Search PubMed⌕ Search

Biomedical subjects

A Rosado

Publications and source records attributed to A Rosado.

At least 55 records · Page 3Linked to original sources
PubMed1990

[Several new concepts on the terminal mechanism of mammal fertilization].

We briefly reviewed some ionic mechanisms participating in the fulfillment of the acrosome reaction processes, indicating the results obtained by the simultaneous and dynamic quantitation of sodium, potassium, calcium and hydrogen concentrations in the in incubation medium of human spermatozoa induced to achieve the acrosome reaction through the addition of cAMP and follicular fluid. At the same time, the participation of zinc and some enzymatic activities, like phospholipase A2, in the occurrence of this process, is indicated. A study is done about the sperm nuclear decondensation mechanisms, pointing at the importance of various participants in this event, like the disulfide groups reducing agents, some metalic ions and the glycosaminoglycanes, as well as a proposal of a mechanism which could be physiologically functional for the in vivo occurrence of this phenomenon. Finally we present some results explaining the DNA synthesis activation, which is repressed in the spermatozoa since the spermiogenesis final stages, and is indispensable for the chromosomic duplication required during egg segmentation.

Acrosome↗
PubMed1990

[New concepts about the terminal mechanism of fertilization in mammals].

We briefly reviewed some ionic mechanisms participating in the fulfillment of the acrosome reaction processes, indicating the results obtained by the simultaneous and dynamic quantitation of sodium, potassium, calcium and hydrogen concentrations in the in incubation medium of human spermatozoa induced to achieve the acrosome reaction through the addition of cAMP and follicular fluid. At the same time, the participation of zinc and some enzymatic activities, like phospholipase A2, in the occurrence of this process, is indicated. A study is done about the sperm nuclear decondensation mechanisms, pointing at the importance of various participants in this event, like the disulfide groups reducing agents, some metal ions and the glycosaminoglycans, as well as a proposal of a mechanism which could be physiologically functional for the in vivo occurrence of this phenomenon. Finally we present some results explaining the DNA synthesis activation, which is repressed in the spermatozoa since the spermiogenesis final stages, and is indispensable for the chromosomic duplication required during egg segmentation.

Acrosome↗
PubMed1989

Isolation and characterization of an antitumor active agar-type polysaccharide of Gracilaria dominguensis.

Cold water extraction of the red alga Gracilaria dominguensis, followed by cetyltrimethylammonium bromide fractionation, gave a highly sulfated, agar-type polysaccharide which inhibited the transplantation of Ehrlich ascites carcinoma in mice. The structure of the polysaccharide has been investigated by methylation analysis, and 1H- and 13C-n.m.r. spectroscopy, and was shown to be mainly composed of alternating (1----3)-linked beta-D-galactopyranosyl 6-sulfate and (1----4)-linked 3,6-anhydro-alpha-L-galactopyranosyl residues.

Animals↗
PubMed1989

Heparin and glutathione: physiological decondensing agents of human sperm nuclei.

It has been proposed that reduced glutathione (GSH) or other thiol reagents may participate in the basic mechanism by which sperm-decondensing activity is accomplished. However, in vitro, these reagents seem to be inactive and require the presence of other chemicals, usually detergents. Heparin binds specifically to the sperm membrane and provokes the decondensation of human sperm and the activation of DNA transcription and synthesis. However, the concentrations at which these effects occur seem to be higher than those expected under physiological conditions. In the present study, thiol reagents at 10 mM concentration, either alone or combined, were completely ineffective in inducing any significant nuclear decondensation after prolonged exposures (24 hr) of incubation. Heparin, 153.8 microM, was capable of inducing only a small increase in nuclear swelling. However, GSH at concentrations as low as 0.1 mM in combination with heparin induces decondensation of human sperm nuclei in vitro. When GSH concentration was kept constant at 5 mM, nuclear decondensation was induced with heparin at concentrations as low as 11.6 microM, and a maximal decondensation (90%) was obtained with only 21.6 microM of heparin. The latter is more than ten times less than the minimal active concentration of heparin used alone.

Cell Nucleus↗
PubMed1989

Effect of cupric ions on the initiation protein synthesis rate in the human endometrium.

The effect of cupric ions on the initiation protein synthesis rate of the human endometrium was studied. Addition of copper to the complete ribosomal system decreased the binding of [3H]Met-tRNA(i) to the isolated ribosomes with a plateau at about 70% inhibition with concentrations higher than 150 microM. The initiation activity was GTP-dependent with a maximum at 2 mM. This activity was very rapid, requiring 5 min to complete the reaction. Incubation of isolated initiation factors with copper (300 microM) inhibited the formation of the ternary complex. When the complete system was reconstituted with salt-washed ribosomes after ternary complex formation, no significant change on the inhibition pattern was observed. Addition of initiation factors to 5-min preincubated salt-washed ribosomes with 300 microM copper, after the elimination of excess copper, induced only a 12% decrease on Met-tRNA(i) binding. This effect was not modified by the presence of Sparsomycin, an elongation inhibitor. It was concluded that copper interferes with the initiation process, probably at the ternary complex formation level.

Adult↗
PubMed1988

Binding of chemotactic peptide to the outer surface and to whole human spermatozoa with different affinity states.

Binding of N-formyl-methionyl-L-leucyl-[3H]phenylalanine (fML[3H]Ph) to human ejaculated spermatozoa and to its isolated plasma membrane was studied. Our data confirm the presence of specific receptors for f-MLPh in the human spermatozoa and suggest that whole spermatozoa receptors exist in two affinity states, one high-affinity, low-capacity specific receptor (Kd = 12.3 +/- 0.5 nM, n = 22,285 +/- 65,008 binding sites per sperm cell) and a second one (Kd = 700 +/- 47 nM) that is not saturable, indicating a low-affinity, high-capacity nonspecific site. In contrast, sperm membrane showed only one class of binding site (Kd = 6.4 +/- 0.12 nM), which was statistically different from that of the high-affinity binding site of intact spermatozoa. To explain this difference we discuss the possibility that first, the two binding affinities represent two interconvertible states of a single receptor population, which, depending on the metabolic activity of spermatozoa, may change its physicochemical properties; or second, they reflect two different processes, binding and/or transport into the spermatozoa.

Cell Membrane↗
PubMed1988

Size-uniform heparin fragments as nuclear decondensation and acrosome reaction inducers in human spermatozoa.

Using size- uniform mixtures of di-, tetra-, octa- and decasaccharides obtained from the depolymerization of heparin with heparinase, we have studied the activity that these low molecular weight heparin fragments may have on the acrosome reaction and sperm nuclei decondensation processess. Swelling of human spermatozoa nuclei was stimulated by heparin and their fragments and was dependent on the incubation time and directly correlated with the size of the fragment tested. Disaccharides were unable to increase the number of swollen nuclei. At short times (2-8 hrs) decasaccharides were the most active substances tested, including heparin. Only heparin and the tetra- and decasaccharides showed a significant increase in the number of acrosome-reacted spermatozoa, both fragments were more active than heparin at 2 hour incubation. Hexa- and octasaccharides induced a slight increase in the number of acrosome reacted spermatozoa and disaccharides were ineffective. The presence in animal systems of oligosaccharides derived from macromolecules and having specific biochemical properties, remembers the recent discovery of to those mediated by oligosaccharins in plants may exist in animals.

Acrosome↗
PubMed1988

Histopathologic effects of ultrasonically induced hyperthermia in intraocular malignant melanoma.

Four cases of human intraocular malignant melanoma were treated with ultrasonically induced hyperthermia immediately before enucleation. Tumors were treated in two regimens: 30 minutes at 43 degrees to 45 degrees C and 5 minutes at greater than 50 degrees C. Temperatures were estimated from applied power levels, based on empirical data and mathematical models. Histopathologic changes observed in human tumors were compared with changes seen in malignant melanoma xenografts in athymic nude mice which were treated with ultrasonically induced hyperthermia for 30 minutes at 42 degrees to 46 degrees C. The effects of treatment were similar to changes seen in the animal model treated under analogous conditions: increased intercellular spacing, cytoplasmic vacuole formation, clumping of chromatin, breaks in cell membranes, and swelling and collapse of cells. Perivascular and peripheral zones sometimes showed decreased damage levels. The high temperature (greater than 50 degrees C) technique is presently being used as a means of "sterilizing" tumors before planned enucleation. The moderate temperature (43 degrees-45 degrees C) technique has been used in combination with radiotherapy to treat tumors when vision can be salvaged.

Animals↗
PubMed1988

Structure of human sperm chromatin: a study on the accessibility of DNA to macromolecules.

The structure of human sperm chromatin compared with somatic chromatin (liver) was studied by titration of the exposed DNA-phosphate groups with poly-1-lysine (3000 and 28,100 MW) and by their susceptibility to the hydrolytic action of micrococcal nuclease and DNase I. With both sizes of polylysine used, the binding values were significantly lower for sperm chromatin (0.31 +/- 0.05) than for liver chromatin (0.52 +/- 0.05), indicating the presence of about 30% and 52% of free phosphate groups, respectively. Interaction with liver chromatin left no polylysine molecules partially unbound ("wastage") even when 28,100 MW polylysine was used; on the contrary, sperm chromatin showed 26% of "wasted" polylysine even when the smaller polymer was used, indicating that in sperm chromatin the accessible DNA zones are usually no longer than 42 A, that is, 12 base pair. Sperm chromatin was notably more susceptible to both micrococcal nuclease and DNase I action than liver chromatin. However, in the presence of saturating concentrations of polylysine they were similarly protected. Micrococcal nuclease and DNase I hydrolysis products of sperm fractions when submitted to electrophoresis produced a polydisperse smearing pattern along the gel that was difficult to correlate with the presence of nucleosomal structure.

Chromatin↗
PubMed1987

Increased acrosome-reaction inducing activity of glycosaminoglycans by partial hydrolysis.

The possibility that partial hydrolysis of glycosaminoglycan-sulfates (GAGs) such as occurs during the last phases of follicular maturation could play some role in the activity of follicular fluid as an inducer of the acrosome reaction was explored. Hydrolysis of follicular fluid GAGs (ff-GAGs) for 30 min with low-pH HNO2 substantially increased (more than 3 times) its capacity to induce the acrosome reaction. This increase was significantly reduced when the time of hydrolysis was either shorter (10 min) or longer (60 min). Partial hydrolysis of spermatozoa GAGs by direct incubation of sperm cells with chondroitinase ABC was also capable of inducing the acrosome reaction.

Acrosome↗
PubMed1987

Mineral deposits formation in bioactive IUD's.

Mineral organic deposits have been observed in inert IUDs. The authors studied the presence of these deposits in bioactive IUDs. Inert, progesterone, and copper-releasing IUDs were removed at 12,24, and 36 months postinsertion. When the devices were cut between their vertical (body) and horizontal (arms) branches, both parts were processed independently. After laxly bound organic material was eliminated, the devices were extracted at 60 degrees Celsius for 90 minutes with 3N HC1, and finally all undissolved material was dissolved in 1N NaOH. In each fraction, protein and inorganic ions were measured. Mineral organic deposits were formed in all types of IUDs. The deposits increased with time in utero in a characteristic device-dependent pattern. The deposits were essentially made of proteins, sodium, and calcium ions and were higher on the inert Lippes Loop D (7.0 +or- 2.4 mg proteins; 2.8 +or- 0.85 mg calcium, and 0.138 +or- 0.048 mg sodium/device); less in the copper IUD (5.7 +or- 1.36 mg proteins, 0.89 +or- 0.12 mg calcium, and 0.180 +or- 0.046 mg sodium/device at 24 months); and even less in the progesterone-releasing IUDs (1.6 +or- 1.3 mg protein, 0.235 +or- 0.028 mg calcium, and 0.262 +or- 0.063 mg sodium/device).

Calcium↗
PubMed1987

Histologic changes in porcine eyes treated with high-intensity focused ultrasound.

High-intensity focused ultrasound (HIFU) has recently been described in the treatment of patients with glaucoma. However, despite previous studies in animal and mathematical models, the mechanisms of action are not completely understood. We therefore undertook a histologic study of 15 porcine eyes to evaluate the effect of HIFU and, in particular, the changes seen after sequential insonification on previously treated areas of sclera. We demonstrated initial scleral swelling that was followed by scleral thinning. The scleral thinning could be maximized by a second superimposed course of HIFU. The most consistent change in the ciliary body was necrosis of the pars plana. Some treated animals developed a hemorrhagic retinal detachment that we believe to be due to the presence of a circumferential blood vessel, which runs in the ora serrata of the pig but which is not present in humans. Based on our observations, possible mechanisms of action of this treatment are discussed.

Animals↗
PubMed1986

Ultrasonic hyperthermia and radiation in the management of intraocular malignant melanoma.

Hyperthermia and radiation were used in combination to treat four patients with choroidal malignant melanoma. This technique uses ultrasonically induced hyperthermia synergistically with radiation to destroy tumor cells. The lower levels of radiation used should avoid the late vascular and inflammatory complications seen in conventional radiation therapy. Tumors were scanned by a computerized diagnostic ultrasound system before treatment and assigned an acoustic tissue type on the basis of a statistical comparison of their ultrasound backscatter spectrum with spectra of tumors of known pathologic status. During the follow-up period, the longest of which was 15 months, all tumors demonstrated regression patterns consistent with choroidal tumors of the same acoustic tissue types treated with conventional radiation therapy.

Aged↗
PubMed1986

Taurine content and amino acid composition of human acrosome.

The presence and concentration of taurine was determined by amino acid analysis in human spermatozoa acrosomes isolated by the method of Srivastava. Taurine is one of the four amino acids whose concentration is higher in the acrosomal extracts, being only lower than histidine, methionine and lysine. It is worth mentioning that these four amino acids constituted 50% the free amino acid concentration in this organelle. The role that this high concentration of taurine, and also the presence of considerable amounts of methyl histidine may have in the functioning of the acrosome, is discussed.

Acrosome↗
PubMed1986

Therapeutic ultrasound.

Currently the most widely applied use of therapeutic ultrasound in ophthalmology is for the treatment of refractory glaucoma. This new technique is described, histologic changes in experimental animals discussed, and mode of action postulated. The intraocular pressure (IOP) results obtained after treatment of 187 patient eyes are presented, with a review of complications and visual acuity changes. This study demonstrates that 70% of patients treated had an IOP reduction to 25 mm Hg or less one year after ultrasound therapy.

Adult↗
PubMed1986

Ultrasonic tissue characterization and histopathology in tumor xenografts following ultrasonically induced hyperthermia.

Cells derived from human skin malignant melanoma were implanted subcutaneously in athymic nude mice. Tumors which developed at the implant site were treated with ultrasonically induced hyperthermia at 49 degrees C for 30 min. Tumors were scanned with a computerized diagnostic ultrasound system before and after treatment. Light (LM) and electron (EM) micrographs of tumors were obtained after scanning. Changes in ultrasonic tissue characterization parameters following treatment were well correlated with histopathologic changes observed in tumors. The results are significant in terms of clinical application of ultrasonically induced hyperthermia for treatment of intraocular tumors and the noninvasive monitoring of tumors by use of diagnostic ultrasound.

Animals↗