Absorption and protein binding of N-2-fluorenylacetamide and its metabolites in the bladder of rabbit

To assess the reactivity of a bladder carcinogen, the absorption by the rabbit (male New Zealand White) bladder mucosa of N-2-acetylaminofluorene (AAF), N-hydroxy-2-acetyl-aminofluorene (N-OH-AAF), and the N-O-glucuronide of AAF (N-OGI-AAF), as well as binding to the protein and RNA of bladder mucosa, was measured in vivo and in vitro. Mucosal pieces incubated for 3 hours in medium containing a carcinogen demonstrated that the fluorene nucleus of both AAF and N-CH-AAF bound equally with cellular proteins, while N-OGI-AAF binding was lower. In the presence of an excess of beta-glucuronidase, however, N-OGI-AAF showed binding equivalent to its metabolic precursor. After a 3-hour instillation into the bladder lumen of radioactive carcinogens suspended in urine in vivo, transmural absorption of AAF and N-OH-AAF (90%) was substantial, while N-OGI-AAF was absorbed less (55%). The renal excretion during this period varied from 18 to 52% of the instilled radioactivity. There was little reactivity of these carcinogens with the mucosal RNA, both in vivo and in vitro. The metabolism of N-OH-AAF and N-OGI-AAF was such, both in vitro and in vivo, that the acetyl group was not included in the final protein-carcinogen complex in what appeared to be an enzyme reaction.

Neuromuscular sensitivity to tubocurarine. A comparison of 10 parameters

The pharmacometrics of neuromuscular block by tubocurarine was studied. Ten parameters were compared for the sensitivity, the scatter and the linearity of response at three levels of block in 11 cats. The fourth twitch of the train-of-four is the most sensitive parameter, followed in order of decreasing sensitivity by the train-of-four fade, the faded tetanus, the tetanus, the single twitch, the post-tetanic twitch and the tetanic fade. At the level of 50% block of the single twitch, all other parameters differ significantly (P less than 0.05) from the single twitch in sensitivity. With the exception of the tetanic fade, all parameters examined correlate with the single twitch (r xy = 0.42-0.77). This permits limited translation of results among various parameters. In cats the scatter of results is least for the most sensitive parameter, and vice versa. We conclude that the train-of-four is the most sensitive parameter, and that the single twitch is valid for an over-all estimation of the neuromuscular block induced by tubocurarine.

Self-antagonism: a possible mechanism of tachyphylaxis in suxamethonium-induced neuromuscular block in man

Twelve adults receiving halothane-nitrous oxide anaesthesia for elective surgery were investigated during suxamethonium-induced neuromuscular block, using the train-of-four twitch for measurement of both the degree of block and the magnitude of fade (decrease in fourth-to-first ratio). The residual neuromuscular block resulting from prolonged exposure to suxamethonium could be antagonized by bolus injections of suxamethonium itself, in doses which increased the block in Phase I. When self-antagonism was demonstrated, larger doses were necessary to increase the residual block, but only after overcoming the self-antagonizing effect. A biphasic response, first antagonizing then increasing the block, was observed following injection of a single bolus of suxamethonium. The self-antagonizing effect was more obvious in the fourth twitch of the train-of-four, resulting in a marked decrease in train-fo-four fade (increase in train-of-four ratio). It was concluded that self-anatagonism may be an important cause of tachyphylaxis in suxamethonium-induced neuromuscular block in man.

Neuromuscular block by neomycin in the cat

The neuromuscular block produced by neomycin is unique. Despite nearly complete blockade of the twitch the tetanus is not blocked and does not fade. The pathognomonic post-tetanic exhaustion has not been reported previously. Anticholinesterases and calcium antagonize the block, but the antagonism may not be complete. Germine antagonizes the block in the cat, but its clinical value has not been tested. These characteristics of neuromuscular block by neomycin strongly suggest respiratory support and sedation to decrease the respiratory drive, rather than attempts at antagonism, as the rational management of patients suffering from toxic paralysis due to neomycin.

Train-of-four fade and edrophonium antagonism of neuromuscular block by succinylcholine in man

Thumb twitch in response to train-of-four stimulation (2 Hz for 2 sec) of the ulnar nerve was measured in 36 patients anesthetized with halothane and N2O and paralyzed with succinylcholine chloride (SCC). Train-of-four fade was detected whenever a block was produced. The train-of-four ratio decreased with continued exposure to SCC. Edrophonium effect was predictable by the train-of-four ratio in a semiquantitative manner, a high ratio predicting block enhancement and a low ratio, antagonism. When calculated at 30 to 50 percent recovery (from complete block), a train-of-four ratio of 0.4 or less reliably predicts antagonism. The magnitude of antagonism is also predictable in a semiquantitative manner, although complete antagonism cannot be ascertained. The lower the ratio, the more effective the antagonism becomes. Train-of-four fade, therefore, appears to be a consistent and sensitive quantitative sign of phase II neuromuscular block by SCC in man.

A model study of facial injury caused by impact while wearing an ophthalmic frame

Damage to facial tissue caused by an ophthalmic frame when there is impact to the face was studied by means of a paraffin-covered mannequin head. Under mild conditions of impact it was easily observed that metal frames and metal components do more tissue damage than is done by a zylframe. A series of the commonly dispensed frames was compared for facial injury potential caused by impact to the face.

Some characteristics of neuromuscular block in the respiratory musculature in anaesthetized man

The ability to breathe against a mild expiratory obstruction was examined in 64 adult patients under halothane-nitrous oxide-oxygen anaesthesia. The trachea of all patients were incubated. It was found that d-tubocurarine 0.11 mg/kg blocked the respiratory musculature by 50 per cent. The onset of block was immediate, with the peak effect reached within one minute. The duration of block was either very short (1 to 2 minutes) or long (paralleling the blockade in the thumb twitch), depending upon the dose of d-tubocurarine. Following injection of a small dose (up to 0.1 mg/kg) the respiratory musculature might be blocked by 30 per cent but for only one minute, disproportionately short as compared with the thumb twitch. Following injection of a large dose (0.1-0.3 mg/kg) the duration was long, but the recovery was only slightly ahead of the thumb. Following an intermediate dose, a biaphasic pattern was observed. An initial partial recovery was observed during the first 1 to 2 minutes. Comparison of the respiratory musculature and the thumb twitch revealed that the respiratory musculature was highly sensitive to block and has a different time course. Succinylcholine 0.08 mg/kg blocked the respiratory force by 50 per cent with a time course similar to the block in the thumb twitch. The clinical significance of these observations are discussed.

Spontaneous recovery of the thumb twitch from neuromuscular block by suxamethonium in anaesthetized man

The neuromuscular blocking effect of repeated bolus administration of suxamethonium 1 mg/kg was observed in 10 healthy surgical patients under enflurane-nitrous oxide-oxygen anaesthesia. Tachyphylaxis and slow recovery of the thumb twitch occurred in close dose-relationships with transition of Phase I block to Phase II, using train-of-four fade as an indicator of the transition. Failure of the thumb twitch to recover to 75% of control, and subsequent step-wise depression from additional doses of suxamethonium had a sudden onset shortly after establishment of marked train-of-four fade.

Suppressive role of indole on 2-acetylaminofluorene hepatotoxicity

Indole is known to suppress the hepatotoxicity and carcinogenicity of 2-acetylaminofluorene (AAF) in rats and hamsters. For elucidation of the mechanism of its protective role, 2 experiments were conducted using young male rats. In the 1st experiment, the 24-hr biliary excretion of N-hydroxy-2-acetylaminofluorene (N-OH-AAF)-glucuronide was measured after 2 and 4 weeks of dietary administration of 0.03% AAF with or without 1.6% indole. The amount of [9-14C]N-OH-AAF that was excreted as the glucuronide following a single i.p. injection of [9-14C]AAF was lower after 2 weeks in animals fed AAF and indole, as compared to those fed AAF alone [1.5 +/- 1.2% versus 19.6 +/- 3.6% S.E. (p less than 0.001)]. After 4 weeks of AAF administration without indole, the biliary excretion fell to 4.8 +/- 2.1%. This was also significantly higher than that of the animals fed both AAF and indole [1.8 +/- 1.2% (p less than 0.025)]. The suppressive role of indole on the conjugate excretion was also reflected in a decreased biliary excretion of all [9-14C]AAF metabolites in animals treated with indole alone. In the 2nd experiment, the protective action of indole was assessed by survival following daily i.p. injections of N-OH-AAF and Na2SO4 solution. Na2SO4 increased the hepatotoxicity of N-OH-AAF. Indole suppressed the toxicity of N-OH-AAF even in the presence of Na2SO4. This protective role of indole was partially overcome only when excess sulfate was coadministered. These results indicate that indole suppresses the biliary excretion of the O-glucuronide of N-OHAAF during the initial exposure of the animal to the carcinogen, possibly reflecting decreased N-OH-AAF formation. Indole also modifies the metabolism of AAF FOLLOWING N-hydroxylation, perhaps activating N-OH-AAF, depending upon the concentration of sulfate available.

Catecholamine-binding brain protein in mice exposed to perinatal malnutrition and neonatal infection

The formation and specific activity of a catecholamine-binding brain protein were studied in mice exposed to perinatal malnutrition and neonatal infection. In the malnourished group, the total norepinephrine (NE)-binding protein was less than in the control group (malnourished 7.1-10.0 mg; control 13.0-14.0 mg), but the dopamine (DM)-binding protein was not significantly affected. In the infected group, the quantity of NE-binding protein was also decreased (infected 6.4-8.0 mg), but the DM-binding protein was higher than in the control group. The specific and total binding activity of [3H]NE to brain protein was greatly reduced in the infected group (infected 22.6 pmol/mg protein; control 88.4 pmol/mg protein), and decreased also in the guanidine-HCl eluate of the malnourished group (56.5 pmol/mg protein). The binding activity of [14C]DM was decreased markedly in the infected group (infected 131 pmol/mg protein; control 330 pmol/mg protein), but its specific binding activity was not as severely affected in the malnourished as in the infected group. The molecular weights of the catecholamine-binding protein were 75,000 in the control, 70,000 in the malnourished and 65,000 in the infected groups. There were no marked differences between the malnourished and control groups with regard to the amino acid composition of the NE-binding protein. The DM-binding protein in these animals had decreased amino acid content. The infected group exhibited remarkable changes in NE- and DM-binding brain protein.

Dose relationships of phase II, tachyphylaxis and train-of-four fade in suxamethonium-induced dual neuromuscular block in man

In man under halothane-nitrous oxide-oxygen anaesthesia, suxamethonium-induced neuromuscular block can be divided into two phases using the train-of-four ratio: the first phase of minimal train-of-four fade and the second phase of marked train-of-four fade. The second phase is characterized by a low train-of-four ratio, 0.3 or less, and resembles tubocurarine-block) in many details. It corresponds to Phase II (dual block in the literature. Contrary to the prevailing belief, Phase II block has a rather abrupt onset. In this study of seven patients, Phase I covered up to a total of 1--3 mg/kg of suxamethonium, while 3--5 mg/kg established Phase II block, with a transitional zone of only 2 mg/kg. Establishment of Phase II also coincided with onset of unequivocal tachyphylaxis. The possibility of a causal relationship between tachyphylaxis and Phase II block is suggested.

Effect of crosslinking on mitochondrial structure and function

Rat liver mitochondria were treated with ethylacetimidate and methylbutyrimidate, monofunctional imidates, and with dimethylsuberimidate, a bifunctional imidate, and the effects on structure and function studied. Mitochondria treated with 5 mM dimethylsuberimidate or greater did not respond osmotically when placed in deionized water. Sodium dodecylsulfate-polyacrylamide gel electrophoresis revealed that at concentrations greater than 5 mM dimethylsuberimidate nearly all mitochondrial polypeptides failed to enter 6% gels, indicating crosslinking of both membrane and soluble proteins. Extensive amidination by ethylacetimidate and methylbutyrimidate had little effect on ascorbate-tetramethylphenylenediamine oxidase while extensive inhibition resulted from dimethylsuberimidate treatment. The possible involvement of molecular motion in electron transport is discussed.

In vitro interaction of estrogen and prolactin on hormone-dependent rat mammory tumors (38511)

Hormone-dependent, regressing mammary tumors in rats were incubated in a chemically defined culture medium containing tritium labeled leucine at 37 degrees for 2 hr. The rate of tritium incorporation into the protein fraction by these tissues was measured with and without the addition of 17beta-estradiol and/or ovine prolactin into the medium. Tumor tissue responded to either estrogen or porlactin by a 6-7% increase in the rate of 3-H-leucine incorporation. When the incubation medium contained both the hormones, the increase in the rate of 3-H leucine incorporation was 19% which was significantly greater than the sum of the effect of each single hormone measured independelntly. These results demonstrate a synergistic effect between estrogen and prolactin on rat mammary tumors.

Estrogen receptor in the rabbit corpus luteum

The rabbit corpus luteum contains a cytoplasmic estrogen receptor substance in concentrations comparable to those found in the uterus. Receptor in corpora lutea of nonpregnant rabbits was highest at midluteal phase and decreased before physical regression of corpora was evident. These results support the view that the corpus luteum in this species is an estrogen-responsive tissue.