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Biomedical subjects

M Brown

Publications and source records attributed to M Brown.

At least 847 records · Page 47Linked to original sources
PubMed1977

The determination of allopurinol and oxipurinol in human plasma and urine.

A method is described for allopurinol and oxipurinol assay within human plasma and urine in the range expected during therapy. The method is based on high-performance ion-exchange chromatography following an efficient sample purification step using Chelex-100 resin in the Cu2+-form. Linear calibration curves are produced for allopurinol over the range 0.05-10 mumole/1 (0.068-1.36 mug/ml) in plasma and 0.005-1 mmole/1 (0.68-136 mug/ml) in urine and for oxipurinol 0.5-100 mumole/1 (0.076-15.2 mug/ml) in plasma and 0.1-2 mmole/1 (15.2-304 mug/ml) in urine.

Allopurinol↗
PubMed1977

Immunologic selection against simian virus-40 transformed cells: concomitnat loss of viral antigens and early viral gene sequences.

A clonal line of highly oncogenic "spontaneously transformed" mouse cells (T AL/N clone 3) was transformed in tissue culture by simian virus 40 (SV40) and subsequently recloned. The clone of SV40-transformed cells (subclone 1) expressed SV40-specific T (nuclear) and transplantation antigens but was 100 times less tumorigenic than the parent T AL/N clone 3 cells. When large numbers of subclone 1 cells (10(4)-10(5)) were injected into syngeneic AL/N mice, tumors were produced. From the tumors, cell lines were established in culture, all of which were consistently negative for T antigen. Tumor lines tested were found not to contain SV40-specific transplantation antigen and had again become highly tumorigenic. The original subclone 1 cells contained about one copy of SV40 DNA per diploid amount of cell DNA, as well as RNA complementary to the early region of the SV40 genome. The T antigen-negative cells from tumor line 124 contained approximately 0.5 copy of SV40 DNA per diploid equivalent and did not synthesize any detectable virus-specific RNA. Reassociation kinetic analysis with restriction enzyme fragments of viral DNA demonstrated that the cells from tumor line 124 (and also the clones of this line) had lost DNA sequences predominantly from the early region of the SV40 genome. The results indicate that a set of stably integrated SV40 DNA sequences can be present in a cell without the expression of viral antigens.

Antigens, Viral↗
PubMed1977

Characterization of early simian virus 40 transcriptional complexes: late transcription in the absence of detectable DNA replication.

Isolation of early viral transcriptional complexes and incorporation in vitro of radiolabeled precursors into nascent RNA has permitted an analysis of early simian virus 40 (SV40) transcription. Under conditions such that viral DNA replication was undetectable, both early and late SV40 RNA were synthesized. This finding provides evidence that viral DNA replication is not an absolute requirement for late transcription and supports earlier observations that late viral RNA is synthesized in SV40-infected nonpermissive mouse cells. The majority of the early viral transcriptional activity can be solubilized, indicating that a substantial portion of this RNA is transcribed from free rather than integrated templates. Sedimentation analysis of the transcriptional complexes resulted in the detection of two separate peaks of activity, suggesting the possibility of two distinct types of early SV40 templates.

Chromosome Mapping↗
PubMed1977

Protease effects on specific growth properties of normal and transformed baby hamster kidney cells.

We have tested the effects of exogenous proteases on the growth of normal and transformed hamster fibroblasts in the classic culture assays for transformation. The results indicate that exogenous proteases act to decrease the serum requirement of normal cells but not nearly to the extent that occurs in the process of viral transformation. Proteases do not further decrease the serum requirement of transformed cells, nor do they affect the maximal saturation density or the plating efficiency in soft agar of either normal or transformed cells. Under conditions optimal for growth stimulation, proteases decrease the strength of cell-to-substrate adhesion but do not affect cellular morphology. In contrast to previous studies, experiments using highly purified trypsin and several different active-site inhibitors strongly suggest that the growth-stimulatory activity of trypsin is not directly related to the proteolytic activity of the molecule.

Agar↗
PubMed1977

The control of SV40 transcription during a lytic infection: late RNA synthesis in the presence of inhibitors of DNA replication.

The transition from early to late transcription of SV40 DNA in productively infected BSC-1 cells was analyzed using both inhibitors of DNA replication, and early (Group A) temperature sensitive (ts) mutants of SV40. Late virus specific cytoplasmic RNA sedimenting at 16S in neutral sucrose gradients and complementary to the plus (L) DNA strand of SV40 was detected in cultures infected in the presence of three inhibitors of DNA replication (Ara-C, FdU, and chloroquine), even though the inhibition of viral DNA replication appeared to be essentially complete. After infection with the early SV40 mutant tsA58, no DNA replication was detected at the restrictive temperature (41 degrees C) and no significant late RNA complementary to the plus (L) strand was found, in either the cytoplasm or nuclei of infected cells. These data support the concept that expression of late viral functions requires the initiation of viral DNA synthesis or a functional gene A protein, or both.

Cell Line↗
PubMed1977

Stimulation in vivo of the secretion of prolactin and growth hormone by beta-endorphin.

Morphine sulfate (MS) and the opioid peptide beta-endorphin beta-LPH-(61-91) stimulate prolactin and growth hormone release in steroid-primed and non-treated male rats when injected intravenously or intracisternally. On a molar basis beta-endorphin is at least 20 times more potent than MS, whereas Met5-enkephalin (beta-LPH-(61-65)) and alpha-endorphin (beta-LPH-(61-76)) are devoid of activity at the dose injected (300 mug). The in vivo stimulatory effects of beta-endorphin on prolactin secretion are reversed by the opiate antagonist naloxone. The absence of in vitro effect of MS and beta-endorphin on prolactin and growth hormone secretion by cultured rat pituitary cells suggest that they have a central nervous system site of action.

Animals↗
PubMed1977

Effect of neurotensin, substance P and morphine sulfate on the secretion of prolactin and growth hormone in the rat.

Neurotensin (NT), substance P (SP) and morphine sulfate (MS) elevate plasma prolactin and growth hormone levels in both normal or estrogen-progesterone pretreated male rats. By contrast, steroid priming is required for TRF to exhibit PRL-releasing activity. Naloxone, an opiate receptor blocker, reverses the stimulatory effect of MS only. Diphenhydramine, a histamine antagonist, inhibits the response to NT, SP and MS without affecting the response to TRF. These results suggest the involvement of a histaminic step in the action of NT, SP and MS. TRF, NT and SP do not appear to stimulate PRL and GH through activation of an opiate receptor.

Animals↗
PubMed1977

Body position and mode of ventilation influences arterial pH, oxygen, and carbon dioxide tensions in halothane-anesthetized horses.

Effects of body position and type of ventilation were determined on arterial blood gases (PaO2, PaCO2) and pH during and immediately following clinical halothane anesthesia in 36 young, physically conditioned horses. Horses in dorsal recumbency had a lower PaO2 than did similarly breathing horses in a lateral position. Predictably controlled positive-pressure ventilation inproved arterial oxygenation and permitted maintenance of a normal PaCO2. Most horses, regardless of type of ventilation and operative body positioning, were hypoxemic in the immediate postanesthetic period.

Anesthesia, Inhalation↗