Use of short-chain cyclopentano-phosphatidylcholines to probe the mode of activation of phospholipase A2 from bovine pancreas and bee venom

A great mystery in the mechanism of phospholipase A2 (PLA2) and many other lipolytic enzymes is the "interfacial activation" induced by micellar but not monomeric substrates. Equally mysterious is the lack of interfacial activation in bee venom PLA2, as opposed to PLA2s from pancreas and other sources. We have probed these problems using the conformationally restricted short-chain cyclopentano-analogues of diacylphosphatidylcholine (Cp-DCnPC, all-trans isomer). In the reaction catalyzed by bovine pancreatic PLA2, Cp-DC8PC behaved differently from DC8PC in that its monomers and micelles showed comparable activities (but lower than the activity of DC8PC). This result suggests that the activity of PLA2 can be regulated by substrate conformation and supports the "substrate conformation model" (Wells, M. A. (1974) Biochemistry 13, 2248-2257), but raises a question as to whether Cp-DC8PC mimics monomers or micelles of DC8PC. Conformational analysis by 1H NMR revealed that monomeric Cp-DC8PC was conformationally restricted near the carbonyl region, a property characteristic of micelles. Thus, monomeric CP-DC8PC can be considered as a conformational analogue of micelles, but the important structural feature lies in the CH2COO region instead of the glycerol backbone. CP-DC8PC was then used to test a previous proposal that the bee venom PLA2 hydrolyzes monomers but not micelles (which would predict little or no activity for Cp-DC8PC since its conformation is micelle-like whether below or above its critical micelle concentration). The results showed that Cp-DC8PC is a relatively good substrate for the bee venom PLA2 in comparison with the pancreatic PLA2. This and other evidence together suggest that the bee venom PLA2 is not sensitive to the conformation of monomeric and micellar substrates and hydrolyzes both monomers and micelles. The results in both PLA2s demonstrate the usefulness of cyclopentano-phospholipids in probing the mechanism of phospholipases and the roles of substrate conformation in the catalysis of PLA2.

Transluminal catheter angioplasty of abdominal aorta in Takayasu's arteritis

Nine patients with Takayasu's arteritis and a long stenotic segment of the abdominal aorta were treated by percutaneous transluminal angioplasty (PTA). Intermittent claudication disappeared in six of seven cases, the femoral pulse reappeared in all five; ankle/arm indices increased in seven cases; elevated blood pressure normalized in seven of eight cases. Seven patients were followed for 3 to 28 months. They were all free of symptoms from the lower extremities. In three patients with or without renal artery stenosis and with hypertension, the blood pressure decreased after PTA of the abdominal aorta only. PTA may be a valuable treatment in Takayasu's arteritis and stenosis of the abdominal aorta.

Tradescantia-Micronucleus (Trad-MCN) tests on 140 health-related agents

The Tradescantia-Micronucleus (Trad-MCN) test is a simple short-term bioassay for various gaseous and liquid forms of chemical agents, and physical agents such as radiation. 140 agents, directly or indirectly related to human health, were screened for their mutagenicity. Plant cuttings of young inflorescences, in which the pollen mother cells undergo various stages of meiosis, were maintained in nutrient solution for experimentation. Treatments were made either by absorption of the soluble agents through the stem, by diffusion of gaseous agents through the leaves and buds, by exposure to internal/external radiation or by in situ exposure to air pollutants. Micronuclei formed from damaged chromosomes served as the indicators of mutagenicity. Results of 140 agents tested are listed in 9 different categories. (1) Carcinogens/mutagens, (2) common beverages, (3) common chemicals, (4) drugs, (5) pesticides, (6) common household chemicals, (7) radiation and radioisotopes, (8) in situ monitoring, (9) complex environmental mixtures. Out of 140 agents tested, 52 showed positive, 20 showed borderline positive responses and 5 showed strong toxicity. Test results of 41 agents in the present study showed 67% congruity with Ames test results found in the literature.

Blood supply of experimental liver tumors after intraarterial embolization with gelfoam powder and absolute ethanol

Twenty rats with implanted liver tumor were studied. Following baseline angiography, the hepatic artery was embolized with Gelfoam powder or ethanol (n = 12) while the controls (n = 8) did not undergo embolization. Postmortem Microfil perfusion was performed in all livers. Filling of tumor lakes from the portal vein was seen more often in embolized animals than in controls, indicating the potential role of the portal venous system in the supply of dearterialized hepatic tumors. We discuss the possible clinical implication of our results.

Postmortem examination of the blood supply and vascular pattern of small liver metastases in man

Thirteen human cadavers with liver metastases were examined. Microfil was injected into the portal vein and hepatic artery. The liver metastases were examined under dissecting microscope, and their vascular supply and patterns were registered. It was found that most metastases had both arterial and portal supply even if the arterial supply dominated. Extensive filling of tumor vessels was observed in both lobes in one liver in which the portal vein of one lobe and the hepatic artery of the other was injected (i.e., the same kind of metastases could be filled from either the hepatic artery or the portal vein). It is suggested that the findings could be of great importance in planning treatment of patients with liver metastases.

Microvasculature architecture of small liver metastases in man. A correlation between microfil vascular preparations and histologic sections

The hepatic artery and the portal vein of 12 human cadaver livers with metastases of various sizes and origins were injected with Microfil. The microvascular appearances of the metastases were studied in order to receive an explanation to findings at angiography and contrast enhanced computed tomography. Histologic examinations were also performed of Microfil-injected specimens.

Portal blood supply of liver metastases

Using Microfil technique, hepatic arteries and portal veins were injected in four human cadaver livers with metastases of different origin. Specimens were dissected under stereomicroscope and vessels supplying the tumor nodules were traced. In all cases, tumor vessels could be filled from the portal side; in three, the supplying portal branches were rather wide. The findings were correlated with histologic sections.

CT demonstration of low density ring in liver metastases

A case of liver metastases from colon carcinoma showing a low density ring sign is presented. Cadaver studies suggest that this sign can be produced by compressed liver cells and sinusoids.

Umbilical and paraumbilical veins in ligamentum teres. Their significance as collaterals in portal hypertension

Twenty-two postmortem specimens of the liver (18 normal livers, three with liver metastases, and one with liver cirrhosis) with attached ligamenta teres were investigated using silicone rubber injection technique. In all cases, the paraumbilical veins were demonstrated. They were usually divided into 2 groups, one on the right and one on the left side of the ligamentum teres, and they terminated in a variable manner into small peripheral portal vein branches in the liver parenchyma. A patent segment of the umbilical vein was found in 7 of the 22 cases. Connections between the umbilical vein and paraumbilical veins were supposed to represent one of the collateral channels in portal hypertension.

Partial ablation of the kidney by intraarterial ethanol in domestic swine

Partial renal ablation was produced in 15/17 swine kidneys after segmental intraarterial injection of 1-2 ml of 95% ethanol. Complications were seen in 3 kidneys, including reflux of ethanol into nontarget vessels with subsequent total infarction of 2 kidneys, and the development of hydronephrosis in 1 kidney. Strictly selective catheterization and a very slow injection of ethanol are essential to avoid complications. This technique may find clinical application and the possible indications are discussed.

Experimental evaluation of a new instrument for transcatheter electrocoagulation

A new coaxial electrode catheter design has been tested in 19 renal arteries of pigs with excellent results, i.e. 100 per cent thrombosis. One vessel ruptured. The electrode (anode) is situated on a thin inner catheter and after electrolysis it is pulled back into a shielding outer catheter. This should reduce downstream embolization. Usual currents have been 8 to 10 mA at 10 V and doses of 16 to 36 C have been used depending on the size of the artery. In the single case of rupture of the vessel a current of 20 mA was used. The method appears to be ready for clinical testing.

Lateral displacement of the right kidney by the ascending colon

A case of lateral displacement of the lower pole of the right kidney caused by an interposing ascending colon is presented. An interposition of this kind is rare and does not cause any gastrointestinal symptoms but is of differential diagnostic importance. In this case computed tomography was a simple noninvasive procedure for correct diagnosis.

In vitro chemotherapeutic testing of urologic tumors

We studied 20 transitional cell tumors of the bladder and 25 adenocarcinomas of the kidney in vitro to determine their chemotherapeutic sensitivity. The different sensitivity patterns among the individual tumors were demonstrated. Identical drug sensitivity patterns could be identified in the primary and metastatic sites, and in tumor tissue removed from the primary and metastatic deposits in the same patient. Human renal adenocarcinoma maintained in the athymic mouse demonstrated identical chemotherapeutic sensitivity patterns in vitro and in vivo. Our data would support that these in vitro chemotherapy studies may assist in the selection of agents to use in human tumor-bearing hosts.

Studies on adrenocorticotropic hormone receptor using isolated rat adrenocortical cells

To clarify the function of ACTH receptors, the actions of ACTH on cyclic AMP formation, Ca2+-influx across cell membrane, and corticoidogenesis were examined using dispersed adrenocortical cells prepared from the rat adrenal gland. 1) There are two types of ACTH receptors from Scatchard analysis of 125I-ACTH1-24 binding to the cell, the one receptor is of high affinity and low capacity (dissociation constant (Kd1) = 2.6 x 10(-19) M and 7,350 sites per cell), and the other one is of low affinity and high capacity (dissociation constant (Kd2) = 7.1 x 10(-9)M and 57,400 sites per cell). 2) Both apparent dissociation constants derived from the effects of ACTH on corticoidogenesis and Ca2+ influx well correspond with Kd1 of the high affinity receptor, 3) Apparent dissociation constant obtained from the effect of ACTH on cyclic AMP formation is in good agreement with Kd2 of the low affinity receptor. Thus it could be deduced from these data that the high affinity receptor is concerned with an increased Ca2+-influx to regulate corticoidogenesis at physiological levels of ACTH, whereas the low affinity receptor is coupled to adenylate cyclase at supraphysiological concentrations of ACTH.

The effect of ethanol ingestion on the aldehyde dehydrogenases of rat liver

The effect of ethanol ingestion on aldehyde dehydrogenase activity in the subcellular fractions of livers from 14 pair-fed male Sprague-Dawley rats was tested. Enzymatic assays were performed at two different concentrations of propionaldehyde (0.068 and 13.6 mM) sufficient to saturate enzymes with high and low affinities for propionaldehyde, respectively. The effect of alcohol ingestion varied depending on the subcellular fraction tested and the propionaldehyde concentration used in the assay. There was a 60% increase in the activity of aldehyde dehydrogenase with high affinity for propionaldehyde in the mitochondrial membranes. Conversely there was a 50% decrease in the activity of aldehyde dehydrogenases with high affinity for propionaldehyde in the microsomal fraction. There was also a 58% decrease in the activity of enzymes from the mitochondrial matrix with low affinity for propionaldehyde. The results suggest that differences in the assay systems employed may account for the conflicting results obtained by previous investigators of the effect of ethanol feeding.