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Biomedical subjects

M Morgan

Publications and source records attributed to M Morgan.

At least 397 records · Page 22Linked to original sources
PubMed1977

Transient hypoxemia in firemen following inhalation of smoke.

Mild to moderately severe hypoxemia was documented in 19 of 21 mostly asymptomatic firemen who were exposed to dense smoke containing polyvinylchloride and other pulmonary irritants. The hypoxemia was transient, with nearly complete reversibility within 24 hours. Subsequent tests for pulmonary function one month later demonstrated that this transient hypoxemia was not related to previous underlying pulmonary disease. The potential for serious complications of inhalation of smoke, particularly smoke from burning plastics, is heightened by the frequent lack of symptoms associated with the type of exposure, despite the development of hemoglobinemia. Precautionary measures should include uninterrupted use of an effective breathing apparatus by firemen exposed to smoke and to noxious fumes and temporary oxygen supplementation, even in asymptomatic firemen, following exposure to dense smoke.

Adult↗
PubMed1976

Influence of 5'-terminal m7G and 2'--O-methylated residues on messenger ribonucleic acid binding to ribosomes.

Removal of 80% of the 5'-terminal 7-methyl-guanosine (m7G) from methylated reovirus mRNA by beta elimination results in a concomitant loss of the ability to bind to wheat germ ribosomes. The mRNA molecules that retain the m7G account for most of the residual binding. Removal of the m7G from all molecules in preparations of methylated reovirus and vesicular stomatitis virus mRNA reduces the extent of binding to wheat germ ribosomes from 80% to 5-7%. In the reticulocyte lysate, however, significant binding (17-34%) of the beta-eliminated viral RNAs occurs. This m7G-independent binding appears to be due to recognition by ribosomes of other structural features of the 5'-proximal sequences. Initiation complexes involving beta-eliminated animal virus mRNAs and rabbit reticulocyte ribosomes appear to be more stable than the more heterologous combination of the same viral mRNAs and wheat germ ribosomes. In addition, evidence is presented to show that the 2'-O-methylated nucleoside of the 5'-terminal cap has a positive influence on the ribosome binding of viral mRNA and of capped synthetic ribopolymers. A model involving recognition of multiple structural features of the 5'-terminal region of mRNA by ribosomes during initiation of protein synthesis is presented.

Animals↗
PubMed1976

Effect of isolation on barbiturate anaesthesia in the rat.

The duration of barbiturate-induced sleeping in rats was found to be reduced by isolation housing. It was also lower in males than females, and lower in the dark phase of the diurnal cycle. These variables were shown to be additive in their effects. Sex differences in barbiturate action were found to be reduced by gonadectomy in males; and the effects of isolation were found to depend upon housing conditions at the time of testing rather than upon early rearing environment. The implication for theories of arousal is discussed.

Anesthesia↗
PubMed1976

Myosin light-chain phosphatase.

1. A method for the isolation of a new enzyme, myosin light-chain phosphatase, from rabbit white skeletal muscle by using a Sepharose-phosphorylated myosin light-chain affinity column is described. 2. The enzyme migrated as a single component on electrophoresis in sodium dodecyl sulphate/polyacrylamide gel at pH7.0, with apparent mol.wt. 70000. 3. The enzyme was highly specific for the phosphorylated P-light chain of myosin, had pH optima at 6.5 and 8.0 and was not inhibited by NaF. 4. A Ca2+-sensitive 'ATPase' (adenosine triphosphatase) system consisting of myosin light-chain kinase, myosin light-chain phosphatase and the P-light chain is described. 5. Evidence is presented for a phosphoryl exchange between Pi, phosphorylated P-light chain and myosin light-chain phosphatase. 6. Heavy meromyosin prepared by chymotryptic digestion can be phosphorylated by myosin light-chain kinase. 7. The ATPase activities of myosin and heavy meromyosin, in the presence and absence of F-actin, were not significantly changed (+/- 10%) by phosphorylation of the P-light chain.

Actins↗
PubMed1976

Structure of cells and nerve endings in abdominal vagal paraganglia of the rat.

The abdominal vagal paraganglia of the rat consist of small groups of cells, interspersed by blood vessels and nerve bundles and lying close to, or within, the vagus nerve or its branches. Each cell group consists of 2-10 Type I cells incompletely invested by 1-3 satellite cells. Type I cells are characterised by the presence of numerous dense-cored vesicles in their cytoplasm and may exhibit 'synaptic'-like contact with each other. Small efferent nerve endings make synaptic contacts with Type I cells. Larger cup-shaped afferent nerve endings also make synaptic contacts of two kinds with Type I cells. Nerve-nerve synapses are often seen within or close to paraganglia. Attention is drawn to the close similarity of fine structure of abdominal vagal paraganglia, carotid body and small intensely fluorescent cells of the superior cervical ganglion in rats. Possible functional implications of this morphological similarity are discussed.

Animals↗
PubMed1976

Methyl labeling of HeLa cell hnRNA: a comparison with mRNA.

The majority of the mRNA molecules in HeLa cells contain 1-2 residue(s) of m6Ap and one blocked, methylated 5' terminal "cap" structure. The hnRNA, which is longer than mRNA, contains both m6Ap and caps but 4-6 times as many m6Ap residues per chain. In addition, nuclear molecules contain T2 RNA ase-resistant, methyl-labeled oligonucleotides ("di-" and "tri-" nucleotides) which are not found in mRNA. Some of the dinucleotides may be precursors to the 2'-0-methylated nucleotides in the cap structures. These results are compatible with internal methylation of hnRNA molecules (both m6Ap and 2'-0-methyl) followed by hnRNA cleavage and the addition of the cap structure to generate at least some of the HeLa cell mRNA. It also appears that some hnRNA molecules, which are longer than most mRNA molecules, contain cap structures suggesting the derivation of some mRNA molecules from the 5' regions of hnRNA.

Cell Nucleus↗
PubMed1976

Effect of dose and premedication on induction complications with etomidate.

The induction characteristics of etomidate, a new i.v. hypnotic agent, were studied in 400 patients. Two hundred were premedicated with atropine and anaesthesia was induced with 0.2, 0.25, 0.3 or 0.35 mg/kg of etomidate. The remainder received one of four standard premedications and anaesthesia was induced with etomidate 0.3 mg/kg. Involuntary muscle movements occurred in more than 60% of patients receiving atropine alone. The frequency was reduced in the second group, but remained unacceptable in over 8% of patients. The incidence of other excitatory phenomena, such as cough and hiccup, was 10% approximately. Cardiovascular changes were minimal and no serious allergic phenomena were observed. Nausea and vomiting occurred after surgery in up to 30% of patients and was unrelated to the dose of etomidate or to premedication. Pain on injection occurred in up to 80% of patients when the drug was injected into small peripheral veins and occurred in more than 7% when using more normal veins.

Adult↗
PubMed1976

Pain during continuous nitrous oxide administration.

The continuous administration of nitrous oxide, in subjects who remain conscious, caused only a relatively small increase in the threshold of appreciation of pain, induced experimentally by tibial pressure and a hot wire applied to the thenar eminence. The threshold reached a maximum at 10 min. A concentration of 50% nitrous oxide caused only a marginally greater effect than 33%. In some subjects pain thresholds returned to control values during administration of the gas. In contrast, when a concentration of 50% nitrous oxide was approached in step changes of 7-10% over a period of 45 min, the effect on the pain threshold was more than doubled. It was concluded that, with respect to analgesia, adaptation of the nervous system to a constant concentration of nitrous oxide can occur in some subjects.

Analgesia↗
PubMed1976

The methylation of adenovirus-specific nuclear and cytoplasmic RNA.

Each poly(A) containing cytoplasmic AD-2 MRNA contains at its 5' terminus the general structure m7 GpppN1 pN2p or m7 GpppN1mpN2mpNp as well as an average of 4 m6A and 0.5-1 m5C residues per molecule. Almost all of the N1m residues are adenine derivatives including Am, m6Am and probably m26,6Am. The N2m is mostly Cm but small amounts of the other three methylated bases are also present. All the methylated constitutents of mRNA are distant from the 3' terminal poly(A). The amount of m6A appears to be greater in larger mRNA than in smaller mRNA. Nuclear Ad-2 specific RNA also contains caps, m6A, and m5C with about twice as much m6A relative to caps as cytoplasmic mRNA. The similarity of Ad-2 nuclear and mRNA to HeLa hnRNA and mRNA suggests that adenovirus mRNA production is a good model for eukaryotic mRNA production.

Adenoviridae↗
PubMed1976

The role of vesico-ureteric (V-U) reflux in the pathogenesis of kidney scars in the rat.

In Wistar rats V-U reflux with distilled water and sterile saline of varying osmolar strength produces scars in the perihilar region of the kidneys in 80% of animals. Using Indian ink as a marker, rupture of the forniceal epithelium regularly followed V-U reflux. Intrapelvic pressure rose to 120 mm Hg during the reflux procedure. A slowing of proximal tubular transit time was observed by the Lissamine Green technique in the nephrons in the perihilar region immediately after the kidney had been subjected to reflux. It is suggested that the kidney scars which develop after reflux of sterile solutions are ischaemic in origin. It was shown that kidneys damaged by reflux have an increased susceptibility to haematogenous infection.

Animals↗
PubMed1976

The effect of halothani-nitrous oxide anaesthesia and spontaneous ventilation on arterial blood oxygenation and physiological deadspace.

Arterial blood, inspired and expired gas samples were taken from seven patients anaesthetized with halothane (1-2 per cent) and nitrous oxide in oxygen and who breathed spontaneously. Over a two hour period, the average arterial oxygen tension was 75 mm Hg and carbon dioxide tension 49 mm Hg. No significant deterioration of either blood gas value occurred during the two hours. The dead-space/tidal volume ratio and alveolar-arterial oxygen tension difference did not alter significantly during the period of the study.

Adult↗
PubMed1976

Maternal complications of obstetric epidural analgesia.

The maternal complications associated with 1,000 consecutive obstetric epidurals are described. Although the analgesia provided was very satisfactory, complications were common. A dural puncture rate of 1-7 per cent resulted in 13 patients suffering from "spinal headache". Blood vessel puncture occurred in 45 patients, while the presence of unblocked segments and unilateral block was troublesome. There were no serious sequelae, but it is suggested that the provision of an epidural service for women in labour requires the immediate availability of an experienced anaesthetist to attend the labour ward.

Anesthesia, Epidural↗
PubMed1975

Translation of silk fibroin messenger RNA in an Ehrlich ascites cell-free extract.

RNA identified by its base composition and T1 RNase oligonucleotide pattern as the message for silk fibroin was purified from mature posterior silk glands of Bombyx mori larvae and used to direct polypeptide synthesis in an Ehrlich ascites cell-free extract. Fibroin mRNA stimulated [3-H]alanine incorporation about 3- to 4-fold in the presence of 80 mM K+ and 4 mM Mg-2+. The stimulation was reduced in the presence of 5 times 10-minus 6 to 10-minus 4 M aurintricarboxylic acid, an inhibitor of the initiation of protein synthesis. The cell-free products were heterogeneous in size, including peptides as large as 100,000 daltons. They co-precipitated with carrier fibroin sequences after digestion with trypsin. A large fraction of the polypeptides synthesized in response to fibroin mRNA was precipitated by antiserum directed against amino acid sequences in noncrystalline region polypeptides of fibroin. Furthermore, after digestion with chymotrypsin, a major fraction of the cell-free products specifically co-precipitated with crystalline region sequences of native fibroin. The size and amino acid composition of the fibroin crystalline region polypeptides isolated from the cell-free products were similar to those from native fibroin.

Amino Acids↗