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Biomedical subjects

A G Campbell

Publications and source records attributed to A G Campbell.

At least 19 recordsLinked to original sources
PubMed1995

Prolonging life and allowing death: infants.

Dilemmas about resuscitation and life-prolonging treatment for severely compromised infants have become increasingly complex as skills in neonatal care have developed. Quality of life and resource issues necessarily influence management. Our Institute of Medical Ethics working party, on whose behalf this paper is written, recognises that the ultimate responsibility for the final decision rests with the doctor in clinical charge of the infant. However, we advocate a team approach to decision-making, emphasising the important role of parents and nurses in the process. Assessing the relative burdens and benefits can be troubling, but doctors and parents need to retain a measure of discretion; legislation which would determine action in all cases is inappropriate. Caution should be exercised in involving committees in decision-making and, where they exist, their remit should remain to advise rather than to decide. Support for families who bear the consequences of their decisions is often inadequate, and facilitating access to such services is part of the wider responsibilities of the intensive care team. The authors believe that allowing death by withholding or withdrawing treatment is legitimate, where those closely involved in the care of the infant together deem the burdens to be unacceptable without compensating benefits for the infant. As part of the process accurate and careful recording is essential.

Brain Diseases↗
PubMed1994

Modeling human lymphoid precursor cell gene therapy in the SCID-hu mouse.

Gene therapy of human T-lymphocyte disorders, including acquired immunodeficiency syndrome (AIDS), would be greatly facilitated by the development of an in vivo system in which transduced human hematopoietic stem cells can be used to reconstitute the T-lymphoid compartment. Here we use the SCID-hu mouse as a recipient for human CD34+ hematopoietic progenitor cells transduced in vitro with a retroviral vector carrying the neomycin resistance gene (neoR). The transduced cells engraft and reconstitute the lymphoid compartments of the human thymus implant with as few as 5 x 10(4) CD34+ cells. The neoR gene was expressed at low levels in human thymocytes and there was no apparent effect on thymocyte differentiation as a result of vector transduction. Thus, this SCID-hu mouse system is the first in vivo model showing human thymopoiesis after transduction of exogenous vectors, and should allow preclinical testing of gene therapeutic reagents designed to function in human cells of the T-lymphoid lineage. Because human immunodeficiency virus type 1 infection induces depletion of human thymocytes in SCID-hu mice, this system may be particularly valuable in evaluating efficacy of gene therapies to combat AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Functional complementation of an Escherichia coli ribonuclease H mutation by a cloned genomic fragment from the trypanosomatid Crithidia fasciculata.

A gene designated Cfa RNH1 has been cloned by complementation of an RNase H deficiency in an Escherichia coli rnhA mutant by using a genomic DNA library from the trypanosomatid Crithidia fasciculata. The encoded RNase H is predicted to have 494 amino acid residues and a molecular mass of 53.7 kDa. The carboxyl half of the protein is homologous to the 155-residue E. coli RNase HI (41% identity) and the 166-residue Saccharomyces cerevisiae RNase HI (33% identity). The recombinant protein has been purified as a six-histidine-tagged fusion protein by metal chelate chromatography and was shown to have RNase H activity. Antibodies against the recombinant protein recognize proteins of approximately 65 kDa and 56 kDa on Western blots of C. fasciculata extracts. These results demonstrate the feasibility of cloning trypanosome genes by complementation of appropriate E. coli mutants with genomic DNA libraries.

Amino Acid Sequence↗
PubMed1990

Glutactin, a novel Drosophila basement membrane-related glycoprotein with sequence similarity to serine esterases.

Glutactin, a new acidic sulfated glycoprotein, was isolated from Drosophila Kc cell culture media. Immunofluorescence microscopy located it to embryonic basement membranes, particularly to the sequentially invaginated envelope of the central nervous system, muscle apodemes and dorsal median cell processes. Its chromosome locus is 29D. The nucleic acid sequence coding for the 1023 residue long polypeptide contains one intron and was confirmed by partial amino acid sequencing. Glutactin has a signal peptide and an amino domain of greater than 500 residues that strongly resembles acetylcholine esterases and other serine esterases, but lacks the catalytically critical serine residue. The amino and carboxyl domains of glutactin are separated by 13 contiguous threonine residues. Glutamine and glutamic acid make up 44% of glutactin's very acidic carboxyl domain. Glutactin preferentially binds Ca2+ in the presence of excess Mg2+ and four of its tyrosines are O-sulfated. Several similarities with mammalian entactin caused our previous, preliminary mention of glutactin as a putative Drosophila entactin, but sequence comparison now shows them to be different proteins.

Amino Acid Sequence↗
PubMed1987

Papilin: a Drosophila proteoglycan-like sulfated glycoprotein from basement membranes.

A sulfated glycoprotein was isolated from the culture media of Drosophila Kc cells and named papilin. Affinity purified antibodies against this protein localized it primarily to the basement membranes of embryos. The antibodies cross-reacted with another material which was not sulfated and appeared to be the core protein of papilin, which is proteoglycan-like. After reduction, papilin electrophoresed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a broad band of about 900,000 apparent molecular weight and the core protein as a narrow band of approximately 400,000. The core protein was formed by some cell lines and by other cells on incubation with 1 mM 4-methylumbelliferyl xyloside, which inhibited formation of the proteoglycan-like form. The buoyant density of papilin in CsCl/4 M guanidine hydrochloride is 1.4 g/ml, that of the core protein is much less. Papilin forms oligomers linked by disulfide bridges, as shown by sodium dodecyl sulfate-agarose gel electrophoresis and electron microscopy. The protomer is a 225 +/- 15-nm thread which is disulfide-linked into a loop with fine, protruding thread ends. Oligomers form clover-leaf-like structures. The protein contains 22% combined serine and threonine residues and 25% combined aspartic and glutamic residues. 10 g of polypeptide has attached 6.4 g of glucosamine, 3.1 g of galactosamine, 6.1 g of uronic acid, and 2.7 g of neutral sugars. There are about 80 O-linked carbohydrate chains/core protein molecule. Sulfate is attached to these chains. The O-linkage is through an unidentified neutral sugar. Papilin is largely resistant to common glycosidases and several proteases. The degree of sulfation varies with the sulfate concentration of the incubation medium. This proteoglycan-like glycoprotein differs substantially from corresponding proteoglycans found in vertebrate basement membranes, in contrast to Drosophila basement membrane laminin and collagen IV which have been conserved evolutionarily.

Amino Acids↗
PubMed1987

Drosophila laminin: characterization and localization.

Drosophila laminin was isolated from the medium of Drosophila Kc cell cultures. It was purified by velocity sedimentation, gel filtration, and chromatography. Drosophila laminin is a disulfide-linked molecule consisting of three chains with apparent molecular masses of 400, 215, and 185 kD. In electron micrographs, it has the cross-shaped appearance with globular domains characteristic of vertebrate laminin with closely similar dimensions. The amino acid composition and lectin-binding properties of Drosophila laminin are given. Polyclonal antibodies to Drosophila laminin were prepared and their specificity was established. In developing embryos immunofluorescence staining was detected between 6 and 8 h of development; and in sections of 8-9-h and older embryos immunostaining was seen at sites where basement membranes are present surrounding internal organs, muscles, underlying the hypodermal epithelium, and in the nervous system. Basement membrane staining was also seen in larva and adults. Cells from Drosophila embryos dissociated at the cellular blastoderm stage were grown in culture and some specific, differentiated cells synthesized laminin after several hours of culture as shown by immunofluorescence. The significance of the evolutionary conservation of the structure of this basement membrane component is discussed.

Amino Acids↗
PubMed1985

Selective vitamin B12 malabsorption without anaemia but with profound failure to thrive.

A 7-month-old boy presented with vomiting and failure to thrive associated with proteinuria, methylmalonic aciduria and macrocytosis, but without anaemia. Plasma vitamin B12 levels were normal by a radio-dilution method. He was treated as an inborn error of metabolism with intramuscular cyanocobalamin and a low protein diet. However when treatment was withdrawn he remained well for 11 months before relapsing with vomiting and weight loss. Re-investigation again showed methylmalonic aciduria, but the haemoglobin was low and plasma vitamin B12 levels by a specific method showed them to be reduced. Studies of vitamin B12 absorption showed the picture of selective malabsorption. He was started on regular cyanocobalamin injections.

Child, Preschool↗
PubMed1984

Maternal serum alpha-fetoprotein levels in low birth weight singleton pregnancies.

Maternal serum alpha fetoprotein (MSAFP) measurement between 16 and 21 weeks gestation is used to define a group of women with an increased risk of fetal abnormality, particularly open neural tube defect. The test is strongly gestation dependent and women with high MSAFP levels require sonar scan examination to define gestation, exclude twins and examine the fetus for obvious malformation or death. It has been reported that women with no primary cause for raised MSAFP have an increased incidence of low birth weight babies. Conflicting reports have separately ascribed these to premature delivery and to intra-uterine growth retardation. We have studied the relationship between MSAFP and low birth weight infants with respect to both prematurity and retarded fetal growth. MSAFP values were expressed as multiples of the appropriate weekly median (MOM) values relating to normal pregnancies with normal outcomes at term. For our normal population an MSAFP value of 2 MOM is the 95% centile, i.e. 5% of normal outcome pregnancies of sure gestation will have MSAFP values in the second trimester which are at or above 2 MOM. Information was available on 389 women whose infants were liveborn singletons weighing 2.5 kg or less. 33 (8.5%) of these women had MSAFP greater than 2 MOM (p less than 0.005) and of the 145 women whose babies weighed less than 2 kg, 17 (11.7%) had MSAFP at this level (p less than 0.001) Tab. I).(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Spontaneous↗
PubMed1983

The right to be allowed to die.

The unbridled use of modern medical skills and technology in preserving life at all costs has stimulated interest in expressing a 'right to die' by the legally competent patient who is anxious to protect his autonomy. Some recent decisions by American courts are seen to threaten this 'right to die' of competent patients and imply that legally incompetent patients including children should not have this right under any circumstances, even when expressed on their behalf by guardians, nearest relatives or parents. It is argued that this is contrary to 'natural justice' as viewed by most people. It should be possible to develop procedures which are protective of the basic 'right to life' of the incompetent yet will recognise circumstances where they could be allowed to die. This paper was presented at the 1983 annual conference of the London Medical Group, 'Human Rights in Medicine'.

Adult↗