Compartmentalization of monoaminergic synaptic vesicles in the storage and release of neurotransmitter

Monoaminergic nerves are characterized by the presence of a population of small synaptic vesicles (40-60 nm in diameter) containing a few large vesicles (80-90 nm in diameter). Thus, although both types of vesicles contain monoamines, the small vesicles must be considered as the organoid responsible for the storage and release of the neurotransmitter, whereas the large ones possibly are involved in the modulation of the process. The small vesicles are electron-lucent or have an osmiophilic electron-dense core that is always linked to the vesicle membrane. Considering morphological and histochemical evidence under different experimental conditions, we proposed the existence of two compartments in the small vesicles: the core and the matrix, corresponding respectively to the electron-dense core and the electron-lucent space between the core and the vesicle membrane in osmium tetroxide fixations. The sizes of both compartments are inversely related, i.e., the smaller the core, the larger the matrix and vice versa. The core even disappears, giving way to a small electron-lucent vesicle made exclusively by the matrix. Thus, the matrix is a constant component of the vesicle, whereas the core is a transient one. Each compartment has a different pool of amine: a loosely bound, easily releasable pool in the matrix and a tightly bound, more resistant pool in the core. These two pools subserve, respectively, a tonic or phasic release of the neurotransmitter, correlated with a tonic or phasic stimulation of the receptor. The core may be considered as a storage or reserve pool. Experimental evidence from our laboratory supports the concept that different mechanisms are operative in both compartments in the release of the neurotransmitter. For instance, a Ca2(+)-independent release would be primarily concerned with the neurotransmitter contained in the matrix, and a Ca2(+)-dependent efflux would be primarily related with the neurotransmitter stored in the core. However, it still must be established that a simple relationship exists between each kind of stimulus and each vesicle compartment, rather than both compartments being integrated in a dynamic functional unit.     

Cimetidine reverses tumor growth enhancement of plasmacytoma tumors in mice demonstrating conditioned immunosuppression

Mice were given repeated injections, at 21 day intervals, of cyclophosphamide paired with a novel taste (saccharin) in the drinking water. Subsequent challenge with a syngeneic plasmacytoma tumor led to elevated tumor growth and mortality only in conditioned mice that were reexposed to saccharin. This effect was abolished by conditioned exposure to a histamine type II-receptor antagonist.     

Ablepharon macrostomia syndrome with associated cutis laxa: Possible localization to 18q

The ablepharon-macrostomia (AMS) and Barber-Say syndromes (BSS) are rare disorders characterized by absence of the eyelids or ectropion, macrostomia, ambiguous genitalia, abnormal ears, rudimentary nipples, and dry, redundant skin. Patients with Barber-Say syndrome also have hypertrichosis. We present a patient with a phenotype similar to AMS who has a complex rearrangement of chromosome 18, involving both an inversion and interstitial deletion. Our patient lacks the typical features of the 18q deletion syndrome. We review AMS and BSS as compared with our patient, and recognize cutis laxa as a feature shared by all. We propose that the gene(s) for this phenotype may lie on chromosome 18 in the region of the deletion or inversion breakpoints. Received: 1 March 1995 / Revised: 20 May 1995     

Schistosoma mansoni: The role of the complement C3-activating system in the cercaricidal action of normal serum

Living Schistosoma mansoni cercariae incubated with normal serum from several species were damaged, as revealed by immobilization of their tails, uptake of methylene blue dye and the incapacity to infect appropriate vertebrate hosts. The following data indicate that the cercaricidal action of normal sera is dependent on the complement system, activation of the system proceeding through the alternate (properdin) pathway: (a) consumption of appreciable amounts of total hemolytic complement during the incubation of fresh serum with living cercariae; (b) the preferential consumption of the late reacting components and except for human C₄, only limited consumption of the classical early components; (c) the inactivity of sera depleted of C₃ or properdin; (d) the selective requirement for the presence of Mg²⁺ in the incubation mixture; (e) the full cercaricidal effect of C₄—deficient guinea pig serum; and (f) the conversion of C₃ after incubation of normal serum with the cercariae to electrophoretically faster migrating products. Immunofluorescence analyses indicated that the structures responsible for the complement activation are present in the cercarial coat.     

Enhanced transport and liquid membranes in bioseparations.

Membranes that use a reversible chemical reaction or sequestration to achieve high selectivities and productivities show great potential for use in bioseparations. The concept of liquid membranes, with and without a complexing agent (carrier), and the types of system configurations and carriers that may be used with these membranes, are discussed.