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Biomedical subjects

K L Becker

Publications and source records attributed to K L Becker.

At least 19 recordsLinked to original sources
PubMed1992

Serum procalcitonin as an index of inhalation injury in burns.

The molecular heterogeneity of serum immunoreactive calcitonin (iCT) was analyzed from a prospective study of 41 burn patients. Using different region-specific anticalcitonin antisera, the ratio of mid-region-recognizing to carboxyl terminal-region-recognizing iCT was found to increase acutely in those who subsequently died. The highest ratios occurred in those who died early of respiratory complications. Sephadex chromatography and reversed-phase HPLC demonstrated that the serum iCT circulated predominantly in the large molecular mass prohormone form (16 kDa). In comparison, iCT of normal human lung and of normal thyroid was shown to consist primarily of smaller monomeric mass forms. Furthermore, in 12 normal volunteers who were evaluated with a calcium-pentagastrin infusion, the ratio of iCT levels did not differ from the baseline ratio despite a 50% increase in serum iCT. These results suggest that in burns, the inhalational injury-associated hypercalcitonemia is characterized by a preferential release of procalcitonin; a form of constitutive secretion. The measurement of serum procalcitonin levels would appear to be a useful prognostic indicator of the severity of inhalational injury occurring in burn patients.

Biomarkers↗
PubMed1990

Pathobiology of lung tumors induced in hamsters by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and the modulating effect of hyperoxia.

Neuroendocrine lung cancer is among the most common types of lung cancers in smokers. We have recently shown that exposure of hamsters to N-nitrosodiethylamine and hyperoxia causes a high incidence of this tumor type. In this study, we show that the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone also causes neuroendocrine lung tumors in hyperoxic hamsters. Animals maintained in ambient air while being treated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone developed pulmonary adenomas composed of Clara cells and alveolar type II cells. Pathogenesis experiments provide evidence for the tumors caused by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in ambient air being derived from Clara cells. In the hyperoxic hamsters, the neuroendocrine carcinogenesis appears to involve two stages: (a) transformation of focal alveolar type II cells into neuroendocrine cells and (b) development of neuroendocrine lung tumors from such foci.

Adenoma↗
PubMed1990

Modulation of pulmonary bombesin by nicotine and vagotomy.

In pregnant hamsters, three transplacental injections of the ganglionic agonist nicotine resulted in a dose-dependent decrease in the concentration of mammalian bombesin (MB) in the lungs of neonatal (1 day old) animals. This decrease in neonatal MB did not occur if nicotine was given only once during gestation, or when it was given three times in conjunction with the ganglionic antagonist mecamylamine. In one week old animals born of mothers who had been exposed to three doses of nicotine during gestation, lung MB had returned to control levels. When nicotine was injected into neonatal animals, lung MB acutely increased. Right sided vagotomy to young hamsters resulted in an increase in the ratio of lung MB (right vs. left lobe) 1 week after surgery. Administration of nicotine to vagotomized animals resulted in decreased total lung MB and normalization of the MB ratio. Thus, nicotine has a potent modulatory influence on lung MB during fetal and neonatal development and maturation. This influence is also present in young animals that are subjected to partial denervation. Our hypothesis is that the innervation of pulmonary neuroendocrine (PNE) cells influences both PNE cell growth and its synthetic function. PNE MB, which is an epithelial and neoplastic growth factor, may play a role in this response.

Animals↗
PubMed1990

Nicotine, acetylcholine and bombesin are trophic growth factors in neuroendocrine cell lines derived from experimental hamster lung tumors.

Neuroendocrine hamster lung tumors, induced by exposure to 60% hyperoxia and subcutaneous administration of the tobacco-specific nitrosamine 4-(methylnitrosamino)-l-(3-pyridyl)-l-butanone (NNK) for 12 weeks, were placed in cell culture. By subsequent selective transfer of epithelial cells and maintenance in an atmosphere of 8% CO2, cell lines with characteristics of neuroendocrine cells were established. The neuroendocrine markers expressed by these cell lines included electron dense neuroendocrine secretion granules as well as secretion of calcitonin and mammalian bombesin. In keeping with data previously reported for a human neuroendocrine lung tumor cell line, nicotine, acetylcholine, and mammalian bombesin (MB) acted as strong growth factors in these neuroendocrine hamster tumor lines. The mitogenic effect of nicotine and acetylcholine was abolished by nicotinic receptor inhibition while the effects of mammalian bombesin were inhibited by an antagonist of MB receptors. Our data suggest that a receptor-mediated mitogenic effect of nicotine on neuroendocrine lung cells may be instrumental in the induction of smoking-associated small cell lung cancer.

Acetylcholine↗
PubMed1990

Pulmonary bombesin and calcitonin in hamsters during exposure to hyperoxia and diethylnitrosamine.

Combined exposure of hamsters to 60% hyperoxia and the carcinogen diethylnitrosamine for 6 wk resulted in the development of lung tumors. This was associated with progressive loss of body weight as well as increases in the pulmonary-associated peptides, mammalian bombesin (MB) and immunoreactive calcitonin (iCT). After 3 wk of exposure, multiple bronchial epithelial hyperplastic foci were noted, along with increased lung levels of MB and iCT as well as increased serum levels of MB. At this time, immunocytochemistry revealed the presence of MB and iCT within hyperplastic pulmonary neuroendocrine (PNE) cells. In addition, the localization of MB to alveolar type II cells was noted, along with the presence of lamellar bodies and secretion granules in these cells on electron microscopy. After 6 wk of exposure, distinctive microscopic pulmonary tumorlets were seen. These tumorlets were associated with a marked increase in lung and serum MB, and to a lesser extent lung and serum iCT. At this time, MB and iCT were localized exclusively to these abnormal PNE cell sites. These results, which may have relevance in humans, suggest that endogenous peptides may be important components in the process of development of neuroendocrine cancer.

Animals↗
PubMed1989

Stimulation of hamster pulmonary neuroendocrine cells and associated peptides by repeated exposure to cigarette smoke.

Although the normal function of pulmonary neuroendocrine (PNE) cells containing bioactive peptides is poorly understood, various pulmonary diseases are associated with hyperplasia of these cells, and they also may be progenitors for small cell lung cancer in humans. In this study we have investigated the effects of subchronic cigarette smoke exposure in the hamster on the PNE cells and their peptide content. Daily exposure to standard research cigarette smoke for as long as 90 days led to progressively higher levels of serum calcitonin (iCT) as well as higher lung tissue iCT and the gastrin releasing-like peptides or mammalian bombesin (MB). Subsequent to a 30-day period during which there was no further exposure to smoke, serum levels returned to control levels, but the lung levels of both iCT and MB remained higher than control levels. Also, after the 90 days of exposure, immunocytochemistry revealed an increase in the number of iCT-containing PNE cells. This increase in the number of PNE cells correlated well with the increased iCT content of the lung tissue. We conclude that subchronic cigarette smoke exposure causes an increase in pulmonary levels of iCT and MB, which may be linked to the observed proliferative response of the PNE cells.

Animals↗
PubMed1988

Primary culture of the enteric nervous system from neonatal hamster intestine. Selection of vasoactive intestinal polypeptide-containing neurons.

The enteric nervous system is a major division of the autonomic nervous system and is responsible for the regulation of gastrointestinal function. The objective of the present study was to develop a simple and effective technique for isolating and culturing neurons of the enteric nervous system that would permit characterization of their development and regulatory peptide content. This was accomplished using a dispersed intestinal cell preparation cultured under conditions designed to support the growth and differentiation of neurons and neuroendocrine cells. Newborn hamster intestine was digested in 0.1% collagenase, mechanically dispersed, and cultured in RPMI 1640 supplemented with 2.5% serum and other additives. Phase and bright-field microscopy demonstrated neuronal cells and fibers after the second day in culture. This was confirmed by immunohistochemistry using antibodies directed against neurofilament and vasoactive intestinal polypeptide. Acetic acid extracts of the culture indicated that during the first 4 days of the culture the content of vasoactive intestinal polypeptide increased, whereas the content of substance P, mammalian bombesin, and neurotensin declined. High-performance liquid chromatography and fast protein liquid chromatography confirmed that the immunoreactive vasoactive intestinal polypeptide coeluted with synthetic and iodinated forms of the peptide. This study describes a technique for primary culture of intestinal tissue that supports the survival of enteric neurons and permits analysis of the development and synthetic and secretory characteristics of the enteric nervous system.

Animals↗
PubMed1988

Evidence for cigarette smoke-induced calcitonin secretion from lungs of man and hamster.

In hamsters, acute cigarette smoke inhalation increased serum levels of the hormone calcitonin; and, in humans, smoking of two high-nicotine content cigarettes increased serum and urine levels of this hormone. The source of this immunoreactive calcitonin (iCT) does not appear to be the thyroid gland, since previously thyroidectomized patients demonstrated a similar response. In the hamster, the increased serum iCT levels were accompanied by a decreased lung tissue iCT content and hypocalcemia. It is suggested that the source of the cigarette smoke-induced hypercalcitonemia is the lung, possibly from the iCT-containing pulmonary neuroendocrine (PNE) cells. Moreover, this response appears to be dependent on the nicotine content of the cigarettes.

Animals↗
PubMed1988

An animal model for neuroendocrine lung cancer.

Neuroendocrine lung cancer is among the most common types of lung tumor in man and demonstrates a strong etiological association with cigarette smoking. However, despite numerous efforts, this cancer type has never been induced in animals. This report describes, for the first time, the reproducible induction of pulmonary neuroendocrine cancer in a readily available hamster model. The data provide evidence that deviations from pre-existing normal pulmonary oxygen levels may be an essential factor for the induction of this malignancy. This new model should greatly facilitate studies of the pathophysiology, biochemistry and therapy of neuroendocrine cancer of the lung.

Animals↗
PubMed1986

Changes in the phenotype of human small cell lung cancer cell lines after transfection and expression of the c-myc proto-oncogene.

Small cell lung cancer growing in cell culture possesses biologic properties that allow classification into two categories: classic and variant. Compared with classic small cell lung cancer cell lines, variant lines have altered large cell morphology, shorter doubling times, higher cloning efficiencies in soft agarose, and very low levels of L dopa decarboxylase production and bombesin-like immunoreactivity. C-myc is amplified and expressed in some small cell lung cancer cell lines and all c-myc amplified lines studied to date display the variant phenotype. To investigate if c-myc amplification and expression is responsible for the variant phenotype, a normal human c-myc gene was transfected into a cloned classic small cell lung cancer cell line not amplified for or expressing detectable c-myc messenger RNA (mRNA). Clones were isolated with one to six copies of c-myc stably integrated into DNA that expressed c-myc mRNA. In addition, one clone with an integrated neo gene but a deleted c-myc gene was isolated and in this case c-myc was not expressed. C-myc expression in transfected clones was associated with altered large cell morphology, a shorter doubling time, and increased cloning efficiency, but no difference in L dopa decarboxylase levels and bombesin-like immunoreactivity. We conclude increased c-myc expression observed here in transfected clones correlates with some of the phenotypic properties distinguishing c-myc amplified variants from unamplified classic small cell lung cancer lines.

Animals↗