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Biomedical subjects

D L Beck

Publications and source records attributed to D L Beck.

At least 19 recordsLinked to original sources
PubMed1998

Transmembrane heme delivery systems.

Heme proteins play pivotal roles in a wealth of biological processes. Despite this, the molecular mechanisms by which heme traverses bilayer membranes for use in biosynthetic reactions are unknown. The biosynthesis of c-type cytochromes requires that heme is transported to the bacterial periplasm or mitochondrial intermembrane space where it is covalently ligated to two reduced cysteinyl residues of the apocytochrome. Results herein suggest that a family of integral membrane proteins in prokaryotes, protozoans, and plants act as transmembrane heme delivery systems for the biogenesis of c-type cytochromes. The complete topology of a representative from each of the three subfamilies was experimentally determined. Key histidinyl residues and a conserved tryptophan-rich region (designated the WWD domain) are positioned at the site of cytochrome c assembly for all three subfamilies. These histidinyl residues were shown to be essential for function in one of the subfamilies, an ABC transporter encoded by helABCD. We believe that a directed heme delivery pathway is vital for the synthesis of cytochromes c, whereby heme iron is protected from oxidation via ligation to histidinyl residues within the delivery proteins.

ATP-Binding Cassette Transporters↗
PubMed1998

Defining the orientation of the human U1A RBD1 on its UTR by tethered-EDTA(Fe) cleavage.

The N-terminal RNA binding domain of the human U1A protein (RBD1) specifically binds an RNA hairpin of U1 snRNA as well as two internal loops in the 3' UTR of its own mRNA. Here, a single cysteine has been introduced into Loop 1 of RBD1, which is subsequently used to attach (EDTA-2-aminoethyl) 2-pyridyl disulfide-Fe3+ (EPD-Fe). This EDTA-Fe derivative is used to generate hydroxyl radicals to cleave the proximal RNA sugar-phosphate backbone in the RNA-RBD complexes. RBD1(K20C)-EPD-Fe cleaves the 5' strand of the RNA hairpin stem, centered four base pairs away from the base of the loop, and cleaves the UTR in two places, again centered on the 5' side of the fourth base pair from each internal loop. These data, extrapolated to the position of Lys 20 in RBD1, orient the two proteins bound to the UTR, and provide direct biochemical evidence for the proposed model of the RBD1:UTR complex.

Base Sequence↗
PubMed1998

Cochlear implantation in sudden bilateral sensorineural hearing loss.

Although 1-4% of all cases of sudden sensorineural hearing loss (SSHL) are bilateral, all such patients reported to date have experienced significant recovery of hearing in at least one ear. We report a case of profound, bilateral idiopathic SSHL without recovery which was treated with cochlear implantation; the first such report to our knowledge. The patient achieved open-set spondee recognition. Individuals with sudden bilateral hearing loss in whom treatable causes have been eliminated may benefit from cochlear implantation.

Acute Disease↗
PubMed1997

Idiopathic bilateral vestibular loss.

We describe the clinical and laboratory features of 13 patients with bilateral loss of peripheral vestibular sensitivity of no known cause. In the office, screening for this condition was possible using illegible e-testing and examination of the patient for refixation saccades after brisk head movements while attempting visual fixation. Diagnosis was confirmed by bilaterally reduced caloric responses (< 20 degrees/second on all 4 caloric irrigations) and abnormally low gain of the vestibulo-ocular reflex on rotational chair testing. The mean age of the patients was 68 years. We noted two patterns of symptom onset: onset associated with vertigo (10 patients) and insidious progressive disequilibrium not associated with vertigo (3 patients). Only 38% of the patients complained of subjective oscillopsia. The subjects performed poorly on platform posturography, particularly when deprived of visual and somatosensory feedback. When associated with vertigo, bilateral vestibular loss may be the result of bilateral sequential vestibular neuritis; when not associated with vertigo, disequilibrium may be caused by slow, symmetrical loss of peripheral function as a result of aging. Although the subjects in this report were elderly, idiopathic bilateral vestibular loss has been reported in patients of all ages.

Aged↗
PubMed1997

Perceived level and sources of stress in university professional schools.

The purpose of this study was to investigate the perception of level and sources of stress in students of two baccalaureate nursing programs, to compare these groups in their perceived stress and to compare the nursing groups to those enrolled in other health-related disciplines: Medicine, Pharmacy and Social Work. The study was descriptive correlational in design. The sample consisted of 552 full-time university students enrolled in years 2, 3 and 4 of their programs in selected disciplines. Data were collected by means of a questionnaire consisting of three main instruments: the Beck-Srivastava Stress Inventory (BSSI), the General Health Questionnaire 30-item version (GHQ-30) and a demographic profile. Data were analyzed using the SPSSx Statistical Package and included analysis of variance, frequency distribution, measures of correlation, item analysis and factor analysis. The results revealed that baccalaureate nursing students, regardless of year in program or university of attendance, experienced higher levels of stress and higher levels of physiological and psychological symptoms than students in other health-related disciplines. Identified stressors among the disciplines are also reported in the article.

Adult↗
PubMed1994

Disruption of virus movement confers broad-spectrum resistance against systemic infection by plant viruses with a triple gene block.

White clover mosaic virus strain O (WClMV-O), species of the Potexvirus genus, contains a set of three partially overlapping genes (the triple gene block) that encodes nonvirion proteins of 26 kDa, 13 kDa, and 7 kDa. These proteins are necessary for cell-to-cell movement in plants but not for replication. The WClMV-O 13-kDa gene was mutated (to 13*) in a region of the gene that is conserved in all viruses known to possess triple-gene-block proteins. All 10 13* transgenic lines of Nicotiana benthamiana designed to express the mutated movement protein were shown to be resistant to systemic infection by WClMV-O at 1 microgram of WClMV virions per ml, whereas all plants from susceptible control lines became systemically infected. Of the 13* transgenic lines, 3 selected for their abundant seed supply were shown to be resistant to systemic infection when challenged by inoculation with three different WClMV strains (O, M, and J) or with WClMV-O RNA at 10 micrograms/ml. Most plants were also resistant to systemic infection at inoculum concentrations up to 250 micrograms of WClMV virions per ml. In addition, the three 13* transgenic plant lines were found to be resistant to systemic infection with two other members of the Potexvirus group, potato virus X and narcissus mosaic virus, and the Carlavirus potato virus S but not to be resistant to tobacco mosaic virus of the Tobamovirus group. These results indicate that virus resistance can be engineered into transgenic plants by expression of dominant negative mutant forms of triple-gene-block movement proteins.

Base Sequence↗
PubMed1994

Characterization of NTPase, RNA-binding and RNA-helicase activities of the cytoplasmic inclusion protein of tamarillo mosaic potyvirus.

The 66-kDa cytoplasmic inclusion protein of tamarillo mosaic potyvirus was purified to near homogeneity using organic solvent clarification, differential centrifugation and sucrose density gradient centrifugation. ATPase and GTPase activities were shown to co-purify with the 66-kDa protein. ATPase activity was stimulated up to fivefold in the presence of 20 microM poly(A). The Km value for ATP hydrolysis (18 microM), was minimally affected upon addition of poly(A). In contrast, the Vmax value for ATP hydrolysis was increased fivefold by the addition of poly(A). Binding of RNA by the cytoplasmic inclusion protein was demonstrated by gel electrophoresis of ultraviolet cross-linked enzyme-RNA complexes. In the absence of added NTP, complexes between the cytoplasmic inclusion protein and single-stranded RNA species formed rapidly in the pH range 3-7, but not at pH 8 or 9. Binding to single-stranded RNA was markedly decreased by the addition of NaCl (10 mM), suggesting a weak association between RNA and enzyme. The cytoplasmic inclusion protein bound single-stranded RNA or partially double-stranded RNA duplexes with single-stranded overhangs of 35 bases and 81 bases, respectively, but did not bind 16-bp blunt-ended double-stranded RNA. RNA binding occurred in the absence of NTP (ATP, GTP, CTP or UTP), whereas dissociation of bound RNA occurred only in the presence of NTP. RNA duplex unwinding (helicase) activity of the enzyme was demonstrated in the presence of any of the above four NTPs using partially double-stranded RNA duplexes with 3' single-stranded overhangs. We propose that the cytoplasmic inclusion protein of tamarillo mosaic virus is an RNA helicase, which translocates in the 3' to 5' direction in an energy-dependent manner, unwinding double-stranded regions.

Acid Anhydride Hydrolases↗
PubMed1993

Nucleotide sequence, serology and symptomatology suggest that vanilla necrosis potyvirus is a strain of watermelon mosaic virus II.

Vanilla necrosis potyvirus (VNV) is the cause of significant losses to the South Pacific islands vanilla crop. The gene for the coat protein of VNV has been cloned and sequenced. Comparison of this gene with other potyviral coat protein sequences revealed 97% nucleotide sequence homology (98% amino acid homology) to a US isolate of watermelon mosaic virus II (WMV-II), 93% nucleotide sequence homology (96% amino acid homology) to an Australian isolate of WMV-II and 81% nucleotide sequence homology (88% amino acid homology) to soybean mosaic virus-N (SMV-N). Serological analysis, by Western blot and ELISA, confirmed the close relationship between VNV and WMV-II. Furthermore, a limited host range determination found VNV and WMV-II able to infect the same series of test plants. However, symptoms differed significantly on three test species demonstrating that VNV and WMV-II are not identical in biological properties. We suggest that VNV be renamed WMV-II (Tonga).

Amino Acid Sequence↗
PubMed1992

The coat protein of white clover mosaic potexvirus has a role in facilitating cell-to-cell transport in plants.

Functions of the coat protein of white clover mosaic potexvirus (WCIMV) were investigated using C-terminal deletion mutants. Whereas plants inoculated with RNA transcripts of a full-length wild-type clone of WCIMV produced typical infections, plants inoculated with transcripts of each mutant did not produce symptoms, and viral RNA species were not detected by Northern analysis. The mutants were able to replicate in protoplasts, although, relative to the wild-type RNA profile, the level of genomic RNA, but not subgenomic RNA, was reduced. These results indicate a role for the coat protein in efficient cell-to-cell transport in plants. Virus-like particles were detected in protoplast extracts inoculated with transcripts of a mutant in which the coat protein was truncated by 31 amino acids. This result suggests that the lack of detectable transport in plants was not due solely to a failure of the mutants to form virus particles. Possible roles for the coat protein in transport and replication are discussed. A 6-kDa open reading frame, internal to the coat protein gene, was shown by mutational analysis not to be essential for replication or transport.

Base Sequence↗
PubMed1991

Influence of the poly(A) tail and putative polyadenylation signal on the infectivity of white clover mosaic potexvirus.

A series of mutations has been constructed in a cDNA clone of white clover mosaic virus (WCIMV) which decreases the poly(A) tail length of run-off transcripts from 74 to 27, 10 or zero 3'-terminal (A) residues. Although transcripts with short poly(A) tails were less infectious than wild-type RNA, complete removal of the (A) tail did not abolish infectivity. Addition of nonviral nucleotides to the 3' terminus of transcripts with no 3'-terminal (A) residues eliminated infectivity. Heterogenous-length poly(A) tails, indistinguishable from the wild type, were synthesized de novo in plants inoculated with transcripts with no 3'-terminal (A) residues, demonstrating the presence of a poly(A) polymerase activity in WCIMV-infected tissue. Mutation of a putative polyadenylation motif found in the 3' noncoding region of WCIMV decreased the efficiency of polyadenylation of the progeny of transcripts with 10 3'-terminal (A) residues. The same mutation in transcripts with no 3'-terminal (A) residues abolished infectivity.

Cloning, Molecular↗
PubMed1991

Triple gene block proteins of white clover mosaic potexvirus are required for transport.

The functions of the protein products encoded by a block of three overlapping genes (the triple gene block) of white clover mosaic potexvirus (WCIMV) have been determined. Mutations were introduced into each of the triple gene block open reading frames and in vitro RNA transcripts assayed in plants and protoplasts. None of the mutants was able to induce symptoms or spread in four systemic hosts and one local lesion host, but all were able to produce progeny genomic RNA, subgenomic RNA, coat protein, and virions in inoculated protoplasts, indicating that all the triple gene block proteins are involved in cell-to-cell spread. Based on observed homologies between the triple gene block proteins of the potex-, carla-, furo-, and hordeivirus groups and Nicotiana velutina mosaic virus, and the demonstrated transport function of the WCIMV and barley stripe mosaic virus triple gene block proteins, these proteins are proposed to constitute a new class of transport proteins.

Amino Acid Sequence↗
PubMed1991

Intraoperative facial nerve monitoring: prognostic aspects during acoustic tumor removal.

Intraoperative facial nerve monitoring with electrical stimulation (IFNMES) has become an integral part of acoustic tumor surgery. We reviewed the records of fifty-six patients who underwent translabyrinthine acoustic tumor removal with IFNMES. There was excellent correlation between intraoperative facial nerve activity and immediate postoperative facial nerve function (24 hours after surgery and at hospital discharge). Our data would suggest that patients who exhibit less than 500 microvolts of ongoing EMG activity during surgery, and who yield at least a 500-microvolt contraction when stimulated with 0.05 milliamps at the brainstem after tumor removal, can expect an excellent immediate facial nerve result (grade I or II).

Ear Neoplasms↗
PubMed1991

Perceived level and sources of stress in baccalaureate nursing students.

The purpose of this study was to investigate the perception of level and sources of stress in nursing students in the various years of the baccalaureate nursing program by identifying the general level of physiological and psychological health, identifying the levels of stress experienced by students in second-, third-, and fourth-year nursing and by identifying the areas that are perceived as being particularly stressful. The method was a descriptive correlational design. The sample consisted of 94 baccalaureate nursing students. Data were collected using two questionnaires--the General Health Questionnaire (GHQ) and the Stress Inventory. Data were analyzed using frequency distributions, t-tests, content analysis, measures of correlation, and analysis of variance. Results showed that the students experienced high stress levels and that they are at risk of having a physical or psychiatric illness. Analysis was done splitting the groups by student status, i.e., RN or generic. Results showed that while both groups are stressed, the generic students report significantly higher levels of stress. Sources of stress also were identified and reported in this article.

Education, Nursing, Baccalaureate↗