Effects of ddC and AZT on locomotion and acoustic startle. I: Acute effects in female rats.

Several synthetic nucleoside analogues, including AZT(RETROVIR), ddC (HIVID), ddI (VIDEX), and d4T (ZERIT), are currently being used in the treatment of HIV infection. Unfortunately, in clinical use the appearance of severe and sometimes debilitating peripheral neuropathy and pain has been associated with the long-term use of several of these drugs (i.e., ddC, ddI and d4T), although not with AZT. To date, standard pre-clinical animal toxicity studies have failed to reveal any adverse neurologic effects of these compounds. However, previously reported preliminary findings suggest that ddC may alter several neuro-behavioral parameters (including locomotor activity, acoustic startle responding, and aggression) in rats and mice following presentation in the animals' drinking water for 7 days. The current series of experiments examined effects of acutely administered ddC and AZT on spontaneous locomotor activity and acoustic startle responses (with and without pre-pulse) in female Sprague-Dawley rats. Following intragastric administration, ddC reduced locomotion at all but the highest dose, whereas AZT had no significant effect on locomotor activity. Acutely administered ddC had no effect on ASR, whereas AZT increased ASR at the highest stimulus intensity. These data support the use of behavioral testing in the development of the antiviral nucleoside analogues, as behavioral testing may be more effective in identifying the neurologically active agents than is standard toxicity testing.

Indomethacin attenuation of radiation-induced hyperthermia does not modify radiation-induced motor hypoactivity.

Exposure of rats to 5-10 Gy of ionizing radiation produces hyperthermia and reduces motor activity. Previous studies suggested that radiation-induced hyperthermia results from a relatively direct action on the brain and is mediated by prostaglandins. To test the hypothesis that hypoactivity may be, in part, a thermoregulatory response to this elevation in body temperature, adult male rats were given indomethacin (0.0, 0.5, 1.0, and 3.0 mg/kg, intraperitoneally), a blocker of prostaglandin synthesis, and were either irradiated (LINAC 18.6 MeV (nominal) high-energy electrons, 10 Gy at 10 Gy/min, 2.8 microseconds pulses at 2 Hz) or sham-irradiated. The locomotor activity of all rats was then measured for 30 min in a photocell monitor for distance traveled and number of vertical movements. Rectal temperatures of irradiated rats administered vehicle only were elevated by 0.9 +/- 0.2 degree C at the beginning and the end of the activity session. Although indomethacin, at the two higher doses tested, attenuated the hyperthermia in irradiated rats by 52-75%, it did not attenuate radiation-induced reductions in motor activity. These results indicate that motor hypoactivity after exposure to 10 Gy of high-energy electrons is not due to elevated body temperature or to the increased synthesis of prostaglandins.

Expression and characterization of two differentiation antigens in human stratified squamous epithelia and carcinomas.

Using viable cells of a human squamous-cell carcinoma (SCC) cell line as immunogen, we generated 2 monoclonal antibodies, MAbs K984 and K928, to SCC surface antigens. Immunoperoxidase staining of frozen sections of normal epidermis revealed that MAb K984 reacts with the poorly differentiated basal cells, while MAb K928 is reactive with the more highly differentiated suprabasal cells. A similar complementary reaction pattern of these antibodies was demonstrated in the majority of well-differentiated human tumors and some moderately differentiated SCCs. In contrast, simultaneous reactivity of MAb K984 and K928 was found for the majority of cells within other well- and moderately differentiated SCCs, as well as all poorly differentiated SCCs. Further biochemical characterization indicated that the antigen recognized by MAb K984 is similar to the one recognized by MAb SF-25. MAb K928 recognizes a 50- to 55-kDa molecule under non-reducing conditions. Antibodies with similar features to MAb K928 have not been described previously. The antigens recognized by MAbs K984 and K928 can be regarded as novel markers associated with cellular maturation in squamous epithelia. The antigen detected by MAb K984 is probably associated with the proliferating fraction in SCCs.

Behavioral toxicity of selected radioprotectors.

Effective radioprotection with minimal behavioral disruption is essential for the selection of protective agents to be used in manned spaceflight. This overview summarizes the studies on the behavioral toxicity of selected radioprotectors classified as phosphorothioates (WR-2721, WR-3689), bioactive lipids (16, 16 dimethylprostaglandin E2(DiPGE2), platelet activating factor (PAF), leukotriene C4), and immunomodulators (glucan, synthetic trehalose dicorynomycolate, and interleukin-1). Behavioral toxicity was examined in laboratory mice using a locomotor activity test. For all compounds tested, there was a dose-dependent decrease in locomotor behavior that paralleled the dose-dependent increase in radioprotection. While combinations of radioprotective compounds (DiPGE2 plus WR-2721) increased radioprotection, they also decreased locomotor activity. The central nervous system stimulant, caffeine, was able to mitigate the locomotor decrement produced by WR-3689 or PAF.

Behavioral and physiological effects of leukotriene C4.

Leukotriene C4 (LTC4), a lipoxygenase metabolite of arachidonic acid, is a biological mediator of vasoregulation, pulmonary activity, shock, and inflammation, that has been demonstrated to have radioprotective efficacy. The effects of LTC4 on locomotor activity, rectal temperature and hematocrit were examined. Subcutaneous administration of doses of 1.0 micrograms LTC4/mouse or less did not affect locomotor activity. Doses of 5 or 10 micrograms LTC4/mouse, however, resulted in almost complete cessation of locomotion within 12-14 min following treatment. At these doses, activity was suppressed for 2 h with complete recovery by 3 h postinjection. While a dose as high as 10 micrograms LTC4 did not affect rectal temperature, 5 and 10 micrograms LTC4 resulted in hematocrit increases of 10% and 40% respectively. Hematocrit returned to baseline within 1 h after a 5 micrograms pretreatment of LTC4, and by 3 h following a 10 micrograms pretreatment. The duration of LTC4-induced locomotor suppression did not correlate with previously determined durations of LTC4-induced radioprotection.

Effect of electron radiation on aggressive behavior, activity, and hemopoiesis in mice.

The behavioral and physiological effects of 10 Gray (Gy) LINAC electrons in male Swiss-Webster mice were followed for 12 days postirradiation (PR). In Experiment 1, aggressive behavior was assessed in irradiated or sham-irradiated resident mice using a resident-intruder paradigm. Aggressive offensive behavior in the irradiated residents was significantly decreased beginning 2 to 5 days PR, and remained suppressed. Defensive behavior in the nonirradiated intruders was decreased significantly by day 5 PR. In Experiment 2, spontaneous locomotor activity was monitored. Ambulation of irradiated mice was significantly depressed from day 5 PR on, while rearing was affected as early as day 2 PR and remained suppressed. Body weights of irradiated animals were significantly decreased by 5 days PR. In Experiment 3, blood parameters were examined. Compared to sham-irradiated controls, leukocytes, erythrocytes, and hematocrit of irradiated mice were reduced significantly beginning on day 1 PR and remained suppressed, while platelets and hemoglobin were decreased beginning day 2 PR. These results demonstrate that 10 Gy of high-energy electrons results in earlier behavioral deficits than has been observed previously with the same dose of gamma photons.

Long-term effects of radioprotector WR-2721 on locomotor activity and body weight of mice following exposure to ionizing radiation.

The effects of 13 Gy gamma-radiation alone and in combination with 200 mg/kg of the radioprotector S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721) on locomotor activity and body weight were examined in CD2F1 mice over a 10-month period. The results confirmed that WR-2721 is an excellent radioprotector against lethality. All mice receiving 13 Gy without WR-2721 died in 5-7 days. For mice that received WR-2721 alone or WR-2721 + radiation, survival at 30 days was 100% and 70%, respectively. Body weights of mice receiving WR-2721 without radiation were comparable to control animals. Body weights of animals given WR-2721 + radiation fell on days 1-5 and then increased until day 11, but remained below control values throughout the experiment. Animals in the radiation-only group did not exhibit any significant reductions in behavior until day 2 post-irradiation. Mice administered WR-2721 alone showed significantly reduced locomotor activity levels on day 0 then completely recovered within 24 h and exhibited normal body weights. Animals given WR-2721 before irradiation showed greater reductions in locomotor activity on day 0 than either the WR-2721 or radiation-only groups and recovered to control level by day 3. Beginning on day 5, they showed significant reductions in activity. Mice pretreated with WR-2721 that survived a normally lethal dose of radiation showed a 20-40% reduction in locomotor performance that recovered in 2-5 months.

Locomotor behavior in mice following exposure to fission-neutron irradiation and trauma.

Locomotor activity, body weights, and food and water consumption were monitored in female mice for 35 d following a sublethal wound (W), burn (B), exposure to 3 Gray fission neutron radiation (R), or combination of these injuries: radiation-wound (RW) and radiation-burn (RB). Activity in groups W and RW was depressed immediately after injury, with recovery to control levels after 5 and 14 d, respectively. Mice that received radiation alone showed a biphasic response with decrements in activity on days 0-4 and 9-11. Groups B and RB exhibited depressed activity levels that differed significantly from control levels until day 17. Food intake was reduced for about 6 d in groups R, W, RW, and RB. Body weights decreased for 4 d in groups R, W, RW, and RB, but returned to control levels by the end of the experiment. Animals in group B did not show significant reduction in food intake or body weight. Water consumption was reduced for 5-6 d in groups R and RB and was increased in groups W, RW, and B. The data suggest that behavioral responses to fission-neutron radiation are exacerbated by tissue trauma.

Dose and time relationships of the radioprotector WR-2721 on locomotor activity in mice.

The effects of the radioprotector S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721) on locomotor activity were evaluated in CD2F1 male mice. Separate groups of animals (N = 10/group) received an IP injection of vehicle, 25, 50, 100, 200, or 400 mg/kg of WR-2721 immediately before testing. Horizontal and vertical activity were measured using a Digiscan automated animal activity monitor. The latency to onset and duration of action of each dose of the radioprotector were recorded. For both behavioral measures, a significant reduction was observed in activity at doses of 200 and 400 mg/kg. A dose of 200 mg/kg had a 12- to 14-min latency to onset and significantly reduced behavioral activity for 3 hr. Mice injected with 400 mg/kg exhibited locomotor deficits within 8-10 min and were affected for up to 9 hr. The ED50 for horizontal and vertical activities at 1 hr postinjection were determined to be 271 and 105 mg/kg, respectively. The results demonstrate that significant reductions in locomotor activity are exhibited at doses of 200 mg/kg or more and that vertical activity was more sensitive to the disruptive effects of WR-2721 than was horizontal activity.

Torquing in class: an interesting twist for orthodontists.

A method of measuring the amount of slack inherent in the system of Edgewise brackets and archwires is presented, and some related problems concerning the use of turrets discussed.

Effects of conditioned fear on responsiveness to pain: long-term retention and reversibility by naloxone.

The effect of a conditioned fear stimulus (CS) on responsiveness to pain was examined in three experiments. In Experiment 1, a CS that signaled shock attenuated freezing in response to shock, with the attenuation occurring several minutes after the shock. Naloxone blocked the effect of the CS. The effect of the CS, including its reversibility by naloxone, was retained over an interval of 90 days. Experiment 2 showed that this effect on freezing is due to associative fear conditioning, rather than blocking of conditioning to context by a novel cue. In Experiment 3, presenting a fear CS just prior to administering a tail-flick (radiant heat) test of nociception increased the tail-flick latencies; that is, the fear CS apparently induced hyperalgesia rather than analgesia. Because this result makes it difficult to interpret the change in freezing seen in the first experiment as reflecting antinociception, it raises questions about how pain might differentially affect different measures of pain responsiveness. A memory hypothesis is advanced to resolve the different effects obtained with the freezing and tail-flick tests.

Retraction of canines using bonded tube-brackets.

Investigations using a Force Analyser were carried out to test the characteristics of retractor springs fitted to a removable appliance and designed for insertion into a tube-bracket, bonded to the buccal surface of a canine. The retractors were shown to produce a counter-rotation couple when activated on the typodont. This type of canine retraction was then used clinically, and was found to produce less distal tilting than is noted with the single-point contact of a cantilever spring. Some spontaneous reduction in overjet was found to occur in each case of a small series. Possible mechanisms to account for this effect are discussed.

Retraction of canines with axial control using extra-oral traction.

Retraction of canines with control of tooth inclination is described, using the direct application of extra-oral traction. the technique requires a modified facebow to be inserted into buccal tubes on canine bands; no archwires or springs are involved. In the upper arch the facebow is connected to a standard variable pull headgear, while a supported cervical strap is required for the lower canines. Preliminary investigations are outlined and the procedure is illustrated by some clinical cases from a pilot feasibility study.