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1.
Eur J Vasc Endovasc Surg ; 51(4): 565-71, 2016 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-26876113

RESUMEN

OBJECTIVE: Critical limb ischemia (CLI) is an increasingly alarming presentation of advanced generalized circulatory failure. Most patients presenting with CLI have profound cardiovascular comorbidities that hinder surgical intervention. Moreover, some patients present with non-reconstructable arterial anatomy. For this vulnerable cohort, primary amputation is often the only available option. This study aims at answering the question: Can sequential pneumatic compression (SPC) preclude amputation? METHODS: A retrospective analysis of 187 patients (262 limbs) prescribed the Artassist SPC compared outcomes between the group of patients who acquired the device and those who did not. The primary end point was limb salvage; secondary end points were amputation-free survival and improvement in toe pressures. RESULTS: The mean age was 74.78 years, the median follow-up was 16 months, and the median duration of usage was 4 months. 81.72% of the patient acquired the device and 18.28% did not. The mean toe pressure was 61.4 mmHg pre-application, and 65 mmHg after application (p = .071). Amputation-free survival was 98% and 96% for those who acquired the device and 90% and 84% for those who did not at 6 and 12 months, respectively. There was a non-significant association between limb salvage and device acquisition (p = .714); however, there was a significant improvement in rest pain (p < .0001), reduction in minor amputation (p = .023), and amputation-free survival associated with using the device (p = .01). CONCLUSIONS: Although limb salvage is the paramount ambition for patients referred to vascular services, some patients with CLI are better served with primary amputation. Although the mechanism of SPC action is still ambiguous, there is strong evidence to support its role in preventing minor amputation, prolonging amputation-free survival, and improving rest pain in patients with non-reconstructable CLI; nevertheless, its role in prevention of major amputation lacks statistical significance.


Asunto(s)
Aparatos de Compresión Neumática Intermitente , Isquemia/terapia , Recuperación del Miembro , Enfermedad Arterial Periférica/terapia , Dedos del Pie/irrigación sanguínea , Anciano , Anciano de 80 o más Años , Amputación Quirúrgica , Presión Sanguínea , Enfermedad Crítica , Supervivencia sin Enfermedad , Diseño de Equipo , Femenino , Humanos , Aparatos de Compresión Neumática Intermitente/efectos adversos , Isquemia/diagnóstico , Isquemia/fisiopatología , Estimación de Kaplan-Meier , Masculino , Enfermedad Arterial Periférica/diagnóstico , Enfermedad Arterial Periférica/fisiopatología , Estudios Retrospectivos , Factores de Riesgo , Factores de Tiempo , Resultado del Tratamiento
2.
Hernia ; 16(1): 59-62, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-21796449

RESUMEN

BACKGROUND: Abdominal wall hernias are a common imaging finding in the abdomen. Ultrasonography (US) is noninvasive and allows the examination of the patient in a physiological manner. High-frequency annular US probes have become an increasingly important diagnostic tool for detecting pathological lesions in superficial organs. OBJECTIVES: To determine the prevalence of paraumbilical hernias among adult patients by abdominal sonography in a tertiary care hospital and to describe the sonographic technique and findings. MATERIALS AND METHODS: During the 2-year period between January 2008 and December 2009, we performed high-resolution US of the anterior abdominal wall on 302 patients who were referred for different reasons other than the examination of the anterior abdominal wall. The images were taken by a radiologist with 12 years of experience in US, and the images were reviewed by three consultant radiologists with expertise in body imaging. RESULTS: A total of 302 patients [169 females (56.0%) and 133 males (44.0%)], ranging in age from 17 to 85 years, with a mean age of 53.5 years, were enrolled in the study. The number of positive cases among females was 42 (24.9%) and that among males was 31 (23.3%). CONCLUSION: High-resolution US is an efficient tool for detecting the presence of paraumbilical hernias and accurately verifying not only their content, but also the possible associated complications.


Asunto(s)
Pared Abdominal/diagnóstico por imagen , Hernia Umbilical/diagnóstico por imagen , Hernia Umbilical/epidemiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Ultrasonografía , Adulto Joven
3.
Int J Bioinform Res Appl ; 5(6): 593-602, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19887334

RESUMEN

The increase of the amount of DNA sequences requires efficient computational algorithms for performing sequence comparison and analysis. Standard compression algorithms are not able to compress DNA sequences because they do not consider special characteristics of DNA sequences (i.e., DNA sequences contain several approximate repeats and complimentary palindromes). Recently, new algorithms have been proposed to compress DNA sequences, often using detection of long approximate repeats. The current work proposes a Lossless Compression Algorithm (LCA), providing a new encoding method. LCA achieves a better compression ratio than that of existing DNA-oriented compression algorithms, when compared to GenCompress, DNACompress, and DNAPack.


Asunto(s)
Algoritmos , ADN/genética , Bases de Datos Genéticas
4.
J Hand Surg Eur Vol ; 34(4): 486-92, 2009 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-19675029

RESUMEN

Seventeen children with Erb's (C5/6 and C5/6/7 types) obstetric brachial plexus palsy who underwent low rotation humeral osteotomy to treat internal rotation contracture of the shoulder were recalled back to the clinic at a mean of 10 (range 8-14) years after surgery. Eight were male and nine female with mean age of 16 (range 13-20) years. The osteotomy procedure was done at a mean age of 6 (range 5-8) years. Preoperative, early postoperative, and late postoperative motor assessments were compared. There was no recurrence of the internal rotation posturing of the shoulder and there was maintenance of the improvements in elbow extension deficit and forearm rotation. The most surprising finding was a significant (P = 0.003) decrease in shoulder abduction on long-term follow-up (the mean shoulder abduction was 135 degrees , 146 degrees and 109 degrees measured pre-, early post- and late postoperatively, respectively). There was no correlation between changes in shoulder abduction and the radiological score of the shoulder.


Asunto(s)
Traumatismos del Nacimiento/cirugía , Neuropatías del Plexo Braquial/cirugía , Plexo Braquial/lesiones , Contractura/cirugía , Húmero/cirugía , Osteotomía/métodos , Adolescente , Traumatismos del Nacimiento/diagnóstico por imagen , Traumatismos del Nacimiento/fisiopatología , Neuropatías del Plexo Braquial/diagnóstico por imagen , Neuropatías del Plexo Braquial/fisiopatología , Articulación del Codo/diagnóstico por imagen , Articulación del Codo/fisiopatología , Femenino , Estudios de Seguimiento , Humanos , Húmero/diagnóstico por imagen , Masculino , Complicaciones Posoperatorias/diagnóstico por imagen , Complicaciones Posoperatorias/fisiopatología , Radiografía , Rango del Movimiento Articular/fisiología , Articulación del Hombro/diagnóstico por imagen , Articulación del Hombro/fisiopatología , Adulto Joven
5.
East Mediterr Health J ; 10(4-5): 620-6, 2004.
Artículo en Inglés | MEDLINE | ID: mdl-16335654

RESUMEN

The prevalence of diabetic nephropathy as a cause of end-stage renal disease (ESRD) in Egypt has been examined in small cross-sectional studies, with conflicting results. The need for a large-scale study prompted us to perform this 6-year multiple cross-sectional study. A sample of ESRD patients enrolled in the Egyptian renal data system was evaluated during the period 1996-2001 for the prevalence of diabetic nephropathy. Prevalence gradually increased from 8.9% in 1996, to 14.5% in 2001. The mean age of patients with diabetic nephropathy was significantly higher than that of patients with ESRD from other causes. Mortality was also significantly higher in diabetic patients with ESRD.


Asunto(s)
Nefropatías Diabéticas/complicaciones , Fallo Renal Crónico/etiología , Adulto , Distribución por Edad , Causalidad , Causas de Muerte/tendencias , Estudios Transversales , Nefropatías Diabéticas/diagnóstico , Nefropatías Diabéticas/epidemiología , Egipto/epidemiología , Glomerulonefritis/complicaciones , Humanos , Hipertensión/complicaciones , Incidencia , Fallo Renal Crónico/epidemiología , Fallo Renal Crónico/terapia , Persona de Mediana Edad , Vigilancia de la Población , Prevalencia , Pielonefritis/complicaciones , Sistema de Registros , Diálisis Renal/tendencias , Salud Rural/estadística & datos numéricos , Esquistosomiasis Urinaria/complicaciones , Factores Socioeconómicos , Tasa de Supervivencia , Salud Urbana/estadística & datos numéricos
6.
(East. Mediterr. health j).
en Inglés | WHO IRIS | ID: who-119458

RESUMEN

The prevalence of diabetic nephropathy as a cause of end-stage renal disease [ESRD] in Egypt has been examined in small cross-sectional studies, with conflicting results. The need for a large-scale study prompted us to perform this 6-year multiple cross-sectional study. A sample of ESRD patients enrolled in the Egyptian renal data system was evaluated during the period 1996-2001 for the prevalence of diabetic nephropathy. Prevalence gradually increased from 8.9% in 1996, to 14.5% in 2001. The mean age of patients with diabetic nephropathy was significantly higher than that of patients with ESRD from other causes. Mortality was also significantly higher in diabetic patients with ESRD


Asunto(s)
Distribución por Edad , Causalidad , Causas de Muerte , Estudios Transversales , Glomerulonefritis , Hipertensión , Fallo Renal Crónico , Esquistosomiasis Urinaria , Nefropatías Diabéticas
7.
Afr. j. urol. (Online) ; 9(2): 53-58, 2003.
Artículo en Inglés | AIM (África) | ID: biblio-1258174

RESUMEN

Objective To evaluate the efficacy of intra-lesional verapamil injection in the treatment of Peyronie's disease. Patients and Methods Twenty-six patients with Peyronie's disease were divided into two groups: the verapamil treatment group (study group) including 13 patients and the saline group (control group) including another 13 patients. The patients' age ranged from 35 to 58 years with a mean age of 43.75 years. The patients in the study group were subjected to a weekly injection of 10 mg verapamil hydrochloride (5 mg / 2 ml) into the plaque for the duration of six weeks. At the same time; the patients in the control group received a weekly injection of normal saline into the plaque; also for the duration of six weeks. The patients' response to the injections was evaluated subjectively with respect to pain and sexual dysfunction and objectively with respect to the plaque volume and the degree of curvature. Results Following therapy; pain was improved in 8 of 9 patients (88.9) of the patients in the verapamil group; while in the control group it was stationary in 6 of 8 patients (75) and had progressed in 2 of 8 patients (25). Curvature was improved in 5 of 10 patients (50) and remained unchanged in 5 of 10 patients (50) of the study group; while no improvement could be recorded in any of the patients of the control group. Three of five patients (60) of


Asunto(s)
Egipto , Inyecciones Intralesiones , Induración Peniana , Induración Peniana/terapia , Verapamilo/administración & dosificación
8.
J Vasc Access ; 3(4): 164-8, 2002.
Artículo en Inglés | MEDLINE | ID: mdl-17639480

RESUMEN

BACKGROUND: Proper choice of the vascular access plays a crucial role in dialysis outcome. The prevalence and types of vascular access have not yet been investigated in Egypt. Our work aims to study prevalence, patency rate, complications and factors affecting different types of vascular access in Egypt. PATIENTS AND METHODS: We studied one thousand hemodialysis patients in eighteen dialysis centers in Egypt. RESULTS: 93% of the patients had natural arteriovenous access while 7% had synthetic arteriovenous grafts. The patency rate of natural fistulae was significantly higher than that of synthetic grafts (3.07 +/- 3 versus 1.5 +/- 2 years respectively). Many arteriovenous grafts were done because natural arteriovenous fistula was unsuitable or after its failure. Natural radiocephalic fistula was the most prevalent type (67.3%), with a patency rate significantly higher than all other sites (3.3 +/- 3 years). Only 10.2% of patients had a fistula created before the start of dialysis. Thrombosis rate was significantly higher in synthetic arteriovenous grafts (32.4%) than in natural arteriovenous fistulae (9.3%). Diabetes and hyperlipidemia significantly decreased the patency rate of natural arteriovenous fistula but not that of synthetic grafts. Patency of arteriovenous fistula in non-diabetics was 3.2 +/- 3.1 years versus 2 +/- 1.9 years in diabetics. Patency of arteriovenous fistula in non-hyperlipidemic patients was 3.1 +/- 3 years versus 1.5 +/- 1.6 years with hyperlipidemia. Temporary vascular access prior to permanent access was used in 90% of patients, of which femoral catheters were used in 53.6%, jugular catheters in 38% and subclavian catheters in 8.4%. The incidence of primary access failure was significantly higher in patients with a previous subclavian catheter insertion. CONCLUSIONS: Natural arteriovenous fistula is the access of choice for hemodialysis patients in Egypt. It has higher patency rate, lower complication rate and nephrologists prefer it. Diabetes and hyperlipidemia decrease patency rate of natural arteriovenous fistula but not synthetic grafts. Subclavian catheter is better avoided due to increased incidence of primary access failure.

9.
Am J Trop Med Hyg ; 64(3-4): 147-53, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11442209

RESUMEN

Residents of Egypt's Nile river delta have among the world's highest seroprevalence of hepatitis C virus (HCV) infection. To assess the impact of HCV on chronic liver disease, we studied the association between HCV, other hepatitis viruses, and cirrhotic liver disease in a cross-sectional, community-based survey of 801 persons aged > or = 10 years living in a semi-urban, Nile delta village. Residents were systematically sampled using questionnaires, physical examination, abdominal ultrasonography and serologically for antibodies to HCV (confirmed by a third-generation immunoblot assay) and to hepatitis A virus (HAV), hepatitis B virus (HBV), and hepatitis E virus (HEV). The seroprevalence of HCV increased with age from 19% in persons 10-19 years old to about 60% in persons 30 years and older. Although no practices that might facilitate HCV transmission were discovered, the seroprevalence of HCV was significantly associated with remote (> 1 year) histories of schistosomiasis. Sonographic evidence of cirrhosis was present in 3% (95% CI: 1%, 4%) of the population (0.7% of persons under 30 years of age and in 5% of older persons), and was significantly associated with HCV seroreactivity. Our findings are consistent with the hypothesis that past mass parenteral chemotherapy campaigns for schistosomiasis facilitated HCV transmission, and that HCV may be a major cause of the high prevalence of liver cirrhosis in this Nile village.


Asunto(s)
Hepacivirus/aislamiento & purificación , Anticuerpos Antihepatitis/sangre , Hepatitis C/epidemiología , Cirrosis Hepática/epidemiología , Adolescente , Adulto , Factores de Edad , Niño , Estudios Transversales , Egipto/epidemiología , Femenino , Hepacivirus/inmunología , Hepatitis C/complicaciones , Hepatitis C/diagnóstico por imagen , Humanos , Immunoblotting , Cirrosis Hepática/diagnóstico por imagen , Cirrosis Hepática/etiología , Masculino , Persona de Mediana Edad , Examen Físico , Estudios Seroepidemiológicos , Encuestas y Cuestionarios , Ultrasonografía
10.
J Egypt Public Health Assoc ; 73(3-4): 369-85, 1998.
Artículo en Inglés | MEDLINE | ID: mdl-17219929

RESUMEN

The objective of this study was to determine the prevalence of abnormal findings detected by abdominal ultrasonography (US) in an Egyptian rural area. This study was a part of a community based cross sectional survey for virus hepatitis carried out at Kalama village in Nile Delta, 40 kilometers north of Cairo. People above 10 years of age living in a 10% systemic random sample of houses in the village were subjects of this study. A member of the team carried out US examination of the liver, biliary tree, spleen, kidneys, pancreas, para aortic areas and the pelvis. Examination included morphological assessment and organometry. All results are recorded on images by videoprinter. Abnormalities in abdominal US was detected in 34% of examined cases. Abnormal liver impressions were detected in 28.3% of cases. Ascites was detected in 13 cases (1.8%). Diseases of the gall bladder and kidneys were detected in 2.7% and 2.1%, respectively. US diagnosed pregnancy in 5 women, one of them had a blighted ovum. Some of these abnormalities were detected in subjects with no complaint. It is concluded that abdominal US may be a tool for early detection of asymptomatic disease.


Asunto(s)
Hepatitis/diagnóstico por imagen , Hepatitis/diagnóstico , Enfermedades Renales/diagnóstico por imagen , Hepatopatías/diagnóstico por imagen , Colecistitis/diagnóstico , Colecistitis/diagnóstico por imagen , Egipto , Femenino , Encuestas Epidemiológicas , Humanos , Enfermedades Renales/diagnóstico , Hepatopatías/diagnóstico , Masculino , Población Rural , Ultrasonografía/métodos
11.
Trans R Soc Trop Med Hyg ; 91(3): 271-4, 1997.
Artículo en Inglés | MEDLINE | ID: mdl-9231192

RESUMEN

Markers of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections were sought in serum samples from 2644 blood donors in 24 of Egypt's 26 governorates. Of the 2644 samples, 656 (24.8%) were shown to contain anti-HCV immunoglobulin G antibody by Abbott second generation enzyme immunoassays (EIA). Of 85 EIA-positive samples tested by recombinant immunoblot assay, 72 (85%) were positive. HCV seroprevalence in the governorates ranged from zero to 38%; 15 governorates (62%) had an HCV antibody prevalence greater than 20%, and 6 (25%) greater than 30%. Governorates with higher sero-prevalences were located in the central and north-eastern Nile river delta, and south of Cairo in the Nile river valley. Subjects from areas in and adjoining the Sinai peninsula, in the eastern and western desert, and in southernmost Egypt, had the lowest prevalence of HCV antibody. The large urban governorates of Cairo and Alexandria had antibody prevalences of 19% and 11%, respectively. A total of 39.4% subjects had evidence of HBV infection (and-HBV core antigen total antibody). HCV infections were detected more frequently in donors with markers for HBV infections than in uninfected subjects (36% versus 18%, P < 0.001).


Asunto(s)
Donantes de Sangre , Anticuerpos contra la Hepatitis C/análisis , Hepatitis C/epidemiología , Egipto/epidemiología , Anticuerpos contra la Hepatitis B/análisis , Hepatitis C/inmunología , Humanos , Inmunoglobulina G/análisis , Prevalencia
12.
Ann Thorac Surg ; 63(1): 64-7, 1997 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-8993242

RESUMEN

BACKGROUND: Acute depletion of plasma fibronectin levels has been reported during and after cardiopulmonary bypass; degradation of fibronectin by proteolytic enzymes has been suggested as one of the causes. This study was designed to assess the possible preservation of fibronectin levels by aprotinin during cardiopulmonary bypass. METHODS: Plasma fibronectin levels were evaluated in 19 patients undergoing either elective coronary artery bypass grafting or a valvular heart operation. The study was conducted prospectively in a controlled, randomized, double-blinded manner. Nine test patients (group A) received intraoperative, intravenous administration of aprotinin; 10 control patients (group B) received equivalent volume of normal saline solution. Fibronectin levels were measured immediately after induction of anesthesia (as the baseline for the study) and at the following times: after 5 minutes on bypass, after 30 minutes on bypass, immediately before the start of rewarming, and after being off bypass for 5 minutes, but before protamine administration. RESULTS: Both groups' basic characteristics were very similar. Group A patients were found to have significantly greater fibronectin levels than group B during and immediately after cardiopulmonary bypass (p < 0.002). CONCLUSIONS: Administration of aprotinin intraoperatively appears to result in better preservation of fibronectin levels during cardiopulmonary bypass. Although the mechanism of action of aprotinin as a proteolytic inhibitor remains unclear, it has been suggested that it exerts an inhibiting effect on proteolytic enzymes by forming an aprotinin-proteinase complex. The clinical implications of the greater level of fibronectin achieved by the intraoperative use of aprotinin during cardiopulmonary bypass need further evaluation.


Asunto(s)
Aprotinina/uso terapéutico , Puente Cardiopulmonar , Fibronectinas/sangre , Inhibidores de Serina Proteinasa/uso terapéutico , Aprotinina/farmacología , Puente de Arteria Coronaria , Método Doble Ciego , Femenino , Prótesis Valvulares Cardíacas , Humanos , Cuidados Intraoperatorios , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Inhibidores de Serina Proteinasa/farmacología , Factores de Tiempo
14.
Lancet ; 342(8880): 1149-50, 1993 Nov 06.
Artículo en Inglés | MEDLINE | ID: mdl-7901480

RESUMEN

Rift Valley fever (RVF) has been recorded in man and in domestic animals in Egypt after a 12-year absence. Human infections were first noted in the Aswan Governorate in late May, 1993. Only cases of ocular disease, an infrequent and late manifestation, were reported. Of 41 cases, 35 were tested serologically and 27 (77%) had RVF virus-specific IgM antibodies. An estimated 600-1500 infections occurred in the region. Abortions in cattle and buffalo were seen concurrently and antibodies to RVFV were present in 39% of domestic livestock, presumably unvaccinated. RVFV was isolated from an aborted water buffalo fetus.


Asunto(s)
Fiebre del Valle del Rift/epidemiología , Virus de la Fiebre del Valle del Rift/aislamiento & purificación , Aborto Veterinario/microbiología , Adulto , Animales , Búfalos , Bovinos , Egipto , Métodos Epidemiológicos , Femenino , Cabras , Humanos , Masculino , Embarazo , Recurrencia , Fiebre del Valle del Rift/inmunología , Fiebre del Valle del Rift/fisiopatología , Virus de la Fiebre del Valle del Rift/inmunología , Ovinos
15.
Int J Gynaecol Obstet ; 40(1): 25-31, 1993 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-8094346

RESUMEN

OBJECTIVE: To describe the clinical outcome of pregnancy and vertical transmission of acute viral hepatitis in pregnancy. METHODS: Forty-eight pregnant patients with acute viral hepatitis were evaluated clinically and by abdominal ultrasonography. Serological studies for hepatitis markers were performed using radioimmunoassay. The results were evaluated using Student's t-test and tests of proportion. RESULT: Thirty-five (72.9%) delivered live birth babies at term, while 13 (27.1%) had fetal complications and/or losses. The percentage of fetal complications and/or losses was higher in patients who had non-A, non-B hepatitis (30.8%) than those who had type B hepatitis (25%). The most common fetal complication was premature delivery (14.9%) followed by stillbirth and abortion (8.3%) for each. The overall percentage of vertical transmission of hepatitis B virus was 2 out of 27 (7.4%). CONCLUSION: Acute viral hepatitis carries a high risk for both mother and fetus. Routine vaccination of all susceptible women and babies against hepatitis B is recommended in endemic areas.


Asunto(s)
Hepatitis Viral Humana , Complicaciones Infecciosas del Embarazo , Resultado del Embarazo , Enfermedad Aguda , Adolescente , Adulto , Femenino , Enfermedades Fetales/inmunología , Antígenos de Superficie de la Hepatitis B/análisis , Hepatitis Viral Humana/inmunología , Hepatitis Viral Humana/transmisión , Humanos , Recién Nacido , Embarazo , Complicaciones Infecciosas del Embarazo/inmunología
17.
Int J Clin Monit Comput ; 7(4): 217-22, 1990.
Artículo en Inglés | MEDLINE | ID: mdl-2099970

RESUMEN

The accuracy of the Ohmeda Biox 3700 pulse oximeter was evaluated in 10 paediatric patients, deliberately surface cooled to 25 degrees C in preparation for cardiac surgery, by comparing the arterial oxygen saturation results obtained from an Ohmeda Biox 3700 and a Radiometer OSM-2 Hemoximeter. Though there was a good correlation between the two series of results, the arterial oxygen saturation was over-estimated by the pulse oximeter compared to the OSM-2 Hemoximeter in the temperature range 36 degrees to 30 degrees C and under-estimated below 30 degrees C. These differences were greatest when the initial saturations were low.


Asunto(s)
Procedimientos Quirúrgicos Cardíacos/instrumentación , Hipotermia Inducida , Oximetría/instrumentación , Procedimientos Quirúrgicos Cardíacos/métodos , Niño , Estudios de Evaluación como Asunto , Humanos
18.
Photosynth Res ; 12(3): 219-35, 1987 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24435689

RESUMEN

The gas exchange characteristics of cassava were compared with one C3 species, common bean, and two C4 species, maize and amaranthus. Cassava leaf photorespiration, about 12% of maximum net photosynthesis in normal air, and the CO2 release in CO2-free air under intense light were lower than the values typically reported for C3 species. The CO2 compensation point of whole leaves (25 cm(3) CO2m(-3)) was intermediate between C3 and C4 species values.Gas exchange was restricted to either the upper or lower surface of amphistomatous leaves by covering one side of the leaf with silicone grease. The CO2 compensation point of the upper leaf surface was less than 6 cm(3) CO2m(-3) and the CO2 release into CO2-free air in the light was essentially zero. On the lower leaf surface considerable CO2 release occurred in both the light and the dark.The hypothesis presented to explain these results is the existence of an efficient CO2 recycling mechanism in the palisade layer in the upper half of the leaf. In the light of recent data (presented in the second paper of this series) indicating that cassava produces C4 acids as primary products of photosynthesis, it is proposed that this hypothesis is consistent with the possible existence of the C4 photosynthetic pathway in the palisade layer of cassava leaves.The results and hypothesis are discussed in relation to the crop's adaptation to the environmental conditions where it is normally grown. The implications of variation in anatomical features such as stomatal distribution on both surfaces of the leaf are analyzed with a view to enhancing the potential productivity of cassava under stress conditions.

19.
Photosynth Res ; 12(3): 237-41, 1987 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24435690

RESUMEN

Cassava, bean and maize leaves were fed with(14)CO2 in light and the primary products of photosynthesis identified 5 and 10 seconds after assimilation. In maize, approximately three quarters of the labelled carbon was incorporated in C4 acids, in beans about two thirds in PGA, and in cassava approximately 40-60% in C4 acids with 30-50% in PGA. These data indicate that cassava possesses the C4 photosynthetic cycle, however due to the lack of typical Kranz anatomy appreciable carbon assimilation takes place directly through the Calvin-Benson-Bassham cycle.

20.
Photosynth Res ; 9(3): 333-43, 1986 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24442365

RESUMEN

Measurements of CO2 and H2O exchange rate and the calculated leaf conductance of attached leaves were conducted over a range of leaf-to-air vapour pressure difference (VPD) (1.5 to 5.5 kPa) to compare the response of the parasitic mistletoe, Phthirusa pyrifolia, with that of its host, the mandarin orange, Citrus reticulata. Seedlings of the host infected with the parasite were grown in well-watered and adequately fertilized large pots outdoors at the CIAT headquarters, Palmira, Colombia, South America. Observations of leaf anatomy of the parasite and nutrient analysis of young tissues of both the parasite and host were made. The photosynthetic rate of the host decreased linearly with increased VPD, whereas the parasite showed a constant rate. This trend coincided with similar responses in leaf conductance. Due to the insensitivity of the parasite stomata, the transpiration rate increased linearly with VPD as compared with an initial increase and then a decrease in the host transpiration rate. The higher photosynthetic rate and the closure of stomata of the host resulted in high water use efficiency as compared with that of the parasite. The parasite accumulated in its leaves more N, P, K and less Ca and Mg than the host. The significance of the host-parasite differential response to air humidity is discussed in relation to mechanism underlying stomatal sensitivity and in the context of host-parasite association.

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