Characterization of cDNA clones encoding two putative isoforms of the alpha 1 subunit of the dihydropyridine-sensitive voltage-dependent calcium channel isolated from rat brain and rat aorta

cDNA clones encoding rat brain and rat aorta isoforms of the alpha 1 subunit of the dihydropyridine-sensitive, voltage-dependent calcium channel were isolated and sequenced. These tissue-specific cDNA clones share significant amino acid similarity with the rabbit skeletal muscle calcium channel alpha 1 subunit (75% and 66% amino acid identity for rat brain and rat aorta isoforms, respectively). Northern analysis revealed transcript sizes of 6.5 and 8.6 kb in aorta and 8.6 kb in brain.

The healing of closed tibial shaft fractures. The natural history of union with closed treatment

One hundred consecutive closed fractures of the adult tibial shaft treated by closed methods were surveyed prospectively in order to observe their natural history. The fractures were analysed with regards to speed of healing and the influence of age, sex, causal force, radiological morphology and concurrent fibular fracture. At 20 weeks 19 fractures had not yet united, but 15 of these had united by 30 weeks with conservative treatment alone. The remaining four cases were operated upon because no further progress in healing was anticipated. These findings suggest that, with regard to healing, open reduction and internal fixation is rarely justified in closed adult tibial shaft fractures.

Sequence and expression of mRNAs encoding the alpha 1 and alpha 2 subunits of a DHP-sensitive calcium channel

Complementary DNAs were isolated and used to deduce the primary structures of the alpha 1 and alpha 2 subunits of the dihydropyridine-sensitive, voltage-dependent calcium channel from rabbit skeletal muscle. The alpha 1 subunit, which contains putative binding sites for calcium antagonists, is a hydrophobic protein with a sequence that is consistent with multiple transmembrane domains and shows structural and sequence homology with other voltage-dependent ion channels. In contrast, the alpha 2 subunit is a hydrophilic protein without homology to other known protein sequences. Nucleic acid hybridization studies suggest that the alpha 1 and alpha 2 subunit mRNAs are expressed differentially in a tissue-specific manner and that there is a family of genes encoding additional calcium channel subtypes.

Specialized ribosome system: preferential translation of a single mRNA species by a subpopulation of mutated ribosomes in Escherichia coli

In Escherichia coli, all mRNAs are translated by one pool of functionally identical ribosomes. Here, we describe a system in which a subpopulation of modified ribosomes are directed to a single mutated mRNA species. This was accomplished by changing the Shine-Dalgarno sequence that precedes the heterologous human growth hormone gene from 5' GGAGG to 5' CCTCC or 5' GTGTG. Translation of these modified mRNAs by wild-type ribosomes is very inefficient. When the anti-Shine-Dalgarno region (i.e., the region complementary to the Shine-Dalgarno sequence) at the 3' end of the gene encoding 16S rRNA (rrnB) was altered from 5' CCTCC to 5' GGAGG or 5' CACAC, thus restoring its potential to base-pair with the mutated human growth hormone mRNA, significant expression of this mRNA occurred. Growth hormone synthesis was dependent on induction of the mutated rrnB operon. Subsequently, these specialized ribosomes were made spectinomycin-resistant by the introduction of a C----U substitution at position 1192 of the 16S rRNA. Thus, host protein synthesis could be shut off by the addition of spectinomycin and the specificity and efficiency of the specialized ribosomes could be assessed. Since the specialized ribosomes represent a nonessential subpopulation in the cell, this system offers an approach to the study of mutations elsewhere in the 16S-rRNA gene that otherwise would be lethal to the cell.

Fetal cardiac tumor: a prenatal echocardiographic marker for tuberous sclerosis

Auscultation of a fetal bradyarrhythmia led to the prenatal echocardiographic detection of an intracardiac tumor. After birth the diagnosis of tuberous sclerosis was established. Therapeutic implications for current and future pregnancies, when a fetal cardiac tumor is found, are discussed.

Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome (AIDS). Diagnosis with bronchial brushings, biopsy, and bronchoalveolar lavage

Sixty-one diagnostic biopsies for Pneumocystis carinii pneumonia were performed on 40 homosexual male patients with acquired immunodeficiency syndrome (AIDS), using flexible fiberoptic bronchoscopy. Bronchial brushings and bronchoalveolar lavage were performed in conjunction with the biopsy in 58 and 29 bronchoscopies, respectively. Using a rapid methenamine silver stain, P carinii pneumonia was diagnosed in 27 (68 percent) of the patients. Twenty of these patients had a repeat biopsy one or more times for evaluation of therapy. Eighteen of the biopsies following two to three weeks of therapy were positive. There was an 84 percent correlation between findings on transbronchial brushing and biopsy (89 percent on initial biopsy before treatment) and an 86 percent correlation between bronchoalveolar lavage and biopsy. Additionally, transbronchial brushing permitted demonstration of Pneumocystis organisms in four follow-up bronchoscopies in which the biopsy was negative or inadequate. Rapid methenamine silver stain of transbronchial brushings permits diagnosis of P carinii pneumonia in patients with AIDS within one-half hour of bronchoscopy.

Mutagenesis of the three bases preceding the start codon of the beta-galactosidase mRNA and its effect on translation in Escherichia coli

The effect on the translation efficiency of various mutations in the three bases (the -1 triplet) that precede the AUG start codon of the beta-galactosidase mRNA in Escherichia coli was studied. Of the 39 mutants examined, the level of expression varies over a 20-fold range. The most favorable combinations of bases in the -1 triplet are UAU and CUU. The expression levels in the mutants with UUC, UCA or AGG as the -1 triplet are 20-fold lower than those with UAU or CUU. In general, a U residue immediately preceding the start codon is more favorable for expression than any other base; furthermore, an A residue at the -2 position enhances the translation efficiency in most instances. In both cases, however, the degree of enhancement depends on its context, i.e. the neighboring bases. Although the rules derived from this study are complex, the results show that mutations in any of the three bases preceding the start codon can strongly affect the translational efficiency of the beta-galactosidase mRNA.

Clinical features and glomerular immunofluorescence of renal biopsies from children with nephrotic syndrome due to minimal change disease and two variants of mesangial proliferative glomerulonephritis

Response to initial course of prednisone and clinical outcome were reviewed in 82 children with nephrotic syndrome (NS) due to minimal change disease (MCD) and 2 variants of mesangial proliferative glomerulonephritis (MesPGN). Renal biopsies in Type I MesPGN showed only increased mesangial cells and matrix, whereas those in Type II MesPGN also showed interstitial fibrosis, tubular atrophy, global glomerulosclerosis and hyalinosis. Response to prednisone was complete in most cases (95% in MCD, 82% in Type I and 72% in Type II MesPGN). Remission of NS for more than 1 year while off prednisone occurred in 91% of patients with Type I MesPGN and 49% with MCD, but in only 14% with Type II MesPGN. The influence of immunoglobulins +/- complement in mesangial regions of glomeruli on initial response and outcome was assessed. Response to prednisone and outcome did not differ in IMF-positive and -negative MCD or in Type I and Type II MesPGN.

A rapid sensitive assay for the quantitation of elastin

A rapid, sensitive and direct assay was developed for the quantitation of elastin using reverse phase high performance liquid chromatography. The method is based on the separation of the alkaline hydrolysis-resistant dipeptide valyl-proline, a dipeptide found in high concentrations in elastin. The methodology is applicable to unlabelled elastin samples in the range of 10-100 micrograms utilizing fluorescamine detection and to hot alkali insoluble as well as soluble forms of elastin. Increased sensitivity was achieved by the use of in vitro radiolabelling of elastin with [3H]proline. This was useful for following synthesis of elastin in cultured cells. Since this technique is not dependent on detection of the elastin-specific crosslink groups, desmosine and isodesmosine, precursor forms of elastin can be measured as well as other forms of elastin deficient in cross-linking. The same chromatographic procedure however, is able to detect these desmosine and isodesmosine crosslinks. Therefore, in cell cultures under the proper radiolabelling conditions, biosynthesis and cross-linking of elastin can be followed simultaneously in a single chromatographic procedure.

Portable Shine-Dalgarno regions: a system for a systematic study of defined alterations of nucleotide sequences within E. coli ribosome binding sites

We have developed a gene expression system in Escherichia coli that contains a portable Shine-Dalgarno region. Transcription of this system is under the direction of a hybrid promoter (tacII) derived from trp and lac-UV5 promoter sequences which is followed by a region that encodes a portable Shine-Dalgarno region (PSDR). Using a series of synthetic PSDRs, we varied the four bases that follow the Shine-Dalgarno (SD) region. We found that the presence of four A residues or four T residues in this position gives the highest translational efficiency. The presence of four C residues reduces the translation efficiency by 50% as compared with PSDRs with A or T residues. The presence of four G residues following the SD region lowers the translational efficiency by at least 75% with respect to PSDRs with A or T residues.

Induction and augmentation of mitogen-induced immune interferon production in human peripheral blood lymphocytes by N alpha-desacetylthymosin alpha 1

Treatment of human peripheral blood lymphocytes with cloned N alpha-desacetylthymosin alpha 1 induced interferon production. The kinetics is similar to that of mitogen-induced interferon induction. N alpha-desacetylthymosin alpha 1, in combination with mitogen, augments the amount of interferon produced. This interferon is immune interferon (IFN-gamma) as determined by sensitivity to pH 2, lack of neutralization by antibodies to IFN-alpha or IFN-beta and absence of activity of MDBK cells. Although the mechanism of induction of IFN-gamma by N alpha-desacetylthymosin alpha 1 is unclear, this compound is not mitogenic at concentrations causing IFN-gamma production. These results indicate that thymic factors may also participate in the regulation of IFN-gamma-production.

Selective area tuberculosis surveys in Singapore 1978

A random population sample survey in Singapore 1975 revealed that a relatively high proportion of active pulmonary tuberculosis patients remained undiagnosed, mainly in the older age groups. Previous studies disclosed the cause to the lack of symptoms of concern in these patients. A new programme was devised to discover hidden elderly patients by mass chest X-ray screening of population aged 45 years and older living in areas with known high incidence of tuberculosis. The yield of cases was less than expected mainly due to the dislocation and dispersion of population from recent extensive urban re-development in Singapore. Nevertheless the results were comparable to the most productive case finding programme carried out in this department.