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Biomedical subjects

A M Gordon

Publications and source records attributed to A M Gordon.

At least 163 records · Page 9Linked to original sources
PubMed1970

Some effects of hypertonic solutions on contraction and excitation-contraction coupling in frog skeletal muscles.

In frog fast skeletal muscle, we find a decline of twitch, tetanus, and maximum K and caffeine contracture tensions as tonicity of the bathing solution is increased. The decline of tension independent of the method of producing contraction indicates that the major effect of hypertonicity is directly on contractile tension probably because of the increased internal ionic strength. However, there is some apparent disruption of excitation-contraction (E-C) coupling in solutions made three times the normal tonicity (3T solutions) since: (a) in 3T solutions tetanic and K contracture tensions decline to zero from a value near the average maximum caffeine contracture tension at this tonicity (10% of 1T tetanic tension). At this time, caffeine contractures of 10% of 1T tetanic tension can be elicited; (b) once the K contracture tension has declined, elevated [Ca(++)](o), 19.8 mM, restores K contracture tension to 13% of 1T tetanic tension. This probable disruption is not caused by changes in mechanical threshold since in 2T solutions the mechanical threshold is shifted by 12 mv in the hyperpolarizing direction. This is consistent with neutralization of fixed negative charges on the inside of the membrane. The repriming curve is also shifted in the hyperpolarizing direction in 2T solutions. Shifts of the repriming curve coupled with membrane depolarizations in 3T solutions (about 20 mv) may produce loss of repriming ability at the resting potential and disruption of E-C coupling.

Amidines↗
PubMed1969

Observations on a new disinfectant.

A disinfectant formula (Resiguard) containing picloxydine digluconate, benzalkonium chloride, and a detergent was examined for antibacterial activity. Studies in vitro with simulated organic contamination were followed by realistic in-use tests employing items of anaesthetic and urological equipment heavily infected with Pseudomonas aeruginosa and contaminated with blood. These showed that a dilution of 1/80 was reliably bactericidal to this resistant organism. It is concluded that Resiguard is a valuable disinfectant which may reliably be employed in the cleaning and disinfection of items of delicate, non-autoclavable, hospital equipment.

Anesthesia↗
PubMed1967

Mycoplasmas and recurrent oral ulceration.

A controlled cultural and serological investigation of mycoplasmas in recurrent oral ulceration was undertaken. No evidence for an aetiological relationship between oral mycoplasmas and this condition was obtained.Mycoplasmas, principally M. orale, were frequently recovered from the oral cavities of individuals with natural teeth, but rarely from edentulous subjects.

Adolescent↗
PubMed1966

Tension development in highly stretched vertebrate muscle fibres.

1. An apparatus is described by which the length of a selected part of an isolated muscle fibre can be held constant, giving isometric conditions, or alternatively its length can be measured while tension is held constant (isotonic). Control can be switched between length and tension so as to carry out afterloaded contractions with a shortening stop.2. When a part of a fibre with uniform striation spacing is stretched so far that there is presumably no overlap of filaments, the tension developed during an isometric tetanus with this apparatus is very small (not more than 3-5% of the tension developed at optimum length).3. If the tendon ends are held stationary, a fibre with the same initial length develops a large amount of tension (order of 30-40% of tension at optimum length) with a slow time course. This additional tension is due to shortening of the end parts of the fibre, where the striation spacing is smaller and overlap of filaments still exists.4. The resistance to elongation of a part of a fibre where there is no overlap is only slightly increased on stimulation.5. To a first approximation, the results are in good agreement with expectations based on the sliding filament theory. The development of detectable amounts of tension, and of a slight increase of stiffness, on stimulation, are however not expected on the simplest form of this theory; possible explanations are discussed.

Animals↗
PubMed1966

The variation in isometric tension with sarcomere length in vertebrate muscle fibres.

1. The variation of isometric tetanus tension with sarcomere length in single fibres from frog striated muscle has been re-investigated with special precautions to ensure uniformity of sarcomere length within the part of the fibre being studied.2. In most respects the results of Ramsey & Street (1940) were confirmed, but (a) the peak of the curve was found to consist of a plateau between sarcomere lengths of 2.05 and 2.2 mu, (b) the decline of tension above this plateau is steeper than found by Ramsey & Street, and (c) the decline of tension below the plateau becomes suddenly steeper at a sarcomere length of about 1.67 mu.3. Many features of this length-tension relation are simply explained on the sliding-filament theory.4. It is concluded that, in the plateau and at greater lengths, the tension on each thin filament is made up of equal contributions from each bridge which it overlaps on adjacent thick filaments.5. Internal resistance to shortening is negligible in this range but becomes progressively more important with shortening below the plateau.

Animals↗
PubMed1966

Bacterial flora in abnormalities of the female genital tract.

The bacterial flora associated with certain common abnormalities of the female genital tract were studied. The abnormalities included were trichomonal infestation of the vagina, the epithelial inflammation and cellular atypia associated with protozoal infestation, and erosions of the cervix. Trichomonas vaginalis infestation and marked epithelial inflammation were associated with a very varied bacterial flora in which Mycoplasma species, streptococci, and ;Haemophilus vaginalis' (Gardner and Dukes, 1955) were often prominent. No cases of vaginitis attributable to Haemophilus vaginalis were detected. An essentially normal bacterial flora accompanied erosions of the cervix.

Candida↗