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Biomedical subjects

M Smith

Publications and source records attributed to M Smith.

At least 1,243 records · Page 69Linked to original sources
PubMed1980

Use of oligodeoxynucleotide primers to determine poly(adenylic acid) adjacent sequences in messenger ribonucleic acid. 3'-Terminal noncoding sequence of bovine growth hormone messenger ribonucleic acid.

Twelve synthetic oligodeoxynucleotide primers of the general sequence d(pT8-N-N') were tested in a reverse transcriptase reaction for specific initiation of complementary deoxyribonucleic acid (cDNA) synthesis at the poly(adenylic acid) junction of a messenger ribonucleic acid (mRNA) template. Only the sequence d(pT8-G-C) functioned as a specific primer of cDNA synthesis with an enriched fraction of bovine growth hormone mRNA from the anterior pituitary gland and produced unique fragments in a dideoxy sequencing reaction. The nucleotide sequence obtained by this method extended into the protein coding region of bovine growth hormone mRNA and was confirmed by chemical sequencing of the cDNA initiated with [5'-32P]d(pT8-G-C). The 3'-untranslated region of bovine growth hormone mRNA is 104 nucleotides in length and contains regions of significant homology with both rat and human growth hormone mRNAs, including the region surrounding the common AAUAAA hexanucleotide. The method presented here for selection of the d(pT8-N-N') primer complementary to the poly(A) junction of mRNA is of general applicability for nucleotide sequence analysis of partially purified mRNAs.

Animals↗
PubMed1980

Fluidised-bead bed in the intensive-therapy unit.

The fluidised-bead bed is a novel way of managing patients in the intensive-therapy unit (ITU) with various nursing problems. It is particularly suitable for the management of pressure areas and for patients at the extremes of weight range. Theoretically, the bed is a way of reducing catabolism, but this has so far not been properly investigated.

Adult↗
PubMed1980

Combined carotid-vertebral vascular disease: a new surgical approach.

Selected patients with vertebral basilar insufficiency may obtain symptomatic relief after carotid endarterectomy. The usual surgical approach is that of initially performing carotid endarterectomy, if appropriate, followed at a second operation by extrathoracic vertebral reconstruction. This surgical approach is based in part on the need for different surgical incisions to reconstruct the cervical carotid and vertebral arteries. We describe a new surgical approach that utilizes a single cervical incision for combined carotid-vertebral reconstruction.

Aged↗
PubMed1980

Mutations at the yeast SUP4 tRNATyr locus: DNA sequence changes in mutants lacking suppressor activity.

Yeast strains harboring indepjendent mutations within the SUP4 tyrosine tRNA gene have been selected by virtue of their inactivating effect upon the SUP4-o UAA suppressor. Three fourths of the mutations at SUP4 are point alterations; the rest resemble the deletions described by Rothstein (1979). A meiotic genetic fine structure map of the locus was made by crossing 69 of the mutants in all combinations and testing for the frequency of SUP4-o recombinants. The sequences of SUP4 genes cloned from 32 mutant strains were determined by the dideoxynucleotide terminator method, using as primer a synthetic oligodeoxynucleotide corresponding to a sequence adjoining the SUP4 3' terminus. The positions of the DNA sequence alterations showed good colinearity with the positions of the mutations on the genetic map. One of the 26 mutant sites found by DNA sequencing lies within the intervening sequence. At this site three repeat mutations were found, each changing AT leads to TA. Whereas mutations were generally rather uniformly distributed throughout the tRNATyr coding sequence, none occurred in the DNA sequences flanking the mature tRNATyr sequence or in a 12 nucleotide sequence including the 10 bp which constitute the 3' side of the intervening sequence.

Base Sequence↗
PubMed1980

Mutations of the yeast SUP4 tRNATyr locus: transcription of the mutant genes in vitro.

Twenty-nine different SUP4-o tRNATyr genes with second-site mutations were transcribed in X. laevis cell-free RNA polymerase III transcription reactions, and the in vitro transcripts were analyzed by polyacrylamide gel electrophoresis. Nineteen mutant genes yield normal amounts of RNA that co-electrophorese with SUP4-o gene transcripts. RNA synthesized from a mutant gene lacing a single base pair migrated slightly faster in gels, as expected. The still shorter transcripts made from seven other mutant genes suggest that several mutations alter transcription starting or stopping points. Fingerprint analyses of transcripts from the two most extreme cases showed that premature termination occurred at new tracts of T residues resulting from the mutations. Two mutations significantly enhance transcription, and two mutations which alter the invariant C within the T psi CG sequence dramatically reduce SUP4-o gene transcription. The regions of the SUP4-o gene that surround these mutations are partially homologous to intragenic sequences in many other eucaryotic tRNA and 5S RNA genes. We hypothesize that these homologous sequences are recognized as promoter regions during RNA polymerase III transcription initiation.

Animals↗
PubMed1980

Site-specific mutagenesis using oligodeoxyribonucleotides: isolation of a phenotypically silent phi X174 mutant, with a specific nucleotide deletion, at very high efficiency.

A decadeoxyribonucleotide, pAAATCCCTCA, was synthesized to complement nucleotides 2920--2930 of coliphage phi X174 viral DNA except that the nucleotide corresponding to position 2925 is deleted. The phage DNA sequence in this region codes for the ribosome-binding site of gene H. The oligodeoxyribonucleotide was integrated into double-stranded phi X174 DNA by using it as a primer for DNA polymerase with wild-type DNA template followed by ligation. The resultant heteroduplex DNA was used to transfect Escherichia coli spheroplasts and progeny bacteriophage were isolated. The synthetic decadeoxyribonucleotide was then used to enrich mutant viral DNA from which nucleotide 2925 had been deleted. After three cycles of enrichment and spheroplast transfection only mutant DNA was detectable. The deletion of nucleotide 2925 from the phi X174 genome seriously disrupts a sequence complementary to the 3'-terminus of the 16S rRNA of E. coli and also eliminates a translation termination codon from that sequence. However, the mutant grows normally with no readily perceptible phenotype. Thus, a short synthetic oligodeoxyribonucleotide has been used to construct, and to isolate with 100% efficiency, a mutant for which there is no biological selection procedure.

Bacteriophage phi X 174↗
PubMed1980

Isolation and sequence of the gene for iso-2-cytochrome c in Saccharomyces cerevisiae.

The two apocytochrome c proteins of yeast are coded for by separate genes. Iso-2-cytochrome c differs from the iso-1 protein at 17 positions within a homologous sequence of 108 amino acids. The previously cloned iso-1-cytochrome c coding sequence has been used to identify lambda-yeast recombinant phage containing the gene for iso-2-cytochrome c. The latter protein contains the dipeptide Ala-Ala which is coded for by the nucleic acid sequence G-C-N-G-C-N. The recognition specificity of restriction endonuclease Fnu4HI for G-C-N-G-C provided a rapid means of locating the region of the cloned fragment which codes for iso-2-cytochrome c. The DNA sequence of this gene has been determined and compared with that of the iso-1-cytochrome c locus. There is no intervening sequence within the gene for iso-2-cytochrome c. At 45 of the 91 positions for which iso-1- and iso-2-cytochrome c have the same amino acid, the codons differ. Such third position variation does not occur within the region coding for amino acids 70-80, the protein sequence that is also most conserved among all eukaryotic cytochromes c.

Apoproteins↗
PubMed1980

Factors contributing to postweaning diarrhoea in a large intensive piggery.

Some aspects of postweaning diarrhoea (PWD) in a piggery during the first week after early weaning were investigated. A haemolytic enterotoxigenic strain of E. coli (O149:K88:H10) was regularly recovered from piglets with PWD while rotavirus was demonstrated on a number of occasions. Prior to weaning piglets were either free of, or shed very few, haemolytic E. coli in their faeces. However, all piglets were excreting haemolytic E. coli between 5 and 7 days after weaning. The role of rotavirus in PWD was unclear. There appeared to be a direct relationship between serum antibodies to rotavirus in the slow at farrowing and those of the piglets soon after birth. The decline of maternal neutralising antibody to rotavirus coincided with the immediate postweaning period (3 to 5 weeks after birth). This was followed by an increase in antibody levels, 5 to 8 weeks after birth. There was no significant difference in the growth rate between affected and unaffected piglets over a period of 120 days. Medication of water during the first week after weaning had no significant effect on the incidence of PWD in the herd. A change in both the weaner diet and the weaning procedure reduced piglet mortality associated with PWD by more than half.

Animals↗
PubMed1980

Escherichia coli and rotavirus infections in four-week-old gnotobiotic piglets fed milk or dry food.

A haemolytic enteropathogenic E. coli (WG) and pig rotavirus were isolated from a field case of postweaning diarrhoea in pigs. Four-week-old gnotobiotic piglets fed on milk diet were found to be extremely susceptible to infection with WG E. coli. Piglets were less susceptible to the infection immediately after the diet was changed from milk to dry food, and were almost completely resistant 4 days after the change to dry food. There was no difference in the clinical response to infection with WG E. coli when the piglets were fed either a high energy diet or low energy diet. Four-week-old piglets fed milk showed mild symptoms of diarrhoea when inoculated with pig rotavirus. Symptoms were more severe when piglets were inoculated immediately after the change from milk to dry food. Piglets inoculated 4 days after the change of diet showed no symptoms of diarrhoea at all. Under the conditions of these experiments the enteropathogenic E. coli produced a more serious disease than did pig rotavirus. Infection of 4-week-old gnotobiotic piglets with both agents given sequentially produced a diarrhoeal disease that was more severe than that produced by each agent separately.

Animals↗
PubMed1980

Assignment of the gene for human neutral alpha-glucosidase C to chromosome 15.

Human neutral alpha-glucosidase C (GANC) can be separated from the homologous mouse isozyme by starch gel electrophoresis at pH 6.5. A total of 40 clones (13 primary and 27 secondary) were derived from eight separate hybridization experiments between the mouse HPRT deficient RAG cell line and eight different human long term lymphoid cell lines or fetal cells. The thirteen primary clones showed 100% concordance between the expression of the human enzyme and the presence or absence of human chromosome 15. Analysis of the 27 secondary clones showed only two subclones discordant for segregation of human GANC and enzyme markers for 15. The two apparently discordant clones for human GANC were both derived from the same RAG X human fetal lung primary clone, and both lacked GANC activity, while retaining a 15. Since human GANC is polymorphic with a null allele at high frequency (MARTINIUK and HIRSCHHORN, 1980), it is possible that these subclones carried one chromosome with a null allele for GANC. Alternatively there could been an undetected chromosome break between the GANC locus and the loci of the marker enzymes. Whatever the reason for the two apparently discordant subclones, combined data from all 40 clones show 95% concordant segregation for human GANC and No. 15.

Animals↗
PubMed1980

Comparison of intraperitoneal, intraportal and intravenous insulin infusion.

In order to avoid complications induced by long-term infusion of insulin into the portal vein, we examined the effect of intraperitoneal (ip) insulin infusion on arterial plasma insulin and glucose concentrations in 6 pigs, made diabetic by a constant intravenous (iv) infusion of glucose, epinephrine and propranolol. Insulin was infused by an electromechanical programmable mini-pump (Pharmaject Micro Infusion System, Pharmacia Electronics) as a booster injection of 46 mU highly purified porcine insulin Leo/kg body weight, followed by 3 infusion periods of 30 min each with stepwise decreasing rates of 1.6--0.8 and 0.2 mU/kg/min in a total volume of 192 microliters. Insulin was infused in a peripheral vein, a portal vein and into the peritoneal cavity. A steep rise of arterial plasma insulin was demonstrated followed by a slow and identical decline in the peripheral and portal experiments, whereas only a small increase of plasma insulin was seen in the ip experiment, indicating insufficient absorption of insulin from the peritoneal cavity. The decrease of plasma glucose was identical in the peripheral and portal vein experiments, indicating that insulin infused in the portal vein does not seem to have a higher hypoglycaemic effect, than insulin infused in a peripheral vein. Intraperitoneal insulin infusion seems not to be a practical substitute for iv insulin infusion.

Animals↗
PubMed1980

The effect of joint position on juxta-articular bone marrow pressure. Relation to intra-articular pressure and joint effusion--an experimental study on horses.

Six metacarpo-phalangeal joints of adult horses were studied. Pressure measurements were made in the joint and the metacarpal bone with simultaneous measurement of the systemic arterial blood pressure. Investigations performed to study the effect of joint position on juxta-articular bone marrow pressure showed that an increase in joint flexion was always followed by a rise in intraosseous pressure with a significant increase at flexion above 60 degrees. Increase in intra-articular pressure which was achieved by injection of saline was always followed by a slower rise in intraosseous pressure. Furthermore, it was shown that even a few millilitres of saline in the joint caused a rise in intra-articular pressure. The findings indicate that changes in joint position as well as effusion may block the drainage vessels from the bone marrow as they pass through the joint.

Animals↗