Evaluation by capacitance measurements of antidiuretic hormone induced membrane area changes in toad bladder.

A technique for estimating effective transepithelial capacitance in vitro was used to investigate changes in epithelial cell membrane area in response to antidiuretic hormone (ADH) exposure in toad bladder. The results indicate that transepithelial capacitance increases by about 30% within 30 min after serosal ADH addition and decreases with ADH removal. This capacitance change is not blocked by amiloride and occurs whether or not there is a transepithelial osmotic gradient. It is blocked by methohexital, a drug which specifically inhibits the hydro-osmotic response of toad bladder to ADH. We conclude that the hydro-osmotic response of toad bladder to ADH is accompanied by addition of membrane to the plasmalemma of epithelial cells. This new membrane may contain channels that are permeable to water. Stimulation of Na+ transport by ADH is not related to membrane area changes, but appears to reflect activation of Na+ channels already present in the cell membrane before ADH challenge.

Effects of intermittent ischemia on contractile properties and myosin isoforms of skeletal muscle.

PURPOSE: This study determined the effects of intermittent ischemia on the contractile properties, fatigue (Tf), and myosin heavy chain composition (MHC) in the rat gastrocnemius-plantarissoleus muscle (GPS) complex. METHODS: Fifty rats were divided into four groups: control (C, N = 12), severed (femoral artery) (S, N = 12), exercise (E, N = 13), and severed/exercise (SE, N = 13). Ischemia was elicited only in the SE group by daily exercise and the other groups served as controls. Exercise in the E and SE groups consisted of running on a treadmill approximately 35 min.d-1, 5 d.wk-1 for 7 wk. RESULTS: Body weight, muscle weight, and absolute force were less in the SE group compared with those in C (12, 18, and 12% respectively). However, relative force (N.g-1 of muscle) was greater in the SE group compared with that in C (8%). Maximal shortening velocity (Vmax) was lower in the SE group compared with that in all others (10-14%). Tf was less in the S group compared with that in C and E (28 and 30%, respectively). Type IIx MHC increased and type IIb decreased in gastrocnemius and plantaris muscles in SE compared with those in C. CONCLUSIONS: These data indicate that intermittent ischemia caused a decrease in muscle mass, maximal force development, and Vmax, but had no effect on Tf. The decrease in Vmax may have been related to myosin alterations in the muscles.

Cellular basis of an avian countercurrent multiplier system.

A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical reptilian-type nephrons (without loops of Henle) and mammalian-type nephrons (with loops) grouped together in medullary cones. The loop of the mammalian-type nephrons has a descending segment composed of thin and highly interdigitated cells. These thin limb cells have few mitochondria (15% of cell volume), undetectable Na+,K(+)-ATPase activity, and virtually no basolateral surface amplification. Prior to the hairpin turn, the descending limb thickens, but the cells continue to lack basolateral amplification. Cells just prior to and within the hairpin turn resemble cells of the entire ascending limb. These cells are thick (there is no thin ascending segment in the avian loop), with extensive infoldings of the basolateral membrane surrounding numerous mitochondria (45% of cell volume). The area of basolateral membrane is 25 times that of the apical membrane. The basolateral membrane (but not the apical membrane) is enriched in Na+,K(+)-ATPase activity. The structure of the avian mammalian-type nephron (as epitomized by the budgie nephron) and the fact that NaCl accounts for over 90% of the osmotic activity of avian urine leads to the conclusion that the countercurrent multiplier of the avian kidney functions by active NaCl transport from the entire ascending limb. No explanation is offered for the transport specializations found in the thick descending segment of the loop, just prior to the hairpin turn.

Cellular differences in ring glands of flesh fly pupae as a consequence of diapause programming.

The ultrastructure of the ring gland (corpus cardiacum (CC), prothoracic gland (PG) and corpus allatum (CA)) was examined in diapausing and nondiapausing flesh fly pupae. The diapause developmental state, which is environmentally regulated and coordinated by the brain-ring gland complex, is associated with differences in the ultrastructure of PG and CA cells but not in the CC. During diapause the PG and CA cells have extensive arrays of rough endoplasmic reticulum and spherical mitochondria. The PG cells also contain lipid droplets surrounded by an electron dense amorphous coat not seen in PG cells from nondiapausing pupae. In nondiapausing pupae, the PG and CA cells contain large amounts of ribosomes throughout the cytoplasm but very little rough endoplasmic reticulum and elongated mitochondria. The fact that ring glands from diapausing pupae readily incorporate (35)S-methioninc indicates that the gland is actively synthesizing proteins, thus the contrasts in ring gland ultrastructure are not due to cellular quiescence during diapause but reflect fundamental cellular and physiological differences between the diapause and nondiapause developmental program.

The CPR: getting physicians on board.

The CPR is a powerful concept. In practice, it collects and presents information. It communicates among patients, health plans and all who participate in the healthcare delivery process. The CPR's value extends from supporting better clinical decision making to helping save time and money while making the clinical practice more rewarding. To get the CPR working in your organization, you must ensure that, aside from all the data collection and analysis benefits it might provide healthcare planners, the system must actively support and reward the clinicians who use it every time they come into contact with it.

Turtle urinary bladder: regulation of ion transport by dynamic changes in plasma membrane area.

Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.

Alpha and beta types of carbonic anhydrase-rich cells in turtle bladder.

The carbonic anhydrase-rich (CA) cell population of the turtle urinary bladder, which is responsible for the secretion of H+ and probably of HCO-3, was studied by freeze-fracture and thin-section electron microscopy. The apical membrane of the major CA cell type (alpha type) was characterized by microplicae and by a coat of studs on its cytoplasmic side; on freeze-fracture, it contained a dense population of rod-shaped intra-membrane particles. When fixed at low CO2 tension, the apical membrane area of the alpha cell was reduced; its surface displayed microplicae as well as microvilli, and the apical cytoplasm contained many vesicles with rod-shaped particles and studs. The apical membrane of the other (beta type) CA cell was characterized by numerous individual microvilli without microplicae and by a relative absence of rod-shaped particles and studs. Instead, the beta cell contained studs and rod-shaped particles in its basolateral membrane. The ultrastructure and frequency of the beta CA cell were not affected by changes in CO2 tension. We suggest that the alpha cell is responsible for H+ secretion. The reversal of the polarity of the membrane elements in the beta cell and failure to respond to CO2 with amplification of its apical membrane are consistent with a role in HCO-3 secretion.

Role of membrane fusion in CO2 stimulation of proton secretion by turtle bladder.

The changes in cell structure produced during stimulation of proton secretion by CO2 in turtle bladder were examined using ultrastructural morphometric methods. One hour after CO2 addition, the area of the luminal membrane of the carbonic anhydrase-containing (CA) cell population was increased 2.5-fold and the volume percent of electron-lucent cytoplasmic vesicles in these CA cells was decreased by 61%. No changes were observed in the epithelial granular cells. These results suggest that during CO2 stimulation the vesicles fuse with the luminal membrane. CO2 stimulation of proton secretion is inhibited by the cytoskeleton-disrupting drugs colchicine and cytochalasin B and by 99% deuterium oxide as the Ringer solvent. Deuterium oxide also inhibits the decrease in cytoplasmic vesicles. Thus stimulation of proton secretion by turtle bladder CA cells depends to a large extent on vesicle fusion and the resultant increase in luminal surface area.

Acute effects of cigarette smoking on pregnant women and nonpregnant control subjects.

The effect of cigarette smoking on the pulse rate and carboxyhemoglobin concentration of the pregnant smoker was studied. The aim of this investigation was threefold: (1) to standardize cigarette consumption for studying short-term smoking effects in pregnant smokers, (2) to test for these effects by use of two noninvasive measures (concentration of carboxyhemoglobin in expired air and digital pulse rate), and (3) to compare the acute effects evidenced by pregnant smokers to those of a carefully matched group of nonpregnant control subjects. Increases in pulse rate and concentration of carboxyhemoglobin were found to be positively correlated with the level of intake of nicotine and concentration of inhaled mainstream smoke, respectively. The results, however, showed no evidence of significant differences between the pregnant and nonpregnant groups on either of the smoking measures. The methodologic implications of these findings are discussed.

Correlation between apical intramembrane particles and H+ secretion rates during CO2 stimulation in turtle bladder.

To correlate the prevalence of rod-shaped intramembrane particles (RSP) in the apical membranes of carbonic anhydrase-rich (CA) cells and the H+ transport rate in turtle urinary bladder, we carried out morphometric studies by means of scanning and freeze-fracture electron microscopy of the alpha and beta subpopulations of CA cells. Correlations were made between the apical membrane areas of alpha cells and H+ transport rate at 0 and 5% ambient CO2. Exposure to CO2 more than doubled the planar area of the luminal surface of alpha cells and increased the degree of folding (amplification) of the apical cell membrane from 2.8 +/- 0.3 to 3.8 +/- 0.3. The actual apical membrane area of alpha cells increased from 176 mm2 to 693 mm2 per 8 cm2 epithelial area. The RSP density also appeared to be increased by about 40%. The total CO2-induced increase in RSPs in position at the luminal surface was 5 fold while the increase in H+ transport was 9-fold. We conclude that stimulation of H+ transport by CO2 involves recruitment of RSP to the apical cell membrane of alpha-type CA cells and that RSPs are associated with active H+ transport. They may represent linear arrays of transmembrane components of H+ pumps.

Ultrastructural characterization of cholesterol distribution in toad bladder using filipin.

The polyene antibiotic filipin was used to characterize the cholesterol distribution in the membranes of the toad bladder epithelium in freeze-fracture replicas. The apical membranes of granular and mitochondria-rich cells incorporate moderate amounts of filipin while the basolateral membranes of both cell types incorporate substantially greater amounts. Intracellular membranes, in general, take up very little filipin. The major exception to this is the granule membrane, which appears to be rich in cholesterol. An inverse correlation was found between the density of filipin-sterol complexes in the apical membrane and the incidence of granules in the cytoplasm. This suggests that fusion of granules with the apical membrane may be responsible for variation in the concentration of cholesterol in the apical membrane. Thirty minutes following vasopressin exposure, there is no consistent change in the cholesterol content of the apical membrane of granular cells as measured by the incidence of filipin-sterol complexes. The lack of change in the amount of membrane cholesterol indicates that the vasopressin-induced increase in transepithelial water permeability is not mediated by a change in cholesterol content of the apical membrane.

Hand-wrist disorders among investment casting plant workers.

A survey of the prevalence of chronic soft tissue disorders of the hand and wrist was conducted 3 years after an initial survey of workers in a midwestern investment casting plant. The second survey of 136 (90%) of the original participants disclosed that (1) approximately 25% had different jobs in 1986, (2) 35% of those who had different jobs in 1986 reported transfers because of disorders, and (3) of those workers with the same job during both surveys, 11% reported temporary job changes due to disorders in the preceding 3 years. Workers with hand-wrist disorders in high-force and high-repetitive jobs tended to transfer out of these jobs more frequently than those in low-force-low-repetitive jobs. We failed to detect a relationship between ergonomic changes and change in prevalence of chronic hand-wrist disorders. This may be because the changes did not substantially alter the force and repetitiveness characteristics of the jobs.

Contribution of renal medullary mitochondrial density to urinary concentrating ability in mammals.

In mammals, the length of the loops of Henle increases with increasing body size without a concomitant rise in urinary concentrating ability. Because mass-specific metabolic rate falls with increasing body mass, this study sought to determine the extent to which this decline in metabolic rate could explain the low urinary concentrating ability of large mammals with long loops of Henle. Mitochondrial ultrastructural parameters were measured in the medullary thick ascending limbs (mTALs) of a series of nine mammalian genera ranging in body mass from 0.011 kg (bats) to approximately 400 kg (horses). The volume of mitochondria as a percent of mTAL cellular volume declined with increasing body mass (Mb-0.056). Inner mitochondrial membrane area per volume of mitochondrion also declined with increasing body mass (Mb-0.034), as did basolateral membrane area per unit mTAL cellular volume (Mb-0.075). Thus, not only do mitochondria occupy more volume of mTAL cells of smaller mammals, but those mitochondria are also more densely packed with cristae. Inner mitochondrial membrane area per unit volume of mTAL cell cytoplasm scaled as Mb-0.092. The decline in inner mitochondrial membrane area and basolateral membrane area per volume of mTAL cell may explain at least in part the relationship between body mass and renal concentrating ability in mammals of different sizes.

Morphologic alterations in the rat medullary collecting duct following potassium depletion.

Freeze-fracture and thin-section electron microscopy and morphometry were used to characterize further the response of the rat medullary collecting duct to potassium depletion. In freeze-fracture replicas, principal cells and intercalated cells were identified based on the assumption that intercalated cells possess a high density of rod-shaped intramembrane particles in their luminal membranes. Potassium depletion caused an increase in the relative number of cells with a high density of rod-shaped particles from the control level of 22% to 31% after 2 weeks and to 36% after 4 weeks. The frequency of intercalated cells identified by thin-section criteria was, however, about 35% in controls and unchanged by potassium depletion. This suggests that intercalated cells can have two types of membrane morphology. In potassium depletion, all intercalated cells display a high density of rod-shaped particles in their luminal membranes. In addition, the luminal membrane area of intercalated cells increased more than threefold, and the density of their rod-shaped particles increased by 21%. These observations suggest that the intercalated cell and its rod-shaped particle may be involved with the potassium reabsorption that occurs in this nephron segment with potassium depletion.

A double-membrane model for urinary bicarbonate secretion.

To define the transport pathway for HCO-3 secretion (JHCO3) across the apical and basolateral membranes of turtle bladder, we examined the effects of cAMP, isobutylmethylxanthine (IBMX), the Cl- channel blocker 9-anthroic acid (9-AA), and the disulfonic stilbene DIDS (4,4'-diisothiocyanostilbene-2,2'-sulfonic acid) on the electroneutral and electrogenic components of JHCO3. Total JHCO3 was measured by pH stat titration of the mucosal compartment after Na+ absorption and H+ secretion were abolished by ouabain and a delta pH, respectively. Addition of cAMP or IBMX increased total JHCO3 and induced a short-circuit current (ISC), accounting for a large part of JHCO3; net Cl- absorption was reduced. Mucosal 9-AA inhibited the IBMX-induced electrogenic component of JHCO3, whereas mucosal DIDS inhibited the electroneutral component and acetazolamide reduced both. We suggest that HCO-3 is generated within the cell by a Na-independent primary active acid-base transport at the basolateral membrane (H+ extrusion into the serosal compartment). Cellular HCO-3 accumulation drives JHCO3 via a Cl-HCO3 exchanger at the luminal membrane. IBMX and cAMP activate a 9-AA-sensitive anion conductance parallel to the exchanger. The apparent reversal of the transport elements between the two cell membranes (compared with H+-secreting cells) led to an ultrastructural examination of the carbonic anhydrase-rich cells.

Morphological heterogeneity of the rabbit collecting duct.

The localization of carbonic anhydrase by histochemistry, of Na-K-ATPase by immunocytochemistry and of rod-shaped intramembranous particles by freeze-fracture electron microscopy, was determined in the collecting duct of rabbits. In the cortical collecting duct (CCD), rod-shaped particles, which are abundant in intercalated cells were observed in both the apical and basolateral membrane of all intercalated cells examined. In the outer stripe of the outer medullary collecting duct (OMCDo) a high density of rod-shaped particles was found only in the apical membrane of intercalated cells. All cells of the inner stripe of the outer medullary collecting duct (OMCDi) had rod-shaped particles in the apical membrane but not in the basolateral membrane. As the collecting duct entered the inner medulla the density of rod-shaped particles decreased until they were virtually absent in the terminal segment. Na-K-ATPase, localized to the basolateral membrane, was more abundant in principal cells than in intercalated cells in the CCD. In the OMCDo, staining was equal in principal and intercalated cells. All cells of the OMCDi and the inner medullary collecting duct (IMCD) stained for Na-K-ATPase. Carbonic anhydrase in the CCD was localized to the cell membranes and cytoplasm of intercalated cells. Principal cells did not stain for carbonic anhydrase. A similar pattern was seen in the OMCDo. In the outer region of the OMCDi most cells did not stain for carbonic anhydrase, whereas in the inner region the apical and lateral membranes of all cells stained for carbonic anhydrase. Weak cytoplasmic staining was occasionally seen. A similar pattern was seen in the initial half of the IMCD, while the terminal half of the IMCD did not stain. In this study, the localization of enzymes and rod-shaped intramembranous particles associated with Na+, K+, and H+ transport shows both segmental and cellular heterogeneity, and correlates with the known transport properties of tubule segments. The distribution of these enzymes and rod-shaped intramembranous particles is different in rabbits and rats, and may explain some of the functional differences between homologous segments in these species.

Cellular ultrastructure of Amphiuma distal nephron: effects of exposure to potassium.

The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was examined by electron-microscopic and stereological techniques before and after exposure to potassium in the ambient environment. The distal nephron of Amphiuma is composed of three ultrastructurally distinct segments: early distal (or diluting segment), late distal, and collecting tubule. The early distal tubule structurally resembles the mammalian thick ascending limb of Henle's loop. Large renin-like granules are present in the smooth muscle cells of the afferent arteriole in the vicinity of the early distal tubule, suggesting the presence of a rudimentary juxtaglomerular apparatus. Late distal tubules are composed of one large cell type characterized by extensive basal membrane invaginations, often extending to the luminal membrane. Collecting tubules contain principal and intercalated cells that are ultrastructurally similar to cells of the mammalian cortical collecting tubule. Exposure to potassium had no effect on the ultrastructure of early distal cells but led to a sharp increase in the basolateral membrane surface density of principal cells in the collecting tubule (1.17 +/- 0.08-1.63 +/- 0.13 micron2/micron3). Potassium adaptation leads to a similar structural response in the mammalian collecting tubule. Since Amphiuma collecting tubules can be isolated and perfused in vitro and impaled with ion- and voltage-sensitive microelectrodes, the observed structural adaptation suggests that the collecting tubule may be a useful preparation to study the cellular mechanisms of potassium adaptation.

Effects of age, sex, and anthropometric factors on nerve conduction measures.

Associations among measures of median, ulnar, and sural nerve conduction and age, skin temperature, sex, and anthropometric factors were evaluated in a population of 105 healthy, asymptomatic adults without occupational exposure to highly repetitive or forceful hand exertions. Height was negatively associated with sensory amplitude in all nerves tested (P less than 0.001), and positively associated with median and ulnar sensory distal latencies (P less than 0.01) and sural latency (P less than 0.001). Index finger circumference was negatively associated with median and ulnar sensory amplitudes (P less than 0.05). Sex, in isolation from highly correlated anthropometric factors such as height, was not found to be a significant predictor of median or ulnar nerve conduction measures. Equations using age, height, and finger circumference for prediction of normal values are presented. Failure to adjust normal nerve conduction values for these factors decreases the diagnostic specificity and sensitivity of the described measures, and may result in misclassification of individuals.