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Biomedical subjects

B Mensch

Publications and source records attributed to B Mensch.

At least 19 recordsLinked to original sources
PubMed1999

Hydrogen bonding and protein perturbation in beta-lactam acyl-enzymes of Streptococcus pneumoniae penicillin-binding protein PBP2x.

A soluble form of Streptococcus pneumoniae PBP2x, a molecular target of penicillin and cephalosporin antibiotics, has been expressed and purified. IR difference spectra of PBP2x acylated with benzylpenicillin, cloxacillin, cephalothin and ceftriaxone have been measured. The difference spectra show two main features. The ester carbonyl vibration of the acyl-enzyme is ascribed to a small band between 1710 and 1720 cm-1, whereas a much larger band at approx. 1640 cm-1 is ascribed to a perturbation in the structure of the enzyme, which occurs on acylation. The protein perturbation has been interpreted as occurring in beta-sheet. The acyl-enzyme formed with benzylpenicillin shows the lowest ester carbonyl vibration frequency, which is interpreted to mean that the carbonyl oxygen is the most strongly hydrogen-bonded in the oxyanion hole of the antibiotics studied. The semi-synthetic penicillin cloxacillin is apparently less well organized in the active site and shows two partially overlapping ester carbonyl bands. The penicillin acyl-enzyme has been shown to deacylate more slowly than that formed with cloxacillin. This demonstrates that the natural benzylpenicillin forms a more optimized and better-bonded acyl-enzyme and that this in turn leads to the stabilization of the acyl-enzyme required for effective action in the inhibition of PBP2x. The energetics of hydrogen bonding in the several acyl-enzymes is discussed and comparison is made with carbonyl absorption frequencies of model ethyl esters in a range of organic solvents. A comparison of hydrolytic deacylation with hydroxaminolysis for both chymotryspin and PBP2x leads to the conclusion that deacylation is uncatalysed.

Acylation↗
PubMed1999

Care and feeding of a staff for filmless radiology.

Texas Children's Hospital, a definitive care pediatric hospital located in the Texas Medical Center, has been constructing a large-scale picture archival and communications system (PACS) including ultrasound (US), computed tomography (CT), magnetic resonance (MR), and computed radiography (CR). Developing staffing adequate to meet the demands of filmless radiology operations has been a continuous challenge. Overall guidance for the PACS effort is provided by a hospital-level PACS Committee, a department-level PACS Steering Committee, and an Operations Committee. Operational Subcommittees have been formed to address service-specific implementation, such as the Emergency Center Operations Subcommittee. These committees include membership by those affected by the change, as well as those effecting the change. Initially, personnel resources for PACS were provided through additional duties of existing imaging service personnel. As the PACS effort became more complex, full-time positions were created, including a PACS Coordinator, a PACS Analyst, and a Digital Imaging Assistant. Each position requires a job description, qualifications, and personnel development plans that are difficult to anticipate in an evolving PACS implementation. These positions have been augmented by temporary full-time assignments, position reclassifications, and cross-training of other imaging personnel. Imaging personnel are assisted by other hospital personnel from Biomedical Engineering and Information Services. Ultimately, the PACS staff grows to include all those who must operate the PACS equipment in the normal course of their duties. The effectiveness of the PACS staff is limited by their level of their expertise. This report discusses our methods to obtain training from outside our institution and to develop, conduct, and document standardized in-house training. We describe some of the products of this work, including policies and procedures, clinical competency criteria, PACS inservice topics, and an informal PACS newsletter. As the PACS system software and hardware changes, and as our implementation grows, these products must to be revised and training must be repeated.

Biomedical Engineering↗
PubMed1999

Maintaining continuity of clinical operations while implementing large-scale filmless operations.

Texas Children's Hospital is a pediatric tertiary care facility in the Texas Medical Center with a large-scale, Digital Imaging and Communications in Medicine (DICOM)-compliant picture archival and communications system (PACS) installation. As our PACS has grown from an ultrasound niche PACS into a full-scale, multimodality operation, assuring continuity of clinical operations has become the number one task of the PACS staff. As new equipment is acquired and incorporated into the PACS, workflow processes, responsibilities, and job descriptions must be revised to accommodate filmless operations. Round-the-clock clinical operations must be supported with round-the-clock service, including three shifts, weekends, and holidays. To avoid unnecessary interruptions in clinical service, this requirement includes properly trained operators and users, as well as service personnel. Redundancy is a cornerstone in assuring continuity of clinical operations. This includes all PACS components such as acquisition, network interfaces, gateways, archive, and display. Where redundancy is not feasible, spare parts must be readily available. The need for redundancy also includes trained personnel. Procedures for contingency operations in the event of equipment failures must be devised, documented, and rehearsed. Contingency operations might be required in the event of scheduled as well as unscheduled service events, power outages, network outages, or interruption of the radiology information system (RIS) interface. Methods must be developed and implemented for reporting and documenting problems. We have a Trouble Call service that records a voice message and automatically pages the PACS Console Operator on duty. We also have developed a Maintenance Module on our RIS system where service calls are recorded by technologists and service actions are recorded and monitored by PACS support personnel. In a filmless environment, responsibility for the delivery of images to the radiologist and referring physician must be accepted by each imaging supervisor. Thus, each supervisor must initiate processes to verify correct patient and examination identification and the correct count and routing of images with each examination.

Computer Communication Networks↗
PubMed1997

Involvement of the chromosomal region 11q13 in renal oncocytoma: case report and literature review.

Renal oncocytomas comprise a cytogenetically heterogeneous group of tumors consisting potentially of cytogenetic distinguishable subgroups. Review of the literature revealed loss of chromosome 1 and Y as a possible anomaly for at least one subset oncocytomas. The frequent finding of rearrangements involving chromosome 11 band q13 characterizes another subset of oncocytomas. We report the cytogenetic and pathological features of a renal oncocytoma diagnosed in a 72-year-old woman and found a t(9;11)(p23;q13) as a consistent abnormality. This supports the idea that translocations involving 11q13 define a further subset of oncocytoma.

Adenoma, Oxyphilic↗
PubMed1996

The quality of abortion services in Turkey.

The quality of abortion in Turkey's public sector hospitals is investigated using multiple research methods including observations of actual procedures, interviews with medical staff and clients, and an inventory of materials and equipment. The results suggest that women who obtain abortions in public sector hospitals have a higher abortion rate than the general population. They are likely to receive a vacuum aspiration with minimal pain control medication. Clinical infection control procedures are insufficient, as are interpersonal communication practices including counseling on reproductive health issues and providing factual information. Links with family planning services are strong and the majority of abortion patients who desire family planning receive a contraceptive method, either through direct provision of postabortion contraceptives or referral.

Abortion, Induced↗
PubMed1993

Hepatic flow scintigraphy in evaluation of hepatic metastases in patients with gastrointestinal malignancy.

OBJECTIVE: To assess the value of hepatic flow scintigraphy for occult metastases. DESIGN: Prospective study, 2 years of follow-up. SETTING AND STUDY PARTICIPANTS: One hundred twenty-nine patients undergoing surgery for gastrointestinal cancer. INTERVENTION: Preoperative hepatic flow scintigraphy (3mCi of technetium-99m). MAIN OUTCOME MEASURE: Development of hepatic metastases. RESULTS: Hepatic flow scintigraphy had a sensitivity of 92% and a specificity of 34%. The positive and negative predictive values were 15% and 97%, respectively. CONCLUSIONS: Hepatic flow scintigraphy could therefore be useful in identifying patients who are at low risk of developing metachronous liver metastases and thus avoid unnecessary adjuvant chemotherapy following resection of the primary tumor.

Female↗
PubMed1993

Utility of thallium-201 and iodine-123 metaiodobenzylguanidine in the scintigraphic detection of neuroendocrine neoplasia.

Metaiodobenzylguanidine (MIBG) is a specific marker for neuroendocrine tumours, such as phaeochromocytoma, neuroblastoma, medullary thyroid cancer (MTC) and paraganglioma, but it suffers in some cases (especially in MTC) from a lack of sensitivity. Thallium is a well-known marker of cellularity with a great sensitivity and a lack of specificity. In order to determine whether the association of these two markers is able to improve the detection of neuroendocrine lesions, 137 scintigraphic examinations using MIBG and thallium were performed in 101 patients referred for suspicion or follow-up of neuroendocrine tumours. Thallium chloride was first injected (1 MBq/kg), images being acquired about 20 min after injection; 123I-MIBG (4 MBq/kg) was then injected and images acquired 5 and 24 h later. In patients with phaeochromocytoma or neuroblastoma, thallium scintigraphy appeared of little help since no tumoural site was discovered by thallium accumulation alone. In contrast, thallium examination seemed of interest in the detection of paraganglioma and MTC, the association of the two radiopharmaceuticals increasing the number of detected sites.

3-Iodobenzylguanidine↗
PubMed1993

Anatomy of a trial: a historical view of the Monroe inactivated hepatitis A protective efficacy trial.

The performance of vaccine protective efficacy trials is often more complex than reports of final results suggest. The current article reviews the background, planning and preparations for the Monroe, NY, protective efficacy trial of a formalin-inactivated, alum-adjuvanted hepatitis A vaccine (VAQTA, manufactured by Merck Research Laboratories). The vaccine trial was carried out at Kiryas Joel, a Hasidic Jewish community which had experienced numerous annual outbreaks in a local environment with similarities to day-care centers. Careful communication, and cooperation of community leadership, a flexible technical resource team, and knowledge of an epidemic already ongoing in a sister community whose members were due to arrive for summer holidays, permitted rapid and efficient completion of the trial with a striking demonstration of protection after a single vaccine dose.

Clinical Protocols↗
PubMed1992

A controlled trial of a formalin-inactivated hepatitis A vaccine in healthy children.

BACKGROUND: Although inactivated hepatitis A vaccine is known to be well tolerated and immunogenic in healthy children and adults, its efficacy has yet to be established. METHODS: To evaluate the efficacy of the hepatitis A vaccine in protecting against clinically apparent disease, we conducted a double-blind, placebo-controlled trial in an Hasidic Jewish community in upstate New York that has had recurrent outbreaks of hepatitis A. At the beginning of a summer outbreak, 1037 healthy seronegative children 2 to 16 years of age were randomly assigned to receive one intramuscular injection of a highly purified, formalin-inactivated hepatitis A vaccine or placebo. A case was defined by the presence of typical signs and symptoms, a diagnostic increase in IgM antibody to hepatitis A, and a serum concentration of alanine aminotransferase at least twice the upper limit of normal. Cases occurring greater than or equal to 50 days after the injection were included in the evaluation of efficacy. The children were followed for a mean of 103 days. RESULTS: A total of 519 children received vaccine, and 518 received placebo. The vaccine was well tolerated, with no serious adverse reactions. From day 50 after the injection, 25 cases of clinically apparent hepatitis A occurred in the placebo group and none in the vaccine group (P less than 0.001), confirming that the vaccine had 100 percent protective efficacy. Before day 21, seven cases occurred in the vaccine group and three cases in the placebo group. After that time, there were no cases among vaccine recipients and 34 cases among placebo recipients. CONCLUSIONS: The inactivated purified hepatitis A vaccine that we tested is well tolerated, and a single dose is highly protective against clinically apparent hepatitis A.

Adolescent↗
PubMed1992

Drug use as a risk factor for premarital teen pregnancy and abortion in a national sample of young white women.

The relationship between adolescent drug use and premarital teen pregnancy and abortion as a pregnancy outcome among sexually active women is investigated in a sample of white women from the National Longitudinal Survey of Youth. Event history analysis is used to explore whether prior drug use has a unique effect on premarital teen pregnancy, with controls for personality, lifestyle, and biological factors. Logistic regression is used to estimate whether drug use affects the decision to terminate a premarital teen pregnancy. The results show that the risk of premarital teen pregnancy is nearly four times as high for those who have used illicit drugs other than marijuana as for those with no history of any prior substance involvement. Furthermore, illicit drug use increases the likelihood of an abortion by a factor of 5. Policy implications of the findings are discussed.

Abortion, Induced↗
PubMed1987

Single isotopic probe for gastro-esophageal reflux diagnosis in children.

Gastro-esophageal reflux (G.E.R.) in children has been implicated in various recurring respiratory diseases. Several techniques including oesophageal pH testing and scintigraphy have been devised to detect and quantify G.E.R. Limitations have been found for each test: short duration with gamma-camera and restricted acceptability of the pH probe by children. A single isotopic probe was designed for a non-invasive screening test of G.E.R. in infants. This device was checked by comparison with oesophageal scintigraphy using a gamma camera. Only 1 discrepancy was detected in 19 reflux episodes. This method, using a relatively inexpensive detector and data acquisition module, seems to be well accepted by children, and may be associated with a pH probe for GER diagnosis.

Adolescent↗
PubMed1976

Comparative assessment of scintillation camera performance.

The performance characteristics of 5 scintillation cameras were compared: Searle 19, Searle 37, Ohio Nuclear, Picker 2C and Toshiba GCA 202. Inherent characteristics including spatial resolution, field uniformity and distortion, energy resolution, count-rate capability and paralyzing time were measured. Extrinsic characteristics such as spatial resolution with emission tests and sensitivity with high resolution, low energy collimators also were measured. The Ohio Nuclear camera gave the best results for most of the parameters studied, followed by Searle 37 PMT, Searle 19 PMT, Picker, and Toshiba. The size of the crystal must also be a criterion for choosing a camera.

Scintillation Counting↗
PubMed1975

[Obstructive pulmonary syndromes in children with alpha 1 antitrypsin deficiency. 3 cases].

During the last six years, the search for a deficiency in alpha-1-antitrypsin (AAT) was carried out in 106 children aged from 5 months to 14 years, having the obstructive pulmonary syndrome. Nine deficiencies were in this manner detected and phenotyped. These are the observations of three of these children which are reported here. Their age ranged between 4 years and a half for two of them and 8 years for the third one, having asthma. The phenotypes are respectively SS, MZ, and ZZ. Following these observations, the problems brought up by the association in AAT deficiency and the obstructive pulmonary syndrome in children are discussed: clinical symptomatology, interpretation of the basic design, pathogenic signification and possible connections with asthma and therapeutic influence. The functional respiratory disorders noted in these children involved a ventilatory asychronism, an overexpansion, and regional abnormalities of ventilation and perfusion. To answer these still outstanding questions, the need for a systematic prospective study carried out on a wide group of children is emphasized.

Adolescent↗
PubMed1975

[Early functional disorders in 3 children exhibiting an obstructive syndrome and an alpha 1 antitrypsin deficiency].

The respiratory function is studied in 3 children, two of which 4 years in age, exhibiting a respiratory obstructive syndrome and an alpha1-antitrypsin deficiency. The study of the respiratory function is global and regional. The disorders noted include a ventilatory asynchronism, a distension, regional anomalies of ventilation and perfusion. The ventilatory asynchronism appears to be an early disorder in the course of alpha1-antitrypsin deficiency. These results have to be related with the development of the elastic fibers during the child's growth.

Child↗