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Biomedical subjects

B Dawson

Publications and source records attributed to B Dawson.

At least 91 records · Page 5Linked to original sources

Treatment of defects of the anterior abdominal wall in newborns.

Primary closure of an omphalocele or gastroschisis may cause respiratory compromise in the neonate. Some authors recommend primary closure of the defect with prolonged respiratory support because of dissatisfaction with staged visceral reduction and use of a Silastic pouch. Our experience with use of a Silastic pouch from 1975 to 1982 was reviewed. Twenty-three newborns with major defects of the abdominal wall (14 omphaloceles and 9 gastroschisis anomalies) were surgically treated, and only one death occurred. The mean birth weight of the infants was 2,927 g; nine of them were premature. Seven infants had major associated anomalies. The goal of the surgical procedure was closure of the abdominal wall without compromise of the cardiorespiratory status. During the operation, muscle relaxants were avoided and the infants breathed spontaneously. If progressive visceral reduction caused tachypnea (rate of more than 70/min) or hemodynamic instability, a Silastic pouch was constructed. Ten patients were treated with primary fascial closure, and 13 were treated with a Silastic prosthesis. The neonates with the prostheses required three to eight reductions, and the prostheses were in place for 4 to 22 days. No patient had wound dehiscence, wound infection, or an intestinal fistula. The one death occurred in an infant with trisomy 18 syndrome and multiple anomalies. Thus, the Silastic pouch was effective when the defect could not be closed primarily without respiratory compromise.

Critical Care↗

A marker X chromosome associated with nonspecific male mental retardation. The first South African cases.

This report describes the first cases of X-linked mental retardation with a marker X chromosome seen in South Africa, and forms part of an ongoing study. The marker was found in 11 affected males and 1 carrier female in 4 families investigated. The demonstration of the marker X chromosome characterized by a fragile site at the long arm (fra(X) (q27) in association with nonspecific X-linked mental retardation heralds a new era in cytogenetics. The attention of human geneticists everywhere is focused on various aspects of this fascinating phenomenon. It has now become possible to diagnose an apparently common familial cytogenetic condition with a high risk of recurrence and to identify female carriers; perhaps in time we will be able to provide prenatal diagnosis. Because of the familial involvement through X-linked inheritance the syndrome is believed to be more common than trisomy 21. The nature of the association of mental retardation with the marker X chromosome is unknown, but it could be related to close linkage with abnormal gene(s) or due to faulty transcription of the genes beyond the fragile site.

Adult↗

Human inherited marker chromosome 22 short-arm enlargement: investigation of rDNA gene multiplicity, Ag-band size, and acrocentric association.

The banding characteristics of an extreme variant familial chromosome 22 short-arm enlargement are described. Ag-AS staining for nucleolar-organizer regions, identified two areas of rDNA actively coding for 18S and 28S rRNA, the one being a broad distal Ag-band and the other a narrower centromeric Ag-band. The DNA in the major portion of the enlarged short arm was highly methylated, as shown by the binding of antibodies to 5-methylcytidine after UV-denaturation of chromosomal DNA. Mean Ag-band size on the aberrant 22p+ correlated with the mean number of 22p+ associations. Association of 22p+ was no greater than that of other acrocentrics, in spite of a presumed excess number of rDNA gene copies. This case represents only the second such normal variant defined by these techniques.

Cell Division↗

PBB inhibits metabolic cooperation in Chinese hamster cells in vitro: its potential as a tumor promoter.

Using an in vitro assay system, polybrominated biphenyl (PBB) was assessed for its ability to inhibit metabolic cooperation between 6-thioguanine sensitive and resistant Chinese hamster V79 cells. Using a nonlethal range of the chemical, PBB was shown to inhibit metabolic cooperation (a form of cell-cell communication) in a manner similar to other known tumor promoters. Results suggest that PBB could act, epigenetically, as a teratogen and a carcinogenic promoter.

Animals↗

Chromosomal aberrations in occupation-associated progressive systemic sclerosis.

An occupational association between progressive systemic sclerosis (PSS) and workers in the goldmining industry in South Africa was first documented in 1957. We investigated the chromosomes of 18 goldminers suspected to be suffering from PSS. Eight patients were classified as definite cases of PSS, and a highly significant increase in unstable (Cu) cells and random aneuploidy was found in this group compared with control subjects (P < 0,001). Ten patients had some of the features of the disease, and in this group there was a significant increase in the number of Cu cells ( P < 0,05) and a highly significant increase in the number of aneuploid cells (P < 0,001). There was a significant increase in the number of sister chromatid exchanges per cell in the 6 patients screened. These findings are similar to those reported in PSS sufferers who have not had occupational exposure.

Adult↗

Saccharin may act as a tumour promoter by inhibiting metabolic cooperation between cells.

The possible role of saccharin in the carcinogenic process is, at present, still unclear. Carcinogenesis is a complex process involving, in many test systems, initiation and promotion phases. Current evidence favours the hypothesis that initiation is due to a mutagenic event, while promotion (at least the early portion) is the result of epigenetic changes. Although saccharin has been reported to be a weak mutagen in various in vitro test systems and a weak initiator in mouse skin, there is increasing evidence from in vitro, as well as in vivo, studies that it might act as a tumour promoter, rather than as a mutagen. Recently L.P.Y. et al and J.E.T. et al. developed an in vitro assay to detect tumour promoters, which has been independently reported by Murray and Fitzgerald. The assay is based on the principle that phorbol ester-type tumour promoters block 'metabolic cooperation' or a type of cell-cell communication between cells. We report here a series of experiments demonstrating the elimination of metabolic cooperation in the hypoxanthine guanine phosphoribosyltransferase (HGPRT) system in Chinese hamster V79 cells, indicating that saccharin shares properties similar to those of other known promoters.

Animals↗

Anaesthesia for day-care surgery: a symposium (III). Anaesthesia for adult surgical out-patients.

This discussion is based on the experience of the Phoenix Surgicenter, where over 60,000 patients have been anaesthetized since 1970. Patients accepted for out-patient surgery are ASA Status I or II, although status III patients may be included if their co-existing disability is under excellent control. Eighty-five per cent of adult patients receive general anaesthesia. A wide variety of local and regional anaesthetic techniques may be used. Efforts during recovery are directed towards preparing the patient for discharge in a "home ready" condition for safe handling by attending relatives. The common complications have been postoperative nausea or emesis and hypotension. The hospital transfer rate has been 0.2 per cent.

Ambulatory Surgical Procedures↗

Two unrelated children with distal long arm deletion of chromosome 7: clinical features, cytogenetic and gene marker studies.

Two phenotypically abnormal, unrelated children with deletion of the distal segment of 7q (7q32 leads to pter) are described. In one instance the mother was the carrier of a balanced translocation between chromosomes 6 and 7, and in the second case the deletion was a de novo event. Their phenotype were compared to previously reported cases and found to have many non-specific clinical features in common. Gene marker studies for some of the genes tentatively localized to chromosome 7 showed no anomalous segregation. The Hageman coagulation factor (Factor XII) activity in both probands was normal, and heterozygosity for alleles of the Kidd blood group in the first proband excludes assignment of the Kidd locus to the distal portion of chromosome 7q.

Abnormalities, Multiple↗

Female phenotype and multiple abnormalities in sibs with a Y chromosome and partial X chromosome duplication: H--Y antigen and Xg blood group findings.

A mentally retarded female child with multiple congenital abnormalities had an abnormal X chromosome and a Y chromosome; the karyotype was interpreted as 46,dup(X)(p21 leads to pter)Y. Prenatal chromosome studies in a later pregnancy indicated the same chromosomal abnormality in the fetus. The fetus and proband had normal female genitalia and ovarian tissue. H--Y antigen was virtually absent in both sibs, a finding consistent with the view that testis-determining genes of the Y chromosome may be suppressed by regulatory elements of the X. The abnormal X chromosome was present in the mother, the maternal grandmother, and a female sib: all were phenotypically normal and showed the karyotype 46,Xdup(X)(p21 leads to pter) with non-random inactivation of the abnormal X. Anomalous segregation of the Xga allele suggests that the Xg locus was involved in the inactivation process or that crossing-over at meiosis occurred.

Abnormalities, Multiple↗

Who accepts first aid training?

The percentage of individuals trained in first aid skills in the general community is inadequate. We report here a study to investigate factors which influence motivation to accept voluntary training in first aid. A group of 700 randomly selected owners of inground swimming pools (a parental high-risk group) was offered a course of formal first aid instruction. Nine per cent attended the offered training course. The time commitment involved in traditional courses (eight training nights spread over four weeks) is not a deterrent, the same percentage accepting such courses as that who accept a course of one night's instruction. Cost is an important deterrent factor, consumer resistance rising over 15 cost units (one cost unit = the price of a loaf of bread). The level of competent first aid training within the community can be raised by (a) keeping to traditional course content, but (b) by ensuring a higher acceptance rate of first aid courses by a new approach to publicity campaigns, to convince prospective students of the real worth of first aid training. Questions concerning who should be taught first aid, and factors influencing motivation, are discussed.

Adult↗

Reduced ferrochelatase activity in fibroblasts from patients with porphyria variegata.

Ferrochelatase deficiency has been shown in both porphyria variegata (PV) and erythropoietic protoporphyria (EPP). It has been suggested that in PV there is a decrease in the enzyme, whereas in EPP the enzyme is unstable. In the present study ferrochelatase activity was measured in skin fibroblasts from three patients with PV and three normal subjects. The enzymatic activity in the patients with PV (17.5 +/- 4.5 pmoles heme formed per 10(7) fibroblasts per hour) was 50% of that of the control group (31.0 +/- 3.2 pmoles heme formed per 10(7) fibroblasts per hour). This supports the contention that the enzyme is deficient in PV and that an inactive ferrochelatase is the primary deficiency in this type of porphyria.

Fibroblasts↗

X;15 translocation in a retarded girl: X inactivation pattern and attempt to localise the hexosaminidase A and other loci.

Cytogenetic studies on a retarded girl showed a complex S;15 translocation, karyotype 45,X,-15,+t(X15). The translocation X chromosome was non-randomly partially inactivated, the inactivation being mainly confined to the X segment and in some cells only to the X long arm. Gene marker studies failed to show anomalous segregation of the hexosaminidase A gene or any other gene markers tested.

Abnormalities, Multiple↗

Structure of human luteinizing hormone alpha subunit.

Structural studies have substantiated the concept that the glycoprotein hormones consist of a "common" alpha subunit and "hormone-specific" beta subunit. Despite this, consensus is still lacking concerning certain portions of the amino acid sequences, including alignment of residues 81--82 in the alpha subunit. We have carried out sequence analysis of the alpha subunit of human luteinizing hormone (hLH) to clarify the assignment of these residues and to examine further the nature of the amino-terminal heterogeneity found among the different alpha subunits. Our structure showed residues 80--84 to be -His-Cys-Ser-Thy-Cys-, consistent with findings of others for human follicle stimulating hormone (hFSH) and human chorionic gonadotropin (hCG). The extensive degree of heterogeneity found in the amino terminal region of hFSH and hCG is present to only a minor extent in hLH. The differences in the pattern of amino-terminal heterogeneity among the various hormones may result from differences in the nature of cleavage of subunit from a larger intracellular precursor peptide.

Amino Acid Sequence↗