PubMed Health⌕ Search

Biomedical subjects

F Allen

Publications and source records attributed to F Allen.

At least 19 recordsLinked to original sources
PubMed2000

An assessment of the accuracy of ridge-mapping in planning implant therapy for the anterior maxilla.

The use of ridge-mapping to assess bone levels available for implant placement in the anterior maxilla avoids some of the problems associated with CT scanning. The aim of this study was to assess the accuracy of ridge-mapping callipers in determining body ridge widths in the anterior maxilla prior to dental implant surgery. A modified surgical stent was designed to locate the beaks of ridge-mapping callipers at the same points on the jaw before and after mucoperiosteal flap reflection. Eleven subjects were included in the study. Measurements (n = 100) were made at 25 implant sites, 50 "pre-operative" and 50 "intra-operative" at 3 mm and 6 mm distances from the crest of the ridge. There were statistically significant (P < 0.0001) differences between pre- and intra-operative measurements. Based on pre-operative measurements, clinical judgements were made as to whether supplementary procedures such as guided bone regeneration would be required. Unanticipated supplementary procedures were required at 10 fixture sites. The findings indicate that ridge-mapping alone is insufficient to accurately predict bone available for implantation in the anterior maxilla. It is suggested that ridge-mapping may provide reliable information about bone levels when the labial aspect of the anterior ridge is not markedly concave.

Alveolar Process↗
PubMed1999

Physician perceptions of barriers to care for inner-city Latino children with asthma.

This article describes physician perspectives on barriers to quality primary care experienced by inner-city children with asthma and presents policy recommendations to reduce these barriers. The authors interviewed 30 physicians who take care of children with asthma in an inner-city Latino neighborhood, conducted a qualitative analysis of interview themes, and used a consensus group method to recommend policy actions. Inner-city physicians described significant access, quality of care, and other barriers in providing state-of-the-art primary care for asthma. Physicians recommended that eliminating financial barriers to care, including lack of health insurance and/or comprehensive health coverage for necessary medications and equipment, is the most important required policy action. In addition, inner-city physicians recommended that medical care and public health programs provide bilingual education for children with asthma and their families and train primary care physicians about how to provide effective asthma care to children with asthma in the inner city.

Adult↗
PubMed1998

The effect of shear stress on fibroblasts derived from Dupuytren's tissue and normal palmar fascia.

This study examines the real-time intracellular calcium changes of palmar fascia from normal and Dupuytren's diseased fibroblasts in response to shear stress. The real-time cytosolic calcium changes were measured using fluorescence microscopy image processing. The preconfluent primary cultured cells were exposed to 1 minute of flow at 25 dyne/cm2 after a 2-minute baseline of no flow. Additionally, the cells were exposed to an influx of Hank's buffered saline solution with 2% newborn bovine serum to examine the response to serum-born (chemical) agonists. Cytosolic calcium changes were measured as the percentage change over the 2-minute baseline of the mean [Ca2+]i peak. The mean change of the peak [Ca2+]i response of the normal palmar fascia was significantly greater than that of the cells from the Dupuytren's nodular and perinodular tissue. The response to the chemical agonist showed a robust but not statistically different response between the 3 cell types. Our work supports the hypothesis that palmar fascia responds to mechanical stress, specifically laminar fluid flow. These findings may help to explain that an underlying abnormality in the cells of the palmar fascia may be expressed by exposure to laminar fluid flow, a physical signal, rather than a chemical agonist.

Adult↗
PubMed1998

Prediction of neuromotor outcome in perinatal asphyxia: evaluation of MR scoring systems.

PURPOSE: We developed a scoring system for the assessment of perinatal asphyxia as depicted on MR images. METHODS: Four scoring systems were derived to evaluate MR images obtained in asphyxiated neonates: the basal ganglia (BG) score, the watershed (W) score, the combined basal ganglia/watershed (BG/W) score, and the sum of the BG and W scores, the summation (S) score. In addition, three MR sequences, T1-weighted, first-echo T2-weighted, and second-echo T2-weighted, were assessed for each patient for each scoring system. Neuromotor examinations were performed at ages 3 and 12 months, and cognitive development was tested at age 12 months. Statistical analysis was then performed to test the relationship between the MR scores and the outcome scores. RESULTS: The BG/W score, obtained with the first-echo T2-weighted sequence, was the most useful overall score for predicting neuromotor outcome at 3 and 12 months and cognitive outcome at 12 months. T1-weighted and first-echo T2-weighted sequences showed a stronger association with outcome in patients imaged during the first postnatal week, whereas second-echo T2-weighted sequences showed a stronger association with outcome in patients imaged during the second postnatal week. CONCLUSION: It appears that, with the use of the BG/W score, MR imaging discriminates accurately between patients with good and poor neuromotor and cognitive outcome at 3 and 12 months. In terms of our scoring systems, the first-echo T2-weighted sequence appears to discriminate best between patients with good and poor 3- and 12-month outcomes. Proper use of the imaging sequences and scoring systems described in this article can increase the knowledge base upon which treatment decisions are made in asphyxiated neonates.

Asphyxia Neonatorum↗
PubMed1995

Day case oral surgery: a review of 25 years experience at the Dublin Dental Hospital.

A retrospective analysis of the changing work-load at the Dublin Dental Hospital oral surgery day case unit was undertaken. This involved 26,697 operations performed during the 25-year period 1968-1992. The results show how the practice of oral surgery has changed over this time. Annual totals ranged from 766 to 1549 operations. While most categories of operations remained largely unchanged, the removal of impacted third molars increased from 10.5% of the annual total to 57.0%. Routine extractions of permanent teeth decreased from 53.9% of the annual total to 18.0%.

Ambulatory Surgical Procedures↗
PubMed1993

Reversal of muscle differentiation during urodele limb regeneration.

Recent studies suggest that maintenance of the differentiated state requires continuous regulation. Limb regeneration in urodele amphibians provides a context in which to address this issue, as limb regeneration may involve the dedifferentiation of multinucleate myotubes to yield mononucleate blastemal cells, which then proliferate and contribute to regenerate tissues. To evaluate this possibility, cultured newt limb myotubes were selectively microinjected with the lineage tracer rhodamine-dextran and introduced into regenerating limbs. In culture, such labeled myotubes were stable after 6-8 weeks, and transfer of the tracer to mononucleate cells was not observed. In contrast, after implantation of labeled myotubes under the wound epidermis of limb blastemas, strongly labeled mononucleate cells were observed after 1 week. These cells could be double-labeled with the cytoplasmic lineage tracer and [3H]thymidine that had been incorporated into the nuclei of implanted myotubes. The number of labeled mononucleate cells increased significantly by 2-3 weeks after implantation, indicating that these cells proliferated. Although the fate of these cells at later times was uncertain, we provide evidence consistent with their subsequent differentiation. These results demonstrate reversal in the mononucleate-to-multinucleate transition of vertebrate myogenesis.

Animals↗
PubMed1992

Inhaled steroids in patients with bronchiectasis.

The effect of inhaled beclomethasone diproprionate (1500 micrograms day-1) on symptoms, pulmonary function and sputum production was examined in a double-blind, placebo-controlled, cross-over study in 20 patients with bronchiectasis. An 18% reduction in daily sputum production (P less than 0.003) was observed on treatment with inhaled steroid compared to placebo. A small, significant, improvement in morning peak expiratory flow rate (P less than 0.03) and forced expiratory volume in 1 s (P less than 0.03) was seen but the absolute changes are unlikely to be of clinical importance. Symptom scores for cough improved significantly (P less than 0.02). Inhaled steroids may have a role in the management of bronchiectasis by reducing cough and sputum production.

Administration, Inhalation↗
PubMed1991

Gap junctional communication during neuromuscular junction formation.

We have tested whether gap junctions form between nerve and muscle during their initial contact, before establishing the chemical synapse. Embryonic Xenopus stage 18-20 myotomes and neural tubes were permeabilized with DMSO to load appropriate reagents, dissociated, and cocultured. When myotomes, loaded with Lucifer yellow, were cocultured with unlabeled neural tube cells, 23% of the neurons contained dye after 24 hr. Affinity-purified gap junction antibodies loaded into myocytes or neurons reduced neuronal labeling significantly to 5%. [3H]uridine nucleotide transfer was observed in both directions between myocytes and neurons. Again gap junction antibodies substantially reduced recipient label. In all cases preimmune IgGs did not reduce transfer. When acetylcholine receptor clustering was examined in cultures containing gap junction antibodies, no difference in the number of neuronally induced AChR clusters was observed. This suggests that the cluster-inducing signal between nerve and muscle does not pass through gap junctions.

Animals↗
PubMed1990

The role of gap junctions in patterning of the chick limb bud.

The role of gap junctional communication during patterning of the chick limb has been investigated. Affinity-purified antibodies raised against rat liver gap junctional proteins were used to block communication between limb mesenchyme cells. Co-injection of the antibodies and Lucifer yellow into mesenchyme cultures demonstrated that communication was inhibited almost immediately. When antibodies were loaded into mesenchyme tissue by DMSO permeabilization, [3H]nucleotide transfer was prevented for at least 16 h. Polarizing region tissue from the posterior limb bud margin causes digit duplications when grafted to the anterior margin. Quail polarizing region cells were loaded with gap junction antibody and grafted into chick wing buds. The antibody had no effect on growth or survival of the grafted cells. As very few polarizing region cells are required to initiate duplications, the number of polarizing region cells in the grafts was reduced by diluting 1:9 with anterior mesenchyme tissue. When either polarizing region or anterior mesenchyme tissue in the graft was loaded separately with antibody, there was little effect on respecification of the digit pattern. However, loading both tissues in the graft caused a significant decrease in duplications. This indicates that a major role of gap junctions in limb patterning may be to enable polarizing region cells to communicate directly with adjacent anterior mesenchyme. A role for gap junctional communication between anterior mesenchyme cells cannot be excluded. The results are discussed in relation to the role of retinoic acid as a putative morphogen.

Animals↗
PubMed1986

Allele frequency distribution of two highly polymorphic DNA sequences in three ethnic groups and its application to the determination of paternity.

The allele frequency distribution of two highly polymorphic DNA sequences has been determined in three ethnic groups (American blacks, Caucasoids, and Hispanics) from the New York metropolitan area. The two loci examined were D14S1 and the flanking region of HRAS-1. The former was analyzed in EcoRI-digested DNA and the latter in TaqI-digested DNA. Approximately 700 DNA samples from unrelated individuals were digested with each of these enzymes and hybridized with the appropriate recombinant DNA probes. The size range of the DNA fragments detected for the D14S1 polymorphism varied from 14.3 to 32.5 kilobase pairs (kbp). The number of alleles identified under the experimental conditions used in this study was more than 40. For the HRAS-1 polymorphism, we have detected 18 different alleles varying in size from 1.85 to 4.5 kbp. Although the number of alleles observed in the different ethnic groups examined was very similar, the relative frequency of them varied significantly. The results presented here can be used as the basis for the utilization of DNA RFLP for the purpose of identity, such as paternity determinations or the analysis of forensic material. As an example, we have compared the results of paternity cases analyzed by HLA typing with those obtained with these two DNA polymorphisms. The values of paternity index and power of exclusion were similar by both procedures.

Alleles↗
PubMed1985

Loss of breast milk nutrients during tube feeding.

Nutrient losses from banked breast milk during tube feeding were determined from laboratory models. Large fat losses occurred, continuous feeding giving rise to significantly greater losses than bolus feeding. More fat loss occurred with low flow rates and there were also significant protein losses.

Dietary Fats↗
PubMed1983

Relationship among esophageal dysfunction, diabetic gastroenteropathy, and peripheral neuropathy.

Esophageal motor function was tested in 12 patients with a clinical diagnosis of diabetic gastroenteropathy by radionuclide transit (RT) studies. Other insulin-dependent diabetics with and without symptoms of peripheral neuropathy but with no symptoms of gastrointestinal disease were similarly studied. Eleven of the 12 patients with gastroenteropathy were found to have abnormal esophageal function, even though only five had esophageal symptoms. Half the diabetics with peripheral neuropathy symptoms, and a quarter of those with no symptoms had abnormal esophageal transit studies. No abnormalities were found in a group of asymptomatic volunteers studied in a similar manner. We conclude that esophageal dysfunction, often subclinical, is present in nearly all patients with suspected diabetic gastroenteropathy. Esophageal dysfunction correlates less well with peripheral neuropathy. This study implies that if a diabetic, presenting with diarrhea or nausea and vomiting, has normal esophageal transit, then a cause for these symptoms, other than diabetic gastroenteropathy, may exist.

Adult↗
PubMed1980

Nodular regenerative hyperplasia of the liver in hematologic disorders: a possible response to obliterative portal venopathy. A morphometric study of nine cases with an hypothesis on the pathogenesis.

Nodular regenerative hyperplasia was found in nine patients who had hematological disease including polycythemia vera, agnogenic myeloid metaplasia, primary thrombocythemia, rheumatoid arthritis with thrombocytosis, multiple myeloma, and erythrocytosis associated with polycystic renal disease. Portal hypertension was suspected in three and features of hypersplenism were present in four. 2. Nodular regenerative hyperplasia occurred in livers which had widespread obliteration of portal vein radicals (obliterative portal venopathy). Morphometric analysis indicated that the portal vein lesions were predominately located in veins up to 0.2 mm in diameter and were significantly more frequent than similar lesions occurring in elderly persons. 3. The following pathogenesis of nodular regenerative hyperplasia is proposed: Thrombi, perhaps largely composed of platelet aggregates formed in the portal venous circulation or spleen, embolize to the liver and results in obliterative vascular lesions. Atrophy and regenerative nodule formation occur in response to the interruption of the portal blood supply.

Adult↗
PubMed1976

Morphology of the ascending thick limb of Henle.

The morphologic characteristics of the medullary and cortical segments of the ascending thick limb of Henle were examined in the rat utilizing light microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The kidneys of six normal female Sprague-Dawley rats were preserved for morphological examination utilizing in vivo intravascular perfusion with 6.25% glutaraldehyde buffered in 0.1m sodium cacodylate. SEM revealed the presence of two distinctly different patterns of surface structure among the population of cells forming the epithelium of the ascending thick limb, a roughsurfaced cell with prominent microvilli (R cell) and a smoothsurfaced cell generally devoid of extensive microvilli except along the lateral cell margins (S cell). This variation in surface structure was confirmed with light microscopy and TEM. Throughout both the medullary and cortical segments of the ascending thick limb, the R cells possessed extensive lateral processes radiating form the main cell body to interdigitate with adjacent cells. Lateral processes of S cells were less common than those of the R cells in the inner stripe of the outer medulla, but increased in number and complexity in the outer stripe of the outer medulla and throughout the cortex. S cells outnumbered R cells in the inner stripe of the outer medulla. As the thick limb transversed the outer medulla and ascended toward the parent renal corpuscle, there was a marked increase in the relative number of R cells. In the cortical segment of the ascending thick limb, both the R and S cells tended to acquire a more extensive population of microvilli over their luminal surface making it increasingly difficult to establish clearcut distinctions between the two surface patterns. With the possible exception that vesicles and tubulovesicular profiles located in the apical region were more numerous in many of the S cells, additional morphological differences between the rough and smoothsurfaced cells were not evident. Whether the morphological results represent two distinct cell types or simply a variation in the structure of a single cell type, their presence must be considered in future structural-functional studies involving the ascending thick limb of Henle in the rat.

Animals↗