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R Nickel

Publications and source records attributed to R Nickel.

52 records · Page 3Linked to original sources
PubMed1995

Analysis of the 170-kDa lectin gene promoter of Entamoeba histolytica.

The promoter region driving the gene for the 170-kDa heavy subunit of the Entamoeba histolytica galactose-inhibitable lectin was analysed by transient transfection using the chloramphenicol acetyltransferase gene as reporter. S1 mapping confirmed our previous notion that the promoter is located within a 1.35-kb intergenic sequence preceding the structural lectin gene. Transcripts derived from the chloramphenicol acetyltransferase gene of transfected trophozoites were found to be polyadenylated and the transcriptional start mapped to a position similar to that of the wild-type lectin gene. By deletion analysis the entire promoter was restricted to a fragment covering about 550 bp upstream from the start of transcription. On the other hand, residual promoter activity required a sequence of about 140 bp only, encompassing a newly identified CCAAT-box like element around position -100, as well as the amebic specific TATA-box. This 140-bp fragment as well as a stretch of 15 bp, which is located some 100 nt further upstream, were found to be conserved within the 5' noncoding region of a second E. histolytica lectin gene. Point-mutation analyses indicated that the 15-bp fragment, the likely CCAAT-box, as well as the TATA-box are required for full promoter activity.

Animals↗
PubMed1994

Transfection and transient expression of chloramphenicol acetyltransferase gene in the protozoan parasite Entamoeba histolytica.

Hybrid plasmids were constructed and used for successful transfection and transient expression of the chloramphenicol acetyltransferase (CAT) gene in the protozoan parasite Entamoeba histolytica. Transfection was performed by electroporation of the amebae in a potassium phosphate-based buffer under conditions of 3000 V/cm and 25 microF, resulting in a time constant of 0.4 ms. Expression of CAT activity was achieved with constructs in which the CAT coding region was flanked by untranslated upstream and downstream sequences of E. histolytica genes. Highest activity was detected after culturing transfected cells for 48 hr. Activity was found to be proportional to the amount of DNA transfected.

Animals↗
PubMed1994

Amoebapores, a family of membranolytic peptides from cytoplasmic granules of Entamoeba histolytica: isolation, primary structure, and pore formation in bacterial cytoplasmic membranes.

Three peptides with pore-forming activity were isolated from the cytoplasmic granules of pathogenic Entamoeba histolytica by acidic extraction, gel filtration and reversed-phase high-performance liquid chromatography. Partial amino acid sequence analysis of the three active peptides revealed that the most abundant of them was amoebapore and the other two were isoforms thereof. Cloning and sequencing of genomic DNA resolved the amino acid sequence of the two newly recognized peptides. The three peptides designated amoebapores A, B and C were found to have the same molecular size but to differ markedly in their primary structure, although all six cysteine residues are conserved. Despite sequence divergence, structural implications predict for the three peptides a similar amphipathic alpha-helical conformation stabilized by disulphide bonds. All three isoforms exhibit pore-forming activity toward lipid vesicles, but they differ in their kinetics. They also are capable of perturbing the integrity of bacterial cytoplasmic membranes and thereby kill Gram-positive bacteria. The amoebapores represent a distinct family of membrane-active peptides that may function intracellularly as antimicrobial agents but may also confer cytolytic activity on the parasite.

Amino Acid Sequence↗
PubMed1993

Neuropathologic analysis of postmortal brain samples of HIV-seropositive and -seronegative i.v. drug addicts.

Between 1987 and 1992 we performed forensic-pathologic and neuropathologic examinations on 70 cases of i.v. drug addicts who died of an overdose. In almost 25% of the cases HIV-positivity was revealed by serological examinations. In all the cases, irrespective of the result of the serological examination, a diffuse, reactive astrocytosis was the most prominent histologic alteration, accompanied by more or less pronounced regressive changes of this cell type in the deep layers of the white matter. Furthermore, also in all the cases, a slight to moderate, reactive proliferation of microglia could be assessed. In a few cases of the HIV-seropositive group a lymphocytic meningitis, viz. meningoencephalitis was found; these changes may indicate an early invasion of the central nervous system (CNS) by the HIV. In spite of these inflammatory alterations, in the latter cases no HIV-specific antigens (p24 and gp41) could be demonstrated in the brain, most probably because of the small number of infectious particles. In order to reveal the earliest phase of invasion of the CNS by the HIV, we performed a search for HIV-specific nucleic acid sequences by the aid of the polymerase chain reaction (PCR) in 8 HIV-seronegative and 8 normal control cases. Although, most probably due to contamination, also the control cases exhibited some PCR-signals, these were more pronounced and appeared with more primer-pairs within the group of HIV-seronegative drug addicts. It is conceivable that HIV penetrates the CNS and is harboured in it in latent form shortly after the primary infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Diseases↗
PubMed1992

[Fertility problems in the bitch].

A short review of the oestrous cycle is given, followed by a more detailed look at fertility problems caused by husbandry aspects, anatomical abnormalities, hormonal disturbances and infectious aetiologies. One of the principal causes of fertility problems appears to be mating at an inappropriate time. The ovulation period and therefore the correct time of mating can however, be defined by measuring progesterone levels in peripheral blood three times a week. Vaginoscopy can also be used for this purpose, but is a subjective and less reliable method. Sterility is normally the single symptom of cystic endometrial hyperplasia(-mucometra). This probable major cause of sterility can sometimes be diagnosed with echoscopy but sometimes only during laparotomy. Additionally, hormonal disturbances can precipitate problems such as a persistent (pro-)oestrus, a split heat, or an abnormally long interoestrous interval. Bromocriptine, 15-20 micrograms/kg body-weight, twice daily orally, can be used to induce oestrus if no obvious abnormalities are diagnosed. Attention is paid to fertility problems with an infectious aetiology, such as herpes virus or Brucella canis. A vaginitis or abnormal bacterial growth in the vagina can also influence fertility. Unfortunately, little is known about bacterial growth in the vagina in relation to fertility problems. More research is needed in this field.

Animals↗
PubMed1992

Primary and secondary structure of the pore-forming peptide of pathogenic Entamoeba histolytica.

A pore-forming peptide is implicated in the potent cytolytic activity of pathogenic Entamoeba histolytica. Using NH2-terminal sequence information of this peptide, the corresponding cDNA was isolated. The cDNA-deduced amino acid sequence revealed a putative signal peptide and a mature peptide of 77 amino acids including six cysteine residues. Computer-aided secondary structure analysis predicted that the peptide would be composed of four adjacent alpha-helices, and CD spectroscopy indicated an all alpha-helical conformation. The tertiary structure appears to be stabilized by three disulfide bonds; the pore-forming activity was not sensitive to heat but was lost in the presence of reducing agents. Sequence homology was found to the saposins and to surfactant-associated protein B, both mammalian polypeptides of similar size and secondary structure but of non-lytic function. In particular, the six cysteine residues were found to be conserved, suggesting a common motif for stabilizing a favourable tertiary structure. Compared with previously characterized toxic peptides also containing three disulfide bonds, the amoeba peptide may represent a distinct class of biologically active peptides.

Amino Acid Sequence↗
PubMed1991

Homologous cysteine proteinases of pathogenic and nonpathogenic Entamoeba histolytica. Differences in structure and expression.

A cDNA clone derived from the gene encoding a cysteine proteinase of pathogenic Entamoeba histolytica was isolated using an antiserum to the purified enzyme. This clone was used to identify the homologous clone in a cDNA library from nonpathogenic E. histolytica. Sequence analysis and comparison of the predicted amino acid sequences revealed a sequence divergence of 16%. Southern blot analyses indicated that (i) pathogenic isolates may contain more genes coding for these or related enzymes than nonpathogenic isolates, (ii) the structure and organization of these genes are conserved within each group of amoebae, and (iii) none of the genes is found in both pathogenic and nonpathogenic E. histolytica, underlining the notion that the two groups are genetically distinct. Northern blot analyses suggested that the cysteine proteinase is expressed by pathogenic isolates in substantially higher amounts than by nonpathogenic isolates. Overexpression of this enzyme may be an important factor in the pathogenicity of E. histolytica.

Amino Acid Sequence↗
PubMed1983

An integrated blood volume pulse biofeedback system for migraine treatment.

A blood volume pulse (BVP) biofeedback system is described that integrates BVP amplitude to provide a signal appropriate for auditory feedback. In comparison to binary BVP feedback methods, this integrated system offers the advantages of continuous feedback and increased scoring ease. The validity of this system was established by correlating the integrated BVP output with trough-to-peak measurements of the raw BVP signal during unassisted relaxation and temporal BVP biofeedback with eight migraine headache patients. Within-subject correlations of the integrated and raw BVP outputs ranged from .82 to .98 (means = .95). Although the integrated method admits unwanted BVP changes in rate, correlation analyses showed this confound factor to be small. Increments in biofeedback training effects were observed during the treatment course. Substantive migraine relief was achieved by the end of treatment and therapeutic gains were maintained at 1-year follow-up. In conclusion, it appears that this method successfully presents continuous auditory feedback from an integrated BVP signal resulting in therapeutic benefits to migraineurs.

Adolescent↗
PubMed1976

Characterization of growth properties and demonstration of the tumor-specific transplantation antigens of Morris hepatomas.

The growth properties of single-tumor-cell suspensions prepared by enzymatic digestion of solid tumors from Morris hepatomas 7777, 5123tc, and 3924a and the presence of tumor-specific transplantation antigen for tumor lines 7777 and 3924a were described. Two of the tumor cell lines (7777 and 3924a) showed consistent i.m. tumor growth following the inoculation of 1 x 10(5) tumor cells, and a similar dose of 5123tc tumor cells resulted in inconsistent tumor growth. Two of the tumor lines (5123tc and 7777) were associated with rapid appearance of lung metastases, whereas with line 3924a metastatic lung lesions rarely developed despite its rapid i.m. tumor growth rate. Tumor resistance to rechallenge with a threshold inoculum of tumor cells was present in approximately 15 to 50% of the animals following amputation of an existing tumor mass. Resistance to a challenge tumor cell inoculum could also be accomplished by immunization with irradiated tumor cells. Tumor-specific resistance was demonstrated to tumor line 3924a in that "immune" animals were able to resist a challenge with 3924a tumor cells but did not resist a challenge with tumor line 9098.

Animals↗
PubMed1976

Effect of anti-alpha1-fetoprotein on alpha1-fetoprotein-producing rat tumors in vivo and in vitro.

Active or passive immunization of rats to alpha1-fetoprotein (AFP) does not consistently inhibit the growth of AFP-producing transplantable hepatomas in vivo, and anti-AFP does not kill these hepatomas in vitro. However, 3 of 14 rats in 1 experiment responded to passive immunization by reversal of tumor growth as evidenced by normalization of elevated AFP serum concentrations, and 1 of 9 rats actively immunized with rat AFP in complete Freund's adjuvant had suppressed growth of transplantable hepatoma 7777.

Animals↗
PubMedDate not supplied

Auxiliary label use by pharmacists in South Carolina.

This study shows the variability in auxiliary labeling recommendations among reference sources as well as the variability in auxiliary label selection by pharmacists. Pharmacists' responses matched the Pharmex, USP DI, and Facts and Comparisons recommendations 6.1, 2.4, and 0.9 percent of the time, respectively. Pharmacists' use of auxiliary labels was correlated to professional setting, computer software, and years of pharmacy practice, but the interaction of these variables was not determined by our study. Finally, pharmacists are not satisfied with current auxiliary reference sources, including computer software programs.

Drug Labeling↗