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Biomedical subjects

M Smith

Publications and source records attributed to M Smith.

At least 37 records · Page 2Linked to original sources
PubMed1979

Rapidly developing tolerance to acute exposures to anesthetic agents.

Following the observation that mice manifest a characteristic withdrawal syndrome after an hour of exposure to nitrous oxide, the authors reasoned that there might be a very rapidly developing tolerance to nitrous oxide. Thus, they determined the inspired concentrations that cause loss of the righting reflex in mice (i.e, the ED50), in the presence of 1 atm of oxygen, of: 1) nitrous oxide alone; 2) cyclopropane alone; 3) nitrous oxide plus 13.6 atm helium; 4) ethylene plus 13.6 atm helium. In each instance the ED50 was determined after averages of 6,34 and 64 min of exposure to the anesthetic agents. For nitrous oxide alone the ED50 at 6 min was 1.18 +/- 0.049 atm, increasing to 1.39 +/- 0.061 atm at 64 min. For ethylene plus helium the ED50 increased from 1.21 +/- 0.033 atm at 6 min to 1.31 +/- 0.039 atm at 64 min, indicating the development of acute tolerance. Neither cyclopropane alone nor nitrous oxide plus helium caused acute tolerance. This absence of tolerance may have resulted from a slower development of an alveolar anesthetic concentration.

Anesthetics↗
PubMed1979

Transcription of the Marek's disease virus genome in virus-induced tumors.

Transcription of the Marek's disease virus (MDV) genome in tumor tissues from MDV-infected chickens has been studied by analyzing the hybridization kinetics of (3)H-labeled MDV DNA with unlabeled RNA extracted from these tissues. Lymphoid tumors of ovary, spleen, liver, and kidney contained MDV genomes, but the virus-specific RNA sequences were transcribed from less than 15% of the viral DNA. A virus nonproductive lymphoblastoid cell line, designated MKT-1, has been established from a kidney lymphoma and contains 15 MDV genomes per cell. In these cells, 12 to 14% of the viral DNA was transcribed. Thus transcription of the MDV genome was restricted both in tumor tissues and MKT-1 cells. A hybridization experiment where RNA extracted from MKT-1 cells and RNA extracted from a spleen tumor were mixed and hybridized to (3)H-labeled MDV DNA indicated that the virus-specific RNAs from the two sources were encoded by the same DNA sequences. The polyribosomal fractions of MKT-1 cells and this spleen tumor contained only a portion of the virus-specific RNA sequences found in whole-cell extracts, indicating the existence of a posttranscriptional control mechanism which prevents the transfer of certain viral RNA transcripts to the polyribosomes. The data suggest that the repressed expression of the viral genome in lymphoid tumor tissues and MKT-1 cells may be the result of precise controls within the cell at the transcriptional and posttranscriptional levels.

Animals↗
PubMed1979

Re-examination of effect of paracetamol on serum uric acid measured by phosphotungstic acid reduction.

The drug paracetamol (N-acetyl-p-aminophenol; acetaminophen) caused a spurious increase in serum uric acid measured by phosphotungstic acid reduction methods. However, the increase was less than 0.12 mmol/1 at plasma levels of paracetamol found in overdosage (40 mg/100 ml) and was small at therapeutic concentrations (less than 4 mg/100 ml). It is concluded that few patients with joint pain who have taken paracetamol paracetamol as an analgesic will have clinically misleading values for serum uric acid.

Acetaminophen↗
PubMed1979

Telephone-skills training for retarded adults: group and individual demonstrations with and without verbal instruction.

Effects of telephone-skills training delivered to institutionalized retarded adults in group and individual demonstrations, both with and without verbal instructions, were examined. The trials effect was significant for four telephone tasks and for the sum of the four tasks. Persons in all conditions, including the practice control condition, significantly improved skill performance. These findings indicate that, for skill development tasks with retarded adults, demonstration and verbal summaries may add little to the practice experience and that group delivery of training procedures appears to be cost-effective.

Adult↗
PubMed1979

Inherent ranges of seminal prolactin in pre- and postvasectomy subjects.

Seminal immunoreactive prolactin (i prolactin) was studied in 14 healthy subjects, ages 31 +/- 2 SEM, before and after undergoing elective vassectomy for birth control. Seminal plasma was separated within 2 hours of ejaculation, and prolactin was measured in duplicate by radioimmunoassay. The difference between the prevasectomy (mean +/- SEM 11.1 +/- 0.8 ng/ml) and postvasectomy seminal i prolactin (mean +/- 9.9 +/- 0.7 ng/ml) was statistically significant (mean +/- SEM 1.21 +/- 0.53 ng/ml, paired t-test, t = 2.36, P < 0.05). The mean prevasectomy seminal prolactin correlated with the corresponding mean postvasectomy value of the same subject (linear regression analyses, r = 0.77, P < 0.001). This study suggested that the accessory sex organs were the major source of seminal immunoreactive prolactin, and that a minor contribution might come from the in vivo presence of spermatozoa and/or testicular secretions. It also suggested that the magnitude of seminal immunoreactive prolactin was characteristic for each individual.

Adult↗
PubMed1979

Congenital entropion in a litter of rabbits.

Conjunctivitis and blepharospasm were observed in a litter of four, 2-week-old New Zealand white rabbits. Corneal opacity and neovascularization of the cornea and entropion of the upper eyelids were observed when the rabbits were examined 10 weeks later. Conjunctival cultures of these rabbits yielded normal bacterial flora. Treatment with a steroid-antibiotic ophthalmic ointment did not alter the ocular abnormalities. Surgical correction of the entropion resulted in a complete regression of all clinical signs.

Animals↗
PubMed1979

[Chronic unilateral obstruction to pulmonary venous return. A study on 6 cases and review of the published literature (author's transl)].

The authors describe 6 cases of unilateral obstruction to pulmonary venous return: two cases of Halasz syndrome and postoperative obstruction of the reimplanted collector vein, one patient with Halasz syndrome and spontaneous obstruction of the vein in the form of a scimitar, one case of neoplastic invasion of the atrium-vein junction, one with unilateral absence of the right intra- and extraparenchymatous regions of the pulmonary veins, and lastly, a case of juxta-auricular interruption in the right pulmonary veins. The anatomy and physiopathology of the collateral venous pathways are briefly described, together with the relations between systemic arterial hypervascularization and pulmonary venous obstruction. The authors then review the radiological, clinical, and angiohemodynamic features of the unilateral venous obstruction syndrome, and conclude that precise diagnosis of venous occlusion, its location, and its tolerance are essential for deciding the therapeutic measures required.

Adult↗
PubMed1978

Mutagenesis at a specific position in a DNA sequence.

Predefined changes in a known DNA sequence were introduced by a general method. Oligodeoxyribonucleotides complementary to positions 582 to 593 of the viral DNA strand of the bacteriophage phiX174 am3 mutant (pGTATCCTACAAA), and to the wild type sequence in this region (pGTATCCTACAAA), were synthesized and used as specific mutagens. Each of these oligonucleotides was incorporated into a complete circular complementary strand when used as primer on a genetically heterologous viral strand template, by the combined action of subtilisin-treated Escherichia coli DNA polymerase I and T4 DNA ligase. Incomplete duplexes were removed or were inactivated by nuclease S1 and the products were used to transfect spheroplasts of E. coli. Both oligonucleotides induced specific mutations at high efficiency when used with heterologous template (15% mutants among progeny phage). The am phages isolated by this procedure are phenotypically gene E mutants, and contain A at position 587 of the viral strand. They thus appear identical with am3 and provide evidence that the change G leads to A at position 587 is sufficient to produce a defective E function. Since the template for the induction of am mutants carried another genetic marker (sB1), the strains carrying the induced mutations have the new genotype am3 sB1. It should be possible to introduce the am3 mutation into any known mutant strain of phi174 using this same oligonucleotide. Both possible transition mutations were induced in these experiments. In principle, the method could also induce transversions, insertions, and deletions. The method should be applicable to other circular DNAs of similar size, for example recombinant DNA plasmids.

Base Sequence↗
PubMed1978

Equilibrium and kinetic studies of unfolding of homologous cytochromes c.

Extensive investigations of the unfolding equilibria and kinetics of oxidized and reduced cytochromes c are reported. It is found that all cytochromes c have similar unfolding free energies (deltaGD = 7 +/- 1 kcal/mol). Differences among species do not correlate in any way with the metabolic differences among species. The stabilization of cytochrome c on reduction is estimated at 1.1 kcal/mol. Stability differences among species are mirrored in their denaturation kinetics. For cytochrome c (III), the unfolding exhibits multiple phases. The rate constants for the two observable phases both change by a factor of 3 between horse cytochrome c (III) and cow cytochrome c (III). On reduction, all unfolding appears to occur in a single step. The rate of this unfolding still varies between species, however, the results can be accommodated to a sequential model, with some assumptions. The observations are consistent with chain reversal occurring at an early stage in the reaction and suggest that previously observed rapid processes may be ligand exchange processes.

Animals↗
PubMed1978

Enzymatic synthesis of oligodeoxyribonucleotides of defined sequence.

Procedures for the controlled addition of one or more deoxyribonucleotide residues to the 3' end of an oligodeoxyribonucleotide primer are described. Polynucleotide phosphorylase (EC 2.7.7.8), purified from Escherichia coli B, catalyzes the reaction using a deoxyribonucleoside 5'-diphosphate as substrate, with Mn2+ as cofactor. Reaction occurs rapidly in aqueous solution, and no protecting groups are required, simplifying recovery and purification of the products. The concentrations of sodium chloride and manganous chloride in the incubation mixture are critical to obtaining good yield of the required product. Primers of chain length from 3 to 12 have been extended by up to 9 deoxyribonucleotide residues to obtain oligodeoxyribonucleotides of chain length up to 13. Yields of single addition products varied from 8 to 59%. Factors which influence these yields are discussed. The effects of added polyamines and some organic solvents on the reaction are described. Spermidine or dimethylsulfoxide in the incubation medium tend to favor the addition of several residues of deoxyribonucleotide to the primer.

Base Sequence↗
PubMed1978

Tubulin and microtubule-like structures in mammalian acrosomes.

Immunofluorescence and electron microscopy were used to demonstrate the presence of tubulin and microtubule-like structures in rabbit and rhesus monkey sperm acrosomes. The distribution of tubulin within the acrosome appeared similar to the distribution of proteolytic activity, suggesting an association of proteinase with these structures. Electron microscopy of rhesus monkey sperm incubated in vitro demonstrated a progressive condensation of the acrosomal matrix into microtubule-like structure. A system of this type could explain the linear patterns of silver-proteinate staining in the pentration tunnel through the zona pellucida.

Acrosome↗