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Biomedical subjects

M J King

Publications and source records attributed to M J King.

At least 37 records · Page 2Linked to original sources
PubMed1996

Activity of asynchronous flight muscle from two bee families during sonication (buzzing).

The indirect flight muscles of bees are used to produce a variety of actions in addition to flight, including sonication, which has a higher frequency than flight. We observed the dynamic movement of the scutum during sonication and the transition from tethered flight to sonication. During sonication, the scutum oscillated above its rest position, indicating that the conformation of the structural components of the thorax had been altered. Sonication vibrations of the thorax occurred by deformation of the scutum rather than by opening of the scutal fissure and are smaller than vibrations associated with flight. During tethered flight, the ratio of muscle activity (recorded via electromyograms) between the dorsal longitudinal muscles and the dorsoventral muscles approached 1, but during sonication the ratio was significantly higher (up to 4.0). This increase may cause the dorsal longitudinal muscles to contract further than the dorsoventral muscles and close the scutal fissure during sonication, so limiting the displacement of the wings and 'decoupling' them from the indirect flight muscles.

Animals↗
PubMed1996

Peritoneal dialysis in the Pacific.

Peritoneal dialysis (PD) in the Pacific is the predominant dialysis modality for home dialysis patients. Patient location, age, personal preference, and medical condition are all taken into consideration. However, with the steadily increasing number of patients on PD, financial constraints are now affecting the nurse-patient ratios. As a consequence, PD nurses are constantly seeking new and improved clinical practice regimes with which they can provide and maintain quality, cost-effective nursing care. To enable PD nurses to provide such care, they are now, more than ever, involved in patient, professional, and management issues. These patient issues include, but are not limited to: the elderly, the diabetic, the indigenous patient, and their carers, peritonitis, exit-site infection, and adequate dialysis. Professional issues include the development of standards of clinical practice, nursing research, quality improvement, and tertiary education. Management issues are constantly encroaching into the clinical practice setting, therefore the PD nurse must now justify spending, develop strategic plans, and meet annual budgets. In conclusion, it can be seen that PD nurses in the Pacific are faced with similar patient-care, professional, and management issues as their counterparts throughout the world.

Adolescent↗
PubMed1996

An initial investigation into the wear and damage within the pivots of three types of bileaflet mechanical heart valves.

Two 29 mm St. Jude Medical valves, two 29 mm CarboMedics valves and two 29 mm Sorin Bicarbon valves were tested in a real time fatigue test rig. The test rig was run at 72 beats/min with a stroke volume of 70 ml for approximately one million cycles. Optical microscopy was used to investigate the valve surfaces. Possible deterioration of the surface finish was observed on the stops of the hinge recesses in the St. Jude Medical and CarboMedics valves. In the Sorin valves areas of the pyrolytic carbon coating was worn away adjacent to and on the valve stops.

Biocompatible Materials↗
PubMed1995

Differential activation of bovine brain N-myristoyltransferase(s) by a cytosolic activator.

N-Myristoyltransferase (NMT) is an essential eukaryotic enzyme that catalyses the transfer of myristate from myristoyl-CoA to the NH2-terminal glycine residue of a number of important proteins of diverse function. Little is known about the control and regulation of NMT in higher eukaryotes. We have identified a N-myristoyltransferase activator (NAF45) which copurified with one form of bovine brain NMT activity which failed to bind to phosphocellulose column chromatography (NMT.PU) and represented 32 +/- 4% of the total NMT activity applied to this column. The NAF45 and NMT activities were resolved by mono Q column chromatography from the NMT.PU fraction. Resolution resulted in a loss of NMT.PU activity. NAF45 was a nondialysable molecule with an apparent molecular mass of 45 kDa. Reconstitution of the NAF45 and NMT resulted in the recovery of NMT activity, indicating that this form of NMT is dependent on the presence of NAF45. NAF45 was able to stimulate other forms of NMT activity (maximum of 3-4 fold) in a highly cooperative fashion (Hills coefficient of approximately 5.5). Stimulation was in terms of both the rate of myristoylation and the overall production of myristoylpeptide, indicating that the end point of the reaction was shifted in favour of myristoylpeptide production. NAF45 was able to compete with NIP71 for NMT [King, M.J. and Sharma, R.K. (1993) Biochem, J. 291, 635-639], although its affinity appeared lower than the NIP71.

Acyltransferases↗
PubMed1995

The antifreeze protein genes of the winter flounder, Pleuronectus americanus, are differentially regulated in liver and non-liver tissues.

The synthesis of winter flounder (Pleuronectus americanus) antifreeze protein (AFP) mRNAs in the liver is seasonally regulated by the pituitary gland. With the recent discovery that AFP mRNAs are also present in several non-liver tissues, the aim of the present investigation was to compare the regulatory mechanisms of AFP genes in liver and non-liver tissues. Northern blot analyses indicate that the level of liver AFP mRNA undergoes a several hundred fold difference between the winter and summer months, while AFP mRNAs from gills and kidneys exhibit only a modest 5-10 fold seasonal variation. As expected, the liver AFP mRNA in the hypophysectomized fish was increased by over 40 fold. However, no significant increase was observed for the non-liver AFP mRNAs upon hypophysectomy. These investigations suggest that AFP mRNAs in liver and non-liver tissues are differentially regulated.

Animals↗
PubMed1995

Reactivity with erythroid and non-erythroid tissues of a murine monoclonal antibody to a synthetic peptide having amino acid sequence common to cytoplasmic domain of human glycophorins C and D.

Three synthetic peptides encompassing the entire cytoplasmic polypeptide sequence (amino acid residues 82-128) of glycophorin C (GPC) and glycophorin D (GPD) were used to immunize mice for the production of monoclonal antibodies (MoAbs). Only the synthetic peptide (GPC-peptide-1) corresponding to C-terminal residues 112-128 elicited a MoAb (named BGRL-100) which could react with native and denatured GPC and GPD. We characterized BGRL-100 by inhibition using GPC-peptide 1 and red cell sialoglycoproteins. The ability of BGRL-100 to interact with native GPC and GPD was assessed by immunoprecipitation with normal red cells (RBCs), and with denatured GPC and GPD by Western blotting of both normal RBCs and RBCs carrying GPC variants. Immunohistochemical staining of human tissue sections was performed using both BGRL-100 and a rat MoAb (named BRAC-1), which is specific for an extracellular domain of GPC and GPD. Both antibodies showed strong staining of erythroid lineage haemopoietic cells in fetal liver, sinusoids of adult liver and RBCs in the blood vessels of all tissues tested. Neither antibody reacted with epithelia from a range of human tissues. However, both MoAbs stained neural tissue in a distinctive fibrillar pattern. This suggests the presence of an analogue of erythroid GPC in neural tissues.

Amino Acid Sequence↗
PubMed1994

Mechanisms of action of NIP71 on N-myristoyltransferase activity.

N-Myristoyl-CoA:protein N-myristoyltransferase (NMT) is the enzyme that catalyses the transfer of myristate from myristoyl-CoA to the N-terminal glycine of protein substrates. NMT was highly purified from bovine brain by procedures involving sequential column chromatography on DEAE-Sepharose CL-6B, phosphocellulose, hydroxylapatite, and mono S and mono Q f.p.l.c.. The highly purified NMT (termed NMT.II) possessed high specific activity with peptide substrates derived from the N-terminal sequences of the cAMP-dependent protein kinase and pp60src (29,800 and 47,600 pmol N-myristoylpeptide formed/min/mg, respectively), intermediate activity with a peptide based on the N-terminal sequence of a viral structural protein (microliter) (M2; 17,300 pmol N-myristoylpeptide formed/min/mg) and very low activity with a peptide derived from the N-terminal sequence of myristoylated alanine-rich C-kinase substrate (MARCKS; 1500 pmol myristoylpeptide formed/min/mg). An NMT protein inhibitor (NIP71) isolated from the particulate fraction of bovine brain (King MJ and Sharma RK: Biochem J 291:635-639, 1993) potently inhibited highly purified NMT activity (IC50 23.7 nM). A minor NMT activity (NMT.PU; 30% total NMT activity), which failed to bind to phosphocellulose, was insensitive to NIP71 inhibition. Inhibition of NMT was observed to be via mixed inhibition with respect to both the myristoyl-CoA and peptide substrates with NIP71 having an apparent higher affinity for NMT than the NMT.myristoyl.CoA complex. Inhibition by NIP71 at subsaturating concentrations of myristoyl-CoA and peptide resulted in a sigmoidal pattern of inhibition indicating that bovine brain possesses a potent and delicate on/off switch to control NMT activity.

Acyltransferases↗
PubMed1994

Blood group antigens on human erythrocytes-distribution, structure and possible functions.

Human erythrocyte blood group antigens can be broadly divided into carbohydrates and proteins. The carbohydrate-dependent antigens (e.g., ABH, Lewis, Ii, P1, P-related, T and Tn) are covalently attached to proteins and/or sphingolipids, which are also widely distributed in body fluids, normal tissues and tumors. Blood group gene-specific glycosyltransferase regulate the synthesis of these antigens. Protein-dependent blood group antigens (e.g., MNSs, Gerbich, Rh, Kell, Duffy and Cromer-related) are carried on proteins, glycoproteins and proteins with glycosylphosphatidylinositol anchor. The functions of these molecules on human erythrocytes remain unknown; some of them may be involved in maintaining the erythrocyte shape. This review describes the distribution, structures and probable biological functions of some of these antigens in normal and pathological conditions.

Blood Group Antigens↗
PubMed1994

Two different glycosyltransferase defects that result in GalNAc alpha-O-peptide (Tn) expression.

This study shows for the first time that different glycosyltransferase defects in the biosynthesis of O-linked oligosaccharides give rise to the same GalNAc alpha-O-Ser/Thr determinant on Tn erythrocytes and colorectal carcinoma cells. The O-linked oligosaccharides isolated from the glycophorins of Tn erythrocytes contained predominantly alpha-N-acetylgalactosamine-O-Ser/Thr (Tn antigen) and sialyl-Tn. A marked reduction in normal sialylated oligosaccharides was also observed. Monoclonal antibody BRIC 111 raised against Tn erythrocytes reacted with both Tn erythrocytes and colorectal carcinoma tissues. Weak staining was detected in the supranuclear area and at the surface membranes in normal colorectal cells, but was absent from goblet cell vesicles. An increase in supranuclear staining over controls was found in tumour tissue and in the majority of resection margin specimens. The highest levels of staining were present in transitional mucosa, adjacent to the tumours where goblet vesicles were also positive. Glycosylation defects in the same patients were further studied by determination of the activity of glycosyltransferases in mucosal tissue from control and cancer patients. The reduction in or loss of beta 1-3 N-acetylglucosaminyl transferase activity to GalNAc-peptide in asialo-ovine submaxillary gland glycoprotein was detected by direct assay and by isolation of the oligosaccharides from the incubation products. No differences in N-acetylglucosaminyl-, galactosyl- or sialyl-transfer to Gal beta 1-3GalNAc in antifreeze glycoprotein or in sialyl transferase to asialo-ovine submaxillary gland glycoprotein were detected. Our study shows that the GalNAc alpha-O-Ser/Thr determinant on Tn erythrocytes and in colorectal carcinoma results from different glycosyltransferase defects in separate biosynthetic pathways for haematopoietic and epithelial tissues.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1994

An assessment of the immunoprecipitation of blood-group antigens using biotinylated red cells.

This study presents a simple protocol for labelling red cell membrane proteins and glycoproteins using biotin. The advantages include an increased capacity to label and process a large number of cell samples of different phenotypes without using large quantities of radionuclides, resulting in no hazardous waste by-products as in radiolabelling methods, and a fast exposure time for detection of the biotinylated component(s). Our assessment on biotinylated red cells was based on the retention of antigenic activity with 14 antibodies (13 monoclonals, one polyclonal), which have specificities for extracellular and cytoplasmic domains of various membrane components, by ELISA, haemagglutination tests and immunoprecipitation. A luminescent method was used to detect the immunoprecipitates on nitrocellulose membrane after SDS-polyacrylamide gel electrophoresis. The development time for band detection was between 5 s and 1 min. Free amino groups that constitute a part(s) of an antigenic determinant were also biotinylated. As a result antibody binding to the red cells was abrogated.

Antibodies, Monoclonal↗
PubMed1993

A point mutation in the GYPC gene results in the expression of the blood group Ana antigen on glycophorin D but not on glycophorin C: further evidence that glycophorin D is a product of the GYPC gene.

Glycophorin C (GPC) and glycophorin D (GPD) are homologous sialoglycoproteins in the human red blood cell membrane. Both are thought to be encoded by the GPC gene (GYPC). We report that the rare blood group antigen, Ana, is expressed on GPD but not on GPC. cDNA was synthesized from total RNA obtained from two unrelated, heterozygous Ana+ blood donors and analyzed by the polymerase chain reaction using primers that spanned sequences encoded by the GYPC gene. The expected 412-bp fragment was generated, and sequencing of the amplified product showed a G-->T substitution at nucleotide 67 of the coding sequence, resulting in the substitution of alanine by serine at amino acid residue 23 of GPC and, presumably, residue 2 of GPD. To explain the expression of Ana on GPD but not on GPC, we postulate that the conformation of the amino acid residues at the N-terminal region of GPD determines the antigenic expression as this conformation would be different from that of the same sequence of amino acids occurring within GPC. Other possible reasons for antigen expression on a shorter protein product but not on the full-length protein product of the same gene are discussed. We extrapolate this reasoning to account for the expression of the common GE2 blood group antigen on GPD but not on GPC.

Amino Acid Sequence↗
PubMed1993

Membrane-associated N-myristoyltransferase activity is reduced in obese (fa/fa) Zucker rat liver.

N-Myristoyltransferase is the enzyme that catalyses the transfer of myristate from myristoyl-CoA to the NH2-terminal glycine residue of a number of protein of diverse functions. Many of the known myristoylated proteins are important in signal transduction. We have compared the activity of rat liver N-myristoyltransferase from lean and obese (fa/fa) Zucker rats (a model for non-insulin dependent diabetes mellitus, NIDDM). N-myristoyltransferase activity isolated from the particulate fraction of obese (fa/fa) Zucker rat liver was approximately 4.7-fold lower than the corresponding activity observed in either the controls or the vanadate-treated obese rat livers. This pattern was only observed in the particulate fraction; the homogenate and soluble N-myristoyltransferase activities were not significantly different to the control activities. N-myristoyltransferase activity isolated from the brain of the four groups showed no significant variations. These results, and previous work [King, M. J., Pugazhenthi, S., Khandelwal, R. L. and Sharma, R. K. (1993) Biochim. Biophys. Acta. 1165, 259-262], would indicate that the rat liver particulate N-myristoyltransferase activity appears to be inversely proportional to the level of plasma insulin, implicating insulin in the control of N-myristoylation. The specific activity of the particulate liver N-myristoyltransferase was approximately 10-fold higher than that of the soluble liver N-myristoyltransferase, raising the possibility that N-myristoyltransferase exists in 2 populations, with the active form of N-myristoyltransferase residing in the membranous fraction. This situation could provide a system whereby N-myristoylation is regulated by the translocation of N-myristoyltransferase from the cytosol to its active site in the membranes.

Acyltransferases↗
PubMed1993

Identification, purification and characterization of a membrane-associated N-myristoyltransferase inhibitor protein from bovine brain.

N-Myristoyl-CoA: protein N-myristoyltransferase (NMT) is the enzyme that catalyses the covalent transfer of myristic acid from myristoyl-CoA to the N-terminal glycine residue of a protein substrate. Subcellular fractionation of bovine brain indicates that NMT activity was located in both the cytosolic and the particulate fraction of the cell. Removal of the particulate fraction resulted in a 2-fold enhancement of NMT activity. Reconstitution of the particulate fraction and cytosolic fraction resulted in inhibition of the elevated cytosolic NMT activity. These results indicated the existence of putative inhibitor(s) activity of NMT located in the particulate fraction of bovine brain. The inhibitor was stable to heat and was identified as a protein, on the basis of its susceptibility to the proteases trypsin and chymotrypsin. Protease degradation first required the delipidation of the particulate fraction. The inhibitor was purified to near-homogeneity by heat treatment, solvent extraction and Sephacryl S-300 gelfiltration column chromatography. The inhibitor was purified 630-fold from the particulate fraction with a 20% yield. The protein inhibitor had an apparent molecular mass of 92 kDa by gel filtration and 71 kDa by SDS/PAGE, indicating the protein is monomeric. The inhibitor did not interact directly with myristoyl-CoA and possessed no protease, thioesterase or demyristoylase activity. Purified inhibitor protein inhibited the formation of 1167 pmol of myristoyl-peptide/min per mg of protein.

Acyl Coenzyme A↗
PubMed1993

Elevated N-myristoyl transferase activity is reversed by sodium orthovanadate in streptozotocin-induced diabetic rat.

N-Myristoyl transferase (NMT) is the enzyme that covalently modifies several proteins important in signal transduction. Streptozotocin-induced diabetes resulted in a 2-fold increase in NMT activity from rat liver as compared to control animals. Administration of sodium orthovanadate to the diabetic rats reduced the activity of the NMT to 75-120% of the control values. Elevated NMT activity was observed with both cAMP-dependent protein kinase-derived and pp60src-derived peptide substrates. No significant change in the apparent Km was observed with the cAMP-dependent protein kinase-derived peptide substrate. Unlike in rat brain, in all conditions highest NMT activity was observed in the particulate fraction of rat liver.

Acyltransferases↗
PubMed1993

Teaching fibreoptic nasotracheal intubation with and without closed circuit television.

We have compared the progress of anaesthetists taught fibreoptic nasotracheal intubation with the aid of a closed circuit television (CCTV) system with that of anaesthetists taught by traditional methods. Twenty anaesthetists were allocated randomly to either the video or traditional training group. A graduated training programme was used in which the first stage was an introduction to techniques and apparatus and the second stage was practice on an airway model. During the third stage, rhinoscopy, pharyngoscopy and laryngoscopy were performed on anaesthetized patients whose lungs were ventilated via an orotracheal tube. A maximum time of 6 min was allowed for completion of laryngoscopy. Trainees aimed to perform five endoscopies in less than 60 s before moving on to the next stage. During the fourth stage, they carried out five traditional nasotracheal intubations (plus two video-controlled intubations for the video group) on apnoeic, anaesthetized patients. The mean number of endoscopies required (11.7 vs 21.8), mean total endoscopy time (21.5 vs 63.1 min) and mean number of failed endoscopies (0.8 vs 3.9) were significantly less in the video group. All the video-controlled intubations were successful. There was no significant difference between the number of successful traditional intubations in the two groups (90% video, 92% traditional). CCTV appears to enhance substantially the rate of acquisition of fibreoptic nasotracheal intubation skills.

Adult↗
PubMed1992

Novel bovine heart calmodulin-dependent protein kinase which phosphorylates a high molecular weight calmodulin-binding protein.

A novel calmodulin-dependent protein kinase has been isolated from bovine cardiac muscle by successive chromatography on DEAE-Sepharose 6B, Calmodulin-Sepharose 4B affinity and Sepharose 6B chromatography columns. The protein kinase was shown by gel filtration chromatography to have a molecular mass of 36,000 daltons. The highly purified protein kinase stoichiometrically phosphorylated the high molecular weight calmodulin-binding protein from cardiac muscle [Sharma RK (1990) J Biol Chem 265, 1152-1157] in a Ca2+/calmodulin-dependent manner. The phosphorylation resulted in the maximal incorporation of 1 mol of phosphate/mol of the high molecular weight calmodulin-binding protein. Other Ca2+/calmodulin-dependent protein kinases failed to phosphorylate the high molecular weight calmodulin-binding protein. The distinct substrate specificity of this protein kinase indicates that it is not related to the known calmodulin-dependent protein kinases and therefore constitutes a novel protein kinase.

Animals↗
PubMed1992

Demonstration of multiple forms of bovine brain myristoyl CoA:protein N-myristoyl transferase.

Four distinct N-myristoyl transferase (NMT) activity peaks, designated I, II, III, and IV, were separated from the cytosolic fraction of bovine brain by DEAE-Sepharose column chromatography. Peaks I, II, III and IV were characterised biochemically with respect to substrate specificity: with cAMP-dependent protein kinase and pp60src derived peptides, and by their apparent molecular mass. The apparent molecular mass of peaks I, II, III and IV were 190 kDa, 224 kDa, 390 kDa and 76 kDa, respectively. These results indicate that bovine brain contains multiple forms of NMT.

Acyltransferases↗