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Biomedical subjects

R Kern

Publications and source records attributed to R Kern.

At least 109 records · Page 6Linked to original sources
PubMed1978

[Complications and their prevention before, during and after the implantation of intraocular lenses (author's transl)].

The complications and their prevention during and after the implantation of iris clip- and iridocapsular lenses are evaluated. The follow-up period varied from 6-72 months. A careful selection of the patients and optimal conditions during the operation in endotracheal intubation are essential. Secondary cataracts (6%) and the lack of capsular synechiae to the haptic portion of the iridocapsular pseudophakos (7%) are the major complications.

Cataract↗
PubMed1978

[Early results with scleral flap by Preziosi's operation (author's transl)].

The antiglaucomatous Preziosi operation leads within some months in a relatively high percentage of cases to a cataract necessary operation. The main cause for the seems to be a flat anterior chamber lasting several days. Posterior synechaie are frequent. Two out of 55 patients developed an infection of the filtration bleb. By additional preparation of a scleral flap over the sclerectomy complications were obviously rarer, and the regulation of the pressure was very good. There was no difference if the operation was done with or without scleral flap. High pressures during the first days after operation normalize themselves spontaneously or by massage of the eye ball, and have no significance the prognosis. In the cases with scleral flap the filtration blebs show good vascularisation, only in a few cases we saw cystic areas without vessels within filtration blebs with good vascularisation. Moreover the anterior chamber is formed much quicker and complications such as cataract are rare.

Cataract↗
PubMed1978

[Unilateral aphakia and pseudophakia].

Aniseikonia as well as binocular vision and depth perception are measured in 114 patients with unilateral pseudophakos. 86% of the cases exhibit a small degree of aniseikonia (3% or less). However, binocular vision and stereopsis remain subnormal or approximatively normal.

Adolescent↗
PubMed1978

[The prognostic significance of cytologic differentiation grades of estrogen-treated prostata carcinoma. Progress control of 496 prostate carcinoma patients treated with estrogen for five years (author's transl)].

The morphologic differentiation grade of cytologic smear preparations proved to be a reliable gradation measurement for the prognosis of 496 patients suffering from prostate cancer and treated with estrogen. Compared with that of other cancer patients, the life expectancy of low-differentiated and anaplastic cancer patients undergoing estrogen treatment is so poor that the rationale of using antiandrogenous treatment in this carcinoma group seems extremely questionable to us. This is why, in view of the predictable prognosis, the differentiation grade of the tumor should be considered when undertaking therapeutic measures.

Adult↗
PubMed1977

Double sucrose gap voltage clamp in cardiac muscle. Indirect assessment of voltage control from tension records.

In double sucrose gap voltage clamp experimetns on frog atrial bundles the configuration of membrane current and contraction was used to estimate the quality of voltage control. Attention was focused on possible action potential activity along the test segment in response to depolarizing clamps. At low depolarizations large Na+ inward currents were observed while any tension response was missing. Transmembrane potential threshold for generation of a mechanical response was evaluated from conditioned (attenuated) action potentials. The mechanical threshold determined from action potential measurements was only slightly higher than that determined from step-clamp depolarizations. With clamp potentials below the threshold, then, any action potential activity induced by the inward current phase is expected to be rudimentary.

Animals↗
PubMed1977

[Advantages and disadvantages of general anesthesia in eye surgery, seen by the ophthalmosurgeon (author's transl)].

General anesthesia in eye surgery necessitates additional investments in equipment, instruments, rooms and employees. It therefore increases the cost of operation. An anaesthesist, not familiar with the specialties of ophthalmic surgery, is a real risk. The advantages of general anesthesia outweigh by far the disadvantages: optimal observation survey and, if necessary supplementary care of the intubationned patient is guaranteed. The surgical treatment can be performed on the completely immobilized patient without any hurry, eventually additionally in controlled hypotension. Special emphasis has to be put on the postoperative care, especially on an immediate, rigorous mobilization of the patient. Under these conditions, the three-years-statistic clearly demonstrates, that the postoperative complications are as rare as those after operations performed in local anesthesia.

Aged↗
PubMed1977

Iridocapsular lenses versus iris-clip lenses: comparison of the results and complications of 100 of each.

The results and complications of implantation of 100 iridocapsular and 100 iris-clip lenses are evaluated. The follow-up period for the first group varied from one to 25 months (mean 12 months) and from one to 43 months (mean 27 months) for the second group. I performed all of the operations and most of the follow-up examinations. Of the patients with iridocapsular lenses, 86 percent and of those with iris-clip lenses, 87 percent obtained a visual acuity of 0.5 (6/12) or better. Binocular vision, positive depth perception, and a small degree of aniseikonia (3% or less) are evident optical benefits. The complicatioons most frequently necessitating a second operation were retained lens material (17%) and repositioning the pseudophakos (6%) in the iridocapsular group. The four-loop lenses caused fewer problems; in one case, posterior luxation necessitated its removal.

Adolescent↗
PubMed1976

Calcium-sodium antagonism on the frog's heart: a voltage-clamp study.

1. In double sucrose-gap voltage-clamped frog atrial fibres the influence of [Ca]o and [Na]o on membrane current and contraction was investigated. 2. The slow (secondary) inward current varied with [Ca]o but was almost insensitive to changes in [Na]o. In contrast, the phasic (transient) contraction initiated by the slow inward current was affected by both [Ca]o and [Na]o. 3. With moderate changes of [Ca]o and [Na]o from normal, the strength of phasic contraction at a given depolarization followed the [Ca]o/[Na]2o ratio approximately. This was best seen at membrane potentials near zero level. 4. Under the same conditions, tonic (sustained) contractions associated with prolonged depolarizations were strictly correlated to the [Ca]o/[Na]2o ratio at any potential. No interrelation between tonic tension and steady-state current was found. 5. With extensive changes in [Ca]o and [Na]o, the sensitivity of both phasic and tonic tension to the [Ca]o/[Na]2o ratio declined, the negative effect of [Na]o becoming smaller than was expected from this ratio. 6. In Na-free choline-Ringer, a strong contracture developed followed by a spontaneous relaxation. Starting from the relaxed state, application of depolarizing clamps gave rise to phasic contractions with a very slow relaxation while tonic contractions were apparently lacking. 7. The results are interpreted in terms of an energy-dependent carrier mechanism exchanging one Ca for two Na ions across the cell membrane. The model implies a strong asymmetry in the rate constants governing the chemical reactions on both sides of the membrane. The system is thought to operate close to equilibrium at any potential, thereby determining the steady level of myoplasmic Ca. The equilibrium itself is considered to shift upon depolarization. Assuming that [Na]i is constant, the steady level of [Ca]i is expected to be proportional to the [Ca]o/[Na]2o ratio, the scale factor being a function of membrane potential. 8. The carrier model suggests the occurrence of a depolarization-induced inward transfer of Ca which might be involved in the generation of tonic contractions. 9. The apparent lack of tonic contractions in the absence of external Na ions may be explained by a suppression of carrier-mediated Ca influx normally occurring upon depolarization. 10. The antagonistic effects of [Ca]o and [Na]o on phasic contraction are understood as being due to alterations of the Ca pumping system rather than changes in slow inward current.

Action Potentials↗
PubMed1975

Effects of prenylamine on cardiac membrane currents and contractility.

The influence of prenylamine on the electrical and mechanical activity of frog atrial muscle fibers has been studied under voltage clamp conditions. At a concentration of 10-4 M, prenylamine blocks the action potential without much affecting the resting potential. The drug depresses the peak transient sodium conductance with a dissociation constant of 1.7 times 10-5 M and on a one-to-one stoichiometric basis. The curve relating peak sodium conductance to membrane potential is slightly shifted in the direction of hyperpolarization. The time to peak sodium current and the rate of sodium inactivation are not significantly altered. With 2 times 10-5 M prenylamine, the steady-state sodium inactivation curve is shifted by 5 mV to more negative membrane potentials but the decreased availability of the sodium system at the resting level is not sufficient to account for the reduction of sodium current. Recovery from sodium inactivation upon repolarization is distinctly slowed. The slow (secondary) inward current carried by calcium and/or sodium and the steady-state outward current are also depressed by prenylamine. The phasic (twitch-like) contraction related to the slow inward current is slightly decreased. The tonic (sustained) contraction associated with long-lasting depolarizations is increased and the time course of relaxation is retarded by prenylamine.

Action Potentials↗