Biomedical subjects

G Berger

Publications and source records attributed to G Berger.

At least 109 records · Page 6Linked to original sources

PubMed1996

The functional role of the adenoids in speech.

Illustrative cases are presented showing a variety of interrelationships between the adenoids and the activity of the velopharyngeal valve in speech. The cases presented were selected from a group of 1000 patients referred because of suspected velopharyngeal diseases. When appropriate, complete velopharyngeal assessment was made including otolaryngological speech and hearing examination, polysomnography, nasendoscopy, multiview videofluoroscopy and cephalometry. New observations are described which further elucidate the mechanism by which the adenoids may change the mechanism of velopharyngeal valving and consequently speech patterns. In conclusion, procedures involving the adenoids and tonsils and surgical correction of velopharyngeal valve abnormalities to improve respiratory function must be performed in a manner which ensures preservation of normal speech activity. Similarly, surgical correction of velopharyngeal valve abnormalities to improve speech activity must preserve its respiratory function. The velopharyngeal valve and the adeno-tonsils must be considered together whenever diagnosis and a therapeutic intervention of either of them is considered. A clinical method for patient evaluation, patient management and the development of a rational therapeutic approach is presented.

Adenoids↗

PubMed1996

[3-D reconstruction of intracranial vessels using a color Doppler energy method--initial experiences].

Transcranial Doppler sonography and colour Doppler imaging provide good information on the basal arterial brain vessels, but cannot provide images comparable to angiographic images. However, comparable displays could be achieved by a 3-dimensional calculation of images collected by a computer. These images of intracranial vessels are supplied by the new Doppler imaging modality Colour Doppler Energy (CDE). Tilting of the acquired data can then be oriented analogous to angiography, CT and MRI projections. Initial results with this method are very promising.

Brain↗

PubMed1996

Beta-carbolines in chronic alcoholics following trauma.

In our society every second polytraumatized patient is a chronic alcoholic. A patient's alcohol-related history is often unavailable and laboratory markers are not sensitive or specific enough to detect alcohol-dependent patients who are at risk of developing alcohol withdrawal syndrome (AWS) during their post-traumatic intensive care unit (ICU) stay. Previously, it has been found that plasma levels of norharman are elevated in chronic alcoholics. We investigated whether beta-carbolines, i.e. harman and norharman levels, could identify chronic alcoholics following trauma and whether possible changes during ICU stay could serve as a predictor of deterioration of clinical status. Sixty polytraumatized patients were transferred to the ICU following admission to the emergency room and subsequent surgery. Chronic alcoholics were included only if they met the DSM-III-R and ICD-10 criteria for alcohol dependence or chronic alcohol abuse/harmful use and their daily ethanol intake was > or =60 g. Harman and norharman levels were assayed on admission and on days 2, 4, 7 and 14 in the ICU. Harman and norharman levels were determined by high pressure liquid chromatography. Elevated norharman levels were found in chronic alcoholics (n = 35) on admission to the hospital and remained significantly elevated during their ICU stay. The area under the curves (AUC) showed that norharman was comparable to carbohydrate-deficient transferrin (CDT) and superior to conventional laboratory markers in detecting chronic alcoholics. Seventeen chronic alcoholics developed AWS; 16 of these patients experienced hallucinations or delirium. Norharman levels were significantly increased on days 2 and 4 in the ICU in patients who developed AWS compared with those who did not. An increase in norharman levels preceded hallucinations or delirium with a median period of approximately 3 days. The findings that elevated norharman levels are found in chronic alcoholics, that the AUC was in the range of CDT on admission and that norharman levels remained elevated during the ICU stay, support the view that norharman is a specific marker for alcoholism in traumatized patients. Since norharman levels increased prior to the onset of hallucinations and delirium it seems reasonable to investigate further the potential role of norharman as a possible substance which triggers AWS.

Journal Article↗

PubMed1996

Comparison between radionuclide ejection fraction and fractional area changes derived from transesophageal echocardiography using automated border detection.

BACKGROUND: Left ventricular fractional area changes (FAC) can be derived from transesophageal echocardiography using an automated border detection system. However, FAC has not yet been compared to left ventricular ejection fraction (EF) evaluated by a reference technique. The aim of this study was to correlate transesophageal echocardiography automated FAC to EF derived from radionuclide angiography to obtain a quantifying method of global left ventricular systolic function at the bedside. METHODS: Ten critically ill patients, whose lungs were mechanically ventilated, were included in this prospective study. Patients were scheduled for radionuclide EF evaluation when at least 75% of the endocardium was clearly visualized on transesophageal echocardiography. Patients with esophageal pathology or cardiac dysrhythmia were excluded. Ejection fraction derived from radionuclide angiography was measured using technetium 99m. Echocardiographic data were obtained using an ultrasound system with automated border capabilities. Simultaneous measurements of left ventricular EF and FAC were obtained for each patient, both before and after starting a dobutamine intravenous infusion to modify left ventricular contractility. RESULTS: Mean values for radionuclide EF and transesophageal echocardiography FAC were, respectively: 55% +/- 19% (range 19-89%) and 46% +/- 18% (range 17-80%). Left ventricular EF and FAC were significantly correlated (r = 0.85, SEE = 9.6%). Variations of EF and FAC, induced by dobutamine, were also correlated (r = 0.70, SEE = 4.9%). CONCLUSIONS: Fractional area changes determined by transesophageal echocardiography using automated border detection correlate well with radionuclide EF and may be used at the bedside to quantify left ventricular function in selected intensive care unit patients.

Echocardiography, Transesophageal↗

PubMed1996

Immunoelectron microscopic changes of the platelet plasma membrane after activation.

The observation of protein redistributions from one compartment to another during platelet activation reflects changes in platelet functionality. At rest alpha-granules express a high level of the main aggregation receptor GPIIb/IIIa, and only a small amount of the adhesion receptor complex GPIb/IX/V which lines the plasma membrane. After activation, the plasma membrane loses GPIb whereas the level of expression of the other aggregative proteins such as GPIIb/IIIa increase. These observations correlate well with the passage of the platelet from an adhesive to an aggregative state.

Antigens, CD↗

PubMed1996

Intensive care unit stay is prolonged in chronic alcoholic men following tumor resection of the upper digestive tract.

BACKGROUND: The prevalence of chronic alcohol misuse in patients with oral, pharyngeal, laryngeal or esophageal carcinomas exceeds 60%. No data is available, to our knowledge, on the morbidity and mortality of chronic alcoholics in surgical intensive care units (ICU) following tumor resection. We investigated whether the subsequent ICU stay in chronic alcoholics following tumor resection was prolonged and whether the incidence of pneumonia and sepsis was increased. METHODS: 213 patients with carcinomas of the upper digestive tract were evaluated regarding their drinking habits. Chronic alcoholics met either the DSM-III-R criteria for alcohol abuse or dependence. Conventional laboratory markers and serum carbohydrate-deficient transferrin were determined preoperatively. Major intercurrent complications during ICU stay such as an alcohol withdrawal syndrome, pneumonia and sepsis as well as the frequency of death were documented. RESULTS: Patients did not differ significantly between groups regarding age or APACHE score on admission to the ICU.121 patients were diagnosed as being chronic alcoholics, 39 as being social drinkers and 61 as being non-alcoholics. In chronic alcoholics the frequency of death was significantly increased. Due to the increased incidence of pneumonia and sepsis the ICU stay was significantly prolonged in chronic alcoholics by approximately 8 days. CONCLUSIONS: The increased mortality and morbidity rate demonstrates that chronic alcoholics undergoing major tumor surgery have to be considered as high-risk patients during their postoperative ICU stay. Further studies are required with respect to the immuno-competence of chronic alcoholics and the prevention of alcohol withdrawal syndrome, pneumonia and sepsis in these patients.

APACHE↗

PubMed1996

Histopathologic changes of the tympanic membrane in acute and secretory otitis media.

The histopathologic changes observed in 40 normal and inflamed temporal bones of infants and children are reported. The tympanic membranes of patients with acute and secretory otitis media underwent considerable swelling compared to those of normal controls. Tympanic membranes with acute otitis media were thicker than those with secretory otitis media, but the difference was not statistically significant. The epithelial layer showed an increase in the number of cell layers. The lamina propria demonstrated the most significant changes of all layers with a marked swelling due to edema, engorged blood vessels, and inflammatory cell infiltration. Increased numbers of distended capillaries were present, predominantly in the subepithelial connective tissue layer, while infiltration of inflammatory cells was mainly in the submucosal connective tissue layer. By contrast, the involvement of the mucosal layer was modest and was composed of cuboidal cells, except for small islands of metaplastic mucosa with mucus production occasionally encountered in specimens with secretory otitis media.

Acute Disease↗

PubMed1996

[Diabetic mastopathy with epithelioid fibroblasts :differential diagnosis from an infiltrating lobular carcinoma of the breast. Report of two cases].

Two cases of diabetic mastopathy are reported. The patients presented with a rapidly increasing mammary mass. The pathologic findings of diabetic mastopathy usually consist of a lymphocytic lobulitis, a dense stromal fibrosis and prominent epithelioid fibroblasts. In our two cases, the latter findings were initially misinterpreted as malignant cells of an invasive lobular carcinoma. These lesions were first described in longstanding insulin dependent diabetics but recent reports showed that they could also occur in patients with other auto-immune disorders (systemic lupus erythematous, hypothyroidism). Diabetic mastopathy may reoccur locally and the treatment remains to be determined.

Adult↗

PubMed1995

Binding sites of quinones in photosynthetic bacterial reaction centers investigated by light-induced FTIR difference spectroscopy: symmetry of the carbonyl interactions and close equivalence of the QB vibrations in Rhodobacter sphaeroides and Rhodopseudomonas viridis probed by isotope labeling.

The photoreduction of the secondary quinone acceptor QB in reaction centers (RCs) of the photosynthetic bacteria Rhodobacter sphaeroides and Rhodopseudomonas viridis has been investigated by light-induced FTIR difference spectroscopy of RCs reconstituted with several isotopically labeled ubiquinones. The labels used were 18O on both carbonyls and 13C either uniformly or selectively at the 1- or the 4-position, i.e., on either one of the two carbonyls. The QB-/QB spectra of RCs reconstituted with the isotopically labeled and unlabeled quinones as well as the double differences calculated from these spectra exhibit distinct isotopic shifts for a number of bands attributed to vibrations of QB and QB-. The vibrational modes of the quinone in the QB site are compared to those of ubiquinone in vitro, leading to band assignments for the C = O and C = C vibrations of the neutral QB and for the C***O and C***C of the semiquinone. The C = O frequency of each of the carbonyls of the unlabeled quinone is revealed at 1641 cm-1 for both species. This demonstrates symmetrical and weak hydrogen bonding of the two C = O groups to the protein at the QB site. In contrast, the C = C vibrations are not equivalent for selective labeling at C1 or at C4, although they both contribute to the approximately 1617-cm-1 band in the QB-/QB spectra of the two species. Compared to the vibrations of isolated ubiquinone, the C = C mode of QB does not involve displacement of the C4 carbon atom, while the motion of C1 is not hindered. Further analysis of the the spectra suggests that the protein at the binding site imposes a specific constraint on the methoxy and/or the methyl group proximal to the C4 carbonyl. The FTIR observations provide compelling evidence for almost identical conformation and identical interactions of the ubiquinone in the QB binding site of Rb. sphaeroides and Rp. viridis in contrast to the X-ray structures, which yield different descriptions for the hydrogen-bonding pattern of QB binding. In the semiquinone state, the bonding interactions of the C***O groups are also symmetrical and the C***C are inequivalent at C1 and C4. However, the interactions are almost the same in the RCs of both species.

Binding Sites↗

PubMed1995

Rapid resorbable, glassy crystalline materials on the basis of calcium alkali orthophosphates.

Materials based on calcium orthophosphates have been developed to crystallize spontaneously and directly from the melt. The main crystalline phase consists of a new synthesized chemical of formula Ca2KNa(PO4)2. This compound crystallizes in a very wide range of chemical compositions as shown. Furthermore, the solubility was tested and compared with that of self-prepared alpha-tricalcium phosphate ceramics and commercial products of hydroxyapatite ceramics and surface-modified alpha-tricalcium phosphate ceramics. The results show that new materials containing the compound Ca2KNa(PO4)2 had the highest solubility in comparison with other tested materials.

Biodegradation, Environmental↗

PubMed1995

Relevance of carbohydrate-deficient transferrin as a predictor of alcoholism in intensive care patients following trauma.

Every second traumatized patient is a chronic alcoholic. Chronic alcoholics are at risk due to an increased morbidity and mortality. Reliable and precise diagnostic methods for detecting alcoholism are mandatory to prevent posttraumatic complications by adequate prophylaxis. The patient's history, however, is often not reliable, and conventional laboratory markers are not sensitive or specific enough. The aim of this study was to investigate whether carbohydrate-deficient transferrin (CDT) is a sensitive and specific marker to detect alcoholism in traumatized patients. One hundred and five male traumatized patients or their relatives gave their written informed consent to participate in this institutionally approved study. All patients were transferred to the intensive care unit after admission to the emergency room, followed by surgical treatment. Diagnostics included an alcoholism-related questionnaire, conventional laboratory markers (mean corpuscular volume, gamma-glutamyltransferase, aspartate aminotransferase, and alanine aminotransferase), and CDT sampling (microanion-exchange chromatography, turbidimetry, and radioimmunoassay, respectively). Only patients in whom a reliable history could be obtained were included. Alcoholism was diagnosed if the patients met the Diagnostic and Statistical Manual of Mental Disorders criteria for chronic alcohol abuse or dependence. The administration of fluids before CDT sampling was carefully documented. Patients did not differ significantly regarding age, Trauma and Injury Severity Score, and Acute Physiology and Chronic Health Evaluation score. The sensitivity of the CDT research kit was 70% and of the commercially available kit CDTect was 65%. Early sampling in the emergency room and before administration of large volumes of fluid increased the sensitivity to 83% for the CDT research kit and 74% for CDTect, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Beta-carbolines in chronic alcoholics undergoing elective tumor resection.

The prevalence of chronic alcoholism in patients with carcinomas of the upper digestive tract exceeds 60%. The patient's history and laboratory markers, preoperatively, are often not sensitive or specific enough to detect alcohol-dependent patients, preoperatively, who are at risk of developing alcohol withdrawal syndrome (AWS) during their postoperative intensive care unit (ICU) stay. Previously, it was found that plasma norharman was elevated in chronic alcoholics, suggesting marker characteristics for chronic ethanol misuse and possibly alcohol dependence. We investigated whether beta-carbolines (i.e., harman and norharman) were different between chronic alcoholics and nonalcoholics with carcinoma, and how the levels change in alcohol-dependent patients during their hospital stay. Ninety-seven patients with oral, pharyngeal, laryngeal, or esophageal carcinomas were evaluated regarding their drinking habits. Sixty patients were transferred to the ICU following tumor resection. Chronic alcoholics met the DSM-III-R and ICD-10 criteria for alcohol dependence or chronic alcohol abuse/harmful use. The daily ethanol intake in chronic alcoholics was > or = 60 g. Blood samples were collected on admission to the hospital, preoperatively, on admission to the ICU and on days 2, 4, and 7 in the ICU. Harman and norharman were determined by HPLC. Elevated norharman was found in chronic alcoholics on admission to the hospital, whereas harman did not differ between groups. On admission, the area under the receiver operating characteristics curve was significantly larger for carbohydrate-deficient transferrin and preoperatively for norharman. The preoperative norharman levels were significantly correlated with the period of mechanical ventilation and the length of ICU stay. Postoperatively, norharman decreased in all patients, except a group of 11 alcohol-dependent patients who developed AWS during their ICU stay. The finding that elevated norharman levels were found in chronic alcoholics on admission to the hospital and preoperatively supports the view of a specific marker for alcoholism. Preoperative norharman was superior to carbohydrate-deficient transferrin and was associated with a prolonged ICU stay and a prolonged period of mechanical ventilation. Further studies are required to determine whether norharman aids in the preoperative diagnosis of chronic alcohol misuse with respect to the prevention of postoperative complications.

Adult↗

PubMed1994

Binding sites of quinones in photosynthetic bacterial reaction centers investigated by light-induced FTIR difference spectroscopy: binding of chainless symmetrical quinones to the QA site of Rhodobacter sphaeroides.

Light-induced FTIR QA-/QA difference spectra corresponding to the photoreduction of the primary quinone acceptor QA have been obtained for Rhodobacter sphaeroides RCs reconstituted with chainless symmetrical quinones in order to study the influence of the side chain and of molecular asymmetry on the binding of natural quinones to the QA site. The main vibrational modes of the quinones in vivo were obtained by analysis of the isotope effects induced by 18O substitution on the carbonyls and by comparison with the IR absorption spectra of the isolated quinones. For isolated 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone (MQ0), 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ), and 2,3-dimethyl-1,4-naphthoquinone (DMNQ), the IR spectra together with mass spectroscopy data of partially 18O labeled quinones show that the labeling of one carbonyl leads to only a minor shift of the vibrational frequency of the opposite carbonyl. This observation demonstrates an essentially uncoupled behavior of the two C = O groups. Upon reconstitution of QA-depleted RCs with these symmetrical quinones, the double-difference spectra calculated from the QA-/QA spectra of the 18O-labeled and unlabeled quinones reveal a splitting of the quinone C = O modes. This splitting and the frequency downshift of the C = O vibrations upon binding to the QA site are comparable to those previously reported for the C = O modes of quinones containing an isoprenoid (Q8, Q6, Q1) or a phytyl chain (vitamin K1) [Breton, J., Burie, J.-R., Berthomieu, C., Berger, G., & Nabedryk, E. (1994) Biochemistry 33, 4953-4965]. This observation demonstrates that the replacement of the side chain by a methyl group does not impair the asymmetrical bonding interactions of the two quinone carbonyls with the protein. This asymmetry is traceable to the two distinct amino acid residues which have been proposed, on the basis of X-ray structural studies, to form hydrogen bonds with the carbonyls of the quinone. The close analogy between the double-difference spectra calculated for RCs reconstituted either with vitamin K1 or with DMNQ shows that the phytyl chain of vitamin K1 imparts no specific constraint on the geometry of the menaquinone head group in its binding site for both the neutral and the semiquinone state. In contrast, the double-difference spectra calculated for RCs reconstituted either with MQ0 or with Q6 (or Q1) exhibited significant differences in the relative amplitudes of the bands assigned to the mixed C = O and C = C modes of the neutral quinones.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗

PubMed1994

Platelet alpha-granule and plasma membrane share two new components: CD9 and PECAM-1.

CD9 (p24) and PECAM1 (CD31) antigens are well-defined components of the platelet plasma membrane. Both are integral glycoproteins (GPs) implicated in the adhesive and aggregative properties of human platelets. In the present report, we have investigated their subcellular localization using immunoelectron microscopy. The monospecificity of the two polyclonal antibodies used was confirmed by immunoblotting. On normal resting platelets, immunolabeling for CD9 and PECAM1 was found lining the plasma membrane and the luminal face of the open canalicular system. Some labeling was also consistently found on the alpha-granule limiting membrane. This was confirmed by double labeling experiments in which fibrinogen and von Willebrand factor (vWF) were used as alpha-granule markers. CD9 and PECAM-1 were found lining the membrane of the same granules that contained fibrinogen and vWF in their matrix. CD9 and PECAM-1 thus appear to have an intracellular distribution identical to GPIIb-IIIa, a major aggregation platelet receptor. To rule out a cross-reactivity of the two polyclonal antibodies with GPIIb/IIIa, we studied PECAM1 and CD9 expression on the platelets from a patient with type I Glanzmann's thrombasthenia whose platelets are devoid of GPIIb/IIIa. The same pattern of labeling was observed for both antigens as for normal platelets. Normal platelets were further observed after stimulation by agonists that either fail to induce (ADP) or induce granule secretion (thrombin). After treatment with ADP, platelets changed shape and centralized their granules; the plasma membrane immunolabeling remained unchanged; and gold particles were still found decorating the periphery of the centralized alpha-granules. After thrombin treatment, alpha-granules fused with the platelet membrane and secretion occurred. A significant increase of labeling was then observed on the platelet surface. From these results we conclude that the alpha-granule membrane contains two additional receptors in common with the plasma membrane. This suggests that alpha-granule membrane receptors may originate from a dual mechanism: direct targeting from the Golgi complex in megakaryocytes (for alpha-granule-specific receptors such as P-selectin) or by endocytosis from the plasma membrane (for proteins distributed in the two compartments).

Adenosine Diphosphate↗

PubMed1994

The binding sites of quinones in photosynthetic bacterial reaction centers investigated by light-induced FTIR difference spectroscopy: assignment of the QA vibrations in Rhodobacter sphaeroides using 18O- or 13C-labeled ubiquinone and vitamin K1.

Light-induced FTIR difference spectra of the photoreduction of the primary quinone acceptor QA have been obtained for Rhodobacter sphaeroides RCs reconstituted with a series of isotopically labeled quinones in order to separate the contributions of the quinone from those of the protein. The isotopic shifts observed in the QA-/QA spectra of RCs reconstituted with ubiquinones (Q1, Q6) or vitamin K1 18O-labeled on their carbonyl oxygens and with fully 13C-labeled Q8 lead to a clear identification of the quinone bands from both the neutral and anion forms. Double-difference spectra from pairs of QA-/QA spectra obtained from 18O/16O Q6, 18O/16O Q1, 13C/12C Q8, 13C18O/12C16O Q8, and 18O/16O vitamin K1 allow the C = O modes of QA in vivo to be identified unambiguously for the first time. For all the investigated unlabeled quinones, two carbonyl bands are demasked, at 1660 and 1628 cm-1 for neutral ubiquinones and at 1651 and 1640 cm-1 for vitamin K1, while C = C bands are found at 1608 and 1588 cm-1 for vitamin K1 and at 1601 cm-1 for ubiquinones. Compared with the spectra of the isolated quinones, the generally smaller width observed for the C = O and C = C bands in vivo suggests precise interactions between the quinone and the contours of the protein at a single, well-defined QA site. The different frequency downshifts of the two C = O bands upon binding to the QA site underscore the inequivalence of the two carbonyls in providing asymmetrical bonding interactions with the protein. The comparison of the isotopic shifts observed for the various quinone C = O and C = C bands in vitro and in vivo demonstrates that the admixture of C = O and C = C characters in these modes is strongly affected by the binding of QA to its anchoring site. In particular, the bands at 1628 and 1601 cm-1 of Q6 in vivo exhibit highly mixed C = O and C = C characters. In contrast, the methoxy groups of the ubiquinones do not appear to suffer large strain upon binding. The closeness of the QA-/QA spectra for Q1 and Q6 indicates that a possible role of the chain in providing the proper positioning of the quinone ring in the site for both the oxidized and reduced states of QA cannot extend significantly beyond the first isoprene unit.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗

PubMed1994

Broadband ultrasonic attenuation imaging: a new imaging technique of the os calcis.

Ultrasound transmission measurement through the os calcis is an emerging technique and a promising clinical tool for early assessment of osteoporosis. However, several previous studies showed that broadband ultrasonic attenuation (BUA) is sensitive to small variations in bone mass or structure. The os calcis is an inhomogeneous bone and therefore, the attenuation depends on the location in the os calcis. BUA distribution within the os calcis can be measured by rectilinear scanning over the entire bone. We used a mechanical scanning device with both unfocused and focused transducers. The spatial resolution of these was about 25 mm and 4 mm, respectively. There was good agreement (r = 0.97) between the results with unfocused and focused transducers. In addition, imaging the variations of BUA is possible with the focused transducers, and high quality images are obtained. These images permit the selection of optimal regions of interest for ultrasound attenuation measurement.

Aged↗

PubMed1994

The role of Mg2+ in the hydrolytic activity of the isolated chloroplast ATPase: study by high-performance liquid chromatography.

The influences of total magnesium ion concentration at different total ATP concentrations, and of total ATP concentration, for different total magnesium ion concentrations, on the enzymatic rate of the isolated chloroplast F1 ATPase, have been followed by a chromatographic method consisting in the separation and determination of ADP. From the various series of curves, it is concluded that the experimental results (position of the maxima, Km values) are better fitted by a mechanism involving the activation of the enzyme by magnesium ion and hydrolysis of free ATP, rather than by the classical mechanism, for which the enzyme hydrolyzes the MgATP complex and is inhibited by Mg2+. Although the equations giving the reaction rate are similar in the two cases, the calculated values of Km are widely different. The value obtained from the classical mechanism does not agree with KD, the dissociation constant of the enzyme-substrate complex, measured by the Hummel and Dreyer method. Moreover, when the total ATP concentration tends toward the total magnesium ion concentration, the nucleotide binding to the enzyme tends toward zero, although it should be maximum if MgATP were the true substrate. Finally, the inhibitory effect of Na+ is more easily explained as a competition between this ion and the activating Mg2+, than by the classical mechanism.

Adenosine Triphosphate↗

PubMed1994

Dissection of the Drosophila pourquoi-pas? promoter: complex ovarian expression is driven by distinct follicle cell- and germ line-specific enhancers.

The pourquoi-pas? (pqp) gene of Drosophila melanogaster encodes a zinc finger protein present in the oocyte nucleus, the nurse cells and, at a lower level, in the follicle cells. Null mutations of the pqp gene lead to female sterility. We have undertaken a functional dissection of the pqp promoter by following the expression of the lacZ reporter gene in the ovaries of transgenic flies. pqp sequences, necessary for expression of the lacZ gene in a pattern similar to that of the endogenous pqp gene, are located between positions -210 and +30, relative to the transcription start site. These sequences, subdivided in follicle cell- and germ line-specific regions, appear to function in a direction-independent and distance-sensitive manner. The -210/-40 region, sharing stretches of sequence similarity with 5' sequences of follicle cell-specific genes, promotes lacZ expression only in the follicle cells. The -80/+30 region is germ line-specific. The promoter limits, deduced from the deletion experiments presented here, are in accordance with the molecular analysis of pqp mutants.

Animals↗