Promotive Effect of C18-Unsaturated Fatty Acids on the Abscission of Bean Petiole Explants

The abscission-promoting effects of C₁₈-unsaturated fatty acidswere studied in bean (Phaseolus vulgaris L. cv. Masterpiece)petiole explants with the junction between the petiole and thepulvinus in the primary leaves in the light. Linolenic, linoleicand oleic acids promoted the abscission of the explants in thelight. Linolenic acid was the most effective among the compoundstested and its promotive effect was evident without any accompanyingincrease in the production of ethylene from the explants, ascompared with non-treated explants. Linolenic acid is easilyconverted to its hydroperoxide during the incubation with explants,as indicated by the formation of the conjugated diene and thegeneration of ethane. The production of ethylene from the explantstreated with linolenic acid was completely inhibited by theaddition of aminoethoxyvi-nylglycine (AVG), but large amountsof ethane were still generated. The promotive effect of linolenicacid was almost eliminated by the addition of scavengers offree radicals. Hydrogen peroxide and tert-butyl hydroperoxidepromoted abscission in the light. From these results, we concludedthat the abscission-promoting effect of linolenic acid are notmediated by the effect of ethylene but by the effect of itshydroperoxide, while the well-established pathway for the biosynthesisof ethylene from S-adenosylmethionine to ethylene, via 1-aminocyclopropane-l-carboxylicacid (ACC), was apparently operative. (Received May 1, 1991; Accepted July 10, 1991)     

Biocompatibility of radiolucent breast implants

Current implants for breast augmentation containing silicone gel, saline, or both are radiopaque on mammographic examination and can totally obscure microcalcifications and soft-tissue masses. The effect of these implants on the detection of early breast cancers in patients who have undergone augmentation mammaplasty remains unproven and controversial. Implants filled with medium-chain triglycerides (peanut oil) are radiolucent on mammographic examination and allow visualization of both soft-tissue masses and microcalcifications. To investigate the biocompatibility of radiolucent implants, 10 cc of sterile, nonpyrogenic peanut oil was injected subcutaneously into rats using silicone gel as a control. Twenty-one rabbits had two 125-cc silicone shell implants inserted on either side of the chest wall. The right-sided shell was filled with 125 cc of sterile saline, and the left-sided shell was filled with 125 cc of sterile, nonpyrogenic peanut oil. Results were determined by both histologic and radiographic examination. Rats injected with peanut oil equivalent to 7 percent of their body weight rapidly absorbed the freely injected oil without detriment. Histologic examination of the lungs, liver, kidneys, and tissues adjacent to the injection sites demonstrated no abnormalities. There was no evidence of allergic, toxic, inflammatory, or neoplastic response. Eighteen of 21 rabbits survived more than 3 months. Radiographs showed the oil-filled implants to be radiolucent, whereas the saline-filled controls obscured the surrounding soft and bony tissues. Histologic examination demonstrated a fibrous capsule surrounding both types of implants. Histologic examination of the lungs, liver, and kidneys showed no significant abnormalities. These and previous studies have shown peanut oil to be biocompatible when freely injected either intramuscularly or subcutaneously. This study demonstrates that a radiolucent, peanut oil-filled implant is biocompatible in animals and that further long-term studies for its use in humans are merited.     

Molecular cloning of the gene coding for the human T cell differentiation antigen CD7

The CD7 molecule is a differentiation antigen found on the surface of T lymphocytes and also on a very minor fraction of acute nonlymphocytic leukemia (ANLL). To study the genomic structure of the CD7 gene, two clones (SY4 and SY22) were isolated by screening a genomic library with a CD7 cDNA probe. Restriction mapping of these two phage clones showed that both overlapped each other, covering a total length of 23 kilobases (kb). Transfection of mouse L cells demonstrated that SY22 contains the gene expressing the CD7 antigen reactive with monoclonal CD7 antibody (Tp40), while SY4 does not. Subcloning of a 10.5 kb fragment from a 14.4 kb insert of SY22 contained the structural gene for the CD7 antigen. Detailed restriction mapping and partial sequence analysis revealed the CD7 gene to consist of four exons. By RNase protection assay, multiple initiation sites — 122 base pairs (bp) to — 38 bp from ATG translation initiation site were demonstrated. The promoter region had high G+C content and contained two SP1 binding sites (CCGCCC) and an AP2 binding site (CCCCAGGC), but lacked CAAT and TATA motifs.     

A novel MHC class I-related molecule expressed on mouse thymic stroma cells and mature lymphocytes

A monoclonal antibody (mAb) TP-3 has been established by immunizing rats with the BALB/c mouse thymic epithelial cell line TEL-2. The TP-3 antigen is expressed on stroma cells of thymus, spleen, and lymph node in syngeneic BALB/c mice (H-2 ^d ). This antigen is also expressed at a low level on the cell surface of immature thymocytes, and at a high level on mature T and B cells. In allogeneic mice such as C57BL/6 (H-2 ^b ) or C3H (H-2 ^k ), no cells expressed the TP-3 antigen. Using H-2 congenic mice, reactivity with mAb TP-3 was found to map to a region of H-2D ^d L ^d or between D ^d and Qa, suggesting that TP-3 is a major histocompatibility complex (MHC) class I antigen. However, immunoprecipitation analysis indicated that this antigen is not identical to the classical mouse class I molecules in terms of molecular size, antigenicity, and tissue distribution.     

Identification of (Na,K)ATPase inhibitor in brine shrimp,Artemia salina,as long-chain fatty acids

Summary An inhibitory activity to (Na,K)ATPase was found in cell extracts of the brine shrimp, Artemia salina, irrespective of its developmental stages. Organic solvent extraction together with gas chromatographic analysis reveals that the inhibitory activity is due to long-chain, non-esterified fatty acids and their derivatives. Unsaturated fatty acids, especially with cis-configuration, are more effective in inhibition than saturated ones.Abbreviations ATPase adenosine triphosphatase - EDTA ethylenediamine-tetraacetate - TLC thin-layer chromatography     

Alterations in cardiac function and subcellular membrane activities after hypervitaminosis D3

The present study was designed to induce massive accumulation of calcium in the myocardium and to evaluate the effect of calcium overload on myocardial contractile function and biochemical activity of cardiac subcellular membranes. Rats were treated with an oral administration of 500,000 units/kg of vitamin D₃ for 3 consecutive days, and their hearts were sampled on the 5th day for biochemical analysis. On the 4th and 5th days, heart rate, mean aortic pressure, left ventricular systolic pressure and left ventricular dP/dt were significantly lowered in vitamin D₃-treated rats, demonstrating the existence of appreciable myocardial contractile dysfunction. Marked increases in the myocardial calcium (67-fold increase) and mitochondrial calcium contents (24-fold increase) were observed by hypervitaminosis D3. Mitochondrial oxidative phosphorylation and ATPase activity were significantly reduced by this treatment. A decline in sarcolemmal Na⁺, K⁺-ATPase activity was also observed, while relatively minor or insignificant changes in calcium uptake and ATPase activities of sarcoplasmic reticulum were detectable. Electron microscopic examination revealed calcium deposits in the mitochondria after vitamin D₃ treatment. The results suggest that hypervitaminosis D₃ produces massive accumulation of calcium in the myocardium, particularly in the cardiac mitochondrial membrane, which may induce an impairment in the mitochondrial function and eventually may lead to a failure in the cardiac contractile function.     

Defining the sequence recognized with BmFTZ-F1, a sequence specific DNA binding factor in the silkworm, Bombyx mori, as revealed by direct sequencing of bound oligonucleotides and gel mobility shift competition analysis.

BmFTZ-F1 is a Bombyx mori homologue of FTZ-F1, a positive regulator of the fushi tarazu gene of Drosophila melanogaster. In order to determine the sequence recognized with this factor, we made three sets of oligonucleotide mixture which contain 4 possible nucleotides at different positions within the previously proposed 12-bp binding consensus sequence. Oligonucleotides which bound to purified BmFTZ-F1 were separated by a gel mobility shift procedure and a binding sequence was determined by direct sequencing through Maxam-Gilbert method. By this analysis, 7 positions showed clear sequence preference and 5 positions showed weak or no sequence preference. The importance of each nucleotide at each position was confirmed by a gel mobility shift competition analysis and results were presented as a quantitative difference in the binding affinity. From these analyses, we conclude that the best binding sequence of BmFTZ-F1 is 5'-PyCAAGGPyCPu-3'. This method may be useful for the determination of a binding sequence of other sequence specific DNA binding factor.     

Halothane, an inhalation anesthetic, activates protein kinase C and superoxide generation by neutrophils

The rate of superoxide generation of guinea pig intraperitoneal neutrophils by a chemotactic peptide or 12-O-tetradecanoylphorbol-13-acetate (TPA) was increased by 2-bromo-2-chloro-1,1,1,-trifluoroethane (halothane), an inhalation anesthetic. This increase was inhibited by 1-(5-isoquinolinesulfonyl)methylpiperazine dihydrochloride (H-7), a specific inhibitor of Ca2+- and phospholipid-dependent protein kinase C (PKC). Halothane was found to significantly activate partially purified PKC. The activation required phosphatidylserine (PS) and Ca2+. Dioleoylglycerol- or TPA-activated PKC activity was further increased by halothane. The cytoplasmic proteins of guinea pig neutrophils phosphorylated by halothane-activated PKC were similar to those phosphorylated by PMA-activated PKC. The phosphorylation of a 48 kDa protein, a phosphorylated protein required for NADPH oxidase activation, was also increased by halothane. These data suggest that the increase of superoxide production by halothane is correlated with its activation of PKC.     

Changes in aerobic and anaerobic ATP-synthesizing activities in hypoxic mouse brain

The changes in cerebral metabolism in mice in severe hypoxia were investigated by analyses of changes in the levels of energy metabolites and near-infrared spectrophotometric assessment of the states of hemoglobin and cytochrome oxidase. Under 4.4% O2, the contribution of anaerobic ATP production was at most about 20% of the demand. However, the cerebral ATP level was kept at the control level until about 1 min before death. Pentobarbital anesthesia, which reduced the cerebral rate of metabolism, prolonged the survival time, although anaerobic ATP production still did not support ATP demand. Under these conditions, deoxygenation of hemoglobin and reduction of cytochrome oxidase proceeded rapidly within 1 min. Hemoglobin reached the maximum state of deoxygenation in the middle phase of hypoxia, with no further change until death. However, cytochrome oxidase was reduced slowly with one phase of partial reoxidation due to increase of cerebral blood volume, and reached the completely reduced state at death. From these results it was concluded that the aerobic ATP synthesis, which supplied more than 80% of the cerebral demand, decreased gradually because of limitation of oxygen supply, and that the failure of oxidative phosphorylation to meet demand triggered the decrease in the cellular ATP level that led to death.     

Membrane-buffer partition coefficients of tetracaine for liquid-crystal and solid-gel membranes estimated by direct ultraviolet spectrophotometry

The membrane-buffer partition coefficient of tetracaine was measured by direct ultraviolet spectrophotometry in dimyristoylphosphatidylcholine unilamellar liposomes at temperatures above and below the main phase transition. The partition coefficients of uncharged tetracaine to solid-gel (18 degrees C) and liquid-crystal (30 degrees C) membranes were 6.9 x 10(4) and 1.2 x 10(5), respectively. Despite the general assumption that local anesthetic binding to the solid membrane is negligible, this study showed that the solid membrane binding amounts to 57.5% of the liquid membrane binding. Binding of the charged form to the liquid or solid membrane was not detectable under the present experimental condition of 0.03 mM tetracaine bulk concentration. The present method measures metachromasia of local anesthetics when bound to lipid membranes. Its advantage is that the separation of the vesicles from the solution is not required. A linearized equation is presented that estimates the partition coefficient or binding constant graphically from a linear plot of the absorbance data. The method is applicable for estimation of drug partition when a measurable spectral change occurs due to complex formation.