Mechanosensitive connective tissue: potential influence on heart rhythm.
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Animals↗
Biomedical subjects
P Kohl
Publications and source records attributed to P Kohl.
Calcium and mechanically induced potentials in fibroblasts of rat atrium.
OBJECTIVES: Electrically non-excitable cardiac fibroblasts in the sino-atrial node region are mechano-sensitive. Rhythmic contraction of adjacent myocardium, or artificial stretch of the tissue, produce a reversible change in the membrane potential: mechanically induced potentials (MIP). Stretch of normal cardiomyocytes can be associated with intracellular calcium changes. The purpose of this study is to use pharmacological interventions to investigate the possibility that stretch-induced Ca2+ entry through ion channels in the sarcolemma and Ca2+ release from internal stores play a role in MIP generation. METHODS: Isolated spontaneously contracting or artificially stretched preparations of right atrium of rat heart were superfused with physiological solutions. An intracellular floating microelectrode recorded fibroblast MIPs and was also used for injection of current. A dye, Lucifer yellow, applied through the micropipette, identified recording sites. We assessed the role of extracellular Ca2+ using EGTA in the bathing solution. For the role of intracellular Ca2+ in the generation of MIP, several substances that influence [Ca2+]i handling were applied intracellularly by diffusion from the recording microelectrode. These include: BAPTA (to chelate intracellular Ca2+); BHQ, thapsigargin and CPA (to deplete Ca2+ from intracellular stores by inhibition of the endoplasmic reticulum (ER) ATP Ca2+ pump), and caffeine and ryanodine (to induce ER Ca2+ release). RESULTS: All the pharmacological compounds which were introduced intracellulary, and EGTA applied extracellularly, decreased the amplitude of the MIP to variable degrees. Only thapsigargin induced a bi-phasic response with an initial increase in MIP amplitude, followed by a decrease. MIP duration was reduced by most interventions, exceptions being low extracellular Ca2+, BHQ and ryanodine. Short duration extracellular application of caffeine, which was added to the perfusate as a secondary contractile stimulus, partly restored the MIPs by activation of cardiac contraction. Intracellular current injection, before any intervention, linearly altered both membrane potential (Em) and MIP amplitude (Vm). Application of compounds listed above introduced non-linearity to the Em/Vm relationship. CONCLUSION: We suggest that mechanically induced Ca2+ influx, induced through stretch-activated channels in the plasma membrane, and release of Ca2+ from the endoplasmic reticulum, play key roles in the mechanism of MIP generation. Further, our results demonstrate the existence of functional ryanodine/caffeine-sensitive Ca2+ stores in cardiac fibroblasts.
Action Potentials↗
The dizzy patient: a review of etiology, differential diagnosis, and management.
BACKGROUND: Dizziness is a lay term used to describe a variety of sensations. Unfortunately, the term "dizziness" does not have a precise medical definition, and additional information is typically required to further define the patient's problem. METHODS: When dizziness is a presenting complaint, distinctions must be made between vertigo (a sense of false movement), near-syncope (a feeling of impending faint), disequilibrium (loss of balance), and ill-defined lightheadedness (an inability to concentrate or focus the mind). Possible causes of dizziness include conflicts between visual and vestibular information, vascular problems, adverse reactions to medication, psychological difficulties, systemic disease, and the effects of aging. RESULTS: Dizziness is a symptom of a physiological or psychological illness, and therefore management is typically directed toward treatment of the underlying illness. In some cases the cause of the dizziness cannot be found, however, or is untreatable. In these cases, management is directed toward symptom reduction. CONCLUSIONS: Dizziness is a relatively common problem that arises from a variety of causes. In many cases, optometrists can participate in the diagnosis and management of patients with complaints of dizziness.
Diagnosis, Differential↗
Prevention of heterotopic ossification with tenoxicam following total hip arthroplasty: a double-blind, placebo-controlled dose-finding study.
The effect of tenoxicam 10 mg and 20 mg, administered daily for 6 weeks to prevent heterotopic bone formation after total hip arthroplasty, was evaluated in a randomized, double-blind, placebo-controlled trial involving 90 patients. After 3 months, patients who had received the active drug, including those who had received only half the recommended anti-inflammatory dosage, had significantly less heterotopic bone formation. After 6 months the difference between treatment groups and placebo became smaller but remained significant. Adverse reactions occurred in only 3 patients, reflecting no differences between the groups. The study results, including radiographic, clinical and biochemical evaluations, demonstrate that treatment with tenoxicam 20 mg daily and even with tenoxicam 10 mg daily for 6 weeks, starting immediately after total hip arthroplasty, is effective in preventing ectopic bone formation.
Adult↗
[Primary extragonadal germ cell tumors. Clinical manifestations, differential diagnosis and therapy].
BACKGROUND: Primary extragonadal germ cell tumors are a rare malignant disease in young males. They account for only 1 to 4% of all germ cell tumors. PATIENTS AND METHODS: In this paper we describe three selected cases of primary extragonadal germ cell tumors. The literature is reviewed with regard to clinical features, differential diagnosis and treatment. RESULTS: Tumor markers alpha-fetoprotein and human chorionic gonadotropin are of considerable diagnostic value if disease distribution is considered. With cisplatin-based combination chemotherapy similar disease-free survival rates are achieved as for testicular tumors with poor-prognosis metastatic disease. Surgical procedures play a role as adjunctive modality. CONCLUSIONS: If young males present with a mass in the retroperitoneum or in the anterosuperior mediastinum, a primary extragonadal germ cell tumor, should be taken into consideration. Tumors of both localisations have distinct clinical features but carry a similar prognosis. Patients benefit from the cumulative experience of a specialist unit.
Adolescent↗
Central nervous system as sanctuary site of relapse in patients treated with chemotherapy for metastatic testicular cancer.
Isolated central nervous system relapse in patients treated successfully with cisplatin-based chemotherapy for testicular cancer has been described infrequently. In a retrospective analysis we identified this complication in six of 417 patients. Five of the six patients had advanced pulmonary dissemination at onset of chemotherapy, and post-chemotherapy surgery did not reveal viable tumour tissue in any of these cases. All six patients developed a single cerebral metastasis during complete remission a median four months after discontinuation of chemotherapy. Five patients were treated with surgery and subsequent radiotherapy, one patient with irradiation alone. Three patients are alive relapse-free 19, 62 and 86 months after diagnosis of cerebral relapse. One patient was alive with cerebral disease for 12 months without evidence of systemic recurrence. Our data demonstrate that the brain may act as a sanctuary site in chemotherapy-treated testicular cancer. A review of the literature shows that an isolated cerebral relapse is an extremely rare complication, but carries a relatively favourable prognosis.
Adult↗
Mechanosensitive fibroblasts in the sino-atrial node region of rat heart: interaction with cardiomyocytes and possible role.
The positive chronotropic response of the heart to stretch of the right atrium is one of the major mechanisms adjusting the heart rate to variations in venous return on a beat-by-beat basis. The precise pathway of this mechano-electric feedback and its cellular basis are uncertain. In this study, a possible contribution of mechanosensitive fibroblasts, abundant in the sino-atrial node region, was investigated using a mathematical model of the electrical interaction of a mechanosensitive fibroblast and a sino-atrial pacemaker cell. Electrophysiological evidence for a bio-electrical interaction of mechanosensitive fibroblasts with surrounding cardiomyocytes has been studied in (i) the isolated spontaneously beating atrium of rat hearts, and (ii) cell cultures of the neonatal rat heart. These investigations were performed using (i) double-barrelled floating microelectrodes for intracellular potential registrations, and (ii) the double whole cell patch-clamp technique. It was shown that cardiac fibroblasts and surrounding cardiomyocytes can be either electrically well isolated from each other, or coupled both capacitively and electrotonically. The electrophysiological data obtained were incorporated into the OXSOFT HEART program. Assuming that equivalent coupling may occur between mechanosensitive fibroblasts and sino-atrial pacemaker cells, a heterologous cell pair consisting of one fibroblast and one sino-atrial node myocyte connected by ten to thirty single gap junctional channels with a conductance of 30 pS was modelled. The model of the electrotonic interaction of these cells showed that stretch of the fibroblast during atrial diastole, simulating increased atrial wall tension during atrial filling, can raise the spontaneous depolarization rate of the pacemaker cell in a stretch-dependent manner by up to 24%. These results show that cardiac mechanosensitive fibroblasts could form a cellular basis for the positive chronotropic response of the heart to stretch of the right atrium.
Animals↗
Testicular tumor after cisplatin-based chemotherapy for germ cell malignancy.
Among 417 patients treated with cisplatin-based chemotherapy for germ cell malignancy (median follow-up 7 years) we observed 6 patients who developed a second tumor of the testis. In 3 cases the first tumor was of testicular origin, whereas in the other cases the initial tumor presented in the retroperitoneal space. Although cisplatin-based chemotherapy may reduce or delay the development of a contralateral testicular tumor, the risk apparently is not completely eliminated. Patients with primary retroperitoneal germ cell tumors need a close and careful follow-up, as they appear to be at an increased risk for developing a testicular tumor.
Adult↗
Comparison of Irlen scotopic sensitivity syndrome test results to academic and visual performance data.
UNLABELLED: Irlen has defined a condition called Scotopic Sensitivity Syndrome (SSS) that is associated with reading problems. According to Irlen, SSS can be treated by the use of colored filters, but there is disagreement about the existence of SSS and the efficacy of colored filter therapy. METHODS: Thirty-nine children participated in the study: 24 were academically normal, nine had specific reading problems, and six had problems in multiple academic areas. SSS levels and preferred overlay colors were determined. Optometric test data were also available for each subject. RESULTS: No significant relationships were found between academic classification and degree of SSS. There were also no significant relationships between preferred overlay color and any other variables. There was, however, a significant tendency for subjects with higher SSS levels to be candidates for vision therapy and to derive greater benefit from the colored overlays. CONCLUSIONS: Many questions about the use of colored filters for the treatment of reading problems remain unanswered. Among these are questions dealing with whether the M-pathway anomalies found in some dyslexics are also present to a lesser degree in other cases of reading disabilities, and how colored filters could re-balance the M- and P-pathways. Is it the color of the filter itself that is critical, or is it the change in luminance or contrast produced by the filter that seems to make it easier for some subjects to read? More research will be needed to answer these questions.
Child↗
[26-year-old patient with excessive, cystic space-occupying lesion of the abdomen].
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Adult↗
[Indurating soft tissue swelling, eosinophilia and increased blood sedimentation rate].
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Aged↗
Mechanosensitive cells in the atrium of frog heart.
Mechanosensitive cells were found in the sinus venosus and right atrium of the frog heart. Their intracellular membrane potentials were studied in spontaneously beating hearts and in artificially stretched preparations. Membrane resistance was indirectly proportional to the stretch applied. The electrophysiological data and distribution of these cells in the heart led to the conclusion that they are cardiac fibroblasts.
Animals↗
Clinical evaluation of the Keeler PULSAIR 2000 tonometer.
Intraocular pressures (IOPs) were obtained from 380 eyes of 190 normal subjects using hand-held Keeler PULSAIR 2000 and slit lamp-mounted Goldmann tonometers. IOPs obtained with the PULSAIR were in close agreement with Goldmann pressures over the range of IOPs represented in the subject population (9-27 mmHg). This agreement is better than that found in a previous study comparing the original PULSAIR model to the Goldmann, and suggests that the model 2000 represents a significant improvement over the original unit.
Adolescent↗
[Second messenger systems in the gastrointestinal tract].
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Animals↗
Clinical comparison of air-puff and Goldmann tonometers.
Intraocular pressures (IOPs) as measured with the Topcon CT-10, Reichert XPERT and NCT II, and Keeler PULSAIR air-puff tonometers were compared to the Goldmann IOPs for 452 eyes ranging in pressure from 6-40 mmHg. For eyes with pressures in the 10-20 mmHg range, the CT-10 read consistently too high. The XPERT and the NCT II read too high in the lower part of this range and too low in the higher part. The PULSAIR read too low across the entire range. At higher pressures, all of the tonometers read too high except the PULSAIR which again read too low. CT-10, XPERT, and NCT II and PULSAIR pressures were within 4.0 mmHg of Goldmann readings for 81, 85, 89 and 72 percent of the eyes, respectively. Subjects selected the XPERT as the most preferred tonometer and the NCT II was the least preferred mainly because of perceived air-puff intensity.
Adolescent↗
[The treatment of aortic dissection in 1988. When should surgery be used?].
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Aortic Dissection↗
Refractive error and preferential looking visual acuity in infants 12-24 months of age: year 2 of a longitudinal study.
This paper presents data from year 2 of a study assessing changes in visual acuity and refractive error in normal, healthy infants between birth and 24 months of age. Visual acuity and refractive error measurements were taken at 2-month intervals on 18 infants, 12-24 months of age. The acuity card preferential looking procedure and Mohindra's near retinoscopy were used for acuity and refractive error measurement. Response to the Stereo Fly was also observed. Mean acuity improved from 6.4 cycles per degree (cpd) (20/93) at 12 months to 20.5 cpd (20/29) at 24 months (SD = 0.5 octave). Refractive error remained in low hyperopia (X = 0.4D, SD = 0.5D). Amount and frequency of astigmatism showed little change. Response to the Stereo Fly improved from 0% at 12 months to 87% at 24 months. The acuity card procedure was easily accomplished, but more difficult with these children at 12-24 months of age than when previously tested between 0-12 months of age.
Analysis of Variance↗
Chromatic imbalance due to commonly used red-green filters reduces accuracy of stereoscopic depth perception.
This study was designed to determine the effect on stereopsis of interocular retinal chromatic and illuminance imbalance in 30 subjects with normal binocularity. A Randot 3 Circle Stereotest, viewed through polarizing glasses only, was the control condition. In each of three additional conditions, illuminance and chromatic imbalances were created by commonly used red and green filters and neutral density filters combined with the polarizing filters. The effect of each of these experimental conditions on stereopsis was determined by comparing total stereo judgement errors on the Randot Circle Stereotest for each condition to the control condition. Total average flux through the filter combinations was held constant by adjusting the luminance level of light reflected from the target. The chromatic imbalance created by the red-green filters significantly increased the number of stereo judgment errors (37%, p less than 0.05). However, illuminance imbalance (0.2 log units) of the magnitude created by the red-green filters did not significantly increase the number of errors (2.9%, p less than 0.65). Finally, the combined illuminance and chromatic imbalance created by the red-green filters significantly increased the error frequency (46%, p less than 0.05). The chromatic imbalance caused by red-green glasses significantly degrades stereopsis, whereas the illuminance imbalance caused by these filters has no significant effect on stereopsis.
Adolescent↗