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Biomedical subjects

J Schmitz

Publications and source records attributed to J Schmitz.

At least 163 records · Page 9Linked to original sources
PubMed1992

Harmonic analysis and clustering of facial profiles.

The profiles of 83 healthy young adults were traced from right-side photographs, and then digitized with an image analyzer; each profile thus consisted of a series of coordinates. A dedicated computer program using Fourier analysis resulted in an equation of a curve that interpolated all profile points. By means of cluster analysis, profile equations were divided; two clusters each were found for male and female subjects. A mean profile was calculated for each of the clusters, so that four mean profiles were obtained. These profiles were compared with esthetic parameters found in literature; the results showed that the conventional parameters could sometimes give misleading information for orthodontic and craniofacial orthopedic treatment plans.

Adult↗
PubMed1992

Familial microvillous atrophy: a clinicopathological survey of 23 cases.

Twenty-three cases of microvillous atrophy were reviewed to determine clinical and morphological characteristics of the disease. Congenital and late-onset forms of presentation were clearly identified in which the late-onset cases appeared to have a better prognosis. Three different, and distinctive, appearances of the proximal small intestinal mucosa were found. Careful orientation of mucosal samples allowed a temporal sequence of events to be delineated in which the first morphological abnormality to be detected in the epithelium was the accumulation of "secretory granules"; microvillous inclusions were seen in older cells in the upper villous region. It is suggested that, in familial microvillous atrophy, diarrhoea and disorganisation of the brush border assembly occur as a consequence of a more fundamental defect that affects the intracellular traffic of certain cell components, as indicated by the accumulation of "secretory granules."

Aminopeptidases↗
PubMed1992

[MR tomographic aspects of olivary pseudohypertrophy].

MRI aspects of olivary pseudohypertrophy (OH) following pontocerebellar lesions of different etiology and localization are reviewed. OH is characterized by unilateral or bilateral enlargement of the inferior olivary nucleus and increased signal intensity in T2- and, especially, in proton-density (PD)-weighted images. Correlations between the extent and the uni- or bilateral presence of olivary hypertrophy and the localization of the primary pontocerebellar lesions are discussed.

Adolescent↗
PubMed1992

Ribosomal frameshifting in plants: a novel signal directs the -1 frameshift in the synthesis of the putative viral replicase of potato leafroll luteovirus.

The 5.8 kb RNA genome of potato leafroll luteovirus (PLRV) contains two overlapping open reading frames, ORF2a and ORF2b, which are characterized by helicase and RNA polymerase motifs, respectively, and possibly represent the viral replicase. Within the overlap, ORF2b lacks an AUG translational start codon and is therefore presumably translated by -1 ribosomal frameshifting as a transframe protein with ORF2a. This hypothesis was studied by introducing the putative frameshift region into an internal position of the beta-glucuronidase (GUS) gene and testing for the occurrence of frameshifting in vivo by transient expression of GUS activity in potato protoplasts as well as in vitro by translation in the reticulocyte system. Both experimental approaches demonstrate that a -1 frameshift occurs at a frequency of approximately 1%. Site-directed mutagenesis identified the frameshift region and the involvement of the novel heptanucleotide motif UUUAAAU in conjunction with an adjacent stem-loop structure. Part of this stem-loop encodes a basic region in the ORF2b moiety of the transframe protein which was shown by binding experiments with PLRV RNA to represent a nucleic acid-binding domain. These data support a possible biological significance of the frameshift to occur at this position of the large overlap by including the putative RNA template-binding site of the PLRV replicase in the ORF2a/ORF2b transframe protein.

Amino Acid Sequence↗
PubMed1991

Nonspiking pathways antagonize the resistance reflex in the thoraco-coxal joint of stick insects.

In the stick insect (Carausius morosus) imposed forward and backward movements of the coxa of the middle leg induce resistance reflexes in the retractor or protractor coxae muscles, depending on the direction of movement. The hairs of the ventral coxal hairplate (cxHPv) function as the primary transducer of the retractor part of the underlying feedback loop: bending of the hairs of the cxHPv during an imposed forward movement of the coxa leads to a reflex activation of the retractor motoneurones, whereas releasing of the hairs causes an inhibition of these motoneurones. Local nonspiking interneurones were investigated, which transmit information from the cxHPv onto the retractor motoneurones: 1) they are depolarized during bending of the hair sensilla of the cxHPv and 2) they decrease the activities of retractor motoneurones. In addition, four of the interneurones drive a protractor motoneurone, when they are depolarized. As bending stimuli at the cxHPv (mimicking an imposed forward movement of the leg) induce reflex activation of the retractor motoneurones and reflex inhibition of the protractor motoneurones, the physiology of the recorded interneurones appears to antagonize the resistance reflex in the thoraco-coxal joint. The results indicate that these nonspiking interneurones take part in the shaping of the reflex response and that furthermore these interneurones are involved in the organization of the motor output to the two antagonistic sets of motoneurones. The possible role of these interneurones might be the adjustment of the gain and of the time constant in the thoraco-coxal feedback loop.

Animals↗
PubMed1991

Intracellular recordings from nonspiking interneurons in a semiintact, tethered walking insect.

Nonspiking interneurons were investigated in a tethered, walking insect, Carausius morosus, that was able to freely perform walking movements. Experiments were carried out with animals walking on a lightweight, double-wheel treadmill. Although the animal was opened dorsally, the walking system was left intact. Intracellular recordings were obtained from the dorsal posterior neuropil of the mesothoracic ganglion. Nonspiking interneurons, in which modulations of the membrane potential were correlated with the walking rhythm, were described physiologically and stained with Lucifer Yellow. Interneurons are demonstrated in which membrane potential oscillations mirror the leg position or show correlation with the motoneuronal activity of the protractor and retractor coxae muscles during walking. Other interneurons showed distinct hyperpolarizations at certain important trigger points in the step cycle, for example, at the extreme posterior position. Through electrical stimulation of single, nonspiking interneurons during walking, the motoneuronal activity in two antagonistic muscles--protractor and retractor coxae--could be reversed and even the movement of the ipsilateral leg could be influenced. The nonspiking interneurons described appear to be important premotor elements involved in walking. They receive, integrate, and process information from different leg proprioceptors and drive groups of leg motoneurons during walking.

Animals↗
PubMed1991

Proliferation of germinal center B lymphocytes in vitro by direct membrane contact with follicular dendritic cells.

In secondary lymphoid organs, follicular dendritic cells (FDC) are located within B cell follicles and germinal centers. Through their cytoplasmic extensions they come into contact with a large number of neighboring lymphocytes. Using an enzyme cocktail to digest human tonsils followed by ultracentrifugation on bovine serum albumin gradients, single cell suspensions were obtained. Immunocytochemistry revealed that 7% of the cells were FDC, 5% T cells, and 5% macrophages. The remaining population were B cells with greater than 95% being of the germinal center phenotype (i.e. CD19-positive, CD39/sIgD negative). After 24 h of culture up to 44% of the lymphocytes were found in clusters centered around FDC. At the start of the culture as well as 24 and 72 h later, between 31 and 55% of the B cells within FDC associated clusters were in late G1 to M phase of the cell cycle. In contrast, less than 10% of the B cells not in contact with FDC (i.e. outside the clusters) were in an activated state. Autoradiography revealed that after three days of incubation the rate of proliferation was 26.2 times higher for the lymphocytes involved in cluster formation as compared to those cells not associated with FDC. Furthermore, the number of viable B cells after a 72 h mitogen-free culture period was determined. By adding FDC to these preparations, 31.9% of the lymphocytes were rescued from dying. These data show that FDC provide a microenvironment which can maintain the viability, activation and proliferation of germinal center B cells in vitro.

Antibodies, Monoclonal↗
PubMed1991

The potato leafroll luteovirus 17K protein is a single-stranded nucleic acid-binding protein.

The potato leafroll luteovirus protein of Mr 17K (pr17), which is encoded by an open reading frame on the 3' half of the viral genome, was expressed by using bacterial expression vector systems. Fusion proteins were obtained for the full-length viral protein as well as its N-terminal acidic (GST/pr17N) and C-proximal (GST/pr17C) basic domains and used in nucleic acid-binding studies. Filter-bound as well as soluble pr17 bound to single-stranded RNA or DNA. The binding domain was shown to reside in the basic C-proximal part of the polypeptide, whereas the N-terminal acidic domain did not show any affinity for nucleic acid. These biochemical properties of pr17 together with its structural features suggest a regulatory role for this protein during virus replication.

Carrier Proteins↗
PubMed1991

Anderson's disease: genetic exclusion of the apolipoprotein-B gene in two families.

Anderson's disease is a recessive disorder characterized by intestinal fat malabsorption, absence of postprandial chylomicrons, and reduced levels of cholesterol, triglycerides, and apoproteins B, AI, and C. We have studied two families with, respectively, three and two children with Anderson's disease. Intestinal apo-B and apo-AIV mRNAs from two Anderson's patients were normal in size but their concentration was decreased fivefold compared with controls. After DNA digestion with seven restriction enzymes, restriction fragment length polymorphisms of apo-B gene did not show conclusive information except for Xba1, which revealed a lack of cosegregation between the restriction fragment length polymorphism and the Anderson's phenotype. Linkage analysis was performed using the polymorphism of the apo-B gene 3'minisatellite. Genomic DNA from parents and children was amplified by polymerase chain reaction using oligonucleotide primers flanking the apo-B gene 3'hypervariable locus. In both families each child inherited different apo-B alleles from at least one parent. According to the recessive mode of transmission of the disease, our results are incompatible with the involvement of the apo-B gene. More likely a posttranslational defect or a mutation in another gene encoding a protein essential for lipoprotein assembly or secretion may be involved.

Adolescent↗
PubMed1991

[Severe Crohn's disease in children. Retrospective study of 38 cases].

Thirty-eight children presenting with severe Crohn's disease (CD) were studied retrospectively over a mean period of 6 years. The severity of CD was estimated according to an activity score. This was initially 66 +/- 19 reaching 100 in 16% of cases. Initial involvement included ileon and large intestine only (n = 23), large intestine (n = 11) and ileon only (n = 4), with upper GI tract or perineal involvement in 32 and 75% of cases respectively. The treatments consisted of corticosteroids (n = 34), azathioprine (n = 11), continuous enteral feeding (CEF) (n = 25), parenteral nutrition (PN) (n = 30). Mean recurrence rates per patient and per year were 0.6 in the groups including ileon and large intestine or the large intestine only and 0.3 in the ileal group. A surgical resection was performed in 20 cases with a mean rate of reoperation of 40% at 5 years. Reoperations were necessary only in the group involving the ileon and large intestine. Mean weight catch-up in 3 months and height growth speed were 6 kg and 1.7 to 3.1 cm/year under CED and/or PN. After a 6 year follow-up the activity index was decreased by 70% with a quality of life considered to be good in 60% of cases.

Child↗
PubMed1991

[Pearson's syndrome. Pancytopenia with exocrine pancreatic insufficiency: new mitochondrial disease in the first childhood].

Pearson's syndrome is a lethal disorder of a still unknown cause, responsible for pancytopenia and exocrine pancreatic dysfunction in the first months of life. Permanent hyperlactacidemia and increased mitochondrial and cytoplasmic oxidoreduction ratios were observed in 6 unrelated children presenting with this disease. This led to study the oxidative phosphorylation in lymphocytes and thus to relate Pearson's syndrome to an enzymatic disease of the respiratory chain (NADH oxidase activity deficiency). The study of the mitochondrial genome allowed identifying major changes in mitochondrial DNA in all patients and all studied tissues. Thus, Pearson's syndrome is the first mitochondriopathy with a non neuromuscular expression reported to date.

DNA, Mitochondrial↗
PubMed1990

Mitochondrial DNA variation in social wasps (Hymenoptera, Vespidae).

Patterns of restriction fragment length polymorphisms (RFLP) of European Vespinae were more similar within genera than between them. Distance trees were constructed that support the hypothesis of monophyly of the genera Vespula and Dolichovespula. Within the genus Vespula, V. germanica was more closely related to V. rufa than to V. vulgaris. The position of the genus Vespa remained uncertain due to the precision limits of the RFLP technique.

Animals↗
PubMed1990

Antigenic phenotyping of human follicular dendritic cells isolated from nonmalignant and malignant lymphatic tissue.

Follicular dendritic cells (FDC) are located within follicles of secondary lymphoid tissue and in lymph nodes of patients with germinal center cell-derived non-Hodgkin lymphomas. Reliable antigenic phenotyping of FDC within tissue sections has been difficult due to simultaneous labeling of the surrounding germinal center cells. Using an enzyme cocktail to digest human tonsils and cervical lymph nodes with subsequent fractionation by albumin gradient centrifugation, cell isolates containing up to 20% FDC were obtained. This preparation allowed the determination of antigenic phenotype on individual FDC. Molecules expressed by FDC were detected by an isotype-specific immunocytochemical double-labeling procedure, i.e. a monoclonal antibody (mAb) specific for FDC (KiM4 or DRC1) in conjunction with a mAb reactive against an additional antigenic determinant. Nonspecific binding of mAb to immunoglobulin Fc receptors located on FDC membranes was avoided by incubation of cells with human IgG aggregates prior to immunostaining. The results revealed that isolated FDC from these lymphoid tissues express transferrin receptors, the intercellular adhesion molecule 1, class II antigens, the B cell antigens CD20 and CD21, and the myelomonocytic properties CD11b and CD14. Immunoglobulin mu or gamma heavy chains and the B cell antigens CD23 and CD24 are detected on 50% of an isolated FDC population. These FDC are negative for the T helper cell antigen CD4, the B cell cell antigens CD19 and CD22, the immunolobulin alpha and delta chains and the S-100 protein. FDC isolated from lymph nodes of patients with low-grade malignant non-Hodgkin lymphoma, identified by DRC1 or KiM4 mAb, presented the same antigenic profile as seen on FDC from nonmalignant tissue. This suggests that FDC from lymphoma tissue isolated in this manner have the same properties as those found in normal tissue.

Antigens, Differentiation↗
PubMed1990

Role of trans-activating proteins in the generation of active chromatin at the PHO5 promoter in S. cerevisiae.

Induction of the PHO5 gene in Saccharomyces cerevisiae by phosphate starvation was previously shown to be accompanied by the removal of four positioned nucleosomes from the promoter. We have now investigated the role of two trans-activating proteins, encoded by PHO2 and PHO4, which bind to the PHO5 promoter. Both proteins are absolutely required for the chromatin transition to occur as shown by analysis of null mutants of the two genes. Transformation of these mutant strains with plasmids containing the respective genes restores the wild type chromatin response. Increasing the gene dosage of PHO2 and of PHO4 makes it possible to differentiate functionally between the two proteins. From over-expressing PHO4 in a wild type and also in a pho2 null mutant strain and complementary experiments with PHO2, it is concluded that the PHO4 protein is the primary trigger for the chromatin transition, consistent with one of its two binding sites being located between positioned nucleosomes in repressed chromatin and thereby accessible. PHO2, the binding site of which is located within a nucleosome under conditions of PHO5 repression, contributes to the chromatin transition either by destabilizing histone-DNA interactions or by under-going interactions with PHO4.

Acid Phosphatase↗
PubMed1990

Pearson's marrow-pancreas syndrome. A multisystem mitochondrial disorder in infancy.

Pearson's marrow-pancreas syndrome (McKusick No. 26056) is a fatal disorder of hitherto unknown etiology involving the hematopoietic system, exocrine pancreas, liver, and kidneys. The observation of high lactate/pyruvate molar ratios in plasma and abnormal oxidative phosphorylation in lymphocytes led us to postulate that Pearson's syndrome belongs to the group of mitochondrial cytopathies. Since rearrangements of the mitochondrial genome between direct DNA repeats were consistently found in all tissues tested, our results show that this disease is in fact a multisystem mitochondrial disorder, as suggested by the clinical course of the patients. Based on these observations, we would suggest giving consideration to the hypothesis of a defect of oxidative phosphorylation in elucidating the origin of other syndromes, especially those associated with an abnormal oxidoreduction status in plasma.

Anemia, Sideroblastic↗
PubMed1990

Description of two different patients with abetalipoproteinemia: synthesis of a normal-sized apolipoprotein B-48 in intestinal organ culture.

We describe here two patients, M. P. and S. L., with recessive abetalipoproteinemia. Analysis of restriction fragments of DNA from both patients using cDNA probes spanning the entire apolipoprotein B gene revealed no major insertions or deletions. Further, as defined by restriction fragment length polymorphism, abetalipoproteinemia, in these patients, did not appear associated with particular alleles of apolipoprotein B. Northern and dot blot analysis of intestinal mRNA of one patient (M. P.) revealed a normal-sized apolipoprotein B mRNA which was present in slightly reduced amounts. At the cellular level apolipoprotein B was detected in both intestinal and hepatic biopsies, of one patient (S. L.), by immunoenzymatic techniques using polyclonal and monoclonal antibodies to apolipoprotein B-48 and/or B-100. The level of apolipoprotein B-48 appeared to increase in the intestine after a fatty meal. In the other patient (M. P.), although no apolipoprotein B was detected in the enterocytes using similar immunoenzymatic techniques, organ culture experiments using [35S]methionine demonstrated the synthesis of a normal-sized apolipoprotein B-48 which appeared to be normally glycosylated. The glycosylation and processing of two intestinal membrane enzymes, sucrase-isomaltase and aminopeptidase N, were also normal. Although lipids and apolipoprotein B-48 were present intracellularly, no lipoprotein-like particles were observed by electron microscopy in the endoplasmic reticulum, the Golgi apparatus, or in the intercellular spaces of intestinal biopsies obtained in the fasted (M. P. and S. L.) or fed state (S. L.). The defect in these cases of abetalipoproteinemia, therefore, does not appear to involve the apolipoprotein B gene nor the synthesis or the glycosylation of the apolipoprotein but instead appears to involve some aspect of lipoprotein assembly or secretion.

Abetalipoproteinemia↗