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Biomedical subjects

S Chang

Publications and source records attributed to S Chang.

At least 397 records · Page 22Linked to original sources
PubMed1983

Construction and characterization of Chinese hamster cell EmtA EmtB double mutants.

Starting with hybrid cell lines between a Chinese hamster cell EmtA mutant and a Chinese hamster cell EmtB mutant, we have constructed cell lines that are homozygous for mutant alleles at both the emtA locus and the emtB locus, by using a two-step segregation protocol. The EmtA EmtB double mutants are approximately 10-fold more resistant to emetine inhibition than either of the parental mutants. Having both the EmtA mutation and the EmtB mutation expressed in the same cell also results in a level of resistance to cryptopleurine that is significantly higher than a simple additive effect of the two mutations alone. Analysis of ribosomal proteins by two-dimensional polyacrylamide gel electrophoresis demonstrated that a parental hybrid and a first-step segregant, which has lost the wild-type emtA allele, synthesize both a normal and an altered form of ribosomal protein S14, whereas an EmtA EmtB double mutant synthesizes only the altered form of this ribosomal protein. This result confirms that the emtB locus is the structural gene for ribosomal protein S14. Our results also suggest that the products of the emtA and emtB loci interact directly, indicating that the emtA locus, like the emtB locus, encodes a component of the ribosome.

Alkaloids↗
PubMed1982

Transcriptional analyses of the Bacillus licheniformis penP gene.

We report the promoter structure of the Bacillus licheniformis 749/C penicillinase (penP) gene. The transcript encoding the penicillinase gene was identified by in vitro run-off transcription using both E. coli RNA polymerase and B. subtilis RNA polymerase. Utilization of this promoter in linearized DNA by the B. subtilis RNA polymerase showed extreme sensitivity to ionic strength. The 5' sequence of the penP mRNA was determined using enzymatic sequencing (1). Holoenzymes from E. coli and B. subtilis (E sigma 55) initiate penP RNA synthesis at the same site. Alignment of this RNA sequence with the reported DNA sequence of ther penP gene (2,3) revealed the "-35 region" and "Pribnow box" sequences that are recognized as 5'TTGCAT and 5'AATACT, respectively. Potential secondary structure within the promoter exists which may play a role in the expression of the penicillinase gene. The location of the penP promoter was further confirmed by molecular cloning of a DNA fragment containing the expected promoter sequence into a promoter-fishing vector useful for monitoring promoter activities in both E. coli and B. subtilis.

Bacillus↗
PubMed1981

The promoter-proximal region of the Bacillus licheniformis penicillinase gene: Nucleotide sequence and predicted leader peptide sequence.

Penicillinase (beta-lactamase) is a major species of secreted protein produced by Bacillus licheniformis 749. From the pTB2 recombinant plasmid containing the cloned entire penicillinase (penP) gene, we have isolated and sequenced a 446-bp HpaII fragment carrying the beginning of penP. The 3'-end coding region of 216-bp on this DNA fragment codes for the first 72 amino acids of the prepenicillinase protein. The deduced structure of the leader peptide consists of a 34 amino acid signal sequence with a hydrophilic N-terminal region and a central hydrophobic core.

Bacillus↗
PubMed1981

The role of onsets in perception of stop place of articulation: effects of spectral and temporal discontinuity.

This study explored the role of onsets on the perception of place of articulation by investigating the effects of later-occurring transitions on the perceptual information residing in the onsets. In particular, the perceptual effects of spectral discontinuities introduced after the burst and early transition of stimulus onset were explored. Identification responses for place of articulation as well as judgment responses for quality and number of syllables were obtained for synthetic CV syllables in which two types of discontinuity were introduced by (1) inserting a silent interval between the stimulus onset (burst and following 3 glottal pulses) and remaining transition and steady-state information, and (2) replacing portions of the transitions and steady-state following the onset with a silent interval. Silent intervals ranged between 8.1 an 56.7 ms. All the stimuli were consistently identified, regardless of the duration of the silent interval or the type of discontinuity introduced. Subjects perceived a discontinuity when the silent interval was greater than 16 ms. These results support the view that the perceptual analysis of stop consonants may be defined in terms of temporally-defined window encompassing the burst and early transition information and further confirms the importance of such onsets as determinants of perception of place of articulation.

Female↗
PubMed1981

Molecular cloning and expression of Bacillus licheniformis beta-lactamase gene in Escherichia coli and Bacillus subtilis.

The chromosomal beta-lactamase (penicillinase, penP) gene from Bacillus licheniformis 749/C has been cloned in Escherichia coli. The locations of the target sites for various restriction enzymes on the 4.2-kilobase EcoRI fragment were determined. By matching the restriction mapping data with the potential nucleotide sequences of the penP gene deduced from known protein sequence, we established the exact position of the penP gene on the fragment. A bifunctional plasmid vector carrying the penP gene, plasmid pOG2165, was constructed which directs the synthesis of the heterologous beta-lactamase in both E. coli and Bacillus subtilis hosts. The protein synthesized in E. coli and B. subtilis is similar in size to the processed beta-lactamase made in B. licheniformis. Furthermore, the beta-lactamase made in B. subtilis is efficiently secreted by the host into the culture medium, indicating that B. subtilis is capable of carrying out the post-translational proteolytic cleavage(s) to convert the membrane-bound precursor enzyme into the soluble extracellular form.

Bacillus↗
PubMed1981

A historical review of echocardiographic detection of pericardial effusion.

The 26 year history of echocardiographic detection of pericardial effusion ideally demonstrates the scientific method. The initial observations by Elder and Hertz in 1954 lead to animal experiments by Feigenbaum an Soulen many years later. Human applications were confirmed again and again with cardiac catheterization, surgery, autopsy and radiologic procedures. Older methods of effusion detection were compared to this new and noninvasive method and found lacking. Echocardiography has been a safe, reliable and accurate method to establish the presence of pericardial effusion in the symtomatic and asymtomatic patient. It has been used as the diagnostic standard for other detection methods. Investigators and clinicians are now utilizing echocardiography to explain cardiac physiology when pericardial effusion is present; and to follow the effects of their therapeutic interventions. While the presence of pericardial effusion has proven to be more prevalent than expected, the pathologic and hemodynamic significance of unsuspected effusion had not yet been established. Experimental and clinical studies are continuing with the aid of computerized technology for data retrieval and analysis. Thousands of patients are examined yearly with echocardiography and their statistics roll from the pages of scientific and clinical publications. The world's literature is at one's fingertips. But--the echocardiogram and its derived data are only as good as the knowledge and skill of the examiner, technologist and physician alike who " ... must understand the physics of ultrasound, the operation of a complex electronic instrument, the nature of intracardiac anatomy, and clinical cardiology as well as echographic manifestations of normal and disease conditions. Information can seldom be extracted retrospectively from the echocardiogram that was not deliberately depicted at the time of examination." More than a quarter of a century has honed present day skills to record and interpret echocardiographic tracings of pericardial effusion. Yet, it is sobering to consider how primitive our best efforts are compared to methods still unknown which will be used by technologists and physicians fifty years from now.

Echocardiography↗
PubMed1980

Phenothiazine levels in plasma and red blood cells. Their relationship to clinical improvement in schizophrenia.

A controlled study investigated the relationship between steady-state plasma and RBC concentrations of the phenothiazine derivative butaperazine maleate and the therapeutic response in 24 hospitalized schizophrenic patients who received constant maintenance doses of butaperazine during the first two weeks of treatment. Butaperazine concentrations in RBCs correlated significantly with clinical improvement in an inverted U-shaped pattern, whereas plasma levels of butaperazine were not significantly related to clinical response. Both plasma and RBC levels of butaperazine showed large interpatient variations. The level of RBC-bound drug might be a better peripheral correlate of drug levels in the brain than are drug levels in plasma. Thus, monitoring drug levels in RBCs might have an advantage over measured drug levels in plasma. These findings might not allow generalization to other antipsychotic agents.

Adolescent↗
PubMed1980

Lithium response in good prognosis schizophrenia.

The authors report the results of a 2-week lithium trial using 31 patients meeting Research Diagnostic Criteria for schizophrenia or schizoaffective disorder who were also diagnosed according to DSM-III criteria. One-third of the patients showed reduction of their schizophrenic-like symptoms during the lithium trial. Seven of the 9 responders (78%) met DSM-III criteria not for schizophrenia but for a schizophreniform disorder. Such patients also met McCabe and associates' criteria for good prognosis schizophrenia. This study lends further support to the growing body of evidence which suggests that schizophreniform disorder and good prognosis schizophrenia may be affective disorders with atypical schizophrenic-like features. The authors cautiously suggest that a lithium trial may be indicated in this subgroup of patients.

Adult↗
PubMed1980

[Comparative study on rat arthritis induced by various immune mechanisms (author's transl)].

Experimental arthritis was induced in rats by the use of horse ferritin as an antigen. The pathological findings were studied and the mechanisms of inflammation were analyzed. Arthritis was induced through various mode of actions: 1. Arthus reaction (antigen-induced arthritis). 2. Passive Arthus reaction. 3. Reverse passive Arthus reaction. 4. Arthritis induced by intra-articular injection of immune complex, by either single shot or repeated injections. 5. Arthritis induced by anamnestic reaction. Arthritis induced by repeated injections of immune complex or that induced by anamnestic reaction exhibited mild chronic synovitis characterized by round cell infiltration without detectable acute phase of inflammation. Arthritis induced through other immunological mechanisms revealed a sequential course of acute synovitis characterized by accumulation of polymorphonuclear leucocytes (PMN) followed by gradual disappearance of PMN and alternative increase of round cells or plasma cells and proliferation of synovial lining cells. All types of arthritis subsided with mild fibrosis of the synovial tissue without lasting over a significantly long time. Although the successful production of a long-lasting chronic arthritis has been reported in rabbits, it was impossible to induce such long standing arthritis through this experiment. The chronicity of the arthritis induced through immunological mechanism may not simply be due to the long-standing retention of immune complex within the involved joint but also due to other factors such as the species of the test animals, the nature of antigen used and local factors produced through acute joint inflammation.

Animals↗
PubMed1980

[Studies on the immuno-suppressive effects of adriamycin and tumor metastasis (author's transl)].

Most of the antineoplastic agents were known to have immuno-suppressive effect. The purpose of the present work is to test the immuno-suppressive effect of adriamycin, an effective and widely used chemotherapeutic agent in the field of clinical orthopedics. Isogenic ACI rats and their transplantable fibrosarcoma AMC-60 were used as test materials. Tumor cells were injected as an artificial model for pulmonary metastasis or inoculated into the tibial bone to examine any metastatic focus other than the inoculated site. Administration of one course of adriamycin in the same way as that was given in patients induced temporarily leucopenia with prominent decrease of granulocytes. Adriamycin suppressed humoral antibody production to sheep erythrocytes in the treated rats and also suppressed cellular immune response expressed by skin reaction to PHA in the treated rats. Administration of adriamycin one week before tumor inoculation into immune rats which have acquired immunity to AMC-60 through preimmunization with the tumor, induced increased incidence of pulmonary metastasis, whereas administration of adriamycin after tumor inoculation resulted in decreased incidence of metastasis or healing of the inoculated tumor. Inoculation of bone marrow cells from healthy rats restored the impaired immunity. In unimmunized rats, pretreatment by adriamycin resulted in accelerated tumor growth at the inoculated site and increased incidence of metastasis. On the other hand, adriamycin given after tumor inoculation suppressed tumor growth and repeated administration of adriamycin induced healing of the inoculated tumor. The present data indicates that even an effective antineoplastic agent will interfere with the immune surveillance system of the host and result in accelerated tumor growth or increased incidence of metastasis when improperly given. A continual efforts to search for a less immuno-suppressive and effective method of administration of a given antineoplastic agent is necessary.

Animals↗
PubMed1979

Prebiotic nucleotide oligomerization in a fluctuating environment: effects of kaolinite and cyanamide.

The day kaolinite was tested for its ability to promote nucleotide oligomerization in model prebiotic systems. Heterogeneous mixtures of clay, water and nucleotide were repeatedly evaporated to dryness at 60 degrees C and redissolved in water in cyclic fashion in the presence or absence of cyanamide and/or ammonium chloride. With or without cycling, kaolinite alone did not promote the oligomerization of nucleotides at detectable levels. Cycling of clay in combination with cyanamide, however, promoted high levels of condensation to a mixture of oligonucleotides and dinucleotide pyrophosphate without requiring ammonium chloride. Although cycling with clay favored synthesis of dinucleotide pyrophosphate, cycling without clay enhanced formation of oligonucleotides. These results support the hypothesis that the presence of clays in fluctuating environments would have influenced the -ourse of prebiotic condensation reactions.

Alkaline Phosphatase↗
PubMed1979

High frequency transformation of Bacillus subtilis protoplasts by plasmid DNA.

A highly efficient method for transformation of Bacillus subtilis by plasmid DNA is reported. The procedure, which involves polyethylene glycol-induced DNA uptake by protoplasts and subsequent regeneration of the bacterial cell wall, yields up to 80% transformants with an efficiency of 4 x 10(7) transformants per microgram of supercoiled DNA. Plasmids constructed by in vitro ligation or endonuclease-generated fragments of linear plasmid DNA can also transform PEG-treated protoplasts, but at a lower frequency.

Bacillus subtilis↗
PubMed1979

Technique of echographic examination of right ventricular wall thickness from the right sternal border.

Right ventricular wall motion was readily accessible for echocardiographic recording along the right sternal border in 27 pediatric patients (age: 24 hrs--12 yrs). Right ventricular epicardial and endocardial wall motion could be recorded only at the right sternal border in 10 of these patients, emphasizing the need for a new, alternative examination site. Calculated measurements of right ventricular wall thickness recorded from both right and left sternal borders (7 pts) were similar (range of diff.=0--0.6 mm; mean of diff.=0.26 mm). Autopsy confirmation of right ventricular wall thickness was obtained in 2 patients. Epicardial motion could not be identified at the left sternal border in 10 patients. In these patients, right ventricular wall thickness was estimated by measuring from the inner chest wall to the endocardium. These measurements were compared to right ventricular wall thickness obtained from the right sternal border. Wall thickness obtained from the left sternal border was significantly underestimated in the absence of a definite epicardial interface (range of diff.=0.2--2.6 mm; mean of diff.=1.3 mm).

Child↗
PubMed1978

Peptide formation in the prebiotic era: thermal condensation of glycine in fluctuating clay environments.

As geologically relevant models of prebiotic environments, systems consisting of clay, water, and amino acids were subjected to cyclic variations in temperature and water content. Fluctuations of both variables produced longer oligopeptides in higher yields than were produced by temperature fluctuations alone. The results suggest that fluctuating environments provided a favorable geological setting in which the rate and extent of chemical evolution would have been determined by the number and frequency of cycles.

Bentonite↗