Dermatan sulphate proteoglycans of human articular cartilage. The properties of dermatan sulphate proteoglycans I and II

Dermatan sulphate proteoglycans were purified from juvenile human articular cartilage, with a yield of about 2 mg/g wet wt. of cartilage. Both dermatan sulphate proteoglycan I (DS-PGI) and dermatan sulphate proteoglycan II (DS-PGII) were identified and the former was present in greater abundance. The two proteoglycans could not be resolved by agarose/polyacrylamide-gel electrophoresis, but could be resolved by SDS/polyacrylamide-gel electrophoresis, which indicated average Mr values of 200,000 and 98,000 for DS-PGI and DS-PGII respectively. After digestion with chondroitin ABC lyase the Mr values of the core proteins were 44,000 for DS-PGI and 43,000 and 47,000 for DS-PGII, with the smaller core protein being predominant in DS-PGII. Sequence analysis of the N-terminal 20 amino acid residues reveals the presence of a single site for the potential substitution of dermatan sulphate at residue 4 of DS-PGII and two such sites at residues 5 and 10 for DS-PGI.

Future prospects for space life sciences from a NASA perspective

As the U.S. Space Program lifted off the ground again on September 29, 1988, along with it came the return of scientific possibilities for the U.S. space science community. The end of that mission, STS-26, marked a new beginning for NASA. The success of STS-26 was critical to the dreams and careers of many people. Many of those dreams had been put on hold and, in fact, were fading as the U.S. watched the rest of the world move ahead rapidly with attempts to gain access to the limited and precious laboratory of space.

Bidirectional transcription footprinting of DNA binding ligands

An in vitro transcription assay has been developed to define the exact location of DNA binding ligands. The method employs two counterdirected Escherichia coli promoters separated by approximately 100 bp. Selective transcription from each promoter yields transcripts up to each ligand site. Nonsaturating levels of ligands result in fractional occupancy of ligand at each site, and hence a range of RNA transcript lengths. The bidirectional promoter system results in a transcription footprint which was derived from transcription from both promoters up to the 5' side of each occupied ligand site and defines the sequence specificity and binding site size of the DNA-bound ligand. The transcriptional footprint is precise to +/- 1 bp from the 5' and 3' ends of each binding site. Multiple ligand sites can be ranked in terms of relative fractional occupancy at each site, and the ranking is comparable from either transcription direction. The method was compared to classical DNase I footprinting with a series of DNA binding drugs [actinomycin D, echinomycin, bis(thiadaunomycin), mithramycin, nogalamycin, and an acridine-tripyrrole]. In all cases, specific binding sites were resolved more clearly by transcription footprinting than by DNase I footprinting. Because of the nature of the transcription assay, all occupied ligand sites were detected by this method, in contrast to DNase I footprinting where many sequences are not probed, and where ligand sites are often not accurately defined.

Prescription of oxygen concentrators: adherence to published guidelines

The indications for the prescription of oxygen concentrators have been assessed in 82 patients against the Department of Health guidelines, except that only one set of blood gas and spirometry measurements was required if the patient's condition was stable. Of the 49 patients recommended for this treatment by a chest physician, 41 (82%) fulfilled the requirements, compared with only 11 of 33 patients where the concentrator was recommended by a general practitioner or non-specialist physician. Eleven patients died within one month of prescription. The results show that many patients are being prescribed oxygen concentrators without assessment and underline the importance of full assessment and attention to prognosis before prescription.

Basal ganglia lesions in the rat: effects on quinolinic acid metabolism

Experimental basal ganglia lesions were produced in order to examine the effect of neuronal loss on quinolinic acid (QUIN) metabolism. The latter was investigated by measuring the activities of QUIN's biosynthetic enzyme, 3-hydroxyanthranilic acid oxygenase (3-HAO) and its degradative enzyme, quinolinic acid phosphoribosyltransferase (QPRT). Striatal ibotenic acid lesions caused a steady increase in striatal QPRT activity, reaching 280% of control levels 21 days after the lesion. In the same tissue, 3-HAO activity, too, was elevated. It rose to 436% of control after 7 days and to a lesser degree (+309%) after 3 weeks. Immunotitration experiments using anti-rat 3-HAO antibodies and kinetic analysis of lesioned and control striata showed that the increase in 3-HAO was due to de novo production of enzyme protein. The large increases in striatal enzyme activities after 7 days were accompanied by smaller increases in both 3-HAO and QPRT activities in the ipsilateral substantia nigra. Physical destruction of corticostriatal glutamatergic fibers resulted in increases in striatal 3-HAO (+216%) and QPRT (+243%) activities after one week. No changes in nigral or striatal QUIN metabolism were recorded 7 days after an intranigral injection of 6-hydroxydopamine. These data confirm the notion of a largely glial localization of the QUIN system in the basal ganglia, and correlate well with recent observations in brain tissue from Huntington's disease victims.

Isolation and characterization of a sodium pump inhibitor from human plasma

An endogenous sodium pump inhibitor has been purified from human plasma. The purification scheme involved large scale dialysis, extraction of lyophilized dialysate by methanol followed by preparative and semipreparative scale reverse-phase high-performance chromatography. A single peak of biologically active material was obtained enriched by a factor of greater than 10 billion. This material showed high chromatographic polarity, was inactivated by charring, strong acid, or alkali, and was resistant to short-term boiling. The purified material had a molecular weight between 300 and 900 g/mol and was insensitive to type I esterase and a variety of proteolytic enzymes. The purified factor inhibited the ouabain-sensitive uptake of 86Rb by human erythrocytes, binding of [3H]ouabain, and activity of dog kidney Na,K-adenosine triphosphatase (ATPase) with high affinity (less than 0.3 nM) in a time- and dose-dependent manner. Maximally effective concentrations of the digitalislike factor showed no effect on either human red blood cell Mg- or Ca-ATPase, rabbit muscle sarcoplasmic reticulum Ca-ATPase, or guinea pig stomach H,K-ATPase. The purified material is a highly potent selective inhibitor of the ion transport, receptor, and hydrolytic functions of the sodium pump. The characteristic properties of this substance suggest it may be a mammalian endogenous digitalis and may be similar to the sodium transport inhibitor detected in the plasma of volume-sensitive forms of experimental and human hypertension.

Sequence-dependent termination of bacteriophage T7 transcription in vitro by DNA-binding drugs

An in vitro T7 bacteriophage transcription system has been utilized in which the RNA was initiated to a specific length (defined by the absence of the appropriate nucleoside triphosphate). When the DNA-RNA-RNA polymerase ternary complex was exposed to nonsaturating levels of DNA-binding ligands (i.e., a small fractional occupancy at each site), and the RNA transcript then allowed to elongate in the presence of all four nucleoside triphosphates, there was a synchronous increase of RNA lengths up to sites occupied by ligands. A unique characteristic is that bacteriophage transcription was completely terminated at every ligand site, in contrast to bacterial RNA polymerases where "read-through" past drug sites occurs and results merely in a delay of transcription at each site due primarily to dissociation of drug from the DNA. Similar termination of transcription at each drug site was observed with T3 and SP6 RNA polymerases. The termination at drug sites in the bacteriophage system results in RNA of specific lengths which define the location of ligand sites, and the RNA concentration provides a measure of relative ligand occupancy at that site. Termination of transcription was observed with four drugs with relatively long DNA residence times (half-life greater than or equal to 300 s at 20 degrees C for nogalamycin, actinomycin, mithramycin, and echinomycin) but to a lesser extent with drugs of intermediate residence times [a bis(thiadaunomycin) and an acridine-tripyrrole, with half-lives of 230 and 7 s, respectively, at 20 degrees C]

DNA sequence-specific adducts of adriamycin and mitomycin C

Adriamycin and mitomycin C were reduced by xanthine oxidase/NADH in the presence of a DNA template comprising a stable initiated ternary transcription complex derived from the lac UV5 promoter. Subsequent elongation of the transcription complex treated with mitomycin C revealed high levels of terminated transcripts one nucleotide prior to G residues on the coding strand (i.e. at X of XpC sequences of the non-coding strand). Lower levels of termination occurred with adriamycin, and these were also one nucleotide prior to G residues of the coding strand, but with greater sequence specificity since they were observed mainly at G of GpC sequences of the non-coding strand. The same sites were also observed with adriamycin in the absence of reducing conditions and the level of termination at these sites was enhanced up to 10-fold by Fe2+ and Fe3+, but not by Cu2+, Zn2+, Co2+ or Ni2+. These results suggest that an iron-adriamycin complex with DNA is highly sequence-specific and results in adducts, similar to those of mitomycin C, which can terminate the transcription process. Such a mechanism offers new insights into the possible mode of action of anthracyclines.

A prospective study of asthma during pregnancy and the puerperium

Thirty-one asthmatic women recruited in an ante-natal clinic were followed during pregnancy and for six weeks of the puerperium. Subjectively 22 (69%) women considered their asthma to have improved, two were worse and in seven (22%) there was no change. Analysis of peak flow rate, symptoms score and bronchodilator use showed that in ten pregnancies there was improvement in the third trimester and that in 11 there was deterioration in the puerperium. The results suggest that in patients with mild or moderate asthma an improvement is likely to occur during pregnancy, particularly in the last trimester, but that in over one-third there may be a post-natal deterioration. Review of the literature suggests that severe asthmatics are at greater risk of deterioration, particularly late in pregnancy.

Drug-DNA dissociation kinetics. In vitro transcription and sodium dodecyl sulphate sequestration

The rate of dissociation of actinomycin D from DNA was measured by sodium dodecyl sulphate (SDS) sequestration (37 degrees) from calf thymus DNA and a 24 base pair (bp) synthetic DNA containing one high affinity AGCT site for the drug. The time constants were 276 and 142 sec, respectively, and suggest a stabilising effect though positive cooperativity in heterogenous DNA, or from specific neighbouring sequences. The time constant for dissociation of actinomycin D from the AGCT site was 2900 sec as measured by an in vitro transcription assay at 37 degrees, and suggests that, under conditions of active transcription of the DNA, the drug-DNA complex has additional stabilising contributions, possibly by a cage effect from RNA polymerase, or by additional drug-RNA polymerase contacts.

Transcriptional analysis of multisite drug-DNA dissociation kinetics: delayed termination of transcription by actinomycin D

An in vitro transcription assay was used to measure the relative occupancy, sequence specificity, and dissociation kinetics of six actinomycin D binding sites on DNA during conditions of active transcription of the DNA from the lac UV5 promoter. Five of the sites contained a GpC sequence, with three of these having a common AGCT sequence that differed by up to an order of magnitude in affinity for the drug, as indicated by their relative occupany and dissociation kinetics. Positive cooperativity was observed by higher occupancy and slower dissociation kinetics for neighboring GpC sites on a different DNA fragment (UV5-lambda PL). Termination of transcription was observed at some drug binding sites, while complete drug-induced termination of transcription was seen 7-10 nucleotides downstream of two drug sites. This delayed termination was minimized when ITP was incorporated into the transcripts and suggests that a time delay is required to enable stable RNA hairpin helices to form. A model is presented of the role of RNA hairpin helices in delayed, drug-induced termination of transcription. The classical picture of DNA-binding drugs as inhibitors of transcription now appears too simplistic as it does not accommodate this phenomenon. It will be important to gain a greater understanding of the mechanism of this phenomenon of drug-induced termination of transcription, as there are many implications for the design of DNA-acting drugs.

Elucidation of the DNA sequence preferences of daunomycin

The sequence specificity of daunomycin was assessed using competition equilibrium dialysis, DNAse I footprinting and an E. coli RNA polymerase transcription inhibition assay; similar studies were performed on adriamycin and a new bis-intercalating daunomycin dimer. The results clearly demonstrate that the highest affinity sites are CA for daunomycin and adriamycin, and CACA for the bis-daunomycin. Other modest affinity (GC, CG, CT, TC, CC, AC) and poor affinity binding sites (AA, AT, TA) were also observed. Our results are in agreement with (a) the observed 5'-pyrimidine-purine-3' sequence preference of intercalating drugs, (b) the reported role played by OH(9) of daunomycin in the stabilization of the drug/DNA intercalation complex, and (c) the thermodynamics of nearest neighbour base-pair unstacking at the intercalation site. The CA specificity of daunomycin and adriamycin suggests that their biological activity may arise from association with the CA containing sequences which are thought to be associated with genetic regulatory elements in eukaryotes. The implications for future anthracycline drug design are presented in this context.

Quinolinic acid phosphoribosyltransferase: purification and partial characterization from human liver and brain

Quinolinic acid phosphoribosyltransferase (QPRT) [EC 2.4.2.19] from human liver and brain was purified to homogeneity. Identity of the pure enzymes isolated from the two organs was proven by biochemical, physiocochemical and, following the production and partial purification of anti-liver QPRT antibodies, immunological techniques. Human QPRT has a molecular weight of 170,000 and consists of five identical subunits. Kinetic analyses revealed a Km of 5.6 microM for the substrate (quinolinic acid) and 23 microM for the co-substrate (phosphoribosylpyrophosphate). Enzyme activity was dependent on Mg2+ (optimal concentration: 1 mM) and was inhibited by the enzymatic by-product, inorganic pyrophosphate. Pure QPRT and its antibodies will constitute useful tools in the examination of the possible role of quinolinic acid in the pathogenesis of human neurodegenerative disorders.

The 5'-CA DNA-sequence preference of daunomycin

The DNA-sequence specificity of daunomycin was investigated by DNase I footprinting and an E. coli RNA polymerase transcription-inhibition assay. The 5'-CA sequence was identified as being the highest affinity binding site, although other modest affinity (5'-GC, CG, CT, TC, AC) and poor affinity sites (5'-AA, AT, TA) were also observed. The preference of daunomycin for 5'-CA nucleotide sequence suggests that its biological activity may arise from association with the 5'-CA-containing sequences thought to be associated with genetic regulatory elements in eukaryotes.

The structure and abundance of cartilage proteoglycans during early development of the human fetus

Proteoglycan was isolated from the epiphyseal cartilage of the knee joint from human fetuses, ranging in age from 11 to 19 wk of gestation. The content of proteoglycan, per wet weight of cartilage, increased with gestational age, and structural changes were observed in the proteoglycan subunits, particularly with respect to hydrodynamic size and the position of sulfation of the chondroitin sulfate chains. While 6-sulfation remained fairly constant on about half the disaccharide residues during the age period examined, the proportion of nonsulfated residues decreased with gestational age and there was a corresponding increase in the proportion of 4-sulfated residues. Other structural parameters showed little change, and after 11 wk of gestation the majority of proteoglycan subunits were able to interact with hyaluronic acid to form aggregates. Link proteins were detected in the cartilage at all ages and their abundance increased with age relative to other cartilage proteins. They showed little change in structural heterogeneity, with the two larger molecular forms predominating. In contrast to the proteoglycans, cartilage proteins were in high abundance at 11 wk of gestation, but decreased considerably with time, although there was little change in the relative proportion of the majority of the components.

Rapid detection of cytomegalovirus by tissue culture, centrifugation, and immunofluorescence with a monoclonal antibody to an early nuclear antigen

A rapid, sensitive and specific assay for the detection of cytomegalovirus (CMV) was developed utilizing MRC-5 cells in 24-well plates containing round coverslips. Centrifugation expedited the detection of CMV early antigen with monoclonal antibody. Immunofluorescent staining 16 h after inoculation with a stock CMV preparation (AD-169), demonstrated an 11-fold increase in the number of nuclear inclusions when the specimens were centrifuged (18 +/- 2.2) as compared to the non-centrifuged specimen (1.6 +/- 0.9). However, the number of nuclear inclusions depended on the age of the MRC-5 cells. They were more sensitive to CMV infection between 4 and 11 days after the cells were seeded into plates. Among 159 patient samples cultured for CMV, 23 (14%) were positive by the rapid method (mean of 32 h) and 18 (11%) by routine tissue culture (mean of 12 days). Cytomegalovirus in urine was detected within 1.3 days, whereas buffy coats (2.3 days) and bronchial washings (2.5 days) took longer. Staining for CMV inclusions at more than one time point was necessary for the optimal detection of CMV by the rapid method. We recommend using this assay system as it is rapid, specific, sensitive and versatile for the detection of CMV in many biological specimens.

Epidemiology, physiopathology, and experimental therapeutics of acute spinal cord injury

This article analyzes the epidemiological factors relating to acute spinal cord injury. It also delineates the anatomical and rheological characteristics of the spinal cord and denotes the latest concepts in autoregulation of spinal cord blood flow. The physiopathology of spinal cord injury is examined in terms of existing animal models, responses of the white and grey matter, and biochemical and biomechanical correlates. Experimental and clinical therapeutic modalities ranging from hypothermia to opioid antagonists, and adrenergic blockers to free radical scavengers are evaluated.