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Biomedical subjects

A Levine

Publications and source records attributed to A Levine.

At least 73 records · Page 4Linked to original sources
PubMed1997

Expression of the pair-rule gene odd Oz (odz) in imaginal tissues.

odd Oz (odz), the only pair-rule gene that does not encode a transcription factor, is expressed in every imaginal disc and imaginal tissue of Drosophila melanogaster, as assessed by immunocytochemical staining for the protein and by odz-enhancer trap line staining. The eye imaginal disc expresses odz at the morphogenetic furrow, in R7 photoreceptor cells, and in adepithelial cells. Genetic evidence indicates that odz is involved in furrow progression, and in R7 cell RTK receptor tyrosine kinase signalling. Expression in the wing pouch appears in a complex pattern that displays a symmetry axis at the dorsal-ventral boundary. In other dorsal thoracic disc sites, Odz appears at specific points of prospective thoracic integument and prospective proximal structures of the wing and haltere. Expression in the leg and antennal discs is strongest in prospective proximal segments at sites homologous between these discs. In addition, odz appears in sensory mother cells (SMCs) in all of the above-mentioned discs. This recurrence indicates the general importance of odz in the development of the peripheral nervous system (PNS), which complements the finding that it is expressed in the CNS, with striking optic lobe staining. odz must be involved in cellular signalling in pleiotropic roles in varied pathway contexts.

Animals↗
PubMed1997

Cell cycle checkpoints in bacteria.

When DNA replication is interrupted in bacteria, a specific inhibitor (SfiA), a component of the SOS system, is synthesised which transiently blocks cell division. This is the prototype, dispensable, cell cycle checkpoint, essential for maximal survival under a particular stress. In contrast, no process specifically signalling the termination of chromosomal replication to activate the subsequent division event, which might be termed an essential checkpoint, has yet been demonstrated. In E coli, a specific mechanism is apparently required to reactivate replication forks blocked by damage, but its molecular basis is unclear. Induction of the stringent response, mediated by RelA via the level of ppGpp, presumably to optimise macromolecular synthesis according to the availability of nutrients, activates a control system which inhibits DNA replication in both E coli and B subtilis. In E coli, this blocks new rounds of initiation at oriC, although the mechanism is not clear. Conversely, initiation is not blocked in B subtilis, but replication is blocked apparently at a number of distinct sites 100-200 kb downstream and either side of oriC. This nutrient-dependent replicating checkpoint specifically requires RTP, the chromosomal terminator protein, and new evidence indicates that specific RTP binding sites may be involved in this post-initiation control mechanism. A similar post-initiation control mechanism appears to block replication reversibly after premature initiation in B subtilis, indicating that this system may have a dual function, limiting replication in starvation conditions and as a mechanism to compensate for premature initiations.

Bacteria↗
PubMed1997

A 10.3 kbp segment from nprB to argJ at the 102 degrees region of the Bacillus subtilis chromosome.

The approximately 10 kbp region encompassing nprB and argJ at 102 degrees on the Bacillus subtilis chromosome was sequenced, revealing 12 ORFs, four known genes (argJ, argC, ipi and nprB) and two genes, yitY and yitS, whose products respectively display significant homology with L-gulono-gamma-lactone oxidase of rat and dihydrofolate reductase of Staphylococcus aureus. The data also indicated that nprB mapped to a different position than previously published.

Bacillus subtilis↗
PubMed1997

Sequencing of regions downstream of addA (98 degrees) and citG (289 degrees) in Bacillus subtilis.

The nucleotide sequence of 17.3 kbp downstream of addA (98 degrees) on the Bacillus subtilis chromosome was determined. Twenty putative ORFs were identified. Three of them coincided with known B. subtilis genes, addA, sbcD and wprA. The product of four other ORFs showed similarity to SbcC of Clostridium perfringens, CotH of B. subtilis, 2-hydroxyhepta-2,4-diene-1,7-diodate isomerase of Methanococcus jannaschi and a putative ORF of Pseudomonas syringae. In addition, a sequence of 7.6 kbp downstream of citG (189 degrees) was analysed. Among 10 putative ORFs identified, two coincided with known genes, citG and mrgA, whilst three showed homology with X86780, a sensory protein kinase of Streptomyces hygroscopicus, an alkaline phosphatase regulatory protein and a hypothetical protease, YyxA, of B. subtilis.

Bacillus subtilis↗
PubMed1997

A Bacillus subtilis chromosome segment at the 100 degrees to 102 degrees position encoding 11 membrane proteins.

The 25.9 kbp region upstream of nprB at 100 degrees-102 degrees on the Bacillus subtilis chromosome was sequenced. This revealed a known gene, degA, which was previously mislocated on the genetic map. A total of 29 putative ORFs were identified including a cluster of three ORFs whose products show clear homology with sulphate adenylyl pathway enzymes and, in addition, 11 ORFs whose products have one or more membrane domains, as indicated by their hydropathy profiles.

Bacillus subtilis↗
PubMed1996

DNA methylation patterns in tumors derived from F9 cells resemble methylation at the blastula stage.

We show here that the genome of F9 teratocarcinoma cells growing in culture is heavily methylated but undergoes massive demethylation in tumors derived by subcutaneous injection of the cells. This demethylation occurs primarily in single copy gene sequences. As a result imprinted genes acquire their characteristic monoallelic methylation patterns while nonimprinted genes undergo demethylation. The overall methylation pattern in the tumors resembles the pattern observed in the mouse preimplantation embryo. The F9 cells in the tumors apparently recognize imprinted genes, distinguish them from non-imprinted genes and change the methylation of both gene classes to the pattern which characterizes the embryo. These cells therefore have the potential of providing an abundant source of protein factors involved in establishing the methylation pattern during embryo developments.

Animals↗
PubMed1996

Calcium-mediated apoptosis in a plant hypersensitive disease resistance response.

BACKGROUND: Avirulent pathogens elicit a battery of plant defenses, often accompanied by collapse of the challenged cells. In soybean cells, sustained accumulation of H2O2 from an oxidative burst cues localized host cell death. Such hypersensitive cell death appears to be an active process, but little is known about the mechanisms underlying cellular collapse. RESULTS: We show that H2O2 stimulates a rapid influx of Ca2+ into soybean cells, which activates a physiological cell death program resulting in the generation of large (approximately 50 kb) DNA fragments and cell corpse morphology--including cell shrinkage, plasma membrane blebbing and nuclear condensation--characteristic of apoptosis. In contrast, H2O2 induction of the cellular protectant gene glutathione S-transferase is Ca(2+)-independent. Apoptosis in soybean cells and leaf tissue was induced by avirulent Pseudomonas syringae pv. glycinea but was not observed at comparable stages of the compatible interaction with the isogenic virulent strain, which fails to elicit a hypersensitive response. Apoptosis was also observed at the onset of the hypersensitive response in Arabidopsis leaves inoculated with avirulent P. syringae pv. tomato and in tobacco cells treated with the fungal peptide cryptogein, which is involved in the induction of non-host resistance to Phytophthora cryptogea. CONCLUSIONS: These observations establish a signal function for Ca2+ downstream of the oxidative burst in the activation of a physiological cell death program in soybean cells that is similar to apoptosis in animals. That the characteristic cell corpse morphology is also induced in Arabidopsis and tobacco by different avirulence signals suggests that apoptosis may prove to be a common, but not necessarily ubiquitous, feature of incompatible plant-pathogen interactions. Emerging similarities between facets of hypersensitive disease resistance and the mammalian native immune system indicate that apoptosis is a widespread defence mechanism in eukaryotes.

Apoptosis↗
PubMed1996

Viral load, CD4 percentage, and delayed-type hypersensitivity in subjects receiving the HIV-1 immunogen and antiviral drug therapy.

Two trials of subjects inoculated with the inactivated, gp120-depleted HIV-1 Immunogen are reported. In one study, in which 19 subjects received ZDV and 8 subjects received ddI, treatment with the HIV-1 Immunogen did not affect the pharmacokinetic parameters of the antiviral drugs. In another study, 65 subjects who were previously immunized with the HIV-1 Immunogen over a mean period of 4.0 years (range, 1.2-5.4 years) received inoculations at 0 and 6 months. At some point during this 48-week study, 72% of the subjects (47/65) were receiving antiviral drug therapy. The HIV-1 DNA load in CD4 cells and CD4 percentage were found to be stable over the 48-week period. Delayed-type hypersensitivity to HIV-1 antigens increased after two inoculations with the HIV-1 Immunogen. In these two trials, no serious treatment-related adverse events were documented in the subjects. The two studies presented herein are the first to suggest that an immune-based therapy such as the HIV-1 Immunogen can be combined safely with antiviral drugs, supporting further study to evaluate the clinical utility of this approach.

AIDS Vaccines↗
PubMed1996

The stressors and stress of being HIV-positive.

Questionnaires were administered to 105 HIV-positive men to assess their stressful life events, rated stress, unhealthy behaviours, and psychological adjustment. Two hypotheses about the effects of stressors and stress were tested. It was found that HIV-positive men experience high numbers of stressors and elevated levels of perceived stress and depression. Stressors in the areas of relationships, finances, and the illness of others were the most problematic and were associated with more depression. Rates of alcohol consumption, smoking, and unsafe sexual behaviours were fairly high. There were some modest, but significant positive correlations between stressors, stress, and risky behaviours. Number of stressors was associated with more alcohol consumption and perceived stress was positively related to more tobacco use and unsafe sexual behaviours. The high levels of stress and stressors and negative effects of stressors have both theoretical and practical implications.

Adaptation, Psychological↗
PubMed1995

The insulin receptor substrate-1-related 4PS substrate but not the interleukin-2R gamma chain is involved in interleukin-13-mediated signal transduction.

Interleukin-13 (IL-13) induced a potent mitogenic response in IL-3-dependent TF-1 cells and DNA synthesis to a lesser extent in MO7E and FDC-P1 cells. IL-13 stimulation of these lines, like IL-4 and insulin-like growth factor-1 (IGF-1), resulted in tyrosine phosphorylation of a 170-kD substrate. The tyrosine-phosphorylated 170-kD substrate strongly associated with the 85-kD subunit of phosphoinositol-3 (PI-3) kinase and with Grb-2. Anti-4PS serum readily detected the 170-kD substrate in lysates from both TF-1 and FDC-P1 cells stimulated with IL-13 or IL-4. These data provide evidence that IL-13 induces tyrosine phosphorylation of the 4PS substrate, providing an essential interface between the IL-13 receptor and signaling molecules containing SH2 domains. IL-13 and IL-4 stimulation of murine L cell fibroblasts, which endogenously express the IL-4 receptor (IL-4R alpha) and lack expression of the IL-2 receptor gamma subunit (IL-2R gamma), resulted in tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1)/4PS. Enhanced tyrosine phosphorylation of IRS-1/4PS was observed in response to IL-4, but not IL-13 treatment of L cells transfected with the IL-2R gamma chain. These results indicate that IL-13 does not use the IL-2R gamma subunit in its receptor complex and that expression of IL-2R gamma enhances, but is not absolutely required for mediating IL-4-induced tyrosine phosphorylation of IRS-1/4PS.

Adaptor Proteins, Signal Transducing↗
PubMed1995

p53 and its 14 kDa C-terminal domain recognize primary DNA damage in the form of insertion/deletion mismatches.

Insertion/deletion (IDL) mismatches in DNA are lesions consisting of extra bases on one strand. Here, the binding of p53 and its 14 kDa C-terminal domain to DNAs containing one or three 3-cytosine IDL mismatches was examined. Electron microscopy showed that both p53 forms bound predominantly as tetramers at the lesions while single-stranded binding proteins did not bind. Gel retardation assays showed that p53 formed highly stable complexes when the DNA contained the IDL mismatches, but only unstable complexes when the DNA lacked lesions (but did contain free ends). The highly stable complexes had a half-life of > 2 hr, suggesting that upon encountering lesions, p53 may recruit other proteins to the site, providing a signal for DNA damage.

Base Composition↗
PubMed1995

Function of the oxidative burst in hypersensitive disease resistance.

Microbial elicitors or attempted infection with an avirulent pathogen strain causes the rapid production of reactive oxygen intermediates. Recent findings indicate that H2O2 from this oxidative burst plays a central role in the orchestration of the hypersensitive response: (i) as the substrate driving the cross-linking of cell wall structural proteins to slow microbial ingress prior to the deployment of transcription-dependent defenses and to trap pathogens in cells destined to undergo hypersensitive cell death, (ii) as a local threshold trigger of this programmed death in challenged cells, and (iii) as a diffusible signal for the induction in adjacent cells of genes encoding cellular protectants such as glutathione S-transferase and glutathione peroxidase. These findings provide the basis for an integrated model for the orchestration of the localized hypersensitive resistance response to attack by an avirulent pathogen.

Journal Article↗
PubMed1995

Outcome and prognostic factors for local recurrence in mammographically detected ductal carcinoma in situ of the breast treated with conservative surgery and radiation therapy.

PURPOSE: We have retrospectively reviewed our institution's experience treating a predominantly mammographically detected population of ductal carcinoma in situ (DCIS) patients with conservative surgery and radiation therapy (CSRT) to determine outcome and prognostic factors for local recurrence. METHODS AND MATERIALS: Between January 1, 1982 and December 31, 1988, 52 consecutive cases of DCIS of the breast were treated with CSRT at William Beaumont Hospital. Forty-six (88%) were mammographically detected nonpalpable lesions. All patients underwent at least an excisional biopsy and 28 (54%) were reexcised. The axilla was surgically staged in 41 (79%) and all were N0. The entire breast was irradiated to 45-50 Gy over 5-6 weeks. The tumor bed was boosted in 49 (94%) so that the minimum dose was 60 Gy. The three patients not boosted received a minimum dose of 50 Gy to the entire breast. Pathologic materials were reviewed by one of the authors. RESULTS: The predominant DCIS pattern was comedo in 40%, cribriform in 28%, solid in 17%, and micropapillary in 15%. The predominant nuclear grade was Grade I in 51%, Grade II in 49%, and Grade III in 0%. The median follow-up is 68 months. There have been three recurrences in the treated breast at a median time to failure of 30 months. The 5- and 8-year actuarial local recurrence rate is 6%. One patient recurred with invasive ductal cancer at 28 months, and the other two recurrences were DCIS at 30 and 50 months. All three patients were treated with salvage mastectomy. The patient who recurred locally with an invasive cancer developed metastasis and died at 64 months. The 5- and 8-year actuarial cause-specific survival rates are 100% and 97%, respectively. The following pathologic factors were analyzed for an association with local recurrence: predominant DCIS histology, predominant nuclear grade, and highest nuclear grade. Of these, the predominant nuclear grade was the best predictor of local recurrence (p = 0.070). No clinical or treatment related factor analyzed was associated with local recurrence. CONCLUSION: Our results indicate that excellent local control (94%) at 8 years is obtainable after CSRT in a mammographically detected population of patients with DCIS. The predominant nuclear grade was the only factor found that may be associated with local recurrence.

Adult↗
PubMed1995

Factors affecting ED length-of-stay in surgical critical care patients.

To determine what patient characteristics are associated with prolonged emergency department (ED) length-of-stay (LOS) for surgical critical care patients, the charts of 169 patients admitted from the ED directly to the operating room (OR) or intensive care unit (ICU) during a 6-week period in 1993 were reviewed. The ED record was reviewed for documentation of factors that might be associated with prolonged ED LOS, such as use of computed tomographic (CT), radiology special procedures, and the number of plain radiographs and consultants. ED LOS was considered to be the time from triage until a decision was made to admit the patient. Using a Cox proportional hazards model, use of CT and special procedures were the strongest independent predictors of prolonged ED length-of-stay. The number of plain radiographs and consultants had only a minimal effect. Use of a protocol-driven trauma evaluation system was associated with a shorter ED LOS. In addition to external factors that affect ED overcrowding, ED patient management decisions may also be associated with prolonged ED length-of-stay. Such ED-based factors may be more important in surgical critical care patients, whose overall ED LOS is affected more by the length of the ED work-up rather than the time spent waiting for a ICU bed or operating suite.

Adolescent↗
PubMed1995

A checkpoint involving RTP, the replication terminator protein, arrests replication downstream of the origin during the Stringent Response in Bacillus subtilis.

Regulation of DNA replication in Bacillus subtilis involves a post-initiation mechanism which is subject to control by the Stringent System, an essential regulatory network, mediated by the alarmone, ppGpp. In detailed studies using DNA-DNA hybridization procedures, we have now shown that, following the induction of the Stringent Response, replication is blocked downstream of the origin, on the left, close to the hut marker (-175 kb) and on the right, beyond the soft10 marker (+199 kb). In addition, we provide evidence that inhibition of replication under these conditions requires the replication terminator protein (RTP). In a mutant lacking RTP, a protein normally involved in termination of chromosomal replication through recognition of specific terminator sequences, replication continues past the sites normally blocked by the Stringent Response. These data strengthen the argument that this second level of control of DNA replication occurs at specific sites, the Strigent Terminus (STer) sites, either side of orlC. Such sites are presumably related to the sequence involved in RTP recognition at the terminus, terC. We propose that the binding of RTP must be modulated, perhaps through the action of ppGpp, to recognize post-initiation control sequences during the Stringent Response, in order to block replisome movement. This, therefore, acts as a checkpoint in chromosome elongation.

Bacillus subtilis↗
PubMed1994

H2O2 from the oxidative burst orchestrates the plant hypersensitive disease resistance response.

Microbial elicitors or attempted infection with an avirulent pathogen strain causes the rapid production of reactive oxygen intermediates. We report here that H2O2 from this oxidative burst not only drives the cross-linking of cell wall structural proteins, but also functions as a local trigger of programmed death in challenged cells and as a diffusible signal for the induction in adjacent cells of genes encoding cellular protectants such as glutathione S-transferase and glutathione peroxidase. Thus, H2O2 from the oxidative burst plays a key role in the orchestration of a localized hypersensitive response during the expression of plant disease resistance.

Blotting, Northern↗