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Biomedical subjects

P M Dunn

Publications and source records attributed to P M Dunn.

At least 19 recordsLinked to original sources
PubMed2003

Erich Bracht (1882-1969) of Berlin and his "breech" manoeuvre.

Erich Bracht, a German gynaecologist, described in 1935 the manoeuvre named after him for delivering the frank breech with minimal interference. In spite of the reported success of his method, it received little attention in the United Kingdom or North America.

Breech Presentation↗
PubMed2003

Andreas Vesalius (1514-1564), Padua, and the fetal "shunts".

Three remarkable medical anatomists working in Padua during the 16th century described the anatomy of the fetal cardiovascular system, thus laying the foundation for William Harvey's discovery and description of the fetal circulation in the following century.

Embryology↗
PubMed2003

Dr Erasmus Darwin (1731-1802) of Lichfield and placental respiration.

Erasmus Darwin was a great philosopher, scientist, inventor, poet, and physician. His creative intellect has been compared with that of Leonardo da Vinci. This brief article draws attention to two perinatal contributions made on placental respiration and management of the umbilical cord.

England↗
PubMed2003

Galen (AD 129-200) of Pergamun: anatomist and experimental physiologist.

Galen was a brilliant anatomist and pioneer of experimental physiology. His many important discoveries exerted a profound influence on medicine during the next 1400 years. However, his wish to solve all the problems of health and disease led him to speculate and draw mistaken conclusions which were widely believed until after the Renaissance.

Anatomy↗
PubMed2002

Sir Leonard Parsons of Birmingham (1879-1950) and antenatal paediatrics.

Born and educated in the Midlands, Sir Leonard Parsons made major contributions to the field of paediatrics in that area and played a leading role in the regional organisation of this specialty throughout the United Kingdom in the later years of his life. He was a founder member and later President of the British Paediatric Association, and later became Vice-President of the International Pediatric Congress and the President of the paediatric section of the Royal Society of Medicine.

England↗
PubMed2002

Sir James Young Simpson (1811-1870) and obstetric anaesthesia.

Sir James Young Simpson of Edinburgh became famous for his discovery of the anaesthetic qualities of chloroform and his championship of obstetric anaesthesia. However, as the outstanding British obstetrician between 1840 and 1870, he also pioneered many other advances in obstetrics.

Anesthesia, Obstetrical↗
PubMed2002

Dr William Farr of Shropshire (1807-1883): obstetric mortality and training.

William Farr, chief statistician to the General Register Office for more than 40 years, was the most significant medical epidemiologist and statistician of the Victorian era. Often working behind the scenes, he helped to bring about many advances in hygiene and public health as well as developing a modern approach to the classification of disease and the collection and analysis of medical information data.

England↗
PubMed2002

John Chassar Moir (1900-1977) and the discovery of ergometrine.

Chassar Moir led the research in the early 1930s that resulted in the discovery and identification of ergometrine, the active water soluble component of ergot of rye. Its use in preventing and controlling postpartum haemorrhage has saved countless lives in the years since. As professor of obstetrics and gynaecology in Oxford, he achieved distinction for his repair of vesicovaginal fistulae.

England↗
PubMed2002

George Armstrong MD (1719-1789) and his dispensary for the infant poor.

George Armstrong published one of the first textbooks on children's diseases in 1767 and two years later opened in London the first dispensary/hospital in the world for sick children. He introduced clinical teaching and may be regarded as the founder of paediatrics and child health in Great Britain.

Child Health Services↗
PubMed2001

SK3 is an important component of K(+) channels mediating the afterhyperpolarization in cultured rat SCG neurones.

1. Our aim was to identify the small-conductance Ca(2+)-activated K(+) channel(s) (SK) underlying the apamin-sensitive afterhyperpolarization (AHP) in rat superior cervical ganglion (SCG) neurones. 2. Degenerate oligonucleotide primers designed to the putative calmodulin-binding domain conserved in all mammalian SK channel sequences were employed to detect SK DNA in a cDNA library from rat SCG. Only a single band, corresponding to a fragment of the rSK3 gene, was amplified. 3. Northern blot analysis employing a PCR-generated rSK3 fragment showed the presence of mRNA coding for SK3 in SCG as well in other rat peripheral tissues including adrenal gland and liver. 4. The same rSK3 fragment enabled the isolation of a full-length rSK3 cDNA from the library. Its sequence was closely similar to, but not identical with, that of the previously reported rSK3 gene. 5. Expression of the rSK3 gene in mammalian cell lines (CHO, HEK cells) caused the appearance of a K(+) conductance with SK channel properties. 6. The application of selective SK blocking agents (including apamin, scyllatoxin and newer non-peptidic compounds) showed these homomeric SK3 channels to have essentially the same pharmacological characteristics as the SCG afterhyperpolarization, but to differ from those of homomeric SK1 and SK2 channels. 7. Immunohistochemistry using a rSK3 antipeptide antibody revealed the presence of SK3 protein in the cell bodies and processes of cultured SCG neurones. 8. Taken together, these results identify SK3 as a major component of the SK channels responsible for the afterhyperpolarization of cultured rat SCG neurones.

Alkanes↗
PubMed2001

P2X receptors in peripheral neurons.

P2X receptors are a family of ligand-gated ion channels, activated by extracellular ATP. The seven subunits cloned (P2X1-7) can assemble to form homomeric and heteromeric receptors. Peripheral neurons of neural crest origin (e.g. those in dorsal root, trigeminal, sympathetic and enteric ganglia) and placodal origin (e.g. those in nodose and petrosal ganglia) express mRNAs for multiple P2X subunits. In this review, we summarize the molecular biological, electrophysiological and immunohistochemical evidence for P2X receptor subunits in sensory, sympathetic, parasympathetic, pelvic and myenteric neurons and adrenomedullary chromaffin cells. We consider the pharmacological properties of these native P2X receptors and their physiological roles. The responses of peripheral neurons to ATP show considerable heterogeneity between cells in the same ganglia, between ganglia and between species. Nevertheless, these responses can all be accounted for by the presence of P2X2 and P2X3 subunits, giving rise to varying proportions of homomeric and heteromeric receptors. While dorsal root ganglion neurons express predominantly P2X3 and rat sympathetic neurons express mainly P2X2 receptors, nodose and guinea-pig sympathetic neurons express mixed populations of P2X2 and heteromeric P2X2/3 receptors. P2X receptors are important for synaptic transmission in enteric ganglia, although their roles in sympathetic and parasympathetic ganglia are less clear. Their presence on sensory neurons is essential for some processes including detection of filling of the urinary bladder. The regulation of P2X receptor expression in development and in pathological conditions, along with the interactions between purinergic and other signalling systems, may reveal further physiological roles for P2X receptors in autonomic and sensory ganglia.

Animals↗
PubMed2001

Multiple P2X receptors on guinea-pig pelvic ganglion neurons exhibit novel pharmacological properties.

1. Application of ATP and alpha,beta-methylene ATP (alpha beta meATP) to voltage-clamped guinea-pig pelvic neurons produced three types of inward currents. A fast-desensitizing response was present in 5% (25/660) of neurons, 70% gave slowly-desensitizing currents, and the remainder had biphasic responses. 2. Slowly-desensitizing responses were characterized pharmacologically. The response to alpha beta meATP 100 microM was 46+/-27% (range 0--100%) of that evoked by ATP 100 microM in the same cell. Cross-desensitization indicated the presence of alpha beta meATP-sensitive and -insensitive receptors. 3. The concentration-response curve for alpha beta meATP had an EC(50) of 55 microM, and a Hill coefficient of 0.99, while at the alpha beta meATP-insensitive receptor, ATP had an EC(50) of 73 microM, with a Hill coefficient of 1.78. 4. The response to alpha beta meATP was blocked by pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), suramin and Cibacron blue. However, the alpha beta meATP-insensitive receptor was inhibited by PPADS, but not by the other two antagonists. 5. 2'- (or 3'-) O-trinitrophenyl-ATP was 10 times more potent in inhibiting responses to alpha beta meATP than to ATP (at the alpha beta meATP-insensitive receptor). 6. Lowering extracellular pH potentiated responses to alpha beta meATP and ATP, while raising pH attenuated them. 7. Co-application of Zn(2+) (3--300 microM) inhibited the responses to alpha beta meATP and ATP, with IC(50) values of 286 and 60 microM, respectively. 8. In conclusion, unlike rat and mouse pelvic ganglion neurons, which only express P2X(2) homomers, at least three distinct P2X receptors are present in guinea-pig pelvic neurons, probably homomeric P2X(2), P2X(3) and heteromeric P2X(2/3) receptors. However, some of the novel pharmacological properties observed suggest that the guinea-pig P2X receptor subtypes may differ from their rat orthologues.

Adenosine Triphosphate↗
PubMed2001

Changes in P2X receptor responses of sensory neurons from P2X3-deficient mice.

Dorsal root ganglion (DRG) neurons respond to ATP with transient, persistent or biphasic inward currents. In contrast, the ATP responses in nodose neurons are persistent. These sustained currents are also heterogeneous, with one component being accounted for by P2X2/3 receptors, and the residual response probably mediated by P2X2 receptors, although the direct evidence for this has been lacking. In the present study, we examined the P2X receptors on DRG and nodose neurons from P2X3-deficient (P2X3-/-) mice, using whole cell voltage-clamp recording and immunohistochemistry. We found that all P2X3-/- DRG neurons lacked rapidly desensitizing response to ATP, and both DRG and nodose neurons from P2X3-null mutant mice no longer responded to alpha,beta-methylene ATP (alphabetameATP). In contrast, ATP evoked persistent inward current in 12% of DRG neurons and 84% of nodose neurons from P2X3-/- mice. This retained persistent response to ATP on nodose neurons had an EC50 for ATP of 77 microm, was antagonized by Cibacron blue and pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid, potentiated by Zn2+ and acidification, but not enhanced by ivermectin or diinosine pentaphosphate. 2',3'-O-Trinitrophenyl-ATP antagonized this response with an IC50 of 8 microm. All these properties are consistent with those of recombinant P2X2 homomeric receptors. Furthermore, specific P2X2 receptor immunoreactivity detected in wild-type sensory neurons was unaltered in null mutant mice. Therefore, the alphabetameATP-insensitive persistent responses on nodose neurons are likely to be mediated by P2X2 homomers, which contribute to 60% of currents evoked by 100 microm ATP in the wild type.

Adenosine Triphosphate↗