[On the acute toxicity of labetalol (AH-5158), a combined alpha-and-beta-adrenoceptor-blocking agent (author's transl)]

Acute toxicity studies in labetalol were performed using mice, rats and rabbits, An oral administration of labetalol produced an increase in salivary secretion due to local irritation. Death followed convulsions by large doses of labetalol. Pathological examinations suggested that the cause of death by labetalol was circulatory disturbances due to the damage of heart muscles and a subsequent respiratory paralysis. Parenteral LD50 showed almost the same values among mice (50 mg/kg iv, 117 mg/kg ip), rats (66 mg/kg iv, 115 mg/kg ip) and rabbits (43 mg/kg iv). However, species difference was seen in oral LD50 values which were enormously large as compared with iv LD50 values.

Dietary and hormonal regulation of the content of acetyl coenzyme A carboxylase-synthesizing polysomes in rat liver

Specific polysomes involved the the synthesis of acetyl-CoA carboxylase [acetyl-CoA: carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] have been identified by the binding of 125I-labeled antiacetyl-CoA carboxylase to rat liver polysomes. The binding is highly specific and occurs through the recognition of the nascent peptide chains on polysomes. With the use of the 125I-labeled antibody binding technique, it has been demonstrated that the relative content of acetyl-CoA carboxylase-synthesizing polysomes in the liver correlates well with the rate of hepatic synthesis of the enzyme in rats subjected to different dietary conditions as well as in alloxan-diabetic rats with or without insulin treatment.

Species difference of mitochondrial respiration in experimentally induced heart failure

In guinea pigs with acute heart failure, a decrease in oxygen consumption (QO2) at state 3 and an increase in QO2 at state 4 were seen and the respiratory control index (RCI) was markedly lowered; ADP/O ratio was not affected. In rabbits with acute heart failure, both RCI and ADP/O ratio showed a statistically significant decrease. In dogs with acute and chronic heart failure, no impairment of respiratory function of mitochondria was seen. These conflicting results may be attributed to the difference in experimental conditions, namely, the species difference and the difference in methods to produce experimental heart failure. With special regard to species difference, it was confirmed that the RCI of myocardial mitochondria of healthy dogs was much lower than that of healthy guinea pigs. It is suggested that the difficulty of obtaining intact mitochondria may be responsible for the species difference in experimentally induced heart failure.

Intrarenal distribution and ATPase inhibiting activity of ouabain in dogs

Experiments were undertaken to substantiate the hypothesis that the mechanism of the direct effect of ouabain on the renal excretion of electrolytes is the result of inhibition of the transport enzyme, (Na, K)-ATPase. In dogs hydrated with saline, an injection of 3H-ouabain into the unilateral renal artery produced a continuing marked increase in excretion of water and sodium from the kidney, but not from the counter kidney. At maximal diuresis--90 min after ouabain injection, both kidneys were removed to assay microsomal ATPase activity and determine radioactivity distributed in subcellular structures. It was demonstrated that 3H-ouabain was deposited in the microsome fraction obtained from the injected kidney in concentrations ranging from 10(-7) to 10(-6) M/kg wet weight, and (Na, K)-ATPase activity of this fraction was inhibited as compared with that of the microsomal fraction obtained from control kidneys. Since (Na, K)-ATPase activity of renal microsomes was significantly inhibited in vitro by more than 10(-7) M of ouabain, ouabain concentration in microsomes obtained from the injected kidney was considered to be sufficient to inhibit ATPase activity. These findings indicate that ouabain diuresis under the present condition is closely related to direct inhibitory effect of ouabain on (Na, K)-ATPase activity of microsomes in tubular cells.

The modification of inotropic action of ouabain by 6-hydroxydopamine and alpha-methyl-p-tyrosine in dogs

The action of ouabain on myocardial inotropism pretreated with 6-hydroxydopamine and alpha-methyl-p-tyrosine was studied. Inotropic action of ouabain was not changed by depletion of catecholamines in the brain, in which the central sympathetic neurons were destroyed by an intraventricular administration of 6-hydroxydopamine. Systemic administration of 6-hydroxydopamine and alpha-methyl-p-tyrosine reduced ventricular catecholamines to 5.3% and 20.8% of the control, respectively. Percent increase of contractility by ouabain after the pretreatment of 6-hydroxydopamine and alpha-methyl-p-tyrosine was reduced to 16.7% and 50.3% of the control, respectively. The results obtained suggest that catecholamines in the myocardium play some important role in producing cardiotonic action of cardiac glycosides. Brain catecholamines or the central sympathetic nervous system do not appear to participate in the exertion of the positive inotropic action of cardiac glycosides.

Discrimination of odors in olfactory bulb, pyriform-amygdaloid areas, and orbitofrontal cortex of the monkey

In the orbitofrontal olfactory area (LPOF) which was delineated in a previous paper, the capacity for odor discrimination was studied and compared with that in the anterior pyriform cortex (AP), the medial portion of the amygdala (MA), and the olfactory bulb (OB). Unanesthetized monkeys were used and eight odors were applied. 1. In the OB, 12.5% of the cells responded to only one odor, and the cells which responded to five odors were most numerous (25%). The total of the cells which responded to two, three, and four odors was 52%, which was less than the total of the cells responding to three, four, and five odors (67.5%). A small number oc cells responded to all eight odors (2.5%). The responses were classified as an increase (+type), a decrease (-type), or no change (no-type) in the rate of spike discharge. 2. In the AP and MA, no difference in the response patterns was found. The cells which responded to only one odor were 12.3% of the total, and the cells which responded to three different kinds of odors were most numerous (34.3%). The total of the cells responding to two, three, and four odors was 80%, much more than that in the OB. In addition, no cell responded to all eight odors. Concerning the response types, an increase followed by a decrease, or vice versa, in the rate of spike discharges (mixed-type) was observed which did not appear in the OB. Thus, an advance was found in the processing of olfactory information when compared with the OB. 3. A most striking finding in the LPOF was that 50% of the cells responded to only one odor. The cells which responded to two, three, and four odors decreased in this order, and no cell responded to more than five odors. These cells never responded to light or sound. 4. Using three very similar odors and five very different odors, it was apparent that the ability to discriminate odors of the same category is far more advanced in the LPOF than in the lower olfactory areas; and, in contrast, the lower olfactory areas also play a significant role in the discrimination of odors which belong to different categories. 5. It was concluded that the capacity for odor discrimination definitely improves along the olfactory nervous system from the lower to the higher areas. It is highly probable that a fine and sepcific discrimination of odors is performed in the LPOF.

An olfactory projection area in orbitofrontal cortex of the monkey

An olfactory projection area was studied in monkeys anesthetized with Nembutal. 1. Evoked potentials were recorded when the olfactory bulb (OB) was electrically stimulated in the lateroposterior portion of the orbitofrontal cortex (LPOF). However, those potentials disappeared when the anterior pyriform cortex (AP) (probably together with the medial portion of the amygdala (MA)) was aspirated or electrically destroyed. 2. In nearly the entire hypothalamic region, evoked potentials were recorded by the same stimulation of the OB. When the hypothalamic region was stimulated, evoked potentials were recorded in the LPOF. 3. The evoked potentials in the LPOF due to the OB stimulation never disappeared even when the thalamus was extensively aspirated or destroyed electrically, but they did disappear when the anterolateral and dorsoposterior portions of the hypothalamus were absorbed or electrocoagulated. 4. Evoked potentials in the mediodorsal nucleus (MD) of the thalamus were recorded when the OB was stimulated. When this nucleus was stimulated, evoked potentials were observed in the broad extent of the orbitofrontal cortex anterior to the LPOF, but never in the LPOF itself. 5. Monkeys were conditioned to discriminate two odors. When the LPOF was removed, such ability strikingly decreased; but when other areas in the prefrontal cortex were removed, the ability decreased only slightly. 6. It was concluded that there exists an olfactory pathway from the OB to the LPOF through the AP (and probably the MA) and the hypothalamus, but none through the thalamus, and that the LPOF plays an important role in the discrimination of odors. 7. It was proved that the entorhinal cortex (ER) is neither located as an intermediate olfactory area nor is it situated as a higher area than the LPOF in the newly found olfactory pathway stated above. It may be a link between the high olfactory area and the limbic system.

Acetyl-coenzyme-A carboxylase from rat liver. Subunit structure and proteolytic modification

The subunit structure of rat liver acetyl-coenzyme-A carboxylase has been studied by polyacrylamide gel electrophoresis in the presence of dodecylsulfate. A number of individual preparations of the enzyme purified by the same procedures exhibited three different types of electrophoretic patterns as follows: first, a single slow-moving protein bands (Mr 230000); secondly, two adjacent fast-moving protein band (M4 124000 and 118 000); finally, all three protein bands. With the use of the [14C]biotin-labelled enzyme, the biotinyl prosthetic group was shown to be associated with the polypeptide of 230000 Mr as well as with that of 124000 Mr, but not with the polypeptide of 118000 Mr. Studies were next made with the labelled enzyme to examine the possibility that the two light polypeptides might have been formed by proteolytic modification of the heavy polypeptide during the procedures used for the purification of the enzyme. Treatment of the enzyme with trypsin or chymotrypsin resulted in cleavage of the heavy polypeptide into two nonidentical polypeptides with molecular weights of approximately 120000. Incubation of the enzyme with proteases derived from rat liver converted the heavy polypeptide into lighter polypeptides of 80000-130000 Mr. Acetyl-CoA carboxylase isolated from crude rat liver extracts by means of immunoprecipitation with specific antibody invariably showed only the heavy polypeptide. The biotin content of the enzyme was found to be 1 mol per 237000 g protein. These results indicate that rat liver acetyl-CoA carboxylase, unlike bacterial and plant biotin enzymes, has only one kind of subunit, which has a molecular weight of 230000 and contains one molecular of biotin. Thus, the mammalian enzyme exhibits a highly integrated subunit structure.

[On the toxicity of CT-1341 evoked by long-term administration. I. Subacute toxicity of the intravenous anesthetic, CT-1341 in rats (author's transl)]

CT-1341, an intravenous anesthetic was given in various daily doses in rats for a period of one month to test the subacute toxicity. The drug was administered intraperitoneally in rats. Rats tolerated to daily administration of CT-1341 at doses of less than 1.8 ml/kg without showing other particular toxic signs than anesthesia. Main pathological findings were swelling of cells in the liver and renal tubules, and perivascular cuffing in lungs. No severe patho-histological changes were observed in any organs. Mortal cases were seen in the group of rats, in which CT-1341 was given in a daily dose of 5.4 ml/kg. A paralysis of respiratory center was suggested to be cause of death, because no severe patho-histological changes were observed in any organs of mortal rats. Survivals of this group showed no particular symptom except anesthesia, but an inhibition of the growth curve was seen in male rats only.