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Biomedical subjects

N Schwartz

Publications and source records attributed to N Schwartz.

At least 19 recordsLinked to original sources
PubMed2003

[Quality assurance in dentistry--past, present and future].

Quality assurance involves the cycle of quality assessment, formal identification of problems, developing a strategy for resolving problems and implementation of changes. Historically, the term "first do not harm" can be considered as the first step in quality assurance. Patients' high expectations from the outcomes of dental treatment, new technology and cost containment changed the perspectives completely. We are facing a new era of an increasing demand for patients' involvement as well as an increasing demand for accountability of the members of the profession. The article describes the development of the issue of quality assurance during the last thirty years and highlights the difficulties encountered by the profession in adjusting the changes due to lack of education, experience, knowledge and absence of a definition for accepted criteria for action. Developing criteria for appropriateness of dental treatment, developing mechanisms for assessing the art of care, development of large data bases and development of consumers' surveys are some of the leading suggestions for future action. The responsibility for quality and quality assurance lies in the hands of the dental profession. Organized dentistry possesses a social and ethical commitment for the society, as well as professional obligation for the members of the profession. Although cost containment gave rise to the issue of quality, quality assurance should not be measured in financial terms, but in terms of accepting responsibility and working for continuous improvement. Steps in the right direction will, hopefully, lead to a better and more efficient utilization of the available resources and will increase the trust of the public in the profession of dentistry. Therefore, organized dentistry should not leave this important issue to be dealt by non-dental professions or commercial organizations.

Cost Control↗
PubMed2002

Percolation in directed scale-free networks.

Many complex networks in nature have directed links, a property that affects the network's navigability and large-scale topology. Here we study the percolation properties of such directed scale-free networks with correlated in and out degree distributions. We derive a phase diagram that indicates the existence of three regimes, determined by the values of the degree exponents. In the first regime we regain the known directed percolation mean field exponents. In contrast, the second and third regimes are characterized by anomalous exponents, which we calculate analytically. In the third regime the network is resilient to random dilution, i.e., the percolation threshold is p(c)-->1.

Journal Article↗
PubMed2002

Influence of diet on the shedding of Candida glabrata by experimentally infected preweaned calves.

The influence of three diets, comprising dam's milk (DM) from the same farm, commercial milk replacer with (CMRL) or without 3.2% lactose (CMR), on the duration and intensity of Candida glabrata shedding in the faeces of preweaned calves following experimental oral infection was examined. Shedding of other potential enteric pathogens was also monitored. The duration and intensity of C. glabrata shedding in DM-fed calves were reduced significantly compared with the calves fed the two diets based on milk replacers. Consequently, feeding calves with DM might disrupt the infective cycle, resulting in the yeast's elimination from a farm. In the CMR and CMRL groups, the periods of intensive shedding of C. glabrata and rotavirus overlapped but no diarrhoea was associated with the shedding of either microorganism. There was no evidence that lactose diminished colonization in vivo.

Animals↗
PubMed2000

Biosynthesis and regulation of expression of proteoglycans.

Proteoglycans are a family of complex macromolecules characterized by the presence of one or more glycosaminoglycan chains covalently linked to a polypeptide backbone. Although originally named and categorized on the basis of the glycosaminoglycan substituent, increasingly they are being identified as members of gene families that encode their different core proteins. Proteoglycans are found predominantly in the extracellular matrix (ECM) or associated with the cell surface of most eucaryotic cells where they bind to other matrix- and cell-associated components. Their ability to be so interactive stems in large part from their structural diversity, which arises from variations in polysaccharide type, size and composition as well as core protein primary sequence, domain arrangement, degree of substitution and distribution of polysaccharide chains. Considering the complexity of proteoglycan molecules, often having modular core protein domains and posttranslational modifications that vary with developmental setting, the various steps of synthesis and processing are most likely highly regulated. Furthermore, regulation of proteoglycan expression is even more complex as they frequently are expressed transiently by multiple cell types and in different developmental time frames. Elucidation of cell- and developmental-specific control elements which regulate the expression of these complex macromolecular families are only beginning.

Animals↗
PubMed1999

Optimal paths in disordered media: scaling of the crossover from self-similar to self-affine behavior.

We study optimal paths in disordered energy landscapes using energy distributions of the type P(log(10) E)=const that lead to the strong disorder limit. If we truncate the distribution, so that P(log(10) E)=const only for E(min) < or =E < or =E(max), and P(log(10) E)=0 otherwise, we obtain a crossover from self-similar (strong disorder) to self-affine (moderate disorder) behavior at a path length l(x). We find that l(x) proportional, variant[log(10)(E(max)/E(min))](kappa), where the exponent kappa has the value kappa=1.60 +/- 0.03 both in d=2 and d=3. We show how the crossover can be understood from the distribution of local energies on the optimal paths.

Journal Article↗
PubMed1999

Ischemia activates actin depolymerizing factor: role in proximal tubule microvillar actin alterations.

Apical membrane of renal proximal tubule cells is extremely sensitive to ischemia, with structural alterations occurring within 5 min. These changes are felt secondary to actin cytoskeletal disruption, yet the mechanism responsible is unknown. Actin depolymerizing factor (ADF), a 19-kDa actin-binding protein, has recently been shown to play an important role in regulation of actin filament dynamics. Because ADF is known to mediate pH-dependent F-actin binding, depolymerization, and severing, and because ADF activation occurs by dephosphorylation, we questioned whether ADF played a role in microvilli microfilament disruption during ischemia. To test our hypothesis, we induced renal ischemia in the rat with the clamp model. Initial immunofluorescence and Western blot studies on cortical tissue documented the presence of ADF in proximal tubule cells. Under physiological conditions, ADF was distributed homogeneously throughout the cytoplasm, primarily in the Triton X-100-soluble fraction, and both phosphorylated (pADF) and nonphosphorylated forms were identified. During ischemia, marked alterations occurred. Intraluminal vesicle/bleb structures contained extremely high concentrations of ADF along with G-actin, but not F-actin. Western blot showed a rapidly occurring duration-dependent dephosphorylation of ADF. At 0-30 min of ischemia, total ADF levels were unchanged, whereas pADF decreased significantly to 72% and 19% of control levels, at 5 and 15 min, respectively. Urine collected under physiological conditions did not contain ADF or actin, whereas urine collected after 30 min of ischemia contained both ADF and actin. Reperfusion was associated with normalization of cellular pADF levels, pADF intracellular distribution, and repair of apical microvilli. These data suggest that activation of ADF during ischemia via dephosphorylation is, in part, responsible for apical actin disruption resulting in microvillar destruction and formation of intraluminal vesicles.

Actin Depolymerizing Factors↗
PubMed1997

Thermometer use among Mexican immigrant mothers in California.

A community-based household survey was utilized to assess the relationship between thermometer use, home treatment and utilization of health care services. Using a cross-sectional design, the study surveyed 688 low income Mexican origin mothers of children between the ages of 8 and 16 months in San Diego County. Mothers were asked how they determine that their child has fever and how often they use a thermometer. Nearly 40% of low income Mexican mothers interviewed in San Diego county never used a thermometer for determining childhood fever. Approximately two-thirds (64.7%) relied either primarily or exclusively on embodied methods such as visual observation or touch to determine fever in their child. A multivariate logistic regression analysis determined that low education and a separated or divorced marital status decreased the odds of thermometer use, whereas regular contact with the health care system doubled the likelihood of thermometer use. Mothers who relied on embodied methods were more likely to use over-the-counter medications than those who relied on thermometers; however, no significant differences were found between groups using other methods of home treatment. Fever determination modalities can be used to screen for lack of access to care and to provide for other health care needs in a culturally appropriate manner. While clinicians' expectations may include parental experience with temperature taking, current pediatric literature questions the need for home-based thermometer use. Possible alternatives to the traditional rectal thermometer might include digital thermometers and color coded thermometer strips.

California↗
PubMed1991

Dibasic amines as competitive ions improve the resolution between polyanionic nucleotides.

Aliphatic diamines when used as single ion pairing reagents were capable of resolving 3'-,5'- and 2'-,5'- nucleotidyl diphosphates from one another while conventional ion pairing reagents did not separate these positional isomers. The use of 1,2-diamines resulted in the greatest resolution while increasing spacing between the amino groups progressively reduced the resolution while increasing the retention volume. A competitive ion pairing system was also developed using triethylamine as an additional ion pairing reagent. Using this system ethylenediamine, 1,2- and 1,3-diaminopropane were nearly equivalent in their ability to resolve adenosine 3'-phosphate 5'-phosphate, from adenosine 2'-phosphate 5'-phosphate, and adenosine 3'-phosphate 5'-beta-methylenephosphosulfate (3'-mePAPS) from adenosine 2'-phosphate 5'-beta-methylenephosphosulfate (2'-mePAPS), respectively. The ability to easily resolve these positional isomers allows the use of a more simplified synthetic procedure that does not involve the use selective protecting groups to specifically phosphorylate the 2' or 3' hydroxyl group. We have used this procedure on a semipreparative scale to obtain small quantities of both mePAPS and 2'-mePAPS for use in enzymatic studies.

Adenine Nucleotides↗
PubMed1989

Malignant hyperthermia in a child with sleep apnea.

Malignant hyperthermia is a syndrome characterized by a hypermetabolic state of skeletal muscle (1, 2). It is transmitted by genetic inheritance. The syndrome has frequently been associated with certain neuromuscular and other disorders (1, 3). A case of the syndrome occurring in a child with sleep apnea syndrome, an association not previously reported, is discussed here.

Child↗