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Summary Obesity is a complex, chronic disease, frequently associated with multiple comorbidities. Its management is hampered by a lack of translation of evidence on chronicity and pathophysiology into clinical practice. Also, it is not well understood how to support effective provider–patient communication that adequately addresses patients’ personal root causes and barriers and helps them feel capable to take action for their health. This study examined interpersonal processes during clinical consultations, their impacts, and outcomes with the aim to develop an approach to personalized obesity assessment and care planning. We used a qualitative, explorative design with 20 participants with obesity, sampling for maximum variation, to examine video‐recorded consultations, patient interviews at three time points, provider interviews and patient journals. Analysis was grounded in a dialogic interactional perspective and found eight key processes that supported patients in making changes to improve health: compassion and listening; making sense of root causes and contextual factors in the patient's story; recognizing strengths; reframing misconceptions about obesity; focusing on whole‐person health; action planning; fostering reflection and experimenting. Patient outcomes include activation, improved physical and psychological health. The proposed approach fosters emphatic care relationships and sensible care plans that support patients in making manageable changes to improve health.

Results are reported on the sensitivity of various gynaecological tumour cell lines to 5-aminolaevulinic acid-induced protoporphyrin IX-sensitised photodynamic therapy (ALA-PDT) in vitro. All cell lines tested accumulated ALA-induced protoporphyrin IX (PpIX) and demonstrated good sensitivity to ALA-PDT. Localisation of PpIX in the mitochondria was demonstrated by fluorescence microscopy. Subcellular damage following ALA-PDT was observed using transmission electron microscopy. This damage was localised initially to the mitochondria, with damage to membranes and the nucleus and complete loss of intracytoplasmic organisation being observed subsequently. There was no apparent difference in ALA-PDT response between a multidrug-resistant ovarian carcinoma cell line and its parent line. These results indicate that ALA-PDT has potential for application to therapy of gynaecological malignancies. Images Figure 5 Figure 6 Figure 7

FK1, a ferret ventricular full-length cDNA clone, encodes a 654-amino acid protein with 98% identity to human K+ transient outward current (Ito)-like HK1 (Tamkun et al. FASEB J.5: 331-337, 1991). FK1 is detectable in ferret brain, atrium, left and right ventricle, and kidney but not in skeletal muscle, endothelial cells, aorta, and liver. In Xenopus oocytes, FK1 cRNA gives rise to a rapidly activating and inactivating Ito-like current, which is highly K+ selective (Na(+)-to-K+ permeability ratio = 0.003). Activation occurs over an approximately 50-mV range (-40 to +10 mV) and displays a sigmoid delay in onset with potential-dependent time constants that decrease with depolarization. Steady-state activation can be described with either a simple Boltzmann relationship [half-activation potential (V1/2) = -25 mV, slope (k) = 10 mV] or a Boltzmann relationship raised to either the third or fourth power (alpha 3: V1/2 = -43 mV, kappa = 13.1 mV; alpha 4: V1/2 = -48 mV, kappa = 13.6 mV, where alpha is the activation variable). Inactivation kinetics are biexponential, with the main fast time constant becoming independent of membrane potential depolarized to 0 mV. Steady-state inactivation can be described with a single Boltzmann relationship (V1/2 = -57 mV, kappa = 5.0 mV). Fast inactivation is removed by NH2-terminal deletions. Recovery from inactivation (-90 mV) is quite slow (half-time = 4.8 +/- 2.5 s). In 2 mM extracellular K+ concentration ([K+]o), FK1 tail currents display conventional deactivation behavior; however, in 98 mM [K+]o the tail currents display "reopening" behavior. These results suggest a molecular basis for the electrophysiological similarities between ferret and human ventricular Ito (Campbell et al. J. Gen. Physiol. 101: 571-601, 1993; Nabauer et al. Circ. Res. 73: 386-394, 1993).

Specific, straightforward, and rapid procedures are required for the detection, identification, and quantification of the potent low molecular weight toxins that are produced by blooms and scums of cyanobacteria (blue-green algae) in waterbodies. Use of the Microtox bioluminescence assay and the brine shrimp (Artemia salina) has been advocated for the initial screening of cyanobacterial blooms for microcystin hepatotoxins. Inhibition of bacterial luminescence in the Microtox assay and brine shrimp mortality were determined with microcystin-containing and nonmicrocystin-containing cyanobacteria. Extraction and fractionation of test samples was undertaken to select and isolate microcystincontaining fractions and reduce interference from other fractions. Maximal inhibition of bacterial luminescence in the Microtox assay occurred with fractions from Microcystis strains and an Anabaena bloom that did not contain microcystins. By contrast, the bioassay of fractions using brine shrimps correlated with the distribution of microcystin-LR in the fractionated Microcystis extracts. © 1994 by John Wiley & Sons, Inc..

Smooth muscle caldesmon was phosphorylated in vitro by sea star p44mpk up to 2.0 mol of phosphate/mol of protein at both Ser and Thr residues. The phosphorylation sites were contained mainly in the COOH-terminal 10-kDa cyanogen bromide fragment which houses the binding sites for calmodulin, tropomyosin, and F-actin. Tryptic peptide maps of 32P-labeled caldesmon by p44mpk and p34cdc2 showed that while both enzymes recognized similar sites of phosphorylation, they have different preferred sites. Phosphorylation of caldesmon attenuated slightly its interaction with actin and had no effect on its binding to calmodulin and tropomyosin. Smooth muscle cell extracts from chicken gizzard and rat aorta contained 42- and 44-kDa proteins, respectively, which were cross-reactive with an antibody to sea star p44mpk. Immunoprecipitates from gizzard and aorta cell extracts, generated with the p44mpk antibody, possessed kinase activities toward myelin basic protein as well as caldesmon. These results suggest that MAP kinase may have functions in the differentiated smooth muscle cells distinct from those involved in the cell cycle.

Vascular mediator synthesis in endothelial cells is Ca 2+ sensitive. Bradykinin increases [Ca 2+ ] i by releasing it from intracellular stores and by increasing influx across the plasmalemma. The latter is believed to occur through receptor-operated channels. Although gating of these plasmalemmal channels is voltage-insensitive, we hypothesized that Ca 2+ influx would still be dependent on the Ca 2+ electrochemical gradient and relative cation permeability. Using cultured bovine pulmonary endothelial cells we therefore measured: membrane voltage ( E m ) in single cells using the “tight seal” whole cell recording technique, Ca 2+ i in endothelial cell monolayers using fura-2, and arachidonic acid (AA) release using 3 H-AA prior to and following exposure to bradykinin at different [K + ] 0 . Our data indicate that the resting membrane potential of these cells is at least −67 mV in physiological saline and that the background resting membrane properties can be described with a ( P Na P K ) ratio of ∼0.027–0.040. Varying [K + ] 0 is shown to be an effective means for altering and controlling membrane potential and thus the calcium electrochemical gradient. Increases in [K + ] 0 lead to a concentration-dependent decrease in the magnitude of the Ca 2+ transient and in the relative amount of arachidonic acid released following exposure to bradykinin suggesting that Ca 2+ influx through the plasmalemma and AA release are regulated by the Ca 2+ electrochemical gradient. In addition, a simple theoretical membrane conductance model is presented which is able to reconcile the wide range in apparent resting membrane potentials which have been reported for endothelial cells.

The gigaohm seal patch clamp (whole cell configuration) and an internal perfusion technique were used to study the effects of sarcoplasmic reticulum (SR) calcium release on L-type calcium current (ICa,L) in ferret enzymatically isolated right ventricular myocytes. ICa,L (22 to 24 degrees C) was isolated by using various sodium- and potassium-free salines, which eliminated or greatly minimized activation of the sodium-calcium exchanger and calcium-activated cation and anion currents. When calcium was the charge carrier, inactivation of ICa,L was nonmonotonic in many myocytes; after an early rapid phase of inactivation, a secondary inward 'hump' component was frequently observed between -40 to -10 mV. The hump component was not present when barium replaced calcium but was observed when calcium carried the current in low intracellular (aspartate) and extracellular (methanesulphonate) chloride solutions. When BAPTA 10 mM was perfused internally the amplitude of ICa,L increased, the kinetics of inactivation slowed and the hump component disappeared. Both caffeine 10 mM and ryanodine 10 microM increased the amplitude of ICa,L in the hyperpolarized range of potentials (negative to 0 mV), slowed the kinetics of ICa,L inactivation and caused the hump component to disappear. Under current clamp mode, both caffeine and ryanodine significantly prolonged the duration of the action potential. Taken in aggregate, preliminary data demonstrate that, in ferret right ventricular myocytes, a secondary inward hump component can be frequently observed after the early rapid phase of inactivation of ICa,L, causing the net inward current to display biphasic, nonmonotonic behaviour. This secondary inward hump current is only present when calcium is the charge carrier, is absent when BAPTA is used as an intracellular calcium chelator and SR calcium release is disrupted by either caffeine or ryanodine, and is not due to activation of either the sodium-calcium exchanger or various putative calcium-activated cation or anion channels. Rather, preliminary results strongly suggest that this secondary inward hump current component is due to modulation of ICa,L by SR calcium release. Possible physiological and theoretical implications of the results are discussed briefly.

Administration of the heme precursor 5-aminolevulinic acid (ALA) leads to the selective accumulation of the photosensitizer protoporphyrin IX (PpIX) in certain types of normal and abnormal tissues. This phenomenon has been exploited clinically for detection and treatment of a variety of malignant and nonmalignant lesions. The present preclinical study examined the specificity of ALA-induced porphyrin fluorescence in chemically induced murine lung tumors in vivo. During the early stages of tumorigenesis, ALA-induced PpIX fluorescence developed in hyperplastic tissues in the lung and later in early lung tumor foci. In early tumor foci, maximum PpIX fluorescence occurred 2 h after the administration of ALA and returned to background levels after 4 h. There was approximately a 20-fold difference in PpIX fluorescence intensity between tumor foci and the adjacent normal tissue. The specificity of ALA-induced fluorescence for hyperplastic tissues and benign tumors in lung during tumorigenesis suggests a possible use for this fluorochrome in the detection of premalignant alterations in the lung by fluorescence endoscopy. Two non-small cell lung cancer cell lines developed ALA-induced PpIX fluorescence in vitro. These lines exhibited a light-dose-dependent phototoxic response to ALA photodynamic therapy (PDT) in vitro. Because PpIX is a clinically effective photosensitizer for a wide variety of malignancies, these results support the possible use of ALA-induced PpIX PDT for lung cancer.

A simple flow cytometric technique for rapid measurement of multilog cytotoxic responses to photosensitization of cellular systems is described. This technique is particularly useful for cell lines with a low colony-forming efficiency, for which a nonclonogenic assay is required. The assay separates cell-sized objects from cellular debris by gating on forward scatter versus side scatter, identifies viable cells by positive calcein AM and negative ethidium homodimer-1 staining and measures cell concentration relative to an internal standard of polystyrene beads. Large numbers of cells can be analyzed rapidly. Two patient-derived small cell lung cancer cell lines, NCI-H209 and SV-E, were used to test the technique. Photordiation survival curves of the response of these cell lines to 5-aminolevulinic acid-induced protoprophyrin IX photosensitization correlated with the extent of photosensitizer accumulation. There was good agreement between the results obtained using the tritiated thymidine incorporation assay and the flow cytometric cytotoxicity assay. The technique can be used to measure cytotoxic responses to photosensitization of cell lines regardless of their plating efficiencies.

We present the results of shock physics and seismological computational simulations that show how energy from a large impact can be coupled to the interior of the Earth. The radially-diverging shock wave generated by the impact decays to linearly elastic seismic waves. These waves reconverge (minus attenuation) along the axis of symmetry between the impact and its antipode. The locations that experience the most strain cycles with the largest amplitudes will dissipate the most energy and have the largest increases in temperature (for a given attenuation efficiency). We have shown that the locus of maximum energy deposition in the mantle lies along the impact axis. Moreover, the most intense focusing is within the asthenosphere at the antipode, within the range of depths where mechanical energy is most readily converted to heat. We propose that if large impacts on the Earth leave geological evidence anywhere other than the impact site itself, it will be at the antipode. We suggest that the most likely result of the focusing for a sufficiently large impact, consistent with features observed in the geological record, would be a flood basalt eruption at the antipode followed by hotspot volcanism. A direct prediction of this model would bemore » the existence of undiscovered impact structures whose reconstructed locations would be antipodal to flood basalt provinces. One such structure would be in the Indian Ocean, associated with the Columbia River Basalts and Yellowstone; another would be a second K/T impact structure in the Pacific Ocean, associated with the Deccan Traps and Reunion.« less

We studied the blocking effects of 4-aminopyridine (4-AP) on a Kv1.4 K+ channel. A permanently charged 4-AP derivative only produced block when applied intracellularly. 4-AP block accumulated from pulse to pulse indicating trapping of 4-AP in deactivated channels. For long trains of depolarizing pulses, 4-AP block increased with decreasing pulse duration. This increase took many pulses (10) to accumulate and was relieved by two to three subsequent pulses of 500 msec duration. We conclude that the time- and voltage-dependence of 4-AP block can not be accounted for solely by either simple pure open channel or pure closed channel blocking schemes. We propose that the data can be explained by a model in which 4-AP binding is most stable when the channel has a symmetric arrangement in the binding regions.

A putative mitogen-activated protein kinase (MAPK) has recently been identified, which potentially phosphorylates the human epidermal growth factor (EGF) receptor at a physiological site (Thr-669) and is distinguished from other MAPKs/extracellular signal-regulated protein kinases (ERKs) on the basis of chromatographic, immunological, and kinetic data. Here we report that this newly discovered MAPK is physically associated with the EGF receptor in A431 cells and with the related receptor/tyrosine kinase HER2 (encoded by c-neu) in enzyme preparations obtained from Wilm's tumors. This human EGF receptor-associated kinase is characterized as a 40-kDa Thr-669 kinase that exists in a high molecular mass complex with the respective growth factor receptor. EGF treatment of A431 cells stimulates the tyrosine phosphorylation of p40 and increases Thr-669 kinase activity in p40-containing fractions. The 40-kDa kinase is recognized by affinity-purified polyclonal antibodies directed against the sea star p44mpk and a Pan-ERK antibody directed against the conserved subdomain VIII of MAPKs/ERKs, but is not recognized by antibodies selective for the rat p44erk1 and/or the p42mapk/erk2 isoforms, thus identifying the EGF receptor-associated kinase as a novel MAPK that may regulate receptor function in vivo.

During 1984 to 1988, the U.S. Occupational Safety and Health Administration (OSHA) investigated 10 incidents, with 11 fatalities, involving the inadvertent connection of air-line respirators to inert gas supplies. Seven deaths resulted from connecting an air-line respirator supply hose to a line which normally carried inert gas. Four deaths were caused by leakage or backfill of inert gas into a line which normally carried breathable air. Ten of the deaths were from nitrogen and one from argon. The circumstances of the 11 deaths indicated that coupling compatibility and supervisory oversight were major factors in the inappropriate supply of irrespirable gas to the respirators worn by these workers. Conscientiousness among safety personnel to the hazards of asphyxiation by inert gas, and compliance with current OSHA regulations, the ANSI Z88.2 standard, and NIOSH respirator certification approval regulations would have prevented these fatalities.

The effects of extracellular ATP on the L-tpe Ca2+ current (ICa), action potential, and resting and intracellular Ca2+ levels were examined in enzymatically isolated myocytes from the right ventricles of ferrets. Extracellular ATP decreased the peak amplitude of ICa in a time- and concentration-dependent manner. The concentration-response relationship for ATP inhibition of ICa was well described by a conventional Michaelis-Menten relationship with a half maximal inhibitory concentration of 1 microM and a maximal effect of 50%. Extracellular ATP did not change the resting myoplasmic Ca2+ levels; however, it did decrease the Ca2+ transient. The effects of extracellular ATP were mediated independently of adenosine A1 receptors and a pertussis-toxin sensitive G protein. Pharmacological characterization of receptor subtype using ATP analogs was consistent with ATP binding to a P2Y type receptor.

Smooth muscle caldesmon was phosphorylated in vitro by sea star p44mpk up to 2.0 mol of phosphate/mol of protein at both Ser and Thr residues. The phosphorylation sites were contained mainly in the COOH-terminal 10-kDa cyanogen bromide fragment which houses the binding sites for calmodulin, tropomyosin, and F-actin. Tryptic peptide maps of 32P-labeled caldesmon by p44mpk and p34cdc2 showed that while both enzymes recognized similar sites of phosphorylation, they have different preferred sites. Phosphorylation of caldesmon attenuated slightly its interaction with actin and had no effect on its binding to calmodulin and tropomyosin. Smooth muscle cell extracts from chicken gizzard and rat aorta contained 42- and 44-kDa proteins, respectively, which were cross-reactive with an antibody to sea star p44mpk. Immunoprecipitates from gizzard and aorta cell extracts, generated with the p44mpk antibody, possessed kinase activities toward myelin basic protein as well as caldesmon. These results suggest that MAP kinase may have functions in the differentiated smooth muscle cells distinct from those involved in the cell cycle.

Vascular mediator synthesis in endothelial cells is Ca2+ sensitive. Bradykinin increases [Ca2+]i by releasing it from intracellular stores and by increasing influx across the plasmalemma. The latter is believed to occur through receptor-operated channels. Although gating of these plasmalemmal channels is voltage-insensitive, we hypothesized that Ca2+ influx would still be dependent on the Ca2+ electrochemical gradient and relative cation permeability. Using cultured bovine pulmonary endothelial cells we therefore measured: membrane voltage (Em) in single cells using the "tight seal" whole cell recording technique, Ca2+i in endothelial cell monolayers using fura-2, and arachidonic acid (AA) release using 3H-AA prior to and following exposure to bradykinin at different [K+]0. Our data indicate that the resting membrane potential of these cells is at least -67 mV in physiological saline and that the background resting membrane properties can be described with a (PNa/PK) ratio of approximately 0.027-0.040. Varying [K+]0 is shown to be an effective means for altering and controlling membrane potential and thus the calcium electrochemical gradient. Increases in [K+]0 lead to a concentration-dependent decrease in the magnitude of the Ca2+ transient and in the relative amount of arachidonic acid released following exposure to bradykinin suggesting that Ca2+ influx through the plasmalemma and AA release are regulated by the Ca2+ electrochemical gradient. In addition, a simple theoretical membrane conductance model is presented which is able to reconcile the wide range in apparent resting membrane potentials which have been reported for endothelial cells.

The recent rise in the awareness of the occurrence of toxic cyanobacterial blooms in aquatic environments, with associated human health problems and animal deaths, has increased the need for rapid, reliable and sensitive methods of determining cyanobacterial toxicity. A luminescent bacterial toxicity test was assessed as a complement to the established mouse bioassay. Seventeen samples including pure cyanobacterial microcystin-LR hepatotoxin, laboratory isolates and natural blooms of cyanobacteria were tested and toxicity data compared with mouse LD50 values. Microcystin-LR and all five microcystin-containing cyanobacterial samples, hepatotoxic by mouse test gave EC50 values of less than 0.46 mg/ml in bioluminescence-based Microtox assays. Of 11 samples non-toxic by mouse bioassay, only two gave an EC50 of less than 0.98 mg/ml by bioluminescence assay. It is suggested that the Microtox bioluminescence assay may prove useful in the preliminary screening of cyanobacterial blooms for microcystin-based toxicity.

We have developed a model of cardiac atrial electrical activity based on voltage-clamp measurements obtained from single cells isolated from the bullfrog atrium. These measurements have allowed us to simulate a number of processes thought to be important in action potential initiation, repolarization, and the excitation-contraction (EC) coupling process. In this atrial model, the cell membrane contains both channel-mediated (Na+, Ca2+, inward rectifier K+, delayed rectifier K+, linear background leak) and transporter-mediated (Na(+)-K+ pump, Na(+)-Ca2+ exchanger, Ca2+ pump) currents. The cell is surrounded extracellularly by a diffusion-limited space. The intracellular volume contains Ca2(+)-binding proteins (calmodulin, troponin). The model makes several important predictions. 1) Incomplete inactivation of the Ca2+ current provides an inward current the maintains the plateau of the action potential. 2) Activation of the delayed rectifier K+ current initiates repolarization. 3) Due to Ca2+ buffering by myoplasmic proteins the Na(+)-Ca2+ exchanger current is relatively small and has little influence on repolarization. 4) The Na(+)-K+ pump current does not play a major role in repolarization. 5) K+ accumulation and Ca2+ depletion may occur in the extracellular spaces. 6) Modulation of EC coupling is governed by interactions between the myoplasmic Ca2(+)-binding proteins; specifically, the inotropic "positive staircase effect" may be explained by interactions between Ca2+ and Mg2+ at a competitive binding site on troponin. When considered in conjunction with the results of our model of primary pacemaking in the sinus venosus [Rasmusson et al., Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H352-H369, 1990], this atrial model shows how the presence or absence of certain transmembrane currents can change action potential characteristics and consequently alter the relative influence of the various transporter-mediated and channel-mediated currents.

Previous models of cardiac cellular electrophysiology have been based largely on voltage-clamp measurements obtained from multicellular preparations and often combined data from different regions of the heart and a variety of species. We have developed a model of cardiac pacemaking based on a comprehensive set of voltage-clamp measurements obtained from single cells isolated from one specific tissue type, the bullfrog sinus venosus (SV). Consequently, sarcolemmal current densities and kinetics are not influenced by secondary phenomena associated with multicellular preparations, allowing us to realistically simulate processes thought to be important in pacemaking, including the Na(+)-K+ pump and Na(+)-Ca2+ exchanger. The membrane is surrounded extracellularly by a diffusion-limited space and intracellularly by a limited myoplasmic volume containing Ca2(+)-binding proteins (calmodulin, troponin). The model makes several predictions regarding mechanisms involved in pacing. 1) Primary pacemaking cannot be attributed to any single current but arises from both the lack of a background K+ current and a complex interaction between Ca2+, delayed-rectifier K+, and background leak currents. 2) Ca2+ current displays complex behavior and is important during repolarization. 3) Because of Ca2+ buffering by myoplasmic proteins, the Na(+)-Ca2+ exchanger current is small and has little influence on action potential repolarization but may modulate the maximum diastolic potential. 4) The Na(+)-K+ pump current does not play an active role in repolarization but is of sufficient size to modulate the rate of diastolic depolarization. 5) K+ accumulation and Ca2+ depletion may occur in the extracellular spaces but play no role in either the diastolic depolarization or repolarization of a single action potential. This model illustrates the importance of basing simulations on quantitative measurements of ionic currents in myocytes and of including both electrogenic transporter mechanisms and Ca2+ buffering by myoplasmic Ca2(+)-binding proteins.

A gas-liquid chromatographic (GLC) method for determining Bolstar insecticide in liquid technical material and emulsifiable concentrate formulations was collaboratively studied using Youden’s matched pair scheme. Three matched sample pairs were analyzed by 21 laboratories using integrator area measurements and/or peak height measurements. Samples of a technical material containing about 78% active ingredient, a commercial 6 lb/ gal. emulsifiable concentrate containing about 64% active ingredient, and a synthetic emulsifiable concentrate containing about 64% active ingredient were dissolved in a measured amount of internal standard solution, tetracosane in toluene, and were subjected to gas-liquid chromatography on a column of 1.5% SE-30 + 1.5% OV-210. Bolstar was detected using flame ionization. The mean coefficient of variation by integrator area measurement for the 6 samples was 1.22%, and the mean coefficient of variation by peak height measurement for the 6 samples was 1.65%. The method was adopted as official first action.

Previous studies of stretch reflexes in patients with spastic hypertonia have emphasized the dynamic character of stretch reflex output. In contrast, our own studies of stretch reflex dynamics in spastic elbow flexor muscles of 14 hemiparetic human subjects have shown that stretch-evoked torque displays a relatively weak dependence on stretch velocity, and there is generally no preferential enhancement of dynamic as compared with static reflex output. Moreover, stretch reflex dynamics are broadly similar in voluntarily activated spastic and normal elbow flexor muscles. These findings support our hypothesis that spastic hypertonia results primarily from a decrease in stretch reflex threshold. The strong velocity dependence of stretch-evoked electromyographic activity in initially inactive spastic muscles could be due to a decrease in reflex threshold with increasing stretch velocity, rather than an abnormal velocity-dependent increase in stretch reflex responsiveness.

1. Voltage clamp recordings of the calcium current (ICa) in single myocytes which were enzymatically isolated from bull-frog atrium show that a genuine reversal of the current flowing through Ca2+ channels can be recorded (ef. Reuter & Scholz, 1977; Lee & Tsien, 1982, 1984; Campbell, Giles & Shibata, 1988c). In normal 2.5 mM [Ca2+]0 Ringer solution this apparent reversal potential (Erev) is near +50 mV, a value well below the predicted thermodynamic Ca2+ equilibrium potential (ECa). 2. None the less, Erev shifts with variations in extracellular divalent ion concentrations (Ca2+, Sr2+ and Ba2+) according to the predictions of a Nernstian divalent cation electrode, i.e. approximately 29 mV per 10-fold change in the external concentration of divalent ion. 3. The existing theoretical analysis of this Erev has been extended in order to clarify its interpretation with regard to the selectivity characteristics of ICa. 4. The apparent reversal potential is analysed using a form of the constant field equation which has been modified to include (i) simultaneous monovalent and divalent cation movements and (ii) the presence of a surface potential (V'). This equation can be solved to yield an explicit expression for Erev. The effects of V' on apparent permeability ratios for the Ca2+ channel Erev are demonstrated. 5. In combination, our experimental results and calculations suggest that: (i) previous estimates of V' which were used to describe permeability (P) ratios of Ca2+ channels in various cardiac preparations may be in error, (ii) in normal [Ca2+]o the PNa/PCa ratio is very small, and (iii) PCa/PK must be greater than 1000. An analysis of the relative selectivity of the channel for divalent cations compared to K+ shows that PCa greater than PSr greater than PBa, assuming that PK remains the same after the divalent substitutions. 6. The Ca2+ channel in bull-frog atrial cells is thus much more selective for Ca2+ ions than had previously been estimated; in particular, inward flow of monovalent cations (e.g. Na+) through these channels does not contribute significantly to the observed ICa. The physiological implications of this high selectivity for Ca2+ ions are discussed.

Reconstituted commercial skim milk powder samples which produced a firm (> 30 g) rennet curd had high levels (> 4 mg N/g) of undenatured whey protein nitrogen (WPN) as measured by the modified Harland–Ashworth test. However, similar samples which also had high levels of WPN (> 6 mg N/g) had low curd firmness or failed to coagulate. Of 24 commercial samples of milk replacers, 2 formed a soft curd; the rest did not coagulate. Five had high levels of WPN (> 6 mg N/g); one sample contained 17.8 mg N/g, well above normal levels of skim milk powder. Plant proteins may have caused high WPN values and interfered with the Harland–Ashworth test. It was concluded that WPN is neither an acceptable index of rennet coagulability of milk replacers, nor a reliable index for selecting commercially produced skim milk powders with good rennet coagulability.

Passive integrated transponder (PIT) tags were injected into 22 largemouth bass (Micropterus salmoides) brood fish to determine the retention rate of the tags, the effect on spawning success, and the utility of the tags as a means of individual fish identification. Fish were evaluated 12, 17, and 24 months after implantation. All tags were retained and all tagged fish were recognized. Tag injection and retention had no discernible effect on spawning success.

The history of the development of fluidized solids technology and its industrial application is interesting since it represents a major new basic operation developed in the present generation. It is especially instructive as an R&D example in that development was compressed into a time span of less than four years from initial concept to successful start-up of full-scale catalytic cracking plants in 1942 (Anon, 1962, Larson, 1971). These commercial plants made a crucial contribution to the war effort including aviation gasoline and raw materials for synthetic rubber (Sweeney, 1978). Although development of fluidized solids operations was expedited because of the war, it provides an example of what might be done to alleviate today’s energy crisis by using our resources of innovation and technology.

Foal heat was significantly delayed in 15 Thoroughbred and Quarter-horse mares by 200 mg progesterone in oil from Days 5--14 post partum. Nine of these mares subsequently received daily i.v. injections of 2 mg of a synthetic GnRH preparation (AY-24,031) from Day 2 of the progesterone-delayed oestrus but this treatment did not significantly shorten oestrus or hasten ovulation. Uterine biopsies taken on Day 15 post partum from all the mares showed a mixed endometrial morphology having both oestrous and dioestrous characteristics. There was an increased proliferation of endometrial glands in these animals at the time of ovulation compared to control mares having a normal foal heat.

Blastic transformation of peripheral blood mononuclear cells and serum neutralization antibody levels for equine herpesivurs type 1 were measured in 19 mares from three farms at the time of termination of their pregnancy by normal foaling or viral abortion. The stimulation indexes of lymphocytes obtained from the mares from two farms (Farm 1 and 2) which had virus abortions, ranged from 2.1 to 10.8. But there was no significant difference in stimulation index levels between the aborting and normal foaling mares on these two farms. Equine herpesvirus type 1 was isolated from the mononuclear cells of one mare (No. 5) about two months after she aborted. The stimulation index of lymphocytes from that mare was not significantly different from that of other mares on these farms. Stimulation index of lymphocytes from the mares on one farm (Farm 3) where there was no virus abortion or previous history of virus abortion but were exposed to virus antigen from vaccination, ranged from 1.6 to 2.9. The serum neutralization antibody levels were low in most mares ranging from 1/4 to 1/20 and in three mares these were higher. There was no direct correlation between the levels of serum neutralization antibody and stimulation index of lymphocytes from the mares on these farms.

1. Experimental measurements and computer simulations have been used in attempts to identify an exchanger current (Iex) generated by an electrogenic Na+-Ca2+ exchanger in single cells from bull-frog atrium. 2. Voltage clamp measurements of an inward 'slow tail' current observed upon repolarization after depolarizing clamp pulses that elicit net inward Ca2+ currents (ICa) (see Campbell, Giles & Shibata, 1988c), show that these slow tails have a cationic dependence different from ICa. Slow tails are large and prominent in normal [Na+]o solutions containing either Ca2+ or Sr2+, but they are markedly reduced or absent in Ba2+, Ca2+-free, and Na+-free solutions. 3. Kinetic measurements on the slow tails show that they are not generated by deactivation of ICa, and suggest that they may be due to activation of Iex at negative potentials (-70 to -100 mV). 4. Computer simulations of the influx, buffering, and extrusion of Ca2+ provide further indirect evidence that the slow tails correspond to Iex. In addition, these calculations give insights into one plausible mechanism of Ca2+ homeostasis in frog atrium. When the Na+-Ca2+ exchanger formalism of Mullins (1979, 1981), as modified by DiFrancesco & Nobel (1985), is combined with equations for intracellular Ca2+ buffering by myoplasmic proteins (cf. Robertson, Johnson & Potter, 1981), slow inward tails are produced which are qualitatively similar to those recorded experimentally. 5. Comparisons of the size and time course of ICa with those of Iex suggest that Iex does not generate a physiologically significant current (or membrane potential change) during the plateau of the action potential. However, at potentials near the resting potential the inward current due to Iex may be significant. 6. Our theoretical results suggest that in the intact single atrial cell myoplasmic Ca2+-binding proteins (e.g. calmodulin and troponin) could be physiologically important modulators of the amplitude, polarity and kinetics of Iex. Hence, the specificity, capacity and kinetics of intracellular Ca2+ binding are essential components of any quantitative treatment of Iex in excitable tissue.

Previous studies of stretch reflexes in patients with spastic hypertonia have emphasized the dynamic character of stretch reflex output. In contrast, our own studies of stretch reflex dynamics in spastic elbow flexor muscles of 14 hemiparetic human subjects have shown that stretch-evoked torque displays a relatively weak dependence on stretch velocity, and there is generally no preferential enhancement of dynamic as compared with static reflex output. Moreover, stretch reflex dynamics are broadly similar in voluntarily activated spastic and normal elbow flexor muscles. These findings support our hypothesis that spastic hypertonia results primarily from a decrease in stretch reflex threshold. The strong velocity dependence of stretch-evoked electromyographic activity in initially inactive spastic muscles could be due to a decrease in reflex threshold with increasing stretch velocity, rather than an abnormal velocity-dependent increase in stretch reflex responsiveness.

1. A single-microelectrode technique has been used to study the voltage dependence and the kinetics of inactivation and reactivation of a tetrodotoxin-resistant inward current (ICa) in single cells from bull-frog atrium. 2. In most cases the kinetics of both inactivation and reactivation can be well described as a single-exponential process. 3. Several different observations indicate that inactivation of ICa in these cells is controlled by both voltage-dependent and current-dependent processes, as has been demonstrated previously in heart (Kass & Sanguinetti, 1984; Lee, Marban & Tsien, 1985) and in other tissues (Hagiwara & Byerly, 1981; Tsien, 1983; Eckert & Chad, 1984). 4. Evidence in favour of a voltage-dependent inactivation mechanism included: (a) In paired-pulse measurements of steady-state inactivation ('f infinity') a 'conventional' steady-state f infinity vs. membrane potential (Vm) relationship was obtained in the range of membrane potentials from -60 to 0 mV. (b) Increasing [Ca2+]o from 2.5 to 7.5 mM, which resulted in a 2-3-fold increase in ICa, did not produce any significant increase in the amount of inactivation. (c) Using a 'gapped' double-pulse protocol non-monotonic U-shaped inactivation relationships were obtained, i.e. positive to approximately +20 mV some removal of inactivation occurred. However, f never approached a value near 1.00 at very depolarized potentials; it reached a maximum between 0.5 and 0.6. (d) In constant [Ca2+]o and at fixed Vm, the kinetics of ICa inactivation were independent of peak size of ICa. This was demonstrated by: (i) varying the holding potential (-90 to -30 mV), (ii) using paired-pulse 'recovery' protocols, and (iii) partial block by La3+ (1-10 microM) and Cd2+ (0.1 mM). (e) Influx of Ca2+ ions was not an obligatory prerequisite for development of inactivation. In all ionic conditions (Ca2+, Sr2+, Ba2+, Na+-free and Ca2+-free Ringer solutions) currents displayed inactivation phenomena, although the extent and kinetics of inactivation were dependent upon ionic conditions. Outward currents recorded above the reversal potential for ICa exhibited time- and voltage-dependent inactivation, and could be inactivated by brief depolarizing pre-pulses that produced no net inward current flow. Evidence against a possible role of the electrogenic Na+-Ca2+ exchanger in producing inactivation of these outward currents was obtained.(ABSTRACT TRUNCATED AT 400 WORDS)

1. Voltage clamp studies on single cells from bull-frog atrium have been carried out to study the ion transfer characteristics of the calcium current, ICa. In agreement with the preliminary results of Hume & Giles (1983), a TTX-resistant, 'second transient inward current' was recorded consistently. Its average peak size at 0 mV in 2.5 mM [Ca2+]o Ringer solution was approximately -200 pA, and it was blocked by Cd2+ and La3+ but not by tetrodotoxin (TTX, 3 x 10(-6) M). 2. The peak size of this current increases by approximately 4 times when [Ca2+]o is raised from 1.25 to 7.5 mM, indicating that Ca2+ is a major charge carrier. 3. A well-defined reversal potential, Erev, for ICa can be recorded in normal Ringer solution and also when Ba2+ or Sr2+ serve as the charge carriers. When [Ca2+]o is changed the shifts in Erev follow the predictions of a Nernstian Ca2+ electrode. However, all Erev values are well below those predicted from the thermodynamic Nernstian ECa values (see Campbell, Giles, Hume, Noble & Shibata, 1988a). 4. The Ca2+ current exhibits voltage-dependent inactivation, whether the direction of net current flow is inward or outward; however, the rate of inactivation is affected by the species of cation carrying the current. Inactivation is reduced substantially in Ba2+ Ringer solution. 5. Magnesium (5 mM) is not a significant carrier or blocker of ICa in normal [Ca2+]o Ringer solution; however, 5 mM [Mg2+]o can block the current carried by either Sr2+ or Ba2+. In the absence of Mg2+, equimolar substitutions of Sr2+ or Ba2+ for Ca2+ result in larger currents than those carried by Ca2+ in the normal Ringer solution. 6. Sodium appears not to be a significant charge carrier in the presence of normal [Ca2+]o. However, after free [Ca2+]o has been reduced to extremely low levels (less than 10(-6) M) Na+ can carry a significant fraction of 'ICa'. Thus, it appears that the high selectivity of ICa for Ca2+ ions depends upon the presence of Ca2+. 7. 'Slow tails' are frequently recorded after repolarizing clamp steps back to the holding potential. These 'slow tails' are prominent in normal [Na+]o, [Ca2+]o and [Sr2+]o Ringer solution; however, they are markedly reduced in [Ba2+]o, in Na+-free and Ca2+-free Ringer solutions. Experimental and theoretical work suggests these slow tails may be generated by an electrogenic Na+-Ca2+ exchanger (see Campbell, Giles, Robinson & Shibata, 1988b).(ABSTRACT TRUNCATED AT 400 WORDS)

Six pony foals, free of detectable serum neutralization (SN) antibody against equine herpesvirus type 1 by the standard virus-neutralization (VN) test, were inoculated with equine herpesvirus type 1. The ponies showed typical clinical signs of respiratory tract disease and developed a transient leukopenia, involving lymphocytes as well as neutrophils. The leukopenia reached its lowest point on postinoculation days (PID) 3 to 5 and then returned to base-line values by PID 8 to 10. On quantitation of lymphocyte subpopulations, T and B lymphocytes were decreased during the onset of leukopenia and then recouped during the recovery from leukopenia. However, the proportions of the T and B lymphocytes remained constant during the lymphopenia, ranging from 70% to 80% and 20% to 30%, respectively. The lymphocyte blastogenic response to mitogens increased to peak by PID 2 to 5 and then decreased to base line values or below by PID 7. Mitogen responses of T lymphocyte and mixed lymphocyte preparations were nearly similar. However, the responses of 2 ponies wee somewhat different from the responses of others in that there was an increase in the B lymphocytes in the range of 40% to 50% during the recovery phase of lymphopenia. Also, the 2 ponies' mixed lymphocyte response to mitogens was considerably higher and the T lymphocyte response to mitogen was lower as compared with that of mixed lymphocyte preparation. The importance of these 2 types of responses is discussed.

The Canadian Arctic Archipelago includes all islands north of the Canadian mainland and west of Greenland, extending north from the mainland a distance of 1,400 miles (2,255 km) and having a maximum E.-W. extent of approx. 1,500 miles (2,415 km). The climate is characterized by long cold winters, short cool summers, and very low precipitation. The remote location, the dearth of permanent settlements and service facilities, and the extremely harsh climate pose many problems for those engaged in exploration work and will contribute peculiar difficulties for future exploitation of the area's immense mineral resources. There are unusual problems which have been or will be encountered when operating in the arctic, but techniques have been developed to overcome them. Despite these adverse factors, it appears that the potential rewards of Arctic exploration are commensurate with the risks.