"Optimization of Surgical Resident Safety and Education During the COVID-19 Pandemic - Lessons Learned"

The COVID-19 pandemic has engendered rapid and significant changes in patient care. Within the realm of surgical training, the resultant reduction in clinical exposure and case volume jeopardizes the quality of surgical training. Thus, our general surgery residency program proceeded to develop a tailored approach to training that mitigates impact on resident surgical education and optimizes clinical exposure without compromising safety. Residents were engaged directly in planning efforts to craft a response to the pandemic. Following the elimination of elective cases, the in-house resident complement was effectively decreased to reduce unnecessary exposure, with a back-up pool to address unanticipated absences and needs. Personal protective equipment availability and supply, the greatest concern to residents, has remained adequate, while being utilized according to current guidelines. Interested residents were given the opportunity to work in designated COVID ICUs on a volunteer basis. With the decrease in operative volume and clinical duties, we shifted our educational focus to an intensive didactic schedule using a teleconferencing platform and targeted areas of weakness on prior in-service exams. We also highlighted critical COVID-19 literature in a weekly journal club to better understand this novel disease and its effect on surgical practice. The long-term impact of the COVID-19 pandemic on resident education remains to be seen. Success may be achieved with commitment to constant needs assessment in the changing landscape of healthcare with the goal of producing a skilled surgical workforce for public service.

Limited hepatitis B immunoglobulin with potent nucleos(t)ide analogue is a cost-effective prophylaxis against hepatitis B virus after liver transplantation

BACKGROUND

Prophylaxis against hepatitis B virus (HBV) recurrence after orthotopic liver transplantation (OLT) includes lifelong hepatitis B immunoglobulin (HBIG) and oral antiviral agent(s). In the presence of high-genetic-barrier nucleos(t)ide analogues, the need for lifelong HBIG is questioned. We evaluated the safety and cost-effectiveness of a limited HBIG course.

METHODS

OLT from 2006 to 2013 were reviewed. Patients with pre-OLT hepatitis B virus surface antigen who received HBV prophylaxis with 2 HBIG doses (anhepatic and first post-operative day; 10,000 units/dose) and potent nucleos(t)ide analogues were included. The primary end point was HBV recurrence (HBV-DNA detection).

RESULTS

Thirteen patients (primary transplants) were included, median Model for End-Stage Liver Disease score was 18, and there was no fulminant failure; HBV-DNA was detected in 4 patients at OLT. After OLT, 10 patients received entecavir and/or tenofovir. Median follow-up was 23 months. One recurrence occurred (7.7%) at month 13 (HBV-DNA: 14 IU/mL); the graft maintained excellent function. This minimal viremic expression is related to hepatocellular carcinoma recurrence with neoplastic replication carrying integrated HBV-DNA; thus, there is no defined HBV viral recurrence. No graft loss or patient death was related to HBV recurrence. The 1-year patient and graft survival rate was 84.6%. Cost-savings in the first year was $178,100 per patient when compared with Food and Drug Administration-approved HBIG dosing.

CONCLUSIONS

In the era of potent oral nucleos(t)ide analogues, a limited HBIG course appears to be cost-effective in preventing HBV recurrence.

Acute postoperative pain following hospital discharge after total knee arthroplasty

OBJECTIVE

The increasingly shorter hospitalization following total knee arthroplasty (TKA) requires patients to assume earlier responsibility to self-manage their pain. Poorly managed acute pain increases the risk of persistent pain, reduces quality of life and increases unnecessary healthcare utilization. This study aims to examine post-discharge pain intensity, pain management behaviors and potential barriers to optimal self-management of pain.

DESIGN

We administered a questionnaire at 2 weeks after discharge to 174 patients undergoing TKA in 10 Australian hospitals. Participants rated pain expectation and severity, use of analgesics and non-pharmacological methods, side-effects, walking and exercise times, perceptions of analgesics, adequacy of pain management information provided and satisfaction with pain relief.

RESULTS

Of 171 (98%) participants who completed the questionnaire, 88 (52%) reported that the worst pain period occurred during the first 2 weeks at home. During the first 2 weeks at home, the average pain was 'severe/extreme' for 40 (23%) participants and 92 (54%) experienced severe pain at least some of the time. Many participants sought further medical help for their pain. Adequate information on analgesics and non-pharmacological methods for pain relief were reported by only 73% and 47%, respectively. Approximately 20% had negative perceptions about analgesic use. Higher pain severity was associated with lower satisfaction and less time spent walking daily.

CONCLUSIONS

Effective pain relief after hospital discharge following TKA is a challenge. Many participants reported significant pain, sought further medical help for pain relief and had inadequate information at discharge to effectively self-manage their postoperative knee pain.

External cooling methods for treatment of fever in adults: a systematic review

BACKGROUND

It is unclear if the use of external cooling to treat fever contributes to better patient outcomes. Despite this, it is a common practice to treat febrile patients using external cooling methods alone or in combination with pharmacological antipyretics.

OBJECTIVE

The objective of this systematic review was to evaluate the effectiveness and complications of external cooling methods in febrile adults in acute care settings.

INCLUSION CRITERIA

We included adults admitted to acute care settings and developed elevated body temperature.We considered any external cooling method compared to no cooling.We considered randomised control trials (RCTs), quasi-randomised trials and controlled trials with concurrent control groups SEARCH STRATEGY: We searched relevant published or unpublished studies up to October 2009 regardless of language. We searched major databases, reference lists, bibliographies of all relevant articles, and contacted experts in the field for additional studies. Two reviewers independently screened titles and abstracts, and retrieved all potentially relevant studies.

CRITICAL APPRAISAL

Two reviewers independently conducted the assessment of methodological quality of included studies.

DATA ANALYSIS

The results of studies where appropriate was quantitatively summarised. Relative risks or weighted mean difference and their 95% confidence intervals were calculated using the random effects model in Review Manager 5. For each pooled comparison, heterogeneity was assessed using the chi-squared test at the 5% level of statistical significance, with I statistic used to assess the impact of statistical heterogeneity on study results. Where statistical summary was not appropriate or possible, the findings were summarised in narrative form.

RESULTS

We found six RCTs that compared the effectiveness and complications of external cooling methods against no external cooling. There was wide variation in the outcome measures between the included trials. We performed meta-analyses on data from two RCTs totalling 356 patients testing external cooling combined with antipyretics versus antipyretics alone, for the resolution of fever. The results did not show a statistically significant reduction in fever (relative risk 1.12, 95% CI 0.95 to 1.31; P=0.35; I =0%).The evidence from four trials suggested that there was no difference in the mean drop in body temperature post treatment initiation, between external cooling and no cooling groups. The results of most other outcomes also did not demonstrate a statistically significant difference. However summarising the results of five trials consisting of 371 patients found that the external cooling group was more likely to shiver when compared to the no cooling group (relative risk 6.37, 95% CI 2.01 to 20.11; P=0.61; I =0%).Overall this review suggested that external cooling methods (whether used alone or in combination with pharmacologic methods) were not effective in treating fever among adults admitted to acute care settings. Yet they were associated with higher incidences of shivering. These results should be interpreted in light of the methodological limitations of available trials.

IMPLICATION FOR PRACTICE

Given the current available evidence, the routine use of external cooling methods to treat fever in adults may not be warranted until further evidence is available. They could be considered for patients whose conditions are unable to tolerate even slight increase in temperature or who request for them. Whenever they are used, shivering should be prevented.

IMPLICATION FOR FURTHER RESEARCH

Well-designed, adequately powered, randomised trials comparing external cooling methods against no cooling are needed.

Massive hemoptysis in an 11-year-old girl with isolated pulmonary arteritis

A 10-year-old girl developed recurrent bouts of massive hemoptysis over a 9-month period. No obvious bleeding source was detected. Her pulmonary angiogram showed a pulmonary aneurysm of the second branch of the left main pulmonary artery as well as widespread irregularities of the pulmonary arteries including areas of stenosis and pruning. Elective embolization of the aneurysm did not control hemoptysis and emergency left upper lobectomy had to be performed. Histology showed large artery wall injury with acute leucocytoclastic inflammation, fibrinoid necrosis, granulomatous inflammation, and ectasia of vessel wall. This combination of abnormalities has not been described to date and represents the first case of isolated pulmonary arteritis in children prior to puberty.

Application of artificial neural networks to establish a predictive mortality risk model in children admitted to a paediatric intensive care unit

INTRODUCTION

Paediatric risk of mortality and paediatric index of mortality (PIM) are the commonly-used mortality prediction models (MPM) in children admitted to paediatric intensive care unit (PICU). The current study was undertaken to develop a better MPM using artificial neural network, a domain of artificial intelligence.

METHODS

The purpose of this retrospective case series was to compare an artificial neural network (ANN) model and PIM with the observed mortality in a cohort of patients admitted to a five-bed PICU in a Hong Kong non-teaching general hospital. The patients were under the age of 17 years and admitted to our PICU from April 2001 to December 2004. Data were collected from each patient admitted to our PICU. All data were randomly allocated to either the training or validation set. The data from the training set were used to construct a series of ANN models. The data from the validation set were used to validate the ANN and PIM models. The accuracy of ANN models and PIM was assessed by area under the receiver operator characteristics (ROC) curve and calibration.

RESULTS

All data were randomly allocated to either the training (n=274) or validation set (n=273). Three ANN models were developed using the data from the training set, namely ANN8 (trained with variables required for PIM), ANN9 (trained with variables required for PIM and pre-ICU intubation) and ANN23 (trained with variables required for ANN9 and 14 principal ICU diagnoses). Three ANN models and PIM were used to predict mortality in the validation set. We found that PIM and ANN9 had a high ROC curve (PIM: 0.808, 95 percent confidence interval 0.552 to 1.000, ANN9: 0.957, 95 percent confidence interval 0.915 to 1.000), whereas ANN8 and ANN23 gave a suboptimal area under the ROC curve. ANN8 required only five variables for the calculation of risk, compared with eight for PIM.

CONCLUSION

The current study demonstrated the process of predictive mortality risk model development using ANN. Further multicentre studies are required to produce a representative ANN-based mortality prediction model for use in different PICUs.

Pediatric interstitial lung disease masquerading as difficult asthma: management dilemmas for rare lung disease in children

Idiopathic nontransplant-related childhood bronchiolitis obliterans is an uncommon disease. Most patients present with chronic recurrent dyspnea, cough and wheezing, which are also features of asthma, by far a much more common condition. The present case study reports on a six-year-old girl who presented to a tertiary care centre with recurrent episodes of respiratory distress on a background of baseline tachypnea, chronic hypoxemia and exertional dyspnea. Her past medical history revealed significant lung disease in infancy, including respiratory syncytial virus bronchiolitis and repaired gastroesophageal reflux. She was treated for 'asthma exacerbations' throughout her early childhood years. Bronchiolitis obliterans was subsequently diagnosed with an open lung biopsy. She did not have sustained improvement with systemic corticosteroids, hydroxychloroquine or clarithromycin. Cardiac catheterization confirmed the presence of secondary pulmonary hypertension. Treatment options remain a dilemma for this patient because there is no known effective treatment for this condition, and the natural history is not well understood. The present case demonstrates the need for careful workup in 'atypical asthma', and the urgent need for further research into the rare lung diseases of childhood.

Prevalence, incidence and predictors of pressure ulcers in a tertiary hospital in Singapore

OBJECTIVE

In 2002 the hospital under study implemented a pressure ulcer standard care plan. This follow-up study aimed to determine the prevalence and incidence of pressure ulcers, whether demographic characteristics and medical diagnosis differed between those individuals who did and those who did not develop ulcers and the predictors of pressure-ulcer formation.

METHOD

The prevalence study used a cross-sectional design, while the incidence study was a prospective cohort study. Participants were scored using the Braden scale and were examined for the presence of pressure ulcers. Those who were ulcer free were monitored twice weekly until they were discharged or for 28 days.

RESULTS

The prevalence of pressure ulcers was 18.1% (95% CI: 15.5-20.9%), while the incidence was 8.1% (95% CI: 6.1-10.4%). Participants with ulcers were older, had a longer mean length of hospital stay, lower Braden scores and were diagnosed with or had a history of cardiovascular diseases or sepsis. Logistic regression found that the total Braden score was the only significant predictor of pressure ulcers. Compared with scores 16-23, the odds ratios were 7.7 (95% CI: 3.5-17.1, p < 0.001) and 12.5 (95% CI: 4.5-34.6, p < 0.001) for scores 12-15 and 6-11 respectively. Demographic characteristics, diagnosis and length of hospital stay were not significant predictors.

CONCLUSION

The study identified a modest decrease in incidence and improvements in nursing care following the implementation of the care plan. It suggests that Braden scores are predictive of those at-risk of developing pressure ulcers.

Skin-prick testing as a diagnostic aid for childhood asthma

Diagnosing asthma is problematic when based solely on reported symptoms. The purpose of this study was to evaluate skin-prick testing as a diagnostic aid for asthma in children. Skin-prick testing (SPT) was undertaken in children aged 2-10 years with either no history of wheeze (n = 149) or recent doctor-observed wheeze which responded to treatment with a bronchodilator, the "gold standard" (n = 164). Children with moderate or severe asthma were excluded. SPT positivity increased sharply at age 5 years in wheezers. Data were therefore divided into two age groups: 2- < 5 years (57 controls, 97 wheezers) and 5-10 years (92 controls, 67 wheezers). The sensitivity, specificity, and likelihood ratios of SPT positivity for wheeze were 32%, 89%, and 2.9, respectively, in the younger children, and 82%, 85%, and 5.5, respectively, in the older children. For a prevalence of 30% for asthma, the positive predictive values of a positive SPT were 55% and 70% for the younger and older age groups, respectively. The test characteristics of SPT for helping diagnose asthma in schoolchildren are good. The prevalence of wheeze in preschool children is high, and so SPT should be helpful even in this group. We suggest that clinicians consider skin-prick testing as a diagnostic aid for asthma.

Diagnostic accuracy of bronchodilator responsiveness in wheezy children

BACKGROUND

The aim of this study was to evaluate the diagnostic accuracy of bronchodilator responsiveness for asthma in 5-10 year old children.

METHODS

Spirometric measurements were made in 142 children (58 wheezers) before and after 400 mug inhaled salbutamol.

RESULTS

On a receiver operating characteristic curve, a 9% increase in predicted forced expiratory volume in 1 second was the cut off point that provided an acceptable balance of sensitivity and specificity for previous wheeze. This figure was 50% (95% CI 38 to 62) sensitive and 86% (95% CI 78 to 92) specific for detecting previous wheeze and multiplied the initial odds in favour of wheeze by a factor of 3.6 (95% CI 2.0 to 6.3).

DISCUSSION

With an estimated pretest probability of wheeze of 10% in the community and 50% in a specialist clinic, the positive predictive values are 29% and 78%, respectively, for a 9% change. The value of bronchodilator responsiveness testing depends on the prevalence of wheeze in the population in which it is to be used.

Principles of a nanoscale DNA scanner

A nanofluidic device for the routine stretching of single DNA molecules was hypothesised and tested. The device consists of an entrance channel leading to a post-field preceding an elongational flow field. The device facilitates each molecule's coil-to-stretch transition, counteracts its entropic recoil, and presents a stream of moving stretched molecules for detailed single-molecule time-of-flight measurements. The physics of DNA stretching was explored in a device where there was a juxtaposition of hexagonal upright post arrays with lithographically defined elongational flow fields.

Normative data for total serum immunoglobulin E measurements in children of three ethnicities

BACKGROUND

It is about 20 years since IgE measurements were published for children without atopic disease. It is possible that the recent increase in atopic disease is reflected in altered measurements in subjects who have no clinical expression of atopy. If the measurement of IgE is to be used as a marker for atopy to characterize disease categories, contemporary normative data must be available.

OBJECTIVE

To measure total serum IgE in healthy children of three ethnicities born and living in an inner city environment.

METHODS

Subjects were aged 1 to < or = 12 years, of Afro-Caribbean, Bangladeshi and white British ethnicities, with no personal history of current atopic disease. An extra 1 mL of blood for the measurement of total serum IgE was collected when blood was taken for other purposes or when a surgical procedure was being undertaken.

RESULTS

Measurements were taken from 151 boys (median age 5.4 years) and 106 girls (median age 6.0 years), who included 127 Bangladeshis, 58 Afro-Caribbeans and 72 white British children. Measurements increased with age but were not related to gender or ethnicity. The data were significantly higher than previous measurements by sixfold.

CONCLUSION

These contemporary normative data allow the generation of z scores for total IgE measurements for clinical or epidemiological use.

Repeatability of airway resistance measurements made using the interrupter technique

BACKGROUND

To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms.

METHODS

Children aged 2-10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, three Rint measurements were made 15 minutes apart, before and after placebo and salbutamol given in random order. Results from those given placebo first were analysed for within-occasion repeatability. Between-occasion repeatability measurements were made 2-20 weeks apart (median 3 weeks).

RESULTS

For 85 pairs of measurements before and after placebo the limits of agreement were 20% expected resistance and were unaffected by age or health status. The change in resistance following bronchodilator in one of 18 healthy children, 12 of 28 with cough, and 22 of 39 with wheeze exceeded this threshold. For between-occasion measurements the limits of agreement were 32% in 72 healthy subjects, 49% in 57 with cough, and 53% in 95 with previous wheeze.

CONCLUSION

The measurement of airways resistance by the interrupter technique is clinically meaningful when change following an intervention such as the administration of bronchodilator is greater than its within-occasion repeatability. Between-occasion repeatability is too poor to judge change confidently.

Association of the HLA A2-B46-DR9 haplotype with autoimmune thyroid dysfunction after bone marrow transplantation in Chinese patients

Autoimmune thyroid disease (AITD) may occur in patients after bone marrow transplantation (BMT). At a median follow-up of 4 years, among 194 allografts and 28 autografts, four patients (three allografts, one autograft) developed AITD. All carried the human leucocyte antigen (HLA) A2-B46-DR9 haplotype, strongly associated with AITD in the Chinese population. No significant thyroid disorder was detected in 190 patients without this haplotype. The frequency of AITD in BMT patients with the HLA A2-B46-DR9 haplotype was 12.5%, with a relative risk of 7.8 times that of non-carriers (P < 0.001). The risk of AITD should be recognized in recipients with high-risk HLA haplotypes, and regular screening might be warranted.

Comparison of counter immunoelectrophoresis with immunoblotting for detection of anti-extractable nuclear antigen antibodies in systemic lupus erythematosus

Anti-extractable nuclear antigen (ENA) antibodies were assayed by counter immunoelectrophoresis (CIE) and immunoblotting in patients with systemic lupus erythematosus (SLE). We found the two methods showed good concordance rates, the lowest being 67% for anti-SS-A. Immunoblotting was more sensitive in detecting anti-Sm, anti-SS-B and anti-PCNA (proliferating cell nuclear antigen); CIE was more sensitive for anti-nRNP and anti-SS-A. Overall, the prevalence of these anti-ENA antibodies in SLE was increased by 9-20% if immunoblotting was used in addition to CIE. Sera specific for the 52 kDa peptide of the SS-A antigen (anti-52kDa SS-A) were better detected by immunoblotting. Anti-PCNA antibody was found in 6.3% of SLE patients and was associated with active disease and hemolytic anemia. The positive rate of anti-Sm was 9% by CIE and 23.7% by immunoblotting and this antibody was a specific marker for SLE using either method. It was concluded that using immunoblotting in addition to CIE, the overall sensitivity of detection of anti-ENA antibodies in SLE was increased and clinically useful antibodies such as anti-52kDa SS-A and anti-PCNA could be detected.

Hypothermic stress leads to activation of Ras-Erk signaling

The small GTPase Ras is converted to the active, GTP-bound state during exposure of vertebrate cells to hypothermic stress. This activation occurs more rapidly than can be accounted for by spontaneous nucleotide exchange. Ras-guanyl nucleotide exchange factors and Ras GTPase-activating proteins have significant activity at 0 degrees C in vitro, leading to the hypothesis that normal Ras regulators influence the relative amounts of Ras-GTP and Ras-GDP at low temperatures in vivo. When hypothermic cells are warmed to 37 degrees C, the Raf-Mek-Erk protein kinase cascade is activated. After prolonged hypothermic stress, followed by warming to physiologic temperature, cultured fibroblasts assume a rounded morphology, detach from the substratum, and die. All of these biologic responses are attenuated by pharmacologic inhibition of Mek. Previously, it had been found that low temperature blocks acute growth factor signaling to Erk. In the present study, we found that this block occurs at the level of Raf activation. Temperature regulation of Ras signaling could help animal cells respond appropriately to hypothermic stress, and Ras-Erk signaling can be manipulated to improve the survival of cells in cold storage.

A novel pathway for tumor necrosis factor-alpha and ceramide signaling involving sequential activation of tyrosine kinase, p21(ras), and phosphatidylinositol 3-kinase

Treatment of confluent rat2 fibroblasts with C2-ceramide (N-acetylsphingosine), sphingomyelinase, or tumor necrosis factor-alpha (TNFalpha) increased phosphatidylinositol (PI) 3-kinase activity by 3-6-fold after 10 min. This effect of C2-ceramide depended on tyrosine kinase activity and an increase in Ras-GTP levels. Increased PI 3-kinase activity was also accompanied by its translocation to the membrane fraction, increases in tyrosine phosphorylation of the p85 subunit, and physical association with Ras. Activation of PI 3-kinase by TNFalpha, sphingomyelinase, and C2-ceramide was inhibited by tyrosine kinase inhibitors (genistein and PP1). The stimulation of PI 3-kinase by sphingomyelinase and C2-ceramide was not observed in fibroblasts expressing dominant-negative Ras (N17) and the stimulation by TNFalpha was decreased by 70%. PI 3-kinase activation by C2-ceramide was not modified by inhibitors of acidic and neutral ceramidases, and it was not observed with the relatively inactive analog, dihydro-C2-ceramide. It is proposed that activation of Ras and PI 3-kinase by ceramide can contribute to signaling effects of TNFalpha that occur downstream of sphingomyelinase activation and result in increased fibroblasts proliferation.

Non-steroidal anti-inflammatory drug-induced apoptosis in gastric cancer cells is blocked by protein kinase C activation through inhibition of c-myc

Apoptosis plays a major role in gastrointestinal epithelial cell turnover, ulcerogenesis and tumorigenesis. We have examined apoptosis induction by non-steroidal anti-inflammatory drugs (NSAIDs) in human gastric (AGS) cancer cells and the role of protein kinase C (PKC) and apoptosis-related oncogenes. After treatment with aspirin or indomethacin, cell growth was quantified by MTT assay, and apoptosis was determined by acridine orange staining, DNA fragmentation and flow cytometry. The mRNA and protein of p53, p21waf1/cip1 and c-myc was detected by Northern and Western blotting respectively. The influence of PKC on indomethacin-induced apoptosis was determined by co-incubation of 12-O-tetradecanoylphorbol 13-acetate (TPA). The role of c-myc was determined using its antisense oligonucleotides. The results showed that both aspirin and indomethacin inhibited cell growth and induced apoptosis of AGS cells in a dose- and time-dependent manner, without altering the cell cycle. Indomethacin increased c-myc mRNA and protein, whereas p53 and p21wafl/cip1 were unchanged. Down-regulation of c-myc by its antisense oligonucleotides reduced apoptosis induction by indomethacin. TPA could inhibit indomethacin-induced apoptosis and accumulate cells in G2/M. Overexpression of c-myc was inhibited by TPA and p21waf1/cip1 mRNA increased. In conclusion, NSAIDs induce apoptosis in gastric cancer cells which may be mediated by up-regulation of c-myc proto-oncogene. PKC activation can abrogate the effects of NSAIDs by decreasing c-myc expression.

Isolation of two chymotrypsins from grass carp

Two chymotrypsins were purified from the hepatopancreas of grass carp (Ctenopharyngodon idellus) by chromatographies on phenyl-Sepharose and Q-Sepharose. The molecular weights of chymotrypsins I and II were 28 and 27 kDa, respectively. The two chymotrypsins showed similar susceptibility to inhibitions by phenylmethylsulfonyl fluoride and soybean trypsin inhibitor, but differed in their response to tosyl-L-phenylalanine chloromethyl ketone and aprotinin in which chymotrypsin I was more resistant. Chymotrypsin I was a less typical chymotrypsin and exhibited lower catalytic efficiency with the chymotrypsin-specific ester and amide substrates, when compared with chymotrypsin II. For both chymotrypsins, optimal activity was detected in the pH range 7.0-8.5.

RasGRP, a Ras guanyl nucleotide- releasing protein with calcium- and diacylglycerol-binding motifs

RasGRP, a guanyl nucleotide-releasing protein for the small guanosine triphosphatase Ras, was characterized. Besides the catalytic domain, RasGRP has an atypical pair of "EF hands" that bind calcium and a diacylglycerol (DAG)-binding domain. RasGRP activated Ras and caused transformation in fibroblasts. A DAG analog caused sustained activation of Ras-Erk signaling and changes in cell morphology. Signaling was associated with partitioning of RasGRP protein into the membrane fraction. Sustained ligand-induced signaling and membrane partitioning were absent when the DAG-binding domain was deleted. RasGRP is expressed in the nervous system, where it may couple changes in DAG and possibly calcium concentrations to Ras activation.

Clinical profiles of Chinese patients with diffuse panbronchiolitis

BACKGROUND

Diffuse panbronchiolitis (DPB), characterised by progressive sinobronchial sepsis, is well characterised in Japanese subjects but not in other ethnic groups. The experience with DPB in seven Chinese patients is described and the clinical profiles compared with those of Japanese subjects.

METHODS

Seven Chinese patients (three women; mean (SD) age 48(18.6) years, all never smokers) who attended a teaching hospital centre and fulfilled the diagnostic criteria for DPB were assessed prospectively for clinical, radiological, lung function, microbiological, and other "characteristic" laboratory parameters.

RESULTS

Lung function assessment showed a typical obstructive pattern (n = 5) and air trapping (n = 7). Typical bronchiolar infiltration by lymphocytes and plasma cells and accumulation of foamy macrophages in the intraluminal tissue were detected in open lung biopsy specimens (n = 2). Chest radiographs and high resolution computed tomographic scans revealed hyperinflation, diffuse nodules, bronchial thickening and dilatation, peripheral hypoattenuation, and bronchiolectasis. Radiological improvement, manifest as a reduction in nodular density and bronchial thickening, and persistence of other abnormalities such as air trapping were not accurately depicted by the classical Nakata or Akira classifications. The other "characteristic" features such as HLA-B54, IgG subclass deficiency, raised CD4/CD8 T lymphocyte ratio, cold haemagglutinaemia, raised IgA, IgG, and rheumatoid factor were not present. Treatment with erythromycin led to excellent responses in symptoms, lung function indices, and the radiological picture. A review of the non-Japanese cases in the literature reveals that this absence of typical "additional features" in DPB might also be applicable to non-Japanese patients.

CONCLUSIONS

We report the only series of non-Japanese Mongoloid patients with well characterised DPB who had uncharacteristic investigation profiles. This experience should help other clinicians in the investigation and management of DPB in non-Japanese patients.

Acute transverse myelopathy in systemic lupus erythematosus: clinical presentation, treatment, and outcome

OBJECTIVE

Acute transverse myelopathy (ATM) is a rare manifestation of systemic lupus erythematosus (SLE). The pathogenesis is unclear and the optimal management strategy is uncertain because of the lack of controlled trials. In this study, the clinical presentation, autoantibody profile, treatment, and outcome of cases of ATM in our local SLE population were retrospectively analyzed and compared with SLE controls.

RESULTS

Ten cases of ATM were identified among 315 patients with SLE studied, giving a prevalence of 3.2%. In 5 of the patients, ATM was the initial manifestation of SLE. The cervical cord was the most common site of involvement (50%). Cerebrospinal fluid abnormalities were present in 63% of the patients, while magnetic resonance imaging (MRI) of the spinal cord revealed abnormal T2 signals in 56%. Only one patient had lupus nephritis. ATM was not associated with antiribosomal P or anti-extractable nuclear antigen (anti-ENA) antibodies. Positive dsDNA antibody was present in 40% of the ATM cases, which was significantly lower than that of patients with active SLE without spinal cord disease (75%; p = 0.04). No significant differences in the prevalence of anticardiolipin antibodies and lupus anticoagulant between the ATM and the non-ATM group were observed. Only 3 patients with ATM showed hypocomplementemia or disease activity in other organs at the time of diagnosis. All the patients with ATM received corticosteroids, while 9 were given cytotoxic agents in addition. The response to treatment was variable -- 40% of patients had complete motor and sphincter recovery and 30% had mild residual spasticity of the lower limbs.

CONCLUSION

In our SLE population, ATM was not associated with antiribosomal P, anti-ENA, or antiphospholipid antibodies. Systemic complement activation was not evident in most patients during the acute phase of myelitis. Early aggressive therapy using a combination of corticosteroid and cytotoxic agents is associated with a satisfactory outcome. Further prospective study is needed to delineate the best treatment and its efficacy in the prevention of relapses.

Identification of an "alcohol dehydrogenase-activating" protease in grass carp hepatopancreas as a chymotrypsin

Previous investigation [Tsui et al. (1996) Biochim. Biophys. Acta 1269: 41-46] showed that two active forms of alcohol dehydrogenase can be purified from grass carp. The use of a protease inhibitor and the results of SDS-PAGE analysis of the enzymes suggest that one form (ADH-C) is a proteolytic product of the other (ADH-I). In this study, the protease responsible for the cleavage was purified. The cleavage enzyme had a subunit molecular weight of 28 kDa. An inhibitor study identified it as a serine protease. It exhibited a strong chymotrypsin activity in both esterase and amidase assays with a pH optimum in the range 7.5-8.5. The purified chymotrypsin also cleaved the intact grass carp ADH-I into the two-fragment ADH-C, with an accompanying increase in enzyme activity. A similar effect was not found using horse liver alcohol dehydrogenase.

Autoantibody formation after allogeneic bone marrow transplantation: correlation with the reconstitution of CD5+ B cells and occurrence of graft-versus-host disease

Manifestations of autoimmune diseases are common in patients who have received allogeneic bone marrow transplantation (BMT). Autoantibodies have been reported in these patients but the source and clinical significance of these autoantibodies are still obscure. In the present study the kinetics of autoantibody formation and the reconstitution of CD5+ B cells was followed in 21 patients who were submitted to allogeneic BMT. Anti-nuclear, anti-smooth muscle, anti-neutrophil cytoplasmic antibodies, anti-reticulin and rheumatoid factor were found at a frequency of 25%, 17%, 24%, 22% and 10% respectively after BMT. Anti-double stranded DNA levels were mildly elevated in 15% of samples. The screening for anti-extractable nuclear antigen, anti-mitochondrial, anti-gastric parietal cell, anti-proteinase III, anti-myeloperoxidase, anti-lactoferrin antibodies was negative. The percentage and absolute count of CD5+ B cells increased with time after allogeneic BMT. Those patients with anti-nuclear or anti-smooth muscle antibodies had significantly higher CD5+ B cell counts than those without these two antibodies. Correlations of CD5+ B cell counts with other autoantibodies were negative. Acute graft-versus-host disease (GVHD) occurred in eight of the patients and chronic GVHD in four patients, but the frequency of autoantibodies had no relationship with the occurrence of acute or chronic GVHD.

Increased rate of apoptosis and decreased expression of bcl-2 protein in peripheral blood lymphocytes from patients with active systemic lupus erythematosus

Defective regulation of apoptosis may play a role in the development of autoimmune diseases, and the proto-oncogene bcl-2 is known to inhibit cells from undergoing apoptosis. We studied the rate of apoptosis with the expression of bcl-2 in peripheral blood lymphocytes of patients with systemic lupus erythematosus (SLE). A lower proportion of lymphocytes were bcl-2+ in SLE patients with active disease (median 84.9%) than in patients with inactive disease or normal (medians 95.3% and 97.1% respectively, p < 0.05). The rate of apoptosis of freshly isolated PBL was significantly higher in SLE patients than in normal (medians 1.2% vs 0.5%, p < 0.05). After 48-hour culture the apoptotic rate was further increased in SLE patients, particularly those with active disease (SLE overall 34.2%, active 62% inactive 27.5%, normal 11.25%). These findings support the theory that in SLE patients increased apoptosis may provide a source of extracellular nuclear antigens which stimulate the autoimmune response and form immune complexes with autoantibodies.

Expression of IL-2R, IL-4R, IL-6R on peripheral blood lymphocytes in systemic lupus erythematosus and correlation with disease activity: a prospective study

AIMS

To study the expression of interleukin-2 receptor (IL-2R), interleukin-4 receptor (IL-4R) and interleukin-6 receptor (IL-6R) on peripheral blood lymphocytes (PBL) in patients with systemic lupus erythematosus (SLE); to correlate the level of expression of these receptors with SLE disease activity.

METHODS

Peripheral blood lymphocytes were studied by a high sensitivity flow cytometry technique using monoclonal antibodies directed against CD25 (IL-2R alpha chain), CD122 (IL-2R beta chain), CD124 (IL-4R), and CD126 (IL-6R). SLE disease activity was scored using the SLE Disease Activity Index, C3 and C4 concentrations, anti-dsDNA level, and absolute lymphocyte count.

RESULTS

Compared with normal controls, PBL from patients with SLE had a higher percentage of CD25+ cells (median 20.8% v 16.5%) and a lower percentage of CD122+ cells (median 13.1% v 22.4%). The difference in CD122+ cells was greater in the CD122weak population than the CD122strong (natural killer cell) population. The percentages of CD124+ and CD126+ PBLs in patients with SLE and controls were similar. On CD25+ cells, the relative antigenic level of the IL-2R alpha chain was significantly higher in patients with SLE (median 2.01 v 1.81). The relative antigenic levels of CD122+, CD124+ and CD126+ cells were similar in patients and controls. Neither the percentages nor the relative antigenic levels of all of these cytokine receptors were correlated with any of the parameters of disease activity.

CONCLUSION

Lymphocyte activation in patients with SLE was evident from the increase in CD25 expression on PBL, with a reciprocal decrease in CD122 expression. As the expression of IL-2R, IL-4R, IL-6R did not correlate with disease activity, it seems that these cytokine/receptor systems do not play a direct role in disease activation in SLE.

Peripheral blood lymphocyte subsets after allogeneic bone marrow transplantation: reconstitution and correlation with the occurrence of acute graft-versus-host disease

Peripheral blood lymphocyte subsets were enumerated at regular intervals during the first year after allogeneic bone marrow transplantation (BMT) in 21 Chinese patients. Eight of these patients had acute graft-versus-host disease (GVHD) while they were assessed at the time of engraftment. Our results show in patients receiving allogeneic BMT: (1) T and NK cells were the predominant lymphocyte subsets in the early reconstitution stage while B cells were severely depleted; (2) absolute numbers of the major lymphocyte subsets normalised in 4-5 months; (3) an increased percentage of T cells that expressed the activation antigen HLA-DR and a reversed CD4:CD8 ratio were observed throughout the first 12 months after BMT; (4) patients with acute GVHD had significantly higher white cell count and NK cell percentage than those not complicated by acute GVHD.

Improved double immunohistochemical staining method for cryostat and paraffin wax sections, combining alkaline phosphatase anti-alkaline phosphatase and indirect immunofluorescence

AIMS

To develop and immunohistochemical staining method for cryostat and paraffin wax sections so that two different antigens in the same section of tissues could be detected by combining immunoenzyme and immunofluorescence techniques.

METHODS

This double immunohistochemical staining method combines alkaline phosphatase-anti-alkaline phosphatase (APAAP) using New Fuchsin as a chromogen and indirect immunofluorescence.

RESULTS

APAAP staining for one antigen of this double immunohistochemical staining method was observed under bright field conditions alternating with immunofluorescence for another antigen under ultraviolet light. The double exposed photograph of both easily identified the two signals within the same cell.

CONCLUSIONS

This double immunohistochemical staining method can overcome the disadvantages of any masking effect of the double immunoenzymatic methods and the background problems of double immunofluorescence method especially when applied to paraffin wax sections. It also permits good morphological identification of the doubly stained cells which may be of crucial importance in studies on pathology specimens.

Movement of apolipoprotein B into the lumen of microsomes from hepatocytes is disrupted in membranes enriched in phosphatidylmonomethylethanolamine

When monolayer cultures of rat hepatocytes are incubated with the ethanolamine/choline analogue, monomethylethanolamine, the secretion of apolipoproteins B100 and B48, as well as the lipid constituents, of very low density lipoprotein (VLDL) is inhibited by approximately 50% (Vance, J. E. (1991) J. Lipid Res. 32, 1971-1982). In the present study we have investigated the mechanism by which monomethylethanolamine disrupts VLDL secretion. Hepatocytes were treated with 400 microM monomethylethanolamine overnight, which resulted in an increase in the cellular content of the derived phospholipid, phosphatidylmonomethylethanolamine, from 0.32 +/- 0.15 to 2.92 +/- 0.74 nmol/mg of cell protein. The biosynthesis of apoproteins B100 and B48 was not impaired by treatment of cells with monomethylethanolamine. However, monomethylethanolamine decreased by approximately 50% the amount of apoproteins B, but not of the typical secretory protein, albumin, present in the luminal content subfraction of microsomes. The intracellular degradation of apoproteins B was also increased in phosphatidylmonomethylethanolamine-enriched, compared with control, cells. Moreover, the pool of apoprotein B present in intact microsomes from hepatocytes incubated with monomethylethanolamine was more accessible to exogenously added trypsin, presumably because a larger pool of the apoprotein B was exposed on the cytosolic surface of these microsomes. The data strongly suggest that an increase in the microsomal content of phosphatidylmonomethylethanolamine diminishes the ability of apoprotein B to translocate across the endoplasmic reticulum membrane into the luminal compartment. Consequently, the association of apoprotein B with lipids and/or the normal assembly of mature VLDL particles is impaired.

CEA tissue staining in colorectal cancer patients--correlation with plasma CEA, histology and staging

To study the expression of tissue carcinoembryonic antigen (CEA) by immunoperoxidase staining in colorectal adenocarcinomas and its relation with preoperative serum CEA and clinicopathological parameters, we studied 85 unselected patients who underwent resective surgery for colorectal adenocarcinomas and were followed up for a mean of 66 mths. All tumors except 2 showed positive staining for CEA. The staining pattern was classifiable into 4 types: apical, cytoplasmic, basolateral and stromal, according to the predominant sites of staining. We found a significant positive correlation between tissue CEA staining pattern and preoperative plasma CEA. Plasma CEA levels were higher when tumor cell staining extended to basolateral regions of the cells and into stromal tissues rather than restricted to apical and cytoplasmic regions (p = 0.012). Furthermore, tissue CEA staining also correlated positively with vascular invasion by tumor cells (p = 0.046), with basolateral and stromal types associated with more frequent vascular invasion than apical and cytoplasmic types. This was in contrast to the preoperative CEA which did not correlate with vascular permeation. We speculate that tissue CEA staining is useful in indicating possible vascular invasion even at early stage whereas vascular invasion by a larger tumor bulk or even tumor metastases may be necessary to produce an increased plasma CEA level that is detectable. On the other hand, preoperative plasma CEA had a strong, positive relationship with tumor stage and mortality (p < 0.001 for both). Preoperative CEA was higher in tumors showing moderate and poor differentiation, although it did not reach statistical significance (p = 0.068), whereas tissue CEA staining had no correlation with tumor differention.(ABSTRACT TRUNCATED AT 250 WORDS)

Only a small proportion of splenic B cells in adults are short-lived virgin cells

A cohort of newly produced virgin B cells was followed from the marrow to the spleen of non-immunized clean rats, which showed minimal antigen-driven proliferation of B cells in their spleens. The progenitors of this cohort of virgin cells were labeled in vivo over 12 h with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdUrd) and their non proliferating progeny left the marrow 2-3 days later. This coincided with the arrival of labeled B cells in the red pulp and T zones of the spleen. These appear to be short-lived as few remained a week after the label was given. The short-lived newly produced virgin B cells can only comprise a minority of splenic B cells, for it is shown that only 20% of splenic B cells are found in the red pulp and T zone. It is calculated that newly produced virgin B cells are likely to make up between 5% and 10% of splenic B cells. In the marginal zones and follicular mantle respective medians of 3.3% and 1.8% were already labeled at 1 day from the start of the BrdUrd pulse. The appearance of these cells seems likely to result from antigen-driven B cell proliferation outside the marrow, for labeled virgin B cells have not started to leave the marrow at this stage. During day 2 and 3 the proportion of labeled follicular mantle B cells rose to 3.4%, which might in part reflect the recruitment of newly produced virgin B cells to the pool of recirculating follicular B cells. After day 3 in the follicles and day 1 in the marginal zones the proportion of labeled cells did not vary significantly through day 7. This appears to confirm the comparative longevity of the cells in these zones, which contain 80% of the non-proliferating splenic B cells of adult rats.

Sites of specific B cell activation in primary and secondary responses to T cell-dependent and T cell-independent antigens

Techniques which identify hapten-specific B cells in tissues have been used to determine the sites of B cell activation in rat spleens in response to T cell-dependent (TD) antigens and T cell-independent type-1 (TI-1) antigens. Surface-associated hapten binding by specific memory B cells and B blasts was distinguished from the strong cytoplasmic hapten binding by specific plasma cells and plasmablasts. Blast cells in S phase were identified in tissue sections by staining cells which had been pulse labeled in vivo with 5-bromo-2'-deoxyuridine. Hapten-specific B blast cells are found in three sites: (a) around interdigitating cells in the T cell-rich zones; (b) in the follicular dendritic cell network and (c) in association with macrophages in the red pulp. Hapten-binding memory B cells, which are not in cell cycle, accumulate in the marginal zones and to a lesser extent the follicular mantles in response to TD and TI-1 antigens. The hapten-specific blast response in T zones is confined to the first few days after antigen is given and is low for primary responses to TD antigens, but massive on secondary challenge, when marginal zone memory B cells migrate to the T zones. Both the primary and secondary T zone responses to TI-1 antigens are impressive and in these responses hapten-specific B blasts are also found in the splenic red pulp. The follicular response to TD antigens starts with a small number of B blasts (fewer than five) entering each follicle. These increase in number exponentially so that by the 4th day after immunization they fill the follicle. The oligoclonality of the response is shown in simultaneous responses to two haptens where 6%-31% of the follicles on day 3 after immunization contain blasts specific for only one of the two haptens. During the 4th day classical zonal pattern of germinal centers develops. The surface immunoglobulin-positive B blasts are lost from the follicle center, while one pole of the follicular dendritic cell network fills with surface immunoglobulin-negative centroblasts. Centroblasts do not increase in numbers but divide to give rise to centrocytes, which re-express sIg and migrate into the follicular dendritic cell network. Cell kinetic studies indicate that the centrocyte population is renewed from centroblasts every 7 h. Centrocytes either leave the germinal center within this time or die in situ.(ABSTRACT TRUNCATED AT 400 WORDS)

Peripheral T-cell lymphoma presenting as hemophagocytic syndrome

Three patients with peripheral T-cell lymphoma presenting with pyrexia, wasting, hepatosplenomegaly and pancytopenia in the absence of myelophthisic lymphomatous involvement are reported. Early in the course of the disease when there was no significant lymphadenopathy, these cases created enormous diagnostic confusion. Although the clinical features were suggestive of malignant histiocytosis (MH), marrow findings showed phagocytic histiocytes which did not appear atypical, and the criteria for diagnosis of MH could not be satisfied. Lymph node enlargement was detected only after 14, 5, and 8 weeks from the onset of symptoms, and the diagnosis of T-lymphoma was then made on lymph node biopsies. Treatment with multiple agent chemotherapy was attempted. Two patients died 3 days and 11 weeks after treatment was started and the third was lost to follow-up. In contrast with most of the cases reported in the literature, our cases show that a reactive hemophagocytic syndrome can be an early and prominent manifestation of an underlying T-cell lymphoma. Differentiation from other causes of hemophagocytic syndrome can be difficult and lack of histological proof of malignancy in the initial stage often delays definitive diagnosis and treatment.

Prognostic factors for relapse after complete response in patients with metastatic germ cell tumors

Among 216 patients with metastatic germ cell tumors who achieved a complete response (CR) to cisplatin-based chemotherapy (CT), 38 have experienced a relapse. Prognostic factors for time to relapse from time of response were considered using the Cox proportional hazards model. Compared with patients who responded to CT and did not require surgery and patients whose surgery showed only either necrotic debris or mature teratoma, those who required surgery for residual tumor after CT were at much higher risk for relapse, although their residual tumor was totally resected. Of the 19 patients who required this surgery, eight have experienced a relapse. Other prognostic factors for relapse included lactate dehydrogenase (LDH) and human chorionic gonadatropin (hCG) at the time of initial CT. Although those who require surgery for residual tumor after CT receive additional CT, there is still a high risk of relapse.

Stage migration and the increasing proportion of complete responders in patients with advanced germ cell tumors

The proportion of patients with metastatic germ cell tumors achieving complete remission increased, and the total survival improved between 1975 and 1982. Several analyses were undertaken to evaluate the influence of stage migration on treatment outcome in patients with germ cell tumors. (a) A logistic regression analysis showed that a formulation of time was an independent statistically significant variable (P = 0.025) in addition to the total number of sites of metastasis (P less than 0.001) and pretreatment values of human chorionic gonadotropin (P less than 0.001) and lactate dehydrogenase (P = 0.002). (b) The proportion of patients with lung metastases and elevated levels of human chorionic gonadotropin and alpha-fetoprotein decreased, and the number of patients with retroperitoneal metastases and without prior radiation therapy increased significantly. (c) The number of patients with a high likelihood of complete response increased significantly over time (P less than 0.001). Computerized tomography of the abdomen permits detection of large but asymptomatic retroperitoneal disease, and such patients are now being treated with chemotherapy rather than surgery and are included in advanced disease treatment results. Stage migration has played a role in the increasing proportion of complete responders in clinical trials of patients with germ cell tumors.

Carcinoma of the esophagus. An autopsy study of 231 cases

Autopsy findings for 231 cases of carcinoma of the esophagus are presented. Cases with tumour resection constituted 57% of the series. Residual malignancy was present in 81% of all cases. Local residual or recurrent tumour was found in 53%, lymph node metastases in 65% and visceral metastases in 54% of cases. Intrathoracic lymph node metastases were present in 41% of patients after tumour resection and were probably significant in the failure of radical surgery. Adequate clearance of intrathoracic lymph nodes during radical surgery may reduce the incidence of tumour recurrence in this group of patients. Survival was poor in patients with or without resection of the primary tumour. Less than 12% were alive 1 yr after presentation. The average duration of dysphagia at presentation was 2.5 mth. The poor survival of our patients suggests that, by the time they presented clinically, the disease was already advanced. Early disease detection is important for a chance of cure in patients with esophageal cancer.

Sustained improvement in diabetic control on long-term self-monitoring of blood glucose

The benefits of self-monitoring of blood glucose (SMBG) were assessed in 38 Chinese adults on conventional insulin regimens who had been performing SMBG for a mean duration of 26 months (range 15-40). For analysis patients were divided into 2 groups. Group A consisted of 27 insulin-requiring patients who were referred for SMBG because of poor control or young age (less than or equal to 35 years). Group B consisted of 11 IDDM patients who were on SMBG from diagnosis. Mean age and duration of SMBG were similar in the 2 groups though group A had longer duration of disease. In group A, mean haemoglobin A1 (HbA1) decreased from 12.4 +/- 0.5% before SMBG to 10.9 +/- 0.5% at 6 months (P less than 0.005), 10.7 +/- 0.5% at 12 months (P less than 0.005) and 10.3 +/- 0.4% after long-term SMBG. This was accompanied by a significant reduction in insulin requirement from 0.82 +/- 0.07 U/kg/day to 0.72 +/- 0.07 U/kg/day (P less than 0.05). In group B, insulin requirement progressively decreased in the first 6 months. At 12 months, mean HbA1 was 9.0 +/- 0.5% and insulin requirement was 0.58 +/- 0.08 U/kg/day. No significant change in HbA1 or insulin requirement was observed beyond the first year. After long-term SMBG, 82% of patients in group B had good control (HbA1 less than or equal to 10%) compared to 45% only in group A (P less than 0.05). Long-term SMBG is associated with sustained improvement in diabetic control and is particularly beneficial if introduced to diabetic patients right from diagnosis.

Effect of lipid soluble antioxidants on cytotoxicity induced by photochemical products of cholesterol

Lipid soluble antioxidants, butylated hydroxytoluene and vitamin E, were shown to suppress cytotoxicity induced by cholesterol-derived photoproducts in Chinese hamster embryo cells. These cholesterol-derived photoproducts were rather toxic.

Near IR interband transitions and optical parameters of metal-germanium contacts

A theoretical and experimental study of the zero-bias quantum efficiency eta(0) for metal (Au, Cu, Ag)-Ge Schottky barrier photodetectors in the near IR range (1.1 microm < lambda < 1.8 microm) has been performed. By an interactive computer programming technique, the optical parameters of the metal thin film electrodes (index of refraction n and extinction coefficient k) as a function of wavelength and of film thickness are determined. Starting with a two-layer calculation of the reflectance R, transmittance T, and absorptance A of the metal electrode, it is found that the eta(0) in this near IR range is dominated by the band-to-band excitation of electrons in the Ge substrate. Using the minority carrier diffusion length L(p) as an adjustable parameter, good agreement between theoretical and experimental results was found for L(p) approximately 150 microm; this value was obtained independent of choice of metal or metal thickness justifying the above procedure.