Molecular isoforms of murine CD44 and evidence that the membrane proximal domain is not critical for hyaluronate recognition

We previously found that the CD44 glycoprotein on some lymphocytes can mediate adhesion to hyaluronate (HA) bearing cells. However, many questions remain about the molecular heterogeneity of CD44 and mechanisms which control its recognition of this ligand. In vitro mutagenesis and DNA sequencing have now been used to investigate the importance of the membrane proximal region of murine CD44 for recognition of soluble or cell surface HA. CD44 with an 83 amino acid deletion in this region mediated binding to soluble ligand and the apparent avidity increased markedly in the presence of a particular antibody to CD44, IRAWB14. The shortened CD44 was however inefficient in mediating adhesion of transfected cells to HA immobilized on cell surfaces. Four new murine isoforms of CD44 were isolated from a carcinoma line by use of the polymerase chain reaction. Only two of them correspond to ones recently discovered in rat and human cells. The longest variant nearly doubled the length of the extracellular portion of the molecule and introduced an additional 20 potential sites for glycosylation. When expressed on T lymphoma cells, all four of the new murine CD44 isoforms were capable of mediating adhesion to HA bearing cells. This result contrasts with a report that a related human CD44 isoform lacks this ability when expressed on B lineage lymphoma cells. The new murine isoforms also conferred the ability to recognize soluble HA and were very responsive to the IRAWB14 antibody. A brief survey of normal murine cell lines and tissues revealed that the hemopoietic isoform was the most abundant species. These findings indicate that the NH2-terminal portion of CD44 is sufficient for HA recognition and that this function is not necessarily abrogated by variations which occur in the membrane proximal domain. They add to the known molecular diversity of CD44 and provide another experimental model in which isoform specific functions can be investigated.

Determination of carcinogenic potency of alkytoxynol-741 (AP-741) by rat peritoneal cell cultures

The carcinogenic potency of AP-741 was tested in rats using the Nashed method of rat peritoneal cell short-term carcinogenic test. N-methyl-N-nitro-N'-nitrosoguanidian (MNNG) was used as positive control; saline and nonoxynol-9 (NP-9) were used as negative control. Two doses of AP-741 (4 mg/kg and 40 mg/kg equivalent to 4 and 40 times human doses) were tested. The result showed that no colonies of more than 9 cells were seen in the saline and NP-9 groups, and the two dose groups of AP-741. However, 12 +/- 8.3 colonies (9-29 cell/colony) and 4.5 +/- 4.2 colonies (30-300 cell/colony) were seen in the MNNG group. According to the Nashed criterion, we can say MNNG has potential carcinogenesis, while AP-741 does not have any potential carcinogenesis and its use as a vaginal contraceptive drug is safe.

Physiologic comparison and validation of Stairobic stepping with bench stepping

To compare the oxygen cost of submaximal exercise on the Stairobic stepping (SS) machine with bench stepping (BS), 12 healthy men and women (mean age 23 years) underwent six different five minute exercise bouts that were randomly assigned. Tests were conducted using standard open circuit calorimetry. SS at 40 and 60 st/min was equal to BS at 20 st/min and SS at 80 st/min was equal to BS at 30 st/min for VE and RER. VO2 was equal at 20 st/min (BS) and 60 st/min (SS), and 30 st/min (BS) and 80 st/min (SS). Stairobic MET (SM) displayed values over-estimated actual MET (AM) values at the two lowest SS rates and under-estimated the AM value at the highest SS rate. Forty-eight observations of the MET response of SS were conducted and analyzed (BMDP2R) in a forward stepping solution. The multiple regression equation calculated for AM was: AM = -0.567 + -0.012 (WT) + 0.063 (rate) + 0.612 (SM) with an adjusted R2 of 0.82 and a SEE of 0.90. The physiologic cost of BS was approximately equal to SS at two to three times the BS rate of stepping.

Determination of trace amounts of estriol and estradiol by adsorptive cathodic stripping voltammetry

Estriol and estradiol are electroinactive in the potential range from -200 to -1000 mV versus a silver-silver chloride electrode at a mercury electrode. The conversion of these estrogens into electroactive nitro derivatives of estrogens, which are used for voltammetric determination, was studied. Such nitro derivatives give a well defined cathodic stripping wave at -600 mV in pH 10.5 borate buffer. Estriol and estradiol are determined in the ranges 1 x 10(-9)-1.5 x 10(-6) and 5 x 10(-9)-2 x 10(-6) mol dm-3, respectively, by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode. Some steroids, such as estrone, interfere because the three estrogens have almost the same molecular structure and have similar nitro derivatives, but progesterone does not interfere and is reduced at significantly more negative potentials than the nitrated estrogens. It can be determined simultaneously with estriol or estradiol. A method was developed for the assay of estriol in pharmaceutical preparations.

Effect of hyperthermia on thymidine salvage as related to DNA synthesis

The effect of increasing temperature up to 43 degrees C on thymidine (TdR) salvage, i.e. uptake of TdR, thymidine kinase (TK) activity, intracellular amount of thymidinetriphosphate (dTTP) and specific activity of 3H-dTTP and incorporation of dTTP into DNA, was studied in ascites tumour cells in vitro. While the uptake of [3H]TdR was almost unchanged up to 40.5 degrees C and 2.4 h followed by a decrease at later times and higher temperatures, TK activity declined already after 30 min in a temperature-dependent way, leading to a decrease in cellular amount of dTTP reaching almost undetectable values at 43 degrees C and 6.0 h. The specific activity of [3H]dTTP in the cell was elevated at 39 degrees C and 43 degrees C, but somewhat reduced at 40.5 degrees C. Incorporation into DNA of [3H]TdR decreased in a temperature-dependent way with increasing incubation time. After correction for specific activity of [3H]dTTP, however, the incorporation of [3H]TdR into DNA at 39 degrees C and 40.5 degrees C was unchanged up to 2.4 h and for 40.5 degrees C up to 6.0 h, while incorporation into DNA at 43 degrees C was still reduced. The overall protein synthesis was also reduced in a temperature-dependent way. We concluded that phosphorylation of TdR to dTMP was more sensitive to moderately elevated temperatures than uptake of TdR and DNA synthesis per se, caused by a reduced TK activity. The decline in TK activity was probably due to a decrease in TK polypeptide synthesis.

Requirements for hyaluronic acid binding by CD44: a role for the cytoplasmic domain and activation by antibody

The CD44-negative T lymphoma AKR1 (CD44.2 genotype) was transfected with a CD44.1 cDNA. The intact cDNA conferred on the transfected cells the ability to bind hyaluronic acid (HA) both from solution and immobilized on culture plates. It also conferred a CD44-dependent and hyaluronidase-sensitive increase in adhesion to a lymph node endothelial cell line. A mutant cDNA which codes for a CD44 molecule lacking most of the cytoplasmic domain of CD44 was also transfected into AKR1, and cell sorting was used to select transfectants expressing levels of cell surface CD44 expression comparable with the line transfected with the wild-type CD44 cDNA. The cells transfected with the mutant construct bound fluoresceinated HA from solution very poorly, but did adhere to immobilized HA, though less well than cells transfected with the wild-type construct. This result indicates that the cytoplasmic domain of CD44 is necessary for binding of HA from solution but is not required for binding to immobilized HA, although it may contribute to adhesion following ligand recognition. A monoclonal antibody (mAb), IRAWB 14, which reacts with CD44 on all CD44+ cells dramatically induced HA binding by some CD44+ cell lines that did not constitutively bind HA. The transfectant expressing a CD44 molecule with a truncated cytoplasmic domain could be induced by this antibody to bind fluoresceinated-HA from solution. Splenic T cells did not bind fluoresceinated HA constitutively. In the presence of the IRAWB 14 mAb, virtually all CD44+ splenic T cells bound HA. Induction was immediate and occurred equally well at room temperature and at 4 degrees C, indicating that the new HA-binding activity was due to preexistent CD44 molecules. These results are compatible with an antibody-induced activation of CD44 by either a conformational change in the CD44 molecule or a change in the distribution of CD44 molecules on the cell surface.

Cell cycle related studies on thymidine kinase and its isoenzymes in Ehrlich ascites tumours

Thymidine kinase (TK) activity was measured in relation to the cell cycle of in vivo growing ascites tumour cells. The cells were synchronized by means of centrifugal elutriation and the cell cycle composition of the cell fractions was determined by flow cytometry. TK activity was low in G1, increased during S phase and declined in G2. A half-life of TK activity of about 45 min was found throughout the cell cycle. Four isoenzymes at pI values of 4.1, 5.3, 6.9 and 8.3, denoted as isoenzymes 1-4, were identified using isoelectric focusing. Isoenzymes 3 and 4 were responsible for the profound cell cycle related changes in the TK activity. Corresponding isoenzymes were also found in the fetal mouse liver. In the adult mouse liver isoenzyme 2 was the dominating isoenzyme. The half-life of the isoenzymes was in the same range as for the total TK activity. We conclude that the low TK activity in G1 is due to degradation of the enzyme in G2 at a normal rate combined with an arrest in the synthesis of TK. We also conclude that isoenzyme 4 and the intermediate isoenzyme 3, which had earlier been suggested to be a mitochondrial form of TK, in fact represent cytoplasmatic forms of TK. According to cell cycle and pI studies, isoenzyme 2 belongs to the mitochondrial form. Studies with various phosphor donors and specific substrates, however, indicate that it also contains a cytoplasmic component.

Lack of correlation between thymidine kinase activity and changes of DNA synthesis with tumour age: an in vivo study in Ehrlich ascites tumour

Thymidine kinase (TK) and its isoenzymes were studied in relation to age of Ehrlich ascites tumour cells growing in vivo. Various steps of the pathway of thymidine through deoxynucleotide metabolism were studied: [3H]-thymidine cellular uptake and incorporation into DNA; the cellular nucleotide pools; and the concentration of thymidine in ascites. In addition, the proportion of cells in the various parts of the cell cycle and the bromodeoxyuridine labelling index were determined. Four isoenzymes at pI 4.1, 5.3, 6.9 and 8.3 were identified using isoelectric focusing. The TK activity declined with age of the tumour by about 90%, mostly due to a decrease of the isoenzyme at pI 8.3. However, this decline was neither related to the changes in DNA synthesis rate of the cells with tumour age, nor to the proportion of cells in S-phase or the bromodeoxyuridine (BrdU) labelling index. In contrast, the contribution of DNA synthesis via the thymidine salvage pathway relative to the total DNA synthesis increased from less than 1% at exponential growth to about 15% at plateau phase of growth. Blocking of DNA synthesis by aphidicolin did not change the TK activity. We therefore conclude that changes in TK activity and changes in cell growth are epiphenomena rather than causally related to each other. All nucleotide pools decreased with tumour age. The inhibition of TK by an increase in the deoxythymidine triphosphate pool could therefore be excluded. With a decrease of the TK activity during tumour growth, increasing amounts of TdR were excreted by the cells and accumulated in the ascites fluid. To explain our results on TK activity we propose a substrate cycle in which thymidine monophosphate supplied by de novo synthesis is dephosphorylated and is then either phosphorylated by TK to thymidine monophosphate or excreted by the cell.

Nd:MgO:LiNbO(3) waveguide laser and amplifier

We report efficient operation of a channel waveguide laser and a channel waveguide amplifier in Nd:MgO:LiNbO(3). For the laser a cw output power of 2.9 mW was obtained for 23.6 mW of absorbed pump power. The absorbed pump power at threshold was 1.5 mW, and a slope efficiency of 13% was achieved. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power.

Sympathetic peripheral chemoreflex is independent of expiratory output neurons in the cat

Previously we reported that activities of certain chemoreflex sensitive cervical preganglionic sympathetic nerves (PSN) were augmented by carotid chemoreceptor stimulation independently of phrenic nerve (PN) activity in the cat. To test the hypothesis that the PSN carotid chemoreflex could have been mediated by the expiratory neuron activity, we studied the relationship between PSN, internal intercostal expiratory nerve (IICEN) and PN activities in vagotomized, anesthetized, paralysed and artificially ventilated cats. We made the following observations. (1) Hypoxia often inhibited IICEN activity while the PN and PSN activities were stimulated. (2) during normoxia, cyanide strongly stimulated PN and PSN discharges but only moderately IICEN discharges. (3) Hyperventilation hypocapnia suppressed or eliminated PSN and PN rhythms and activities, but made some IICEN fibers fire continuously. (4) During hypocapnic apnea, cyanide stimulated PSN activity before PN and IICEN activities, although some PSN fibers were stimulated simultaneously with PN fibers. Accordingly we conclude that IICEN activity does not significantly influence chemoreflex stimulation of PSN activity and that a direct chemoreflex stimulation of IICEN is minimal in the cat. Thus, the chemoreflex PSN response is in part independent of respiratory chemoreflex pathways.

Activation of T lymphocytes via monoclonal antibodies against rat cell surface antigens with particular reference to CD2 antigen

In the rat, monoclonal antibodies (mAbs) against the T-lymphocyte receptor (TCR), CD3 antigen and CD2 antigen are mitogenic for T lymphocytes. Antibodies against CD43 (leukosialin) and CD5 are not, but can enhance the effects of other stimuli. Activation of a T-lymphocyte cell line in terms of triggering an increase in free cytoplasmic Ca2+ [( Ca2+]i) was mediated by mAbs against Class 1 MHC and CD4 in addition to the mitogenic mAbs. In the presence of non-activating levels of anti-TCR mAb a strong synergistic signal was seen with anti-CD4, but incubation with anti-CD4 prior to activation with anti-CD3 inhibited the CD3 signal. Stimulation of DNA synthesis in resting T cells via anti-CD2 mAbs required a combination of two non-competitive antibodies and addition of a third anti-CD2 mAb inhibited the activation. The anti-CD2 mAbs were active on all types of mature T cells from peripheral lymphoid organs and the thymus, but cells in the thymus that lacked a TCR could not be activated via CD2. Rat CD2 was transfected into Jurkat cells and cross-linking with anti-rat CD2 mAbs gave an increase in [Ca2+]i similar to that seen with an anti-human CD3 mAb. All three types of anti-rat CD2 mAbs gave a signal including the mAb that inhibited mitogenesis. Signal transduction via CD2 was not seen in L cells and was only weakly observed in TCR-ve Jurkat cells that had been transfected with rat CD2. The cytoplasmic domain of transfected CD2 was shown to be important for the signal transduction since no increase in [Ca2+]i could be triggered in cells expressing mutant CD2 that lacked the cytoplasmic domain. Mutant forms with increasing lengths of cytoplasmic domain showed functions that progressively approached that of the native function.

Effects of adriamycin and hyperthermia on cellular uptake of [3H]thymidine and its significance for the incorporation into DNA

Inhibition of the salvage DNA synthesis was studied in ascites tumour cells up to 240 min at moderately increased temperatures of 39 degrees C, 40.5 degrees C and 43 degrees C alone or in combination with adriamycin (ADR). Hyperthermia and ADR acted additively on salvage DNA synthesis. The [3H]thymidine (TdR) incorporation was strongly related to the cellular uptake of [3H]TdR. In order to evaluate the significance of the decrease in [3H]TdR uptake for the incorporation into DNA, the thymidine kinase (TK) has also been studied. TK activity started to decrease at a temperature of 39 degrees C, probably due to inhibition of translation and/or transcription of the enzyme, and was almost completely inhibited at 43 degrees C. ADR did not affect TK activity. Inhibition of DNA synthesis by aphidicolin neither decreased the ability of the cell to take up [3H]TdR nor the ability to affect TK activity. We concluded that moderate increases in temperature alone, or in combination with ADR, inhibit salvage DNA synthesis by inhibition of TdR uptake, possibly due to inhibition of phosphorylation; ADR, on the contrary, inhibits TdR uptake by other mechanisms such as changes in membrane function.

[T-lymphocyte subsets in peripheral blood and pleural effusion in tuberculous pleurisy and carcinomatous pleurisy: analysis by monoclonal antibodies]

By using monoclonal antibodies, OKT8(pant), OKT4(inducer/helper),OKT8(suppressor/cytotoxic) T-lymphocyte subsets were examined in 25 patients with tuberculous pleurisy and 15 patients with carcinomatous pleurisy. The results showed that percent and absolute counts of OKT8,OKT4,OKT8 in tuberculous pleural effusion were significantly higher than those in carcinomatous pleural effusion. Percent and absolute counts of OKT8, OKT4, in tuberculous pleural effusion were significantly higher than those in peripheral blood. OKT8% in peripheral blood of carcinomatous pleural effusion was significantly lower than that in peripheral blood of control group. When OKT8% greater than 65, OKT4% greater than 45, OKT8 number/mm8 greater than 1,000, OKT4 number/mm8 greater than 800, OKT8 number/mm8 greater than 500 in pleural effusion, it suggests pleural effusion is tuberculous. when OKT8% less than 55, OKT4% less than 45, OKT5 number/mm8 less than 500, OKT4 number/mm8 less than 300, OKT8 number/mm8 less than 200, it suggests pleural effusion is carcinomatous pleural effusion.

A role in transmembrane signaling for the cytoplasmic domain of the CD2 T lymphocyte surface antigen

The CD2 antigen can mediate mitogenesis of T lymphocytes after binding combinations of monoclonal antibodies. To examine the importance of the cytoplasmic domain in signaling, rat CD2 cDNA has been transfected into the human Jurkat cell line and triggering of an increase in cytoplasmic free Ca2+ concentration [( Ca2+]i) has been assayed. In cells expressing full-length CD2, a clear signal was triggered with anti-CD2 monoclonal antibodies. In contrast, a barely detectable increase in [Ca2+]i occurred with mutant rat CD2 molecules that included only 6 or 40 amino acids of the full-length cytoplasmic domain of 116 residues. It thus appears that the CD2 cytoplasmic domain plays a role in the signaling event.