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Biomedical subjects

E Rumberger

Publications and source records attributed to E Rumberger.

15 recordsLinked to original sources
PubMed1991

[Ryanodine-induced contractures for the diagnosis of malignant hyperthermia susceptibility].

The halothane-caffeine contracture test is presently the most well-established method for identification of malignant hyperthermia susceptibility (MHS) or non-susceptibility (MHN). However, 10-20% of the patients tested are classified as equivocal (MHE), i.e. their susceptibility remains uncertain. A genetic disorder of the calcium releasing ryanodine receptor has been postulated recently. Therefore, 12 patients were tested in addition to the protocol of the European Malignant Hyperthermia Group (EMHG) for dose- and time-dependent contracture after ryanodine application. In this study, contracture of 0.2g appeared significantly earlier in MHS patients (17.5 +/- 1.7 min; n = 5) during cumulative ryanodine exposition (0.4-0.8-1.6-10.0 mumol/l) than in MHN (38.2 +/- 5.4 min; n = 5). A significant difference between MHS (10.0 +/- 1.7 min; n = 6) and MHN (19.8 +/- 0.6 min; n = 3) was also seen after bolus application of ryanodine (10.0 mumol/l). One patient classified as MHE according to the EMHG protocol, manifested as MHN after the ryanodine contracture test. This study supports previous work suggesting the ryanodine contracture test as an improvement in the in-vitro diagnosis of MH susceptibility.

Adolescent↗
PubMed1990

[Clinical value of new tonometers].

In a clinical study four different tonometers [a hand-held applanation tonometer (HAT), a tonometer that works according to the principle of Mackay-Marg and two noncontact tonometers (NCT A und NCT B)] were compared with respect to accuracy and precision. In a randomized sequence, two physicians took six measurements of both eyes of 99 patients using the four different instruments. The interval between the two measurements in one eye was 3 min. The correlations of repetitive measurements for one tonometer in one eye showed good results for HAT (r = 0.985, SD = 1.66 mmHg), but significantly worse values for the other three tonometers (Mackay-Marg type: r = 0.85, SD = 3.5 mmHg; NCT A and NCT B: r = 0.91, SD = 2.93 mmHg). To establish the accuracy, the pressure values of the Mackay-Marg type and NCT A and NCT B were compared with those of the well-established HAT. The results were as follows: Mackay-Marg type: r = 0.84, SD = 3.78 mmHg; NCT A: r = 0.86, SD = 4.55 mmHg; NCT B: r = 0.89, SD = 3.26 mmHg). We conclude that the three tonometers tested (one based on the Mackay-Marg principle and the other two on the non-contact principle) are not suitable for clinical and scientific use.

Adolescent↗
PubMed1989

Microprocessor controlled tonometry.

Microprocessors have enabled new techniques to be applied to the design of tonometers. Three new microprocessor controlled tonometers, one operating to the principle of Mackay-Marg (Tono-Pen) and two non-contact airstream tonometers (Pulsair and CT-10) have been examined using as a reference Goldmann and the Hand Held Applanation Tonometers (Draeger-HAT) which used the Goldmann applanation principle. The non-contact tonometers produce a conically formed airstream with top speeds of 90 m/s (CT-10) and 70 m/s (Pulsair) which at the moment of pressure measurement applanates the cornea exactly with a diameter of 4 mm. The readings of the microprocessor controlled tonometers correlate well with the readings of HAT (Tono-Pen r = 0.8414 and s = 3.783, CT-10 r = 0.8606 and s = 4.5477, Pulsair r = 0.8968 and s = 3.2641, where r is the correlation coefficient and s is the standard deviation in mmHg). Repeated measurements with one tonometer give the following standard deviations (HAT 1.6617, Tono-Pen 3.4969, CT-10 2.9179, Pulsair 2.9434). Although the three new instruments are able to measure the intraocular pressure in a wide range they do not work with the same precision as the classical applanation tonometer.

Evaluation Studies as Topic↗
PubMed1989

[Clinical and experimental evaluation of the so-called Tono-Pen tonometer].

The measuring accuracy and reliability of the new Tono-Pen tonometer, which works on the Mackay-Marg principle, were tested on isolated human and pigs' bulbi and on 24 patients. On isolated pigs' bulbi the Tono-Pen indicated the true pressure, whereas the pressures measured on isolated human bulbi were too high and the range of scatter was wider. On patients' eyes the values obtained with the Tono-Pen correlated well with those measured with the hand applanation tonometer (r = 0.92), although the values measured with the Tono-Pen again higher (mean 4.5 mm Hg). As indicated by autocorrelation of repeated measurements, the Tono-Pen appears to be mainly responsible for the difference between the two instruments. The standard deviation of the autocorrelation of the Tono-Pen values was 4.5 mm Hg, that of the hand applanation tonometer only 1.2 mm Hg. The considerable standard deviation of the Tono-Pen measurements may be due to the structure of the human cornea, and in particular Bowman's membrane. The reproducibility of Tono-Pen measurements is too low for it to be recommended for ophthalmological diagnosis.

Animals↗
PubMed1989

[Accommodation-convergence coupling using the stereomicroscope].

The term "instrument myopia" means an accommodative effort caused by the view into the microscope. This accommodation may be connected with the convergence position of the eye. Heterophoria should be developed if accommodation-induced convergence of the eyes does not harmonize with convergence of the ocular axes of a stereomicroscope. In 16 probands, an accommodation of 1.1 +/- 0.72 dpt and esophoria of +11.1 +/- 8.5 pdpt were measured at parallel ocular axes. The accommodation increased by 0.12 dpt/degree convergence with increasing convergence angle of the ocular axes. When the visual field was unrestricted, this line intersected the accommodation convergence line at 6.7 degrees. The esophoria decreased with increasing convergence angle and passed over to exophoria. At 8 degrees convergence, heterophoria amounted to -0.2 +/- 2.9 pdpt, and at 16 degrees exophoria was -12 +/- 9.5 pdpt. The minor degree of heterophoria and especially the very minor heterophoria at 8 degrees convergence support the view that the optimum convergence of the ocular axes is near where both accommodation convergence lines intersect.

Accommodation, Ocular↗
PubMed1989

[Comparative studies of the calibration of new electronic automatic tonometers].

Over the last years the number of newly developed automatic microprocessor controlled tonometers has been increasing. These devices follow totally different measurement principles. Therefore the physical methods for calibration of these tonometers differ widely. Described is the possibility of calibration of new microprocessor-controlled tonometers. First the Tonopen, which follows the Mackay-Marg principle was tested. Its accuracy in measuring the intraocular pressure and its independency of position was examined. Moreover, the non-contact tonometers were tested. Especially the airstream of non-contact tonometers (CT 10, Pulsair) was measured with a Constant Temperature Anemometer (CTA). The topspeed of the airstream was 335 km/h for the CT 10 and 249 km/h for the Pulsair tonometer. The profile of the airstream was paraboloid. The base measured about 5 mm in diameter. For detection of the effect of the airstream to the cornea, a camera was connected over a special interface with the CT 10 and triggered with a flashlight generator. The airstream produced at the moment of pressure measurement an exact applanation of the cornea with a diameter of about 4 mm. The results demonstrate the possibility of physical calibration, but this does not substitute biometrical measurements.

Calibration↗
PubMed1987

Nonoptical definition of applanation surface.

Based on the Imbert-Fick law and the theoretical considerations of Goldmann, new applanation tonometers were designed, still using an applanation diameter of 3.06 mm to avoid a new biometric calibration. Three different electronic recording devices were used for the area assessment. An optical, a capacitance and a digital line sensor were tested in first calibration experiments.

Animals↗
PubMed1987

[Possibility of surface-independent tonography and tonometry].

A method of simultaneous measurement of intraocular pressure and volume displacement is reported. An electronic pressure sensor (diameter 3 mm) was positioned in the centre of the base of a transparent applanation body (diameter 9 mm). The corneal applanation area could be changed by different applanation forces and was measured photographically. In isolated human and porcine eyes, sensor signal and intraocularly measured pressure were related linearly and independently of the applanation area. In human eyes in situ, the rigidity coefficient decreased with increasing pressure. Adhesive forces and stiffness of the cornea obviously only falsify tonometry at the margin of the applanation area.

Biomechanical Phenomena↗
PubMed1986

[Electrophysiologic and intropic effects of dantrolene on isolated ventricular myocardium. Studies on guinea pig papillary muscle].

The effect of dantrolene (D) on transmembrane potential and contractile force was examined in electrically driven right ventricular papillary muscles of guinea-pigs. Independent of stimulation frequency D (100 mumol/l) caused a significant reduction of contractility by ca. 40% from control levels. Action potential duration measured at the 90% and 50% repolarisation level was significantly increased while plateau phase was slightly depressed by D. Resting membrane potential, action potential amplitude and maximum rate of depolarisation in phase 0 were unaffected. The effect of D on action potential duration was significantly dependent upon the frequency of stimulation. At faster rates action potential duration was increased relatively more than at slower rates. Slow response action potentials were unaffected by D. Unlike Ryanodine D did not flatten the force-frequency-relationship curve and did not influence the force-interval-relationship under extrastimulation. - It is concluded that the direct negative inotropic effect of D is not accompanied by a transsarcolemmal influence such as an inhibition of fast Na+- or slow Ca++-channels. The results are compatible with an intracellular site of action of D as postulated for skeletal muscle. D acts differently from ryanodine, another presumed inhibitor of sarcoplasmic reticulum.

Action Potentials↗
PubMed1976

Age-changes of the force-frequency-relationship and the duration of action potential of isolated papillary muscles of guinea pig.

The force-frequency-relationship and the duration of the action potential recorded intracellularly were compared on isolated isometrically arranged papillary muscles of young (3--4 months old) and senile (36--40 months old) guinea pigs. The muscles were in Krebs-Henseleit-solution at 37 degrees C electrically stimulated with frequencies between 30 and 420 imp./min. The following results were obtained: 1. The isolated papillary muscles of the two groups are almost similar with respect to length, weight and cross-sectional are. 2. In the range of stimulation rate from 30--420 imp./min the duration of action potential in the senile group was 120--135% of that in the young group. 3. The shape of slow repolarization of action potential was steeper in the senile group. 4. The time to peak tension and the relaxation time were longer in the senile group. 5. The maximally developed tension was the same in both groups, but in the senile group it was reached at a stimulation rate of 120 imp./min whereas in the young group, the optimal frequency was 290 imp./min. 6. The greatest value for the maximal rate of tension rise was 2.4 times smaller in the senile group. The results are discussed in relation to the age dependent intensity of membrane currents and to a possible altered activity of sarcoplasmic reticulum.

Action Potentials↗
PubMed1976

The role of the sarcoplasmic reticulum in the pure frequency potentiation: the effect of ryanodine.

The dependence of the contraction amplitude of the isolated papillary muscle of the guinea pig on the stimulation pattern is probably caused by a well working sarcoplasmic reticulum. This view is supported by the finding that the alkaloid ryanodine flattens the curve of the force-frequency relationship and abolishes the pure frequency potentiation. Ryanodine is said to destroy exclusively the connection between T-tubulus and sarcoplasmic reticulum.

Alkaloids↗
PubMed1976

[The effect of sudden changes in the stimulation rate of the heart on peak systolic pressure (author's transl)].

The changes in systolic pressure were studied in 48 patients during artificially (by electrical stimulation) induced sudden increases and consecutive decreases in heart rate. Various patterns could be separated respective to phase A (sudden switch from low (80-120 impulses/min) to higher heart rate (140-180 impulses/min)) and to phase B (sudden switch-back from high to lower (control) beating rate): AI) The systolic peak-pressure of the first contraction after the shortened stimulation interval is very low and often stays ineffective (below the aortic opening pressure). The second contraction develops already a higher pressure than the first one, during the consecutive beats the systolic pressure increases gradually until a new steady state is reached, which is usually lower than the systolic pressure during the foregoing lower beating rate. Sometimes however it can be equal or even higher. Accordingly after an elevation of heart rate arterial mean pressure can drop, stay constant or increase. AII) The systolic peak-pressure of the first contraction after the shortened stimulation interval stays relatively high and drops continuously with the succeeding contractions until a new steady state is reached according to the higher heart rate, it is however always lower than the one at a lower stimulation rate. Therefore arterial mean pressure is always decreased. AIII) Finally we observed changes in arterial systolic pressure in some patients that could not be grouped according to one or to the other pattern described above.- BI) The systolic peak of the first contraction after the switch-back from the high to the lower (control) rate is much higher than that of the last at the higher rate. The peak pressures of the consecutive contractions are then dropping continuously to the new steady-state, that can be higher, equal or lower than that at the higher stimulation rate. BII) ....

Adolescent↗
PubMedDate not supplied

The influence of calcium and beta-sympathomimetics on force-frequency relationship and resting potentiation in guinea pig papillary muscle.

The influence of various calcium concentrations and of the beta-sympathomimeticum orciprenaline (Alupent) on the force-frequency relationship and on the resting potentiation of isolated isometrically contracting papillary muscles of the guinea pig heart was studied. Elevation of Ca concentration and/or addition of orciprenaline augment the amplitudes of contractions elicited by rhythmical stimulation, but they diminish the amplitudes of test contractions elicited after a test interval of 1-2 s. It is suggested that calcium and orciprenaline strengthen the calcium loss from the sarcoplasmic reticulum out of the cell during a prolonged interval.

Animals↗