Patient and Provider Perspectives on Processes of Engagement in Outpatient Treatment for Opioid Use Disorder: A Scoping Review.

Effective treatment for opioid use disorder (OUD) is available, but patient engagement is central to achieving care outcomes. We conducted a scoping review to describe patient and provider-reported strategies that may contribute to patient engagement in outpatient OUD care delivery. We searched PubMed and Scopus for articles reporting patient and/or provider experiences with outpatient OUD care delivery. Analysis included: (1) describing specific engagement strategies, (2) mapping strategies to patient-centered care domains, and (3) identifying themes that characterize the relationship between engagement and patient-centered care. Of 3,222 articles screened, 30 articles met inclusion criteria. Analysis identified 14 actionable strategies that facilitate patient engagement and map to all patient-centered care domains. Seven themes emerged that characterize interpersonal approaches to OUD care engagement. Interpersonal interactions between patients and providers play a pivotal role in encouraging engagement throughout OUD treatment. Future research is needed to further evaluate promising engagement strategies.

Latent variable modeling to develop a robust proxy for sensitive behaviors: application to latrine use behavior and its association with sanitation access in a middle-income country.

BACKGROUND: Globally, diarrhea is a leading cause of child morbidity and mortality. Although latrines are integral for reducing enteric pathogen transmission, several studies have shown no evidence that latrine ownership improved child health. There are a number of explanations for these results. One explanation is that latrine access does not equate to latrine use. Latrine use, however, is difficult to accurately ascertain, as defecation behavior is often stigmatized. To address this measurement issue, we measure latrine use as a latent variable, indicated by a suite of psychosocial variables. METHODS: We administered a survey of 16 defecation-related psychosocial questions to 251 individuals living in rural Ecuador. We applied latent class analysis (LCA) to these data to model the probability of latrine use as a latent variable. To account for uncertainty in predicted latent class membership, we used a pseudo-class approach to impute five different probabilities of latrine use for each respondent. Via regression modeling, we tested the association between household sanitation and each imputed latrine use variable. RESULTS: The optimal model presented strong evidence of two latent classes (entropy = 0.86): consistent users (78%) and inconsistent users (22%), predicted by 5 of our 16 psychosocial variables. There was no evidence of an association between the probability of latrine use, predicted from the LCA, and household access to basic sanitation (OR = 1.1, 95% CI = 0.6-2.1). This suggests that home access to a sanitation facility may not ensure the use of the facility for every family member at all times. CONCLUSION: Effective implementation and evaluation of sanitation programs requires accurate measurement of latrine use. Psychosocial variables, such as norms, perceptions, and attitudes may provide robust proxy-measures. Future longitudinal studies will help to strengthen the use of these surrogate measures, as many of these factors may be subject to secular trends. Additionally, subgroup analyses will elucidate how our  proxy indicators of latrine defecation vary by individual-level characteristics.

A re-activation model for 169Yb intensity modulated brachytherapy sources accounting for spatiotemporal isotopic composition.

BACKGROUND: Intensity modulated brachytherapy based on partially shielded intracavitary and interstitial applicators is possible with a cost-effective 169Yb production method. 169Yb is a traditionally expensive isotope suitable for this purpose, with an average γ-ray energy of 93 keV. Re-activating a single 169Yb source multiple times in a nuclear reactor between clinical uses was shown to theoretically reduce cost by approximately 75% relative to conventional single-activation sources. With re-activation, substantial spatiotemporal variation in isotopic source composition is expected between activations via 168Yb burnup and 169Yb decay, resulting in time dependent neutron transmission, precursor usage, and reactor time needed per re-activation. PURPOSE: To introduce a generalized model of radioactive source production that accounts for spatiotemporal variation in isotopic source composition to improve the efficiency estimate of the 169Yb production process, with and without re-activation. METHODS AND MATERIALS: A time-dependent thermal neutron transport, isotope transmutation, and decay model was developed. Thermal neutron flux within partitioned sub-volumes of a cylindrical active source was calculated by raytracing through the spatiotemporal dependent isotopic composition throughout the source, accounting for thermal neutron attenuation along each ray. The model was benchmarked, generalized, and applied to a variety of active source dimensions with radii ranging from 0.4 to 1.0 mm, lengths from 2.5 to 10.5 mm, and volumes from 0.31 to 7.85 mm3, at thermal neutron fluxes from 1 × 1014 to 1 × 1015 n cm-2 s-1. The 168Yb-Yb2O3 density was 8.5 g cm-3 with 82% 168Yb-enrichment. As an example, a reference re-activatable 169Yb active source (RRS) constructed of 82%-enriched 168Yb-Yb2O3 precursor was modeled, with 0.6 mm diameter, 10.5 mm length, 3 mm3 volume, 8.5 g cm-3 density, and a thermal neutron activation flux of 4 × 1014 neutrons cm-2 s-1. RESULTS: The average clinical 169Yb activity for a 0.99 versus 0.31 mm3 source dropped from 20.1 to 7.5 Ci for a 4 × 1014 n cm-2 s-1 activation flux and from 20.9 to 8.7 Ci for a 1 × 1015 n cm-2 s-1 activation flux. For thermal neutron fluxes ≥2 × 1014 n cm-2 s-1, total precursor and reactor time per clinic-year were maximized at a source volume of 0.99 mm3 and reached a near minimum at 3 mm3. When the spatiotemporal isotopic composition effect was accounted for, average thermal neutron transmission increased over RRS lifetime from 23.6% to 55.9%. A 28% reduction (42.5 days to 30.6 days) in the reactor time needed per clinic-year for the RRS is predicted relative to a model that does not account for spatiotemporal isotopic composition effects. CONCLUSIONS: Accounting for spatiotemporal isotopic composition effects within the RRS results in a 28% reduction in the reactor time per clinic-year relative to the case in which such changes are not accounted for. Smaller volume sources had a disadvantage in that average clinical 169Yb activity decreased substantially below 20 Ci for source volumes under 1 mm3. Increasing source volume above 3 mm3 adds little value in precursor and reactor time savings and has a geometric disadvantage.

What is the most effective and safest Non-steroidal anti-inflammatory drug for treating osteoarthritis in patients with comorbidities?

INTRODUCTION: Understanding what the most effective and safe non-steroidal anti-inflammatory drug (NSAID) is for managing osteoarthritis (OA) is complicated. OA is prevalent worldwide and people living with OA commonly have multiple comorbidities. The efficacy and safety of NSAIDs in a patient are influenced by their intrinsic and extrinsic factors. Current guidelines recommend the lowest dose for the shortest duration, monitoring patients for risk factors and comorbidities but generally do not specify, which NSAID is most suitable for a patient with specific comorbidities. AREAS COVERED: This paper looks at the mechanism of action of all NSAIDs and reviews the current literature concerning their safety in patients with and without comorbidities. Relevant publications were identified by searching PubMed and Cochrane Library using key terms. The search was conducted from inception to 18 July 2023 and included results published before 18 July 2023. The search results and their references were then manually reviewed. EXPERT OPINION: In the paper, we determine whether the current practice of 'lowest dose for shortest duration' is in fact the best approach for prescribing NSAIDs and identify which NSAIDs are most suitable given a patient's risk factors and comorbidities. Our aim is to help guide health professionals in recommending the most suitable NSAID for each patient.

The population percentile allowance method for determining systematic spatial error tolerances for temporary intensity modulated brachytherapy.

BACKGROUND: Multiple approaches are under development for delivering temporary intensity modulated brachytherapy (IMBT) using partially shielded applicators wherein the delivered dose distributions are sensitive to spatial uncertainties in both the applicator position and shield orientation, rather than only applicator position as with conventional high-dose-rate brachytherapy (HDR-BT). Sensitivity analyses to spatial uncertainties have been reported as components of publications on these emerging technologies, however, a generalized framework for the rigorous determination of the spatial uncertainty tolerances of dose-volume parameters is needed. PURPOSE: To derive and present the population percentile allowance (PPA) method, a generalized mathematical and statistical framework to evaluate the tolerance of temporary IMBT approaches to spatial uncertainties in applicator position and shield orientation. METHODS: A mathematical formalism describing geometric applicator position and shield orientation shifts was derived that supports straight and curved applicators and applies to serial and helical rotating shield brachytherapy (RSBT) and direction modulated brachytherapy (DMBT). The PPA method entails defining the percentage of a patient population receiving a given therapy that is, allowed to receive dose-volume errors in the target volume and specified organs at risk of a defined percentage or less, then determining what combinations of applicator position and shield orientation systematic errors would be expected to produce that outcome in the population. The PPA method was applied to the use case of multi-shield helical 169 Yb-based RSBT for cervical cancer, with 45° and 180° shield emission angles. A total of 37 cervical cancer patients were considered in the population, with average (± 1 standard deviation) HR-CTV volumes of 79 cm3  ± 37 cm3 and optimized baseline treatment plans (no spatial uncertainties applied) created for each patient to meet dose-volume requirements of 85 GyEQD2 (equivalent uniform dose in 2 Gy fraction), with D2cc tolerance doses of 90 GyEQD2 , 75 GyEQD2 , and 75 GyEQD2 for bladder, rectum, and sigmoid colon, respectively. RESULTS: For the PPA requirement that 90% of cervical cancer patients receiving multi-shield helical RSBT could have a maximum dose-volume uncertainty of 10% for high-risk clinical target volume (HR-CTV) D90 (minimum dose to hottest 90%) and bladder, rectum, and sigmoid colon D2cc (minimum dose to hottest 2 cm3 ), the tolerance systematic applicator position and shield orientation uncertainties were approximately ± 1.0 mm and ± 4.25°, respectively. For ± 1.5 mm and ± 5° systematic applicator position and shield orientation tolerances, 90% of the patients considered would have a maximum dose-volume uncertainty of 12.8% or less. CONCLUSION: The PPA method was formalized to determine the temporary IMBT spatial uncertainty tolerances that would be expected to result in an allowed percentage of a population of patients receiving relative dose-volume errors above a defined percentage. Multi-shield, helical 169 Yb-based RSBT for cervical cancer was evaluated and tolerances determined, which, if applied on each treatment fraction, would represent an extreme situation. The PPA method is applicable to a variety of temporary IMBT approaches and can be used to rigorously determine the design parameters for the delivery systems such as mechanical driver motor accuracy, shield angle backlash, applicator rotation, and applicator fixation stability.

Will Residency Program Directors Look at My United States Medical Licensing Examination (USMLE) Step 1 Score During the 2022-2023 Application Cycle? A National Survey of Program Directors.

Background The 2022-2023 residency match cycle will be the first cycle that program directors will have to consider some applicants with a numerical United States Medical Licensing Examination (USMLE) Step 1 score while other applicants will only report pass/fail for USMLE Step 1. Previous studies have explored how USMLE Step 1 becoming pass/fail will alter the residency selection process, but it is not yet known when program directors from each specialty expect those changes to be implemented. Methods Residency program director's contact information was extracted from the American Medical Association (AMA) residency program site, Fellowship and Residency Electronic Interactive Database (FREIDA). Of the 5190 programs, 4877 were determined eligible for this study of which 1274 (26.8%) responded. Results Of the 1274 US residency program directors included in this survey, 77.0% do not intend to adjust their usage of USMLE Step 1 as a metric in candidate evaluation until the score is no longer reported. Conclusion Residency candidates applying during the upcoming cycle can expect the majority of residency programs will not significantly alter their previous utilization of an applicant's USMLE Step 1 score during the current 2022-2023 residency match cycle.

Mosquito mass rearing technology: a cold-water vortex device for continuous unattended separation of Anopheles arabiensis pupae from larvae.

In mass rearing of anopheline mosquitoes, pupae are usually separated from larvae on a daily basis to prevent unwanted adult emergence from trays. Depending on the device and species, 2 physical characteristics have most often been used for separation: buoyant density and size. In this report, we describe a system for continuous separation of Anopheles arabiensis larvae from pupae based on the natural difference in buoyant density and behavior between the 2 stages. We determined that temperatures 4-15 degrees C caused neither mortality nor reduction in likelihood of pupation or emergence. Separation improved as temperatures decreased down to 4 degrees C. We devised and demonstrated a 15 degrees C water vortex separator that we anticipate can process approximately 1 million larvae and pupae per hour with a < 0.3% pupal contamination rate and which operates unattended.

Efficient 169 Yb high-dose-rate brachytherapy source production using reactivation.

PURPOSE: To present and quantify the effectiveness of a method for the efficient production of 169 Yb high-dose-rate brachytherapy sources with 27 Ci activity upon clinical delivery, which have about the same dose rate in water at 1 cm from the source center as 10 Ci 192 Ir sources. MATERIALS: A theoretical framework for 169 Yb source activation and reactivation using thermal neutrons in a research reactor and 168 Yb-Yb2 O3 precursor is derived and benchmarked against published data. The model is dependent primarily on precursor 168 Yb enrichment percentage, active source volume of the active element, and average thermal neutron flux within the active source. RESULTS: Efficiency gains in 169 Yb source production are achievable through reactivation, and the gains increase with active source volume. For an average thermal neutron flux within the active source of 1 × 1014  n cm-2  s-1 , increasing the active source volume from 1 to 3 mm3 decreased reactor-days needed to generate one clinic-year of 169 Yb from 256 days yr-1 to 59 days yr-1 , and 82%-enriched precursor dropped from 80 mg yr-1 to 21 mg yr-1 . A resource reduction of 74%-77% is predicted for an active source volume increase from 1 to 3 mm3 . CONCLUSIONS: Dramatic cost savings are achievable in 169 Yb source production costs through reactivation if active sources larger than 1 mm3 are used.

A model for delivering subspecialty pediatric surgical care in low- and middle-income countries: one organization's early experience.

Delivery of humanitarian global surgical aid to low-middle income countries (LMICs) often occurs as a "fly-in, fly-out" marathon of operations. Unfortunately, the sustainability and efficacy of these missions remain questionable because they are difficult to reproduce and they have limited ability to provide peri-operative care. The goal of this project was to describe the Moore Pediatric Surgery Center (MPSC) in Guatemala City as an alternative model that provides a centralized structure to the interaction between surgical providers and patients in the operative and peri-operative periods. We also describe the Center's patient population and present feedback from surgical teams visiting the MPSC. A retrospective chart review was performed to quantify the number of patients, procedures, and post-operative complications at the MPSC between January 2011 and December 2014. We also performed a cross-sectional sociodemographic survey of MPSC patients and conducted a satisfaction survey of patients and surgical team members visiting the Center. Since 2011, the MPSC has hosted 42 surgical teams representing 7 different specialties. During its first four years, the surgery center hospital performed 2260 operations with a 1.07 % peri-operative complication rate and 0 % peri-operative mortality rate. All surgeries were performed free-of-charge to children from low-income households. Furthermore, the MPSC was rated highly among visiting team members (range 4.5-6 on a 7-point Likert scale) for quality metrics including organization, physical space, and collaboration with local staff. The MPSC represents a model for delivering multi-specialty surgical aid in low- and middle-income countries by providing modern surgical facilities with quality-assured post-operative care for the treatment of childhood surgical diseases.

Measurement error affects risk estimates for recruitment to the Hudson River stock of striped bass.

We examined the consequences of ignoring the distinction between measurement error and natural variability in an assessment of risk to the Hudson River stock of striped bass posed by entrainment at the Bowline Point, Indian Point, and Roseton power plants. Risk was defined as the probability that recruitment of age-1+ striped bass would decline by 80% or more, relative to the equilibrium value, at least once during the time periods examined (1, 5, 10, and 15 years). Measurement error, estimated using two abundance indices from independent beach seine surveys conducted on the Hudson River, accounted for 50% of the variability in one index and 56% of the variability in the other. If a measurement error of 50% was ignored and all of the variability in abundance was attributed to natural causes, the risk that recruitment of age-1+ striped bass would decline by 80% or more after 15 years was 0.308 at the current level of entrainment mortality (11%). However, the risk decreased almost tenfold (0.032) if a measurement error of 50% was considered. The change in risk attributable to decreasing the entrainment mortality rate from 11 to 0% was very small (0.009) and similar in magnitude to the change in risk associated with an action proposed in Amendment #5 to the Interstate Fishery Management Plan for Atlantic striped bass (0.006)--an increase in the instantaneous fishing mortality rate from 0.33 to 0.4. The proposed increase in fishing mortality was not considered an adverse environmental impact, which suggests that potentially costly efforts to reduce entrainment mortality on the Hudson River stock of striped bass are not warranted.

Interstitial rotating shield brachytherapy for prostate cancer.

PURPOSE: To present a novel needle, catheter, and radiation source system for interstitial rotating shield brachytherapy (I-RSBT) of the prostate. I-RSBT is a promising technique for reducing urethra, rectum, and bladder dose relative to conventional interstitial high-dose-rate brachytherapy (HDR-BT). METHODS: A wire-mounted 62 GBq(153)Gd source is proposed with an encapsulated diameter of 0.59 mm, active diameter of 0.44 mm, and active length of 10 mm. A concept model I-RSBT needle/catheter pair was constructed using concentric 50 and 75 µm thick nickel-titanium alloy (nitinol) tubes. The needle is 16-gauge (1.651 mm) in outer diameter and the catheter contains a 535 µm thick platinum shield. I-RSBT and conventional HDR-BT treatment plans for a prostate cancer patient were generated based on Monte Carlo dose calculations. In order to minimize urethral dose, urethral dose gradient volumes within 0-5 mm of the urethra surface were allowed to receive doses less than the prescribed dose of 100%. RESULTS: The platinum shield reduced the dose rate on the shielded side of the source at 1 cm off-axis to 6.4% of the dose rate on the unshielded side. For the case considered, for the same minimum dose to the hottest 98% of the clinical target volume (D(98%)), I-RSBT reduced urethral D(0.1cc) below that of conventional HDR-BT by 29%, 33%, 38%, and 44% for urethral dose gradient volumes within 0, 1, 3, and 5 mm of the urethra surface, respectively. Percentages are expressed relative to the prescription dose of 100%. For the case considered, for the same urethral dose gradient volumes, rectum D(1cc) was reduced by 7%, 6%, 6%, and 6%, respectively, and bladder D(1cc) was reduced by 4%, 5%, 5%, and 6%, respectively. Treatment time to deliver 20 Gy with I-RSBT was 154 min with ten 62 GBq (153)Gd sources. CONCLUSIONS: For the case considered, the proposed(153)Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%-44% if the clinician allows a urethral dose gradient volume of 0-5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed (153)Gd-based I-RSBT technique in reasonable treatment times.

A genetic defect in the biosynthesis of dermatan sulfate proteoglycan: galactosyltransferase I deficiency in fibroblasts from a patient with a progeroid syndrome.

A small proteoglycan that contains only a single dermatan sulfate chain is the main proteoglycan synthesized by skin fibroblasts. Fibroblasts from a patient with progeroidal appearance and symptoms of the Ehlers-Danlos syndrome have a reduced ability of converting the core protein of this proteoglycan into a mature glycosaminoglycan chain-bearing species. This abnormality is the consequence of a deficiency in galactosyltransferase I (xylosylprotein 4-beta-galactosyltransferase; EC 2.4.1.133), which catalyzes the second glycosyl transfer reaction in the assembly of the dermatan sulfate chain. The glycosaminoglycan-free core protein secreted by the patient's fibroblasts bears an unsubstituted xylose residue. The mutant enzyme is abnormally thermolabile. Preincubation of fibroblasts at 41 degrees C leads to a further reduction in the production of mature proteoglycan and affects the capacity for glycosaminoglycan synthesis on p-nitrophenyl beta-D-xyloside more strongly in the mutant than in control cells.

Complement activation in patients with renal failure as detected through the quantitation of fragments of the complement proteins C3, C5, and factor B.

Using sensitive and highly specific enzyme-linked immunosorbent assays fragments of the complement proteins C3, C5, and factor B were quantitated in patients with renal failure. During hemodialysis on new cuprophan membranes raised levels not only of C3a, but in addition of activated C3, C5a, and Ba were demonstrated. In patients with chronic renal failure and end-stage renal disease plasma concentrations of Ba and activated C3 were markedly elevated independent of hemodialysis. This finding is taken as an indication of a continuous recruitment of the alternative pathway of complement in these patients. As the detected complement protein fragments are known to exert immune regulatory functions these findings may imply that these peptides are involved in the maintenance of the immune suppressed state in renal failure.

[Renal cancer today - suspicion, diagnosis or therapy? (author's transl)]. / Der Nierenkrebs in heutiger Sicht- ein Problem der Verdachterhebung, Diagnostik oder Therapie

The present-day situation of recording and diagnosis of malignant renal tumours was investigated on 50 patients recently seen by us. It was found that the complex radiological diagnosis (composed of excretion urography, isotope nephrography, renoscintigraphy, renovasography and additional investigations) is very well suited to show renal cancer in all stages taking into consideration localisation, extent and relations to surrounding tissue. As ever, the difficulty for a clarifying diagnosis still lies in seeing the patient as early as possible. This is due to the almost exclusively uncharacteristic symptoms which, additionally, very frequently coincide with symptoms of other diseases. The only chief symptom is clearly 'painless haematuria'. Relatively large renal tumours also escape palpation. The possibility of tracing haematurias during screening tests with 'Reagnost haemoglobin' tablets is discussed.

Temperature dependence of the coupling efficiency of rat liver oxidative phosphorylation: role of adenine nucleotide translocator.

We have reinvestigated the temperature dependence of the coupling efficiency of energy conversion in isolated rat liver mitochondria. We observed that respiratory control increased with temperature. Moreover, in the same conditions, the ATP/O ratio increased. The measurement of the control coefficients of adenine nucleotide translocator on respiratory and ATP synthesis rates showed that at 28 degrees C, this translocator exerted the same control (about 0.5) on both fluxes. At 4 degrees C, it no longer exerted control on respiratory flux when its control on ATP synthesis flux came close to 1. In addition, ATP/O ratio values and control coefficients on ATP synthesis flux were bound by a unique linear relationship irrespective of temperature. In conclusion, the decrease in ATP/O ratio with temperature is a direct consequence of an increase in the kinetic control exerted by the adenine nucleotide translocator on ATP synthesis.

Glycosaminoglycan-free small proteoglycan core protein is secreted by fibroblasts from a patient with a syndrome resembling progeroid.

A male patient, 4 years 9 mo old and having progeroidal appearance, exhibited delayed mental development and multiple abnormalities of connective tissues including growth failure, osteopenia of all and dysplasia of some bones, defective deciduous teeth, loose but elastic skin, delayed wound healing with formation of thin atrophic scars, scanty scalp hair, hypotonic muscles, and hypermobile joints. Skin fibroblasts of the patient converted only about half of the core protein of the small proteodermatan sulfate to a mature glycosaminoglycan chain-bearing proteoglycan. The remaining core protein, which contained complex-type asparagine-bound oligosaccharides, was secreted with almost normal kinetics. Xylosyltransferase activity and the synthesis of other proteoglycan types were normal. Normal induction of glycosaminoglycan synthesis occurred in the presence of 1 mM, but there was very little induction in the presence of 0.01 mM p-nitrophenyl-beta-xyloside. An antibody against an N-terminal pentadecapeptide of the core protein recognized the glycosaminoglycan-free core protein from the patient less well than the chain-bearing protein treated with chondroitin ABC lyase. Though these results do not define the basic defect unambiguously, they provide the first report of a disorder being due to an abnormality in small proteoglycan biosynthesis.

[Modification of atrial natriuretic peptide (ANP) and cyclic GMP by hemofiltration and hemodialysis]. / Beeinflussung von atrialem natriuretischen Peptid (ANP) und zyklischem GMP durch Hämofiltration und Hämodialyse.

ANP and c-GMP concentrations in 7 patients with chronic renal failure (CRF) undergoing regular hemofiltration (HF) were determined. After switching to hemodialysis (HD) under identical ultrafiltration and treatment time no significant difference of the ANP and c-GMP profiles was detected, suggesting that the type of treatment does not affect ANP and c-GMP plasma levels. In both procedures a continuous decrease of ANP and c-GMP was observed. Head down tilting to compensate hypotension during HD was immediately followed by an increase in ANP and c-GMP during ultrafiltration. An acute onset of tachyarrhythmia absoluta during HD was also accompanied by a rise in ANP plasma concentrations. This demonstrates that ANP secretion is not altered in patients with CRF. Since ANP plasma levels closely correlate with intravascular volume, periodic determination of this hormone in HD/HF patients may provide diagnostic information to detect volume overload.

A novel large dermatan sulfate proteoglycan from human fibroblasts.

Human skin fibroblasts express, in addition to versican, a second large chondroitin sulfate/dermatan sulfate proteoglycan, which has been investigated with the aid of a specific antiserum in cultures of fetal fibroblasts. Its core protein, obtained after chondroitin ABC lyase treatment, exhibits an apparent molecular mass of about 740 kDa in the absence of a reducing agent whereas reduction produces two core proteins of 460 and 300 kDa, respectively. Both subunits carry one or very few dermatan sulfate chains of about 20 kDa which are of similar chemical composition irrespective of the type of subunits to which they are attached. Tryptic peptide maps of [35S]methionine-labeled core proteins indicated that both subunits are related neither to each other nor to versican, suggesting that the proteoglycan exists predominantly as a heterodimeric molecule. It is insensitive to collagenase and does not interact with hyaluronan. Pulse-chase experiments suggested that the core proteins are different gene products. Dimerization begins soon after core protein synthesis but requires more than 2 h for completion. Glycosaminoglycan synthesis occurs immediately prior to secretion. A small proportion of both subunits may be secreted in form of a monomeric proteoglycan. The heterodimeric proteoglycan is a major proteoglycan species of fetal fibroblasts. The secreted product represents 10-20% of [35S]methionine and about 5-10% of [35S]sulfate incorporated into secreted proteoglycans.