MEIOSIS IN COPRINUS: VI. THE CONTROL OF THE INITIATION OF MEIOSIS

1974 ◽  
Vol 16 (1) ◽  
pp. 155-164 ◽  
Author(s):  
B. C. Lu
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Mycelial Growth ◽  
Dark Period ◽  
Continuous Light ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Light Cycle ◽  
Sensitive Stage ◽  
Dark Regime

Meiosis in Coprinus lagopus is normally initiated at night under normal diurnal conditions. This timing can be shifted to 0900-1000 h by using a 16h light-8h dark regime with the light cycle commencing at 1600 h. For the initiation of meiosis, C. lagopus is temperature sensitive (35 C) under continuous light. The temperature sensitivity can be overcome by a dark period. The sensitive period occurs within 7 h of karyogmay. Only the first 2 h, however, are sensitive to light and high temperature. A shift-up to restrictive conditions before the sensitive stage effectively arrests the process leading to karyogamy. The arrest is reversible within 20 h. Upon returning to a 25 C chamber, karyogamy begins in 6 h in all basidiocarps. Thus using this technique accurate control of the initiation of meiosis can be achieved. Howeevr, prolonged arrest beyond 16 h causes the basidia to revert to mitosis and mycelial growth. The nucleolus is reduced in size and exhibits a large vacuole and a lack of granular components as shown by electron microscopy.

SD-72 has a temperature-sensitive period during spermiogenesis

1983 ◽  
Vol 25 (6) ◽  
pp. 662-667 ◽  
Author(s):  
Kathleen Matthews ◽  
Mark A. Mortin
Keyword(s):  
Drosophila Melanogaster ◽  
High Temperature ◽  
Segregation Distortion ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Proximate Cause ◽  
Naturally Occurring ◽  
Segregation Distorter

Segregation distorter (SD) chromosomes in Drosophila melanogaster are naturally occurring second chromosomes which produce greatly altered transmission frequencies when present in heterozygous males (Hartl and Hiraizumi 1976). The proximate cause of segregation distortion is abortion of spermatids carrying the non-SD homologue (Tokuyasu et al. 1977). SD-72, a chromosome previously shown (Mange 1968) to be unaffected by high temperature treatment of spermatocytes, a stage when several SD genotypes are temperature sensitive, has a temperature-sensitive period during spermiogenesis. SD-72/cn bw males exposed to a 24-h pulse of 29 °C, then brooded for 24 h, experience a decrease in segregation distortion of approximately two-thirds. The timing of the reduction in distortion indicates that the temperature-sensitive period is postmeiotic.

scholarly journals SEX CHROMOSOME MEIOTIC DRIVE SYSTEMS IN DROSOPHILA MELANOGASTER I. ABNORMAL SPERMATID DEVELOPMENT IN MALES WITH A HETEROCHROMATIN-DEFICIENT X CHROMOSOME (sc  4  sc  8)

Genetics ◽  
1975 ◽  
Vol 79 (4) ◽  
pp. 613-634
Author(s):  
W J Peacock ◽  
George L Gabor Miklos ◽  
D J Goodchild
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Sex Chromosome ◽  
Light And Electron Microscopy ◽  
Temperature Shift ◽  
Meiotic Drive ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Electron Microscopes ◽  
Drive Systems

ABSTRACT The meiotic drive characteristics of the In(1)sc4Lsc8R/Y system have been examined by genetic analysis and by light and electron microscopy. sc4sc8/Y males show a direct correlation between nondisjunction frequency and meiotic drive. Temperature-shift experiments reveal that the temperature-sensitive period for nondisjunction is at meiosis, whereas that for meiotic drive has both meiotic and post-meiotic components. Cytological analyses in the light and electron microscopes reveal failures in spermiogenesis in the testes of sc  4  sc  8 males. The extent of abnormal spermatid development increases as nondisjunction becomes more extreme.

Albumins as Embedding Media for Electron Microscopy

1969 ◽  
Vol 27 ◽  
pp. 422-423 ◽  
Author(s):  
J. L. Farrant ◽  
J. D. McLean
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Temperature ◽  
Biological Material ◽  
Globular Proteins ◽  
The Past ◽  
Antibody Staining ◽  
Thin Sectioning ◽  
Embedding Medium

For electron microscope techniques such as ferritin-labeled antibody staining it would be advantageous to have available a simple means of thin sectioning biological material without subjecting it to lipid solvents, impregnation with plastic monomers and their subsequent polymerization. With this aim in view we have re-examined the use of protein as an embedding medium. Gelatin which has been used in the past is not very satisfactory both because of its fibrous nature and the high temperature necessary to keep its solutions fluid. We have found that globular proteins such as the serum and egg albumins can be cross-linked so as to yield blocks which are suitable for ultrathin sectioning.

An Environmental Wet Cell For High Voltage Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 18-19
Author(s):  
N.J. Tighe ◽  
H.M. Flower ◽  
P.R. Swann
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Image Quality ◽  
Inelastic Scattering ◽  
High Voltage ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Environmental Cell ◽  
Water Saturated ◽  
High Temperature Gas

A differentially pumped environmental cell has been developed for use in the AEI EM7 million volt microscope. In the initial version the column of gas traversed by the beam was 5.5mm. This permited inclusion of a tilting hot stage in the cell for investigating high temperature gas-specimen reactions. In order to examine specimens in the wet state it was found that a pressure of approximately 400 torr of water saturated helium was needed around the specimen to prevent dehydration. Inelastic scattering by the water resulted in a sharp loss of image quality. Therefore a modified cell with an ‘airgap’ of only 1.5mm has been constructed. The shorter electron path through the gas permits examination of specimens at the necessary pressure of moist helium; the specimen can still be tilted about the side entry rod axis by ±7°C to obtain stereopairs.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

Analysis of FSRAM Single Bit Failures Due to Unique Dislocations

1998 ◽  
Author(s):  
Phil Schani ◽  
S. Subramanian ◽  
Vince Soorholtz ◽  
Pat Liston ◽  
Jamey Moss ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Random Access ◽  
Random Access Memory ◽  
Static Random Access Memory ◽  
Temperature Sensitive ◽  
Wafer Level ◽  
Top Down ◽  
Access Memory ◽  
Transmission Electron ◽  
Contact Processing

Abstract Temperature sensitive single bit failures at wafer level testing on 0.4µm Fast Static Random Access Memory (FSRAM) devices are analyzed. Top down deprocessing and planar Transmission Electron Microscopy (TEM) analyses show a unique dislocation in the substrate to be the cause of these failures. The dislocation always occurs at the exact same location within the bitcell layout with respect to the single bit failing data state. The dislocation is believed to be associated with buried contact processing used in this type of bitcell layout.

scholarly journals Genetic analysis of temperature-sensitive lethal mutants of Salmonella typhimurium.

Genetics ◽  
1989 ◽  
Vol 123 (4) ◽  
pp. 625-633 ◽  
Author(s):  
M B Schmid ◽  
N Kapur ◽  
D R Isaacson ◽  
P Lindroos ◽  
C Sharpe
Keyword(s):  
High Temperature ◽  
Genetic Analysis ◽  
Salmonella Typhimurium ◽  
Complex Medium ◽  
Temperature Sensitive ◽  
Nonpermissive Temperature ◽  
Anaerobic Conditions ◽  
Temperature Growth ◽  
Lethal Phenotype ◽  
Lethal Mutations

Abstract We have isolated 440 mutants of Salmonella typhimurium that show temperature-sensitive growth on complex medium at 44 degrees. Approximately 16% of the mutations in these strains have been mapped to 17 chromosomal locations; two of these chromosomal locations seem to include several essential genes. Genetic analysis of the mutations suggests that the collection saturates the genes readily mutable to a ts lethal phenotype in S. typhimurium. Physiological characteristics of the ts lethal mutants were tested: 6% of the mutants can grow at high temperature under anaerobic conditions, 17% can grow when the medium includes 0.5 M KCl, and 9% of the mutants die after a 2-hr incubation at the nonpermissive temperature. Most ts lethal mutations in this collection probably affect genes required for growth at all temperatures (not merely during high temperature growth) since Tn10 insertions that cause a temperature-sensitive lethal phenotype are rare.

scholarly journals 111 Artificial Light-Triggered Sleep Deprivation May Lead to Allodynia in Rodent Model

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A45-A46
Author(s):  
Skyler Kanegi ◽  
Armen Akopian
Keyword(s):  
Sleep Deprivation ◽  
Light Exposure ◽  
Light Stimulus ◽  
Continuous Light ◽  
Artificial Light ◽  
Light Cycle ◽  
Tissue Samples ◽  
Mechanical Threshold ◽  
Dim Light ◽  
Von Frey Filaments

Abstract Introduction The combination of artificial light and lack of exposure to natural light can delay the circadian clock, dysregulate the circadian cycle, and decrease alertness upon waking. This effect has been especially significant during the COVID-19 pandemic, where overexposure to artificial light at improper hours has contributed to increased rates of clinical insomnia. Artificial light may also contribute to concomitant neurological conditions such as primary headache, but the mechanisms by which light triggers sleep deprivation-induced headache are not well-understood. Methods To measure pain sensitivity, we habituated 13 wild-type male mice to von Frey filaments applied to the periorbital area until there was no response to 0.6g stimulus. We then applied 5 lux of continuous dim light to mice during their usual 12-hour dark cycle. The 12-hour light cycle remained unchanged with 200 lux continuous light. Three groups of mice experienced the dim light stimulus for one, three, or five consecutive days. Ambulation and rest activity were measured using SOF-812 Activity Monitor machines. After the experiment concluded, we waited 24 hours and measured mechanical threshold using von Frey filaments at 1, 3, 5, 8, and every 3 days subsequently until mice no longer responded to 0.6g stimulus. Results Artificial light triggered changes in circadian behavior including increased number of rest periods during 12-hour dark (dim light) cycle and shortened sleep duration during 12-hour light cycle. Following the artificial light stimulus, there was a significant decrease in mechanical threshold (P<0.05), representing allodynia. The one-day group displayed one day of significant allodynia. The three-day group displayed three days of significant allodynia. The five-day group displayed five days of significant allodynia. Conclusion Artificial light may trigger circadian dysregulation, and the duration of artificial light exposure seemed to be directly correlated to the duration of allodynia up to one week after the stimulus was removed. We will repeat these experiments and analyze CNS and PNS tissue samples to understand the underlying physiological and biochemical bases of how artificial light triggers sleep deprivation-induced headache. This knowledge could increase our understanding of the pathophysiology and comorbidity of sleep deprivation and headache. Support (if any) Funding was received from the National Institute of Health (NS104200).

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