[Disappearance of the sleep apnea syndrome in a female patient after surgery of a hypophyseal adenoma with acromegaly]

The association of the syndrome of sleep apnoea and acromegaly was described in the literature. However, so far no satisfactory explanation was given of the more frequent concomitant incidence of these diseases. The authors describe the disappearance of the sleep apnoea syndrome in a female patient after removal of an intrasellar microadenoma of the pituitary with overproduction of growth hormone.

Mechanism of activation of a response regulator: interaction of NtrC-P dimers induces ATPase activity

NtrC is the transcriptional activator for nitrogen-regulated promoters and, as a response regulator, belongs to the protein family of two-component systems. The activity of all response regulators is modulated by phosphorylation of the conserved N-terminal receiver domain. Phosphorylation of the dimeric NtrC has two consequences: (i) a strong increase in the cooperative binding of NtrC to two adjacent binding sites and (ii) activation of NtrC as an ATPase. Here we show that phosphorylation of NtrC is not sufficient for activation of NtrC. At low protein concentrations (50 nM), phosphorylated NtrC was only active as an ATPase upon cooperative binding to DNA. At high protein concentrations (above 50 nM), NtrC was active in the absence of DNA, and activation occurred in parallel with the formation of high-molecular-weight aggregates. We infer that activation of NtrC involves an interaction between two NtrC-P dimers and proceeds in two steps. The first step is the phosphorylation of NtrC. The second step is the interaction between two NtrC-P dimers. This interaction induces the conformational change in NtrC-P to the active conformation.

A common switch in activation of the response regulators NtrC and PhoB: phosphorylation induces dimerization of the receiver modules

During signal transduction, response regulators of two-component systems are phosphorylated in a conserved receiver module. Phosphorylation induces activation of the non-conserved output domain. We fused various domains of the response regulators NtrC, PhoB or CheB to the DNA binding domain of lambda repressor. Analysis of these hybrid proteins shows that the receiver modules of NtrC and PhoB are potential dimerization domains. In the unphosphorylated proteins, the ability of the receiver modules to dimerize is masked due to inhibition by their output domains. Inhibition can be relieved in two ways: phosphorylation of the receiver module or deletion of the output domain. In contrast, the receiver module of CheB lacks this ability for dimerization. We propose a model which groups response regulators into two classes. Common to both classes is the interaction between receiver and output domain in the unphosphorylated protein. In class I (e.g. NtrC and PhoB), this interaction leads to the inhibition of the receiver module. Phosphorylation relieves inhibition, thereby inducing activation via dimerization of the receiver modules. In class II (e.g. CheB), the interaction between receiver and output domain results in inhibition of the output domain. Phosphorylation relieves inhibition, thereby activating the output domain.

[The sleep apnea syndrome in patients with acromegaly]

The authors examined 19 nonselected patients with acromegaly (8 women and 11 men), incl. 16 where the disease was hormonally active, 3 had normal growth hormone values, 11 patients had a surgical operation of the pituitary. The examination was made by the MESAM 4 method (all-night recording of the heart rate, respiratory sounds, body position and arterial oxygen blood saturation). The sleep apnoea syndrome was diagnosed in 10 patients (52.6%). In patients where the sleep apnoea syndrome was not confirmed by MESAM 4, so-called intermittent snoring was found, an indirect sign of impaired ventilation during sleep.

Spatial-frequency response of holographic gratings photodeposited from inorganic colloids

Surface photodeposition is a photon-assisted process by which thin films are formed on substrates immersed in colloid solutions. We experimentally evaluate the resolution capabilities of the photodeposition process with amorphous selenium colloids by recording holographic gratings at different spatial frequencies, up to 2200 lines/mm. The experimental diffraction efficiencies are analyzed in terms of a theoretical model, which relates the spatial-frequency response to optical recording parameters and colloid particle sizes. The maximal experimental diffraction efficiency reaches 13% with a spatial frequency of f = 1100 lines/mm. The diffraction efficiencies decrease monotonically with spatial frequency, and drop to half of the maximal diffraction efficiency at f ≈ 1500 lines/mm. These resolution capabilities are achieved with colloid particle sizes extending up to 80 nm. The theoretical derivation indicates that to obtain spatial frequencies above 3000 lines/mm, one should restrict the colloid particle size to a(max) ≤ 30 nm.

Phosphorylation of nitrogen regulator I of Escherichia coli induces strong cooperative binding to DNA essential for activation of transcription

We studied the effect of phosphorylation of nitrogen regulator I (NRI) on its binding properties. Both phosphorylated and unphosphorylated NRI bind linearly to a single binding site but cooperatively to two adjacent binding sites. Cooperative binding of NRI is severely affected by phosphorylation: half-maximal binding of NRI-phosphate is at 20-fold lower concentrations than that of unphosphorylated NRI. This is more due to a huge increase in the cooperativity constant--which is the strength of interaction between two NRI dimers--than to an increase in the microscopic binding constant which is the binding affinity to a single binding site. In vitro transcription and DNA footprinting experiments showed that occupation of a single binding site by NRI is not enough for efficient activation and that activation only occurs at a higher NRI concentration. We propose an activation mechanism for NRI in which the phosphorylation of NRI induces a conformational change in the N-terminal domains of the NRI-phosphate dimers, which now interact strongly with each other, leading to a tetramerization of NRI upon binding to two adjacent binding sites. We propose that not the phosphorylation of NRI itself but rather the tetramerization of NRI-phosphate on DNA binding induces the conformational change of the central domain to the active conformation.

Preservation of the myocardial collagen framework by human growth hormone in experimental infarctions and reduction in the incidence of ventricular aneurysms

We administered human growth hormone to a group of rats with experimental myocardial infarctions, in order to observe its action on the connective tissue repair process and the consequent effect on postinfarction ventricular aneurysms. Myocardial connective tissue displays a complex layout around each myocyte and among neighboring ones. It has been shown to be highly vulnerable to acute coronary ischemia which affects its diverse components in accordance with a precise timetable. The ultimate consequence of ischemia on connective tissue is the disappearance of intermyocytic links and the collagen weave that surrounds each cell. Damage to this collagen framework of the heart is responsible for the final disarray of myocytes, with a parallel effect to the myocytolytic actions of ischemia within the very structure of each cell. Hence, the appearance of postinfarction ventricular aneurysms seems to be related to failure in normal repair processes resulting from maturation of new collagen tissue into the area of myocardial necrosis. It has been shown that, besides the well-known actions on chondrocytes, hypothalamic-hypophyseal human growth hormone and somatomedins activate the fibroblasts. Administration of human growth hormone resulted in a significant decrease in the incidence of ventricular aneurysms. Scanning electron microscopy showed a good preservation of connective tissue components of myocardium. A different histological pattern of necrosis resulted in the treated group.

Bivalent effects of human growth hormone in experimental myocardial infarcts. Protective when administered alone and aggravating when combined with beta blockers

Human growth hormone (hGH) administered alone revealed itself as a useful drug to prevent ventricular aneurysm formation in experimental myocardial infarctions in rats and is also able to diminish and change the usually expected pattern of wall necrosis. A protective action on the collagen framework of myocytes has been confirmed as one of the main causes responsible for the above mentioned findings. There are other positive metabolic actions on the myocardial cell although not completely known yet. These actions are revealed by an atypical picture of infarction which appears regionally reduced and with a patchy intracellular distribution. In an opposite fashion, when hGH was administered together with beta blockers, a rapid and extensive deleterious action occurred at the ventricular wall, a very high incidence of ventricular aneurysms and an increased extension of myocardial infarcts were the most outstanding features. The histologic picture in this series resembles that of a rapidly evolving diabetic cardiomyopathy.

Holographic elements with high efficiency and low aberrations for helmet displays

A recursive design technique for forming holographic elements which can be incorporated into helmet displays has been developed. To ensure that the holographic elements have low aberrations and high diffraction efficiency they must be recorded with complex wavefronts. These wavefronts are derived from relatively simple intermediate holograms whose readout geometry and wavelength differ from those during recording. The overall recursive design technique is illustrated for a single holographic helmet display element having resolution of less than 0.8 mrad and diffraction efficiency of more than 80 percent over a field of view of 16 degrees x 16 degrees .

Phosphorylation of nitrogen regulator I (NRI) of Escherichia coli

It has previously been shown that phosphorylated nitrogen regulator I (NRI-phosphate) is the activator responsible for increasing the transcription of glnA, the structural gene for glutamine synthetase, and that NRII catalyzes the transfer of the gamma-phosphate of ATP to NRI. We have now shown that the reaction of ATP with NRII results in the reversible transfer of the gamma-phosphate of ATP to a histidine residue of NRII. In turn, NRII-phosphate transfers its phosphate reversibly to an aspartic residue of NRI. NRI-phosphate is hydrolyzed to NRI and inorganic phosphate in a divalent cation-requiring autocatalytic reaction.

Plasma serine proteinase inhibitors (serpins) exhibit major conformational changes and a large increase in conformational stability upon cleavage at their reactive sites

Intact and proteolytically modified human serpins, alpha 1-proteinase inhibitor, antithrombin III, alpha 1-antichymotrypsin, and C1 inhibitor, were compared by circular dichroism, fluorescence spectroscopy, and resistance against unfolding by guanidine HCl. The modified proteins were prepared from the intact and active inhibitors by selective proteolytic cleavage in their reactive site loops and tested for complete loss of activity. Significant differences in the spectral properties between intact and modified inhibitors indicate that a major conformational rearrangement is triggered by the cleavage. This leads to a large increase in conformational stability as demonstrated by large shifts of the transition profiles recorded as a function of guanidine HCl concentration at 20 degrees C by circular dichroism at 220 nm. Intact inhibitors were unfolded in two steps of about equal size centered at 0.8-1.7 and 2.5-3.5 M concentrations of the denaturant, respectively. Under identical conditions modified inhibitors are completely stable, and their denaturation occurs only well above 4 M guanidine HCl in one or two steep transition steps. From the similarity of the spectral changes and shifts in transition profiles for all four serpins studied it is concluded that the conformational changes and stabilization triggered by the modification hit is an important common mechanistic feature of this class of inhibitors. This is supported by the observation that ovalbumin, which is homologous with the serpins but apparently lacks inhibitory activity, exhibits neither spectral changes nor a significant change in stability upon proteolytic modification.

[Immunologic aspects in disorders of male fertility]

The spermatozoa may in some circumstances induce immunological response mechanisms and evoke sperm autoimmunization. Different types of sperm antigens can be found in the seminal fluid and on the spermatozoa. New techniques: the radio-immunoassay (RIA) and the enzyme linked immunosorbent assay (ELISA) become more and more significant in the detecting of spermaantibodies. In some cases genital infections presented at the same time can be treated. Common use is the empirical therapy with steroids, successful in about 30%. May be in future a specific immunotherapy with allergenic extracts is possible.

Functional model of subcomponent C1 of human complement

The domain organization of the zymogen subunits of the first component of human complement C1s, C1r2 and the complex C1s-C1r2-C1s was studied by electron microscopy. In the absence of Ca2+, monomeric C1s was visualized as a dumb-bell-shaped molecule consisting of two globular domains (center-to-center distance 11 nm) connected by a rod. One of the globular domains is assigned to the light chain (B-chain) of the activated molecule, which is homologous to trypsin and other serine proteases. The second globular domain and the rod are assigned to the heavy chain (A-chain) of CIs. The subunit C1r is a stable dimer in the presence or absence of Ca2+. This dimer C1r2 was visualized as composed of two dumb-bells of dimensions similar to those observed for C1s. These are connected near the junctions between the rod and one of the globular domains. This leads to the structure of an asymmetrical X with two inner closely spaced globules (center-to-center distance 7 nm) and two outer globules at a larger distance (14 nm). By comparison with fragment C1rII2, in which part of the A-chain is removed, the inner globular domains were assigned to the catalytic B-chains. This characteristic structure of C1r2 is readily recognized in the central portion of the thread-like 54 nm long C1s-C1r2-C1s complex formed in the presence of Ca2+. By affinity-labeling of C1s with biotin and visualization of avidin-ferritin conjugates in the reconstituted complex, it was demonstrated that C1s forms the outer portion of the complex. A detailed model of C1s-C1r2-C1s is proposed, according to which two C1s monomers bind to the outer globes of C1r2 by contacts between their heavy chains and those of C1r. According to this model the catalytic domains of C1r are located in the center and those of C1s at the very tips of the C1s-C1r2-C1s complex. On the basis of the structure of C1s-C1r2-C1s, we derived a detailed model of the C1 complex (composed of C1q and the tetrameric complex) and we discuss this model with a view to finding a possible activation mechanism of C1.(ABSTRACT TRUNCATED AT 400 WORDS)

[Retrospective evaluation of the findings in male fertility disorders with special reference to spermiograms and hormone analyses]

736 ejaculates from 384 patients in the andrological outpatient clinic in Giessen were classified in fertile, subfertile and infertile Groups. Regarding volume, pH-value and fructose content of the ejaculate no differences were found among the three groups. Important for the classification is sperm count/ml and the progressive motility. Additional Hormone analyses showed a negative correlation between sperm count and FSH-Values. Disturbances in spermiogenesis are often connected with high LH-Values.

[Characteristics of middle-latency auditory evoked potentials in awake and anesthetized patients]

Late auditory evoked potentials (50-500 msec latency) can be evoked by tonal stimuli but their instability prevents their use in many clinical situations. In contrast, the early responses (up to 10 msec) are stable, regardless of sleep or sedation, but they can only be evoked by transient, non-tonal stimuli. Therefore neither type may be used for an evaluation of frequency thresholds. The middle latency responses represent a compromise: first, they can be evoked by tonal stimuli of the tone-pip type and, second, they are relatively stable. For these reasons the authors have carried out a general study on the middle latency responses in subjects with normal hearing, in patients with impaired hearing and in patients under a variety of surgical anesthesia. The middle latency response evoked by clicks and tone-pips (4 sines of 500, 1000, 2000 and 4000 Hz) have a series of characteristic waves named, according to their latency, A(V), B(No), C(Po), D(Na), E(Pa). The threshold of visual detection for these potentials is situated near that of the psycho-acoustic threshold (0-20 dB). The authors point out the clinical utilization of the middle latency response especially in cases in which one desires an objective evaluation of the auditory threshold in the lower frequency range. It is important to know that the middle latency response remains present using some types of anesthesia (Ketalar, ataralgesy), disappears partially with neuroleptanesthesia and completely with inhalation anesthesia (fluothane, halothane).

Heparin-stimulated modification of C1-inhibitor by subcomponent C1s of human complement

C1-inhibitor and C1s form a very stable complex which migrates with an apparent molecular mass of 180 kDa in dodecyl sulfate gel electrophoresis. A small fraction of the inhibitor (100 kDa) was found to be converted to a large (95 kDa) and a small (2 to 5 kDa) fragment during this reaction. It is concluded that C1-inhibitor is modified by C1s in a similar way as are the related plasma inhibitors alpha 1-proteinase inhibitor, antithrombin III and antiplasmin by their specific proteinases. The fraction of modified C1-inhibitor increased when heparin was present during complex formation. This reaction was complete after 15 s and is comparable with the fast heparin induced formation of modified antithrombin III. Treatment with hydroxylamine led to a complete dissociation of the inhibitor-enzyme complex by dodecyl sulfate. The large inhibitor fragment (and not unmodified inhibitor as reported by other authors) was released.

Chronic infection with cutaneous herpes simplex in a patient with systemic lupus erythematosus

A 68-year-old black woman with systemic lupus erythematosus being managed by systemic corticosteroids developed large ulcerated lesions in a dermatomal distribution on the flank and abdomen. Subsequently, large ulcers developed progressively in the perianal region, the buttocks, the perivaginal region, and the thighs. The clinical diagnosis was vasculitis of systemic lupus erythematosus. Biopsy from the margin of an ulcer showed changes in the epidermis that are specific for infections by herpesvirus. Electron microscopy revealed viral particles of herpesvirus. Cultures from the perianal lesions grew Herpesvirus hominis. This is the first report to our knowledge of "chronic cutaneous herpes infection" in a patient with systemic lupus erythematosus.