Syncytium-inducing mutations localize to two discrete regions within the cytoplasmic domain of herpes simplex virus type 1 glycoprotein B

Herpes simplex virus type 1 glycoprotein B (gB) is essential for virus entry, an event involving fusion of the virus envelope with the cell surface membrane, and virus-induced cell-cell fusion, resulting in polykaryocyte, or syncytium, formation. The experiments described in this report employed a random mutagenesis strategy to develop a more complete genetic map of mutations resulting in the syn mutant phenotype. The results indicate that syn mutations occur within two essential and highly conserved hydrophilic, alpha-helical regions of the gB cytoplasmic domain. Region I is immediately proximal to the transmembrane domain and includes residues R796 to E816/817. Region II is localized centrally in the cytoplasmic domain and includes residues A855 and R858. Positively charged residues were particularly affected in both regions, suggesting that charge interactions may be required to suppress the syn mutant phenotype. No syn mutations were identified within the transmembrane domain. A virus containing a rate of entry (roe) mutation at residue A851, either within or immediately proximal to syn region II, was isolated. Since roe mutations have also been discovered in the external domain of gB, it appears likely that the external and cytoplasmic domains cooperate in virus penetration. Moreover, the observation that both roe and syn mutations occur in the cytoplasmic domain further suggests that gB functions in an analogous manner in both membrane fusion events. It might be predicted from these observations that membrane fusion involves transduction of a fusion signal along the gB molecule through the transmembrane domain. Communication between the external and cytoplasmic domain may thus be required for gB-mediated membrane fusion events.

Coulometric electrochemical detection of hydroxyproline using 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole

A new method for detection of hydroxyproline has been developed. Hydroxyproline was derivatized using 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole; separation and detection were accomplished using HPLC with coulometric electrochemical detection. Derivatized hydroxyproline was initially detected using a 16 channel coulometric electrochemical array system. The assay was slightly modified for use with a simpler 2-channel coulometric electrochemical detector. Both detectors are sensitive into the upper fmol range. Derivatization of hydroxyproline occurs in 5 min and the derivative is stable for several hours at 0 degrees C. The techniques were used to quantitate hydroxyproline in purified type I collagen and other biological samples.

Bacteria reactive to plaque-toxin-neutralizing monoclonal antibodies are related to the severity of gingivitis at the sampled site

Certain monoclonal antibodies (Mabs) neutralize the inhibition of HL60 cell growth by bacterial plaque extracts. The aim of this study was to enumerate and identify the bacteria reactive to these Mabs at sites where periodontal disease was measured by gingival index, pocket depth and attachment loss. The bacterial colonies were grown on blood agar and the colonies counted directly and after immunoblotting. Sites that bled on probing (n = 15) had a mean of 3.35% Mab-positive colonies (SEM = 0.52%) and sites that did not bleed (n = 9) had a mean of 1.61% (SEM = 0.41%). The percentage of Mab-positive colonies also correlated with gingival index but not with the total number of colonies sampled, attachment loss or pocket depth. Antigen was expressed by 4 genera: strains of Streptococcus sanguis and/or Eikenella corrodens (8 sites), Staphylococcus epidermidis (4 sites) and Corynebacterium minutissimus (1 site). The results suggest that the antigens detected on these bacteria by the Mabs may be processed to form toxins and maintain gingivitis by irritating the surrounding cells.

Binding affinities and cooperative interactions with bHLH activators delimit threshold responses to the dorsal gradient morphogen

The dorsal (dl) morphogen gradient initiates the formation of the mesoderm, neuroectoderm, and dorsal ectoderm by setting different limits of regulatory gene expression along the dorsoventral axis of the early Drosophila embryo. In this paper, we show that low affinity dl-binding sites restrict target gene expression to the ventralmost regions (presumptive mesoderm), where there are peak levels of dl, while high affinity sites permit expression in ventrolateral regions (mesoderm and mesectoderm) containing intermediate levels of the morphogen. Activation by low levels of dl in lateral regions (the presumptive neuroectoderm) depends on cooperative DNA binding interactions between dl and bHLH proteins. The snail repressor blocks this interaction and restricts expression to the neuroectoderm. We discuss how enhancers serve as templates to bring weakly interacting regulatory factors into close proximity so that they can function combinatorially to activate and repress transcription.

Antibody avidity measurement and immune complex dissociation for serological diagnosis of vertically acquired HIV-1 infection

Differences in avidity between HIV-1 antibodies transmitted passively and antibodies synthesized by children born to HIV-1-positive mothers can be measured using a commercially available competitive enzyme immunoassay kit. The avidity determination method is based on the competition between an anti-HIV-1-peroxidase-labeled antibody at a stable and known concentration and the anti-HIV-1 antibodies (IgA, IgG, IgM) present in the child's serum at various and increasing dilutions. The shift in the competition/dilution curves between serum samples taken at the third and the sixth month of the child's life showed either the loss or the synthesis of anti-HIV-1 antibodies. The antibody avidity determination combined with a test detecting free or complexed p24 antigen is a workable and inexpensive serological method for the follow-up of children born to seropositive mothers. Combining these two complementary methods, HIV-1 infection has been established at 6 months of age in 13 of 13 infants, and positive results were confirmed by coculture and by PCR. An HIV-1 infection was excluded at 6 months of age in 17 of 17 infants, results otherwise confirmed by virological and clinical follow-up. These new and convenient approaches to the diagnosis of vertically acquired HIV-1 could be used worldwide, including in developing countries.

Acquired sideroblastic anaemia during treatment of Wilson's disease with triethylene tetramine dihydrochloride

We report one case of acquired sideroblastic anaemia in a patient treated for Wilson's disease with triethylene tetramine dihydrochloride (TTH). No other cause of acquired sideroblastic anaemia was found, and neither iron nor pyridoxine therapy could correct this anaemia. In contrast, decreasing the dose of TTH led to disappearance of ringed sideroblasts. Thus TTH should be added as a further cause of secondary acquired sideroblastic anaemia. The pathophysiology of this finding, probably linked to an abnormality of mitochondrial iron metabolism, is briefly discussed.

Comparative effects of bicarbonate, tris-(hydroxymethyl)aminomethane and dichloroacetate in newborn swine with normoxic lactic acidosis

A total of 20 newborn piglets age 11.5 +/- 0.3 days and weighing 3.7 +/- 0.1 kg were studied under pentobarbital anesthesia. After stabilization following surgical procedures, baseline values for blood gases, base excess (BE), heart rate (HR), aortic pressure (AoP), left-ventricular contractility (LV dP/dtmax), carotid artery flow (CarF) and renal artery flow (RenF) were measured and normal lactic acid 0.2 ml/kg was infused over 1 h and the same parameters repeated. Then sodium bicarbonate (BC, n = 8), Tris-(hydroxymethyl)aminomethane (THAM, n = 6) or dichloroacetate (DCA, n = 6) were infused over 1 h. The doses of BC and THAM were calculated from the standard formula: Mmol = Base deficit x kg x 0.3. DCA was given at a dose of 300 mg/kg. Following lactic acid infusion, pH was 7.00 +/- 0.4 and BE was -20.6 +/- 1.2. Acidosis was associated with a significant (p < 0.05) increase in AoP (+18.6 +/- 7.4%) and decreases in HR (-13.9 +/- 2.7%) and RenF (-43.8 +/- 10.4%). Values of dP/dtmax and CarF were higher during acidosis in all but 3 animals. Following infusion of alkalizing agents pH and BE values were highest with BC and lowest with DCA and the differences were statistically significant (p < or = 0.05). In general, all three alkalizing agents reversed, in part or completely, the changes in cardiovascular parameters associated with acidosis so that following alkali infusion the changes were not statistically significant when compared to baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of ascorbic acid transport in human neutrophils by glucose

Because of the structural similarity between glucose and ascorbic acid, we investigated the effect of glucose on uptake and accumulation of ascorbic acid in isolated normal human neutrophils. Ascorbic acid accumulation was determined using high-performance liquid chromatography with coulometric electrochemical detection, in conjunction with liquid scintillation spectrometry. Ascorbic acid accumulation in neutrophils is mediated by a high and a low affinity transport activity. In neutrophils from different volunteers, glucose inhibited uptake and accumulation of ascorbic acid by both transport activities 3-9-fold. The mechanism of inhibition was different for each transport activity: inhibition of the high affinity transport activity was noncompetitive, while inhibition of the low affinity activity was competitive. Glucose-induced inhibition of both ascorbic acid transport activities occurred in neutrophils of all donors tested and was fully reversible. Although the mechanism of ascorbic acid accumulation appeared to be different than that for glucose transport, other monosaccharides and glucose transport inhibitors also inhibited ascorbic acid accumulation. These are the first data to suggest that ascorbic acid accumulation in neutrophils can be regulated by compounds of similar structure.

Hemostatic alterations in cancer patients

Nearly all patients with cancer manifest laboratory evidence of hypercoagulability and some develop clinical thromboembolic disease (TED). Routine laboratory studies of blood coagulation have been performed in several large, prospective trials of the use of anticoagulant drugs in cancer treatment. The results of these studies, as well as data from several smaller studies of more sensitive tests of hypercoagulability [e.g. fibrinopeptide A (FPA); thrombin-antithrombin (TAT) complexes; prothrombin fragment F1 + 2)], indicate that the levels of some clotting proteins parallel disease activity. However, no studies of sound methodologic design have yet been performed to indicate that any of these tests of blood coagulation can serve as adequate predictors of TED in patients with cancer. In addition to the important role played by tumor-related procoagulants, several other mechanisms may be involved in the pathogenesis of thromboembolic events in patients with cancer, including stasis and endothelial damage. Considerable variability in the relative importance of these mechanisms in the pathogenesis of TED may exist among patients with different types of cancer. The risk for TED associated with surgical procedures in cancer patients is substantial and prophylactic antithrombotic therapy should be considered for most of these patients. Chemotherapy and hormonal therapy of cancer probably increases the likelihood of TED, particularly in those subjects with indwelling venous catheters. This risk has been particularly well-studied in patients with breast cancer treated with tamoxifen plus cytotoxic drugs. The pathogenic mechanisms may be complex but vascular injury is likely as a proximate cause of venous access catheter thrombosis and can be prevented with low dose coumadin therapy. The utility of low dose coumadin anticoagulation in reducing the risk for TED during breast cancer treatment is unknown but is currently being tested in a large, multiinstitutional study. Since chronic coumadin anticoagulation of cancer patients, and single pulse dose heparin prior to intravenous chemotherapy, both prevent thrombin generation, these agents may be of use in reducing the risk of chemotherapy-associated thrombosis. Prophylactic anticoagulation should be considered for high risk patients.

Regulation of even-skipped stripe 2 in the Drosophila embryo

In an effort to determine how crude gradients of transcriptional activators and repressors specify sharp stripes of gene expression in the early embryo, we have conducted a detailed study of even-skipped (eve) stripe 2. A combination of promoter fusions and P-transformation assays were used to show that a 480 bp region of the eve promoter is both necessary and sufficient to direct a stripe of LacZ expression within the limits of the endogenous eve stripe 2. The maternal morphogen bicoid (bcd) and the gap proteins hunchback (hb), Kruppel (Kr) and giant (gt) all bind with high affinity to closely linked sites within this small promoter element. Activation appears to depend on cooperative interactions among bcd and hb proteins, since disrupting single binding sites cause catastrophic reductions in expression. gt is directly involved in the formation of the anterior border, although additional repressors may participate in this process. Forming the posterior border of the stripe involves a delicate balance between limiting amounts of the bcd activator and the Kr repressor. We propose that the clustering of activator and repressor binding sites in the stripe 2 element is required to bring these weakly interacting regulatory factors into close apposition so that they can function both cooperatively and synergistically to control transcription.

The relationship between environmental temperature, metabolic rate, sleep state, and evaporative water loss in infants from birth to three months

We have investigated the effect of changing environmental temperature on metabolic rate, sleep state, and water loss in a longitudinal study of 22 lightly clothed babies from 2 d to 3 mo of age. Studies were performed in a modified barometric plethysmograph while recording sleep state, oxygen consumption, and skin and axillary temperatures. Oxygen consumption was higher in rapid eye movement sleep than in quiet sleep at all ages and varied widely between infants at each temperature. Within the first week, there was a 19% rise in oxygen consumption on cooling to 19-22 degrees C during rapid eye movement sleep and a 6% rise during quiet sleep. The median duration of quiet sleep periods was reduced from 17 to 12 min on cooling within the first week. No such change was seen at 1, 2, and 3 mo. Axillary temperature was reduced at 3 mo during cooling. This may be a part of normal patterns of change in temperature during sleep, unrelated to cooling. At each age, total evaporative water loss fell linearly with falling environmental temperature both within and below the temperature range at which metabolic rate was minimal. The evaporative water losses were greater than expected and suggested that sweating was occurring, both at temperatures at which metabolic rate was minimal and at those at which it was increased. The metabolic response to cooling and the process of sweating appear to be in dynamic equilibrium across this temperature range. Thus, it was not possible to define a temperature range over which both metabolic rate and evaporative water loss were at minimum values.

Opioid receptor modulation of postexercise hypotension

Previous studies of both hypertensive and normotensive individuals have indicated a prolonged reduction in blood pressure for several hours after aerobic exercise. In related studies of spontaneously hypertensive rats, this postexercise hypotension has been prevented with naloxone. The purpose of the present investigation was to examined whether the postexercise hypotension may be reversed by antagonism of opioid sensitive receptors with naloxone in normotensive humans. Eight males 22-34 yr of age, participated in two 60-min cycling trials at 60% of VO2 peak, followed by 29 min of recovery. Beginning at 7-min recovery, naloxone or saline (control) was administered intravenously through an indwelling catheter. Blood pressure and heart rate were monitored every 15 min during exercise and every 2 min during recovery. Heart rate was significantly elevated (P < 0.05) over basal levels for the first 11 min of recovery, but from 13 to 29 min was not different from that measured at rest. In both trials, after 11 min of recovery, systolic and mean arterial blood pressures were significantly (P < 0.05) lower than pre-exercise levels (9 +/- 1 mm Hg and 4 +/- 1 mm Hg, respectively). Injection of naloxone (0.1 mg.kg-1) reversed the hypotensive response. However, the reversal was transient, lasting from minutes 15 to 27. Since naloxone reverses postexercise hypotension, opioid sensitive receptors appear to be involved in the reduction in systolic blood pressure following a single bout of submaximal exercise in normotensive humans.

Prophylactically equivalent doses of Enoxaparin and unfractionated heparin inhibit in vivo coagulation to the same extent

This study compared how Enoxaparin and unfractionated (UF) heparin influenced in vivo coagulation in patients randomized to receive, by twice daily subcutaneous injections, either 30 mg of Enoxaparin or 7500 I.U. of UF heparin after elective hip surgery. These two regimens were equally effective in reducing the incidence of post-operative deep vein thrombosis DVT. We compared the concentrations of endogenous thrombin-antithrombin III in pre- and post-surgical plasmas to determine how each prophylactic regimen influenced prothrombinase activity in vivo, and found the same concentrations of endogenous thrombin-antithrombin III in post-heparin and post-Enoxaparin plasmas. However, significantly higher concentrations of endogenous thrombin-antithrombin III were found in pre- and post-surgical plasmas of patients who developed post-operative DVT than the levels found in comparable plasmas of patients who remained DVT-negative, regardless of the drug received for prophylaxis. Human factor Xa was added to an equal volume of each patient's plasmas and the amount of added enzyme inactivated by antithrombin III measured using an enzyme-linked immunosorbent assay for factor Xa-antithrombin III. Post-heparin and post-Enoxaparin plasmas inactivated approximately 4 times more factor Xa than the pre-surgical plasmas, regardless of the clinical outcome. Thus, before and after surgery, a higher than normal in vivo prothrombinase activity may be a significant risk factor for developing post-operative DVT.

A cell-free recombination system for site-specific integration of multigenic shuttle plasmids into the herpes simplex virus type 1 genome

This report describes a novel method for complementation studies of defective herpes simplex virus (HSV) genes. Viral test gene and nonviral reporter gene cassettes were rapidly integrated into the HSV genome in a site-specific and reversible manner by using the P1 phage-based Cre-lox recombination system. Shuttle plasmids contained a functional loxP recombination site, an expressible form of the bacterial lacZ gene, and a copy of the wild-type glycoprotein B (gB) gene or double mutant gB allele containing both a temperature-sensitive (ts) mutation and a syncytium (syn)-forming mutation. A recipient viral genome, K delta T::lox1, was constructed from the HSV type 1 (syn) gB-deficient mutant virus, K delta T, by marker transfer of the loxP recombination site into the viral thymidine kinase locus. Shuttle plasmids of up to 12.9 kb in length were recombined with high efficiency (11 to 20%) into the K delta T::lox1 genome in cell-free, Cre-mediated recombination reactions. Expression of a functional wild-type or double mutant gB polypeptide complemented the nonfunctional polypeptide expressed from the deleted, normal gB locus and allowed production of either wild-type or Syn- plaques on Vero cells. The latter recombinant virus was also ts for growth. The ability to express viral genes from plasmids which can be shuttled into and out of the HSV genome in cell-free recombination reactions makes this a powerful method for performing genetic studies of the biologic properties of viral gene products.

A parkinsonian syndrome induced in the goldfish by the neurotoxin MPTP

Parkinson's disease has been modeled in humans, lower primates, and to a lesser extent in some other vertebrates by administration of the potent neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine). The MPTP model has thus drawn considerable attention as a system to search for anti-Parkinson's disease drugs, although the cost and scarcity of primates has limited extensive applications. We now report that a parkinsonian syndrome can be elicited in the common goldfish (Carassius auratus) by a single dose of MPTP. The syndrome is characterized by profound bradykinesia (slow movement), the full extent of which is reached 3 days after MPTP administration. The reduction in movement is paralleled by loss of dopamine and norepinephrine from the forebrain and midbrain and in other brain regions as well. The toxic oxidative product of MPTP, MPP+, is also accumulated predominantly in forebrain and midbrain, and pretreatment with the monoamine oxidase blocker tranylcypromine substantially reduces accumulation of the toxic metabolite. A barely perceptible coarseness in balance adjustment also occurs in treated animals. The MPTP-treated goldfish recover normal movement and normal brain monoamine levels within 10-13 days after administration of the drug. We interpret these and other data to indicate that MPTP can induce a Parkinson's disease-like syndrome in the goldfish that is similar in many aspects to the syndrome induced by MPTP in humans and other primates. This remarkable parallel may permit the goldfish to supplement expensive and scarce primates for the purpose of searching and screening neuroprotective drugs with specific relevance to Parkinson's disease.

The dorsal gradient morphogen regulates stripes of rhomboid expression in the presumptive neuroectoderm of the Drosophila embryo

rhomboid (rho) encodes a putative transmembrane receptor that is required for the differentiation of the ventral epidermis. It is initially expressed before the completion of cellularization in lateral stripes within the presumptive neuroectoderm. Here, we present evidence that the maternal morphogen dorsal (dl) acts in concert with basic helix-loop-helix (b-HLH) proteins, possibly including twist (twi), to activate rho in both lateral and ventral regions. Expression is blocked in ventral regions (the presumptive mesoderm) by snail (sna), which is also a direct target of the dl morphogen. A 300-bp region of the rho promoter (the NEE), which is sufficient for neuroectoderm expression, contains a cluster of dl and b-HLH activator sites that are closely linked to sna repressor sites. Mutations in these binding sites cause genetically predicted changes in the levels and limits of rho expression. In particular, the disruption of sna-binding sites causes a derepression of the pattern throughout ventral regions, providing evidence that sna is directly responsible for establishing the mesoderm/neuroectoderm boundary before gastrulation. The tight linkage of activator and repressor sites in the rho NEE is similar to the arrangement of binding sites observed in the even-skipped stripe 2 element, which is regulated by bicoid (bcd). This suggests that the dl and bcd morphogens use a similar mechanism to make stripes in the Drosophila embryo.

Ectopic expression of the Drosophila tramtrack gene results in multiple embryonic defects, including repression of even-skipped and fushi tarazu

The tramtrack (ttk) gene of Drosophila encodes 69-kDa and 88-kDa proteins through alternative splicing of the primary ttk transcript. The two proteins share a common amino-terminal sequence, but contain different carboxy-terminal portions, each of which has a distinct zinc finger domain with a unique DNA binding specificity. The 69-kDa ttk protein has been shown to bind multiple sites within important regulatory elements of the pair-rule genes even-skipped (eve) and fushi tarazu (ftz), and it has been suggested that this protein may function as a repressor of ftz transcription. Here we present evidence that the 69-kDa ttk protein can indeed repress expression not only of ftz, but also of eve. Ectopic expression of the 69-kDa protein, but not of the 88-kDa form, was found to nearly abolish the striped patterns of expression of both eve and ftz in transgenic embryos. These findings, coupled with our detection of significant levels of ttk protein in ovaries and 0-2-h embryos, support the idea that maternally supplied ttk protein serves to prevent premature activation of eve and ftz, thereby helping to establish the timing of the onset of zygotic expression of these two genes. Furthermore, gross defects in the larval cuticle resulting from misexpression of the 69-kDa protein suggest that this protein performs additional functions in the early embryo.

Genetic analysis of type-specific antigenic determinants of herpes simplex virus glycoprotein C

Herpes simplex virus type 1 (HSV-1) glycoprotein C (gC-1) elicits a largely serotype-specific immune response directed against previously described determinants designated antigenic sites I and II. To more precisely define these two immunodominant antigenic regions of gC-1 and to determine whether the homologous HSV-2 glycoprotein (gC-2) has similarly situated antigenic determinants, viral recombinants containing gC chimeric genes which join site I and site II of the two serotypes were constructed. The antigenic structure of the hybrid proteins encoded by these chimeric genes was studied by using gC-1- and gC-2-specific monoclonal antibodies (MAbs) in radioimmunoprecipitation, neutralization, and flow cytometry assays. The results of these analyses showed that the reactivity patterns of the MAbs were consistent among the three assays, and on this basis, they could be categorized as recognizing type-specific epitopes within the C-terminal or N-terminal half of gC-1 or gC-2. All MAbs were able to bind to only one or the other of the two hybrid proteins, demonstrating that gC-2, like gC-1, contains at least two antigenic sites located in the two halves of the molecule and that the structures of the antigenic sites in both molecules are independent and rely on limited type-specific regions of the molecule to maintain epitope structure. To fine map amino acid residues which are recognized by site I type-specific MAbs, point mutations were introduced into site I of the gC-1 or gC-2 gene, which resulted in recombinant mutant glycoproteins containing one or several residues from the heterotypic serotype in an otherwise homotypic site I background. The recognition patterns of the MAbs for these mutant molecules demonstrated that (i) single amino acids are responsible for the type-specific nature of individual epitopes and (ii) epitopes are localized to regions of the molecule which contain both shared and unshared amino acids. Taken together, the data described herein established the existence of at least two distinct and structurally independent antigenic sites in gC-1 and gC-2 and identified subtle amino acid sequence differences which contribute to type specificity in antigenic site I of gC.