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M J Solomon

Publications and source records attributed to M J Solomon.

At least 37 records · Page 2Linked to original sources
PubMed2000

Kinetic analysis of the cyclin-dependent kinase-activating kinase (Cak1p) from budding yeast.

Cak1p, the Cyclin-dependent kinase-activating kinase from budding yeast, is an unusual protein kinase that lacks many of the highly conserved motifs observed among members of the protein kinase superfamily. Cak1p phosphorylates and activates Cdc28p, the major cyclin-dependent kinase (CDK) in yeast, and is thereby required for passage through the yeast cell cycle. In this paper, we explore the kinetics of CDK phosphorylation by Cak1p, and we examine the role of the catalytic step in the reaction mechanism. Cak1p proceeds by a sequential reaction mechanism, binding to both ATP and CDK2 with reasonable affinities, exhibiting K(d) values of 7.2 and 0.6 microm, respectively. Interestingly, these values are approximately the same as the K(M) values, indicating that the binding of substrates is fast with respect to catalysis and that the most likely reaction mechanism is rapid equilibrium random. Cak1p is a slow enzyme, with a catalytic rate of only 4.3 min(-)(1). The absence of a burst phase indicates that product release is not rate-limiting. This result, and a solvent isotope effect, suggests that a catalytic step is rate-limiting.

Adenosine Triphosphate↗
PubMed2000

The effects of changing the site of activating phosphorylation in CDK2 from threonine to serine.

Cyclin-dependent kinases (CDKs) that control cell cycle progression are regulated in many ways, including activating phosphorylation of a conserved threonine residue. This essential phosphorylation is carried out by the CDK-activating kinase (CAK). Here we examine the effects of replacing this threonine residue in human CDK2 by serine. We found that cyclin A bound equally well to wild-type CDK2 (CDK2(Thr-160)) or to the mutant CDK2 (CDK2(Ser-160)). In the absence of activating phosphorylation, CDK2(Ser-160)-cyclin A complexes were more active than wild-type CDK2(Thr-160)-cyclin A complexes. In contrast, following activating phosphorylation, CDK2(Ser-160)-cyclin A complexes were less active than phosphorylated CDK2(Thr-160)-cyclin A complexes, reflecting a much smaller effect of activating phosphorylation on CDK2(Ser-160). The kinetic parameters for phosphorylating histone H1 were similar for mutant and wild-type CDK2, ruling out a general defect in catalytic activity. Interestingly, the CDK2(Ser-160) mutant was selectively defective in phosphorylating a peptide derived from the C-terminal domain of RNA polymerase II. CDK2(Ser-160) was efficiently phosphorylated by CAKs, both human p40(MO15)(CDK7)-cyclin H and budding yeast Cak1p. In fact, the k(cat) values for phosphorylation of CDK2(Ser-160) were significantly higher than for phosphorylation of CDK2(Thr-160), indicating that CDK2(Ser-160) is actually phosphorylated more efficiently than wild-type CDK2. In contrast, dephosphorylation proceeded more slowly with CDK2(Ser-160) than with wild-type CDK2, either in HeLa cell extract or by purified PP2Cbeta. Combined with the more efficient phosphorylation of CDK2(Ser-160) by CAK, we suggest that one reason for the conservation of threonine as the site of activating phosphorylation may be to favor unphosphorylated CDKs following the degradation of cyclins.

Amino Acid Substitution↗
PubMed2000

Biofeedback for fecal incontinence using transanal ultrasonography: novel approach.

PURPOSE: Neosphincter procedures may prove to be the treatment of choice for patients with neuropathic fecal incontinence but are rarely proposed for milder forms of the disease. Biofeedback may prove beneficial to these patients but is yet unproven. The objectives of this study were to develop a method of performing biofeedback using transanal ultrasound to teach the patient to contract repetitively and to determine biologic measures of sphincter function using transanal ultrasound in healthy and incontinent patients. METHODS: Initial uncontrolled studies were performed to determine the compliance, normal values, biologic measures of external sphincter strength (isotonic and isometric fatigue times), and early efficacy data using continence scores and visual analog scale scores. RESULTS: Forty-four patients were assessed during three months, with relative improvements in continence scores (St. Mark's Hospital, 40 percent; Pescatori, 20 percent) and patient and investigator visual analog scale scores (38 percent for both) and measurable increase in biologic fatigue times measured by transanal ultrasound. CONCLUSIONS: Transanal ultrasound seems to be a method of teaching external sphincter contraction and measuring sphincter strength with good initial compliance. Clinically and statistically significant improvements in incontinence scores, visual analog scale scores, and biologic strength of the external sphincter were detected in the short-term follow-up with uncontrolled data. The randomized, controlled trial that we have begun will either confirm or refute these results.

Adult↗
PubMed2000

Analysis of CAK activities from human cells.

The cdk-activating kinase (CAK) activates cyclin-dependent kinases (cdks) that control cell-cycle progression by phosphorylating a threonine residue conserved in cdks. CAK from humans contains p40MO15 (cdk7), cyclin H and MAT1, which are also subunits of transcription factor IIH where they phosphorylate the C-terminal domain of the large subunit of RNA polymerase II. In contrast, budding yeast Cak1p is a monomeric enzyme without C-terminal domain kinase activity. Here, we analyze CAK activities in HeLa cells using cdk2-affinity chromatography. In addition to MO15, a second CAK activity was detected that runs on gel filtration at 30-40 kDa. This activity phosphorylated and activated cdk2 and cdk6. Furthermore, this 'small CAK' activity resembled Cak1p rather than MO15 in terms of substrate specificity, reactivity to antibodies against MO15 and Cak1p, and sensitivity to 5'-fluorosulfonylbenzoyladenosine, an irreversible inhibitory ATP analog. Our findings suggest the presence of at least two different CAK activities in human cells.

CDC2-CDC28 Kinases↗
PubMed2000

Activating phosphorylation of the Saccharomyces cerevisiae cyclin-dependent kinase, cdc28p, precedes cyclin binding.

Eukaryotic cell cycle progression is controlled by a family of protein kinases known as cyclin-dependent kinases (Cdks). Two steps are essential for Cdk activation: binding of a cyclin and phosphorylation on a conserved threonine residue by the Cdk-activating kinase (CAK). We have studied the interplay between these regulatory mechanisms during the activation of the major Saccharomyces cerevisiae Cdk, Cdc28p. We found that the majority of Cdc28p was phosphorylated on its activating threonine (Thr-169) throughout the cell cycle. The extent of Thr-169 phosphorylation was similar for monomeric Cdc28p and Cdc28p bound to cyclin. By varying the order of the addition of cyclin and Cak1p, we determined that Cdc28p was activated most efficiently when it was phosphorylated before cyclin binding. Furthermore, we found that a Cdc28p(T169A) mutant, which cannot be phosphorylated, bound cyclin less well than wild-type Cdc28p in vivo. These results suggest that unphosphorylated Cdc28p may be unable to bind tightly to cyclin. We propose that Cdc28p is normally phosphorylated by Cak1p before it binds cyclin. This activation pathway contrasts with that in higher eukaryotes, in which cyclin binding appears to precede activating phosphorylation.

Antibody Specificity↗
PubMed2000

Hsl1p, a Swe1p inhibitor, is degraded via the anaphase-promoting complex.

Ubiquitination and subsequent degradation of critical cell cycle regulators is a key mechanism exploited by the cell to ensure an irreversible progression of cell cycle events. The anaphase-promoting complex (APC) is a ubiquitin ligase that targets proteins for degradation by the 26S proteasome. Here we identify the Hsl1p protein kinase as an APC substrate that interacts with Cdc20p and Cdh1p, proteins that mediate APC ubiquitination of protein substrates. Hsl1p is absent in G(1), accumulates as cells begin to bud, and disappears in late mitosis. Hsl1p is stabilized by mutations in CDH1 and CDC23, both of which result in compromised APC activity. Unlike Hsl1p, Gin4p and Kcc4p, protein kinases that have sequence homology to Hsl1p, were stable in G(1)-arrested cells containing active APC. Mutation of a destruction box motif within Hsl1p (Hsl1p(db-mut)) stabilized Hsl1p. Interestingly, this mutation also disrupted the Hsl1p-Cdc20p interaction and reduced the association between Hsl1p and Cdh1p in coimmunoprecipitation studies. These findings suggest that the destruction box motif is required for Cdc20p and, to a lesser extent, for Cdh1p to target Hsl1p to the APC for ubiquitination. Hsl1p has been previously shown to inhibit Swe1p, a protein kinase that negatively regulates the cyclin-dependent kinase Cdc28p, by promoting Swe1p degradation via SCF(Met30) in a bud morphogenesis checkpoint. Results of the present work indicate that Hsl1p is degraded in an APC-dependent manner and suggest a link between the SCF (Skp1-cullin-F box) and APC-proteolytic systems that may help to coordinate the proper progression of cell cycle events.

Amino Acid Motifs↗
PubMed2000

Neoplastic progression occurs through mutator pathways in hyperplastic polyposis of the colorectum.

AIM: Colorectal cancer has been described in association with hyperplastic polyposis but the mechanism underlying this observation is unknown. The aim of this study was to characterise foci of dysplasia developing in the polyps of subjects with hyperplastic polyposis on the basis of DNA microsatellite status and expression of the DNA mismatch repair proteins hMLH1, hMSH2, and hMSH6. MATERIALS AND METHODS: The material was derived from four patients with hyperplastic polyposis and between one and six synchronous colorectal cancers. Normal (four), hyperplastic (13), dysplastic (13), and malignant (11) samples were microdissected and a PCR based approach was used to identify mutations at 10 microsatellite loci, TGFbetaIIR, IGF2R, BAX, MSH3, and MSH6. Microsatellite instability-high (MSI-H) was diagnosed when 40% or more of the microsatellite loci showed mutational bandshifts. Serial sections were stained for hMLH1, hMSH2, and hMSH6. RESULTS: DNA microsatellite instability was found in 1/13 (8%) hyperplastic samples, in 7/13 (54%) dysplastic foci, and in 8/11 (73%) cancers. None of the MSI-low (MSI-L) samples (one hyperplastic, three dysplastic, two cancers) showed loss of hMLH1 expression. All four MSI-H dysplastic foci and six MSI-H cancers showed loss of hMLH1 expression. Loss of hMLH1 in MSI-H but not in MSI-L lesions showing dysplasia or cancer was significant (p<0.001, Fisher's exact test). Loss of hMSH6 occurred in one MSI-H cancer and one MSS focus of dysplasia which also showed loss of hMLH1 staining. CONCLUSION: Neoplastic changes in hyperplastic polyposis may occur within a hyperplastic polyp. Neoplasia may be driven by DNA instability that is present to a low (MSI-L) or high (MSI-H) degree. MSI-H but not MSI-L dysplastic foci are associated with loss of hMLH1 expression. At least two mutator pathways drive neoplasia in hyperplastic polyposis. The role of the hyperplastic polyp in the histogenesis of sporadic DNA microsatellite unstable colorectal cancer should be examined.

Aged↗
PubMed1999

Transforming growth factor beta targeted inactivation of cyclin E:cyclin-dependent kinase 2 (Cdk2) complexes by inhibition of Cdk2 activating kinase activity.

Transforming growth factor beta (TGF-beta)-mediated G(1) arrest previously has been shown to specifically target inactivation of cyclin D:cyclin-dependent kinase (Cdk) 4/6 complexes. We report here that TGF-beta-treated human HepG2 hepatocellular carcinoma cells arrest in G(1), but retain continued cyclin D:Cdk4/6 activity and active, hypophosphorylated retinoblastoma tumor suppressor protein. Consistent with this observation, TGF-beta-treated cells failed to induce p15(INK4b), down-regulate CDC25A, or increase levels of p21(CIP1), p27(KIP1), and p57(KIP2). However, TGF-beta treatment resulted in the specific inactivation of cyclin E:Cdk2 complexes caused by absence of the activating Thr(160) phosphorylation on Cdk2. Whole-cell lysates from TGF-beta-treated cells showed inhibition of Cdk2 Thr(160) Cdk activating kinase (CAK) activity; however, cyclin H:Cdk7 activity, a previously assumed mammalian CAK, was not altered. Saccharomyces cerevisiae contains a genetically and biochemically proven CAK gene, CAK1, that encodes a monomeric 44-kDa Cak1p protein unrelated to Cdk7. Anti-Cak1p antibodies cross-reacted with a 45-kDa human protein with CAK activity that was specifically down-regulated in response to TGF-beta treatment. Taken together, these observations demonstrate that TGF-beta signaling mediates a G(1) arrest in HepG2 cells by targeting Cdk2 CAK and suggests the presence of at least two mammalian CAKs: one specific for Cdk2 and one for Cdk4/6.

CDC2-CDC28 Kinases↗
PubMed1999

Dephosphorylation of cyclin-dependent kinases by type 2C protein phosphatases.

Activating phosphorylation of cyclin-dependent protein kinases (CDKs) is necessary for their kinase activity and cell cycle progression. This phosphorylation is carried out by the Cdk-activating kinase (CAK); in contrast, little is known about the corresponding protein phosphatase. We show that type 2C protein phosphatases (PP2Cs) are responsible for this dephosphorylation of Cdc28p, the major budding yeast CDK. Two yeast PP2Cs, Ptc2p and Ptc3p, display Cdc28p phosphatase activity in vitro and in vivo, and account for approximately 90% of Cdc28p phosphatase activity in yeast extracts. Overexpression of PTC2 or PTC3 results in synthetic lethality in strains temperature-sensitive for yeast CAK1, and disruptions of PTC2 and PTC3 suppress the growth defect of a cak1 mutant. Furthermore, PP2C-like enzymes are the predominant phosphatases toward human Cdk2 in HeLa cell extracts, indicating that the substrate specificity of PP2Cs toward CDKs is evolutionarily conserved.

CDC28 Protein Kinase, S cerevisiae↗
PubMed1999

The CDK-activating kinase (Cak1p) from budding yeast has an unusual ATP-binding pocket.

Cak1p is an essential protein kinase that phosphorylates and thereby activates the major cyclin-dependent kinase in budding yeast, Cdc28p. The sequence of Cak1p differs from other members of the protein kinase superfamily in several conserved regions. Cak1p lacks the highly conserved glycine loop motif (GXGXXG) that is found in the nucleotide binding fold of virtually all protein kinases and also lacks a number of conserved amino acids found at sites throughout the protein kinase core sequence. We have used kinetic and mutagenic analyses to investigate whether these sequence differences affect the nucleotide-binding properties of Cak1p. Although Cak1p differs dramatically from other protein kinases, it binds ATP with a reasonable affinity, with a KM of 4.8 microM. Mutations of the putative invariant lysine in Cak1p (Lys-31), homologous to a residue required for activity in virtually all protein kinases and that interacts with the ATP phosphates, moderately reduced the ability of Cak1p to bind ATP but did not dramatically affect the catalytic rate of the kinase. Similarly, Cak1p is insensitive to the ATP analog 5'-fluorosulfonylbenzoyladenosine, which inhibits most protein kinases through covalent modification of the invariant lysine. We found that Cak1p is tolerant of mutations within its glycine loop region. Remarkably, Cak1p remains functional even following truncation of its first 31 amino acids, including the glycine loop region and the invariant lysine. We conclude that the Cak1p nucleotide-binding pocket differs significantly from those of most other protein kinases and therefore might provide a specific target for an inhibitory drug.

Adenosine Triphosphatases↗
PubMed1999

Abdominal surgery in the older Crohn's population.

BACKGROUND: The surgical literature perceives that the elderly cohort of Crohn's patients may have increased risk with surgery. METHODS: A retrospective review and prospective database analysis of all patients with histologically proven Crohn' s disease who had a laparotomy at a single Sydney teaching hospital were performed. The last laparotomy of each patient was included in the analysis for morbidity and mortality to assess whether an older cohort was at an increased risk. RESULTS: A total of 156 patients had 298 laparotomies for histopathologically proven Crohn's disease. The frequency distribution of age at last laparotomy was bimodal, and the statistically determined cut-off age between younger and older cohorts was 55 years. Thirty-three patients were older than 55 years. There was no difference in duration of symptoms before first diagnosis (older, 17 months vs younger, 25 months), previous number of Crohn's operations (42.4 vs 39.8%), or duration of known Crohn's disease. Isolated large bowel disease was more common in the elderly cohort (42.4 vs 18.7%, chi2 = 8.09, P < 0.01). Small bowel and ileocaecal resections were more common in the younger cohort (72.4 vs 51.6%, chi2 = 5.19, P < 0.025). There was one death in each cohort (overall mortality 1.3%) and anastomotic leak rates (defined as the number of leaks per number of patients with anastomoses), were 4.3% (older) vs 5.3% (younger) despite frank sepsis present in 21.2% of all subjects at the time of surgery. The older group had more cardiac (18.2 vs 0.8%, P < 0.001) and respiratory complications (18.2 vs 2.4%; P = 0.0003) and a longer mean but not median postoperative hospital admission. CONCLUSIONS: In conclusion, clinical features and presentation are similar in the older and younger Crohn's patients having a laparotomy. However, in the older patient there is a greater likelihood of large bowel disease, ileocaecal resection is done less commonly, there is a higher risk of minor cardiopulmonary postoperative complications, but with similar mortality and anastomotic leak rates to the younger patient.

Abdomen↗
PubMed1999

Pyogenic liver abscess: a review of 10 years' experience in management.

BACKGROUND: Over the past 15 years, diagnostic and interventional radiology techniques have allowed accurate localization of liver abscesses and image-guided percutaneous drainage. This review examines whether these technical advances improve clinical results and discusses the selection of treatment for patients with liver abscesses. METHODS: Ninety-eight patients were treated for pyogenic liver abscess (PLA) at the Royal Prince Alfred Hospital, Sydney, between January 1987 and June 1997. The hospital records were examined and clinical presentation, laboratory, radiological and microbiological findings were recorded. Associations between these findings and failure of initial non-operative management were determined using odds ratios with 95% confidence intervals. Independent predictors were then determined by logistic regression. This analysis was repeated to determine factors associated with mortality. RESULTS: Cholelithiasis and previous hepatobiliary surgery were the most frequently identifiable causes of PLA, each responsible in 15 patients. All 98 patients were treated with intravenous antibiotics and in 13 patients this was the only therapy. Of the remaining 85 patients, six proceeded straight to laparotomy and 79 had percutaneous drainage, of whom 15 required subsequent laparotomy. Factors predicting failure of initial non-operative management were unresolving jaundice, renal impairment secondary to clinical deterioration, multiloculation of the abscess, rupture on presentation and biliary communication. The overall hospital mortality rate was 8%. CONCLUSION: Pyogenic liver abscess remains a disease with significant mortality. Image-guided percutaneous drainage is appropriate treatment for single unilocular PLA. Surgical drainage is more likely to be required in patients who have abscess rupture, incomplete percutaneous drainage or who have uncorrected primary pathology.

Adolescent↗
PubMed1999

Evolution of the pelvic pouch procedure at one institution: the first 100 cases.

BACKGROUND: Total extirpation of the colon with pelvic pouch formation, and the avoidance of a permanent stoma, continues to pose a challenge for better results, both technically and functionally. The aims of this study were to investigate the first 100 pelvic ileal-pouch procedures, assessing changes in surgical technique, their relationship to morbidity and long-term outcome, and compare this to the few large international series. METHODS: Between 1984 and 1997, 100 patients had a pelvic J-shaped ileal-pouch formed, 58 two-stage and 42 three-stage procedures. Fifty had a hand-sewn pouch-anal anastomosis and 50 a double-stapled anastomosis. Seventy-three were for ulcerative colitis, five for indeterminate colitis, 20 for familial adenomatous polyposis (FAP), one for multiple primary colorectal cancers, and one for constipation. RESULTS: After a median follow-up of 68 months, 97% of patients still have a functioning pouch. There were two postoperative deaths (one after-pouch formation and one after-stoma closure). Morbidity occurred in 52 patients, including three patients with pouch leaks and three pouch-anal anastomosis leaks (6% leak rate), 27% with a small bowel obstruction (2% early, 20% late, 5% both), a 19% anal stricture rate, and a 9% pouchitis rate. Three pouches have been removed (all for Crohn's disease). Median number of bowel movements per day was six, with 85% of patients reporting a good quality of life. Patients following a double-stapled procedure have less anal seepage and improved continence over those with a hand-sewn ileal pouch-anal anastomosis. CONCLUSIONS: Despite high morbidity rates, pelvic pouch formation provides satisfactory long-term results for patients requiring total proctocolectomy, with functional results and morbidity rates comparable to larger overseas series.

Adenomatous Polyposis Coli↗
PubMed1999

Outcome of vitreoretinal surgery and penetrating keratoplasty using temporary keratoprosthesis.

PURPOSE: The use of a temporary keratoprosthesis has allowed earlier surgical intervention in eyes with coexisting vitreoretinal and corneal disease. We analyzed our experience with this type of surgery. METHODS: We retrospectively reviewed charts of patients in whom a temporary keratoprosthesis was used between 1987 and 1998. Analysis was focused on ocular history, indications for surgery, visual acuity (VA), intraocular pressure, anatomic results, and complications. RESULTS: A temporary keratoprosthesis was used in 31 eyes, 22 (71.0%) of which were for trauma-related indications. In 6 (19.4%) of the operated eyes, the fellow eye also had severely reduced VA. Retinal detachments were present in 30 (96.8%) eyes; most had evident proliferative vitreoretinopathy. Twelve (38.7%) eyes had vitreous hemorrhage, and 20 (64.5%) had corneal scars. Improvement in VA was seen initially in 45.1% of patients, and 51.6% maintained equal or better VA at their final visit as compared with before surgery. The common documented reasons for poor final VA were recurrent retinal detachments deemed inoperable (32.3%), phthisis (22.6%), and optic atrophy or macular scar (16.1%). Corneal grafts remained clear in 41.9%. Nine patients had further surgery. The most significant complication was one case of sympathetic ophthalmia. CONCLUSIONS: Combined vitreoretinal and corneal surgery using temporary keratoprostheses has been used in our institution to treat eyes with extreme abnormalities. Outcomes were less favorable than some reported in the literature, probably because of the severity of disease for which temporary keratoprostheses were reserved. Although results are probably better than the natural course of the disease, patients should be informed of realistic expectations for improvement and potential complications when offered this option.

Adolescent↗
PubMed1999

Activating phosphorylation of the Kin28p subunit of yeast TFIIH by Cak1p.

Cyclin-dependent kinase (CDK)-activating kinases (CAKs) carry out essential activating phosphorylations of CDKs such as Cdc2 and Cdk2. The catalytic subunit of mammalian CAK, MO15/Cdk7, also functions as a subunit of the general transcription factor TFIIH. However, these functions are split in budding yeast, where Kin28p functions as the kinase subunit of TFIIH and Cak1p functions as a CAK. We show that Kin28p, which is itself a CDK, also contains a site of activating phosphorylation on Thr-162. The kinase activity of a T162A mutant of Kin28p is reduced by approximately 75 to 80% compared to that of wild-type Kin28p. Moreover, cells containing kin28(T162A) and a conditional allele of TFB3 (the ortholog of the mammalian MAT1 protein, an assembly factor for MO15 and cyclin H) are severely compromised and display a significant further reduction in Kin28p activity. This finding provides in vivo support for the previous biochemical observation that MO15-cyclin H complexes can be activated either by activating phosphorylation of MO15 or by binding to MAT1. Finally, we show that Kin28p is no longer phosphorylated on Thr-162 following inactivation of Cak1p in vivo, that Cak1p can phosphorylate Kin28p on Thr-162 in vitro, and that this phosphorylation stimulates the CTD kinase activity of Kin28p. Thus, Kin28p joins Cdc28p, the major cell cycle Cdk in budding yeast, as a physiological Cak1p substrate. These findings indicate that although MO15 and Cak1p constitute different forms of CAK, both control the cell cycle and the phosphorylation of the C-terminal domain of the large subunit of RNA polymerase II by TFIIH.

Animals↗
PubMed1998

Localization and regulation of the cdk-activating kinase (Cak1p) from budding yeast.

Eukaryotic cell cycles are controlled by the activities of cyclin-dependent kinases (cdks). The major cdk in budding yeast, Saccharomyces cerevisiae, is Cdc28p. Activation of Cdc28p requires phosphorylation on threonine 169 and binding to a cyclin. Thr-169 is phosphorylated by the cdk-activating kinase (CAK), Cak1p, which was recently identified as the physiological CAK in budding yeast. Here we present our further characterization of yeast Cak1p. We have found that Cak1p is dispersed throughout the cell as shown by immunofluorescence; biochemical subcellular fractionation confirmed that most of the Cak1p is found in the cytoplasm. Cak1p is a monomeric enzyme in crude yeast lysates. Mutagenesis of potential sites of activating phosphorylation had little effect on the activity of Cak1p in vitro or in vivo. Furthermore, Cak1p contains no posttranslational modifications detectable by two-dimensional isoelectric focusing. We found that Cak1p is a stable protein during exponential growth but that its expression decreases considerably when cells enter stationary phase. In contrast, Cak1p levels oscillate dramatically during meiosis, reflecting regulation at both the transcriptional and post-translational level. The localization and regulation of Cak1p are in contrast to those of the known vertebrate CAK, p40(MO15).

Amino Acid Sequence↗
PubMed1998

Surgery and the randomised controlled trial: past, present and future.

Randomised controlled trials (RCTs), with their prospective definition of methods and outcome measures, double-blind assessment of outcomes and unbiased selection of subjects and controls, provide the best possible evidence for deciding the value of a medical or surgical intervention. Few surgical studies are designed as RCTs, and those that are should be of a higher quality. The lack of good surgical RCTs may be a result of surgeons lacking the necessary training, expertise and desire to perform RCTs, inadequate funding from granting agencies, difficulties in securing patient consent or a lack of sufficient patient numbers. If an RCT is not feasible for a particular study, then alternative research designs, such as prospective matched-pair trials, may need to be better developed and used. If RCTs can be performed, other strategies to increase the number and quality of RCTs may be needed: Education of surgeons in clinical research methods Improved funding of surgical RCTs Compulsory evaluation of new techniques and technology before their general adoption is permitted.

Evidence-Based Medicine↗