Biomedical subjects
Publications and source records attributed to D White.
During glycerol-induced myxospore formation in Myxococcus xanthus, cellular neutral polysaccharide increases by approximately 200%, respiration decreases by 80%, and net phospholipid synthesis ceases.
Cisternographic examinations have become a relatively common procedure in the evaluation of patients with suspected communicating hydrocephalus. Adverse reactions to radiopharmaceuticals are relatively uncommon, particularly with the commonly used agents such as 111-In-DTPA and 169-Yb-DTPA. Adverse reactions after lumbar intrathecal instillation of 111-In-DTPA in three patients are described.
We investigated the accuracy and the sensitivity of a modification of the acetylene inhalation technique for the determination of lung tissue volume (Vt) during various grades of hemodynamic pulmonary edema in 23 dogs. After base-line acetylene measurements were obtained, intravascular driving force (pulmonary wedge pressure minus intravascular colloid osmotic pressure) was varied between -8 and +71 mm Hg by the inflation of an intra-aortic ballon and the infusion of isotonic saline. After 30 minutes at this new driving force, four timed acetylene samples were again collected. Vt (when factored by alveolar volume, VA) increased from base line to 0.23 plus or minus 0.07 ml/ml between a driving force of 0 and + 17 mm Hg. This same change in Vt/VA was accompanied by an increase in the lung wet weight-dry weight ratio from 3.84 plus or minus 0.31 to 5.2 plus or minus 0.25. Vt was 271 plus or minus ml compared with an actual lung wet weight of 288 plus or minus 57 g; Vt tended to overestimate lung wet weight in severe pulmonary edema. Alloxan-induced pulmonary edema (6 dogs) tended to parallel these data. We conclude that the acetylene method may ve a relatively accurate noninvasive method for the determination of increasing lung water in pulmonary edema.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
In view of previously published reports of localized membrane growth in exponentially growing Bacillus megaterium and in sporulating Bacillus cereus, an attempt was made to describe phospholipid metabolism and the topology of membrane synthesis during sporulation in B. megaterium. The cells were pulsed with radioactive glycerol or acetate at the time of septum formation, and the specific activity of the lipid fraction was measured at various times through the free spore stage. The bulk of the material labeled during septation could not be recovered in the spore. Rather, it was found that the labeled lipid fraction underwent considerable turnover during spore development. Additionally, other experiments revealed that the lipid made before the initiation of sporulation was also subject to extensive turnover. In order to minimize both the confounding effects of lipid turnover and the possible presence of lateral diffusion of labeled lipid in the membrane, autoradiography of cells pulse labeled with radioactive glycerol at the time of septation was performed; a symmetrical grain distribution resulted. Thus, despite previously published suggestions to the contrary, the current experimental techniques could not demonstrate the existence of localized membrane synthesis in B. megaterium during sporulation.
The inactivation of isocitrate lyase which occurs during late stages of myxospore formation in Myxococcus xanthus was studied. Several findings are reported. (i) Protein synthesis is required over a specific time interval in order for isocitrate lyase inactivation to occur at a later time. (ii) Metabolic energy is required at all times during myxospore development if the inactivation is to occur. (iii) It was possible to inhibit protein turnover to a considerable extent without affecting the net loss in isocitrate lyase activity.
The following enzymatic activities were demonstrated in Myxococcus xanthus during growth and myxospore formation: l-alanine dehydrogenase (EC 1.4.1.1), l-glutamic acid dehydrogenase (EC 1.4.1.2), glycine dehydrogenase (EC 1.4.1.5), l-glutamic glyoxylate aminotransferase (EC 2.6.1.4), and l-alanine glyoxylate aminotransferase (EC 2.6.1.12).
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Evidence is presented suggesting the presence of galactosyl transferases and galactosyl acceptors on the outer surfaces of intact Balb/c 3T3 cells. In addition, the data indicate that these transferases may only be capable of transferring galactose from uridine diphosphate galactose to galactosyl acceptors on adjacent cells after intercellular contact is made (trans-glycosylation). Intact Balb/c 3T12 cells, by contrast, show no requirement for intercellular contact in order to carry out this reaction suggesting that these cells, which do not exhibit contact inhibition of growth, may be able to transfer galactose to acceptors situated on the same cell as the enzyme (cis-glycosylation). Electrophoretic and radioautographic assays were used to detect surface transferase activities in these two cell lines. Results of experiments on cells from sparse and dense cultures, and under conditions where intercellular contact was regulated, are consistent with the above hypothesis.
Activities of the glyoxylate cycle enzymes isocitrate lyase (EC 4.1.3.1) and malate synthase (EC 4.1.3.2) were assayed in extracts prepared at different stages of myxospore formation in liquid cultures of Myxococcus xanthus. Activities of both enzymes attained peak values during conversion of rods to spheres. Isocitrate lyase activity decreased after reaching its peak value. Malate synthase activity also declined but at a much slower rate. The loss of isocitrate lyase activity could be prevented by the addition of chloramphenicol to cultures early in myxospore formation (during the initial rise in enzyme activity), but not by such addition at later stages of myxospore formation. The increase in glyoxylate cycle enzymes was not observed in a mutant unable to form myxospores in liquid culture under conditions suitable for morphological conversion of the wild type, or in wild-type cells incubated in the absence of an inducer for myxospore formation. It is concluded that the changes in the glyoxylate cycle enzymes represent regulatory phenomena associated with the development of the myxospore.
Vegetative cells of Myxococcus xanthus (strain FB) were induced to form myxospores by the glycerol induction technique. Several structural changes took place in the peptidoglycan during myxospore formation. The percent of the peptidoglycan comprised of monomer (disaccharide peptide) decreased from about 20% to approximately 7%. The proportion of the total diaminopimelic acid possessing a free amino group decreased about 11%. A carbohydrate containing only glucose was found to be bound, possibly covalently, to the vegetative cell and myxospore peptidoglycan. The amount of carbohydrate relative to peptidoglycan decreased by two-thirds during myxospore formation. None of the above changes in the peptidoglycan were observed in a mutant (strain GNI) of M. xanthus which was unable to convert to myxospores when incubated in the glycerol induction medium, or in the parental wild type (FB) when it was incubated in induction medium lacking the myxospore inducer, glycerol.
Flexibacter FS-1, a gram-negative gliding bacterium was grown in liquid culture as long (over 100-mum) filaments. The filaments possessed a triple-track wall which resembled that found in other gram-negative bacteria. Although phase-contrast microscopy indicated that the long filaments were nonseptate, electron microscopy revealed three or four septa along the length of each filament. The septa contained lysozyme-sensitive, electron-opaque material, presumed to be peptidoglycan, sandwiched between cell membranes. The outer triple track wall was not part of the septum. Mesosomes were seen in various areas of the cell and frequently were observed attached to septa in different stages of completion. Studies of the organism in slide culture revealed that individual filaments grew in an exponential fashion and divided in the middle despite the long length and multiseptate condition. When the temperature of a liquid culture growing exponentially with a generation time of 90 minutes was shifted from 30 to 35 C, the filaments fragmented into three or four shorter cells within 120 min. The short cells continued to grow exponentially at 35 C at approximately the same rate as at 30 C. When the culture was shifted back to 30 C, the cells immediately stopped dividing and began to elongate. After a period of 2 to 3 hr, cell division resumed. It is suggested that the shift-up in temperature induced the completion of the cross wall (centripetal growth of the triple-track wall) and cell separation at the sites of previously formed septa, whereas the shift-down in temperature caused a transient inhibition of cross-wall formation but not of growth. Fragmentation was inhibited by sodium azide but took place despite the inhibition of protein synthesis by chloramphenicol or the inhibition of deoxyribonucleic acid synthesis by mitomycin C.
Explore the source record for details and available documents.