Brainstem-evoked responses of guinea pigs exposed to high noise levels in utero

Pregnant guinea pigs were exposed to loom room noise at 115 dB A for 7.5 hr/day for various periods during the last one-third of pregnancy. When the hearing of their offspring was tested by auditory brain stem-evoked response techniques at 6-dB intervals, peak IV latencies of exposed pups were found to be significantly longer than those of otherwise similar control pups. The latency differences corresponded to a 5-dB increase in stimulus at medium stimulus levels and 10–12 dB near threshold. The results indicate that it is possible for noise-induced hearing loss to occur in utero in mammals whose auditory maturation process is complete, or nearly so, before birth.     

Differentiation of hepatic hemangiomas from metastases by dynamic contrast-enhanced MR imaging

Twenty-nine patients with hepatic hemangiomas (n = 14) and hepatic metastases (n = 15) underwent magnetic resonance (MR) imaging prior to and after an intravenous bolus injection of Gd-diethylenetriamine pentaacetic acid (0.2 mmol/kg). Before contrast application, a T2-weighted spin echo sequence (SE 1,600/105) and a T1-weighted gradient echo sequence (GE 315/14/90 degrees pulse angle) were performed. Beginning with injection of the contrast agent, a dynamic study was conducted for 10 min using a moderately T1-weighted gradient echo sequence (GE 40/14/40 degrees) with an acquisition time of 10.2 s per image. Delayed (11 min) and late (60 min) postcontrast images were obtained using a T1-weighted sequence (GE 315/14/90 degrees). In the dynamic study (0-10 min) the hemangiomas were characterized by peripheral contrast enhancement and a subsequent hyperintense fill-in. The metastases showed very mixed patterns of enhancement after contrast administration, and their signal intensity remained low compared with that of the hepatic tissue. In the delayed postcontrast examination (11 min) the hemangiomas had a very high and homogeneous signal intensity and the metastases were characterized by an inhomogeneous, hypointense to isointense signal. The contrast between tumor and liver [signal-difference-to-noise ratio (SD/N)] was higher for all hemangiomas than it was for the metastases. In the T2-weighted precontrast examination, on the other hand, five hemangiomas and seven metastases showed an overlap in the SD/N. The late postcontrast images (60 min) did not yield any further diagnostic information. We conclude that the combination of a dynamic MR study with delayed postcontrast T1-weighted imaging is a useful method of diagnosing hepatic hemangiomas.     

Arteriovenous fistula of the internal maxillary artery: treatment with transarterial embolization

Six patients with arteriovenous fistulas of the internal maxillary artery were treated with transarterial embolization. The patients ranged in age from 19 to 47 years, with a mean of 26.5 years. Each had a lifelong history of symptoms suggestive of a congenital origin of symptoms. There was no history of trauma. The most common initial symptoms were bruit (83%), pulsatile mass (67%), and pain (50%). In one patient prior surgical ligation of the external carotid artery had been attempted, but it led to aggravation of headaches. All patients were treated with placement of a detachable balloon at the fistula site. In one patient the balloon migrated through the fistula, which was retreated with coils. Complete obliteration of the fistula was achieved in all patients. The follow-up ranged from 2 months to 10 years, with a mean of 5.2 years. Congenital arteriovenous fistulas of the internal maxillary artery are rare and can be treated effectively with transvascular techniques.     

Calculations for beta dosimetry using Monte Carlo code (OREC) for electron transport in water

A Monte Carlo computer code (OREC) for calculating the detailed transport and energy deposition for primary electrons and all of their secondaries in liquid water has been investigated for use in beta-ray dosimetry. Some modifications have been made in the original code for its application to tissue and tissue-equivalent materials. The code gives reasonably good agreement with beta spectral data and depth-dose curves measured in tissue-equivalent plastics for several calibrated beta sources. The calculations permit a direct evaluation of the skin dose equivalent, i.e., the dose equivalent, Hs (0.07), at a depth of 0.070 mm in tissue. Calculations are presented for monoenergetic electrons, showing the distributions in the maximum depth of penetration and in the total pathlength traveled. Direct comparisons are made between depth-dose curves calculated for 99Tc and 147Pm plaque sources and measurements made with extrapolation chambers. The energy spectrum of beta particles emerging from a thick 99Tc plaque source also is calculated, and the angular distribution is found to be almost independent of the energy. The pulse-height spectrum in a tissue-equivalent plastic scintillator calculated for this source shows good agreement with the measured spectrum. The calculations also provide the Hs(0.07) dose equivalent for the 99Tc source, which is found to be consistent with that inferred independently from the spectral measurements. A calculated curve for converting spectrometer measurements to Hs(0.07) dose equivalent is in good agreement with a semi-empirical curve that was developed independently. It appears that calculations made with the electron transport code for water can provide useful information for beta dosimetry.     

Contractions of single motor units are reflected in membrane potential changes of homonymous alpha-motoneurons

In anesthetized cats 3 medial gastrocnemius (MG) motor units (MUs) were electrically activated with independent pseudorandom patterns at physiological mean rates. Recordings of isometric MG tension (T) and membrane potential changes (PSPs) in MG alpha-motoneurons (MNs) were averaged with respect to each stimulus train. The resulting T and PSP trajectories displayed the responses of each MN to the 3 average MU twitches. These responses could vary from no response to a sequence of depolarizing and hyperpolarizing waves in a PSP trajectory. The results are consistent with the known behavior of muscle stretch receptors to muscle and MU twitches and the receptors' connections to homonymous MNs.     

Efficacy of different irrigation methods and concentrations of root canal irrigation solutions on bacteria in the root canal.

The effectiveness of two different root canal irrigating solutions, each in two different concentrations or formulations, with two different irrigation methods was compared in vitro by means of bacterial survival determinations. 75 human root canals were enlarged, sterilized and inoculated with a mixed culture of Escherichia coli and Streptococcus mutans. After inoculation, the root canals were irrigated either manually or with an ultrasonic device for equal times (20s) with the same amount (5 ml) of sodium hypochlorite (1% and 2%), Fokalhydran I and Fokalhydran II. Sodium hypochlorite (1% and 2%) was used in a 1:100 dilution. Fokalhydran I and II were used in a 1:10 dilution. In the sodium hypochlorite group, the 1% concentration applied with a syringe proved to be most effective against Escherichia coli and Streptococcus mutans. The least effective concentration and application method against both bacteria species was obtained with 2% NaOCL and ultrasonics. Against Escherichia coli and Streptococcus mutans, a significantly lower effectiveness was found with 2% NaOCL applied with ultrasonics with respect to the rest of the sodium hypochlorite group. Fokalhydran I was significantly better than Fokalhydran II against Escherichia coli. However, no significant differences could be seen against Streptococcus mutans within this group.