Salmonella typhi rpoS mutant is less cytotoxic than the parent strain but survives inside resting THP-1 macrophages

Transcription of the stationary-phase sigma factor RpoS of Salmonella typhi increased in the macrophage. A single rpoS mutant of S. typhi was constructed to analyze the role of RpoS in intracellular multiplication of the bacterium and host cell killing. This mutant was sensitive to starvation, low pH and hydrogen peroxide; however, it could still multiply inside resting macrophages and was less cytotoxic than the wild-type strain. Therefore, S. typhi might produce RpoS-dependent factors which could contribute to host cell death.

Vi-deficient and nonfimbriated mutants of Salmonella typhi agglutinate human blood type antigens and are hyperinvasive

We generated nonfimbriated mutants from both Vi-positive and -negative Salmonella typhi to analyze the role of type 1 fimbriae and Vi-antigen in bacterial invasion. A Vi-defective mutant of S. typhi GIFU 10007-3 was more invasive than the wild-type strain GIFU 10007. The wild-type strain expressing Vi-antigen did not agglutinate both Saccharomyces cerevisiae and human erythrocytes but Vi-defective mutants were able to agglutinate S. cerevisiae and human erythrocytes. Nonfimbriated mutants from Vi-negative GIFU 10007-3 lost the ability to adhere to S. cerevisiae but still could agglutinate human erythrocytes. The Vi-negative mutant increased secreted proteins and became 5-fold more invasive than the wild-type strain. Nonfimbriated Vi mutants became 50-120-fold more invasive than the wild-type GIFU 10007. To determine why nonfimbriated Vi mutants still agglutinate human red blood cells, we searched bacterial proteins that could bind human blood-type antigens. We finally identified a candidate 37 kDa outer membrane protein that recognized fucosyl-galactose, a structure common to blood type A, B and H antigens.

Description of Arthrobacter creatinolyticus sp. nov., isolated from human urine

Three strains of creatinine-hydrolysing bacteria isolated from human urine were characterized taxonomically. They were aerobic, non-spore-forming, Gram-positive rods with the peptidoglycan of the cell wall containing lysine. MK-8 and MK-9 were found to be the major types of menaquinone. The G + C content of the DNA was 66-67 mol%. The 16S rRNA sequence of one strain (GIFU 12498) was determined and aligned with other high-G + C-content Gram-positive rods from different genera. Following phylogenetic analysis, this strain was placed in the genus Arthrobacter. Arthrobacter protophormiae was the most closely related species in the phylogenetic tree, and this species also showed the highest sequence homology value (97%) with GIFU 12498. However, DNA-DNA hybridization indicated that GIFU 12498 did not belong to A. protophormiae (33.8 +/- 3.5% chromosomal similarity). The three urine strains belonged to one species because they shared more than 95% DNA-DNA similarity. It is proposed that these strains are placed in the genus Arthrobacter as a new species, Arthrobacter creatinolyticus sp. nov. The type strain of A. creatinolyticus is GIFU 12498, which has been deposited in the Japan Collection of Microorganisms (JCM) with the accession number JCM 10102.

A T cell activation antigen, Ly6C, induced on CD4+ Th1 cells mediates an inhibitory signal for secretion of IL-2 and proliferation in peripheral immune responses

A T cell activation antigen, Ly6C, is considered to be involved in the autoimmunity of some autoimmune-prone mice; however, the function of Ly6C remains largely unknown. We prepared a rat anti-mouse Ly6C monoclonal antibody (mAb) (S14) that inhibits the proliferation of peripheral T cells stimulated with anti-CD3 mAb in vitro. S14 mAb, the specificity of which is confirmed by a cDNA transfectant, recognizes Ly6C antigen preferentially expressed on a part of CD8+ T cells in peripheral lymphoid organs. The immunohistochemical analysis demonstrates that Ly6C appears on CD8+ T cells in the conventional T cell-associated area of BALB/c but not of nonobese diabetic (NOD) mice, confirming the absence of Ly6C+ T cells in NOD mice. Addition of soluble S14 mAb to the culture does not influence the proliferation of T cells in vitro; however, the S14 mAb coated on the plate clearly inhibits the proliferation and IL-2 production of anti-CD3-stimulated peripheral T cells. The T cells are arrested at the transitional stage from G0/G1 to S+G2/M phases, but they are not induced to undergo apoptotic changes in vitro. This inhibitory signal provided through the Ly6C molecule inhibited IL-2 secretion in a subpopulation of the activated CD4+ T cells. Ly6C is expressed on T cell clones of both Th1 and Th2 cells, but the cytokine secretion from Th1 clones is preferentially inhibited. These results suggest that Ly6C mediates an inhibitory signal for secretion of cytokines from Th1 CD4+ T cells, potentially causing the inhibition of immune response in peripheral lymphoid tissues.

Determination of 23S rRNA sequences from members of the genus Streptococcus and characterization of genetically distinct organisms previously identified as members of the Streptococcus anginosus group

The 23S rRNA gene sequences of eight type strains of the genus Streptococcus were determined. Three species-specific probes for the three members of the Streptococcus anginosus group and one group-specific probe for these three species were designed. The PCR-amplified 23S rRNA gene sequences of 28 clinical strains were examined by hybridization with the four oligonucleotide probes. They were suspected to be members of the S. anginosus group by biochemical tests; however, only 21 strains (75%) hybridized to one of the three species probes. Seven biochemically atypical strains did not hybridize to these species-specific probes. Of the seven strains, three hybridized to the group-specific probe. The 23S ribosomal RNA sequences of these three strains differed by three bases within the 20-base probe area of S. anginosus. The phylogenetic tree of the 16S rRNA of these three strains located them within the branch of S. anginosus. The remaining four strains, which did not hybridize to group- or species-specific probes, had a raffinose-positive and VP-negative phenotype. The probe hybridization results showed that these four strains did not belong to the S. anginosus group and were closely related to S. parasanguis according to partial sequences of their 16S rRNA genes.

A new technique for repairing a blunt injured duodenum

Repairing a blunt injured duodenum remains a problem for surgeons because of the difficulty in early diagnosis, associated organ injuries, and frequent anastomotic site leakage. We have devised a simpler and safer procedure for transecting the ligament of Treitz and performing a debridement of the duodenum The duodenum is freed and exposed by transecting the ligament of Treitz. The injured site is then resected with appropriate debridement. The remnant stumps of the duodenum and the jejunum are anastomosed. The advantages of our method are less invasion, a more physiologic state, and no retention of food in the repaired duodenum. This technique reduces tension in the repaired wound and also reduces mortality and morbidity.

Reduction of cisplatin toxicity and lethality by sodium malate in mice

The effects of oral treatment with sodium malate, an active ingredient of Juzen-taiho-to, on the nephrotoxicity, bone marrow toxicity, hepatotoxicity and gastrointestinal toxicity caused by i.p. administration of 9 doses of 3.0 mg/kg/d cisplatin (CDDP) (on days 3, 4, 5, 6, 7, 8, 10, 11 and 12) were examined in ddY mice inoculated with sarcoma 180 (S-180) cells on day 1 of the study. The CDDP-induced increases in blood urea nitrogen, serum creatinine, serum glutamic-oxaloacetic transaminase, serum glutamic-pyruvic transaminases and relative stomach weight and the decreases in food intake and body weight were inhibited nearly to the control levels without reducing the antitumor activity of CDDP against S-180 by the oral treatment with sodium malate of 12 doses of more than the equimolar amount of CDDP (on days 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14 and 15). However, the CDDP-induced decreases in white blood cell and platelet counts and relative spleen and thymus weight could not be inhibited completely by combination with sodium malate, even at a dose of twice the equimolar amount of CDDP. The sodium malate-induced reduction of CDDP-induced nephrotoxicity and hepatotoxicity was observed after oral administration, as well as with i.p., s.c. and i.v. administration, and the effect was almost the same for each route of administration. Sodium malate also reduced the toxicity induced by high doses of CDDP (4.5, 6.0, 7.5, 9.0 and 12.0 mg/kg/d) at doses of twice the equimolar amount of CDDP. Sodium malate at a dose of 10.68 mg/kg/d (twice as high as carboplatin, CBDCA) did not reduce the nephrotoxicity, bone marrow toxicity, hepatotoxicity and gastrointestinal toxicity caused by i.p. administration of 9 doses of 15.0 mg/kg/d CBDCA on days 3, 4, 5, 6, 7, 8, 10, 11 and 12 in ddY mice inoculated with sarcoma 180 (S-180) cells on day 1 of the study. From this study, it was suggested that sodium malate could become a useful agent for the reduction of CDDP-induced toxicity, particularly nephrotoxicity and hepatotoxicity.

Amplification of rfbE and fliC genes by polymerase chain reaction for identification and detection of Salmonella serovar Enteritidis, Dublin and Gallinarum-Pullorum

Polymerase chain reaction (PCR) primers for O9 antigen (rfbE) and phase 1 flagellin antigen (fliC) were designed for the rapid identification and detection of Salmonella serovar Enteritidis and Dublin. The rfbE primer pairs selectively amplified the rfbE region of group O9 Salmonella serovars. The fliC primer pairs amplified the DNAs of g,m and g,p-type flagellar antigen; Salmonella serovar Enteritidis, Dublin, and Essen. However, DNA from flagellar-negative Salmonella serovar Gallinarum-Pullorum was also amplified. The sensitivity of PCR primer pairs was 10(4) CFU/assay by boiled DNA preparation and 10(2) CFU/assay by proteinase K-treated DNA preparation.

[Clinical evaluation of a reagent for detection of DNA of Mycobacterium tuberculosis complex using the ligase chain reaction (LCR) method]

We evaluated the clinical efficacy of LCR MTB, a reagent developed by Abbott in the USA, in the full automatic ligase chain reaction (LCR) for detection of DNA of M. tuberculosis complex using a thermostable ligase. Using 458 samples isolated from patients with tuberculosis, LCR was compared with a smear method and with a culture method, and was also compared with two other methods of gene amplification, MTD and Amplicor, using 340 and 200 of the 458 samples, respectively. The LCR method detected M. tuberculosis in 49.8% (228/458) of the samples, and was superior to the smear method (31.9%, 146/458) and the culture method (39.1%, 179/458) in sensitivity. The LCR method was also superior to the MTD and Amplicor methods; sensitivity were 37.9% (129/340) for MTD vs. 47.6% (162/340) for LCR, and 56.5% (113/200) for Amplicor vs. 59.5% (119/200) for LCR. These favorable results and the convenience of the LCR method, which enables rapid detection of target genes with a high degree of sensitivity, strongly suggest that LCR MTB is useful as a reagent for detection of M. tuberculosis using nucleic acid amplification.

Laboratory investigation of enteroaggregative Escherichia coli O untypeable:H10 associated with a massive outbreak of gastrointestinal illness

A massive outbreak of gastrointestinal illness occurred in Tajimi city, Gifu prefecture, in June of 1993 in which 2,697 children in elementary and junior high schools developed severe diarrhea. Stool specimens from 30 children with severe protracted diarrhea were studied. Twenty-seven strains of enteroaggregative Escherichia coli (EAggEC) isolated from 12 of 30 patients all belonged to the same serotype, O untypeable (OUT):H10, and showed the same biochemical characteristics and antibiotic susceptibility pattern. These strains were negative for the virulence factors of the four standard categories of diarrheagenic E. coli (enterotoxigenic, enteropathogenic, enteroinvasive, and enterohemorrhagic). However, the isolates showed an aggregative pattern of adherence to HEp-2 cells and had a 60-MDa plasmid and an astA gene, which encodes heat-stable enterotoxin-1 production. These data suggested that the EAggEC serotype OUT:H10 was associated with this massive outbreak of gastrointestinal illness.

Endoscopic lithotomy of common bile duct stones with sublingual nitroglycerin and guidewire

OBJECTIVE

In 21 patients, our objective was the endoscopic removal of common bile duct stones by sphincter dilation with the application of sublingual nitroglycerin.

METHODS

Nitroglycerin 0.3-0.6 mg was needed for proper dilation of the orifice and for successful cannulation of the Dormia basket into the bile duct. Cannulation of the Dormia basket was simplified by placing the guidewire in the common bile duct beforehand. Because of possible stone impaction, a mechanical lithotriptor was applied smoothly in two patients.

RESULTS

Complete stone removal was successful in 18 of the 21 (86%) patients. One patient who developed a mild form of acute pancreatitis recovered in a few days by conservative management with drip infusion of protease inhibitor. Blood pressure dropped transiently in a patient receiving nitroglycerin, but the general condition of the patient was stable.

CONCLUSIONS

This procedure was found to be safe, easy, and effective in extracting common bile duct stones.

[Isolation of Legionella pneumophila from 24 hr-home bath water and an eradication trial of the bacteria from the bath]

Contamination of 24 hr home bath with Legionella pneumophila is recently well recognized. Eradication of the water-bath contamination from L. pneumophila and other bacteria is an important matter to prevent the infection because the 24 hr-bathing facility is widely accepted in Japanese houses. Among the 16 bathing water samples we tested, Legionella pneumophia was isolated from 6 cases (37.5%) when the bathing water was not treated with disinfectants. Number of L. pneumophila increased up to 10(3) cfu/ml and total culturable bacterial counts reached to 10(5) cfu/ml within 5 days when the water was not treated. We selected 5 water baths among 6 positive cases to study the bactericidal effect of chlorine. As a result we concluded that the growth of L. pneumophila in 24 hr-water bath could be stopped by the 2 ppm chlorination program every day.

Hepatic venous injury; a case report of atriocaval shunt by a centrifugal pump

Injury of hepatic vein confluence and retrohepatic vena cava is serious and often fatal. We report one such case that was successfully treated by the Biopump (Medtronic Bio-Medicus, Inc., Eden Prairie, Minn). A 21-year-old man was admitted due to a steering-wheel injury in a motor vehicle accident. CT scan showed extravasated contrast material around the right hepatic lobe, and a large low density area in the right hepatic lobe adjacent to the inferior vena cava, suggesting injury of the hepatic vein confluence or the retrohepatic vena cava. The patient underwent surgical treatment. Laceration of the liver was extended to the hepatic vein confluence. Right hepatic lobectomy and repair of the middle hepatic vein was successfully performed under atriocaval shunting by the Biopump.

Rapid screening of point mutations of the Neisseria gonorrhoeae parC gene associated with resistance to quinolones

To detect quinolone resistance-associated mutations within the Asp-86, Ser-87, Ser-88, and Glu-91 codons of the Neisseria gonorrhoeae parC gene, we developed a rapid and simple assay based on amplification of the regions of the parC gene containing the mutations sites by PCR and digestion of the PCR products with restriction enzymes. By using the method of primer-specified restriction site modification, artificial SalI, PstI, EcoRI, and HinfI restriction sites were created in the regions containing the Asp-86, Ser-87, Ser-88, and Glu-91 codons, respectively. The mutations generating alterations at Asp-86, Ser-87, Ser-88, and Glu-91 were detected as failures of SalI, PstI, EcoRI, and HinfI to digest the respective PCR products. Fifty-five clinical strains of N. gonorrhoeae were examined for mutations in the parC gene by this assay. Appropriate mutations at either the Asp-86, Ser-87, Ser-88, or Glu-91 codon were detected in each of 11 strains in which a mutation had previously been observed by DNA sequencing. This rapid and simple assay could be a useful device for screening genetic alterations in the parC gene associated with resistance to quinolones in N. gonorrhoeae.

Does a long pre-operative hospital stay before hepatectomy improve liver dysfunction in HCC patients with chronic liver disease?

BACKGROUND/AIMS

We retrospectively evaluated whether or not hepatic dysfunction improved in patients with chronic liver disease who had been waiting to undergo a hepatectomy after admission.

MATERIALS AND METHODS

Fifty-two hepatocellular carcinoma patients had been admitted for more than 2 weeks prior to undergoing a hepatectomy. They had a liver function test twice, at admission and just before surgery, during the hospitalization period. Twenty-six of them were histologically diagnosed as having chronic hepatitis while the remainder had liver cirrhosis. In the liver function test, the serum levels of albumin, total bilirubin, glutamic pyrubic transaminase (alanine transaminase), total cholesterol and the Child grade were examined.

RESULTS

First, including the pre-operative treatment cases for small tumors under angiography, the total bilirubin and transaminase levels improved in the chronic hepatitis patients with a statistically significant difference, but no difference was observed in the Child grade. In the examined cirrhotic patients, no significant difference was shown in the tests. Second, after excluding the pre-operative treatment cases, we performed the same investigation as that for chronic liver disease cases and only the transaminase level significantly improved.

CONCLUSIONS

A long pre-operative hospital stay might only by justified in patients with a high level of transaminase corresponding to chronic active hepatitis.

Thymic nurse cells forming a dynamic microenvironment in spontaneous thymoma BUF/Mna rats

Thymic nurse cells (TNCs) were studied using an animal model, BUF/Mna rats, which spontaneously develop benign thymomas of epithelial origin with age. The unusual increment and high availability of TNCs in this thymus enabled us to analyze TNCs directly either in tissue sections or on smears after enzymatic isolation. No structural or phenotypical abnormality in these TNCs was detected as assessed by electron microscopy and immunohistochemistry. Typical TNCs were widely distributed in the cortical areas but not in the medullary areas. They showed characteristic euchromatic bright nuclei and enclosed intra-TNC cells with an investment of relatively light cytoplasm with abundant small vesicles and rough-endoplasmic reticulum. The intra-TNC cells were mostly double positive (CD4+CD8+) cortical thymocytes, though macrophage populations could also be distinguished by their content of membrane-bounded phagosomes, multivesicular bodies and other inclusion bodies, and by their lack of cytoskeletal keratin filaments. High voltage electron microscopy revealed that intra-TNC cells were separated into several compartments by extremely thin internal veils of the TNC processes. The outer veils of the TNCs were continuous with occasional small gaps through which intra-TNC cells could migrate in and out of the compartments. Immunohistochemical analyses revealed that the TNCs per se were positive for MHC class I and class II, keratin and thymulin, but lacked both lymphocyte and macrophage markers. Among all adhesion molecules tested, ICAM-1 was strongly expressed on almost all TNCs. A minority of TNCs also contained either LFA-1 alpha or LFA-1 beta positive cells. These results suggest that TNCs may form a rather dynamic microenvironment for T cell development where either nursing or clearance of thymocytes take place, depending on the cellular components of intra-TNC cells. Macrophage populations may also play crucial roles as the third component within TNCs.

A novel migration pathway for rat dendritic cells from the blood: hepatic sinusoids-lymph translocation

The migration pathways for dendritic cells (DC) from the blood are not yet completely resolved. In our previous study, a selective recruitment of DC progenitors from the blood to the liver was suggested. To clarify the role of the hepatic sinusoids in the migration of blood DC, relatively immature DC and mature DC were isolated from hepatic and intestinal lymph, and intravenously transferred to allogeneic hosts. It was then possible to detect small numbers of DC within secondary lymphoid tissues either by immunostaining for donor type major histocompatibility complex class I antigen or, at much higher sensitivity, for bromodeoxyuridine incorporated by proliferating cells (mainly T lymphocytes), which responded to the alloantigen presented by the administered DC. The intravenously injected DC accumulated in the paracortex of regional lymph nodes of the liver via a lymph-borne pathway. Intravenously injected fluorochrome-labeled syngeneic DC behaved similarly. In contrast, very few DC were found in spleen sections and were hardly detectable in other lymph nodes or in other tissues. An in situ cell binding assay revealed a significant and selective binding of DC to Kupffer cells in liver cryosections. It is concluded that rat DC can undergo a blood-lymph translocation via the hepatic sinusoids, but not via the high endothelial venules of lymph nodes. Hence the hepatic sinusoids may act as a biological concentrator of blood DC into the regional hepatic nodes. Kupffer cells may play an important role in this mechanism.

Survival of Vi-capsulated and Vi-deleted Salmonella typhi strains in cultured macrophage expressing different levels of CD14 antigen

We examined the intracellular survival of Vi-capsulated (lipopolysaccharide; (LPS)-masked) and Vi-deleted (LPS-exposed) Salmonella typhi strains inside macrophage cell lines. Growth of LPS-exposed S. typhi was inhibited in both mouse and human macrophage cell lines. However, the LPS-exposed strain survived in a CD14-deficient mouse macrophage cell lines. Wild-type S. typhi strain, which expressed the Vi antigen and masked LPS, survived in the resting human macrophage cell line. When the Vi-capsulated S. typhi entered the cells, the production of tumor necrosis factor-alpha (TNF-alpha) was suppressed. In contrast, S. typhimurium and LPS-exposed S. typhi stimulated the macrophages to produce a high level of TNF-alpha.

Hepatocyte growth factor and digital clubbing

The cause of digital clubbing is unknown. Hepatocyte growth factor (HGF) is a pleotrophic factor which has various biological effects. We measured serum HGF in 12 patients with digital clubbing; the underlying diseases of these patients were: lung cancer, 2; cystic fibrosis, 2; idiopathic pulmonary fibrosis, 3; lung cancer with idiopathic pulmonary fibrosis, 1; chronic hepatitis, 1; interstitial pneumonia with collagen disease, 2; and bronchiectasis, 1; nine hundred and fifty-seven normal volunteers and 17 lung cancer patients without clubbing served as the control. As a result, the serum HGF concentration in patients with digital clubbing (0.47 +/- 0.29 ng/ml) was significantly higher when compared to that of lung cancer patients without digital clubbing (0.15 +/- 0.04, p < 0.01). Therefore, we suggest that HGF may play a role in the formation of digital clubbing.

Genetic identification of members of the genus Corynebacterium at genus and species levels with 16S rDNA-targeted probes

16S rRNA gene-targeted probes were designed for the identification of corynebacteria at the genus and species levels. The genus-specific probe hybridized all clinically important members of the genus Corynebacterium and could distinguish them from other coryneform bacteria and phylogenetically related high G+C% gram-positive bacteria, including Actinomyces, Rhodococcus, Gordona, Nocardia, Streptomyces, Brevibacterium and Mycobacterium. The species-specific probes for C. jeikeium and C. diphtheriae could differentiated these two species from other members of this genus. The probes were used to select corynebacteria among gram-positive clinical isolates which had been tentatively identified as corynebacteria by biochemical tests. We screened 59 strains with the genus-specific probe; 51 strains hybridized to the genus-specific probe, 8 did not. Of the 51 strains that hybridized to the genus-specific probe, 1 hybridized to the C. diphtheriae species probe and 13 hybridized to the C. jeikeium species probe. The 8 strains that did not hybridize to the genus probe were further characterized by analyzing cell wall diaminopimelic acid and partial 16S rRNA sequencing. The results indicated that these strains were distributed in the genera Arthrobacter and Brevibacterium.

[Antigen retrieval: its significance and drawbacks in immunohistochemistry]

One of the biggest problems in immunohistochemistry has been how to maintain both good morphology and the immunoreactivity of antigens in tissue sections. Various techniques to retrieve the immunoreactivities of antigens (unmasking) after routine tissue preparations, such as fixation, dehydration and embedding, have been devised and are now finding their way into use for immunostainings in not only cytohistological investigations but also pathoclinical diagnoses. In this report, first, the mechanisms and significance of both fixation and antigen retrieval were surveyed from the viewpoint of protein inactivation. Second, some practical problems and notes in two of the most popular unmasking techniques, enzyme digestion and heat-induced epitope retrieval (HIER), were reviewed in order to adapt the techniques precisely in immunohistochemistry. The major artifact induced by fixation is the masking of tissue antigens due to cross-linking among the amino-acid residues of proteins. It is important to choose a proper fixing condition for each antigen considering its biochemical nature and resistance to the fixation. (Table 2), and to keep the fixing conditions to a minimum so that the immunoreactivity of the antigen can be readily retrieved by various unmasking techniques (Table 3, Fig. 1). Antigen retrieval per se is the process causing protein denaturation in tissues, just like many other protein inactivation processes (Table 1). Enzyme digestion may etch the masking parts of proteins around an antigen to expose its epitope. Although enzyme digestion is relatively simple and its treatment condition easy to control, the results are not necessarily dramatic and consistent depending on the types or lots of enzymes. Thus, one must find his/her own digestion manual to achieve the best staining result for each antigen (e.g., Table 4). For example, pepsin digestion gave the best results in the immunostaining of bromo-deoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA), whereas other enzymes had little effect (Table 5). Heating may also cleave the polypeptide backbone and disrupt the cross-links produced by fixation. The heating effect on antigen retrieval is temperature-dependent and seems to be proportional to the product of temperature and time. In the case of PCNA immunostaining on paraformaldehyde-fixed paraffin-embedded sections, heating at 90 degrees C for at least 3 min was required, however, as the heating condition became more severe, non-specific background stains also increased (Table 6), which is one of the most serious problems in antigen retrieval (Fig. 2a, c). One possible choice for avoiding such undesirable results is the combination of suboptimal heating (at 80 degrees C for 10-15 min) and pepsin digestion (Fig. 2b, d). An important theoretical consideration for employing such a dramatic method of denaturation is whether the masked antigen epitopes can be adequately exposed without giving rise to false-positive (or false-negative) results with previously trusted antibodies. It seems that each antigen requires a "tailor-made" tissue preparation for optimal preservation of its antigenicity and precise localization. In accordance with the development of immunology, molecular biology, genetics or embryology, the need for multiple immunostaining in combination with other technologies like in situ hybridization should increase in order to analyze the spatial and functional relationships among various molecules in situ. Antigen retrieval would then become a powerful strategy.

Molecular cloning of rat macrophage-stimulating protein and its involvement in the male reproductive system

Macrophage-stimulating protein (MSP), a member of the hepatocyte growth factor family, is a ligand for receptor tyrosine kinase STK/RON. Here we isolated a full-length cDNA of rat MSP and a partial cDNA of rat STK/RON, then characterized their expression in the male reproductive system. In situ hybridization revealed that MSP mRNA was localized to spermatogonia and spermatocytes in the testis and the epithelium lining the lumen of the epididymis. On the other hand, RT-PCR analysis showed that STK/RON mRNA was expressed in sperm collected from both testis and epididymis. These findings suggest that locally produced MSP may play a vital role in germ cell-germ cell interaction during spermatogenesis as well as in the acquisition of sperm motility and/or fertilizing capacity in the epididymis. Our findings reveal new possible roles of the MSP-STK/RON signaling pathway.