GENETIC CONTROL OF CYTODIFFERENTIATION

The cells of the anterior region of the larval fatbody of Drosophila melanogaster accumulate kynurenine at the end of the third larval instar, whereas the cells of the posterior region are involved in pteridine metabolism. Through a series of transplantation experiments it has been demonstrated that the anterior fat cells synthesize kynurenine. The mutant vermilion lacks kynurenine, and the anterior fat cells of this mutant strain lack the autofluorescence characteristic of kynurenine. When the non-allelic suppressor gene is combined with vermilion, the synthesis of kynurenine is restored in the anterior fat cells, and some of the cells of the posterior region contain kynurenine as well. A similar extension in the number of cells containing kynurenine can be induced in the normal Ore-R strain by feeding the precursor tryptophan. It has been concluded that the absence of a physiological process in a differentiated cell does not necessarily represent a loss of the genetic potential for that process. The normal allele at the suppressor locus inhibits the occurrence of kynurenine in the posterior fat cells, whereas the mutant allele su²-s allows the expression of this potential. An inducer such as tryptophan can overcome this inhibition in the normal strain, and as a result the cells which are normally differentiated as "isoxanthopterin cells" may produce kynurenine as well.     

PSYCHOLOGICAL ASPECTS OF PAIN IN PATIENTS WITH TERMINAL CANCER

The dying patient reacts emotionally to the problems encountered in the terminal period according to his established pattern of response to stress. The nature of this pattern will play a part in his experience of pain. Some of the types of reaction include the bizarre misinterpretation of bodily sensation of the psychotic, the development of conversion symptoms, the increase in pain through muscle tension in the anxious but overcontrolled person, and the stoical acceptance by guilt-ridden patients. Physicians are sometimes reluctant to devote full attention to the care of the terminally ill for a number of reasons, including the attitude that "curing" is the only worthwhile activity of a doctor of medicine. Observers have found that the physician's attention to the day to day anxieties of the patient in a terminal stage may contribute substantially to his comfort.     

Functional significance of the crystal cells in the larva of Drosophila melanogaster

Cytoplasmic crystalline inclusions are found in some larval haemocytes of Drosophila melanogaster. Blackening can be experimentally induced in these cells, and previously it was suggested that either the substrate or enzyme for the tyrosine-tyrosinase system leading to melanin production in Drosophila larvae is found in these inclusions in the crystal cells. The present report is an attempt to further localize the enzyme and substrate. Larvae have been fed on food containing alpha-C(14)-tyrosine and autoradiographs of the blood cells taken from these larvae subsequently prepared. The C(14) activity in the crystal cells is restricted to the crystal inclusions in the cells and is significantly higher than that found in the other type of haemocytes, the plasmatocytes. When samples of the blood cells are incubated in DOPA solution, the extra-crystalline cytoplasm becomes blackened while the crystals themselves remain colorless. These observations are consistent with the hypothesis that the substrate is localized in the crystal inclusions whereas enzyme is found in the surrounding cytoplasm. An in vivo structural isolation would serve to separate enzyme and substrate rather than an inhibition by dehydrogenases as postulated by previous authors. In vitro examination with the phase microscope has shown that the crystal cells rupture easily and the crystals dissolve in the haemolymph. Therefore any treatment which tends to disrupt the structural integrity of the cell will allow the enzyme and substrate to come together. Humoral factors preceding metamorphosis might account for the in vivo release of the enzymatic reaction by initially altering the permeability of the cell.     

Phenethylbiguanide in diabetic patients; clinical and metabolic effects

Phenethylbiguanide (DBI) was given to 70 unselected but not obese diabetic patients who were receiving restricted diabetic diets. The only side effects attributed to the drug were anorexia, nausea, vomiting and diarrhea in 28 patients. These symptoms subsided with reduction of dosage. No evidence of serious toxicity has been demonstrated in clinical and metabolic studies. In 27 of the 70 patients diabetes was controlled adequately with DBI alone, and more stable control was obtained in 11 labile diabetics who received DBI in combination with insulin.The mechanism of action is not definitely known.