Inhalation exposure-rate of ethylene oxide affects the level of DNA breakage and unscheduled DNA synthesis in spermiogenic stages of the mouse

The effect of ethylene oxide (EtO) inhalation-exposure rate on the induction of DNA breakage in late spermatids and on unscheduled DNA synthesis (UDS) in early spermatids was studied. The exposures were 450 parts per million (ppm) for 4 h, 900 ppm for 2 h, and 1800 ppm for 1 h. Thus, the total exposure was always 1800 ppm-h. Both DNA breakage and UDS were found to increase by a factor of approximately 3 in going from the low to high EtO concentration, suggesting that the molecular dose of EtO to the testis had increased by a similar factor. Our results are consistent with the EtO exposure-rate effect found by Generoso et al. (1986) for induction of dominant-lethal mutations in late spermatids and early spermatozoa.     

Mutagen-induced fetal anomalies and death following treatment of females within hours after mating

In an earlier study (Generoso et al., 1987), it was observed that the mutagen, ethylene oxide (EtO), produced remarkable increases in the incidence of developmental abnormalities and death of fetuses when early zygotic stages were exposed. This is a major finding in experimental induction of embryopathy, implicating genetic damage to the zygotes as the likely cause. In the subsequent study reported here, 3 other mutagens--ethyl methanesulfonate (EMS), ethyl nitrosourea (ENU), and triethylene melamine (TEM), were studied for embryopathic effects following exposure of dictyate oocytes, prefertilization oviducal eggs and sperm, early pronuclear zygotes, zygotes undergoing pronuclear DNA synthesis, and two-cell embryos. All 4 mutagens produced developmental abnormalities among living fetuses following exposure of early pronuclear zygotes (the only stage studied for this endpoint in this report). With respect to stage specificity and gestational timing of death of conceptuses, EMS and EtO on one hand and ENU and TEM on the other, are very similar to one another. EMS, like EtO, produced a high incidence of midgestation and late fetal deaths only in prefertilization oviducal eggs and sperm and in early pronuclear eggs. In contrast, ENU and TEM produced high losses of conceptuses in all postmating stages studied but death occurred primarily prior to or around the time of implantation. Thus, the frequency of induction and the expression of embryopathy, which ranged from early embryonic preimplantation and late fetal deaths to subtle fetal anomalies, are dependent upon the stage exposed and the mutagen used.     

Effects of Dose on the Induction of Dominant-Lethal Mutations and Heritable Translocations with Ethyl Methanesulfonate in Male Mice

Genetic damage by ethyl methanesulfonate (EMS) in male mice was measured at doses ranging from 50 to 300 mg/kg with dominant-lethal mutations and reciprocal translocations as endpoints. No appreciable increase in dominant-lethal mutations was detected following a dose of 100 mg/kg. Dominant lethals induced by EMS were convincingly detected only after a dose of 150 mg/kg, but in the translocation experiment an increase in the genetic effect was detectable at the 50 mg/kg dose. It is likely that dominant lethals had also been induced at the 50 and 100 mg/kg doses, but were not detected due to the relative insensitivity of the dominant..lethal procedure. Thus, for detection of low levels of EMS-induced chromosome breakage, translocations are a much more reliable endpoint than are dominant-lethal mutations. A procedure for large-scale screening of induced translocations is described.—The dominant-lethal dose-response curve, plotted on the basis of living embryos as a percentage of the control value, is clearly not linear as it is markedly concave downward. Similarly, the translocation dose-response curve showed a more rapid increase in the number of translocations with dose than would be expected on the basis of dose-square kinetics. It is clear for both of these endpoints that the effectiveness of EMS in inducing chromosome breakage is proportionately much lower at low doses.     

Increased incidence of developmental anomalies among descendants of carriers of methylenebisacrylamide-induced balanced reciprocal translocations

N,N'-Methylenebisacrylamide (MBA), a dimer of the monomeric acrylamide, was studied for induction of clastogenic effects in germ cells of male mice. It was found to be effective in inducing dominant-lethal mutations and heritable translocations in maturing sperm. The semisterile translocation carriers and their normal counterparts were used to determine the health impact of transmitted chromosomal rearrangements through anatomical analysis of their immediate descendants in utero. As expected, semisterility resulted primarily from embryonic death during the periimplantation stages presumably caused by sperm segregants with unbalanced chromosome complement fertilizing some of the eggs. Among conceptuses that survived to mid- and late-gestation stages, there was an increased incidence of developmental anomalies including fetal death and phenotypic defects. These anomalies are assumed to be caused by certain types of unbalanced segregants that are compatible with survival beyond the periimplantation period. This class of unbalanced segregants represent in humans a major health problem to the mother and her conceptus.     

Screening for point mutations in exon 10 of the low density lipoprotein receptor gene by analysis of single-strand conformation polymorphisms: detection of a nonsense mutation — FH469→Stop

DNA from 40 unrelated familial hypercholesterolemia (FH) heterozygotes were subjected to analyses of single-strand conformation polymorphisms (SSCPs) of exon 10 of the low density lipoprotein receptor (LDLR) gene. Four different SSCP patterns were observed. The underlying mutations were characterized by DNA sequencing. Three of the patterns represented the three genotypes of a recently described sense mutation in codon 450. A method based upon the polymerase chain reaction (PCR) was developed to analyze this mutation. The frequencies of the wild-type (G at nucleotide 1413) and mutant (A at nucleotide 1413) alleles were 0.56 and 0.44, respectively. The fourth pattern was found in only one FH heterozygote and was caused by heterozygosity at nucleotide 1469 (G/A). Nucleotide 1469 is the second base of codon 469_Trp(TGG). The GA mutation changes this codon into the amber stop codon, and is referred to as FH_469Stop. The mutant receptor consists of the amino terminal 468 amino acids. Because the truncated receptor has lost the membrane-spanning domain, it will not be anchored in the cell membrane. FH_469Stop destroys an AvaII restriction site, and this characteristic was used to develop a PCR method to establish its frequency in Norwegian FH subjects. Two out of 204 (1%) unrelated FH heterozygotes possessed the mutation.     

Oxyprenylated secondary metabolites: a survey of their innovative extraction methodologies

Phytochemistry Reviews - Oxyprenylated secondary metabolites of plant, fungal, and microbial origin have emerged as biologically active natural compounds with a great potential for the next future....     

Time of recombination in the Drosophila melanogaster Oocyte

A test has been carried out to determine if the restrictive temperature (31°) acts to reduce recombination in the temperature-sensitive recombination-deficient genotype rec-1 ²⁶/rec-1 ¹⁶ by reducing or eliminating the synaptonemal complex. Measurements of the length of synaptonemal complexes in heat-treated and untreated stage 1 oocytes, following termination of the temperature-sensitive period, reveal less than a 5% difference, with the greater length present in the treated oocytes. Alterations are not observed in synaptonemal complex distribution within the nucleus or in its fine structure. Parallel genetic studies confirm earlier observations that the restrictive temperature, whose action is confined to a 36-h sensitive period virtually coextensive with premeiotic-S, drastically reduces recombination to 10% of normal. The results are most simply interpreted to mean that the restrictive temperatures acts directly on the recombination process.     

A temporal study at the ultrastructural level of the developing pro-oocyte of Drosophila melanogaster

The first pro-oocyte in developing pupal germaria of females grown at 25 ° has been followed at 6 h intervals from its formation at 129 h post-ovipostion until Stage 1, to provide an unambiguous temporal order. EM autoradiographs were made of sectioned germaria, scanned at lower magnification for location of the pro-oocyte(s) within the most posterior 16-cell cyst and photographed at higher magnification to show the presence of label indicating DNA replication and synaptonemal complex indicating synapsis in the same pro-oocyte nucleus. Label, detected at 132 h and at all subsequent intervals up to and including 162 h, delimited an S-phase of 30 h and identified this period as premeiotic interphase. Extensive SCs (av. length 50 m/genome) measured in serial sections at 132 h provide irrefutable evidence that synapsis in Drosophila begins close to both pro-oocyte formation and initiation of premeiotic interphase. Measurements of SCs at 6 h intervals during interphase reveal a sharp increase between 132 and 138 h, a peak length (75 m/genome) at 144 h, a decrease and subsequent plateau ( 60 m/genome) from 150–162 h and a further drop (R~50 m/genome) at Stage 1. Maximal extension of SC at 144 h coincides with maximal genome response to heat (Grell and Day, 1974) and with midpremeiotic-S. Spherical nodules, detected at 1/genome between 138 and 150 h would, on the questionable assumption that they are the sites of recombination, provide proof of recombination during early interphase, as genetic evidence strongly implies. Evidence contrary to interpretations of fibrillar material within the nucleus as either precursor of the central region of the SC or sagittal sections of the central element of the SC, is presented. No structure corresponding to the polytene chromocenter was observed.     

Increased kynurenine-to-tryptophan ratio in the serum of patients infected with SARS-CoV2: An observational cohort study.

Immune dysregulation is a hallmark of patients infected by SARS-CoV2 and the balance between immune reactivity and tolerance is a key determinant of all stages of infection, including the excessive inflammatory state causing the acute respiratory distress syndrome. The kynurenine pathway (KP) of tryptophan (Trp) metabolism is activated by pro-inflammatory cytokines and drives mechanisms of immune tolerance. We examined the state of activation of the KP by measuring the Kyn:Trp ratio in the serum of healthy subjects (n = 239), and SARS-CoV2-negative (n = 305) and -positive patients (n = 89). Patients were recruited at the Emergency Room of St. Andrea Hospital (Rome, Italy). Kyn and Trp serum levels were assessed by HPLC/MS-MS. Compared to healthy controls, both SARS-CoV2-negative and -positive patients showed an increase in the Kyn:Trp ratio. The increase was larger in SARS-CoV2-positive patients, with a significant difference between SARS-CoV2-positive and -negative patients. In addition, the increase was more prominent in males, and positively correlated with age and severity of SARS-CoV2 infection, categorized as follows: 1 = no need for intensive care unit (ICU); 2 ≤ 3 weeks spent in ICU; 3 ≥ 3 weeks spent in ICU; and 4 = death. The highest Kyn:Trp values were found in SARS-CoV2-positive patients with severe lymphopenia. These findings suggest that the Kyn:Trp ratio reflects the level of inflammation associated with SARS-CoV2 infection, and, therefore, might represent a valuable biomarker for therapeutic intervention.