Origin of Pulmonary Megakaryocytes

1. Evidence is presented which indicates that pulmonary megakaryocytesdo not originate in the lungs but elsewhere in the body and are carried tothe lungs in the venous blood.

2. Some megakaryocytes in the lungs evidently deliver platelets to theblood.

3. Surgery is a potent stimulus to megakaryocyte production; the numbersof megakaryocytes found in the lung postoperatively is significantly increased.

Submitted on July 3, 1964 Accepted on September 19, 1964     

Heinz Body Anemia: An Ultrastructural Study. II. Red Cell Sequestration and Destruction

This study reports electron microscope observations on the process of redcell sequestration and destruction in the spleen and liver of the phenylhydrazine-treated rabbit. Damaged red cells are recognized by virtue oftheir Heinz bodies, a morphologic manifestation of the oxidative injury whichthey have sustained. Sequestration, in the spleen, involves the selective accumulation of damaged cells within the vascular spaces of the Billroth cords.Erythrophagocytosis and the intracellular digestion of red cells followssequestration. More severely injured cells may undergo intravascular hemolysiswithin the splenic red pulp. In the liver, however, no evidence for the intravascular sequestration of injured red cells is observed. Damaged cells areremoved directly from the sinusoidal blood by erythrophagocytosis. Theselectivity of spleen and liver for red cells subjected to different degrees ofinjury is discussed in terms of the observed differences in the vasculararchitecture of the two organs.

Submitted on November 15, 1964 Accepted on November 22, 1964     

Oxygen and Redox-Active Drugs: Shared Toxicity Sites

Oxygen and Redox-Active Drugs: Shared Toxicity Sites. Brown,O.R. and Seither, R.L. (19S3).Fundam. Appl. Toxicol. 3:209-214.Paraquat and nitrofurantoin can accept single electrons and,under appropriate conditions in tissues and cells, can passthese electrons to oxygen, thus participating in redox cycling.Similarities in the response of the target organ (the lung)and in subsequent pathology have also been observed among animalspoisoned by oxygen and by these chemicals. We report evidenceprimarily obtained from Escherichia coli for common biochemicalsites of toxicity for these agents. Common sites for oxygenand paraquat involve biosynthesis of specific amino acids, inductionof genetic stringency via unloaded tRNAs resulting from aminoacid deficiencies, decreased thiamin content, and impaired biosynthesisof pyridine nucleotide coenzyme biosynthesis for paraquat andoxygen. Inhibition of specific amino acid biosynthesis and inductionof stringency also have been observed for nitrofurantoin. RNAand DNA biosynthesis are also impaired by oxygen; this has notbeen examined for paraquat or nitrofurantoin. There is a biochemicalbasis and preliminary data to support inhibition of NAD biosynthesisas a component of mammalian toxicity for these agents. Niacinmay act to circumvent the consequences of the biochemical lesionat quinolinate phosphori-bosyl transferase in NAD biosynthesis.     

Pelvic Dosimetry Comparison of Two Manual Afterloading Systems

Two different, manually afterloaded, gynaecological applicators for intracavitary therapy are compared in a study of the pelvic dose distribution in 114 patients. The applicators have a similar shape but the source geometry in the vaginal ovoids is significantly different. The change in the geometry accounts for a 17% reduction in the dose to the recto-vaginal septum. One of the applicators is constructed from stainless-steel, the other from polyvinyl chloride. On the average, the mid-line symmetry appeared better with the plastic applicators, but the variation between patients was greater.     

A light for anaesthetists

A new type of lighting device is incorporated into the ether screen cross-bar, enabling better illumination of the patient's face. A 12-V, DC power supply is used. The temperature, with vacuum-assisted cooling, should not cause burns to an unconscious patient. Assessment of patient colour was evaluated and found to be reliable. The lamp must not be used with flammable anaesthetic agents.     

Verrucous carcinoma of the laryn

Verrucous carcinmoma of the larynx is an uncommon but distinct variety of well differentiated squamous carcinoma and accounts for 1–2% of all laryngeal squamous carcinomata. Awareness of the condition both by clinician and histopathologist is essential otherwise the diagnosis may not be made. From a review of the literature and personal assessment of the cases presented here it would appear that local conservative endoscopic treatment with careful follow-up may be the treatment of choice for certain verrucous carcinomata. Such treatment may be either suction diathermy or cryosurgery or laser surgery. Anaplastic transformation has been said to occur following irradiation of these tumours, though this view is not held by all clinicians, some of whom recommend radiotherapy for selected cases.     

Involvement of tobacco in alcoholism and illicit drug use

Survey data from the United States indicate that tobacco use is associated with the initiation of use of other addicting substances, and that increasing levels of tobacco use are associated with increasing levels of use of other psychoactive substances. Furthermore, factors affecting initiation, abstinence, and relapse to the use of tobacco, alcohol, and opioids are similar in nature. In addition, there are similarities in the addictive processes underlying the use of these substances. Taken together, these data suggest that tobacco use is involved, possibly more than by simple association, in the use of other substances containing psychoactive chemicals. In the present paper we discuss the involvement of tobacco in the use of alcohol, opioids, cocaine, and other substances, as well as some of the implications of these observations for researchers and clinicians. One such implication is that it may be possible to use tobacco and nicotine as models for phenomena of interest to other substance use researchers. For example, drug abuse treatment and prevention strategies could be explored using tobacco use as a target behavior, and biological phenomena such as the development of tolerance and physical dependence may be more readily studied with nicotine than with many other drugs. Certain pharmacologic differences across substances are also discussed in tight of their implications for development of treatment and drug control policies.