Photoelectric recording of mechanical responses of cardiac myocytes

A method to monitor contraction of isolated myocytes by transmicroscopic photometry is illustrated. Two photodiodes are mounted inside an inverse microscope used for visual control of a cell. Illumination of one diode varies in proportion to changes in cell length. The contraction signal is amplified in a comparator circuit. Spatial resolution of the device is in the order of 1 m which corresponds to about 5% of cell shortening in the fully activated state of contraction. The method was tested on isolated myocytes from guinea-pig ventricle. Optical records of contraction in response to action potentials or during voltage clamp compare well with the contractile behaviour of multicellular preparations.     

Histidine-rich protein genes and their transcripts in Plasmodium falciparum and P. lophurae

The presence of histidine-rich protein (HRP) related genes and gene products in Plasmodium falciparum was demonstrated using a synthetic pentahistidine-encoding oligonucleotide and a cloned HRP cDNA probe prepared from the avian parasite P. lophurae. In Northern blotting experiments, two knobby clones of P. falciparum were found to contain a 3500 nucleotide RNA species that hybridized with the oligonucleotide and HRP cDNA probes. As this component had the expected size for an mRNA encoding an 80-90 kDa protein and was absent from two knobless clones of P. falciparum, we concluded that it represented a 'knob protein' mRNA. Using the restriction enzyme EcoRI, three identical cross-hydribizing HRP gene fragments were found in the DNA of both knobby and knobless clones of P. falciparum. These fragments differed in size from those present in P. lophurae. These results suggest that the absence of knob protein mRNA in knobless clones is not due to loss of the corresponding gene(s).     

Extracting information on pneumonia in infants using natural language processing of radiology reports

Natural language processing (NLP) is critical for improvement of the healthcare process because it can encode clinical data in patient documents. Many clinical applications such as decision support require coded data to function appropriately. However, in order to be applicable for healthcare, performance must be adequate. A valuable automated application is the detection of infectious diseases, such as surveillance of pneumonia in newborns (e.g., neonates) because the disease produces significant rates of morbidity and mortality, and manual surveillance is challenging. Studies have demonstrated that automated surveillance using NLP is a useful adjunct to manual surveillance and an effective tool for infection control practitioners. This paper presents a study evaluating the feasibility of an NLP-based monitoring system to screen for healthcare-associated pneumonia in neonates. We estimated sensitivity, specificity, and positive predictive value by comparing results with clinicians' judgments. Sensitivity was 71% and specificity was 99%. Our results demonstrated that the automated method was feasible.     

Automated DNA fingerprinting analysis of Mycobacterium tuberculosis using fluorescent detection of PCR products.

DNA fingerprints of Mycobacterium tuberculosis are produced by restriction fragment length polymorphism analysis of the insertion element IS6110. We modified a PCR-based subtyping method, mixed-linker PCR with fluorescent-labeled IS6110-specific oligonucleotides, to demonstrate rapid, automated, and unattended electrophoretic analysis. Variation in band sizing (normally occurring with fragment mobility), an artifact of lane-to-lane and gel-to-gel differences, was controlled with an internal lane standard, resulting in accurate and precise DNA sizing. By using this method, fingerprint analysis can be performed using actual fragment length rather than estimated position analysis.     

Characterization of Haemophilus influenzae type b fimbriae.

We confirmed that the fimbriae of Haemophilus influenzae type b conferred hemagglutinating activity (HA) towards human erythrocytes, and erythrocytes of certain other species. Most (17/25) cerebrospinal fluid isolates lacked detectable HA on direct testing, but selective enrichment for fimbriation (f+) indicated that 22 of 25 strains could produce these surface structures. HA was unchanged from pH 4.5 to 9.5 and was not inhibited by mannose or certain other simple sugars. The HA titer of a suspension of three f+ strains was slightly decreased at 50 degrees C; HA was lost by heating at 60 degrees C for 3 min. Growth on a variety of solid and liquid media and under differing degrees of oxygenation did not change the HA titer of a suspension of three f+ strains. Fimbriation was not lost on repeated subculture. Wild-type fimbriated strains, and those derived by transformation, did not contain detectable plasmid DNA. Transformation of a strain lacking fimbriae to f+ was associated with the appearance of an outer membrane protein of 24 kilodaltons. This protein was purified from one strain to homogeneity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis by selective detergent solubilization and ammonium sulfate fractionation. Colonization capacity was equivalent with an isogenic untypable strain lacking or possessing fimbriae. Fimbriae of type b H. influenzae possess characteristics similar to those structures on other gram-negative bacteria; their role in cell physiology or pathogenesis of invasive disease is unknown.     

Spontaneous production of α- and β-interferon in human lymphoblastoid and lymphoma cell lines

Summary A large number of human haematopoietic cell lines was examined for spontaneous production of interferon. Unconcentrated culture supernatants from 70 out of 71 B-lymphoblastoid cell lines contained considerable amounts of interferon (median titer 22 units per ml); a few lines produced more than 100 units/ml with peak values up to 500 units/ml. In contrast, only one B-lymphoma line out of 18 genuine lymphoma, myeloma, and leukaemia cell lines tested spontaneously produced small amounts of interferon. Following treatment with 5-bromodeoxyuridine (BrdUrd), interferon was produced without further induction in most B-lymphoid cell lines, but not in any of the non-B, non-T, T-lymphoid or myeloid lines examined.Modulation of spontaneous interferon production by chemicals (sodium butyrate, dexamethasone, dimethylsulfoxide, a phorbol ester, and BrdUrd) was studied in more detail in three B-lymphoblastoid and four B-lymphoma cell lines. The patterns of responses observed were different for the action of different chemicals on a given cell line as well as between lymphoblastoid and lymphoma lines in general; furthermore, several lines of evidence suggest that chemicals can differentially influence spontaneous and virus-induced interferon production in a given cell line.The composition of spontaneously produced interferon was analysed using antisera specific for HuIFN- and HuIFN-. Interferons produced by untreated as well as BrdUrd-treated lymphoblastoid cells contained more than 95 per cent IFN-, whereas BrdUrd-treated lymphoma cells produced IFN- as well as minor amounts (cell lines Namalwa and NC-37) or even over 90 per cent of IFN- (Daudi).With 2 Figures     

Molecular epidemiology of tuberculosis in Denmark in 1992.

The incidence of tuberculosis (TB) is increasing all over the world, including in countries with a high standard of living and good social security. Denmark represents such a region. Furthermore, it is a small country (5 million inhabitants) with a long tradition in TB control, including a centralization of the bacteriological diagnostic facility. The present study was intended to analyze the transmission of Mycobacterium tuberculosis in a country in which TB has low endemicity by a combination of conventional epidemiological approaches and DNA fingerprinting techniques, whereby individual bacterial strains can be traced. M. tuberculosis isolates from 92% of all new cases of bacteriologically verified TB in Denmark during 1992 were subjected to IS6110 DNA fingerprinting to visualize the DNA restriction fragment length polymorphism (RFLP) patterns of the isolated strains. The data obtained from the RFLP analyses were interpreted by using demographic data, such as age, sex, ethnicity, and residence, for the patients. The risk factors among the patients for being part of an active chain of transmission, as opposed to demonstrating reactivation of a previously acquired latent infection, were estimated by statistical analyses. The magnitude of TB transmission in 1992 in Denmark was determined, and transmitted infections were shown to comprise at least one quarter of the total number of cases. Almost half of the TB cases involved patients of foreign origin. However, most of these isolates showed unique DNA fingerprint patterns and were rarely part of an active chain of transmission. The major chains of recent transmission were localized to distinct geographical regions in the country.(ABSTRACT TRUNCATED AT 250 WORDS)     

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Diagnosis of rhabdomyosarcomas with HHF35, a monoclonal antibody directed against muscle actins.

The authors have recently developed a monoclonal antibody, HHF35, that recognizes the muscle-specific isoforms of actin. To determine its potential usefulness in the differential diagnosis of "small, round, blue cell" tumors of childhood, they immunolabeled formalinor B-5-fixed tissue sections from known cases of rhabdomyosarcoma or rhabdomyoma (30), neuroblastoma (9), retinoblastoma (2), and Ewing's sarcoma (9) with HHF35 and with antibodies to creatine kinase M, myoglobin, vimentin, and neuron-specific enolase. HHF35 reacted with 29 of 30 cases of rhabdomyosarcoma, whereas antibodies to creatine kinase M and myoglobin were positive on only 12 and 7 tumors, respectively. HHF35 did not react with any case of neuroblastoma, retinoblastoma, or Ewing's sarcoma when the antibody diluent contained 50 mM EDTA. These results indicate that HHF35 is a highly sensitive and specific marker for myogenic differentiation and that it will be useful in the differential diagnosis of rhabdomyosarcomas.