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K L Bennett

Publications and source records attributed to K L Bennett.

At least 37 records · Page 2Linked to original sources
PubMed1995

CD44 isoforms containing exon V3 are responsible for the presentation of heparin-binding growth factor.

Glycosaminoglycan-modified isoforms of CD44 have been implicated in growth factor presentation at sites of inflammation. In the present study we show that COS cell transfectants expressing CD44 isoforms containing the alternatively spliced exon V3 are modified with heparan sulfate (HS). Binding studies with three HS-binding growth factors, basic-fibroblast growth factor (b-FGF), heparin binding-epidermal growth factor (HB-EGF), and amphiregulin, showed that the HS-modified CD44 isoforms are able to bind to b-FGF and HB-EGF, but not AR. b-FGF and HB-EGF binding to HS-modified CD44 was eliminated by pretreating the protein with heparitinase or by blocking with free heparin. HS-modified CD44 immunoprecipitated from keratinocytes, which express a CD44 isoform containing V3, also bound to b-FGF. We examined whether HS-modified CD44 isoforms were expressed by activated endothelial cells where they might present HS-binding growth factors to leukocytes during an inflammatory response. PCR and antibody-binding studies showed that activated cultured endothelial cells only express the CD44H isoform which does not contain any of the variably spliced exons including V3. Immunohistological studies with antibodies directed to CD44 extracellular domains encoded by the variably spliced exons showed that vascular endothelial cells in inflamed skin tissue sections do not express CD44 spliced variants. Keratinocytes, monocytes, and dendritic cells in the same specimens were found to express variably spliced CD44. 35SO4(-2)-labeling experiments demonstrated that activated cultured endothelial cells do not express detectable levels of chondroitin sulfate or HS-modified CD44. Our results suggest that one of the functions of CD44 isoforms expressing V3 is to bind and present a subset of HS-binding proteins. Furthermore, it is probable that HS-modified CD44 is involved in the presentation of HS-binding proteins by keratinocytes in inflamed skin. However, our data suggests that CD44 is not likely to be the proteoglycan principally involved in presenting HS-binding growth factors to leukocytes on the vascular cell wall.

Alternative Splicing↗
PubMed1995

Regulation of CD44 binding to hyaluronan by glycosylation of variably spliced exons.

The hyaluronan (HA)-binding function (lectin function) of the leukocyte homing receptor, CD44, is tightly regulated. Herein we address possible mechanisms that regulate CD44 isoform-specific HA binding. Binding studies with melanoma transfectants expressing CD44H, CD44E, or with soluble immunoglobulin fusions of CD44H and CD44E (CD44H-Rg, CD44E-Rg) showed that although both CD44 isoforms can bind HA, CD44H binds HA more efficiently than CD44E. Using CD44-Rg fusion proteins we show that the variably spliced exons in CD44E, V8-V10, specifically reduce the lectin function of CD44, while replacement of V8-V10 by an ICAM-1 immunoglobulin domain restores binding to a level comparable to that of CD44H. Conversely, CD44 bound HA very weakly when exons V8-V10 were replaced with a CD34 mucin domain, which is heavily modified by O-linked glycans. Production of CD44E-Rg or incubation of CD44E-expressing transfectants in the presence of an O-linked glycosylation inhibitor restored HA binding to CD44H-Rg and to cell surface CD44H levels, respectively. We conclude that differential splicing provides a regulatory mechanism for CD44 lectin function and that this effect is due in part to O-linked carbohydrate moieties which are added to the Ser/Thr rich regions encoded by the variably spliced CD44 exons. Alternative splicing resulting in changes in protein glycosylation provide a novel mechanism for the regulation of lectin activity.

Alternative Splicing↗
PubMed1995

Caenorhabditis elegans cyclin A- and B-type genes: a cyclin A multigene family, an ancestral cyclin B3 and differential germline expression.

We have cloned cDNAs for Caenorhabditis elegans cyclins A1, B and B3. While cyclins A1 and B are most closely related to either A- or B-type cyclins of other species, cyclin B3 is less related to these cyclins. However, this cyclin is most similar to the recently identified chicken cyclin B3. Our identification of a Caenorhabditis homolog demonstrates that cyclin B3 has been conserved in evolution. Cyclin A1 is a member of an A-type multigene family; however the cyclin A1 cDNA only recognizes a single band on northern blots. A single-sized RNA is also observed for the cyclin B3 cDNA. In contrast, three different transcripts are observed for the cyclin B cDNA. Based on our analyses using RNAs from germline-defective mutants and from populations enriched for males, one cyclin B transcript is specific to the paternal germline. The two other cyclin B transcripts, as well as the cyclin A1 and cyclin B3 transcripts, are most abundant in the maternal germline and are only present at low levels in other tissues. Moreover, the 3' untranslated regions of each Caenorhabditis cyclin cDNA possess several copies of potential translational control elements shown in Xenopus and Drosophila maternal cyclin mRNAs to function during oogenesis and early embryogenesis.

Amino Acid Sequence↗
PubMed1994

Resiniferatoxin and piperine: capsaicin-like stimulators of oxygen uptake in the perfused rat hindlimb.

The naturally occurring capsaicin-like molecules, resiniferatoxin (RTX, Euphorbia spp.) and piperine (Piper nigrum), each stimulated oxygen uptake (VO2) in association with increased vascular resistance in a concentration-dependent manner when infused into the perfused rat hindlimb. 5 microM glyceryl trinitrate (GTN, a nitrovasodilator) significantly blocked the oxygen and pressure responses to both RTX and piperine, indicating a close relationship between changes in VO2 and the vasoconstriction. Concentrations greater than those required for maximal VO2 resulted in an inhibition of VO2, although perfusion pressure continued to increase. Time course studies showed that both RTX and piperine at high doses resulted in a tri-phasic response. An initial phase of transient VO2 stimulation was followed by a second phase of inhibition. A third phase involving an often larger but transient stimulation of VO2 followed removal of the agents and continued after the pressure returned to basal. The actions of RTX and piperine were similar to those of other active capsaicin-like molecules tested previously in this system, including capsaicinoids (Capsicum spp.), gingerols (Zingiber officinale), and shogoals (Zingiber officinale). RTX was the most potent, and piperine the least potent of this series. Although receptor involvement has yet to be unequivocally established, the data are consistent with the presence of a functional capsaicin-like (vanilloid) receptor in the vasculature of the rat hindlimb that mediates vasoconstriction and oxygen uptake. These findings may have implications for the future development of thermogenic agents.

Alkaloids↗
PubMed1994

The role of the sarcoplasmic reticulum in the response of isolated ferret cardiac muscle to beta-adrenergic stimulation.

beta-Adrenergic stimulation of cardiac muscle leads to an increase in the strength of contraction and an abbreviation of its time course. We have investigated the role of the sarcoplasmic reticulum in these changes by monitoring force and cytoplasmic [Ca2+] in ferret papillary muscles, and the Ca2+ current in isolated ferret myocytes, during the application of isoprenaline in the absence and presence of the sarcoplasmic reticulum inhibitor ryanodine (10(-6) mol/l). Isoprenaline (10(-6) mol/l) led to a marked increase in the size of both the twitch and Ca2+ transient, and a decrease in their duration. In the presence of ryanodine, application of isoprenaline had no significant effect on either the size or the time course of the twitch. However, the increase in the Ca2+ current in response to isoprenaline was the same in the absence and presence of ryanodine. Increasing bathing [Ca2+] led to a prolongation of both the twitch and the Ca2+ transient. In the presence of ryanodine, increasing bathing [Ca2+] still increased the size, but decreased the duration, of the twitch. These data provide direct evidence that both the inotropic and lusitropic effects of isoprenaline are mediated via the sarcoplasmic reticulum.

Animals↗
PubMed1993

glh-1, a germ-line putative RNA helicase from Caenorhabditis, has four zinc fingers.

We have cloned a family of putative RNA helicases from the free-living nematode Caenorhabditis elegans. One of these, a cDNA that we call glh-1, most closely matches in sequence and expression the previously described germ-line helicases PL10 from mouse and vasa from Drosophila. The amino terminus of the predicted protein of glh-1 contains a set of glycine-rich repeats similar in location and sequence to those in the predicted vasa protein. However, unlike all other putative RNA helicases, glh-1 also contains four retroviral-type zinc fingers. The RNA expression pattern of this Caenorhabditis helicase correlates with the presence of germ-line tissue in the parasitic nematode Ascaris lumbricoides var. suum and with the presence of germ cells in wild type and several germ-line mutants of Caenorhabditis. In the germ-line mutants glp-4 and glp-1, additional larger species of glh-1 RNA exist, which correspond to different adenylylated forms of the glh-1 transcript; these may be specified by motifs in the 3' untranslated region of glh-1 that are similar to adenylylation control elements and nos response elements.

Amino Acid Sequence↗
PubMed1993

Sequence conversion during postreplicative adenovirus overlap recombination.

Sequence conversion efficiently transfers genetic information in high yield during postreplicative adenovirus overlap recombination. This process is intrinsically nonreciprocal, depends on adenovirus-specific strand-displacement replication by both partner molecules, and requires that complementary sequences on displaced strands must exceed a minimal length to form a heteroduplex intermediate.

Adenoviridae↗
PubMed1992

Regulation of amphiregulin mRNA by TGF-beta in the human lung adenocarcinoma cell line A549.

Transforming growth factor beta is a strong growth inhibitor for many types of normal and transformed cells, although little is known on the mechanism of this anti-proliferative effect. The human lung adenocarcinoma cell line A549 is growth arrested by TGF-beta 1 and serves as a model for studying this effect. We describe that, concurrent with the inhibition of A549 cell growth, TGF-beta 1 treatment causes a dramatic reduction in the level of expression of the amphiregulin (AR) gene, a recently identified member of the EGF/TGF alpha family. Similar results were also observed with TGF-beta 2. Peak inhibition occurred at 24 hr of treatment and was reversible upon removal of TGF-beta 1. The level of AR protein secreted by A549 cells was also decreased by TGF-beta 1. In contrast, TGF-alpha mRNA was not detected in these cells regardless of TGF-beta 1 treatment. Another TGF-beta inhibited cell line, PC-3 (human prostatic adenocarcinoma) also exhibited a decrease in AR message levels following exposure to TGF-beta 1. The growth inhibitory effects of TGF-beta may in part be mediated by modulation of AR expression.

Adenocarcinoma↗
PubMed1989

Transcription in nematodes: early Ascaris embryos are transcriptionally active.

In this report we analyze early zygotic gene expression in the parasitic nematode Ascaris lumbricoides var. suum. Using synchronous populations of early embryonic stages, nuclei were isolated, and in vitro run-off transcription assays were performed. We find transcriptional activity as early as the 4- to 8-cell stage. The percentage of RNA polymerase II activity, as measured in these assays, is greater than 80% of the total transcription at the 60-cell stage. Furthermore, we show that a specific transcript (actin) can be identified in all early stages tested.

Actins↗
PubMed1989

Effect of the cessation of an infusion of vasopressin in acutely hypophysectomized anaesthetized dogs.

Stimulation of left atrial receptors in dogs anaesthetized with chloralose results in a reflex diuresis and a small decrease in the plasma concentration of vasopressin. It has been suggested that this diuretic response is solely mediated by the antidiuretic hormone, vasopressin (Gauer & Henry, 1976; Ledsome, 1985). The present investigation was designed to determine how these anaesthetized dogs, which are thought to be insensitive to changes in plasma vasopressin, respond to small decreases in plasma vasopressin similar to those observed during stimulation of left atrial receptors. In the event it was shown for the first time that it is possible to obtain a water diuresis in an anaesthetized animal in response to a small fall in the concentration of plasma vasopressin. In order to produce changes in plasma vasopressin similar to those seen during stimulation of left atrial receptors the pituitary gland was removed and an intravenous infusion of arginine vasopressin was given in eleven dogs anaesthetized with chloralose; a small decrease in plasma vasopressin was then produced by replacing the vasopressin with an infusion of saline for 30 min. A decrease in the plasma concentration of 1.29 pg cm-3 from a control concentration of 1.85 pg cm-3 resulted in a 96.7% increase in urine flow. The fall in concentration of vasopressin consequent upon stimulation of atrial receptors could, therefore, explain the water diuresis in the anaesthetized dog preparation.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1988

Diuresis from atrial receptors after hypophysectomy and local ablation with no changes in plasma vasopressin.

Stimulation of the left atrial receptors in dogs anaesthetized with chloralose results in a reflex diuresis and natriuresis. The efferent limb of this reflex is though to have at least three components: nervous, haemodynamic and humoral. The present study was designed to investigate the humoral component in dogs anaesthetized with chloralose; to determine whether a humoral agent, other than vasopressin, might be causative in this reflex diuresis. The nervous and haemodynamic components were prevented by pharmacological denervation. Any possible contribution to the diuresis by a decrease in the plasma concentration of vasopressin was prevented by the removal of the pituitary gland. In animals in which a spontaneous diuresis followed hypophysectomy, an infusion of arginine vasopressin sufficient to maintain urine flow in the normal range for these dogs anaesthetized with chloralose was given. Distension of small balloons at the pulmonary vein-atrial junctions and in the left atrial appendage discretely to stimulate the atrial receptors in eleven dogs anaesthetized with chloralose resulted in a significant diuresis. It was concluded that a blood-borne agent other than vasopressin was responsible for the observed diuresis. At the moment it is not known whether vasopressin or the diuretic agent, or both, are involved in the diuresis accompanying the stimulation of atrial receptors.

Animals↗
PubMed1986

Neither a germ line-specific nor several somatically expressed genes are lost or rearranged during embryonic chromatin diminution in the nematode Ascaris lumbricoides var. suum.

Ascaris lumbricoides var. suum is a parasitic nematode of pigs. Its embryos undergo chromatin diminution between the third and fifth cleavages, resulting in the loss of about 30% of the DNA from all somatic precursor cells while the germ line DNA stays intact. Most of the eliminated DNA has been shown to be satellite sequences. Theodor Boveri [(1910) In "Festschrift fur R. Hertwig, III," Vol. 3, pp. 131-214, Fischer] proposed that functions essential only to the germ line might be lost from the soma. We have examined this proposal by cloning a gene encoding the major sperm protein (MSP) using a cloned MSP gene from Caenorhabditis elegans as a probe. The MSP appears to be expressed only in the testis of Ascaris, as it is in Caenorhabditis. Actin and alpha tubulin were also cloned to serve as somatically expressed gene controls. By probing Southern blots of somatic and germ line DNA with these cloned genes, it was found that none of them was lost or rearranged during chromatin diminution. Thus at least one germ line-specific gene is neither lost nor rearranged during chromatin diminution. We also found that the two nematode species differ widely in their numbers of both MSP and actin genes. Caenorhabditis has greater than 30 MSP genes, but Ascaris has no more than three; whereas Ascaris has many more actin genes than Caenorhabditis.

Actins↗
PubMed1985

Steroid-dependent survival of identifiable neurons in cultured ganglia of the moth Manduca sexta.

Adult emergence at the end of metamorphosis in the moth Manduca sexta is followed by the death of abdominal interneurons and motoneurons. Abdominal ganglia removed from insects before this period of naturally occurring cell death and maintained in vitro showed neuronal death confined to the same cells that normally die in vivo. Addition of physiological levels of the steroid 20-hydroxyecdysone to the culture system prevented the selective death of these motoneurons.

Animals↗
PubMed1984

Looking for relationships between the most repeated dispersed DNA sequences in the mouse: small R elements are found associated consistently with long MIF repeats.

Four highly-repeated dispersed DNA sequence families have been described in the mouse genome. These are the three small elements B1, B2 and R and the large (6 kb) MIF element. Together these comprise approximately 10% of the mouse genome. Possible relationships between these families are pertinent to the genome as a whole. We report here that the B1s, B2s and Rs are all randomly organized in the genome with respect to each other. Surprisingly though, the R and MIF families are found together consistently in a set of random genomic clones and in selected clones. We find Rs often located on one end of the MIF at a consistent site and conclude that a minority of Rs are an integral part of MIF while the majority of Rs are not associated with MIFs. We propose that isolated R elements are truncated forms of MIF. Also we speculate on the mechanism of dispersal of these elements through the mouse genome.

Animals↗
PubMed1984

The atrial receptors responsible for the decrease in plasma vasopressin caused by distension of the left atrium in the dog.

In dogs anaesthetized with chloralose, the effects of cooling the cervical vagi on the reflex decrease in plasma concentration of vasopressin, caused by distension of a large balloon in the lumen of the left atrium, were examined. Distension of the balloon in ten dogs with the vagi at 37 degrees C resulted in a decrease in plasma concentration of vasopressin and, as before, an increase in urine flow. The responses were not significantly affected by cooling to 16-18 degrees C but were abolished at 9 degrees C. At 16-18 degrees C the increase in activity in myelinated vagal afferent fibres is largely unchanged and at 9 degrees C is abolished (Kappagoda, Linden & Sivananthan, 1979; Sivananthan, Kappagoda & Linden, 1981). It is concluded that the decrease in plasma concentration of vasopressin during distension of the left atrium is mediated by the Paintal-type atrial receptors with myelinated vagal afferent fibres.

Afferent Pathways↗