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Biomedical subjects

R W Parks

Publications and source records attributed to R W Parks.

At least 19 recordsLinked to original sources
PubMed2001

Impairment of Gag-specific CD8(+) T-cell function in mucosal and systemic compartments of simian immunodeficiency virus mac251- and simian-human immunodeficiency virus KU2-infected macaques.

The identification of several simian immunodeficiency virus mac251 (SIV(mac251)) cytotoxic T-lymphocyte epitopes recognized by CD8(+) T cells of infected rhesus macaques carrying the Mamu-A*01 molecule and the use of peptide-major histocompatibility complex tetrameric complexes enable the study of the frequency, breadth, functionality, and distribution of virus-specific CD8(+) T cells in the body. To begin to address these issues, we have performed a pilot study to measure the virus-specific CD8(+) and CD4(+) T-cell response in the blood, lymph nodes, spleen, and gastrointestinal lymphoid tissues of eight Mamu-A*01-positive macaques, six of those infected with SIV(mac251) and two infected with the pathogenic simian-human immunodeficiency virus KU2. We focused on the analysis of the response to peptide p11C, C-M (Gag 181), since it was predominant in most tissues of all macaques. Five macaques restricted viral replication effectively, whereas the remaining three failed to control viremia and experienced a progressive loss of CD4(+) T cells. The frequency of the Gag 181 (p11C, C-->M) immunodominant response varied among different tissues of the same animal and in the same tissues from different animals. We found that the functionality of this virus-specific CD8(+) T-cell population could not be assumed based on the ability to specifically bind to the Gag 181 tetramer, particularly in the mucosal tissues of some of the macaques infected by SIV(mac251) that were progressing to disease. Overall, the functionality of CD8(+) tetramer-binding T cells in tissues assessed by either measurement of cytolytic activity or the ability of these cells to produce gamma interferon or tumor necrosis factor alpha was low and was even lower in the mucosal tissue than in blood or spleen of some SIV(mac251)-infected animals that failed to control viremia. The data obtained in this pilot study lead to the hypothesis that disease progression may be associated with loss of virus-specific CD8(+) T-cell function.

Animals↗
PubMed2000

Changes in gastrointestinal morphology associated with obstructive jaundice.

Bacterial translocation has been consistently demonstrated in experimental models of obstructive jaundice. An important factor which promotes this phenomenon is physical injury of the intestinal mucosa. Some previous studies have presented suggestive evidence of this, following bile duct ligation. The aims of this study were to analyse objectively intestinal mucosal morphometric characteristics, to examine for evidence of bacterial translocation, and to assess enterocytes for ultrastructural abnormalities. Adult female Wistar rats were assigned to one of three groups: control (n=8), bile duct ligation (BDL; n=11), or sham operation (n=10). One week later, portal blood, mesenteric lymph nodes, liver, and spleen were harvested and cultured aerobically and anaerobically for evidence of bacterial translocation. Segments of jejunum, ileum, caecum, and large bowel were examined histologically, using light microscopy and morphometrically, using an image analysis system. Electron microscopy was performed on regions of the gastrointestinal tract where significant morphometric alterations had been identified. Significant bacterial translocation was identified following BDL (63. 6% BDL vs. 0% sham vs. 0% control, p<0.01, Fisher's exact test). There was a significant reduction in total mucosal thickness (standard error) [650 microm (23) BDL vs. 731 microm (27) sham vs. 744 microm (95) control] and villous height [451 microm (20) BDL vs. 515 microm (18) sham vs. 559 microm (79) control] in jaundiced animals, compared with sham-operated and control animals (p<0.02, Mann-Whitney U-test). Electron microscopy revealed oedematous change associated with mild inflammation, disruption of desmosomes, and the formation of lateral spaces between enterocytes. In addition, enterocytes showed vacuolation of their cytoplasm and mitochondrial swelling. Increased numbers of bacteria appeared to be attached to the mucosa. These data provide evidence of physical disruption of intestinal mucosa in jaundiced animals, most marked in the distal ileum. Significant bacterial translocation occurs following bile duct ligation and this supports the hypothesis of gut barrier dysfunction with obstructive jaundice.

Animals↗
PubMed2000

Management of pancreatic pseudocysts.

BACKGROUND: This review analyses the outcome for patients with acute and chronic pancreatic pseudocysts managed in two major referral centres. PATIENTS AND METHODS: From 1987 to 1997, 33 patients were treated with either acute (n = 19) or chronic (n = 14) pseudocysts. Procedures performed included cystgastrostomy (64%), cystduodenostomy (6%), cystjejunostomy (3%), distal pancreatectomy with resection of pseudocyst (12%), laparotomy with external drainage (9%), endoscopic transpapillary stenting (3%) and endoscopic pancreatic duct sphincterotomy with percutaneous drainage of the pseudocyst (3%). RESULTS: All patients had resolution of their pseudocyst and no patient developed recurrence. There were no deaths in this series. There was a 9% incidence of major complications and a 21% incidence of minor complications. Outcome was excellent in 63% and good in 27% of patients. Two patients (6%) had persistent chronic pain and one patient (3%) had evidence of exocrine pancreatic insufficiency with malabsorption. CONCLUSIONS: Surgical internal drainage of pancreatic pseudocysts can be performed safely with low morbidity and mortality provided patients are carefully selected and their medical management is optimized. Although minimally invasive techniques now offer a variety of treatment options, open surgical drainage is still indicated for a significant number of cases.

Acute Disease↗
PubMed1999

Management of liver trauma.

BACKGROUND AND METHODS: Management of blunt or penetrating injuries to the liver remains a significant challenge. This review discusses the mechanisms of liver injury, grading system for severity, available diagnostic modalities and current management options. It is based on a Medline literature search and the authors' clinical experience. RESULTS: Unstable patients require immediate laparotomy, but selected patients who are haemo- dynamically stable may be managed without operation. The preferred operative techniques include resectional debridement, hepatotomy with direct suture ligation and perihepatic packing; anatomical resection, hepatic artery ligation and various bypass techniques have a limited, more defined role for selected injuries. Major complications include haemorrhage, sepsis and bile leak. CONCLUSION: Enhanced resuscitation, anaesthesia and intensive care have contributed to a significant reduction in mortality rates from liver trauma. Optimum results are obtained with a specialist team that includes an experienced liver surgeon, anaesthetist, endoscopist and interventional hepatobiliary radiologist with expertise in managing postoperative complications.

Humans↗
PubMed1998

Renal function in jaundiced patients: a prospective analysis.

A prospective analysis was undertaken to assess renal function in patients with obstructive jaundice. A total of 59 jaundiced patients (serum bilirubin > 100 mumol/l) undergoing biliary decompression by surgical, endoscopic or radiological means received prophylactic fluid volume expansion (3 litres crystalloid fluid intravenously) during the 24 hours before intervention. Renal function (urea and electrolytes, creatinine, creatinine clearance, urinary output) was assessed preoperatively and on days 1-7 and on day 28 postoperatively. Two jaundiced patients (3.4%) developed renal failure (urinary output < 400 ml in 24 hours in the presence of an increased serum urea and/or creatinine) and subsequently died. The overall incidence of post-procedural renal impairment (urinary output < 800 ml in 24 hours) was 10.2%. It is concluded that, with vigilant control of fluid and electrolyte balance and pre-procedural intravenous volume expansion, the incidence of renal dysfunction in patients with obstructive jaundice is not as high as previously reported.

Aged↗
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↗