Ischemic preconditioning is associated with a delay in ischemia-induced reduction of beta-adrenergic signal transduction in rabbit hearts

BACKGROUND

It has been reported that the A1-adenosine receptor mediates the cardioprotective effect of ischemic preconditioning. This receptor couples inhibitory guanine nucleotide-binding protein (Gi) and inhibits adenylate cyclase activity. However, the role of adenylate cyclase in preconditioning is unknown.

METHODS AND RESULTS

We compared the effects of ischemia on the sarcolemmal beta-adrenergic receptor density (Bmax), the stimulatory guanine nucleotide-binding protein (Gs) activity as determined by reconstitution with S49 lymphoma cyc- membranes, and baseline and maximally stimulated adenylate cyclase activities (ACAs) in control and preconditioned rabbit hearts. The control population (n = 28) received 0, 10, 20, and 60 minutes of coronary occlusion (n = 6 to 8 per stage), and preconditioned rabbits (n = 24) received two cycles of alternating 5-minute occlusion and reperfusion before sustained ischemia (n = 6 per stage). In control hearts, occlusion induced rapid and progressive reductions in the Bmax, Gs, and ACAs after 10 to 60 minutes of ischemia. Preconditioning did not affect the reduction in Bmax, but it preserved reductions in Gs activity and ACAs after 10 to 20 but not 60 minutes of sustained ischemia. In another study, 18 rabbits were treated with pertussis toxin 48 hours before surgery to block Gi. During treatment, no significant difference was observed in the ischemia-induced reduction in ACAs in the ischemic region between control (n = 8) and preconditioned (n = 10) animals after 20 minutes of ischemia.

CONCLUSIONS

Preconditioning delays ischemia-induced reductions in beta-adrenergic signal transduction. Inhibition of ACA is not the target effect of the A1-adenosine receptor-Gi pathway responsible for the cardioprotective role of preconditioning.

Therapeutic effect of intradermal injections with difucosyl lactosamine (dimeric Lex) on patients with rheumatoid arthritis

As reported by us, a new myeloid cell population with an oncofetal membrane marker, dimeric Lex (di-Lex; III3FucV3 FucnLc6), was found in the epiphyseal bone marrow adjacent to the involved joints of patients with severe rheumatoid arthritis (RA). Patients with RA received intradermal (id) injections of di-Lex incorporated in liposome or of high molecular weight glycoprotein, or tumor associated carbohydrate antigen (TCA), containing the same carbohydrate epitope as di-Lex. The epiphyseal myeloid cells were reduced or sometimes eliminated during id injection. In random trials of id injection, observation under clinical and laboratory conditions showed improvement in 63% (17/27) of the patients treated for 6 months with appropriate doses of di-Lex (III3FucnLc4), and in 72% (31/43) of those treated with an identical protocol for TCA. However, id injection with monomeric Lex had no effect.

[A case of sho-saiko-to-induced pneumonitis, diagnosed by lymphocyte stimulation test using bronchoalveolar lavage fluid]

A 66-year-old Japanese man was admitted to our hospital with fever, cough and dyspnea. He had been taking Sho-Saiko-to, a traditional Chinese medicine, for twenty days. On admission, chest X-ray examination revealed a reticular pattern in the bilateral lungs, and respiratory failure was evident. Serum levels of CRP and LDH were elevated. A differential cell count of the bronchoalveolar lavage fluid (BALF) showed that lymphocytes and eosinophils were increased. Alveolitis with lymphocyte and plasma cell infiltration was observed in a pathological specimen obtained by transbronchial lung biopsy. After all drugs had been discontinued, PaO2, serum CRP and serum LDH improved, and the reticular pattern in the bilateral lungs gradually resolved without administration of corticosteroids or antibiotics. A lymphocyte stimulation test for Sho-Saiko-to using BALF gave a positive result, although LST using blood gave a doubtful reaction. The diagnosis of Sho-Saiko-to-induced pneumonitis was made from the clinical course, laboratory findings, BALF cell analysis, pathological findings and LST using BALF. Only 13 cases of pneumonitis due to administration of traditional Chinese medical drugs have been reported. This case suggests that LST using BALF is useful for the diagnosis of drug-induced pneumonitis.

Effects of cromakalim on the electrical slow wave in the circular muscle of guinea-pig gastric antrum

1. In circular muscle strips of the antrum of guinea-pig stomach, the effects of cromakalim were studied on mechanical activity and intracellular membrane potential. 2. Cromakalim inhibited mechanical activity at concentrations higher than 1 microM, accompanied by membrane hyperpolarization and a decrease in membrane resistance. The hyperpolarization was markedly potentiated in K(+)-free solution and was still observed in the absence of Na+. 3. Slow wave electrical activity was relatively resistant to cromakalim. Changes in its amplitude and frequency were not consistent but blockade of slow waves was never observed. In many preparations cromakalim induced spike-like potentials at the top of slow waves, or when spike-like potentials already existed they were potentiated. However, mechanical activity was always inhibited. 4. Inhibition by cromakalim of the phasic contractions associated with the slow waves, could not be reversed by increasing the external K+ concentration (12-30 mM). 5. The results suggest that in guinea-pig stomach muscle mechanical suppression by cromakalim does not simply result from membrane hyperpolarization or from inhibition of slow waves. A clear dissociation was found between the mechanical and electrical activities. Slow waves, particularly their frequency, are relatively insensitive to membrane hyperpolarization.

The clinical and radiological evaluation of primary brain neoplasms in children, Part II: Radiological evaluation

Data collected over the past 8 years on the radiological appearance of common pediatric primary brain neoplasms are presented. An emphasis is placed on the newer radiological imaging modality of magnetic resonance imaging (MRI). Part I of this article emphasized the clinical evaluation of these brain neoplasms. Three hundred eighty-five children with known brain neoplasms ranging in age from newborn to 18 years were evaluated with one or all of the following radiological modalities: MRI, computed tomography (CT), water-soluble myelography (WSM), WSM with CT, and angiography. Contrast-enhanced MRI and CT scans both were accurate in delineating these brain neoplasms although MRI provided better resolution and delineation than CT. Angiography provided information on the vascularity of the neoplasms and their relationship to prominent arterial and venous structures. Water-soluble myelography with CT and gadolinium-enhanced MRI of the spine were equally accurate in demonstrating metastatic spread to the spinal canal and spinal cord. Magnetic resonance imaging with gadolinium was more accurate than CT with contrast in demonstrating recurrent or residual neoplasm at the operative site and metastatic spread to the brain. Magnetic resonance imaging with gadolinium is the best radiological modality to fully evaluate pediatric brain neoplasms.

[Aniline-induced methemoglobinemia monitored by pulse oximetry]

A case of aniline-induced methemoglobinemia is reported. When the pulse oximeter reading (SpO2) was 80%, the oxygen saturation measured by a co-oximeter (SaO2) was 61.2%, the oxygen saturation calculated from PaO2 values was 98.9% and methemoglobin level was 38.8%. After methylene blue injection, methemoglobin level decreased gradually. With a decrease of methemoglobin level, SpO2 approached SaO2. If disparity between SpO2 and the oxygen saturation calculated from PaO2 values is noted, the presence of methemoglobinemia must be suspected. In clinical situations, the pulse oximeter permits the continuous noninvasive monitoring of oxygen saturation. It is necessary, however, to consider the potential errors in pulse oximetry.

The clinical and radiological evaluation of primary brain tumors in children, Part I: Clinical evaluation

In Part I of this article, we present our data collected over the past 8 years on the clinical evaluations of pediatric brain tumors with an emphasis placed on the more common neoplasms. Our data consists of 385 children ranging in age from newborn to 18 years. The majority of children presented with signs of raised intracranial pressure (including nausea, vomiting, and headaches), seizures or other focal neurologic deficits. Five percent of our children presented to outlying hospitals with symptoms that retrospectively turned out to be due to brain neoplasms but were misdiagnosed as "gastroenteritis," "viral upper respiratory tract infection," or even viral meningitis. These delays in diagnosis can cause serious negative outcomes for these patients and can be avoided through more careful neurologic and ophthalmologic examination at the time of first presentation. Central nervous system neoplasms are not uncommon in children and any child presenting with nausea, vomiting, and headaches should raise the suspicion of a primary brain tumor and should receive both a thorough neurologic exam and screening for papilledema. If papilledema is present, these children should be referred for proper neuroradiologic evaluation (which will be addressed in Part II.

Profile of prostatic-specific antigen in prostatic carcinomas

Prostatic carcinomas (PCs) may be divided into two distinct categories: latent PCs, found mostly at autopsy, and clinical cases, which present with signs and symptoms. These two categories correspond fairly well to histologic grading of PCs and immunoperoxidase staining for prostatic specific antigen (PSA). The objective of this study was to find quantitative and qualitative differences if any, of PSA in PCs, corresponding to Gleason's histologic grade. By radiometric assay of PSA in tissue cytosol, PCs especially those of high histologic grade, were found to have lower PSA concentrations than normal and glandular hyperplastic prostatic tissue. Western blotting of cytosol was performed to detect differences between immunoreactive PSA of PCs compared with noncancerous tissue using both polyclonal and monoclonal antibodies against PSA. Western blotting with anti-PSA revealed some different bands between cancerous and noncancerous cytosols. Western blotting of cancerous and noncancerous cytosols was also performed using anti-prostatic acid phosphatase and anti-beta micro-seminoprotein. Reduced PSA concentration and different immunoblotting pattern of PSA were found to be characteristic for PCs, especially in carcinomas with grades higher than 7, which usually present with more aggressive invasion and metastases.

Effects of magnesium on isolated canine coronary arterial tension

The effects of magnesium on the tension of isolated canine coronary arterial strips were studied. In the solution containing K+ of 20 mEq.l(-1), Ca2+ of 4 mEq.l(-1), and Na+ of 127 mEq.l(-1), the tension was 811 +/- 111 mg with Mg2+ of 1 mEq.l(-1), 494 +/- 135 mg with Mg2+ of 10 mEq.l(-1), 272 +/- 126 mg with Mg2+ of 20 mEq.l(-1), -52 +/- 63 mg with Mg2+ of 30 mEq.l(-1), -69 +/- 80 mg with Mg2+ of 40 mEq.l(-1). In the solution containing K+ of 20 mEq.l(-1), Na+ of 12 mEq.l(-1) and Ca2+ of 0 mEq.l(-1), the tension was 102 +/- 22 mg with Mg2+ of 1 mEq.l(-1), 3 +/- 35 mg with Mg2+ of 10 mEq.l(-1), -49 +/- 33 mg with Mg2+ of 20 mEq.l(-1), -59 +/- 49 mg with Mg2+ of 30 mEq.l(-1), -65 +/- 54 mg with Mg2+ of 40 mEq.l(-1). The data demonstrated that Mg2+ above 30 mEq.l(-1) inhibited the increase in tension caused by Ca2+ and Mg2+ above 20 mEq.l(-1) inhibited the increase in tension caused by low Na+ concentration.

Differential function of the costal and crural diaphragm during emesis in canines

In six mongrel dogs under thiopental anesthesia, piezoelectric transducers and bipolar electromyographic (EMG) wires were installed onto left costal, medial crural and lateral crural segments of the diaphragm. During CO2 rebreathing, shortening and EMG activity increased significantly in all three regions of the diaphragm compared to resting breathing. During emesis, (1) both shortening and EMG activity significantly increased compared to resting in costal segment; however, (2) lateral crural shortening was not increased in spite of significant increase in EMG activity; furthermore, (3) the medial crural segment lengthened without any increased EMG activity. These results demonstrate a differential recruitment of costal and crural diaphragm segments, and an additional differential activity within the crural segment between medial and lateral crural regions, during emesis. This activity of the canine diaphragm is consistent with a central influence of emesis upon individual regions of the diaphragm.

Lymphangioma of the jejunal mesentery in an adult: a case report and a review of the Japanese literature

A rare case of lymphangioma of the jejunal mesentery in a 34-year-old woman is presented. She was diagnosed as having an ovarian cyst preoperatively, but laparotomy revealed a cystic tumor of the mesentery that was histologically diagnosed as lymphangioma. Thus far, 44 cases of adult mesenteric lymphangioma have been reported in Japan. In nine cases, accurate diagnosis of mesenteric cysts was obtained preoperatively. In 31 cases, complete excision with or without bowel resection was done, whereas two cases were partially resected and one case was drained.

[A case of T-cell lymphoma showing multiple nodular shadows and an elevated titer of human T-lymphotropic virus type I (HTLV-I) antibody]

A 42-year-old man, born in Chiba prefecture, was admitted to our hospital because of multiple nodular shadows on chest X-ray film and an elevated titer of human T-lymphotropic virus type I (HTLV-I) antibody. The pulmonary lesion was diagnosed as T-cell lymphoma by open lung biopsy. There has been only one previous report of T-cell lymphoma showing multiple nodular shadows on chest X-ray. The elevated titer of HTLV-I antibody strongly suggested that the present case was one of adult T-cell lymphoma.

Assembly and channel-forming activity of a naturally-occurring nicked molecule of Staphylococcus aureus alpha-toxin

From the culture supernatant of Staphylococcus aureus Wood 46, we obtained a naturally-occurring nicked molecule of staphylococcal alpha-toxin. The nicked alpha-toxin consisted of non-covalently-linked 8-kDa and 25-kDa polypeptides, which were derived, respectively, from the N-terminal and the C-terminal part of the toxin nicked at the peptide bond between Glu-71 and Gly-72. The nicked toxin, as well as native alpha-toxin, bound to and oligomerized in the liposome membranes composed of choline-containing phospholipids (i.e., phosphatidylcholine and sphingomyelin) and cholesterol, and formed membrane channel in the liposome membranes. However, the channel-forming activity of the nicked toxin, assessed as a toxin-induced carboxyfluorescein leakage from the liposomes, was approx. 20-fold lower than that of native alpha-toxin. Channel-forming activity of the nicked toxin as well as native toxin was inhibited by divalent cations including Zn2+, Cd2+, Ca2+ and Mg2+, and degree of the inhibitory effect of the divalent cations was in the following order: Zn2+ > Cd2+ > Ca2+ > Mg2+. Thus, although the cleavage of alpha-toxin at the position between Glu-71 and Gly-72 drastically reduced channel-forming activity of the toxin, the nicked toxin retained the ability to oligomerize in phospholipid-cholesterol membranes and the characteristics of channel-forming activity in terms of the specificity for phospholipids and the susceptibility to divalent cations.

Correction of absorption spectra of a pH-sensitive dye for intracellular pH estimation in smooth muscle

Methods of correction for intracellular pH (pHi) estimation from the absorbance of the pH-sensitive dye, 4',5'-dimethyl-5-(and -6-) carboxy-fluorescein (Me2CF), were described. In the guinea-pig vena cava, a reasonable estimation of pHi changes was obtained when the distortion of the spectrum was corrected using the tissue absorbance at wavelengths longer than 570 nm.

Radical resections of childhood craniopharyngiomas

A series of 27 children with craniopharyngiomas is presented. All the craniopharyngiomas were detected by computed tomography, and radical total resection was attempted. Postoperative evaluations were done by a series of computed tomography and magnetic resonance imaging scans. Twenty patients who had total resection confirmed by surgical and radiographic observations showed no recurrence during the follow-up period of from 1 to 12 years. It is emphasized that total resection using modern diagnostic and surgical methods is the mainstay for childhood craniopharyngiomas.

Inhibitory effects of cyanide on mechanical and electrical activities in the circular muscle of gastric antrum of guinea-pig stomach

Effects of cyanide (CN) on spontaneous mechanical and electrical activities were studied in the circular muscle of the guinea-pig gastric antrum. CN (0.05-0.5 mM) inhibited both mechanical and electrical activities, but the inhibition was stronger in the former than the latter (slow wave). When glucose was removed for more than 30 min, slow wave was also blocked by CN. It is likely that ATP necessary for the generation of spontaneous activity can be supplied through either glycolysis or oxidative phosphorylation. CN slightly depolarized the membrane and the inhibition by CN was not affected by glibenclamide, a blocking agent of ATP-regulated K+ channel, suggesting that this channel is not activated by CN treatment. Basal level of intracellular Ca2+ measured with fura-2 tended to increase during the mechanical inhibition by CN. This was also clearly demonstrated in excess (60 mM) K+ solution. These results suggest that intracellular Ca2+ regulation is impaired and that there is uncoupling between intracellular Ca2+ and tension development in the presence of CN.

Intracellular alkalinization caused by chloride removal in the smooth muscle of guinea-pig vena cava

Intracellular pH (pHi) of smooth muscle of guinea-pig vena cava was measured with a pH-sensitive dye, 4',5'-dimethyl-5-(and -6-)carboxyfluorescein. Sustained intracellular alkalinization (pHi 7.46) was produced when Cl- was replaced with gluconate in the presence of HCO3-, but not produced in the absence of HCO3-. Alkalinization caused by Cl- removal was nearly completely blocked by 200 microM DIDS, a Cl- transport inhibitor. In the solution containing normal Cl- concentration, pHi (7.15) was not affected by DIDS, and pHi was also nearly the same in the presence and absence of HCO3-. When full alkalinization was developed in Cl(-)-deficient solution, HCO3- removal produced only a weak recovery. A carbonic anhydrase inhibitor, acetazolamide (100 microM) had no clear effect on pHi in both normal and Cl(-)-deficient solutions. Intracellular acidification caused by Na+ removal was much less when NaCl was replaced with sucrose than with N-methyl-D-glucamine chloride. It is concluded that when Cl- is removed, pHi can be strongly altered by a Cl(-)-HCO3- exchange mechanism in the guinea-pig vena cava. A contribution of this mechanism to pHi is, however, probably rather minor under physiological conditions.

[Prediction of nocturnal desaturation in elderly patients with chronic respiratory disease]

Previous reports suggest that nocturnal disorders of sleep and breathing have increased prevalence among the elderly, and episodic nocturnal oxygen desaturation (NOD) has an increased incidence in patients with chronic respiratory disease. Current Japanese criteria for home low flow oxygen therapy (LFOT), recommend LFOT for patients with daytime PaO2 < 55 torr or with daytime PaO2 < or = 60 torr who have significant NOD. Strict adherence to these LFOT criteria requries full overnight monitoring of arterial oxygen saturation (SaO2) in all patients with daytime PaO2 < or = 60 torr. Since widespread nocturnal oximetry involves significant expenditure of time and resources, it is important among patients with chronic respiratory diseases to predict those who will have significant NOD. The aim of the present study was to formulate criteria for identification of patients who are most likely to demonstrate significant NOD based upon daytime respiratory function data. Subjects included 34 elderly patients with daytime PaO2 > or = 55 torr, who had stable severe chronic respiratory disease (15 chronic emphysema, 6 chronic bronchitis, 12 post-tuberculosis, and 1 kyphoscoliosis). Study data included medical history, assessment of dyspnea by Hugh-Jones classification, and measurement of daytime, awake arterial blood gases and spirometry. Each subject underwent full overnight oximetry monitoring. The percentage of total sleep time recorded with SaO2 < or = 85% was noted (DST85), and NOD was defined as DST85 > or = 1%. Of the 34 patients, 11 were identified as NOD, and 23 as non-NOD patients. Duration and severity of dyspnea were not different between NOD and non-NOD patients.(ABSTRACT TRUNCATED AT 250 WORDS)

[Protein binding of cephems in the elderly]

The serum protein-binding of 12 representative cephems (CET, CEZ, CZX, CPZ, CZON, CPM, CDZM, CFX, CMZ, CTT, LMOX, FMOX) was assessed, using sera from young healthy subjects (mean age, 28.6 years old) and elderly healthy subjects (mean age, 69.7 years old), applying equilibrium dialysis under the same conditions in vitro. The protein-binding capacity of 12 cephems in elderly subjects was significantly less than that in young subjects, and marked increase in free drug concentration was observed in elderly subjects. This decrease in the protein binding capacity of cephems in elderly subjects was possibly caused by decreased serum albumin and change in non-esterified fatty acid constitution related to aging. As free-drug concentration participates in the appearance of effects and adverse reactions, the possibility of an enhanced pharmacological effects and increased adverse reactions of cephems due to decrease of protein binding in elderly subjects should be considered.

C-cell hyperplasia in secondary hyperparathyroidism

Calcitonin is a hypocalcaemia producing hormone and is secreted by C-cells of the thyroid. The current study was undertaken on a hypothesis that C-cell hyperplasia may develop in the secondary hyperparathyroidism of chronic renal failure in response to sustained hypercalcaemia. With an immunoperoxidase staining method for calcitonin, C-cell hyperplasia was noted in four of six cases of autosomal dominant polycystic kidney disease and in three of six cases of acquired renal cystic disease, an overall incidence of 58% compared with an incidence of 36% (five of 14) in cases of primary hyperparathyroidism with parathyroid adenoma. Thus, both primary and secondary hyperparathyroidism may trigger C-cell hyperplasia in an attempt to produce a hypocalcaemic effect.

Long-term effects of treatment for childhood brain tumors

Recent studies have recognized brain tumor to be the most important solid malignancy in childhood. Improved diagnostic methods and advances in surgical technology and instrumentation have significantly lowered operative mortality, facilitating more precise and radical surgical resections.

[Adverse reactions to low osmolar iodine contrast media (second report)]

From January to December 1990, we performed a prospective survey of adverse reactions to contrast media at two different institutes of Juntendo University. We collected a total of 4555 case sheets during the period. The radiological procedures we investigated were computed tomography, intravenous urography, arteriography, venography and myelography. Low osmolar iodine contrast medium was used almost exclusively (except for five cases). The overall incidence of adverse reactions was 7.0%, and there were no severe or fatal reactions. The incidence of adverse reactions was higher in females (8.5%) than in males (6.1%). The incidence of adverse reactions increased according to the dose of contrast medium, especially when more than 101 ml was injected. Intra-arterial injection caused adverse reactions most often, followed by regular intravenous injections, followed by bolus intravenous injections. Adverse reactions occurred most often during injection. The next occurred in 5 minutes after injection, and then, 5-10 minutes after the injection of contrast medium. The incidence of adverse reactions was higher in patients with a history of allergy or previous reactions. Allergic adverse reactions were observed at a higher frequency. Pretesting was performed in 56.7% of the cases.

Reduced functions of intracellular Ca2+ in aggregation, secretion and protein phosphorylation of permeabilized platelets from stroke-prone spontaneously hypertensive rats

Aggregation, secretion and 47kDa protein (P47) phosphorylation by various agonists such as thrombin, ADP and ionophore A23187 were markedly reduced in platelets from stroke-prone spontaneously hypertensive rats (SHRSP) compared with those of age-matched Wistar Kyoto rat (WKY) platelets, suggesting defective functions of intracellular Ca2+ in SHRSP platelets (Tomita et al. Hypertension 1989; 14: 304-315). To clarify the mechanism of the platelet hypofunctions, saponin permeabilized platelets were prepared to compare the responses of platelets from both rats in varying concentrations of extracellular Ca2+. The leakage of lactate dehydrogenase from saponin (15 micrograms/ml)-treated platelets was approx. 5% of total activity; the degree of the leakage in both platelets did not differ. In saponin-treated platelets, extracellular Ca2+ alone did not induce either aggregation or secretion in both strains. However, in the presence of 1-oleoyl-2-acetylglycerol (10 micrograms/ml), Ca2+ dose dependently stimulated both aggregation and secretion. Under this condition, Ca2+ sensitivity of aggregation, secretion and P47 phosphorylation in SHRSP platelets were significantly reduced compared with those in WKY platelets. These results strongly suggest that intracellular Ca2+ functions are impaired in SHRSP platelets.

Effects of intracellular ATP on calcium current in freshly dispersed single cells of guinea-pig portal vein

In smooth muscle cells freshly dispersed from the guinea-pig portal vein, inward currents were recorded with the whole-cell clamp method in the presence of 2.4 mM Ca2+ under the condition in which outward K+ currents were suppressed and the effects of ATP in patch pipettes were studied. There was a large variation of the rate of current decay, the half-decay time ranging from 20 to 80 ms, but it was difficult to demonstrate clearly the presence of fast (T-type) and slow (L-type) Ca2+ channels based on threshold, the effects of changing holding potential, and of nicardipine, a dihydropyridine Ca2+ channel blocker. Intrapipette ATP had a weak potentiating effect on inward current, but did not seem to influence the correlation between peak current amplitude and current configuration. Cyanide (0.5 mM) reduced inward currents, particularly when ATP concentration was low and only limited recovery was observed. It was concluded that the amplitude and the rate of current decay of inward currents are not only determined by intracellular ATP, but also significantly influenced by some other factor, such as that involved in 'run-down' of Ca2+ currents.

Processing of structural polypeptides of infectious flacherie virus of the silkworm, Bombyx mori: VP1 and VP4 are derived from VP0

Infectious flacherie virus of the silkworm, Bombyx mori, contains five major polypeptides termed VP0, VP1, VP2, VP3, and VP4 in the order of descending molecular weight. Immunoblot analysis with specific antisera against each of these structural polypeptides showed that antisera against VP1 and VP4 unequivocally reacted with VP0 as well as their homologous structural polypeptides. Limited proteolysis of VP0 and VP1 by Staphylococcus aureus V8 protease gave several common polypeptide fragments. Amino acid sequence analysis showed that VP0 and VP4 shared a common NH2-terminal amino acid sequence. These results indicate that VP1 and VP4 are generated from VP0 and that VP4 occupies the NH2-terminal portion of VP0.