The double catalytic triad, Cys25-His159-Asp158 and Cys25-His159-Asn175, in papain catalysis: role of Asp158 and Asn175

The 1.65 A X-ray structure of papain, which exhibits a Cys25-His159-Asn175 triad, does not correspond to the catalytically active ion pair state since Cys25 is oxidized to cysteic acid and His159 is predominantly neutral. Thus, stochastic boundary molecular dynamics simulations starting from the 1.65 A X-ray structure of papain have been performed for Cys25 and His159 in the SH-ImH+, SH-Im, S(-)-ImH+ and S(-)-Im states and for Asp158 mutated to Asn, Glu and Gly in the ion pair state. By comparing the resulting averaged structures and analyzing the trajectories of certain interatomic distances, important differences in the active-site geometry of papain have been found. In particular, the initial Cys25(S-)-His159(ImH+)-Asn175(C = O) triad found in the X-ray structure is retained in all the structures except the wild type and Asp158-->Asn ion pair states where there is a conformational transition to form the triad, Cys25(S-)-His159(ImH+)-Asp158(COO-). Both triads, Cys25(S-)-His159(ImH+)-Asp158(COO-) and Cys25(S-)-His159(ImH+)-Asn175(C = O) are postulated to participate in catalysis and their roles are discussed. Thus, catalysis does not take place from a single steric position but a two-state mechanism.

Effect of ethanol on prostaglandin E2 receptor in rat submandibular salivary glands

The dose-dependent effects of acute ethanol treatment on the prostaglandin E2 (PGE2) receptor in submandibular salivary glands was investigated. Rat submandibular-gland segments were preincubated with Dulbecco's modified Eagle's medium in the absence and the presence of various concentrations of ethanol (0.1-5%). After incubation, membranes were prepared and assayed for PGE2 receptor binding using [3H]-PGE2. Ethanol had no effect on receptor binding at concentrations below 1%, but binding was stimulated by higher concentrations. A 30% increase in binding occurred with 2.5% ethanol and 50% with 5% ethanol. This increase was due to an alteration of the binding characteristics. Scatchard analysis of the data from the control and 5% ethanol groups revealed that the ethanol-induced increase in PGE2 receptor binding was mainly due to a 26 and 58% decrease in the dissociation constant (Kd) for the high- and low-affinity binding sites, respectively. A 31% decrease of binding capacity (Bmax) was also observed in the low-affinity binding sites. The results demonstrate that PGE2 receptor binding in submandibular glands is not altered by acute treatment with ethanol at physiological doses. The receptor binding is also relatively stable on pretreatment with 1% ethanol. It is suggested that the increase of receptor binding induced by high concentrations of ethanol may be a spontaneous response to the decrease of PGE2 synthesis in the tissues.

Cigarette smoking reduces human salivary eicosanoids

The effect of cigarette smoking on salivary eicosanoid levels was investigated in 10 smoker and 10 non-smoker volunteers. The smokers consumed an average of 20 cigarettes/day for the past 5 years or longer. The smoking status was validated by salivary cotinine level. Eicosanoids were extracted from saliva with ethanol, and the radioimmunoassay was performed to determine the concentrations of four major eicosanoids, i.e. prostaglandin E2 (PGE2), PGF2 alpha, 6-sulphidopeptide-containing leukotrienes (LTs) and 12-hydroxyeicosatetraenoic acid (12-HETE). The levels of PGE2, PGF2 alpha, and LTs were significantly lower in the saliva of smokers as compared to that of the non-smokers (1.74 +/- 0.32 vs 2.41 +/- 0.64, p = 0.006; 0.36 +/- 0.12 vs 0.54 +/- 0.18, p = 0.04; 2.24 +/- 0.96 vs 4.92 +/- 1.29, p = 0.006; mean +/- SD, ng/ml saliva). No significant differences were found in the levels of 12-HETE between the two groups. The results suggest that cigarette smoking reduces the concentrations of both the cyclooxygenase and 5-lipoxygenase products in saliva.

Visual field differences for clockwise and counterclockwise mental rotation

Geometric line drawings were presented to normal subjects in the left visual field (LVF) or right visual field (RVF) at various degrees of rotation from a centrally presented vertical standard. The task of the subject was to indicate with a reaction time (RT) response whether the laterally presented stimulus could be rotated into the vertical standard or if it was a rotated mirror image of the standard. In Study 1, an overall right hemisphere superiority was found for RT and accuracy on match trials. Most interestingly, interactions between Visual Field and Rotation Angle for the match accuracy data and between Visual Field and Direction of Rotation (clockwise or counterclockwise) for the match RT slopes were found. These interactions suggested that clockwise rotations were more readily performed in the LVF and counterclockwise rotations in the RVF, consistent with other literature for mental rotation. The purpose of Study 2 was to replicate this finding of visual field differences for rotation direction using a design in which direction and degree of rotation were varied orthogonally. No main effect of Visual Field was found. However, significant interactions between Visual Field and Rotation Angle were found for both RT and accuracy, confirming the presence of visual field differences for rotation direction in a new sample of subjects. These differences were discussed in terms of the possibly greater relevance of medially directed stimuli and a possible hemispheric bias for rotation direction, and in terms of interhemispheric transmission factors.

Hemodynamic effects of carvedilol after acute oral administration in hypertensive and normal subjects

Forearm hemodynamics using pulsed Doppler flowmetry were studied in nine healthy volunteers and 12 patients with mild-to-moderate hypertension before and after acute oral administration of the beta-blocking and vasodilating agent carvedilol. Both the 25- and the 50-mg dose produced a significant blood pressure reduction by comparison with placebo in normotensive and hypertensive subjects. Only the 50-mg dose caused a decrease in forearm vascular resistance in hypertensive subjects. The decrease disappeared after wrist occlusion. Although brachial artery diameter did not change, a significant decrease in tangential tension was observed. This study provides evidence that carvedilol produced arteriolar dilation within the forearm of hypertensive subjects in association with a decrease in brachial artery tangential tension.

Hippocampus and the blood supply to TE: parahippocampal pial section impairs visual discrimination learning in monkeys

In the base of each temporal lobe in 4 monkeys (Macaca fascicularis) we sectioned the pia mater in an antero-posterior line along the most medial part of the inferior temporal visual association cortex (area TE), lateral to the parahippocampal cortex. This pial section interrupts the blood flow in branches of the posterior cerebral artery which cross the parahippocampal gyrus en route to area TE. Histologically, the brains of 2 of these animals did not show any abnormalities in cresyl violet stained material, apart from the small cortical damage along the line of the pial section itself. Of the remaining two animals, one had a small unilateral infarct in TE and one had bilateral infarcts in TE. All of these animals were impaired in visual discrimination learning, and the severity of impairment was correlated only imperfectly with the severity of infarction. These results show that pial section along the medial boundary of area TE can affect visual discrimination learning without producing large infarcts. Further, since aspiration lesions of the hippocampal formation require the pia mater to be sectioned in a similar way to that reported here, the effects of such aspiration lesions on visual learning and memory may be mediated in part by effects on TE.

Effect of electroconvulsive therapy on serum concentration of alpha-1-acid glycoprotein

Recent studies have shown significant alterations in serum alpha-1-acid glycoprotein (AGP) concentration in epileptic patients, the major protein to which basic drugs bind in serum. To date, there have been no reports in the literature investigating the effects of generalized seizures as a result of repeatedly administered electroconvulsive therapy (ECT) on this serum protein. As the cyclic antidepressants are basic drugs that bind avidly to AGP, an alteration of AGP concentration by ECT could represent a mechanism of interaction between two somatic treatments for depression. We therefore determined the serial AGP concentrations of 10 patients undergoing repeated ECT. AGP concentrations were determined by radial immunodiffusion on serum samples obtained at each treatment session (course of treatment ranged from 4 to 12 sessions over 8 to 32 days). The mean (SD) AGP concentrations prior to and at the end of ECT were 88.7 (18.3) mg/dl and 97.8 (24.8) mg/dl, respectively. Variability in AGP concentration was observed over the course of treatments with no consistent trend (intrapatient coefficients of variation averaged 11.5%). These data suggest that serial ECT does not produce consistent, significant changes in serum AGP concentrations and should have limited effects on altering the serum protein binding and, therefore, pharmacological effects of concurrently administered cyclic antidepressants.

Impairment by ethanol of prostaglandin production in rat salivary glands

Sublingual salivary acini and submandibular tissue were incubated in DMEM medium in the presence of various concentrations (0-5%) of ethanol and the content of the three major prostaglandins, PGE2, PGF2 alpha and 6-keto-PGF1 alpha, were determined by radioimmunoassay. In In the sublingual gland, ethanol caused a decrease in PGE2 and PGF2 alpha levels, but had no effect on 6-keto-PGF1 alpha, while all three prostaglandins were affected in the submandibular gland. At 2.5% ethanol, the production of PGF2 alpha and PGE2 in sublingual gland decreased by 10% and reached maximum inhibition at 5% ethanol, at which concentration there was a 20 and 30% decrease in their levels. In submandibular gland, 2.5% ethanol caused a 20% decrease in PGE2, 30% in PGF2 alpha and 50% in 6-keto-PGF1 alpha; 40% inhibition in PGE2, 57% in 6-keto-PGF1 alpha and 65% in PGF2 alpha occurred in the presence of 5% ethanol. These findings suggest that alcohol impairs the function of salivary glands by inhibiting prostaglandin production.

Stereoselective protection of exogenous and endogenous atrial natriuretic factor by enkephalinase inhibitors in mice and humans

We compared the relative potencies of sinorphan and retorphan, the S- and R-enantiomers of acetorphan a potent inhibitor of enkephalinase (EC 3.4.34.11), to inhibit membrane metalloendopeptidase in vivo and to protect exogenous and endogenous ANF after oral administration. In mice, sinorphan was 2-3 fold as potent as retorphan in inhibiting the specific in vivo binding of [3H]acetorphan to kidney enkephalinase. The same potency ratio was found for the enhancement of trichloroacetic acid-precipitated radioactivity in kidneys of mice that had received 125I-ANF, which is used as a test for the protection of the hormone against inactivation in vivo. In nine healthy human volunteers who had received a low oral dosage of sinorphan or retorphan in a double-blind, placebo-controlled, randomized trial, sinorphan was also 2-3 fold more potent than retorphan in inhibiting plasma enkephalinase activity. These effects were accompanied by a related rise in plasma ANF immunoreactivity, which also reflected the difference in the effectiveness of the two compounds. Sinorphan was also more potent than retorphan in enhancing urinary cyclic GMP excretion and sodium excretion in five of these subjects. These data indicate that, in humans as in rodents, enkephalinase plays a crucial role in the inactivation of ANF, its partial inhibition in vivo being accompanied by a significant protection of the exogenous or endogenous hormone as well as by typical ANF-like responses. Thus orally administered sinorphan appears to be a promising compound for therapeutic use in cardiovascular and renal diseases in which ANF has been postulated to exert beneficial effects.

Hangman's fracture: radiologic assessment in 27 cases

Traumatic spondylolisthesis of C-2, frequently referred to as the hangman's fracture, is typically regarded as a hyperextension injury with rare neurologic sequelae by virtue of decompression of the neural canal. The authors retrospectively evaluated their radiographic experience with this injury in 27 patients over a 24-month period. Lateral cervical spine studies and computed tomography (CT) scans (21 patients) were analyzed. CT studies provided better delineation of the fracture in all 21 patients and significant additional information in five patients (24%). Seven patients (26%) suffered initial neurologic sequelae in association with the C-2 injury. Nine patients had additional sites of fracture, including seven with associated C-1 ring disruption (26%). Extension of the fracture line into the transverse vertebral artery foramen led to vertebral artery injury and cerebellar embolization in one patient. Angiography may be necessary to detect intimal injury to the vertebral arteries when the fracture extends through the transverse foramina and to indicate the need for anticoagulation when clinically feasible.

Effects of glucocorticoids on the growth of human fibrosarcoma cell line HT-1080

The human fibrosarcoma cell line HT-1080 exhibits rapid growth following s.c. inoculation in 4-6-week-old male athymic mice. Cytosols from tumors carried in athymic mice bind glucocorticoid (Kd, 1.8 +/- 0.48 X 10(-8) M; Bmax, 240.5 +/- 35.3 fmol/mg cytosol protein, mean +/- SEM). Receptor sediments primarily in the 8-9S region on 5-20% sucrose gradients and is specific for the glucocorticoids. HT-1080 growth in vitro (as measured by cell count) was inhibited over a range of 10(-6)-10(-8) M after 7 days of incubation with dexamethasone and triamcinolone acetonide. Progesterone, estradiol, and dihydrotestosterone had no effect on HT-1080 growth in vitro. Preincubation with a 100-fold excess of progesterone reversed the growth inhibition observed with triamcinolone acetonide but not dexamethasone acetate. HT-1080 tumor cell growth responded biphasically to dexamethasone in vivo. Athymic mice given s.c. injections every other day with 5 or 25 micrograms dexamethasone showed an increase in tumor size inversely proportional to dose. In contrast, 200 micrograms of dexamethasone significantly inhibited tumor growth. Adrenalectomy did not significantly alter HT-1080 growth or glucocorticoid binding to tumor cytosols (Kd, 3.4 X 10(-8) +/- 1.1, Bmax, 236.9 +/- 9.9 fmol/mg cytosol protein, mean +/- SEM) although tumor incidence was decreased in sham adrenalectomized mice. Glucocorticoid binding in tumors grown in vivo was decreased by increasing amounts of dexamethasone. High pharmacological doses of glucocorticoids inhibit the growth of human fibrosarcomas in vivo and in vitro.

Changing patterns of transfusion practice in a tertiary care hospital from 1977 to 1984

Patterns of blood transfusion practice over an eight-year-period (1977-1984) are described. Use of blood and blood products increased annually as did the number of patients crossmatched and transfused. Programs such as the "Blood Group & Antibody Screen" and the "Maximum Surgical Blood Order Schedule" were important in improving transfusion practices. There was improvement in blood use by all subspecialties; the overall C:T (crossmatched:transfused blood) ratio declined from 4.4 to 2.8. Approximately a quarter of both crossmatches performed and transfusions of red cells were associated with cardiac surgery. Incidence of outdated units of blood declined markedly (2.6 per cent in 1984), as did requests for and administration of single unit transfusions. Seven per cent of patients received one unit of blood during hospitalization; since 85 per cent of these were associated with surgery (57 per cent cardiac surgery), it is suggested that single unit transfusions may sometimes be more appropriate than inappropriate. Two per cent of patients had clinically significant alloantibodies. About two per cent of patients had positive direct antiglobulin tests; nine per cent of the sera of these patients contained both auto and alloantibodies. Such data are important for transfusion quality assurance as well as for optimal logistical use of facilities both at hospital Blood Bank and blood collection agency levels.

Sensitive method for detecting low numbers of verotoxin-producing Escherichia coli in mixed cultures by use of colony sweeps and polymyxin extraction of verotoxin

High titers of Verotoxin (VT) were released from cell pellets of VT-producing Escherichia coli (VTEC; corresponding to E. coli strains producing "high" levels of Shiga-like toxin) after incubation in polymyxin B (0.1 mg/ml) for 30 min at 37 degrees C. Maximal titers of polymyxin-releasable VT occurred in cells obtained from 5-h Penassay broth cultures and were up to eightfold higher than the peak culture supernatant VT titers which occurred in 8-h cultures. Polymyxin-releasable cell extracts of 5-h broth cultures inoculated with mixtures of VT-positive (VT+) and VT-negative strains had easily detectable VT titers when the proportion of VT+ cells in the mixture was about 1.0%, but culture supernatants were negative for VT even when this proportion was 20%. The results were the same whether the initial inoculum consisted of broth culture mixtures of VT+ and VT-negative strains or colony sweeps (loopfuls of confluent bacterial growth) taken from solid plate media previously inoculated with the broth mixtures. In a clinical study, 80 stool cultures from patients with hemolytic uremic syndrome and family contacts with diarrhea were tested for free fecal VT, VT in polymyxin extracts of colony sweeps (VT/PECS), and VTEC (examination of 20 separate E. coli colonies from primary media for VT production). Of the 80 samples, 40 were positive for at least one of these three tests; all 40 were positive for free fecal VT, and 20 of these were positive for VT/PECS. VTEC (as few as 1 colony out of 20) were only isolated from 14 of the 20 cultures that were positive for VT/PECS. In six cases, the VT/PECS was positive even when none of 20 colonies tested were VT+, suggesting that the procedure was able to detect a proportion of VTEC that was less than one in 20(5%). We conclude that the VT/PECS method is highly sensitive for detecting low concentrations of VTEC in stools and provides a rapid method for screening out stools that are negative for VTEC. The technique should also be of value in epidemiological studies for detecting low numbers of VTEC in animal feces, foods, and environmental samples.

The association between idiopathic hemolytic uremic syndrome and infection by verotoxin-producing Escherichia coli

Forty pediatric patients with idiopathic hemolytic uremic syndrome (HUS) were investigated for evidence of infection by Verotoxin-producing Escherichia coli (VTEC). Fecal VTEC (belonging to at least six different O serogroups including O26, O111, O113, O121, O145, and O157) or specifically neutralizable free-fecal Verotoxin (VT) or both were detected in 24 (60%) patients but were not detected in 40 matched controls. Ten of 15 of the former developed fourfold or greater rises in VT-neutralizing antibody titers, as did six other patients who were negative for both fecal VTEC and VT. A total of 30 (75%) patients had evidence of VTEC infection by one or more criteria. We concluded that a significant association exists between idiopathic HUS and infection by VTEC. The detection of free-fecal VT was the most important procedure for the early diagnosis of this infection because, in our study, VTEC were never isolated in the absence of fecal VT, whereas fecal VT was often present even when VTEC were undetectable.

Maternal-child hepatitis B virus transmission in Singapore

A study of maternal-infant transmission of hepatitis B virus (HBV) was conducted in Singapore between June 1980 and June 1982. HBsAg carrier rate was highest among Chinese (6.2%) followed by Malay (2.3%) and Indian (0.6%) mothers. The presence of HBeAg in maternal sera correlated well with high titre HBsAg (p = 7.34 X 10(-5)). Overall HBV transmission occurred in 27/56 (48.2%) infants from carrier mothers. The majority of the transmission was perinatal. There was a very strong correlation between transmission and HBeAg status of the mother (p = 1.85 X 10(-9); odds ratio = 68.44) and to a lesser extent with high titre HBsAg (p = 0.002; odds ratio = 6.38). A strong negative correlation was seen between transmission and anti-HBeAg (p = 8.19 X 10(-7); odds ratio = 0.04). At one year 19 (70.4%) infants were still HBsAg positive while seven (25.9%) lost the antigenemia and acquired anti-HBsAg and one developed HBsAg after one year. It could be calculated that perinatal HBV transmission contributed about 18% to the total pool of HBsAg positive infants of one year of age.

Sporadic cases of haemolytic-uraemic syndrome associated with faecal cytotoxin and cytotoxin-producing Escherichia coli in stools

A cytotoxin active on Vero cells, less active on hela cells, and inactive on WI38 cells (Vero toxin [VT]) was detected in stool isolates of Escherichia coli from 8 of 15 sporadic cases of haemolytic uraemic syndrome (HUS). Stools from 5 of these 8 patients were examined for faecal VT activity, and all were positive. Of the 7 of 15 patients who did not have VT+ E. coli, 2 were positive for faecal VT, and a third (patient K) had strong serological evidence of VT+ E. coli infection. 2 HUS patients, including patient F, had siblings with uncomplicated diarrhoea who had both VT+ E. coli in the stools and faecal VT activity. Thus 11 of 15 (73%) of the HUS cases had evidence of infection by VT+ E. coli, suggesting that there was an association between these organisms and these cases of HUS. The clustering of 2 HUS patients and their siblings with VT+ E. coli accords with this suggestion, as do the rising titres of VT-neutralising antibody in 2 HUS patients.

On the formation of ethoxy alcohols from reaction of trans-1,2-Epoxy-3-methyl-1,3-diphenylbutane and 1,2-Epoxyoctane with boron trifluoride etherate

Reaction of trans-1,2-epoxy-3-methyl-1,3-diphenylbutane (1) with boron trifluoride etherate in benzene gave 3-methyl-2,3-diphenylbutanal (3), shown by deuterium labelling experiments to be formed by C1-O cleavage and alkyl migration, and (1RS,2RS)-l-ethoxy-3-methyl-1,3-diphenyl- butan-2-ol (16) in a process involving retention of configuration at Cl. In ether as solvent the epoxide gave, in addition to aldehyde (3) and ethoxy alcohol (16), 3-methyl-1,3-diphenylbutan-2-one (11) and vinyl ethers (19) and (20). Reaction of 1,2-epoxyoctane (17a) with boron trifluoride etherate in ether gave 1-ethoxyoctan-2-ol (18a) shown by deuterium labelling experiments to be formed by inversion of configuration at C1. The mechanistic implications of these results are discussed.