Expression of manganese superoxide dismutase mRNA in reproductive organs during the ovulatory process and the estrous cycle of the rat

Expression of manganese superoxide dismutase (Mn-SOD) mRNA during the pregnant mare serum gonadotrophin (PMSG)/human chorionic gonadotrophin (HCG)-induced ovulatory process, and during the estrous cycle was examined in rat female reproductive organs. Mn-SOD mRNA levels in theca interna cells markedly increased in PMSG-primed rats and high levels of the transcripts were maintained after HCG injection. The PMSG-enhanced expression of Mn-SOD mRNA in follicular epithelial cells increased concomitantly with luteinization of these cells. The levels of Mn-SOD mRNA remained high and became equivalent in both granulosa and theca lutein cells 24 h after HCG injection. Neither luteinization nor the expression of Mn-SOD mRNA was observed in the epithelial cells of unovulated follicles. Luteal bodies had formed 3 days after HCG injection, and the same level of Mn-SOD mRNA expression continued in lutein cells, but not in stromal cells. During the estrous cycle, Mn-SOD mRNA was localized to theca interna cells on proestrus, to the epithelial cells of luteinizing follicles on estrus, and to newly formed luteal bodies on diestrus. The epithelial cells in the oviduct did not express Mn-SOD mRNA throughout the ovulatory process or the estrous cycle. Expression of Mn-SOD mRNA in the luminal epithelial cells of the uterus increased after PMSG injection, reaching a maximum after 24 h, and became relatively negative 3 days after HCG injection when corpora lutea had formed in the ovary. During the estrous cycle, uterine epithelial cells and leukocytes showed marked increases in Mn-SOD mRNA expression on estrus and on proestrus, respectively. Expression in the vaginal epithelium became apparent 3 days after HCG injection and continued for at least 12 days after HCG injection. The expression was localized to the superficial layer of the epithelium. During the estrous cycle, expression occurs in the basal layer on proestrus and estrus, transferring to the superficial layer on diestrus day 1, and expression stops on diestrus day 2. The relationship between the expression of Mn-SOD mRNA and hormone-induced metabolic changes, including steroidogenesis, is discussed.

Antihypertensive and metabolic effects of doxazosin in hypertensive patients with concomitant non-insulin-dependent diabetes mellitus

In this multicentre, non-randomized clinical study, 35 hypertensive patients with concomitant non-insulin-dependent diabetes mellitus were treated with the selective alpha 1 adrenoceptor blocker doxazosin mesilate for 24 weeks, either alone or together with existing antihypertensive therapy. The effects of the drug on blood pressure, glucose and lipid metabolism were examined. Daily administration of 0.5-8 mg doxazosin caused a significant reduction in both systolic and diastolic blood pressure decreased from 172 +/- 15/90 +/- 11 mmHg at the beginning, to 149 +/- 19/80 +/- 12 mmHg at the end of the trial. Heart rate was not affected. The plasma glucose level showed no change, whereas the haemoglobin A1c level decreased significantly from 7.4 +/- 1.2% to 7.1 +/- 1.2% (P < 0.01). Total and high-density lipoprotein cholesterol levels remained unchanged. The triglycerides level, however, decreased from 113 +/- 54 mg/dl at the beginning to 98 +/- 49 mg/dl at the end of the trial (P < 0.05). In a subgroup of patients, who showed hypercholesterolaemia ( > or = 220 mg/dl, n = 9) at the beginning, the total cholesterol level decreased from 252 +/- 33 mg/dl to 220 +/- 33 mg/dl (P < 0.05). Two patients complained of abdominal fullness or diarrhoea, but both were easily manageable. The results indicate that doxazosin is effective and safe in the treatment of hypertension in non-insulin-dependent diabetics and does not affect glucose metabolism. As for lipid metabolism in non-insulin-dependent diabetic patients, doxazosin seems to have a beneficial effect.

Beta-catenin expression in human cancers

Cell-cell adhesion in tissue is mainly regulated by homotypic interaction of cadherin molecules, which are anchored to the cytoskeleton via cytoplasmic proteins, including alpha- and beta-catenin. Although we previously demonstrated that alpha-catenin is crucial for cadherin function in vivo, little is known about the role of beta-catenin. We examined the expression of beta-catenin in human carcinoma samples along with normal tissue (esophagus, stomach, and colon) by immunostaining using our antibody for beta-catenin. Normal epithelium strongly expressed beta-catenin. However, beta-catenin expression was frequently reduced in primary tumors of the esophagus (10 of 15, 67%), stomach (9 of 19, 47%), and colon (11 of 22, 50%). From an immunoprecipitation study, we found that beta-catenin forms a complex with E-cadherin not only in the normal epithelium but also in cancerous tissues. In coexpression patterns of E-cadherin and beta-catenin, 43 (77%) of the 56 tumors showed a similar expression of both molecules, whereas the other 13 tumors (23%) showed positive staining for E-cadherin and reduced expression of beta-catenin. These findings suggest that beta-catenin forms a complex with E-cadherin in vivo and down-regulation of beta-catenin expression is associated with malignant transformation.

Analysis of transmural trend of myocardial integrated ultrasonic backscatter in patients with old myocardial infarction

Changes in myocardial integrated backscatter (IB) reflect myocardial viability in patients with myocardial infarction. IB may be obtained separately in the subendocardial and subepicardial layers to establish a transmural trend. The purpose of this study is to examine the possibilities that the measurement of the transmural trend in myocardial IB may provide a new estimate of transmurality of infarction in patients with old myocardial infarction. A calibrated myocardial IB and its transmural trend were measured both in the septum and posterior wall in 21 normal subjects, 24 patients with anteroseptal old myocardial infarction (13 patients with Q-wave myocardial infarction and 11 patients with non-Q-wave myocardial infarction). The transmural trend in myocardial IB was assessed by measuring the acoustic parameter separately in the right and left ventricular halves of the septum, and in the endocardial and epicardial halves of the posterior wall. The magnitude of cyclic variation of IB (a difference between minimum and maximum peaks) was lower, and calibrated myocardial IB (the maximum value of myocardial IB at end diastole calibrated with the power of Doppler signals from the blood along the same ultrasound beam) was higher in patients with anteroseptal old myocardial infarction in the septum, compared with normal subjects. Among patients with myocardial infarction, the difference in these IB parameters between the right and left ventricular halves of the septum was found only in patients with non-Q-wave myocardial infarction. The transmural trend of myocardial IB was likely to reflect the transmurality of myocardial infarction. Therefore, our data give another insight into the assessment of transmural inhomogeneity of myocardial fibrosis or viability in patients with myocardial infarction.

Is the presence of hyperlipidemia associated with impairment of endothelium-dependent neointimal relaxation after percutaneous transluminal coronary angioplasty?

To determine whether hyperlipidemia affects the endothelium-dependent vasomotor response along the dilated vessel after percutaneous transluminal coronary angioplasty (PTCA), we evaluated 32 patients with one-vessel disease, 3-6 months after successful PTCA without restenosis. Fourteen patients had mild stenotic lesions not subjected to PTCA (non-PTCA sites) in addition to the PTCA sites. Vessel diameter changes at 32 PTCA and 36 non-PTCA sites were assessed by quantitative angiography, before and after intracoronary injection of acetylcholine (20 micrograms to the right and 50 micrograms to the left coronary artery) and of nitroglycerin (0.1-0.3 mg). The acetylcholine response ranged from 46% (dilation) to -100% (constriction). All coronary arteries were dilated in response to nitroglycerin, which suggested preservation of the function of vascular smooth muscle, and the presence of an abnormality in endothelial function in those patients with a constrictor response to acetylcholine. There was a negative correlation between the acetylcholine response and the serum total cholesterol level at PTCA sites (r = -0.37; P = 0.038) and at non-PTCA sites (r = -0.46; P = 0.005). These findings indicate that hyperlipidemia is associated with a loss of endothelium-dependent vasodilation, not only at non-PTCA but also at PTCA sites, at which restoration of endothelial function might have occurred. They also suggest that hyperlipidemia may be related to the functional state of the regenerated endothelium at sites where PTCA had been previously performed.

Lack of immunoreactivity for myoglobin in skeletal muscle of acute stroke patients

Sternothyroid muscle biopsy specimens, obtained during tracheostomies from 15 patients with acute stroke and respiratory failure, were examined immunohistochemically to immunoreactivity to myoglobin (Mb). A marked decrease or lack of Mb immunoreactivity in association with hyaline degeneration was observed in 0.8 to 44.4% of the muscle fibers on both the paretic and non-paretic sides of all patients. The percentages of negative staining for Mb were less than 3.1% in 5 patients with acute respiratory failure due to causes other than stroke. The pattern and incidence of attenuated Mb immunoreactivity in the muscle fibers was found to be distinctively different in the two patients groups. In one group of 5 patients, a large number of muscle fibers (24.8 +/- 15.6%) had no Mb staining and were clearly bordered and grouped. In another 10-patient group, only a limited number of muscle fibers (3.3 +/- 2.5%) had no staining for Mb and these fibers were scattered. Four patients in the former group had catastrophic outcomes, while all the patients in the latter group survived. Ischemia, produced by an increase in catecholamines, and the consequent vasoconstriction, rather than hypoxemia seemed to be the cause of the negative immunoreactivity for Mb in the group pattern. In contrast, hypoxemia may have caused the scattered pattern of negative Mb immunoreactivity. It was concluded that negative immunostaining for Mb in muscle fibers represents a common and characteristic complication in acute stroke patients.

Successful treatment of bronchial mucoepidermoid carcinoma in an 11-year-old boy by bronchoplasty: report of a case

We report herein the rare case of an 11-year-old boy in whom mucoepidermoid carcinoma of the right upper lobe bronchus was successfully treated by bronchoplasty. The patient underwent bronchoscopy to investigate the cause of relapsing respiratory infections over the past 2 years, which revealed a tumor at the orifice of the right upper lobe bronchus. Thus, a right upper sleeve lobectomy was effectively carried out, preserving right pulmonary function. The tumor was observed to partially invade the bronchial wall, but not the lung parenchyma. Histological examination confirmed a diagnosis of mucoepidermoid carcinoma, classified as grade 2 by Conlan's classification. The patient has been well and free of recurrence for 3 years postoperatively.

Influence of preload, afterload, and contractility on myocardial ultrasonic tissue characterization with integrated backscatter

Influence of hemodynamic changes in preload, afterload and contractility on myocardial integrated backscatter (IB) was studied in 26 adult mongrel dogs by measuring myocardial IB calibrated with the backscatter from the blood during volume infusion (preload alteration), during aortic constriction (afterload alteration), and during dobutamine or propranolol infusion (contractility alteration). Changes in preload, afterload or contractility did not significantly affect the calibrated myocardial IB either in the septum or in the posterior wall. Changes in preload and afterload did not affect the magnitude of cyclic variation in IB. However, dobutamine produced a significant increase in the magnitude of cyclic variation in IB and propranolol significantly decreased the magnitude of cyclic variation in IB. These data indicated that the calibrated myocardial IB is independent of preload, afterload and contractility, and that the magnitude of cyclic variation in IB is influenced by contractility. We may estimate static (related to histological changes such as fibrosis, edema, necrosis, and so on) and dynamic (related to myocardial contraction such as sarcomere length, muscle fiber orientation, and so on) properties of the myocardium more precisely using myocardial IB calibrated with the backscatter from the blood in addition to the magnitude of cyclic variation in IB.

Use of enzyme-linked-immunosorbent assay for detection of IgG and IgM antibodies to Fusobacterium necrophorum in cattle

An enzyme-linked-immunosorbent assay (ELISA) with HCl heat-extracted antigen of Fusobacterium necrophorum was conducted to detect specific immunoglobulins G and M in infected cattle. The ELISA revealed an increase (> 0.40) in specific IgG in most of the animals with hepatic abscesses but not that in specific IgM. All the lesions were positive for F. necrophorum. These findings indicated that the ELISA for immunoglobulin G detection may prove to be a useful tool for predictive serodiagnosis of F. necrophorum infection in cattle.

Mechanism that regulates nitric oxide production by lipopolysaccharide-stimulated rat Kupffer cells

Mechanism that regulates nitric oxide (NO) production by stimulated Kupffer cells was studied. Lipopolysaccharide (LPS) stimulated NO production by primary-cultured Kupffer cells in a time- and dose-dependent manner. Twenty-four h after incubation with 1 microgram/ml of LPS, the nitrite concentration in the culture medium increased from 2.87 +/- 1.4 to 73.6 +/- 6.9 nmol/ml. NO production started to increase around 6 h after adding LPS and reached a maximum within 24 h. NO production was inhibited by 0.3 mM of NG-monomethyl-L-arginine and was reversed by adding 3 mM of L-arginine. When incubated with 1 microgram/ml of LPS for 24 h, NO synthase activity in Kupffer cells increased from 0.164 +/- 0.035 to 3.16 +/- 0.11 nmol/min/mg protein. Dexamethasone and prednisolone significantly inhibited the induction of NO synthase and NO production in Kupffer cells. Expression of mRNA for inducible type of NO synthase (iNOS) started to increase around 4 h after adding LPS (1 microgram/ml) and reached a maximum by about 20 h. The enhanced expression of iNOS mRNA was also suppressed by 1 microM dexamethasone. On the other hand, calcium ionophore A23187 significantly enhanced the induction of NO synthase and iNOS mRNA expression in LPS-stimulated Kupffer cells. In addition, a tyrosine kinase inhibitor, genistein (100 microM), significantly inhibited NO production by LPS-stimulated Kupffer cells. Neither phorbol 12-myristate 13-acetate, dibutyryl cAMP, indomethacin nor a protein kinase C inhibitor H-7 affected NO production by Kupffer cells. These results suggested that iNOS mRNA expression, NO synthase activity and NO production increased in LPS-stimulated Kupffer cells by a glucocorticoid-inhibitable mechanism and that Ca2+ and tyrosine phosphorylation might play important roles in LPS-dependent induction of NO synthase.

Microsatellite instability and alterations in the hMSH2 gene in human ovarian cancer

The role of the replication error-positive (RER+) phenotype in the development of specific subtypes of sporadic ovarian carcinomas was examined by screening for the presence of microsatellite instability (MI) in 47 tumors. The overall frequency of ovarian MI was 17% only. However, MI occurred in 50% of the ovarian endometrioid-type tumors, which was significantly more often than in all the other histological subtypes combined (8%). Five of the 8 RER+ tumors exhibited most marked type I instability, possibly representing a different mechanism than for the remaining type 2 tumors. The cDNA of the mutation suppression gene hMSH2, the gene most often associated with MI, was screened for alterations in 8 MI-positive and 5 MI-negative ovarian tumors. Only 3 changes were found. Complete loss of hMSH2 mRNA expression was detected in I tumor, while another expressed only an abnormal transcript containing a deletion of exon 3. One additional RER+ serous adenocarcinoma contained a rare polymorphism with a non-conservative amino acid change. One of 8 RER+ tumors showed loss of heterozygosity at the hMSH2 loci. Genetic instability, caused in part by alterations in the hMSH2 gene, may play an important role in the sporadic endometrioid subtype of ovarian tumors. Other mutator-phenotype genes may be responsible for the remaining cases of RER+ ovarian tumors.

Effect of inhibin, follistatin, or activin infusion into the lateral hypothalamus on operant behavior of rats fed lysine deficient diet

To identify brain mechanisms which mediate hunger for amino acid (e.g. L-lysine; Lys) deficiency, rats were trained to bar press (FR30 schedule) to receive 50 mg pellets of a complete diet. Rats given a lysine deficient (Lys-def) diet ad libitum maintained a high rate of bar pressing but when allowed ad libitum access to 0.4 M Lys to drink had a significant decrease in pressing. Also, Lys continuously infused by minipump into the lateral hypothalamic area (LHA) inhibits pressing by rats given a Lys-def diet. The threshold maximal dose is between 0.1-0.5 nmol Lys/h. Therefore, animals lacking dietary Lys will work to receive complete diet, but replacement of Lys by voluntary consumption or by direct infusion into the LHA inhibits bar pressing for complete diet. The ratio of brain activin and inhibin may modulate motivation to work for a complete diet, since continuous inhibin or follistatin, but not activin, infusion into the LHA was found to inhibit bar pressing, which is normally quite strong in rats maintained on Lys-def diet. The inhibitory effect of LHA inhibin infusion was replicated, and concurrent availability of Lys solution ad libitum was additive with LHA inhibin infusion to depress responding further. This inhibitory effect of inhibin or follistatin did not result from altered ad lib. consumption of Lys-def diet. Although LHA Lys infusion did decrease consumption of a concurrently available Lys solution, inhibin did not change ad libitum Lys consumption. This indicates that inhibin may work in the LHA to inhibit bar pressing for complete diet via other mechanisms than sensation of Lys deficiency.

[Penetrating injury of the head, neck and chest by a nail-gun: a case report]

A very rare case of directly penetrating injury of the head, neck and chest caused by a nail-gun was reported. A 56-year-old male was admitted to our critical care center due to chest injury. On admission, he showed numbness of the hand & leg, left hemiparesis and hypalgesia. Physical examination disclosed three nails on the left anterior chest, but other wounds or nails were not found. Chest films showed three nails penetrating the lung without reaching the heart, but other nails were found by skull and neck films. One nail had penetrated the cervical canal at the C1 level through the posterolateral cervical region. Two other nails were demonstrated at the right temporal and the left frontal region, Computed tomography revealed no massive cerebral hemorrhage and cerebral angiography showed no extravasation and no passage through main vessels. Emergency surgery was performed uneventfully and the nails in the chest, neck and head were totally removed. He was discharged one month after surgery. Some injuries caused by a nail-gun have been reported in the world literature but in Japan this multiple injury case was the first reported. Since nail-gun injuries can cause multiple damage, systemic X-ray examination was very important.

Adoptive immunotherapy of poorly immunogenic tumors with in vitro sensitized cells generated by intratumoral administration of biological response modifiers

We investigated the efficacy of intratumoral administration of biological response modifiers (BRM) in induction of in vitro sensitized (IVS) cells for adoptive immunotherapy of the poorly immunogenic MCA 102 sarcoma and B16-BL6(BL6) melanoma. We used the bacterial immunoadjuvant Nocardia rubra cell wall skeleton (N-CWS), and a streptococcal preparation, OK-432, for MCA 102 and BL6, respectively. After C57BL/6(B6) mice were inoculated subcutaneously (s.c.) with viable MCA 102 or BL6 tumor cells in the foot-pad, mice were injected intratumorally (i.t.) with N-CWS ranging from 10 to 400 micrograms or OK-432 ranging from 1 to 100 micrograms. Draining popliteal lymph nodes (LN) were harvested 7 days after i.t. administration of BRM, and LN cells were cultured with irradiated tumor cells in the presence of IL-2 for 11 days. These IVS cells (7.5 x 10(6) or 2 x 10(6)) were transferred intravenously (i.v.) to B6 mice with 4 day pulmonary metastases established by i.v. injection of viable MCA 102 cells (1 x 10(6)) or viable BL6 cells (3 x 10(5)). The mice were also received intraperitoneally 4 x 10(4) IU/day of IL-2 for 4 days after adoptive transfer. The transfer of IVS cells from mice immunized by i.t. injection of 100 micrograms of N-CWS 1 week after inoculation of tumor cells significantly reduced MCA 102 pulmonary metastases, compared with control IVS cells without administration of N-CWS. Moreover, the transfer of IVS cells from mice immunized by i.t. injection of 10 micrograms of OK-432 3 days after inoculation of tumor cells significantly reduced BL6 pulmonary metastases compared with control IVS cells without administration of OK-432. The administration of N-CWS resulted in no enhancement of in vitro cytotoxicity. Although the administration of 10 micrograms of OK-432 augmented in vitro cytotoxicity of IVS cells against BL6, cytotoxic activity was lower than that of IVS cells immunized with N-CWS. The major phenotype was CD8+ cells in IVS cells immunized with N-CWS or OK-432. These results suggest that i.t. administration of N-CWS and OK-432 facilitates the production of sensitized T-cells, and this administration route of BRM may be useful in the adoptive immunotherapy of human cancer.

[Diagnostic assistance system based on possibility for evaluation of long bone tumorous lesions]

We constructed a diagnostic assistance system for long bone lesions using a relational data base management system, in which we categorized radiographic findings of all parameters in various lesions and stored them as degrees of possibility. Possible diagnoses of unknown lesions were listed by max-min calculation between the data base and findings of the lesions. Integration of parameters narrowed the scope of possible diagnoses. Fifty-six cases with long bone lesions were tested. Experts diagnosed correctly up to 64 percent, while the system showed a correct diagnosis rate of 43 percent as the first rank of possibility. However, the system gave 75 percent correct diagnosis when listed up to the third rank, and this increased up to 100 percent at the ninth rank. The rate of true diagnosis by experts did not exceed 73 percent. The diagnostic assistance system based on possibility analysis proved to be useful for suggesting differential diagnoses in diagnosing long bone tumorous lesions from plain radiographs.

Characterization of a new plasmid-mediated extended-spectrum beta-lactamase from Serratia marcescens

A new extended spectrum beta-lactamase was detected in Serratia marcescens 42039 that was isolated from urine of patients with complicated urinary tract infection in Japan. This stain produced three different beta-lactamase types (TEM-1, a cephalosporinase, and a new beta-lactamase: CKH-1). The TEM-1 and CKH-1 encoding genes were conjugated from S. marcescens 42039 to Escherichia coli K-12 at frequencies of 10(-5) to 10(-6). The MICs of beta-lactams against the transconjugant were: ampicillin > 1600, piperacillin 800, cephalothin 1600, ceftazidime 6.25, cefotaxime 100, and ceftriaxone 200 micrograms/ml. The CKH-1 enzyme was purified to more than 90% by ion-exchange chromatography. The molecular weight of purified CKH-1 was 30 K dalton and the isoelectric point was 8.2. Relative Vmax/Km values (cephaloridine = 100) of penicillin G, cephalothin, and oxyiminocephalosporins such as cefuroxime, ceftriaxone, and cefotaxime, were 256, 226, 116, 87, and 49, respectively. The I50 values of tazobactam, BRL-42715, and clavulanic acid against CKH-1 enzyme were 0.0011, 0.0002, and 0.097 microM respectively. The enzymatic activity of CKH-1 was not inhibited by EDTA and anti-TEM-1 serum. These findings indicate that CKH-1 is a member of the groups of class A beta-lactamases. This is the first report of a plasmid-mediated oxyiminocephalosporin hydrolyzing broad-spectrum beta-lactamase from clinical isolates of S. marcescens.

Action of endothelins on hepatic stellate cells

To elucidate the role played by hepatic sinusoidal cells in the regulation of the circulatory status in the liver, the effect of endothelins (ETs) on primary-cultured stellate cells was examined. Kinetic analysis with 125I-labeled ET-1 revealed that stellate cells have ET receptors with a Kd value of 141 pM and a Bmax of 12.3 fmol/10(5) cells. ET-1, -2, and -3 dose-dependently increased inositol monophosphate (InsP) levels in stellate cells with an EC50 of 0.53, 1.63, and 1.88nM, respectively. Binding of 125I-labeled ET-1 to stellate cells and the ET-enhanced InsP formation were suppressed by preincubating the cells with 10 nM of unlabeled ET-1 or ET-3 for more than 3 h, indicating down-regulation and desensitization of ET receptors by homologous ligands. Binding of ETs to surface receptors induced a marked contraction of stellate cells. Stellate cells rapidly reacted to ETs, as detected by the flexible silicone-rubber-membrane method; 78%, 73%, and 58% of the stellate cells contracted 2.5 min after the addition of 10 nM of ET-1, ET-2, or ET-3, respectively. On the other hand, ETs also triggered a long-lasting contraction of the cells, as revealed with hydrated collagen gels. The ET-induced contraction of stellate cells decreased the diameter of the collagen lattice by about 60%, and this action was inhibited either by cytochalasin B or by H-7, a protein kinase C inhibitor. These and other results suggest that ETs induced cell contraction by some mechanism that involved protein kinase C.

Reliability of the task-related component (P3b) of P3 event-related potentials

Within session and between session reliabilities of the task-related component (P3b) of the P3 measures (amplitude, area and latency) and their habituation across eight sessions separated by 7-10 days, except for an interval of 1 month between the 6th and 7th sessions, were studied based on the difference waves, which were obtained by subtracting the ignored infrequent event-related potentials (ERP) from the target ERP elicited by a standard auditory oddball paradigm with eyes-open or eyes-closed conditions in 10 normal subjects. The within session reliabilities represented as Pearson correlation coefficients (r) were 0.57-0.66 for the three measures except for those for the latency and amplitude under the eyes-closed condition. The between session reliabilities expressed as intraclass correlation coefficients (R) ranged from 0.54 to 0.60 except for that for latency under eyes-closed conditions. Long-term habituation occurred within the first six sessions for the P3b amplitude and area, and dishabituation took place in the 7th session after an interval of 1 month, whereas no such phenomenon was observed for the P3b latency. Implications of the present results are discussed in terms of the clinical application of the P3 measures.

Autolysis of methicillin-resistant Staphylococcus aureus is involved in synergism between imipenem and cefotiam

Imipenem-induced autolysis and the activity of imipenem plus cefotiam were studied in 16 strains of methicillin-resistant Staphylococcus aureus (MRSA). The degree of imipenem-induced autolysis and the rate of synergistic action of imipenem plus cefotiam varied among strains and did not correlate with susceptibility to either imipenem or cefotiam. However, the degree of autolysis correlated well with susceptibility to the synergistic action of imipenem plus cefotiam. In methicillin-susceptible S. aureus strains, both imipenem-induced autolysis and the synergistic activity of the combined drugs were less than those observed in MRSA strains. Differences in the degree of autolysis were not due to differences in autolytic enzyme production. The autolysis of imipenem-pretreated MRSA was enhanced further by cefotiam, while treatment of cells in the reverse order did not enhance autolysis. These findings indicate that cell wall impairment in MRSA is caused by exposure to imipenem but not to cefotiam and that this difference in drug actions results in synergism between imipenem and cefotiam. The possible participation of penicillin-binding proteins PBP 2' and PBP4 in the observed effect is discussed.