Cryptococcus neoformans meningitis in the rat

The primary clinical manifestation of Cryptococcus neoformans infection in humans is meningoencephalitis. To study the defense mechanisms that participate in the host response against C. neoformans infection of the central nervous system (CNS), we have developed a new model of cryptococcal meningitis in rats. Intracisternal inoculation of C. neoformans produced a granulomatous meningitis with minimal brain parenchymal involvement, resembling cryptococcal meningitis in immunocompetent patients. The granulomas were composed of T cells (CD4+ and CD8+) and macrophages (CD11b/c+); a subpopulation of the macrophages expressed inducible nitric oxide synthase (NOS2). In this model, C. neoformans disseminated to systemic organs early in the course of infection and provoked granuloma formation and NOS2 expression. The temporal profile of inflammation indicated that the CNS inflammatory response is delayed relative to that in the lung and the spleen, which suggests that the effective inflammatory response within the CNS may follow activation of T cells in the periphery and their subsequent entry into the CNS. Inflammation in the meninges was associated with signs of subpial and subependymal glial activation, including enhanced expression of CD11b/c and CD4 in microglia and glial fibrillary acidic protein in astrocytes. Neither cells, however, expressed NOS2. Although C. neoformans invasion to the brain parenchyma was rare, soluble polysaccharide was commonly associated with reactive glial cells. Necrosis was not a feature of C. neoformans granulomas, but, instead, inflammatory cells underwent apoptosis in inflamed organs. The current rat intrathecal cryptococcosis model has several unique advantages for the study of human cryptococcal meningoencephalitis that include close resemblance of histopathologic changes to those in humans, easy accessibility to the cerebrospinal fluid compartment, and no requirement of immunosuppressive agents for establishment of infection.

[A case of total cavopulmonary connection with preceding tricuspid valve closure in pulmonary atresia and intact ventricular septum, right ventricular-coronary artery fistulae, and coronary artery stenoses]

More than half of the patients with pulmonary atresia and intact ventricular septum (PA/IVS) are known to complicate right ventricular-coronary artery fistula (fistulae) and particularly those with coronary artery stenoses bear a high mortality rate and remain in a surgical challenge. A 4-year-old girl was first admitted to our hospital at 5 days of age and right ventriculogram revealed markedly hypoplastic tripartite ventricle and multiple fistulae through which both coronary arteries and aortic root were retrogradely opacified. Echocardiographically measured diameter of the tricuspid valve was 5 mm (Z value: 4). She underwent pulmonary valvotomy and central aorto-pulmonary (AP) shunt at 16 days of age. Repeat right ventriculogram at 1.9 years of age disclosed multiple stenoses in left anterior descending coronary artery (LAD) with proximal dilatation and tortuosity. Additional findings of left ventricular dysfunction (LVEF of 61.5%) and depressed ST segment in left precordial leads prompted us to proceed to the second palliation which comprised take-down of central AP shunt, bidirectional cavopulmonary shunt and closure of tricuspid and pulmonary valves. Catheterization at 3.4 years of age disclosed antegradely filled LAD with apparent relief of stenoses and improvement of LVEF to 68.9%. She underwent definitive repair of total cavopulmonary connection at 4.0 years of age and is leading a normal life 2 years after surgery. This experience draws us to conclude that tricuspid valve closure is a meaningful palliative procedure for PA/IVS with fistulae and coronary artery stenoses, provided that proximal segments of both coronary arteries remain intact.

Intramolecular disulfide bonds enhance the antimicrobial and lytic activities of protegrins at physiological sodium chloride concentrations

Protegrins are 2-kDa antimicrobial peptides that contain 16-18 amino acid residues and two intramolecular disulfide bonds. We studied the contribution of these disulfide bonds to the bactericidal activity of protegrins in physiological concentrations of NaCl by comparing protegrin PG-1 with variants that lacked one or both cysteine disulfides. Whereas the bactericidal and liposome-lytic properties of protegrin PG-1 were enhanced by adding 100 mM NaCl to the phosphate-buffered medium, NaCl addition strongly inhibited the effects of its linearized, disulfide-free variant, [A6, A8, A13, A15]protegrin-1. Whereas protegrin PG-1 manifested beta-sheet structure by CD (circular dichroism) and ATR-FTIR (attenuated-total-reflectance-Fourier-transform-infrared) spectroscopy in buffer or membrane-mimetic environments, [A6, A8, A13, A15]protegrin-1 manifested disordered structure in phosphate buffer and alpha-helical characteristics in membrane-mimetic environments. Both single-disulfide protegrin variants, [A8, A13]protegrin-1 and [A6, A15]protegrin-1, assumed beta-sheet conformations with liposomes that simulated bacterial membranes, and both retained substantial bactericidal activity when 100 mM NaCl was present. These findings demonstrate that the intramolecular disulfide bonds of protegrins are required for their antiparallel beta-sheet conformation in membrane-mimetic environments and for their potent antimicrobial activity in media containing NaCl concentrations comparable to those found in serum and extracellular fluids.

Characterization of aggregates of recombinant human factor VIII by size-exclusion chromatography and immunoassay

The presence of aggregates of Factor VIII (FVIII) was assessed for a highly purified form (rFVIII) and for the formulated preparation containing human serum albumin (rFVIIIf). Size-exclusion chromatography (SEC) on Sepharose CL-6B and TSK 4000 matrices under native conditions revealed < 1% aggregates of FVIII in either rFVIII or rFVIIIf, as determined by FVIII immunoassay of chromatographic fractions. No degradation products were observed. The immunoassay was capable of detecting FVIII immunoreactivity to levels of approximately 5 ng/ml. Overlap of FVIII clotting (FVIII:c) and immunoassay (FVIII:cAg) activities was observed for SEC fractions. Heat stressing of rFVIIIf (47.5 degrees C for 24 h) resulted in a quantitative increase in FVIII-positive material in the void volume of a TSK 4000 column, demonstrating that aggregates of FVIII can be produced and detected by this method. We conclude that aggregates of FVIII in rFVIII and rFVIIIf constitute < or = 1% by the method described.

Twenty-year follow-up on the effect of HLA matching on kidney transplant survival and prediction of future twenty-year survival

The difficulty in achieving long-term survival is demonstrated by the fact that an improvement of 30 percentage points in 1-year cadaver donor survival resulted in only a 10-percentage point improvement over 20 years. In early transplants from 1965 to 1974, the 20-year survival rate of HLA identical siblings was 46%, of parental donors 27%, and of cadaver donors 12%. More recent grafts, performed since 1987, had a projected survival of 57% for identical donors, 30% for parental donors, and 18% for cadaver donors. With respect to HLA matching for cadaver donor kidney transplants, a 0 AB-antigen mismatch produced higher graft survival than did mismatched transplants during the 20-year period from 1965 to 1984. After the introduction of HLA Class II typing in 1980 and general improvements in typing for transplants performed after 1987, the 0 ABDR-mismatched grafts have a projected 20-year survival of 40%. The projected survival rates for transplants with one or more mismatches fall progressively to 13% for transplants that have 6 ABDR mismatches. Thus, the success due to HLA matching has improved ever since the introduction of cyclosporine because of the concurrent improvements in tissue typing for Class I and Class II specificities.

Retinoic acid-induced transition from protein kinase C beta to protein kinase C alpha in differentiated F9 cells: correlation with altered regulation of proto-oncogene expression by phorbol esters

Retinoic acid (RA) induced differentiation of F9 embryonal carcinoma cells is accompanied by changes in cellular responsiveness to extracellular signals. These changes include an increase in the AP1 transcription factor that is associated with the expression of differentiation markers (e.g., cytokeratin 18 and plasminogen activator). Since AP1 activity is a target for protein kinase C (PKC)-regulated changes in gene expression, we have examined the effects of RA on the expression and function of the PKC isozymes. F9 stem cells express PKC beta, delta, epsilon, and zeta. RA-induced differentiation to primitive endoderm led to a transition from PKC beta to PKC alpha expression. Additional treatment with dibutyryl cyclic AMP (dbcAMP), required for terminal differentiation into parietal endoderm, further increased PKC alpha expression and total PKC activity. RA and dbcAMP had negligible effects on the expression of PKC delta, epsilon, and zeta. The PKC beta to PKC alpha transition was specific for parietal endoderm; aggregation of RA-treated F9 cells induced visceral endoderm differentiation with elevated expression of PKC beta. The PKC activation with phorbol esters induced the expression of c-fos, c-jun, and junB proto-oncogenes in F9 stem cells. In the presence of either RA or RA and dbcAMP, phorbol ester treatment enhanced the expression of type IV collagen, a parietal endoderm marker. It also increased the expression of c-jun gene but not c-fos. The specific involvement of PKC beta in c-fos induction and PKC alpha in type IV collagen induction was confirmed in each PKC isozyme-transfected F9 cells. Together, our data demonstrate that the RA-induced (and dbcAMP-induced) changes in conventional PKC expression alters gene expression during parietal endoderm formation.

Expression of inducible nitric oxide synthase in rat pulmonary Cryptococcus neoformans granulomas

Rats, like humans, have extremely effective immune mechanisms for controlling pulmonary Cryptococcus neoformans infection. The mechanism(s) responsible for efficient immunity in rat experimental infection is unknown. Recently, induction of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) have been implicated as an important microbicidal mechanism by which activated macrophages effect cytotoxicity against microbes. In this report, we investigated the expression of iNOS in rat pulmonary cryptococcosis. Localization and regulation of NO production was studied by immunohistochemistry for iNOS in conjunction with immunohistochemistry for cell markers, cytokines, and cryptococcal capsular polysaccharide. iNOS immunoreactivity was detected in macrophages, neutrophils, vascular endothelium, and respiratory epithelium. Double-immunolabeling studies revealed that the most prominent iNOS immunoreactivity was localized to epithelioid macrophages (CD11b/c+) within granulomas; CD4+ and CD8+ T cells were numerous around granulomas but did not express iNOS. iNOS immunoreactivity was detected in a selective population of epithelioid macrophages within some granulomas but not others. iNOS- granulomas were identical to iNOS+ granulomas with respect to morphology and immunohistochemical profiles. Macrophage iNOS immunoreactivity was detected 1 week after infection in one out of four rats and was strongly expressed in all rats at 2 weeks (in up to 50 percent of the granulomas) but declined considerably by 25 days. iNOS expression coincided with granuloma formation and preceded a decrease in lung fungal burden, suggesting an anticryptococcal role for NO. By double labeling, cytokines that have been shown to promote (interferon-gamma, granulocyte/macrophage colony-stimulating factor) and inhibit (transforming growth factor-beta) macrophage iNOS expression were detected around iNOS+ granuloma. iNOS immunoreactivity was expressed in selected neutrophils (1 and 2 weeks) and endothelial cells (1 and 2 weeks and 25 days) in the inflamed lung. Airway iNOS immunoreactivity was limited to the luminal border of rare bronchiolar epithelial cells. iNOS immunoreactivity was not detected in uninfected rats. The present study provides the first evidence for association of iNOS expression with protective cellular responses to cryptococcal infection in vivo.

Nesidioblastosis in an adult with hyperinsulinemic hypoglycemia

A 50-year-old Korean man with repeated episodes of temporary loss of consciousness was diagnosed as having hyperinsulinemic hypoglycemia. Under the tentative diagnosis of insulinoma, localization procedures were carried out but no tumor was found. By percutaneous transhepatic portal venous sampling, no definite gradient in insulin concentration was found. During exploratory laparotomy no tumor was palpable in the pancreas, and intraoperative ultrasonography showed low echogenicity in the pancreatic head. Whipple's operation was performed and 70% of the proximal pancreas was removed. Histomorphometric examination of the resected specimen revealed graded hyperplasia of the islet cells. The most profuse hyperplasia was noted in the head with progressive decrease in the degree of hyperplasia to the body and tail. The patient remains euglycemic and tolerates 24 h fasting without any medication until 15 months after operation.

Nutritional modulation of guinea pig skin hyperproliferation by essential fatty acid deficiency is associated with selective down regulation of protein kinase C-beta

In a previous study we demonstrated that 13-hydroxyoctadecadienoic acid (13-HODE), a 15-lipoxygenase metabolite of linoleic acid is incorporated into epidermal phosphatidyl 4,5-bisphosphate (PtdIns 4,5-P2) and released as 13-HODE-containing-diacylglycerol (13-HODE-DAG). In vitro, 13-HODE-DAG was shown to selectively inhibit epidermal total protein kinase C (PKC-beta) activity. To determine whether these observations are relevant in vivo, guinea pigs were made essential fatty acid deficient (EFAD) by feeding them a basal diet supplemented with 4% hydrogenated coconut oil for 8 wk. Tissue levels of putative 13-HODE-DAG, protein kinase C (PKC) isozymes and tissue hyperproliferation were determined in the epidermal preparations from skin of control safflower oil-fed guinea pigs, those fed EFAD diet and those fed EFAD diet followed by the control diet for 2 wk. Our data revealed that cutaneous 13-HODE and 13-HODE-DAG were significantly lower in EFAD animals than in safflower-fed controls. These reductions were associated with both elevated epidermal hyperproliferation and elevated expressions and activities of PKC-alpha and beta-isozymes. Refeeding the animals with safflower oil for 2 wk replenished tissue levels of 13-HODE-DAG, which inversely correlated with the selective down regulation of PKC-beta expression and activity and the reversal of hyperproliferation. In contrast, although, the expression and activity of PKC-alpha was elevated in the epidermis of the EFAD guinea pigs, this elevated PKC-alpha expression was not down regulated after refeeding the safflower oil diet to the animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Probing the roles of active site residues in D-xylose isomerase

The roles of active site residues His54, Phe94, Lys183, and His220 in the Streptomyces rubiginosus D-xylose isomerase were probed by site-directed mutagenesis. The kinetic properties and crystal structures of the mutant enzymes were characterized. The pH dependence of diethylpyrocarbonate modification of His54 suggests that His54 does not catalyze ring-opening as a general acid. His54 appears to be involved in anomeric selection and stabilization of the acyclic transition state by hydrogen bonding. Phe94 stabilizes the acyclic-extended transition state directly by hydrophobic interactions and/or indirectly by interactions with Trp137 and Phe26. Lys183 and His220 mutants have little or no activity and the structures of these mutants with D-xylose reveal cyclic alpha-D-xylopyranose. Lys183 functions structurally by maintaining the position of Pro187 and Glu186 and catalytically by interacting with acyclic-extended sugars. His220 provides structure for the M2-metal binding site with properties which are necessary for extension and isomerization of the substrate. A second M2 metal binding site (M2') is observed at a relatively lower occupancy when substrate is added consistent with the hypothesis that the metal moves as the hydride is shifted on the extended substrate.

Extraction of quasi-straightforward-propagating photons from diffused light transmitting through a scattering medium by polarization modulation

The utilization of light polarization is proposed to extract quasi-straightforward-propagating photons from diffused light transmitting through a scattering medium under continuously operating conditions. Removal of a floor level normally appearing on the dynamic range over which the extraction capability is maintained is demonstrated. By use of pulse-based observations this cw scheme of extraction of quasi-straightforwardpropagating photons is directly shown to be equivalent to the use of a temporal gate in the pulse-based operation.

Properties of acetylcholinesterase reconstituted in liposomes of a different charge

Acetylcholinesterase (AChE) purified from mouse brain was reconstituted in liposomes of a different charge, and the properties of liposome-associated AChE were investigated. Relative to the Km value (38.5 microM) of AChE bound to a neutral liposome, the value of AChE reconstituted in a negatively-charged liposome decreased to 23.3 microM, whereas that of AChE in a positively-charged liposome increased to 90.9 microM. Additionally, AChE bound to a positively-charged liposome expressed a wider range of optimum pH than the enzyme in a negatively-charged liposome. In a stability study, it was found that soluble AChE was unstable at pH 5.5 and 7.4, while it was relatively stable at pH 10. Noteworthy, the immobilization of AChE to liposome enhanced the stability of soluble enzyme at acidic and neutral pH. Moreover, in the stabilization of the enzyme, a neutral liposome was more effective than charged liposomes, of which a positively-charged liposome was more effective than a negatively-charged liposome at acidic pH. Based on these results, it is proposed that while the Km value and the pH dependence of AChE activity are affected by the charge of liposome, the stability of AChE is determined mainly by a hydrophobic binding to a phospholipid membrane.

Identification of CG-1, a natural peptide antibiotic derived from human neutrophil cathepsin G

Cathepsin G is a neutral serine protease of the granzyme B family which is found in human PMN, cells known to be important in the defense of the periodontium against periodontal bacteria. We propose that cathepsin G serves as a "pro-antibiotic" containing peptide domains which express selective antibiotic properties. In this study, we used HPLC to separate the low-molecular-weight peptides derived from the ultrafiltrate of a granule extract from unstimulated PMN. One of the peptides exhibited intense bactericidal activity as determined by radial diffusion overlay assay (against Escherichia coli ML-35P), an amino-terminal sequence "RVSSFLPWIR...", and a 3.1-kDa molecular mass determined by electrospray ionization-mass spectrometry. The sequence and mass are consistent with the C-terminus of cathepsin G deduced by cDNA analysis. These findings support the hypothesis that antibiotic peptides derived from cathepsin G occur naturally in human PMN. Since this is the first naturally occurring antibiotic peptide derived from cathepsin G, we designate it "CG-1".

Bactericidal properties of murine intestinal phospholipase A2

We purified a molecule from the murine small intestine that killed both Escherichia coli and Listeria monocytogenes, and identified it as intestinal phospholipase A2 (iPLA2) by NH2-terminal sequencing and enzymatic measurements. The ability of iPLA2 to kill. L. monocytogenes was greatly enhanced by 5 mM calcium, inhibited by EGTA and abolished after reduction and alkylation, suggesting that enzymatic activity was required for iPLA2-mediated bactericidal activity. A mouse-avirulent phoP mutant, S. typhimurium 7953S, was 3.5-fold more susceptible to iPLA2 than its isogenic virulent parent, S. typhimurium 14028S (estimated minimal bactericidal concentrations 12.7 +/- 0.5 micrograms/ml vs. 43.9 +/- 4.5 micrograms/ml P < 0.001). Overall, these findings identify iPLA2 as part of the antimicrobial arsenal that equips Paneth cells to protect the small intestinal crypts from microbial invasion. Because iPLA2 is identical to Type 2 phospholipase A2 molecules found in other sites, including spleen, platelets and inflammatory exudate cells, this enzyme may also contribute to antibacterial defenses elsewhere in the body.

[A case of successful surgical treatment for coarctation of the aorta associated with ruptured cerebral aneurysm]

We present a case of a sixteen year old boy with coarctation of the aorta who suffered ruptured cerebral aneurysm. Both cerebral and aortic lesions were successfully corrected. He complained of sudden headache and nausea. Subarachnoid hemorrhage was diagnosed by computed tomography of the head. Cerebroangiography demonstrated coarctation of the aorta. Clipping of cerebral aneurysm was done at first, then three months later, complete resection of the aortic coarctation and artificial graft replacement was done by using femoral veno-arterial cardiopulmonary bypass.

[The surgical treatment of coarctation of the aorta and interruption of the aortic arch in the first three months of life--effectiveness of temporary bypass between the pulmonary artery and the descending aorta]

From February 1987 to January 1994, we operated on 24 patients with coarctation of the aorta (CoA) and 9 patients with interruption of the aortic arch (IAA). A policy of staged repair was followed, consisting of reconstruction of the aortic arch with pulmonary artery banding and ligation of the ductus arteriosus in the first stage and intracardiac repair with pulmonary artery band removal in the second stage. In recent cases an extended aortic arch anastomosis was performed using a heparin-coated "shunt tube" between the pulmonary artery and the descending aorta to maintain blood flow to the lower half of the body during aortic cross-clamping. The use of the shunt increased intraoperative urine output (p < 0.05). This technique may allow patients whose condition is poor to undergo aortoplasty more safely. One patient died. This patient had CoA and total anomalous pulmonary venous return, who underwent a one-stage repair, in violation of our policy (early mortality 3.0%). There were two interim deaths before the second stage repair. At present, 18 patients have undergone staged intracardiac repair, including VSD closure (14 cases), Jatene's procedure (1), Ratelli's procedure (1), Damus-Kaye-Stansel (DKS) procedure (1), total cavo-pulmonary connection (TCPC) + DKS procedure+annuloplasty of a common atrioventricular valve (1). There were two early deaths and one late death following intracardiac repair, all in patients with IAA plus VSD.

Improved expression for the time-bandwidth product of picosecond optical pulses from gain-switched semiconductor lasers

An improved expression for the time-bandwidth product (DeltatDeltaf) of picosecond optical pulses from gain-switched semiconductor lasers was obtained by a series of numerical simulations based on rate equations without making any assumption for a particular pulse shape and chirp condition. The relation can be expressed by [Equation] as a function of the linewidth-enhancement factor alpha. The influence of the spontaneous emission factor beta on the relation is also examined.

Crystal structure of a p53 tumor suppressor-DNA complex: understanding tumorigenic mutations

Mutations in the p53 tumor suppressor are the most frequently observed genetic alterations in human cancer. The majority of the mutations occur in the core domain which contains the sequence-specific DNA binding activity of the p53 protein (residues 102-292), and they result in loss of DNA binding. The crystal structure of a complex containing the core domain of human p53 and a DNA binding site has been determined at 2.2 angstroms resolution and refined to a crystallographic R factor of 20.5 percent. The core domain structure consists of a beta sandwich that serves as a scaffold for two large loops and a loop-sheet-helix motif. The two loops, which are held together in part by a tetrahedrally coordinated zinc atom, and the loop-sheet-helix motif form the DNA binding surface of p53. Residues from the loop-sheet-helix motif interact in the major groove of the DNA, while an arginine from one of the two large loops interacts in the minor groove. The loops and the loop-sheet-helix motif consist of the conserved regions of the core domain and contain the majority of the p53 mutations identified in tumors. The structure supports the hypothesis that DNA binding is critical for the biological activity of p53, and provides a framework for understanding how mutations inactivate it.

Differential inhibition of soluble and membrane-bound acetylcholinesterase forms from mouse brain by choline esters with an acyl moiety of an intermediate size

Differential inhibitions of soluble and membrane-bound acetylcholinesterase forms purified from mouse brain were examined by the comparison of kinetic constants such as a Km value, a Kss value (substrate inhibition constant), and IC50 values of active site-selective ligands including choline esters. Membrane-bound acetylcholinesterase form (solubilized only in the presence of detergent) showed lower Km and Kss values than soluble acetylcholinesterase form (easily solubilized without detergent). Edrophonium expressed a slightly but significantly (p < 0.01) higher inhibition of detergent-soluble acetylcholinesterase form than aqueous-soluble acetylcholinesterase form, while physostigmine inhibited both forms with a similar potency. A remarkable difference in inhibition was observed using choline esters; although choline esters with acyl chain of a short size (acetyl- to butyrylcholine) or a long size (heptanoyl- to decanoylcholine) showed a similar inhibitory potency for two forms of acetylcholinesterase, pentanoylcholine and hexanoylcholine inhibited more strongly aqueous-soluble acetylcholinesterase than detergent-soluble acetylcholinesterase. Thus, it is suggested that the two forms of AChE may be distinguished kinetically by pentanoyl- or hexanoylcholine.

13-Hydroxyoctadecadienoic acid reverses epidermal hyperproliferation via selective inhibition of protein kinase C-beta activity

13-Hydroxyoctadecadienoic acid (13-HODE) is a major lipoxygenase metabolite of linoleic acid in epidermis. Employing a docosahexaenoic acid (22:6n-3) induced model of hyperproliferative guinea pig epidermis, we demonstrated reversal of hyperproliferation by topical 13-HODE. To delineate a possible mechanism for 13-HODE effect, we demonstrated that topical 13-HODE was incorporated into 13-HODE-containing diacylglycerol (13HODE-DAG). This novel substituted-DAG which was markedly depleted in the hyperproliferative skin paralleled the increased activities of PKC-alpha and beta. Replenishment of the hyperproliferative epidermis with topical 13-HODE resulted in the accumulation of tissue 13HODE-DAG and the selective suppression of PKC-beta activity. These data taken together suggest that the generation of putative 13-HODE-DAG and the selective suppression of PKC-beta isozyme activity may play a role in modulating epidermal hyperproliferation.

Expression of protein kinase C isozymes in guinea pig epidermis: selective inhibition of PKC-beta activity by 13-hydroxyoctadecadienoic acid-containing diacylglycerol

Prompted by the reversal of skin hyperproliferation to normal by 13-hydroxyoctadecadienoic acid (13-HODE), a 15-lipoxygenase metabolite of linoleic acid, we investigated a possible mechanism for this antiproliferative action. To address this we first demonstrated that 13-HODE is incorporated into epidermal phosphatidyl 4,5-bisphosphate (PtdIns4,5-P2) and released as 13-HODE-containing diacylglycerol by epidermal phospholipase C. Secondly, we tested the possibility whether this putative 13-HODE-containing DAG (13HODE-DAG) could exert a modulatory effect on epidermal protein kinase C (PKC) activity which previously has been associated with skin hyperproliferation. Unlabeled 13HODE-DAG was generated from 13-HODE-containing phosphatidylcholine after phospholipase C hydrolytic cleavage. The effects of the 13HODE-DAG were determined on: i) total epidermal PKC activity; ii) diolein-activated PKC activity; and iii) the two identified epidermal PKC-isozymes (PKC-beta and PKC-alpha). Our data revealed over a twofold activation of total basal PKC activity by diolein. In contrast, replacement of diolein (1,2-dioleoylglycerol) with 13HODE-DAG (1-palmitoyl,2-13HODE-glycerol) in the incubation mixture exerted no effect on total basal PKC activity. In an another experiment, 13HODE-DAG inhibited diolein-activated PKC activity in a dose-dependent manner. To determine whether the effects of 13HODE-DAG are selective, we tested its effects on DEAE-Sephacel-purified and Western blot-confirmed PKC isozymes. Our data revealed that 13HODE-DAG selectively inhibited the activity of PKC-beta isozyme, while exerting negligible effect on the PKC-alpha isozyme. This selective inhibitory effect of 13HODE-DAG on a major epidermal PKC isozyme activity suggests that 13HODE-containing DAG seemingly can modulate epidermal PKC activity, which purportedly is associated with epidermal hyperproliferation.

Probing the retinol-binding site of bovine beta-lactoglobulin

The retinol-binding site of beta-lactoglobulin has been located by selective modification of amino acid residues which reside in the two putative binding sites. Based upon two separate crystallographic analyses of bovine beta-lactoglobulin, different binding sites for retinol have been proposed: one proposal favors an interior cavity, the other a surface cleft. To discriminate between these two models, we have made four separate site-directed mutations introducing a W19A or a K70M in the interior pocket and a F136A or K141M in the surface pocket. The K70M beta-lactoglobulin exhibited a marked decrease in its binding of retinoic acid compared to the F136A, K141M, and wild-type proteins. Retinyldenepropylamine, a retinyl Schiff base analog of retinol, was synthesized and its absorption spectrum when bound to the wild-type, K70M, and K141M proteins was examined to probe its interaction with the respective lysine residues. The retinylidenepropylamine bound in the K70M beta-lactoglobulin exhibited a kinetic red shift as distinct from the blue shift observed when it is bound to either the K141M or wild-type beta-lactoglobulins. The blue shift indicates protonation of the Schiff base. The resulting tagged peptide was isolated after cyanogen bromide cleavage and found to be the Ala25-Met107 peptide, consistent with the Lys70 being the residue which interacts with the bound retinol. These results support the proposal that retinol binds to an evolutionarily conserved interior cavity rather than the surface pocket.

Thermostable variants of bovine beta-lactoglobulin

The thermal stability of bovine beta-lactoglobulin (BLG) has been enhanced by the introduction of an additional disulfide bond. Wild-type BLG has two disulfide bonds, C106-C119 and C66-C160, with a free cysteine at position 121. We have designed, with the aid of molecular modeling calculations, two mutants of a recombinant BLG (rBLG), L104C and A132C. Molecular dynamics simulations were performed at 300K to study the effect of these alterations on the conformation of the protein. These mutants were then created by site-directed mutagenesis and purified from Escherichia coli carrying a tac expression vector using a two-step renaturation method. Formation of disulfide linkages in the correct arrangement, as designed, was confirmed by peptide mapping. In contrast to wild-type rBLG, which polymerizes at temperatures > 65 degrees C, neither of the mutant proteins polymerized. The conformational stability of the L104C and A132C mutant proteins against thermal denaturation has been substantially increased (8-10 degrees C) as compared with wild-type rBLG. Furthermore, the A132C rBLG exhibits an enhanced stability against denaturation by guanidine hydrochloride as compared with the wild-type or L104C rBLG.

Incorporation of 13-hydroxyoctadecadienoic acid (13-HODE) into epidermal ceramides and phospholipids: phospholipase C-catalyzed release of novel 13-HODE-containing diacylglycerol

Ceramides and phospholipids constitute two important structural lipids of normal skin that are notably rich in polyunsaturated fatty acids. Although linoleic acid (LA) is high in the ceramides, the localization of its 15-lipoxygenase product, 13-hydroxyoctadecadienoic acid (13-HODE) in the epidermis is unknown. In this study, we investigated the relative incorporation of [14C]LA and [14C]13-HODE into ceramides and phospholipids in isolated epidermal slices. Our data revealed minor incorporation of [14C]LA and [14C]13-HODE into ceramides. In contrast, both [14C]LA and [14C]13-HODE are markedly incorporated into phospholipids, particularly, phosphatidylcholine (PC) and phosphatidylinositol (PtdIns). The incorporation of 13-HODE into the PtdIns pool in particular prompted us to investigate into its fate in the signal transduction process and its possible incorporation into diacylglycerol. Our data revealed that 13-HODE is incorporated into epidermal phosphatidylinositol 4,5-bisphosphate (PtdIns4,5-P2) resulting in epidermal phospholipase C-catalyzed release into a novel 13-HODE-containing diacylglycerol (1-acyl-2-13-HODE-glycerol). The possibility now exists that this novel 13-HODE-containing diacylglycerol could function to modulate the activity of epidermal protein kinase C and hyperproliferation/differentiation.

Perturbing the metal site in D-xylose isomerase. Effect of mutations of His-220 on enzyme stability

The histidine residue at position 220 in the Streptomyces rubiginosus D-xylose isomerase is conserved in all D-xylose isomerases. The three-dimensional structure of D-xylose isomerase reveals that His-220 is part of the octahedral coordination sphere of M2, one of two metal ions (Mn2+) in the active site. This work describes the effects of replacing His-220 with Ser, Glu, Asn, and Lys. The consequences of these amino acid substitutions on enzyme activity, thermostability, and structure were analyzed by kinetic, denaturation, and crystallographic methods. The kcat values H220S, H220N, and H220E are only 0.3-0.5% of the wild-type values, and the Km for each of these mutant enzymes increased by 30-40-fold over the wild-type value. The mutant enzyme H220K did not exhibit any measurable activity. Thermal denaturation studies (Tm values) indicate that the H220S and H220N mutant enzymes are approximately 5-8 degrees C less stable than the wild-type enzyme, whereas H220E and H220K are 13-24 degrees C less stable than the wild-type enzyme. To analyze the molecular basis for this decreased thermostability, the crystal structures of the H220S, H220N, and H220E mutant enzymes complexed with Mn2+ have been determined at 1.95, 1.90, and 1.75 A, respectively. In the H220S structure, a water molecule effectively replaces the N epsilon-2 atom of the imidazole ring of His-220 and mediates the interaction between Mn2+ at the M2 site and Ser-220. A similar water-mediated interaction between the metal ion and Asn-220 is observed in H220N. No direct or water-mediated interactions between the carboxyl group of Glu-220 and the metal are observed in H220E. Whereas octahedral coordination is maintained for the metal at the M2 site in H220S and H220N, a pentahedral coordination with the metal at the M2 site is observed in H220E. Metal activation measurements support the observation that metal binding is perturbed and is responsible for thermal lability of His-220 mutants.

Crystal structure of adenylosuccinate synthetase from Escherichia coli. Evidence for convergent evolution of GTP-binding domains

The structure of the P2(1) crystal form of adenylosuccinate synthetase from Escherichia coli has been determined to a resolution of 2.8 A. The refined model for the enzyme gives an R factor of 0.20 and a root-mean-square deviation from expected bond lengths and angles of 0.016 A and 2.27 degrees, respectively. The dominant structural element of each monomer of the homodimer is a central beta-sheet of 10 strands. The first nine strands of the sheet are mutually parallel with right-handed crossover connections between the strands. The 10th strand is antiparallel with respect to the first nine strands. In addition, the enzyme has two antiparallel beta-sheets, comprised of two strands and three strands each, 11 alpha-helices and two short 3/10-helices. The overall fold of the polypeptide chain has not been observed heretofore in any other protein structure. Residues tentatively assigned to the active site of the enzyme on the basis of chemical modification and directed mutation cluster in two separate regions. Gly12, Gly15, Gly17, Lys18, Ile19, and Lys331 lie at one end of a crevice that measures 12 A by 30 A by 12 A deep. Lys140 and Arg147 are not part of this crevice, but instead lie at the interface between monomers of the dimer. Lys140 makes a salt link with Asp231 of a monomer related by molecular symmetry and Arg147 binds to the carbonyl of the same Asp231. Superposition of the p21 ras protein (Pai, E. F., Kabsch, W., Krengel, U., Holmes, K., John, J., and Wittinghofer, A. (1989) Nature 341, 209-214) onto the synthetase reveals significant correspondences between side chains of the two proteins. Residues which interact with GTP in the p21ras protein have structurally equivalent residues in the synthetase. The GTP molecule, when transformed to the coordinate frame of the synthetase, falls into the crevice defined by studies in directed mutation. We suggest that the similarities in the GTP-binding domains of the synthetase and the p21ras protein are an example of convergent evolution of two distinct families of GTP-binding proteins.

2D 1H and 31P NMR spectra and distorted A-DNA-like duplex structure of a phosphorodithioate oligonucleotide

Assignment of the 1H and 31P NMR spectra of a phosphorodithioate modified oligonucleotide decamer duplex, d(CGCTTpS2-AAGCG)2 (10-mer-S; a site of dithioate substitution is designated with the symbols pS2-), was achieved by two-dimensional homonuclear TOCSY, NOESY and 1H-31P Pure Absorption phase Constant time (PAC) heteronuclear correlation spectroscopy. In contrast to the parent palindromic decamer sequence (1) which has been shown to exist entirely in the duplex B-DNA conformation under comparable conditions (100 mM KCl), the dithiophosphate analogue forms a hairpin loop. However, the duplex form of the dithioate oligonucleotide can be stabilized at lower temperatures, higher salt and strand concentration. The solution structure of the decamer duplex was calculated by an iterative hybrid relaxation matrix method (MORASS) combined with 2D NOESY-distance restrained molecular dynamics. These backbone modified compounds, potentially attractive antisense oligonucleotide agents, are often assumed to possess similar structure as the parent nucleic acid complex. Importantly, the refined structure of the phosphorodithioate duplex shows a significant deviation from the parent unmodified, phosphoryl duplex. An overall bend and unwinding in the phosphorodithioate duplex is observed. The structural distortion of the phosphorodithioate duplex was confirmed by comparison of helicoidal parameters and groove dimensions. Especially, the helical twists of the phosphorodithioate decamer deviate significantly from the parent phosphoryl decamer. The minor groove width of phosphorodithioate duplex 10-mer-S varies between 8.4 and 13.3 A which is much wider than those of the parent phosphoryl decamer d(CGCTTAAGCG)2 (4.2 approximately 9.4 A). The larger minor groove width of 10-mer-S duplex contributes to the unwinding of the backbone and indicates that the duplex has an overall A-DNA-like conformation in the region surrounding the dithiophosphate modification.

The progression of retinopathy of prematurity and fluctuation in blood gas tension

In this study, the relationship between the fluctuation in blood oxygen and carbon dioxide tension and the progression of acute retinopathy of prematurity (ROP) was evaluated. Eighteen extremely premature infants were selected on the basis of the following criteria: gestational age less than 26 weeks, oxygen supply or mechanical ventilation for more than 50 days, transcutaneous oxygen pressure (TcPO2) recorded almost once per hour, and arterial oxygen pressure (PaO2) and arterial carbon dioxide pressure (PaCO2) measured intermittently, for over 8 weeks after birth. All of these infants developed ROP, which ceased progressing in 7 infants (group I, stage 1 or 2 ROP, international classification), but advanced in 11 (group II, stage 3 or 3+). The fluctuations in TcPO2, PaO2, and PaCO2 are represented as coefficients of both variation (CV) and mean difference (D) in these two groups. The results demonstrate that both the CV and D values of TcPO2 are significantly elevated in group II infants compared with group I infants, in the first and second 3-weeks periods, and over the entire 9-week period after birth. The incidences of extreme hyperoxemia (TcPO2 > or = 100 mm Hg) and hypoxemia (TcPO2 < 30 mm Hg) in recorded TcPO2 time series show no significant differences between these two groups. We conclude that extremely premature infants with widely fluctuating arterial oxygen tension may have a greater chance of developing progressive ROP.

Vasovasostomy in rabbits using fibrin adhesive prepared from a single human source

We were interested in determining whether fibrin glue derived from a single human source could be used effectively to produce a sutureless vasovasostomy in the rabbit model. Fifteen rabbits were divided into two groups (7 control, 8 experimental) and underwent vasal transection and reanastomosis by conventional microsurgical suture techniques (control group) and sutureless anastomosis using single source fibrin glue (experimental group). The patency and tensile strength of the anastomoses were compared at four weeks and the anastomotic sites underwent histologic examination. This study demonstrated that a vasovasal anastomosis in the rabbit could be achieved using human single source fibrin glue with patency equivalent to a standard sutured anastomosis. The tensile strength of the glued anastomosis at four weeks was greater than the tensile strength of the sutured anastomosis.

A report from the UNOS Scientific Renal Transplant Registry

The UNOS Kidney Transplant Registry is now fully operational. Aside from scientific reports from UCLA, analysis of the same data base from investigators who initiate projects through UNOS central in Richmond, as well as from HICFA and USRDS, can be anticipated. Plans are underway to simplify the reporting process. With the large number of accumulated cases, it should be possible to analyze many factors in the future. Presently, histocompatibility differences in living related vs cadaver donors and degrees of HLA mismatching among recipients of cadaveric kidneys are major factors. Immunization by transplant rejection is the second most important factor.

Uptake of glutamate and cysteine in C-6 glioma cells and in cultured astrocytes

The uptake of glutamate in rat glioma C-6 cells and cultured astrocytes derived from rat cerebral hemispheres was found to be mediated by a Na(+)-dependent and a Na(+)-independent system. The Na(+)-dependent system was inhibited by aspartate and was consistent with the commonly occurring system designated system X-AG. The Na(+)-independent system was inhibited by cystine and was consistent with system x-c described in various types of cells in the periphery. It was also found that quisqualate selectively and competitively interfered with the Na(+)-independent glutamate uptake. In C-6 cells, the glutamate uptake via systems X-AG and x-c accounted for approximately 35% and 55% of the total uptake, respectively, at 0.05 mM glutamate. In cultured astrocytes, the glutamate uptake via system X-AG was very potent, whereas the uptake via system xc- was relatively weak and its contribution to the total uptake of glutamate seemed almost negligible. However, in both C-6 cells and astrocytes, system xc- was necessary for the uptake of cystine, another substrate of system xc-. Cystine in the culture medium was an essential precursor of glutathione, and the inhibition of the cystine uptake by excess glutamate as a competitor led to a severe deficiency in glutathione, followed by cell degeneration.

Endothelial attachment and plasmalemmal apposition in the transcellular movement of intravascular leukemic cells entering the myeloid parenchyma

The plasmalemmal relationship between metastases-forming leukemia cells and myeloid sinus endothelium during the transmural passage of the leukemia cells has been studied in rat bone marrow. After the myeloid vascular system was freed from normal circulating blood cells, the bone marrow was perfused with a suspension of leukemia cells derived from an ascites tumor. The bone marrow was then fixed by perfusion with double aldehyde with and without the addition of tannic acid. Leukemia cells were seen adhering to the adluminal aspect of the sinus endothelium and in all stages of endothelial penetration. The penetration of the sinus wall was independent of endothelial junctions; i.e., the transmural passage into the myeloid parenchyma was transcellular. At these sites, there were restricted areas of close plasmalemmal appositions of the two cell types where the intraplasmalemmal space was reduced to 2.3 nm. This space was interrupted by electron densities of 5 nm diameter and spaced 9 nm center to center. These close plasmalemmal appositions extended over distances ranging from 150 nm to 200 nm. It is suggested on the basis of the structural similarity that these heptalaminar complexes of close plasmalemmal apposition represent the structural equivalent of gap junctions and may be sites of intercellular communication requisite for transmural passage. When tannic acid was added to the fixative, there were extended areas of apparent fusion of the plasmalemmas of the two cell types, at the sites both of adhesion and of endothelial penetration. This fusion was limited to the outer leaflets of the two plasmalemmas, resulting in a single pentalaminar complex. These pentalaminar complexes extended over decidedly longer distances than the presumed gap junctions seen in the nontannic-acid-fixed material. The tannic acid material did not show the heptalaminar gap junction type of plasmalemmal apposition. It is believed likely that the tannic-acid-induced pentalaminar complexes may incorporate the smaller heptalaminar ones. The factors underlying the plasmalemmal configurational differences between the tannic acid and non-tannic-acid material remain undetermined.

Kinetic analysis of new formation, internalization, and turnover of bristle coated pits of the myeloid sinuses

The rate of new formation of bristle coated pits (BCP) of the myeloid sinuses, their internalization, and turnover was determined by labeling of BCP with bovine albumin adsorbed to colloidal gold (Au) at low temperatures (0 degrees C to 4 degrees C), followed by endothelial activation with balanced saline at 38 degrees C to 40 degrees C for graded periods of time. New formation of BCP was practically instantaneous, occurring within 28 seconds, a time span which includes the in situ assembly of the coating protein clathrin as well as of the material effecting the binding of the ligand. Almost the entire population of BCP was turned over in 6 minutes, a time period which encompasses the initial formation of the plasmalemmal bristle coated binding site to the internalization of BCP. The number of BCP varied within a narrow range indicating a substantial degree of physiological constancy resulting from a quantitative parallelism between internalization and new formation of bristle coated binding sites. The number of BCP is markedly reduced in the prolonged (greater than 12 minutes) absence of endocytosable material. The reduction in the number of BCP is reversible. The binding to BCP at low temperatures (0 degrees C to 4 degrees C) of a series of proteinaceous substances adsorbed to Au was examined for the following Au complexes: bovine albumin/Au, rat albumin/Au, IgG/Au, orosomucoid/Au, ovalbumin/Au, fetuin/Au, transferrin/Au, insulin/Au, low density lipoprotein/Au, alpha 2 macroglobulin/Au, and Au stabilized by polyethylene glycol. All these Au complexes bound to BCP although there were differences in the degree of affinity as judged by the number of BCP labeled and by the number of Au/complex particles present in the labeled BCP. Au stabilized by polyethylene glycol did not bind to BCP. Under the condition of these experiments, bovine albumin/Au had the highest degree of affinity for BCP and was therefore selected for the kinetic studies.

Internal structure of the postcapillary high-endothelial venules of rodent lymph nodes and Peyer's patches and the transendothelial lymphocyte passage

Scanning electron microscopy (SEM) shows that the postcapillary high-endothelial venules of lymph nodes and Peyer's patches consist of two segments each with a different surface relief: a proximal segment with a cobblestone surface pattern and a distal segment of interlacing cytoplasmic plates. Both segments have deep adluminal crevices in which lymphocytes are lodged. The internal structural configuration of this endothelium has been examined by transmission electron microscopy (TEM) of serial sections of lymph nodes and Peyer's patches of mice, rats, and guinea pigs. The serial sections revealed that the endothelial cell bodies and their cytoplasmic extensions were disposed in a direction generally lateral to the luminal surface and intruded into the intercellular spaces of similarly disposed neighboring endothelial cells, resulting in a complex interlacing cellular pattern. Lymphocytes penetrated the endothelial cell body and secondarily followed an intracellular pathway through which they entered the extravascular compartment. At the exposed surfaces of the adluminal venule wall, recirculating lymphocytes were seen in SEM images to enter the endothelium by penetrating the endothelial cell body. The mode of migration of lymphocytes lodged in the endothelial crevices could be determined by SEM and has been examined by TEM of serial sections. At these locations as at the exposed surfaces, lymphocytes also entered the venule by penetrating the endothelial cell body. At both sites this transcellular pathway was followed by lymphocyte entry into the intercellular spaces from which they migrated into the extravascular compartment.

In vivo exocytosis of lysosomes by the endothelium of the venous sinuses of bone marrow and liver: visualization at normal and low body temperature

We have visualized the exocytosis of lysosomes into the peripheral circulation by the phagocytic endothelia of the venous sinuses of liver and bone marrow of rats. Perfusion fixation at normal body temperature produced images of the earliest stages of lysosomal exocytosis. After fixation at low body temperatures (7-12 degrees C), advanced stages of this process became evident, showing extrusion of lysosomes and their contents into the circulation. It is postulated that this form of exocytosis has escaped structural detection because of its rapidity and relative infrequency as compared to merocrine secretory exocytosis, and that fixation at low body temperatures arrests or slows down these exocytic events in sufficient measure for ultrastructural visualization. The possibility that this lysosomal exocytosis contributes to the presence of lysosomal enzymes detected in the peripheral blood should be considered. In addition, it is likely that lysosomal degradation products may be discharged by exocytosis into the circulation.

Acid-labile interferon produced in human peripheral leukocytes by induction with Sendai virus

An acid-labile interferon-alpha (IFN-alpha) exists in IFN produced in human peripheral leukocytes with Sendai virus. This activity was found in fractions of molecular weights about 100 000 (100K), 58K and 44K. The IFN activity in the 100K fraction was neutralized with anti-HuIFN-alpha serum alone, but activity in the 58K and 44K fractions was neutralized only by a mixture of anti-HuIFN-alpha and anti-HuIFN-beta sera.