Structure-activity relations of the molluscan neuropeptide FMRFamide on some molluscan muscles

Analogs of the molluscan neuropeptide FMRFamide were tested on four different molluscan muscle preparations which show qualitatively different responses to the peptide; the structure-activity relations are basically similar, but not identical. The C-terminal amide and the Arg³ residue are critical for FMRFamide-like activity on all four preparations. In contrast, analogs extended at the N-terminal or with conservative substitutions for the Phe¹ or Met² residue are approximately equipotent to FMRFamide. These structural requirements parallel those for the C-terminal tetrapeptide amide of gastrin.     

Allium cepa L. Cultivars from Four Continents Compared by Flow Cytometry show Nuclear DNA Constancy

In 1965 Van't Hof estimated the nuclear DNA amount of an unidentifiedAllium cepa L. cultivar as 2C = 33.55 pg (Experimental CellResearch39: 8–58). This value has been adopted by commonusage as the main calibration standard for angiosperm DNA C-valueestimations. However, different cultivars have been used whileassuming species DNA C-value constancy. Surprisingly this assumptionhas never been tested. A. cepa is an outbreeder with telomericheterochromatic segments, so intraspecific variation in C-value,possibly correlated with environmental factors as seen in Zeamays L., might be expected. We used laser flow cytometry tocompare nuclear DNA amounts in roots of six A. cepa cultivarsused as calibration standards or from different environments.Tissues from one cultivar, or similar volumes of tissue fromtwo cultivars, were run and the variance between nuclei in 2Cpeaks compared. Only one shoulderless 2C peak was seen for allpairs of co-chopped cultivars. Thus, no large differences inC-value between cultivars from different environments were found.Moreover, comparing cultivars run singly or as pairs showedno evidence for increased variation in 2C peaks in the latter,and hence of critical differences in DNA amounts between ‘AilsaCraig’ and another cultivar. Such variation was insufficientto make their use as alternative calibration standards, or thepractice of imputing Van't Hof's original C-value estimate tothem, unacceptable for most practical purposes. Given the mechanismsknown which can generate genome size variation, the degree ofconstancy in DNA C-value found seems remarkable. Copyright 2000Annals of Botany Company Allium cepa, onion cultivars, calibration standards, DNA C-value constancy, flow cytometry     

Primary structure of bovine matrix Gla protein, a new vitamin K-dependent bone protein

The complete amino acid sequence of bovine bone matrix Gla protein (MGP) was determined by automatic sequence analysis of the intact protein and of peptides isolated from tryptic and BNPS-skatole digests. This 79-residue, vitamin K-dependent protein contains a single disulfide bond and 4.8 gamma-carboxyglutamate (Gla) residues, one each at positions 37, 41, 48, and 52, and 0.8 Gla and 0.2 Glu at position 2. There is sufficient sequence homology between MGP and bone Gla protein (BGP) to indicate that these two bovine bone proteins arose by gene duplication and subsequent divergent evolution. Although MGP has a very low solubility in water compared to BGP, there is no hydrophobic domain in MGP which could account for its insolubility, and the overall fraction of hydrophobic residues is 32% for MGP compared to 43% for BGP. MGP is the first vitamin K-dependent protein to be discovered which has several non-gamma-carboxylated residues to the NH2-terminal side of its Gla residues. The presence of NH2-terminal Glu residues between the putative targeting domain for the gamma-carboxylase in the MGP leader sequence and the mid-molecule Gla residues suggests that the gamma-carboxylase may have additional, as yet unrecognized, specificity requirements which determine the susceptibility of Glu residues for gamma-carboxylation.     

The HsdS polypeptide of the Type IC restriction enzyme Eco R124 is a sequence-specific DNA-binding protein

The HsdS and HsdM polypeptides of the type IC restriction enzyme EcoR124 have been purified independently and used in a set of gel retardation experiments to determine the minimum requirements for sequence-specific recognition of DNA by this enzyme. The HsdS polypeptide alone is able to bind to DNA in a sequence-specific manner. In addition, whilst the presence of the HsdM polypeptide gives rise to a stimulation of DNA binding by the HsdS subunit it is not clear whether, under the conditions of the experiments reported here, the HsdS subunit maintains the same interactions with the HsdM subunits observed in the absence of DNA.     

Early Inhibition of Acetylcholinesterase and Choline Acetyltransferase Activity in Herpes simplex Virus Type 1 Infection of PC12 Cells

Abstract: Early in the course of productive Herpes simplex virus type 1 (HSV-1) infection of PC12 cells, activities of both acetylcholinesterase (AChE) and choline acetyltransferase (CAT) fell. Studies using metabolic inhibitors and a temperature-sensitive mutant of the virus suggested that the decline in activities of both enzymes was associated with events occurring early in the replicative cycle related to expression of the immediate-early (α) group of viral polypeptides. HSV-1 gene products thus may alter specialized cell functions well before the production of viral progeny and initiation of cell lysis. The early clinical manifestations of nervous system viral infection may reflect focal metabolic disturbance rather than, or in addition to, simple cell death.     

Neuronal precursor cells in the rat hippocampal formation contribute to more than one cytoarchitectonic area.

We have tested the hypothesis that cell lineage restriction boundaries define the borders between cytoarchitectonic areas in the cerebral cortex. Clonally related cells were identified using a retroviral marking technique, and the dispersion of neuronal clones was examined with respect to the transitions between cortical areas. We chose to study the hippocampal formation because we found that clones of hippocampal neurons, unlike those in neocortex, are compact and readily identifiable in the adult and that transitions between areas in the hippocampus are sharp relative to the spread of a typical clone. We conclude, contrary to the hypothesis, that clones of neurons transgress the boundaries between areas in the hippocampal formation, that border-crossing clones are observed as frequently as would be expected if clones spread freely over the hippocampus with no constraint imposed by area borders, and that different types of pyramidal neurons, characteristic of different areas, may appear to a single clone. different areas, may appear in a single clone.     

Suction lipoplasty: biohazardous aerosols and exhaust mist--the clouded issue

With the increased popularity of suction lipoplasty procedures, attention has been focused on their safety. One significant concern involves the rotary vane aspirators used to provide the suction required for the procedure. A series of experiments was carried out to determine whether aerosols are produced during the use of a rotary vane aspirator, since aerosols are known to be hazardous under appropriate conditions. Using a viable strain of Pseudomonas aeruginosa, we challenged the system through the suction port, and the exhaust from the aspirator was then cultured in a particle sampler. Results indicate that viable pathogens are released from the exhaust in physiologically significant particles capable of penetrating to the level of the alveolus in the normal human lung. These infectious particles were produced for 3 hours after the initial challenge. When an appropriate filtration device was attached to the aspirator outflow, the aspirator pump and environment were protected. In the absence of an appropriate filtration device, the aerosolized particles may constitute a hazard to patients or medical workers in the vicinity of the aspirator.