Conformational interconversion in protein crystals

We present evidence that the structure of carbonmonoxy myoglobin crystals can be altered by lowering the pH. This structural change is monitored by the characteristic Fe-CO Raman modes at 508 and 491 cm-1 and is thought to involve a localized distal pocket transition from a "closed" conformation at pH 7 to a more "open" conformation at pH 4. These changes take place in the crystal without loss of intensity of a conformationally sensitive Raman mode at 252 cm-1 that signals a partial unfolding of the globin structure in solution. Quantitative studies, which monitor the open and closed populations as a function of laser photolysis, demonstrate that the interconversion rates (k+/-) in solution at 298 K are fast compared to the photolysis and CO entry rates (i.e. k+/- much greater than 10(3) s-1), while in frozen samples the interconversion is much slower than the experimental time scale (minutes). Since the open conformation is a minority species at pH 7, rapid exchange in aqueous solution is a necessary condition for this species to play a functional role. In the crystal, the interconversion rates are slowed compared to solution and begin to approach the photolysis rate (i.e. k+/- approximately 10(3) to 10(4) s-1). This indicates that the barriers for conformational exchange are increased in the crystal environment, compared to the solution, apparently due to the packing forces of the surrounding molecules. X-ray and neutron diffraction studies of MbCO crystals at high and low pH are needed to characterize the details of the structural changes and to test the hypothesis that closed and open distal pocket structures are associated with the 508 and 491 cm-1 Fe-CO modes.

Molecular cloning of the cDNA for the catalytic subunit of human DNA polymerase delta

The cDNA of human DNA polymerase delta was cloned. The cDNA had a length of 3.5 kb and encoded a protein of 1107 amino acid residues with a calculated molecular mass of 124 kDa. Northern blot analysis showed that the cDNA hybridized to a mRNA of 3.4 kb. Monoclonal and polyclonal antibodies to the C-terminal 20 residues specifically immunoblotted the human pol delta catalytic polypeptide. A multiple sequence alignment was constructed. This showed that human pol delta is closely related to yeast pol delta and the herpes virus DNA polymerases. The levels of pol delta message were found to be induced concomitantly with DNA pol delta activity and DNA synthesis in serum restimulated proliferating IMR90 cultured cells. The human pol delta gene was localized to chromosome 19 by Southern blotting of EcoRI digested DNA from a panel of rodent/human cell hybrids.

Histological examination of the auricular cartilage and pseudocyst of the auricle

In our histological examination of 42 ears (auricles) which were taken from 18 fetus and three adults, the intracartilaginous fibrous tissue with blood vessels and lymphatics were found in 12 ears and interruption of the auricular cartilage in 22 ears. The intracartilaginous connective tissue with blood vessels and lymphatics were linked together with the connective tissue outside the auricular cartilage in other sections. These findings support the hypothesis of congenital embryonic dysplasia as the origin of the formation of pseudocyst of the auricle.

[Distribution of microfilaments in rat Sertoli cells in vivo and in vitro]

The distribution of microfilaments (MFs) in rat Sertoli cells in vivo and in vitro was studied with electron microscopy and the TRITC-phalloidin staining method. The results revealed the following: The MFs of the Sertoli cells in vivo are arranged in bundles just beneath the cell membrane. MF bundles may form a band-like structure circumscribing the basal region of each Sertoli cell. The filaments and bundles are parallel with each other and their arrangement is symmetrical on the opposite sides of two adjacent Sertoli cell membranes. In vitro, the arrangement and distribution of MF bundles are closely related with the living and spreading state of the cell. In a fully spread cell, MFs bundles are arranged in parallel just beneath the cell membrane. We conclude that MFs in rat Sertoli cells are mainly arranged in bundles and stretched beneath the cell membrane. They may play an important role in maintaining the shape of the cell and the blood-testis barrier.

[Composition of essential oil from inflorescences of Rhaponticum uniflorum (L.) DC]

The essential oil was extracted from the inflorescences of Rhaponticum uniflorum which are used as a Mongolian drug. 30 compounds in the oil were identified by GC-MS and their percentages were determined by GC.

Energy and dose-rate dependence of neoplastic transformation and mutations induced in mammalian cells by fast neutrons

Since our original observation that low-dose, low-dose-rate JANUS neutrons produced more transformation in C3H 10T1/2 cells than equivalent doses at high dose rate (Hill, Buonaguro, Myers, Han, and Elkind, Nature 298, 67-69, 1982), there have been many reports on the dose-rate dependence of a variety of high-LET radiations. Some of these have qualitatively supported our original and subsequent observations, and some have found no evidence for a dose-rate effect. Thus there remain questions about the generality, size, tissue specificity, and reproducibility of these observations. Furthermore, there are no well-established mechanistic descriptions or observations to account for such effects. In this report studies are presented using a range of neutron energies produced by the UCLA cyclotron from 12- to 46-MeV protons on beryllium. In particular, emphasis is placed on comparing results between energies for neoplastic transformation and mutation end points, and preliminary data are presented on the molecular and mechanistic aspects of neutron-induced damage.

[The effect of plaque fluid on demineralization of enamel powder]

The aim of this study was to explore any substance in dental plaque which might affect the demineralization of enamel. Plaque fluid was prepared by centrifugation of pooled plaque from 56 young adults without periodontal diseases. Enamel was separated from healthy teeth of adolescents and crushed into powder. The enamel powder was treated separately by plaque fluid and synthetic plaque fluid (as a control, with similar calcium, fluoride content and pH as the natural). After this, the enamel powder was washed with PBS. Both the plaque fluid-treated and synthetic plaque fluid-treated enamel powder were demineralized by mixed organic acid (pH 4.5). The calcium content in both plaque fluids, PBS and organic acid after treatment with enamel powder was analysed by atomic absorption spectrophotometer. The results showed that there was no promoting effect in plaque fluid on demineralization of enamel, but, on the other hand, some protecting action was observed which might contribute to the presence of proteins in plaque fluid.

[The influence of vagotomy on stomach endocrine cells in rat]

The effects of unilateral truncal vagotomy (UTV) and bilateral truncal vagotomy (BTV) on antrum EC cells, G cells and oxyntic gland area argyrophil cells were studied in rats by using immunohistochemistry processes, Grimelius argyrophil stain and microscopic image analysis technique.

RESULTS

(1) In UTV animals, two weeks postoperation, the sectional areas of EC cells were significantly smaller in denervated side than In the other side (17%, P less than 0.05). In the innervated side of antrum, the sectional areas of EC cells were larger than those in controls (13.5%, P less than 0.05). But, five weeks after UTV, the size of EC cells was not significantly different in all animals. These suggest that vagal denervation can inhibit relatively the functional activity in a short period, but this inhibition could be compensated later. (2) There were no morphological changes in G cells of UTV rats. In BTV animals, the quantity of G cells in antrum increased by 36.2% (P less than 0.05) and their sectional areas were larger than those in sham by 26.2% (P less than 0.05). These indicate that the function of G cells is more active in BTV animals and the functional change of G cells is related to the pH value of gastric juice. (3) In UTV rats, the oxyntic gland area argyrophil cells (ECL cells are dominant) were significantly reduced in two weeks (26.8%, P less than 0.01) and in five weeks (20.1%, P less than 0.05) in denervated side after UTV. The cells became smaller also. These suggest that vagus can influence the function, proliferation and growth of ECL cells.

O6-methylguanine-DNA methyltransferase and human cancer chemotherapy

Two kinds of human tumor cell strains having different activity of O6-methylguanine-DNA methyltransferase (O6-MT) were transplanted into nude mice. Then the mice were injected intraperitoneally with bifunctional alkylating agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU). The tumors with low O6-MT activity were quickly suppressed or cured. The result suggests that some tumors, if provisionally determined with low O6-MT activity, might be efficiently cured by treatment with ACNU. This probably opens a new way for human cancer chemotherapy.

[Hemolytic reaction resulting from propafenone administration]

Although adverse reactions of many kinds caused by propafenone have been observed, yet there has been no documented report of hemolytic reaction. Four episodes of hemolytic reaction in three patients receiving intravenous propafenone were reported. These reactions took place a few hours after the administration and one of the episodes was complicated with acute left ventricular heart failure and shock. Cessation of propafenone administration together with relevant therapeutic measures tide the patients over and hemolysis disappeared in several hours. Toxicological examination revealed no physical or chemical deterioration and biological contamination of the remaining medication and no such reaction was noted when the drug of the same batch was given to other patients. It is considered that the hemolytic episodes were related to allergic constitution of the patients. Judging from the clinical manifestations, these episodes were hemolytic reactions of immune complex type.

Effective endothelialization of polyurethane surfaces. Response to shear stress and platelet adhesion

Biomer and Mitrathane are thromboresistant polyurethane ureas that are suitable for coating artificial valves. Degeneration of the surface coatings, however, does occur over time, and in experimental animal studies adherent thrombi have been observed as a complication. In this study, morphometric techniques applied to scanning electron microscopy were used to assess whether vascular endothelial cells harvested from jugular veins of fetal lambs could be grown to confluence on these polyurethane surfaces, whether the monolayer would remain intact under conditions of shear stress (104 dynes/cm2), and whether this would result in decreased platelet adherence of sheep platelets relative to nonendothelialized surfaces. The results have shown that both Biomer and Mitrathane could be endothelialized: 88.8 +/- 5.1% of the Biomer surface consisted of intact confluent endothelial cells, as did 95.45 +/- 1.7% of the Mitrathane surface. After 6 hr of shear stress, a significant reduction in this feature was observed (p = 0.02), but both materials still maintained a high percentage of confluent endothelial cells (78.65% for Biomer and 85.58% for Mitrathane). After 48 hr of shear stress, however, the percent confluence was similar to control values, which suggested new cell growth. Endothelialized Biomer compared with Mitrathane had fewer adherent single platelets, or small or large aggregates (p = 0.001, p = 0.01, and p = 0.05, respectively); this feature was not affected by shear stress. Whereas endothelialization of the surface clearly decreased platelet adherence on Mitrathane (p = 0.01), only a trend was seen with Biomer. These studies therefore show that endothelialization of these polyurethane surfaces is feasible.

[Scanning electron microscope observation on proximal enamel surfaces of normal teeth]

This observation was made on the proximal surfaces of normal permanent molars. Observations were concentrated mainly on those teeth with abraded contact areas on the mesial surface and the unabrasive distal surfaces if the partially or wholly embedded third molars. The results showed that the surfaces of the abraded contact areas were plain than those outside the contact. There were lots of pitted holes or fissures on the surfaces outside the contact areas. In the holes accumulations of bacteria could be seen. These holes and fissures could also be seen on the unexposed distal surfaces of the third molars, but no clear-defined traces of bacteria were observed in the holes.

Transcriptional control of the invariant chain gene involves promoter and enhancer elements common to and distinct from major histocompatibility complex class II genes

The invariant chain (Ii) is a glycoprotein coexpressed with the major histocompatibility complex (MHC) class II antigens. Although Ii is encoded by a single gene unlinked to the MHC gene complex, Ii and MHC class II appear to have similar patterns of tissue specific expression and generally are coordinately regulated by cytokines. Here we present evidence that transcription of the murine Ii gene is controlled by multiple cis-acting elements. The 5' regulatory region of the Ii gene appears to be combined of conserved class II regulatory elements with promoter elements commonly found in other eucaryotic genes. A region containing characteristic class II promoter elements (H box, X box, and a modified Y box) serves as an upstream enhancer in the Ii gene and might contribute to the coexpression of MHC class II and Ii genes. A series of positive control elements, the kappa B element, Sp1-binding site, and CCAAT box, are present in the Ii promoter and apparently serve distinct regulatory functions. The kappa B site in the Ii gene is a cell type-specific element, contributing to expression in a B-cell line but not in a fibroblast cell line, and the Sp1 site is required by the H-X-Y' enhancer element to stimulate promoter activity. In addition, an Ii enhancer in the first intron that specifically stimulates its own promoter has been identified. Our results suggest that a sequence match between enhancers and certain promoter elements is critical.

[Effects of proteolytic enzymes on demineralization of enamel]

Papain, trypsin and collagenase were used in the experiment for the study of their effects on the demineralization of enamel surface by organic acids in vivo. No effect of any of the enzymes was observed. The use of papain and trypsin in treating tooth surfaces in vitro, no matter whether sodium bisulfite was used, showed no effect on the demineralization of the enamel by mixed organic acids. But, by the analysis of amino acids in the enzyme solutions before and after treating tooth surface, it was shown that some proteinous substances were destroyed. Accordingly, it can be suggested that the enzyme takes no part in the destruction of the inorganic tooth substance.

Cytolysis of corneal epithelial cells by hydrogen peroxide

Superoxide radicals or products generated by these radicals in a xanthine/xanthine oxidase system lyse cultured rat and human corneal epithelial cells as measured in a chromium-51 release assay. Partial protection from this lysis is afforded by superoxide dismutase and complete protection is obtained with catalase. Hydrogen peroxide, a product of the dismutation of superoxide radicals, lyses these cells directly and is implicated as the toxic agent in the xanthine/xanthine oxidase reaction. Hydrogen peroxide also decreases cell proliferation and decreases the intact DNA. Therefore, hydrogen peroxide appears to be toxic to corneal epithelial cells. The implications of these data on the safety of hydrogen peroxide as a contact lens disinfectant are discussed.

Synthesis, characterization, and biodistribution of [113mIn]TE-BAT: a new myocardial imaging agent

In order to develop a new myocardial perfusion agent, new lipid-soluble complexes containing a net charge of +1 were evaluated. Synthesis, radiolabeling, characterization, and biodistribution of a unique indium complex, [113mIn]TE-BAT (tetraethyl-bis-aminoethanethiol), are described. The complex formation between In +3 and TE-BAT ligand is rapid, simple, and of high yield (greater than or equal to 95%). This process is amenable to kit formulation. The complex has a net charge of +1 and an In/ligand ratio of 1:1. Biodistribution in mice shows higher heart uptake and longer retention as compared to 201TI. This complex, when labeled with 111In, shows promise as a possible tracer for myocardial perfusion imaging.

[Screening for alpha-thalassemia using DNA analysis]

alpha-thalassemia was sought by gene mapping in 258 subjects selected on the basis of origin (25%), microcytosis (7%), or origin and microcytosis combined (64%). Abnormal fragments (Xba I/probe alpha) were found in 58 cases (22.5%). Using other restriction enzymes it was possible to determine the genotype alpha-/aa in 39 patients and the genotype alpha-/alpha- in 13 patients; 2 patients also exhibited hemoglobin H (alpha-/--) disease. alpha triplication anti-3.7 kb was found in 2 subjects and zeta-thalassemia in 2 other samples. 57 out of 58 patients originated from the thalassemia belt or from Africa. alpha-thalassemia is the most frequent hemoglobinopathy (21% of patients at risk) and hematologically is characterized by microcytosis. The Hb A2 level is decreased only in the alpha-/-- form of the disease. The main advantage of diagnosing zeta-thalassemias and alpha triplications lies in the possible clinical implications in the event of association with other hemoglobinopathies or beta-thalassemia.

UL5, a protein required for HSV DNA synthesis: genetic analysis, overexpression in Escherichia coli, and generation of polyclonal antibodies

The mutations in two DNA-negative ts mutants of herpes simplex virus type 1 (HSV-1), tsK13 and tsM19, have been previously mapped to a 2.0-kb fragment (coordinates 0.095-0.108) at the left end of the genome (S. Weller, D. Aschman, W. Sacks, D. Coen, and P. Schaffer, 1983, Virology 130, 290-305). Sequence analysis of the HSV-1 genome has revealed the existence of two open reading frames, UL5 and UL6, within this fragment (D. McGeoch, M. Dalrymple, A. Dolan, D. McNab, L. Perry, P. Taylor, and M. Challberg, 1988, J. Virol. 62, 444-453). In this paper we report fine mapping and sequence analysis of the mutations in tsK13 and tsM19 which unambiguously localize the mutations to UL5, predicted to encode a 99-kDa polypeptide. The mutation in tsK13 was shown to result in a single amino acid substitution, Pro236 to Leu, whereas tsM19 contains two substitutions, Pro236 to Ser and Ala249 to Val. Thus, both mutants are altered in Pro236. Temperature-shift experiments indicated that the UL5 gene product is required continuously during viral DNA synthesis, suggesting a direct role for the 99K protein in viral DNA synthesis. The UL5 gene product was overexpressed in Escherichia coli and used to generate polyclonal antibodies which detected proteins in HSV-1-infected cell extracts from 4 hr postinfection. Although a faint band of the predicted size (99 kDa) was observed, the majority of the immunoreactive material migrated as smaller bands which represent either proteolytic degradation during extraction or post-translational proteolytic modification of the UL5 gene product. Indirect immunofluorescence staining revealed that the UL5 gene product localizes to the nucleus in two patterns: diffuse staining throughout the nucleus and in discrete globules which appear at the periphery of the nucleus. Sequence analysis of the UL5 gene predicts that the 99-kDa protein contains a consensus sequence for an ATP binding site. Possible roles of this protein in viral DNA synthesis are discussed.

tRNA nucleotidyltransferase is not essential for Escherichia coli viability

The role of tRNA nucleotidyltransferase in Escherichia coli has been uncertain because all tRNA genes studied in this organism already encode the -C-C-A sequence. Examination of a cca mutant, originally thought to contain 1-2% enzyme activity, indicated that it actually produces an inactive fragment of 40 kd compared to 47 kd for the wild-type enzyme due to a nonsense mutation in its cca gene. To confirm that the residual activity in extracts of this strain is due to another enzyme, and that tRNA nucleotidyltransferase is non-essential, we have interrupted the cca gene in vitro, and transferred this mutant gene to a variety of strains. In all cases mutant strains are viable, although as much as 15% of the tRNA population contains defective 3' termini, and no tRNA nucleotidyltransferase is detectable. Mutant strains grow slowly, but can be restored to more normal growth by a relA mutation or by a decrease in RNase T activity. In the latter case the amount of defective tRNA decreases dramatically. These findings indicate that tRNA nucleotidyltransferase is not essential for E. coli viability, and therefore, that all essential tRNA genes in this organism encode the -C-C-A sequence.

[Comparison of nucleolar organizer regions (NORs) on chromosomes of cultured lymphocytes from cancer patients, high risk cancer family members and normal subjects]

Using the technique of AG-NORs, the number of silver-stained NORs on chromosomes of the peripheral lymphocytes from 10 cancer patients, 10 high risk cancer family members and 10 normal individuals was compared. It was found that the total mean value of AG-NORs was 5.46 +/- 0.00/per cell in cancer patients, 5.62 +/- 0.01/per cell in high risk cancer family members and 7.03 +/- 0.07/per cell in normal subjects. The total mean value of AG-NORs was markedly lower in the first two groups than in the third group (P less than 0.001). It seems to be due to the decrease of the transcribed activity of rRNA gene on chromosomes of the cultured lymphocytes in the first two groups. A probable relation between the carcinogenesis and decrease of NORs is shown. The transcribed activity of rRNA gene gives the expression to AG-NORs numbers with which the relation to carcinogenesis is briefly discussed with a review of the literature.