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Biomedical subjects

M Munson

Publications and source records attributed to M Munson.

7 recordsLinked to original sources
PubMed1992

Differences between steady-state and transient post-synaptic potentials elicited by stimulation of the sural nerve.

In cat medial gastrocnemius motoneurons, single stimuli to the cutaneous sural nerve evoke a post-synaptic potential with a mixture of depolarization and hyperpolarization, depolarization being dominant in type F cells and hyperpolarization in type S cells. This pattern is consistent with previous reports showing that activation of the sural nerve can sometimes reverse the normal order of motor unit recruitment by inhibiting S motor units while simultaneously exciting F motor units. However, during repetitive stimulation for 1-2 s, we found that the hyperpolarizing component of the sural input to medial gastrocnemius motoneurons was not persistent, but instead gave way to depolarization after the first 30 ms. The net steady-state response after 0.5-1.0 s of stimulation was depolarization in all cells, regardless of motor unit type. This suggests that tonic sural input may be incapable of producing prolonged recruitment reversals.

Animals↗
PubMed1989

A simple and rapid method for determining the linearity of a flow cytometer amplification system.

We describe a simple and rapid method for determining the linearity of a flow cytometer amplification system. The method is based on a fundamental characteristic of linear amplifiers: The difference between two amplified signals increases linearly with increasing amplifier gain. Two populations of beads or cells, differing slightly in fluorescence intensity, are analyzed by the flow cytometer at increasing photomultiplier tube high-voltage settings. The distribution of the populations' mean difference versus mean position is a straight line intersecting the origin for linear amplifiers. Although some types of nonlinearities cannot be detected with this technique, deviations from linearity indicate nonlinear components in the flow cytometer amplification system. The correlation coefficient is used to quantify degree of nonlinearity. We also describe a method for amplifier nonlinearity compensation.

Amplifiers, Electronic↗
PubMed1987

Localization of neutralizing regions of the envelope gene of feline leukemia virus by using anti-synthetic peptide antibodies.

We synthesized 27 synthetic peptides corresponding to approximately 80% of the sequences encoding gp70 and p15E of Gardner-Arnstein feline leukemia virus (FeLV) subtype B. The peptides were conjugated to keyhole limpet hemocyanin and injected into rabbits for preparation of antipeptide antisera. These sera were then tested for their ability to neutralize a broad range of FeLV isolates in vitro. Eight peptides elicited neutralizing responses against subtype B isolates. Five of these peptides corresponded to sequences of gp70 and three to p15E. The ability of these antipeptide antisera to neutralize FeLV subtypes A and C varied. In certain circumstances, failure to neutralize a particular isolate corresponded to sequence changes within the corresponding peptide region. However, four antibodies which preferentially neutralized the subtype B viruses were directed to epitopes in common with Sarma subtype C virus. These results suggest that distal changes in certain subtypes (possibly glycosylation differences) alter the availability of certain epitopes in one virus isolate relative to another. We prepared a "nest" of overlapping peptides corresponding to one of the neutralizing regions of gp70 and performed slot blot analyses with both antipeptide antibodies and a monoclonal antibody which recognized this epitope. We were able to define a five-amino-acid sequence required for reactivity. Comparisons were made between an anti-synthetic peptide antibody and a monoclonal antibody reactive to this epitope for the ability to bind both peptide and virus, as well as to neutralize virus in vitro. Both the anti-synthetic peptide and the monoclonal antibodies bound peptide and virus to high titers. However, the monoclonal antibody had a 4-fold-higher titer against virus and a 10-fold-higher neutralizing titer than did the anti-synthetic peptide antibody. Competition assays were performed with these two antibodies adjusted to equivalent antivirus titers against intact virions affixed to tissue culture plates. The monoclonal antibody had a greater ability to compete for virus binding, which suggested that differences in neutralizing titers may relate to the relative affinities of these antisera for the peptide conformation in the native structure.

Amino Acid Sequence↗
PubMed1979

The amnion regulates movement of fetally derived alpha-fetoprotein into maternal blood.

The present investigation documents that, under normal conditions, most fetally produced AFP reaches the maternal circulation via diffusion across the amnion from amniotic fluid. This has been determined by comparing maternal serum AFP levels with amniotic fluid albumin concentrations in paired samples. The proportionally demonstrated between them indicates a proportional, transamniotic exchange of the two proteins, each originating on opposite sides of the amnion. Albumin is known to reach amniotic fluid by transamniotic diffusion from maternal blood. All amnions restrict AFP movement into maternal serum, but some are distinctly more restrictive than others; in such cases, a relatively greater increase in amniotic fluid AFP concentration would likely have to occur from a fetal lesion before being reflected in maternal serum. Inconsistencies found in several paired samples identify that other variables may also influence passage of AFP to the mother.

Amnion↗