1,4-Methylhistamine is a specific substrate for type B monoamine oxidase

1,4-Methylhistamine was characterized as substrate for monoamine oxidase (MAO) in rat liver mitochondria. The $\text{K}$_m and $\text{V}$_max values were 38.8 μM and 6.33 nmoles/mg protein/60 min, respectively. The inhibition experiments with clorgyline and deprenyl, the selective inhibitors for type A and type B MAO, showed that 1,4-methylhistamine was specific for type B MAO.     

Photocontrol of the germination of onoclea spores: v. Analysis of germination processes by means of temperature

The physiological nature of photoinduced germination of Onoclea sensibilis L. spores was investigated by temporarily applying a range of temperatures, particularly 40 C, before and after short light treatment. Controls were germinated at 25 C.     

Rate of skin blood flow in various regions of the body.

Skin blood flow was measured by local clearance of 133Xe, and skin temperature was measured by medical thermography in various parts of the body. 1. A significant linear decrease in skin blood flow was observed with increasing age in the deltoid region. 2. The skin blood flow in the facial and pectoral areas was considerably higher than in the deltoid region. 3. The skin blood flow in the posterior cervical, lateral thoracic, lateral abdominal, and gluteal sites was less than in the deltoid region.     

Ionic currents across pancreatic acinar cell membranes and their role in fluid secretion

Fluid and enzyme secretion from a number of mammalian exocrine glands is controlled by the action of neurotransmitters and hormones on acinar cell membranes. Sustained stimulation evoking sustained fluid and enzyme secretion also evokes sustained membrane depolarization and increase in conductance. Mouse and rat pancreatic fluid and enzyme secretion, as well as membrane depolarization and conductance increase evoked by sustained stimulation with acetylcholine or cholecystokinin-gastrin peptides, are acutely dependent on extracellular calcium. However, the initial stimulant-evoked conductance increase and secretion appear to be triggered by calcium released from inside the cells. Direct measurement of membrane current during sustained stimulation in voltage-clamp experiments with resolution of the total current into its Na, Cl and K components has allowed calculations of stimulant-evoked Na and Cl uptake into the acinar cells. The NaCl uptake is quantitatively sufficient to account for the stimulant-evoked fluid secretion. The role of the stimulant-evoked transmembrane ionic current appears to be the supply of salt for the fluid secretion. Calcium derived from intracellular sources in the initial phase of secretion, and from the extracellular fluid in the sustained phase, couples fluid and enzyme secretion to hormone-receptor interaction.     

A new method for thawing frozen ram semen

The purpose of this work was to facilitate the on-farm use of frozen semen by initially thawing the straws in laboratory treated sperm (TS) rather than on-farm control sperm (CS), as is usually done. After thawing, TS was diluted, centrifuged, and extended in skim milk for storage at +15° C until utilized 3 to 6 hours later. $\text{In}$$\text{vitro}$: immediately after preparation and addition of skim milk for TS and thawing for CS, the percentage of stained cells and abnormal cells was higher (P < 0.01) in TS than in CS. In contrast, following a 3 hour incubation, TS and CS had the same proportion of motile cells. $\text{In}$$\text{vivo}$: fertility and prolificacy of FGA + PMSG-treated ewes were slightly higher following AI (1 AI/female) with TS than with CS: 52.4% $\text{vs}$ 44.2% and 155.0% $\text{vs}$ 148.0%, respectively. Fertility was also higher (P < 0.01) with fresh semen than with TS, but the difference was only 9.2 points (70.3% $\text{vs}$ 61.1% for the respective 798 and 242 ewes inseminated once). Prolificacy rates were similar (164.3% $\text{vs}$ 167.6%).     

The ‘fluid mosaic model’ and the ‘lattice model’ as two nonequilibrium states of the same membrane and the significance for biochemical control

Summary Biochemical control involves steep and hysteretic response. But the law of mass action does not allow for cooperativity. Therefore resort is classically made to concerted conformational change of protomers. This explanation of steepness and hysteresis by cooperativity is supported by regular surface patterns often observed by electron microscopy. But at other times the lattice appearance which gave rise to the lattice model is not observed. By contrast, a random appearance is observed and the fluid mosaic model of the membrane is assumed. So we are faced with the choice between the fluid mosaic model and the lattice model. Recently the fluid mosaic model is favoured but unlike the lattice model it does not explain the steep hyteretic response.It is suggested that the lattice model and the fluid mosaic model are in fact expression of two states of the very same membrane. The random state corresponds to a resting state. The lattice state corresponds to an active or inhibited state. Thus the transition from random distribution to hexagonal distribution provides simultaneously for triggering and hysteretic cycle with respect to both chemical production and transport across the membrane. This is a universal mechanism for rapid responsiveness and cyclic activity which is largely independent of the chemical mechanism assumed. It is based on the law of mass action supplemented by lateral diffusion. Conformational change and cooperativity are not invoked at all.     

Thiaminepyrophosphatase activity in the plasma membrane of microglia

An intense thiaminepyrophosphatase (TPPase) activity was demonstrated in glial cells and blood vessels in the central nervous system (CNS), when incubation was carried out with thiaminepyrophosphte (TPP, cocarboxylase), using the method of Novikoff and Goldfischer (1961). Glial cells with TPPSase activity were identified as microglia because they were morphologically similar to microglial cells in the sections stained with silver impregnation. TPPase activity was localized in the microglial perikaryon and in the processes, as viewed under a light microscope. Electron microscopically, enzyme activity was localized in the plasma membrane of microglia. We consider this activity to be a true TPPase activity hydrolyzing TPP, and we then went on to examine the substrate specificity, optimum pH, effect of chemical inhibitors and activators, and the effect of glutaraldehyde fixation. Our data are reported herein.