Solubility of the neurosecretory products of Crepidula fornicata Phil., a prosobranch mullusk]

Study of solubility of neurosecretory products in Crepidula fornicata shows that the presence of ethanol in the fixative is incompatible with good fixation. This character permits the choice of a more effective extraction technique. An experimental study in organ culture shows that the action of differentiation of brain appears in the extract obtained by this method.     

The lambda phage att site: functional limits and interaction with Int protein

Site specific integrative recombination of bacteriophage lambda involves unequal partners. The minimal phage att site is composed of approximately 240-base pairs and four distinct binding sites for Int protein, at least three of which are crucial for function. This 'donor site' recombines efficiently with a smaller 'recipient site' that lacks the extensive interactions with Int protein.     

Regulation of non-muscle myosin assembly by calmodulin-dependent light chain kinase

The presence of actin and myosin in non-muscle cells suggests that they may be involved in a wide range of cellular contractile activities. The generally accepted view is that interaction between actin and myosin in these cells and in vertebrate smooth muscle, is regulated by the level of phosphorylation of the 20,000-molecular weight (MW) light chain. In the absence of calcium, this light chain is not phosphorylated and the myosin cannot interact with actin. Calcium activates a specific calmodulin-dependent kinase which phosphorylates the light chain, initiating actin-myosin interaction. Although most studies on the role of phosphorylation have concentration on the regulation of actin-activated myosin Mg-ATPase activity, phosphorylation of the light chain also seems to control the assembly of smooth muscle myosin into filaments. Using purified smooth muscle light chain kinase, we have confirmed this observation. We report here studies of myosins isolated from the two non-muscle sources, thymus cells and platelets. We observed that these myosins are assembled into filaments at physiological ionic strength and Mg-ATP concentrations, only when the 20,000-MW light chain is phosphorylated.     

Sulfhydryl group reagents: Effect on intestinal smooth muscle

Zusammenfassung Die Acetylcholinkontraktion an Ratten-Jejunumstücken wird durch NEM gehemmt, was aber durch Vorbehandlung mit einem Reduktionsmittel nicht verstärkt wird. Sowohl NEM wie auch PCMB hemmen auch die Kaliumkontraktur, so dass die Hemmung der Acetylcholinkontraktion offenbar nicht auf den Rezeptor bezogen werden kann.

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The present studies were supported by USPHS Grant No. NB-07273. The authors thank MissTanga Dickerson for technical assistance.