Cloning and expression of a pathway for benzene and toluene from Bacillus stearothermophilus

Bacillus stearothermophilus strain BR325 demonstrating broad aromatic substrate capability was isolated from petroleum-contaminated soil. The chromosomally-located aromatic pathway from this isolate was cloned into Escherichia coli as a 32 kb insert in cosmid pHC79, conferring growth on benzene, phenol, and toluene as sole carbon sources.

Pandas, people and policy

Panda conservation in China has been plagued by controversy and cultural and political differences. But international cooperation, together with new studies identifying the main threats, offer renewed hope for the species' survival.

Mutations in the K+ channel signature sequence

Potassium channels share a highly conserved stretch of eight amino acids, a K+ channel signature sequence. The conserved sequence falls within the previously defined P-region of voltage-activated K+ channels. In this study we investigate the effect of mutations in the signature sequence of the Shaker channel on K+ selectivity determined under bi-ionic conditions. Nonconservative substitutions of two threonine residues and the tyrosine residue leave selectivity intact. In contrast, mutations at some positions render the channel nonselective among monovalent cations. These findings are consistent with a proposal that the signature sequence contributes to a selectivity filter. Furthermore, the results illustrate that the hydroxyl groups at the third and fourth positions, and the aromatic group at position seven, are not essential in determining K+ selectivity.

[The pressor response induced by electrical stimulation of hypothalamic paraventricular nucleus in the cat]

The experiments were performed on 24 adult cats anesthetized with chloralose and urethane, paralyzed and artificially ventilated. Electrical stimulation of the hypothalamic paraventricular nucleus (PA) with a 12s train of 0.1-0.5 mA and 0.2ms square wave pulses at a frequency of 80 Hz induced a marked increase in arterial blood pressure (n = 19). The 22 points stimulated with maximum responses were clustered in the posterior dorsomedial part of the PA, among them 11 points were associated with an increase in heart rate and 7 a decrease. The remaining 4 points were associated with no change of heart rate, and situated in the anterior part of the PA. Electrolytic lesion of bilateral caudal half of the nucleus of solitary tract (NTS) had no significant effect on cardiovascular responses elicited from electric stimulation of the PA (n = 5). The results suggest that the PA is one of the important centers regulating cardiovascular activity; the NTS may not be involved in the PA pressor response.

Evaluation of filter-based aerosol measurements during the 1987 Southern California Air Quality Study

The Southern California Air Quality Study (SCAQS) was conducted during the summer and fall of 1987 to assess the causes of elevated ozone and suspended particulate matter concentrations in California's South Coast Air Basin (SoCAB). Extensive gaseous (i.e. nitric acid, ammonia, sulfur dioxide) and particle (i.e. PM2.5 and PM10 mass, elements, ions, carbon) measurements were acquired for 11 days during the summer at nine locations, and six days during the fall at six locations. Outliers were identified so that they could be excluded from further statistical analyses. Carbon and elemental measurements were found to be negatively biased by ∼ 20% owing to inhomogenous aerosol deposits on the SCAQS filters and analysis methods which were applied to a portion of the filters. These biases seem relatively consistent, however, and should not affect conclusions drawn from data analysis efforts if they are appropriately considered. Significant fractions (30-60%) of ammonium nitrate volatilized during the summer when temperatures were higher. Less than 10% typically volatilized during the fall when temperatures were lower. Anion/cation balances support the accuracy and precision estimates of the nitrate, sulfate, and ammonium measurements. Coarse particle sulfate was generally low, while coarse particle nitrate was most pronounced at the coastal sites.This paper documents SCAQS filter-based aerosol measurement methods, and evaluates the accuracy, precision, and validity of the data set. Various comparisons were made for: (1) PM2.5/PM10 ratios for mass and major chemical species; (2) sum of chemical species versus measured mass; (3) sulfate versus sulfur ratios; (4) PM2.5 particulate nitrate versus nitric acid-denuded nitrate; and (5) anion/cation balances. The measurement and evaluation techniques presented in this paper serve as a guideline for other data analysis and modeling studies.

Cholecystokinin gene expression in rat amygdaloid neurons: normal distribution and effect of morphine tolerance

Previous studies have shown that repeated opioid administration induces a tolerance to opioid, presumably due in part to an opioid-mediated compensatory increase in brain cholecystokinin (CCK) synthesis and/or release. In this study, in situ hybridization histochemistry was used to examine the effect of morphine tolerance on CCK gene expression in the amygdala of rat brains, by using a 35S-labeled synthetic oligonucleotide probe. CCK mRNA-positive neurons in normal rats were seen throughout the amygdaloid complex, with the most heavily labeled neurons in lateral, basal, and cortical nuclei, followed by the medial nucleus. Only a few labeled neurons were found in central and intercalated nuclei. The development of morphine tolerance in the rat was associated with increased hybridization signals for CCK mRNA in each subnucleus of the amygdala. Increases were seen in the numbers of positively labeled neurons and/or the numbers of hybridization grains per positively labeled neuron. Furthermore, differential patterns of increase in CCK mRNA in morphine tolerant rats occurred in different subnuclei of the amygdala, with the highest magnitude of increase in the cortical nucleus, followed in order by the medial, central, basal, intercalated and lateral nuclei. The present study demonstrated that repeated administration of morphine increased CCK gene expression in the amygdaloid complex, and suggested that the development of the tolerance to morphine analgesia is due, in part, to an increase in CCK activity in the amygdaloid complex. These findings substantiate the hypothesis that long-term administration of opioid may induce a compensatory increase in CCK synthesis and/or release, which then results in a progressive antagonism of opioid analgesia.

[A new natural focus of scrub typhus found in Hunchun]

From May to June 1992, Apodemus agrarius and Apodemus speciosus were captured in Hunchun, Jilin Province. Four strains of Rickettsia tsutsugamushi were isolated from viscera of rats and trombiculid mites. At the same time, the antibody against Rickettsia tsutsugamushi was assayed in the sera of the local people and the wild rats. The positive rates were 15.2% and 16.4%, respectively. The above results showed that a natural focus of scrub typhus exists in Hunchun area.

Amplification of Salmonella chromosomal DNA using the polymerase chain reaction

A Salmonella-specific polymerase chain reaction (PCR) was developed and standardized. The origin of the primers was a recombinant clone (C7) that contained Salmonella-specific HindIII fragment DNA of 2.1-kilobase pairs. Based on the sequence data of Salmonella enteritidis recombinant clone C7, two primers designated NK1 (21 nucleotides) and NK2 (24 nucleotides) were synthesized for use in the PCR. A Salmonella-specific 2.0-kilobase pair DNA product was amplified by the primers from 23 species of Salmonella, but not from 19 enteric and non-enteric bacteria. As little as 330 fg of Salmonella DNA was detected using either ethidium bromide/ultraviolet exposure of gels or Southern blot hybridization with a C7 clone.

The deduced amino-acid sequence of the cloned cpxR gene suggests the protein is the cognate regulator for the membrane sensor, CpxA, in a two-component signal transduction system of Escherichia coli

The cpxA gene of Escherichia coli K-12 encodes a membrane-associated sensor element of a two-component signal transduction system in bacteria. The cognate regulator element, however, has not yet been definitively identified. A 2.1-kb segment upstream from cpxA was amplified by polymerase chain reaction, cloned and sequenced. An open reading frame encoding 232 amino acids was found. It showed high homology to the regulator elements of two-component transduction systems. The newly identified gene, designated as cpxR, may encode the cognate protein receiving signals from CpxA.

Quantitative aspects of the mutant analysis by PCR and restriction enzyme cleavage (MAPREC)

Quantitation of virus revertants by PCR and restriction enzyme cleavage may give nonlinear results and, in some cases, produce artifacts caused by nucleotide misincorporation and heteroduplex formation, occurring during PCR. Modifications of the procedure allowed us to overcome these problems and develop a highly sensitive and reliable method of mutant quantitation. This procedure can be used to assess the quality of live vaccines and to study heterogeneity of viral and bacterial populations.

Dihydropyrimidine dehydrogenase activity in human peripheral blood mononuclear cells and liver: population characteristics, newly identified deficient patients, and clinical implication in 5-fluorouracil chemotherapy

Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (FUra), one of the most widely used anticancer drugs. Previous studies from our laboratory demonstrated the clinical importance of DPD in cancer patients (G. D. Heggie, J-P. Sommadossi, D. S. Cross, W. J. Huster, and R. B. Diasio. Cancer Res., 47: 2203-2206, 1987; B. E. Harris, R. Song, S-j. Soong, and R. B. Diasio. Cancer Res., 50: 197-201, 1990), particularly in those with DPD deficiency who experience severe FUra toxicity (including death) following FUra treatment [R. B. Diasio, T. L. Beavers, and J. T. Carpenter. J. Clin. Invest., 81: 47-51, 1988; B. E. Harris, J. T. Carpenter, and R. B. Diasio. Cancer (Phila.), 68: 499-501, 1991]. We now suggest that measurement of DPD activity may be useful in routine screening of cancer patients prior to FUra treatment. In this paper, we describe the following serial studies: (a) we developed a sensitive, accurate, and precise DPD assay and a storage method to stabilize DPD activity, permitting large scale DPD screening in cancer patients; (b) we demonstrated a normal distribution (Gaussian distribution) of human DPD activity from peripheral blood mononuclear cells (PBM-DPD) in a population study. Baselines for PBM-DPD with fresh and frozen samples were 0.425 +/- 0.124 (SD) and 0.189 +/- 0.064 nmol/min/mg protein, respectively. The 95% and 99% distribution ranges for both fresh and frozen samples were also determined, providing criteria for detection of DPD-deficient patients; (c) we identified nine new patients with profound or partial DPD deficiency; (d) we determined a baseline for human liver DPD activity, which was shown to be 0.360 +/- 0.182 nmol/min/mg protein (frozen samples); (e) we did a preliminary evaluation of liver DPD from deficient patients. Low liver DPD activity in two deficient patients correlated with low PBM-DPD activity. Using a polyclonal antibody raised against human liver DPD in our laboratory (Z. Lu, R. Zhang, and R. B. Diasio. J. Biol. Chem., 267: 17102-17109, 1992), Western blot analysis demonstrated decreased DPD protein in the liver cytosol from DPD-deficient patients compared to normal subjects. These results may be useful in improving the effectiveness and/or lessening the toxicity of FUra chemotherapy.

Transcripts for the high and low affinity hexose transporters in rat myoblasts

The present investigation examined the glucose transporter (GLUT) transcript levels in glucose-grown rat L6 myoblasts, which possessed a high (HAHT) and a low (LAHT) affinity hexose transport system. The most prominent GLUT transcript detected in these cells was a GLUT 3-recognizable 4.1-kilobase transcript. Mutants defective in HAHT contained only residual levels of the GLUT 3 transcript and transporter. Corresponding changes in GLUT 3 transcript levels and HAHT activity were observed in myotubes, confluent cultures, and myogenesis-impaired cells. The other prominent GLUT transcripts detected were the GLUT 4-recognizable 2.8- and 1.4-kilobase transcripts. The close correlation between the GLUT 4 isoform and LAHT activity was indicated by the absence of this isoform in LAHT- mutants, and their corresponding changes in myoblasts grown under different conditions. These findings suggested the HAHT and LAHT transporters might be coded or regulated by the genes responsible for the GLUT 3 and 4 transcripts, respectively. Although relatively high levels of the GLUT 1 transcript and transporter were detected in glucose-grown HAHT-LAHT- mutants, these cells did not exhibit any GLUT 1 transport activity. Since the GLUT 1 transporter was not functional, it was not likely responsible for the HAHT and LAHT activities observed in glucose-grown L6 myoblasts.

Characterization of the pea chloroplast DNA OriA region

One of the two origins of replication in pea chloroplast DNA (oriA) maps in the rRNA spacer region downstream of the 16S rRNA gene, and further characterization of this origin is presented here. End-labeling of nascent DNA strands from in vivo replicating ctDNA was used to generate probes for Southern hybridization. Hybridization data identified the same region that was previously mapped to contain D-loops by electron microscopy. Subclones of the oriA region were tested for their ability to support in vitro DNA replication using a partially purified pea ctDNA replication system. Two-dimensional agarose gel electrophoresis identified replication intermediates for clones from the region just downstream of the 16S rRNA gene, with a 450-bp SacI-EcoRI clone showing the strongest activity. The experiments presented in this paper identify the 940 base pair region in the rRNA spacer between the 3' end of the 16S rRNA gene and the EcoRI site as containing oriA. Previous studies by electron microscopy localized the D-loop in the spacer region just to the right of the BamHI site, but the experiments presented here show that sequences to the left of the BamHI site are required for replication initiation from oriA. DNA sequence analysis of this region of pea ctDNA shows the presence of characteristic elements of DNA replication origins, including several direct and inverted repeat sequences, an A + T rich region, and dnaA-like binding sites, most of which are unique to the pea ctDNA oriA region when compared with published rRNA spacer sequences from other chloroplast genomes.

The time of administration of 3'-azido-3'-deoxythymidine (AZT) determines its host toxicity with possible relevance to AZT chemotherapy

3'-Azido-3'-deoxythymidine (AZT) is the drug most widely used in the treatment of AIDS. Its major drug-related toxicity is bone marrow suppression, which limits the dose of AZT that can be used. It is essential that AZT be phosphorylated for antiviral effect. We have recently demonstrated that thymidine kinase (TK), the initial enzyme in AZT anabolism, follows a circadian pattern in rat bone marrow. The present study was undertaken to determine whether AZT toxicity is related to the time of its administration and whether the variation in toxicity is correlated with the circadian variation in TK activity. Male Sprague-Dawley rats were housed under standardized conditions of light and dark (lights on 0600 to 1800 and lights off 1800 to 0600) for 4 weeks. The animals were randomly divided into seven groups; six groups were administered AZT by intraperitoneal injection at the same dose of 750 mg/kg of body weight at various times (0400, 0800, 1200, 1600, 2000, and 2400), and one group was used as a control. AZT-related toxic effects, including bone marrow toxicity, differed significantly among the treatment groups, depending on the time of AZT administration (by analysis of variance and Cosinor analysis, P < 0.001). The least toxicity was observed in rats receiving AZT at 1600 (10 h after light onset [10 HALO], in late sleep span) and the greatest toxicity was observed in those injected at 0400 (22 HALO, in late activity span). To verify these results, we administered AZT by intraperitoneal injection at an approximately 50% lethal dose (1,500 mg/kg) to two groups of rats, one at 1200 (6 HALO, in the middle of the sleep span) and the other at 2400 (18 HALO, in the middle of the activity span). AZT lethality was significantly higher in rats receiving AZT at 2400 (18 HALO, in the middle of the activity span). Further statistical analysis demonstrated that the variation in AZT toxicity was correlated with the circadian variation in TK activity in bone marrow of the same species (peak activity at 0400 [22 HALO, in late activity span] and trough activity at 1600 [10 HALO, in late sleep span]), suggesting that the circadian variation in TK activity may be the biochemical basis for the observed circadian variation in AZT toxicity. These results may be useful in the design of improved AZT chemotherapeutic regimens.

Platelet activating factor-induced microvascular permeability increases in the cat hindlimb

Changes in microvascular permeability induced by platelet activating factor (PAF) were measured in the isolated, perfused cat hindlimb preparation, and compared to the effect produced by another inflammatory mediator, histamine. Permeability was assessed from changes in the protein reflection coefficient, as measured from changes in hematocrit and protein concentration resulting from microvascular fluid filtration. The findings were 1) PAF produces transient increases in permeability similar to histamine, but PAF is approximately 30 times as potent; 2) the permeability changes induced by 76 nM PAF can be totally inhibited by the specific PAF receptor blocker WEB-2086, but the blocker can only partially inhibit 380 nM PAF, a dose that produces a maximal increase in permeability; 3) Diphenhydramine (2 microM), an H1-receptor blocker, totally inhibits the transient permeability increase produced by 2 microM histamine; 4) Cimetidine (2 or 20 microM), an H2 blocker, could not inhibit this latter increase; 5) Isoproterenol (1 microM), a beta-agonist, totally inhibited the permeability increase produced by 1 microM histamine, but 10 microM isoproterenol only partially inhibited the maximal permeability increase produced by 10 microM histamine; 6) Isoproterenol could not inhibit PAF's permeability effect; and 7) PAF's effects were unchanged by depletion of white blood cells in the perfusate. These results suggest that PAF and histamine work through different pathways to increase permeability, but the final step of endothelial contraction, which opens large inter-endothelial gaps, occurs in response to both mediators. In addition, when concentrations of these inflammatory agents are sufficient to produce maximal permeability increases, as can occur in shock situations, then the permeability increases are more sustained and resistant to receptor inhibition.

Three adjacent genes of African swine fever virus with similarity to essential poxvirus genes

Nucleotide sequencing of the right end of the SalIj fragment of the highly virulent Malawi Lil20/1 strain of African swine fever virus (ASFV) has revealed three adjacent genes with similarity to: serine-threonine protein kinases; members of the putative helicase superfamily SF2; and the vaccinia virus 56 kDa abortive late protein. All three genes are transcribed to the left with respect to the orientation of the ASFV genome. Gene L19IL predicts a protein similar to serine-threonine protein kinases including vaccinia virus gene B1R. Gene L19KL predicts a protein that is likely to be a nucleic acid-dependent ATPase, as it has similarity to both the poxvirus 70 kDa early transcription factor subunit and the poxvirus nucleoside triphosphatase I gene. Gene L19LL has extensive similarity to the vaccinia virus 56 kDa abortive late protein.

Phase I trial of low-dose, prolonged continuous infusion fluorouracil plus interferon-alfa: evidence for enhanced fluorouracil toxicity without pharmacokinetic perturbation

PURPOSE

To determine the maximum-tolerable dose (MTD) of fluorouracil (5-FU) administered as a low-dose, prolonged continuous intravenous infusion (PCI) plus interferon-alfa (IFN-alpha) that would permit treatment for at least 28 consecutive days, and to determine the effect of IFN-alpha on 5-FU pharmacokinetics.

PATIENTS AND METHODS

Twenty-six assessable patients with advanced cancer received low-dose PCI 5-FU (150, 200, 250, and 300 mg/m2/d) plus IFN-alpha, 5 x 10(6) IU/m2 administered subcutaneously (SC) at hour 48 of the 5-FU infusion, then thrice weekly thereafter in cohorts of at least three patients. Treatment continued until treatment-limiting toxicity (TLT) developed, such as mucositis, diarrhea, or fatigue. Escalation to the next 5-FU dose level occurred if none of three or zero to two of six patients developed TLT before day 28. Quantitation of plasma 5-FU concentration by high-performance liquid chromatography was performed in 15 patients. Data were standardized using the Cosinor method and compared before and after IFN-alpha administration using the paired t test.

RESULTS

The mean number of days of continuous 5-FU therapy for patients receiving 150, 200, 250, and 300 mg/m2/d of 5-FU plus IFN alfa-2a (IFN-alpha 2a) was 75, 54, 37, and 22 days, respectively. The MTD of PCI 5-FU by our criteria that could be combined with IFN-alpha was 250 mg/m2/d. Comparison of the standardized pharmacokinetic data showed no significant effect of IFN-alpha on plasma 5-FU concentration, and no alteration of the normal circadian variation in plasma 5-FU concentration that was evident before IFN-alpha administration. Objective response occurred in patients with adenocarcinoma of the pancreas (n = 3), kidney (n = 2), and lung (n = 1).

CONCLUSION

IFN-alpha substantially enhanced the gastrointestinal toxicity of low-dose PCI 5-FU without affecting 5-FU pharmacokinetics, contrary to previous reports using alternative 5-FU schedules in which IFN-alpha-related enhancement of 5-FU toxicity was attributable to reduced 5-FU clearance. Our findings suggest that under certain conditions, mechanisms other than altered 5-FU pharmacokinetics may be responsible for the ability of IFN-alpha to enhance the toxic effects of 5-FU.

Acoustic response properties of single units in the torus semicircularis of the goldfish, Carassius auratus

Single units of the goldfish torus semicircularis (TS) were recorded in response to pure tones. Response areas (RA) were obtained by recording the number of spikes evoked by tones in a range of frequencies and levels within the units' dynamic range. RAs gave estimates of best sensitivity (BS), characteristic frequency (CF), most excitatory frequency at each level (BF), and Q10dB. Peri-stimulus-time histograms (PSTH), interspike interval histograms (ISIH), and period histograms were obtained at various frequencies and levels to describe the units' temporal response patterns. The distribution of CF is nonuniform with modes at 155, 455, and 855 Hz. The distribution of the coefficient of synchronization to standard tones is also nonuniform, revealing a dichotomy between units with little or no phase-locking and those that phase-lock strongly. PSTHs for units without significant phase-locking vary widely and include patterns resembling those of the mammalian auditory brainstem. Compared with saccular afferents, torus units tend to have lower spontaneous rates, greater sensitivity, and sharper tuning. Unlike saccular afferents, BF is independent of level for most torus units. Some torus units are similar to saccular afferents while others reveal significant transformations of information between the periphery and the midbrain.

An African swine fever virus gene with similarity to the proto-oncogene bcl-2 and the Epstein-Barr virus gene BHRF1

An open reading frame, LMW5-HL, in the African swine fever virus genome displays a high degree of similarity to the proto-oncogene bcl-2 and, to a lesser degree, the Epstein-Barr virus gene BHRF1. A highly conserved central region is found in all three proteins. LMW5-HL encodes a protein of 18 kDa that is present in infected porcine macrophages at both early and late times postinfection. The similarity of LMW5-HL to bcl-2 and BHRF1 suggests a role for it in cell maintenance during productive or persistent viral infection.

Relationship between circadian-dependent toxicity of 5-fluorodeoxyuridine and circadian rhythms of pyrimidine enzymes: possible relevance to fluoropyrimidine chemotherapy

Previous studies in experimental animals and patients have suggested a circadian variation in host toxicity following administration of 5-fluorodeoxyuridine (FdUrd) although the biochemical mechanisms are not fully understood. Thymidine kinase (TK; EC 2.7.1.21), the initial enzyme in the thymidine-phosphorylation pathway, is the first enzyme in the anabolism of FdUrd. Dihydropyrimidine dehydrogenase (DPD; EC 1.3.1.2), is the rate-limiting enzyme in the pyrimidine catabolic pathway and has been shown to be the key enzyme in FdUrd catabolism. The present study examined the relationship between the suggested circadian variation in FdUrd toxicity and potential circadian variations in the activity of these enzymes. Initial studies in Sprague-Dawley rats confirmed that the time of FdUrd administration affected death rate and other drug-related toxicities including loss of body weight, diarrhea, and bone marrow suppression, with the least toxicity and highest survival rate being observed in rats receiving FdUrd at 12:00 noon and 4:00 p.m. and the greatest toxicity and lowest survival rate at 12:00 midnight and 4:00 a.m. Statistical analysis revealed a circadian pattern in FdUrd toxicity (Cosinor analysis, P < 0.001). In subsequent studies with the same species, we simultaneously measured TK and DPD activities in several tissues at various times over 24 h. Under standardized light conditions (lights on, 6:00 a.m. to 6:00 p.m.; lights off, 6:00 p.m. to 6:00 a.m.), with sampling at 4-h intervals (4:00 and 8:00 a.m.; 12:00 noon; 4:00 and 8:00 p.m., and 12:00 midnight), a circadian variation in TK activity was observed (P < 0.0001, Cosinor analysis) in bone marrow, intestinal mucosa, liver, and spleen. In the same group of animals, a circadian pattern of DPD activity in liver and bone marrow was also observed (Cosinor analysis, P < 0.0001) that was inverse compared to the circadian variation in TK activity (Pearson correlation analysis, P < 0.05). Further statistical analysis indicated that the observed circadian variation in FdUrd toxicity was correlated with the circadian variation of TK activity and inversely correlated with DPD activity (Pearson correlation analysis, P < 0.05). Based on the above data, we conclude that the circadian pattern of TK and DPD activity may explain the observed circadian variation in toxicity as the time of FdUrd administration is varied. These results may be useful in the design of improved chemotherapeutic regimens using time-modified administration of FdUrd.

Hemodynamic effects of terazosin in congestive heart failure

To determine the hemodynamic effects of a new alpha-1 blocker, terazosin, in congestive heart failure, 10 patients with this condition underwent hemodynamic testing at rest. Thirty minutes after the oral administration of 4 mg terazosin, mean right atrial pressure, mean pulmonary artery pressure and pulmonary capillary wedge pressure were found to be decreased, while the cardiac index was increased significantly. Improvement in hemodynamics persisted for more than 15 h, without an increase in heart rate. It is suggested that terazosin may have effective applications in the treatment of congestive heart failure.

[Effects of interfacial state and bonding on the biostrength of plat castable ceramics crown]

Plat castable ceramics (PCC) restorations depend primarily on their biostrength. In our experiment the human oral physiological environment was simulated and we studied the effects of restoration-tooth interfacial state and bonding on the biostrength of PCC crowns. The bond strength affects the biostrength of PCC crowns obviously. The interfacial treatment affects not only the bond strength between PCC crown and tooth structure but also the biostrength of the crown cemented.

Tension transients initiated by photogeneration of MgADP in skinned skeletal muscle fibers

Addition of MgADP to skinned skeletal muscle fibers causes a rise in Ca(2+)-activated isometric tension. Mechanisms underlying this tension increase have been investigated by rapid photogeneration of ADP within skinned single fibers of rabbit psoas muscle. Photolysis of caged ADP (P2-1(2-nitrophenyl)ethyladenosine 5'-diphosphate) resulted in an exponential increase in isometric tension with an apparent rate constant, kADP, of 9.6 +/- 0.3 s-1 (mean +/- SE, n = 28) and an amplitude, PADP, of 4.9 +/- 0.3% Po under standard conditions (0.5 mM photoreleased MgADP, 4 mM MgATP, pH 7.0, pCa 4.5, 0.18 M ionic strength, 15 degrees C). PADP depended upon the concentration of photoreleased MgADP as well as the concentration of MgATP. A plot of 1/PADP vs. 1/[MgADP] at three MgATP concentrations was consistent with competition between MgADP and MgATP for the same site on the crossbridge. The rate of the transient, kADP, also depended upon the concentration of MgADP and MgATP. At both 4 and 1 mM MgATP, kADP was not significantly different after photorelease of 0.1-0.5 mM MgADP, but was reduced by 28-40% when 3.5 mM MgADP was added before photorelease of 0.5 mM MgADP. kADP was accelerated by about twofold when MgATP was varied from 0.5 to 8 mM MgATP. These effects of MgATP and MgADP were not readily accounted for by population of high force-producing states resulting from reversal of the ADP dissociation process. Rather, the results suggest that competition between MgADP and MgATP for crossbridges at the end of the cycle slows detachment leading to accumulation of force-generating crossbridges. Elevation of steady-state Pi concentration from 0.5 to 30 mM caused acceleration of kADP from 10.2 +/- 0.5 to 27.8 +/- 1.8 s-1, indicating that the tension rise involved crossbridge flux through the Pi dissociation step of the cycle.

Lysine 87 in the beta subunit of tryptophan synthase that forms an internal aldimine with pyridoxal phosphate serves critical roles in transimination, catalysis, and product release

This study provides valuable insights into the functions of the lysine residue that forms an internal aldimine with pyridoxal phosphate in the beta subunit of tryptophan synthase from Salmonella typhimurium. Our spectroscopic and kinetic studies demonstrate that a mutant alpha 2 beta 2 complex having beta subunit lysine 87 replaced by threonine forms external aldimines with several amino acids including L-serine, beta-chloro-1-alanine, L-tryptophan, and D-tryptophan. Because the rates of aldimine formation are very slow, we conclude that one role of lysine 87 in the wild type enzyme is to facilitate formation of external aldimines by transimination. Lysine 87 is an essential catalytic residue because the mutant alpha 2 beta 2 complex has no measurable activity in reactions catalyzed by the beta subunit and does not convert external aldimines to products. The mutant enzyme carries out two slow partial beta-elimination reactions: the conversion of beta-chloro-L-alanine and L-serine to enzyme-bound aminoacrylate. The reaction with L-serine is catalyzed by ammonia, which partially replaces the deleted epsilon-amino group. Lysine 87 is important for substrate and product release because L-serine, L-tryptophan, and aminoacrylate dissociate very slowly from the mutant alpha 2 beta 2 complex. Our ability to prepare very stable derivatives of the mutant alpha 2 beta 2 complex containing tightly bound aldimines with a substrate, a product, or a reaction intermediate provides valuable materials for ongoing x-ray crystallographic investigations and future kinetic analyses of the allosteric activation of the alpha subunit by beta subunit ligands.

Circadian rhythm of rat spleen cytoplasmic thymidine kinase

The activity of thymidine kinase (TK, EC 2.7.1.21), the first enzyme of the thymidine phosphorylation pathway, was measured at various times over a 24-hr period in the spleens of Sprague-Dawley rats that had been housed under standardized conditions of light and dark for at least 4 weeks before the study. Spleen cytoplasmic TK activity was assayed with [2-14C]thymidine as substrate. Under "normal" light conditions (lights on 6:00 a.m.-6:00 p.m. and lights off 6:00 p.m.-6:00 a.m.), a circadian variation of TK activity was observed (P < 0.0001), Cosinor analysis) with peak activity (1.98 nmol product/hr/mg protein) at 1:00 a.m. (19 hr after light onset, HALO) and trough activity (0.40 nmol product/hr/mg protein) at 1:00 p.m. (7 HALO). Maximum enzyme activity exceeded minimum activity by approximately 5-fold. Reversing the light-dark cycle resulted in a corresponding shift in TK activity. Under these "reverse" conditions (lights on 6:00 p.m.-6:00 a.m. and lights off 6:00 a.m.-6:00 p.m.), a circadian variation in TK activity was also observed (P < 0.0001, Cosinor analysis) with peak activity (1.14 nmol product/hr/mg protein) at 12:00 noon (18 HALO) and trough activity (0.32 nmol/hr/mg protein) at 12:00 a.m. (6 HALO). Maximum enzyme activity exceeded minimum activity by approximately 4-fold. In summary, this study demonstrated for the first time that TK activity varies over a 24-hr period in association with the light-dark cycle.

Investigations of kinase substrate specificity with aqua Rh(III) complexes of adenosine 5'-triphosphate

In this paper the substrate activities and binding affinities of the stereoisomers of the beta,gamma-bidentate Rh(H2O)4ATP and alpha,beta, gamma-tridentate Rh(H2O)3ATP complexes toward selected members of the kinase family of enzymes are reported. Hexokinase and glycerokinase were found to be specific for the delta beta, gamma-bidentate Rh(H2O)4ATP isomer as substrate while adenylate kinase was found to specifically catalyze the reaction of the delta beta,gamma-bidentate Rh(H2O)4ATP isomer. Pyruvate kinase recognized both the delta beta,gamma-bidentate Rh(H2O)4ATP isomer and the delta beta-P, exo alpha-P alpha,beta,gamma-tridentate Rh(H2O)3ATP isomer as substrates in the catalyzed phosphorylation of the alternate substrate, glycolate. 31P NMR analysis of the respective product complexes showed that alpha-P phosphoryl ligand exchange had not preceded or followed catalysis. Creatine kinase was found to be specific for the delta beta-P, exo alpha-P alpha,beta,gamma-tridentate Rh(H2O)3ATP isomer. Discrimination of the Rh(H2O)nATP isomers via preferential binding of the substrate-active isomer was observed for hexokinase and adenylate kinase but not for glycerokinase, fructose-6 phosphate kinase, creatine kinase, arginine kinase, or acetate kinase.

Thymic carcinoid tumor--a report of 7 cases

The thymic carcinoid tumor is a rare neoplasm which is often clinically misdiagnosed as thymoma. But the two differ in origin, biological behavior, accompanying syndromes, pathological features, and prognosis. The characteristics of the thymic carcinoid tumor are: difficulty in diagnosis, high malignancy, frequent recurrence and extrathoracic metastasis over a prolonged period postoperatively. Complete surgical resection of original and recurrent tumors is the important treatment. Microscopic, electron microscopic and immunohistochemical examinations may be required in making an accurate pathological diagnosis. This paper reports 7 cases of thymic carcinoid tumor.

[An investigation of the effect of rostral ventrolateral medulla lesion on pressor response induced by electrical stimulation of hypothalamic paraventricular nucleus in the cat]

The experiments were performed on 20 adult cats anesthetized with chloralose and urethane, paralyzed and artificially ventilated. The rostral ventrolateral medulla (RVL) was explored by electrical stimulation. We found that an area, 3-5 mm rostral to the obex, 3-4 mm lateral to the midline, and 0-1 mm from the ventral surface of the medulla, was the most effective region for producing a pressor response. After bilateral microinjection of kainic acid into or electrolytic lesion of the above-mentioned active RVL area, a large decrease in arterial blood pressure was elicited, and the pressor response induced by electrical stimulation of the hypothalamic paraventricular nucleus (PA) was nearly eliminated. The results suggest that the RVL mediates the PA pressor response.

[Study on the color modification buring surface staining of PLAT castable ceramic restorations]

The surface staining of castable ceramic restorations is a technique-dependent process. So it is inevitable that the color of restorations mismatch the color of natural teeth. This study was conducted to explore the possibility of modifying the color by selected use of special colored stains. Eighty PLAT castable ceramic samples were machined, 16 mm in diameter, 1.2 mm in thickness. Thirty-two samples were stained with yellow stain and 32 samples orange. Sixteen samples were stained with red, green, blue and violet stains, respectively. To the yellow and orange stained samples, we applied correspondingly the same stain, red, green, blue and violet stains. The color of each sample was evaluated with a colorimeter and translated to Munsell notations. The results indicated that chroma was intensified by each application of the same stain. Red and green stains made the hue reddish and greenish. Blue and violet stains could effectively decrease the chroma of yellow or orange. Meanwhile, the hue was also slightly changed to greenish and reddish.

Clothing prevents ultraviolet-B radiation-dependent photosynthesis of vitamin D3

Photoprotection of the skin is mainly a function of clothing, although the effectiveness of the latter against UV-B solar radiation (wavelengths 290-320 nm) has not been measured in vivo. Since UV-B mediates the cutaneous formation of vitamin D3, we examined the attenuation of that photosynthetic reaction by the commonly used fabrics cotton, wool, and polyester in black and white colors. Direct transmission of UV-B was attenuated the most by black wool (98.6% of incident irradiance) and the least by white cotton (47.7%). None of the fabrics allowed the photoproduction of previtamin D3 from 7-dehydrocholesterol irradiated in vitro with up to 40 min of simulated sunlight or the elevation of serum vitamin D3 after irradiation with approximately one minimal erythema dose (MED) of UV-B in volunteers wearing jogging garments made of these fabrics. Increasing the whole body irradiation dose to six MEDs still failed to produce a serum vitamin D3 response in garment-clad subjects. Regular (seasonal) street clothing also prevented an elevation of the vitamin D3 in response to UV-B radiation. We conclude that clothing prevents or significantly impairs the formation of vitamin D3 after photostimulation with up to six MEDs of UV-B.

Early markers of pancreas transplant rejection

To compare the predictive value of urinary amylase (UA), urinary insulin (UI), and urinary prostaglandin (PGE2), whole pancreas isografts or allografts from (ACI rat donors, RT1a) with bladder drainage of exocrine secretions were performed in Lewis rats (RT1(1)) with streptozotocin-induced diabetes. UA, UI, PGE2 and plasma glucose levels were measured daily. Euglycemia was restored on Postoperative Day 1 in all the recipients of isografts (N = 6) and was maintained for over a year. UI concentrations and PGE2 outputs were stable, with low levels ranging between 0.3 +/- 0.2 to 7 +/- 2 ng/ml and 56 +/- 15 to 164 +/- 48 ng/24 hr, respectively, while UA levels were significantly elevated compared to normal controls (> 1,000 U/ml vs 29 +/- 16 U/ml). In the allograft group (N = 12), rejection occurred on Days 7 through 9, with a mean graft survival time of 8.1 +/- 0.1 days. UA dropped from a post-transplant peak of 2,422 +/- 353 U/ml on Postoperative Day 4 to below 1,380 +/- 256 U/ml 3 days before rejection (Day -3). UI increased to 83 +/- 16 ng/ml (P < 0.05) on Day -6 and reached a post-transplant peak of 140 +/- 24 ng/ml on Day -5, while PGE2 output rose from a pretransplant level of 18 +/- 2 to 92 +/- 25 ng/24 hr on Postoperative Day 1, followed by a significant elevation on Day 4 (-4).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic observation and treatment approach for patients with angina decubitus

In order to investigate the mechanism and treatment of angina decubitus, 20 patients (18 men and 2 women aged 36-70 years) were studied during hospitalization. All patients were found to have an increased heart rate x systolic blood pressure product before the onset of angina decubitus, indicating that this type of angina pectoris belongs to the category of effort angina. Of the 11 patients investigated by continuous hemodynamic monitoring, 3 had significant progressive increases in pulmonary artery systolic pressure (PASP) and pulmonary artery diastolic pressure (PADP) before onset: their episodes of angina could not be completely controlled by digoxin and diuretics, but quickly subsided after beta blockers were added. Among the other 8 patients, PADP increased slightly in 5 and remained unchanged in 3 cases before onset: these patients had no manifestations of LV dysfunction, and beta blockers combined with coronary vasodilators produced satisfactory effects. These results indicate that LV failure is not a major factor in the pathogenesis of angina decubitus. The LV diastolic dysfunction seen in 8/11 cases may have been related to LV hypertrophy caused by long-term hypertension or chronic persistent ischemia.

Identification of an African swine fever virus gene with similarity to a myeloid differentiation primary response gene and a neurovirulence-associated gene of herpes simplex virus

Here we describe an open reading frame (LMW23-NL) in the African swine fever virus genome that possesses striking similarity to a murine myeloid differentiation primary response gene (MyD116) and the neurovirulence-associated gene (ICP34.5) of herpes simplex virus. In all three proteins, a centrally located acidic region precedes a highly conserved, hydrophilic 56-amino-acid domain located at the carboxy terminus. LMW23-NL predicts a highly basic protein of 184 amino acids with an estimated molecular mass of 21.3 kDa. The similarity of LMW23-NL to genes involved in myeloid cell differentiation and viral host range suggests a role for it in African swine fever virus host range.

[Study on casting precision of plat castable ceramic crowns]

The plat castable ceramic crown was made with investment material prepared in our college with our own casting technique by a Chinese-made casting machine. The accuracy and fitness of the crown were studied and appraised. Results show that the margin of fitness is 46 microns and that the cement film thickness of the dies in the spacer material group is 65.13 microns. Hence the results are satisfactory. The Plat castable ceramic crown might be used in clinical dentistry.

Myelin proteolipid protein: minimum sequence requirements for active induction of autoimmune encephalomyelitis in SWR/J and SJL/J mice

Proteolipid protein (PLP) is the major protein constituent of mammalian central nervous system myelin. We have previously identified two different PLP encephalitogenic T cell epitopes in two mouse strains. Murine PLP peptides 103-116 YKTTICGKGLSATV and 139-151 HCLGKWLGHPDKF are encephalitogenic determinants in SWR/J (H-2q) and SJL/J (H-2s) mice, respectively. The purpose of the present study was to determine the minimum sequence requirements for each of these PLP encephalitogens. In SWR/J mice, at least two distinct overlapping peptides can induce experimental autoimmune encephalomyelitis (EAE). The eleven residue sequences PLP 105-115 TTICGKGLSAT and PLP 106-116 TICGKGLSATV are encephalitogenic in SWR/J mice, but PLP 106-115 TICGKGLSAT, the decapeptide indigenous to both sequences, is non-encephalitogenic. In contrast, the shortest PLP sequence capable of inducing EAE in SJL/J mice is the nonapeptide 141-149 LGKWLGHPD. These data indicate that encephalitogenic determinants of PLP are short contiguous peptide sequences similar in length and diversity to those of MBP.

(Aminoalkoxy)chromones. Selective sigma receptor ligands

A series of (aminoalkoxy)chromones has been prepared, members of which bind potently (16-100 nM) at the sigma binding site and bind weakly (greater than 1000 nM) at the dopamine D2 receptor and 33 other receptors, second messenger systems, and ion channels. At the sigma receptor, the preferred position of attachment for the aminoalkoxy side chain to the chromone ring followed the rank order: 7-position greater than 5-position greater than 6-position. Chromones that contained a 2-substituent that was not coplanar with the chromone ring system showed improved binding over compounds with coplanar substituents. The most potent compound at the sigma site, 7-[[7-(4-hydroxypiperidyl)heptyl]oxy]-2-phenylchromone (74), had receptor affinities (IC50) of 16 nM at the [3H]DTG site, 19 nM at the [3H]-(+)-3-PPP site, and 4000 nM (Ki) at the dopamine D2 receptor. The most selective compound examined, 6-[[6-(4-hydroxypiperidyl)hexyl]-oxy]-2-cyclopentylchromone (58), exhibited IC50s of 51 nM at the [3H]DTG site, 55 nM at the [3H]-(+)-3-PPP site, and 21,000 nM (Ki) at the dopamine D2 receptor. Compound 44 (6-[[6-(4-hydroxypiperidyl)hexyl]oxy]-3-methylflavone, NPC 16377) was systemically effective (ip and po) in two behavioral models predictive of antipsychotic compounds and systemically active in animal models of ischemia.

Effects of Ca2+ on the kinetics of phosphate release in skeletal muscle

The process of phosphate dissociation during the muscle cross-bridge cycle has been investigated by photoliberation of inorganic phosphate (Pi) within skinned fibers of rabbit psoas muscle. This permitted a test of the idea that Ca2+ controls muscle contraction by regulating the Pi release step of the cycle. Photoliberation of Pi from structurally distinct "caged" Pi precursors initiated a rapid tension decline of up to 12% of active tension, and this was followed by a slower tension decline. The apparent rate constant of the fast phase, kPi, depended on both [Pi] and [Ca2+], whereas the slow phase generally occurred at 2-4 s-1. At maximal Ca2+, kPi increased in a nonlinear manner from 43 +/- 2 s-1 to 118 +/- 7 s-1, as Pi was raised from 0.9 to 12 mM. This was analyzed in terms of a three-state kinetic model in which a force-generating transition is coupled to Pi dissociation from the cross-bridge. As Ca(2+)-activated tension was reduced from maximal (Pmax) to 0.1 Pmax, (i) kPi decreased by up to 2.5-fold, (ii) the relative amplitude of the rapid phase increased 2-fold, and (iii) the relative amplitude of the slow phase increased about 6-fold. Changes in the rapid phase are compatible with Ca2+ influencing an apparent equilibrium constant for the force-generating transition. By comparison, kPi was faster than the rate constant of tension redevelopment, ktr, and was influenced less by Ca2+. Ca2+ effects on the caged Pi transient cannot account for the large effects of Ca2+ on actomyosin ATPase rates or cross-bridge cycling kinetics but may be a manifestation of reciprocal interactions between the thin filament and force-generating cross-bridges, and may represent Ca2+ regulation of the distribution of cross-bridges between non-force-and force-generating states.

Enhanced Photosynthesis and Stomatal Conductance of Pima Cotton (Gossypium barbadense L.) Bred for Increased Yield

Yield of Pima cotton (Gossypium barbadense L.) has tripled over the last 40 years with the development of new cultivars. Six genetic lines representing successive stages in the breeding process (one primitive noncultivated accession, four cultivars with release dates from 1949 to 1983, and one unreleased breeding line) were grown in a greenhouse, and their gas exchange properties were compared. Among the cultivated types, genetic advances were closely associated with increasing single-leaf photosynthetic rate (A) and stomatal conductance (g(s)), especially in the morning. The A and g(s) of the primitive line approached those of the cultivated types early in the morning, but were much lower for the rest of the day. In both morning and afternoon, A was correlated with g(s) across genotypes but was not correlated with leaf thickness, concentrations of chlorophyll or starch, or intercellular CO(2) concentration (c(i)). In the oldest cultivar, the relationship of A to c(i) did not change between morning and afternoon. In the two most recent lines, the slopes of the A:c(i) curves at limiting c(i) exceeded that of the oldest cultivar by 25 to 50% in the morning, but the differences were much smaller in the afternoon. The maximum A of the newer lines at high c(i) exceeded that of the oldest cultivar only in the morning. Breeding for increasing yield has enhanced the photosynthetic capacity and stomatal conductance of Pima cotton and altered the diurnal regulation of photosynthesis.

Intravenous recombinant tissue-type plasminogen activator in acute myocardial infarction

The efficacy and safety of intravenously administered recombinant tissue-type plasminogen activator (rt-PA, Boehringer Ingelheim Corp.) was investigated in 10 patients with acute myocardial infarction (AMI). rt-PA was given as a 10 mg bolus dose followed by infusions of 50 mg, 20 mg and 20 mg in three successive hours. All patients underwent baseline coronary angiography before thrombolytic therapy. Ninety minutes after the initiation of rt-PA infusion, recanalization of infarct-related coronary arteries as confirmed by angiography was achieved in 7 patients. The largest reduction in circulating fibrinogen was observed 4 to 6 h after the start of rt-PA infusion--14.3%. Moderate hemorrhage at the sites of arterial puncture occurred in 2 cases, probably as a result of heparin anticoagulation. No other side effects occurred. So rt-PA is an effective and safe thrombolytic agent.