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L K Anderson

Publications and source records attributed to L K Anderson.

At least 19 recordsLinked to original sources
PubMed2005

Recombination nodules in plants.

The molecular events of recombination are thought to be catalyzed by proteins present in recombination nodules (RNs). Therefore, studying RN structure and function should give insights into the processes by which meiotic recombination is regulated in eukaryotes. Two types of RNs have been identified so far, early (ENs) and late (LNs). ENs appear at leptotene and persist into early pachytene while LNs appear in pachytene and remain into early diplotene. ENs and LNs can be distinguished not only on their time of appearance, but also by such characteristics as shape and size, relative numbers, and association with unsynapsed and/or synapsed chromosomal segments. The function(s) of ENs is not clear, but they may have a role in searching for DNA homology, synapsis, gene conversion and/or crossing over. LNs are well correlated with crossing over. Here, the patterns of ENs and LNs during prophase I in plants are reviewed.

DNA, Plant↗
PubMed2001

A model for chromosome structure during the mitotic and meiotic cell cycles.

The chromosome scaffold model in which loops of chromatin are attached to a central, coiled chromosome core (scaffold) is the current paradigm for chromosome structure. Here we present a modified version of the chromosome scaffold model to describe chromosome structure and behavior through the mitotic and meiotic cell cycles. We suggest that a salient feature of chromosome structure is established during DNA replication when sister loops of DNA extend in opposite directions from replication sites on nuclear matrix strands. This orientation is maintained into prophase when the nuclear matrix strand is converted into two closely associated sister chromatid cores with sister DNA loops extending in opposite directions. We propose that chromatid cores are contractile and show, using a physical model, that contraction of cores during late prophase can result in coiled chromatids. Coiling accounts for the majority of chromosome shortening that is needed to separate sister chromatids within the confines of a cell. In early prophase I of meiosis, the orientation of sister DNA loops in opposite directions from axial elements assures that DNA loops interact preferentially with homologous DNA loops rather than with sister DNA loops. In this context, we propose a bar code model for homologous presynaptic chromosome alignment that involves weak paranemic interactions of homologous DNA loops. Opposite orientation of sister loops also suppresses crossing over between sister chromatids in favor of crossing over between homologous non-sister chromatids. After crossing over is completed in pachytene and the synaptonemal complex breaks down in early diplotene (= diffuse stage), new contractile cores are laid down along each chromatid. These chromatid cores are comparable to the chromatid cores in mitotic prophase chromosomes. As an aside, we propose that leptotene through early diplotene represent the 'missing' G2 period of the premeiotic interphase. The new chromosome cores, along with sister chromatid cohesion, stabilize chiasmata. Contraction of cores in late diplotene causes chromosomes to coil in a configuration that encourages subsequent syntelic orientation of sister kinetochores and amphitelic orientation of homologous kinetochore pairs on the spindle at metaphase I.

Chromosomes↗
PubMed2001

The distribution of early recombination nodules on zygotene bivalents from plants.

Early recombination nodules (ENs) are protein complexes approximately 100 nm in diameter that are associated with forming synaptonemal complexes (SCs) during leptotene and zygotene of meiosis. Although their functions are not yet clear, ENs may have roles in synapsis and recombination. Here we report on the frequency and distribution of ENs in zygotene SC spreads from six plant species that include one lower vascular plant, two dicots, and three monocots. For each species, the number of ENs per unit length is higher for SC segments than for (asynapsed) axial elements (AEs). In addition, EN number is strongly correlated with SC segment length. There are statistically significant differences in EN frequencies on SCs between species, but these differences are not related to genome size, number of chromosomes, or phylogenetic class. There is no difference in the frequency of ENs per unit length of SC from early to late zygotene. The distribution of distances between adjacent ENs on SC segments is random for all six species, but ENs are found at synaptic forks more often than expected for a random distribution of ENs on SCs. From these observations, we conclude that in plants: (1) some ENs bind to AEs prior to synapsis, (2) most ENs bind to forming SCs at synaptic forks, and (3) ENs do not bind to already formed SCs.

Chromosomes↗
PubMed2000

Imipramine compliance in adolescents.

OBJECTIVE: To investigate side effects, medication compliance, and assumption of medication assignment in adolescents taking imipramine versus placebo in a clinical trial. METHOD: Sixty-three anxious-depressed adolescents in an 8-week double-blind study of imipramine versus placebo, each in combination with cognitive-behavioral therapy for school refusal, were evaluated. Measures of side effects, global improvement, family functioning, medication compliance based on pill counts, and guesses of drug assignment (imipramine versus placebo) were analyzed. RESULTS: Mean side effects ratings were significantly higher for the imipramine group compared with the placebo group (p = .001). Side effects were not associated with noncompliance or with dropping out. Oppositional defiant disorder (ODD) in the adolescents was significantly associated with medication noncompliance (p = .036). On the Family Adaptability and Cohesion Evaluation Scale II (FACES II), low family adaptability (i.e., rigidity), low family cohesion (i.e., disengagement), and extreme family type were significantly associated with greater noncompliance with medications. Accuracy rates for guessing medication assignment (imipramine versus placebo) were 66% for subjects, 62.5% for mothers, and 79.5% for the psychiatrist. Logistic regression demonstrated that side effects (p = .005) and global improvement scores (p = .06) predicted the psychiatrist's guesses of drug assignment. CONCLUSIONS: Side effects were not associated with noncompliance. Nonadherence with taking medications was associated with ODD in the adolescents and problematic family functioning on FACES II. The psychiatrist, who was blind to treatment condition, guessed the subjects' medication assignments with high accuracy. Thus, because of expectancy bias, the data support the use of blind independent evaluators for rating changes in medication trials.

Adolescent↗
PubMed1999

Distribution of crossing over on mouse synaptonemal complexes using immunofluorescent localization of MLH1 protein.

We have used immunofluorescent localization to examine the distribution of MLH1 (MutL homolog) foci on synaptonemal complexes (SCs) from juvenile male mice. MLH1 is a mismatch repair protein necessary for meiotic recombination in mice, and MLH1 foci have been proposed to mark crossover sites. We present evidence that the number and distribution of MLH1 foci on SCs closely correspond to the number and distribution of chiasmata on diplotene-metaphase I chromosomes. MLH1 foci were typically excluded from SC in centromeric heterochromatin. For SCs with one MLH1 focus, most foci were located near the middle of long SCs, but near the distal end of short SCs. For SCs with two MLH1 foci, the distribution of foci was bimodal regardless of SC length, with most foci located near the proximal and distal ends. The distribution of MLH1 foci indicated interference between foci. We observed a consistent relative distance (percent of SC length in euchromatin) between two foci on SCs of different lengths, suggesting that positive interference between MLH1 foci is a function of relative SC length. The extended length of pachytene SCs, as compared to more condensed diplotene-metaphase I bivalents, makes mapping crossover events and interference distances using MLH1 foci more accurate than using chiasmata.

Adaptor Proteins, Signal Transducing↗
PubMed1998

A model for early events in the assembly pathway of cyanobacterial phycobilisomes.

Biological self-assembly is remarkable in its fidelity and in the efficient production of intricate molecular machines and functional materials from a heterogeneous mixture of macromolecules. The phycobilisome, a light-harvesting structure of cyanobacteria, presents the opportunity to study an in vivo assembly process in detail. The phycobilisome molecular architecture is defined, and crystal structures are available for all major proteins, as are a large sequence database (including a genome sequence) and effective genetic systems exist for some cyanobacteria. Recent studies on subunit interaction, covalent modification, and protein stability suggest a model for the earliest events in the phycobilisome assembly pathway. Partitioning of phycobilisome proteins between degradation and assembly is proposed to be controlled by the interaction equilibria between phycobilisome assembly partners, processing enzymes and chaperones. The model provides plausible explanations for existing observations and makes predictions that are amenable to direct experimental investigation.

Bacterial Proteins↗
PubMed1998

Bilin deletions and subunit stability in cyanobacterial light-harvesting proteins.

Light-harvesting in cyanobacteria and red algae is a function of the biliproteins, which have covalently bound bilin chromophores. The biliproteins are assembled with linker proteins into the phycobilisome, a large complex that resides on the surface of the photosynthetic membranes. Early steps in the phycobilisome assembly pathway include the folding of biliprotein alpha- and beta-subunits, covalent modification of subunits by bilin attachment and formation of the primary assembly unit, the alphabeta heterodimer. The potential role of bilins in subunit structure and assembly is examined in this study by site mutagenesis of biliprotein genes. Phycocyanin subunits from Synechocystis sp. 6701 that were unable to bind chromophores at specific sites were generated by changing the codons for bilin-binding cysteines to alanine residues. The altered genes were then expressed in a phycocyanin-minus mutant of the transformable Synechocystis sp. strain 6803. Single and multiple chromophore deletions cause specific and reproducible variations in phycobilisome-associated phycocyanin that do not correlate with transcript levels. Sedimentation equilibrium studies with purified proteins showed that bilin absence reduces the strength of alphabeta interaction in the heterodimer. These results suggest that phycocyanin instability in bilin-deletion mutants is a consequence of diversion of unassembled alpha- and beta-subunits to a degradation pathway. Attachment of the central bilin, which is common to all biliprotein subunits, may facilitate alphabeta interaction by completing the final stage of subunit folding and stabilizing the contact domains of binding partners in the heterodimer.

Bacterial Proteins↗
PubMed1997

RecA-like proteins are components of early meiotic nodules in lily.

Early meiotic nodules (also called recombination nodules) are proteinaceous structures about 100 nm in diameter that are associated with forming synaptonemal complexes (SCs) during early prophase I of meiosis. Although their function is unknown, early nodules may be involved in searching for DNA homology before synaptic initiation. Two potential components of early nodules are Rad51 and Dmc1 proteins. These proteins are important for meiotic recombination in eukaryotes and are homologous to RecA, the major protein that catalyzes homologous pairing and DNA strand exchange in prokaryotes. In addition, Rad51 has been localized by immunofluorescence in abundant foci that may correspond to early nodules in yeast, lily, and mouse. In yeast and lily, Dmc1 and Lim15, the lily homolog of Dmc1, colocalize with Rad51. Here, using electron microscopic immunogold localization to spreads of zygotene and early pachytene SCs from lily, we confirm that RecA-like proteins are components of early nodules. The antibody used was generated to full-length tomato Rad51 protein and binds to both Rad51 and Lim15 in immunoblots of lily primary microsporocyte proteins. The labeled early nodules are heterogeneous in size and are associated with both axial elements and SCs. There are two classes of early nodules, those that are densely labeled with gold and those that are not labeled at all. This result may be due to technical limitations associated with using spread preparations or to differences in the nodules themselves. The presence of Rad51 and/or Lim15 proteins in early nodules supports the hypothesis that early nodules are involved in recombination-related events during meiosis.

Journal Article↗
PubMed1995

Subunit interactions and protein stability in the cyanobacterial light-harvesting proteins.

Strain 4R is a phycocyanin-minus mutant of the unicellular cyanobacterium Synechocystis sp. strain 6803. Although it lacks the light-harvesting protein phycocyanin, 4R has normal levels of phycocyanin (cpc) transcripts. Sequence analysis of the cpcB gene encoding the phycocyanin beta subunit shows an insertion mutation in 4R that causes early termination of translation. Other work has shown that the phycocyanin alpha subunit and the linker proteins encoded on the cpc transcripts are all functional in 4R, yet the defective phycocyanin beta subunit results in the complete absence of the alpha subunit and the linkers. Phycocyanin-minus mutants were constructed in a wild-type background by interruption of cpcB and cpcA with an antibiotic resistance gene and were compared with the 4R strain. Immunoblot analysis of the mutants demonstrated that interruption of one subunit was accompanied by a complete absence of the unassembled partner subunit. Phycocyanin assembly begins with the formation of the alpha beta heterodimer (the monomer) and continues through higher-order trimeric and hexameric aggregates that associate with linker proteins to form the phycobilisome rods. The results in this paper indicate that monomer formation is a critical stage in the biliprotein assembly pathway and that unassembled subunits are subject to stringent controls that prevent their appearance in vivo.

Amino Acid Sequence↗
PubMed1995

Heterologous assembly and rescue of stranded phycocyanin subunits by expression of a foreign cpcBA operon in Synechocystis sp. strain 6803.

Light harvesting in cyanobacteria is performed by the biliproteins, which are organized into membrane-associated complexes called phycobilisomes. Most phycobilisomes have a core substructure that is composed of the allophycocyanin biliproteins and is energetically linked to chlorophyll in the photosynthetic membrane. Rod substructures are attached to the phycobilisome cores and contain phycocyanin and sometimes phycoerythrin. The different biliproteins have discrete absorbance and fluorescence maxima that overlap in an energy transfer pathway that terminates with chlorophyll. A phycocyanin-minus mutant in the cyanobacterium Synechocystis sp. strain 6803 (strain 4R) has been shown to have a nonsense mutation in the cpcB gene encoding the phycocyanin beta subunit. We have expressed a foreign phycocyanin operon from Synechocystis sp. strain 6701 in the 4R strain and complemented the phycocyanin-minus phenotype. Complementation occurs because the foreign phycocyanin alpha and beta subunits assemble with endogenous phycobilisome components. The phycocyanin alpha subunit that is normally absent in the 4R strain can be rescued by heterologous assembly as well. Expression of the Synechocystis sp. strain 6701 cpcBA operon in the wild-type Synechocystis sp. strain 6803 was also examined and showed that the foreign phycocyanin can compete with the endogenous protein for assembly into phycobilisomes.

Amino Acid Sequence↗
PubMed1994

A monoclonal antibody to lateral element proteins in synaptonemal complexes of Lilium longiflorum.

To identify synaptonemal complex (SC) proteins in Lilium longiflorum (lily), monoclonal antibodies were generated using mice immunized with isolated pachytene nuclei. While most of the resulting monoclonal antibodies recognized nucleolar or chromatin proteins, one monoclonal antibody (anti-LE) was found that binds to lateral elements. Anti-LE bound more to lateral elements of SCs digested with DNase than to lateral elements that had not been digested with DNase. The opposite pattern of labeling was observed using monoclonal antibodies to lily chromatin and nucleolar proteins. These results indicate that anti-LE is specifically recognizing lateral element proteins and not chromatin or nucleolar proteins surrounding the lateral elements. On immunoblots, anti-LE binds to three pachytene nuclear proteins (Mr 60000, 66000 and 70000), two tetrad (early microspore) nuclear proteins (Mr 60000 and 70000), and two root tip nuclear proteins (Mr 52000 and 60000). However, anti-LE does not bind to proteins from leaf nuclei. Of these four tissues, leaf is the only one that does not have actively dividing cells. This observation suggests that at least some SC proteins are related to nuclear proteins from mitotically active cells.

Animals↗
PubMed1994

The relationship between synaptonemal complex length and genome size in four vertebrate classes (Osteicthyes, Reptilia, Aves, Mammalia).

We investigated the relationship between synaptonemal complex (SC) length and genome size in 18 species of vertebrates from the classes Osteicthyes (bony fish), Reptilia (reptiles), Aves (birds), and Mammalia (mammals). When total SC length was plotted against genome size for all 18 vertebrate species, there did not appear to be a correlation between the two variables. However, when birds were excluded from the data and a linear regression analysis was performed, variation in genome size accounted for approximately 50% of the variation in total SC length (r2 = 0.47). Dividing the average total SC length for a species by its 4C DNA amount yields the species' SC/DNA ratio. SC/DNA ratios of birds were approximately twice as high as the SC/DNA ratios of reptiles and mammals. Bony fish showed intraclass divergence in SC/DNA ratios. The sunfish (Centrarchidae) had SC/DNA ratios almost as high as those of birds, while the remaining fish in the study had SC/DNA ratios similar to those of reptiles and mammals. These observations indicate that inter and intraclass divergence in the relationship between total SC length and genome size has occurred in the vertebrates. Coupled with evidence from the literature, our results also suggest that SC/DNA ratios are positively correlated with crossover frequency.

Animals↗
PubMed1994

Total quality management approach improves medication replacement.

Total quality management (TQM) is based on understanding customer needs, improving key processes that affect customer satisfaction, and creating cross-functional teams to resolve process problems. This article describes application of TQM principles and problem-solving processes to improve one OR's medication exchange system. The problem was excessive monthly pharmacy medication replacement costs. The goal was to reduce the monthly medication replacement costs by 50%. Within four months, monthly medication replacement charges decreased from $656 to $302, and by one year, monthly charges decreased to $160. The new process had fewer steps, fewer staff members involved, and fewer delays in medication replacement.

Costs and Cost Analysis↗
PubMed1993

Teams: group process, success, and barriers.

The business philosophy of total quality management is saturating the healthcare arena, and with it brings new meaning to the old concept of team. Nurses are not exempt from this concept, and will be expected to become effective team leaders and team members. The author reviews the literature on teams to define the concept of teams in the context of group process, and discuss effective team characteristics and barriers that often impede the success of teams. Whether the nurse carries the hat of educator, administrator, practitioner, or staff nurse, all will be part of a team within the changing healthcare environment.

Group Processes↗
PubMed1991

Orientation based on nursing diagnoses. Old concepts in today's practice.

Although many operating room orientation programs contain content necessary to meet accrediting guidelines, very few tie the nursing process to the content. Our orientation is structured within a nursing framework (ie, Dr Gordon's "Eleven Functional Health Patterns") and emphasizes nursing diagnoses, theory, and clinical competencies. Although the new orientation program has been in effect for only two years, we feel the following list reflects the positive outcomes so far: decreased staff turnover (ie, one nurse out of 26 full-time equivalents in 18 months), increased success in recruiting nurses into the operating room (ie, multiple applicants as positions open), new nurses demonstrate comfort with basic perioperative nursing practice with-in six months, and nurses who did not complete new orientation program are requesting all or portions of the content. By using this plan, essential aspects of perioperative practice are consistent with hospital-wide nursing practice, practice standards for the operating room, and accrediting standards.

Curriculum↗
PubMed1990

Genes for phycocyanin subunits in Synechocystis sp. strain PCC 6701 and assembly mutant UV16.

The cyanobacterial phycobilisome is a large protein complex located on the photosynthetic membrane. It harvests light energy and transfers it to chlorophyll for use in photosynthesis. Phycobilisome assembly mutants in the unicellular cyanobacterium Synechocystis sp. strain 6701 have been characterized. One such mutant, UV16, contains a defect in the assembly of the biliprotein phycocyanin. We report the cloning and sequencing of the phycocyanin genes from wild-type Synechocystis strain 6701 and demonstrate an alteration in the gene for the phycocyanin alpha subunit in UV16. Possible consequences of the lesion on phycobilisome assembly were assessed from its position in the phycocyanin tertiary and quaternary structures. The UV16 phenotype is complex and includes a reduced level of phycocyanin relative to that in the wild type. To determine whether the lower phycocyanin content results from lower transcript levels, a fragment of cpcBA was used as a probe for quantitating phycocyanin mRNA. Both the wild type and UV16 contained two phycocyanin transcripts of approximately 1.4 and 1.5 kilobases that were equal in abundance and that did not vary with light quality during cell growth. Equal levels of these transcripts in the wild type and UV16 suggest that the lower phycocyanin content in the mutant may be due to posttranscriptional events. The 5' ends of the two phycocyanin mRNAs were mapped at 100 and 223 base pairs upstream of the cpcB initiation codon. Homologous regions upstream of the putative transcription initiation sites may be important for maintaining high levels of transcription from the Synechocystis strain 6701 phycocyanin gene set.

Amino Acid Sequence↗