Properties of Chicken Lens MIP Channels Reconstituted into Planar Lipid Bilayers

Membrane fractions highly enriched in chicken lens MIP (MIP28) were found to form ion channels when incorporated into planar lipid bilayers. The channels displayed prominent unitary conductances of about 60 and 290 pS in symmetric 150 mm KCl solution and were slightly anion selective. For both depolarizing and hyperpolarizing voltages, voltage sensitivity of the MIP28-induced conductance could be fit by a Boltzmann relation, symmetric around zero mV, with V ₀ = 18.5 mV, n= 4.5 and g _min/g _max= 0.17. Channel properties were not appreciably altered by pH in the range of 5.8 to 7, although channel incorporation was observed to occur more frequently at lower pH values. Calcium, at millimolar concentrations, decreased the channel mean open time. Partial proteolysis of MIP28 to yield MIP21 did not appreciably affect single-channel conductance or voltage sensitivity of the reconstituted channels. MIP28 was not phosphorylated by cAMP dependent protein kinase (PKA). Although unitary conductance and selectivity of the chicken MIP channel are similar to those reported for the bovine MIP (MIP26), the voltage sensitivity of MIP28 was higher than that of the bovine homologue, and voltage sensitivity of MIP28 was not modulated by treatments previously shown to affect MIP26 voltage gating (partial proteolysis and protein phosphorylation by PKA: (Ehring et al., 1990). The existence of such strikingly different functional properties in highly homologous channel isoforms may provide a useful system for exploration of the structure-function relations of MIP channels. Received: 27 March 1996/Revised: 5 August 1996     

Efficacy of transfer factor in treating patients with recurrent ocular herpes infections

Recurrent ocular herpes is an insoluble problem for the clinician. As cellular immunity plays an important role in controlling herpes relapses, and other studies have shown the efficacy of HSV-specific transfer factor (TF) for the treatment of herpes patients, an open clinical trial was undertaken in 134 patients (71 keratitis, 29 kerato-uveitis, 34 uveitis) suffering from recurrent ocular herpetic infections. The mean duration of the treatment was 358 days, and the entire follow-up period 189121 before, and 64062 days after TF treatment. The cell-mediated immune response to the viral antigens, evaluated by the lymphocyte stimulation test (LST) and the leucocyte migration test (LMT) (P<0.001), was significantly increased by the TF treatment. The total number of relapses was decreased significantly during/after TF treatment, dropping from 832 before, to 89 after treatment, whereas the cumulative relapse index (RI) dropped, during the same period, from 13.2 to 4.17 (P<0.0001). No side effects were observed. It is concluded that patients with relapsing ocular herpes can benefit from treatment with HSV-specific TF.     

Parasite community diversity in two Mediterranean labrid fishes Symphodus tinea and Labrus merula

Examination of 111 peacock wrasse [Symphodus tinea (L.)] and 97 brown wrasse ( Labrus merula L.) from the Valencian coast (Spain) yielded 24 metazoan parasite species (11 Digenea, three Cestoda, four Nematoda. one Acanlhocephala, five Crustacea). Eighteen species were from 5. tinea and 17 from L. merula; 11 of the 24 species were common to both hosts. Brillouin's diversity index, was applied to fully censused parasite infracommunities. This is the first time that all the metazoan parasites (internal and external) in any position in the host have been analysed for diversity. High values of prevalence, intensity, and diversity parameters indicate that these labrid fishes support diverse parasite communities. This may be due to their diverse diet, mainly marine invertebrates which are possible intermediate hosts; they also support certain netnatodes and crustaceans which have direct life-cycle.     

Sensorimotor transformation from light reception to phototactic behavior inDrosophila larvae (Diptera: Drosophilidae)

In this paper we examine theDrosophila melanogaster larval response to light. We survey the morphology of the larval visual and motor systems in relation to larval locomotory behavior and phototaxis. In addition, this paper proposes a model of sensorimotor transformation and examines the reversal in taxis occurring at theD. melanogaster larval wnadering stage.     

Recent advances in the understanding of polyamine functions during plant development

Suggested roles for polyamine function, and the evidence for these functions, is reviewed. These include membrane stabilization, free radical scavenging, effects on DNA, RNA and protein synthesis, effects on the activities of RNase, protease and other enzymes, the interaction with ethylene biosynthesis, and effects on second messengers. It is concluded that in addition to interacting with plant hormones, polyamines are able to modulate plant development through a fundamental mechanism(s) common to all living organisms.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - ADC arginine decarboxylase - Chl chlorophyll - DAP diaminopropane - DFMA DL--difluoromethylarginine - DFMO DL--difluoromethylornithine - PAs polyamines - Put putrescine - SAM S-adenosylmethionine - Spd spermidine - Spm spermine     

Observations on the reproductive biology of two parasites ofHylesinus varius andPhloeotribus scarabaeoides (Col: Scolytidae): Cheiropachus quadrum (Hym: Pteromalidae) andDendrosoter protuberans (Hym: Braconidae)

Observations on the biology ofCheiropachus quadrum (Hym: Pteromalidae) andDendrosoter protuberans (Hym: Braconidae), were conducted. Both species are the main parasites of the olive bark beetlesHylesinus varius andPhloeotribus scarabaeoides (Col: Scolytidae) in the South of Spain. Results have shown that an increase in body size of the host does not imply an increase in parasite efficiency. In fact, host size inversely affects parasite efficiency forC. quadrum. Bearing in mind this fact, the abundance of the host and the ease of its rearing in the lab, it is therefore advisable to useP. scarabaeoides as the host for mass rearing of the parasites studied here. On the other hand, the presence of white light is a negative factor for parasite longevity and fecundity. The pupae and all larval instars are parasitised.C. quadrum does not have a preference for any particular stage or larval instar of the host whilst there is a preference for the third and fifth larval instar byD. protuberans. With respect to the sex ratio of parasites, an increase in the number of males increases the fecundity of the females. The results obtained in this study can be considered essential in the development of a biological control system for olive bark beetle pests based on an increase in the population ofC. quadrum andD. protuberans.     

Relationships between cell surface protease and acid phosphatase activities ofLeishmania promastigote

A correlation between the ratio of the cell surface protease activity to phosphatase activity and the complexity of the pattern of cell surface exposed polypeptides ofLeishmania promastigotes was demonstrated for various strains grown under similar conditions. The ratio of the cell surface protease activity to acid phosphatase activity was high forL. major andL.b. panamensis and it correlates with the expression of a single polypeptide of 63 KDa on their cell surface. Intermediate and lower ratios of these enzymatic activites relate with more complex radio-iodinated patterns: two main bands inL.b. guyanensis (70 and 58 KDa) andL.b. braziliensis (72 and 60 KDa) and three main bands 65, 50, 27 KDa in allL.m. mexicana strains tested. Evidence is presented that the acid phosphatase located on theL.m. mexicana cell surface is not an artifact due to a secondary absorption of the secreted acid phosphatase from the culture medium. These results confirm theLeishmania antigen cell surface heterogeneity. The implications on the biology ofLeishmania and the clinical manifestation of leishmaniasis are discussed.     

Morphology, ontogeny and histochemistry of secretory trichomes of Geranium robertianum (Geraniaceae)

Geranium robertianum bears three types of glandular uniseriate trichomes which originate from a single protodermal cell and develop through periclinal divisions. Type I trichomes are procumbent and have an oval apical cell, two stalk cells and a basal cell. Type II trichomes are erect and have a pear shaped apical cell, two stalk cells and a basal cell. Type III trichomes are much longer than the other two types and have an elongated apical cell, five long stalk cells and a basal cell. Type I and type II trichomes are common on leaves while III trichomes are more abundant on flower structures.
Type I and type II trichomes secrete terpenoids and phenols. Type III trichomes are characterized by the accumulation of anthocyanins in the apical cell and secrete flavonoids.     

Binding of vinyl polymers to anionic model membranes.

The association of poly2-vinylpyridine (P2VPy) and poly4-vinylpyridine (P4VPy) to dimyristoylphosphatidic acid (DMPA) small unilamellar vesicles (SUVs) was studied as a function of pH, ionic strength (I), polymer concentration and temperature using spectrofluorimetry. Poly(vinylpyridine) (PVPy) data were transformed into association isotherms and analyzed in terms of binding and partition models. In the case of polyions, the inclusion of the activity coefficient in both models was essential. Moreover, a relating equation was proposed to compare parameters based on both theoretical approaches. On the basis of the results obtained, a model was developed to analyze polymer adsorption at the surface level, in which the length of the hydrophobic chain and the position of the N atom in the pyridinium ring play an important role. Transition temperature (Tc) for DMPA (ca. 55 degrees C) is decreased between 15 degrees C-19 degrees C in the presence of PVPy. Van't Hoff isochore showed that the binding constant (KA) accounted for average PVPy-DMPA two-dimensional solid and liquid interactions. KA decreased with I in the presence of both polymers, but was more sensitive to I in the case of P2VPy. Likewise, the number of phospholipid heads (N) involved in the binding process decreased with I in the presence of PVPy. The influence of I was more significant on N than on KA.     

Experimental tendon repair: glycosaminoglycan arrangement in newly synthesized collagen fibers.

Changes in the macromolecular orientation and metachromasy of glycosaminoglycans (GAG) in newly synthesized and assembled collagen fibers in rat Achilles tendon after tendon excision were investigated in toluidine blue (TB)-stained preparations, based in the selective absorption of polarized light (= linear dichroism, LD) and of absorption of unpolarized light in situ. Extrinsic LD was observed microspectrophotometrically from the early phases of tendon repair onwards, although the absorption peaks in both parallel and perpendicular directions with respect to the plane of polarized light and the long axis of the collagen fibers occurred at the same wavelength, and thus differed from the pattern situation in normal adult controls. Compared to normal adult tendons, the pattern of LD in newly synthesized and assembled fibers was still not fully attained 110 days after surgical tendon removal. This incomplete recovery possibly reflected the influence of aging during the repair process. There was no correlation between LD and metachromasy. The highest absorption values for metachromatic staining occurred on the 7th day after tendon removal, at a time when LD was not intense. Treatment with hyaluronidase showed that the LD in the early stages of tendon repair was mostly due to hyaluronate whereas the LD in the later stages was due to chondroitin sulfates. The changes in LD during Achilles tendon repair were attributed to gradual modifications in the composition and macromolecular orientation of GAGs relative to the long axis of the collagen fibers.