Lisfranc Fixation Techniques and Postoperative Functional Outcomes: A Systematic Review

The optimal method of fixation of acute Lisfranc injuries is yet to be established. We aim to systematically review the literature to identify the impact of fixation method on postoperative functional outcomes. A systematic review was undertaken using the PRISMA framework to identify all studies reporting postoperative functional outcomes in patients who underwent open-reduction internal fixation of acute Lisfranc injuries. Studies reporting outcomes of numerous fixation methods were divided into fixation subcohorts. Studies comparing bridge plate with transarticular screw fixation were included for meta-analysis, conducted using a random-effects model. Seventeen studies (20 subcohorts) with 462 patients were included. Mean patient age was 29.6 (rang, 15-81) years. Mean follow-up was 38.7 (range 11 to 287) months. American Academy of Orthopaedic Surgeons midfoot score (AOFAS-MF) was the most frequently reported functional outcome (16/20 subcohorts). Overall weighted mean AOFAS-MF was 76.3 ± 9.4 for all cases, with 74.2 ± 9.4 for transarticular screws and 79.2 ± 8.3 for bridge plates. The mean difference between screw and plate was not statistically significant (mean difference = 5.0, 95% confidence interval, -4.8 - 14.8, p = .3). A single study reported AOFAS-MF mean of 92 using suture button fixation. Meta-analysis of the 2 available comparative studies revealed higher postoperative AOFAS-MF with bridge plate fixation (pooled standardized mean difference, 0.51; 95% confidence interval, 0.15-0.87, p = .006). There is scarcity of literature examining the impact of fixation method on postoperative functional outcomes in acute Lisfranc injuries. A small number of studies have reported superior functional outcomes with use of bridge plate fixation. Further evidence is needed to ascertain which injuries are best managed with each fixation method or whether 1 fixation construct is universally superior.

Factors influencing reoperation following breast-conserving surgery

BACKGROUND

Reoperation rates after breast-conserving surgery are highly variable and the best techniques for optimizing margin clearance are being evaluated. The aim was to identify the reoperation rate at our centre and identify influential factors, including a change in guidelines on margin recommendations and the introduction of in-theatre specimen X-ray.

METHODS

A retrospective review of medical records was undertaken to identify 562 patients who underwent breast conservation at The Royal Melbourne Hospital and Royal Women's Hospital between 2013 and 2015. All cases that underwent subsequent re-excision or total mastectomy were captured and factors influencing margin excision recorded.

RESULTS

Reoperation was undertaken in 19.5% of patients (110; 86 re-excisions and 24 total mastectomies). There was a reduction in reoperation rate from 25% to 17% (P = 0.01) with adoption of the margin guidelines in 2014, but no significant reduction with the introduction of in-theatre specimen X-ray in 2015 (21% versus 16%, P = 0.14). On multivariate analysis, factors that significantly influenced reoperation rates were the presence of multifocality on mammogram (odds ratio (OR): 5.3, 95% confidence interval (CI): 1.6-16.7, P < 0.01); lesion size on mammogram (OR: 2.2 per 10 mm, 95% CI: 1.4-3.6, P < 0.01); smaller excision specimen weight (OR: 0.5 per 25 g of resection, 95% CI: 0.3-0.8, P < 0.01); and pure ductal carcinoma in situ on final pathology (OR: 5.9, 95% CI: 1.9-16.7, P < 0.01).

CONCLUSION

Optimizing reoperation rates following breast-conserving surgery remains a surgical challenge, particularly in patients with in situ or multifocal disease. Adoption of international margin guidelines reduced reoperation rates at our centre; however, introduction of intraoperative specimen X-ray had no influence.

Modified Dorsal Approach in the Management of Lisfranc Injuries

BACKGROUND

Open reduction and internal fixation of Lisfranc injuries has typically used multiple longitudinal incisions or a single transverse incision to approach the tarso-metatarsal joint (TMTJ). The incidence of wound-related complications is considerable. We describe a novel single-incision approach that utilizes subcutaneous windows to the medial TMTJ.

METHODS

A retrospective review identified 150 patients who underwent open reduction and internal fixation for Lisfranc injuries, via the modified dorsal approach, at our center between January 2011 and June 2016. Removal of hardware (ROH) was routinely undertaken in 105 patients at a median of 210 days postoperatively. Medical records were reviewed to record patient demographics, mechanism of injury, and operative details. Outpatient notes were reviewed to identify wound-related complications, including delayed wound healing, superficial infection, wound dehiscence, deep infection, complex regional pain syndrome (CRPS), neuroma, and impaired sensation. Median age was 37 years (range, 19-78 years). Seventy-three percent of patients (110) were male. Most frequent mechanisms of injury were motor vehicle accident (MVA), 39%; motorbike accident (MBA), 19%; and fall, 18%. Sixteen percent (24) of injuries were open. Five patients required soft tissue reconstruction at the primary operation. Median follow-up was 144 (range, 27-306) weeks.

RESULTS

Following the primary procedure, 14% of patients experienced wound-related complications including delayed healing (3%), superficial infection (5%), dehiscence (3%), complex regional pain syndrome (CRPS) (1%), and impaired sensation (1%). MBA injuries were at 15.1 times odds of superficial infection ( P =.01) than were MVA injuries. Following ROH, 13% of patients experienced wound-related complications, including delayed healing (2%), superficial infection (8%), dehiscence (1%), CRPS (2%), and neuroma (1%). Overall, 5 patients returned to surgery for soft tissue reconstruction for wound dehiscence.

CONCLUSION

The modified dorsal approach using intervals to the midfoot offers a viable alternative with comparable wound complication rates to existing midfoot approaches.

LEVEL OF EVIDENCE

Level IV, case series.

Predictive outcomes of revision total hip replacement--a consecutive series of 1176 patients with a minimum 10-year follow-up

The burden of revision total hip replacement (THR) surgery is increasing. With an increasing life expectancy and younger age of primary surgery this trend is set to continue. There are few data on the long-term outcome of revision THR. This retrospective study of 1176 consecutive revision THRs with a minimum 10-year follow-up from a University Teaching Hospital was undertaken to review implant survival and patient reported outcomes. Mean follow-up was 11 years with implant survival at 10 years of 82% (CI: 80-85). Implant survival varied between 58% (unexplained pain) to 84% (aseptic loosening) depending on the indication for revision surgery. Positive predictors of survival were age greater than 70 at the time of surgery (p=0.011), revision for aseptic loosening (p<0.01) and revision of both components or just the acetabular component (p<0.01). At the last review, mean Oxford Hip Score (OHS) was 34 (SD: 11.3) and 92% of the living patients with unrevised hips were satisfied with the outcome of revision surgery. This long term study has demonstrated that positive predictors of survival and outcome of revision THR surgery are age greater than 70 years, revision for aseptic loosening and component revision. This should aid surgeons in their counselling of patients prior to surgery.

Caveat anicula! Beware of quiet little old ladies: demographic features, pharmacotherapy, readmissions and survival in a 10-year cohort of patients with heart failure and preserved systolic function

OBJECTIVE

To determine whether heart failure with preserved systolic function (HFPSF) has different natural history from left ventricular systolic dysfunction (LVSD).

DESIGN AND SETTING

A retrospective analysis of 10 years of data (for patients admitted between 1 July 1994 and 30 June 2004, and with a study census date of 30 June 2005) routinely collected as part of clinical practice in a large tertiary referral hospital.

MAIN OUTCOME MEASURES

Sociodemographic characteristics, diagnostic features, comorbid conditions, pharmacotherapies, readmission rates and survival.

RESULTS

Of the 2961 patients admitted with chronic heart failure, 753 had echocardiograms available for this analysis. Of these, 189 (25%) had normal left ventricular size and systolic function. In comparison to patients with LVSD, those with HFPSF were more often female (62.4% v 38.5%; P = 0.001), had less social support, and were more likely to live in nursing homes (17.9% v 7.6%; P < 0.001), and had a greater prevalence of renal impairment (86.7% v 6.2%; P = 0.004), anaemia (34.3% v 6.3%; P = 0.013) and atrial fibrillation (51.3% v 47.1%; P = 0.008), but significantly less ischaemic heart disease (53.4% v 81.2%; P = 0.001). Patients with HFPSF were less likely to be prescribed an angiotensin-converting enzyme inhibitor (61.9% v 72.5%; P = 0.008); carvedilol was used more frequently in LVSD (1.5% v 8.8%; P < 0.001). Readmission rates were higher in the HFPSF group (median, 2 v 1.5 admissions; P = 0.032), particularly for malignancy (4.2% v 1.8%; P < 0.001) and anaemia (3.9% v 2.3%; P < 0.001). Both groups had the same poor survival rate (P = 0.912).

CONCLUSIONS

Patients with HFPSF were predominantly older women with less social support and higher readmission rates for associated comorbid illnesses. We therefore propose that reduced survival in HFPSF may relate more to comorbid conditions than suboptimal cardiac management.

Cell cycling and differentiation do not require the retinoblastoma protein during early Xenopus development

The retinoblastoma protein (pRb) is a central regulator of the cell cycle, controlling passage through G1 phase. Moreover, pRb has also been shown to play a direct role in the differentiation of multiple tissues, including nerve and muscle. Rb null mice display embryonic lethality, although recent data have indicated that at least some of these defects are due to placental insufficiency. To investigate this further, we have examined the role of pRb in early development of the frog Xenopus laevis, which develops without the need for a placenta. Surprisingly, we see that loss of pXRb has no effect on either cell cycling or differentiation of neural or muscle tissue, while overexpression of pXRb similarly has no effects. We demonstrate that, in fact, pXRb is maintained in a hyperphosphorylated and therefore inactive state early in development. Therefore, Rb protein is not required for cell cycle control or differentiation in early embryos, indicating unusual control of these G1/G0 events at this developmental stage.

[p27Kip1 independently promotes neuronal differentiation and migration in the cerebral cortex]

The generation of glutamatergic neurons by stem and progenitor cells is a complex process involving the tight coordination of multiple cellular activities, including cell cycle exit, initiation of neuronal differentiation and cell migration. The mechanisms that integrate these different events into a coherent program are not well understood. Here we show that the cyclin-dependent kinase inhibitor p27Kip1 plays an important role in neurogenesis in the mouse cerebral cortex, by promoting the differentiation and radial migration of cortical projection neurons. Importantly, p27Kip1 promotes neuronal differentiation and neuronal migration via two distinct mechanisms, which are themselves independent of the cell cycle regulatory function of p27Kip1. p27Kip1 inactivation by gene targeting or RNA interference results in neuronal differentiation and radial migration defects, demonstrating that p27Kip1 regulates cell migration in vivo. The differentiation defect, but not the migration defect, is rescued by overexpression of the proneural gene Neurogenin 2. p27Kip1 acts by stabilizing Neurogenin 2 protein, an activity carried by the N-terminal half of the protein. The migration defect resulting from p27Kp1 inactivation is rescued by blocking RhoA signalling, an activity that resides in the c-terminal half of p27Kip1. Thus, p27Kip1 plays a key role in cortical development, acting as a modular protein that independently regulates and couples multiple cellular pathways contributing to neurogenesis.

Development of a regimen for rapid initiation of perhexiline therapy in acute coronary syndromes

Perhexiline is a prophylactic anti-anginal agent that ameliorates the metabolic basis for myocardial ischaemia and is increasingly used in the management of acute coronary syndromes. No intravenous preparation is available and usual oral loading regimens require 2-3 days to achieve therapeutic drug levels. Two patients presenting to hospital with single-dose over-dosage of perhexiline (6500 mg and 1000 mg, respectively) provided a basis for examining the safety of large single dosage of perhexiline and associated time-course of drug levels. Neither patient had previously taken perhexiline. Peak plasma perhexiline concentrations occurred within 12 h of ingestion and were 2.58 and 0.50 mg/L, respectively (therapeutic range 0.15-0.60 mg/L). The first patient developed transient nausea and vomiting; the second patient had no adverse effects. Subsequently, a series of 10 patients with acute coronary syndromes received an 800-mg loading dose. Peak concentrations occurred within 12 h postdose; the mean levels achieved were 0.40 +/- 0.16 mg/L (standard error of the mean). No serious adverse effects were seen. Two patients reported transient nausea or vomiting within 24 h of the loading dose. The utility of this rapid loading regimen for incremental suppression of myocardial ischaemia remains to be assessed.

Cell cycle and cell fate in the nervous system

Recently, a number of molecules originally thought to have a primary role in cell determination have been shown to affect the cell cycle at specific check points, while other molecules discovered for their roles in the cell cycle progression are known to affect the determination and differentiation of neurons. These discoveries have led to a more detailed investigation of the complex molecular machinery that co-ordinates proliferation and differentiation.

Inhibiting mutations in the transforming growth factor beta type 2 receptor in recurrent human breast cancer

Members of the transforming growth factor beta (TGF-beta) family are potent inhibitors of the growth of many epithelial cell types. Transmembrane signaling by TGF-beta occurs via a complex of the serine/threonine kinases TGF-beta type 1 receptor and TGF-beta type 2 receptor (TGFBR2), and inactivating mutations in the latter have recently been detected in some primary tumors and in several types of tumor-derived cell lines. The most common mutations that have been identified in TGFBR2 are frameshifts in a repetitive polyadenine region in replication error-positive colorectal carcinomas that result in a truncated protein and absence of receptor expression at the cell surface. A number of point mutations in the highly conserved serine/threonine kinase domain of TGFBR2 have also been reported, some of which have been correlated with either loss of trans-phosphorylation of TGF-beta type 1 receptor or constitutive activation of trans-phosphorylation. No TGFBR2 mutations have been reported in human breast tumors, but anomalous expression of TGF-beta in breast carcinomas suggests that TGF-beta signaling may be defective. We have therefore systematically examined unmatched sets of 17 primary and 17 recurrent breast tumor samples for mutations in TGFBR2, restricted to those regions of the gene in which mutations have previously been reported. None of the previously reported mutations was detected, but four novel mutations (V387M, N435S, V447A, and L452M) were found in the kinase domain in recurrent tumors. No mutations were detected in primary tumors. TGF-beta signaling was significantly inhibited by each of the N435S, V447A, and L452M mutations.

Nuclear chaperones

We discuss nuclear chaperones that bind correctly folded protein subunits and mediate molecular interactions, particularly between proteins and nucleic acids. The charge of these chaperones helps to prevent non-specific electrostatic interactions between the components. Thus, an ordered assembly of macromolecular complexes is mediated, most notably in the formation and maintenance of chromatin, though similar principles are likely to apply in ribonucleoprotein assembly. Here, we discuss roles for nuclear chaperones in mediating nucleosome assembly and remodelling during DNA replication and transcription, and upon fertilisation.

p27Xic1, a Cdk inhibitor, promotes the determination of glial cells in Xenopus retina

p27Xic1, a member of the Cip/Kip family of Cdk inhibitors, besides its known function of inhibiting cell division, induces Müller glia from retinoblasts. This novel gliogenic function of p27Xic1 is mediated by part of the N-terminal domain near but distinct from the region that inhibits cyclin-dependent kinases. Cotransfections with dominant-negative and constitutively active Delta and Notch constructs indicate that the gliogenic effects of p27Xic1 work within the context of an active Notch pathway. The gradual increase of p27Xic1 in the developing retina thus not only limits the number of retinal cells but also increasingly favors the fate of the last cell type to be born in the retina, the Müller glia.

Comparison of the effects of diazepam on the fear-potentiated startle reflex and the fear-inhibited light reflex in man

It has been shown previously that the amplitude of the acoustic startle reflex is enhanced, and the amplitude of the light reflex reduced, when subjects anticipate an aversive event, compared to periods when subjects are resting ('fear-potentiated startle reflex' and 'fear-inhibited light reflex'). We examined whether the anxiolytic diazepam would reverse the effects of threat on the startle and pupillary reflexes. Twelve male volunteers participated in three weekly sessions in which they received oral treatment with placebo, diazepam 5 mg and diazepam 10 mg, according to a balanced crossover double-blind design. One hour after ingestion of the treatments, miotic responses to light pulses and electromyographic responses of the orbicularis oculi muscle to sound pulses were elicited during alternating periods in which the threat of an electric shock (electrodes attached to the subject's wrist) was present (THREAT) and absent (SAFE). The THREAT condition was associated with a significant increase in the amplitude of the electromyographic (EMG) response, a significant reduction of the miotic response amplitude, and an increase in self-rated anxiety. Diazepam attenuated all these effects of THREAT. Diazepam did not affect the amplitude of the miotic response under the SAFE condition, but did suppress the EMG response under this condition. These results confirm the validity of the fear-potentiated startle reflex and fear-inhibited light reflex as laboratory models of human anxiety, and reveal some differences between the effects of diazepam on the two reflexes.

Giant eyes in Xenopus laevis by overexpression of XOptx2

Overexpression of XOptx2, a homeodomain-containing transcription factor expressed in the Xenopus embryonic eye field, results in a dramatic increase in eye size. An XOptx2-Engrailed repressor gives a similar phenotype, while an XOptx2-VP16 activator reduces eye size. XOptx2 stimulates bromodeoxyuridine incorporation, and XOptx2-induced eye enlargement is dependent on cellular proliferation. Moreover, retinoblasts transfected with XOptx2 produce clones of cells approximately twice as large as control clones. Pax6, which does not increase eye size alone, acts synergistically with XOptx2. Our results suggest that XOptx2, in combination with other genes expressed in the eye field, is crucially involved in the proliferative state of retinoblasts and thereby the size of the eye.

Neuronal differentiation and patterning in Xenopus: the role of cdk5 and a novel activator xp35.2

Cdk5, a member of the cyclin-dependent kinase family, has been shown to play an important role in development of the central nervous system in mammals when partnered by its activator p35. Here we describe the cloning and characterization of a novel activator of cdk5 in Xenopus, Xp35.2. Xp35.2 is expressed during development initially in the earliest differentiating primary neurons in the neural plate and then later in differentiating neural tissue of the brain. This is in contrast to the previously described Xenopus cdk5 activator Xp35.1 which is expressed over the entire expanse of the neural plate in both proliferating and differentiating cells. Expression of both Xp35.1 and Xp35.2 and activation of cdk5 kinase occur when terminal neural differentiation is induced by neurogenin and neuro D overexpression but not when only early stages of neural differentiation are induced by noggin. Moreover, blocking cdk5 kinase activity specifically results in disruption and reduction of the embryonic eye where cdk5 and its Xp35 activators are expressed. Thus, cdk5/p35 complexes function in aspects of neural differentiation and patterning in the early embryo and particularly in formation of the eye.

The role of cyclin-dependent kinase 5 and a novel regulatory subunit in regulating muscle differentiation and patterning

Cyclin-dependent kinase 5, coupled with its activator p35, is required for normal neuronal differentiation and patterning. We have isolated a novel member of the p35 family, Xp35.1, from Xenopus embryos which can activate cdk5. Xp35.1 is expressed in both proliferating and differentiated neural and mesodermal cells and is particularly high in developing somites where cdk5 is also expressed. Using dominant-negative cdk5 (cdk5 DN), we show that cdk5 kinase activity is required for normal somitic muscle development; expression of cdk5 DN results in disruption of somitic muscle patterning, accompanied by stunting of the embryos. Using explants of animal pole tissue from blastula embryos, which will differentiate into mesoderm in response to activin, we show that blocking cdk5 kinase activity down-regulates the expression of the muscle marker muscle actin in response to activin, whereas the pan-mesodermal marker Xbra is unaffected. Expression of MyoD and MRF4 (master regulators of myogenesis) is suppressed in the presence of cdk5 DN, indicating that these myogenic genes may be a target for cdk5 regulation, whereas the related factor Myf5 is largely unaffected. In addition, overexpression of Xp35.1 disrupts muscle organization. Thus, we have demonstrated a novel role for cdk5 in regulating myogenesis in the early embryo.

Molecular and cellular characterization of CRP1, a Drosophila chromatin decondensation protein

CRP1, a Drosophila nuclear protein that can catalyze decondensation of demembranated Xenopus sperm chromatin was cloned and its primary structure was deduced from cDNA sequence. Alignment of deduced amino acid sequence with published sequences of other proteins revealed strong homologies to Xenopus nucleoplasmin and NO38. CRP1 is encoded by one or several closely related genes found at a single locus, position 99A on the right arm of chromosome 3. CRP1 mRNA is expressed throughout Drosophila development; it is highest during oogenesis and early embryogenesis. mRNA levels correlate closely with levels of protein expression measured previously. Results of chemical crosslinking indicate that CRP1 is either tetrameric or pentameric; similar ambiguity was revealed by direct visualization using scanning transmission electron microscopy. Consistent with previously published results, parallel crosslinking studies of Xenopus nucleoplasmin suggested a pentameric structure. Scanning transmission electron microscopic examination after negative staining revealed that CRP1 and Xenopus nucleoplasmin are morphologically similar. CRP1 is able to substitute for nucleoplasmin in Xenopus egg extract-mediated sperm chromatin decondensation. In vitro, CRP1-induced decondensation is accompanied by direct binding of CRP1 to chromatin.

Hyperphosphorylation of nucleoplasmin facilitates Xenopus sperm decondensation at fertilization

Previous studies showed that the nuclear phosphoprotein nucleoplasmin performs the first stage of chromatin decondensation of Xenopus sperm at fertilization. It binds and removes sperm basic proteins replacing them with histones. We now show that this activity depends upon the massive hyperphosphorylation of nucleoplasmin that occurs when oocytes mature into eggs. Egg extracts or purified hyperphosphorylated egg nucleoplasmin decondense sperm chromatin and remove sperm basic proteins much faster than oocyte extracts or hypophosphorylated oocyte nucleoplasmin. Furthermore, dephosphorylation of egg nucleoplasmin slows sperm decondensation and prevents basic protein removal from sperm chromatin. We conclude that hyperphosphorylation of nucleoplasmin is used to modulate the rapid changes in chromatin structure that accompany early development in Xenopus.

E2F and its developmental regulation in Xenopus laevis

The transcription factor E2F has been implicated in cell cycle control by virtue of its association with cyclins, cyclin-dependent kinases, and pRb-related tumor suppressor gene products. Eggs and embryos from the frog Xenopus laevis have been used to investigate the characteristics of E2F-like molecules in the Xenopus cell cycle and throughout early development. We find multiple E2F species in Xenopus eggs, at least one of which is modified by phosphorylation. The vast majority of E2F remains in the free form throughout the very early embryonic cell cycle, and it also remains predominantly free until some time after the mid-blastula transition, the onset of zygotic transcription. At this time, E2F complexes significantly to pRb but not to cdk2, although cdk2 binding is found in tissue culture cells from a very advanced stage in embryogenesis. This suggests that the complexing of E2F to cyclins, cyclin-dependent kinases, and tumor suppressor gene products may be controlled separately in early Xenopus development. Thus, the association of E2F with other molecules may not result solely from processes affecting cell cycle progression but may also reflect developmental and differentiation cues.

Chromatin decondensation in Drosophila embryo extracts

Decondensation of sperm chromatin in cell-free Drosophila embryo extracts was efficient, rapid, and synchronous. The decondensation activity was N-ethylmaleimide-resistant, soluble, and heat-stable. Two specific proteins, X and Y, were removed selectively from Xenopus sperm coincident with morphological decondensation. A heat-stable protein, p22, was purified to apparent homogeneity from Drosophila melanogaster embryos by a procedure optimized for the purification of Xenopus laevis nucleoplasmin. Although itself capable of catalyzing decondensation of Xenopus sperm, the precise relationship of Drosophila p22 to Xenopus nucleoplasmin is unclear. Drosophila p22 and Xenopus nucleoplasmin were immunologically distinct. Moreover, p22 was present as a nuclear protein throughout Drosophila development as determined both by immunoblot and by indirect immunofluorescence analyses. Drosophila embryo extracts largely or completely immunodepleted of p22 lost some but not all heat-stable decondensation activity. These observations lead to the conclusion that Drosophila embryo extracts contain at least two heat-stable sperm decondensation factors.

The role of nucleoplasmin in chromatin assembly and disassembly

Nucleoplasmin is the most abundant nuclear protein in Xenopus oocytes and eggs. The term 'molecular chaperone' was coined to describe its role in the assembly of the nucleosome subunits of chromatin. Although histones and DNA can self-assemble into nucleosomes, nucleoplasmin can facilitate this process in vitro by competing against non-specific charge interactions. In vivo nucleoplasmin binds histones H2A and H2B and transfers them to DNA. Another acidic nuclear protein, N1, binds and transfers histones H3 and H4. Nucleoplasmin has at least one other role in modulating chromatin structure in Xenopus eggs. It is required for the first stage of sperm chromatin decondensation. It binds and removes sperm basic proteins and replaces them by histones H2A and H2B, again forming nucleosomes, and resulting in decondensation of the compacted sperm chromatin. In addition we propose that the properties of the nuclear localization signal of nucleoplasmin can be explained by a model in which heat shock cognate protein hsc70 has a chaperone role in signal presentation during nuclear transport.

Nucleoplasmin remodels sperm chromatin in Xenopus egg extracts

Nucleoplasmin is necessary and sufficient for the initial stage of Xenopus sperm decondensation in egg extracts. In this article we show that sperm decondensation is accompanied by loss of two sperm-specific basic proteins (X and Y) and gain of histones H2A and H2B, resulting in nucleosome formation. Purified nucleoplasmin alone removes X and Y and assembles purified H2A and H2B on decondensing sperm chromatin, forming nucleosome cores. Immunodepletion of nucleoplasmin from extract prevents removal of X and Y and addition of H2A and H2B, while adding back nucleoplasmin restores decondensation and X and Y removal. Thus, nucleoplasmin acts as both an assembly and a disassembly factor for remodeling sperm chromatin at fertilization.

Academic performance in children of divorce: psychological resilience and vulnerability

Parental divorce can be conceptualized as a stressful event for all children, but one must recognize that reactions to divorce can vary widely among children. This investigation was based on two basic ideas: 1) children of divorce as a group would show deficits in academic performance compared to children from intact families, even several years after their parents' separation, and 2) because factors that promote psychological resilience and vulnerability, we expected to find normal heterogeneity within the divorce sample. Among 96 middle-school adolescents from a suburban school district near Denver, children of divorce showed significant performance deficits in academic achievement, as reflected in grade-point average and scholastic motivation in middle school, but not in nationally normed tests of scholastic aptitude and other less direct measures of behavioral conformity. An analysis of GPA over time revealed strikingly disparate patterns of achievement between divorce and control groups. Corresponding patterns of scholastic aptitude scores, absence from school and comportment revealed no systematic differences over time. These results suggest strongly that parental divorce can be a critical event in the academic development of children. Large differences in academic achievement between our divorce group as a whole and the controls cannot be attributed, at least at the time of sampling, to differences in social class or intellectual ability. Despite a similar family background, i.e., marital dissolution, a minority of the children of divorce showed vulnerability in the pattern of academic achievement over time while the majority demonstrated academic careers not unlike that of the controls.

Sperm decondensation in Xenopus egg cytoplasm is mediated by nucleoplasmin

At fertilization, sperm chromatin decondenses in two stages, which can be mimicked in extracts of Xenopus eggs. Rapid, limited decondensation is followed by slower, membrane-dependent decondensation and swelling. Nucleoplasmin, an acidic nuclear protein, occurs at high concentration in Xenopus eggs and has a histone-binding role in nucleosome assembly. Immunodepleting nucleoplasmin from egg extracts inhibits the initial rapid stage of sperm decondensation, and also the decondensation of myeloma nuclei, relative to controls of mock depletion and TFIIIA depletion. Readdition of purified nucleoplasmin recues depleted extracts. A physiological concentration of purified nucleoplasmin alone decondenses both sperm and myeloma nuclei. We conclude that nucleoplasmin is both necessary and sufficient for the first stage of sperm decondensation in Xenopus eggs.

Semantic interference from subliminal stimuli in a dichoptic viewing situation

In Expt 1 subjects named words, shapes or colours presented to one eye while words or shapes were presented to the other eye subliminally. The subliminal stimuli were found to slow naming responses when they had the same name as the stimulus to be named or a closely related name, compared with random letter strings or blank cards. This result was replicated in a second experiment which also included unrelated words as subliminal stimuli. On these trials latencies were midway between those for trials with blank cards or random letter strings as the subliminal stimuli, and trials with the same name or a closely related name as the subliminal stimuli. The results imply that stimuli related in meaning compete for common analysing mechanisms.