The effects of exogenous histamine in isolated rat hearts

The role of histamine in cardiac physiology and pathophysiology is not clarified, but is dependent on species. The effects of exogenous histamine in Langendorff-perfused rat hearts were investigated. 1 mM, 100, 10, 1 and 0.1 M of histamine (n=7 each) as 15 min infusions were employed in a dose-response study, and compared to control perfused hearts (n=7). In another experimental series, 100 M histamine (n=15) was added during reperfusion after 25 min global ischemia, and compared to control ischemia-reperfusion (n=15). The maximal response to histamine in the dose-response study (100 M) was an increase of left ventricular developed pressure to 126±8% of initial value (mean±SEM, p<0.04), and increase of coronary flow to 152+6% (p<0.02) after 5 min infusion. 100 M histamine did not significantly influence heart rate or rhythm. The lowest concentration (0.1 M) did not have effects cardiac performance. Reperfusion with histamine for 2 min after ischemia reduced left ventricular developed pressure to 68±10% of initial value versus 116+17% in ischemic controls (p<0.05), and increased left ventricular end-diastolic pressure to 24±8 mmHg compared to 6±2 mmHg in controls (p<0.04). Left ventricular pressures were similar in hearts reperfused with histamine and in ischemic controls for the rest of the observation. Coronary flow increased during reperfusion in hearts given histamine. Histamine had a dose-dependent positive inotropic and vasodilatory effect in isolated rat hearts. Exogenous histamine had only minor effects on post-ischemic cardiac function.     

Change in substrate metabolism in isolated mouse hearts following ischemia-reperfusion

Several genetic and transgenic mouse models are currently being used for studying the regulation of myocardial contractility under normal conditions and in disease states. Little information has been provided, however, about myocardial energy metabolism in mouse hearts. We measured glycolysis, glucose oxidation and palmitate oxidation (using ³H-glucose, ¹⁴C-glucose and ³H-palmitate) in isolated working mouse hearts during normoxic conditions (control group) and following a 15 min global no-flow ischemic period (reperfusion group). Fifty min following reperfusion (10 min Langendorff perfusion + 40 min working heart perfusion) aortic flow, coronary flow, cardiac output, peak systolic pressure and heart rate were 44 ± 4, 88 ± 4, 57 ± 4, 94 ± 2 and 81 ± 4% of pre-ischemic values. Rates of glycolysis and glucose oxidation in the reperfusion group (13.6 ± 0.8 and 2.8 ± 0.2 mol/min/g dry wt) were not different from the control group (12.3 ± 0.6 and 2.5 ± 0.2 mol/min/g dry wt). Palmitate oxidation, however, was markedly elevated in the reperfusion group as compared to the control group (576 ± 37 vs. 357 ± 21 nmol/min/g dry wt, p < 0.05). This change in myocardial substrate utilization was accompanied by a marked fall in cardiac efficiency measured as cardiac output/oxidative ATP production (136 ± 10 vs. 54 ± 5 ml/mol ATP, p < 0.05, control and reperfusion group, respectively). We conclude that ischemia-reperfusion in isolated working mouse hearts is associated with a shift in myocardial substrate utilization in favour of fatty acids, in line with previous observations in rat.     

Effects of GABA antagonists,SR 95531 and bicuculline,on GABAA receptor-regulated chloride flux in rat cortical synaptoneurosomes

Synaptoneurosomes isolated from cerebral cortices of male Sprague-Dawley rats were used for studying GABA_A receptor-regulated chloride influx. The in vitro effects of GABA antagonists, SR 95531 (a pyridazinyl GABA derivative) and bicuculline, on pentobarbital-stimulated, muscimol-stimulated or flunitrazepam-enhanced, muscimol-stimulated chloride uptake were studied. The chloride uptake was determined at 30°C, for 5 sec. Pentobarbital and muscimol produced a maximal stimulation of chloride uptake in cortical synaptoneurosomes at 500 M and 50M, respectively. SR 95531 as well as bicuculline had no effect on the basal uptake of chloride. Whereas, SR 95531 (0.3–30 M) and bicuculline (0.1–100 M), when added 5 min before muscimol (50 M), produced a significant concentration-dependent inhibition of muscimol (50 M)-stimulated chloride uptake (IC₅₀ s of 0.89±0.11 M and 13.45±2.10M, respectively). In studies of the inhibitory effects of SR 95531 and bicuculline on pentobarbital (500 M)-stimulated chloride uptake, the IC₅₀ s were 0.81±0.12 M and 3.86±1.14 M, respectively. SR 95531 exhibited a more potent inhibitory effect than bicuculline on flunitrazepam-enhanced, muscimol-stimulated chloride uptake. The results revealed that SR 95531 has a more potent antagonistic effect than bicuculline on GABA_A-regulated chloride flux.     

Analysis of Different Methodological Approaches to Measuring Microtubule Length in the Cytoplasm of Cultured Cells

It is generally assumed that microtubules in tissue culture cells extend from the centrosome to cell periphery, and the length of individual microtubules averages several dozens of microns. However, direct electron-microscopic measurements have cast some doubt on this assumption. In this study, the average length of microtubules in cultured Vero cells was estimated using a combined approach. The length of free cytoplasmic and centrosomal microtubules was determined by means of electron microscopy in serial sections; concurrently, the length of free microtubules in the lamella was measured in preparations stained with tubulin antibodies (an indirect immunofluorescent method), by tracing saltatory particle movements along the microtubules in living cells. According to the data of immunofluorescent microscopy, microtubule length in the lamella averaged 4.57 ± 3.69 m. However, since two or more microtubules can overlap, their length may be slightly overestimated by this method. On the other hand, saltatory movements are easy to monitor and measure fairly accurately, but their range may be shorter than the actual microtubule length because of a limited processiveness of motors (kinesin and dynein). On average, the trajectories of saltatory movements in living cells were 3.85 ± 0.72 m long. At the electron-microscopic level, microtubule length was analyzed using pseudo-three-dimensional reconstructions of the microtubule systems around the centrosome and in the lamella. The length of free microtubules in the lamella reached 18 m, averaging 3.33 ± 2.43 m; the average length of centrosomal microtubules was 1.49 ± 0.82 m. Good correspondence between the data on microtubule length and arrangement obtained by different methods allows the conclusion that most of the free microtubules in Vero cells actually have a length of 2–5 m; i.e., they are much shorter than the cell radius (about 25 m). Microtubules extending from the centrosome are shorter still and do not reach the cell periphery. Thus, most microtubules in the lamella of Vero cells are free and their ordered arrangement is not associated with their attachment to the centrosome.     

Clonal propagation of Callistemon by tissue culture techniques

Callus development in Callistemon viminalis was readily achieved when axillary buds derived from nodal tissue were placed in a medium containing macro- and micro-nutrients, sucrose (0.06 M), inositol (300 M), nicotinic acid (20 M), pyridoxine hydrochloride (3 M), thiamine hydrochloride (2 M), riboflavin (10 M), cytokinins (5 M) and auxins (0.1 M). The presence of benzylaminopurine (5 M) and p-chlorophenoxyacetic acid (0.1 M) promoted the most vigorous callus development and sprout formation. Rooting of nodal material was rare but occurred readily following the transference of sprouts developed on callus to a basal medium containing sucrose and salts. Root initiation was stimulated, however, by the presence of auxins. Chlorophenoxyacetic acid while stimulating root initiation repressed root growth. Indole butyric acid stimulated both root initiation and shoot growth at concentrations of 0.005 to 0.1 M. The treatment of choice for rooting and shoot growth was the addition of indole butyric acid at a concentration of 0.01 M.     

Fine structure of abscission zones

Summary Electron micrographs of the zone of separation in flower pedicels of Lycopersicon esculentum and Nicotiana tabacum are presented with particular reference to the indentation of epidermal tissue in the abscission zone, subcellular organelles, and the cell wall. The indentation or groove which delineates the abscission zone extends some distance into the pedicel with branchings off the main groove. These branches are approximately 20 m in width while the main groove averages approximately 200 m in width. Invaginations of the plasmalemma are observed with considerable frequency. within these invaginations one observes a material of about the same density as the cell wall except that it is more fibrillar. Plasmodesmata are also observed, with considerable branching into middle lamellae of cells comprising the abscission zones. Microbodies with crystalloid cores appear with considerable frequency in cells of the abscission zone. The crystalloids appear to be cubical in shape and are composed of parallel sheets of osmiophilic material. The sheets average about 6 m in thickness and are spaced at 4 m intervals. The microbodies with crystalloid cores are observed to be characteristically of two size groupings. In tobacco the microbodies average 900 m and 1,500 m in profile. In tomato they average 300 m and 500 m. Chloroplasts contain a granular component which is membrane-enclosed. The component is large in comparison with the plastid in which it occurs, averaging 1.2–1.4 in diameter in chloroplasts ranging from 1.6 to 2.2 in diameter. The inner membrane of the chloroplast is highly invaginated, and DNA- and phytoferritin-like materials are observed within the plastids. Microtubules with an average diameter of 20 m are observed adjacent and parallel to the plasmalemma, primarily in the corners of the cells. Micrographs of other normally occurring cytoplasmic inclusions are also presented.     

Influence of plant growth regulators,basal media and carbohydrate levels on the in vitro development of Pinus ponderosa (Dougl. ex Law.) cotyledon explants

Applications of in vitro screening techniques for Pinus ponderosa resistance to Peridermium harknessii could be beneficial in a tree breeding program. Plant growth regulators, basal media formula and carbohydrate levels were examined to determine the various effects each would have on excised cotyledon growth and development. Proliferating green callus was initiated from cotyledon explants on SH basal medium containing 4.4 M BA:5.4 M NAA and 1% sucrose. Subsequent subculturing onto LS medium supplemented with 44.0 M BA: 5.4 M NAA and 2% sucrose improved callus maintenance. The highest frequency of caulogenesis from cotyledon explants occurred on a modified GD medium containing 44.0 M BA: 0.054 M NAA and 4% glucose. The influence of nitrogen source, osmoticum and medium salt concentrations are discussed relative to callus initiation and caulogenesis.Abbreviations BA 6-benzyladenine - NAA -naphthaleneacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - CD Campbell & Durzan - GD Gresshoff & Doy - LP Le Poivre - LS Linsmaier & Skoog - MC McCown - SH Schenk & Hildebrandt     

Locations and central projections of neurons associated with the retrocerebral neuroendocrine complex of the cockroach Periplaneta americana (L.)

Summary Retrograde diffusion and precipitation of Co²⁺ reveals in the ipsilateral pars lateralis (PL) and contralateral pars intercerebralis (PI) of the brain neurons that enter the corpus cardiacum (CC), and, possibly, the corpus allatum (CA) on each side. The PL group consists of 29.6±8.4 somata that fill. Of these, 5.6±0.6 exceed 25 m in diameter, 14.3±2.7 range from 15–25 m, and 9.6±7.6 are smaller than 15 m. After CoCl₂ was applied to the right CC-CA of two males, 239 and 265 somata in the left PI stained. Except for 16 ranging from 30–45 m and chiefly located anteriorly, a majority of these somata measured 10–25 m.The only somata revealed by staining whole brains with the performic acid-resorcin fuchsin method are neurosecretory cells 10–20 m in diameter located within the PI. In starved adult males there are 92.4±8.1 on the right, and 93.2±6.9 on the left. The largest somata in the PL group contain numerous granules that stain with paraldehyde fuchsin. These somata also fill with Co²⁺, and belong to neurosecretory cells that extend into the CC-CA.The cerebral distribution of branches from the PL group, and the relationship of these to the corpora pedunculata, central body, and arborizations from the PI decussation are described.     

Excitation-calcium release uncoupling in aged single human skeletal muscle fibers

The biological mechanisms underlying decline in muscle power and fatigue with age are not completely understood. The contribution of alterations in the excitation-calcium release coupling in single muscle fibers was explored in this work. Single muscle fibers were voltage-clamped using the double Vaseline gap technique. The samples were obtained by needle biopsy of the vastus lateralis (quadriceps) from 9 young (25–35 years; 25.9 ± 9.1; 5 female and 4 male) and 11 old subjects (65–75 years; 70.5 ± 2.3; 6 f, 5 m). Data were obtained from 36 and 39 fibers from young and old subjects, respectively. Subjects included in this study had similar physical activity. Denervated and slow-twitch muscle fibers were excluded from this study. A significant reduction of maximum charge movement (Q_max) and DHP-sensitive Ca current were recorded in muscle fibers from the 65–75 group. Q_max values were 7.6 ± 0.9 and 3.2 ± 0.3 nC/F for young and old muscle fibers, respectively (P < 0.01). No evidences of charge inactivation or interconversion (charge 1 to charge 2) were found. The peak Ca current was (–)4.7 ± 0.08 and (–)2.15 ± 0.11 A/F for young and old fibers, respectively (P < 0.01). The peak calcium transient studied with mag-fura-2 (400 m) was 6.3 ± 0.4 m and 4.2 ± 0.3 m for young and old muscle fibers, respectively. Caffeine (0.5 mm) induced potentiation of the peak calcium transient in both groups. The decrease in the voltage-/ Ca-dependent Ca release ratio in old fibers (0.18 ± 0.02) compared to young fibers (0.47 ± 0.03) (P < 0.01), was recorded in the absence of sarcoplasmic reticulum calcium depletion. These data support a significant reduction of the amount of Ca available for triggering mechanical responses in aged skeletal muscle and, the reduction of Ca release is due to DHPR-ryanodine receptor uncoupling in fast-twitch fibers. These alterations can account, at least partially for the skeletal muscle function impairment associated with aging.This work was supported by Grant-in-Aid from the American Heart Association (National) and Muscular Dystrophy Association, and National Institutes of Health (2-P60AG18484-06)     

Axillary shoot induction and plant regeneration in Plantago ovata Forssk

Axillary shoot induction and plant regeneration were obtained in Plantago ovata. The optimum medium for inducing axillary shoots was Murashige & Skoog (MS) medium [5] supplemented with 4.6 M kinetin and 0.05 M NAA. Rooting of shoots was best on half-strength MS medium containing 5.0 M IBA and 0.05 M kinetin. The regenerated plants were similar to the control plants in karyotypic and phenotypic details.     

Functional analysis of actin fibrils in Physarum polycephalum

Summary Fluorochromed heavy meromyosin (TRITC-HMM) was microinjected as a molecular probe into small sandwich-plasmodia of Physarum polycephalum with the aim to demonstrate the spatial morphology and to analyze the dynamic activity of the fibrillar actin system in the living state. The plasmodia display different fibrillar organizations with a polygonal arrangement in the front region (FR) and a parallel or helical arrangement along protoplasmic veins in the intermediate (IR) and uroid region (UR). Quantitative evaluations by measuring the total length, lifetime, dynamic activity, long-term stability and optical density of fibrils reveal distinct differences between the three plasmodial regions: The total length (FR = 27.1 ± 18.5 m, IR = 24.8 ± 12.9 m, UR= 12.3 ± 4.7 m), the lifetime (FR = 12.2 ± 3.4 min, IR=10.5 ± 3.7 min, UR = 6.0 ± 3.4 min), and the dynamic activity as measured in length changes per min (FR = 17.9 ± 11.3 m, IR = 13.1 ± 3.9 m, UR = 8.3 ± 3.9 m) distinctly decrease from the front to the uroid region. On the other hand, the greatest stability as determined by lifetime changes in length (FR = -2.4 ± 16.2 m, IR = 0.3 ± 10.1 m, UR = -6.6 ± 8.9 m) and the highest optical density as expressed in grey-values (FR = 57.0 ± 14.1 gv, IR = 115.6 ± 26.1 gv, UR 62.5 ± 8.1 gv) were found for actomyosin fibrils of the intermediate region. The morphological and physiological data of the present paper are discussed with respect to the biological significance of the fibrillar microfilament system in Physarum polycephalum.     

Lipid peroxidation as the mechanism of modification of brain 5′-nucleotidase activity in vitro

The effect of lipid peroxidation on the Mg²⁺-independent and Mg²⁺-dependent activity of brain cell membrane 5-nucleotidase was determined and the affinity of the active sites of Mg²⁺-dependent enzyme for 5-AMP (substrate) and Mg²⁺ (activator) was examined. Brain cell membranes were peroxidized at 37°C in the presence of 100 M ascorbate and 25 M FeCl₂ (resultant) for 10 min. The activity of 5-nucleotidase and lipid peroxidation products (thiobarbituric acid reactive substances) were determined. At 10 min, the level of lipid peroxidation products increased from 0.20±0.10 to 17.5±1.5 nmoles malonaldehyde/mg membrane protein. The activity of Mg²⁺-independent 5-nucleotidase increased from 0.201±0.020 in controls to 0.305±0.028 mol Pi/mg protein/hr in peroxidized membranes. In the presence of 10mM Mg²⁺, the activity increased by 5.8-fold in the peroxidized membrane preparation in comparison to 14-fold in control In peroxidized preparation, the affinity of active site of Mg²⁺-dependent 5-nucleotidase for 5-AMP tripled, as indicated by a significant decrease inK _m (K _m=95±2 M AMP for control;K _m=32±2 MAMP for peroxidized).V _max was significantly reduced from 3.35±0.16 in control to 1.70±.09 moles Pi/mg protein in peroxidized membranes. The affinity of the active site for Mg²⁺ significantly increased (K _m=6.17±0.37 mM Mg²⁺ for control;K _m=4.0±0.31 peroxidized). The data demonstrate that lipid peroxidation modifies the Mg²⁺-dependent 5-nucleotidase function by altering the active sites for both the substrate and the activator. The modification of the 5-nucleotidase activity and the loss of Mg²⁺-dependent activation observed in this in-vitro study are similar to the changes previously observed by us in the hypoxic brain in-vivo. This suggests that lipid peroxidation which specifically alters the active site may be the underlying mechanism of the modification of 5-nucleotidase during hypoxia.     

Donors of nitric oxide mimic effects of ischaemic preconditioning on reperfusion induced arrhythmias in isolated rat heart

NO has been implicated in the mechanism of ischaemic preconditioning. To verify this hypothesis further we have attempted to reproduce effects of ischaemic preconditioning by nitric oxide donors administration prior to the ischaemia. The effect of glyceryl trinitrate (GTN) and 3-morpholino-sydnonimine-hydrochloride (SIN- 1), NO donors, on reperfusion induced ventricular tachycardia (VT) and ventricular fibrillation (VF) in Langendorff perfused rat hearts subjected to 10 min regional ischaemia followed by 10 min reperfusion were examined. Results: GTN, 500 M and SIN-1, 10 M, administered for 5 min and washed for another 5 min prior to ischaemia (to mimic ischaemic preconditioning), almost completely abolished reperfusion induced VF. GTN and SIN-1, administered at the time of reperfusion, increased the incidence of sustained VF and the duration of VT and VF. When given 5 min before the ischaemia and throughout the ischaemia and the reperfusion, SIN-1 abolished VF. Adenosine, 10 M, applied according to the above three protocols, did not affect reperfusion arrhythmias, although adenosine induced changes in coronary flow and post-ischaemic reflow were similar to those produced by the NO donors. In conclusions: (1) NO is able to mimic the effect of ischaemic preconditioning on reperfusion arrhythmias in rat heart, supporting the view that NO may be one of the endogenous substances triggering ischaemic preconditioning; (2) In crystalloid-perfused heart, NO may be deleterious when its administration is restricted to the reperfusion period.     

In vitro comparison of ceftazidime,aztreonam, cefpirome,gentamicin, imipenem,enoxacin, and ticarcillin plus clavulanic acid against 108 strains ofPseudomonas maltophilia

Pseudomonas maltophilia is an uncommon cause of hospital-acquired infection and is resistant to most of the antimicrobial agents used in the treatment of gram-negative infections. Susceptibility of 108 isolates ofP. maltophilia to ceftazidime, aztreonam, defpirome, gentamicin, imipenem, enoxacin, and ticarcillin plus clavulanic acid was determined by an agar dilution method. The isolates were in general resistant to the antibiotics. Imipenem and cefpirome were not active at clinically achievable levels. Of the isolates, 20% were susceptible to 16 g/ml ceftazidime, 53% were susceptible to 4 g/ml enoxacin, 10% were susceptible to 4 g/ml gentamicin, and 25% were susceptible to 64 g/ml ticarcillin plus 2 g/ml clavulanic acid.     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

Inhibitory effect of menaquinone-7 (vitamin K2) on the bone-resorbing factors-induced bone resorption in elderly female rat femoral tissues in vitro

A number of data are consistent with the hypothesis that increases in intracellular Na⁺ concentration (Na⁺ _i) during ischemia and early reperfusion lead to calcium overload and exacerbation of myocardial injury. However, the mechanisms underlying the increased Na⁺ _i remain unclear. ²³Na nuclear magnetic resonance spectroscopy was used to monitor Na⁺ _i in isolated rat hearts perfused with a high concentration of fatty acid as can occur under some pathological conditions. Whole-cell patch-clamp experiments were also performed on isolated cardiomyocytes in order to investigate the role of voltage-gated sodium channels. Na⁺ _i increased to substantially above control levels during no-flow ischemia. The results show that a pharmacological reduction of Na⁺ _i increase by cariporide (1 mol/L, a Na⁺/H⁺ exchange blocker) is not the only protection against ischemia-reperfusion damage, but that such protection may also be brought about by metabolic action aimed at reducing fatty acid utilization by myocardial cells. This action was obtained in the presence of etomoxir (0.1 mol/L), an inhibitor of carnitine palmitoyltransferase-1 (the key enzyme involved in fatty acid uptake by the mitochondria) which also decreases long-chain acyl carnitine accumulation. The possibility of Na⁺ channels participating in Na⁺ _i increase as a consequence of alterations in cardiac metabolism was studied in isolated cells. Sustained I_Na was stimulated by the presence of lysophosphatidylcholine (LPC, 10 mol/L) whose accumulation during ischemia is, at least partly, dependent on increased long-chain acyl carnitine. Current activation was particularly significant in the range of potentials between –60 and –20 mV. This may have particular relevance in ischemia. The quantity of charge carried by sustained I_Na was reduced by 24% in the presence of 1 mol/L cariporide. Therefore, limitation of long-chain fatty acid metabolism, and consequent limitation of ischemia-induced long-chain acyl carnitine accumulation, may contribute to reducing intracellular Na⁺ increase during ischemia-reperfusion.     

Polyamines and proline are affected by cadmium stress in nodules and roots of soybean plants

The effect of moderate (50 M) and high (200 M) doses of Cd were studied in relation to polyamine (Pas) metabolism, proline level and the glutamine synthetase/glutamate synthase system (GS/GOGAT) activity in nodules and roots of soybean plants during 6 days of treatment. The lower Cd concentration increased putrescine (Put) in both nodules and roots, while 200 M Cd increased Spm only in nodules and Put in roots. Spermidine (Spd) decreased in roots under both Cd concentrations. Arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) were both involved in Put biosynthesis in roots. In nodules, Put formation could mainly be attributed to ODC activity. Diamine oxidase (DAO) activity was severely reduced by 50 and 200 M Cd either in nodules or roots. The GS/GOGAT system activity was depressed either with 50 or 200 M Cd, but most significantly with the highest metal concentration. Under 200 M Cd, GS activity decayed to 25% or 60% of the control in nodules and roots, respectively, while GOGAT decreased 85% in nodules and 79% in roots by day 4 of treatment. Ammonium increased greatly in nodules (200% over the controls) and roots (100%) under 200 M Cd. Proline concentration increased significantly in nodules and roots under both Cd treatments, more markedly under 200 M Cd. The relationship between Pas and proline accumulation and nitrogen assimilation is discussed.     

Macrocompartmentation of total creatine in cardiomyocytes revisited

Distribution of total creatine (free creatine + phosphocreatine) between two subcellular macrocompartments – mitochondrial matrix space and cytoplasm – in heart and skeletal muscle cells was reinvestigated by using a permeabilized cell technique. Isolated cardiomyocytes were treated with saponin (50 g/ml for 30 min or 600 g/ml for 1 min) to open the outer cellular membrane and release the metabolites from cytoplasm (cytoplasmic fraction, CF). All mitochondrial population in permeabilized cells remained intact: the outer membrane was impermeable for exogenous cytochrome c, the acceptor control index of respiration exceeded 10, the mitochondrial creatine kinase reaction was fully coupled to the adenine nucleotide translocator. Metabolites were released from mitochondrial fraction (MF) by 2–5% Triton X100. Total cellular pool of free creatine + phosphocreatine (69.6 ± 2.1 nmoles per mg of protein) was found exclusively in CF and was practically absent in MF. When fibers were prepared from perfused rat hearts, cellular distribution of creatine was not dependent on functional state of the heart and only slightly modified by ischemia. It is concluded that there is no stable pool of creatine or phosphocreatine in the mitochondrial matrix in the intact muscle cells, and the total creatine pool is localized in only one macrocompartment – cytoplasm.     

Lateral bud culture of papaya (Carica papaya L.) for clonal propagation

Lateral buds may be preferred to shoot tips for in vitro propagation of papaya because of its unbranched nature. Proliferating shoot cultures from lateral buds appeared extremely compact with shortened internodes and leaf lamina of the cytokinin level (BAP 2 M) reported for multiple shoot production from shoot tips. ZEA (4 M) and 2iP (8 M) although reduced the proliferation rate, resulted in better growth of the shoot from lateral bud. Rooting was observed with IBA 20 M but plantlets so produced remained stunted.     

In vitro organogenesis of elephant apple (Feronia limonia)

Elephant apple (Feronia limonia L.). was micropropagated on MS medium containing 4.4 M benzyladenine and 4.6 M kinetin using cotyledon explants taken from in vitro-grown seedlings. Adventitious buds formed on the cotyledon developed into shoots that were rooted in half-strength MS medium containing 0.57 M indoleacetic acid and 0.49 M indolebutyric acid. Plants were successfully established in soil.Abbreviations BA 6-benzyladenine - IAA 3-indoleacetic acid - IBA 3-indolebutyric acid - MS Murashige & Skoog