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Biomedical subjects

R Beck

Publications and source records attributed to R Beck.

At least 145 records · Page 8Linked to original sources
PubMed1987

Ventricular electrophysiological properties: is interspecies variability related to thyroid state?

Whereas action potential (AP) duration, area, and repolarization vary considerably, ventricular AP characteristics such as resting membrane potential, AP amplitude, and maximal upstroke velocity of phase 0 depolarization appear similar in a variety of mammalian species. As it has been shown that modifications of the thyroid state are associated with alterations in ventricular electrophysiological properties, we hypothesized that some variations in transmembrane potentials among mammalian species result in part from differences in the individual thyroid states. To test this hypothesis, we used standard microelectrode techniques to study ventricular APs in the dog, mole-rat, guinea pig, rat, mouse, and shrew, which encompass a wide range of thyroid states. In these species O2 consumption ranges from 0.38 (in the shrew) to 4.05 ml O2 X g-1 X h-1 (in the dog). We found that resting membrane potential and AP amplitude, duration, and area were inversely correlated with O2 consumption. The correlation coefficients between these parameters with O2 consumption were -0.92, -0.78, -0.91, and -0.92, respectively. We further tested the hypothesis in guinea pigs in which we modified the thyroid state in opposite directions by thyroxine administration and by propylthiouracil treatment. In the hypothyroid myocardium, AP duration (cycle length = 2,000 ms) markedly increased (P less than 0.001), whereas in the hyperthyroid myocardium, resting membrane potential and AP amplitude (P less than 0.01) and duration (P less than 0.001) decreased. We conclude that interspecies variations in ventricular electrophysiological properties can be correlated with the thyroid state, which may be an important determinant of these properties.

Action Potentials↗
PubMed1987

Term abdominal pregnancy, meconium aspiration, and extracorporeal membrane oxygenation.

This report describes a term gestation abdominal pregnancy resulting in meconium aspiration syndrome (MAS) complicated by pulmonary hypertension. These cases occur infrequently. In this instance, extracorporeal membrane oxygenation (ECMO) was successfully utilized to support the infant after conventional neonatal medical support failed to yield sufficient oxygenation.

Adult↗
PubMed1987

Cavernous sinus syndrome as the initial manifestation of multiple myeloma.

A 76-year-old man developed a cavernous sinus syndrome as the initial manifestation of multiple myeloma. Although clinically the patient had stage IA disease, which is typically associated with a favorable response to therapy, his disease was rapidly fatal. This case emphasizes a weakness of the traditional staging system because it does not take into account certain clinical and histopathologic aspects of myeloma relevant to extramedullary plasmacytomas. Since disorders of ocular motility are more likely to be associated with extramedullary myeloma than myeloma confined to the marrow, clinicians need to be aware of the limitations in the clinical staging system and the potential problems associated with anaplastic plasmacytomas.

Aged↗
PubMed1987

Tuberous sclerosis.

Tuberous sclerosis is a multisystem disorder characterized by changes primarily involving the skin, eye, and central nervous system. Although the disease often produces mental retardation and seizures, this is not universal, and some patients with tuberous sclerosis lead a relatively normal life.

Diagnosis, Differential↗
PubMed1987

[Contrast enhancement of the nipple in nuclear magnetic resonance tomography of the breast with Gd-DTPA].

Contrast enhancement around the nipple has been evaluated retrospectively in 51 of 70 patients in respect of the underlying breast disease. 2 of the patients had to be considered separately because of malignant disease of the nipple or areola itself. The remaining 49 patients showed no close relation between the underlying breast disease and the amount of contrast enhancement in the nipple. This phenomenon of a non-pathological significant contrast enhancement of the nipple appears important to avoid false positive diagnoses in MRI of the breast with Gd-DTPA.

Breast↗
PubMed1987

MRI of the breast--histopathologic correlation.

132 solid breast masses have been examined at our institution by MR and have consequently been histopathologically correlated. T1- and T2-weighted SE and multi-echo sequences have been evaluated visually. It was found that signal intensities of tissues on T2-weighted images correlated with the contents of fibrosis, cells or water. Thus in some lesions (which consisted of different tissue components), a characteristic internal structure was visible on T2-weighted images, reflecting their histopathologic structure. Corresponding to their different composition, differences of signal intensity have also been noted between those fibroadenomas with a high contents of fibrosis and all other well-circumscribed breast lesions (fibroadenomas, carcinomas). However, for the majority of lesions with irregular contours a discrimination based on signal intensities or calculated T1- and T2-values did not seem possible. This overlap can also be explained by the macroscopically similar composition (amount of fibrosis, water or cells) of benign and malignant irregular lesions.

Breast↗
PubMed1986

Criteria for extracorporeal membrane oxygenation in a population of infants with persistent pulmonary hypertension of the newborn.

Extracorporeal membrane oxygenation (ECMO) has been available since 1975 as a therapy of last resort to provide adequate oxygenation for term infants with acute lung disorders that do not respond to maximal medical therapy. Virtually all term infants with serious lung disease have persistent pulmonary hypertension of the newborn (PPHN) characterized by significant right-to-left shunting of blood and severe diffusion defects manifested as increased alveolar-arterial oxygen gradients (AaDO2). Criteria for initiation of ECMO therapy have been developed in several institutions but at the present time there are no universal criteria applicable to all infants with PPHN. We have attempted to establish entry criteria that may be used for different populations of infants with PPHN. Based on a retrospective review of 30 infants with PPHN in our institution, we have defined standards of maximal medical therapy. An alveolar-arterial oxygen difference (AaDO2) of greater than or equal to 610 for 8 hours has been shown to be associated with 79% mortality in this population. This AaDO2/time interval is established as a major criterion for institution of extracorporeal membrane oxygenation.

Carbon Dioxide↗
PubMed1986

[Use of Gd-DTPA in the nuclear magnetic resonance study of the breast].

55 patients with altogether 60 breast masses have been examined postoperatively by plain MR, MR with Gd-DTPA and mammography at our institution. All breast carcinomas and fibroadenomas did enhance significantly. Non-proliferative dysplasia, normal breast tissue and scar tissue did not enhance significantly. Borderline enhancement has been found in cases of proliferative dysplasia. The diagnostic accuracy has been improved by MR with Gd-DTPA. Advantages have been an improved visualization of tumors in dense breasts, an improved differentiation between irregular dysplasia and carcinoma and an improved differentiation between post-therapeutic changes (after radiation, surgery or silicon implants) and carcinoma. Nevertheless both technical improvements and further clinical experience is necessary.

Breast↗
PubMed1986

Biochemical characterization of the T-cell mitogen derived from Mycoplasma arthritidis.

A biochemical procedure is described to purify the T-cell mitogen in the supernatant of cultured Mycoplasma arthritidis organisms. The mitogenic material was bound on an affigel blue column. The eluate of this column was then acylated at 0 degrees C for 1.5 h and subsequently chromatography on a Sepharose Cl 6B and a Superose 12HR column were performed. SDS-PAGE showed a major band at MW 26,000 and some minor bands at 50,000. With this material biological tests were performed, including induction of lymphoproliferation and interferon induction in murine spleen cell cultures. Purified Mycoplasma arthritidis supernatant (MAS) vigorously stimulated spleen cell cultures of A/J, CBA, C3H/He, and DBA/2 mice, whereas a low-grade but definitive response was observed in C57BL/6 spleen cells. Cultures of Balb/c nu/nu mice, in contrast to those of their euthymic littermates, were non-reactive. When induction of interferon was tested, a marked response to purified MAS was observed in CBA and C3H/HeJ spleen cell cultures, whereas C57BL/6 spleen cells were non-reactive.

Animals↗
PubMed1986

Malnutrition: a cause of elevated sweat chloride concentration.

In order to document the frequency and causes of elevated sweat chlorides we reviewed all sweat chloride determinations performed over a 2-year period. Seven hundred and thirty-five quantitative tests were performed. Three hundred and three positive or borderline results were obtained from 133 patients. Thirty-three of these patients did not have clinical evidence of CF. Fourteen of them (42%) suffered from malnutrition or growth stunting when tested. The remaining patients who were normally nourished, represented a very heterogeneous group with no unifying diagnosis. Initial sweat chlorides in 11/14 malnourished children were in the abnormal range (greater than 60 mmol/l). These tended to revert to normal coincident with improvement in nutritional status. Less remarkable elevations in sweat chloride levels were noted in the normally nourished patients, since almost 50% (9/19) were in the intermediate range (50-60 mmol/l). We conclude that malnutrition can be the cause of elevated sweat chlorides, which may lead to an erroneous diagnosis of cystic fibrosis. Clinicians should be aware of this association and adhere to strict criteria for the diagnosis of cystic fibrosis. Also, repeated sweat chloride determinations should be obtained, preferably following re-nutrition.

Adolescent↗