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Biomedical subjects

S Norton

Publications and source records attributed to S Norton.

At least 19 recordsLinked to original sources
PubMed1998

Ovulatory delay alters postnatal growth, behavior, and brain structure in rats.

To investigate the effect of a delay in ovulation on postnatal growth and development in resultant rat offspring, a 1-day ovulatory delay was induced by sodium pentobarbital, animals mated, and the offspring monitored. There were no differences between control and 1-day delayed offspring in the number of live or dead births, number of males or females, nor in the ratio of sexes. Delayed pups had a slightly lower birth weight, but then recovered to weigh more than controls by day 12. In the first two weeks post-parturition, delayed pups displayed an earlier ability to reorient themselves in a negative geotaxis test, but no differences by the righting reflex and reflex suspension tests. At postnatal day (pnd) 28, delayed pups exhibited decreased activity in a continuous corridor test, but no alterations in gait. At this time, the brains of delayed animals revealed thickening of cortical layers V plus VI. There were significant correlations between various developmental endpoints (body weight, negative geotaxis, continuous corridor activity, and gait) and the cortical layer thicknesses. The results indicate that ovulatory delay produces changes in brain cortical thickness, with correlative changes in growth and behavior. Although the mechanisms by which ovulatory delay alters postnatal development and brain structure are unknown, ovulatory delay may alter the uterine environment during early pregnancy.

Animals↗
PubMed1998

An exploration of methodological pluralism in nursing research.

The purpose of this article is to describe some important differences in methodological perspectives within the discipline of nursing. Four research traditions (empiric analytic, grounded theory, Heideggerian hermeneutic, and participatory action research) and the philosophical assumptions that inform them are presented. The discussion touches on criticisms that arise from within and from outside each tradition, as well as how each addresses the usefulness of research. Finally, ways in which specialized language is simultaneously necessary and problematic in advancing scholarly debate are illuminated.

Humans↗
PubMed1995

Ethanol tolerance of immobilized brewers' yeast cells.

A method based on the survival of yeast cells subjected to an ethanol or heat shock was utilized to compare the stress resistance of free and carrageenan-immobilized yeast cells. Results demonstrated a significant increase of yeast survival against ethanol for immobilized cells as compared to free cells, while no marked difference in heat resistance was observed. When entrapped cells were released by mechanical disruption of the gel beads and submitted to the same ethanol stress, they exhibited a lower survival rate than entrapped cells, but a similar or slightly higher survival rate than free cells. The incidence of ethanol- or heat-induced respiratory-deficient mutants of entrapped cells was equivalent to that of control or non-stressed cells (1.3 +/- 0.5%) whereas ethanol- and heat-shocked free and released cells exhibited between 4.4% and 10.9% average incidence of respiration-deficient mutants. It was concluded that the carrageenan gel matrix provided a protection against ethanol, and that entrapped cells returned to normal physiological behaviour as soon as they were released. The cell growth rate was a significant factor in the resistance of yeast to high ethanol concentrations. The optimum conditions to obtain reliable and reproducible results involved the use of slow-growing cells after exhaustion of the sugar substrate.

Culture Media↗
PubMed1995

Measurement accuracy: a comparison of two intra-oral digital radiographic systems, RadioVisiography-S and FlashDent, with analog film.

OBJECTIVES: To compare the accuracy of measurement algorithms incorporated into the software provided with two CCD-based digital radiographic systems and compare assessments using intra-oral film. METHODS: A test object with three radiopaque reference points was imaged using Ektaspeed intra-oral film, both with and without an overlaid 1 mm reference grid, the RVG-S, the measurement software of which overlays a 2 mm grid, and the FlashDent, which uses a mouse-driven cursor to estimate distances. Geometric factors, including source-to-object and receptor-to-object distances, vertical and horizontal cone angulation, and vertical angulation of receptor, were successively altered. Six viewers estimated vertical, horizontal and diagonal distances for each image. RESULTS: Increased source-to-object distance resulted in a 5-10% reduction in image dimensions, whereas increased receptor-to-object distance produced a magnification of 15-20% with all techniques. Increased vertical and horizontal cone angulation resulted in slight increases in magnification (0-5%) whereas greater receptor angulation resulted in noticeable magnification under all test conditions (10-15%). Estimated values for vertical, horizontal and diagonal measurements were approximately 5-10% higher than the actual dimensions, irrespective of the technique used. The FlashDent mouse-driven cursor system and direct measurement of distances from conventional film were more accurate in horizontal and diagonal dimension estimates than using an overlaid grid. Intra-observer and inter-observer differences were found for specific situations. CONCLUSION: The mouse-driven computerized measurement cursor and intra-oral film assessment using a ruler provided the most accurate, reliable and consistent dimensional measurements.

Analysis of Variance↗
PubMed1995

Open cholecystectomy in the age of the laparoscope.

We reviewed our experience with open cholecystectomy since laparoscopic cholecystectomy became the treatment of choice for symptomatic gallstones. Over a 3 year period 35 open (6%) and 578 laparoscopic cholecystectomies (94%) were performed. Fourteen trainee surgeons performed only 16 open cholecystectomies and assisted at 19. The proportion of open cholecystectomies declined through the study period. Ten emergency cholecystectomies were performed for empyema, gallbladder perforation, severe acute cholecystitis, liver abscess, and cholangitis. In 12 patients, laparoscopic surgery was converted to an open procedure because of severe inflammation, empyema, dense adhesions, carcinoma of the gallbladder, cholecystoduodenal fistula, and perforated small bowel. Ten patients underwent open cholecystectomy and bile duct exploration after failure to clear duct stones endoscopically, and three patients had Mirizzi's syndrome. Open cholecystectomy is infrequently performed giving trainee surgeons little experience. However, such cases are occasionally inevitable and laparoscopic surgeons need to have the appropriate skills.

Cholecystectomy↗
PubMed1994

Petrol octane booster and methaemoglobinaemia.

We highlight the case of a 35-year-old male who suffered a respiratory arrest as a result of methaemoglobinaemia secondary to skin contamination and inhalation of petrol octane booster following a road traffic accident. It is important that petrol octane booster is stored safely in leak-proof containers and that suitable warnings are displayed to alert the user of potential toxicity.

Adult↗
PubMed1994

Food bioconversions and metabolite production using immobilized cell technology.

This review explores recent advances in the use of immobilized cells for the production of metabolites used in the food industry, such as enzymes, amino acids, organic acids, alcohols, aroma compounds, polysaccharides, and pigments. Some food bioconversions such as fermentation of soy sauce and various hydrolysis are also considered. Special emphasis was placed on existing or potential industrial processes. This article also reports the effects of the reactor (configuration and working conditions), the immobilized cell physiological status (growing, nongrowing, or permeabilized), and of the carrier type, configuration, and size on the performance of immobilized cell systems. Compared with free cell fermentation, the main advantage of using immobilized cells is an increase in productivity, particularly in the case of continuous fermentation. For monoenzymatic reactions, nongrowing immobilized cells are often reported to exhibit a higher stability than free or immobilized enzymes.

Fermentation↗
PubMed1994

Effect of in utero radiation dose fractionation on rat postnatal development, behavior and brain structure: 3-hour interval.

Effect of In Utero Radiation Dose Fractionation on Rat Postnatal Development, Behavior and Brain Structure: 3-Hour Interval. Neurotoxicology 15(1): 183-190, 1994. We have previously shown that exposure of the rat fetus to ionizing radiation produces dose-dependent (0.25-1.25 Gy) changes in postnatal growth and behavior, and decreases in cerebral cortex thickness. Pregnant rats were exposed to single doses of 0.5 or 1.0 Gy, or to two doses of 0.5 Gy (separated by a 3 h interval) on gestational day 15. Pups were weighed and subjected to behavioral tests (righting reflex; reflex suspension; negative geotaxis; continuous corridor; and length, width, and sine of gait) over postnatal days 7-28. The rats were then sacrificed and brains removed for histology. The fractionated doses produced responses that were generally intermediate between those produced by the single doses and which, by interpolation, could be expressed as equivalent to a single dose between 0.5 and 1.0 Gy. Overall, exposure of the fetal rat to two doses of 0.5 Gy separated by 3 h produced effects equivalent to a single dose of 0.85 Gy. We conclude that fractionation of radiation dose results in less damage to the developing rat cerebral cortex, as measured by postnatal growth, behavioral tests, and morphological assessment.

Animals↗
PubMed1993

Perceived costs and benefits of membership in a self-help group: comparisons of members and nonmembers of the Alliance for the Mentally Ill.

We assess the utility of looking at the costs/barriers and benefits/incentives of belonging to an Alliance for the Mentally Ill (AMI) self-help group. Support for bimotivational factors of costs and benefits was found. Comparisons were made between members vs. nonmembers and between more active vs. less active members. Implications for theory and application are discussed.

Community Mental Health Centers↗
PubMed1993

Radioprotection of mice by dietary squalene.

Male C3H mice were fed a diet containing 2% squalene for 14 d prior to and 30 d subsequent to exposure to 6, 7 or 8 Gy of whole body gamma-irradiation (Cesium-137). After 14 d on squalene-supplemented diet, plasma and jejunal tissue squalene levels were 2X and 15X that of controls. Seven days after irradiation, total white cell counts and total lymphocyte counts were substantially depressed in a radiation dose-dependent manner. Although counts in the squalene group were consistently (18-119%) higher than those in the corresponding dietary control group, the differences between dietary groups at any single dose were not significant. Nuclear area of villus cells in the jejunum of both dietary groups was significantly reduced (20%) by day 11 post-irradiation but the nuclear area in squalene-fed mice was significantly greater (15%) than in controls, before and after irradiation. There were no differences in body weight as a function of either diet or radiation dose prior to the first observations of animal lethality. Animal survival was decreased from 100 to 0% at 30 d post-irradiation by radiation doses of 6-8 Gy, with the greatest difference between dietary groups being observed at 7 Gy (median survival times of 12 and 16 d for control and squalene groups, respectively). Overall, survival of squalene-fed mice was significantly prolonged compared with control-fed mice (P = 0.0054 by censored multiple regression analysis). It is concluded that squalene conferred some cellular and systemic radioprotection to mice receiving these lethal whole-body radiation doses.

Animals↗
PubMed1993

Effect of in utero irradiation on the postnatal development, behavior, and brain structure of rats: dose fractionation with a 6-h interval.

Based on previous studies showing that exposure of the rat fetus to ionizing radiation produces dose-dependent (0.25-1.25 Gy) changes in postnatal development of behavior and decreases in the thickness of the cerebral cortex, we examined the extent to which dose fractionation would reduce expression of damage. Pregnant rats were exposed to single doses of 0.5 or 1.0 Gy, or to two doses of 0.5 Gy 6 h apart on day 15 of gestation. Offspring were subjected to four behavioral tests on postnatal days 7-28; the rats were then sacrificed and their brains removed and processed for histology. For all end points, the fractionated dose produced an effect that was intermediate between that of the 0.5- and 1.0-Gy doses and which, by interpolation, could be expressed as equivalent to a single dose between 0.5 and 1.0 Gy. The equivalent single dose was not significantly different from the 1.0-Gy dose for negative geotaxis (0.54 Gy), reflex suspension (0.80 Gy), and continuous corridor (0.85 Gy). For sine of the angle of the advance of hind feet (0.58 Gy), width of stride (0.69 Gy), length of stride (0.75 Gy), body weight (0.73 Gy), and cerebral cortex thickness (0.69 Gy), the fractionated dose produced effects significantly different (P < 0.05) from the 1.0-Gy dose. Overall, exposure of fetal rats to two doses of 0.5 Gy separated by 6 h produced effects equivalent to a single dose of 0.70 Gy, as measured by postnatal behavioral tests and morphological assessment of brain structure.

Animals↗
PubMed1991

Effects of hyperglycemia on mitochondrial morphology in the region of the anterior neuropore in the explanted rat embryo model: evidence for a modified Reid hypothesis as a mechanism for diabetic teratogenesis.

Congenital malformations are the leading cause of the increased perinatal mortality in the infants of insulin-dependent diabetic mothers. The mechanisms(s) of diabetic teratologic development has yet to be defined. Hyperglycemia is known to depress aerobic metabolism in many organisms and cell lines. Reid hypothesized that exposure to hyperglycemia could result in decreased mitochondrial biogenesis in embryonic cells. Should these cells suddenly be changed to an environment of lower glucose concentration, decreased energy capabilities would exist until sufficient numbers of mitochondria could be regenerated. Such cells may not be capable of meeting temporal-spatial requirements, thereby resulting in structural abnormalities. In our study the explanted rat embryo model demonstrated that in the head-fold region hyperglycemia produced morphologic alterations of mitochondria but no difference in the number of mitochondria per cell. Specifically, embryos cultured in euglycemia demonstrated orthodox mitochondrial configuration, whereas those cultured in hyperglycemia had mitochondria in a condensed configuration. These findings were reversible. A modification of Reid's original hypothesis may provide an explanation for the mechanism of diabetic teratologic development.

Abnormalities, Multiple↗
PubMed1991

Pulsed ultrasound and the hyperbarically exposed mouse fetus.

To enhance the likelihood of cavitation, pregnant mice were subjected to hyperbaric conditions and quickly returned to atmospheric pressure. Following this treatment, they were exposed to spatial average, pulse average intensities of 100 W/cm2 (2.2-MHz, 20-microseconds pulses with a duty cycle of 1/1000 or a temporal average spatial average intensity of 0.1 W/cm2). Fetal weights, deaths and malformations were scored. No statistically significant effects were observed in the offspring.

Animals↗
PubMed1991

Influence of rapeseed meal, whole rapeseed, and soybean meal on fatty acid composition and cholesterol content of muscle and adipose tissue from ram lambs.

Twenty-four Suffolk x Hampshire ram lambs (average 46 kg) were assigned to one of three diets containing rapeseed meal (RM), soybean meal (SBM), or whole rapeseed-soybean meal (RSSBM) as the protein source. Diets contained 75% roughage, 14% CP and 2.0 Mcal of ME/kg and lambs were allowed ad libitum access to diets for 35 d. Lipid composition of the longissimus, semimembranosus, and triceps brachii muscles and their corresponding s.c. adipose tissue was determined by gas-liquid chromatography (GLC). The total lipid content in either muscle or subcutaneous fat was not different (P greater than .01) by diet. In lean tissue, palmitic and palmitoleic acids were higher and stearic acid was lower (P less than .01) in rams fed RM than in rams fed RSSBM or SBM, regardless of anatomical location. In the s.c. adipose tissue, the amounts of myristoleic, pentadecylic, and palmitoleic acids were lower and the amount of stearic acid was higher (P less than .01) in rams fed RSSM than in those fed RM or SBM, regardless of anatomical location. The semimembranosus and triceps brachii muscles from all treatments contained 12 to 19% more polyunsaturated fatty acids (PUFA) than the longissimus muscle. The cholesterol content of the three muscles was highest in SBM-fed lambs, lowest in RM-fed lambs, and intermediate in RSSBM-fed lambs. These results demonstrate that dietary treatments of the types used in the present study elicit changes in fatty acid composition of both adipose and muscle tissue without affecting the quantity of total lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

Prenatal and postnatal consequences in the brain and behavior of rats exposed to ultrasound in utero.

As a result of a prior experiment demonstrating damage to the developing cortex of the fetal rat 24 hours after maternal exposure to ultrasound, postnatal consequences of similar exposure on rat behavior were examined. No decrease in postnatal weight or growth rate was found and no significant decrease in cortical thickness was present postnatally at 28 days. In two of four behavioral tests, rats exposed to ultrasound in utero resembled similarly treated controls. In one test, ultrasound-exposed rats showed slower performance, and in one, faster performance. These data provide no consistent evidence that ultrasound exposure resulted in deleterious postnatal effects.

Animals↗
PubMed1991

Basic animal research.

Recent research with animal models of the fetal alcohol syndrome has resulted in advances in the areas of prenatal and postnatal growth retardation, facial dysmorphology, immune system deficiencies, endocrine dysfunction, and central nervous system alterations, including behavior. The rat is the most common species used in these studies, although similar experimental changes have been produced in a limited number of studies in other species. The specific deleterious effects of ethanol on the fetus are dose-related and dependent on the stage of gestation, as with other fetotoxic agents. However, the precise timing and dose-effect curves have yet to be established for most types of ethanol-induced damage. Various exposure regimens have been employed, including inhalation of ethanol vapor and intraperitoneal injection, as well as oral exposure by gavage, diet, or drinking water. In the early postnatal period, following gestational exposure, altered function is most marked, with recovery in some measurements with postnatal maturation. The present literature clearly defines developmental damage from gestational exposure to ethanol as well as areas for additional research.

Animals↗
PubMed1990

Acute response of the fetal telencephalon to short-term maternal exposure to ethanol in the rat.

Pregnant rats were exposed to either ethanol (total dose 18 g/kg) on gestational days 14 and 15 or whole-body ionizing radiation (0.5 Gy) on gestational day 15. On gestational day 16, 24 h following the last dose of ethanol or exposure to ionizing radiation, the developing cerebral cortex of the fetus was examined histologically. Ionizing radiation caused extensive cell death within the fetal cerebral cortex whereas ethanol caused more subtle morphological changes such as cortical thinning and petechial intraventricular hemorrhages. These findings suggest that ethanol, unlike ionizing radiation, acts by some mechanism other than cell death to cause cortical thinning and cortical malformations. The pathogenesis of ethanol-induced cortical dysgenesis may include fetal hypoxia and inhibition of neuroblast proliferation within the developing cerebral cortex.

Animals↗