A Note on Circular Nonparametrical Classification

Following the linear approach by Stoller a circular discriminant analytical method is described. Marginally, following Ling, a simple method is mentioned to find clusters on a circle. Both methods are distribution-free and invariant under rotation.     

Enamel Microstructure of Rodent Molars, Classification, and Parallelisms, with a Note on the Systematic Affiliation of the Enigmatic Eocene Rodent Protoptychus

To investigate the diversity of the enamel structures in rodent molars, the schmelzmuster of more than 270 genera from the various fossil and extant groups was investigated. Only three basic types of schmelzmuster were recognized. The most prominent one, the C-type, is characterized by a basal ring of lamellar enamel (BRLE) surrounding the molars at the base of the crown. It occurs in most murids (cricetids) and other Myodonta. It is shared by the Dipodidea, Eomyidae, Geomyidae, and Gliridae. The C-type schmelzmuster was not found in any of the other rodents groups (Sciuromorpha, Anomaluromorpha, Sciuravida, Hystricognathi, Bathyergomorphi, and Caviida). Despite the rare occurrence of the P-type schmelzmuster with radial enamel only, most of these rodents have thick Hunter–Schreger bands (HSB) in their molars (S-type schmelzmuster). Although the C-type schmelzmuster is strictly limited to the Myomorpha (sensu McKenna and Bell), the fossil record shows that this structure does not form a synapomorphy but developed in parallel mostly from the P-type, but in Gliridae from the S-type schmelzmuster. On the basis of molar and incisor enamel the systematic position of Protoptychus can be evaluated.     

Sterols of the Toxic Marine Dinoflagellate,Pyrodinium bahamense

Pyrodinium bahamense is a dinoflagellate of concern in subtropical and tropical coastal environments. To date, there is only a single published study on its fatty acids, but no published data on its sterol composition. Sterols, which are membrane‐reinforcing lipids in eukaryotes, display a great diversity of structures in dinoflagellates, with some serving as chemotaxonomic markers. We have examined the sterol compositions of two isolates of P. bahamense from Indian River Lagoon and Tampa Bay, Florida, and have found both to produce three sterols: cholesterol, dinosterol, and 4α‐methylgorgostanol. All three sterols are found in closely related, armored taxa.     

Sterols and membrane dynamics

The effect of sterols from mammals, plants, fungi, and bacteria on model and natural membrane dynamics are reviewed, in the frame of ordering–disordering properties of membranes. It is shown that all sterols share a common property: the ability to regulate dynamics in order to maintain membranes in a microfluid state where it can convey important biological processes. Depending on the sterol class, this property is modulated by molecular modifications that have occurred during evolution. The role of sterols in rafts, antibiotic complexes, and in protecting membranes from the destructive action of amphipathic toxins is also discussed.     

Sterols of bryophytes

Sterol compositions of six species of bryophytes were studied. The major sterols identified were campesterol, 22-dihydrobrassicasterol, sitosterol, clionasterol, stigmasterol, cholesterol, 24-methyl-5,22-cholestadienol and 24-methyl-5,7,22-cholestatrienol. The quantitative determinations of the α- and β-epimers of 24-methyl and 24-ethylcholesterols were made based on 220 MHz ¹H NMR spectroscopy and capillary gas chromatography. Sterol compositions of bryophytes from other studies are reviewed, and possible sterol biosynthetic pathways in bryophytes are discussed.     

Sterols of Glaucocystophytes

Glaucocystophytes are a group of evolutionarily important freshwater algae that have an almost intact cyanobacterium, referred to as a cyanelle, as the photosynthetic organelle. Because of this, they have been the subject of a large number of studies over the past few decades on how a cyanobacterium transitioned into a chloroplast. However, studies on their lipid composition have lagged behind those on other areas of glaucocystophyte cell biology. To this end, we have examined the sterol composition of Cyanophora paradoxa Korshikov and Glaucocystis nostochinearum Itzigsohn in order to identify sterols left unidentified in previous studies. We have found that two isolates of G. nostochinearum and one of C. paradoxa uniformly produced three sterols: 24‐methylcholest‐5‐en‐3β‐ol, 24‐ethylcholesta‐5,22E‐dien‐3β‐ol, and 24‐ethylcholest‐5‐en‐3β‐ol.     

Sterols,aromatic compounds,and cerebrosides from the Hericium erinaceus fruiting body

Chemical investigation of the methanolic extract from the fruiting bodies of Hericium erinaceus, led to the isolation of fifty-one compounds including thirty-five ergostane-type sterols (1–35), fourteen aromatic compounds (36–49), and two cerebrosides (50 and 51). Their structures were identified based on spectroscopic analyses and by comparison of their spectral data with those reported in literature. This is the first comprehensive low-polarity chemical investigation of H. erinaceus. Thirty-one of the compounds (6–8, 11–35, 39, 41, and 49) were isolated for the first time from the genus Hericium and the family Hericiaceae. The chemotaxonomic relationship between H. erinaceus and other Hericium species was also discussed.     

Sterols of the fungi: Distribution and biosynthesis

The importance of sterols in the growth and reproduction in fungi is becoming increasingly apparent. This article concerns the composition and biosynthesis of ergosterol in these organisms. Comparison to plant and animal sterol formation are made.     

Sterols of Candida tropicalis grown on N-alkanes

Six sterols isolated from the yeast Candida tropicalis were identified as ergosterol (major component), (22E)-ergosta-5,7,9(11),22-tetraen-3β     

Sterols in a psychrophilic methanotroph, Methylosphaera hansonii

A suite of six sterols, lanosterol, lanost-8(9)-en-3beta-ol, 4, 4-dimethylcholesta-8(14),24-dien-3beta-ol, 4, 4-dimethylcholest-8(14)-en-3beta-ol, 4-methylcholesta-8(14), 24-dien-3beta-ol and 4-methylcholest-8(14)-en-3beta-ol, were identified in the psychrophilic methanotrophic bacterium, Methylosphaera hansonii. Their presence suggests that the capacity for sterol biosynthesis in methanotrophic bacteria is limited to the family Methylococcaceae but which have widely different optimal growth temperatures.