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Biomedical subjects

P Dickens

Publications and source records attributed to P Dickens.

At least 19 recordsLinked to original sources
PubMed2003

Schwann cell dynamics with respect to newly formed motor-nerve terminal branches on mature (Bufo marinus) muscle fibers.

A study has been made of the formation of synaptic terminals from long processes formed at the end of motor nerve branches of endplates in mature amphibian (Bufo marinus) muscle. Injection of fluorescent dyes into individual motor axons showed the full extent of their branches at single endplates. Synaptic vesicle clusters at these branches were identified with styryl dyes. Some terminal branches consisted of well separated varicosities, each possessing a cluster of functioning synaptic vesicles whilst others formed by the same axon consisted of closely spaced clusters of vesicles in a branch of approximately uniform diameter. All the varicosities gave rise to calcium transients on stimulation of their parent axon. Both types of branches sometimes possessed short processes (<5 microm long) or very long thin processes (>10 microm long) which ended in a bulb that possessed a functional synaptic vesicle cluster. These thin processes could move and form a varicosity along their length in less than 30 min. Injection of a fluorescent dye into terminal Schwann cells (TSCs) at an endplate showed that they also possessed very long thin processes (>10 microm long) which could move over relatively short times (<30 min). Injecting fluorescent dyes into both axons and their associated TSCs showed that on some occasions long TSC processes were accompanied by a long nerve terminal process and at other times they were not. It is suggested that the mature motor-nerve terminal is a dynamic structure in which the formation of processes by TSCs guides nerve terminal sprouting.

Animals↗
PubMed2000

Sudden death from massive pulmonary tumor embolism due to hepatocellular carcinoma.

Massive pulmonary embolism in cancer patients can be due to detached thrombi or tumor. Pulmonary tumor embolism is often undiagnosed antemortem. We report a 52-year-old Chinese man admitted for management of hepatocellular carcinoma (HCC). Computerized tomography showed tumor involvement of hepatic vein and inferior vena cava. He died suddenly on the day of admission. At autopsy the main pulmonary arteries of both lungs were blocked by large tumor emboli, the immediate cause of death. Although rapid death in patients with HCC is usually caused by intraperitoneal hemorrhage from spontaneous rupture of tumor, massive pulmonary tumor embolism should also be considered in these patients, especially when antemortem evidence of hepatic vein and/or inferior vena cava invasion is present.

Carcinoma, Hepatocellular↗
PubMed2000

Quantal potential fields around individual active zones of amphibian motor-nerve terminals.

The release of a quantum from a nerve terminal is accompanied by the flow of extracellular current, which creates a field around the site of transmitter action. We provide a solution for the extent of this field for the case of a quantum released from a site on an amphibian motor-nerve terminal branch onto the receptor patch of a muscle fiber and compare this with measurements of the field using three extracellular electrodes. Numerical solution of the equations for the quantal potential field in cylindrical coordinates show that the density of the field at the peak of the quantal current gives rise to a peak extracellular potential, which declines approximately as the inverse of the distance from the source at distances greater than about 4 microm from the source along the length of the fiber. The peak extracellular potential declines to 20% of its initial value in a distance of about 6 microm, both along the length of the fiber and in the circumferential direction around the fiber. Simultaneous recordings of quantal potential fields, made with three electrodes placed in a line at right angles to an FM1-43 visualized branch, gave determinations of the field strengths in accord with the numerical solutions. In addition, the three electrodes were placed so as to straddle the visualized release sites of a branch. The positions of these sites were correctly predicted on the basis of the theory and independently ascertained by FM1-43 staining of the sites. It is concluded that quantal potential fields at the neuromuscular junction that can be measured with available recording techniques are restricted to regions within about 10 microm of the release site.

Algorithms↗
PubMed1998

Fatal gastrointestinal haemorrhage due to coexisting primary aorto-enteric and aorto-colic fistulae. Complicating untreated atheromatous abdominal aortic aneurysm.

We report a case of aorto-enteric and aorto-colonic fistulae in a 73 year old man with no previous abdominal surgery which resulted in massive gastrointestinal haemorrhage and death and was undiagnosed despite several hospital admissions and endoscopic examinations. This case serves to highlight an extremely rare but fatal condition, which is potentially treatable, if an early diagnosis is made.

Aged↗
PubMed1998

Soft tissue rapid prototyping in neurosurgery.

As part of our research into the fluid hydrodynamics of the human ventricular system, a fused deposition model of the human ventricular system was made using magnetic resonance imaging (MRI) data. This article describes the manufacturing of a positive cast of the ventricles as a first step in the construction of a hollow model. After decryption of the original MRI file (ACR-Nema format), the MRI slices were reassembled semiautomatically and a rapid prototyping station produced a resin model. Because of its ease and speed, this method harbors great potential for teaching purposes, research, and preoperative planning in complex three-dimensional soft tissue targets.

Cerebral Ventricles↗
PubMed1998

The likely implications of the 1997 Coroners Ordinance on the autopsy service of a teaching hospital.

The new Hong Kong Coroners Ordinance was published in April 1997. It introduced an expanded set of guidelines for reporting deaths to the coroner as well as the threat of criminal proceedings for non-compliance. The Ordinance is due to be implemented in early 1998. The aim of this study is to determine the likely effect of the new law on the relative proportion of coroner's and hospital (consent) autopsies. A total of 352 consecutive autopsy cases were reviewed; 170 (48.3%) were referred for coroner's autopsies and 182 (51.7%) for hospital autopsies. But applying the criteria of the current ordinance, there should have been 213 (60.5%) coroner's cases and 139 (39.5%) hospital autopsies-that is, 43 hospital autopsies should have been coroner's autopsies. Under the new Coroners Ordinance, there would be 300 (85.2%) coroner's autopsies and only 52 (14.8%) hospital autopsies. The new Coroners Ordinance is likely to result in a greater number of requests for coroner's autopsies with a corresponding decline in hospital autopsies---in our case, a shift from 48.3% of all autopsies performed to 85.2%! This increase would be due largely to the requirement for reporting stillbirths but would also be due to increased reporting for fear of 'criminal proceedings' for non-compliance. An absolute increase in the number of autopsies is also anticipated, although the magnitude cannot as yet be predicted.

Journal Article↗
PubMed1997

Fatal pulmonary embolism: a comparative study of autopsy incidence in Hong Kong and Cardiff, Wales.

All autopsy reports from 1990-1994 inclusive of the Department of Pathology, University of Hong Kong and the Wales Institute of Forensic Medicine were examined and cases of death due to massive pulmonary embolism were noted. The incidence of this condition was calculated and found to be insignificantly lower in the Hong Kong series than the Welsh series by statistical analysis, both in the crude incidence in all autopsies and when correcting for different case mixes in the two locations. The majority of cases in both locations were in the over-60 age group. The study helps refute the longstanding belief among Hong Kong physicians that fatal massive pulmonary embolism is rare in Hong Kong (with approximately 98% Chinese population) in comparison with a predominantly Caucasian population.

Adolescent↗
PubMed1997

Serum interleukin-6 levels correlate with the severity of dementia in Down syndrome and in Alzheimer's disease.

INTRODUCTION: Inflammatory processes are suspected in the pathomechanism of Alzheimer's dementia (AD) but the serum and cerebrospinal fluid (CSF) levels of inflammatory cytokines are not yet determined in the different forms of the disorder. SUBJECTS AND METHODS: Interleukin-6 (IL-6) levels were examined in the sera and CSF of patients with mild-moderate and severe stage of late onset sporadic type of AD and in the sera of demented Down syndrome (DS) probands with similar stages of AD and compared with data of age-matched healthy controls. RESULTS: Normal serum IL-6 levels were found in the mild-moderate stage, but significantly increased levels were found in the severe stage of both dementia groups. The CSF concentrations remained within the normal range in all groups. Positive correlations between the serum IL-6 levels and age and the severity of the disease were present. CONCLUSION: These findings suggest a disease stage dependent general activation of the immune system both in sporadic AD and in DS with AD.

Aged↗
PubMed1996

Detection of Epstein-Barr virus-infected mucosal lymphocytes in nasal polyps.

Primary nasal lymphomas of T or NK cell origin are known to be associated with Epstein-Barr virus (EBV). However, it is not known whether EBV is normally present in nasal mucosa as distinct to nasopharyngeal tissue. This study investigates the prevalence of EBV infection in 13 cases of nasal polyps. EBV DNA was detected in 2 of 13 (15%) by Southern blot hybridization and in 9 of 13 (69%) by polymerase chain reaction. In situ hybridization for EBV-encoded small nuclear RNAs (EBER) was positive in 11 of 13 (85%) cases; the virus was present in stromal lymphocytes only and not in the epithelial cells. Immunohistochemistry for EBV proteins in 7 cases revealed EBV nuclear antigen (EBNA)-2, latent membrane protein (LMP)-1, and ZEBRA (the switch protein encoded by gene BZLF1) expression in rare isolated stromal lymphocytes in 3 cases. Double immunostaining in 1 case showed that the LMP-1+ cells were B or T cells. Immunohistochemistry for EBV lytic proteins showed very rare viral capsid antigen (VCA)+ and membrane antigen (MA)+ cells in 1 case and very rare diffuse early antigen (EA-D)+ and VCA+ cells in 1 other case. The expression of ZEBRA, EA-D, VCA, and MA suggested a disruption of latency in very rare stromal lymphocytes leading to a productive cycle. Although the incidence of EBV positivity in nasal polyps in our population is high (85%), very low numbers of EBV+ cells are found in each case. Nevertheless, they indicate that nasal mucosa could be one of the sites of EBV persistence through a low level of infection of the resident lymphocytes and thereby provide a possible setting for the emergence of virally associated tumors in this site.

Adult↗
PubMed1995

Sudden death from ruptured septic myocardial infarct in an intravenous drug addict.

A case of ruptured septic myocardial infarct with death from cardiac tamponade in an intravenous drug addict with left-sided infective endocarditis and septic coronary artery embolism is described. To the best of our knowledge, there is no previous report of such a case in the literature. Although uncommon, infective endocarditis with coronary embolisation is a well-documented cause of myocardial infarction, although not normally associated with ventricular free wall rupture, and should be considered in intravenous drug addicts who present with cardiac symptoms and signs of sepsis.

Coronary Thrombosis↗
PubMed1994

Fatal accidental aconitine poisoning following ingestion of Chinese herbal medicine: a report of two cases.

Two Hong Kong Chinese adults were prescribed aconitine-containing herbal preparations by Chinese herbal practitioners for relief of minor musculoskeletal pain. After ingestion both quickly developed ventricular tachycardia followed by ventricular fibrillation and cardiac arrest refractory to resuscitation; death in both cases occurred within 12 h of ingestion. Neither had a history of cardiac disease. Coroners' autopsies showed no significant macroscopic or microscopic findings, with no evidence of ischaemic heart disease or other cardiac disease. Toxicological examination of stomach contents showed a trace of hydrolysed aconitine in one case but was negative in the other. Analysis of the herbal preparations consumed, however, confirmed the presence of the aconitine-containing herbs in quantities greatly in excess of the maximum recommended in the P.R. China pharmacopoeia. Both patients therefore consumed an accidental overdose of aconitine, which has a narrow safety margin between therapeutic analgesic effect and its known cardiotoxic effect. These particular herbal medicines are controlled substances in mainland China and Taiwan, but no controls on their dispensing exist in Hong Kong. Together with reported non-fatal cases of aconitine poisoning, these cases emphasise that legal controls of the dispensing and use of aconitine-containing herbal preparations are necessary in Hong Kong.

Aconitine↗
PubMed1994

Squamous cell carcinoma of the oesophagus with mucin-secreting component (muco-epidermoid carcinoma and adenosquamous carcinoma): a clinicopathologic study and a review of literature.

The clinicopathological features of 11 cases of primary oesophageal squamous cell carcinomas with mucin-secreting component (eight muco-epidermoid and three adenosquamous carcinomas) are presented. The incidence was 2.2% of all resected primary oesophageal tumors. The mean age was 64 years and the male to female ratio was 4.5:1. The mean diameter of these tumours was 4 cm. Twenty-seven per cent of these tumours were in the upper, 46% in the middle and 27% in the lower portion of the oesophagus. The age, sex and site distribution of these tumors were similar to those of squamous cell carcinomas. The medium survival of these patients was 15 months. The world literature concerning this rare entity was reviewed and compared with the findings of the present study. No major racial differences were noted. In addition, the classification of this group of tumours was also discussed.

Aged↗
PubMed1993

Sudden death associated with bloodless aortic dissection.

We report a case of rapidly fatal aortic dissection which was unusual because no intimal tear was present and no blood was present in the dissected aortic wall, although the dissection involved the entire aorta. Death was considered to be due to acute myocardial ischaemia from dissection involving the left coronary artery. Prominent cystic medial necrosis was present. There was no history of hypertension and only histological evidence of left ventricular hypertrophy. No other clinical or pathologic states associated with aortic dissection were present. Although cystic medionecrosis was the probable cause in this case, it is present in only a small proportion of patients in the absence of Marfan's syndrome, and more recently investigated defects in the composition of aortic wall connective tissue components may be more relevant factors in the causation of many cases of aortic dissection.

Aortic Dissection↗
PubMed1993

Tumors of the heart. A 20-year experience with a review of 12,485 consecutive autopsies.

Cardiac involvement by primary and secondary tumors is one of the least investigated subjects in oncology. Seven cases of primary and 154 cases of secondary cardiac tumors from autopsies performed over a 20-year period (1972 through 1991) at Queen Mary Hospital, Hong Kong, were reviewed. During this period, 12,485 autopsies were performed, and the autopsy incidence for primary and secondary heart tumors is thus 0.056% and 1.23%, respectively. Only seven primary cardiac tumors were found, including two myxomas, two rhabdomyomas, two hemangiomas, and one lipoma. For secondary tumors involving the heart (including both metastasis and local extension), important primary tumors in male subjects were carcinoma of the lung (31.7%), esophageal carcinoma (28.7%), lymphoma (11.9%), carcinoma of the liver (6.9%), leukemia (4.0%), and gastric carcinoma (4.0%), while in female subjects, carcinoma of the lung (35.9%), lymphoma (17.0%), carcinoma of the breast (7.5%), and pancreatic carcinoma (7.5%) predominated. Overall, the three most common malignant neoplasms encountered were carcinoma of the lung, esophageal carcinoma, and lymphoma. Pericardium, including epicardium, was the most common location of cardiac involvement by secondary tumors, followed by myocardium and endocardium. The present study showed a higher percentage of esophageal carcinoma and carcinoma of the liver (reflecting the higher incidence of these tumors in Hong Kong Chinese), but a lower incidence of carcinoma of the breast when compared with other series. The metastatic lung tumors showed an unusual predominance of adenocarcinoma.

Adolescent↗
PubMed1993

Isolated right-sided endocarditis in Hong Kong Chinese.

Thirteen histologically-proven cases of endocarditis confined to the right side of the heart were found in 9406 consecutive autopsies. Eleven cases involved the tricuspid valve and two the atrial endocardium. Nine cases were in males and 4 in females. Only one case showed underlying valvular/endocardial disease. Eight cases were infective, with Staphylococcus aureus being the predominant organism, and 5 non-infective. For the infective cases, intravenous drug abuse was the commonest predisposing factor, and malignancy the commonest association for the non-infective. The commonest overall complication was lung abscess due to septic emboli in the 3 drug addicts, a common association in other reported series. These latter cases are particularly important to recognize, being generally more responsive to treatment than left-sided infective endocarditis.

Causality↗
PubMed1992

Acute hemorrhagic myocarditis in systemic lupus erythematosus.

We report a 46-year-old patient with longstanding systemic lupus erythematosus (SLE) who developed rapidly progressive heart failure and died. At postmortem, there was a unique picture of hemorrhage and mild inflammation present in the myocardium causing the heart failure. As far as we are aware, this picture has not been described before in SLE and is similar to that seen in the cardiac allograft hyperacute rejection.

Coronary Vessels↗