Cartilage-shaving procedure for the control of tracheal cartilage invasion by thyroid carcinoma

This study was carried out to ascertain whether the cartilage-shaving procedure is appropriate to control thyroid carcinoma with tracheal cartilage invasion. Of 432 thyroid carcinoma patients treated between 1979 and 1988, 16 had tracheal cartilage invasion only. This patient population was made up of 3 men and 13 women, with a mean age of 55.8 years. Fourteen were diagnosed histologically as having papillary carcinoma and the remaining two as having follicular carcinoma. Cartilage shaving was the primary treatment in all the patients, and subsequent radioactive iodine (131I) or external-beam radiotherapy was administered to control any possible residual disease. Lifelong thyroid hormone replacement was instituted in all patients, and the follow-up period averaged 70.7 months. Only four of the 16 patients remained disease free; the disease was not controlled in the other 12, and seven of this latter group eventually died of their disease. We feel that a more extensive resection procedure than cartilage shaving should be considered, even in patients with superficial tracheal invasion, to increase the disease-free survival rate.

A rapid and simple microfluorometric phagocytosis assay

A microfluorometric method for phagocytosis study has been developed using fluorescein conjugated Escherichia coli K-12 particles. This technique is based on the uptake of fluorescent particles and quenching of extracellular fluorescence at the end of the assay. A murine macrophage cell line, J774, was used as a phagocyte model. The cells were harvested from tissue culture flasks and adjusted to 1 x 10(6) cells/ml. They were then dispensed into a 96-well tissue culture plate, 100 microliters/well, and incubated at 37 degrees C in 5% CO2 for 1 h to allow cells to adhere to the bottom of the wells. The culture medium was aspirated and 100 microliters of fluorescent E. coli particles suspended in Hanks' buffer were added. The plates were further incubated for various time periods. Buffer solution in the wells was removed by aspiration. Extracellular fluorescence was then quenched by adding 100 microliters of trypan blue (250 micrograms/ml, pH 4.4). The dye was removed after 1 min. The intensity of fluorescence associated with intracellular fluorescent particles was measured directly in the wells using a computerized microplate fluorometer at 485 nm excitation and 530 nm emission. This assay provided a rapid and objective measurement of phagocytosis activity. Using a cultured cell line and a 96-well microtiter plate format, this assay can facilitate the screening of a large number of various biological and pharmacological substances for their modulating effects on phagocytosis.

Diagnostic approach to thyroid carcinoma in Graves' disease

Among 545 surgically treated Graves' disease patients, 17 were found to have coexisting thyroid neoplasms. Of these 17 patients, 11 turned out to have thyroid carcinomas. These patients could be divided into 2 groups; Group I with a diffusely enlarged gland with a clinically palpable nodule (n = 6) and Group II without a palpable nodule (n = 5). In Group I, 4 patients were diagnosed by preoperative fine needle aspiration cytology, and the remaining 2 by intraoperative frozen-section examination. In Group II, none of the patients were suspected of any concurrent thyroid carcinoma preoperatively, and only 2 were identified by intraoperative frozen-section examination. Thus, 8 of the 11 patients were diagnosed preoperatively or intraoperatively. These observations suggest that in all patients with Graves' disease and concurrent thyroid nodules, the suspicion of associated malignancy may be raised. And also, fine needle aspiration cytology in every case of Graves' disease with a palpable nodule and intraoperative frozen-section examination of the suspicious lobe in the cases of non-palpable nodules appear worthwhile in detecting a concurrent thyroid carcinoma.

Surgical repair of esophageal perforation due to pneumatic dilatation for achalasia. Is myotomy really necessary?

Esophageal perforation is a rare complication of pneumatic dilatation for achalasia. The few clinical series reported in the literature recommend, under most circumstances, esophageal repair combined with esophagocardiomyotomy. However, the superiority of this technique over repair alone has never been proven. We reviewed our experience, since 1979, with six operative cases of esophageal perforation from pneumatic dilatation for achalasia. After débridement, the esophagus was repaired and, if possible, buttressed with a gastric fundal patch. There was only one late postoperative death due to sepsis and one upper gastrointestinal bleeding complication in our series. Follow-up (1 to 12 years) revealed no dysphagia in any of the five surviving patients and mild gastroesophageal reflux in two. From a review of the literature we found no reports of similarly treated patients experiencing recurrent symptoms of achalasia. In these acutely ill patients, our operative strategy is more feasible than repair and esophagocardiomyotomy and equally effective.

Serial fiberoptic bronchoscopic observations of endobronchial tuberculosis before and early after antituberculosis chemotherapy

STUDY OBJECTIVE

To evaluate the antituberculous treatment responsiveness of endobronchial tuberculosis in the different stages of evolution.

DESIGN

A prospective study before and after trial with 9 months of antituberculosis chemotherapy without steroid.

PATIENTS AND INTERVENTION

One hundred thirty-six endobronchial lesions in 62 patients were subdivided into four types according to initial fiberoptic bronchoscopic (FOB) findings. Follow-up FOB was performed in 29 patients with 56 endobronchial lesions to detect the changes in the initial endobronchial lesion and bronchostenosis within 3 months after completion of 9 months of chemotherapy.

RESULTS

The endobronchial lesions could be classified into four types: exudative (59 lesions, 43.3 percent), ulcerative (13 lesions, 9.7 percent), cicatricial (36 lesions, 26.5 percent), and bronchoglandular (28 lesions, 20.5 percent). In the reassessment of 56 lesions, all 19 exudative and all 9 ulcerative lesions showed complete improvement. Of the cicatricial lesions, most (10 of 12 lesions) showed no change in bronchostenosis, whereas 2 lesions showed improvement. In the bronchoglandular lesions, 6 of 18 lesions showed progressed bronchostenosis. Overall, we observed improved responses in 53.6 percent, progressed bronchostenosis in 10.7 percent, and stationary responses in the remaining 35.7 percent. The progressed lesions were found only in the bronchoglandular lesions.

CONCLUSION

In the exudative, ulcerative, and cicatricial lesions, the administration of antituberculous chemotherapy alone resulted in favorable responses in the early posttreatment period.

Antigenic and nucleic acid analysis of nosocomial isolates of respiratory syncytial virus

Monoclonal antibodies and ribonuclease protection were used to analyze antigenic and genomic diversity among 42 isolates of group A respiratory syncytial virus (RSV) from studies of nosocomial RSV carried out at the University of Rochester during the 1974-1975 and 1975-1976 RSV seasons. Three distinct subgroups or lineages and a total of 12 viral variants were present. Against this background of diversity, an outbreak was recognized that included 13 indistinguishable isolates occurring during a 2-week period. This outbreak accounted for 6 of the 8 infants with nosocomial infection. In contrast to the limited diversity of the nosocomial isolates, isolates from the 10 infants with community-acquired infection included 8 variants. Like those from community outbreaks of RSV, isolates of RSV from hospitalized patients are virologically heterogeneous. However, discrete outbreaks associated with transmission of a single strain can occur.

Soluble interleukin-2 receptor and cellular profiles in bronchoalveolar lavage fluid from patients with bronchial asthma

BACKGROUND

To elucidate the role of T-cell activation in the physiologic changes and cellular infiltrations in the bronchial tree of patients with symptomatic bronchial asthma, we measured the concentration of soluble interleukin-2 receptor (sIL-2R), cellular compositions and IL-2R expression on cells in bronchoalveolar lavage (BAL) fluid. We also measured physiologic parameters, including a provocation concentration of histamine required to reduce the forced expiratory volume in 1 second by 20% of the prechallenge baseline (PC20).

RESULTS

The concentration of sIL-2R and the ratio of IL-2R expression on CD3 positive lymphocytes were significantly higher in BAL fluid from 20 patients with symptomatic bronchial asthma than concentrations in fluid from nine healthy controls (p < 0.01) and six asymptomatic patients with bronchial asthma (p < 0.05). The concentration of sIL-2R correlated with the percentage of IL-2R expression on CD3 positive lymphocytes (rs = 0.709, p < 0.01). There was no difference in sIL-2R concentration of BAL fluid between the healthy control and the patient with asymptomatic bronchial asthma. Among the inflammatory cells recovered in BAL fluid, the percentages of eosinophils showed significant positive correlation with the concentration of sIL-2R in BAL fluid in the patients with bronchial asthma. The concentration of sIL-2R significantly correlated with forced expiratory volume one second, peak expiratory flow rate, and PC20 when observed in all study subjects, but not in the patients with bronchial asthma.

CONCLUSION

We conclude that T-cell activation within the bronchial tree appears to have a role in the infiltration of eosinophils into the bronchial tree, which may lead to enhanced bronchial hyperreactivity in patients with bronchial asthma.

Lipotrope-modified diets enhance nitrosomethylurea-induced mammary carcinogenesis in female rats

This study was conducted to determine the effects of lipotrope-modified (deficient or supplemented) diets on nitrosomethylurea- (NMU) induced mammary tumorigenesis. Eighty female Sprague-Dawley rats (4 wks old) were assigned to one of the following groups: control-synthetic diet (CSD), containing all required lipotropes; choline-methionine-deficient diet (CMD); methyl-deficient diet (MDD), lacking all lipotropes; and methyl-supplemented diet (MSD), containing twice as much of each lipotrope as the CSD diet. All animals were injected with NMU after a three-week dietary treatment period. MDD and MSD groups had shorter tumor latency periods (73 and 74 days, respectively) than the CSD group (105 days). Number of tumors per rat was significantly increased in the MDD group (4.6) compared with CSD (1.6), CMD (2.1), and MSD (2.5) groups. The results indicate that dietary manipulation of lipotropes in young female rats enhanced NMU-induced mammary tumorigenesis.

Spinal epidural granulocytic sarcoma preceding acute myelogenous leukemia

A rare case of spinal epidural granulocytic sarcoma (GS) preceding acute myelogenous leukemia is described. A 10-year-old boy presented with lower leg weakness. The initial diagnosis was a histiocytic lymphoma, and he was treated accordingly. No evidence of bone marrow involvement was found at that time. The correct diagnosis of epidural GS was made possible in retrospect by using immunoperoxidase staining for lysozyme fourteen months later when the patient showed the full-blown features of leukemia. This rare tumor should be considered in the differential diagnosis of an epidural mass with cord compression in patients with or even without acute leukemia, because early diagnosis followed by appropriate combined chemotherapy and radiation may obviate surgical intervention and eventually prevent leukemic transformation.

Complete one-hour immunocytochemistry based on capillary action

We describe a less than one-hour manual method for immunocytochemical analyses of B5 or formalin-fixed, paraffin-embedded tissue sections. The method employs capillary action to sequentially apply, incubate and remove liquid reagents from apposed pairs of up to 20 glass microscope slides and allows for simultaneous immunocytochemical analyses of as many as 10 different antigens. The method described here uses a) positively charged glass slides to rapidly immobilize tissue sections; b) rapid deparaffinization techniques; c) multipurpose reagents; d) ethanol-enriched buffer washes to improve capillary action and reduce nonspecific background; e) a single broad spectrum streptavidin-peroxidase or streptavidin-alkaline phosphatase detection system that identifies most primary monoclonal and polyclonal antibodies; and f) specific immunocytochemical signal amplification by cyclic chromogen enhancement.

Mapping function to structure in a channel-blocking peptide: electrostatic mutants of charybdotoxin

Electrostatic interactions between charybdotoxin (CTX), a specific peptide pore blocker of K+ channels, and a Ca(2+)-activated K+ channel were investigated with a genetically manipulable recombinant CTX. Point mutations at certain charged residues showed only small effects on the binding affinity of the toxin molecule: Lys11, Glu12, Arg19, His21, Lys31, and Lys32. Replacement by Gln at Arg25, Lys27, or Lys34 strongly decreased the affinity of the toxin. These affinity changes were mainly due to large increases of toxin dissociation rates without much effect on association rates, as if close-range interactions between the toxin and its receptor site of the channel were disrupted. We also found that the neutralization of Lys27 to Gln removed the toxin's characteristic voltage dependence in dissociation rate. Mutation and functional mapping of charged residues revealed a molecular surface of CTX which makes direct contact with the extracellular mouth of the K+ channel.

Interaction of charybdotoxin with permeant ions inside the pore of a K+ channel

Charybdotoxin (CTX) blocks high conductance Ca(2+)-activated K+ channels by binding to a receptor site in the externally facing "mouth." Toxin bound to the channel can be destabilized from its site by K+ entering the channel from the opposite, internal, solution. By analyzing point mutants of CTX expressed in E. coli, assayed with single Ca(2+)-activated K+ channels reconstituted into planar lipid bilayers, we show that a single positively charged residue of the peptide, Lys-27, wholly mediates this interaction of K+ with CTX. If position 27 carries a positively charged residue, internal K+ accelerates the dissociation rate of CTX in a voltage-dependent manner; however, if a neutral Asn or Gln is substituted at this position, the dissociation rate is completely insensitive to either internal K+ or applied voltage. Position 27 is unique in this respect; charge-neutral substitutions made at other positions fail to eliminate the K+ destabilization phenomenon. The results argue that CTX bound to the channel positions Lys-27 physically close to a K(+)-specific binding site on the external end of the conduction pathway and that a K+ ion occupying this site destabilizes CTX via direct electrostatic repulsion with the epsilon-amino group of Lys-27.

Developmental stages and energy restriction affect cellular oncogene expression in tissues of female rats

The influence of developmental stages and energy restriction on c-Ha-ras and c-fos cellular oncogene mRNA level was examined in mammary tissue and liver of female rats. c-Ha-ras and c-fos RNA transcripts in mammary tissue peaked at 9 wk of age, decreased during pregnancy, were lowest at mid-lactation and then increased at 25 wk. c-Ha-ras in liver showed highest expression at 5 wk and was hardly detectable at 11 wk, mid-pregnancy, mid-lactation and 25 wk. Liver c-fos and c-Ha-ras mRNA levels were similar. Lower c-Ha-ras and c-fos mRNA levels were observed in mammary tissue of energy-restricted (to 70% of ad libitum intake) rats at 25 wk compared with those allowed ad libitum access to food. Energy restriction did not affect liver c-Ha-ras and c-fos mRNA levels throughout the experimental period. These results demonstrate that developmental stages and energy restriction affect cellular oncogene mRNA levels with tissue-specific patterns.

A monoclonal antibody to common acute lymphoblastic leukemia antigen (CALLA) and its expression on several human tumor cell lines

We describe a newly-made murine monoclonal antibody to the common acute lymphoblastic leukemia antigen (CALLA), named SHB-10. The antigen detected by SHB-10 has a molecular weight of about 105 kDa. This antibody is very similar to that of conventional anti-CD10 Ab on indirect flowcytometric analysis using lymphoid malignant cell lines and peripheral lymphocytes of acute lymphoblastic leukemia (ALL) patients. The binding of anti-CD10 to Daudi cell and peripheral lymphocytes of ALL patients is blocked by SHB-10. Thus this monoclonal antibody is thought to detect the CALLA. The distribution of antigen detected by SHB-10 on several cell lines of neuroectodermal tumor and lymphoid malignancy was analysed and a slight difference in their cell surface expression is observed when compared with that by conventional anti-CD10. Further biochemical analysis is now under way for a better characterization of this antigen.

Epstein-Barr virus infection-associated renal disease: diagnostic use of molecular hybridization technology in patients with negative serology

There are only a few reports of renal disease associated with Epstein-Barr virus (EBV) infection. The diagnosis of EBV infection in these previously reported patients was based primarily on positive serology. Two patients with renal disease who, despite repeatedly negative serologies, were shown by molecular hybridization techniques--in situ hybridization (ISH) and polymerase chain reaction (PCR)--to have EBV infection are reported here. Site-specific molecular probes directed against specific, tandemly repeated EBV genomic regions were used. A synthetic 23-mer terminally biotin-labeled oligonucleotide probe selected from the EBV NotI region was used for ISH. For PCR, oligonucleotide primers were designed from sequences of the highly conserved, long internal direct repeat region of EBV to specifically amplify a 110-base-pair segment. The first patient, a 3-yr-old girl with a 1-yr history of fatigue, fever, splenomegaly, and lymphadenopathy developed hematuria. A renal biopsy revealed widespread glomerular mesangiolysis admixed with segmental mesangial sclerosis; no immune deposits were noted by electron microscopy or immunofluorescence. ISH on paraffin sections of the resected spleen and lymph nodes was positive for EBV. The second patient, a 28-yr-old male renal allograft recipient, received a double dose of OKT3. Seven weeks after transplantation, a renal biopsy revealed a lymphoproliferative disorder. Paraffin sections of the nephrectomy specimen were positive for EBV by both ISH and PCR. It was concluded that (1) EBV cannot be excluded on the basis of multiple negative serologies in some patients, and (2) ISH and PCR may lead to the detection of viral genomic information in renal and nonrenal tissues.

Surgical intervention in patients with aplastic anemia

Eighteen surgical procedures have been performed on 14 cases of aplastic anemia (AA). Of the 10 major surgical procedures, 7 were emergency and 3 elective. The median duration from the diagnosis of AA to major surgery was 0.5 months (3 days-47.3 months), and the median survival after surgery was 12.3 months (4 days-38 months). The hematological status of AA at the time of major surgery were 3 in partial response (PR), 2 with no response (NR) and 5 at diagnosis, respectively; and those after major surgery were 2 with complete response (CR), 2 in PR, 1 with minimal response, and 2 in NR. Three postoperative complications were sepsis, pneumonia and atelectasis encountered in 2 cases. A total of 3 deaths were caused by infection and cancers. Considering the fact that surgery may not only control complications, but offer the opportunity to give effective therapy for AA and therefore improves chances for survival, it is strongly suggested that active surgical intervention should be performed if the patient's status is not terminal.

Energy restriction and testosterone implants alter ornithine decarboxylase gene expression in kidney of female rats

Effects of testosterone and energy restriction (30%) on enzyme activity and mRNA level of ornithine decarboxylase (ODC) were studied in 19-wk-old female Sprague-Dawley rats. Testosterone implantation for 1 wk elicited a sixfold increase in ODC activity and a fourfold increase in ODC mRNA transcripts in the kidney. Energy restriction also increased renal ODC activity. Further, the 56% increase in ODC enzyme activity observed in the testosterone-implanted, energy-restricted group was greater than the 24% increase in the placebo-implanted, energy-restricted group. No changes in renal ODC mRNA levels were observed in the energy-restricted groups. These observations suggest that translational or post-translational mechanism(s) are involved in the greater renal ODC activity in energy-restricted rats.

Calcium-dependent inhibitory step in control of renin secretion

The regulatory step for Ca(2+)- and calmodulin-dependent control of renin secretion was studied in rabbit renal cortical slices. Renin secretion was stimulated by adding the K(+)-H+ exchange ionophore nigericin or a weak base, benzylamine, to Ca(2+)-free incubation medium. Both nigericin and benzylamine can produce chemiosmotic swelling of acidic intracellular organelles in a pH gradient-dependent manner. Swelling of renin secretory granules may account for the stimulatory effects of these two agents on renin secretion. The stimulation of renin secretion by each of these agents was prevented by including Ca2+ in the incubation medium. The inhibitory effects of Ca2+ were reversed by the calmodulin antagonist calmidazolium, suggesting that the Ca2+ inhibition may be mediated by calmodulin. However, when renin secretion was first stimulated by nigericin or benzylamine in Ca(2+)-free medium, subsequent addition of Ca2+ to the incubation medium failed to reverse the stimulation. These results therefore suggest that Ca2+ acting through calmodulin may exert its inhibitory effects on renin secretion by blocking an early step in the cellular events that lead to renin secretion such as pH gradient-dependent swelling of renin secretory granule.

Nosocomial Legionnaire's disease--a case report and review of the literature

We report a case of nosocomial legionellosis in a 63 year-old man who was managed with neurosurgery under the diagnosis of subarachnoidal hemorrhage and complicated pneumonia in the intensive care unit. A legionella species was reported from sputum culture and direct immunofluorescent antibody test revealed L. pneumophila (serogroup 2). Our patient's pneumonia was cured with medical therapy including erythromycin and was the first case of microbiologically confirmed legionellosis in Korea.

Coexisting mycosis fungoides and Hodgkin's disease as a composite lymphoma: a case report

Within the past few years, an increasing number of reports of Hodgkin's disease following the diagnosis of, and frequently coexisting with, mycosis fungoides have appeared. Previously, Hodgkin's disease found in the lymph nodes of the patient diagnosed as mycosis fungoides was considered as a transformed form of the mycosis fungoides. But, now it has been proven that Hodgkin's disease and mycosis fungoides are histologically and immunohistochemically distinct disease entities. We report a well-documented case of a man who developed Hodgkin's disease and mycosis fungoides simultaneously as a composite lymphoma. Our case emphasizes the importance of considering the diagnosis of another lymphoma in patients with mycosis fungoides who have lymphadenopathy. The cutaneous mycosis fungoides and the Hodgkin's disease should be treated as an independent disease.

Mechanisms of ionophore-induced stimulation of renin secretion with special reference to a chemiosmotic hypothesis

The effects of several ionophores on renin secretion were investigated in rabbit renal cortical slices. When slices were incubated in the absence of Ca++, the K+ ionophore valinomycin (10(-5) approximately 5 x 10(-4) M) or the monovalent cation ionophore nonactin (10(-4) M) stimulated renin secretion about 2-fold. The renin secretion stimulated by valinomycin was further increased by inclusion of the H+ ionophore, carbonylcyanide m-chlorophenylhydrazone. The electroneutral K+/H+ exchange ionophore nigericin (10(-5) approximately 5 x 10(-4) M) stimulated renin secretion in a dose-dependent manner, producing a maximal stimulation of about 17-fold. Another electroneutral exchange ionophore, monensin, also significantly stimulated secretion. The stimulation by both valinomycin and nigericin was apparent whether slices were incubated in Na(+)-rich or K(+)-rich media. The extent of stimulation by the two ionophores was dependent upon the presence of anion with acetate greater than Cl greater than isethionate greater than thiocyanate. Thiocyanate itself markedly inhibited renin secretion. Incubating of slices in an iso-osmotic ammonium acetate medium which is known to induce rapid swelling of secretory granules, stimulated renin secretion to the magnitude comparable to that of maximal stimulation by nigericin in a potassium acetate medium. The pattern of response to these ionophores indicates that changes in K+, H+ and anion gradients across the renin secretory granule may modulate renin secretory rate. It is proposed that conditions which allow accumulation of K+ and anion within acidic renin secretory granules lead to osmotic swelling of the granules and that granule swelling may promote exocytosis.

Neurilemmomas of the cervical vagus nerve

Four patients were seen with neurilemmoma which arose in the cervical vagus nerve. Three tumors arose in the upper third of the lateral neck, and the remaining one in the lower third. Lateral neck mass was a prominent symptom in 3 patients, and parapharyngeal mass in the remaining one. The parapharyngeal mass bulged into the oropharynx in the tonsillar and retrotonsillar region and caused mild swallowing difficulty. Complete surgical extirpation by means of intracapsular enucleation was possible in all 4 patients. All patients remained free of disease for periods ranging from 15 to 75 months following surgery. It would appear that an intracapsular enucleation may be advisable for clearance of this kind of tumor.

Role of membrane sulfhydryl groups in stimulation of renin secretion by sulfhydryl reagents

The present study was designed to address the reactivity and accessibility of the particular class of sulfhydryl groups involved in the regulatory process of renin secretion. Both mercurial (such as P-chloromercuriphenyl sulfonate [PCMPS] and non-mercurial sulfhydryl reagents (for example, 6,6-dithiodinicotinic acid [DTDN]), which very slowly penetrate the cell membrane of intact cells, stimulated renin secretion. The membrane permeant sulfhydryl reagent N-ethylmaleimide had no effect on renin secretion but its membrane impermeant derivative, stilbene maleimide, strongly stimulated secretion. Furthermore, disulfide reducing agents such as dithiothreitol (DTT) had no effect on renin secretion at low concentrations, but strongly inhibited it at high concentrations. Several reagents which are known to primarily deplete cellular reduced glutathione were without effect on renin secretion. The stimulation of renin secretion by PCMPS was rapid in onset, and prevented and reversed by DTT and L-cysteine. Furthermore, the maximal stimulatory effect of PCMPS was not additive to that by diuretics with sulfhydryl reactivity (such as, ethacrynic acid and mersalyl). The stimulatory effect of PCMPS was not affected by diuretics which lack sulfhydryl reactivity (such as, bumetanide and furosemide). These results suggest that sulfhydryl reagents of both with and without diuretic activity stimulate renin secretion by reacting with specific class of sulfhydryl groups which are readily accessible from the extracellular compartment. In addition, these results provide further support the possibility that a sulfhydryl-disulfide interchange in the membrane may play a regulatory role in the renin secretory process.

Cellular mechanism of stimulation of renin secretion by the mercurial diuretic mersalyl

The aim of the present study was to elucidate the cellular mechanism by which the mercurial diuretic mersalyl stimulates renin secretion in rabbit renal cortical slices in vitro. The stimulatory effect of mersalyl on renin secretion was rapid, reversible and concentration dependent. The stimulation was not dependent on the presence of ions such as Na+, Cl- and Ca++, and it was unaffected by inhibitors of Na+/K+/2Cl- cotransport, such as bumetanide and furosemide. However, the stimulation was blocked and reversed by thiols, such as L-cysteine and dithiothreitol. Furthermore, the maximal stimulatory effect of mersalyl on renin secretion was not additive to that produced by the non-diuretic mercurial sulfhydryl reagent P-chloromercuriphenylsulfonate nor to that produced by the non-mercurial diuretic sulfhydryl reagent, ethacrynic acid. These results support the hypothesis that mersalyl stimulates renin secretion by forming a reversible mercaptide bond with sulfhydryl groups, located perhaps on the plasma membrane of juxtaglomerular cells. These particular sulfhydryl groups appear to have no functional role in the diuretic action of mersalyl.