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Biomedical subjects

M R Davies

Publications and source records attributed to M R Davies.

At least 19 recordsLinked to original sources
PubMed2001

Pathophysiological mechanisms of vascular calcification in end-stage renal disease.

Vascular calcification has been clearly defined as a risk factor for cardiovascular mortality in the general population and is highly prevalent in end-stage renal disease (ESRD), where it is associated with a number of markers of increased mortality such as left ventricular hypertrophy. The pattern of calcification in ESRD is characterized by mineral deposition in the tunica media, in contrast to non-ESRD populations, where calcification of atheromatous plaque predominates. This difference may have important clinical implications. The pathophysiological mechanisms underlying both types of vascular calcification remain to be clarified; however, current evidence suggests that they are active processes rather than passive mineral precipitation, and the presence in the vasculature of cells expressing an osteoblastic phenotype may be of central importance. In ESRD, the presence of secondary and tertiary hyperparathyroidism, disordered calcium and phosphate homeostasis, and the use of vitamin D- and calcium-based treatments in its therapy may all contribute to vascular calcification. These issues and the impact on other current and future therapies have great importance for clinical nephrology, and a better understanding of vascular calcification through a focused research effort is essential.

Calcinosis↗
PubMed1999

In vitro agonist effects of nociceptin and [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) in the mouse and rat colon and the mouse vas deferens.

Nociceptin is an endogenous ligand of the opioid receptor-like (ORL1) receptor, a G-protein coupled receptor with sequence similarities to the opioid receptors. ORL1 receptors are present at both central and peripheral sites in several mammalian species but their functions are as yet poorly understood. The main aim of this investigation was to study the effects of nociceptin and the putative ORL1 receptor antagonist [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) in two peripheral tissues, the isolated proximal colon of the mouse and the distal colon of the rat. Nociceptin, [D-Ala(2), MePhe(4), Gly-ol(5)]enkephalin (DAMGO; mu-opioid receptor selective) and [D-Pen(2), D-Pen(5)]enkephalin (DPDPE; delta-opioid receptor selective) caused concentration-dependent contractions of mouse and rat isolated colon preparations (nociceptin EC(50)=1.20 and 0.28 nM in the mouse and rat, respectively). Des[Phe(1)]nociceptin (250 nM) had no contractile effect. Naloxone (300 nM) antagonised the effects of DAMGO and DPDPE but had no effect in either preparation on contractions seen in response to nociceptin. [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) also caused contractions in the colonic preparations (EC(50)=6.0 and 3.1 nM in the mouse and rat, respectively); there was no evidence of any antagonist activity. Tetrodotoxin (1 microM) abolished the contractile effects of nociceptin in the mouse colon but had no effect in the rat. In the vas deferens preparation isolated from DBA/2 mice, nociceptin caused concentration-dependent inhibitions of electrically-evoked contractions which were antagonised by [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) (apparent pK(B)=6. 31). However, [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) (0.3-10 microM) also possessed agonist activity in this preparation, as it inhibited the electrically-evoked contractions in a concentration-dependent manner. These observations do not support the proposal that [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) has agonist activity at central ORL1 receptors but is an antagonist in the periphery and that these differences in efficacy point to differences in the receptors. Rather, these data along with those of others suggest that [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin(1-13)NH(2) is a partial agonist and that differences in receptor reserve can account for the varied pharmacological actions of this pseudopeptide at central and peripheral sites.

Animals↗
PubMed1999

Antegrade continence enema and its application in Africa.

BACKGROUND: Antegrade continent enema (ACE) procedure has been accepted worldwide as the salvage procedure for intractable constipation and faecal incontinence after anorectal malformation surgery. Its application only has been reported from the developed countries. METHODS: The authors performed four such operations on incontinent children in a poor socioeconomic group in South Africa. RESULTS: Three patients had previous surgery for anorectal malformation, and one had intractable encopresis. The patients kept clean with water washouts only, starting 1 week after the operation. CONCLUSIONS: The ACE procedure can be used easily by patients in disadvantaged communities of Africa, and its use requires minimal but sympathetic supervision only. The authors recommend that all pediatric surgeons dealing with these unfortunate children should perform this procedure after a trial period of medical treatment. This is also the first report of the ACE procedure performed for an encopretic child.

Anal Canal↗
PubMed1997

Iatrogenic hepatic rupture in the newborn and its management by pack tamponade.

BACKGROUND/PURPOSE: This report compares the ultrastructure of the newborn and adult liver and emphasizes that the newborn liver is very prone to iatrogenic rupture resulting in a high morbidity and mortality. This study describes the methods used to treat this condition and suggests that pack tamponade may be the method of choice to control hemorrhage. METHODS: latrogenic liver rupture with blood loss greater than 35% estimated blood volume occurred in seven patients. Cause of rupture included perihepatic dissection (left lobe mobilization [n = 2], capsule breached surgically [n = 1]), and retraction (n = 3) or prosthetic silo manipulation (n = 1). RESULTS: Initial attempts to control the hemorrhage were unsuccessful in six of seven patients. The only secure method to obtain long-term control of the bleeding was perihepatic pack tamponade. Control was incomplete in one patient who had an associated coagulopathy. Transfusion-induced clotting defects were present in four cases. Pack removal at 24 to 96 hours was successful in five of six patients where the bleeding was stopped, the patient fully stabilized and coagulopathy was corrected. Pack removal caused renewed bleeding in one patient, and repacking was unsuccessful. Ultrastructural differences between newborn and adult livers were investigated. The newborn liver contains little fibrous stroma and has a very thin capsule. Suture hepatorraphy therefore is an inappropriate technique in most instances and contraindicated if a coagulopathy is present. Surface coagulation and pack tamponade may be the only options available. A single patient in this series survived this complication. CONCLUSIONS: This review documents the serious nature of iatrogenic liver injury. Blood loss must be strictly limited by obtaining immediate control of the hemorrhage. If surface control is unsuccessful, pack tamponade should be used. Suturing the newborn liver (especially premature) produces unpredictable results. These observations suggest that pack tamponade is an effective method of controlling bleeding from the liver surface.

Female↗
PubMed1997

Anatomy of the nerve supply of the rectum, bladder, and internal genitalia in anorectal dysgenesis in the male.

Using a posterior sagittal approach to expose retroperitoneal viscera and nerves, the anatomy of the pelvic autonomic nerve plexus was studied in normal and abnormal male cadaver specimens. This plexus is found on the anterolateral surface of the lower rectum surrounded by endopelvic fascia. The autonomic nerves that supply the plexus reach it from posterior, lateral to the midline by passing over the surface of the rectum. The nerves of this plexus are distributed with the terminal branches of the internal iliac arteries, mainly with the vessels of the inferior vesical plexus. The rectum receives its autonomic nerves with its arterial blood supply, the superior rectal artery. The nerves of the pelvic plexus supply the genitourinary viscera that lie anterior to the rectum and in front of the fascia of Denonvilliers. The named fascial layers of the pelvis play a major role in determining the anatomic plane of these structures. In anorectal agenesis the plexus becomes a more midline structure. Because the pelvic fascia is often deficient in these cases these nerves lie vulnerable to inappropriate midline dissection.

Anal Canal↗
PubMed1997

Thymectomy in black children with juvenile myasthenia gravis.

Fifteen black children with juvenile myasthenia gravis presented to our institution over a 10-year period at ages ranging from 18 months to 7 years, 4 males and 11 females. Twelve presented with progressive, generalised weakness and 3 had bulbar manifestations. Ocular signs were absent in 2 patients. All 15 patients were placed on pyridostigmine bromide (Mestinon) and 1 also required steroids and plasmapheresis. Medical therapy only was instituted in 5 patients, of whom 2 came to surgery, 2 died, and 1 was lost to follow-up. Thymectomy was performed in 12 children (including the 2 with failed medical therapy) via a median sternotomy with no mortality or morbidity related to the operation. The timing of surgery was less than 3 months in 75% of the children. Thymic hyperplasia was noted in 10 glands and 2 were reported as normal. Of the children in the operative group, 83% are on minimal medication or in total remission. Better results were noted in young patients with early thymectomy and diseased glands.

Black People↗
PubMed1996

Anatomy of the extrinsic motor nerve supply to mobilized segments of the oesophagus disrupted by dissection during repair of oesophageal atresia with distal fistula.

Atresia of the oesophagus occurs near to the site of convergence of the foregut with structures of branchial arch origin. This is a confluence of a striated muscle tube with a somatic nerve supply and a smooth muscle tube with an autonomic nerve supply. The implications, with regard to function, of denervating the oesophagus during operation are influenced by this anatomy. During dissection of a cadaver with oesophageal atresia and distal fistula, the sites of potential nerve injury were displayed. Damage to these nerves occurs during routine primary repair and may contribute to oesophageal motor dysfunction after successful surgery.

Cadaver↗
PubMed1993

Burns in Madras, India: an analysis of 1368 patients in 1 year.

Analyses were made of 1368 patients who attended Kilpauk Medical College Hospital, Madras with burns between 1 May 1987 and 30 April 1988. Nine hundred and sixty-five patients were admitted, of whom 505 died. The peak age incidence was in young adults (11-30 years; 58.9 per cent of all burns). Three quarters of the patients came from the low family income group, 39.5 per cent were illiterate and 86.2 per cent of burns occurred in the home. Of those admitted 81 per cent of the injuries were flame burns; in 31.3 per cent the burn affected more than half of the body surface. Of the 505 deaths 94.8 per cent were the result of flame burns (at least 323 being caused by kerosene), and 20.4 per cent were suicide. Most of the deaths (91 per cent) occurred in the first 5 days. The urgent need for burn prevention in the Madras area is discussed.

Adolescent↗
PubMed1993

Massive foetal pericardiomegaly causing pulmonary hypoplasia, associated with intra-pericardial herniation of the liver.

The clinical features, investigation, treatment and outcome of four newly born babies with the following recognisable triad of findings are presented: Bilateral pulmonary compression with or without hypoplasia. Massive pericardial effusion without cardiac compromise. An intrapericardial hernia containing part of the liver. The primary event in the causation of this triad is a congenital defect in the central tendon of the diaphragm. Compromised hepatic venous outflow involving the herniated part of the liver is the postulated origin of the fluid within the pericardium (Budd-Chiari-like effect). Although rare, this triad is clinically identifiable. Sonar imaging clinches the diagnosis. Surgical correction is simple but the prognosis depends on the presence of pulmonary hypoplasia which caused death in two cases and on other described lethal associated anomalies which were not encountered in the reported patients.

Diaphragm↗
PubMed1993

Paediatric surgery in the RSA--practice and training.

A survey of the current practice of general paediatric surgery in South Africa and Namibia was conducted by means of a postal questionnaire. One hundred and eighty-one replies were obtained (52%). Analysis showed that although surgeons are located predominantly in the major cities, 18% practised in the larger towns or rural areas. Although paediatric surgery represents a small volume of their work, most surgeons do attend to the surgical needs of children. The majority of surgeons have received some paediatric surgical training but this was considered inadequate by nearly half of all surgeons and by 60% of those who qualified in the last 10 years. Current postgraduate training at most of our universities involves a 3-6-month rotation, but from our survey this is considered insufficient in practice and there appears to have been some deterioration in paediatric surgical training in recent years. Steps needed to maintain paediatric surgical standards are discussed.

Child↗
PubMed1992

Facilitating the operative exposure of the portal plate in cases of biliary atresia by dislocating the whole liver onto the abdominal wall.

Obtaining adequate exposure of the portal plate in cases with biliary atresia can tax the ingenuity of the surgeon. The successful completion of a hepatic portoenterostomy depends on it. Mobilising the liver and dislocating it into an ex vivo-like position on the anterior abdominal wall simplifies this step of the operation. It achieves maximal visualisation and access to the anatomy of the liver port. When used correctly by the surgeon this technique is not complicated by hepatic or caval blood flow occlusion. Its use in over 40 clinical cases has not resulted in any major mishap.

Abdominal Muscles↗
PubMed1992

Life-threatening respiratory distress caused by a mediastinal teratoma in a newborn.

Mediastinal teratomas rarely cause symptoms in newborns. Case reports drawing attention to this presentation have appeared in the literature. A 2-day-old baby with respiratory distress treated by intubation and mechanical ventilation underwent an urgent thoracotomy to alleviate tracheal compression that was caused by a teratoma. The clinical, radiological, and surgical features related to this case are reported.

Humans↗
PubMed1990

The use of nasogastric intubation in the radiological diagnosis of oesophageal atresias.

Correctly performed oesophageal intubation determines the presence of atresia. The physical properties of the nasogastric tube used determines the place of radiology in this diagnosis. The appearance of a curled tube (hoop sign) in the proximal oesophagus in the newborn is diagnostic of atresia, as it clearly delineates the oesophageal pouch. The performance of a contrast study to establish this diagnosis is never indicated, since it is impossible to eliminate aspiration completely.

Esophageal Atresia↗
PubMed1988

Intestinal obstruction in the newborn with congenital syphilis.

Four newborn patients with congenital syphilis and intestinal obstruction are discussed in this report. In three cases, the obstruction was due to inspissated meconium, simulating the features of meconium ileus in one, meconium plug in the second, and associated with perforation of the terminal ileum in the third. An exocrine pancreatic insufficiency and a motility disturbance of the intestine due to syphilitic infection during fetal life could be the probable etiologic factor. The fourth patient had multiple ileal stenoses. Ischemia due to the prenatal syphilitic arteritis of the bowel wall can be responsible for this pathology. Attention is drawn to the association between congenital syphilis and neonatal intestinal obstruction.

Female↗