Stereoscopic digital fluorescein and indocyanine green videoangiography.
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Coloring Agents↗
Biomedical subjects
M L Klein
Publications and source records attributed to M L Klein.
Sorsby fundus dystrophy. A family with the Ser181Cys mutation of the tissue inhibitor of metalloproteinases 3.
Sorbsy fundus dystrophy (SFD) is an autosomal dominant disorder that is characterized by bilateral loss of central vision secondary to choroidal neovascularization and/or pigment epithelial atrophy in the macula, with onset of visual symptoms usually in the fourth or fifth decade. Drusenlike changes may occur, with impaired dark adaptation and abnormal electroretinographic results.
Adult↗
Association of elevated serum lipid levels with retinal hard exudate in diabetic retinopathy. Early Treatment Diabetic Retinopathy Study (ETDRS) Report 22.
OBJECTIVE: To evaluate the relationship between serum lipid levels, retinal hard exudate, and visual acuity in patients with diabetic retinopathy. DESIGN: Observational data from the Early Treatment Diabetic Retinopathy Study. PARTICIPANTS: Of the 3711 patients enrolled in the Early Treatment Diabetic Retinopathy Study, the first 2709 enrolled had serum lipid levels measured. MAIN OUTCOME MEASURES: Baseline fasting serum lipid levels, best-corrected visual acuity, and assessment of retinal thickening and hard exudate from stereoscopic macular photographs. RESULTS: Patients with elevated total serum cholesterol levels or serum low-density lipoprotein cholesterol levels at baseline were twice as likely to have retinal hard exudates as patients with normal levels. These patients were also at higher risk of developing hard exudate during the course of the study. The risk of losing visual acuity was associated with the extent of hard exudate even after adjusting for the extent of macular edema. CONCLUSIONS: These data demonstrate that elevated serum lipid levels are associated with an increased risk of retinal hard exudate in persons with diabetic retinopathy. Although retinal hard exudate usually accompanies diabetic macular edema, increasing amounts of exudate appear to be independently associated with an increased risk of visual impairment. Lowering elevated serum lipid levels has been shown to decrease the risk of cardiovascular morbidity. The observational data from the Early Treatment Diabetic Retinopathy Study suggest that lipid lowering may also decrease the risk of hard exudate formation and associated vision loss in patients with diabetic retinopathy. Preservation of vision may be an additional motivating factor for lowering serum lipid levels in persons with diabetic retinopathy and elevated serum lipid levels.
Adult↗
Ab initio molecular dynamics study of proton transfer in a polyglycine analog of the ion channel gramicidin A.
Proton transfer in biological systems is thought to often proceed through hydrogen-bonded chains of water molecules. The ion channel, gramicidin A (gA), houses within its helical structure just such a chain. Using the density functional theory based ab initio molecular dynamics Car-Parrinello method, the structure and dynamics of proton diffusion through a polyglycine analog of the gA ion channel has been investigated. In the channel, a proton, which is initially present as hydronium (H3O+), rapidly forms a strong hydrogen bond with a nearest neighbor water, yielding a transient H5O2+ complex. As in bulk water, strong hydrogen bonding of this complex to a second neighbor solvation shell is required for proton transfer to occur. Within gA, this second neighbor shell included not only a channel water molecule but also a carbonyl of the channel backbone. The present calculations suggest a transport mechanism in which a priori carbonyl solvation is a requirement for proton transfer.
Biophysical Phenomena↗
Molecular dynamics simulations of a protein on hydrophobic and hydrophilic surfaces.
Molecular dynamics simulations have been used to investigate the behavior of the peripheral membrane protein, cytochrome c, covalently tethered to hydrophobic (methyl-terminated) and hydrophilic (thiol-terminated) self-assembled monolayers (SAMs). The simulations predict that the protein will undergo minor structural changes when it is tethered to either surface, and the structures differ qualitatively on the two surfaces: the protein is less spherical on the hydrophilic SAM where the polar surface residues reach out to interact with the SAM surface. The protein is completely excluded from the hydrophobic SAM but partially dissolves in the hydrophilic SAM. Consequently, the surface of the thiol-terminated SAM is considerably less ordered than that of the methyl-terminated SAM, although a comparable, high degree of order is maintained in the bulk of both SAMs: the chains exhibit collective tilts in the nearest-neighbor direction at angles of 20 degrees and 17 degrees with respect to the surface normal in the hydrophobic and the hydrophilic SAMs, respectively. On the hydrophobic SAM the protein is oriented so that the heme plane is more nearly parallel to the surface, whereas on the hydrophilic surface it is more nearly perpendicular. The secondary structure of the protein, dominated by alpha helices, is not significantly affected, but the structure of the loops as well as the helix packing is slightly modified by the surfaces.
Binding Sites↗
Molecular dynamics investigation of the structure of a fully hydrated gel-phase dipalmitoylphosphatidylcholine bilayer.
We report the results of a constant pressure and temperature molecular dynamics simulation of a gel-phase dipalmitoylphosphatidylcholine bilayer with nw = 11.8 water molecules/lipid at 19 degrees C. The results of the simulation were compared in detail with a variety of x-ray and neutron diffraction data. The average positions of specific carbon atoms along the bilayer normal and the interlamellar spacing and electron density profile were in very good agreement with neutron and x-ray diffraction results. The area per lipid and the details of the in-plane hydrocarbon chain structure were in excellent agreement with wide-angle x-ray diffraction results. The only significant deviation is that the chains met in a pleated arrangement at the bilayer center, although they should be parallel. Novel discoveries made in the present work include the observation of a bimodal headgroup orientational distribution. Furthermore, we found that there are a significant number of gauche conformations near the ends of the hydrocarbon chains and, in addition to verifying a previous suggestion that there is partial rotational ordering in the hydrocarbon chains, that the two chains in a given molecule are inequivalent with respect to rotations. Finally, we have investigated the lipid/water interface and found that the water penetrates beneath the headgroups, but not as far as the carbonyl groups, that the phosphates are strongly hydrated almost exclusively at the nonesterified oxygen atoms, and that the hydration of the ammonium groups is more diffuse, with some water molecules concentrated in the grooves between the methyl groups.
1,2-Dipalmitoylphosphatidylcholine↗
Role of nonspecific cross-reacting antigen, a CD66 cluster antigen, in activation of human granulocytes.
Nonspecific cross-reacting antigen (NCA) is the name of a family of highly glycosylated bacterial-binding receptors found on human granulocytes and other tissues. These glycoproteins are members of the immunoglobulin supergene family and are related structurally to carcinoembryonic antigen. In this study, we demonstrate that ligation of granulocyte NCA results in the activation of the cells, as measured by degranulation and the flux of intracellular calcium. These studies further the proposition that NCA has a function in the immune response of granulocytes against bacterial infections.
Antibodies, Monoclonal↗
A simple protocol for identification of helical and mobile residues in membrane proteins.
A simple molecular dynamics (MD) simulations is protocol shown to predict whether a residue is in a structured alpha-helical segment or in a mobile loop or terminal segment of a membrane protein. The results are verified by comparisons with experimental NMR data. The protocol consists of performing several independent MD simulations on a polypeptide sequence of interest in a dielectric continuum with a relative permittivity epsilon = 2. The time histories of the individual angles between NH bond vectors at time 0 and time t later are calculated, and then Gaussian smoothing of typically 50 ps is applied. The smoothed data are subtracted from the original data to yield the short time fluctuations of the NH bond vectors, and then the rms deviations of the angles are calculated and compared to experimental NMR results. Pf1 coat protein and the c subunit of the E. coli F1F0 ATP synthase are used as examples of membrane proteins. The calculated NH bond rms fluctuations are in qualitative agreement with experimental NMR data in showing that each of these proteins has a mobile segment connecting two helices, as well as mobile N and C-terminal regions. This MD simulations protocol can demonstrate the presence of both the amphipathic and hydrophobic helices while hydropathy plots are able to detect only the hydrophobic helices present in membrane proteins.
Capsid↗
Effects of aspirin on vitreous/preretinal hemorrhage in patients with diabetes mellitus. Early Treatment Diabetic Retinopathy Study report no. 20.
OBJECTIVE: To assess whether the use of aspirin exacerbates the severity or duration of vitreous/preretinal hemorrhages in patients with diabetic retinopathy. DESIGN: The Early Treatment Diabetic Retinopathy Study (ETDRS), a multicenter randomized clinical trial, was designed to assess the effect of photocoagulation and aspirin on 3711 patients with mild to severe nonproliferative or early proliferative diabetic retinopathy. INTERVENTION: Patients were randomly assigned to either an aspirin (650 mg/d) or a placebo group. One eye of each patient was randomly assigned to early photocoagulation and the other to deferral of photocoagulation. MAIN OUTCOME MEASURES: The severity and duration of the vitreous/preretinal hemorrhages were determined from gradings of the annual, seven standard stereoscopic field, fundus photographs. Clinical examinations scheduled every 4 months also provided information on the presence and duration of hemorrhages. RESULTS: Annual fundus photographs of eyes assigned to deferral of photocoagulation revealed vitreous/preretinal hemorrhages at some time during follow-up in 564 patients (30%) assigned to the placebo group and 585 patients (32%) assigned to the aspirin group (P = .48). Based on gradings of fundus photographs, there were no statistical differences in the severity of vitreous/preretinal hemorrhages (P = .11) or their rate of resolution (P = .86) between the groups. Clinical examination of eyes assigned to deferral of photocoagulation revealed 721 eyes (39%) assigned to the aspirin group and 689 (37%) assigned to the placebo group that had vitreous/preretinal hemorrhages during the course of the study (P = .30). Again, no statistically significant difference was found between the rates of resolution, as assessed clinically, between the two treatment groups (P = .43). CONCLUSIONS: As previously reported, the use of aspirin did not increase the occurrence of vitreous/preretinal hemorrhages in patients enrolled in the ETDRS. The data presented in this report demonstrate that the severity and duration of these hemorrhages were not significantly affected by the use of aspirin and that there were no ocular contraindications to its use (650 mg/d) in persons with diabetes who require it for treatment of cardiovascular disease or for other medical indications.
Adult↗
Constant pressure and temperature molecular dynamics simulation of a fully hydrated liquid crystal phase dipalmitoylphosphatidylcholine bilayer.
We report a constant pressure and temperature molecular dynamics simulation of a fully hydrated liquid crystal (L alpha) phase bilayer of dipalmitoylphosphatidylcholine at 50 degrees C and 28 water molecules/lipid. We have shown that the bilayer is stable throughout the 1550-ps simulation and have demonstrated convergence of the system dimensions. Several important aspects of the bilayer structure have been investigated and compared favorably with experimental results. For example, the average positions of specific carbon atoms along the bilayer normal agree well with neutron diffraction data, and the electron density profile is in accord with x-ray diffraction results. The hydrocarbon chain deuterium order parameters agree reasonably well with NMR results for the middles of the chains, but the simulation predicts too much order at the chain ends. In spite of the deviations in the order parameters, the hydrocarbon chain packing density appears to be essentially correct, inasmuch as the area/lipid and bilayer thickness are in agreement with the most refined experimental estimates. The deuterium order parameters for the glycerol and choline groups, as well as the phosphorus chemical shift anisotropy, are in qualitative agreement with those extracted from NMR measurements.
1,2-Dipalmitoylphosphatidylcholine↗
Natural course of perfused central retinal vein occlusion.
OBJECTIVE: To investigate the visual prognosis in perfused (nonischemic) central retinal vein occlusion (CRVO), to determine the frequency of conversion from perfused to nonperfused CRVO, and to identify risk factors for poor visual outcome. DESIGN: Case series. SETTING: Retina referral centre in Portland, Ore. PATIENTS: Fifty-eight patients (59 eyes) with perfused CRVO followed for at least 1 year (average 2.5 years). MAIN OUTCOME MEASURES: Visual acuity, progression to nonperfused CRVO. RESULTS: At the final follow-up visit the visual acuity had improved by two or more lines in 9 eyes (15%), remained the same in 33 eyes (56%) and decreased by two or more lines in 17 eyes (29%). Factors significantly related to visual outcome were initial visual acuity (p = 0.0001) and age, older patients having a worse visual outcome (p = 0.0029). Nine eyes (15%) progressed to nonperfused CRVO. None of the factors analysed, including age, sex, duration of symptoms and initial visual acuity, were predictive of progression. CONCLUSIONS: Perfused CRVO frequently results in significant, permanent visual loss, and a poor visual outcome is most likely in older patients and those with poor initial visual acuity.
Adult↗
The interaction of cytochrome c and the heme domain of cytochrome P-450BM-3 with the reductase domain of cytochrome P-450BM-3.
Cytochrome P-450BM-3 from Bacillus megaterium is a soluble, catalytically self-sufficient fatty acid mono-oxygenase that resembles the Class II P-450 systems of the eukaryotic endoplasmic reticulum. Its single polypeptide chain contains both a P-450 heme domain and an NADPH:P-450 reductase domain, each of which bears significant structural and functional homology with its microsomal counterparts. We report here that cytochrome c, which can accept NADPH-derived electrons from the reductase domain of P-450-BM-3, did not inhibit myristate hydroxylation catalyzed by P-450BM-3 or by two reductase domain mutant enzymes (W574Y, W574F) which have diminished hydroxylase activity relative to wild-type enzyme but retain cytochrome c reductase activity levels comparable to wild-type enzyme. Because reduced cytochrome c generated independently of the reductase domain of P-450BM-3 did not support myristate hydroxylation, it seems likely that cytochrome c binds to a site on the reductase domain which does not overlap the site of the heme domain interaction. We also found that myristate did not inhibit P-450BM-3-mediated cytochrome c reduction. Since neither substrate inhibited the conversion of the other, we conclude that the rate-limiting steps for both myristate hydroxylation and cytochrome c reduction by P-450BM-3 do not involve electron transfer through the reductase domain.
Bacillus megaterium↗
Heredity and age-related macular degeneration. Observations in monozygotic twins.
OBJECTIVE: To determine the concordance of age-related macular degenerative changes in monozygotic twins. PATIENTS: Between 1984 and 1993, we examined a total of nine pairs of monozygotic twins with substantial age-related macular degenerative changes in at least one member of the pair, ranging from extensive large drusen to advanced atrophic and/or disciform scarring. Eight pairs were female and one pair was male. Ages ranged from 62 to 88 years. Monozygosity was confirmed by genetic testing in each of the seven twin pairs on whom it was performed. RESULTS: In eight of the nine twin pairs, the fundus appearance and the incidence of visual impairment were similar. In the ninth pair, one twin had advanced exudative age-related macular degeneration with vision loss in one eye, while the other had large, confluent drusen and good visual function in both eyes. Environmental factor, including diet, geographic background, and medical history, were essentially similar in the twin pairs. CONCLUSION: Although selection factors and similar environmental influences might impact our findings, the markedly similar incidence of macular degenerative changes in these monozygotic twins suggests that a substantial genetic component may exist in a potentially large proportion of patients with age-related macular degeneration. Further studies are warranted to define this hereditary influence.
Aged↗
Critical residues involved in FMN binding and catalytic activity in cytochrome P450BM-3.
Cytochrome P450BM-3 from Bacillus megaterium is a soluble, catalytically self-sufficient fatty acid mono-oxygenase that, in structural organization and amino acid sequence, resembles the Class II (microsomal) P450 systems. Its single polypeptide chain contains both a P450 heme domain and an NADPH:P450 reductase domain, each of which bears significant homology with its microsomal counterparts. We report here the critical nature of three amino acids in the reductase domain of this enzyme with respect to FMN binding and catalytic activity. We used site-directed mutagenesis to change glycine 570 to bulkier amino acids; none of these mutant enzymes contained FMN after purification. We also made substitutions for tryptophan 574 and tyrosine 536, which by sequence analogy (Porter, T. D. (1991) Trends Biochem. Sci. 16, 154-158) were proposed to bind FMN through stacking of the aromatic rings with the isoalloxazine ring of the flavin. Mutants of tryptophan 574 which retained the aromatic side chain contained no less than 0.85 mol of FMN per mol of enzyme, while aspartate and glycine substitutions yielded enzymes which did not incorporate FMN. Substitution of tyrosine 536 with aspartate gave an enzyme which contained 0.44 mol of FMN per mol of enzyme but was inactive as a fatty acid hydroxylase and had only 2% of wild-type cytochrome c reductase activity, while the glycine mutant at this position bound no FMN. Furthermore, although all of the mutant enzymes contained 1 mol of FAD per mol of enzyme, the Y536D mutant and those entirely lacking FMN retained no more than 40% of wild-type ferricyanide reductase activity. By assaying these enzymes in the presence of added FMN, we were able to assess the relative importance of the residues in the wild-type sequence with respect to their contribution to FMN binding. In addition, the aromatic mutants of tryptophan 574, which were nearly as active in cytochrome c reduction as wild-type P450BM-3, were only 20% as active in myristate hydroxylation as the wild-type enzyme, suggesting that this amino acid plays an important role in the flow of electrons between the P450 heme and reductase domains.
Animals↗
Molecular dynamics simulation of Pf1 coat protein.
The results of molecular dynamics simulations of Pf1 coat protein are described and compared to experimental NMR data on both the membrane bound and structural forms of this viral coat protein. Molecular dynamics simulations of the 46 residue coat protein and related model sequences were performed according to a simple protocol. The simulations were initiated with the polypeptides in a completely uniform alpha helical conformation in a dielectric continuum (epsilon = 2) and the motions of individual residues were followed as a function of time by monitoring the angular fluctuations of amide NH bond vectors. The simulations of Pf1 coat protein were able to identify the same mobile and structured segments found in experimental NMR studies of the membrane bound form of the protein (Shon, K.-J., Y. Kim, L. A. Colnago, and S. J. Opella. 1991. Science (Wash. DC). 252:1303-1305). Significantly, in addition to mobile amino and carboxyl terminal regions, a mobile internal loop was found that connects the rigid hydrophobic and amphipathic helices in the protein. NMR experiments show that this mobile loop is present in both the viral and membrane bound forms of the protein and that it plays a role in viral assembly (Nambudripad, R., W. Stark, S. J. Opella, and L. Makowski. 1991. Science (Wash. DC) 252:1305-1308). The results of simulations of several alanine based 46 residue polypeptides with some of the charged residues present in the Pf1 coat protein sequence suggest that interactions between the Asp 14 and Asp 18 sidechains and the peptide backbone are responsible for the formation of the mobile loop. The agreement between the results of the calculations presented here and the previously reported NMR experiments suggest that molecular dynamics simulations might be useful in the prediction of the secondary structure and dynamics of individual residues in membrane and structural proteins with predominantly alpha helical secondary structure.
Bacteriophages↗
Purtscher's-like retinopathy in chronic renal failure.
PURPOSE: The authors describe the clinical findings of three young women with the previously unreported association of Purtscher's-like retinopathy and chronic renal failure. METHODS: The authors reviewed the clinical records of three women with chronic renal failure who had been seen at the Oregon Health Sciences University with acute, profound visual loss associated with a severe vaso-occlusive Purtscher's-like retinopathy. RESULTS: Two of the three patients previously had renal transplants, and both were experiencing allograft rejection. One of these two patients was undergoing hemodialysis. The retinopathy was bilateral in two patients, and unilateral in the third. Each of the 5 affected eyes had severe initial loss of vision to less than 20/400, and only one of these eyes had significant visual recovery. None of the patients had recent trauma, pancreatitis, autoimmune disease, or other condition known to be associated with Purtscher's-like retinopathy. CONCLUSION: A retinal vaso-occlusive disorder resembling Purtscher's retinopathy can occur in patients with chronic renal failure, even in the absence of trauma, pancreatitis, or known autoimmune disease. While the precipitating factor(s) remains unclear, it appears that the retinopathy in this setting may be more severe and associated with a poorer visual prognosis.
Adult↗
Visual function and the subsequent development of exudative age-related macular degeneration.
The eyes of 47 subjects with exudative age-related macular degeneration in the fellow eye were tested with a battery of visual function tests at baseline and followed for at least 18 mo. Fundus photographs also were obtained at baseline. These photographs were used to verify the absence of exudative lesions in the 47 eyes tested. Functional and funduscopic baseline data each were compared against outcome data obtained typically at 18 mo. The baseline data were analyzed for their ability to distinguish eyes that had developed detectable exudative age-related macular degeneration from eyes that had not. Eyes with relatively slow foveal dark adaptation rates despite low foveal quantum absorption capabilities (as inferred from the effects of test area on the Rayleigh color match) were especially likely to develop subretinal neovascularization. The resulting sensitivity/specificity and odds ratios were comparable to those of the most effective funduscopic risk indicators. Low S (blue) cone-mediated sensitivity also was associated with an exudative outcome.
Aged↗
Relations between fundus appearance and function. Eyes whose fellow eye has exudative age-related macular degeneration.
Foveal visual function was compared with fundus appearance for 41 eyes that had good acuity but whose fellow eye had exudative age-related macular degeneration (AMD). The visual functions tested were among those reported to be compromised by AMD. They included: (1) dark adaptation, (2) absolute sensitivity, (3) S cone-mediated sensitivity, and (4) color matching. The fundus features used to evaluate the risk of developing exudative AMD included: (1) drusen confluence, (2) drusen size, and (3) focal hyperpigmentation. For the group of eyes defined by the presence of one or more high-risk fundus characteristics, all visual functions were compromised significantly. In particular, all 21 eyes with abnormally slow rates of dark adaptation had high-risk fundi, and all 16 eyes with abnormal color matching (ie, a small effect of test area on the color match or rejection of all potential color matches) had high-risk fundi. Conversely, 30 of the 32 eyes with high-risk fundi had abnormally slow rates of dark adaptation or abnormal color matching. In addition, reduced acuity in the fellow exudative eye was associated significantly with a high-risk fundus in the nonexudative eye.
Aged↗