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Biomedical subjects

A E Roth

Publications and source records attributed to A E Roth.

12 recordsLinked to original sources
PubMed2006

Utilizing list exchange and nondirected donation through 'chain' paired kidney donations.

In a list exchange (LE), the intended recipient in an incompatible pair receives priority on the deceased donor waitlist (DD-waitlist) after the paired incompatible donor donates a kidney to a DD-waitlist candidate. A nondirected donor's (ND-D) kidney is usually transplanted directly to a DD-waitlist candidate. These two established practices would help even more transplant candidates if they were integrated with kidney paired donation (KPD). We consider a scenario in which the donor of an LE intended recipient (LE-IR) donates to a compatible KPD intended recipient (KPD-IR), and the KPD donor (KPD-D) donates to the waitlist (an LE-chain). We consider a similar scenario in which an ND-D donates to a KPD-IR and the KPD-D donates to the DD-waitlist (an ND-chain). Using data derived from the New England Program for Kidney Exchange (NEPKE) and from OPTN/SRTR recipient-donor distributions, simulations are presented to evaluate the potential impact of chain exchanges coordinated with KPD. LE donors (LE-D) and ND-D who are ABO-O result in the highest number of additional transplants, while results for ABO-A and B donors are similar to each other. We recommend that both LE and ND donations be utilized through chain exchanges.

ABO Blood-Group System↗
PubMed2006

Beneficial non-targeted effects of BCG--ethical implications for the coming introduction of new TB vaccines.

Non-targeted effect of BCG: Several recent studies suggest that BCG has beneficial non-targeted effects on general child survival in low-income countries. Studies of the effect of BCG on morbidity in humans are scarce; some found a positive effect of BCG and others show no effect. Non-targeted effects of vaccines-possible bias and confounding: The major argument against comparing vaccinated and unvaccinated groups is that there is a beneficial social selection bias for vaccinated children-the "Healthy vaccinee effect". However, controlling for various social and health-related background factors in the survival analyses had no effect on the estimates, making this source of bias less likely. A more powerful argument that the findings are not due to the healthy vaccinee effect is that differential non-targeted effects of other vaccines have been observed; diphteria-tetanus-pertussiss vaccination has marked negative effects on child survival, whereas measles vaccine has a positive effect in several studies. Several studies have shown better survival for children reacting to their BCG vaccination with a BCG scar or tuberculin skin test reaction (TST). It could be argued that the reacting children were immunologically stronger and therefore more likely to survive-the "Healthy reactor effect". However, recent findings show that a BCG scar and a TST reaction depend to a large extent on the vaccination technique. Hence, the BCG responses may reflect a true vaccine effect and not merely the health status of the children. Since HIV-1 has been shown to suppress both TST and BCG scar reaction in response to BCG, it is an obvious contributor to the healthy reactor effect, but excluding deaths of children with HIV-1 infection from analysis did not affect the beneficial effect of having a positive TST. Excluding children exposed to tuberculosis (TB) in the household did not affect the estimates either. Furthermore, there are strong sex-differential effects of BCG in both mortality and morbidity data, BCG being more beneficial for girls. These observations cannot consistently be explained by the healthy vaccinee or healthy reactor effects. Ethical implications: For future TB-vaccine studies, these findings imply that: These recommendations might be considered to delay or to be a too large obstacle for the development and trials of new TB vaccines. However, most of the non-targeted beneficial effects of BCG have been observed in children below 2 years of age, which is not a long follow-up time in a TB-vaccine trial. Furthermore, considering the difficulty in setting the TB diagnose in children and the lack of reliable TB-protection markers, it does not seem unreasonable to argue for monitoring of general morbidity and survival in future TB-vaccine trials.

BCG Vaccine↗
PubMed1997

The effects of the change in the NRMP matching algorithm. National Resident Matching Program.

CONTEXT: Following 2 years of heated controversy about the resident match, the National Resident Matching Program (NRMP) recently voted to replace the existing matching algorithm with a newly designed applicant-proposing algorithm. OBJECTIVE: To design an applicant-proposing algorithm for the match and compare it with the existing NRMP algorithm to determine how many applicants and residency programs could be expected to receive better or worse matches from the 2 algorithms, how the different algorithms influence the opportunity for strategic behavior, and what advice can be given to participants. DESIGN: Computational experiments compared the newly designed applicant-proposing algorithm with the existing NRMP algorithm on the rank order lists (ROLs) submitted by all applicants and residency programs in the 1987 and 1993 through 1996 NRMP matches. RESULTS: Differences in the matchings produced by the 2 algorithms are small: fewer than 1 in 1000 applicants would have received a different match. Most (but not all) of the few applicants who are matched to different positions by the 2 algorithms do better when the applicant-proposing algorithm is used; the opposite is true for programs. Opportunities for profitable strategic behavior are very rare for both applicants and programs under either algorithm. With either algorithm, both applicants and programs can be advised that trying to get a preferred match by behaving strategically is far more likely to harm than to help them. CONCLUSIONS: The existing NRMP algorithm and the newly designed applicant-proposing algorithm perform similarly. Both algorithms make it sensible for applicants and residency programs to arrange their ROLs based solely on their preferences for possible matches. The choice of algorithms will systematically affect the matches of only a small group of applicants (<0.1%). The NRMP's recent decision to use the applicant-proposing algorithm starting in 1998 reflects a judgment about the impact of this difference on applicants and programs.

Algorithms↗
PubMed1994

The two nonallelic Xenopus insulin genes are expressed coordinately in the adult pancreas.

We have previously shown that the two nonallelic insulin genes in Xenopus laevis are expressed differentially during neurulation in prepancreatic embryos (Shuldiner et al., 1991, Proc. Natl. Acad. Sci. USA 88, 7679-7683). We now examine pancreatic expression with alterations in ambient temperature, glucose administration, fasting and feeding, somatostatin analog treatment, as well as during postmetamorphic growth. Insulin I and II mRNAs were quantitated by slot blot hybridization with specific probes and were expressed as the number of copies (x 10(8)) per 5 micrograms total RNA +/- SEM. Frogs maintained at 12 degrees showed no significant changes when compared to frogs maintained at 20 degrees. There was a coordinate decrease in insulin I and II mRNA levels in frogs maintained at 29 degrees (Ins I 20, 3.41 +/- 0.34 vs Ins I 29, 2.39 +/- 0.17; Ins II 20, 2.59 +/- 0.36 vs Ins II 29, 1.67 +/- 0.09; P < 0.05). When compared to fasting animals, both insulin I and II mRNA levels decreased slightly in frogs given repeated intraperitoneal injections of glucose and in those fed ad libitum; there were no changes after a single dose of glucose or in frogs given somatostatin. When compared to young frogs (6 to 24 months), older frogs (36 months) had higher insulin I and II mRNA levels (e.g., Ins I 6mo, 2.14 +/- 0.15 vs Ins I 36mo, 3.68 +/- 0.43; Ins II 6mo, 1.21 +/- 0.06 vs Ins II 36mo, 3.26 +/- 0.38; P < 0.05). Further, there was a modest reduction in the percentage of insulin I mRNA with aging (e.g., 6 months 63.6 +/- 3.1% vs 36 months 53.9 +/- 2.7%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A natural experiment in the organization of entry-level labor markets: regional markets for new physicians and surgeons in the United Kingdom.

The histories of seven regional markets for new physicians and surgeons in the United Kingdom are considered. Like the American market, these markets have experienced failures that led to the adoption of centralized market mechanisms. Because different regions employ different centralized mechanisms, these markets provide a test of the hypothesis that the success of the American market is related to the fact that it produces matches which are stable in the sense that no two agents mutually prefer to be matched to one another than to their assigned partners. Even in the more complex U.K. markets, this kind of stability plays an important role. Centralized markets that produced unstable matches in environments in which agents could act upon instabilities fared no better than the decentralized markets they replaced.

Algorithms↗
PubMed1990

New physicians: a natural experiment in market organization.

The National Resident Matching Program is a centralized clearinghouse through which new medical graduates in the United States obtain their first positions. The history of this market, from the market failures that the centralized system was designed to address, to the present, is discussed, and a hypothesis about the behavior of such markets is presented. New evidence is then presented from a set of similar centralized markets in the United Kingdom. Because some of these latter markets have failed, while others have succeeded, they provide a natural experiment that permits the hypothesis to be tested. The new evidence also suggests directions in which modifications of existing procedures might be considered.

Algorithms↗
PubMed1970

Plasmodium ovale malaria acquired in Viet-Nam.

Four cases of Plasmodium ovale malaria are reported among US servicemen stationed in Viet-Nam between January 1966 and March 1969. Taken together with other cases cited by the authors, these provide strong evidence of the existence (sometimes disputed) of this Plasmodium in continental South-East Asia.None of the men had served in any other area of endemic malaria and their travel and medical histories suggest that all 4 infections were acquired by mosquito transmission. They constitute only 0.066% of the 6036 malaria cases reported among servicemen returning from Viet-Nam during this period and represent only 0.11% of the blood films from 3686 individuals examined at the US National Malaria Repository during the same period.Serological testing for malaria antibodies with the indirect fluorescent technique corroborated the diagnosis of P. ovale in 1 case. Speciation was not possible in the other 3 cases since titres to P. vivax and P. ovale antigens were identical. Only 1 of the patients reported previous experience with vivax malaria.Most of the parasites seen in thin blood films were developing trophozoites and immature schizonts; ring forms and gametocytes were rare; mature schizonts were not found. The morphology of the parasites was typical of P. ovale, with more than 50% of the infected cells showing fimbriations, an oval shape or both.

Adult↗