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Biomedical subjects

J A Medeiros

Publications and source records attributed to J A Medeiros.

11 recordsLinked to original sources
PubMed2005

Microvascularization and angiogenic activity of equine corpora lutea throughout the estrous cycle.

Corpus luteum growth and endocrine function are closely dependent on the formation of new capillaries. The objectives of this study were to evaluate (i) tissue growth and microvascular development in the equine cyclic luteal structures; (ii) in vitro angiogenic activity of luteal tissues in response to luteotrophic (LH, PGE(2)) and luteolytic (PGF(2alpha)) hormones and (iii) to relate data to luteal endocrinological function. Our results show that microvascular density was increased in the early and mid luteal phase, followed by a fall in the late luteal phase and a further decrease in the corpus albicans. Hyperplasia of luteal tissue increased until the mid luteal phase and it was followed by tissue regression. Luteal explants were cultured with no hormone added, or with PGF(2alpha), LH, PGE(2), LH+PGE(2) or LH+PGF(2alpha). Media conditioned by equine luteal tissue from different stages of the luteal phase were able to stimulate mitogenesis of bovine aortic endothelial cells (BAEC), suggesting the presence of angiogenic activity. No difference was observed among luteal structures on their mitogenic capacity, for any treatment used. Nevertheless, Late-CL conditioned-media with PGF(2alpha) showed a significant decrease in BAEC proliferation (p<0.05) and LH+PGF(2alpha) a tendency to reduce mitogenesis. Thus, prostaglandin F(2alpha) may play a role on vascular regression of the CL during the late luteal phase in the mare. These data suggest that luteal angiogenesis and vascular regression in the mare are coordinated with the development of non-vascular tissue and might be regulated by many different factors.

Animals↗
PubMed2001

Decay of 72Ga.

The gamma-ray spectrum of 72Ge following the beta- decay of 72Ga has been studied using both single and gamma-gamma coincidence spectroscopy techniques. The energies and intensities of 110 gamma-rays have been determined, 26 of them were observed for the first time and 20 have been confirmed. Of the total number of gamma-rays observed, 95 have been placed in a proposed level scheme containing 31 levels. This includes five new levels at 2303, 2694, 3067, 3097 and 3420 keV.

Journal Article↗
PubMed1997

Is colonic electrical activity a similar phenomena to small-bowel electrical activity?

PURPOSE: This study was designed to investigate colonic spike bursts regarding 1) their migration behavior, 2) their pressure correlates, and 3) comparing colonic short spike bursts with spike bursts from migrating myoelectric complex from the small bowel. METHODS: Rectosigmoid electromyography and manometry were recorded simultaneously in seven normal volunteers and electromyography alone in five others during two hours of fasting and for two hours after one 2,100-kJ meal. One patient with an ileostomy was also studied by the same method to record the migrating myoelectric complex from the terminal ileum during fasting. RESULTS: Three kinds of spike bursts were observed in the pelvic colon: rhythmic short spike bursts, migrating long spike bursts, and nonmigrating long spike bursts. The meal significantly increased the number of migrating and nonmigrating long spike bursts (from 25 to 38.7 percent of the recording time; P < 0.01). These bursts of potentials showed a peak 15 minutes after the meal, which may be caused by the gastrocolic reflex. Migrating long spike bursts started anywhere along the rectosigmoid and migrated from there aborad 82 percent of the time and orad or in both directions in 10 or 7 percent of the time, respectively. They originated pressure waves 99 percent of the time. Short spike bursts were more frequent before the meal (15.1 percent before and 9.6 percent after the meal), but the difference was not significant; they neither propagated nor initiated pressure waves detected by the mini-balloon. CONCLUSIONS: Migrating long spike bursts were the only potentials that migrated, sometimes for short distances. Short spike bursts are a different phenomenon from the small-bowel migrating myoelectric complex because they do not migrate; they can occur during the postprandial period and never originated intraluminal pressure waves.

Adolescent↗
PubMed1996

Electromyography and manometry of the pelvic colon--a contribution to the understanding of its function.

OBJECTIVE: To study the adaptation of the rectum to pressure waves in the sigmoid and the motility response to the administration of a bile salt microenema. DESIGN: Electrical and motor activity was studied in 20 men and 20 women during a 2-h fast and for 2 h after a 1000-kcal meal, and also after a bile salt microenema. METHODS: An intraluminal probe with three sets of two electrodes and one miniballoon was used for simultaneous EMG and manometry recording. RESULTS: Four types of spike bursts were observed: (1) migrating long spike bursts that initiated propagating pressure waves on 99% of occasions; (2) non-migrating long spike bursts that did not originate pressure waves; (3) rhythmic short spike bursts that were also not related to pressure waves; and (4) rhythmic long spike bursts that originated rhythmic segmental pressure waves frequently brought up by a migrating long spike burst. The meal significantly increased the duration of activity of the migrating long spike bursts in the sigmoid colon (from 16.8% before the meal to 21.8% after it, P < 0.05) and the motility index, P < 0.05, both of them in two peaks. A rectosigmoidal pressure gradient was shown. The bile salt microenema produced a desire to defecate and increased motility in only half of the cases. CONCLUSION: The rectosigmoidal pressure gradient was due to: (1) higher-amplitude pressure waves in the sigmoid colon than in the other two sites, and (2) propagating relaxation waves in the rectum and in the rectosigmoid junction.

Adolescent↗
PubMed1982

Arterial branching in man and monkey.

Vessel diameters and branching angles are measured from a large number of arterial bifurcations in the retina of a normal human subject and in that of a rhesus monkey. The results are compared with each other and with theoretical results on this subject.

Animals↗
PubMed1979

High resolution microchemical analysis using soft X-ray lithographic techniques.

High resolution x-ray lithographic studies of cells from chick embryo hearts dried by the CO2 critical point method have been made with soft x-ray radiation of different wavelengths. A marked difference in the relief replica in polymethyl methacrylate (PMMA) resulting from the differential absorption by the dried cells of carbon K alpha radiation at 4.48 nm and broad band synchrotron radiation (SR) with lambda is greater than 1.5 nm demonstrates the potential usefulness of the technique in making high resolution (approximately or equal to 10 nm) chemical identification of the constitutents which make up the various parts of the cell.

Animals↗
PubMed1979

Arterial bifurcations in the human retina.

The branching angles and relative diameters of blood vessels in 51 arterial bifurcations in the retina of a normal human eye were measured. In eight other bifurcations, only the total branching angles were measured. The results are compared with theoretical predictions in an attempt to understand the physiological principles governing branching in the cardiovascular system.

Adult↗
PubMed1979

Application of optical transform techniques to laser irradiation of retina.

Novel retinal irradiation techniques for laser damage studies are described; these are straightforward applications of the Fourier transform properties of an optical system. Interposing an appropriate diffracting screen between the laser source and the test eye enables one to simultaneously induce a number of discrete and precisely located retinal exposures with a known gradation of energy. Various kinds of diffracting objects are considered, and it is seen that transparent sinusoidal phase gratings offer the most promise for damage threshold studies. The method provides an objective measure of the ocular focal length at the time of the exposure. The production of arbitrary retinal irradiation patterns for more general research or clinical applications is possible with the extension of the technique by the use of simple holographic methods for forming the appropriate diffracting screens.

Animals↗
PubMed1977

Fusing human rod outer segments from an eye enucleated for choroidal melanoma.

In the retina from an eye enucleated for choroidal melanoma apposed rod outer segments were seen by transmission electron microscopy to be fusing together in groups by the confluence of their plasma membranes and the formation of cytoplasmic bridges between adjacent outer segments. These fusions were seen in areas distant from the melanoma but where the retina was not normal in appearance.

Cell Membrane↗
PubMed1977

Scanning electron microscopy of normal and lased rabbit pigment epithelium.

Scanning electron microscopic (SEM) observations of the rabbit retinal pigment epithelium (RPE) are reported both for normal tissue and for tissue subjected to laser radiation. In normal RPE, cells were observed to be closely packed and to have the characteristic hexagonal shape. The microvilli were abundant and of two types. Suprathreshold lesions were produced with 0.4 musec pulses of high-intensity yellow light (585 nm.) from a dye laser. In the lased RPE, cells were denuded of their microvilli, and a number of cells with single discrete holes were observed. Hypertrophied cells were always present. Within 5 days of irradiation groups of small proliferating RPE cells were found in the lesion area.

Animals↗