RESUMO
BACKGROUND: Alzheimer's disease (AD) is a progressive, neurodegenerative disease presenting along a continuum ranging from asymptomatic disease to mild cognitive impairment (MCI), followed by dementia characterized as mild, moderate, or severe. OBJECTIVES: To better understand the medical journey of patients with all-cause MCI or mild AD dementia from the perspective of patients, care partners, and physicians. DESIGN: Cross-sectional study. SETTING: Online surveys in the United States between February 4, 2021, and March 1, 2021. PARTICIPANTS: 103 patients with all-cause MCI or mild AD dementia and 150 care partners participated in this survey. 301 physicians (75 of whom were neurologists) completed a survey. MEASUREMENTS: The surveys included questions regarding attitudes, experiences, and behaviors related to diagnosis and management of MCI and mild AD dementia. For the patient and care partner surveys, questions regarding healthcare received for MCI and mild AD dementia were only asked of care partners. RESULTS: Most patients (73%) had a similar medical journey. The majority (64%) initially consulted a primary care physician on average 15 months after symptom onset, with symptoms primarily consisting of forgetfulness and short-term memory loss. About half (51%) of patients in the typical medical journey were diagnosed by a neurologist. Upon diagnosis, most neurologists reported having discussions with patients and care partners about the potential causes of MCI or mild AD dementia (83%); of these physicians, 83% explained the effect other conditions have on the risk of the diagnoses and symptom progression. Neurologists (52%) consider themselves the coordinator of care for patients with MCI or mild AD dementia. Amongst patients and care partners, about one-third (35%) perceive the neurologists to be the coordinating physician. CONCLUSIONS: Neurologists commonly diagnose MCI and mild AD dementia but are typically not the first point of contact in the medical journey, and patients do not consult with a physician for over a year after symptom onset. Neurologists play a key role in the medical journey for patients and care partners, and could help ensure earlier diagnosis and treatment, and improve clinical outcomes by coordinating MCI and mild AD dementia care and collaborating with primary care physicians.
Assuntos
Doença de Alzheimer , Disfunção Cognitiva , Demência , Doenças Neurodegenerativas , Humanos , Doença de Alzheimer/terapia , Doença de Alzheimer/tratamento farmacológico , Estudos Transversais , Neurologistas , Cuidadores , Demência/diagnóstico , Demência/terapia , Disfunção Cognitiva/psicologiaRESUMO
BACKGROUND: We present a national data series to determine the incidence, outcomes and training opportunities for laparoscopic cholecystectomy among children <16yrs in Scotland as performed by paediatric surgeons. METHODS: A retrospective cohort study was performed reviewing laparoscopic cholecystectomy performed at the three children's hospitals in Scotland. Using the National Records Scotland Database mid-year population estimates; age and sex specific annual incidence rates of laparoscopic cholecystectomy were calculated between 1998-2015. Trends in the observed case mix were tested using univariate linear regression and students t-test. RESULTS: Between 1998-2015; 141 paediatric laparoscopic cholecystectomies were performed. The annual rate of cholecystectomy increased from 0.10/100,000 to 0.88/100,000 (p = 0.069). Sex specific incidences were identified; 0.00-0.90/100,000 (p = 0.098) in girls and 0.20-0.86/100,000 in boys (p = 0.28). Cholecystectomy was more frequent in girls (63%; p = 0.04). No major complications, defined as common bile duct injury or mortality were identified. Overall; 75% of cases were performed by consultants (n = 17 consultants, median = 5 cases, p < 0.05) and 25% by trainees. CONCLUSION: We have demonstrated that despite a low national case load (8 laparoscopic cholecystectomies per year) paediatric surgeons have been able to perform laparoscopic cholecystectomy safely without major morbidity.
Assuntos
Colecistectomia Laparoscópica , Criança , Colecistectomia , Feminino , Humanos , Incidência , Masculino , Estudos Retrospectivos , Escócia/epidemiologiaRESUMO
BACKGROUND: Low molecular weight heparin is routinely used for thromboprophylaxis in pregnancy and the puerperium. Consensus guidelines recommend waiting 10-12h after administration of a thromboprophylactic dose of low molecular weight heparin before performing a neuraxial block or removing an epidural catheter. Thromboelastography (TEG®) has been reported to be sensitive to the effects of enoxaparin 4h after administration. The purpose of this study was to use TEG to examine coagulation changes in the first 10h after a thromboprophylactic dose of tinzaparin in an attempt to ratify the current consensus guidelines about timing of neuraxial blockade and epidural catheter removal. METHODS: Twenty-four women who had undergone caesarean delivery and were classified as low or intermediate risk of thrombosis were recruited. Blood samples were taken before subcutaneous administration of tinzaparin 4500IU, and at 4, 8 and 10h post-dose. Standard TEG analyses were performed using plain and heparinase cuvettes and samples were also sent for laboratory anti-Xa assay. Thromboelastograph profiles were analysed for a low molecular weight heparin effect. RESULTS: Analysis revealed no significant differences in R time, K time, alpha angle or maximum amplitude between plain and heparinase samples at any time point. Apart from a small statistically significant (P=0.033) decrease in maximum amplitude of 2.8% (95% CI 0.3 to 5.4%) at 4h, there were no significant changes in coagulation for any TEG parameter. Anti-Xa levels were virtually undetectable in all patients over the 10h period (median 0.00U/mL; range 0.00-0.13U/mL). CONCLUSION: A thromboprophylactic dose of tinzaparin 4500IU had little detectable effect on coagulation as assessed by TEG and anti-Xa assay. These findings support consensus guidelines which state that it is acceptable to perform neuraxial blockade or remove an epidural catheter 10-12h after a thromboprophylactic dose of tinzaparin. Rather than suggesting a lack of anticoagulant activity, the findings indicate that TEG may not have the sensitivity to detect a tinzaparin effect when this dose is used in this patient group.
Assuntos
Anticoagulantes/farmacologia , Cesárea , Heparina de Baixo Peso Molecular/farmacologia , Complicações Pós-Operatórias/prevenção & controle , Tromboelastografia/métodos , Adulto , Feminino , Humanos , Pessoa de Meia-Idade , Gravidez , Tinzaparina , Adulto JovemRESUMO
Colonic pseudo-obstruction (Ogilvie's Syndrome) in children is relatively uncommon. We report an unusual case of colonic pseudo-obstruction in an 8-year-old child with cerebral palsy and long-term hypomotility issues being treated for drooling with the anticholinergic medication trihexyphenidyl. He presented as an emergency with severe abdominal distension, abdominal tenderness and vomiting. An emergency laparotomy revealed colonic dilatation and a defunctioning ileostomy was created. To our knowledge, this is the first case reporting colonic pseudo-obstruction as a possible complication of treatment with trihexyphenidyl. We suggest prescribers should exercise caution when prescribing trihexyphenidyl in patients with long-term intestinal hypomotility issues.
Assuntos
Pseudo-Obstrução do Colo/induzido quimicamente , Antagonistas Muscarínicos/efeitos adversos , Triexifenidil/efeitos adversos , Paralisia Cerebral/complicações , Criança , Humanos , Masculino , Sialorreia/tratamento farmacológico , Sialorreia/etiologiaRESUMO
We assessed the ability of palpating the radial arterial pulse and observing the oximeter trace to estimate the automated non-invasive systolic pressure reading in 20 healthy female volunteers and 20 parturients undergoing spinal anaesthesia for elective caesarean section. Using real-time values of cuff pressure during inflation/deflation, the pressure was recorded when the manually palpated radial arterial pulse or pulse oximeter waveform disappeared and reappeared. The actual measured systolic pressure was noted and the results compared using Bland-Altman analysis. In the volunteers, the bias/precision for radial arterial palpation was -12.9/22.1 mmHg (inflation) and -9.7/16.7 mmHg (deflation), and for oximetry 29.5/18.8 mmHg (inflation) and -20.7/21.7 mmHg (deflation). In the parturients, the bias/precision was -19.0/47.6 mmHg (inflation) and -15.5/51.0 mmHg (deflation) for arterial palpation, and 22.6/16.1 mmHg (inflation) and -14.2/19.9 mmHg (deflation) for oximetry. Our results suggest that neither method is accurate at estimating the non-invasive systolic pressure, with all except oximetry (inflation) underestimating it by approximately 10-20 mmHg and with poor precision.
Assuntos
Anestesia Obstétrica/métodos , Raquianestesia/métodos , Cesárea , Monitorização Intraoperatória/métodos , Artéria Radial/fisiologia , Adolescente , Adulto , Pressão Sanguínea/fisiologia , Feminino , Humanos , Pessoa de Meia-Idade , Oximetria/métodos , Palpação , Gravidez , Adulto JovemRESUMO
BACKGROUND: Expression of the DNA repair protein O (6)-methylguanine-DNA methyltransferase (MGMT) correlates with resistance to irinotecan in colorectal cancer cell lines. This phase I study evaluated the maximum tolerated dose (MTD) of lomeguatrib, an inactivating pseudosubstrate of MGMT, in combination with irinotecan in patients with metastatic colorectal cancer and assessed the safety, toxicity and clinical pharmacology of combination treatment. PATIENTS AND METHODS: Patients with metastatic colorectal cancer received lomeguatrib (10-80 mg PO) on days 1-5 with irinotecan (250-350 mg/m(2) IV) on day 4 of a 21-day cycle. RESULTS: Twenty-four patients, pre-treated with a median of 2 lines of chemotherapy, received 104 cycles of treatment. The MTD was defined as 80 mg/day lomeguatrib with 300 mg/m(2) irinotecan. The main toxicities observed were neutropaenia and diarrhoea. Lomeguatrib of 80 mg/day produced complete MGMT depletion in all available peripheral blood mononuclear cells (PBMCs) and paired tumour biopsies (one patient). There was no pharmacokinetic interaction between the drugs. In 22 patients assessable for tumour response, one achieved a partial response and 16 had stable disease. CONCLUSION: This study defined a tolerable dose of irinotecan in combination with lomeguatrib in patients with metastatic colorectal cancer. Combination treatment gave a similar response rate to irinotecan monotherapy in this heavily pre-treated patient group.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias Colorretais/tratamento farmacológico , O(6)-Metilguanina-DNA Metiltransferase/efeitos dos fármacos , Adulto , Idoso , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Camptotecina/administração & dosagem , Camptotecina/análogos & derivados , Neoplasias Colorretais/patologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Feminino , Humanos , Irinotecano , Masculino , Dose Máxima Tolerável , Pessoa de Meia-Idade , Metástase Neoplásica , O(6)-Metilguanina-DNA Metiltransferase/metabolismo , Purinas/administração & dosagem , Resultado do TratamentoRESUMO
We evaluated the pharmacodynamic effects of the O(6)-methylguanine-DNA methyltransferase (MGMT) inactivator lomeguatrib (LM) on patients with melanoma in two clinical trials. Patients received temozolomide (TMZ) for 5 days either alone or with LM for 5, 10 or 14 days. Peripheral blood mononuclear cells (PBMCs) were isolated before treatment and during cycle 1. Where available, tumour biopsies were obtained after the last drug dose in cycle 1. Samples were assayed for MGMT activity, total MGMT protein, and O(6)-methylguanine (O(6)-meG) and N7-methylguanine levels in DNA. MGMT was completely inactivated in PBMC from patients receiving LM, but detectable in those on TMZ alone. Tumours biopsied on the last day of treatment showed complete inactivation of MGMT but there was recovery of activity in tumours sampled later. Significantly more O(6)-meG was present in the PBMC DNA of LM/TMZ patients than those on TMZ alone. LM/TMZ leads to greater MGMT inactivation, and higher levels of O(6)-meG than TMZ alone. Early recovery of MGMT activity in tumours suggested that more protracted dosing with LM is required. Extended dosing of LM completely inactivated PBMC MGMT, and resulted in persistent levels of O(6)-meG in PBMC DNA during treatment.
Assuntos
Dano ao DNA , Dacarbazina/análogos & derivados , Melanoma/tratamento farmacológico , Melanoma/genética , O(6)-Metilguanina-DNA Metiltransferase/metabolismo , Purinas/toxicidade , Antineoplásicos/toxicidade , Biópsia , Dano ao DNA/efeitos dos fármacos , Reparo do DNA/efeitos dos fármacos , Replicação do DNA/efeitos dos fármacos , DNA de Neoplasias/genética , DNA de Neoplasias/isolamento & purificação , Dacarbazina/toxicidade , Progressão da Doença , Humanos , Cinética , Melanoma/patologia , O(6)-Metilguanina-DNA Metiltransferase/antagonistas & inibidores , O(6)-Metilguanina-DNA Metiltransferase/efeitos dos fármacos , TemozolomidaRESUMO
AIMS: The true mortality associated with congenital diaphragmatic hernia (CDH) is hidden because survival analyses do not include fetuses with CDH. A retrospective review of all postmortems (PMs) with a diagnosis of CDH over a 20-year period was carried out to highlight this hidden mortality and also measure the nature and number of associated anomalies. METHODS: Postmortem case record details were reviewed for the period January 1986 to December 2005. Data were collected on live birth, stillbirth, therapeutic abortion, and spontaneous abortion. RESULTS: There was a decline in the annual number of PMs during the period of the study. The median for the four 5-year intervals being 609 (570-657), 528 (488-565), 515 (413-537), and 373 (357-388). A total of 130 PMs were identified, which included a diagnosis of CDH; 97 (75%) were left sided, 22 (17%) were right sided, and 11 (8%) were bilateral. There were 69 live births, 46 therapeutic abortions, 10 stillbirths, and 5 intrauterine deaths; 22% were right sided/bilateral in the live and therapeutic abortion groups, whereas 53% were right sided/bilateral in the latter 2 groups. Of 130, 82 (63%) had major associated anomalies, and 50% of these had at least 1 further major anomaly. The commonest categories of anomalies were cardiac (30), gastrointestinal/abdominal wall defect (28), and neural tube defects (25). CONCLUSIONS: The true incidence of CDH is considerably higher than that seen in neonatal surgical practice. The decline in number of PMs in our region will exacerbate the underestimation of the true incidence. There is a higher incidence of right-sided/bilateral hernias and more than one major anomaly in those who die in utero.
Assuntos
Hérnia Diafragmática/mortalidade , Hérnias Diafragmáticas Congênitas , Hérnia Diafragmática/diagnóstico , Humanos , Recém-Nascido , Estudos Retrospectivos , Fatores de TempoRESUMO
Three cases of urinary ascites are presented, each with a different underlying aetiology. The age and modes of presentation also varied and management strategies were accordingly tailored to each patient's clinical requirements. All 3 patients survived and subsequently were discharged with good renal function. Although a rare condition, infants with urinary ascites can present as clinical emergencies in need of prompt resuscitation with subsequent drainage of the urine and decompression of the urinary tract. The ultimate management regime will vary and depend upon site of urinary extravasation and underlying aetiology.
Assuntos
Ascite/etiologia , Descompressão Cirúrgica , Divertículo/complicações , Divertículo/cirurgia , Drenagem , Humanos , Lactente , Recém-Nascido , Imageamento por Ressonância Magnética , Masculino , Doenças da Bexiga Urinária/complicações , Doenças da Bexiga Urinária/cirurgia , Refluxo Vesicoureteral/complicaçõesRESUMO
We report 4 cases of the rare condition, congenital colonic atresia, presenting over 9 years. Two patients had dilated loops of bowel noted on routine ante-natal ultrasound. Three had primary anastomosis for lesions in transverse or distal descending colon and one had a staged procedure with colostomy formation. All had type III atresia. One patient had an early leak following primary colo-colic anastomosis for atresia extending from the hepatic flexure to the sigmoid colon. If it is desired to preserve the proximal colon in a right sided lesion with significant loss of colonic length then primary anastomosis may not be safe and we would advocate a staged procedure. Otherwise we would support current moves towards primary anastomosis in this condition. We also urge early investigation in all patients who exhibit intestinal dilatation on antenatal ultrasound.
Assuntos
Doenças do Colo/cirurgia , Atresia Intestinal/cirurgia , Anastomose Cirúrgica , Doenças do Colo/congênito , Colostomia , Feminino , Humanos , Recém-Nascido , MasculinoRESUMO
Analyses of survival data of neonates born with congenital diaphragmatic hernia (CDH) can be misleading. There is a hidden mortality only apparent when fetuses with CDH are included in the analysis. A retrospective review of all post mortems with a diagnosis of CDH in the West of Scotland over a 10-year period was carried out. Congenital anomalies were identified and heart and lung weights were compared with controls (infants dying of non-cardiorespiratory causes). 70 Pm reports were studied. Major congenital anomalies were present in 53% (18/ 47 live born, 19/23 not live born). Neural tube defects, cardiac and chromosomal anomalies were the most common. Antenatal detection rate was 17% in live-born infants. In infants dying within the first week of life lung weights showed severe pulmonary hypoplasia, but heart weights were within the normal range. Detailed antenatal scanning needs to be considered if the detection rate for CDH is to improve in this region.
Assuntos
Doenças Fetais/patologia , Hérnia Diafragmática/patologia , Hérnias Diafragmáticas Congênitas , Autopsia , Humanos , Recém-Nascido , Estudos RetrospectivosAssuntos
Hérnia Diafragmática/diagnóstico , Hérnias Diafragmáticas Congênitas , Administração por Inalação , Oxigenação por Membrana Extracorpórea , Feminino , Doenças Fetais/diagnóstico , Doenças Fetais/cirurgia , Hérnia Diafragmática/cirurgia , Humanos , Recém-Nascido , Óxido Nítrico/administração & dosagem , Gravidez , Diagnóstico Pré-Natal , Respiração Artificial , Tensoativos/administração & dosagemRESUMO
The majority of fatal acute myocardial infarctions occur in the elderly. Since these events are predominantly thrombotic, we studied the cross-sectional associations of the anticoagulant proteins Antithrombin, Protein C, Protein S. and Tissue Factor Pathway Inhibitor (TFPI) in a subgroup (n = 400) of the Cardiovascular Health Study (a study of healthy men and women > or = 65 years) free of clinical cardiovascular disease (CVD). We did not observe any strong age-associated trends, although Protein C was lower in older women (p < or = 0.001), and TFPI was higher in older men (p < or = 0.01). The inhibitors were highly intercorrelated, and were associated with increased levels of inflammation-sensitive proteins (e.g., fibrinogen. plasminogen), lipids (especially total and LDL-cholesterol), and coagulation factors, such as Factors VIIc, IXc, and Xc. None was associated with the procoagulant markers Prothrombin Fragment F1-2 or Fibrinopeptide A. Only TFPI was associated with subclinical atherosclerosis: ankle-arm index and internal carotid artery stenosis, p trend < or = 0.01; and carotid wall thickness, p trend < or = 0.05. In multivariate analysis the independent predictors of TFPI were levels of fibrinogen; the fibrinolytic marker plasmin-antiplasmin complex; LDL-cholesterol; and carotid wall thickness (R2 for the model = 0.35). In summary, the inhibitors did not appear to increase with age, and were predominantly associated with inflammation markers and lipids. Since markers of thrombin production do increase with age, we hypothesize that an age-related hemostatic imbalance may ensue, with associated increased thrombotic risk. Only TFPI was associated with subclinical CVD, suggesting that it may more closely reflect endothelial damage.
Assuntos
Anticoagulantes/metabolismo , Trombose/metabolismo , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Antitrombina III/metabolismo , Biomarcadores/sangue , Estudos Transversais , Suscetibilidade a Doenças/fisiopatologia , Feminino , Humanos , Lipoproteínas/metabolismo , Masculino , Prevalência , Proteína C/metabolismo , Proteína S/metabolismo , Valores de Referência , Fatores de RiscoRESUMO
BACKGROUND: The place of cholangiography has been controversial in the conventional and now in the laparoscopic setting. The aim of this study was to evaluate laparoscopic cholangiography and compare use of a portable C-arm image intensifier with conventional radiography. METHODS: One hundred and ninety-seven consecutive patients undergoing laparoscopic cholecystectomy were randomized before operation to cholangiography by either C-arm image intensifier or conventional radiography. Data were collected on a pro forma completed immediately after the operation. RESULTS: Cholangiography was successful in 93.0 per cent of patients. Cholangiography with an image intensifier was significantly faster. In 19 patients the ductal system was obscured by a cannula; in 17 of these cases a metal cannula was used. In 31.6 per cent of patients the clip on the cystic duct was within 1 cm or less of the common bile duct (CBD). CONCLUSION: Laparoscopic cholangiography is a safe procedure. Use of an image intensifier should be the preferred method of obtaining images. Metal cannulas are more likely to obscure the ductal system. The proximity of the clip on the cystic duct to the CBD highlights the potential for injury caused by electrocautery or erroneous clip application.
Assuntos
Doenças dos Ductos Biliares/diagnóstico por imagem , Colangiografia/métodos , Laparoscopia/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Doenças dos Ductos Biliares/cirurgia , Colangiopancreatografia Retrógrada Endoscópica , Colecistectomia Laparoscópica/métodos , Feminino , Cálculos Biliares/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Intensificação de Imagem RadiográficaRESUMO
Forty suprarenal glands were studied, 20 being dissected from aborted fetuses of 9 to 36 weeks' gestation and 20 obtained from human cadavers of ages 1 day to 60 years. All the specimens were from a Northern India population. The side and shape of each suprarenal gland was noted and documented. The length, breadth, thickness and volume of each gland were measured and tabulated in terms of age. The mean length, breadth and thickness in fetuses of 9-36 weeks were found to be 1.4 cm, 1 cm and 0.45 cm respectively. In the postnatal age group the measurements were 4.5 cm, 2.08 cm and 0.66 cm respectively. The commonest shape of the suprarenal glands on left side was semilunar but on the right side it was highly variable: triangular, tetrahedral, inverted Y or V shaped. On comparison of the gross measurements with available ultrasound and CT scan data it was found that both the length and thickness in the population studied were greater than reported in the literature. A knowledge of these variations is very important in diagnosis of abnormalities of the suprarenal gland, of which tumoral enlargement is rather common.
Assuntos
Glândulas Suprarrenais/anatomia & histologia , Adolescente , Doenças das Glândulas Suprarrenais/diagnóstico , Neoplasias das Glândulas Suprarrenais/diagnóstico , Glândulas Suprarrenais/diagnóstico por imagem , Glândulas Suprarrenais/embriologia , Adulto , Fatores Etários , Cadáver , Criança , Pré-Escolar , Feto , Idade Gestacional , Humanos , Índia , Lactente , Recém-Nascido , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X , UltrassonografiaRESUMO
We previously identified a high affinity Ca2+ binding site in the protease domain of factor IXa involving Glu235 (Glu70 in chymotrypsinogen numbering; hereafter, the numbers in brackets refer to the chymotrypsin equivalents) and Glu245[80] as putative ligands. To delineate the function of this Ca2+ binding site, we expressed IXwild type (IXWT), IXE235K, and IXE245V in 293 kidney cells and compared their properties with those of factor IX isolated from normal plasma (IXNP); each protein had the same Mr and gamma-carboxyglutamic acid content. Activation of each factor IX protein by factor VIIa.Ca2+.tissue factor was normal as analyzed by sodium dodecyl sulfate-gel electrophoresis. The coagulant activity of IXaWT was approximately 93%, of IXaE235K was approximately 27%, and of IXaE245V was approximately 4% compared with that of IXaNP. In contrast, activation by factor XIa.Ca2+ led to proteolysis at Arg318-Ser319[150-151] in the protease domain autolysis loop of IXaE245V with a concomitant loss of coagulant activity; this proteolysis was moderate in IXaE235K and minimal in IXaWT or IXaNP. Interaction of each activated mutant with an active site probe, p-aminobenzamidine, was also examined; the Kd of interaction in the absence and presence (in parentheses) of Ca2+ was: IXaNP or IXaWT 230 microM (78 microM), IXaE235K 150 microM (145 microM), IXaE245V 225 microM (240 microM), and autolysis loop cleaved IXaE245V 330 microM (350 microM). Next, we evaluated the apparent Kd (Kd,app) of interaction of each activated mutant with factor VIIIa. We first investigated the EC50 of interaction of IXaNP as well as of IXaWT with factor VIIIa in the presence and absence of phospholipid (PL) and varying concentrations of factor X. At each factor X concentration and constant factor VIIIa, EC50 was the free IXaNP or IXaWT concentration that yielded a half-maximal rate of factor Xa generation. EC50 values for IXaNP and IXaWT were similar and are as follows: PL-minus/X-minus (extrapolated), 2.8 microM; PL-minus/X-saturating, 0.25 microM; PLplus/X-minus, 1.6 nM; and PL-plus/X-saturating, 0.09 nM. Further, Kd,app of binding of active site-blocked factor IXa to factor VIIIa was calculated from its ability to inhibit IXaWT in the Tenase assay. Kd,app values in the absence and presence (in parentheses) of PL were: IXaNP or IXaWT, 0. 19 microM (0.07 nM); IXaE235K, 0.68 microM (0.26 nM); IXaE245V, 2.5 microM (1.35 nM); and autolysis loop-cleaved IXaE245V, 15.6 microM (14.3 nM). We conclude that (a) PL increases the apparent affinity of factor IXa for factor VIIIa approximately 2,000-fold, and the substrate, factor X, increases this affinity approximately 10-15-fold; (b) the protease domain Ca2+ binding site increases this affinity approximately 15-fold, and lysine at position 235 only partly substitutes for Ca2+; (c) Ca2+ binding to the protease domain increases the S1 reactivity approximately 3-fold and prevents proteolysis in the autolysis loop; and (d) proteolysis in the autolysis loop leads to a loss of catalytic efficiency with retention of S1 binding site and a further approximately 8-fold reduction in affinity of factor IXa for factor VIIIa.
Assuntos
Fator IXa/metabolismo , Fator VIIIa/metabolismo , Ácido 1-Carboxiglutâmico/análise , Benzamidinas/metabolismo , Sítios de Ligação , Ligação Competitiva , Cálcio/metabolismo , Ativação Enzimática , Fator IXa/genética , Fator VIIa/farmacologia , Fator X/farmacologia , Fator XIa/farmacologia , Modelos Químicos , Modelos Moleculares , Mutação , Fragmentos de Peptídeos/farmacologia , Fosfolipídeos/farmacologia , Ligação Proteica/efeitos dos fármacos , Análise de SequênciaRESUMO
Human factor X is a two-chain, 58-kDa, vitamin K-dependent blood coagulation zymogen. The light chain of factor X consists of an NH2-terminal gamma-carboxyglutamic acid (Gla) domain, followed by a few helical hydrophobic residues and the two epidermal growth factor-like domains, whereas the heavy chain contains the serine protease domain. In this study, native factor X was found to contain three classes of Ca2+-binding sites: two high affinity (Kd 100 +/- 30 microM), four intermediate affinity (Kd 450 +/- 70 microM), and five to six low affinity (Kd 2 +/- 0.2 mM). Decarboxylated factor X in which the Gla residues were converted to Glu retained the two high affinity sites (Kd 140 +/- 20 microM). In contrast, factor X lacking the Gla domain as well as a part of the helical hydrophobic residues (des-44-X) retained only one high affinity Ca2+-binding site (Kd 130 +/- 20 microM). Moreover, a synthetic peptide composed of residues 238-277 (58-97 in chymotrypsinogen numbering) from the protease domain of factor X bound one Ca2+ with high affinity (Kd 150 +/- 20 microM). From competitive inhibition assays for binding of active site-blocked factor Xa to factor Va in the prothrombinase complex, the Kd for peptide-Va interaction was calculated to be approximately 10 microM as compared with 30 pM for factor Xa and approximately 1.5 microM for decarboxylated factor Xa. A peptide containing residues 238-262(58-82) bound Ca2+ with reduced affinity (Kd approximately 600 microM) and did not inhibit Xa:Va interaction. In contrast, a peptide containing residues 253-277(73-97) inhibited Xa:Va interaction (Kd approximately 10 microM) but did not bind Ca2+. In additional studies, Ca2+ increased the amidolytic activity of native and des-44-Xa toward a tetrapeptide substrate (benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide) by approximately 1.6-fold. The half-maximal increase was observed at approximately 150 microM Ca2+ and the effect was primarily on the kcat. Ca2+ also significantly protected cleavage at Arg-332-Gln-333(150-151) in the protease domain autolysis loop. Des-44-Xa in which the autolysis loop was cleaved possessed =5% of the amidolytic activity of the noncleaved form; however, the S1 binding site was not affected, as determined by the p-aminobenzamidine binding. Additionally, autolysis loop-cleaved, active site-blocked native factor Xa was calculated to have approximately 10-fold reduced affinity for factor Va as compared with that of the noncleaved form.
Assuntos
Cálcio/metabolismo , Fator Va/metabolismo , Fator X/metabolismo , Ácido 1-Carboxiglutâmico/metabolismo , Autólise , Sítios de Ligação , Catálise , Humanos , Cinética , Modelos Químicos , Modelos Moleculares , Ligação Proteica , Protrombina/metabolismo , Estrôncio/metabolismo , Relação Estrutura-AtividadeAssuntos
Pênis/anormalidades , Adulto , Humanos , Masculino , Pênis/diagnóstico por imagem , Pênis/cirurgia , RadiografiaRESUMO
The outcome of lower limb amputation in the Grampian Region has been studied. In the years 1990-1991, 93 patients had 104 amputations for vascular disease. Rehabilitation was supervised by a multidisciplinary team. The amputation level was: unilateral and below-knee (BKA), 55 patients; unilateral and above-knee (AKA), 27 patients; and bilateral (BA) in 11 patients. At a median follow-up of 27 months, survivors who had had a limb fitted were sent a questionnaire to assess their physical mobility. The response rate was 95%. There were 33 (60%) survivors in the BKA group. Fourteen patients (25%) indicated good mobility and seven (13%) indicated fair mobility. There were five (19%) survivors in the AKA group, only one of whom described fair mobility with a prosthetic limb. There were 5 (46%) survivors of BA. Two described good and one fair mobility. Although vascular amputees have a high mortality rate, physical mobility tends to be good in those fitted with a prosthesis after BKA.