Effect of recipient doe genotype on survival rate at birth of frozen rabbit embryos

Binding of human-recombinant transforming growth factor-beta 1 (TGF-beta 1) to the neonatal rat heart-muscle cell (cardiomyocyte) was characterized as a potential element in the cardioprotective pharmacology of this growth factor. The cardiomyocytes were found to express a single class of specific, high-affinity TGF-beta 1 binding sites. Ligand binding to these sites was rapid, saturable, selective, and reversible, characteristics of a receptor-mediated process. Scatchard and iterative non-linear least-squares regression analyses demonstrated that the cardiomyocyte TGF-beta 1 receptor had a Kd < or = 40 pM, a Bmax of approximately 3.4 fmol/10(6) cells, and a density of approximately 2000 binding sites/cell. Binding was selective for TGF-beta 1 as compared with other TGF-beta isoforms (i.e. TGF-beta 2 and -beta 3) and nonrelated cytokines (e.g. acidic fibroblast growth factor). Affinity-binding experiments to probe the molecular nature of the specific binding revealed three types of cardiomyocyte TGF-beta 1 binding proteins, the most prominent of which corresponded to the high-molecular-mass proteoglycan observed in nonmuscle cell types. These data raise the possibility that the known pharmacological effects of TGF-beta 1 on heart muscle may be direct actions via specific receptor-mediated events.     

The effect of dimethyl sulfoxide on the changes in the lymph microcirculation induced by staphylococcal toxin

The effect of dimethyl sulfoxide (dimexid, DMSO) on the lymph microvessels of the rat mesentery was studied by vital biomicroscopy. It was found that 30% DMSO increases the tonus of intact lymph microvessels and stimulates their phase contractions. Action of the agent for more than 15 min leads to the development of lymphostasis. DMSO has a pronounced corrective effect on disorders of lymph microcirculation caused by the staphylococcal toxin. It removes the main lymphopathogenic effects of the poison and normalizes the drainage function of the lymphangions. The correcting effect of DMSO on lymph circulation is attended with attenuation of the fatal effect of the toxin.     

The effect of propanediol on the morphology of fresh and frozen equine embryos

Seventeen horse embryos recovered on the sixth day after spontaneous ovulation were; 1) washed in PBS (n = 6), 2) treated with 1.5 M 1-2 propanediol (n = 6) or, 3) frozen and thawed using 1.5 M propanediol as the cryoprotectant (n = 5). After treatment, the embryos were incubated for 6 h in medium before they were fixed, serially sectioned and examined microscopically to count the total numbers of interphase, mitotic and pycnotic nuclei. Significant differences were measured only in the mean proportions of pycnotic cells (+/- s.d.), both between the control (9.2 +/- 7.3%) and frozen-thawed embryos (52.8 +/- 37.1%; P<0.05) and between the propanediol-treated (10.8 +/- 4.6%) and the frozen-thawed embryos (P<0.01). Propanediol appears to be minimally toxic to equine embryos but it is a poor cryoprotectant.     

The influence of in-vitro culture and cooling on the survival and development of cow embryos

Cow morulae cultured in a phosphate-buffered medium containing serum developed normally and retained viability when transferred to recipients. Unlike earlier cleavage stages, cow blastocysts tolerated cooling to 0 degrees C and retained viability after storage for 48 hr at 0 degrees C when transferred to recipients.     

The effect of cooling rate on the strength of brazed joints

Experimental data are presented on the influence of cooling rate on the strength and deformation of thin Ag-4 pct Pd brazed joints in Fe-3 pct Si. It is observed that increasing the cooling rate (via water quenching vs furnace cooling) from the braze temperature can cause a drastic reduction in the strength of cylindrical butt brazed joints with a thickness to diameter ratio less than 0.02. The decrease in fracture strength is attributable to residual stresses and plastic strain caused by rapid cooling. The nature of the fracture process is unaffected by the cooling cycle and is always observed to be ductile failure caused by the growth and coalescence of microscopic shrinkage voids. Using hydrostatic annealing treatments, it is possible to restore the strength of rapidly cooled joints to values above those for furnace-cooled joints. This increase in strength is associated with a decrease in the volume fraction of microvoids accompanying the hydrostatic anneal.     

The effect of cooling rate on the solidification of INCONEL 718

The superalloy INCONEL 718 (IN718) is a commonly used material in aerospace and turbine components. The advantage of this type of material with sluggish precipitation-hardening kinetics is that IN718 is readily weldable. Both wrought and cast parts are used and welded together. While the alloy has been studied previously, new production processes such as laser treatment demand better knowledge of the solidification process in IN718, especially at high cooling rates. In this investigation, the solidification process was studied over a wide range of cooling rates by three different experimental techniques: differential thermal analysis (DTA), mirror furnace (MF), and levitation casting. The solidification sequence and the reaction temperatures were identified. The microstructure and the change in growth morphology were also studied. Segregation measurements were performed, and the distribution of Nb was analyzed in detail for the different types of samples, because of its strong impact on the solidification sequence and microstructure. New observations are that the latent heat decreases and the effective partition coefficient increases with increasing cooling rate. The diffusion rate also seems to be enhanced in the first part of primary solidified dendrites. It is suggested that the new observations can be explained by an increased number of lattice defects formed in the solid as the cooling rate increases.     

The effect of cooling rate and coiling temperature on the microstructure and mechanical properties of a plain carbon steel

The effects of cooling rate and coiling temperature on microstructure and mechanical properties of a plain carbon steel were investigated by combining metallography and tensile experiments.The results indicate that ferrite grain size is refined and bainite transformation occurs to ensure high strength and elongation,as the cooling rate is quick enough.Yield strength and tensile strength improve with the decreased finish cooling temperature,but the elongation decreases too significantly to meet the requirements.Thus,the cooling rate must be quick enough,and the appropriate coiling temperature should be carefully selected to obtain refined ferrite and a small amount of bainite to improve the strength while the plasticity is also ensured.Under this condition,the Mn element concentration can be reduced to save cost or produce higher strength steel with same chemical composition.     

The effect of cooling rate on the microstructures formed during solidification of ferritic steel

This article describes in detail the effect of cooling rate on the microstructure of a low-carbon Fe-12 pct Cr alloy. The alloy was prepared using a relatively simple technique, i.e., rapid cooling of the melt in a copper wedge mold. The dependence of microstructure on the cooling rate (∼40 to 10⁵ K/s) has been determined by X-ray diffraction (XRD), microhardness measurement, optical microscopy (OM), and transmission electron microscopy (TEM). It has been found that the matrix structure over a large cooling rate range is composed of columnar ferrite grains, the size of which decreases with increasing cooling rate. Precipitation of second phases has been observed at either the ferrite grain boundaries or within the ferrite grains. The former takes place along the entire wedge sample, whereas the latter characterizes a region 12 mm away from the tip of the wedge sample. The essential structure of the grain boundary precipitates was identified as martensite, which is a transformation product of austenite precipitated at high temperatures. Retained austenite was identified at the tip region as isolated particles (<4 μm). The precipitates within the ferrite grains appeared as planar colonies consisting of two sets of needles. The density of these precipitates increases with increasing the cooling rate while their size decreases. Characteristic precipitate-free zones (PFZs) at the ferrite grain boundaries were observed and are discussed.     

The effect of a reduction in temperature on the quantal release of transmitter at the mouse neuromuscular junction

1. The effects of a reduction in temperature were examined on evoked and spontaneous release of transmitter quanta and on presynaptic negative signals, blocked by Cd2+, measured externally at neuromuscular junctions in mouse diaphragm muscles in low-Ca2+, high-Mg2+ Krebs-Ringer solutions. 2. The evoked release was enhanced with lowering of the temperature, whereas the extent of spontaneous release was reduced. Cooperativity of Ca2+ in the evoked release was slightly reduced by lowering the temperature. 3. The presynaptic negative signals increased in duration with lowering of the temperature. 4. These results support the hypothesis that the effect of a reduction in temperature reflects the improved efficacy of the calcium-mediated mechanism of transmitter release, manifested as a prolongation of the inflow of Ca2+. The process involved in the evoked release is probably attributable to an almost passive mechanism.     

The effect of cooling rate from the melt on the recrystallization behavior of aluminum alloy 6013

In most commercial operations, the plant metallurgist likely has little control over the solidification rate of the process. However, solidification rate is affected by the dimensions of the ingot, and product form (plate ingot vs extrusion billet, for example) determines the dimensions of the ingot to be cast. Consequently, understanding the effects of solidification rate might be useful in explaining differences in microstructure that are often observed in various product forms cast from equivalent compositions. To provide this microstructural information, the effect of cooling rate from the melt on the microstructural changes in hot-rolled and solution heat treated (SHT) aluminum alloy 6013 was investigated. The range of cooling rates in this investigation is comparable to what might be observed through the thickness of a plate ingot. Over the cooling rate range investigated (0.5 to 5 K/s), recrystallization behavior of the alloy appears to be primarily affected by the size and number density of the coarse α(AlFeMnSi) constituent particles, which act as sites for particle stimulated nucleation (PSN) of recrystallized grains. At intermediate cooling rates (1.5 K/s), the resistance to recrystallization is at a minimum. As the cooling rate increases beyond 1.5 K/s, the number of particles available for PSN decreases; thus, there is a decrease in the fraction of recrystallized grains after heat treating. On the other hand, as the cooling rate is decreased from 1.5 K/s, the size of the constituents increases; however, their number decreases, once again leading to a decrease in the fraction of recrystallized grains observed after heat treatment.     

The effect of multiple cryopreservation procedures and blastomere biopsy on the in-vitro development of mouse embryos

Preimplantation genetic diagnosis is currently used in clinical practice. In experienced hands the biopsy procedure alone does not affect the further in-vitro and in-vivo developmental potential of animal and human embryos. No data exist on the combination of cryopreservation of embryos at the pronuclear and/or 8-cell stage and/or biopsy at the 8-cell stage. Pronuclear stages of mouse F1 hybrids (C57Bl/jxCBA) were harvested and divided into several experimental groups. The developmental rates of zygotes, which were neither biopsied nor cryopreserved were used as data control. Others were only cryopreserved at the pronuclear stage (C-PN), or at the cleavage stage (C-CS), or both. Each of these groups was also combined with or without a biopsy. Only the hatched blastocyst rate (HBR), but not the 'simple' blastocyst rate, showed significant differences between groups. Neither C-PN (HBR = 60.42%), nor C-CS (63.16%), nor a combination of both (59.46%) had an impact on the hatched blastocyst rate when compared with that of the control group (67.46%). The biopsy procedure (55.93%) also proved not to be harmful for the embryos. The embryos, which were C-PN and C-CS, and subsequently biopsied, showed a significantly lower hatched blastocyst rate (39.62%) than that of the control, C-PN, C-CS, and C-PN/C-CS groups (P < 0.05). The combination of C-PN and cleavage-stage biopsy also lead to a lower hatched blastocyst rate (42.22%), compared with that of the control group (P < 0.05). It was concluded that couples must be advised that an effect on embryos which have undergone a combined cryopreservation and micromanipulation procedure cannot be ruled out. However, cryopreservation at the pronuclear or at the 8-cell stage alone, or in combination with a biopsy procedure, does not influence the further development of the embryo.     

The positive effect of pretreatment with serotonin and gangliosides on the development of early mouse embryos after cryopreservation

Blood pressure (BP) during siesta declines to levels similar to those of night time sleep. The objective of the study was to assess the effect of siesta on 24-h ambulatory BP (ABP) data. Two different approaches were employed for the definition of day and night periods: (1) actual patient reported day and night intervals (ACT) with siesta period analysed as a third time period; and (2) arbitrary day and night time intervals (ARB) with the presence of siesta being ignored. A total of 203 24-h ABP recordings were analysed, with a siesta during ABP monitoring reported in 154 of them. Mean siesta BP was very close to ACT night time BP. Among recordings with a siesta, ACT daytime BP was higher and night time BP lower than the corresponding ARB BPs (P < 0.001). The magnitude of night time BP drop was greater with ACT intervals, resulting in a lower percentage of non-dippers (P < 0.001). Among 49 recordings without a siesta, differences between ACT and ARB BPs were less pronounced for daytime but not for night time. Differences in the magnitude of nocturnal BP drop between ACT and ARB periods, although statistically significant, did not affect the prevalence of non-dippers. In conclusion, analysis of 24-h BP profiles by using ARB instead of ACT day and night intervals results in underestimation of the nocturnal BP drop and overestimation of the proportion of non-dippers. This bias is more pronounced in patients who take a siesta during ABP monitoring.     

The effect of strain rate and depressed temperature on the low cycle deformation behavior of alpha iron

The low cycle deformation saturation stress in Ferrovac-E a-iron was studied using diametral plastic strain (0.001 ≤ Δε_dp/2 ≤ 0.0135) as the control variable. Increasing strain rate (6 × 10^•5 s^•1 • 4 × 10^•3 s^•1) and decreasing temperature (295 to 173 K) increased the saturation stress levels. The cyclic work hardening coefficient decreased from 0.18 at 295 K to 0.10 at 173 K, which is consistent with previous studies of monotonie deformation. The temperature dependence of both the saturation stress and the strain rate sensitivity, as measured during cyclic deformation, were similar to that measured during monotonic tensile tests. The temperature dependence of the dislocation velocity indexm* was in good agreement with published values from high cycle fatigue and monotonie tensile tests. Thus the same deformation mechanisms are believed to occur in both monotonie and large plastic cyclic deformation (Δε_dp/2 ≥ 0.001) of a-iron.     

The effect of grain size, strain rate, and temperature on the mechanical behavior of commercial purity aluminum

Commercial purity aluminum AA1050 was subjected to equal channel angular extrusion (ECAE) that resulted in an ultrafine-grained (UFG) microstructure with an as-received grain size of 0.35 μm. This UFG material was then annealed to obtain microstructures with grain sizes ranging from 0.47 to 20 μm. Specimens were compressed at quasi-static, intermediate, and dynamic strain rates at temperatures of 77 and 298 K. The mechanical properties were found to vary significantly with grain size, strain rate, and temperature. Yield stress was found to increase with decreasing grain size, decreasing temperature, and increasing strain rate. The work hardening rate was seen to increase with increasing grain size, decreasing temperature, and increasing strain rate. The influence of strain rate and temperature is most significant in the smallest grain size specimens. The rate of work hardening is also influenced by strain rate, temperature, and grain size with negative rates of work hardening observed at 298 K and quasi-static strain rates in the smallest grain sizes and increasing rates of work hardening with increasing loading rate and grain size. Work hardening behavior is correlated with the substructural evolution of these specimens.     

The effect of frequency on the cyclic strain and low cycle fatigue behavior of cast Udimet 500 at elevated temperature

An experimental investigation was undertaken on cast Udimet 500 to study principally the effect of frequency on low cycle fatigue at temperatures from 730° to 900°C, but mostly at 815°C (1500°F). Total strain range and stress range vs fatigue life relationships were determined which included the frequency following the form of author's recent work. The stress range was found to obey a power law relationship involving the fatigue life and frequency, such that at a specific stress range, a ten-fold decrease in frequency corresponded to a 3.7-fold decrease in life. While stress results were well-ordered with frequency, the scatter in the cyclic strain data was severe. A random crystallographic orientation of the few grains in the cross-section led to an anisotropy in the material which produced as much as a three-fold variation in diametral strain around the circumference. Results were compared to those for directionally solidified Mar-M200. In load-controlled applications cast U-500 gave better life, while in strain-controlled situations, the directionally solidified material excelled. ForN _f>1000 cycles, the difference in life was related to elastic modulus. Evidence for cyclic strain aging is given, the peak effect occurring at 790°C. This temperature corresponding to that where the well-documented tensile ductility minimum occurs.