Decreased vasopressin-mediated renal water reabsorption in rats with chronic aldosterone-receptor blockade

Previous studies have suggested that mineralocorticoids are needed for a normal action of vasopressin on collecting duct osmotic water permeability. However, the mechanisms behind this are unknown. To investigate if aldosterone-receptor blockade influences vasopressin type 2 receptor (V(2))-mediated renal water reabsorption and the renal expression of the vasopressin-regulated water channel aquaporin-2 (AQP2), rats were treated with the aldosterone-receptor antagonist canrenoate (20 mg/day iv) for 4 wk. Daily urine flow was increased significantly by 44%, and urine osmolality was decreased by 27% in canrenoate-treated rats. Acute V(2)-receptor blockade (OPC-31260, 800 microgram. kg(-1). h(-1)) was performed under conditions in which volume depletion was prevented. In control rats, OPC-31260 induced a significant increase in urine flow rate (V, +25%) and free water clearance (C(H(2)O), -29%). In canrenoate-treated rats, the effect of OPC-31260 was significantly reduced, and semiquantiative immunoblotting demonstrated a significant reduction (45%) in AQP2 expression. Because rats with common bile duct ligation (CBL) have a reduced vasopressin-mediated water reabsorption compared with normal rats (V: -24%; C(H(2)O): -28%, and 86% downregulation of AQP2), the effect of canrenoate combined with OPC-31260 was tested. Canrenoate treatment of CBL rats significantly increased daily urine flow, decreased urine osmolality, and impaired the aquaretic response to OPC-31260 (V: -23%; C(H(2)O): -31%) with maintained suppression of the renal AQP2 expression. Thus canrenoate treatment of normal and CBL rats showed 1) increased urine production, 2) reduced aquaretic effect of acute V(2)-receptor blockade, and 3) a marked reduction in AQP2 expression. This strongly supports the view that aldosterone plays a significant role for vasopressin-mediated water reabsorption.

Target specificity of the endonuclease from the Xenopus laevis non-long terminal repeat retrotransposon, Tx1L

Elements of the Tx1L family are non-long terminal repeat retrotransposons (NLRs) that are dispersed in the genome of Xenopus laevis. Essentially all genomic copies of Tx1L are found inserted at a specific site within another family of transposable elements (Tx1D). This suggests that Tx1L is a site-specific retrotransposon. Like many (but not all) other NLRs, the Xenopus element encodes an apparent endonuclease that is related in sequence to the apurinic-apyrimidinic endonucleases that participate in DNA repair. This enzyme is thought to introduce the single-strand break in target DNA that initiates transposition by the target-primed reverse transcription (TPRT) mechanism. To explore the issue of target specificity more fully, we expressed the polypeptide encoded by the endonuclease domain of open reading frame 2 from Tx1L (Tx1L EN) and characterized its cleavage capabilities. This endonuclease makes a specific nick in the bottom strand precisely at one end of the presumed Tx1L target duplication. Because this activity leaves a 5'-phosphate and 3'-hydroxyl at the nick, it has the location and chemistry required to initiate new insertion events by TPRT. Tx1L EN does not make a specific cut at a preferred target site for Tx1D elements, ruling out the alternative possibility that the composite Tx1L-Tx1D element moves as a unit under the control of functions encoded by Tx1L. Further characterization revealed that the endonuclease remains active for many hours at room temperature and that it is capable of enzymatic turnover. Scanning substitution mutagenesis located the recognition site for Tx1L EN within 10 bp surrounding the primary nick site. Implications of these features for natural transposition events are discussed.

An automated technique for most-probable-number (MPN) analysis of densities of phagotrophic protists with lux AB labelled bacteria as growth medium

An automated modification of the most-probable-number (MPN) technique has been developed for enumeration of phagotrophic protozoa. The method is based on detection of prey depletion in micro titre plates rather than on presence of protozoa. A transconjugant Pseudomonas fluorescens DR54 labelled with a luxAB gene cassette was constructed, and used as growth medium for the protozoa in the micro titre plates. The transconjugant produced high amounts of luciferase which was stable and allowed detection for at least 8 weeks. Dilution series of protozoan cultures and soil suspensions were inoculated into micro titre plates amended with a suspension of the transconjugant. After 45 days measurement of light emission allowed detection of individual wells in the titre plates, where protozoan grazing had removed the inoculated bacteria.

X-ray structure of Novamyl, the five-domain "maltogenic" alpha-amylase from Bacillus stearothermophilus: maltose and acarbose complexes at 1.7A resolution

The three-dimensional structure of the Bacillus stearothermophilus "maltogenic" alpha-amylase, Novamyl, has been determined by X-ray crystallography at a resolution of 1.7 A. Unlike conventional alpha-amylases from glycoside hydrolase family 13, Novamyl exhibits the five-domain structure more usually associated with cyclodextrin glycosyltransferase. Complexes of the enzyme with both maltose and the inhibitor acarbose have been characterized. In the maltose complex, two molecules of maltose are found in the -1 to -2 and +2 to +3 subsites of the active site, with two more on the C and E domains. The C-domain maltose occupies a position identical to one previously observed in the Bacillus circulans CGTase structure [Lawson, C. L., et al. (1994) J. Mol. Biol. 236, 590-600], suggesting that the C-domain plays a genuine biological role in saccharide binding. In the acarbose-maltose complex, the tetrasaccharide inhibitor acarbose is found as an extended hexasaccharide species, bound in the -3 to +3 subsites. The transition state mimicking pseudosaccharide is bound in the -1 subsite of the enzyme in a 2H3 half-chair conformation, as expected. The active site of Novamyl lies in an open gully, fully consistent with its ability to perform internal cleavage via an endo as opposed to an exo activity.

Analgesic efficacy of the cyclooxygenase-2-specific inhibitor rofecoxib in post-dental surgery pain: a randomized, controlled trial

Previous data have suggested that rofecoxib, a cyclooxygenase (COX)-2-specific inhibitor, had analgesic effects similar to those of the nonsteroidal anti-inflammatory drugs when tested in the post-dental surgery pain model. The objective of this parallel-group, double-masked, randomized, placebo- and active comparator-controlled clinical trial was to assess more fully the analgesic efficacy of rofecoxib in the treatment of postoperative dental pain. After dental surgery, 151 patients (50.3% women; mean age, 18.3 years; 93.4% white) experiencing moderate-to-severe pain were to receive a single dose of placebo, rofecoxib 50 mg, or ibuprofen 400 mg. Analgesic efficacy was assessed for up to 24 hours postdose using self-administered questionnaires. Tolerability was assessed using spontaneous reports of adverse experiences, physical findings, and laboratory measurements. The results of this study demonstrated that rofecoxib 50 mg was more effective than placebo on all measures of analgesic efficacy. Rofecoxib 50 mg exhibited overall analgesic effects, onset of analgesia, and peak analgesic effects that were not significantly different from those of ibuprofen 400 mg, with a significantly longer duration of action (P < 0.05). We concluded that rofecoxib was efficacious in the treatment of postoperative dental pain and that COX-2-derived prostanoids play a role in treatment of the pain associated with dental surgery.

Effects of supplemental coverage on use of services by Medicare enrollees

This article estimates the extent to which private insurance supplements affect use of services by Medicare enrollees. Three types of supplements to Medicare's coverage are examined--Health Maintenance Organizations (HMOs), medigap (MGP) plans, and employment-based indemnity (EBI) plans. While each kind of supplement reduces cost sharing on Medicare-covered services, only HMOs do so without increasing enrollees' overall use of services. Use of services by HMO enrollees is about 4 percent lower than use by similar Medicare enrollees with no insurance supplement. By contrast, use of services by enrollees with MGP coverage is 28 percent higher, and use of services by enrollees with EBI plans is 17 percent higher.

Effects of chronic octreotide treatment on renal changes during cirrhosis in rats

We examined the effect of a new long-acting release formula (LAR) of the somatostatin analogue, octreotide, on development of sodium retention and functional and structural changes in the thick ascending limb of Henle's loop (TAL) in rats with cirrhosis induced by common bile duct ligation (CBL). CBL and sham-operated control rats were treated with octreotide-LAR (10 mg/kg body weight subcutaneously, as a single dose) or vehicle at the time of CBL or sham-CBL. The rats were instrumented with chronic catheters, and sodium balance and renal function were examined 4 weeks after CBL or sham operation. Octreotide-LAR treatment significantly inhibited sodium retention in CBL rats and prevented renal vasodilatation without changes in glomerular filtration rate (GFR). The natriuretic response to a test dose of furosemide (7.5 mg/kg body weight intravenously) was significantly increased in CBL rats, and when expressed in terms of natriuretic efficiency (mmol Na/mg furosemide in urine), the natriuretic response was increased by 57% relative to sham-operated controls. Stereological examination of kidneys demonstrated a 53% increase in the volume of the inner stripe of the outer medulla and a 108% increase in the volume of TAL epithelium in cirrhotic rats relative to controls. The increased natriuretic efficiency of furosemide as well as the hypertrophy of the inner stripe and the TAL in this renal zone were absent in CBL rats treated with octreotide-LAR. These results suggest that octreotide-LAR treatment inhibits sodium retention in cirrhotic rats, partly by inhibition of increased furosemide-sensitive sodium reabsorption in the TAL.

The value of scintigraphy in hips with slipped capital femoral epiphysis and the value of radiography and MRI after 10 years

Preoperative bone scintigraphy of the femoral head in 33 hips with slipped capital femoral epiphysis, showed no relation to duration of symptoms or degree of slip. The preoperative uptake was always normal or increased. Two hips had postoperative femoral head uptake below normal, both had complications affecting the vascular supply, resulting in necrosis of the femoral head and severe arthrosis. At follow-up after 10 (5-15) years of 28 hips, no relation could be demonstrated between Adolescent Hip Questionnaire which included clinical data, and radiography or magnetic resonance imaging. We only recommend scintigraphy after complications jeopardizing the vascular supply of the femoral head in slipped capital femoral epiphysis.

Perceived discomfort in running: scale development and theoretical considerations

The aim of this study was to develop a discomfort questionnaire to elicit the feelings and thoughts of people engaged in running activities. Ten runners who completed a particularly demanding 9-km run were asked to express their feelings and thoughts during the run they had just completed. These responses were recorded and later used as the first pool of items (k = 36). The questionnaire was then given to 171 runners in different distance races throughout the 1995 competitive season. These responses were analysed using exploratory factor analytic techniques and Rasch probabilistic analysis, as well as traditional reliability and validity procedures. The final version of the questionnaire consisted of 32 items divided into eight correlated subscales: proprioceptive symptoms, leg symptoms, respiratory difficulties, disorientation, dryness and heat, task completion thoughts, mental toughness, and head or stomach symptoms. These eight categories can be collapsed into three global categories suggested by researchers of pain: sensory-discriminative, motivational-affective and cognitive-evaluative. Rasch analysis suggested that the motivational-affective and cognitive-evaluative dimensions (i.e. the psychological) are the most experienced (i.e. rated highest). The eight subscales have ecological validity and were found to alter with the demands of different running distances.

RNA expression from a site-specific non-LTR retrotransposon microinjected into Xenopus oocytes

Tx1L is a site-specific non-LTR retrotransposon (NLR) that has been identified in the genome of Xenopus laevis. Using microinjection into Xenopus oocytes, several aspects of RNA expression by these elements were investigated. With constructs carrying various parts of the element we saw no evidence of promoter activity, unlike what has been shown for several other elements of this class. Tx1L transcription was induced by linking a whole element to a promoter that is active in oocytes. Among the RNAs produced, about half had 3' ends located near the end of the element, suggesting that instruction for 3' end formation are encoded in the element or its target. Deletion of the 3' UTR of Tx1L and of surrounding target sequences indicated that these regions are not required for termination or processing of the RNA. PolyA or very A-rich sequences were added at these 3' ends, despite the absence of canonical polyA addition signals. A significant proportion of non-A residues was found in the 3' untemplated tails, and this is reminiscent of non-templated insertions often found at the 3' junction of new genomic copies of some NLRs.

Aldosterone receptor blockade inhibits increased furosemide-sensitive sodium reabsorption in rats with liver cirrhosis

We examined the role of chronic aldosterone receptor blockade on the altered furosemide-sensitive sodium reabsorption in rats with liver cirrhosis induced by common bile duct ligation. CBL and sham-operated control animals were treated with the aldosterone receptor antagonist canrenoate (20 mg/day i.v.) for 4 weeks. Untreated CBL and sham-CBL served as control groups. The plasma concentration of aldosterone was within the normal range in all groups. Sodium balance studies showed that aldosterone receptor blockade prevented sodium retention in cirrhotic rats. Clearance studies showed that the glomerular filtration rate was unchanged, whereas the renal plasma flow was increased in CBL rats. A test dose of furosemide (7.5 mg/kg b.wt. i.v.) produced significantly greater diuretic (+59%) and natriuretic (+56%) responses in CBL rats than in sham-operated controls. The urinary furosemide excretion rate (UFURV) reflects delivery of furosemide to the thick ascending limb. When the natriuresis was expressed relative to UFURV (i.e., the natriuretic efficiency), we found that natriuretic efficiency of furosemide was significantly increased in untreated CBL rats (+59%). However, the natriuretic efficiency of furosemide was normalized in CBL rats treated with canrenoate. The urinary excretion of furosemide was unchanged in untreated CBL rats, but it was significantly increased in cirrhotic rats treated with canrenoate (+43%). This suggests that in CBL rats, chronic canrenoate treatment increases the renal elimination of furosemide as a consequence of reduced metabolism. These data suggest that chronic aldosterone receptor blockade with canrenoate prevents sodium retention in cirrhotic rats partly by inhibition of increased sodium reabsorption in the thick ascending limb.

SB 207499 (Ariflo), a second generation phosphodiesterase 4 inhibitor, reduces tumor necrosis factor alpha and interleukin-4 production in vivo

The ability of the second generation phosphodiesterase 4 inhibitor SB 207499 (Ariflo), [c-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl)-r-l-cyclohexane carboxylic acid], to inhibit inflammatory cytokine production in vivo was evaluated and compared to that of rolipram, a first generation phosphodiesterase 4 inhibitor. To examine human tumor necrosis factor alpha (TNFalpha) production, human monocytes were adoptively transferred into Balb/c mice and challenged with lipopolysaccharide (LPS). In this model, SB 207499 inhibited human TNFalpha production with oral ED50 of 4.9 mg/kg. Similarly, R-rolipram inhibited human TNFalpha production with an ED50 of 5.1 mg/kg, p.o. In contrast to their equipotent activity against TNFalpha production, SB 207499 (ED50 = 2.3 mg/kg, p.o.) was 10-fold less potent than R-rolipram (ED50 = 0.23 mg/kg, p.o.) in reversing reserpine-induced hypothermia, a model of antidepressant activity. In time course studies, SB 207499 (30 mg/kg, p.o.) inhibited TNFalpha production for at least 10 hr; substantial plasma concentrations of SB 207499 were detected over the same interval. The ability of SB 207499 to modulate interleukin-4 production in vivo was assessed in a chronic oxazolone-induced contact sensitivity model in Balb/c mice. In this model, topical administration of SB 207499 (1000 microgram) inhibited intralesional concentrations of interleukin-4 (55%; P <.01). The results demonstrate that SB 207499 is a potent inhibitor of inflammatory cytokine production in a variety of settings in vivo. Moreover, although it is as potent as R-rolipram in inhibiting TNFalpha production, it has substantially less central nervous system activity. Thus SB 207499 represents an excellent candidate with which to evaluate the antiinflammatory potential of PDE4 inhibitors.

Plant development: the making of a leaf

A transcription factor of the Myb family has been found to couple dorsoventral patterning and proximodistal outgrowth during leaf development.

Decreased vasopressin-mediated renal water reabsorption in rats with compensated liver cirrhosis

Experiments were performed to investigate vasopressin type 2 receptor (V2)-mediated renal water reabsorption and the renal expression of the vasopressin-regulated water channel aquaporin-2 (AQP-2) in cirrhotic rats with sodium retention but without ascites. In addition, the expression of the furosemide-sensitive type 1 Na-K-2Cl cotransporter (BSC-1) and the natriuretic response to an intravenous test dose furosemide (7.5 mg/kg) during acute V2-receptor blockade was measured. Acute V2-receptor blockade with the selective nonpeptide antagonist OPC-31260 (800 microg . kg-1 . h-1) was performed during conditions in which volume depletion was prevented by computer-driven, servo-controlled intravenous volume replacement with 150 mM glucose. OPC-31260 produced a significantly smaller increase in urine flow rate (-26%) and free water clearance (-18%) in cirrhotic rats than in control rats. The natriuretic response to an intravenous test dose furosemide (7.5 mg/kg) was significantly increased in cirrhotic rats (+52%), but pretreatment with OPC-31260 did not affect the natriuretic response to furosemide in neither cirrhotic nor in control rats. Semiquantitative immunoblotting showed a significant downregulation of AQP-2 in the renal cortex (-72%) and in the outer medulla (-44%). The relative expression of BSC-1 in the outer medulla was unchanged in cirrhotic rats. The corticopapillary gradient of Na was significantly increased in cirrhotic rats. Since daily urine flow rate was similar in cirrhotic and sham-operated rats, we suggest that non-vasopressin-mediated water reabsorption is increased in cirrhotic rats probably as a result of an increased corticomedullary gradient due to exaggerated NaCl reabsorption in the thick ascending limb of Henle's loop.

[Patients and attitudes to a palliative unit in H:S--a questionnaire study]

A questionnaire was mailed to 42 representative in-patient departments of hospitals in the City of Copenhagen asking the medical staff to state what number of their patients could possibly be referred to a future hospital--associated palliative care unit. All-together 215 answers were returned from two questionnaire dates two weeks apart, comprising more than 1750 patients each day. Furthermore, 42 of 60 general practitioners answered another questionnaire on the same topic. From the hospital questionnaire it was concluded that approximately 8% of all patients were admitted for palliative care reasons, 75% suffering from incurable cancer. More than 50% of patients admitted for palliative care reasons were assessed to be suitable candidates for a palliative care unit. The general practitioners recognised at least 50 patients treated only for palliative reasons. In the same month the general practitioners referred more than 20 patients to hospital wards, but two-thirds of the practitioners would have preferred that these patients could have had the option of staying at home for terminal care. In general, more than 50% of the medical staff opted for establishing a palliative care unit.

[Teratogenic effects of ACE-inhibitors and angiotensin II receptor antagonists]

Since the introduction of angiotensin converting enzyme-inhibitors (ACE-inhibitors) in the 1980's, more than 50 cases of foetotoxic effects ascribed to intrauterine exposure to inhibitors have been published. Among the most commonly reported effects are: Hypotension, renal dysplasia, anuria/oliguria, oligohydramios, intrauterine growth retardation, pulmonary hypoplasia, unclosed ductus arteriosus, incomplete ossification of the skull, intrauterine og neonatal death. Recent animal studies have confirmed that intrauterine or neonatal exposure to ACE-inhibitors or the AT1-receptor antagonist losartan can cause death and serious, irreversible organ damage. These effects are similar to the complications previously reported in humans. Animal studies suggest that the foetotoxic actions are most common after exposure during the last trimester. However, due to the severity of these complications, the use of ACE-inhibitors and AT1-receptor antagonists should be avoided throughout pregnancy and in women who are breast feeding.

Model explaining the relation between distal nephron Li+ reabsorption and urinary Na+ excretion in rats

Li+ may be reabsorbed via an amiloride-sensitive mechanism in the collecting ducts of rats administered a low-Na+ diet. This was investigated by measuring the increase in fractional urinary excretion of Li+ (FELi) in response to amiloride in conscious rats at two different levels of plasma Li+ concentration and after administration of bendroflumethiazide (BFTZ), angiotensin III (ANG III), and aldosterone (Aldo). The results confirmed that amiloride increased (FELi) in rats on a low-Na+ diet (20 +/- 1 to 35 +/- 1%, means +/- SE), whereas no increase was observed in rats on a normal Na+ diet (37 +/- 1 to 38 +/- 1%). The lithiuretic effect of amiloride was 1) abolished by preadministration of BFTZ (32 +/- 1 to 33 +/- 2%) to Na(+)-deprived rats and 2) increased by ANG III (27 +/- 3 to 33 +/- 2%) and Aldo (25 +/- 2 to 37 +/- 2%) in Na(+)-replete rats. Amiloride-induced changes in FELi were independent of plasma Li+ concentration but inversely related to the fractional excretion of Na+ and the amiloride-sensitive excretion of K+. These results are compatible with the hypothesis that a low tubular Na+ concentration reduces end-tubular Na+ reabsorption and results in hyperpolarization of the apical membrane, thus favoring Li+ uptake into the cells.

Mechanism of antidiuresis caused by bendroflumethiazide in conscious rats with diabetes insipidus

1. The mechanism underlying the antidiuretic effect of thiazide diuretics in diabetes insipidus (DI) is unknown. This study addressed two specific questions: is the reduction in urine flow rate (V) related to a decrease in the delivery of fluid from the pars recta of the proximal tubules ('distal delivery'), and are there any changes in the expression and/or intracellular distribution of vasopressin stimulated water channels (AQP2) in the collecting ducts, during chronic thiazide-induced antidiuresis? 2. Nine Brattleboro rats with vasopressin-deficient DI were treated for 5 days with bendroflumethiazide (BFTZ), 9 mg kg(-1) day(-1) orally, and 9 Brattleboro rats were left untreated. BFTZ-treated DI rats showed a fall in V from approximately 200 to approximately 75 ml day(-1) and an increase in urine osmolality from approximately 130 to approximately 400 mosmol kg(-1). 3. BFTZ-induced antidiuresis was associated with a persistent loss of sodium, but not of potassium. After 5 days of treatment, clearance studies in conscious rats showed a tendency towards decreases in effective renal plasma flow (-7%), GFR (-12%) and lithium clearance (C(Li); used as marker for distal delivery) (-25%), compared with untreated controls, but none of these changes were statistically significant. There was no apparent relationship between C(Li) and V in BFTZ-treated or untreated DI rats. 4. BFTZ treatment did not change the expression of AQP2 in homogenates of cortex, outer or inner medulla from DI rats, or from normal Long Evans rats. Light and electron microscopic immunocytochemistry revealed no changes in intracellular distribution of AQP2 in principal cells from inner medullary collecting ducts of BFTZ-treated DI rats. 5. We concluded, (i) that although the antidiuretic effect of BFTZ in rats with DI is associated with a net loss of Na, the decrease in V shows no association with changes in distal delivery, as estimated by C(Li). (ii) Antidiuretic treatment with BFTZ does not alter the expression of subcellular distribution of AQP2 water channels in the collecting ducts. The mechanism underlying the chronic antidiuresis caused by thiazide diuretics in DI remains elusive.

Experience with once daily dosing of gentamicin: considerations regarding dosing and monitoring

Plasma concentrations of gentamicin following a fixed dose of 240 mg once daily to patients with normal renal function were measured. The purpose was to establish guidelines to achieve a sufficiently high peak concentration with an appropriately low risk of accumulation. In 40 patients, 1-hour concentrations of plasma gentamicin had a median of 9.3 mg/l (range: 4.5-19.0 mg/l) and 9.7 mg/l (range: 3.6-14.6 mg/l) on days 1 and 3 of gentamicin treatment, respectively. Thirty-nine patients had 1-hour concentrations > 5 mg/l. The 1-hour concentrations varied considerably intra- and interindividually but showed a significant inverse correlation with body weight, surface area and the estimated endogenous creatinine clearance. The plasma gentamicin elimination half-life correlated significantly with age and inversely with body weight and creatinine clearance. There was no increase in the mean plasma creatinine from day 0 to day 4. No patients showed signs of nephrotoxicity, although 2 patients, both elderly and with low body weight, showed signs of beginning gentamicin accumulation. In conclusion, gentamicin treatment with the dose of 240 mg once daily in 3 days to adults with normal kidney function generally does not require adjustment or monitoring. However, the dose should be increased in young patients with an excessive body weight, and decreased doses are needed for old and underweight patients. Monitoring of trough plasma gentamicin concentration is not necessary with treatment duration of 3 days or less.

Influence of renal nerves and sodium balance on the acute antidiuretic effect of bendroflumethiazide in rats with diabetes insipidus

To examine the role of the renal nerves and sodium depletion for the acute antidiuretic response to bendroflumethiazide (BFTZ; 25 microg/hr) in rats with diabetes insipidus (DI), renal clearance experiments were performed in the following groups of conscious, chronically instrumented male Brattleboro rats with vasopressin-deficient DI: Control (n = 7), BFTZ (n = 9), BFTZ + sodium replacement (n = 7) and BFTZ + chronic bilateral renal denervation (n = 6). Urine flow rate and urinary sodium concentration were measured drop-by-drop with a sodium-sensitive electrode and by collection of urine in vials placed on an electronic balance. This allowed computer driven, servo-controlled, independent i.v. replacement of sodium and fluid losses, respectively. Mean arterial pressure, glomerular filtration rate (GFR) and proximal tubular water and sodium handling, assessed by lithium clearance (C(Li)), were stable in the control group. BFTZ produced a marked antidiuretic response (deltaV = -79%; deltaUrine osmolality = +218%) associated with decreases in GFR (-28%), C(Li) (-62%), free water clearance (-100%) and plasma Na (-5 mM). Fractional water reabsorption was increased by 19% in the proximal tubules and by 7% in segments beyond. Sodium replacement did not modify the fall in GFR or the antidiuresis, but partly prevented the increase in fractional proximal water reabsorption. Bilateral renal denervation did not affect the response to BFTZ. We conclude that the acute antidiuretic effect of BFTZ is independent of sodium balance and renal nerve activity and is elicited by a reduction in GFR accompanied by an increase in fractional water reabsorption in the proximal tubules and in the distal nephron.

Functional domains of LAG-2, a putative signaling ligand for LIN-12 and GLP-1 receptors in Caenorhabditis elegans

The LAG-2 membrane protein is a putative signaling ligand for the LIN-12 and GLP-1 receptors of Caenorhabditis elegans. LAG-2, like its Drosophila homologues Delta and Serrate, acts in a conserved signal transduction pathway to regulate cell fates during development. In this article, we investigate the functional domains of LAG-2. For the most part, mutants were constructed in vitro and assayed for activity in transgenic animals. We find a functional role for all major regions except one. Within the extracellular domain, the N-terminal region, which bears no known motif, and the DSL domain are both required. By contrast, the region bearing epidermal growth factor-like repeats can be deleted with no apparent reduction in rescuing activity. The intracellular region is not required for activity but instead plays a role in down-regulating LAG-2 function. Finally, membrane association is critical for mutant rescue.

Ribonucleoprotein formation by the ORF1 protein of the non-LTR retrotransposon Tx1L in Xenopus oocytes

The Tx1L elements constitute a family of site-specific non-LTR retrotransposons found in the genome of the frog Xenopus laevis . The elements have two open reading frames (ORFs) with homology to proteins of retroviruses and other retroelements. This study demonstrates an expected activity of one of the element-encoded proteins. The RNA binding properties of ORF1p, the product of the first ORF of Tx1L, were examined after expression from RNA injected into Xenopus oocytes. Using sucrose gradient sedimentation and non-denaturing gel electrophoresis, we show that ORF1p associates with RNA in cytoplasmic ribonucleoprotein (RNP) particles. Discrete RNPs are formed with well-defined mobilities. The ORF1p RNPs are distinct from endogenous RNPs that contain stored oocyte mRNAs and two specific endogenous mRNAs do not become associated with ORF1p. ORF1p appears to be capable of associating with its own mRNA and with other injected RNAs, independent of specific recognition sequences. Although nuclear localization of ORF1p was anticipated, based both on the supposed mechanism of transposition and on the presence of a potential nuclear localization signal, no significant fraction of the protein was found in the oocyte nucleus. Nonetheless, the RNA binding capability of ORF1p is consistent with the proposed model for transposition of non-LTR retrotransposons.

Renal function after myocardial infarction and cardiac arrest in rats: role of ANP-induced albuminuria?

Renal function was measured by clearance technique before and after acute myocardial infarction (MI) induced by left coronary artery ligation in male Sprague-Dawley rats. The animals were anaesthetized with halothane-nitrous oxide, paralysed with pancuronium and artificially ventilated. All parameters were stable throughout the experiment in sham-operated time control animals (n = 8). After MI, rats developed left ventricular dysfunction with increased left ventricular end-diastolic pressure and decreased mean arterial pressure. MI produced antidiuresis and antinatriuresis without changes in glomerular filtration rate (GFR), lithium clearance or renal albumin excretion (n = 8). The antidiuretic and antinatriuretic responses to MI were similar in rats with chronic bilateral renal denervation (n = 5). Three additional rats with chronic bilateral renal denervation had cardiac arrest and were resuscitated with cardiac massage, i.v. lidocaine and intracardiac adrenaline administration. These animals showed a transient increase in urine flow rate, sodium and albumin excretion with maximum 30-60 min after resuscitation, while GFR and lithium clearance were normal. Since cardiac ischaemia and sympathetic stimulation are strong stimuli for the release of atrial natriuretic peptide (ANP), we examined if ANP (0.25, 0.50, and 1.00 microg kg(-1) min(-1), n = 8 per dose) affects urinary albumin excretion. ANP increased dose-dependently the urine/plasma concentration ratio of albumin relative to inulin, which suggests that ANP increases the glomerular permeability for albumin. We conclude that MI causes stimulation of renal tubular sodium and water reabsorption by a mechanism which is independent of intact renal innervation. MI does not produce any change in renal albumin excretion in rats, but transient albuminuria may be observed in rats following cardiac arrest and/or manoeuvres used in cardiac resuscitation. Since ANP produces albuminuria, we speculate that ANP may be an important mediator of albuminuria in states with elevated plasma concentrations of ANP.

Functional and structural changes in the thick ascending limb of Henle's loop in rats with liver cirrhosis

Five weeks after common bile duct ligation (CBL), Wistar rats had histologically verified liver cirrhosis with sodium retention but without ascites. Plasma concentrations of vasopressin and aldosterone were normal. Glomerular filtration rate was unchanged, although renal plasma flow was increased. A test dose of furosemide (7.5 mg/kg body wt iv) produced significantly greater diuretic (+59%) and natriuretic (+66%) responses in Wistar CBL rats than in sham-operated controls. Stereological examination of kidneys demonstrated a 47% increase in the volume of the inner stripe of the outer medulla, with a 55% increase in the volume of thick ascending limb of Henle's loop (TALH) epithelium in cirrhotic Wistar rats relative to controls. CBL produced a similar degree of liver cirrhosis in vasopressin-deficient Brattleboro rats. However, both functional and structural renal changes observed in cirrhotic Wistar rats were absent in vasopressin-deficient cirrhotic Brattleboro rats. These results suggest a permissive action of vasopressin for the adaptive changes in TALH in rats with experimental liver cirrhosis. Our results are consistent with the hypothesis that increased sodium chloride reabsorption in the TALH may contribute to the early sodium retention that precedes ascites formation in rats with secondary biliary liver cirrhosis.

Antihypertensive action of non-natriuretic doses of furosemide in Dahl salt-sensitive rats

BACKGROUND

That non-natriuretic doses of loop diuretics exert an antihypertensive action has been suggested, but not confirmed, by simultaneous measurements of the arterial pressure and sodium balance during therapy.

OBJECTIVE

To examine the relationship between changes in arterial pressure and changes in sodium balance during furosemide treatment.

DESIGN

Twenty hypertensive Dahl salt-sensitive rats fed a 4% NaCl diet were allocated to four groups and administered the following treatments: placebo once a day intraperitoneally, continuous infusion of 4 mg/day furosemide intraperitoneally, 4 mg furosemide once a day intraperitoneally and 12 mg furosemide once every third day intraperitoneally.

METHODS

The mean arterial pressure (MAP) was measured continuously with radiotelemetry and the sodium balance was measured with the rats in metabolic cages.

RESULTS

Administration of furosemide as a bolus injection once a day (P < 0.01) or once every third day (P < 0.05) lowered the MAP significantly compared with placebo, whereas continuous infusion of furosemide had no significant effect on the MAP (P < 0.07). Fast Fourier transformation analysis detected an acute antihypertensive action related to the temporary diuretic and natriuretic responses during the period 0-6 h after intraperitoneal bolus injections of 4 and 12 mg furosemide. None of the treatment regimens produced 24 h sodium or potassium losses. At the end of the study, the total body water, extracellular fluid volume, total body sodium and potassium were similar for rats in all groups.

CONCLUSIONS

Furosemide has an acute antihypertensive action in Dahl salt-sensitive rats fed a 4% NaCl diet that is related to renal sodium and volume losses whereas the long-term antihypertensive effect is independent of changes in extracellular fluid volume, total body water, sodium and potassium.

Comparative and environmental genotoxicity of antimony and arsenic

Antimony and arsenic compounds are known to have a genotoxic potential. Soil contamination with these elements can be due to the presence of natural ore sources of fahlore (gray copper). As a result, human and animal populations may be highly exposed. The sister chromatid exchange (SCE) test is an adequate tool for the sensitive detection of antimony and arsenic genotoxicity. We used this assay to investigate the coergism of the two elements in vitro to gain data for the assessment of a putative risk from coexposure. The combinative effect of antimony and arsenic in the SCE test appeared subadditive. Additionally, the SCE served to determine the genotoxic potential in extracts of contaminated fahlore soil samples gained under mildly acidic conditions. The genotoxicity observed was very low because antimony and arsenic predominated in the pentavalent, non-genotoxic state, but, the partial antagonism observed in the in vitro experiments could be an additional explanation for the low genotoxicity.

Cardiovascular actions of chronic intracerebroventricular administration of metformin in normotensive rats

Acute intracerebroventricular administration of the antihyperglycaemic agent metformin (0.25-1 mg) elicits sympathoinhibitory responses in spontaneously hypertensive rats. However, cardiovascular actions of chronic intracerebroventricular metformin administration are unknown. To define the dose-response relationship during chronic intracerebroventricular metformin administration, mean arterial pressure, heart rate, and locomotor activity were measured continuously by radiotelemetry in 40 normotensive rats. After a 10 day control period, an intracerebroventricular cannula was implanted and connected to an osmotic minipump which delivered metformin in the following doses: 0 [saline]. 0.01, 0.1, 1, and 10 mg/day. LD50 was 1.5 mg/day. Metformin, 1 mg/day attenuated the nocturnal, physiological increase in mean arterial pressure (-7.3 +/- 1.6% versus before metformin), produced behavioural changes and tended to increase locomotor activity. Lower doses of intracerebroventricular metformin (0.1 and 0.01 mg/day) did not affect mean arterial pressure, heart rate or locomotor activity. In conclusion, chronic intracerebroventricular administration of high dose metformin (1.0 mg/day) attenuates the nocturnal, physiological increase in mean arterial pressure. These findings are compatible with a toxic, sympathoinhibitory action of high doses of metformin intracerebroventricularly.

Effects of relaxation on the delayed-type hypersensitivity (DTH) reaction to diphenylcyclopropenone (DCP)

Delayed-type hypersensitivity (DTH) reactions to the experimental allergen diphenylcyclopropenone (DCP) were measured in four groups, which either trained (+) or did not train in relaxation (-) during the sensitization and/or the challenge phase. All groups consisted of high and low hypnotic susceptible subjects. While there were no differences in erythema, the mean induration of the group which trained in relaxation in both the sensitization and the challenge phase (+/+) was significantly greater than that of the group which trained in relaxation in the challenge phase only (-/+). Significant correlations were found between induration and hypnotic susceptibility scores, and between induration and degree of perceived relaxation during challenge. High hypnotic susceptible subjects experienced a higher degree of perceived relaxation and exhibited greater indurative and erythematous DTH reactions to DCP than low hypnotic susceptible subjects in all four experimental conditions. Though the mediating mechanisms remain unclear, our results suggest that relaxation may affect the DTH reaction, and support previous findings of higher psychophysiologic reactivity of high hypnotic susceptible subjects.

On the role of calcium in the regulatory volume decrease (RVD) response in Ehrlich mouse ascites tumor cells

The putative role for Ca2+ entry and Ca2+ mobilization in the activation of the regulatory volume decrease (RVD) response has been assessed in Ehrlich cells. Following hypotonic exposure (50% osmolarity) there is: (i) no increase in cellular Ins(1,4,5)P3 content, as measured in extracts from [2-3H]myoinositol-labeled cells, a finding at variance with earlier reports from our group; (ii) no evidence of Ca2+-signaling recorded in a suspension of fura-2-loaded cells; (iii) Ca2+-signaling in only about 6% of the single, fura-2-loaded cells at 1-mm Ca2+ (1% only at 0.1-mM Ca2+ and in Ca2+-free medium), as monitored by fluorescence-ratio imaging; (iv) no effect of removing external Ca2+ upon the volume-induced K+ loss; (v) no significant inhibition of the RVD response in cells loaded with the Ca2+ chelator BAPTA when the BAPTA-loading is performed in K+ equilibrium medium; (vi) an inhibition of the swelling-induced K+ loss (about 50%) at 1-mM Ba2+, but almost no effect of charybdotoxin (100 nm) or of clotrimazole (10 microM), reported inhibitors of the K+ loss induced by Ca2+-mobilizing agonists. Thus, Ca2+signaling by Ca2+ release or Ca2+ entry appears to play no role in the activation mechanism for the RVD response in Ehrlich cells.

Assignment of a single disulphide bridge in human alpha2-antiplasmin: implications for the structural and functional properties

Human alpha2-antiplasmin (alpha2AP) is a serpin involved in the regulation of blood coagulation. Most serpins, unlike smaller serine proteinase inhibitors, do not contain disulphide bridges. alpha2AP is an exception from this generalization and has previously been shown to contain four Cys residues organized into two disulphide bridges [Lijnen, Holmes, van Hoef, Wiman, Rodriguez and Collen (1987) Eur. J. Biochem. 166, 565-574]. However, we found that alpha2AP incorporates iodo[14C]acetic acid, suggesting that the protein contains reactive thiol groups. This observation prompted a re-examination of the state of the thiol groups, which revealed (i) a disulphide bridge between Cys43 and Cys116, (ii) that Cys76 is bound to a cysteinyl-glycine dipeptide, and (iii) and Cys125 exists as either a free thiol or in a mixed disulphide with another Cys residue. The disulphide identified between Cys43 and Cys116 appears to be conserved in orthologous proteins since the homologous Cys residues form disulphide bonds in bovine and possibly mouse alpha2AP. The conservation of this disulphide bridge suggests that it is important for functional aspects of alpha2AP. However, the structural and functional analysis described in this study does not support this conclusion.

Effects of perindopril and hydrochlorothiazide on the long-term progression of lithium-induced chronic renal failure in rats

Administration of lithium in the diet to new-born rats induces chronic renal failure associated with hypertension, proteinuria and irreversible tubulo-interstitial morphological changes. In the present study we induced chronic renal failure by administration of lithium for 16 weeks to new-born rats, and examined the spontaneous course of this nephropathy and the effects of antihypertensive treatment with either perindopril (12 mg/kg diet) or hydrochlorothiazide (500-1000 mg/kg diet) during a 24 weeks follow up period without lithium. In the placebo group, progression to terminal uraemia occurred in all rats with severe renal failure (initial Purea > 15 mM) (10 of 18). Rats with mild-moderate renal failure (Purea 9-15 mM) showed no deterioration in renal function despite persistent systolic hypertension and irreversible structural renal changes. Perindopril normalized the blood pressure in all rats but did not prevent the progression to terminal uraemia (8 to 18). Hydrochlorothiazide partially controlled the hypertension and accellerated the progression of uraemia without increasing the mortality (7 of 17). Irrespective of treatments, the predominant quantitative structural changes (e.g. decreased volume of proximal tubular cells) showed significant correlations with the degree of renal dysfunction, but not with systolic blood pressure in the surviving rats. It is concluded that progression of lithium-induced nephropathy to terminal uraemia occurs when the nephrotoxic insult results in a more than 50% reduction of the glomerular filtration rate, judged from Purea levels. The failure of effective antihypertensive treatment with an angiotension-converting enzyme inhibitor to modify the progression suggests that in this model, systemic or glomerular hypertension may not be an important pathophysiological factor. The structural and functional deterioration observed in Li-uraemic rats during treatment with hydrochlorothiazide remains unexplained.

Effects of renal papillary-medullary lesion on the antihypertensive effect of furosemide and development of salt-sensitive hypertension in Dahl-S rats

To test the hypothesis that the long-term antihypertensive action of furosemide is mediated by a renomedullary vasodepressor substance, we measured mean arterial pressure (MAP) by radiotelemetry in Dahl-S rats with either intact or bromoethylamine-induced (BEA, 100 mg/kg i.p.) lesion of the renal papilla and medulla. Seven days of recovery after BEA administration, the rats diet was changed from 1 to 4% NaCl, and during days 8 to 31, rats were randomized to daily treatment with placebo or furosemide (50 mg/kg p.o.). Then furosemide treatment was stopped and the rat food was changed to 1% NaCl diet. After a 10-day wash-out period, renal function was measured. BEA produced a rapid (within min) and sustained increase in MAP which was accelerated during 4% NaCl diet. Furosemide prevented 4% NaCl-induced hypertension in both rats with intact kidneys and in rats with BEA-induced renal papillary-medullary lesion. A significant decrease in renal plasma flow (-34%) and glomerular filtration rate (-40%) was observed in all BEA-treated rats independent of previous furosemide treatment. In response to an i.v. load of isotonic saline (10% body weight), rats with renal papillary-medullary lesion had an impaired ability to excrete sodium. Histological examination showed that BEA-treated rats had severe lesions of the renal papilla and medulla, with light-to-moderate changes in the renal cortex. It is concluded that the antihypertensive effect of furosemide is not mediated by a renomedullary vasodepressor substance. The accelerated NaCI-sensitive hypertension in rats with BEA-induced renal papillary-medullary lesion is related to an impaired ability to excrete excess NaCl.

[Ultrasound examination of the liver in HELLP syndrome]

A 33-year-old multiparous woman in the 34th gestational week presented with severe upper abdominal pain, nausea and vomiting. Clinical examination revealed severe epigastric tenderness. Abdominal ultrasound examination showed geographical areas with increased echogenicity in the right lobe of the liver. Through haematological examination, we found severe thrombocytopenia and fibrinolysis. The diagnosis of HELLP syndrome was suspected and a caesarean section was performed. We suggest that obstetrical patients with upper abdominal pain and abnormal liver sonography should immediately be haematologically investigated to exclude the life-threatening condition of the HELLP syndrome.

Effects of supplemental coverage on use of services by Medicare enrollees

This article estimates the extent to which private insurance supplements affect use of services by Medicare enrollees. Three types of supplements to Medicare's coverage are examined--Health Maintenance Organizations (HMOs), medigap (MGP) plans, and employment-based indemnity (EBI) plans. While each kind of supplement reduces cost sharing on Medicare-covered services, only HMOs do so without increasing enrollees' overall use of services. Use of services by HMO enrollees is about 4 percent lower than use by similar Medicare enrollees with no insurance supplement. By contrast, use of services by enrollees with MGP coverage is 28 percent higher, and use of services by enrollees with EBI plans is 17 percent higher.

Comparison of the renal effects of six sedating agents in rats

This study was designed to compare the renal effects of sedation with alphaxalone-alphadolone, etomidate, propofol, midazolam, fentanyl-fluanisone, and thiopental in rats. The sedative dose was defined as the highest dose that abolished the escape response without affecting the righting reflex. Female Wistar rats were chronically catheterized with a jugular vein catheter, and urine flow rate and renal clearances of inulin (glomerular filtration rate = GFR), sodium, and lithium (used as an index of proximal tubular function) were measured in the conscious, unrestrained state (n = 107 experiments). In a separate series (n = 70 experiments), the effect of sedative doses of each drug on the nociceptive threshold was tested with the tail-flick test. Responses in sedated animals were compared to responses in animals infused with the vehicle. Fentanyl-fluanisone and thiopental had hypoalgesic actions in sedating doses. Propofol, fentanyl-fluanisone, and thiopental reduced GFR by 20-30%. Urine flow rate was significantly decreased by propofol (-24%) and thiopental (-48%). Propofol and fentanyl-fluanisone reduced fractional lithium excretion by 9-13%. Only alphaxalone-alphadolone, etomidate, and midazolam produced sedation without affecting renal function in rats. Because midazolam produced the most consistent degree of sedation, we conclude that midazolam is the least confounding sedative agent for renal function studies in conscious rats.

Activated human plasma carboxypeptidase B is retained in the blood by binding to alpha2-macroglobulin and pregnancy zone protein

A 66-kDa glycosylated carboxypeptidase, plasma pro-carboxypeptidase B (pro-plasma CPB), has recently been identified in human blood (Eaton, D. L., Malloy, B. E., Tsai, S. P., Henzel, W., and Drayna, D. (1991) J. Biol. Chem. 266, 21833-21838). The pro-enzyme binds to plasminogen and the active enzyme is specific for COOH-terminal Lys or Arg residues. These properties implicate a role in the fibrinolytic or coagulation system. However, we show that the molecular mass of the active plasma CPB is approximately 36 kDa, which is below the glomerular filtration limit. Since activated plasma CPB no longer binds plasminogen, the active enzyme may not be retained in the circulation. To investigate this, we performed plasma elimination studies in mice which showed that 125I-plasma CPB remains in the circulation despite its small size. Native polyacrylamide gel electrophoresis of blood samples removed from the mice revealed that plasma CPB migrated as a high molecular weight band. Similar bands were observed in vitro when 125I-plasma CPB was added to plasma from humans and other species. The plasma CPB-binding proteins were purified from human plasma and identified as alpha2-macroglobulin (alpha2M) and pregnancy zone protein. Only the active enzyme bound to the two alpha-macroglobulins, and the interaction was specific for alpha2M in its native conformation, but not its receptor recognized forms. The complex between human alpha2M and plasma CPB dissociated during SDS-polyacrylamide gel electrophoresis and transverse urea gel electrophoresis suggesting that the interaction was noncovalent and depended on the tertiary structure of the native alpha2M molecule. The catalytic activity of plasma CPB was not significantly affected by its binding to alpha2M. The specific binding of plasma CPB to alpha-macroglobulins suggest that these proteins may function as a "shuttle" in vivo to modulate the clearance of plasma CPB from the circulatory system.

lag-1, a gene required for lin-12 and glp-1 signaling in Caenorhabditis elegans, is homologous to human CBF1 and Drosophila Su(H)

The homologous receptors LIN-12 and GLP-1 mediate diverse cell-signaling events during development of the nematode Caenorhabditis elegans. These two receptors appear to be functionally interchangeable and have sequence similarity to Drosophila Notch. Here we focus on a molecular analysis of the lag-1 gene (lin-12 -and glp-1), which plays a central role in LIN-12 and GLP-1-mediated signal transduction. We find that the predicted LAG-1 protein is homologous to two DNA-binding proteins: human C Promoter Binding Factor (CBF1) and Drosophila Suppressor of Hairless (Su(H)). Furthermore, we show that LAG-1 binds specifically to the DNA sequence RTGGGAA, previously identified as a CBF-1/Su(H)-binding site. Finally, we report that the 5′ flanking regions and first introns of the lin-12, glp-1 and lag-1 genes are enriched for potential LAG-1-binding sites. We propose that LAG-1 is a transcriptional regulator that serves as a primary link between the LIN-12 and GLP-1 receptors and downstream target genes in C. elegans. In addition, we propose that LAG-1 may be a key component of a positive feedback loop that amplifies activity of the LIN-12/GLP-1 pathway.

Occupational injuries among fishermen

A sample of 187 medically treated injuries among fishermen was the basis for this study. Nearly half the injuries occurred while shooting or hauling fishing gear. The most common injuries were in the upper extremities (48.7%). Twenty-two percent of the injuries occurred while working with winches ropes and wires and about 30% were caused by falls or slips. Seventy-five percent of accidents occurred on trawlers, where the trawl doors (other boards) are a special hazard. Medical treatment ashore was delayed for more than 24 hours in 35% of the injuries, showing the need for providing optimal treatment facilities on board. Prevention measures should include technical improvements, safety training courses and efforts to enhance the motivation for safe work. The fishermen's proposals for prevention seem to be most useful and should be used to the full extent.

Reductant-independent ATP hydrolysis catalyzed by homologous nitrogenase proteins from Azotobacter vinelandii and heterologous crosses with Clostridium pasteuranium

Reductant-independent ATPase activity was initiated and studied for Azotobacter vinelandii and Clostridium pasteuranium nitrogenase proteins (Av1, Cp1 and Av2, Cp2, 1 designating the iron molybdenum protein and 2 the iron protein) and their heterologous crosses by two methods: (1) allowing dithionite to be depleted from a normal assay in the presence of substrate levels of MgATP and (2) using reduced but reductant-free nitrogenase proteins in the presence of substrate levels of MgATP. In both cases, at a 1:1 protein ratio, MgATP is converted initially to MgADP with a specific activity of 400-500 nmol MgATP hydrolyzed/min.mg Av1, but in slower steps the MgADP is converted to AMP and, after 12 h, AMP is ultimately converted to adenosine. This reactivity requires the presence of both proteins, increases with increasing Av2/Av1 ratio, and is not a result of unique redox states of either protein. For Av1-Av2, ATP hydrolysis in the absence of Mg2+ occurred at nearly the same rate as reductant-dependent MgATP hydrolysis. Reductant-independent ATPase activity also occurred for the Av1-Cp2 and Cp1-Av2 heterologous crosses and was 2-fold and 18-fold slower than the Av1-Av2 or Cp1-Cp2 combinations. In both cases further hydrolysis of MgADP to AMP and AMP to adenosine occurred. A unique nucleotide hydrolysis system is apparently operating in the complex formed between the two nitrogenase proteins in the absence of reductant. The relationship between the reductant-independent and reductant-dependent activities of nitrogenase catalysis is explored.

Supra-additive natriuretic synergism between bendroflumethiazide and furosemide in rats

To examine the diuretic and natriuretic synergism between bendroflumethiazide (BFTZ) and furosemide (FUR), the acute diuretic and natriuretic response to BFTZ was compared when given alone, during acute and during chronic FUR infusion. Responses to diuretics were assessed in conscious, chronically instrumented rats and, to avoid confounding influences of diuretic-induced volume contraction, extracellular fluid volume was kept constant by a computer-driven servo-control technique. Two groups were pretreated with osmotic minipumps chronically infusing either FUR (0.25 mg/hr; group CF; n = 9) or vehicle (8% ethanolamine; group CV; n = 8) i.p. for 7 days before the experiment. During the experiment, two other groups received either acute infusion with FUR (0.25 mg/hr; group AF; n = 16) or acute infusion with vehicle (150 mM glucose; group AV; n = 11). After a 60-min control period, BFTZ (0.083 mg; 0.25 mg/hr) was administered for 90 min to all four groups. Whereas the diuretic and natriuretic response to BFTZ was similar in groups AF, AV and CV, a supra-additive response was observed in the CF group (vs. group CV: delta urine flow rate: +78%; delta urinary Na excretion: +69%). BFTZ had no effect on the fractional excretion of Li, which suggests that the supra-additive effect was due to inhibition of an enhanced distal tubular Na reabsorption induced by chronic FUR administration. Because before BFTZ administration urinary Na excretion was 3-fold higher during acute than during chronic FUR infusion, an increased delivery of NaCl to the thiazide segment cannot by itself explain the exaggerated BFTZ response during chronic FUR treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Smooth muscle myosin II and alpha smooth muscle actin expression in the baboon (Papio anubis) uterus is associated with glandular secretory activity and stromal cell transformation

The objective of this study was to investigate the localization and hormonal regulation of smooth muscle myosin II (SMM II) and alpha smooth muscle actin (alpha SMA) in the baboon uterus, since cytoskeletal proteins are involved in secretory function and morphological transformation. Uterine tissue was obtained from baboons 1) during the menstrual cycle, 2) following steroid treatment of ovariectomized baboons, 3) during pregnancy (Days 14-60 postovulation [PO]), and 4) during simulated pregnancy (Days 18-32 PO). Tissues were processed for immunocytochemical localization of SMM II or alpha SMA with specific polyclonal or monoclonal antibodies, respectively. SMM II stained all smooth muscle cells of blood vessels and myometrium regardless of treatment. Glandular epithelial staining was present only in endometrium obtained during the luteal phase or following estrogen and progesterone treatment. Staining intensity was greater in the basalis than in the functionalis. The number of glands staining positive for SMM II on Days 18-32 of pregnancy and simulated pregnancy was variable. Glandular stain was absent after Day 32 PO. These immunocytochemical data were confirmed by immunoblot analysis of glandular cytosolic extracts. Stromal staining for SMM II was present under the luminal epithelium during simulated pregnancy (Days 18-32), on Day 25 of steroid treatment in the simulated-pregnant controls, and in nonimplantation sites during pregnancy. In contrast, alpha SMA staining was low or absent in all uterine cell types in ovariectomized baboons. Under estrogen-dominated conditions (follicular phase and estrogen treatment), alpha SMA staining was present in smooth muscle cells, and this staining persisted throughout the remaining treatment periods. Glandular epithelial staining for alpha SMA was absent in all treatment groups. However, alpha SMA staining in stromal fibroblasts underneath the luminal epithelium was evident as early as Day 14 of pregnancy and Day 18 of simulated pregnancy. The number of stromal fibroblasts that stained positive increased in the surface region of the functionalis between Days 18 and 32 PO, and the staining extended throughout the upper functionalis region. There was a decrease in the number of positively stained stromal fibroblasts, particularly at the implantation site, between Days 32 and 40 of pregnancy. By Days 50-60 of pregnancy, this staining was almost absent. The induction of alpha SMA in stromal fibroblasts in the functionalis region in pregnant baboons was confirmed by immunoblot analysis of stromal cell cytosol extracts. We conclude that the progesterone-induced glandular expression of SMM II may be involved in uterine secretory function and that alpha SMA expression in stromal fibroblasts during pregnancy and after long-term steroid treatment is associated with the decidualization process.

Sodium dodecyl sulfate-stable complexes between serpins and active or inactive proteinases contain the region COOH-terminal to the reactive site loop

Recently inhibitors of the serpin family were shown to form complexes with dichloroisocoumarine (DCI)-inactivated proteinases under native conditions (Enghild, J. J., Valnickova, Z., Thøgersen I., and Pizzo, S. V. (1994) J. Biol. Chem. 269, 20159-20166). This study demonstrates that serpin-DCI/proteinase complexes resist dissociation when analyzed in reduced SDS-polyacrylamide gel electrophoresis. Previously, SDS-stable serpin-proteinase complexes have been observed only between serpins and catalytically active proteinases. The stability of these complexes is believed to result from an acyl-ester bond between the active site Ser195 of the proteinase and the alpha-carbonyl group of the scissile bond in the reactive site loop. We have further analyzed the structure of the SDS-stable serpin-proteinase and serpin-DCI/proteinase complexes. The results of these studies demonstrate the presence of the COOH-terminal region of the serpin in both complexes. Since (i) modification of Ser195 does not prevent formation of SDS-stable complexes and (ii) COOH-terminal peptides are present in both complexes, the previously described mechanism does not sufficiently explain the formation of SDS-stable complexes.

[Occupational accidents in the fishing industry. A survey of fishing-related accidents treated at the Bornholm Central Hospital in Rønne as well as in general practice 1987-1990]

Over a two year period from 1987-1989 all fishing-related injuries treated in the Emergency Room at Bornholm's central hospital in Rønne and at some general practices were registered prospectively. One hundred injuries were registered altogether. Accidents occurring in connection with putting out and recovering apparatus constituted respectively 14% and 36%. Working with the trawler scoop was responsible for 18% of the accidents and was the most common direct cause, followed by work with winches which constituted 11%. Falls made up almost a quarter of the accidents. Finger injuries constituted 33%, and hand and wrist injuries 17%. Trawler scoop injuries most commonly involved the fingers and hands and fish-cleaning injuries the hands, wrists and fingers. Prophylactic efforts concerning safety in work with trawler scoops, winches and steering systems should be made.