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Biomedical subjects

M McCaffrey

Publications and source records attributed to M McCaffrey.

At least 19 recordsLinked to original sources
PubMed1999

Bacterial vaginosis in lesbians: evidence for lack of sexual transmission.

The effect of non-heterosexual factors on the vaginal flora has been studied. Ninety-one lesbians attending a specialist genitourinary medicine service for lesbians were studied. Bacterial vaginosis (BV) was diagnosed in 51.6% of them. While most of the women had previously had a male sexual partner, the presence of BV was not associated with a male sexual partner in the previous 12 months. A detailed analysis of lesbian sexual practices in the group did not relate BV to any sexual practice which would have the propensity to pass vaginal secretions from one to the other.

Female↗
PubMed1998

Distinct Rab-binding domains mediate the interaction of Rabaptin-5 with GTP-bound Rab4 and Rab5.

Rabaptin-5 functions as an effector for the small GTPase Rab5, a regulator of endocytosis and early endosome fusion. We have searched for structural determinants that confer functional specificity on Rabaptin-5. Here we report that native cytosolic Rabaptin-5 is present in a homodimeric state and dimerization depends upon the presence of its coiled-coil predicted sequences. A 73 residue C-terminal region of Rabaptin-5 is necessary and sufficient both for the interaction with Rab5 and for Rab5-dependent recruitment of the protein on early endosomes. Surprisingly, we uncovered the presence of an additional Rab-binding domain at the N-terminus of Rabaptin-5. This domain mediates the direct interaction with the GTP-bound form of Rab4, a small GTPase that has been implicated in recycling from early endosomes to the cell surface. Based on these results, we propose that Rabaptin-5 functions as a molecular linker between two sequentially acting GTPases to coordinate endocytic and recycling traffic.

Amino Acid Sequence↗
PubMed1997

Targeting determinants and proposed evolutionary basis for the Sec and the Delta pH protein transport systems in chloroplast thylakoid membranes.

Transport of proteins to the thylakoid lumen is accomplished by two precursor-specific pathways, the Sec and the unique Delta pH transport systems. Pathway selection is specified by transient lumen-targeting domains (LTDs) on precursor proteins. Here, chimeric and mutant LTDs were used to identify elements responsible for targeting specificity. The results showed that: (a) minimal signal peptide motifs consisting of charged N, hydrophobic H, and cleavage C domains were both necessary and sufficient for pathway-specific targeting; (b) exclusive targeting to the Delta pH pathway requires a twin arginine in the N domain and an H domain that is incompatible with the Sec pathway; (c) exclusive targeting to the Sec pathway is achieved by an N domain that lacks the twin arginine, although the twin arginine was completely compatible with the Sec system. A dual-targeting signal peptide, constructed by combining Delta pH and Sec domains, was used to simultaneously compare the transport capability of both pathways when confronted with different passenger proteins. Whereas Sec passengers were efficiently transported by both pathways, Delta pH passengers were arrested in translocation on the Sec pathway. This finding suggests that the Delta pH mechanism evolved to accommodate transport of proteins incompatible with the thylakoid Sec machinery.

Amino Acid Sequence↗
PubMed1995

Management of female genital mutilation: the Northwick Park Hospital experience.

OBJECTIVE: To outline the problems associated with female genital mutilation and to highlight the need for deinfibulation before delivery. DESIGN: A review of women attending a newly established African Well Woman Clinic. Age at infibulation, gravidity of clinic attenders and adequacy of introitus for management of labour were assessed. SETTING: Northwick Park Hospital, Harrow, Middlesex. SUBJECTS: Fifty women attending a newly established African Well Woman Clinic, of whom 13 were nulliparous, 14 were primigravid and 23 were multigravid. RESULTS: The average age at which infibulation had occurred was 6.7 years. At the time of clinic attendance the mean age of pregnant and nonpregnant patients was 26 and 23.3 years, respectively. Of the 14 primigravid patients, only 50% had an adequate introitus to allow management of the first and second stages of labour. Five had deinfibulation performed antenatally or at delivery. Ninety-three percent of the primigravid patients and 74% of the multigravid patients had a vaginal delivery. CONCLUSIONS: We believe that the Northwick Park Hospital management policy for infibulated women closely mirrors the cultural practices in Somalia. The policy also improves obstetric management of infibulated patients. Twenty-six percent of referrals were of nonpregnant women, and this practice is to be encouraged.

Adolescent↗
PubMed1993

Comparison of the biochemical properties of unprocessed and processed forms of the small GTP-binding protein, rab6p.

The rab6 protein (rab6p) belongs to a large family of ras-like low-molecular-mass GTP-binding proteins thought to be involved in the regulation of intracellular transport in mammalian cells. When expressed in the baculovirus/insect cell system, two major forms of rab6p are obtained; a 24-kDa cytosolic unprocessed form and a 23-kDa membrane-bound form which represents the processed lipid-modified protein. Here, we have purified both forms to homogeneity and we have studied and compared their biochemical properties. Unprocessed and processed rab6p display similar binding-rate constants (kon) for GDP and GTP (1-1.9 microM-1 min-1). However, significant differences exist in the dissociation constants of bound guanine nucleotides. Processed rab6p in low and high magnesium solutions displays similar koff values for GTP and GDP. However, unprocessed rab6p has a koff value higher for GDP than for GTP in both low and high magnesium solutions. Their intrinsic GTPase activities also differ; unprocessed rab6p has an almost undetectable GTPase activity, whereas that of processed rab6p is in the same range as that reported for other ras and ras-like GTP-binding proteins (0.012 +/- 0.002 min-1). These results suggest that post-translational modifications of rab6p might induce subtle changes in the three-dimensional structure of the protein which affect the guanine-nucleotide-binding/hydrolysis activity.

Animals↗
PubMed1992

Biochemical and morphological differentiation of the human colonic epithelial cell line SW620 in the presence of dimethylsulfoxide.

In vitro models of intestinal cell differentiation provide an important adjunct for studying normal and abnormal intestinal epithelial cell differentiation. The studies reported herein describe morphologic and biochemical changes in the colonic epithelial cell line SW620 following dimethylsulfoxide (DMSO) incubation. Cells cultured in the presence of DMSO showed striking changes in morphology characterized by enlargement, elongation, and formation of process-like structures by light microscopy and a propensity to form microvillus-like structures by electron microscopy. These changes were accompanied by significant differences in the expression of the cell surface markers CD4 (HIV gp120 receptor), CD44 (hyaluronate receptor), and KS1 (adenocarcinoma/epithelial specific antigen). There was a marked decrease in CD4 expression (38% to 2%), an increase in CD44 expression (4% to 50%) and a decrease in KS1 expression (98% to 66%) as detected by flow cytometry following incubation of SW620 cells in DMSO. Parallel changes in the expression of these markers were seen by metabolic and surface labeling studies. Although SW620 cells were infected by HIV-1, DMSO-treated SW620 cells could not be infected. DMSO-induced changes in surface expression of CD4, CD44, and KS-1 were reversible over time upon removal of DMSO from the culture medium. Secretory component, sucrase, neuron-specific enolase, chromogranin-A, and mucin were not detectable in SW620 cells with or without DMSO treatment. SW620 cells provide a useful model for studying specific biochemical and molecular events involved in intestinal epithelial cell differentiation and function.

Antigens, Neoplasm↗
PubMed1991

Phosphorylation of two small GTP-binding proteins of the Rab family by p34cdc2.

Entry of a cell into mitosis induces a series of structural and functional changes including arrest of intracellular transport. Knowledge of how the mitotic cycle is driven progressed substantially with the identification of the p34cdc2 protein kinase as a subunit of maturation-promoting factor, the universal regulating component of the mitotic cycle. Activation of the kinase at the onset of mitosis is thought to trigger the important mitotic events by phosphorylating key proteins. Small guanine nucleotide-binding proteins have been implicated in regulating transport pathways. For instance, two small Ras-related GTP-binding proteins, Sec4p and Ypt1p, control distinct stages of the secretory pathway in budding yeast. The GTP-binding proteins of the Rab family in rats and humans display strong homologies with Sec4p and Ypt1p, and might therefore also be involved in regulating intracellular transport. Indeed, distinct Rab proteins are located in the exocytotic and endocytotic compartments. Interruption of vesicular transport during mitosis might involve modification of these proteins. We now present biochemical evidence for a mitosis-specific p34cdc2 phosphorylation of Rab1Ap and Rab4p. By contrast, Rab2p and Rab6p are not phosphorylated. We also show that the distribution of Rab1Ap and Rab4p between cytosolic and membrane-bound forms is different in interphase and mitotic cells. This may provide a clue to the mechanism by which phosphorylation could affect membrane traffic during mitosis.

Amino Acid Sequence↗
PubMed1991

The small GTP-binding protein Rho1p is localized on the Golgi apparatus and post-Golgi vesicles in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae the ras-related protein Rho1p is essentially the only target for ADP-ribosylation by exoenzyme C3 of Clostridium botulinum. Using C3 to detect Rho1p in subcellular fractions, Rho1p was found primarily in the 10,000 g pellet (P2) containing large organelles; small amounts also were detected in the 100,000 g pellet (P3), and cytosol. When P2 organelles were separated in sucrose density gradients Rho1p comigrated with the Kex-2 activity, a late Golgi marker. Rho1p distribution was shifted from P2 to P3 in several mutants that accumulate post-Golgi vesicles. Rho1p comigrated with post-Golgi transport vesicles during fractionation of P3 organelles from wild-type or sec6 cells. Vesicles containing Rho1p were of the same size but different density than those bearing Sec4p, a ras-related protein located both on post-Golgi vesicles and the plasma membrane. Immunofluorescence microscopy detected Rho1p as a punctate pattern, with signal concentrated towards the cell periphery and in the bud. Thus, in S. cerevisiae Rho1p resides primarily in the Golgi apparatus, and also in vesicles that are likely to be early post-Golgi vesicles.

Blotting, Western↗
PubMed1987

Motor evoked potential as a predictor of recovery in chronic spinal cord injury.

In injury to the spinal cord, motor function is the most critical system affected. The introduction of motor evoked potential (MEP) monitoring techniques over the past 5 years has opened new possibilities for the assessment of motor function. We examined the MEP change in 30 cats that received weight drop injuries to the thoracic spinal cord and correlated it with function. The MEPs were recorded above and below the injury and in the sciatic nerves. In these animals, we found that the peripheral nerve response to the MEP was the most sensitive to injury, disappearing immediately upon weight drop. The MEP at the spinal cord level was somewhat more sensitive to injury than the SSEP at the cord level, and the SSEP at the cortex was the least sensitive to injury. The MEP spinal cord signal below the lesion showed both a latency increase and a substantial amplitude decrease after impact. The latency increase, however, was of relatively small absolute magnitude making the amplitude change easier to monitor. The animals were followed chronically, and 17 of the 30 regained ambulation. In all animals (followed up to 2 months), the peripheral nerve signals returned at or immediately before the time of ambulation. In none of the animals who failed to regain a peripheral nerve response was ambulation attained. This supports a strong correlation of the peripheral nerve response with walking. However, the peripheral nerve response was only a short term predictor. Examination of the spinal cord signal showed that the MEP spinal cord signal below the lesion as a percentage above the lesion was a significant correlate of current ambulation recovery, with a correlation coefficient of 0.55. This suggests that evaluation of the SSEP and MEP spinal cord signals may be able to predict longer term recovery in animals and perhaps humans.

Animals↗
PubMed1986

Motor evoked potential in cats with acute spinal cord injury.

We have previously reported that a motor evoked potential (MEP) can be produced by transcranial stimulation of the motor cortex in cats and humans. This signal travels in both dorsolateral and ventral spinal cord. We report here the evaluation of this evoked potential in comparison to the somatosensory evoked potential (SEP) in an acute spinal cord weight drop model. In all animals, the peripheral nerve signal was the component of the MEP most sensitive to injury. Often, it was significantly reduced in amplitude by incidental manipulation of the spinal cord during a careful laminectomy and then returned. It was lost first in animals with weight drop spinal cord injury and was abolished with as little as 50 to 75 g/cm of force. The spinal cord signal of the MEP was consistently more sensitive to injury than the SEP and was abolished at about 100 to 150 g/cm of impact. The cortical SEP was abolished at about 200 to 250 g/cm, and the spinal cord SEP was abolished at similar levels. The SEP returned earlier after injury than the MEP. Anesthetic agents had an effect on the MEP in the spinal cord and substantially changed the peripheral nerve signal, in both wave form shape and optimal stimulation frequency. Marginal cord injury and abnormal metabolic conditions caused the peripheral nerve signal to decrement in amplitude with increasing trial numbers during a run and become unstable. These latter effects need further characterization and are critical guides to investigative and clinical use of this test. This study indicates that the MEP is more sensitive than the SEP in detecting spinal cord injury.

Animals↗