Genetic analysis of type 5 capsular polysaccharide expression by Staphylococcus aureus

Capsules are produced by over 90% of Staphylococcus aureus strains, and approximately 25% of clinical isolates express type 5 capsular polysaccharide (CP5). We mutagenized the type 5 strain Reynolds with Tn918 to target genes involved in CP5 expression. From a capsule-deficient mutant, we cloned into a cosmid vector an approximately 26-kb EcoRI fragment containing the transposon insertion. In the absence of tetracycline selection, Tn918 was spontaneously excised, thereby resulting in a plasmid containing 9.4 kb of S. aureus DNA flanking the Tn918 insertion site. The 9.4-kb DNA fragment was used to screen a cosmid library prepared from the wild-type strain. Positive colonies were identified by colony hybridization, and a restriction map of one clone (pJCL19 with an approximately 34-kb insert) carrying the putative capsule gene region was constructed. Fragments of pJCL19 were used to probe genomic DNA digests from S. aureus strains of different capsular serotypes. Fragments on the ends of the cloned DNA hybridized to fragments of similar sizes in most of the strains examined. Blots hybridized to two fragments flanking the central region of the cloned DNA showed restriction fragment length polymorphism. A centrally located DNA fragment hybridized only to DNA from capsular types 2, 4, and 5. DNA from pJCL19 was subcloned to a shuttle vector for complementation studies. A 6.2-kb EcoRI-ClaI fragment complemented CP5 expression in a capsule-negative mutant derived by mutagenesis with ethyl methanesulfonate. These experiments provide the necessary groundwork for identifying genes involved in CP5 expression by S. aureus.

A requirement of hydrophobic and basic amino acid residues for substrate recognition by Ca2+/calmodulin-dependent protein kinase Ia

The substrate recognition determinants of Ca2+/calmodulin-dependent protein kinase Ia were investigated by using peptide analogues based on the amino acid sequence around Ser-9 of synapsin I. The Km and Vmax for the synthetic peptide Leu-Arg-Arg-Arg-Leu-Ser-Asp-Ala-Asn-Phe are 3.9 microM and 18.5 mumol/(min.mg), respectively. Deletion of Leu at the -5 position lowers the Vmax/Km by 470-fold. The requirement for a hydrophobic residue at -5 was confirmed by the 90- to 2400-fold reduction in Vmax/Km produced by Arg, Ala, or Asp substitutions, but only 2.6-fold decrease after Phe substitution at this position. A hydrophobic residue is similarly required at the +4 position. Deletion of Phe at this position produces a 67-fold reduction, and substitution of Ala for Phe a 43-fold reduction in Vmax/Km. In contrast, substitution with Leu increases Vmax/Km by 1.8-fold. Arg at -3 is also required for recognition as shown by an approximately 240-fold decrease in Vmax/Km after Ala substitution at this position. Positions -2, -4, and +1 appear to play secondary roles in substrate recognition. Arg at -2 and -4 are positive determinants, since Ala substitution at these positions decreases Vmax/Km by 4.7- and 11-fold, respectively. Asp at +1 is a negative influence, since Ala and Leu substitutions at this position increase Vmax/Km by 2.3- and 6.3-fold, respectively. Substitution of Ala for Leu at -1 or Thr for Ser at the 0 position has little effect on phosphorylation kinetics. Thus, Ca2+/calmodulin-dependent protein kinase Ia has the minimal substrate recognition motif of Hyd-Xaa-Arg-Xaa-Xaa-(Ser*/Thr*)-Xaa-Xaa-Xaa-Hyd, where Hyd represents a hydrophobic amino acid residue.

Random amplified polymorphic DNA polymerase chain reaction (RAPD PCR) fingerprints in forensic species identification

The random amplified polymorphic DNA (RAPD) method was used to identify the species of forensic biological samples. Neither genomic DNA sequence nor two polymerase chain reaction (PCR) cycle programs is required. Only single 10-nt primer and one PCR program are used. We demonstrated that this method can be used to identify animals including bovine, goat, pig, dog, rat, rabbit, chicken, duck, and human by comparing their RAPD PCR fingerprints. This study provides a simple, fast and sensitive fingerprinting method in species identification for crime scene evidence or food products of endangered species.

Hyperammonemic encephalopathy due to essential amino acid hyperalimentation

Hyperammonemic encephalopathy has occasionally been reported in uremic patients receiving hyperalimentation with essential amino acid (EAA) as a source of nitrogen as one of the remaining treatment options when the enteric routes were prohibited. We encountered this complication in a patient with normal renal function. A rat animal model was designed to elucidate the mechanism of hyperammonemia resulting from hyperalimentation with EAA as a source of nitrogen. Sixty-four male Long-Evan rats were divided into eight groups receiving feeds ad libitum or different formula of hyperalimentation. Hyperammonemia was found in every rat given hyperalimentation with EAA as the only nitrogen source. Using the Tukey honestly significant difference test, the results were significantly higher (p < 0.001) than that of the control group which were given feeds ad libitum and those groups given hyperalimentation for the same number of days but with mixed amino acid (MAA) as the nitrogen source. Adding arginine to EAA for a further four days after initial administration of EAA hyperalimentation for three days only slightly lowered the mean serum ammonia level. When compared to that of the three-day EAA hyperalimentation group, the difference was not statistically significant. Adding arginine, citrulline, and ornithine to EAA for a further four days significantly lowered the mean serum ammonia level. When we changed EAA hyperalimentation to MAA hyperalimentation for a further four days, the mean serum ammonia level decreased dramatically to nearly normal. Hyperalimentation using EAA as the exclusive source of nitrogen resulted in hyperammonemia. A deficiency of arginine or other amino acids of the urea cycle failed to account completely for the hyperammonemia observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of the tumour suppressor gene p53 in nasopharyngeal carcinoma in Hong Kong Chinese

This study has investigated the expression of the p53 tumour suppressor gene in 41 cases of primary nasopharyngeal carcinomas (NPC) using the p53 monoclonal antibody BP53-12. Moderate p53 expression was found in 54% and strong expression in 12% of the specimens. There was no correlation between p53 expression and any of the clinicopathological parameters or survival. Surprisingly, three research groups have investigated p53 mutations in NPC and found no fresh tumour specimens to contain p53 mutations in exons 4-8 of the gene. It may be argued that as p53 overexpression has been demonstrated in 70% of the patients investigated in this study, that the mutations lie outside the 4-9 exon region. We are in the process of testing this hypothesis.

Radiolabeled polymerase chain reaction assay for detection of ras oncogene point mutations in tumors

The human ras gene plays a fundamental role in the transduction of extracellular signals to the nucleus, thereby regulating cell growth and differentiation. Point mutations in the ras gene convert it into a transforming oncogene that has been found in many solid and hematologic malignancies. We describe a rapid and sensitive assay based on a radiolabeled polymerase chain reaction followed by restriction enzyme digestion that we have adapted for differentiating between the wild-type and mutant ras genes. This assay should prove useful in the analysis of ras gene point mutations in clinical tumor specimens in which ras oncogene activation is an early event in carcinogenesis.

Radiolabeled polymerase chain reaction assay for detection of ras oncogene point mutations in tumors

The human ras gene plays a fundamental role in the transduction of extracellular signals to the nucleus, thereby regulating cell growth and differentiation. Point mutations in the ras gene convert it into a transforming oncogene that has been found in many solid and hematologic malignancies. We describe a rapid and sensitive assay based on a radiolabeled polymerase chain reaction followed by restriction enzyme digestion that we have adapted for differentiating between the wild-type and mutant ras genes. This assay should prove useful in the analysis of ras gene point mutations in clinical tumor specimens in which ras oncogene activation is an early event in carcinogenesis.

Electrostatic forces contribute to interactions between trp repressor dimers

The trp repressor of Escherichia coli (TR), although generally considered to be dimeric, has been shown by fluorescence anisotropy of extrinsically labeled protein to undergo oligomerization in solution at protein concentrations in the micromolar range (Fernando, T., and C. A. Royer 1992. Biochemistry. 31:3429-3441). Providing evidence that oligomerization is an intrinsic property of TR, the present studies using chemical cross-linking, analytical ultracentrifugation, and molecular sieve chromatography demonstrate that unmodified TR dimers form higher order aggregates. Tetramers and higher order species were observed in chemical cross-linking experiments at concentrations between 1 and 40 microM. Results from analytical ultracentrifugation and gel filtration chromatography were consistent with average molecular weight values between tetramer and dimer, although no plateaus in the association were evident over the concentration ranges studied, indicating that higher order species are populated. Analytical ultracentrifugation data in presence of corepressor imply that corepressor binding destabilizes the higher order aggregates, an observation that is consistent with the earlier fluorescence work. Through the investigation of the salt and pH dependence of oligomerization, the present studies have revealed an electrostatic component to the interactions between TR dimers.

Altered mechanical responses of malignant hyperthermic skeletal muscle during repetitive stimulation

This investigation examined the mechanical responses of malignant hyperthermic (MH) and normal porcine skeletal muscle to repetitive stimulation. Twitch and maximal tetanic tensions were not significantly different between muscle types. Tensions produced during stimulation at 20-80 Hz were significantly less in MH muscle than in normal muscle. In addition, MH muscle showed significantly greater force decline (tetanic fade) at the end of contractions evoked by 20-80 Hz stimulation. When stimulated to fatigue, both normal and MH muscle exhibited similar rates of tension decline during the initial minutes. Further stimulation caused additional decline in normal muscle, but a tension plateau in MH muscle. In all cases, normal muscle had greater magnitudes of fatigue than did MH muscle. Results show that there are marked differences between MH and normal muscle in the mechanical responses to repetitive stimulation. Due to its inability to properly regulate intracellular Ca2+ exchange, it is possible that MH muscle might be a useful tool for identifying the mechanisms of muscle fatigue in normal muscle.

Construction of a dimeric repressor: dissection of subunit interfaces in Lac repressor

Formation of the lactose repressor tetramer is postulated to involve two subunit interfaces, one primarily contributing to monomer-monomer assembly to dimer and the second to dimer-dimer association to tetramer. The latter interface requires a heptad repeat of three leucines at the C-terminus of lac repressor that is presumed to form an abbreviated coiled-coil motif [Chakerian, A. E., Tesmer, V. M., Manly, S. P., Brackett, J. K., Lynch, M. J., Hoh, J. T., & Matthews, K. S. (1991) J. Biol. Chem. 266, 1371-1374; Alberti, S., Oehler, S., von Wilcken-Bergmann, B., Krämer, H., & Müller-Hill, B. (1991) New Biol. 3, 57-62; Chen, J., & Matthews, K. S. (1992) J. Biol. Chem. 267, 13843-13850]. To strengthen the dimer-dimer interface, this motif was extended by the addition of one and two leucine heptad repeat units to the C-terminus by site-specific insertion mutagenesis. The tetrameric products displayed operator and inducer affinity essentially indistinguishable from the wild-type repressor. In order to probe the effect of the elongated coiled-coil on assembly of the repressor tetramer, the other of the two postulated subunit interfaces was disrupted by introducing a point mutation (Y282D) that yields a monomeric protein in the wild-type background. Both elongated mutant repressors were able to assemble into dimeric species, apparently due to the strengthened subunit association at the C-terminal region compared to the wild-type repressor. These results further confirm the role of a coiled-coil structure in the formation of tetramer in the lac repressor.(ABSTRACT TRUNCATED AT 250 WORDS)

A protein activator of Ca(2+)-calmodulin-dependent protein kinase Ia

A protein activator of Ca(2+)-calmodulin-dependent protein kinase Ia (CaM kinase Ia) was purified to near homogeneity from pig brain. In the final step of purification, sucrose density gradient centrifugation, CaM kinase Ia activating activity correlated with the presence of a approximately 52-kDa protein band detected by SDS-polyacrylamide gel electrophoresis. Comparison of this value with estimations of its molecular mass under nondenaturing conditions indicated that CaM kinase Ia activator is a slightly asymmetric monomer. After removal of endogenous CaM kinase Ia activator, the activity of CaM kinase Ia was 2% of its activity in the presence of a maximally stimulating concentration (15 nM) of the purified activator. In its activated state, CaM kinase Ia retained complete dependence of its activity upon Ca(2+)-CaM. The activation of CaM kinase Ia was rapid (t1/2 < 1 min) and required the combined presence of CaM kinase Ia activator, Ca(2+)-CaM, and MgATP. Similarly, in addition to MgATP, the phosphorylation of CaM kinase Ia required CaM kinase Ia activator and Ca(2+)-CaM. CaM kinase Ia activator was capable of Ca(2+)-dependent binding to CaM-Sepharose. The requirement of the combined presence of CaM kinase Ia activator, Ca(2+)-CaM, and MgATP for both the activation and phosphorylation of CaM kinase Ia is discussed in terms of potential mechanisms for CaM kinase Ia activation.

[The development of German social medicine in the nineteenth century]

In his influential treatise System einer vollständigen medizinischen Polizey, Johann Peter Frank (1745-1821) made significant contributions to the establishment of the concept of medical police, which has been understood as the forerunner of social medicine. Cameralism, the German version of mercantilism, became the very basis on which Frank and other German writers developed the framework of medical police. 'Medical reform' was the catchword of German medical men in the 1840s. The medical reform movement of 1848 was partially caused by a deep political, economic, and social crisis. Although Industrial Revolution began in Germany later than in England and France during the first half of the nineteenth century, by 1848 the formation of German industrial working-class made medical reformers recognize the causal relationships between social and health problems. The outstanding figures in the German medical reform movement of this period were Rudolf Virchow (1821-1902), Solomon Neumann and Rudolf Leubuscher. In his famous Report on the Typhus Epidemic in Upper Silesia, Virchow proposed several radical measures that could be used against the epidemic: the absolute separation of the schools from the church, the establishment of self-government in the state and community, unlimited democracy, road building, and the improvement of agriculture and horticulture. ...

The detection of the c-myc and ras oncogenes in nasopharyngeal carcinoma by immunohistochemistry

Forty-one paraffin embedded specimens of primary nasopharyngeal carcinoma (NPC) were examined to investigate the expression of c-myc and ras oncogenes. Sections were stained with the monoclonal antibodies myc 1-9E10 or ras Y13-259 and binding was detected using the ABC method. The intensity of staining for each tumour was assessed as nil, moderate or intense. The results indicated that 9 (22%) had intense staining for the c-myc oncogene, 28 (68%) had moderate staining and only 4 (10%) showed no staining. For the ras oncogene, 8 (19%) had intense staining, 22 (54%) moderate staining and 11 (27%) showed no staining. The patient's clinical data indicated no correlation between the expression of either c-myc or ras p21 and age, sex, smoking, tumour stage, antibody titre to EBV, or family history. No correlation was found between ras p21 expression and survival; however, overexpression of the c-myc oncogene correlated with a poor prognosis (p < 0.05). This study is consistent with investigations demonstrating that c-myc expression correlates with poor survival in head and neck tumours.

[A comparative analysis of two historical approaches to the formation of the modern clinical medicine]

From the perspective of research methodology, it may be said to exist two kinds of different historical approaches with regards to the formation of modern clinical medicine at the turn of the nineteenth century. One is to explain this in terms of the agency or structure that is associated with research topic. This historical view assumes that the Western scientific rationalism is characterized by the unity of Western tradition and its evolution as continuity. Its main focus is given either on how French revolution and war affected the growth of clinical medicine and the hospital reform movement or on how Paris Clinical School contributed to the birth of modern clinical medicine. The other is, according to Michel Foucault, to analyze how medical discourses are related to social (institutional) practices. Following Canguilhem's history of concepts, Foucault traces the historical development of the concept of disease. Elizabeth A Williams, another proponent of this method, conceptualizes the eighteenth-century medicine as three different medical discourses--anthropology, physiology and philosophical medicine, and analyzes how their structural fragmentation were transformed into the modern establishment of clinical medicine in the nineteenth century. ...

Superinfection-induced apoptosis and its correlation with the reduction of viral progeny in cells persistently infected with Hz-1 baculovirus

Differential induction of necrosis or apoptosis was found upon challenge of cells of the insect Spodoptera frugiperda productively or persistently infected with Hz-1 baculovirus, respectively. Unlike parental SF9 cells, which were essentially all killed by virally induced necrosis, persistently infected cells underwent a process of massive cell death by apoptosis; cells which were not killed by apoptosis then reestablished a cell monolayer. Upon viral challenge, the yield of viral progeny was reduced greatly in persistently virus-infected cells but not in parental cells. Immunolabelling of individual cells revealed that upon viral challenge, production of viral progeny was detectable only in necrotic cells and not in apoptotic cells. These results indicated that induction of apoptosis greatly reduces the yield of viral progeny in cells persistently infected with Hz-1 baculovirus. This is the first report of apoptosis induction in persistently infected cells upon viral superinfection.

Susceptibility of intra-abdominal isolates at operation: a predictor of postoperative infection

Antimicrobial resistance of operative site flora was correlated with postoperative infection in 175 patients undergoing operation for intra-abdominal sepsis: Diagnoses for study patients were acute or gangrenous appendicitis in 48 (27%), complicated appendicitis in 98 (56%), perforated viscus other than appendix in 21 (12%), and eight (5%) had other intra-abdominal infections. One hundred thirty-six (78%) patients were males. The average age was 33 +/- 14 years, average number of hospital days was 11.6 +/- 13.5, and average number of days on antibiotics was 6.9 +/- 2.5. Overall recovery without infection was 75 per cent (131/175). Analysis of susceptibility of 939 intraoperative isolates indicated a significant relationship (P = 0.0002) between resistance to the empiric antimicrobials received and postoperative infection. Of 131 patients with resolution of the intra-abdominal infection, 57 (44%) had resistant isolates while 36 (82%) of 44 patients with postoperative infectious complications had resistant isolates. Streptococcus Group D, Escherichia coli, and Bacteroides fragilis were the most prevalent resistant organisms isolated from both intra- and postoperative cultures. Other variables that were significantly different between those without complications and those who had complications were, respectively: average age 31 versus 38; admission WBC 14.5 versus 16.7; and diagnosis, acute appendicitis 28 per cent versus 2 per cent. A stepwise logistic regression analysis confirmed the predictive value of intraoperative isolate resistance, age, and admission WBC, in that order, on outcome.

Nasopharyngeal carcinoma: genetic changes, Epstein-Barr virus infection, or both. A clinical and molecular study of 36 patients

BACKGROUND

The pathogenesis of nasopharyngeal carcinoma has been under intense investigation, especially of its peculiar predominance in southern China. The authors previously reported consistent loss of genetic material on the short arm of chromosome 3 in a few nasopharyngeal carcinoma cases. In this study, the authors examined the genetic changes as well as the presence of Epstein-Barr virus (EBV) genome on 36 nasopharyngeal carcinoma primary biopsy specimens of the undifferentiated type and the correlation of the findings to patients' clinical status.

METHODS

The authors examined the DNA from tumor tissue and from matched blood leukocytes of 36 patients who suffered from nasopharyngeal carcinoma by the restriction fragment length polymorphism analysis. The genotyping for EBV was carried out by polymerase chain reaction using primers complementary to both types of EBV and probes specific to EBNA-2A (EBV-A) or EBNA-2B (EBV-B).

RESULTS

A consistent deletion at two specific locus of the short arm of chromosome 3 was observed in all informative cases. The authors also found that EBV genome, especially type A, was present in 35 of 36 cases. In the remaining one case, EBV-B was detected.

CONCLUSIONS

As the same tumor tissue was used for both genetic and viral studies in each case, the results may represent sequential genetic lesions in the pathogenesis and/or summation of genetic events. Moreover, 7 of 32 informative tumors were from patients of early staging (Stages I and II), which suggests the genetic changes may occur in the early development of nasopharyngeal carcinoma. Difference in allele frequency in specific locus was also noted between Asian and white patients for the first time.

A quantitative study of the interphasic nucleolar organizer regions in two human cervical carcinoma cell lines

We have studied the relationship between interphase nucleolar organizer regions (NORs) distribution and nucleolar size in cancer cells under prolonged culture. Six morphometric parameters (NUCLEAR SIZE, NOR NUMB, AREA SUM, MEAN AREA, SIZE RATIO and SIZE RATIO MEAN) of AgNORs in cancer cells were analyzed by an image analyzing system. The results show that the parameters NORN NUMB, AREA SUM and NUCLEAR SIZE demonstrate the most consistent changes in the two cervical carcinoma cell lines studied. These three parameters of AgNORs appear to be correlated with the degree of "dedifferentiation" that occurred in tumor cells under prolonged culture.

Altered expression of cell adhesion molecules in uninvolved gut in inflammatory bowel disease

Adhesion of circulating cells to vascular endothelium occurs in the early phase of inflammation, and is mediated by specific cell adhesion molecules. Many such adhesion molecules are increased in inflamed regions of ulcerative colitis (UC) and Crohn's disease (CD) but there is limited knowledge of their expression in the uninvolved gut, adjacent to inflammation. We investigated immunohistochemically the expression of platelet endothelial cell adhesion molecule-1 (PECAM-1), intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) on resected specimens taken at a distance of 2-4 cm from the inflamed area and without histological signs of inflammation. Compared with normal gut, we found (i) a significant increase of PECAM-1-positive vessels in the mucosa of uninvolved UC (149.0 +/- 24.1 vessels/mm2 (mean +/- s.d.); normal colon = 123.1 +/- 21.6; P = 0.004); (ii) a significant decrease of ICAM-1-positive vessels in uninvolved CD (111.9 +/- 22.6 vessels/mm2; normal ileum = 136.9 +/- 27.6; P = 0.04); and (iii) a moderate but statistically insignificant increase of LFA-1-positive cells in the mucosa of uninvolved UC and Crohn's ileitis. This altered expression of cell adhesion molecules may contribute to the early lesion in inflammatory bowel disease and provide new therapeutic opportunities.

The growth and behaviour of pig retinal pigment epithelial cells in culture

The retinal pigment epithelium contains melanin and lipofuscin. It is believed that in the in vivo system, the incomplete degradation of phagocytosed outer segment discs leads to the formation of lipofuscin. Our results showed that pig RPE cells can be successfully cultured using standard culture techniques without addition of specific growth factors. In this system, the autofluorescent material is formed mainly from the degradation of pigment granules. This culture system may provide an excellent model for studying of diseases related to the retina.