Histochemical studies of developing human fetal small intestine

Summary The histochemical characteristics of absorptive and mucus-producing cells have been described in 16 specimens of small intestine from human fetuses between 7 and 22 weeks of age. In the youngest specimens a slight to moderate reaction was found for all enzymes examined which included those known from biochemical or ultrastructural studies to be located predominantly in Golgi apparatus (thiamine pyrophosphatase), surface membrane (alkaline phosphatase, adenosine triphosphatase, leucine aminopeptidase), lysosomes (acid phosphatase), and mitochondria (succinic dehydrogenase). Mucus granules of somehat unusual location and staining properties were also found at this time. A progressive intensification of a majority of these histochemical reactions was observed between 3 and 6 fetal months.These findings indicate that the histochemical apparatus for degradation and absorption of nutrients and for elaboration of protein and mucus is already well established in the human fetus by the end of this 6 month period. It is not known, however, whether these activities occur in utero or whether they contribute significantly to fetal nutrition.     

Genetic Location in Escherichia coli K-12 of the Ultraviolet-Sensitive Mutation uvrD3

A host cell reactivation-negative mutation, uvrD3, in Escherichia coli K-12 is located between ilv and metE.     

Variability in Complementarity for Chloroplastic and Cytoplasmic Ribosomal Ribonucleic Acid among Plant Nuclear Deoxyribonucleic Acids

The nuclear DNAs from a number of angiosperm species were tested for hybridization to the RNAs contained in 70 S (chloroplastic) and 80 S (cytoplasmic) ribosomes. All of the DNAs contained regions complementary to RNAs from chloroplastic as well as cytoplasmic ribosomes. DNAs from closely related plants varied widely in their proportion of coding for these RNAs. About 0.15% of the DNAs from a number of different species of Nicotiana were found to be complementary to the RNAs of each kind of ribosome; however, DNAs from some other members of this genus had more than three times this proportion of coding for ribosomal RNAs. These and other data suggest that hybridization percentage for ribosomal RNA is not a familial or generic characteristic.     

Gradient-thickness thin-layer chromatography for the isolation and analysis of trace amounts of free fatty acids in large lipid samples

A thin-layer chromatographic method for quantitative isolation of free fatty acids is described. This method appears to be more satisfactory than existing methods in offering the combination of advantages of specificity, simplicity, rapidity, reproducibility, accuracy, high sensitivity, and applicability as a preparative technique. The method involves chromatography on a thin-layer plate on which the layer of Silica Gel G decreases linearly in thickness from 1000 micro at the base to 125 micro at the upper end. This gradient-thickness design allows the separation and densitometric quantitation of very small traces of free fatty acids from relatively large and complex lipid samples in a single chromatographic step. The method has been shown to be applicable directly to the crude total lipid extracts of several mammalian tissues. It appears to generate little if any artifactual free fatty acids from the breakdown of complex lipids, in contrast to the undesirable behavior of silicic acid columns in this respect. Gradient-thickness thin-layer chromatography promises to be useful for the quantitative isolation of trace amounts not only of other types of lipids but also of classes of compounds other than lipids.     

Stability of the brain fatty acid pattern in adult rats during extreme starvation

Abstract— Adult rats were denied food for 7 days. As compared with a control group, this severe starvation reduced the mean total body weight by 44 per cent, the weight of the diaphragm by 33 per cent and liver by 67 per cent, the total lipid content of the diaphragm by 57 per cent and liver by 69 per cent, and the total lipid phosphorus content of the diaphragm by 19 per cent and liver by 68 per cent. The decrease in lipid phosphorus contents indicates that the diaphragm and liver catabolized membrane phospholipids as well as triglycerides. In contrast, the fresh weight of the brain and the total lipid content of the brain were not significantly altered by starvation. The fatty acid patterns of the total lipid of the diaphragm and liver (determined by GLC) were grossly altered by starvation. In the brain, however, 17 of the 21 fatty acids measured did not change significantly (P > 0.05) and the remaining four changed, with borderline statistical significance, by only 2 to 13 per cent. There was no significant effect of starvation of the pattern of the brain polyunsaturated fatty acids when measured by alkali isomerization. In contrast to the liver and diaphragm, the brain is apparently unable to utilize its lipids appreciably as an energy source. Presumably the lipids of the brain are preserved to permit this organ to function properly, even in the last stages of starvation.     

Localization and distribution of Microccus lysodeikticus membrane ATPase determined by ferritin labeling

Antiserum to Ca²⁺-activated ATP phosphohydrolase (EC 3.6.1.3) isolated and purified from membranes of Micrococcus lysodeikicus was prepared in rabbits and guinea pigs. The γ-globulin fractions of these antisera reacted with and inhibited ATPase activity in isolated membranes but failed to absorb to intact protoplasts or purified mesosome fractions. ATPase activity was not detectable in the purified mesosomal preparations and trypsin treatment and sonication failed to release any activity. Ferritin conjugated to the γ-globulin fractions of the antiserum reacted with the ATPase particles on the membrane as visualized in negatively stained preparations examined in the electron microscope. Labeled membranes showed a distribution of ferritin very similar to the patterns observed for ATPase particles on untreated membranes. No significant labeling occurred when the ferritin conjugate was reacted with intact protoplasts or mesosome fractions. Thin sections of ferritin-labeled membranes established the asymmetric disposition of the ATPase, with the conjugate visible on only one side of the membrane. The results indicate that the ATPase protein occurs on the inner face of the membrane. All labeling experiments were verified immunologically. When ferritin-labeled membranes were subjected to the selective release procedure used in releasing the ATPase-like particles from the membranes, a complex of ferritin-conjugate associated with the ATPase particles was released. The selective release of ferritin-antibody-enzyme complexes from the membrane opens up a new way of studying the molecular architecture of cell membranes.     

Role of the Sympathetic Innervation of the Pacinian Corpuscle

An investigation was made into the nature of the role played by the noradrenergic innervation of the pacinian corpuscle. Corpuscles of the cat mesentery and mesocolon were used in all experiments. Blockade of noradrenergic beta receptors by dichloroisoproterenol and interference with norepinephrine release by reserpine are each capable of reversibly blocking mechanoelectric transduction by the pacinian corpuscle. The monoamine oxidase inhibitors iproniazid and phenelzine are capable of protecting the transducer from the blocking effects of reserpine. It is concluded that the presence of norepinephrine, as maintained by sympathetic tonus, is required for the afferent nerve terminal of the pacinian corpuscle to be mechanosensitive.