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Biomedical subjects

S Sugai

Publications and source records attributed to S Sugai.

At least 127 records · Page 7Linked to original sources
PubMed1991

Synthesis of 5-keto-5-oxime derivatives of milbemycins and their activities against microfilariae.

Starting from milbemycin D (1), milbemycin A4 (2) and milbemycin A3 (3), a series of 5-keto-5-oxime derivatives were synthesized by selective oximation at the alpha,beta-conjugated carbonyl function of the 5-ketomilbemycins (4-6). The activities of the synthesized compounds were studied in dogs naturally infested with microfilariae of Dirofilaria immitis. The 5-keto-5-oximes of milbemycin D (7), A4 (8) and A3 (9) had quite high efficacy to control the microfilariae and more potency than their parents, while the 5-O-acyl oximes (11-15) also exhibited high activity.

Animals↗
PubMed1991

Altered permeability of iris vessels following posterior chamber lens implantation: an electron microscopic study.

Altered permeability of the iris vessels of monkey eyes following extra-capsular cataract extraction and posterior chamber intraocular lens implantation was studied by transmission electron microscopy using horseradish peroxidase (HRP) as a tracer. In control animals, HRP-reaction products were confined to the vascular lumens and to a small number of vesicles on the luminal side of the endothelial cells. In experimental animals, however, the interendothelial junctions of the iris vessels were filled with HRP-reaction products, and the endothelial cells of the iris vessels contained a large number of HRP-labeled plasmalemmal vesicles that opened into the basal lamina. HRP-reaction products were also found in the surrounding iris stroma of these experimental animals.

Animals↗
PubMed1990

Kinetics of disulfide bond reduction in alpha-lactalbumin by dithiothreitol and molecular basis of superreactivity of the Cys6-Cys120 disulfide bond.

Kinetics of disulfide reduction in alpha-lactalbumin by dithiothreitol are investigated by measuring time-dependent changes in absorption at 310 nm and in CD ellipticity at 270 nm (pH 8.5 or 7.0, and 25 degrees C). When the disulfide-intact protein is folded, the kinetics are biphasic. The disulfide bond between the half-cystines-6 and -120 is reduced in the fast phase, and the other three disulfide bonds are reduced in the slow phase. The apparent rate constants of the two phases are both proportional to the concentration of dithiothreitol, indicating that both phases are expressed by bimolecular reactions. However, detailed molecular mechanisms that determine the reaction rates are markedly different between the two phases. The slow phase shows a sigmoidal increase in the reaction rate with increasing concentration of a denaturant, urea, and is also accelerated by destabilization of the native state on removal of the bound Ca2+ ion in the protein. The disulfide bonds are apparently protected against the reducing agent in the native structure. The fast phase reaction rate is, however, decreased with an increase in the concentration of urea, and the disulfide bond shows extraordinary superreactivity in native conditions. It is 140 times more reactive than normal disulfides in the fully accessible state, and three-disulfide alpha-lactalbumin produced by the fast phase assumes nativelike structure under a strongly native condition. As ionic strength does not affect the superreactivity of this disulfide bond, electrostatic contributions to the reactivity must be negligible. Inspection of the disulfide bond geometry based on the refined X-ray coordinates of baboon alpha-lactalbumin [Acharya et al. (1989) J. Mol. Biol. 208, 99-127] and comparison of the geometry with those in five other proteins clearly demonstrate that the superreactivity arises from the geometric strain imposed on this disulfide bond by the native structure folding. Relationships of the disulfide strain energy to the protein stability and the disulfide reactivity are discussed.

Chemical Phenomena↗
PubMed1990

An early immunoreactive folding intermediate of the tryptophan synthease beta 2 subunit is a 'molten globule'.

The refolding kinetics of the tryptophan synthase beta 2 subunit have been investigated by circular dichroism (CD) and binding of a fluorescent hydrophobic probe (ANS), using the stopped-flow technique. The kinetics of regain of the native far UV CD signal show that, upon refolding of urea denatured beta 2, more than half of the protein secondary structure is formed within the dead time of the CD stopped-flow apparatus (0.013 s). On the other hand, upon refolding of guanidine unfolded beta 2, the fluorescence of ANS passes through a maximum after about 1 s and then 'slowly' decreases. These results show the accumulation, in the 1-10 s time range, of an early transient folding intermediate which has a pronounced secondary structure and a high affinity for ANS. In this time range, the near UV CD remains very low. This transient intermediate thus appears to have all the characteristics of the 'molten globule' state [(1987) FEBS Lett. 224, 9-13]. Moreover, by comparing the intrinsic time of the disappearance of this transient intermediate (t1/2 35 s) with the time of formation of the previously characterized [(1988) Biochemistry 27, 7633-7640] early immunoreactive intermediate recognized by a monoclonal antibody (t1/2 12 s), it is shown that this native-like epitope forms within the 'molten globule', before the tight packing of the protein side chains.

Circular Dichroism↗
PubMed1990

DNA autosensitivity in two Japanese sisters.

Two cases of DNA autosensitivity in Japanese sisters are reported. Both patients developed painful ecchymoses and other bleeding disorders. Skin tests with autologous leukocyte lysates and calf thymus DNA produced intermediate-type reactions that were identical to spontaneous skin reactions. Pretreatment of DNA with either DNase or chloroquine sulfate inhibited these reactions. Our studies suggest that anti-DNA antibodies might contribute to the clinical symptoms of this disorder.

Adult↗
PubMed1990

Cellular adhesiveness on implanted lenses in monkeys.

Cells are known to adhere to implanted intraocular lenses (IOLs), but the mechanisms of this adhesiveness are not known. We studied cellular adhesiveness on four posterior chamber IOLs that had been implanted into monkey eyes. The animals were killed at 4 and at 7 days after lens implantation. The IOLs were removed and examined by transmission electron microscopy. At 4 days after IOL implantation, macrophages were attached to the IOL surface; at 7 days after implantation, multinucleated giant cells were attached to the IOL surface. These cells had bundles of microfilaments in the subplasmalemmal region of areas of close cell-IOL apposition. These microfilaments may play an important role in the cellular adhesiveness on the surface of implanted IOLs.

Animals↗
PubMed1990

Conformational comparisons among homologous bony fish 5S ribosomal RNAs.

The reversible thermal melting of homologous 5S ribosomal RNAs of three bony fishes, rainbow trout (Salmo gairdneri), carp (Cyprinus carpio), and dog salmon (Onchorhynchus keta), were compared in aqueous salts (sodium chloride and/or divalent metal chlorides) by means of differential optical absorption at 260 and 280 nm, and c.d. at 265 nm. The melting parameters of the multiphasic melting process were conserved among the homologous RNAs, and it was shown that they did not depend on the methods of measurement but on concentrations of [Na+] and of [metal2+]. Other physicochemical methods, such as FT-IR absorption, gave the same melting profiles as the u.v. methods. The c.d. spectrum was homologous among the ribosomal RNAs. The melting is explained by changes in local structures in the 'consensus secondary structure model'. Also, stabilization of the secondary and tertiary structures by binding of Mg2+ and Ca2+, and the catalysed hydrolysis of the main chains by various divalent ions are discussed.

Animals↗
PubMed1990

Cellular reaction on the surface of intraocular lenses removed from human eyes.

We studied four angle-supported anterior chamber lenses whose optics and haptics were made of poly(methyl methacrylate). All four lenses had been removed from human eyes because of bullous keratopathy. Using light and electron microscopy, we compared the cellular reaction on the optics, which had been in the anterior chamber, with that on the haptics, which had been in touch with the iris stroma. A typical foreign body granuloma was seen around the haptics, while the optics were free of foreign body reaction.

Aged↗
PubMed1990

Light and electron microscopic study of vacuolated cells in immunoblastic lymphadenopathy-like T-cell lymphoma.

Three cases of immunoblastic lymphadenopathy (IBL)-like T-cell lymphoma were analyzed immunologically, and the ultrastructure of mononuclear cells in the lymph nodes and peripheral blood was examined. In the peripheral blood, light microscopic examination revealed vacuolated lymphocytes. These vacuolated lymphocytes formed rosettes with sheep erythrocytes, and they were CD3- and CD4-positive using the avidin-biotin method in cases 1 and 2. Electron microscopic examination revealed two kinds of abnormal lymphocytes. One kind was of B-cell nature with rich lamellated rough-surfaced endoplasmic reticulum and mitochondria. The other kind had a large cytoplasm, in which Golgi apparatus, some endoplasmic reticulum, some mitochondria and a few vacuoles were seen. Some of these vacuoles had remnants of mitochondrial cristae or were enlarged endoplasmic reticulum. The vacuolated T lymphocytes and activated lymphocytes of B-cell nature disappeared with chemotherapy but reappeared with relapse of the disease. These observations suggest that vacuolated cells are related to pale cells in lymph node sections. In other words when these vacuolated cells are found in the peripheral blood of patients with lymphoid malignancies, IBL-like T-cell lymphoma can be suspected.

Aged↗
PubMed1990

Studies on eye irritation caused by chemicals in rabbits--1. A quantitative structure-activity relationships approach to primary eye irritation of chemicals in rabbits.

A quantitative structure-activity relationship (QSAR) approach has been applied to the analysis of the relation between the structural features of chemicals and the primary eye irritation in rabbits. One hundred thirty one heterogeneous chemicals including medicals, pesticides, detergents and organic solvents were used in this study. The eye irritation ratings were made in three classes on the basis of the recovery time of corneal and conjunctival damages. Thirty six descriptors were used to describe the molecules. To correlate eye irritation ratings with the descriptors, a QSAR model was formulated by the adaptive least-squares method. A three-class discrimination was made as follows; class I included 23 chemicals which induced the damages recovering within 24 hr, class II included 64 chemicals which induced the damages persisting for more than 24 hr but recovering within 21 days, class III included 44 chemicals which induced the damages not recovering within 21 days. The discriminant function included 18 descriptors. The accuracy in classifying the chemicals was 86.3% in the recognition and 74.0% in the leave-one-out prediction. These results suggest that QSAR analysis is valuable to predict the primary eye irritation of chemicals.

Animals↗
PubMed1990

[Immunohistochemical study of the surface membrane on a intra-ocular lens].

Surface membranes of intraocular lenses implanted in three rabbit, were studied immunohistochemically with anti-rabbit fibronectin serum and anti-rabbit whole serum antiserum. The specimens were embedded in an epoxy resin and cut at 1 micron. Before the immunostaining procedure, the sections were placed in a solution of saturated NaOH in absolute ethanol to remove the epoxy resin. Immunostaining procedure was performed by routine avidin-biotin-peroxidase technique. The surface membranes showed positive reactions against both anti-sera. These results indicated that the surface membrane of implanted intraocular lenses was composed of fibronectin with some other serum proteins.

Animals↗
PubMed1990

[Identification of cells in deposits on the intraocular lens surface].

We performed posterior chamber lens implantation in a monkey eye and removed the lens on the 14th day after implantation. Cellular deposits on the IOL were observed by a dissecting microscope. Two kinds of cells, large and small, were observed on the lens surface. The large cells constituted the major proportion of the deposits. The same cellular deposits, which were observed by the dissecting microscope, were examined by scanning electron microscopy and then by transmission electron microscopy. The large cells had the structural features of multinucleated giant cells, and the small cells were macrophages.

Animals↗
PubMed1990

[Morphological study of the disruption of the blood-aqueous barrier following paracentesis].

Long-term morphological changes of the blood-aqueous barrier following paracentesis were studied in monkeys. Horseradish peroxidase molecules given intravenously were detected in the intercellular space beyond the tight junction between the nonpigmented ciliary epithelial cells in a monkey 7 days after the operation. The data demonstrated that the breakdown of the blood-aqueous barrier was not functionally repaired 7 days after the operation. Cysts were observed at the most anterior portions of the ciliary processes in monkeys surviving for 14 days to 1 year. These cysts consisted of two layers of both pigmented and nonpigmented epithelial cells. These findings suggest that the breakdown of the blood-aqueous barrier remains not to be repaired for log periods.

Animals↗
PubMed1989

Hydrogen exchange of the tryptophan residues in bovine, goat, guinea pig, and human alpha-lactalbumin.

Hydrogen exchange of the individual tryptophan residues of bovine, goat, guinea pig, and human alpha-lactalbumin has been studied by both ultraviolet and NMR spectra. The assignment of the slowly exchanging imino proton resonances to the tryptophan residues (Trp26 and Trp60) was obtained by comparison of the nuclear Overhauser effect difference spectra of bovine, guinea pig, and human alpha-lactalbumin. Taking account of the thermal unfolding of each alpha-lactalbumin, the hydrogen exchange rates of the individual tryptophan residues are analyzed. The temperature dependence of the exchange rates classified their exchange mechanisms into two exchange processes: the "low activation energy process" and the "high activation energy process" which is associated directly with the global thermal unfolding of the protein. Trp26 of alpha-lactalbumin exchanges through the high activation energy process. The exchange behavior of Trp26 of guinea pig alpha-lactalbumin suggests a difference of the globally unfolded state of the protein from the other species. The exchange mechanism of Trp60 of human alpha-lactalbumin is the low activation energy process in contrast with those of the bovine and goat proteins, although their global thermodynamic properties are similar to each other. Trp104 and Trp118 of alpha-lactalbumin exchange through the low activation energy process, and the reaction rates are affected by the local structural differences around the tryptophan residues among these proteins. The results presented in this paper indicate that the hydrogen exchange rate through the low activation energy process provides the information only about the local nature of a protein while that through the high activation energy process provides the information about the global nature of a protein.

Animals↗
PubMed1989

The evolution of lysozyme and alpha-lactalbumin.

From the analysis of phylogenetic trees constructed from the amino acid sequences and metal-binding properties of various lysozymes c and alpha-lactalbumins, it was found that before the divergence of the lineages of birds and mammals, calcium-binding lysozyme diverged from non-calcium-binding lysozyme. alpha-Lactalbumin evolved from the calcium-binding lysozyme along the mammalian lineage after the divergence of birds and mammals. Rapid evolution took place, not in the process of acquisition of the activity of alpha-lactalbumin, but after the loss of lysozyme activity, due to the change in the distribution of selective pressure on each amino acid site. A general process for the change in function of a protein during evolution is suggested to be as follows: after duplication of the gene, one of their protein products acquires a new function, besides that already present; the old function is eventually lost.

Amino Acid Sequence↗