Correlation between Histopathology and Signal Loss on Spin-Echo T2-Weighted MR Images of the Inner Ear: Distinguishing Artifacts from Anatomy

BACKGROUND AND PURPOSE

MR imaging of the inner ear on heavily T2-weighted sequences frequently has areas of signal loss in the vestibule. The aim of the present study was to correlate the anatomic structures of the vestibule with areas of low signal intensity.

MATERIALS AND METHODS

We reviewed T2-weighted spin-echo MR imaging studies of the internal auditory canal from 27 cases and cataloged signal intensity variations in the vestibulum of inner ears. Using a histologic preparation of a fully mounted human ear, we prepared 3D reconstructions showing the regions of sensory epithelia (semicircular canal cristae, utricular, and saccular maculae). Regions of low signal intensity were reconstructed in 3D, categorized by appearance, and compared with the 3D histologic preparation.

RESULTS

The region corresponding to the lateral semicircular canal crista showed signal loss in most studies (94%). In the utricle, a focus of signal loss occurred in the anterior-cranial portion of the utricle and corresponded to the location of the utricular macula and associated nerve on histopathologic specimens (63% of studies). Additional areas of low signal were observed in the vestibule, corresponding to the fluid-filled endolymphatic space and not to a solid anatomic structure.

CONCLUSIONS

Small foci of signal loss within the inner ear vestibule on T2-weighted spin-echo images correlate with anatomic structures, including the lateral semicircular canal crista and the utricular macula. More posterior intensity variations in the endolymphatic space are likely artifacts, potentially representing fluid flow within the endolymph caused by magneto-hydrodynamic Lorentz forces.

Biologic markers in blood reflecting thyroid hormone effect at peripheral tissue level in patients receiving levothyroxine replacement for hypothyroidism

Plasma fibronectin, serum procollagen-III-peptide and sex-hormone binding globulin as not specific markers of thyroid hormone effect at peripheral tissue level were determined and their values were related with serum levels of TSH, free-thyroxine and triiodothyronine during levothyroxine sodium replacement therapy for hypothyroidism. Low levels of biologic markers characteristic of hypothyroidism were normalized in consequence of hormone replacement and a negative correlation between their serum levels and TSH concentration was demonstrated in most subjects. However, in some patients a discrepancy in the response to levothyroxine between the pituitary and other target organs could be revealed. Additional evidence was disclosed that the pituitary thyrotroph sensitizes a minor decrease in serum thyroxine level, which would not be recognized by other target organs. Furthermore, it was revealed that during L-T4 replacement therapy in a large fraction of patients with subnormal serum TSH concentration blood levels of the measured markers often exceeded the upper limit of the normal range indicating the possibility of "tissue"-thyrotoxicosis beside the pituitary in other target organs, too. According to the present study which takes into consideration markers reflecting end-organ responsiveness to thyroid hormones it is recommended to adjust the dose of levothyroxine to maintain serum TSH in the normal range. For patients with subnormal TSH concentration a close follow-up is obligatory and in case od concomitantly raised free-thyroxine level the reduction of the levothyroxine dosage is proposed.

Non-invasive measurements of intralabyrinthine pressure changes by electrocochleography and otoacoustic emissions

By varying the mechanical load on the stapes footplate, intralabyrinthine pressure (ILP) influences the stiffness of the middle ear and modifies its transfer function. This results in a characteristic phase shift of the otoacoustic emissions (OAEs) around 1kHz [Buki, B., Avan, P., Lemaire, J.J., Dordain, M., Chazal, J., Ribari, O., 1996. Otoacoustic emissions: a new tool for monitoring intracranial pressure changes through stapes displacements. Hear. Res. 94, 125-139]. This finding provides non-invasive means of monitoring changes of ILP and indirectly of intracranial pressure. Yet the vulnerability of OAEs to sensorineural hearing loss excludes many patients from being monitored in this manner. Being dependent on the middle-ear transfer function, the phase of the cochlear microphonic potential (CM) around 1kHz should also respond to ILP changes while being less affected by impaired hearing than OAEs. Here, normal volunteers were subjected to body tilt resulting in stepwise changes in their intracranial pressure and ILP. Their CM around 1kHz was recorded by extratympanic electrocochleography and its dependence on body position was compared to that of distortion-product OAEs. The posture-induced CM changes were also monitored in ears with sensorineural deafness and impaired OAEs to assess the usefulness of CM in the presence of hearing impairment. Last, OAEs and CM were simultaneously monitored in gerbils during intracranial pressure changes brought about via an intracranial catheter. The phase and level shifts induced by body tilt in man and intracranial pressure changes in gerbils showed up both in distortion-product OAEs and CM with similar time courses. In normally-hearing subjects, the mean phase shifts reached 16.3 degrees for CM and 41.6 degrees for OAEs, and CM remained large enough in hearing-impaired subjects for ILP to be monitored. The ratio of about two of OAEs to CM phase shifts matched the prediction of middle-ear models allowing for the fact that CM does not travel back through the middle ear while OAEs do. It follows that CM phase around 1kHz provides non-invasive access to ILP changes even if OAEs cannot be measured due to sensorineural hearing loss.

Middle-ear influence on otoacoustic emissions. II: contributions of posture and intracranial pressure

Although it seems likely that body tilt or surgically provoked variations in intracranial pressure (ICP) can result in variations of intralabyrinthine pressure, the channels for pressure transmission remain controversial and the reasons why evoked otoacoustic emissions (EOAEs) exhibit attendant modifications are unclear. The theoretical framework implemented in the companion paper [Avan et al. part I, 2000] provides sensitive and non-invasive means to identify the middle-ear mechanism(s) entailed in EOAE changes. It was thus applied to analyze the influence of posture on EOAE phases and magnitudes as a function of frequency, in a series of experiments involving body tilt from sitting to supine (0 degrees or -30 degrees ). Controlled ICP variations were surgically carried out in a series of hydrocephalic patients and the resulting EOAE changes were compared to posture data and model predictions. In all cases, the EOAE changes closely resembled those due to an increase in the stiffness of the stapes' annular ligament, in keeping with the assumption that ICP gets transmitted to intralabyrinthine spaces and modifies the hydrostatic load on the stapes, thereby influencing EOAE features. A small additional contribution of middle-ear pressure to EOAE changes was identified in addition to the main stapes component. Dynamical EOAE measurements showed that sudden ICP changes were transmitted to the inner ear within 8-30 s. The high sensitivity of EOAE phases below 2 kHz to ICP changes, together with the absence of any significant confounding middle-ear effect, favors EOAEs for a reliable non-invasive monitoring of ICP and intralabyrinthine pressures.

Middle ear influence on otoacoustic emissions. I: noninvasive investigation of the human transmission apparatus and comparison with model results

Evoked otoacoustic emissions (EOAEs) are generated within the cochlea in response to external sounds, and they can be acoustically detected in the external auditory meatus after backward propagation through the middle ear. In addition to being used to probe the cochlear mechanisms, they are expected to be sensitive to minute changes in middle ear impedance. Systematic measurements of the changes in the vectorial components of EOAEs were carried out after various manipulations of the human middle ear in order to characterize the influence of stiffness and inertia of the stapes and tympanic-membrane systems. For this purpose, stapedius muscle contractions were elicited by high-level contralateral sound, controlled changes in middle ear pressure (range +/-100 daPa) were produced and the tympanic membrane was loaded with water droplets. A computer model of the middle ear network was implemented using a standard lumped-element electric analog of the middle ear (Zwislocki's model). Forward and backward transmission changes were simulated and model predictions were compared to experimental data. Apart from the case of positive middle ear pressures, a close qualitative correspondence was found between model and real-ear results. Each of the effects was characterized by a unique pattern of phase and magnitude changes as a function of frequency, in relation to the mechanical characteristics of the involved subsystem (i.e. stapes stiffness, tympanic-membrane stiffness or mass) and its resonance properties. Owing to their high sensitivity, EOAEs could be helpful for an accurate individual multifrequency analysis of middle ear impedance by comparisons under rest and test conditions.

Olivocochlear efferent vs. middle-ear contributions to the alteration of otoacoustic emissions by contralateral noise

The medial olivocochlear efferent bundle is the key element of a bilateral efferent reflex activated by sound in either ear and acting directly on cochlear outer hair cells (OHC) via numerous cholinergic synapses. It probably contributes to regulating the mechanical activity of the cochlea. Otoacoustic emissions, being sounds emitted by the cochlea as a reflection of its activity and suppressed by efferent activation, are increasingly considered to be the privileged tool for a noninvasive assessment of the efferent reflex. However, confounding effects on otoacoustic emissions can occur. A primary influence is middle-ear muscle reflex activation, which shares common features with the effects of cochlear efferent activation. We report a systematic comparison of the responses of human otoacoustic emissions to efferent activation by low-level noise in the contralateral ear to various middle-ear manipulations (reflex contractions of the stapedius muscle induced by high-level contralateral noise; moderate middle-ear pressure changes). The profiles of level and phase changes of otoacoustic emissions as a function of frequency were highly specific to the origin of the effects. The changes induced by middle-ear manipulations matched the predictions computed from a standard lumped-element middle-ear model, with one or two peaks around the resonance frequency(ies) of the involved subsystem, stapes or tympanic membrane. In contrast, the efferent effect was completely different, exhibiting a broadband-level suppression associated with a small phase lead. We propose that a careful vector analysis of otoacoustic emission modifications enables the identification of the contribution of the efferent reflex without ambiguity even when it is mixed with middle-ear effects. Thereby, otoacoustic emissions can be used more reliably as noninvasive probes of efferent olivocochlear function.

Detection of early ototoxic effect in testicular-cancer patients treated with cisplatin by transiently evoked otoacoustic emission: a pilot study

The outlook for patients with testicular germ cell cancer was dramatically improved by the introduction of cisplatin. Well-known side effects of cisplatin (nausea, vomiting, nephrotoxicity, myelosuppression) can be managed with preventive methods. The long life expectancy after this therapy draws attention to long-term side effects. The ototoxic side effects were scarcely studied, although nowadays, they can be a dose-limiting side effect of cisplatin.

PATIENTS AND METHODS

As the literature shows, the ototoxic side effects of cisplatin have been studied mostly by conventional methods. The authors used transiently evoked otoacoustic emissions to determine whether the administration of 20 mg/m2 body surface cisplatin daily (in combination with other antitumor drugs) for 5 days alters the amplitude of the transient otoacoustic emission.

RESULTS

The results did not show any significant amplitude change after 20 mg/m2 cisplatin daily for 5 days, in contrast with other studies that described a broad frequency reduction of the emission amplitude in 30-86% of cases treated with 100 mg/m2 of cisplatin for 1 day.

CONCLUSION

The authors suggest that between similarly effective regimens, those containing lower daily cisplatin doses should be used.

[Non-invasive monitoring of intracranial pressure changes through the ear]

Otoacoustic emissions are low energy vibrations generated by the inner ear during the physiologic process of hearing. The authors measured transiently evoked otoacoustic emissions in normal hearing individuals placed in Trendelenburg position and during diagnostic elevation of intracranial pressure in neurosurgical patients. In Trendelenburg position and at elevated intracranial pressure and reproducible phase shift of otoacoustic emissions could be observed. This phase shift was linear to the pressure increase of intracranial liquids. According to the hypothesis of the authors intracranial pressure increase is transmitted to the inner ear (possibly by the cochlear aqueduct) and thereby the mechanical load on the stapes footplate is elevated. This, in turn, causes a stiffening of the annular ligament which changes the angle of the impedance vector and thereby the phase of the whole vibrating system. By measuring the phase of otoacoustic emissions it is possible to monitor intracranial pressure in various clinical states.

[Urinary calcium excretion. (Normal values for urinary calcium/creatinine ratio in Hungary). Multicenter study]

Metabolic bone disorders have attracted increasing attention in Hungary due to their significant impact on public health care. Measuring urinary calcium excretion is the first step in the biochemical assessment of bone metabolism. Fasting urinary calcium corrected by creatinine excretion is widely used all over the world. The aim of the present study was to establish standard methods and normal values for the calcium/creatinine ratio in Hungary. Twenty-four centers specializing in metabolic bone diseases participated in the study. Urine standards were sent out to these centers for calcium and creatine determinations. Based on the collected data, methods were corrected in order to achieve similar results for the standards. In the second phase of the study, the normal values for calcium/creatinine ratio were determined in SI units based on the data from 1846 healthy subjects (age 20-80 yrs) including 944 females and 902 males. The normal value for females was 0.438 +/- 0.391 (means +/- SD), and 0.395 +/- 0.352 for males, respectively (p < 0.03). The ratio increased with age in both sexes. The highest values were observed between 60-64 years in women and 70-74 years in men, respectively. After this peak, the calcium/creatinine ratio decreased. The values before and after 45 years of age were significantly different both in women (0.37 +/- 0.36, vs. 0.52 +/- 0.41, p < 0.001; and men (0.32 +/- 0.23, vs. 0.47 +/- 0.45, p < 0.001). The use of this distinction is recommended in the everyday practice.

Otoacoustic emissions: a new tool for monitoring intracranial pressure changes through stapes displacements

Changes in hydrostatic intracranial pressure (ICP) are thought to be transmitted to cochlear liquids, thereby altering the mechanical load on the stapes footplate. Hence the stiffness of stapes' annular ligament is expected to reflect ICP changes. Corresponding middle-ear transmission changes have been assessed using click-evoked otoacoustic emissions (EOAE) in two experiments. The first one was performed in 22 normal human subjects submitted to posture changes. In the second one, controlled ICP increases were applied to 18 patients in neurosurgery operating theater. EOAEs were monitored in these subjects throughout the experiments and their phases and amplitudes were analyzed as a function of frequency. ICP affected EOAEs in a systematic manner in both experiments, i.e., the main effect of ICP increase was phase lead of EOAE components below 2 kHz without any significant amplitude or frequency shift. Their variations were much more evident than the modifications in middle-ear impedance assessed by standard impedance or admittance measurements. The second experiment led to a quantitative linear relationship between ICP and EOAE phases. It demonstrated that the sensitivity of EOAE phase monitoring technique proves to be quite high, i.e., 55 daPa increases in ICP are readily detected in all subjects. The results are consistent with the predictions of classical middle-ear models as to the transmission alterations induced by ICP-related changes in the stiffness of the annular ligament of the stapes. Non-invasive monitoring of ICP in patients with hydrocephalus treated with ventriculo-peritoneal shunts might be attempted with this technique, although it is restricted to patients with detectable EOAEs (i.e., about 50% in this series).

Moving time window analysis of transiently evoked otoacoustic emissions

We have developed a technique for off-line analysis of transient otoacoustic emissions. The correlation of two curves was calculated in a moving time-window of 1 ms time sections. By this method it is possible to recognize high-correlation parts, time sections with low correlation, and thus the duration of the emission can be determined. The mean absolute duration of transiently evoked otoacoustic emissions in 36 normal ears was 15.1 +/- 0.69 ms (mean +/- SE). The duration was significantly shorter (9.34 +/- 0.43) in 75 ears with different grades of sensorineural hearing loss. The breakdown of this group into sub-groups according to the width of the high frequency band with elevated threshold showed a correlation between the severity of the hearing loss and the absolute duration.

Transitory evoked otoacoustic emission (TEOAE) in a child with profound hearing loss

The case of a 3-month-old, prematurely born boy with auditory brainstem response (ABR), verified profound hearing loss and normal transitory evoked otoacoustic emission is presented. Isolated retrocochlear deafness which did not influence TEOAE is hypothesised as a possible cause. The critical evaluation of results when using TEOAE as a screening method is suggested.

Auditory brainstem potentials in uraemia

Evoked response audiometry was carried out to assess the viability of the auditory pathway in haemodialysed patients. The latency of the waves III and V and I-V interpeak latencies were significantly longer in the renal patients compared to the control group. The I-V interpeak latency was longer in 8 of our 13 patients than the upper limit (4.38 ms) in our laboratory. The possible cause for the central auditory dysfunction may be multifactorial, including the effect of metastatic calcifications, repeated occurrence of disequilibrium syndrome, or some small, molecular, toxic, metabolic substance. The significance of the different factors may vary among different haemodialysis centres.

[Otoacoustic emission audiometry in neonates and adults]

The authors discuss the clinical use of the otoacoustic emission audiometry. During the physiological process of sound amplification in the cochlea vibration energy escapes from the inner ear. By the analysis of this sound it is possible to gain information about the function of the cochlea. According to the experiences of the authors the method is extremely useful for screening audiometry in pathological and normal neonates. In adults it can be used for monitoring the cochlear function during ototoxic therapy or noise exposure.

[Determination of hepatitis C antibodies, using the Abbott and the Ortho anti-HCV EIA kits, in chronic liver diseases and patients under hemodialysis for chronic renal failure]

The diagnostic usefulness of anti HCV EIA test of Abbott and Ortho companies were compared. The anti HCV levels determined in the sera of 173 patients with chronic liver diseases and of 17 haemodialysed kidney patients. 109 of 190 (57%) sera were found to be negative and 81 (43%) positive determined by Abbott kit, while 127 (67%) were negative and 63 (30%) were positive by the Ortho kit. Positive results in patients with chronic liver disease were found in 66 patients by Abbott and 58 patients with Ortho Kit. Distribution of positive cases according to the diagnosis is as follows: 29 (57%) out of 51 chronic hepatitis, 17 (61%) out of 28 cirrhosis. Conflicting results were obtained in 20 cases of 190 (11%) when 17 sera were positive by Abbott and negative by ORTHO, and 3 sera were negative by Abbott, and positive by Ortho. The samples close to the cut off and with low positivity with conflicting results were checked again by the neutralization HCV EIA Abbott assay. We found the Abbott HCV EIA test more sensitive in our excellent for screening of large numbers of samples, we recommend to confirm the positive results by a neutralization type test.

[Biological markers reflecting peripheral effects of thyroid hormones in autonomous thyroid adenoma]

In some patients with functioning thyroid autonomous nodules preclinical hyperthyroidism is detected. It is important to know, whether in this intermediate clinical state beside the suppression of pituitary TSH secretion other target organs are also affected by serum free-thyroxine and free-triiodothyronine levels still within the normal range. Determining some sensitive, but not specific biologic markers reflecting the impact of thyroid hormones at the peripheral tissue level, it was demonstrated that in the group of preclinical hyperthyroidism the mean level of plasma fibronectin exceeded that of the controls (mean +/- S. D.: 583.5 +/- 163.9 vs. 424.2 +/- 84.1 micrograms/ml, p less than 0.001), serum procollagen-III-peptide concentration was already significantly raised, though its value was still within the normal range (mean +/- S. D.: 0.73 +/- 0.17 vs. 0.57 +/- 0.16 U/ml, p less than 0.05), conversely, mean sex-hormone binding globulin level was the same as in euthyroid controls (mean +/- S. D. 47.4 +/- 18.2 vs. 48.3 +/- 16.3 nmol/l). The value of all three parameters was significantly elevated in patients with toxic nodular goiter. Based on the results of this study "tissue"-thyrotoxicosis is suspected in some patients with preclinical hyperthyroidism, which may have therapeutical implications.

[Decreased serum osteocalcin level in non-alcoholic and alcoholic chronic liver diseases]

Serum level of osteocalcin (OC) is believed to be a specific biochemical parameter of bone formation. Decreased serum OC has been reported in alcohol-intoxicated subjects, in patients with primary biliary cirrhosis and in patients with chronic alcoholic liver disease. The question was, whether lower OC level could be detected in patients with nonalcoholic and non-cholestatic chronic liver disease. The serum OC was measured by RIA developed in our laboratory. Results were compared to age and sex matched controls. Decreased OC level was found in 35 out of 47 (74%) patients with non-alcoholic and non-cholestatic liver disease as chronic persistent hepatitis, chronic active hepatitis, fatty liver and cirrhosis, in 21 out of 26 (80%) patients with alcoholic liver disease and in 8 out of 15 (53%) primary biliary cirrhosis. None of the patients had elevated value. There was no correlation between the decreased OC level and the duration or severity of the liver disease and the laboratory parameters as bilirubin, AST, ALT, alkaline phosphatase, albumin, prothrombin, and serum 25-OH-D3 vitamin level. Decreased OC was found also in the patients without cirrhosis. The possible causes are discussed. Relying upon these findings it is supposed that chronic liver disease by itself can influence the osteoblast activity also by some unknown mechanism.

[The significance of hypocitruria in calcium oxalate induced nephrolithiasis]

The citrate concentration of the daily collected urine was measured by citrate lyase method in 25 untreated patients with recurrent calcium stone disease (10 hypercalciuric and 15 normocalciuric) and in 11 patients with stone disease treated with hydrochlorothiazide and in 16 healthy controls. We found a great variancy of the results what rather looks like biological than methodic type. The concentration (1.99 +/- 1.33 mmol/l in normocalciuric and 2.77 +/- 1.62 in hypercalciuric stone formers but 5.06 +/- 2.81 in controls) and the daily output of the urinary citrate (2.74 +/- 1.38 mmol/d and 4.24 +/- 1.69 vs. 4.41 +/- 1.85) but not the citrate/creatinine ratio was significantly less in about the half of stone formers. The hypocitraturia was frequent in the normocalciuric and very rare in the hypercalciuric group of the renal stone patients. Measurement of the urine citrate concentration is more sensitive tool in the diagnosis of hypocitraturic state than daily citrate output while the latter is more characteristic for the patient, so common study of the two parameters is recommended.

[Plasma fibronectin level in thyroid disease]

Fibronectins are widespread components of connective tissues and their production is partly under hormonal control. A study was undertaken to reveal the influence of thyroid diseases on plasma fibronectin level. It is stated that compared with a euthyroid control group (n = 33; 436 +/- 82 micrograms/ml) plasma fibronectin content is significantly higher in untreated, overt hyperthyroidism (n = 27; 1036 +/- 389 micrograms/ml), while its plasma level is lower in hypothyroidism (n = 18; 230 +/- 123 micrograms/ml). Data hint to the possibility that the measurement of plasma fibronectin level may yield a help to assess the effect of thyroid hormones at target organ (connective tissue) level.

Different types of false positive anti-HIV reactions in patients on haemodialysis

Serum samples of 589 haemodialysis patients were screened for HIV antibody by ELISA methods. Of these, 36 samples were found to be repeatedly reactive. None of the 36, however, could be confirmed by competitive enzyme immunoassays and Western blot; therefore, they were considered to be false positive. The sera could be divided in two groups. The sera of Group 1 were designated as the usual type of false positivity, caused most probably by anti-lymphocyte antibodies. In 19 sera, however, a special type of false positivity was found. These sera reacted strongly with the plates coated with the supernatants of HIV-infected cells but not with those of uninfected H9 cells. Three and two sera showed, respectively, positive immunofluorescence reaction with the HIV-infected, but not with the uninfected, H9 and CEM cells. Reactivity to HIV-infected H9 cells could be adsorbed from a part of these samples with lesser amounts of HIV-infected than uninfected H9 cells. This special type of false positivity was observed frequently (7/65) in patients who rejected a kidney graft. These findings suggest that this type of anti-HIV false positivity is due to antibodies reacting with cellular antigens present in HIV-infected but not in uninfected lymphocytes. Their appearance seems to be associated with the immunological activation occurring at graft rejection.

[False positive results of HIV virus tests in patients undergoing chronic hemodialysis]

The sera of 173 haemodialysis patients treated in two dialysis centers in Hungary were tested for the presence of HIV (HTLV III/LAV) antibodies. Four different commercial enzyme immunoassay (EIA) kits and two types (CEM/LAV, and H9/HTLV III) of indirect immunofluorescence assay (IFA) were used. The Western blot technique was applied as confirmatory test in the study. No confirmed positive results were found in any of the cases. However, in 15 patients (8.7%) false positive (not confirmable by the Western blot assay) results were obtained in at least one but mostly in all of the three type 1 EIA kits (ORGANON, ELECTRONUCLEONICS, SORIN) applied. In 4 patients, the IFA assay also gave false positive results which could be repeated in sequential samples taken from the same patients. Increased reactivity in the control plate (coated with a concentrate of cellular material shed by uninfected H9 cell line) of the SORIN kit was found only in a few false positive samples and no fluorescence with the uninfected H9 or CEM cells was observed in any of the sera showing a false positive IFA. These results indicate that the false positive anti-HIV results frequently observable in haemodialysis patients are not simply the consequence of the presence of antibodies reacting with the uninfected H9 and/or CEM cells but they are most probably due to antibodies against antigens expressed on these cells only after infection with the human immunodeficiency virus.

A simple method for detecting HIV antibodies hidden in circulating immune complexes

A method previously used for studying the specificity of antibody components of circulating immune complexes in different diseases has been applied to analyse circulating immune complexes in HIV-infected patients. Antibodies against HIV antigens hidden in circulating immune complexes were studied in 14 sera from 13 patients with asymptomatic HIV infection (group 1) and in 11 sera from seven patients with HIV symptoms (group 2). HIV antigen-coated wells from the Vironostika kit as well as core and envelope antigen-coated beads from the Abbott confirmatory kit were used as solid-phase antigen. Using the Vironostika plates, HIV antibodies were demonstrated in circulating immune complexes in three and five sera in groups 1 and 2, respectively. Anti-core antibodies hidden in circulating immune complexes were present in three out of eight and two out of nine sera, respectively, in groups 1 and 2, whereas anti-envelope antibodies were present in circulating immune complexes in one out of eight and six out of nine sera in the same groups. These findings demonstrate that not only core-anti-core but also envelope-anti-envelope immune complexes are present in the sera of HIV infected patients.

Polyphosphoinositide metabolism in adrenal glomerulosa cells

We examined the effect of angiotensin II, a calcium-mobilizing hormone on polyphosphoinositide metabolism in isolated rat adrenal glomerulosa cells. In cells preloaded with [32P]phosphate or with [3H]inositol, stimulation with angiotensin resulted in an approx. 40% reduction in the radioactivity of triphosphoinositide (PtdIns4,5P2) within 15 s. Only a slight increase in radioactivity was observed in the subsequent 30 min. Changes in labelling of diphosphoinositide (PtdIns4P) showed similar kinetics. Incorporation studies also showed a reduction in the pool size of [32P]PtdIns4P and [32P]PtdIns4,5P2 in response to angiotensin. Production of inositol phosphates in the absence or presence of lithium, a cation-inhibiting myo-inositol-1-phosphatase, was examined in cells preloaded with [3H]inositol. The results indicate that the production rate of inositol tris- and bisphosphate shows a manifold increase in the first seconds of stimulation and remains enhanced for at least several minutes. The present data suggest that the rate of resynthesis of polyphosphoinositides also increases shortly after the activation of PtdIns4,5P2 phosphodiesterase. Corticotropin, a hormone acting via cyclic AMP, neither affected polyphosphoinositide metabolism nor modified the action of angiotensin II.

Insulin, C-peptide and glucagon levels during OGTT in hepatic cirrhosis and in patients with prehepatic block

In order to investigate pancreatic B-cell function in hepatic cirrhosis and to elucidate the role of porto-caval shunt-circulation in the development of hyperinsulinism and hyperglucagonemia in cirrhotic patients, blood glucose, plasma insulin and glucagon, and serum C-peptide concentrations were measured during OGTT in 11 control and 16 cirrhotic subjects as well as in 7 patients with prehepatic block secondary to thrombosis of the portal vein. Insulin and glucagon levels were significantly higher in the cirrhotic than in the control group (for insulin: p less than 0.01, less than 0.001, less than 0.01 and less than 0.05 at 0, 60, 90 and 120 min, respectively; for glucagon: p less than 0.01, less than 0.01, and less than 0.05 at 0, 30 and 60 min, respectively). Serum C-peptide levels were, however, similar in the two groups with the exception of the 30-min value, which was significantly lower in the cirrhotic group (p less than 0.05). Plasma insulin and glucagon concentrations in patients with prehepatic block were similar to those of the controls but significantly lower than the values found in cirrhotic patients (for insulin: p less than 0.05 at 0, 30, 60 min, respectively). Serum C-peptide levels of these patients were not significantly different either from the control values or from those obtained in the cirrhotic group. Accordingly, pancreatic B-cell secretion is not increased in hepatic cirrhosis. Hence, the hyperinsulinism is due to decreased heptic degradation of the hormone. Decreased degradation of both insulin and glucagon should be attributed mainly to parenchymal liver damage, rather than porto-systemic shunting.