Audiologic evaluation of hearing-impaired infants and children.

With the advent of auditory brainstem response (ABR) and otoacoustic emission (OAE) testing, as well as the widespread use of universal hearing screening programs, the audiologic assessment of hearing-impaired infants and young children has become more frequent in recent years. When assessing a hearing-impaired infant, it is necessary to obtain as much frequency and ear specific information as possible prior to selection of hearing amplification. An overview of the battery of tests and the need for a diagnostic center that is well versed in both physiologic and behavioral tests will be addressed.

Interference between effector RNAs expressed from conventional dual-function anti-HIV retroviral vectors can be circumvented using dual-effector-cassette retroviral vectors.

Coexpression of different effector molecules from a single vector (a dual-function vector) may provide enhanced efficacy. Thus far most of the reported anti-HIV dual-function vectors express different effector RNAs as a chimeric molecule. In our study involving retroviral vectors coexpressing a U5 ribozyme and either an anti-tat or anti-rev antisense RNA, chimeric vectors exhibit poor potency in several important functional aspects, including inhibition of HIV replication, protection against cytopathic effects, and suppression of target gene function. Surprisingly, such a poor efficacy of chimeric vector function was not associated with a lower level of effector RNA expression. These results indicate that expression of two effector RNAs as a chimeric molecule can lead to interference, reducing their global biological effects. More importantly, we have demonstrated that such interference can be avoided by coexpressing these effector RNAs as separate molecules through a new dual-function vector, called a dual-effector cassette (Dec) vector, developed in this study. We also define some of the design alterations that might affect the efficacy of the Dec vector and demonstrate that forward-designed Dec vectors are more efficacious than reverse-designed Dec vectors, which express a lower level of effector RNA owing to the instability of the 5' effector cassettes in the provirus. We believe that the principle of Dec vector design may also be applicable for the coexpression of other therapeutic RNA effectors in many gene therapy applications.

Large vestibular aqueduct syndrome: an overlooked etiology for progressive childhood hearing loss.

If a drastic change in hearing has occurred in a child following a minor head trauma, change in barometric pressure, or physical exertion, large vestibular aqueduct syndrome (LVAS) should be considered. Most audiologists are unaware of LVAS or do not suspect it, in part due to the presence of a conductive component. LVAS can be seen in conjunction with Mondini's dysplasia or may appear by itself and is easily identified by a computed tomography scan. We present five cases of LVAS and discuss the natural history, audiologic and imaging findings, and relevant literature.

Enhancement or inhibition of HIV-1 replication by intracellular expression of sense or antisense RNA targeted at different intermediates of reverse transcription.

OBJECTIVES: To construct retroviral vectors expressing sense or antisense RNA targeted at HIV reverse transcription intermediates, and to test the anti-HIV properties of these constructs in transduced T cells. DESIGN: Five double-copy retroviral vectors were constructed, in which the expression of the sense or antisense RNA corresponding to HIV minus- or plus-strand strong-stop DNA was driven by the human tRNA(met) promoter. METHOD: The templates for the sense or antisense RNA were polymerase chain reaction-cloned from HIV pNL43 into a murine leukaemia virus-based vector and corresponding defective virions were packaged in PA317 cells. Human Jurkat T cells transduced with these vectors were challenged with HIV and monitored for viral RNA, viral DNA and p24 production for 23 weeks. RESULTS: Intracellular expression of HIV sense RU5 sequences (RNA complementary to minus-strand strong-stop DNA) enhanced HIV replication in T cells. Expression of HIV sense or antisense U3RU5 sequences (identical or complementary to plus-strand strong-stop DNA) conferred long-term inhibition of HIV replication, despite continuous presence of viral challenge in the transduced cell cultures. CONCLUSION: Plus-strand strong-stop DNA as an intermediate in the early process of viral reverse transcription can be explored as an additional target for anti-HIV gene therapy.

Long-term protection against HIV-1 infection conferred by tat or rev antisense RNA was affected by the design of the retroviral vector.

We have constructed a series of retroviral vectors in which the expression of antisense RNA targeted at the full length coding sequence of HIV-1 tat or rev was driven by three different promoters and in the context of double-copy or single-copy vectors. Jurkat cells transduced by these vectors were shown to express the expected tat or rev antisense RNA without alteration in cell proliferation or surface CD4 expression. After challenge with HIV, four patterns of protection were identified, with the degree of protection being determined primarily by the design of the expression system. In those patterns showing long-term complete protection, we could detect no HIV p24 in the culture supernatants or in the cells, and no HIV RNA or HIV proviral DNA (by PCR), during a 23-week follow-up. Experiments designed to rescue any live virus still formed in the culture after 20 weeks' challenge demonstrated that, with some constructs, infectious virus could no longer be isolated, while with other constructs, only a low level of infectious virus was still being formed and providing a continuing virus challenge, although all other markers of infection remained undetectable. Our results demonstrated that antisense RNA expression driven by tRNA promoter in the context of a double-copy vector conferred better long-term protection against HIV infection compared to that driven by HIV LTR or MLV LTR promoters, and that the optimized vectors may be useful in developing a gene therapy against HIV-1 infection and AIDS.

Healing of benign gastric ulcer. A placebo-controlled comparison of two dosage regimens of misoprostol, a synthetic analog of prostaglandin E1.

Misoprostol, a synthetic prostaglandin E1 methyl ester analog with gastric antisecretory and cytoprotective properties, prevents the development of acute experimental gastric and duodenal ulcers in various animal models. This study was designed as a multicenter randomized double-blind parallel-group comparison of the effects of two dosage strengths (25 and 100 micrograms q.i.d.) of orally-administered misoprostol and placebo on the healing of endoscopically-proven benign gastric ulcer in 299 out-patients. Safety was evaluated by comparison of pre- and post-treatment physical examinations, clinical laboratory tests, gastric antral biopsies and monitoring of adverse experiences. A statistically significant difference in gastric ulcer healing rate was seen at eight weeks among the treatment groups in the Intent-to-Treat Cohort: misoprostol 100 micrograms (62.0%), misoprostol 25 micrograms (50.0%), placebo (44.7%). The proportion of subjects healed in up to eight weeks of treatment was greatest in the misoprostol 100 micrograms group in all cohorts. Ulcer pain decreased in all treatment groups in successive weeks and there were no statistical differences among any of the three treatment groups. Diarrhea was the most frequently reported adverse experience: misoprostol 100 micrograms (9.8%), misoprostol 25 micrograms (7.7%), placebo (1.9%). The diarrhea was mild and self-limiting despite continued use of misoprostol. Overall evaluation of gastric antral biopsies showed no adverse changes in the morphology of the antral mucosa. We conclude that misoprostol 100 micrograms q.i.d. for up to eight weeks is safe and effective in the treatment of benign gastric ulcer.

Gastric antisecretory effects of propantheline bromide and metiamide in rhesus monkeys.

The effects of propantheline bromide (PB) and metiamide (M), two dissimilar classes of gastric secretory inhibitors, were studied in chronic gastric fistula rhesus monkeys. Basal and stimulated gastric secretory studies were conducted in conscious monkeys. Multiple s.c. injections of either histamine or pentagastrin were given hourly for four consecutive hours. One hour after the injection of the stimulants a constant plateau of gastric secretion was reached, and the test compounds were then administered as a single i.v. bolus dose. Propantheline bromide at doses of 0.03--0.3 mg/kg inhibited basal and pentagastrin stimulated gastric secretion, but had no effect on histamine stimulation. Total acid output paralleled inhibition of volume of secretion, while there was little or no effect on acid concentration. Metiamide at the doses of 1--10 mg/kg inhibited basal, pentagastrin and histamine stimulated gastric secretion. Metiamide was equally effective in inhibiting the volume of secretion and acid concentration. The scope of the gastric secretory inhibition in the rhesus monkey achieved with these pharmacological agents is very similar to man. These results suggest that the rhesus monkey is an important animal model for predicting clinically useful gastric secretory inhibitors.

Effects of E prostaglandins on canine gastric potential difference.

Measurement of the gastric transmucosal potential difference (PD) was used to study the effect of gastric antisecretory prostaglandins on the integrity of the gastric mucosa of the Heidenhain pouch dog. Intragastric administration of SC-29333 [(+/-)-15-deoxy-16-alpha,beta-hydroxy-16-methyl PGE1 methyl ester] slightly but significantly increased the transmucosal PD when compared to vehicle control. In addition, SC-29333 administered either intravenously or intragastrically, significantly inhibited the PD fall induced by aspirin, a well-established barrier breaker. In contrast, the intragastric administration of 16,16-dimethyl PGE2 methyl ester (Me-PGE2) significantly lowered the transmucosal PD and failed to modify the actions of aspirin on the integrity of the gastric mucosa. However, the intravenous administration of either prostaglandin did not affect the basal transmucosal PD values. These studies suggest that SC-29333 may strengthen the integrity of the gastric mucosal barrier against aspirin, and this could have important therapeutic potential.

Gastric antisecretory effects of E prostaglandins in Rhesus monkeys.

The gastric antisecretory actions of prostaglandin E1 methyl ester (PGE1ME) and prostaglandin E2 (PGE2) were evaluated in unanesthetized gastric fistula rhesus monkeys. Basal and stimulated gastric secretory studies were conducted. Multiple subcutaneous injections of either histamine or pentagastrin were given hourly for four consecutive hours. When a constant plateau of gastric secretion was reached, the PGs were administered as a single intravenous bolus at doses of 10-100 mug/kg. PGE1ME inhibited basal, histamine- and pentagastrin-stimulated gastric secretion. PGE2 was found to inhibit the histamine- stimulated gastric secretion. The PGs showed greater sensitivity to the inhibition of acid concentration rather than the volume of secretion. The PGs signfiicantly altered gastric juice concentration of hydrogen and sodium ion inversely, while potassium and chloride concentration were not altered. These experiments suggest that the rhesus monkey is a useful species for studying the gastric antisecretory effects of E prostaglandins.

Gastric antisecretory actions of (15S)-15-methyl prostaglandin E2 methyl ester and natural prostaglandin E2 in rhesus monkeys.

The gastric antisecretory actions of (15S)-15-methyl prostaglandin E2 methyl ester (Me-PGE2) and Prostaglandin E2 (PGE2) were evaluated in the unanesthetized gastric fistula rhesus monkey. Secretion was submaximally stimulated by multiple subcutaneous injections of histamine acid phosphate given every hour for four consecutive hours. When a steady-state plateau of gastric secretion was reached, the PG's were administered as a single bolus dose either intravenously (i.v.) or intragastrically (i.g.). Both PG's inhibited histamine-stimulated gastric secretion. The PG's showed greater sensitivity in inhibiting acid concentration while not affecting volume output. Active i.v. and i.g. antisecretory doses of ME-PGE2 ranged from 3 to 10 mug/kg, while PGE2 showed significant antisecretory activity at i.v. bolus doses of 30-100 mug/kg and i.g. bolus dose of 1.0 mg/kg. Thus, Me-PGE2 is estimated to be at least 10 and 300 times more potent than PGE2 by the i.v. and i.g. administration routes, respectively. These findings indicate that the rhesus monkey shows some similarities to man in responsiveness to gastric secretory inhibition by E-prostaglandins.