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Biomedical subjects

A Daniel

Publications and source records attributed to A Daniel.

At least 19 recordsLinked to original sources
PubMed2000

Early development of the Drosophila mushroom body: the roles of eyeless and dachshund.

The mushroom body (MB) is a uniquely identifiable brain structure present in most arthropods. Functional studies have established its role in learning and memory. Here we describe the early embryonic origin of the four neuroblasts that give rise to the mushroom body and follow its morphogenesis through later embryonic stages. In the late embryo, axons of MB neurons lay down a characteristic pattern of pathways. eyeless (ey) and dachshund (dac) are expressed in the progenitor cells and neurons of the MB in the embryo and larva. In the larval brains of the hypomorphic ey(R) strain, we find that beside an overall reduction of MB neurons, one MB pathway, the medial lobe, is malformed or missing. Overexpression of eyeless in MBs under the control of an MB-specific promoter results in a converse type of axon pathway abnormality, i.e. malformation or loss of the dorsal lobe. In contrast, loss of dachshund results in deformation of the dorsal lobe, whereas no lobe abnormalities can be detected following dachshund overexpression. These results indicate that ey and dachshund may have a role in axon pathway selection during embryogenesis.

Animals↗
PubMed1999

The control of cell fate in the embryonic visual system by atonal, tailless and EGFR signaling.

We describe here the role of the transcription factors encoding genes tailless (tll), atonal (ato), sine oculis (so), eyeless (ey) and eyes absent (eya), and EGFR signaling in establishing the Drosophila embryonic visual system. The embryonic visual system consists of the optic lobe primordium, which, during later larval life, develops into the prominent optic lobe neuropiles, and the larval photoreceptor (Bolwig's organ). Both structures derive from a neurectodermal placode in the embryonic head. Expression of tll is normally confined to the optic lobe primordium, whereas ato appears in a subset of Bolwig's organ cells that we call Bolwig's organ founders. Phenotypic analysis, using specific markers for Bolwig's organ and the optic lobe, of tll loss- and gain-of-function mutant embryos reveals that tll functions to drive cells to optic lobe as opposed to Bolwig's organ fate. Similar experiments indicate that ato has the opposite effect, namely driving cells to a Bolwig's organ fate. Since we can show that tll and ato do not regulate each other, we propose a model wherein tll expression restricts the ability of cells to respond to signaling arising from ato-expressing Bolwig's organ pioneers. Our data further suggest that the Bolwig's organ founder cells produce Spitz (the Drosophila TGFalpha homolog) signal, which is passed to the neighboring secondary Bolwig's organ cells where it activates the EGFR signaling cascade and maintains the fate of these secondary cells. The regulators of tll expression in the embryonic visual system remain elusive, as we were unable to find evidence for regulation by the 'early eye genes' so, eya and ey, or by EGFR signaling.

Animals↗
PubMed1998

The role of morphogenetic cell death during Drosophila embryonic head development.

This article addresses the role of programmed cell death (apoptosis) during embryonic head development of Drosophila. Previous studies showed that reaper (rpr) is expressed in and required by cells undergoing apoptosis. We have analyzed the correlation between the pattern of expression of rpr and morphogenetic movements affecting head development. Furthermore, we have investigated the defects in head development resulting from the absence of apoptosis in embryos deficient for rpr. Our results show that, in the head, domains of high incidence of cell death as marked by expression of rpr correlate with regions where most morphogenetic movements occur; these regions are involved in formation of mouth structures, the internalization of neural progenitors, and head involution. Cellular events driving these movements are delamination, invagination, and intercalation as well as disruption and reformation of contacts among epithelial cells. The analysis of rpr-deficient embryos demonstrates that, despite of the widespread occurrence of apoptosis during normal head morphogenesis, many aspects of this process proceed in an apparently unperturbed manner even when cell death is blocked. In particular, movements that happen early during embryonic development and that are evolutionarily more ancient (e.g., formation of the dorsal ridge and the pharynx) take place almost normally in rpr-deficient embryos. Later events which are mostly associated with head involution (e.g., retraction of the clypeolabrum, formation of the dorsal pouch, fusion of lateral gnathal lobes) are evolutionarily more recent and fail to occur normally in rpr-deficient embryos.

Animals↗
PubMed1998

A study of early amniocentesis for prenatal cytogenetic diagnosis.

A prospective pilot study for early amniocentesis was conducted over 4 years including 279 early amniocenteses (EAs at 10-14 weeks' gestation) and 181 mid-trimester amniocenteses (MAs at 15 weeks upwards). The study was performed with EA and MA utilizing the same proceduralists, techniques, and cytogenetics laboratory. Patients were offered either procedure and the cytogenetics laboratory was not prospectively informed of the gestational age of each sampled pregnancy. In the early amniocenteses, less fluid was sampled and there were trends for (i) less cells and clones being available for analysis, less successful cultures, and a slightly longer reporting time; (ii) more multiple insertions (12.9 per cent of specimens vs. 9.9 per cent) and more bloody fluids (5.4 per cent specimens vs. 4.4 per cent); and (iii) a higher rate of pregnancy loss (2.2 per cent of EA vs. 0.6 per cent of MA). The multiple insertion rates for both EA and MA were comparatively high and were related to an increased frequency of blood-stained fluids. For EA specimens, the rates of amniotic fluid leakage, preterm delivery, and pregnancy loss were moderate and not significantly increased over the MA group. This study adds more weight to the view that EA is a reasonably safe procedure and a reliable alternative to chorionic villus biopsy to provide early prenatal cytogenetic diagnosis.

Adult↗
PubMed1997

Kinesin-driven microtubule motility in the presence of alkaline-earth metal ions: indication for a calcium ion-dependent motility.

We studied the effect of alkaline-earth metal ions on the kinesin-driven gliding of microtubules, using a narrow glass chamber enabling the exchange of buffer components without interrupting microscopic observation. Under standard conditions (0.5 mM Mg2+), microtubules were found to glide at a mean velocity of about 0.6 micron/s. Motility was widely ceased after removing Mg2+. Subsequent addition of Ca2+ restored motility (maximal mean gliding velocity measured: 0.26 micron/s at 2.5 mM Ca2+). Also in the presence of Sr2+ or Ba2+ a slow gliding could be observed (0.025 micron/s and 0.014 micron/s, respectively, at 0.5 mM). After removal of Ca2+, Sr2+, or Ba2+ and re-addition of Mg2+, the gliding velocities reached approximately the values determined under standard conditions. Motility was not changed when 0.5 mM Ca2+, Sr2+, or Ba2+ were applied together with Mg2+. Microtubule gliding stopped after substitution of 0.5 mM BeCl2 for Mg2+. When both BeCl2 and Mg2+ were present, the mean gliding velocity was reduced to 0.29 micron/s. In addition, many microtubules were released from the kinesin coated glass surface, indicating that the beryllium salt disorders the binding between kinesin and microtubules. Our results confirm that Mg2+ is the most suitable cofactor for kinesin driven microtubule motility. However, they also demonstrate that brain kinesin can generate motility when Ca2+ was substituted for Mg2+.

Animals↗
PubMed1997

The effect of antibody against TNF alpha on cytokine response in Jarisch-Herxheimer reactions of louse-borne relapsing fever.

Severe Jarisch Herxheimer reaction (J-HR) precipitated by antibiotic treatment of louse-borne relapsing fever (LBRF) is associated with a transient, marked rise in circulating tumour necrosis factor alpha (TNF alpha), interleukin 6 (IL-6) and interleukin 8 (IL-8). Ovine polyclonal anti-TNF alpha antibody fragments (Fab) were used in a randomized double blind placebo controlled trial in an attempt to prevent this reaction. Within 4 h after penicillin, in controls (n = 29), a several-fold rise in cytokines occurred, concomitant with a fall in spirochaetes and maximal clinical manifestations of the J-HR. An intravenous infusion of anti-TNF alpha Fab, 30 min before penicillin in 20 patients reduced peak plasma levels of IL-6 and IL-8 (but not IL-1 beta) compared with controls (p = 0.01 and < 0.001, respectively) and the incidence of the J-HR, indicating some neutralization of TNF alpha. An apparent fall in TNF alpha reflected interference of anti-TNF alpha in the immunoassay.

Adolescent↗
PubMed1997

Complex regulatory region mediating tailless expression in early embryonic patterning and brain development.

tailless encodes a transcription factor expressed in multiple domains in the developing embryo. Early and transient expression at the posterior pole is required to establish a domain from which the eighth abdominal segment, telson and posterior gut arise. Just a few nuclear cycles later, a brain-specific domain is initiated at the anterior; expression in this domain is maintained with complex modulations throughout embryogenesis. Expression of tailless in this domain is required to establish the most anterior region of the brain. To understand the function and regulation of these different domains of expression, we provide a detailed description of tailless expression in brain neuroblasts and show that this expression is not detectably regulated by the head gap genes buttonhead or orthodenticle, by the proneural gene lethal of scute or by tailless itself. We show that approximately 6 kb of sequenced upstream regulatory DNA can drive lacZ expression in a pattern that mimics the full tailless embryonic expression pattern. Within this sequence we identify multiple modules responsible for different aspects of the tailless pattern. In addition to identifying additional torso response elements that mediate early blastoderm polar expression, we show that the complex brain expression pattern is driven by a combination of modules; thus expression at a low level throughout the brain and at a high level in the dorsal medial portion of the brain and in the optic lobe, as well as neuroblast-specific repression are mediated by different DNA regions.

Animals↗
PubMed1996

Nasal mucosal cells in human immunodeficiency virus type 1-seropositive patients with sinusitis.

Recently, sinusitis has been recognized as a frequent clinical problem in human immunodeficiency virus (HIV-1)-infected individuals. We hypothesized that quantitative defects in immune cells in the nasal mucosa of HIV-positive subjects might mirror those in the peripheral blood and explain a predisposition to sinus disease in this population. Nasal mucosa biopsies were obtained from three different groups of patients-HIV-1 seropositive with sinusitis, HIV-1 seronegative with sinusitis, and HIV-1 seronegative without sinusitis (normal volunteer)-and phenotyped for cluster of differentiation antigen (CD) markers. In this study, we found patients with HIV-1 and sinus disease to have significantly lower numbers of both CD3 and CD4 nasal mucosa lymphocytes than seronegative controls in the nasal mucosa (P < 0.05, P < 0.01, respectively). A correlation between nasal mucosal CD4 cells and peripheral-blood CD4 cells was noted (R = 0.67, P < or = 0.01). No deficiency in the number of nasal mucosa T or TC type mast cells was noted for the HIV-1-positive sinusitis group. Further study is warranted to define more completely the pathophysiology and microbiology of, and therapy for, this important clinical problem.

Acquired Immunodeficiency Syndrome↗
PubMed1996

A pseudoknot ribozyme structure is active in vivo and required for hepatitis delta virus RNA replication.

The ribozymes of hepatitis delta virus (HDV) have so far been studied primarily in vitro. Several structural models for HDV ribozymes based on truncated HDV RNA fragments, which are different from the hammerhead or the hairpin/paperclip ribozyme model proposed for plant viroid or virusoid RNAs, have been proposed. Whether these structures actually exist in vivo and whether ribozymes actually function in the HDV replication cycle have not been demonstrated. We have now developed an in vivo ribozyme self-cleavage assay capable of detecting self-cleavage of dimer or trimer HDV RNA in vivo. By site-directed mutagenesis and compensatory mutations to disrupt and restore potential base pairing in the ribozyme domain of the full-length HDV RNA according to the various structural models, a close correlation between the detected in vivo and the predicted in vitro ribozyme activities of various mutant RNAs was demonstrated. These results suggest that the proposed in vitro ribozyme structure likely exists and functions during the HDV replication cycle in vivo. Furthermore, the pseudoknot model most likely represents the structure responsible for the ribozyme activity in vivo. All of the mutants that had lost the ribozyme activity could not replicate, indicating that the ribozyme activities are indeed required for HDV RNA replication. However, some of the compensatory mutants which have restored both the cleavage and ligation activities could not replicate, suggesting that the ribozyme domains are also involved in other unidentified functions or in the formation of an alternative structure that is required for HDV RNA replication. This study thus established that the ribozyme has important biological functions in the HDV life cycle.

Base Sequence↗
PubMed1994

Identification of marker chromosomes in thirteen patients using FISH probing.

Fourteen marker chromosomes were studied by FISH (fluorescence in-situ hybridization) in cytogenetic preparations from 13 patients. The derived markers were identified as one isodicentric bisatellited mar(22), one fragment sized r(X), one fragment sized r(Y), one i(18p), small autosomal ring markers in three different patients derived from chromosomes 2, 8, and 8, a marker comprised of 9p and part of 9qh, and 3 bisatellited apparently monocentric markers; one of each from chromosomes 13 or 21, 14 or 22, and 15. Two fragment sized small ring markers in one patient and a small ring marker in another were negative with all twenty-two different probes used. In addition, the small ring marker Y chromosome that was found in a boy with karyotype 46,X,-Y,+mar was negative with both pDXZ1 and pDYZ3. This anomaly of negative results with the battery of centromeric alphoid probes can be explained if one breakpoint for some small ring markers is very near to or within the centromere. Only some of the pericentromeric repetitive sequences in the normal chromosome would be represented in the chromosome specific alphoid probes, and presumably those corresponding to the currently available probes are truncated during the formation of the unidentified markers. In three of the small ring markers the FISH signal on the marker was much stronger than on the normal homologues in various proportions of cells, and this may indicate that some of the fragment sized small rings were multicentric. The literature was reviewed for Distamycin A/DAPI negative small ring markers that were present as extra chromosomes. There were only single published cases of most small rings but there were three r(8) cases, two r(1) cases, two r(12) cases, and two r(20) cases, uncomplicated by the presence of other chromosome abnormalities. Most cases with similar small rings were quite dissimilar phenotypically and syndrome identification was not possible, but in pooled data, 18/23 (about 80%) were developmentally and/or phenotypically abnormal. Some patients (5/23, about 20%) with small rings were dysmorphic without intellectual handicap. Of 28 such patients with small ring markers (Distamycin/Dapi negative) in pooled data there are 6 (about 20%) with multiple markers mostly derived from different chromosomes. This is a very high figure and would suggest that the ring formation events, although involving different chromosomes, must be related and must be an indicator of the mechanism of origin of this group of markers.

Adolescent↗
PubMed1994

Bone marrow adherent layers inhibit apoptosis of acute myeloid leukemia cells.

Human acute myeloid leukemia (AML) cells, like normal hematopoietic progenitors, die rapidly by apoptosis when cultured under serum-free conditions. Apoptosis was demonstrated by electron microscopy and agarose gel electrophoresis and quantified by flow cytometry. Culturing AML blasts in the presence of a bone marrow fibroblast (BMF) monolayer reduced the percentage of AML blasts undergoing apoptosis in the majority of cases studied. The effect was more pronounced when AML cells were cultured in the presence of an adherent long-term bone marrow (LTBM) stroma rather than BMF. Overall, the mean percentage of AML cells with fragmented DNA fell from 85 +/- 8% in control cultures to 20 +/- 9% in cultures with adherent stroma (p = 0.0004, n = 7). Supplementation of serum-free medium with recombinant cytokines, including stem cell factor, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor (TNF)-alpha or with human placenta-conditioned medium (HPCM) matched the degree of inhibition of apoptosis induced by BMF in only 50% of cases. Granulocyte colony-stimulating factor (G-CSF), interleukin-1 beta (IL-1 beta), and IL-6 were completely ineffective. Consistent with this observation, direct contact between leukemic cells and adherent layers was essential for maximum inhibition of leukemic-cell DNA fragmentation. Separation by a porous membrane allowing passage of soluble growth factors, but interrupting direct cell contact, was associated with significantly greater DNA fragmentation and cell death. Inhibition of leukemic-cell apoptosis correlated with improved survival and growth of malignant clonogenic cells. Colonies grown in cultures were identified as leukemic by morphology and by fluorescence in in situ hybridization to demonstrate numerical chromosomal abnormalities identified at diagnosis. Close contact between leukemic cells and bone marrow inhibits blast cell apoptosis and directly promotes survival of clonogenic AML cells.

Acute Disease↗
PubMed1993

The effect of interdialytic weight gain on predialysis blood pressure.

Interdialytic weight gain is believed to influence predialysis blood pressure. Since interdialytic weight gains vary among treatments for individual patients, blood pressure and weight gain data could be examined to determine how weight variations correlate with differences in blood pressure. Therefore, the quantitative effect on prehemodialysis blood pressure of typical interdialytic weight gains was prospectively studied in 19 nondiabetic patients on chronic hemodialysis. Over a mean of 23.6 treatments (range 17-25), the slope of each patient's prehemodialysis blood pressure versus excess weight (prehemodialysis weight minus baseline dry weight) was determined. The mean slope of the prehemodialysis mean blood pressure/excess weight regression line was 1.2 mm Hg/lb excess weight. No significant correlation was found between individual prehemodialysis blood pressure/excess weight slopes and patient age (r = 0.20), months on dialysis (r = 0.33), dry weight (r = 0.05), or mean excess weight (r = 0.19). Slopes did not differ for 3-day versus 2-day interdialytic intervals, hypertension-treated versus untreated patients, or men versus women. In 5 patients, individual prehemodialysis mean blood pressure/excess weight slopes were significantly greater than 0, averaging 2.4 mm Hg/lb excess weight (vs. 0.8 mm Hg/lb in the remaining patients). These 5 volume-responsive patients did not differ clinically from the 14 volume-resistant patients. The weight gains commonly observed in patients undergoing chronic hemodialysis have only a modest effect on prehemodialysis blood pressure in the majority of patients.

Adult↗
PubMed1993

A spreadsheet program measuring laboratory productivity in several ways: an application of College of American Pathology scores and other data to assess the overall economics of clinical laboratories.

A spreadsheet has been designed that measures the productivity of hospital or other clinical laboratories using several methods, one of which, used as a yardstick, is based on College of American Pathology (CAP) workload test scores with some departures from CAP conventions. In this method the CAP-assessed proportion of a laboratory's time utilised in performing pathology or other tests is compared with the time allocated to non-testing departmental activities as a group. A premise in the approach is that variation in the time allocated to these latter activities, in addition to variation in the efficiency of testing, also contributes significantly to the productivity and economics of hospital laboratories. The workload measure of productivity used in the study is referred to as total staff-paid-productivity (TSPP)--allied to paid-productivity of the CAP Manual 1991--and it is suggested that it be used together with several other result parameters to assess laboratories. However, there are two differences from CAP in the TSPP parameter: the salaries and hours of all staff whether medical, technical or scientific are included; and the professional component (time necessary for test interpretation) is also included where applicable. Necessary data include the goods and services costs, the total test-generated income, the total number of full-time staff equivalents and their hours in each unit or work group, the numbers of tests and raw CAP scores and in addition, an estimation of the professional/interpretive component of each test until the generation of a report. The method is illustrated with examples from six different departments with total staff-paid-productivities covering a wide range beyond the typical values of 65 per cent to 75 per cent. When the data for the laboratories are compared, it is observed that the various admixtures of non-testing activities are a stronger influence on differences in total staff-paid-productivity than the interpretative components of tests, although the latter vary markedly from discipline to discipline. When the interpretative components are included in workload measurements, it enables the productivity of different laboratories to be compared across disciplines. It is suggested that for laboratories to generate ongoing productivity they should be staffed at a rate that produces approximately a maximum total staff-paid-productivity of about 75 per cent.

Australia↗