Unaltered Rate Research Articles

Hypertension due to loss of water

In the current issue of Acta Physiologica, two papers are published investigating the development of arterial hypertension under conditions of pathological loss of free water in two disease models. Kovaric et al 1 studied rats with chronic renal failure, shedding excessive free water via their remnant kidney due to a hypostenuric concentrating defect. Wild et al. 2 investigated a transgenic mouse model for psoriasis, losing free water via the psoriatic skin lesions. In both cases the animals displayed hypertension, cutaneous vasoconstriction, and metabolic adaptations towards enhanced production of urea and organic osmolytes typical for a phylogenetically ancient water conservation response termed aestivation 3 . The international consortia of investigators spearheaded by Titze, Karbach, and Kitada therefore conclude that in both cases the hypertension was due to cutaneous vasoconstriction in an attempt to limit epidermal water loss. Because in either case the hypertension was associated with loss of water, and thus with hypo- rather than hypervolemia, the authors argue, that this concept of pathogenesis of hypertension is antipodal to the classic view that relies on hypervolemia due to sodium retention.

Effects of Rate Manipulation on Intelligibility in Children With Cerebral Palsy.

Purpose We evaluated the effects of a speech supplementation strategy to reduce rate and improve intelligibility in children with cerebral palsy. Method Twenty-five children with cerebral palsy (M age = 12.08 years) completed a structured speaking task in 2 speech conditions: habitual speech and slow speech. Fifteen children had mild intelligibility deficits; 10 had moderate-severe intelligibility deficits. In each condition, children repeated utterances of 2-7 words in length. In the habitual speech condition, children used their natural and unaltered speaking rate. In the slow speech condition, children were cued to insert pauses between words. Intelligibility ratings were obtained from orthographic transcriptions by unfamiliar adult listeners (n = 100). Speech rate, in words per minute, was measured for each utterance. Results All children, regardless of severity group, were able to reduce their rate of speech when implementing the slow speech strategy. Only children in the moderate-severe group showed an improvement in intelligibility when implementing the slow speech strategy. Although there was considerable individual variability, there was a greater improvement in intelligibility for longer utterances compared to shorter ones. Conclusion A slow speech strategy may be beneficial for children with moderate-severe intelligibility deficits who speak in longer utterances. Future studies should seek to further examine the clinical feasibility of slow speech for children with reduced intelligibility.

<strong>Influence of food availability, predation risk and initial body size on growth and maturation of <em>Cloeon dipterum</em> (Ephemeroptera: Baetidae)</strong>

Larval growth and maturation in aquatic insects are phenotypically plastic and can change in response to the amount and quality of resources, or under predation risk. While better food conditions typically lead to faster growth and earlier maturation at larger body size and hence higher fecundity, the effects of predation risk can vary depending on its strength and selectivity with respect to size or stage. Studies on lotic mayflies (Ephemeroptera) have reported two direct and two indirect life history responses to increased predation risk: slower growth rate and later maturation at the same or smaller size, and faster or unaltered growth rate and earlier maturation at smaller body size. However, life history responses of standing water mayflies to predation risk are unknown. To fill this gap, we carried out a full-factorial laboratory experiment to study the influence of food availability (full/reduced) and predation risk (present/absent predator cues) by dragonfly larvae on growth and maturation of larvae of the lentic mayfly Cloeon dipterum. Males and females responded similarly to food limitation and predation risk. Predation risk had no effect on maturation size, larval mortality and metamorphic failure. However, growth rate, number of moults and development time were all affected by predation risk, and its net effect was modified by food availability and initial body size of the larvae. These results suggest that life history responses to suboptimal conditions depend on body size at the onset of such conditions. Finally, a small group of larvae grew at much slower rates and developed much longer than other individuals of similar initial size, possibly due to bet-hedging or inclusion of multiple genotypes in the experiment.

GENO-11PERIOSTIN MAINTAINS A MESENCHYMAL PROGRAM IN GLIOBLASTOMA STEM CELLS

Our radiogenomic screen identified Periostin (POSTN) to be highly expressed in glioblastoma (GBM) with high edema/FLAIR. Subsequently, POSTN is implicated in glioblastoma invasion and recruitment of tumor associated macrophages. However, its impact on glioblastoma stem cells (GSC) biology/properties is largely unknown. Here GSC lines with high endogenous POSTN expression levels were used to generate inducible shRNA mediated loss of function (LOF) clones. GSCs with low/undetectable levels of POSTN expression were used to generate Gain of function (GOF) clones. In vitro tests were performed to assess the impact of POSTN LOF and GOF on GSC properties such as self-renewal, BrdU label retention, differentiation potential etc. We show that GSCs with POSTN LOF acquired an increased stem like state with unaltered proliferation rate. When these clones were implanted at orthotopic locations in mouse, POSTN LOF was associated with increased survival of mice. Cells of human origin were isolated from tumors using human specific HLA Class I ABC antibody by FACS. Total RNA from these sorted cells (without cell-culture) were used for expression profile analysis by HTA 2.0 array from affymetrix. Transcriptome analyses of POSTN LOF cells show inhibition of multiple mesenchymal associated networks such as CEBPB (a master regulator of mesenchymal program in GBM), PRDM1, TGFB1, FGF2, WNT3A, HIF1A etc. with concomitant activation of MYCN network, indicating a mesenchymal to proneural switch. We have generated POSTN and CEBPB dual knockdown clones and are currently investigating the molecular link between these two key mesenchymal genes in GSC context. Our results show that POSTN maintains a mesenchymal program in GSC by coopting with intracellular factors such as CEBPB. Therefore, neutralizing extracellular POSTN will have far reaching impact in terms of therapeutics where while blocking GBM invasion and it may simultaneously block a mesenchymal program in stem cell niche in GBM.

Nanocomposite Elastomeric Biomaterials for Myocardial Tissue Engineering Using Embryonic Stem Cell‐derived Cardiomyocytes

AbstractRegeneration or repair of the damaged myocardium requires different strategies including engineered constructs for more efficient cell delivery. This study was undertaken to examine the potential of a new nanostructured elastomer to deliver embryonic stem cell‐derived cardiomyocytes (ESC‐CM) to an infarcted area of the myocardium. Engineered materials were biocompatible, mechanically stable, and elastomeric nanocomposites serving as substrates for delivery of ESC‐CM and as a left ventricular support device in myocardial regeneration strategies. Materials investigated were soft and strong poly(aliphatic/aromatic‐ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized fatty acid, i.e., dilinoleic acid (DLA) soft segments, respectively, with and without addition of 0.2 wt% TiO2 nanoparticles to form nanocomposites. The PET/DLA‐TiO2 nanocomposite exhibited over 8 MPa tensile strength and 900% elongation at break. Addition of TiO2 nanoparticles significantly altered surface roughness and enhanced adhesion and spreading of ESC‐CM derived from mouse and human embryonic stem cells. The newly developed materials did not affect the functional activity of spontaneously beating hESC‐CM, as demonstrated by unaltered rate of their beating, and the cells continued to demonstrate contractile activity on the materials for more than two months in culture (the longest time tested). Quantitative proliferation and survival assays using fibroblasts confirmed the ability of the new materials to support cells as well as or better than the present commercial‐type thermoplastic elastomer analog. The results indicate that PET/DLA and PET/DLA‐TiO2 are promising candidates for the manufacture of engineered patches to deliver ESC‐CMs.

Inhibition of Alloantigen‐Primed Memory CD4+ and CD8+ T Cells by Hematopoietic Chimerism in Mice

Donor-reactive memory T cells present a special hurdle in transplantation. Although hematopoietic chimerism is effective for inducing donor-specific tolerance, the effects on memory T cells are unclear. Here, we induced stable chimerism and tolerance in mice (Tolerance group, n = 6) by donor-specific transfusion (DST) plus anti-CD154 monoclonal antibody (mAb), avoiding the toxic myeloablative conditioning treatment to assist bone marrow transplantation (DST/aCD154&BMTx). We then transferred memory CD4(+) or CD8(+) T cells from donor antigen primed mice to the tolerance-induced recipients 4 days after heart transplantation (Tol/CD4(+) Tm group and Tol/CD8(+) Tm group, n = 6, respectively), but neither of these memory T-cell subsets had an effect on the permanent graft survival (median survival time > 100 days). The unaltered rate of memory T cells in spleen and anergy to donor antigen in vitro demonstrated that these memory T cells were well controlled. The chimerism-promoting protocol DST/aCD154&BMTx produced an immune environment that included high levels of regulatory T cells (Tregs), microchimerism and TGF-beta, all of which may act in suppressing the donor-reactive memory CD4(+) or CD8(+) T cells. These findings have potentially important implications for designing approaches to suppressing memory T cells for success of transplantation.

Hydrodynamics of cytoplasmic streaming and the cytoskeletal tubulin component in cells of Elodea densa internodes

A spin-echo NMR method was applied to study hydrodynamic parameters of cytoplasmic streaming and to examine translational diffusion of cytoplasmic water in stems of elodea (Elodea densa (Planch.) Casp.) treated with antimitotic drugs. Within the first few hours after colchicine treatment, the dynamics of translational displacement followed the curve with a transient maximum. The action of vinblastine was manifested in a monotonic decrease of the translational diffusion. After 24-h treatments with colchicine and vinblastine, the translational diffusion was slowed down. All these changes induced by antimitotic drugs were observed on the background of unaltered rate of cytoplasmic streaming.

Mitochondrial Calcium Transport and Mitochondrial Dysfunction After Global Brain Ischemia in Rat Hippocampus

Here we report effect of ischemia-reperfusion on mitochondrial Ca2+ uptake and activity of complexes I and IV in rat hippocampus. By performing 4-vessel occlusion model of global brain ischemia, we observed that 15 min ischemia led to significant decrease of mitochondrial capacity to accumulate Ca2+ to 80.8% of control whereas rate of Ca2+ uptake was not significantly changed. Reperfusion did not significantly change mitochondrial Ca2+ transport. Ischemia induced progressive inhibition of complex I, affecting final electron transfer to decylubiquinone. Minimal activity of complex I was observed 24 h after ischemia (63% of control). Inhibition of complex IV activity to 80.6% of control was observed 1 h after ischemia. To explain the discrepancy between impact of ischemia on rate of Ca2+ uptake and activities of both complexes, we performed titration experiments to study relationship between inhibition of particular complex and generation of mitochondrial transmembrane potential (DeltaPsi(m)). Generation of a threshold curves showed that complex I and IV activities must be decreased by approximately 40, and 60%, respectively, before significant decline in DeltaPsi(m) was documented. Thus, mitochondrial Ca2+ uptake was not significantly affected by ischemia-reperfusion, apparently due to excess capacity of the complexes I and IV. Inhibition of complex I is favourable of reactive oxygen species (ROS) generation. Maximal oxidative modification of membrane proteins was documented 1 h after ischemia. Although enhanced formation of ROS might contribute to neuronal injury, depressed activities of complex I and IV together with unaltered rate of Ca2+ uptake are conditions favourable of initiation of other cell degenerative pathways like opening of mitochondrial permeability transition pore or apoptosis initiation, and might represent important mechanism of ischemic damage to neurones.

Tuber-specific Cytosolic Expression of a Bacterial Phosphoglucomutase in Potato (Solanum tuberosum L.) Dramatically Alters Carbon Partitioning

Constitutive antisense inhibition of the cytosolic isoform of phosphoglucomutase in the potato (Solanum tuberosum L.) results in restriction of photosynthesis, growth inhibition and modified tuber morphology, and a severe restriction of tuber starch synthesis. Here we describe the consequences of the tuber-specific expression of an Escherichia coli phosphoglucomutase in the cytosol. Analysis of [14C]glucose metabolism by tuber discs isolated from wild type and transformants revealed that the rates of sucrose and starch synthesis were unaltered but that the rate of glycolysis was depressed in the transgenics. The transformant tubers also contained dramatically reduced amino acid content and significantly higher levels of ADP, but were characterized by elevated levels of Krebs cycle intermediates and an unaltered rate of respiration. In addition to these metabolic consequences of the overexpression of the E. coli enzyme, we observed morphological changes in tubers, with the transformants having a smaller number of larger tubers which exhibited delayed rates of sprouting with respect to the wild type. These results are discussed with respect to current models of the regulation of central plant metabolism and tuber dormancy.

Insulin sensitivity and lipolysis in adolescent girls with poorly controlled type 1 diabetes: effect of anticholinergic treatment

Increased GH secretion could be one factor behind the impaired glycaemic control often seen in adolescent girls with type 1 diabetes. Because GH induces insulin resistance, treatment with anticholinergic agents, such as pirenzepine (PZP), has been used to reduce GH secretion. However, in a previous study of adolescent girls with type 1 diabetes, we observed an improvement in glycaemic control during 12 weeks of PZP therapy despite unchanged excretion of GH in urine. Considering the complex mechanisms behind urinary GH excretion, the effects of PZP on pituitary GH secretion or secretory pattern cannot be excluded. Thus, to assess the effect of anticholinergic treatment on metabolic control in adolescent girls with diabetes, we have investigated GH secretion, insulin sensitivity and lipolysis before and during treatment with PZP. Eleven adolescent girls with type 1 diabetes and poor metabolic control were investigated before and after treatment with PZP, 100 mg orally, twice a day for 3 weeks. Serum samples for analysis of haemoglobin A1c and IGF-I were obtained in addition to serum profiles of GH, insulin and IGFBP-1 before and after 3 weeks of PZP treatment. Effects on insulin sensitivity and lipolysis were also assessed. IGFBP-1 was measured every hour, whereas serum GH and insulin were measured every 20 min for 24 h. Insulin sensitivity was analysed with the hyperinsulinaemic euglycaemic clamp technique. The rate of lipolysis was assessed under basal conditions following a constant rate infusion of [1,1,2,3,3-2H5]-glycerol. In five girls, lipolysis was also estimated during the hyperinsulinaemic euglycaemic clamp. There was a significant reduction in haemoglobin A1c levels (9.9 +/- 0.2%vs. 9.1 +/- 0.2; P < 0.0001) during 3 weeks of PZP treatment. In additional, the glucose requirement during the euglycaemic hyperinsulinaemic clamp increased by more than 30% (72.5 +/- 4.9 vs. 96.8 +/- 8.5 mg/m2/min; P = 0.003). However, we could not demonstrate any significant changes in GH secretion (area under the curve, basal levels or peak amplitude) or in the GH secretory pattern (peak height, peak length or interpeak interval). Concordantly, the IGF-I levels were statistically unchanged, as were IGFBP-1 concentrations. The rate of lipolysis did not change under basal conditions (3.40 +/- 0.53 vs. 3.04 +/- 0.54 micro mol/kg/min, n = 11, P = 0.54) or during the hyperinsulinaemic euglycaemic clamp (1.58 +/- 0.21 vs. 2.08 +/- 0.26 micro mol/kg/min; n = 5, P = 0.32). Our observations of an increased glucose requirement during the clamp as well as a decrease in haemoglobin A1c demonstrate improved insulin sensitivity in the adolescent girls with diabetes following pirenzepine therapy. The mechanism behind the improvement is not clear, as neither secretion nor the secretory pattern of GH changed significantly. The persistently high levels of GH might explain the unaltered rate of lipolysis despite the improved insulin sensitivity. The observed improvement in glycaemic control in adolescent girls with type 1 diabetes following pirenzepine therapy is promising, although more studies on this topic are needed.

Uterine nitric oxide and prostaglandin E during embryonic implantation in non-insulin-dependent diabetic rats.

In the process of embryo implantation in the rat, both nitric oxide and prostaglandins act as vascular and myometrial regulators. The aim of the present work was to evaluate the effect of diabetes on the synthesis of both agents during embryo implantation. In diabetic rats, uterine activity of the enzyme nitric oxide synthase and prostaglandin E production were increased during peri-implantation compared to the control group (P < 0.05 and P < 0.001, respectively). Both parameters showed a prolonged increase in temporal profile during peri-implantation days. Local production of nitric oxide and prostaglandin E in the implantation sites was higher in diabetic rats (P < 0.05), but the intersite:site ratio was similar to that of the control group. On the other hand, the implantation rate and the timing of the beginning of this process were not altered in the diabetic group. These results suggest that the vasoactive modulators of the implantation process, nitric oxide and prostaglandins, are increased in this diabetic pathology, and that this increase is probably functioning as a compensatory mechanism, so as to allow an unaltered rate of embryo implantation in this model.

Small-molecule-substrate interactions with a self-aminoacylating ribozyme

A self-aminoacylating RNA catalyst is shown to carry out the chemistry required for turnover, being reacylated several times from aminoacyl-AMP with an unaltered rate, thereby meeting one definition of an enzyme. Furthermore, a newly applied gel electrophoresis assay suggests first order kinetics in RNA and saturation kinetics in the substrate aminoacyl-adenylate, implying a Michaelis complex. AMP is a competitive inhibitor, though phenylalanine is not detectably inhibitory, consistent with a Michaelis complex through the AMP moiety of phenylalanyl-adenylate substrate. This idea is supported by measurement of elevated acylation velocities with seryl and alanyl-adenylates. The rate of aminoacylation increases with pH, consistent with attack of a terminal ribose oxyanion on the carbonyl carbon atom of the adenylate.

Pentagastrin increases pepsin secretion without increasing its fractional synthetic rate

We studied the effects of increasing doses of pentagastrin on gastric secretion of pepsin and on incorporation of L-[1-13C]leucine into gastric aspirate protein as an index of pepsin synthesis. Pentagastrin (0.25-4.0 micrograms.kg-1.h-1) significantly increased pepsin output from basal 76 mg/h to < or = 181 mg/h but did not significantly alter incorporation of L-[1-13C]leucine from the basal fractional synthetic rate of 3.63 +/- 0.05%/h. In four subjects in whom infusion of tracer leucine was continued for > 1 day, aspiration of pepsin between 24 and 27 h demonstrated that plateau 13C labeling of leucine in pepsin had been attained, but at a value that was only 48% of the 13C labeling of plasma alpha-ketoisocaproic acid (alpha-KIC) [0.730 +/- 0.02 (SE) vs. 1.520 +/- 0.14 atoms %excess]. This suggests that actual rates of pepsin synthesis were approximately double those calculated on the basis of alpha-KIC labeling. The results are consistent with an interpretation that increasing doses of pentagastrin cause increased secretion of pepsinogen by recruitment of gastric chief cells, each synthesizing pepsinogen at an unaltered rate. Plateau 13C enrichment of alpha-KIC may not be a valid surrogate for plateau 13C leucine enrichment when fractional synthetic rates of some secreted proteins are calculated.

Evidence for substrate-assisted catalysis in the DNA cleavage of several restriction endonucleases

Substrate-assisted catalysis was suggested to be involved in the DNA cleavage reaction of the restriction endonucleases (ENases) EcoRI and EcoRV, because experimental evidence exists that the phosphate group 3′ to the scissile bond serves to deprotonate the attacking water. Here, we have addressed the question whether this is a general mechanistic feature of the reactions catalyzed by ENases. For this purpose, the cleavage rates of modified and unmodified oligodeoxyribonucleotides (oligos), in which the phosphate group 3' to the scissile bond is substituted by a methyl phosphonate, were measured for 17 enzymes. Only five turned out not to be inhibited by this modification ( BglII, BstI, BstYI, Cfr10I and MunI); all others cleave the modified substrate at a strongly reduced rate or not at all. By employing a hemisubstituted oligo substrate we were able to further investigate the mechanism of inhibition of the latter group of ENases. Some of them cleave the unmodified strand of the modified substrate with a nearly unaltered rate, whereas the modified strand is cleaved very slowly or not at all ( BamHI, Bsp143I, Eco72I, MflI, NdeII, Sau3AI, XhoII). The others ( AluI, Cfr9I, DpnII, MboI, PvuII) cleave the modified strand of the modified substrate with a largely reduced rate or not at all. These ENases, however, cleave the unmodified strand with a reduced rate, too. Based on these results we conclude that BamHI, Bsp143I, Cfr9I, DpnII, Eco72I, MboI, MfII, NdeII, PvuII, Sau3AI and XhoII may possibly employ substrate assistance in catalysis.

Hexose metabolism in pancreatic islets

In rat pancreatic islets, a rise in extracellular D-glucose concentration is known to cause a greater increase in the oxidation of D-[6-14C]glucose than utilization of D-[5-3H]glucose. In the present study, such a preferential stimulation of acetyl residue oxidation relative to glycolytic flux was mimicked by nutrient secretagogues such as 2-aminobicyclo[2,2,1]heptane-2-carboxylate, 3-phenylpyruvate, L-leucine, 2-ketoisocaproate, D-fructose and ketone bodies. The preferential stimulation of D-[6-14C]glucose oxidation by these nutrients was observed at all hexose concentrations (0.5, 6.0 and 16.7 mM), coincided with an unaltered rate of D-[3,4-14C]glucose oxidation, was impaired in the absence of extracellular Ca2+, and failed to be affected by NH4+. Although the ratio between D-[6-14C]glucose oxidation and D-[5-3H]glucose utilization in islets exposed to other nutrient secretagogues could be affected by factors such as isotopic dilution and mitochondrial redox state, the present data afford strong support to the view that the preferential stimulation of oxidative events in the Krebs cycle of nutrient-stimulated islets is linked to the activation of key mitochondrial dehydrogenases, e.g. 2-ketoglutarate dehydrogenase. The latter activation might result from the mitochondrial accumulation of Ca2+, as attributable not solely to stimulation of Ca2+ inflow into the islet cells but also to an increase in ATP availability.

Area Under the Curve Monitoring of Cyclosporine Therapy

The impact of a new monitoring strategy on whole blood concentrations of cyclosporine measured by a specific monoclonal radioimmunoassay was investigated in a group of 37 renal transplant patients. Before transplantation, the patients received a standard intravenous (i.v.) and oral (p.o.) test dose of cyclosporine to calculate their individual i.v. and p.o. starting dose rates to achieve a certain target steady-state cyclosporine concentration. After transplantation, the designated i.v. dose rate was continuously infused for 2 days, at which time the steady-state concentration was measured. Then, the designated oral dose for 24 h was administered while the infusion was continued at an unaltered rate. The oral absorption of cyclosporine was documented by blood samples over the following 8 h. If necessary, this overlap of i.v. and p.o. dosing was repeated until blood concentrations of cyclosporine rose at least 700 ng/ml over the steady-state concentration. By that time, the infusion was stopped and oral dosing continued. Individualized infusions led to steady-state concentrations within a range that did not exceed 1.1 times the median concentration of 472 ng/ml. Standard infusion rates in the past produced a much wider range of steady-state concentrations (9.6 times the median). Individualized infusions reached the target steady-state concentration with a significant positive bias of 17% (SEM = +/- 32%, range of -36 to +105%). Individualized oral doses reached the target average steady-state concentration (calculated by dividing the area under the concentration-time curve by the dosing interval) with an inferior precision (median = 2.6%, range of -54 to +130%) but without a positive or negative bias.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of rolipram on the cyclic 3′,5′adenosine monophosphate response to histamine and adenosine in slices of guinea-pig cerebral cortex

The effect of the phosphodiesterase (PDE) inhibitor rolipram on the cyclic AMP responses to adenosine, histamine and combinations of these two agonists, was examined in [ 3H]adenine-labelled slices of guinea-pig cerebral cortex. Constant levels of [ 3H]-cyclic AMP were achieved within 10 min of agonist addition, both in the presence and absence of rolipram (0.1 mM). Histamine (1 mM) produced an 8-fold increase in [ 3H]-cyclic AMP (compared with basal) which was increased 7-fold by rolipram. The responses to adenosine (0.1 mM) and adenosine and histamine in combination were larger than that to histamine alone (46-fold or more compared with basal) but the potentiation by rolipram was much smaller (2.5-fold or less). With both agonists the effect of rolipram was dose-dependent, the steady state [ 3H]-cyclic AMP levels increasing 1-2-fold for a 10-fold increase in rolipram concentration. Removal of the histamine or adenosine stimulus once steady state had been reached resulted in a rapid fall in [ 3H]-cyclic AMP levels with a half time of less than 5 min. Rolipram (0.1 mM) did not significantly alter the initial rates of fall in [ 3H]-cyclic AMP levels but increased the time taken for them to return to basal levels. The findings of higher steady state levels of cyclic AMP in the presence of rolipram, together with an almost unaltered rate of cyclic AMP turnover, are consistent with an interaction of rolipram with PDE which is overcome by an increase in cyclic AMP concentration. However, the relatively smaller effects of rolipram on the higher steady levels of cyclic AMP produced by adenosine and the rather shallow dose-dependence of the PDE inhibitor on the responses to both agonists are inconsistent with a simple competitive inhibition of total PDE activity in responding cells. The results can be explained, however, by the involvement of different forms of PDE, with the rolipram-sensitive, calcium-independent form dominating at low cyclic AMP levels and the rolipram-insensitive, calcium-dependent form becoming more important when cyclic AMP levels are higher.

EFFECTS OF PHOTON IRRADIANCE ON THE GROWTH OF SHOOTS AND ROOTS, ON THE RATE OF INITIATION OF MYCORRHIZAL INFECTION AND ON THE GROWTH OF INFECTION UNITS IN TRIFOLIUM SUBTERRANEUM L.

SUMMARYThe effects of photon irradiance on the growth of young plants (up to three weeks old) of Trifolium subterraneum L. and on the development of mycorrhizal root systems were studied with plants grown in a soil/sand mixture inoculated with Glomus mosseae (Nicol. &amp; Gerd.) Gerdemann &amp; Trappe. Total plant growth was lower when photon irradiance was 100 μmol m−2 s−1, compared with 450 μmol m−2 s−1. Fresh weight of shoots was unaffected, but the fresh weight/dry weight ratio was increased at the lower irradiance in shoots, but not in roots. The main effect of decreased irradiance on the growth of the root system was a reduction in the numbers of first‐ and second‐order lateral roots initiated. The average rate of extension of axial and lateral roots was only slightly reduced. The fraction of the root length infected was lower at the lower irradiance, particularly in the first two weeks. Development of infection was analyzed in terms of the role of formation of mycorrhizal entry‐points (A) and the average rate of growth of infection units (B). Reduction in the fraction of the root length infected was found to be due to a reduction in A. B was remarkably constant at the two irradiances and in the different root subsystems. Thus both roots and infection units respond by making fewer units of unaltered rate of growth.

Roles of adrenergic drugs in the renal pelvic pacemaker control of ureteral peristalsis.

Experiments were performed to explore the influence of noradrenaline and isoproterenol on the ureteral peristalsis in the canine pelviureteral system in vitro. The rhythmic changes of intrapelvic pressure no longer became manifest, and simultaneously recorded electromyograms revealed disappearance of peristalsis at sites distal to the upper region of the renal pelvis following application of isoproterenol, while the pacemaker at the pelvicalyceal border continued to discharge at an unaltered rate. It is concluded from our findings that both noradrenaline and isoproterenol act upon conduction of peristalsis rather than on the pacemaker as such, thereby facilitating or inhibiting the conduction, respectively, in their behavior toward ureteral peristalsis. The results also have demonstrated that the renal pelvic pressure recorded during treatment with isoproterenol did not reflect pacemaker activity of the renal pelvis.

Effect of different doses of D-penicillamine and combined administration of D-penicillamine and methylprednisolone on collagen, glycosaminoglycans, DNA and RNA of granulation tissue, skin, bone and aorta in rats.

D-penicillamine (D-pen) in doses of 20, 100 and 500 mg/kg/day or D-pen 100 mg/kg/day plus methylprednisolone (MP) 2.0 mg/kg/day was administered daily for 42 days to rats implanted with viscose-cellulose sponges. Operated, pairfed rats served as controls. D-pen increased the DNA content of granulation tissue, but had no effect on the amount of tissue produced. In contrast, high dose D-pen reduced the content of DNA and collagen in skin. A dose related inhibition of collagen crosslink formation occurred in all tissues, particularly in skin, as indicated by increased proportions of extractable collagen with increased alpha/beta chain ratio and aldehyde content. Moreover, low doses of D-pen increased the hydroxyproline/proline ratio of acid soluble skin collagen, presumably due to solubilization of type III collagen as demonstrated by SDS-polyacrylamide gel electrophoresis in the presence of 3.6 M urea. These changes were associated with increased skin fragility and edema plus excess elastin deposition in the aorta after high dose D-pen treatment. Low dose D-pen stimulated the 35S-sulphate uptake into the sulphated glycosaminoglycans (GAGs) of granulation tissue without altering their relative amounts, whereas high dose D-pen reduced the concentration of chondroitin-4/6-sulphate in skin. MP antagonized the solubilizing effect of D-pen on collagen, probably by inhibition of the collagen synthesis. In addition, MP inhibited the cell proliferation and GAG metabolism. Food restriction reduced the DNA content of granulation tissue. The inhibitory effect of D-pen on the formation of granuloma collagen crosslinks in the presence of unaltered rate of collagen biosynthesis may diminish the amount of fibrotic tissue due to increased degradability of crosslink deficient collagen. Simultaneous administration of MP may facilitate this effect by inhibiting the biosynthesis of collagen. However, long-term D-pen treatment seems to increase the susceptibility of normal tissues to mechanical injury.