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Biomedical subjects

W W Young

Publications and source records attributed to W W Young.

At least 19 recordsLinked to original sources
PubMed1996

Beta1,4-N-acetylgalactosaminyltransferase (GM2 synthase) is released from Golgi membranes as a neuraminidase-sensitive, disulfide-bonded dimer by a cathepsin D-like protease.

Many Golgi membrane-bound glycosyltransferases are released from cells in a soluble form. To characterize this release process, we stably transfected Chinese hamster ovary cells with three myc epitope-tagged forms of cloned beta1, 4-N-acetylgalactosaminyltransferase (GalNAcT); two of these forms resided in the Golgi, while the third was retained in the ER. GalNAcT was released into the culture medium from cells transfected with the Golgi forms but not with the ER form of the enzyme. The medium from cells transfected with the Golgi forms contained disulfide-bonded dimers of GalNAcT, which carried neuraminidase sensitive, complex N-linked carbohydrate chains. This soluble species represented the major degradation product of cellular GalNAcT, which turned over with a half-time of about 1.7 h. The soluble species consisted of a mixture of truncated GalNAcT molecules, the major form of which was produced by cleavage near the boundary between the transmembrane and lumenal domains between Leu-23 and Tyr-24. This cleavage site fits the sequence pattern for sites cleaved by cathepsin D (van Noort, J.M., and van der Drift, A. C.M. (1989) J. Biol. Chem. 264, 14159-14164). These findings suggest that GalNAcT is converted from a membrane-bound to a soluble form as a result of cleavage by a cathepsin D-like protease in a compartment late in the Golgi secretory pathway.

Animals↗
PubMed1996

Cloned beta 1,4N-acetylgalactosaminyltransferase: subcellular localization and formation of disulfide bonded species.

Cloned human beta 1,4N-acetylgalactosaminyltransferase (GalNAcT) catalyzes the synthesis of the glycosphingolipids GM2, GD2, and gangliotriosylceramide. To determine the subcellular location of this enzyme and whether it exists in intermolecular disulfide bonded species, we stably transfected Chinese hamster ovary (CHO) cells with three myc epitope-tagged forms of the GalNAcT gene: the native enzyme; the lumenal domain of GalNAcT fused to the cytoplasmic and transmembrane domains of N-acetylglucosaminyltransferase I (GNT); and the transmembrane and lumenal domains of GalNAcT fused to the cytoplasmic domain of the Iip33 form of human invariant chain in order to retain the enzyme in the endoplasmic reticulum (ER). Immunoelectron microscopic analysis with anti-myc revealed that GalNAcT/myc was present throughout the Golgi stack, the GNT/GalNAcT/myc form was restricted primarily to the medial Golgi cisternae, and the Iip33/GalNAcT/myc form was restricted to the ER. Cells transfected with each of the three constructs contained high levels of GM2 synthase activity in vitro, but only the GalNAcT/myc form and the GNT/GalNAcT/myc forms were able to synthesize the GM2 product in vivo. The enzyme produced by all three constructs was present in the transfected cells in a disulfide bonded form having a molecular size consistent with that of a homodimer or higher aggregate.

Animals↗
PubMed1996

Dissemination of clinical results. Mastectomy versus lumpectomy and radiation therapy.

OBJECTIVES: This study is an assessment of the extent to which clinical findings concerning mastectomy versus lumpectomy with radiation treatment have been disseminated in practice over time. METHODS: The authors examined the use of breast-conserving surgery followed by radiation therapy as an alternative treatment to mastectomy for early-stage breast cancer by analyzing 5 years (1986-1990) of inpatient and outpatient claims data from four insurers: Medicare, Medicaid, Blue Cross of Western Pennsylvania, and Pennsylvania Blue Shield. The 9,288 women who were eligible for either a lumpectomy or mastectomy during the study period represented approximately 90% of south western Pennsylvania's adult female population. Given the efficacy of both procedures, the authors expected a trend toward more BCS. RESULTS: By 1990, the use of lumpectomy increased significantly to 42.4% from 35.2%. The choice of lumpectomy was associated with younger women, private health insurance, absence of axillary node metastases, and treatment in urban hospitals. The authors also found, however, that only 45.3% of women with Medicaid coverage who had a lumpectomy during the study period received the requisite follow-up radiation therapy, compared with 77.5% of private insurance subscribers and 88.1% of Medicare beneficiaries. This finding is troubling even though there was substantially more compliance in the later years of the study, with 60.0% of eligible Medicaid beneficiaries receiving follow-up radiation therapy in 1990. CONCLUSIONS: This research illustrates the usefulness of administrative claims data in describing trends and practice patterns as well as the need for a different type of research to discover the reasons for the lack of compliance with treatment protocols by women or physicians.

Adult↗
PubMed1995

Are small firms greater health risks?

To test whether use of health care services is a function of firm size, we analyzed a three-year database (1988-1990) of private insurance claims, representing 28,990 firms and approximately 1.4 million subscribers in western Pennsylvania. In this database both small and large firms had higher medically underwritten costs than mid-size firms had. Furthermore, risk-pooling alternatives that included small companies had a lower cost per subscriber than the risk pools that included large companies, especially companies of more than 500 contract holders. Age, sex, health status, and the types of hospitals used for inpatient care of pooled subscribers, in combination, were found to be the important determinants of costs. With risk adjustment based on these factors to correct for adverse risk selection, community rating can be a feasible approach to increasing the affordability and accessibility of health insurance to the majority of those who lack it.

Adult↗
PubMed1994

Cloned beta 1,4 N-acetylgalactosaminyltransferase synthesizes GA2 as well as gangliosides GM2 and GD2. GM3 synthesis has priority over GA2 synthesis for utilization of lactosylceramide substrate in vivo.

Earlier studies reached conflicting conclusions as to the ability of the beta 1,4 N-acetylgalactosaminyltransferase (GalNAc-T) that synthesizes gangliosides GM2 and GD2 to also produce gangliotriosylceramide (GA2). We constructed an experimental system in which to address this question. Wild type Chinese hamster ovary (CHO) cells contain ganglioside GM3 as the most complex glycosphingolipid (GSL), whereas the CHO glycosylation mutant Lec2, which is deficient in sialylation, accumulates lactosylceramide with little GM3 being produced. We transfected both cell types with a plasmid containing a cloned GalNAc-T. Whereas transfected CHO cells produced GM2 as the major complex GSL, the major product in transfected Lec2 cells was GA2. Both types of transfected cells but not the untransfected cells expressed the transfected gene and contained high levels of enzyme activity for synthesizing both GM2 and GA2 in vitro. In summary, these results indicate that this enzyme can in fact synthesize GA2 as well as GM2 and GD2. In addition, these findings suggest that in CHO cells the synthesis of GM3 in vivo has priority over GA2 synthesis for utilization of the substrate lactosylceramide, resulting in little GA2 being produced even though GalNAc-T is present and active. Thus, competition for substrate between glycosylation pathways may have profound effects on the GSL pattern of cells.

Animals↗
PubMed1994

Transport of newly synthesized glucosylceramide to the plasma membrane by a non-Golgi pathway.

High-gradient magnetic affinity chromatography (HIMAC) has been used to obtain highly enriched plasma membranes, free of intracellular membrane contaminants, from cultured Chinese hamster ovary (CHO) cells in yields of > or = 80%. Using this procedure we have characterized the transport of glucosylceramide (GlcCer) and the ganglioside GM3 to the plasma membrane. Newly synthesized GlcCer reaches the plasma membrane in 7.2 min, whereas GM3 requires 21.5 min to reach the plasma membrane. Brefeldin A prevents transport of newly synthesized GM3 and sphingomyelin to the plasma membrane but has no effect on the transport of GlcCer. Similarly, incubation of CHO cells at 15 degrees C blocks transport of GM3 and sphingomyelin to the plasma membrane but has no effect on GlcCer movement. We propose that carrier-mediated transport accounts for a major fraction of the plasma membrane GlcCer. Pulse-chase studies with either [3H]glucose or [3H]palmitate indicate that newly synthesized GlcCer which has reached the plasma membrane is not utilized for the synthesis of GM3 but is instead rapidly either degraded or converted into an as yet unidentified product. Our results indicate that in addition to serving as a precursor for higher glycosylation in the Golgi, a major fraction of newly synthesized GlcCer is rapidly transported to the plasma membrane by a non-Golgi pathway and then rapidly turned over.

Animals↗
PubMed1994

Using Medicare claims for outcomes research.

Medicare claims databases have several advantages for use in constructing episodes of care for outcomes research. They are population-based, relatively inexpensive to obtain, include large numbers of cases, and can be used for long-term follow-up. However, the sheer size of these claims databases, along with their primarily administrative (as opposed to clinical) nature, requires that researchers take special care in using them. The 10 PORTs using Medicare claims provided information on their approach to several key issues in working with these data, including: 1) identifying the index cases or patient cohorts to be studied; 2) defining the length of the episode; and 3) measuring outcomes. This paper reports the experience and knowledge gained by these PORTs in using these claims to create and analyze episodes of care.

Databases, Factual↗
PubMed1994

PMC Patient Severity Scale: derivation and validation.

OBJECTIVE: This study describes the derivation and validation of the Patient Management Category (PMC) Severity Scale, which provides a method of assessing the overall severity of a hospitalized patient's illnesses, based on the patient's unique clinical conditions, their interaction, and the resultant, combined risk of morbidity and mortality. DATA SOURCES: Derivation of the PMC Severity Scale was based on clinical judgment together with empirical analysis of more than a half million patients discharged from acute care hospitals in Maryland during 1989. The scale was validated by using two distinct calendar years (1988 and 1990) of patients data from the same Maryland hospitals and a six-month patient database from California (1990). STUDY DESIGN: The PMC Severity Scale is an ordinal scale with seven levels: Level 7 represents the greatest likelihood of death and major disease burden. The scale quantifies the severity of each of the patient's disease(s) and accounts for the effect of all coexisting conditions and complications. DATA EXTRACTION METHODS: Publicly available, statewide all-payer claims databases were acquired from Maryland and California. PRINCIPAL FINDINGS: The independent relationships between the PMC Severity Scale with mortality and with length of stay are statistically different across severity levels within each population tested, but the relationships are statistically similar over time. Further, the PMC Severity Scale was determined to be a stable predictor of mortality and LOS across two diverse geographic regions. CONCLUSIONS: Since the severity of a patient's illness is one of the factors that influences the outcomes of care, the PMC Severity Scale can be used successfully as a risk adjustment tool in a variety of quality applications.

California↗
PubMed1993

Determination of plasma membrane lipid mass and composition in cultured Chinese hamster ovary cells using high gradient magnetic affinity chromatography.

We have utilized wheat germ agglutinin conjugated to iron/dextran particles in conjunction with high gradient magnetic affinity chromatography (HIMAC) to prepare plasma membranes from cultured cells. Membrane-impermeable succinimidyl esters inactivate alkaline phosphodiesterase 1 (APDE-1) and were used to establish the proportion of APDE-1 expressed at the cell surface. The yield of inhibitable APDE-1 provides an accurate indication of plasma membrane yield, which was > 90% for Chinese hamster ovary (CHO) cells. Plasma membranes prepared by HIMAC contained < 5-13% of endoplasmic reticulum, Golgi, mitochondria, lysosomes, or endosomes. Pulse-chase experiments performed with the alpha 5 beta 1 integrin receptor confirmed the high yield of plasma membrane and demonstrated the utility of this procedure for examining trafficking of proteins to and from the plasma membrane. We determined the lipid content of plasma membranes prepared by HIMAC. CHO plasma membranes contain 49% of total cellular phospholipid, 69% of sphingomyelin, and 64% of cholesterol. Phosphatidylserine was the only glycerophospholipid highly enriched (71%) in the retained fraction. The glycosphingolipids lactosylceramide and ganglioside GM3 were enriched in the plasma membrane fraction to the same extent as sphingomyelin. The major fraction of the glycosphingolipid precursors glucosylceramide and ceramide was localized to intracellular membranes. These findings indicate that the plasma membrane of CHO cells contains approximately half of the total cellular phospholipids and an even higher percentage of sphingomyelin and cholesterol. The high efficiency and rapidity of this isolation procedure should aid the analysis of plasma membrane components significantly.

Animals↗
PubMed1993

An Ambulatory Service Weighting System: making sense out of millions of ambulatory claims.

This paper describes a cost-based relative value scale to use in measuring the intensity and costs of hospital services, regardless of the place of service--inpatient or outpatient. The Pittsburgh Research Institute's AMBULATORY SERVICE WEIGHTING SYSTEM (ASWS) is a service-driven relative value scale. The major components of the system are: 1) a classification of services and procedures provided in ambulatory settings; 2) a cost-based relative intensity weight for each service; and 3) a computerized system that assigns a relative weight to each ambulatory patient based on the specific services recorded on the patient bill and rendered during a particular visit or in multiple encounters. Computerized decision rules are also incorporated as edits to adjust for inconsistent revenue or procedure coding practices. The system basically standardizes the millions of outpatient claims received by third party payors so that intensity can be measured consistently across providers, and payment systems can be modified accordingly. The ASWS identifies service intensity on the same relative value scale as inpatient care, and thus, it can serve as a site-neutral classification of health care services for prospective payment and utilization management as well as a measure of resource intensity.

Ambulatory Care↗
PubMed1992

Endogenous glycosphingolipids move to the cell surface at a rate consistent with bulk flow estimates.

The bulk flow model of intracellular trafficking predicts that forward transport from the ER through the Golgi to the plasma membrane proceeds by default without a special signal being required (Wieland, F.T., Gleason, M. L., Serafini, T. A., and Rothman, J. E. (1987) Cell 50, 289-300). We tested a crucial prediction of this model, which is that the endogenous lipid components of the transport vesicles would reach the plasma membrane at the rapid rate of bulk flow. The rate at which endogenous glycosphingolipids moved from the ER through the Golgi to the plasma membrane was determined in Chinese hamster ovary cells using metabolic labeling with tritiated palmitate and oxidation of cell surface ganglioside NeuAc alpha 2----3Gal beta 1----4Glc beta 1----4Cer (GM3) with periodate. Whereas radioactive precursor became incorporated into ceramide and glucosyl ceramide without a detectable lag, synthesis of labeled lactosyl ceramide and ganglioside GM3 did not begin until 5-6 min and 11-12 min, respectively, after addition of labeled precursor. Labeled GM3 reached the plasma membrane 5-6 min following its synthesis. Overall, approximately 18 min transpired from the time that the ceramide precursor was synthesized in the ER until labeled GM3 reached the plasma membrane. These results indicate that lipid transport vesicles move rapidly to the plasma membrane at a rate consistent with bulk flow estimates.

Animals↗
PubMed1992

Sexual assault: review of a national model protocol for forensic and medical evaluation. New Hampshire Sexual Assault Medical Examination Protocol Project Committee.

A national hospital/community model protocol was developed for the forensic and medical examination of victims of sexual assault. This review is designed to assist states in the development of sexual assault protocols. Controversial issues were addressed, including the collection of hair evidence, the importance of semen, mandatory reporting, pregnancy testing and prophylaxis, and sexually transmitted diseases including human immunodeficiency virus. The current role of DNA profiling is reviewed. These issues at the interface of medicine, forensic science, victim advocacy, and the law are analyzed. Representatives of the medical, legal, law enforcement, victim advocacy, and forensic science communities contributed to the development of the protocols at the national and state levels. The importance of a collaborative effort is emphasized. The broad protocol goals are to minimize the physical and psychological trauma to the victim while maximizing the probability of collecting and preserving physical evidence for potential use in the legal system.

Clinical Protocols↗
PubMed1991

Ganglioside GM1 and asialo-GM1 at low concentration are preferentially incorporated into the gel phase in two-component, two-phase phosphatidylcholine bilayers.

Multilamellar liposomes composed of 1:1 dielaidoylphosphatidylcholine: dipalmitoylphosphatidylcholine at 20 degrees C contain laterally separated gel and liquid-crystalline phases that can be identified by electron microscopy in freeze-etch replicas on the basis of their distinctive morphology. Visualization of marker proteins that specifically bind to glycosphingolipids included in these liposomes has revealed that, at 1 mol % or less, the ganglioside GM1 and the neutral asialo-GM1 derived from it are localized within the gel-phase regions exclusively. Increasing the mole fraction of the glycosphingolipids results in the appearance of marker in the fluid-phase regions. Another neutral glycosphingolipid, Forssman, does not display a phase preference and is found in both phases at a low mole percent. The phase preference of these three glycosphingolipids depends primarily upon interactions between the hydrophobic moieties of these molecules and the matrix phosphatidylcholines.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Kinetics of transition of anhydrous carbamazepine to carbamazepine dihydrate in aqueous suspensions.

When suspended in water, anhydrous carbamazepine (C15H12N2O; 1) was transformed to carbamazepine dihydrate (C15H12N2O.2H2O; 2). Compound 1 was dispersed in water at 25 degrees C, and an aliquot of the slurry was taken at periodic intervals and immediately filtered under conditions which removed all the physically bound water from the solid. The weight fractions of 1 and 2 in the solid were quantified by two methods: (a) by determining the weight loss on drying the solid at 60 degrees C under reduced pressure to a constant weight and (b) by a quantitative powder X-ray diffraction technique. There was good agreement between the above two methods. More than 95% (w/w) of 1 was converted to 2 in 1 h and the decrease in the weight fraction of 1 with time was approximately a first-order process.

Carbamazepine↗
PubMed1991

Defining the major trauma patient and trauma severity.

Criteria for defining the major trauma patient have been specified by physicians using Injury Patient Management Categories (PMCs), a computerized classification that can be used effectively with routinely collected discharge abstract data from non-trauma center hospitals as well as trauma centers. These criteria for major trauma not only include the more severe and complex single injuries, but also include criteria for identifying combinations of injuries that require tertiary level care. Major trauma patients identified as tertiary using PMCs are compared with existing and frequently used measures of injury severity such as AIS and ISS. Analyses suggest that the Injury PMCs identify major trauma patients accurately and more specifically than other indicators of severity that are commonly used. In addition, unlike other measures that are generally limited to registries, PMC tertiary patient criteria differentiate major trauma patients at both trauma centers and non-trauma centers without additional data collection. Using this method thus facilitates trauma systems evaluation and patient outcome assessment.

Databases, Factual↗