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Biomedical subjects

T L Johnson

Publications and source records attributed to T L Johnson.

At least 19 recordsLinked to original sources
PubMed2006

Fixed film phosphorus removal--flexible enough?

While biological phosphorus removal (BPR) has been practised for 30 years, up to recently it has been restricted mainly to activated sludge processes, with the corresponding need for large basin volumes. Yet, research with biofilm reactors showed that the principle of alternate anaerobic and aerated conditions was applicable to fixed bacteria by changing the conditions in time rather than in space. Attached growth enhanced biological phosphorus removal (EBPR) systems are attractive because of their compactness and capability to retain high biomass levels. However, the phosphorus extraction depends on backwashes to enhance the phosphorus-rich attached biomass, and correct control of unsteady effluent quality created by frequently modified process conditions. Accordingly, EBPR remains a challenging task in terms of combining nitrogen and phosphorus removal using attached growth systems. Nevertheless, a combination of activated sludge and biofilm carriers, in the integrated fixed-film activated sludge system, provides treatment opportunities not readily available using suspended growth systems. Current practice is only at the beginning of exploiting the full potential of this combination, but the first full-scale results show that compact tankage and low nutrient results based on biological principles are possible.

Aerobiosis↗
PubMed2001

Characterization of U4 and U6 interactions with the 5' splice site using a S. cerevisiae in vitro trans-splicing system.

Spliceosome assembly has been characterized as the ordered association of the snRNP particles U1, U2, and U4/U6.U5 onto pre-mRNA. We have used an in vitro trans-splicing/cross-linking system in Saccharomyces cerevisiae nuclear extracts to examine the first step of this process, 5' splice site recognition. This trans-splicing reaction has ATP, Mg(2+), and splice-site sequence requirements similar to those of cis-splicing reactions. Using this system, we identified and characterized a novel U4-5' splice site interaction that is ATP-dependent, but does not require the branch point, the 3' splice site, or the 5' end of the U1 snRNA. Additionally, we identified several ATP-dependent U6 cross-links at the 5' splice site, indicating that different regions of U6 sample it before a U6-5' splice site interaction is stabilized that persists through the first step of splicing. This work provides evidence for ATP-dependent U4/U6 association with the 5' splice site independent of ATP-mediated U2 association with the branch point. Furthermore, it defines specific nucleotides in U4 and U6 that interact with the 5' splice site at this early stage, even in the absence of base-pairing with the U1 snRNA.

5' Untranslated Regions↗
PubMed2001

Quinazolines as cyclin dependent kinase inhibitors.

Quinazolines have been identified as inhibitors of CDK4/D1 and CDK2/E. Aspects of the SAR were investigated using solution-phase, parallel synthesis. An X-ray crystal structure was obtained of quinazoline 51 bound in CDK2 and key interactions within the ATP binding pocket are defined.

Binding, Competitive↗
PubMed2001

Electricity from fossil fuels without CO2 emissions: assessing the costs of carbon dioxide capture and sequestration in U.S. electricity markets.

The decoupling of fossil-fueled electricity production from atmospheric CO2 emissions via CO2 capture and sequestration (CCS) is increasingly regarded as an important means of mitigating climate change at a reasonable cost. Engineering analyses of CO2 mitigation typically compare the cost of electricity for a base generation technology to that for a similar plant with CO2 capture and then compute the carbon emissions mitigated per unit of cost. It can be hard to interpret mitigation cost estimates from this plant-level approach when a consistent base technology cannot be identified. In addition, neither engineering analyses nor general equilibrium models can capture the economics of plant dispatch. A realistic assessment of the costs of carbon sequestration as an emissions abatement strategy in the electric sector therefore requires a systems-level analysis. We discuss various frameworks for computing mitigation costs and introduce a simplified model of electric sector planning. Results from a "bottom-up" engineering-economic analysis for a representative U.S. North American Electric Reliability Council (NERC) region illustrate how the penetration of CCS technologies and the dispatch of generating units vary with the price of carbon emissions and thereby determine the relationship between mitigation cost and emissions reduction.

Air Pollution↗
PubMed2001

GDF-5 deficiency in mice leads to disruption of tail tendon form and function.

Although the biological factors which regulate tendon homeostasis are poorly understood, recent evidence suggests that Growth and Differentiation Factor-5 (GDF-5) may play a role in this important process. The purpose of this study was to investigate the effect of GDF-5 deficiency on mouse tail tendon using the brachypodism mouse model. We hypothesized that GDF-5 deficient tail tendon would exhibit altered composition, ultrastructure, and biomechanical behavior when compared to heterozygous control littermates. Mutant tail tendons did not display any compositional differences in sulfated glycosaminoglycans (GAG/DNA), collagen (hydroxyproline/DNA), or levels of fibromodulin, decorin, or lumican. However, GDF-5 deficiency did result in a 17% increase in the proportion of medium diameter (100-225 nm) collagen fibrils in tail tendon (at the expense of larger fibrils) when compared to controls (p < 0.05). Also, mutants exhibited a trend toward an increase in irregularly-shaped polymorphic fibrils (33% more, p > 0.05). While GDF-5 deficient tendon fascicles did not demonstrate any significant differences in quasistatic biomechanical properties, mutant fascicles relaxed 11% more slowly than control tendons during time-dependent stress-relaxation tests (p < 0.05). We hypothesize that this subtle alteration in time-dependent mechanical behavior is most-likely due to the increased prevalence of irregularly shaped type I collagen fibrils in the mutant tail tendons. These findings provide additional evidence to support the conclusion that GDF-5 may play a role in tendon homeostasis in mice.

Animals↗
PubMed2001

Tapeworm identification in the fat sand rat (Psammomys obesus obesus).

The identification of a tapeworm (Rodentolepis nana, formerly named Hymenolepis nana) infection in a research breeding colony of sand rats (Psammomys obesus obesus) was complicated because of the unexpected long length (< 150 mm) of the worms. Other morphologic features that were consistent with this identification included the number (24), size (16 mm), and shape of the hooks on the rostellum. No evidence of intermediate hosts was found in the colony. Previous surveys of natural populations of sand rats had not identified this tapeworm. However, a detailed search of the literature revealed that variation in the size of R. nana had been reported, thus supporting the final identification of the tapeworm. R. nana is important and interesting because of its zoonotic potential and because it is the only tapeworm that is able to infect its definitive host without use of an intermediate host. This report is presented to help clarify the ambiguity found in the laboratory animal literature about the differences in the size of R. nana among rodent species used in research.

Animals↗
PubMed2000

Continuing participation supports ultrasound screening for ovarian cancer.

The effect of ovarian cancer screening on survival is enabled by women who continue to actively participate in screening. In this report, factors that affect participation are examined. Participants included 13,963 Kentucky women who received 56,392 screens accounting for a 46,113 screening year experience. Background, health history and reasons for participating in transvaginal sonographic screening were collected via a self-reported questionnaire. Screening participants were characterized as > 50 years old, mostly married, well educated, medically insured, health conscious women, living in the vicinity of the screening centre or 51-150 miles away. Approximately 70% of the participants can be considered active in the study based upon a screening visit during the 1997-1998 2-year period. The probabilities of a return screen at 1, 2, 5 and 7.5 years were 77.8%, 72.0%, 58.7% and 50.6%, respectively. A total of 96% of return visits occurred within 2 years, with 33.7% having intervals of < 1 year. Perceived family history was not observed to affect continuation. However, abnormal findings were associated with a shortened participation. These high levels of continuation in ultrasound screening indicate that women take this disease seriously and demonstrate that this disease is of consequence to them.

Adult↗
PubMed2000

G8363A mutation in the mitochondrial DNA transfer ribonucleic acidLys gene: another cause of Leigh syndrome.

We identified a G-->A transition at nt-8363 in the mitochondrial DNA transfer ribonucleic acidLys gene in blood and muscle from a 13-month-old girl who had clinical and neuroradiologic evidence of Leigh syndrome and died at age 27 months. The mutation was less abundant in the same tissues from the patient's mother, who developed myoclonus epilepsy with ragged red fibers (MERRF) in her late 20s. In both mother and daughter, muscle histochemistry showed ragged red and cytochrome c oxidase-negative fibers and biochemical analysis showed partial defects of multiple respiratory-chain enzymes. A maternal half-sister of the proband had died at 2.5 years of age from neuropathologically proven Leigh syndrome. The G8363A mutation, which previously had been associated with cardiomyopathy and hearing loss, MERRF, and multiple lipomas, also should be included in the differential diagnosis of maternally inherited Leigh syndrome.

Adult↗
PubMed2000

Pilot study of dental hygienists' comfort and confidence levels and care planning for patients with disabilities.

A questionnaire assessing comfort levels and behaviors of dental hygienists concerning treatment of patients with special needs or disabilities was mailed to a random sample of 175 practicing dental hygienists in Idaho. All respondents had seen patients with disabilities, although 53 percent had never completed a formal course or received training directed specifically toward this population. Survey respondents were moderately to always comfortable treating special needs and disabled patients. Use of a wheelchair was the only disability in which clinicians were significantly more comfortable with treatment following completion of a course or receipt of training. Severity of a patient's disability and limited time were considered moderate to very high barriers to the provision of dental hygiene care. Recommended treatment planning techniques are being used to a limited extent, and respondents were slightly to moderately confident using alternative communication and treatment techniques. The findings suggest that although education or training was not strongly associated with comfort and confidence levels of these dental hygienists, they were interested in opportunities for further training in caring for patients with special needs.

Attitude of Health Personnel↗
PubMed1999

A skin blister method to study epidermal nerves in peripheral nerve disease.

Skin is a reservoir of sensory and autonomic nerve fibers that are potential indicators of peripheral nerve disease. Biopsies of skin have shown that sensory nerves in the most superficial layer of skin, the epidermal nerve fibers (ENFs), are reduced in patients with polyneuropathy. This report describes a minimally invasive skin blister method to isolate, image, and obtain quantitative analysis of ENFs. Blisters are made by applying a suction capsule to skin. The epidermal roof of the blister is excised, immunostained, whole mounted, and analyzed for ENF number and distribution. A reduction in number and abnormal distribution of ENFs are early indicators of peripheral nerve disease. Illustrations of skin blister and skin biopsy specimens from patients with different types of peripheral nerve disorders are included. These patients were chosen because their findings demonstrate the complementary information obtained by the blister and biopsy methods and the potential of the blister procedure to evaluate single nerve lesions and polyneuropathy and to follow the progress of ENF degeneration and regeneration.

Adult↗
PubMed1999

Partial tracheal obstruction due to chondromas in ball pythons (Python regius).

Over a 9-mo period, three adult ball pythons (Python regius) (one male, two females) were evaluated for severe dyspnea. Partial obstructions of the tracheal lumen were identified radiographically and/or visualized with a 3.0-mm rigid laparoscope inserted into the tracheal lumen in all three snakes. Administration of systemic antibiotics and nebulization resulted in partial improvement of the dyspnea. In two snakes, the tracheal lesions were removed with a rigid laparoscope and a flexible biopsy instrument inserted into the tracheal lumen. The other snake died and was necropsied. Histologically, the lesions from two snakes were determined to be benign chondromas. The chondromas were composed of a variably disorganized chondroid matrix populated by quiescent, normal-appearing chondrocytes within lacunae, although the chondrocytes were increased in density compared with normal hyaline cartilage and contained rare mitotic figures. The tracheal masses in one snake grew by expansion, not invasion, and were focally continuous with a mineralized cartilage tracheal ring, suggesting a benign nature. This is the second report of tracheal chondroma in ball pythons. Tracheal chondromas are exceedingly rare in humans and domesticated animals, suggesting a possible predisposition of ball pythons for this neoplasm.

Animals↗
PubMed1998

Health care needs of medically underserved women of color: The role of the Bureau of Primary Health Care.

The Bureau of Primary Health Care (BPHC) was developed to increase access to comprehensive primary and preventive health care and to improve the health status of medically underserved populations. Approximately 43 million Americans fall into this category, and the majority are poor, female, young, and uninsured. Under the Public Health Services Act, BPHC does not provide direct services, but rather assist local communities in identifying populations at risk of poor health outcomes and helps these communities through various programs. One of the newest initiatives of BPHC is the Office of Minority and Women's Health, developed with a mission to help reduce the disparities in the health status of women of racial and ethnic minority populations. This article outlines these disparities and discusses proposals for reducing them.

Ethnicity↗
PubMed1997

Physician gender and women's preventive services.

OBJECTIVE: To determine whether the gender of women's regular physicians, controlling for physician specialty, is associated with women's receiving key preventive services within recommended intervals. DESIGN: Cross-sectional, nationally representative women's health telephone survey conducted by Louis Harris and Associates in February and March 1993 for The Commonwealth Fund. PARTICIPANTS: A total of 2,525 women in the continental United States, > or = 18 years old, including oversamples of African-American and Hispanic women. MAIN OUTCOME MEASURES: Receipt of each of five preventive services (blood pressure reading, Pap smear, cholesterol test, clinical breast examination, and mammogram) within specific periods. RESULTS: Physician gender makes a significant difference for two specialty areas and for three preventive services. Patients of women family or general practitioners are more likely than the patients of men to have received a Pap smear or a blood cholesterol test within the last 3 years, and the patients of women internists are more likely to have received a Pap test. Physician gender is associated with a higher likelihood of mammography, but this finding was limited to patients ages 40-49 of women family or general practitioners. Physician gender does not affect receipt of blood pressure screening or breast examination. CONCLUSIONS: Analyses reveal limited evidence that physician gender affects women's receipt of preventive services. Physician specialty appears to be a more powerful predictor of preventive services received. The limited evidence for a physician gender effect, however, is relevant for those women who rely on a family or general practitioner or an internist for regular care.

Adolescent↗
PubMed1996

Structure-activity relationships of the antimalarial agent artemisinin. 5. Analogs of 10-deoxoartemisinin substituted at C-3 and C-9.

Novel 3- and 9-substituted analogs (4-19) of 10-deoxoartemisinin, 3, were prepared from the corresponding known lactones by one-pot reduction with sodium borohydride and boron trifluoride etherate. Reproducibility problems associated with this heterogeneous reaction were encountered on small reaction scales, and thus alternative methodology was sought for this reduction. Conversion of the lactones to tetrahydropyrans via the corresponding intermediate lactols was made more reproducible using a two-step sequence involving low-temperature reduction with diisobutylaluminum hydride followed by deoxygenation with boron trifluoride etherate in the presence of triethylsilane. In this manner, 10-deoxoartemisinin (3) could be obtained from artemisinin (1) in greater than 95% overall yield. All analogs were tested in vitro against W-2 and D-6 strains of Plasmodium falciparum. Several of the analogs were much more active than the natural product (+)-artemisinin (1) or 10-deoxoartemisinin (3). Conventional structure-activity relationships are discussed in relation to the bioassay data.

Animals↗
PubMed1996

Endometrial metaplasia as a source of atypical glandular cells in cervicovaginal smears.

Cytohistological correlation of abnormal cervicovaginal smears indicates that endometrial metaplasia may be associated with the presence of atypical glandular cells. Seven patients with histologically confirmed endometrial metaplasia had atypical glandular cells in cervicovaginal smears; five smears were interpreted as being suspicious for endometrial adenocarcinoma. Most of the patients (5/7) were postmenopausal (mean age = 61.3 years), and three of seven patients had abnormal vaginal bleeding. The corresponding endometrial tissue specimens demonstrated various combinations of eosinophilic, papillary, squamous, and tubal metaplasia; in one case tubal metaplasia occurred in association with an endometrial polyp. Cytologic features noted in the cervicovaginal smears from all seven patients were similar and included small clusters of atypical glandular cells in an inflammatory background. Intracytoplasmic vacuoles were often present, and a moderate degree of aniosonucleosis was noted. Enlarged glandular nuclei contained finely granular chromatin and distinct nucleoli. The differential diagnosis of atypical glandular cells includes endometrial hyperplasia and well-differentiated endometrial adenocarcinoma. The atypical cells associated with endometrial metaplasia were characterized by a relatively low N:C ratio and evenly distributed chromatin. In contrast, the cells of endometrial carcinoma typically demonstrate increased N:C ratios and irregularly distributed chromatin.

Adenocarcinoma↗
PubMed1996

Metaplastic breast carcinoma: a cytohistologic and clinical study of 10 cases.

Metaplastic breast carcinomas (MBC) account for < 5% of breast malignancies and have an uncertain prognostic significance. The tumors tend to grow rapidly, and most are negative for hormone receptors. Adenosquamous carcinomas and various types of carcinosarcomas may be classified as MBC. We evaluated the cytologic, histologic, and clinical parameters of 10 MBC to determine important diagnostic features of these tumors. A cytologic diagnosis of MBC, based on the identification of two distinct malignant components, was made preoperatively in five of 10 (50%) cases, and retrospectively in two additional cases; two specimens were inadequately cellular. Poorly-differentiated adenocarcinoma was the most frequently encountered component of MBC. It is recommended that malignant breast aspirates be carefully scrutinized for multiple neoplastic components. Our series of MBC differs from previous reports in that two cases presented as inflammatory breast cancer, one case was pregnancy-associated, and there was a higher incidence of estrogen and progesterone receptor positivity. No cancer-related deaths occurred during a mean follow-up period of over 6 yr.

Adult↗
PubMed1995

Squamous cell carcinoma of the cervix metastatic to an ovarian Brenner tumor.

Metastatic tumors account for approximately 10 to 15% of surgically excised ovarian malignancies (Semin Diagn Pathol 8:250-276, 1991). Although the majority of tumors arise within the female genital tract, cervical cancer is a rare source of metastasis to the ovary. Cervical carcinomas with ovarian involvement are usually advanced lesions with lymph node involvement (Am J Obstet Gynecol 166:50-53, 1992; Cancer 71:407-418, 1993). We present a case of Stage IIB squamous cell carcinoma of cervix metastatic to an ovarian Brenner tumor. Our purpose in presenting this case is to report useful histologic features in the diagnosis of this rare combination of tumors. We are not aware of any other published reports of this entity.

Brenner Tumor↗