Biomedical subjects
Publications and source records attributed to P E Pedersen.
A gene encoding an alkaline protease was cloned from an alkalophilic bacillus, and its nucleotide sequence was determined. The cloned gene was used to increase the copy number of the protease gene on the chromosome by an improved gene amplification technique.
BACKGROUND: This report presents a summary of preclinical data concerning the use of estramustine, an antimicrotubule agent against human glioblastoma cells. The strategy for the investigation of estramustine is predicated on the unique affinity of this agent for microtubule-associated proteins (MAPs). METHODS: A series of laboratory investigations were used to demonstrate antiproliferative effects (MTT assay, colony forming assay, thymidine incorporation), cell cycle synchronization (flow cytometry), intracellular localization of binding sites (immunocytochemistry, electron microscopy), and activity in subcutaneous xenografts of human glioblastoma. RESULTS: Estramustine has potent in vitro activity against human glioblastoma cells and can enhance the cytotoxic effects of ionizing radiation. Estramustine-binding protein was abundantly expressed in glioblastoma cells and may contribute to the selective effects of estramustine on neoplastic cells. This agent has activity against subcutaneous xenografts of human glioblastoma. Synthesized novel estrogen carbamates also can inhibit proliferation of glioblastoma cells. CONCLUSIONS: Cytoskeletal elements (MAPs) of glioblastoma cells may provide a useful target for therapy with agents like estramustine because of the potent antimitotic effects of this agent and its affinity to a protein that is expressed in glioma cells. These observations have stimulated a search for other estrone carbamates with antimitotic activity that exceeds more conventional antimicrotubule agents.
The spatial organization of olfactory nerve projections was examined in the rat. The pathway was traced by orthograde transport of HRP following nasal lavage and by retrograde transport of HRP following injections into the olfactory bulb. The results indicated that there was a broad relationship between the epithelium and the olfactory bulb. Specific regions of the olfactory bulb received input from a large region of the epithelium. However, there was evidence that olfactory nerve terminations were not uniformly dense across their terminal fields. The results suggest that there may be finer sorting of olfactory nerves based on functional specificity.
The septal organ of Masera is a distinct patch of olfactory epithelium on the septal wall of the nasal cavity. It lies ventral to the main olfactory receptor sheet. Central projections of the septal organ to the main and/or accessory olfactory bulb were studied with punctate HRP injections into the posterior dorsomedial olfactory bulb of rat pups. Injection sites encompassed 2-8% of the main olfactory bulb glomeruli and some injection sites were confined to the accessory olfactory bulb glomeruli. The distribution of receptor neurons in the septal organ that were labeled as a result of retrograde transport from the injection sites was determined. Olfactory receptor neurons were labeled in septal organs of those animals with injection sites confined to the main olfactory bulb. Subsequent to the posterior dorsomedial bulbar injections of this study, labeled receptor neurons were preferentially located in the posterior portion of the septal organ and were clustered about a plane dorsal to the plane bisecting the organ. Injections confined to the accessory olfactory bulb only labeled vomeronasal organ receptor neurons. Thus it is likely that the main olfactory bulb and not the accessory olfactory bulb is the bulbar terminus of septal organ receptor neurons. To date, experimental evidence suggests that the septal organ system may comprise an anatomically and functionally unique chemosensory pathway for odor detection.
An anatomically distinct group of glomeruli, termed the modified glomerular complex (MGC), is present in the posterior dorsomedial portion of the main olfactory bulb. This region has been strongly implicated as part of the pathway that processes odor cues for suckling in neonatal rat pups. We studied the distribution pattern of olfactory receptor neurons that project to the MGC region after ionophoretic injections of WGA-HRP into the olfactory bulbs of 12-day-old rat pups. HRP label was confined to an identifiable localized region in the MGC of the main olfactory bulb. Label extended over 2-7% of the glomerular sheet of the main olfactory bulb, including the MGC. Olfactory receptor neurons within the olfactory epithelium of the nasal cavity were labeled with HRP ipsilateral to the injected side. Maps constructed of the olfactory epithelium revealed that the labeled neurons occurred within topographically defined regions. Anteriorly, labeled olfactory neurons were confined to a narrow strip medial to the dorsal recess, and, more posteriorly, this strip widened medially along the septal wall and laterally onto a limited area on the nasal turbinates. Only a portion of the receptor population within a region was labeled. The boundaries between labeled and unlabeled regions were sharp. These findings support the concept that the olfactory epithelium is an anatomical mosaic in which receptors with different glomerular projections sites are intermingled. In conjunction with previous evidence on the functional specificity of the MGC, and staining of receptor neuron subgroups with monoclonal antibodies, these findings further suggest that olfactory receptor neurons form a functional mosaic within the olfactory epithelium.
A detailed physical and genetic map of a previously cloned 5.5-kilobase segment of Treponema pallidum DNA is described. This segment expressed two proteins that are cell membrane associated in Escherichia coli. The structural genes of these treponemal membrane proteins, tmpA and tmpB, are coordinately expressed, and transcription in E. coli can start from at least two different treponemal promoters. The tmpA and tmpB proteins are the products of in vivo proteolytic cleavage from precursor proteins which are 2 and 4 kilodaltons larger, respectively, than the mature proteins. Because the sizes of the corresponding proteins produced in T. pallidum were identical to those of the mature membrane proteins in E. coli, we concluded that a similar proteolytic processing takes place in both E. coli and T. pallidum. Although tmpA and tmpB were controlled by the same transcription signals, tmpB was expressed to a higher extent than tmpA, and only the tmpB product could be overproduced by placing the left lambda promoter in front of the structural genes. The nucleotide sequence of the T. pallidum tmpA gene was established. This is the first T. pallidum gene sequenced. Codon usage and the nature of transcriptional and translational signals are discussed. The deduced amino acid sequence indicated the presence of a sequence that was characteristic for a signal peptide. This sequence information allowed the construction of hybrid genes coding for proteins having beta-galactosidase enzyme activity as well as TmpA epitopes. The enzyme-linked antigen was expressed at a high level in E. coli when transcriptional and translational signals from coliphage lambda were used. In this case the protein produced was a sandwich protein consisting of 21 amino acids of the lambda cro protein, 204 amino acids of the T. pallidum TmpA protein, and 1,020 amino acids of the E. coli lambda-galactosidase. The potential use of this enzyme-linked antigen for the serodiagnosis of syphilis is discussed.
A critical gap exists in our knowledge of the topographical relationship between the olfactory epithelium and olfactory bulb. The present report describes the application to this problem of a method involving horseradish peroxidase conjugated to wheat germ agglutinin. This material was iontophoretically delivered to circumscribed glomeruli in the olfactory bulb and the characteristics and distribution of retrogradely labeled receptor cells were assessed. After discrete injections into small glomerular groups in the caudomedial bulb, topographically defined populations of receptor cells were labeled. Labeled receptor cell somata appeared at several levels within the epithelium. The receptor cell apical dendrites followed a tight helical course towards the surface of the epithelium. The data thus far demonstrate that functional units within the olfactory system may include not only glomeruli as previously suggested but, in addition, a corresponding matrix of receptor cells possessing functional and topographical specificity.
Pregnant rats received 2-[14C]deoxy-D-glucose (2DG) intravenously on the last day of gestation, and their fetuses were delivered 1 hour later by cesarean section. Fetal brains showed high 2DG uptake spread throughout the accessory olfactory bulb and little or no differential uptake in the main olfactory bulb. These findings demonstrate that functional activity occurs in the accessory olfactory bulb in utero and suggest that the accessory olfactory system may be the pathway by which fetal rats detect the odor quality of their intrauterine milieu.
Conditions under which an odor could elicit the 1st nipple attachment in albino rats were investigated. In Experiment I rats exposed prenatally and immediately after birth to citral, a lemon scent, suckled the washed nipples of an anesthetized, parturient dam when the nipples had been scented with citral. Moreover, these rats did not suckle the normal, unwashed nipples of these dams. In Experiment II rats were exposed to citral either (a) in utero, (b) immediately after birth, (c) both pre- and postnatally, or (d) not at all. Only rats in Group (c) attached to washed, citral-scented nipples and did not suckle the normal unwashed nipples that elicited suckling in control rats. These findings suggest that prenatal and postnatal events can determine which olfactory stimuli elicit the newborn rat's 1st nipple attachment.
The circumstances under which a novel odor could elicit nipple attachment behavior in 3-day-old albino rats were investigated. In Experiment 1, rats suckled washed nipples scented with citral (a lemon odor) only if they either had received tactile stimulation (by stroking with a soft artist's brush) or had been administered amphetamine in the presence of citral prior to the suckling test. Pups stimulated in citral's absence or simply exposed to citral without stimulation failed to suckle such nipples. In Experiment 2, rats stimulated in a benzaldehyde (an almond odor) ambience suckled washed nipples scented with benzaldehyde but not those with citral scent. The opposite held for rats stimulated in a citral-rich environment. The stimulus conditions that support this conditioning were investigated in Experiment 3. Simultaneously increasing citral concentration and raising ambient temperature markedly attenuated the phenomenon. Experiment 4 demonstrated that not all classes of stimulation produced conditioning. Caffeine, in a wide range of doses, did not allow citral to elicit suckling on washed nipples. These findings are discussed within a framework of higher order conditioning. They may provide a mechanism by which naturally occurring stimuli come to elicit the species- and age-typical behavior of suckling.
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