Ion-induced release of calcium from isolated sarcoplasmic reticulum

Summary The structural consequences of clamping the transepithelial potential difference across the toad's urinary bladder have been examined. Reducing the potential to zero (short-circuiting) produced no apparent changes in the morphology of any of the four cell types which comprise the epithelium. Computer assisted, morphometric analysis of quick frozen specimens revealed no measurable difference in granular cell volume between open- and short-circuited preparations. However, when the open-circuit potential was quantitatively reversed (serosa negative with respect to mucosa), some of the preparations showed a marked increase in granular cell volume. To examine this more systematically twelve preparations were voltage-clamped at 50 mV (serosa negative); eight of the twelve revealed prominent granular cell swelling relative to control, short-circuited preparations. Only in this group of eight had the external circuit current fallen substantially during the clamping interval. Mitochondria-rich cells were not affected detectably. Application of the diuretic amiloride prior to clamping at reversed potential prevented granular cell swelling in every case. Goblet cells which were often affected by the –50 mV clamp were not protected by the diuretic. Granular cell swelling thus appeared to be dependent on sodium entry at the mucosal surface. We also observed that, after voltage reversal, the apical tight junctions of the bladders were blistered as they are with hypertonic mucosal media. This blistering was associated with an increase in passive ionic permeability and was not prevented by application of amiloride. This finding is consistent with the evidence that the junction is a complex barrier with asymetric, and hence, rectifying properties for intrinsic ionic conductance as well as hydraulic permeability. These findings, together with others from the literature, lead to the conclusion that the granular cells constitute the principal, if not sole, elements for active sodium transport across toad urinary bladder and that they swell when sodium entry exceeds the transport capacity of the pump at the basal-lateral surface.     

PHYTOPLANKTON LIPIDS: INTERSPECIFIC DIFFERENCES AND EFFECTS OF NITRATE,SILICATE AND LIGHT-DARK CYCLES1

The lipid content of various phytoplankton species was measured in response to nitrogen and silicon limitation and over the cell cycle in synchronized cultures. In a survey of 30 species it was found that during log-phase growth, green algae contained an average of 17.1% total lipids (% of total dry weight), whereas diatoms contained an average of 24.5%. Nitrogen deprivation for 4 to 9 days resulted in 2- to 3-fold increases in the lipid content of green algae, whereas both increases and decreases were noted in diatoms, depending on the species. The greatest lipid content measured in the study was 72% in Monallantus salina (strain GSB Sticho) which had been deprived of nitrogen for 9 days. Nitrate replenishment in a nitrogen starved culture of Oocystis polymorpha Groover & Bold showed that the excess cellular lipids do not rapidly disappear during recovery, until cell division occurs. A silicate deprivation experiment with Cyclotella cryptica Reimann, Lewin & Guillard (strain 7c) showed an increase in the total cellular lipid fraction from. 30 to 42% of dry weight within 6 h of the onset of silicon limitation, while the mass of lipid material per cell doubled within 12 h. The total lipid fraction in O. polymorpha was found to remain constant over the cell cycle in synchronized cultures regardless of the light regime. The data presented provided the first internally consistent study of phytoplankton lipids for a wide range of species and several growth conditions.     

Distribution of podolactone-type plant growth inhibitors in the coniferae

Plant growth inhibitors of the podolactone-type have been detected by bioassay in ten further species of Podocarpus. The most active extracts in P. elatus were from root tips, root cortex and very young leaves. Fifty-seven other conifers were examined for this type of activity. It is present in Cephalotaxus harringtonia where it is probably due to the presence of harringtonolide, which, like momilactone B from rice husks, shows podolactone-type inhibition of the growth of etiolated dwarf pea hooks.     

Immune cytolysis of human malignant melanoma by antibody to oncofetal antigen-I (OFA-I)

Summary IgG anti-OFA-I found in melanoma patients was tested for its ability to lyse human tumor cells in antibody-dependent cell-mediated cytotoxicity (ADCC). Sera from 89 stage II melanoma patients which contained non-HLA-related IgG antibody to an OFA-I-positive melanoma cell line (M14) as tested by indirect membrane immunofluorescence (IMI) were originally chosen as possible sources of IgG anti-OFA-I. Of those tested for specific IgG activity to OFA-I by IMI, anti-OFA-I was found only in those patients immunized with OFA-I-positive tumor cells. When the same sera were tested in ADCC, no non-HLA-related activity could be demonstrated. This result was confirmed with purified IgG fractions that could, nevertheless, show anti-OFA-I reactivity in a complement-dependent cytotoxicity assay. The fact that naturally occurring IgG anti-OFA-I antibody was not readily detectable in patients' sera and that induced IgG anti-OFA-I did not participate in ADCC indicates that OFA-I-related tumor cell lysis via ADCC is an unlikely phenomenon in cancer patients.     

Direct assay for creatine kinase by reversed-phase high-performance liquid chromatography

A direct assay for creatine kinase (CK) activity was developed based on the separation and quantitation of adenosine triphosphate (ATP) by high-performance liquid chromatography. The total incubation time is 13 min and the elution time for ATP is 16 min. Using lyophilized CK as the sample, a sensitivity in the range of 8 U/l (units/liter) was obtained. The method presented also has clinical significance in that CK levels in serum can easily be determined with minimal sample preparation. Using serum samples from a healthy patient and a heart attack victim, activities of 26.6 U/l and 609.0 U/l, respectively, were obtained. Because of the direct measurement of ATP, this method eliminates the coupled reactions encountered in the common spectrophotometric and colorimetric methods of analysis resulting in a simpler and inexpensive assay.     

Evidence that calmodulin may be involved in phytohaemagglutinin-stimulated lymphocyte division

Phytohaemagglutinin-stimulated and non-stimulated incorporation of [³H]thymidine into human peripheral blood lymphocytes is inhibited by the calcium antagonist PY 108–068 and by the calmodulin antagonists trifluo-perazine andN-(6-aminohexyl)-5-chloro-l-naphthalene sulphonamide (W7). It is argued that calmodulin may be involved in both non-stimulated [³H]thymidine uptake in lymphocytes and also in the lymphocyte response to phytohaemagglutinin.     

Effect of adenosine deaminase inhibitors on Fcμ receptor expression in human T-cell cultures

Incubation of human peripheral blood T-lymphocyte cultures with 100 μM EHNA or 1 μM pentostatin results in the delayed appearance of Fcμ, receptor-bearing cells. The percentage of Tμ-positive cells approaches control levels by 24–30 hr despite the lack of detectable adenosine deaminase activity. Tγ to Tμ transition was more effectively inhibited than To to Tμ in studies with the individual subpopulations. The inhibitory effect of pentostatin or EHNA on the appearance of Fcμ receptor-positive cells was reversible with exogenous undine or 2′-deoxycytidine. These results indicate that pyrimidine deprivation affects the appearance of Fcμ receptors in T-cell cultures, and that despite the continued inhibition of ADA the effect on Fcμ is reversible by 24 hr without the addition of exogenous pyrimidines.     

Simultaneous analysis of phenylglycols and phenylethanols in human urine by gas chromatography—mass spectrometry

A method is described for the determination of the neutral metabolites formed from catecholamines and various other structurally related phenylethylamines by using gas chromatography—chemical ionization—mass spectrometry. These metabolites (phenylglycols and phenylethanols) were extracted from urine specimens and converted to pentafluoropropionyl derivatives which were separated on either 3% OV-1, 3% SP-2250, or 3% QF-1 packed columns. Our results demonstrate the presence in human urine of p-hydroxyphenylglycol, a metabolite of octopamine. One patient excreted 13 and 91 μg/day of free and total (free + conjugated) p-hydroxyphenylglycol, respectively. Treatment with a monoamine oxidase inhibitor reduced the excretion of total p-hydroxyphenylglycol to 30% of baseline level.     

Molecular characterization of Ascaris suum DNA and of chromatin diminution

A technique for the extraction of pure somatic (post-diminution) and germ line (pre-diminution) DNA from the parasitic nematode Ascaris is described. Uncontaminated post- and pre-diminution DNAs were sheared and reassociated to different C₀t values. Computer analysis of the complete reassociation kinetics determined that 33% of the germ line genome is eliminated during the process of chromatin diminution. The eliminated DNA is comprised of repetitive and unique sequences in an approx. 1:1 ratio.     

Phenolic O-methyltransferase from Lentinus lepideus (basidiomycete)

The fungus, Lentinus lepideus, produces crystalline methyl p-methoxycinnamate in stationary cultures. O-methylation and methyl ester formation of hydroxycinnamic acids were examined with enzyme preparations of the fungus. Using S-adenosylmethionine-¹⁴CH3, it was found that only the methyl esters of the hydroxycinnamic acids are substrates for O-methylation and not the free acids. Benzoic acids and their methyl esters are not substrates. The activity of the enzyme is p-specific and its specific activity decreases with increasing number of hydroxyl groups in the substrate. The same enzyme preparations catalyze the formation of the methyl ester of cinnamic acid from the free acid.