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Kinetics of synthesis and degradation of chicken liver xanthine dehydrogenase
The role of synthesis and degradation in controlling enzyme
concentrations was studied.
Concentrations of chloride and arginine were determined for
blood and liver at various stages of development from the embryo to
the 8 day old chicken. The chloride concentrations were used to
obtain the volume of extracellular blood in the liver. Using these
values together with the data for total arginine, it was possible to
calculate the intracellular and extracellular arginine concentrations
in the liver. Extracellular arginine represented. 19%, 15% and 26%
of the total arginine in the 14 day embryo, 1 day old. chick and 8 day
old chick respectively.
The kinetics of incorporation of L-(guanido- 14 C)-arginine and.
L-valine- 14 C(u) into the blood amino acid pool and intracellular liver
amino acid pool of the chick during various stages of development were measured. Intravenous injection of isotopic amino acid leads to results similar to a pulse labeling pattern, since more than 80% of
the tracer is consumed after 60 minutes. The time-integrated radioactive
amino acid pools were determined for each age of chick.
Thirty minutes after injection of radioactive arginine or valine,
40% of the radioactivity remaining in the amino acid pools is found in
compounds other than arginine or valine. These results are indicative
of probable matabolism of these amino acids into other compounds.
Xanthine dehydrogenase concentrations and the wet weight of
liver also were measured during development. The liver wet weight
increases most rapidly in the embryo. The enzyme activity is low in
the embryo, rises rapidly upon hatching and reaches a high level by
the eighth day after hatch.
The rate constants of synthesis and degradation were determined
for xanthine dehydrogenase during chick liver development, by purifying
the labeled enzyme and measuring the rate of incorporation of
label from arginine or valine into the protein. The rate constants for
synthesis using L-(guanido- 14 C)-arginine are 3.7 x 10- 12
2.8 x 10 12 and. 0.8x 10-12 moles XDH per minute per gram of liver
for the 8 day chick, 1 day chick and 14 day embryo respectively. The
t l/2 values for the 8 day chick, 1 day chick and 14 day embryo are 17,
[infinity], and [infinity] hours respectively. When L-valine- 14 C(u) is used as substrate, the rate constant for synthesis is 7. 0 x 10-12 moles XDH per
minute per gram of liver for the 1 day chick. The rate of synthesis
of XDH relative to the rate of synthesis of total soluble protein for the
1 day chick is 1. 7 for valine as substrate and. 0. 9 for argiriine. The
role of synthesis and degradation in determining enzyme concentrations
is discussed. Also included. is a critique of the methodology
Association Between Race, Neighborhood, and Medicaid Enrollment and Outcomes in Medicare Home Health Care
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142524/1/jgs15082_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142524/2/jgs15082.pd
Year 1 of the Bundled Payments for Care Improvement-Advanced model
BACKGROUND: The Center for Medicare and Medicaid Innovation launched the Medicare Bundled Payments for Care Improvement-Advanced (BPCI-A) program for hospitals in October 2018. Information is needed about the effects of the program on health care utilization and Medicare payments.
METHODS: We conducted a modified segmented regression analysis using Medicare claims and including patients with discharge dates from January 2017 through September 2019 to assess differences between BPCI-A participants and two control groups: hospitals that never joined the BPCI-A program (nonjoining hospitals) and hospitals that joined the BPCI-A program in January 2020, after the conclusion of the intervention period (late-joining hospitals). The primary outcomes were the differences in changes in quarterly trends in 90-day per-episode Medicare payments and the percentage of patients with readmission within 90 days after discharge. Secondary outcomes were mortality, volume, and case mix.
RESULTS: A total of 826 BPCI-A participant hospitals were compared with 2016 nonjoining hospitals and 334 late-joining hospitals. Among BPCI-A hospitals, the mean baseline 90-day per-episode Medicare payment was 78 per quarter. Among nonjoining hospitals, the mean baseline 90-day per-episode Medicare payment was 26 per quarter (difference between nonjoining hospitals and BPCI-A hospitals, 26,807; the change in the quarterly trends as compared with baseline was 82 [95% CI, 41 to 122] per quarter; P\u3c0.001; 0.3% of the baseline payment). There were no meaningful differences in the changes with regard to readmission, mortality, volume, or case mix.
CONCLUSIONS: The BPCI-A program was associated with small reductions in Medicare payments among participating hospitals as compared with control hospitals. (Funded by the National Heart, Lung, and Blood Institute.)
Association of physician group practice participation in bundled payments with patient selection, costs, and outcomes for joint replacement
IMPORTANCE: Medicare\u27s Bundled Payments for Care Improvement (BPCI) program, which ran from 2013 to 2018, was an important experiment in physician-focused alternative payment models. However, little is known about whether the program was associated with better quality or outcomes or lower costs.
OBJECTIVE: To determine whether participation in BPCI among physician group practices was associated with advantageous or deleterious changes in costs or patient outcomes.
DESIGN SETTING AND PARTICIPANTS: This cross-sectional study used 2013 to 2017 Medicare files and difference-in-differences (DID) models to compare the change over time in Medicare payments, patient selection, and clinical outcomes between 91 orthopedic groups in BPCI Model 2 and 169 propensity-matched controls for patients undergoing joint replacement. Analyses were performed between December 2019 and February 2021.
EXPOSURES: Voluntary participation in BPCI.
MAIN OUTCOMES AND MEASURES: The primary outcome was 90-day Medicare payments; secondary outcomes were patient selection (volume, comorbidities) and clinical outcomes (30-day and 90-day emergency department visits, readmissions, mortality, and healthy days at home).
RESULTS: There were 74 343 patient episodes in the baseline period and 102 790 during the intervention in BPCI practices, and 88 147 patient episodes in the baseline period and 120 253 during the intervention in control practices; 291 214 of 461 598 (63.1%) patients were women, and 419 619 (90.9%) were White. At baseline, mean episode payments among BPCI-participating practices were 15 320 during the intervention, while control practices decreased from 16 170 (DID, -1565 to -$795;
CONCLUSIONS AND RELEVANCE: Group practice participation in BPCI for joint replacement was associated with reduced Medicare payments and improvements in clinical outcomes
Geographic Variation in Out‐of‐Pocket Expenditures of Elderly Medicare Beneficiaries
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107567/1/jgs12834.pd
How Good a Deal Was the Tobacco Settlement?: Assessing Payments to Massachusetts
We estimate the increment in Massachusetts Medicaid program costs attributable to smoking from December 20, 1991, to 1998. We describe how our methods improve upon earlier estimates of analogous costs at the national level. Current costs to the Massachusetts Medicaid program approximate the payments to Massachusetts under the tobacco settlement of November 1998. Whether these payments are viewed as appropriate compensation for Medicaid costs over time depends upon the rate of increase in future health care costs, the rate of decline in smoking, the proportion of smoking that should be attributed to the actions of the tobacco companies and the liklihood that state would have prevailed at trial. The costs to the Medicaid program are dwarfed by the internal costs to smokers themselves.
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