Kazuyuki Terayama

Effects of Acute Lead Acetate Exposure on Adult Guinea Pigs: Electrophysiological Study of the Inner Ear

The effects on humans of lead acetate exposure may involve the cranial nerves, since vertigo and sensory neuronal deafness have been reported in lead workers; however, there exist only a few reports concerning the dose effects of lead acetate both on the cochlea and the eighth cranial nerve. The effects of lead acetate on the cochlea and the eighth nerve were investigated systematically using cochlear microphonics (CM), whole-nerve action potential (AP), and endocochlear potential (EP) in guinea pigs (male albino Hartley). Guinea pigs were injected with 2 ml of a 1% solution of lead acetate (20 mg) once a week for 1-5 weeks. The threshold of whole-nerve AP (N1) was elevated by injection of lead acetate, even 40 mg, and whole-nerve AP (N1) output voltage decreased after injection of 100 mg of lead acetate. On the other hand, no change was observed in CM after lead acetate injection (100 mg) or in EP after lead acetate exposure (40 mg). The blood concentrations of lead acetate were as follows (mean): control, 4.5 micrograms/dl; Expt 1, 80 micrograms/dl; Expt 2, 126 micrograms/dl; Expt 3, 142 micrograms/dl. We conclude that dysfunction of the eighth nerve is induced by high-dose lead exposure, but that lead exposure does not induce electrophysiological dysfunction of the organ of Corti and the stria vascularis.

Effect of short physical exercise on the levels of zinc and carbonic anhydrase isoenzyme activities in human erythrocytes

SummaryStudies of the influences of physical exercise of short duration (bicycle ergometer, 200 W for 30 min) on the activities of carbonic anhydrase isoenzymes (CA-B and CA-C types) and zinc concentration in erythrocytes were made on 5 untrained healthy male volunteers. The subjects were rested for 30 min after the exercise. There were significant decreases in the levels of zinc, CA-B, total carbonic anhydrase activity and CA-B-dependent activity immediately after exercise, but after 30 min of rest they all returned to their pre-exercise levels. No significant change in CA-C level or CA-C-dependent activity was found after exercise. Immediately after exercise, total carbonic anhydrase activity and CA-B-dependent activity following the addition of Zn2+ showed significant increases, compared with their respective activities without Zn2+ addition. However, no such effects were observed just before exercise or after rest; the addition of Zn2+ had no effect on CA-C-dependent activity at any time. A significant correlation was found between the changes in concentration of zinc and CA-B-dependent activity after exercise (r=0.711). The findings of the present study suggest that active CA-B enzymes are converted in part to inactive enzymes during acute physical exercise, possibly by decreased zinc binding. Moreover, the change in CA-B-dependent activity correlated well with the changes in pH and HCO3 concentrations in venous blood (r=0.853 and r=0.718, respectively). One may speculate that an adaptive decrease in CA-B-dependent activity in erythrocytes occurs with increased acidification in blood during heavy physical exercise of short duration.

Effects of lead acetate on guinea pig—Cochear microphonics, action potential, and motor nerve conduction velocity

Segmental demyelination and axonal degeneration of motor nerves induced by lead exposure is well known in man, and animals. The effect of lead acetate exposure to man may involve the cranial nerves, since vertigo and sensory neuronal deafness have been reported among lead workers. However, there are few reports concerning the dose-effects of lead acetate both to the peripheral nerve and the cranial VII nerve with measurement of blood lead concentration. The authors investigated the effects of lead acetate to the cochlea and the VIII nerve using CM (cochlear microphonics) and AP (action potential) of the guinea pigs. The effects of lead acetate to the sciatic nerve were measured by MCV of the sciatic nerve with measurement of blood lead concentration.

Effect of lead on electrophoretic mobility of rat erythrocytes.

Lead often affects the erythrocyte membrane. The relationship between the changes in erythrocyte membrane and the anemia caused by lead is still unclear. Initially, the effect of lead injected intraperitoneally on the electrophoretic mobility of rat erythrocytes was investigated in order to study the relationship between them. As indices of lead exposure, hemoglobin (Hb) levels, hematocrits (Ht), delta-aminolevulinic acid dehydratase (ALA-D) activities and blood lead (blood Pb) levels in the injected rats were also examined. Exposure to lead significantly decreased the mobility of rat erythrocytes. The changes in mobility seemed to be less sensitive than those in ALA-D activity, however, the decreases in mobility were simultaneous with or prior to those in Hb level and Ht. The decreases in mobility were evident to some extent below a blood Pb level of 100 micrograms/100 ml and generally present at a level of 100 micrograms/100 ml and over. In the rats exposed to lead a significant negative correlation was found between the mobilities and the logarithms of blood Pb level.

Effect of physical exercise on the specific activity of carbonic anhydrase isozyme in human erythrocytes.

Significant decreases in the levels of both carbonic anhydrase type B and total esterase activity of human erythrocytes were observed after physical exercise (bicycle ergometer, 150 W for 30 min). Since carbonic anhydrase B-dependent esterase activity likewise decreased, the decrease in the total esterase activity would be caused by the decrease of carbonic anhydrase B activity. The specific activity of carbonic anhydrase B tended to decrease after the exercise. On the other hand no such effects were noted for carbonic anhydrase type C.

Motor Nerve Conduction Velocity (MCV) and Lead Content in Sciatic Nerve of Lead-Exposed Rats

There have been many pathological and electrophysiological studies of peripheral nerves in inorganic lead intoxication. Peripheral nerve conduction velocity (NCV) has been used as an objective measure of the effects of lead on the peripheral nerve function and has been examined with blood lead content. There have been few reports on the changes in NCV related to lead content in the peripheral nerve tissue under lead poisoning. In the present study, the authors have examined motor nerve conduction velocity (MCV) of the tail by a non-invasive method and lead content of the peripheral nerve in lead-exposed rats. Furthermore, they have attempted to assess the relationship between these two parameters.

Effects of lead on sialic acid content and survival of rat erythrocytes

The anemia frequently observed in lead poisoning is thought to result from a shortening of erythrocyte survival in combination with inhibition of hemoglobin synthesis. However, the exact mechanism by which lead shortens erythrocyte survival remains unclear. In the present study, the effects of lead, injected intraperitoneally, on sialic acid content and survival of rat erythrocytes were investigated in order to study the relationship between them. As indices of lead exposure, hemoglobin (Hb) levels, hematocrits (Ht) and blood lead (blood Pb) levels in the injected rats were also examined. Exposure to lead significantly decreased the sialic acid content of the erythrocyte membrane. The decreases in sialic acid content were evident to some extent below a blood Pb level of 100 micrograms/100 ml and generally present at a level of 100 micrograms/100 ml and higher. In the rats exposed to lead a significant negative correlation was found between sialic acid content and the logarithm of blood Pb level. A shortening of erythrocyte survival was also observed in the rats exposed to lead.

Effects of repeated reversal of the light-dark cycle on the peripheral nervous system, blood and spontaneous activity of lead-exposed rat

The purpose of the experiment was to investigate if biological effects on lead acetate (Pb(AcO)+2)-exposed rats under the reversal light-dark (LD) cycle (12∶12) could be different from those under the normal LD cycle (L: 0700-1900, D: 1900-0700). The reversal of LD condition was repeatedly produced by alternation of LD cycle every 3 days for 53 days. Motor nerve conduction velocity (MCV), Ht and Hb, lead contents in blood and sciatic nerve tissue, and spontaneous activity were measured. Either 10 mg or 20 mg (Pb(AcO)+2) was i.p. injected once a week, 8 times in total. The pattern of spontaneous activity under the reversal rhythm became desynchronized with the LD cycle, while that under the normal rhythm synchronized with the LD cycle through the experiment. From the 5th week, the MCV in the lead-exposed groups under the reversal rhythm decreased significantly compared with that in the control under the normal rhythm. From the 6th week, there were also significant differences in MCV of the 20-mg groups between the normal and reversal rhythms. However, there were not significant differences between the normal and the reversal rhythms in the body weight, the lead contents of the blood and the sciatic nerve, Ht, and Hb in any of the control, 10-mg and 20-mg groups.

Studies on bacterial aerosol. Part 10. Species classification and antibiotic susceptibility of airborne staphylococci in hospital

A new scheme for species-classification of staphylococci was applied to 124 strains of airborne staphylococci (A. S.) isolated from the air in hospital wards. For comparison, 204 strains of A. S. dispersed from healthy subjects and 521 strains of staphylococci isolated from their skin were also classified. In addition, both strains of A. S. in hospital wards and from the healthy subjects were tested for susceptibility to 11 major antibiotics (penicillin G, methicillin, cloxacillin, ampicillin, cephaloridine, erythromycin, chloramphenicol, streptomycin, tetracycline, kanamycin and gentamycin).The results obtained were as follows:1. One of the 124 strains of A. S. from the hospital wards was identified as Staphylococcus aureus (S. aureus). The remaining 123 strains of coagulase-negative staphylococci (CNS) were classified into S. epidermidis (35.5%), S. haemolyticus (11.3%) and other species, except for 41 strains (33.1%) which were not classified. Most of the staphylococcal strains isolated from the healthy human skin were identified as S. epidermidis (82.0%). On the other hand, a large number of unclassifiable strains (76.5%) were observed in A. S. from the healthy subjects.2. The airborne CNS strains from the hospital wards showed marked differences in minimal inhibitory concentration (MIC) for all antibiotics tested when compared to those from the healthy subjects. Particularly, half of them were resistant to penicillin G, methicillin, ampicillin and kanamycin. Similarly, the rate of airborne CNS strains in hospital wards was much higher for multi-drug resistance than those from the healthy subjects.The results suggest that some airborne CNS in hospital wards may act as opportunistic pathogens.