Role for sulfur-containing groups in the Na+-Ca2+ exchange of cardiac sarcolemmal vesicles

Different amino acid residues in cardiac sarcolemmal vesicles were modified by incubation with various chemical reagents. The effects of these modifications on sarcolemmal Na+-Ca2+ exchange were examined. Dithiothreitol, an agent that maintains sulfur-containing residues in a reduced state, caused a time- and concentration-dependent decrease in Na+-Ca2+ exchange. The treatment with dithiothreitol resulted in a decrease in Vmax values but did not alter the Km for Ca2+ for the Na2+-Ca2+ exchange reaction. If Na+ replaced K+ as the ion present during the modification of sarcolemmal membranes with dithiothreitol, there was substantially less of an inhibitor effect on Na+-Ca2+ exchange. Similar results were obtained with reduced glutathione, a reagent that also maintains sulfur-containing residues in a reduced state. Two sulfhydryl modifying reagents, methylmethanethiosulfonate and N'-ethylmaleimide, were capable of altering Na+-Ca2+ exchange, and the type of ion present during modification significantly affected the extent of this alteration. Almost all of the chemical reagents investigated that modified other amino acid resides (carboxyl, lysyl, histidyl, tyrosyl, tryptophanyl, arginyl and hydroxyl) had the capacity to alter Na+-Ca2+ exchange after preincubation with the sarcolemmal membrane vesicles. However, the sulfur residue-modifying reagents were the only compounds to exhibit significant differences in their action on Na+-Ca2+ exchange, depending on whether Na+ or K+ was present in the preincubation modification medium. The tryptophan modifier, N-bromosuccinimide, was the sole reagent that elicited a substantial increase in membrane permeability. The evidence is consistent with the hypothesis that sulfur-containing residues interact with a Na+-binding site for Na+-Ca2+ exchange in cardiac sarcolemmal vesicles.

Chemical analysis of compounds extracted from the tergal "spots" of Lutzomyia longipalpis from Brazil

The chemical composition of the compounds contained in the tergal spots of Lutzomyia longipalpis was investigated. Four populations of L. longipalpis were examined, originating from: Sobral, Ceará, Brazil (one spot and two spot populations), Santarém, Pará, Brazil (one spot) and Marajó Island, Pará, Brazil (one spot). The tergal spots were dissected out, extracted in hexane and analysed on a gas chromatograph/mass spectrometer. Two compounds were found, identical to compounds found in earlier studies, but there was no correlation between number of tergal spots and type of compound present. It was suggested that the number of tergal spots could not be used as a marker for reproductively isolated populations, and that analysis of the compound present within the spots might be necessary to characterize potentially good vector populations.

Ca2+ transport capacity of sarcolemmal Na+-Ca2+ exchange. Extrapolation of vesicle data to in vivo conditions

Na+-Ca2+ exchange activity is high in cardiac sarcolemmal vesicles suggesting an important physiologic role. Vesicular Na+-Ca2+ exchange, however, is usually measured under conditions which are far from physiologic. Using sarcolemmal vesicles, we have estimated the possible significance of both Ca2+ influx and efflux mediated by Na+-Ca2+ exchange under approximate in vivo ionic conditions. In this situation, Na+-Ca2+ exchange activity is far from maximal with intracellular Mg2+ causing significant inhibition. The capacity of the Na+-Ca2+ exchange system to extrude intracellular Ca2+ (at [Ca2+] = 6.0 microM) is about 1.2 mumol Ca2+/kg wet weight/s and approximately equals the capacity of the sarcolemmal ATP-dependent Ca2+ pump. The capacity of the sarcoplasmic reticular Ca2+ pump to remove cytoplasmic Ca2+ is much larger. Significant Ca2+ influx through the exchanger is unlikely to occur in normal mammalian myocardium and would require reduced extracellular Na+ or elevated intracellular Na+.

Treatment of NZB/NZW mice with total lymphoid irradiation: long-lasting suppression of disease without generalized immune suppression

We used total lymphoid irradiation (TLI; total dose = 3400 rad) to treat the lupus-like renal disease of 6-mo-old female NZB/NZW mice. Similar to our past studies, this treatment resulted in a marked prolongation of survival, decrease in proteinuria, and decrease in serum anti-DNA antibodies compared with untreated littermate controls. Although there was no evidence of disease recurrence in TLI-treated mice until after 12 mo of age, the in vitro proliferative response to phytohemagglutinin by NZB/NZW spleen cells recovered within 6 wk such that responses were greater than control NZB/NZW animals. A similar recovery and overshoot after TLI were evident in the primary antibody response to the T cell-dependent antigen sheep red blood cells (SRBC). Both the total and IgG anti-SRBC antibody responses after TLI were greater than those of untreated NZB/NZW controls, and were comparable with those of untreated non-autoimmune mice. Despite this increased response to mitogens and antigens after TLI, we noted a decrease in spontaneous splenic IgG-secreting cells and a decrease in IgG but not IgM antinuclear antibody production. Nonspecific suppressor cells of the mixed leukocyte response were detectable in the spleens of NZB/NZW mice early after TLI. However, the disappearance of suppressor cells was not associated with recrudescence of disease activity. Furthermore, transfer of large numbers of spleen cells from TLI-treated NZB/NZW mice did not result in disease suppression in untreated age-matched recipients. In summary, treatment of NZB/NZW mice with TLI results in a prolonged remission in autoimmune disease, which is achieved in the absence of generalized immunosuppression.

Treatment of NZB/NZW mice with total lymphoid irradiation: long-lasting suppression of disease without generalized immune suppression

We used total lymphoid irradiation (TLI; total dose = 3400 rad) to treat the lupus-like renal disease of 6-mo-old female NZB/NZW mice. Similar to our past studies, this treatment resulted in a marked prolongation of survival, decrease in proteinuria, and decrease in serum anti-DNA antibodies compared with untreated littermate controls. Although there was no evidence of disease recurrence in TLI-treated mice until after 12 mo of age, the in vitro proliferative response to phytohemagglutinin by NZB/NZW spleen cells recovered within 6 wk such that responses were greater than control NZB/NZW animals. A similar recovery and overshoot after TLI were evident in the primary antibody response to the T cell-dependent antigen sheep red blood cells (SRBC). Both the total and IgG anti-SRBC antibody responses after TLI were greater than those of untreated NZB/NZW controls, and were comparable with those of untreated non-autoimmune mice. Despite this increased response to mitogens and antigens after TLI, we noted a decrease in spontaneous splenic IgG-secreting cells and a decrease in IgG but not IgM antinuclear antibody production. Nonspecific suppressor cells of the mixed leukocyte response were detectable in the spleens of NZB/NZW mice early after TLI. However, the disappearance of suppressor cells was not associated with recrudescence of disease activity. Furthermore, transfer of large numbers of spleen cells from TLI-treated NZB/NZW mice did not result in disease suppression in untreated age-matched recipients. In summary, treatment of NZB/NZW mice with TLI results in a prolonged remission in autoimmune disease, which is achieved in the absence of generalized immunosuppression.

Mucus degradation by pepsin: comparison of mucolytic activity of human pepsin 1 and pepsin 3: implications in peptic ulceration

The ability to digest mucus, mucolytic activity of isolated pepsins and samples of human gastric juice has been assayed by measuring the fall in viscosity when incubated with purified pig gastric mucus glycoprotein. Pure human pepsin 1, the peptic ulcer associated pepsin, digested gastric mucus glycoprotein at a faster rate than did pure human pepsin 3 (the principal human pepsin), or the equivalent pig pepsin (pepsin A). At pH 2.0 pepsin 1 had twice the mucolytic activity of pepsin 3. Above pH 3.8 this difference became more marked and whereas pepsin 1 caused substantial mucolysis up to and including pH 5.1, pepsin 3 had minimal activity. At pH 4.0 pepsin 1 had six times the mucolytic activity of pepsin 3. Gastric juices from patients with duodenal ulcer each exhibited substantial mucolytic activity between pH 2 to 5, similar to that of pepsin 1. In contrast, gastric juice from non-symptomatic volunteers exhibited little mucolytic activity above pH 4. Analysis of the mucus glycoprotein by gel filtration showed that an increase in lower molecular weight, pepsin degraded, glycoprotein was associated with the fall in mucus viscosity for all enzyme preparations. These results showed that pepsin 1 can digest the mucus more effectively than pepsin 3 and at higher pH values. The raised concentrations of pepsin 1 in the juice of peptic ulcer patients may thus promote the ulcerative process by increased erosion of the mucus barrier under conditions likely to pertain in the duodenal bulb as well as the stomach.

Effects of fatty acids on Na+-Ca2+ exchange and Ca2+ permeability of cardiac sarcolemmal vesicles

We have previously reported that anionic phospholipids (Philipson, K.D., and Nishimoto, A.Y. (1984) J. Biol. Chem. 259, 16-19) and other anionic amphiphiles (Philipson, K.D. (1984) J. Biol. Chem. 259, 13999-14002) stimulate Na+-Ca2+ exchange in cardiac sarcolemmal vesicles. To further these studies, we have now investigated the effects of a variety of fatty acids on both Na+-Ca2+ exchange and passive Ca2+ permeability. Na+-Ca2+ exchange was stimulated by fatty acids by up to 150%. Unsaturated fatty acids were more potent than saturated fatty acids, and the stimulation was primarily due to a decrease in the apparent KM (Ca2+). There was a positive correlation between the ability of a fatty acid to stimulate Na+-Ca2+ exchange and to increase passive Ca2+ permeability. The methyl esters of fatty acids had no effects on either exchange or permeability indicating the importance of anionic charge. We conclude that the combination of local lipid disorder and anionic charge regulate Na+-Ca2+ exchange. Perturbations of the bilayer hydrophobic region and increased negative surface charge are both required for fatty acids to increase passive Ca2+ flux. Na+-Ca2+ exchange is stimulated when the ratio of membrane free fatty acid to phospholipid is about 5%. This level of fatty acid is achieved during 1 h of myocardial ischemia (Chien, K. R., Han, A., Sen, A., Buja, L. M., and Willerson, J. T. (1984) Circ. Res. 54, 313-322), indicating that ischemia could induce altered sarcolemmal Ca2+ transport due to fatty acid accumulation.

A procedure for the investigation of anesthetic/surgical deaths

A procedure for the investigation of surgical/anesthetic deaths is presented which allows for clearly defined jurisdictional assessment and correlates the autopsy and toxicological findings with the pathophysiology of the anesthetic/surgical event. This procedure facilitates an accurate certification of the cause of death in patients who die during surgery and anesthesia.

Brain size and shape in strongly and weakly lateralized mice

Mice from two selected lines differing markedly in their degree of lateralization, and from a random-bred control line, were studied. The brains of strongly lateralized mice were found to be heavier, and those of weakly lateralized mice to be lighter, than those of control mice of equivalent body weight; the degree of cerebral asymmetry was found to be least in weakly lateralized mice; and the corpora callosa of both selected lines were smaller than those of control mice. These findings are tentatively interpreted in terms of the effects of different behavioral strategies on the development of the central nervous system.

Glycerol kinase deficiency inhibits glycerol utilization in phosphoglyceride and triacylglycerol biosynthesis

Glycerol 3-phosphate is an initial metabolite in the biosynthesis of phosphoglycerides and triacylglycerols. Both glycerol and glucose are precursors of glycerol 3-phosphate. Cultured skin fibroblasts from patients with glycerol kinase deficiency utilized glucose, but not glycerol in the biosynthesis of phosphoglycerides and triacylglycerols. Phosphoglyceride and triacylglycerol biosynthesis in glycerol kinase deficiency fibroblasts is not diminished by the inability to use glycerol as a precursor of glycerol 3-phosphate.

Antiserum to prolactin lowers blood pressure (BP) in spontaneously hypertensive rats

The role of PRL in the development of hypertension in the SHR was examined by administering PRL antiserum to neonatal SHR. On days 2-7 post partum, male SHR were injected with 50 microliters/day of either antiserum to PRL (which chronically lowers plasma PRL), normal rabbit serum (NRS), or 0.9% NaCl. Heart rate, BP, and body weight were measured biweekly on weeks 6-14 of age. Anti-PRL lowered BP vs. NaCl on weeks 6, 8, 12, and 14 (range 7-17 mm Hg lower). NRS animals showed BP differences from the NaCl group only on weeks 6 and 14, with no consistent effect. Heart rates fell during the study in the NaCl and anti-PRL groups but not in the NRS group. Anti-PRL and NRS groups had higher heart rates than did the NaCl group. Body weights did not differ between groups except on week 14, when the NRS group weighed less than the NaCl group. These results suggest that while PRL is involved in BP regulation in the SHR, it is not involved in the pathogenesis of the genetic hypertension seen in the strain. In addition, the results suggest that the serum treatment may have caused heart damage which led to an elevation in the heart rates of the serum-treated groups.

Attenuation of psychosocial stress-induced hypertension by gamma-linolenic acid (GLA) administration in rats

This study investigated a model of psychosocial stress-induced hypertension in the rat, and examined effects of the prostaglandin E precursor, gamma-linolenic acid (GLA) on the development of hypertension during psychosocial stress. In the first study, male rats were housed four/cage for an acclimation period of 21 days, followed by a 14-day control period. An experimental group (N = 12) was then placed in isolation cages for 14 days, then regrouped for a 7-day recovery period. Controls (N = 12) remained group-housed. Eight animals per group were sacrificed after the experimental period, and four per group after recovery for organ weight analysis. Mean systolic blood pressure (BP) was similar between groups during the control period (126 +/- 2 and 125 +/- 2 mm Hg), but increased during isolation, reaching 140 +/- 2 mm Hg (P less than 0.001) by Day 14. During recovery BP returned to control levels. No changes in heart rate, heart weight/body weight or adrenal weight were seen. The second study utilized a protocol similar to that of the experimental group of the first study, minus the recovery period. On Day 1 of the control period 28-day osmotic pumps were implanted ip, releasing olive oil or GLA in olive oil. Four groups of rats (N = 8/group) received either (i) olive oil (controls), (ii) 0.018 mg GLA/hr, (iii) 0.040 mg GLA/hr, or (iv) 0.040 mg GLA/hr with no stress. Organ weights were obtained following stress in groups 1-3. Controls developed a sustained elevation in BP within 24 hr of isolation. Animals receiving 0.018 mg GLA/hr developed elevated BP upon isolation, but the BP was less than that of controls on Days 1 (P less than 0.05) and 14 (P less than 0.001) of isolation. Animals receiving 0.040 mg GLA/hr demonstrated a greatly attenuated rise in BP vs controls (P less than 0.001) on all isolation days. GLA in unstressed rats had no effect on BP. Heart rate, heart weight/body weight, and adrenal weight were unchanged in all groups. These data suggest that (i) isolation is a useful tool for investigating reversible psychosocial stress-induced hypertension, and (ii) GLA, while not affecting BP in unstressed animals, produces a dose-dependent attenuation of the BP response to chronic stress.

IgE myeloma associated with plasma cell leukaemia

A patient presented with plasma cell leukaemia and was found to have an IgE secreting multiple myeloma. IgE myeloma is very rare with only 18 cases recorded. However, this case is the fifth recorded of IgE myeloma associated with plasma cell leukaemia. Since plasma cell leukaemia only occurs in 1.6% of all cases of myeloma, it seems certain that this is a significant association.

[Quantitative effects of retinal degeneration in mice]

The thickness of two layers of the retina (the inner plexiform layer and the inner nuclear layer), together with the density of cells in the ganglion cell layer, were measured in a sample of mice from a population segregating for albinism and retinal degeneration. The expression of retinal degeneration was found to involve not only the disappearance of retinal receptors but also a reduction in thickness of the inner plexiform layer and a reduction of cell density in the ganglion cell layer: these changes were found to be associated with a reduction of neuronal density in the lateral geniculate nucleus, but not in the superior colliculus. The expression of retinal degeneration was also found to be unaffected either by albinism or by dark-rearing.

Influence of ozone and nitrogen dioxide on hepatic microsomal enzymes in mice

Since ambient concentrations of ozone and nitrogen dioxide increase drug-induced sleeping time in female mice, potential mechanisms were sought by investigating the effects of these gases on hepatic microsomal mixed-function oxidases in female CD-1 mice. A 3-h exposure to 9800 microgram O3/m3 (5 ppm) or 9400 microgram NO2/m3 (5 ppm) did not change the concentration of cytochrome P-450 significantly. Aniline hydroxylase, but not aminopyrine N-demethylase or p-nitroanisole O-demethylase, activities were increased following a 3-h exposure to 9400 microgram O3/m3 (5 ppm). Aniline hydroxylase activity was also increased after a 2-d (5 h/d) exposure to 1960 microgram O3/m3 (1 ppm). None of these enzyme activities were affected by a 3-h exposure to 9400 microgram NO2/m3 (5 ppm). In these studies, O3 sometimes increased wet liver weight, and thus additional experiments were conducted. A 5-h exposure to 1960 microgram O3/m3 (1 ppm) caused a lesser decrease in body weight than the decrease observed after a similar air exposure. Liver wet weights were elevated after O3 exposure. However, there were no significant changes in liver dry weight, liver dry-to-wet-weight ratio, or ratios of liver (wet or dry) weight to body weight. From these data, it is concluded that mechanisms other than those investigated are responsible for the effect of O3 and NO2 on drug-induced sleeping time. However, the activity of one mixed-function oxidase was slightly increased by O3, indicating a hitherto unrecognized systemic effect of O3 exposure.