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Biomedical subjects

J C Miller

Publications and source records attributed to J C Miller.

At least 145 records · Page 8Linked to original sources
PubMed1977

In vitro and in vivo studies of extrapineal N-acetyltransferase of rat brain.

In a series of experiments, extrapineal rat brain N-acetyltransferase was further characterized and was demonstrated to have a similar pH optimum and similar activity to that of the low activity daytime pineal N-acetyltransferase. Experiments in vivo indicate that N-acetylation may be a possible alternative metabolic pathway for biogenic amines and that brain N-acetyltransferase activity may be regulated by a beta-adrenergic mechanism.

Acetylation↗
PubMed1977

Sleep at altitude.

The effects of hypobaric hypoxia upon the electrophysiologically assessed sleep of four male and four female subjects--18-29 years old--were measured during two successive nights at 493 torr (3500 m) in a hypobaric chamber. Five subjects experienced varied levels of acute mountain sickness (AMS). Sleep disturbance was primarily manifested as "insomnia" in two subjects experiencing higher levels of AMS. Relatively normal amounts of synchronized sleep were observed at 493 torr, implying the occurrence of sleep hypoventilation.

Adolescent↗
PubMed1977

Cardiac output during sleep at altitude.

The effects of hypobaric hypoxia and sleep, assessed by EEG, upon cardiac output (Q) were studied by impedance cardiography using two male and two female subjects. Three nights were spent at 746 torr (152 m) followed by two nights at 493 torr (3500 m), all in a hypobaric chamber. Relatively normal sleep was observed except in the presence of Acute Mountain Sickness (AMS). The occurrence of normal levels of synchronized sleep implied that sleep hypoventilation occurred. A nadir of Q was observed at about 0500 hours, implying reduced O2 delivery. It was suggested that hypobaric hypoxia, sleep hypoventilation, and reduced O2 delivery may have interacted to produce AMS.

Altitude↗
PubMed1977

Magnesium deficiency in embryos of Xenopus laevis.

Embryos of Xenopus laevis reared in media with various low (less than or equal to 10(-5) M) magnesium ion concentrations will exhibit differing degrees of a potentially lethal magnesium starvation syndrome depending on the ion concentration and rearing temperature. The higher the rearing temperature or the lower the magnesium ion content of the medium the more severely the syndrome will be expressed. (Normal development can be expected at temperatures 13-30 degrees C and magnesium ion concentrations greater than 10(-5)M to 10(-2) M.). The magnesium deficiency syndrome in Xenopus embryos is described in detail and compared with the normal and anucleolate conditions. The deficiency condition becomes manifest after hatching as retarded growth and differentiation with progressive paralysis and edema. At the same time alterations are observed in the pattern of soluble proteins. The use of magnesium ions as a probe for investigating developing systems is discussed.

Age Factors↗
PubMed1977

Physiological analysis of repetitive lifting.

It was hypothesized that physical factors associated with the act of lifting, and also known to adversely affect cardiovascular functions (e.g., increased intrathoracic and intraabdominal pressures), would disturb the linear relationships normally noted among measures of cardiopulmonary variation during exercise. Data collected during repetitive lifting, performed on a unique ergometer (described in the paper), did not support the hypothesis. It was concluded that relationships among energy expenditure rate, pulmonary ventilation, heart rate, and workload were essentially linear through the range of lifting workloads from 1 to 50 W for 18 male Caucasians ranging in age from 21 to 55 years.

Adult↗
PubMed1976

Cardiac output during human sleep.

Impedance cardiogram and sleep EEG were recorded from four male and four female subjects, aged 21 to 22 years, during one night in the laboratory following one adaptation night. Cardiac output fell approximately 26% during the night as a consequence of diminished stroke volume, the lowest values of both occurring during the latter portion of the night, dominated by SREM (rapid-eye-movement stage). Intracycle comparisons between SREM and SWS (slow wave sleep) or between eye movement burst and non-burst SREM showed no significant differences in stroke volume or cardiac output. Pre-ejection period and systolic ejection period were measured and discussed. The non-coincidence of the nadir of metabolic activity, expressed as cardiac output, and the apex of slow-wave sleep activity supported the concept of slow-wave sleep as a period of physiological restoration.

Adult↗
PubMed1971

Amino acid sequences around the cysteine residues of rabbit muscle triose phosphate isomerase.

1. The nature of the subunits in rabbit muscle triose phosphate isomerase has been investigated. 2. Amino acid analyses show that there are five cysteine residues and two methionine residues/subunit. 3. The amino acid sequences around the cysteine residues have been determined; these account for about 75 residues. 4. Cleavage at the methionine residues with cyanogen bromide gave three fragments. 5. These results show that the subunits correspond to polypeptide chains, containing about 230 amino acid residues. The chains in triose phosphate isomerase seem to be shorter than those of other glycolytic enzymes.

Amino Acid Sequence↗
PubMed1971

The active centre of rabbit muscle triose phosphate isomerase. The site that is labelled by glycidol phosphate.

1. Glycidol (2,3-epoxypropanol) phosphate is a specific irreversible inhibitor of rabbit muscle triose phosphate isomerase (EC 5.3.1.1); the site of attachment has now been studied. 2. The labelled enzyme was digested with pepsin and a modified peptide isolated. The sequence of the peptide is: Ala-Tyr-Glu-Pro-Val-Trp. 3. It is the glutamic acid residue in this peptide that is labelled: the peptide is thus a gamma-glutamyl ester derived from glycerol phosphoric acid. The same site is labelled by a mixture of glycidol and inorganic phosphate. 4. Kinetic and stereochemical features of these reactions are discussed.

1-Propanol↗