Evaluation of different speech and touch interfaces to in-vehicle music retrieval systems.

In-vehicle music retrieval systems are becoming more and more popular. Previous studies have shown that they pose a real hazard to drivers when the interface is a tactile one which requires multiple entries and a combination of manual control and visual feedback. Voice interfaces exist as an alternative. Such interfaces can require either multiple or single conversational turns. In this study, each of 17 participants between the ages of 18 and 30 years old was asked to use three different music retrieval systems (one with a multiple entry touch interface, the iPod, one with a multiple turn voice interface, interface B, and one with a single turn voice interface, interface C) while driving through a virtual world. Measures of secondary task performance, eye behavior, vehicle control, and workload were recorded. When compared with the touch interface, the voice interfaces reduced the total time drivers spent with their eyes off the forward roadway, especially in prolonged glances, as well as both the total number of glances away from the forward roadway and the perceived workload. Furthermore, when compared with driving without a secondary task, both voice interfaces did not significantly impact hazard anticipation, the frequency of long glances away from the forward roadway, or vehicle control. The multiple turn voice interface (B) significantly increased both the time it took drivers to complete the task and the workload. The implications for interface design and safety are discussed.

August Krogh Lecture. The renal concentrating mechanism in insects and mammals: a new hypothesis involving hydrostatic pressures.

Water moves from compartments of higher to compartments of lower water potential. Osmotically active solutes and negative hydrostatic pressure both lower water potential by stretching the hydrogen bonds between water molecules (Hammel-Scholander hypothesis). In trees the negative hydrostatic pressure in the sap is balanced by the osmotic pressure of the leaves. In response to differences in water potential, water flows across biological membranes through water-filled pores. Protein molecules, aquaporins, forming hourglass-shaped pores have been identified, cloned, and located in plasma membranes in mammalian as well as other tissues. Water molecules flow single file through aquaporins. Insects concentrate the urine in the rectum. Mammals concentrate the urine in the collecting ducts in the inner medulla. In both, a compartment with a high osmotic concentration is created through ion transport. Both have a muscular coat surrounding the tissue, which shows peristaltic contractions. In insects it is the muscular layer around the rectum; in mammals it is the renal pelvic wall that surrounds the papilla. Mechanisms are proposed whereby these peristaltic contractions, through the creation of positive and negative hydrostatic pressures in the tissues, can lead to hyperosmotic excreta.

Uncoupling of glomerular and tubular regulations of urea excretion in rat.

Renal adjustments to diets varying in protein and sodium content were studied in young anesthetized Munich-Wistar rats. Diets were as follows: high (50%) protein (HP), normal (24%) protein (NP), reduced (8%) protein without extra salt (RPNS), and RP with extra salt (RPWS, 2.8% extra salt). Rats grew at the same rate on all diets. Glomerular filtration rate (GFR), urea, sodium, and osmolar clearances were measured. In series 1, groups of rats were maintained for 4 wk on the four diets and one group on changed diet (CP2d, RPWS diet for 4 wk changed to NP diet for 2 days). GFR was reduced compared with NP rats by 12% in RPNS and RPWS, and by 16% in CP2d rats, but the differences were not statistically significant. Fractional excretion of urea (FEurea) was significantly changed compared with NP. It was 40% higher in HP rats, and 50 and 56% lower in RPNS and RPWS, respectively. In the CP2d group it had increased to the NP value. In series 2, groups of rats were maintained on the RPNS diet for 1, 2, 3, and 4 wk, respectively. GFR decreased 21.6% after only 1 wk but after 4 wk it was not significantly lower than in the NP group. In contrast, no significant reduction was found in FEurea after 1 wk, whereas it decreased by 40% during the 2nd wk, with no further decrease after 3 and 4 wk. GFR was not directly related to protein or salt intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical and morphological differences in the kidney zones of the elasmobranch, Raja erinacea mitch.

The histological investigation of the kidney of the skate Raja erinacea revealed a thin cap of dorsal bundles, which contain segments of single nephrons that are arranged separately in a countercurrent manner, and a large ventral zone, where the second proximal segments (PII) and parts of the lower nephron are located. This zonation is apparent in fresh, unfixed material and makes it possible to separate small tissue samples under a dissecting microscope. The osmolality in both zones does not differ. The dorsal bundle zone had a lower urea concentration and a higher sodium concentration than the ventral zone. The differences in the mean concentrations of the tissue samples indicate a gradient for the two substances along the bundles. Determinations of amounts of water and solutes per mg solute-free, dry tissue of the two zones, showed that the amounts of water, total osmolytes, Na and K were greater in the bundle zone than in the ventral zone, while the amount of urea was identical in the two zones. This indicates that the lower urea concentration in the bundle zone is established through an accumulation of Na and water in the interstitium. The countercurrent arrangement of very early and late segments of single renal tubules supports the concept of passive reabsorption of urea in the kidney of the marine elasmobranch.

Early changes in renal function following chemically induced nephropathy.

The functional changes in the rat kidney 24 h after administration of 2-bromoethanamine hydrobromide (BEA) have been extensively described. There is, however, little information regarding earlier alterations. The present study was designed to measure early changes in renal function in order to clarify further pathomechanisms of the BEA-induced lesion. Experiments were performed in two groups of Wistar rats with different infusion rates during the first 3 h following injection of 100 mg/kg BW BEA compared to sham-injected rats. Analysis included measuring urine flow, osmolality, urea, sodium and potassium as well as inulin and para-aminohippuric acid clearance. Our studies show a tubular as well as a glomerular involvement in BEA-induced nephropathy. A significantly higher urine flow occurred already in the first 30 min following injection of BEA. Urine osmolality began to decrease after 90 min, Na excretion was elevated at 3 h, K excretion was not significantly different from the control group, urea excretion was increased after 30 min. Contrary to other studies we found a continuously decreasing glomerular filtration rate and PAH clearance during the first 3 h. Our results suggest an early effect of BEA on tubular function (increasing sodium excretion), papillary concentration capacity (increasing urine flow combined with decreasing osmolality) and glomerular function (decreasing glomerular filtration rate).

Physiological and morphological responses of the rat kidney to reduced dietary protein.

Renal physiological and morphological adjustments to a reduced protein diet were studied in young Munich-Wistar rats. Two groups of animals were used for the correlative physiological-morphological studies: normal protein (NP, 24% dietary protein) rats and reduced protein (LP, 8% dietary protein) rats. Both groups were fed their respective diets for 4-5 wk and had free access to drinking water. Physiological measurements of GFR and urea clearance were made on five animals from each group. These data showed that the changes in renal function specifically and almost exclusively affected the handling of urea. There was no difference in GFR between the NP and LP rats. Urea clearance was substantially reduced in LP rats. Morphological analyses were made on perfusion-fixed kidneys of five animals from each group. Selected slices were examined and photographed by light and electron microscopy. These data showed no difference in size and number of elements within the vascular bundles but showed significantly smaller lumina of the thin limbs of the short-looped nephrons and a significant thinning of the wall of the thin descending limbs of the long-looped nephrons. These morphological changes may in part be responsible for the observed physiological adjustments to a reduced protein diet. An additional group of rats (6 NP and 5 LP, all dehydrated) were analyzed for distribution of solutes within the inner medulla. The data showed that the concentration of urea, but not that of Na+, was reduced at the papillary tip in LP rats.

August and Marie Krogh and respiratory physiology.

August and Marie Krogh first met in 1904 in the laboratory of Christian Bohr, a well-known Danish physiologist, where August was a teaching assistant and Marie Jørgensen a medical student. August, the oldest son of a brewer in Grenaa, Denmark, had recently obtained his doctorate for his work on respiration in frogs. Marie Jørgensen, the daughter of a farmer in Fyn, had at the age of six decided to pursue a medical career. August and Marie were married in 1905, and she joined him in some of his research. Christian Bohr was a staunch proponent of the theory that O2 was secreted across the lung epithelium. August Krogh at first set out to prove this hypothesis through precise and accurate measurements of gases in arterial blood and alveolar air with new apparatus he had constructed. Marie joined in this work, but the results they obtained did not support Bohr's hypothesis; to the contrary a series of very careful studies definitively proved that O2 is transported across the alveolar epithelium by diffusion alone. Due to the conflict with Bohr's views they delayed publication of the results until 1910. Marie Krogh, who finished her medical degree in 1907 and had begun a family, undertook an investigation of CO diffusion capacity through human lungs. This was to test if the rate of O2 diffusion was sufficient to account for the O2 uptake even at high altitudes or during various pulmonary diseases. Thirty-five years later the CO method, as described by Marie Krogh, was rediscovered and is now used extensively as a clinical test. August, in his continued studies of respiration in animals and humans, became interested in the delivery of O2 from the capillaries to the tissue. The studies that followed led to his discovery of the regulation of capillary circulation, for which he was awarded the Nobel Prize in 1920.

Water removal and solute additions determining increases in renal medullary osmolality.

Osmolality and solute concentrations of the mammalian renal medulla increase and decrease with changing urine osmolality. These changes are brought about by addition or removal of solute or water to or from the renal medullary tissue. In Munich-Wistar rats and Syrian hamsters, males and females, actual amounts of and the various solutes involved in these changes were determined. Kidneys were removed from animals killed in different stages of water diuresis and antidiuresis. The renal medulla was analyzed by a new method that permits determination of water and solutes on the same piece of tissue. Removal of water and addition of urea were the two most important factors in raising inner medullary osmolality. Papillary water content was inversely related to the papillary osmolality and was 50% lower in extreme antidiuresis compared with water diuresis. Rats had higher papillary water content than hamsters. In the outer medulla, water removal was significant in the hamsters but not in the rats. Addition of urea to the papillary tissue exceeded the osmotic equivalent of NaCl by a factor of 2.8 in both rats and hamsters. Females of both species showed greater changes than males in amounts of urea in the inner medulla.

Changes in fluid compartments in hamster renal papilla due to peristalsis in the pelvic wall.

The pelvic peristalsis "milks" the renal papilla in rodents. This study investigates the effect of the pelvic contractions upon the fluid in papillary loops of Henle (LH) and capillaries (cap) and on the volume of collecting duct (CD) cells, papillary epithelial (PE) cells and interstitium. In the anesthetized antidiuretic hamsters the urine was made green by an intravenous infusion of lissamine green. A snare was placed loosely around the papilla. The peristalsis was recorded on a Grass recorder using a fiberoptic light signal which changed intensity with the events in the pelvis and papilla. In one group of hamsters the snare was tightened during the contraction and in another group at the beginning of the relaxation. The papilla within the pelvis was then fixed immediately. It was epon-embedded for light and electron microscopy. In the group with contracted pelvis CD, LH, and cap were all closed and empty; the papilla was elongated. In the group with relaxed pelves these structures were full and open spaces were seen between the cells of CD and PE. Morphometric measurements showed that the intercollecting duct volume was larger in the papillae with relaxed pelvis, but that cell volume of PE was larger in the papillae with contracted pelvis. It is suggested that fluid moves into the cells during contraction when urine flows through the CD and into the interstitium during relaxation.

Peristaltic flow of urine in the renal capillary collecting ducts of hamsters.

Urine movements in the papillary collecting ducts were studied visually, in vivo, through the intact renal pelvic wall in anesthetized (Inactin 150 mg/kg) hamsters having a normal range of urine flow rates (0.5 to 3.8 microliters.min(-1).100 g of body wt-1). Urine was given a contrasting color by a continuous i.v. infusion of lissamine green (0.5 to 2%) in saline. The lower renal pelvis with about 1.3 mm of the renal papilla was illuminated with a fiber optic light, and the movements of urine in the medullary collecting ducts were observed and filmed through a dissecting microscope. Urine flow was determined indirectly by measuring changes in the urinary bladder diameter, and the rate of urine formation was manipulated by changing the rate of lissamine green-saline infusion. Urine, propelled by pelvic peristaltic waves, moved as discreet boluses in a pulsatile fashion through the papillary collecting ducts. The length of the urine boluses and the percent of time the papillary collecting ducts were in contact with urine increased in direct proportion to urine flow. At the lowest urine flow rate, the papillary collecting ducts (at 1.0 mm from the tip) were empty 94% of the time. The velocity (1.6 +/- 0.1 mm.sec-1) and frequency (12.6 +/- 0.5 contractions.min-1) of the pelvic peristaltic waves were not related to urine flow rate. The renal pelvic contractions were also observed to cause discontinuous blood flow in the vasa recta. In the context of Stephenson's mass balance equation for the concentration ratio of the kidney, the discontinuous fluid movements imposed by the renal pelvis may resulted in an increased urine concentrating ability.

Occurrence of renal pelvic refluxes during rising urine flow rate in rats and hamsters.

Retrograde movements of urine into the renal pelvic space (pelvic refluxes) were studied in anesthetized Munich Wistar rats and hamsters. The urine was made green by a continuous i.v. infusion of lissamine green in saline, and the experimental kidney was either placed on a shallow trough or left in situ. The renal pelvis was exposed and illuminated with a fiber optic light, and urine movements were observed through the transparent but intact pelvic wall. Urine was collected from both kidneys in the rats. In both rats and hamsters, the inner medulla of the kidney was analyzed for solutes at the end of the experiment. The experimental procedures did not interfere with the normal function of the experimental kidney, and the results were the same in rats and hamsters. During constant urine flow, full refluxes did not occur. Urine either moved straight down the ureter after it exited from the ducts of Bellini or it briefly bathed the papillary tip. In rats, full pelvic refluxes started approximately 0.8 min after a bolus injection (0.5 ml of isosmotic saline, i.v.), at a time corresponding to a steep rise in urine flow (2 microliter.min-2.100 g body wt-1). Following increased infusion rate, full refluxes were associated with an increase in urine flow of 0.05 g microliter.min-2.100 g body wt-1. Full refluxes were also seen in the hamsters following a bolus injection or increased infusion rate. Increasing intrapelvic pressure by 1 cm H2O also caused full pelvic refluxes. When full refluxes occurred, urine came into contact with all areas of the renal pelvis. Because full pelvic refluxes occur only during rising urine flow, this mechanism would bring urine with decreasing osmolality into contact with the outer medullary areas facing the pelvic space.

Urinary concentrating processes in vertebrates.

Avian and mammalian kidneys can produce a urine hyperosmotic to the blood by means of a renal countercurrent system. Birds are uricotelic; mammals are ureotelic. It is proposed that the inner medulla present in mammalian, but not in avian kidneys serves specifically to accumulate urea in the inner and outer medulla. Among mammalian kidneys the degree to which urea accumulates in the inner medulla is inversely related to the complexity of the vascular bundles (in the outer medulla) and the cortical urea recycling index. A model is proposed for urea recycling via the vascular bundles. The renal pelvis varies in size among mammals. Its relative size is unrelated to the type of vascular bundles, cortical recycling index; or urea accumulation in the inner medulla. Since urine refluxes into the renal pelvis during rising urine flow only, the function of the pelvis could be that of bringing the more dilute urine into contact with the outer medulla and underlying capillaries, thereby aiding in reducing the urea concentration in outer and inner medulla during rising urine flow. The size of the renal pelvis may be related to the volume of the inner medulla. Other factors may also be involved.

Ultrastructural organization of the hamster renal pelvis.

The renal pelvis of the hamster has been studied by light microscopy (epoxy resin sections), transmission electron microscopy, and morphometric analysis of electron micrographs. Three morphologically distinct epithelia line the pelvis, and each covers a different zone of the kidney. A thin epithelium covering the outer medulla (OM) consists of two cell types: (1) granular cells are most numerous and have apically positioned granules which stain intensely with toluidine blue, are membrane-bound, and contain a fine particulate matter that stains light grey to black in electron micrographs. (2) Basal cells do not have granules, are confined to the basal lamina region, and do not reach the mucosal epithelial surface. The inner medulla (IM) is covered by a pelvic epithelium morphologically similar to collecting duct epithelium of IM. Some cells in this portion of the pelvic epithelium (IM) stain intensely dark with toluidine blue, osmium tetroxide, lead, and uranyl acetate. Transitional epithelium, which separates cortex (C) from pelvic urine, has an asymmetric luminal plasma membrane and discoid vesicles, each of which is similar to those previously observed in mammalian ureter and urinary bladder epithelia. Based on morphological comparisons with other epithelia, the IM and OM pelvic epithelia would appear permeable to solutes and/or water, while the transitional epithelium covering the C appears relatively impermeable. It would also appear that the exchange of solutes and water between pelvic urine and OM would involve capillaries, primarily, since morphometric analysis showed that both fenestrated and continuous capillaries of the OM were extremely abundant (greater than 60% of OM pelvic surface area) just under the thin pelvic epithelium.

Anatomy of the renal pelvis in the hamster.

The hamster renal pelvis has been studied by means of low-power light microscopy, scanning electron microscopy and morphometric analyses. The results of this study are highly suggestive that the contact of pelvic urine with the other medulla as well as with the inner medulla may be an important aspect of final urine formation. The outer medulla constituted nearly 50% of the total pelvic surface area, with the inner stripe of the outer medulla more than twice the pelvic surface area of the outer stripe of the outer medulla. The large outer medullary pelvic surface area was accounted for by the elaboration of the upper pelvic walls into peripelvic columns, opercula ("secondary pyramids"), fornices and secondary pouches. A thin simple-squamous to low cuboidal pelvic epithelium separated pelvic urine from outer medullary parenchyma. The inner medulla which constituted about one quarter of the total pelvic surface area was covered by a cuboidal to columnar pelvic epithelium which appeared morphologically similar to the papillary collecting duct epithelium. Tubules and capillaries of the inner medulla did not appear as closely juxtaposed to the pelvic epithelium as did those of the outer medulla. Cortical tissue comprised only 11.7% of the total pelvic surface area and was covered by transitional epithelium similar to that of ureter and bladder. The previously reported impermeability of this epithelium suggests that pelvic urine contact with the cortex is unimportant in final urine formation. The rich layer of smooth muscle under the transitional epithelium probably functions to move urine into and out of the pelvis during pelvic peristalsis, which has been observed in vivo.