Expression of voltage-dependent sodium and transient potassium currents in an identified sub-population of dorsal root ganglion cells acutely isolated from 12-day-old mouse embryos

The electrophysiological properties of a subset of dorsal root ganglion (DRG) neurons microdissected from 12-day-old (E12) mouse embryos and acutely isolated were analyzed as soon as 3 after their isolation. Two classes of neurons were defined according to their mean diameter. The larger diameter class was examined in this study. They display uniform cytoskeletal properties with co-expression of vimentin and neurofilament triplet proteins. Patch-clamp methods also revealed a homogeneous and limited repertoire of ionic channels that included (1) a TTX-sensitive Na⁺ current whose properties are similar to that reported in mature mammalian neurons, and (2) two types of K⁺ currents that can be compared with the delayed rectifier (I _k ) and the transient (I _a) potassium currents found in other mammalian preparations. It may be possible to use this in vitro model to examine the development of new types of currents, such as Ca²⁺ currents during neuronal growth and differentiation.     

In vitro biosynthesis and core glycosylation of the histidine-rich protein of Plasmodium lophurae

We have characterized the early biosynthetic forms of the histidine-rich protein (HisRP), a major, granule-bound protein (Mr 58 000) of the avian malarial parasite Plasmodium lophurae. We have translated poly(A)-containing, size-selected parasite mRNA in the wheat germ cell-free system in the presence of [3H]histidine. HisRP was synthesized as a larger precursor (Mr 63 000). When dog pancreas microsomal membranes were present in the cell-free system during translation, a still larger form of HisRP (Mr 66 000) was detected. This larger form was segregated into the dog pancreas microsomal vesicles and was core glycosylated. Presumably, it corresponds to an intermediate form located in the parasite rough endoplasmic reticulum (RER). The difference in the Mr of approx. 8 000 between this RER associated 'pro' form and the granule-bound, mature form of HisRP suggests that proteolytic processing occurs upon transport from the RER to the granule. Segregation and core glycosylation were strictly coupled to translation and were not observed upon posttranslational addition of microsomal membranes. Thus, the early events in the biosynthesis of HisRP are similar to those established for secretory and lysosomal proteins.     

Role of the kallikrein-kinin system of the kidneys in sodium and water transport and its modification by indomethacin

Direct correlation was found in intact rats between the kallikrein activity of the urine, on the one hand, and the diuresis, sodium excretion, and ability of the kidneys to concentrate the urine on the other hand. Small doses of indomethacin (2 mg/kg for 5 days) increased the kallikrein activity of the urine four-fold and, at the same time, increased the diuresis; large doses (5 mg/kg for 5 days) lowered the kallikrein activity of the urine and halved the diuresis, reduced the sodium excretion by two-thirds, and depressed the ability of the kidneys to concentrate the urine. Indomethacin may perhaps modify the synthesis not only of prostaglandins, but also of kallikrein, and this is reflected in the state of the kidney function.All-Union Cardiological Scientific Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR E. I. Chazor.) Translated from Byulleten' Éxperimental'noi Biologii i Meditsiny, Vol. 83, No. 4, pp. 399–400, April, 1977.     

Discharge activity of single muscle vasoconstrictor efferents in cats during opposite changes in arterial pressure

Signals of individual muscle vasoconstrictor efferents of gastrocnemius muscle were recorded in narcotized cat during rise and fall of systemic arterial pressure induced by phenylephrine and sodium nitroprusside, respectively. In control, mean discharge rate of these efferents was 2.0±0.4 Hz. Phenylephrine (45 g/kg) increased arterial pressure from 120.3±4.2 to 170.7±8.2 mm Hg. This increase was accompanied by a short-term (5-10 sec) decrease in discharge rate of muscle vasoconstrictor efferents to 0.5±0.3 Hz followed by virtually complete recovery of muscle discharge rate against the background of increased arterial pressure. Sodium nitroprusside (30 g/kg) decreased arterial pressure from 132.8±6.2 to 64.1±4.3 mm Hg. Under these conditions the discharge rate of vasoconstrictor efferents increased to 3.5±0.6 Hz and remained at this level throughout the hypotension period (2-3 min). Unloading of baroreceptors (occlusion of the carotid artery) increased the discharge rate of muscle vasoconstrictor efferents throughout the occlusion period (up to 30 sec). Thus, blood pressure rise and drop induced asymmetric by their duration changes in the discharge responses of muscle vasoconstrictor efferents. Phenylephrine increased asymmetry of the vasoconstrictor component of the baroreflex and induced cumulative rise of discharge rate of muscle vasoconstrictor efferents in response to a series of short-term reversible blood pressure jumps caused by repeated occlusions of the abdominal aorta. Our findings extend our knowledge on the efferent component of the baroreflex regulation and on possible mechanisms of hypertension.     

Lack of effect of ouabain on sodium transport across the rat placenta

The umbilical vascular bed of the rat placenta was perfused in situ. Ouabain (10^–4M) in the perfusion fluid had no effect on the unidirectional flux of Na⁺ from the maternal (electrically negative) to the foetal (electrically positive) side of the placenta, or on the transplacental potential difference. This was taken to indicate that there is no significant active transport of Na⁺ across the placenta of the rat.     

The COX-2 inhibitor, rofecoxib, ameliorates dextran sulphate sodium induced colitis in mice

Objective: We have evaluated the efficacy of the selective cyclo-oxygenase (COX)-2 inhibitor, rofecoxib, for the prevention of experimental colitis.Material and methods: To induce colitis BALB/c mice received 5% dextran sulphate sodium (DSS) in their drinking water continuously for 7 days. Rofecoxib (2.5–10 mg/kg body weight, p.o.) was administered throughout the treatment period with DSS. Colitis was quantified by a clinical damage score, colon length, weight loss, stool consistency and rectal bleeding. Inflammatory response was assessed by neutrophil infiltration, determined by histology and myeloperoxidase (MPO) activity. Interleukin (IL)-1, prostaglandin (PG)E₂ and PGD₂ levels in colon mucosa and the immunohistochemical expression of COX-1 and –2 were also studied.Results: The COX-2 inhibitor ameliorated severe colitis, reduced the degree of inflammation through reduction of neutrophil infiltration and IL-1 levels. PGE₂, and PGD₂ synthesis were significantly reduced in DSS-treated groups. Indeed, treatment with rofecoxib diminished the lost of COX-1 caused by DSS in the crypt epithelium whereas expression of COX-2 remained unaffected.Conclusions: Rofecoxib is protective in acute DSS – induced colitis, probably by reducing neutrophil infiltration, inhibiting up-regulation of IL-1 and returning to normal COX-1 expression in the inflamed colonic mucosa.Received 19 April 2004; returned for revision 17 June 2004; accepted by I. Ahnfelt-Rønne 23 November 2004     

Central effects of aldosterone infused into the rat subcommissural organ region

D-Aldosterone (5 ng/microliter/h) was infused for 6 days into the region of the subcommissural organ (SCO) of conscious, adult male Sprague-Dawley rats. Aldosterone increased urinary sodium loss and the sodium/potassium ratio. Although probably central in origin, these effects still occurred when cannulae were displaced up to 1 mm from the targeted SCO placement. Aldosterone decreased adrenal medullary cross-sectional area without affecting cell density. This effect was highly dependent on proper cannula placement and was not observed when the cannula tip was not in contact with the cerebrospinal fluid of the pineal recess over the rostral two-thirds of the SCO. We conclude that aldosterone increases sodium excretion by an action in the SCO and/or adjacent structures. We also postulate a negative trophic relationship between mineralocorticoids and the adrenal medulla mediated by the SCO.     

Effects of calcium supplementation and deoxycorticosterone on plasma atrial natriuretic peptide and electrolyte excretion in spontaneously hypertensive rats

The effects of calcium and the mineralocorticoid deoxycorticosterone (DOC) on blood pressure were studied in four groups of spontaneously hypertensive rats (SHR): (1) control; (2) calcium; (3) deoxycorticosterone and; (4) deoxycorticosterone + calcium. Calcium was given as 1.5% calcium chloride in drinking fluid and deoxycorticosterone by weekly subcutaneous injections (25 mg kg^-1). During the nine weeks of treatment the increase in systolic blood pressure was enhanced in the deoxycorticosterone and attenuated in the calcium group, whereas the deoxycorticosterone + calcium group did not deviate from control. Total plasma calcium was elevated in the calcium group. Plasma concentrations of sodium and atrial natriuretic peptide (ANP) were increased by deoxycorticosterone while neither of the calcium-treated groups differed from control in these respects. Urinary excretions of calcium and sodium were increased in both groups receiving calcium, and also the deoxycorticosterone group excreted more calcium into urine than the control. Adrenergic nerve density in a section of the mesenteric artery and the urinary excretion of noradrenaline and adrenaline were similar in all study groups. The results indicate that calcium supplementation can attenuate the development of hypertension and prevent the deoxycorticosterone-induced blood pressure rise in SHR, possibly by influencing sodium metabolism as seen in increased natriuresis, and by preventing the actions of deoxycorticosterone on sodium balance.     

Protein micelles of human histocompatibility antigens (HLA-A and HLA-B)

Human histocompatibility antigens (HLA-A and -B) are membrane proteins which have large hydrophilic domains outside the cell membrane and a small hydrophobic portion in the lipid bilayer. In this paper we describe optimal conditions for preparing micelles of detergent-solubilized HLA-A2 and -B7 antigens. These homogeneous protein aggregates are water soluble and free of detergent and lipid. Hydrophobic interactions between the intramembraneous portions of the HLA antigens are the driving forces in the formation of these protein micelles. The papain-solubilized fragment of the HLA antigens is not included in the micelle. The average molecular weight of the HLA micelles is around 9 × 10⁵ daltons, which suggests sixteen HLA-A2 and/or HLA-B7 antigenic molecules per protein aggregate. Electron microscopic studies revealed that the most frequent size of the micelles is 12 mm and that HLA-micelles are similar but not identical to micelles from Sindbis Virus glycoproteins (E1 and E2) The HLA-A2 and -B7 micelles retained full antigenic activity as judged by precipitations with allo- and heteroantisera. Such micelles will no doubt be important tools in further studies of the role of histocompatibility antigens.     

Guinea-pig peritoneal macrophage receptor for IgG--II. Purification of the receptor and its partial characterization

The Fc gamma receptor of guinea-pig peritoneal macrophages was purified by affinity chromatography by using rabbit IgG or guinea-pig IgG2 coupled to Sepharose. Lysates prepared by treatment of 125I-labeled macrophages with NP-40 were first applied to BSA-Sepharose and then to IgG-Sepharose and eluted with 0.5 M acetic acid containing 1% NP-40. The specific binding was determined by interaction of the 125I-labeled receptor with IgG-Sepharose in the presence and absence of soluble IgG. The specific binding of the purified receptor was 42-82%. Interactions of the purified receptor with IgG-Sepharose were equally well inhibited by soluble rabbit IgG or guinea-pig IgG2, but not by F(ab')2 fragments. Inclusion of NP-40 in the buffer used in the assay reduced nonspecific binding of the receptor to the affinity gels. The purified receptor can be stored for 20 days at 4 degrees C without a significant loss of the specific binding activity. Analysis of the receptor by SDS-polyacrylamide gel electrophoresis, under nonreducing and reducing conditions, revealed two major peaks of radioactivity corresponding to mol. wts of about 50,000 and 25,000, and one very minor peak corresponding to a mol. wt of about 30,000. The results obtained suggest that the protein of the second major peak is a product of the dissociation of the protein of the first major peak rather than a product of its reduction by 2-mercaptoethanol.