Minimizing gain transient dynamics by optimizing the erbium concentration and cavity length of a gain clamped EDFA

Erbium doped fiber amplifier (EDFA) gain transient dynamics are studied in the context of their application in optically reconfigurable networks. We address the question of how to design the EDFA in order to minimize the gain transients present in the output signals of the EDFA when the system is optically reconfigured such that the total average input power levels and wavelengths are changed. Both experimental measurements and theoretical simulations show that the amplitude transients depend on the length of the erbium doped fiber (EDF) and the erbium concentration. We show how it may be possible to reduce the gain transients by appropriate design of the EDFA.

Outcome and late failures compared in 4 techniques of microsurgical vasoepididymostomy in 153 consecutive men

PURPOSE

Vasoepididymostomy remains one of the most technically challenging procedures in all of microsurgery. The technique has evolved from an end-to-end, to an end-to-side technique, then to intussusception end-to-side methods. We recently reported the superiority of 2-suture longitudinal and 3-suture triangulation intussusception techniques in rats. In the present study we report our results in humans. We evaluated all vasoepididymostomies performed by 1 surgeon from January 1992 until the present for patency, pregnancy and for disappearance of sperm after initial return of sperm to the ejaculate.

MATERIALS AND METHODS

We recorded the results of 153 consecutive vasoepdidymostomies done by 1 surgeon (MG) from January 1992 until February 2004. Four techniques were used, namely end-to-end (EE), end-to-side (ES), 3-suture triangulation intussusception (TIVE) and 2-suture longitudinal intussusception (LIVE). Data collected included technique, months of followup, sperm density, motility and morphology (WHO 1992 criteria), pregnancy outcome and late failures. Late failures were defined as having return of sperm to the ejaculate after vasoepididymostomy and then becoming azoospermic on at least 2 subsequent semen analyses.

RESULTS

A total of 153 men underwent bilateral vasoepididymostomies. The most recent 17 were LIVE, preceeded by 38 TIVE, 32 ES and 66 EE. Mean followup for the groups were 17.2 (LIVE), 70.8 (TIVE), 116.7 (ES) and 140.2 (EE) months, respectively. Intact sperm were seen in the ejaculates of 12 men (80%) in the LIVE group, 16 in the TIVE group (84%), 20 in the ES group (74%) and 30 men in the EE group (73%). Motile sperm were found in the ejaculates of 10 of 15 (67%) in the LIVE group, 13 of 19 (68%) in the TIVE group, 10 of 27 (37%) in the ES group and 20 of 41 (49%) in the EE group (p =0.2). Mean times for return of sperm to the ejaculate were 2.9, 2.8, 2.8 and 3.5 months, respectively. Pregnancies were reported by 4 men in the LIVE group all before 12 months, 6 in the TIVE group and 3 were by 12 months, and 4 each by the ES and EE groups with 3 and 2 by 12 months (p =0.07). Thus far, there have been no late failures in the LIVE group, only 1 in the TIVE group (8%), 5 in the ES group (50%) and 6 in the EE group (30%) (p =0.04).

CONCLUSIONS

Although vasoepididymostomy remains a technically demanding microsurgical procedure, recent technical innovations of TIVE and LIVE offer better or comparable outcomes compared with EE and ES procedures with the use of fewer sutures, which simplifies the performance of the anastomosis. In addition, the late failure rate is lower with the use of the intussusception techniques (LIVE and TIVE) with only 1 late failure in 22 men with return of sperm to the ejaculate procedures (4%) compared with 11 of 30 (37%) in the nonintussusception groups (p =0.006).

Natural history of fixed flexion deformity following total knee replacement: a prospective five-year study

We investigated fixed flexion deformity (FFD) after total knee replacement (TKR). Data relating to 369 cruciate-retaining unilateral TKRs performed at a single institution were collected prospectively. Fixed flexion was measured pre-operatively and at one week, six months, 18 months, three years and five years after surgery. Using binary logistic regression, pre-operative FFD was a predictor of post-operative FFD > 10 degrees at one week (p = 0.006) and six months (p = 0.003) following surgery. Gender was a predictor at one week (p = 0.0073) with 24% of women showing a FFD > 10 degrees compared with 37% of men. We have shown that a gradual improvement in knee extension can be expected up to three years after surgery in knees with FFD. By this time residual FFD is mild or absent in the majority of patients, including those who had a severe pre-operative FFD.

Weight change following total hip replacement: A comparison of obese and non-obese patients

BACKGROUND

Weight loss is desirable in obese patients prior to hip replacement but poor mobility secondary to hip dysfunction may limit attempts at weight reduction because of reduced exercise tolerance.

METHODS

We followed 140 patients prospectively to investigate weight change and functional outcome in obese and non-obese patients following total hip arthroplasty. Weight and the Harris hip score was measured one week prior to surgery and three years post-operatively.

RESULTS

Fifty nine patients were obese (BMI > or = 30). The mean weight of obese patients increased from 88 kg pre-operatively to 92 kg following surgery (p<0.001). In non-obese patients pre-operative weight was 69 kg and post-operative weight 70 kg (p=0.106). In the obese group 75% of patients gained a mean of 6.77 kg (p<0.001) and 19% of patients lost a mean of 4.8 kg (p<0.01). In the non-obese group, 60% of patients gained a mean of 4.2 kg (p<0.001) and 31% of patients lost an average of 4.7 kg (p<0.001). The mean Harris hip score was 90 in non-obese patients and 85 in obese patients three years post-operatively (p<0.01).

CONCLUSION

Weight increase is common following total hip replacement despite improved function but the magnitude of weight increase appears to be greater in patients who are obese. Obesity was also associated with lower functional hip scores but the differences were small and unlikely to be of clinical significance.

Active mobilisation after flexor tendon repair: comparison of results following injuries in zone 2 and other zones

PURPOSE

To prospectively study the role of active mobilisation after flexor tendon repair.

METHODS

The standard modified Kessler's technique was used to repair 46 digits in 32 patients with flexor tendon injuries. Early active mobilisation of the repaired digit was commenced on the third postoperative day. Range of movement was monitored and recovery from injury in zone 2 was compared with injury in other zones.

RESULTS

There were 24 and 22 injuries in zone 2 and other zones respectively. The total active motion score of the American Society for Surgery of the Hand was measured. Patients with zone-2 injuries achieved similar results to those with other-zone injuries apart from a 3-week delay in recovery. The final results were good to excellent in 71% and 77% of zone-2 and other-zone cases respectively (p < 0.05). There were 2 ruptures in zone-2 and one rupture in zone-3 repairs (6.5%).

CONCLUSION

Preliminary results of this study showed that active mobilisation following flexor tendon repair provides comparable clinical results and is as safe as conventional mobilisation programmes although recovery in patients with zone-2 injury was delayed.

Inhibition of angiotensin II induced endothelin-1 gene expression by 17-beta-oestradiol in rat cardiac fibroblasts

OBJECTIVE

To examine whether 17-beta-oestradiol (E(2)) may alter angiotensin II (Ang II) induced cell proliferation and to identify the putative underlying signalling pathways in rat cardiac fibroblasts.

DESIGN

Cultured rat cardiac fibroblasts were preincubated with E(2) then stimulated with Ang II. [(3)H]Thymidine incorporation and endothelin-1 (ET-1) gene expression were examined. The effect of E(2) on Ang II induced NADPH oxidase activity, reactive oxygen species (ROS) formation, and extracellular signal regulated kinase (ERK) phosphorylation were tested to elucidate the intracellular mechanism of E(2) in proliferation and ET-1 gene expression.

RESULTS

Ang II increased DNA synthesis, which was inhibited with E(2) (1-100 nmol/l). E(2), but not 17-alpha-oestradiol, inhibited Ang II induced ET-1 gene expression as shown by northern blotting and promoter activity assay. This effect was prevented by co-incubation with the oestrogen receptor antagonist ICI 182,780 (1 micromol/l). E(2) also inhibited Ang II increased NADPH oxidase activity, ROS formation, ERK phosphorylation, and activator protein-1 mediated reporter activity.

CONCLUSIONS

The results suggest that E(2) inhibits Ang II induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway through attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of oestrogen on the cardiovascular system.

Use of convalescent plasma therapy in SARS patients in Hong Kong

In order to evaluate the efficacy of convalescent plasma therapy in the treatment of patients with severe acute respiratory syndrome (SARS), 80 SARS patients were given convalescent plasma at Prince of Wales Hospital, Hong Kong, between 20 March and 26 May 2003. Good outcome was defined as discharge by day 22 following the onset of SARS symptoms. Poor outcome was defined as death or hospitalization beyond 22 days. A higher day-22 discharge rate was observed among patients who were given convalescent plasma before day 14 of illness (58.3% vs 15.6%; P<0.001) and among those who were PCR positive and seronegative for coronavirus at the time of plasma infusion (66.7% vs 20%; P=0.001).

Endoluminal repair of anastomotic false popliteal aneurysm using the Wallgraft endoprosthesis

The aim of this study was to present the endoluminal repair of a false anastomotic popliteal aneurysm on a previous polytetrafluoroethylene (PTFE) above knee bypass using a Wallgraft endoprosthesis. A 53-year-old man who underwent a left femoro-popliteal above knee PTFE bypass 13 years before was admitted with a painful pulsatile mass in the above knee area. Nine months previously he developed sudden pain around the knee extending to the foot associated with coldness and numbness after he was handling some fishing gear in a crouching position for about 1 hour, but this episode spontaneously resolved. Duplex scanning and angiography revealed a 3 x 2.5 cm false aneurysm, which was successfully treated by deploying a Wallgraft endoprosthesis as the patient declined surgical repair. The graft was detected as being occluded on the 3-month follow-up but no further action was taken because the patient experienced only non-limiting claudication and he refused again surgical treatment. Endoluminal repair of perianastomotic false aneurysms in the popliteal artery with Wallgraft endoprosthesis seems feasible and safe, but until its durability is validated in larger series surgical repair remains the treatment of choice.

Clinical Significance of Superficial Vein Thrombosis

OBJECTIVE

To evaluate the clinical implications of superficial thrombophlebitis (STP) including its demographic characteristics, distribution, risk factors, relationship with deep vein thrombosis (DVT), pulmonary embolism (PE), diagnosis and management.

METHODS

Data were collected from relevant papers using a MEDLINE search and an extensive bibliography review. Studies were considered only when they contained pertinent material to STP. Thirty-seven papers were analysed.

RESULTS

The diversity of patients and methods used in the different studies made the comparison among them difficult. STP is a common condition with an underestimated prevalence. There are many risk factors associated with STP but the strongest relation was seen with hypercoagulable states. Malignancy may be another important factor but the strength of this association remains unknown. Coexistence with DVT was found in 6-53%. PE occurred in 0-33.3%. Propagation to DVT ranged from 2.6 to 15%. Treatment has not been standardised and may include elastic compression, anti-inflammatory drugs, anticoagulation and surgery.

CONCLUSION

The limited number of prospective randomised studies on STP does not allow strong recommendations to be given. Although STP most often is perceived as benign, it can coexist with or progress to DVT, and even give rise to PE. It is also associated with hypercoagulability and malignancy.

VEGF and VEGF receptor expression in human chronic critical limb ischaemia

OBJECTIVE

This study quantified endogenous VEGF and VEGF receptor expression in limbs of patients with chronic critical limb ischaemia (CLI).

METHODS

Skin and muscle biopsies were obtained from the legs of 25 patients undergoing limb amputation for CLI. Samples were obtained at the amputation level (thigh or calf) and, distally, from the foot and in the vicinity of ischaemic ulcers and gangrene. Control biopsies were obtained from patients undergoing amputation for non-arterial reasons or knee arthroplasty (n=7). VEGF protein levels in tissue lysates were measured by ELISA, and VEGF and KDR mRNA levels were determined using quantitative PCR.

RESULTS

At the amputation level, VEGF protein and VEGF and KDR mRNA levels in CLI limbs were similar to those in controls. In the foot VEGF mRNA in skin (P=0.005) and VEGF protein levels in muscle (P=0.02) were elevated compared to levels in a proximal biopsy from the same limb. VEGF and KDR mRNA levels in the vicinity of gangrene/ulcers (VEGF P=0.01, KDR P=0.03) also were elevated.

CONCLUSIONS

VEGF expression is not deficient in CLI. Indeed, it is elevated at distal sites in the ischaemic limb. These findings question the rationale for VEGF supplementation in CLI.

Saphenofemoral Venous Channels Associated with Recurrent Varicose Veins are not Neovascular

BACKGROUND

Recurrence of varicose veins after apparently adequate surgery is common. Neovascularisation, the formation of new vascular channels between a venous surgery site and new varicosities, is thought to be an important cause of recurrence. The aim of this study was to provide histological evidence of the 'neovascularisation'process.

METHOD

Tissue samples from the region of the previously ligated saphenofemoral junction (SFJ) were taken from 14 limbs with recurrent varicose veins and from nine control limbs. Tissue samples were analysed histologically for overall vascularity, and the presence of intimal circular fibrosis, intimal eccentric fibrosis, medial thickened elastosis, and thrombosis in the microscopic thin walled vessels within the tissue. The same samples were analysed immunohistoligically for S100, a neural marker, and Ki-67 (Mib 1), a marker of endothelial proliferation. Absent S100 and positive Ki-67 were considered as evidence of new vessels.

RESULT

No significant difference was found between the venous recurrence and control groups in respect to histological features. S100 positive nerve fibrils were seen associated with dilated venous channels in the majority of both redo and control groups (p=1, Fisher's exact test). Only one section stained positively with Ki-67 (Mib1) in a single vascular channel for a few endothelial cells. The remaining control and redo cases were negative for Mib 1 (p=1, Fisher's exact test).

CONCLUSION

We found little evidence of neovascularisation associated with recurrent varicose veins in the saphenofemoral region. The venous channels that develop at the previously ligated SFJ may represent adaptive dilatation of pre-existing venous channels (vascular remodelling), probably in response to abnormal haemodynamic forces.

Retrospective comparison of convalescent plasma with continuing high-dose methylprednisolone treatment in SARS patients

Treatment of severe acute respiratory syndrome (SARS) is experimental, and the effectiveness of ribavirin–steroid therapy is unclear. Forty SARS patients with progressive disease after ribavirin treatment and 1.5 g of pulsed methylprednisolone were given either convalescent plasma (n = 19) or further pulsed methylprednisolone (n = 21) in a retrospective non‐randomised study. Good clinical outcome was defined as discharge by day 22 following the onset of symptoms. Convalescent plasma was obtained from recovered patients after informed consent. Patients in the plasma group had a shorter hospital stay (p 0.001) and lower mortality (p 0.049) than the comparator group. No immediate adverse effects were observed following plasma infusion.

A review of research related to blood transfusion in Canada, 2000-2002

The former National Blood Safety Council undertook a comprehensive review of blood transfusion research in Canada for the years 2000 through 2002. Data were acquired by direct contact with agencies which support such research and by searches of the relevant websites. Total grant support increased markedly over the 3-year period, from 4.1 million dollars to 18.5 million dollars. Publicly funded granting agencies, biopharmaceutical companies, the blood services and the province of Ontario were major supporters. Much smaller amounts were granted from charitable organizations. Clinical research attracted the majority of the funding, although a larger number of projects were basic science in nature. Most research was carried out in the provinces of Ontario, Québec and British Columbia. Although we have not assessed the productivity of blood-related research, it appears that substantial amounts of funding were allocated to these projects between 2000 and 2002. These data may provide a helpful perspective to investigators in transfusion medicine elsewhere, who may also be assessing the relative priority given to this field of research in their own countries.

Recurrent appendicitis as a cause of recurrent right iliac fossa pain

Recurrent appendicitis is defined when patients with recurring similar right iliac fossa pain had acute appendicitis confirmed at the time of operation and the pain completely subsided after surgery. We conducted a retrospective study on our patients with appendicitis. There were 290 patients with appendicitis over a two-year period and 33 patients (11%) had reported recurring pain prior to the presentation. Majority had one prior episode but 15% had multiple episodes of right iliac fossa pain. Fifty-eight percent of the episode occur within six months of the presentation. We conclude that recurrent appendicitis should be considered as a differential diagnosis in patients with recurrent right iliac fossa pain.

Chemical-specific alterations in ras, p53, and beta-catenin genes in hemangiosarcomas from B6C3F1 mice exposed to o-nitrotoluene or riddelliine for 2 years

The most prominent neoplastic lesions in mice in the 2-year studies of o-nitrotoluene and riddelliine were hemangiosarcomas. Fifteen o-nitrotoluene-induced hemangiosarcomas of the skeletal muscle, subcutaneous tissue, and mesentery; 12 riddelliine-induced hemangiosarcomas of the liver; and 15 spontaneous subcutaneous hemangiosarcomas were examined for genetic alterations in ras, p53, and beta-catenin genes. Mutations in at least one of these genes were identified in 13 of 15 (87%) of the o-nitrotoluene-induced hemangiosarcomas with missense mutations in p53 exons 5-8 detected in 11 of 15 (73%) of these neoplasms. Seven of 15 (47%) hemangiosarcomas from mice exposed to o-nitrotoluene had deletions at exon 2 splice sites or smaller deletions in the beta-catenin gene. K-ras mutation was detected in only 1 of the 15 (7%) o-nitrotoluene-induced hemangiosarcomas. In contrast to the o-nitrotoluene study, 7/12 (58%) riddelliine-induced hemangiosarcomas had K-ras codon 12 GTT mutations and, when screened by immunohistochemistry, 9/12 (75%) had strong staining for the p53 protein in malignant endothelial cells, the cells of origin of hemangiosarcomas. Riddelliine-induced hemangiosarcomas were negative for the beta-catenin protein. Spontaneous hemangiosarcomas from control mice lacked both p53 and beta-catenin protein expression and ras mutations. Our data indicated that p53 and beta-catenin mutations in the o-nitrotoluene-induced hemangiosarcomas and K-ras mutations and p53 protein expression in riddelliine-induced hemangiosarcomas most likely occurred as a result of the genotoxic effects of these chemicals. It also suggests that these mutations play a role in the pathogenesis of the respective hemangiosarcomas in B6C3F1(1) mice.

Structure-activity study of novel tricyclic benzazepine arginine vasopressin antagonists

Novel tricyclic benzazepine derivatives were synthesized as arginine vasopressin (AVP) antagonists. Several tricyclic compounds showed potent antagonistic activity in rat AVP receptors V(1a) and V(2). Derivatives containing pyrrolo-tricyclic amines, 13i-k, 30, and 31 also showed selectivity for the V(2) receptor.