Generation time of leukaemic blast progenitor cells

Previous studies have indicated that the generation time of human leukaemic cells is longer than that of normal haematopoietic cells. We have employed a modification of the thymidine (TdR)-suicide technique to measure directly the generation time of leukaemic progenitor cells capable of colony formation. The results obtained with two human leukaemic cell lines (KG-1 and HL-60) and with blast progenitor cells from two patients with acute myelogenous leukaemia indicate generation times ranging from 9 X 0-22 X 0 hr and S-phase durations ranging from 5 X 5-8 X 0 hr. Using the same technique, the generation time of normal bone marrow CFU-c was determined to be 9-11 hr. These findings suggest that the proliferation rate of human leukaemic blast progenitor cells is similar to that of normal haematopoietic stem cells.

UV-induced second readout of LiF thermoluminescent dosimeters in the therapeutic dose range

A previously developed technique for reading out LiF thermoluminescent dosimeters (TLD) a second and subsequent time by means of ultraviolet (UV)-induced repopulation of dosimetry traps was studied to determine the feasibility of maintaining a second readout capability in a radiotherapy clinical setting. It was found that with grouping of the TLDs according to second readout sensitivity, the UV-induced readout attained a precision comparable to that of the initial readout. However, the UV-induced TL response retained a strong previous dose memory following a standard high-temperature anneal, and routine calibration before each reuse is recommended.

The effects of halothane on sympathetic ganglionic transmission

The effects of halothane on ganglionic transmission were studied in the stellate ganglion of the guinea pig using intracellular recordings in vitro. Depression of synaptic transmission is one of the actions common to many general anesthetics. The aim of this study was to investigate which of the processes involved in synaptic transmission are affected by halothane in concentrations comparable to those used during surgical anesthesia. The neurons of the stellate ganglion were depolarized using preganglionic nerve stimulation, postganglionic nerve stimulation, and intracellular stimulation before ad after introduction of halothane (vaporizer settings of 0.75% and 1.5% produced bath concentrations of 8 and 18 mg/dl, respectively). Halothane at both concentrations depressed sympathetic ganglionic transmission which was induced by stimulation of preganglionic nerves. Axonal transmission and the excitability of the postganglionic neurons to direct intracellular stimulation was far less sensitive to halothane than synaptic transmission. The depression of ganglionic transmission seen in the present study was most likely due to a decrease in transmitter release although alterations in postsynaptic receptor properties could have been involved as well. The decrease in sympathetic activity resulting from depression of ganglionic transmission probably contributes to the arterial hypotension seen during halothane anesthesia, along with direct myocardial depression, inhibition of catecholamine release from the adrenal medulla, direct action on vascular smooth muscle, and central sympathetic depression.

Isolation of genome-enzyme complex from cytoplasmic polyhedrosis virus of silkworm Bombyx mori

The genome-enzyme complex is isolated from the silkworm cytoplasmic polyhedrosis virus with DEAE-Sephadex column chromatography after ultraviolet irradiation. The genome-enzyme complex shows both RNA-polymerase and methyltransferase activities while using 3H-UTP and [3H-methyl]-S-adenosyle-L-methionine as substrates. Like the double-stranded RNA genome of CPV, the genome-enzyme complex could be separated into nine segments on polyacrylamide gel electrophoresis. It is demonstrated that the RNA polymerase and methyl-transferase are tightly bound to the double-stranded RNA genome and that the individual segments of the genome-enzyme complex all possess RNA-polymerase and methyltransferase activities. It appears that each segment of the double-stranded RNA genome is transcribed independently.

The morphological changes of the endothelium to venous stasis as observed under the scanning electron microscope

In this study using the pig, venous stasis is produced artificially by placing a pneumatic cuff around the hind leg of the anaesthetised animal and the cuff inflated intermittently. The period of stasis is three hours. The leg vein distal to the cuff is biopsied before and at intervals after the onset of stasis. The endothelium of the vein is examined under the scanning electron microscope. These findings suggest that venous stasis has a traumatic effect on the endothelium and cell injury is demonstrated within three minutes of the onset of stasis. With increasing period of stasis the endothelial cells are desquamated resulting in the exposure of the subendothelial basement membrane and collagen fibres. This is followed by aggregation of platelets and fibrin. It is postulated that the effect of venous stasis on the endothelium is a primary factor and may be important in the aetiology of clinical thrombogenesis.

Hemoglobin affinity for oxygen during short-term exhaustive exercise

We assessed hemoglobin affinity for oxygen (standard P50: pH 7.40, PCO2 40 Torr, temperature 37 degrees C) in 3 series of studies of 16 male subjects who performed exhaustive treadmill exercise of 10 min duration. Standard P50 was significantly elevated (0.7--2.5 Torr) during the last minute of and for 30 min following exercise. Exercise while carboxyhemoglobin (HbCO) was acutely elevated to 5% did not affect std P50 any differently than exercise alone. 2,3-Diphosphoglycerate (2,3-DPG) was significantly elevated after exercise, but not during or 30 min postexercise, and it correlated significantly with P50 in 2 studies (r, 0.43--0.68). ATP (mumol/100 ml) was significantly elevated only 3 min postexercise. Serum [Na+], [K+], [Cl-], osmolarity, and hemoglobin (Hb) concentration were significantly elevated during exercise with [Na+] osmolarity, and [Hb] remaining significantly elevated postexercise. There was no significant correlation between std P50 and any of these variables. Multiple correlation regression analysis between P50 and 2,3-DPG, ATP, and [Na+] yields a coefficient of 0.86. We conclude this type of exercise is unique in causing a small change in std P50 that appears to be mediated by several factors.

A simple method of producing a monolayer of cervical cells for digital image processing

A manual method of producing a monolayer of isolated and evenly distributed cervical epithelial cells has been developed for use in an automated digital image analysis system. The cervical scrape specimen is vortexed from the spatula into a solution of Mucosol. The suspension is filtered through a 10 micro nylon mesh to remove polys and debris and then syringed to disaggregate epithelial clumps. The cells are plated out on a Nuclepore filter. The filter is touched directly onto a glass microscopic slide to transfer cells, which are then fixed and stained in a routine manner. Cell counts reveal elimination of 92% polys, with only 2% loss of squamous cells.

Stereoelectronic factors in the binding of substrate analogues and inhibitors to purine nucleoside phosphorylase isolated from human erythrocytes

Several aspects of the stereoelectronic requirements of substrates of human erythrocytic purine nucleoside phosphorylase (E.C. 2.4.2.1) were elucidated providing the following information: (a) the N1 position cannot have a nonhydrogen substituent; (b) the 5'-OH group must be present for catalytic activity to be exhibited but is not an essential functional group for inhibitory action to be observed; (c) on the C8 position groups larger than -NH2 or -Br cannot be accommodated; (d) the syn-glycosyl conformation (i.e., 8-bromoguanosine) is acceptable but may not be an absolute requirement for phosphorolysis; (e) among nucleic base inhibitors methylation at N3, N7, or N9 vastly decreases the inhibitory properties as does a nitrogen in lieu of C-H in the 8 position. The results clearly indicate that this enzyme differs in its stereoelectronic requirements from the Escherichia coli enzyme.

Mass fragmentographic determination of pentachlorophenol in rainbow trout

Pentachlorophenol (PCP) is extracted from selected tissues of rainbow trout and converted to pentachloroanisole (PCA) by means of alkylation in the presence of potassium carbonate as a condensing agent. Pentachlorophenetole (PPT) is used as an internal standard. The electron impact mass fragmentography is carried out by monitoring m/e 280 (PCA), 294 (PPT), and 237. A plot of peak height vs. concentration is linear from 0.03 to 4.0 ng. Accuracy and precision of the method is +/-2% (N - 36). The results are accurate enough to warrant the use of this method for determining PCP in fish, as well as for monitoring PCP from various environmental sources. In addition, this technique provides a simple and rapid method by which a mixture of PCA and PCP can be determined simultaneously.

Dosimetry measurements and analyses of 10-MV x rays for Clinac-18

Radiation parameters for two Varian Clinac-18 10-MV x-ray units were measured and compared with the same parameters for the Toshiba LMR-13 and the Arco Mevatron XII. Comparison of the percentage depth dose, surface dose, and depth of maximum ionization as a function of field size are presented.

Carboxyhemoglobin trend in Chicago blood donors, 1970-1974

An 18% reduction in the carboxyhemoglobin (HbCO) saturation in nonsmoking Chicago blood donors occurred between 1970 and 1974, indicating that current donors are being exposed to a lower average carbon monoxide (CO) concentration than had been experienced by 1970 donors. In contrast to the situation in 1970, when it was discovered that 74% of the nonsmokers in Chicago were being exposed to CO in excess of the amount permitted by the federal air quality standards, in 1974 only 41% of the nonsmokers were being overexposed. The observed reduction in HbCO correlates well with both the ambient CO levels recorded at the air monitoring stations and the reduction in CO emission from automobiles. If the current trend continues, Chicago should reach compliance with air quality standards for CO by 1985. The measurement of HbCO in a representative urban population is an accurate index of actual CO exposure and supplements the air pollution data provided by air monitoring stations.