Biomedical subjects

L A Maginniss

Publications and source records attributed to L A Maginniss.

16 recordsLinked to original sources

PubMed2001

Effects of environmental dilution on body fluid regulation in the yellow stingray, Urolophus jamaicensis.

Adult yellow stingrays (Urolophus jamaicensis), collected off the southeast Florida coast, were maintained in filtered and re-circulated synthetic sea water (33 per thousand) for 5-13 days at 30 degrees C. Animals exposed to 82%, 74% and 66% SW in gradual steps exhibited rapid and significant weight gains followed by recovery to pre-dilution levels in 2-6 days. Acclimated animals at each salinity [100% (N=12), 82% (7), 74% (4) and 66% SW (3)] were anesthetized (MS222) and bled from the caudal vein. In 100% SW, stingray plasma was slightly hypo-osmotic to the external medium. Plasma osmolality decreased with stepwise dilutions, but became increasingly hyperosmotic to the bathing media. Plasma [Na] and [Cl] each decreased by approximately 13%, 23% and 16%, respectively, in 82%, 74% and 66% SW. Plasma [urea] decreased by 21%, 25% and 59%, respectively. Changes in plasma [K] and [Ca] were minor. Mean corpuscular [Hb] measurements suggest that stingray red cells swelled less at each dilution than predicted for a passive erythrocyte osmometer. RBC [K] decreased by 12%, 36% and 29%, respectively, in 82%, 74% and 66% SW. Quantitatively, the other measured electrolytes (Cl, Na and Ca) changed by lesser amounts. Results suggest that for mild and moderate dilutions (82% and 74% SW), yellow stingrays release both ions and urea from intracellular and extracellular compartments. With further dilution (66% SW), the elasmobranchs retain electrolytes at the expense of urea.

Animals↗

PubMed1999

In vivo blood oxygen binding in hypoxic lesser spear-nosed bats: relationship to control of breathing.

The hypoxic ventilatory threshold of many mammals correlates with their hemoglobin-oxygen affinity (P50). Yet, in some small mammals ventilation actually declines, rather than increases, with exposure to decreasing PaO2; their air convection requirement (V(E)/V(O2)), however, is elevated in hypoxia. We propose that the threshold of the hypoxic V(E)/V(O2) of small mammals coincides with the inflection ('knee') of their in vivo O2 equilibrium curve (O2EC). In vivo blood gas and pH data were obtained from normoxic and hypoxic lesser-spear nosed bats, Phyllostomus discolor; in vitro blood O2EC were also generated for normoxic bats at 32 and 37 degrees C and at three P(CO2)'s. The hypoxic V(E)/V(O2) threshold of P. discolor occurs at PaO2 = 39 Torr; the corresponding in vivo O2 saturation is 0.70, approximating the inflection of the O2EC. This animal has a high blood O2 affinity (P50 = 27.5 Torr at pH 7.40 and 37 degrees C; P50 = 30.8 Torr at in vivo pH of 7.31 and TB of 37.4 degrees C). As PaO2 is reduced, a pronounced hypoxia-induced respiratory alkalosis and hypothermia help maintain SaO2 near the O2EC inflection (0.64-0.70 S(O2)).

Acid-Base Equilibrium↗

PubMed1997

Transit time heterogeneity in canine small intestine: significance for oxygen transport.

We previously found that local O2 extraction efficacy in isolated pump-perfused intestine was enhanced when systemic reflex vasoconstriction was stimulated by hypovolemia (Samsel, R.W., and P.T. Schumacker. 1994. J. Appl. Physiol. 77: 2291-2298). The microvascular mechanism underlying this beneficial effect could involve a redistribution of flow between mucosa and serosa, or an adjustment in the heterogeneity of perfusion within those regions. We measured regional blood flows and distributions of flow and capillary erythrocyte transit times in two segments of small intestine in anesthetized dogs (n = 10). Each vascularly isolated segment of intestine was pump-perfused under high flow (O2 supply-independent VO2) and low flow (O2 supply-dependent) conditions. During the first gut segment, the animal was kept normovolemic using i.v. fluids to minimize reflex vasoconstriction. During the second, the animal was hemorrhaged to augment vasoconstriction (n = 7), or kept normovolemic to control for the effects of time (n = 3). Blood flow distributions were measured using 15 microm radiolabeled microspheres. Tissue blood volume was measured using 99mTc-labeled red blood cells. Capillary volume was determined as the product of tissue blood volume and the histologically derived fraction of vascular volume in the capillaries. Transit times were calculated as the ratio of capillary volume to flow. Each gut segment was fixed and sectioned into 350 approximately 100 mg tissue pieces for analysis. Data revealed significant spatial heterogeneity of blood flow and capillary transit times in both mucosa and muscularis, with relative dispersions (SD/Mean) ranging from 23 to 97%. Hypovolemia caused an increase in flow heterogeneity in muscularis at both high and low flow states, and in mucosa under high flow conditions. However, hypovolemia also elicited changes in capillary volume, such that transit time heterogeneity remained unchanged. Augmentation of vasoconstrictor tone caused a redistribution of flow toward mucosa (P < 0.003) under high and low flow conditions. This redistribution correlated with the improvements in O2 extraction ratio (P = 0.022). Thus, the improvement in gut O2 extraction efficacy seen with increased vasoconstriction may be explained mostly by an intramural redistribution of flow between mucosa and muscularis. Capillary transit time heterogeneity remained unchanged, suggesting that this variable is tightly regulated.

Animals↗

PubMed1995

Hemoglobin function in a skin-breathing aquatic salamander, Desmognathus quadramaculatus.

Adult black-bellied salamanders (Desmognathus quadramaculatus) were maintained in humidified gas at 12 degrees C. Hypoxic salamanders were exposed to 8.1-9.6% O2 for 10-11 days; normoxic animals were maintained in air (20.9% O2). Hypoxia acclimation had no effect on blood O2 affinity, O2 equilibrium curve shape or CO2 Bohr effect. At pH 7.7, P50 values for hypoxic and normoxic salamanders were 28.2 +/- 0.4 and 28.6 +/- 0.8 Torr, respectively. Hill plots were curvilinear for both treatments; Hill's n increased from values of 2.1-2.2 below 40% saturation (S) to 2.6 above 50% S. CO2 Bohr slopes (delta log P50/delta pH) were -0.19 +/- 0.01 and -0.23 +/- 0.02 for hypoxic and normoxic animals, respectively. Resting MO2 for a separate group of normoxic salamanders fell into two categories; low MO2 (1.46 +/- 0.16 mumol.g-1.h-1) and high MO2 (3.51 +/- 0.52) animals. Exposures to 5 and 25% CO had no effect on MO2 of low metabolism Desmognathus, but reduced MO2 of high metabolism animals to levels similar to the low MO2 group. Hb-O2 binding results suggest that D. quadramaculatus blood is ideally suited for respiratory O2 exchange during normoxic activity. While submerged and inactive, hypoxic boundary layers surround the skin-breather. Contributions of Hb during hypoxic inactivity may be to augment O2 content and increase blood buffering capacity.

Animals↗

PubMed1994

Effects of hibernation on blood oxygen transport in the golden-mantled ground squirrel.

Isocapnic O2 equilibrium curves (O2EC) were generated for winter hibernating and summer active ground squirrels (Spermophilus lateralis) at 7 degrees and 37 degrees C using thin blood film techniques. Half-saturation PO2 at 7 degrees C and pHa 7.46 were 5.8 +/- 0.1 and 6.9 +/- 0.2 Torr for hibernating and summer squirrels, respectively; P50 values at 37 degrees C and pHa 7.49 were 15.3 +/- 0.1 and 18.1 +/- 0.5 Torr, respectively. This increased blood O2 affinity in the winter animal results, in part, from reductions of RBC organic phosphates. The molar ratio ([ATP] + [DPG])/[Hb4] decreased from 1.55 in summer squirrels to 0.91 in winter hibernators. O2EC shape and CO2 Bohr effect were similar for the two animal groups, but varied with blood temperature. At 7 degrees C, Hill plots were nonlinear; Hill's n increased from values of 2.2-2.4 below 40% S to 2.7-2.9 above 60% S. At 37 degrees C, Hill plots were reasonably linear (n = 2.5). CO2 Bohr slopes (delta log P50/delta pH) for hibernating and euthermic squirrels were -0.37 +/- 0.02 and -0.40 +/- 0.03 at 7 degrees C, respectively, and -0.62 +/- 0.04 and -0.60 +/- 0.02 at 37 degrees C, respectively. Blood O2 capacity was significantly greater (P < 0.001) in the hibernator; hematocrit (55%) and [Hb] (19.1 g/dl) exceeded the summer squirrel values by 20% and 25%, respectively. Estimated PvO2 values for summer and winter animals at 7 degrees C and pH 7.46 were 7.25 and 6.94 Torr, respectively. This suggests that the effect of increased Hb-O2 affinity on PvO2 is offset by increased circulating [Hb]. We conclude that seasonal changes in the O2 transport properties of squirrel blood do not contribute to the depression of aerobic metabolism during winter hibernation.

Animals↗

PubMed1994

Adrenergic vasoconstriction augments tissue O2 extraction during reductions in O2 delivery.

When systemic O2 delivery is reduced, increases in systemic O2 extraction are facilitated by sympathetically mediated increases in vascular resistance that limit blood flow to regions with low metabolic demand. Local metabolic vasodilation competes with this vasoconstriction, thereby effecting a balance between tissue O2 supply and demand. This study examined the role of sympathetically mediated vasoconstriction on the critical level of O2 extraction in hindlimb and whole body during progressive reductions in O2 delivery. In anesthetized dogs, the left hindlimb was vascularly isolated and its O2 delivery was decreased in stages by reducing the speed of an occlusive pump. In a normovolemic group (n = 6), blood volume was maintained to minimize sympathetic tone while flow to the hindlimb was reduced. In a hypovolemic group (n = 6), blood volume was removed in stages to augment sympathetic tone progressively while flow to the limb was reduced simultaneously. A phenoxybenzamine group (n = 6) was identical to the hypovolemic group, except that alpha-adrenergic effects were inhibited with phenoxybenzamine (3 mg/kg). The systemic critical O2 extraction ratio in the phenoxybenzamine group (0.60 +/- 0.06) was less than for the hypovolemic group (0.71 +/- 0.04; P = 0.004). In the hindlimb, critical O2 extractions were significantly less in the normovolemic (0.46 +/- 0.17) and phenoxybenzamine (0.49 +/- 0.10) groups compared with the hypovolemic group (0.72 +/- 0.10; P < or = 0.008).(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗

PubMed1989

Blood oxygen binding properties for the burrowing owl, Athene cunicularia.

Isocapnic O2 equilibrium curves (O2ECs) were generated for whole blood of 4 adult burrowing owls (Athene cunicularia) using thin film techniques. At in vivo pHa (7.49 +/- 0.02; mean +/- 1 SEM) and 41 degrees C, the PO2 at half saturation (P50) was 42.3 +/- 0.8 Torr. CO2 and fixed acid (H+) Bohr slopes (delta log P50/delta pH) were -0.46 +/- 0.01 and -0.42 +/- 0.02, respectively, demonstrating a small specific CO2 effect. CO2 and H+ Bohr slopes were saturation-independent between 0.1 and 0.9 S. Hill plots for Athene blood were non-linear; the Hill coefficient (n) increased from 2.6 below 0.4 S to 3.4 above 0.6 S. Owl equilibrium data were accurately described by the equation: S = [(7.7 x 10(6]/(P4 + 44P3 - 108P2 + 3.5 x 10(4)P) + 1]-1. This complex O2EC shape may result from Hb heterogeneity; isoelectric focusing showed 4 isoHbs with a molar ratio of 9:1:1:1. This study revealed no apparent adaptations of Athene blood for hypoxic and hypercapnic conditions. We conclude that the observed blood O2 binding properties promote tissue O2 delivery during periods of surface activity. While occupying its burrow, the owl compensates for moderate alterations in inspired gas composition partly through increased ventilation.

Acid-Base Equilibrium↗

PubMed1987

Acid-base status and electrolytes in red blood cells and plasma of turtles submerged at 3 degrees C.

Two groups of adult Chrysemys picta bellii were studied; control turtles were maintained at 24 degrees C with free access to air, and diving animals were continuously submerged for 8.5-9.5 wk in aerated water at 3 degrees C. Cold submergence elicited a substantial lactic acidosis (blood pH 7.70; plasma [lactate-] 42.5 meq/l H2O). This acid load was largely balanced by changes in plasma strong ions; [Cl-] decreased, and [Ca2+] and [Mg2+] increased. Phosphorus nuclear magnetic resonance showed a significant reduction in the transerythrocyte pH gradient of diving animals (control, delta pH 0.66-0.90; diving, 0.00-0.11). This relative alkalosis of submerged turtle red cells was related to changes in blood cell (RBC) volume and composition; mean corpuscular concentration of hemoglobin [( Hb]) and RBC H2O content measurements revealed a 39% increase in RBC volume. Cell volume change was effected by a proportionally greater influx of K+ than Cl-, providing ionic compensation for the lactic acidosis. The obligatory H2O influx, which decreased the effective concentration of protein anion, and a 77% reduction of RBC [ATP] further contributed to the relative alkalosis. The combined effects of RBC alkalization and reduced [ATP] account for the observed Hb-O2 binding properties previously reported for submerged turtles at 3 degrees C (15).

Acid-Base Equilibrium↗

PubMed1987

Biological effects of short-term, high-concentration exposure to methyl isocyanate. IV. Influence on the oxygen-binding properties of guinea pig blood.

Whole blood oxygen equilibrium curves (O2 ECs), blood buffer lines, and several hematologic properties were determined for adult guinea pigs exposed to 700 ppm methyl isocyanate (MIC) for 15 min. MIC inhalation effected a significant reduction of blood O2 affinity; the half-saturation pressure (P50) at 38 degrees C increased from the control (untreated) level of 22.8 +/- 0.1 mm Hg to values ranging from 28.5 to 43.7 mm Hg for experimental animals. MIC exposure had no apparent influence on O2 EC shape or CO2 Bohr effect. Erythrocyte volume, [metHb], O2 binding capacity, and combined red cell organic phosphate concentration (DPG + ATP) were not affected by MIC treatment. However, experimental animals experienced a severe metabolic acid-base disturbance; blood lactate concentration ranged from 8.6 to 24.0 mmole/L. Results indicate that lactic acidosis was solely responsible for increased blood P50 of MIC-treated animals. No direct effects of MIC on hemoglobin function were observed. Reduced Hb-O2 affinity, in conjunction with severe hypoxemia, compromised the guinea pigs' capacity for pulmonary O2 loading; at PaO2 of 30 mm Hg, Hb-O2 saturation (S) decreased from 66% S for controls to 42% S for MIC-treated animals.

Acidosis↗

PubMed1986

Intrapulmonary and extrapulmonary shunt in ducks.

We measured shunt in seven anesthetized, mechanically ventilated Pekin ducks by the multiple inert gas elimination technique (MIGET) and by the oxygen method during 100% O2 breathing (O2 shunt). MIGET shunt measures only intrapulmonary shunt but O2 shunt measures intra- and extrapulmonary shunt (e.g. bronchial drainage). O2 shunt was calculated from oxygen contents of blood estimated from measured PO2 and standard O2 equilibrium curves at appropriate pH and hematocrit measured in 4 other ducks. In normal lungs MIGET shunt was 1.3 +/- 0.4 (mean +/- SEM) percent of cardiac output and O2 shunt was 6.3 +/- 1.3%. O2 shunt exceeded MIGET shunt by 5.4 +/- 1.4% which we attribute to extrapulmonary shunts. These include part of the bronchial circulation, thebesian veins and vertebral venous-pulmonary circulation connections. Both MIGET and O2 shunts increased when water was introduced into lungs. Overall, the relationship between % MIGET shunt and % O2 shunt was described by the equation: O2 shunt = 0.86 X MIGET + 5.67 (r = 0.96, n = 24).

Animals↗

PubMed1986

Oxygen equilibrium curve shape and allohemoglobin interaction in sheep whole blood.

Adult sheep (Ovis aries) exhibit hemoglobin heterogeneity controlled by two autosomal alleles with codominant expression (Hb AA, AB, BB). Isoelectric points for Hb A and Hb B were 6.94 and 7.15, respectively; for Hb AB animals, the two allohemoglobins were present in equimolar concentrations (Hb A = 52%, Hb B = 48%). Dynamic O2 equilibrium curves (O2ECs) were generated for sheep whole blood at 39 degrees C using thin-film techniques. Half-saturation PO2 values (P50) at pH 7.50 were 31.3, 35.7, and 40.7 Torr for Hb AA, AB, and BB, respectively. CO2 Bohr coefficients at saturation (S) = 0.5 (delta log P50/delta pH) were similar for all phenotypes, ranging from -0.38 to -0.40. The Bohr slopes were also saturation independent between 0.2 and 0.8 S. Standard O2ECs for each phenotype were accurately fitted to three-constant third-order polynomial expressions. Sheep equilibrium curves were not isomorphic with other mammalian O2ECs (e.g., human and dog); sheep curves exhibited greater sigmoidicity. Furthermore, allohemoglobin interaction was not detected in heterozygous sheep. The blood O2 binding characteristics (P50, curve shape, and delta log PO2/delta pH) for Hb AB sheep and an experimental blood mixture containing equal proportions of Hb AA and Hb BB erythrocytes were equivalent.

Alleles↗

PubMed1985

Red cell organic phosphates and Bohr effects in house sparrow blood.

CO2 and fixed acid Bohr effects (d log PO2/d pH) were determined for fresh whole blood of adult house sparrow (Passer domesticus) at 35, 41 and 45 degrees C. At each temperature, the effects of titrating blood with CO2 at constant base excess (CO2 Bohr effect) were similar at P50 (35 degrees, -0.48; 41 degrees, -0.49; 45 degrees, -0.49). The CO2 Bohr slopes were also reasonably saturation independent between 10 and 90% S. Fixed acid Bohr values, determined by titrating sparrow blood with HCl and NaHCO3 at 4% CO2, were significantly less than the corresponding CO2 coefficients at half saturation (35 degrees, -0.43; 41 degrees, -0.39; 45 degrees, -0.41). The difference between CO2 and H+ Bohr effects, assumed here to represent carbamino CO2 binding to hemoglobin, decreased in magnitude with increasing saturation at each temperature. Inositol pentaphosphate (IPP, 3.1 mumol/ml RBC) and ATP (7.7 mumol/ml RBC) were the major organic phosphates present in Passer erythrocytes. CO2 and organic phosphates are known to complete for common binding sites on the Hb molecule. Because of IPP's strong binding affinity and high concentration in most avian red cells, carbamate formation is generally suppressed in bird blood. The presence of a small but significant specific CO2 effect in Passer blood may indicate that one or both sparrow isohemoglobins has reduced affinity for IPP and/or ATP, permitting CO2 to compete more effectively in Hb-carbamate formation.

Adenosine Triphosphate↗

PubMed1983

Effect of chronic cold and submergence on blood oxygen transport in the turtle, Chrysemys picta.

Whole blood oxygen equilibrium curves (O2EC's) and related hematologic properties are reported for the turtle Chrysemys picta exposed to two experimental conditions. Summer turtles were maintained at 24 degrees C with free access to air; winter turtles were submerged for 4-12 wk in N2-bubbled water at 3 degrees C. Half-saturation Po2's at 3 degrees C for blood from summer and winter animals were 4.1 and 4.5 Torr, respectively. At 24 degrees C, summer and winter P50's were 20.2 and 22.7 Torr, respectively. The winter turtle P50 values were lower than predicted since prolonged submergence effected a severe metabolic acidosis; blood pH's for winter turtles were 0.65 pH unit lower than for summer animals at both temperatures. Cold submergence also had a profound influence on O2EC shape. Winter turtle curves exhibited high O2 affinity below P50 while they were distinctly right-shifted above 50% S. Winter animals also exhibited reduced CO2-Bohr coefficients (delta log Po2/delta pH) at 3 and 24 degrees C. Prolonged submergence did not affect the animal's isohemoglobin profile (demonstrated by isoelectric focusing) or [metHb]. The [ATP] and [DPG] in winter turtle red cells, however, decreased significantly; the ratio of organic phosphate ([ATP] + [DPG]) to Hb tetramer fell from 1.4 in summer animals to 0.5 in winter turtles. These findings suggest that the effect of chronic cold and prolonged submergence on turtle O2EC position and shape may result from reduction in RBC organic phosphates. Furthermore, these observed changes in blood oxygen transport may facilitate O2 loading during winter submergence via extrapulmonary gas exchange.

Acid-Base Equilibrium↗

PubMed1980

Oxygen equilibria of ectotherm blood containing multiple hemoglobins.

Complete isocapnic O2 equilibrium curves (O2EC's) and related blood-gas properties are reported for whole blood of the bullfrog (Rana catesbeiana) and the aquatic turtle (Pseudemys scripta) at temperatures ranging from 5 to 35 degrees C. P50's for bullfrog and turtle blood at physiological pH and 25 degrees C were 36.6 Torr (pH 7.83) and 19.3 Torr (pH 7.55), respectively. Elevation of blood temperature significantly reduced hemoglobin oxygen affinity in both species (delta H = -8.1 and -7.8 kcal/mol O2 for Rana and Pseudemys, respectively). Bullfrog and turtle oxygen equilibrium data revealed non-standard curve shapes when compared with the Severinghaus curve for human blood (1979); ectotherm O2EC's rose more steeply below P50 (less sigmoid) and were distinctly flattened (linear) above 50% saturation. The CO2-Bohr effect for bullfrog and turtle blood varied significantly as a function of saturation. In addition, both species exhibited non-linear Hill relationships (logS/1-s vs. log PO2). These results indicate that the oxygen binding properties of the multiple hemoglobin bloods of Rana and Pseudemys (demonstrated by isoelectric focusing) are more complex than those exhibited by normal human blood. As a consequence, these ectotherm blood oxygen data are not well characterized by the limited number of simple descriptive parameters (P50, Hill's n and delta log P50/delta pH) commonly used to delineate predominantly single hemoglobin systems.

Acid-Base Equilibrium↗

PubMed1980

Effects of organic solutes on transmural PD and Na transport in freshwater prawn intestine.

Addition of 1 mM L-alanine or 0.5 mM D-glucose to the mucosal surface of freshwater prawn (Macrobrachium rosenbergii) intestine rapidly increased transmural potential difference (PD) (serosa became more positive). Luminal perfusion with 1 mM D-alanine did not affect the spontaneous PD. Addition of 10 mM serosal L-alanine induced a slow elevation in PD with the same polarity as shown with luminal alanine. The alanine-evoked PD was a hyperbolic function of luminal alanine concentration and was reduced to zero with 0.5 mM serosal ouabain. Luminal 1 mM L-alanine stimulated JNanet from mucosa to serosa from 1.29 +/- 0.45 to 2.83 +/- 0.66 mu mol . cm-2 . h-1. Extensive metabolic breakdown of L-alanine and D-glucose occurred during intestinal transit resulting in a small, but significant, net flux of unaltered sugar from lumen to blood (103.9 +/- 23.1 nmol . cm-2 . h-1) and an absence of net amino acid flow. While 1 mM alanine influx into the epithelium was largely Na dependent, quantitatively insigificant amounts of Na were cotransported into the cell with amino acid (approx 52 nmol . cm-2 . h-1) to account for increased JNanet observed in the presence of this organic solute. Electrogenic effects of luminal nutrients result from their catabolism to fuels for the basolateral Na pump, Increased Na-pump activity stimulates Na entry into the cell by allosteric apical carrier proteins and enhances transmural PD by accelerating net movement of cation across the tissue.

Alanine↗

PubMed1977

Kinetics of glucose transport by the perfused mid-gut of the freshwater prawn Macrobrachium rosenberg ii.

1. Mucosal influx of [3H]glucose was examined in the mid-gut of a freshwater prawn, Macrobrachium rosenbergii, using an in vitro perfusion technique. 2. [3H]glucose transfer across the apical cell membrane of the epithelium exhibited Michaelis-Menten kinetics (Jmax.in = 0-15 mumole glucose equiv/g. min, Kt = 0-17 mM). Under Na-free conditions, glucose influx was significantly reduced and a linear function of substrate concentration, indicative of either slow cellular diffusion (KD = 7-6 X 10(3) mumole glucose equiv/g. min. mM) or a facilitated process with a low carrier affinity for the sugar. 3. Phlorizin was a potent competitive inhibitor of glucose influx (K1 = 3-6 X10(-3) mM), galactose and 3-O-methylglucose (3-O-MG) were weak inhibitors, and fructose had no evident effect on glucose uptake. Azide, but not iodoacetate (IAA), significantly depressed influx. 4. Absorbed [3H]glucose was rapidly metabolized by the mid-gut. The majority of accumulated activity within the tissue was in the form of phosphorylated compounds and tritiated water (THO), while only 0-3% was recovered as a free-glucose. 5. Preliminary studies examining transmural [3-H]glucose transport, however, demonstrated a significant net mucosal to serosal free-glucose flux across the prawn mid-gut which was Na-dependent and IAA- and phlorizin-sensitive. Two alternative interpretations of the data are advanced as possible mechanisms for transepithelial glucose transport: (1) group translocation, or (2) the operation of an energized, high affinity, baso-lateral sugar transport carrier.

Animals↗