Decompressive craniectomy to cranioplasty: a retrospective observational study using Hospital Episode Statistics in England.

Objectives: To investigate the longitudinal trends of decompressive craniectomy (DC) following traumatic brain injury (TBI) or stroke and explore whether the timing of cranial reconstruction affected revision or removal rates using Hospital Episode Statistics (HES) between 2014 and 2019. Design: Retrospective observational cohort study using HES. The time frame definitions mirror those often used in clinical practice. Setting: HES data from neurosurgical centres in England. Participants: HES data related to decompressive craniectomy procedures and cranioplasty following TBI or stroke between 2014 and 2019. Main outcome measures: The primary outcome was the timing and rate of revision/removal compared with cranioplasty within <12 weeks to ≥12 weeks. Results: There were 4627 DC procedures, of which 1847 (40%) were due to head injury, 1116 (24%) were due to stroke, 728 (16%) were due to other cerebrovascular diagnoses, 317 (7%) had mixed diagnosis and 619 (13%) had no pre-specified diagnoses. The number of DC procedures performed per year ranged from 876 in 2014-2015 to 967 in 2018-2019. There were 4466 cranioplasty procedures, with 309 (7%) revisions and/or removals during the first postoperative year. There was a 33% increase in the overall number of cranioplasty procedures performed within 12 weeks, and there were 1823 patients who underwent both craniectomy and cranioplasty during the study period, with 1436 (79%) having a cranioplasty within 1 year. However, relating to the timing of cranial reconstruction, there was no evidence of any difference in the rate of revision or removal surgery in the early timing group (6.5%) compared with standard care (7.9%) (adjusted HR 0.93, 95% CIs 0.61 to 1.43; p=0.75). Conclusions: Overall number of craniectomies and the subsequent requirements for cranioplasty increased steadily during the study period. However, relating to the timing of cranial reconstruction, there was no evidence of an overall difference in the rate of revision or removal surgery in the early timing group.

Expression of a gene for mouse eucaryotic elongation factor Tu during murine erythroleukemic cell differentiation.

The eucaryotic elongation factor Tu (eEF-Tu) is a single polypeptide with an approximate Mr of 53,000. During protein synthesis eEF-Tu promotes the binding of aminoacyl-tRNA to the ribosome. To study the expression of the gene(s) for this factor, a genomic clone was isolated that contains a mouse eEF-Tu gene. We screened a phage genomic library with a synthetic oligonucleotide probe complementary to a region of the Saccharomyces cerevisiae and Artemia sp. eEF-Tu genes which codes for an area that is highly conserved between both yeast and Artemia sp. eEF-Tu. From approximately 75,000 phage plaques we obtained five isolates with apparently identical inserts. All five clones contained a 3.8-kilobase EcoRI fragment that hybridized to additional oligonucleotide probes corresponding to different conserved regions of eEF-Tu. We sequenced the 5' end of one genomic clone and determined the length of the cloned fragment that was protected by eEF-Tu mRNA in S1 nuclease protection assays. A quantitative S1 nuclease protection assay was used to compare the relative steady-state levels of eEF-Tu mRNA in total mRNA in total RNA isolated from hexamethylene-bisacetamide-induced murine erythroleukemia cells. The results show a dramatic reduction in the steady-state level of eEF-Tu mRNA as differentiation proceeds. A similar reduction in transcription of eEF-Tu mRNA was observed in isolated nuclei. Finally, we examined the in vivo synthesis of eEF-Tu during differentiation and found that it declined in a manner parallel to the decline in the steady-state level of eEF-Tu mRNA. In addition, we have isolated and sequenced a cDNA clone for mouse eEF-Tu. The derived amino acid sequence is compared with sequences from other eucaryotes.

Hexamethylene bisacetamide-induced differentiation of Friend virus-transformed murine erythroleukemia cells is associated with parallel changes in casein kinase II and guanine nucleotide exchange factor activities.

In mammalian cells, the guanine nucleotide exchange factor (GEF, eIF-2B) plays a major role in the regulation of initiation of protein synthesis. It catalyzes the exchange of eukaryotic chain initiation factor (eIF)-2-bound GDP for GTP and facilitates the recycling of eIF-2 during polypeptide chain initiation. We used the Friend virus-transformed murine erythroleukemia (MEL) cell system to elucidate the translational regulatory processes that occur during growth and hexamethylene bisacetamide (HMBA)-induced cell differentiation. GEF activity is increased during growth and decreased during MEL cell differentiation, and this parallels the overall changes in protein synthesis during this period. Inhibition of GEF activity in induced cells may occur indirectly by phosphorylation of the alpha-subunit of eIF-2. However, the decrease in GEF activity in induced cells cannot be reversed by increasing the concentration of eIF-2-GDP added as a substrate in the GEF assay. This is diagnostic for the presence of eIF-2 alpha(P)-GDP in cell lysates and suggests that regulation of GEF activity may occur by one or more mechanisms other than eIF-2(alpha) phosphorylation. We have previously shown that the activity of GEF may be influenced directly by phosphorylation with casein kinase II (CK-II) of the 82-kD subunit of the factor. CK-II activity parallels the changes in GEF activity and the rate of protein synthesis during growth and differentiation of MEL cells. Addition of 1mM spermidine, a stimulator of CK-II but not of purified GEF, in induced MEL cell extracts enhances both CK-II and GEF activities approximately 48 and 32%, respectively. The results presented suggest that the inhibition of protein synthesis during MEL cell differentiation may be linked to the decreased CK-II and GEF activities.

The surgical treatment of anterior knee pain due to infrapatellar fat pad pathology: A systematic review.

BACKGROUND: Anterior knee pain (AKP) encompasses a range of pathologies. As a result, there are a number of therapeutic options used to treat AKP. The non-operative treatments have been analysed in a number of randomised controlled trials and systematic reviews. There is however a scarcity of such publications covering the surgical management of AKP. There are no systematic reviews that have investigated surgical interventions for AKP due to pathology of the infrapatellar fat pad (IFP). The aims of this study were to review the literature systematically, to establish which surgical procedures have been used to treat IFP disease and to determine their efficacy. METHODS: The review was conducted in accordance with the PRISMA reporting guidelines. A search of the literature was performed on 1st January 2014 using multiple databases including CENTRAL, MEDLINE, EMBASE, PubMed, and Google Scholar. The quality of the studies was assessed using Oxford Evidence-Based Medicine Levels of Evidence guidelines and the GRADE approach. RESULTS: Twenty-four eligible studies were found and included. The critical appraisal identified that the current evidence-base has low methodology quality. The clinical findings indicated that there is a positive trend towards the surgical management of IFP disease for AKP symptoms. Excision of IFP tumours and resection of the IFP in Hoffa's disease can lead to improvements in symptoms and function. CONCLUSIONS: Truly robust evidence to support the surgical management of IFP pathology requires randomised controlled trials; however the expenses involved to design such trials means that they are unlikely to be undertaken for this uncommon disorder. Consequently well-designed and well-reported case series need to be undertaken to improve our current understanding that includes recording quantitative measures such as range of knee motion, VAS Pain scores and a validated scoring system.

Isolation and mapping of a gene for protein synthesis initiation factor 4A and its expression during differentiation of murine erythroleukemia cells.

Eukaryotic protein synthesis initiation factor 4A (eIF-4A), a 46-kDa polypeptide, is involved both in mRNA cap recognition and in the binding of mRNA to 40S ribosomal subunits. A 41-mer oligodeoxynucleotide probe was synthesized complementary to a portion of the published coding sequence of eIF-4A mRNA [Nielsen et al., Nucleic Acids Res. 13 (1985) 6867-6870] and used to screen a mouse genomic library. We have isolated and characterized a full-length clone from that library. The eIF-4A sequence is contained in eleven exons. The eleventh exon also has the 3'-nontranslated sequence and two separate polyadenylation sites. Northern-blot analysis of mouse poly(A)+RNA indicates that there are several distinct mRNA species coding for eIF-4A. Two of these contain the same coding sequence and differ only in the length of the 3'-nontranslated region. Two of the eIF-4A mRNAs are therefore likely to be the result of differential processing at the 3'-end. We have used a fragment of the genomic clone to measure the steady-state levels of eIF-4A mRNA during the induced differentiation of murine erythroleukemia cells. S1 nuclease protection experiments demonstrated that by the fourth day after induction eIF-4A mRNA declined to 25% of its steady-state level in uninduced cells. In contrast, the steady-state level of beta-globin mRNA increased dramatically during differentiation. In vitro transcription assays using nuclei isolated from uninduced and induced cells show that the rate of transcription of eIF-4A mRNA was 40% greater in differentiated cells, indicating a posttranscriptional component is involved in the regulation of the steady-state mRNA level.

Relaxation kinetics of E. coli ribosomes: evidence for the reaction of 30S . IF3 complex with 50S ribosomal subunits.

Addition of initiation factor IF3 to solutions of E. coli ribosomes dramatically alters their behavior in pressure-jump relaxation kinetic experiments in which 90 degrees light-scattering is used to monitor the macromolecular reaction. The effect of IF3 on relaxation processes attributed to "tight" couples is strongly dependent on the Mg2+ concentration. At 2.5 mM Mg2+, addition of 1 molar equivalent of IF3 decreases the relaxation amplitude by a factor of 3 relative to ribosome solutions without IF3. However, at 5.0 mM Mg2+, addition of 1 molar equivalent of IF3 produces a marked increase in the relaxation amplitude, by a factor of 2-8 fold relative to ribosomes in the absence of IF3. IF3 has no effect on the relaxation process attributed to "loose" couples at 10 mM Mg2+. While we are unable to propose a precise mechanism for IF3 action with the data on hand, our results require that the 30S . IF3 complex either reacts with the 50S subunit, forming a 70S . IF3 intermediate, or acts as a pool of reactive 30S subunit. Further kinetic evidence is required to distinguish between these possible pathways.

Relaxation kinetics of E coli ribosomes: evidence for the reaction of 30S . IF3 complex with 50S ribosomal subunits.

Addition of initiation factor IF3 to solutions of E.coli ribosomes dramatically alters their behavior in pressure-jump relaxation kinetic experiments in which 90 degrees light-scattering is used to monitor the macromolecular reaction. The effect of IF3 on relaxation processes attributed to "tight" couples is strongly dependent on the Mg2+ concentration. At 2.5 mM Mg2+, addition of 1 molar equivalent of IF3 decreases the relaxation amplitude by a factor of 3 relative to ribosome solutions without IF3. However, at 5.0 mM Mg2+, addition of 1 molar equivalent of IF3 produces a marked increase in the relaxation amplitude, by a factor of 2-8 fold relative to ribosomes in the absence of IF3. IF3 has no effect on the relaxation process attributed to "loose" couples at 10 mM Mg2+. While we are unable to propose a precise mechanism for IF3 action with the data on hand, our results require that the 30S . IF3 complex either reacts with the 50S subunit, forming a 70S . IF3 intermediate, or acts as a pool of reactive 30S subunit. Further kinetic evidence is required to distinguish between these possible pathways.

Purification and some properties of an oxydative inhibitor in rabbit reticulocyte lysates.

Protein synthesis in rabbit reticulocyte lysates in the presence of heme is inhibited by 50% by the addition of 4 mM GSSG (oxidized glutathione). The incubation of the rabbit reticulocyte lysate with 4 mM GSSG at 30 degrees C for 30 min will cause activation of an inhibitor of protein synthesis which could be purified from the lysates through a five-step procedure. The inhibitor results in a 70-80% inhibition after a 1 h incubation. The inhibitor consists of one polypeptide of 23 kDa apparent molecular weight and is 90% pure as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. However, in the presence of cAMP (10 mM) or GEF (guanine nucleotide exchange factor) (0.3 microgram), protein synthesis in the inhibited reticulocyte lysate will be already recovered.

Phosphorylation of the guanine nucleotide exchange factor from rabbit reticulocytes regulates its activity in polypeptide chain initiation.

We have demonstrated that the purified guanine nine nucleotide exchange factor (GEF) may be isolated as a complex with NADPH. Complete inhibition of the GEF-catalyzed exchange of eukaryotic initiation factor 2-bound GDP for GTP was observed in the presence of either 0.5-0.75 mM NAD+ or NADP+. Incubation of GEF with ATP results in the phosphorylation of its Mr 82,000 polypeptide. This phosphorylation is strongly inhibited by heparin but is not affected by heme or H8 (N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride), an inhibitor of cAMP- and cGMP-dependent protein kinases and protein kinase C. The purification of GEF was modified to eliminate any contaminating kinase activity and the isolated protein appears to be homogeneous as judged by NaDodSO4/polyacrylamide gel electrophoresis and silver staining. The Mr 82,000 subunit of GEF is phosphorylated only upon addition of ATP and casein kinase II. The extent of phosphorylation is approximately equal to 0.55 mol of phosphate per mol of GEF, and this results in a 2.3-fold increase in the guanine nucleotide exchange activity. Following treatment of the phosphorylated GEF with alkaline phosphatase, the activity of the protein is reduced by a factor of 5. Rephosphorylation of GEF increases its specific activity to that of the phosphorylated protein. The results of this study suggest that phosphorylation/dephosphorylation of GEF plays a role in regulating polypeptide chain initiation.

Mechanism of the nucleotide exchange reaction in eukaryotic polypeptide chain initiation. Characterization of the guanine nucleotide exchange factor as a GTP-binding protein.

Polypeptide chain initiation in mammalian systems is regulated at the level of the guanine nucleotide exchange factor (GEF). This multisubunit protein catalyzes the exchange of GDP bound to eukaryotic initiation factor 2 (eIF-2) for GTP. Although various models have been proposed for its mode of action, the exact sequence of events involved in nucleotide exchange is still uncertain. We have studied this reaction by three different experimental techniques: (a) membrane filtration assays to measure the release of [3H]GDP from the eIF-2.[3H]GDP binary complex, (b) changes in the steady-state polarization of fluorescamine-GDP during the nucleotide exchange reaction, and (c) sucrose gradient analysis of the total reaction. The results obtained do not support the reaction as written: eIF-2.GDP + GEF in equilibrium eIF-2.GEF + GDP. The addition of GEF alone does not result in the displacement of eIF-2-bound GDP. The release of bound GDP is dependent on the presence of both GTP and GEF, and this argues against the possibility of a substituted enzyme (ping-pong) mechanism for the guanine nucleotide exchange reaction. An important finding of the present study is the observation that GTP binds to GEF. The Kd value of 4 microM for GTP was estimated (a) by the extent of quenching of tryptophan fluorescence of GEF in the presence of GTP and (b) by the binding of [3H]GTP to GEF as measured on nitrocellulose membranes. The GEF-dependent release of eIF-2-bound GDP was studied at several constant concentrations of one substrate (GTP or eIF-2.GDP) while varying the second substrate concentration, and the results were then plotted according to the Lineweaver-Burk method. Taken together, the results of GTP and eIF-2.GDP binding to GEF and the pattern of the double-reciprocal plots strongly suggest that the guanine nucleotide exchange reaction follows a sequential mechanism.

Regulation of protein synthesis in eukaryotic cells by the guanine nucleotide exchange factor and chain initiation factor 2.

In eukaryotes, the guanine nucleotide exchange factor (eIF-2B) is a key protein in the control of polypeptide chain initiation. It catalyzes the exchange of chain initiation factor (eIF)-2-bound GDP for GTP and facilitates the formation of a ternary complex (eIF-2.GTP.Met-tRNAf). The activity of eIF-2B is inhibited indirectly by phosphorylation of the smallest subunit of eIF-2 which sequesters eIF-2B into an inactive eIF-2(alpha P).eIF-2B complex. On the other hand, eIF-2B activity may be regulated directly by covalent modification of its largest subunit with different kinases, such as casein kinase (CK)-I, CK-II and glycogen synthase kinase (GSK)-3. After stimulation of mammalian cells by insulin or growth factors, the allosteric activation of eIF-2B activity by sugar phosphates and inositol phosphates may also provide an important parameter in the regulation of protein synthesis.

Allosteric activation of rabbit reticulocyte guanine nucleotide exchange factor activity by sugar phosphates and inositol phosphates.

Sugar phosphates are required to maintain active rates of translation in gel-filtered rabbit reticulocyte lysates. They may stimulate polypeptide chain initiation by acting as NADPH generators or by a direct interaction with initiation factor(s). We now provide evidence for the allosteric activation of the purified guanine nucleotide exchange factor (eIF-2B) by sugar phosphates and inositol phosphates. In the presence of microM fructose 1,6-bisphosphate, the rate of eIF-2B-catalyzed GDP/GTP exchange is increased approximately 2-fold. The half-maximal concentration for stimulation of eIF-2B activity (SC50) is 57 microM. The binding of GTP to isolated eIF-2B is stimulated 1.5-fold, whereas GTP-binding to ALP-treated eIF-2B is not affected by sugar phosphates. Inositol 1,4-bisphosphate, like fructose 1,6-bisphosphate, stimulates 2-3-fold the activity of the isolated eIF-2B (SC50, 140 microM).

The isolation and characterization from rabbit reticulocytes of two forms of eukaryotic initiation factor 2 having different beta-polypeptides.

We have isolated from the high salt wash of rabbit reticulocyte ribosomes two forms of the polypeptide chain initiation factor 2 (eIF-2) which differ with respect to their beta-subunit, GDP content, and sensitivity to Mg2+ in ternary (eIF-2 X GTP X Met-tRNAf) and binary (eIF-2 X GDP) complex formation. The form of eIF-2 eluting first from a cation exchange (Mono S, Pharmacia) column has a beta-subunit of lower molecular weight (eIF-2(beta L] and a more acidic pI value than the form eluting at a higher salt concentration (eIF-2(beta H]. These two forms of eIF-2 beta-polypeptides are also detected in reticulocyte lysates when the proteins are resolved by two-dimensional isoelectric focusing-dodecyl sulfate polyacrylamide gel electrophoresis followed by immunoblotting. The peptide mapping of the isolated beta-subunits after limited proteolysis by papain, pancreatic protease, alpha-chymotrypsin, or Staphylococcus aureus V8 protease further demonstrates that the two forms of beta-subunits are not the product of a non-specific proteolytic action that occurred during the purification procedure, but rather reflects the existence in vivo of both forms of eIF-2. The GDP content of eIF-2(beta L) and eIF-2(beta H) is approximately 0.85 and 0.22 mol of GDP/mol of eIF-2, respectively. The KD for GDP of eIF-2(beta L) was lower (2.2 X 10(-9) M) than that of eIF-2(beta H) (6.0 X 10(-8) M). In the presence of 1 mM Mg2+, the activities of eIF-2(beta L) and eIF-2(beta H) in forming a binary and a ternary complex are inhibited 90 and 25%, respectively. The extent of Mg2+ inhibition and its reversal by the guanine nucleotide exchange factor is directly proportional to the amount of GDP bound to eIF-2. No inhibition by Mg2+ is observed when eIF-2-bound GDP is removed by alkaline phosphatase. In the presence of the guanine nucleotide exchange factor, both forms of eIF-2 are equally active in ternary complex formation, and the complex formed is quantitatively transferred to 40 S ribosomal subunits.