Viable Nematodes from Late Pleistocene Permafrost of the Kolyma River Lowland.

We have obtained the first data demonstrating the capability of multicellular organisms for longterm cryobiosis in permafrost deposits of the Arctic. The viable soil nematodes Panagrolaimus aff. detritophagus (Rhabditida) and Plectus aff. parvus (Plectida) were isolated from the samples of Pleistocene permafrost deposits of the Kolyma River Lowland. The duration of natural cryopreservation of the nematodes corresponds to the age of the deposits, 30 000-40 000 years.

[Microbial communities of ancient seeds derived from permanently frozen Pleistocene deposits].

Microbial communities from the surface of ancient seeds of higher plants and embedding frozen material dated to the late Pleistocene (formed about 30 thousand years ago) were studied by various methods: scanning electron microscopy, epifluorescence microscopy, and inoculation of nutrient media, followed by identification of isolated cultures. Both prokaryotic and eukaryotic microorganisms were found on the surface of ancient seeds. The total quantity of bacterial cells determined by direct counting and dilution plating (CFU) for the samples of ancient seeds exceeded the value in the embedding frozen material by one to two orders of magnitude. This pattern was not maintained for mycelial fungi; their quantity in the embedding material was also rather high. A significant difference was revealed between the microbial communities of ancient seeds and embedding frozen material. These findings suggest that ancient plant seeds are a particular ecological niche for microorganisms existing in permafrost and require individual detailed study.

[The possible contribution of late pleistocene biota to biodiversity in present permafrost zone]. / O vozmozhnosti uchastiia pozdnepleistotsenovoi bioty v formirovanii bioraznoobraziia sovremennoi kriolitozony.

During the last decade a wide range of biological objects, which have preserved their viability for tens and hundreds of thousands of years, was found in the samples of permafrost sediments from North-East Eurasia. Among them are bacteria, fungi, algae, moss spores, seeds of higher plants, protists. Along with physiological mechanisms of cryoconservation and constant low temperature of great importance for long-term preservation of biological objects in permafrost layers are ways of burying the organisms and conditions that prevail before the transition of sediments to the permafrost state. The analysis of viability showed by preserved biological objects gives reasons to suppose that some representatives of Pleistocene biota buried in permafrost thickness may contribute to the biodiversity of present cryolite zone.

STM study of morphology and electron transport features in cytochrome c and nanocluster molecule monolayers.

The morphology and electron tunneling through single cytochrome c and nanocluster Pt(5)(CO)(7)[P(C(6)H(5))](4) molecules organized as monolayer Langmuir-Blodgett (LB) films on graphite substrate have been studied experimentally using scanning tunneling microscopy (STM) and spectroscopy techniques with sub-nanometer spatial resolution in a double barrier tunnel junction configuration STM tip-monomolecular film-conducting substrate at ambient conditions. STM images of the films revealed globular structures with characteristic diameters (approximately 3.5 nm for the protein molecule and approximately 1.2 nm for the nanocluster). The spectroscopic study by recording the tunneling current-bias voltage (I-V) curves revealed tunneling I-V characteristics with features as steps of different width and heights that are dependent on the STM tip position over the molecule in the monolayer, giving evidence for sequential discrete electron-tunneling effects with the combination of the single electron Coulomb-charging energy and the electronic energy level separation (molecular spectrum) in such immobilized metalloprotein and nanocluster structures that can be of interest for the development of bioelectronic and hybrid functional nanosystems.

Angiotensin-converting enzyme inhibition and the norepinephrine spillover response to dynamic exercise.

To determine whether prejunctional angiotensin II receptors facilitate norepinephrine (NE) release during exercise, normal volunteers exercised at approximately 25 or approximately 65% of maximal O2 consumption (VO2max) on two occasions. Steady-state NE kinetics were determined at rest and during exercise by using infusions of [3H]NE. Arterial plasma NE and [3H]NE were determined for calculation of NE spillover and clearance. Before the second bout of exercise at approximately 25% of VO2max later that day, enalaprilat (n = 8) or nitroprusside (n = 5) was administered intravenously to lower blood pressure to a comparable level and saline was infused as a time control (n = 4). Exercise at 25% of VO2max increased heart rate from 73 to 100 beats/min, plasma NE from 296 to 626 pg/ml, and NE spillover from 1.56 to 3.32 nmol.min-1.m-2. The exercise effect was significant in each subgroup. At rest and during exercise, the decrease in blood pressure and the increase in plasma NE and NE spillover were similar with enalaprilat and nitroprusside. There was no drug effect in the saline group. In a separate group (n = 7), exercise at approximately 65% of VO2max increased heart rate from 76 to 170 beats/min, plasma NE from 338 to 2,656 pg/ml, and NE spillover from 1.87 to 11.65 nmol.min-1.m-2. In this group, 3 days of oral enalapril did not affect the NE spillover response to exercise. Because the angiotensin-converting enzyme inhibitor did not attenuate the NE spillover response to exercise, we conclude that at the exercise levels tested, prejunctional angiotensin II receptors do not appear to facilitate NE release.

Prejunctional angiotensin II receptors. Facilitation of norepinephrine release in the human forearm.

To determine if peripheral angiotensin II (Ang II) prejunctional receptors facilitating NE release exist in humans, we used [3H]NE kinetic methodology to measure forearm NE spillover during intrabrachial arterial Ang II infusions in eight normal male subjects. We used the following protocol to optimize conditions for demonstrating these receptors: (a) lower body negative pressure (-15 mmHg) to increase sympathetic nerve activity to skeletal muscle; and (b) intraarterial nitroprusside to maintain a high constant forearm blood flow (approximately 10 ml/min.100 ml) to maximize the proportion of neuronally released NE that spills over into the circulation. During lower body negative pressure, the following were infused intraarterially for three consecutive 20-min periods: saline, Ang II (4 ng/min), and Ang II (16 ng/min). During the Ang II infusions, forearm venous NE increased significantly from 173 to 189 and 224 pg/ml (P < 0.01), and forearm NE spillover increased from 384 to 439 and 560 ng/min.100 ml (P < 0.05 for high Ang II). Forearm NE clearance was unchanged. During low and high dose Ang II, the plasma venous Ang II concentrations were 25 and 97 pM, respectively. Since normal subjects increase plasma Ang II from 4 to 20-22 pM with exercise, standing, or diuretic administration, and patients with severe congestive heart failure can have a plasma Ang II of approximately 25 pM at rest, we suggest that Ang II might facilitate NE release in severe congestive heart failure, especially under conditions of stress.

Effects of exercise intensity and duration on norepinephrine spillover and clearance in humans.

During dynamic exercise, blood flow to exercising muscle is closely matched to metabolic demands. This is made possible by metabolic vasodilation, vasoconstriction in inactive vascular beds, and a rise in cardiac output. The sympathetic nervous system plays an important role in regulating this exercise response. In this study, we used steady-state infusions of tritiated norepinephrine ([3H]NE) to determine the magnitude and time course of the arterial NE spillover response to sustained upright bicycle exercise at low (n = 11) and moderate-to-high (n = 14) exercise intensity (25 and 65% of maximum work load, respectively) in normal young subjects. In addition, we sought to examine whether exercise was associated with a change in NE clearance. During 30 min of low-level exercise, arterial NE spillover increased from 1.45 +/- 0.13 to 3.14 +/- 0.30 nmol.min-1 x m-2 (P < 0.01) and appeared to plateau at 20-30 min of exercise; NE clearance remained unchanged. During 20 min of moderate-to-high-intensity exercise, we found a substantial and progressive rise of arterial NE spillover from 2.15 +/- 0.27 to 13.52 +/- 1.62 nmol.min-1 x m-2 (P < 0.01). NE clearance decreased from 0.91 +/- 0.05 to 0.80 +/- 0.05 l.min-1 x m-2 (P < 0.05). These data suggest that, during dynamic exercise, sympathetic nervous system activity is related to exercise intensity, and there appears to be an interaction between the effects of exercise intensity and duration on NE spillover. In addition, at moderate-to-high exercise intensity, a small decrease of NE clearance contributes to the rise in plasma NE.

Non-invasive assessment of ventricular damage in rats with myocardial infarction.

OBJECTIVE: The aim was to evaluate whether two dimensional echocardiographic/Doppler (echo/Doppler) techniques could be used to detect left ventricular damage rapidly, accurately, and non-invasively in rats with a myocardial infarction. METHODS: Female Wistar rats were initially subjected to either a sham operation or surgery to induce a myocardial infarct by ligating the left main coronary artery. Following a minimum of six weeks to recover from the surgery, all rats were re-anaesthetised and cardiac and stroke indexes were determined at similar heart rates, using echo/Doppler techniques. Postmortem histological assessment of myocardial infarct size was compared with the non-invasive detection of left ventricular wall motion abnormalities, left ventricular dilatation, and the presence of a left ventricular aneurysm found in the living animal. RESULTS: Rats with myocardial infarction (n = 8) showed a 33(SEM 4)% reduction (p < 0.01) in cardiac index (due to a 33% reduction in stroke index) when compared to their non-infarcted counterparts (n = 5). In addition, a significant correlation (r = 0.84; n = 25; p < 0.01) was found between the assessment of left ventricular damage via non-invasive echo/Doppler measurements and the histological determination of infarct size. CONCLUSIONS: These results support the conclusion that two dimensional echo/Doppler techniques can be used to estimate rapidly and non-invasively the degree of left ventricular damage produced in living rats with myocardial infarction when compared to non-infarcted controls.

The effects of phenylephrine on right ventricular performance in patients with pulmonary hypertension.

Pulmonary hypertension causes right ventricular ischemia and failure as a result of increased afterload combined with reduced coronary blood flow. Increasing coronary driving pressure by raising aortic pressure with phenylephrine has been shown to reverse right ventricular ischemia from pulmonary hypertension in animals. Since vasodilators often fail to reduce afterload, we tested whether raising the coronary driving pressure would improve right ventricular function in man. Ten patients with pulmonary hypertension had hemodynamics and right ventricular coronary driving pressure measured before and 10 minutes after a steady state was reached with a phenylephrine infusion titrated to raise aortic pressure by 25 percent. Phenylephrine caused a significant (p less than .01) increase in mean aortic pressure (84 to 108 mm Hg) and right ventricular coronary driving pressure (46 to 69 mm Hg). In response, there was a significant (p less than .01) rise in mean pulmonary artery pressure (58 to 67 mm Hg), right ventricular end-diastolic pressure (10 to 16 mm Hg) and wedge pressure (5 to 9 mm Hg), and an insignificant fall in cardiac output (3.26 to 3.09 L/min) and pulmonary artery O2 saturation (57 to 49 percent). Although phenylephrine increased right ventricular coronary driving pressure, it worsened right ventricular function as manifest by a rise in end-diastolic pressure and fall in cardiac output. Any benefit of raising right ventricular coronary driving pressure may have been offset by alpha vasoconstriction of right ventricular coronary blood flow and/or pulmonary arterial vasoconstriction. Phenylephrine does not appear to be a useful therapy of right ventricular failure from pulmonary hypertension in patients who fail vasodilators.

Graded exercise testing.

The graded exercise test can be used for both diagnosis and functional assessment. Indications for diagnostic testing include pain, palpitation, elevated systemic blood pressure and potential problem. Functional testing is performed to determine prognosis, progression of cardiac disease, post-therapy status and physical fitness. For the diagnostic study, medications other than sublingual nitroglycerin should be avoided. For the functional study, the patient's medication should usually be continued.