were based on the assumption that in HRCT, contiguous sections were scanned without the intersection gaps of 10 or 20 mm that are used clinically.

SUBJECTS AND METHODS

We used radiotherapy verification film to measure the skin radiation dose in 56 patients who had chest CT scans. Twenty-two had 1.5-mm collimation HRCT scans at 10-mm intervals, 15 had 1.5-mm collimation HRCT scans at 20-mm intervals, and 19 had 10-mm collimation conventional CT scans at 10-mm intervals. Scan parameters were identical in all cases: 120 kVp, 200 mA, 2 sec. Step wedges were used to generate calibration films with identical beam quality on the CT scanner, and exposure was measured with an ionization chamber. Calibration films and patients' radiotherapy verification films were digitized, and the radiation dose was calculated.

RESULTS

Mean skin radiation dose was 4.4 (standard error [SE], 0.2) mGy for 1.5-mm HRCT scans at 10-mm intervals, 2.1 (SE, 0.1) mGy at 20-mm intervals, and 36.3 (SE, 0.9) mGy for conventional 10-mm scans at 10-mm intervals.

CONCLUSION

HRCT scanning at 10- and 20-mm intervals produced 12% and 6%, respectively, of the radiation dose associated with conventional CT. This is considerably less radiation than suggested in earlier studies. Combining HRCT scans at 20-mm intervals with low-dose scan (20 mA, 2-sec scans) would result in an average skin dose comparable with the dose administered with chest radiography.

Coping strategies used by U.S. Olympic wrestlers

Extensive in-depth interviews were conducted with all 20 members of the 1988 U.S. Olympic Wrestling Team regarding their efforts to cope with stress experienced during the Seoul Olympics. Qualitative analyses revealed that the wrestlers employed a variety of coping strategies including: (a) thought control strategies (blocking distractions, perspective taking, positive thinking, coping thoughts, and prayer), (b) task focus strategies (narrow, more immediate focus, concentrating on goals), (c) behavioral based strategies (changing or controlling the environment, following a set routine), and (d) emotional control strategies (arousal control, visualization). In accordance with the observations of Compas (1987) and Folkman and Lazarus (1985), the coping efforts of the Olympic wrestlers were not limited to particular strategies nor to single approaches to dealing with a particular stressor but, rather, reflected a dynamic complex process involving a number of strategies, often in combination. The results also suggested that the degree to which coping strategies are well learned or automatized is related to their perceived effectiveness.

The effect of dopamine on graft function in patients undergoing renal transplantation

We studied the effect of a low-dose dopamine infusion on graft function in 60 patients undergoing transplantation with cadaveric kidneys in a prospective controlled trial. Recipients were allocated to either a control or a dopamine group, the latter receiving a 3 micrograms.kg-1 x min-1 infusion of dopamine starting intraoperatively. Evaluation of dopamine's effect was undertaken in two stages, namely, (i) initial graft function 1 wk after transplantation and (ii) graft survival at 3 mo. Initial graft function was determined by the ability of the transplanted kidney to reduce serum creatinine, and the development of acute tubular necrosis as confirmed by renal biopsy. Of the dopamine group 33.3% developed acute tubular necrosis compared to 23.3% of the control group. The second-stage evaluation was based on plasma creatinine levels and the requirement for dialysis within 3 mo of transplantation. 92.8% of the dopamine group and 76.9% of the control group had good graft function. No statistically significant difference between the two groups was found. The perioperative infusion of dopamine at 3 micrograms.kg-1 x min-1 was not shown to have any beneficial effect on the transplanted kidney in patients who do not have serious vascular disease, or who do not receive kidneys subjected to prolonged hypotension or prolonged preservation or anastomotic times.

Identification of novel peptide antagonists for GPIIb/IIIa from a conformationally constrained phage peptide library

Methods have recently been developed to present vast libraries of random peptides on the surface of filamentous phage. To introduce a degree of conformational constraint into random peptides, a library of hexapeptides flanked by cysteine residues (capable of forming cyclic disulfides) was constructed. This library was screened using the platelet glycoprotein, IIb/IIIa, which mediates the aggregation of platelets through binding of fibrinogen. A variety of peptides containing the sequence Arg-Gly-Asp or Lys-Gly-Asp were discovered and synthesized. The cyclic, disulfide-bonded forms of the peptides bound IIb/IIIa with dissociation constants in the nanomolar range, while reduced forms or an analogue in which Ser replaced the Cys residues bound considerably less tightly. These results demonstrate the feasibility for introducing conformational constraints into random peptide libraries and also demonstrates the potential for using phage peptide libraries to discover pharmacologically active lead compounds.

Evaluation of a personal computer-based quantitative coronary analysis system for rapid assessment of coronary stenoses

Quantitative coronary analysis (QCA) is a technique that is rarely used because of the complexity and expense of existing systems. We studied a new personal computer-based QCA system that is capable of both geometric and densitometric analysis and compared it to a previously validated QCA system. Both systems performed extremely well in phantom analysis with 11 phantoms filmed in both 5-inch and 7-inch magnifications (R greater than 0.97 and SEE less than 0.33 mm for all modes). In 28 abnormal coronary angiograms analyzed at end diastole, stenosis and reference diameter correlations between the two systems were excellent (R = 0.90 and 0.96 and SEE = 0.43 and 0.33 mm for densitometric and geometric modes, respectively). Intraobserver and interobserver correlation was also excellent for both analysis modes. The new QCA system was able to perform analysis in approximately one third the time required by previously validated system and was much less expensive. We conclude that personal computer-based coronary analysis is an accurate, quick, and relatively inexpensive means for performing QCA that may help to make this technique feasible for nonresearch settings.

Aerobic heat shock activates trehalose synthesis in embryos of Artemia franciscana

Encysted embryos (cysts) of the brine shrimp, Artemia franciscana, contain large amounts of trehalose which they use as a major substrate for energy metabolism and biosynthesis for development under aerobic conditions at 25 degrees C. When cysts are placed at 42 degrees C (heat shock) these pathways stop, and the cysts re-synthesize the trehalose that was utilized during the previous incubation at 25 degrees C. Glycogen and glycerol, produced from trehalose at 25 degrees C, appear to be substrates for trehalose synthesis during heat shock. Anoxia prevents trehalose synthesis in cysts undergoing heat shock. These results are consistent with the view that trehalose may play a protective role in cells exposed to heat shock, and other environmental insults, in addition to being a storage form of energy and organic carbon for development.

Regional observer performance variation in the evaluation of gated cardiac blood pool studies

Receiver operating characteristic (ROC) analysis demonstrated that regional variations of sensitivity exist in the detection of wall motion abnormality in cardiac blood pool imaging studies. The observer response is significantly better in the apex than either the septum or posterolateral wall segments. The observer errors tend to be false-negative in the posterolateral wall segment and false-positive in the other two segments. Image presentation can make a significant difference to the overall sensitivity, and the monochrome cine-sequence performed best in this study.

A comparative study of the nephrotoxicity of iohexol, iopamidol and ioxaglate in peripheral angiography

Iohexol (Omnipaque 350) and iopamidol (Isovue 370) are nonionic monomers; ioxaglate (Hexabrix 320) is an ionic dimer. We compared the nephrotoxicity of these three media by a prospective double-blind evaluation in 500 patients who underwent peripheral angiography during a 6-month period. Serum creatinine levels were determined before injection of the contrast medium and 72 hours after in 478 patients. In 308 (64%) patients there was an average increase in the serum creatinine level of 18.1 mumol/L after injection of an average volume of 123 ml of contrast medium. A subset of 80 patients who had an elevated baseline creatinine level (more than 110 mumol/L) had an average increase in the serum creatinine level of 40.45 mumol/L. Of patients who had arterial injections, 182 (72%) had an increase in serum creatinine level (20.7 mumol/L), but of those who had peripheral venous injections, only 43 (45%) had an elevated creatinine level (9.2 mumol/L), and of those who had central venous injections, 83 (63.8%) had an elevated level (17.0 mumol/L). In most patients elevation of the serum creatinine level was not of clinical importance. High-risk patients with an elevated serum creatinine level were found to be most vulnerable to contrast nephrotoxicity. Although mean differences were not statistically significant, there were consistent trends which suggested that ioxaglate was the least nephrotoxic of the three agents studied.

Glucose metabolism and the channeling of glycolytic intermediates in permeabilized L-929 cells

L-929 cells (mouse fibroblasts) permeabilized with dextran sulfate (DSP cells) carry out vigorous and linear rates of glycolysis when supplied with a suitable incubation medium. Glycolysis in DSP cells is pH dependent, being strongly inhibited at pH 6.5. Compared to their nonpermeabilized counterparts, DSP cells exhibit faster glycolytic rates, but tend to convert a smaller proportion of the glucose utilized to lactate. [14C]Glucose is converted to lactate by DSP cells without dilution from endogenous substrates. When exogenous 12C-labeled glycolytic intermediates (12C-I) are added to glycolyzing DSP cells the [14C]lactate produced from [14C]glucose is diluted to varying extents, depending on the intermediate. However, the extent of that dilution (reduced specific activity) is not that expected from the complete mixing of exogenous 12C-I with their corresponding 14C-labeled intermediates coming from [14C]-glucose. DSP cells also respire and convert glucose to CO2. The amount of 14CO2 produced from [14C]glucose is also reduced by addition of most 12C-I, an interesting exception being pyruvate, which had no measurable effect on 14CO2 production and caused only a modest stimulation of respiration in glycolyzing DSP cells. These results suggest that channeling, or some other form of coupling, takes place between the glycolytic production of pyruvate and its further oxidation. These observations confirm previously published data and add further support to the proposition that channeling of glycolytic intermediates occurs in DSP cells but is of the "leaky" type. Although abundant evidence in the literature indicates that various glycolytic enzymes associate with F-actin, as well as other elements of the cytomatrix, we observed no effect of cytochalasin D on lactate production even at very high concentrations of this compound. Our results are compared with those from other laboratories and discussed in the context of metabolic organization.

Glycolysis compared in intact, permeabilized and sonicated L-929 cells

The effects of incubation time and cell density on glycolytic rate were examined in suspensions of intact, permeabilized and sonicated L-929 cells. Sonicates exhibited strong dependence on cell density and a distinct lag in glycolytic rate, while intact cells showed no cell density dependence and linear glycolytic rates. Permeabilized cells exhibited linear glycolytic rates, but sometimes showed dependence on cell density. Rates of lactate production (nmol at 30 min/10(6) cells) were highest in sonicates and lowest in intact cells. These results are interpreted as support for the previously proposed hypothesis that enzymes of the glycolytic pathway are highly organized in intact L-929 cells.

Effects of reduced cell volume and water content on glycolysis in L-929 cells

Mouse L-929 cells were subjected to increasing concentrations of sorbitol, which remove cell water and reduce volume osmotically. The rate of lactate production from glucose was significantly higher in osmotically perturbed cells than in controls, both in monolayers and in suspensions. L cells can apparently use sorbitol as a glycolytic substrate; however, studies using other solutes (trehalose and sucrose) and permeabilized cells showed that the major effect of sorbitol on glycolysis in intact cells is mediated through a reduction in cell water content and volume. It is possible to explain some of these results by an increase in the chemical potentials of dissolved components of the glycolytic pathway caused by water loss; however, the relationship between water loss and glycolytic rate increase in not a simple linear one, suggesting that the situation is more complex than would result merely from increased concentrations of pathway components. Whatever the complete explanation might be, these studies show that glycolysis continues in an orderly fashion in cells that have lost about 85% of their original water content, suggesting that the operation of this pathway is not unduly sensitive to events taking place in the bulk aqueous phase.

Evidence for intermediate channelling in the glycolytic pathway of permeabilized L-929 cells

L-929 cells permeabilized by dextran sulfate (DSP cells) carry out vigorous and linear rates of glycolysis when supplied with a suitable incubation medium. Unlabeled 3-phosphoglycerate (PGA) added to DSP cells reduces the specific activity of lactate coming from [14C]glucose but the extent of this reduction can not be accounted for on the basis of free diffusion of PGA coming from [14C]glucose. Studies on other glycolytic intermediates, although preliminary, yield similar results. PGA also inhibits the production of lactate from glucose; however, this effect, like that of the reduction of lactate specific activity, becomes apparent only at concentrations of PGA well in excess of those considered to be physiological. We conclude that channelling of PGA, and probably other intermediates, occurs but is of the "leaky" type.