Drug-induced ototoxicity. Pathogenesis and prevention

Ototoxicity is a disabling adverse effect of several widely used classes of drugs, such as diuretics, anti-inflammatory agents, antineoplastic agents and aminoglycoside antibiotics. High-dose therapy with either diuretics or anti-inflammatory agents is primarily associated with acute and transient impairment of hearing or tinnitus. In contrast, long term treatment with antineoplastic agents or aminoglycoside antibiotics is typically associated with delayed and irreversible loss of hearing; lesion in the organ of Corti include the destruction of auditory sensory cells. Vestibular function can also be compromised by ototoxic drugs. Occasional cases of ototoxicity have been reported for a variety of other therapeutic compounds and environmental toxins. In addition, the simultaneous administration of multiple agents which are potentially ototoxic can lead to synergistic loss of hearing. Exposure to loud noise may also potentiate the hearing loss due to cochleotoxic drugs. Ototoxic agents can impair the sensory processing of sound at many cellular or subcellular sites. However, the molecular mechanisms of ototoxicity have not been established for most of these drugs, and structure-toxicity relationships have not been determined. It has therefore been difficult to predict the ototoxic potential of new drugs, and rational approaches to the prevention of ototoxicity are still lacking. The clinical and experimental features of ototoxicity are reviewed for several classes of drugs, with an emphasis on current knowledge of the mechanism and the possibilities for the prevention of ototoxicity for each.

Insulin suppresses hepatitis B surface antigen expression in human hepatoma cells

The human hepatoma Hep3B cells contain integrated hepatitis B viral genome and continually secret hepatitis B surface antigen (HBsAg). The production of HBsAg (but not alpha-fetoprotein) was suppressed by addition of low concentrations (0.1-1 nM) of insulin into serum-free medium. In addition, the suppression of HBsAg production by insulin was paralleled with the decrease in HBsAg mRNA abundance. Insulin also cause a rapid rate of disappearance of HBsAg mRNA (t 1/2, 2 h) in Hep3B cells. The Hep3B cells carry specific receptor with high affinity for insulin (Kd = 1.8 nM). The receptor showed an insulin-dependent protein tyrosine kinase activity. The half-maximal insulin concentration for the activation of the receptor kinase was about 5 nM. Only very high concentrations of insulin-like growth factor I and human proinsulin can compete for the insulin receptor binding and suppress HBsAg production, this suggests that insulin may act through its receptor binding to suppress HBsAg expression in human hepatoma Hep3B cells.

[Rectal examination for extent of perirectal infiltration in rectal carcinoma]

From 1983 to 1985, 214 patients with rectal carcinoma were assessed for the conformation rate of the rectal examination to the gross findings of the extent of perirectal infiltration in the resected specimens. It was found that the conventional classification of the extent of rectal infiltration by rectal examination, 1/4, 1/3, 2/4, 3/4 and 4/4 of the circumference, had only a conformation rate of 32.7% to the gross findings. According to the classification of 1/4 or less and more, the conformation rate could reach 93%. It was also found that the extent of perirectal infiltration, being closely related to the regional lymph node metastasis and the depth of invasion, was only demonstrated by this latter classification, which was not shown in the conventional classification. Hence, it is suggested that the rectal examination implying the extent of perirectal infiltration by simply classified into two groups: equal to or less than 1/4 and more than 1/4 of the circumference of the rectal wall.

Selective suppression of insulin-induced proliferation of cultured human hepatoma cells by somatostatin

The effects of somatostatin (SRIF), insulin, and triiodothyronine (T3) on the growth of human hepatoma cells were investigated on the well-differentiated human hepatoma cell line Hep3B. Results showed that both insulin and T3 can stimulate cell growth of serum starved Hep3B cells at physiological concentrations. SRIF alone showed little growth-promoting activity. When added concurrently with insulin, however, SRIF suppressed the insulin-induced cell proliferation in a dose-dependent manner. On the other hand, SRIF had no inhibitory effect on T3-induced cell proliferation. SRIF is labile in the medium, with a half-life of about 2 h during culture incubation. SRIF did not disturb the insulin binding to its surface receptors nor inhibit the insulin-dependent receptor kinase activity of Hep3B cells in vitro. These results suggest that postreceptor regulation may be involved. The selective suppression by SRIF of insulin-induced cell growth provides an unique approach to the study of insulin actions on proliferation of human hepatoma cells.

Result of treatment of patients with stage D1 prostatic carcinoma

Between 1972 and 1982, 59 patients who had documented pelvic lymph node metastases, proved by pelvic lymphadenectomy, were available for analysis. Radical retropubic prostatectomy was the primary treatment in 33 patients with or without other therapies, while 23 patients received external beam radiation therapy as their primary treatment. Three patients received hormonal therapy alone. Forty-two of 59 patients are alive for a crude survival of 71 per cent. Sixteen patients have died of metastases. Patients with low-grade tumors, small tumor burden, and limited lymph node metastases had excellent short-term survival after radical prostatectomy.

The management of superficial bladder tumors and carcinoma in situ with intravesical bacillus Calmette-Guerin

A phase II study was performed to assess the role of bacillus Calmette-Guerin as a prophylaxis against recurrent stages O and A bladder tumors, and in the treatment of existing superficial bladder tumors and carcinoma in situ. Tice strain bacillus Calmette-Guerin (1 vial, 2 to 8 times 10(8) organisms in 60 cc saline) was instilled intravesically without cutaneous inoculation. Instillations were given weekly for 6 weeks and then monthly or until recurrence in 22 patients with a history of recurrent tumors, while 22 with existing stages O and A transitional cell carcinoma, and 19 with carcinoma in situ were treated weekly for 8 weeks and then monthly for 12 months or until failure. Complications included cystitis in 88 per cent of the patients (severe in 20 per cent), fever in 15 per cent, a flu-like syndrome in 13 per cent, edema and pruritus in 1.5 per cent, and ureteral stenosis in 1.5 per cent. Twelve patients (19 per cent) did not complete the study owing to toxicity. Of the patients in the prophylaxis group 67 per cent have had no tumor recurrence 10 to 26 months (mean 15 months) after therapy. Of the patients with existing tumors 36 per cent had complete regression following bacillus Calmette-Guerin therapy and 23 per cent had a partial response. Among the patients with carcinoma in situ 13 (68 per cent) had reversal to normal urothelium and 3 (16 per cent) had marked improvement. None of the patients had recurrence at 11 to 20 months. Intravesical Tice strain bacillus Calmette-Guerin is effective as a prophylaxis against recurrent superficial bladder tumors and in the treatment of carcinoma in situ.

Steroid concentrations in isolated theca and granulosa layers of preovulatory follicles during the ovulatory cycle of the domestic hen

The purpose of the present investigation was to measure the concentrations of progesterone (P4), testosterone (T) and estradiol-17 beta (E2) in isolated theca and granulosa layers of the five preovulatory follicles of the domestic hen. The largest follicle (F1), the second largest (F2), third largest (F3), fourth largest (F4) and fifth largest (F5) follicles were removed at 24, 18, 12, 6 and 2 h before the expected ovulation. Theca and granulosa layers were isolated and P4, T, E2 and protein concentrations determined. Protein concentrations of the granulosa and theca layers increased 5- and 15-fold, respectively, during the five ovulatory cycles prior to ovulation. As the follicle approached ovulation, there was a linear decrease in E2 concentration of the theca layer with the most significant decrease (P less than 0.001) occurring between 24 and 18 h of the ovulatory cycle. In the F3 and F4 theca layers, there was a significant increase (P less than 0.005) in E2 at 6 h of the ovulatory cycle. Fluctuations in T concentrations in theca and granulosa layers were similar. There was a significant increase (P less than 0.05) in T in both layers of the F2, F3 and F4 follicles at 6 h followed by a decrease (P less than 0.005) in the theca layers at 2 h of the ovulatory cycle. The P4 concentration of the granulosa layer increased gradually during follicular maturation, with the greatest increase occurring in the F2 and F1 granulosa layers between 18 and 12 h of the ovulatory cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic interaction between valproic acid and free fatty acids in rhesus monkeys

The interaction between valproic acid (VPA) and free fatty acids (FFA) was investigated at a systemic level in eight rhesus monkeys. Intralipid emulsion (I.L.) was infused to increase plasma FFA levels. During I.L. treatment, plasma FFA levels were elevated in all cases (12 cases) with increases ranging from 38 to 525% (median, 102%). Valproate free fraction (fp) was elevated in 11 of 12 cases, with increases ranging between 7 and 100% (median, 18%). A positive correlation between the relative increase in FFA and the corresponding increase in fp of VPA was obtained. Intralipid infusion was associated with changes in the systemic clearance of VPA (an increase in five cases and a decrease in seven cases). The intrinsic clearance (Clint) of VPA was decreased in 9 of 12 cases with decreases ranging from 13 to 78% (median, 22%). Urinary excretion of valproate glucuronide was decreased in three of four monkeys during I.L. treatment. A significant positive correlation (p less than 0.05) between the relative increase in FFA levels and the decrease in Clint of VPA were also observed. The mechanism of interaction between VPA and FFA in rhesus monkey is more complex than a simple protein binding displacement and involves at least one metabolic inhibition component such as glucuronidation.