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Biomedical subjects

J Knight

Publications and source records attributed to J Knight.

At least 55 records · Page 3Linked to original sources
PubMed1995

Co-crystallization of an ETS domain (PU.1) in complex with DNA. Engineering the length of both protein and oligonucleotide.

The PU.1 transcription factor is a member of the ets gene family of regulatory proteins. These molecules play a role in normal development and also have been implicated in malignant processes such as the development of erythroid leukemia. The Ets proteins share a conserved DNA-binding domain (the ETS domain) that recognizes a purine-rich sequence with the core sequence: 5'-C/AGGAA/T-3'. This domain binds to DNA as a monomer, unlike many other DNA-binding proteins. The ETS domain of the PU.1 transcription factor has been crystallized in complex with a 16-base pair oligonucleotide that contains the recognition sequence. The crystals formed in the space group C2 with a = 89.1, b = 101.9, c = 55.6 A, and beta = 111.2 degrees and diffract to at least 2.3 A. There are two complexes in the asymmetric unit. Production of large usable crystals was dependent on the length of both protein and DNA components, the use of oligonucleotides with unpaired A and T bases at the termini, and the presence of polyethylene glycol and zinc acetate in the crystallization solutions. This is the first ETS domain to be crystallized, and the strategy used to crystallize this complex may be useful for other members of the ets family.

Amino Acid Sequence↗
PubMed1995

Eicosanoid generating capacities of different tissues from the rainbow trout, Oncorhynchus mykiss.

The eicosanoid generating potential of the brain, gills, skin, ovary, muscle, eye, liver, spleen, heart, and alimentary canal in the rainbow trout, Oncorhynchus mykiss, was examined. All the organs/tissues examined synthesized the 12-lipoxygenase products, 12-hydroxyeicosatetraenoic acid (12-HETE), and 12-hydroxyeicosapentaenoic acid (12-HEPE), implying the widespread nature of this enzyme in trout. Both prostaglandin E and LTC were also found in variable amounts in the organs, with the greatest amount of PGE found in the gill. Leukotriene (LT) B4 and LTB5 were found in supernatants from calcium ionophore-challenged brain, skin, ovary, liver, spleen, and heart, but the lipoxins A4 and A5 were only present in brain, ovary, and spleen in relatively small amounts. As lipoxins have previously been shown to be synthesized by macrophages in rainbow trout [Pettitt et al., J. Biol. Chem. 266, 8720-8726 (1991)], and related cells (microglial cells) are found in the brain of mammals, the localization of macrophage-like cells in trout brain was investigated immunocytochemically. Monoclonal antibodies specific for trout leucocytes failed to identify any microglial-like cells in sections of the brain, although microvessels containing immuno-positive reaction products were observed. A number of distinct lipoxygenase products were found in supernatants of ionophore-challenged gill, including 14-hydroxydocosahexaenoic acid, 12-HETE, and 12-HEPE, and a large number of dihydroxy fatty acid derivatives with conjugated triene chromophores. One of these products was tentatively identified as 8(R),15(S)-dihydroxyeicosatetraenoic acid, a dual 12- and 15-lipoxygenase product, but apparently no LTB4 was generated by this tissue.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1995

Oncogenic conversion of a novel orphan nuclear receptor by chromosome translocation.

A recurrent t(9;22) (q22;q12) chromosome translocation has been described in extraskeletal myxoid chondrosarcoma (EMC). Fluorescent in situ hybridization experiments performed on one EMC tumour indicated that the chromosome 22 breakpoint occurred in the EWS gene. Northern blot analysis revealed an aberrant EWS transcript which is cloned by a modified RT-PCR procedure. This transcript consists of an in-frame fusion of the 5' end of EWS to a previously unidentified gene, which was named TEC. This fusion transcript was detected in six of eight EMC studied, and three different junction types between the two genes were found. In all junction types, the putative translation product contained the amino-terminal transactivation domain of EWS linked to the entire TEC protein. Homology analysis showed that the predicted TEC protein contains a DNA-binding domain characteristic of nuclear receptors. The highest identity scores were observed with the NURR1 family of orphan nuclear receptors. These receptors are involved in the control of cell proliferation and differentiation by modulating the response to growth factors and retinoic acid. This work provides, after the PML/RAR alpha gene fusion, the second example of the oncogenic conversion of a nuclear receptor and the first example involving the orphan subfamily. Analysis of the disturbance induced by the EWS/TEc protein in the nuclear receptor network and their target genes may lead to new approaches for EMC treatment.

Amino Acid Sequence↗
PubMed1995

Intrahepatic bile duct dilatation and cholestasis in autosomal recessive polycystic kidney disease. Demonstration with hepatobiliary scintigraphy.

Fifteen patients with the clinical and radiologic features of autosomal recessive polycystic kidney disease were investigated with radionuclide hepatobiliary scintigraphy. In nine patients (60%), cholestasis and intrahepatic bile duct dilatation were demonstrated. A 10th child had scintigraphic evidence of cholestasis, but the bile ducts were not dilated. The other five children has normal h hepatobiliary scans. The authors conclude that intrahepatic bile duct dilatation with cholestasis (Caroli's disease) is part of the clinical spectrum of autosomal recessive polycystic kidney disease and that hepatobiliary scintigraphy can be of value in determining the extent of hepatobiliary disease in this group of patients.

Bile Ducts↗
PubMed1995

Volumetric bone mineral density--a potential role in paediatrics.

The use of areal bone mineral density (aBMD) in paediatric populations has aroused some concern, as it fails to take the age-related increase in bone thickness into account. We have developed a measure of true bone density, volumetric bone mineral density (vBMD), which is independent of age and height. In order to examine the relationship between growth parameters, aBMD and vBMD, we studied patients with phenylketonuria (PKU, n = 40), chronic renal failure (CRF, n = 27) and chronic asthma (n = 19). aBMD of the femoral neck and the mid-femoral shaft was measured using dual energy X-ray absorptiometry (DXA), vBMD was calculated on the basis of values of bone mineral content and bone dimension provided by DXA, with the assumption that both sites are cylinders. aBMD and vBMD were then compared with the normal reference, expressed as a standard deviation score (SDS). aBMD and vBMD were normal in the femoral neck region of the PKU group, but aBMD, either standardized for age or for height, was low in the femoral shaft region (p < 0.01). In the CRF group, profound growth retardation was seen (mean height SDS, -3.2) and aBMD and vBMD were both low in the femoral shaft region but not in the femoral neck. In the asthma group, aBMD for age was low at both sites, but vBMD did not differ from that seen in normal individuals. We conclude that the true vBMD provides a different interpretation of bone density compared with aBMD and requires further evaluation in paediatrics because of its age and height independence.

Absorptiometry, Photon↗
PubMed1995

Immunoregulatory activities of eicosanoids in the rainbow trout (Oncorhynchus mykiss).

Eicosanoids such as prostaglandins (PG), leukotrienes (LT) and lipoxins (LX) have been shown to be potent immunoregulatory molecules in mammals. To determine if they have similar roles in 'lower' animals, rainbow trout (Oncorhynchus mykiss) were immunized with either sheep erythrocytes or Aeromonas salmonicida in the presence or absence of the stable analogue of PGE2, 16,16-dimethyl-PGE2, and the number of plaque-forming cells (PFC) or specific antibody levels determined. The higher dose of 16,16-dimethyl-PGE2 (200 micrograms/kg body weight) caused a significant reduction in both PFC number and antibody titre compared with the control. The effect of PGE2, PGE3, 16,16-dimethyl-PGE2, LTB4, LTB5, LXA4, 12-HETE and 12-HEPE on PFC generation following the in vitro challenge of trout splenocytes with sheep erythrocytes was also determined. All of the prostaglandins tested showed a dose-dependent inhibition of PFC after 11 days in culture, while of the remaining eicosanoids only LXA4 had any effect on PFC number, with a dose-dependent stimulatory effect. The cyclo-oxygenase inhibitor, indomethacin, also caused a stimulation in the number of PFC generated, with a maximal effect at c. 25 microM, while the lipooxygenase inhibitors, esculetin and nordihydroguaiaretic acid (5-100 microM), had no significant effect on PFC generation at all concentrations tested. The present results show that, as in mammals, prostaglandins and the cyclo-oxygenase pathway are also important in the regulation of the piscine humoral immune response. Of the lipoxygenase products tested, however, only LXA4 had any significant effect on PFC generation, suggesting that these compounds have only a limited role to play in immune regulation in this organism. Overall this work shows that eicosanoids have a long evolutionary history in immunoregulation, probably dating back at least to the appearance of bony fish some 400 million years ago.

16,16-Dimethylprostaglandin E2↗
PubMed1994

Eicosanoid generation and effects on the aggregation of thrombocytes from the rainbow trout, Oncorhynchus mykiss.

Fish blood lacks anucleate platelets but contains a nucleated cell type termed the thrombocyte that is thought to be functionally analogous. Thrombocytes were purified from the peripheral blood of the rainbow trout, Oncorhynchus mykiss, by a two step gradient centrifugation method. Following this procedure, the recovered thrombocytes were 78-86% pure as defined by immunoreactivity to a panel of monoclonal antibodies and were of variable morphology from round to spindle-shaped. Incubation of thrombocyte suspensions with either calcium ionophore, A23187, platelet-activating factor or a thromboxane (TX) mimetic, U-46619, generated a range of eicosanoids derived from arachidonic acid including 12-hydroxyeicosatetraenoic acid (12-HETE), TXB2, prostaglandin (PG) E2, leukotriene (LT) B4 and lipoxin (LX) A4. The equivalent products derived from eicosapentaenoic acid were also formed. Co-incubation of thrombocytes with either erythrocytes or granulocytes/monocytes in the presence of calcium ionophore did not result in the formation of any further new lipoxygenase products. Incubation of isolated thrombocytes in plasma-free conditions with U-46619 (0.03-10 microM) resulted in a rapid, dose-dependent aggregatory response. This effect was markedly augmented in the presence of mammalian fibrinogen (400 micrograms ml-1). Thrombin (0.1-1.3 units ml-1), like U-46619, was also a potent proaggregatory compound for trout thrombocytes. LXA4 and LTB4 had limited aggregatory potential and then only at high concentrations (10 microM), while 12-HETE and PAD had no significant effect at all concentrations tested. These results demonstrate that some of the eicosanoids released during the activation of trout thrombocytes are involved in the aggregatory behaviour of this cell type.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

The effects of hypothermic and normothermic cardiopulmonary bypass on glyceryl trinitrate activity.

Glyceryl trinitrate (GTN) is used to control arterial blood pressure during cardiopulmonary bypass (CPB) procedures, but its effects are often decreased during the period of extracorporeal support. The plasma and urine concentrations of GTN and glyceryl-1,2-dinitrate (1,2-GDN) and glyceryl-1,3-dinitrate (1,3-GDN) for male and female patients who received GTN during hypothermic CPB, and male and female patients who were given GTN during normothermic CPB, were measured by gas-liquid chromatography. During hypothermic CPB, the male and female subjects experienced significant decreases in GTN clearance (P < 0.05), 66% and 52%, respectively. Neither the males nor the females who underwent normothermic CPB experienced any significant change in GTN clearance. These results suggest that the lower core temperature during hypothermic CPB may decrease the biotransformation of GTN to GDNs and nitric oxide, thereby resulting in less dilation of blood vessels. Furthermore, the males in the hypothermic CPB group had significantly greater urinary concentrations of 1,3-GDN and 1,2-GDN than the females (P < 0.05), and the normothermic CPB males had a significantly greater urinary concentration of 1,2-GDN than the females in that group. The normothermic CPB males also had significantly higher plasma concentration of GTN at two time points, and 1,3-GDN at one time point, than the females. These data suggest that there may be a gender difference in GTN biotransformation.

Aged↗
PubMed1993

Effect of lipoxins and other eicosanoids on phagocytosis and intracellular calcium mobilisation in rainbow trout (Oncorhynchus mykiss) leukocytes.

Rainbow trout (Oncorhynchus mykiss) macrophages generated lipoxin (LX) A4, LXA5, leukotriene (LT) B4, LTB5 and 12-hydroxyeicosatetraenoic acid (12-HETE) during the phagocytosis of zymosan and Escherichia coli, but not of the yeast Saccharomyces cerevisiae. Prostaglandin (PG) E2 was also detected in supernatants from macrophages incubated with either zymosan or calcium ionophore A23187. LXA4 (10(-8)-10(-6) M) and LTB4 (10(-9)-10(-7) M) provoked rapid and transient dose-dependent increases in intracellular calcium ([Ca]i) concentrations in leukocyte suspensions containing 40-60% macrophages. EC50 values were 14.9 and 1.2 nM, respectively. PGE2 and 12-HETE had no effect on [Ca]i at concentrations up to 30 microM. PGE2 and 12-HETE (10(-5)-10(-10) M) enhanced the in vitro phagocytosis of yeast test particles by trout macrophages, whereas LXA4 and LTB4 had no demonstrable effect on the responses of these cells at concentrations up to 10(-5) M. In conclusion, the processes involved in trout macrophage stimulation are complex but involve generation of both cyclooxygenase and lipoxygenase products. The increase in [Ca]i caused by LXA4 and LTB4 may form part of the chemotactic transduction mechanism that recruits granulocytes and macrophages to sites of inflammation. The effects of eicosanoids on phagocytosis appear to be independent of changes in [Ca]i.

Animals↗
PubMed1992

Pholasin: a new chemiluminescent probe for the detection of chloramines derived from human phagocytes.

We have previously reported that normal human polymorphonuclear neutrophils (PMN) release taurine-chloramine, a long-lived oxidant, in response to stimulation by phorbol myristate acetate (PMA) or opsonized zymosan in the presence of exogenous taurine. We now describe a new, simple, and highly sensitive method for the detection of chloramines, including taurine-chloramine, using the chemiluminescent probe Pholasin, the luciferin of the mollusc Pholas dactylus. Taurine-chloramine (N-chlorotaurine) detection was assessed with both a colorimetric method (based on the oxidation of potassium iodide) and with the Pholasin-dependent chemiluminescence (CL) method. The taurine-chloramine concentration in PMN supernatants determined using the potassium iodide (KI) method correlated closely with Pholasin-dependent CL. This CL was also assessed in nonoxidative conditions. No taurine-chloramine was detected in supernatants of lymphocytes and PMN from patients with an oxidative burst defect (chronic granulomatous disease, CGD) with the KI method, but Pholasin-dependent CL was consistently observed. The use of methionine, a specific chloramine scavenger in our incubation conditions, allowed us to define a methionine-inhibitable fraction of Pholasin-dependent CL (i.e., chloramine-induced CL).

Child↗
PubMed1992

Can autoimmune mechanisms account for the genetic predisposition to schizophrenia?

Applications of molecular genetic techniques to schizophrenia have shown great initial promise but have then proved disappointing. In order to maximise chances of elucidating the genetic mechanism underlying schizophrenia, diverse strategies and diverse perspectives must be adopted. Most studies begin with the premise that, although schizophrenia may be a heterogeneous collection of diseases, some subtypes will be primarily single-gene disorders. We are concerned that this single-gene hypothesis may be incorrect. Schizophrenia research may benefit from application of knowledge from other disciplines and from other diseases which, in terms of epidemiology and apparent genetic mechanisms, bear some resemblance to schizophrenia.

Autoantibodies↗
PubMed1991

Ketoconazole-induced fulminant hepatitis necessitating liver transplantation.

The most serious side effect of ketoconazole is hepatitis, which has proved fatal in seven reported cases. We present a case of fulminant hepatic failure in a 45-year-old Oriental woman that probably would have been fatal except for a successful liver transplant. A review of the literature of fatalities associated with ketoconazole is presented.

Candidiasis↗
PubMed1990

Screening for prolonged incubation of HTLV-I infection in British and Jamaican relatives of British patients with tropical spastic paraparesis.

OBJECTIVE: To compare the prevalence of antibody to and proviral DNA of the retrovirus HTLV-I in relatives of 11 British patients with tropical spastic paraparesis who had migrated from Jamaica before they developed symptoms, and to examine factors possibly related to transmission of HTLV-I. DESIGN: Migrant, family study. Antibody state was determined by several methods and confirmed by western blotting; the polymerase chain reaction was used to detect proviral DNA. SETTING: Britain and Jamaica. SUBJECTS: All available first degree relatives: those born and still resident in Jamaica (group 1); those born in Jamaica who migrated to Britain (group 2); and index patients' children who were born and resident in Britain (group 3). All had been breast fed and none had had blood transfusions. RESULTS: Of the 66 living relatives, 60 were traced. Seroprevalence among those born in Jamaica (irrespective of current residence) was 22% (10/46; 95% confidence limits 9 to 34%) compared with zero among British born offspring (0/14) and was higher in group 2 at 33% (7/21; 12 to 55%) than in group 1 at 12% (3/25; 0 to 25%). (Patients in group 1 had the greatest mean age.) Proviral DNA was not detected in any subject negative for HTLV-I antibody, making prolonged viral incubation in those negative for the antibody unlikely. CONCLUSION: In this sample factors related to place of birth and early residence were more important in transmission of HTLV-I than maternal or age effects. In areas with a low to moderate prevalence policies of preventing mothers who are carriers of the virus from breast feeding would be premature.

Base Sequence↗