Biomedical subjects
Publications and source records attributed to C Sapienza.
Natural selection operating within genomes will inevitably result in the appearance of DNAs with no phenotypic expression whose only 'function' is survival within genomes. Prokaryotic transposable elements and eukaryotic middle-repetitive sequences can be seen as such DNA's and thus no phenotypic or evolutionary function need be assigned to them.
The results of screening of 29 diverse cyanobacterial (blue-green algal) strains for plasmid (CCC DNA) content are reported. Approximately one-half of the strains were shown to contain one or more CCC DNAs. CCC DNAs from four unicellular marine cyanobacteria were characterized in more detail. These strains contained multiple plasmids. Two kinds of Southern hybridization experiments allowed us to show that different plasmids within the same strain, and different plasmids within different strains, can ( but do not always) contain restricted regions of sequence homology. We suggest that these regions of homology may be analogous to the transposable genetic elements of bacterial plasmids. This, together with indirect but compelling evidence for interspecific (or intergeneric) plasmid transfer, indicates that CCC DNAs (although as yet genetically cryptic) may play a role in the ecology and evolution of obligately autotrophic prokaryotes, as they do in the ecology and evolution of the better-known heterotrophic bacteria.
A recent model for the transcriptional control of gene expression in neural cells involves a dispersed repetitive DNA sequence termed the identifier (ID) sequence. However, the model is based on circumstantial evidence from studies on rat brain gene expression. Furthermore, available data are complicated by observations from several laboratories which suggest that the ID sequence is a family of mobile genetic elements. Although this does not preclude a role for some family members in regulating gene expression, the contention that these sequences are transcribed tissue-specifically is not proof of such a role. We have now measured the genomic copy number and tissue pattern of transcription of ID sequences in the rat, mouse and hamster, and have found that ID-homologous, BC1-like RNAs are restricted to brain in all three species, but that ID-homologous transcripts occur in total cellular RNAs of brain, liver and kidney of all three organisms. The genomic copy number of the ID sequences varies over two orders of magnitude between these species. Our data suggest that most ID sequences in these genomes are dispersed at random with respect to transcription units. A cis-acting, transcriptional-level controlling role for the ID therefore seems unlikely.
Data derived from both pronuclear transplantation experiments and classical genetic experiments indicate that the maternal and paternal genetic contributions to the mammalian zygote nucleus do not function equivalently during subsequent development. These observations have been interpreted as resulting from differential 'genome imprinting' during male and female gametogenesis. The molecular mechanism responsible for genome imprinting is unknown, but data gathered to date require that the mechanism fulfill at least four criteria: (1) the imprint must be physically linked to the pronucleus; (2) the imprint must persist through DNA replication and cell division; (3) the mechanism must be capable of affecting gene expression; and (4) the mechanism must be capable of switching the identity of the imprint from one sex to the other in successive generations. One molecular mechanism which could satisfy the first three criteria is differential DNA methylation during gametogenesis itself, or before formation of the zygote nucleus during embryogenesis. We present data indicating that the methylation patterns of exogenous DNA sequences in transgenic mice can be changed by switching their gamete of origin in successive generations. These data suggest that DNA methylation can also satisfy the fourth criterion for an imprinting mechanism.
We have analyzed X-chromosome inactivation patterns in lymphocytes of 264 females from 38 families not known to have any genetic disease. Quantitative measures of X-inactivation showed strong sister-sister correlation in the degree of departure from equal numbers of cells having each X chromosome active, suggesting heritability of this phenotype. Strong sister-sister correlation was also observed for the fraction of cells having the same parent's X chromosome active, consistent with the possibility that this trait might be controlled by a cis-acting, X-linked gene. We used a sib-pair approach to determine whether X-inactivation phenotype was linked to loci in any region of the X chromosome. Both quantitative and discrete measures of X-inactivation phenotype showed evidence of linkage to markers in the region of the X inactivation center (XIC). The quantitative measure of X-inactivation phenotype used in our study also showed linkage to loci at Xq25-q26. This study provides the first evidence for X-linked inheritance of X chromosome inactivation phenotype derived from linkage analysis in phenotypically normal human families.
The authors present their experience on surgical treatment of intestinal fistulas based on personal cases treated from 1981 to 1990. The cases are divided into two groups: the first: the first group of patients was treated only surgically (1981-1984); the second group was treated with surgery and artificial nutrition (1984-1990). The mortality rates are much lower in the second group. The conclusion is that is always necessary to associate a form of artificial nutrition to surgery because the percentage of healing is statistically higher.
The authors reported their experience of 13 patients with pancreatic pseudocyst observed within the period 1982-1987. Three patients underwent external drainage, 9 internal drainage and 1 exeretic operation. On the base of the results the authors conclude that the internal drainage should be considered the choice operation of pancreatic pseudocysts because of the lower mortality and morbidity.
Ogilvie's Syndrome is defined as acute distension of the colon without any mechanical obstruction. We reported two new cases who underwent surgical treatment and the revision of the literature. Four hundred eight-six cases are described until now. The physiopathology is unknown. The diagnosis is done with abdominal x-ray, barium enema must be used with attention. The more frequent symptoms are nausea, vomiting, diarrhea, and abdominal pain. The perforation of the colon is possible with a diameter of 9-12 cm. The mortality was 11.3% in two hundred ninety patients (59.6%) who underwent conservative treatment. In one hundred ninety-six patients who underwent surgical treatment the mortality was 28.5%. The treatment is conservative, medical or endoscopic. The best surgical treatment is the tube cecostomy.