scholarly journals Variations in Sulfhydryl Concentration During Microsporocyte Meiosis in the Anthers of Lilium and Trillium

1958 ◽  
Vol 4 (2) ◽  
pp. 157-161 ◽  
Author(s):  
Herbert Stern
Keyword(s):  
Sporogenous Tissue ◽  
Marked Drop

Anthers of lily and trillium were followed with respect to variations in protein and soluble sulfhydryls during meiosis and mitosis of the sporogenous tissue. In lily, the meiotic and mitotic cycles are each preceded by a rise in soluble —SH; in trillium there is only one rise which precedes meiosis. During division there is a marked drop in soluble —SH and a rise in soluble disulfides. Protein —SH remains approximately constant until diakinesis or metaphase when it falls briefly.

Swelling pressure and microstructure of an activated swelling clay with temperature

Clay Minerals ◽  
1998 ◽  
Vol 33 (2) ◽  
pp. 255-267 ◽  
Author(s):  
D. Tessier ◽  
M. Dardaine ◽  
A. Beaumont ◽  
A. M. Jaunet
Keyword(s):  
Room Temperature ◽  
Swelling Pressure ◽  
Radioactive Waste Disposal ◽  
Basic Medium ◽  
Hydraulic Pressure ◽  
Swelling Behaviour ◽  
Transmission Electron ◽  
Ca Ions ◽  
Na Ions ◽  
Marked Drop

AbstractClay from Fourges has been selected by the Commissariat à l'Energie Atomique as a support in radioactive waste disposal studies. This material was activated by adding Na2CO3, then compacted at 60 MPa. Subsequently, its swelling behaviour was monitored at 90°C and 145°C for 330 days and at the end of this period the samples were examined by transmission electron microscopy (TEM). For this, they were embedded in a resin then sectioned with an ultramicrotome for mineralogical and chemical analyses. The initial material is essentially composed of kaolinite and smectite. Addition of Na2CO3 at room temperature induces a replacement of Ca ions by Na ions and the precipitation of finely divided carbonates on the surface of the constituents. At the end of 330 days at 90°C under a hydraulic pressure of 1 MPa, the initial particles combine and the material exerts a swelling pressure of 20 MPa. A complete reorganisation of the clay crystallites is observed without significant dissolution of the solid phases. After the same time at 145°C under a hydraulic pressure of 10 MPa, in a basic medium, the combined conditions are such that a high proportion of the clay is dissolved with formation of amorphous aluminosilicates correlated with a marked drop in the swelling pressure to 5 MPa. This work establishes the advantages of following the macroscopic properties in parallel with the microstructure variations for understanding the changes in the properties of clays.

scholarly journals Historical patterns of wildfire ignition sources in California ecosystems

2018 ◽  
Vol 27 (12) ◽  
pp. 781 ◽  
Author(s):  
Jon E. Keeley ◽  
Alexandra D. Syphard
Keyword(s):  
Fire Hazard ◽  
Fire Frequency ◽  
Federal Agencies ◽  
The State ◽  
United States Forest Service ◽  
The Past ◽  
Design Fire ◽  
Fire Ignition ◽  
Over Time ◽  
Marked Drop

State and federal agencies have reported fire causes since the early 1900s, explicitly for the purpose of helping land managers design fire-prevention programs. We document fire-ignition patterns in five homogenous climate divisions in California over the past 98 years on state Cal Fire protected lands and 107 years on federal United States Forest Service lands. Throughout the state, fire frequency increased steadily until a peak c. 1980, followed by a marked drop to 2016. There was not a tight link between frequency of ignition sources and area burned by those sources and the relationships have changed over time. Natural lightning-ignited fires were consistently fewer from north to south and from high to low elevation. Throughout most of the state, human-caused fires dominated the record and were positively correlated with population density for the first two-thirds of the record, but this relationship reversed in recent decades. We propose a mechanistic multi-variate model of factors driving fire frequency, where the importance of different factors has changed over time. Although ignition sources have declined markedly in recent decades, one notable exception is powerline ignitions. One important avenue for future fire-hazard reduction will be consideration of solutions to reduce this source of dangerous fires.

In vitro studies on the induction of sporogenous tissue on leaves of cinnamon fern. I. Environmental factors

1972 ◽  
Vol 50 (12) ◽  
pp. 2673-2682 ◽  
Author(s):  
William H. Harvey ◽  
James D. Caponetti
Keyword(s):  
Environmental Factors ◽  
Light Intensity ◽  
Environmental Conditions ◽  
Light Exposure ◽  
Progressive Increase ◽  
Light Phase ◽  
Sporogenous Tissue ◽  
Light Darkness

Intact, set III, cinnamon fern cataphyll and frond primordia, which were shown to have no predisposition to fertility in situ, produced sporangia when excised and cultured under sterile conditions in Knudson's medium supplemented with various levels of sucrose and maintained on 11 different regimens of light, darkness, and temperature for 10 weeks. Increasing levels of sucrose resulted in increased fertility under all environmental conditions, but the highest percentage of fertility was obtained under conditions of continuous dark at 26 °C. As the length of the light phase of the photoperiods decreased, a progressive increase in induction of fertile leaves was observed, suggesting that periods of long light exposure are inhibitory to the initiation of sporangia. Conversely, as the light intensity was increased, an inhibition of sporophyll differentiation occurred. Sporangia excised from dark-induced sporophylls and cultured in the light produced viable spores which germinated yielding haploid gametophytes that ultimately produced sporophytes.

Cell proliferation in the developing wing-bud of normal and talpid3 mutant chick embryos

Development ◽  
1975 ◽  
Vol 34 (3) ◽  
pp. 589-607
Author(s):  
D. A. Ede ◽  
O. P. Flint ◽  
P. Teague
Keyword(s):  
Cell Cycle ◽  
Early Stage ◽  
Mitotic Rate ◽  
Mitotic Division ◽  
Chick Embryos ◽  
Division Rate ◽  
Cell Cycle Time ◽  
Continuous Sampling ◽  
Wing Bud ◽  
Marked Drop

Previous measurements on mitotic division rate or cell cycle time have been made on samples from a few discrete limb regions or by continuous sampling, but only down a unidimensional limb axis, disregarding morphological discontinuities such as the presence or absence of cartilage. This study presents a new analysis on normal and talpid3 mutant chick embryos, measuring mitotic rate and also cell density through the central proximo-distal axis and at the limb periphery, taking into account the development of cartilage regions. Differentiation of cartilage is correlated with a marked drop in mitotic rate, accounting for a proximo-distal gradient of mitosis in central counts which was not observed at the limb periphery. Talpid3 limbs at an early stage show a central mitotic gradient, but the reverse of that observed in normal limbs.

scholarly journals 3H Leucine Incorporation Into Myofibrils of Normal and Dystrophic Mouse Skeletal Muscle

1975 ◽  
Vol 2 (1) ◽  
pp. 1-4 ◽  
Author(s):  
G. Monckton ◽  
H. Marusyk
Keyword(s):  
Skeletal Muscle ◽  
Muscular Dystrophy ◽  
Leucine Incorporation ◽  
Mouse Skeletal Muscle ◽  
Dystrophic Mouse ◽  
Before And After ◽  
Em Autoradiography ◽  
Marked Drop

SUMMARY:The study of 3H leucine incorporation into skeletal muscle of mouse muscular dystrophy (129 ReJ/dy Bar Harbour strain) shows the uptake of isotope into myofibrils. The techniques employed were light and EM autoradiography before and after glycerination (Szent-Gyorgyi 1947). The results indicate a marked drop in uptake of the 3H-Leucine into myofibrils in the dystrophic animals, supporting the contention of Nihei et al (1971) that reduced myosin synthesis occurs in mouse muscular dystrophy.

scholarly journals Late Renal Allograft Rupture Associated with Cessation of Immunosuppression following Graft Failure

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Sumayah Askandarani ◽  
Noura Aloudah ◽  
Hanan Al Enazi ◽  
Khaled O. Alsaad ◽  
Abdulrahman Altamimi
Keyword(s):  
Graft Failure ◽  
Unusual Case ◽  
Renal Allograft ◽  
Time Interval ◽  
Antibody Mediated Rejection ◽  
Immunosuppressive Medications ◽  
Peritubular Capillaries ◽  
Long Time ◽  
Cellular Rejection ◽  
Marked Drop

A 29-year-old man developed chronic allograft nephropathy 63 months after renal transplantation. He became symptomatic with advanced chronic graft failure; his immunosuppressive medications were reduced and he was commenced on haemodialysis. Two months following the withdrawal of immunosuppression, he presented with abdominal pain, haematuria, and a marked drop in haemoglobin. The patient was taken to the operating room, where the renal allograft was found to be ruptured, and graft nephrectomy was subsequently performed. Histological examination of the graft specimen showed severe haemorrhagic acute vascular cellular rejection in a background of marked chronic allograft vasculopathy. Immunostaining for C4d showed diffuse, strong, linear circumferential staining of the peritubular capillaries, indicating a concurrent antibody-mediated rejection. We report herein an unusual case of spontaneous renal allograft rupture that occurred long time after transplantation due to severe acute rejection following cessation of immunosuppressive medications for advanced chronic allograft failure. To the best of our knowledge, the time interval between transplantation and the rupture of this allograft is the longest of those reported in the literature.

Seasonal temperature variations influence tapetum mitosis patterns associated with reproductive fitness

Genome ◽  
2014 ◽  
Vol 57 (9) ◽  
pp. 517-521 ◽  
Author(s):  
Umesh C. Lavania ◽  
Surochita Basu ◽  
Jyotsana Singh Kushwaha ◽  
Seshu Lavania
Keyword(s):  
Climate Change ◽  
Temperature Change ◽  
Reproductive Fitness ◽  
Seasonal Temperature ◽  
Seed Fertility ◽  
Mild Winter ◽  
Differential Behavior ◽  
Sporogenous Tissue ◽  
Differential Behaviour ◽  
Environmentally Sensitive

Environmental stress in plants impacts many biological processes, including male gametogenesis, and affects several cytological mechanisms that are strongly interrelated. To understand the likely impact of rising temperature on reproductive fitness in the climate change regime, a study of tapetal mitosis and its accompanying meiosis over seasons was made to elucidate the influence of temperature change on the cytological events occurring during microsporogenesis. For this we used two species of an environmentally sensitive plant system, i.e., genus Cymbopogon Sprengel (Poaceae), namely Cymbopogon nardus (L.) Rendle var. confertiflorus (Steud.) Bor (2n = 20) and Cymbopogon jwaruncusha (Jones) Schult. (2n = 20). Both species flower profusely during extreme summer (48 °C) and mild winter (15 °C) but support low and high seed fertility, respectively, in the two seasons. We have shown that tapetal mitotic patterns over seasons entail differential behavior for tapetal mitosis. During the process of tapetum development there are episodes of endomitosis that form either (i) an endopolyploid genomically imbalanced uninucleate and multinucleate tapetum, and (or) (ii) an acytokinetic multinucleate genomically balanced tapetum, with the progression of meiosis in the accompanying sporogenous tissue. The relative frequency of occurrence of the two types of tapetum mitosis patterns is significantly different in the two seasons, and it is found to be correlated with the temperature conditions. Whereas, the former (genomically imbalanced tapetum) are prevalent during the hot summer, the latter (genomically balanced tapetum) are frequent under optimal conditions. Such a differential behaviour in tapetal mitosis vis-à-vis temperature change is also correspondingly accompanied by substantial disturbances or regularity in meiotic anaphase disjunction. Both species show similar patterns. The study underpins that tapetal mitotic behaviour per se could be a reasonable indicator to elucidate the effect of climate change on reproductive fitness.

MINI PLASMINOGEN-LIKE MOLECULE IN SEPTIC PATIENTS

1987 ◽  
Author(s):  
L Kodrich ◽  
P Porterie ◽  
O Lago ◽  
G Bergonzelli ◽  
B Sassetti ◽  
...  
Keyword(s):  
Binding Sites ◽  
Blood Cultures ◽  
Enzyme Linked Immunosorbent Assay ◽  
Normal Range ◽  
Leukocyte Elastase ◽  
Functional Activities ◽  
Group B ◽  
Sepharose 4B ◽  
Normal Controls ◽  
Marked Drop

We have previously described (Thromb.Res.44(6),1986) an altered relation Plasminogen (Pig)/α2~antiplasmin (APL) (Plg/APL<0.6) in the plasma of septic patients. A probable explanation of the mechanism whereby this alteration takes place would be the degradation of Pig to fragments of lower molecular weight due to the action of leukocyte elastase.In order to confirm this we studied 10 patients with sepsis, which did not have clinicalorlaboratory evidence of disseminated intravascular coagulation or septic shock, with positive blood cultures for bacterial germs .Elastase-α1proteinase inhibitor complexes were measured by an enzyme-linked immunosorbent assay (mean:510±181.9ug/l;normal range:86±28.5ug/l). Pig and APL functional activities were assayed by the amidolytic method; Pig: 40±8.9%; normal range: 100±20% .APL: 95±10.1% formal range 100+20%. Two different behaviors were observed in the plasma Pig of these patients with regard to their capacity to bind to Lysi-ne-Sepharose 4B.0n the basis of this observation the patients were divided into two group.Group A(4 patients) only presented Pig activity in fraction 1 (Pig without lysine binding sites : LBS). Group B (6 patients) presented Pig activity in fraction 1 and in fraction 2 (Pig with LBS).The normal controls presented Pig activity only in fraction 2. All the fractions which presented functional Pig activity also presented immunologic Pig activity and developed areas of lysis in heated fibrin plates after activation with urokinaseIt seems tenable the hypothesis that the action of the leukocyte elastase is responsible for the degradation of Pig and this modification in the molecule would give rise to a greater depuration thus explaining the marked drop of the plasmatic levels seen in septic patients.

scholarly journals Mechanisms of the negative potential associated with Leão’s spreading depolarization: A history of brain electrogenesis

2020 ◽  
Vol 40 (10) ◽  
pp. 1934-1952 ◽  
Author(s):  
Oscar Herreras ◽  
Julia Makarova
Keyword(s):  
Membrane Potential ◽  
Negative Potential ◽  
Extracellular Potential ◽  
Field Potentials ◽  
Volume Conduction ◽  
Inward Current ◽  
Spreading Depolarization ◽  
Numerous Cell ◽  
History Of ◽  
Marked Drop

Spreading depolarization (SD) is a self-propagated wave that provokes transient disorder of numerous cell and tissue functions, and that may kill neurons in metabolically compromised tissue. We examined the mechanisms underlying the main hallmark of SD, a giant extracellular potential (ΔVo) for which multiple electromotive forces have been proposed. The end-point is that neurons and not glia, dendritic channels and not spatial currents, and increased sodium conductance rather than potassium gradients, appear to be the main actors in the generation of the negative ΔVo. Neuronal currents are established by two mechanisms, a voltage independent dendritic current, and the differential polarization along the neuron membranes. Notably, despite of a marked drop of ion gradients, these evolve significantly during SD, and yet the membrane potential remains clamped at zero no matter how much inward current is present. There may be substantial inward current or none in function of the evolving portion of the neuron dendrites with SD-activated channels. We propose that the ΔVo promotes swelling-induced dendritic damage. Understanding SD electrogenesis requires all elements relevant for membrane potential, action currents, field potentials and volume conduction to be jointly considered, and it has already encouraged the search for new targets to limit SD-related pathology.

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