Showing papers by "Virginia Commonwealth University published in 1976"

Retinal sensitivity to damage from short wavelength light

Abstract: A GROWING body of literature attests to the deleterious effects of long term exposure to light1–8. To define more critically the differences between thermal and photochemical effects, we have exposed the retinae of rhesus monkeys to eight monochromatic laser lines from 1,064–441.6 nm. Thermal damage to the retina is to be expected for the 1,064-nm line since the photopigments are not involved and energy absorption takes place predominantly in the melanin granules of the pigment epithelium and the choroid. Although data on pathogenesis are not yet available, we found some interesting differences in retinal sensitivity in going from the near infrared to the blue wavelengths in the visible spectrum.

Antagonism of stimulation-produced analgesia by naloxone, a narcotic antagonist

Abstract: Analgesia produced by focal electrical stimulation of the brain is partially reversed by the narcotic antagonist naloxone. The absence of complete reversal does not appear to be caused by inadequate doses of naloxone since doses higher than 1 milligram per kilogram of body weight did not increase the antagonism. It is suggested that stimulation-produced analgesia may result, at least in part, from release of an endogenous, narcotic-like substance, such as that recently reported by other investigators.

Patterns of Lipid Storage and Utilization in Birds

Abstract: synopsis. Nowhere among the vertebrates does the capability for storing and using triglyc? eride as an energy reserve exceed the level found in the class Aves. Adult avian depot fats are composed largely of 16- and 18-carbon fatty acids and are mostly unsaturated. Variation in fatty acid composition among species may be attributed to dietary differences and physiological state of the bird. Storage occurs mainly by addition of lipid to adipocyte vacuoles without an increase in cell number. Daily cycles of fat deposition and use are of greater amplitude at higher latitudes, but in general the lipid stored during the day will only provide energy for the overnight fast plus a few daylight hours. Storage levels may be minimized due to the disadvantages of increased wing-loading. A variety of behavioral, physiological and morphological adaptations may be used to reduce the need for overnight energy reserves. Migratory fattening is largely a function of migration speed, magnitude of barriers to be crossed and aerodynamic considerations. Lipid reserves are greatest in eggs of precocial birds and are retained longer in precocial young. Adaptive strategies of fat deposition in young birds are related largely to the ability of adults to feed young before and after fledging.

Polyimide structure-property relationships. II - Polymers from isomeric diamines

Abstract: An extensive study of the effects of stereoisomeric variations in aromatic polyimide structures on polyimide properties was conducted. The structural variations were incorporated into the polyimides through the use of two complete series of isomeric aromatic diamine monomers, the diaminodiphenylmethanes and the diaminobenzophenones, as well as several pairs of diamine isomers. The ability of the diamines to polymerize was related to the basicities, and thus reactivities, of the amino groups. Diamines with an amino group located ortho to the group connecting the two aromatic rings were successfully polymerized with dianhydrides for the first time to high molecular weight poly(amic acids). The stereoisomeric polyimides were characterized by determining the glass transition temperatures Tg, mechanical properties, and thermooxidative stabilities of thin films of the polymers. The polymers prepared from p-diamines were shown to have the highest softening points and thus, the most rigid molecular structures. Those synthesized from m-diamines had the lowest Tg values, inferring the most flexible molecular backbone. With limited exceptions, the use of diamines with ortho-oriented amine groups failed to improve the flexibility of the polyimides since their Tg values were usually as high as those of polymers made from p-diamines. Only slight differences in mechanical properties of the isomeric polyimide films were attributable to the variations in isomeric structure, except for those properties dependent upon Tg changes, such as elevated temperature mechanical properties. A study of the thermooxidative stability of the polyimides showed little difference between the polymers prepared from the diaminobenzophenones, but marked differences were observed between the individual members of the diaminodiphenylmethane-derived polyimides.

Mechanism of action of methotrexate. IV. Free intracellular methotrexate required to suppress dihydrofolate reduction to tetrahydrofolate by Ehrlich ascites tumor cells in vitro.

Abstract: Incubation of Ehrlich ascites tumor cells in vitro with [3H]dihydrofolate results in its rapid conversion to [3H]tetrahydrofolate and other radiolabeled compounds, so that dihydrofolate cannot be detected in the cell. When cells are exposed to 10µM methotrexate for 30 min, a condition sufficient to generate intracellular methotrexate in excess of the tightly bound fraction within the cell (exchangeable methotrexate), following which exchangeable intracellular methotrexate is eliminated, conversion of dihydrofolate to tetrahydrofolate is negligibly affected. Even when cells are maintained in a medium containing 0.05 µM methotrexate, following exposure to 10 µM methotrexate, there is virtually no inhibition of dihydrofolate metabolism. However, as the extracellular methotrexate level is increased to 0.1, 1.0, and 10 µM in the second incubation, there is progressive inhibition of tetrahydrofolate synthesis along with a progressive increase in the level of dihydrofolate within the cells, complete at the highest methotrexate concentration employed. Fifty percent inhibition of the cell tetrahydrofolate level requires an extracellular methotrexate concentration of approximately 0.2 µM, comparable to an exchangeable intracellular level of about 0.15 µM. In contrast to the results with dihydrofolate, after treatment of cells with 10 µM methotrexate for 30 min followed by removal of exchangeable drug, there is marked (approximately 85%) inhibition of folic acid reduction to tetrahydrofolate. Residual reduction of folic acid is completely eliminated when the cells are continuously exposed to 10 µM methotrexate. The requirement for free intracellular methotrexate to abolish tetrahydrofolate synthesis appears to be the basis for the observations from this laboratory that free intracellular methotrexate is necessary to suppress [3H]deoxyuridine incorporation into DNA and [14C]formate incorporation into RNA, DNA, and protein. The demonstration in other studies that mammalian cells have a limited capacity to accumulate free intracellular methotrexate supports the concept that this intracellular component of the drug may be an important determinant of cytotoxicity.

Modulation of Ca2+ control of dog and rabbit cardiac myofibrils by Mg2+. Comparison with rabbit skeletal myofibrils.

Abstract: Increases in free Mg2+ from 0.04 to 10.0 mM with constant pH 7.0 TO 0.10 M ionic strength, and 2 mM MgATP2- caused a rightward shift of the free Ca-relative ATPase relation for both cardiac skeletal myofibrils. The specific activity of cardiac myofibrillar ATPase over a wide range of free Ca2+ was, however, depressed in 0.04 vs. 1.0 mM Mg2+, whereas a similar decrease in free Mg2+ slightly enhanced skeletal myofibrillar ATPase. Lowering free Mg2+ from 1.0 to 0.04 mM caused similar increases in cardiac and skeletal myofibrillar bound calcium, which were largely attributable to increased calcium binding to myofibrillar myosin. Raising free Mg2+ from 1.0 to 10.0 mM caused only a slight decrease of skeletal myofibrillar bound calcium, and this change was attributable to myofibrillar myosin. The same increase in free Mg2+ caused cardiac myofibrils to bind increased amounts of calcium and this change was not attributable to myofibrillar myosin. By subtracting calcium bound to myofibrillar myosin, we were able to estimate calcium binding by myofibrillar troponin. The transition between basal and maximal ATPase in 1.0 and 10 mM Mg2+ was found to be assocciated with binding of an additional 2 mol/mol of either skeletal or cardiac myofibrillar troponin.

Inadequate parathyroid response in acute pancreatitis.

Abstract: We studied nine consecutive hypocalcemic patients with acute pancreatitis to elucidate the mechanism of hypocalcemia. Mean serum ionized calcium, 0.97 mM, was below the normal mean of 1.16 mM (P less than 0.001). Seven of eight patients tested had normal parathyroid hormone levels. All responded to parenteral parathyroid extract by increasing serum ionized calcium and urinary cyclic AMP, indicating parathyroid-hormone-responsive target organs. Calcitonin and glucagon concentrations were increased above normal in some patients, but there was no relation with serum ionized calcium. Parenteral glucagon had no significant effect on serum ionized calcium or calcitonin concentrations. These findings suggest that neither glucagon nor calcitonin was primarily responsible for the hypocalcemia, which did not produce expected increases in serum parathyroid hormone concentrations. Relative parathyroid insufficiency may account for the persistent hypocalcemia frequently observed in patients with acute pancreatitis.

Substance stimulating the differentiation of spores of the blue-green alga Cylindrospermum licheniforme

Abstract: THE study of intercellular inductions in higher plants and animals is hindered by the complexity of the multicellular tissues involved. Sporulation of filamentous blue-green algae is a relatively simple process to study because these algae contain, in linear array, only three types of cells. There are vegetative cells, and heterocysts and spores which form by differentiation of vegetative cells. Wolk1,2 showed that heterocysts of the blue-green alga Anabaena cylindrica Lemm. induce adjacent vegetative cells to differentiate into spores. We report here that a substance produced by the related alga, Cylindrospermum licheniforme, greatly stimulates sporulation of that same alga.

In-Home Shoppers—An Overview: This article reviews findings on in-home shoppers and points out further research needs.

Abstract: U NTIL quite recently, marketing literature overlooked shopping at home as a significant contributor to retail sales. Today, after years of relative neglect by marketing authors, in-home retailing is becoming recognized for what it has been for several decades: a modem, fast-growing, urban-oriented method of selling.' This recognition of in-home retailing's promise has produced a growing literature profiling the in-home shopper. The published studies, still relatively few, reveal some useful insights on in-home shoppers and shopping, but the evidence is scattered, sometimes conflicting, and a clear picture of the inhome shopper has yet to emerge. This article reviews available findings in an attempt to clarify what is known and not yet known about this promising market. It is perhaps useful to look first at in-home expenditures on both aggregate and household levels. An overview of these data illustrates both the growing size and diversity of the in-home market.

Cutaneous protothecosis. Successful treatment with amphotericin B.

Abstract: • A patient had cutaneous protothecosis because of the alga-like organism, Prototheca wickerhamii . In vitro sensitivity tests showed that the organism was sensitive to amphotericin B, and the patient was treated successfully with this polyene antibiotic. As with treatment of some fungal infections, a clinical response was achieved when therapy with low doses of amphotericin B was given during a short period of time. The basis of the amphotericin B response may have been due to a combination of its immunostimulatory and antibiotic properties. ( Arch Dermatol 112:1749-1752, 1976)

The Impact of Devotionalism and Attendance on Ordinary and Emergency Helping Behavior

Abstract: In this study a theoretical model is presented which highlights the reinforcing potential of religious reality construction and the mobilizing potential of formal religious organizations. It is hypothesized that rates of devotionalism (a measure of the intensity of religious organizational participation) are positively related to the performance of helping behavior. A qualification by type of helping behavior (emergency or ordinary) is presented. Sequential stepwise multiple regression analysis indicated that devotionalism was a predictor of three of the four types of ordinary helping behavior examined while church attendance consistently predicted emergency helping behavior. The introduction of a subjective religiosity measure did not increase the R2. The effect of church attendance on emergency helping behavior is found to be primarily through churches' provision of organizational means for participation. Implications of the findings for the exchange-reinforcement perspective are discussed.

Exchangeable Intracellular Methotrexate Levels in the Presence and Absence of Vincristine at Extracellular Drug Concentrations Relevant to Those Achieved in High-Dose Methotrexate-Folinic Acid “Rescue” Protocols

Abstract: Studies were undertaken to ( a ) assess intracellular methotrexate (MTX) levels at extracellular drug concentrations comparable to those achieved in high-dose MTX-folinic acid rescue protocols and ( b ) establish whether there is a rationale for the use of vincristine in these regimens. The data indicate that only low levels of exchangeable MTX (intracellular MTX in excess of the tightly bound fraction) accumulated in Ehrlich ascites tumor cells at high extracellular MTX concentration. For instance, the exchangeable steady-state intracellular MTX level was ∼6.5 μm when the extracellular drug concentration was 85 μm. Over the interval of these experiments, exchangeable intracellular MTX did not exceed ∼10 μm even when extracellular MTX was raised to 250 μm. These exchangeable intracellular MTX concentrations are comparable to those levels required experimentally to suppress ( a ) tetrahydrofolate synthesis from dihydrofolate and ( b ) tetrahydrofolate-dependent purine, pyrimidine, and amino acid synthesis in these cells in vitro . Vincristine (10 μm) augmented net MTX accumulation when the extracellular MTX level was 10, 100, or 250 μm. The limited capacity of cells to accumulate exchangeable intracellular MTX and the apparent role for this intracellular MTX component in achieving the metabolic effects of this agent may account for the necessity for high MTX blood levels in the treatment of some tumors and may be the basis, in part, for the enhanced chemotherapeutic efficacy of high-dose MTX regimens. These studies provide a rationale for the combined use of vincristine and MTX in high-dose MTX protocols. The addition of vincristine may permit the achievement of the level of exchangeable intracellular MTX that is required to critically inhibit tetrahydrofolate synthesis without an increase in the extracellular MTX concentration. This may permit a reduced MTX dose, diminishing the excretory load on the kidney and minimizing nephrotoxicity due to deposition of MTX in the renal tubule and interstitium. While the data indicate that the ratio of the concentration of exchangeable intracellular MTX to the extracellular drug concentration may be very low under steady-state conditions at high extracellular drug levels, further studies are required to establish that these steady-state gradients for MTX represent nonequilibrium conditions.

Time and frequency resolution of CS2 fluorescence excited by a nitrogen laser

Abstract: The fluorescence of CS 2 vapor, excited by a nitrogen laser, is dispersed. It reveals several identifiable ν″ 2 progressions in the near ultraviolet and irregular bands overlying an apparent continuum in the visible. Temperature studies indicate that the spectrum is temperature sensitive and that the banded structure is principally due to excitation from ν″ 2 = 1 while the continuum is from ν″ 2 = 2. Time resolved studies confirm a two exponential decay and assign the shorter (2.9 μs) lifetime to the bands and the longer (17 μs) one to the continuum. It is suggested that the laser populates two vibronic levels of the T 1 A 2 state and that these two levels have different radiative properties. Reasons for this difference and the nature of the continuum are discussed.

Effects of phototherapy on platelet counts in low-birthweight infants and on platelet production and life span in rabbits.

Abstract: The effects of conventional phototherapy on platelets in vivo were studied in rabbits and in low-birthweight infants. Rabbits were divided into three groups and individually treated continuously for 96 hours, with blue light, daylight, or no phototherapy. Incorporation of selenomethionine Se75 was used to evaluate platelet production and life span. Platelet turnover was significantly increased in the blue-light phototherapy group, and was also increased in the daylight group but to a lesser degree. Daily platelet counts and hematocrits were performed in infants weighing less than 2,000 gm at birth randomized at 24 +/- 12 hours of life to receive daylight phototherapy continuously for 96 hours (31 infants) or no phototherapy (26 infants). In 12 treated infants (38.7%) platelet counts fell below 150,000/cu mm whereas this occurred in only 3 (11.5%) of the controls. These two lower platelet count subgroups differed significantly in mean gestational age and birthweight with the phototherapy group being the more mature. Pre-phototherapy, the mean platelet count of these 12 infants was lower than the mean of the entire control group, suggesting that these infants had borderline marrow reserve before phototherapy was given. These results suggest that phototherapy increases the rate of platelet turnover. When bone marrow compensation is inadequate, the platelet count may fall.

Antagonism of stimulation-produced analgesia by naloxone, a narcotic antagonist

Abstract: Analgesia produced by focal electrical stimulation of the brain is partially reversed by the narcotic antagonist naloxone. The absence of complete reversal does not appear to be caused by inadequate doses of naloxone since doses higher than 1 milligram per kilogram of body weight did not increase the antagonism. It is suggested that stimulation-produced analgesia may result, at least in part, from release of an endogenous, narcotic-like substance, such as that recently reported by other investigators.

Aflatoxin occurrence on raw and cooked york soybeans inoculated with three aspergillus isolates.

Abstract: Raw and cooked soybean media were inoculated in separate experiments with Aspergillus flavus NRRL 3251, A. flavus ATCC 15548, and A. parasiticus NRRL 2999 isolates. The toatl quantity of aflatoxins produced and the percentage distribution of aflatoxins B1, B2, G1, and G2 varied with the state of the medium (raw or cooked) and with the fungal isolate used. Cooked soybean medium supported higher aflatoxin productions by A. flavus NRRL 3251 and A. parasiticus NRRL 2999 than did raw medium. Larger quantities of aflatoxins B1, B2, G1, and G2 were produced by A. flavus ATCC 15548 on raw soybean medium than were produced by any of the isolates on cooked medium. Application of these data is discussed briefly in relation to possible use of soybean media as a source of aflatoxin production.

Investigating Group Differences An Explication of the Sociological Potential of Discriminant Analysis

Abstract: Frequently, sociologists encounter research problems which call for assessing the extent to which two or more categories of people or events can be maximally distinguished from one another with respect to a number of common variable attributes. Unfortunately, predictive models which evidently accomplish just this, in addition to providing rules for the classification of new entities, have been conspicuously absent from the literature. Discriminant analysis, a multivariate technique extensively employed in physical anthropology, clinical psychology, and the biological sciences, has made scant headway in sociology, even though many of our most interesting substantive investigations are clearly amenable to it. The purpose of this paper, then, is first to suggest numerous research situations in which two-group and multiple discriminant analyses might be productively applied. By way of illustration, a brief example of the use of discriminant analysis for data on student politics will be presented. Second, the ...

Multiple lead ECG submaximal treadmill exercise tests in angiographically documented coronary heart disease.

Abstract: One hundred patients underwent submaximal exercise tolerance testing and coronary cineangiography. Sixty-six percent of the exercise tests were diagnostic including 48 positive and 18 negative tests; 34 patients had indeterminate test results. The occurrence of exercise induced ventricular premature beats was not related to significant coronary artery disease. Ventricular asynergy was significantly more frequent in patients with positive exercise tests (p less than .0001). Application of the age-adjusted target heart rate criterion recommended from Scandinavia and Myrtle Beach to patients with indeterminate results due to failure to reach target heart rate resulted in six false negative tests and lowered sensitivity. The number of positive diagnostic responses achieved using a multiple electrocardiographic lead system was compared with positive diagnostic responses detected in a single lead (V5) and the number of positive tests identified by the additional leads was highly significant (p less than .0001). A high incidence of indeterminate test results due to failure to achieve target heart rate is noted.