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Biomedical subjects

A C Mason

Publications and source records attributed to A C Mason.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of radiology residency programs in ten countries.

The purpose of our study was to compare various aspects of radiology training schemes in ten countries. A questionnaire was sent to senior residents in the UK, USA, Canada, Australia, New Zealand, Italy, Egypt, India, Malaysia and Greece. The questions concerned length of training, required pre-training experience, the organization of the training scheme, teaching, resources, stages at which residents can independently perform and report examinations, fellowships, and progression to jobs. A wide variety of training, ranging from highly scheduled programs with detailed aims and objectives, to self-learning occurs across the world. Examinations and assessments are also variable. There are lessons to be learned from varying practices; more exchanges of ideas should be encouraged. In view of the "internationalization" of radiology services and the variation in training styles an international qualification for quality assurance purposes may be desirable.

Asia↗
PubMed2002

Epidemiological differences between adenocarcinoma of the oesophagus and adenocarcinoma of the gastric cardia in the USA.

BACKGROUND AND AIMS: It has been suggested that gastric cardia adenocarcinoma (GCA) is a distinct entity from oesophageal adenocarcinoma (OA). We examined several epidemiological features of GCA and OA in the USA to elucidate differences/similarities between these malignancies. METHODS: Using the database of Surveillance, Epidemiology, and End Results (SEER) program, we examined incidence rates for temporal changes, and ethnic and age distributions, and performed birth cohort analyses for cases with morphologically and histologically confirmed OA or GCA. RESULTS: The age adjusted incidence rates of OA rose progressively, reaching 1.8 per 100 000 (95% confidence interval 1.7-1.9) during 1987-1991 and 2.5 per 100 000 (2.3-2.6) during 1992-1996. In 1992-1996, Whites were affected five times more than Blacks, and men eight times more than women. A significant increase in incidence occurred among younger persons aged 45-65 years. Irrespective of age, OA was characterised by higher incidence rates among more recent birth cohorts: a 40% increase in incidence for each five year increase in the date of birth--a "birth cohort effect". On the other hand, the incidence rates of GCA reached their highest level of 3.3 per 100 000 (3.2-3.4) in 1987-1991 and subsequently declined during 1992-1996 to 3.1 per 100 000 (3.0-3.3). Whites were affected twice more than blacks and men five times more than women. Most patients with GCA were older than 60 years with no increase among younger persons and no birth cohort effect (p=0.99). CONCLUSION: Several significant epidemiological differences exist between OA and GCA. These differences suggest that these two malignancies are separate entities with different risk factors.

Adenocarcinoma↗
PubMed2001

Hyperacute directional hearing in a microscale auditory system.

The physics of sound propagation imposes fundamental constraints on sound localization: for a given frequency, the smaller the receiver, the smaller the available cues. Thus, the creation of nanoscale acoustic microphones with directional sensitivity is very difficult. The fly Ormia ochracea possesses an unusual 'ear' that largely overcomes these physical constraints; attempts to exploit principles derived from O. ochracea for improved hearing aids are now in progress. Here we report that O. ochracea can behaviourally localize a salient sound source with a precision equal to that of humans. Despite its small size and minuscule interaural cues, the fly localizes sound sources to within 2 degrees azimuth. As the fly's eardrums are less than 0.5 mm apart, localization cues are around 50 ns. Directional information is represented in the auditory system by the relative timing of receptor responses in the two ears. Low-jitter, phasic receptor responses are pooled to achieve hyperacute timecoding. These results demonstrate that nanoscale/microscale directional microphones patterned after O. ochracea have the potential for highly accurate directional sensitivity, independent of their size. Notably, in the fly itself this performance is dependent on a newly discovered set of specific coding strategies employed by the nervous system.

Animal Communication↗
PubMed2001

Protein digestibility-corrected amino acid scores for bean and bean-rice infant weaning food products.

Vegetable proteins are an integral part of infant weaning diets in Latin America. Protein quality in plant-based products, however, is constrained by amino acid composition and intrinsically present antinutritional factors. The goal of this study was to improve bean protein quality by utilizing fermentation and germination processing. The objectives were to determine if protein quality, as measured by Food and Agricultural Organization (FAO) approved True Protein Digestibility (TPD) and Protein Digestibility-Corrected Amino Acid Scores (PDCAAS), of formulated bean-based weaning products could be improved upon fermentation and germination and if protein quality could be further improved when processed beans were combined with cooked rice. Results showed that the highest TPD and PDCAAS values were obtained for cooked germinated beans combined with rice. The TPD values for products ranged from 80 to 91%, and the PDCAAS values were 0.38-0.51. There was no significant increase (P < 0.05) of either TPD or PDCAAS values upon fermentation. Germination increased TPD of cooked bean products; this increase was not, however, accompanied by an increase in PDCAAS. When combined with rice, the PDCAAS values for all bean products improved significantly, thus supporting the concept of cereal-legume complementation. In conclusion, this study showed the range of PDCAAS in processed black bean and bean-rice infant weaning food products. The potential for incorporation of these products into the diets of weaning age Latin American children would, however, be confirmed only after validation with growth or metabolic balance studies in human infants.

Amino Acids↗
PubMed2001

Iron and zinc bioavailability in rats fed intrinsically labeled bean and bean-rice infant weaning food products.

Beans are the core of the Latin American diet and contain iron and zinc. However, the bioavailability of these trace minerals from beans is low. The objective of this study was to determine if the bioavailability of iron and zinc could be improved with the use of fermentation and germination processing technologies. Black beans native to Costa Rica were grown hydroponically with either radioactive iron or zinc. The influence of fermentation and germination on iron and zinc bioavailability from intrinsically labeled infant weaning food products based on black beans and beans-rice was determined in rats. Mineral bioavailability was determined using whole-body (59)Fe retention for iron, and whole-body (65)Zn retention and incorporation of radiolabel into bone for zinc. Percent absorption of (59)Fe from fermented products ranged between 48.0 and 58.0. Percent absorption of (65)Zn ranged from 57.0 to 64.0. Fermentation did not increase iron bioavailability in rats fed fermented beans without rice. Fermentation of cooked beans significantly increased zinc retention. Germination significantly enhanced iron retention from cooked beans from 46 to 55% and from cooked beans-cooked rice from 34 to 48%. Germination significantly improved zinc absorption and retention from cooked beans without added rice.

Absorption↗
PubMed2001

Trends in survival of patients with hepatocellular carcinoma between 1977 and 1996 in the United States.

The recent increase in the incidence of hepatocellular cancer in the United States is thought to underlie the rising mortality of this malignancy. However, it remains unknown whether survival of patients with hepatocellular carcinoma (HCC) has changed during the same time period. Using the SEER database (Surveillance, Epidemiology, and End Results) of the National Cancer Institute, we examined the temporal changes and determinants of survival among patients with histologically proven HCC over a 20-year period. Between 1977 and 1996, 7,389 patients diagnosed with HCC were followed in the survival database of SEER. The overall 1-year relative survival rate increased from 14% (95% confidence intervals (CI): 12-16) during 1977-1981 to 23% (95% CI: 21-24) during 1992 to 1996. Between the same two time periods, less improvement was seen in the 5-year survival rates, which increased from 2% (95% CI: 1-3) to only 5% (95% CI: 4-7). The median survival increased slightly from 0.57 years during 1977 to 1981 to 0.64 years during 1992 to 1996. In general, there were no significant differences in survival between men and women or between ethnic groups. During 1987 to 1991, a small fraction (0.8%) of patients underwent radical surgery; these patients had 1-year survival of 59% (95% CI: 35-83%), and 5-year survival of 35% (95% CI: 12-58%). Similar rates were seen during 1992-1996. In conclusion, a small improvement in survival of patients with HCC was seen between 1977 and 1996. Most of this apparent benefit is restricted to the first year following cancer diagnosis, raising the possibility of lead-time bias. There were no significant differences related to gender or ethnicity.

Adult↗
PubMed2000

Risk factors for the rising rates of primary liver cancer in the United States.

BACKGROUND: A recent increase in the incidence of hepatocellular carcinoma was reported in the United States. The cause of this witnessed rise remains unknown. METHODS: We examined the temporal changes in both age-specific and age-standardized hospitalization rates of primary liver cancer associated with hepatitis C, hepatitis B, and alcoholic cirrhosis in the Department of Veterans Affairs Medical Center's Patient Treatment File. RESULTS: A total of 1605 patients were diagnosed with primary liver cancer between 1993 and 1998. The overall age-adjusted proportional hospitalization rate for primary liver cancer increased from 36.4 per 100,000 (95% confidence interval [CI], 34.0-38.9) between 1993 and 1995 to 47.5 per 100,000 (95% CI, 44.6-50.1) between 1996 and 1998. There was a 3-fold increase in the age-adjusted rates for primary liver cancer associated with hepatitis C virus, from 2.3 per 100,000 (95% CI, 1. 8-3.0) between 1993 and 1995 to 7.0 per 100,000 (95% CI, 5.9-8.1) between 1996 and 1998. Concomitant with this rise, the age-specific rates for primary liver cancer associated with hepatitis C also shifted toward younger patients. During the same periods, the age-adjusted rates for primary liver cancer associated with either hepatitis B virus (2.2 vs 3.1 per 100,000) or alcoholic cirrhosis (8. 4 vs 9.1 per 100,000) remained stable. The rates for primary liver cancer without risk factors also remained without a statistically significant change, from 17.5 (95% CI, 15.8-19.1) between 1993 and 1995 to 19.0 per 100,000 (95% CI, 17.3-20.7) between 1996 and 1998. CONCLUSIONS: Hepatitis C virus infection accounts for most of the increase in the number of cases of primary liver cancer among US veterans. The rates of primary liver cancer associated with alcoholic cirrhosis and hepatitis B virus infection have remained stable. Arch Intern Med. 2000;160:3227-3230.

Adult↗
PubMed2000

Low grade gastric MALT Lymphoma: radiographic findings.

AIMS: Gastric MALT (mucosa-associated lymphoid tissue) lymphoma is now recognized as a distinct entity within extranodal non-Hodgkin's lymphoma. The purpose of this study was to describe the radiographic findings in low grade gastric MALT lymphoma. MATERIALS AND METHODS: We retrospectively reviewed the radiographic findings in 22 cases of low-grade gastric MALT lymphoma. The study group consisted of 15 men and seven women (median age 68 years, range 41-91 years). Lesions were designated as infiltrative or polypoid by consensus of two radiologists. Polypoid lesions were categorized by number and size. Anatomical site within the stomach and presence of transpyloric or oesophagogastric extension was determined for each case. The presence of abdominal lymphadenopathy was categorized as regional or distant. The presence of Helicobacter pylori was determined from endoscopic and surgical biopsies. RESULTS: Computed tomography (CT) revealed abnormalities of the stomach in 19 cases of the 21 in which it was performed. There were 14 infiltrative lesions and five polypoid lesions. Of the 14 infiltrative lesions, the mean gastric wall thickness was 2.2 cm (range 0.8-6.0 cm). There were three single and two multiple polypoid lesions (mean size 2.2 cm, range 1. 5-2.7 cm). Transpyloric extension was observed in two cases and oesophagogastric extension in one. Abdominal lymphadenopathy was observed in 10 of 21 patients. Helicobacter pylori was found in 19 of 22 cases (86%). CONCLUSION: Low grade B cell gastric MALT lymphomas present with an infiltrative form on CT in about three-quarters of cases and a polypoid pattern in the remainder. Abdominal lymphadenopathy is seen in approximately one-half of cases. There is a high association with Helicobacter pylori.

Adult↗
PubMed2000

Management of alcohol withdrawal in microvascular head and neck reconstruction.

Alcohol use is a risk factor for head and neck cancer. One of the primary therapeutic modalities is surgical tumor ablation followed by immediate reconstruction. Such therapy places patients in a controlled environment, without alcohol, creating the risk of alcohol withdrawal syndrome. The authors attempted to identify the incidence of alcohol withdrawal among patients undergoing free-flap reconstruction for head and neck cancer and were interested in the effect of alcohol withdrawal on the postoperative course of affected patients. In this retrospective review of 51 patients, six experienced alcohol withdrawal or delirium tremens. No difference in the rate of overall complications was seen between the patients who experienced withdrawal and those who did not, although patients who experienced withdrawal did have a statistically significant ratio of non-flap-related to flap-related complications. A review of the current management for alcohol withdrawal is included and places an emphasis on preoperative screening, close observation, rapid diagnosis, and immediate medical care.

Adult↗
PubMed2000

Occult craniocerebral injuries from dog bites in young children.

Although dog bite injuries to the head and scalp of children occur frequently, penetrating dog bite wounds to the cranial vault occur only occasionally and may go unnoticed on initial examination. Substantial morbidity and mortality can ensue if these penetrating injuries are not detected and treated. The authors detail the evaluation of dog bites of the scalp in young children. They highlight the ease with which puncture wounds of the calvarium may be missed during physical examination as a result of scalp displacement at the time of puncture. The cranial puncture may not be large and may later be covered by scalp that returns to its native position. Well-scrutinized skull films and a careful, methodical physical examination are advocated. Recognized craniocerebral injuries should be explored. Depressed cranial fractures should be irrigated, debrided, and elevated. Dural tears should be repaired. Expedient management is necessary to prevent meningitis and its associated sequelae.

Animals↗
PubMed1999

Rising incidence of hepatocellular carcinoma in the United States.

BACKGROUND AND METHODS: Clinical observations have suggested that the number of cases of hepatocellular carcinoma has increased in the United States. We analyzed data from the Surveillance, Epidemiology, and End Results (SEER) data base to determine the age-adjusted incidence of hepatocellular carcinoma from 1976 to 1995, data from the U.S. vital-statistics data base to determine age-adjusted mortality rates from 1981 to 1995, and data from the Department of Veterans Affairs to determine age-adjusted rates of hospitalization for the disease from 1983 to 1997. RESULTS: The incidence of histologically proved hepatocellular carcinoma increased from 1.4 per 100,000 population (95 percent confidence interval, 1.3 to 1.4) for the period from 1976 to 1980 to 2.4 per 100,000 (95 percent confidence interval, 2.3 to 2.4) for the period from 1991 to 1995. Among black men, the incidence was 6.1 per 100,000 for the period from 1991 to 1995, and among white men, it was 2.8 per 100,000. There was a 41 percent increase in the mortality rate from primary liver cancer and a 46 percent increase in the proportion of hospitalizations attributable to this disease during the periods studied. The incidence increased significantly among younger persons (40 to 60 years old) during the period from 1991 to 1995 as compared with earlier periods. CONCLUSIONS: An increase in the number of cases of hepatocellular carcinoma has occurred in the United States over the past two decades. The age-specific incidence of this cancer has progressively shifted toward younger people.

Adult↗
PubMed1999

Peripheral frequency mis-match in the primitive ensiferan Cyphoderris monstrosa (Orthoptera: Haglidae).

Peripheral auditory frequency tuning in the ensiferan insect Cyphoderris monstrosa (Orthoptera: Haglidae) was examined by comparing tympanal vibrations and primary auditory receptor responses. In this species there is a mis-match between the frequency of maximal auditory sensitivity and the frequency content of the species' acoustic signals. The mis-match is not a function of the mechanical properties of the tympanum, but is evident at the level of primary receptors. There are two classes of primary receptors: low-tuned and broadly tuned. Differences in the absolute sensitivity of the two receptor types at the male song frequency would allow the auditory system to discriminate intraspecific signals from sounds containing lower frequencies. Comparisons of tympanal and receptor tuning indicated that the sensitivity of the broadly tuned receptors did not differ from that of the tympanum, while low-tuned receptors had significantly narrower frequency tuning. The results suggest that the limited specialization for the encoding of intraspecific signals in the auditory system of C. monstrosa is a primitive rather than a degenerate condition. The limited specialization of C. monstrosa may reflect the evolutionary origin of communication-related hearing from a generalized precursor through the addition of peripheral adaptations (tympana, additional receptors) to enhance frequency sensitivity and discrimination.

Acoustic Stimulation↗
PubMed1999

Newly diagnosed cystic fibrosis in adults: pattern and distribution of bronchiectasis in 12 cases.

OBJECTIVE: The aim of this study was to analyse the type and distribution of bronchiectasis at computed tomography (CT) in adults with recently diagnosed cystic fibrosis. METHODS: The CT examinations of 12 consecutive patients diagnosed with cystic fibrosis in adulthood (six male, six female; age range at diagnosis 25-63 years) were analysed retrospectively using a modified Bhalla scoring system. Bronchiectasis was catergorized by Reid type and by location within the affected lobe (peripheral, central or mixed). RESULTS: Bronchiectasis was identified in 70 of 71 lobes. Two or more bronchopulmonary segments were involved in 67 of 71 lobes. The majority of lobes demonstrated cylindrical bronchiectasis as the predominant type (n = 51), with varicose (n = 11) and cystic (n = 8) less commonly seen. Bronchiectasis was mainly central in 16 lobes, and both central and peripheral in 54 lobes. The severity of bronchial dilatation was greatest for the upper lobes (mean score, 1.75 right, 1.58 left) compared with the middle lobe/lingula (mean score, 1.42 right, 1.17 left) and lower lobes (mean score, 1.09 right, 1.17 left). CONCLUSION: Bronchiectasis in patients with cystic fibrosis diagnosed in adulthood is usually widespread, predominantly cylindrical, and is more severe in the upper lobes. The diagnosis of cystic fibrosis should be considered in adults with 'idiopathic' bronchiectasis showing these features on CT.

Adult↗
PubMed1999

Thoracic foreign bodies in adults.

AIM: The aim of this pictorial essay is to illustrate a range of imaging manifestations of thoracic foreign bodies. METHODS AND RESULTS: The essay includes documented intrathoracic foreign bodies introduced by inhalation, aspiration, penetrating trauma or ingestion. Imaging modalities include chest radiography and computed tomography (CT). CONCLUSIONS: The majority of foreign bodies are seen on the plain chest radiograph. CT is helpful in demonstrating the presence of radiolucent foreign bodies and determining the exact location of the foreign bodies within the airways or lung parenchyma.

Adult↗
PubMed1999

Tissue expander infections in children: look beyond the expander pocket.

Infection of the expander pocket is the most common complication encountered with soft-tissue expansion. It is usually due to direct inoculation with skin flora either at the time of expander insertion or from extrusion of the device. The authors report two cases of infection of tissue expanders in which the children had concomitant infected sites distant from the prosthesis. Etiological bacteria of common pediatric infections like otitis media and pharyngitis were cultured from the infected expander pocket, raising suspicion that translocation of the organism to the expander had occurred. Aggressive antibiotic treatment, removal of the prosthesis, and flap advancement is advocated.

Child, Preschool↗