Mammalian heterogeneous ribonucleoprotein A1 and its constituent domains. Nucleic acid interaction, structural stability and self-association

With a view toward further understanding the structure-function relationships of the eukaryotic heterogeneous ribonucleoprotein (hnRNP) A1, and in particular its multiplicity of nucleic acid-interactive domains, we have studied the nucleic acid binding properties of the globular N-domain (UP1) and sequence-repetitive, flexible C-domain, the thermal denaturation of UP1 and the concomitant effects of binding polynucleotide, and the self-associative properties of the full-length protein. Utilizing protein tryptophan fluorescence as a probe, polynucleotide binding was shown to stabilize UP1 against thermal unfolding. The denaturation profile of UP1-poly(thymidylic acid) complexes was biphasic, suggesting that unfolding of the two subdomains of UP1 can occur independently. This is in agreement with a previously proposed structure in which only one of the two UP1 subdomains binds the nucleic acid. The subdomains of UP1 can be prepared by controlled proteolysis of A1, further indicating that these two globular segments within A1 are connected by an exposed, flexible linkage. Circular dichroism measurements on UP1 confirm previous data that this portion of A1 binds single-stranded nucleic acids non-co-operatively. UP1 clearly shows a preference for single-stranded nucleic acids with a 2'-OH, since its affinity for poly(U) is three times higher than for poly(dU), and five times higher than its affinity for poly(2'-OCH3U). The nucleic acid-interactive properties of the C-domain were further examined by preparing a synthetic peptide polymer (M(r) approximately 12,000) containing about seven repeats of a 16-residue sequence, GNFGGGRGGNYGGSRG, which in turn comprises two copies of the C-terminal consensus, GN(F/Y)GG(G/S)RG. The polymer of this sequence exhibited significant affinity for the fluorescent polyribonucleotide, poly(ethenoadenylic acid), binding stoichiometrically at < or = 0.2 M-Na+. Complex formation was accompanied by an increase in aggregate formation, as indicated by the appearance of scattering. For purposes of comparison, the data were analyzed via the linear co-operative model of McGhee and von Hippel, though this model may not be fully descriptive of the protein-nucleic acid complex(es) formed in this case. In contrast to the non-co-operative binding mode of the UP1 domain, the C-polymer exhibited moderate co-operativity, comparable to that seen with full-length A1. Although addition of sufficient NaCl reversed the interaction, a sigmoidal binding isotherm could still be observed (with sufficient added polymer) at 0.8 M-NaCl. This suggests that non-electrostatic interactions contribute significantly to the free energy of binding.(ABSTRACT TRUNCATED AT 400 WORDS)

Phospholipid biosynthesis in protozoa

Because of the diverse nature of the organisms which are all classed as 'protozoa' (and because of the lack of detailed information on phospholipid metabolism about most of them), it will probably never be possible to generalize phospholipid metabolism to the degree that it has been possible to characterize a mammalian metabolism. Nonetheless, patterns have begun to emerge (i.e. the similarities among the ciliates Entodinium, Paramecium and Tetrahymena) and will not doubt be expanded upon in the future.

A canine model for studying laryngospasm and its prevention

Laryngospasm, if prolonged, can result in serious sequelae due to the lack of a uniformly effective treatment. Prevention, therefore, through pharmacologic intervention, is an attractive concept. In order to study the effects of various drugs in preventing laryngospasm, a reliable animal model capable of producing sequential, repetitive episodes of laryngospasm is necessary. In this study, the canine model of laryngospasm previously described by Aviv, et al. was modified to overcome technical factors which limited its use in this regard. Details of the technique and the results from eight animals will be presented. Results in two animals with the use of prophylactic topical lidocaine will also be discussed. The reliability and reproducibility of this model make it ideal for the study of laryngospasm and open the way for investigation into its prevention.

Severe hypercholesterolemia and atherosclerosis in apolipoprotein E-deficient mice created by homologous recombination in ES cells

apoE-deficient mice have been created by homologous recombination in ES cells. On a low fat, low cholesterol chow diet these animals have plasma cholesterol levels of 494 mg/dl compared with 60 mg/dl in control animals, and when challenged with a high fat Western-type diet, these animals have plasma cholesterol levels of 1821 mg/dl compared with 132 mg/dl in controls. This marked hypercholesterolemia is primarily due to elevated levels of very low and intermediate density lipoproteins. At 10 weeks of age, apoE-deficient mice have already developed atherosclerotic lesions in the aorta and coronary and pulmonary arteries. apoE-deficient mice are a promising small animal model to help understand the role of apoE in vivo and the genetic and environmental determinants of atherosclerosis.

Multistate outbreak of hepatitis A associated with frozen strawberries

A multistate outbreak of hepatitis A was traced to frozen strawberries processed at a single plant. Among 827 students and 60 teachers at an elementary school in Georgia during a 2-week period, 15 developed hepatitis A. Three months later, among 174 residents and 467 staff in an institution for the developmentally disabled in Montana during a 3-week period, 13 developed hepatitis A. Primary attack rates were 10% in the school and 8% in the institution. Cohort analysis in the school implicated consumption of strawberry shortcake in hepatitis A virus (HAV) infection (relative risk, 7.6; 95% confidence interval, 1.04-55.6). In the institution, such analysis implicated desserts and uncooked strawberries as the most biologically plausible vehicle of HAV transmission. Molecular analysis of HAV from patients in the two outbreaks revealed that the viral genomes were genetically identical and distinct from other known US strains. Contamination of food products before retail distribution is rare but should be considered in investigating common-source outbreaks of hepatitis A.

Extensive peptide ligand exchange by surface class I major histocompatibility complex molecules independent of exogenous beta 2-microglobulin

Certain class I major histocompatibility complex molecules expressed on live cells have been shown to bind exogenous peptide ligands. However, it remains controversial whether this binding occurs by peptide exchange or to empty surface class I molecules. In this report we compare the surface binding and dissociation of two virus-derived ligands of the Ld class I molecule of the mouse. The peptide ligands were previously identified in immune responses to cytomegalovirus or lymphochoriomeningitis virus as immunodominant, optimally sized, and Ld restricted. Ligand dissociation was monitored on live cells indirectly by measuring the surface turnover of Ld-peptide complexes or directly by using labeled peptides. The cytomegalovirus-derived and lymphochoriomeningitis virus-derived peptides appeared to dissociate relatively rapidly; however, the cytomegalovirus-derived peptide had a more rapid off-rate than the lymphochoriomeningitis-derived peptide. Furthermore, these rates of dissociation appear to span that seen with endogenous Ld-associated peptides expressed by cells at 37 degrees C. Exploiting the extraordinary accessibility of the surface Ld ligand binding site we developed an assay to quantitate peptide ligand exchange. Cells were precoated with saturating amounts of unlabeled peptide by overnight incubation and were then tested for secondary binding of labeled peptides in a 4-h assay. Our results unequivocally demonstrate the potential for surface class I molecules to undergo peptide exchange. Furthermore, peptide exchange was found to be largely independent of exogenous beta 2-microglobulin. This result implies that beta 2-microglobulin association and not beta 2-microglobulin exchange is the critical factor in peptide exchange by surface class I molecules. Because of the exquisite ability of T cells to discriminate different amounts of ligand bound to class I, the binding of exogenous peptides could play a critical role in normal or aberrant immune responses.

Specificity of lymphocytotoxic antibodies formed after cardiac transplantation and correlation with rejection episodes

Eighty-two patients have been studied to determine the class and specificity of lymphocytotoxic antibodies produced during the 6 months following cardiac transplantation. Weekly serum samples were monitored for panel-reactive lymphocytotoxic antibodies (PRA) and donor reactive lymphocytotoxic antibodies using dithiothreitol to determine immunoglobulin class. Sera containing donor-reactive antibodies were further analyzed in a cytotoxic inhibition assay to determine whether the antibodies were directed against HLA or non-HLA determinants. A total of 67 (82%) of the patients produced detectable PRA following transplantation, no correlation was found between PRA and the incidence and severity of rejection. In 33 cases where an HLA specificity was defined, the antibody was not directed against the donor HLA phenotype. In contrast, the 32 (53%) recipients who had formed donor-reactive antibodies within 6 months of operation had required significantly more antirejection therapy (methylprednisolone) than the crossmatch-negative recipients (P less than 0.01). This was the case for both IgG and IgM responses. Of 24 positive donor responses, 18 were found to be specific for HLA antigens. These were both IgM (6 cases) and IgG (12 cases) HLA-specific antibodies, and their occurrence was strongly correlated with rejection (P less than 0.001).

Polymorphism in the human apolipoprotein A-I gene promoter region. Association of the minor allele with decreased production rate in vivo and promoter activity in vitro

We investigated a common polymorphism in the human apolipoprotein A-I gene promoter at a position 76 bp upstream of the transcriptional start site. 54 human subjects, whose apoAI production rates had been determined by apoAI turnover studies, were genotyped at this polymorphic position by a novel technique using polymerase chain reaction followed by primer extension. 35 subjects were homozygous for a guanosine (G) at this locus and 19 were heterozygous with a guanosine and adenosine (A). The apoAI production rates were significantly lower (by 11%) in the G/A heterozygotes than in the G homozygotes (P = 0.025). In spite of the apparent effect of this apoAI gene promoter polymorphism on the apoAI production rate, there was no effect on HDL cholesterol or apoAI levels. To investigate whether the observed difference in apoAI production rates was related to differential gene expression of the two alleles, promoters containing either allele were linked to the reporter gene chloramphenicol acetyltransferase, and relative promoter efficiencies were determined after transfection into the human HepG2 hepatoma cell line. The A allele expressed only 68% +/- 5% as well as the G allele, a result consistent with the in vivo apoAI production rate data.

4-Amido-2-carboxytetrahydroquinolines. Structure-activity relationships for antagonism at the glycine site of the NMDA receptor

trans-2-Carboxy-5,7-dichloro-4-amidotetrahydroquinolines, evolved from the lead 5,7-dichlorokynurenic acid, have been synthesized and tested for in vitro antagonist activity at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Optimization of the 4-substituent has provided antagonists having nanomolar affinity, including the urea trans-2-carboxy-5,7-dichloro-4[[(phenylamino)carbonyl]amino]-1,2,3, 4-tetrahydroquinoline (35; IC50 = 7.4 nM vs [3H]glycine binding; Kb = 130 nM for block of NMDA responses in the rat cortical slice), which is one of the most potent NMDA antagonists yet found. The absolute stereochemical requirements for binding were found to be 2S,4R, showing that, in common with other glycine-site NMDA receptor ligands, the unnatural configuration at the alpha-amino acid center is required. The preferred conformation of the trans-2,4-disubstituted tetrahydroquinoline system, as shown by X-ray crystallography and 1H NMR studies, places the 2-carboxyl pseudoequatorial and the 4-substituent pseudoaxial. Modifications of the 4-amide show that bulky substituents are tolerated and reveal the critical importance for activity of correct positioning of the carbonyl group. The high affinity of trans-2-carboxy-5,7-dichloro-4-[1-(3-phenyl-2-oxoimidazolidinyl)]- 1,2,3,4-tetrahydroquinoline (55; IC50 = 6 nM) suggests that the Z,Z conformer of the phenyl urea moiety in 35 is recognized by the receptor. Molecular modeling studies show that the 4-carbonyl groups of the kynurenic acids, the tetrahydroquinolines, and related antagonists based on N-(chlorophenyl)glycine, can interact with a single putative H-bond donor on the receptor. The results allow the establishment of a three-dimensional pharmacophore of the glycine receptor antagonist site, incorporating a newly defined bulk tolerance/hydrophobic region.

Invasive Haemophilus influenzae disease in adults. A prospective, population-based surveillance. CDC Meningitis Surveillance Group

OBJECTIVE

To define the incidence of and possible risk factors for invasive Haemophilus influenzae disease in adults.

DESIGN

Prospective, population-based surveillance of hospital and referral bacteriology laboratories.

SETTING

Metropolitan Atlanta, Georgia community.

PATIENTS

All patients with H. influenzae isolated from normally sterile sites (blood, cerebrospinal fluid, joint, pleura) from 1 December 1988 through 31 May 1990.

MEASUREMENTS

Isolates of H. influenzae were analyzed for serotype and biotype status, outer membrane proteins, lipooligosaccharide phenotypes, ribotyping patterns and beta-lactamase production.

RESULTS

A total of 194 cases of invasive H. influenzae occurred (annual incidence of 5.6 cases/100,000 population), of which 47 (24%) were in adults 18 years old or older (annual incidence 1.7 cases/100,000 adults). Adults with invasive H. influenzae ranged from 18 to 96 years; 79% were women. Bacteremic pneumonia accounted for 70% of the adult cases. Other sources for invasive H. influenzae in adults were obstetric infections, epiglottitis, and tracheobronchitis; one patient had meningitis. Underlying conditions were noted in 92% of the patients. Chronic lung disease was the most common risk factor, but pregnancy (annual incidence, 4.9/100,000 pregnant women), HIV infection (annual incidence, 41/100,000 known HIV-infected adults), and malignancy were also important. Overall mortality was 28% in adults, and over half of pregnancy-related infections resulted in fetal death. Fifty percent of the 40 isolates available for testing were serotype b; 47.5%, nontypable; and 2.5%, serotype f. Sixteen of the 45 isolates (36%) were ampicillin-resistant. Based on biotypes, outer membrane protein profiles, lipooligosaccharide phenotypes, and ribotyping patterns, the type b isolates showed less heterogeneity than the nontypable isolates but were distinguishable from one another.

CONCLUSIONS

Adult cases currently represent one quarter of all cases of invasive H. influenzae disease. Half of the reported adult cases were caused by type b H. influenzae, and the rate of ampicillin resistance in H. influenzae isolates from adults was higher than previously reported. Haemophilus influenzae is an important cause of bacteremia in compromised adults.

Feeding studies in rats with mineral hydrocarbon food grade white oils

This investigation compared the effects of feeding rats diets containing food grade white oil processed by either conventional oleum treatment or the more modern method of catalytic hydrogenation. In two separate experiments, male or female Fischer-344 rats were given free access for 90 days to diets containing 0, 10, 100, 500, 5,000, 10,000, or 20,000 ppm of either oleum-treated white oil (OTWO) or hydrotreated white oil (HTWO). There were no mortalities and no adverse clinical signs associated with feeding either white oil. Treatment-related effects evidenced by hematological, clinical chemical, and pathological changes were generally dose-related and more marked in female than in male rats, and the OTWO caused a greater pathological response than the HTWO. Tissue residues of saturated hydrocarbons were up to 5.2 times higher in female rats than in males. Rats fed 5,000 ppm or more of either white oil showed dose-related alterations in several hematological and clinical chemistry variates associated mainly with hepatic damage or functional alteration. At necropsy, mesenteric lymph nodes were enlarged, and increases in weight of liver, kidney, and spleen were significant. Microscopic changes were characterized by multifocal lipogranulomata in mesenteric lymph node and liver. No changes were observed in rats fed OTWO or HTWO for 90 days at dietary concentrations of 10 or 100 ppm, equivalent to a minimum intake of 0.65 and 6.4 mg/kg/day, respectively. Differences in degree of pathological response associated with each oil may have been due to their differences in specification rather than processing method.

Kynurenic acid analogues with improved affinity and selectivity for the glycine site on the N-methyl-D-aspartate receptor from rat brain

The glycine site on the N-methyl-D-aspartate (NMDA) subtype of receptors for the excitatory neurotransmitter glutamate is a potential target for the development of neuroprotective drugs. We report here two chemical series of glycine site antagonists derived from kynurenic acid (KYNA), with greatly improved potency and selectivity. Disubstitution with chlorine or bromine in the 5- and 7-positions of KYNA increased affinity for [3H]glycine binding sites in rat cortex/hippocampus P2 membranes, with a parallel increase of potency for antagonism of NMDA-evoked responses in the rat cortical wedge preparation. The optimal compound was 5-I,7-Cl-KYNA, with an IC50 for [3H]glycine binding of 29 nM and an apparent Kb in the cortical wedge preparation of 0.41 microM. Reduction of the right-hand ring of 5,7-diCl-KYNA reduced affinity by 10-fold, but this was restored by substitution in the 4-position with the trans-phenylamide and further improved in the trans-benzylamide. The optimal compound was the transphenylurea (L-689,560), with an IC50 of 7.4 nM and an apparent Kb of 0.13 microM. Both series of compounds displayed a high degree of selectivity for the glycine site, having IC50 values of greater than 10 microM versus radioligand binding to the glutamate recognition sites of NMDA, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), and kainate receptors and the strychnine-sensitive glycine receptor. Selectivity versus AMPA receptor-mediated responses was also apparent in the rat cortical wedge and in patch-clamp recordings of cortical neurons in culture. Experiments using [3H]dizocilpine (MK-801) binding indicated that 5,7-diBr-KYNA, 5,7-diCl-KYNA, 5-I,7-Cl-KYNA, and L-689,560 all behaved as full antagonists and were competitive with glycine. Patch-clamp recordings of cortical neurons in culture also indicated that NMDA-induced currents were antagonized by competition for the glycine site, and gave no evidence for partial agonist activity. pKi values for 5,7-diBr-KYNA and L-689,560 in these experiments were 7.2 and 7.98, respectively, similar to the affinities of these compounds in the glycine binding assay. The high affinity and selectivity of these new derivatives make them useful tools to investigate the function of the glycine site on the NMDA receptor.

Reversible renal failure in the nephrotic syndrome

Acute, usually reversible, renal failure has been observed in patients with normal or minimally altered glomeruli on renal biopsy. This review aims to examine the clinical features of acute renal failure in these patients and to evaluate factors that may contribute to the reduction in glomerular filtration rate (GFR). In an analysis of 79 cases affecting 75 patients reported in the English literature since 1966, with acute renal failure associated with minimal change disease or mild histopathological changes in glomeruli, the average age was 58 +/- 2 years (mean +/- 5 SEM), urine protein excretion 11.6 +/- 0.6 g/d, and serum albumin level 19 +/- 1 g/L (1.9 +/- 0.1 g/dL). Acute renal failure was documented an average of 29 +/- 5 days after onset of nephrotic syndrome, and persisted for 7 weeks in 62 episodes in the 58 patients in whom recovery of renal function occurred. Fourteen patients died of uremia or required chronic dialysis, and 3 were lost to follow-up. Although plasma volume depletion was sometimes cited as the cause of renal failure, objective signs of hypovolemia were not documented and most patients did not improve after treatment designed to correct volume deficits. In contrast, histopathological changes consistent with acute tubular necrosis (ATN) were observed in at least 60% of cases. Since the pathogenesis of acute renal failure in minimal change nephrotic syndrome is unknown, we evaluated hemodynamic determinants of GFR in patients with minimal change disease with normal or near-normal renal function, and in relevant animal models, to obtain insights into the effect of nephrotic syndrome on GFR. Although acute renal failure is uncommon, GFR is reduced concurrently with nephrotic syndrome in approximately 30% of children and adults. Absolute and effective blood volume and renal plasma flow are relatively well preserved. However, clinical and experimental observations suggest that the glomerular ultrafiltration coefficient may be reduced by as much as 50%. These findings, together with renal biopsy changes in cases with acute renal failure, suggest that severe reductions in GFR in some patients with minimal change nephrotic syndrome may result from an interaction between acute ischemic tissue injury and preexisting intrinsic renal abnormalities.

Disparate interaction of peptide ligand with nascent versus mature class I major histocompatibility complex molecules: comparisons of peptide binding to alternative forms of Ld in cell lysates and the cell surface

To determine the mechanism and structural consequences of peptide binding to class I molecules, we have studied the Ld molecule of the mouse. Previous studies have shown that a significant proportion of surface and intracellular Ld molecules can be detected in an alternative conformation designated Ldalt. Ldalt molecules are non-ligand associated and show weak if any beta 2-microglobulin (beta 2m) association. We report here that Ld molecules have a relatively rapid surface turnover compared with other class I molecules and that exogenous peptide dramatically prolongs Ld surface half-life. By contrast, Ldalt molecules are stably expressed on the surface and their half-life is unaffected by exogenous peptide. To study the surface interaction of peptide with Ld, live cells were incubated with iodinated peptides and Ld molecules were precipitated from cells precoated with monoclonal antibody before lysis. Using this assay, peptide binding to surface Ld molecules was found not to depend upon exchange with exogenous beta 2m, but did correlate with the level of beta 2m association. To study the intracellular interaction of peptide with Ld, cell lysates were used. In cell lysates, peptide was found to convert Ldalt molecules to properly folded Ld. This peptide-induced folding was almost complete at earlier but not later time points in pulse-chase analyses. Furthermore, conversion of Ldalt to Ld was found to affect almost exclusively immature (Endo Hs) class I molecules. Thus intrinsic properties of immature Ldalt molecules or their associated chaperonins are maintained in cell lysates that allow them to undergo de novo folding in vitro. These combined results demonstrate that immature Ldalt molecules are precursors awaiting constituents such as peptide and beta 2m that influence folding, whereas surface Ldalt molecules appear refractory to association with peptide, beta 2m, and consequent folding.

Treatment outcomes of impaired physicians in Oklahoma

Data on one hundred twenty impaired physicians were analyzed to determine treatment outcomes from three differing types of chemical dependency treatment. The data showed that long-term (three to four months) treatment geared specifically to health care professionals was the most effective treatment modality, showing higher rates of favorable treatment outcomes measured by abstinence from alcohol and other drugs.

Binding of substituted and conformationally restricted derivatives of N-(3-phenyl-n-propyl)-1-phenyl-2-aminopropane at sigma-receptors

Certain benzomorphans, such as N-allylnormetazocine, are classical "sigma-opiates" that bind both at sigma and phencyclidine (PCP) binding sites with modest affinity. Recently, we identified N-substituted 2-phenylaminoethane as being the primary sigma-pharmacophore of the benzomorphans and demonstrated that 1-phenyl-2-aminopropane (2) derivatives, depending upon their terminal amine substituents, constitute a novel class of high-affinity sigma-selective agents. With this pharmacophore, it is shown in the present investigation that the aromatic hydroxyl group (a prime feature of all the sigma-opiates) contributes little to the binding of 2 at sigma-sites. It is also demonstrated that an N-substituted aminotetralin moiety (such as 17, a conformationally restricted analogue of 2) may also be considered a sigma-opiate pharmacophore. Unlike the sigma-opiates, derivatives of 2 and 17 display no affinity for PCP sites and must consequently lack those structural features important for the binding of benzomorphans at PCP sites. Because 3-phenylpiperidines and related sigma-ligands also possess a phenylalkylamine imbedded within their structures, we propose that the 2-phenylaminoethane moiety is a common sigma-pharmacophore for derivatives of 2, the 3-phenylpiperidines, and the sigma-opiates.

Identification and exploitation of the sigma-opiate pharmacophore

Certain benzomorphan "sigma-opiates" such as N-allylnormetazocine (NANM) bind at sigma receptors with modest affinity and with little selectivity (i.e., they also bind at phencyclidine or PCP sites). In order to identify the primary pharmacophore of the benzomorphans, we prepared several amine-substituted derivatives of 1-phenyl-2-aminopropane. Several simple alkyl-substituted analogues were shown to bind at sigma sites with affinities comparable to that of NANM itself; among these was the N-benzyl derivative 9 (Ki = 117 nM). Lengthening the spacer between the terminal amine and the phenyl group from one to five methylene units resulted in a significant increase in affinity (e.g. 15, Ki = 6.3 nM). In addition, unlike the benzomorphans, these phenalkylamines do not bind at PCP sites. The results of the present study reveal that (a) the 1-phenyl-2-aminopropane nucleus of the benzomorphans is sufficient for binding at sigma sites provided that the terminal amine is not a primary amine and that (b) introduction of (phenylalkyl)amine substituents affords compounds that represent a new class of high-affinity sigma-selective agents.

Effect of movement and position on muscle activity in tension headache sufferers during and between headaches

This paper presents the results of two studies. In the first, 20 tension headache subjects were evaluated in both a headache and non-headache state on bilateral trapezius and unilateral frontalis electromyographic activity during six positions: standing, bending from the waist, rising, sitting with back unsupported, sitting with back supported, and prone. Results indicated no effect of headache state on either measure. In a second study, 11 of the tension headache sufferers in Study One and 11 age-matched controls were compared on the same measures (controls were assessed two times, with a one-week duration separating evaluations). Results indicated a diagnosis by position interaction, with post-hoc tests revealing the muscle activity of tension headache sufferers to be considerably higher during the prone position than that of non-headache controls. Non-significant trends were found when examining the data for clinically significant abnormalities (90% of the headache sufferers were found to have significant clinical abnormalities).

Cerebral-blood-flow-velocity measurements in neonates: technique and interobserver reliability

The interobserver reliability for absolute cerebral-blood-flow-velocity measurements by colour and duplex Doppler sonography was tested in 32 neonates with a mean birth weight of 1489 (SD 644) g, and a gestational age of 29.9 (SD 3.5) weeks. Using standardized technique, two observers recorded on videotape, the Doppler spectrum of the anterior cerebral artery, the intracranial internal carotid artery and the middle cerebral artery. Peak systolic flow, end diastolic flow, mean flow velocity, resistive index and pulsatility index were computed from 3 consecutive waveforms by each observer. The estimates of interobserver reliability using the intraclass correlation coefficient of the examiners varied from 0.95 to 1.00. Therefore, cerebral blood flow velocity can be reliably measured in premature infants.