The cytogenetic effects of restriction endonucleases following their introduction into cells by electroporation.
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Animals↗
Biomedical subjects
J W Phillips
Publications and source records attributed to J W Phillips.
Restriction endonucleases do not induce sister-chromatid exchanges in Chinese hamster ovary cells.
Bacterial restriction enzymes offer the unique opportunity to determine the biological and cytogenetic consequences of DNA double-strand breakage. To examine the role of various types of breaks in sister-chromatid exchange (SCE) formation, we used restriction enzymes with different recognition sequences and different cutting frequencies to generate DNA double-strand breaks in Chinese hamster ovary (CHO) cells. The restriction enzymes were introduced by electroporation into exponentially growing cells during the second replication cycle in bromodeoxyuridine, and SCEs were analyzed at mitosis. Contrary to results reported by others, we found no increase in SCE frequency in cells exposed to restriction enzymes despite the presence of numerous cells with chromatid aberrations. These data suggest that DNA double-strand breaks do not lead to SCE formation.
Animals↗
Obstruction of the small bowel in the early postoperative period.
To analyze factors related to etiology, diagnosis, and outcome, we reviewed the records of 26 patients in whom a clinical picture of small bowel obstruction developed within one month after abdominal surgery. The initial operation was an emergency procedure in 20 cases and an exploratory laparotomy after trauma in 11. The colon was the organ most commonly operated upon initially, being involved in ten procedures (38%), all of which were emergencies. The clinical diagnosis of bowel obstruction was made within ten days postoperatively in most cases. Surgical reexploration was required in 15 patients (58%), whereas the obstructive symptoms resolved with nasogastric suction in 11. Two patients, both of whom survived, required resection of strangulated bowel; in both a treatment delay of at least 72 hours was documented. There were two deaths (8%), neither of which was directly related to the bowel obstruction. Diagnosis of this clinical entity requires a high index of suspicion, especially after emergency procedures that involve the colon. Optimal survival is achieved by prompt recognition and early intervention when a mechanical bowel obstruction is suspected in the early postoperative period.
Abdomen↗
Bahia grass pollen, a significant aeroallergen: evidence for the lack of clinical cross-reactivity with timothy grass pollen.
Thirty-eight subjects were challenged (25 nasal, 13 bronchial) with Bahia grass, Paspalum notatum, pollen extract. A positive Bahia intradermal skin test predicted a positive challenge to Bahia in all (11/11) of the nasal challenges and 75% (6/8) of the bronchial challenges. All 19 subjects with negative Bahia intradermal skin tests had negative challenges with Bahia. Specific IgE antibodies to Bahia pollen were detected by conventional RAST (greater than or equal to 2+) in 82% (14/17) of subjects with positive challenges and in 5% (1/20) of subjects with negative challenges. Eight subjects had positive intradermal skin tests to either Bahia (three) or timothy, Phleum pratense (five). Seven of the eight subjects reacted exclusively to either Bahia or timothy nasal challenge as predicted by their skin tests. Bahia grass is a significant aeroallergen, which in some subjects can be demonstrated not to cross-react with timothy.
Allergens↗
Intracellular mitochondrial membrane potential as an indicator of hepatocyte energy metabolism: further evidence for thermodynamic control of metabolism.
The lipophilic triphenylmethylphosphonium cation (TPMP+) has been employed to measure delta psi m, the electrical potential across the inner membrane of the mitochondria of intact hepatocytes. The present studies have examined the validity of this technique in hepatocytes exposed to graded concentrations of inhibitors of mitochondrial energy transduction. Under these conditions, TPMP+ uptake allows a reliable measure of delta psi m in intracellular mitochondria, provided that the ratio [TPMP+]i/[TPMP+]e is greater than 50:1 and that at the end of the incubation more than 80% of the hepatocytes exclude Trypan blue. Hepatocytes, staining with Trypan blue, incubated in the presence of Ca2+, do not concentrate TPMP+. The relationships between delta psi m and two other indicators of cellular energy state, delta GPc and Eh, or between delta psi m and J0, were examined in hepatocytes from fasted rats by titration with graded concentrations of inhibitors of mitochondrial energy transduction. Linear relationships were generally observed between delta psi m and delta GPc, Eh or J0 over the delta psi m range of 120-160 mV, except in the presence of carboxyatractyloside or oligomycin, where delta psi m remained constant. Both the magnitude and the direction of the slope of the observed relationships depended upon the nature of the inhibitor. Hepatocytes from fasted rats synthesized glucose from lactate or fructose, and urea from ammonia, at rates which were generally linear functions of the magnitude of delta psi m, except in the presence of oligomycin or carboxyatractyloside. Linear relationships were also observed between delta psi m and the rate of formation of lactate in cells incubated with fructose and in hepatocytes from fed rats. The linear property of these force-flow relationships is taken as evidence for the operation of thermodynamic regulatory mechanisms within hepatocytes.
Adenine Nucleotides↗
Evidence that stimulation of gluconeogenesis by fatty acid is mediated through thermodynamic mechanisms.
We have studied the stimulatory effects of palmitate on the rate of glucose synthesis from lactate in isolated hepatocytes. Control of the metabolic flow was achieved by modulating the activity of enolase using graded concentrations of fluoride. Unexpectedly, palmitate stimulated gluconeogenesis even when enolase was rate-limiting. This stimulation was also observed when the activities of phosphoenolpyruvate carboxykinase and aspartate aminotransferase were modulated using graded concentrations of quinolinate and aminooxyacetate, respectively. Linear force-flow relationships were found between the rate of gluconeogenesis and indicators of cellular energy status (i.e. mitochondrial membrane and redox potentials and cellular phosphorylation potential). These findings suggest that the fatty acid stimulation of glucose synthesis is in part mediated through thermodynamic mechanisms.
Aminooxyacetic Acid↗
Plasma and tumor concentrations of cisplatin following intraperitoneal infusion or bolus injection with or without continuous low-dose-rate irradiation.
Our purpose of this study was to determine whether whole-body, continuous low-dose-rate irradiation (CLDRI) alters the plasma and/or tumor platinum pharmacokinetics after ip bolus injection or ip infusion as a possible mechanism of interaction between CLDRI and cisplatin. The C3Hf/Sed mice bearing SCCVII/SF tumors were given 6 mg cisplatin/kg ip by bolus injection or an ip infusion of 0.25 mg cisplatin.kg-1.hour-1 for 48 hours with and without CLDRI at 0.56 Gy/hr for 24 or 48 hours. Plasma and tumor platinum concentrations were determined with an atomic absorption spectrophotometer at appropriate intervals during infusion and up to 48 hours after drug administration. Both total and ultrafilterable plasma platinum followed a biphasic elimination after ip bolus injection, whereas only a prolonged single-phase elimination was seen after ip infusion. Tumor uptake of platinum appeared to follow a passive diffusion pattern with a prolonged cellular retention of platinum. Whole-body CLDRI had no apparent effect on the pharmacokinetics of plasma and tumor platinum administered by ip bolus injection or prolonged continuous infusion.
Animals↗
Linear relationships between mitochondrial forces and cytoplasmic flows argue for the organized energy-coupled nature of cellular metabolism.
We have studied rates of formation of glucose, urea and lactate by isolated hepatocytes incubated with a variety of inhibitors of energy transduction. Linear relationships have been found between these metabolic rates and mitochondrial forces (membrane, redox and phosphorylation potentials). The findings are suggestive of extensive enzyme organization within these metabolic pathways.
Animals↗
Preparation of cytoplasmic bodies (cytospheres) from isolated hepatocytes and their biochemical properties.
The controlled centrifugation of isolated rat hepatocytes at 260 000 g results in the formation of membrane-bounded cell fragments that we have termed 'cytospheres'. A method is described for the isolation of these cytospheres. Cytospheres are spherical, have a mean diameter of 9.2 +/- 3.2 microns (SD) and a protein content of 225 +/- 12 mg/g wet wt. About 3% of the protein from the original isolated hepatocyte suspension is recoverable. Transmission electron microscopy (TEM) shows cytospheres to possess a trilaminar membrane, and a finely granular hyaloplasm generally devoid of organelles, filaments and microtubules. Freeze-fracture studies reveal a membrane structure typical of a plasma membrane. Ouabain and wheat germ agglutinin (WGA)-binding studies indicate that the original orientation of the plasma membrane is maintained throughout the formation of the cytospheres. The cytospheres have also been characterized biochemically. Cytospheres are enriched in the enzymes normally associated with the hyaloplasm, whereas the activities of enzymes localized in organelles are greatly diminished. Lipid analysis of the cytosphere membrane indicates that it is derived from the plasma membrane of the hepatocyte. Cytospheres are sensitive to changes in the osmolarity and ionic composition of their environment. Cytospheres should therefore prove a useful preparation for the study of hyaloplasm metabolism and of plasma membrane receptor and permeability properties.
Animals↗
Oncotic therapy of experimental cerebral oedema.
A series of experiments were undertaken to compare oncotic gradients with osmotic gradients in the treatment of experimental cerebral oedema. Oedema was produced in dogs by a left parietal cold lesion. Animals were divided into three treatment groups. Group 1, the control animals, received intravenous crystalloid solutions after the cold lesion. Group 2 animals received mannitol, 1 gm/kg IV, one and four hours after the lesion. Group 3 animals received albumin, 1 gm/kg IV, one hour after the lesion, then a continuous albumin infusion. Serum osmotic and oncotic pressures were monitored hourly. Animals were sacrificed six hours after creation of the lesions. Effect of therapy was evaluated by determining water content of the lesion hemisphere and of the opposite hemisphere. Osmotic and oncotic pressures were changed little by the mannitol and albumin dosages employed. Water content in the areas of the cold lesions was significantly greater than that in the contralateral hemisphere in all three groups. Water content in the nonlesion hemisphere of dogs receiving albumin or mannitol was 1% less than in the control, nonlesion hemisphere, an insignificant reduction of water content. Further studies of the effects of oncotic gradients for cerebral dehydration are indicated.
Albumins↗
Properties and biosynthetic connection of the nucleotide pyrophosphatases of rat liver plasma membrane and endoplasmic reticulum.
The detergent-solubilized nucleotide pyrophosphatases of the rat liver plasma membrane and endoplasmic reticulum fractions were purified by lectin affinity chromatography. They have the same molecular mass of 148 000 dalton; their catalytic properties are also very similar and correspond to those of the trypsin-solubilized activities from the same membrane preparations. Pulse-chase experiments on isolated perfused livers using [3H]leucine indicated different labelling kinetics of the proteins isolated from plasma membrane and endoplasmic reticulum. The plasma membrane enzyme became only slightly labelled in the presence of 100 microM vinblastine. The data support a precursor-product relationship of the nucleotide pyrophosphatases from endoplasmic reticulum and plasma membrane.
Animals↗
New compounds: organoboron derivatives of tetracyclines I: synthesis of carboxamido derivative of tetracycline with perhydro-2-phenyl-1,3,6,2-dioxazaborocine.
An organoboron carboxamido derivative of tetracycline, designed for use in the 105B-thermal neutron-capture treatment of cancer, was synthesized under the conditions of the Mannich reaction using perhydro-2-phenyl-1,3,6,2-dioxazaborocine as the amine component. Spectral data (UV, IR, and NMR) for the compound and its hydrolytic stability are discussed.
Boron Compounds↗
Gluconeogenesis in vertebrate livers.
1. The hypothesis is advanced that it would be logical for a tissue (liver) to evolve as a gluconeogenic organ in order to recover the lactate produced as a result of rapid and sustained contraction of skeletal muscle. 2. Lactate was present in skeletal muscle of all animals examined and increased following electrical stimulation. It was also present in the blood. 3. Gluconeogenesis from lactate occurred in liver slices of all animals excepting amphibia. However, livers of these animals also contained much glycogen and are probably gluconeogenic. 4. Phosphoenolpyruvate carboxykinase was present in all animals investigated; pyruvate carboxylase was present in all animals excepting the toad.
Ambystoma↗
Ketogenesis in vertebrate livers.
1. The hypothesis is advanced that a gluconeogenic organ such as the liver would evolve to oxidise fatty acids as its source of ATP for gluconeogenesis. It is also argued that such an organ might, in the light of current knowledge, be expected to be ketogenic. The animals investigated were lamprey, rainbow trout, eel, toad, axolotl, lizard and rat. 2. The respiratory quotients of liver slices from all animals was close to 0.74. Ketone bodies were produced from butyrate by all livers excepting the lamprey and ketone bodies were present in all blood samples examined. 3. There was no convincing evidence that direct deacylation of acetoacetyl CoA was important in any liver. HMGCoA synthase activity could not be found in the livers of the lamprey and eel. This enzyme was present in livers of the other animals. There was a large amount of acetoacetyl CoA-succinate transferase in the livers of the rainbow trout and eel, but only small amounts in the higher animals. 4. It is suggested that, initially the transferase was the important ketogenic pathway and the HMGCoA pathway evolved later.
Acyl Coenzyme A↗
Lactic acid formation in crustaceans and the liver function of the midgut gland questioned.
1. The possibility of the midgut gland of the crustacean (Cherax destructor) functioning as a liver has been investigated. 2. Seven species of crustaceans accumulate lactic acid in the haemolymph when exercised. The rate of disappearance of lactate in Homarus gammarus and in C. destructor is very slow when compared with man. 3. In the midgut gland of C. destructor no firm evidence was obtained for gluconeogenesis from lactate and for ketogenesis from fatty acids. 4. It is concluded that there is at present no justification for the common practice of calling the midgut gland an hepatopancreas.
Animals↗
A strategy for progress in health planning.
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Documentation↗
The impact of laparoscopy in gynecological practice.
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Female↗
Comprehensive health planning in the states.
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Dentistry↗