[The role of MRI in the valuation of disorders involving the bone marrow]

MR is the most accurate imaging technique in bone marrow evaluation since it allows to recognize and distinguish its red and yellow components. MR shows high sensitivity but low specificity. At present, its role in bone marrow diseases evaluation is that of depicting the extent of the disease process and monitoring the effects of treatment.

Molecular bases of hexokinase deficiency

Hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1; HK) deficiency is a rare disease where the predominant clinical effect is nonspherocytic hemolytic anemia. We have previously shown that the only patient for which hexokinase deficiency has been so far investigated at molecular level is a double heterozygote carrying a T1667 --> C substitution on one HK type I allele and a 96 bp deletion (concerning nucleotides 577 to 672 in the HK cDNA sequence) in the other allele. To investigate whether these mutations found in the patient with the hexokinase variant referred to as 'HK-Melzo' could be associated with hexokinase deficiency, we have expressed in E. coli the wild-type human hexokinase type I and two different mutants carrying the T --> C nucleotide substitution at position 1667 and the nt 577-672 deletion, respectively. Wild-type human recombinant hexokinase is expressed in bacterial cells as a soluble catalytically active enzyme that, upon purification to homogeneity, exhibited the same kinetic properties of human placenta hexokinase type I. Both mutant hexokinases were also expressed as soluble recombinant proteins under the same conditions, but they showed an impaired catalytic activity with respect to the wild-type enzyme. In particular, the T1667 --> C substitution, causing the amino acid change from Leu529 to Ser, is responsible for the complete loss of the hexokinase catalytic activity, while the 96 bp deletion causes a drastic reduction of the hexokinase activity. Taken together, both mutations explain the hexokinase deficiency found in the patient with the 'HK-Melzo' variant.

Isometric handgrip exercise increases endothelin-1 plasma levels in patients with chronic congestive heart failure

This study demonstrated an immediate and short-lasting endothelin-1 release in the circulation of patients with severe chronic congestive heart failure during isometric handgrip exercise, but not in normal subjects. Our data suggest that endothelin-1 levels may increase transiently during daily physical activity, thus contributing to progressive deterioration of left ventricular function.

Benign paroxysmal positional vertigo of posterior semicircular canal: results in 160 cases treated with Semont's maneuver

One hundred sixty patients affected by benign paroxysmal positional vertigo of the posterior semicircular canal were treated with Semont's maneuver. Complete recovery after only one session was achieved in more than 50% of cases. After a maximum of five sessions, almost all patients had recovered; only 8 needed another kind of rehabilitation. No drug therapy was required for any patient.

[Artificial ventilation in children during anesthesia]

The authors describe the advantages and disadvantages, the indications and benefits on gas exchange as a result of mechanical ventilation during anaesthesia. The two models of ventilation most commonly used have been analyzed: pressure ventilators and volume preset ventilators. The former are used only in cases of short-term anaesthesia or when volume ventilators are not available. Both the most appropriate settings and ventilatory modes have been discussed regarding different paediatric ages. Particular attention has been given to the oxygen concentration in the ventilated gases (oxygen toxicity > 40%) and to barotrauma connected with high peak pressure (> 30 cm H2O). The authors suggest the type and caliber of endotracheal tube and the tidal volume for paediatric ages.

Lipomatous tumors of the uterus: ultrasonographic findings in 11 cases

We reviewed the ultrasonographic findings in eight patients with 11 lipomatous uterine tumors studied with transabdominal (eight cases) and transvaginal (six cases) techniques. A transvaginal color Doppler study was obtained in five patients. Two patients had more than one nodule (two and three uterine nodules, respectively). All lipomatous tumors had regular margins and were hyperechoic. Transvaginal sonography allowed the identification of one small previously undetected tumor but was not able to image the entire extent of two large lipomatous masses. In one case, it helped to establish the actual uterine origin of an eccentric pelvic mass. Color Doppler sonography showed complete absence of flow in all tumors examined. We believe that lipomatous tumors of the uterus can be diagnosed with a high degree of certainty by ultrasonography if a homogeneously hyperechoic avascular mass can be clearly identified to be of uterine origin.

High resolution sonography of the flexor tendons in trigger fingers

A sonographic study was conducted to analyze changes of the flexor tendons in patients with trigger fingers. We evaluated thickness and echotexture of the flexor tendons of the fingers in 54 patients with 66 symptomatic digits using 10 and 13 MHz "small parts" transducers; the results were compared with those observed in 20 normal controls. Images were obtained on the volar surface of the hand, at the head of metacarpals, and at the base of first phalanx, where the first annular pulley of the digital canal is located and where the changes occurring during passive assisted extension of the fingers were evaluated. Normal tendons were 2.9 to 4.4 mm thick (mean, 3.71 +/- 0.46) and had fibrillar echotexture. Patients had tendons ranging from 3.8 to 6.7 mm (mean, 5.41 +/- 0.94); the difference from controls was highly significant (P < 0.001). A cyst was attached on the volar surface of the involved tendons in 15 cases. Diffuse thickening of the synovial sheath was present in 20 tendons, whereas 17 tendons had irregular internal echotexture. Extension movements caused changes in shape of both cysts and peritendinous envelopes. In conclusion, sonography seems able to identify a variety of pathologic changes affecting tendons in these patients and may help both to explain the pathophysiology of their clinical situation and guide therapeutic decisions.

High-level expression and purification of a human "mini"-hexokinase

Human hexokinase type I is a 100-kDa enzyme with the catalytic site located in the C-terminal domain. We had previously expressed this domain in Escherichia coli, however only a small amount of the recombinant enzyme was catalytically active. To overcome this problem we have now expressed the "mini"-hexokinase using the pET expression system. An average of 1000 U of enzyme per liter of culture was obtained. The recombinant enzyme was purified to homogeneity by a combination of ion-exchange chromatography, affinity chromatography, and dye-ligand chromatography. The enzyme was unstable under ultrafiltration; thus, a multicolumn purification procedure was developed in order to avoid the ultrafiltration steps. The recombinant "mini"-hexokinase was found to have the same kinetic properties as the entire enzyme. Using the method described, the enzyme can be obtained in sufficient quantities for biophysical and biochemical investigations.

Compliance to compulsory vaccination: strategies and results

This report is devoted to analyze the effect that compulsory vaccination has on the compliance of the population, compared with the results obtained by massive campaigns for optional vaccinations. The implementation of a specific software for the management of individual schedules helps to reach a substantial complete coverage of the individuals for the first ones, while improving but incomplete results regard the vaccines against pertussis and measles-mumps-rubella, optional in Italy. The optimization of data management at the local health unit level improves the quality and the satisfaction of the work performed by the personnel, but has a limited effect on the already nearly complete coverage for the compulsory immunizations. The mounting percentage of children immunized with optional vaccines can be explained both by the massive campaigns of information conducted in recent years and by the better tracking of individual immunization schedules.

[Retrospective analysis of color Doppler ultrasonography and flowmetry findings in solid nodular pathology of the breast]

The authors tried to identify useful flowmetric values and color-Doppler patterns for the differential diagnosis between benign and malignant solid breast lesions. To this purpose, 106 patients with breast nodules detected at mammography and/or high resolution US were examined. A US scanner with a linear 7.5 MHz transducer, a narrow sample volume, a PRF ranging (650-800 Hz) and a wall filter value of 50 Hz were used. Three parameters were considered: the number vascular sites, systolic peak velocity and pulsatility index. All these parameters related to tumor volume. Several (> 2) vascular sites, high peak velocity and quite high pulsatility index were demonstrated in malignant tumors (46 lesions). Among benign tumors no vascular site was identified in 32 of 60 lesions and no more than 2 sites were identified in 26 of 60 lesions, except for 2 phylloides tumors. Sensitivity, specificity, positive and negative predictive values and overall accuracy rates were, as for the "vascular sites" parameter, 78%, 96%, 94%, 85%, 88%, respectively; as regards the "peak systolic velocity" 81%, 86%, 89%, 75%, 83% respectively; as regards the "pulsatility index" 100%, 85%, 100%, 85%, 94% respectively.

The soluble but not mitochondrially bound hexokinase is a substrate for the ATP- and ubiquitin-dependent proteolytic system

Intracellular protein degradation is highly selective, however, the mechanism(s) underlying this selectivity are not fully understood. We have previously shown that purified rabbit hexokinase type I, an enzyme present in mammalian brain both in soluble and mitochondrial bound form, is conjugate to ubiquitin and then degraded by a rabbit reticulocyte fraction II. In the present study we report that the mitochondrial bound hexokinase is stable for several hours in the same proteolytic system both in the presence or absence of ATP. E1, E2 and E3, the enzymes of the ubiquitin conjugating system, are able to incorporate 125I- or biotin-labelled ubiquitin in an ATP-dependent manner in soluble hexokinase as well as in a number of mitochondrial proteins. Furthermore, the mitochondria by themselves have a pronounced ATP-dependent ability to conjugate 125I-ubiquitin. However, Western blotting experiments, using a specific antibody against hexokinase, or against ubiquitin, showed that the mitochondrial bound enzyme is neither ubiquitinated nor degraded. This result has been confirmed by purification of bound hexokinase from the brain mitochondrial fraction or following the incubation of intact mitochondria with ATP, 125I-ubiquitin and E1, E2 and E3. Thus, mitochondrial bound hexokinase is not recognized by the ubiquitin conjugating system while the soluble enzyme is conjugate to ubiquitin and then degraded. Furthermore, the soluble hexokinase from rabbit brain was isolated by immunoaffinity chromatography and shown to be recognized by an anti-ubiquitin antibody. These results suggest that the intracellular distribution of protein is an important feature of a protein which determines its susceptibility to ubiquitin-dependent degradation.

[Influence of antihypertensive therapy on the "white coat effect"]

The aim of this study was to evaluate the alarm reaction when hypertensive patients either receiving or not receiving drug therapy have their blood pressure measured (the so-called "White coat effect"). A group of 64 patients (38 males and 26 females, mean age 52 +/- 11 years, OMS stage I-II) was studied. Twenty-three patients were not receiving antihypertensive therapy, 41 patients were regularly taking antihypertensive therapy prescribed by their own doctors. Non-invasive monitoring of arterial pressure (AP) and heart rate (HR) was carried out in all patients. The following parameters were examined in this study: mean of 3 measurements of AP and HR before monitoring (CAP, CHR), daily mean of AP and HR monitoring (MAP, MHR). The following results were obtained: 1) non-treated patients, CAP 157/108 +/- 19/11 mmHg, CHR 83 +/- 11 b/min, MAP 155/100 +/- 20/7 mmHg, MHR 76 +/- 7 b/min; 2) treated patients, CAP 151/96 +/- 21/16 mmHg, CHR 73 +/- 16 b/min, MAP 142/86 +/- 15/12 mmHg, MHR 70 +/- 10 b/min. The two-tailed "t"-test for paired data showed a statistically significant difference (p < 0.001) between diastolic CAP and diastolic MAP in both groups of patients. Systolic CAP was significantly greater than systolic MAP in treated patients (p < 0.01), whereas CHR was significantly higher than MHR in non-treated patients (p < 0.001). These data demonstrate that the alarm reaction to measuring blood pressure is present in both treated and non-treated hypertensive patients. Antihypertensive treatment appears to lessen the chronotropic but not the pressure response to measurement of AP in a hospital setting.

[Doppler color-echo and flowmetric evaluations in ovarian tumors in postmenopausal patients]

The use of color Doppler techniques in transvaginal sonography (US) permitted the identification of some typical flowmetric patterns of malignant ovarian cancers, because of such characteristics of neoplastic vessels as no media in the vessel wall, the presence of A-V shunts, and so on. These features reduce vascular impedance, from which low pulsatility index and resistance index values result. Eighty-one patients with ovarian masses were examined: in 19 of them histopathology revealed malignant lesions in different stages. Eighteen of those lesions exhibited suspect transvaginal patterns; in one case only the US patterns suggested a benign lesion, which was a serous cystadenocarcinoma with thin and regular septa. In all the malignant lesions flow could be sampled in six sites at least; the lowest pulsatility index values, obtained by multiple samplings in the same lesion, were considered as the most representative of the histologic features of the lesion. The average of the lowest pulsatility index values in 18 of 19 malignant lesions was 0.75. In one case only (the only false negative in the series) the lowest pulsatility index value was 1.20. Doppler signals were detected in 58 of 62 benign lesions only and the average of the lowest pulsatility index values was 1.80. The only kind of condition with low pulsatility index was the inflammatory disease (all the 6 sampled cases). If we consider a pulsatility index < 1 as the cut-off value for malignant lesions, the sensitivity and the specificity of color Doppler US were 95% and 91%, respectively, in our series. The positive predictive value of the exam was 75% and its negative predictive value was 95%.

Auditory evoked potentials at 40 Hz (SSR40Hz) in post-trauma coma patients

The authors evaluated auditory evoked steady state rest potentials at 40 Hz (SSR40Hz) in 21 post-trauma coma patients and compared their predictive value for prognosis of survival and quality of life with the results of the electroencephalogram (EEG), the computed tomography (CT) scan, and the Glasgow Coma Scale. SSR40Hz potentials recorded immediately after trauma had a maximum (100%) sensibility and specificity for a fetal prognosis and a high value for life prognosis. Consequently they appear to be a useful parameter for deciding on organ explant procedures. The EEG was more reliable in predicting a quality of life prognosis.

[Voluntary dilating pneumosinus (secondary hernia)]

In the present work authors describe an unusual case of pneumosinus dilatans caused willingly by a patient himself operated on a frontal-ethmoidal mucocele. They take the opportunity to summarize what it is known about the etiopathogenesis and the form of display of this uncommon disease.

[The use and the potential of auditory electrophysiology in patients in posttraumatic coma]

21 patients in post-traumatic coma status were submitted to a auditory electrophysiological valuation together with EEG, TC, and "Glasgow Coma Scale" (GCS) with the purpose to obtain the relative prognostic value quoad vitam and quoad valetudinem. In particular it was carried out the brainstem auditory evoked potentials (ABR) and the auditory middle latency potentials (MLR and SSR-40 Hz). 12 patients survived and their clinical conditions were classified according to the "Glasgow Outcome Scale"; 9 of 21 patients died. With the aim of quoad vitam prognosis, the ABR showed a good reliability whereas GCS, EEG, TC and MLR proved not much usefulness. On the contrary the absence of SSR-40 Hz always coincided with the subsequent patients death. With the aim of GOS a meaningful relationship was found between the clinical outcome conditions from coma and the improvement in MLR and EEG.

Intracellular distribution of hexokinase in rabbit brain

Hexokinase in mammalian brain is particulate and usually considered to be bound to the outer mitochondrial membrane. Investigation of rabbit brain mitochondria prepared either by differential centrifugation and discontinuous density gradient centrifugation has provided evidence that this particulate fraction also contains endoplasmic vesicles and synaptosomes. Solubilization of the bound hexokinase by different combinations of detergents and metabolites has proved the existence of different hexokinase binding sites. Electron microscopic examination of hexokinase location by immuno-gold labelling techniques confirmed that hexokinase is indeed predominantly bound to mitochondria but that a significant proportion is also bound to non-mitochondrial membranes. Attempts to quantify this distribution were unsuccessful since different figures were obtained using anti-hexokinase IgG affinity purified on immobilized native or denatured hexokinase. Binding studies of the purified rabbit brain mitochondrial hexokinase to rabbit liver mitochondria and microsomes confirmed that in addition to a binding site on mitochondria there is another binding site on microsomes. The N-terminal sequence of hexokinase has been shown to be important for mitochondria binding and also for microsome binding. These results suggest that the intracellular localization of hexokinase in rabbit brain is not exclusively mitochondrial and that the metabolic role of this enzyme should be reconsidered by including a binding site on the endoplasmic reticulum.

Acoustic structure of vocalization and stapedius muscle activity during vocal development in chickens (Gallus gallus)

The link between stapedius muscle activity and acoustic structure of vocalization was analysed in cocks of age 20-30 to 90-100 days old. The results show that stapedius muscle activation depends on the acoustic structure of vocalization and changes during vocal development. This dependence was observed in spontaneous calls and in vocalizations elicited by stimulating the mesencephalic "calling area". In 30-day-old cocks stapedius muscle EMG response is never associated with vocalizations with an acoustic energy content which is always distributed at frequencies higher than 2000 Hz. The coupling between vocalization and stapedius muscle activity begins later, when birds produce vocalizations with acoustic energy shifted towards lower frequencies. Overall, stapedius muscle activity is related to a bird's production of high amplitude low frequencies. These results support the hypothesis that the primary role of the stapedius muscle during normal vocal development is to dampen the amplitude of low frequency energy that reaches the cochlea during vocalization.

[The role of echography in osteolytic tubercular abscesses]

Tubercular abscesses are relatively common complications of tubercular spondylodiscitis. Fifty-one patients with suspected abscesses were selected from a group of 97 patients with tubercular spondylodiscitis and submitted to US. In 10 cases CT was performed before US and detected 7 abscesses, all of them confirmed by US. In the extant 41 cases, CT followed US; in 13 cases only US poorly visualized ilio-psoas muscles. As for the group of 23 patients who underwent both CT and US, if the former method is assumed as the reference gold standard, overall US sensitivity is 97% (1 false negative) and its specificity is 100%. In all cases where US findings were accurate and specific enough, CT was not performed; the patients were followed every seventh month and no abscesses found. US showed abscesses in the iliac fossa in 20 cases, along the psoas fascia in 6 and in the thighs in 3 cases. Two cases of gluteal localization were observed, together with 1 Grynfelt's triangle abscess, 1 Petit's triangle and 1 Scarpa's triangle abscesses; finally, 1 abscess was found in the knee. The most common appearance of tubercular abscesses is a hypoechoic and inhomogeneous pattern; sometimes caseum makes the abscess solid and hyperechoic. Calcifications were unusual in our series. All patients were submitted to percutaneous drainage under US guidance. The results proved US to allow the early and unquestionable diagnosis of tubercular abscesses and to confirm clinical suspicion. Moreover, US is also useful to guide percutaneous drainage and to follow the patients after drainage. As for CT, it remains the method of choice to depict vertebral involvement, but, in our series, it exhibited no significant advantages over US in the study of abscessual lumbar collections.

Carotid body tumors: US evaluation

The ultrasound (US) findings in 20 patients with 23 carotid-body chemodectomas were reviewed. Twenty-two of 23 tumors could be seen at US; the remaining lesion could not be differentiated from surrounding enlarged lymph nodes resulting from thyroid cancer. The lesions were solid, slightly heterogeneous masses that ranged in size from 1.2 to 5.0 cm and were located within the carotid bifurcation. Pulsed Doppler analysis of blood flow within the tumor mass was possible in eight patients with nine chemodectomas, and low-resistance waveforms were obtained from multiple sites within the mass in all cases. The diagnostic possibility of a chemodectoma has to be considered when a solid mass is detected within the carotid bifurcation. On the basis of these findings, as US diagnosis was possible in 18 of 20 patients in the authors' series. Doppler analysis of the mass to evaluate intratumor blood flow is helpful in differentiating chemodectomas from other solid, nonhypervascular masses.

Evidence for a particulate location of ubiquitin conjugates and ubiquitin-conjugating enzymes in rabbit brain

Conjugate ubiquitin was previously found in the nucleus, cytoplasm, and membranes of eukaryotic cells while the enzymes of the ubiquitin-conjugating system appear to be cytoplasmic. We have prepared the mitochondrial fraction from rabbit brain by discontinuous density gradient ultracentrifugation and by Western blotting, using a specific antibody against conjugate ubiquitin, showing that it contains ubiquitin conjugates in a very wide molecular weight range. Electron microscopy and measurement of specific enzyme markers show that this fraction not only contains mitochondria but also some endoplasmic reticulum vesicles. Immunostaining with anti-ubiquitin IgG followed by immunodecoration with colloidal gold particles provides evidence for the presence of conjugate ubiquitin both in mitochondria and in the endoplasmic reticulum. Furthermore, this "mitochondrial fraction" shows a pronounced ATP-dependent ability to conjugate 125I-ubiquitin into a number of endogenous proteins as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Addition of E1, E2, and E3, the enzymes of the ubiquitin conjugating system purified from rabbit reticulocytes, does not further increase this ubiquitination nor incorporate 125I-ubiquitin into additional protein bands. The same mitochondrial fraction is not able to carry out any ATP-dependent degradation of 125I-albumin; however, it contains an isopeptidase activity able to release the covalently incorporated 125I-ubiquitin and is also able to conjugate 125I-ubiquitin to exogenous proteins as oxidized RNase. By affinity chromatography on ubiquitin-agarose of fraction II of a crude Triton X-100 extract of the mitochondrial fraction, several proteins corresponding in Mr to the E1 and E2s enzymes were obtained. These proteins were also able to form specific ubiquitin-thiol ester bounds on sodium dodecyl sulfate-polyacrylamide gels and to support 125I-ubiquitin conjugation to oxidized RNase. Detergent fractionation of the mitochondrial fraction provided evidence for a possible localization of the ubiquitin conjugating activity in the mitochondrial external membrane and endoplasmic reticulum. The presence of an active ubiquitin protein conjugating system in mitochondria and endoplasmic reticulum may be related to the turnover of organelle proteins as well as to specific cell functions such as import of proteins into mitochondria and ubiquitination of externally oriented membrane-bound proteins.

Human hexokinase type I microheterogeneity is due to different amino-terminal sequences

Human placenta hexokinase type I was previously shown to be present in two subtypes with similar isoelectric points but different molecular masses of 112 and 103 kDa, respectively. In order to exclude that these subtypes arise by artifact(s) occurring during the protein purification, we have developed a single-step immunoaffinity chromatography for the isolation of microgram quantities of hexokinase. The results obtained confirmed the presence of both hexokinase subtypes in human placenta. By Northern blot analysis a single mRNA species that hybridized with a hexokinase-I cDNA was found to be present in human placenta. Furthermore, in vitro translation of placenta mRNA in a rabbit reticulocyte lysate followed by hexokinase immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography showed that only one hexokinase with apparent molecular mass of about 112 kDa is expressed in this tissue and suggests a post-translational modification as a probable cause of hexokinase I microheterogeneity. To further investigate this point we have purified the high and low Mr hexokinase and determined their NH2-terminal sequences. The results obtained show that when compared with the amino acid sequence deduced from a cDNA the high Mr hexokinase starts at amino acid 11 while the low Mr hexokinase starts at amino acid 103. Since the first 10 amino acids are involved in the binding of hexokinase to mitochondrial porin these data provide an explanation both for the inability of these hexokinases to bind to mitochondria and for their differences in Mr.

Whole-blood filterability in sudden deafness

Sixteen patients with sudden deafness (SD), diagnosed on the basis of a battery of audiometric tests, but with no other medical or surgical pathology requiring drug treatment, underwent monitoring of their hemorheological profiles to see whether disturbances in the microcirculation could be linked to SD. Plasma viscosity, the filterabilities, (using a low-shear positive pressure system) through 5-microns-diameter pore Nuclepore filters, of whole blood and red and unfractionated white cells were monitored in 16 SD patients and 32 controls matched for age, sex and socioeconomic status. Whole blood filterability and the filterability of the red blood cells were significantly impaired in the SD patients, which suggests that alterations in the microcirculation are linked, in some way, to sudden deafness.

Preparation and characterization of monoclonal antibodies to human hexokinase type I

1. Three different immunization protocols and several screening procedures were used to prepare seven mouse monoclonal antibodies to human placenta hexokinase type I. None of these monoclonals were able to recognize the native enzyme but all detected hexokinase when adsorbed onto polystyrene plates or on immunoblots after SDS/polyacrylamide-gel electrophoresis. 2. All seven monoclonals recognize the two different subtypes of human hexokinase I equally well. Limited tryptic digestion of hexokinase followed by Western blotting and immunodetection show that these monoclonals recognize epitopes that lie in different tryptic peptides. 3. Comparative ELISA studies showed that human hexokinase types I and II have great immunological similarities while hexokinase I from different mammalian species and yeast hexokinase are recognized with different affinities.

Similarities and differences between human and rat hexokinases type I

The intracellular distribution and several properties of hexokinases type I purified to homogeneity from human placenta and rat brain were compared. The specific activity of the human enzyme was 190 +/- 5 U/mg protein; 140 +/- 5 U/mg protein that of the rat hexokinase. Comparative peptide mapping after limited tryptic digestion indicates a similar domain structure, however analogous experiments performed in the presence of substrates or effectors of the enzyme provide evidence of significant differences among hexokinases. Similarly, immunological studies with polyclonal and monoclonal antibodies while confirming some common epitopes also disclose important differences that cannot be expected on the basis of amino acid composition and of an in vivo identical function. These results are consistent with suggestions by several investigators that amino acid substitutions in mammalian hexokinases have occurred at a relatively fast rate during hexokinase type I evolution.

Auditory steady-state responses in the rabbit

The authors have studied auditory brainstem (ABRs), middle latency (MLRs) and steady-state potentials (SSRs) in 15 adult male rabbits weighing between 2.5 and 3 kg in order to verify if SSRs are due to a mere superimposition of ABRs and MLRs or to a resonance phenomenon. Ten of them were awake while 5 were studied under urethane anesthesia. Acoustic stimuli consisted in 0.1-ms square-wave pulses delivered at presentation rates ranging between 1 and 80/s at a stimulus intensity of 80 dB p.e. SPL. Our data show that reliable auditory SSRs can be obtained in the rabbit at a presentation rate of 30 stimuli/s, probably due to the superimposition of ABRs and MLR Pb waves which show an interwave interval of about 35 ms. The nonlinear aspects which can be detected are probably due to the effect of decreasing interstimulus intervals on the duration and amplitude of the Pb wave. It can then be concluded that SSRs in the rabbit are due more to a superimposition of ABR and MLR waves than to a resonance phenomenon.

Improved stability of 2,3-bisphosphoglycerate during storage of hexokinase-overloaded erythrocytes

Human red blood cells were overloaded with homogeneous human hexokinase using a procedure of encapsulation based on hypotonic hemolysis and isotonic resealing and reannealing to achieve a final activity that was 15 times higher than that in control cells. Storage for 5 weeks at 4 degrees C of hexokinase-overloaded erythrocytes shows that these cells undergo small K+ leakage and mean cell volume increase compared with control cells. Furthermore, after these 5 weeks of storage the 2,3-bisphosphoglycerate content was normal while the ATP concentration was slightly reduced. These results and other properties suggest that encapsulation of key glycolytic enzymes in erythrocytes can provide a new way to maintain in vitro functionally active red blood cells for at least 5 weeks.

Effects of Ca2+ and lipoxygenase inhibitors on hexokinase degradation in rabbit reticulocytes

In rabbit reticulocytes more than half of the total hexokinase activity is mitochondrial bound and shows a fast decay during reticulocyte maturation. During in vitro incubation of rabbit reticulocytes, Ca2+ increases the decay of hexokinase while salicylhydroxamate (SHAM), an inhibitor of lipoxygenase, reduces the decay. Swelling of mitochondria, by incubation of the cells in hypotonic solutions, greatly enhances hexokinase decay, but both the Ca2+ and SHAM are still appreciable suggesting that Ca2+ and the swelling act by additive mechanisms, both able to influence hexokinase decay. This was confirmed by incubation of rabbit brain mitochondria in hypotonic solutions which does not promote any hexokinase decay, while the presence of Ca2+ does. Analyses of hexokinase isozymic pattern after incubation of reticulocytes in hypotonic solution both with and without Ca2+ and SHAM showed that the decay of hexokinase mainly involves the mitochrondrial bound isozymic forms.

Human red blood cell loading with hexokinase-inactivating antibodies. An in vitro model for enzyme deficiencies

The primary cause of red cell destruction in enzymopathies of anaerobic remains controversial and difficult to investigate especially because the erythrocyte population in enzymopenic patients is largely heterogeneous. We have shown that loading human erythrocytes with monospecific enzyme-inactivating antibodies could be useful in understanding the biochemical modifications occurring in enzymopenic erythrocytes and the mechanisms leading to red cell destruction. Hexokinase-inactivating antibodies were prepared and loaded in human erythrocytes using a procedure of encapsulation based on hypotonic hemolysis, isotonic resealing and reannealing. Red blood cells loaded with anti-hexokinase IgG showed 20 +/- 3% residual hexokinase activity while all other enzymes were normal. Lactate production by these cells was 30% of controls while the amount of glucose metabolized in the hexose monophosphate pathway (HMP) was unchanged under resting conditions. However, in the presence of methylene blue HMP rates were only 12% of controls. Determination of adenine nucleotide levels suggests that the antihexokinase-loaded red blood cells are not able to maintain, in vitro, their ATP level as well as their 2,3-diphosphoglycerate. Osmotic fragility, methemoglobin, and reduced glutathione content were near normal. These and other properties of the antihexokinase-loaded erythrocytes were similar to those found in cases of hexokinase deficiency. When the antibody-loaded erythrocytes were chromatrographed on immobilized Protein A columns 66-70% of cells were retained by the column against 0-10% of controls suggesting that hexokinase inactivation promotes autologous IgG binding. Since the phenomenon is known to be associated with red cell phagocytosis, it could be concluded that in hexokinase deficiency red cells are mainly removed by phagocytosis, and that hemolysis probably occurs in cases of oxidative stress when the production of a large amount of reducing equivalents (NADPH) is needed but not provided by the hexokinase-deficient erythrocytes.

[Several properties of human red cells subjected to hypotonic dialysis and resealing to use them as vehicles for bioreactors]

The morphological and metabolic properties of red blood cells submitted to the procedure of loading by hypotonic hemolysis and isotonic resealing were compared with the controls. No appreciable differences could be detected concerning glycolytic ability, the amount of glucose metabolized in the hexose monophosphate pathway and the concentrations of glycolytic intermediates of ATP and of 2,3-DPG. Instead the concentration of reduced glutathione and the MCV were slightly reduced. These manipulated erythrocytes can be used as potential bioreactors or as carriers of exogenous substances.

Hexokinase type I multiplicity in human erythrocytes

Hexokinase I in human erythrocytes exists in multiple molecular forms that differ in isoelectric points. By means of Western blotting and immunodetection of total glucose-phosphorylating activity by using an antibody raised in rabbit against homogeneous human placenta hexokinase I, a single protein band was detected. Identical results were also obtained by immunoaffinity chromatography of the partially purified enzyme. Separation of the three major hexokinase I subtypes (Ia, Ib and Ic) by h.p.l.c. ion-exchange chromatography and immunodetection following electrophoretic blotting confirmed that each hexokinase subtype showed the same apparent Mr of 112,000, which is the value obtained for the high-Mr hexokinase I from human placenta. Purification of erythrocyte hexokinase by a combination of several procedures including dye-ligand and affinity chromatography that were previously successfully applied to the purification of other mammalian hexokinases type I produced a 35,000-fold-purified enzyme that showed several contaminants after SDS/polyacrylamide-gel electrophoresis. Only one of these peptides was found to be recognized by anti-(hexokinase I) IgG, suggesting that proteolytic degradation does not occur and that hexokinases Ia, Ib and Ic have the same apparent Mr.

Role of hexokinase in the regulation of erythrocyte hexose monophosphate pathway under oxidative stress

Human erythrocytes overloaded with homogeneous human hexokinase (up to 15-times the activity of normal RBC) show almost unmodified rates of glucose metabolized in the HMP, however hexokinase-loaded RBC are able to metabolize 1.5 fold more glucose than controls through the HMP when an oxidizing agent like methylene blue (5 to 100 microM) is present. Similarly, RBC loaded with inactivating anti-hexokinase IgG (12 +/- 3% residual hexokinase activity) show HMP rates unchanged under resting conditions, but only 12% of the HMP rate found in normal controls under oxidative stress. These data provide clear evidence that the HMP rate under conditions of oxidative stress is controlled by hexokinase activity and suggest that RBC from patients with hexokinase deficiency are not able to increase the HMP rate under oxidative stress like erythrocytes from individuals with G6PD deficiency.

The interaction of phosphorylated sugars with human hexokinase I

Glucose 6-phosphate as well as several other hexose mono- and diphosphates were found by kinetic studies to be competitive inhibitors of human hexokinase I (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) versus MgATP. Limited proteolysis by trypsin does not destroy the hexokinase activity but produces as well-defined peptide map when the digested enzyme is electrophoresed in the presence of sodium dodecyl sulfate. MgATP at subsaturating concentration protects hexokinase from trypsin digestion, while phosphorylated sugars, Mg2+, glucose and inorganic phosphate have no effect. Addition of glucose 6-phosphate to the MgATP-hexokinase complex at a concentration 100-times higher than its Ki was not able to reverse the MgATP-induced conformation of hexokinase, suggesting that the binding of glucose 6-phosphate and MgATP are not mutually exclusive. Similar evidence was also obtained by studies of the induced modifications of ultraviolet spectra of hexokinase by the binding of MgATP, glucose 6-phosphate and both compounds. Among a library of monoclonal antibodies produced against rat brain hexokinase I and that recognize human placenta hexokinase I, one (4A6) was found to be able to modify the Ki of glucose 6-phosphate (from 25 to 140 microM) for human hexokinase I. The same antibody also weakens the inhibition by all the other hexoses phosphate studied without affecting the apparent Km for MgATP (from 0.6 to 0.75 mM) or for glucose. These data support the view for the binding of glucose 6-phosphate at a regulatory site on the enzyme.

Quantitation of electrophoretic eluted proteins

Quantitation of stained, electroeluted proteins by the classical Lowry and Bradford protein assay is not possible because of some different interferences. In particular we have found that the substance interfering in the Lowry method cannot be removed by trichloroacetic acid precipitation nor can be compensated for by the appropriate blank. Interferences in the Bradford protein assay are due to detergents and pH of the protein buffer as well as to Coomassie brilliant blue R250 electroeluted with the protein sample. However, while these interferences can be compensated for by appropriate blank and standard curves, others (probably due to acrylamide fines) cannot be corrected. All these problems can be overcome by concentration and dialysis of electroeluted samples which permit the removal of interfering substances and the use of Bradford and Lowry protein assay in the 1-20 micrograms range, respectively. Successful applications are described for electroeluted bovine serum albumin, human hexokinase and phosphoglucomutase.

Purification, properties, and evidence for two subtypes of human placenta hexokinase type I

In human placenta 85% of total hexokinase activity (EC 2.7.1.1) was found in a soluble form. Of this, 70% is hexokinase type I while the remaining 30% is hexokinase type II. All the bound hexokinase is type I. Soluble hexokinase I was purified 11,000-fold by a combination of ion-exchange chromatography, affinity chromatography, and dye-ligand chromatography. The specific activity was 190 units/mg protein with a 75% yield. The enzyme shows only one band in nondenaturing polyacrylamide gel electrophoresis that stains for protein and enzymatic activity; however, two components (with Mr 112,000 and 103,000) were constantly seen in sodium dodecyl sulfate-gel electrophoresis. Many attempts were made to separate these two proteins under native conditions; however, only one peak of activity was obtained when the enzyme was submitted to gel filtration (Mr 118,000), preparative isoelectric focusing (pI 5.9), anion-exchange chromatography, hydroxylapatite chromatography, and affinity chromatography on immobilized dyes and immobilized glucosamine. The high and low molecular weight hexokinases show the same isoelectric point under denaturing conditions as determined by two-dimensional gel electrophoresis. Each hexokinase subtype was obtained by preparative sodium dodecyl sulfate electrophoresis followed by electroelution. Monospecific antibodies raised in rabbits against electroeluted high and low molecular weight hexokinases were not able to recognize the native enzymes but each of them detected both hexokinases on immunoblots. Amino acid compositions and peptide mapping by limited proteolysis of the high and low molecular weight hexokinases were also performed and suggested a strong homology between these two subtypes of human hexokinase I.

Role of hexokinase in the regulation of glucose metabolism in human erythrocytes

Red blood cell glucose metabolism was studied in erythrocytes from a patient with trisomy 10 p which resulted in + 50% hexokinase specific activity, in normal controls and in cases of heterozygous hexokinase deficiency. The results obtained show that the hexokinase activity level is an important factor in the control of the erythrocyte's glycolytic rate while having no appreciable effect on the hexose monophosphate pathway under resting conditions. No clear conclusion could be drawn when an oxidative stress was present.

Rabbit red blood cell hexokinase. Decay mechanism during reticulocyte maturation

In rabbit reticulocytes, the hexokinase (EC 2.7.1.1)-specific activity is 4-5 times that of corresponding mature red cells. Immunoprecipitation of hexokinase by a polyclonal antibody made in vitro shows that this maturation-dependent hexokinase decay is not due to accumulation of inactive enzyme molecules but to degradation of hexokinase. A cell-free system derived from rabbit reticulocytes, but not mature erythrocytes, was found to catalyze the decay of hexokinae activity and the degradation of 125I-labeled enzyme. This degradation is ATP-dependent and requires both ubiquitin and a proteolytic fraction retained by DEAE-cellulose. Maximum ATP-dependent degradation was obtained at pH 7.5 in the presence of MgATP. MgGTP could replace MgATP with a relative stimulation of 0.90. 125I-Hexokinase incubated with reticulocyte extract in the presence of ATP forms high molecular weight aggregates that reach a steady-state concentration in 1 h, whereas the degradation of the enzyme is linear up to 8 h, suggesting that the formation of protein aggregates precedes enzyme catabolism. These aggregates are stable upon boiling in 2% sodium dodecyl sulfate, 3% mercaptoethanol and probably represent an intermediate step in the enzyme degradation with hexokinase and other proteins covalently conjugate to ubiquitin. That hexokinase could be conjugated to ubiquitin was shown by the formation of 125I-ubiquitin-hexokinase complexes in the presence of ATP and the enzymes of the ubiquitin-protein ligase system. Thus, the decay of hexokinase during reticulocyte maturation is ATP- and ubiquitin-dependent and suggests a new physiological role for the energy-dependent degradation system of reticulocytes.

Human erythrocyte hexokinases are immunologically related

Human erythrocytes contain three major hexokinase isoenzymes eluted by DE-52 chromatography between hexokinase type I and type II. Cross-reactivities of these isoenzymes were studied by means of a monospecific rabbit antibody against purified human placenta hexokinase type I. It was shown that the three hexokinase isoenzymes were immunologically related, supporting the concept of a postsynthetic mechanism(s) as their origin.

Rat red blood cell hexokinase purification, properties and age-dependence

Rat erythrocytes, in contrast to red blood cells from other mammals, have been shown to contain only one hexokinase isozymic form identified as type I by chromatographic and kinetic properties. Rat reticulocytes contain 3.6-times the hexokinase activity found in mature erythrocytes but exactly the same isozyme. By a combination of ion-exchange chromatography, dye-ligand chromatography and high-pressure liquid chromatography the rat erythrocyte hexokinase was purified more than 84 000-fold to a specific activity of 143 units/mg protein and shown to be homogeneous by sodium dodecyl sulfate-gel electrophoresis. The native protein showed a molecular weight of 100 000 by gel-filtration and an apparent molecular weight of 98 000 under denaturating conditions in sodium dodecyl sulfate-gel electrophoresis. The isoelectric point was shown to be 6.3 pH units. This data provides evidence of only one form of hexokinase in the erythrocytes of a mammal.

Location of central venous catheters in children by endocavitary ECG: A new technique

A new technique to establish the position of a central venous catheter (CVC) by endocavitary ECGraphy is described. The principle is based on the fact that the catheter itself may be considered as an electrical conductor by means of its liquid content (saline solution), therefore acting as an exploring electrode. The intrinsic deflection of the P wave shows the proper position of the CVC tip at the sinus node level. The technique has been successfully utilised in 52 children needing antineoplastic chemotherapy and/or total parenteral nutrition, thus avoiding chest X-ray control, which is troublesome and potentially harmful in neonates and infants.