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Biomedical subjects

J L Atkinson

Publications and source records attributed to J L Atkinson.

64 records · Page 4Linked to original sources
PubMed1989

Angiographic frequency of anterior circulation intracranial aneurysms.

A retrospective angiographic analysis was designed to extrapolate the frequency of angiographically defined asymptomatic intracranial aneurysms in the anterior circulation from a relatively unbiased clinical series. A total of 9295 angiograms were reviewed from January, 1980, to January, 1987, and, based on these, 278 patients with minimal bias for the presence of an aneurysm were selected. Three patients were found to have incidental aneurysms; thus, the angiographic frequency of patients with asymptomatic aneurysms in this series was 1%. This patient population is skewed toward the older age groups and probably over-represents the incidence of these aneurysms in the population at large. Comparing current subarachnoid hemorrhage statistics and the low frequency of asymptomatic aneurysms suggests that a larger percentage of these aneurysms than was previously thought subsequently rupture. This study contrasts sharply with previous reports quoting a high incidence of aneurysms, and significantly alters the concept and treatment of this disease.

Adolescent↗
PubMed1988

Heparin-induced thrombocytopenia and thrombosis in ischemic stroke.

We reviewed the records of all patients who underwent carotid endarterectomy at our institution during the period from January 1970 through December 1986 to determine the frequency of postoperative occlusions and the role of heparin-induced thrombosis in patients with such occlusions. After 2,527 carotid endarterectomies, a total of 19 occlusions occurred in 18 patients. Of these 18 patients, 6 had an associated heparin-induced coagulation disorder, 3 of whom are described in detail. Although heparin is a useful anticoagulant, it may precipitate occlusion of vessels after an endarterectomy procedure, either at the endarterectomy site or elsewhere. Physicians should be aware of the potentially increased risk for embolic or thrombotic cerebrovascular events in patients who receive heparin therapy.

Aged↗
PubMed1987

Evaluation of the net energy value of glucose (cerelose) and maize starch in diets for rainbow trout (Salmo gairdneri).

1. Quadruplicate groups of rainbow trout (Salmo gairdneri) (mean body-weight 24.9 g) were reared on six dietary treatments (practical-type diets) in a modified paired-feeding experiment for 12 weeks at 15 degrees to determine the net energy (NE) value of starch and glucose to rainbow trout. 2. Three test diets were prepared to contain (g/kg): 0 supplemented carbohydrate (diet 1), 250 maize starch (diet 2) and 250 glucose (diet 3) and were given ad lib. to the trout with the feeding rate of the glucose- and starch-fed groups being monitored after each feeding. The remaining three treatments involved controlled feeding of the trout with diet 1 at 75% of the feed intake of trout reared on diets 2 and 3, so as to provide the same levels of protein and lipids without carbohydrate, and with diet 2 at 100% of the feed intake of trout reared on diet 3. 3. The difference in the final carcass energy of the ad lib.-fed group and the respective controlled-fed group divided by the amount of dietary glucose or starch energy consumed by the trout is the NE value for that carbohydrate. 4. The determined NE value of glucose was 3.99 kJ/g and starch 2.17 kJ/g, which is 24.6 and 12.6% respectively of the gross energy values of these carbohydrates in rainbow trout. 5. The results indicate that digestible energy and calculated metabolizable energy values for carbohydrates in rainbow trout overestimate the utilizable energy content of the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Proline as an essential amino acid for the young pig.

1. The catabolism of L-[1-14C]phenylalanine was used to indicate the effects of single amino acid supplementation of an inadequate protein diet (200 g crude protein (nitrogen x 6.25)/kg) on the utilization of dietary amino acids in pigs of 2.5 kg body-weight reared on an adequate protein diet (240 g crude protein/kg) containing skim milk and a mixture of free amino acids. 2. The oxidation of phenylalanine was decreased by the addition of proline or arginine to the inadequate protein diet but not by the addition of threonine, methionine, lysine or a mixture of essential amino acids, indicating that proline and arginine were limiting the utilization of dietary amino acids in the inadequate protein diet. 3. Dietary proline concentrations of 13.9 and 14.2 g/kg minimized phenylalanine oxidation in diets containing 200 or 260 g protein/kg. This indicates a dietary proline requirement of 14 g/kg. 4. Increasing the dietary arginine concentration in a diet containing 240 g protein/kg showed that an arginine concentration of 5.1 g/kg minimized phenylalanine oxidation. However, increasing the arginine concentration in a diet containing 200 g protein/kg increased phenylalanine oxidation, suggesting an amino acid imbalance involving arginine at this lower level of protein.

Amino Acids, Essential↗
PubMed1982

Response of rainbow trout (Salmo gairdneri) to increased levels of available carbohydrate in practical trout diets.

1. The physiological response of rainbow trout (Salmo gairdneri) reared on different levels of available carbohydrate in practical trout diets having the same levels of energy and nitrogen for 16-24 weeks was determined. 2. Weight gain was significantly reduced in trout reared on the highest level of available carbohydrate, 210 g cerelose (alpha-glucose) kg, and there was a significant linear regression (R2 0.88 of dietary carbohydrate on weight gain. 3. Liver: body-weight values and liver glycogen levels increased in relation to increased dietary carbohydrate. 4. Liver glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity increased and liver phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity decreased per kg body-weight of fish with increasing dietary carbohydrate. However, no significant effect was noted on the activity of these liver enzymes above a dietary cerelose level of 140 g/kg. 5. Liver fructose diphosphatase (EC 3.1.3.11) activity increased with increasing dietary carbohydrate has been interpreted as meaning a recycling of triosephosphate to glucose-6-phosphate. 6. Dietary carbohydrate level had no significant effect on the liver pyruvate kinase (EC 2.7.1.40) activity, the rate of glucose utilization or the percentage conversion of [14C]alanine to glucose in the plasma of trout. 7. The results indicate that rainbow trout have a limited ability to adapt to increased dietary carbohydrate and a level in excess of 140 g/kg of the diet is not efficiently utilized.

Alanine↗
PubMedDate not supplied

A combined, minimally invasive transnasal approach to the sella turcica.

The increasing use of endonasal techniques and a new 3-dimensional CT-guided imaging system have allowed us to develop a combined, minimally invasive endonasal approach to the pituitary gland. Thus far, more than 30 patients have undergone an endonasal transsphenoidal approach to the sella using a combined endoscopic approach, with additional selective use of the Instatrak CT-guided imaging system for real-time imaging. Our current technique involves obtaining a preoperative CT using a plastic head frame with registration markers. By using this head frame intraoperatively, real-time localization with CT images in axial, coronal, and sagittal planes can be performed. Using endoscopic techniques and a Papavero-Caspar speculum, the sella is exposed. A combined approach using endoscopes, the operating microscope, and real-time localization is undertaken to expose and resect tumors. We have encountered minimal associated complications in our series, and this method has been progressively modified to improve exposure and safety. Because we are able to visualize the sella without a sublabial incision or septal resection, we have nearly eliminated the need for nasal packing, reduced the average hospital stay to 2.5 days, and improved patient satisfaction.

Adolescent↗
PubMedDate not supplied

Endoscopic transnasal pituitary surgery: report on 180 cases.

The endoscopic transnasal approach is an evolving technique for treating lesions in the sella turcica. Since this method was introduced at our institution 4 years ago, the majority of transsphenoidal procedures are performed with it. The records of all patients having endoscopic transnasal hypophysectomy at the Mayo Clinic during the last 4 years were reviewed retrospectively. The criteria analyzed were safety, functional and cosmetic outcome, and complications. During the 4-year period, the operative procedure was modified to improve operative exposure and safety. The results of our review showed a significant decrease in length of hospital stay, reduced operative time, reduced need for nasal packing, and elimination of a sublabial incision. The complication rate was equivalent to that reported for the traditional transseptal transsphenoidal approach. As the neurosurgeons at our institution gained experience with this approach, an increasing number of pituitary microadenomas were resected safely and successfully. In addition, because of the limited septal dissection, this approach is particularly helpful for revision operations. This approach also can be used for the full range of pituitary lesions and in conjunction with adjunctive techniques, including frontal craniotomy and gamma-knife irradiation. Currently, the endoscopic transsphenoidal approach is the method preferred for surgically treating pituitary lesions in adults at our institution.

Adenoma↗