Biomedical subjects
Publications and source records attributed to A Graham.
By sequence analysis of the complete protein-coding region of the human alpha-1-antitrypsin gene using polymerase chain reaction techniques, we have characterised one of the normal variants, M3. We have identified a single point mutation between M1 Val213 and M3 at codon position 376 which is a GAA(Glu) to GAC(Asp) transversion.
The origin and cell lineage of stromal cells in the bone marrow is uncertain. Whether a common stem cell exists for both haemopoietic and stromal cells or whether these cell lines arise from distinct stem cells is unknown. Using in situ hybridisation for detection of the Y chromosome, we have examined histological sections of bone marrow from seven patients who received marrow transplants from HLA-matched donors of the opposite sex. Stromal cells (adipocytes, fibroblasts, endothelial cells, osteoblasts and osteocytes) were identified in these recipients as being of host origin. This result is consistent with the concept of a distinct origin and separate cell lineage for cells of the haemopoietic and stromal systems. It also shows that engraftment of marrow stromal cell precursors does not occur and that host stromal cells survive conditioning regimens for marrow transplantation. With the exception of one case, with a markedly hypocellular marrow, mixed chimaerism was seen in haemopoietic cells, indicating that this is not a rare event after marrow transplantation.
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In situ hybridization analysis of mouse embryos shows the seven members of the Hox-2 complex to be differentially expressed in the central and peripheral nervous system and in mesodermal derivatives (somites and lung). Beginning at the 5' end of the cluster, each successive gene displays a more anterior boundary of expression in the central nervous system. A gene's position in the Hox-2 cluster therefore reflects its relative domain of expression along the anteroposterior axis of the embryo, a feature observed with Drosophila homeotic genes. Sequence comparisons of the Hox-2 cluster with other mouse and Drosophila homeobox genes have defined subgroups of related genes; in the mouse there are four clusters related by duplication and divergence. Alignment shows a clear relationship among genes in the mouse and Drosophila complexes, based on relative position, sequence identity, and domains of expression along the rostral-caudal axis. Our results argue that these complexes arose from a common ancestor, present before the divergence of lineages that gave rise to arthropods and vertebrates.
We have improved the "polymerase chain reaction" (PCR) to permit rapid analysis of any known mutation in genomic DNA. We demonstrate a system, ARMS (Amplification Refractory Mutation System), that allows genotyping solely by inspection of reaction mixtures after agarose gel electrophoresis. The system is simple, reliable and non-isotopic. It will clearly distinguish heterozygotes at a locus from homozygotes for either allele. The system requires neither restriction enzyme digestion, allele-specific oligonucleotides as conventionally applied, nor the sequence analysis of PCR products. The basis of the invention is that unexpectedly, oligonucleotides with a mismatched 3'-residue will not function as primers in the PCR under appropriate conditions. We have analysed DNA from patients with alpha 1-antitrypsin (AAT) deficiency, from carriers of the disease and from normal individuals. Our findings are in complete agreement with allele assignments derived by direct sequencing of PCR products.
Three mutations causing alpha-1-antitrypsin deficiency have been identified by gene amplification and direct DNA sequencing. In the Pi (proteinase-inhibitor) nullcardiff gene, the codon for aspartate at position 256 has mutated to encode valine. In PiMmalton and Pi I, the respective mutations are the deletion of the codon for a phenylalanine residue at position 51 or 52, and a single base substitution resulting in arginine being replaced by cysteine at position 39. Examination of the protein tertiary structure suggests that all of these mutations are likely to result in folding abnormalities that may explain the deficiency states.
Two unusual cases of injury to the sesamoids of the M.P. joint of the thumb are described. An anatomical dissection of the M.P. volar plate region, including the sesamoids, was undertaken to delineate the details of the sesamoids' relationship to the M.P. joint, flexor tendon, flexor tendon sheath and capsule of the joint. Histological studies were carried out to demonstrate a tendinous extension of the muscles that attach to the sesamoids.
The lux C, D, and E genes of the Vibrio fischeri luminescence operon code for three polypeptides of 54, 33, and 42 kDa, respectively, which are required for synthesis of the aldehyde substrate for the luminescent reaction. These polypeptides have been identified in V. fischeri and V. harveyi as well as in recombinant E. coli harboring the cloned genes by specific acylation with [3H]fatty acid, showing that they are components of a fatty acid reductase system with reductase, synthetase and transferase activities. By using glycerol in the assay and/or extraction buffer and decreasing the reducing agent, the levels of the acylation of the 54 and 42 kDa polypeptides have been greatly increased. As a consequence, it was possible to demonstrate that the 54 kDa polypeptide coded by the lux C gene has reductase activity. In a subclone missing the lux E gene, the 42 kDa polypeptide was missing and the 54 kDa polypeptide could not be acylated in vitro with tetradecanoic acid (+ATP) and only to a low level in vivo indicating that the synthetase enzyme, responsible for fatty acid activation, is coded by the lux E gene. In vitro acylation with tetradecanoyl CoA of the 33 kDa polypeptide coupled with the specific cleavage of acyl-ACP only in E. coli extracts transformed with DNA containing the lux D gene, demonstrated that the lux D gene coded for the transferase enzyme.
A man aged 31 presented to hospital with acute onset of weakness in the legs, sensory loss, and disturbance of bladder and bowel function. Incomplete Brown-Séquard syndrome secondary to meningovascular syphilis of the spinal cord was diagnosed after serological tests for syphilis gave positive results. His condition was probably caused by endarteritis of the arteria radicularis magna of Adamkiewicz. He was treated with procaine penicillin 1.8 MIU intramuscularly once a day and probenecid 0.5 g by mouth three times a day for 21 days followed by physiotherapy and rehabilitation. Considerable neurological recovery was expected. To our knowledge this association has not been reported previously in detail in an English publication.
An image understanding machine vision system for histological diagnoses is based on three interacting expert systems: a diagnostic expert system utilizing terms familiar to pathologists, an interpretive expert system relating human diagnostic concepts to computable histometric features and a scene segmentation expert system which extracts the diagnostic information from the imagery. The control software for the image understanding system resides on a multiprocessor computer. This article details measures to maintain system efficiency and to accommodate the requirements of interprocess communication and processing task scheduling.
We have compared sequencing of cloned "polymerase chain reaction" (PCR) products and the direct sequencing of PCR products in the examination of individuals from six families affected with alpha 1-antitrypsin (AAT) deficiency. In families where paternity was in question we confirmed consanguinity by DNA fingerprinting using a panel of locus-specific minisatellite probes. We demonstrate that direct sequencing of PCR amplification products is the method of choice for the absolutely specific diagnosis of AAT deficiency and can distinguish normals, heterozygotes and homozygotes in a single, rapid and facile assay. Furthermore, we demonstrate the reproducibility of the PCR and a rapid DNA isolation procedure. We have also shown that two loci can be simultaneously amplified and that the PCR product from each locus can be independently examined by direct DNA sequencing.
1. The synthesis and secretion of glycerolipid by monolayer cultures of rat hepatocytes was measured by determining the incorporations of [3H]glycerol, [3H]oleate and [14C]choline and by the absolute concentration of triacylglycerol. 2. The presence of albumin in the medium stimulated the accumulation of lysophosphatidylcholine in the medium by 11-13-fold. 3. Cycloheximide did not significantly alter the accumulation of lysophosphatidylcholine. 4. This process was particularly sensitive to inhibition by chlorpromazine and verapamil, compared with the secretion of triacylglycerol and phosphatidylcholine. By contrast, it was relatively less sensitive to EGTA. 5. It is suggested that intracellular Ca2+ may be important in the production of lysophosphatidylcholine, which then accumulates in the medium by binding to albumin. In vivo this lysophosphatidycholine may be a means of delivering choline and polyunsaturated fatty acids to other organs.
1. The synthesis and secretion of glycerolipids by monolayer cultures of rat hepatocytes was measured by using radioactive choline, glycerol and fatty acids and by measuring the concentration of triacylglycerols in the cells. 2. The incorporation of glycerol into triacylglycerol and the accumulation of this lipid in hepatocytes showed little specificity for fatty acids, except for eicosapentaenoate, which stimulated least. Oleate was more effective at stimulating triacylglycerol secretion than were palmitate, stearate, arachidonate and eicosapentaenoate. 3. Linoleate, linolenate, arachidonate and eicosapentaenoate stimulated the incorporation of glycerol and choline into phosphatidylcholine that was secreted into the medium. By contrast, palmitate and stearate produced relatively high incorporations into the phosphatidylcholine that remained in the cells. 4. The incorporation of glycerol and choline into lysophosphatidylcholine in the medium was stimulated 2-3-fold by all of the unsaturated fatty acids tested, whereas palmitate and stearate failed to stimulate if the acids were added separately. When 1 mM-stearate was added with 1 mM-linoleate, the incorporation of linoleate into lysophosphatidylcholine was about 4 times higher than that of stearate. 5. It is proposed that the secretion of lysophosphatidylcholine by the liver could provide a transport system for choline and essential unsaturated fatty acids to other organs.
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A case report of bilateral mixed Warthin's tumors with nonuniform uptake demonstrated by Tc-99m pertechnetate imaging is presented. The findings are compared to CT, surgical, and pathology results.
The Hox-2 locus on chromosome 11 represents one of the major clusters of homeo-box-containing genes in the mouse. We have identified two new members (Hox-2.6 and Hox-2.7), which form part of this cluster of seven linked genes, and it appears that the Hox-2 locus is related by duplication and divergence to at least one other mouse homeo box cluster, Hox-1. The Hox-2.6 gene encodes a predicted protein of 250 amino acids, which displays extensive similarity in multiple regions to certain mouse, human, Xenopus, and zebra fish homeo domain proteins. The Drosophila Deformed (Dfd) gene also shares these same regions of similarity, and based on this sequence conservation, we suggest that Hox-2.6 forms part of a vertebrate 'Dfd-like' family. Hox-2.6 is expressed in fetal and adult tissues and is modulated during the differentiation of F9 teratocarcinoma stem cells. In situ hybridization analysis of mouse embryos shows that the Hox-2.6 is expressed in ectodermal derivatives: spinal cord, hindbrain, dorsal root ganglia, and the Xth cranial ganglia. In the central nervous system, expression is observed in the most posterior parts of the spinal cord, with the anterior limit residing in a region of the hindbrain and no expression in the mid- or forebrain. In mesodermal structures, Hox-2.6 is expressed in the kidney, the mesenchyme of the stomach and lung, and the longitudinal muscle layer of the gut. Expression has not been observed in derivatives of embryonic endoderm. The patterns of Hox-2.6 expression in both mesoderm and ectoderm are spatially restricted and may reflect a role for the gene in the response to or establishment of positional cues in the embryo.
The results of recent studies by ourselves and others have demonstrated the feasibility of revascularizing severely ischemic limbs by means of staged arteriovenous reversal at the popliteal level. The results of investigations we did, both clinically and in an animal model, revealed the development of an intense vascular network in the region of the arteriovenous anastomosis as an important component of the revascularization process. To determine the role of ischemia in this process, four groups consisting of three dogs each underwent a popliteal artery to vein anastomosis. In group I, there was no ischemia; group II, distal ischemia only; group III, partial ischemia, and group IV, total ischemia. Angiography at four weeks in all dogs demonstrated that the intense neovascular network seen in previous studies developed only in the limbs of the dogs in group IV. We conclude that the neovascular process seen after creation of arteriovenous reversal develops as a response to severe ischemia. Further studies are needed to better characterize the nature of these vessels, and it is our hope that, in doing so, means of enhancing development of these vessels in order to indirectly revascularize otherwise unsalvagable extremities will be realized.