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Biomedical subjects

C J Andrews

Publications and source records attributed to C J Andrews.

At least 37 records · Page 2Linked to original sources
PubMed1985

Effect of low temperature and calcium on survival and membrane properties of isolated winter wheat cells.

Isolated cells obtained by enzymic digestion of young primary leaves of cold-hardened, dark-grown Kharkov winter wheat (Triticum aestivum L.) were exposed to various low temperature stresses. The initial uptake of (86)Rb was generally decreased by increasing concentrations of Ca(2+), but after longer periods of incubation, the inhibiting effect of high Ca(2+) levels diminished. Viability of isolated cells suspended in water declined rapidly when ice encased at -1 degrees C, while in the presence of 10 millimolar Ca(2+) viability declined only gradually over a 5-week period. Ice encasement markedly reduced (86)Rb uptake prior to a significant decline in cell viability or increased ion efflux. Cell damage increased progressively when the icing temperature was reduced from -1 to -2 and -3 degrees C, but the presence of Ca(2+) in the suspending medium reduced injury. Cell viability and ion uptake were reduced to a greater extent following slow cooling than after rapid cooling to subfreezing temperatures ranging from -10 to -30 degrees C. The results from this study support the view that an early change in cellular properties due to prolonged ice encasement at -1 degrees C involves the ion transport system, whereas cooling to lower subfreezing temperatures for only a few hours results in more general membrane damage, including loss of semipermeability of the plasma membrane.

Journal Article↗
PubMed1984

Efficiency of cold hardiness induction by desiccation stress in four winter cereals.

A number of defined desiccation treatments without low temperature exposure were able to induce freezing tolerance in 20 cultivars of winter cereals. A maximal degree of freezing tolerance was induced in epicotyls at 24 degrees C in 24 hours at 40% relative humidity in rye and wheat, 7 days at 54% RH in barley, and 4 days at 70% RH in oats. Freezing tolerance was not correlated to water content of the plants after desiccation treatment but was related to the genetic capacity of the cultivars to frost harden. Levels of freezing tolerance induced by desiccation were similar to those induced by cold acclimation in rye and wheat, but considerably less in barley and oats. This is associated with a more rapid desiccation injury in barley and oats, precluding the completion of the hardening process.

Journal Article↗
PubMed1984

Ventilatory effects of nitrous oxide during continuous infusion of fentanyl or alfentanil.

Two groups of eight patients received infusions of either fentanyl at 3 micrograms kg-1 h-1 or alfentanil at 20 micrograms kg-1 h-1 as supplements to 66% N2O in oxygen anaesthesia, during and after body surface surgery. At the end of surgery, the N2O was reduced to 50% and after measurement of ventilatory frequency, minute ventilation, and the ventilatory response to carbon dioxide, N2O was discontinued. The opioid infusions were continued for a further hour and the ventilatory measurements repeated. Both sets of measurements were compared with preoperative values. Minute ventilation (P less than 0.01), frequency (P less than 0.01) and the response to carbon dioxide (P less than 0.01) were reduced during the infusion of fentanyl with N2O; with fentanyl alone, minute ventilation (P less than 0.05) and the response to carbon dioxide (P less than 0.01) were reduced but to a lesser degree. The elimination of nitrous oxide from the inspired gas mixture produced an increase in frequency (P less than 0.05) and increases in the slope (P less than 0.01) and ventilation at 7.3 kPa (P less than 0.025) of the carbon dioxide response curve. Minute ventilation (P less than 0.01) frequency (P less than 0.05) and response to carbon dioxide (P less than 0.01) were all reduced during the infusion of alfentanil with nitrous oxide; with alfentanil alone, minute ventilation (P less than 0.01), tidal volume (P less than 0.05), the slope (P less than 0.025) and the ventilation at 7.3 kPa (P less than 0.01) of the carbon-dioxide response curve were still reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Anesthesia↗
PubMed1983

Interactions among Flooding, Freezing, and Ice Encasement in Winter Wheat.

Exposure of winter wheat (Triticum aestivum L.) to various combinations of flooding and freezing stresses induces much greater damage than the individual stresses. Cold-hardened plants flooded for 1 week or exposed to -6 degrees C for 1 week show 100% survival, while survival of plants exposed to both stresses simultaneously is reduced by 20 to 30%, and cold hardiness decreases by several degrees. The level of nonstructural carbohydrates increases in crown tissue during cold acclimation, but decreases when the plants are exposed to flooding or to -6 degrees C for 1 week. The respiratory capacity of crown tissue segments declines when the plants are stressed. Uptake of (86)Rb by the roots of intact seedlings declines after exposure to either freezing or flooding, whereas passive efflux of amino acids is observed after freezing but not following flooding. This study has shown that detectable stress-induced metabolic changes occur in winter wheat before the applied stress is severe enough to reduce survival.

Journal Article↗
PubMed1983

Membrane properties of isolated winter wheat cells in relation to icing stress.

Isolated cell preparations of winter wheat (Triticum aestivum L.) were utilized to examine the effect of ice encasement at -1 degrees C and exposure to ethanol on metabolic and biochemical properties of cells. Following icing and ethanol treatments, passive efflux of amino acids increased gradually with duration of exposure to the stress, and closely paralleled the decline in viability of cells. In contrast, uptake of (86)Rb declined much more rapidly than viability following exposure to icing or ethanol. Electron spin resonance spectroscopy studies revealed no significant change in molecular ordering within the cell membranes following icing or exposure to ethanol, whereas a small but significant increase in order was detected in the noniced controls. O(2) consumption by isolated cells declined only gradually due to icing and ethanol treatments, and remained relatively high even when cell viability was severely reduced. These results indicate that the plasma membrane is a primary site of injury during ice encasement and that damage to the ion transport system is the earliest manifestation of this injury.

Journal Article↗
PubMed1983

Dose-response relationships for infusions of Althesin or methohexitone.

A technique is described for the determination of equipotent rates of infusion of intravenous hypnotic agents. Two end points have been defined; the rates needed to suppress the initial response to the surgical incision in 50% (ED50) and 95% (ED95) of patients receiving continuous infusion anaesthesia to supplement 67% nitrous oxide in oxygen. For patients aged 20-60 years, and premedicated with morphine 0.15 mg/kg intramuscularly, the ED50 values for Althesin (as alphaxalone) and methohexitone by infusion were 13.7 and 48.8 micrograms/kg/minute respectively. The ED95 values were 18.1 and 75.9 micrograms/kg/minute. For patients of a similar age premedicated with diazepam 10 mg orally, the ED50 values for Althesin and methohexitone were 18.5 and 66.0 micrograms/kg/minute respectively; while the ED95 values were 24.2 and 80.8 micrograms/kg/minute.

Adult↗
PubMed1983

Ventilatory effects during and after continuous infusion of fentanyl or alfentanil.

The opioid drugs fentanyl and alfentanil were infused at a constant rate as supplements to nitrous oxide in oxygen anaesthesia throughout the period of surgery. These infusions were continued into the period after operation for 1 h after the discontinuation of anaesthesia. Continuous infusion of alfentanil 20 micrograms kg-1 h-1 and fentanyl 3 micrograms kg-1 h-1 resulted in depression of the carbon dioxide response curve with a lesser effect on frequency and minute ventilation. One hour after discontinuing the infusions the degree of ventilatory depression was only marginally less with fentanyl, but considerably less with alfentanil, reflecting the shorter terminal half-life of that drug.

Adult↗
PubMed1979

Toxicity of Anaerobic Metabolites Accumulating in Winter Wheat Seedlings during Ice Encasement.

Ice encasement damages cold-hardened winter wheat without major disruption of cellular organelles. CO(2) accumulates during total ice encasement to higher levels in Kharkov than in less hardy Fredrick wheat. Partial ice encasement and exposure to a nitrogen atmosphere at -1 C allows greater CO(2) accumulation but neither treatment is as damaging as total ice encasement. Lactic acid accumulates to low levels only during the 1st day of encasement and thereafter remains constant. Exposure of plants to a combination of 50% CO(2) and 5% ethanol reduces survival, with a cultivar difference similar to that found in ice-encased plants. Plants in CO(2) and ethanol show a proliferation of membranes and nuclear condensation similar to that in cells of ice-encased plants. Permeability increases markedly in the presence of CO(2) and ethanol, to levels similar to or greater than those of iced plants. Ethanol alone does not increase permeability but in combination with CO(2) raises permeability of the less hardy Fredrick, although not of Kharkov, but reduces survival of both cultivars. A comparison of the endogenous levels of ethanol, CO(2), and lactic acid at the 50% kill point of plants due to ice encasement or due to externally supplied metabolite indicates that only CO(2) accumulates to independently toxic levels. Permeability and ultrastructural evidence suggest that CO(2) and ethanol in combination are the agents reducing plant viability during ice encasement.

Journal Article↗
PubMed1979

Metabolic and ultrastructural changes associated with flooding at low temperature in winter wheat and barley.

Cold-hardened winter wheat (Triticum aestivum L. cv. Fredrick) and winter barley (Hordeum vulgare L. cv. Dover) were exposed to total flooding at 2 C. Dover seedlings were damaged more quickly than Fredrick, and after 3 weeks of flooding the survival of Dover was reduced to 10% and Fredrick to about 50%. Tissue moisture was slightly greater in Dover than Fredrick throughout the 4-week flooding period. Carbon dioxide and ethanol accumulated throughout the 4-week flooding period in both cultivars. Lactic acid increased rapidly during the 1st week of flooding, and remained relatively constant during the remainder of the flooding period. Oxygen consumption of seedling shoot tissue after exposure to flooding declined abruptly after only 1 day of flooding, but recovered somewhat during the subsequent 2 weeks. The effect of flooding was more pronounced on the ultrastructure of Dover than Fredrick. Although proliferation of endoplasmic reticulum was observed in the early stages of flooding in both cultivars, the occurrence of distinct parallel arrays and concentric whorls of membranes was prevalent in the flooded barley. Severe ultrastructural damage to a large proportion of apical cells in both cultivars was observed after 2 to 3 weeks of flooding.

Journal Article↗
PubMed1979

Ultrastructural and Enzymic Studies of Cell Membranes from Ice-encased and Noniced Winter Wheat Seedlings.

A marked increase in the amount of cisternal-like cytoplasmic membranes was observed after ice encasement of winter wheat (Triticum aestivum L.) seedlings. Linear sucrose gradients were employed to separate the various membrane components of the microsomal membrane fraction. NADH- and NADPH-cytochrome c reductase, two specific enzyme markers for plant endoplasmic reticulum (ER) were used to locate the ER in the linear gradients. The identity of the ER fraction was confirmed by determining the effect of EDTA and Mg(2+) in the preparative media on the distribution of NADH- and NADPH-cytochrome c reductase activity within the gradient. In the presence of EDTA which dissociates ribosomes from ER, peaks of activity for the two enzymes were observed at a density corresponding to that for "smooth" ER. When the media also contained an appropriate concentration of Mg(2+) to maintain the attachment of ribosomes to the ER, the peaks of activity for the enzymes shifted to a density corresponding to that for "rough" ER. NADH-cytochrome c reductase activity was similar for 24 C-grown and 2 C-grown iced seedlings, but significantly lower for 2 C noniced seedlings. No preferential increase in uptake of radioactive leucine or choline in the ER was observed during ice encasement. The accumulation of electron microscopically visible membrane arrays was not inhibited by the presence of protein synthesis inhibitors at concentrations which severely inhibited incorporation of [1-(14)C]leucine into membrane protein, but did not affect survival and growth of the seedlings. These observations indicate that the apparent proliferation of ER during ice encasement does not result from net membrane synthesis, but rather from reorganization of existing membrane elements within the cell.

Journal Article↗
PubMed1979

The relation between structure and function of bile ducts in man, some laboratory animals and the Adelie penguin.

The biliary trees of man, dog, cat, rabbit, rat, guinea pig and penguin were examined in histological sections and by latex casts. The trees of man, dog, and cat were similar with only minor differences. Tubulo-alveolar glands were present in all three species around large intrahepatic ducts and in large portal tracts there were zones of ductules (areas with many small bile ducts), surrounded by small vessels with no apparent relation to hepatocytes. Both these features were present in the guinea pig and tubulo-alveolar glands were present in the penguin liver. The biliary epithelium of the rat was comparatively simple but that of the rabbit appeared to be highly specialized. An estimation of the complexity of the biliary tree was obtained in the mammals by comparing the circumference of small portal venous branches with the circumference of the accompanying bile ducts, and obtaining a ratio. Man, dog, and cat had fewer and smaller bile ducts than the other species. The literature on the rate of formation and composition of bile in the species studied here was reviewed and it appears that the physiology of bile secretion can be related to the morphology of the biliary tree.

Animals↗
PubMed1978

Metabolic and Ultrastructural Changes in Winter Wheat during Ice Encasement Under Field Conditions.

The effect of ice encasement on the physiological, metabolic, and ultrastructural properties of winter wheat (Triticum aestivum L.) grown under field conditions was examined by artificially encasing winter wheat in ice during early winter. Cold hardiness and survival of ice-encased seedlings declined less rapidly in Kharkov, a cold-hardy cultivar than in Fredrick, a less hardy cultivar. Ethanol did not accumulate in non-iced seedlings, but increased rapidly upon application of an ice sheet. Lactic acid accumulated in both cultivars during late autumn, prior to ice encasement, and elevated levels of lactic acid were maintained throughout the winter in seedlings from both iced and non-iced plots. The rate of O(2) consumption of shoot tissue of seedlings from non-iced plots remained relatively constant throughout the winter, but declined rapidly in seedlings from ice encased plots. Major ultrastructural changes did not occur in shoot apex cells of non-iced winter wheat seedlings during cold hardening under field conditions. However, the imposition of an ice cover in early January resulted in a proliferation of the endoplasmic reticulum membrane system of the cells, frequently resulting in the formation of concentric whorls of membranes, often enclosing cytoplasmic organelles. Electrondense areas within the cytoplasm which appeared to be associated with the expanded endoplasmic reticulum were also frequently observed.

Journal Article↗
PubMed1978

Spontaneous and bile salt stimulated bile secretion in the Adelie penguin (Pygoscelis adeliae).

The flow rate and ionic composition of bile during spontaneous secretion were measured in anaesthetized penguins in which the enterohepatic circulation had been interrupted and with i.v. injection of saline to replace secretory loss. During the first two hours the rate of flow increased, and then remained relatively constant for a further two and a half hours. During this time the concentration of bile salt fell, but the concentrations of other ions showed small fluctuations only. Sodium taurocholate increased the rate of bile flow and the excretion of ions, except that of bicarbonate. Sodium taurolithocholate initially produced cholestasis but later apparently increased bile flow and had an overall choleretic effect. It is suggested that the active excretion of bicarbonate ions by the bile ducts is the predominant regulator of bile secretion in the penguin.

Animals↗
PubMed1977

Mitochondrial Activity and Ethanol Accumulation in Ice-encased Winter Cereal Seedlings.

Cold-hardened dark-grown seedlings of winter wheat (Triticum aestivum L.) and winter rye (Secale cereale L.) are killed during total encasement in ice at -1 C at a rate related to the initial cold hardiness of the cultivars. Few plants remain alive after 7 days of encasement. Nonhardened seedlings are rapidly killed in ice. The respiratory properties of mitochondria isolated from plants after increasing periods of ice encasement decline slowly, and activity is little impaired when intact plants are about 50% killed. Electron microscopy indicates that mitochondrial structure is not disrupted until 3 weeks of ice encasement. Ethanol accumulates in hardened and nonhardened plants in ice, but at levels which are not toxic to the plants.

Journal Article↗
PubMed1976

A trial of Fortagesic and Paramol 118 in osteoarthritis.

Fortagesic was compared with Paramol 118 in a fourteen day single-blind crossover study in patients with moderate pain due to osteoarthritis. Both preparations were shown to be similarly effective. More side-effects were seen with Paramol 118 than with Fortagesic and more patients preferred Fortagesic. These differences were not statistically significant, but it is concluded that Fortagesic is a useful effective analgesic for standard use in moderate pain.

Acetaminophen↗
PubMed1976

Casts of hepatic blood vessels: a comparison of the microcirculation of the penguin, Pygoscelis adeliae, with some common laboratory animals.

Latex casts of the hepatic blood vessels of the penguin, Pygoscelis adeliae, and of some common laboratory animals were compared. There was general similarity between the different species, but the portal venous and hepatic arterial systems of the penguin were simpler than those of other species. Measurements were made of the volume and length of portal veins and it appears that the portal venous system is capable of being a more efficient blood reservoir in the penguin than in other species studied. The peribiliary plexus was especially well formed in the penguin and was drained by long veins which usually joined portal venous branches. Some of the long veins drained directly into the hepatic venous tree: these translobular veins were more prominent than in mammals. Anastomoses between hepatic artery and portal vein were not present in penguins, and the supply to the sinusoids appeared to be separate. The morphology of small hepatic veins of all the species appeared to be similar.

Animals↗