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Biomedical subjects

K Jansen

Publications and source records attributed to K Jansen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Hemodilution, cerebral O2 delivery, and cerebral blood flow: a study using hyperbaric oxygenation.

Hemodilution reduces blood viscosity and O2 content (CaO2) and increases cerebral blood flow (CBF). Viscosity and CaO2 may contribute to increasing CBF after hemodilution. However, because hematocrit is the major contributor to blood viscosity and CaO2, it has been difficult to assess their relative importance. By varying blood viscosity without changing CaO2, prior investigation in hemodiluted animals has suggested that both factors play roughly equal roles. To further investigate the relationship of hemodilution, blood viscosity, CaO2, and CBF, we took the opposite approach in hemodiluted animals, i.e., we varied CaO2 without changing blood viscosity. Hyperbaric O2 was used to restore CaO2 to normal after hemodilution. Pentobarbital sodium-anesthetized rats underwent isovolumic hemodilution with 6% hetastarch, and forebrain CBF was measured with [3H]nicotine. One group of animals did not undergo hemodilution and served as controls (Con). In the three experimental groups, hematocrit was reduced from 44% to 17-19%. Con and hemodiluted (HDil) groups were ventilated with 40% O2 at 101 kPa (1 atmosphere absolute), which resulted in CaO2 values of 19.7 +/- 1.3 and 8.1 +/- 0.7 (SD) ml O2/dl, respectively. A second group of hemodiluted animals (HBar) was ventilated with 100% O2 at 506 kPa (5 atmospheres absolute) in a hyperbaric chamber, which restored CaO2 to an estimated 18.5 +/- 0.5 ml O2/dl by increasing dissolved O2. A fourth group of hemodiluted animals (HCon) served as hyperbaric controls and were ventilated with 10% O2 at 506 kPa, resulting in CaO2 of 9.1 +/- 0.6 ml O2/dl. CBF was 79 +/- 19 ml. 100 g-1. min-1 in the Con group and significantly increased to 123 +/- 9 ml. 100 g-1. min-1 in the HDil group. When CaO2 was restored to baseline with dissolved O2 in the HBar group, CBF decreased to 104 +/- 20 ml. 100 g-1. min-1. When normoxia was maintained during hyperbaric exposure in the HCon group, CBF was 125 +/- 18 ml. 100 g-1. min-1, a value indistinguishable from that in normobaric HDil animals. Our data demonstrate that the reduction in CaO2 after hemodilution is responsible for 40-60% of the increase in CBF.

Animals↗
PubMed1999

Organotypic suprachiasmatic nuclei cultures of adult voles reflect locomotor behavior: differences in number of vasopressin cells.

This study is the first to demonstrate organotypic culturing of adult suprachiasmatic nuclei (SCN). This approach was used to obtain organotypic SCN cultures from adult vole brain with a previously determined state of behavioral circadian rhythmicity. We examined vasopressin (AVP) immunoreactivity in these organotypic slice cultures. AVP is one of the major neuropeptides produced by the SCN, the main mammalian circadian pacemaker. AVP immunoreactivity in the SCN of adult common voles in vivo has been shown to correlate with the variability in expression of circadian wheel-running behavior. Here, cultures prepared from circadian rhythmic and nonrhythmic voles were processed immunocytochemically for AVP. Whereas in all cultures AVP could be observed, AVP immunoreactivity differed considerably between vole SCN cultures. SCN cultures from rhythmic voles contained significantly lower numbers of AVP immunoreactive (AVPir) cells per surface area than cultures from nonrhythmic voles. The correlation between timing of behavior and AVP immunoreactivity in vitro is similar to the correlation found earlier in vivo. Apparently, such correlation depends on intrinsic AVP regulation mechanisms of SCN tissue, and not on neural or hormonal input from the environment, as present in intact brain.

Animals↗
PubMed1998

Concurrent decrease of vasopressin and protein kinase Calpha immunoreactivity during the light phase in the vole suprachiasmatic nucleus.

Vasopressin (AVP) is a major neuropeptide in the suprachiasmatic nucleus, the mammalian hypothalamic circadian pacemaker. Protein kinase Calpha is a putatively coupled intracellular messenger. Mean numbers of AVP- and protein kinase Calpha-immunoreactive neurons were determined in the suprachiasmatic nucleus of common voles, entrained to a 12:12 h light-dark (LD) cycle, at the beginning of the light period (zeitgeber time zero) and 6 h later (zeitgeber time six). At zeitgeber time zero, mean numbers of AVP- and protein kinase Calpha- immunoreactive neurons were 2194 and 9897, respectively. Both numbers decreased significantly with about 40% at zeitgeber time six. This concurrent decrease was most pronounced in the dorsomedial aspect of the suprachiasmatic nucleus. These findings are consistent with the findings of a peak of AVP release in rats during the early light phase.

Animals↗
PubMed1998

Specific gene blockade shows that peptide nucleic acids readily enter neuronal cells in vivo.

Peptide nucleic acids (PNAs) are DNA analogs that can hybridize to complementary sequences with high affinity and stability. Here, we report the first evidence of intracellular delivery of PNAs in vivo. Two CNS receptors, an opioid (mu) and a neurotensin (NTR-1), were targeted independently by repeated microinjection of PNAs into the periaqueductal gray. Behavioral responses to neurotensin (antinociception and hypothermia) and morphine (antinociception) were lost in a specific manner. Binding studies confirmed a large reduction in receptor sites. The loss of behavioral responses was long lasting but did fully recover. The implications of specifically and readily turning off gene expression in vivo are profound.

Animals↗
PubMed1997

Characterization of pars intermedia connections in amphibians by biocytin tract tracing and immunofluorescence aided by confocal microscopy.

Biocytin, recently introduced in neuroanatomical studies, was used as a retrograde tract tracer in combination with immunofluorescence in order to analyse the neurochemical characters of some central neuronal projections to the pars intermedia in two amphibian species, the anuran Rana esculenta and the urodele Triturus carnifex. After biocytin insertions in the pars intermedia, neurons became retrogradely labelled in the suprachiasmatic hypothalamus and the locus coeruleus of the brainstem in both species. Some scattered biocytin-labelled neurons were observed in the preoptic area. Moreover, working on the same sections, immunofluorescence revealed a number of codistributions and, in some cases, colocalization in the same neurons of biocytin labellings and immunopositivity for (1) tyrosine hydroxylase in the suprachiasmatic hypothalamus and the locus coeruleus of Rana and Triturus, (2) gamma-aminobutyric acid in the suprachiasmatic hypothalamus of Rana and Triturus and (3) neuropeptide Y in the suprachiasmatic hypothalamus of Rana. The specificity of such colocalizations was fully confirmed using dual-channel confocal laser scanning microscopy analysis.

Afferent Pathways↗
PubMed1996

Virus-like particles and E1-E4 protein expressed from the human papillomavirus type 11 bicistronic E1-E4-L1 transcript.

Detection of E1-E4 protein in human papillomavirus (HPV 11)-infected tissue is tightly linked to detection of L1 major capsid protein. The only L1-containing transcript identified in HPV 11-infected tissue is the bicistronic E1-E4-L1 mRNA, potentially encoding both the E1-E4 and the L1 proteins. It has not been established that these proteins can be expressed from the E1-E4-L1 transcript. The HPV 11 E1-E4-L1 sequence was cloned by reverse transcriptase polymerase chain reaction into the p1393 vector to produce recombinant baculoviruses. Immunoblots of recombinant baculovirus-infected Sf9 cell lysates demonstrated both the E1-E4 and the L1 proteins. An ELISA was performed on infected Sf9 cells using a monoclonal antibody specific for nondenatured L1, demonstrating that 10 ng of native L1 protein was present per microgram of total nuclear protein. Electron microscopic analysis revealed 50- to 60-nm icosahedral virus-like particles. In vitro transcription/translation was performed using pSPORT constructs containing the E1-E4-L1 sequence or, as controls, monocistronic pSPORT-E1-E4 or L1 constructs. The pSPORT-E1-E4-L1 construct produced the E1-E4 and L1 proteins at a ratio of 17:1. For E1-E4 protein, expression was greater from the pSPORT-E1-E4-L1 construct than from the monocistronic pSPORT-E1-E4 construct. In contrast, more L1 protein was expressed from pSPORT-L1 than from pSPORT-E1-E4-L1. A mutant E1-E4-L1 construct containing no E1-E4 start codon expressed L1 protein in amounts nearly equal to that expressed from the pSPORT-L1 construct. Addition of an antisense oligonucleotide directed at the E1-E4 start codon region to in vitro reactions using pSPORT-E1-E4-L1 was associated with inhibition of E1-E4 protein synthesis and increased translation of L1 protein.

Animals↗
PubMed1996

Virus-like Particles and E1AE4 Protein Expressed from the Human Papillomavirus Type 11 Bicistronic E1AE4AL1 Transcript

Detection of E1AE4 protein in human papillomavirus (HPV 11)-infected tissue is tightly linked to detection of L1 major capsid protein. The only L1-containing transcript identified in HPV 11-infected tissue is the bicistronic E1AE4AL1 mRNA, potentially encoding both the E1AE4 and the L1 proteins. It has not been established that these proteins can be expressed from the E1AE4AL1 transcript. The HPV 11 E1AE4AL1 sequence was cloned by reverse transcriptase polymerase chain reaction into the p1393 vector to produce recombinant baculoviruses. Immunoblots of recombinant baculovirus-infected Sf9 cell lysates demonstrated both the E1AE4 and the L1 proteins. An ELISA was performed on infected Sf9 cells using a monoclonal antibody specific for nondenatured L1, demonstrating that 10 ng of native L1 protein was present per microgram of total nuclear protein. Electron microscopic analysis revealed 50- to 60-nm icosahedral virus-like particles. In vitro transcription/translation was performed using pSPORT constructs containing the E1AE4AL1 sequence or, as controls, monocistronic pSPORT-E1AE4 or L1 constructs. The pSPORT-E1AE4AL1 construct produced the E1AE4 and L1 proteins at a ratio of 17:1. For E1AE4 protein, expression was greater from the pSPORT-E1AE4AL1 construct than from the monocistronic pSPORT-E1AE4 construct. In contrast, more L1 protein was expressed from pSPORT-L1 than from pSPORT-E1AE4AL1. A mutant E1AE4AL1 construct containing no E1AE4 start codon expressed L1 protein in amounts nearly equal to that expressed from the pSPORT-L1 construct. Addition of an antisense oligonucleotide directed at the E1AE4 start codon region to in vitro reactions using pSPORT-E1AE4AL1 was associated with inhibition of E1AE4 protein synthesis and increased translation of L1 protein.

Journal Article↗
PubMed1996

Loss of A1 adenosine receptors in human temporal lobe epilepsy.

Using quantitative receptor autoradiographic methods we have examined A1 adenosine receptors, adenosine uptake sites, benzodiazepine receptors, NMDA, AMPA, and kainic acid receptors in temporal lobes removed from patients suffering from complex partial seizures and in normal control post-mortem temporal cortex. Binding to A1 adenosine receptors and NMDA receptors was reduced in epileptic temporal cortex, while the other neurochemical parameters were unchanged. The reason for this A1 receptor loss is unclear as it occurred in both idiopathic and symptomatic cases and thus may be a consequence rather than an initial cause of seizures. However, because adenosine is a powerful anticonvulsant substance, loss of anticonvulsant A1 receptors may contribute to the human epileptic condition. It is also possible that the observed differences in A1 binding are due to autopsy vs. biopsy changes in the levels of A1 adenosine receptors.

Adolescent↗
PubMed1994

Long-range interactions between DNA-bound ligands.

We have studied the interaction of the A:T specific minor-groove binding ligand 4',6-diamidino-2-phenylindole (DAPI) with synthetic DNA oligomers containing specific binding sites in order to investigate possible long-range interactions between bound ligands. We find that DAPI binds cooperatively to the oligomers. The degree of cooperativity increases with increasing number of binding sites and decreases with the separation between them. This dependence is paralleled by changes in the induced circular dichroism spectrum of DAPI, which decreases in intensity at 335 nm and increases at 365 nm. These results are consistent with an allosteric interaction of DAPI with DNA, where bound ligands cooperatively alter the structure of the DNA molecule. This structural change seems possible to induce under various conditions, including physiological. One consequence of allosteric binding is that ligands bound at a distance from each other sense each other's presence and influence each others' properties. If some regulatory proteins induce the same conformational change as DAPI, novel mechanisms for controlling gene expression can be anticipated.

Adenine↗
PubMed1993

Binding of DAPI analogue 2,5-bis(4-amidinophenyl)furan to DNA.

The binding of 2,5-bis(4-amidinophenyl)furan (APF) to calf thymus DNA, [poly(dA-dT)]2, and [poly(dG-dC)]2 has been studied with flow linear dichroism and circular dichroism spectroscopy. The electronic excited states of the APF chromophore were first characterized using experimental and quantum mechanical methods: it is shown that the low-energy absorption band (320-400 nm) originates from only a single electronic transition which is polarized along the long axis of the molecule, information that is crucial for the structural interpretation of the linear and circular dichroism spectra of the APF-DNA complexes. By contrast, in the unsymmetric analogue 4',6-diamidino-2-phenylindole (DAPI) two overlapping transitions, with somewhat divergent polarizations, both contribute to the first absorption band. Upon binding to DNA the spectroscopic behavior of APF strongly resembles that of DAPI. The linear dichroism data show that the drug binds to calf thymus DNA and [poly(dA-dT)]2 with an angle of 46 degrees +/- 2 degrees between its symmetry long axis and the DNA helix axis, confirming that APF, just like DAPI, is an AT-specific minor-groove binder. Upon binding to [poly(dG-dC)]2, however, the orientation of the long axis is parallel with the plane of the DNA bases, a geometry which excludes binding parallel to the grooves but could be consistent with intercalation. However, a short axis polarized transition is strongly inclined to the base plane and, furthermore, the persistence length of the polynucleotide is markedly reduced, observations that contradict classical intercalation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A new pair of surface molecules involved in human IgE regulation.

The molecules controlling IgE production are the subject of intense study in the effort to find new ways to treat allergic diseases. One candidate, the CD23 molecule, a low affinity receptor for IgE, was recently identified to interact with another molecule, named CD21, in the regulation of IgE production.

B-Lymphocytes↗
PubMed1992

Demonstration of a second ligand for the low affinity receptor for immunoglobulin E (CD23) using recombinant CD23 reconstituted into fluorescent liposomes.

Recombinant full-length human CD23 has been incorporated into fluorescent liposomes to demonstrate the existence of a ligand for CD23 that is different from the previously known ligand, immunoglobulin E (IgE). The novel ligand for CD23 is expressed on subsets of normal T cells and B cells as well as on some myeloma cell lines. The interaction of full-length CD23 with its ligand is specifically inhibited by anti-CD23 monoclonal antibodies and by IgE, and it is Ca2+ dependent. Moreover, tunicamycin treatment of a CD23-binding cell line, RPMI 8226, significantly reduced the binding of CD23 incorporated into fluorescent liposomes, and a sugar, fucose-1-phosphate, was found to inhibit CD23-liposome binding to RPMI 8226 cells, suggesting the contribution of sugar structures on the CD23 ligand. In addition, CD23-transfected COS cells were shown to form specific conjugates with the cell line RPMI 8226. These data demonstrate that CD23 interacts with a ligand, which is different from IgE, and that CD23 can be considered as a new surface adhesion molecule involved in cell-cell interactions.

Antibodies, Monoclonal↗
PubMed1992

Purification and characterization of biologically active human recombinant 37 kDa soluble CD23 (sFc epsilon RII) expressed in insect cells.

Human recombinant soluble 37 kDa CD23 has been expressed in insect cells and secreted into the culture medium using the IL-2 leader sequence. The 37 kDa CD23 was purified 600-fold to homogeneity by monoclonal antibody affinity chromatography and gel filtration. The pure protein is monomeric, glycosylated, depleted of one N terminal amino acid and contains four disulphide bonds. It degrades into smaller fragments of 33, 29 and 25 kDa if purified in the absence of protease inhibitors. The same pattern of proteolytic fragments is observed when the pure preparation is incubated at room temperature for 3 weeks. Physical characterization of the 37 kDa CD23 by circular dichroism indicates that the protein contains mainly beta sheet and 20% of alpha helical structures. Specific binding of IgE to natural CD23 (low affinity IgE receptor) was inhibited by purified recombinant 37 kDa CD23. Moreover, purified recombinant 37kDa CD23 and interleukin-1 promoted the survival of germinal centre B cells.

Amino Acid Sequence↗