26 research outputs found
Impact of the stringency of cell selection on plastid segregation in protoplast fusion-derived Nicotiana regenerates.
Vegetative segregation of a mixed plastid population
in protoplast fusion-derived cell lines can be directed
by a selection favouring the multiplication of one
of the parental plastid types. This report defines some of
the critical conditions leading to a homogeneous plastid
population in cybrid plants generated by protoplast fusion
between Nicotiana plumbaginifolia and an albino
and streptomycin-resistant N. tabacum plastid mutant.
Light (1,500 Ix) conferred a strong selective advantage to
chloroplasts versus albino plastids, while the lack of this
effect in dim light (300 Ix) indicated that a sufficient light
intensity is essential to the phenomenon. Selection on
streptomycin-containing medium in the dark, however,
led to the preferential multiplication of resistant plastids.
Streptomycin selection of resistant chloroplasts in the
light, consequently, results in a plastid selection of doubled
stringency. In another experiment a definite, but leaky,
selection for chloroplast recombination (selection for
greening on streptomycin-containing medium in dim
light) was used to reveal various recombination products.
Protoplast fusion in fact resulted in cybrid plants showing
only simple chimeric segregation of unchanged
parental plastids. These results demonstrate the essential
requirement for stringent plastid selection, as defined by
cell culture conditions, to precede the formation of
shoots expected to possess the desired plastid genetic
composition
Impact of the stringency of cell selection on plastid segregation in protoplast fusion-derived Nicotiana regenerates.
Vegetative segregation of a mixed plastid population
in protoplast fusion-derived cell lines can be directed
by a selection favouring the multiplication of one
of the parental plastid types. This report defines some of
the critical conditions leading to a homogeneous plastid
population in cybrid plants generated by protoplast fusion
between Nicotiana plumbaginifolia and an albino
and streptomycin-resistant N. tabacum plastid mutant.
Light (1,500 Ix) conferred a strong selective advantage to
chloroplasts versus albino plastids, while the lack of this
effect in dim light (300 Ix) indicated that a sufficient light
intensity is essential to the phenomenon. Selection on
streptomycin-containing medium in the dark, however,
led to the preferential multiplication of resistant plastids.
Streptomycin selection of resistant chloroplasts in the
light, consequently, results in a plastid selection of doubled
stringency. In another experiment a definite, but leaky,
selection for chloroplast recombination (selection for
greening on streptomycin-containing medium in dim
light) was used to reveal various recombination products.
Protoplast fusion in fact resulted in cybrid plants showing
only simple chimeric segregation of unchanged
parental plastids. These results demonstrate the essential
requirement for stringent plastid selection, as defined by
cell culture conditions, to precede the formation of
shoots expected to possess the desired plastid genetic
composition
From Newborn to Senescence Morphological and Functional Remodeling Leads to Increased Contractile Capacity of Arteries
Aging induces substantial morphological and functional changes in vessels. We hypothesized that due to morphological remodeling the total contractile forces of arteries increase, especially in older age as a function of age. Mean arterial blood pressure of rats and morphological and functional characteristics of isolated carotid arteries rats, from newborn to senescent, were assessed. The arterial blood pressure of rats increased significantly from 0.25 to the age of 6 months, and then it reached a level, which was maintained until age of 30 months. Wall lumen and wall thickness increased with age, mostly due to media (smooth muscle) thickening, whereas wall tension gradually reduced with age. Contractions of arteries to nonreceptor-mediated vasomotor agent (KCl, 60mM) increased in three consecutive age groups, whereas contractility first increased (until 2 months), then it did not change further with aging. Norepinephrine-induced contractions initially increased in young age and then did not change further in older age. These findings suggest that during normal aging due to remodeling of arterial wall (smooth muscle) the contractile capacity of arteries increases, which seems to be independent from systemic blood pressure. Thus, arterial remodeling can favor the development of increased circulatory resistance in older age
Impact of the stringency of cell selection on plastid segregation in protoplast fusion-derived Nicotiana regenerates.
Vegetative segregation of a mixed plastid population
in protoplast fusion-derived cell lines can be directed
by a selection favouring the multiplication of one
of the parental plastid types. This report defines some of
the critical conditions leading to a homogeneous plastid
population in cybrid plants generated by protoplast fusion
between Nicotiana plumbaginifolia and an albino
and streptomycin-resistant N. tabacum plastid mutant.
Light (1,500 Ix) conferred a strong selective advantage to
chloroplasts versus albino plastids, while the lack of this
effect in dim light (300 Ix) indicated that a sufficient light
intensity is essential to the phenomenon. Selection on
streptomycin-containing medium in the dark, however,
led to the preferential multiplication of resistant plastids.
Streptomycin selection of resistant chloroplasts in the
light, consequently, results in a plastid selection of doubled
stringency. In another experiment a definite, but leaky,
selection for chloroplast recombination (selection for
greening on streptomycin-containing medium in dim
light) was used to reveal various recombination products.
Protoplast fusion in fact resulted in cybrid plants showing
only simple chimeric segregation of unchanged
parental plastids. These results demonstrate the essential
requirement for stringent plastid selection, as defined by
cell culture conditions, to precede the formation of
shoots expected to possess the desired plastid genetic
composition
Impact of the stringency of cell selection on plastid segregation in protoplast fusion-derived Nicotiana regenerates.
Vegetative segregation of a mixed plastid population
in protoplast fusion-derived cell lines can be directed
by a selection favouring the multiplication of one
of the parental plastid types. This report defines some of
the critical conditions leading to a homogeneous plastid
population in cybrid plants generated by protoplast fusion
between Nicotiana plumbaginifolia and an albino
and streptomycin-resistant N. tabacum plastid mutant.
Light (1,500 Ix) conferred a strong selective advantage to
chloroplasts versus albino plastids, while the lack of this
effect in dim light (300 Ix) indicated that a sufficient light
intensity is essential to the phenomenon. Selection on
streptomycin-containing medium in the dark, however,
led to the preferential multiplication of resistant plastids.
Streptomycin selection of resistant chloroplasts in the
light, consequently, results in a plastid selection of doubled
stringency. In another experiment a definite, but leaky,
selection for chloroplast recombination (selection for
greening on streptomycin-containing medium in dim
light) was used to reveal various recombination products.
Protoplast fusion in fact resulted in cybrid plants showing
only simple chimeric segregation of unchanged
parental plastids. These results demonstrate the essential
requirement for stringent plastid selection, as defined by
cell culture conditions, to precede the formation of
shoots expected to possess the desired plastid genetic
composition
Hemolyzed Blood Elicits a Calcium Antagonist and High CO2 Reversible Constriction via Elevation of [Ca2+]i in Isolated Cerebral Arteries
During acute subarachnoid hemorrhage, blood is hemolyzed, which is followed by a significant cerebrovascular spasm resulting in a serious clinical condition. Interestingly, however, the direct vasomotor effect of perivascular hemolyzed blood (HB) has not yet been characterized, preventing the assessment of contribution of vasoconstrictor mechanisms deriving from brain tissue and/or blood and development of possible treatments. We hypothesized that perivascular HB reduces the diameter of the cerebral arteries (i.e., basilar artery [BA]; middle cerebral artery [MCA]) by elevating vascular tissue [Ca2+.]i level. Vasomotor responses were measured by videomicroscopy and intracellular Ca2+. by the Fura2-AM ratiometric method. Adding HB to the vessel chamber reduced the diameter significantly (BA: from 264 +./- 7 to 164 +./- 11 mum; MCA: from 185 +./- 15 to 155 +./- 14 mum), which was reversed to control level by wash-out of HB. Potassium chloride (KCl), HB, serum, hemolyzed red blood cell (RBC), plasma, and platelet suspension (PLTs) elicited significant constrictions of isolated basilar arteries. There was a significant increase in K+. concentration in hemolyzed HB (7.02 +./- 0.22 mmol/L) compared to Krebs\u27 solution (6.20 +./- 0.01 mmol/L). Before HB, acetylcholine (ACh), sodium-nitroprussid (SNP), nifedipin, and CO2 elicited substantial dilations in cerebral arteries. In contrast, in the presence of HB dilations to ACh, SNP decreased, but not to nifedipine and CO2. After washout of HB, nitric oxide-mediated dilations remained significantly reduced compared to control. HB significantly increased the ratiometric Ca signal, which returned to control level after washout. In conclusion, perivascular hemolyzed blood elicits significant-nifedipine and high CO2 reversible-constrictions of isolated BAs and MCAs, primarily by increasing intracellular Ca2+., findings that can contribute to the refinement of local treatment of subarachnoid hemorrhage
Bioassay-comparison of the antioxidant efficacy of hydrogen sulfide and superoxide dismutase in isolated arteries and veins
Recent studies suggest that hydrogen sulfide (H2S) exhibits potent antioxidant capacity and improves vascular and tissue functions. Thus we aimed to compare the antioxidant efficacy of H2S to that of superoxide dismutase (SOD).Isometric force of isolated rat carotid arteries and gracilis veins was measured with a myograph. The vasomotor effect of the superoxide-generator pyrogallol (10−5M) was obtained in control conditions, and then in the presence of SOD (120 U/ml) or H2S (10−5M or 10−4M), respectively. Spectrophotometric measurements were performed to detect the effect of SOD and H2S on the auto-oxidation of pyrogallol.Pyrogallol increased the isometric force of carotid arteries (9.7 ± 0.8 mN), which was abolished by SOD (5.3 ± 0.8 mN), was not affected by 10−5M H2S (9.1 ± 0.5 mN), whereas 10−4M H2S slightly, but significantly reduced it (8.1 ± 0.7 mN). Pyrogallol significantly increased the isometric force of gracilis veins (1.3 ± 0.2 mN), which was abolished by SOD (0.9 ± 0.2 mN), whereas 10−5M (1.3 ± 0.2 mN), or 10−4M H2S (1.2 ± 0.2 mN) did not affect it. Pyrogallol-induced superoxide production was measured by a spectrophotometer (A420 = 0.19 ± 0.0). SOD reduced absorbance (A420 = 0.02 ± 0.0), whereas 10−5M H2S did not (A420 = 0.18 ± 0.0) and 10−4M H2S slightly reduced it (A420 = 0.15 ± 0.0).These data suggest that H2S is a less effective vascular antioxidant than SOD. We propose that the previously described beneficial effects of H2S are unlikely to be related to its direct effect on superoxide