Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVIII platypus (Ornithorhynchus anatinus) and saltwater crocodile (Crocodylus porosus)

As part of a programme of comparative measurements of P _d (diffusional water permeability) the RBCs (red blood cells) from an aquatic monotreme, platypus (Ornithorhynchus anatinus), and an aquatic reptile, saltwater crocodile (Crocodylus porosus) were studied. The mean diameter of platypus RBCs was estimated by light microscopy and found to be ～6.3 μm. P _d was measured by using an Mn²⁺‐doping 1H NMR (nuclear magnetic resonance) technique. The P _d (cm/s) values were relatively low: ～2.1×10^?3 at 25°C, 2.5×10^?3 at 30°C, 3.4×10^?3 at 37°C and 4.5 at 42°C for the platypus RBCs and ～2.8×10^?3 at 25°C, 3.2×10^?3 at 30°C, 4.5×10^?3 at 37°C and 5.7×10^?3 at 42°C for the crocodile RBCs. In parallel with the low water permeability, the E _a,d (activation energy of water diffusion) was relatively high, ～35 kJ/mol. These results suggest that “conventional” WCPs (water channel proteins), or AQPs (aquaporins), are probably absent from the plasma membranes of RBCs from both the platypus and the saltwater crocodile.     

Oxygen Diffusion from the Roots of Rice Grown under Non-waterlogged Conditions

Three rice varieties, cv. Norin 36, cv. Norin 37 and cv. Yubae, were grown in a loam with a 20 cm water-table which gave aerobic conditions to a depth of not less than 15 to 17 cm. Under these conditions Norin 36 grew more vigorously and tillered more frequently than the other two varieties. The rates of oxygen diffusion at 23°C from roots up to 11 cm in length were however appreciably lower for Norin 36 (4.3 × 10^?8g · cm^?2 of root surface · min^?1) than for Norin 37 or Yubae (c. 7.8 × 10^?8g). A considerable increase (up to 200 %) in the oxygen diffusion rate (ODR) from the roots occurred if they were cooled to 3°C, and at this temperature differences in ODR between the varieties were not significant. For a purely physical system, because of the decrease in the diffusion coefficient of oxygen in water, and, the increase in oxygen solubility, a drop of c. 20 % in ODR should accompany the above 20°C drop in temperature. A 16 % drop was recorded for artificial ‘roots’ under these conditions. It was concluded that respiratory activity at the higher temperature must have been responsible for the low readings and intervarietal differences observed at 23°C. By increasing the 3°C values by 25 % a mean value of 14.2 × 10^?8g · cm^?2 of root surface · min^?1 was recorded for the three varieties, being the probable ODR at 23°C in the absence of a respiratory factor. Calculations show that respiratory activity removed enough oxygen to reduce the ODR for Norin 36 by more than 9 × 10^?8g, and for Norin 37 and Yubae by c. 6.7 × 10^?8g · cm^?2 of root surface · min^?1. Anatomical investigations showed that cortical breakdown was always extensive at 4 to 4.5 cm from the apex of the roots. In some cases however breakdown had not occurred in the basal segment of the root. No opinion could be formed as to whether differences in the amount of cortical breakdown between the varieties might have occasioned the respiratory differences observed. An interesting feature of the root anatomy was the failure of breakdown in those regions of the roots through which lateral roots emerged.     

Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVI Dingo (Canis familiaris dingo) and dog (Canis familiaris)

As part of a programme of comparative measurements of P _d (diffusional water permeability) the RBCs (red blood cells) from dingo (Canis familiaris dingo) and greyhound dog (Canis familiaris) were studied. The morphologies of the dingo and greyhound RBCs [examined by light and SEM (scanning electron microscopy)] were found to be very similar, with regard to aspect ratio and size; the mean diameters were estimated to be the same (～7.2 μm) for both dingo and greyhound RBCs. The water diffusional permeability was monitored by using an Mn²⁺‐doping ¹H NMR technique at 400 MHz. The P _d (cm/s) values of dingo and greyhound RBCs were similar: 6.5×10^?3 at 25°C, 7.5×10^?3 at 30°C, 10×10^?3 at 37°C and 11.5×10^?3 at 42°C. The inhibitory effect of a mercury‐containing SH (sulfhydryl)‐modifying reagent PCMBS (p‐chloromercuribenzene sulfonate) was investigated. The maximal inhibition of dingo and greyhound RBCs was reached in 15–30 min at 37°C with 2 mmol/l PCMBS. The values of maximal inhibition were in the range 72–74% when measured at 25°C and 30°C, and ～66% at 37°C. The lowest value of P _d (corresponding to the basal permeability to water) was ～2–3×10^?3 cm/s in the temperature range 25–37°C. The E _a,d (activation energy of water diffusion) was 25 kJ/mol for dingo RBC and 23 kJ/mol for greyhound RBCs. After incubation with PCMBS, the values of E _a,d increased, reaching 46–48 kJ/mol in the condition of maximal inhibition of water exchange. The electrophoretograms of membrane polypeptides of the dingo and greyhound RBCs were compared and seen to be very similar. We postulate that the RBC parameters reported in the present study are characteristic of all canine species and, in particular in the two cases presented here, these parameters have not been changed by the peculiar Australian habitat over the millennia (as in the case of the dingo) or over shorter time periods, decades or centuries (as in the case of the domestic greyhound).     

Comparative studies of water permeability of red blood cells from humans and over 30 animal species: an overview of 20 years of collaboration with Philip Kuchel

NMR measurements of the diffusional permeability of the human adult red blood cell (RBC) membrane to water (P _d) and of the activation energy (E _a,d) of the process furnished values of P _d ~ 4 × 10^?3 cm/s at 25 °C and ~6.1 × 10^?3 cm/s at 37 °C, and E _a,d ~ 26 kJ/mol. Comparative NMR measurements for other species showed: (1) monotremes (echidna and platypus), chicken, little penguin, and saltwater crocodile have the lowest P _d values; (2) sheep, cow, and elephant have P _d values lower than human P _d values; (3) cat, horse, alpaca, and camel have P _d values close to those of humans; (4) guinea pig, dog, dingo, agile wallaby, red-necked wallaby, Eastern grey kangaroo, and red kangaroo have P _d values higher than those of humans; (5) mouse, rat, rabbit, and “small and medium size” marsupials have the highest values of P _d (>8.0 × 10^?3 cm/s at 25 °C and >10.0 × 10^?3 cm/s at 37 °C). There are peculiarities of E _a,d values for the RBCs from different species. The maximum inhibition of diffusional permeability of RBCs induced by incubation with p-chloromercuribenzene sulfonate varied between 0 % (for the chicken and little penguin) to ~50 % (for human, mouse, cat, sheep, horse, camel, and Indian elephant), and ~60–75 % (for rat, guinea pig, rabbit, dog, alpaca, and all marsupials). These results indicate that no water channel proteins (WCPs) or aquaporins are present in the membrane of RBCs from monotremes (echidna, platypus), chicken, little penguin and saltwater crocodile whereas WCPs from the membranes of RBCs from marsupials have peculiarities.     

Comparative nuclear magnetic resonance studies of diffusional water permeability of red blood cells from different species. V—Rabbit (Oryctolagus Cuniculus)

• 1.1. The diffusional water permeability (P_d) of rabbit red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulfonate (PCMBS).
• 2.2. The values of P_d were around 6.3 × 10⁻³ cm/sec at 15°C, 7.0 × 10⁻³cm/sec at 20°C, 8.0 × 10⁻³ cm/sec at 25°C, 9.1 × 10⁻³ cm/sec at 30°C and10.7 × 10⁻³ cm/sec at 37°C.
• 3.3. Systematic studies on the effects of PCMBS on water diffusion indicated that the maximal inhibition was reached in 15 min at 37°C with 0.5 mM PCMBS.
• 4.4. The values of maximal inhibition were around 71–74% at all temperatures.
• 5.5. The basal permeability to water was estimated as 1.6 × 10⁻³cm/sec at 15°C, 2.0 × 10⁻³cm/sec at 20°C, 2.4 × 10⁻³cm/sec at 25°C, 2.6 × 10⁻³cm/sec at 30°C, and 3.1× 10^{−3 cm/secat 37°C}.
• 6.6. The activation energy of water diffusion was around 18 kJ/mol and increased to 27 kcal/mol after incubation with PCMBS in conditions of maximal inhibition of water diffusion.
• 7.7. The membrane polypeptide electrophoretic pattern of rabbit RBCs has been compared with its human counterpart.
• 8.8. The rabbit membrane contained a higher amount of spectrin (bands 1 and 2), while the band 6 (glyceraldehyde-3-phosphate dehydrogenase) was markedly less intense.
• 9.9. Considerable differences in the electrophoretic patterns of the two sources of RBC membranes appeared in the bands migrating in the band 4.5 region and in front of band 7, where some polypeptides were apparent in higher amounts in the rabbit RBC membrane.

     

Effect of temperature on permeation of low‐density lipoprotein particles through human carotid artery tissues

Quantification of the diffusion of small molecules and large lipid transporting lipoproteins across arterial tissues could be useful in elucidating the mechanism(s) of atherosclerosis. Optical coherence tomography (OCT) was used to determine the effect of temperature on the rate of diffusion of glucose and low‐density lipoproteins (LDL) in human carotid endarterectomy tissue in vitro. The permeability rate for glucose was calculated to be (3.51 ± 0.27) × 10^–5 cm/s (n = 13) at 20 °C, and (3.70 ± 0.44) × 10^–5 cm/s (n = 5) at 37 °C; for LDL the rate was (2.42 ± 0.33) × 10^–5 cm/s (n = 5) at 20 °C and (4.77 ± 0.48) × 10^–5 cm/s (n = 7) at 37 °C, where n is the number of samples. These results demonstrate that temperature does not significantly influence the permeation of small molecules (e.g. glucose), however, raising the temperature does significantly increase the permeation of LDL. These results provide new information about the capacity of an atherogenic lipoprotein to traverse the intimal layer of the artery. These results also demonstrate the potential of OCT for elucidating the dynamics of lipoprotein perfusion across the arterial wall. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetics of the acid hydrolysis of heparin from its Cu (II) complex and its relation to biological activity

The acid-catalyzed hydrolysis of heparin from Cu(II) complex was studied as a function of time and temperature. Four independent calculations showed that the hydrolysis, during the 5-hr period examined, obeys the first-order kinetic law. Specific rate constants, calculated at 50°C, 57°C, 65°C, 71°C, and 80°C, were 3.3 × 10^?5 sec^?1, 6.5 × 10^?5 sec^?1, 10.4 × 10^?5 sec^?1, 15.1 × 10^?5 sec^?1, and 26.6 × 10^?5 sec^?1, respectively. Arrhenius plots of the data yielded 14.7 kcal as the energy of activation. An independent run of the self-hydrolysis of heparin at 57°C also obeyed first-order kinetics and its specific rate constant of 6.4 × 10^?5 sec^?1 is in excellent agreement with that of the hydrolysis of Cu(II)-heparin at 57°C. The anticoagulant activity of heparin and of the Cu(II)-heparin are not appreciably different. Further, the inactivation of heparin closely parallels Cu(II) release from the Cu(II) complex which in turn parallels desulfation.     

Interaction of Growth Retardants and Temperature in Growth, Flowering, Regeneration, and Auxin Activity of Begonia × cheimantha Everett

Soil application of CCC reduced stem and leaf growth in Begonia plants. This effect was evident with all concentrations tested at 18°C, whereas at 21 and 24°C no growth–retarding effect was observed with 2 × 10^?2 M CCC, and with 5 × 10^?3 M growth was even stimulated. Flowering was promoted by CCC in long day and neur–critical temperature, particularly under low light intensity in the winter. The formation of adventitious buds in leaves of plants grown at 21 and 24°C was stimulated when the plants received 5 × 10^?2 and 2 × 10^?2 M CCC, while 8 7times; 10^?2 M was inhibitory. In plants grown at 18°C bud formation was inhibited by all CCC concentrations. Root formation in the the leaves was usually stimulated by high CCC concentrations, while root elongation was reduced. The level of ether–extractable. acidic auxin (presumably IAA) in the leaves was lowered by CCC treatment of the plants, hut this required higher CCC concentrations at higt than at low temperature. When applied to detached leaves CCC stimulated bud formation at concentrations ranging from 10^?4 to 10^?2 M in leaves planted at 18 and 21°C. At 24°C budding was inhibited by 10^?2 M CCC, the lower concentrations being stimulatory also at this temperature. Root formation and growth were not much affected by CCC treatment of the leaves, but increased with the temperature. Soil application of Phosfon (4 × 10^?4 M) had no effect on growth and flowering, nov did it affect the subsequent regeneration of buds and roots in the leaves. In detached leaves Phosfon stimulated bud formation with au optimum at 10^?6 M. Root formation was stimulated by Phosfon at all temperatures, the optimal concentration being 10^?5 M, whereas root length was conversely affected. Foliar application of B-995 to intact plants and treatment of detached leaves greatly inhibited the formation of buds and had little effect on root formation. B-99D reduced the growth and delayed flowering in the plants.     

Environmental factors affecting hatching of rotifer (Brachionus plicatilis) resting eggs

Hatching experiments were carried out on a population of Brachionus plicatilis (Dor strain) resting eggs produced in batch laboratory cultures under controlled conditions and then stored for at least one month at 4 °C in the dark. Light was found to be obligatory for termination of dormancy. Over the temperature range of 10–30 °C (at 9.0‰ salinity), hatching was optimal (40–70%) at 10–15 °C and decreased linearly with the rise in incubation temperature. Resting eggs incubated over a salinity range of 9–40‰ (at 15 °C) showed optimal hatching at 16‰. Incubation of resting eggs in distilled water permitted normal embryonic development, but neonates died at eclosion. Presence of algae, Chlorella stigmatophora (0.5 × 10⁶ cell ml^?1), was found to aid hatching.     

Immobilization of d-glucose oxidase onto a hydrogen peroxide permselective membrane and application for an enzyme electrode

A hydrogen peroxide permselective membrane with asymmetric structure was prepared and d-glucose oxidase (EC 1.1.3.4) was immobilized onto the porous layer. The activity of the immobilized d-glucose oxidase membrane was 0.34 units cm^?2 and the activity yield was 6.8% of that of the native enzyme. Optimum pH, optimum temperature, pH stability and temperature stability were found to be pH 5.0, 30–40°C, pH 4.0–7.0 and below 55°C, respectively. The apparent Michaelis constant of the immobilized d-glucose oxidase membrane was 1.6 × 10^?3 mol l^?1 and that of free enzyme was 4.8 × 10^?2 mol l^?1. An enzyme electrode was constructed by combination of a hydrogen peroxide electrode with the immobilized d-glucose oxidase membrane. The enzyme electrode responded linearly to d-glucose over the concentration 0–1000 mg dl^?1 within 10 s. When the enzyme electrode was applied to the determination of d-glucose in human serum, within day precision (CV) was 1.29% for d-glucose concentration with a mean value of 106.8 mg dl^?1. The correlation coefficient between the enzyme electrode method and the conventional colorimetric method using a free enzyme was 0.984. The immobilized d-glucose oxidase membrane was sufficiently stable to perform 1000 assays (2 to 4 weeks operation) for the determination of d-glucose in human whole blood. The dried membrane retained 77% of its initial activity after storage at 4°C for 16 months.     

The effects of temperature on swimming performance of juvenile shortnose sturgeon (Acipenser brevirostrum)

The swimming performance of juvenile shortnose sturgeon (～16 cm TL, ～20 g), Acipenser brevirostrum, was quantified with regards to temperature (5 to 25°C) using both increased (U_crit) and fixed velocity (endurance) tests in a laboratory setting. Sturgeons were found to show reduced U_crit values at 5 and 10°C (25.99 and 28.86 cm s^?1 respectively), with performance beginning to plateau at 15°C through 25°C (33.99 cm s^?1). For the endurance protocol, fish were tested at speeds of 35, 40 and 45 cm s^?1 at 5, 15 and 25°C. Performance within a single speed was similar at all temperatures, indicating the usage of anaerobic metabolism to fuel locomotion at these higher velocities. Overall, shortnose sturgeon demonstrated high tolerance towards a wide range of temperatures but showed few differences between performance levels at colder or warmer water conditions.     

The Effect of Leaf Water Potential, Leaf Temperature and Light Intensity on Leaf Diffusion Resistance and the Transpiration of Leaves of Malus sylvestris

The relationship between leaf resistance to water vapour diffusion and each of the factors leaf water potential, light intensity and leaf temperature was determined for leaves on seedling apple trees (Malus sylvestris Mill. cv. Granny Smith) in the laboratory. Leaf cuticular resistance was also determined and transpiration was measured on attached leaves for a range of conditions. Leaf resistance was shown to be independent of water potential until potential fell below — 19 bars after which leaf resistance increased rapidly. Exposure of leaves to CO₂-free air extended the range for which resistance was independent of water potential to — 30 bars. The light requirement for minimum leaf resistance was 10 to 20 W m^?2 and at light intensities exceeding these, leaf resistance was unaffected by light intensity. Optimum leaf temperature for minimum diffusion resistance was 23 ± 2°C. The rate of change measured in leaf resistance in leaves given a sudden change in leaf temperature increased as the magnitude of the temperature change increased. For a sudden change of 1°C in leaf temperature, diffusion resistance changed at a rate of 0.01 s cm^?1 min^?1 whilst for a 9°C leaf temperature change, diffusion resistance changed at a rate of 0.1 s cm^?1 min^?1. Cuticular resistance of these leaves was 125 s cm^?1 which is very high compared with resistances for open stomata of 1.5 to 4 s cm^?1 and 30 to 35 s cm^?1 for stomata closed in the dark. Transpiration was measured in attached apple leaves enclosed in a leaf chamber and exposed to a range of conditions of leaf temperature and ambient water vapour density. Peak transpiration of approximately 5 × 10^?6 g cm^?2 s^?1 occurred at a vapour density gradient from the leaf to the air of 12 to 14 g m^?3 after which transpiration declined due presumably to increased stomatal resistance. Leaves in CO₂-free air attained a peak transpiration of 11 × 10^?6 g cm^?2 s^?1 due to lower values of leaf resistance in CO₂ free air. Transpiration then declined in these leaves due to development of an internal leaf resistance (of up to 2 s cm^?1). The internal resistance was masked in leaves at normal CO₂ concentrations by the increase in stomatal resistance.     

Experimentelle Untersuchungen zum Stockwachstum und zur Medusenbildung bei dem marinen HydrozoonEirene viridula

The development of both slide-grown and non-substrate bound colonies ofE. viridula (Thecata-Leptomedusae) ranging in size from 1 to 50 hydranths was investigated under various temperature conditions. The majority of slide-grown colonies reached a larger final size than non-substrate bound ones, in 20°, 25° and 29° C. Raising the temperature did not stimulate propagation of hydranths as expected. Most of the colonies transferred to 25° or 29° C finally were even smaller than those reared at 20° C. This was partially due to resorption of several hydranths about 9 days after the temperature rise; the influence of “physiological competition” between development of new hydranths and budding of medusae on colony growth is discussed. Transfer from higher to lower temperatures affected colony growth negatively. Raising the temperature from 20° to 25° or 29° C initiated formation of gonozooids from the distal part of hydranth stalks and development of medusa buds in both types of colonies. With the exception of slide-grown colonies transferred to 25° C, also young medusae were budded off. There was a remarkable coincidence in predominance of colony growth in slide-grown colonies and of medusa budding in non-substrate bound cultures. In the latter, medusa buds developed 1 to 2 days earlier. Most buds did not differentiate into liberated medusae, but were resorbed. Transformation of medusa buds into hydranths was not observed. In the clone ofE. viridula, onset of medusa budding did not depend on a “minimal colony size”. Even single hydranths were able to produce medusa buds after transfer to higher temperatures; budded off medusae were recorded from non-substrate bound colonies with an initial size of 3 hydranths. In slide-grown cultures, medusa buds developed into colonies with an initial size of only 3 hydranths. No hydranth propagation prior to medusa budding occurred in these cases. After raising temperature from 25° to 29° C medusa buds were observed in nonsubstrate bound colonies only; a small number of medusae were budded off from some of these colonies. Lowering the temperature from 29° or 25° to 20° C caused resorption of existing medusa buds. In several non-substrate bound colonies, transfer from 29° to 25° C induced development of gonozooids with medusa buds and, in some cases, of young medusae. Incubation with the alkylating cytostaticTrenimon and transfer from 20° to 25° C caused irreversible resorption of all hydranths when 4 × 10^?2 mg/ml were administered for 10 mins. Thereafter, only development of stolonial structures was observed. With one exception, the colonies treated with 4 × 10^?3 mg/ml, and all others submitted to 4 × 10^?4 mgTrenimon/ml were able to produce new hydranths and also medusa buds; some of the colonies first had to overcome a degressive phase. Treatment with 4 × 10^?2 mg destroyed all interstitial cells (I-cells). Incubation with 1 × 10^?3 or 1 × 10^?4 mg/ml left the I-cells at least partially intact. It is concluded that I-cells are indispensable for hydranth and medusan morphogenesis inE. viridula.     

Remediation of Explosive-Contaminated Soils: Alkaline Hydrolysis and Subcritical Water Degradation

Alkaline hydrolysis and subcritical water degradation were investigated as ex-situ remediation processes to treat explosive-contaminated soils from military training sites in South Korea. The addition of NaOH solution to the contaminated soils resulted in rapid degradation of the explosives. The degradation of explosives via alkaline hydrolysis was greatly enhanced at pH ≥12. Estimated pseudo-first-order rate constants for the alkaline hydrolysis of 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in contaminated soil at pH 13 were (9.6?±?0.1)×10^?2, (2.2?±?0.1)×10^?1, and (1.7?±?0.2)×10^?2 min^?1, respectively. In the case of subcritical water degradation, the three explosives were completely removed at 200–300°C due to oxidation at high temperatures and pressures. The degradation rate increased as temperature increased. The pseudo-first-order rate constants for DNT, TNT, and RDX at 300°C were (9.4?±?0.8)×10^?2, (22.8?±?0.3)×10^?2, and (16.4?±?1.0)×10^?2, respectively. When the soil-to-water ratio was more than 1:5, the extent of alkaline hydrolysis and subcritical water degradation was significantly inhibited.     

Determination of the kinetics of permeation of dimethyl sulfoxide in isolated corneas

Corneal cryopreservation requires that endothelial cells remain viable and intercellular structure be preserved. High viability levels for cryopreserved endothelial cells have been achieved, but preserving intercellular structure, especially endothelial attachment to Descemet's membrane, has proved difficult. Cell detachment apparently is not caused by ice, suggesting osmotic or chemical mechanisms. Knowledge of the permeation kinetics of cryoprotectants (CPAs) into endothelial cells and stroma is essential for controlling osmotic and chemical activity and achieving adequate tissue permeation prior to cooling. Proton nuclear magnetic resonance (NMR) spectroscopy was used to assess the permeation of dimethyl sulfoxide (DMSO) into isolated rabbit corneas. Corneas with intact epithelia were exposed to isotonic medium or 2.0 mol/L DMSO for 60 min and subsequently transferred to 2.0 or 4.0 mol/L DMSO, respectively, at 22, 0, or −10°C. DMSO concentration in the cornea was measured vs time. The Kedem-Katchalsky model was fitted to the data. Hydraulic permeability (m³/N·s) is 7.1×10⁻¹³+216%-11% at 22°C, 8.2×10⁻¹³+235%−21% at 0°C, and 1.7×10⁻¹⁴+19% −16% at −10°C. The reflection coefficient is 1.0+2%−1% at 22°C and 0°C, and 0.9±5% at −10°C. Solute mobility (cm/s) is 5.9×10⁻⁶+6%–11% at 22°C, 3.1×10⁻⁶+12%−11% at 0°C, and 5.0×10⁻⁸ cm/s+59%−40% at −10°C.     

Biochemical properties of the 1 alpha, 25-dihydroxyvitamin D3 cytoplasmic receptors from human and chick parathyroid glands

Cytoplasmic receptors for 1α, 25-dihydroxyvitamin D₃ from human parathyroid adenoma tissue and rachitic chick parathyroid glands have been characterized with regard to a number of physical, chemical, and ligand binding properties. Both receptors are 3.6–3.7 S proteins with molecular weights of approximately 75,000 and Stoke's molecular radii of 36 Å. It was found that the receptors possess a cysteine residue in or near the 1α, 25-dihydroxyvitamin D₃ binding site which is critical for ligand binding activity. The receptors both have equilibrium dissociation constants for 1α, 25-dihydroxyvitamin D₃ in the range of 2 to 5 × 10^?10m at 4 °C and second-order association rate constants for their seco-steroid ligand of 1 × 10⁷, m^?1 min^?1 (0 °C). The dissociation rate constants were found to be 5.3 × 10^?4 min^?1 (4 °C) for the human receptor and 1.3 × 10^?5 min^?1 (4 °C) for the chick receptor. The great deal of similarity which exists between the cytoplasmic 1α, 25-dihydroxyvitamin D₃ receptors from avian and mammalian parathyroid glands suggests a homologous function for these molecules in the two tissues.     

Uptake of L-[3H] glutamic acid by crude and purified synaptic vesicles from rat brain

Rat brain synaptic vesicles suspended in a medium comprised of potassium tartrate displayed saturable accumulation of L-[³H] glutamic acid at 37° (Km 2.0 × 10^?4M; 311±13 pmol/mg protein), which was stable for periods up to 60 min. The accumulation was temperature sensitive and partially ATP-dependent, uptake levels being reduced to 18.7±0.8 pmol/mg protein at 4°, and to 141±4 pmol/mg protein in the absence of ATP. Fractionation of a crude vesicle preparation on a discontinuous sucrose gradient demonstrated the accumulation to be specifically associated with the synaptic vesicle fraction.     

Heart rate as an indicator of metabolic rate and activity in adult Atlantic salmon, Salmo salar

Telemetered heart rate (f_H) was examined as an indicator of activity and oxygen consumption rate (VO₂) in adult, cultivated, Atlantic salmon, Salmo salar L. Heart rate was measured during sustained swimming in a flume for six fish at 10° C [mean weight, 1114 g; mean fork length (f. l.), 50·6 cm] and seven fish at 15° C (mean weight, 1119 g; mean f. l., 50·7 cm) at speeds of up to 2·2 body lengths/s. Semi–logarithmic relationships between heart rate and swimming speed were obtained at both temperatures. Spontaneously swimming fish in still water exhibited characteristic heart rate increases associated with activity. Heart rate and Vo₂ were monitored simultaneously in a 575–1 circular respirometer for six fish (three male, three female) at 4° C (mean weight, 1804 g; mean F. L., 62· cm) and six fish (three male, three female) at 10° C (mean weight, 2045 g; mean f. l., 63·2 cm) during spontaneous but unquantified activity. Linear regressions were obtained by transforming data for both f_H and Vo₂ to log values. At each temperature, slopes of the regressions between f_H and Vo₂ for individual fishes were not significantly different, but in some cases elevations were. All differences in elevation were between male and female fish. There were no significant differences in regression slope or elevation for fish of the same sex at the two temperatures and so regressions were calculated for the sexes, pooling data from 4 and 10° C. There was no significant difference in the mean ± S. D. Vo₂ between the sexes at 4° C (male, 66·0 ± 59·6 mgO₂ kg^?1 h^?1; female, 88·0 ± 60·1 mgO₂ kg^?1 h^?1) or 10° C (male, 166·2 ± 115·4 mgO₂ kg^?1 h^?1; female, 169·2 ± 111–1 mgO₂ kg^?1h^?1). Resting Vo₂ (x?± s. d.) at 4°C was 36·7 ± 8.4 mgO₂ kg^?1 h^?1, and 10° C was 72·8 ± 11·9 mgO₂ kg^?1 h^?1. Maximum Vo₂ (x?± S. D.) at 4° C was 250·6 ± 40·2 mgO₂ kg^?1 h^?1, and at 10° C was 423·6 ± 25·2 mgO₂ kg^?1 h^?1. Heart rate appears to be a useful indicator of metabolic rate over the temperature range examined, for the cultivated fish studied, but it is possible that the relationship for wild fish may differ.     

Electron microscopy of human interphase nuclei

Quantitative electron microscopy was used to analyze surface-spread, critical-point-dried human interphase nuclei and chromatin. The following information is presented: (1) Unstimulated interphase nuclei of lymphocytes from peripheral blood have a mean dry mass of 50.30×10^?12 g. The mean dry mass of stimulated nuclei of lymphocytes was determined to be 59.34×10^?12 g, a significant statistical difference from the unstimulated ones. (2) Mean diameter of chromatin fibers and mean fiber mass per micron were 199ű15% coefficient of variation (C.V.) and 5.95×10^?16g×29% C.V., respectively. (3) A line of regression of fiber mass on fiber diameter for 83 fibers indicated that a 200-Å fiber has a mass of 5.86×10^?16g/μ, or almost the same as the mean fiber mass of 5.95× 10^?16g/μ. (4) With the value 7×10^?12g for the DNA content of an unstimulated lymphocyte nucleus, a total length of 215 cm is calculated for the DNA double helix. When this length is compared to the mean length of chromatin fiber per nucleus (7.59 cm), a ratio of 28.3 to 1 results, which is called the DNA-packing ratio. (5) This DNA-packing ratio of 28.3 is reasonably close to the packing ratio of 26.9 suggested from model calculations for the second DNA supercoil in a 200-Å chromatin fiber.     

Kinetics of Water Transport in Eel Intestinal Vesicles

Brush border membrane vesicles, BBMV, from eel intestinal cells or kidney proximal tubule cells were prepared in a low osmolarity cellobiose buffer. The osmotic water permeability coefficient P _f for eel vesicles was not affected by pCMBS and was measured at 1.6 × 10⁻³ cm sec⁻¹ at 23°C, a value lower than 3.6 × 10⁻³ cm sec⁻¹ exhibited by the kidney vesicles and similar to published values for lipid bilayers. An activation energy E _a of 14.7 Kcal mol⁻¹ for water transport was obtained for eel intestine, contrasting with 4.8 Kcal mol⁻¹ determined for rabbit kidney proximal tubule vesicles using the same method of analysis. The high value of E _a , as well as the low P _f for the eel intestine is compatible with the absence of water channels in these membrane vesicles and is consistent with the view that water permeates by dissolution and diffusion in the membrane. Further, the initial transient observed in the osmotic response of kidney vesicles, which is presumed to reflect the inhibition of water channels by membrane stress, could not be observed in the eel intestinal vesicles. The P _f dependence on the tonicity of the osmotic shock, described for kidney vesicles and related to the dissipation of pressure and stress at low tonicity shocks, was not seen with eel vesicles. These results indicate that the membranes from two volume transporter epithelia have different mechanisms of water permeation. Presumably the functional water channels observed in kidney vesicles are not present in eel intestine vesicles. The elastic modulus of the membrane was estimated by analysis of swelling kinetics of eel vesicles following hypotonic shock. The value obtained, 0.79 × 10⁻³ N cm⁻¹, compares favorably with the corresponding value, 0.87 × 10⁻³ N cm⁻¹, estimated from measurements at osmotic equilibrium. Received: 28 January 1999/Revised: 15 June 1999