Purification and characterization of histidyl-transfer RNA synthetase from Neurospora crassa

Histidyl-tRNA synthetase (L-histidine:tRNAHis ligase (AMP-forming), EC 6.1.1.21) has been purified 921-fold from crude extracts of lyophilized mycelia of Neurospora crassa. Sodium dodecyl sulfate gel electrophoresis at pH 8.9 of the purified enzyme yields one band with an apparent Mr of 62 500. The estimated Mr by Sephadex gel filtration is 125 000. Thus the native histidyl-tRNA synthetase of N. crassa is a dimer, composed of two identical subunits. The Km values determined in the enzyme-catalyzed esterification of [14C]-histidine to tRNAHis are: for histidine, 5.8 x 10(-6 M, for ATP, 5.9 x 10(-4) M, and for tRNAHis, 1.2 x 10(-7) M. Effects of various intermediates of the histidine, tryptophan and arginine biosynthetic pathways on histidyl-tRNA synthetase activity were studied. The Ki values for imidazoleglycerol phosphate and histidinol (histidine intermediates and competitive inhibitors of the enzyme) are 1.1 x 10(-2) M, 1.3 x 10(-6) M, respectively. The Ki for indoleglycerol phosphate (a tryptophan intermediate and non-competitive inhibitor) is 1.2 x 10(-3) M.

A new approach to visualize the left main coronary artery using apical cross-sectional echocardiography

Patients undergoing coronary arteriography were studied to evaluate the feasibility of use of cross-sectional echocardiography to detect the left main coronary artery. Visualization of the left main coronary artery from the cardiac apex was attempted using a cranial transducer angulation. With this approach, the left main coronary artery was adequately visualized in 27 of 35 consecutive patients (77 percent) who were prospectively evaluated; in 12 of the 27 the bifurcation was clearly seen. In 26 of the 27 patients cross-sectional echocardiography correctly assessed the patency of the left main coronary artery as judged with coronary angiography. One patient had a false positive echocardiographic study; there were no false negative studies. A comparison of the short axis versus apical cross-sectional techniques in another group of 30 patients revealed the superiority of the apical approach in visualization of the left main coronary artery and its bifurcation; combined use of both techniques allowed for a 93 percent (rate of) success. Thus, apical cross-sectional echocardiography permits visualization of the left main coronary artery and its bifurcation and, therefore, has the potential for detecting left main coronary obstructive lesions.

Noninvasive diagnosis of the cardiomyopathies

The presenting clinical features of the cardiomyopathies are nonspecific. Echocardiography is useful in detecting patients with cardiomyopathy and determining proper management. Echocardiography can be used to determine both cardiac structural measurements and cardiac function.

Regeneration of human liver after hepatic lobectomy studied by repeated liver scanning and repeated needle biopsy

Regeneration of the residual lobe of the liver after hepatic lobectomy in humans was studied by repeated liver scanning in seven noncirrhotic and three cirrhotic patients. Each patient was studied for several months during the study which lasted from 1-12 years. Regeneration was apparent in noncirrhotic liver remnants following hepatic lobectomy. In the case of a long standing, space occupying lesions such as benign giant cysts, the liver remnant would complete its regeneration process rather early, usually within a few months of hepatic lobectomy. In hepatoma cases, however, regeneration of the residual lobe after hepatic resection usually took five or six months for completion. On the contrary, no definite increase in the size of the liver remnant was seen on repeated liver scanning in cirrhotic patients. Histologic study of the residual lobe was repeated on needle biopsy specimens in two noncirrhotic and four cirrhotic patients. Regenerative hyperplasia of liver cells with large hyperchromatic, or double nuclei never seen in the preresection liver appeared in the liver remnant five, 11, and 27 days after hepatic lobectomy in noncirrhotic patients. In cirrhotics, however, there were no histologic changes between the preresection liver and the postresection remnant studied three, five, 15, 40 days or even two years and 8 months after hepatic lobectomy.

Evidence for lack of phosphatidic acid and phospholipase D activity in milk

Phosphatidic acid could not be demonstrated when milk was assayed for phospholipase D activity even when lecithin was added. The concentration of "free" choline in milk remained the same before and after addition of lecithin. However, phosphatidic acid and an increased concentration of "free" choline were demonstrated when cabbage phospholipase D was added to raw milk. The concentration of phosphatidic acid and "free" choline in milk increased appreciably when both lecithin and cabbage phospholipase D were added to raw milk. Phospholipase D activity in milk was assayed at 23.5 C, pH 5.6, in the presence of 10% vol/vol of diethyl ether and .015M calcium chloride. "Free" choline was determined by adjusting the acid whey from milk to pH 11 and adding a freshly prepared 3% methanolic solution of ammonium reineckate. The precipitated choline reineckate was washed, dissolved in acetone, and its absorbance measured at 520 nm. The absence or presence of phosphatidic acid was shown by thin-layer chromatography. These results refute a previous report which proposed that both phosphatidic acid and phospholipase D were in milk.

Comparison of thioredoxin reductases from Novikoff ascites hepatoma cells and normal liver of rats

Adult rat liver contained variant forms of thioredoxin reductase with isoelectric points at pH 4.9 and at approximately pH 4.7 compared to pH 5.1 for the enzyme from Novikoff ascites hepatoma. Fetal and regenerating liver contained only the form with the isoelectric point at pH 4.9. All three enzymes precipitated with and were inhibited by a rabbit antibody to purified enzyme from Novikoff tumor.

Phosphorylation of nuclear proteins in rat regenerating liver

In studies of the phosphorylated proteins in rat liver and Walker-256, it was established that the ratio of various fractions of P-N linkages to P-O linkages varies from 0.6 to 3.1. In rat regenerating liver nuclei, the ratio of P-N and P-O varies with time after partial hepatectomy. Using [3H]-lysine and 32Pi, it is shown that phosphoryllysine forms in some new and, presumably, some preexisting H1 molecules. Using [3H]histidine and 32Pi, it is shown that phosphohistidine forms exclusively in preexisting H4. The half-life of H4 phosphohistidine appears to be about 2 h.

Response of temperature-sensitive medullary neurons to acetylcholine, norepinephrine, and 5-hydroxytryptamine

Single unit activity was recorded by means of five-barrel micropipettes from temperature-sensitive neurons in the reticular formation of the medulla oblongata in urethanized cats. Acetylcholine (ACh), norepinephrine (NE) and 5-hydroxytryptamine (5-HT) were applied microiontophoretically to the immediate vicinity of the neurons. Both thermally sensitive and insensitive units responded to ACh (82.0%) and 5-HT (93.0%) by increasing discharge rate. Iontophoretically applied atropine, but not hexamethonium, antagonized the excitatory responses to ACh. NE was shown to have different effects on the medullary neurons. Most temperature-insensitive units were either nonresponsive (52.4%) or excited (28.6%) by NE, while a majority of warm-sensitive (61.8%) and cold-sensitive (55.6%) neurons were inhibited by NE. Iontophoretically application of the alpha-adrenergic blocking agent, phentolamine, or the beta-antagonists, propranolol, or sotalol, produced no effect on the inhibitory responses to NE. These results tend to support the current concept of the transmitter role of monoamines in thermoregulation.

Medullary unit responses to changes in local and hypothalamic temperatures in the cat

Single unit activity was recorded with glass microelectrodes in the reticular formation of the medulla oblongata of cats lightly anesthetized with urethan, while medullary temperature was changed by surface irrigation with warm or cold artificial cerebrospinal fluid. In addition, water-perfusion thermodes were implanted over the preoptic anterior hypothalamus (POAH) region, and the effects of heating and cooling of the POAH on firing rate of medullary units were studied. One hundred and twenty-five temperature-sensitive neurons were studied in the medullary reticular formation. Out of these 125 neurons, 80 were warm-sensitive and 45 were cold-sensitive. Sixteen warm-sensitive medullary neurons were examined in responses to changes of POAH temperature. Ten units (62.5%) responded, and the remaining 6 units were not responsive to changes of the POAH temperature. Of 13 cold-sensitive neurons examined, 10 units (77.0%) responded. On the other hand, only 1 out of 7 (14.3%) temperature-insensitive neurons tested did respond to changes in the POAH temperature. These results suggest that the temperature signals sent out from thermosensitive structures in the hypothalamus might be transmitted to a major portion of temperature-sensitive neurons in the medullary reticular formation.

In vitro development of plants from microspores of rice

Rice (Oryza sativa L., 2n=24) anthers containing microspores in the early-uninucleate to first-mitosis stages were induced successfully to develop into plants in vitro through an intermediary step of callus formation. Callus initiation occurred with highest frequency in anthers containing mid-uninucleate imcrospores. The callus derived from different stages of microspore development differed in the potential to differentiate into plants. The plants regenerated from pollen callus were predominantly haploid or diploid; polyploid and aneuploid plants were relatively infrequent. The first division of the uninucleate microspores was asymmetrical, resulting in the formation of large vegetative and small generative nuclei. The vegetative nucleus divided repeatedly and assumed the major role in the formation of callus, whereas the generative nucleus degenerated rapidly. Simultaneous division of the two nuclei was observed in a few pollen grains. Nuclear fusion during the very initial stages of pollen development was postulated to account for the occurrence of the diploid and polyploid plants.

The diagnostic value of serum lysozyme activity in inflammatory bowel disease

Serum lysozyme (muramidase) activity was determined by the Lyso-Plate diffusion technic in 419 subjects consisting of normal persons and patients with Crohn's disease, ulcerative colitis, nonspecific diarrhea and various other disorders. Lysozyme activity in the normal subjects did not exceed 37.8 microgram/ml. The values in the several groups of patients overlapped markedly with each other and with the normal range. Approximately two-thirds (62.1%) of the 37 patients with Crohn's disease had values that were within the normal range. In about half (51.8%) of the patients with this disease in whom the process was clinically active, serum lysozyme activity was increased. Of 10 patients with Crohn's disease who had undergone resection, heightened serum lysozyme activity was found only in the three patients in whom there was clinical evidence of recurrence of the disease. It is concluded that serum lysozyme activity is not a dependable means of distinguishing Crohn's disease from ulcerative colitis or nonspecific diarrheas. The determination would appear to be of value, however, in helping to identify activity, recurrence, or extension of the disease in patients with Crohn's disease.

The effect of diethylcarbamazine treatment on the development of bancroftian microfilariae in Culex p. fatigans

Bancroftian microfilarie survived after one to three courses of diethylcarbamazine treatment in carriers and the larvae able to reach the infective stage in Culex p. fatigans. The infection rate and the development of infective larvae per infected mosquito from DEC-treated carriers was much lower than from the untreated carrier. The fact that surving MF can develop to infective stage in their vector indicates that such filarial carriers may be important sources for transmission of filariasis in the endemic areas after suspension of control measures.

Purification of thioredoxin reductase from the Novikoff rat tumor

Thioredoxin reductase (E.C.1.6.4.5.) has been purified to about 95% homogeneity from the Novikoff ascites rat tumor. The enzyme contained two subunits of approximately 58,000 daltons, with one FAD per subunit. The amino acid analysis is reported. An immunoadsorbent was prepared and used for affinity chromatography in order to improve the yield of the enzyme.

Ventilation in conscious dogs during acute and chronic hypercapnia

Minute ventilation was measured in conscious dogs, at rest and during exercise (1 mph), over 60 min immediately following the acute inhalation of 5% carbon dioxide in air and at 2, 4, 7, and 14 days while breathing the same gas mixture in a chamber. The dogs were also studied in the immediate period of air recovery from chronic hypercapnia and 1 day later. Control studies were carried out with the dogs breathing air in the chamber under comparable conditions. A triphasic ventilation change was ovserved in dogs at rest over the 14 days of hypercapnia. After an initial marked increase in ventilation during acute hypercapnia, ventilation returned to control levels by 2 days and then appeared to be elevated above control studies from 4 to 14 days at a time when blood acid-base balance became compensated. When the same dogs were studied during exercise, ventilation was also not different from air control at 2 days of hypercapnia; however during exercise, unlike the resting studies, there was only a tendency for a secondary increase in ventilation at 7 and 14 days of hypercapnia. During the immediate recovery from chronic hypercapnia when the dogs breathed air there was no evidence of hypoventilation either at rest or exercise despite arterial alkalosis. At 24 h of recovery it appeared that dogs while at rest had a slightly reduced ventilatory response to 5% carbon dioxide relative to control studies. The findings provide suggestive evidence that other factors, in addition to acid-base balance, might contribute to the regulation of ventilation during chronic hypercapnia and the recovery from chronic hypercapnia.

Successful prolonged heparinless venoarterial bypass in sheep

In order to investigate the safety of prolonged heparinless venoarterial bypass (HL-VAB), we subjected 18 sheep to prolonged HL-VAB for up to 6 days. Three animals died of granulomatous lung abscess and one died from intra-abdominal abscess. One animal died of generalized thromboembolism secondary to mechanical damage of the nonthrombogenic coating occurring at the time of cannulation. HL-VAB was successfully carried out in 13 sheep. Although clots were found at all tubing connections where blood turbulence occurred, only the previously mentioned animal showed evidence of thromboembolism. Damage to the nonthrombogenic tubing exposed to the roller pump head was seen in all animals, and its severity appeared to be related to the duration of bypass. Scanning electron microscopic examination revealed scattered platelet aggregates on the nonthrombogenic coated surfaces without clinical evidence of embolization. Hematocrit values, leukocyte counts, platelet counts, prothrombin time (PT), activated partial thromboplastin time (PTT), thrombin time (TT), plasma fibrinogen levels, and factor V and VIII levels remained unchanged, whereas free plasma hemoglobin levels rose slightly during 6 days of HL-VAB. HL-VAB for up to 6 days appears to have little adverse effect on blood cells and blood coagulation factors. For current clinical use, the nonthrombogenic coated tubing circuit should be changed every 48 hours because of time-related trauma to the coated tubing from the roller pump.

Mode of action of Vibrio cholerae enterotoxin in cultured adrenal tumor cells

The effects of Vibrio cholerae enterotoxin on steroidogenesis and on formation of adenosine 3':5'-cyclic phosphate (cyclic AMP) in two adrenal tumor cell lines were compared. Steroidogenesis was half-maximal at concentrations of 1 ng of cholera toxin/ml in the mutant OS-3 cells and 3 ng of cholera toxin/ml in the parent Y-1 cells. At the end of an 8-hr incubation, toxin-induced formation of cyclic AMP in the mutant cell line was reduced by 90%. A molar ratio of GM1 ganglioside (galactosyl-N-acetylgalactosaminyl [sialosyl] lactosyl ceramide; GGnSLC) to cholera toxin of 3:1 caused half-maximal inhibition of steroidogenesis in both cell lines. When equine antiserum to choleragenoid was added to adrenal cells 15 min after cholera toxin, there was marked inhibition of cyclic AMP formation and of steroidogenesis. Pretreatment of Y-1 cells with adrenocorticotropin rendered them unresponsive to hormonal induction of cyclic AMP formation, but these cells had an unimpaired response to cholera toxin. These studies, utilizing two adrenal cell lines, suggest important differences between the mode of action of cholera toxin and that of adrenocorticotropin in cultured adrenal tumor cells.

Blood coagulation studies during six day heparinless venoarterial bypass in sheep

Heparinless venoarterial bypass (HL-VAB) was carried out in 16 sheep for 6 days, by means of a closed circuit tubing coated with nonthrombogenic polyurethane-polyvinyl-graphite (PPG) and a roller pump. Nine experiments were completed uneventfully. Seven sheep died during bypass. The causes of death were pneumonia (2), caseous granulomatous lung abscess (3) or abdominal abscess (1), and thromboembolism (1). The last complication was caused by inadverten trauma to the PPG coating at the time of tubing connection. In the animals in which HL-VAB was uneventful, no significant changes were noted in the hematologic studies including white blood counts, platelet counts, hematocrit, plasma fibrinogen levels, prothrombin time, thrombin time, activated partial thromboplastin time, Factors V and VIII, and free plasma hemoglobin levels. Inconsistant changes in the above parmeters were noted in the animals which died of complications. In conclusion, prolonged HL-VAB has no adverse effects on blood coagulation mechanism.

Mutagenicity testing with Salmonella typhimurium strains. II. The effect of unusual phenotypes on the mutagenic response

The enhanced sensitivity of some Salmonella typhimurium strains to the mutagenic action of a number of chemicals appears to be due to the defect in the uvrB gene product and not to an inability to produce H-2-S or to the absence of formic acid hydrogenlyase which also characterizes these strains.

Negative arterial-mixed expired PC02 gradient during acute and chronic hypercapnia

In resting conscious dogs physiological dead space was calculated using the Bohr equation and measurements of arterial and mixed expired carbon dioxide tension. Whenever dogs inhaled carbon dioxide mixtures (5-10%) that had normal or low oxygen concentrations, the calculated dead space became negative. This paradox was based on the fact that the mixed expired carbon dioxide tension in resting hypercapnic dogs. Under these circumstances carbon dioxide was produced from the lung as measured by gas analyses and blood analyses. By the lung as measured by gas analyses and blood analyses. By reasoning this implies that "alveolar" carbon dioxide tension was higher than pulmonary venous carbon dioxide tension. The negative carbon dioxide gradient persisted at 14 days of chronic hypercapnia and reverted to normal within 10 min of breathing air after chronic hypercapnia. These findings suggest that the exchange of carbon dioxide in the lung cannot be explained solely on the basis of passive diffusion.

In vitro studies of effects of light and riboflavin on DNA and HeLa cells

The widespread use of phototherapy for neonatal hyperbilirubinemia has caused some concern since substances other than bilirubin may be photoactivated. The toxic properties of these photoactivated substances might prove to be more harmful to the neonatal infant than bilirubin. The purpose of the present study was to investigate the effect of photoactivated riboflavin in low concentration, on purified DNA. The results demonstrate extensive changes in the structure of DNA (see Table 1) manifested by (1) a change in the peak absorbance in the ultraviolet, (2) a decrease in the temperature of the thermal helix-coil transition, (3) a slight decrease in the sedimentation coefficient, and (4) an increase in the buoyant density values (1.704-1.709). These observations are consistent with the interpretation that there has been an alteration of one of the base moieties with minimal cleavage of the phosphodiester linkages. Results with human cells in tissue culture indicate that a similar photodynamic effect of riboflavin on the DNA occurs in living cells.