[Observation on enhanced adhesion to dentin by amino acid]

An amino acid was adopted to pretreat the surface of dentin. The bond strength between GP adhesive and dentin mediated by the amino acid was enhanced after the pretreatment. Furthermore, the longer the stored time of extracted tooth was, the better the effect of adhesion was. This pretreatment will benefit the adhesive restoration for dead tooth or low activity tooth clinically.

Relative adherence of Bacteroides species and strains to Actinomyces viscosus on saliva-coated hydroxyapatite

The study was designed to compare the adherence of several Bacteroides species to A. viscosus. Using 3H, we labeled 24 laboratory strains, including 13 Bacteroides species and 11 fresh clinical isolates of three Bacteroides species. Their adherence to A. viscosus bound to a saliva-coated mineral surface was quantified by liquid scintillation. Adherence relative to a standard strain, B. gingivalis 2561, was compared. Among the lab bacteroides, those of B. gingivalis (eight strains) were the greatest binders (mean, 80.5 +/- 12.4%). Strains of other lab bacteroides bound less well (mean, 33.4 +/- 6.3%). The difference in means was statistically significant (p less than 0.01). The mean for B. gingivalis strains was also significantly greater than that for strains of B. intermedius (51.7 +/- 6.2%). Attachment of B. gingivalis was saturable in experiments in which either input concentration or time was the independent variable, indicating that B. gingivalis cells do not accumulate in this vitro simulation of plaque formation by binding to each other. Subculture did not seem to affect the degree of binding.

Proteolytic processing of a coleopteran-specific delta-endotoxin produced by Bacillus thuringiensis var. tenebrionis

Insecticidal protein delta-endotoxin crystals harvested from sporulated cultures of Bacillus thuringiensis var. tenebrionis contain a major polypeptide of 67 kDa and minor polypeptides of 73, 72, 55 and 46 kDa. During sporulation, only the 73 kDa polypeptide could be detected at stage I. The 67 kDa polypeptide was first detected at stage II and increased in concentration throughout the later stages of sporulation and after crystal release, with a concomitant decrease in the 73 kDa polypeptide. This change could be blocked by the addition of proteinase inhibitors. Trypsin or insect-gut-extract treatment of the delta-endotoxin crystals after solubilization resulted in a cleavage product of 55 kDa with asparagine-159 of the deduced amino acid sequence of the toxin [Höfte, Seurinck, van Houtven & Vaeck (1987) Nucleic Acids Res. 15, 71-83; Sekar, Thompson, Maroney, Bookland & Adang (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 7036-7040; McPherson, Perlak, Fuchs, Marrone, Lavrik & Fischhoff (1988) Biotechnology 6, 61-66] at the N-terminus. This polypeptide was found to be as toxic in vivo as native delta-endotoxin.

[Inhibition of release of prostaglandins and leukotrienes from calcimycin-induced mouse peritoneal macrophages and bovine aorta endothelial cells by anisodamine]

[3H]Arachidonic acid (AA)-prelabeled mouse peritoneal macrophages were stimulated by calcium ionophore A-23187 to release [3H]AA metabolites. The major labeled products which were co-chromatographed with the authentic PG and LT standards by TLC and determined by liquid scintillation were 6-keto-PGF1 alpha, PGE2, LTC4, and LTB4. Anisodamine (Ani) significantly inhibited the A-23187-induced release of PG and LT from mouse macrophages in a dose-dependent manner. In the presence of Ani at 0.5 mmol/L, the A-23187-induced release of 6-keto-PGF1 alpha, PGE2, LTC4 and LTB4 was reduced by 57%, 20%, 53% and 49%, respectively. A-23187-induced release of 6-keto-PGF1 alpha measured by RIA from bovine aorta endothelial cells was also significantly inhibited by Ani in a dose-dependent manner. These results indicate that the calcium-antagonistic effects of Ani may not only play a significant role in its inhibiting release of PG and LT, but also contribute to its salutary effects in the treatment of septic shock.

Overproduction of the protein encoded by the maize transposable element Ac in insect cells by a baculovirus vector

The polypeptide encoded in the Activator (Ac) element of Zea mays L. has been expressed in Spodoptera frugiperda insect cells using plasmids which carry the strong polyhedrin promoter of the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV). Recombinant AcNPVs with the Ac-cDNA integrated and under the control of the viral polyhedrin promoter have been isolated and their genomes have been partly characterized as to the location of the foreign DNA insert. Upon infection of S. frugiperda cells with the recombinant AcNPV, maize Ac element specific messenger RNAs, as well as a newly synthesized polypeptide with an apparent molecular weight of about 116 kDa, have been detected in extracts of recombinant infected cells. This polypeptide is absent from extracts of wild-type infected cells expressing the polyhedrin polypeptide which can be recognized by the presence of nuclear inclusion bodies. Recombinant infected cells lack this protein. The Ac specific polypeptide is detected by antisera, which have been raised against fusion proteins containing Ac sequences synthesized in Escherichia coli, both in immunoprecipitation and in Western blotting experiments. The Ac specific protein is a nuclear phosphoprotein and represents about 1%-2% of the newly synthesized protein.

Purification and properties of the NusB protein of Escherichia coli

Mutations in the nusB gene of Escherichia coli block transcriptional antitermination mediated by the N gene protein of bacteriophage lambda. We describe here two methods of overproducing the NusB protein in E. coli and a method of purifying NusB to apparent homogeneity on a large scale. Purified NusB directly stimulates transcriptional antitermination by the lambda N protein in vitro. It behaves as a monomer (Mr = 15,689) during gel permeation chromatography and gradient sedimentation. The number of NusB molecules in a wild type E. coli K12 cell ranges from about 3,000 to about 6,000 molecules/cell, depending on the growth medium, and is about 50-80% of the number of molecules of the core component of RNA polymerase in the cell. This implies that NusB has a major role in regulating chain elongation during the transcription of E. coli genes. Many E. coli strains with nusB mutations cannot grow at low temperature. However, a sup+ strain with the suppressible amber mutation nusBam115 can grow at 42 degrees C. Since such a strain does not produce NusB protein detectable by immunoprecipitation with anti-NusB, normal amounts of NusB are not essential for the survival of E. coli at 42 degrees C.

Trace element content in drinking water of nasopharyngeal carcinoma patients

Chinese in the Xiangxi region of Hunan province in China have a high incidence of nasopharyngeal carcinoma (NPC). For analyzing the relation between NPC and trace elements, the concentrations of 7 trace elements in drinking water (well water) of high- and low-incidence areas were measured (75 samples). The results showed that the concentrations of Ni, Zn and Cd in drinking water of high-incidence areas were significantly higher than those in low-incidence areas. Especially, the Ni level in drinking water had a significant positive correlation with NPC mortality. These observations are consistent with earlier studies. We also found a highly positive correlation between Ni/pH value in drinking water and NPC mortality. This suggests that only considering the ion concentration in drinking water is not enough, we should also pay attention to the pH of the drinking water when we study the relation between NPC and trace elements. Because the pH of the medium can strongly affect trace element chemical characteristics and its metabolic state in living systems, the M/pH (M, metal concentration) may be an important factor worthy of further research.

An elongation control particle containing the N gene transcriptional antitermination protein of bacteriophage lambda

The N gene transcriptional antitermination protein of bacteriophage lambda is incorporated in vitro into transcriptional elongation complexes containing the E. coli proteins NusA and NusB. The binding of NusA to elongating RNA polymerase is sequence-independent and follows the release of sigma 70. Incorporation of N into the elongation complex requires an N utilization site (nut site) on the DNA template. Incorporation of NusB into the complex requires NusA, ribosomal protein S10, and the boxA component of the nut site. T1 RNAase releases N, but not NusB, from the elongation complex. We therefore propose that an N-modified termination-resistant elongation complex includes an elongation control particle (ECP) containing at least NusA, NusB, S10, N, and an RNA transcript of the nut site.

Formation of lymphocyte colonies under serum-free culture conditions in normal individuals and patients with chronic lymphocytic leukemia

This paper describes a culture system which supports the formation of B cell and some T cell colonies under serum-free conditions in peripheral blood samples of normal individuals and patients with chronic lymphocytic leukemia (CLL) of B cell type. In this system, serum is replaced by bovine serum albumin, transferrin, cholesterol, insulin and catalase or horseradish peroxidase. In addition, it is necessary to add staphylococcus protein A, mitomycin-treated T cells as feeders and phytohemagglutinin leukocyte-conditioned medium as a source of growth factors. The plating efficiency is greatly enhanced when normal cells are incubated with galactose oxidase prior to plating and when CLL cells are exposed sequentially to neuraminidase and galactose oxidase.

[Preliminary study on the nucleic acid hybridization technic in detecting HSV-2 DNA corresponding sequence of cancer tissues of the uterine cervix]

In this paper, 34 samples, 25 from 18 cervical carcinoma patients and 9 from 8 non-cervical carcinoma patients, were assayed using (alpha-32P) dCTP HSV-2 DNA probe and nucleic acid hybridization technic. It was shown that the positive rates of HSV-2 DNA corresponding sequence were 50% (2/4), 36% (5/14) and 12% (1/8) in the in situ cancer, invasive cancer and non-cervical cancer tissues. No HSV was isolated from 7 cancer specimens which showed a positive reaction by nucleic acid hybridization.

Reversal of the effects of cyclosporin A on the production of human interferon-gamma

Previous reports have documented that cyclosporin A (CsA) can inhibit the production of interferon-gamma (HuIFN-gamma) and interleukin-2 (IL-2). In this report we have extended these earlier findings and have demonstrated that the defect in the production of HuIFN-gamma persists even after the CsA is removed and is associated with altered synthesis of other lymphokines, mainly a cytotoxin and leukocyte migration inhibition factor. In the presence of recombinant exogenous IL-2, the effect of CsA on the synthesis of HuIFN-gamma can be reversed depending on the concentrations of both the IL-2 and CsA. In addition, the presence of the calcium ionophore A23187 partially reverses the inhibitory effect of CsA by synergistically enhancing the synthesis of HuIFN-gamma.

First report of an epidemic of diarrhoea in human neonates involving the new rotavirus and biological characteristics of the epidemic virus strain (KMB/R85)

An outbreak of diarrhoea in neonates occurred at the nurseries of the Department of Obstetrics of Zhao Tong Regional Hospital, Yunnan Province, from the middle of August to the end of November, 1985. Fifty-one percent of children were affected 2-8 days after birth. The clinical symptoms were mild; patients mainly had diarrhoea and did not vomit. Rotaviruses were detected in 66.7% by RNA PAGE and in 72.7% by EM. The virus strain designated as KMB/R85 had a typical morphology, which was indistinguishable from that of infantile rotaviruses by EM. The viral RNA genome was composed of 11 segments. The buoyant density in CsCl was 1.377 g/cm3. The KMB/R85 strain possessed a hemagglutinin for rhesus monkey erythrocytes. By ELISA, IEM, and HAI, it was found that KMB/R85 strain did not possess the common group antigen shared by group A rotaviruses and was antigenically similar to the Chinese adult diarrhoea rotavirus (serogroup B).

Size and shape of the Escherichia coli lactose permease measured in filamentous arrays

The Escherichia coli lactose permease has been purified on cation exchanger to contain a minimal amount of phospholipids, i.e., 4-5 mol/mol of permease, in the presence of the detergent dodecyl beta-maltoside at its critical micelle concentration. This preparation is active in galactoside binding. When the detergent level is further reduced by dialysis, the lactose permease forms filaments one molecule wide and up to several micrometers long. The filaments tend to associate laterally to form sheets. Analysis of electron micrographs of negatively stained filamentous arrays indicates an average filament spacing of 51 A and a subunit period of 26-30 A along individual filaments. These values most probably correspond to the dimensions of the lactose permease molecule measured parallel to the membrane plane. In many filaments, the subunits show a stain-penetrated cleft. It suggests that the lactose permease molecule comprises two domains, which may be correlated with internal repeats between the N- and C-terminal halves of the polypeptide sequence.

Demographic variation and survival in discrete population models

Persistence and extinction attributes of a discrete population model are explored on both a finite and an infinite time horizon. For a first-order autonomous nonlinear difference equation, a classification is found of when, for each positive integer N, trajectories go to extinction at time N. The dynamic complexity that is known to permeate difference-equation models is also present in the survival analyses developed here. Also found is an interesting decomposition of the continuum of initial population sizes into intervals where populations are persistent at time N and intervals leading to extinction at time n less than or equal to N.