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Biomedical subjects

G Aguirre

Publications and source records attributed to G Aguirre.

At least 19 recordsLinked to original sources
PubMed1992

Unique topographic separation of two spectral classes of cones in the mouse retina.

We have found two immunologically distinguishable cone types in the retina of the mouse, each localized to two opposite halves of the eye. One cone type was labelled by the monoclonal antibody COS-1 specific to the middle-to-long wave sensitive visual pigment of the mammals, while the other type was stained by the shortwave-specific monoclonal antibody (OS-2). These results were confirmed with other antibodies directed against specific sequences of the visual pigments. As a result of the uneven distribution of the two cone types the mouse retina is divided into two fields separated by an oblique meridional line. The middlewave sensitive cones were present exclusively in the dorsal half of the mouse retina (M-field). The overwhelming majority of the shortwave sensitive cones occupied the ventral half (S-field), and only a small number was scattered among the middlewave sensitive cones in the dorsal retina. The ratio of the two cone types in the M-field corresponds to what has been found in the retina of other mammals, including rodents such as the gerbil and the rat. The S-field represents an entirely unique area with the unusually great number of shortwave sensitive cones and with the complete lack of the middlewave sensitive ones. The present study provides the structural basis for dichromacy in a rodent species considered for a long time to be monochromat. In addition, it shows that the ventral retina, containing exclusively S-cones in a relatively high density, is a unique retinal field not present in other mammalian species studied so far.

Animals↗
PubMed1992

The beta subunit of cyclic GMP phosphodiesterase mRNA is deficient in canine rod-cone dysplasia 1.

Irish setter dogs affected with rod-cone dysplasia 1 have elevated levels of retinal cGMP resulting from deficient rod-specific cGMP phosphodiesterase (cGMP PDE) activity. We investigated the mRNAs coding for the three subunits of cGMP PDE and for the proteins involved in the activation/deactivation of this enzyme in the retinas of developing affected and control dogs. While the photoreceptor cells are viable in the diseased retinas, opsin, transducin alpha 1 and beta 1, 48 and 33 kd proteins, and cGMP PDE alpha and gamma mRNAs have normal transcript sizes and levels. In contrast, a different pattern of cGMP PDE beta mRNAs with lower than normal concentrations is present in the developing affected retinas prior to degeneration. Our observations suggest that an abnormality involving cGMP PDE beta expression is implicated in rod-cone dysplasia 1.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

Reciprocal corneal transplantation fails to correct mucopolysaccharidosis VI corneal storage.

This report contains the results of studies designed to evaluate corneal clearing in mucopolysaccharidosis VI (MPS VI)-affected cats. Corneal buttons from affected cats were transplanted into normal cat corneas and, as controls, normal-to-normal and normal-to-affected transplants also were done. No clearing of the MPS VI graft or host beds occurred, nor was there any clouding of the normal donor or recipient corneal tissues. This assessment was made by serial clinical examinations over a 14-30 mo period and by light and electron microscopic examination of the corneal tissues at the end of the study. Lack of corneal clearing under conditions that would maximize such a process in this animal model indicates that corneal clearing is not an appropriate index for measuring the success of systemic therapy in MPS VI.

Animals↗
PubMed1991

Glycosaminoglycan and collagen metabolism in arylsulfatase B-deficient retinal pigment epithelium in vitro.

Regional differences in retinal pigment epithelial (RPE) cell glycosaminoglycan (GAG) and collagen metabolism were studied using cells obtained from normal cats and those with deficient activity of arylsulfatase B (ASB), a lysosomal enzyme involved in GAG catabolism. Control and ASB-deficient RPE cultures initiated from superior equatorial (superior) and inferior equatorial (inferior) regions of the eye were radiolabeled for 72 hr with 35SO4, and GAGs from the media and cell layers were analyzed separately. In ASB-deficient RPE, there was an accumulation of dermatan/chondroitin sulfate in the cell layer of cultures initiated from the superior region of the eye but not in those initiated from the inferior region. This agrees with previous in situ and in vitro morphologic observations that accumulation of inclusions in ASB-deficient RPE was greater in the superior region of the eye than in the inferior region. By contrast, media from ASB-deficient cultures initiated from the inferior region of the eye contained much higher levels of radiolabeled dermatan/chondroitin sulfate than ASB-deficient cultures from the superior region or normal cultures. Increased GAG content in the media may result from increased secretion of proteoglycans, increased turnover of cell surface or extracellular matrix components, or extrusion of lysosomal contents. These results indicate that one or more of these mechanisms vary regionally throughout the eye in the RPE of ASB-deficient animals. Collagen production was determined in normal and ASB-deficient RPE cultures. In normal RPE, no differences in collagen synthesis were noted between the inferior and superior regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of cyclohexane, an industrial solvent, on the yeast Saccharomyces cerevisiae and on isolated yeast mitochondria.

Little information on the effects of cyclohexane at the cellular or subcellular level is available. In Saccharomyces cerevisiae, cyclohexane inhibited respiration and diverse energy-dependent processes. In mitochondria isolated from S. cerevisiae, oxygen uptake and ATP synthesis were inhibited, although ATPase activity was not affected. Cyclohexane effects were similar to those reported for beta-pinene and limonene, suggesting that the cyclohexane ring in these monoterpenes may be a determinant for their biological activities.

Adenosine Triphosphate↗
PubMed1989

Essential hypertension in a dog.

Severe hypertension was diagnosed in a dog that initially was referred for evaluation of visual deficits and retinal hemorrhage and eventually was donated for medical treatment of hypertension. Initial blood pressure measured by direct methods was markedly high (systolic, 275 mm of Hg; diastolic, 170 mm of Hg). Measures of renal function were within normal limits, with the exception of hypotonic urine. A test protocol was designed to exclude possible secondary causes of hypertension; negative results of such tests allowed the diagnosis of essential hypertension. The consistency of the hypertension and its response to medical control were studied for 5 years. Blood pressure while the dog was untreated during those years was 240 +/- 24 mm of Hg (systolic) and 146 +/- 14 mm of Hg (diastolic). Plasma renin activity was within normal limits, and the response of the renin-angiotensin system to varied salt intake was normal. The most effective medications used to lower blood pressure were propranolol and captopril, both of which were more effective than salt restriction alone. Five years after the diagnosis of hypertension, the dog was euthanatized because of chronic renal failure secondary to pyelonephritis. Hypertension was less severe as the condition progressed into chronic renal failure. Complete necropsy did not reveal an obvious cause of the hypertension, and histopathologic changes were limited to the cardiovascular system, eyes, and kidneys.

Animals↗
PubMed1988

Inherited rod-cone dysplasia: abnormal distribution of cyclic GMP in visual cells of affected Irish setters.

Light-adapted retinas from Irish setters affected with inherited rod-cone dysplasia accumulate high concentrations of cyclic GMP in the outer plexiform layer (OPL). A 29-fold difference in OPL cGMP levels between affected and normal occurs at 19-20 days. However, the highest concentration, 550 mumol kg-1 (dry) wt, is reached at about 4 weeks of age, at which time OPL cyclic GMP is 20-fold higher than cGMP in the OPL of normal control retinas. Levels remain high in affected OPL until about 7 weeks of age; after this, the cyclic GMP level falls and the peak shifts to the outer nuclear layer (ONL). In the normal retina on the other hand, the highest cyclic GMP levels are in the outer segments (OS). The result is that cyclic GMP is highest at opposite ends of the photoreceptor neuron in normal and affected retinas during the first 7 weeks of development. These differing distributions are established as early as postnatal day 10, before signs of degeneration become evident, as determined by either ERG or morphological examination. Moreover, a 38-fold rise in cyclic GMP occurs in the ONL of affected retinas between 1 and 3 weeks of age significantly before the degeneration of nuclei begins at 4 to 5 weeks. The early differences in cyclic GMP distribution are probably not due to differences in guanylate cyclase activity since enzyme levels in normal and affected photoreceptor cells are virtually identical until about 4 weeks of age. Since cGMP has been observed to reach high levels in normal dark-adapted rabbit and frog OPL, the extraordinary OPL levels seen in affected setters may indicate the importance of cGMP in both normal synaptic function and in the disease process.

Aging↗
PubMed1988

S-antigen in a hereditary visual cell disease. Immunocytochemical and immunological studies.

S-antigen is a photoreceptor-specific and potentially autoantigenic protein. Using light microscopic immunocytochemistry, the localization of S-antigen was studied in the retinas of normal dogs and Irish setters affected with rod-cone dysplasia, a hereditary retinal degeneration characterized by abnormal cGMP metabolism and arrested outer segment differentiation. Normal and affected dogs were also tested for the presence of humoral and cellular immunity to S-antigen. S-antigen was present in both rods and cones during inner and outer segment differentiation, but there was an apparent loss of immunoreactivity in cones as the retina matured. The developmental appearance and localization of S-antigen in affected retinas was similar to that of normals. S-antigen immunoreactivity decreased during the early stages of rod loss (39-57 days), but was still present in photoreceptor somata in the late stages of retinal degeneration. No significant difference was found between normal and affected setters in humoral immunity to S-antigen, indicating that it probably does not stimulate autoimmunity in red 1. Because normal dog lymphocytes failed to respond when sensitized to bovine S-antigen, cellular immunity to S-antigen in this disease cannot be ruled out.

Animals↗
PubMed1987

Nomarski evaluation of rod outer segment renewal in a hereditary retinal degeneration. Comparison with autoradiographic evaluation.

Differential interference contrast (Nomarski) optics and autoradiography were used to estimate independently the rate of outer segment renewal in the early stages of progressive rod-cone degeneration (PRCD) in dogs. We have found that significant reductions in renewal rate are demonstrable using the two methods of analysis: autoradiography = 34% reduction; Nomarski method = 18% reduction. Nomarski analysis of affected rod outer segments (ROS) demonstrated optical periodicities (light/dark bands) extending from the base to the tip of the outer segment. Nineteen percent of the cells, however, showed areas where the light/dark bands were not apparent. These homogeneous, "optically silent" regions were interpreted to possibly represent areas where the disc orientation was not perpendicular to the long axis of the ROS.

Animals↗
PubMed1986

Genetic expression of cyclic GMP phosphodiesterase activity defines abnormal photoreceptor differentiation in neurological mutants of inherited retinal degeneration.

We have examined cyclic GMP concentrations, guanylate cyclase activities, and cyclic GMP phosphodiesterase (PDE) activities in developing retinas of congenic mice with different allelic combinations at the retinal degeneration (rd) and retinal degeneration slow (rds) loci. Although guanylate cyclase activities were found to be uniformly low in the mutant retinas, striking differences in PDE activity and cyclic GMP levels were observed in retinas of the various genotypes. Homozygous rds mice, which lack receptor outer segments, showed reduced retinal PDE activity and cyclic GMP concentration in comparison to normal animals. In heterozygous rds/+ mice with abnormal outer segments, the levels were intermediate. In retinas of homozygous rd mice, PDE activity was lower than in rds retinas and cyclic GMP levels were much higher. In mice homozygous for both rd and rds genes, retinal PDE activities were even lower than in single homozygous rd mice; the cyclic GMP level reached the same high value as in the rd animals, persisted for a longer time at this high level, and did not correlate with the rate of photoreceptor cell loss. Thus, a marked variation in PDE activity appears to be the major manifestation of abnormal outer segment differentiation and eventual degeneration of photoreceptor cells in these neurological mutants. An increased cyclic GMP level seems to be an essential corollary in the expression of the rd gene even in the absence of outer segments, but it appears unlikely that an abnormally high nucleotide level in itself causes photoreceptor cell death.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Angiographically normal central retinal artery following the total resection of an optic nerve glioma.

Although the central retinal artery and its collateral circulation, especially within the anterior optic nerve, have been extensively studied, there continues to be controversy regarding the existence and significance of anastomoses between the central retinal artery and ciliary circulation. We present the case of a 16-year-old boy who underwent total resection of an optic nerve glioma beginning proximally at the chiasm and ending distally flush with the globe. After resection, heavy bipolar cautery was applied. Postoperatively, normal central retinal artery circulation was documented angiographically, suggesting that, at least in some cases, significant anastomoses can develop between the central retinal artery and ciliary circulation in the laminar and prelaminar areas.

Adolescent↗
PubMed1986

Morphological and biochemical studies of canine progressive rod-cone degeneration. 3H-fucose autoradiography.

Visual cell pathology and rod outer segment renewal were investigated in normal and PRCD-affected miniature poodles using 3H-fucose autoradiography. Twenty-four hours following the intravitreal injection of 3H-fucose, label accumulated diffusely over cone OS and in a banded pattern at the rod OS base. In normal rods, the band of 3H-label was displaced sclerad with time. PRCD-affected rods in the early stages of the disease (stages 0-1) also showed a similar 3H-label pattern but a significantly (P less than 0.001) reduced renewal rate (control = 2.35 +/- 0.43 mu/24 hr; affected = 0.99 +/- mu/24 hr). This abnormal renewal rate was present in central, equatorial, and peripheral visual cells and was not associated with the presence or density of pigment in the RPE cell layer. Biochemical studies indicated that the 3H-label was present as an integral membrane component in the rod OS and confirmed that canine rhodopsin is a fucosylated glycoprotein. The 3H-band in the rod OS layer disappeared in stage 2 of the disease; diffuse label now was present over rod OS that had decreased length and were reduced in number. At this stage of the disease, interphotoreceptor space was invaded by phagocytic cells, and photoreceptor nuclei were lost from the outer nuclear layer. These late degenerative changes were more extensive in the superior and inferior retinal meridians.

Animals↗
PubMed1985

Disease expression in cultured pigment epithelium. Feline mucopolysaccharidosis VI.

Primary cultures of retinal pigment epithelial (RPE) cells from cats with mucopolysaccharidosis VI (MPS VI) have been initiated from mixed populations of cells (ie, derived from the entire eyecup and represented by both pigmented and nonpigmented RPE cells). The cells were enzymatically dissociated from the eyecup and seeded at 6 X 10(4) cells/cm2. Cells from normal and affected cats formed confluent monolayers of polygonal cells between 5-10 days in culture and maintained most of their in vivo morphologic characteristics. The only abnormality observed in the MPS VI-affected cultures was the accumulation of vacuolated intracytoplasmic inclusions; when numerous, these vacuoles caused cellular hypertrophy. Hypertrophy was present only in cells devoid of pigment. Pigmented cells adjacent to or near the hypertrophied cells exhibited little or no accumulation of vacuoles. The inclusions were indistinguishable from those observed in vivo in terms of size, distribution, and appearance. The MPS VI-affected RPE exhibited deficient arylsulfatase B (ASB) activity (RPE-ASB activity: normal = 506 nmol/hr/mg protein; affected = 22 nmol/hr/mg protein), whereas the activities of two other lysosomal enzymes, arylsulfatase A and alpha-L-iduronidase, were normal. A method was developed to initiate primary cultures of RPE cells from defined regions of normal and MPS VI-affected eyes. Studies indicated that cultures initiated from superior-equatorial regions (RPE nonpigmented) contained more vacuolated cytoplasmic inclusion than those initiated from inferior-equatorial regions (RPE pigmented). These findings indicated that the spatial distribution characteristic of the disease in vivo was maintained in culture and that disease expression was inversely correlated with pigmentation.

Animals↗
PubMed1985

Selecting and maintaining a supported office computer system.

Many costly errors can be made in selecting an in-office computer system. When selecting a system, several guidelines should be followed carefully: A professional computer consultant perhaps should be considered, depending on your level of experience and knowledge of computers. Look specifically at what you want your hardware and software to do, for this will determine the size and character of your system. Evaluate the size and potential size of your practice, as this will also determine the size and expansion capabilities of your system. Carefully evaluate your hardware and software for reputation, system support, maintenance costs, flexibility, and expandability. Carefully evaluate your cost/benefit ratio: is it worth your money to buy a computer in the first place? When evaluating the costs, don't forget the many hidden costs that may be present, in addition to the hardware/software purchase price. Computers will serve you well in the practice and business of medicine. However, in this rapidly changing technologic/informational field, the key words are knowledge and caution.

Computers↗