Embryonic disc development and subsequent viability of cattle embryos following culture in two media under two oxygen concentrations

Bovine embryos were produced in vitro using a 2 x 2 design of modified medium (KSOM or SOF) and oxygen concentration (5% or 20%). Day 7 blastocysts were transferred in bulk (n = 11, on average) to recipient heifers and recovered non-surgically at Day 14. In two replications of a Latin square, eight heifers received embryos from each combination of factors. Recovered embryos were evaluated for trophoblast length and width, as well as the presence and diameter of an embryonic disc (ED). An ED was detected in a higher percentage of embryos that had been cultured in KSOM than SOF (72% v. 46%, respectively; P < 0.05). The aim of a second series of experiments was to associate Day 14 morphology with subsequent developmental capacity. In vitro-produced blastocysts were transferred (n = 17-20) on Day 7 to each of eight heifers and recovered at Day 14. Thirty-eight blastocysts were retransferred to heifers following morphological evaluation. Embryos in which an ED with no signs of degeneration had been detected maintained more pregnancies than other embryos in which an ED had either shown signs of degeneration or had not been detected (5/8 v. 2/30, respectively; P < 0.01). Further investigation into ED integrity at the elongating stage may contribute to our understanding of pregnancy establishment and maintenance.     

The 1996 welfare law: key elements and reauthorization issues affecting children

The Personal Responsibility and Work Opportunity Reconciliation Act of 1996 changed the social policy landscape for children in many ways. It replaced the prior welfare program with block grants to the states entitled Temporary Assistance for Needy Families, and modified a broad array of other programs and initiatives affecting low-income children. This article describes the key themes dominating the debate over welfare reform in 1996, specifically: Increased state discretion in program design, leading to more variability in states' eligibility requirements and services provided to low-income families; More stringent work requirements even for parents of very young children; Time limits on the use of federal funds for cash assistance, and a strong focus on caseload reduction; Increased emphasis on parental responsibility, with stronger child support requirements; and Increased emphasis on reducing out-of-wedlock births, including bonuses to states with the largest reductions, and special requirements for unmarried teen parents who seek welfare. Although child well-being received little attention during the congressional debates in 1996, the authors conclude with the hope that improving child outcomes and child well-being will emerge as a key theme when the law is reauthorized in 2002.     

Exponential processes in human auditory excitation and adaptation

Peripheral auditory adaptation has been studied extensively in animal models, and multiple exponential components have been identified. This study explores the feasibility of estimating these component processes for human listeners with a peripheral model of adaptation. The processes were estimated from off-frequency masked detection data that probed temporal masking responses to a gated narrowband masker. The resulting response patterns reflected step-like onset and offset features with characteristically little evidence of confounding backward and forward masking. The model was implemented with linear combinations of exponential functions to represent the unadapted excitation response to gating the masker on and then off and the opposing effects of adaptation in each instance. The onset and offset of the temporal masking response were assumed to be approximately inverse operations and were modeled independently in this scheme. The unadapted excitation response at masker onset and the reversed excitation response at masker offset were each represented in the model by a single exponential function. The adaptation processes were modeled by three independent exponential functions, which were reversed at masker offset. Each adaptation component was subtractive and partially negated the unadapted excitation response to the dynamic masker. This scheme allowed for quantification of the response amplitude, action latency, and time constant for the unadapted excitation component and for each adaptation component. The results reveal that (1) the amplitudes of the unadapted excitation and reversed excitation components grow nonlinearly with masker level and mirror the 'compressive' input-output velocity response of the basilar membrane; (2) the time constants for the unadapted excitation and reversed excitation components are related inversely to masker intensity, which is compatible with neural synchrony increasing at masker onset (or offset) with increasing masker strength; (3) the composite strength of adaptation levels off at high masker levels; this 'saturation' response is consistent with a diminished contribution from peripheral neural adaptation processes at high sound levels; and (4) the response dynamics for two of the adaptation components correspond generally to those for the 'very rapid'/'rapid' processes and 'short-term' processes described in animal studies of peripheral neural adaptation. The action latency of a third adaptation component suggests the role of a second-order peripheral or central process. This modeling exercise (1) indicates that multiple adaptation processes, whatever their origins, contribute substantively to the form of the temporal masking response and (2) supports a sum-of-exponentials scheme for estimating properties of the component processes.     

Treatment of osteomyelitis with local antibiotics delivered via bioabsorbable polymer

The purpose of the current study was to show the efficacy and safety of an absorbable polymer (polycaprolactone) as an antibiotic delivery vehicle for treatment of osteomyelitis. An intramedullary osteomyelitis was induced in the femur of adult rabbits by Staphylococcus aureus inoculation after use of a sclerosing agent, and then treatment was done with intramedullary irrigation and implantation of a rod made of polycaprolactone, polycaprolactone plus 6% tobramycin, or polymethylmethacrylate plus 6% tobramycin. A control group received irrigation only. At defined intervals, the animals were euthanized and culture of the inoculated site was done. In addition, histologic sections of body tissues were made to look for signs of systemic toxicity of the implant. After 4 weeks of treatment, a statistically significant difference was found between the animals that were treated with irrigation alone and the animals that were treated with antibiotic-laden rods of polycaprolactone or polymethylmethacrylate. There was no difference between the antibiotic rod types. No histologic evidence of toxicity was found. Bioabsorbable rods of polycaprolactone are a safe and effective means of antibiotic delivery for treatment of osteomyelitis.     

Evaluation of cytotoxicity of some Mannich bases of various aryl and arylidene ketones and their corresponding arylhydrazones.

Mannich bases were synthesized and converted to the corresponding arylhydrazones. X-ray analysis of a ketone (1a) and a hydrazone (4d) revealed structural features of interest. All of the compounds showed cytotoxicity toward murine lymphocytic leukemia L1210 cells in the 4.9-25.0-microM range. The correlation coefficients generated by plotting the IC50 values (the concentrations of compounds that inhibit the growth of tumors by 50%) of some hydrazones against certain electronic, hydrophobic, and steric constants of the aryl substituents indicated only weak correlations. A few ketones and hydrazones displayed significant cytotoxicity to the WiDr human colon cancer cells, and these derivatives, especially the ketones, may serve as prototypes for future drug development. The KB tumor (a human epidermoid carcinoma of the nasopharynx) was somewhat refractory to selected compounds. In an in vitro assay conducted by the National Cancer Institute and involving approximately 53 tumor cell lines originating from eight neoplastic diseases, 65% of the compounds showed some selectivity toward one or more groups of cancers, principally leukemia, melanoma, and colon cancer. The bioevaluation of the ketones and hydrazones against the L1210, WiDr, and KB tumors, as well as evidence from proton nuclear magnetic resonance studies did not support the suggestion that hydrazones may be prodrugs of the corresponding ketones.