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Biomedical subjects

M Walden

Publications and source records attributed to M Walden.

At least 19 recordsLinked to original sources
PubMed2001

Purification and characterization of the first archaeal aconitase from the thermoacidophilic Sulfolobus acidocaldarius.

The first archaeal aconitase was isolated from the cytosol of the thermoacidophilic Sulfolobus acidocaldarius. Interestingly, the enzyme was copurified with an isocitrate lyase. This enzyme, directly converting isocitrate, the reaction product of the aconitase reaction, was also unknown in crenarchaeota, thus far. Both proteins could only be separated by SDS gel electrophoresis yielding apparent molecular masses of 96 kDa for the aconitase and 46 kDa for the isocitrate lyase. Despite of its high oxygen sensitivity, the aconitase could be enriched 27-fold to a specific activity of approximately 55 micromol x min(-1) x mg(-1), based on the direct aconitase assay system. Maximal enzyme activities were measured at pH 7.4 and the temperature optimum for the archaeal enzyme was recorded at 75 degrees C, slightly under the growth optimum of S. acidocaldarius around 80 degrees C. Thermal inactivation studies of the aconitase revealed the enzymatic activity to be uninfluenced after one hour incubation at 80 degrees C. Even at 95 degrees C, a half-life of approximately 14 min was determined, clearly defining it as a thermostable protein. The apparent K(m) values for the three substrates cis-aconitate, citrate and isocitrate were found as 108 microM, 2.9 mM and 370 microM, respectively. The aconitase reaction was inhibited by the typical inhibitors fluorocitrate, trans-aconitate and tricarballylate. Amino-acid sequencing of three internal peptides of the S. acidocaldarius aconitase revealed the presence of highly conserved residues in the archaeal enzyme. By amino-acid sequence alignments, the S. acidocaldarius sequence was found to be highly homologous to either other putative archaeal or known eukaryal and bacterial sequences. As shown by EPR-spectroscopy, the enzyme hosts an interconvertible [3Fe--4S] cluster.

Aconitate Hydratase↗
PubMed1999

Problem-based learning in the NICU.

Problem-based learning has been used by individuals from various professions and in a wide array of academic and clinical settings. The primary benefits of PBL are that it allows learners to be actively engaged in the learning process and that it can help to strengthen problem-solving skills for learners on any level. PBL can be used effectively in the NICU for both novice and advanced practice nurses.

Clinical Competence↗
PubMed1998

Autoradiographic identification of a gastrin receptor on the human parietal cell.

Gastrin plays an important role in regulating gastric acid secretion and gastrointestinal mucosal growth but its cellular sites of action in man have not been determined. Using cryostat sections of gastric mucosal tissue we have identified (125I-gastrin binding followed by fixation-wet emulsion autoradiography) and characterized (125I-gastrin binding followed by counting) a gastrin receptor binding site in the human stomach. This site displayed binding characteristics similar to those observed in isolated cell systems: specifically, 125I-gastrin binding was rapid (t1/2 approximately 10 min at 37 degrees C), temperature-dependent (3.5 fold more radioligand bound at 22 degrees C than at 4 degrees C) and saturable. The binding of the radioligand was also tissue specific and was five-fold greater in the gastric body than in the gastric antrum and duodenum. In the autoradiographs, silver grains were localized only to parietal cells and not to other epithelial cell types. In the presence of 40 nM gastrin grains were no longer present over parietal cells demonstrating that these sites were both saturable and of high affinity. These data provide the first demonstration of gastrin binding sites (putative receptors) on parietal cells in the human stomach and suggest that gastrin acts directly on these cells to help regulate gastric acid secretion and/or mucosal growth.

Adult↗
PubMed1998

A novel gastrin-binding protein in the human eosinophil.

A specific and saturable interaction between 125I-gastrin and eosinophils was discovered in autoradiographs of human gastric mucosal tissue and confirmed in isolated and enriched preparations of WBC's. Gastrin displaced 125I-gastrin from eosinophils in a dose-dependent manner with a D50 = 11 uM. Scatchard analysis of the saturation curve indicated a single binding site of low affinity (Kd = 4.14 uM) and high capacity (Bmax = 430 umoles/mg protein). The gastrin binding protein was localized to the granular core of the eosinophil and found to have a molecular weight of approximately 15 kDa following chemical crosslinking of radioligand to granules and SDS/PAGE. Based on its molecular weight and granular location and the charge characteristics of gastrin, the gastrin binding protein in the human eosinophil is most likely major basic protein. In vivo this interaction might act to limit the cytotoxic potential of MBP on tissues and/or attentuate gastrin concentrations thereby helping regulate gastric acid secretion and mucosal growth.

Autoradiography↗
PubMed1996

Individualized developmental care for very low-birth-weight infants: a critical review.

Developmental care has been widely accepted and implemented in neonatal intensive care units across the country. Its proponents suggest that individualized developmental care is effective in reducing infant morbidity and length of hospital stay and improving neurodevelopmental outcomes. Although individual components of developmental care have been researched in more depth, few studies have examined a total developmental care protocol. This article critically examines the research base on individualized developmental care and discusses implications for clinical practice and future research.

Child Development↗
PubMed1993

Controversies in the resuscitation of infants of borderline viability.

Advances in perinatal technology have led to a preponderance of ethical dilemmas regarding the resuscitation of extremely preterm infants weighing between 500 and 750 grams. Although a review of the literature indicates poor outcomes in many of these infants, an equal number of studies documenting positive outcomes has been reported. A point/counterpoint format is used to discuss the issues related to the borderline viable infant. Strategies for resolution are formulated based on the issues of concern. Prevention of preterm birth, discussion of the resuscitation plan before delivery and initial resuscitation with the option to withdraw treatment are critical solutions to consider. Additional strategies include the establishment of definitive care guidelines and a standardized definition of quality of life. Other options worthy of consideration are discussed.

Cost of Illness↗
PubMed1991

Prenatal screening for hemoglobinopathies. I. A prospective regional trial.

Prenatal hemoglobinopathy screening was chosen as a model system for the study of patient receptivity to unsolicited genetic information. Providers of prenatal care in Rochester, NY, were offered free testing of all their prenatal patients and genetic counseling of women found positive. The 18,907 prenatal samples tested in a 5-year period represented 35.1% of the pregnancies in the Rochester metropolitan region. A hemoglobinopathy was found in 810 pregnancies (4.3%). Of the 21 different types of hemoglobinopathies detected, the most common were sickle cell trait (59%), hemoglobin C trait (19%), beta-thalassemia trait (11%), and hemoglobin E trait (5%). At the time of phlebotomy, 75% of the pregnancies were of less than 18 wk duration. Sixty-six percent of the pregnancies occurred in patients unaware of their diagnosis, and 80% occurred in patients unaware that they might be at risk for a child with a serious blood disorder. Of the 810 positive pregnancies, 551 (68%) occurred in patients who came for counseling. Of 453 women counseled during their first screened pregnancy, 390 (86%) said they wanted their partners tested and 254 (55%) had their partner tested. In the 77 pregnancies thus found to be at risk, the couple was too late for prenatal diagnosis in 12 cases, and the condition for which the fetus was at risk was too mild in 12 cases. Prenatal diagnosis was offered in the remaining 53 pregnancies and was accepted by 25 couples (47%). These results indicate that unselected patients in the primary care setting in this region, even though pregnant, are receptive to and utilize genetic information.

Adult↗
PubMed1991

Prenatal screening for hemoglobinopathies. II. Evaluation of counseling.

Learning during genetic counseling is often below expectations, especially in the context of genetic screening. In this report we describe learning as a result of genetic counseling of 298 pregnant women identified as hemoglobinopathy carriers, 234 with sickle cell trait and 64 with beta-thalassemia trait. Counseling was designed to provide the information needed in a simple, clear, and nondirective manner. A special videotape produced for this purpose provided dramatization and a role model illustrating an appropriate response. After viewing the videotape the counselee had an opportunity to question the counselor and to have any misconceptions corrected. Questionnaires revealed significantly increased knowledge as a result of counseling in each of the three hemoglobinopathy subject areas tested-namely, clinical manifestations, genetics, and prenatal diagnosis. Five factors correlated with higher knowledge scores after counseling-namely, a younger patient age, more years of education, knowledge of having trait before this identification, knowledge of the baby's father having trait before counseling, and having no prior children.

Female↗
PubMed1991

Prenatal screening for hemoglobinopathies. III. Applicability of the health belief model.

A comprehensive prenatal hemoglobinopathy screening program in Rochester, NY, has been described in a preceding paper in this issue of the Journal. A woman identified as a carrier may face three decisions. The first is whether to accept the offer of counseling. The second is whether to have her partner tested. If her partner also tests positive, then the third decision is whether to accept the offer of prenatal diagnosis. This report analyzes factors affecting her decision, with special attention being given to factors invoked by the Health Belief Model. Factors predicting that a patient who we identified as a carrier would come for counseling included the following: patient had no prior knowledge that she is a carrier (P less than .001), a gestational age less than 18 wk (P less than .01), and Caucasian race (P less than .05). For sickle cell trait counselees and beta-thalassamia trait counselees, factors found to predict patient's intent to have partner tested were the following: a greater postcounseling knowledge of the disease (P less than .009), a lesser perceived burden of intervention (P less than .011), and belief that the partner is also a carrier (P less than .008). Also for sickle cell trait counselees and beta-thalassemia trait counselees, factors predicting that the partner actually will be tested were the following: living with the partner (P less than .001), gestational age at identification less than or equal to 18 wk (P less than .001), a lesser perceived burden of intervention (P less than .002), and a greater perceived seriousness of the disease (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude to Health↗
PubMed1989

Do pregnant women benefit from hemoglobinopathy carrier detection?

A 45% sample of all pregnancies in Rochester, N.Y. over a five-year period showed that 4.2% of pregnant women had a hemoglobinopathy. Sixty-six percent of these women did not know they had such an abnormality, and 80% did not understand its reproductive significance. Sixty-eight percent of women informed they were positive came for counseling. Fifty-seven percent of counseled women had the baby's father tested. Forty-seven percent of couples at risk offered amniocentesis wanted it. (table; see text) A woman was more likely to want her partner tested if she had a more thorough knowledge of the disease or viewed having an affected child as more burdensome. The partner was more likely to come for testing if the couple were living together than if living apart. Prenatal hemoglobinopathy screening is accepted by providers and pregnant women, at least when expert services are provided at no charge to either. Women and couples use the information provided to pursue their reproductive goals.

Female↗
PubMed1989

Nifedipine-haloperidol combination in the treatment of Gilles de la Tourette's syndrome: a case study.

Anecdotal case reports have been published describing the use of the calcium channel blockers verapamil and nifedipine to provide rapid and dramatic relief in refractory Gilles de la Tourette's syndrome (TS). The authors' case presentation illustrates that, although these two drugs may not always work alone, they can be successfully used in combination with other medications for treating refractory TS.

Administration, Oral↗
PubMed1988

Catatonia as a manifestation of paraneoplastic encephalopathy.

The psychopathological, electrophysiological, and pathological features of a 58-year-old woman suffering from anaplastic lung carcinoma with paraneoplastic encephalopathy are presented. The predominant behavioral manifestation was a catatonic syndrome that was partially responsive to clonazepam. Although a variety of neurological, psychiatric, and other causes of catatonia have been reported, this is the first reported case of catatonia caused by paraneoplastic encephalopathy.

Brain Diseases↗
PubMed1986

Source of calcium and cholinergic contraction of the rat portal vein and the sheep coronary artery.

To demonstrate the heterogeneity in behavior of the rat portal vein and the sheep coronary artery, we studied the effect of cholinergic stimulation and its dependence upon extracellular ions. Since acetylcholine produces a contraction antagonized by atropine (pA2 9.5), these effects must be mediated by muscarinic receptors. alpha- and beta-adrenergic blocking agents or a drug which destroys noradrenergic nerve endings (6-hydroxydopamine) do not modify the effects of acetylcholine. In a calcium-free medium (EGTA 10(-4) M), the portal vein, unlike the coronary artery, doses not contract to acetylcholine or caffeine. In the coronary artery only the phasic component of the cholinergic contraction is maintained in a calcium-free medium. Verapamil and cobalt abolish the cholinergic contraction of the portal vein, but inhibit only the tonic component in the coronary artery. In a calcium-free medium, hyperosmotic solutions (290 mM sucrose) produce a moderate contraction which occurs slowly in both vessels. In the coronary artery, a sodium-calcium exchange does not appear to participate in the sustained tonic component of the cholinergic contraction. Electron microscopy demonstrates differences between the two blood vessels regarding the size of the sarcoplasmic reticulum. The coronary artery uses calcium both from extra- and intracellular sources. Portal vein is extremely dependent of the extracellular calcium but we were unable to give direct evidence of the utilization of calcium from intracellular pools during the cholinergic contraction of the rat portal vein.

Acetylcholine↗
PubMed1985

Stress fracture of the navicular bone. Nine cases in athletes.

Nine cases of stress fractures of the tarsal navicular bone were treated in athletes. The diagnosis was made with radiographs and bone scan within 6 months. Only two patients were treated surgically. The only poor result was seen in a patient in whom the fracture was only explored.

Adolescent↗
PubMed1984

The binding characteristics of 125I-gastrin and 125I-CCK8 to guinea pig fundic gastric glands differ: is there more than one binding site for peptides of the CCK-gastrin family?

The binding of biologically active 125I-labeled derivatives of the C-terminal octapeptide of cholecystokinin (125I-CCK8) and gastrin (125I-G) to dispersed guinea pig fundic glands were compared at 24 degrees C. Although both peptides share the same C-terminal pentapeptide sequence, differences were found in the amount of each radioligand bound to fundic glands, their dissociation behavior, and their Scatchard plots. However, each peptide was able to displace the other radioligand from the glands at nM concentrations which indicated that both peptides bound to the same site. The different binding characteristics observed for 125I-G and 125I-CCK8 most likely resulted from the different dissociation rates of each peptide.

Animals↗