Phase transition kinetics of phosphatidic acid bilayers A stopped-flow study of the electrostatically induced transition

The kinetics of the electrostatically induced phase transition of dimyristoyl phosphatidic acid bilayers was followed using the stopped-flow technique. The phase transition was triggered by a fast change in the pH or the magnesium ion concentration and followed by recording the time dependence of the absorbance. When the phase transition was induced by a pH jump the time course of the absorbance could be described by two exponentials, their time constants displaying the for cooperative processes characteristic maximum at the transition midpoint. The time constants are in the 10 and 100 ms range for the H⁺ triggered transition from the fluid to the ordered state. A third slower process shows no appreciable temperature dependence and is probably caused by vesicle aggregation. For the OH^--induced transition fron the ordered to the fluid state the time constants are in the 100 and 1000 ms range. The fluid-ordered transition could also be triggered by addition of magnesium ions. Of the several observed processes only the fastest in the 10–100 ms time range could definitely be assigned to the fluid-ordered transition while the others are due to aggregation phenomena. The experimental data were compared with results obtained from pressure jump experiments and could be interpreted on the basis of theories for non-equilibrium relaxation.     

Iron and Porphyrin Trafficking in Heme Biogenesis

Iron is an essential element for diverse biological functions. In mammals, the majority of iron is enclosed within a single prosthetic group: heme. In metazoans, heme is synthesized via a highly conserved and coordinated pathway within the mitochondria. However, iron is acquired from the environment and subsequently assimilated into various cellular pathways, including heme synthesis. Both iron and heme are toxic but essential cofactors. How is iron transported from the extracellular milieu to the mitochondria? How are heme and heme intermediates coordinated with iron transport? Although recent studies have answered some questions, several pieces of this intriguing puzzle remain unsolved.     

Enhancement of shoot regeneration potential by liquid medium culture from mature cotyledons of sunflower (Helianthus annuus L.)

We describe here a liquid culture system for the regeneration of shoots at high frequencies from mature cotyledon tissues of three genotypes of sunflower (Helianthus annuus L.) one of which had previously been found to be recalcitrant to regeneration when cotyledons were cultured on solid medium. Cotyledons were excised from 2-day-old seedlings and incubated in liquid Murashige and Skoog's modified medium supplemented with 5.4 M naphthaleneacetic acid (NAA) and 4.4 M benzylaminopurine (BAP). After two weeks in culture, the whole upper surface of regenerating explants was covered with green shootlets. The percentages of regenerating explants of three genotypes varied between 60 and 70%, and the number of shoots per regenerating explant was highly increased. The shootlets were transferred to solid Murashige and Skoog's medium allowing shoot development, then to rooting medium. Rooted plantlets were successfully acclimatized and gave fertile plants. The role of liquid medium culture in the induction of sunflower regeneration is discussed.Abbreviations BAP 6-benzylaminopurine - NAA 1-naphthaleneacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid     

A high-resolution map of the vicinity of the R1 locus on chromosome V of potato based on RFLP and AFLP markers

The R1 allele confers on potato a race-specific resistance to Phytophthora infestans. The corresponding genetic locus maps on chromosome V in a region in which several other resistance genes are also located. As part of a strategy for cloning R1, a high-resolution genetic map was constructed for the segment of chromosome V that is bordered by the RFLP loci GP21 and GP179 and includes the R1 locus. Bulked segregant analysis and markers based on amplified fragment length polymorphisms (AFLP markers) were used to select molecular markers closely linked to R1. Twenty-nine of approximately 3200 informative AFLP loci displayed linkage to the R1 locus. Based on the genotypic analysis of 461 gametes, eight loci mapped within the GP21–GP179 interval. Two of those could not be seperated from R1 by recombination. For genotyping large numbers of plants with respect to the flanking markers GP21 and GP179 PCR based assays were also developed which allowed marker-assisted selection of plants with genotypes Rr and rr and of recombinant plants.     

Calcium activated proteolysis of fibrous proteins in central nervous system

A Ca²⁺ activated protease(s) capable of hydrolyzing several polypeptides at neutral pH including cytoskeletal proteins, actin, myosin, tubulin and neurofilament triplet was identified in calf brain cortex. The enzyme activity precipitates at 75 mM KCl, pH 6.5 – 7.0 and is inhibited by the sulfhydryl inhibitors, N-ethylmaleimide and para-chloromercuribenzoate and the protease inhibitors, antipain, pepstatin and leupeptin, leupeptin being the most effective.     

Predicting major complications in patients undergoing laparoscopic and open hysterectomy for benign indications

Background:Hysterectomy, the most common gynecological operation, requires surgeons to counsel women about their operative risks. We aimed to develop and validate multivariable logistic regression models to predict major complications of laparoscopic or abdominal hysterectomy for benign conditions.Methods:We obtained routinely collected health administrative data from the English National Health Service (NHS) from 2011 to 2018. We defined major complications based on core outcomes for postoperative complications including ureteric, gastrointestinal and vascular injury, and wound complications. We specified 11 predictors a priori. We used internal–external cross-validation to evaluate discrimination and calibration across 7 NHS regions in the development cohort. We validated the final models using data from an additional NHS region.Results:We found that major complications occurred in 4.4% (3037/68 599) of laparoscopic and 4.9% (6201/125 971) of abdominal hysterectomies. Our models showed consistent discrimination in the development cohort (laparoscopic, C-statistic 0.61, 95% confidence interval [CI] 0.60 to 0.62; abdominal, C-statistic 0.67, 95% CI 0.64 to 0.70) and similar or better discrimination in the validation cohort (laparoscopic, C-statistic 0.67, 95% CI 0.65 to 0.69; abdominal, C-statistic 0.67, 95% CI 0.65 to 0.69). Adhesions were most predictive of complications in both models (laparoscopic, odds ratio [OR] 1.92, 95% CI 1.73 to 2.13; abdominal, OR 2.46, 95% CI 2.27 to 2.66). Other factors predictive of complications included adenomyosis in the laparoscopic model, and Asian ethnicity and diabetes in the abdominal model. Protective factors included age and diagnoses of menstrual disorders or benign adnexal mass in both models and diagnosis of fibroids in the abdominal model.Interpretation:Personalized risk estimates from these models, which showed moderate discrimination, can inform clinical decision-making for people with benign conditions who may require hysterectomy.

Hysterectomy is one of the most frequently performed surgical procedures. Canada has one of the highest rates of hysterectomy globally, with one-third of women undergoing this procedure before 60 years of age.¹ Minimal access approaches are favoured by both clinicians and patients,² and the proportion of hysterectomies being undertaken by a laparoscopic approach has increased substantially in many countries over the last 10 years.^3–7 The evidence-based medicine paradigm for surgical approaches to hysterectomy for benign disease advocates that the chosen surgical approach should be discussed with the patient by their surgeon and decided in light of the relative benefits and risks.² This advice is echoed by national guidelines.^8,9Most clinicians undertaking hysterectomy will intuitively identify patient characteristics that have the potential to increase the complexity and complications of surgery. A 2016 systematic review of studies that reported significant associations between patient characteristics and surgical outcomes for laparoscopic hysterectomy and a 2020 population-based prospective cohort study using data from the Danish hysterectomy database have suggested that older age, race, raised body mass index (BMI), diabetes mellitus, increased uterine weight, fibroids, endometriosis and adhesions are predictors of complications in patients undergoing hysterectomy for benign indications.^10,11 However, assimilating this information to individualize and anticipate the precise risk for each patient if there are multiple factors present can be challenging. A 2020 systematic review reported that surgeons in other specialties were outperformed by risk prediction models in estimating postoperative risk and outcomes; their discriminatory ability showed greater variation (C-statistic 0.51–0.75) than other risk prediction tools.¹²Patients should be given information about potential risks before surgery to manage expectations.¹³ This is especially important when surgery is considered for benign disease because nonsurgical options are often available.Our aim was to generate prediction models that can be used in conjunction with a surgeon’s intuition to enhance preoperative patient counselling and match the advances made in the technical aspects of surgery. We sought to quantify the proportion of patients who underwent hysterectomy for benign disease and will have a major complication, and to develop and validate prognostic models to individualize this risk, using a national data set.