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Biomedical subjects

J Lou

Publications and source records attributed to J Lou.

At least 91 records · Page 5Linked to original sources
PubMed1996

Role of phosphorolytic cleavage in cellobiose and cellodextrin metabolism by the ruminal bacterium Prevotella ruminicola.

In bacteria, cellobiose and cellodextrins are usually degraded by either hydrolytic or phosphorolytic cleavage. Prevotella ruminicola B(1)4 is a noncellulolytic ruminal bacterium which has the ability to utilize the products of cellulose degradation. In this organism, cellobiose hydrolytic cleavage activity was threefold greater than phosphorolytic cleavage activity (113 versus 34 nmol/min/mg of protein), as measured by an enzymatic assay. Cellobiose phosphorylase activity (measured as the release of P(i)) was found in cellobiose-, mannose-, xylose-, lactose-, and cellodextrin-grown cells (> 92 nmol of P(i)/min/mg of protein), but the activity was reduced by more than 74% for cells grown on fructose, L-arabinose, sucrose, maltose, or glucose. A small amount of cellodextrin phosphorylase activity (19 nmol/min/mg of protein) was also detected, and both phosphorylase activities were located in the cytoplasm. Degradation involving phosphorolytic cleavage conserves more metabolic energy than simple hydrolysis, and such degradation is consistent with substrate-limiting conditions such as those often found in the rumen.

Animals↗
PubMed1996

Lungs in thalassaemia major patients receiving regular transfusion.

Progressive tissue iron deposition from multiple blood transfusions is common in beta-thalassaemia and pulmonary iron deposition may result in parenchymal damage. The objectives of this study were to: 1) determine the predominant pulmonary dysfunction in patients with thalassaemia major; and 2) demonstrate that parenchymal disease, if present, is at the level of the alveolocapillary membrane. Fourteen thalassaemia major patients (13 nonsmokers) receiving regular blood transfusion and without any history of chronic respiratory disease were recruited. Pulmonary function tests and echocardiography were performed before the scheduled transfusions. Three patients with the most restricted lung function were selected for high resolution computerized tomography (CT) of the lungs. One patient had an obstructive pattern with a forced expiratory volume in one second as percentage of forced vital capacity (FEV1/FVC) of 71%. Four patients demonstrated a restrictive pattern, as defined by total lung capacity (TLC) less than 80% predicted with normal FEV1/FVC%. Twelve patients had pulmonary transfer factors for carbon monoxide (TL,CO) below 80% pred, even after correction for the anaemia, indicating parenchymal disease. Eight of these 12 patients had alveolocapillary membrane defect, as demonstrated by a gas transfer factor of the pulmonary membrane (Tm) less than 80% pred. Mean resting arterial oxygen saturation was 95 +/- 2 (range 92-98) %. Eleven patients had oxygen desaturation of 5% or more during exercise on a bicycle ergometer, consistent with interstitial lung disease. There was no clinical or echocardiographic evidence of heart failure. Percentage predicted TLC was inversely correlated with age (r = -0.547; p = 0.043). Both percentage predicted TLC and TL,CO were not correlated with iron burden or desferoxamine ratio. High resolution CT in the three selected patients showed no evidence of pulmonary fibrosis. We conclude that thalassaemia major patients have a predominant restrictive lung dysfunction with pulmonary parenchymal disease and alveolocapillary membrane block. The restrictive and interstitial lung disease could not be accounted for by iron loading or pulmonary fibrosis in our patients.

Adolescent↗
PubMed1996

Detection of PML-RAR alpha in patients with APL during follow-up period.

OBJECTIVE: To evaluate the significance of PML-RAR alpha transcripts in patients with acute promyelocytic leukemia (APL) during remission period and to follow up the patients through monitoring aberrant gene expression. PATIENTS AND METHODS: This study included 17 patients with APL (5 females and 12 males). Another 19 APL patients during relapse served as control. RNA extraction was obtained through the single-step method. By means of reverse transcriptase polymerase chain reaction (PCR), the PML-RAR alpha was detected in the sample mRNA. RESULTS: Nine out of 10 patients with complete remission (CR) duration shorter than 3 years were positive. Four cases became negative and three remained positive among 7 cases in a long remission of over 3 years. The difference of the positive rate of PML-RAR alpha transcripts between the 2 groups was significant (P < 0.05). Four among 12 positive cases relapsed. No evidence of relapse was present in the 5 negative patients after 9.6 +/- 3.9-month follow-up. Further treatment was therefore given to the 4 positive patients whose treatment was already ceased at that time. By this management they were all in CR during the following 10-month observation. CONCLUSIONS: RT-PCR detection for PML-RAR alpha transcripts was useful in monitoring MRD and guiding further treatment to obtain a long remission. Persistently positive transcripts were closely associated with the relapse.

Adolescent↗
PubMed1996

The molecular genetics of retinoic acid receptors: cardiovascular and limb development.

The vitamin A metabolite retinoic acid (RA) is utilized as a signalling molecule in wide variety of developmental processes, defined by defects which occur after nutritional vitamin A deficiency or after exposure to excess vitamin A. We have initiated a genetic analysis of RA function through the establishment of lines of mice which carry germline mutations in the genes which encode retinoid receptors. Defects which result from developmental RA deficiency or excess have been recovered in embryos which are deficient in various combinations of retinoid receptors. In this chapter, our current understanding of the role of RA and retinoid receptors in cardiovascular and limb development are described, as for these our level of understanding is most advanced.

Animals↗
PubMed1996

Experience of varicella vaccination in acute lymphoplastic leukaemia.

Varicella is a common benign childhood illness. Rarely, serious complications arise. Immunocompromised patients usually suffer a more serious form of the illness. It is therefore prudent to prevent the infection in this group of patients. Varicella vaccination has been proven by several workers to be effective in both healthy children and adults as well as in leukaemic children. As the vaccine had not been licensed for sale in Singapore, we could only import 10 doses of the vaccine under special license. This was given to 8 leukaemic children. Of this, 5 seroconverted after the first dose. Two patients had the benefit of a repeat vaccination 3 months later. Both subsequently seroconverted. Two of the patients died from a relapse of the illness, a year and 2 years after the vaccination. None of the patients developed any side effects of fever and pain or varicella or zoster after the immunisation even though there was close contact with chicken pox. Although the study sample was small, it appeared that the vaccine was safe and efficacious in leukaemic children, especially after a 2-dose injection.

Chickenpox↗
PubMed1995

Vesicular stomatitis virus infection induces a nuclear DNA-binding factor specific for the interferon-stimulated response element.

Vesicular stomatitis virus (VSV) has a broad host range. It replicates in the cytoplasm and causes rapid cytopathic effects. We show that following VSV infection, a nuclear factor that binds to a select set of interferon-stimulated responsive elements (ISRE) is induced in many cell types. This factor, tentatively called VSV-induced binding protein (VIBP), was estimated to have an approximate molecular mass of 50 kDa and was distinct from known members of the interferon regulatory factor family, that are known to bind to the ISRE. Induction of VIBP required tyrosine kinase activity but did not require cellular transcription. Treatment of cells with cycloheximide, which inhibits translation, only partially inhibited induction of VIBP. However, type I interferons and staurosporine, both of which inhibit VSV transcription, inhibited VIBP induction. Moreover, a double-stranded RNA analog, poly(I)-poly(C) also induced a DNA-binding activity very similar to that of VIBP. These results indicate that a preexisting cellular protein is activated upon VSV infection and that this activation requires primary viral transcripts. The functional activity of VIBP was analyzed in cells stably transfected with a herpesvirus thymidine kinase-luciferase reporter gene that is under control of the ISRE. While activity of the control promoter without ISRE was strongly inhibited following VSV infection (as a result of virus-mediated transcriptional shutdown of the host cell), the inhibition was reversed by the ISRE-containing promoter, albeit partially, which suggests that VSV infection differentially affects transcription of host genes. Although VIBP was induced in all other cells tested, it was not induced in embryonal carcinoma cells after VSV infection, suggesting developmental regulation of VIBP inducibility.

Amino Acid Sequence↗
PubMed1995

[Preparation and identification of monoclonal antibody against sterigmatocystin].

Compound antigen, bovine serum albumin-sterigmatocystin (BSA-ST) or hemocyanin sterigmatocystin (H-ST) was prepared by converting ST to its hemiacetal group in ST and taking ST conjugated to BSA or H. Balb/c mice were immunized with BSA-ST, and then their spleen cells were isolated and fused with SP2/0 murine myeloma cells. A hybridoma cell strain that could stably secrete monoclonal antibody against ST (McAb-ST) was selected, and both of their ascites and serum were rich in McAb-ST induced by cells of this strain. McAb-ST was identified as Ig-Gi with a molecular weight of 168,000 kd (53,000 for heavy chain and 31,000 for light one), and with an affinity constant of H-ST reaction of 1.29 x 10(9) mol/L measured by indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). Relative cross reaction of McAb-ST with ST analogues was less than 2%. The minimal 0.5 pg/25 microliters of ST can be detected with IC-ELISA using McAb-ST and ST simultaneously, with a linear range of 0.1-10 ng/ml.

Animals↗
PubMed1995

[Determination of sterigmatocystin in cancerous tissues, blood and urine in patients with liver and stomach cancer].

Sterigmatocystin (ST) was determined with modified Southern-Western blot and indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) for 28 specimens of cancerous tissues, 13 of blood and 20 of urine in 14 patients with liver and stomach cancer. Results showed DNA-ST adduct was detected in 14 specimens of cancerous tissues and/or pericancerous tissues. ST values were higher in four of 13 patients (65-113 micrograms/kg), as compared only in one of 14 healthy persons (68 micrograms/kg). And, ST values all were very low in urine, with a maximum of 13 micrograms/kg.

DNA Adducts↗
PubMed1995

[Production and characterization of sterigmatocystin].

Two strains of Aspergillus versicolor producing ST at 550.8 mg.kg-1 substrate and 1160.8 mg.kg-1 substrate were selected to inoculate 4 kg solid ST-producing media. After 35 days stationary incubation at 28 degrees C in the dark, 2271.6 mg of pale-yellow needle-shaped crystals were isolated and purified from the culture with a procedure applying column chromatography and recrystallization method. The crystal was proved to be sterigmatocystin by spectroanalysis and some physico-chemical analysis. The purity of the final material obtained were more that 99.9% as shown by HPLC and TLC detection. With this procedure, ST was obtained at about one tenth of its commercial cost.

Aspergillus↗
PubMed1994

Astrocyte response and transforming growth factor-beta localization in acute spinal cord injury.

STUDY DESIGN: An experimental histologic and immunohistological investigation of acute spinal cord injury was performed in a rat model. OBJECTIVE: This study determined (1) the immediate cellular and molecular responses within the spinal cord that result from a clinically relevant compression injury, (2) the acute astrocytic response to injury using the astrocyte specific GFAP antibody, and (3) the temporal pattern of cellular and extracellular localization of transforming growth factor-beta 1 (TGF-beta 1) within the spinal cord injury zone immediately after injury. SUMMARY OF BACKGROUND DATA: Ultimate neurologic outcome from spinal cord injury results from both the primary mechanical trauma and a subsequent cascade of cellular and molecular events that are termed the secondary injury. Efforts aimed at improving neurologic outcome may depend on the manipulation of cellular and molecular mechanisms that are responsible for propagating this secondary injury cascade. Astrocytes and TGF-beta are two potentially key components of this secondary injury. METHODS: Twenty-one Sprague-Dawley adult rats underwent open thoracic spinal cord injuries using the Allen weight-drop technique. Spinal cord specimens were harvested at 0, 1, 2, 4, 8, 24, and 72 hours after injury for histologic and immunohistochemical evaluation. Harvesting of injured and surrounding uninjured cord was performed before sectioning in sagittal and transverse planes. These paraffin-embedded sections were stained with polyclonal antibodies against glial fibrillary acidic protein (GFAP, an astrocytic cytoskeleton marker) and TGF-beta 1. RESULTS: A complex astrocytic response to the spinal cord injury was found within 24 hours of injury. Both the geographic and temporal patterns of astrocyte localization suggest a role in the regulation of spinal cord injury propagation. High concentrations of extracellular TGF-beta were seen immediately after injury within the hematoma at the zone of impact. Subsequently, intracellular TGF-beta was seen in astrocytic nuclei and cytoplasm, intramedullary and extramedullary capillary endothelial cells, and in motor neurons. CONCLUSIONS: The neurologic outcome in patients with SCI results in part from a secondary injury whose cellular and molecular mechanisms are poorly understood. This study suggests that both astrocytes and TGF-beta are involved in the regulation of spinal cord secondary injury. An improved understanding of their specific roles may result in novel treatments to improve the outcome from SCI.

Acute Disease↗
PubMed1994

The endoplasmic reticular heat shock protein gp96 is transcriptionally upregulated in interferon-treated cells.

A cDNA clone complementary to an interferon (IFN)-induced mRNA approximately 3 kb in length was identified and sequenced revealing homology with the endoplasmic reticular heat shock protein/ATPase gp96. Both IFN-alpha and -gamma transcriptionally upregulate expression of this gene. gp96 transcripts, protein, and ATPase activity are shown to be enhanced as a result of IFN treatment in two human cell lines and this effect requires de novo protein synthesis. gp96 molecules have recently been implicated in the presentation of endogenous antigens. A number of the key elements in this pathway, the transporter proteins, the major histocompatibility complex (MHC)-linked units of the proteasomes and the MHC class I molecules are known to be IFN inducible. Our results show that yet another molecule suggested to play an accessory role in the endogenous presentation pathway is IFN inducible. Further, our studies represent the first demonstration of modulation of expression of a heat shock protein by a cytokine and identify a new enzymatic activity upregulated in IFN-treated cells.

Adenosine Triphosphatases↗
PubMed1994

Suppression of mitochondrial mRNA levels and mitochondrial function in cells responding to the anticellular action of interferon.

A lambda cDNA library prepared from polyadenylated RNA isolated from Daudi cells was differentially screened to isolate cDNAs that recognize mRNA whose levels are reduced following interferon (IFN) treatment. Southern blot and DNA sequence analysis of 20 cDNA clones that were isolated revealed that they represented mitochondrially encoded mRNAs for the following proteins: cytochrome c oxidase subunits II and III, ATPase 6, cytochrome b, and subunit 1 of the NADH dehydrogenase. Northern blot analysis employing these cDNAs and oligonucleotides generated to the remaining mitochondrially encoded mRNAs demonstrated that IFN-alpha treatment of Daudi cells mediates a time-dependent suppression of the level of all of the mitochondrially encoded mRNAs. Study of this IFN-mediated effect reveals that: (i) the suppression of the level of these mRNAs is dependent on protein synthesis, (ii) it can be observed to occur prior to any detectable effect on thymidine incorporation, (iii) the degree of suppression correlates with the sensitivity of the cells to the anticellular action of IFN, and (iv) the suppression of the level of these RNAs appears to result from an effect on the level of transcription rather than on the stability of these mRNAs. A study of the level of cellular respiration in IFN-treated Daudi cells reveals a clear suppression 3 h following IFN treatment.

Base Sequence↗
PubMed1992

Halothane, enflurane, and isoflurane stimulate calcium leakage from rabbit sarcoplasmic reticulum.

The sarcoplasmic reticulum (SR) controls uptake and release of Ca2+ in muscle. Little information is available regarding the effect of volatile anesthetics on Ca2+ release from SR isolated from normal skeletal muscle, even though an abnormality of Ca2+ handling is implicated in malignant hyperthermia. In this study we used a Ca2+ electrode to monitor continuously the release of Ca2+ from SR and the effect of volatile anesthetics on this process. We found that halothane, enflurane, and isoflurane at 0.6, 0.7, and 0.8 vol%, respectively, each increased the velocity of Ca2+ leakage by at least 150% when compared to control. Ruthenium red, a blocker of the SR Ca(2+)-release channel, was shown to have no effect on the velocity of Ca2+ leakage. Halothane and isoflurane both shortened the time at which Ca2+ leakage began (T) in a dose-dependent fashion. Halothane at 4.8 vol% decreased T from 293 +/- 21 s to 149 +/- 20 s. Isoflurane (4.8 vol%) decreased T to 203 +/- 16 s, and enflurane at 5 vol% had little effect, decreasing T to 259 +/- 19 s. We noted a marked stimulation in the ATPase activity of the SR by all three volatile anesthetics. Halothane at 0.63 vol%, isoflurane at 0.42 vol%, and enflurane at 0.62 vol% each increased ATPase activity by at least 300%. We conclude that the stimulation of the velocity of Ca2+ leakage by the volatile anesthetics is related to the more rapid depletion of ATP, but that the shortening of the onset of Ca2+ leakage is a independent phenomenon with a markedly different dose dependence.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1991

Rapid and efficient purification of native histidine-tagged protein expressed by recombinant vaccinia virus.

Vaccinia virus has been used as a vector to express foreign genes for the production of functional and posttranslationally modified proteins. A procedure is described here that allows the rapid native purification of vaccinia-expressed proteins fused to an amino-terminal tag of six histidines. Extracts from cells infected with recombinant vaccinia virus are loaded onto Ni2+.nitrilotriacetic acid (Ni2+.NTA)-agarose and histidine-tagged proteins are selectively eluted with imidazole-containing buffers. In the case of the human serum response factor (SRF), a transcription factor involved in the regulation of the c-fos protooncogene, the vaccinia-expressed histidine-tagged SRF (SRF-6His) could be purified solely by this step to greater than 95% purity. SRF-6His was shown to resemble authentic SRF by functional criteria: it was transported to the nucleus, bound specifically the c-fos serum response element, interacted with the p62TCF protein to form a ternary complex, and stimulated in vitro transcription from the serum response element. Thus, the combination of vaccinia virus expression and affinity purification by Ni2+.NTA chromatography promises to be useful for the production of proteins in a functional and posttranslationally modified form.

Amino Acid Sequence↗
PubMed1990

Necrotising fasciitis in leukaemic children.

This is a report of necrotising subcutaneous infection in the perineum of three young girls with acute lymphoblastic leukaemia (ALL). This occurred during induction therapy when they were granulocytopenic. Pseudomonas aeroginosa was isolated from both blood and affected sites. With aggressive chemotherapy and extensive surgical debridement, two patients were salvaged but one perished from the septicaemia. Necrotizing Fasciitis is an uncommon progressive infection of the subcutaneous tissue. It occurs more frequently in adults following surgery or trauma and rarely arises spontaneously. In the paediatric literature, reports are few and mainly in healthy children occurring post-operatively. There was only one case of this occurring in a boy with Aplastic anaemia. Early recognition and aggressive therapy helps to improve the morbidity and mortality of this devastating condition.

Bacterial Infections↗
PubMed1989

Acute gastroenteritis in children--aetiology and comparison of two modes of treatment.

287 patients with Acute Gastroenteritis were studied. Rotavirus accounted for 29.7% and bacterial aetiology for 9.3% of the cases. In the early infant age group (0-6 months), bacterial aetiology (28.8%) was commoner than Rotavirus aetiology (7.7%). In the older age groups, Rotavirus was more common than bacteria as a cause for Gastroenteritis.

Acute Disease↗