Molecular characterization of de novo secondary trisomy 13.

Unbalanced Robertsonian translocations are a significant cause of mental retardation and fetal wastage. The majority of homologous rearrangements of chromosome 21 in Down syndrome have been shown to be isochromosomes. Aside from chromosome 21, very little is known about other acrocentric homologous rearrangements. In this study, four cases of de novo secondary trisomy 13 are presented. FISH using alpha-satellite sequences, rDNA, and a pTRI-6 satellite I sequence specific to the short arm of chromosome 13 showed all four rearrangements to be dicentric and apparently devoid of ribosomal genes. Three of four rearrangements retained the pTRI-6 satellite I sequence. Case 1 was the exception, showing a deletion of this sequence in the rearrangement, although both parental chromosomes 13 had strong positive hybridization signals. Eleven microsatellite markers from chromosome 13 were also used to characterize the rearrangements. Of the four possible outcomes, one maternal Robertsonian translocation, two paternal isochromosomes, and one maternal isochromosome were observed. A double recombination was observed in the maternally derived rob(13q13q). No recombination events were detected in any isochromosome. The parental origins and molecular chromosomal structure of these cases are compared with previous studies of de novo acrocentric rearrangements.     

SEXUAL DIFFERENTIATION OF GRIFFITHSIA (CERAMIALES, RHODOPHYTA): NUCLEAR PLOIDY LEVEL OF MIXED-PHASE PLANTS IN G. JAPONICA1

Mixed-phase plants of Griffithsia japonica Okamura spontaneously occurred in a laboratory culture. Four female plants produced tetrasporangia and spermatangia in addition to their normal female reproductive structures (bisexual/mixed-phase plants), and four male plants produced tetrasporangia as well as spermatangia (male/mixed-phase plants). To determine the nuclear ploidy level of these mixed-phase plants, relative nuclear sizes of male, female, tetrasporangial, and mixed-phase plants were measured using a microscopic image analysis system. Haploid gametophytes could be distinguished from diploid tetrasporophytes by relative nuclear sizes, with the later having nuclei twice the size of the former. Relative nuclear sizes of the mixed-phase plants were similar to those of the haploid plants. Thus, the mixed-phase plants were determined to be haploid. Haploid mixed-phase plants of G. japonica have a potential to produce male, female and tetrasporangial reproductive structures. Sex determination models are discussed to explain "haploid" mixed-phase phenomena in red algae .     

Genomic fingerprints of Salmonella species generated with repetitive element sequence-based PCR

We describe the use of repetitive element sequence-based PCR (rep-PCR) on the two repetitive sequences, REP and ERIC elements, to distinguish members of closely related Salmonella species. Within the species, ERIC–PCR showed a higher discriminative potential than REP–PCR, but by using a combination of the two PCR methods it was possible to distinguish all the isolates examined. The rep-PCR fingerprints of Salmonella organisms were distinctly different from some Gram-positive bacteria, for example Staphylococcus, Bacillus megaterium, and even the closely related Escherichia coli and Serratia marcescens. Identical fingerprints were observed with whole-cell preparations. Rapid specimen preparation has enhanced the value of rep-PCR in timely analysis of epidemiological relationships.     

Exfoliative cytology in the evaluation of interferon treatment of cervical intraepithelial neoplasia

Local interferon injection in four patients with cervical intraepithelial neoplasia (CIN) regularly elicited progressive regression of the lesions. The response was observed with exfoliative cytology after each injection, guided by colposcopic examination. The cytologic changes showed a cytocidal effect mainly on the dyskaryotic cells, preceded by cellular degeneration not unlike that of nonspecific inflammation and accompanied by an increase in neutrophil infiltration. The cytologic response was closely correlated with partial or complete clinical regression based on the absence of viable or degenerated dyskaryotic cells in the cervical smears. Three patients showed complete clinical regression after treatment. One patient showed recurrent viable dyskaryotic cells when the dosage was reduced, and treatment was suspended temporarily although her lesion had regressed completely after five injections. Clinical recurrence was noted one week after viable dyskaryotic cells reappeared in her smears. These observations suggest that cytology may be a useful means of monitoring interferon treatment in CIN.     

Inactivation of aminated horseradish peroxidase by interaction with S-Sepharose

Horseradish peroxidase which had been aminated by periodate oxidation and reductive amination was purified by cation-exchange chromatography on S-Sepharose. Instead of the expected single peak of aminated enzyme, two distinct peaks of protein were eluted from the column. Evaluation of the protein in each of the two distributions showed that peak number 1 had spectral properties and specific activity similar to those of native enzyme. Distribution number 2 had a threefold reduction in the extinction in the Soret region at 404 nm and was completely devoid of enzymatic activity. This inactivation was caused by a specific interaction between the aminated peroxidase and the S-Sepharose matrix, resulting in a displacement of the heme prosthetic group out of its native orientation. The inactivation of the aminated peroxidase was found to be dependent on time, pH, and the support matrix itself. These results indicate that the S-Sepharose and Mono-S resins are not interchangeable, despite the chemical similarities of the two resins.     

A simple enzyme assay for dry matter digestibility and its value in studying food selection by generalist herbivores

Summary The dry matter digestibility of 94 species of leaf was assayed by a simple method involving sequential treatment with pepsin and fungal cellulase enzymes. It was demonstrated that for foliage from rainforest trees of a wide range of dicotyledonous plant families the assay showed high positive correlation with estimates of dry matter digestibility obtained using rumenliquor from a fistulated steer. Both assays were found to reflect negative correlates of digestibility, notably fibre and condensed tannin, rather than the nutritional value of an item. The higher dry matter digestibility of immature leaves relative to mature leaves appeared to be accounted for by their lower fibre content. It is suggested that the pepsin/cellulase assay offers a cheap, quick, routine method of gaining information on the effects of some types of plant secondary compounds (digestibility reducers) on the food potential of different kinds of foliage to herbivores. Its use in studies of herbivory in rainforest areas in relation to analyses for plant secondary compounds and food selection by herbivores is discussed.Publication 20-018 of the Wisconsin Regional Primate Research Center     

Genetics of the mammalian phenylalanine hydroxylase system. II. Immunological and two-dimensional gel electrophoretic studies of phenylalanine hydroxylase in cultured normal and mutant rat hepatoma cells

We have examined 11 previously described cultured rat hepatoma mutants with absent or reduced phenylalanine hydroxylase activity (Choo and Cotton, 1977). Immunological and electrophoretic methods failed to detect any structurally altered protein in these mutants. In nine independently isolated revertants from four different mutants, wild-type protein was regained (or accentuated). This evidence suggests that the mutation involved in these mutants is most likely to be regulatory in nature. These studies have provided three reasons for believing that in cultured rat hepatoma cells one gene codes for a single polypeptide chain, a number of which combine to form the active phenylalanine hydroxylase multimer: (1) Analysis of the purified protein by two-dimensional electrophoresis revealed only a single polypeptide chain. (2) This polypeptide was diminished or undetectable in crude extracts of 11 independently isolated mutants with absent of reduced activity. (3) In none of these 11 mutants was the polypeptide we have designated to be phenylalanine hydroxylase present at normal levels, as would be expected if the mutation were at another locus responsible for a possible second subunit.