Substance P abolishes the facilitatory effect of ATP on spontaneous glycine release in neurons of the trigeminal nucleus pars caudalis.

Glycine release was facilitated by the activation of presynaptic ATP receptors (P(2X)-type) in a preparation of dissociated trigeminal nucleus pars caudalis neurons in which the native synaptic boutons were preserved. The action of ATP was completely blocked by substance P (SP) without alteration of the miniature IPSC (mIPSC) amplitude distribution. SP itself had no effect on mIPSC frequency or amplitude. The inhibitory effect of SP on ATP action was blocked by CP99994, indicating that the SP receptors are of the neurokinin-1 type. The ATP-induced facilitation of the mIPSC frequency was unaffected by Cd(2+). Moreover, SP did not inhibit the increase in mIPSC frequency induced high K(+) application, suggesting that SP did not modulate voltage-dependent calcium channels or subsequent steps in the release process. KT5720 and phorbol 12-myristate 13-acetate did not block SP action, indicating that neither the cAMP-protein kinase A nor the protein kinase C pathway mediates the SP effects. However, in the presence of N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7), SP was no longer able to inhibit the ATP-induced stimulation of mIPSC frequency. 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-l-tyrosyl]-4-phenylpiperazine also suppressed the SP action, suggesting that SP modulates P(2X) receptors via a Ca(2+)/calmodulin-dependent protein kinase II-mediated pathway. In conventional whole-cell mode, the presence of W-7 in the patch pipette did not affect the SP inhibitory action. Thus, SP is not likely to be generating its modulation through the production of a retrograde signal (involving calmodulin) from the postsynaptic cell to the presynaptic boutons. These results are the first demonstration of the modulation of one presynaptic receptor by another. Because SP inhibits the ATP stimulation of glycine release, SP may play a significant role in hyperalgesia or chronic pain.

Quantitative assessment of a circulating depolarizing factor in shock.

Sustained depolarization of cell membranes and cellular edema are known to accompany various forms of circulatory shock and probably contribute to hypovolemia and cellular dysfunction. It has been proposed that a circulating protein is responsible for these effects. In the present study we have confirmed the existence of a circulating depolarizing factor (CDF) in hemorrhagic shock, burn shock, sepsis, and cardiopulmonary bypass. Plasma samples from pigs or sheep in shock were quantitatively assayed for depolarizing activity using a microelectrode method on rat diaphragm in vitro. The depolarizing effect of CDF in vitro was similar in magnitude to that of shock in situ. We conclude that CDF can entirely account for membrane depolarization during shock. The depolarizing effect of CDF was dose-dependent and saturable; it could be reversed by rinsing the diaphragm with Ringer's or control plasma. CDF activity was detectable in plasma within 5 min after a severe scald and gradually increased over the next 25 min. Resuscitation of hemorrhaged pigs, but not burned sheep, eliminated plasma CDF activity.

Regulatory volume decrease and intracellular Ca2+ in murine neuroblastoma cells studied with fluorescent probes.

The possible role of Ca2+ as a second messenger mediating regulatory volume decrease (RVD) in osmotically swollen cells was investigated in murine neural cell lines (N1E-115 and NG108-15) by means of novel microspectrofluorimetric techniques that allow simultaneous measurement of changes in cell water volume and [Ca2+]i in single cells loaded with fura-2. [Ca2+]i was measured ratiometrically, whereas the volume change was determined at the intracellular isosbestic wavelength (358 nm). Independent volume measurements were done using calcein, a fluorescent probe insensitive to intracellular ions. When challenged with approximately 40% hyposmotic solutions, the cells expanded osmometrically and then underwent RVD. Concomitant with the volume response, there was a transient increase in [Ca2+]i, whose onset preceded RVD. For hyposmotic solutions (up to approximately -40%), [Ca2+]i increased steeply with the reciprocal of the external osmotic pressure and with the cell volume. Chelation of external and internal Ca2+, with EGTA and 1,2-bis-(o -aminophenoxy) ethane-N,N,N ',N '-tetraacetic acid (BAPTA), respectively, attenuated but did not prevent RVD. This Ca2+-independent RVD proceeded even when there was a concomitant decrease in [Ca2+]i below resting levels. Similar results were obtained in cells loaded with calcein. For cells not treated with BAPTA, restoration of external Ca2+ during the relaxation of RVD elicited by Ca2+-free hyposmotic solutions produced an increase in [Ca2+]i without affecting the rate or extent of the responses. RVD and the increase in [Ca2+]i were blocked or attenuated upon the second of two approximately 40% hyposmotic challenges applied at an interval of 30-60 min. The inactivation persisted in Ca2+-free solutions. Hence, our simultaneous measurements of intracellular Ca2+ and volume in single neuroblastoma cells directly demonstrate that an increase in intracellular Ca2+ is not necessary for triggering RVD or its inactivation. The attenuation of RVD after Ca2+ chelation could occur through secondary effects or could indicate that Ca2+ is required for optimal RVD responses.

Presynaptic calcium currents at voltage-clamped excitor and inhibitor nerve terminals of crayfish.

1. A two-electrode voltage clamp was used to record calcium currents from the excitatory and inhibitory nerve terminals that innervate the crayfish (Procambarus spp.) opener muscle. Other voltage-dependent currents were blocked with tetrodotoxin, 3,4-diaminopyridine, 4-aminopyridine and tetraethylammonium. 2. The presynaptic calcium current at both excitatory and inhibitory synapses was blocked by cadmium and omega-agatoxin IVA but was not affected by omega-conotoxin GVIA, omega-conotoxin MVIIC or nifedipine, suggesting that the calcium currents flow through P-type calcium channels. 3. Current-voltage (I-V) relations at both excitatory and inhibitory synapses are similar, with current activation near -40 mV, peak current near -10 mV and current reversal at membrane potentials greater than +25 mV. I-V relations were scaled along the current axis by partial calcium current blockade with cobalt, suggesting that series resistance and space-clamp errors were small. 4. A subset of terminals on one muscle fibre was locally superfused with a physiological saline containing barium; the rest of the preparation was superfused with a physiological saline containing calcium channel antagonists. Under such conditions the characteristics of the I-V relation were very similar to the I-V relations recorded when the entire preparation was bathed in physiological levels of calcium, suggesting that the space clamp was adequate. 5. Calcium channel activation, as determined from tail current analyses, was similar when the entire preparation was bathed in physiological levels of calcium or if terminals on one muscle fibre were locally superfused with barium. 6. During a 30 ms depolarization, calcium currents inactivated to a greater extent in inhibitory than in excitatory terminals. The inactivation was of small magnitude (< 20%) and was eliminated by intracellular injection of the calcium chelator BAPTA, suggesting that the inactivation was calcium dependent. 7. These data show that biophysical and pharmacological properties of calcium currents at crayfish neuromuscular junctions resemble those found at stellate synapses in squid.

Calcium currents, transmitter release and facilitation of release at voltage-clamped crayfish nerve terminals.

1. The presynaptic terminals at crayfish (Procambarus spp.) opener neuromuscular junctions were voltage clamped. Calcium currents were measured during (ICa) and following (tail ICa) presynaptic depolarizations; EPSPs or IPSPs were simultaneously recorded from the (postsynaptic) muscle fibre directly beneath the presynaptic impalement. 2. For short (< or = 6 ms) presynaptic depolarizations, most of the transmitter release occurred during the tail ICa. EPSP or IPSP amplitudes at the end of the 6 ms pulse (end EPSP or end IPSP) increased monotonically with the integral of the ICa ([symbol: see text]ICa). The suppression potential for transmitter release was near the apparent reversal potential for ICa. 3. When the end EPSP or end IPSP amplitude was plotted against the peak ICa elicited during a presynaptic pulse (peak ICa), large and small depolarizations which evoked the same peak ICa evoked different amounts of transmitter release. The differences in transmitter release were eliminated when end EPSP amplitude was plotted against [symbol: see text] ICa, suggesting that transmitter release during a depolarization depends only upon calcium current and not upon a subsequent voltage-dependent step. 4. The synaptic transfer function of various measurements of EPSP or IPSP amplitude vs. [symbol: see text]ICa evoked during a presynaptic depolarization was a power function having an exponent of about 3. Similar measurements of EPSP amplitude vs. [symbol: see text]tail ICa evoked following a presynaptic depolarization had an exponent of about 2. 5. Facilitation of an EPSP or IPSP was not due to increases in calcium current at the test depolarization. 6. When the conditioning depolarization was increased and the test depolarization remained constant, EPSP amplitude at the test depolarization and facilitation increased . When the conditioning depolarization remained constant and the test depolarization was increased, EPSP amplitude at the test depolarization increased, while facilitation decreased. 7. Our data suggested that transmitter release at crayfish neuromuscular junctions is a non-linear function of calcium influx, and that facilitated release utilizes intracellular calcium differently from non-facilitated release. These data contradict simple models of facilitation which combine the residual calcium hypothesis with the calcium co-operativity hypothesis of non-facilitated release.

Diet, aging, and cancer.

As we consider the epidemiologic evidence on diet-cancer associations, we should keep in mind the geographical differences in cancer incidence that stimulated us to look for a diet-cancer link in the first place. For many cancers, the variation in geographic incidence is in the range of an order of magnitude (see Table 2). Thus, if variation in dietary components are primarily responsible for these huge geographic variations in cancer incidence, then the effect of dietary components will not be subtle. Based on the magnitude of geographic variation, one might be primed to look for large differences in cancer incidence associated with different dietary intakes--relative risks of two or greater. This is not to say that a true relative risk of 1.2 or 0.8 for cancer associated with some dietary habit is not potentially important, but it will not get us very far along the way of explaining the geographic variation. The recommendation of the National Research Council is the consumption of five servings of fruit and vegetables daily. This level of consumption would place one in the "high consumption" group in most of the epidemiological studies showing a strong association between fruit and vegetable intake and cancer. Unfortunately, only 10% of the U.S. population actually consumes the recommended amount. Conversely, 20% to 35% of the U.S. population consume levels of fruits and vegetables that put them in the "low consumption" groups. Although causality cannot be established, the evidence is overwhelming that some constituent(s) of fruits and vegetables is (are) protective; low intake carries a greater than two-fold risk of cancer. The risk of cancer associated with low fruit or vegetable consumption may only be exceeded by that of smoking. In the typical diet in the United States, the main source of antioxidant nutrients vitamin C, carotenoids, and vitamin E comes from fruit and vegetable consumption. Without a complete understanding of the mechanism for the effect of fruits and vegetables or antioxidants, the epidemiologic evidence strongly supports the clinical benefits that can be achieved by promotion of consumption (Table 5).

Presynaptic calcium-activated potassium channels and calcium channels at a crayfish neuromuscular junction.

1. We used a two-microelectrode current clamp to investigate various characteristics of the Ca(2+)-activated K+ conductance [gK(Ca)] and Ca2+ conductance (gCa), and transmitter release in presynaptic terminals of excitatory neuromuscular junctions in the crayfish walking leg. 2. Voltage-activated Na+ conductances (gNa) and K+ conductances [gK(v)] were blocked with tetrodotoxin and 3,4-diaminopyridine, respectively. Under these conditions, presynaptic depolarization produced by a first (conditioning) pulse admitted Ca2+ into the presynaptic terminals and activated gK(Ca), which modulated the amplitude of the depolarization produced by a second (test) pulse. The relative amount of gK(Ca) measured at the test pulse increased with increased magnitude or duration of the conditioning pulse. 3. A brief hyperpolarization immediately after a conditioning pulse substantially reduced gK(Ca). 4. gK(Ca) activation was blocked by funnel web spider toxin (a Ca2+ channel blocker) or by injection of the presynaptic terminal region with a calcium chelator, bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA). Under current-clamp conditions, gK(Ca) was not blocked by charybdotoxin or iberiotoxin [specific gK(Ca) blockers]. 5. When gK(Ca) was blocked or reduced, the amplitude of the depolarizing afterpotential of action potentials was increased. When gK(v) was blocked or reduced, the duration of action potentials was increased. 6. Intracellular injection of BAPTA into the presynaptic terminal region eliminated evoked neurotransmitter release before test pulse modulation was affected, suggesting that the K(Ca) channel had a greater sensitivity (greater affinity or lower stoichiometry) for Ca2+ than did the transmitter release machinery. BAPTA reduced neurotransmitter release by 66-78%, but did not affect facilitation of neurotransmitter release. 7. When gNa, gK(v), and gK(Ca) were blocked, we detected a membrane depolarization produced by an increase in presynaptic gCa that was eliminated by 2 mM Cd2+ or 0 mM Ca2+.

Streaming potentials reveal a short ryanodine-sensitive selectivity filter in cardiac Ca2+ release channel.

Single cardiac sarcoplasmic reticulum Ca2+ release channels were reconstituted into planar bilayer membranes. Streaming potentials were measured in osmotically asymmetric solutions as a shift in the reversal potential. Potential changes induced by water movement through the bilayer (concentration polarization) and reduced ion activity in the concentrated non-electrolyte solutions were determined using valinomycin. In 400 mM symmetrical CsCH3SO3, the average streaming potential was 2.74 +/- 0.2 mV (n = 5, mean +/- SE; 2 osmol/kg) and independent of the osmoticant used (sucrose or diglycine). Identical streaming potential magnitudes were obtained regardless of which side of the membrane the nonelectrolyte was placed. This suggests that the narrow part of the pore where single file diffusion occurs is relatively short (i.e., accommodates a minimum of 3 H2O molecules). This value is comparable to similar measurements in a variety of surface membrane channels. Ryanodine-modified channels had no measurable streaming potential, an increased Tris+ permeability relative to Cs+, and decreased divalent selectivity (PCs/PTris 5.1 +/- 1.1 to 1.7 +/- 0.3, n = 3; PBa/PCs 8.2 +/- 0.7 to 1.8 +/- 0.5, n = 4). Cation/anion selectivity was essentially unaltered in ryanodine-modified channels. These results suggests that the narrow region of the permeation pathway (i.e., the selectivity filter) is relatively short and widens after ryanodine modification.

Contrasting actions of cocaine, local anaesthetic and tetrodotoxin on discharge properties of rat aortic baroreceptors.

1. Effects of cocaine, lignocaine, benzocaine and tetrodotoxin (TTX) on the simultaneously measured pressure- and diameter-discharge frequency relations of single fibre baroreceptors were compared in rat in vitro aortic arch-aortic nerve preparations. 2. Between 1 and 10 microM, cocaine produced selective increases in the pressure threshold shifting the pressure-response curve without altering the gain or threshold frequency. At near-blocking concentrations, gain was depressed as well. Cocaine experiments were done in nitroprusside (NP, 1 microM). Neither NP or NP with cocaine altered diameter (P > 0.36). 3. Lignocaine (at > 10 microM) and benzocaine (at > 100 microM) shifted pressure-response curves to higher pressures and generally depressed discharge by increasing pressure threshold and decreasing maximum discharge frequency (P < 0.05). Gain decreased and threshold frequency increased at higher concentrations. Diameter was unaffected by lignocaine or benzocaine (P > 0.14). 4. TTX increased thresholds and discharge frequencies at threshold but did not shift pressure-discharge curve locations. This produced superimposable discharge curves with changes occurring as losses of discharge points in the threshold region. Diameter was unaffected by TTX (P > 0.80). 5. The contrasting patterns of effects between TTX and local anaesthetics suggest that blockade of TTX-sensitive sodium channels alone may not be responsible for the effects of cocaine, lignocaine and benzocaine.

Residual free calcium is not responsible for facilitation of neurotransmitter release.

An increase in internal free calcium ([Ca2+]i) in the presynaptic terminal is often assumed to directly produce facilitation of neurotransmitter release. Using a Ca(2+)-activated potassium conductance as a bioassay for free [Ca2+]i in the presynaptic terminal of the crayfish (Procambarus clarkii) opener neuromuscular junction, we now demonstrate that free [Ca2+]i has a decay time constant (tau) of 1-4 msec, whereas facilitation of neurotransmitter release has a decay tau of 7-43 msec. In addition, facilitation of neurotransmitter release can be markedly different at times when free [Ca2+]i values and presynaptic membrane voltages are equal. We conclude that free [Ca2+]i in the presynaptic terminal is not directly responsible for facilitation of neurotransmitter release. Our data suggest that facilitation results from bound Ca2+ or some long-lived consequence of bound Ca2+.

A community-based epidemiologic study of health sequelae of exposure to hydrofluoric acid.

An accident at an oil refinery in Texas City, Texas, released around 40,000 lb of hydrogen fluoride, exposing the community to the highly toxic and corrosive substance. A population-based epidemiologic study was conducted to evaluate the impact of the accident on the health of the community. Exposure assessment was done using a multipronged approach through a door-to-door survey of 10,811 individuals. A symptom survey resulting in 1994 completed interviews was conducted with a stratified random sample selected from the exposure study database. The sampling was balanced with respect to age, gender, and predisposition across the three ordinal exposure categories. The results show a strong dose relationship (P < 10(-4)) between the exposure and symptoms reported following the accident and 2 years later, most notably breathing and eye symptoms. However, substantial improvement in health was reported over the 2-year period regardless of the level of exposure. Problems of recall bias and behavioral sensitization are considered and it is recognized that the study may have overestimated the effect. It is also recognized that the study may not have completely unraveled the relative importance of exposure and host response in health outcome, since the two were probably conflated in the exposure measure. Nevertheless, the independence of predisposition and reported level of exposure, the magnitude of effect and its consistency, the unmistakable dose response, the large sample size, and the mutual corroboration of various findings make it difficult to dismiss the interpretation that the hydrofluoric acid exposure indeed caused health problems in the community that continued for at least 2 years after the accident.

Effects of osmotic stress on mast cell vesicles of the beige mouse.

The large size of the vesicles of beige mouse peritoneal mast cells (4 microns in diameter) facilitated the direct observation of the individual osmotic behavior of vesicles. The vesicle diameter increased as much as 73% when intact cells were perfused with a 10 mM pH buffer solution; the swelling of the vesicle membranes exceeded that of the insoluble vesicle gel matrix, which resulted in the formation of a clear space between the optically dense gel matrix and the vesicle membrane. Hypertonic solutions shrank intact vesicles of lysed cells in a nonideal manner, suggesting a limit to the compressibility of the gel matrix. The nonideality at high osmotic strengths can be adequately explained as the consequence of an excluded volume and/or a three-dimensional gel-matrix spring. The observed osmotic activity of the vesicles implies that the great majority of the histamine known to be present is reversibly bound to the gel matrix. This binding allows vesicles to store a large quantity of transmitter without doing osmotic work. The large size of the vesicles also facilitated the measurement of the kinetics of release as a collection of individual fusion events. Capacitance measurements in beige mast cells revealed little difference in the kinetics of release in hypotonic, isotonic, and hypertonic solutions, thus eliminating certain classes of models based on the osmotic theory of exocytosis for mast cells.

Presynaptic facilitation at the crayfish neuromuscular junction. Role of calcium-activated potassium conductance.

Membrane potential was recorded intracellularly near presynaptic terminals of the excitor axon of the crayfish opener neuromuscular junction (NMJ), while transmitter release was recorded postsynaptically. This study focused on the effects of a presynaptic calcium-activated potassium conductance, gK(Ca), on the transmitter release evoked by single and paired depolarizing current pulses. Blocking gK(Ca) by adding tetraethylammonium ion (TEA; 5-20 mM) to a solution containing tetrodotoxin and aminopyridines caused the relation between presynaptic potential and transmitter release to steepen and shift to less depolarized potentials. When two depolarizing current pulses were applied at 20-ms intervals with gK(Ca) not blocked, the presynaptic voltage change to the second (test) pulse was inversely related to the amplitude of the first (conditioning) pulse. This effect of the conditioning prepulse on the response to the test pulse was eliminated by 20 mM TEA and by solutions containing 0 mM Ca2+/1 mM EGTA, suggesting that the reduction in the amplitude of the test pulse was due to activation of gK(Ca) by calcium remaining from the conditioning pulse. In the absence of TEA, facilitation of transmitter release evoked by a test pulse increased as the conditioning pulse grew from -40 to -20 mV, but then decreased with further increase in the conditioning depolarization. A similar nonmonotonic relationship between facilitation and the amplitude of the conditioning depolarization was reported in previous studies using extracellular recording, and interpreted as supporting an additional voltage-dependent step in the activation of transmitter release. We suggest that this result was due instead to activation of a gK(Ca) by the conditioning depolarization, since facilitation of transmitter release increased monotonically with the amplitude of the conditioning depolarization, and the early time course of the decay of facilitation was prolonged when gK(Ca) was blocked. The different time courses for decay of the presynaptic potential (20 ms) and facilitation (greater than 50 ms) suggest either that residual free calcium does not account for facilitation at the crayfish NMJ or that the transmitter release mechanism has a markedly higher affinity or stoichiometry for internal free calcium than does gK(Ca). Finally, our data suggest that the calcium channels responsible for transmitter release at the crayfish NMJ are not of the L, N, or T type.

Calcium-activated potassium conductance in presynaptic terminals at the crayfish neuromuscular junction.

Membrane potential changes that typically evoke transmitter release were studied by recording intracellularly from the excitor axon near presynaptic terminals of the crayfish opener neuromuscular junction. Depolarization of the presynaptic terminal with intracellular current pulses activated a conductance that caused a decrease in depolarization during the constant current pulse. This conductance was identified as a calcium-activated potassium conductance, gK(Ca), by its disappearance in a zero-calcium/EGTA medium and its block by cadmium, barium, tetraethylammonium ions, and charybdotoxin. In addition to gK(Ca), a delayed rectifier potassium conductance (gK) is present in or near the presynaptic terminal. Both these potassium conductances are involved in the repolarization of the membrane during a presynaptic action potential.

Ionic control of the size of the vesicle matrix of beige mouse mast cells.

Isolated matrices of the giant secretory vesicles of mast cells of the beige mouse were reliably produced by the osmotic lysis of isolated vesicles. These matrices maintained their form, and their sizes were easily measured using Nomarski optics. The size of the matrix depended on the ionic composition of the bathing solution. The physiologically relevant ions, histamine and serotonin, contracted the matrix. Multivalent cations condensed the matrix relative to univalents. Ag+, acid pH (below 5), and basic pH (above 9) expanded the matrix. In the presence of 10 mM histamine, lowering the pH from 9 to 5 contracted the matrix more than can be attributed to the pH-dependent matrix contraction in zero histamine. The nontitratable organic cation, dimethonium, contracts the matrix with little effect of pH in the range of 5-9. These results suggest that histamine acts as a matrix contractor in the divalent form. The dose-response (contraction) relation for histamine was gradual from micromolar to 316 mM (millimolar) histamine. Experiments with mixtures of histamine and sodium show antagonistic effects on the matrix but are inconsistent with either a model where ions compete for identical sites or a parallel model where ions interact with separate independent sites. In vigorous histamine washoff experiments, the half time for vesicle expansion in 10(-4) M pH buffer was approximately 4 s; in isotonic NaCl solution, it was 0.5 s. When 1 M histamine was presented to closely apposed matrices, fusion resulted. The matrix material returned to its initial shape after being mechanically deformed with a glass probe. These results suggest that the matrix size is controlled by its ion exchange properties. The matrix expansion can quantitatively account for the vesicular size increase observed upon exocytosis (as a postfusional event) and the osmotic nonideality of intact vesicles. The mechanical expansion is probably significant in the widening of the exocytotic pore and the dispersal of the vesicular contents.

On the time course of surgically induced compensatory muscle hypertrophication of the rat plantaris muscle.

1. The time course of the hypertrophy and hyperplasia of the rat plantaris muscle was determined from measurements of total muscle mass and cross-section analysis of fixed muscle. 2. Muscle enlargement was induced by the surgical removal of the plantaris synergist muscles, the gastrocnemius and the soleus. 3. From the date of surgery through the third post-operative week, muscle enlargement is due to fiber hypertrophication (approximately 100% increase in diameter). After post-operative week three, muscle enlargement is due to a combination of hyperplasia and hypertrophy. At week four the cross-sectional areas return to control values. 4. The neuromuscular junction area was determined by measuring Karnovsky stained post-synaptic membrane. Only a modest 10-30% increase was noted at weeks 2 and 3 with a return to control levels at week 4. The differences were not statistically different.

Scaling of response scale adverbs among black-American adults.

Although some attention has been given to the scale characteristics of modifying adverbs in Likert scales, the existing work has been concerned primarily with majority group members. Toward the goal of identifying valid labels for use on Likert scales with black-American respondents, 105 black-American adults scaled each of 27 adverbs (e.g., very, most) on four different adjectives (e.g., important). Four criteria for a set of ideal adverbs were identified for univalent scales. No set of four adverbs, however, met the criteria. Differences in the mean ratings of eight of the adverbs were found by sex group and across the four adjectives modified. The adverbs were not scored at the extremes of the continuum, despite our asking the respondents to rate the adverbs used to define the end points of the continuum. High variances were found across all adverbs. Further research must address the respondents' perceptual frame in the use of such scales.

Assessing the functional status of older patients with chronic illness.

The purpose of this study was to investigate the value of using a validated functional assessment instrument, the Sickness Impact Profile (SIP), with older, chronically ill patients seeking care at the family physician's office. The SIP was completed by the patient and the family physician on patients 55 years of age or older who were seen at a family practice residency clinic. The study used stratified, random assignment in an experimental design to compare physician and patient reaction to the SIP. Both physicians (residents and faculty) and patients felt the SIP was useful in detecting disabilities. Approximately half of the physicians felt the SIP was helpful in patient management. Patients reported twice as many disabilities as were reported by physicians. Half of the clinic physicians had the opportunity to review a patient's SIP immediately prior to a visit. They recognized more disabilities and agreed more often with the patients about the presence of a disability. The physicians felt the SIP was too lengthy to assimilate easily into the clinic setting. Use of a functional assessment instrument is advocated because of its ability to increase both physician awareness and physician-patient communication regarding the presence of a functional deficit.

The interaction of intracellular Mg2+ and pH on Cl- fluxes associated with intracellular pH regulation in barnacle muscle fibers.

The intracellular dialysis technique was used to measure unidirectional Cl- fluxes and net acid extrusion by single muscle fibers from the giant barnacle. Decreasing pHi below normal levels of 7.35 stimulated both Cl- efflux and influx. These increases of Cl- fluxes were blocked by disulfonic acid stilbene derivatives such as SITS and DIDS. The SITS-sensitive Cl- efflux was sharply dependent upon pHi, increasing approximately 20-fold as pHi was decreased from 7.35 to 6.7. Under conditions of normal intracellular Mg2+ concentration, the apparent pKa for the activation of Cl- efflux was 7.0. We found that raising [Mg2+]i, but not [Mg2+]o, had a pronounced inhibitory effect on both SITS-sensitive unidirectional Cl- fluxes as well as on SITS-sensitive net acid extrusion. Increasing [Mg2+]i shifted the apparent pKa of Cl- efflux to a more acid value without affecting the maximal flux that could be attained. This relation between pHi and [Mg2+]i on SITS-sensitive Cl- efflux is consistent with a competition between H ions and Mg ions. We conclude that the SITS-inhibitable Cl- fluxes are mediated by the pHi-regulatory transport mechanism and that changes of intracellular Mg2+ levels can modify the activity of the pHi regulator/anion transporter.