A new family of lipolytic plant enzymes with members in rice, arabidopsis and maize

We have noted a striking similarity between the sequences of proteins in a novel family of lipases we recently reported [Upton, C. and Buckley, J. T. (1995) Trends Biol. Sci. 20, 178-9] and more than 120 sequences from the database of Expressed Sequence Tags (dbEST) which correspond to at least 30 unique genes from arabidopsis, rice and maize. A cDNA (Arab-1) corresponding to one of these sequences was isolated, sequenced and translated. There was significant similarity to sequences in the new lipase family over the entire open reading frame of Arab-1 and when expressed in E. coli, the gene product was lipolytic. Arab-1 and genes for some of the other plant proteins appear to be differentially expressed. They may play a role in the regulation of lipid metabolism during plant development.     

Myocardial ischemic tolerance following heat stress is abolished by ATP-sensitive potassium channel blockade

The purpose of this study was to compare the effect, both in vitro and in vivo, of cefepime with those of four other cephalosporins, namely ceftriaxone, cefotaxime, cefuroxime and cephalothin, against penicillin-resistant pneumococci. One hundred pneumococcal strains, 31 penicillin-susceptible, 30 penicillin-intermediate-resistant and 39 penicillin-resistant pneumococci, were used in MIC studies. Time-kill experiments were carried out for four strains. In the mouse peritonitis model, the dose that gave protection to 50% of mice challenged with a lethal dose of pneumococci (ED50) was determined for three pneumococci and five cephalosporins. The MICs of all five cephalosporins and penicillin correlated significantly with each other. In vitro, the most potent cephalosporins against pneumococci were cefotaxime, ceftriaxone and cefepime, followed by cefuroxime and cephalothin. In time-kill experiments, carried out for four pneumococci, no differences were found in the killing effect of these five cephalosporins in relation to MICs. In the mouse peritonitis model, there was no significant correlation between log(MIC) and log(ED50) for the five cephalosporins against three pneumococci (Spearman's rho = 0.39, P = 0.16). However, if the values for cefepime against the three pneumococci were excluded, there was a significant correlation for the remaining four cephalosporins (Spearman's rho = 0.62, P = 0.04). For all three pneumococci, the ED50s of cefepime were lower than expected from the MICs. It was not possible to explain this beneficial difference in the effect of cefepime in terms of in-vitro bactericidal activities, serum protein binding or pharmacodynamic parameters.     

The orphan granzymes of humans and mice

The granzyme/perforin pathway is a central pathway for lymphocyte-mediated killing in both the innate and adaptive immune systems. This pathway is important in a variety of host defenses, including viral clearance and tumor cell killing, and its dysregulation results in several human and rodent diseases. To date, the majority of reports in this field have concentrated on the functions of granzymes A and B. Recent reports, however, suggest that the non-A/non-B 'orphan' granzymes found in both humans and mice are potentially significant. Although the functions of these orphan granzymes have yet to be fully established, initial data suggests their importance in both immune and nonimmune cells.     

Heme oxygenase-2 is a hemoprotein and binds heme through heme regulatory motifs that are not involved in heme catalysis

The heme oxygenase (HO) system degrades heme to biliverdin and CO and releases chelated iron. In the primary sequence of the constitutive form, HO-2, there are three potential heme binding sites: two heme regulatory motifs (HRMs) with the absolutely conserved Cys-Pro pair, and a conserved 24-residue heme catalytic pocket with a histidine residue, His151 in rat HO-2. The visible and pyridine hemochromogen spectra suggest that the Escherichia coli expressed purified HO-2 is a hemoprotein. The absorption spectrum, heme fluorescence quenching, and heme titration analysis of the wild-type protein versus those of purified double cysteine mutant (Cys264/Cys281 --> Ala/Ala) suggest a role of the HRMs in heme binding. While the His151 --> Ala mutation inactivates HO-2, Cys264 --> Ala and Cys281 --> Ala mutations individually or together (HO-2 mut) do not decrease HO activity. Also, Pro265 --> Ala or Pro282 --> Ala mutation does not alter HO-2 activity. Northern blot analysis of ptk cells indicates that HO-2 mRNA is not regulated by heme. The findings, together with other salient features of HO-2 and the ability of heme-protein complexes to generate oxygen radicals, are consistent with HO-2, like five other HRM-containing proteins, having a regulatory function in the cell.     

Low- and high-density lipoproteins as mitogenic factors for vascular smooth muscle cells: individual, additive and synergistic effects

The mitogenic activities of low (LDL)- and high (HDL)-density lipoproteins have been examined in cultures of human vascular smooth muscle cells (VSMC). LDL and HDL3 dose-dependently (EC50 values approximately 50 micrograms/ml) stimulated DNA and protein synthesis ([3H]-thymidine and [3H]-leucine incorporation, respectively) in the absence of exogenously added mitogens. The synthetic responses of VSMC to combinations of LDL and HDL3 were additive, indicating that each lipoprotein mediates discrete effects. LDL or HDL3 promoted VSMC proliferation under strict mitogen-free conditions, but this growth response was not sustained. VSMC exposed to combinations of lipoproteins (either LDL or HDL3) and growth factors (either PDGF-BB, EGF, bFGF or IGF) exhibited synergistic DNA synthesis responses. In the combined presence of PDGF-BB and either LDL or HDL3, VSMC proliferation was sustained. Anionized lipoprotein preparations (oxidized, acetylated, carbamylated or malonimylated) also stimulated DNA and protein synthesis. Since the antioxidant beta-hydroxylated toluene did not block the effect of native LDL on DNA synthesis, and fucoidin, a specific competitor for the 'scavenger' receptor, did not inhibit oxidized LDL-induced DNA synthesis, activation of mitogenic signals by lipoproteins does not depend on lipid peroxidation. Rather, the apparent intrinsic mitogenic potential of lipoproteins may depend upon their direct activation of replication-coupled signal transduction systems.     

Risk of human immunodeficiency virus infection among pregnant crack cocaine users in a rural community

OBJECTIVE: To investigate why women who use crack cocaine are at increased risk of human immunodeficiency virus (HIV) infection. METHODS: One thousand one hundred fifty-two (99.7%) of 1155 consecutive prenatal patients attending a rural public health clinic were interviewed about drug use and sexual practices and tested for HIV infection and other sexually transmitted diseases. RESULTS: Fifty-one (4.7%) of 1096 pregnant women reported ever using crack cocaine, but only five (10%) of the crack cocaine users had ever injected drugs. Eighteen (35%) of the crack users were HIV infected compared with 22 (2%) of the 1045 women who reported never using crack (odds ratio 25, 95% confidence interval 12-52; P < .001). Crack users were more likely to have had a known HIV-infected sex partner, exchanged sex for money or drugs, and tested positive for syphilis than were non-crack users (for each comparison, P < .001). Before using crack, 18% of crack users had exchanged sex for money or drugs and 8% had averaged three or more sex partners per month; in contrast, after beginning to use crack, 76% of crack users exchanged sex for money or drugs and 63% averaged three or more sex partners per month (for both comparisons, P < .001). Crack users who were not HIV infected were more likely to have almost always used condoms and/or had fewer than three sex partners per month than were HIV-infected crack users (P < .01). CONCLUSION: Women who reported using crack cocaine were at an increased risk of HIV infection because crack use was associated with a significant increase in unprotected sexual contact.