PubMed Health⌕ Search

Biomedical subjects

A Froese

Publications and source records attributed to A Froese.

At least 19 recordsLinked to original sources
PubMed1998

Mechanical performance of clinically available, neonatal, high-frequency, oscillatory-type ventilators.

OBJECTIVE: To perform a functional evaluation of five different high-frequency, oscillatory-type ventilators that are currently being marketed for neonatal high-frequency oscillation. DESIGN: Observational animal study. SETTING: Laboratory. SUBJECTS: New Zealand White male rabbits. INTERVENTIONS: Oscillator waveforms and delivered volumes were measured plethysmographically for the following ventilators: the SensorMedics 3100 A; the Dräger Baby Log 8000; the Metran Humming V; the Infant Star; and the Infant Star 950. The independent variables which were adjusted included frequency (5 to 15 Hz), amplitude (25% to 100%), mean airway pressure (5 to 25 cm H2O) and lung injury. MEASUREMENTS AND MAIN RESULTS: At 15 Hz, the volume delivered at the 100% amplitude setting varied from 2.1 to 8.8 mL. Generally, the delivered volume decreased with increasing frequency, and with increased percentage of amplitude. Volume delivery was relatively unaffected by mean airway pressure but decreased with lung injury. Waveforms ranged from pure sinusoidal to a complex square wave. The handling of inspiration/expiration time ratios was ventilator specific. The SensorMedics inspiration/ expiration ratio is user selected over a range from 1:2.3 (30% inspiratory time) to 1:1 (50% inspiratory time) and once selected it is consistent over its entire range of operating frequencies. The Drager ratio is machine determined and varied from 1:2.5 at 5 Hz to 1:1 at 15 Hz. Inspiratory time of the Infant Star is machine set at 18 msecs such that the inspiration/expiration ratio is 1:10.1 at 5 Hz and 1:2.7 at 15 Hz. The Humming V has a fixed inspiration/expiration ratio of 1:1. The relationship of the mean airway pressure displayed on the ventilator to the alveolar occlusion pressure varied considerably among devices. The displayed mean pressure could either overestimate (SensorMedics at 33% inspiratory time or Infant Star), approximate (Humming V), or underestimate (Dräger) the mean lung distending pressure measured during a brief occlusion maneuver. CONCLUSIONS: The findings demonstrate large variations in machine performance. The ventilators also differed profoundly in complexity of operation and versatility as neonatal ventilators.

Animals↗
PubMed1997

Child psychiatric consultation service to community agencies: a collaborative approach involving three community agencies.

OBJECTIVE: To report the early experience of a multiagency child psychiatric consultation service. METHOD: The program is described, and the demographic characteristics of clients referred to the consultation program over the first 25 months of operation are presented. Referrals were examined for demographics and the questions consultees wanted to have answered. RESULTS: In 59 of 100 consultations, physical and/or sexual abuse was proved or highly suspected. In 82 of the 100 cases, consultees had questions pertaining to management issues. Questions related to diagnostic issues numbered 62, and there were 45 questions about safety issues. CONCLUSION: Effective psychiatric consultations services to rural areas can be established. Once established, the questions of consultees can provide an effective training ground for future community-oriented child psychiatrists.

Adolescent↗
PubMed1996

Building curriculum for training in community, child psychiatry.

OBJECTIVE: To present a practical approach to curriculum design for community-based care in child psychiatry. METHOD: A design template is presented, steps for a curriculum review are derived from it, and as an example, a small academic division's program is reviewed. RESULTS: The division's curriculum was developed according to the template, resulting in an enhanced focus and improved coverage of topics through a combination of experiential and didactic teaching. CONCLUSION: The suggested format is considered applicable to child psychiatric training programs of all sizes and offers an opportunity to review or initiate the teaching of community child psychiatry.

Child Psychiatry↗
PubMed1995

Phenotypic changes among hybrid rat mast cells.

Rat peritoneal mast cells and 6-thioguanine-resistant rat basophilic leukemia cells, representative of connective tissue-type (CTMC) and mucosal (MMC) mast cells, respectively, were fused using polyethylene glycol. Four out of 14 primary hybrid mast cell lines contained more than 50% of CTMC as demonstrated by histochemical staining. Two cell lines, one predominantly of the CTMC and the other of the MMC phenotype, were selected for further study. Among these, the phenotype was also confirmed by analysis for rat mast cell protease I and by mediator release triggered by compound 48/80 and ionophore A23187. The CTMC phenotype disappeared after culturing cells for 2 weeks. The change in phenotype did not significantly alter the mediator release due to calcium ionophore A23187. Repeated cloning of cells bearing the CTMC phenotype did not yield a cloned line of cells expressing the CTMC phenotype only, although it prolonged the persistence of this phenotype. During the period of CTMC phenotype loss, a drop in cellular DNA content occurred, suggesting that chromosome instability may, at least partially, have been responsible for the phenotypic changes.

Animals↗
PubMed1993

The N-linked oligosaccharides of the Fc epsilon receptors of rat basophilic leukemia cells.

This study was undertaken to investigate the nature and microheterogeneity of the carbohydrate moiety of the Fc epsilon receptors of RBL-CA10 and RBL-CA10.7 cells. Treatment using the glycosylation processing inhibitors, castanospermine (CN), 1-deoxymannojirimycin (DMJ), and swainsonine (SW) resulted in a decrease of the relative molecular mass (M(r)) of both the alpha-chain of the high affinity receptor for IgE, Fc epsilon RI(alpha), and the low affinity receptor for IgE, Fc epsilon RL. Exposure to DMJ had the greatest effect on the M(r), while CN seemed to lead to a decreased cell surface expression of Fc epsilon RI. Both receptors are largely resistant to endoglycosidase H as their M(r) decreased only by approximately 2 kDa. These results suggest that both receptors are composed primarily of complex oligosaccharides with a single high mannose, N-glycosylated site. Both Fc epsilon receptors become endoglycosidase H sensitive if first exposed to DMJ which indicates that the carbohydrate composition is indeed altered by this processing inhibitor presumably by blocking the formation of complex structures. When the Fc epsilon receptors were reduced and hydrolyzed by N-glycanase, the M(r) values for Fc epsilon RI(alpha) and Fc epsilon RL decreased to approximately 28 and 34-38 kDa respectively. In the case of Fc epsilon RI(alpha), this implies the presence of only a small amount of O-linked oligosaccharides.

Amidohydrolases↗
PubMed1991

Establishment and characterization of hybrid rat mast cells.

Rat peritoneal mast cells (RPMC) and rat basophilic leukemia (RBL) cells are representative of connective tissue-type (CTMC) and mucosal-type (MMC) mast cells, respectively. Using polyethylene glycol, we have fused RPMC with 6-thioguanine resistant, HAT (hypoxanthine, aminopterin, thymidine) sensitive RBL-CA10.7 or RBL-CK2 cells, yielding several hybrid rat mast cell lines (HRMC). The hybridomas exhibited different size and cytoplasmic granularity when compared with parental cell lines. Analysis of both high (Fc epsilon RI) and low affinity (Fc epsilon RL) receptors for IgE revealed that the hybrid lines had more variable receptor patterns than the parent lines. Three hybridoma lines were chosen for further study. Differential histochemical staining with alcian blue and safranin O dyes indicated the hybrids to be predominantly of the MMC type: however, a few cells of one of these uncloned hybridomas were found to be of the CTMC type. Attempts to isolate the CTMC hybridomas yielded one culture which was predominantly of the CTMC phenotype and in a number of other cultures, cells were found expressing simultaneously both the CTMC and the MMC phenotype. After 3 weeks in culture, however, all hybridomas, including those which were cloned further, expressed only the MMC histochemical phenotype. This was found to correlate with the presence of rat mast cell protease II (RMCPII) and the absence of RMCPI in all hybridomas, as detected by Western blot analysis. In addition, the histamine content of all cells was significantly lower than that of the parent RPMC. Most hybrid mast cells expressed both Fc epsilon RI and Fc epsilon RL which in some cases exhibited significant variations in the Mr. These results indicate that somatic cell hybrids expressing the MMC and CTMC phenotype can be produced by the fusion of RBL and RPMC. The CTMC phenotype, however, is unstable, and possible reasons for this are discussed.

Animals↗
PubMed1990

Characterization of rat tissue cultured mast cells.

Twelve continuous rat tissue cultured mast cell (MC) lines were established by prolonged culture of rat peritoneal MC in the absence of added factors or feeder layers. Two of these lines, RCMC1 and RCMC2, have been briefly described previously, seven others are now also described. Both RCMC1 and RCMC2 lack a marker chromosomes present on RBL-CA10.7 cells. All lines were found to express the phenotype of mucosal MC as defined by alcian blue-positive and safranin O-negative staining, the presence of rat MC protease II and a low histamine content. When analyzed for high-(Fc epsilon RI) and low-affinity (Fc epsilon RL) receptors for IgE, the various lines yielded a variety of receptor patterns. Northern blot analysis of the RNA of RCMC1, RCMC2 and RBL-CA10.7 revealed that all three cell lines contained the same mRNA species for the alpha, beta and gamma subunits for Fc epsilon RI previously found in another rat basophilic leukemia cell line. Quantitation of the relative amounts of alpha, beta and gamma mRNA did not correlate with the expression of the relative amounts of Fc epsilon RI(alpha) in these cells. The relative amounts of mRNA for all these subunits of RCMC2 were equal or higher than those of RCMC1, suggesting that the low expression of Fc epsilon RI(alpha) on the former was a consequence of post-transcriptional events. Analysis of a RCMC1 clone over a 6-month period revealed changes in the expression of both Fc epsilon RI(alpha) and Fc epsilon RL.

Animals↗
PubMed1990

Differential IgE receptor development on rat tissue cultured mast cells.

Rat tissue cultured mast cells established previously were cloned and subcloned by limiting dilution and analyzed for surface expression of both high- (Fc epsilon RI) and low-affinity (Fc epsilon RL) receptors for IgE. Analysis of receptor development in continuous culture over a period of 24 weeks revealed that Fc epsilon RL expression increased with time in all cases, irrespective of initial receptor density on the cell surface. Expression of Fc epsilon RI as measured in terms of its alpha-chain showed more clonal variation, exhibiting increases, decreases, as well as relative constancy over the time period. These results suggest that the two types of receptors are regulated independently and that some of the rat tissue cultured mast cell clones studied represent different stages of mast cell development.

Animals↗
PubMed1989

Isolation and characterization of IgE receptors from rat intestinal mucosal mast cells.

High-(Fc epsilon RI) and low-(Fc epsilon RII) affinity IgE receptors were isolated from surface radioiodinated, Nonidet-P40-solubilized rat intestinal mucosal mast cells (IMMC) and compared with those on rat peritoneal mast cells (PMC) and rat basophilic leukemia (RBL) cells. Fc epsilon RII were isolated by affinity chromatography using IgE-Sepharose or by anti-Fc epsilon RII antisera and protein A-Sepharose. The surface-exposed, IgE-binding alpha subunits of Fc epsilon RI [Fc epsilon RI alpha] were isolated by affinity chromatography using IgE and anti-IgE-Sepharose. Fc epsilon RI alpha on IMMC had an apparent molecular mass of 59 kDa, somewhat larger than that of PMC (51 kDa), RBL-2H3 cells (51 kDa) or RBL-CA10.7 cells (46 kDa). Brief (45 s) incubation of IMMC or PMC in glycine-HCl, pH 3, prior to iodination removed much of the surface-bound IgE. This permitted more thorough labeling of the receptors, but had no affect on the estimate of receptor size. Surprisingly and in contrast to acid-treated PMC, upon anti-IgE-Sepharose isolation acid-treated IMMC yielded an intensely radioactive Fc epsilon RI alpha band in the absence of added IgE. Such a finding suggests that IMMC, more so than PMC, may have an intracellular store of IgE, as has been suggested by many others. IMMC also differed from PMC in the number of forms of Fc epsilon RII isolated; 50-kDa and 58-kDa forms of Fc epsilon RII were obtained from IMMC, whereas PMC yielded most often a single 56-kDa Fc epsilon RII band. These results were mimicked by the two RBL cell sublines: RBL-2H3 cells yielded two Fc epsilon RII (46 kDa and 55 kDa), but only one form of Fc epsilon RII (54-kDa) was obtained from RBL-CA10.7 cells. Thus, the two subtypes of rat mast cells, which have previously been shown to differ in mediator profile and responsiveness to secretagogues and antiallergic drugs, are also distinguished by differences in IgER profile.

Animals↗
PubMed1989

IgE receptors from rat intestinal mucosal and peritoneal mast cells show mast cell subtype-specific differences.

High- (alpha chain) and low-affinity IgE receptors from purified populations of rat intestinal mucosal (IMMC) and peritoneal mast cells (PMC) were characterized by SDS-PAGE. Receptor expression and molecular weight were compared. IMMC yielded 59-kilodalton (kDa) alpha chains of the high-affinity receptors and two forms (58, 50 kDa) of low-affinity receptors, whereas PMC possessed only 51-kDa alpha chains and 56-kDa low-affinity receptors. These differences extend the evidence for functional diversity between mast cell subtypes.

Animals↗
PubMed1988

The interaction of IgG subclasses with solubilized Fc receptors of rat basophilic leukemia cells.

Rat basophilic leukemia (RBL) cells carry two surface glycoprotein molecules named R (or alpha) and H which, when detergent solubilized, bind to rat IgE-Sepharose. The same two molecules also bind to rat IgG-Sepharose but with a lower affinity. R is a component of the high affinity Fc receptor for IgE. In the present study the inhibition of the binding of R and H to rat IgG-Sepharose by various homologous and heterologous immunoglobulins was used to assess their relative affinities for the two receptor molecules. Ranking the rat immunoglobulins in order of their affinities for the R receptor yielded: IgE much greater than IgG2a greater than IgG1 greater than IgG2b; and for H: IgE greater than IgG2b greater than IgG1 greater than IgG2a. Rat IgG2c inhibited the binding of both R and H but a precise ranking could not be assigned. Conclusive evidence has been obtained for the Fc specificity of these interactions. The affinities of the mouse IgG subclass/R interactions can be ranked: IgG1 greater than IgG2a greater than IgG2b; and for the H receptor: IgG1 greater than IgG2b greater than IgG2a. All of the mouse proteins and other heterologous IgGs, such as those of sheep, goat, equine and rabbit origin, interacted considerably more strongly with H than with R. No interaction with mouse IgG3 could be detected under the conditions tested.

Animals↗
PubMed1988

Factor-independent tissue cultured mast cells: establishment from rat peritoneal mast cells.

We report here that extended culture of purified rat peritoneal mast cells (RpMC), typical of the connective tissue-type (CTMC), gives rise to continuously proliferative cell lines without the requirement of exogenous growth factors such as IL-3 and IL-4 or accessory cells. Two of the cell lines established, RCMC1 and RCMC2, are described here. Both cell lines have been maintained in continuous culture in vitro for over a year. Although these cell lines were derived from CTMC, they exhibit phenotypic characteristics of mucosal-type mast cells, i.e., they contain rat mast cell protease II (RMCP II), low levels of histamine and stain alcian blue+/safranin-. Previous studies have identified both high and low affinity receptors for IgE, designated Fc epsilon RI and Rc epsilon RII, respectively, on RpMC and rat basophilic leukemia (RBL) cells. At the early stages of cell culture, RCMC1 expressed predominantly Fc epsilon RI and a gradual increase in the expression of Fc epsilon RII has been observed with time in culture. By comparison, RCMC2 expressed predominantly Fc epsilon RII throughout its entire period of cell culture.

Animals↗
PubMed1987

A microassay for studies of the interaction between Fc receptors and low affinity ligands.

A microassay using 10 microliter of a conjugate of rat IgG and Sepharose was developed for the study of the interaction between the solubilized receptors for IgE of rat basophilic leukemia (RBL) cells, designated H and R, and a variety of low affinity immunoglobulins. Rat IgG2a was used as the model of a low affinity ligand by serving as an inhibitor of the interaction between IgG-Sepharose and the receptors for IgE. Ligand concentrations 2.24 X 10(-7) to 5.37 X 10(-5) M were used along with detergent extracts of 2 X 10(5) RBL cells.

Animals↗
PubMed1987

Mycoplasma-induced degradation of IgE bound by Fc epsilon receptors of rat basophilic leukemia cells.

Previous studies from this laboratory have shown that Mycoplasma hyorhinis interacts with some unoccupied, high-affinity 45-kDa receptors for IgE on rat basophilic leukemia (RBL) cells to induce the formation of 71-kDa receptors for IgE. The present study demonstrates that when IgE is bound to the high-affinity receptors, exposure of RBL cells to mycoplasma leads to a time-dependent degradation of the cell-bound IgE into fragments of 186 kDa, 158 kDa and 115 kDa, all of which remain bound to the receptors. Upon reduction, these fragments yield 67-kDa and 55-kDa epsilon chain-derived polypeptides. The degradation appears to start at the N-terminus of the IgE, leading eventually to a complete loss of L chains. In the absence of mycoplasma, the IgE remains relatively intact throughout the same time period with a molecular mass of 210 kDa. The observed degradation of receptor-bound IgE by mycoplasma, should it also occur in vivo, could have important consequences as far as the IgE-dependent mediator release is concerned.

Animals↗
PubMed1987

Arterial PaO2 and PaCO2 influence seizure duration in dogs receiving electroconvulsive therapy.

The influence of arterial O2 and CO2 tensions on electroconvulsive seizure duration was investigated in five mongrel dogs under consistent anaesthetic conditions. Seizure durations were measured in a randomized protocol of nine possible combinations of arterial gas tension spanning increased, normal or decreased levels of PaO2 and PaCO2. Seizure duration was directly related to PaO2 (p less than 0.00001) and inversely related to PaCO2 (p less than 0.0001). A significant synergism was evident at the extremes of PaO2 and PaCO2, with seizure duration being greater than predicted for hyperoxia-hypocapnia and hypoxia-hypercapnia and shorter than predicted for hypoxia-hypocapnia and hyperoxia-hypercapnia. We conclude that arterial gas tensions strongly influence ECT-induced seizure duration and through this may influence the therapeutic efficacy of electroconvulsive therapy.

Animals↗
PubMed1986

Effects of mycoplasma infection on Fc receptors for IgE of rat basophilic leukemia cells.

Earlier studies from this laboratory had shown that rat basophilic leukemia cells carry two major receptors for IgE, named R and H, and a third minor receptor, designated 71K. It is now apparent that 71K is induced by the action of Mycoplasma hyorhinis, a common contaminant of tissue cultures. This induction is reversible. Decontamination either in in vitro or in vivo leads to a disappearance of 71K and re-infection causes its reappearance. The 71K receptor appears to be induced by the action of the mycoplasma on a surface molecule, most likely R, present on the cells at the time of infection. When receptors are occupied by IgE, 71K induction is inhibited. Other effects of mycoplasma infection include the significant reduction in the expression of transferrin receptors and increased histamine content of infected cells.

Animals↗