In vitro squelching of activated transcription by serum response factor: evidence for a common coactivator used by multiple transcriptional activators

Low amounts of serum response factor (SRF) activate transcription in vitro from a fos promoter construct containing an SRF binding site. Using this human HeLa cell-derived in vitro transcription system, we have found that high amounts of SRF inhibited, or 'squelched', transcription from this construct. Transcription from several other promoters activated by different gene-specific factors, including CREB and the acidic activator VP16, was also inhibited by high amounts of SRF. Basal transcription, from TATA-only promoters, however, was not inhibited. These results suggest that SRF binds to a common factor(s) (termed coactivator) required for activated transcription by a diverse group of transcriptional activators. Inhibition of transcription by SRF could be blocked by a double stranded oligonucleotide containing an SRF binding site. Mutations in SRF which abolished its DNA binding activity also reduced its ability to inhibit transcription. In addition, a C-terminal truncation of SRF which reduced its ability to activate transcription also reduced SRF's ability to inhibit transcription. These results suggest that activation and inhibition of transcription may be mediated by SRF binding to the same factor and that SRF can only bind to this factor when SRF is bound to plasmid DNA.

pH fluctuations versus reflux episodes in patients with gastroesophageal reflux disease: their optimal thresholds and significance in diagnosis

In physiological and pathological conditions, pH monitoring in the esophagus shows small variations as well as more pronounced deflections. However, only the latter are traditionally taken into account in 24-hour pH monitoring analysis. The present study was designed to establish optimal thresholds of pH fluctuations versus reflux episodes in separating physiological and pathological gastroesophageal reflux (GER) and to evaluate their significance in the diagnosis. Twenty-four-hour intraesophageal pH monitoring and endoscopy were performed in 62 patients with GER symptoms and in 42 healthy controls. The results showed that the percentages of the time with pH fluctuations in patients with and without esophagitis and in healthy controls were, on average, 12.65, 9.5 and 2.76% in 24 h, respectively, and the respective percentages of the time with reflux episodes in the same groups in 24 h were, on average, 3.12, 2.04 and 0.18%, respectively. Using a receiver-operating-characteristic curve analysis, less than 6.7% of the time with pH fluctuations and less than 0.1% of the time with reflux episodes were defined as the combined thresholds for physiological versus pathological reflux. The sensitivity of the combined thresholds for the detection of GER patients with and without esophagitis was 96.7 and 90%, respectively, and their specificity for the diagnosis of patients with abnormal GER was 100%. It is concluded that pH fluctuations and reflux episodes, when evaluated together, are more useful for classifying patients with GER and their combined thresholds yield higher diagnostic accuracy in assessing patients with gastroesophageal disease.

Polarized distribution of coated pits and coated vesicles in the rat lens: an electron microscopy and WGA-HRP tracer study

The presence and distribution of coated pits (CPs) and coated vesicles (CVs) in the rat lens were studied by thin-section electron microscopy (TEM) and wheat germ agglutinin-horseradish peroxidase (WGA-HRP) as a tracer. TEM revealed that CPs and CVs were approximately 150 nm in diameter, of which the characteristic clathrin coat was approximately 20 nm thick. CPs and CVs were found in both epithelium and superficial fiber cells of the entire lens, and were distributed preferentially along the basal membrane facing the lens capsule. It was estimated that more than 80% of CPs and CVs in the entire epithelium were seen along the basal membrane. The number of CPs and CVs along the basal membrane in the equatorial epithelium (4.4 per 10 microns membrane) was similar to that at the central zone (3.8 per 10 microns membrane), but there was a significant increase along the apical and lateral surfaces of the equatorial epithelium compared to that of the central epithelium, although the overall number was considerably smaller. In the lens fibers, CPs and CVs were usually found within 2-3 superficial layers of fiber cells. The number of CPs and CVs along the basal membrane of young fibers at the post-equatorial region (3.1 per 10 microns membrane) was 3-fold greater than that of the mature fibers at the posterior polar area (1 per 10 microns membrane). Thus, CPs and CVs along the entire basal membrane showed a gradual decrease in number from the anterior (and equatorial) regions to the posterior polar surface of the lens. WGA-HRP experiments showed that approximately 80% of tracer-carrying pits and vesicles were also found along the basal surface of the equatorial epithelium. This study suggests that a polarized distribution of CPs and CVs along the basal surface of epithelium and superficial fiber cells may facilitate receptor-mediated endocytosis of important macromolecules directly from the aqueous humor and vitreous body into metabolically active lens cells.

Regulation of cardiac gene expression during myocardial growth and hypertrophy: molecular studies of an adaptive physiologic response

Studies from both in vivo and in vitro model systems have provided an initial skeleton of the potential signaling pathways that might regulate cardiac genes during growth and hypertrophy. One of the first detectable changes in cardiac gene expression is the activation of a program of immediate early gene expression, which is distinct for the hypertrophic response, and is conserved in multiple models of both in vivo and in vitro hypertrophy. Diverse and distinct hormonal stimuli have been documented to activate several features of the hypertrophic response, including several autocrine and paracrine factors. Although the signaling mechanisms that link these factors with the activation of cardiac gene expression are unclear, recent studies suggest that the activation of protein kinase C may represent one of the most proximal common events in this signaling cascade. The activation of cardiac target genes induces a program of embryonic gene expression, including the atrial natriuretic factor (ANF) gene. The cis sequences that mediate cardiac-specific and inducible expression of an embryonic marker gene (ANF) can be segregated by studies in both cultured cell models and in vivo models of hypertrophy in transgenic mice, suggesting that specific sets of regulatory elements may exist for inducible expression of this class of cardiac gene responses. However, the induction of a constitutively expressed contractile protein gene (MLC-2) is mediated by a set of conserved elements that regulate both cardiac-specific and inducible expression. Finally, a subset of cardiac muscle genes appears to be noninducible during in vivo or in vitro hypertrophy in myocardial cells, demonstrating specificity of transcriptional activation during the hypertrophic process. The development of a bona fide in vivo pressure overload model of hypertrophy in a small animal model that can be genetically manipulated, such as the in vivo murine model recently described, should allow a rigorous analysis of the role of these specific signaling mechanisms in the activation of the responses of cardiac genes during the hypertrophic process in vivo.

Diazemuls versus diazepam as premedication in upper gastrointestinal endoscopy: a randomised cross-over study

The efficacy and tolerability of Diazemuls versus conventional diazepam as endoscopic premedication was evaluated in a study with a cross-over design performed in 26 patients undergoing upper gastrointestinal tract endoscopy. No statistically significant differences were found between the two forms of premedication with regard to degree of sedation, patient compliance or recovery of psychomotor function. With respect to short-term amnesic effects, efficacy and tolerability Diazemuls was comparable to the conventional formulation of diazepam. Diazemuls may therefore be proposed as an alternative premedication for endoscopy.

[A distinct centro-peripheral gradient of development in dopaminergic amacrine cells of cat retina]

The centro-peripheral gradient of development in dopaminergic (DA) amacrine cells of cat retina has been studied by TH immunocytochemical method. Type I of TH immunoreactive neurons is typical DA cell. They reveal a clear centro-peripheral gradient of differentiation and maturation in space and time course during postnatal development. (1) At P1 stage, the TH I cells vary in TH immunoreactivity, soma sizes and dendritic maturation. Responding to degree of development, they can be divided into I1, I2 and I3. The more differentiated I1 cells, larger and darkly immuno-stained stellate cells mostly concentrates at central retina, while the less differentiated I3 cells, smaller and lightly immunostained irregular cells concentrate at peripheral retina. I2 cells of moderate differentiation distribute over all the retina. (2) During the postnatal development, from P1 to P13, the dense area of the TH I1 cells spreads peripherally in company with the increase of the total number of TH I1 cells, comprising the central 30% of the retina at P1, 65% at P6 and almost the whole of the retina by P13. After eye opening, as the TH I cells have spread at far peripheral region, the differences in soma diameters and dendritic maturation of TH I cells between central and peripheral retina decrease gradually and the centro-peripheral gradient of maturity of TH I cells becomes less distinct. At P23, no significant difference is visible in either soma diameter or dendritic maturation in these two areas: thus, the centro-peripheral gradient is no longer apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum response factor affects preinitiation complex formation by TFIID in vitro

Serum response factor (SRF), a transcription factor that binds to the serum response element (SRE) of the c-fos proto-oncogene, activates transcription of an SRE-containing reporter plasmid in vitro. We describe here preincubation experiments which indicate that SRF activates transcription by facilitating the formation of active preinitiation complexes. Full activation by SRF occurred if SRF was preincubated with the general transcription factors. However, if the general transcription factors were preincubated and SRF was added subsequently, only poor activation of transcription was observed. This suggests that SRF must be present during preinitiation complex formation and that this complex is refractory to activation if SRF is absent during its formation. We have fractionated the general transcription factors and found that only a highly purified fraction containing the TATA-binding factor TFIID (and other unidentified components) must be present during preincubation for maximal transcriptional induction by SRF. This supports a model in which SRF activates transcription by affecting the conformation of TFIID bound to the promoter. Also of interest was the finding that recombinant human TFIID expressed in bacteria cannot mediate SRF-activated transcription, although it does support basal transcription. These results suggest that SRF may affect TFIID via a cofactor or coactivator.

[Reflux esophagitis: therapy with H2-blockers, and motility disorders]

In order to investigate the response of gastroesophageal reflux after medically induced healing of esophagitis and its relation to the occurrence of relapse during prophylactic treatment, 20 patients with erosive/ulcerative esophagitis underwent 24 hour esophageal pH monitoring before and after healing achieved with 12 to 24 weeks with ranitidine 150 or 300 mg bd. Compared with pretreatment values, after macroscopic healing, a significant reduction in daytime median percentage of reflux time and median number of reflux episodes lasting more than 5 min were observed, whereas during the night time reflux frequency and severity did not change. During maintenance treatment with ranitidine at half the acute dosage five of the six patients who had shown no improvement in gastroesophageal reflux after acute healing, relapsed. These results suggest that, in contrast to previous work, a decrease in gastroesophageal reflux in patients with reflux esophagitis can be achieved after macroscopic healing obtained with H2-antagonists, and that the occurrence of such a reduction after acute healing is predictive of a good response to long-term treatment.

[Gas chromatograms of fatty acids from Rickettsia and their similarities]

Fatty acid compositions of 7 strains of Rickettsia were analyzed by a on-line GC/MS system. These strains were R. prowazekii E, R. conorii Simko, R. rickettsii R, R. sibirica Barbash and 246, R. sinkiangensis Jinghe, and R. heilungkiangensis 54. The samples were purified by means of the concentrated salt-ether method. There were about 50 peaks in the fatty acid profiles, and 16 of these peaks were determined, i.e. C22:0, C19:0, C18:0, C18:1, C18:2, C17:0, C16:0, C16:1, 3-OH-C14:0, C15:0, C14:0, C13:0, 2-OH-C12:0, C12:0, 2-OH-C10:0, and C11:0. The major fatty acids were the saturated straight chain acids (e.g. C16:0, C18:0, C14:0) and the unsaturated straight chain acids (e.g. C18:1, C18:2, C16:1). Similarities of fatty acid profiles of tested strains were discriminated by the improved Kulik-Vincent method. The result showed that the KV's coefficient of strains Jinghe and 246 was 97.0%, and the KV's coefficient of strains 54 and the others was 81.6-94.6%.

A conserved 28-base-pair element (HF-1) in the rat cardiac myosin light-chain-2 gene confers cardiac-specific and alpha-adrenergic-inducible expression in cultured neonatal rat myocardial cells

To study the transcriptional regulatory mechanisms which mediate cardiac-specific and inducible expression during myocardial cell hypertrophy, we have extensively characterized the rat cardiac myosin light-chain-2 (MLC-2) gene as a model system. The MLC-2 gene encodes a relatively abundant contractile protein in slow skeletal and cardiac muscle and is upregulated during in vivo cardiac hypertrophy and alpha-adrenergic-mediated hypertrophy of neonatal rat myocardial cells. In transient expression assays employing a series of MLC-2-luciferase constructs, recent studies have identified a 250-bp fragment which is sufficient for both cardiac-specific and alpha-adrenergic-inducible expression. Within this 250-bp fragment lie three regions (HF-1, HF-2, and HF-3), each greater than 10 bp in length, which are conserved between the chicken and rat cardiac MLC-2 genes, suggesting their potential role in the regulated expression of this contractile protein gene. As assessed by substitution mutations within each of the conserved regions, the present study demonstrates that HF-1 and HF-2 are important in both cardiac-specific and inducible expression, while HF-3 has no detectable role in the regulated expression of the MLC-2 gene in transient expression assays. HF-1 sequences confer both cardiac-specific and inducible expression to a neutral promoter-luciferase construct but have no significant effect in the skeletal muscle or nonmuscle cell contexts. Thus, these studies have identified a new cardiac-specific regulatory element (HF-1) which plays a role in both cardiac-specific and inducible expression during myocardial cell hypertrophy.

Mutational analysis of the functional domains of yeast K1 killer toxin

To determine the functional domains of K1 killer toxin, we analyzed the phenotypes of a set of mutations throughout regions encoding the alpha- and beta-toxin subunits that allow secretion of mutant toxins. A range of techniques have been used to examine the ability of mutant toxins to bind to beta-glucan cell wall receptor and to form lethal ion channels. Our results indicate that both the alpha and beta subunits are involved in beta-glucan receptor binding. Defects in ion channel formation and toxin immunity are confined to the hydrophobic alpha subunit of the toxin.

[Morphology and development of dopaminergic neurons in the cat retina]

Morphology and development of dopaminergic neurons has been studied in the kitten retina, using tyrosine hydroxylase (TH) immunocytochemistry. TH immunoreactive (TH+) cells are already presented in whole amount and sectioned retina at first postnatal day (P1). According to soma size, shape, dendritic process pattern and immunoreactivity, two classes, type I or large dark staining TH+ cells and type II or small light staining TH+ cells are recognized. The TH I cells which consisting of normal placed DA amacrine cells, displaced DA amacrine cells and DA interplex-form-like cells, gradually mature during postnatal development, while TH II cells decrease quickly and through disappear at P30. After eye opening TH I amacrine cells, especially their dendrites develop quickly. The soma diameters increase from 11.8 microns (P1) to 14.2 microns (P30). The dendritic fields increase in size and complexity. At P1 the thick radiating dendrites emerge from the cell body with small or large "spines" and many growth cones. At P13 the dendritic field is markedly enlarged and only a few growth cones can be seen on some stained dendrites. In addition, the dendritic spines are no longer apparent and they are a part of rudimentary rings. By P30 the dendritic plexus of TH+ dendrites and rings in the out most part of IPL, typical of the adult cells, are complete. The influence of light on the development of DA cells after eye opening and the possibility of neurotransmitter changing are discussed.

Effect of radix Salviae miltiorrhizae extract injection on survival of allogeneic heart transplantation

The effect of Radix Salviae Miltiorrhizae (RSM), a commonly used herbal blood circulation invigorator for the treatment of blood stasis in traditional Chinese medicine, on the duration of allograft survival following heterotopic heart transplantation in experimental animals was observed. The results in three heart transplantation models--auricular free graft in mice, abdominal graft in rats and cervical graft in rabbits--suggested that RSM injection in an appropriate dosage prolonged the survival time of cardiac allograft. The herb showed no significant toxicity. It was also found that RSM injection had a synergic effect with corticosteroids against graft rejection.

[Analysis of cellular fatty acids of Enterobacteria species by gas chromatography-mass spectrometry]

Cellular fatty acid compositions of 15 Enterobacteria were analyzed by gas chromatography-mass spectrometry(GC-MS). About 30 fatty acids were detected in chromatograms, and 13 of them were chemically identified, e.i. C11:0, C12:0, C13:0, C14:0, C15:0, 2OH-C14:0, 3OH-C14:0, C16:1, C16:0, aC17:0, delta C17:0, C18:1 and C18:0. The major cellular fatty acids in all fifteen species were C16:0, C18:1, C15:0, C14:0, C16:1, C13:0, 3OH-C14:0 and C18:0. The cellular fatty acids of Enterobacteria species were characterized by normal straight-chain saturated acids and monounsaturated acids, of which the most abundant fatty acid was C16:0. 3OH-C14:0 was found in all strains of Enterobacteria, whereas 2OH-C14:0 was only found in strains of Serratia species. Other unknown compositions also would have been certain characteristics for bacteria. The present paper would provide some of useful reference data for chemotaxonomy and molecular microbiology of Enterobacteria.

[Repair of cicatricial deformities in neck region with trapezius musculocutaneous flap]

Dr. Demergasso was the first one who applied the musculocutaneous flap of trapezius clinically in plastic surgery in 1975. Here the author had obtained satisfactory results in five cases by using the similar musculocutaneous flap to repair cicatricial deformity on the same side of the neck. The author held that this flap is easy to be dissected and moved forward to repair some areas on the neck, between mandible and thorax, and in front of larynx. There is no consequent deformation in the donor region which is hidden backward. The blood supply of trapezius is rich enough to keep from any local necrosis of the flap after transplantation. The color of the skin is usually like the origin one.

Yeast K1 killer toxin forms ion channels in sensitive yeast spheroplasts and in artificial liposomes

The patch-clamp technique was used to examine the plasma membranes of sensitive yeast spheroplasts exposed to partially purified killer toxin preparations. Asolectin liposomes in which the toxin was incorporated were also examined. Excised inside-out patches from these preparations often revealed at 118 pS conductance appearing in pairs. The current through this conductance flickered rapidly among three states: dwelling mostly at the unit-open state, less frequently at the two-unit-open state, and more rarely at the closed state. Membrane voltages from -80 to 80 mV had little influence on the opening probability. The current reversed near the equilibrium potential of K+ in asymmetric KCl solutions and also reversed near O mV at symmetric NaCl vs. KCl solutions. The two levels of the conductance were likely due to the toxin protein, as treatment of spheroplasts or liposomes with extracellular protein preparations from isogenic yeasts deleted for the toxin gene gave no such conductance levels. These results show that in vivo the killer-toxin fraction can form a cation channel that seldom closes regardless of membrane voltage. We suggest that this channel causes the death of sensitive yeast cells.

Establishment of an axenic culture of Giardia lamblia through preliminary passage in suckling gerbil

Cysts of Giardia lamblia from fresh stool specimens of a 13-year-old boy, who lived in suburban Beijing and had suffered from recurrent diarrheas for years, were concentrated, purified and suspended in physiological saline. Six suckling gerbils (Meriones unguiculatus) were each inoculated with 0.2 ml of this suspension which contained 20,000 cysts/ml. On day 8 after inoculation, the infected animals were sacrificed and trophozoites of G. lamblia which appeared numerous in the upper small intestines were isolated aseptically. The trophozoites were inoculated into modified TYI-S-33 medium and cultivated at 37 C. On day 14 of cultivation, the organism grew luxuriantly and formed a cellular monolayer on the inner wall of the culture tube. The organism replicated every 15 +/- 2 hours and the peak growth occurred 120 hours after seeding. No bacterial growth was detected by repeatedly transferring the culture onto blood agar plates and into beef broths. Several lots of the culture have been subjected to cryopreservation in liquid nitrogen and the viability of the thawed organism ranged from 50% to 80% 1-10 weeks after being cryopreserved. The thawed parasites grew well in subcultures. This axenic culture has been maintained for one year and 4 months, and more than 150 subcultures have been made.

[Survey and analysis of incidence and relevant factors of osteoporosis in the elderly (with a report of 2041 cases)]

This paper reports the results of roentgenography of calcaneum in 2,041 persons without any underlying disease causing osteoporosis. The trabecular patterns of calcaneum were divided into 5 grades according to Jhamaria method. The incidence of osteoporosis is 18.18%, 25.96%, 54.80%, 67.33%, 85.45% and 90% and the average grading of calcaneum were 2.98, 2.96, 2.53, 2.11 and 2.14 in male and 3.50, 2.89, 2.50, 2.06, 1.60 and 1.61 in female in these aged groups respectively Serum Ca, P, Mg and Vitamin D were determined in 1,798 persons over 60 years of age. There is no significant difference among them Bone density was determined in 381 cases, showing 0.507 +/- 0.003, 0.598 +/- 0.095, 0.673 +/- 0.052, and 0.0645 +/- 0.095 among Jhamaria grading index I, II, III, IV. There is significant difference between 1-2 and 3-4 grading index, suggesting Jhamaria method gives a reliable, simple and applicable criterion for diagnosis of osteoporosis. The relevant factors influencing osteoporosis are discussed.

The nuclear SUV3-1 mutation affects a variety of post-transcriptional processes in yeast mitochondria

The SUV3-1 mutation was isolated earlier as a suppressor of a deletion of a conserved RNA processing site (dodecamer) near the 3' end of the var1 gene. Previous studies indicate that the suppressor enhances translation of mutant var1 messages; unexpectedly, it also causes over-accumulation of excised intron RNA of the large rRNA gene intron and blocks cleavage at the dodecamer site within that intron. In this study most mitochondrial genes in SUV3-1 and suv3 nuclear contexts are surveyed for changes in levels of mRNA, for interference with dodecamer cleavage and splicing and for levels of excised intron RNAs. SUV3-1 has little or no effect on the size or abundance of unspliced RNAs tested. It results, however, in a marked increase in the abundance of seven of eight excised group I intron RNAs tested, most of which are not detectable in wild-type (suv3) strains. The suppressor lowers levels of the cob and coxl mRNAs about 2-5 and 20-fold, respectively. The effect on coxl mRNA results from a decrease in the splicing of its intron 5 beta. Despite the reduction in these mRNA levels, the amounts of coxl and cyt b polypeptides were close to wild-type levels in SUV3-1 cells. These data show that the suv3 gene plays a prominent role in post-transcriptional and translation events in yeast mitochondria.

Genetic and molecular approaches to synthesis and action of the yeast killer toxin

The K1 killer toxin of Saccharomyces cerevisiae is a secreted, virally-coded protein lethal to sensitive yeasts. Killer yeasts are immune to the toxin they produce. This killer system has been extensively examined from genetic and molecular perspectives. Here we review the biology of killer yeasts, and examine the synthesis and action of the protein toxin and the immunity component. We summarise the structure of the toxin precursor gene and its protein products, outline the proteolytic processing of the toxin subunits from the precursor, and their passage through the yeast secretory pathway. We then discuss the mode of action of the toxin, its lectin-like interaction with a cell wall glucan, and its probable role in forming channels in the yeast plasma membrane. In addition we describe models of how a toxin precursor species functions as the immunity component, probably by interfering with channel formation. We conclude with a review of the functional domains of the toxin structural gene as determined by site-directed mutagenesis. This work has identified regions associated with glucan binding, toxin activity, and immunity.

[Study on the discrimination of bacteria by gas chromatographic profiles of cellular monosaccharides]

A procedure for obtaining gas chromatographic (GC) profiles of bacterial cellular monosaccharides was described. Some of the unknown component peaks in these profiles were identified. And, based on the complete linkage cluster analysis with the Euclidean distance coefficient, the interpretation of the resulting cellular monosaccharides of bacteria were performed by mini-computer. By means of this method, the discrimination of 5 species (24 strains) of aerobic endospore-forming bacteria. The results showed that there were defined differences between the profiles of cellular monosaccharides of B. anthracis and B. cereus. This procedure has provided a useful method for the classification and identification of microorganisms, for their physiological and biochemical studies, and for studies on their subcellular components.

Detection of beta-thalassemia mutations in the Chinese using amplified DNA from dried blood specimens

This paper describes DNA polymerase chain reaction (PCR) amplification directly from dried blood specimens for the detection of the beta-thalassemia mutation in China. Target DNA was amplified to span the beta-globin gene regions, which included ten types of mutation sites specific for Chinese beta-thalassemias. Ten kinds of oligonucleotide probes were constructed and used to hybridize with the amplified DNA. A total of 170 beta-thalassemia alleles originating from eastern, southwestern and southern China were analyzed. The results revealed that the distributions of different types of mutations were different in the three regions. The most common types in southern China were a frameshift at codons 41/42 and a C----T substitution at IVS II n.654, the most frequent types in southwestern China were codon 17 and IVS II n.654 mutations, and the predominant mutations in eastern China were frameshifts at codons 41/42 and 71/72.

Functional expression of a yeast mitochondrial intron-encoded protein requires RNA processing at a conserved dodecamer sequence at the 3' end of the gene

All mRNAs of yeast mitochondria are processed at their 3' ends within a conserved dodecamer sequence, 5'-AAUAAUAUUCUU-3'. A dominant nuclear suppressor, SUV3-I, was previously isolated because it suppresses a dodecamer deletion at the 3' end of the var1 gene. We have tested the effects of SUV3-1 on a mutant containing two adjacent transversions within a dodecamer at the 3' end of fit1, a gene located within the 1,143-base-pair intron of the 21S rRNA gene, whose product is a site-specific endonuclease required in crosses for the quantitative transmission of that intron to 21S alleles that lack it. The fit1 dodecamer mutations blocked both intron transmission and dodecamer cleavage, neither of which was suppressed by SUV3-1 when present in heterozygous or homozygous configurations. Unexpectedly, we found that SUV3-1 completely blocked cleavage of the wild-type fit1 dodecamer and, in SUV3-1 homozygous crosses, intron conversion. In addition, SUV3-1 resulted in at least a 40-fold increase in the amount of excised intron accumulated. Genetic analysis showed that these phenotypes resulted from the same mutation. We conclude that cleavage of a wild-type dodecamer sequence at the 3' end of the fit1 gene is essential for fit1 expression.

[Streptococcus mutans glucosyltransferase: isolation and its ability to synthesize polysaccharides]

The extracellular glucosyltransferases (GTF, EC 2.4.1.5) were extracted from trypticase yeast L-cystine culture supernatant of streptococcus mutans strains SSMC 167(g), 6715(g), SSMC 100 (c) and Ingbritt (c) by 60% saturated ammonium sulphate precipitation. The yield was more than 50%. All the enzyme preparations could synthesize both water-soluble and insoluble glucans. The results of polyacrylamide gel electrophoresis of enzyme preparations illustrated the complexity and multicomponent nature of the GTF of S. mutans. The abilities of synthesizing polysaccharides were different between S. mutans serotype g and serotype c. The ability of synthesizing water-soluble glucan was almost the same as that of synthesizing water-insoluble glucan for GTFs from the two S. mutans strains of serotype g, but the ability of synthesizing water-soluble glucan was 10-fold to that of synthesizing water-insoluble glucan for GTFs from other two strains serotype c. No frucotosyltransferase activity was found.

The role of a conserved dodecamer sequence in yeast mitochondrial gene expression

All mRNAs on the yeast mitochondrial genome terminate at a conserved dodecamer sequence 5'-AAUAAUAUUCUU-3'. We have characterized two mutants with altered dodecamers. One contains a deletion of the dodecamer at the end of the var1 gene, and the other contains two adjacent transversions in the dodecamer at the end of the reading frame of fit1, a gene within the omega+ allele of the 21S rRNA gene. In each mutant, expression of the respective gene is blocked completely. A dominant nuclear suppressor, SUV3-1, was isolated that suppresses the var1 deletion but is without effect on the fit1 dodecamer mutations. Unexpectedly, however, we found that SUV3-1 blocks expression of the wild-type fit1 allele by blocking processing at its dodecamer. SUV3-1 has pleiotropic effects on mitochondrial gene expression, affecting RNA processing, RNA stability, and translation. Our results suggest that RNA metabolism and translation may be part of a multicomponent complex within mitochondria.

Determination of the carboxyl termini of the alpha and beta subunits of yeast K1 killer toxin. Requirement of a carboxypeptidase B-like activity for maturation

The carboxyl-terminal sequences of the two polypeptide chains of the Saccharomyces cerevisiae K1 killer toxin were determined by protein sequencing and amino acid analysis of peptide fragments generated from the mature, secreted toxin. The COOH-terminal amino acid of the beta chain is histidine 316, the final residue encoded by the precursor gene. The COOH terminus of the alpha chain is at alanine 147 of the preprotoxin. Amino acid composition data for the purified toxin are consistent with that predicted from the gene sequence of the preprotoxin where the alpha and beta subunits consist of amino acid residues 45-147 and 234-316, respectively. The molecular weight of the mature alpha beta dimer is about 20,658. The COOH-terminal sequence determination completes the location of the toxin subunits in the precursor, and its configuration may be represented as prepropeptide-Pro-Arg-alpha-Arg-Arg-gamma-Lys-Arg-beta, where gamma represents the interstitial glycosylated peptide. The COOH terminal side of the paired basic residues (Arg-148 Arg-149 and Lys-232 Arg-233 of preprotoxin) are endoproteolytic processing sites for the product of the KEX2 gene (Julius, D., Brake, A., Blair, L., Kunisawa, R., and Thorner, J. (1984) Cell 37, 1075-1089), and thus maturation of the alpha subunit of killer toxin apparently requires a carboxypeptidase B-like activity. A possible candidate for this activity is the product of the KEX1 gene (Dmochowska, A., Dignard, D., Henning, D., Thomas, D.Y., and Bussey, H. (1987) Cell, in press).

RNA processing and expression of an intron-encoded protein in yeast mitochondria: role of a conserved dodecamer sequence

The 3' ends of most Saccharomyces cerevisiae mitochondrial mRNAs terminate at a conserved dodecamer sequence, 5'-AAUAAUAUUCUU-3', of unknown function. We have studied the consequences of mutations within a dodecamer found in an 1,143-base-pair optional intron of the mitochondrial large (21S) rRNA gene on RNA processing. The dodecamer is situated at the 3' end of an expressed open reading frame (ORF) within that intron, and the mutations are two adjacent transversions that extend the intron ORF by 51 nucleotides. The strain harboring these mutations, L5-10-1, is defective in biased intron transmission in crosses to strains that lack the intron, as are other mutants which contain nucleotide changes within the ORF (I. G. Macreadie, R. M. Scott, A. R. Zinn, and R. A. Butow, Cell 41:395-402, 1985). However, unlike these other mutants, wild-type strains, or petites which retain the intron allele, L5-10-1 is defective in processing at the intron dodecamer. In addition, L5-10-1 lacks a prominent 2.7-kilobase RNA containing both intron and exon sequences and at least two of four RNAs that correspond to various forms of the excised intron. We propose that these RNAs, missing in L5-10-1 but present in all other strains examined, arise in part by processing at the intron dodecamer. In addition, in all strains examined, we have detected a novel processing activity in which precursor 21S rRNA transcripts are cleaved in the upstream exon, about 1,500 nucleotides from the 5' end of the RNA. This activity, together with 3' intron dodecamer cleavage, probably accounts for the 2.7-kilobase RNA species, a candidate for the mRNA for the intron-encoded protein.

Dextrorphan: an antagonist for phencyclidine receptors

Radio-binding assay, bioassay and HPLC detection were used to observe the antagonistic effects of dextrorphan on PCP's actions. Dextrorphan displayed high affinity to PCP receptor in the rabbit mesenteric blood vessels. It had weak PCP-like bioactivity, but could antagonize PCP's action dose-dependently in vitro study with the rabbit ear artery preparation and shifted the dose-response curve of PCP to the right. After PCP administration, the content of norepinephrine in the vascular bath medium was increased, which was reversed by dextrorphan. Thus suggests that dextrorphan is an antagonist with very mild agonistic action for PCP receptors.

Regulation of aromatase activity of rat granulosa cells: induction of synthesis of NADPH-cytochrome P-450 reductase by FSH and dibutyryl cyclic AMP

Aromatase is an enzyme complex that is composed of a specific form of cytochrome P-450 and a flavoprotein, NADPH-cytochrome P-450 reductase. Aromatase activity of granulosa cells is increased markedly by follicle-stimulating hormone (FSH) and by analogs of cyclic AMP. It was the objective of the present study to investigate the effects of FSH and dibutyryl cyclic AMP (Bt2cAMP) on the synthesis of NADPH-cytochrome P-450 reductase in rat granulosa cells maintained in vitro. Granulosa cells were obtained from the ovaries of diethylstilbestrol (DES)-treated immature rats and were incubated in the presence of DES (10(-7) M), DES + FSH (250 ng/ml), or DES + Bt2cAMP (1 mM) for up to 72 h. After 72 h of incubation, aromatase activity of cells incubated with DES alone was 5 pmoles estrogen formed 2 h-1 mg-1 protein and was increased greater than 60-fold in cells incubated with FSH or Bt2cAMP. NADPH-cytochrome P-450 reductase was immunoisolated from [35S]methionine-labeled lysates of granulosa cells incubated for 72 h in the absence or presence of stimulatory factors. The rate of synthesis of reductase was found to be increased about 3-fold in cells incubated with DES + FSH or DES + Bt2cAMP as compared to cells incubated with DES alone. By immunoblot analysis we found that the cellular content of reductase was increased about 2-fold by FSH and Bt2cAMP treatment. Reductase specific activity was 10 nmoles min-1 mg-1 protein in membrane fractions of DES-treated cells and was increased 1.6-fold by FSH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)