Mesencephalic reticular formation lesions made after habituation training abolish long-term habituation of the acoustic startle response in rats.

Lesions to the mesencephalic reticular formation (MRF) in rats severely attenuate the acquisition of long-term habituation of the startle response when the lesions are made prior to habituation training. The present experiments extend the finding of habituation deficits to animals with MRF damage made after the animals have habituated to an auditory stimulus. Following habituation training, some animals received lesions to the MRF. The startle amplitudes of these animals immediately changed from control levels to levels indistinguishable from those of animals that never habituated across days--animals with MRF lesions made prior to habituation training. The mechanism responsible for long-term habituation appears to be a progressive increase in activity within a long-term habituation pathway extrinsic to the reflex circuit for the startle response, but the synaptic mechanisms responsible for this change are unknown.

Habituation of the acoustic startle response in rats after lesions in the mesencephalic reticular formation or in the inferior colliculus.

Extensive damage to the mesencephalic reticular formation (MRF) in rats altered long-term habituation of the acoustic startle response without disrupting short-term habituation. The MRF lesions did not alter initial startle amplitudes, but the animals with lesions were unable to attain as low a long-term asymptote of habituation as could control animals. Subsequent manipulation of stimulus intensity and interstimulus interval revealed no differences in short-term habituation between the two groups. Large lesions to the inferior colliculus (IC) did not disrupt long-term habituation of the acoustic startle response, but these animals were unable to suppress responding as much as controls to intense stimuli presented rapidly. The deficits in long-term habituation following MRF lesions suggested a disruption of an extrinsic, inhibitory mechanism of habituation. The deficits following IC lesions could be due either to a disruption of a short-term habituation mechanism or to an increase in response sensitization produced by the lesions.

Behçet's syndrome associated with pregnancy.

A case of Behçet's syndrome diagnosed during pregnancy is reported. It is believed that this condition is more common in the United States than previously thought. It should be considered in the differential diagnosis of genital ulceration.

Comparison of the skin irritation potential of two testosterone transdermal systems: an investigational system and a marketed product.

Effective transdermal therapy provides controlled release of the appropriate amount of a therapeutic agent while minimizing local irritation. Transdermal administration of testosterone has the potential to produce skin irritation. This open-label, randomized, 14-day, outpatient study compared the skin irritation of an investigational testosterone transdermal system (System I) with that of a marketed testosterone transdermal system (System II) in healthy men. In Part 1 of the study. System I was applied 10 times over 14 days to the same skin site on the backs of 26 healthy men. In Part 2, the skin irritation resulting from daily application of Systems I and II was assessed over 14 days in 17 men less than 65 years of age and 16 men 65 years of age or older. At the end of Part I of the study, 65.4% of the subjects experienced no erythema, 15.4% of subjects had faint erythema, and 19.2% had moderately intense erythema immediately after System I removal. At the completion of Part 2, none of the System I application sites were assessed as having moderately intense erythema, whereas one third (33.3%) of System II application sites demonstrated moderately intense erythema. There were no differences in erythema rates between younger and older subjects with either transdermal system. During this study, repeated application of System I to the same skin site resulted in acceptable noncumulative irritation, suggesting that application-site rotation may not be necessary. A comparison of the two systems demonstrates that System I results in significantly less application-site irritation than does System II and that older men do not have a higher rate of skin reactions.

Leukocyte migration inhibition assay (LIF) in nickel contact dermatitis.

A direct assay using the mixed leukocyte migration inhibition technique for leukocyte inhibition factor (LIF) production has shown that nickel-sensitive subjects can be distinguished from nonallergic controls. The difference between the two groups' migrating indexes was obtained with nickel sulfate in 199 medium at a concentration of 150 mug/ml and without prior coupling to a carrier protein. A concise review of the principal in vitro assays for cell-mediated immunity is included.

Atypical fibroxanthoma in a patient with xeroderma pigmentosum.

A 3-year-old boy with xeroderma pigmentosum developed a papule on the right ala nasi that had the light-microscopic, immunohistochemical, and ultrastructural features of atypical fibroxanthoma. This lesion most commonly arises on the sun-exposed skin of older adults. The occurrence of an atypical fibroxanthoma in such a patient adds weight to the concept that this tumor of "fibrohistiocytic" origin is induced by ultraviolet exposure. Mechanisms of tumor formation in a patient with xeroderma pigmentosum may be similar to those occurring in the more typical situation in adults.

Allergic contact dermatitis to underwear elastic. Chemically transformed by laundry bleach.

Six subjects, allergic to the elastic in their undergarments, were patch test-negative to the rubber components and new elastic from the suppliers. However, washing the rubber with sodium hypochlorite gave the subjects allergic responses due to the effect of bleach on the rubber accelerator, zinc dibenzyldithiocarbamate (ZDC). To identify the allergen, ZDC was reacted with the sodium hypochlorite, and the resultant gum was extracted with diethyl ether. Eight compounds were identified in the reaction mixture by gas chromatography-mass spectrometry. The individual components were tested on volunteers after sensitization to the reaction mixture was produced in 14 of 25 volunteers. One component, N,N-dibenzylcarbamyl chloride produced an allergic response in each sensitized volunteer.

Topical clindamycin therapy for acne vulgaris. A cooperative clinical study.

Eleven institutions participated in an eight-week controlled clinical study to evaluate treatment of acne vulgaris with topical clindamycin hydrochloride and clindamycin phosphate. Three hundred fifty-eight patients with comparable baseline pustule, papule, and nodule counts applied 1%, clindamycin hydrochloride, 1% clindamycin phosphate, or a hydroalcoholic vehicle twice daily. Every two weeks, lesions were counted, and patients' evaluations of their acne conditions were scored. By week 8, pustule and papule counts in the groups who were receiving clindamycin were significantly lower than those in the group receiving placebo. Also, more patients who were receiving clindamycin thought their acne improved by week 8 (with significantly higher change-in-acne scores) than did the patients receiving placebo. Patients receiving clindamycin reported 12 episodes of diarrhea; only one episode was considered to be treatment related. These results substantiate the clinical impression that topical clindamycin is effective treatment for acne.

Contextual control of long-term habituation in rats.

This study examined contextual control of long-term habituation and whether such effects are dependent on the habituating response system. Habituation of the acoustic startle response transferred from the home cage to the testing context, whereas habituation of lick suppression was context specific (Experiments 1 and 2). Contextual control of habituation was demonstrated between 2 experimental contexts for lick suppression to a tone (Experiment 3) and bar-press suppression to a light (Experiment 4). Experiment 5 extinguished habituation of lick suppression and the orienting response to a tone with 27 exposures to the habituation context. Context specificity of both responses also was found. Previous failures to demonstrate contextual control of habituation may be due to the choice of response system and to less sensitive procedures to detect response recovery. The habituation mechanism for startle is independent from the process or processes that underlie habituation in other response systems, but the nature of these mechanisms is not yet known.

Daily fluoxetine administration impairs avoidance learning in the rat without altering sensory thresholds.

1. Male rats given daily intraperitoneal injections of fluoxetine (10 mg/kg) were slower to escape foot shock by jumping a low barrier. 2. When switched to a shuttle task requiring two crosses to terminate shock, the FLU-treated animals failed to learn in 55 trials. 3. A second experiment found FLU-treated animals could learn a one-way avoidance response, but were significantly slower to learn than control animals. 4. FLU-treated animals were no different than controls on tests of sensory thresholds for foot shock or heat. 5. Tests of motor behaviors revealed no differences in latency to traverse a narrow beam to reach a goal box, however FLU-treated animals were less active in an open field. 6. Several hypotheses can account for these data, the most promising being that a central motivational system (fear) is less active in FLU-treated animals.

Startle habituation in rats after lesions in the brachium of the inferior colliculus.

Bilateral interruption of the primary ascending auditory pathway at the level of the brachium of the inferior colliculus (BIC) did not affect short- or long-term habituation of the startle response provoked by auditory stimuli. Animals with BIC lesions and control animals exhibited comparable habituation following manipulations of stimulus intensity, inter-stimulus interval, and intensity of background noise, although animals with lesions in the BIC were more responsive than controls to auditory stimuli and to tactile stimuli. The integrity of the primary auditory pathway above the inferior colliculus is not necessary for short- or long-term habituation of the acoustic startle response.

Long- and short-term habituation of acoustic startle is not frequency specific in the rat.

Two experiments examined the frequency specificity of habituation of the acoustic startle response in the rat. Following the long-term habituation of startle to one of two pure tone stimuli in Experiment 1, animals were presented with the other stimulus. Startle response asymptotes were unaffected by this change in stimulus frequency. Short-term habituation of startle also was insensitive to stimulus frequency. In Experiment 2, pure tone stimuli were used to provoke both a startle response and the interruption of drinking. Long-term habituation of startle to either stimulus was unaffected by a change in frequency. Animals that received the two stimuli on alternating days showed as rapid a habituation as did the groups receiving only one stimulus frequency during acquisition. Conversely, the lick suppression measure was found to be frequency specific. Lick suppression durations rose to pre-habituation levels when the frequency of the stimulus was changed. Animals that received the two stimuli on alternating days showed retarded habituation compared to those groups presented with only one stimulus frequency during acquisition. Although long-term habituation of startle is not stimulus specific, it is mediated by central processes and thus remains a valuable model in the study of neurophysiological mechanisms of behavioral change.

Further evidence for latent learning in hippocampal-lesioned rats.

Rats with substantial dorsolateral lesions to the hippocampal formation showed significant latent learning of a complex spatial maze. Their overall maze performance, however, was characteristically impaired. Behavior during the pre-exposure phase of the experiment was useful in predicting test maze behavior. Three measures in particular had predictive value: entrances into the maze alley leading to the final choice point, behavior at that choice point, and goal box entries.

DERM/INFONET achieves "very friendly" status.

DERM/INFONET, a group of dermatologic data bases, has been reorganized for easy log-ons and log-offs, plus fast, unambiguous selections from simplified menus. DERM/RX and DERM/PHARM data bases are dermatologic exclusives. The medical literature search will retrieve the most unencumbered dermatologic information for both the academician and clinician for getting the day's work done.

Pressure dermatitis from an implanted pacemaker.

In this eleventh report of dermatitis conforming to the outline of an underlying pacemaker, the authors suggest that most of these reactions are isomorphic responses to expansion of the subcutaneous tissues by the hard device. Allergic contact dermatitis has been documented in a few cases.

Anatomic complications of abdominal surgery with special reference to the ureter.

Respect and knowledge of and for the ureter should be in every surgeons armamentarium. An intravenous pyelogram should be done in selected cases for precise definition of the location and nature of any pathologic or anamolous condition of the ureters.

Element content in tissues of four rodent species sampled in the Geysers geothermal steamfield.

Liver and kidney tissue samples from four rodent species collected in the Geysers geothermal steamfield of northern California were analyzed for content of 28 elements. Element concentrations in samples from the developed region of the Geysers were compared with samples from undeveloped reference regions to determine the influence of geothermal power development on element content in small mammal tissues. Eight elements (B, Ca, Cu, Mg, Mn, P, Sr, Ti) were enriched in samples from the Geysers, 12 (Ag, Al, Co, Cr, Fe, K, Mo, Na, Ni, Pb, Si, Zn) were decreased within the Geysers, Ba and Li were inconclusive, and six (As, Be, Cd, Hg, Sn, V) were below the minimum analytical limits. The longest-lived species (Neotoma fuscipes) had the greatest occurrence of statistically significant differences in element content. Sites in grassland habitat produced more significant differences in element content than either chaparral or streamside habitats for samples from Peromyscus maniculatus. Peromyscus boylii and P. truei provided additional data, but no distinct advantages for element monitoring. The data indicate regional influences from geothermal power development on element levels in rodent tissues.

Clinical evaluation of the contact sensitization potential of a transdermal nicotine system (Nicoderm)

BACKGROUND: Transdermal nicotine therapy has shown promise as a smoking cessation aid, but questions about its contact sensitization potential and long-term topical safety have been raised. The purpose of this study was to determine the contact sensitization potential of one nicotine transdermal system (Nicoderm, Marion Merrell Dow Inc, Kansas City, Mo, and ALZA Corporation, Palo Alto, Calif) in a population who were allowed to continue smoking. METHODS: This study comprised two phases separated by a 2-week rest interval. During phase 1, a 42-day open-label induction period, subjects wore only active transdermal nicotine systems. During phase 2, a 4-day double-blind challenge period, subjects wore active and placebo systems concurrently. Upon removal of each patch, skin sites were evaluated for signs of irritation, and subjective complaints such as itching or burning were recorded. RESULTS: Of the 186 subjects completing the study, 3 (1.6%) exhibited evidence of delayed contact sensitization manifested as erythema with or without infiltration and confined solely to sites of active transdermal nicotine system application. Nonallergic skin irritation was observed in less than 3% of all applications. All reactions resolved without incident. No subjects developed systemic reactions. CONCLUSIONS: The transdermal nicotine system used in this trial had a low contact sensitization incidence and was well tolerated topically with minimal irritation.