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K Anderson

Publications and source records attributed to K Anderson.

At least 199 records · Page 11Linked to original sources
PubMed1995

Actin filament organization in the fish keratocyte lamellipodium.

From recent studies of locomoting fish keratocytes it was proposed that the dynamic turnover of actin filaments takes place by a nucleation-release mechanism, which predicts the existence of short (less than 0.5 microns) filaments throughout the lamellipodium (Theriot, J. A., and T. J. Mitchison. 1991. Nature (Lond.). 352:126-131). We have tested this model by investigating the structure of whole mount keratocyte cytoskeletons in the electron microscope and phalloidin-labeled cells, after various fixations, in the light microscope. Micrographs of negatively stained keratocyte cytoskeletons produced by Triton extraction showed that the actin filaments of the lamellipodium are organized to a first approximation in a two-dimensional orthogonal network with the filaments subtending an angle of around 45 degrees to the cell front. Actin filament fringes grown onto the front edge of keratocyte cytoskeletons by the addition of exogenous actin showed a uniform polarity when decorated with myosin subfragment-1, consistent with the fast growing ends of the actin filaments abutting the anterior edge. A steady drop in filament density was observed from the mid-region of the lamellipodium to the perinuclear zone and in images of the more posterior regions of lower filament density many of the actin filaments could be seen to be at least several microns in length. Quantitative analysis of the intensity distribution of fluorescent phalloidin staining across the lamellipodium revealed that the gradient of filament density as well as the absolute content of F-actin was dependent on the fixation method. In cells first fixed and then extracted with Triton, a steep gradient of phalloidin staining was observed from the front to the rear of the lamellipodium. With the protocol required to obtain the electron microscope images, namely Triton extraction followed by fixation, phalloidin staining was, significantly and preferentially reduced in the anterior part of the lamellipodium. This resulted in a lower gradient of filament density, consistent with that seen in the electron microscope, and indicated a loss of around 45% of the filamentous actin during Triton extraction. We conclude, first that the filament organization and length distribution does not support a nucleation release model, but is more consistent with a treadmilling-type mechanism of locomotion featuring actin filaments of graded length. Second, we suggest that two layers of filaments make up the lamellipodium; a lower, stabilized layer associated with the ventral membrane and an upper layer associated with the dorsal membrane that is composed of filaments of a shorter range of lengths than the lower layer and which is mainly lost in Triton.

Actins↗
PubMed1995

T-tubule depolarization-induced SR Ca2+ release is controlled by dihydropyridine receptor- and Ca(2+)-dependent mechanisms in cell homogenates from rabbit skeletal muscle.

In vertebrate skeletal muscle, the voltage-dependent mechanism of rapid sarcoplasmic reticulum (SR) Ca2+ release, commonly referred to as excitation-contraction (EC) coupling, is believed to be mediated by physical interaction between the transverse (T)-tubule voltage-sensing dihydropyridine receptor (DHPR) and the SR ryanodine receptor (RyR)/Ca2+ release channel. In this study, differential T-tubule and SR membrane monovalent ion permeabilities were exploited with the use of an ion-replacement protocol to study T-tubule depolarization-induced SR 45Ca2+ release from rabbit skeletal muscle whole-cell homogenates. Specificity of Ca2+ release was ascertained with the use of the DHPR antagonists D888, nifedipine and PN200-110. In the presence of the "slow" complexing Ca2+ buffer EGTA, homogenates exhibited T-tubule depolarization-induced Ca2+ release comprised of an initial rapid phase followed by a slower release phase. During the rapid phase, approximately 20% of the total sequestered Ca2+ (approximately 30 nmol 45Ca2+/mg protein), corresponding to 100% of the caffeine-sensitive Ca2+ pool, was released within 50 ms. Rapid release could be inhibited fourfold by D888. Addition to release media of the "fast" complexing Ca2+ buffer BAPTA, at concentrations > or = 4 mM, nearly abolished rapid Ca2+ release, suggesting that most was Ca2+ dependent. Addition of millimolar concentrations of either Ca2+ or Mg2+ also greatly reduced rapid Ca2+ release. These results show that T-tubule depolarization-induced SR Ca2+ release from rabbit skeletal muscle homogenates is controlled by T-tubule membrane potential- and by Ca(2+)-dependent mechanisms.

Animals↗
PubMed1995

Influenza A virus--induced acute otitis media.

To better understand the significance of viral upper respiratory tract infections in the pathogenesis of acute otitis media (OM), 27 adults underwent intranasal inoculation with influenza A virus. Monitoring consisted of antibody titer determination, tympanometry, and otoscopy. Microbiologic analysis consisted of cultures and polymerase chain reaction (PCR)-based detection for influenza A virus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. All subjects became infected with the challenge virus. By day 4, 16 (59%) developed middle ear pressures of -100 mm H2O or below and 4 (25%) of them developed OM. One subject (4%) developed purulent OM requiring myringotomy for pain relief. Middle ear effusion cultures were negative. PCR analysis of that subject's middle ear effusion and nasal washes were positive for influenza A virus and S. pneumoniae. These findings support a causal role for viral upper respiratory tract infections in the pathogenesis of OM, possibly mediated by middle ear underpressures and viral and bacterial middle ear infection.

Acute Disease↗
PubMed1995

Genetic and antigenic properties of Dobrava virus: a unique member of the Hantavirus genus, family Bunyaviridae.

We examined the genetic and antigenic properties of Dobrava (DOB) virus, a hantavirus associated with severe haemorrhagic fever with renal syndrome in Europe. Cloning and sequence analyses revealed the DOB M segment to consist of 3644 nucleotides, with a coding capacity of 1134 amino acids in the virus complementary-sense RNA (cRNA). Seven potential asparagine-linked glycosylation sites were identified in the M segment gene product, one in the G2 and six in the G1 coding regions. The S segment is 1667 nucleotides long, and has a single ORF in the cRNA capable of encoding a protein of 428 amino acids. Phylogenetic comparisons of the M and S segments of DOB virus to those of other hantaviruses indicated that DOB virus is similar to, but clearly distinct from Hantaan (HTN) and Seoul (SEO) viruses. Certain G2-specific, but not G1-specific monoclonal antibodies to HTN virus reacted to the same titre with DOB and homologous viral antigen. Plaque-reduction neutralization tests indicated that, of the sera tested, only antisera to SEO virus were able to neutralize DOB virus to a titre greater than 1:10; however, this neutralization titre was eightfold lower than that observed with homologous SEO virus. The data reported here confirm that DOB virus is a unique species in the Hantavirus genus, family Bunyaviridae.

Animals↗
PubMed1995

Immunoglobulin gene sequence analysis to further assess B-cell origin of multiple myeloma.

To further characterize the B-cell origin of multiple myeloma, our laboratory performed immunoglobulin gene sequence analyses of four cases of myeloma (three immunoglobulin A and one immunoglobulin G). Three tumors expressed VH3 genes and one expressed a VH1 gene, while the light chains included two V lambda and one V kappa III; one light chain was not isolated. The closest homology to published germ line genes ranged from 91 to 97%. In two cases, the expressed VH genes were compared with the putative germ line precursor VH genes isolated from autologous granulocyte DNA and appeared to have mutated randomly from the germ line gene. By sequencing multiple clonal isolates from each tumor sample, we found no evidence for ongoing mutation in three cases; in one case, however, clonotypic heterogeneity was evident. The analysis of DH- and JH-region genes revealed (i) limited or absent N nucleotide insertions (two of four cases), (ii) the presence of a DH-JH junction resulting from sequence overlap between the DH and JH genes (one of four cases), (iii) the absence of somatic mutations (two of four cases), and (iv) restricted JH gene usage of a JH6 polymorphism (three of four cases). These analyses of DH and JH genes suggest that multiple myeloma, similar to what has been proposed for chronic lymphocytic leukemia, may derive from B cells which have rearranged during fetal development rather than during adult life.

Amino Acid Sequence↗
PubMed1995

Characterization of the metabolites of the peptidomimetic human immunodeficiency virus type 1 protease inhibitor SK&F 107461 in rats using liquid chromatography/mass spectrometry.

The metabolic fate of SK&F 107461 [Cbz-Ala-Ala-Phe psi [CHOHCH2] Gly-Val-Val-OMe], a potent and specific inhibitor of the protease encoded by human immunodeficiency virus type 1, in male Sprague-Dawley rats is described. SK&F 107461 is a hexapeptide analog containing a hydroxyethylene linkage in place of one of the peptide bonds, and in which the amino terminus is blocked with a carbobenzyloxy group and the carboxy terminus is modified to a methyl ester. The major metabolites of SK&F 107461 found in bile and urine after intravenous administration of 3H-labeled compound were characterized by LC/MS using either thermospray or continuous flow/FAB models of ionization. Approximately 80% of the administered radioactivity was recovered in the bile of bile duct-exteriorized rats following an intravenous dose. Radiochromatographic profiling indicated that SK&F 107461 was subject to extensive biotransformation. Structures were determined for three major biliary and five major urinary metabolites. Two of the major circulating plasma metabolites observed after intravenous bolus administration had similar retention times to metabolites that were observed in both bile and urine. A pathway for the biotransformation of SK&F 107461 in the rat is proposed. The parent molecule underwent two primary modes of metabolism. Hydrolysis of the carboxy-terminal ester or hydrolysis of the Ala-Ala peptide bond near the amino terminus were the primary metabolic events. All of the other metabolites characterized can be accounted for by exopeptidase activity subsequent to one or both of these primary events. There were no major metabolites observed resulting from anything other than hydrolysis of the ester or peptide bonds in the parent molecule.

Amino Acid Sequence↗
PubMed1995

Primate rod and cone photoreceptors may differ in glucose accessibility.

PURPOSE: Glucose is crucial for the function of retinal photoreceptors, other retinal neurons, and glial cells. Exogenous glucose can be extracted from the retinal and choroidal circulation, and endogenous glucose may be generated from breakdown of intracellular glycogen stores. Because glucose deprivation is a critical component of retinal ischemia, the authors sought to determine the sites of glucose entry into and generation within the retina. METHODS: The localization of the glucose transporter, GluT-1, and the brain and muscle isozymes of glycogen phosphorylase, GlyP, was studied by immunohistochemistry of adult human and monkey retinas. RESULTS: Brain glycogen phosphorylase (B-GlyP) immunoreactivity was found in cone, but not rod, photoreceptors. There was immunostaining of foveal and peripheral cones throughout the cytoplasm from the outer segment to the synaptic pedicle. Short wavelength ("blue") cones were positive for B-GlyP. Diffuse staining of the inner and outer plexiform and the nerve fiber layers did not resemble the distinct morphology of Müller cells. Immunoreactivity to muscle GlyP (M-GlyP) was confined to selected synaptic layers of the inner plexiform layer in monkey retina. Staining with antibody to GluT-1 demonstrated diffuse reactivity throughout the retina, including the blood-retinal barrier cells, retinal pigment epithelium, and vascular endothelium. Ultrastructural immunohistochemistry showed staining of rod and cone inner and outer segments. CONCLUSIONS: These immunohistochemical studies indicate that rod and cone photoreceptors have the biochemical capability to transport exogenous glucose from the circulation. Only cones appear capable of using endogenous glycogen stores. These findings imply that cones could be more resistant to acute reductions in circulating glucose during hypoglycemia. However, during hypoxic insult, glycogenolysis and anaerobic glycolysis could result in increased production of intracellular lactic acid, potentially predisposing the cone to acidotic damage.

Animals↗
PubMed1995

Structural and functional features of one- and two-headed biotinated kinesin derivatives.

The oligomeric structure was determined for four recombinant kinesin derivatives containing N-terminal fragments of the kinesin alpha-subunit. Some of the proteins were dimeric (two-headed) molecules with mechanochemical properties similar to those of intact kinesin. Comparison of the primary and quaternary structures of the derivatives with those of intact kinesin suggests that structures distinct from the long alpha-helical coiled-coil rod domain contribute to subunit self-association. Three of the proteins contain a single engineered site for post-translational biotination in vivo; this facilitates analysis of motility in experiments in which the proteins are specifically bound to streptavidin-conjugated microscopic plastic beads. One of the derivatives is monomeric (one-headed); like the two-headed derivatives, it is functional in the motility assay and is a microtubule-dependent ATPase. Unlike intact kinesin and the two-headed derivatives, the one-headed enzyme fails to track microtubule protofilaments. This confirms a prediction of proposed "hand-over-hand" mechanisms of kinesin movement. The ability of molecules with a one-headed solution structure to generate movement is consistent with a translocation-generating conformational change internal to the kinesin head. A simple set of coupling rules can be used to formulate consistent mechano-chemical mechanisms that explain movement by both one- and two-headed kinesin molecules.

Adenosine Diphosphate↗
PubMed1995

New antiplatelet agents: platelet GPIIb/IIIa antagonists.

The GPIIb/IIIa (alpha IIb beta 3) receptor plays a crucial role in platelet aggregation and platelet thrombus formation. Inhibition of GPIIb/IIIa with the Fab fragment of the mouse/human chimeric monoclonal antibody 7E3, snake venom peptides containing the arginine-glycine-aspartic acid (RGD) sequence, or peptides or peptidomimetics based on the RGD sequence results in abolition of platelet aggregation and platelet thrombus formation. This results in profound inhibition of thrombotic occlusions in animal models. The Phase III EPIC study demonstrated that c7E3 Fab, given as bolus followed by a 12 h infusion, reduced the risk of acute ischemic complications after coronary angioplasty by approximately 35% in patients at high risk of suffering such complications. Treated patients had an approximately 2-fold increased risk of major bleeding, but no increase in cerebral hemorrhage or lethal bleeding. Treatment with c7E3 Fab may have had a beneficial effect on clinical restenosis at 6 months, but this needs to be confirmed. A possible anticoagulant effect of c7E3 Fab was also identified in EPIC, and in vitro studies support this possibility. With the approval of c7E3 Fab (abciximab; ReoPro) for patients undergoing high-risk angioplasty in the US and several European and Scandinavian countries, GPIIb/IIIa inhibition joins the armamentarium of antithrombotic agents.

Abciximab↗
PubMed1994

A phase II study of continuous infusion recombinant human granulocyte-macrophage colony-stimulating factor as an adjunct to autologous bone marrow transplantation for patients with non-Hodgkin's lymphoma in first remission.

Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) clearly hastens myeloid recovery in patients with relapsed hematologic malignancies undergoing autologous bone marrow transplantation (ABMT). In efforts to further improve neutrophil engraftment and shorten hospital stay in ABMT patients, rhGM-CSF was administered by a potentially more potent route (continuous infusion) to non-Hodgkin's lymphoma (NHL) patients with better BM reserve (first remission). Time to myeloid engraftment was compared with that of NHL patients treated in first remission at our institution on a similar ABMT protocol but without growth factor support (controls). Median neutrophil engraftment (absolute neutrophil count, 500 cells/microL) in first remission patients treated with rhGM-CSF was 14 days, compared with 22 days in controls (P = .0001). Hospital stays were also significantly reduced for rhGM-CSF patients (P = .0003). Platelet engraftment did not differ between the two groups. Persistent fever and generalized serositis were the primary toxicities. rhGM-CSF, delivered by this route, was efficacious but more toxic than 2-hour rhGM-CSF infusions previously reported by other investigators. Future alterations in both dose and schedule may retain comparable efficacy yet diminish toxicity.

Adult↗
PubMed1994

Drug and alcohol abuse by doctors.

OBJECTIVE: To determine whether doctors who abuse substances differ from controls in terms of their physical and psychological well-being, and their marital and occupational functioning. DESIGN AND PARTICIPANTS: The 44 doctors concerned in all cases of substance abuse which came before the Medical Board of Victoria between 1984 and 1990 were invited to complete a demographic questionnaire, psychological tests and a semi-structured interview. A control group of 42 doctors, obtained from the Medical Register, was also invited, and the groups were compared. SETTING: The study was carried out at St Vincent's Hospital, Melbourne, under the auspices of the Medical Board of Victoria. RESULTS: Questionnaires were returned by 70% of the drug-dependent doctors and 83% of the controls. However, interviews were given by only 20% of the drug-dependent doctors. The groups differed significantly in terms of marital status (P < 0.002), overall health (P < 0.003), general wellbeing (P < 0.0009), and having experienced physical illness (P < 0.02) and psychiatric illness (P < 0.006) since graduation. No differences were found on the standardised questionnaires; this may reflect successful treatment. CONCLUSION: Substance abuse in medical practitioners is a major problem and is associated with considerable morbidity. Prevention and early intervention are crucial.

Adult↗
PubMed1994

2.2 Mb of contiguous nucleotide sequence from chromosome III of C. elegans.

As part of our effort to sequence the 100-megabase (Mb) genome of the nematode Caenorhabditis elegans, we have completed the nucleotide sequence of a contiguous 2,181,032 base pairs in the central gene cluster of chromosome III. Analysis of the finished sequence has indicated an average density of about one gene per five kilobases; comparison with the public sequence databases reveals similarities to previously known genes for about one gene in three. In addition, the genomic sequence contains several intriguing features, including putative gene duplications and a variety of other repeats with potential evolutionary implications.

Animals↗
PubMed1994

Effects of cocaine on fixed-interval behavior and schedule-induced alcohol consumption in male and female rats.

Three male and three female Wistar rats pressed a lever on a fixed-interval 60-s schedule of food reinforcement while they had simultaneous access to an alcohol solution. They were challenged with different doses of cocaine hydrochloride (vehicle, 1, 3, 10, and 30 mg/kg) once lever press rates and lick rates had stabilized. Low doses of cocaine (1 and 3 mg/kg) did not systematically affect lever press rates or lick rates. The administration of 10 and 30 mg/kg cocaine dose-dependently decreased lever press rates and schedule-induced licking to a greater extent in female than in male rats. Lick rates decreased even when cocaine administration did not affect the number of pellets obtained during an experimental session. Lever press rates accelerated throughout the interreinforcement interval during control sessions. Licking was mostly limited to the first 10 s (males) or 20 s (females) after pellet presentation. Cocaine administration did not affect the distribution of lever presses and licks during the interreinforcement interval. The results of the present experiment extend previous observations that cocaine's rate-dependent effects on lever press rates may be limited to situations in which changes in lever press frequency and/or distribution negatively affect reinforcement frequency and/or the physiological consequences of schedule-induced behavior.

Alcohol Drinking↗
PubMed1994

The IgE and IgG antibody responses to aerosols of Nephrops norvegicus (prawn) antigens: the association with clinical hypersensitivity and with cigarette smoking.

Raised levels of serum IgE antibodies to prawn antigens were found in 15 of 26 seafood factory process workers with respiratory symptoms and in one of 26 case-matched asymptomatic controls (P < 0.001). Raised IgG antibody titres against the same antigens were found in 18 subjects in each symptom grouping, and the median titres of this antibody did not differ significantly between the groups. The prawn-specific IgE antibody response was significantly associated with atopy (IgE antibody response to common allergens) and with a history of cigarette smoking, confirmed by level of serum cotinine, a major nicotine metabolite. Non-atopic non-smokers were unlikely to become sensitized. The titre of the prawn-specific IgE antibody correlated with the duration of exposure and with the duration of symptoms. Discriminant analysis of the serological profile (anti-prawn IgE, total IgE and cotinine) was sufficient to assign individuals correctly into symptomatic or asymptomatic categories in 77% of subjects. The titres of the IgE and IgG antibody responses to prawn antigens did not correlate, and the main factor which seemed to determine the antibody isotype response to these inhaled antigens was cigarette smoking. IgE antibody was produced mainly by smokers, whereas IgG antibody was the predominant isotype produced by non-smokers.

Adolescent↗
PubMed1994

High-affinity [3H]PN200-110 and [3H]ryanodine binding to rabbit and frog skeletal muscle.

In vertebrate skeletal muscle, the voltage-dependent mechanism of sarcoplasmic reticulum (SR) Ca2+ release, commonly referred to as excitation-contraction (E-C) coupling, is mediated by the voltage-sensing dihydropyridine receptor (DHPR), which is believed to affect SR Ca2+ release through a physical interaction with the SR ryanodine receptor (RYR)/Ca2+ release channel. Scatchard analysis of ligand binding of [3H]PN200-110 to the DHPR and [3H]ryanodine to the RYR indicated the presence of high-affinity sites in muscle homogenates, with maximum binding (Bmax) values of 72 +/- 26 and 76 +/- 30 pmol/g wet wt for rabbit skeletal muscle, and 27 +/- 14 and 44 +/- 13 pmol/g wet wt for frog skeletal muscle, respectively. The Bmax values corresponded to a PN200-110-to-ryanodine binding ratio of 0.98 +/- 0.26 and 0.61 +/- 0.24 for rabbit and frog skeletal muscle, respectively, and were found by Student's t test to be significantly different (P < 0.02, n = 7). These results are compared with measurements with isolated rabbit skeletal muscle membrane fractions and discussed in relation to our current understanding of the mechanism of E-C coupling in skeletal muscle.

Animals↗
PubMed1994

Posterior tibial tendinitis. A literature review with case reports.

Overuse posterior tibial tendinitis is caused by the increased stress placed on the tendon as it tries to compensate for the increased subtalar joint pronatory movement and velocity during physical activity. The stress can cause microtrauma and rupture of some of the fibers of the tendon. This leads to an inflammatory process and the classical clinical signs and symptoms. Therapy is directed at reducing the inflammation, minimizing the fibrosis buildup, re-strengthening the weakened tissue, and controlling the pronatory force. The two case reports illustrate typical clinical signs, symptoms, and treatment for this injury.

Ankle Injuries↗