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Biomedical subjects

B Armstrong

Publications and source records attributed to B Armstrong.

At least 19 recordsLinked to original sources
PubMed1992

Decreased plasma atriopeptin response to volume-overloading maneuvers and exercise after atriopulmonary anastomosis of Fontan.

Atriopulmonary anastomosis results in a chronic right atrial pressure-volume overload. Water and salt retention is a frequent clinical observation in patients after atriopulmonary anastomosis. The purpose of this study was to examine if this could be related to an inability to increase already elevated circulating atriopeptin (ANP) in response to central volume-overloading conditions. Eighteen patients (mean age 16 +/- 6 years) with an atriopulmonary anastomosis underwent routine cardiac catheterization during which a 5-minute head-down 10 degrees tilt was performed. Peripheral venous and right atrial blood samples were obtained under basal conditions, and after tilting and angiography for determination of ANP concentrations. At a different time, circulating ANP levels were measured during a maximal graded exercise protocol. Increased circulating ANP concentrations were found under basal conditions (114 +/- 10 pg/ml). Tilting and cardioangiography resulted in significant increases in mean atrial pressure (basal: 12 +/- 0.7 mm Hg; tilt: 13.4 +/- 0.63 mm Hg; after angiography: 15.8 +/- 0.8 mm Hg), but not in atrial or peripheral ANP. Compared with the expected threefold increase in plasma ANP induced by maximal exercise in healthy control subjects, only a slight (0.25-fold) increase was found in patients. These observations suggest a reduced stimulus-release response after atriopulmonary anastomosis, which could be related to a loss of atrial stretch receptor sensitivity, achievement of the limit for maximal right atrial secretion, or an alteration in right atrial compliance, or a combination.

Adolescent↗
PubMed1991

Frequent activation of the Ki-ras oncogene at codon 12 in N-methyl-N-nitrosourea-induced rat prostate adenocarcinomas and neurogenic sarcomas.

Rat neoplasms induced by methylating carcinogens frequently contain ras genes activated by a single point mutation. Rat prostatic tumors induced by a combination of a single injection of N-methyl-N-nitrosourea (MNU) and long-term treatment with testosterone were examined for the presence of such activating point mutations in ras genes. These tumors, which arose exclusively in the dorsolateral prostate, included both adenocarcinomas and sarcomas. Activating mutations in codon 12 of the Ki-ras gene were found in 7 of 10 carcinomas and 4 of 5 sarcomas, using selective oligonucleotide hybridization analysis of DNA amplified by the polymerase chain reaction (PCR). However, no mutated Ha-ras oncogenes were detected. The presence of PCR-engineered Hphl restriction sites created by the existence of a G35----A mutation in the rat Ki-ras oncogene identified the mutation as a GC----AT transition at the second position of codon 12. Production of O6-methylguanine adducts in the Ki-ras codon 12 followed by base mispairing during replicative DNA synthesis is thus the likely molecular mechanism of initiation of prostatic carcinogenesis by MNU in the rat. Three of the four sarcomas positive for the Ki-ras G35----A mutation were immunohistochemically defined as of Schwann cell origin, indicating that involvement of the ras gene family is possible in tumorigenesis of this cell lineage. Loss of the wild-type Ki-ras allele was also observed in all four of these sarcomas.

Adenocarcinoma↗
PubMed1979

Urinary sodium and blood pressure in vegetarians.

Urinary sodium, potassium urea, creatinine, uric acid, plasma urea, creatinine, cholesterol, blood pressures, height, weight, and skinfold thickness were measured in some or all of 106 matched pairs of vegetarians (mainly Seventh-Day Adventists) and nonvegetarians. Mean blood pressures were lower in vegetarians (141.9/88.9 mm) than nonvegeterians (148.0/90.9 mm) but the urinary excretion of sodium was higher, although not significantly, in the vegetarians (mean of 169.7 compared with 161.2 mmole/day). The vegetarians also had a higher urinary potassium excretion (62.9 mmole/day) than the nonvegetarians (54.8 mmole/day) thus giving them a lower mean sodium to potassium ratio (3.0 compared with 3.3). Both systolic and diastolic blood pressures correlated positively with plasma cholesterol levels which were less in vegetarians (6.0 mmole/liter) than nonvegetarians (6.6 mmole/liter). They also correlated positively with the urinary sodium to potassium ratio, but only in nonvegetarians. It was concluded that dietary sodium does not explain the blood pressure differences between vegetarians and nonvegetarians.

Adolescent↗
PubMed1979

Incidence and etiology of primary liver cancer in the Pacific Basin.

The incidence of PLC in the Pacific Basin varies from 0.9/100,000 (age-standardized) in women in New South Wales, Australia, to 34.2/100,000 in Singapore Chinese men. Proportional incidence data suggest that other areas of the Pacific Basin, such as Hong Kong, Taiwan, Indonesia, and Papua New Guinea, may have PLC incidence rates as high or higher than those in Singapore Chinese. Infection with hepatitis-B virus has been associated with PLC in some areas, and aflatoxin contamination of food has also been demonstrated. The extent to which these or other factors explain the geographical variation in liver cancer rates in the Pacific Basin is uncertain.

Adolescent↗
PubMed1978

Disruptive behavior: a dietary approach.

The effect of particular foods on levels of hyperactivity, uncontrolled laughter, and disruptive behaviors was studied in an 8-year-old autistic boy. The floor of the child's room was taped off into six equal-sized rectangles to measure general activity level. Frequency data were recorded on screaming, biting, scratching, and object throwing. A time-sample technique was used to record data on laughing. Data were gathered during four phases. During an initial 4-day period the child was fed a normal American diet. A 6-day fasting period followed, during which time only spring water was allowed. The third phase lasted 18 days and involved the presentation of individual foods. During the final phase of the study the child was given only foods that had not provoked a reaction in the third phase. Results showed that foods such as wheat, corn, tomatoes, sugar, mushrooms, and dairy products were instrumental in producing behavioral disorders with this child.

Autistic Disorder↗
PubMed1977

Blood pressure in Seventh-day Adventist vegetarians.

The blood pressures (BP) in 418 vegetarian Seventh-day Adventist (SDA) volunteers in Western Australia were compared with those in 290 non-vegetarian volunteers in Narrogin, a Western Australian country town. The mean systolic and diastolic BPs in the SDAs, adjusted for age, sex, height and weight (128.7/76.2 mm of mercury) were significantly less than those in the Narrogin residents (139.3/84.5). It appeared unlikely that these differences could be explained by differences in alcohol, tobacco, tea, coffee or egg consumption, socioeconomic status or physical activity. There was, however, a gradient toward increasing BP with increasing egg intake in SDAs, and SDAs who drank tea or coffee had a higher mean diastolic BP than those who did not (mean difference of 4.2 mm of mercury). The possibility that selective bias or unmeasured environmental differences might explain the difference in BP between the two groups is discussed.

Adult↗