A calorimetric study of the influence of calcium on the stability of bovine alpha-lactalbumin.

Bovine alpha-lactalbumin has been studied by differential scanning calorimetry with various concentrations of calcium to elucidate the effect of this ligand on its thermal properties. In the presence of excess calcium, alpha-lactalbumin unfolds upon heating with a single heat-absorption peak and a significant increase of heat capacity. Analysis of the observed heat effect shows that this temperature-induced process closely approximates a two-state transition. The transition temperature increases in proportion with the logarithm of the calcium concentration, which results in an increase in the transition enthalpy as expected from the observed heat capacity increment of denaturation. As the total concentration of free calcium in solution is decreased below that of the proteins, there are two temperature-induced heat absorption peaks whose relative area depends on the calcium concentration, such that further decrease of calcium concentration results in a increase of the low-temperature peak and a decrease of the high-temperature one. The high-temperature peak occurs at the same temperature as the unfolding of the holo-protein, while the low-temperature peak is within the temperature range associated with the unfolding of the apo-protein. Statistical thermodynamic modeling of this process shows that the bimodal character of the thermal denaturation of bovine alpha-lactalbumin at non-saturated calcium concentrations is due to a high affinity of Ca2+ for alpha-lactalbumin and a low rate of calcium exchange between the holo- and apo-forms of this protein. Using calorimetric data, the calcium-binding constant for alpha-lactalbumin has been determined to be 2.9 x 10(8) M-1.

Can restrictions on reimbursement for anti-ulcer drugs decrease Medicaid pharmacy costs without increasing hospitalizations?

OBJECTIVE: To examine the impact of a policy restricting reimbursement for Medicaid anti-ulcer drugs on anti-ulcer drug use and peptic-related hospitalizations. DATA SOURCES/STUDY SETTING: In addition to U.S. Census Bureau data, all of the following from Florida: Medicaid anti-ulcer drug claims data, 1989-1993; Medicaid eligibility data, 1989-1993; and acute care nonfederal hospital discharge abstract data (Medicaid and non-Medicaid), 1989-1993. STUDY DESIGN: In this observational study, a Poisson multiple regression model was used to compare changes, after policy implementation, in Medicaid reimbursement for prescription anti-ulcer drugs as well as hospitalization rates between pre- and post-implementation periods in Medicaid versus non-Medicaid patients hospitalized with peptic ulcer disease. PRINCIPAL FINDINGS: Following policy implementation, the rate of Medicaid reimbursement for anti-ulcer drugs decreased 33 percent (p < .001). No associated increase occurred in the rate of Medicaid peptic-related hospitalizations. CONCLUSIONS: Florida's policy restricting Medicaid reimbursement for anti-ulcer drugs was associated with a substantial reduction in outpatient anti-ulcer drug utilization without any significant increase in the rate of hospitalization for peptic-related conditions.

Characterization of interactions between the mammalian polycomb-group proteins Enx1/EZH2 and EED suggests the existence of different mammalian polycomb-group protein complexes.

In Drosophila melanogaster, the Polycomb-group (PcG) and trithorax-group (trxG) genes have been identified as repressors and activators, respectively, of gene expression. Both groups of genes are required for the stable transmission of gene expression patterns to progeny cells throughout development. Several lines of evidence suggest a functional interaction between the PcG and trxG proteins. For example, genetic evidence indicates that the enhancer of zeste [E(z)] gene can be considered both a PcG and a trxG gene. To better understand the molecular interactions in which the E(z) protein is involved, we performed a two-hybrid screen with Enx1/EZH2, a mammalian homolog of E(z), as the target. We report the identification of the human EED protein, which interacts with Enx1/EZH2. EED is the human homolog of eed, a murine PcG gene which has extensive homology with the Drosophila PcG gene extra sex combs (esc). Enx1/EZH2 and EED coimmunoprecipitate, indicating that they also interact in vivo. However, Enx1/EZH2 and EED do not coimmunoprecipitate with other human PcG proteins, such as HPC2 and BMI1. Furthermore, unlike HPC2 and BMI1, which colocalize in nuclear domains of U-2 OS osteosarcoma cells, Enx1/EZH2 and EED do not colocalize with HPC2 or BMI1. Our findings indicate that Enx1/EZH2 and EED are members of a class of PcG proteins that is distinct from previously described human PcG proteins.

Health plan accreditation: NCQA, JCAHO, or both?

Currently the National Committee for Quality Assurance (NCQA) and the Joint Commission on the Accreditation of Healthcare Organizations (the Joint Commission) accredit managed care organizations (MCOs), but is competition in the market for plan accreditation beneficial or counterproductive? This paper presents the results from two surveys that were administered to a group of large public and private purchasers, and representatives from the American Association of Health Plans and the Centers for Disease Control, who attended the Lovelace Health System (LHS) "Accreditation Experience" program. The LHS program was designed to inform purchasers about the NCQA and Joint Commission accreditation processes. The surveys captured purchaser views about the advantages and disadvantages of both accreditation processes, the value of accreditation, and the use of plan performance measures.

Energetics of structural domains in alpha-lactalbumin.

alpha-Lactalbumin is a small, globular protein that is stabilized by four disulfide bonds and contains two structural domains. One of these domains is rich in alpha-helix (the alpha-domain) and has Cys 6-Cys 120 and Cys 28-Cys 111 disulfide bonds. The other domain is rich in beta-sheet (the beta-domain), has Cys 61-Cys 77 and Cys 73-Cys 91 disulfide bonds, and includes one calcium binding site. To investigate the interaction between domains, we studied derivatives of bovine alpha-lactalbumin differing in the number of disulfide bonds, using calorimetry and CD at different temperatures and solvent conditions. The three-disulfide form, having a reduced Cys 6-Cys 120 disulfide bond with carboxymethylated cysteines, is similar to intact alpha-lactalbumin in secondary and tertiary structure as judged by its ellipticity in the near and far UV. the two-disulfide form of alpha-lactalbumin, having reduced Cys 6-Cys 120 and Cys 28-Cys 111 disulfide bonds with carboxymethylated cysteines, retains about half the secondary and tertiary structure of the intact alpha-lactalbumin. The remaining structure is able to bind calcium and unfolds cooperatively upon heating, although at lower temperature and with significantly lower enthalpy and entropy. We conclude that, in the two disulfide form, alpha-lactalbumin retains its calcium-binding beta-domain, whereas the alpha-domain is unfolded. It appears that the beta-domain does not require alpha-domain to fold, but its structure is stabilized significantly by the presence of the adjacent folded alpha-domain.

Botulinum toxin for achalasia: long-term outcome and predictors of response.

BACKGROUND & AIMS: Botulinum toxin injection into the lower esophageal sphincter of patients with achalasia results in effective short-term relief of symptoms. The aims of this study were to examine the long-term outcome of these patients and to determine the predictors of response to this therapy. METHODS: Thirty-one patients with achalasia treated with botulinum toxin were followed up prospectively for a median duration of 890 days. RESULTS: Twenty-eight patients improved initially, but only 20 patients had sustained improvement beyond 3 months; the latter patients were classified as responders. The response rate was greater in patients older than 50 years of age (82% vs. 43% in younger patients; P = 0.03) and in patients with vigorous achalasia (100% vs. 52% with classic achalasia; P = 0.03). Duration of illness, previous dilation, and baseline radiological characteristics did not influence outcome. Nineteen responders eventually had relapse after a median duration of 468 days (range, 153 - 840 days). Fifteen of these patients received a second injection with satisfactory results obtained in the majority of patients. CONCLUSIONS: Botulinum toxin is an effective treatment for achalasia in about two thirds of patients, with a duration of response averaging 1.3 years. Age and type of achalasia seem to be important predictors of response.

Intrasphincteric botulinum toxin for the treatment of achalasia.

BACKGROUND: Achalasia is a disorder of swallowing in which the lower esophageal sphincter fails to relax. We report the use of botulinum toxin, a paralytic agent, for the treatment of this condition. METHODS: In a double-blind trial, 21 patients with achalasia received either 80 units of botulinum toxin or placebo, injected endoscopically into the lower esophageal sphincter. One week later, the response to treatment was assessed on the basis of changes in the symptom scores (measured on a scale from 0 to 9), pharyngoesophagograms, and results of esophageal manometric and scintigraphic studies. Patients who received placebo initially were subsequently treated with botulinum toxin. After six months, esophageal scintigraphy was repeated. RESULTS: One week after treatment, the mean decrease in the symptom score was 5.4 points for the patients treated with botulinum toxin and 0.5 point for the placebo group (P = 0.001). The mean decrease in the pressure of the lower esophageal sphincter was 33 percent in the treatment group, as compared with a mean increase of 12 percent in the placebo group (P = 0.02), and the mean increase in the width of the opening of the lower esophageal sphincter was 204 percent in the treatment group, as compared with a mean decrease of 14 percent in the placebo group (P = 0.02). Nineteen of the 21 patients treated with botulinum toxin had symptomatic improvement initially; after six months 14 patients were still in remission. This improvement was accompanied by a decrease in esophageal retention that was sustained at six months (46 percent, as compared with a pretreatment value of 77 percent; P = 0.04). There were no serious adverse effects. CONCLUSIONS: Injection of botulinum toxin into the lower esophageal sphincter is an effective, safe, and simple method of treatment for achalasia, with results that are sustained for several months.

pH monitoring: is it the gold standard for the detection of gastroesophageal reflux disease?

Ambulatory, long term (24-h) intraluminal esophageal pH monitoring is the "gold standard" for detection and quantification of gastroesophageal reflux. Is it, however, the "gold standard" for the diagnosis of gastroesophageal reflux disease (GERD)? The answer depends in part on how GERD is defined. Is it to be defined on the basis of symptoms, inflammatory changes in the esophageal mucosa, extent of the exposure of the esophagus to acid or some combination of these factors? Since the correlation between acid exposure of the esophageal mucosa and either symptoms or histologic changes is poor at best, it seems there must be factors in addition to acid exposure that determine the severity of symptoms and histologic damage. One such is the resistance of the individual patient's mucosa to injury by acid exposure. In view of the above, it is not surprising that no specific value for acid exposure of the esophagus can be equated with the diagnosis of GERD. The addition of the symptom index, the frequency with which symptoms coincide with reflux episodes, has done little to increase the sensitivity and specificity of pH recording in the diagnosis of GERD. Another variable only occasionally considered is the day to day variation in the frequency and duration of acid reflux. Finally, intraesophageal pH recording measures only the intensity of acid exposure but we have no clinical measure of mucosa resistance to acid-induced injury, the other factor contributing to the pathogenesis of GERD.

Art and science of history taking in the patient with difficulty swallowing.

History taking is the first step in the evaluation of a patient. An analysis of the information obtained provides the basis for the choice and order of diagnostic tests. In addition, it provides the clinician with the necessary information to determine the relevance of "abnormal tests" to the patient's problem. Dysphagia is a reliable symptom that indicates an abnormality in the swallowing mechanism. The history should contain a detailed description of the symptoms associated with dysphagia from the onset. Especially relevant are questions to determine if dysphagia is experienced every day or intermittently, with solid food or liquids or both, as well as presence and timing of associated symptoms such as, choking, coughing and regurgitation, changes in speech, heartburn and chest pain. It is clinically useful to divide swallowing into three phases: oral, pharyngeal and esophageal. Oral dysphagia is usually due to a neurologic disorder, decreased salivary flow or painful oropharyngeal lesions. Pharyngeal dysphagia is most frequently caused by neuromuscular disorders and less frequently by a Zenker's diverticulum, neoplasm or a mucosal web. Esophageal dysphagia is caused by a structural narrowing, such as produced by a peptic stricture, neoplasm or a Schatzki's ring or by a primary motility abnormality, such as achalasia or diffuse esophageal spasm or by motility abnormalities produced by inflammation caused by gastroesophageal reflux, medication-induced esophageal ulceration or infectious esophagitis.

Coordination of peristalsis in pharynx and esophagus.

When a swallowed liquid bolus is followed from mouth to stomach in man by contrast studies or manometry, it traverses its course without hesitation even though the bolus is propelled by striated muscle contraction in the first part of its journey and smooth muscle in the latter part. The striated muscle is innervated by excitatory cholinergic nicotinic cranial nerves whereas the smooth muscle of the esophagus is innervated by the enteric nervous system (ENS) through excitatory and inhibitory nerves. These differences can be demonstrated by observing the inhibitory effects of curare and atropine, the first blocking nicotinic receptors and the second muscarinic receptors. Early students of esophageal motility recognized that peristalsis could be initiated in two ways. The first is initiated by a swallow and is called primary peristalsis and the second called secondary peristalsis is initiated by distension of the esophagus. It was proposed that primary peristalsis was initiated by a single sensory input activated by the bolus entering the pharynx which in turn activated a motor program in the brain stem. Secondary peristalsis was believed to be stimulated by multiple afferent impulses arriving from the esophagus as the bolus passed down the esophagus. More recent studies using manometric techniques have suggested that the only difference between primary and secondary peristalsis is the afferent stimuli and the effector mechanism is the same. Subsequent studies of carefully timed, paired swallows, transection of vagus nerves and esophagus, and single nerve recordings suggest that the answer lies between the two extremes noted above.(ABSTRACT TRUNCATED AT 250 WORDS)