Plant Nucleases: V. Survey of Corn Ribonuclease II Isoenzymes

Corn (Zea mays L.) ribonuclease II of the root microsomal fraction was isolated from 11 inbreds and seven hybrids. Polyacrylamide gel electrophoresis revealed a total of five bands of activity among corn lines tested. Most inbreds had only one isoenzyme, but three had two isoenzymes. The hybrids tested contained all of the isoenzymes found in the parental inbreds.     

Light-harvesting pigment-protein complex deficiency in Hosta (Liliaceae)

A yellow-leaved plastome mutant of Hosta (Hosta sieboldii Ingram complex, Liliaceae) known as Wogan Gold lacks normal granal stacks, but has numerous stroma lamellae extending throughout the chloroplast. The chlorophyll a/b ratio is 0.76 in the mutant and 2.9 in wild type. The mutant contains a qualitatively normal pattern of other photosynthetic co-pigments. SDS-polyacrylamide gel electrophoresis showed a deficiency in the photosystem (PS) II light-harvesting complex. Since PS II is localized mainly in the granal region, the absence of the light-harvesting complex may explain the loss of granal stacking in this mutant.Abbreviation PS photosystem     

Death on Denali: Fatalities Among Climbers in Mount McKinley National Park From 1903 to 1976—Analysis of Injuries,Illnesses and Rescues in 1976

Between 1903 and 1975 about 1 percent of climbers on Mount McKinley (Denali) and Mount Foraker in Alaska died. In 1976 a total of ten (1.7 percent) of 587 mountaineers died, but this rate of death was not significantly higher than previously.Nineteen percent of climbers in 1976 suffered major or minor injuries, illness or death. Acute mountain sickness (AMS), frostbite and fractures were common. Thirty-three rescues or retrievals of bodies were mounted at a cost of more than $82,000.Inexperience (particularly with arctic mountaineering), poor leadership, faulty equipment and undue reliance on rescue by helicopter contributed to the alarming incidence of accident, illness and death on big peaks in Mount McKinley National Park in 1976.     

Plane penetration of uterine muscle by intrauterine shields

A finite element approach is used to predict stress and deformation states of uterine muscle tissue under plane strain indentation by a flexible shield. Realistic, one-dimensional "punch" elements at the shield edges assure that muscle shear stresses remain bounded within experimentally measured values. For typical tissue, bearing pressure, deformation flow fields and edge slip stresses leading to tissue damage are calculated. Penetration depth to shield width ratios are up to 3.0. A piecewise linear, elastic approximation to the highly variable, nonlinear mechanical behavior of the tissue is used. Results are applied to the prediction of possible tissue damage by a flexible shield intrauterine contraceptive device, in place and in equilibrium with typical multiparous uteri.     

Amaurosis fugax and carotid artery disease: indications for angiography.

A prospective study of 80 patients presenting with amaurosis fugax was performed in an attempt to relate clinical features to angiographic findings in the internal carotid artery. Carotid bruit, transient cerebral ischaemic attacks, hypertension, and claudication were associated with a high prevalence of angiographic abnormality. Every patient who showed all these features had an operable lesion, as did 88% of those who had three features. In patients over 50 years of age carotid stenosis and atheromatous ulceration were occasionally found in the absence of bruit and transient cerebral ischaemia, but only one patient aged under 50 had an operable lesion and no associated features. Clinical features were therefore valuable in predicting the outcome of angiography, but it seems prudent to restrict angiography to patients aged over 50, who are most likely to benefit from surgery on the carotid artery.     

Prospectively randomised trial of proximal gastric vagotomy either with or without pyloroplasty in treatment of uncomplicated duodenal ulcer.

A consecutive series of 100 men with uncomplicated duodenal ulcer was randomly divided into two groups: one group of 52 underwent proximal gastric vagotomy (PGV), the other group (48) underwent PGV with pyloroplasty (PGVP). Preoperative peak acid output (PAOP) was measured in all patients. Those with a higher preoperative PAOP were significantly more likely to develop recurrent ulceration. Three patients developed recurrent ulceration after PGV and seven after PGVP. Dumping was both more common and more severe after PGVP than PGV. An overall satisfactory result was achieved in 92% after PGV and 81% after PGVP. We conclude that combining pyloroplasty with PGV has no appreciable advantages.     

Inhibition of lymphoma cell proliferation by supernatant from fibrosarcoma cultures: Preliminary evidence that the inhibitory material is prostaglandin E

Supernatants obtained from mouse fibrosarcoma cultures 48 hr after the addition of fresh medium contained dialyzable material which inhibited the proliferation of syngeneic lymphoma cells , as measured by ³H-thymidine incorporation. Three lines of evidence indicate that the supernatant inhibitory material is probably prostaglandin (PG) E. First, the supernatant and dialysate of the supernatant contained a substance with the same characteristics as PGE₁ or PGE₂ as detected by thin layer chromatography. Second, PGE₂-treatment of lymphoma cells mimicked the inhibition of proliferation observed with supernatant inhibitory substance. Third, indomethacin treatment of fibrosarcoma cultures reduced the amount of supernatant inhibitory substance present.     

The spatial frequency sensitivity of bipolar cells

Retinal bipolar cells constitute the output stage of the outer layer of the retina. There are several constraints on the ability of the bipolar cell array to respond to the different spatial frequency components of the visual image, including (i) electrical coupling in the dendritic tree receiving receptor input; (iii) the "lateral inhibition" mediated by horizontal cells. Using simple mathematical models, we derive analytical expressions for the spatial frequency response of the bipolar cell array for the case in which horizontal cells are presynaptic to bipolar cells (feedforward model) and also for the case in which horizontal cells are presynaptic to receptors (feedback model). The results illustrate the importance of the three factors mentioned in determining the bipolar cells' properties. The optimal spatial frequency for stimulating the bipolar cell array, and the range of spatial frequencies transmitted onward to the inner plexiform layer, are thus related to the anatomical and electrical properties of the cells in the outer plexiform layer.