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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
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↗
PubMed1990

Infectious transcripts and nucleotide sequence of cloned cDNA of the potexvirus white clover mosaic virus.

The complete nucleotide sequence of white clover mosaic virus (WCIMV) strain O has been determined and compared to the WCIMV strain M sequence. The two virus strains show 12% divergence at the nucleotide level and 3% divergence at the amino acid level (open reading frames 1 to 5). Two open reading frames, 10 and 21 kDa, identified in the strain M sequence were not found in the strain O sequence. High levels of infectious RNA transcripts were produced from a full-length cDNA clone of strain O constructed downstream of the SP6 RNA polymerase promoter (greater than 2 micrograms RNA/micrograms template DNA). Symptoms characteristic of WCIMV developed when host plants were inoculated with SP6 RNA transcripts. The specific infectivity of transcript RNA produced in the presence of m7GpppG was similar to that of virion RNA. The SP6 transcripts lacked 5' nonviral nucleotides, but contained 6, 14, or 198 3' nonviral nucleotides (derived from the pUC19 vector). Transcripts were infectious without m7GpppG, or with long nonviral 3' nucleotide stretches. Progeny virus RNA from infections initiated with transcripts containing 198 nonviral 3' nucleotides did not maintain these sequences.

Base Sequence↗
PubMed1990

Deletion of repeated sequences from tobacco mosaic virus mutants with two coat protein genes.

Tobacco mosaic virus (TMV) hybrids were constructed in vitro with an extra coat protein gene (gene order 5'- 126K/183K gene-30K gene-first coat protein gene-subgenomic mRNA promoter:second coat protein gene-3'). One coat protein gene was wild type and the other was derived from one of three coat protein mutants that elicit distinctive phenotypic responses. The hybrids contained large sequence repeats (up to 747 nucleotides). RNA transcripts of each of seven hybrid constructs initiated infections in host plants, but the progeny virus contained only one coat protein gene with no additional or missing nucleotides. Progeny of mutants with the two functional coat protein genes in different order within the genome retained coat protein gene sequence predicted by the number of repeated nucleotides 3' and 5' of the differential nucleotides. In contrast, progeny that resulted from virus hybrids with a wild-type and a nonfunctional coat protein gene possessed only the wild-type coat protein gene, even when the predicted progeny was a free-RNA virus. This demonstrated that selection strongly affected which progeny became predominant in the resulting populations.

Base Sequence↗
PubMed1990

Facial nerve monitoring in otologic surgery: clinical indications and intraoperative technique.

While identification of the intratemporal portion of the facial nerve is mandatory in most otologic surgical procedures, inadvertent instrumentation, traction, or thermal injury may still result from inaccurate delineation, purposeful avoidance, or false protection of this critical structure. Improved functional preservation of the facial nerve has been achieved in acoustic neuroma surgery through the monitoring of evoked facial electromyographic activity. This technique may also be used during otologic procedures in which facial nerve manipulation is anticipated in the management of recurrent cholesteatoma, temporal bone trauma, congenital deformity, or purposeful access for cochlear implantation. Potential indications for using facial nerve monitoring in contemporary otologic surgery are detailed through illustrative case presentations, and necessary instrumentation and techniques are briefly reviewed. Intraoperative monitoring can assist the surgeon in isolating the facial nerve when chronic inflammation, traumatic injury, or anomalous development has resulted in distortion or absence of microanatomic landmarks.

Adult↗
PubMed1990

Intraoperative facial nerve monitoring. Technical aspects.

Intraoperative facial nerve monitoring (FNM) is widely used as a method of assessing the anatomic and physiologic integrity of the facial nerve during procedures in which the nerve may be in jeopardy. The doctors of the Otologic Medical Group use intraoperative FNM during all neurotologic procedures. This technique can also be used for congenital ear surgery and complicated revision chronic ear surgery. On the basis of experience gained from more than 200 cases in which FNM has been used, definitive conclusions can be made in regard to technical aspects. This article will discuss indications for intraoperative FNM, electrode design, visual and auditory feedback, and the particulars about stimulators.

Facial Nerve↗