Cutaneous evaporimetry. IX. Cutaneous water loss in old age

The cutaneous water loss (CWL) were investigated in 15 old human subjects by Evaporimeter Ep-1. The mean value of the CWL resulted 11,9 +/- 4,3 g/h. This result is significantly lower compared with the value of normal people equal to 17, 5 +/- 4,0 g/h as reported in foregoing notes.     

Cutaneous evaporimetry. VII. Cutaneous water loss in Basedow's disease

The cutaneous water loss was investigated in 12 patients affected with Basedow's disease by Evaporimeter Ep-1. The mean value of the CWL resulted 49,8 +/- 18,2 g/h. This result is significantly higher compared with the value of normal somali people equal to 25,24 +/- 14,6 g/h.     

Development of skin structure and cutaneous water loss in nestling desert house sparrows from Saudi Arabia

The outer layer of the epidermis, the stratum corneum (SC), contains lipids and corneocytes, which together form layers that limit cutaneous water loss (CWL). We examined the development of structure of the SC and CWL in nestling House Sparrows (Passer domesticus) from Saudi Arabia. We measured CWL of nestlings, and characterized development of their epidermis using electron microscopy. We tested two antagonistic hypotheses, that CWL decreases as nestlings age, a response to increased thickness of SC, and an opposite idea that CWL increases as nestlings age even though the number of layers of the SC remains constant. CWL of nestling House Sparrows varied with developmental stages, in a non-linear fashion, but not significantly so. CWL of nestlings averaged 7.31+/-1.5 g H(2)O/(m(2) h), whereas for adults it was 4.95 g/(m(2) h); adult CWL was 67.7% that of nestlings. We found that morphology of the SC did not change linearly with age, but seemed to vary with developmental stage. CWL decreased as the SC thickness increased and as the total thickness of the corneocytes increased. Further, we found that CWL decreased as the thickness of the extracellular space increased, number of corneocytes increased, and proportion of the SC that is extracellular space increased.     

Biodiesel production from isolated oleaginous fungi Aspergillus sp. using corncob waste liquor as a substrate

The study documented the potential of isolated filamentous fungus Aspergillus sp. as whole cell biocatalyst for biodiesel production using Sabourauds dextrose broth medium (SDBM) and corncob waste liquor (CWL) as substrates. SDBM showed improvement in both biomass production (13.6 g dry weight/1000 ml) and lipid productivity (23.3%) with time. Lipid extraction was performed by direct (DTE) and indirect (IDTE) transesterification methods. DTE showed higher transesterification efficiency with broad spectrum of fatty acids profile over IDTE. CWL as substrate showed good lipid productivity (22.1%; 2g dry biomass; 48 h) along with efficient substrate degradation. Lipids derived from both substrates depicted high fraction of saturated fatty acids than unsaturated ones. Physical characteristics of fungal based biodiesel correlated well with prescribed standards. CWL derived biodiesel showed relatively good fuel properties (acid number, 0.40 mg KOH/g of acid; iodine value, 11 g I?/100 g oil; density, 0.8342 g/cm3) than SDBM derived biodiesel.     

Cutaneous water evaporation--I. Its significance in heat-stressed birds

In a comparative study on avian cutaneous evaporation, two species of Phasianidae, Japanese quail Coturnix coturnix japonica and chukar partridge Alectoris chukar, and three species of Columbidae, palm dove Streptopelia senegalensis, collared turtle dove Streptopelia decaocto and rock pigeon Columbia livia, were investigated. The skin resistance to vapor diffusion (rs) and cutaneous water loss (CWL) were studied in these birds exposed to air temperatures (Ta) between 20 and 52 degrees C. The skin resistance was measured with Lambda instrument diffusive resistance meter. Skin resistance within the thermo-neutral zone varied between a minimum of 62 sec/cm in the palm dove exposed to 20 degrees C and a maximum of 309.1 sec/cm in the partridge exposed to 36 degrees C. The CWL values were 2.5 mg H2O/cm2.hr and 0.51 mg H2O/cm2.hr respectively. Maximum CWL of the quail and partridge was 1.9-2.1 mg H2O/cm2.hr, equivalent to a cooling capacity of about 17% of metabolic heat production at 45 degrees C Ta. In the palm dove, collared dove and pigeon CWL reached 6.8, 13.1 and 20.9 mg H2O/cm2.hr and rs values reached 31.2, 16.2 and 9.4 sec/cm respectively. The cooling capacity amounted to 51.5, 86.1 and 96.5% of metabolic heat during heat stress (52 degrees C). The significance of skin evaporation in body temperature regulation of heat-stressed birds is discussed.     

Cutaneous and respiratory water loss in larks from arid and mesic environments

Birds from deserts generally have lower total evaporative water loss (TEWL), the sum of cutaneous (CWL) and respiratory water loss (RWL), than species from mesic areas. We investigated the role of CWL and RWL as a function of air temperature (T(a)) in hoopoe larks (Alaemon alaudipes) and Dunn's larks (Eremalauda dunni) from the Arabian Desert and skylarks (Alauda arvensis) and woodlarks (Lullula arborea) from temperate mesic grasslands. The proportional contribution of CWL to TEWL in all larks at moderate T(a) ranged from 50% to 70%. At high T(a) (40 degrees -45 degrees C), larks enhanced CWL by only 45%-78% and relied on an increase in RWL by 676%-2,733% for evaporative cooling. Surface-specific CWL at 25 degrees C was 29% lower in the arid-zone species than in the mesic larks. When acclimated to constant T(a), 15 degrees C-acclimated hoopoe larks increased CWL by 22% compared with 35 degrees C-acclimated birds, but the other species did not change CWL. This study is consistent with the hypothesis that larks from deserts have a reduced CWL at moderate and low T(a) but provided no support for the hypothesis that at high T(a) larks from arid regions rely more on CWL than larks from mesic environments. Interspecific differences in CWL cannot be attributed to acclimation to environmental temperature and are possibly the result of genetic differences due to natural selection or of phenotypically plastic responses to divergent environments during ontogeny.     

Phenotypic flexibility in cutaneous water loss and lipids of the stratum corneum in house sparrows (Passer domesticus) following acclimation to high and low humidity

Resistance to water-vapor diffusion through the skin is thought to be conferred by lipids in the stratum corneum (SC), the outer layer of the epidermis. We tested the effect of ambient humidity on cutaneous water loss (CWL) and lipid composition of the SC by acclimating house sparrows (Passer domesticus) to either a dry (6.5 g/m(3) absolute humidity) or a humid (31 g/m(3)) environment for 3 wk at a thermoneutral temperature (30 degrees C). Sparrows in the dry-acclimated group reduced CWL by 36% compared with those in the humid environment. Relative to initial values, both groups of sparrows decreased CWL, 45% in the dry-acclimated group and 23% in the humid group, suggesting that temperature is also an important stimulus for CWL apart from humidity. Both groups of acclimated sparrows decreased quantities of cholesterol, free fatty acids, and cerebrosides and increased the proportion of ceramides in their SC. Lipid amounts or proportions in the SC did not differ between dry- and humid-acclimated sparrows, but the free fatty acid : ceramide ratio was significantly lower in dry-acclimated birds. Also, lipid composition was only correlated with CWL in dry-acclimated sparrows, suggesting that structural changes to SC lipids are more tightly linked to CWL regulation in response to low humidity. Our results demonstrate phenotypic flexibility in CWL and lipid composition of the SC and provide support for a functional relationship between these traits.     

Quantitation of cerebral blood volume in human infants by near-infrared spectroscopy

Current methods for measuring cerebral blood volume (CBV) in newborn infants are unsatisfactory. A new method is described in which the effect of a small change (5-10%) in arterial oxygen saturation (SaO2) on cerebral oxyhemoglobin [HbO2] and deoxyhemoglobin [Hb] concentration is observed by near-infrared (NIR) spectroscopy. Previous experiments in which the NIR absorption characteristics of HbO2 and Hb and the pathlength of NIR light through the brain were defined allowed changes in [HbO2] and [Hb] to be quantified from the Beer-Lambert law. It is shown here that CBV can then be derived from the expression CBV = (delta[HbO2] - delta[Hb])/(2. delta SaO2.H.R.), where H is the large vessel total hemoglobin concentration and R to the cerebral-to-large vessel hematocrit ratio. Observations on 12 newborn infants with normal brains, born at 25-40 wk of gestation and aged 10-240 h, gave a mean value for CBV of 2.22 +/- 0.40 (SD) ml/100 g, whereas mean CBV was significantly higher 3.00 +/- 1.04 ml/100 g in 10 infants with brain injury born at 24 to 42 wk of gestation and aged 4-168 h (P less than 0.05).     

The Relationship between Cutaneous Water Loss and Thermoregulatory State in Kuhl's Pipistrelle Pipistrellus kuhlii, a Vespertillionid Bat

Abstract Total evaporative water loss is the sum of respiratory water loss (RWL) and cutaneous water loss (CWL) and constitutes the main avenue of water loss in bats. Because bats fly and have large surface-to-volume ratios, they potentially have high rates of RWL and CWL. Most species of small insectivorous bats have the ability to reduce their body temperature (T(b)) at rest, which substantially reduces energy expenditure and water loss. We hypothesized that bats reduce evaporative water loss during bouts of deep hypothermia (torpor) by decreasing RWL and CWL. We measured T(b), RWL, CWL, and resting metabolic rate (RMR) in Kuhl's pipistrelle Pipistrellus kuhlii, a small insectivorous bat. In support of our hypothesis, we found that RWL decreased with decreasing RMR. We found that CWL was lower in torpid individuals than in normothermic bats; however, bats in deep torpor had similar or higher CWL than bats in shallow torpor, suggesting that they exert a less effective physiological control over CWL when in deep torpor. Because insectivorous bats spend most of their lives in torpor or hibernation, the regulation of CWL in different heterothermic states has relevant ecological and evolutionary consequences.     

Measurement of cutaneous evaporation. 5. Cutaneous water loss in peripheral vascular disease

The purpose of this research is the measurement of the cutaneous water loss in 19 angiopathie patients by the Evaporimeter. Ep I in order to compare it with the values of normal people. We found a statistical significant increase of the CWL without difference between the normal and pathologic limb.     

Early developmental changes in intracellular Ca2+ stores in rat brain.

Developmental changes in intracellular Ca2+ stores in brain was studied by examining: (1) IP3- and cADPR-induced increase in [Ca2+]i in synaptosomes; (2) Ca(2+)-ATPase activity and ATP-dependent 45Ca2+ uptake into Ca2+ store in ER microsomes; (3) TG-induced inhibition of Ca(2+)-ATPase activity and ATP-dependent 45Ca2+ uptake into Ca2+ store in ER microsomes; and (4) gene expression of Ca(2+)-ATPase pump in neurons obtained from brains of the new-born and the 3-week-old rats. IP3 (EC50 310 +/- 8 nM, 200% maximum increase in [Ca2+]i) and cADPR (EC50 25 +/- 3 nM, greater than 170% maximum increase in [Ca2+]i) both were potent agonist of Ca2+ release from internal stores in synaptosomes obtained from the 3-week-old rats. However, IP3 (EC50 250 +/- 10 nM, 175 maximum increase in [Ca2+]i) was a potent, but cADPR (EC50 300 +/- 20 nM, 75% maximum increase) was a poor agonist of Ca2+ release from intracellular stores in synaptosomes obtained from the new-born rats. [3H]IP3, [32P]cADPR and [3H]Ry binding in the new-born samples were significantly less than that in the 3-week-old samples. [3H]Ry binding to its receptor was more sensitive to cADPR in microsomes from the 3-week-old rats than those from the new-born rats. Microsomes from the new-born rats exhibited TG-sensitive (IC50 30 +/- 4 nM) and TG-insensitive forms of Ca(2+)-ATPase, while microsomes from the 3-week-old rats exhibited only the TG-sensitive form of Ca(2+)-ATPase (5 +/- 1 nM IC50). Microsomes from the 3-week-old rats were more sensitive to TG but less sensitive to IP3, while microsomes from the new-born rats were more sensitive to IP3 but less sensitive to TG. The lower TG sensitivity of the new-born Ca2+ store may be because they poorly express a 45 amino acid C-terminal tail of Ca(2+)-ATPase that contains the TG regulatory sites. This site is adequately expressed in the older brain. This suggests that: (1) the new-born brain contains fully operational IP3 pathway but poorly developed cADPR pathway, while the older brain contains both IP3 and cADPR pathways; and (2) a developmental switch occurs in the new-born Ca(2+)-ATPase as a function of maturity.     

Cysteamine can induce duodenal ulceration in rats without depletion of immunoreactive somatostatin.

Single subcutaneous administration of cysteamine (2-aminoethanethiol, CSH) produces duodenal ulceration in rats within 24 h. Depletion of circulating and tissue somatostatin (SOM), hypergastrinemia and gastric acid hypersecretion have all been postulated as the pathophysiological response to CSH leading to ulceration. The purpose of this study was to analyze the synthesis, storage and secretion of gastrin and SOM as well as structural changes in SOM peptide after CSH treatment. Injection of 300 mg/kg (s.c.) of CSH caused macroscopic duodenal ulcers in seven out of eight rats at 24 h. Hypergastrinemia was seen within 30 min (from 23 +/- 4 to 74 +/- 20 pmol/l), and persisted for 4 h. Antral gastrin content was elevated at 30 min (2539 +/- 114 pmol/g) when compared to saline controls (1589 +/- 101 pmol/g). Plasma SOM did not change over the 24 h but antral SOM increased at 30 min (from 120 +/- 3 to 230 +/- 23 pmol/g) and remained elevated at 2 h (374 +/- 48 pmol/g) and 4 h (357 +/- 37 pmol/g). Fundic and duodenal SOM followed a similar pattern. Antral SOM mRNA was also elevated over the first 4 h (3-fold increase, P less than 0.05). HPLC analysis of antral tissue extracts revealed the presence of additional molecular forms of SOM which, however, differed from the major products of in vitro reduction with either CSH or dithiothreitol. Thus, the in vivo effect of CSH on SOM cannot be solely explained by a reductive opening of the disulphide bond. These results suggest that duodenal ulceration in rats treated with CSH is not related in a simple fashion to depletion of immunoreactive SOM. Early induction of hypergastrinemia may be important in the onset of ulceration. The value of CSH as a SOM depleting tool in gastrointestinal tissue must remain in doubt.     

A method for maintaining normoglycemia during labour and delivery in insulin-dependent diabetic women.

The effectiveness of combining the subcutaneous administration of short- and intermediate-acting insulin with the intravenous infusion of glucose in maintaining normoglycemia during labour and delivery in insulin-dependent diabetic women was tested. Fifty women were given intermediate-acting insulin twice daily in doses that were fractions of their usual dose, based on the projected duration of labour. In addition, they were given regular (i.e., short-acting) insulin every 6 hours, the dose being 1% of their total daily insulin dose for every increase of 10 mg/dl above 100 mg/dl (5.6 mmol/l) in the plasma glucose level 1 hour previously; the levels were measured every 3 hours. All the patients were fasting and received a basal intravenous infusion of 6 g/h of glucose; the rate of infusion was increased by 1 g/h for every decrease of 10 mg/dl in the plasma glucose level below 100 mg/dl. The mean plasma glucose levels (+/- standard deviation) were 90 +/- 46 mg/dl after 3 hours of labour, 92 +/- 35 mg/dl after 6 hours, 97 +/- 49 mg/dl after 9 hours and 107 +/- 65 mg/dl after 12 hours. With only one exception, in a premature infant, the 5-minute Apgar scores were identical to those of the infants of nondiabetic women.     

Cutaneous water loss and lipids of the stratum corneum in two syntopic species of bats

The lipid matrix of the stratum corneum (SC), the outer layer of the epidermis of mammals and birds, constitutes the barrier to diffusion of water vapor through the skin. The lipids of the SC are structured in the intercellular spaces of the mammalian epidermis in ordered layers, called lamellae, which have been postulated to prevent water loss. Lipids in the mammalian SC are mainly cholesterol, free fatty acids and ceramides, the latter forming the structural support for the lamellae. However, knowledge on how the lipid composition of the SC alters cutaneous water loss (CWL) in mammals is rudimentary, and is largely derived from studies on laboratory animals and humans. We measured CWL of individuals of two species of syntopic bats, Tadarida brasiliensis and Myotis velifer. In the first study of its kind on wild mammals, we correlated CWL with the lipid composition of the SC, measured using thin layer chromatography and high performance liquid chromatography coupled with atmospheric pressure photoionization mass spectrometry. Surface-specific CWL was 20.6% higher in M. velifer than in T. brasiliensis, although differences were not significant. Compared with individuals of M. velifer, individuals of T. brasiliensis had more classes, and a higher proportion, of polar ceramides in the SC, a feature associated with lower CWL. Individuals of T. brasiliensis also had a class of non-polar ceramides that presumably spans the lamellae and gives more cohesiveness to the lipid matrix of the SC. We conclude that qualitative and quantitative modifications of the lipid composition of the SC contribute to regulate CWL of these two species of bats.     

Nitric oxide production in newborns under phototherapy.

Nitrogen monoxide (NO) is a potent endogenous vasodilator and is involved in cytotoxicity, neurotransmission, and immunological defense mechanisms. Phototherapy has long been known to change the distribution of blood flow throughout the body in newborn infants. The objective of this study was to investigate the effect of phototherapy on NO production in otherwise healthy newborns. Urinary NO levels were measured before and 6 h after phototherapy by a chemiluminescence method using Sievers NOA. Ten newborns (gestational age, 36.4 +/- 3.9 weeks; birth weight, 2863 +/- 677.44 g; postnatal age, 5.1 +/- 2.72 days) were started on phototherapy according to AAP guidelines and urine for NO measurement was collected prior to therapy and 6 h after the commencement of treatment. Urinary NO levels measured during phototherapy were significantly higher (108.8+/-50.69 micromol/mmol creatinine) than the levels measured before phototherapy (73.13+/-34.15 micromol/mmol creatinine; P < 0.05). These results suggest that newborns receiving phototherapy might have increased NO production, which might result in hemodynamic changes. However, further studies on the effects of phototherapy on NO and photorelaxation are needed before reaching firm conclusions.     

Cutaneous water loss and the development of the stratum corneum of nestling house sparrows (Passer domesticus) from desert and mesic environments

Evaporation through the skin contributes to more than half of the total water loss in birds. Therefore, we expect the regulation of cutaneous water loss (CWL) to be crucial for birds, especially those that live in deserts, to maintain a normal state of hydration. Previous studies in adult birds showed that modifications of the lipid composition of the stratum corneum (SC), the outer layer of the epidermis, were associated with changes in rates of CWL. However, few studies have examined the ontogeny of CWL and the lipids of the SC in nestling birds. In this study, we measured CWL and the lipid composition of the SC during development of nestlings from two populations of house sparrows, one from the deserts of Saudi Arabia and the other from mesic Ohio. We found that desert and mesic nestlings followed different developmental trajectories for CWL. Desert nestlings seemed to make a more frugal use of water than did mesic nestlings. To regulate CWL, nestlings appeared to modify the lipid composition of the SC during ontogeny. Our results also suggest a tighter regulation of CWL in desert nestlings, presumably as a result of the stronger selection pressures to which nestlings are exposed in deserts.     

beta-Glucocerebrosidase activity in the stratum corneum of house sparrows following acclimation to high and low humidity

Skin is an important avenue of water loss in terrestrial birds, so environmental conditions that necessitate water conservation should favor physiological mechanisms that reduce cutaneous water loss (CWL). Skin resistance to CWL is conferred by a barrier of lipid molecules located in the stratum corneum (SC), the outer layer of the epidermis. In mammals, SC barrier function depends on the conversion of cerebrosides to ceramides by the enzyme beta -glucocerebrosidase ( beta -GlcCer'ase). Avian SC contains both cerebrosides and ceramides, suggesting that observed plasticity in CWL may be mediated by changes in beta -GlcCer'ase activity and resultant SC lipid composition. We tested the hypothesis that changes in ambient humidity would alter beta -GlcCer'ase activity by acclimating house sparrows (Passer domesticus) to either dry (6.5 g H(2)O m(-3) absolute humidity) or humid (31 g H(2)O m(-3)) conditions for 5 and 21 d at 30 degrees C and then measuring beta -GlcCer'ase activity from SC homogenates. Our results provide the first characterization of beta -GlcCer'ase activity in any nonmammalian vertebrate. Relative to nonacclimated controls, both dry- and humid-acclimated sparrows had significantly elevated beta -GlcCer'ase activity at 21 d postacclimation. Across individuals, we observed negative correlations between beta -GlcCer'ase activity and both CWL and SC ceramide content. Although dry- and humid-acclimated sparrows did not differ in beta -GlcCer'ase activity, these results are consistent with our findings that both humidity treatments caused a reduction in CWL and similar changes in SC lipid composition. Our results demonstrate physiological plasticity in CWL and provide tentative support for a role of beta -GlcCer'ase in mediating this response.     

The purine nucleotide cycle in the regulation of ammoniagenesis during induction and cessation of chronic acidosis in the rat kidney.

The effect of chronic acid feeding and its subsequent withdrawal was determined on the amounts of the metabolic intermediates and enzymic activities of the purine nucleotide cycle. Sprague-Dawley rats were given 1.5% (w/v) NH4Cl in their drinking water for 5 days. The renal excretion of NH3 rose 70-fold and the rats developed acidosis. The amount of renal IMP rose from a control value of 4.5 +/- 2.2 to 20.4 +/- 3.7nmol/g of kidney after 48h of acid feeding (P less than 0.001) and fell to normal within 48h of the recovery. Adenylosuccinate concentrations fell from a control value of 4.5 +/- 0.9nmol/g of kidney to 1.2 +/- 0.3nmol/g (P less than 0.005) by day 5 of acidosis and continued to fall to undetectable values by 48h after recovery. The amount of AMP remained constant through the acid-feeding and the recovery periods. The activity of adenylosuccinate synthetase, the rate-limiting enzyme of the purine nucleotide cycle, paralleled the rise and fall in NH3 excretion. The activities of phosphate-dependent glutaminase and glutamate dehydrogenase were elevated during the acid-feeding and the recovery period. Thus changes in the purine nucleotide cycle correlate with changes in NH3 excretion to a more parallel degree than does the activity of glutaminase or glutamate dehydrogenase.     

Surfactant disaturated phosphatidylcholine kinetics in infants with bronchopulmonary dysplasia measured with stable isotopes and a two-compartment model.

We previously found a shorter surfactant disaturated phosphatidylcholine palmitate (DSPC-PA) half-life in infants with bronchopulmonary dysplasia (BPD) by using a single stable isotope tracer and simple formulas based on a one-exponential fit of the final portion of the enrichment decay curve. The aim of this study was to apply noncompartmental and compartmental analysis on the entire enrichment decay curve of DSPC-PA and to compare the kinetic data with our previous results. We analyzed 10 preterm newborns with BPD (gestational age 26 +/- 0.6 wk, weight 777 +/- 199 g) and 6 controls (gestational age 26 +/- 1.4 wk, weight 787 +/- 259 g). All took part in our previous study. Endotracheal 13C-labeled dipalmitoyl phosphatidylcholine was administered, and the 13C-enrichment of surfactant DSPC-PA was measured from serial tracheal aspirates by gas chromatography-mass spectrometry. Noncompartmental and compartmental models were numerically identified from the tracer-to-tracee ratio and kinetic parameters related to the accessible (pool accessible to sampling, likely to be the lung alveolar pool) and to the nonaccessible pools (pools not accessible to samplings, likely to be the intracellular storage pool) were estimated in the two study groups. Comparison was performed by Mann-Whitney test. A two-compartment model provided the most reliable assessment of DSPC-PA kinetics. In BPD vs. controls, mean +/- SE residence time of DSPC-PA in the accessible was 17.5 +/- 2.6 vs. 32.2 +/- 6.4 h (P < 0.05), whereas it was 49.7 +/- 3.5 vs. 54.4 +/- 3.9 h (NS, not significant) in the nonaccessible pool; DSPC-PA recycling was 0.26 +/- 0.05 vs. 0.43 +/- 0.04% (NS), respectively. A two-compartment model of surfactant DSPC-PA kinetics allowed a thorough assessment of DSPC-PA kinetics, including masses, synthesis, and fluxes between pools. The most important findings of this study are that in BPD infants DSPC-PA loss from the alveolar pool was higher and recycling through the intracellular pool lower than in controls.     

The prenatal and postnatal development of UDP-glucuronyltransferase activity towards bilirubin and the effect of premature birth on this activity in the human liver.

Liver UDP-glucuronyltransferase activity towards bilirubin was studied in a total of 88 human subjects, including foetuses, premature and full-term newborn babies, infants, children, and adults. Determination of very low enzyme activity was performed by high-pressure liquid chromatography. Prenatal and postnatal changes of the activity can be divided into four developmental phases, i.e. middle foetal, late foetal, neonatal and early infantile, and mature. The activities of the first three phases corresponded to about 0.1, 0.1-1 and 1-100%, respectively, of the mature-phase values (mean +/- S.D.: 1320 +/- 514 microgram/h per g of liver, n = 27).