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Biomedical subjects

L Goldstein

Publications and source records attributed to L Goldstein.

At least 37 records · Page 2Linked to original sources
PubMed2000

Exposure stratified case-cohort designs.

A variant of the case-cohort design is proposed for the situation in which a correlate of the exposure (or prognostic factor) of interest is available for all cohort members, and exposure information is to be collected for a case-cohort sample. The cohort is stratified according to the correlate, and the subcohort is selected by stratified random sampling. A number of possible methods for the analysis of such exposure stratified case-cohort samples are presented, some of their statistical properties developed, and approximate relative efficiency and optimal allocation to the strata discussed. The methods are compared to each other, and to randomly sampled case-cohort studies, in a limited computer simulation study. We found that all of the proposed analysis methods performed well and were more efficient than a randomly sampled case-cohort study.

Biometry↗
PubMed2000

An efficacy and cost-effectiveness analysis of combination hepatitis B immune globulin and lamivudine to prevent recurrent hepatitis B after orthotopic liver transplantation compared with hepatitis B immune globulin monotherapy.

Orthotopic liver transplantation (OLT) for hepatitis B virus (HBV) infection was limited until recently by poor graft and patient outcomes caused by recurrent HBV. Long-term immunoprophylaxis with hepatitis B immune globulin (HBIG) dramatically improved post-OLT survival, but recurrent HBV still occurred in up to 36% of the recipients. More recently, combination HBIG and lamivudine has been shown to effectively prevent HBV recurrence in patients post-OLT. The aim of the current study is to determine long-term outcome and cost-effectiveness of using combination HBIG and lamivudine compared with HBIG monotherapy in patients who undergo OLT for HBV. A retrospective chart review identified 59 patients administered combination HBIG and lamivudine and 12 patients administered HBIG monotherapy as primary prophylaxis against recurrent HBV. Lamivudine, 150 mg/d, was administered orally indefinitely. HBIG was administered under a standard protocol (10,000 IU intravenously during the anhepatic phase, then 10,000 IU/d intravenously for 7 days, then 10,000 IU intravenously monthly) indefinitely. A decision-analysis model was developed to evaluate the potential economic impact of prophylaxis against HBV with combination therapy compared with monotherapy. Recurrent HBV was defined as the reappearance of hepatitis B surface antigen (HBsAg) after its initial disappearance post-OLT. In the combination-therapy group, no patient redeveloped serum HBsAg or HBV DNA during mean follow-ups of 459 and 416 days, respectively. In the monotherapy group, 3 patients (25%) had reappearance of HBsAg in serum during a mean follow-up of 663 days. Combination therapy resulted in a dominant, cost-effective strategy with an average cost-effectiveness ratio of $252,111/recurrence prevented compared with $362,570/recurrence prevented in the monotherapy strategy. Combination prophylaxis with HBIG and lamivudine is highly effective in preventing recurrent HBV, may protect against the emergence of resistant mutants, and is significantly more cost-effective than HBIG monotherapy with its associated rate of recurrent HBV.

Adolescent↗
PubMed2000

Quality Enhancement Research Initiative in stroke: prevention, treatment, and rehabilitation.

Stroke is the third leading cause of death and a leading cause of adult disability in the United States. Both within and outside of the Veterans Health Administration (VHA), the lack of a systematic approach to stroke prevention and treatment may have contributed to reduced rates of compliance with recommended practices and increased rates of stroke. Gaps in the knowledge base inhibit a systematic approach to high-quality care within the veteran population. Initial recommendations for closing those gaps are proposed. In some cases (eg, systematic anticoagulation management), the VHA is perceived as a leader in applied research; therefore, a systematic national policy for implementing these clinics may significantly reduce stroke rates. In other areas (eg, carotid endarterectomy), databases exist that would help advance quality and outcomes, but short-term studies are necessary to establish their utility. To promote strategic improvement in prevention, treatment, and rehabilitation for veterans who may be at risk or have had a stroke, specific objectives are proposed to (1) identify best practices for the effective delivery of long-term anticoagulation and enhance veterans' access to these services, (2) develop risk-adjusted models for the surgical preventive procedure carotid endarterectomy to understand facility variation in outcomes so practices can be improved, (3) define a systematic acute stroke management system so that high-quality stroke-related care can be generalizable to a variety of VHA settings, and (4) assess the impact of poststroke rehabilitation on risk adjustment and the location of outcomes so as to facilitate the implementation of best rehabilitation practices.

Adult↗
PubMed2000

Osmolyte channel regulation by ionic strength in skate RBC.

The aim of this study was to determine whether the opening of the osmolyte channel in skate red blood cells (RBC) is regulated by intracellular electrolyte concentration and conductivity. Consistent with previous studies, experiments with hyperosmotic preincubation before cell swelling or swelling with an isosmotic electrolyte (e.g., ammonium chloride) showed that an increase in ionic strength inhibits the opening of the taurine channel. However, a decrease in intracellular ionic strength did not always stimulate taurine efflux to the same degree. Whereas hyposmotic swelling caused a large increase in taurine efflux, swelling induced by treatment with isosmotic nonelectrolytes produced much smaller stimulation. Results with assays for band 3 phosphorylating enzymes were consistent with those from the taurine efflux studies; stimulation of enzyme activity was lower in cells that were swollen with isosmotic nonelectrolyte media than in cells swollen in hyposmotic media. These results indicate that a decrease in ionic strength is not the only signal for the opening of the taurine channel in skate RBC. Ionic strength does affect channel activity, but there must also be some other regulator.

Animals↗
PubMed1999

Trimethylamine oxide transport across plasma membranes of elasmobranch erythrocytes.

The aim of this study was to characterize the erythrocyte cell membrane transport of trimethylamine oxide (TMAO) in the little skate, Raja erincea. Uptake of TMAO occurs by two processes, Na(+)-dependent and Na(+)-independent. 2,4 dinitrophenol (2,4 DNP), a known ATP synthesis inhibitor, inhibited TMAO uptake, suggesting the involvement of the Na(+)/K(+)-ATP pump in Na(+)-dependent TMAO transport. Na(+)-independent TMAO uptake was stimulated by cell swelling when erythrocytes were incubated in hypotonic elasmobranch incubation medium. Swelling-activated, Na(+)-independent TMAO uptake was inhibited by the anion transport inhibitors quinine and 4, 4'-diisthiocyanostilbene-2,2'-disulfonic acid (DIDS), two blockers of the swelling-activated osmolyte channel in skate erythrocytes. TMAO efflux was stimulated by hypotonic stress in the erythrocytes of the spiny dogfish, Squalus acanthias. DIDS also inhibited this efflux, indicating that TMAO is transported by the organic osmolyte channel in the erythrocytes of this elasmobranch as well. J. Exp. Zool. 284:605-609, 1999.

2,4-Dinitrophenol↗
PubMed1999

Patients with early stage invasive cancer with close or positive margins treated with conservative surgery and radiation have an increased risk of breast recurrence that is delayed by adjuvant systemic therapy.

PURPOSE: The association between a positive resection margin and the risk of ipsilateral breast tumor recurrence (IBTR) after conservative surgery and radiation is controversial. The width of the resection margin that minimizes the risk of IBTR is unknown. While adjuvant systemic therapy may decrease the risk of an IBTR in all patients, its impact on patients with positive or close margins is largely unknown. This study examines the interaction between margin status, margin width, and adjuvant systemic therapy on the 5- and 10-year risk of IBTR after conservative surgery and radiation. METHODS AND MATERIALS: A series of 1,262 patients with clinical Stage I or II breast cancer were treated by breast-conserving surgery, axillary node dissection, and radiation between March 1979 and December 1992. The median follow-up was 6.3 years (range 0.1-15.6). The median age was 55 years (range 24-89). Clinical size was T1 in 66% and T2 in 34%. Seventy-three percent of patients were node-negative. Only 5 % of patients had tumors that were EIC-positive. Forty-one percent had a single excision, and 59% had a reexcision. The final margins were negative in 77%, positive in 12%, and close (< or = 2 mm) in 11%. The median total dose to the tumor bed was 60 Gy with negative margins, 64 Gy with close margins, and 66 Gy with positive margins. Chemotherapy +/- tamoxifen was used in 28%, tamoxifen alone in 20%, and no adjuvant systemic therapy in 52%. RESULTS: The 5-year cumulative incidence (CI) of IBTR was not significantly different between patients with negative (4%), positive (5%), or close (7%) margins. However, by 10 years, a significant difference in IBTR became apparent (negative 7%, positive 12%, close 14%, p = 0.04). There was no significant difference in IBTR when a close or positive margin was involved by invasive tumor or DCIS. Reexcision diminished the IBTR rate to 7% at 10 years if the final margin was negative; however, the highest risk was observed in patients with persistently positive (13%) or close (21%) (p = 0.02) margins. The median interval to failure was 3.7 years after no adjuvant systemic therapy, 5.0 years after chemotherapy +/- tamoxifen, and 6.7 years after tamoxifen alone. This delay to IBTR was observed in patients with close or positive margins, with little impact on the time to failure in patients with negative margins. The 5-year CI of IBTR in patients with close or positive margins was 1% with adjuvant systemic therapy and 13% with no adjuvant therapy. However, by 10 years, the CI of IBTR was similar (18% vs. 14%) due to more late failures in the patients who received adjuvant systemic therapy. CONCLUSION: A negative margin (> 2 mm) identifies patients with a very low risk of IBTR (7% at 10 years) after conservative surgery and radiation. Patients with a close margin (< or = 2 mm) are at an equal or greater risk of IBTR as with a positive margin, especially following a reexcision. A margin involved by DCIS or invasive tumor has the same increased risk of IBTR. A reexcision of an initially close or positive margin that results in a negative final margin reduces the risk of IBTR to that of an initially negative margin. A close or positive margin is associated with an increased risk of IBTR even in patients who are EIC-negative or receiving higher boost doses of radiation. The median time to IBTR is delayed; however, the CI is not significantly decreased by adjuvant systemic therapy in patients with close or positive margins-the 5 year results in these patients underestimate their ultimate risk of recurrence.

Adult↗
PubMed1999

Organic osmolyte channels in cell volume regulation in vertebrates.

Volume-activated organic osmolyte channels are found in a variety of vertebrates and cell types and show both common and disparate features. Upon exposure to hypotonic conditions, organic compounds such as taurine are released through these channels, reducing the intracellular solute concentration and thereby restoring cell volume. Various structurally diverse membrane proteins have been proposed as the channel. Accumulating evidence suggests that some of these proteins may play a more significant role as regulators than as the channel itself. Intracellular ionic strength may also modulate the release of organic osmolytes through these channels.

Animals↗
PubMed1999

Volume expansion stimulates p72(syk) and p56(lyn) in skate erythrocytes.

Hypotonic volume expansion of skate erythrocytes rapidly stimulates the tyrosine phosphorylation of band 3, the membrane protein thought to mediate the osmotically sensitive taurine efflux. Skate erythrocytes possess numerous tyrosine kinases including p59fyn, p56lyn, pp60(src), and p72(syk), demonstrated by immune complex assays measuring autocatalytic kinase activity. Inclusion of the cytoplasmic domain of band 3 in this assay showed that only Syk and Lyn can directly phosphorylate the cytoplasmic domain of band 3. Upon cell volume expansion, Syk activity was increased as assessed by three different assays (immune complex assay measuring autophosphorylation, assay of the level of phosphotyrosine of the immunoprecipitated kinase, and assay of level of 32P in the kinase immunoprecipitated from cells prelabeled with 32PO4 and then volume-expanded). The tyrosine kinase Lyn was also stimulated by volume expansion, most notably when analyzed by the latter two methods. Volume expansion stimulated a large increase in the ability of Syk to phosphorylate band 3 at times that coincide with the stimulation of taurine flux. The stilbene piceatannol inhibited Syk preferentially over Lyn and other tyrosine kinases and inhibited volume-stimulated taurine efflux in a concentration-dependent manner similar to that for the inhibition of Syk. Two major phosphorylation peaks were detected in tryptic digests of cdb3 separated by reverse phase HPLC. Edman degradation demonstrated a phosphotyrosine in a YXXL motif. In conclusion, p72(syk) appears to be a strong candidate as a pivotal signal-transducing step in the volume-activated taurine efflux in skate red cells. The level of band-3 phosphorylation may be regulated, in addition, by a protein-tyrosine phosphatase of the 1B variety.

Animals↗
PubMed1999

The timing of XIST replication: dominance of the domain.

Contiguous replicons are coordinately replicated and may be organized in temporal-spatial domains with early replication domains containing expressed genes and late ones carrying silent genes. XIST is silent on the active, early replicating X chromosome and expressed from the inactive, late replicating homolog. These circumstances potentially deviate from the aforementioned generalization and make studies of replication timing for XIST of special interest. Although earlier investigations of XIST replication in fibroblasts based on analysis of extracted DNA from cells at different stages of the cell cycle suggested that the silent gene does replicate before the expressed allele, studies using FISH technology produced the opposite results. Because the FISH replication studies could not directly distinguish between the active and inactive X chromosomes in the same cell, we undertook a re-investigation of this question utilizing FISH analysis under conditions that allowed us to make that distinction using cells sorted into different cell cycle stages by flow cytometry. The findings reported here indicate that the silent XIST gene on the active X chromosome does replicate before the expressed allele on the inactive X, supporting the view that the time of a gene's replication is determined by the large, multi-replicon domain in which it is located and not necessarily its expression state.

Alleles↗
PubMed1999

Ascertainment bias in rate ratio estimation from case-sibling control studies of variable age-at-onset diseases.

Motivated by a Finnish case-control study of early onset diabetes in which diabetic children are matched to sibling controls, we investigate ascertainment bias of the usual rate ratio estimator from case-control data under simplex complete ascertainment of families during a fixed interval of time. Analytic results indicate that the assumptions necessary for valid estimation are that the disease is rare and the factors under study are exchangeable--essentially that the covariate distribution does not depend on calendar time or birth order. Further, we found that the rare disease assumption could be dropped by restricting to cases that were diagnosed during the enrollment period of the study or including all cases but eliminating the proband as a control for non-enrollment-period cases. An important consequence of this work is that standard family-based case-control studies are subject to ascertainment bias if exchangeability of the covariates under investigation does not hold.

Age of Onset↗
PubMed1999

Postmenopausal hormone replacement therapy: effect on diagnosis and outcome in early-stage invasive breast cancer treated with conservative surgery and radiation.

PURPOSE: To compare the pretreatment characteristics and outcome of postmenopausal women with stage I-II breast cancer treated with conservative surgery and radiation who had a history of hormone replacement therapy (HRT) with those who had never received HRT. MATERIALS AND METHODS: From 1979 to 1993, 485 postmenopausal women underwent excisional biopsy, axillary dissection, and radiation for stage I-II breast cancer. The median follow-up was 5.9 years. One hundred forty-one patients reported a history of HRT. The median length of use was 5 years. Three hundred forty-four patients reported no history of HRT. RESULTS: Statistically significant differences between the two groups were observed for median age (HRT 60 years v no HRT 64 years; P =.0009), median weight (HRT 142 lbs v no HRT 152 lbs; P =.004), clinical tumor size < or = 2 cm (HRT 77% v no HRT 66%; P =.02), and the use of re-excision (HRT 62% v no HRT 49%; P =.01). The method of detection by mammogram only (HRT 52% v no HRT 42%; P =.06) was of borderline statistical significance. The HRT patients had a statistically significant increased cumulative incidence of ipsilateral breast tumor recurrence (8% v 2%; P =.02), a statistically significant decreased cumulative incidence of distant metastases (HRT 6% v no HRT 17%; P =.01), and a borderline statistically significant improvement in cause-specific survival at 10 years (HRT 92% v no HRT 86%; P =.07). Postmenopausal women with a history of HRT did not have an increased risk of contralateral breast cancer or second non-breast cancer malignancy. CONCLUSION: This study failed to identify an adverse effect of HRT on breast cancer mortality in patients with stage I-II disease treated with conservative surgery and radiation.

Adult↗
PubMed1998

Attenuation of skeletal muscle wasting with recombinant human growth hormone secreted from a tissue-engineered bioartificial muscle.

Skeletal muscle wasting is a significant problem in elderly and debilitated patients. Growth hormone (GH) is an anabolic growth factor for skeletal muscle but is difficult to deliver in a therapeutic manner by injection owing to its in vivo instability. A novel method is presented for the sustained secretion of recombinant human GH (rhGH) from genetically modified skeletal muscle implants, which reduces host muscle wasting. Proliferating murine C2C12 skeletal myoblasts stably transduced with the rhGH gene were tissue engineered in vitro into bioartificial muscles (C2-BAMs) containing organized postmitotic myofibers secreting 3-5 microg of rhGH/day in vitro. When implanted subcutaneously into syngeneic mice, C2-BAMs delivered a sustained physiologic dose of 2.5 to 11.3 ng of rhGH per milliliter of serum. rhGH synthesized and secreted by the myofibers was in the 22-kDa monomeric form and was biologically active, based on downregulation of a GH-sensitive protein synthesized in the liver. Skeletal muscle disuse atrophy was induced in mice by hindlimb unloading, causing the fast plantaris and slow soleus muscles to atrophy by 21 to 35% ( < 0.02). This atrophy was significantly attenuated 41 to 55% (p < 0.02) in animals that received C2-BAM implants, but not in animals receiving daily injections of purified rhGH (1 mg/kg/day). These data support the concept that delivery of rhGH from BAMs may be efficacious in treating muscle-wasting disorders.

Animals↗
PubMed1998

Hypotonicity stimulates translocation of ICln in neonatal rat cardiac myocytes.

Cell volume expansion stimulates the efflux of solutes, including the amino acid taurine, to accomplish a regulatory volume decrease (RVD). One protein that may play a role in taurine efflux is the cytosolic protein ICln. In rat neonatal cardiac myocytes under isotonic conditions, ICln is found predominantly (greater than 90%) in the cytosol. However, after cell volume expansion by exposure to hypotonic medium, ICln rapidly translocates to the particulate fraction (the Triton X-114-insoluble fraction). After 2 min in hypotonic medium the percentage of ICln in the particulate fraction increases to 30%, 46% at 5 min, 40% at 10 min, and 25% at 30 min. The time course of this response is similar to that of hypotonicity-stimulated taurine efflux. Hypotonicity-stimulated taurine efflux as well as ICln translocation parallel the reduction in medium osmolarity. As osmolarity decreases, taurine efflux and ICln movement increase. The movement of ICln from the particulate back to the cytosolic fraction is accelerated when volume-expanded cells are returned to isotonic medium. When ICln is analyzed under non-denaturing conditions, a dimer is detected in the particulate fraction of volume-expanded cells, along with the monomer. This dimer is not detected in the cytosol. Treatment of the particulate fraction from volume-expanded cells with the lyotropic agent KSCN caused release of ICln but not Na-K-ATPase into the soluble fraction, indicating that translocated ICln associates with membranes in the particulate fraction rather than inserting into them.

Actins↗
PubMed1998

Utilities for major stroke: results from a survey of preferences among persons at increased risk for stroke.

BACKGROUND: Patient beliefs, values, and preferences are crucial to decisions involving health care. In a large sample of persons at increased risk for stroke, we examined attitudes toward hypothetical major stroke. METHODS AND RESULTS: Respondents were obtained from the Academic Medical Center Consortium (n = 621), the Cardiovascular Health Study (n = 321 ), and United Health Care (n = 319). Preferences were primarily assessed by using the time trade off (TTO). Although major stroke is generally considered an undesirable event (mean TTO = 0.30), responses were varied: although 45% of respondents considered major stroke to be a worse outcome than death, 15% were willing to trade off little or no survival to avoid a major stroke. CONCLUSIONS: Providers should speak directly with patients about beliefs, values, and preferences. Stroke-related interventions, even those with a high price or less than dramatic clinical benefits, are likely to be cost-effective if they prevent an outcome (major stroke) that is so undesirable.

Adult↗
PubMed1998

The perception of speech gestures.

Two experiments examined the effects of temporal overlap of speech gestures on the perception of stop consonant clusters. Sequences of stop consonant gestures that exhibit temporal overlap extreme enough to potentially eliminate the acoustic evidence of (at least) one of the consonants were obtained from x-ray microbeam data. Subjects were given a consonant monitoring task using stimuli containing stop sequences as well as those containing single stops. Results showed that (1) the initial consonant in the stop sequences was detected significantly less often than in the single stops; (2) bilabial gestures were considerably more effective at obscuring a preceding alveolar than the reverse; and (3) the detection rate correlated with an index of overlap between lip and tongue tip gestures. Experiment 2 employed stimuli that were truncated during the closure for the critical stop or stop sequence, so as to eliminate any information occurring in the acoustic signal at the stop release. This experiment showed that removing release information decreased detectability of the consonants generally. However, consistent with the observed gestural patterns, removing the release did not decrease detection of the alveolar stop when it was the first consonant of a sequence, indicating that there was no information about the alveolar stop present in acoustic realization of the second stop release. These experiments show that certain gestural patterns actually produced by English speakers may not be completely recoverable by listeners, and further, that it is possible to relate recoverability to particular metric properties of the gestural pattern.

Analysis of Variance↗