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Biomedical subjects

J F Morgan

Publications and source records attributed to J F Morgan.

8 recordsLinked to original sources
PubMed1979

Complications associated with contact lens solutions.

The complications that have been seen when hydrophilic lenses are cared for by chemical decontamination are reviewed. The findings that help to differentiate lens-induced changes from chemical-care-produced changes are presented. Incompatibilities between care methods are illustrated. The complications are discussed in terms of changes produced in the cornea, conjunctiva, flora of the cul-de-sac, and lens.

Chlorhexidine↗
PubMed1978

Ca2+-controlled conformational states of the Ca2+ transport enzyme of sarcoplasmic reticulum.

The fluorescent reagent, S-mercuric N-dansyl-cysteine, reacts specifically with thiols of the purified Ca2+-ATPase of the sarcoplasmic reticulum, producing an increase of fluorescence of fluorescence intensity at 500 nm (lambda ex = 335 nm). The reaction is stoichiometric, and the increase of the fluorescence intensity is proportional to the number of blocked thiols. Twelve reactive thiols per 10(5) daltons of ATPase peptide fall into roughly three classes. Blocking of the most reactive thiol entails little inhibition of enzyme activity. Blocking of the five thiols reacting next (intermediate class) results in almost complete inhibition of both phosphorylated intermediate formation and ATP hydrolysis. The second order rate constants of the reaction of thiols have been determined by stopped flow studies. The most reactive thiol and the six least reactive thiols can each be treated as a single class with respect to the rate constant; five thiols of intermediate reactivity appear to have different rate constants (k2, k3, ..k6). Of these constants, k1, corresponding to the most reactive thiol, does not change with [Ca2+]. Upon increasing [Ca2+] from 10(-9) to 10(-5) M, k2 increase and k7-12 decreases; the changes roughly parallel the activation of ATPase activity and the Ca2+ binding to the high affinity alpha sites (Ikemoto, N. (1975) J. Biol. Chem. 250, 7219-7224). Upon further increase of [Ca2+] k2 decreases and k7-12 increase, in parallel with the inhibition of ATPase activity and with the Ca2+ binding to the low affinity gamma sites.

Animals↗
PubMed1975

Comparison of the effects of biogenic amines on cyclic GMP and cycle AMP levels in mouse cerebellum in vitro.

Norepinephrine (NE) elevates levels of both 3',5'-guanosine monophosphate (cyclic GMP) and 3',5'-adenosine monophosphate (cyclic AMP) in incubated slices of mouse cerebellum. As little as 1 muM NE is capable of increasing the level of either cyclic nucleotide. Maximal elevations of cyclic AMP and cyclic GMP levels produced by NE are 15- to 40-fold and 2- to 4-fold, respectively. Dopamine, serotonin and histamine, other biogenic amines considered to be neurotransmitters in CNS, have no effect on mouse cerebellum cyclic nucleotide levels except at relatively high (1 mM) concentrations. NE-induced accumulation of cyclic GMP, but not cyclic AMP, is blocked by omission of Ca2+ from the incubation media. Theophylline does not alter the effect of this catecholamine on either cyclic nucleotide. In tissue slices incubated in buffered sucrose or in choline-Krebs buffer, NE is still capable of increasing both cyclic GMP and cyclic AMP levels; however, these elevations are less than those observed in brain slices incubated in Krebs-Ringer buffer. NE, in combination with glutamate, produces supra-additive elevations of both cyclic GMP and cyclic AMP levels. However, NE in combination with adenosine or high levels of K+ only has a synergistic effect on cyclic AMP and not on cyclic AMP and not on cyclic GMP combination. The elevation of cyclic AMP levels produced by NE appears to be mediated via both alpha- and beta-adrenergic receptor sites. In contrast, the receptor site(s) mediating cyclic AMP accumulation do not appear to be either typical alpha- or beta-adrenergic receptors.

Adenosine↗
PubMed1975

Induced corneal astigmatism with hydrophilic contact lenses.

Changes in keratometer readings were measured in 87 patients, wearing hydrophilic contact lenses for three to more than eighteen months. Twenty-four eyes in the group had an increase of +0.75 or more in the keratometer readings, which invariably involved the vertical reading and was often associated with a distortion of the mire reflex. The change was high as +2.75 diopters. If greater than +1.00 diopter, it was associated with decreased visual acuity with forward correction and with the hydrophilic contact lenses. All but one of the patients who showedchanges of greater than +0.75 diopters over their baseline keratometer readings, were wearing their lenses on an average of 14-16 hours a day. The keratometer readings reverted to the baseline levels with a loss of the distrotion, if the patient reduced the wearing time to less than 12 hours daily. We believe that a maximum average daily wearing time of 12 hours is the safety limit required to minimize the development of induced corneal astigmatism.

Adolescent↗