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Biomedical subjects

R Freeman

Publications and source records attributed to R Freeman.

At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

Management of inadvertent injury to the carotid artery during head and neck surgery.

Rare, inadvertent injury to the carotid artery during head and neck surgery may result in disastrous neurologic sequelae or even death. Several cases are presented and used as the stimulus for an analytical discussion of the pathogenesis and management of cerebrovascular complications following head and neck surgery. The major pathogenetic mechanisms are identified as (1) microembolism from an ulcerated plaque; (2) intravascular thrombus with occlusion; (3) unintentional ligation, laceration, or transection; (4) ligation of a dominant external carotid; and (5) transient reduction in cerebrovascular perfusion pressure. Methods for identifying and evaluating the patient at risk for developing cerebrovascular complications are discussed and recommendations are made. The central question in the management of inadvertent arterial injury concerns whether to ligate the vessel or to restore blood flow. The controversies surrounding this issue are discussed in perspective through an analysis of current physiological concepts and of the collective clinical experiences of head and neck, vascular, and neurological surgeons handling extracranial cerebrovascular occlusive disease, penetrating injuries to the carotid artery, and tumor-related carotid catastrophes. Several factors are considered critical in determining appropriate management of any individual case; these include (1) whether recognition of the injury occurs intraoperatively or postoperatively; (2) the presence and severity of neurological deficits; (3) time from the injury to its recognition; (4) a quantitative assessment of collateral circulation; (5) a history of wound contamination or radiation therapy; (6) overall prognosis. These and other considerations are organized into a working framework through which the otolaryngologist and head and neck surgeon can better understand and manage the problem of inadvertent injury to the carotid artery.

Adult↗
PubMedDate not supplied

Defective stem cell factor expression in c-myb null fetal liver stroma.

High levels of c-Myb are observed in immature precursor myeloid and lymphoid cells, while downregulation of c-myb accompanies terminal differentiation to a mature phenotype. This has established c-Myb as a crucial transcription factor for hematopoiesis. Further evidence for this is the embryonic death of the c-myb homozygous mutant mouse at ED15 due to defective fetal liver erythropoiesis. Cells from fetal liver of wild-type and c-myb-/- embryos were examined in detail for their hematopoietic potential and the capacity of the stroma to support wild-type hematopoiesis. The c-myb-/- fetal liver was shown to harbor sevenfold fewer spleen focus-forming cells and a similarly lower number of cells with long-term repopulating capacity (high proliferative potential cells). However, shorter term repopulating cells were not substantially reduced. c-myb-/- stromal cells were unable to support the proliferation of wild-type bone marrow lineage-negative cells. This was found to be partly due to a decrease in stem cell factor (SCF) expression while partial rescue of the stromal cell cultures was achieved through the addition of exogenous SCF. DNA binding studies for two sites within the SCF promoter demonstrated an in vitro interaction between the SCF promoter and c-Myb and transient transfection studies demonstrated that c-Myb could substantially transactivate the SCF promoter in HEK293 cells. These data explain why the c-myb-/- embryos are so impaired in their ability to establish hematopoiesis.

Animals↗
PubMedDate not supplied

A family study of bipolar I disorder in adolescence. Early onset of symptoms linked to increased familial loading and lithium resistance.

Lifetime rates of psychiatric illness were compared in relatives of adolescent probands with bipolar I disorder and in relatives of age-matched schizophrenic controls. Familial aggregation of major affective disorders was observed in bipolar probands, the rate of bipolar I disorder greatly exceeding that reported in relatives of adult bipolar probands. Adolescent probands with childhood onset of psychiatric disturbance were distinguished from probands who had no premorbid childhood psychiatric abnormality in two ways: (1) significantly increased aggregation of bipolar I disorder in first-degree relatives; and (2) poorer antimanic response to lithium carbonate. These data underscore important heterogeneity in adolescent-onset bipolar disorder.

Adolescent↗
PubMedDate not supplied

Neural and perceptual adjustments to dim light.

At reduced luminance levels, the visual system integrates light over extended periods of time. Although the general effects of this process are known, specific changes in the visual cortex have not been identified. We have studied the physiological changes that occur during a transition from high to low luminance by measurements of single neurons in the cat's primary visual cortex. Under low-luminance conditions, we find increased latencies, expanded temporal responses, and a loss of temporal structure. This results in temporal-frequency tuning curves that are peaked at relatively low frequencies. To examine parallel perceptual changes, we compared perceived temporal frequency in human subjects under high- and low-luminance conditions. Low-luminance flickering patterns are perceived to modulate at relatively high rates. This occurs even though peak sensitivity is shifted to relatively low temporal frequencies. To explore further the perceptual component, we measured perceived temporal frequency in human subjects with unilateral optic neuritis for whom optic nerve transmission is known to be relatively slow and generally similar to the normal physiological state under low luminance. These subjects also perceive relatively high modulation rates through their affected eye. Considered together, these results demonstrate an inverse relationship between the physiological and the perceptual consequences of reduced stimulus luminance. This relationship may be accounted for by shifts of neuronal population responses between high- and low-luminance levels.

Animals↗
PubMedDate not supplied

Genetic study of norepinephrine in brains of mice selected for differences in blood pressure.

Norepinephrine concentration of the whole brain was found to be statistically different between the HBP and LBP mouse stains that had been selectively bred for high and low systolic blood pressure, respectively. Crosses between these strains resulted in statistically different NE levels between the reciprocal F1 males and the genetical analysis revealed a significant sex-linked factor or factors. Dissection of the brain into eight regions and subsequent biochemical analyses revealed statistically higher NE content in the LBP compared to the HBP for midbrain and cerebellum. Midbrain NE was also significantly different between the reciprocal F1's. NE concentration was then related to known behavioral characteristics in these strains.

Animals↗
PubMedDate not supplied

Addressing children's oral health inequalities in Northern Ireland: a research-practice-community partnership initiative.

OBJECTIVE: Northern Ireland has a high prevalence of childhood dental caries, reflecting heavy consumption of cariogenic snack foods. To develop a policy to promote and facilitate healthier eating, researchers, practitioners, and the school community formed a partnership, together creating the Boost Better Breaks (BBB) school-based policy. The policy was developed with and supported by dieticians, health promotion officers, teachers, school meal advisors, and local suppliers of school milk. Eighty percent of primary schools and preschool groups within the Southern Health and Social Services Board are involved in the program, which permits the consumption of only milk and fruit at break time. METHODS: The authors assessed the effectiveness of the partnership using data from its first two years. RESULTS: Results of the first two years of evaluation are positive. Initial findings indicate that the program had a positive effect in increasing the mean number of sound teeth in children attending schools in areas in which socioeconomic conditions are poor. CONCLUSION: This initiative suggests that collaboration can facilitate improvement in children's dental health and that careful targeting of the policy to schools in poor areas has the potential to narrow disparities.

Child↗
PubMedDate not supplied

Characterization of Aspergillus isolates by pyrolysis mass spectrometry.

Pyrolysis mass spectrometry (PYMS) is a useful typing method for many bacterial and Candida species. We attempted to type Aspergillus spp. by PYMS. Four distinct A. fumigatus isolates could not be distinguished from each other, whereas one A. niger and one A. terreus could. Poor reproducibility was shown using multiple identical cultures of a single A. fumigatus isolate and several isolates of the same DNA type. PYMS is obviously an unsuitable typing method for Aspergillus spp.

Aspergillosis↗
PubMedDate not supplied

Successful treatment with trisodium phosphonoformate for primary cytomegalovirus infection after heart transplantation.

Primary cytomegalovirus infection in the patient who is receiving immunosuppression therapy is associated with a high morbidity and mortality. We report a patient who developed primary cytomegalovirus infection 37 days after heart transplantation with a rapidly deteriorating course. Treatment with the new antiviral drug trisodium phosphonoformate (Foscarnet-Astra) was initiated as a lifesaving measure with rapid, dramatic improvement in the patient's condition and subsequent recovery.

Cytomegalovirus Infections↗
PubMedDate not supplied

Pulmonary "cyclosporinoma" mimicking infection after heart transplantation.

Tissue from a transthoracic needle biopsy, which was performed as part of the investigation of an undiagnosed left upper lobe opacity in a patient after orthotopic heart transplantation, revealed numerous macrophages loaded with oil globules. No causative organisms were present. High-pressure liquid chromatography showed a similar profile to the oil in which cyclosporine is suspended. The lesion appears to have been caused by aspiration of cyclosporine.

Adult↗