FATIGUE LIFE ENHANCEMENT OF BUTT WELDS USING A THERMO-MECHANICAL TECHNIQUE

Previous investigations have shown that the introduction of a compressive residual stress at critical locations enhances the fatigue life of welds. In the present study a combination of heat and applied stress is used to induce a compressive residual stress at critical locations such as the weld toe. The theory of the technique is discussed and an experimental study is carried out to investigate the effect of the technique on the fatigue behaviour of transverse butt welded specimens made from C-Mn steel.     

One-year experience with subdermal contraceptive implants in the United States

Women who received Norplant contraceptive implants from any of fifteen clinical settings in southeast Texas, U.S.A., were followed for one year to determine their reactions to the method. Of 1,385 who enrolled to receive Norplant implants, 1,253 had implants inserted. Side effects were reported by 78% of those receiving implants and 70% described changes in bleeding patterns. Spotting or irregular bleeding, weight gain and headaches were the conditions reported most frequently. Nine pregnancies were reported during the study period. Six of these, however, existed before the implants were inserted. At the one year anniversary, 143 of women receiving implants had had them removed. Those who discontinued method use were less satisfied, reported more side effects and were more likely to have planned to have another child, thus using the method for spacing, or to have had a change in their marital status while they were using the contraceptive. Providers should counsel patients to focus attention on plans for the future in selecting their contraceptive method. In addition, we recommend, as does the product's distributor, that providers confirm that patients are not pregnant prior to inserting implants.     

Improved success of living unrelated renal transplantation with cyclosporine immunosuppression

Kidney transplantation with a living unrelated donor was performed in 13 patients. The donors comprised 10 spouses, 2 brothers-in-law and 1 stranger. All donor-recipient pairs were red blood cell compatible with a negative T cell crossmatch. Five patients underwent transplantation before 1984 without cyclosporine immunosuppression; the 1-year patient and graft survival rates in this group were 40% and 20%, respectively. Eight patients have undergone transplantation since 1985 with cyclosporine immunosuppression. The 1-year patient and graft survival rates in this group were 100% and 88%, respectively (p = 0.03). Currently, 6 patients in the latter group have a well functioning graft with serum creatinine levels of 1.2 to 2.0 mg./dl. (mean 1.5 mg./dl.) and with followup of 1 to 6 years (mean 2.9 years). Excellent graft survival results can now be achieved with living unrelated donors and their expanded use can provide an important additional source of organs for transplantation.     

ADP-ribosylation factor 1 transiently activates high-affinity adaptor protein complex AP-1 binding sites on Golgi membranes

Association of the Golgi-specific adaptor protein complex 1 (AP-1) with the membrane is a prerequisite for clathrin coat assembly on the trans-Golgi network (TGN). The AP-1 adaptor is efficiently recruited from cytosol onto the TGN by myristoylated ADP-ribosylation factor 1 (ARF1) in the presence of the poorly hydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). Substituting GTP for GTPgammaS, however, results in only poor AP-1 binding. Here we show that both AP-1 and clathrin can be recruited efficiently onto the TGN in the presence of GTP when cytosol is supplemented with ARF1. Optimal recruitment occurs at 4 microM ARF1 and with 1 mM GTP. The AP-1 recruited by ARF1.GTP is released from the Golgi membrane by treatment with 1 M Tris-HCl (pH 7) or upon reincubation at 37 degreesC, whereas AP-1 recruited with GTPgammaS or by a constitutively active point mutant, ARF1(Q71L), remains membrane bound after either treatment. An incubation performed with added ARF1, GTP, and AlFn, used to block ARF GTPase-activating protein activity, results in membrane-associated AP-1, which is largely insensitive to Tris extraction. Thus, ARF1. GTP hydrolysis results in lower-affinity binding of AP-1 to the TGN. Using two-stage assays in which ARF1.GTP first primes the Golgi membrane at 37 degreesC, followed by AP-1 binding on ice, we find that the high-affinity nucleating sites generated in the priming stage are rapidly lost. In addition, the AP-1 bound to primed Golgi membranes during a second-stage incubation on ice is fully sensitive to Tris extraction, indicating that the priming stage has passed the ARF1.GTP hydrolysis point. Thus, hydrolysis of ARF1.GTP at the priming sites can occur even before AP-1 binding. Our finding that purified clathrin-coated vesicles contain little ARF1 supports the concept that ARF1 functions in the coat assembly process rather than during the vesicle-uncoating step. We conclude that ARF1 is a limiting factor in the GTP-stimulated recruitment of AP-1 in vitro and that it appears to function in a stoichiometric manner to generate high-affinity AP-1 binding sites that have a relatively short half-life.     

Sleep and circadian rhythms in four orbiting astronauts

This experiment measured the sleep and circadian rhythms of four male astronauts aboard a space shuttle (STS-78) orbiting the Earth for 17 days. The space mission was specially scheduled to minimize disruptions in circadian rhythms and sleep so that the effects of space flight and microgravity per se could be studied. Data were collected in 72-h measurement blocks: one block 7 days before launch, one early within the mission (3 days after launch), one late in the mission (12 days after launch), and one 18 days after landing. Within each measurement block, all sleep was recorded both polysomnographically and by sleep diary. Core body temperature was sampled every 6 mins. Actillumes were worn continuously. All urine samples were collected separately. Performance was assessed by a computerized test battery (3/day) and by end-of-shift questionnaires (1/day); mood and alertness were measured by visual analogue scales (5/day). Circadian rhythms in orbit appeared to be very similar in phase and amplitude to those on the ground, and were appropriately aligned for the required work/rest schedule. There was no change from early flight to late flight. This was also reflected in mood, alertness, and performance scores, which were satisfactory at both in-flight time points. However, in-flight sleep showed a decreased amount of sleep obtained (mean = 6.1 h), and all four astronauts showed a decrease in delta sleep. No further degradation in sleep was seen when early flight was compared to late flight, and no other sleep parameters showed reliable trends.     

Targeting of DNA gyrase in Streptococcus pneumoniae by sparfloxacin: selective targeting of gyrase or topoisomerase IV by quinolones

gyrA and parC mutations have been identified inn Streptococcus pneumoniae mutants stepwise selected for resistance to sparfloxacin, an antipneumococcal fluoroquinolone. GyrA mutations (at the position equivalent to resistance hot spot Ser-83 in Escherichia coli GyrA) were found in all 17 first-step mutants examined and preceded DNA topoisomerase IV parC mutations (at Ser-79 or Glu-83), which appeared only in second-step mutants. The targeting of gyrase by sparfloxacin in S. pneumoniae but of topoisomerase IV by ciprofloxacin indicates that target preference can be altered by changes in quinolone structure.     

Changes in the subnuclear distribution of two RNA metabolism-related proteins can be detected in nuclear scaffold or matrix prepared by different techniques

The nuclear scaffold or matrix is a mainly proteinaceous structure thought to act as a nucleoskeleton determining the higher order organization of eukaryotic chromatin. These structures are prepared from isolated nuclei by a series of extraction steps involving the use of ionic detergents or high salt, and restriction enzymes or non-specific nucleases to remove chromatin and other loosely bound components. Since these treatments are harsh and unphysiological, the question remains open as to whether or not these structures, isolated in vitro, correspond to a nucleoskeleton existing in vivo. Recently, it has been demonstrated that the majority of nuclear matrix proteins are involved in RNA metabolism. In this study we have employed a morphological approach involving the use of confocal laser scanning microscopy and indirect immunofluorescence techniques to analyze whether two widely employed methods to prepare the nuclear scaffold or matrix can maintain the spatial distribution of two polypeptides involved in RNA metabolism, i.e., a 105-kDa component of spliceosomes and a ribonucleoprotein antigen. We demonstrate that the localization of these polypeptides changes, in some cases dramatically, in the final nucleoskeletal structures when compared with intact cells. Only when isolated nuclei were stabilized in vitro with the cross-linking agent sodium tetrathionate (NaTT) prior to extraction with 2 M NaCl and DNase I digestion, were the immunofluorescent patterns displayed by the nuclear matrix indistinguishable from those detected in intact cells. These results emphasize the usefulness of NaTT in studying putative nucleoskeletal structures, but also show that the methods currently employed to prepare the nuclear scaffold or matrix may create in vitro artifacts.