Time-dependent blockade of STP and LTP in hippocampal slices following acute stress in mice

The characteristics of short-term potentiation (STP) and long-term potentiation (LTP) in the CA1 region of hippocampal slices were determined at various times following exposure to acute stress produced by restraint and tail-shock in mice. In slices prepared from control animals, theta-burst stimulation resulted in a large increase in evoked field excitatory postsynaptic potentials (EPSPs) amplitude and slope that remained stable at least up to 30 min after stimulation. Slices prepared 1 h after stress exhibited a marked decrease in the extent of both STP and LTP. STP and LTP magnitude were still significantly decreased 24 h after stress exposure and were completely restored to control levels by 48 h. These results provide evidence for a reversible impairment of STP and LTP in CA1 following an acute episode of stress, and suggest that stress activates processes different from those activated by LTP-inducing stimuli.

Activation of STAT transcription factors by herpesvirus Saimiri Tip-484 requires p56lck

Signal transducers and activators of transcription (STATs) relay signals from activated cell surface receptors directly to the nucleus. Previously, a protein required for T-cell transformation by the DNA tumor virus herpesvirus saimiri (HVS) and designated tyrosine kinase interacting protein (Tip-484) was shown to interact with and dramatically upregulate the activity of p56lck. p56lck is a nonreceptor tyrosine kinase that is essential for signaling by the T-cell receptor and also interacts with the CD4, CD8, and interleukin-2 receptors. The present data show activation of STAT1 and -3 by Tip-484. STAT1 and -3 were also found to complex with glutathione S-transferase-Tip-484 only in the presence of p56lck, and STAT3 was shown to be phosphorylated by the Tip-484-p56lck multiprotein complex in vitro. Infection of T cells with HVS or expression of recombinant Tip-484 significantly increased the DNA-binding activity of the STAT1 and STAT3 transcription factors in nuclear extracts and also increased the phosphorylation of STAT3 in vivo. This is the first report of STAT activation by a DNA tumor virus protein. Moreover, these studies demonstrate that p56lck is required for STAT activation by Tip-484.

Renal angiotensin II receptor regulation in two-kidney, one clip hypertensive rats: effect of ACE inhibition

Local renal and plasma renin-angiotensin systems (RAS) both play an important role in blood pressure regulation during the development of two-kidney, one clip Goldblatt hypertension (2K1C) through their vasoactive component, angiotensin II (Ang II). Our goal was to characterize glomerular and preglomerular vascular Ang II receptors during the different stages of development of hypertension in 2K1C rats (2-, 4-, 8-, and 16-weeks postoperative) using Ang II antagonists [Sar1,Ile8]-Ang II, losartan, and PD 123319 and their regulation after angiotensin-converting enzyme (ACE) inhibition by captopril. Competitive binding studies showed that the only Ang II receptor detected on both glomeruli and preglomerular vessels of all groups (2-, 4-, 8-, and 16-week 2K1C rats, control rats, and captopril-treated rats) was the Ang II type 1 receptor (AT1). Vascular AT1 receptor density (Bmax) was significantly lower in only the 16-week 2K1C group, whereas glomerular Bmax was significantly lower in 2K1C rats at 2-, 4-, and 8-weeks. Vascular and glomerular receptor densities were both significantly higher in captopril-treated rats than in nontreated rats. We therefore conclude that in 2K1C rats, Ang II receptors on preglomerular vessels and glomeruli are regulated differentially during the development of hypertension and after ACE inhibition. Our results suggest that glomerular Ang II receptors are regulated by systemic plasma Ang II levels, whereas vascular Ang II receptors are not. However, when renal and systemic RASs are both blocked, these receptors are upregulated but are no longer differentially regulated.

Cysteine residues in human lysosomal acid lipase are involved in selective cholesteryl esterase activity

Human lysosomal acid lipase (LAL) catalyses the deacylation of triacylglycerol and cholesteryl esters in the acidic lysosomal compartment. Treatment of LAL with the reducing agent dithiothreitol affected the triacylglycerol and cholesteryl esterase activities differentially, suggesting the involvement of cysteine residues in determining substrate specificity. To identify the residues involved, human LAL cDNA, under the control of the T7 promoter and tagged with a herpes simplex virus coding epitope, was specifically mutated in order to introduce single amino acid substitutions of each of the six cysteine residues of mature LAL. All Cys-227 mutants showed selectively decreased activity towards cholesteryl oleate, while preserving that towards trioleylglycerol. Substitutions of Cys-236, Cys-240 and Cys-244 affected catalysis towards the two substrates to a variable degree, depending on the side chain of the amino acid introduced. The replacement of Cys-41 or Cys-188 did not result in the preferential cleavage of either one of the two substrates. These data indicate that Cys-227, Cys-236, Cys-240 and Cys-244 play a crucial role in determining LAL substrate specificity. We propose that these cysteine residues are involved in the hydrolysis of cholesteryl ester by affecting selectively the access of this substrate to the catalytic active site. In addition, the fact that the catalytic activity is never completely abolished in cysteine mutants demonstrates that LAL is not a thiol enzyme.

Fish oil-supplemented feeding does not attenuate warm liver ischemia and reperfusion injury in the rat

Liver ischemia and reperfusion injury is mediated by oxygen free radicals, cytokines, and prostanoids produced by Kupffer cells and infiltrating neutrophils. Fish oil-supplemented diets alter membrane phospholipid composition and modify prostanoids and cytokine production in response to ischemia and reperfusion. This study tested the hypothesis that a fish oil-supplemented diet would attenuate warm liver ischemia and reperfusion injury in the rat. Male Sprague-Dawley rats were fed Vital HN supplemented with either fish oil (FO) or corn oil (CO) by the continuous duodenal infusion for 5 days. Total dietary fat (26% of total calories), caloric intake (70 cal/day), and volume (60 ml/day) were identical between two groups. Plasma eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels increased significantly in rats fed fish oil (0 to 16.3% for EPA and 2 to 12% for DHA). Liver histology was similar in both groups before ischemia. On Day 6, rats were subjected to 60 min of reversible hepatic ischemia. Plasma TNF levels, 1 and 24 hr after reperfusion, were not different between FO and CO rats. Liver injury assessed by bile flow, histology, plasma ALT, and bile glutathione efflux did not differ between groups. We conclude that our fish oil-supplemented enteral diet does not attenuate warm liver ischemia and reperfusion injury in rats.

Contextual conditioned fear blocks the induction but not the maintenance of lateral septal LTP in behaving mice

High-frequency stimulation (HFS) of the fimbria induces long-term potentiation (LTP) in the lateral septum. This study was aimed at investigating the effect of contextual fear conditioning on septal LTP with the use of behaving C57 BL/6 mice as subjects. For the acquisition of contextual fear conditioning, animals were placed in a conditioning chamber, where they were subjected to footshocks (FSs, 0.6 mA); the following day (retention), animals were reexposed to the chamber. Animals from the first group received HFS in their home cages before being submitted to conditioning; animals from the second group were first submitted to conditioning before receiving HFS during reexposure to the conditioning chamber; animals from the third group were submitted to the same regimen as those from the second group, except that no FS was delivered in the conditioning chamber; and animals from the fourth group received FS in the conditioning chamber but were maintained in their home cages the day after for LTP induction. Before conditioning, animals from the first group, placed in a familiar context (home cage), displayed an LTP of the N3 wave of septal field potential. After conditioning, reexposure of these animals to the conditioning chamber produced a transient decrease in the amplitude of N3 but did not interfere with the duration of maintenance of LTP. Conversely, in animals from the second group, when HFS was applied during reexposure to the conditioning chamber the induction of LTP was totally blocked. However, mice from the two other groups (3rd and 4th) displayed normal levels of LTP. Taken together with previous findings, these data suggest that contextual conditioned fear may interfere with certain forms of learning via blockade of hippocampal-septal LTP.

Occupational allergy in saffron workers

Sensitization to the flower of saffron, a plant commonly grown in Spain for commercial purposes, and its clinical significance as an occupational allergen were studied. The prick test and RAST, with saffron pollen, stamen, and pistil extracts, were used to evaluate the cutaneous and specific antibody responses in the studied population. Provocation tests in patients with clinical findings were used to verify the implication of saffron components in these symptoms. Fifty saffron workers were evaluated. Three of them were sensitized to saffron pollen and stamen proteins, giving prick and RAST positive values. One patient presented asthma, showing a positive bronchial provocation test, and two patients rhinoconjunctivitis, showing positive conjunctival provocation tests. Of a general allergic population of 237, 10 patients also presented cutaneous test and IgE positive to saffron. Saffron allergens (from pollen and stamens) were characterized by SDS-PAGE immunoblotting. A relevant allergen of 15.5 kDa with profilinic nature was detected and further purified by high-resolution gel filtration chromatography. No allergenic components were demonstrated in pistils. Cross-reactivity of saffron extracts was evaluated by RAST inhibition with respect to other pollen species commonly causing sensitization in the same area of study. A significant degree of cross-reactivity was demonstrated between saffron and Lolium, Salsola, or Olea. The identification of the protein components involved in the cross-reactions was investigated by blot inhibition.

Using slaughter inspections to evaluate sarcoptic mange infestation of finishing swine

Sarcoptic mange is one of the common swine diseases worldwide. Although mange-free populations can be established with caesarean derived stock, by herd repopulation programmes or by eliminating mange with ivermectin, mange remains prevalent in many countries. Field and experimental studies indicate that hypersensitive mange is detrimental to performance of growing pigs. Typically, producers tolerate mange infestation in their herds and control measures are often haphazard. This tolerance to mange infestation is attributable to the covert nature of the losses (reduced growth rate and feed efficiency without mortality) and to the fact that clinical signs of hypersensitive mange (pruritus) are usually viewed as normal. Lack of tools to evaluate mange severity in pigs and to demonstrate its importance has hindered the efforts of veterinarians to control the disease. Traditionally, veterinarians have used slaughter inspections to assess respiratory diseases such as enzootic pneumonia and atrophic rhinitis. Much of the value of slaughter inspections is as a tool with which veterinarians can educate and motivate their clients to improve disease control measures. The potential for evaluating hypersensitive mange by inspecting slaughtered pigs for lesions of papular dermatitis was recognised some time ago, but quantitative evaluation of the reliability of this approach has been lacking. We have conducted several studies in Australia, the USA, Canada, Europe and Latin America to evaluate associations between Sarcoptes infestation and the severity of papular dermatitis at slaughter, using a simple ordinal scale for classifying carcasses. Our initial field and experimental data in Australia indicated the specificity of localised dermatitis to be in the order of 75-80%, but that the generalised dermatitis was highly specific (> 98%) for mange. Subsequent studies in the US Midwest yielded almost identical results, and indicated that the method may also have some utility for surveillance of mange-free herds. Results from other locations invariably have shown significant associations between dermatitis lesions and mange infestation. Relative to other methods such as skin scrapings and monitoring pruritus, this method is simple and relatively objective, and should be considered for routine inclusion in slaughter inspection protocols.

Nosocomial respiratory syncytial virus infections: prevention and control in bone marrow transplant patients

OBJECTIVE

To assess the effectiveness of a multifaceted infection control strategy in limiting the nosocomial transmission of respiratory syncytial virus (RSV) infection to patients in a bone marrow transplant (BMT) unit.

DESIGN

Before/after trial.

SETTING

University-affiliated tertiary cancer center.

PATIENTS

Adult BMT recipients hospitalized during two consecutive wintertime community outbreaks of RSV infection.

INTERVENTIONS

An infection control strategy against nosocomial RSV infection was implemented in the BMT unit in February 1993. The strategy involved prompt identification, isolation, and cohorting of RSV-infected patients; prompt therapy with aerosolized ribavirin; use of masks and gloves by anyone entering an infected BMT patient's room; screening visitors for respiratory symptoms; restricting visitation by all children under 12 years of age and all family members and other visitors with RSV symptoms; and restricting symptomatic hospital staff from working in the BMT unit.

RESULTS

After implementation of the multifaceted infection-control strategy, there were four cases of nosocomial RSV infection in 3,870 patient days (incidence density, 1.0 case/1,000 patient days) compared with 14 cases of nosocomial RSV infection in 3,152 patient days (incidence density, 4.4 cases/1,000 patient days) during the 1992-1993 RSV season (rate ratio, 4.4; 95% confidence interval [CI95]. 1.4-17.9: P < .01). This decrease in incidence occurred despite a comparable prevalence of community-acquired RSV cases between the two seasons (2.2% vs 3.2% in 1992-1993 and 1993-1994, respectively; prevalence ratio, 0.7; CI95, 0.2-2.1; P = 0.5).

CONCLUSION

Institution of a multifaceted infection control strategy significantly reduced the frequency of nosocomial RSV infection in a high-risk group of adult BMT recipients.

Long-term toxicity and neuropathology associated with the sequencing of cranial irradiation and enhanced chemotherapy delivery

OBJECTIVE

The goal was to evaluate, at 1 year, 75 Long-Evans rats for survival rates and toxicity associated with the sequencing of cranial irradiation and enhanced chemotherapy delivery.

METHODS

Seventy-five Long-Evans rats were randomized into four groups and evaluated at 1 year for survival rates and toxicity associated with the sequencing of cranial irradiation and enhanced chemotherapy delivery. Radiation (2,000 cGy) was administered as a single fraction, by using parallel opposed portals, 30 days before chemotherapy (Group 1), 24 hours before chemotherapy (Group 2), 30 days after chemotherapy (Group 3), or without chemotherapy or without radiation (control group, Group 4). Five subgroups within each treatment group included rats receiving intra-arterially administered methotrexate (1 g/m2) or intravenously administered etoposide (200 mg/m2) combined with intra-arterially administered carboplatin (200 mg/m2), administered with or without osmotic blood-rain barrier disruption, and a group receiving normal saline solution after blood-brain barrier disruption.

RESULTS

There was a significant increase in total toxic effects when the three experimental groups were compared with the control group (P = 0.001, 0.006, and 0.013 for Groups 1, 2, and 3, respectively). All groups receiving radiation and chemotherapy (particularly carboplatin and etoposide) had an increased incidence of hind limb paralysis, resembling experimental allergic neuritis (P = 0.053). Statistical analysis showed a trend toward increased mortality rates in Group 1 (antecedent radiation), compared with the control group (P = 0.082), and an increased incidence of intracerebral calcification (P = 0.019). No differences in mortality rates were observed for Group 2 or 3, compared with the control group.

CONCLUSION

Radiation before chemotherapy was a more toxic sequence and, surprisingly, carboplatin/etoposide administered in combination with radiotherapy was more detrimental than methotrexate. Additional studies are in progress to evaluate the toxicity and efficacy of sequences of cranial irradiation and enhanced chemotherapy in tumor-bearing rats.

Strain reorganizes focal adhesions and cytoskeleton in cultured airway smooth muscle cells

Abnormal mechanical stress on pulmonary structures is associated with increased airway resistance and impaired gas exchange as a result of increased airway smooth muscle (ASM) deposition. Using an in vitro system with cultured ASM cells, we have demonstrated that cyclic deformational strain increases ASM cellular myosin and myosin light chain kinase. To determine if these contractile protein increases were accompanied by ultrastructural changes in cells indicating phenotypic modulation, cells subjected to strain were compared to cells grown under static conditions by transmission electron microscopy (TEM) and fluorescent staining. The strained ASM cells oriented perpendicular to the strain direction were more elongated and contained more actin stress fibers than identical cells grown under physically static conditions. The stress fiber bundles were thicker and reorganized parallel to the long axis of the cell. Marked increases in the numbers and lengths of focal adhesions between the cell membrane and the substratum were found by both TEM and immunostaining for talin. Mechanical strain thus increases organization of cytoskeletal elements in cultured ASM cells. Similar effects in vivo may serve to promote the expression of the contractile phenotype of cultured ASM cells independent of other in vivo factors and alter cell contractility. Increased organization of cytoskeletal elements might also increase the efficiency of signal transduction from the extracellular matrix into the cell interior.

[HIV-1 env glycoprotein gp120 and gp160 expressed in vaccinia virus system and their antigenicity analysis]

Human immunodeficiency virus type 1 (HIV-1) is the principal causative agent of AIDS that is an important concerns to human being health. The most important antigen of HIV-1 is its envelope glycoprotein gp160 (gp120 + gp41). By means of genetic engineering techniques, HIV-1 gp120 and gp160 were constructed and expressed in the recombinant vaccinia virus system under the control of bacteriophage T7 promoter or vaccinia virus p7.5 promoter. The results showed that the recombinant gp120 and gp160 expressed in this system exist in the form as glycoproteins, resuming the native epitope conformation of the viruses from which they were derived. These recombinant gp120 and gp160 could be recognized by the virus-specific neutralizing monoclonal antibodies. The findings suggested that the recombinant HIV-1 gp120 and gp160 could be used as a candidate recombinant protein vaccines.

Remodeling of the temporomandibular joint condyle. Following direct trauma to the mandible

A patient involved in a bicycle accident received direct trauma to the mandible and the maxillary anterior teeth. The injuries were demonstrated using x-rays, tomography and magnetic resonance imaging (MRI).

Role of nitric oxide in autocrine control of growth and apoptosis of endothelial cells

Nitric oxide (NO) is a growth inhibitor for diverse cellular types. In the present study, we have found that the inhibition of NO production in bovine endothelial cells by an L-arginine competitive antagonist induces DNA replication and promotes the transition from prereplicative to replicative phases of the endothelial cell cycle and an increase in c-myc and c-fos oncogene-encoded protein expression. The inhibition of NO generation had, however, a markedly different outcome depending on the state of confluence of the cells, i.e., proliferation was found in subconfluent cells, whereas apoptosis occurred in confluent cells. Moreover, Western blot analysis revealed differences in the constitutive NO synthase expression in proliferating compared with growth-arrested cells. In conclusion, these results disclose an alternative mechanism of endothelial cell apoptosis at the confluent state, which is related to NO inhibition. Moreover, the fact that the apoptotic phenomenon occurred in the presence of growth factors indicates the existence of apoptotic mechanisms that do not require growth factor deprivation.

Effect of angiotensin-converting enzyme two-week inhibition on renal angiotensin II receptors and renal vascular reactivity in SHR

We recently reported that intrarenal vascular AT1 angiotensin II (ANG II) receptors are major determinants of the increased vascular resistance and reactivity to ANG II observed in the kidney of spontaneously hypertensive rats (SHR). We decided to test the hypothesis that, by modifying plasma ANG II levels by inhibiting the ANG II-converting enzyme (ACE) with captopril, we would modify intrarenal ANG II receptors, and therefore the renal vascular response to ANG II. Two approaches were taken: (1) radioligand binding assays were performed on membrane preparations of purified renal microvessels and glomeruli, with displacement of 125I-[Sar-Ile8]-ANG II by specific non-peptide antagonists of AT (losartan) and AT2 (PD 123319): (2) dose-response curves to ANG II on the isolated perfused kidney were studied. Two weeks of captopril treatment significantly reduced blood pressure (BP) and relative heart weight, and increased plasma renin activity. The binding assays showed that renal microvessels and glomeruli expressed a single receptor population (AT1) for ANG II. The density of glomerular AT1 was not modulated by captopril treatment (600 +/- 174 v 573 +/- 97 fmol/mg protein in non-treated and treated SHR respectively); however. AT1 density on the intrarenal arteries increased 3-fold (55 +/- 20 v 154 +/- 30 fmol/mg protein in non-treated and treated SHR respectively. P < 0.05). Experiments with isolated perfused kidneys demonstrated that captopril did not improve the compliance of intrarenal vessels to high flow but increased their reactivity to ANG II (ED50 = 18 nM v 0.5 pM, P < 0.01). We conclude that treatment with an ACE inhibitor increases vascular reactivity to ANG II which may be mediated by an upregulation of renal vascular ANG II receptors.

ZD9583, an orally effective thromboxane A2 synthase inhibitor and receptor antagonist with a sustained duration of action in rat and dog

The thromboxane A2 (TXA2) synthase inhibitory activity and the TXA2 receptor (TP-receptor) blocking action of ZD9583 ((4Z)-6-[(2S,4S,5R)-2-(1-[2-cyano-4-methylphenoxy]-1-methylethyl) -4-(3-pyridyl)-1,3-dioxan-5-yl]hex-4-enoic acid) has been evaluated in-vitro by use of whole blood and platelets from man, and ex-vivo by use of platelets and whole blood from rats and dogs. ZD9583 caused concentration-dependent inhibition of human platelet microsomal TXA2 production with an IC50 of 0.017 +/- 0.003 microM; this inhibition was associated with an increase in prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) formation. ZD9583 also inhibited collagen-stimulated TXA2 synthesis in whole blood from man, rat and dog giving IC50 values of 0.027 +/- 0.005, 0.02 +/- 0.006 and 0.013 +/- 0.01 microM, respectively. The drug did not modify platelet cyclooxygenase activity as inhibition of thromboxane B2 (TXB2) formation was associated with a concomitant increased synthesis of prostaglandin D2 (PGD2), PGE2 and PGF2 alpha. ZD9583 had little effect on cultured human umbilical vein endothelial cell prostacyclin synthase giving an IC50 of 24.2 +/- 4.9 microM. In-vitro ZD9583 caused concentration-dependent inhibition of U46619-induced aggregation responses of platelets from man, rat and dog, yielding apparent log A2 values of 8.7 +/- 0.12, 8.8 +/- 0.2 and 9.3 +/- 0.2, respectively. The drug was selective; at concentrations up to 100 microM it did not affect 5-hydroxytryptamine or the primary phases of adenosine diphosphate and adrenaline-induced aggregation. ZD9583 (100 microM) did not, furthermore, modify the platelet inhibitory effects of PGD2, prostaglandin E1 (PGE1) and prostacyclin. Oral administration of ZD9583 (3-10 mg kg-1) to both rats and dogs caused dose-dependant inhibition of collagen-stimulated TXA2 production ex-vivo which persisted for up to 12 h. The drug also caused profound TXA2 receptor blockade in both species for in excess of 12-h after an oral dose of 3 mg kg-1. ZD9583 (3 mg kg-1, p.o.), when administered to dogs over a five-day period at 12 h intervals, did not cause either tachyphylaxis or an accumulation of effect. We conclude that ZD9583 is a potent, selective, orally active thromboxane synthase inhibitor and TXA2 receptor antagonist.

Effects of atrial natriuretic factor on glucose metabolism in isolated adipocytes

To investigate the role of natriuretic peptide receptors (NPRs) on adipocytes, the effect of atrial natriuretic factor (ANP) on the incorporation of glucose into lipids and CO2 production was studied. Rat adipocytes from the white fat surrounding the mesenteric artery were used. ANP (10(-6) M) significantly increased basal CO2 production (1.36 fold), but had no effect in the presence of insulin. ANP did not modify lipid incorporation. Incubations were carried out with < 4 x 10(5) cells ml-1 as the effects of ANP diminished with higher concentrations. The increase generated by ANP was dose dependent (EC50, 4 x 10(-9) M), and was not reproduced by des [Gln18, Ser19, Gly20, Leu21, Gly22) ANP(4-23) NH2 (c-ANP, 10(-7) M), C-type natriuretic peptide (CNP, 10(-7) M) or 8-bromo-cGMP (10(-3) M). However, co-incubation of c-ANP (10(-7) M) and CNP (10(-7) M) increased CO2 production. In the presence of isoproterenol (10(-6) M), ANP had no effect. Incubation with isobutylmethylxanthine (0.5 x 10(-3) M) significantly decreased basal CO2 production (to 30%), and this was not altered by ANP co-incubation. Thus, ANP appears to act via NPR-A to modulate oxidative glucose metabolism, but not through alteration of cGMP or cAMP production.

Modulation of renal glomerular angiotensin II receptors by ace inhibition and AT1 receptor antagonism

Angiotensin-converting enzyme inhibitors (ACE-I) and specific nonpeptide angiotensin II (ANG II) receptor antagonists have been used extensively to treat a variety of cardiovascular disorders in experimental animals and humans. Despite their widespread use, only a limited amount of data has been published regarding the effect that renin-angiotensin system (RAS) blockade may have on ANG II receptors, and very often this information is contradictory. The present study was designed to investigate whether changes in plasma ANG II levels induced by RAS blockade could alter glomerular ANG II receptor characteristics. Captopril was employed as an ACE-I with losartan and TCV-116, two AT1 receptor antagonists of different chemical structure. Two experimental protocols were established. Protocol 1 contained 3 experimental groups: controls (Sprague-Dawley rats, 250-300 g BW), and animals treated with either captopril (0.5 g/l via drinking water) or losartan (10 mg/kg BW p.o.). In protocol 2, the animals were treated as in protocol 1 except that losartan was replaced by TCV-116 (1 mg/kg BW p.o.). At the end of treatment (3 days), all groups were killed by decapitation, blood was collected for plasma renin activity (PRA) measurement, and hearts and kidneys were excised. ANG II receptors were assessed by radioligand binding assays on membrane preparations of purified glomeruli, by displacement of 125I-[Sar1, Ile8]-ANG II with specific nonpeptide antagonists of AT1 (losartan) and AT2 (PD 123319) receptor subtypes. RAS blockade by either ACE-I or AT1 antagonists increased PRA. The binding assays showed that renal glomeruli from treated rats and controls expressed a single population (AT1) of ANG II receptors. The density of glomerular AT1 receptors was not modulated by captopril, but was significantly lower in animals treated with either losartan (Bmax: 854 +/- 169 vs. 379 +/- 79 fmol/mg protein and Kd: 59 +/- 6 vs. 45 +/- 6 nM for controls and losartan, respectively) or TCV-116 (480 +/- 72 vs. 188 +/- 16 fmol/mg protein and Kd: 45 +/- 9 vs. 37 +/- 18 nM for controls and TCV-116, respectively) than in their controls. No changes in receptor affinity (Kd) were detected. Previous membrane "acid-wash" did not modify the results. We conclude that short-term RAS blockade by AT1 antagonists, but not by ACE-I, induces true downregulation of renal glomerular ANG II receptors. No AT2 receptor subtype was detected.

In vitro study of the potential role of quinupristin/dalfopristin in the treatment of catheter-related staphylococcal infections

The susceptibility of clinical isolates of methicillin-susceptible and -resistant staphylococci from cancer patients with central venous catheter bacteremia to quinupristin/dalfopristin, a semisynthetic streptogramin, was determined in vitro. Susceptibility of these isolates to nine other antistaphylococcal antibiotics was also determined for comparison. A total of 197 staphylococcal strains were tested from 1983 to 1992. Quinupristin/dalfopristin was bactericidal against all isolates, independent of their resistance to methicillin. Its activity was similar to that of vancomycin but superior to that of teicoplanin. Quinupristin/dalfopristin may prove to be an important addition to our armamentarium against catheter-related staphylococcal infections.

L273S missense substitution in human lysosomal acid lipase creates a new N-glycosylation site

Human lysosomal acid lipase (LAL), when expressed in HeLa cells using the Vaccinia T7 expression system, showed four major molecular forms ranging from 42 to 54 kDa. Treatment with endoglycosidase H resulted in a 42 kDa protein, indicating that the molecular weight variations were due to N-glycosylation. A missense substitution, L273S, previously detected in a patient with cholesteryl ester storage disease (CESD), produced catalytically inactive LAL showing a largest molecular mass form of 56 kDa instead of 54 kDa. Analysis of the amino acid sequence in the close proximity of the mutation (NMS- NML) indicated that the L273S mutation creates an additional N-glycosylation consensus (N-X-S/T) in this region. Two site directed mutants disrupting this consensus, QMS and QML, when expressed in HeLa cells, did not show the 56 kDa form but the normal 54 kDa band whereas deglycosylation always resulted in the major 42 kDa form, as observed with normal LAL and the L273S mutant. These data confirmed that an additional N-glycosylation at N271 was responsible for the 56 kDa form of the protein produced from the L273S allele. Furthermore, deglycosylation of normal LAL reduced the acid hydrolase activity towards both tri-oleyl glycerol and cholesteryl oleate by 50%, strongly suggesting that N-linked carbohydrate residues are important for optimal catalytic activity.