Chemical constituents of Packera coahuilensis and Packera bellidifolia.
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Journal Article↗
Biomedical subjects
A Arciniegas
Publications and source records attributed to A Arciniegas.
In vitro evaluation of the amebicidal activity of Buddleia cordata (Loganiaceae, H.B.K.) on several strains of Acanthamoeba.
Infectious diseases produced by free-living amoebae from the genus Acanthamoeba have been recently recognized. The need for antiamebic compounds is urgent as the occurrence of these diseases is being registered more frequently since the late sixties. We screened the aqueous and methanolic extract of a plant used by folk medicine (Buddleia cordata) against eye and skin inflammation for antiamebic activity. We tested the extracts on 29 strains of free-living amoebae, with the result that they were amebostatic for 14 and 15 strains, respectively. We obtained linarin and vanillic acid from the extracts, but only linarin was amebostatic to all the strains and vanillic acid had no activity. However, acetyl vanillic acid had similar effects on amoebae to linarin. Threshold values of these two active compounds ranged from 31.25 microg/ml to 4 mg/ml and from 31.25 microg/ml to 8 mg/ml for linarin and acetyl vanillic acid, respectively. These differences in threshold values were observed even on several strains belonging to the same species (as in the case of A. castellanii and A. polyphaga) indicating the need of susceptibility testing for each clinical isolate of free-living amoebae.
Acanthamoeba↗
Mode of action of Buddleja cordata verbascoside against Staphylococcus aureus.
We evaluate the mode of action of verbascoside obtained from Buddleja cordata against Staphylococcus aureus by killing kinetics and incorporation of precursors methods. Verbascoside induced lethal effect on S. aureus, by affecting protein synthesis and inhibiting leucine incorporation.
Anti-Bacterial Agents↗
Iodanthine, a pyrrolizidine alkaloid from senecio iodanthus and senecio bracteatus
A phytochemical study of Senecio iodanthus and Senecio bracteatus afforded the new pyrrolizidine alkaloid iodanthine (3) in addition to the four known alkaloids retroisosenine (1), bulgarsenine (2), mulgediifoliine (4), and (12S)-12-hydroxyretroisosenine (6). The structure and absolute stereochemistry of the new compound (3) were determined by its spectral properties and confirmed by an X-ray diffraction analysis.
Journal Article↗
Callosine, a 3-alkyl-substituted pyrrolizidine alkaloid from senecio callosus
Two collections of Senecio callosus from different regions of Mexico contained a structural diversity of pyrrolizidine alkaloids (PAs), which may contribute to the easy adaptation of this species. In addition to some known compounds, two new PAs (1 and 2) were isolated, and their structures were established by chemical transformations and spectroscopic studies.
Journal Article↗
Myopic astigmatism and simple myopia correction.
A new technique for the treatment of myopic astigmatism and simple myopia correction is described. The technique is based on bioengineering concepts previously studied by the authors that accurately and mathematically describe the transformation of an ellipsoidal surface (astigmatic eye) into a spheroidal one (nonastigmatic eye) by means of minimal cuts (keratotomies). The surgical procedure is described using selected cases to illustrate the alternatives the model can handle. The model itself is not presented because the calculations were done by computer.
Adolescent↗
Our experience in intraocular foreign-body removal.
Foreign bodies embedded in the retina and choroid that cannot be extracted by a magnet and require vitreous surgery for their removal comprise a separate group. A retrospective review of 40 consecutive cases (between 1977-1990) showed that this type of trauma frequently accompanied extensive ocular damage, including corneal and or scleral perforation, disruption of the lens, significant vitreous hemorrhage, retinal and choroid hemorrhage, and retinal detachment. Intraoperative and late complications occurred frequently, making the visual and structural outcomes of such eyes uncertain; therefore, another alternative must be sought that might improve the prognosis of these eyes. In this review, we emphasize (1) the time elapsed between the accident and the removal of the foreign body and (2) the final visual acuity and the time before the surgery.
Adolescent↗
Our experience in the removal of intravitreal and subretinal cysticerci.
Ocular cysticercosis is a rather infrequent entity even in developing countries. Several treatments have been proposed depending on the location of the organism within the eye. Three cases are described, emphasizing treatment of a subretinal cysticercus with sclerotomy instead of photocoagulation.
Adult↗
Mechanical behavior of the sclera.
Induced deformations, similar to the posterior pole deformations due to advanced myopia, were studied in a series of 30 rabbits. The induced deformations were produced by means of a specially designed cup. An analysis of the applicability of the shell theory is made, and it is concluded that the thin shell theory is applicable to the mechanical study of the eyes. The basic experiment consisted of introducing a controlled deformation at different pressure levels; a wide range of types of increments and times of substained deformations were studied. It is concluded that the scleral tissue is an elastic material and has a fairly high 'Creep' rate. The material properties indicate that the eye can reaccommodate induced pressure, and thus glaucoma and myopia could be present without external indications of 'high pressure' in the eye.
Accommodation, Ocular↗
Treating the complications of diabetic retinopathy with pars plana vitrectomy.
The results of 150 cases of pars plana vitrectomy performed at the Clínica Barraquer, Bogotá, Colombia were studied as a treatment of diabetic retinopathy. Factors considered in this study were age, indication for surgery, type of surgery, insulin dependence, risk of complication, and postoperative treatment.
Adult↗
Mathematical model of geometry of the eye.
A computer program was written in order to construct a geometric model of the human eye, having as a base some subroutines from the SAP IV program designed by the University of California. It was written in Fortran. In order to generate the proposed geometry, it was necessary to divide the eye into three zones, each one corresponding to a plane geometric figure, since the human eye does not correspond to any one shape. When the three zones are joined together, they form an eyeball.
Humans↗
Corneal curvature modification by scleral surgery: preliminary results.
The preliminary results of a scleral technique designed to correct mixed and myopic compound astigmatism are given, and the mathematical basis of this technique is explained. The amount of scleral resection per diopter of astigmatism is indicated. This procedure steepens the flattest meridian and flattens the meridian localized at 90 degrees from the first one.
Astigmatism↗
Retinal detachment surgery with the OPMI-6 surgical microscope.
Various aspects of retinal detachment surgery using the OPMI-6 surgical microscope as a visual aid are discussed. The following point is made: Provided that subretinal fluid has been drained prior to retinal detachment surgery, holes or tears in the retina will be clearly visible through the OPMI-6, eliminating the need for a posterior mirror lens as a supplemental visual aid.
Evaluation Studies as Topic↗
Treatment of the occlusion of the central retinal vein by section of the posterior ring.
Forty-four patients with central retinal vein occlusion, who had been treated with decompression of the central retinal artery and vein by section of the posterior scleral ring were studied, in order to evaluate the benefit of the surgery. Our results were compared with others in which the disease was left to follow its natural course, without any treatment. The most common associated vascular disease was systemic hypertension. The visual prognosis was better in venous stasis retinopathy than in hemorrhagic retinopathy. In the present article, special emphasis was placed on the occurrence of neovascular glaucoma after surgery.
Adolescent↗
Experimental modification of the corneal curvature by means of scleral surgery.
Most surgical procedures for correcting astigmatism are done on the cornea. The present article shows the modification of the corneal curvature by scleral surgery. The experiments were conducted on rabbit eyes. The most spherical eyes were chosen according to the keratometric measurements. A geometrical analysis of the astigmatism shows that beginning with an ellipse (image of an astigmatic eye in the corneascope), by modifying the main radii of the ellipse, while the perimeter is maintained constant a perfect circle is thus obtained. This analysis enables us to calculate the amount of sclera surgery required to obtain a given correction for a given degree of astigmatism. Four scleral procedures were investigated: folds, resections, imbrications, and sclerotomies; the results show that the first three procedures steepen the meridian where the surgery is performed while flattening simultaneously the ortogonal meridian. The main advantages of scleral surgery vs corneal surgery for correction of astigmatism are: (a) the cornea remains untouched, (b) the surgical area will be protected by the conjunctiva, (c) the stitches are left permanently, and (d) larger astigmatic errors can so be corrected.
Animals↗
Bio-structural model of the human eye.
As part of a bio-engineering approach to study myopia, a structural model of the eye is proposed. The model is based on structural laws as employed by civil engineers, and on mechanical properties of the sclera and vitreous previously analyzed by the authors. The described structural behavior relates many loose clinical observations and indicates that progressive myopia should be considered a mechanical problem due to an abnormal vitreous pressure rather than an optics problem. From this bio-engineering approach, vitrectomy is suggested as the appropriate solution.
Biomechanical Phenomena↗
Mechanical analog for the study of the internal forces of the eye.
As part of the bio-engineering approach to study myopia and also as a complement to the bio-structural model of the eye presented by the authors, an analog for the study of internal forces is analyzed. The behavior of the model indicates not only that the forces involved in the development of progressive myopia, but those of pre- and post-trabecular glaucomas could be studied and related with such an analog model, supporting the author's feelings that many medical problems could be successfully explained by engineering methods and techniques.
Biomechanical Phenomena↗
Mechanical behavior of the iris-lens-zonule-ciliary body system.
The mechanical behavior of athe iris-lens-zonule-ciliary body (ILZC) system under intraocular pressure variations, measured with Scan A, is studied on a series of 20 rabbit eyes. The experiments indicate that the ILZC system behaves like a partition between the anterior and vitreous chambers and not like a supporting structural member. The observed behavior is related to previous clinical observations and to the biostructural model of the eye described in a previous paper by the authors.
Animals↗