PubMed Health⌕ Search

Biomedical subjects

J Baum

Publications and source records attributed to J Baum.

At least 19 recordsLinked to original sources
PubMed1992

1H-NMR assignments and local environments of aromatic residues in bovine, human and guinea pig variants of alpha-lactalbumin.

1H-NMR assignments have been defined for the aromatic-ring protons of the bovine, guinea pig and human variants of alpha-lactalbumin. Spin-system networks were identified by means of double-quantum-filtered two-dimensional J-correlated spectroscopy and two-dimensional relayed coherence spectroscopy data. Analysis of two-dimensional nuclear-Overhauser-enhancement spectroscopy data of the proteins indicated that in each case two clusters of aromatic residues exist. The two clusters are also evident in the crystal structure of the human protein, and this evidence, in conjunction with sequence differences between the three proteins, permitted sequence-specific assignments to be made for the majority of aromatic residues. Remaining ambiguities in the assignments could be resolved by analysis of photochemically induced dynamic nuclear polarization (PCIDNP) effects. Comparison of the PCIDNP spectra of the three proteins indicated the presence of only minor differences in the surface exposure of conserved aromatic residues. Taken together, these results indicate that the environments of the conserved aromatic residues in bovine, guinea pig and human alpha-lactalbumin in solution are very similar to each other, and that the solution and the crystal forms of at least the human protein are similar.

Amino Acid Sequence↗
PubMed1992

Nuclear magnetic resonance and circular dichroism studies of a triple-helical peptide with a glycine substitution.

The triple-helical conformation has the stringent amino acid sequence constraint that every third residue must be a glycine, (X-Y-Gly)n. We use nuclear magnetic resonance and circular dichroism to quantify the consequences of a substitution in the glycine position of a triple-helical peptide, and to enhance our understanding of interactions in this basic structural motif. A 30-residue peptide with a Gly----Ala change forms a stable trimer at a folding rate somewhat less than that of the unsubstituted peptide, and the substitution results in a marked decrease in thermal stability and a conformational perturbation of about 30% of the triple-helical structure. Two models were generated for this peptide, one with the alanine residues packed inside the triple helix and one with a looping out of the chain at the substitution site. Studies on the Gly----Ala peptide are useful in understanding connective tissue diseases which result from the substitution of one glycine residue in the triple-helix of fibrillar collagens.

Circular Dichroism↗
PubMed1992

NMR and CD studies of triple-helical peptides.

Triple-helix formation of the peptide (Pro-Hyp-Gly)10 was monitored by nmr and CD spectroscopy. The two-dimensional nmr spectra indicated that the Gly C alpha H and Pro C delta H proton resonances shift upfield in going from the nonhelical to helical form, while hydroxy-proline resonances are unchanged. The integrated areas of the helical and nonhelical resonances could be monitored in the one-dimensional nmr spectrum, and indicate that in the (Pro-Hyp-Gly)10 about 90% of the residues are in a defined triple-helical conformation. The introduction of a glycine to alanine substitution or the deletion of a single hydroxyproline residue in the stable triple-helical peptide (Pro-Hyp-Gly)10 still allows trimers to be formed, but the trimers show a substantial loss of triple helix and decreased thermal stability compared with (Pro-Hyp-Gly)10. Two computer models were generated for the Gly----Ala peptide, one with the Ala side chains packed inside the helix and the other with the region containing the alanines forming a beta-bend that loops out from the helix. The nmr data is more consistent with the latter model.

Amino Acid Sequence↗
PubMed1992

Acanthamoebae bind to glycolipids of rabbit corneal epithelium.

By use of a thin-layer chromatogram (TLC) overlay procedure, 35S-labeled acanthamoebae were shown to bind to seven glycolipids of rabbit corneal epithelium. Corneal epithelial cells were grown in culture and were subjected to Folch extraction to isolate a chloroform-rich lower phase containing neutral glycosphingolipids (NGSL) and an aqueous upper phase containing gangliosides, i.e., sialic acid-containing glycolipids. Thin-layer chromatography of the upper phase revealed the presence of 10 ganglioside components. Acanthamoebae were shown to bind to four of these components, referred to as 2, 3, 6, and 7. On TLC plates, ganglioside components 2 and 3 migrated slightly ahead of the glycolipid standard GD1a, component 7 comigrated with standard GM3, and component 6 migrated a little more slowly than GM3. Likewise, of the 10 NGSL known to be present in the lower phase, acanthamoebae bound to components 1, 5, and 6. NGSL components 1, 5, and 6 migrated on TLC plates with relative mobilities similar to those of standards asialo GM1, asialo GM2, and ceramidetrihexoside, respectively. We propose that one or more of the Acanthamoeba-reactive glycolipids of corneal epithelium identified in this study may play a role in the pathogenesis of Acanthamoeba keratitis by mediating the adherence of the parasites to the cornea.

Acanthamoeba↗
PubMed1992

An improved apparatus for transscleral iontophoresis of gentamicin.

The authors previously found that positively charged substances are less well-transported into the vitreous humor by transscleral iontophoresis than are negatively charged substances. There was more bubble formation in the eye cup with positively charged than with negatively charged substances. The authors hypothesized that these bubbles might account for the poorer conductance of the positively charged species by causing interruptions of the current. Therefore, the authors developed a modified eye cup in which the diameter of the fluid column was larger than that in the old device (1.0 rather than 0.5 mm). This modification allowed larger voltage to be applied than with the older device, because bubbles could be more easily cleared from the conjunctiva than with the narrower-bore eye cup. Although the efficiency of the apparatus was the same with the two eye cups (micrograms per milliliter in vitreous humor divided by milliampere minutes of current applied), vitreal concentrations of gentamicin with the modified eye cup were fourfold higher than with the older eye cup (83 versus 19 micrograms/ml; P < 0.001). These studies suggest that modifying the eye cup to permit easier removal of bubbles resulted in improved delivery of gentamicin into the ocular humors.

Animals↗
PubMed1992

Decreased tear osmolarity and absence of the inferior marginal tear strip after sleep.

To better understand some of the clinical syndromes that patients experience on eyelid opening in the morning, we examined four patients clinically and measured tear osmolarity immediately after sleep and later in the day. The inferior marginal tear strip was absent, and tear osmolarity was at its nadir on eyelid opening after sleep. We propose a mechanism whereby decreased osmolarity, together with a probable decrease in tear volume, may increase lid-corneal and soft contact lens-corneal adhesion during sleep, and help explain both the development of recurrent corneal erosions on awakening and the tendency of soft contact lenses to adhere to the cornea overnight.

Adult↗
PubMed1991

Proton NMR assignments and secondary structure of the snake venom protein echistatin.

The snake venom protein echistatin is a potent inhibitor of platelet aggregation. The inhibitory properties of echistatin have been attributed to the Arg-Gly-Asp sequence at residues 24-26. In this paper, sequence-specific nuclear magnetic resonance assignments are presented for the proton resonances of echistatin in water. The single-chain protein contains 49 amino acids and 4 cystine bridges. All of the backbone amide, C alpha H, and side-chain resonances, except for the eta-NH of the arginines, have been assigned. The secondary structure of the protein was characterized from the pattern of nuclear Overhauser enhancements, from the identification of slowly exchanging amide protons, from 3JC alpha H-NH coupling constants, and from circular dichroism studies. The data suggest that the secondary structure consists of a type I beta-turn, a short beta-hairpin, and a short, irregular, antiparallel beta-sheet and that the Arg-Gly-Asp sequence is in a flexible loop connecting two strands of the distorted antiparallel beta-sheet.

Amino Acid Sequence↗
PubMed1991

Clinical and histopathologic studies of two families with lattice corneal dystrophy and familial systemic amyloidosis (Meretoja syndrome).

Lattice corneal dystrophy associated with familial systemic amyloidosis (Meretoja syndrome) has rarely been described other than in patients of Finnish origin. The authors report two North American patients with this disease who manifest blepharochalasis, lattice corneal dystrophy, open-angle glaucoma, and cranial neuropathy. In one patient, a corneal intraepithelial and subepithelial pseudodendrite was managed by superficial keratectomy, and this same patient benefited from surgical brow suspension for facial muscular weakness. In the second patient, penetrating keratoplasty was complicated by a neurotrophic persistent epithelial defect. Corneal tissue from both superficial keratectomy and penetrating keratoplasty exhibited ultrastructurally characteristic amyloid filaments and associated elastoid material. Transmission electron microscopy of conjunctiva and skin biopsies similarly revealed amyloid deposits associated with most basement membranes, the perineurium and endoneurium of most peripheral nerves, and the intima and media of arteries. By immunoperoxidase staining, the corneal amyloid deposits were positive for the amyloid P-component protein but negative for the nonimmunoglobulin amyloid A protein and prealbumin. Serum prealbumin and amyloid A related protein were normal.

Aged↗
PubMed1991

[Capnometry and capnography as safety factors in anesthesia].

Continuous measurement and monitoring of the expiratory carbon dioxide concentration can be performed with modern measurement devices routinely without any problem today. After a short introduction to measurement techniques the comprehensive monitoring possibilities of this method are described by multiple examples. No only actual disturbances of the ventilation, the circulation and the metabolism, but also malfunction or inadequate control of the anaesthesia machine can be recognized without substantial time delay. But an actual alteration of the CO2 value necessitates careful analysis of the underlying problem which is greatly facilitated by a graphic display of the CO2 signal, the capnogram. The knowledge of possibly occurring artificial alterations of the CO2 measurement, which are demonstrated too, prevents dangerous misinterpretations. By continuous measurement of the expiratory CO2 concentration, not only can the ventilation parameters be set optimally, but multiple life threatening complications can be detected very early and corrected immediately. Thus, this monitoring technique essentially contributes to the patients safety during anaesthesia.

Anesthesia↗
PubMed1991

Neuraminidase activity in acanthamoeba species trophozoites and cysts.

Acanthamoeba species, a widely distributed group of free-living amoeba, can infect humans and spread hematogenously after direct interaction with the mucosal surfaces. The mechanism underlying Acanthamoeba damage to the target cell is unknown. The authors report that trophozoites and cysts of Acanthamoeba species exhibit a neuraminidase activity that is membrane associated and released into the culture medium at the start of the logarithmic phase of growth. The enzyme activity is optimal at pH 5 and at 25-30 degrees C. Live parasites release sialic acid from human cells. Therefore, the neuraminidase of Acanthamoeba species could be relevant in the colonization and damage of the sialic acid-rich corneal epithelium and in the alterations of glycolipids associated with meningoencephalitis.

Acanthamoeba↗
PubMed1991

Auranofin therapy for juvenile rheumatoid arthritis: results of the five-year open label extension trial.

Eighty-eight children with juvenile rheumatoid arthritis (JRA) who completed a double blind, randomized placebo controlled trial of oral gold were entered into an open label extension phase during which they received auranofin (AF) at a dosage of 0.15-0.2 mg/kg/day (9 mg/day maximum). Eleven (12.5%) patients completed 5 years of AF therapy; 77 (87.5%) did not. Fifteen (17%) of the 88 were in disease remission at the final visit. Mean duration of therapy for those who discontinued was 646 days. Parental/patient decision and insufficient therapeutic effect were the 2 most frequent reasons for early termination, followed by adverse effects. Though relatively well tolerated, AF provides adequate longterm management for only a small percentage of patients with JRA.

Administration, Oral↗
PubMed1990

Bacterial adherence to extended wear soft contact lenses.

The authors studied the adherence of Pseudomonas aeruginosa and Staphylococcus aureus to extended wear soft contact lenses (EWSCLs) with and without focal deposits using both a radiolabeling technique and electron microscopy. P. aeruginosa showed significant adherence to contact lenses in vitro. In contrast, S. aureus failed to show significant adherence to contact lenses in vitro (i.e., the radioactive uptake was not significantly above background). The extent of adherence of Pseudomonas was proportional to the number of focal deposits on the lenses. Results of electron microscopic examination showed the bacteria to be adherent primarily to large focal deposits (greater than or equal to 150 microns). There was no pseudomonal adherence to the small focal deposits (less than or equal to 50 microns) and little adherence to the areas in between the focal deposits. The authors hypothesize that worn lenses, especially those with large focal deposits, serve as a vehicle for the transport of P. aeruginosa to the cornea. This hypothesis could be a partial explanation for the high incidence of keratitis caused by P. aeruginosa in EWSCL patients.

Bacterial Adhesion↗