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Biomedical subjects

D Schneider

Publications and source records attributed to D Schneider.

At least 19 recordsLinked to original sources
PubMed1992

Selection of high affinity RNA ligands to the bacteriophage R17 coat protein.

RNA ligands with high affinity for the bacteriophage R17 coat protein were isolated from a pool of random RNA molecules using SELEX. Of the 38 ligands isolated, 36 were found to contain a hairpin very similar to the naturally occurring coat protein binding site in the R17 genome. The common features of these 36 sequences provide a consensus binding site and predict components of a hairpin that promote favorable interaction with the coat protein. These include a tetraloop of primary sequence AUCA and a variable-length stem with a bulged adenosine residue at a specific stem position. The predicted consensus agrees well with the highest-affinity RNA binding site of the R17 coat protein, identified through classical but laborious techniques. These results demonstrate the value of SELEX as a tool for isolating high affinity RNA ligands to a specific target protein, and the further value of those ligands to point the researcher toward natural sequences for that target protein.

Allosteric Regulation↗
PubMed1992

Genetic instability in Streptomyces ambofaciens: inducibility and associated genome plasticity.

DNA amplification and deletions occur at high frequency in unstable regions localized on the Streptomyces ambofaciens chromosome. The structure of these regions was investigated, leading to the identification of internal reiterations which could play a role in the deletion and/or amplification mechanism(s). UV irradiation and treatments with mitomycin C, oxolinic acid and novobiocin were shown to efficiently induce genetic instability. Finally, mutator strains were isolated, in which genetic instability was dramatically increased. The involvement of an SOS-like response in genetic instability in S. ambofaciens is proposed.

Amino Acid Sequence↗
PubMed1992

Kinetics of nuclear translocation and turnover of the vitamin D receptor in human HL60 leukemia cells and peripheral blood lymphocytes--coincident rise of DNA-relaxing activity in nuclear extracts.

High affinity receptors (VDR) for 1,25-dihydroxycholecalciferol (calcitriol) are expressed in HL60 human leukemia cells and in low numbers in peripheral blood lymphocytes (PBL). HL60 cells, expressing some characteristics of promyelocytes, can be induced to monocytoid differentiation by calcitriol. Specific nuclear translocation of [3H]calcitriol/VDR was examined after exposure of whole cells to 10(-9) M/l calcitriol in the presence and absence of a 500-fold excess of unlabeled ligand and subsequent isolation of nuclei. Specific nuclear translocation of [3H]calcitriol/VDR was found to be time dependent reaching a maximum of approximately 2100 binding sites/nucleus after 3 h of incubation in HL60 cells, whereas a maximum of approximately 310 binding sites/nucleus was found after 3 h in PBL. Pulse exposure of HL60 to radiolabeled hormone for 3 h followed by culture in medium without serum and calcitriol lead to nuclear retention of approximately 1600 radiolabeled VDR by 8 h and approximately 1000 VDR by 24 h. Radiolabeled VDR disappeared from the nuclear compartment with a halflife of approximately 30 min if cells were cultured with identical concentrations of unlabeled hormone after the pulse (pulse/chase-experiments). No difference of VDR retention in pulse and pulse/chase-experiments was seen in PBL, where VDR halflife was approximately 30 min. No specific translocation into the nuclear compartment was seen when isolated nuclei were incubated in [3H]calcitriol. Radiolabeled hormone/receptor complexes of nuclei isolated from cells exposed for 3 h to radiolabeled hormone--in contrast to identical experiments with intact cells--did not disappear from the nuclear compartment upon incubation of nuclei with identical concentrations of the unlabeled compound. The activity of DNA relaxing enzymes (e.g. topoisomerases I and II) in nuclear extracts was measured using a PBR 322-relaxation-assay. Enhanced overall enzyme activity was found in nuclear extracts by 1 h after incubation with calcitriol (final ethanol concentration 0.0001% v/v) in HL60 and PBL. The enhanced activity disappeared after 2 h in PBL, whereas it was still enhanced by 4 h in HL60. No effect was seen in ethanol treated controls. We conclude that a specific nuclear translocation mechanism exists for calcitriol in both cell types examined, most likely due to translocation of receptor proteins after hormone binding. Translocated hormone/receptor complexes compete for a limited number of specific nuclear binding sites. Enhanced activity of topoisomerases in nuclear extracts upon translocation of VDR might reflect interaction of both within the nuclear compartment, thus initiating DNA-unwinding, a prerequisite of transcription initiation.

Biological Transport↗
PubMed1992

Hysteroscopic findings after missed abortion.

OBJECTIVE: To identify the relation of missed abortions and intrauterine pathology. DESIGN: A postabortal hysteroscopy was performed 8 to 12 weeks after a dilatation and curettage (D&C) for missed abortion. SETTING: Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, Israel. PATIENTS: Sixty patients after a D&C for a missed abortion. MAIN OUTCOME MEASURES: The hysteroscopic appearance of the uterine cavity. RESULTS: Intrauterine adhesions occurred in only 10 patients (16.7%) with most of them of the mild type. A previous missed abortion was recorded in 60% of these cases. Uterine anomaly was found in one quarter of the cases, mainly an incomplete uterine septum. CONCLUSION: We believe that missed abortion does not predispose for intrauterine adhesions to the extent that was previously believed. A partial uterine septum is a major factor predisposing for the occurrence of missed abortion. Hysteroscopy after a missed abortion is an easy and efficient means for both identifying such uterine anomaly and excluding intrauterine adhesions.

Abortion, Missed↗
PubMed1992

Hypercalciuria in children with renal glycosuria: evidence of dual renal tubular reabsorptive defects.

During the past 5 years, we have identified idiopathic hypercalciuria in five of seven patients referred for evaluation of renal glycosuria between 1985 and 1991. The children, all boys, ranged in age from 6 to 12 years. Endocrine function was normal, and none of the patients had hyperparathyroidism, hypercalcemia, renal tubular acidosis, or other secondary causes of hypercalciuria. The calcium/creatinine ratio in a fasting urine specimen was elevated in all five children who had hypercalciuria, with a mean value (+/- SD) of 0.34 +/- 0.06 (normal, < 0.2). In one child who had renal colic with spontaneous passage of gravel-like material, the idiopathic hypercalciuria persisted after 1 week on a diet containing 2000 mg of sodium and 300 mg of calcium. On the basis of studies that examined the site along the nephron responsible for hypercalciuria in rats with streptozocin-induced diabetes, we speculate that in children with renal glycosuria, there is defective reabsorption of glucose and calcium in the straight portion of the proximal tubule or in the collecting duct. It is likely that a similar mechanism accounts for the idiopathic hypercalciuria in children with diabetes mellitus.

Absorption↗
PubMed1992

Choice of exercise: a predictor of behavioral risks?

After controlling for differences in gender, educational achievement, and exercise duration among a sample of 7,248 Americans 18-34 years old, we found that runners-joggers-fast walkers (RJWs) and tennis players were less likely to be obese, smoke, consume large quantities of alcohol, and drive without seat belts than those who participate in team and an aggregate of other sports. These behavioral differences might be explained by imprecise data, intervening variables such as exercise intensity, or other variables that were not measured. But a more interesting explanation is that running-jogging-fast walking and playing tennis are integral components of healthy lifestyles, and team sports and some other exercise behaviors are part of riskier ways of living. No consistent association was found between duration of exercise and behavioral risk.

Adolescent↗
PubMed1992

Region of birth and mortality of blacks in the United States.

Analysis of black American death rates by region of birth and region of residence showed that southern-born blacks had the highest mortality rates and western-born blacks the lowest mortality rates. Blacks born in the northeast, midwest, and outside the US had rates intermediate between southern and western-born black rates. Blacks born in one region and who died in another had age-specific and age-adjusted mortality rates similar to their region of birth rather than their region of residence.

Adolescent↗
PubMed1992

Immunological detection of the oestradiol receptor protein in cell lines derived from the lymphatic system and the haematopoietic system: variability of specific hormone binding in vitro.

Extracts of human MCF 7 mammary carcinoma cells, the human lymphoblastoid cell lines AEH 1 and IM 9, T-cell derived CCRF cells, HL 60 myeloic leukaemia cells and murine myeloma cells SP 0 and NS I were analysed for immunoreactivity with polyclonal goat antibodies raised against homogeneous preparations of C-terminal fragments (32 kDa) of porcine uterine oestradiol receptor (ER). Whole cells and low speed cytosols were analysed for specific oestradiol-binding activity. ERs were enriched from cell extracts by either fractionated ethanol precipitation (0-25% (v/v) ethanol) and/or microscale-immunoaffinity chromatography. Immunoreactive proteins of identical molecular weight (approximately 65 kDa) were detected in all cell lines examined. Whole cell binding assays showed specific oestradiol-binding activity in MCF 7, IM 9 and CCRF cells. Borderline binding was found in HL 60 myeloid cells. No specific binding could be detected in AEH 1, NS I and SP 0 cells. Identical results were obtained using agar-electrophoresis after dextran-coated charcoal treatment. Immunoaffinity purified ERs from MCF 7, AEH 1 and HL 60 cells were subjected to limited proteolysis, where identical tryptic fragments were generated. In conclusion, we have confirmed by immunological methods that ERs are expressed in a variety of cell lines derived from the immune system and the haematopoietic system. The lack of specific hormone binding or very low-affinity hormone binding in some of the cells examined may be due to post-translational events or point mutations.

Blotting, Western↗
PubMed1992

Violence as a public health priority for black Americans.

This study investigated the extent to which black public health and political leaders believe that reducing violence should be a national public health priority for black Americans when compared with other public health problems such as acquired immunodeficiency syndrome, low birthweight, and access to health care. A survey asking whether violence in the black community is amendable to change and who (or what institutions) should be responsible for the reduction of violence was sent to 427 black health leaders, 326 black mayors, and 467 black legislators. Three hundred twenty responses were returned. Virtually all respondents placed violence as one of the top five, if not the highest, public health priority for black Americans. Health and political leaders differed in their beliefs about whether violence and violence-related behaviors can be ameliorated, and who should bear responsibility for the reduction of violence. While this survey had limitations, more than 300 black public health and political leaders indicated that violence among black Americans should be made a national public health priority. Policy implications are discussed, and a proactive role for the National Medical Association is advocated.

Black or African American↗
PubMed1992

Childhood and young adult cancer in New Jersey.

Cancer incidence rates for 0 to 24 years of age were examined for New Jersey for 1979-1985. New Jersey rates generally were higher than the comparison states. They were most like those of Connecticut, the state most similar in demographics, geography, and degree of urbanization.

Adolescent↗
PubMed1991

An anterior appositional electron field technique with a hanging lens block in orbital radiotherapy: a dosimetric study.

A technique for orbital radiotherapy is presented consisting of an anterior, appositional electron beam with a hanging lens block. The beam was modified by introducing two 1.6 mm thick plastic spoilers, at about 3 cm and 15 cm from the lens, to boost in-scattering of electrons under the block. The 9 mm diameter, 2 cm long stainless steel cylindrical block was suspended 0.5-1.0 cm above the eye. We performed film, TLD (Thermo Luminescent Dosimetry), and diode dosimetry to determine the dose fill-in behind the lens. The introduction of the spoilers dramatically changed the dose distribution. The maximum dose under the block increased from 66% to 85% of the open field dose. Moreover, the dose to the posterior surface of the globe directly underneath the block, at a depth of 3 cm, increased from 48% to 76% of maximum dose, while the dose to the lens was still below 20%. This is a simple and easily reproducible treatment and is an improvement on a previously described technique. The dose distribution is adequate for cases where the target volume surrounds and is posterior to the globe.

Electrons↗
PubMed1991

The potential of perturbed angular correlation of gamma rays as a tool for dynamic studies of peptides/proteins.

Four peptides and serum albumin have been derivatized with the bicyclic anydride of diethylenetriamine-pentaacetic acid. Procedures were developed to isolate the labelled species and determine the degree of derivatization. By using perturbed angular correlation of gamma-ray spectroscopy it is possible, through the determination of rotational correlation times, to decide whether labelled peptides interact with other molecules (receptors). In the case of the peptide cholecystokinin it is shown that the interaction between the peptide and its corresponding polyclonal antibody can be determined down to 1 pmol hormone. Experiments on 111In- and 111mCd-labelled Gly-Trp showed that, where the 111Cd PAC spectrum directly reflected the rotational motion of the molecule, the 111In PAC spectrum was affected by the nuclear transitions to 111mCd.

Anisotropy↗
PubMed1991

Fertility before and after surgery for primary ovarian pregnancy.

Primary ovarian pregnancy usually occurs in parous fertile women. It is an accidental event probably related to the presence of the IUD affecting implantation rather than an indicator of altered fertility. Reproductive performance postoperatively remains unmodified.

Abortion, Spontaneous↗
PubMed1991

Metabolic and cardiorespiratory responses to the performance of Wing Chun and T'ai Chi Chuan exercise.

The primary purpose of this study was to examine the metabolic and cardiorespiratory responses to the continuous performance of Wing Chun and T'ai Chi Chuan exercise. No significant differences in VO2max or HRmax obtained during treadmill exercise were found between the practitioners of the two styles. Average values for oxygen uptake (VO2) were 23.3 +/- 7.5 ml.kg-1.min-1 (6.6 METS) and 16.0 +/- 3.9 ml.kg-1.min-1 (4.6 METS) for Wing Chun and T'ai Chi Chuan exercise, respectively. Mean heart rates obtained during exercise were 137 +/- 25 beats.min-1 for Wing Chun and 116 +/- 22 beats.min-1 for T'ai Chi Chuan exercise. These exercise values corresponded to 52.4% of VO2max and 70.5% of HRmax for Wing Chun and only 36.4% of VO2max and 59.8% of HRmax for T'ai Chi Chuan exercise. Thus, only the continuous performance of Wing Chun exercise elicited VO2 and HR responses that would be expected to bring about a cardiorespiratory training effect in subjects with a relatively low initial VO2max. The ventilatory equivalent for oxygen (VE/VO2) obtained during T'ai Chi Chuan exercise (21.7) was significantly lower than for Wing Chun exercise (24.2), suggesting that T'ai Chi practitioners utilize efficient breathing patterns during exercise. Both Wing Chun and T'ai Chi Chuan styles may have a small static component that produces a slightly elevated heart rate relative to metabolic load when compared to traditional aerobic activities. However, the effect was not severe and these forms of exercise should not be considered dangerous for individuals at high risk for cardiovascular disease.

Adult↗
PubMed1991

Noradrenaline release in the rat vena cava is inhibited by gamma-aminobutyric acid via GABAB receptors but not affected by histamine.

1. Segments of the rat vena cava preincubated with [3H]-noradrenaline were superfused with [3H]-noradrenaline-free solution containing desipramine and corticosterone and the effects of gamma-aminobutyric acid (GABA) receptor ligands and of histamine on tritium overflow evoked by transmural electrical stimulation were studied. 2. GABA inhibited, and histamine failed to affect, the electrically (0.66 Hz) evoked tritium overflow both in the absence and presence of rauwolscine (which was present in the superfusion medium in the subsequent experiments). The effect of GABA was less pronounced at a stimulation frequency of 2 Hz. 3. The inhibitory effect of GABA (pIC35 5.83) on the electrically (0.66 Hz) evoked overflow was mimicked by the GABAB receptor agonist, R-(-)-baclofen (6.07) and less potently by S-(+)-baclofen (3.30) and the GABAA receptor agonist, muscimol (3.70). The concentration-response curve of GABA was shifted to the right by the GABAB receptor antagonist, CGP 35348 (P-(3-aminopropyl)-P- diethoxymethyl-phosphinic acid; apparent pA2 4.76), but not affected by the GABAA receptor antagonist, (-)-bicuculline methiodide 100 mumol l-1. Given alone, (-)-bicuculline methiodide slightly increased, and CGP 35348 did not affect, the evoked overflow. 4. The effect of GABA in veins from rats treated for 14 days with RS-baclofen (10 mg kg-1, i.p. once daily) did not differ from that in veins from rats which received the vehicle instead. The effect of GABA also did not differ in veins from rats treated once either with RS-baclofen or with its vehicle. 5. The results suggest that the postganglionic sympathetic nerve fibres in the rat vena cava are endowed with presynaptic GABAB receptors, but not with receptors for histamine. (-)-Bicuculline methiodide increases noradrenaline release by a mechanism not related to GABAA, GABAB, alpha2-receptors or noradrenaline uptake.

Animals↗