Molecular basis for the species selectivity of the neurokinin-1 receptor antagonists CP-96,345 and RP67580.

Two non-peptide substance P antagonists exhibit opposite rank orders of potency for the human and rat neurokinin-1 receptors. CP-96,345 shows selectivity for the human receptor, whereas RP67580 shows selectivity for the rat receptor. Amino acid sequence comparison of the two receptors reveals 22 divergent residues. To elucidate the molecular basis for the species selectivity of these antagonists, divergent residues in the human neurokinin-1 receptor were substituted by the rat homologs. Analysis of mutant receptors revealed that substitution of 2 residues (V116L and I290S) in the transmembrane domain of the human neurokinin-1 receptor is both necessary and sufficient to reproduce the antagonist binding affinities of the rat receptor. The nature of these substitutions and the magnitude of the changes in binding affinity suggest that residues 116 and 290 do not interact directly with the antagonist molecules. The present results support a model in which phylogenetically conserved residues interact directly with the antagonists, while phylogenetically divergent residues affect the local helical packing of the receptor. Such a change in local structure would lead to increased binding affinity for one class of antagonists and decreased affinity for another.     

The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions.

Accumulating evidence suggests that the matrix (MA) protein of retroviruses plays a key role in virus assembly by directing the intracellular transport and membrane association of the Gag polyprotein. In this report, we show that the MA protein of human immunodeficiency virus type 1 is also critical for the incorporation of viral Env proteins into mature virions. Several deletions introduced in the MA domain (p17) of human immunodeficiency virus type 1 Gag polyprotein did not greatly affect the synthesis and processing of the Gag polyprotein or the formation of virions. Analysis of the viral proteins revealed normal levels of Gag and Pol proteins in these mutant virions, but the Env proteins, gp120 and gp41, were hardly detectable in the mutant virions. Our data suggest that an interaction between the viral Env protein and the MA domain of the Gag polyprotein is required for the selective incorporation of Env proteins during virus assembly. Such an interaction appears to be very sensitive to conformational changes in the MA domain, as five small deletions in two separate regions of p17 equally inhibited viral Env protein incorporation. Mutant viruses were not infectious in T cells. When mutant and wild-type DNAs were cotransfected into T cells, the replication of wild-type virus was also hindered. These results suggest that the incorporation of viral Env protein is a critical step for replication of retroviruses and can be a target for the design of antiviral strategies.     

Karyotypes of Pneumocystis carinii from Korean rats.

Molecular karyotyping was applied to Pneumocystis carinii(Pc) from two strains of experimental rats, Sprague Dawley(SD) and Fisher(F), in Korea. Field inversion gel electrophoresis and contour clamped homogeneous electric field electrophoresis resolved 15 chromosomal bands from the Pc. The size of the bands was estimated 270kb to 684kb from SD rats, and 273kb to 713 kb from F rats. The bands of 283 kb from SD rats and of 273 kb from F rats stained more brightly suggesting duplicated bands. Total number of chromosomes was at least 16, and total genomic size was estimated 7 x 10(6) bp. All of the bands from F rats hybridized to the probe of repeated DNA sequences of Pc and the band of 448 kb size was proved to contain rDNA sequences, but Pc. chromosome bands from SD rats showed no reactions to the probes. The 2 different karyotypes of P. carinii from 2 strains of rats were maintained consistently for 2 years.     

Effects of chronic clonidine administration on parasympathetic-evoked rat saliva.

Effects of chronic administration of clonidine on parasympathetic-evoked saliva from both parotid and submandibular glands were investigated. Clonidine at 1 mg/kg/day for 5 or 7 days caused a significant reduction in the salivary secretion (flow rate and total volume) evoked by parasympathetic nerve stimulation of parotid but not submandibular glands. Ion concentrations (Na, K and Ca) of parasympathetically nerve-evoked parotid saliva were not altered. However, the total protein concentration as well as output, amylase activity, and output of such saliva were markedly increased. Possible mechanisms for clonidine-induced increase in nerve-elicited salivary protein concentration include release of neuropeptides, and changes in adrenergic receptor binding which need further study.     

Anticlastogenic effect of flavonoids against mutagen-induced micronuclei in mice.

14 flavonoids, including flavone and flavonol derivatives, were tested for their anticlastogenic effect against induction of micronuclei by benzo[a]pyrene in polychromatic erythrocytes of mice. When each flavonoid was administered orally, together with intraperitoneally administered benzo[a]pyrene, most flavonol derivatives showed an anticlastogenic effect. The data suggest that the 2,3-double bond and 3,5,7-hydroxyl groups in the flavonoid molecules may be essential to produce anticlastogenic effects against benzo[a]pyrene. Galangin, one of the active compounds, and (-)-epicatechin, a weak one, were administered to mice in order to compare their anticlastogenic effect against 3 different kinds of carcinogens: ethyl methanesulfonate, 7,12-dimethylbenz[a]anthracene, and adriamycin. Galangin showed a stronger anticlastogenic effect than (-)-epicatechin against ethyl methanesulfonate and 7,12-dimethylbenz[a]anthracene. However, there was no significant effect against adriamycin-induced micronuclei by both compounds. Our study indicates that most flavonoids are anticlastogenic agents. Their anticlastogenic effects are apparently independent of their own clastogenic activities. Furthermore, their anticlastogenic activities do not apply universally to all types of genotoxic chemicals.     

Maturation and fertilization of porcine oocytes in vitro

Four experiments were conducted to study 1) factors affecting porcine oocyte maturation in culture medium and 2) a new method for oocyte maturation outside the porcine body. In Experiment 1, five groups of oocytes were cultured in m-TCM199 or m-KRB medium for 24 to 28, 32 to 36 or 40 to 42 hours and then were fertilized in vitro. The cleavage rate (two to four-cell stage) of oocytes cultured for 32 to 36 hours was significantly higher than those of the other oocytes. The results indicate that a suitable culture period for the in vitro maturation of porcine oocytes is 32 to 36 hours. In Experiment 2, four groups of oocytes were cultured in m-KRB or m-KRB supplemented with PFF, PMSG or FSH for in vitro maturation, and the cleavage rates of oocytes were 7.94, 22.56, 30.23 and 23.26%, respectively, after in vitro fertilization. The results show that porcine follicular fluid (PFF) and gonadotrophins added to the culture medium promote porcine oocyte maturation in vitro. In Experiment 3, oocytes were cultured in m-KRB or m-TCM199, supplemented with both gonadotrophin and pocine folliclar fluid for maturation in vitro. After fertilization in vitro, the cleavage rates of oocytes were 26.32 and 27.93% for the two media. The results indicate that the difference between m-KRB and m-TCM199 was insignificant when the media were used to culture porcine oocytes. But there was a significant difference when PFF and gonadotrophins were added to the basic media. In Experiment 4, porcine oocytes were transferred into the reproductive tracts of other animals for maturation. After 34 to 36 hours, the oocytes were collected and fertilized in vitro. The cleavage rates of oocytes were 10.42, 28.45, 3.33 and 36.36%, respectively, for the oocytes matured in mouse uterine horns, rat uterine horns, rat oviducts or rabbit oviducts. The results show that porcine oocytes can be matured in the reproductive tracts of other animals.     

Complementing amino acid substitutions within loop 6 of the alpha/beta-barrel active site influence the CO2/O2 specificity of chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase

Photosynthesis-deficient mutant 45-3B of the green alga Chlamydomonas reinhardtii contains a chloroplast mutation that causes valine-331 to be replaced by alanine within the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. This amino acid substitution occurs in loop 6 of the alpha/beta-barrel active site, three residues distant from catalytic lysine-334. The mutation reduces the specific activity of the enzyme and also reduces its CO2/O2 specificity factor by 42%, but the amount of holoenzyme is unaffected. In a previous study, an intragenic-suppressor mutation, named S40-9D, was selected that causes threonine-342 to be replaced by isoleucine, thereby increasing the CO2/O2 specificity of the mutant enzyme by 36%. To determine which other residues might be able to complement the original mutation, nine additional genetically independent revertants have now been analyzed. Another intragenic suppressor, represented by mutation S61-2J, causes glycine-344 to be replaced by serine. This change increases the CO2/O2 specificity of the mutant enzyme by 25%. Of the revertants recovered and analyzed, the mutant enzyme was improved only due to true reversion or by intragenic suppression mediated by substitutions at residues 342 or 344. Changes in the physical properties of the two pairs of complementing substitutions indicate that steric effects within loop 6 are responsible for the observed changes in the CO2/O2 specificity of the enzyme.     

Quantitative cell composition of human and bovine corpora lutea from various reproductive states

The cell composition of human and bovine corpora lutea (CL) from various reproductive states was investigated by computerized video-based interactive Bioquant image analysis system IV and by light microscope immunocytochemistry. Human and bovine CL contained more nonluteal cells than luteal cells. Human CL contained a lower number of luteal and a greater number of nonluteal cells than bovine CL. Regardless of the reproductive state, human CL contained more small luteal cells than large luteal cells. In all reproductive states except in the late luteal phase, the bovine CL also contained more small luteal cells than large luteal cells. The average sizes of all the cells in human CL were smaller than in bovine CL. Human CL contained more vascular space than bovine CL during mid and late luteal phases. The number of luteal cells increased and nonluteal cells decreased from early to mid luteal phase, and then luteal cells decreased and nonluteal cells increased in late luteal phase and in degenerating human and bovine CL. While the change of number of small and large luteal cells first occurred from early to mid luteal phase in human CL, it did not take place until the late luteal phase in bovine CL. The average size of large luteal cells in humans and of small luteal cells in cattle did not change, whereas size of the other cells changed in different reproductive states in both human and bovine CL. The cell composition of term pregnancy human CL was similar to mid or late luteal phase, whereas the cell composition of early pregnancy bovine CL was similar to mid luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunocytochemical localization of relaxin in human corpora lutea: cellular and subcellular distribution and dependence on reproductive state

Relaxin is one of the hormones present during pregnancy and it is synthesized primarily by corpora lutea (CL). Other reproductive tissues including CL of the menstrual cycle may also synthesize this hormone. Very little is known, however, about the cellular and subcellular distribution of relaxin in human CL and dependence of luteal relaxin on the reproductive state. The light and electron microscope immunocytochemical studies described here were undertaken to obtain this information using antisera to porcine and human relaxin. Immunostaining was found in large luteal cells (17-30 microns) but not in small luteal cells (7-16 microns) or in nonluteal cells in any of the reproductive states or in human hepatocytes. Luteal immunostaining was low in early luteal phase; it increased progressively, reaching the highest level in late luteal phase, and then decreased greatly in corpora albicantia. Term pregnancy CL contained similar immunostaining as early luteal phase CL. Mid luteal phase CL contained more immunostained cells than late luteal phase CL, but the late luteal phase CL contained a greater amount of immunostaining per cell than mid luteal phase CL. The immunogold particles due to relaxin were primarily present in secretory granules and to a small extent in rough endoplasmic reticulum. Quantitation revealed that secretory granules contained a much higher number of gold particles than did rough endoplasmic reticulum. These two organelles from late luteal phase CL contained greater numbers of gold particles than those from mid luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protection against acute paraquat toxicity by ambroxol

An expression vector for G-CSF, pASLB3-3, was constructed and introduced into Namalwa KJM-1 cells (Hosoi et al., 1988), and cells resistant to 100 nM of methotrexate (MTX) were obtained. Among them, the highest producer, clone SC57, was selected and the productivity of this clone was further characterized. The maximal production of G-CSF was at the most 1.8 g/ml/day using a 25 cm² tissue culture flask, even though the cell number was above 7×10⁵ cells/ml. The limiting factors at high density were analyzed as the deficiency of nutrients, such as glucose, cysteine and serine, and pH control. The depression of specific G-CSF productivity per cell under the batch culture conditions was overcome by using a perfusion culture system, Biofermenter^TM (Sato, 1983) with modifications of nutrients supplementation by a dialysis membrane and/or dissolved oxygen (DO) supplementation by microsilicone fibers. ITPSGF medium was modified to elevate concentrations of amino acids and glucose by 2.0- and 2.5-times, respectively. Under the control of pH at 7.4 and DO at 3 ppm, the specific G-CSF productivity was not depressed even at high cell density (above 1×10⁷ cells/ml), and the amount of G-CSF reached 41 g/ml. These results indicated the possibility of finding the optimum culture conditions for the production of recombinant proteins by Namalwa KJM-1 cells.Abbreviations ABTS 2,2-Azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid - BSA Bovine Serum Albumin - BSA-PBS Phosphate-buffered Saline without Ca²⁺ and Mg²⁺ containing Bovine Serum Albumin - dhfr Dihydrofolate Reductase - DO Dissolved Oxygen - G-CSF Granulocyte Colony-stimulating Factor - HEPES 4-(2-Hydroxyethyl)-1-piperazineethansulfonic Acid - IFN Interferon - MTX Methotrexate - PBS(-) Phosphate-buffered saline without Ca²⁺ and Mg²⁺ - Tween-PBS Phosphate-buffered saline without Ca²⁺ and Mg²⁺ containing 0.05% of Tween 20