Pregnancies in women with Turner syndrome: a retrospective multicentre UK study.

OBJECTIVE: To determine the characteristics and outcomes of pregnancy in women with Turner syndrome. DESIGN: Retrospective 20-year cohort study (2000-20). SETTING: Sixteen tertiary referral maternity units in the UK. POPULATION OR SAMPLE: A total of 81 women with Turner syndrome who became pregnant. METHODS: Retrospective chart analysis. MAIN OUTCOME MEASURES: Mode of conception, pregnancy outcomes. RESULTS: We obtained data on 127 pregnancies in 81 women with a Turner phenotype. All non-spontaneous pregnancies (54/127; 42.5%) were by egg donation. Only 9/31 (29%) pregnancies in women with karyotype 45,X were spontaneous, compared with 53/66 (80.3%) pregnancies in women with mosaic karyotype 45,X/46,XX (P < 0.0001). Women with mosaic karyotype 45,X/46,XX were younger at first pregnancy by 5.5-8.5 years compared with other Turner syndrome karyotype groups (P < 0.001), and more likely to have a spontaneous menarche (75.8% versus 50% or less, P = 0.008). There were 17 miscarriages, three terminations of pregnancy, two stillbirths and 105 live births. Two women had aortic dissection (2.5%); both were 45,X karyotype with bicuspid aortic valves and ovum donation pregnancies, one died. Another woman had an aortic root replacement within 6 months of delivery. Ten of 106 (9.4%) births with gestational age data were preterm and 22/96 (22.9%) singleton infants with birthweight/gestational age data weighed less than the tenth centile. The caesarean section rate was 72/107 (67.3%). In only 73/127 (57.4%) pregnancies was there documentation of cardiovascular imaging within the 24 months before conceiving. CONCLUSIONS: Pregnancy in women with Turner syndrome is associated with major maternal cardiovascular risks; these women deserve thorough cardiovascular assessment and counselling before assisted or spontaneous pregnancy managed by a specialist team. TWEETABLE ABSTRACT: Pregnancy in women with Turner syndrome is associated with an increased risk of aortic dissection.

Maternal and fetal outcomes in pregnancies complicated by the inherited aortopathy Loeys-Dietz syndrome.

OBJECTIVE: Pregnancies in women with Loeys-Dietz syndrome (LDS) are rare and are typically documented in case reports only. Early reports suggested high rates of maternal complications during pregnancy and the puerperium, including aortic dissection and uterine rupture, but information on fetal outcomes was very limited. DESIGN: A retrospective cohort study. SETTING: Eight specialist UK centres. SAMPLE: Pregnant women with LDS. METHODS: Data was collated on cardiac, obstetric, and neonatal outcomes. MAIN OUTCOME MEASURES: Maternal and perinatal outcomes in pregnancies complicated by LDS. RESULTS: Twenty pregnancies in 13 women with LDS were identified. There was one miscarriage, one termination of pregnancy, and 18 livebirths. In eight women the diagnosis was known prior to pregnancy but only one woman had preconception counselling. In four women the diagnosis was made during pregnancy through positive genotyping, and the other was diagnosed following delivery. Five women had a family history of aortic dissection. There were no aortic dissections in our cohort during pregnancy or postpartum. Obstetric complications were common, including postpartum haemorrhage (33%) and preterm delivery (50%). In all, 14/18 (78%) of deliveries were by elective caesarean section, at a median gestational age at delivery of 37 weeks. Over half the infants (56%) were admitted to the neonatal unit following delivery. CONCLUSION: Women with LDS require multidisciplinary specialist management throughout pregnancy. Women should be referred for preconception counselling to make informed decisions around pregnancy risk and outcomes. Early elective preterm delivery needs to be balanced against a high infant admission rate to the neonatal unit. TWEETABLE ABSTRACT: Pregnancy outcomes in women with Loeys-Dietz syndrome.

Hyperbaric vs. isobaric bupivacaine for spinal anaesthesia for elective caesarean section: a Cochrane systematic review.

Both isobaric and hyperbaric bupivacaine have been used for spinal anaesthesia for elective caesarean section, but it is not clear if one is better than the other. The primary objective of this systematic review was to determine the effectiveness and safety of hyperbaric bupivacaine compared with isobaric bupivacaine administered during spinal anaesthesia for elective caesarean section. We included 10 studies with 614 subjects in the analysis. There was no evidence of differences either in the risk of conversion to general anaesthesia, with a relative risk (95%CI) of 0.33 (0.09-1.17) (very low quality of evidence), or in the need for supplemental analgesia, the relative risk (95%CI) being 0.61 (0.26-1.41) (very low quality of evidence). There was also no evidence of a difference in the use of ephedrine, the amount of ephedrine used, nausea and vomiting, or headache. Hyperbaric bupivacaine took less time to reach a sensory block height of T4, with a mean difference (95%CI) of -1.06 min (-1.80 to -0.31). Due to the rarity of some outcomes, dose variability, use of adjuvant drugs and spinal technique used, future clinical trials should look into using adequate sample size to investigate the primary outcome of the need for supplemental analgesia.

Is arterial base deficit still a useful prognostic marker in trauma? A systematic review.

BACKGROUND: Arterial base deficit (BD) has been widely used in trauma patients since 1960. However, trauma management has also evolved significantly in the last 2 decades. The first objective of this study was to systematically review the literature on the relationship between arterial BD as a prognostic marker for trauma outcomes (mortality, significant injuries, and major complications) in the acute setting. The second objective was to evaluate arterial BD as a prognosis marker, specifically, in the elderly and in patients with positive blood alcohol levels. METHODS: MEDLINE, EMBASE, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews were searched from January 1, 1990, to August 6, 2015. Bibliographies of articles were also hand searched for relevant citations. RESULTS: Thirty-four studies were included in this review. The studies consistently showed that a higher arterial BD was associated with increased mortality, significant injuries, and major complications. The threshold BD value of 6 mmol/L was also useful in discriminating for poorer outcomes. The presence of alcohol did not affect the ability of arterial BD to discriminate between major and minor injuries. Elderly patients had higher mortality in all arterial BD categories compared to the younger age group. CONCLUSIONS: Despite the advances in trauma care in the last 2 decades, arterial BD remains a useful prognostic marker in trauma patients, even in elderly patients and in patients who had consumed alcohol. The threshold BD value of 6 mmol/L was useful to prognosticate poorer outcomes.

Molecular detection identified a type six secretion system in Campylobacter jejuni from various sources but not from human cases.

AIM: To determine the presence of the T6SS in Campylobacter jejuni from diverse sources. METHODS AND RESULTS: The recently identified type VI secretion system (T6SS) is a bacterial injection machinery that plays a role in virulence, symbiosis, bacterial interactions and environmental stress responses. This system has been recently discovered in the major enteric pathogen Camp. jejuni. In this study, we used multiplex PCR (mPCR), based on conserved genetic markers of the T6SS, to screen 366 Pakistani Camp. jejuni isolates from humans, poultry, cattle, wildlife or waste-water sources. We identified the T6SS in isolates from all of these sources except humans. The overall prevalence of the T6SS among the isolates was 17/366 (4·6%) and the T6SS positive isolates clustered into four different groups. Transcription of the T6SS genes, determined using RT-PCR, was observed in bacteria cultured at 37 or 42°C but not in 37°C cultures adjusted to pH3. CONCLUSIONS: Campylobacter jejuni isolates harbouring T6SS markers genes were identified in livestock and non-livestock sources but in this study we did not identify human diarrhoeal isolates which possessed the T6SS. We demonstrated down-regulation of T6SS in an acidic environment. SIGNIFICANCE AND IMPACT OF THE STUDY: This study questions the role of the T6SS in human diarrhoeal disease. Moreover this study did not identify a clear association of Camp. jejuni isolates harbouring T6SS with any of the niches tested. Our study highlights the need to establish the role of the T6SS in environmental survival or virulence.

The role of diffusion-weighted MRI in the accurate diagnosis of vertebral compression fractures: A comparative study.

INTRODUCTION: Accurately distinguishing between benign and malignant vertebral compression fractures is crucial for clinical management. This study evaluated the predictive accuracy of diffusion-weighted imaging (DWI) in differentiating the cause of vertebral fractures using MRI. METHODS: A longitudinal cross-over study was conducted at Jinnah Postgraduate Medical Centre (JPMC) Karachi from July 2018 to January 2021. Patients with vertebral compression fractures underwent T1-weighted, T2-weighted, and DWI imaging with ADC mapping on a 1.5 T MRI scanner. Imaging findings were compared with histopathologic results and clinical follow-up. Sensitivity, specificity, and ROC curve analyses were performed. RESULTS: The study enrolled 303 patients with a mean age of 43.6 ± 10.9 years, of whom 118 were male. DWI demonstrated high accuracy in predicting the cause of vertebral compression fractures, with a sensitivity of 96.2 %, a specificity of 76.2 %, and an area under the ROC curve of 0.857. The optimal ADC cut-off value was 0.82 × 10˄-3 mm˄2/s, which yielded a positive predictive value of 79.7 % and a negative predictive value of 95.4 %. CONCLUSIONS: DWI is a safe and non-invasive imaging modality with excellent predictive accuracy in differentiating between benign and malignant vertebral compression fractures. Iso- or hypointensity of collapsed vertebral bodies on DWI suggests a benign lesion, while T2-weighted hyperintensity is highly indicative of malignancy. Low signal on ADC is also highly indicative of malignant vertebral fractures. Incorporating DWI improves accuracy in assessing vertebral lesions, especially when standard sequences are inconclusive. IMPLICATIONS FOR PRACTICE: DWI revolutionizes vertebral compression fracture diagnosis, distinguishing between benign and malignant cases. This precision guides treatment decisions, minimizing the necessity for invasive procedures like biopsy. As a safe and reliable imaging method, DWI elevates patient care, ensuring accurate diagnostics and improved outcomes.

A Comprehensive Approach to the Diagnosis and Management of Klippel Feil Syndrome.

Klippel-Feil Syndrome (KFS) is a rare genetic disorder characterized by the abnormal development of the cervical spine, leading to the fusion of two or more cervical vertebrae. The syndrome presents diverse symptoms, including limited neck movement, chronic pain, and neurological manifestations such as limb numbness or weakness. The severity of KFS can vary significantly, and treatment primarily focuses on symptom management and preventing complications such as scoliosis or spinal cord compression. Surgical interventions are often necessary for patients with complex forms of the syndrome. Interestingly, Chiari 1 malformation, a cranial anomaly affecting the brainstem, can coincide anatomically with KFS. In this case report, we present the case of a 9-year-old patient who sought medical attention due to persistent, unchanging neck pain. The patient's medical history was notable for developmental delays and cervical restraint observed during physical examination. Magnetic resonance imaging (MRI) findings revealed hydrocephalus and brainstem descent, indicating the presence of Chiari 1 malformation. Comprehensive MRI and CT scans were performed, and a management plan was formulated, primarily involving cranial surgery and physiotherapy. Implementation of the treatment approach resulted in significant improvement in the patient's symptoms. This case highlights the significance of considering Chiari 1 malformation as a potential comorbidity in patients diagnosed with KFS who present with persistent neck pain. Early detection and appropriate management of both conditions are crucial for achieving favorable outcomes and enhancing the quality of life for affected individuals. Understanding the complex interplay between KFS and Chiari 1 malformation is essential for providing comprehensive care and tailored treatment strategies. Further research is warranted to elucidate the underlying mechanisms linking these two conditions and to explore optimal management approaches for patients with dual pathology. By reporting this case, we contribute to the existing literature and increase awareness among healthcare professionals regarding the potential coexistence of KFS and Chiari 1 malformation. Continued efforts in identifying associated anomalies and optimizing therapeutic interventions will aid in improving patient outcomes and ensuring optimal care for individuals affected by these conditions.

Systematic review of outcomes of liver resection for early hepatocellular carcinoma within the Milan criteria.

BACKGROUND: Long-term overall survival after liver resection in patients with hepatocellular carcinoma (HCC) within the Milan criteria has been reported to improve in recent years. This study systematically reviewed the outcomes of surgical resection for HCC in patients with good liver function and meeting the Milan criteria for early HCC, published in the past 10 years. METHODS: A literature search was conducted in PubMed for papers on outcomes of surgical resection for HCC published between January 2000 and December 2010. Cochrane systematic review methodology was used for this review. The primary outcome was overall survival. Secondary outcomes included operative mortality and disease-free survival. Studies that focused on geriatric populations, paediatric populations, a subset of the Milan criteria (such solitary tumours) or included patients with incidental tumours were excluded, as were case reports, conference abstracts, and studies with a large proportion of Child-Pugh grade C liver cirrhosis or unknown Child-Pugh status. RESULTS: Of 152 studies reviewed, two randomized clinical trials and 27 retrospective case series were eligible for inclusion. The 5-year overall survival rate after resection of HCC ranged from 27 to 81 (median 67) per cent, and the median disease-free survival rate from 21 to 57 (median 37) per cent. There was a trend towards improved overall survival in recent years. The operative mortality rate ranged from 0 to 5 (median 0·7) per cent. CONCLUSION: Surgical resection offers good overall survival for patients with HCC within the Milan criteria and with good liver function, although recurrence rates remain high. Outcomes have tended to improve in more recent years.

Management of ruptured amoebic liver abscess: 22-years experience.

BACKGROUND: Amoebiasis affects approximately 10% of the population all over the world. Amoebic liver abscess (ALA) is the commonest complication of amoebiasis affecting 3-9% victims. It is an ancient disease as Hippocrates notified large hepatic abscesses likely to be amoebic abscesses. Objective of this study was to see the efficacy of conservative treatment in the management of ruptured amoebic liver abscess. METHODS: Record of 1,083 patients of amoebic liver abscess, who were treated and managed at Liaquat University Hospital between January 1986 and December 2007, was reviewed retrospectively. Amongst these, 36 (3.32%) patients, found to have intra-peritoneal rupture of the liver abscess were included in this study. The record of these patients was reviewed. The patients were divided into group A and B depending upon the mode of treatment employed. Group A included 16 (44.44%) patients in whom exploratory laparotomy was performed while group B included 20 (55.55%) patients who were treated conservatively. RESULTS: Group A consisted of 16 (44.4%) patients who underwent laparotomy for acute peritonitis due to non-availability of ultrasound in the initial period of the study. In group B, all twenty patients were treated conservatively after a diagnosis of ruptured amoebic liver abscess made by ultrasound guided percutaneous aspiration of pus. These patients were treated with ultrasound guided aspiration of pus with placement of peritoneal drain under local anaesthesia. Six patients in group A died compared to one patient in group B. the overall mortality of ruptured amoebic liver abscess was 19.4%. It was higher in patients treated surgically (37.5%) compared to patients who were treated conservatively (5%). CONCLUSION: Conservative treatment is an effective modality of treatment for ruptured liver abscess with minimum mortality and mortality if diagnosis is made early.

Dataset on critical parameters of dispersion stability of Cu/Al2O3 nanofluid and hybrid nanofluid for various ultra-sonication times.

The data presented in this data article comprises the critical parameters of dispersion stability such as the particle effective diameter, zeta potential, sedimentation velocity and stability factor for Cu/Al2O3 single particle nanofluid and hybrid nanofluid samples at various ultra-sonication times, that is, 0.5 h, 1.0 h, 2.0 h and 3.0 h. The data for effective diameter and zeta potential was generated using the particle size analyser and zeta potential analyser respectively. The measured data for effective diameter and zeta potential was processed to generate the data for sedimentation velocity and stability factor. The ultra-sonication time with maximum value of stability factor was used for sample preparation of Cu/Al2O3 single particle nanofluid and hybrid nanofluid in the related research article "On trade-off for dispersion stability and thermal transport of Cu-Al2O3 hybrid nanofluid for various mixing ratios" (Siddiqui et al., 2019) [1].

Malignant hemangiopericytoma in the gluteal region: a rare entity.

We present here a case of malignant hemangiopericytoma in a 40-year-old female who presented with a history of slowly growing mass in left gluteal region for about 1.5 years. She was evaluated and a mass of 10 x 7.5 x 5.5 cm 3 was found on computed tomography. The tumor was resected and was sent for histopathological evaluation. Grossly the tumor was encapsulated and on cut section it was nodular. Microscopy showed spindle cells forming cords and sheets separated by thin delicate stroma consisting largely of thin-walled vessels revealed by reticulin stain. Pleomorphism and mitotic figures were seen. It was diagnosed as a case of malignant hemangiopericytoma of gluteal region. The patient underwent radiotherapy and did apparently well. She is on regular follow-up because long-term follow-up is essential in all cases as recurrence can occur several years after treatment.

Novel platelet-agglutinating protein from a thrombotic thrombocytopenic purpura plasma.

A novel platelet-agglutinating protein (PAP) was purified approximately 2,000-fold from the plasma of a patient with thrombotic thrombocytopenic purpura (TTP) by ammonium sulfate fractionation, DEAE-Sephacel and concanavalin A-Sepharose chromatographies. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with and without reduction, this preparation revealed a major protein band with a molecular weight of 37,000, and a minor band with a molecular weight of 32,000-34,000. After elution from the gel, only the 37,000-mol wt protein corresponding to the major band induced the platelet agglutination. When four normal plasmas and the recovery plasma from the same TTP patient were subjected to the similar purification steps, the 37,000-mol wt major band was absent. The 125I-PAP bound to the platelets in a concentration-dependent manner. The platelet agglutination induced by PAP was not inhibited by hirudin, heparin in the presence of antithrombin III, phenylmethylsulfonyl fluoride, apyrase, aspirin, or prostaglandin I2. However, it was inhibited by IgG from normal adults and from the same TTP patient after recovery. The anti-37,000-mol wt PAP antiserum prepared in the rabbit formed a single precipitin line against the highly purified PAP. Using this antiserum in the Western immunoblotting, the 37,000-mol wt protein band was found in the three TTP plasmas, of which the platelet-agglutinating activity was inhibited by the anti-37,000-mol wt PAP IgG. The 37,000-mol wt immunoprecipitin band was absent in the plasmas obtained from another two TTP patients, two normal subjects, two patients with idiopathic thrombocytopenic purpura, and two patients with disseminated intravascular coagulation. These results suggest that the 37,000-mol wt PAP is present only in certain cases of TTP, and is likely to be responsible for the formation of platelet thrombi in the microcirculation.

Inhibition of platelet-aggregating activity in thrombotic thrombocytopenic purpura plasma by normal adult immunoglobulin G.

Plasma from patients with thrombotic thrombocytopenic purpura (TTP) caused the aggregation of autologous and homologous platelets, and effect which was inhibited by normal plasma. IgG purified from seven normal adults at a concentration of 0.7 mg/ml completely inhibited the platelet aggregation induced by plasma obtained from two TTP patients with active disease. The inhibition of platelet aggregation by human adult IgG was concentration dependent, and the inhibitory activity of human IgG was neutralized by rabbit antihuman IgG. Fab fragments inhibited the TTP plasma-induced platelet aggregation as well as intact IgG, whereas Fc fragments had no effect. Platelet aggregation caused by ADP, collagen, epinephrine, or thrombin was not affected by purified human IgG. The prior incubation of IgG with TTP plasma caused a significantly greater reduction of platelet aggregation by TTP plasma than that of IgG and platelet suspension, suggesting that the IgG inhibits TTP plasma-induced platelet aggregation through direct interaction with platelet aggregating factor in TTP plasma. IgG obtained initially from five infants and young children under the age of 4 yr did not possess any inhibitory activity. When one of the children reached 3 yr of age, his IgG inhibited the aggregation induced by one TTP plasma, but not that caused by another plasma. The IgG procured from the same boy at 4 yr of age inhibited the aggregation induced by both TTP plasmas. The IgG purified from the TTP plasma during active disease failed to inhibit the aggregation caused by the same plasma. After recovery, however, the IgG effectively inhibited aggregation. These observations suggest that platelet-aggregating factors present in the TTP plasma are heterogeneous in nature and that the IgG present in the normal adult plasma, which inhibits the TTP plasma-induced platelet aggregation, may be partially responsible for the success of plasma infusion therapy in TTP.

Synergistic activity and heterogeneous acquired resistance of combined MDM2 and MEK inhibition in KRAS mutant cancers.

There are currently no effective targeted therapies for KRAS mutant cancers. Therapeutic strategies that combine MEK inhibitors with agents that target apoptotic pathways may be a promising therapeutic approach. We investigated combining MEK and MDM2 inhibitors as a potential treatment strategy for KRAS mutant non-small cell lung cancers (NSCLC) and colorectal carcinomas that harbor wild-type TP53. The combination of pimasertib (MEK inhibitor) and SAR405838 (MDM2 inhibitor) was synergistic and induced the expression of PUMA and BIM, led to apoptosis and growth inhibition in vitro, and tumor regression in vivo. Acquired resistance to the combination commonly resulted from the acquisition of TP53 mutations, conferring complete resistance to MDM2 inhibition. In contrast, resistant clones exhibited marked variability in sensitivity to MEK inhibition, which significantly impacted sensitivity to subsequent treatment with alternative MEK inhibitor-based combination therapies. These results highlight both the potential promise and limitations of combining MEK and MDM2 inhibitors for treatment of KRAS mutant NSCLC and colorectal cancers.

The Effect of Phentolamine on Reversing Soft Tissue Anesthesia: An Oral Health Technology Assessment Report.

Long-lasting numbness of soft tissues such as lips, tongue, and cheeks after dental anesthesia is not only unpleasant but has the potential to cause self-inflicted damage to the numb tissue. Phentolamine mesylate, when injected in vicinity to the site of local anesthesia, accelerates the absorption of local anesthesia. Dental use of this drug was approved in the United States and Canada in 2008 and 2014, respectively. The rapidly increasing popularity of this novel technology (intraoral phentolamine injections) warrants a health technology assessment for clinicians. A medical librarian conducted a systematic literature search (up to March 1, 2016) for any clinical study involving intraoral phentolamine injection. Meta-analysis of the efficacy data from 4 clinical studies supports the role of intraoral phentolamine injections in shortening the duration of numbness after local anesthesia. No publication bias was found in the selected studies. The selected studies identified no serious adverse events other than pain at the site of injection and some postprocedural pain. Our cost-effectiveness analysis shows phentolamine mesylate to be an effective treatment modality when compared with no treatment, sham, or placebo injection. Phentolamine mesylate incurs an additional cost (in US dollars) of $0.13 to $0.16 per minute of reversing the soft tissue local anesthesia and $0.38 to $0.46, when compared with sham or placebo injection, after a noninvasive dental procedure. The literature lacked substantial evidence in favor of clinical benefits, such as a decrease in self-inflicted injuries. Only a subgroup of the dental patient population undergoing specific dental procedures would benefit from accelerated recovery from numbness. Knowledge Transfer Statement: Intraoral phentolamine to reverse numbness is a new intervention with ambiguous utility. With consideration of cost and patient preference, evidence generated by this report may be used in clinical decision making and case selection for this intervention.

Effect of early adjunctive use of oral sildenafil and inhaled nitric oxide on the outcome of pulmonary hypertension in newborn infants. A feasibility study.

INTRODUCTION: Inhaled nitric oxide (iNO) is the standard therapy for infants with persistent pulmonary hypertension of the newborn (PPHN). Recently, sildenafil has been evaluated as an alternative or adjunctive pulmonary vasodilator. OBJECTIVE: To assess the effectiveness of adding sildenafil as an early adjunctive therapy together with iNO when treating newborns with PPHN and/or hypoxemic respiratory failure. METHODS: This is a randomized placebo trial on newborns with gestational age > 34 weeks, postnatal age < 48 hours, and diagnosed with PPHN (oxygen index (OI) ≥ 20). Newborns were randomized to two groups: Group A- received oral sildenafil and iNO, and group B- received placebo and iNO. Initial and follow up echocardiography were performed over 14 days period. RESULTS: A total of 24 newborns were recruited; 13 of them received sildenafil in addition to iNO and 11 received iNO and placebo. The most common causes of PPHN were meconium aspiration syndrome, pneumonia, and RDS. At the starting point, OI was marginally higher in the intervention group without statistical significance (29 vs 28). There were no differences between the two groups regarding surfactant administration, incidence of pneumothoraces, and the underlying causes of PPHN. Sildenafil or placebo treatment started within 12 hours after starting iNO (8 vs 6 hours). CONCLUSION: Early use of oral sildenafil next to iNO in cases of PPHN was tolerated well by newborns and it did not show significant adverse effects. Further studies with a larger sample size is needed to assess its effecacy.

Purification and immunological characterization of DNA polymerase-alpha from human acute lymphoblastic leukemia cells.

DNA polymerase-alpha was purified from the cytosol of blast cells of a patient with acute lymphoblastic leukemia by ammonium sulfate fractionation and successive column chromatographies. The purified enzyme had a specific activity of 2943 units/mg protein with activated calf thymus DNA as a template. The enzyme sediments under high-salt conditions as a homogeneous band at 7.2 S and free from other DNA polymerases (beta, gamma) and terminal deoxynucleotidyl transferase activity. The native molecular weight of the enzyme from gel filtration and glycerol gradient centrifugation was found to be 175 000. The values of Stokes radius (53 A), diffusion coefficient (4.05 x 10(-7) cm2/s) and frictional ratio (1.42) determined by gel filtration suggest that the native enzyme is compact and globular. Antibodies to DNA polymerase-alpha were raised in rabbits. These antibodies, partially purified by 50% ammonium sulfate saturation and Sephadex G-200 chromatography, gave one precipitin band on immunodiffusion and inactivate DNA polymerase-alpha-. This antibody preparation also inhibited, in vitro, the activity of DNA polymerase-alpha from calf thymus, phytohemagglutinin-stimulated normal human lymphocytes, as well as that from other leukemic cells. Thus, DNA polymerase-alpha from calf thymus and human leukemic cells resemble each other in antibody specificity.

Generation of multiple forms of methionyl-tRNA synthetase from the multi-enzyme complex of mammalian aminoacyl-tRNA synthetases by endogenous proteolysis.

Methionyl-tRNA synthetase occurs free and as high-molecular-weight multi-enzyme complexes in rat liver. The free form is purified to near homogeneity by conventional column chromatography and affinity chromatography on tRNA-Sepharose. The native molecular weight of free methionyl-tRNA synthetase is 64 500, based on its sedimentation coefficient of 4.5 S and Stokes radius of 33 A. The free methionyl-tRNA synthetase apparently belongs to alpha-type subunit structure, since the subunit molecular weight is 68 000, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Methionyl-tRNA synthetase is dissociated from the high-molecular-weight synthetase complex by controlled trypsinization, according to Kellermann, O., Viel, C. and Waller, J.P. (Eur. J. Biochem. 88 (1978) 197-204). The dissociated, free methionyl-tRNA synthetase is subsequently purified to near homogeneity. The subunit structure of dissociated methionyl-tRNA synthetase is identical to that of endogenous free methionyl-tRNA synthetase. Anti-serum raised against Mr 104 000 protein in the synthetase complex, specifically inhibited methionyl-tRNA synthetase in both the free and the high-molecular-weight forms to the same extent. These results suggest that the occurrence of multiple forms of methionyl-tRNA synthetases in mammalian cells may, in part, be due to proteolytic cleavage.