Lymph node metastasis in small peripheral adenocarcinoma of the lung

OBJECTIVE

Our aim in this study is to clarify the clinical and pathologic features of small peripheral adenocarcinoma of the lung with special emphasis on intraoperative identification of lymph node metastasis.

PATIENTS AND METHODS

Between 1980 and 1996, 157 patients underwent lobectomy and complete hilar/mediastinal lymphadenectomy for small (1.1 to 2.0 cm in diameter) peripheral adenocarcinoma of the lung. The intraoperative assessment, the distribution of metastatic lymph nodes, and the association between the tumor's histopathologic characteristics and lymph node metastasis were retrospectively investigated in this study.

RESULTS

Postoperative examination revealed lymph node metastasis in 27 (17%) patients. Lymph node metastases were not noticed during the operation in 19 of these 27 patients. Metastases were localized in single lymph nodes in 10 patients; the metastases were distributed over a segmental, a lobar, an interlobar, and a mediastinal lymph node. The prevalence of lymph node metastasis was as follows: Of 92 patients with well-differentiated adenocarcinoma, seven (8%) had lymph node metastases; of the 65 patients with other types of tumors, 20 (31%) had lymph node metastases. Of 120 patients without pleural involvement, 13 (11%) had lymph node metastases; of the 37 with pleural involvement, 14 (38%) had lymph node metastases. Five-year survivals were estimated at 91% +/- 6% (mean +/- 95% confidence interval) for 130 patients with N0 tumor and 30% +/- 22% for 27 patients with N1 or N2 tumor.

CONCLUSIONS

Intraoperative assessment is not reliable for identifying lymph node metastasis. Lobectomy and complete hilar/ mediastinal lymphadenectomy are necessary to determine N stage rigidly. Histologic degree of differentiation and pleural involvement are significantly associated with lymph node metastasis.

Familial neurilemoma of the spinal cord in a mother and daughter

Neurilemoma of the spinal cord occurred in a mother and daughter. Case 1 was a 75-year-old woman with gait disturbance. Examination revealed weakness of the lower extremities, and magnetic resonance (MR) imaging showed an intradural extramedullary tumor at T12. After laminectomy, the histologic diagnosis was mixed Antoni type A and B neurilemoma. Case 2 was a 48-year-old woman (daughter of case 1). She presented with cervical pain and numbness of both hands. Examination revealed weakened intrinsic muscles of the right hand and paresthesia of the right upper arm. MR imaging showed a giant hourglass-shaped extradural tumor at C2 and C3. The histologic diagnosis was Antoni type A neurilemoma. Only six families with neurilemoma have been reported, including our patients. Gene analysis of such patients may clarify the etiology of neurilemoma.

Ultrastructure of human scalp hair shafts as revealed by freeze-substitution fixation

Human scalp hair is important as a diagnostic clue to many diseases, in medical jurisprudential investigations, and also as a subject of cosmetic treatments. While many ultrastructural studies of the human hair root including the hair follicle have been reported, few studies have been done on the human hair shaft. We report here the ultrastructure of human scalp hair shafts prepared by a rapid-freezing technique followed by freeze-substitution fixation that allows the observation of fine cell structures. Healthy scalp hair shafts from Japanese females 12-13 years of age were rapid-frozen and then freeze-substituted in OsO4-acetone. In addition, this technique was applied to the study of some changes of the hair shafts (i.e., hair damaged by thioglycolic acid cold permanent waving and white hair). By this method, the hair shaft was rapid-frozen throughout without appreciable ice damage although the hair shaft was nearly 100 microm in diameter. The rapid-freezing technique resulted in excellent preservation of the ultrastructure of the hair shafts: lamellar structures in the cuticle and fine fibrous ultrastructures in the cortex were observed without chemical treatments. Thioglycolic acid treatment affected the ultrastructure of both the cuticle and the cortex. Except for the absence of melanin granules, no significant differences in the ultrastructure were observed between white hair and black hair. The rapid-freezing technique followed by freeze-substitution fixation appears to be the most reliable approach for the morphological evaluation of fully keratinized cells and tissues.

Ultrasmall immunogold particles: important probes for immunocytochemistry

In this article, we review the immunocytochemical literature with respect to a comparison between conventional colloidal gold and ultrasmall gold particles as immunoprobes. We discuss the relative advantages and disadvantages of each of these types of particles for immunocytochemical applications. We present results from our own laboratories, in which we compared these immunoprobes in selected experimental situations. In addition, we discuss our work on the use of a fluorescently labeled ultrasmall immunoprobe for correlative microscopy.

Efficient gene transfer into cardiac myocytes using adeno-associated virus (AAV) vectors

Adeno-associated virus (AAV) vectors, derived from a non-pathogenic parvovirus, are considered to be an appropriate gene transfer vehicle for both dividing and non-dividing cells. In the present study, we investigated whether the rat heart could be efficiently transduced with AAV vectors. Rat cardiac myocytes (CM) were infected with AAV-lacZ vector containing beta-galactosidase (beta-gal) gene in vitro, and the expression of beta-gal in CM was evaluated by X-gal staining and beta-gal ELISA. With increasing multiplicities of infection (MOI), more than 60% of CM were stained positively with X-gal, and the beta-gal expression increased to 31.1 +/- 4.6 ng/mg protein in a MOI-dependent manner (MOI: 10(4) to 10(6) particles/cell). The beta-gal expression was also increased in an incubation period-dependent manner (1-24 h). beta-gal expression was maximal at day 3 and then gradually decreased with time. However, beta-gal expression at day 14 was almost the same level as that at day 1 (45.5 +/- 5.9 v 55.2 +/- 6.2 ng/mg protein). Excised rat right ventricular papillary muscles were also infected with AAV-lacZ ex vivo. When the beta-gal expression was evaluated by X-gal staining, more than 80% of CM in the papillary muscles were stained positively, indicating efficient gene transfer into CM using AAV vectors. These findings suggest that AAV vectors are promising for cardiac gene therapy.

[Construction and its characteristic on the concept of a 'health culture']

Toward the 21st century, subjects and methods of hygiene and public health will be specialized and subdivided. However, practical approaches to human health need an integrated method focusing to a structure of human life. Under these circumstances, the concept of 'health culture' becomes prevalent. The role of hygiene related to the improvement of life style, the development of re-cycle system, and fulfillment of a barrier-free system focussed on the handicapped and the elderly have become increasingly important. Therefore, an increase in the recognition to the concept of 'health culture' is essential to the research of hygiene. The purpose of this paper is to make a historical and theoretical analysis of health culture', in order to promote it as the leading concept of all activities concerned with health in the 21st century. The methods of this paper are mainly historical and theoretical review. 'Health culture' was introduced in American and European societies a hundred years ago. Health culture in the USA involves knowledge and skills applied to actual daily life, refrecting pragmatism as the ideal feature of American society. In Germany, the concept of 'Hygienishe Kultur' was established at the field of social hygiene by Grotjahn and by Fischer in the early 20th century. This concept recognized the importance of the development of culture and independence of life in labour based on the evolution of the concept of 'Hygienishe Kultur'. In Japan, under the influence of German social hygiene, the social hygienic theory flourished. A social hygienist, Tetsuo Hoshino used the term 'hygienic culture' in the context of life creation toward a healthy life. Health culture is the total system concerning knowledge, experience, skill, and norms related to health, which has developed with the development of society. It has fundamental function promotes the creation of culture and self-cultivation of living man, whereas, it contributes to the realization of health based on individuality, in conjunction with the co-operation of medical and health sciences. The contemporary representation of health culture includes new health care activities such as self-care, a self-help movement, and health volunteer activities. It means the basic shift of the function of health culture is from that of life style to life movement. Nowadays, the role of hygiene in the total health care system is seriously considered. The goal, objects, and methods of hygiene should be re-evaluated under the concept of 'health culture', in order to re-define hygiene as the science for people living in a society.

Intravascular ultrasound imaging of atherosclerotic renal arteries: comparison between in vitro and in vivo studies

BACKGROUND

Intravascular ultrasound (IVUS) imaging, a new modality, may be feasible and useful for the assessment of atherosclerotic renal arteries. However, comparison between in vivo and in vitro studies to confirm pathological changes corresponding with IVUS findings obtained from renal arteries was not fully evaluated.

METHODS

We evaluated ultrasound images of 18 post-mortem human renal arteries and cross-sectional IVUS images of main renal arteries in five patients with renal artery stenosis (RAS) or essential hypertension.

RESULTS

In vitro studies have shown that renal-artery images had three layers when the arteries had fibrous intimal thickening and medial hypertrophy. Renal arteries, in which the fibrous intima was not well developed, showed circumferentially homogeneous bright echoes. In patients with atherosclerotic RAS and essential hypertension, IVUS images showed hyperechoic areas in the renal arterial walls, probably due to atherosclerosis. Typical three-layered ultrasound appearance was not easily seen during in vivo studies.

CONCLUSION

Our findings suggest that hyperechoic images can be a diagnostic clue of atherosclerosis However, in vitro results do not always correspond exactly to in vivo findings, and caution is needed when findings from in vitro IVUS imaging studies are applied to in vivo studies.

Intensive extrusion and occlusion of water in ganglioside micelles with thermal reversibility

By using a shell-modeling analysis for small-angle scattering data of ganglioside micellar dispersion, we recently reported that the elevation of temperature induces a significant shrinkage of the hydrophilic region of the ganglioside micelle, suggesting that the oligosaccharide chains with sialic acid residues of ganglioside molecules change the conformation, sensitively responding to a change in temperature (Hirai et al., 1996. Biophys. J. 70:1761-1768; J. Phys. Chem. 100:11675-11680). We have carried out further analyses of the temperature dependence of the structural parameters reported previously, and we have found clear evidence of reversible extrusion and occlusion of a large amount of water in the hydrophilic region of the ganglioside micelle in the physiological temperature range of 6-60 degrees C. The present results suggest a remarkable function of ganglioside molecules: they change the hydrophilicity of the cell surface locally as a response to variations in temperature. This phenomenon might be involved in various surface events, such as cell-cell interaction and cell surface-protein interaction.

[Comparative study on quality of life between weekly and monthly chemotherapy with cisplatin, vindesine and mitomycin C in patients with non-small cell lung cancer]

A comparative study between weekly and monthly chemotherapy with CDDP, VDS and MMC was performed on the basis of QOL in patients (stage III A/III B/IV) with non-small lung cancer from September 1993 to August 1996. Arm A received CDDP (80 mg/m2) monthly on day 1, VDS (3 mg/m2) on days 1 and 8, MMC (8 mg/m2) on day 1. Arm B received CDDP (40 mg/m2), VDS (3 mg/m2) and MMC (4 mg/m2) on day 1, and followed by CDDP (20 mg/m2), VDS (1.5 mg/m2) and MMC (2 mg/m2) weekly. A diary-type QOL self-rating questionnaire was devised for this study, consisting of 5 scales including 13-item questionnaires and a face scale as the global scale. Chronological QOL data from 20 days during chemotherapy (total dose of CDDP was 80 mg/m2 in both A and B arm) were analyzed using summary measures. In the 78 eligible subjects of the study, 34 were QOL subjects of the 27 eligible subjects, 13 were in arm A and 14 in arm B. 1. The questionnaire was confirmed to be satisfactory with regard to reliability and validity as a questionnaire for the evaluation of this study by factor and correlation analysis. 2. Although each scale changed to the worth level after chemotherapy, there was no significant difference between arm A and B. 3. Summary statistics were assessed using indices of the area under the curve (AUC) and the maximum fluctuations of QOL scores (Dif max) arm B showed a tendency to smaller changes than arm A in AUC and Dif max. There was a significant difference in the physical well-being scale of Dif max. 4. Three items, including the physical well-being in arm B, revealed a better score than those of arm A. Abdominal condition showed a significant difference between the two arms. 5. No obvious difference in anti-cancer effectiveness was found between arm A and B. Arm B showed a longer median survival, less nausea and vomiting, leukopenia and thrombocytopenia compared with arm A. The above results suggested that weekly chemotherapy is as effective, less toxic and shows less influence against patients QOL than the conventional monthly chemotherapy in this study.

Co-expression of Fas and Fas-ligand on the surface of influenza virus-infected cells

Influenza virus-infected cultured cells undergo apoptosis after an increment of Fas (APO-1/CD95) on the cell surface. By flow cytometry, cell surface Fas-ligand was detected in virus-infected cells with a time course similar to that of Fas. Moreover, Fas and Fas-ligand were co-expressed in those cells. The mode of induction, however, appeared to be distinct for the two proteins. Influenza virus infection induced the externalization of phosphatidylserine on the cell surface at the early stage of apoptosis, an event that has been observed in cells undergoing Fas-mediated apoptosis. In fact, apoptosis of the virus-infected cells was inhibited in the presence of an antagonistic anti-Fas-ligand monoclonal antibody. These results suggest that influenza virus infection causes augmented expression of both Fas and Fas-ligand and apoptosis is induced when the infected cells come into contact with each other.

Clinical analysis of small-sized peripheral lung cancer

OBJECTIVE

In Japan, with the initiation of the lung cancer screening program, small-sized peripheral lung cancer in which the diameter is 2 cm or less has been increasing. The purpose of this study is to determine the clinicopathologic behavior of small-sized lung cancer.

METHODS

Four hundred ninety-six patients with cT1 N0, peripheral, resected non-small-cell lung cancer, who were operated on between 1980 and 1996, were selected, grouped by tumor diameter or histologic type, and then analyzed for clinicopathologic behavior. On the basis of measured diameter roentgenographically, the patients were divided into two groups; group c-S with lesions 2 cm or less in diameter and group c-L with lesions 2.1 to 3 cm in diameter.

RESULTS

Lymph node metastasis was recognized in 18% of group c-S, in 23% of group c-L, and in 21% for the entire clinical group. The rate of those with the progressive state was 19% in group c-S and 26% in group c-L. The 5-year survival was 79.5% in group c-S and 69.3% in group c-L (i.e., there was a significant difference between the two groups).

CONCLUSION

Compared with the patients with lesions 2.1 to 3 cm in diameter, the patients with small-sized lung cancer had a milder progressive state and a better prognosis.

Foreign body gonitis caused by a broken poly-L-lactic acid screw

Poly-L-lactic acid (PLLA), a biodegradable polymer, is generally considered to be gradually degraded without causing any severe tissue reaction. However, we encountered a patient who developed foreign body gonitis caused by screw breakage after fixation of an intercondylar prominence fracture with PLLA screws. This case suggests that care should be taken when PLLA materials are used to fix intraarticular fractures.

The antioxidative substances in cacao liquor

The antioxidative substances contained in cacao liquor, which is one of the major ingredients of chocolate, were separated by column chromatography and high-performance liquid chromatography. Three major compounds were purified and two of them were identified by 1H, 13C NMR and mass spectra as (-)-epicatechin (EC) and (+)-catechin (CA). Their antioxidative activity was measured by monitoring the peroxide value of linoleic acid and the thiobarbituric acid-reactive substance values of erythrocyte ghost membranes and microsomes. EC and CA had strong antioxidative effects in all three methods, but one unidentified peak was found to be less effective. Additionally, we analyzed the polyphenol concentration of cacao liquor extractions produced in several countries. The total polyphenol concentration was 7.0 to 13.0%, catechin concentration was 0.31 to 0.49%, and epicatechin concentration was 0.35 to 1.68% in the extractions. It is believed that chocolate is stable against oxidative deterioration on account of the presence of these polyphenolic compounds, and it is also expected to have a protective role against lipid peroxidation in living systems.

Interaction of gangliosides with proteins depending on oligosaccharide chain and protein surface modification

By using neutron and synchrotron x-ray small-angle scattering techniques, we investigated the process of the complexation of gangliosides with proteins. We treated monosialoganglioside (G(M1)), disialoganglioside (G(D1a)), and a mixture of G(M1)/G(D1a). Proteins used were bovine serum albumins whose surfaces were modified with different sugars (deoxy-D-galactose, deoxy-L-fucose, deoxymaltitol, and deoxycellobiitol), which were used as model glycoproteins in a membrane. We found that the complexation of gangliosides with albumins greatly depends on the combination of ganglioside species and protein surface modification. With a varying protein/ganglioside ratio in a buffer solution at pH 7, the complexation of G(M1) or G(D1a) with albumins modified by monosaccharides appears to be less destructive for ganglioside aggregate structures in forming large complexes; the complexation of G(D1a) with the albumins modified by disaccharides induces the formation of complexes with a dimeric structure; and the complexation of G(M1) with albumins modified by disaccharides, to form small complexes, is very destructive. The present results show a strong dependence of the interaction between ganglioside and protein on the characteristics of the ganglioside and protein surface, which would relate to a physiological function of gangliosides, such as a function regulating the receptor activity of glycoproteins in a cell membrane.

Increased ductal responsiveness to PGE2 after maternal treatment with aspirin and ibuprofen

This work was conducted to determine whether aspirin and ibuprofen, when administered prenatally may potentiate a reopening of the neonatal ductus arteriosus (DA) induced by PGE2 after postnatal closure. In the first experiment, a subcutaneous injection of PGE2 (4 microgram(s)) was administered to newborn rats 3 hr after a Cesarean delivery from pregnant females which had been orally given 100 or 300 mg/kg/day of aspirin and 10 or 30 mg/kg/day of ibuprofen on days 18, 19 and 20 of gestation. The ratio of the DA to the pulmonary artery (PA) was determined at intervals after the injection. The DA/PA ratio was significantly higher in newborn rats from mothers who were transplacentally administered these agents than the control. We also examined the hypothesis that maternal treatment with nonsteroidal anti-inflammatory drugs (NSAID), such as aspirin and ibuprofen, inhibits the catabolism of PGE2 and that the increased reopening of the DA was partly due to this inhibition. 15-hydroxy prostaglandin dehydrogenase (15-PGDH) in neonatal lungs, the key enzyme involved in catalyzing PGE2 to convert it to its inactive metabolite 15-keto-PGE2, was not affected by maternal treatment with aspirin and ibuprofen. These results suggest that the increased ductal responsiveness to PGE2 in newborn rats was a common response after maternal NSAID treatment, but the catabolism of PGE2 in the lungs did not always contribute to this response.

Tissue and developmental distribution of Six family gene products

To examine the presence and distribution of Six family gene products in a variety of tissues at various developmental stages and in various cell types, we prepared specific antibodies against recombinant Six gene products. The distribution of Six2 and Six4 was examined by immunostaining in the developing mouse embryo. Production of Six2 was detected at E8.5 mainly in the mesenchyme, while Six4 was present in nuclei of neuronal cells in the peripheral region of the mantle layer of developing brain and spinal cord and in various ganglia at E10.5 and E11.5. Specific DNA binding activities of the Six proteins were analyzed by gel retardation super-shift assays using nuclear extracts from different rat tissues and cell lines. Six5 was the dominant isoform observed in the adult kidney, liver and lung but not in the brain. Six4 was not detected in all tested adult tissues, however, it was present in embryonic (FD21) lung nuclear extracts. In contrast, Six4 was detected in a variety of cultured cell lines, including HeLa, 3T3, MDCK and C2C12. Our results suggest that Six4 plays a specific role in the differentiation or maturation of neuronal cells, while Six5 is an adult type Six gene isoform product and is distributed in the kidney, liver and lung.

Antioxidative Polyphenols Isolated from Theobroma cacao

The antioxidant components of cacao liquor, which is a major ingredient of chocolate, were isolated with column chromatography and high-performance liquid chromatography. Quercetin and its glucoside were identified by spectrometric methods. Clovamide and deoxyclovamide were characterized by (1)H and (13)C NMR and MS spectrometry. Their antioxidative activity was measured by peroxide value of linoleic acid and thiobarbituric acid reactive-substance value of erythrocyte ghost membranes and microsomes. In the bulk oil system, clovamide had the strongest antioxidative activity but was less active in the other experiments. In the case of the two hydrophilic systems, flavans such as quercetin and epicatechin were more potently effective than the glucosides. It is considered that chocolate is stable against oxidative deterioration due to the presence of these polyphenolic compounds.

Ultrastructural localization of enzymes in biomembranes as revealed by new enzyme cytochemical techniques

In this mini-review, we describe new enzyme cytochemical methodology combined with cryotechniques, which we have developed in order to reveal the ultrastructural localization of enzymes in biological membranes. This combined approach has been shown to be a valuable tool to study topology, dynamics, and function of enzymes in a more lifelike state.

Sarcoplasmic reticulum genes are selectively down-regulated in cardiomyopathy produced by doxorubicin in rabbits

The clinical utility of doxorubicin, an antineoplastic agent, is limited by its cardiotoxicity. Our objective was to determine whether expression of genes encoding proteins that affect Ca2+ homeostasis were altered in the hearts of rabbits chronically treated with doxorubicin. Twelve male New Zealand white rabbits received an injection of doxorubicin (2.5 mg/kg i.v.) once a week for 8 weeks. Eight rabbits were similarly injected with saline as controls. The cardiac function of both groups was evaluated 8 weeks after the final injection, as were the levels of expression of mRNA for Ca2+ transport proteins in the sarcoplasmic reticulum and plasma membrane. The amount of the sarcoplasmic reticulum Ca2+-ATPase and the Ca2+ uptake capacity of the protein were also quantitated. Cardiac output was significantly decreased in the doxorubicin-treated group (71+/-21 ml/min, P<0.05) compared with the control group (118+/-15 ml/min). The mRNA levels for the sarcoplasmic reticulum proteins were significantly diminished in the doxorubicin-treated hearts: ryanodine receptor-2 (relative expression level compared with controls, 0.35+/-0.13, P<0.01), sarcoplasmic reticulum Ca2+-ATPase (0.56+/-0.13, P<0.01), phospholamban (0.62+/-0.20, P<0.01) and cardiac calsequestrin (0. 57+/-0.26, P<0.01). In addition, both relative amount of sarcoplasmic reticulum Ca2+-ATPase protein (doxorubicin-treated group, 69+/-17% of control, P<0.01) and the Ca2+ uptake capacity (46. 9+/-9.8 nmol Ca2+/mg protein-5 min in doxorubicin group v 63.2+/-10. 4 in the control group, P<0.01) were concomitantly decreased with its mRNA expression level. Conversely, the mRNA levels for the plasma membrane proteins did not differ from those of control rabbits: the dihydropyridine receptor (relative expression level, 1. 03+/-0.30, N.S.), plasma membrane Ca2+-ATPase (0.93+/-0.33, N.S.) and the Na+/Ca2+ exchanger (0.87+/-0.34, N.S.). These findings suggest that a selective decrease in mRNA expression for sarcoplasmic reticulum Ca2+ transport proteins is responsible for the impaired Ca2+ handling, and thus, for the reduced cardiac function seen in the cardiomyopathy induced in rabbits by the long-term treatment with doxorubicin.

A new method of hemostasis for cementless total knee arthroplasty

Heavy bleeding often occurs following cementless total knee arthroplasty (TKA) and it is difficult to control. We devised a new method of hemostasis after cementless TKA. In brief, the implant was inserted after coating the exposed surface of the cancellous bone with fibrin glue. Before removal of the tourniquet after completion of the operation a cocktail of hemostatic agents (containing 25 mg of carbazochrome sodium sulfonate and 250 mg of tranexamic acid) in 50 ml of physiological saline was injected into the joint cavity via the drain tube and the drain was clamped for about 30 min after removal of the tourniquet. After removal of the clamp, standard negative pressure suction was performed. This method was used on 84 knees in 42 patients who underwent simultaneous bilateral cementless TKA and 64 knees in 64 patients who underwent unilateral TKA. The mean total amount of blood loss during and after the operation was 235 +/- 178 ml in the unilateral TKA patients and 402 +/- 208 ml in the bilateral TKA patients. No patient required blood transfusions postoperatively. This method was effective for achieving hemostasis after cementless TKA.

A resected case of hilar type double primary lung cancer following endobronchial brachytherapy

A 61-year-old man with squamous cell carcinoma of the right B1 and the left second carina which extended to the left main bronchus, was treated with low dose rate brachytherapy bilaterally prior to resection. A complete response was gained at the right B1 and the left main bronchus, a resection of the left apical segment and the second carina was carried out with bronchoplastic procedures. The patient remains disease-free 2 years after the operation and maintains a good quality of life. In this case, the preoperative treatment with brachytherapy was effective.

Light-induced cGMP-phosphodiesterase activity in intact rat retinal rod cells as revealed by rapid-freezing enzyme cytochemistry

Cyclic guanosine monophosphate (cGMP)-phosphodiesterase (PDE) in the outer segment of vertebrate retinal rod cells is one of key enzymes mediating phototransduction. We report here on light-induced PDE activity in intact rat retinal rod cells processed by rapid-freezing enzyme cytochemistry, a new morphological technique that is a combination of rapid-freezing, freeze-substitution fixation, and subsequent enzyme cytochemistry. This technique quickly immobilizes and preserves both enzyme activity and the cell ultrastructure in a state approximating living conditions; consequently, it has proved useful for cytochemical detection of light-induced PDE activity. Using this technique we observed that the catalytic site of PDE molecules in rapid-frozen outer segments was predominantly located in the extradiscal spaces; PDE activity was significantly greater in light than in darkness; and illumination elicited marked increases in PDE activity in dark-adapted cells. Light-induced PDE activity was first cytochemically detected after 3 s of illumination and reached a peak within 5 s, at which time it was in virtually the same as that seen in fully light adapted cells. In addition, cytochemical guanosine triphosphatase (GTPase) activity in dark-adapted cells, as well as corresponding PDE activity, increased in a time-dependent manner with illumination duration; this acceleration in GTPase activity closely paralleled the PDE activity. Thus, our results suggest, in part, the existence of reciprocal regulation of PDE and activated transducin alpha subunit, thereby modulating light adaptation in rod cells.