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Biomedical subjects

A Medina

Publications and source records attributed to A Medina.

At least 145 records · Page 8Linked to original sources
PubMed1989

[Coronary transluminal angioplasty and determination of the intracoronary gradient with a new monorail system].

STUDY OBJECTIVE: To evaluate the results obtained in coronary angioplasty using the new very low profile monorail catheter. DESIGN: A retrospective study to define the causes and frequency of successful and unsuccessful coronary angioplasty on proximal and distal lesions located in the three coronary vessels. SETTING: Patients referred to the Hemodynamic Unit for coronary angioplasty. PATIENTS: Coronary angioplasty was performed in 106 patients with cardiac ischemic disease (stable angina, unstable angina and myocardial infarction after thrombolytic therapy). INTERVENTIONS: To perform coronary angioplasty using a monorail system, including dilatation of vessels (angioplasty) and to measure the intracoronary gradient. RESULTS: A high success rate was achieved (92%) independent of vessel dilated or of the position of the stenosis. There was a lower success rate in complex lesions. CONCLUSION: In this study, this newly modified system for coronary angioplasty with balloon catheter and monorail pressure catheter gave a very high performance.

Aged↗
PubMed1989

Stage III carcinoma of the endometrium. Results of treatment.

The impact of treatment on survival was analysed in 45 patients with stage III carcinoma of the endometrium. Our results indicate that patients treated with a combination of surgery and radiation therapy did significantly better than those treated with radiation alone. The five-years survival was 57.3% and 17.5%, respectively (p = 0.01). Patients with clinical stage III (CS III) whose tumor could not be resected surgically did poorly than patients with pathological stage III (PS III). This difference, however, was not statistically significant (p = greater than 0.05). Treatment related complications were minimal. Overall survival of patients of 33.8% was directly attributable to increased pelvic and/or extra pelvic recurrences.

Adult↗
PubMed1989

[Aortic valvuloplasty using the transatrial route in aortic valve stenosis].

We describe a new technique for aortic valvuloplasty in four patients. The balloon catheter was inserted percutaneously from the right femoral vein over a long guidewire introduced into the right femoral vein and advanced transseptally to the left atrium and left ventricle and drawn out of the body through the left femoral artery using an intravascular retriever set. With both ends of the long guidewire under manual control outside the body, the balloon could be easily fixed during inflation. The procedure was easy to perform and caused no complications.

Adolescent↗
PubMed1988

Sperm tail differentiation in the nudibranch mollusc Hypselodoris tricolor (Gastropoda, Opisthobranchia).

The sperm axoneme of Hypselodoris tricolor forms from a single centriole that is located initially beneath the plasma membrane and then migrates to the nuclear surface. A conspicuous centriolar adjunct-like formation is present in the neck of midspermatids, but it becomes very reduced at the end of spermiogenesis. In spermatocyte and spermatid mitochondria, intracristal bodies originate from the accumulation of a dense material in some cristae. From our observations and foregoing reports, it may be concluded that the process of sperm tail differentiation in opisthobranchs resembles that in pulmonates, whereas it differs in many respects from that occurring in prosobranchs. The appearance of intracristal bodies in modified mitochondria seems to be a special feature of spermatogenesis in the opisthobranchs that does not occur in the two other groups of gastropod molluscs.

Animals↗
PubMed1988

Influence of photoperiod on differentiation of male cells in Helix aspersa. An autoradiographic study.

Hibernating snails (Helix aspersa) were activated by placing them in environmental chambers under either long-day (LD 18:6) or short-day (LD 8:16) lighting conditions. One day after activation all the snails were injected with (3H-thymidine (5 microCi/g wet weight) in order to estimate the duration of spermatogenic phases under long and short-day cycles. Our histological and autoradiographic observations show that long-day cycles have a positive influence on the development of the male cell line, which becomes apparent from the third week of exposure. While in long-day snails labeled spermatozoa were identifiable 28 days after (3H)-thymidine injection, in short-day snails neither labeled spermatozoa nor spermatids were present in the gonads of animals killed as late as 39 days post-injection. These data strongly suggest that the photoperiod, besides acting on spermatogonial proliferation (Sokolove et al., 1983; Gomot and Griffond, 1987), has an important effect on the second meiotic division. In the course of spermatogenesis in Helix aspersa, the step from secondary spermatocyte to spermatid is probably the most sensitive to environmental factors.

Animals↗
PubMed1988

A novel high-frequency visual acuity chart.

A high-frequency eye test chart using letters or figures of alternating black and white stripes (or dots) on a grey background was developed. Any cross-section of the letters has a Fourier transform with a zero frequency component equal to the luminance of the grey background. When the letters are out of focus, their image on the retina fades rapidly into the grey background, rendering them invisible rather than merely blurred as in a standard chart. The chart was calibrated by simulating refractive errors with defocusing lenses applied to a photographic camera and to subjects' eyes. No constant ratio was found between the size of the Snellen letters and the size of the high-frequency letters for equal visibility. The new chart requires letters for 20/200 acuity to be only 3.6 times larger than those for 20/20 vision. Results confirm the arbitrary nature of the Snellen fraction and warn about the accuracy of visual acuity determined by using charts of different letter types, calibrated by Snellen's system.

Equipment Design↗
PubMed1987

A model for emmetropization. The effect of corrective lenses.

A mechanism called emmetropization appears to control the ocular focus over the years. Emmetropization could regulate the refractive media (dimensions of cornea, lens, and axial length), detecting the focus or refractive error of the eye at rest and initiating changes to reduce the refractive error; this concept suggests that a feedback loop is operational. A feedback mechanism for ocular refraction implies that correcting ametropia with lenses initiates a change in the refractive state of the eye. The long-term effect of corrective lenses on ocular refraction is investigated with a mathematical feedback model that can predict the extent and direction of this change. The results indicate that lenses worsen existing ametropia conditions. However, the use of appropriate lenses in early life can reduce and correct developing ametropia.

Contact Lenses↗
PubMed1987

A model for emmetropization: predicting the progression of ametropia.

The response of a second-order feedback system is used to describe the controlling process that regulates the refraction of the human eye to achieve optimal visual acuity over the years (emmetropization). From data collected in past refractions, the equation of the feedback system has been derived for individual eyes and used to predict changes in their refraction with age with an accuracy of 0.50 diopters for 89.1% of the eyes tested. If the model is applied to other populations, the root mean square error of prediction will be between 0.20 and 0.36 diopters with a 95% degree of confidence. The model indicates that corrective lenses applied to the eyes, especially in the early years of life, will cheat the servo system and defeat the emmetropization process.

Adolescent↗