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Biomedical subjects

D J King

Publications and source records attributed to D J King.

At least 19 recordsLinked to original sources
PubMed1992

5-Hydroxyindoleacetic acid in cerebrospinal fluid and prediction of suicidal behaviour in schizophrenia.

Low concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF) are associated with suicidal behaviour in patients with depressive illness, but studies of the relation between CSF 5-HIAA and suicide in schizophrenia have been inconclusive and have not included long-term follow-up. In a prospective study, we measured 5-HIAA in CSF taken from 30 schizophrenic patients in a drug-free state, and followed these patients for 11 years. 10 patients made suicide attempts during follow-up. Suicide attempters had significantly lower concentrations of CSF 5-HIAA at initial evaluation than non-attempters (mean [SE] 6.7 [2.2] vs 23.6 [5.6] ng/ml, p < 0.05). Our findings provide further evidence of the relation between serotoninergic dysfunction and suicide, and suggest a role for drugs with serotoninergic effects in schizophrenia.

Female↗
PubMed1992

Crystal structure of a chimeric Fab' fragment of an antibody binding tumour cells.

The crystal structure of a chimeric Fab' fragment of a monoclonal antibody is presented. The Fab' comprises the murine light chain and heavy chain variable domains of the carcinoma-binding antibody B72.3 fused to the constant domain of human kappa, and the first constant domain and hinge domain of human gamma 4, respectively. A model for the Fab' has been determined by molecular replacement and refined to a resolution of 3.1 A with an R-factor of 17.6%. The additional residues that distinguish a Fab' from a Fab fragment are seen to be disordered in the crystals. The H3 hypervariable loop is short and adopts a sharp hairpin turn in a conformation that results from an interaction between the lysine side-chain of H93 and the main-chain carbonyl group of H96. The remaining hypervariable loops display conformations similar to those predicted from the canonical structures approach, although loop H2 is apparently displaced by a salt-bridge formed between H55 Asp and the neighbouring H73 Lys. These and other features of the structure likely to be important in grafting the hypervariable loops to an otherwise human framework are discussed.

Amino Acid Sequence↗
PubMed1992

Significant telomere shortening in childhood leukemia.

Telomere length was studied by Southern analysis in five cases of childhood acute leukemia. In four cases, the length of the telomere sequence of the blast phase cells was shortened as compared with that of the cells examined during remission. Study of telomere length during chemotherapy for hematologic malignancies may show rapidly dividing subpopulations of malignant cells and thereby guide further treatment needs. In addition, such loss of telomere sequence would give rise to chromosomal instability and could be one of the mechanisms of oncogene activation in acute leukemia.

Blotting, Southern↗
PubMed1992

Expression, purification and characterization of a mouse-human chimeric antibody and chimeric Fab' fragment.

B72.3 is a mouse monoclonal antibody against a tumour-associated antigen, TAG72, which recognizes breast, ovarian and colorectal tumour tissue. A mouse-human chimeric version of B72.3 has been expressed in Chinese-hamster ovary cells. This molecule has the binding specificity of B72.3 and constant regions from human IgG4. The chimeric B72.3 assembles to intact IgG and recognizes TAG72 as well as B72.3 in competitive binding assays. A proportion of the chimeric B72.3 (approx. 10%) does not form inter-heavy-chain disulphide bonds but still assembles into the IgG tetramer. This appears to be a general property of human IgG4 molecules. Co-expression of the chimeric light chain with a chimeric Fd' gene resulted in the expression of functional Fab'. Very little F(ab')2 is produced, although the Fab' can be oxidized to the dimeric F(ab')2 in vitro. The production of Fab' and F(ab')2 by this method is an attractive alternative to proteolytic digestion of IgG. The ability to produce these molecules in large quantities will allow the production and testing of a range of anti-tumour antibody and antibody fragment conjugates.

Animals↗
PubMed1992

A placebo controlled trial of remoxipride in the prevention of relapse in chronic schizophrenia.

Sixty-two DSM III chronic schizophrenic inpatients were selected for a double-blind, placebo controlled, multi-centre, relapse prevention study of remoxipride, a selective dopamine (D2)-receptor antagonist. After a 1 month placebo washout, 23 patients had relapsed and were withdrawn. Of the remaining patients 19 were randomised to remoxipride (150-300 mg daily) and 20 to placebo. Their median age was 58 years, 26 were male, and the median duration of illness was 33 years. After 24 weeks a further total of 8 remoxipride and 17 placebo patients had been withdrawn. Excluding three patients withdrawn for reasons other than relapse, the comparative relapse rates were 37% and 75%, respectively (P = 0.015). Efficacy analyses using clinical global impression (P = 0.04) and change in BPRS scores (P = 0.016) were in favour of remoxipride. Extrapyramidal symptoms were minimal in both groups. Treatment emergent adverse events were similar in the two groups. Remoxipride is therefore of potential value as a safe drug which is both effective and well tolerated in the long term management of chronic schizophrenic patients.

Adult↗
PubMed1992

The McCollough effect as a measure of central cholinergic activity in man.

The McCollough Effect (ME) is an orientation contingent colour after-effect which has been proposed as an indicator of central neurotransmitter activity. Shute (1979) suggested that the ME could reflect a hippocampal "forgetting" mechanism which should be inhibited by GABAergic neurones and stimulated by cholinergic neurones. The purpose of the present study was to demonstrate that the ME is in fact sensitive to cholinergic and anticholinergic drugs and to compare its sensitivity to more conventional tests of psychomotor and cognitive function. Ten healthy subjects received single doses of physostigmine (0.75 mg SC), hyoscine (1.2 mg), temazepam (20 mg), flecainide (200 mg) or placebo in a double-blind double-dummy presentation. Subjects were tested on a battery of psychomotor and cognitive function tests at baseline and 1 h, and adapted to the ME at 1.5 h. Visual analogue rating scales and conventional tests of psychomotor function and saccadic eye movements indicated that both subjective and objective measures of arousal were impaired by temazepam. The subjective, but not the objective, measures of arousal were also impaired by both hyoscine and physostigmine, but not by flecainide. Initial strength and duration of the ME were decreased by physostigmine and increased by hyoscine and temazepam, relative to placebo (P less than 0.01). Thus, the ME is capable of detecting cholinergic, anticholinergic and GABA mimetic drug effects in man, in therapeutic doses.

Adaptation, Ocular↗
PubMed1992

Purification of recombinant chimeric B72.3 Fab' and F(ab')2 using streptococcal protein G.

Streptococcal protein G has been used extensively for the purification of antibodies using the interaction of the Fc region with protein G. Many antibodies also interact with protein G through a low-affinity binding site for the Fab region. The exploitation of this low-affinity interaction for the purification of Fab' fragments is described here. Chimeric mouse-human B72.3 Fab' and F(ab')2 fragments were expressed by CHO cells and purified from CHO cell supernatant using protein G-Sepharose. Since chimeric B72.3 Fab' bound weakly to the protein G-Sepharose it could be separated from F(ab')2 and eluted with a pH 7 wash whereas B72.3 F(ab')2 required elution at pH 2. Both Fab' and F(ab')2 were recovered with full immunoreactivity and could be further purified using gel-filtration chromatography to greater than 99% purity. This method allows the simple purification of directly expressed Fab' or F(ab')2 fragments from CHO cell supernatant.

Animals↗
PubMed1992

The effect of neuroleptics on cognitive and psychomotor function. A preliminary study in healthy volunteers.

The effects of haloperidol (1 mg), benzhexol (5 mg), diazepam (10 mg) and caffeine (400 mg) on subjective and objective measures of cognitive and psychomotor function were compared with placebo in 20 healthy volunteers. While both diazepam and benzhexol were associated with highly significant impairments in subjective altertness, critical flicker fusion threshold and choice reaction time (CRT), haloperidol could not be distinguished from placebo in most tests but was actually associated with an apparent improvement in CRT (in males) and simple visual reaction time. The perceptual maze test detected impairment by benzhexol on processing speed but was not sensitive to any other drug effects. Multiple-dose studies are required to establish if there is a true activating effect of haloperidol using a test of sustained attention. No effect of Eysenck personality subtype or life events on baseline or drug response data was detected.

Adult↗
PubMed1991

Matrix-assisted UV-laser desorption/ionization mass spectrometric analysis of monoclonal antibodies for the determination of carbohydrate, conjugated chelator, and conjugated drug content.

The chemically averaged molecular weights of a variety of native and conjugated monoclonal antibodies, approximately 150,000, were measured by matrix-assisted UV-laser desorption/ionization mass spectrometry. The average mass of the carbohydrate present in a monoclonal antibody was estimated from the difference between the measured mass of the monoclonal antibody and the mass of the protein present in the monoclonal antibody computed from the amino acid translation of the DNA sequence. The loading of chelators and anticancer drugs conjugated to a monoclonal antibody was quantitated from the difference in the measured masses for the conjugated and untreated monoclonal antibody relative to the expected mass change upon conjugation of 1 mol of chelator or drug. The loading results obtained by mass spectrometry were consistent in most cases with measurements obtained by radioactivity trace assay or UV spectrometry. Similar matrix-assisted UV-laser desorption/ionization mass spectrometric studies were also made after reducing untreated and conjugated monoclonal antibodies with dithiothreitol to determine the distribution of carbohydrate and chelator between the light and heavy chains of the molecules. Matrix-assisted UV-laser desorption/ionization mass spectra were used to compute loading values for covalently bound drugs and proteins, while the loading values obtained by use of gel-filtration HPLC and UV spectrometry cannot distinguish between covalently and noncovalently bound drugs and proteins.

Antibodies, Monoclonal↗
PubMed1991

Crystallization and preliminary X-ray diffraction study of a chimaeric Fab' fragment of antibody binding tumour cells.

Crystals have been obtained of a chimaeric Fab' fragment that binds to a tumour-associated mucin-like glycoprotein TAG72. The Fab' fragment comprises the variable heavy and light-chain domains of a murine monoclonal antibody, B72.3, coupled to human gamma 4 and kappa constant regions. The crystals are orthorhombic and belong to the space group P2(1)2(1)2(1), with unit cell dimensions a = 67.9 A, b = 94.2 A and c = 208.8 A. Diffraction to 2.6 A resolution was observed using synchrotron radiation. Despite the acute radiation sensitivity of the crystals a full native data set has been collected using the Weissenberg camera at the Photon Factory synchrotron. These data will be used for molecular replacement calculations in an attempt to elucidate the structure of this chimaeric Fab' fragment.

Animals↗
PubMed1991

Transfusion and the use of blood products.

I have reviewed areas of development in the use of blood and blood products, placing emphasis on the complications of transfusion, particularly transmission of infection. Alloimmunization in relation to transfusion of red cells and platelets has been covered and suggestions for reducing this problem assessed. The potential methods of avoiding the infective complications have been discussed including the screening of blood for infective agents, the virucidal treatment of blood products during the manufacturing process and white cell depletion. The use of recombinant DNA technology to produce coagulation factors offers the possibility of further reducing infective risks. An area of clinical promise is the use of haematopoietic growth factors to treat bone marrow failure, either congenital or acquired, such as the myelosuppressive effects of cancer chemotherapy, and reduce reliance on blood products. The aim of the chapter is to encourage the rational use of a limited resource by considering the risks inherent in transfusion and alternative strategies. In doing this it is important to audit current and future practice, and it is suggested that reference is made to the suggestions of Hume (1989) for quality assessment and assurance in paediatric transfusion medicine.

Acquired Immunodeficiency Syndrome↗
PubMed1991

A preliminary study of the effects of flosequinan on psychomotor function in healthy volunteers.

The central nervous system effects of flosequinan (100 mg), a chemically novel quinolone vasodilator, were assessed by a double-blind crossover comparison with placebo and diazepam (10 mg) in 12 healthy volunteers. After five practice sessions on a battery of automated psychomotor tests, assessments of psychomotor function and mood ratings were made on each volunteer at baseline and 1, 3, 6 and 24 h after dosing. Compared with placebo, diazepam (10 mg), the verum control, significantly (p less than 0.05) reduced subjective alertness, impaired critical flicker fusion threshold at 1 and 3 h, digit symbol substitution at 6 h, overall total choice reaction time and overall rate on two of five finger tapping tests. Flosequinan (100 mg), however, was indistinguishable from placebo in all tests with two contrasting exceptions: improved alternate right and left finger tapping (mean 5.1/s) compared to either diazepam (4.7/s) or placebo (4.8/s) (p less than 0.05), and impaired digit symbol substitution at 6 h (45.7/min) in comparison with placebo (50.7/min) (p less than 0.01). Ten volunteers reported 12 adverse effects after flosequinan treatment (10 of which were headaches), two reported drowsiness after diazepam and one reported headache after placebo. It was concluded that flosequinan has no central nervous system depressant effects despite the occurrence of headache in 10 volunteers.

Administration, Oral↗
PubMed1991

The clinical correlates of neurological soft signs in chronic schizophrenia.

Among 16 chronic schizophrenic in-patients, all had at least one neurological soft sign (NSS), and 6 (40%) had definite neurodysfunction. NSS and TD scores were highly intercorrelated, and NSS were significantly correlated with neuroleptic drug exposure. NSS correlated positively with both positive and negative symptoms and cognitive impairment but not with cerebral ventricular size on CT. Patients with neurodysfunction had more positive and negative psychopathology, cognitive impairment and TD than those without. Cerebral ventricular sizes and family histories of schizophrenia were similar in both NSS groups. The presence of NSS may be a simple but important way of identifying a subgroup of schizophrenics with neurodevelopmental predisposing abnormalities, and vulnerability to TD.

Adult↗
PubMed1990

Plasma and red blood cell fatty acids of low-birth-weight infants fed their mother's expressed breast milk or preterm-infant formula.

The fatty acid composition of plasma phospholipids, red blood cell (RBC) phosphatidylcholine (PC), and phosphatidylethanolamine (PE) was determined for low-birth-weight (LBW) infants when full oral feeding commenced (day 0) and after a further 28 d (day 28). They were fed their mother's expressed breast milk (PTM, n = 9), formula (SCF, n = 16) with 2% 18:3n-3 fatty acids, 20% 18:2n-6 fatty acids, or a combination of SCF and PTM (n = 11). Concentrations of all 20- and 22-carbon n-6 and n-3 fatty acids were similar among the infant groups on days 0 and 28 (mean postnatal age 42 +/- 1.3 d). The results suggest that formula with greater than or equal to 2% 18:3n-3 and a ratio of 18:2n-6 to 18:3n-3 similar to that of human milk may permit incorporation of n-3 fatty acids in LBW infant tissues equivalent to that from human milk.

Erythrocytes↗
PubMed1990

Site-specific attachment to recombinant antibodies via introduced surface cysteine residues.

Many diagnostic and therapeutic applications of monoclonal antibodies require the covalent linking of effector or reporter molecules to the immunoglobulin polypeptides. Existing methods generally involve the non-selective modification of amino acid side chains, producing one or more randomly distributed attachment sites. This results in heterogeneous labelling of the antibody molecules and often to a decrease in antigen-binding due to the modification of residues close to the antigen-binding site. We report a novel strategy for site-specifically labelling antibodies through surface cysteine residues. Examination of molecular structures was used to identify amino acids of the CH1 domain of the IgG heavy chain that were accessible to solvent but not to larger molecules. Site-directed mutagenesis was used to substitute cysteine residues at these positions in the heavy chain of a mouse/human chimaeric version of the tumour-binding monoclonal antibody, B72.3. Expression of the modified antibody genes in mammalian cells yielded correctly assembled proteins that had thiol groups in pre-determined positions and showed no loss of antigen-binding activity. One of the mutants was used to demonstrate the site-specific attachment of a radio-iodinated ligand to the chimaeric B72.3 antibody.

Algorithms↗