(n.) A commissure; especially, the optic commissure, or crucial union of the optic nerves.
Example Sentences:
(1) For the case described by the author primary tearing of the chiasma due to sudden applanation of the skull in the frontal region with burstfractures in the anterior cranial fossa is assumed.
(2) There were, however, significant differences among investigators in reported mean chiasma frequencies.
(3) In only one case was the B chromosome significantly associated with an increase chiasma frequency.
(4) Chromosomal analysis of cells undergoing diakinesis showed significantly lower chiasma frequency in elderly men, compared with a group of younger control males and also with infertile males.
(5) Furthermore we found increased chiasma frequencies in diakinesis--metaphase I (MI) and reduced nondisjunction frequencies at anaphse I as a result of the treatments applied.
(6) A case of cystic optic glioma involving chiasma and bilateral posterior optic pathway was reported.
(7) CT revealed a calcified lesion which must be a vessel in the chiasma cistern just adjacent to the basilar artery which was relatively larger than normal.
(8) In the unanaesthetised animals the proportions of units responding were high (60%) and did not differ significantly between regions for each type of stimulation investigated: visual, auditory and optic chiasma shocks.
(9) Tangential, centrifugal and incerta sedis-fibres, which originate either from cell bodies in the cell body layer at the periphery of the outer chiasma or more centrally, terminate in the synaptic region of the lamina.
(10) This new function is derived by assuming that all chromosome arms except the short arms of acrocentric chromosomes hav an obligatory chiasma, and that the remaining chiasmata are distributed at random; assumptions which may correspond reasonably well to reality.
(11) Thus from just beyond the chiasma the fibres had already achieved the major uniaxial rearrangement necessary to establish a normal tract distribution despite the eye translocation.
(12) Pathologically there was necrosis of the optic chiasma and focal areas of myelin sheath vacuolation or demyelination in certain areas of the brain, especially in the cerebellar peduncles.
(13) Predictions from the chiasma map can be confirmed or refuted only by genetic evidence for which the estimates of this paper serve as initial values to begin maximum likelihood iteration.
(14) Male meiosis in Mesostoma ehrenbergii ehrenbergii (2x = 10) is characterized by extreme restriction of chiasma formation; 3 pairs of chromosomes form bivalents at metaphase I which are associated by single very distally localized chiasma, while two pairs of chromosomes remain as unpaired univalents.
(15) It was found that both of the heat-induced decreases in chiasma frequency which can be obtained (Effects 2 and 3), were dominant over both of the different types of increase (Effects 1 and 4), with the largest decrease (Effect 3) being dominant over all others.
(16) In precocious puberty we found 1 ectopic pinealoma and 2 gliomas of the chiasma.
(17) The latter refers to the Willis atypical polygons, which determine important atipies in the topographical distribution of the chiasma's arteries and optical bandelets.
(18) In the rostral third of the SCN there are relatively few optic synapses which are found close to the optic chiasma.
(19) In addition to this abnormality there is a misrouting of the optic nerve fibers, with some fibers from the temporal retina following a crossed route at the chiasma and terminating in the contralateral cortical hemisphere.
(20) The chiasma frequency estimates were based on 15 son-sire pairs, the translocation heterozygotes being maintained in a Swiss random-bred genetic background.
Meiosis
Definition:
(n.) Diminution; a species of hyperbole, representing a thing as being less than it really is.
Example Sentences:
(1) To this end, a meiosis-defective mating-type mutation was used as a marker for the plus segment, by taking advantage of its suppressibility by a nonsense suppressor.
(2) When multiple probes were informative, the meiotic exchange points for each meiosis were located in individual families.
(3) This observation suggests that testosterone acts to inhibit meiosis at a site beyond the function of the puromycin-sensitive proteins or that testosterone causes a reduction in the turnover rate of these proteins.
(4) Commitment to meiosis occurs during the prezygotene interval at about the time when S-phase replication is completed.
(5) Meiosis is too complex to have arisen at once full blown and a stepwise scheme is proposed for its evolution, where each step is believed to have provided an immediate selective advantage: (1) The first step in this tentative sequence is the development of a haploidization process by means of a rapid series of mitotic non-disjunctions, turned on under conditions where haploidy is favored.
(6) Recently, cDNA clones encoding several bovine CKI isoforms have been sequenced that show high sequence identity to the HRR25 gene product of the budding yeast Saccharomyces cerevisiae; HRR25 is required for normal cellular growth, nuclear segregation, DNA repair, and meiosis.
(7) They proceed through meiosis normally, as judged by the occurrence of meiotic recombination, the production of haploid nuclei, and the formation of multinucleate cells visible after Giemsa staining.
(8) In continuation of the research on male human meiosis within the study of pachytene bivalents, results from the analysis of 125 cells are presented.
(9) The absence of these mRNAs in mitosis and their disappearance at 4 hr and later in meiosis suggest that the rec7 and rec8 gene products may be involved primarily in the early steps of meiotic recombination in S. pombe.
(10) This trisomy arose through aberrant segregation of translocation chromosome during meiosis in the patient's mother, who is a balanced heterozygote for a complex translocation involving chromosomes 9, 21 and 22.
(11) Chemicals were injected into mice at the MI (meiosis I) stage or 3 hours before the MI stage in order to examine their toxicity.
(12) In the immunogold staining assay a post-fixation and nuclear staining procedure was developed which allowed identification of isolated germ cells, revealing clearly, for all seven MAbs, that the determinants were expressed on germ cells but not on somatic cells and, for WCS 7, 11 and 12 only, that the determinants first appeared on small spermatogonia prior to meiosis.
(13) A 'small' CG-free area of the cortex, with prominent cytoplasmic protrusions, appeared twice during the progression of meiosis.
(14) An attractive explanation for these results is that long tandem arrays of simple repeated sequences are generated at high frequency throughout the genome and that they are retained for a longer time on the Y chromosome due to the absence of homologous pairing at meiosis.
(15) Expression of one of the three genes was found to be limited to a single cell type during the 5-6 day period from late meiosis to immature pollen formation.
(16) Analysis of RNA from different developmental stages and from enriched populations of spermatogenic cells revealed that this gene is expressed during the prophase stage of meiosis.
(17) In fission yeast the ability to undergo meiosis and sporulation is conferred by the matP+ and matM+ genes of the mating-type locus.
(18) The binding of in vivo labeled RNA to the corresponding DNAs increased 3- to 12-fold at the time of meiosis I, in parallel with the accumulation of the SPR transcripts.
(19) It was concluded that meiosis and spore formation in Saccharomycopsis lipolytica seem to represent parallel and coordinated processes which generally resemble those recorded for Saccharomyces cerevisiae and Hansenula species.
(20) Neither meiosis nor mutagenesis increased the revertant frequency, nor did incubation at elevated temperatures lower it.