Thermal effects on neuronal activity in suprachiasmatic nuclei of hibernators and nonhibernators

1994 ◽  
Vol 266 (4) ◽  
pp. R1259-R1266 ◽  
Author(s):  
J. D. Miller ◽  
V. H. Cao ◽  
H. C. Heller
Keyword(s):  
Thermal Sensitivity ◽  
Large Population ◽  
Ground Squirrels ◽  
Neuronal Firing ◽  
Temperature Sensitive ◽  
Suprachiasmatic Nuclei ◽  
Circadian Fluctuation ◽  
Cold Sensitive ◽  
Deep Hibernation

The temperature sensitivity of neuronal firing rates in the suprachiasmatic nuclei (SCN) of the hypothalami of rats and ground squirrels was studied in vitro. SCN from euthermic squirrels were studied during the hibernation season (winter) and during the summer. SCN from hibernating squirrels were also studied. Most properties of SCN cells from hibernators and nonhibernators were similar. Warm- and cold-sensitive neurons were observed in all groups, but cold-sensitive neurons were more common in SCN from hibernating squirrels. No evidence for temperature compensation of firing rate was accumulated; no cell was observed to fire below 16.6 degrees C. If the persistence of circadian rhythmicity is a function of action potential-dependent neurotransmission from the SCN, these results suggest that deep hibernation (5-17 degrees C) should be characterized by an absence of circadian fluctuation in temperature. Two possible adaptations for the shallow torpor seen at somewhat higher temperatures were observed in the SCN: 1) a relatively large population of cold-sensitive neurons and 2) a population of neurons with very high activation energies. Activation energy analysis suggested that most of the temperature-sensitive properties of these cells could be explained in terms of the thermal sensitivity of the sodium channel.

scholarly journals Condensin locates at transcriptional termination sites in mitosis, possibly releasing mitotic transcripts

Open Biology ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 190125 ◽  
Author(s):  
Norihiko Nakazawa ◽  
Orie Arakawa ◽  
Mitsuhiro Yanagida
Keyword(s):  
Transcriptional Activation ◽  
Temperature Sensitive ◽  
Growth Defects ◽  
Transcriptional Termination ◽  
Genome Wide ◽  
Transcription Sites ◽  
Cold Sensitive ◽  
Inducible Genes ◽  
Mitotic Chromosome Condensation

Condensin is an essential component of chromosome dynamics, including mitotic chromosome condensation and segregation, DNA repair, and development. Genome-wide localization of condensin is known to correlate with transcriptional activity. The functional relationship between condensin accumulation and transcription sites remains unclear, however. By constructing the auxin-inducible degron strain of condensin, herein we demonstrate that condensin does not affect transcription itself. Instead, RNA processing at transcriptional termination appears to define condensin accumulation sites during mitosis, in the fission yeast Schizosaccharomyces pombe . Combining the auxin-degron strain with the nda3 β-tubulin cold-sensitive (cs) mutant enabled us to inactivate condensin in mitotically arrested cells, without releasing the cells into anaphase. Transcriptional activation and termination were not affected by condensin's degron-mediated depletion, at heat-shock inducible genes or mitotically activated genes. On the other hand, condensin accumulation sites shifted approximately 500 bp downstream in the auxin-degron of 5′-3′ exoribonuclease Dhp1, in which transcripts became aberrantly elongated, suggesting that condensin accumulates at transcriptionally terminated DNA regions. Growth defects in mutant strains of 3′-processing ribonuclease and polyA cleavage factors were additive in condensin temperature-sensitive (ts) mutants. Considering condensin's in vitro activity to form double-stranded DNAs from unwound, single-stranded DNAs or DNA-RNA hybrids, condensin-mediated processing of mitotic transcripts at the 3′-end may be a prerequisite for faithful chromosome segregation.

A Mutation in a Methionine tRNA Gene Suppresses the prp2-1 Ts Mutation and Causes a Pre-mRNA Splicing Defect in Saccharomyces cerevisiae

Genetics ◽  
1999 ◽  
Vol 153 (3) ◽  
pp. 1105-1115
Author(s):  
Dong-Ho Kim ◽  
Gretchen Edwalds-Gilbert ◽  
Chengzhen Ren ◽  
Ren-Jang Lin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Trna Gene ◽  
Mrna Splicing ◽  
Cold Sensitivity ◽  
Temperature Sensitive ◽  
Growth Defects ◽  
Splicing Defect ◽  
Allele Specific ◽  
Cold Sensitive

Abstract The PRP2 gene in Saccharomyces cerevisiae encodes an RNA-dependent ATPase that activates spliceosomes for the first transesterification reaction in pre-mRNA splicing. We have identified a mutation in the elongation methionine tRNA gene EMT1 as a dominant, allele-specific suppressor of the temperature-sensitive prp2-1 mutation. The EMT1-201 mutant suppressed prp2-1 by relieving the splicing block at high temperature. Furthermore, EMT1-201 single mutant cells displayed pre-mRNA splicing and cold-sensitive growth defects at 18°. The mutation in EMT1-201 is located in the anticodon, changing CAT to CAG, which presumably allowed EMT1-201 suppressor tRNA to recognize CUG leucine codons instead of AUG methionine codons. Interestingly, the prp2-1 allele contains a point mutation that changes glycine to aspartate, indicating that EMT1-201 does not act by classical missense suppression. Extra copies of the tRNALeu(UAG) gene rescued the cold sensitivity and in vitro splicing defect of EMT1-201. This study provides the first example in which a mutation in a tRNA gene confers a pre-mRNA processing (prp) phenotype.

Temperature sensitivity of renin-angiotensin system in the ground squirrel

1987 ◽  
Vol 253 (3) ◽  
pp. F471-F475
Author(s):  
C. T. Harker ◽  
M. J. Kluger ◽  
R. L. Malvin
Keyword(s):  
Ground Squirrel ◽  
Renin Angiotensin System ◽  
Ground Squirrels ◽  
Renin Release ◽  
Temperature Sensitive ◽  
Beta Adrenoceptors ◽  
Beta Agonists ◽  
Alpha Agonist

The alteration of renin release by alpha- and beta-adrenoceptors located on the juxtaglomerular cells has been shown to be temperature sensitive in nonhibernating mammals. These experiments investigate the effects of temperature on renin secretion by cortical slices of kidneys from the thirteen-lined ground squirrel Spermophilus tridecemlineatus. At 37 degrees C, beta-stimulation (isoproterenol 10(-7) M) increased the release of renin by slices taken from nonhibernating ground squirrels but had no effect on those taken from hibernating squirrels. The alpha-agonist phenylephrine (10(-5) M) had no effect on slices from nonhibernating squirrels but enhanced the release rate in those from hibernating ground squirrels, providing the first evidence of in vitro stimulation of renin release by an alpha-agonist. When incubated at 11 degrees C, kidney slices from both hibernating and nonhibernating animals were unresponsive to both alpha- and beta-agonists until incubation times were doubled. Under these prolonged conditions, phenylephrine again stimulated renin release. These results indicate that both in vitro and in vivo cooling alter the responses of alpha- and beta-adrenoceptors to renin-releasing stimuli.

scholarly journals Suppression of Temperature-Sensitive Chromosome Replication of an Escherichia coli dnaX(Ts) Mutant by Reduction of Initiation Efficiency

2003 ◽  
Vol 185 (12) ◽  
pp. 3583-3595 ◽  
Author(s):  
Alexandra Blinkova ◽  
Mary Jo Hermandson ◽  
James R. Walker
Keyword(s):  
Dna Polymerase ◽  
Temperature Sensitivity ◽  
Temperature Sensitive ◽  
Dna Polymerase Iii ◽  
Suppressor Mutations ◽  
Polymerase Iii ◽  
Initiation Frequency ◽  
Cold Sensitive ◽  
Ts Mutant

ABSTRACT Temperature sensitivity of DNA polymerization and growth of a dnaX(Ts) mutant is suppressible at 39 to 40°C by mutations in the initiator gene, dnaA. These suppressor mutations concomitantly cause initiation inhibition at 20°C and have been designated Cs,Sx to indicate both phenotypic characteristics of cold-sensitive initiation and suppression of dnaX(Ts). One dnaA(Cs,Sx) mutant, A213D, has reduced affinity for ATP, and two mutants, R432L and T435K, have eliminated detectable DnaA box binding in vitro. Two models have explained dnaA(Cs,Sx) suppression of dnaX, which codes for both the τ and γ subunits of DNA polymerase III. The initiation deficiency model assumes that reducing initiation efficiency allows survival of the dnaX(Ts) mutant at the somewhat intermediate temperature of 39 to 40°C by reducing chromosome content per cell, thus allowing partially active DNA polymerase III to complete replication of enough chromosomes for the organism to survive. The stabilization model is based on the idea that DnaA interacts, directly or indirectly, with polymerization factors during replication. We present five lines of evidence consistent with the initiation deficiency model. First, a dnaA(Cs,Sx) mutation reduced initiation frequency and chromosome content (measured by flow cytometry) and origin/terminus ratios (measured by real-time PCR) in both wild-type and dnaX(Ts) strains growing at 39 and 34°C. These effects were shown to result specifically from the Cs,Sx mutations, because the dnaX(Ts) mutant is not defective in initiation. Second, reduction of the number of origins and chromosome content per cell was common to all three known suppressor mutations. Third, growing the dnaA(Cs,Sx) dnaX(Ts) strain on glycerol-containing medium reduced its chromosome content to one per cell and eliminated suppression at 39°C, as would be expected if the combination of poor carbon source, the Cs,Sx mutation, the Ts mutation, and the 39°C incubation reduced replication to the point that growth (and, therefore, suppression) was not possible. However, suppression was possible on glycerol medium at 38°C. Fourth, the dnaX(Ts) mutation can be suppressed also by introduction of oriC mutations, which reduced initiation efficiency and chromosome number per cell, and the degree of suppression was proportional to the level of initiation defect. Fifth, introducing a dnaA(Cos) allele, which causes overinitiation, into the dnaX(Ts) mutant exacerbated its temperature sensitivity.

scholarly journals Genetic interactions between the yeast RNA helicase homolog Prp16 and spliceosomal snRNAs identify candidate ligands for the Prp16 RNA-dependent ATPase.

Genetics ◽  
1994 ◽  
Vol 137 (3) ◽  
pp. 677-687 ◽  
Author(s):  
H D Madhani ◽  
C Guthrie
Keyword(s):  
Rna Helicase ◽  
Dominant Negative ◽  
Temperature Sensitive ◽  
Factor X ◽  
Nucleotide Substitutions ◽  
Site Analysis ◽  
U6 Snrna ◽  
Cold Sensitive ◽  
Rna Ligands

Abstract Pre-mRNA splicing occurs in a large and dynamic ribonucleoprotein complex, the spliceosome. Several protein factors involved in splicing are homologous to a family of RNA-dependent ATPases, the so-called DEAD/DEAH proteins. A subset of these factors exhibit RNA helicase activity in vitro. The DEAD/DEAH proteins involved in splicing are thought to mediate RNA conformational rearrangements during spliceosome assembly. However, the RNA ligands for these factors are currently unknown. Here, we present genetic evidence in Saccharomyces cerevisiae for a functional interaction between the DEAH protein Prp16, and the U6 and U2 spliceosomal snRNAs. Using a library of mutagenized U6 snRNA genes, we have identified 14 strong suppressors of the cold-sensitive (cs) allele, prp16-302. Remarkably, each suppressor contains a single nucleotide deletion of 1 of the 6 residues that lie immediately upstream of a sequence in U6 that interacts with the 5' splice site. Analysis of site-directed mutations revealed that nucleotide substitutions in the adjacent U2-U6 helix I structure also suppress prp16-302, albeit more weakly. The U6 suppressors tested also partially reverse the phenotype of two other cs alleles, prp16-1 and prp16-301, but not the four temperature-sensitive alleles tested. Finally, overexpression of each cs allele exacerbates its recessive growth phenotype and confers a dominant negative cs phenotype. We propose that the snRNA suppressors function by destabilizing an interaction between the U2-U6 complex and a hypothetical factor (X), which is trapped by cs mutants of PRP16. The phenotypes of overexpressed prp16 alleles are consistent with the model that this trapped interaction inhibits the dissociation of Prp16 from the spliceosome. We discuss the intriguing possibility that factor X is Prp16 itself.

Do the suprachiasmatic nuclei oscillate in old rats as they do in young ones?

1993 ◽  
Vol 265 (5) ◽  
pp. R1216-R1222 ◽  
Author(s):  
E. Satinoff ◽  
H. Li ◽  
T. K. Tcheng ◽  
C. Liu ◽  
A. J. McArthur ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Brain Slices ◽  
Neuronal Firing ◽  
Suprachiasmatic Nuclei ◽  
Firing Rates ◽  
Behavioral Rhythms ◽  
Behavioral Rhythm ◽  
Old Rats ◽  
The Brain

The basis of the decline in circadian rhythms with aging was addressed by comparing the patterns of three behavioral rhythms in young and old rats with the in vitro rhythm of neuronal activity in the suprachiasmatic nuclei (SCN), the primary circadian pacemaker. In some old rats, rhythms of body temperature, drinking, and activity retained significant 24-h periodicities in entraining light-dark cycles; in others, one or two of the rhythms became aperiodic. When these rats were 23-27.5 mo old they were killed, and single-unit firing rates in SCN brain slices were recorded continuously for 30 h. There was significant damping of mean peak neuronal firing rates in old rats compared with young. SCN neuronal activities were analyzed with reference to previous entrained behavioral rhythm patterns of individual rats as well. Neuronal activity from rats with prior aperiodic behavioral rhythms was erratic, as expected. Neuronal activity from rats that were still maintaining significant 24-h behavioral rhythmicity at the time they were killed was erratic in most cases but normally rhythmic in others. Thus there was no more congruence between the behavioral rhythms and the brain slice rhythms than there was among the behavioral rhythms alone. These results, the first to demonstrate aberrant SCN firing patterns and a decrease in amplitude in old rats, imply that aging could either disrupt coupling between SCN pacemaker cells or their output, or cause deterioration of the pacemaking properties of SCN cells.

scholarly journals DiaA, a Novel DnaA-binding Protein, Ensures the Timely Initiation ofEscherichia coliChromosome Replication

2004 ◽  
Vol 279 (44) ◽  
pp. 45546-45555 ◽  
Author(s):  
Takuma Ishida ◽  
Nobuyoshi Akimitsu ◽  
Tamami Kashioka ◽  
Masakazu Hatano ◽  
Toshio Kubota ◽  
...  
Keyword(s):  
Gel Filtration ◽  
Replication Initiation ◽  
Temperature Sensitive ◽  
Minichromosome Maintenance ◽  
Chromosomal Replication ◽  
Timely Initiation ◽  
Initiation Of Replication ◽  
Direct Binding ◽  
Cold Sensitive

The DnaA protein is the initiator ofEscherichia colichromosomal replication. In this study, we identify a novel DnaA-associating protein, DiaA, that is required for the timely initiation of replication during the cell cycle. DiaA promotes the growth of specific temperature-sensitivednaAmutants and ensures stable minichromosome maintenance, whereas DiaA does not decrease the cellular DnaA content. AdiaA::Tn5mutation suppresses the cold-sensitive growth of an overinitiation typednaAmutant independently of SeqA, a negative modulator of initiation. Flow cytometry analyses revealed that the timing of replication initiation is disrupted in thediaAmutant cells as well as wild-type cells with pBR322 expressing thediaAgene. Gel filtration and chemical cross-linking experiments showed that purified DiaA forms a stable homodimer. Immunoblotting analysis indicated that a single cell contains about 280 DiaA dimers. DiaA stimulates minichromosome replication in anin vitrosystem especially when the level of DnaA included is limited. Moreover, specific and direct binding between DnaA and DiaA was observed, which requires a DnaA N-terminal region. DiaA binds to both ATP- and ADP-bound forms of DnaA with a similar affinity. Thus, we conclude that DiaA is a novel DnaA-associating factor that is crucial to ensure the timely initiation of chromosomal replication.

Novel Phytochemical Constituents and their Potential to Manage Diabetes

2020 ◽  
Vol 26 ◽  
Author(s):  
Shaik Ibrahim Khalivulla ◽  
Arifullah Mohammed ◽  
Kokkanti Mallikarjuna
Keyword(s):  
Natural Products ◽  
Large Population ◽  
World Health ◽  
In Vivo Studies ◽  
Antidiabetic Activity ◽  
Therapeutic Drug ◽  
Pharmacological Activities ◽  
Chemical Structures

Background: Diabetes is a chronic disease affecting a large population worldwide and stands as one of the major global health challenges to be tackled. According to World Health Organization, about 400 million are having diabetes worldwide and it is the seventh leading cause of deaths in 2016. Plant based natural products had been in use from ancient time as ethnomedicine for the treatment of several diseases including diabetes. As a result of that, there are several reports on plant based natural products displaying antidiabetic activity. In the current review, such antidiabetic potential compounds reported from all plant sources along with their chemical structures are collected, presented and discussed. This kind of reports are essential to pool the available information to one source followed by statistical analysis and screening to check the efficacy of all known compounds in a comparative sense. This kind of analysis can give rise to few numbers of potential compounds from hundreds, whom can further be screened through in vitro and in vivo studies, and human trails leading to the drug development. Methods: Phytochemicals along with their potential antidiabetic property were classified according to their basic chemical skeleton. The chemical structures of all the compounds with antidiabetic activities were elucidated in the present review. In addition to this, the distribution and their other remarkable pharmacological activities of each species is also included. Results: The scrutiny of literature led to identification of 44 plants with antidiabetic compounds (70) and other pharmacological activities. For the sake of information, the distribution of each species in the world is given. Many plant derivatives may exert antidiabetic properties by improving or mimicking the insulin production or action. Different classes of compounds including sulfur compounds (1-4), alkaloids (5-11), phenolic compounds (12-17), tannins (18-23), phenylpropanoids (24-27), xanthanoids (28-31), amino acid (32), stilbenoid (33), benzofuran (34), coumarin (35), flavonoids (36-49) and terpenoids (50-70) were found to be active potential compounds for antidiabetic activity. Of the 70 listed compounds, majorly 17 compounds are from triterpenoids, 13 flavonoids and 7 are from alkaloids. Among all the 44 plant species, maximum number (7) of compounds are reported from Lagerstroemia speciosa followed by Momordica charantia (6) and S. oblonga with 5 compounds. Conclusion: This is the first paper to summarize the established chemical structures of phytochemicals that have been successfully screened for antidiabetic potential and their mechanisms of inhibition. The reported compounds could be considered as potential lead molecules for the treatment of type-2 diabetes. Further, molecular and clinical trials are required to select and establish the therapeutic drug candidates.

scholarly journals Evaluation of the Safety and Immune Efficacy of Recombinant Human Respiratory Syncytial Virus Strain Long Live Attenuated Vaccine Candidates

2021 ◽  
Author(s):  
Li-Nan Wang ◽  
Xiang-Lei Peng ◽  
Min Xu ◽  
Yuan-Bo Zheng ◽  
Yue-Ying Jiao ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Gene Deletion ◽  
Human Respiratory Syncytial Virus ◽  
Temperature Sensitive ◽  
T7 Promoter ◽  
Vaccine Candidates ◽  
Rsv Infection ◽  
Syncytial Virus

AbstractHuman respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract illness (LRTI), and no vaccine against LRTI has proven to be safe and effective in infants. Our study assessed attenuated recombinant RSVs as vaccine candidates to prevent RSV infection in mice. The constructed recombinant plasmids harbored (5′ to 3′) a T7 promoter, hammerhead ribozyme, RSV Long strain antigenomic cDNA with cold-passaged (cp) mutations or cp combined with temperature-sensitive attenuated mutations from the A2 strain (A2cpts) or further combined with SH gene deletion (A2cptsΔSH), HDV ribozyme (δ), and a T7 terminator. These vectors were subsequently co-transfected with four helper plasmids encoding N, P, L, and M2-1 viral proteins into BHK/T7-9 cells, and the recovered viruses were then passaged in Vero cells. The rescued recombinant RSVs (rRSVs) were named rRSV-Long/A2cp, rRSV-Long/A2cpts, and rRSV-Long/A2cptsΔSH, respectively, and stably passaged in vitro, without reversion to wild type (wt) at sites containing introduced mutations or deletion. Although rRSV-Long/A2cpts and rRSV-Long/A2cptsΔSH displayed  temperature-sensitive (ts) phenotype in vitro and in vivo, all rRSVs were significantly attenuated in vivo. Furthermore, BALB/c mice immunized with rRSVs produced Th1-biased immune response, resisted wtRSV infection, and were free from enhanced respiratory disease. We showed that the combination of ΔSH with attenuation (att) mutations of cpts contributed to improving att phenotype, efficacy, and gene stability of rRSV. By successfully introducing att mutations and SH gene deletion into the RSV Long parent and producing three rRSV strains, we have laid an important foundation for the development of RSV live attenuated vaccines.

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