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K L Anderson

Publications and source records attributed to K L Anderson.

At least 55 records · Page 3Linked to original sources
PubMed1998

Conjugal transfer of transposon Tn1545 into the cellulolytic bacterium Eubacterium cellulosolvens.

Tn1545, a self-mobilizing transposon, was introduced into the chromosome of the ruminal cellulolytic bacterium Eubacterium cellulosolvens. This was achieved by conjugal transfer of the transposon from Clostridium beijerinckii at a frequency of 1 per 10(6) recipient cells. Transconjugants of Eu. cellulosolvens were resistant to both tetracycline and erythromycin, and were able to mobilize Tn1545 back into Cl. beijerinckii. Southern blot hybridization of representative transconjugants did not reveal site-specific insertion. This potential randomness of the transposon insertion site may prove useful in the development of Tn1545 as a tool for mutagenesis of Eu. cellulosolvens.

Animals↗
PubMed1998

Mutations in CYP1B1, the gene for cytochrome P4501B1, are the predominant cause of primary congenital glaucoma in Saudi Arabia.

The autosomal recessive disorder primary congenital glaucoma (PCG) is caused by unknown developmental defect(s) of the trabecular meshwork and anterior chamber angle of the eye. Homozygosity mapping with a DNA pooling strategy in three large consanguineous Saudi PCG families identified the GLC3A locus on chromosome 2p21 in a region tightly linked to PCG in another population. Formal linkage analysis in 25 Saudi PCG families confirmed both significant linkage to polymorphic markers in this region and incomplete penetrance, but it showed no evidence of genetic heterogeneity. For these 25 families, the maximum combined two-point LOD score was 15.76 at a recombination fraction of .021, with the polymorphic marker D2S177. Both haplotype analysis and homozygosity mapping in these families localized GLC3A to a 5-cM critical interval delineated by markers D2S2186 and D2S1356. Sequence analysis of the coding exons for cytochrome P4501B1 (CYP1B1) in these 25 families revealed three distinctive mutations that segregate with the phenotype in 24 families. Additional clinical and molecular data on some mildly affected relatives showed variable expressivity of PCG in this population. These results should stimulate a study of the genetic and environmental events that modify the effects of CYP1B1 mutations in ocular development. Furthermore, the small number of PCG mutations identified in this Saudi population makes both neonatal and population screening attractive public health measures.

Adult↗
PubMed1998

Comparison of staining techniques for scanning electron microscopic detection of ultrastructural protuberances on cellulolytic bacteria.

Cell surface protuberances found on cellulolytic bacteria, but not on noncellulolytic bacteria, can be detected by scanning electron microscopy. Cationized ferritin typically has been used as a stain to increase the microscopic resolution of these protuberances; however, as a cation it binds only to negatively charged molecules. Thus, binding of cationized ferritin to cell surface molecules can be affected by the cell's physiological state. We incubated the noncellulolytic bacterium, Clostridium beijerinckii, in different media at various temperatures to obtain cells with different growth rates and physiological states. Staining of these cells with cationized ferritin showed that slower growing cells exhibited more protuberant structures than faster growing cells. This provided a clear correlation of ultrastructural protuberances with physiological changes associated with growth rate. On the other hand, cells stained with osmium tetroxide exhibited no protuberant structures regardless of growth rate. Because various cations are known to induce aggregation of surface proteins on some cellulolytic Clostridia, we incubated the cellulolytic bacterium, Clostridium cellulovorans, in media containing glucose, cellobiose, or cellulose. Ultrastructural protuberances were evident on all cells stained with cationized ferritin, but extensive protuberances were detected only on cells grown in cellulose and stained with osmium tetroxide. For cells stained with cationized ferritin, the presence of ultrastructural protuberances was correlated with growth rate rather than induction of cellulolytic systems. By contrast, cells stained with osmium tetroxide showed a clear correlation between protuberant structures and cellulolytic activity.

Clostridium↗
PubMed1998

Cationized ferritin as a stain for electron microscopic observation of bacterial ultrastructure.

The electron microscope has proven very effective for visualization of various morphological features of bacteria. Cationized ferritin (CF) is a stain commonly used to increase the electron microscopic resolution of bacterial cells, thereby enabling detailed analysis of their morphological and structural features. CF has been useful for microscopic examination of the bacterial capsule, cell wall, S-layer, and various unique morphological structures. In addition, as a cation, CF binds only to negatively charged molecules. Thus, CF has been used to identify sites of anionic charge on the bacterial cell surface, which has led to insights concerning the formation and turnover of bacterial peptidoglycan and the S-layer proteins. As a cation, however, CF may also interact with certain cellular components, causing erroneous interpretation of microscopic results. This review provides a discussion of both the strengths and weaknesses of CF when used as a stain for electron microscopy.

Bacteria↗
PubMed1998

Evaluation of a hand-held electrical conductivity meter for detection of subclinical mastitis in cattle.

OBJECTIVE: To assess, under field conditions, whether a hand-held electrical conductivity (EC) meter could be used to detect subclinical mastitis caused by pathogens most commonly associated with mastitis in dairy cows. ANIMALS: 425 lactating cows on 15 dairies in Costa Rica. PROCEDURE: Immediately prior to milking, milk samples from each quarter were tested, using a hand-held EC meter. A milk sample from the quarter with the highest score was submitted for bacteriologic culture. Results of bacteriologic culture were compared with highest absolute EC score for each cow and with differential EC score (ie, difference between the highest and lowest absolute EC scores for the 4 quarters of each cow). RESULTS: Absolute EC score for cows with subclinical mastitis was significantly higher than that for cows without subclinical mastitis, and absolute EC score was significantly associated with detection of subclinical mastitis. If absolute EC score > or = 7 was considered indicative of subclinical mastitis, sensitivity was 0.43, specificity was 0.83, predictive value of a positive result was 0.39, and predictive value of a negative result was 0.85. Differential EC score for cows with mastitis was significantly higher than that for cows without subclinical mastitis. If differential EC score > or = 2 was considered indicative of subclinical mastitis, sensitivity was 0.53, specificity was 0.77, predictive value of a positive result was 0.37, and predictive value of a negative result was 0.87. CLINICAL IMPLICATIONS: A hand-held EC meter may be used to screen cows for subclinical mastitis.

Animals↗
PubMed1998

Detection of milk antibiotic residues by use of screening tests and liquid chromatography after intramammary administration of amoxicillin or penicillin G in cows with clinical mastitis.

OBJECTIVE: To compare results of 6 commercially available milk antimicrobial screening tests with results of liquid chromatography (LC) when testing milk samples from individual cows treated for mild clinical mastitis by intramammary (IMM) infusion with amoxicillin or penicillin G. ANIMALS: 6 cows with noninduced clinical mastitis: 3 treated by IMM infusion with amoxicillin and 3 treated by IMM infusion with penicillin G. PROCEDURE: Composite milk samples were collected before, during, and after treatment. Samples were assayed by use of the screening tests and their results and those of LC were compared. The LC results were assumed to represent the true result. RESULTS: Results of screening tests compared well with results of LC, with agreement of 94%. Positive screening test results for samples containing drug values below the established tolerance or safe level, as evaluated by LC, were obtained from 2 cows in which abnormal milk, as well as marked increases in composite milk somatic cell count, were observed. With the exception of 1 test in 1 cow, all screening tests had negative results at the end of the labeled milk-withholding time. CONCLUSIONS AND CLINICAL IMPLICATIONS: On the basis of results of the limited sample reported, the screening tests appeared to provide good agreement overall, compared with LC results, when testing milk of individual cows treated by IMM infusion with amoxicillin or penicillin G. Positive screening test results for milk samples containing amoxicillin or penicillin G at values below the established tolerance or safe level, as evaluated by LC, may occasionally be obtained.

Amoxicillin↗
PubMed1997

The microtubule-dependent motor centromere-associated protein E (CENP-E) is an integral component of kinetochore corona fibers that link centromeres to spindle microtubules.

Centromere-associated protein E (CENP-E) is a kinesin-related microtubule motor protein that is essential for chromosome congression during mitosis. Using immunoelectron microscopy, CENP-E is shown to be an integral component of the kinetochore corona fibers that tether centromeres to the spindle. Immediately upon nuclear envelope fragmentation, an associated plus end motor trafficks cytoplasmic CENP-E toward chromosomes along astral microtubules that enter the nuclear volume. Before or concurrently with initial lateral attachment of spindle microtubules, CENP-E targets to the outermost region of the developing kinetochores. After stable attachment, throughout chromosome congression, at metaphase, and throughout anaphase A, CENP-E is a constituent of the corona fibers, extending at least 50 nm away from the kinetochore outer plate and intertwining with spindle microtubules. In congressing chromosomes, CENP-E is preferentially associated with (or accessible at) the stretched, leading kinetochore known to provide the primary power for chromosome movement. Taken together, this evidence strongly supports a model in which CENP-E functions in congression to tether kinetochores to the disassembling microtubule plus ends.

Cell Cycle↗
PubMed1997

Fibroblast dependency during early thymocyte development maps to the CD25+ CD44+ stage and involves interactions with fibroblast matrix molecules.

We have investigated the role of specific components of the thymic stroma during development of CD4-8-T cell precursors by separating and reaggregating precursor subsets with individual or combinations of stromal cells. We show that while the development of CD25+ 44+ precursors is dependent upon a combination of major histocompatibility complex (MHC) class II+ thymic epithelial cells and fibroblasts, their direct descendants, CD25+ 44- precursors, develop to the CD4+ 8+ stage in the presence of MHC class II+ thymic epithelial cells alone. Thus, CD25+ 44+ precursors are the last developmental stage to be dependent upon fibroblast support. In addition, while metabolically inactive, 1-ethyl-3-(3'-dimethylaminopropyl) carbodiimide (ECDI)-treated fibroblasts retain the ability to promote T cell development, prior treatment with hyaluronidase abrogates this effect, suggesting that fibroblast-associated extracellular matrix components are the key elements involved. In support of this, we show that fibroblasts are located in cortical regions of the thymus where T cell precursors are known to reside, and that these fibroblasts are associated with an extensive extracellular matrix not found on thymic epithelial cells. Finally, antibodies to alpha 4 integrin and CD44 interfere with the efficiency with which CD4+ 8+ cells are generated from CD25+ 44+ precursors in reaggregate cultures and also reduce the binding of the latter to 3T3 fibroblasts, suggesting these molecules play a role in bringing T cell precursors into contact with fibroblast-associated extracellular matrix.

3T3 Cells↗
PubMed1997

Polysaccharide inducible outer membrane proteins of Bacteroides xylanolyticus X5-1.

Little is known about how bacteria degrade structural polysaccharides or the regulatory systems that control this degradation. Bacteroides xylanolyticus X5-1 is a Gram-negative, anaerobic bacterium that can grow on structural polysaccharides such as xylan and pectin. In order to determine the response of this organism to specific substrates,B. xylanolyticus was grown on a variety of mono-, di-, and polysaccharides. Electrophoretic analysis revealed no distinct differences in the polypeptide profile of the inner membrane enrichments of cells grown on different carbohydrates. However, distinct differences in protein composition of outer membrane enrichments were clearly observed. The profiles from cells grown on starch, xylan, and pectin were distinct from each other and their respective monosaccharide. In addition, cells initially grown on xylan did not alter their total membrane protein composition after three generations of growth in medium containing xylan and glucose. Thus,B. xylanolyticus X5-1 altered its outer membrane protein composition in response to specific polysaccharide substrates, but analysis of this specific response revealed no evidence that glucose was preferred over xylan as a substrate.

Journal Article↗
PubMed1997

ALS-linked SOD1 mutant G85R mediates damage to astrocytes and promotes rapidly progressive disease with SOD1-containing inclusions.

High levels of familial Amyotrophic Lateral Sclerosis (ALS)-linked SOD1 mutants G93A and G37R were previously shown to mediate disease in mice through an acquired toxic property. We report here that even low levels of another mutant, G85R, cause motor neuron disease characterized by an extremely rapid clinical progression, without changes in SOD1 activity. Initial indicators of disease are astrocytic inclusions that stain intensely with SOD1 antibodies and ubiquitin and SOD1-containing aggregates in motor neurons, features common with some cases of SOD1 mutant-mediated ALS. Astrocytic inclusions escalate markedly as disease progresses, concomitant with a decrease in the glial glutamate transporter (GLT-1). Thus, the G85R SOD1 mutant mediates direct damage to astrocytes, which may promote the nearly synchronous degeneration of motor neurons.

ATP-Binding Cassette Transporters↗
PubMed1997

A photoreceptor cell-specific ATP-binding transporter gene (ABCR) is mutated in recessive Stargardt macular dystrophy.

Stargardt disease (STGD, also known as fundus flavimaculatus; FFM) is an autosomal recessive retinal disorder characterized by a juvenile-onset macular dystrophy, alterations of the peripheral retina, and subretinal deposition of lipofuscin-like material. A gene encoding an ATP-binding cassette (ABC) transporter was mapped to the 2-cM (centiMorgan) interval at 1p13-p21 previously shown by linkage analysis to harbour the STGD gene. This gene, ABCR, is expressed exclusively and at high levels in the retina, in rod but not cone photoreceptors, as detected by in situ hybridization. Mutational analysis of ABCR in STGD families revealed a total of 19 different mutations including homozygous mutations in two families with consanguineous parentage. These data indicate that ABCR is the causal gene of STGD/FFM.

ATP-Binding Cassette Transporters↗
PubMed1997

Genetic manipulation of anaerobic cellulolytic bacteria.

Transposon Tn1545 was introduced into the chromosome of the ruminal cellulolytic bacterium Eubacterium cellulosolvens. This was achieved by conjugal transfer of the transposon from Clostridium beijerinckii at a frequency of about 1 per 10(4) recipient cells. Transconjugants of E. cellulosolvens were resistant to both tetracycline and erythromycin. E. cellulosolvens could also serve as a donor for conjugal transfer of Tn1545 back into C. beijerinckii.

Animals↗
PubMed1996

PU.1 but not ets-2 is essential for macrophage development from embryonic stem cells.

Transcription factors play an important role choreographing lineage commitment and expansion of blood cells. Nuclear factors that are expressed primarily or exclusively in hematopoietic cells are likely candidates for regulating blood cell development. The transcription factor PU.1 is found only in hematopoietic cells, whereas ets-2, a related family member, is ubiquitously expressed. To compare the role of these two transcription factors in macrophage development, embryonic stem (ES) cells with a homozygous disruption of either the PU.1 or the ets-2 gene were generated. The ability of both knockout ES cells to differentiate to macrophages was tested. Normal development of macrophages, as determined by histochemical and immunohistochemical analysis, from PU.1 knockout ES cells was significantly blocked. Furthermore, the expression of known markers associated with macrophages, such as c-fms, CD11b, CD18 and granulocyte-macrophage colony-stimulating factor receptor, were not detected by reverse transcriptase-polymerase chain reaction. In contrast to the PU.1 knockout ES cells, macrophages, development from the ets-2 knockout ES cells was normal. Although both PU.1 and ets-2 are found in macrophages, these data show a distinct role for the lineage-restricted PU.1 transcription factor in macrophage development.

Animals↗
PubMed1996

Targeted disruption of the PU.1 gene results in multiple hematopoietic abnormalities.

PU.1 is a member of the ets family of transcription factors and is expressed exclusively in cells of the hematopoietic lineage. Mice homozygous for a disruption in the PU.1 DNA binding domain are born alive but die of severe septicemia within 48 h. The analysis of these neonates revealed a lack of mature macrophages, neutrophils, B cells and T cells, although erythrocytes and megakaryocytes were present. The absence of lymphoid commitment and development in null mice was not absolute, since mice maintained on antibiotics began to develop normal appearing T cells 3-5 days after birth. In contrast, mature B cells remained undetectable in these older mice. Within the myeloid lineage, despite a lack of macrophages in the older antibiotic-treated animals, a few cells with the characteristics of neutrophils began to appear by day 3. While the PU.1 protein appears not to be essential for myeloid and lymphoid lineage commitment, it is absolutely required for the normal differentiation of B cells and macrophages.

Animals↗
PubMed1996

Effect of vaccination with an Escherichia coli bacterin-toxoid on milk production in dairy cattle.

OBJECTIVE: To determine whether vaccination of lactating cattle with an Escherichia coli J5 bacterin-toxoid would produce a significant short-term change in milk production. DESIGN: Randomized, controlled clinical trial. ANIMALS: 84 healthy, lactating cows (42 Holsteins and 42 Jerseys). PROCEDURE: Control and vaccinated cows were paired on the basis of breed, days in milk, daily milk production 1 week prior to vaccination, and parity. One cow in each pair was inoculated IM with a commercially available bacterin-toxoid according to label directions; the other cow was given saline solution. Cows were milked twice daily for 5 days before and 5 days after inoculation. Milk production was compared by ANCOVA. RESULTS: Vaccinated cows produced significantly less milk than did control cows at the second and third milkings after inoculation. At these milkings, milk production in vaccinated cows was approximately 7% less than that of controls. CLINICAL IMPLICATIONS: Vaccination of lactating cattle with an E coli J5 bacterin-toxoid may cause a significant short-term decrease in milk production.

Animals↗
PubMed1996

Intracellular signaling pathways involved in the induction of apoptosis in immature thymic T lymphocytes.

We describe a novel technique for studying the signaling pathways that control thymocyte negative selection which maintains the essential interactions between thymocytes and thymic stromal cells. Bisected lobes from newborn mouse thymus are maintained in organ culture for up to 36 h, and the thymocytes analyzed by flow cytometry. Inclusion of [3H]inositol during culture allows measurements of phosphatidylinositol 4,5-biphosphate (PtdIns(4,5)P2) hydrolysis and inositol phosphate accumulation. Using this technique we have compared the thymocyte responses induced by anti-CD3, anti-Fas, Con A, and beta-adrenergic stimulation. We show that PtdIns(4,5)P2 hydrolysis precedes anti-CD3-induced thymocyte apoptosis, but not the apoptosis induced by anti-Fas. In contrast, Con A stimulates PtdIns(4,5)P2 hydrolysis, but does not induce thymocyte apoptosis. Anti-CD3, anti-Fas, and Con A all fail to change thymic cAMP levels, but beta-adrenergic stimulation causes a large increase in intracellular cAMP, and agents that elevate cAMP induce thymocyte apoptosis. Inhibition of protein synthesis (with cycloheximide or emetine) prevents the apoptosis induced by anti-CD3 and elevated cAMP, but not that induced by anti-Fas, whereas protease inhibition (with 3,4-dichloroisocoumarin or N(alpha)-tosyl-phenylalanine chloromethyl ketone) prevents the apoptosis caused by all of the effective stimuli. These results offer three important conclusions. First, activation of a variety of different signaling pathways can bring about thymocyte apoptosis. Second, ligation of the thymocyte TCR/CD3 complex provokes PtdIns(4,5)P2 hydrolysis, but signaling through this pathway alone does not necessarily lead to apoptosis. Third, by whichever signaling pathway the response is initiated, the activity of one or more protease enzymes appears to form an essential component in the final common pathway leading to apoptosis.

Adrenergic beta-Agonists↗
PubMed1996

Cloning of GRK2 cDNA from S49 murine lymphoma cells.

Beta-adrenergic receptor kinase is a member of the G protein-linked receptor kinase (GRK1) family that elicits receptor desensitization. We have cloned GRK2 from S49 mouse lymphoma cells. The nucleotide sequences of rat GRK2 and GRK3 were aligned and conserved primers chosen for use in reverse transcription-polymerase chain reaction (RT-PCR) of S49 mRNA. Direct sequencing of the PCR fragment provided a rapid means to identify the expression of the GRK2 but not the GRK3 transcript in these cells. Unique expression of GRK2 in S49 cells was confirmed by Western blotting. Three additional pairs of primers were chosen from the rat GRK2 sequence to amplify overlapping regions that together encompassed the entire coding sequence. After attempts to ligate the four fragments of S49 cell GRK2 cDNA by using PCR proved unsuccessful, the intact cDNA was assembled by digesting the PCR products in the region of the overlaps and ligating them in a single step into pBlue-script SK(+).

Animals↗