Anthropogenic change decouples a freshwater predator's density feedback.

Intraspecific interactions within predator populations can affect predator-prey dynamics and community structure, highlighting the need to better understand how these interactions respond to anthropogenic change. To this end, we used a half-century (1969-2018) of abundance and size-at-age data from Lake Erie's walleye (Sander vitreus) population to determine how anthropogenic alterations have influenced intraspecific interactions. Before the 1980s, the length-at-age of younger walleye (ages 1 and 2) negatively correlated with older (age 3 +) walleye abundance, signaling a 'density feedback' in which intraspecific competition limited growth. However, after the early 1980s this signal of intraspecific competition disappeared. This decoupling of the density feedback was related to multiple anthropogenic changes, including a larger walleye population resulting from better fisheries management, planned nutrient reductions to improve water quality and transparency, warmer water temperatures, and the proliferation of a non-native fish with novel traits (white perch, Morone americana). We argue that these changes may have reduced competitive interactions by reducing the spatial overlap between older and younger walleye and by introducing novel prey. Our findings illustrate the potential for anthropogenic change to diminish density dependent intraspecific interactions within top predator populations, which has important ramifications for predicting predator dynamics and managing natural resources.

Positive fluid balance is associated with complications after elective open infrarenal abdominal aortic aneurysm repair.

BACKGROUND: Open abdominal aortic aneurysm (AAA) repair is associated with cardiac and respiratory complications and an overall mortality rate of 2 to 8%. We hypothesised that excessive fluid administration during the perioperative period contributes to complications and poor outcome after AAA repair. METHODS: This was a retrospective cohort study. Medical records were analysed for fluid balance and complications in 100 consecutive patients treated by open AAA repair at a single centre between 2002-2005. Mortality and all major adverse events (MAE) such as myocardial infarction (MI), cardiac arrhythmia (Arr), pulmonary oedema (PO), pulmonary infection (PI), and acute renal failure (ARF) were included in the analysis. Level of care and hospital stay, were also recorded. RESULTS: There were no in-hospital deaths. MAE occurred in 40/100 (40%): MI (6%); Arr (14%); PO (14%); PI (25%); ARF (8%). Complications were not predicted by preoperative cardiovascular risk factors, operative and clamp time, or blood loss. Patients with complications had significantly greater cumulative positive fluid balance on postoperative day 0 (p<0.01), day 1 (p<0.05), day 2 (p<0.03) and day 3 (p<0.04). This relationship also existed for individual complications such as MI, and pulmonary oedema. These patients had significantly longer ICU/HDU (p<0.002) and hospital stay (p<0.0001). CONCLUSIONS: Serious complications are common after elective open AAA repair, and we have shown that positive fluid balance is predictive of major adverse events increased HDU/ICU and overall hospital stay.

Periods of low atmospheric pressure are associated with high abdominal aortic aneurysm rupture rates in Northern Ireland.

Seasonal and circadian variation in the incidence of ruptured abdominal aortic aneurysm (RAAA) has been reported. We explored the role of atmospheric pressure changes on rupture incidence and its relationship to cardiovascular risk factors. During a three year-period, 1st April 1998 and 31st March 2001, data was prospectively acquired on 144 Ruptured Abdominal Aortic Aneurysm (RAAA) presenting to the Regional Vascular Surgery Unit at the Royal Victoria Hospital, Belfast, Northern Ireland. For each patient the chronology of acute onset of symptoms and presentation to the regional vascular unit was recorded, along with details of standard cardiovascular risk factors. During the same period meteorological data including atmospheric pressure and air temperature were recorded daily at the regional meteorological research unit, Armagh. We then analyzed the monthly mean values for daily rupture incidence in relation to the monthly values for atmospheric pressure, pressure change and temperature. Furthermore atmospheric pressure on the day of rupture, and day preceding rupture, were also analyzed in relation to days without rupture presentation and between individual ruptures for various cardiovascular risk factors. Data demonstrated a significant monthly variation in aneurysm rupture frequency, (p<0.03, ANOVA). There was also a significant monthly variation in mean barometric atmospheric pressure, (p<0.0001, ANOVA), months with high rupture frequency also exhibiting low average pressures in the months of April (0.24 +/- 0.04 ruptures per day and 1007.78 +/- 1.23 mB) and September (0.16 +/- 0.04 ruptures per day and 1007.12 +/- 1.14 mB), respectively. The average barometric pressures were found to be significantly lower on those days when ruptures occurred (n=1127) compared to days when ruptures did not occur (n=969 days), (1009.98 +/- 1.11 versus 1012.09 +/- 0.41, p<0.05). Full data on risk factors was available on 103 of the 144 rupture patients and was further analyzed. Interestingly, RAAA with a known history of hypertension, (n=43), presented on days with significantly lower atmospheric pressure than those without, (n=60), (1008.61 +/- 2.16 versus 1012.14 +/- 1.70, p<0.05). Further analysis of ruptures grouped into those occurring on days above or below mean annual atmospheric pressure 1013.25 (approximately 1 atmosphere), by Chi-square test, revealed three cardiovascular risk factors significantly associated with low-pressure rupture, (p<0.05). Data represents mean +/- SEM, statistical comparisons with Student t-test and ANOVA. These data demonstrate a significant association between periods of low barometric pressure and high incidence of ruptured aneurysm, especially in those patients with known hypertension. The association between rupture incidence and barometric pressure warrants further study as it may influence the timing of elective AAA repair.

Major arteriovenous fistula complicating aorto-iliac aneurysms.

Seven cases of fistula developing between aortic or iliac aneurysms and adjacent major venous trunks are presented. The clinical diagnosis and principles of management of this exceptionally rare complication are discussed in the light of the literature on the subject.

Cross leg flap in a bilateral traumatic amputee.

A case report of a bilateral traumatic amputee who underwent a cross leg flap to preserve a knee disarticulation level amputation is presented. Salvage of amputated parts in the lower extremities to preserve stamp length provided our patient with better stability and decreased energy expenditure with ambulation.

The Belfast approach to managing complex lower limb vascular injuries.

INTRODUCTION: Complex lower limb vascular injuries (CLVIs) in high-energy penetrating or blunt trauma are associated with an unacceptably high incidence of complications including amputation. Traumatic ischaemia and ischaemia-reperfusion injury (IRI) of skeletal muscle often lead to limb loss, the systemic inflammatory response syndrome (SIRS) which affects remote organs and even the potentially fatal multiple organ dysfunction syndrome (MODS). Surgical care of CLVIs everywhere, including Northern Ireland until 1978, was governed by an anxiety to restore arterial flow quickly often using expedient and flawed repair techniques while a damaged major vein was frequently ligated. MATERIALS AND METHODS: A new policy centred on early intraluminal shunting of both artery and vein, restoring arterial inflow and venous outflow, respectively, was introduced at the Regional Vascular Surgery Unit of The Royal Victoria Hospital, Belfast in 1979. It imposed a disciplined one-stage comprehensive approach to treatment involving a sequence of operative manoeuvres in which all damaged anatomical elements receive meticulous and optimal attention unshackled by time constraints. RESULTS: Comparisons drawn between the pre-shunt period of unplanned treatment (1969-1978) and the post-shunt period centred on the use of shunts (1979-2000) showed that early shunting of both artery and vein in both penetrating (P) and blunt (B) injuries significantly reduced the necessity for fasciotomy (P: p=0.016, B: p=0.02) and caused a significant fall in the incidence of contracture (P: p=0.018, B: p=0.02) and of amputation (P: p=0.009, P: p=0.012). CONCLUSIONS: The policy of early shunting of artery and vein in CLVIs has proved to be of great benefit in terms of significantly improved outcomes, better operative discipline and harmonious collaboration among the specialists involved.

Bipolar coagulation at different energy levels: effect on patency.

Determining the extent of damage caused by bipolar coagulation at different levels is critical in microsurgery. If no significant damage occurs at known levels, this technique can be used instead of ligation, saving considerable time. One hundred eighty Sprague-Dawley rats were divided into six groups of 30 each. The effects of bipolar coagulation were assessed at either 2 or 10.4 watts at the junction between the common femoral artery and a branch vessel. Three common clinical settings were used: branch coagulation without interruption of blood flow in the common femoral artery; branch coagulation with interruption of blood flow for 30 minutes; and branch coagulation with arterial anastomosis 3-5 mm distal to the branch. Control procedures without coagulation were performed on the contralateral vessels. The animals were re-explored at 5-7 days. No differences occurred in patency of the coagulated vessels at 2 or 10.4 watts of delivered energy as compared with controls. Recanalization of the side branch occurred in approximately 80% (144/180) of specimens. Extensive damage to endothelium, tunica intima, and tunica media occurred for 1-2 mm around the site of the coagulated branch. The forceps pick-up test demonstrated little difference in flow of the cauterized vessel compared with controls. However, the cauterized vessel had a clinically weaker pulse stream of the transected common femoral artery. Recanalization of the coagulated side branch commonly occurred with a fibrin cap at the end of the vessel. Manipulation of the branch vessel frequently caused rebleeding. Our study shows that bipolar coagulation can be used effectively if coagulation is located at least 2 mm from the main vessel.

Fractures of the distal interphalangeal joint.

Fractures at the distal interphalangeal joint present a therapeutic challenge to the hand surgeon because of the relatively small bones and joint surfaces involved and the limited internal fixation devices available. Knowing which patients and which fractures are best treated surgically is key to a successful result. The normal anatomy and biomechanics of the joint are outlined and overviewed and the anatomy, etiology, therapy, and classification are discussed. Comminuted fractures of the articular surface of the distal phalanx are presented as are epiphyseal fractures of the distal phalanx. Avulsion of the profundus tendon (jersey finger) is discussed, emphasizing Leddy and Packer's Types I, II, and III injuries and the recommended treatment. Condylar fractures of the articular surface of the middle phalanx at the distal interphalangeal joint are the subject of the next section, with London's classification scheme and recommended treatment. Finally, complex open injuries and replantation through the distal interphalangeal joint are presented with guidelines for salvage and treatment.

A mathematical approach to the analysis of diversity in antibody gene families.

In this article, we develop a mathematical approach for the analysis of diversity in antibody gene families. This approach is arrived at by examing two general questions about protein populations: (1) What is a relative measure of the diversity exhibited by one protein family when compared with a second? (2) What is the probability that two protein populations were derived from a single common population? These quantitative approaches permit a variety of precise evolutionary, genetic, and developmental questions to be asked of antibody gene families. Using this methodology, we demonstrate that the diversity in mouse K-immunoglobulin chains is considerably greater than in their human K counterparts. We also show that the variable (Vl) regions of light chains associated with IgG and IgA immunoglobulins in the mouse appear to have been derived from a common population of Vl genes. This approach also can be used to analyse sequence data from other informational multigene families.

A computer simulation of evolutionary forces controlling the size of a multigene family.

A Monte Carlo-type simulation of the evolution of a multigene family was performed. The model was designed to study the selective forces which may control the size of a multigene family. As expected, we find that direct selection on the size of the multigene family can control its size. More important, we find that selection acting upon the family as a single functional unit, in conjunction with homologous but unequal crossing over, can also control the size of a multigene family.

On the evolution of beta-galactosidase.

The amino acid sequence of beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) has been compared to itself and to other proteins. Two segments, each of about 380 amino acids, comprising the first three-fourths of the polypeptide chain, were found to be very similar to each other. It is concluded that they are homologous. The carboxyl-terminal fourth has a high percentage of amino acid identities with dihydrofolate reductase of Escherichia coli, suggesting these sequences also are homologous. A model for the origin of beta-galactosidase is presented. The overall similarity of beta-galactosidase to lac repressor does not appear to be significant.

Role of antibiotics in open fractures of the finger.

The role of antibiotics was investigated prospectively in 91 open fractures of the finger. Antibiotics were administered to alternate patients with open phalangeal fractures. Only finger fractures distal to the metacarpophalangeal joint were included. Both groups were treated with aggressive surgical irrigation and debridement. In four patients in each group clinical signs of infection eventually developed; osteomyelitis did not develop in any patients, and no secondary surgical procedures were required in either group. This data indicates that vigorous irrigation and debridement is adequate primary treatment for open phalangeal fractures in fingers with intact digital arteries.

Predictive value of perioperative gastric acid tests.

Preoperative acid studies and early postoperative insulin tests in 275 patients undergoing various forms of vagotomy have been related to recurrent ulceration. Follow-up time has been from two to nine years, mean 4-3 years. Recurrence is directly related to basal acidity in both tests but is not related to stimulated acid levels preoperatively. In the insulin tests higher levels of acidity after insulin are associated with a higher incidence of recurrence. When positive, Hollander's and multiple criteria are both associated with a higher recurrence rate.

Risk of rupture of postangiographic femoral false aneurysm.

The surgical management of 50 false aneurysms caused by transfemoral arterial catheterization was reviewed to document the incidence and effects of rupture before repair. Twelve false aneurysms ruptured, leading to shock in six patients, distal ischaemia in three and stroke in one. The mean(s.d.) time from catheterization to rupture was 2.8(1.7) (range 1-6) days. Postoperative complications occurred in seven patients with ruptured and eight with non-ruptured aneurysms (P < 0.04). The mean(s.d.) age of patients with ruptured aneurysms was 67.2(6.3) (95 per cent confidence interval 63.5-70.8) years and those without 58.5(9.1) (95 per cent confidence interval 55.3-61.7) years (P < 0.008). On multiple regression analysis, age, peripheral vascular disease and raised plasma liver enzyme levels on admission were found to be significant independent predictive variables for rupture (all P < 0.05). It is recommended that patients with these risk factors undergo urgent operative correction of femoral false aneurysm.

Penetrating injuries of the popliteal vein: a report on 34 cases.

The results of treatment in 34 cases of penetrating injury to the popliteal vein are presented. In 26 cases there was associated damage to the popliteal artery. Satisfactory venous repair by lateral suture was achieved in 11 of 12 limbs. Autogenous vein grafts were used to repair the damaged popliteal vein in 10 limbs. In 4 the saphenous vein was anastomosed directly to the popliteal vein; in 6 cases it was used as a wide-bored panel or compilation graft. Three popliteal veins were ligated. Major postoperative limb oedema and chronic venous insufficiency were not a problem in those cases where the veins were repaired. Fasciotomy was performed in 19 of the 34 cases of venous injury. In 12 of these cases fasciotomy, performed as part of the original operation to repair the vascular injury, led to an excellent clinical result.