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Biomedical subjects

D Schneider

Publications and source records attributed to D Schneider.

At least 55 records · Page 3Linked to original sources
PubMed2001

Generalized transduction in Streptomyces coelicolor.

We report the isolation of generalized transducing phages for Streptomyces species able to transduce chromosomal markers or plasmids between derivatives of Streptomyces coelicolor, the principal genetic model system for this important bacterial genus. We describe four apparently distinct phages (DAH2, DAH4, DAH5, and DAH6) that are capable of transducing multiple chromosomal markers at frequencies ranging from 10(-5) to 10(-9) per plaque-forming unit. The phages contain DNA ranging in size from 93 to 121 kb and mediate linked transfer of genetic loci at neighboring chromosomal sites sufficiently close to be packaged within the same phage particle. The key to our ability to demonstrate transduction by these phages was the establishment of conditions expected to severely reduce superinfection killing during the selection of transductants. The host range of these phages, as measured by the ability to form plaques, extends to species as distantly related as Streptomyces avermitilis and Streptomyces verticillus, which are among the most commercially important species of this genus. Transduction of plasmid DNA between S. coelicolor and S. verticillus was observed at frequencies of approximately 10(-4) transductants per colony-forming unit.

Bacteriophages↗
PubMed2001

Observation of high-energy neutrinos using Cerenkov detectors embedded deep in Antarctic ice.

Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations.

Journal Article↗
PubMed2001

A regulatory role of the PetM subunit in a cyanobacterial cytochrome b6f complex.

To investigate the function of the PetM subunit of the cytochrome b6f complex, the petM gene encoding this subunit was inactivated by insertional mutagenesis in the cyanobacterium Synechocystis PCC 6803. Complete segregation of the mutant reveals a nonessential function of PetM for the structure and function of the cytochrome b6f complex in this organism. Photosystem I, photosystem II, and the cytochrome b6f complex still function normally in the petM- mutant as judged by cytochrome f re-reduction and oxygen evolution rates. In contrast to the wild type, however, the content of phycobilisomes and photosystem I as determined from 77 K fluorescence spectra is reduced in the petM- strain. Furthermore, whereas under anaerobic conditions the kinetics of cytochrome f re-reduction are identical, under aerobic conditions these kinetics are slower in the petM- strain. Fluorescence induction measurements indicate that this is due to an increased plastoquinol oxidase activity in the mutant, causing the plastoquinone pool to be in a more oxidized state under aerobic dark conditions. The finding that the activity of the cytochrome b6f complex itself is unchanged, whereas the stoichiometry of other protein complexes has altered, suggests an involvement of the PetM subunit in regulatory processes mediated by the cytochrome b6f complex.

Cloning, Molecular↗
PubMed2001

Evidence for highly charged ion Coulomb crystallization in multicomponent strongly coupled plasmas.

Multicomponent non-neutral ion plasmas in a Penning trap consisting of Be(+) and highly charged Xe ions, having different mass-to-charge ratios than Be(+), are cooled to form strongly coupled plasmas by applying a laser-based collisional cooling scheme. The temperature of the plasma was determined from a Doppler broadened transition in Be(+). For the Xe ions, which are centrifugally separated from the Be, the Coulomb coupling parameter was estimated to be approximately 1000. Molecular dynamics simulations of the ion mixture show ordered structures, indicating crystallization of the Xe.

Journal Article↗
PubMed2001

Antenatal sonographic findings of right pulmonary agenesis with ipsilateral microtia: a possible new laterality association.

Right pulmonary agenesis is a rare congenital malformation which results in secondary dextrocardia in situs solitus. Ipsilateral microtia in this context composes a laterality syndrome. The prenatal sonographic findings of this abnormality have not been previously reported. We describe the association of dextrocardia in situs solitus, intact diaphragm and right microtia. This was sonographically diagnosed at mid-gestation in an euploid fetus. Surgical evacuation of the pregnancy confirmed the external malformation. Laterality association should be assessed in a fetus with sonographic findings of pulmonary agenesis. The differential diagnosis and updated literature review is presented.

Adult↗
PubMed2001

The effect of leptin treatment on the development of obesity in overfed suckling Wistar rats.

OBJECTIVE: To identify the role of hyperleptinaemia in mediating the effects of early postnatal overfeeding in a rat strain known to be prone to manipulations of the early environment which result in predispositions for obesity and associated metabolic and cardiovascular disturbance in later life. DESIGN: Wistar rats were reared in normal litters (NL, 10--12 pups) or small litters (SL, four pups) from postnatal day 3 and killed for determination of body composition and plasma leptin and insulin concentrations on day 7 or day 21 after having been treated with recombinant leptin (2 x 50 (pmol/g)/day) or saline from day 1. RESULTS: Rearing in SL doubled the body fat content and plasma leptin levels in comparison to NL pups by 21 days of age. Under leptin-treatment throughout suckling age, NL pups remained leptin responsive, ie the difference in body fat content was progressively reduced relative to the controls. Until 7 days of age, despite the body fat content of untreated SL pups being 2-fold higher and their plasma leptin level 7-fold higher than that of NL pups, leptin treatment caused the same percentage decreases in body fat in SL than in NL pups. But in contrast to NL pups, the SL pups became leptin resistant thereafter. Plasma insulin levels in 7-day-old leptin-treated SL pups were 3-fold higher than in untreated littermates and 5-fold higher than in the NL groups. CONCLUSION: Prophylactic leptin treatment does not prevent hyperinsulinaemia and excessive fat deposition in SL pups. On the other hand, selective hyperleptinaemia during suckling age does not trigger leptin resistance and obesity in NL pups. Rather than hyperleptinaemia per se, other factors associated with early postnatal overnutrition, for example, the concurrent hyperinsulinaemia, seem to play a pivotal role for the development of leptin-resistance and life-long obesity risk in SL rats.

Animals↗
PubMed2001

Antioxidative effects of lemon oil and its components on copper induced oxidation of low density lipoprotein.

Oxidation of low density lipoprotein (LDL) has been implicated in atherogenesis since several years. Therefore many researchers are looking for potent antioxidants which are able to inhibit LDL-oxidation and thus lower the risk for atherosclerosis. In particular several flavonoids have been investigated for their antioxidant capacity and it was shown that many factors influence the ability of flavonoids to retard LDL-oxidation, among others their lipophilic character. Since essential oils and some of their components which are highly lipophilic, have been shown to possess antioxidant properties, their effects on copper-induced LDL-oxidation were analysed. Plasma was incubated with different terpenoid substances and subsequently the LDL was isolated. It could be demonstrated that the terpenoids were enriched in LDL after incubation with plasma. To follow the kinetics of copper induced LDL-oxidation formation of conjugated dienes as well as loss of tryptophan fluorescence were measured. Furthermore the antioxidants alpha-tocopherol, beta-carotene and lycopene were quantified in LDL. It could be shown that particularly lemon oil and one of its components, gamma-terpinene, are efficiently slowing down the oxidation of LDL. This effect is independent of alpha-tocopherol stability in LDL, whereas the loss of carotenoids during oxidation is strongly retarded.

Antioxidants↗
PubMed2001

[Vestibular toxicity of gentamycin in newborn infants].

BACKGROUND: Gentamicin known as ototoxic drug is routinely used for treatment of vital infections in neonatologic departments. The aim of the present study is to clarify whether gentamicin has a vestibulotoxic effect when used in therapeutic levels in the newborn phase. METHOD: Children were taken on the knees of the mother or relative sitting on an electronically driven rotating chair. The rotatory stimulation consisted of an undamped sinusoidal stimulus pattern which was performed in total darkness. Horizontal and vertical eye movements were recorded electronystagmographically. PATIENTS: The patient group consisted of 30 children aged between 3.1 and 32.9 months. These children had been treated with gentamicin during the newborn period. A group of 30 healthy children of similar age without gentamicin treatment was the control group. RESULTS: The statistical means of the nystagmus reactions during sinusoidal rotation were similar in both groups. No increase of spontaneous eye movements was seen in the patients or in the control group. CONCLUSIONS: Gentamicin is an important antibiotic for treatment of life-threatening infectious diseases, which acts less ototoxically in controlled therapeutic doses in newborns than in later childhood or in adults.

Bacterial Infections↗
PubMed2001

[Influence of an internal nasal dilator (Nasanita) on nasal flow in healthy adults].

Influence of an Internal Nasal Dilator (Nasanita) on Nasal Flow in Healthy Adults. In a prospective, randomized study the influence of dilatation of the vestibulum nasi by an internal dilatator type Nasanita on the nasal flow of healthy adult persons was tested. Primary target was the inspiratory nasal flow as measured by rhinomanometry. Secondary targets were subjective evaluation of the nasal breathing and the judgement of the subjects on the comfort of carrying the stent. The insertion of the stent type Nasanita increased the nasal flow from 614 +/- 151 ccm/sec about 54 % to 920 +/- 198 ccm/sec (p = 0,00000016). The expiratory nasal flow increased from 622 +/- 169 ccm/sec about 55 % 928 +/- 230 ccm/sec (p = 0,0000008). Subjectively the insertion of the stent improved the nasal breathing slightly to significantly. The comfort of wearing was classified mostly indifferent to slightly unpleasantly. The internal nasal stent Nasanita has proven to be an agent to increase nasal flow significantly.

Adult↗
PubMed2001

Attributes and practices of oral and maxillofacial radiology departments in US and Canadian dental schools.

OBJECTIVE: To assess the actual state of oral and maxillofacial radiology departments in US and Canadian dental schools against the ideal characteristics defined by the American Academy of Oral and Maxillofacial Radiology (AAOMR) 1997 position paper. STUDY DESIGN: Cross-sectional survey of all 65 US and Canadian dental schools. RESULTS: Sixty-four surveys were returned (98%). At most schools, oral and maxillofacial radiology (OMR) was an identifiable division of a department, established policies, and had operational authority for radiographic practices in the primary radiology clinic. The majority of full-time faculty (72%) had formal training in OMR; the majority of part-time faculty (86%) did not. Full-time faculty spent approximately 60% of their time teaching, with the remainder of their time divided among research and scholarship, faculty practice, and service. Routine x-ray equipment was universally available; advanced imaging technologies were not. OMR faculty involvement in the interpretation of radiographs varied across diseases and conditions. Most published scholarship (85%+) was produced by full-time faculty. Average output was 1 paper per person per year, but a relatively small cadre of OMR faculty generated most papers. CONCLUSIONS: In some attributes, the status of OMR closely approximated the ideal characteristics established in the AAOMR report. Among the remaining attributes, bridging the difference between the actual and the ideal will be the challenge for the next 5 years.

Canada↗
PubMed2001

Accuracy of cancer-risk assessment in primary care practice.

BACKGROUND: Primary care physicians (PCPs) are expected to play a central role in assessing cancer risk. This study was designed to evaluate how accurately PCPs would triage individuals at increased risk for cancer when presented with clinical vignettes. METHODS: Surveys evaluated practice demographics, attitudes, and responses to clinical scenarios. Answers were compared with guidelines and graded for consistency with the risk assessment. RESULTS: PCPs were inaccurate in assessing risk (p < 0.0001) and inconsistent in recommending screening (p < 0.001). Older physicians were more consistent (p < 0.02). No attitudinal bias was identified. CONCLUSION: Continuing education of PCPs is important for cancer-risk assessment and management.

Education, Medical, Continuing↗
PubMed2001

Immunohistochemical comparison of primary peritoneal and primary ovarian serous papillary carcinoma.

Twenty-six patients, meeting strict criteria for primary peritoneal serous papillary carcinoma (PPSPC), were matched to 22 patients with ovarian serous papillary cancer (OSPC) for age and stage. Immunohistochemistry was used to determine the status of estrogen receptors (ER), progesterone receptors (PR), the expression of cell proliferation marker Ki-67, and the overexpression of HER-2/neu and p53 protein. Of the PPSPCs, 53.8% were poorly differentiated, as were 18.2% of the OSPCs (p = 0.012). Positive immunostaining for ER and PR was less in PPSPCs (30.8% and 46.2%, respectively) than OSPCs (72.7% and 90.9%; p = 0.003 and p = 0.001, respectively). Conversely, a significant increase in the expression of Ki-67 was found in PPSPCs (37.7%) versus OSPCs (26.8%) (p = 0.039). The same trend was found for HER-2/neu, being overexpressed in 38.5% of the PPSPC versus 9.1% of the OSPCs (p = 0.019). Overexpression of p53 was found in 30.8% of the PPSPCs and 45.4% of the OSPCs (not significant). There was a significantly worse survival rate for PPSPCs than for OSPCs (p = 0.017), yet none of the studied parameters were significantly correlated with survival within the PPSPC and OSPC groups. The significantly different immunohistochemical expression of ER, PR, Ki-67, and HER-2 in PPSPCs compared with OSPCs suggests that different molecular events may lead to tumorigenesis in these two cancers.

Cell Division↗
PubMed2001

Development of a nondestructive compliance test for resilient denture liners.

PURPOSE: Resilient denture liners are prescribed for patients who cannot adjust to hard-based dentures because of a thin mucosa or severe alveolar ridge resorption. A nondestructive test to evaluate compliance of new soft liner materials will be useful in clinical trials. The purpose of this study was to evaluate a nondestructive compliance testing technique designed to characterize long-term, silicone-based resilient denture liner materials. MATERIALS AND METHODS: Samples of thicknesses of 1.1, 2.2, 3.3, and 4.4 mm of 2 materials (MPDS-SL [Lai Laboratories, Inc, Burnsville, MN] and Molloplast-B [Buffalo Dental, New York, NY]) were assessed for compliance using a closed-loop servohydraulic testing system, applying a 3 lb force following a squarewave pattern; force and position values were recorded using a storage oscilloscope. The oscilloscope values were analyzed using computer software to determine compliance values. The effect of material thickness was examined by testing wedges of the 2 materials. RESULTS: The testing technique used showed that differing thicknesses had significantly different compliance values (p <.0001). In the materials used to evaluate the technique, MPDS-SL behaved more elastically than did Molloplast-B (p <.0001). Material thicknesses beyond 2.2 mm did not increase compliance, although MPDS-SL had a steeper thickness-compliance curve than Molloplast-B. CONCLUSIONS: The method used to test compliance proved to be sufficiently sensitive to distinguish between 2 materials and between varying thicknesses. The sensitivity and nondestructive nature of this test show its suitability for clinical evaluation of resilient denture liners.

Analysis of Variance↗
PubMed2001

Mechanisms causing rapid and parallel losses of ribose catabolism in evolving populations of Escherichia coli B.

Twelve populations of Escherichia coli B all lost D-ribose catabolic function during 2,000 generations of evolution in glucose minimal medium. We sought to identify the population genetic processes and molecular genetic events that caused these rapid and parallel losses. Seven independent Rbs(-) mutants were isolated, and their competitive fitnesses were measured relative to that of their Rbs(+) progenitor. These Rbs(-) mutants were all about 1 to 2% more fit than the progenitor. A fluctuation test revealed an unusually high rate, about 5 x 10(-5) per cell generation, of mutation from Rbs(+) to Rbs(-), which contributed to rapid fixation. At the molecular level, the loss of ribose catabolic function involved the deletion of part or all of the ribose operon (rbs genes). The physical extent of the deletion varied between mutants, but each deletion was associated with an IS150 element located immediately upstream of the rbs operon. The deletions apparently involved transposition into various locations within the rbs operon; recombination between the new IS150 copy and the one upstream of the rbs operon then led to the deletion of the intervening sequence. To confirm that the beneficial fitness effect was caused by deletion of the rbs operon (and not some undetected mutation elsewhere), we used P1 transduction to restore the functional rbs operon to two Rbs(-) mutants, and we constructed another Rbs(-) strain by gene replacement with a deletion not involving IS150. All three of these new constructs confirmed that Rbs(-) mutants have a competitive advantage relative to their Rbs(+) counterparts in glucose minimal medium. The rapid and parallel evolutionary losses of ribose catabolic function thus involved both (i) an unusually high mutation rate, such that Rbs(-) mutants appeared repeatedly in all populations, and (ii) a selective advantage in glucose minimal medium that drove these mutants to fixation.

Adaptation, Physiological↗
PubMed2001

Prospective value of perfusion and X-ray attenuation imaging with single-photon emission and transmission computed tomography in acute cerebral ischemia.

BACKGROUND AND PURPOSE: The aim of the present study was to test the hypothesis that perfusion single-photon emission computed tomography (SPECT), carried out in addition to transmission computed tomography (TCT), improves the predictive value of brain imaging within the therapeutically relevant time window after acute cerebral ischemia. METHODS: Using TCT and [(99m)Tc]ethyl cysteinate dimer (ECD)-SPECT within 6 hours after symptom onset, we examined 108 patients (44 women, 64 men; mean age 65+/-13 years) with acute ischemic stroke attributed to the territory of the middle cerebral artery (MCA). In each case, 3 experts prospectively evaluated the early SPECT and TCT images. We correlated these ratings with follow-up TCT findings for the final infarction as well as with clinical outcome (Scandinavian Stroke Scale, Barthel Index, Modified Rankin Scale) after 30 and 90 days. RESULTS: Severe activity deficits on SPECT, not caused by local atrophy on TCT, were the best predictors (positive predictive value [PPV ]94%, 95% CI 89% to 99%; negative predictive value [NPV] 90%, 95% CI 78% to 100%; P<0.001) for evolving cerebral infarction. Complete MCA infarctions were predicted with significantly higher accuracy with early SPECT (area under receiver operating characteristic curve [AUC] index 0.91) compared with early TCT (AUC index 0.77) and clinical parameters (AUC index 0.73, P<0.05). Logistic regression analysis revealed 1 independent predictor for completed MCA territory infarction: SPECT activity deficits in the corresponding areas (PPV 88%, 95% CI 65% to 100%; NPV 96%, 95% CI 92% to 100%; P<0.001). Furthermore, death after stroke was optimally predicted by [(99m)Tc]ECD-SPECT. Clinical outcome up to 90 days after the stroke event best correlated with the degree of activity deficits in early SPECT (r=0.53, P<0.001). CONCLUSIONS: [(99m)Tc]ECD brain perfusion SPECT that completes TCT definitely improves the predictive value of brain imaging after acute cerebral ischemia. Thus, the combined imaging of brain edema and of cerebral perfusion early after stroke is recommended for clinical use.

Acute Disease↗
PubMed2001

Field conditions for agricultural workers in the El Paso, Texas region.

Agricultural workers labor long hours under difficult conditions in many of the nations fields and orchards. Agricultural workers are primarily minority populations, the most dominant group being Hispanic/Latino. The Rural Coalition and the Environmental and Occupational Health Sciences Institute were funded under the National Institute of Environmental Health Sciences (NIEHS) Environmental Justice Program, to investigate health and environmental issues that impact agricultural workers along the Texas-Mexican border area. A Spanish-language field conditions survey was developed and distributed to the workers entering the Sin Fronteras Organizing Project in El Paso, Texas. There were 841 valid surveys collected and analyzed for the calendar year 1998. Workers age mean was 51, with 18.6 years of work experience in agriculture. In the time period surveyed, workers labored for 7.2 hours per day. The primary crop in which they worked were chilies. Of particular concern were issues concerning food, water, and hygiene. Almost all workers stated they had access to fresh drinking water (97 percent), 20 percent did not have access to food, and 30 percent were offered alcohol for purchase. Almost one-third of the workers did not have water available for hand washing in the field. Only 8 percent of the workers reported pesticides used in the fields in which they were working; this number is lower and may be a reflection of the improved training and caution taken by the workers. Clearly additional research in the area of field conditions and the impact and enforcement of state and federal regulation needs to be carried out.

Journal Article↗
PubMed2001

Outcome of surgical treatment for superficial dyspareunia from vulvar vestibulitis.

OBJECTIVE: To evaluate the results of surgical treatment for superficial dyspareunia, as manifested by patient satisfaction, as well as epidemiologic characteristics of women with this medical problem. STUDY DESIGN: A questionnaire was sent to 69 women six months after the operation. It included questions about treatment before surgery and the impact of pain on the sexual relationship before and after the operation. Demographic, social and general health data were recorded before the operation. All patients returning the questionnaire were examined. RESULTS: Fifty-four (78%) patients replied. Half of those abstained from sexual relations before surgical treatment. Sixty-seven percent of patients required more than six visits to various physicians, before vestibulitis was diagnosed. Prior to surgery, 80% of patients received conservative treatment, whereas after surgery only 34% required it. A moderate to excellent improvement was reported after surgery by 45 (83%) patients. Repeat surgery (n = 7) resulted in further improvement in four patients. There were no major operative complications. Forty-five patients (83%) were satisfied with the results and would recommend the surgery to other women with this clinical problem. CONCLUSION: Surgical treatment for superficial dyspareunia from vestibulitis is quite safe and results in a high rate of patient satisfaction.

Adult↗