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Biomedical subjects

B Mai

Publications and source records attributed to B Mai.

At least 19 recordsLinked to original sources
PubMed2006

Mendelian segregation for two-factor apomixis in Erigeron annuus (Asteraceae).

The inheritance of asexual seed development (apomixis) in Erigeron annuus (Asteraceae) was evaluated in a triploid (2n=3x=27) population resulting from a cross between an apomictic tetraploid (2n=4x=36) pollen parent and a sexual diploid (2n=2x=18) seed parent. Diplospory (unreduced female gametophyte formation) and autonomous development (embryo and endosperm together) segregated independently in the population yielding four distinct phenotype classes: (1) apomictic plants combining diplospory and autonomous development, (2) diplosporous plants lacking autonomous development, (3) meiotic plants with autonomous (though abortive) development and (4) meiotic plants lacking autonomous development. Each class was represented by approximately one-quarter of the population (n=117), thus corresponding to a two-factor genetic model with no linkage (chi(2)=2.59, P=0.11). Observations demonstrate that autonomous embryo and endosperm development (jointly) may occur in either reduced or unreduced egg cells. The cosegregation of the traits is attributed to tight linkage or pleiotropy. The data are consistent with the hypothesis that autonomous development in E. annuus is regulated by a single fertilization factor, F, which initiates development of both the embryo and the endosperm in the absence of fertilization.

Crosses, Genetic↗
PubMed2004

[A set of questionnaires for the assessment (screening) of psychological disorders and social problems in cardiac rehabilitation patients].

A set of questionnaires for the assessment (screening) of psychological and social problems in cardiac rehabilitation patients is analyzed for its psychometric properties. The test battery had before been consented by a task force of the German Association for the Prevention and Rehabilitation of Cardiovascular Disease, DGPR. It integrates generally approved and well-tried assessments for depression/anxiety, social isolation (vocational) stress, and subjective vocational disability. The questionnaire was administered to a convenience sample of 426 patients undergoing inpatient cardiac rehabilitation. Results on the psychometric properties, a comparison of the cardiac sample to the general population, as well as distributions of quartile ranges are reported. Also, a preliminary appraisal of the need for further assessment or treatment is made. The results confirm that the short test battery is suited for assessing psychological and social problems in cardiac rehabilitation patients.

Adult↗
PubMed2001

Explosive vaporization of metallic sodium microparticles by CW resonant laser radiation.

Explosive vaporization of metallic Na microparticles stimulated by resonant cw laser radiation has been observed in a glass cell. Vaporization occurs at low laser-power density. The effect consists in the generation of optically thick and sharply localized Na vapor clouds propagating in the cell against the laser beam. The effect is explained by laser excitation of Na atoms, which collide onto the surface of the microparticles and transfer their internal energy. This causes other atoms to be vaporized and to continue the avalanche process.

Journal Article↗
PubMed2001

Early cell cycle box-mediated transcription of CLN3 and SWI4 contributes to the proper timing of the G(1)-to-S transition in budding yeast.

The Cln3-Cdc28 kinase is required to activate the Swi4-Swi6 transcription complex which induces CLN1 and CLN2 transcription in late G(1) and drives the transition to S. Cln3 and Swi4 are both rate limiting for G(1) progression, and they are coordinately transcribed to peak at the M/G(1) boundary. Early cell cycle box (ECB) elements, which confer M/G(1)-specific transcription, have been found in both promoters, and elimination of all ECB elements from the CLN3 promoter causes both a loss of periodicity and Cln3-deficient phenotypes, which include an extended G(1) interval and increased cell volume. Mutants lacking the ECB elements in both the CLN3 and SWI4 promoters have low and deregulated levels of CLN transcripts, and the G(1)-to-S transition for these mutants is delayed and highly variable. These observations support the view that the coordinated rise of Cln3 and Swi4 levels mediated by ECB-dependent transcription controls the timing of the G(1)-to-S phase transition.

Blotting, Northern↗
PubMed2001

Field monitoring of toxic organic pollution in the sediments of Pearl River estuary and its tributaries.

Field monitoring of the toxic organic compounds (PCBs, PAHs, organochlorine pesticides) in the top sediments of Pearl River Estuary and its up-streams were made. It was found that the highest concentrations of these toxic organic compounds occurred in the sediment sampled at Macau inner harbor (ZB013), which is a sink of suspended fine particles transported from the upstream waterways. Because of the affinity of the hydrophobic organic compounds (PAHs, PCBs) for the solid phase, these fine particle depositions led to accumulation of these compounds in the sediment of Macau. The atmospheric dry deposition may be another source of the toxic organic pollution in the sediment.

Air Movements↗
PubMed2001

[Vertical distribution characteristics of organochlorinated pesticides in sediment core from Macao estuary, Pearl River delta].

This work presents the analysis result of concentration for organochlorinated pesticides in a sedimentary core sample. Pesticides were quantified by GC/ECD with the internal standard material. The core dated by 210Pb methods. The vertical distribution of pesticides concentration with the depth was discussed. The results showed the concentration of BHCs and DDTs in the core ranged from 0.48 ng/g to 26.28 ng/g and 1.92-39.13 ng/g respectively. The distributing characteristics of organochlorinated pesticides in the core varied with the water fluxes of Pearl River. Organochlorinated pesticides may come from the residue of agricultural soils. Concentration of DDTs was above the effects range-low value for marine and estuarine sediments.

Geologic Sediments↗
PubMed2000

CLN1 and its repression by Xbp1 are important for efficient sporulation in budding yeast.

Xbp1, a transcriptional repressor of Saccharomyces cerevisiae with homology to Swi4 and Mbp1, is induced by stress and starvation during the mitotic cycle. It is also induced late in the meiotic cycle. Using RNA differential display, we find that genes encoding three cyclins (CLN1, CLN3, and CLB2), CYS3, and SMF2 are downregulated when Xbp1 is overexpressed and that Xbp1 can bind to sequences in their promoters. During meiosis, XBP1 is highly induced and its mRNA appears at the same time as DIT1 mRNA, but its expression remains high for up to 24 h. As such, it represents a new class of meiosis-specific genes. Xbp1-deficient cells are capable of forming viable gametes, although ascus formation is delayed by several hours. Furthermore, Xbp1 target genes are normally repressed late in meiosis, and loss of XBP1 results in their derepression. Interestingly, we find that a deletion of CLN1 also reduces the efficiency of sporulation and delays the meiotic program but that sporulation in a Deltacln1 Deltaxbp1 strain is not further delayed. Thus, CLN1 may be Xbp1's primary target in meiotic cells. We hypothesize that CLN1 plays a role early in the meiotic program but must be repressed, by Xbp1, at later stages to promote efficient sporulation.

Base Sequence↗
PubMed1999

Analysis of mouse dendritic cell migration in vivo upon subcutaneous and intravenous injection.

Dendritic cells (DC) have an increasingly important role in vaccination therapy; therefore, this study sought to determine the migratory capacity and immunogenic function of murine bone-marrow (BM)-derived DC following subcutaneous (s.c.) and intravenous (i.v.) injection in vivo. DC were enriched from BM cultures using metrizamide. Following centrifugation, the low-buoyant density cells, referred to throughout as DC, were CD11c(high), Iab(high), B7-1(high) and B7-2(high) and potently activated alloreactive T cells in mixed lymphocyte reactions (MLR). In contrast, the high-density cells expressed low levels of the above markers, comprised mostly of granulocytes based on GR1 expression, and were poor stimulators in MLR. Following s.c. injection of fluorescently labelled cells into syngeneic recipient mice, DC but not granulocytes migrated to the T-dependent areas of draining lymph nodes (LN). DC numbers in LN were quantified by flow-cytometric analysis, on 1, 2, 3, 5 and 7 days following DC transfer. Peak numbers of around 90 DC per draining LN were found at 2 days. There was very little migration of DC to non-draining LN, thymus or spleen at any of the time-points studied. In contrast, following i.v. injection, DC accumulated mainly in the spleen, liver and lungs of recipient mice but were largely absent from peripheral LN and thymus. The ability of DC to induce T-cell-mediated immune responses was examined using trinitrobenzenesulphate (TNBS)-derivatized DC (TNBS-DC) to sensitize for contact hypersensitivity responses (CHS) in naive syngeneic recipients. Following s.c. injection, as few as 105 TNBS-DC, but not TNBS-granulocytes, sensitized for CHS responses. However, the same number of TNBS-DC failed to induce CHS following i.v. injection. In summary, this study provides new and quantitative data on the organ specific migration of murine BM-derived DC following s.c. and i.v. injection. The demonstration that the route of DC administration determines the potency of CHS induction, strongly suggests that the route of immunization should be considered in the design of vaccine protocols using DC.

Adoptive Transfer↗
PubMed1998

Molecular cloning and functional expression of a protein-serine/threonine phosphatase from the hyperthermophilic archaeon Pyrodictium abyssi TAG11.

An open reading frame coding for a putative protein-serine/threonine phosphatase was identified in the hyperthermophilic archaeon Pyrodictium abyssi TAG11 and named Py-PP1. Py-PP1 was expressed in Escherichia coli, purified from inclusion bodies, and biochemically characterized. The phosphatase gene is part of an operon which may provide, for the first time, insight into a physiological role for archaeal protein phosphatases in vivo.

Amino Acid Sequence↗
PubMed1997

Xbp1, a stress-induced transcriptional repressor of the Saccharomyces cerevisiae Swi4/Mbp1 family.

We have identified Xbp1 (XhoI site-binding protein 1) as a new DNA-binding protein with homology to the DNA-binding domain of the Saccharomyces cerevisiae cell cycle regulating transcription factors Swi4 and Mbp1. The DNA recognition sequence was determined by random oligonucleotide selection and confirmed by gel retardation and footprint analyses. The consensus binding site of Xbp1, GcCTCGA(G/A)G(C/A)g(a/g), is a palindromic sequence, with an XhoI restriction enzyme recognition site at its center. This Xbpl binding site is similar to Swi4/Swi6 and Mbp1/Swi6 binding sites but shows a clear difference from these elements in one of the central core bases. There are binding sites for Xbp1 in the G1 cyclin promoter (CLN1), but they are distinct from the Swi4/Swi6 binding sites in CLN1, and Xbp1 will not bind to Swi4/Swi6 or Mbp1/Swi6 binding sites. The XBP1 promoter contains several stress-regulated elements, and its expression is induced by heat shock, high osmolarity, oxidative stress, DNA damage, and glucose starvation. When fused to the LexA DNA-binding domain, Xbp1 acts as transcriptional repressor, defining it as the first repressor in the Swi4/Mbp1 family and the first potential negative regulator of transcription induced by stress. Overexpression of XBP1 results in a slow-growth phenotype, lengthening of G1, an increase in cell volume, and a repression of G1 cyclin expression. These observations suggest that Xbp1 may contribute to the repression of specific transcripts and cause a transient cell cycle delay under stress conditions.

Amino Acid Sequence↗
PubMed1996

CD40 is functionally expressed on human keratinocytes.

The CD40/gp39 pathway is known to be an important feature of B/T cell collaboration leading to T cell-dependent activation, proliferation or differentiation of B cells. Additionally, CD40 is involved in the regulation of B cell survival and apoptosis. Recently, CD40 has been shown to be expressed functionally on non-hematopoietic cells, i.e. endothelial cells. Here, we demonstrate that human keratinocytes (KC) cultured in vitro express CD40 constitutively. The surface expression of CD40 is markedly up-regulated following stimulation with interferon (IFN)-gamma, but not with tumor necrosis factor-alpha or interleukin (IL)-1 beta. This process is regulated at the CD40 mRNA level as demonstrated by Northern blot analysis. Furthermore, ligation of CD40 via soluble gp39, the CD40 ligand, enhances intercellular adhesion molecule (ICAM)-1 and Bcl-x up-regulation on IFN-gamma-stimulated KC, but not lymphocyte function-associated antigen (LFA)-3, B7-2, HLA-DR, or Fas expression. The release of IL-8 is also induced following CD40 ligation on KC. In psoriasis, a T cell-mediated inflammatory skin disease, KC have a markedly enhanced expression of CD40. This expression co-localizes with the expression of ICAM-1, Bcl-x, and an influx of CD3+ T cells. These findings suggest a functional role of CD40 on KC in inflammatory skin disorders such as psoriasis and could make a therapeutic intervention by disrupting the CD40/gp39 pathway an approach to consider in these inflammatory skin diseases.

Adult↗
PubMed1995

Suppression of HPA-axis activity by haloperidol after experimentally induced heat stress.

1. Healthy male volunteers were exposed to either a heat condition (52 degrees C) or normal temperature (28 degrees C) receiving a single oral dose of 3 mg haloperidol or placebo in a double-blind design. 2. Ratings on aversiveness as well as on intensity of ambient temperature and saliva samples for determination of cortisol were sampled at defined intervals. Body core temperature and sweat loss were measured continuously throughout the three hour experiment. 3. Results indicate increased levels of cortisol after exposure to heat but not after a pretreatment with haloperidol. 4. The findings of this study suggest that D2-receptors of tuberoinfundibular neurons are blocked by haloperidol which suppresses the dopamine mediated release of vasopressin induced by dehydration and the subsequent stimulation of CRH.

Adult↗
PubMed1995

Verapamil reverses abnormal [Ca2+]i and carbohydrate metabolism of PMNL of dialysis patients.

The basal levels of cytosolic calcium ([Ca2+]i) of polymorphonuclear leukocytes (PMNL) are elevated in hemodialysis (HD) patients, and this abnormality has been implicated in the dysfunction of the PMNL of these patients. The elevated [Ca2+]i appears to be due to PTH-induced entry of calcium into PMNL, an action that may be prevented by calcium channel blockers. We examined [Ca2+]i and carbohydrate metabolism of PMNL of normal subjects and of HD patients before, after eight to nine weeks of verapamil therapy (120 mg/day), and after eight to ten weeks of discontinuation of verapamil treatment. In HD patients, the basal levels of [Ca2+]i of PMNL are elevated and their glucose uptake, the activity of total and active forms of glycogen synthetase, and glycogen content are reduced compared to values in normal subjects (P < 0.01). These derangements were normalized after verapamil therapy and re-emerged after discontinuation of treatment with verapamil despite no change in blood levels of PTH. The results indicate that the elevation in [Ca2+]i of PMNL and the consequent derangements in carbohydrate metabolism of these cells are treatable with a calcium channel blocker. The data assign a valuable role for calcium channel blockers for the amelioration of some aspects of cell dysfunction of uremia.

Aged↗
PubMed1995

Effect of immunoglobulin light chains from hemodialysis and continuous ambulatory peritoneal dialysis patients on polymorphonuclear leukocyte functions.

Circulating plasma factors accumulating in the serum of uremic patients have the potential to inhibit essential functions of polymorphonuclear leukocytes (PMNL). As a consequence, these factors can contribute to the increased risk for bacterial infections generally found in uremic patients. Free immunoglobulin light chains that are present in the serum of healthy adults at low levels appear in the serum of uremic patients at significantly higher levels. Therefore, kappa and lambda light chains in their monomeric and dimeric forms were isolated from hemodialysis and continuous ambulatory peritoneal dialysis patients and their potential to inhibit essential PMNL functions in in vitro assays was tested. It was found that all isolates tested were able to inhibit deoxyglucose uptake, a measure for the state of activation of PMNL, as well as chemotaxis. In contrast, free immunoglobulin light chains had no influence on the phagocytotic functions of PMNL. It was concluded that free immunoglobulin light chains are able to act as uremic toxins by interfering with essential PMNL functions and that their serum levels and fate during the treatment of uremic patients should be taken into consideration.

Chemotaxis↗
PubMed1994

Cloning and chromosomal organization of a gene encoding a putative amino-acid permease from Saccharomyces cerevisiae.

A new member of the yeast amino acid (aa) permease gene family has been cloned, mapped and sequenced. The sequence of the PAP1 (putative aa permease 1) gene contains an open reading frame of 566 aa corresponding to a polypeptide with a calculated M(r) of 62,704. Its hydropathy profile suggests the presence of 13 membrane-spanning regions and a charged N-terminal domain. It does not resemble hydrophobic signal sequences found in secreted proteins. Hence, PAP1 encodes a protein with characteristics typical of integral membrane proteins translocating ligands across cellular membranes. Sequence comparisons indicate strong homology to the five known aa permeases of Saccharomyces cerevisiae and to an aa transporter in Trichoderma harzianum. Primer extension analysis revealed one major and one minor transcription start point located 121 and 125 nucleotides upstream from the ATG start codon, corresponding to a 2.1-kb transcript. PAP1 was mapped in a contig of three known (DBF4, TPI and HEM12), but so far unlinked, genes on chromosome IV.

Amino Acid Sequence↗
PubMed1994

Impaired cellular host defence in peritoneal dialysis by two granulocyte inhibitory proteins.

Bacterial and fungal peritonitis is associated with a high risk of morbidity and mortality in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Impaired cellular host defence in the peritoneal cavity underlies this risk. Two granulocyte inhibitory proteins with a molecular weight of 28,000 dalton (GIP I) and about 9500 dalton (GIP II) with homology to light-chain proteins and beta 2-microglobulin, respectively, were isolated from peritoneal dialysis effluents. In vitro, both granulocyte inhibitory proteins inhibit PMNL glucose uptake, phagocytosis and intracellular killing of bacteria. The IC50 of GIP I or GIP II required for inhibition of half-maximal FMLP-induced or PMA-stimulated PMNL function was found to be in the nanomolar range, suggesting very specific inhibition. These data may explain, at least in part, defective local cellular host defence in CAPD patients.

Cytokines↗
PubMed1994

Studies of biocompatibility of different dialyzer membranes: role of complement system, intracellular calcium and inositol-triphosphate.

PMNLs are activated during extracorporeal circulation. The aim of this cross-over biocompatibility study was to investigate the role of complement system, intracellular calcium [Ca2+]i and inositol-triphosphate (IP3) on PMNL degranulation during hemodialysis (HD) with following membranes: polyamide, hemophane and cuprophane. In a second study the effect of complement system, intracellular calcium and IP3 on lactoferrin release during HD with polysulfone and polymethylmethacrylate (PMMA) was also investigated. HD with cuprophane leads to the highest formation of terminal complement component (TCC) followed by PMMA and hemophane. There was a strong correlation between maximal arterial TCC formation and procentual increase of plasma lactoferrin during hemodialysis treatment with all membranes. Both HD with PMMA and hemophane leads to a significant increase of resting [Ca2+]i after 30 minutes of HD. Lowest TCC formation and lowest rise in [Ca2+]i were observed with polysulfone and polyamide. Procentual and absolute increase of [Ca2+]i did also correlate with maximal TCC formation during HD using PMMA, hemophane, polyamide and polysulfone. Since cuprophane induces an initial drop of PMNLs, these cells could not be isolated during HD with cuprophane membranes. Resting PMNL IP3 values were similar before and 30 minutes after begin of hemodialysis and comparable with all membranes used. These data indicate that TCC and intracellular calcium are important signals for PMNL degranulation during HD with cuprophane, PMMA and hemophane. However, mild degranulation of specific PMNL granules can also occur in the absence of significant change in TCC, [Ca2+]i or IP3 levels during HD with polyamide or polysulfone.

Biocompatible Materials↗