Differing activities of medullary respiratory neurons in eupnea and gasping

Our purpose was to compare further eupneic ventilatory activity with that of gasping. Decerebrate, paralyzed, and ventilated cats were used; the vagi were sectioned within the thorax caudal to the laryngeal branches. Activities of the phrenic nerve and medullary respiratory neurons were recorded. Antidromic invasion was used to define bulbospinal, laryngeal, or not antidromically activated units. The ventilatory pattern was reversibly altered to gasping by exposure to 1% carbon monoxide in air. In eupnea, activities of inspiratory neurons commenced at various times during inspiration, and for most the discharge frequency gradually increased. In gasping, the peak discharge frequency of inspiratory neurons was unaltered. However, all commenced activities at the start of the phrenic burst and reached peak discharge almost immediately. The discharge frequencies of all groups of expiratory neurons fell in gasping, with many neurons ceasing activity entirely. These data are consistent with the hypothesis that brain stem mechanisms controlling eupnea and gasping differ fundamentally.

Activities of two new antiviral agents against guinea pig lymphotropic herpesvirus infection in vitro

Two new antiviral agents, compound 164, also known as 2'-nor-cGMP (9-[(2-hydroxy-1,3,2-dioxaphosphorinan-5-yl)oxymethyl]-guani ne P-oxide), and compound 102 [4-amino-5-bromo-7-(2-hydroxyethoxymethyl)-pyrrolo(2,3-d)pyrimidine], together with acyclovir for comparison, were evaluated for activities against the guinea pig lymphotropic herpesvirus infection in vitro by plaque reduction and virus yield reduction assays in guinea pig embryo cells. The two new compounds were demonstrated to be more potent against guinea pig lymphotropic herpesvirus infections than acyclovir. Compound 164 was the most potent of the three; drug concentrations required to reduce the number of plaques by 50% were 2, 35.5, and 144.5 microM for compounds 164, 102, and acyclovir, respectively. The two new compounds were cytostatic but not cytotoxic to guinea pig embryo cells in cultures. Attempts were made to investigate the inhibition of viral replication by these compounds, and the influence of test conditions on antiviral evaluations is discussed.

Evaluation of new antiviral agents: I. In vitro perspectives

A variety of different methods for the evaluation of antiviral agents in cell culture systems are briefly reviewed. It has been repeatedly noted that many test conditions such as the cell culture system, virus strain, virus challenge dose, virus input multiplicity of infection, and time of harvesting, etc., can substantially affect or even alter the test results, thus making comparative studies and unambiguous evaluations very difficult. Attempts are made to discuss previous test methods together with our recent studies with the aim to simplify test procedures and assay methods. Suggestions are proposed for in vitro evaluation of new antiviral agents. It is hoped that this review will alarm investigators to the problems of assaying new antiviral agents. If the suggestions made in this review can be followed, the screening of the enormous number of promising antiviral compounds may be made more efficiently in the near future.

[Studies on the origin of different discharge pattern of the two types of phrenic motoneurones by cross-correlation analysis]

Experiments were performed on twenty five anesthetized, paralyzed, vagotomized and artificially ventilated rabbits. Discharges of single phrenic nerve fibers were recorded. According to their discharge patterns, phrenic motoneurones were divided into two types: tonic units (TU) and phasic units (PU). A cross-correlation analysis was done between TU and TU, PU and PU, or TU and PU. In 21/36 pairs of phrenic motoneurones, the cross-correlation histogram showed a significant central peak, which represented synchronization of the pair of units resulting from a common input. There were three types of synchronization: short-term, broad peak and high frequency-oscillatory synchronization. The difference in synchronization number between heterogeneous pairs (1 TU and 1PU, 2/10 showing synchronization) and homogeneous pairs (2 TU or 2 PU, 19/26 showing synchronization) was statistically significant (x2-test, P less than 0.05). These results suggest that TU and PU have different central inputs, which result in their different discharge patterns between the TU and PU.

Metal-binding abilities of radioprotective aminoalkyl disulfides and thiosulfates

Mental-binding stability constants for several heterocyclic aminoalkyl disulfides and thiosulfates with Ni(II) and Al(III) were determined. The data obtained indicated that both classes of compounds were acting as bidentate chelating agents and that the heterocyclic rings apparently prevented tridentate behavior of the disulfides because of steric hindrance. The magnitude of the constants indicated that metal complexes of these compounds could exist in a cellular environment, but no correlation with radiation-protective activity was apparent.

A facile method of purification of neocarzinostatin, an antitumor protein

A three-step column chromatographic method for the purification of neocarzinostatin (NCS) from a crude preparation was described. The purified material was homogeneous by acrylamide gel electrophoresis, isoelectric focusing, amino terminal analysis, and immunologic criteria. Purified NCS was 40 times as active in the inhibition of growth of Sarcina lutea and twice as active against CCRF-CEM human leukemia cells in vitro as was the starting material. When assayed against P388 and L1210 mouse leukemias in vivo, the purified material showed a median increase in life-span of 119 and 72%, respectively.