Biomedical subjects

H J Matthies

Publications and source records attributed to H J Matthies.

At least 19 recordsLinked to original sources

PubMed2001

Drosophila fragile X-related gene regulates the MAP1B homolog Futsch to control synaptic structure and function.

Fragile X mental retardation gene (FMR1) encodes an RNA binding protein that acts as a negative translational regulator. We have developed a Drosophila fragile X syndrome model using loss-of-function mutants and overexpression of the FMR1 homolog (dfxr). dfxr nulls display enlarged synaptic terminals, whereas neuronal overexpression results in fewer and larger synaptic boutons. Synaptic structural defects are accompanied by altered neurotransmission, with synapse type-specific regulation in central and peripheral synapses. These phenotypes mimic those observed in mutants of microtubule-associated Futsch. Immunoprecipitation of dFXR shows association with futsch mRNA, and Western analyses demonstrate that dFXR inversely regulates Futsch expression. dfxr futsch double mutants restore normal synaptic structure and function. We propose that dFXR acts as a translational repressor of Futsch to regulate microtubule-dependent synaptic growth and function.

Animals↗

PubMed2001

Orphan kinesin NOD lacks motile properties but does possess a microtubule-stimulated ATPase activity.

NOD is a Drosophila chromosome-associated kinesin-like protein that does not fall into the chromokinesin subfamily. Although NOD lacks residues known to be critical for kinesin function, we show that microtubules activate the ATPase activity of NOD >2000-fold. Biochemical and genetic analysis of two genetically identified mutations of NOD (NOD(DTW) and NOD("DR2")) demonstrates that this allosteric activation is critical for the function of NOD in vivo. However, several lines of evidence indicate that this ATPase activity is not coupled to vectorial transport, including 1) NOD does not produce microtubule gliding; and 2) the substitution of a single amino acid in the Drosophila kinesin heavy chain with the analogous amino acid in NOD results in a drastic inhibition of motility. We suggest that the microtubule-activated ATPase activity of NOD provides transient attachments of chromosomes to microtubules rather than producing vectorial transport.

Adenine↗

PubMed1999

Mutations in the alpha-tubulin 67C gene specifically impair achiasmate segregation in Drosophila melanogaster.

Drosophila melanogaster oocytes heterozygous for mutations in the alpha-tubulin 67C gene (alphatub67C) display defects in centromere positioning during prometaphase of meiosis I. The centromeres do not migrate to the poleward edges of the chromatin mass, and the chromatin fails to stretch during spindle lengthening. These results suggest that the poleward forces acting at the kinetochore are compromised in the alphatub67C mutants. Genetic studies demonstrate that these mutations also strongly and specifically decrease the fidelity of achiasmate chromosome segregation. Proper centromere orientation, chromatin elongation, and faithful segregation can all be restored by a decrease in the amount of the Nod chromokinesin. These results suggest that the accurate segregation of achiasmate chromosomes requires the proper balancing of forces acting on the chromosomes during prometaphase.

Animals↗

PubMed1999

The bipolar kinesin, KLP61F, cross-links microtubules within interpolar microtubule bundles of Drosophila embryonic mitotic spindles.

Previous genetic and biochemical studies have led to the hypothesis that the essential mitotic bipolar kinesin, KLP61F, cross-links and slides microtubules (MTs) during spindle assembly and function. Here, we have tested this hypothesis by immunofluorescence and immunoelectron microscopy (immunoEM). We show that Drosophila embryonic spindles at metaphase and anaphase contain abundant bundles of MTs running between the spindle poles. These interpolar MT bundles are parallel near the poles and antiparallel in the midzone. We have observed that KLP61F motors, phosphorylated at a cdk1/cyclin B consensus domain within the BimC box (BCB), localize along the length of these interpolar MT bundles, being concentrated in the midzone region. Nonphosphorylated KLP61F motors, in contrast, are excluded from the spindle and display a cytoplasmic localization. Immunoelectron microscopy further suggested that phospho-KLP61F motors form cross-links between MTs within interpolar MT bundles. These bipolar KLP61F MT-MT cross-links should be capable of organizing parallel MTs into bundles within half spindles and sliding antiparallel MTs apart in the spindle midzone. Thus we propose that bipolar kinesin motors and MTs interact by a "sliding filament mechanism" during the formation and function of the mitotic spindle.

Anaphase↗

PubMed1999

Identification of novel Drosophila meiotic genes recovered in a P-element screen.

The segregation of homologous chromosomes from one another is the essence of meiosis. In many organisms, accurate segregation is ensured by the formation of chiasmata resulting from crossing over. Drosophila melanogaster females use this type of recombination-based system, but they also have mechanisms for segregating achiasmate chromosomes with high fidelity. We describe a P-element mutagenesis and screen in a sensitized genetic background to detect mutations that impair meiotic chromosome pairing, recombination, or segregation. Our screen identified two new recombination-deficient mutations: mei-P22, which fully eliminates meiotic recombination, and mei-P26, which decreases meiotic exchange by 70% in a polar fashion. We also recovered an unusual allele of the ncd gene, whose wild-type product is required for proper structure and function of the meiotic spindle. However, the screen yielded primarily mutants specifically defective in the segregation of achiasmate chromosomes. Although most of these are alleles of previously undescribed genes, five were in the known genes alphaTubulin67C, CycE, push, and Trl. The five mutations in known genes produce novel phenotypes for those genes.

Animals↗

PubMed1996

Anastral meiotic spindle morphogenesis: role of the non-claret disjunctional kinesin-like protein.

We have used time-lapse laser scanning confocal microscopy to directly examine microtubule reorganization during meiotic spindle assembly in living Drosophila oocytes. These studies indicate that the bipolarity of the meiosis I spindle is not the result of a duplication and separation of centrosomal microtubule organizing centers (MTOCs). Instead, microtubules first associate with a tight chromatin mass, and then bundle to form a bipolar spindle that lacks asters. Analysis of mutant oocytes indicates that the Non-Claret Disjunctional (NCD) kinesin-like protein is required for normal spindle assembly kinetics and stabilization of the spindle during metaphase arrest. Immunolocalization analyses demonstrate that NCD is associated with spindle microtubules, and that the centrosomal components gamma-tubulin, CP-190, and CP-60 are not concentrated at the meiotic spindle poles. Based on these observations, we propose that microtubule bundling by the NCD kinesin-like protein promotes assembly of a stable bipolar spindle in the absence of typical MTOCs.

Animals↗

PubMed1993

Calmodulin binding to and cAMP-dependent phosphorylation of kinesin light chains modulate kinesin ATPase activity.

Kinesin is an ubiquitous heterotetrameric microtubule-based motor which translocates membrane-bound organelles. Since organelle motility and motor protein function can be regulated by components of signaling pathways, the ability of purified bovine brain kinesin (kinesin) to be phosphorylated and to recognize calmodulin (CaM) was tested. Extensively purified "kinesin" was found to consist of several forms of both heavy (KHC) and light (KLC) chains. Phosphorylation of kinesin by a variety of protein kinases was examined; cAMP-dependent protein kinase (cAMP-PK) was the most active enzyme leading to the incorporation of up to 8 mol P/mol kinesin. Phosphorylation occurred predominantly on the KLCs and led to substantial acidic pI shifts. Peptide maps indicated that multiple phosphorylation sites exist on each KLC. Incubation of kinesin in vitro with protein kinase C (PKC) led to the phosphorylation of both KHCs and KLCs. In vivo phosphorylation of KHC and KLCs was demonstrated by immunoprecipitation of [32P]-labeled kinesin from cultured rat hippocampal pyramidal neurons; kinesin phosphorylation was stimulated by 8-chlorophenyl-thio-cAMP or 12-O-tetradecanoylphorbol-13-acetate. Native bovine brain kinesin was shown to bind 125I-CaM by nucleotide-dependent pelleting with stable microtubules. Specific calcium-dependent binding of 125I-CaM to KLCs but not KHC was found using a ligand blotting assay. cAMP-PK phosphorylated kinesin bound 125I-CaM less well than untreated protein in both ligand blotting and microtubule-pelleting paradigms. Calcium-dependent binding of CaM to kinesin inhibited the ATPase activity of native kinesin but not of cAMP-PK phosphorylated kinesin. These results suggest that the KLCs have a regulatory function and integrate information coming from diverse signaling pathways to modulate the activity and function of kinesin.

Adenosine Triphosphatases↗

PubMed1991

[Electroneurographic findings in workers exposed to mercury].

25 mercury-exposed workers as well as 27 age-matched controls were investigated in an electroneurographic study. The population of mercury-exposed workers was found to have --an increased latency of distal motor action potential at both median and peroneal nerves --an increased latency of distal sensory action potential at median nerve --a decrease of amplitudes of evoked muscle potentials at both median and peroneal nerves --a reduced motor nerve conduction velocity at both examined nerves --a reduced antidromic sensory nerve conduction velocity at median nerve. To detect early changes in nerval function we recommend regularly electroneurographic examinations of mercury-exposed people.

Adolescent↗

PubMed1988

Calmodulin- and protein phosphorylation-independent release of catecholamines from PC-12 cells.

Catecholamine secretion from PC-12 cells can be triggered by agents that increase intracellular Ca2+ and is enhanced by phorbol esters and agents that elevate intracellular cAMP concentrations. In mutant PC-12 cells lacking cAMP-dependent protein kinase (PK-A) in which protein kinase C (PK-C) was down-regulated, Ca2+-dependent secretion occurred normally but was no longer enhanced by cAMP or phorbol esters. In digitonin-permeabilized PC-12 cells that lacked PK-C and PK-A, a range of calmodulin (CaM) inhibitors failed to block Ca2+-triggered catecholamine release. Moreover, Mn2+, a CaM activator, failed to trigger catecholamine release whereas Ba2+, which does not activate CaM, supported secretion. These results indicate that the basic mechanism of stimulus/secretion coupling in PC-12 cells does not absolutely require a regulated protein phosphorylation- or calmodulin-dependent step.

Adrenal Gland Neoplasms↗

PubMed1988

The effect of down regulation of protein kinase C on the inhibitory modulation of dorsal root ganglion neuron Ca2+ currents by neuropeptide Y.

Dorsal root ganglion (DRG) neurons cultured from neonatal rats contained high concentrations of protein kinase C (PKC). Normally, the majority of the enzyme activity was found in the cytosol and considerably less was associated with the membrane fraction. Upon incubation with the phorbol ester phorbol dibutyrate (PDBu, 10(-6) M) for 20 min, PKC activity increased in the membrane-associated fraction and decreased in the cytoplasmic fraction. Longer incubations with phorbol ester also induced a decline in membrane-associated PKC activity. If incubations were continued for periods of over 10 hr, both membrane and cytosolic PKC activity declined essentially to zero. Down-regulation of PKC had no effect on the number or affinity of 125I-neuropeptide Y (NPY) binding sites on DRG cells or on the absolute magnitude of the DRG Ca2+ current. However, the ability of NPY to inhibit the DRG Ca2+ current was greatly reduced. When sustained Ca2+ currents were evoked from depolarized holding potentials (-40 mV), all concentrations of NPY (10(-10)-10(-7) M) were less effective. In contrast, higher concentrations of NPY still blocked the transient portion of the DRG Ca2+ current evoked from hyperpolarized holding potentials. These results support the suggestion that PKC is involved in the inhibitory modulation of DRG Ca2+ currents by neurotransmitters. The precise role of PKC may vary depending on the type of Ca2+ channel involved.

Animals↗

PubMed1987

Down regulation of protein kinase C in neuronal cells: effects on neurotransmitter release.

We investigated the effects of phorbol esters on protein kinase C (PKC) activity and on neurotransmitter release from cultured neuronal cells. Both differentiated and undifferentiated PC12 pheochromocytoma cells contained high levels of protein PKC. Under normal conditions all the enzyme activity was found in the cytoplasm. Addition of the phorbol esters phorbol 12-myristate-13-acetate (TPA) or phorbol 12,13-dibutyrate (PDBu) caused a rapid translocation of PKC from the cytoplasm to the particulate fraction. Continued culture of cells with these phorbol esters resulted in the decline of total PKC activity. After 10-20 hr of culture, both membrane and cytoplasmic PKC activity had declined to background levels. cAMP-dependent and Ca2+/calmodulin-dependent protein kinase activities were only slightly affected by chronic phorbol ester treatment. Addition of active phorbol esters to PC12 cells produced an enhancement of the depolarization-induced release of 3H-norepinephrine. Following chronic phorbol ester treatment, the ability of these substances to enhance evoked catecholamine release was lost. Furthermore, depolarizing stimuli released considerably less 3H-norepinephrine than in control untreated cells. Phorbol esters also enhanced depolarization-induced 3H-norepinephrine release from primary cultures of rat sympathetic neurons. Chronic treatment of these neurons with phorbol esters also resulted in the loss of their ability to enhance transmitter release and in a large reduction in the extent of depolarization-evoked transmitter release. Chronic phorbol ester treatment also resulted in the disappearance of PKC from sympathetic neurons, but had little effect on cAMP-dependent or Ca2+/calmodulin-dependent kinase activities. These results demonstrate that PKC-deficient neurons can be prepared. The data also demonstrate that depolarization-induced neurotransmitter release is mediated by both protein kinase C-dependent and independent pathways.

Animals↗

PubMed1985

Benign breast lesions with malignant clinical and mammographic presentations.

Nine cases of benign breast disease in which mammograms had been false-positive were collected at Northwestern Memorial Hospital. In all but one case the patients had presented initially with questionable masses that required biopsies with requests for frozen section diagnoses. Included in the study were three cases of indurative mastopathy, three cases of fibrocystic disease with sclerosing adenosis, and one case each of sclerosing papillary proliferation, infarcted intraductal papilloma, and fat necrosis with foreign body giant cell reaction. The mammographic and histologic findings for all cases were reviewed. Indurative mastopathy is a poorly known entity with radiologic features highly suggestive of malignancy. As described previously (Cancer 47:561, 1981), the lesion consists of a central nidus of elastosis with irregular projections radiating into the adjacent breast tissue. Peripheral areas of the infarcted papilloma and sclerosing papillary proliferation could be confused with infiltrating carcinoma in frozen sections. Familiarity of pathologists with these lesions is essential for avoiding the overdiagnosis of carcinoma.

Adult↗

PubMed1985

Indurative mastopathy: a cause of false-positive mammograms.

Indurative mastopathy is a benign, elastotic lesion of the breast characterized by a stellate appearance, with surrounding compressed and distorted ducts causing a pseudo-infiltrative pattern. In previously reported cases of benign sclerosing lesions of the breast there has been no evidence of local recurrence of metastasis following excisional biopsy. The significance of identifying indurative mastopathy lies in recognizing its benign nature despite clinical, radiographic, and gross histologic features that are indistinguishable from malignancy, thereby saving the patient additional surgery or radiotherapy once an excisional biopsy has been performed.

Adult↗

PubMed1985

Mammography in women less than 40 years of age.

Carcinoma of the breast in women less than 40 years old is a significant problem, representing 7.4 per cent of the total number of carcinomas of the breast at our institution. It is apparent that mammography in this age group is of value in confirming the clinical suspicion of a malignant condition of the breast and in evaluating the remainder of the parenchyma of the breast for clinically occult lesions. However, one cannot over emphasize that a negative result from the mammogram should not delay biopsy in the presence of clinically suspicious lesions (1, 4). It is obvious that a larger series of patients is necessary to define the role of mammography in "young women."

Adult↗

PubMed1984

Transfer of cholesterol from its site of synthesis to the plasma membrane.

We have followed the transfer of newly synthesized cholesterol to the plasma membrane in cultured fibroblasts using cholesterol oxidase as a probe. Since the enzyme has access only to the plasma membrane in intact cells, it permits the discrimination of cell surface and endogenous cholesterol. Cholesterol synthesized from radiolabeled acetate was transferred to the plasma membrane in a strictly first order fashion with a half-time of 1-2 h at 37 degrees C. The rate of transfer was similar in rapidly growing and confluent cells and was not affected by preincubating the cells in lipoprotein-deficient serum which greatly stimulated cholesterol synthesis. We used equilibrium density gradient centrifugation of homogenates from cholesterol oxidase-treated cells to examine further the distribution of newly synthesized cholesterol between cellular pools. We identified membrane fractions enriched in newly synthesized cholesterol yet inaccessible to cholesterol oxidase. The cholesterol in these membranes eventually moved to the plasma membrane. The movement of exogenous radiocholesterol from the plasma membrane to the cell interior also was examined by this method. No detectable transfer was observed over several hours, during which time endogenous cholesterol moved to the plasma membrane. We conclude that the transfer of newly synthesized cholesterol to the plasma membrane is a vectorial process and is not mediated by a simple diffusional equilibrium.

Acetates↗

PubMed1980

[The effect of orotic acid and sodium orotate on organ cultures of the hippocampus of embryonic rats].

Organ cultures of hippocampus from fetal rats were cultivated in Maximow chambers with semisynthetic media up to 12 days in vitro and fixed after 1, 5 and 12 days in culture, cuted 15 micrometer and coloured with the method of Klüver-Barrera. The effect of 5 x 10(-6) M sodiumorotate and 6 x 10(-6) M orotic acid was tested. 1. The density of cells is related to the zone of cells, the drug and time of incubation. 2. The density of cells increased in the zone of matrix after application of sodiumorotate and orotic acid. The density of cells significantly decreased in the migration zone. The density of neurons significantly increased in the region CA 3. 3. Orotic acid and sodiumorotate influenced the migration of cells in vitro. Sodiumorotate stimulated migration and differentiation. Longtime cultured hippocampi degenerated in vitro after influence of orotic acid. 4. The area of nuclei from neurons increased up to 12 days in vitro, when the cultures were tested with sodiumorotate. Only within the first 24 hours orotic acid effected an increase of the area of nuclei from matrix cells. It is discussed, sodiumorotate influenced in vitro metabolic processes in suitable systems.

Animals↗

PubMed1978

Dose reduction in mammography.

The Min-R system is more than a satisfactory substitute for xerography. At equal distances, the images obtained are equivalent. Radiation exposure was 25 per cent of xerography, a significant reduction in exposure. By using a long cone and improving geometry, superior images were obtained in 4 per cent of 400 comparison patients. If mammography is to be used as an early detection device in patients with carcinoma of the breast, modalities with lower exposure requirements must be used. Min-R, a new film screen system, fulfills the requirement of reduced patient exposure without loss of diagnostic accuracy.

Female↗

PubMed1976

[Effect of orotic acid on the in vitro cultured nerve tissue].

Cell- and explantcultures of the hippocampus of 18 days old fetal rats and explantcultures of the ganglion trigeminal of 9 days old chick embryos were cultivated in Maximow-chambers. Orotic acid, Sodiumorotate and methylglucaminorotate by concentrations of 10(-3)...10(-7) g/ml medium were added to the cultures. By concentrations of 10(-7) g/ml medium in the CNS-cultures and 10(-6) g/ml medium in the PNS-cultures is stimulated the nerve fiber growth and is increased the nerve fiber index. After three weeks in vitro is a higher number of neurons in the cultures compared to the controls.

Animals↗