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Biomedical subjects

J Smit

Publications and source records attributed to J Smit.

At least 91 records · Page 5Linked to original sources
PubMed1988

Pregnancies after ultrasound-guided fallopian insemination with cryostored donor semen.

Twenty-nine patients, previously treated unsuccessfully with a median 9.5 cycles of conventional intracervical donor insemination, were offered fallopian catheterization on the side of the dominant follicle and direct insemination at the presumed site of fertilization, the ampullary-isthmic junction. Forty-five of 50 cycles were associated with successful tubal catheterization and 6 of these cycles were conceptional. Five viable intrauterine pregnancies resulted. We conclude: (1) that direct sperm transfer to the fallopian tubes is possible without the need for anesthesia or operation; and (2) that at the time of ovulation, the fallopian tube isthmus can be catheterized without later interfering with ovum or embryo transport to the uterus. Optimum timing for fallopian catheterization in relation to ovulation and the risk of side effects both remain to be established.

Clinical Trials as Topic↗
PubMed1988

Characterization of the adhesive holdfast of marine and freshwater caulobacters.

Caulobacters are prosthecate (stalked) bacteria that elaborate an attachment organelle called a holdfast at the tip of the cellular stalk. We examined the binding of lectins to the holdfasts of 16 marine Caulobacter strains and 10 freshwater species or strains by using a panel of fluorescein-conjugated lectins and fluorescence microscopy. The holdfasts of all the marine isolates bound to only wheat germ agglutinin (WGA) and other lectins that bind N-acetylglucosamine (GlcNac) residues. The freshwater caulobacters showed more variability in holdfast composition. Some bound only to WGA and comparable lectins as the marine strains did. Others bound additional or other lectins, and some did not bind to the lectins tested. The binding of WGA appeared to involve the regions of the holdfast involved with adhesion; a holdfast bound to WGA was significantly less adhesive to glass. Competition experiments with WGA-binding holdfasts and oligomers of GlcNac demonstrated that trimers of GlcNac (the preferred substrate for WGA binding) were more effective than dimers or monomers in preventing WGA binding to holdfasts, suggesting that stretches of contiguous GlcNac residues occur in the WGA-binding holdfasts. In addition, differences between freshwater and marine holdfasts in the strength of WGA binding were noted. The effect of a number of proteolytic and glycolytic enzymes on holdfast integrity was examined; the proteases had no effect for all caulobacters. None of the glycolytic enzymes had an effect on marine caulobacter holdfasts, but chitinase and lysozyme (both attack oligomers of GlcNac) disrupted the holdfasts of those freshwater caulobacters that bound WGA. Despite some similarity to chitin, holdfasts did not bind Calcofluor and no measurable effects on holdfast production were detectable after cell growth in the presence of diflubenzuron or polyoxin D, inhibitors of chitin synthesis in other systems. Finally, the holdfasts of all caulobacters bound to colloidal gold particles, without regard to the coating used to stabilize the gold particles. This binding was stronger or more specific than WGA binding; treatment with colloidal gold particles prevented WGA binding, but the reverse was not the case.

Journal Article↗
PubMed1988

Transcriptional analysis of the major surface array gene of Caulobacter crescentus.

The major component of the paracrystalline surface array of Caulobacter crescentus CB15 and one of the most abundant cellular proteins is a protein designated 130K. We have determined the DNA sequence of the 5' portion of the 130K gene, including the N-terminal one-third of the protein coding region, and analyzed the transcription of the gene. The site of transcription initiation was determined by S1 mapping of Caulobacter RNA. Although the DNA sequence upstream from the transcription start site showed significant homology to the consensus promoter sequences of Escherichia coli, S1 analysis of RNA from E. coli carrying the 130K gene on a plasmid indicated that the 130K promoter was not transcribed by E. coli RNA polymerase in vivo. Quantitative S1 analysis of RNA isolated from synchronously growing Caulobacter cells suggested that this promoter was not under developmental regulation; the amount of 130K transcript varied no more than 1.5-fold during the cell cycle. The length of the 130K mRNA was determined to be 3.3 kilobases by Northern (RNA blot) analysis, indicating that the 130K mRNA is not part of a polycistron. The amino acid sequence predicted from the DNA sequence agreed well with the N-terminal amino acid sequence determined by sequencing of the 130K protein. The 130K protein appears to be synthesized without an N-terminal leader sequence, but the N-terminal 20 amino acids are relatively hydrophobic and may function like a signal sequence during transmembrane translocation.

Amino Acid Sequence↗
PubMed1987

Localizing the subunit pool for the temporally regulated polar pili of Caulobacter crescentus.

The pili of the stalked bacterium Caulobacter crescentus are assembled at a specific time in the life cycle at one pole of the cell and are composed of the monomer protein, pilin. A previous study demonstrated that the onset of pilin synthesis occurs well before pili appear on the surface, suggesting that pilin accumulates within the cell. In the present study, an electron microscope immunocytochemistry assay was used to determine the subcellular location of this unassembled pilin and its fate during pilus assembly and cell division. Populations of synchronously growing cells were embedded in epoxy resin at selected times during the cell cycle. Ultrathin sections were treated with pilin-specific antibody, followed by protein A coupled to colloidal gold. It was determined that the cellular location for unassembled pilin was the cell cytoplasm. All cell membranes and regions of nuclear material were poorly labeled. Quantitation demonstrated that label density increased during the period of pilin synthesis and declined during the period of pilus assembly and maintenance. The pilin pool was not unequally segregated at division; e.g., to the daughter cell that is elaborating pili. Mutants which have simultaneously lost the ability to produce flagella, pili, and other polar organelles, possibly due to alterations in the specialized region of polar organelle assembly, were also examined by the immunocytochemistry technique. There was no significant difference in the pilin pool size relative to the wild type, indicating that pilin synthesis continues in the absence of a functioning assembly site. This pattern of synthesis and assembly for the pilus is significantly different from that of the polar flagellum which is produced at the same time and location on the cell surface. These findings are discussed in relation to the hypothesized organization center at the cell pole which may have a major role in directing the assembly of all the polar structures.

Bacteria↗
PubMed1986

Onyalai--therapeutic effects of vincristine sulphate. A prospective randomized trial.

Twenty out of 40 patients with onyalai admitted to Rundu State Hospital, Kavango, SWA/Namibia, were randomized to receive a vincristine sulphate bolus of 1.5 mg/m2 or an equivalent volume of normal saline intravenously on days 8 and 15 when haemorrhage or a platelet count of less than 50 X 10(9)/l persisted for more than 1 week after admission. All patients were observed in hospital for at least 21 days. Five out of 10 patients who received vincristine achieved a platelet count in excess of 100 X 10(9)/l on day 21 and only 2 out of 10 patients who received placebo achieved a similar rise in the platelet count. Two patients, neither of whom was treated with vincristine, died of cerebral haemorrhage.

Adolescent↗
PubMed1986

Mechanisms by which acute phase proteins enhance development of liver fibrosis: effects on collagenase and prolyl-4-hydroxylase activity in the rat liver.

Previous experiments showed that the presence of high levels of acute phase reactants (APR) enhance CCl4-induced liver fibrosis in the rat. A high correlation was found between the degree of fibrosis and alpha 2-macroglobulin of the rat (alpha 2-macrofetoprotein, alpha M-FP) used for monitoring the acute phase response. This acute phase reaction was provoked by epinephrine just before CCl4 treatment was started. In the present study we analyzed the effect of APR by repeating these experiments and estimating liver neutral collagenase with a synthetic substrate and endogenous collagen as a substrate, and liver prolyl-4-hydroxylase. A strong depression of liver collagenase activity was found in rats with a preceding acute phase reaction contrary to the rats that underwent CCl4 treatment only. A high level of alpha M-FP correlated negatively with collagenase activity. Also in vitro alpha M-FP proved to inhibit collagenase activity. Prolyl-4-hydroxylase was increased in the rats during acute phase reaction and correlated highly and positively with alpha M-FP, haptoglobin, and ceruloplasmin. Thus high levels of APR promote development of CCl4-induced fibrosis, partly by anticollagenase activity and partly because of enhancement of prolyl-4-hydroxylase activity. The latter phenomenon can also be explained by the presence of APR, but this has to be proved.

Acute-Phase Proteins↗
PubMed1985

A comparison of techniques for isolation of the outer membrane proteins of Haemophilus influenzae type b.

We compared several rapid techniques used for extraction of outer membrane proteins from gram-negative enteric bacteria to Haemophilus influenzae type b. After lysis of cells with a French press, the inner and outer membranes were separated by isopycnic centrifugation. Each membrane was identified by density, morphology, enzymatic activity, and susceptibility to solid-phase iodination of intact cells. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we identified 10 polypeptides which were enriched in the outer membrane band compared to the inner membrane band. Using these proteins, we compared the polypeptide pattern of outer membranes with that obtained by (1) selective solubilization with sodium dodecyl-beta-D-maltoside, octyl-beta-D-glucopyranoside, Triton X-100, sodium, or cholamidopropyl dimethylaminopropanesulfonate; (2) extraction with chaotropic agents and heat; and (3) differential centrifugation of vesicles shed during transition from log growth phase to stationary growth phase. There were definable differences between the polypeptide pattern of membranes obtained with each rapid technique compared to the polypeptide pattern of isolated outer membranes. The polypeptide pattern of lithium extracts and the Triton X-100 insoluble fractions of total membranes most closely approximated the polypeptide pattern of isopycnically isolated outer membranes. Depending on the outer membrane protein sought, one of these rapid techniques can be utilized when a rapid method of outer membrane protein isolation is required.

Bacterial Outer Membrane Proteins↗
PubMed1985

Lymphadenopathy morphologically consistent with Hodgkin's disease associated with Epstein-Barr virus infection.

This case report describes a case of chronic Epstein-Barr virus infection resulting in lymphadenopathy morphologically indistinguishable from Hodgkin's disease. Morphologic, immunologic, and virologic studies could be performed on three consecutive lymph nodes. For the first time in the literature, Epstein-Barr Nuclear Antigen (EBNA) could be demonstrated in the nuclei of Sternberg-Reed cells.

Aged↗
PubMed1984

Treatment of onyalai with prednisolone, intravenous gammaglobulin and ascorbic acid. A prospective clinical trial.

Forty-two patients in the acute phase of onyalai were admitted to hospital and randomly divided into three groups of 14 to receive prednisolone 3 mg/kg/d for 1 week, intravenous gammaglobulin 100 mg/kg on 2 successive days, or ascorbic acid 1000 mg 3 times a day for 1 week. The groups were comparable with regard to sex and age distribution, initial platelet counts and initial haemoglobin values. No statistical difference was observed between the three treatment groups with regard to changes in the platelet counts during the period of observation. One patient died from haemorrhagic shock. The low mortality rate in this series suggests that admission to hospital and early correction of blood loss are important factors in reducing the mortality rate associated with onyalai.

Adolescent↗
PubMed1984

Expression of a Trypanosoma brucei brucei variant antigen in Escherichia coli.

A cDNA library derived from antigenically homogeneous bloodstream stage Trypanosoma brucei brucei was screened with an antiserum directed against the variant surface antigen (VSA) using an enzyme-linked filter immunoassay. Several recombinant clones were detected and the clone giving the most intense reaction was further analyzed. It contained a VSA-specific cDNA insert and synthesized a protein of the expected molecular weight bearing VSA determinants. The nucleotide sequence of the insert was determined and shown to have the unusual codon bias characteristic of T. brucei VSAs, frequently employing codons specifying tRNAs rare in Escherichia coli. These results indicate that a codon bias very different from that of E. coli does not preclude the expression of a cloned sequence to detectable levels in this heterologous host.

Amino Acid Sequence↗