Local hemodynamics of the vascular access for hemodialysis

Vascular access is called Achilles' heel of hemodialysis because it is associated with a substantial morbidity. A permanent vascular access is created either by a direct connection of the patient's own artery and vein or by the interposition of a graft. Arteriolar beds are bypassed, which leads to a substantial increase in arterial (and venous) flow and the vessels adapt to it by a complex of interesting processes. These are reviewed together with some pathophysiological mechanisms of access complications.

Understanding the dialysis access steal syndrome. A review of the etiologies, diagnosis, prevention and treatment strategies

Distal hypoperfusion ischemic syndrome (DHIS), commonly referred to as hand ischemia or 'steal' after dialysis access placement, occurs in 5-10% of cases when the brachial artery is used, or 10 times that of wrist arteriovenous fistulas (AVFs) using the radial artery. It is typically seen in elderly women with diabetes, and may carry severe morbidity including tissue or limb loss if not recognized and treated. Three distinct etiologies include (1) blood flow restriction to the hand from arterial occlusive disease either proximal or distal to the AV access anastomosis, (2) excess blood flow through the AV fistula conduit (true steal), and (3) lack of vascular (arterial) adaptation or collateral flow reserve (ie atherosclerosis) to the increased flow demand from the AV conduit. These three causes of steal may occur alone or in concert. The diagnosis of steal is based on an accurate history and physical examination and confirmed with tests including an arteriogram, duplex Doppler ultrasound (DDU) evaluation with finger pressures and waveform analysis. Treatment of steal includes observation of developing symptoms in mild cases. Balloon angioplasty is the appropriate intervention for an arterial stenosis. At least three distinct surgical corrective procedures exist to counteract the pathophysiology of steal. The ultimate treatment strategy depends on severity of symptoms, the extent of patient co-morbidity, and the local dialysis access technical team support and skills available.

A computational model for shape from texture

Shape from texture is best analysed in a two-stage framework analogous to stereopsis and structure from motion: (a) computing the 'texture distortion' from the image; and (b) interpreting the 'texture distortion' to infer the orientation and shape of the scene surface in 3D. We model the texture distortion at a point in any particular direction on the image plane as an affine transformation and derive the relationship between the parameters of the affine transformation and the surface shape and orientation. We have developed a technique for estimating affine transforms between nearby image patches which is based on solving a system of linear constraints derived from a differential analysis. It is not necessary explicitly to identify texels or make restrictive assumptions about the nature of the image texture like isotropy. We have developed two different models for recovering surface orientation (slant and tilt) and shape (principal curvatures and directions) based on the estimated affine transforms in a number of directions. Experimental results are presented on images of planar and curved surfaces under perspective projection.

Dyslipidemia and anemia in chronically hemodialyzed patients

More than 50% of end-stage renal disease subjects treated by chronic hemodialysis die from cardiovascular events. Although there is some information regarding to anemia compensation and to the levels of biochemical risk factors of atherosclerosis in other countries, the data from the Czech Republic are missing. The aim of this study was to estimate mean cholesterol, triglyceride and hemoglobin levels in hemodialyzed subjects in the Czech Republic and to compare them with current guidelines. During the years 2001-2006, nephrologists of all subjects screened by duplex Doppler ultrasonography of our department were asked to fill in questionnaires with basic history and laboratory data. Hemoglobin concentration was calculated separately for years 2001-2004 and 2005-2006 because of the change of recommended target value from 105 to 110 g/l in 2004. A total of 258 subjects were included, aged 65 +/- 14 years, 93 of them males. Patients came from 46 different hemodialysis centers in the Czech Republic. The presence of hypertension and diabetes was in 72.5% and 39.5%, respectively. Only 13.2% of subjects had the smoking history, and another 10% currently smoked. The mean +/- SD laboratory results were as follows: total cholesterol 5.0 +/- 1.1 mmol/l, triglycerides (2.5 +/- 1.4 mmol/l). Hemoglobin concentration was 104.4 +/- 14.4 g/l (mean +/- SD) in years 2001-2004 and 110.1 +/- 16.2 g/l in years 2005-2006. Hemoglobin full blood concentration was lower than recommended 105 g/l in 55% of hemodialyzed subjects during years 2001-2004, and it was lower than 110 g/l during years 2005-2006 in 47% of patients. Hypercholesterolemia above recommended 5.17 mmol/l was present in 39% of subjects. Triglycerides were elevated above 1.69 mmol/l in 64% of patients. Only 10% of subjects were treated by lipid-lowering drugs. We can conclude that in the Czech Republic, patients treated by chronic hemodialysis frequently suffer from anemia, despite the growing evidence of erythrocyte stimulating agents treatment benefit. Similarly, considerable number of these subjects has hypercholesterolemia and hypertriglyceridemia, only rarely treated by lipid-lowering drugs. However, this therapy is still not adequately supported by clinical research evidence.

Matrix metalloproteinases in isolated hypercholesterolemia

AIM

Levels of circulating matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are altered in subjects with atherosclerosis. We hypothesized that also otherwise healthy hypercholesterolemic subjects will have altered MMP/TIMP concentrations. To validate this hypothesis, we compared MMPs/TIMPs in patients with moderate isolated hypercholesterolemia before and after atorvastatin therapy and in healthy normolipidemic controls.

METHODS

Twenty-seven otherwise healthy subjects with isolated hypercholesterolemia (total cholesterol 8.3+/-0.3 mmol/L) and 29 healthy normolipidemic controls were included. Patients were treated by atorvastatin for 10 weeks. We studied plasma levels of MMPs (MMP)-2, -3, and -9 and of their TIMPs (TIMP)-1 and -2.

RESULTS

Patients differed from controls by significantly lower MMP-3 [11.6 (5.7-21) vs 18.4 (12-22) ng/mL, P<10-4 (median, range 25-75%)] and TIMP-2 [13.3 (8.8-30.5) vs 22.1 (10.8-39) ng/mL, P=0.02] and by higher TIMP-1 [496 (461-538) vs 483 (456-500) ng/mL, P=0.004]. Atorvastatin decreased significantly TIMP-1 [from 496 (461-538) to 476 (451-525) ng/mL].

CONCLUSIONS

Isolated hypercholesterolemia per se is associated with similar alterations of circulating MMPs and TIMPs as developed symptomatic atherosclerosis. Most consistent link to serum lipids was observed in case of TIMP-1. MMP and TIMP levels probably reflect the atherogenic process in its early stages in these subjects.

Orbital embryonal rhabdomyosarcoma in Karachi (1998-2002)

OBJECTIVE

To study the epidemiology of ocular Rhabdomyosarcoma (ORMS) in Karachi.

METHODS

Incident ORMS cases resident of Karachi, registered at Karachi Cancer Registry (KCR) during 1st January 1998 to 31st December 2002 were included in the study. The data were classified using ICD-O2; computerized with Canreg-3, and analyzed using SPSS 10.0.

RESULTS

Ten cases of ORMS were reported to KCR during 1998-2002. RMS originated in the orbit in eight cases, conjunctiva in one and eyelid in one. Nine cases presented with proptosis, associated with conjunctivitis in four cases. One case presented with eyelid swelling. The crude annual incidence rate was 0.13/100,000, the age standardized rate was 0.3/100,000. The mean age of childhood cases was 10.4 years (95% CI 4.0; 16.7); and adult cases was 24.8 years (95% CI 12.8; 36.7). At presentation, eight patients were older than 10 years and three were older than 20 years. Five cases were categorized as childhood malignancies. Tumors were a TNM stage III disease at presentation in eight cases; survival at the end of one year was 70%, and at the end of two years 20%. There were no survivors at the end of three years.

CONCLUSION

ORMS in Karachi is a disease with a dismal survival. It may reflect a late presentation, or shorter adult ORMS survival or a manifestation of a different genetic pattern, associated with rapid evolution and poor prognosis. Health education for the population, especially parents and health providers is essential for early ORMS diagnosis. Pediatricians, ophthalmologists and health professionals, can play a vital role. Healthcare planning should focus on capacity building for ophthalmologic screening. Cytogenetic studies are advised to determine the genetic pattern.

Cancer esophagus Karachi 1995-2002: epidemiology, risk factors and trends

OBJECTIVE

To study the trends of cancer esophagus in Karachi South during 1995-2002 and identify risk factors.

METHODS

Incident esophageal cancer cases recorded at the Karachi Cancer Registry for Karachi South, during 1st January 1995 to 31st December 2003 were reviewed. For maximum completion of data, incident cases registered from 1st January 1995 to 31st December 2002 were included for final analyses.

RESULTS

The Age Standardized Incidence Rates (ASIRs) of cancer esophagus in Karachi South for males were 6.5/100,000 (1995-1997) and 6.4/100,000 (1998-2002). In females the observed rates were 7.0/100,000 (1995-1997) and 8.6/100,000 (1998-2002).

CONCLUSION

In the moderately high incidence, cancer esophagus zone of Karachi, the ASIRs in males remained stable during the last decade, but in females, an upward trend was observed suggesting a progressively higher exposure to risk factors in the latter. The potential risk factors in Karachi are use of all forms of tobacco, areca nut, infrequent consumption of raw fruits and vegetables and diet deficiencies. There is a necessity to actively control the proven risk factors and address the existence of other risk factors. The primary recommended strategy for the control of cancer esophagus would therefore be legislation against tobacco and areca nut in Pakistan and public health education. The risk factors of cancer esophagus identified in this article need to be further confirmed.

Cancer patterns in Quetta (1998-1999)

INTRODUCTION

Quetta, the capital of Baluchistan, is located at latitude 30.25; longitude 67.00. It has a population of 759,245; 425,474 males (56%) and 333,771 females (44%); Census 1998. The majority of residents are Persian or Baluchi speaking Baluchs.

METHODOLOGY

The cancer cases from Quetta reported to the Karachi Cancer Registry were reviewed. The data included cases from the Aga Khan University Hospital (AKUH), Pathology Department (Quetta collection point) and health care facilities in Karachi. The residents of Baluchistan were ascertained and cancer cases residents of Quetta identified with the help of recorded addresses and retraceable telephone numbers.

RESULTS

During a 2-year period, 1st January 1998 to 31st December 1999 the Karachi Cancer Registry received 1077 cancer notifications from Quetta. Approximately half the cases were registered from the AKUH Quetta collection point. Others were the referral patterns in Karachi. The age-standardized incidence rate (ASR) of cancer, all sites (1998-99) was 137.0 for males and 92.8/100,000 for females. The commonest cancer in the males and females was cancer of the esophagus (ICD-10 categories C15; males- ASR 25.5, 17.2%; females-ASR 23.4,23.1%). One ofthe highest in the world, for both genders. Incidence of cancer breast in the females (ICD-10 categories C50; ASR 11.8, 13.3%) was low.

CONCLUSION

The cancer data from Quetta is quite distinct from the cancer pattern of Karachi. It represents only a part of the cancer burden of Quetta; nonetheless it gives a glimpse into the cancer profile of Baluchistan. The high incidence of esophageal cancer indicates an extension of the geographical limits of the esophageal cancer belt.

Cancer patterns in Karachi division (1998-1999)

OBJECTIVE

A minimal cancer incidence data for Karachi, the largest city of Pakistan, is being presented here, for the years 1998-1999. The city has a population of 9,802,134; males 5,261,712 (52.6%) and females 4,540,422 (47.4%); census 1998.

METHODOLOGY

A predominantly mixed (passive and active) registration system has evolved in Karachi, the data sources being the hospitals within the Karachi Division. The reported/retrieved cancer data sets at the Karachi Cancer Registry are checked, coded, computerised in an analytical format and analysed.

RESULTS

The incident cancer cases registered in Karachi, during the 2-year period, 1st January 1998 to 31st December 1999 were analysed. The age-standardised incidence rate (ASR) of cancer, all sites was 132.4/100,000 for the males. Cancer of the lung 10.8%; ASR 17.3 was the most frequently recorded malignancy, followed by oral cavity 10.5%; ASR 13.2 and larynx 5.0%; ASR 7.4. The age-standardised incidence rate (ASR) of cancer, all sites was 133.0/100,000 in the females. Cancer of the breast, 32.0%; ASR 40.7 was the most frequently recorded malignancy, followed by oral cavity 8.1%; ASR 11.7 and gall bladder 3.6%; ASR 5.5.

CONCLUSION

The present data has been calculated with an estimated 15-20% probable under ascertainment. Tobacco-associated cancers in Karachi were responsible for 38.3% of the tumours diagnosed amongst the males. Two principal cancers, breast and oral cavity were responsible for 40.1% of the cancers in females. A rare finding was the high incidence of gall bladder cancer in the females. At present it is difficult to determine whether this indicates a genuine high risk or a selection bias. A continuous process of cancer registration to study the trends in the incidence and an adequate cancer control program are possible and essential for Pakistan and can be based on the pattern being practiced in Karachi.

Both fenofibrate and atorvastatin improve vascular reactivity in combined hyperlipidaemia (fenofibrate versus atorvastatin trial--FAT)

OBJECTIVE

It has been repeatedly proven that statins improve endothelial function in isolated hypercholesterolaemia but there is far less evidence in the case of combined hyperlipidaemia. Studies assessing the effects of fibrates on endothelium have been neglected. Therefore, we conducted a trial in which the effects of fenofibrate and atorvastatin monotherapy on both endothelium-dependent vascular reactivity and biochemical parameters were compared in patients with combined hyperlipidaemia.

METHODS

29 otherwise healthy males (aged 47.4+/-7.8 years) with combined hyperlipidaemia (total cholesterol 7.55+/-1.20 mmol/l, triglycerides 5.41+/-4.54 mmol/l) were included into the randomised, single-blind, cross-over study to receive either 200 mg of micronised fenofibrate or 10 mg of atorvastatin daily--each of the drugs for a period of 10 weeks. Analysed biochemical parameters were as follows: serum total-, LDL- and HDL-cholesterol, apolipoproteins A-I and B, triglycerides, fibrinogen, uric acid, C-reactive protein (CRP), insulin, and homocysteine. Endothelial function was investigated by duplex Doppler ultrasonography at the brachial artery. Two indices of endothelial-dependent postischaemic changes were used - the recently introduced index of peak blood flow (PBF) representing the level of reactive hyperaemia and traditional flow-mediated dilatation (FMD).

RESULTS

We observed a small improvement in FMD after both fenofibrate and atorvastatin (from 2.26% to 2.98% and 2.87%, respectively; NS). PBF increased from 448 ml/min to 536 ml/min after fenofibrate (P=0.04) and to 570 ml/min after atorvastatin (P=0.03). The effects of both fenofibrate and atorvastatin on endothelial function did not differ significantly (P-values of 0.82 and 0.47 for FMD and PBF, respectively). Significant correlations (P<0.01) between the changes of vascular reactivity and biochemical indices were found between FMD and CRP (r=-0.60) and between both FMD and PBF, and insulinaemia (r=-0.48 and -0.56, respectively) only during treatment with fenofibrate.

CONCLUSIONS

Both fenofibrate and atorvastatin significantly improved endothelium-dependent vascular reactivity without mutual difference. The PBF was superior to FMD for the detection of this improvement. The beneficial effect of both drugs did not correlate with the change of lipid profile during therapy. The improvement of vascular reactivity during treatment with fenofibrate (opposed to atorvastatin) was related to the reduction of indirect marker of chronic vessel wall inflammation and of insulin resistance. The PBF was more reproducible than FMD because of considerably lower intra-subject variability.

Image recognition: visual grouping, recognition, and learning

Vision extracts useful information from images. Reconstructing the three-dimensional structure of our environment and recognizing the objects that populate it are among the most important functions of our visual system. Computer vision researchers study the computational principles of vision and aim at designing algorithms that reproduce these functions. Vision is difficult: the same scene may give rise to very different images depending on illumination and viewpoint. Typically, an astronomical number of hypotheses exist that in principle have to be analyzed to infer a correct scene description. Moreover, image information might be extracted at different levels of spatial and logical resolution dependent on the image processing task. Knowledge of the world allows the visual system to limit the amount of ambiguity and to greatly simplify visual computations. We discuss how simple properties of the world are captured by the Gestalt rules of grouping, how the visual system may learn and organize models of objects for recognition, and how one may control the complexity of the description that the visual system computes.

Stereoscopic occlusion junctions

Portions of surfaces in a binocularly viewed scene may be 'half occluded', that is, visible in only one eye. The human visual system uses zones of half occlusion to help segment the visual scene and infer figure-ground relationships at object boundaries. We developed a quantitative model of the depth-discontinuity cue provided by half occlusion. Half occlusions are revealed by two-dimensional interocular displacements of binocularly viewed occlusion junctions, such as T junctions. We derived a formula relating this two-dimensional displacement, or 'pseudodisparity', to binocular disparities and orientations of occluding and occluded contours. In human psychophysical experiments, perceived depth and contour orientation quantitatively depended on pseudodisparity, as predicted by our model, implying that the visual system senses quantitative variations in interocular junction position to reconstruct occlusion geometry.

Presenting features in Pakistani patients suffering from the antineutrophil cytoplasmic antibody--classical subtype (c-ANCA) associated vasculitis

OBJECTIVES

To study the clinicopathological features in c-ANCA positive patients suffering from vasculitis with a view to find out the most common mode of presentation.

STUDY DESIGN

Retrospective.

SETTINGS

Department of Immunology, AFIP, Rawalpindi, MH Rawalpindi, CMH Rawalpindi, Department of Rheumatology, PIMS, Islamabad, RGH Rawalpindi, FFH, Rawalpindi.

SUBJECTS

Seventeen patients suffering from vasculitis and found to be positive for c-ANCA.

MAIN OUTCOME MEASURES

Clinico-pathological features at presentation.

RESULTS

There were 9 males in age range 11-60 years (mean age 32.5 years) and 8 females in age range 26-42 years (mean age 32.3 years). Common presenting features were a combination of cough, blocked nose and post nasal drip 14/17 (82%) followed by nose bleed and haematuria 11/17 (65%). Six patients were demonstrated to be suffering from Wegener's granulomatosis after biopsy. C-ANCA was detected by indirect immunofluorescence in the titre range of 8-640. The auto antibody levels related to disease activity.

CONCLUSION

c-ANCA associated vasculitis is a rare (17 patients in five years) but aggressive form of vasculitis. It must be suspected in patients with persistent respiratory tract related symptoms associated with fever and joint pains which fail to respond to adequate treatment for infections. The c-ANCA estimations can be utilised as sensitive and specific diagnostic and prognostic marker in this form of vasculitis.

Surface orientation from texture: isotropy or homogeneity (or both)?

We examine two models for human perception of shape from texture, based on two assumptions about the surface texture: isotropy and homogeneity. Observers made orientation judgments on planar textured surfaces. Surface textures were either isotropic or anisotropically stretched or compressed. If subjects used an isotropy assumption, they would make biased orientation estimates for the anisotropic textures. In some conditions some observers showed no bias for the anisotropic textures relative to the isotropic textures. In general, even when the observers showed bias, the biases were significantly less than those predicted if the observer used only deviation from isotropy as a cue. Observers appear to use both the deviation from isotropy and a texture gradient or affine texture distortion cue for shape from texture.

Consistency and validity of patient administered assessment of quality of life by the MOS SF-36; its association with disease activity and damage in patients with systemic lupus erythematosus

OBJECTIVE

To investigate the metric properties and validity of the assessment of quality of life by the MOS Short Form 36 (SF-36) in patients with systemic lupus erythematosus (SLE) and to examine the effect of disease on quality of life.

METHODS

Cross sectional study of 150 patients with SLE (age: mean 39.7 yrs, SD 11.4 yrs; 95% female) attending 2 specialist lupus clinics between November 1994 and April 1995. Shortly before or after the consultation patients completed the SF-36 and the MOS SF-20 with an additional question about fatigue (SF-20+) in random order. Disease activity was measured by the British Isles Lupus Activity Group System (BILAG), disease damage by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage index (SLICC).

RESULTS

SF-36 domains were shown to be internally consistent (Cronbach's coefficient alpha > or = 0.71). Significant associations of the SF-36 domains with the corresponding domains of the SF-20+ and with global disease activity measured by BILAG were observed. SF-36 scores in patients with SLE were significantly lower than in controls. Different disease activity levels were significantly associated with different quality of life scores, with excellent ability to record the continuum from good health to serious illness by the SF-36. Disease activity had greater effect on quality of life than age, cumulative damage, or disease duration.

CONCLUSION

This study shows the SF-36 is internally consistent and proves construct, discriminatory, and criterion validity for the SF-36 and construct validity for the SF-20+ in patients with SLE. The SF-36 is preferred because of its broader scope of questions, its widespread use, and previous international validation for a wide variety of diseases.

Association of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index with measures of disease activity and health status in patients with systemic lupus erythematosus

OBJECTIVE

To examine the internal consistency and validity of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) with respect to disease activity, health status, and medication score.

METHODS

A prospective cross sectional study of patients with systemic lupus erythematosus (SLE) attending a specialist lupus outpatient clinic between July 1994 and February 1995. The internal consistency of the SDI components was examined using Cronbach's coefficient alpha. The associations of the SDI components with disease activity measured by the British Isles Lupus Assessment Group (BILAG) index, health status measured by the Medical Outcomes Study (MOS) Short Form 20, and with a medication score were analyzed using Spearman's rank correlation coefficient (p).

RESULTS

133 women and 8 men ranging in age from 20.1 to 88.7 years (mean 41.1, SD 12.5) were studied. With few exceptions, the components of the SDI that reflect damage in different organ systems were not associated with each other. We found a significant although weak relationship between some related SDI and BILAG components (p 0.25 to 0.28; p < 0.01). While damage to the musculoskeletal system was associated with limitations in physical functioning measured with the MOS Short Form 20 (p-0.30; p < 0.01) and renal damage inversely with fatigue (p-0.23; p < 0.01) there was no significant relationship of other SDI components with the MOS Short Form 20. Renal and neuropsychiatric damage were associated significantly with the medication score (p 0.27 and 0.23; p < 0.01).

CONCLUSION

The components of the SDI are valid in that they are associated with disease activity in the respective organ systems and some of them with a medication score. However, damage in different organ systems in SLE does not follow a common pattern. It is thus suggested that the SDI profile be used in addition to the SDI total score as an endpoint in clinical and epidemiological studies.

Further validation of the BILAG disease activity index in patients with systemic lupus erythematosus

OBJECTIVE

To examine the association among the BILAG disease activity index components and their relations with global assessments, health status, and laboratory tests with regard to the validity of the BILAG index.

METHODS

A cross sectional study of consecutive patients with systemic lupus erythematosus (SLE) attending a specialist lupus outpatient clinic between July 1994 and February 1995. The internal consistency of the British Isles Lupus Assessment Group (BILAG) index-a disease activity assessment system for SLE patients, based on the principle of the physician's intention to treat-was examined using Cronbach's coefficient alpha. The association of the components of the BILAG index with health status as measured with the MOS Short Form 20 (SF-20), with patients' and doctors' global assessments of patient wellbeing and with laboratory tests was analysed with Spearman rank correlations.

RESULTS

133 female and eight male patients, age 20.1 to 88.7 years (mean 41.1, SD 12.5), were included. With few exceptions, the components of the BILAG index which reflect disease activity in different organ systems were not associated with each other. With the exception of the mucocutaneous component, we found a significant relation between all components of BILAG and global assessment of patient wellbeing, health status, erythrocyte sedimentation rate, or serum C3 level.

CONCLUSIONS

The study confirms the validity of all but the mucocutaneous component of the BILAG index. However, disease activity in different organ systems in SLE does not follow a common pattern. Thus the individual BILAG components should be used rather than the total BILAG score as a primary endpoint in clinical and epidemiological studies. To capture the total effect of SLE on an individual measures of disease activity, damage, and health status are all needed.

Ventriculoatrial shunt via the transverse sinus: technical note

A technique to divert cerebrospinal fluid into the right atrium via the transverse sinus is described. This has proven effective when the peritoneum becomes unavailable as the primary receptor site for cerebrospinal fluid drainage.

A neurosurgical approach to far-lateral disc herniation. Technical note

A technique for exposing far-lateral intervertebral disc herniations without disrupting the facet is described. This technique is a simple modification of the standard neurosurgical approach.

The herbicide glyphosate

Glyphosate has broad spectrum herbicidal activity against a wide range of annual and perennial weeds. The environmental properties of this herbicide such as its soil immobility, rapid soil inactivation and soil biodegradation are outstanding. This herbicide is practically non-toxic to non-plant life forms such as aquatic and avian species, animals and man. Metabolism studies with pure bacterial cultures indicate that glyphosate is metabolized to either aminomethylphosphonate and glyoxylate or sarcosine and phosphate in most bacteria. The enzyme C-P lyase, which catalyzes the cleavage of the carbon-phosphorus bond of phosphonates including glyphosate, appears to be complex, containing multiple subunits. Mode of action studies have demonstrated that glyphosate kills plants by inhibiting the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, involved in the biosynthesis of aromatic compounds. The status of our understanding of these aspects of glyphosate is reviewed.