Search PubMed⌕ Search

Biomedical subjects

J M Jacobs

Publications and source records attributed to J M Jacobs.

138 records · Page 8Linked to original sources
PubMed1971

Characterization of the late steps of microbial heme synthesis: conversion of coproporphyrinogen to protoporphyrin.

Cell-free extracts of various cytochrome-containing, heterotrophic microorganisms were examined for ability to convert coproporphyrinogen to protoporphyrin. Extracts of Escherichia coli and Pseudomonas denitrificans readily accumulated large amounts of protoporphyrin when assayed under aerobic conditions. However, protoporphyrin did not accumulate under either aerobic or anaerobic conditions of assay or in the presence of various supplements in extracts of the aerobe Micrococcus lysodeikticus, the facultative anaerobe Staphylococcus aureus, or the anaerobe Vibrio succinogenes. Protoporphyrin also accumulated when extracts of E. coli and P. denitrificans were incubated aerobically with the early heme precursor, delta-amino levulinic acid (ALA). This protoporphyrin accumulation was markedly stimulated by the iron chelator, o-phenanthroline. Extracts of S. aureus and M. lysodeikticus accumulated coproporphyrin, but not protoporphyrin when incubated with ALA. The enzyme system in extracts of E. coli which converts coproporphyrinogen to protoporphyrin under aerobic conditions of assay was also partially characterized. This conversion was stimulated by the iron chelator, o-phenanthroline, the respiratory inhibitor, cyanide, and the reducing agent, thioglycolate. Dialysis of the extract did not diminish enzyme activity. Certain alternate electron acceptors and nitrite caused a marked inhibition of the conversion. These results indicate that this late step in heme synthesis, the conversion of coproporphyrinogen to protoporphyrin, can be readily demonstrated in extracts of some, but not all, cytochrome-containing bacteria and that the aerobic conversion in E. coli exhibits many characteristics similar to those demonstrated for the aerobic conversion previously studied in liver mitochondria.

Aerobiosis↗
PubMed1970

Formation of protoporphyrin from coproporphyrinogen in extracts of various bacteria.

The enzyme system capable of converting coproporphyrinogen to protoporphyrin was demonstrated in the soluble fraction of extracts of Pseudomonas fluorescens grown aerobically, of P. denitrificans grown anaerobically under denitrifying conditions, and of Escherichia coli grown both aerobically and anaerobically. Protoporphyrin accumulation by each of these extracts occurred only if the assay was conducted aerobically. Attempts to replace this oxygen requirement with several alternate electron acceptors were not successful. The conversion of coproporphyrinogen to protoporphyrin could not be demonstrated in extracts of the heme-containing organisms Staphylococcus epidermidis and Bacillus subtilis.

Bacillus subtilis↗
PubMed1969

Effect of oxygen on heme and porphyrin accumulation from delta-aminolevulinic acid by suspensions of anaerobically grown Staphylococcus epidermidis.

The effect of various conditions on the accumulation of porphyrins and heme by resting suspensions of anaerobically grown cells of Staphylococcus epidermidis was examined. Anaerobically grown cells contain 10 to 15% of the amount of protoheme found in cells grown aerobically. Resting suspensions of anaerobically grown cells, when incubated aerobically in buffer with delta-aminolevulinic acid and glucose for 60 min, exhibited a fourfold increase in protoheme content. At high levels of delta-aminolevulinic acid, there was also a significant accumulation of porphyrins with the solubility and chromatographic properties of coproporphyrin and uroporphyrin. Protoporphyrin was not accumulated. When oxygen was excluded from the incubation mixture, accumulation of protoheme was prevented, but accumulation of coproporphyrin and total porphyrin was enhanced. Nitrate served as an electon acceptor as indicated by its reduction to nitrite; however, nitrate did not substitute for oxygen in causing the accumulation of protoheme. These results suggested that oxygen is required for one of the late steps of heme synthesis in S. epidermidis, possibly for the conversion of coproporphyrinogen to protoporphyrin. The inability of nitrate to substitute for oxygen suggests a role for molecular oxygen as a substrate rather than as an electron acceptor for heme synthesis.

Chromatography, Thin Layer↗
PubMedDate not supplied

Occurrence, regulation, and significance of progesterone receptors in human meningioma.

The abundant expression of progesterone receptors (PR) in human meningiomas is well established. It is unknown, however, how PR expression is regulated, especially since estrogen receptors (ER) are virtually absent in these tumors. At the mRNA level, ER splice variants occur in meningioma but these appear not to be involved in the apparently autonomous PR expression. In an earlier study, because other ER-inducible proteins were either not expressed at all (pS2) or were expressed at a very low level compared to their expression in breast cancer (Cathepsin-D), the authors have postulated that the autonomous PR expression in meningioma is PR promoter-related rather than ER-related and have studied PR expression in cultured meningioma cells. PR levels appeared to decrease rapidly in vitro in monolayer as well as in three dimensional spheroid cultures. Culture conditions thus are not yet sufficient for the quantitative evaluation of PR expression. To evaluate whether PR deterioration is associated with cell turnover (meningiomas grow much faster in vitro than in vivo), the relationship between expression of the apoptotic proteins Bcl-2 and Bax and PR expression was investigated. Bcl-2 expression was found to be highest in meningioma with low PR levels, and in breast cancer tissue with high PR levels. Bax expression was not related to PR expression in any of the two tissues. Given the potential benefit of antiprogestin treatment and the occurrence in meningiomas of a protein capable of binding to the estrogen-responsive element, the expression of PR in meningioma remains a fascinating phenomenon which requires further investigation.

Female↗
PubMedDate not supplied

Management options for the child with spastic cerebral palsy.

Knowledge of spasticity management for the child with cerebral palsy begins with understanding how cerebral palsy and spasticity are defined and related. The next step is learning what the treatment options are and how they can impact the child. There are many strategies for managing spasticity. This article focuses on pharmacologic and surgical approaches. Pharmacologic is further subdivided into medications taken by mouth, given through an injection (Botox) or delivered by a pump (baclofen). Surgery includes neurosurgical and orthopaedic procedures. Each treatment is reviewed using rationale, patient selection, delivery methodology, and management technique citing the advantages and disadvantages of each modality.

Baclofen↗
PubMedDate not supplied

Deflation of detachable balloons in the cavernous sinus by percutaneous puncture.

The authors show that percutaneous puncture of balloons within the cavernous sinus is technically feasible and allows further access to the cavernous sinus after balloon detachment. Complete closure of a large carotid cavernous fistula was achieved in the 37-year-old trauma victim they treated using this technique.

Adult↗