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Biomedical subjects

R Beck

Publications and source records attributed to R Beck.

At least 109 records · Page 6Linked to original sources
PubMed1994

Expression of human placental alkaline phosphatase in Escherichia coli.

The human placental alkaline phosphatase gene was subcloned for expression in Escherichia coli. A shortened form of the alkaline phosphatase, lacking 29 C-terminal amino acids which constitute a membrane anchoring domain, is expressed to about 5% of total protein. Most of the enzyme is present in an insoluble form; however, soluble enzyme can be detected in Western blots and activity tests. The protein is located in the periplasm since its signal peptide is cleaved off. Like the wild-type enzyme, recombinant, shortened placental alkaline phosphatase is inhibited by L-phenylalanine. The amount of active enzyme can be increased by addition of magnesium but not zinc to the medium. Using optimized fermentation conditions, 11 kU of soluble and active alkaline phosphatase are produced per liter. Coexpression of potential folding aids like peptidyl-prolyl cis-trans isomerase or disulfide isomerase does not lead to an increase of soluble enzyme, either when overexpressed separately or from an operon.

Alkaline Phosphatase↗
PubMed1994

Comparative analysis of intrathecal antibody synthesis and DNA amplification for the diagnosis of cytomegalovirus infection of the central nervous system in AIDS patients.

We evaluated 49 paired cerebrospinal fluid (CSF) and serum samples of 35 patients infected with the human immunodeficiency virus type 1 (HIV-1) for laboratory evidence of cytomegalovirus (CMV) infection. The patients were grouped according to clinical criteria as probable CMV encephalitis/polyradiculomyelitis, CMV retinitis, cerebral toxoplasmosis, progressive multifocal leukoencephalopathy, HIV-1-related cognitive/motor complex, HIV-1-associated myelopathy, and other neurological diseases. Paired CSF and serum samples were analysed for CMV deoxyribonucleic acid (DNA) by polymerase chain reaction (PCR), quantitative intrathecal synthesis of immunoglobulin G (IgG) antibodies specific for recombinant phosphoprotein 150 (pp150) of CMV and CMV-specific serum IgM. Intrathecal synthesis of pp150-specific IgG was detected in 26% of patients (9/35), serum IgM was found in 23% of patients (8/35), and PCR of CSF was positive in 11% of patients (4/35). Detection of CMV-specific DNA in CSF preceded the intrathecal antibody synthesis in three patients for whom serial samples were available. PCR results of the CSF became negative in one patient with CMV polyradiculomyelitis after successful therapy with 9-[2-hydroxy-1-(hydroxymethyl) ethoxymethyl] guanine (DHPG). PCR has a higher diagnostic specificity in the acute phase of CMV infection than intrathecal antibody synthesis. The serum IgM response to CMV cannot be used to monitor a compartmentalized immune response in the central nervous system while an intrathecal immune response seems to be associated with recovery either spontaneously or as a result of treatment.

AIDS-Related Opportunistic Infections↗
PubMed1994

Comparison of cord blood and adult blood lymphocyte normal ranges: a possible explanation for decreased severity of graft versus host disease after cord blood transplantation.

Lymphocyte subpopulations in cord blood (CB; collected at birth from full-term babies) were compared with that of adult blood (AB) and found to contain significantly different numbers and percentages of lymphocyte subpopulations. The absolute lymphocyte count was greater in CB (4.8 +/- 1.1 x 10(9)/L) than in AB (1.69 +/- 0.38 x 10(9)/L), with CB having significantly higher absolute numbers of lymphocyte subsets even though CB percentages were significantly lower. Significant differences in percentages were found between cord and adult T cells (CB 58% vs AB 74%), NK cells (CB 19% vs AB 7%) and their subsets. CD38, a marker of activation and immaturity, was present on virtually all cord T cells and approximately half the adult T cells. CD45RA, a marker considered to define unprimed or naive cells, was expressed on 82% of cord lymphocytes as compared with 48% in AB. CD45RO was expressed on 16% of CB lymphocytes and 49% of AB lymphocytes. Cord blood contains a higher percentage and total number of immature and immunologically naive lymphocytes than AB.

Adolescent↗
PubMed1994

Contrast-enhanced MR imaging of the breast: comparison of two different doses of gadopentetate dimeglumine.

PURPOSE: To optimize detection and diagnosis of breast lesions with contrast-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: A three-dimensional fast low-angle shot pulse sequence was used for a group comparison consisting of 76 high-dose (0.16 mmol gadopentetate dimeglumine per kilogram of body weight) and 76 low-dose (0.1 mmol/kg) examinations. Intraindividual comparisons were possible in a subgroup of 20 patients. RESULTS: Enhancement with the high dose was about 1.5 times higher for benign and malignant tissues. With the lower dose, no false-positive findings could be avoided and definition of a threshold that excluded false-negative findings was problematic. Conspicuity of malignant lesions was much improved with the higher dose (a good to excellent rating in 81% vs 26% with the lower dose). Three small foci were visible only with the higher dose. CONCLUSION: The higher dose of contrast material allowed much better results. Dose comparison studies are also recommended for other techniques.

Breast↗
PubMed1993

[Acute cytomegalovirus gastritis after kidney transplantation. Its diagnosis by the polymerase chain reaction, antigenemia assay and immunohistochemistry].

To diagnose possible cytomegalovirus (CMV) infection in a 64-year-old man after renal transplantation, polymerase chain reaction (PCR), pp65 antigenaemia assay (pAA) and virus isolation in cell culture were routinely performed on a weekly basis. The PCR obtained virus DNA in peripheral blood lymphocytes for the first time in the fifth week. Two weeks later the patient complained of feeling unwell with abdominal pain and vomiting on eating. Two days later he developed a fever up to 38 degrees C and nocturnal sweats. Gastroscopy revealed marked antral gastritis which histologically showed typical cytomegalic "owl-eye" cells. The pAA was clearly positive and the cell culture started in the fifth week now showed a cytopathogenic effect. CMV gastritic having been diagnosed treatment consisted of 175 mg ganciclovir intravenously twice daily for 10 days. He became symptom-free after two days. The only side effects were thrombocytopenia down to 67,000/microliters and a rise in transaminase activities, changes which regressed later. To ensure early diagnosis and treatment of any CMV infection, specific virus diagnostic tests should be routinely undertaken after transplantation of organs from CMV-positive persons into CMV-negative patients.

Acute Disease↗
PubMed1993

Fatal inhalational isopropyl alcohol poisoning in a neonate.

A 37 weeks gestation, 1500 gram male infant with multiple dysmorphic features underwent surgery for gastroschisis several hours after birth. During post-operative mechanical ventilation, 70% isopropyl alcohol was accidentally placed in the humidifier of the ventilator, resulting in an estimated 2 h exposure. While the baby seemed clinically stable, initial neurological examination was confounded by recent sedation and pancuronium paralysis. Initial post-operative hypotension was corrected with fluid administration and remained stable for the remainder of the clinical course. By 2 h post-exposure, he was moving, breathing spontaneously and opening his eyes. Isopropyl alcohol and acetone levels at 1, 6, 10 h post exposure were 31/10, 22/15, 15/20 mmol/L respectively. Isopropyl alcohol elimination t1/2 was 9.6 h. Dialysis or exchange transfusion were considered but due to their high risk and the stable infant condition, it was elected to continue with supportive care only. 12.5 h post-exposure, he suddenly became cyanotic, bradycardic, then asystolic. Resuscitation efforts were unsuccessful. To our knowledge, this is the youngest patient reported to have toxic inhalational exposure to isopropyl alcohol and the first report on isopropyl alcohol pharmacokinetics at this age.

1-Propanol↗
PubMed1992

Development of a rate adaptive pacemaker based on the maximum rate-of-rise of right ventricular pressure (RV dP/dtmax).

The maximum rate of rise of right ventricular pressure (RV dP/dtmax) may change in response to physiological stress and thereby provide an appropriate parameter upon which to base rate adaptive pacing. Initial feasibility testing was carried out in six patients using externally closed loop rate adaptive pacing with a pressure sensing lead (Model 6220) and an investigational VVI pulse generator (Medtronic, Model 2451). During exercise, maximum positive RV dP/dtmax increased from 223 +/- 55 to 405 +/- 181 mmHg.sec.1 (P less than 0.05). Based on these results, rate adaptive pulse generators using maximum positive RV dP/dt were implanted in 12 patients (Medtronic, Model 2503). Exercise treadmill testing in the VVI mode resulted in heart rates ranging from 69 +/- 6 beats/min at rest to 79 +/- 14 beats/min (n = 12; P greater than 0.05). In contrast, VVIR mode pacing rates ranged from 71 +/- 11 beats/min to 115 +/- 24 beats/min (n = 17; P less than 0.05). Holter recording showed heart rates ranging from 51 +/- 6 to 110 +/- 22 beats/min during activities of normal daily living (n = 9; P less than 0.05). Passive postural tilt resulted in rates of 69 +/- 8 beats/min in the supine position increasing to 74 +/- 14 beats/min with 60 degrees upright tilt (n = 16; P greater than 0.05). With up to 5-year follow-up data, there have been no late failures of pacing but one lead showed insulation failure with over- and undersensing after 4.5 years. A number of deficiencies were identified in the prototypes leading to modifications of a subsequent generation of rate responsive pacemaker based on RV dP/dtmax. These initial data demonstrate that rate adaptive pacing based on RV dP/dtmax responds in a physiological manner. This rate responsive system is of particular interest as it is based on a beat-to-beat parameter of cardiac mechanical function.

Activities of Daily Living↗
PubMed1992

Histamine challenge in young children using computerized lung sounds analysis.

The use of the histamine challenge test (HCT) for the diagnosis of asthma has so far been limited to older children who can perform spirometry consistently. Recently, wheeze detection by tracheal auscultation with analog recording into a tape recorder has been utilized in young children in place of spirometry. Wheezing can also be identified using computerized lung sounds analysis (LSA) by a typical pattern on spectral analysis. Our aim was to develop a practical computerized system in which the response to histamine could be identified in an objective manner and documented on hard copy. Lung sounds were recorded with a Hewlett-Packard HP 21050A contact sensor placed over the right upper anterior chest. Sounds were amplified, band-filtered (50 to 2,000 Hz), and digitized at a sampling rate of 5.5 kHz into a Macintosh SE computer, and spectral LSA was performed. To validate our method, six older children (ages 9 to 16 years) with mild or moderate asthma underwent HCT. The identification of typical wheezing pattern (discrete, high-amplitude power peaks) on LSA was compared to 20 percent fall in FEV1 (PC20) and symptoms (cough, wheeze, chest tightness). In five children, the histamine concentration required to produce the characteristic wheezing pattern on LSA was half that required to produce a 20 percent fall in FEV1. In the sixth patient, wheezing on LSA and PC20 occurred at the same histamine concentration. To determine the technique's applicability to young children, we then studied six young asthmatic children (age 2 to 5 years). All children showed the wheezing pattern at a histamine concentration of 25 percent or 50 percent (one or two steps prior) to that producing symptoms (cough, wheeze, chest tightness) or wheezing on tracheal auscultation. Six age- and sex-matched nonasthmatic children (control subjects) did not show this pattern on LSA and had no symptoms or tracheal wheeze with HCT. We describe a sensitive method enabling application of HCT to young children who are unable to perform spirometry. This method is as sensitive as, and often more sensitive than, conventional PC20 with spirometry or tracheal auscultation.

Adolescent↗
PubMed1992

Randomized controlled study of a retiree health promotion program. The Bank of American Study.

The initial results of a 12-month controlled trial of a health promotion program in 5686 Bank of America retirees, randomized into full program, questionnaire only, and insurance claims only groups, were analyzed to determine whether the health promotion program was effective. Comparisons were between program and questionnaire only groups for self-reported health habit changes, health risk scores, medical care utilization, and days confined to home, and between all groups for insurance claims data. The intervention, or full program, included health habit questionnaires administered every 6 months, individualized time-oriented health risk appraisals, personal recommendation letters, self-management materials, and a health promotion book. Twelve-month changes in health habits, health status, and economic variables favored the full program group in 31 of 32 comparisons and were statistically significant at the .05 level in two-tailed tests in 19 comparisons and at the .01 level in two-tailed tests in 13 comparisons. Over 12 months, overall computed health risk scores decreased by 4.3% in the full program experimental group and increased by 7.2% in the questionnaire only control group. Total direct and indirect costs decreased by 11% in the experimental group and increased by 6.3% in the questionnaire only control group. Analysis of claims data confirmed these trends. A low-cost health promotion program for retirees was effective in changing health behaviors and has potential to decrease health care utilization.

Aged↗
PubMed1992

Fatal neonatal pneumonia caused by adenovirus type 35. Report of one case and review of the literature.

A 3680-g term male neonate developed bilateral bronchopneumonia at 9 days of age. The labor, delivery, and immediate postnatal period had been unremarkable. Despite standard antibiotic therapy, the patient progressed to respiratory failure and died 4 days later. Adenovirus particles were found in oropharyngeal secretions 1 day prior to death. Autopsy revealed an extensive necrotizing bronchiolitis and alveolitis with frequent "smudge cells." Adenovirus was identified by culture, electron microscopy, and in situ DNA hybridization. The adenovirus was serotyped as type 35, which, to our knowledge, has not been previously described in neonatal adenovirus pneumonia.

Adenovirus Infections, Human↗
PubMed1991

Time-related effects of gonadotropin-releasing hormone analog treatment in experimentally induced endometriosis in the rat.

The purpose of our study was to characterize the time-dependent effect of gonadotropin-releasing hormone analog (GnRH-a) therapy on endometriosis explant using the rat model. Endometriosis was induced in 60 mature female rats. One group of treated animals as well as controls were killed at 2, 4, 6 and 8 weeks of treatment at which time the explant was evaluated. Explant volume was significantly reduced in all treatment groups, an effect that was more significant in animals treated for greater than or equal to 4 weeks compared with those treated for only 2 weeks. We conclude that GnRH-a treatment caused gradual regression of endometrial explant that was effectively complete by 4 weeks of treatment. We further conclude that this experimental model may be useful in the evaluation of other modes of endometriosis therapy.

Analysis of Variance↗
PubMed1991

[Digital peripheral angiography with pace shifting and subtraction. Comparison with the standard procedure].

In a prospective randomised study including 60 patients digital peripheral angiography with stepping and subtraction (DPSA) was compared to DPA without subtraction (DPA), DSA without stepping and conventional angiography. Using conventional angiography, complementary series were necessary in 8 out of 20 patients. This number could be reduced to 3 out of 20 patients using DPSA and DSA respectively. Examination time could thus be shortened by about 20%. The amount of contrast medium could also be reduced by 15 to 20%. Both digital subtraction techniques supplied superior image quality especially in the lower limb in comparison with conventional and digital peripheral angiography without subtraction. X-ray exposure was similar for conventional angiography and DPSA. DSA without subtraction revealed a three times increased dose. Our results indicate that DPA with the possibility of image subtraction is a desirable new technique and might become the method of choice in peripheral angiography in the future.

Angiography↗
PubMed1991

Radiation-induced optic neuropathy: a magnetic resonance imaging study.

Optic neuropathy induced by radiation is an infrequent cause of delayed visual loss that may at times be difficult to differentiate from compression of the visual pathways by recurrent neoplasm. The authors describe six patients with this disorder who experienced loss of vision 6 to 36 months after neurological surgery and radiation therapy. Of the six patients in the series, two had a pituitary adenoma and one each had a metastatic melanoma, multiple myeloma, craniopharyngioma, and lymphoepithelioma. Visual acuity in the affected eyes ranged from 20/25 to no light perception. Magnetic resonance (MR) imaging showed sellar and parasellar recurrence of both pituitary adenomas, but the intrinsic lesions of the optic nerves and optic chiasm induced by radiation were enhanced after gadolinium-diethylenetriaminepenta-acetic acid (DTPA) administration and were clearly distinguishable from the suprasellar compression of tumor. Repeated MR imaging showed spontaneous resolution of gadolinium-DTPA enhancement of the optic nerve in a patient who was initially suspected of harboring recurrence of a metastatic malignant melanoma as the cause of visual loss. The authors found the presumptive diagnosis of radiation-induced optic neuropathy facilitated by MR imaging with gadolinium-DTPA. This neuro-imaging procedure may help avert exploratory surgery in some patients with recurrent neoplasm in whom the etiology of visual loss is uncertain.

Aged↗