Non-coordinate expression of collagen mRNAs during carbon monoxide-induced cardiac hypertrophy

Collagen gene expression during volume overload-induced cardiac hypertrophy was investigated in adult male rats. Hypertrophy of the left ventricle (22%) and right ventricle (37%) occurred following 27 days continuous exposure to 700 ppm carbon monoxide; hematocrit increased nearly 47%. To examine potential cellular and molecular control of restructuring in the heart, we investigated the expression of two specific procollagen mRNAs for collagen types which have different structural-functional roles [Type I (alpha-1) & Type IV]. Type I (interstitial) mRNA levels increased at least 100% relative to controls within 3 days of initial exposure to 700ppm CO, then declined afterwards; type IV(basement membrane) mRNA levels increased more modestly at first, and increased further afterwards. The ratio of type I/type IV RNA's also increased initially, then later declined, with the greatest differences in the relative responses of type I and IV mRNAs seen in the right ventricle. These data suggest that types I and IV collagen mRNA expression is not coordinately expressed during this type of volume overload-induced hypertrophy in rat heart.     

Plasma volume, osmolarity, total protein and electrolytes during treadmill running and cycle ergometer exercise

While haemoconcentration due to loss of plasma volume is well established during cycling, the existence of similar changes during running remains contentious. This study compared the changes in plasma volume and associated blood indices during 60 min of running and cycling at the same relative intensity (approximately 65% VO2max), with all changes referenced to blood indices obtained after 30 min seated at rest on a cycle ergometer. Plasma osmolarity increased similarly with both forms of exercise but was less than predicted for water loss alone, such that there was a net loss of sodium during exercise and of potassium postexercise, with essentially no loss of protein. Plasma volume decreased similarly (approximately 6.5%) in both exercise trials, but while that with cycling was initiated by exercise itself and was essentially maximal within 5 min, the reduction in plasma volume in the running trial was induced by adopting the upright posture and was complete before exercise began. These data would indicate that different mechanisms are responsible for the changes in plasma volume induced by running and cycling, while the similarity of change would suggest that there is a lower limit to any reduction in plasma volume, regardless of mechanism. Furthermore, the observation that the changes in plasma volume were complete before or early in exercise, would imply that oral water ingestion during prolonged exercise, which is essential for thermoregulation, may be more concerned with homeostasis of extravascular water rather than plasma volume.     

咽喉部高频喷射通气调节各参数对狗肺通气效率的影响

用相关和回归处理方法,研究了8条正常狗咽喉部高频喷射通气时,调节驱动压、呼吸比和频率对喷气量、吸入气氧浓度、动脉血气及气道内压的作用。结果显示,驱动压和呼吸此对各观察指标几乎有同等重要的作用,频率的影响很小,喷气量与吸入气氧浓度、动脉血气、气道内压间存在显著的正相关关系。说明调节参数的意义主要在于改变了喷气量。     

Water and solute regulation in Procephalothrix spiralis Coe and Clitellio arenarius (Müller) III. Long-term acclimation to diluted seawaters and effect of putative neuroendocrine structures

When acutely transferred to diluted seawater (SW), Procephalothrix spiralis and Clitellio arenarius regulate water content (g H₂O/g solute free dry wt = s.f.d.w.) via loss of Na and Cl (µmoles/g.s.f.d.w.). The present study extends these observations to a greater range of salinities and determines the effects of long-term, stepwise acclimation to diluted seawaters. Final exposure to a given experimental seawater (70, 50, 30, 15%) was 48 hours. Osmolality (mOsm/kg H₂O) and Na, K, and Cl ion concentrations (mEq/l) were determined in total tissue water and in the extracellular fluid of C. arenarius. Extracellular volume was determined as the ¹⁴C-polyethylene glycol space. Both species behaved as hyperosmotic conformers in diluted seawaters. However, reduction of the osmotic gradient between worm and medium occurred in P. spiralis, but not C. arenarius, in 30 and 15% SW. In both species, osmolality and Na, Cl, and K concentrations in total tissue water decreased with increased dilution of the SW. Water content increased with dilution of the medium but was lower than that which would be predicted based on approximation of the van't Hoff relation. This indicated the occurrence of regulatory volume decrease (RVD). In P. spiralis, in 70 or 50% SW, RVD was accompanied by loss of Na and Cl contents. However, in 30 or 15% SW, Na and Cl contents increased and in worms in 15% SW K content decreased. The latter movements of Na, Cl and K are indicative of cellular hysteresis and were associated with decreased viability, indicating the lower limits of regulatory ability in this species. In comparison, RVD in C. arenarius occurred in all diluted seawaters and was accompanied by loss of Na and Cl contents. In C. arenarius, evidence for reduced viability was absent. Removal of the supra- and subesophageal ganglia of C. arenarius resulted in retention of water, Na and Cl (g H₂O or µmoles/g s.f.d.w.) in worms acclimated to 70% SW. Removal of the cerebral ganglia and cephalic glands of P. spiralis did not significantly influence regulation of water content.     

Separate,Ca2+-activated K+ and Cl− transport pathways in Ehrlich ascites tumor cells

Summary The net loss of KCl observed in Ehrlich ascites cells during regulatory volume decrease (RVD) following hypotonic exposure involves activation of separate conductive K⁺ and Cl^– transport pathways. RVD is accelerated when a parallel K⁺ transport pathway is provided by addition of gramicidin, indicating that the K⁺ conductance is rate limiting. Addition of ionophore A23187 plus Ca²⁺ also activates separate K⁺ and Cl^– transport pathways, resulting in a hyperpolarization of the cell membrane. A calculation shows that the K⁺ and Cl^– conductance is increased 14-and 10-fold, respectively. Gramicidin fails to accelerate the A23187-induced cell shrinkage, indicating that the Cl^– conductance is rate limiting. An A23187-induced activation of⁴²K and³⁶Cl tracer fluxes is directly demonstrated. RVD and the A23187-induced cell shrinkage both are: (i) inhibited by quinine which blocks the Ca²⁺-activated K⁺ channel. (ii) unaffected by substitution of NO ₃ ^– or SCN^– for Cl^–, and (iii) inhibited by the anti-calmodulin drug pimozide. When the K⁺ channel is blocked by quinine but bypassed by addition of gramicidin, the rate of cell shrinkage can be used to monitor the Cl^– conductance. The Cl^– conductance is increased about 60-fold during RVD. The volume-induced activation of the Cl^– transport pathway is transient, with inactivation within about 10 min. The activation induced by ionophore A23187 in Ca²⁺-free media (probably by release of Ca²⁺ from internal stores) is also transient, whereas the activation is persistent in Ca²⁺-containing media. In the latter case, addition of excess EGTA is followed by inactivation of the Cl^– transport pathway. These findings suggest that a transient increase in free cytosolic Ca²⁺ may account for the transient activation of the Cl^– transport pathway. The activated anion transport pathway is unselective, carrying both Cl^–, Br^–, NO ₃ ^– , and SCN^–. The anti-calmodulin drug pimozide blocks the volume- or A23187-induced Cl^– transport pathway and also blocks the activation of the K⁺ transport pathway. This is demonstrated directly by⁴²K flux experiments and indirectly in media where the dominating anion (SCN^–) has a high ground permeability. A comparison of the A23187-induced K⁺ conductance estimated from⁴²K flux measurements at high external K⁺, and from net K^– flux measurements suggests single-file behavior of the Ca²⁺-activated K⁺ channel. The number of Ca²⁺-activated K⁺ channels is estimated at about 100 per cell.     

An examination of the method of sizing the spermatozoa of the domestic fowl and duck with an electronic counter

Although many estimations have been made electronically of mammalian sperm volume, detailed investigations have not been reported for avian spermatozoa with an electronic counter. In the present study, sizing of spermatozoa of fowls and Muscovy and Pekin drakes was examined using a Coulter counter (model ZB). In our preliminary work on fowl sperm volumes, we found mono- or di-morphic distribution displays that were modified depending on the combination of amplification (AMP) and aperture current (APC). Therefore, methodology to estimate the fowl and drake sperm volume was examined. Dilution of semen had no effect on the dimorphic distribution pattern of the sperm volume. Density-gradient centrifugation did not separate two kind of particles in the semen in either continuous or discontinuous Percoll gradients; therefore, we varied settings of AMP and APC, and found that the most suitable settings for measuring sperm volumes of these birds are 1 for AMP and 8 for APC. With these settings, mean volumes of spermatozoa were 5.1 μm³ for fowls, 5.7 μm³ for Muscovy drakes, and 5.6 μm³ for Pekin drakes.     

General method for the derivation and numerical solution of epithelial transport models

Summary A general method is presented for the formulation and numerical evaluation of mathematical models describing epithelial transport. The method is based on the principles of conservation of mass, and maintenance of electroneutrality within the cells and bathing solutions. It is therefore independent of the specific membrane transport mechanisms, and can be used to evaluate different models describing arbitrary transport processes (including passive, active and cotransport processes). Detailed numerical methods are presented that allow computation of steady-state and transient responses under open-circuit, current-clamp and voltage-clamp conditions, using a general-purpose laboratory minicomputer. To evaluate the utility of this approach, a specific model is presented that is consistent with the Koefoed-Johnson and Ussing hypothesis of sodium transport in tight epithelia (Acta Physiol. Scand. 42:298–308, 1958). This model considers passive transport of an arbitrary number of permeant solutes, active transport of sodium and potassium, and osmotically induced water transport across the apical and basolateral membranes. Results of the model are compared to published experimental measurements in rabbit urinary bladder epithelium.     

Transient breakdown in the selective permeability of the plasma membrane ofChlorella emersonii in response to hyperosmotic shock: Implications for cell water relations and osmotic adjustment

Summary In osmotic experiments involving cells of the euryhaline unicellular green algaChlorella emersonii exposed to hyperosmotic stress by immersion in a range of low molecular weight organic and inorganic solutes, a temporary breakdown in the selective permeability of the plasma membrane was observed during the initial phase of transfer to media of high osmotic strength (up to 2000 mosmol kg^–1). Thus, although the cells appeared to obey the Boyle-van't Hoff relationship in all cases, showing approximately linear changes in volume (at high salinity) as a function of the reciprocal of the external osmotic pressure, the extent of change was least for the triitols, propylene glycol and glycerol, intermediate for glucose, sorbitol, NaCl and KCl, with greatest changes in media containing the disaccharides sucrose and maltose. In NaCl-treated cells, uptake of external solute and loss of internal ions was observed in response to hyperosmotic treatment while sucrose-treated cells showed no significant uptake of external solute, although loss of intracellular K⁺ was observed. These observations suggest that the widely used technique of estimating cellular turgor, and osmotic/nonosmotic volume by means of the changes in volume that occur upon transfer to media containing increasing amounts of either a low molecular weight organic solute or an inorganic salt may be subject to error. The assumption that all algal cells behave as ideal osmometers, with outer membranes that are permeable to water but not to solutes, during the course of such experiments is therefore incorrect, and the data need to be adjusted to take account of hyperosmotically induced external solute penetration and/or loss of intracellular osmotica before meaningful estimates of cell turgor and osmotic volume can be obtained.