Synthesis of a chiral aryl-ferrocenyl ligand, by intramolecular coupling to a biaryl-related lactone.
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Journal Article↗
Biomedical subjects
J Hinrichs
Publications and source records attributed to J Hinrichs.
Effect of the fat globule sizes on the meltdown of ice cream.
The meltdown of ice cream is influenced by its composition and additives and by fat globule size. The objective of this study was to examine the effect of fat globule size and fat agglomerate size on the meltdown stability of ice cream. Therefore, an ice cream mix (10% milk fat) was homogenized at pressures ranging from 0 to 30 MPa in single-stage, double-stage, and selective homogenization processes. The ice cream, produced on a continuous ice cream freezer, was characterized by an optimized meltdown test while, in addition, the fat globule sizes and the free fat content were determined in the mix and the molten ice cream. The meltdown was dependent on the fat agglomerate sizes in the unfrozen serum phase. Agglomerates smaller than a critical diameter led to significantly higher meltdown rates. Homogenization pressures of at least 10 MPa were sufficient to produce a stable ice cream. Furthermore, proof was provided that double-stage homogenization is not necessary for fat contents up to 10% and that selective homogenization is possible to produce stable ice creams. Based on these results a model was deduced describing the stabilizing mechanisms during the meltdown process.
Chemical Phenomena↗
Nondynamic kinetic resolution of configurationally stable biaryl lactones by reduction with oxazaborolidine-activated borane: AM1 studies and experimental verification
The complete mechanistic course of the atroposelective ring opening of a lactone-bridged biaryl, dinaphth[2,1-c:1',2'-e]oxepin-3-(5H)-one (3), with a chiral oxazaborolidine-BH3 complex was calculated using the semiempirical AM1 method. The first hydride transfer to the activated carbonyl function of the adduct complexes was elaborated to be the selectivity-determining step in the postulated five-step mechanism. The calculated enantioselectivity is in good accordance with the experimental results, so that related calculations were performed on the atroposelective ring opening of a sterically strongly hindered and therefore also configurationally stable six-membered biaryl lactone, 1,3-di-tert-butyl-6H-benzo[b]naphtho[1,2-d]pyran-6-one (6f). These calculations predicted a highly (M)-selective reduction of 6f (kM/kP = 358 at -78 degrees C), which, after the smooth preparation of 6f by intramolecular biaryl coupling in high yields, was fully confirmed experimentally (kM/kP > 200 at -78 degrees C). Isolation of the intermediate hydroxy aldehyde (M)-14 at the beginning of the reaction with the same enantiomeric excess as found for the corresponding alcohol (M)-7f conclusively showed the first hydride transfer step to determine the selectivity of this process. The good agreement of computationally predicted and experimentally confirmed values proves the suitability of the AM1 method for mechanistic studies on even such complex reactions and opens a most efficient overall synthesis of sterically highly hindered biaryls, in excellent chemical (for the ring closure) and optical (for the ring cleavage) yields and for any desired axial configuration.
Journal Article↗
Position paper: sonic and ultrasonic scalers in periodontics. Research, Science and Therapy Committee of the American Academy of Periodontology.
Ultrasonic and sonic scalers appear to attain similar results as hand instruments for removing plaque, calculus, and endotoxin. Ultrasonic scalers used at medium power seem to produce less root surface damage than hand or sonic scalers. Due to instrument width, furcations may be more accessible using ultrasonic or sonic scalers than manual scalers. It is not clear whether root surface roughness is more or less pronounced following power-driven scalers or manual scalers. It is also unclear if root surface roughness affects long-term wound healing. Periodontal scaling and root planing includes thorough calculus removal, but complete cementum removal should not be a goal of periodontal therapy. Studies have established that endotoxin is weakly adsorbed to the root surface, and can be easily removed with light, overlapping strokes with an ultrasonic scaler. A significant disadvantage of power-driven scalers is the production of contaminated aerosols. Because ultrasonics and sonics produce aerosols, additional care is required to achieve and maintain good infection control when incorporating these instrumentation techniques into dental practice. Preliminary evidence suggests that the addition of certain antimicrobials to the lavage during ultrasonic instrumentation may be of minimal clinical benefit. However, more randomized controlled clinical trials need to be conducted over longer periods of time to better understand the long-term benefits of ultrasonic and sonic debridement.
Aerosols↗
pH gradients in immobilized amidases and their influence on rates and yields of beta-lactam hydrolysis.
The pH gradients developing within immobilized biocatalysts during hydrolysis of penicillin G and glutaryl-7-aminocephalosporanic acid have been estimated both theoretically and experimentally. For the latter a fluorimetric method for the direct measurement of the average pH value within the carrier during reaction has been developed using the pH-dependent fluorescence intensity of an enzyme-bound fluorophore determined with a fiber bundle. The theoretical calculations were based on a model for the hydrolysis with immobilized enzymes using a kinetic expression with five pH-dependent, measurable kinetic and equilibrium constants. The transport reaction differential equation which considers the laminar boundary layer has been solved numerically for the key component. The calculated values agreed well with the experimental data. Under the typical reaction conditions of penicillin G hydrolysis the average pH value in the carrier was 1 and 2.5 pH units below the bulk pH (=8) with and without buffer, respectively. The corresponding changes for the hydrolysis of glutaryl-7-aminocephalosporanic acid at bulk pH 8 in the presence of buffer was 0.5. This demonstrates the existence of considerable pH gradients in carriers during hydrolytic reactions, even in buffered systems with negligible mass transfer resistance. The low pH value causes suboptimal reaction rates, reduced equilibrium conversion, and reduced enzyme stability. These pH gradients can be minimised by using buffers with pK values approximately equal to the bulk pH used for the hydrolysis. The prediction quality of the model has been tested applying it to fixed bed reactor design. The reduction in rate and yield due to concentration and pH gradients can be overcome with simple measures such as high initial pH value and pH adjustments in segmented or recycling fixed bed reactors. Thus, enzymatic conversions with high yield and high operational effectiveness are achieved.
Amidohydrolases↗
A hypersensitive response-like mechanism is involved in resistance of potato plants bearing the Ry(sto) gene to the potyviruses potato virus Y and tobacco etch virus.
Potato plants carrying the Ry(sto) gene from Solanum stoloniferum are extremely resistant to a number of potyviruses, but it is not known at what stage of infection the resistance is expressed. The resistance may be due to Ry(sto) or to a closely linked gene. In this investigation, we used potato virus Y (PVY) and a tobacco etch virus construct that encodes beta-glucuronidase (TEV-GUS) to monitor virus infections of potato plants. Systemic spread of either virus in resistant potato plants was not detectable by serology, RT-PCR, GUS assay or bioassay although each replicated in the initially infected cells of leaves from resistant potato cultivars and was transported into neighbouring cells. However, 3 days post-inoculation (p.i.) a necrotic reaction set in that stopped movement and accumulation of both viruses by 7 days p.i. The resistance reaction (probably a hypersensitive reaction) became visible as necrotic streaks on veins on the lower leaflet surfaces of some potato cultivars carrying the Ry(sto) gene and may be elicited by a common potyviral gene product.
Genes, Plant↗
Effectiveness of a sonic toothbrush in maintenance of dental implants. A prospective study.
This study assessed the efficacy of a sonic and a manual toothbrush in reducing plaque and gingivitis around dental implants. Subjects were randomly assigned to either sonic (n = 16) or manual (n = 15) study groups. Groups were balanced according to baseline levels of plaque and gingivitis. The plaque (PI), gingival (GI), and bleeding (BI) indices as well as probing depths were determined at baseline, and at 4, 8, 12, and 24 week follow-up visits. Mean scores per person were calculated for each clinical parameter. Oral hygiene habits, compliance and acceptance were also evaluated over the study period. Within group comparisons from baseline throughout the study, as well as between group comparisons (i.e., sonic versus manual), were determined. Overall, plaque, gingival, and bleeding indices in both groups were lower at each follow-up visit when compared to the baseline. Within group comparisons demonstrated that both the sonic toothbrush subjects and the manual toothbrush subjects had significantly lower PI, GI, and BI scores at each post-baseline visit (4, 8, 12, and 24 weeks) than at baseline (p<0.005). In addition, the sonic toothbrush subjects also had significantly lower probing depths at each post-baseline visit than at baseline (p < 0.005). Between group comparisons demonstrated that the sonic toothbrush subjects over time had significantly lower PI and BI scores around dental implants than the manual toothbrush subjects (Repeated measures MANOVA; PI, p = 0.01; BI, p = 0.017). The sonic toothbrush subjects had lower GI scores and reduced probing depths over time when compared to manual toothbrush subjects but these scores were not statistically significant (GI; probing depth, p > 0.05). No implant problems (e.g., loose screws) were attributable to the sonic toothbrush. Relevant to oral hygiene habits, subjects in both groups demonstrated a high level of compliance with their assigned toothbrush. Overall, the results of this study demonstrated that sonic toothbrushing significantly reduced plaque, gingival inflammation and bleeding, and probing pocket depths around implants over the 6-month trial period. It is concluded that sonic brushing is an effective means of dental implant maintenance.
Adolescent↗
Induction of antibodies to plant viral proteins by DNA-based immunization.
DNA-based immunization is a promising new technique for generating antibodies in laboratory animals for diagnostic purposes in biological science. The main advantages are the elimination of time and labor and the technically demanding steps of antigen purification. The DNA sequence of the protein of interest, cloned in a suitable in vivo expression vector that is administered intramuscularly or intradermally, is sufficient to induce an immune response in animals. We report the induction of antibodies to tobacco mosaic virus (TMV) coat protein (CP) as a highly immunogenic structural protein and potato virus Y (PVY) P1 protein (P1) as a nonstructural protein. The appropriate nucleotide sequences were introduced in a mammalian expression vector (pSG5) and injected intramuscularly into New Zealand White rabbits (Oryctolagus cuniculus). By 10 days post-injection (dpi) a specific immune response was detected against TMV-CP, while it took about 5 weeks for a response to PVY P1. In both cases the antibody titers were significantly above the corresponding pre-immune serum, however, they were considerably below the titer of the matching conventionally produced antiserum. To our knowledge, this is the first report of DNA-based immunization in order to generate antibodies to plant viral proteins, but further improvements are necessary to increase antibody titers before this promising new technique can be introduced broadly in plant science for diagnostic purposes.
Animals↗
[Thyroid gland volumes and the incidence of focal changes in euthyroid men and women in various age groups].
Thyroid size and the prevalence of focal changes were determined by ultrasound on 450 euthyroid men and women living in Kiel (Schleswig-Holstein). The results were grouped into three age ranges (20-35, 36-50 and 51-85). Volumes were calculated from length x width x thickness x correction factor and expressed in ml. Thyroid volume was increased in 24.7%. Men had significantly larger volumes than women; in both sexes the right lobe was significantly larger than the left one. Focal changes (cysts, nodules, calcifications) were recorded in 21%, with a peak among women in the 36-50 year age group. This latter increase was due to a high incidence of cystic changes. Cysts were noted in 11%, nodules in 10% of the entire sample. A statistically significant increase in the number of nodules was noted for both sexes in the 51-85 age groups. Calcifications were recorded in 2% of cases, with about equal rates among men and women.
Adult↗
Evaluation of five different cochlear implant designs: audiologic assessment and predictors of performance.
The audiologic performance of 54 postlingually deafened adults wearing cochlear implants was uniformly evaluated. The participants had 9 months' or more experience with one of five different cochlear prostheses (Los Angeles Single Channel (N = 11), Vienna Single Channel (N = 4), Melbourne Multichannel (N = 18), Utah Multichannel (N = 19), San Francisco Multichannel (N = 2). The multichannel designs enabled participants to recognize more environmental sounds, provided more speech reading enhancement, and enabled most users to understand limited speech in the sound-only condition, compared to the single-channel implant group.
Adult↗
Evaluation of a new screening system for enteric pathogens.
The two-hour Rapid SST strip (DMS Laboratories, Inc.) was compared with our standard screening system (triple sugar iron agar, lysine iron agar, and urea) for enteric pathogens. We tested 50 stock cultures of enteric pathogens and 213 stool cultures received in the Barnes Hospital Clinical Microbiology Laboratory over a two-month period. All enteric pathogens from the stock cultures and clinical specimens were identified correctly with the Rapid SST system. More false-positive reactions were observed with the Rapid SST system (34%) than with the conventional system (23%). However, the costs associated with using both systems were equivalent and the test results were available one day faster with the Rapid SST system. Thus, the Rapid SST is a rapid, accurate, and cost-effective method for screening stool specimens for enteric pathogens.
Bacteriological Techniques↗
The 10 most common interviewing mistakes.
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Interviews as Topic↗
Immune enhancement in mice by ara-A.
Ara-A in single, apparently nontoxic doses stimulates murine immune responses to several well-defined antigens. Both humoral and cell-mediated responses are enhanced by ara-A, but not all mouse strains respond equally well. In certain mouse strains, ara-A also promotes increased (or decreased) survival during experimental infection with Cryptococcus neoformans, suggesting that clinically significant effects on host resistance may result from the use of ara-A as an antiviral therapeutic agent. The biochemical mechanisms of action of the aranucleosides suggest that the immunostimulation produced by ara-A depends on suppressor cell toxicity.
Adjuvants, Immunologic↗
Cryptococcal pyelonephritis and disseminated cryptococcosis in a renal transplant recipient.
Symptomatic cryptococcal pyelonephritis, meningitis, and disseminated cryptococcosis are described in a renal cadaver transplant recipient who subsequently died of Klebsiella pneumoniae sepsis. The presence of cryptococcuria and a subsequent positive CSF India ink stain led to the initial diagnosis of disseminated cryptococcosis. Therapy with 0.511 g of amphotericin B and 112.5 g of flucytosine for four weeks did not eradicate Cryptococcus from the kidney and was associated with hepatotoxicity. The importance of urinary examination and culture for C neoformans is emphasized. Cryptococcal pyelonephritis should be considered in the differential diagnosis of allograft rejection in the renal transplant patient.
Cadaver↗