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Biomedical subjects

R W Parks

Publications and source records attributed to R W Parks.

At least 55 records · Page 3Linked to original sources
PubMed1997

Parallel distributed processing and executive functioning: Tower of Hanoi neural networkmodel in healthy controls and left frontal lobe patients.

Previous clinical studies have demonstrated that executive functioning has a significant association with the frontal lobes. In this study we examined executive functioning with parallel distributed processing (PDP) methodology by attempting to replicate Tower of Hanoi (TOH) neuropsychological test performance differences in normal healthy controls vs. left frontal lobe patients. Initial theoretical experiments were carried out to solve computer subprocessing constraints of the TOH partially by determining the programming prerequisites for a specific number of rings, efficient sequencing, and a general learning rule. These preliminary studies were then modified using a back-propagation neurocomputational approach. Computer program output showed a resemblance to normal controls' TOH moves. Degrading of the left frontal lobe patients' network resulted in characteristic impairments of executive functioning, i.e., perseveration and rule-braking.

Algorithms↗
PubMed1997

Surgical biliary bypass for benign and malignant extrahepatic biliary tract disease.

BACKGROUND: The optimal management of patients with benign and malignant disease affecting the extrahepatic biliary tract remains unresolved. A retrospective study was undertaken of all surgical biliary bypass procedures performed in one hepatobiliary unit. METHODS: A total of 121 patients treated in a 9-year period and comprising 60 patients with benign disease and 61 with malignant disease were reviewed. RESULTS: There was no significant difference in 30-day mortality rate between patients with benign and malignant disease (2 versus 8 per cent respectively, P = 0.22). There was no significant difference between surgery for benign and malignant disease in early morbidity rate (13 versus 21 per cent respectively, P = 0.36) or late morbidity rate (20 versus 25 per cent, P = 0.70). The median postoperative stay in both groups of patients was 10 days. The median survival of all patients with malignant disease was 7 months, being significantly more favourable for those with cholangio-carcinoma (18 months) than for those with pancreatic carcinoma (6.5 months) (P < 0.01). CONCLUSION: Biliary bypass procedures can be undertaken with acceptable rates of morbidity and mortality, and therefore should be considered in all patients with malignant disease of the extrahepatic biliary tract. If there is evidence of advanced malignancy, or if the patient is unfit for surgical intervention, non-operative procedures are a suitable alternative.

Adolescent↗
PubMed1997

Pathogenesis, clinical features and management of hidradenitis suppurativa.

Hidradenitis suppurativa is a chronic skin condition involving the apocrine glandular zones. Affected patients may present with acute abscesses, but the condition often progresses to a chronic state with persistent pain, sepsis, sinus tract and fistula formation, purulent discharge and dermal scarring. Treatment of patients with severe disease can be difficult and may require complex surgical intervention. This review encompasses the pathogenesis, clinical manifestations and management options for patients with hidradenitis suppurativa.

Axilla↗
PubMed1997

Adenomyoepithelioma of the breast.

Adenomyoepithelioma is a rare disorder characterised by simultaneous proliferation of ductal epithelium and myoepithelial cells. It is more common in salivary glands or skin, and only rarely found in breast tissue. Adenomyoepithelioma of the breast was first described in 1970 by Hamperl. Since then, approximately 55 cases have been described in the literature; the largest review, by Tavassoli in 1991, reported 27 of these cases. Because of the small number of cases reported, the natural history of adenomyoepithelioma of the breast remains uncertain. We report a further case which was treated by local excision, and follow-up for two years has revealed no evidence of local recurrence or metastatic spread.

Adult↗
PubMed1996

Intestinal barrier dysfunction in clinical and experimental obstructive jaundice and its reversal by internal biliary drainage.

Intestinal mucosal barrier function in obstructive jaundice was assessed in an animal model and in patients. The effect of internal biliary drainage in patients was also examined. Bile duct ligation for 1 week in the rat resulted in significant bacterial translocation (in seven of 12 animals following ligation versus none of the shamoperated controls, P < 0.01). Intestinal permeability, measured by the urinary recovery of orally administered polyethylene glycol, was also significantly increased (+66.2 per cent for ligation versus -11.6 per cent for sham, P < 0.01). A prospective study was performed on 33 patients with obstructive jaundice undergoing internal biliary drainage, and results were compared with those in six non-jaundiced patients undergoing laparotomy or endoscopic retrograde cholangiopancreatography and in 11 health volunteers. The lactulose: mannitol ratio was used as an intestinal permeability index. Mean(s.e.m.) intestinal permeability assessed before operation was significantly increased in jaundiced patients compared with control patients (0.050(0.010) versus 0.016(0.003), P < 0.005). The mean(s.e.m.) lactulose: mannitol ratio in the healthy volunteers was 0.020(0.003), which was similar to that in control patients. In the jaundiced group of patients the intestinal permeability index fell to within normal levels after 28 days of internal biliary drainage (0.050 before operation versus 0.021 at 28 days, P < 0.02). These data indicate that intestinal barrier function is impaired in obstructive jaundice and that this impairment is reversed by return of bile to the gastrointestinal tract.

Animals↗
PubMed1996

Increased regional cerebral glucose metabolism and semantic memory performance in Alzheimer's disease: a pilot double blind transdermal nicotine positron emission tomography study.

Nicotinic receptor dysfunction and impaired semantic memory occur early in Alzheimer's disease patients (AD). Previous research implied that nicotine's ability to enhance alertness, arousal, and cognition in a number of nonclinical populations was a function of its ability to stimulate CNS nicotinic cholinergic receptors. In this study it was hypothesized that transdermal administration of nicotine would increase both regional cerebral glucose metabolism (rCMRglc) and semantic memory (as assessed by verbal fluency). Two mild AD and two elderly controls underwent positron emission tomography scanning during a double blind nicotinic agonist verbal fluency challenge procedure. rCMRglc increases occurred in both AD patients, but not controls. In the two AD patients, verbal fluency scores increased by an average of 17%. One elderly control's verbal fluency increased, and the other decreased. These findings suggest that nicotine's effect on metabolism and verbal fluency is due to its ability to stimulate the cholinergic system.

Alzheimer Disease↗
PubMed1996

Benign gastrocolic fistula associated with peritonitis.

Gastrocolic fistula is most often related to malignancy or previous gastric surgery. It is an uncommon complication of benign gastric ulceration in patients who have not had a previous operation. Benign gastrocolic fistula associated with peritonitis is extremely rare--this case is only the fourth ever reported. The patient presented with an acute abdomen, and subsequent investigations demonstrated a gastrocolic fistula of benign aetiology.

Adult↗
PubMed1996

Bacterial translocation and gut microflora in obstructive jaundice.

Bacterial translocation from the gut is implicated in the pathophysiology of complications associated with obstructive jaundice. Absence of intraluminal bile salts and their antiendotoxic effects may result in overgrowth of bacteria, promoting bacterial translocation. The large bowel is the largest source of gram negative bacteria but the small bowel is more permeable. This study investigated the effect of obstructive jaundice on bacterial translocation and on the indigenous luminal microflora at 3 sites in the gastrointestinal tract. Significant bacterial translocation was demonstrated following 7 d of bile duct ligation compared with control or sham operated groups. A qualitative disturbance of the caecal indigenous microflora was demonstrated in jaundiced rats. There was no 'site-to-site' variation in the indigenous microflora at the 3 intestinal sites studied. We conclude that experimental obstructive jaundice for 1 wk promotes bacterial translocation without significant quantitative disturbance of the intestinal microflora in the small intestinal or caecum.

Animals↗
PubMed1995

Renal dysfunction in obstructive jaundice.

The association between renal dysfunction and obstructive jaundice is well established. Despite a substantial number of clinical reviews and prospective studies, the exact incidence and extent of the problem has not been determined accurately. Various pathogenic mechanisms and therapeutic strategies have been proposed but renal dysfunction remains a persistent problem in hepatobiliary practice. The intention of this review is to determine the current extent of the problem, outline the proposed pathophysiological mechanisms and assess the current therapeutic options.

Acute Kidney Injury↗
PubMed1995

Non-surgical trauma to the extrahepatic biliary tract.

Non-surgical trauma to the extrahepatic biliary tract is uncommon and encountered only rarely by surgeons outside specialist hepatobiliary centres. Such injury often results in significant morbidity and mortality. This review outlines the incidence, classification, mechanisms of injury, presentation, diagnostic techniques and management options. Depending on the type of biliary injury identified, an optimal method of repair is suggested. Recommendations are made for surgeons who encounter this type of injury and do not have the appropriate expertise for definitive management.

Adolescent↗