Search PubMed⌕ Search

Biomedical subjects

M Crandall

Publications and source records attributed to M Crandall.

17 recordsLinked to original sources
PubMed2001

The tissue distribution and functional characterization of human VR1.

The irritant action of capsaicin is mediated by the vanilloid receptor, VR1, which is expressed in sensory neurons termed nociceptors. Capsaicin also desensitizes nociceptors and, thus, is useful clinically as an analgesic. Given the potential importance of VR1 in pain, we have cloned the human capsaicin receptor, hVR1, from a human dorsal root ganglia (DRG) cDNA library. Human VR1 protein is 85% identical to the rat VR1 and many of the amino acid differences are concentrated at the amino and carboxyl termini. VR1 is expressed in DRG as an approximately 4.2 kilobase RNA, and is also expressed in the central nervous system and in the kidney. Capsaicin (EC(50) = 853 nM), low pH (<5.5), and noxious heat (44 degrees C) activate hVR1 expressed in Xenopus oocytes. Subthreshold pH (6.4) sensitizes VR1 to capsaicin (EC(50) = 221 nM). This study demonstrates the similarity of human and rat VR1 in integrating multiple noxious stimuli.

Amino Acid Sequence↗
PubMed1987

Segregation of proteinase-negative mutants from heterozygous Candida albicans.

The extracellular acidic proteinase (EC 3.4.23.6) produced by Candida albicans has been reported to be a virulence factor. In studying the role of this proteinase in human disease, we determined the optimum conditions for stimulating proteinase production in order to isolate proteinase-negative (Prt-) mutants. We found that in liquid medium containing bovine serum albumin (BSA) as the sole nitrogen source, at pH 4 and 27 degrees C, the sensitivity of proteinase detection was considerably greater than when assayed on BSA agar at 37 degrees C. This observation is due, in part, to temperature sensitivity of proteinase induction. Nitrogen starvation did not induce proteinase. Proteinase production on agar was increased by adding 0.01% yeast extract (YE) to BSA medium. Using BSA + YE agar to isolate mutants, it was discovered that C. albicans ATCC 28366 was heterozygous for a Prt- mutation. Spontaneous Prt- mutants occurred at a frequency of 2 x 10(-3). Ultraviolet light increased the mitotic segregation of Prt- cells to a frequency of 1 x 10(-2). The Prt- phenotype showed a large inoculum effect, Prt- segregants reverted with a high frequency, and the revertants were unstable.

Aspartic Acid Endopeptidases↗
PubMed1980

Sporulation in Hansenula wingei is induced by nitrogen starvation in maltose-containing media.

The sexually agglutinative yeast Hansenula wingei lives in association with bark beetles that inhabit coniferous trees. This yeast was induced to sporulate by malt extract, which contains a high percentage of maltose (50%) and a low percentage of nitrogen (0.5%). A solution of 1.5% maltose without any growth factors also induced ascosporogenesis in H. wingei. Thus, only a carbon source is required for sporulation as in Saccharomyces. However, potassium acetate did not induce sporulation in H. wingei as it does in S. cerevisiae. Instead, disaccharides (such as maltose, sucrose, or cellobiose) promote sporulation better than either monosaccharides (such as dextrose, fructose, or mannose) or respiratory substrates (such as ethanol or glycerol). The specificity of disaccharides in promoting sporulation in H. wingei may be considered an adaptation since these disaccharides are present in the natural environment of this yeast. In addition, the specificity of disaccharides may be related to the induction of the disaccharidase because cells precultured on dextrose sporulate well on maltose, but cells precultured on maltose sporulate poorly on maltose. When (NH(4))(2)SO(4) was added at a low concentration (3 mM) to synthetic sporulation medium (1.5% maltose solution), sporulation was abolished, whereas other salts and nitrogen sources inhibited to a lesser extent and vitamins and trace elements had no effect. Oxygen was required for sporulation, as expected for an obligate aerobe. Maximal sporulation was achieved in 2% malt extract broth at high cell density (10(9) cells per ml), pH 5, and 25 degrees C. By using these optimal physiological conditions and hybrid strains selected from an extensive genetic breeding program, about 30% asci (10% tetrads) were obtained routinely. Thus, the genetics of cell recognition in this yeast can now be studied.

Aerobiosis↗
PubMed1976

Alternaria IgG precipitins and adverse reactions.

Late reactions consisting of fever, malaise, and swelling at the site, 4 to 6 hr after injections of Alternaria extract occurred in several patients receiving immunotherapy with Alternaria. These patients had in common serum IgG precipitins and exquisite leukocyte histamine release sensitivity to Alternaria. Such precipitins were 3 times more frequent in patients receiving Alternaria immunotherapy than a control group of patients receiving immunotherapy with other antigens. A prospective study revealed that 5 of 23 Alternaria-sensitive persons had precipitins before immunotherapy and another 6 developed precipitins during therapy. Only one of the 23 experienced a late Alternaria reaction. Thus, precipitins to Alternaria are common and do not seem to be the basis for the late reactions we observed. The finding of precipitins does not contraindicate immunotherapy.

Alternaria↗
PubMed1974

Molecular complementarity of yeast glycoprotein mating factors.

Cell fusion between opposite mating types 5 and 21 of the yeast Hansenula wingei is initiated by a strong sexual agglutination reaction. The mating factors responsible for the specificity of cellular recognition are complementary glycoproteins which form a physical complex in vitro. The complex is assayed by recovery of agglutination activity of the multivalent 5-factor after the univalent 21-factor has been inactivated by treatment of the complex with alkali. The 5-factor.21-factor complex, purified on Sepharose 6B, is large (several million daltons) and heterogeneous. The three peaks of 5-factor activity contain a number of combining sites proportional to molecular size.

Binding Sites↗
PubMed1971

Temperature-sensitive mutants of Escherichia coli affecting beta-galactoside transport.

Six different temperature-sensitive (ts) mutants have been isolated which have parental beta-galactoside permease levels at low temperatures but have decreased permease levels when grown at high temperatures. These mutants were derived from Escherichia coli ML308 (lacI(-)Y(+)Z(+)A(+)). After N-methyl-N'-nitro-N'-nitro-soguanidine mutagenesis, ampicillin was used to select for cells unable to grow on low lactose concentrations at 42 C. Temperature-sensitive mutants were assayed for galactoside permease activity after growth in casein hydrolysate medium at 25 or 42 C by measuring both radioactive methylthio-beta-d-galactoside uptake and in vivo o-nitrophenyl-beta-d-galactoside hydrolysis. The six conditional isolates have decreased levels of galactoside permease which are correlated with decreased growth rates at elevated temperatures. The low permease levels are not due to a temperature labile lacY gene product but rather to a temperature labile synthesis rate of functional permease. Some of the mutants exhibit a ts increase in permeability as shown by the increased leakage of intracellular beta-galactosidase and by the increased rate of in vivo o-nitrophenyl-beta-d-galactoside hydrolysis via the nonpermease mediated entry mechanism. Preliminary evidence indicates that transport in general is decreased in these mutants, yet there is some specificity in the mutational lesion since glucoside transport is unaffected. All these observations suggest that these mutants have ts alterations in membrane synthesis which results in pleiotropic effects on various membrane functions.

Ampicillin↗