Silver positivity of the NORs during embryonic development of Xenopus laevis

Transcriptional activity of ribosomal RNA (rRNA) genes is detectable around blastula-gastrula transition during the embryonic development of amphibians and other non-mammalian systems. The silver staining reaction, known to selectively stain transcriptionally active nucleolus organizer regions (NORs) both in interphase and metaphase chromosomes allowed us to follow the activation of the NORs during the embryonic development of Xenopus laevis.

Silver staining of the nucleolus organizer regions (NOR) requires clusters of sulfhydryl groups

Silver stainability of nucleolus organizer regions (NORs) appears to be correlated with the presence of grouped sulfhydryl (SH) side chains of proteins. In fact, heavy metals with high affinity for SH groups, such as Hg and Cu, do prevent the silver staining reaction. Ferricyanide, which is known to oxidize SH to disulfides, also prevents any further reaction with silver. On the other hand, alkali and reducing agents (mercaptoethanol, cyanide) do not affect silver stainability of the NORs. These results show that the silver staining reaction is not related to disulfide or persulfide groups and that alkali-soluble, acidic nuclear proteins per se do not play a major role in this process.

Cytogenetic and clinical studies in gonadal dysgenesis with 46,X,Xt(qter leads to p221::p223 leads to qter) karyotype: review and phenotype/karyotype correlations

Chromosome analysis by Q, R, and C banding was performed in a case diagnosed clinically as gonadal dysgenesis and the karyotype was shown to be 46,X,Xt(qter leads to p221::p223 leads to qter). Localisation of the breakpoints in the fused X chromosomes and replication studies have led to a hypothesis on the origin of the translocation. A comparison of clinical and cytogenetical findings in this and other published cases has also been made in an attempt to detect some phenotype/karyotype correlations.

A new translocation involving chromosomes no. 5 and no. 12 t(5;12) (5q15;12p13)

A new case of translocation between chromosomes No. 5 and No. 12 is described. The translocation t(5;12) (5q15;12p13) is apparently balanced and was found in a child aged 3 1/2 years who was affected with severe psychomotor retardation. On the basis of the clinical picture it is suggested that the phenotype could be not dependent on the chromosomal alteration.

Autoradiographic study of DNA synthesis in homologous chromosomes distinguishable by morphology

Autoradiographic terminal labeling studies performed on leukocyte cultures of a man (A. de J.) and his son (H. de J.), both carriers of an enlarged satellite on a D-group chromosome, demonstrated that the morphological marker was a No. 15. Counts of grains on the long arms of the two chromosomes 15 showed that the marker chromosome was less heavily labeled than its normal homolog. This difference was highly significant in both cases. The marker chromosome was also shorter than its homolog, though not significantly so in one case. Possible interpretations of these findings, i.e., chromosomal polymorphism or autosomal lyonization, were discussed.

Presumptive C-15 translocation and familial large Y identified by autoradiography

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Detection of minute deletions in human karyotypes

Minute deletions of the B-group short arm have been demonstrated in five of six cases with clinical features suggestive of a deletion of chromosome 4 or 5, but with grossly normal chromosomes. A deletion as small as 8% of the short arm was detectable by each of five observers when randomly arranged cells from controls, cases with large deletions and the cases with suspected minute deletions were scored blindly for the presence of a deletion. Another two cases were shown to have deletions of only 4% of the short arm by measurement studies, although the deletion in these cases could not be detected visually in the blind study. The presence of the deletion was confirmed in one case by DNA-labelling studies showing that the putative deleted chromosome consistently had the replication pattern of chromosome 4. In another two cases measurement of the long arm confirmed that the deleted chromosome was a chromosome 5.

Translocation heterozygosis: a cause of five cases of the cri du chat syndrome and two cases with a duplication of chromosome number five in three families

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Distinction between chromosome 4 and chromosome 5 by replication pattern and length of long and short arms

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