Probing the metal binding sites of Escherichia coli isoleucyl-tRNA synthetase

The metal binding properties of isoleucyl-tRNA synthetase (IleRS) from Escherichia coli were studied by in vivo substitution of the enzyme-bound metals. Purified E. coli IleRS was shown to have two tightly bound zinc atoms per active site. Cobalt- and cadmium-substituted IleRS were also found to contain two tightly bound Co2+ and Cd2+ atoms per polypeptide chain, respectively. The d-d transitions in the low energy absorption spectrum of Co(2+)-substituted IleRS were characteristic of that expected for two tetrahedrally coordinated Co2+ metals. Apo-IleRS was found to be inactive in both the aminoacylation of tRNA(Ile) and in the isoleucine-dependent ATP-pyrophosphate exchange reactions. Both Co(2+)- and Cd(2+)-substituted IleRS were found to have kcat/Km values in the isoleucine-dependent ATP-pyrophosphate exchange assay approximately 5-fold lower than the native Zn2+ enzyme. A single enzyme-bound Zn2+ or Co2+ atom per polypeptide chain could be removed by dialysis of Zn(2+)- or Co(2+)-substituted IleRS against 1,10-phenanthroline. Removal of one of the two enzyme-bound Zn2+ atoms per polypeptide chain with 1,10-phenanthroline was found to decrease (kcat/Km)Ile by approximately 130-fold. The dependence of the kinetic parameters on the identity and number of enzyme-bound metals in the isoleucine-dependent ATP-pyrophosphate exchange reaction suggests that at least one enzyme-bound metal is indirectly involved in aminoacyladenylate formation. Metal substitution or removal of one of the two enzyme-bound metals in IleRS was found to have little effect on the Km value for tRNA(Ile) or the kcat value for aminoacylation of tRNA(Ile).(ABSTRACT TRUNCATED AT 250 WORDS)

Intronless celB from the anaerobic fungus Neocallimastix patriciarum encodes a modular family A endoglucanase

The cDNA designated celB from the anaerobic rumen fungus Neocallimastix patriciarum contained a single open reading frame of 1422 bp coding for a protein (CelB) of M(r) 53,070. CelB expressed by Escherichia coli harbouring the full-length gene hydrolysed carboxymethylcellulose in the manner of an endoglucanase, but was most active against barley beta-glucan. It also released reducing sugar from xylan and lichenan, but was inactive against crystalline cellulose, laminarin, mannan, galactan and arabinan. The rate of hydrolysis of cellulo-oligosaccharides by CelB increased with increasing chain length from cellotriose to cellopentaose. The predicted structure of CelB contained features indicative of modular structure. The first 360 residues of CelB constituted a fully functional catalytic domain that was homologous with bacterial endoglucanases belonging to cellulase family A, including five which originate from three different species of anaerobic rumen bacteria. Downstream from this domain, and linked to it by a serine/threonine-rich hinge, was a non-catalytic domain containing short tandem repeats, homologous to the C-terminal repeats contained in xylanase A from the same anaerobic fungus. Unlike previous fungal cellulases, genomic celB was devoid of introns. This lack of introns and the homology of its encoded product with rumen bacterial endoglucanases suggest that acquisition of celB by the fungus may at some stage have involved horizontal gene transfer from a prokaryote to N. particiarum.

Occurrence of specific sterols in Pneumocystis carinii

We have examined the sterol composition and biosynthesis of rat Pneumocystis carinii. We found a number of lipid components among the nonsaponifiable fraction that appear unique to P. carinii. These lipids are present in P. carinii purified preparations and P. carinii-infected whole lungs but absent from control lungs. They show chromatographic properties typical of sterols on GC and HPLC; they are present in free and esterified sterol fractions isolated by thin layer chromatography, they are precipitated by digitonin and they are labeled upon incubation of purified P. carinii cell suspensions with [3H] mevalonate and [3H] squalene. The finding of these sterols opens new opportunities for the identification of chemotherapeutic targets against P. carinii.

The detection and quantification of retinopathy using digital angiograms

An algorithm is presented for the analysis and quantification of the vascular structures of the human retina. Information about retinal blood vessel morphology is used in grading the severity and progression of a number of diseases. These disease processes are typically followed over relatively long time courses, and subjective analysis of the sequential images dictates the appropriate therapy for these patients. In this research, retinal fluorescein angiograms are acquired digitally in a 1024x1024 16-b image format and are processed using an automated vessel tracking program to identify and quantitate stenotic and/or tortuous vessel segments. The algorithm relies on a matched filtering approach coupled with a priori knowledge about retinal vessel properties to automatically detect the vessel boundaries, track the midline of the vessel, and extract useful parameters of clinical interest. By modeling the vessel profile using Gaussian functions, improved estimates of vessel diameters are obtained over previous algorithms. An adaptive densitometric tracking technique based on local neighborhood information is also used to improve computational performance in regions where the vessel is relatively straight.

Characterization of the gene for the human high affinity IgE receptor (Fc epsilon RI) alpha-chain

The Fc epsilon RI couples the mast cell-surface binding of IgE and Ag to a complex series of intracellular events culminating in cell activation and degranulation. The alpha-chain of Fc epsilon RI constitutes the Ig-binding subunit of this heterotetrameric receptor, and is itself a member of the Ig gene superfamily. We have isolated a human genomic DNA clone containing the entire Fc epsilon RI alpha gene, and completely sequenced a region from 1257 bp 5' of the transcription start site, to 513 bp 3' of the last exon of the gene. As with the previously characterized rat and mouse genes, human Fc epsilon RI alpha consists of five exons and four introns, and spans 5889 bp of genomic DNA. The splice donor and acceptor sites deduced by comparison with the cDNA sequence corresponded exactly to the locations found in analogous rodent genes. By mapping the 5' end of Fc epsilon RI alpha transcripts we found three major transcription initiation sites 24, 27, and 29 bp upstream of the ATG translation initiation codon. As well, several longer minor transcripts were seen, with a maximum of 60 nt of 5'-untranslated sequence. About 650 bp of DNA upstream of the ATG translation initiation codon were compared among human, rat, and mouse Fc epsilon RI alpha sequences in search of common motifs that might mediate conserved regulatory interactions with DNA binding proteins. A 172-bp region of the human Fc epsilon RI alpha 5'-flanking sequence was highly conserved in both rodent species. Further studies will be required to determine whether these or other sequences are involved in Fc epsilon RI alpha gene regulation.

Characterization of the gene for the human high affinity IgE receptor (Fc epsilon RI) alpha-chain

The Fc epsilon RI couples the mast cell-surface binding of IgE and Ag to a complex series of intracellular events culminating in cell activation and degranulation. The alpha-chain of Fc epsilon RI constitutes the Ig-binding subunit of this heterotetrameric receptor, and is itself a member of the Ig gene superfamily. We have isolated a human genomic DNA clone containing the entire Fc epsilon RI alpha gene, and completely sequenced a region from 1257 bp 5' of the transcription start site, to 513 bp 3' of the last exon of the gene. As with the previously characterized rat and mouse genes, human Fc epsilon RI alpha consists of five exons and four introns, and spans 5889 bp of genomic DNA. The splice donor and acceptor sites deduced by comparison with the cDNA sequence corresponded exactly to the locations found in analogous rodent genes. By mapping the 5' end of Fc epsilon RI alpha transcripts we found three major transcription initiation sites 24, 27, and 29 bp upstream of the ATG translation initiation codon. As well, several longer minor transcripts were seen, with a maximum of 60 nt of 5'-untranslated sequence. About 650 bp of DNA upstream of the ATG translation initiation codon were compared among human, rat, and mouse Fc epsilon RI alpha sequences in search of common motifs that might mediate conserved regulatory interactions with DNA binding proteins. A 172-bp region of the human Fc epsilon RI alpha 5'-flanking sequence was highly conserved in both rodent species. Further studies will be required to determine whether these or other sequences are involved in Fc epsilon RI alpha gene regulation.

The replication fate of R- and S-styrene oxide adducts on adenine N6 is dependent on both the chirality of the lesion and the local sequence context

In order to deduce the biological fate of adducts formed by the reaction of styrene oxide, a suspected carcinogen, with DNA, four oligodeoxynucleotides were synthesized which contained either R- or S-styrene oxide lesions on the N6 position of neighboring adenines within the human N-ras codon 61. When these adducted oligodeoxynucleotides were ligated into the single-stranded vector M13mp7L2 and the modified DNA used to transform repair-deficient Escherichia coli, the resultant plaque-forming abilities were found to vary as much as 300-fold, depending on the stereochemical configuration of the styrene oxide lesion and the sequence context in the vicinity of the damage. The frequency of mutations caused by the various styrene oxide adducts were similarly dependent on both their chirality and local sequence context. Oligodeoxynucleotide templates bearing these same four adducts were also constructed in order to evaluate their replication in vitro by the Klenow fragment. Three of the four styryl-modified templates yielded significant levels of fully extended primer upon polymerization. In contrast, the template containing R-styrene oxide at the second position of N-ras 61 was a very poor substrate for replication, a result which correlates well with the observed lethality of this lesion in vivo.

Brn-3b: a POU domain gene expressed in a subset of retinal ganglion cells

A search for POU domain transcription factors in human retina cDNA has led to the identification of Brn-3b, a class IV POU domain protein. Immunohistochemical experiments show that chicken, mouse, rabbit, monkey, and human retinas contain Brn-3b exclusively within a subpopulation of ganglion cells. In the adult mouse brain, Brn-3b is found only within cells in the deep layers of the superior colliculus, in the dorsal periaqueductal gray, and in a small cluster of cells in the brain stem near the area postrema. During the immediate postnatal period, cells containing Brn-3b are distributed in a number of regions within the brain stem and cerebellum. These data suggest that Brn-3b plays a role in determining and/or maintaining the identities of a small number of neurons, including a subset of visual system neurons.

[The facial skeletal characteristics for adults in Shanghai with normal occlusion;the quadrilateral analysis]

60 adults of Han nationalities in Shanghai with normal occlusion were selected for the quadrilateral analysis of cephalograms.The study showed that there existed a definite ratio between the jaw bone and the tooth.The purpose of his investigation was to obtain the ratio and the nature of the malocclusion and make up a reasonable orthodontic treatment plan.

Interactions of transforming growth factor-alpha and -beta and luteinizing hormone in the regulation of plasminogen activator activity in avian granulosa cells during follicular development

This study examined the influence of transforming growth factor-alpha (TGF alpha), TGF beta, and LH on progesterone (P4) secretion and plasminogen activator (PA) activity in cultured avian granulosa cells from the first (F1), third (F3), and fifth and sixth (F5-6) preovulatory follicles during a 21-h incubation period. PA activity in the cell (PAc) and the medium (PAm) fractions was measured by fibrinolysis and fibrin overlay methods. P4 was determined by RIA. Basal PAc and PAm activities were highest in cell cultures from the less mature (F5-6) follicles and decreased as follicles matured to the F1 stage of development. PAc activity was greater than PAm activity regardless of the stage of follicular maturation. TGF alpha (0.1-10 ng/ml) increased PA activity in cultures of granulosa cells from F1, F3, and F5-6 follicles in a concentration-dependent manner. TGF alpha-induced PAc and PAm activities were observed by 6 and 15 h of incubation, respectively, and increased rapidly between 15-21 h. LH (100 ng/ml) attenuated TGF alpha-induced PA activity by 15 h in cultures of granulosa cells from F1 and F3, but not F5-6, follicles. Basal PA activities were unaffected by the gonadotropin. TGF beta (2-100 ng/ml) stimulated PAc activity in a dose-dependent manner only in cultures of granulosa cells from F5-6 follicles and significantly enhanced TGF alpha-induced PAc and PAm activities in cell cultures from F3 and F5-6, but not F1, follicles. Basal and growth factor-induced PAc and PAm activities corresponded to a mol wt of about 35 kDa, a value consistent with that of the low mol wt uPA species. TGF alpha and TGF beta, alone or in combination, had no effect on basal P4 secretion at all stages of follicular development. TGF alpha, however, decreased LH-induced P4 secretion in F1 and F3 cultures. These results demonstrate a tightly controlled interaction of TGF alpha, TGF beta, and LH in regulating PA activity and P4 secretion during follicular development in the domestic hen.

[Analysis of fatty acid composition of spotted fever group rickettsiae isolated in China by gas chromatography]

In present paper, fatty acid composition of seven Chinese isolates of SFG rickettsiae and six prototype strains of SFG rickettsiae were analyzed by GC-MS. Tested prototype strains of SFG rickettsiae were R. sibirica (strains 232 and 246), R. conorii (Simko), R. rickettsi (R), R. akari (Kaplan), R. australis (W58); Chinese isolates were An-84, Se-85, W-88 (human strain), MT-84, FT-84 (D. nuttalli strain), TO-85 (ova of nuttalli) and Chinese reference strain -JH-74 (D. nuttalli). They were propagated in yolk sacs of embryonated hen eggs and purified by centrifugation in a 30%-36%-42% discontinuous renografin density gradient. The fatty acid composition of selected strains of SFG rickettsiae was analyzed by gas chromatography, and then comparison being carried out by single linkage on mini-computer. Identification of the strains was performed based on the results obtained from GC-MS. Results showed that the fatty acid profiles of all the isolates from China were quantitatively similar to that of R. sibirica and quite different from other prototype strains of SFG rickettsiae.

Cardiovascular effects of chloroethylclonidine, an irreversible alpha 1B-adrenoceptor antagonist, in the unanesthetized rat: a pharmacological analysis in vivo and in vitro

The role of vascular alpha 1B-adrenergic receptors in the regulation of arterial pressure (MAP) and heart rate (HR) was examined by assessing the effect of i.v. chloroethylclonidine (CEC; irreversible alpha 1B antagonist) in unanesthetized, normotensive Long-Evans rats. MAP, HR and the pressor response to i.v. phenylephrine (PE) were monitored for 24 hr after saline or CEC (15 mg/kg and 25 mg/kg) injection. Neither i.v. saline nor CEC affected MAP or HR throughout the course of the study, yet the PE response was maximally inhibited (> 75% at 15 min) by both doses of CEC. The PE response recovered by 2 hr at the 15-mg/kg dose but remained inhibited up to 4 hr at 25 mg/kg. At 24 hr, all cardiovascular parameters returned to control levels. CEC (100 microM, 30 min) produced irreversible blockade of norepinephrine-induced contractions in rat aortic rings; prazosin (10 nM) and sodium thiosulphate (1 mM, a reagent that inactivates aziridinium ions) reversed CEC's inhibitory effect. Precyclized CEC and its hydrolysis product beta-hydroxyethylclonidine (beta-HEC) poorly antagonized aortic alpha 1B-receptors. Ex vivo analysis of aortic rings from saline and CEC-treated rats showed that PE-induced contractions were shifted to the right and maximally depressed in a dose-dependent manner after 24 hr. These results suggest that 1) CEC produces long lasting blockade of alpha 1B-adrenoceptors in vitro and in vivo via formation of an aziridinium ion intermediate and 2) vascular alpha 1B-adrenoceptors are not coupled to the tonic physiological regulation of MAP in the rat.

[The effect of high energy shock waves on growth and metastasis of implanted tumors of nude mice in vivo]

We observed the effect of high energy shock waves (HESW) on tumor growth, histological and ultrastructural variations, and metastasis to lymph nodes and viscera in nude mice with implanted tumors. HESW was cytotoxic to tumors in vivo, and acted on levels of cell membrane, cytoplasmic organelles, and nuclear chromatins. At definite working voltage, this effect was positively proportional to the impulse number. Histological examination showed no metastatic focci to lymph nodes and viscera of nude mice with implanted tumors. The possible mechanism of HESW in vivo may be direct mechanical damage and indirect inhibition of tumor growth due to damage to the blood supply. Other hypotheses were also discussed.

[The stimulatory effect of dorsal vagal complex injection of pentagastrin on gastric motility in rats]

Changes in antral motility induced by pentagastrin (G5) microinjected into the dorsal vagal complex (DVC) were investigated in fasting conscious rats. Antral motility was monitored by using chronically implanted force transducer sutured to the antrum. DVC injection of G5 markedly stimulated the amplitude of gastric contraction in a dose-dependent manner. The effect, being rapid in onset and long lasting, could not be mimicked by intravenous administration of G5 but could be markedly inhibited by microinjection of antigastrin serum into DVC. Atropine (100 micrograms.kg-1.h-1) and vagotomy could also abolish the G5 induced antral motility. No significant changes in plasma motilin were observed in portal venous blood after administration of G5 in DVC. These results suggested that DVC is an important site of action for G5 induced stimulation of gastric contraction as mediated by vagal cholinergic pathway.

Influence of recreational activity and muscle strength on ulnar bending stiffness in men

Bone bending stiffness (modulus of elasticity [E] x moment of inertia [I]), a measure of bone strength, is related to its mineral content (BMC) and geometry and may be influenced by exercise. We evaluated the relationship of habitual recreational exercise and muscle strength to ulnar EI, width, and BMC in 51 healthy men, 28-61 yr of age. BMC and width were measured by single photon absorptiometry and EI by mechanical resistance tissue analysis. Maximum biceps strength was determined dynamically (1-RM) and grip strength isometrically. Subjects were classified as sedentary (S) (N = 13), moderately (M) (N = 18), or highly active (H) (N = 20) and exercised 0.2 +/- 0.2; 2.2 +/- 1.3; and 6.8 +/- 2.3 h.wk-1 (P < 0.001). H had greater biceps (P < 0.0005) and grip strength (P < 0.05), ulnar BMC (P < 0.05), and ulnar EI (P = 0.01) than M or S, who were similar. Amount of activity correlated with grip and biceps strength (r = 0.47 and 0.49; P < 0.001), but not with bone measurements, whereas muscle strength correlated with both EI and BMC (r = 0.40-0.52, P < 0.005). EI also correlated significantly with both BMC and ulnar width (P < 0.0001). Ulnar width and biceps strength were the only independent predictors of EI (r2 = 0.67, P < 0.0001). We conclude that levels of physical activity sufficient to increase arm strength influence ulnar bending stiffness.

Automation of temperature control for large-array microwave surface applicators

An adaptive temperature control system has been developed for the microstrip antenna array applicators used for large area superficial hyperthermia. A recursive algorithm which allows rapid power updating even for large antenna arrays and accounts for coupling between neighbouring antennas has been developed, based on a first-order difference equation model. Surface temperatures from the centre of each antenna element are the primary feedback information. Also used are temperatures from additional surface probes placed within the treatment field to protect locations vulnerable to excessive temperatures. In addition, temperatures at depth are observed by mappers and utilized to restrain power to reduce treatment-related complications. Experiments on a tissue-equivalent phantom capable of dynamic differential cooling have successfully verified this temperature control system. The results with the 25 (5 x 5) antenna array have demonstrated that during dynamic water cooling changes and other experimentally simulated disturbances, the controlled temperatures converge to desired temperature patterns with a precision close to the resolution of the thermometry system (0.1 degree C).

Characterization of a receptor for macrophage inflammatory protein 1 alpha and related proteins on human and murine cells

Macrophage inflammatory protein 1 alpha (MIP-1 alpha) is a potent stem cell inhibitor and a member of a large and expanding family of related cytokines. In an effort to understand the molecular basis of the activities of MIP-1 alpha, we have sought to characterize the cellular receptors for this molecule. Our results demonstrate the presence of abundant MIP-1 alpha receptors on both human and murine cells. The receptor on K562 cells can bind a range of members of the MIP-1 alpha family and may thus be a general MIP-1 alpha family receptor. Murine FDCPmix cells also bind a range of members of this peptide family, although the receptor(s) that they express appear somewhat more selective for peptides capable of displaying stem cell inhibitory properties. The human and murine receptors do not bind members of the related interleukin 8 family of peptides and are thus distinct from the recently cloned interleukin 8 receptor. We suggest that the receptor on the murine cell is a candidate for the receptor responsible for articulating stem cell inhibitory signals following MIP-1 alpha binding.

[Generation and characterization of monoclonal antibody GCF-5 to human giant cell tumor of bone]

Hybrid cell line has been derived from fusion of mouse myeloma (Sp2/0-Ag14) cell and spleen cell from mouse which was immunized with cultured cells of giant cell tumor of bone (GCT). Hybrid cells produce monoclonal antibody against GCT associated antigen in the surface of the tumor cells. The monoclonal antibody was detected by immunoperoxidase staining and was designated by GCF-5. There were more than eighty per cent of tested GCT which showed this antigen. It had no cross reaction with many kinds of normal tissue, HLA antigen, alpha-Fetal Protein, Carcino-Embryonic Antigen and beta-Microglobulin. The subclass of the antibody is IgG1. The hybridoma has been cultured and stored under -196 degrees C for more than eight months and its secretion remains stable.

[Changes of endogenous opioid peptides content in RPGL during acupuncture analgesia]

By push-pull perfusion technique and RIA of neuro-peptides, it was found that after 20 minutes' electroacupunture (EA), the release of LEK from the RPGL in the EA group was significantly higher than that in the control group (P < 0.05). The release of beta-EP from the RPGL in the EA group with higher efficacy was significantly higher than that in the control group (P < 0.05), but no significant changes were found in the EA group with lower efficacy. There was a positive correlation between the changes of release of LEK or beta-EP and the increase of pain threshold. The release of DynA1-13 tends to show a barely significant extent (P > 0.05). The results indicate that acupuncture analgesia is able to increase the release of LEK and beta-EP in the RPGL.