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Biomedical subjects

C Tobias

Publications and source records attributed to C Tobias.

At least 19 recordsLinked to original sources
PubMed2006

Denitrification across landscapes and waterscapes: a synthesis.

Denitrification is a critical process regulating the removal of bioavailable nitrogen (N) from natural and human-altered systems. While it has been extensively studied in terrestrial, freshwater, and marine systems, there has been limited communication among denitrification scientists working in these individual systems. Here, we compare rates of denitrification and controlling factors across a range of ecosystem types. We suggest that terrestrial, freshwater, and marine systems in which denitrification occurs can be organized along a continuum ranging from (1) those in which nitrification and denitrification are tightly coupled in space and time to (2) those in which nitrate production and denitrification are relatively decoupled. In aquatic ecosystems, N inputs influence denitrification rates whereas hydrology and geomorphology influence the proportion of N inputs that are denitrified. Relationships between denitrification and water residence time and N load are remarkably similar across lakes, river reaches, estuaries, and continental shelves. Spatially distributed global models of denitrification suggest that continental shelf sediments account for the largest portion (44%) of total global denitrification, followed by terrestrial soils (22%) and oceanic oxygen minimum zones (OMZs; 14%). Freshwater systems (groundwater, lakes, rivers) account for about 20% and estuaries 1% of total global denitrification. Denitrification of land-based N sources is distributed somewhat differently. Within watersheds, the amount of land-based N denitrified is generally highest in terrestrial soils, with progressively smaller amounts denitrified in groundwater, rivers, lakes and reservoirs, and estuaries. A number of regional exceptions to this general trend of decreasing denitrification in a downstream direction exist, including significant denitrification in continental shelves of N from terrestrial sources. Though terrestrial soils and groundwater are responsible for much denitrification at the watershed scale, per-area denitrification rates in soils and groundwater (kg N x km(-2) x yr(-1)) are, on average, approximately one-tenth the per-area rates of denitrification in lakes, rivers, estuaries, continental shelves, or OMZs. A number of potential approaches to increase denitrification on the landscape, and thus decrease N export to sensitive coastal systems exist. However, these have not generally been widely tested for their effectiveness at scales required to significantly reduce N export at the whole watershed scale.

Agriculture↗
PubMed2004

Medication adherence for HIV positive women caring for children: in their own words.

Few studies have directly focused on adherence to highly active antiretroviral medication (HAART) in HIV positive women caring for children. These women may have unique barriers and facilitators to taking medication, and a deeper understanding of their adherence patterns could enhance intervention strategies. A total of 36 HIV positive women who care for children less than 18 years of age were interviewed regarding their patterns and decision around taking HAART. The study group was comprised of 19 Latinas, 10 Euro-Americans, five African Americans and two Cape Verdeans. The mean length of time the women knew they were HIV positive was 11.15 years. Adherence patterns shifted over the course of the women's HIV history. The participants continually discussed medication adherence within the context of events and relationships that either upset or stabilized their adherence. The following themes emerged: (1) shifting adherence patterns; (2) reasons for adherence; (3) reasons for non-adherence; (4) the relationship between distress level and medication adherence; (5) interpersonal relationship as barrier or facilitator of medication adherence; and (6) children as facilitators in adherence. Providers need to be aware of the shifting nature of adherence and its relationship to psychosocial functioning.

Adult↗
PubMed2002

Transplantation of genetically modified cells contributes to repair and recovery from spinal injury.

The effects of transplantation of fibroblasts genetically modified to produce brain derived neurotrophin factor (Fb/BDNF) on rescue of axotomized neurons, axonal growth and recovery of function was tested in a lateral funiculus lesion model in adult rats. Operated control animals included those in which the lesion was filled with gelfoam implant (Hx) and those in which the cavity was filled with unmodified fibroblasts (Fb). Both Fb/BDNF and Fb transplants survived and filled the lesion site. Unoperated control groups showed a marked retrograde death of Red nucleus neurons contralateral to the lesion; Fb/BDNF recipients showed a significant rescue effect. Anterograde and retrograde labeling studies indicated no regeneration of rubrospinal axons into the lesion/transplant in operated control animals, but regeneration into, around, and through the transplant into the host was seen in the Fb/BDNF recipients. All animals showed deficits on the more challenging behavioral tests but the Fb/BDNF recipients showed fewer deficits, particularly in tests of spontaneous vertical exploration, horizontal rope crossing and a sensory test (patch removal). The improved function on these tests in the Fb/BDNF recipients was abolished by a second lateral funiculus lesion rostral to the transport site. These results indicate that delivery of neurotrophic factors by grafting genetically modified cells can improve repair and function after spinal injury.

Animals↗
PubMed2001

An investigation of why eligible patients do not receive HAART.

Treatment with highly active antiretroviral therapy (HAART) decreases morbidity and mortality for persons with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) and reduces costs of care. Yet many patients for whom HAART is indicated do not receive it. This study investigated the reasons why certain patients of a community health center with HIV/AIDS did not receive HAART between 1997 and 1998. Medical record reviews were performed to determine which patients for whom HAART was indicated (according to United States Public Health Service guidelines) were not prescribed HAART. Chart reviews and patient interviews were conducted to determine why they did not receive HAART. Of the 88 patients eligible for HAART, 60 (69%) had it prescribed in 1997-1998. Of the remaining 28 patients, 3 did not receive HAART because their provider never discussed it with them. For 6 patients (21%), the provider discussed HAART but did not recommend it; 16 patients (57%) declined HAART although their provider recommended it, and 3 (11%) accepted their provider's recommendation but never started HAART. Patients' most common reasons for refusing HAART were not being ready for strict adherence to a complex regimen (7/16) and fear of side effects (6/16). Other reasons included active drug use, religious beliefs, homelessness, confidentiality concerns, depression, and feeling well without HAART. Providers did not recommend HAART because of active drug use (4/6), lack of engagement with care (2/6) as well as homelessness, depression, and the perception that the patient was doing well without HAART. Providers should be trained to offer all patients the opportunity to develop a plan to address barriers to adherence and the support needed to implement it. Resources should also target the treatment of substance abuse and mental illness to improve the usage of HAART.

Anti-HIV Agents↗
PubMed1999

Reliability of the Salford Needs Assessment Schedule for Adolescents.

BACKGROUND: For adolescents, there is no specific needs assessment instrument that assesses significant problems that can benefit from specified interventions. A new instrument (S.NASA) was developed by incorporating and adapting three well established adult needs assessment instruments. The S.NASA covers 21 areas of functioning including social, psychiatric, educational and life skills. METHOD: Client and carer interviews were conducted by different researchers. A week later the interviews were repeated using a crossover design. Significant (cardinal) problems were generated from the clinical interviews using a pre-defined algorithm. Final need status (three categories) was made by clinicians assessing the cardinal problems against defined interventions. The interventions were generated from discussions with clinicians and a survey of appropriate professionals working with adolescents. RESULTS. Pre-piloting led to the final version being administered to 40 adolescents from secure units, forensic psychiatric and adolescent psychiatric services. There were 25 males and 15 females, mean age 15.5 years. Overall there were moderate to good inter-rater and test-retest reliability coefficients, the test-retest reliability coefficients for the total scores on the needs assessment interviews ranged from 0.73 to 0.85. Consensual and face validity was good, the adolescents and staff finding the instrument useful and helpful. CONCLUSIONS: This new needs assessment instrument shows acceptable psychometric properties. It should be of use in research projects assessing the needs and the provision of services for adolescents with complex and chronic problems.

Adolescent↗
PubMed1998

Quality management by state Medicaid agencies converting to managed care: plans and current practice.

CONTEXT: Enrollment in Medicaid managed care plans has increased more than 5-fold in this decade, but how states monitor and encourage quality of care in these programs is not known. OBJECTIVE: To characterize the quality monitoring and assurance activities of state Medicaid agencies for Medicaid beneficiaries enrolled in comprehensive prepaid managed care programs. DESIGN: Structured telephone survey conducted between October 1996 and January 1997. SETTING: State Medicaid agencies. PARTICIPANTS: Representatives from all state Medicaid agencies, including the District of Columbia, with beneficiaries enrolled in comprehensive prepaid managed care plans as of July 1, 1996. MAIN OUTCOME MEASURES: Proportion of states with specific quality monitoring and assurance activities for Medicaid managed care. RESULTS: We surveyed all 34 states enrolling beneficiaries in comprehensive managed care programs. In 1996, all 34 states enrolled the population receiving assistance from the Aid to Families With Dependent Children (AFDC) program, while only 21 (62%) and 15 (44%) enrolled the disabled and elderly populations, respectively. In the period 1995 to 1996, 19 states (63%) collected data on satisfaction with care, and 25 states (83%) collected data on childhood immunizations. No more than half of the states collected data on other selected measures of access and quality, but a substantial number planned to collect such data in 1997. While at most 37% of states were providing comparative data to health plans, up to 80% were planning to provide such information in 1997. Similarly, while at most 10% of states provided beneficiaries with such information, up to 38% planned to do so in 1997. The breadth of contracting requirements designed to assure quality varied substantially across states. CONCLUSIONS: State Medicaid agencies have already begun adapting to their new roles as purchasers of health care. Continued monitoring is essential to ensure that state agencies implement planned programs and that quality of care for Medicaid enrollees is preserved or improved.

Health Care Surveys↗
PubMed1996

The Community Medical Alliance: an integrated system of care in Greater Boston for people with severe disability and AIDS.

The Community Medical Alliance in Boston has adapted principles of prepaid managed care to redesign service delivery for people with severe physical disability and with late-stage AIDS. Experience to date suggests that the flexibility of capitation can be used to substantially shift care from its usual hospital focus to clinicians in home and community settings, especially nurse practitioners, with a high degree of patient satisfaction and without apparent compromise in quality. Instead of limiting access, managed care can use prepayment to support early interventions, coordination, and the development of services specifically designed to meet the needs of the target population.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Triphenyl phosphite-induced neuropathy in the avian forebrain: a silver impregnation study of the visual and auditory systems of the Japanese quail.

Single subcutaneous injections of triphenyl phosphite (TPP) (62.5-500 mg/kg body weight) were made in the Japanese quail (Coturnix coturnix japonica). The extent and density of resultant central nervous system degeneration were mapped by using the Fink-Heimer silver impregnation method to selectively impregnate degenerating axons and terminals. In addition to resulting in degeneration in the medulla and cerebellum, exposure to TPP also resulted in axonal and terminal degeneration in specific midbrain and forebrain nuclei and tracts related to the auditory and visual systems. Auditory system nuclei containing axonal and terminal degeneration included the lateral mesencephalic nucleus, pars dorsalis, the nucleus ovoidalis, and area L of Rose in the caudal neostriatum. Anterograde degeneration was also noted in nuclei and tracts related to the visual tectofugal system-the brachium of the superior colliculus, nucleus rotundus, pretectal nuclei, and the ectostriatum. Additional degeneration was noted in the paleostriatum primitivum, dorso-intermediate posterior thalamic nucleus, lateral spiriform nucleus, and the pedunculopontine tegmental nucleus, all of which are related to visuomotor control. These results indicate that in the Japanese quail, exposure to TPP yields anterograde degeneration in nuclei and tracts involved with the transmission and processing of higher order visuomotor, visual sensory, and auditory sensory information.

Animals↗
PubMed1995

Organophosphorus-induced delayed neurotoxicity: a comparative study of the effects of tri-ortho-tolyl phosphate and triphenyl phosphite on the central nervous system of the Japanese quail.

The neurotoxic effects of single oral doses of tri-ortho-tolyl phosphate (TOTP) (500 mg/kg body weight) or single subcutaneous injections of triphenyl phosphite (TPP) (62.5-500 mg/kg body weight) were investigated in the Japanese quail (Coturnix coturnix japonica). Oral doses of TOTP resulted in no detectable clinical signs while injections of TPP resulted in mild ataxia to severe paralysis depending upon the dosage level. At 24 hr postdosing, whole-brain activity of neuropathy target esterase (NTE) was inhibited by 90% in birds exposed to TOTP and by 11-87% in birds injected with TPP. Oral doses of TOTP resulted in only sparse Fink-Heimer silver-impregnated degeneration in the white matter of the cerebellum with no degeneration noted in any other region of the brain. Injections of TPP resulted in widespread degeneration in large numbers of brainstem nuclei and tracts and in all cerebellar foliae and deep nuclei. These results indicate that the Japanese quail responds differentially to exposure to TOTP and TPP. Oral doses of TOTP do not result in clinical signs or in significant amounts of degeneration in the brain even though NTE activity is inhibited by 90%. In contrast, injections of TPP at higher dosage levels yield severe clinical signs, widespread axonal and terminal degeneration in the CNS, and significant inhibition of NTE activity. This sharp dichotomy in relative sensitivity to TOTP and TPP in the Japanese quail suggests that each compound may have its own unique effect on CNS structure and function. In addition, the relationship between levels of NTE inhibition and the onset of clinical signs or neuropathology remains unclear.

Animals↗
PubMed1990

A comparison of coping strategies used effectively by older Anglo and Mexican-American widows: a longitudinal study.

This longitudinal study of older Anglo and Mexican-American widows provides data on coping strategies and coping effectiveness as measured by perceived physical and psychological health. Previous health levels were the best predictors of later physical and psychological symptoms. Contrary to expectations, both ethnic groups preferred nonconfrontational strategies for widowhood problems, with the Mexican Americans using more confrontational strategies. Ways of coping with problems during the first months of widowhood had significant long-term effects upon the widow's health. The most effective coping methods over the first year involved combinations of independent action and emotional release. Over a longer period, more effective strategies included being able to ignore problems, accept the situation, and release tensions, or to actively seek advice about general problems. Contradictory findings over the two time periods for those Mexican Americans using independent action and emotional release strategies appear to be related to cultural patterns of familial support after a death occurs.

Adaptation, Psychological↗
PubMed1989

Repair and misrepair of heavy-ion-induced chromosomal damage.

The premature chromosome condensation (PCC) technique was used to investigate chromosomal damage, repair, and misrepair in the G phase of a human/hamster hybrid cell line that contains a single human chromosome. Plateau-phase cell cultures were exposed to either x-rays or a 425 MeV/u beam of neon ions near the Bragg peak where the LET is 183 kev/micrometers. An in situ hybridization technique coupled to fluorescent staining of PCC spreads confirmed the linearity of the dose response for initial chromatin breakage in the human chromosome to high doses (1600 cGy x-ray or 1062 cGy Ne). On Giemsa-stained slides, initial chromatin breakage in the total genome and the rejoining kinetics of these breaks were determined. As a measure of chromosomal misrepair, ring PCC aberrations were also scored. Ne ions were about 1.5 x more effective per unit dose compared to x-rays at producing the initially measured chromatin breakage. 90% of the x-ray-induced breaks rejoined in cells incubated at 37 degrees C after exposure. In contrast, only 50% of Ne-ion-induced breaks rejoined. In the irradiated G1 cells, ring PCC aberrations increased with time apparently by first order kinetics after either x-ray or Ne exposures. However, far fewer rings formed in Ne-irradiated cells after a dose giving a comparable initial number of chromatin breaks. Following x-ray exposures, the yield of rings formed after long repair times (6 to 9 hrs) fit a quadratic dose-response curve. These results indicate quantitative and qualitative differences in the chromosomal lesions induced by low- and high-LET radiations.

Animals↗
PubMed1989

Cell-cycle radiation response: role of intracellular factors.

We have been studying variations of radiosensitivity and endogenous cellular factors during the course of progression through the human and hamster cell cycle. After exposure to low-LET radiations, the most radiosensitive cell stages are mitosis and the G1/S interface. The increased activity of a specific antioxidant enzyme such as superoxide dismutase in G1-phase, and the variations of endogenous thiols during cell division are thought to be intracellular factors of importance to the radiation survival response. These factors may contribute to modifying the age-dependent yield of lesions or more likely, to the efficiency of the repair processes. These molecular factors have been implicated in our cellular measurements of the larger values for the radiobiological oxygen effect late in the cycle compared to earlier cell ages. Low-LET radiation also delays progression through S phase which may allow more time for repair and hence contribute to radioresistance in late-S-phase. The cytoplasmic and intranuclear milieu of the cell appears to have less significant effects on lesions produced by high-LET radiation compared to those made by low-LET radiation. High-LET radiation fails to slow progression through S phase, and there is much less repair of lesions evident at all cell ages; however, high-LET particles cause a more profound block in G2 phase than that observed after low-LET radiation. Hazards posed by the interaction of damage from sequential doses of radiations of different qualities have been evaluated and are shown to lead to a cell-cycle-dependent enhancement of radiobiological effects. A summary comparison of various cell-cycle-dependent endpoints measured with low- or high-LET radiations is given and includes a discussion of the possible additional effects introduced by microgravity.

Cell Cycle↗
PubMed1989

Fluoxetine: prescribing guidelines for the newest antidepressant.

Fluoxetine is an antidepressant drug with a unique chemical configuration which enhances serotoninergic transmission by inhibiting serotonin uptake. The chronic presence of serotonin in the synaptic cleft reduces postsynaptic receptors, a postulated explanation for its antidepressant efficacy. Comparative studies show that the therapeutic effectiveness of fluoxetine is equal to that of imipramine, amitriptyline, and doxepin. A 20 mg morning dose alleviates most depressions. The long half-life of one to three days for the parent compound and seven to 15 days for the active metabolite, desmethylfluoxetine, is largely unaffected by age or renal impairment. Nausea, nervousness, insomnia, and headache are the most common side effects. Therapeutic doses do not affect cardiac conduction or cause orthostasis. A primary benefit of this drug is its significant relative safety in overdoses as compared to other antidepressants.

Depressive Disorder↗
PubMed1975

Herpes zoster in general practice.

Eighty-seven patients with the clinical diagnosis of herpes zoster were seen during a one-year period in eight general practices in Glasgow, the rate per 1,000 practice population being approximately 2.4. Of these, 78 (90 per cent) had serological evidence of active infection with herpes zoster. The anatomical location of the skin eruption was most common in the areas of the fifth cranial nerve, middle and lower trunk and thigh. A possible reactivating agent (trauma four, steroids two, irradiation one) was found in only seven patients. The illness as assessed by systemic upset and dissemination of lesions was generally not severe. Post-herpetic neuralgia was the most troublesome complication, found in 44 per cent of 64 patients revisisted 3-18 months after the acute illness.

Adult↗