Structure-activity relationships of cephalosporins having a (dimethylisoxazolidinio)vinyl moiety at their 3-position

A series of cephalosporins having a (dimethylisoxazolidinio)vinyl group at their 3-position were synthesized to investigate their structure-activity relationships. With regard to the olefin geometry, the (E)-vinyl compound exhibited higher in vitro activity than the (Z)-compound. Regarding the C-7 substituents, the replacement of 2-aminothiazole with 5-amino-1,2,4-thiadiazole increased the anti-pseudomonal activity. Determination of the absolute configuration of the C-3 substituent is also presented. Among the compounds synthesized, we selected 7 beta-[(Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(fluoromethoxyimi no)acetamido]-3-[(E)-2-((S)-2,2-dimethyl-5-isoxazolidinio)vinyl ]-3-cephem-4-carboxylate (YM-40220), which showed well-balanced in vitro activity and an excellent in vivo efficacy against Staphylococcus aureus Smith, as a candidate for further development.

Impaired endothelial function with essential hypertension assessed by ultrasonography

The objective of this investigation was to evaluate the role of hypertension in endothelial function, changes in which are known to be an early event of atherosclerosis. We assessed endothelial function in 13 subjects with normal blood pressure and 13 subjects with essential hypertension who had never been treated for hypertension or hyperlipidemia and who had no history of smoking or coronary or cerebrovascular disease. B-mode ultrasonography was used to measure the diameter of the brachial artery. Endothelium-dependent dilatation was assessed as the change in diameter of the artery during reactive hyperemia. Endothelium-independent dilatation was evoked, as a control, by sublingual administration of isosorbide dinitrate. Despite similar ages and lipid and glucose levels in the study groups, endothelium-dependent dilatation was less in patients with hypertension (13.1% +/- 1.6%) than in subjects with normal blood pressure (18.5% +/- 1.9%) (p < 0.05), whereas isosorbide dinitrate-induced changes were similar. Systolic and diastolic blood pressure were significantly correlated with endothelium-dependent vasodilatation (r = -0.57 and r = -0.53, respectively) but not with the change by isosorbide dinitrate. These results suggest that endothelial dysfunction exists in patients with hypertension and precedes overt atherosclerotic disease.

Effects of ONO-1101, a novel beta-antagonist, on action potential and membrane currents in cardiac muscle

Direct effects of ONO-1101 ¿(-)-[(S)-2,2-dimethyl-1,3-dioxolan-4-yl]methyl-3-[4-[(S) -2-hydroxy-3-(2-morpholino carbonylamino)ethylamino] propoxy]phenylpropionate monohydrochloride), a novel beta-antagonist, on action potential parameters and membrane currents, and its beta adrenoceptor antagonism were examined in cardiac muscle. Action potential-parameters in papillary muscle of reserpinized animals and membrane currents recorded from single myocytes obtained from guinea pig and rabbit hearts were not affected by 1 to 100 microM ONO-1101. On the other hand, ONO-1101 markedly inhibited the potentiation of Ca current by isoproterenol in single cardiac myocytes of the guinea pig. The concentration-response relationship of Ca current for isoproterenol was shifted to the right. This effect resembled that of esmolol, which is also a beta adrenoceptor antagonist. A Schild plot analysis revealed the slope and pA2 value of each antagonist (ONO-1101, 0.94, 8.0; and esmolol, 0.98, 7.3, respectively) and demonstrated that ONO-1101 is about 5 times more potent than esmolol as a beta-antagonist. Two other effects of isoproterenol: 1) potentiation of delayed rectifier K current and 2) activation of chloride current, were also inhibited by ONO-1101. The time required for 50% removal of beta-antagonism of ONO-1101 and esmolol after the washout was estimated as 4 and 6 min, respectively, in depolarized papillary muscle. These results suggest that ONO-1101 is a potent beta-antagonist whose effects were removed quickly by washout. When applied at what is thought to be a clinical dosage, ONO-1101 had no direct effects on action potential-parameters and membrane currents in cardiac muscle. These characteristics of ONO-1101 suggest that this agent may be effective in clinical use.

Progressive jaundice due to lymphangiosis carcinomatosa of the liver: CT appearance

In a case of progressive jaundice, contrast-enhanced CT demonstrated unevenly distributed areas of periportal low attenuation throughout the liver that were demonstrated to be dilated lymphatics with multiple carcinomatous thrombi at postmortem study. This CT appearance may be characteristic of lymphangiosis of the liver.

Novel blockade of Ca2+ current by quinacrine in smooth muscle cells of the guinea pig

Effects of quinacrine on voltage-dependent Ca2+ channel current (ICa) were examined using whole cell voltage clamp in single smooth muscle cells isolated from vas deferens and urinary bladder and single cardiac myocytes from ventricle of the guinea pig. When ICa was elicited by depolarization from a holding potential of -60 to 0 mV for 150 msec every 15 sec in vas deferens myocytes, external application of quinacrine reduced the amplitude of ICa in a concentration-dependent manner in a range of 0.1 approximately 30 microM, and the IC50 of quinacrine was 1.3 microM. The block was at least partly removed by washout. The block of ICa by 1 microM quinacrine in vas deferens myocytes greatly depended upon the activation potentials but only slightly on the holding potentials. Use-dependent development of the block was also observed. Addition of 300 microM quinacrine to the pipette-filling solution did not significantly affect ICa. The IC50 of quinacrine for ICa block in urinary bladder myocytes was 1.1 microM and comparable to that in vas deferens. On the other hand, IC50 for the block of ICa elicited by depolarization from -45 to 0 mV in cardiac ventricular myocytes was 5.6 microM. It is concluded that quinacrine is a potent blocker of L-type Ca2+ channels in two types of smooth muscle myocytes and that the potency appeared to be approximately five times higher than that in cardiac myocytes. The action of quinacrine may be due to the direct block of Ca2+ channels from outside of the cell membrane.

Opening of Ca(2+)-dependent K+ channels by nordihydroguaiaretic acid in porcine coronary arterial smooth muscle cells

Effects of nordihydroguaiaretic acid (NDGA) on the Ca(2+)-dependent K+ channel (BK channel) were examined by the patch clamp technique in single smooth muscle cells of porcine coronary artery. The open probability of BK channels in inside-out patches increased by about 30 times at the holding potential of 0 mV, when 10 microM NDGA was added to the bathing solution (pCa 7.0). The effect of NDGA was concentration-dependent in the range of 1-100 microM and partly removed by washout. The enhancement of BK channels by NDGA was not observed when the cytosolic Ca2+ concentration was very low (pCa > 8.5). These results clearly indicate that NDGA possesses a BK channel opening property in coronary arterial myocytes.

Organization of F-actin filaments in human glioma cell lines cultured on extracellular matrix proteins

Extracellular matrix (ECM) constituents likely play an important role in cell proliferation and the invasion of malignant human gliomas. We examined the formation of stress fibers and the growth of the human glioblastoma cell lines A172 and T98G cultured on collagen types I, IV, and V, laminin (LN), and fibronectin (FN). A172 cells cultured on LN and FN formed complete F-actin filaments after 24 h of culture and grew logarithmically after 48 h. In contrast, T98G cells on LN and FN reorganized only short F-actin filaments after 24 h of culture and grew rapidly after 72 h. However, on the collagen preparations, neither cell line formed definite stress fibers and both showed lower rates of cellular proliferation. Significantly positive correlation was observed between the relative intensity of F-actin filaments and the cell proliferation. The results indicate that the ability of ECM components to modulate the growth and differentiation of malignant glioma cells may be mediated, in part, by the assembly and disassembly of F-actin filaments.

Renal responses to atrial natriuretic peptide (ANP) in rats with non-oliguric acute renal failure induced by cisplatin

This study was designed to compare the renal effects of atrial (A-type) natriuretic peptide (ANP) on control (saline-injected) rats and rats with non-oliguric acute renal failure induced by cisplatin. The results obtained here are summarized as follows: (1) In the metabolic cage study, cisplatin-treated rats showed increases in blood urea nitrogen and serum creatinine while creatinine clearance decreased to the lowest levels on day 4. A transient increase in urinary protein was observed at day 4. (2) ANP infusion significantly increased urine flow rate (UFR), creatinine clearance (CCr), fractional excretion rates of sodium (FENa) and chloride (FECl), and urinary phosphorus and magnesium (Mg) excretions in a dose-dependent manner without affecting renal plasma flow and fractional excretion rates of potassium and urea in cisplatin-treated rats. (3) Renal effects of ANP on UFR, CCr, FENa, FECl and excretion of Mg were more pronounced in cisplatin-treated rats compared to control rats although markedly blunted responses to ANP have been reported in nephrotic patients and nephrotic animals induced by adriamycin and aminonucleoside. (4) Histological examination showed extensive necrosis of the S3 segment of the proximal tubule located in the outer stripe of the outer medulla with minimal glomerular abnormalities in the kidney of cisplatin-treated rats. In conclusion, the main mechanism of the increased renal responses to ANP is considered to be due to an increased delivery of sodium, fluid and ANP itself to the inner medullary collecting duct which is the major renal site of action of ANP under the condition of acute proximal tubular necrosis by cisplatin.

Role of C5a-ase in group B streptococcal resistance to opsonophagocytic killing

Type III group B streptococci (GBS) can be subdivided into three subtypes, RDP III-1, III-2, and III-3, on the basis of numerical analysis of HindIII restriction endonuclease digestion patterns (HindIII RDP) with their chromosomal DNAs. In the present study, the effect of C5a on opsonophagocytic killing of a representative strain from each RDP type was investigated by using a novel optical method for determining opsonophagocytic killing, and the effect of C5a-ase treatment of C5a on opsonophagocytic killing was also investigated. Pre-stimulation of polymorphonuclear leukocytes (PMNs) with C5a significantly increased opsonophagocytic killing of all three strains. The increase in killing was abolished by pretreating the C5a with GBS that express C5a-ase, a treatment that also destroyed the chemoattractant activity of the C5a. The kinetics of killing of the RDP III-2 strain differed from those of the other two strains. The survival of the RDP III-2 bacteria continued to decline over the entire 60-min incubation of the opsonophagocytic assay when PMNs were prestimulated with C5a or with C5a that had been inactivated with GBS C5a-ase (dC5a). In contrast, killing of the RDP III-1 and III-3 strains almost ceased after 20 or 60 min when PMNs were prestimulated with dC5a or C5a, respectively. A difference in bacterial killing between the III-2 strain and the III-1 and III-3 strains therefore became increasingly apparent with prolonged incubation time. The percentage of bacteria surviving in the extracellular fluid was approximately the same as the percentages of bacteria surviving in both intracellular and extracellular locations when PMNs were prestimulated with either C5a or dC5a. These data imply that the majority of bacterial killing occurred following phagocytosis and suggest that the enhanced killing of GBS following prestimulation of PMNs with C5a resulted from increased ingestion of the bacteria.

Such hydrophobic peptides as dansylated mastoparan can elevate the fertilization membrane of sea urchin eggs

Melittin is known to be a major hydrophobic peptide component in honeybee venom that can cause as much elevation of fertilization membrane of sea urchin eggs as normal fertilization. The action of melittin has been thought to be closely related with its ability to facilitate the phospholipase A2 activity on the eggs. However, another peptide "mastoparan" from wasp venom was not found here to cause any elevation of the membrane, although it can activate the enzyme as well as melittin. On the other hand, mastoparan was found to get the membrane-elevating activity only when its amino groups were modified with hydrophobic substituents. N epsilon-Substituted mastoparan with a dansyl group in Lys11 residue was most effective among the analogs examined here. Our findings indicate that the facilitation of phospholipase by the peptides have little relation with the membrane generation. Such hydrophobic moiety as the dansyl group in the peptides must cause the cortical reaction on the eggs in cooperation with peptide moiety. The dansylated peptide will be a useful tool to induce the artificial fertilization of sea urchin eggs.

Modulation of calcium channel currents by arachidonic acid in single smooth muscle cells from vas deferens of the guinea-pig

1. Effects of arachidonic acid (AA) on voltage-dependent Ca channel currents were investigated by whole-cell-clamp methods in single smooth muscle cells freshly isolated from vas deferens of the guinea-pig. 2. Ca channel current was decreased by application of 1-30 microM AA in a concentration-dependent manner. When Ca2+ or Ba2+ was the charge carrier, Ca channel current (ICa or IBa) was reduced by AA to a similar extent (IC50 = 10 and 6 microM, respectively). Addition of 15 mM BAPTA to the pipette solution did not affect the reduction of IBa by 10 microM AA. 3. The effect of AA on IBa was not prevented by internal application of 1 mM nordihydroguaiaretic acid (NDGA) and 1 mM indomethacin (Indo). When the pipette solution contained 0.1 mM guanosine-5'-triphosphate (GTP), IBa was decreased slightly but significantly by application of 30 microM prostaglandin F2 alpha (PGF2 alpha) but not by PGE2. This effect of PGF2 alpha was irreversible or not observed when the pipette solution contained 0.3 mM guanosine-5'-(3-thiotriphosphate) (GTP gamma S) or both GTP or guanosine-5'-O-(2-thiodiphosphate) (GDP beta S), respectively. 4. External application of 100 units ml-1 superoxide dismutase slightly but significantly attenuated the inhibition of IBa by 1-30 microM AA. Intracellular application of 1 mM GDP beta S or 0.3 mM GTP gamma S did not significantly change the effect of AA. Intracellular application of 0.1 mM 1-(5-isoquinolinesulphonyl)-2-methylepiperazine (H-7) also did not change the effect of AA. 5. These results indicate that the decrease in Ca channel currents in vas deferens smooth muscle cells is mainly due to AA itself, as opposed to its metabolites. The effect of AA may be due to AA itself, as opposed to its metabolites. The effect of AA may be due to its direct action on Ca channels or membrane phospholipids, but may not be mediated by activation of GTP binding proteins or protein kinase C. The inhibition of Ca channel current by AA may be partly induced by superoxide radicals derived from AA oxidation. PGF2A also reduces Ca channel currents but probably by a separate mechanism via activation of a GTP binding protein.

[Pharmacological properties of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent (I). Effect of chitosan DAC in normal rats]

The effects of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent of urea and ammonia, were examined in an in vitro adsorption study and in normal rats. Chitosan DAC showed high adsorption capacity for urea and ammonia in an in vitro study using the diluted supernatant of rat gastrointestinal fluid. In contrast, Kremezin, an oral charcoal adsorbent (AST-120), had little influence on these substances. In normal rats fed diets containing chitosan DAC (1, 2, 3, 4, 5, 7, and 10% content) for three weeks, increases in fecal wet weight, fecal dry weight and fecal water content were observed in a dose-dependent manner. In addition, chitosan DAC feeding increased fecal excretion of nitrogen and electrolytes (sodium, potassium and chloride ions) and decreased the apparent protein ratio in a dose-dependent manner. There were no obvious effects in serum parameters except that increased levels of protein and albumin and decreased levels of blood urea nitrogen, cholesterol and glucose were observed in rats fed a high concentration of chitosan DAC. In conclusion, these findings suggest the possibility that chitosan DAC treatment might be effective for improving chronic renal failure.

[Pharmacological properties of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent (II). Effect of chitosan DAC on rats with chronic renal failure induced by adriamycin]

The effects of chitosan-coated dialdehyde cellulose (Chitosan DAC), a newly developed oral adsorbent of urea and ammonia, were examined in rats with progressive chronic renal failure (CRF) induced by adriamycin. CRF rats induced by repeated injections of adriamycin were fed a diet containing chitosan DAC (5% content) or Kremezin (5% content), an oral charcoal adsorbent (AST-120) under strict paired-feeding for four months. CRF rats that received both a normal diet and Kremezin showed progressive azotemia, hyperphosphatemia, hyperlipidemia, proteinuria, and anemia, and began to die from 9 weeks after feeding started. In contrast, chitosan DAC-treatment showed marked prolongation of the survival period and decreases in blood urea nitrogen, serum creatinine, and serum phosphate. In addition, chitosan DAC-treatment ameliorated anemia in CRF rats, although hyperlipidemia and proteinuria were not improved. Furthermore, fecal weight, fecal water content, fecal nitrogen and fecal sodium were markedly increased, and the apparent protein ratio was decreased in CRF rats fed a diet containing chitosan DAC for 9 weeks. In contrast, none of these effects were observed in CRF rats receiving Kremezin. These observations suggest the further possibility of using oral adsorbent therapy for CRF patients.

Transient expression of type I collagen in glomeruli with anti-Thy-1 antibody-induced mesangial proliferative lesions

Glomerular expression of extracellular matrices at the protein and mRNA levels was examined in rats with mesangial proliferative glomerulonephritis induced by the intravenous administration of a monoclonal anti-rat Thy-1 antibody. In close association with the mesangial proliferative lesion, type I collagen was immunostained at day 8 but not demonstrated at day 28 in the glomeruli of the kidneys. Type I collagen mRNA expression prominently increased in the nephritic glomeruli at day 4, prior to the appearance of type I collagen protein. In addition, fibronectin expression was also elevated in the diseased glomeruli at both the protein and mRNA levels. These results indicated that glomerular, probably mesangial cells, change their phenotypes during this disease, to synthesize abnormal extracellular matrices that lead to the progression of glomerular sclerosis.

Immunohistochemical quantitation for extracellular matrix proteins in rats with glomerulonephritis induced by monoclonal anti-Thy-1.1 antibody

Extracellular matrix proteins (type I collagen and fibronectin) in frozen histologic sections of kidney cortex from rats with glomerulonephritis induced by a single intravenous administration of anti-Thy 1.1 antibody were quantified using an immunohistochemical micromethod. Type I collagen and fibronectin contents in renal cortex of rats with experimental glomerulonephritis (4.33 +/- 0.79 and 10.41 +/- 2.01 microgram/mg of total protein, respectively) were 262% and 151%, respectively, higher than in control rats given normal mouse IgG (1.65 +/- 0.16 and 6.88 +/- 0.95 microgram/mg, respectively; p < 0.01 in each case). In the glomerulonephritic rats, the increase in the contents of extracellular matrix proteins, especially type I collagen, correlated with increasing glomeruli with expansion of mesangial areas. The increase in type I collagen content correlated well with increasing urinary protein excretion and blood urea nitrogen and serum total cholesterol levels (r = 0.851, 0.812, and 0.837, respectively; p < 0.05 in each case). The decrease in creatinine clearance correlated with increasing content of type I collagen (r = 0.781; p < 0.05). The immunohistochemical micromethod may make it possible to evaluate the histopathological diagnosis of mesangial proliferative glomerulonephritis quantitatively.

[Stereotactic radiosurgery with the gamma knife for brain metastases in patients with lung cancer]

Between February 1992 and April 1993, six patients with lung cancer were treated with gamma knife radiosurgery for brain metastases. Five patients had adenocarcinoma, and one patient had small cell carcinoma. Two patients had solitary metastases, and four patients had multiple metastases. Twelve metastases were treated with the gamma knife (peripheral dose between 12 Gy and 25 Gy). After radiosurgery, three complete and eight partial responses were achieved, which resulted in an overall response rate of 92%. In two patients, histological studies showed that few viable cells were surrounded by necrosis. Neurological status improved in all patients, and none died of complications. However, four of six patients later developed new intracranial metastases outside the treatment field. These data suggest that radiosurgery with the gamma knife is effective against brain metastases in patients with lung cancer, especially when the lesions are deep in the brain.

Immunohistochemical microquantification of fast-myosin in frozen histological sections of mammalian skeletal muscles

Fast-myosin in frozen histological sections was quantified by an immunohistochemical micromethod based on the ELISA. Frozen tissue sections mounted on glass slides were used analogously to the antigen-precoated wells of ELISA plates. The intensity of immunoreactivity of frozen sections to an anti-fast-myosin monoclonal antibody was quantified directly from the color developed with the second antibody coupled with peroxidase using phenol-4-aminoantipyrine as a substrate. Fast-myosin levels in the masseter muscles of pigs, rats, and rabbits were 185 +/- 6, 223 +/- 9, and 178 +/- 12 mg/g of total protein, respectively, and those in the gastrocnemius muscles from cows, pigs, goats, rats, and rabbits were 172 +/- 12, 211 +/- 7, 177 +/- 9, 211 +/- 10, and 205 +/- 10 mg/g, respectively. In the masseter of cows and goats, fast-myosin was not detected. The results obtained by this immunohistochemical micromethod were in good agreement with those obtained by histomorphometrical and biochemical analyses. This immunohistochemical micromethod could be used to quantitatively evaluate the muscle contractile characteristics that determine meat quality.

Role of glucose intolerance in cardiac diastolic function in essential hypertension

Insulin resistance and glucose intolerance have been suggested to be involved in the pathogenesis of various cardiovascular diseases. We examined the role of glucose intolerance in cardiac performance and cardiac hypertrophy in 33 patients with essential hypertension (28 to 71 years of age, mean +/- SD: 53 +/- 13 years) who had never been treated. Patients with obesity (body mass index > 30 kg/m2) or overt diabetes were excluded. Plasma glucose and insulin were measured after oral administration of 75 g glucose. The incremental areas of glucose and insulin were used as indices of glucose intolerance and insulin resistance, respectively. Patients with impaired glucose tolerance according to World Health Organization criteria (n = 12) showed a significantly higher ratio of peak velocity during atrial contraction to early left ventricular filling phase (A/E ratio) than those with normal glucose tolerance (n = 21) despite similar age, blood pressure, and left ventricular mass index. By regression analysis, left ventricular mass index positively correlated with systolic blood pressure (r = .392, P < .05) but not with any parameters of glucose and insulin metabolism. A/E ratio determined by a Doppler system significantly correlated with age ( r = .776) and fasting and peak levels and incremental area of plasma glucose (r = .529, r = .468, and r = .634) but not with those parameters of insulin. In contrast, ejection fraction was not related to blood pressure, glucose tolerance, or insulin resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on beta-lactam antibiotics. IV. An improved synthesis of 3-(isothiazolylthiomethyl)cephalosporins and its application to new derivatives

An improved synthesis and in vitro activity of cephalosporins with a (4-carboxy-3-hydroxy-5-isothiazolyl)thiomethyl group at the 3-position and its application to the preparation of new derivatives are described. These compounds showed excellent activity against Gram-negative bacteria including beta-lactamase producing strains. Among them, 2f was the most interesting because of its broad spectrum of antibacterial activity, including Gram-positive bacteria, and its outstanding inhibitory potency against Pseudomonas aeruginosa.

[Risk factors related to the wall thickness of carotid artery assessed by ultrasonography]

Progression of atherosclerotic lesion of the carotid artery is suggested to induce the development of cerebrovascular events. We evaluate the risk factors related to carotid artery, wall thickness by ultrasonography. A total of 159 patients, who had received no medication for hypertension or hyperlipidemia were enrolled in this study. The wall thickness of carotid artery was evaluated as an intima-media (IM) complex measured by B-mode ultrasonography with a 7.5 MHz probe. Simple regression analysis demonstrated significant correlation between the IM complex and both age and systolic blood pressure, but not with fasting levels of plasma glucose, hemoglobin A1c, total and HDL cholesterol, triglyceride or gender. Stepwise regression analysis showed age and systolic blood pressure contribute to IM thickness (r = 0.623). However, in patients aged 60 or over, blood pressure did not contribute to the IM wall thickness. Smoking was not a risk factor for IM thickness, but the Brinkman Index (daily consumption of cigarettes x years smoking) was significantly higher in patients with plaques in the carotid artery than those without it. These results suggest that high blood pressure is a risk factor for mild atherosclerotic lesions of the carotid artery for those aged under 60. Smoking may contribute to the formation of plaque, which may consequently lead to the ischemic cerebrovascular disease.

Immunohistochemical microquantitation method for type I collagen in kidney histological section of the rats

An immunohistochemical micromethod for quantitation of type I collagen in frozen histological section of rat kidney was developed. A principle of this method is enzyme-linked immunosorbent assay (ELISA). The intensity of immunoreactivity of the section to an anti-type I collagen antibody was quantitated, and then the total protein content in the same section was measured colorimetrically. Type I collagen content was expressed as mg of type I collagen per g of total protein. In this micromethod, the minimum area and optimum thickness of the section were 5 mm2 and 10 microns, respectively. Type I collagen content in the rat kidney section was 3.02 +/- 0.12 mg/g. This method should be useful for diagnosis of renal failure.

A new immunohistochemical method for quantification of fast-myosin in frozen histologic sections of the rat skeletal muscles

An immunohistochemical micromethod for quantification of fast-myosin in frozen histologic sections of rat skeletal muscles was developed. The principle of this method was enzyme-linked immunosorbent assay (ELISA). We used frozen tissue sections as models of the antigen-coated wells of ELISA plate. The intensity of immunoreactivity of the frozen section to an anti-fast-myosin monoclonal antibody was quantified directly from the color developed with the second antibody coupled with peroxidase using phenol-4-aminoantipyrine as a substrate. Then, the same section was incubated in 0.01 M acetic acid solution to cleave antigen-antibody complexes, followed by colorimetric measurement to obtain the absolute value of total protein per section. Fast-myosin content in the frozen tissue section was expressed as mg of fast-myosin per g of total protein. In this micromethod, the minimum area and the optimum thickness of the section were 5 mm2 and 10 microns, respectively. Fast-myosin contents in the extensor digitorum longus and soleus muscles were 185.0 +/- 6.1 and 17.5 +/- 2.4 mg/g, respectively. The results obtained by this micromethod were in good agreement with those obtained by two conventional methods, immunohistochemical morphometry and biochemical determination. This micromethod is useful for a quantitative evaluation of the contractile function of the mammalian skeletal muscles.