Hemodynamic observations following orthotopic cardiac transplantation: hemodynamic responses to upright exercise at 1 year.

Central hemodynamic responses during upright exercise were studied at 1 year in 40 orthotopic cardiac transplant recipients. Hemodynamic responses were characterized by slow rise in heart rate and blunted peak exercise heart rate response, a significant early increase in stroke index followed by a plateau phase, and a steady increase in ventricular filling pressures and pulmonary artery pressure. In spite of exclusive utilization of the Frank-Starling mechanism to augment cardiac output during early exercise, the pressure responses were comparable to those reported in normal subjects. Our observations also indicate that similarly to normal subjects, the heart rate response plays an important role in the cardiac output achieved at maximum exercise. Although patients with younger donor hearts achieved a more favorable maximum heart rate, the other hemodynamic parameters showed no correlation with the donor heart age. Thus, no hemodynamic disadvantage of older donor hearts could be demonstrated. These data provide further enlightenment regarding the mechanisms of the well-preserved functional capacity noted in these patients.     

Thyrotropin-releasing hormone (TRH) is not thyrotropic but somatotropic in fed and starved adult chickens.

Adult fed and starved Warren chickens, 2 yr of age, and approaching the end of the second laying year, were injected iv with 1 of the following products: 10 micrograms of thyrotropin releasing hormone (TRH); 100 micrograms of bovine thyrotropin (bTSH); 100 micrograms of ovine growth hormone (oGH); saline. The influence on plasma concentrations of thyroxine (T4), triiodothyronine (T3) or chicken GH (cGH) were followed. Prior to injection, it was clear from the control values that starvation for 3 d decreased plasma levels of T3 and increased cGH, whereas 7 d of fasting increased T4 and cGH. The plasma levels of cGH were elevated greater than 10-fold at 15 min following the TRH challenge in food-deprived chickens compared to a less than 4-fold increase in normal fed hens. This increase was followed by a rise in T3 after 1 h, which was also more pronounced in the starved animals, whereas T4 decreased or remained unaffected. Increases in T4 can, however, be obtained with 100 micrograms TSH in normal fed (2-fold) or starved animals (greater than 3-fold). Following injection of 100 micrograms oGH, a significant increase in T3 levels was observed which in fed animals was already present at 30 min, but the higher levels persisted for 1 and 2 h in fed and starved hens. At the same time, a decrease in T4 was observed in both groups of GH-treated chickens. It is concluded that TRH at the dose used is not thyrotropic but has a somatotropic effect and is responsible for the peripheral conversion of T4 into T3.     

Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

Summary

The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development.     

Oesophageal acid stimulation in humans: does it alter baroreflex function?

The aim of this study was to investigate if oesophagel acid stimulation (Bernstein test) had an influence on heart rate and blood prsure variability and baroreflex gain. We compared the cardiovascular responses in 10 patients with established gastro-esophageal reflux disease (Group 1) and 10 control subjects (Group 2) during esophageal saline and 0.1 mol/l hydrochloric acid instillation. Indices of heart rate and blood pressure variability and baroreflex gain (derived from linear spontaneous sequences and cross spectral analysis) were calculated. In Group 1 the standard deviation of RR intervals (SDRR: 46 ms vs 51 ms, p=0.030) and the root mean square of successive differences (RMSSD: 24 ms vs. 26 ms p=0.027) were significantly lower during acid infusions, than during saline. We found no significant difference in minimum, maximum and mean RR intervals and systolic blood pressures and in the percentage of RR intervals, which differed from adjacent cycles by more than 50 ms (PNN50). The power spectra of RR intervals in the high frequency band tended to be lower during acid infusion (p=0.055). There was no significant difference in blood pressure spectra, neither in low nor in high frequency band. In Group 2 there was no significant difference between any parameters measured during acid and saline. The baroreflex gain was not changed during the studied conditions in any group. Neither increased vagal tone, nor increased vagal variability occurred and the baroreflex gain was not altered during oesophageal acid simulation.     

Plant transposable elements and their application in genetics and biotechnology

Data concerning plant transposable elements and their contribution to plant genome evolution are reviewed. Much attention is focused on utilization of transgenic plants as heterologous hosts of transposons for investigation of transposition mechanisms and gene cloning. Probable ways of the use of plant transposons as genetic tools in biotechnology are discussed.     

Construction of a GFP-BAR plasmid and its use for switchgrass transformation

 A dual marker plasmid comprising the reporter gene sgfp (green fluorescent protein) and the selectable bar gene (Basta tolerance) was constructed by replacing the uidA (β-glucuronidase, GUS) gene in a uidA-bar construct with sgfp. A particle inflow gun was used to propel tungsten particles coated with this plasmid into immature inflorescence-derived embryogenic callus of switchgrass (Panicum virgatum L.). GFP was observed in leaf tissue and pollen of transgenic plants. Nearly 100 plants tolerant to Basta were obtained from the experiments, and Southern blot hybridization confirmed the presence of both the bar and sgfp genes. Plants regenerated from in vitro cultures of transgenic plants grew on medium with 10 mg l^–1 bialaphos. When the pH indicator chlorophenol red was in the medium, the transgenic plantlets changed the medium from red to yellow. Basta tolerance was observed in T₁ plants resulting from crosses between transgenic and nontransgenic control plants, indicating inheritance of the bar transgene. Received: 11 May 2000 / Revision received: 21 August 2000 / Accepted: 22 August 2000