Biomedical subjects
Publications and source records attributed to C Gray.
In March Charlotte Gray attended a luncheon on Parliament Hill where a message on prostate cancer was served along with the meatballs. Thirty MPs attended the event, and organizer Ted White hopes the prevention message delivered by Dr. Martin Gleave will eventually trickle down to politicians in other levels of government.
Haemophilus influenzae is a bacterium of pharmaceutical interest of which the entire genome has been sequenced. Identification of low-abundance proteins in a two-dimensional map is important for the detection of new drug targets. We applied chromatography on Polybuffer Exchanger (chromatofocusing) in order to fractionate and enrich H. influenzae proteins, possibly low-copy-number gene products, from larger volumes. Two proteins, major ferric iron-binding protein (HI0097) and 5'-nucleotidase (HI0206) were obtained in pure form and hypothetical protein HI0052 was purified to near homogeneity by this single purification step. Four other proteins, aspartate ammonia lyase (HI0534), peptidase D (HI0675), elongation factor Ts (HI0914) and 5-methyltetrahydropteroyltriglutamate methyltransferase (HI1702), were strongly enriched so that chromatography on Polybuffer Exchanger can be used as an initial step for their isolation. Approximately 125 proteins were identified in the fractions collected from the column. Seventy of these were for the first time identified after chromatography on Polybuffer Exchanger. The proteins enriched by the chromatofocusing step include both low-abundance as well as high-copy-number gene products. They do not belong to a single protein class and the majority of them are enzymes with various functions. The results include a list and a two-dimensional map of the proteins enriched by chromatofocusing. They may be useful in the search of drug targets and in the design of purification protocols for the isolation of homologous proteins from related microorganisms.
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While researching her best-selling biography, Mrs. King: The Life and Times of Isabel Mackenzie King, CMAJ contributing editor Charlotte Gray discovered a wealth of information about Dr. Dougal Macdougall (Max) King. Although he never became as famous as his older brother Mackenzie, Gray presents a convincing argument that Dr. Max King's life and early death speak volumes about medicine and the medical profession at the turn of the century. She also argues that Mackenzie King's own life would have been much different had his brother not died at the too young age of 42. Gray's book was nominated for the Viacom Award, which honours the best nonfiction book published annually in Canada.
The 1998 federal budget received less than glowing reviews for its provisions regarding health care, but Charlotte Gray says this lack of health care initiatives should surprise no one. After all, there won't be a federal election for another 3 years.
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As debate about the legalization of marijuana continues in Canada, physicians are joining the fray. Ottawa family physician Don Kilby is working hard to make it easier for ill patients to use the marijuana that alleviates their symptoms. A recent case in Toronto indicates that the courts are starting to share these views.
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The disaster involving blood-borne pathogens and Canada's blood system was in the spotlight in November with the release of the Krever inquiry report. Many physicians consider the report anticlimactic because action has already been taken on several fronts and the use of donated bloods has declined, but it will still have a far-reaching impact.
Influenza virus hemagglutinin (HA) has served as a paradigm for both pH-dependent and -independent viral membrane fusion. Although large conformational changes were observed by X-ray crystallography when soluble fragments of HA were subjected to fusion-pH conditions, it is not clear whether the same changes occur in membrane-bound HA, what the spatial relationship is between the conformationally changed HA and the target and viral membranes, and in what way HA perturbs the target membrane at low pH. We have taken a spectroscopic approach using an array of recently developed FTIR techniques to address these questions. Difference attenuated total reflection FTIR spectroscopy was employed to reveal reversible and irreversible components of the pH-induced conformational change of the membrane-bound bromelain fragment of HA, BHA. Additional proteolytic fragments of BHA were produced which permitted a tentative assignment of the observed changes to the HA1 and HA2 subunits, respectively. The membrane-bound HA1 subunit undergoes a reversible conformational change, which most likely involves the loss of a small proportion of beta-sheet at low pH. BHA was found to undergo a partially reversible tilting motion relative to the target membrane upon exposure to pH 5, indicating a previously undescribed hinge near the anchoring point to the target membrane. Time-resolved amide H/D exchange experiments revealed a more dynamic (tertiary) structure of membrane-bound BHA and its HA2, but not its HA1, subunit. Finally BHA and, to a lesser degree, HA1 perturbed the lipid bilayer of the target membrane at the interface, as assessed by spectral changes of the lipid ester carbonyl groups. These results are discussed in the context of a complementary study of HA that was bound to viral membranes through its transmembrane peptide (Gray C, Tamm LK, 1997, Protein Sci 6:1993-2006). A distinctive role for the HA1 subunit in the conformational change of HA becomes apparent from these combined studies.
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Immunoreactive relaxin activity and progesterone concentrations in weekly plasma samples were measured throughout six pregnancies in five Asian elephants (Elephas maximus). One animal aborted, one delivered a stillborn calf at term and the remaining pregnancies concluded normally with living young. Immunoreactive relaxin activity increased by week 20 of pregnancy to reach a mean peak concentrations of > 6 ng/ml in the second trimester. This was followed by a slow decline beginning approximately at 30 weeks before term. A smaller, secondary relaxin rise was observed during the final eight weeks preceding parturition and circulating concentrations remained above pre-pregnancy baseline values for 72 h after birth. In contrast, progesterone concentrations increased immediately after mating and rose to a maximum of > 2 ng/ml by mid-gestation. As with relaxin, progesterone concentrations began to decline gradually approximately 30 weeks before birth. More frequently collected samples before, during and after parturition revealed a decline to pre-pregnancy levels between 2-5 days before parturition, in contrast to elevated relaxin levels (1 ng/ml) during this time. The aborted pregnancy at week 35 was accompanied by a precipitous decline in both immunoreactive relaxin and progesterone concentrations one week before the visible termination of the pregnancy. The delivery of the term stillborn calf occurred five weeks after both immunoreactive relaxin and progesterone concentrations had declined to pre-pregnancy values. Results suggest that immunoreactive relaxin may be important, along with progesterone, in the maintenance of pregnancy in the Asian elephant as well as playing a role in preparation for birth and possibly to indicate foetal well-being.
A novel neurotrophic factor named Persephin that is approximately 40% identical to glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) has been identified using degenerate PCR. Persephin, like GDNF and NTN, promotes the survival of ventral midbrain dopaminergic neurons in culture and prevents their degeneration after 6-hydroxydopamine treatment in vivo. Persephin also supports the survival of motor neurons in culture and in vivo after sciatic nerve axotomy and, like GDNF, promotes ureteric bud branching. However, in contrast to GDNF and NTN, persephin does not support any of the peripheral neurons that were examined. Fibroblasts transfected with Ret and one of the coreceptors GFRalpha-1 or GFRalpha-2 do not respond to persephin, suggesting that persephin utilizes additional, or different, receptor components than GDNF and NTN.
Parathyroid hormone (PTH) provokes cell division of osteoblasts in vitro and is anabolic in vivo when administered intermittently. We studied the effect on bone formation in vitro by rat primary calvarial osteoblasts of the short-term addition of rat PTH(1-34) (10(-12), 10(-9), and 10(-7) mol/L) to the medium. Our aim was to determine whether intermittent PTH(1-34) would promote osteogenesis in an experimental system designed to promote appositional bone formation. Unexpectedly, whether the exposure to PTH(1-34) was for 24 h only on days 3 or 12, or 24 h on both days 3 and 12, or a pulse for 6 h every 48 h, we observed suppression of bone formation even at the lowest concentration of added PTH(1-34). Our finding that cells which are of the osteoblastic phenotype can be entirely prevented from making appositional bone by high concentrations of PTH(1-34) for 1 day in a week, and have their osteogenic capacity suppressed by lower concentrations even when the PTH(1-34) is administered in brief pulses every other day, suggests that pulses of PTH administered in vivo may not increase bone formation by already differentiated osteoblasts.
We have used high-density oligonucleotide probe arrays (chips) for bacterial transcript imaging. We designed a chip containing probes representing 106 Hemophilus influenzae genes and 100 Streptococcus pneumoniae genes. The apparent lack of polyadenylated transcripts excludes enrichment of mRNA by affinity purification and we thus used total, chemically biotinylated RNA as hybridization probe. We show that hybridization of Streptococcus RNA to a chip allows simultaneous quantification of the transcript levels. The sensitivity was found to be in the range of one to five transcripts per cell. The quantitative chip results were in good agreement with conventional Northern blot analysis of selected genes. This technology allows simultaneous and quantitative measurement of the transcriptional activity of entire bacterial genomes on a single oligonucleotide probe array.
The discovery of the PS proteins, the complexities of their biochemistry and their potential involvement in signalling pathways and in apoptosis have galvanized research into AD. To date, the aspect of the functionality of the PSs most relevant to the pathology of AD is the effect of PS FAD mutants to increase the proportion of A beta 42 produced from cells. This, coupled to the observation that gamma-secretase cleavage is considerably reduced in neurons derived from PS-1 knockout mice, argues strongly that PS plays a very direct role in the proteolytic processing of APP.
Twenty-four patients, showing a good clinical recovery from coma-inducing injury and coping well with the activities of everyday living, were tested, at least 1 year after trauma, on motor speed and reaction time, and given a neuropsychological examination. While the patients generally performed within the normal range on the neuropsychological tests, their motor speeds and reaction times--both simple (SRT) and complex (CRT)--were significantly slower than those of matched controls. This points to a subclinical bradykinesia. The patients' motor speed scores did not correlate significantly with any of the neuropsychological tests; nor did SRT or CRT. While the difference between simple and complex reaction time was significantly greater in the patient group, the percentage difference was not significantly different between the two groups. Collectively, these results suggest that bradykinesia and bradyphrenia do not necessarily overlap. Finally, there was no significant correlation between motor performance and severity of original injury, whether the latter was measured by number and size of lesions or by duration of post-traumatic amnesia.