Yuji Makita

Testicular toxicity evaluation of arsenic-containing binary compound semiconductors, gallium arsenide and indium arsenide, in hamsters

The testicular toxicities of gallium arsenide (GaAs), indium arsenide (InAs) and arsenic trioxide (As2O3) were examined by repetitive intratracheal instillation using hamsters. GaAs (7.7 mg/kg) and As2O3 (1.3 mg/kg) were instilled twice a week a total of 16 times and InAs (7.7 mg/kg) was instilled a total of 14 times. GaAs caused testicular spermatid retention and epididymal sperm reduction, though the degrees were less severe than those in rats shown in our previous experiment. InAs and As2O3 did not show any testicular toxicities. Serum arsenic concentration in GaAs-treated hamsters was less than half of that in As2O3-treated hamsters in which no testicular toxicities were found. Serum molar concentration of gallium was 32-times higher than that of arsenic in GaAs-treated hamsters. Therefore gallium may play a main role in the testicular toxicity of GaAs in hamsters.

Long Term Pulmonary Toxicity of Indium Arsenide and Indium Phosphide Instilled Intratracheally in Hamsters

Long Term Pulmonary Toxicity of Indium Arsenide and Indium Phosphide Instilled Intratracheally in Hamsters: Koji Yamazaki, et al. Department of Hygiene, Graduate School of Medical Sciences, Kyushu University—We examined the long‐term toxicological effects of III‐V semiconductor particles on laboratory animals. Eight‐week‐old male Syrian golden hamsters were given 4 mg/kg indium arsenide (InAs) or 3 mg/kg indium phosphide (InP) particles, both containing 2.4 mg/kg as indium, intratracheally twice a week for 8 weeks. Control hamsters were given only a vehicle, phosphate buffer solution. Over a 2‐yr period, these animals were euthanized serially and the biological effects were determined. Weight gain was significantly suppressed in both InAs and InP groups, compared to the control group, with greater suppression in the InAs group. The serum indium concentration in the InAs group was about twice as high as that in the InP group, in each period. Histopathologically, severe pulmonary inflammation and localized lesions with bronchiolo‐alveolar cell hyperplasia were present in both InAs and InP groups from just after the last administration. The localized lesions gradually transformed to proteinosis‐like lesions with periodic acid Schiff reagent positive exudation after 16 wk. By means of immunostaining of proliferating cell nuclear antigen and argyrophilic proteins associated with nucleolar organizer regions staining, proliferative activities were evidenced in the localized lesions at each time and were noticeable in their early stage. K‐ras, a known oncogene, was not mutated in association with these lesions. In conclusion, InAs and InP particles caused severe systemic toxicity and pulmonary localized hyperplastic lesions with proliferative activity were derived via the respiratory route. Neoplastic change was nil even in a 2‐yr observation period.

Effects of nifedipine derivatives on smooth muscle cells and neuromuscular transmission in the rabbit mesenteric artery

SummaryThe effects of nifedipine and its derivatives, nisoldipine, nimodipine and nitrendipine, on smooth muscle cells and neuromuscular transmission were investigated in the rabbit mesenteric artery. These agents in concentrations of up to 2×10−7 M modified neither the membrane potential nor the membrane resistance, yet did inhibit the spike potential evoked by direct muscle stimulation in the presence of TTX or by perivascular nerve stimulation. The inhibitory action of nitrendipine was weaker than that of the other derivatives. These agents had no effect on the miniature excitatory junction potentials (m.e.j.ps) and e.j.ps evoked by the first stimuli and after completion of the facilitation in a train stimulation. Nifedipine and its derivatives had no effect on the K-induced depolarization but did have a marked effect on the K-induced contraction. Nisoldipine showed the highest inhibitory potency for the K-induced contraction [IC50 was 1.2×10−9 M for the 128 mM (K)o-induced contraction]. Noradrenaline depolarized the membrane (>5×10−7 M) and produced contraction (>3×10−7 M). The contraction evoked by high concentrations of noradrenaline was inhibited by these agents to a greater extent than that evoked by low concentrations. The contraction evoked by perivascular nerve or direct muscle stimulation was partly inhibited by nifedipine and its derivatives. The contraction elicited by Na-free solution was inhibited by these agents but the noradrenaline-or caffeine-induced contraction in Ca-free solution was not. These results indicate that in smooth muscle cells of the rabbit mesenteric artery, nifedipine and its derivatives inhibit the voltage dependent Ca-influx which occurs during the spike potential and in response to K-, electrically- or nor-adrenaline-induced depolarization. These derivatives appear to have no effect on the adrenoceptor operated Ca increase in myoplasm which occurs in the absence of depolarization at low noradrenaline concentrations. The derivatives act as Ca antagonists with a quantitative difference in potency, i.e. the strongest action was observed with nisoldipine and the weakest with nitrendipine.

Changes in the testicular damage caused by indium arsenide and indium phosphide in hamsters during two years after intratracheal instillations

Changes in the Testicular Damage Caused by Indium Arsenide and Indium Phosphide in Hamsters during Two Years after Intratracheal Instillations: Minoru Omura, et al. Department of Hygiene, Graduate School of Medical Sciences, Kyushu University—Change in the testicular damage caused by indium arsenide (InAs) and indium phosphide (InP) was examined during two yr after repetitive intratracheal instillations in hamsters. In this study, 4.0 mg/kg body weight/day of InAs or 3.0 mg/kg body weight/day of InP was instilled intratracheally twice weekly for eight wk. A single instillation dose of indium was 2.4 mg/kg body weight in both groups. Testicular damage was evaluated 0, 8, 16, 40, 64 and 88 wk after the last instillation. Both InAs and InP were proved to be definite testicular toxicants. Both materials decreased reproductive organ weight and caudal sperm count, and caused severe histopathologic changes in the testes. InAs‐induced testicular damage was always more serious than InP‐induced testicular damage. The serum indium concentration in the InAs group was always higher than that in the InP group, and indium was probably a toxic element in both materials. In the histopathologic examination, vacuolization of seminiferous epithelium was frequently observed as an early histopathologic change and spermatogonia remained in general even in the seminiferous tubules with severe histopathologic changes in both groups. It is therefore estimated that Sertoli cells, not stem cell spermatogonia, were the target cells of these indium‐containing compound semiconductor materials. The threat of InAs and InP to male reproduction was proved in this study. We concluded that male reproductive disorders should not be overlooked when severe exposure to indium‐containing compound semiconductor materials is apparent in human subjects.

Modulation of neuromuscular transmission by endogenous and exogenous prostaglandins in the guinea-pig mesenteric artery

1. At concentrations of 2·8 × 10−8‐2·8 × 10−6 M, prostaglandins (PGs; PGE1, PGE2 and PGF2α) had no effect on membrane potential and resistance of smooth muscles of the guinea‐pig mesenteric artery. PGs (2·8 × 10−8 M) suppressed the contraction evoked by perivascular nerve stimulation, but did not suppress the contraction evoked by direct muscle stimulation.

Effects of prostaglandin I2 and carbocyclic thromboxane A2 on smooth muscle cells and neuromuscular transmission in the guinea‐pig mesenteric artery

1 In the guinea‐pig mesenteric arteries neither prostacyclin (PGI2) nor carbocyclic thromboxane A2 (cTxA2) affected membrane potential in concentrations below 1 × 10−6 m. Increasing the concentration to 3 × 10−6 m either slightly hyperpolarized or depolarized the membrane with little change in membrane resistance. 2 At a concentration of 1 × 10−7 m, the amplitude of the first e.j.p. and the enlarged amplitudes of the subsequent e.j.ps evoked by trains of stimuli were reduced consistently by PGI2 or cTxA2. Facilitation was unaffected by either agent. 3 The inhibitory actions of PGI2 were partly overcome by increased concentrations of 5 mm [Ca]o and were accelerated by a reduced concentration of 1.25 mm [Ca]o. 4 The amplitude of the contraction evoked by perivascular nerve stimulation was inhibited to a greater extent by PGI2 than by cTxA2 at concentrations below 1 × 10−6 m. 5 The contraction evoked by 5 × 10−6 m noradrenaline (NA) or excess concentrations of 20.2 mm [K]o was enhanced by 1 × 10−8 m — 1 × 10−6 m cTxA2 and suppressed by 1 × 10−8 m — 1 × 10−6 m PGI2. The minimum concentration of cTxA2 required to produce the contraction was 1 × 10−8 m. 6 These results indicate that transmission at the neuromuscular junction was inhibited consistently by PGI2 or cTxA2, presumably due to inhibition of NA release by suppression of the Ca influx at the nerve terminals. Whereas PGI2 inhibited, cTxA2 enhanced the mechanical response by a direct action on the smooth muscle cells.

Effects of adrenoceptor agonists and antagonists on smooth muscle cells and neuromuscular transmission in the guinea-pig renal artery and vein.

1 In the guinea‐pig renal artery and vein, the membrane potential was — 66.8 mV and — 46.8 mV, the length constant 0.54 mm and 0.43 mm, and the time constant 240 ms and 98 ms, respectively. The maximum slope of the depolarization produced by a 10 fold increase [K]o was 46 mV in the renal artery and 39 mV in the renal vein. 2 Noradrenaline (NA over 5 × 10−7m in the artery and over 10−7m in the vein) depolarized the membrane and slightly reduced the membrane resistance, assessed from relative changes in the amplitude of electrotonic potential. The action of NA was suppressed by prazosin in the artery but by yohimbine in the vein, i.e. the α1‐adrenoceptor is present in the extra junctional muscle membrane in the renal artery while the α2‐adrenoceptor is present in the renal vein. Dopamine and isoprenaline did not modify the membrane properties. 3 In the renal artery, repetitive perivascular nerve stimulation (0.1 ms, 50 Hz, 5 shocks) evoked excitatory junction potential (e.j.p.). Applications of guanethidine (10−6m) or tetrodotoxin (3 × 10−7m) abolished the generation of the e.j.p. Low concentrations of phentolamine (5 × 10−7 m), prazosin (10−7 m) and yohimbine (5 × 10−7 m) enhanced the e.j.p. amplitude, while high concentrations of phentolamine (10−5 m) and prazosin (> 10−5 m) reduced the amplitude of e.j.p.s. NA, dopamine and Clonidine consistently suppressed the amplitude of e.j.ps, at any given concentration over 10−7m. 4 Spontaneously generated miniature e.j.ps (m.e.j.ps) were recorded on rare occasions. Phentolamine and yohimbine both at 5 × 10−7m and prazosin 10−7m increased the appearance of m.e.j.ps. 5 In the renal vein, repetitive nerve stimulation failed to generate the e.j.p. Sympathetic innervation to this tissue seems to be sparse. 6 Specificity of innervation and adrenoceptors present on smooth muscle cells in both the renal artery and vein are discussed, and the presynaptic regulation of NA release is compared with findings in other vascular tissues.

Renal Oncocytoma Developed in a Long-Term Hemodialysis Patient

A case of renal oncocytoma which developed in a 38-year-old Japanese woman after 7 years of maintenance hemodialysis is reported. An encapsulated round tumor with a diameter of about 5 cm was incidentally discovered by abdominal echography. This is the first case of renal oncocytoma found in a long-term hemodialysis patient. Identification and differentiation of this subgroup from renal carcinomas are very important because of its benign nature. Careful clinicopathological investigation of renal tumors should therefore be required in hemodialysis patients.

Effects of Perinatal Simultaneous Exposure to Tributyltin (TBT) and p, p′-DDE (1,1-Dichloro-2,2-Bis(p-Chlorophenyl) Ethylene) on Male Offspring of Wistar Rats

p,p′-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene; DDE] and tributyltin (TBT) are ubiquitous in the environment and in Japan were shown to bioaccumulate in marine products. Thus these chemicals serve as a source of contaminant in the mammalian food chain. Fetuses and neonates through maternal ingestion may be exposed to DDE and TBT. Therefore, the effects of concurrent exposure to DDE and TBT were investigated in male Wistar rat offspring of dams ingesting these two contaminants. In this study, TBT suppressed the growth and delayed eye opening. However, both growth retardation and delayed eye opening produced by TBT failed to occur in the presence of DDE. Unexpectedly, the prostate weight of male rat offspring was significantly reduced with the administration of TBT but restored in the presence of DDE. These results indicate that TBT and DDE affected the development of male rat offspring following maternal exposure, and simultaneous administration of DDE prevented some of the observed effects of TBT, especially of an antagonistic nature, through a mechanism, still to be determined.

Systemic Effects of Orally Administered p, p'-DDE on Immature Male Wistar Rats during Pubertal Period

Systemic Effects of Orally Administered p, p’‐DDE on Immature Male Wistar Rats during Pubertal Period: Yuji Makita, et al. Department of Hygiene, Graduate School of Medical Sciences, Kyushu University—Systemic effects of p, p’‐DDE (1, 1‐dichloro‐2, 2 bis (p‐chlorophenyl) ethylene; DDE) on immature male rats were investigated in pubertal Wistar rats after oral administration of DDE. Special rat chow containing 125 ppm DDE (approximately 10 mg/kg DDE) had been administered daily for 42 d since 6 wk of age and its effects had been observed until 12 wk of age. The administration of DDE did not produce any overt signs of toxicity. Neither physical development nor sexual maturation was affected, and serum biochemistry was not impaired at the dose used in this experiment. Moreover, the male reproductive organs and epididymal sperm count were not affected by the administration of DDE during the pubertal period. Our results showed that even immature male rats were resistant to DDE exposure at the daily dose of ca. 10 mg/kg, but metabolic and immunological changes still remained uncertain. Further investigation should be conducted to reveal all the effects of DDE on immature male rats.