Marine mammal chemoreception

The presence or absence of a chemoreceptive capacity in marine mammals has drawn relatively little attention from the research community outside the Soviet Union. Toothed whales are typically labelled anosmic (lacking a sense of smell) since they do not have the peripheral olfactory structures typically associated with terrestrial mammals. Baleen whales are known to possess reduced olfactory tracts; their olfactory bulbs also may be reduced or absent. Although the neural structures that mediate taste in terrestrial mammals have been reported to be present in both groups of whales, cetaceans have been considered to have a poor sense of taste because typical mammalian taste receptors have been thought to be absent. Soviet researchers, however, recently have reported that gustatory receptors are present on some cetacean tongues and that the tongue of Tursiops truncatus appear to be well innervated. These workers also have been conducting investigations which seem to be aimed at describing a specialized gustatory capability in cetaceans. No experimental work has been reported by Western scientists. Little work has been done by either Western or Soviet researchers with regard to chemoreception among the other orders of marine mammals (Pinnipedia, Carnivora and Sirenia). Pinnipedia are typically labelled microsmatic (having a poor sense of smell); research has been restricted to histological examination of the nasal pathways, and neural anatomy. Sea otters are credited with a keen sense of smell, but no quantitative work has been reported. The chemosensory abilities of Sirenia remain unknown. The tongues of non-cetacean marine mammals have been histologically examined and found to resemble those of terrestrial mammals. No other investigations of gustation in non-cetacean marine mammals have been reported.     

Ultrastructural Investigation of the Integument of Tubiluchus philippinensis (Priapulida, Tubiluchidae)

The integument of Tubiluchus philippinensis van der Land, 1984 has been investigated by means of scanning and transmission electron microscopy. The ultrastructure of the cuticle corresponds principally to what has been found in Priapulidae. The tumuli are mere cuticular thickenings. Setae, tubuli, flosculi and scalids are receptor organs. Tubuli additionally serve a second function: they produce a secretion. The male genital area is equipped with various receptor organs, the internal morphology of which has been described. All receptor cells are characterized by apical cilia, which may be surrounded by a circlet of microvilli. They sometimes bear a rather complicated rootlet apparatus.     

THE MOLECULAR EVOLUTION OF PITUITARY HORMONES

1. The pituitary hormones can be divided into 4 families; within each the members are structurally related and have probably evolved from a common ancestor by a process of gene duplication and divergence. 2. Recent structural studies have revealed much about the evolution of proteins. The roles of point mutation, gene duplication and partial gene duplication in molecular evolution have been highlighted, and the nature of the evolutionary forces involved has been extensively debated. The information available about the evolution of proteins in general provides a background for consideration of pituitary hormone evolution. 3. The structure and function of the mammalian neurohypophysial hormones (oxytocin and vasopressin) has been studied in detail. Related (structurally similar) peptides have been found in the neurohypophyses of lower vertebrates and have been Characterized in many instances. Several schemes have been proposed for the evolution of these hormones. 4. The vasopressins of the pig and its relatives show a genetic polymorphism. The roles of neurohypophysial hormones in lower vertebrates are very varied and not fully understood. 5. The ACTHs and MSHs are members of a second family of pituitary hormones. They are polypeptides of moderate size. Studies on amino-acid sequences have been carried out for ACTHs and MSHs from several mammals. α-MSH is identical in all cases studied in detail, but β-MSH and ACTH vary to some extent. There is considerable sequence homology between the hormones in this family - indicating a common phylogenetic origin and several gene duplications. 6. Dogfish MSH is the only non-mammalian hormone of the ACTH-MSH family to have been studied in detail. Two MSHs have been isolated from this species; both resemble the a-MSH of mammals in amino-acid sequence. ACTH-like and MSH-like hormones exist in many other vertebrate groups, but have not been characterized fully. 7. Structure-function relationships have been widely studied in the ACTH-MSH family, and have some interesting evolutionary implications. Polymorphism of P-MSHs is found in some mammals. 8. A third family of protein hormones includes pituitary prolactin and growth hormone, and placental lactogen. These are proteins of moderate size which have been shown to be widely distributed among the vertebrates. Species specificity can be recognized with regard to biological, immunological and structural properties. 9. Amino-acid sequences have been determined for growth hormones and prolactins from several mammals. There is sequence homology between growth hormone and prolactin. Human placental lactogen closely resembles human growth hormone. A phylogenetic tree has been constructed for this protein family. Rates of evolution within the group are rather variable. 10. The fourth family of pituitary hormones (FSH, LH, TSH and some related placental hormones) are all glycoproteins and have a subunit structure. Extensive sequence studies have been carried out on the hormones from some mammals, and show that there is considerable homology between the various subunits. The α-subunits of human TSH, LH and HCG (and probably FSH) are very similar. The β-subunits are different, but homologous. Evolution of this family clearly took place by a series of gene duplications followed by gene divergence. Schemes whereby this could have occurred have been discussed. Related hormones occur in lower vertebrates, but have not been fully characterized. Some lower vertebrates may possess only one gonado-trophin. 11. The pituitary hormones provide an interesting range of evolutionary problems, and are useful models for the study of molecular evolution. The evolutionary processes involved in their diversification have been discussed, with particular reference to the co-evolution of hormones and their receptors. Neutral mutations and gene duplications may have played a role in providing co-existing variation of hormones and receptors. 12. A speculative model for the evolution of neurohypophysial hormones is proposed, as an example of how molecular evolution may have operated in this and other hormone groups. 13. Homologies have been proposed between the various families of pituitary hormones, and between pituitary proteins and other entero-secretory proteins. The pituitary protein hormones were probably elaborated from smaller molecules by a process of partial gene duplication.     

The organization of capsaicin-sensitive visceral afferent systems

It has become clear that a number of neuropeptides are found in sensory nerves, some of which have been identified in visceral afferents. The best studied peptide is substance P, which has been localized in a population of capsaicin-sensitive visceral afferents. It has been established that there are a varied proportion of substance P-containing afferents in different visceral structures. In general, the peripheral termination of these nerves is around blood vessels. The central terminations of visceral afferents are in laminae I and V in the dorsal horn of the spinal cord. Substance P has been localized in these laminae and appears to be capsaicin-sensitive and therefore of sensory origin. Recently, substance K, which is derived from the same gene as substance P, has been found in visceral structures. Calcitonin gene-related peptide has been found in certain viscera to be contained in capsaicin-sensitive nerves. The contribution that other peptides make to visceral afferent innervation is not known.     

The enzymatic synthesis of antiviral agents.

The majority of potential antiviral agents which are currently undergoing clinical trials are inhibitors of the replication of nucleic acids. The most common class of these inhibitors are nucleoside analogues and the elucidation of synthetic routes to these compounds has been of interest for many years as many are anticancer agents. One synthetic development has been the application of bio-transformations to nucleoside syntheses. This topic has been reviewed recently (Shirae et al., 1991) but this review is not widely available. In the present review, the application of biotechnology to the synthesis of antiviral agents including those which are not nucleoside analogues will be discussed. Enzymatic syntheses of nucleosides can be simpler and quicker than syntheses carried out by chemical methods. The most useful enzymes are those found in catabolic pathways. Nucleoside phosphorylases and N-deoxyribosyltransferases have both been widely used for nucleoside synthesis catalysing the transfer of sugar residues from a donor nucleoside to a heterocyclic base. Enzymatic methods have also been applied to the resolution of racemic mixtures and adenosine deaminase is a convenient catalyst for the hydrolysis of amino groups on purines and purine analogues. Regioselective deprotection of nucleoside esters has been achieved with lipases and these enzymes have also been applied to the synthesis of esters of sugar-like alkaloids. The latter have potential as inhibitors of the replication of HIV. Esterases have also been used in combined chemical and enzymatic syntheses of organophosphorus antiviral agents.     

Fossilized soft tissues in a Silurian platyceratid gastropod

Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknown, and have not been reported previously from the Palaeozoic. Here, we describe a Silurian (approx. 425 Myr) platyceratid gastropod from the Herefordshire Lagerst?tte that preserves the oldest soft tissues yet reported from an undoubted crown-group mollusc. The digestive system is preserved in detail, and morphological data on the gonads, digestive gland, pedal muscle, radula, mouth and foot are also available. The specimen is preserved three-dimensionally, and has been reconstructed digitally following serial grinding. Platyceratids are often found attached to echinoderms, and have been interpreted as either commensal coprophages or kleptoparasites. The new data provide support for an attached mode of life, and are suggestive of a coprophagous feeding strategy. The affinities of the platyceratids are uncertain; they have been compared to both the patellogastropods and the neritopsines. Analysis of the new material suggests that a patellogastropod affinity is the more plausible of these hypotheses.     

On the respiratory organs of amphipnous cuchia (Ham Buch)

The respiratory organs of Amphipnous cuchia comprise a pair of aicsacs, vestigial gill filaments borne on second gill arch and vascular folds of the third gill arch. The volume of each air-sac, its surface area and its reltionship with the body weight of the fish have been determined. The air-sac is lined by a respiratory mucosa which is composed of vascular and non-vascular areas. Each vascular area, called here the ‘respiratory islet,’ studded with hundreds of vascular rosettes, which are formed of collagenous material and supported by endothelial cells. Pilaster cells are absent. The ‘islets’ are covered over by a single layer of squamous type of epithelial cells. The non-vascular areas (lanes') are the stratified part of the respiratory epithelium and contain a large number of mucous glands which secrete mainly acid mucopolysaccharides. The vascularisation of the gills have been studied by India ink injection methods. The secondary gill lamellae are absent, their place being taken up by coiled vascular loops. A quantitative estimation of haemoglobin in blood of ‘cuchia’ and other air- and water-breathing fishes have been made by colorimetric method and the results have been discussed in relation to their habit and habitats. The cranial muscles which are involved in respiration of ‘cuchia’ and the mechanics of muscle action in breathing have been described.     

Breast augmentation using the expander mammary prosthesis

The expandable mammary prosthesis that has been successfully used for breast reconstruction has been modified for breast augmentation procedures. A new microreservoir that can be buried subcutaneously for extended periods has been developed. The unique design of this implant allows its size to be adjusted postoperatively as many times as desired, thus eliminating the possibility of a second operation to replace an implant whose size is unsatisfactory. Accurate, aesthetically satisfactory results are possible because the volume adjustments are made after the swelling has decreased and the implant has settled into position. Almost all patients offered this opportunity requested postoperative volume adjustments. The results of 59 patients are reported. The surgery was performed over a 3-year period, with the average follow-up time being 6 months. The incidence of capsular contracture has been less than 10 percent. Leakage was a problem in the original implant design; however, since the introduction of the new valve, there has been no leakage to date.     

Plant aspartic proteinases: enzymes on the way to a function

Plant aspartic proteinases have been characterized from seeds, flowers and leaves of a number of different species. The enzymes are generally either monomeric or heterodimeric, containing two peptides processed from the same precursor protein. The plant enzymes, like their mammalian and microbial counterparts, are active at acidic pH and inhibited by a class specific inhibitor pepstatin A. Plant aspartic proteinases are generally either secreted or targeted to the vacuolar/protein storage body compartment. The primary sequences of many of these enzymes have been determined and are very homologous with each other as well as with enzymes from mammalian and microbial origins. Plant aspartic proteinases, however, have a very unique plant specific region, which is not found in mammalian, microbial, or viral aspartic proteinases. The function of this region has not been elucidated. A role for these plant enzymes in protein processing or degradation has been proposed, however, more studies are required to confirm their in vivo functions. Recent intriguing results suggest possible roles for these enzymes in programmed cell-death of tissues and in pathogen resistance.     

A potentiometric sensor designed on the basis of urease immobilized in polyelectrolyte microcapsules

A potentiometric biosensor has been designed on the basis of glass pH-electrode with a sensing device of the microcellular polyelectrolytic coating containing urease. The polymeric walls of the coating are readily permeable for low-molecular weight compounds, including urea, but are impermeable for macromolecules. The main characteristics of the biosensor in various experimental solutions containing urea, low-molecular-weight salt, and buffer have been obtained. The sensor has been shown to be stable for at least three weeks. The standard curves of the sensor are linear in the range of urea concentrations from 0.2 to 20 mM.     

Antimutagenicity profiles for some model compounds

The concept of activity profile listings and plots, already applied successfully to the display of mutagenicity data, has been modified for application to antimutagenicity data. The activity profiles are bar graphs that have been organized in two general ways: for antimutagens that have been tested in combination with a given mutagen and for mutagens that have been tested in combination with a given antimutagen. Doses from both the mutagen and the antimutagen are displayed and plotted together with results on enhancement or inhibition of mutagenic activity. The short-term tests that have been used extensively to identify mutagens and potential carcinogens are increasingly being used to identify antimutagens and potential anticarcinogens. Three model mutagens, N-methyl-N'-nitro-N-nitrosoguanidine, aflatoxin B1 and benzo[a]pyrene, and 4 model antimutagens, butylated hydroxyanisole, butylated hydroxytoluene, glutathione and disulfiram, were selected from the data surveyed in the published literature. It is not clear at the present time whether the inhibition of carcinogen-induced mutation is a good indicator of anticarcinogenic properties, and further research is needed. Nevertheless, the activity profiles are useful for the assessment of the available antimutagenesis data by providing rapid visualization of considerable dose information and experimental results.     

Surface configuration of mesothelial cells in effusions. A comparative light microscopic and scanning electron microscopic study.

Surface configuration of mesothelial cells identified by light microscopy (LM) has been studied by scanning electron microscopy (SEM). It has been shown that mesothelial cells may have a variable SEM appearance. The surfaces of a small proportion of mesothelial cells are covered by regular microvilli (MV) and show openings of the pinocytotic vesicles. The surfaces of the majority of these cells are covered by vesicles or blebs. An intermediate population of mesothelial cells, i.e., cells displaying side-by-side blebs and MV, has also been observed. The latter cells no longer display pinocytotic vesicles. Occasional mesothelial cells have smooth surfaces. It has been shown by LM and transmission electron microscopy that cells with blebs are viable and capable of mitotic activity. It is concluded that mesothelial cells, detached from their epithelial setting, lose microvilli and pinocytotic vesicles and acquire surface blebs. The possible relationship between mesothelial cells and macrophages based on surface features has been discussed.     

Bacterial glycoproteins: functions,biosynthesis and applications

Although widely distributed in eukaryotic cells glycoproteins appear to be rare in prokaryotic organisms. The prevalence of the misconception that bacteria do not glycosylate their proteins has been a subject matter of discussion for a long time. Glycoconjugates that are linked to proteins or peptides, generated by the ribosomal translational mechanism have been reported only in the last two to three decades in a few prokaryotic organisms. Most studied prokaryotic glycoproteins are the S-layer glycoproteins of Archeabacteria. Apart from these, membrane-associated, surface-associated, secreted glycoproteins and exoenzymes glycoproteins are also well documented in both, Archea and Eubacteria. From the recent literature, it is now clear that prokaryotes are capable of glycosylating proteins. In general, prokaryotes are deprived of the cellular organelles required for glycosylation. In prokaryotes many different glycoprotein structures have been observed that display much more variation than that observed in eukaryotes. Besides following similar mechanisms in the process of glycosylation, prokaryotes have also been shown to use mechanisms that are different from those found in eukaryotes. The knowledge pertaining to the functional aspects of prokaryotic glycoproteins is rather scarce. This review summarizes developments and understanding relating to characteristics, synthesis, and functions of prokaryotic glycoproteins. An extensive summary of glycosylation that has been reported to occur in bacteria has also been tabulated. Various possible applications of these diverse biomolecules in biotechnology, vaccine development, pharmaceutics and diagnostics are also touched upon.     

Synthesis and biological evaluation of thioglycosylated porphyrins for an application in photodynamic therapy.

The aim of this work is the synthesis of a new family of glycosylated porphyrins in which the sugar moieties are linked to the tetrapyrrole ring by a thioglycosidic bond. Two series have been designed. The first one corresponds to meso-aryl porphyrin derivatives. The second one has been obtained from protoporphyrin IX derivatization. Aryl-porphyrins were prepared from tristolyl o- and p-hydroxyporphyrins followed by bromoallylation and thioglycosylation with peracetylated S-glucose, mannose and galactose and deprotection. The other series has been synthesized from protoporphyrin IX dimethylester with a regioselective glycosylation of terminal alkenyl carbon. The UV-visible, NMR and MALDI mass spectra are presented. Photocytotoxicities of the synthesized compounds against K562 chronic leukaemia cell line has been evaluated.     

A two-dimensional finite element analysis of a bioprosthetic heart valve

A finite element scheme has been developed using total Lagrangian techniques for the two-dimensional analysis of bioprosthetic heart valve leaflets undergoing large deformation. Two models of a leaflet, namely a radial and a circumferential slice, have been analysed. The attachment of the slice to the stent was simulated by progressive contact on a circular former and the coaptation of the leaflets in the centre of a heart valve by a straight line of contact. For the circumferential model, different initial configurations have been considered. The prolapse pressure under which the heart valve closes has been shown to be small in comparison with the normal pressure a heart valve sustains. The regions of the valve that are most heavily stressed are subjected to a strong component of bending. The amount is sensitive to the details of the boundary conditions and to the initial configuration of the valve. These observations are likely to be significant in the use of this kind of stress analysis to improve the design of this type of valve.     

Pulsed mode of a negative corona in nitrogen: I. Experiment

The pulsed mode of a negative corona discharge in air has long been known; however, in electropositive gases, this mode has not been previously observed. This paper presents the results from a systematic study of a newly discovered pulsed mode of a negative corona in nitrogen over a wide range of experimental parameters. The conditions under which the pulsed mode is realized are described in detail. The dynamic characteristics of current pulses are determined. The shapes and parameters of current pulses in nitrogen and air are compared.     

The organization of ribosomal genes in vertebrates

The organization of the repeat unit of the ribosomal genes has been determined in 15 different species of vertebrates. The EcoRI and BamHI restriction maps of the rDNA from single individuals of different species of fishes, amphibians, and reptiles have been analysed. Two rDNA clones from Xenopus laevis (representing one complete repeat unit) were used as probes in Southern blots to detect restriction fragments containing ribosomal genes. The results obtained indicate that the transcribed regions are highly conserved in length and sequence inside the same zoological class. These regions are less conserved when species from different classes are compared but a general trend has been observed. In contrast, the length and sequence of the spacer regions are very variable, even within the same zoological class. Different types of heterogeneity have been observed; examples range from a single type of ribosomal repeat unit within a species to the absence of any detectable regular tandem array of units.     

Atherogenesis: a dysimmune disease

The immuno-inflammatory response is central to the development of atherosclerosis. The important players of the adaptive immune system are all involved in this pathologic process. Several antigens have been identified these last years and they are mostly self-molecules that have been modified due to the complex microenvironment that is generated within the diseased artery. Pro-atherogenic autoreactive T cells have been characterized. The presence of auto-reactive natural antibodies has also been confirmed in the lesions. All these, together with the data showing that adoptive transfer of lymphocytes is able to modulate the disease, fulfill the criteria put forth by Witebsky and Rose to define a disease as being autoimmune. However, the complexity of the disease process extends to the immune system. Although T cells are known to be pro-atherogenic, B cells have been clearly shown to be athero-protective. The fine balance between the two extensions of the adaptive immune response is the key to a successful therapeutic approach towards atherosclerosis.     

Definition of bacteriophage groups according to their lytic action on mesophilic lactic streptococci

The lytic activity of 132 phages isolated during slow acid production in cheese factories situated in all the dairying regions of France during the past 16 years has been determined on 291 strains of mesophilic lactic streptococci. The results have been treated according to a method of analysis of data so as to establish a classification. Six groups of phages have thus been formed. Sixty-six percent of the phages studied, which are very similar and for the most part nonspecific to one species, have been gathered together in one group. On the other hand, a classification of the bacterial strains has been made on their sensitivity to the phages. Six groups, each corresponding to one of these groups of phages, have thus been defined. One of them accounts for 40% of the strains studied, of which certain ones are sensitive to a large number of phages.