Developmental Exposure to Aroclor 1254 Produces Low-Frequency Alterations in Adult Rat Brainstem Auditory Evoked Responses

Developmental exposure of Long—Evans rats to 0, 1, 4,or 8 mg/kg/day Aroclor 1254 (A1254) from Gestational Day 6 throughPostnatal Day 21 produces an elevated behavioral threshold fora 1-kHz tone. Brahistem auditory evoked responses (BAERs) wereassessed in a subset of these animals (about 1 year old) usingfiltered clicks at 1 (65 and 80 dB SPL), 4 (60 and 80 dB SPL),16 (40 and 80 dB SPL), and 32 (40 and 80 dB SPL) kHz. Aroclor1254 decreased BAER amplitudes at 1 and 4 kHz, but not at 16or 32 kHz. A dose-related decrease in the baseline-to-peak P_1Aamplitude was observed for the 1-kHz (80-dB) stimulus. Dosesof 1, 4, or 8 mg/kg/day A1254 decreased the peak-to-peak amplitudeof both P_1AN₁ and P_1BN₁ for a 1-kHz (80-dB) stimulus. Dosesof 4 and 8 mg/kg/day A1254 decreased the peak-to-peak amplitudeof N₁P₂ and P₂N₂ for a 4-kHz (60-dB) or 1-kHz (80-dB) stimulus.At 8 mg/kg/day, A1254 also increased the latency of peak P₄at 1 kHz (65 dB). The decreases in peak P_1A amplitudes are consistentwith a dysfunction of the cochlea and/or auditory nerve. Together,the data confirm that developmental exposure of rats to A1254produces a permanent low- to mid-frequency auditory dysfunctionand suggest a cochlear and/or auditory nerve site of action.     

How useful are verbal autopsies to estimate childhood causes of death?

Verbal autopsies (VAs) are widely used to describe causes ofdeath in individuals who die outside hospital or clinic settings.However, they have received surprisingly little validation.The technique assumes that diseases which cause death can bereadily distinguished from one another by distinct syndromes,and that these can be reported accurately by lay respondents.This paper describes the potential problems of syndrome definitionand the likely biases introduced through poor recognition andrecall by bereaved relatives; how these may be tested; and finally,what can be done where the VA proves unable to identify causeof death.     

Histopathology of Acute Toxic Response in Rats and Mice Exposed to Methyl Chloride by Inhalation

Histopathology of Acute Toxic Response in Rats and Mice Exposedto Methyl Chloride by Inhalation. Morgan, K.T., Swenberg, J.A.,Hamm, T.E., Jr., Wolkowski-Tyl, R. and Phelps, M. (1982). Fundam.Appl. Toxicol. 2:293-299. Both sexes of one strain of rat (F344),two strains of mice (C3H and C57BL/6) and the cross (B6C3F1)of these 2 strains of mice were exposed by inhalation to methylchloride for 6 hours per day for up to 12 days. Methyl chlorideconcentrations in air were 0, 500, 1000, or 2000 ppm for mice,and 0, 2000, 3500 or 5000 ppm for rats. All male B6C3F1 miceexposed to 2000 ppm were dead or moribund by day 2, and allmale and female mice in the remaining 2000 ppm groups were moribundby day 5. Prior to death many of these mice exhibited ataxia,and hematuria with the latter occurring mainly in females. Treatmentassociated lesions in mice included hepatocellular degenerationand necrosis, degeneration and necrosis of proximal convolutedtubules and/or basophilic tubules in the renal cortex, and focalareas of necrosis of the internal granular layer of the cerebellum.Brain lesions were most severe in female C57BL/6 mice, whilehepatocellular degeneration was most severe in male C57BL/6and B6C3F1 strains. Approximately 50% of the male and femalerats exposed to 5000 ppm were killed in extremis on day 5. Theprincipal clinical signs, which were confined to the 5000 and3500 ppm groups, included severe diarrhea, incoordination ofthe fore-limbs, and in a small number of animals, hind limbparalysis and convulsions. In rats, lesions were observed inthe liver, kidney and brain which resembled those seen in micebut were generally less severe. Lesions observed in tissuesexamined only in rats included vacuolar degeneration of thezona fasciculata of the adrenal glands and degenerative changesin the seminiferous tubules and epididymis. Rats appeared torespond in a similar manner to mice but were more resistantto methyl chloride toxicity. These findings demonstrate species,strain and sex differences in susceptibility to methyl chloride.     

Computed Tomography During Experimental Balloon Dilatation For Calcific Aortic Stenosis. A Look into the Mechanism of Valvuloplasty

Thin-slice contiguous computed tomographic scanning was performed in four postmortem hearts with calcific aortic valve stenosis (mean weight: 583 ± 78 g; mean age: 65 ± 10 years) before, during, and after balloon valvuloplasty. Balloons of increasing diameter (15–19 mm single balloons, and 3 × 12-mm trefoil-shaped balloon) were positioned across the aortic valve and manually inflated to pressures of 3 to 4 atmospheres. During inflation of the 3 × 12-mm balloon a larger residual orifice, potentially free for blood passage, was observed in the two cases with bicuspid valves and in one case with a fused tricuspid valve, while the reverse was noted in one case with a tricuspid valve without fusion. In most cases valvular orifice enlargement only occurred with larger diameter balloons. After valvuloplasty aortic valve area increased from 0.72 (range 0.20–0.95) cm² to 2.36 (range 0.95–3.14) cm². The smallest orifice enlargement after dilatation occurred in case 1, where valvular calcified deposits had the largest volume and the highest computed tomographic attenuation value. In each patient macroscopic changes (fracture of nodular calcifications, commissural splitting, tearing of the central raphe) were noted. No calcium dislodgement or aortic ring damage was observed. In autopsy specimens computed tomography provided accurate evaluation of aortic valve morphology, extent of valve calcification, balloon-leaflet relationship during inflation, and effects of the dilatation on valve leaflets and commissures. Advances in computed tomographic cardiovascular imaging may achieve similar results in the clinical setting, and allow a more rational, individualized approach to the valvuloplasty procedure. (J Interven Cardiol 1988:1:2)     

Current Method of Repair of Truncus Arteriosus

Surgical treatment of truncus arteriosus has been demonstrated to be optimized when approached in early infancy. In the past, the materials available, namely the 12-mm porcine valve Dacron conduit, restricted the size of the patient in whom early repair could be performed with increasing risk associated with decreasing age and size. The availability of homografts for reconstruction of right ventricular pulmonary artery continuity has allowed repair even in the neonatal period. Two hundred forty-four patients with truncus arteriosus have been operated on at the University of California San Francisco since 1975. In the past 5 years, 49 have been repaired using homograft reconstruction. The method of repair differs markedly from that of Dacron conduits, and specific points concerning homograft insertion including orientation, method of proximal anastomosis, and sizing are discussed in detail and the difference in insertion from the Dacron bovine heterograft conduit are discussed.     

A Comprehensive Approach to the Recognition, Diagnosis, and Severity-Based Treatment of Focal Hyperhidrosis: Recommendations of the Canadian Hyperhidrosis Advisory Committee

BACKGROUND: Hyperhidrosis can have profound effects on a patient's quality of life. Current treatment guidelines ignore disease severity. OBJECTIVE: The objective was to establish clinical guidelines for the recognition, diagnosis, and treatment of primary focal hyperhidrosis. METHODS AND MATERIALS: A working group of eight nationally recognized experts was convened to develop the consensus statement using an evidence-based approach. RECOMMENDATIONS: An algorithm was designed to consider both disease severity and location. The Hyperhidrosis Disease Severity Scale (HDSS) provides a qualitative measure that allows tailoring of treatment. Mild axillary, palmar, and plantar hyperhidrosis (HDSS score of 2) should initially be treated with topical aluminum chloride (AC). If the patient fails to respond to AC therapy, botulinum toxin A (BTX-A; axillae, palms, soles) and iontophoresis (palms, soles) should be the second-line therapy. In severe cases of axillary, palmar, and plantar hyperhidrosis (HDSS score of 3 or 4), both BTX-A and topical AC are first-line therapy. Iontophoresis is also first-line therapy for palmar and plantar hyperhidrosis. Craniofacial hyperhidrosis should be treated with oral medications, BTX-A, or topical AC as first-line therapy. Local surgery (axillary) and endoscopic thoracic sympathectomy (palms and soles) should only be considered after failure of all other treatment options. CONCLUSIONS: These guidelines offer a rapid method to assess disease severity and to treat primary focal hyperhidrosis according to severity.     

VISUAL PERCEPTION AND READING DISABILITIES

In simple animals eg Toads visual function occurs at a lower level. In man where a cortex develops visual perception occurs. Perception is discussed. Learning defects and reading disabilities can occur where perception is impaired. Good reading requires an adequate perceptual system.     

The effect of intravascular transfusion for rhesus haemolytic disease on umbilical artery Doppler flow velocity waveforms

Summary. To test the hypothesis that an increase in fetal blood viscosity is associated with an increase in resistance to flow, the effect on Doppler flow velocity waveforms of percutaneous umbilical blood sampling and intravascular transfusion was studied in 20 patients undergoing a total of 35 procedures. All but four of the 22 transfusions were associated with a decrease in resistance to flow, as shown by a reduction in the umbilical artery systolic/diastolic ratio, and this also occurred on 10 of the 13 occasions when blood sampling only was performed. These findings suggest that acute changes in blood viscosity following intravascular transfusion arc not associated with an increase in resistance to flow as assessed by Doppler velocimetry. Umbilical blood sampling per se may be associated with a Immorally mediated reduction in placental vascular resistance to flow.