The absorbance spectrum and photosensitivity of a new synthetic "visual pigment" based on 4-hydroxyretinal

The firefly squid, Watasenia scintillans, is the only animal known to possess a visual pigment in which the chromophore is 4-hydroxyretinal. This paper describes the absorbance spectrum and some properties of a synthetic "A4" visual pigment generated from bovine opsin and 4-hydroxyretinal. The absorbance spectrum of this pigment is compared with (a) bovine rhodopsin and (b) a rhodopsin template with the same lambda max as the synthetic visual pigment. The A4 pigment is shown to have an absorbance spectrum that is almost identical to that of a rhodopsin template. It is also shown that the photosensitivity and thermal stability of the A4 pigment, dispersed in detergent micelles, is essentially similar to that of rhodopsin.

[Surgical decisions for active infective endocarditis in patients with acute neurological complications]

The surgical management of 7 patients with active infective endocarditis and recent (within 16 days) neurological injury was presented. All patients had preoperative computed tomographic scans which revealed no evidence of intracranial hemorrhage and underwent successful corrective cardiac surgery. In the early postoperative period, 4 patients died of cerebral hemorrhage, subarachnoid hemorrhage, or progression of cerebral edema. Two of the 3 surviving patients showed no aggravation of cerebral infarcts postoperatively. In the remaining surviving patient, intracerebral mycotic aneurysms were resolved spontaneously after postoperative antibiotic therapy, although new cerebral hemorrhage, a complication of emboli, occurred after open heart surgery. The results of this study indicated that 1) cerebrovascular complications were the causes of the 4 deaths in this series, and 2) although heparinization during open heart surgery may result in intracerebral hemorrhage from mycotic aneurysm or infarction, early surgical intervention after recent cardiogenic embolic strokes may save patients with minor cerebral infarcts.

Effects of volatile anesthetics on bacteriorhodopsin in purple membrane, Halobacterium halobium cells and reconstituted vesicles

In this study, we have investigated effects of volatile anesthetics on absorption spectra, proton pumping activity and decay of photointermediate M of bacteriorhodopsin (bR) in differently aggregated states. Anesthetics used in this study are ether-type general anesthetics; enflurane and sevoflurane. The observed effects on bR depend not only on variety or concentration of anesthetics but also strongly on the aggregation state of bR molecules in the membrane. In purple membrane (PM), bR having maximum light absorption at 567 nm (bR567) is formed in the presence of sevoflurane or a small amount of enflurane, while a species absorbing maximally at 480 nm (bR480) is formed upon the addition of large amounts of enflurane. X-ray diffraction studies show that the former species maintains crystallinity of PM, but the latter does not. In reconstituted vesicles where bR molecules exist as monomer, even sevoflurane forms bR480. Flash photolysis experiments show that bR567 contains a shorter-lived M intermediate absorbing maximally at 412 nm in the photoreaction cycle than bR does and that bR480 contains at least two long-lived M intermediates which seem to absorb maximally near and at lower than 380 nm. The measurements of light-induced pH changes of the whole cells and of the reconstituted vesicles in the presence of the anesthetics indicate that bR567 has a enhanced proton pumping efficiency, while bR480 has a quite low or no activity. No significant difference was observed in the anesthetic action between two inversely pumping vesicles. These observations suggest that on the formation of bR480, anesthetics enter into the membrane and affect the protein-lipid interaction.

[Invasive treatment in patients with prior coronary artery bypass grafting]

In eight hundred eighty three patients with prior coronary bypass grafting (CABG), cardiac symptoms were recurred in 179 patients in late follow-up period (mean 5 +/- 2.8 years). Of 179 patients, 43 patients had PTCA eventually. In these, 57 times of angioplasties were attempted. Twenty-one lesions in venous bypass grafts and 50 in native coronary arteries were performed, respectively. The initial success rate per bypass graft and per stenosis of native coronary artery were 68% and 74%, respectively. Five patients had elective CABG following failed PTCA. There were no emergency CABG procedures required after unsuccessful PTCA. Intracoronary thrombolysis (ICT) were performed in 13 patients. In these, 15 ICT attempts were made. Nine lesions in venous bypass grafts, 9 for native coronary arteries, and 3 for both were attempted. The primary success rate per occlusion was 67%. Twenty reoperation were done. There was one hospital death and one late death due to congestive heart failure 4 years after the reoperation. In conclusion, invasive treatments in patients with prior CABG can be performed with satisfactory safety and good results. Therefore, invasive treatment should be considered in the patients with CABG if cardiac symptoms are disabling and angiographically suitable lesions are present in the native coronary arteries or vein grafts.

Percutaneous transluminal coronary angioplasty and coronary artery bypass surgery--early and follow-up clinical results

To evaluate the efficacies of percutaneous transluminal angioplasty (PTCA) and coronary artery bypass grafting (CABG) for angina pectoris, early and follow-up data were reviewed in 495 patients who had undergone these procedures from 1986 to 1988. In 173 patients with single vessel disease, there were no significant differences in initial success rate and early and late incidences of major complications or cardiac death between 152 patients with elective PTCA and 21 with urgent. When compared in 161 patients with multivessel disease, however, significant differences in success rate were found between 130 patients in the elective PTCA group and 31 in whom PTCA was urgent (81.6% vs. 64.5%, p less than 0.05). Significant differences were also found in early incidence of major complications (3.1% vs. 12.9%, p less than 0.01), early mortality (1.5% vs. 9.7%, p less than 0.01), and the late incidence of cardiac events (6.2% vs. 25.0%, p less than 0.01). These results show that freedom from cardiac death and overall cardiac events in the elective PTCA group as significantly better than that in the urgent group at 42 months of follow-up. Comparing early and follow-up results, on the other hand, there was no statistically significant difference between the elective and urgent CABG groups. Thus, there appear to be limitations on the urgent use of PTCA for refractory unstable angina caused by multivessel disease, and urgent CABG was recommended to high-risk patients of urgent PTCA.

Practical assessment of natural heart function using echocardiography in mechanically assisted patients

Left ventricular assist systems (LVAS) can maintain the systemic circulation of patients with acute, profound heart failure. The assessment of natural heart (NH) function, however, is difficult in the clinical setting. The authors introduced a new index, heart rate-corrected ejection time/left atrial pressure (ETc/LAP) using echocardiography to evaluate NH function in 15 adult patients on the original LVAS for greater than 2 days. Bypass flow (BF) was gradually decreased according to the recovery of NH. Five patients were weaned from LVAS within 15 days, and LV function was well maintained (Group 1). Another six patients were weaned from LVAS within 21 days but died within 2 weeks (Group 2). The other four patients died on LVAS without recovery of NH (Group 3). In Group 1 patients, ejection time/pre-ejection period (ET/PEP) with LVAS assist increased continuously. In Groups 2 and 3, ET/PEP increased slowly and reached a plateau at approximately 10 days or remained low. Group 1 patients reached an ETc/LAP of 35 +/- 10 on LVAS within 7 days. Group 2 and Group 3 patient values were 18 +/- 2 (p less than 0.05) and 9 +/- 6 (p less than 0.01), respectively, on the seventh day. Based on these data, this new index provides an estimate of global NH function and a prediction of the probability of NH recovery.

[Long-term follow-up results on Bentall's and our modified procedure]

Replacement of the ascending aorta and the aortic valve with composite graft, including reimplantation of coronary ostia, were performed in 84 patients from October, 1978 to December, 1989. Annuloaortic ectasia was the most common indication for surgery (76 patients). Thirty patients (36%) had the Marfan syndrome. Thirty-five patients were performed with original Bentall's procedure. Thirty patients were carried out with our modified technique like Inberg's, the coronary arteries were excised with attachment of the selected piece of the aortic wall, and implanted to the tube prosthesis with continuous suture. Nineteen patients were operated with modified technique by Cabrol or other interposition graft method. The actuarial free of death related to the operation of 4 years was 83%, 88%, and 74% (p = NS) in each methods respectively. The complications of anastomosis, for example, leakage and dilatation of coronary ostia were not seen in our modified Bentall's procedure. In conclusion, our modified method is proved to be reliable and competent.

Conformation changes of cuttlefish (Euprymna morsei) rhodopsin following photoconversion

Cuttlefish (Euprymna morsei) rhodopsin solubilized in lauryl ester of sucrose and its photoproduct, acid metarhodopsin, were examined by small-angle X-ray scattering and chromatofocusing to investigate the conformation changes of visual pigment following photoconversion. From spectroscopic studies, it was found that more than 93% of Euprymna rhodopsin could be converted to meta form under the condition of red light irradiation at neutral pH. Since almost pure acid metarhodopsin solution was prepared without changing the specimen concentration, the small-angle X-ray scattering intensities of both pigment-detergent complexes were directly compared. The radius of gyration increased on going from rhodopsin to acid metarhodopsin by approximately 1.5%. There were also discernible changes in the secondary peak intensities. The distribution function, derived by the Fourier transformation of intensity data, showed a significant change around 55 A. The maximum linear dimension of the rhodopsin-detergent complex was about 95 A and hardly changed after illumination. Intensity at zero angle did not change after illumination, suggesting that the aggregation did not occur. The change of the intensity profile could be due to the conformational change of the pigment-detergent monomers. The pI value of rhodopsin determined by chromatofocusing was 5.32 and that of acid metarhodopsin was 5.06, indicating that a few carboxyl groups are newly dissociated. The shift of the protein mass and the charge redistribution were observed following photoconversion.

Recurrent epicardial fibrosarcoma which arose 12 years after the first resection

Primary malignant tumours of the heart are very rare, with an incidence of only 0.0017%-0.03% in consecutive autopsy series. Fibrosarcoma of the heart is also rare, representing only about 0.3% of all cardiac tumours. We observed a case of epicardial fibrosarcoma which developed 12 years after the first resection of an epicardial tumour. A 31-year-old woman was referred to our hospital because of fatigue, nausea and right back pain. She had had surgery to resect an epicardial tumour when she was 19 years old. On admission, there was a huge, heterogeneous tumour on the right inferior side of the heart. At surgery, the tumour was totally resected and a pathological diagnosis of fibrosarcoma was made. The patient was free of symptoms for 6 months, but died of a recurrence 11 months after the operation. It is postulated that the epicardial tumour had only been partially resected and had been latent for a rather long period but began to grow rapidly 12 years after the initial resection.

Light-induced, GTP-binding protein mediated membrane currents of Xenopus oocytes injected with rhodopsin of cephalopods

Xenopus oocytes that were injected with rhabdomeric membranes of squid and octopus photoreceptors acquired light sensitivity. The injected oocytes showed a light-induced current having characteristics similar to other G-protein-mediated Cl- currents induced by the activation of other membrane receptors. Pretreatment of the oocytes with pertussis toxin before the injection suppressed the generation of the light-induced current, indicating an ability of cephalopod rhodopsin to cross-react with an endogenous G-protein of Xenopus oocytes.

[Influences of intra-aortic balloon pumping on peripheral hemodynamics]

The influences of intra-aortic balloon pumping (IABP) on peripheral dynamics were assessed by Doppler echocardiography. The subjects were 20 patients requiring IABP support, postoperatively, to control low cardiac output state. The flow velocity integral in systole (Int S) and that in diastole (Int D) were measured from left common carotid, superior mesenteric, and terminal aortic flow pattern, and the sum of Int S and Int D (Int S + Int D) was calculated with and without balloon pumping. 1) IABP increased cardiac output significantly (p less than 0.01). 2) Common carotid flow: IABP increased Int S significantly (p less than 0.01), but neither Int S nor Int S + Int D changed significantly with IABP. 3) Superior mesenteric flow: IABP increased Int D significantly (p less than 0.01), but both Int S and Int S + Int D remained unchanged with IABP. 4) Terminal aortic flow: None of Int S, Int D and Int S + Int D changed significantly with IABP. These results suggest that the carotid area can receive much of the increase in cardiac output in systole with IABP, and that the superior mesenteric area can receive much of the volume of blood displaced in the aorta by balloon inflation in diastole.

[Emergency coronary artery bypass grafting (CABG) for complications of percutaneous transluminal coronary angioplasty (PTCA)]

Eighteen cases of emergency coronary artery bypass for complications of PTCA were carried out. Nine cases were in cardiogenic shock, and 3 cases of them died. All these 3 cases had acute occlusion of donor arteries for jeopardized collaterals. It is important not to lose a timing of surgical therapy, especially in cardiogenic shock case.

[Influences of intra-aortic balloon pumping on superior mesenteric flow dynamics]

The influences of intra-aortic balloon pumping (IABP) on arterial flow of the superior mesenteric artery were assessed by Doppler echocardiography. The subjects were 13 patients postoperatively, requiring IABP support to control low cardiac output state, in which distal aspects of balloons were distal to the superior mesenteric artery. Superior mesenteric flow velocity integral in systole (IntS) and that in diastole (IntD) were measured from superior mesenteric flow pattern, and the sum of IntS and IntD (IntS + IntD) was calculated ON and OFF balloon pumping (IABP ON-OFF test). The same parameters were obtained with balloon inflating on every other beat (IABP 1:2 test); the cardic cycle with balloon assist was defined as "1:2 ON", and that without balloon assist was defined as "1:2 OFF". 1) IABP ON-OFF test. IABP increased IntS from 7.07 +/- 2.56 cm to 9.20 +/- 3.19 cm (p less than 0.05), IntD from 3.00 +/- 1.18 cm to 3.62 +/- 1.40 cm (p less than 0.05), and IntS + IntD from 10.07 +/- 3.48 cm to 12.82 +/- 4.04 cm. Cardiac output increased from 3.89 +/- 1.34 l/min to 4.24 +/- 1.64 l/min with IABP support. The increments in IntS, IntD and IntS + IntD with IABP are attributed, to a large extent, to an increase in cardiac output. 2) IABP 1:2 test. Without balloon inflation, IntS increased (1:2 ON; 7.16 +/- 2.91 cm, 1:2 OFF; 8.41 +/- 3.30 cm, p less than 0.05), and IntD decreased (1:2 ON; 3.51 +/- 1.60 cm, 1:2 OFF; 2.33 +/- 1.25 cm, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[A case report of coronary artery fistula into the left ventricle]

Communication of the right coronary artery with the left ventricle is considerably rare. We report a case of congenital fistula of the left ventricle. Closure of the fistula was successfully done by Symbas' modification. Thirty cases with coronary artery fistula to the left ventricle reported in Japanese literatures, including our case were reviewed in regard to its surgical treatment.

[A successfully operated case of tetralogy of Fallot with marked left ventricular dysfunction in adult]

Adults, especially high-aged patients with tetralogy of Fallot (TOF) are said to have a higher operative risk than younger ones because of fragility of their myocardium, bleeding from rich collateral circulation to lungs, and other complications such as brain abscess and endocarditis. It is often difficult to determine the surgical risk for total correction in cases of high-aged patients who have such complications. We report a successfully operated high-aged case of TOF with marked left ventricular dysfunction. A 52-year-old male was referred to our hospital because of exertional dyspnea and cyanosis. He had a history of cerebral embolism and meningitis several months prior to admission. On admission, he was NYHA class 3, and cyanosis and clubbed fingers were present. Cardiac catheterization showed a large VSD, 50% over-riding of the aorta and an infundibular pulmonary stenosis. Right to left shunt was 60% and Qp/Qs was 0.38. The left ventricular end diastolic volume index was 109 ml/m2, slightly larger than normal, and the ejection fraction was only 30%. This left ventricular dysfunction was thought to be caused by fibrosis of the myocardium due to longstanding hypoxemia and hypoxemia itself. There is no previous case report dealing with a successful total correction for a high-aged patient with TOF associated with such a severe left ventricular dysfunction. Congestive heart failure in the post-operative period was successfully treated by catecholamine for two weeks. Postoperative cardiac catheterization showed a small left-to-right shunt, and an improvement of left ventricular ejection fraction from 30% to 38%.(ABSTRACT TRUNCATED AT 250 WORDS)

[Late results of coronary bypass grafting in patients with concomitant multifocal arteriosclerotic vascular diseases]

Late results of coronary bypass graftings (CABG) in the patients with multifocal arteriosclerotic vascular diseases were reviewed. Between September 1978 and July 1989, 819 consecutive patients underwent CABG. There were 693 males and 126 females, mean ages 58 +/- 8.5 years. Of 819 consecutive patients underwent CABG, 95 patients had the coexistence of multifocal atherosclerosis (Group A). Seventy two patients had aortoiliac or femoropopliteal disease, and 29 patients had aortic aneurysm. The remaining 724 patients had no coexistence of multifocal atherosclerosis (Group B). The mean follow-up periods was 4.0 +/- 2.1 years, and the follow-up ratio was 99.4%. The 5- and 10-year survival rates were 80% and 52% in group A, and 92% and 82% in Group B, respectively. The 5- and 10-year free ratio from cardiac events were 79% and 42% in Group A, and 85% and 61% in Group B, respectively. The 5- and 10-year free ratio from noncardiac events were 53% and 38% in Group A, and 85% and 76% in Group B, respectively. The results showed that the coexistence of multifocal atherosclerotic vascular disease in patients underwent CABG significantly increase the ratio of noncardiac and cardiac events, and decreased life expectancy.

[Middle term follow-up and comparative study of valve replacement with four kinds of new model bovine pericardial xenografts]

Our early clinical experience (up to 4 year's follow-up) with four new pericardial xenografts were reviewed. During the period July 1983 to December 1986, 148 Ionescu-Shiley Pericardial Xenografts (ISL) in 130 patients, 68 Carpentier-Edwards pericardial xenografts (CEP) in 65, 32 Mitroflow pericardial xenografts (MF) in 29 and 36 Hancock pericardial xenografts (HP) in 29 have been implanted. The actuarial survival rates at 3.3 years are 89.9 +/- 2.7% for ISL, 92.3 +/- 3.3% for CEP, 93.1 +/- 4.7% for MF and 93.1 +/- 4.7% for HP. Fifteen cases of primary tissue failure (PTF) were caused in all groups but CEP. The actuarial free rates from PTF at 3.3 years were 92.9 +/- 2.4% for ISL, 100% for CEP, 95.5 +/- 4.4% for MF, 82.6 +/- 7.9% for HP. All bioprostheses explanted because of PTF showed commissural tears occurred at the top of the stent posts or at the edge of the stent. In this respect, it is the reason why the cases with CEP were free from PTF that CEP has been achieved to be improved its frame design. The incidences of prosthetic valve endocarditis were not different among these kinds of bioprosthetic valves. The free rates from thromboembolism at 3.3 years were 97.5 +/- 1.5% for ISL, 98.3 +/- 1.7% for CEP, 96.0 +/- 3.9% for MF and 88.7 +/- 6.1% for HP. There was no patient with CEP and MF suffered from thromboembolism with sinus rhythm. In comparison of these 4 valves, we conclude that CEP is useful clinically because of its satisfactory durability and antithrombogenicity.

[Comparative analysis of long-term results with porcine-aortic, bovine pericardial and tilting disc valves]

The three series with the first-generation valve prostheses were reviewed for long-term clinical evaluation in isolated aortic and mitral valve replacement. Hancock porcine xenograft was implanted in 71 patients from 1977 to 1979, ionescu-Shiley pericardial xenograft (standard model) in 271 patients from 1979 to 1983, and Bjork-Shiley tilting disc valve in 194 from 1978 to 1986. In aortic position, no any significant difference among three valve types could be demonstrated in the actuarial survival and freedom from thromboembolism and valve infection, while the actuarial freedom from valve dysfunction in lonescu-Shiley valve was significantly lower than that in other two valves. Björk-Shiley valve in mitral position showed satisfactory clinical performance in terms of valve-related complications and survival in comparison with two types of bioprosthetic valves. In our conclusion at present time, Björk-Shiley valve is suitable for the first choice of both aortic and mitral valve prostheses. In case of valve replacement with a bioprosthesis, however, porcine aortic valve is a better choice for aortic, and bovine pericardial valve likely for mitral replacement.

[Late cardiac events of coronary bypass surgery]

The cardiac events of 598 patients undergoing coronary bypass surgery were analyzed. The hospital and late death was 4.9% and 3.8%, respectively. The late death were caused by cardiac events in 7 patients and non-cardiac events in 16 patients. Of 7 cardiac death, 5 patients were died of acute myocardial infarction (AMI), and 2 patients were died of congestive heart failure. 5-year survival rate, 5-year event free ratio, and 5-year non-cardiac event free ratio were 88%, 70% and 91%, respectively. Of 18 patients who suffered from AMI after operation, 5 patients died. The causes of AMI were grafts occlusion in 9 patients, progression of coronary lesions in 5 patients and unknown in 4 patients. PTCR, PTCA and rebypass surgery were performed in 4, 9 and 8 patients, respectively.

Treatment of acute myocardial infarction with cardiogenic shock using left ventricular assist device

We have treated ten cardiogenic shock patients after acute myocardial infarction (AMI) with a left ventricular assist device (LVAD). These patients were later divided into three groups: the first group with ventricular septal perforation, the second with aorto-coronary bypass grafting (ACBG) before LVAD implantation and the third group without ACBG. LVAD maintained the systemic circulation in each group, and cardiac function recovered enough to remove LVAD in 70% of the total patients. Two of three patients in the first group were discharged from hospital. Two weaned cases in the second group died of multiple organ failure and one was discharged, and hemorrhagic necrosis was seen in the bypassed area of the myocardium. One patient of the third group could not be weaned from LVAD because of respiratory failure though his heart function began to recover. Another case in the third group underwent bypass grafting after removal of LVAD. However ACBG surgery should be done very carefully because a patient in shock is occasionally intolerant to major surgery. In all groups, the major cause of death was multiple organ failure which was probably caused by the prolonged low output condition prior to LVAD application. In the light of this experience, it appears that LVAD should be applied before irreversible damage occurs to major organs, including the heart itself. To ensure the timely application of LVAD, some way must be found to introduce systematic application of LVAD into the normal course of AMI treatment.

[Results of tricuspid valve replacement using xenograft bioprostheses]

Thirty-two cases of tricuspid valve replacement were done with bioprostheses during the period from 1979 to 1986 at our institution. In these cases there were 19 cases of acquired valvular diseases, 10 cases of congenital types of heart diseases and other 2 cases were another genesis. Seven different kinds of bioprostheses were utilized: 30 were bovine pericardial xenografts and 2 were porcine xenografts. In postoperative hemodynamic study, right ventricular end-diastolic pressure and right atrial pressure significantly decreased after tricuspid valve replacement. RV ejection fraction were reduced but there was no statistic significance when compared to the preoperative data. There were 5 patients who showed postoperative atrio-ventricular block and two of them needed permanent pacemaker implantation. Six patients died in postoperative period and other 3 died in late follow-up period. However, these was no mortality directly related to prosthetic valvular failure. In follow-up study, there was no episode of valve thrombosis nor pulmonary embolism. Prosthetic endocarditis was not encountered during this observation period. One patient showed mild degree of tricuspid regurgitation who had severe pulmonary hypertension even after the operation. Based on our experience, we concluded that the bovine pericardial xenograft may be the best choice for the TVR because of its anti-thrombogenicity. However, mechanical valve will be better choice for the patients who are complicated with severe pulmonary hypertension.

[Follow-up study of coronary artery bypass grafting after Kawasaki disease--early and late postoperative evaluation]

In our hospital, 22 patients with severe coronary arterial lesion after Kawasaki disease underwent coronary artery bypass grafting (CABG) since 1982. The age of the cases at surgery ranged from 1 year to 19 years. Mean age was 8.3 years. Fifteen cases were bypassed using internal mammary artery (IMA) and 5 cases using IMA and autologous saphenous vein (SVG). Two cases were bypassed using only SVG. They have been examined until now by catheterization, by Treadmill test, and by Tl-201 myocardial imaging, around 1 month (Study 1) and around 1 year (Study 2) after surgery for the evaluation of results of CABG. One patient died from acute myocardial infarction 3 months after surgery and one patient shows return of anginal attack due to graft stenosis. Other patients are almost uneventful. In the study 1,20 (100%) IMA were patent, and 7 (88%) SVG were patent. In the study 2, 11 (92%) IMA and 6 (67%) SVG remained patent. Development of left anterior descending artery distal to IMA anastomosis was shown in 8 cases in the study 2. On the follow-up study with TI-201 myocardial imaging, disappearance or decrease of perfusion defect was seen in 7 cases (59%) in the study 1 and 9 cases (75%) in the study 2. On the Treadmill test, disappearance or improvement of ischemic change was seen in 15 cases (88%) in the study 1 and 10 cases (84%) in the study 2. These results suggest that IMA is more preferable for than SVG for young children who has an indication of CABG after Kawasaki disease.

Amino acid sequence of the retinal binding site of squid visual pigment

The retinylpeptides of visual pigments of two species of squid were identified in invertebrate visual pigments. Their primary structures were identical: H-Phe-Ala-Lys-Ala-Ser-Ala-Ile-His-Asn-pro-Hse(Met)-OH. The sequence was homologous to those of the corresponding region of other visual pigments, but the eighth amino acid, His, was found in squid visual pigments. In this experiment the retinylpeptides of eleven amino acid residues were isolated by monitoring the absorbance spectrum of the reduced retinal Schiff base without using radio-active [3H]retinal. This method is valid for the isolation and identification of retinylpeptides of other invertebrate visual pigments in which the chromophore is not exchangeable.